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      Articles written in Pramana – Journal of Physics

    • Volume and surface polarization of electrets

      M R Bhiday U Gupta M Ranade S Rao

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      An attempt is made, to obtain mathematical relations correlating the volume and surface effects of the dielectric to those of the electrical impedance of the dielectric system exhibited in the presence of a quasistatic sinusoidal electrical field. A new experiment is described to differentiate clearly the two types of polarizations in an electret.

    • Structure determination of Ls-threonine by neutron diffraction

      M Ramanadham S K Sikka R Chidambaram

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      The structure of the aminoacid, Ls-threonine [NH3+ CH(CHOHCH3)COO], space groupP212121,a=13.630(5),b=7.753(1),c=5.162(2) Å,z=4, has been determined from neutron diffraction data using direct methods. The intensities of 1148 neutron Bragg reflections were measured from a single crystal. The structural parameters were refined by the method of least squares using anisotropic temperature factors. The finalR(F2) is 0.068. The structure was also refined from the x-ray data of Shoemakeret al (1950J. Am. Chem. Soc.72 2328); there is good agreement between the two sets of heavy atom parameters. The parameters of hydrogen atoms are of course more precisely determined in our neutron study. The molecular conformation and the hydrogen bonding scheme are discussed. Weighted average values of bond distances and angles from 14 aminoacid structures with ionized carboxylic groups studied by neutron diffraction at Brookheven and Trombay are also presented.

    • Orbit of the spectroscopic binary b Persei

      R Rajamohan M Parthasarathy

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      New spectroscopic orbital elements have been derived for the close binary system b Persei. The period is improved to 1.527360 days. Earlier observations by Cannon (1914), Harper (1930) and Heard (1938) have been reanalysed and the reality of the variations in the orbital elements is established. The change inω indicates an aspidal motion period of about 60 years. Changes in some of the orbital elements may be due to the distortion of the radial velocity curve by gas streams present in the system. In view of the flaring radio emission detected from this system and the variations of the orbital elements, we believe that the close binary system b Persei is in an active mass transfer phase.

    • A kinematical basis for power form factors

      S G Kamath M Gupta S Chakrabarty A N Mitra

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      A kinematical basis is proposed for form factors of the power type associated with multiple derivative couplings, on the basis of a Lorentz contraction effect on the external momenta involved in the transition matrix elements for mesons and baryons as appropriate quark composites. The argument (due to Licht and Pagnamenta) which applies separately to the Breit and c.m. frames for a decay matrix element provides a formal theoretical justification for thead hoc power form factors used by the Delhi group in a series of applications to hadronic processes over the past few years. The radius of interaction finds a natural place in this description simply from dimensional considerations, and its rather small magnitude, less than 0.5F, estimated fromfits to the data indicates a relatively small role played by structure effects. The Breit frame form factors, which work somewhat better than the c.m. frame ones (effectively used in the earlier studies), give a rather impressive sets of fits to the baryon decays in the (L + 1) wave (consistently for both vertical and horizontal) and the (L − 1) wave (mainly horizontal). The mesonic decays, the data for which are available mostly for the (L + 1) wave, are also fitted with an equal degree of consistency without any extra assumptions.

    • Phenomenological effective interaction for40K

      M Prakash Y R Waghmare

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      Effective interactions of various forms incorporating central, spin-orbit and tensor dependences of two-nucleon potential are parametrized so as to give a satisfactory description of energy levels of40K. These parameters are applied to calculate energy levels of38Cl. Except for the lowest 3 level, the agreement is satisfactory.

    • The emission band system c2Σ+ — x2Π of NH+

      G Krishnamurthy M Saraswathy

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      Five red degraded bands belonging to theC2Σ+X2Π system of NH+ were excited in a mild condensed discharge through flowing ammonia and were photographed on a 3.4 meter Ebert grating spectrograph at a dispersion of 2.5 A/mm. The rotational analyses of these bands enabled us to evaluate the vibrational and rotational constants accurately. The rotational energy levels of theΠ+ andΠ levels of theν=0 and 1 levels of the ground state,X2Π, were fitted in James expression using two sets of rotational constants. The perturbations observed in theX2Π state caused by thea4Σ state were examined in greater detail.

    • Velocity gradient driven flute instabilities in plasmas

      M Sinha A K Sundaram

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      The effect of velocity gradient across the magnetic field on the low frequency flute modes is examined in detail, using the normal mode analysis. It is shown that some new type of instabilities driven primarily by the velocitygradient arise and these excited modes eventually attain the convective saturation. The onset of plasma turbulence due to these instabilities may possibly be one of the major contributors for anomalous heating process and enhanced plasma resistivity.

    • Gravity induced magnetic instability

      M Sinha

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      In the presence of a gravitational field the stability of a magnetoplasma is studied against electromagnetic perturbations. We have shown that a pinching type of instability can be triggered with a sizable growth rate affecting the equilibrium configuration of the confining magnetic field. This might have a profound effect on the magnetic fields of astrophysical bodies.

    • The ionospheric absorption at Gauhati

      M Devi A K Barbara

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      Some problems encountered in the process of estimation of calibration constantI0h0 have been discussed. The discrepancies observed in theI0h0 value determined by different methods were found to be mostly due to focussing. The difference observed between noontime values of absorption measured from different order echoes could be removed by a correction factor found after Piggot. But in certain cases the discrepancy in the reflection characteristics of single and multiple echoes were such that this correction factor did not give a consistent value. Such changes might be linked with sporadicE.

    • High resolution gamma-ray spectroscopy of the27Al(p,γ)28Si resonance reaction

      M A Rahman M A Awal M Rahman H M Sengupta S K Gupta

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      High resolution gamma-ray spectra have been measured from the27Al (p,γ)28Si reaction for the resonances atEp=2·482, 2·511 and 2·735 MeV at ϑpγ=0°, 30°, 55° and 90° using a Ge (Li) gamma spectrometer. From the spectra and the angular distributions the properties of the resonance states have been obtained. These states are the isobaric analogues of the levels at 4·69, 4·75 and 4·93MeV levels respectively in the parent nucleus A28l.

    • The dirac-schwinger covariance condition in classical field theory

      K Babu Joseph M Sabir

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      A straightforward derivation of the Dirac-Schwinger covariance condition is given within the framework of classical field theory. The crucial role of the energy continuity equation in the derivation is pointed out. The origin of higher order derivatives of delta function is traced to the presence of higher order derivatives of canonical coordinates and momenta in the energy density functional.

    • Nuclear spin-lattice and nuclear spin-spin relaxation time measurements in EuB6 at low temperatures using the spin-echo technique

      MM Bajaj M Kasaya

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      Experimental results on the nuclear spin-lattice and nuclear spin-spin relaxation times in the ferromagnetic EuB6 at temperatures below 4·2 K are presented using the external magnetic field,Hext, in the range of 0 ⩽Hext ⩽ 10 kG. Nuclear spin-spin relaxation time computed on the basis of the Suhl-Nakamura process turns out to be 3·2µs, which compares well with the experimental value 11·1µs obtained with the 10 kG magnetic field at 1·7 K. It is found that in the ferromagnetic EuB6,T1 is approximately 5 × 103 times larger thanT2 at 1·7 K with the 10 kG magnetic field. Thus the effect ofT1 onT2 can be neglected. From the experimental value ofT2, the value of the homogeneous line broadening is found to be 14 kHz. The corresponding value obtained from the cw method is 175 kHz. This evidently shows the presence of the inhomogeneous line broadening in the cw NMR.

    • Fourier transform of the collagen triple-helical structure and its significance

      M Bansal

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      The Fourier transforms of the collagen molecular structure have been calculated taking into consideration various side chain atoms, as well as the presence of bound water molecules. There is no significant change in the calculated intensity distribution on including the side chain atoms of non-imino-acid residues. Taking into account the presence of about two bound water molecules per tripeptide unit, the agreement with the observed x-ray pattern is slightly improved. Fourier transforms have also been calculated for the detailed molecular geometries proposed from other laboratories. It is found that there are no major differences between them, as compared to our structure, either in the positions of peak intensity or in the intensity distribution. Hence it is not possible to judge the relative merits of the various molecular geometries for the collagen triple helix from a comparison of the calculated transforms with the meagre data available from its x-ray fibre pattern. It is also concluded that the collagen molecular structure should be regarded as a somewhat flexible chain structure, capable of adapting itself to the requirements of the different side groups which occur in each local region.

    • Search for superheavy elements in monazite from beach sands of South India

      S S Kapoor V S Ramamurthy M Lal S K Kataria

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      Monazite minerals obtained from beach sands of South India were examined for the presence of superheavy elements with photon-induced x-ray fluorescence method. The accumulated data of a number of runs each of several days duration do not show any convincing peaks above the background at the expected locations for superheavy elements which are above the present sensitivity of detection of about 10 ppm by weight for element 126. However, some intriguing features pertaining to structures in the x-ray spectra around 27 keV were observed, which are of interest for further investigations.

    • Photo and electroluminescence of ZnO : Er and ZnO : Ag, Er electroluminors

      S Bhushan M Saleem S Chandra

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      A number of ZnO : Er and ZnO : Ag, Er electroluminors have been prepared and their photo (PL) and electroluminescent (EL) properties investigated. While the addition of Ag slightly shifts the PL spectra towards longer wavelength side, the EL spectra not only shift but consist of some new transitions. In ZnO : Er electroluminors, additional transitions also exist at higher frequencies of excitations. Brightness waves for this system consist of two secondary peaks during each half cycle of exciting field. Temperature dependence shows two broad peaks. While voltage dependence of ZnO : Er satisfies the relationB=B0 exp(−b/V1/2), the relationB=B0V exp(−b/V1/2) is found to be suitable for ZnO : Ag, Er electroluminor. Possible mechanisms for these phenomena have been proposed.

    • A study of the reaction19F(α, n)22Na in the bombarding energy range 2·6 to 5·1 MeV

      M Balakrishnan S Kailas M K Mehta

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      The total (α, n) reaction cross section for19F has been measured as a function of alpha energy in the energy range 2·6 to 5·1 MeV with a thin target. The excitation function exhibits a large number of resonances. The prominent amongst these for which theJπ values are known have been analysed to extract the partial widthsΓα and Γn. Statistical analysis of the data in terms of strength function and average level spacing distribution has also been performed.

    • An angular momentum expansion of energy and structure of high spin states

      M Satpathy R Sahu A Ansari L Satpathy

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      A new angular momentum expansion of level energies of ground-state band of even-even nuclei has been obtained which is found to converge rapidly even for the most back-bending nuclei. Attempts have been made to interpret the parameters and calculate them microscopically. It is found that nuclear structure in the forward bending region is quite different compared to that in the back-bending region.

    • A bag model study ofD mesons

      K Babu Joseph M Sabir M N Sreedharan Nair

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      An investigation of the newly discovered charmed mesonsD 0 andD +, particularly their non-leptonic decay modes, is carried out in the framework of the MIT bag model. The amplitude for a number of two-body final state decays are explicitly evaluated and compared with other available estimates.

    • Analysis of multiparticle production data on proton-nucleus collisions using a new variable

      T Aziz M Zafar M Irfan A Ahmad M Shafi

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      Multiparticle production data on proton-nucleus collisions have been analyzed taking the number of ‘created’ charged particles instead of the observed number of shower particles as the variable. The mean normalized multiplicity,RA, has been found to be independent of energy in the energy range (7–8000) GeV and its mass number dependence has been obtained. The modified analysis introduces some more regularities in the experimental results onp-nucleus collisions like the invariance with respect to energy of the relationshipRA = α + βNh and the KNO-like scaling of the multiplicity distributions of the created charged particles. The functional form of the scaling function has been calculated.

    • Output characteristics of a 400 MW Nd:glass laser system

      R Bhatnagar P D Gupta B S Narayan M Anwar B L Gupta D D Bhawalkar

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      The paper discusses the performance characteristics of a Nd: glass laser system designed for laser produced plasma studies. It consists of aQ-switched oscillator followed by two amplifier stages. The output behaviour of the oscillator, i.e. laser pulse duration, peak power and optimum coupling, has been studied and is in good agreement with theory. Gain characteristics of amplifiers were obtained as a function of various parameters. Energies in excess of 7 J with pulse durations as small as 18 nsec were obtained giving rise to 400 MW peak power.

    • Long range interactions between some charged solitons

      M Raj Lakshmi

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      A procedure is offered for evaluating the forces between classical, charged solitons at large distances. This is employed for the solitons of a complex, scalar two-dimensional field theory with a U(1) symmetry, that leads to a conserved chargeQ. These forces are the analogues of the strong interaction forces. The potential,U(Q, R), is found to be attractive, of long range, and strong when the coupling constants in the theory are small. The dependence ofU(Q, R) onQ, the sum of the charges of the two interacting solitons (Q will refer to isospin in the SU(2) generalisation of the U(1) symmetric theory) is of importance in the theory of strong interactions; group theoretical considerations do not give such information. The interaction obtained here will be the leading term in the corresponding quantum field theory when the coupling-constants are small.

    • Scattering contributions to the internal partition function of a diatomic molecular system

      B Talukdar M Chatterji P Banerjee

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      An analytical expression for the phase shift contribution to the internal partition function for the Morse potential is derived by using an approximate Jost function. This function is shown to be a convergent sum. The numerical results obtained for H2 and HCl show the partition function to be a monotonically increasing function of temperature. This observation agrees with the results of Rogers and co-workers.

    • A model for multiparticle production in high energy hadronic collisions

      T Aziz M Zafar

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      A model for multiparticle production process in high-energy hadronic collisions is proposed. In the centre of mass (CM) system of colliding particles the target and the projectile are assumed to pass through each other sharing energies allowed by kinematical constraints. Thus in app collision the energy associated with each is √S/2 (S being the square of the CM energy) which is taken to be the real variable that governs the number of particles produced. In the case of hadronnucleus collisions the projectile and the target ofv nucleons lying in a (Lorentz contracted) tube pass through each other sharing energies ⋍ √SA2, whereSAvS. Before the final state particles emerge from these systems, the constituents of the target, i.e.,v nucleons share equally (= √SA2v) the total energy associated with the target and become the centres from which final state particles stem out. Several results have been discussed.

    • On the problem of constraints in minimally coupled relativistic wave equations for particles of unique mass

      M Seetharaman T R Govindarajan P M Mathews

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      We study the problem of a possible change in the number of constraints in linear relativistic wave equations (-μμ+m)ψ=0 for particles of unique mass, on introduction of minimal coupling to an external electromagnetic field. Complementing our earlier work in which we obtained conditions for non-loss of constraints in equations characterised by the minimalβ-algebraβ05 =β03 we derive here the conditions for such theories not to generate more constraints than in the free case. The results are illustrated by considering specific equations and a fallacy in certain conclusions of Kobayashi and Shamaly on this problem is pointed out.

    • Microwave propagation through modulated air plasma

      S K Varshney M Sakuntala

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      When a microwave propagates through a plasma in which electron density and electron collision frequency periodically vary, the propagating wave is modulated in amplitude and phase. An approximate theory is derived to suit the laboratory experimental conditions. Introducing the amplitude and phase difference, the dependence of electron density and electron collision frequency has been derived for different radio frequency modulation and frequency parameter. A scanning double probe technique is used to measure the exact time variation in the plasma parameters at any fixed position during a single cycle of the applied field. Theoretical values agree with those of experiment.

    • On the normal vibrations of nonrigid molecule B(CH3)3

      T S G Krishna Murty L S R K Prasad M Kondala Rao

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      Treating the symmetry operations as transformations in higher dimensional space, it is shown that Wigner’s method can be straightaway extended to study the vibrations of nonrigid molecules exhibiting free or nearly free internal rotations. The molecule B(CH3)3 is illustrated.

    • Two-potential formula continued off-the-energy-shell

      B Talukdar M Chatterji M Kundu

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      We derive an off-energy-shell generalization of the two-potential formula by using a coordinate-space approach and apply the formalism to construct algorithms for studying spatial behaviour of the fully off-shellT matrix. We also suggest some future applications of the proposed theory.

    • On the energy spectra of one-dimensional anharmonic oscillators

      P M Mathews M Seetharaman Sekhar Raghavan V T A Bhargava

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      In this paper we present explicit and simple analytical formulae for the energy eigenvaluesEn (λ) of one-dimensional anharmonic oscillators characterized by the potentials 1/22x2x withα=2, 3 and 4. A simple intuitive criterion supplemented by the requirement of correct asymptotic behaviour, has been employed in arriving at the formulae. Our energy values over a wide range ofn andλ are in good agreement with the numerical values computed by earlier workers through very elaborate techniques. To our knowledge this is the first time that formulae of such wide validity have been given. The results for pure power oscillators are trivially obtained by going over to theω→0 limit. Approximate analytic expressions for the low order even moments ofx are also given.

    • X-ray K-absorption edge shifts due to chemical combination

      K S Srivastava Shiv Singh Pratibha Gupta A K Srivastava V Kumar M Husain M K Prasad

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      A possible explanation is given of the chemical shifts of x-ray K-absorption edges of metals when they undergo a chemical combination and form compounds. It is proposed that when a metal forms a compound its Fermi edge changes. It explains the numerical order as well as the nature of the chemical shifts. A fairly good agreement between the calculated and observed values has been obtained.

    • Generalized interacting boson model and the collective behaviour in nuclei

      M Suguna R D Ratna Raju V K B Kota

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      The effect of including the high spin bosons on the manifestation of collective behaviour in nuclei is examined by plotting theB(E2; 2+→0+) rates as a function of neutron number for various values ofη, whereη is the highest angular momentum of the bosons included in the calculation.B(E2; 2+→0+) values of a large number of nuclei in various regions of the nuclear periodic table are calculated with a single value for the effective charge in the generalized scheme. Irreducible representations of SU(3) contained in the symmetric partition [N] of U(15) are worked out for integersN uptoN=15, to enable the explicit inclusion of theg boson into calculations. The experimentally observed odd-K bands in234U and184W are described as a direct consequence of theg boson.

    • Isospin violations in largePT pion inclusive processes in perturbative quantum chromodynamics

      H S Mani M Noman M Rafat R Ramachandran

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      We investigate the asymmetries arising due to electromagnetic interactions in largePT pion inclusive processes. The hardqcd processes that contribute to such asymmetries areq+gq+γ,q+qg+γ etc. which are suspected to be substantial, as indicated by theqcd predictions for a significant and increasingγ/πo ratio at largePT. We calculate the expected isospin related asymmetries and propose tests that might detect them. Our estimates indicate that the effects are much smaller than may be naively expected. We also observe a remarkable scaling of asymmetries in the variablePT/(s)1/2.

    • Reaction48Ca (p, n)48Sc fromEp=1.885 to 5.1 MeV

      Gulzar Singh S Kailas S Saini A Chatterjee M Balakrishnan M K Mehta

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      The total (p, n) reaction cross section for48Ca has been measured as a function of proton energy in the energy range 1.885 to 5.100 MeV with an overall resolution of ∼ 2 keV and in ∼ 5 keV energy steps. The fluctutions in fine resolution data have been analysed to determine the average coherence width 〈Γ〉. The excitation function averaged over large energy intervals has been analyzed in terms of the optical model. The isobaric analogue resonances atEp ∼ 1.95 and 4 MeV have been shape-analyzed to extract the proton partial width and the spectroscopic factorSn. A comparison of the gross structures observed in ∼ 55 keV averaged excitation function with the predictions of Izumo’s partial equilibrium model has also been made.

    • Multiple focus formation in a Mather gun device

      Anurag Shyam M Srinivasan

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      Along with the normally produced pulses of dI/dt, x-ray, optical emission, neutrons and ions by a Mather type plasma focus gun, one more set of pulses were observed to be generated by a low energy device at Trombay, a few 100 ns after the first set of pulses, in majority of the discharges. In a small number of discharges even three or more sets of pulses were observed. Signals from pick-up probes placed in the run down region of the device suggest formation of more than one sheath which subsequently may form more than one focus which in turn is responsible for the second and subsequent sets of pulses.

    • First passage time distributions for finite one-dimensional random walks

      M Khantha V Balakrishnan

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      We present closed expressions for the characteristic function of the first passage time distribution for biased and unbiased random walks on finite chains and continuous segments with reflecting boundary conditions. Earlier results on mean first passage times for one-dimensional random walks emerge as special cases. The divergences that result as the boundary is moved out to infinity are exhibited explicitly. For a symmetric random walk on a line, the distribution is an elliptic theta function that goes over into the known Lévy distribution with exponent 1/2 as the boundary tends to ∞.

    • Mechanoluminescence of coloured KCl crystals

      M Elyas S K Shukla B P Chandra

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      The gamma-irradiated KCl crystals exhibit mechanoluminescence during elastic, plastic and fracture deformation. The mechanoluminiscence (ml) intensity varies linearly with the number of newly-created dislocations and decreases with successive application and release of uniaxial pressure. The totalml intensity increases with applied pressure as well as with the temperature of the crystals. On the basis of the movement of the dislocations, the pressure and temperature dependence ofml is discussed.

    • First passage time and escape time distributions for continuous time random walks

      V Balakrishnan M Khantha

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      We consider an arbitrary continuous time random walk (ctrw)via unbiased nearest-neighbour jumps on a linear lattice. Solutions are presented for the distributions of the first passage time and the time of escape from a bounded region. A simple relation between the conditional probability function and the first passage time distribution is analysed. So is the structure of the relation between the characteristic functions of the first passage time and escape time distributions. The mean first passage time is shown to diverge for all (unbiased)ctrw’s. The divergence of the mean escape time is related to that of the mean time between jumps. A class ofctrw’s displaying a self-similar clustering behaviour in time is considered. The exponent characterising the divergence of the mean escape time is shown to be (1−H), whereH(0<H<1) is the fractal dimensionality of thectrw.

    • On the calculation of second order properties: An equation of motion approach

      M Gupta S Bhattacharyya

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      In the light of the equation of motion method a general expression for polarisability calculation has been derived. From this general expression, different approximation methods can be deduced for different choices of ground state and excitation manifold. Among these the coupled Hartree-Fock theory is the most extensively used one for polarisability calculations. It has also been shown that this theory has a simple relationship with random phase approximation.

    • Probing proton spin structure through hadronic reactions

      M Rafat R Ramachandran

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      Inclusive and semi-inclusive photon producing polarized proton reactions have been employed to probe the spin structure of the proton. Combinations of cross-sections are suggested which may measure valence quarks polarization and gluon polarization in the proton separately. The general formalism is used to predict numerical results using a model of spin structure based on Altarelli-Parisi equations.

    • Lattice imperfection studies in polycrystalline materials by x-ray diffraction line-profile analysis

      M De S P Sen Gupta

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      This review concerns our recent investigations with a series of binary fcc Ag- and Cu-base alloys (viz Ag-Ga, Ag-Ge, Ag-Al and Cu-Ga, Cu-Ge) from detailed analyses of x-ray diffraction line profiles, the importance of which has been briefly summarized. The theoretical formulations of the Warren-Averbach’s method of Fourier analysis of peak-shapes along with the methods of peak-shift and peak-asymmetry have been outlined. A preview on the significant studies carried out earlier with Ag- and Cu-base (fcc) binary alloys has been made in short. A detailed analyses on the recorded profiles in the present considerations revealed, in general, quantitative estimates of several microstructural parameters characterising the deformed state of the materials namely, propensity of stacking faults (intrinsic, extrinsic and twin faults), rms microstrains, coherent domain sizes, long-range residual stresses, lattice parameter changes, dislocation density and stacking fault energy. The results indicate a general trend of increase in the concentrations of stacking faults, primarily, of intrinsic character, with increase in solute concentrations; which are solely responsible for the observed peak-shifts as well as domain size broadening. Small asymmetry in the profiles is due to the presence of extrinsic stacking faults, relatively less in magnitude compared to the intrinsic ones while the deformation twin faults are almost absent—an observation with significance. The dislocation density, quite appreciable in magnitude, has been evaluated from the anisotropic values of the coherent domain sizes and rms microstrains. The stacking fault energies of pure Ag and Cu, an important parameter have also been estimated and compared with those obtained from electron microscopy. Annealing experiments with a Ag-5·8% Al alloy, aluminium being a precipitating solute, do not reveal any detectable evidence of solute segregation at the stacking faults. The occurrence of stacking faults in the alloy systems has been correlated with a number of physical factors involving solvent-solute types.

    • Lattice dynamical study of alkali metals: An unified approach based on CGW model

      V Ramamurthy M Satishkumar

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      The phonon dispersion relations for lithium, sodium, potassium, rubidium and cesium along the principal symmetry directions as well as their lattice specific heats have been deduced using Clark, Gazis and Wallis angular force model. This model which conforms to the translational symmetry of the lattice, reproduces the observed crossover in lithium along [ζ00] direction at ζ = 0·49, without producing any crossovers in other alkali metals. Besides, the theoretical dispersion curves of all alkali metals are in excellent agreement with the corresponding experimental or homologous dispersion relations and theirϑD values compare well with the experimental values over a wide temperature range. It is shown that the strength of electron-ion interactions plays a significant role in the success of any unified lattice dynamical study of alkali metals while the three-body interactions of thecgw model do not. The importance of umklapp processes, failure of the earlier models to produce a crossover and the experimentalϑD-T curve in lithium as well as the apparent variation in the nature and range of atomic interactions of alkali metals are discussed.

    • Exact energy eigenvalues by summation of thejwkb series

      M Seetharaman S S Vasan S Ravichandran

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      For the potentialV(x)=V0 tan2x, the corrections to the lowest orderjwkb (Bohr-Sommerfeld) energy quantization rule are non-zero. These higher order corrections are explicitly computed using the formalism of Dunham. The resultingjwkb series for the energy eigenvalues is summable, and yields the exact bound state spectrum.

    • On the peripheral nature of the target fragmentation phenomena

      M Satpathy L Satpathy

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      The mechanism of target fragmentation phenomena is explored in a statistical model. It is shown that peripheral interaction arising out of large impact parameter can describe the mass yield distribution of the products from the fragmentation of63Cu by the bombardment ofp,12C and40Ar with energies of 28, 25 and 80 GeV respectively. Important insights into the dynamics is obtained from these reactions as the target remaining the same, the projectile mass varies by forty units and the incident energy per nucleon by fourteen units. Surface properties of the target and projectile are shown to play an important role. Other features like limiting fragmentation and projectile dependence are also borne out in this study.

    • Growth of single crystals of copper and their thermal profile estimation

      S K Khanna M Sekar A Michael David K Govinda Rajan P Bhaskar Rao

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      Copper crystals have been grown by Czochralski technique in a 6-bar argon gas environment. X-ray analysis shows that these are single crystals and are strain-free. A slight pressure environment that is truly hydrostatic seems to improve the quality of the crystals. Thermal profile estimation results show that the values of temperature which decrease upto the neck region are same in magnitude as those measured during the experiments and that necking improves the thermal profile and, consequently, the crystal quality. No facet formation has been observed in these crystals.

    • Low energy scattering data and phase shifts

      M Z Rahman Khan M Shoeb

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      We point out that at any given low energyσtot and a ratio of integrated scattering data likeF/B can, in principle, be used unambiguously to finds-andp-wave phase shifts. Thus efforts to obtain other low energy data like elastic dσ/dΩ andP/E are unnecessary. It is also indicated that the mere knowledge whetherF/B is greater than or less than unity enables us to draw important conclusions about the nature of the interaction in thep-state without performing detailed calculations. Thus a strong case is made out for obtaining much more preciseF/B data than are presently available. The discussion refers mainly to low energy ∧p scattering data.

    • Effect of random density irregularities on nonlinear evolution of Langmuir waves in interplanetary medium

      B Buti M Mohan S K Alurkar

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      The evolution of nonlinear Langmuir waves in the interplanetary medium is investigated by appropriately accounting for the random density irregularities of the medium. A pair of modified Zakharov equations, which describe these waves, is solved numerically as an initial value problem for large scale (≫ 102 km) initial pertubations. For an ion acoustic-Langmuir solitary wave, the random irregularities damp the Langmuir wave by way of scattering and let the ion density perturbation radiate away in a few days. However an initial solitary or shock-like Langmuir wave excites the ion density perturbations within a fraction of a second, and then itself gets damped. These effects will strongly decelerate the collapse of large scale Langmuir waves. The possibility of detecting these processes, by means of interplanetary scintillation, is discussed.

    • Spherically symmetric free fall collapse

      J Krishna Rao M Annapurna

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      The general dynamical equations for spherical gravitational collapse are derived by introducing the eigenvalue of the conformal Weyl tensor in the 2-2 component of the Einstein tensor and assuming the material content of the models to be a perfect fluid. Since this eigenvalue is coupled always with the material energy density, it has been interpreted as theenergy density of the free gravitational field whose presence is related with anisotropy and inhomogeneity. As a particular case, the collapse of a spherically symmetric dust (zero pressure) with vanishing radial acceleration (free fall collapse) is discussed. It is shown that the model is inhomogeneous with non-vanishing shear of the congruence of world lines of the dust particles. The model contains gravitational radiation by Szekere’s criterion since both shear invariant and the spatial gradient of density are non-vanishing. This is in contrast to the Oppenheimer-Synder model for which both the above mentioned characteristics are absent. A particular solution which is anisotropic and inhomogeneous has been given to prove the emission of gravitational radiation by the freely falling dust and in this case the energy density of the free gravitational field contains a typeN term superposed on the coulombian field.

    • Elastic and inelastic scattering of 270 MeV3He particles from58Ni,90Zr,116Sn and208Pb

      P P Singh Q Li P Schwandt W W Jacobs M Saber E J Stephenson A Saxena S Kailas

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      Differential cross-section angular distributions for the elastic scattering of 270 MeV3He particles from58Ni,90Zr,116Sn and208Pb have been measured. Optical model analysis of the cross-sections has yielded the optical model parameters for3He particles at 270 MeV. Angular distributions have also been measured for the inelastic excitation of the low-lying levels in the above mentioned nuclei. A collective model analysis using the distorted wave Born approximation (DWBA) of these cross-sections with the distorted waves generated by the optical model parameters determined from the elastic scattering analysis, has yielded the reduced transition probability (B(EL)) values consistent with those reported in the literature.

    • Magnetic moments of octet baryons in a chiral potential model

      N Barik M Das

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      Incorporating the lowest-order pionic correction, the magnetic moments of the nucleon octet have been calculated in a chiral potential model. The potential, representing phenomenologically the nonperturbative gluon interactions including gluon self-couplings, is chosen with equally mixed scalar and vector parts in a power-law form. The results are in reasonable agreement with experiment.

    • Precession photography of fibres: Prediction of patterns

      M Sundaramoorthy

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      The Buerger precession method of recording x-ray diffraction patterns can also be used for fibres. This method has some advantages over the conventional flat plate method. Since the fibre has inherent cylindrical symmetry, the precession photograph of the fibre is equivalent to the ‘rotation-precession’ photograph of a single crystal. An analytical prediction of diffraction patterns of the rotation-precession photography is discussed. Also, experimental data are provided to confirm the validity of the equations derived.

    • Dielectric polarization of the solutions of nitrotoluene and cyclohexane

      M Śliwińska-Bartkowiak B Szurkowski T Hilczer

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      Dielectric properties of the solutions of nitrotoluene in cyclohexane showing a far pre-critical state are discussed. Dipolar polarization of the solutions was calculated on the lines of the Onsager model of local field, while the energy of interdipolar interactions was calculated with the help of the dipole-dipole coupling model given by Piekara. The character of interdipolar interactions in the solutions studied was found to be analogous to those in critical solutions at the temperatures from 10 to 20 K higher than the critical temperature.

    • Optical birefringence and order parameter of three nematogens

      M Mitra S Paul R Paul

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      Results of the measurement of refractive indices and densities of three nematic liquid crystals at different temperatures are reported. The molecular polarizabilities have been calculated from refractive indices using both the Vuks’ and the Neugebauer’s relations. The orientational order parameters are determined from the polarizability values. The variation of order parameter with temperature for these compounds shows a reasonably good agreement with Maier and Saupe theory except near the clearing points where the experimental values are less than those obtained from the theory. The possible reasons for this have been discussed.

    • X-ray and dielectric studies of Sm2(MoO4)3

      M Roy R N P Choudhary H N Acharya

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      The polycrystalline samples of Sm2(MoO4)3 have been prepared by heating appropriate quantities of oxides. The X-ray powder diffraction technique has been used to provide information about lattice parameter, space group and basic structure. The dielectric constant has been measured as a function of frequency (560 Hz-13 MHz) and temperature (30–220°C) to know the ferroelectric transition temperature.

    • Voltage current and power relation in an arc plasma in a variable axial magnetic field

      S N Sen M Gantait

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      The variation of voltage, current and output power in a mercury arc plasma has been investigated in an axial magnetic field (0–1350 G) for three values of discharge current namely 3, 4 and 5 A. The voltage increases and current decreases almost linearly and the output power also increases with increase of the magnetic field. The conductivity value in magnetic field has been calculated and an analytical expression presented to represent the variation of conductivity in the magnetic field. Utilizing this expression the variation of output power with magnetic field can be explained.

    • Measurement and analysis of alpha-induced reactions on Ta, Ag and Co

      M Ismail A S Divatia

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      Excitation functions for the reaction181Ta (α,xn)185−xRe,107,109Ag (α, ypxn) and59Co (α, ypxn) were obtained from measurements of residual activity of stacked foils from threshold to 60 MeV. The excitation functions for the production of181Re,182Re,183Re,184Re,105Ag,111In,54Mn,56Co,58Co, and60Co, are being presented. The experimental data are compared with calculations considering equilibrium as well as pre-equilibrium reactions according to the hybrid model of Blann. High energy part of the excitation functions is dominated by the pre-equilibrium reaction mechanism. Calculations were done using a priori calculational method of Overlaid Alice Code of Blann. Most of the excitation functions in the energy range mentioned above could be very well fitted with the hybrid model calculation for exciton numbern=4 withnp=2 andnn=2. The overall agreement with theory is good. Certain discrepancies, however, indicate the necessity to revise the hybrid model with respect to emission of complex particles.

    • Fine-hyperfine structures of$$c\bar c$$ and$$b\bar b$$ systems in a non-relativistic Hulthen plus linear potentialsystems in a non-relativistic Hulthen plus linear potential

      M Mishra S N Jena T N Tiwari

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      The heavy mesons of the charmonium and upsilon family are described in an alternative static potential model chosen in a combination of Hulthen and linear potential. We find that the quark-confining potential in the form of an equal admixture of vector and scalar parts successfully explains the fine-hyperfine structures of$$c\bar c$$ and$$b\bar b$$ systems in a flavour-independent manner. The leptonic decay widths of the vector mesons ofψ and γ families are calculated taking into account the Poggio-Schnitzer correction. We obtain some of the bound states of the yet-to-be observed$$t\bar t$$ system for thet-quark mass ranging from 50 to 200 GeV.

    • Determination of eigenvalues of real symmetric para-p diagonal matrices

      V T A Bhargava P M Mathews M Seetharaman

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      A method is presented for an accurate numerical determination of eigenvalues of real symmetric para-p diagonal matrices. The method takes advantage of the band structure to break up the matrix intop ×p blocks and performing algebraic operations including inversions on these blocks only, no matter what the size of the matrix is. The eigenvalues are determined independently one at a time. Thus any error in the determination of one eigenvalue does not affect the other eigenvalues. The method is ideally suited for the Schrödinger eigen alue problem of the anharmonic potentials, which is taken up in the following paper.

    • Anharmonic oscillators in higher dimension: Accurate energy eigenvalues and matrix elements

      V T A Bhargava P M Mathews M Seetharaman

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      Energy eigenvalues and matrix elements of various anharmonic oscillators are determined to a high accuracy by applying a method for determining the eigenvalues and eigenvectors of real symmetric para-p diagonal matrices (described in the preceding paper). Our results for the 2- and 3-dimensional oscillators are new and complement similar accurate results for the one dimensional oscillators available in the literature.

    • Statistical theory of hot nuclei and high spin states

      M Rajasekaran N Arunachalam T R Rajasekaran V Devanathan

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      The hot rotating compound systems formed in heavy ion collisions are studied using the statistical theory with a view to determine the spin and temperature dependence of nuclear shapes. Shape transitions are observed for these systems at particular spin values. The neutron and proton separation energies for heavier high spin systems have been evaluated. Results are presented for70170Yb and78194Pt.

    • Hybrid model analysis of the excitation function for alpha induced reaction on121Sb and123Sb

      M Ismail

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      Excitation functions for the reactions121Sb(α, xn)125−xI,123Sb(α, xn)127−xI and121Sb(α, p3n)121Te were obtained from the measurements of the residual activity of stacked foils of antimony trioxide evaporated on Al backings from threshold to 60 MeV. The excitation functions for the production of121I,123I,124I,126I and121Te are presented. The experimental data are compared with calculations considering equilibrium as well as pre-equilibrium reaction mechanism according to the hybrid model of Blann. The high energy part of the excitation functions are dominated by the pre-equilibrium reaction mechanism. Calculations were done using a priori calculational method of Overlaid Alice Code of Blann. Most of the excitation functions in the energy range mentioned above could very well be fitted with the hybrid model calculation for exciton numbern=4 withnn=2 andnp=2. The overall agreement with the theory is good. Certain discrepancies for example121Sb(α, p3n)121Te excitation function, indicate that the production mechanism is different from the one presumed for the calculation.

    • Anharmonic oscillators in higher dimension: Accurate energy eigenvalues and matrix elements

      V T A Bhargava P M Mathews M Seetharaman

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    • Analytic structure of dynamical systems

      M Tabor

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      The study of the analytic structure of nonlinear ordinary and partial differential equations is shown to provide a unified approach to determining their properties and finding their solutions.

    • Ignition and increase in Pease limit on current in an ohmically heated high densityZ-pinch

      A Shyam V Chitra M Srinivasan

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      Energetics of an ohmically heated deuterium-tritium high densityZ-pinch has been computed taking into account the energy deposited by the alpha particles produced by fusion. As a result, at higher plasma densities (>1027/m3) and temperatures (>4keV), the pinch current can cross Pease limit and the plasma can get ignited, yielding higher energy gain and neutron yield in a shorter confinement time.

    • A microprocessor based autoscanner for electromigration studies in thin films

      M Dhanabalan Y Syamasundara Rao K V Reddy

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      Mass transport due to electromigration can be estimated if the diffusion coefficientD and the electromigration effective charge numberZ* are known. Neutron activated tracer scanning method determine the radioactivity at different positions. An automatic scanning system for determining the radioactive concentration profiles developed using a microprocessor is described in this paper. Using the radioactive concentration profiles the electromigration shift is determined. From this shift the electromigration effective charge numberZ* is calculated. The system developed was tested for tin thin films.

    • Infrared and raman studies on neodymium pentaphosphate and metaphosphates

      V Ramakrishnan J Kumar M Thirumavalavan F D Gnanam P Ramasamy

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      The infrared and Raman spectra of crystalline samples of NdP5O14, NaNdP4O12 and KNdP4O12 are recorded. The spectra are analysed on the basis of vibrations of P=O, P-O, PO2 and P-O-P groups. The P4O124− ion has cyclic structures both in NaNdP4O12 and KNdP4O12 crystals. It has been inferred that the P-O-P bridges are stronger in metaphosphates.

    • Detection limits of high temperature superconducting materials on various substrates by energy dispersive X-ray fluorescence and proton induced X-ray emission methods

      M Lal H N Bajpai D Joseph R K Choudhury

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      Application of energy dispersive X-ray fluorescence (EDXRF) and proton induced X-ray emission (PIXE) methods has been demonstrated for determining the elemental composition of thin film superconducting materials. The results of analysis carried out by EDXRF method have been compared with those obtained by PIXE method. Thin films of YBa2Cu3O7 superconducting material were deposited on various substrates such as thin mylar sheet and thick substrates of SrTiO3, MgO and Al2O3. In thin backing the minimum detection limits obtained for Cu, Y, Ba by the PIXE method are 20 ng, 70 ng and 800 ng respectively and the corresponding values by the EDXRF method are 3000 ng, 600 ng and 1000 ng. Detection limits for samples on thick backings deteriorated to a large extent by both methods.

    • Spherically symmetric static inhomogeneous cosmological models

      J Krishna Rao M Annapurna

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      Spherically symmetric static cosmological models filled with black-body radiation are considered. The models are isotropic about a central observer but inhomogeneous. It is suggested that the energy density of the free gravitational field, which is coupled to the isotropic radiation energy density, might play an important role in generating sufficient field (vacuum) energy (when converted into thermal energy) and initiate processes like inflation. On the central world line the energy density of the free gravitational field vanishes whereas the proper pressure and density of the isotropic black-body radiation are constants. Further, it is shown that the cosmological constant is no more arbitrary but given in terms of the central pressure and density. Also, at its maximum value the energy density of the free gravitational field is proved to be equal to one third of the combined value of radiation pressure and density.

    • Point contact tunnelling studies on ceramic YBCO with scanning tunnelling microscope tips

      H Srikanth M Rajeswari A K Raychaudhuri

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      A detailed study of point contact tunnelling into ceramic YBCO with electrochemically etched tips of Pt, Nb and W is reported. The superconducting gap parameter (Δ) has been extracted fromIV and dI/dVV curves using various procedures. Our results indicate a gap value of about 20 meV. We observe that the zero bias conductance is strongly dependent on the junction resistance. The normal state conductance varies linearly with bias voltage and the conductance curves are asymmetric with respect to polarity of the bias voltage. With contacts of very high junction resistance, we observe G(0)/G(100 mV) has a value as low as 1/6. This may be the lowest value reported so far.

    • Vibrational spectra of (NH4)3ZnCl5

      M Balasubramanian V Ramakrishnan S Rajendran

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      IR and Raman spectra of (NH4)3ZnCl5 have been recorded. The observed spectra have been analysed on the basis of the vibrations of ZnCl42− and NH4+ ions. The appearance of multiple Raman bands indicates the presence of two different types of ammonium ions. The effect of anisotropic crystalline field over the ZnCl4 and NH4 tetrahedra is also discussed. The assignment of internal modes has been verified by the potential energy distribution calculations.

    • Modified Hill determinant approach to the eigenvalues of the anharmonic oscillator

      R N Chaudhuri M Mondal

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      The unperturbed Hamiltonian of quantum anharmonic oscillator is modified by introducing a simple variational scale parameter. A suitable choice of this parameter makes the eigenvalues rapidly convergent for small size of the determinant in the method of infinite Hill determinant. Simple analytic expressions for the eigenvalues are obtained by matrix diagonalization method.

    • Path integral analysis of harmonic oscillators with time-dependent mass

      M Sabir S Rajagopalan

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      Two cases of forced harmonic oscillators with time dependent mass for which exact propagators can be evaluated are presented. From the exact propagators, normalized solutions of the corresponding Schrödinger equations are arrived at. Time-dependent invariants are also found.

    • Electron microscopy study of aggregation of microclusters of sulphur

      M Abdulkhadar K C George

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      A study of aggregation of sulphur particles in colloidal suspension of sulphur in water-methanol mixture using TEM and electron diffraction is reported. From the micrographs the aggregates formed have been found to be random and tenuous indicating a fractal structure. The electron diffraction patterns of the aggregates are used to study the mechanism of diffusion and reaction limited aggregation.

    • Transition from order to chaos in SU(2) Yang-Mills-Higgs system

      M P Joy M Sabir

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      Time-dependent spherically symmetricSU(2) Yang-Mills-Higgs system is shown to be chaotic near the ’t Hooft-Polyakov monopole solution by calculating the maximal Lyapunov exponents. A phase transition like behaviour from order to chaos is observed as a parameter depending on the self interaction constant of scalar fields increases.

    • Relation between Green’s functions for different potentials

      S S Vasan M Seetharaman K Raghunathan

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      A general relation between the energy-dependent Green’s functions for different potentials is derived in a simple and direct manner. This interesting connection enables the eigenstates of one physical system to be deduced from those of a related system. The derivation is based on the Schrödinger equation and provides an independent justification for the technique of path-dependent time transformation used in path integration.

    • Spherical gravitational collapse with photon emission and a generalized Schwarzchild interior solution

      J Krishna Rao M Annapurna

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      The general dynamical equations for perfect fluid filled spheres with an outward flux of photons are derived. The vital role played by the energy density of the free gravitational field in accelerating photon production has been emphasized. It is pointed out that even when the material energy density is finite, the energy density of the free gravitational field can take infinitely large values resulting in vanishing surface area of the star. A generalized Schwarzschild interior solution with conformally flat geometry but with photon emission has been obtained. It is pointed out that the interior conformal coordinate system bears a strong resemblance to the exterior Krushkal coordinates. It is shown that for spherical star the invariant velocity of the fluid particles, falling towards the centre, is proportional to its radius suggesting that the outer envelopes collapse at a faster rate than the core part. It is shown that the interior radiating solution can be matched with generalized Schwarzchild exterior solution.

    • Yields of evaporation residues and average angular momentum in heavy ion induced fusion reactions leading to compound nucleus96Ru

      M Dasgupta A Navin Y K Agarwal C V K Baba H C Jain M L Jhingan A Roy

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      Cross-sections for production of evaporation residues from the compound nucleus96Ru* formed by fusion reactions28Si+68Zn,32S+64Ni,37Cl+59Co and45Sc+51V have been obtained from the yields of their characteristicγ-rays. The measurements span an excitation energy range of 55 MeV to 70 MeV of the compound nucleus. The evaporation residue (ER) cross-sections have been analysed in terms of statistical model for the decay of the compound nucleus. A good agreement is found between statistical model calculation and the experimental evaporation residue cross-sections in all the four cases. It is shown that the average angular momentum$$\bar \ell $$ of the compound nucleus can be deduced from a comparison of the experimentally measured and the statistical model predictions for the ER cross-sections. The validity of this method of deriving$$\bar \ell $$ has been discussed for the case of16O+154Sm system.

    • Beam couplings and phase conjugate effects in reflection and transmission in BaTiO3

      Putcha Venkateswarlu M Moghbel P Chandra Sekhar M C George

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      The details of experiments showing the effects of self-pumped phase conjugation on reflection and on transmission in barium titanate crystal are given. The specular reflection and the second-surface reflection of an extraordinary polarized beam, incident on the face of the crystal parallel to itsc-axis, get reduced in intensity as the phase conjugation develops. It has been found that parts of the self-pumped phase conjugate beam emerge out of the crystal as additional transmission beams. They grow in intensity as the phase conjugation develops. Other measurements which combine coherent or incoherent coupling beams are presented and used to explain the observations.

    • Photoionization of the ground1Se and twenty lowest excited states of the Ne-like Fe16+

      M Mohan M Le Dourneuf Vinod Prasad A Kumar

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      TheR-matrix method is used to calculate cross-sections for the photoionization of Ne-like Fe16+ from ground 2s22p61Se and excited states belonging to 2s2p6 3l and 2s22p5 3l configurations. Configuration interaction wavefunctions are used to represent two target states of Fe17+ ion retained in theR-matrix expansion. The cross-sections are obtained as a function of kinetic energy (εk) of the ejected electron from 10 to 24 Ry. For low kinetic energy the cross-sections show series of Rydberg states which converge onto2Se threshold Fe17+. The calculations are carried out in the LS coupling.

    • Exact bound-state solutions of the cut-off Coulomb potential inN-dimensional space

      R N Chaudhuri M Mondal

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      Exact solutions of the potentialV(r)=−Ze2/(r+β),β>0 are obtained in theN-dimensional space for certain values ofβ by means of factorization of infinite Hill determinant. We discuss some features of the radial wave Schrödinger equation in theN-dimensional space.

    • Finite size nucleonic effects in the nuclear medium

      M Rajasekaran N Meenakumari

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      The finite size effects of nucleons inside a nucleus is investigated. This new approach is entirely different from Hagedorn’s volume correction method and is more rigorous. The size of the nucleon is varied and the magnitude of the hard-core potential is extracted by minimising the energy with respect to the nuclear radius.

    • On the solution of an anisotropic nonquadratic potential

      S S Vasan M Seetharaman K Raghunathan

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      The Schrodinger-Green function is constructed for an anisotropic non-quadratic potential which has been studied in recent literature. The eigen energies and wavefunctions are readily obtained. Our analysis shows that the wavefunctions given in earlier literature are incorrect and the source of the error is pointed out. A semiclassical treatment of the problem is also presented in support of some of our observations.

    • Chaos and curvature in a quartic Hamiltonian system

      M P Joy M Sabir

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      Chaotic behaviour of a quartic oscillator system given byH l/2(p12+p22)+ (1/12)(1 -α) (q14+q24)+1/2q12q22 is studied. Though the Riemannian curvature is positive the system is nonintegrable except when S/B α = 0. Calculation of maximal Lyapunov exponents indicates a direct correlation between chaos and negative curvature of the potential boundary.

    • A JWKB analysis of the sextic anharmonic oscillator in d dimensions

      S S Vasan M Seetharaman L Sushama

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      On the basis of a radial generalization of the JWKB quantization rule, which incorporates higher orders of the approximation, an explicit analytical formula is derived for the energy levels of the three-dimensional sextic anharmonic oscillator. The formula exhibits the scaling property of the exact eigenvalues, and is readily generalized to any dimension. The predicted results are in good agreement with known numerical values.

    • Measurement of excitation functions and mean projected recoil ranges of nuclei in α-induced reactions on F, Al, V, Co and Re nuclei

      M Ismail

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      Excitation function and mean projected recoil ranges of nuclei produced in theα-particle induced reactions on F, Al, V, Co and Re targets were measured by conventional thick target thick recoil catcher technique for bombarding energiesEα≤65 MeV. The measured cross-sections are compared with calculations considering equilibrium as well as pre-equilibrium reaction mechanism according to the hybrid and geometry dependent hybrid (GDH) model of Blann using the code Alice/85/300. High energy part of the excitation functions are dominated by pre-equilibrium reaction mechanism whereas the low energy parts are dominated by evaporation with its characteristic peak. In this paper emphasis will be placed on the GDH model, for it provides a potentially better description of the physical process i.e., a higher probability of peripheral collisions to undergo precompound decay than for central collisions. Geometry dependent model with initial exciton numbern0=4 (nn=2,np=2,nk=0) gives better fits compared to hybrid model with same initial exciton configuration andmfp parameterk=1.0 forα-induced reactions on F, V, Co and Re. Whereas forα-induced reaction on Al comparatively large initial exciton configurations (8/4/4/0) or (10/5/5/0) were required to fit the excitation functions reasonably well. Recoil ranges were converted into recoil momentum and vice versa using Lindhard, Scharff and Schiott (LSS) and Blaugrund theories. These theories were also used to calculate projected recoil ranges for full momentum transfer pertaining to fusion reactions. The momentum transfer information was used to get clues about some aspect of the interaction from the trends and magnitudes of the observed ranges.

    • High pressure investigations on amorphous selenium

      N V Chandra Shekar M Yousuf P Ch Sahu M Mahendran K Govinda Rajan

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      We report the diamond anvil cell (DAC) high pressure powder X-ray diffraction studies on amorphous selenium (a-Se) under truly hydrostatic pressure condition up to 20 GPa. Amorphous selenium exhibits a sharp and irreversible transition to a hexagonal structure at 10.6 ± 0.1 GPa. It is also known that metallization occurs in a-Se around this pressure. Some plausible arguments are provided to suggest that the amorphous to crystalline transition may be driven by metallization.

    • TDPAC studies of Hf doped YBCO

      R Govindaraj M Premila Padma Gopalan K P Gopinathan

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      Time differential perturbed angular correlation measurements of the 133–482 keVγ-γ cascade of181Ta in Hf-doped YBa2Cu3O7−x are presented. The181Hf precurser nuclei are incorporated into the sample by thermal neutron irradiation. Two quadrupole interaction frequencies are observed in the as-irradiated sample:vQ1=161±10 MHz with intensityf1=75%, asymmetry parameterη1=0.32 and damping parameter Λ1=0.42, andvQ2=1108±40 MHz withf2=25%,η2=0.62, and Λ2=0.60. On annealing the sample in air at various temperaturesTa and quenching to room temperature,f1 remained nearly constant forTa<600°C andvQ1 for all annealing temperatures indicating that these are insensitive to oxygen stoichiometry. This frequency is interpreted to be due to181Hf substitutingY sites. BeyondTa=600°C,f1 increased and reached a constant value of 90% forTa=800°C. The value ofvQ2 showed a slight variation between 1086 and 1160 MHz, whilef2 remained nearly constant at 25% forTa<600°C. This component is identified to be due to181Hf substituting Cu 1 sites in the Cu-O chains of YBCO. Above 600°CvQ2 decreased and reached a value of 808 MHz beyond 750°C.

    • A translational energy spectrometer to probe interatomic potentials: Dissociation dynamics of CO2+ ions

      M Krishnamurthy U T Raheja D Mathur

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      A new ion translational energy spectrometer has been developed to carry out low-energy, gas-phase ion-molecule collision experiments which aim to probe molecular potential energy surfaces. The collisional technique employed relates small changes in the kinetic energy of a projectile ion after it has undergone collision with a static neutral atom/molecule to changes in the overall potential energy of the collision system; information can be furnished about the interaction potential between the projectile and the target. First measurements are reported of a high resolution target excitation spectrum obtained in 1.8 keV collisions of H2+ ions with N2. New results pertaining to collision-induced dissociation of CO2+ ions are presented and discussed in terms of potential functions of low-lying electronic states of the molecular ion.

    • Electron impact excitation of Ni XIX using theR-matrix method

      Man Mohan M Le Dourneuf A Hibbert V M Burke

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      Collision strengths for all the transitions between the 15 lowest states of neon-like Ni XIX have been calculated for electron impact in the 80–140 Ry energy range. Configuration-interaction wavefunctions have been used to represent the target states. The standardR-matrix code has been used to calculate the lower scattering partial waves (L≤9), while a no-exchange version of the same code has been used to compute efficiently the higher partial waves (L≥10). Effective collision strengths for 105 excitation transitions between the ground state 2s22p61Se and the 142s22p53l Rydberg states are tabulated for electron temperatures in the range logT=5.40 to logT=7.00, withT expressed in °K.

    • A model for the analysis of the heat release from a supercooled liquid at the glass transition

      M Rajeswari A K Raychaudhuri

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      In this paper we present a phenomenological model to analyze the heat release at the glass transition as observed in the continuous cooling calorimetry when a supercooled liquid freezes into the glassy state. We developed this model for the quantitative analysis of the experimental data to obtain the specific heat and the parameters which govern the structural relaxation. A description of the model and the detailed analysis are presented and the relaxation parameters are compared with the corresponding values obtained from the specific heat spectroscopy. Our analysis reveals several interesting aspects which include the effects of delayed enthalpy relaxation and the nonequilibrium structural relaxation time on the observed specific heat, the temperature dependence of the equilibrium configurational specific heat and the validity of the Vogel-Fulcher equation for the relaxation time.

    • Plasma-maser interaction of langmuir wave with kinetic Alfvén wave turbulence

      Bipuljyoti Saikia B K Saikia S Bujarbarua M Nambu

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      A theoretical study is made on the generation mechanism of Langmuir mode wave in the presence of kinetic Alfvén wave turbulence in a magnetized plasma on the basis of plasma-maser interaction. It is shown that a test high frequency Langmuir mode wave is unstable in the presence of low frequency kinetic Alfvén wave turbulence. The growth of the Langmuir wave occurs due to direct and polarization coupling terms. Because of the universal existence of the kinetic Alfvén waves in large scale plasmas, the results have potential importance in space and astrophysical radiation processes.

    • A new perturbative approach to the classical anharmonic oscillator

      S S Vasan M Seetharaman

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      The periodic motion of the classical anharmonic oscillator characterized by the potentialV(x)=1/2x2+λ/2k x2k is considered. The period is first determined to all orders inλ in a perturbative series. Making use of this, the solution of the nonlinear equation of motion is then expressed in the form of a Fourier series. The Fourier coefficients are obtained by solving simple algebraic relations. Secular terms are inherently absent in this perturbative scheme. Explicit solution is presented for generalk up to the second order, from which the Duffing and the sextic oscillator results follow as special cases.

    • The Coulomb Green’s function revisited

      S S Vasan M Seetharaman

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      It is demonstrated how the energy-dependent Green’s function for the Schrödinger-Coulomb problem can be deduced from a knowledge of the harmonic oscillator time-propagator. All the known results of the Coulomb system are shown to be elegantly derivable from such a connection.

    • Theoretical calculation of acoustic non-linearity parameter B/A of binary mixtures

      J Jugan Roshan Abraham M Abdulkhadar

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      Acoustic non-linearity parameter B/A is calculated for five binary liquid mixtures using Tong and Dong equation along with the Flory’s statistical theory. Similar to other excess thermodynamical quantities an excess non-linearity parameter (B/A)E is defined for binary liquid mixtures. The interactions in the liquid mixtures are explained on the basis of the excess non-linearity parameter.

    • Dielectric properties of nano-particles of zinc sulphide

      Binny Thomas M Abdulkhadar

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      The dielectric properties of nano-particles of ZnS have been studied over a temperature range from 300 to 525 K. The dielectric constant, dielectric loss and ac conductivity of the samples are larger than those of bulk ZnS crystals. Dielectric properties of composites consisting of nano-particles of Ag of different concentrations dispersed in nano-particles of ZnS have also been studied.

    • Generation of picosecond optical pulses from single heterostructure GaAs diode laser and their emission characteristics

      V N Rai M Shukla H C Pant

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      Emission characteristics of a single heterostructure GaAs diode laser are reported using a simple driver circuit. It provides a single picosecond time duration optical pulse, a pulse train or a broad optical pulse depending on the amplitude and time duration of the electrical pump pulse. Results show that relaxation oscillation frequency depends on the amplitude of pumping current pulse as well as on some inherent property of diode laser, which seems to be the level of impurity in lasing medium. Variation of relaxation oscillation frequency with amplitude of current pulse shows only the qualitative agreement with the reported theoretical predictions.

    • Scaling laws for plasma transport due toηi-driven turbulence

      C B Dwivedi M Bhattacharjee

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      The scale invariance technique has been employed to discuss theηi-driven turbulent transport under a new fluid model developed by Kimet al [1]. Our analysis reveals that the finite Larmour radius effect plays a decisive role to determine the scaling behaviour of the energy transport under the new fluid model. However, the overall scaling of the transport coefficient remains unchanged as compared to that derived by Connor [2] under the traditional fluid model. The approximations considered by Connor [2] are qualified with additional requirements within the new fluid approach. In the dissipative case, which has not been discussed earlier, additional constraints on the power scaling laws of the transport properties are imposed due to the dissipative mechanisms in the basic governing equations.

    • Surface enhanced Raman scattering studies of acetophenone on colloidal silver particles

      S Edwin Jayaraj V Ramakrishnan S Perumal M Gurunathan

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      Intense Raman scattering by acetophenone molecules adsorbed on colloidal silver particles is reported. Greater enhancement is observed for the ring breathing and ring stretching vibrations. The orientation determination analysis shows that the adsorption of acetophenone molecule is neither through its co-ordinating site nor through itsπ-orbital system and there is no strong chemical interaction. However significant intensity enhancement for several vibrations suggests that the contribution is from classical electromagnetic field on the rough surface.

    • Impurity mediated mechanism of photorefractive effect in BaTiO3: A combination of sangster and piezoelectric effects

      M D Sastry M Moghbel Putcha Venkateswarlu

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      An impurity mediated mechanism of photorefractive effect in BaTiO3 is proposed. The photoinduced changes in the relative concentration of Fe3+ in BaTiO3 results in an electro-optic coupling through a combination of the Sangster and piezoelectric effects. This is based on the examination of the extensive results on the EPR of Fe3+ in the BaTiO3 lattice. This model explains the improved photorefractive behavior of BaTiO3 on doping with Co2+.

    • Localized coherent structures of (2+1) dimensional generalizations of soliton systems

      M Lakshmanan R Radha

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      We briefly review the recent progress in obtaining (2+1) dimensional integrable generalizations of soliton equations in (1+1) dimensions. Then, we develop an algorithmic procedure to obtain interesting classes of solutions to these systems. In particular using a Painlevé singularity structure analysis approach, we investigate their integrability properties and obtain their appropriate Hirota bilinearized forms. We identify line solitons and from which we introduce the concept of ghost solitons, which are patently boundary effects characteristic of these (2+1) dimensional integrable systems. Generalizing these solutions, we obtain exponentially localized solutions, namely the dromions which are driven by the boundaries. We also point out the interesting possibility that while the physical field itself may not be localized, either the potential or composite fields may get localized. Finally, the possibility of generating an even wider class of localized solutions is hinted by using curved solitons.

    • Collisional excitation among the seven lowest states of TiXII

      M Mohan A Hibbert

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      Collision strengths have been calculated for electron impact excitation of sodium-like TiXII for all 21 transitions amongst its lowest seven states. Configuration interaction wave functions have been used to represent the target states. The standard and no-exchangeR-matrix codes have been used to calculate the contribution of partial waves withL⩽8 andL>8 respectively. Collision strengths are tabulated at selected energies in the range 26 to 50 Ryd. Effective collision strengths are tabulated for electron temperatures in the range logTe=4.0 to logTe=6.0, withTe in K. This is the first detailed calculation on this ion in which the effects of exchange, channel couplings and short-range correlation are taken into account.

    • Measurement of excitation functions and mean projected recoil ranges of nuclei in12C-induced reactions on vanadium

      M Ismail R P Sharma M H Rashid

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      Excitation function and mean projected recoil ranges of nuclei produced in the12C-induced reactions on51V target were measured by conventional stacked foil and thick-target thick-recoil-catcher technique for bombarding energiesE ≤ 84 MeV for12C ion beam. The measured recoil ranges are converted to momentum transfer. Information on momentum transfer was used to get clues about some aspects of the interaction such as complete fusion which corresponds to full momentum transfer and incomplete fusion reaction mechanism. The measured excitation functions are compared with the calculation based on the statistical model which describes only equilibrium decay of the compound nucleus using the Cascade code and the geometry dependent hybrid model which describes equilibrium as well as pre-equilibrium decay of the compound nucleus using the Alice/91 code. The measured excitation functions and average ranges of the radioisotope products of the reactions12C on51V indicate that the three separate reaction mechanisms could be attributable to complete fusion of12C, incomplete fusion of8Be and incomplete fusion of4He respectively with the target. The8Be and4He are the break-up component of12C into8Be +4He. The predictions of the codes, especially the Cascade, generally agree with the measured cross-sections which could be attributed to complete fusion of12C with the target51V.

    • Measurement and analysis of the excitation function and isomeric cross section ratios forα-induced reaction on Ir, Au, Re and Ta nuclei

      M Ismail

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      Excitation functions and a few isomeric cross-section ratios for production of (1)192Au,193Au,194Au,195Au and192Ir nuclides inα-induced reactions on191,193Ir, (2)197Tl,197mHg,198m,gTl,199Tl and200Tl nuclides inα-induced reaction in197Au and (3)183Re and184m,gRe nuclides inα-induced reaction in181Ta and185Re are obtained from the measurements of the residual activities by the conventional stacked-foils technique from threshold to 50MeV. The excitation function and isomeric cross-section ratios for nuclear reaction181Ta(α,n)184m,gRe are compared with the theoretical calculation using the code Stapre which is based on exciton model for pre-equilibrium phase and Hauser-Feshbach formalism taking angular momentum and parity into account for the equilibrium phase of the nuclear reaction. All other experimental excitation functions are compared with the calculations considering equilibrium as well as pre-equilibrium reaction mechanism according to the geometry dependent hybrid (GDH) model and hybrid model of Blann using the code Alice/91. The high energy part of the excitation functions are dominated by pre-equilibrium reaction mechanism whereas the low energy parts are dominated by equilibrium evaporation with its characteristic peak. The GDH model provides a potentially better description of the physical process (i.e., a higher probability for peripheral collisions to undergo precompound decay than for central collisions) compared to hybrid model. However in the energy range of present measurement most of the excitation functions are fitted reasonably well by both GDH model and hybrid model with initial exciton numberN0=4(Nn=2,Np=2,Nh=0). Barring a few reactions we have found the overall agreement between theory and experiment is reasonably good taking the limitations of the theory into account.

    • Quasi-one dimensional electrical conductivity and thermoelectric power studies on a discotic liquid crystal

      V S K Balagurusamy S Krishna Prasad S Chandrasekhar Sandeep Kumar M Manickam C V Yelamaggad

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      We have studied the electrical conductivity of well aligned samples of hexahexylthiotriphenylene (HHTT) in the pure as well as doped states. The dopant used was a small concentration (0.62 mole %) of the electron acceptor trinitrofluorenone (TNF). In the columnar phases, doping causes the AC(1 kHz) conductivity along the columnar axis (σ) to increase by a factor of 107 or more relative to that in undoped samples; σ attains a value of 10−2S/m, which was the maximum measurable limit of our experimental set up. On the other hand, in the isotropic phase doping makes hardly any difference to the conductivity. The frequency dependence of the conductivity has been investigated. The DC conductivity of doped samples exhibits an enormous anisotropy, σ/σ ≥ 1010, which is 7 orders higher than that reported for any liquid crystalline system, and, to our knowledge, the largest observed in an organic conductor.

      We also report the first thermoelectric power studies on these ‘molecular wires’. The sign of the thermoelectric power is in conformity with the expected nature of the charge carriers, namely, holes.

    • Natural optical activity and liquid crystals

      C Oldano M Becchi

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      Optical activity of matter is related to the chirality of its constitutive molecules. In liquid crystals, chiral molecules can give rise to superstructures in which the local dielectric tensor rotates in space describing a helix, a fact which greatly enhances the optical activity of the medium. The structures and the optical properties of some helical phases are well-known, as for instance the cholesteric and some chiral smectic phases. For short enough helix pitches, the periodic medium can be considered optically as homogeneous and described by the same constitutive equations used to define the optical properties of solid crystals. Such liquid crystal phases represent an ideal tool to apply the methods, used since a long time in optics, to define homogeneous models for non homogeneous media and to discuss their limits of validity. A brief account is given of the main results recently found in this research area.

    • Structure and dynamics of charged macromolecules: Minimal representation of biological systems

      M Muthukumar

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      Structures and functions of various biological macromolecules at cellular levels are controlled by electrostatic, excluded-volume, macromolecular topological connectivity, and hydrodynamic forces. Some aspects of these challenging issues will be addressed. Specifically we will focus our discussions on (a) pattern recognition by macromolecules and complexation, (b) coupling between conformational transitions and phase transitions, (c) chromosomal condensation, (d) collective behavior of charged macromolecules in crowded environments, (e) coupled dynamics of macromolecular assemblies in charged solutions, and (f) polymer transport through pores. Even the simpler synthetic systems exhibit many puzzles which will be resolved using our theoretical formulation. In addition to exploring an understanding of biological processes, the context of fabrication of new synthetic materials will be remarked.

    • Beta decay of 125Sb and level structures in 125Te

      M Sainath K Venkataramaniah P C Sood

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      The decay of 2.76y 125Sb to levels of 125Te has been studied using an HPGe detector for gamma-ray and a mini orange electron spectrometer for conversion electron measurements. We identify 38 transitions in this decay, including 13 gamma rays and 4 conversion electron lines being reported for the first time. New results also include E1 multipolarity assignments to 3 newly observed transitions and M-shell conversion coefficient for the 109 keV M4 transition. A revised 125Te level scheme is constructed using Ritz combination principle. While confirming the existence of 10 well established levels below 700 keV excitation, we introduce 3 other levels at 402.0, 538.6 and 652.9 keV. Interpretation of the observed levels in terms of various theoretical approaches is briefly discussed. The newly introduced 538.6 keV (1/2+) and 652.9 keV (3/2+) levels are seen as the two missing members of the (s1/2 ⊗ 2+) and (d3/2 ⊗ 2+) sextuplet in the quasiparticle-phonon coupling scheme.

    • Experimental investigations of the nuclear level density by using heavy ion reactions

      G Viesti M Lunardon D Fabris G Nebbia M Cinausero E Fioretto G Prete JB Natowitz K Hagel R Wada

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      The transition of the level density parameter aoff from the low excitation energy value aoff=A/8 MeV−1 to the Fermi gas value aFGA/15 MeV−1 was discovered a few years ago studying particle spectra evaporated from hot compound systems of A∼ 160. A number of experiments have been recently performed to confirm the earlier findings and extend the investigation to other mass regions and to higher excitation energies. Furthermore, precision coincidence experiments have been done in the lead region in which evaporation residues are tagged by low energy gammarays. Those experiments open the possibility of a detailed study of the level densities in nuclei where the shell effects are important.

    • Fusion-fission dynamics in the superheavy nucleus production

      G Giardina P D’Agostino G Fazio M Herman AI Muninov A Nasirov G Oliva R Palamara R Ruggeri

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      The fusion-fission reaction mechanism leading to the massive nucleus formation is studied. We investigate the superheavy nucleus formation in heavy-ion induced reactions by analysing the evaporation residue (ER) production in order to study the fusion dynamics and the decay properties of nuclei close to the stability island at Z=114. We consider the 61Ni+208Pb, 48Ca+238U and 48Ca+244Pu reactions that lead to the Z=110, 112 and 114 superheavy elements respectively.

      By using the dinuclear system (DNS) concept of the two interacting nuclei we calculate the quasifission-fusion competition in the entrance channel and the fission-evaporation competition along the de-excitation cascade of the compound nucleus. The dynamics of the entrance channel allows us to determine the beam energy window which is favorable to the fusion, while the dynamic evolution of the compound nucleus on the shell correction to the fission barrier and the dissipative effects influence the fission-evaporation competition in order to obtain the residue nuclei from the superheavy nucleus formation. We also calculate the τntot ratio at each step of the de-excitation cascade of the compound nucleus and we present a systematics of τntot (at first step of the cascade) for many reactions that lead to nuclei with Z=102–114.

    • Fluctuations of the second order observables for dissipative processes in 19F+27Al system

      I Berceanu A Andronic M Duma D MoisĂ M Petrovici A Pop V Simion A del Zoppo G D’Erasmo G Imme G Lanzano A Pagano A Pantaleo G Raciti

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      The excitation function (EF) data for dissipative processes in 19F + 27Al system in the incident energy interval from 113.5 to 130 MeV are used to obtain the dependence of the charge variance and of the interaction time as a function of the incident energy. Fluctuations are observed in the EFs of both these secondary observables. Their correlation is supported by a mechanism based on stochastic exchange of nucleons.

    • Dissipative processes in light heavy ion collisions

      A Pop A Andronic I Berceanu M Duma D MoisĂ M Petrovici V Simion G Immé G Lanzanò A Pagano G Raciti R Coniglione A Del Zoppo P Piatelli P Sapienza N Colonna G d’Erasmo A Pantaleo

      More Details Abstract Fulltext PDF

      The characteristics of the dissipative processes in the collisions of light heavy ion systems at incident energies below 10 MeV/nucleon have been studied. The correlations between different experimental observables show similar trends as those known at much heavier systems and semiempirical relationships are established starting from assumptions on the nature of the microscopic mechanisms. The charge equilibration process in light systems is also studied.

    • Exploiting barrier distributions to investigate breakup effects in the fusion of 9Be+208Pb

      M Dasgupta D J Hinde R D Butt A C Berriman C R Morton J O Newton K Hagino

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      The availability of precisely measured fusion excitation functions have allowed the determination of experimental fusion barrier distributions. This concept is utilised in 9Be+208Pb reaction, to reliably predict the expected complete fusion cross-sections. However, the measured cross-sections are found to be only 68% of those predicted. The large cross-sections observed for incomplete fusion products support the interpretation that this suppression of fusion is caused by 9Be breaking up into charged fragments before reaching the fusion barrier.

    • Nuclear orbiting and anomalies in nuclear reactions

      A De A Mitra A Ray SR Banerjee M Sengupta A Chatterjee S Kailas HS Patel MG Betigiri SK Dutta

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      In this paper, we report our measurements of back-angle oxygen and carbon particle yields from 16O+89Y, 12C+93Nb reactions forming the same compound nucleus 105Ag at the same excitation energy and spin distribution. We find anomalously large oxygen yield and entrance channel dependence at high excitation energies from 16O+89Y reaction implying formation of a dinuclear orbiting complex. Possible connection between nuclear orbiting and fast fission is also discussed.

    • Fission fragment angular distributions in 16O+181Ta

      Bivash R Behera Subinit Roy P Basu M K Sharan S Jena M Satpathy SK Datta L Satpathy ML Chatterjee

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      Time of flight and energy of fission fragments were measured using pulsed beam. Fission fragment mass and energy integrated angular distributions were extracted. Fission fragment anisotropy was explained in the framework of saddle point model.

    • Mass measurements of relativistic projectile fragments in the storage ring ESR

      T Radon H Geissel F Attallah K Beckert F Bosch A Dolinskiy H Eickhoff M Falch B Franczak B Franzke Y Fujita M Hausmann M Hellström F Herfurth Th Kerscher O Klepper H-J Kluge C Kozhuharov Yu Litvinov KEG Löbner G Münzenberg F Nolden Yu Novikov Z Patyk W Quint H Reich C Scheidenberger B Schlitt J Stadlmann M Steck K Sümmerer L Vermeeren M Winkler Th Winkler H Wollnik

      More Details Abstract Fulltext PDF

      Two experimental methods of measuring masses of exotic nuclei in the storage ring ESR are presented. Bismuth and nickel fragments were produced via projectile fragmentation, separated and investigated with the combination of the fragment separator FRS and the ESR: (i) Direct mass measurements of relativistic projectile fragments were performed using Schottky mass spectrometry (SMS), i.e., exotic nuclei were stored and cooled in the ESR. Applying electron cooling, the relative velocity spread of circulating low intensity beams can be reduced below 10−6. Under this condition a mass resolving power of up to m/Δm=6.5·105 (FWHM) was achieved in a recent measurement. Previously unknown masses of more than 100 neutron-deficient isotopes have been measured in the range of 60≤Z≤84. Using known Qα values the area of known masses could be extended to more exotic nuclei and to higher proton numbers. The results are compared with mass models and extrapolations of experimental values. In a second experiment with 209Bi projectiles the area of the measured masses was extended to lower proton numbers. Due to various improvements at the ESR the precision of the measurements could be raised. (ii) Exotic nuclei with half-lives shorter than the time needed for SMS (present limit: T1/2 ≈ 5 sec) can be investigated by time-of-flight measurements whereby the ESR is operated in the isochronous mode. This novel experimental technique has been successfully applied in first measurements with nickel and neon fragments where a mass resolving power of m/Δm=1.5·105 (FWHM) was achieved.

    • A rare nuclear decay process: The internal conversion between bound atomic states

      J F Chemin T Carreyre M Aiche F Attallah G Bogaert J P Grandin M Harston W E Meyerhof J N Scheurer

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      We shall report on the recently observed dependence of the lifetime of the first excited state in 125Te on the ionic charge state. Then we shall give an interpretation of the dependence of the half-life in terms of a new type of nuclear internal conversion without emission of the electron into the continuum of electron energies. We have named this process internal conversion between bound atomic states or BIC. The resonant character of the BIC will be established and the main parameters governing the decay process will be discussed [1–3].

      Finally the results of a recent experiment performed at the GANIL accelerator attempting to measure directly the value of the internal conversion coefficient associated with BIC in 125Te ions with charge states ranging between 44+ and 48+ will be given.

      In conclusion we shall discuss the relation between the BIC and nuclear excitation by electron transition, NEET, in the excitation of some nuclear isomeric states.

    • Fission experiments with secondary beams

      J Benlliure S Steinhäuser C Böckstiegel A Grewe H-G Clerc A heinz M de Jong A R Junghans J Müller K-H Schmidt M Pfützner

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      Nuclear fission from excitation energies around 11 MeV was studied at GSI, Darmstadt for 76 neutron-deficient actinides and pre-actinides by use of relativistic secondary beams. The characteristics of multimodal fission of nuclei around 226Th are systematically investigated and related to the influence of shell effects on the potential-energy and on the level density between saddle point and scission. A systematic view on the large number of elemental yields measured gave rise to a new interpretation of the enhanced production of even elements in nuclear fission and allowed for a new understanding of pair breaking in fission.

    • Statistical fluctuations in hot rotating nuclei

      M Rajasekaran D Caleb Chanthi Raj

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      Thermal fluctuations in angular momentum due to excitation is investigated. Shape changes or structural rearrangement are observed as a consequence of fluctuation in second moment of spin. The uncertainty in angular momentum is considerably enhanced due to thermal fluctuation and is strongly dependent on spin and structural changes.

    • Calculation of magnetic multipole moment integrals using translation formulas for Slater-type orbitals

      I I Guseinov BA Mamedov T Özdoğan M Orbay

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      Using translation formulas for Slater type orbitals (STO’s) the infinite series through the overlap integrals are derived for the magnetic multipole moment integrals. By the use of the derived expressions the magnetic multipole moment integrals, therefore, the magnetic properties of molecules can be evaluated most efficiently and accurately. The convergence of the series is tested by calculating concrete cases. An accuracy of 10−5 for the computer results is obtained in the case 2p-pole magnetic moment integrals for 1 ≤ v ≤ 5, and for the arbitrary values of internuclear distances and screening constants of atomic orbitals.

    • Photoionization of Al IV (neon-type) from its ground 2s22p61Se and excited 2s22p53p3,1P03Se states using the R-matrix method

      Man Mohan M Le Dourneuf A Hibbert PG Burke

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      The R-matrix method is used to calculate the total photoionization cross-sections from the ground 2s22p61Se and the first three excited 2s22p53p3,1Se states of Al IV, for photon energies ranging from the first ionization threshold to just above the second threshold of the residual ion Al V. The two lowest LS terms of Al V − 2s22p52P0, 2s2p62Se, 2s2p62Se, represented by sophisticated configuration interaction wavefunctions, are included in the R-matrix calculation. The resulting cross-sections are affected by Rydberg series of resonances converging to the 2s2p62Se excited threshold.

    • Static charged spheres with anisotropic pressure in general relativity

      J Krishna Rao M Annapurna MM Trivedi

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      We report a generalization of our earlier formalism [Pramana, 54, 663 (1998)] to obtain exact solutions of Einstein-Maxwell’s equations for static spheres filled with a charged fluid having anisotropic pressure and of null conductivity. Defining new variables: w=(4π/3)(ρ+ε)r2, u=4πξr2, vr=4πprr2, v=4πpr2[ρ, ξ(=−(1/2)F14F14), pr, p being respectively the energy densities of matter and electrostatic fields, radial and transverse fluid pressures whereas ε denotes the eigenvalue of the conformal Weyl tensor and interpreted as the energy density of the free gravitational field], we have recast Einstein’s field equations into a form easy to integrate. Since the system is underdetermined we make the following assumptions to solve the field equations (i) u=vr=(a2/2κ)rn+2, v=k1vr, w=k2vr; a2, n(>0), k1, k2 being constants with κ=((k1+2)/3+k2) and (ii) w+u=(b2/2)rn+2, u=vr, vvr=k, with b and k as constants. In both cases the field equations are integrated completely. The first solution is regular in the metric as well as physical variables for all values of n>0. Even though the second solution contains terms like k/r2 since Q(0)=0 it is argued that the pressure anisotropy, caused by the electric flux near the centre, can be made to vanish reducing it to the generalized Cooperstock-de la Cruz solution given in [14]. The interior solutions are shown to match with the exterior Reissner-Nordstrom solution over a fixed boundary.

    • Correlation between deformation bleaching and mechanoluminescence in coloured alkali halide crystals

      B P Chandra M Ramrakhiani P Sahu A M Rastogi

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      The present paper reports the correlation between deformation bleaching of coloration and mechanoluminescence (ML) in coloured alkali halide crystals. When the F-centre electrons captured by moving dislocations are picked up by holes, deep traps and other compatible traps, then deformation bleaching occurs. At the same time, radiative recombination of dislocation captured electrons with the holes gives rise to the mechanoluminescence. Expressions are derived for the strain dependence of the density of colour centres in deformed crystals and also for the number of colour centres bleached. So far as strain, temperature, density of colour centres, Ea and volume dependence are concerned, there exists a correlation between the deformation bleaching and ML in coloured alkali halide crystals. From the strain dependence of the density of colour centres in deformed crystals, the value of coefficient of deformation bleaching D is determined and it is found to be 1.93 and 2.00 for KCl and KBr crystals, respectively. The value of (D+χ) is determined from the strain dependence of the ML intensity and it is found to be 2.6 and 3.7 for KCl and KBr crystals, respectively. This gives the value of coefficient of deformation generated compatible traps χ to be 0.67 and 1.7 for KCl and KBr crystals, respectively.

    • Foreword

      J M Kohli M Kaur

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    • Collapse of a charged radiating star with shear

      S D Maharaj M Govender

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      The junction conditions for a magnetohydrodynamic fluid sphere undergoing dissipative gravitational collapse in the form of a radial heat flux with shear are obtained. These conditions extend particular results of earlier treatments. We demonstrate that the pressure is proportional to the magnitude of the heat flux as is the case in shear-free models. However in our case the gravitational potentials must be solutions of the Einstein-Maxwell system of equations. The mass function m(v) is increased by a factor related to the charge Q of the radiating star. Physical quantities relating to the local conservation of momentum and surface redshift are obtained.

    • Coherent structures in presence of dust charge fluctuations

      M Kakati K S Goswami

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      This paper shows the formation of nonlinear coherent structures in a dusty plasma in presence of dust charge fluctuations. Using the typical plasma parameters the potential of the nonlinear coherent structures is derived.

    • Impact of electron irradiation on particle track etching response in polyallyl diglycol carbonate (PADC)

      R Mishra S P Tripathy A Kul Shrestha A Srivastava S Ghosh K K Dwivedi D T Khathing M Müller D Fink

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      In the present work, attempts have been made to investigate the modification in particle track etching response of polyallyl diglycol carbonate (PADC) due to impact of 2 MeV electrons. PADC samples pre-irradiated to 1, 10, 20, 40, 60, 80 and 100 Mrad doses of 2 MeV electrons were further exposed to 140 MeV28 Si beam and dose-dependent track registration properties of PADC have been studied. Etch-rate values of the PADC irradiated to 100 Mrad dose electron was found to increase by nearly 4 times that of pristine PADC. The electron irradiation has promoted chain scissioning in PADC, thereby converting the polymer into an easily etchable polymer. Moreover, the etching response and the detection efficiency were found to improve by electron irradiation. Scanning electron microscopy of etched samples further revealed the surface damage in these irradiated PADCs.

    • Possible lattice formation of new materials within a piezoelectric semiconductor plasma

      M Salimullah S Ghosh M R Amin

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      The possible lattice formation of grains of chosen material in a magnetized current carrying n-type piezoelectric semiconductor plasma has been examined. In addition to the repulsive Coulomb potential, there appears a non-Coulombic oscillatory potential among the highly charged grains due to the strong resonant collective interaction of the grains and the electron-acoustic mode of the host semiconductor giving rise to the possibility of the lattice formation of grains of new materials.

    • Quantum chromodynamics: Working group report

      Sourendu Gupta D Indumathi S Banerjee R Basu M Dittmar RV Gavai F Gelis D Ghosh Sourendu Gupta D Indumathi Asmita Mukherjee

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      This is the report of the QCD working group at WHEPP-6. Discussions and work on heavy ion collisions, polarized scattering, and collider phenomenology are reported.

    • Annealing effect on transport properties of Nd0.67Sr0.33MnO3 thin films

      M Pattabiraman P Murugaraj G Rangarajan V Prasad S V Subramanyam V S Sastry Sang-Mo Koo K V Rao

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      Annealing dependence of the lattice parameter, resistivity, magnetoresistance and thermopower have been studied on Nd0.7-Sr0.33MnO3 thin films deposited on LaAlO3 and alumina substrates by pulsed laser ablation. Upon annealing at 800°C and 1000°C the lattice constant of the LaAlO3 film tends toward that of the bulk target due to reduction in oxygen vacancies. This results in a metal-insulator transition at temperatures which increase with progressive annealing along with a decrease in the observed low temperature MR. Using a magnon scattering model we estimate the eg bandwidth of the film annealed at 1000°C and show that the magnon contribution to the resistivity is suppressed in a highly oxygen deficient film and gains prominence only upon subsequent annealing. We also show that upon annealing, the polaron concentration and the spin cluster size increases in the paramagnetic phase, using an adiabatic polaron hopping model which takes into account an exchange dependent activation energy above the resistivity peak.

    • Internal magnetic field measurement in tokamak plasmas using a Zeeman polarimeter

      M Jagadeeshwari J Govindarajan

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      In a tokamak plasma, the poloidal magnetic field profile closely depends on the current density profile. We can deduce the internal magnetic field from the analysis of circular polarization of the spectral lines emitted by the plasma. The theory of the measurement and a detailed design of the Zeeman polarimeter constructed to measure the poloidal field profile in the ADITYA tokamak are presented. The Fabry-Perot which we have employed in our design, with photodiode arrays followed by lock-in detection of the polarization signal, allows the measurement of the fractional circular polarization. In this system He-II line with wavelength 4686 Å is adopted as the monitoring spectral line. The line emission used in the present measurement is not well localized in the plasma, necessiating the use of a spatial inversion procedure to obtain the local values of the field.

    • Density oscillations in laser produced plasma decelerated by external magnetic field

      V N Rai M Shukla H C Pant

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      This paper presents the dynamics as well as the stability of laser produced plasma expanding across the magnetic field. Observation of some high frequency fluctuations superimposed on ion saturation current along with structuring in the pin hole images of x-ray emitting plasma plume indicate the presence of instability in the plasma. Two type of slope in the variation of x-ray emission with laser intensity in the absence and presence of magnetic field shows appearance of different threshold intensity of laser corresponding to each magnetic field at which this instability or density fluctuation sets on. This instability has been identified as a large Larmor radius instability instead of classical Rayleigh-Taylor (R-T) instability.

    • Multiple charge states of titanium ions in laser produced plasma

      M Shukla S Bandhyopadhyay V N Rai A V Kilpio H C Pant

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      An intense laser radiation (1012 to 1011 W/cm−2) focused on the solid target creates a hot (≥1 keV) and dense plasma having high ionization state. The multiple charged ions with high current densities produced during laser matter interaction have potential application in accelerators as an ion source. This paper presents generation and detection of highly stripped titanium ions (Ti) in laser produced plasma. An Nd:glass laser (KAMETRON) delivering 50 J energy (λ=0.53 µm) in 2.5 ns was focused onto a titanium target to produce plasma. This plasma was allowed to drift across a space of ∼3 m through a diagnostic hole in the focusing mirror before ions are finally detected with the help of electrostatic ion analyzer. Maximum current density was detected for the charge states of +16 and +17 of Ti ions for laser intensity of ∼1011 W/cm−2.

    • Microwave plasma deposition of diamond like carbon coatings

      D S Patil K Ramachandran N Venkatramani M Pandey R D’Cunha

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      The promising applications of the microwave plasmas have been appearing in the fields of chemical processes and semiconductor manufacturing. Applications include surface deposition of all types including diamond/diamond like carbon (DLC) coatings, etching of semiconductors, promotion of organic reactions, etching of polymers to improve bonding of the other materials etc. With a 2.45 GHz. 700 W, microwave induced plasma chemical vapor deposition (CVD) system set up in our laboratory we have deposited diamond like carbon coatings. The microwave plasma generation was effected using a wave guide single mode applicator. We have deposited DLC coatings on the substrates like stainless steel, Cu-Be, Cu and Si. The deposited coatings have been characterized by FTIR, Raman spectroscopy and ellipsometric techniques. The results show that we have achieved depositing ∼95% sp3 bonded carbon in the films. The films are unform with golden yellow color. The films are found to be excellent insulators. The ellipsometric measurements of optical constant on silicon substrates indicate that the films are transparent above 900 nm.

    • Effect of radiative cooling on collapsing charged grains

      BP Pandey Vinod Krishan M Roy

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      The effect of the radiative cooling of electrons on the gravitational collapse of cold dust grains with fluctuating electric charge is investigated. We find that the radiative cooling as well as the charge fluctuations, both, enhance the growth rate of the Jeans instability. However, the Jeans length, which is zero for cold grains and nonradiative plasma, becomes finite in the presence of radiative cooling of electrons and is further enhanced due to charge fluctuations of grains resulting in an increased threshold of the spatial scale for the Jeans instability.

    • First experimental test of bell inequalities performed using a non-maximally entangled state

      M Genovese G Brida C Novero E Predazzi

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      We describe the realisation of a new test of Bell inequalities using a new scheme obtained by the superposition of type I parametric down conversion produced in two different non-linear crystals pumped by the same laser, but with different polarisations. This experiment is the first test of Bell inequalities using a non-maximally entangled state and thus represents an important step in the direction of eliminating the detection loophole.

    • RF breakdown by toroidal helicons

      SKP Tripathi D Bora M Mishra

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      Bounded whistlers are well-known for their efficient plasma production capabilities in thin cylindrical tubes. In this paper we shall present their radio frequency (RF) breakdown and discharge sustaining capabilities in toroidal systems. Pulsed RF power in the electronmagnetohydrodynamic (EMHD) frequency regime is fed to the neutral background medium. After the breakdown stage, discharge is sustained by toroidal bounded whistlers. In these pulsed experiments the behaviour of the time evolution of the discharge could be studied in four distinct phases of RF breakdown, steady state attainment, decay and afterglow. In the steady state average electron density of ≈1012 per cc and average electron temperature of ≈20 eV are obtained at 10−3 mbar of argon filling pressure. Experimental results on toroidal mode structure, background effects and time evolution of the electron distribution function will be presented and their implications in understanding the breakdown mechanism are discussed.

    • Calculation of minor hysteresis loops under metastable to stable transformations in vortex matter

      P Chaddah M Manekar

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      We present a model in which metastable supercooled phase and stable equilibrium phase of vortex matter coexist in different regions of a sample. Minor hysteresis loops are calculated with the simple assumption of the two phases of vortex matter having field-independent critical current densities. We use our earlier published ideas that the free energy barrier separating the metastable and stable phases reduces as the magnetic induction moves farther from the first order phase transition line, and that metastable to stable transformations occur in local regions of the sample when the local energy dissipation exceeds a critical value. Previously reported anomalous features in minor hysteresis loops are reproduced, and calculated field profiles are presented.

    • Experimental evidence of photoinduced valence change of Fe3+ in BaTiO3 and mechanism for growth of new grating in depleted pump condition: An EPR investigation

      M D Sastry M Moghbel Putcha Venkateswarlu A Darwish

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      With a view to understanding the role of photo-induced valence changes of impurities in BaTiO3 in the phenomena of photorefraction, EPR experiments were conducted under in situ He-Ne laser illumination. These experiments gave evidence for photoinduced valence change of Fe in BaTiO3 at room temperature. The EPR signal due to trivalent iron was found to reduce in intensity with laser illumination The kinetics of the valence change has been investigated. Under large fringe width condition, the time constant of the decay is identified as the dielectric relaxation time τd. The changes in line shape on laser illumination to Dysonian form, appeared most predominantly in mechanically poled crystal compared to electrically poled single domain crystals. This demonstrated the possible role of domain walls and the defects there, as source or sinks of charge carriers on photo excitation. It is observed, that there is transient growth of Fe3+, when the laser illumination was put on, before its decay. This was attributed to charge transfer between electrons in oxygen vacancies and Fe4+. This predicted the growth of a transient grating under depleted pump condition in a two beam coupling experiment. This was experimentally proved by following the diffracted signal of the reading beam under the depleted pump condition.

    • On the computation of molecular auxiliary functions An and Bn

      I I Guseinov B A Mamedov M Kara M Orbay

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      Molecular auxiliary functions An(p) and Bn(pt), arising in the Hartree-Fock-Roothaan (HFR) approximation for molecules, Ewald’s crystal lattice theory, electromagnetic stopping theory, and other approximate methods, are evaluated and analysed in the range of 17≤n≤60 and 25≤pt≤60.

    • The leak microstructure

      M Lombardi C Baiocchi A Battistella G Balbinot H Huo-Ja Guoxiang F S Lombardi

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      The capabilities of a new microstructure, anode point based, for the detection of gas ionizing radiations are presented. For every single detected ionizing radiation it gives a pair of ‘induced’ charges (anodic and cathodic) of the same amount (pulses of the same amplitudes), of opposite sign, with the same collection time and essentially in time coincidence, that are proportional to the primary ionization collected. Each pulse of a pair gives the same energy and timing information, thus one can be used for these information and the other for the position. The complete lack of insulating materials in the active volume of this microstructure avoids problems of charging-up and makes stable and repeatable its behavior. It is possible to observe primary avalanches with a size of more than 2.5 × 107 electrons (4 pC), which give current pulses with a peak of more than 0.26 mA on 100 Ohm and about 30 ns duration, with 5.9 KeV X-rays of 55Fe working in proportional region in 760 Torr of isobutane gas. Single electrons emitted by a heated filament (Ec<1 eV) can also be detected in 760 Torr of isobutane; with an estimated gas gain of 1.2 × 106 and a counting rate up to 800 Kpulses/sec per single microstructure. Some new features and three different types of sensitive-position two-dimensional read-out detectors based on these microstructures, which are in developmental stage, are presented.

    • Gamma-ray spectroscopy with relativistic exotic heavy-ions

      Samit Mandal J Gerl H Geissel K Hauschild M Hellström Z Janas I Kojouharov Y Kopatch RC Lemmon P Mayet Z Podolyak PH Regan H Schaffner C Schlegel J Simpson HJ Wollersheim

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      Feasibility of gamma-ray spectroscopy at relativistic energies with exotic heavy-ions and new generation of germanium detectors (segmented Clover) is discussed. An experiment with such detector array and radioactive is discussed.

    • Fusion around the barrier for 7Li+12C

      A Mukherjee M Dasgupta DJ Hinde CR Morton AC Berriman RD Butt JO Newton H Timmers

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      Fusion cross-sections for the 7Li + 12C reaction have been measured at energies above the Coulomb barrier by the direct detection of evaporation residues. The heavy evaporation residues with energies below 3 MeV could not be separated out from the α-particles in the spectrum and hence their contribution was estimated using statistical model calculations. The present work indicates that suppression of fusion cross-sections due to the breakup of 7Li may not be significant for 7Li + 12C reaction at energies around the barrier.

    • Measurement of fission anisotropy for 16O+181Ta

      Bivash R Behera Subinit Roy P Basu M K Sharan S Jena M Satpathy M L Chatter Jee S K Datta

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      Anisotropies in fission fragment angular distributions measured for the system 16O + 181Ta over a range of bombarding energies from 83 MeV to 120 MeV have been analysed. It is shown that statistical transition state model (TSM) with pre-scission neutron correction described adequately the measured anisotropy data. Strong friction parameter is found to be necessary to estimate the pre-saddle to pre-scission neutron ratio.

    • Deformation effects in the 28Si+12C and 28Si+28Si reactions

      C Bhattacharya M Rousseau C Beck V Rauch R M Freeman R Nouicer F Haas O Dorvaux K Eddahbi P Papka O Stezowski S Szilner D Mahboub A Szanto de Toledo A Hachem E Martin S J Sanders

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      The possible occurrence of highly deformed configurations is investigated in the 40Ca and 56Ni di-nuclear systems as formed in the 28Si + 12C, 28Si reactions by using the properties of emitted light charged particles. Inclusive as well as exclusive data of the heavy fragments and their associated light charged particles have been collected by using the ICARE charged particle multidetector array. The data are analysed by Monte Carlo CASCADE statistical-model calculations using a consistent set of parameters with spin-dependent level densities. Significant deformation effects at high spin are observed as well as an unexpected large 8Be cluster emission of a binary nature.

    • Multiplicity distributions and charged-neutral fluctuations

      Tapan K Nayak MM Aggarwal A Agnihotri Z Ahammed ALS Angelis V Antonenko V Arefiev V Astakhov V Avdeitchikov TC Awes PVKS Baba SK Badyal A Baldine L Barabach C Barlag S Bathe B Batiounia T Bernier KB Bhalla VS Bhatia C Blume R Bock E-M Bohne D Bucher A Buijs E-J Buis H Büsching L Carlen V Chalyshev S Chattopadhyay KE Chenawi R Cherbatchev T Chujo A Claussen AC Das MP Decowski V Djordjadze P Donni I Doubovik AK Dubey MR Dutta Majumdar S Eliseev K Enosawa H Feldmann P Foka S Fokin V Frolov MS Ganti S Garpman O Gavrishchuk FJM Geurts TK Ghosh R Glasow SK Gupta B Guskov HA Gustafsson HH Gutbrod R Higuchi I Hrivanacova M Ippolitov H Kalechofsky R Kamermans K-H Kampert K Karadjev K Karpio S Kato S Kees H Kim BW Kolb I Kosarev I Koutcheryaev A Kugler P Kulinich V Kumar M Kurata K Kurita N Kuzmin I Langbein A Lebedev YY Lee H Löhner DP Mahapatra V Manko M Martin A Maximov R Mehdiyev G Mgebrichvili Y Miake D Mikhalev GC Mishra Y Miyamoto B Mohanty D Morrison DS Mukhopadhyay V Myalkovski H Naef BK Nandi SK Nayak TK Nayak S Neumaier A Nianine V Nikitine S Nikolaev S Nishimura P Nomokov J Nystrand FE Obenshain A Oskarsson I Otterlund M Pachr A Parfenov S Pavliouk T Peitzmann V Petracek F Plasil ML Purschke B Raeven J Rak R Raniwala S Raniwala VS Ramamurthy NK Rao F Retiere K Reygers G Roland L Rosselet I Roufanov JM Rubio SS Sambyal R Santo S Sato H Schlagheck H-R Schmidt G Shabratova I Sibiriak T Siemiarczuk BC Sinha N Slavine K Söderström N Solomey G Sood SP Sørensen P Stankus G Stefanek P Steinberg E Stenlund D Stüken M Sumbera T Svensson MD Trivedi A Tsvetkov C Twenhöfel L Tykarski J Urbahn NV Eijndhoven WHV Heeringen GJV Nieuwenhuizen A Vinogradov YP Viyogi A Vodopianov S Vörös MA Vos B Wyslouch K Yagi Y Yokota GR Young

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      Results from the multiplicity distributions of inclusive photons and charged particles, scaling of particle multiplicities, event-by-event multiplicity fluctuations, and charged-neutral fluctuations in 158A GeV Pb+Pb collisions are presented and discussed. A scaling of charged particle multiplicity as Npart1.07±0.05 and photos as Npart1.12±0.03 have been observed, indicating violation of naive wounded nucleon model. The analysis of localized charged-neutral fluctuation indicates a model-independent demonstration of non-statistical fluctuations in both charged particles and photons in limited azimuthal regions. However, no correlated charged-neutral fluctuations are observed.

    • First results from RHIC-PHENIX

      Tarun Kanti Ghosh K Adcox S S Adler N Ajitanand Y Akiba J Alexander L Aphecetche Y Arai S H Aronson R Averbeck T C Awes K N Barish P D Barnes J Barrette B Bassalleck S Bathe V Baublis A Bazilevsky S Belikov F G Bellaiche S T Belyaev M J Bennett Y Berdnikov S Botelho M L Brooks D S Brown N Bruner D Bucher H Buesching V Bumazhnov G Bunce J Burward-Hoy S Butsyk T A Carey P Chand J Chang W C Chang L L Chavez S Chernichenko C Y Chi J Chiba M Chiu R K Choudhury T Christ T Chujo M S Chung P Chung V Cianciolo B A Cole D G D’Enterria G David H Delagrange A Denisov A Deshpande E J Desmond O Dietzsch B V Dinesh A Drees A Durum D Dutta K Ebisu Y V Efremenko K El Chenawi H En’yo S Esumi L Ewell T Ferdousi D E Fields S L Fokin Z Fraenkel A Franz A D Frawley S-Y Fung S Garpman T K Ghosh A Glenn A L Godoi Y Goto S V Greene M Grosse Perdekamp S K Gupta W Guryn H-Å Gustafsson J S Haggerty H Hamagaki A G Hansen H Hara E P Hartouni R Hayano N Hayashi X He T K Hemmick J Heuser J C Hill D S Ho K Homma B Hong A Hoover T Ichihara K Imai M S Ippolitov M Ishihara B V Jacak W Y Jang J Jia B M Johnson S C Johnson K S Joo S Kametani J H Kang M Kann S S Kapoor S Kelly B Khachaturov A Khanzadeev J Kikuchi D J Kim H J Kim S Y Kim Y G Kim W W Kinnison E Kistenev A Kiyomichi C Klein-Boesing S Klinksiek L Kochenda D Kochetkov V Kochetkov D Koehler T Kohama A Kozlov P J Kroon K Kurita M J Kweon Y Kwon G S Kyle R Lacey J G Lajoie J Lauret A Lebedev D M Lee M J Leitch X H Li Z Li D J Lim M X Liu X Liu Z Liu C F Maguire J Mahon Y I Makdisi V I Manko Y Mao S K Mark S Markacs G Martinez M D Marx A Masaike F Matathias T Matsumoto P L McGaughey E Melnikov M Merschmeier F Messer M Messer Y Miake T E Miller A Milov S Mioduszewski R E Mischke G C Mishra J T Mitchell A K Mohanty D P Morrison J M Moss F Mühlbacher M Muniruzzaman J Murata S Nagamiya Y Nagasaka J L Nagle Y Nakada B K Nandi J Newby L Nikkinen P Nilsson S Nishimura A S Nyanin J Nystrand E O’Brien C A Ogilvie H Ohnishi I D Ojha M Ono V Onuchin A Oskarsson L Österman I Otterlund K Oyama L Paffrath A P T Palounek V S Pantuev V Papavassiliou S F Pate T Peitzmann A N Petridis C Pinkenburg R P Pisani P Pitukhin F Plasil M Pollack K Pope M L Purschke I Ravinovich K F Read K Reygers V Riabov Y Riabov M Rosati A A Rose S S Ryu N Saito A Sakaguchi T Sakaguchi H Sako T Sakuma V Samsonov T C Sangster R Santo H D Sato S Sato S Sawada B R Schlei Y Schutz V Semenov R Seto T K Shea I Shein T-A Shibata K Shigaki T Shiina Y H Shin I G Sibiriak D Silvermyr K S Sim J Simon-Gillo C P Singh V Singh M Sivertz A Soldatov R A Soltz S Sorensen P W Stankus N Starinsky P Steinberg E Stenlund A Ster S P Stoll M Sugioka T Sugitate J P Sullivan Y Sumi Z Sun M Suzuki E M Takagui A Taketani M Tamai K H Tanaka Y Tanaka E Taniguchi M J Tannenbaum J Thomas J H Thomas T L Thomas W Tian J Tojo H Torii R S Towell I Tserruya H Tsuruoka A A Tsvetkov S K Tuli H Tydesjö N Tyurin T Ushiroda H W van Hecke C Velissaris J Velkovska M Velkovsky A A Vinogradov M A Volkov A Vorobyov E Vznuzdaev H Wang Y Watanabe S N White C Witzig F K Wohn C L Woody W Xie K Yagi S Yokkaichi G R Young I E Yushmanov W A Zajc Z Zhang S Zhou

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      The PHENIX experiment consists of a large detector system located at the newly commissioned relativistic heavy ion collider (RHIC) at the Brookhaven National Laboratory. The primary goal of the PHENIX experiment is to look for signatures of the QCD prediction of a deconfined high-energy-density phase of nuclear matter quark gluon plasma. PHENIX started data taking for Au+Au collisions at √sNN=130 GeV in June 2000. The signals from the beam-beam counter (BBC) and zero degree calorimeter (ZDC) are used to determine the centrality of the collision. A Glauber model reproduces the ZDC spectrum reasonably well to determine the participants in a collision. Charged particle multiplicity distribution from the first PHENIX paper is compared with the other RHIC experiment and the CERN, SPS results. Transverse momentum of photons are measured in the electro-magnetic calorimeter (EMCal) and preliminary results are presented. Particle identification is made by a time of flight (TOF) detector and the results show clear separation of the charged hadrons from each other.

    • Meson production in p + d reactions

      H Machner M Betigeri J Bojowald A Budzanowski A Chatterjee J Ernst L Freindl D Frekers W Garske K Grewer A Hamacher J Ilieva L Jarczyk K Kilian S Kliczewski W Klimala D Kolev T Kutsarova J Lieb H Machner A Magiera H Nann L Pentchev HS Plendl D Protić B Razen P Von Rossen BJ Roy R Siudak J Smyrski RV Srikantiah A Strzałkowski R Tsenov K Zwoll

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      Total and differential cross sections for the reactions p + d3He + m0 with m=π, η and p + d3H+π+ were measured with the GEM detector at COSY for beam momenta between threshold and the maximum of the corresponding baryon resonance. For both reactions a strong forward-backward asymmetry was found. The data were compared with model calculations. The aspect of isospin symmetry breaking is studied.

    • Parametrization of nuclear parton distributions

      M Hirai S Kumano M Miyama

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      Optimum nuclear parton distributions are obtained by analysing available experimental data on electron and muon deep inelastic scattering (DIS). The distributions are given at Q2=1 GeV2 with a number of parameters, which are determined by a X2 analysis of the data. Valencequark distributions are relatively well determined at medium x, but they are slightly dependent on the assumed parametrization form particularly at small x. Although antiquark distributions are shadowed at small x, their behavior is not obvious at medium x from the F2 data. The gluon distributions could not be restricted well by the inclusive DIS data; however, the analysis tends to support the gluon shadowing at small x. We provide analytical expressions and computer subroutines for calculating the nuclear parton distributions, so that other researchers could use them for applications to other high-energy nuclear reactions.

    • Open problems in formation and decay of composite systems in heavy ion reactions

      G Viesti V Rizzi M Barbui D Fabris M Lunardon G Nebbia S Moretto S Pesente M Cinausero E Fioretto G Prete D Shetty

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      New highly exclusive experiments in the field of formation and decay of composite systems in heavy ion reactions are presented. Dynamical effects are reviewed in the light of recent works on the role of the N/Z asymmetry between projectile and target. The possibility of extracting directly from the experimental data the emission barrier of alpha particles emitted from highly excited nuclei is discussed. Finally, the first experimental evidence of double giant resonance excitation in fusion-evaporation reaction is presented.

    • Structure of light neutron-rich nuclei through coulomb dissociation

      U Datta Pramanik T Aumann D Cortina H Emling H Geissel M Hellström R Holzmann N Iwasa Y Leifels G Münzenberg M Rejmund C Scheidenberger K Sümmerer A Leistenschneider Th W Elze A Grünschloss S Ilievski K Boretzky J V Kratz R Kulessa E Lubkiewicz E Wajda W Walus P Reiter H Simon

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      Coulomb breakup of neutron-rich nuclei around mass A ∼ 20 has been studied experimentally using secondary beams (∼ 500–600 MeV/u) of unstable nuclei produced at GSI. The spectroscopic factor deduced for the neutron occupying s1/2 level in 15C ground state is consistent with the earlier reported value. The data analysis for Coulomb breakup of 17C shows that most of the cross section yields the 16C core in its excited state. For 17–22O, the low-lying E1 strength amounts up to about 12% of the energy weighted dipole sum rule strength depending on neutron excess. The cluster sum rule limit with 16O as a core is almost exhausted for 17,18O, while for more neutron rich isotopes the strength with respect to that limit decreases.

    • Near surface composition of some alloys by X-ray photoelectron spectroscopy

      M Sreemany T B Ghosh

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      Chemical compositions of the alloys of CuNi (Cu0.10Ni0.90, Cu0.30Ni0.70, Cu0.70Ni0.30) and BiSb (Bi0.80Sb0.20, Bi0.64Sb0.34, Bi0.55Sb0.45) are determined by X-ray photoelectron spectroscopy. The stoichiometries are determined and are compared with the bulk compositions. Possible sources of systematic errors contributing to the results are discussed. Errors arising out of preferential etching in these alloys have been investigated. It has been inferred from such studies that the preferential etching does not enrich the surface composition with a particular component for the two systems reported here. Quantitative results of CuNi system indicate that the surface regions of the Cu0.70Ni0.30 alloy is Cu-rich, although no such evidence is observed in case of BiSb system.

    • Optical fiber communication—An overview

      M Arumugam

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      This paper deals with the historical development of optical communication systems and their failures initially. Then the different generations in optical fiber communication along with their features are discussed. Some aspects of total internal reflection, different types of fibers along with their size and refractive index profile, dispersion and loss mechanisms are also mentioned. Finally the general system of optical fiber communication is briefly mentioned along with its advantages and limitations. Future soliton based optical fiber communication is also highlighted.

    • Shape changing collisions of optical solitons, universal logic gates and partially coherent solitons in coupled nonlinear Schrödinger equations

      M Lakshmanan T Kanna

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      Coupled nonlinear Schrödinger equations (CNLS) very often represent wave propagation in optical media such as multicore fibers, photorefractive materials and so on. We consider specifically the pulse propagation in integrable CNLS equations (generalized Manakov systems). We point out that these systems possess novel exact soliton type pulses which are shape changing under collision leading to an intensity redistribution. The shape changes correspond to linear fractional transformations allowing for the possibility of construction of logic gates and Turing equivalent all optical computers in homogeneous bulk media as shown by Steiglitz recently. Special cases of such solitons correspond to the recently much discussed partially coherent stationary solitons (PCS). In this paper, we review critically the recent developments regarding the above properties with particular reference to 2-CNLS.

    • A variational approach to nonlinear evolution equations in optics

      D Anderson M Lisak A Berntson

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      A tutorial review is presented of the use of direct variational methods based on Rayleigh-Ritz optimization for finding approximate solutions to various nonlinear evolution equations. The practical application of the approach is demonstrated by some illustrative examples in connection with the nonlinear Schrödinger equation.

    • Charge densities and charge noise in mesoscopic conductors

      M Büttiker

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      We introduce a hierarchy of density of states to characterize the charge distribution in a mesoscopic conductor. At the bottom of this hierarchy are the partial density of states which represent the contribution to the local density of states if both the incident and the out-going scattering channel is prescribed. The partial density of states play a prominent role in measurements with a scanning tunneling microscope on multiprobe conductors in the presence of current flow. The partial density of states determine the degree of dephasing generated by a weakly coupled voltage probe. In addition the partial density of states determine the frequency-dependent response of mesoscopic conductors in the presence of slowly oscillating voltages applied to the contacts of the sample. The partial density of states permit the formulation of a Friedel sum rule which can be applied locally. We introduce the off-diagonal elements of the partial density of states matrix to describe charge fluctuation processes. This generalization leads to a local Wigner-Smith life-time matrix.

    • Magnetotransport of the low-carrier density one-dimensional S=1/2 antiferromagnet Yb4As3

      P Gegenwart H Aoki T Cichorek J Custers M Jaime A Ochiai F Steglich

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      The transport properties of the semimetallic quasi-one-dimensional S=1/2 antiferromagnet Yb4As3 have been studied by performing low-temperature (T≥0.02 K) and high magneticfield (B≤60 T) measurements of the electrical resistivity ρ(T, B). For T ≿ 2 K a ‘heavy-fermion’-like behavior Δρ(T)=AT2 with huge and nearly field-independent coefficient A ≈ 3 µΩ cm/K2 is observed, whereas at lower temperatures ρ(T) deviates from this behavior and slightly increases to the lowest T. In B>0 and T ≾ 6 K the resistivity shows an anomalous magnetic-history dependence together with an unusual relaxation behavior. In the isothermal resistivity Shubnikov-de Haas (SdH) oscillations, arising from a low-density system of mobile As-4p holes, with a frequency of 25 T have been recorded. From the T- and B-dependence of the SdH oscillations an effective carrier mass of (0.275±0.005)m0 and a charge-carrier mean-free path of 215 Å are determined. Furthermore, in B≥15 T, the system is near the quantum limit and spin-splitting effects are observed.

    • X-ray magnetic circular dichroism at IrL2,3 edges in Fe100−xIrx and Co100−xIrx alloys: Magnetism of 5d electronic states

      V V Krishnamurthy M Suzuki N Kawamura T Ishikawa

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      The formation of induced 5d magnetic moment on Ir in Fe100−xIrx (x=3, 10 and 17) and Co100−xIrx (x=5, 17, 25 and 32) alloys has been investigated by X-ray magnetic circular dichroism (XMCD) at Ir L2,3 absorption edges. Sum rule analysis of the XMCD data show that the orbital moment of Ir is in the range of −0.071(2)µB to −0.030(1)µB in Fe-Ir alloys and −0.067(2)µB to 0.024(1)µB in Co-Ir alloys. We find that the total moment of Ir in Fe-Ir alloys is approximately 1/5 of the total 3d moment on Fe at all the three compositions. In contrast, the total moment on Ir in Co-Ir alloys varies between 1/6 to 1/16 of the 3d moment on cobalt. The observed trends of Ir moments and the role of interatomic exchange interactions in 5d moment formation are discussed.

    • Spin-glass, antiferromagnetism and kondo behavior in Ce2Au1−xCoxSi3 alloys

      Subham Majumdar EV Sampathkumaran St Berger M Della Mea H Michor E Bauer M Brando J Hemberger A Loidl

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      Recently, the solid solution Ce2Au1−xCoxSi3 has been shown to exhibit many magnetic anomalies associated with the competition between magnetic ordering and the Kondo effect. Here we report high pressure electrical resistivity of Ce2AuSi3, ac susceptibility (X) and magnetoresistance of various alloys of this solid solution in order to gain better knowledge of the magnetism of these alloys. High pressure resistivity behavior is consistent with the proposal that Ce2AuSi3 lies at the left-hand side of the maximum in Doniach’s magnetic phase diagram. The ac X data reveal that there are in fact two magnetic transitions, one at 2 K and the other at 3 K for this compound, both of which are spin-glass-like. However, as the Co concentration is increased, antiferromagnetism is stabilized for intermediate compositions before attaining non-magnetism for the Co end member.

    • Studies on the valence electronic structure of Fe and Ni in FexNi1−x alloys

      DK Basa S Raj HC Padhi M Polasik F Pawlowski

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      Kβ-to-Kα X-ray intensity ratios of Fe and Ni in pure metals and in FexNi1−x alloys (x=0.20, 0.50, 0.58) exhibiting similar crystalline structure have been measured following excitation by 59.54 keV γ-rays from a 241Am point source, to understand as to why the properties of permalloy Fe0.2Ni0.8 is distinct from other alloy compositions. It is observed that the valence electronic structure of Fe0.2Ni0.8 alloy is totally different from other alloys which may be attributed to its special magnetic properties.

    • Comment on magnetism and superconductivity in rutheno cuprates: RuSr2GdCu2O8 and RuSr2Gd1.5Ce0.5Cu2O10

      VPS Awana M Karppinen H Yamauchi

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      Both RuSr2GdCu2O8-δ (Ru-1212) and RuSr2Gd1.5Ce0.5Cu2O10-δ (Ru-1222) exhibits magnetism and superconductivity, as seen by magnetization vs. temperature behavior measured in 5 Oe field. Zero-field-cooled (ZFC) and field-cooled (FC) magnetization data show branching at around 140 K and 100 K with a cusp at 135 K and 80 K and a diamagnetic transition around 20 K and 30 K in the ZFC part, for Ru-1212 and Ru-1222, respectively. The isothermal magnetization possesses a non-linear contribution due to a ferromagnetic component at low temperatures below 50 K for both samples. The resistance vs. temperature behavior of the samples in applied fields of 0, 3 and 7 T confirmed superconductivity, with a different type of broadening of the superconductivity transition under magnetic fields for Ru-1212 from that known for conventional high-Tc superconductors. The magnetoresistance (MR) is negative above the Ru magnetic ordering temperature at 135 K. Below the Ru magnetic ordering temperature, MR displays a positive peak at low fields and becomes negative at higher fields for Ru-1212. For Ru-1222, MR remains negative both above and below the ordering temperature. A maximum of 2% is observed for the negative MR value at the Ru magnetic ordering temperature. An electron diffraction pattern obtained for the Ru-1212 sample shows two types of superstructure: one has a weak spot at the centre of the a–b rectangle, and the other only along the b direction. Interestingly, Ru-1222 shows only clean a–b and a–c planes, without any superstructures.

    • Structural studies and Tc dependence in La2−xDyxCayBa2Cu4+yOz type mixed oxide superconductors

      S Rayaprol Krushna Mavani CM Thaker DS Rana Keka Chakravorty SK Paranjape M Ramanadham Nilesh A Kulkarni DG Kuberkar

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      A new series of mixed oxide superconductors with the stoichiometric composition La2−xDyxCayBa2Cu4+yOz (x=0.0 − 0.5, y=2x) has been studied for structural and superconductiong properties. Our earlier studies on La2−x(Y/Er)xCayBa2Cu4+yOz series, show a strong dependence of Tc on hole concentration (psh). In the present work, the results of the analysis of the neutron diffraction measurements at room temprerature on x=0.3 and 0.5 samples are reported. It is interesting to know that Ca substitutes for both La and Ba site with concomitant displacement of La onto Ba site. Superconductivity studies show that maximum Tc is obtained for x=0.5, y=1.0 sample (Tc ∼ 75 K), for La1.5Dy0.5Ca1Ba2Cu5Oz (La-2125).

    • Polarized Raman scattering in single crystals of Nd0.7Sr0.3MnO3

      M Pattabiraman G Rangarajan Kwang-Yong Choi P Lemmens G Guentherodt G Balakrishnan DMcK Paul MR Lees

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      We report polarized Raman scattering in single crystals of Nd0.7Sr0.3MnO3. The temperature dependence of the MnO6 octahedral bending and stretching modes observed in the XX spectra points to the existence of local lattice distortions, possibly polarons. The XY spectra have been analyzed using a collision-dominated model, which allows the extraction of the carrier scattering rate.

    • A new ultrasonic method to detect chemical additives in branded milk

      S Mohanan P G Thomas Panicker Lilly Iype M Laila I Domini RG Bindu

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      A new ultrasonic method — thermoacoustic analysis — is reported for the detection of the added chemical preservatives in branded milk. The nature of variation and shift in the thermal response of the acoustic parameters specific acoustic impedance, adiabatic compressibility and Rao’s specific sound velocity for different samples of branded milk as compared to the chemical added pure milk are explained as due to the presence of chemicals in these branded samples.

    • Mechanical design of the recirculating, terminal pumping in the lund pelletron, and experimental experience

      R Hellborg K Hākansson M Faarinen M Kiisk P Persson G Skog K Stenström

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      A recirculating terminal pumping system has been installed in the 3 MV Pelletron tandem accelerator in Lund. An extremly limited space in the high voltage terminal and the absence of electrical power in the terminal, forced us to provide a unique design for the installation and powering of the new pumps. Details of the technical design, as well as experience of the use of the new system for accelerator mass spectrometry, will be given.

    • New modifications in 15 UD pelletron at nuclear science centre

      S Chopra N S Pawar M P Singh Rakesh Kumar J Prasad V P Patel Raj Pal B Kumar S Ojha K Devarani T Nandi M Sota P Barua S Gargari R Joshi D Kanjilal SK Datta

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      The 15 UD pelletron at NSC has been operational and performed well during the last 11 years. There have been major modifications performed for upgradation of pelletron system over this period. Major upgradations which have been implemented are new resistor network system for voltage gradient, doublet to singlet unit conversion for accelerator units, turbopump based gas stripper system etc. In addition accelerator mass spectroscopy program has also been started. A new multi-cathode source, Wien filter etc. have been procured and will be added soon in the system. An overview of the most significant upgradations undertaken and other activities for the system are being reported in the present paper.

    • An EBIS for charge state breeding in the SPES project

      V Variale G Brautti T Clauser A Rainò V Stagno G Lamanna V Valentino A Boggia Y Boimelshtein P Logatchov B Skarbo M Tiunov

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      The ‘charge state breeder’, BRIC (breeding ion charge) is in construction at the INFN section of Bari (Italy). It is based on EBIS scheme and it is designed to accept radioactive ion beam (RIB) with charge state +1 in a slow injection mode. This experiment can be considered as a first step towards the design and construction of a charge breeder for the SPES project.

      The new feature of BRIC, with respect to the classical EBIS, is given by the insertion, in the ion chamber, of a rf-quadrupole aiming at filtering the unwanted masses and then making a more efficient containment of the wanted ions. In this paper, the breeder design, the simulation results of the electron and ion beam propagation and the construction problems of the device will be reported.

    • The design of a radio frequency quadrupole LINAC for the RIB project at VECC Kolkata

      V Banerjee Alok Chakrabarti Arup Bandyopadhyay T K Bhaumik M Mondal T K Chakraborty H Pande O Kamigaito A Goto Y Yano

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      A radio frequency quadrupole LINAC has been designed for the VECC-RIB project for an input beam energy of 1.0 keV/u and q/A≥1/16. The output energy will be about 90 keV/u for a 3.4 m long, 35 MHz structure. A half-scale cold model of the RFQ has been fabricated and tested for rf structure design study. The beam dynamics and rf-structure design along with the results of the cold model tests will be presented.

    • A small and compact AMS facility for tritium depth profiling

      M Friedrich W Pilz N Bekris M Glugla M Kiisk V Liechtenstein

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      Depth profiling measurements of tritium in carbon samples have been performed during the past seven years at the AMS facility installed at the Rossendorf 3 MV Tandetron. The samples have been cut from the inner walls of the fusion experiments ASDEX-upgrade/Garching and JET/Culham. The tritium content of the samples from JET required a dedicated AMS facility to prevent any contamination of the versatile 3 MV Tandetron. On the basis of an air-insulated 100 kV tandem accelerator equipped with a gas stripper an AMS facility exclusively devoted to tritium depth profiling was installed, tested and used for routine measurements. After additional successful tests employing diamond-like carbon (DLC) stripper foils at this accelerator, another small and compact 100 kV tandem accelerator with SF6 insulation and a DLC stripper has been installed at the AMS facility. Results obtained with the different tandem accelerators are presented.

    • A high resolution AMS-injector for the Pelletron in Lund

      R Hellborg S Bazhal M Faarinen K Håkansson C-E Magnusson P Persson G Skog K Stenström

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      A high resolution injector system has recently been installed at the Lund 3 MV tandem Pelletron accelerator. The new injector, designed mainly for 26Al ions, will increase the experimental potential of the Lund AMS facility considerably. High quality energy- and mass-resolution is obtained by using a 90° spherical electrostatic analyzer followed by a 90° magnetic analyzer. The injector is equipped with a high intensity sputtering source with a spherical ionizer.

      A new analytical technique for acceptance calculations as well as PC-based computational methods have been used in the design of the ion optical system of the new injector.

      Compared to our old injector system which has a magnetic analyzer with a bending angle of only 15°, the new system has a more than ten times better resolution. The beam optics of the new system is also better designed to match the accelerator acceptance. In this way the ion transmission from the ion source to the detector, for different ions of interest in our AMS programme, has been increased.

    • Optimization and performance of a high-speed plasma position digital control system

      M Emami A R Babazadeh H Rasouli

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      This paper addresses optimization of a high-speed digital feedback controller for a plasma position in Damavand tokamak. Damavand tokamak discharges have plasma currents up to 40 kA with discharge duration greater than 15 ms and toroidal magnetic fields up to 1.2 T. The plasma position is measured using saddle-loops and Rogowski coil and is controlled by electromagnetic forces generated by passing currents through control coils placed around the plasma. A desired control objective is maintaining the plasma in the center of vacuum vessel and to stabilize the plasma in the presence of disturbances in a time domain of the order of few milliseconds. In order to achieve maximum performance it is essential to optimize the control system. In this paper plasma position measurement and the details of implementing high-speed PID controllers based on a TMS320c25 digital signal processor along with the system optimization are presented.

    • Polymer mixtures in confined geometries: Model systems to explore phase transitions

      K Binder M Müller A Cavallo E V Albano

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      While binary (A,B) symmetric polymer mixtures ind = 3 dimensions have an unmixing critical point that belongs to the 3d Ising universality class and crosses over to mean field behavior for very long chains, the critical behavior of mixtures confined into thin film geometry falls in the 2d Ising class irrespective of chain length. The critical temperature always scales linearly with chain length, except for strictly two-dimensional chains confined to a plane, for whichTcN5/8 (this unusual exponent describes the fractal contact line between segregated chains in dense melts in two spatial dimensions,d = 2). When the walls of the thin film are not neutral, but preferentially attract one species, complex phase diagrams occur due to the interplay between capillary condensation and wetting phenomena. For ‘competing walls’ (one wall prefers A, the other prefers B) particularly interesting interface localization-delocalization transitions occur, while analogous phenomena in wedges are related to the ‘filling transition’.

    • Measuring information networks

      K Sneppen A Trusina M Rosvall

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      Traffic and communication between different parts of a complex system are fundamental elements in maintaining its overall cooperativity. Because a complex system consists of many different parts, it matters where signals are transmitted. Thus signaling and traffic are in principle specific, with each message going from a unique sender to a specific recipient. In the current paper we review some measures of network topology that are related to its ability to direct specific communication.

    • Fusion of biological membranes

      K Katsov M Müller M Schick

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      The process of membrane fusion has been examined by Monte Carlo simulation, and is found to be very different than the conventional picture. The differences in mechanism lead to several predictions, in particular that fusion is accompanied by transient leakage. This prediction has recently been verified. Self-consistent field theory is applied to examine the free energy barriers in the different scenarios.

    • Combined neutron and synchrotron studies of magnetic films

      Sunil K Sinha S Roy M R Fitzsimmons S Park M Dorn O Petracic I V Roshchin Zhi Pan Li X Batlle R Morales A Misra X Zhang K Chesnel J B Kortright Ivan K Schuller

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      We discuss specular reflectivity and off-specular scattering of neutrons and X-rays from magnetic films. Both these techniques are capable of providing information about the morphology of the chemical and magnetic roughness and the magnetic domain structure. The use of neutrons with polarization analysis enables the spatial distribution of different vector components of the magnetization to be determined, and the use of resonant magnetic X-ray scattering enables magnetization in a compound system to be determined element-selectively. Thus both these methods provide powerful and complementary new probes for studying magnetism at the nanoscopic level in a variety of systems such as those exhibiting exchange bias, giant magnetoresistance, spin injection, etc. We shall illustrate with an example of both techniques applied to an exchange bias system consisting of a single crystal of antiferromagnetic FeF2 capped with a ferromagnetic Co film, and discuss what has been learned about how exchange bias works in such a system.

    • Metal-insulator transition in Ni-doped Na0.75CoO2: Insights from infrared studies

      M Premila A Bharathi N Gayathri P Yasodha Y Hariharan C S Sundar

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      Nickel substitution at the cobalt site in Na0.75CoO2 induces an upturn in the resistivity on lowering the temperature, with the metal-to-insulator transition temperature (TMIT) increasing with the Ni content. Low temperature far infrared measurements on polycrystalline samples of Na0.75CoO2 and Na0.75Co0.95Ni0.05O2, the latter having TMIT ∼ 175 K, have been carried out. Dramatic changes in the Na mode frequencies, and relative intensities of the out-of-plane modes corresponding to the two Na sites are observed, coincident with the MIT in Na0.75Co0.95Ni0.05O2. It is argued that these changes are associated with a charge ordering of the CoO2 layer, associated with the metal-insulator transition.

    • Ballistic transport in semiconductor nanostructures: From quasi-classical oscillations to novel THz-emitters

      G H Döhler M Eckardt A Schwanhäußer F Renner S Malzer S Trumm M Betz F Sotier A Leitenstorfer G Loata T Löffler H Roskos T Müller K Unterrainer D Driscoll M Hanson A C Gossard

      More Details Abstract Fulltext PDF

      By suitable design it is possible to achieve quasi-ballistic transport in semiconductor nanostructures over times up to the ps-range. Monte-Carlo simulations reveal that under these conditions phase-coherent real-space oscillations of an electron ensemble, generated by fs-pulses become possible in wide potential wells. Using a two-color pump-and-probe technique we have been able to observe this new phenomenon in excellent agreement with the theoretical predictions. Apart from its fundamental significance, ballistic transport in nanostructures can also be used for high-efficiency coherent THz-sources. The concept of these THz-emitters and its experimental confirmation will also be presented.

    • Elliptic flow in a hadron-string cascade model at 130 GeV energy

      P K Sahu A Ohnishi M Isse N Otuka S C Phatak

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      We present the analysis of elliptic flow at $$\sqrt s $$=130 A GeV energy in a hadron-string cascade model. We find that the final hadronic yields are qualitatively described. The elliptic flow v2 is reasonably well-described at low transverse momentum (pt<1 GeV/c) in mid-central collisions. On the other hand, this model does not explain v2 at high pt or in peripheral collisions and thus generally, it underestimates the elliptic flow at RHIC energy.

    • Working group report: Astroparticle and neutrino physics

      Raj Gandhi Subhendra Mohanty Tarun Souradeep S Agarwalla K Bhattacharya B Brahmachari R Crittenden S Goswami P Ghoshal M Lindner H S Mani S Mitra S Pascoli S Panda R Rangarajan S Ray T Roy Choudhury R Saha S Sarkar A Srivastava R Sheth S Uma Sankar U Yajnik

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      The working group on astroparticle and neutrino physics at WHEPP-9 covered a wide range of topics. The main topics were neutrino physics at INO, neutrino astronomy and recent constraints on dark energy coming from cosmological observations of large scale structure and CMB anisotropy.

    • Beyond the new standard model in neutrino oscillations

      M Zrałek

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      We discuss effects of new physics (NP) in neutrino oscillation experiments. Such effects can modify a production neutrino flux, a detection cross-section and a matter transition. As a result, the NP effects change neutrino oscillations both in vacuum and in matter. A relation between the small effects of NP and the oscillation parameters is discussed. It is shown for which parameters the NP effects are suppressed and when they are potentially large. Oscillations of non-unitary mixed neutrinos are presented in more details.

    • Hierarchy of rational order families of chaotic maps with an invariant measure

      M A Jafarizadeh M Foroutan S Ahadpour

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      We introduce an interesting hierarchy of rational order chaotic maps that possess an invariant measure. In contrast to the previously introduced hierarchy of chaotic maps [1–5], with merely entropy production, the rational order chaotic maps can simultaneously produce and consume entropy. We compute the Kolmogorov-Sinai entropy of these maps analytically and also their Lyapunov exponent numerically, where the obtained numerical results support the analytical calculations.

    • Pulsed pump: Thermal effects in solid state lasers under super-Gaussian pulses

      H Nadgaran M Sabaian

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      Solid state laser (SSL) powers can be realistically scaled when pumped by a real, efficient and multimode pulse. In this work, a fourth-order super-Gaussian pulse was assumed as a pump for SSL’s and a complete analytical expression for the thermal phase shift is given. Moreover, the focal length of thermal lens in paraxial ray approximation regime was studied. The results when applied to a Ti: sapphire crystal show an appreciable correction for abberation compared to a top-hat pulse.

    • The influence of fragmentation models in the production of hadron jets in electron–positron annihilation

      Hasheminia M Mirjalili A Zomorrodian M E Sepehri A

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      The analysis of electron–positron annihilations to hadrons at high energies shows that apart from two-jet events, there are also signs of three-jet events which are interpreted according to the QCD, as a gluon radiated by a quark. In this paper, we investigate the fragmentation of quarks and gluons to hadron jets. We show that gluon jets have a higher multiplicity compared to quark jets of the same energy. Furthermore, inclusion of different flavours in the distributions shows that quark jets are flavour-dependent, but gluon jets are not. The differences between quark and gluon jets also manifest themselves in the fragmentation functions. We observe that the fragmentation for gluon jet is softer than that for quark jet, because the radiation of soft gluons is larger for gluon jetsand that gluon cannot be present as a valence parton inside a produced hadron. We provide possible explanations for these features in this paper.

    • Structural investigation on gamma-irradiated polyacrylamide hydrogels using small-angle neutron scattering and ultraviolet–visible spectroscopy

      Sivananatham M Tata B V R Aswal V K

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      Small-angle neutron scattering (SANS) and ultraviolet (UV)–visible spectroscopictechniques are used to investigate the microstructural changes in polyacrylamide (PAAm) hydrogels on gamma irradiation. SANS measurements have revealed the presence of inhomogeneities in nanometre scale and reduction of their size with increase in dose. Analysis of SANS data alsorevealed the increase in the correlation length with increase in dose. The extinction coefficient obtained from the UV–visible spectroscopic studies exhibited $\lambda^{−\beta}$ dependence between 500 and 700 nm and is understood to arise from the existence of scatterers (inhomogeneities) in submicron scale in PAAm hydrogels. The increase in value of exponent $\beta$ with increase in dose indicates that the size of scatterers decrease with increase in dose.

    • Influence of soliton distributions on the spin-dependent electronic transport through polyacetylene molecule

      Ketabi S A Nakhaee M

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      In this paper, a detailed numerical study of the role of selected soliton distributions on the spin-dependent transport through {\it trans}-polyacetylene (PA) molecule is presented. The molecule is attached symmetrically to magnetic semi-infinite three-dimensional electrodes. Based on Su–Schrieffer–Heeger (SSH) Hamiltonian and using a generalized Green’s function formalism, wecalculate the spin-dependent currents, the electronic transmission and tunnelling magnetoresistance (TMR). We found that the presence of a uniform distribution of the soliton centres along the molecular chain reduced the size of the band gap of {\it trans}-PA molecule. Moreover, a sublattice of the correlated solitons as binary clusters, which are randomly distributed along the chain, can induce extended electronic states in the band gap of the molecule. In this case, the band gap of the molecule is suppressed and at lower voltages, the TMR bandwidth is narrowed. The current–voltage characteristic then shows an ohmic-like behaviour.

    • Simulation of a quantum NOT gate for a single qutrit system

      Avila M Rueda-Paz J

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      A three-level system based an a three-level atom interacting with a detuned cavity is considered. Because of the fact that the three-level atom defines a total normalized state composed of superposition of three different single-level states, it is assumed that such a system implements a qutrit. In order to achieve a quantum NOT gate for a single qutrit, the respective Schrödinger equation is solved numerically within a two-photon rotating wave approximation. For small values of one-photon detuning, there appear decoherence effects. Meanwhile, for large values of onephoton detuning, an ideal quantum NOT gate for a single qutrit is achieved. An expression for the execution time of the quantum NOT gate for a single qutrit as a function of the one-photon detuning is found.

    • Defect characterization of Ga$_4$Se$_3$S layered single crystals by thermoluminescence

      Isik M Delice S Gasanly N

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      Trapping centres in undoped Ga$_4$Se$_3$S single crystals grown by Bridgman method were characterized for the first time by thermoluminescence (TL) measurements carried out in the low temperature range of 15−300 K. After illuminating the sample with blue light (∼470 nm) at 15 K, TL glow curve exhibited one peak around 74 K when measured with a heating rate of 0.4 K/s.The results of the various analysis methods were in good agreement about the presence of one trapping centre with an activation energy of 27 meV. Analysis of curve fitting method indicated that mixed order of kinetics dominates the trapping process. Heating rate dependence and distribution of the traps associated with the observed TL peak were also studied. The shift of peak maximum temperature from 74 to 113 K with increasing rate from 0.4 to 1.2 K/s was revealed. Distribution of traps was investigated using an experimental technique based on cleaning the centres giving emission at lower temperatures. Activation energies of the levels were observed to be increasing from 27 to 40 meV by rising the stopping temperature from 15 to 36 K.

    • A novel approach for solving fractional Fisher equation using differential transform method


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      In the present paper, an analytic solution of nonlinear fractional Fisher equation is deduced with the help of the powerful differential transform method (DTM). To illustrate the method, two examples have been prepared. The method for this equation has led to an exact solution. The reliability, simplicity and cost-effectiveness of the method are confirmed by applying this method on different forms of functional equations.

    • Exact solutions of the Drinfel’d–Sokolov–Wilson equation using Bäcklund transformation of Riccati equation and trial function approach


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      In this paper, two integration schemes are employed to obtain solitons, singular periodic waves and other types of solutions of the Drinfel’d–Sokolov–Wilson equation. The two schemes studied in this paper are the Bäcklund transformation of Riccati equation and the trial function approach. The corresponding constraint conditions of the solutions are also given.

    • Analytical treatment for synchronizing chaos through unidirectional coupling and implementation of logic gates


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      The idea of synchronization can be explicitly demonstrated by both numerical and analytical means on a nonlinear electronic circuit. Also, we introduce a scheme to obtain various logic gate structures, using synchronization of chaotic systems. By a small change in the response parameter of unidirectionally coupled nonlinear systems, one is able to construct various logic behaviours by both numerical and analytical methods.

    • Momentum distribution of charged particles in jets in dijet events and comparison to perturbative QCD predictions


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      Inclusive momentum distributions of charged particles are measured in dijet events. Events were produced at the AMY detector with a centre of mass energy of 60 ${\rm GeV}$. Our results were compared, on the one hand to those obtained from other $e^+ e^-$, $ep$ as well as CDF data, and on the other hand to the perturbative QCD calculations carried out in the framework of the modified leading log approximation (MLLA) and assuming local parton--hadron duality (LPHD). A fit of the shape of the distributions yields $\scr Q_{eff} = 263 \pm 13 {\rm MeV}$ for the AMY data. In addition, a fit to the evolution of the peak position with dijet mass using all data from different experiments gives $\scr Q_{eff} = 226 \pm 18 {\rm MeV}$. Next, αs was extracted using the shape of the distribution at the Z0 scale, with a value of 0.118 \pm 0.013. This is consistent, within the statistical errors, with many accurate measurements. We conclude that it is the success of LPHD + MLLA that the extracted value of $\alpha_{s}$ is correct. Possible explanations for all these features will be presented in this paper.

    • Space–time transformation for the propagator in de Broglie–Bohm theory


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      A linear space–time transformation proposed to calculate the propagator in the de Broglie–Bohm theory, is viewed as an expansion of the guiding wave function over the velocity space. It is shown that the quantum evolution is preserved in its semiclassical scheme through this change. The case of variable-frequencyharmonic oscillator is presented as an example.

    • Analysis of tokamak plasma confinement modes using the fast Fourier transformation


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      The Fourier analysis is a satisfactory technique for detecting plasma confinement modes in tokamaks. The confinement mode of tokamak plasma was analysed using the fast Fourier transformation (FFT). For this purpose, we used the data of Mirnov coils that is one of the identifying tools in the IR-T1 tokamak, with and without external field (electric biasing), and then compared it with each other. After the Fourier analysis of Mirnov coil data, the diagram of power spectrum density was depicted in different angles of Mirnov coils in the ‘presenceof external field’ as well as in the ‘absence of external field’. The power spectrum density (PSD) interprets the manner of power distribution of a signal with frequency. In this article, the number of plasma modes and the safety factor $q$ were obtained by using the mode number of $q = m/n$ ($m$ is the mode number). The maximum MHD activity was obtained in 30–35 kHz frequency, using the density of the energy spectrum. In addition, the number of different modes across 0–35 ms time was compared with each other in the presence and absence of theexternal field.

    • Effects of non-extensive electrons and positive/negative dust particles on modulational instability of dust-ion-acoustic solitary waves in non-planar geometry


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      The nonlinear propagation of cylindrical and spherical dust-ion-acoustic (DIA) envelope solitary waves in unmagnetized dusty plasma consisting of dust particles with opposite polarity and non-extensive distribution of electron is investigated. By using the reductive perturbation method, the modified nonlinear Schrödinger (NLS) equation in cylindrical and spherical geometry is obtained. The modulational instability (MI) of DIA waves governed by the NLS equation is also presented. The effects of different ranges of the non-extensive parameter $q$ on the MI are studied. The growth rate of the MI is also given for different values of $q$. It is found that the basic features of the DIA waves are significantly modified by non-extensive electron distribution, polarity of the netdust-charge number density and non-planar geometry.

    • Bound-state energy of double magic number plus one nucleon nuclei with relativistic mean-field approach


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      In this work, we have obtained energy levels and charge radius for the $\beta$-stability line nucleus, in relativistic shell model. In this model, we considered a close shell for each nucleus containing double magicnumber and a single nucleon energy level. Here we have taken $^{41}$Ca with a single neutron in the $^{40}$Ca core as an illustrative example. Then we have selected the Eckart plus Hulthen potentials for interaction between the coreand the single nucleon. By using parametric Nikiforov–Uvarov (PNU) method, we have calculated the energy values and wave function. Finally, we have calculated the charge radius for 17O, $^{41}$Ca, $^{49}$Ca and $^{57}$Ni. Our results are in agreement with experimental values and hence this model can be applied for similar nuclei.

    • Influence of absorbed pump profile on the temperature distribution within a diode side-pumped laser rod


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      In this paper, an analytical model for temperature distribution of the side-pumped laser rod is extracted. This model can be used for side-pumped laser rods whose absorbed pump profile is a Gaussian profile. Then, it is validated by numerical results which exhibit a good agreement with the analytical results. Afterwards, by considering a general expression for super-Gaussian and top-hat profiles, and solving the heat equation, the influence of profile width and super-Gaussian exponent of the profile on temperature distribution are investigated.Consequently, the profile width turns out to have a greater influence on the temperature compared to the type of the profile.

    • Modified function projective combination synchronization of hyperchaotic systems


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      In this work, a novel combination synchronization scheme in which synchronization of a new combination hyperchaotic drive system formed by combining state variables of the original drive system with appropriate scaling factors with a response hyperchaotic system is considered. A self-combination system is constructed from hyperchaotic Lorenz system by combining state variables of the Lorenz system with appropriate scaling factors. Modified function projective synchronization between the newly constructed combination hyperchaotic Lorenz system and hyperchaotic Lu system is investigated using adaptive method. By Lyapunov stability theory, the adaptive control law and the parameter update law are derived to make the state of two systems as modified function projective synchronized. Numerical simulations are done to show the validity and effectiveness of the proposed synchronization scheme.

    • A review on the solution of Grad–Shafranov equation in the cylindrical coordinates based on the Chebyshev collocation technique


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      Equilibrium reconstruction consists of identifying, from experimental measurements, a distribution of the plasma current density that satisfies the pressure balance constraint. Numerous methods exist to solve the Grad–Shafranov equation, describing the equilibrium of plasma confined by an axisymmetric magnetic field. In this paper, we have proposed a new numerical solution to the Grad–Shafranov equation (an axisymmetric,magnetic field transformed in cylindrical coordinates solved with the Chebyshev collocation method) when the source term (current density function) on the right-hand side is linear. The Chebyshev collocation method is a method for computing highly accurate numerical solutions of differential equations. We describe a circular crosssection of the tokamak and present numerical result of magnetic surfaces on the IR-T1 tokamak and then compare the results with an analytical solution.

    • A comparative analysis of the density distributions and the structure models of $^{9}$Li

      M AYGUN

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      In the present study, we have analysed the elastic scattering cross-section data of $^{9}$Li + $^{12}$C system at $E_{lab}$ = 540 MeV and $^{9}$Li + $^{208}$Pb system at $E_{c.m.}$ = 28.3 MeV for some cluster models and various density distributions of the $^{9}$Li nucleus. First, we have obtained five different density distributions of the $^{9}$Li nucleus to generate real potentials with the help of double-folding model. For these densities, we have calculated the elastic scattering angular distributions. Secondly, using a simple approach, we have investigated some cluster models of the $^{9}$Li nucleus consisting of $^{6}$He + $^{3}$H and $^{8}$Li + n systems. We have presented the comparison of elastic scattering angular distributions for each system with each other as well as with the experimental data. Finally, we have given the cross-section values obtained from the theoretical calculations for all the systems studied in this paper.

    • Nonplanar electrostatic shock waves in an opposite polarity dust plasma with nonextensive electrons and ions


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      A rigorous theoretical investigation has been carried out on the propagation of nonplanar (cylindrical and spherical) dust-acoustic shock waves (DASHWs) in a collisionless four-component unmagnetized dusty plasmasystem containing massive, micron-sized, positively and negatively charged inertial dust grains along with $q$ (nonextensive) distributed electrons and ions. The well-known reductive perturbation technique has been used to derive the modified Burgers equation (which describes the shock wave properties) and its numerical solution. It has been observed that the effects of charged dust grains of opposite polarity, nonextensivity of electrons and ions, and different dusty plasma parameters have significantly modified the fundamental properties (viz., polarity, amplitude, width, etc.) of the shock waves. The properties of DASHWs in nonplanar geometry are found tobe significantly different from those in one-dimensional planar geometry. The findings of our results from this theoretical investigation may be useful in understanding the nonlinear features of localized electrostatic disturbancesin both space and laboratory dusty plasmas.

    • Entanglement of a nonlinear two two-level atoms interacting with deformed fields in Kerr medium


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      In this paper we investigate the entanglement dynamics between two two-level atoms interacting with two coherent fields in two spatially separated cavities which are filled with a Kerr-like medium. We examine the effect of nonlinear medium on the dynamical properties of entanglement and atomic occupation probabilities in the case of even and odd deformed coherent states. The results show that the deformed fields play important roles in the evolution of entanglement. Also, the results demonstrate that entanglement sudden death, sudden birth and long-distance can be controlled by the deformation and nonlinear parameters.

    • Anisotropic stars obeying Chaplygin equation of state


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      In this work we provide a framework for modelling compact stars in which the interior matter distribution obeys a generalised Chaplygin equation of state. The interior geometry of the stellar object is described by a spherically symmetric line element which is simultaneously co-moving and isotropic with the exterior space–time being vacuum. We are able to integrate the Einstein field equations and present closed form solutions which adequately describe compact strange star candidates such as 4U 1538-52, PSR J1614-2230, Vela X-1 and Cen X-3 (Gangopadhyay $\it{et al, Mon. Not. R. Astron. Soc.} \bf{431}$, 3216 (2013)).

    • Optical characteristics of a RF DBD plasma jet in various $\rm{Ar/O_{2}}$ mixtures


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      In this paper, using the optical emission spectroscopy (OES) technique, the optical characteristics of a radiofrequency (RF) plasma jet are examined. The $\rm{Ar/O_2}$ mixture is taken as the operational gas and, the Ar percentage in the $\rm{Ar/O_2}$ mixture is varied from 70% to 95%. Using the optical emission spectrum analysis of the RF plasma jet, the excitation temperature is determined based on the Boltzmann plot method. The electron density in the plasma medium of the RF plasma jet is obtained by the Stark broadening of the hydrogen Balmer $H_\beta$. It is mostly seen that, the radiation intensity of Ar $\rm{4p\rightarrow 4s}$ transitions at higher argon contributions in $\rm{Ar/O_2}$ mixture is higher. It is found that, at higher Ar percentages, the emission intensities from atomic oxygen (O) are higher and, the line intensities from the argon atoms and ions including O atoms linearly increase. It is observed that the quenching of $\rm{Ar}^\ast$ with $\rm{O}_2$ results in higher O species with respect to $\rm{O}_2$ molecules. In addition, at higher percentages of Ar in the $\rm{Ar/O_2}$ mixture, while the excitation temperature is decreased, the electron density is increased.

    • Neutron energy measurement for practical applications


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      Industrial demand for neutrons constrains careful energy measurements. Elastic scattering of monoenergetic $\alpha$-particles from neutron collision enables neutron energy measurement by calculating the amount of deviation from the position where collision takes place. The neutron numbers with specific energy is obtained by counting the number of $\alpha$-particles in the corresponding location on the charged particle detector. Monte Carlo simulation and COMSOL Multiphysics5.2 are used to account for one-to-one collision of neutrons with $\alpha$-particles.

    • Activation cross-section data for $\alpha$-particle-induced nuclear reactions on natural vanadium for practical applications


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      Excitation functions for α-induced reactions on natural vanadium were measured in the energy range up to 20 MeV. The stacked-foil activation technique was used. The experimental results were compared with the theoretical calculations using EMPIRE-3.1, EMPIRE-3.2.2 and TENDL 2015, and with earlier experimental results. Thick target yields were calculated for the production of $^{54}\rm{Mn}$ and for the associated impurity $^{52}\rm{Mn}$.

    • Role of hydrothermal temperature on crystallinity, photoluminescence, photocatalytic and gas sensing properties of $TiO_{2}$ nanoparticles


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      $TiO_{2}$ nanoparticles were synthesised by hydrothermal method. The degree of crystallinity and phase purity were confirmed from the Raman spectra and X-ray diffraction. By increasing the hydrothermal temperature,crystallinity and AC conductivity of the $TiO_{2}$ nanoparticles increase. Nitrogen adsorption–desorption measurements confirmed that the samples were mesoporous with an average pore diameter of 4.4–7.45 nm. Photocatalytic activity of $TiO_{2}$ nanoparticles was evaluated and the sample hydrothermally treated at 160$^\circ$C has the highest photocatalytic activity. In gas sensing measurements, sensitivity increases as a function of concentration and the response to ethanol vapour was better compared to other gases for the sample synthesised at 160$^\circ$C.

    • Volterra integral equation-factorisation method and nucleus–nucleus elastic scattering


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      An approximate solution for the nuclear Hulthén plus atomic Hulthén potentials is constructed by solving the associated Volterra integral equation by series substitution method. Within the framework of supersymmetry-inspired factorisation method, this solution is exploited to construct higher partial wave interactions. The merit of our approach is examined by computing elastic scattering phases of the $\alpha−\alpha$ system by the judicious use of phase function method. Reasonable agreements in phase shifts are obtained with standard data.

    • Exciton binding energy in a pyramidal quantum dot


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      The effects of spatially dependent effective mass, non-parabolicity of the conduction band and dielectric screening function on exciton binding energy in a pyramid-shaped quantum dot of GaAs have been investigatedby variational method as a function of base width of the pyramid. We have assumed that the pyramid has a square base with area $a \times a$ and height of the pyramid $H = a/2$. The trial wave function of the exciton has been chosen according to the even mirror boundary condition, i.e. the wave function of the exciton at the boundary could be non-zero. The results show that (i) the non-parabolicity of the conduction band affects the light hole (lh) and heavy hole (hh) excitons to be more bound than that with parabolicity of the conduction band, (ii) the dielectric screening function (DSF) affects the lh and hh excitons to be more bound than that without the DSF and (iii) the spatially dependent effective mass (SDEM) affects the lh and hh excitons to be less bound than that without the SDEM. The combined effects of DSF and SDEM on exciton binding energy have also been calculated. The results are compared with those available in the literature.

    • Shape, size and temperature dependency of thermal expansion, lattice parameter and bulk modulus in nanomaterials


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      A theoretical model is described here for studying the effect of temperature on nanomaterials. The thermodynamic equation of state (EoS) proposed by Goyal and Gupta in High Temp.-High Press. 45, 163 (2016); Oriental J. Chem. 32(4), 2193 (2016), is extended in the present study using Qi and Wang model [Mater. Chem. Phys. 88, 280 (2004)]. The thermal expansion coefficient is expressed in terms of shape and size and used to obtain the isobaric EoS of nanomaterials for the change in volume $V/V_{0}$. The variation in $V/V_{0}$ with temperature is estimatedfor spherical nanoparticles, nanowires and nanofilms. It is found that the volume thermal expansivity decreases as size of the nanomaterial increases, whereas $V/V_{0}$ increases with temperature across nanomaterials of different sizes. The lattice parameter variation with temperature is studied in Zn nanowires, Se and Ag nanoparticles. It is found that lattice constant increases with increase in temperature. Also, bulk modulus is found to increase with temperature in nanomaterials. The results obtained from the present model are compared with the available experimental data. A good consistency between the compared results confirms the suitability of the present model for studying thermalproperties of the nanomaterials.

    • Strange non-chaotic attractors in a state controlled-cellular neural network-based quasiperiodically forced MLC circuit


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      In this paper, we report the dynamical transitions to strange non-chaotic attractors in a quasiperiodically forced state controlled-cellular neural network (SC-CNN) based MLC circuit via two different mechanisms, namely the Heagy–Hammel route and the gradual fractalisation route. These transitions were observed through numerical simulations and hardware experiments and confirmed using statistical tools, such as maximal Lyapunov exponent spectrum and its variance and singular continuous spectral analysis. We find that there is a remarkable agreement of the results from both numerical simulations as well as from hardware experiments.

    • Aspects of improved heat conduction relation and chemical processes in 3D Carreau fluid flow


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      This article communicates the numerical consideration of 3D Carreau liquid flow under the impact of chemical responses over a stretched surface. Moreover, the heat transfer exploration is carried out with a view to improve the heat flux relation. This phenomenon is established upon the theory of Cattaneo–Christov heat flux relation that contributes by the thermal relaxation. On exploitation of an appropriate transformation a system of nonlinear ODEs is attained and then elucidated numerically by means of bvp4c scheme. The descriptions of temperature and concentration fields equivalent to the frequent somatic parameters are graphically scrutinised.Our analysis carries that the concentration of the Carreau liquid displays similar tendency and decline as theheterogeneous–homogeneous reaction parameters ($k_{2}, k_{1}$) augment. Furthermore, it is notable that for shear thinning ($n$ & lt; 1) liquid, the influence of local Weissenberg numbers ($We_{1}, We_{2}$) are absolutely conflicting compared with the instance of shear thickening ($n$ & gt; 1) liquid. Additionally, validation of numerical results is done via benchmarking with previously stated limiting cases with two different schemes namely, homotopy analysis method (HAM) and bvp4c scheme. These comparisons initiate a superb correspondence with these outcomes.

    • Impact of autocatalysis chemical reaction on nonlinear radiative heat transfer of unsteady three-dimensional Eyring–Powell magneto-nanofluid flow


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      The pursuit of superior working liquids for heat/mass transfer mechanisms in engineering is on the rise, not only to maximise revenue but also to accommodate heat dissipation or chemical separation under extreme conditions. The addition of a small amount of nanoparticle, i.e. a product called nanofluid, has been initiated over the last decade. In this paper, we present a comprehensive study of unsteady three-dimensional (3D) flow of the Eyring–Powell nanofluid under convective and nanoparticles mass flux conditions. The effects of constructive/destructivechemical reactions and nonlinear thermal radiation are also considered in the Eyring–Powell nanofluid model. Additionally, suitable transformations are utilised to obtain coupled ordinary differential equations (ODEs) from the system of partial differential equations (PDEs) and the numerical solution of the system of the coupled ODEs is obtained by means of the bvp4c scheme. The obtained numerical data are plotted for the temperature and concentration profiles of nanofluids for various and converging values of physical parameters. Our findings demonstrate that the temperature of the Eyring–Powell nanofluid fall-off by changing the heat sink parameter. Furthermore, it is perceived from the sketches that the concentration of Eyring–Powell magneto-nanofluid decays at higher values of chemical reaction parameter.

    • Design and study on square lattice-based photonic crystal fibre under different air holes for supercontinuum generation


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      In this work, a comparative study is made on photonic crystal fibre (PCF) with circular and elliptical air holes in square lattice for supercontinuum generation. Using finite-element method analysis in COMSOL MULTIPHYSICS 4.3b software, numerical investigation on optical parameters such as dispersion, confinement loss, birefringence and nonlinearity has been carried out. Change in each optical parameter is observed by varying the radius of the circular air hole and the radius of the major axis of the elliptical air hole. The supercontinuum generation for the proposed PCF is also numerically simulated and studied under different power and pulse width.

    • Lasing without population inversion in a four-level Y-type configuration in double quantum dot system


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      This work discusses lasing without inversion in Y-scheme in a double quantum dot nanostructure. This new type of lasing, which results from the quantum interference of spontaneous emission components, was not discussed earlier in quantum dot nanostructures. It is found that both pumping and cycling fields control the laser emission. The decrease of the cycling detuning increases the possibility of lasing. Probe detuning controls the width of the absorption bath (electromagnetic-induced transparency window) of this structure. This phenomenon canhave an interesting application for developing sources of coherent radiation in a region of electromagnetic spectrum where the implementation of traditional laser schemes is difficult.

    • Aharonov–Bohm effect in the ghost interference


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      In the ghost interference experiment, a pair of entangled particles is sent in the opposite directions; one of the particles passes through a Young double-slit while the other continues its way freely. It turns out that the particles passing through the slits do not show any first-order interference while those propagating freely constitute an interference pattern when they are detected in coincidence with those which pass through the slits and detectedat a fixed position. In this work, we consider that the particles are charged and the effect of a confined magnetic field is analysed between the slits in an Aharonov–Bohm configuration.

    • Shape, size and phonon scattering effect on the thermal conductivity of nanostructures

      M GOYAL

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      A phenomological model is described here to study the effect of size, shape and phonon scattering on the thermal conductivity of nanostructures. Using the classical model proposed by Guisbiers et al (Phys. Chem. Chem. Phys. 12, 7203 (2010), J. Phys. Chem. C 112, 4097 (2008)) in terms of the melting temperature of nanostructures, the expression for variation of thermal conductivity is obtained in terms of shape and size parameter. An additional term is included in the expression of thermal conductivity to consider the impact of phonon scattering due to the surface roughness with a decrease in size. The expression of thermal conductivity is obtained for spherical nanosolids, nanowires and nanofilms. The thermal conductivity is found to decrease in nanostructures in comparison with the counterpart bulk material. The values of thermal conductivity obtained from the present model are found to be close to the available experimental data for different values of roughness parameter which verifies the suitability of the model.

    • One-dimensional nuclear design analyses of the SST-2


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      Steady State Tokamak-2 (SST-2) will be an intermediate fusion machine before Indian DEMOnstration power reactor (DEMO) development to realise the reactor technologies. It is designed for fusion gain Q = 5 andfusion power in the range of 100–300 MW. Nuclear design analyses of SST-2 machine have been carried out to support the conceptual design work. Analyses have been carried out for two breeding blanket concepts: Indian lead–lithium ceramic breeder (LLCB) and helium-cooled ceramic breeder (HCCB). The analyses assess the tritium production and radiation shielding capability of the machine referring to the engineering design parameters. In this study, one-dimensional radiation transport calculations have been performed to assess the SST-2 nuclear responses for 1 full power year (FPY) operation. Nuclear responses such as tritium breeding ratio (TBR), various radiation loads to toroidal field (TF) coil have been calculated to obtain the radial build-up of SST-2 capable of breeding tritium and satisfying the shielding requirements. The assessment has been made using the ANISEN code andFENDL 2.1 cross-section library. It is observed that the TBRs with LLCB and HCCB blankets are 0.85 and 0.94, respectively. Shielding calculations confirm that the radial build is sufficient to protect the superconducting TF coils for 1 FPY.

    • Numerical interpretation of autocatalysis chemical reaction for nonlinear radiative 3D flow of cross magnetofluid


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      A simple relation of chemical processes for three-dimensional flow of a cross magnetofluid over bidirectional stretched surface is constructed. The impact of convective heat transport in the manifestation of non-linear thermal radiation and features of heat source–sink are also considered for heat transfer mechanism.Furthermore, in this research paper, the innovative relation between heterogeneous and homogeneous responses with equivalent diffusivities for reactant and autocatalysis is exploited. Apposite alterations are guaranteed to obtain ordinary differential equations (ODEs) with high nonlinearity. Numerically, the bvp4c technique is exploited to the interpret the structure of ODEs. Portrayals of temperature and concentration for cross liquid equivalent to abundant somatic parameters are presented graphically as well as in tabular form. Our results reveal that the temperature of the cross fluid decreases with fluctuation in the heat sink parameter. Furthermore, it is perceived from the figuresthat the concentration of the cross fluid reduces for higher values of chemical reaction parameters.

    • Heat transfer enhancement for Maxwell nanofluid flow subject to convective heat transport


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      Nanoliquids possess remarkable features that have fascinated numerous researchers because of their utilisation in nanoscience and nanotechnology. A mathematical relation for the two-dimensional flow of Maxwell nanoliquid over a stretching cylinder is established. Buongiorno’s relation is considered here to visualise the impact of Brownian moment and thermophoresis mechanisms on Maxwell liquid. The convective heat transport is deliberated for heat transfer mechanisms. Transformation procedure yields nonlinear differential system which is then computed through the homotopic approach. The results obtained are studied in detail in relation to somatic parameters. It is notable that the velocity of Maxwell liquid shows conflicting behaviour for curvature parameter $\alpha$ and Deborah number $\beta$. Moreover, the liquid temperature increases for increased values of Brownian motion $N_{b}$ and thermophoresis parameter $N_{t}$ . Additionally, the authentication of numerical consequences is prepared via benchmarking with formerly identified restrictive circumstances and we initiate a splendid communication with these results.

    • Theoretical aspects of thermophoresis and Brownian motion for three-dimensional flow of the cross fluid with activation energy


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      The current review proclaims the forced convective flow and heat–mass transfer characteristics of cross nanofluid past a bidirectional stretched surface. The most significant aim of the current review is to incorporatethe features of Buongiorno relation, activation energy, nonlinear thermal radiation and heat sink–source for a three-dimensional flow of the cross fluid. Appropriate transformations are employed to transform the modelledpartial differential equations (PDEs) of momentum, temperature and concentration into coupled nonlinear ordinary differential equations (ODEs). The governing boundary value problem is numerically integrated with the help of bvp4c scheme. The obtained numerical data are plotted for the temperature and concentration profiles of nanofluid for various converging values of physical parameters. The dependence of increasing thermophysical parameters on temperature and concentration profiles of the cross nanofluid is graphically demonstrated. Furthermore, detailedstudy reveals that the concentration of the cross nanofluid decreases for increasing values of Brownian motion parameter. It is also perceived from the sketches that the concentration of the cross nanofluid decreases for higher values of chemical reaction parameter. The validity of the achieved numerical outcomes is ensured by making a comparison with the existing work as special cases.

    • Beyond the conventional collisional absorption of laser light in under-dense plasma: A particle-in-cell simulation study

      M KUNDU

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      Collisional absorption of laser light in an under-dense plasma is studied by particle-in-cell (PIC) simulation with Monte Carlo binary Coulomb collisions between charge particles. For a given plasma thickness of a few times the wavelength of 800 nm laser, fractional absorption ($\alpha$) of the laser light due to Coulomb collisions (mainly between electrons and ions) is calculated at different electron temperature $T_{e}$ with a total velocity $v = (v^{2}_{th} + v^{2}_{0}/2)^{1/2}$ dependent Coulomb logarithm ln $\Lambda(v)$, where $v_{th}$ and $v_{0}$ are thermal and ponderomotive velocity of an electron. In the low-temperature regime ($Te \lesssim 15 eV$), it is found that $\alpha$ increases with increasing laser intensity $I_{0}$ up to a maximum corresponding to an intensity $I_{c}$, and then it drops (approximately) obeying the conventional scaling of $\alpha \varpropto I^{−3/2}_{0}$ when $I_{0}$ > $I_{c}$. Such a non-conventional increase of $\alpha$ with $I_{0}$ in the low intensity regime was demonstrated earlier in experiments, and recently explained by classical and quantum models [Phys. Plasmas 21, 13302 (2014); Phys. Rev. E 91, 043102 (2015)]. Here, for the first time, we report this non-conventional collisional laser absorption by PIC simulation, thus bridging the gap between models, simulations, and experimental findings. Moreover, electron energy distributions naturally emanating during the laser interaction(in PIC simulations) are found to be anisotropic and non-Maxwellian in nature, leading to some deviations from the earlier analytical predictions.

    • C-matrix and invariants in chemical kinetics: A mathematical concept


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      To treat a realistic chemical system, such as a liquid phase dehydrogenation reaction, a chemical scheme, which describes the chemical kinetics in terms of the small number of reaction progress variables is needed. Based onthe matrix algebra, we analyse the key components, elements and reactions in the mechanism, C-matrix. Reduction techniques exploit the time-scale separation into fast and slow modes by computing the dimension reduced model via the elimination of fast mode subjecting them to the slow one. The two-step reversible reaction mechanism is considered for model reduction and to simplify the complexity of reaction mechanisms. They give a meaningful picture, but for maximum clarity, the phase flow of the solution trajectories near the equilibrium point is exploited. The Lyapunov function is applied for the stability analysis. To describe the physical behaviour of the reaction mechanism, graphical results are measured while refinement of the initial approximation is tabulated at the end.

    • Numerical solution of regularised long ocean waves using periodised scaling functions


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      In this paper, a numerical technique for solving the regularised long wave equation (RLW) is presented using a wavelet Galerkin (WG) method in space and a fourth-order Runge–Kutta (RK) technique in time.We study the convergence analysis of the obtained numerical solutions and investigate the results for the motions of doubleand single solitary waves, undular bores and conservation properties of mass, energy and momentum in order to verify the applicability and performance of the proposed method. Simulation results are further compared with the known analytical solutions and some previous published numerical results. It is concluded that the present method remarkably improves the accuracy of the Galerkin-based methods for numerically solving a large class of nonlinear and weakly dispersive ocean waves.

    • Assessment of the mass attenuation coefficients of granite, basalt, andesite and tuff stones with the Geant4 model of a high-purity germanium detector


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      In this work, the radiation shielding properties of various natural stones, such as granite, basalt, andesite and tuff, were determined by using Monte-Carlo simulations performed with the Geant4 model of a high-purity germanium (HPGe) detector.Mass attenuation coefficients were calculated for $\gamma$ -ray energies of 80.9, 140.5, 356.5, 661.6, 1173.2 and 1332.5 keV and for the sample thicknesses between 1 and 7 cm. The results of this study indicate that the stone samples have lower mass attenuation values varying in the range from −28.8% to −3.7% compared to lead. Among the measured stone samples, the mass attenuation values of tuff stone are closest to lead (above661.6 keV).

    • The Weyl equation under an external electromagnetic field in the cosmic string space–time


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      In this paper we have considered a massless spinor Dirac particle in the presence of an external electromagnetic field in the cosmic string space–time. To study the Weyl equation in the cosmic string framework using the general definition of Laplacian in the curved space, elements of covariant derivative have been constructed and the Weyl equation has been rewritten in the considered framework. Then we have obtained the equation ofenergy eigenvalues by using the Nikiforov–Uvarov (NU) method. The wave function has been obtained in terms of Laguerre polynomials. An important result obtained is that the degeneracy of the Minkowski space spectral is broken in the transition from Minkowski to cosmic string space.

    • On physical limitations of mathematical constructions used in mathematical models


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      Physical limitations of mathematical constructions are discussed, which should be taken into account in developing or modifying mathematical models. We begin with consideration of the method of describing physical objects using numbers and restrictions followed from this method. Next, we formulate some general recommendations concerning procedures for modifying mathematical models. Since models of physical phenomena are considered, it is natural to provide a physical interpretation for each stage of the model development. Unfortunately, some of transformations used are treated as purely technical tricks, and therefore the question of the physical meaning is not raised in such cases. The lack of physical meaning of some mathematical procedures does not make them unambiguously unacceptable. However, this marks out the place that requires a reasonable interpretation because the final result should possess the physical meaning. Finally, we discuss the issues related to the dimensionality of the space of places of a model. The above-mentioned physical limitations often are left without necessary attention. Sometimes this leads to various undesirable consequences, which may include excessive complication of the problem, an implicit substitution of the declared problem with another one or, finally, the absence of solution of the formulated problem.

    • Numerical treatment of activation energy for the three-dimensional flow of a cross magnetonanoliquid with variable conductivity


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      This research demonstrates the diverse characteristics of the cross fluid in the presence of Lorentz’s forces. Moreover, this work reviews the characteristics of variable diffusivity and variable conductivity. Mathematical modelling of the presented physical model is carried out in the Cartesian coordinate system and the formulated system of partial differential equations (PDEs) is simplified in ordinary differential equations (ODEs). Numerical algorithm leads to solution computations. Velocity, temperature and concentration are numerically analysed for the cross fluid. Outcomes of the current physical model are presented through graphical data and in tabular form. It is noted that variable conductivity and variable diffusivity significantly affect heat–mass transport mechanisms. Furthermore, graphical analysis reveals that the concentration of the cross nanofluid increase for increased values of variable diffusivity. Furthermore, this research reveals that concentration distribution is a reducing function of chemical reaction parameters.

    • Analysis with relativistic mean-field density distribution of elastic scattering cross-sections of carbon isotopes ($^{10–14,16}\rm{C}$) by various target nuclei

      M AYGUN

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      A microscopic study of elastic scattering of carbon isotopes from different target nuclei at various incident energies is presented by using density distributions derived for $^{10–14,16}\rm{C}$ nuclei using relativistic mean field (RMF) theory. To obtain the real part of the optical potential, the double folding model is used.Woods–Saxon potential is used for the imaginary part. The theoretical results are discussed and compared with each other as well as with the experimental data. It is seen that the agreement between theoretical results and experimental data is very good. Also, new global equations for the imaginary potentials of the $^{10–14,16}\rm{C}$ nuclei are derived from the results of the theoretical analysis.

    • Commissioning and validation of the injector and electron beam transport systems for the IR-FEL at RRCAT


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      The first observation of lasing in an infra-red free electron laser (IR-FEL) at the Raja Ramanna Centre for Advanced Technology has been reported recently with a measured power output, i.e. $\sim10^{5}$ times higher than the expected spontaneous radiation power for the electron beam parameters used in the experiment. IR-FEL design simulations, however, estimate a power gain of $10^{7}$ which is three orders of magnitude higher than the experimentally achieved value. To understand this difference between the measured and the expected power output from the IR-FEL, the electron beam used in the experiments has been characterised and FEL simulations have been repeated after considering the measured electron beam parameters. A reasonably good agreement is obtained between the measured results and those predicted by FEL simulations. Experiments have also been performed to study the expected variation in electron beam properties over a macropulse, which should be minimum for an oscillator FEL like the IR-FEL. This paper reports the results from the experiments for characterisation of the electron beam in the IR-FEL set-up and the results from FEL simulations, considering these measured electron beam parameters.

    • Some exactly solvable $\mathcal{PT}$ -invariant potentials with real spectra via the (extended) Nikiforov–Uvarov method


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      The (extended) Nikiforov–Uvarov method is employed to find exact solutions of the Schrödinger operator for three $\mathcal{PT}$ -invariant potentials (periodic exponential, cotangent and $\mathcal{PT}$ -symmetric harmonic plus centrifugal). It is shown that their corresponding Schrödinger operators can exhibit real energy eigenvalues. The results are compared with similar works but with different methods. The comparisons led to Rodrigues formulas of some functions of interest. The eigenfunctions of these examples are expressed in terms of Hankel functions, Romanovski polynomials and Heun functions. The method is proved to be felicitous and leads to closed energy formulas for the potentials under study.

    • Investigation of the radiation shielding capability of $\rm{xPbO–(50 − x)BaO–50B_{2}O_{3}}$ glass system using Geant4, Fluka, WinXCOM and comparison of data with the experimental data


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      In this study, mass attenuation coefficient ($\mu_{\rm{m}}$), transmission fractions ($T$), effective atomic numbers ($\rm{Z_{eff}}$) and half-value layer (HVL) of the $\rm{xPbO–(50 − x)BaO–50B_{2}O_{3}}$ (where x = 10, 20, 30, 40 mol%) glass system have been determined from the Monte Carlo simulations carried out with Geant4 and Fluka simulation toolkits and WinXCOM database software. The calculated results were compared with the experimentally obtained $\mu_{m}$ values of the selected glass in order to validate the Geant4 model of HPGe detector and Fluka model of NaI(Tl) detectors. $T$, $\rm{Z_{eff}}$ and $\rm{HVL}$ shielding parameters of the studied glass system indicate that increase of PbO content from 10 to 40% results in a better shielding behaviour thanks to the high atomic number of lead.

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