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      Volume 80, Issue 2

      February 2013,   pages  187-367

    • Fermionic particles with position-dependent mass in the presence of inversely quadratic Yukawa potential and tensor interaction

      M K Bahar F Yasuk

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      Approximate solutions of the Dirac equation with position-dependent mass are presented for the inversely quadratic Yukawa potential and Coulomb-like tensor interaction by using the asymptotic iteration method. The energy eigenvalues and the corresponding normalized eigenfunctions are obtained in the case of position-dependent mass and arbitrary spin-orbit quantum number k state and approximation on the spin-orbit coupling term.

    • Covariant anomalies and Hawking radiation from Kaluza–Klein AdS black holes

      Chuan-Yi Bai

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      In this paper, Hawking radiation is studied from four-dimensional (4D) Kaluza–Klein (KK) AdS black holes via the method of anomaly cancellation. The {|bf KK-AdS} black hole considered is a non-extremal charged rotating solution in the theory of 4D gauged supergravity. Its Hawking fluxes of electric charge, angular momentum and energy momentum tensor are derived here. Our results support the common view that Hawking radiation is the quantum effect arising at the event horizon.

    • Generalized entropy production fluctuation theorems for quantum systems

      Subhashis Rana Sourabh Lahiri A M Jayannavar

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      Based on trajectory-dependent path probability formalism in state space, we derive generalized entropy production fluctuation relations for a quantum system in the presence of measurement and feedback. We have obtained these results for three different cases: (i) the system is evolving in isolation from its surroundings; (ii) the system being weakly coupled to a heat bath; and (iii) system in contact with reservoir using quantum Crooks fluctuation theorem. In Case (iii), we build on the treatment carried out by H T Quan and H Dong [arXiv/cond-mat:0812.4955], where a quantum trajectory has been defined as a sequence of alternating work and heat steps. The obtained entropy production fluctuation theorems (FTs) retain the same form as in the classical case. The inequality of second law of thermodynamics gets modified in the presence of information. These FTs are robust against intermediate measurements of any observable performed with respect to von Neumann projective measurements as well as weak or positive operator-valued measurements.

    • Complete switched modified function projective synchronization of a five-term chaotic system with uncertain parameters and disturbances

      Fei Yu Chunhua Wang Qiuzhen Wan Yan Hu

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      A five-term three-dimensional (3D) autonomous chaotic system with an exponential nonlinear term is reported in this paper. Basic dynamical behaviours of the chaotic system are further investigated. Then a new synchronization phenomenon, complete switched modified function projective synchronization (CSMFPS), for this novel five-term chaotic system with uncertain parameters and disturbances is investigated. This paper extends previous work, where CSMFPS of chaotic systems means that all the state variables of the drive system synchronize with different state variables of the response system. As the synchronization scheme has many combined forms, it is a promising type of synchronization and can provide greater security in secure communication. Based on Lyapunov stability theory, a robust adaptive controller is contrived to acquire CSMFPS, parameter identification and suppress disturbances simultaneously. Finally, the Lorenz system and the new five-term chaotic system are taken as examples and the corresponding numerical simulations are presented to verify the effectiveness and feasibility of the proposed control scheme.

    • Quadrupole moments of low-lying baryons with spin $-\dfrac{1}{2}^{+}$ spin$-\dfrac{3}{2}^{+}$ and spin $-\dfrac{3}{2}^{+} \rightarrow \dfrac{1}{2}^{+}$ transitions

      Neetika Sharma Harleen Dahiya

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      The chiral constituent quark model (𝜒 CQM) with general parametrization (GP) method has been formulated to calculate the quadrupole moments of the spin $-\dfrac{3}{2}^{+}$ decuplet baryons and spin $-\dfrac{3}{2}^{+} \rightarrow \dfrac{1}{2}^{+}$ transitions. The implications of such a model have been investigated in detail for the effects of symmetry breaking and GP parameters pertaining to the two- and three-quark contributions. It is found that the 𝜒CQM is successful in giving a quantitative and qualitative description of the quadrupole moments.

    • Equilibrium and pre-equilibrium calculations of cross-sections of $(p, xn)$ reactions on 89Y, 90Zr and 94Mo targets used for the production of 89Zr, 90Nb and 94Tc positron-emitting radionuclides

      R Baldik H Aytekin E Tel

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      In this study, the pre-equilibrium and equilibrium calculations of cross-sections of 89Y$(p, xn)$, 90Zr$(p, xn)$ and $^{94}Mo$(p, xn)$ reactions, which were used for the production of 89Zr, 90Nb and 94Tc positron-emitting radioisotopes, have been investigated. Pre-equilibrium calculations have been performed at different proton incident energies by using the hybrid, geometry-dependent-hybrid and full exciton models. The Weisskopf–Ewing model is used for calculating the equilibrium effects at the same incident energies. The calculated results have been discussed and compared with the experimental results.

    • Measurement, analysis and correction of the closed orbit distortion in Indus-2 synchrotron radiation source

      Riyasat Husain A D Ghodke Surendra Yadav A C Holikatti R P Yadav P Fatnani T A Puntambekar P R Hannurkar

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      The paper presents the measurement, analysis and correction of closed orbit distortion (COD) in Indus-2 at 550 MeV injection energy and 2 GeV synchrotron radiation user run energy. The measured COD was analysed and fitted to understand major sources of errors in terms of the effective quadrupole misalignments. The rms COD was corrected down to less than 0.6 mm in both horizontal and vertical planes. A golden orbit was set for the operating synchrotron radiation beamlines. With COD correction, the injection efficiency at 550 MeV was improved by $\sim 50$% and the beam lifetime at 2 GeV was increased by $\sim8$ h. In this paper, the method of global COD correction based on singular value decomposition (SVD) of the orbit response matrix is described. Results for the COD correction in both horizontal and vertical planes at 550 MeV injection energy and at 2 GeV synchrotron radiation user run energy are discussed.

    • Planar electron beams in a wiggler magnet array

      Arti Hadap K C Mittal

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      Transport of high current (∼kA range with particle energy $\sim 1$ MeV) planar electron beams is a topic of increasing interest for applications in high-power (1–10 GW) and high-frequency (10–20 GHz) microwave devices such as backward wave oscillator (BWO), klystrons, gyro-BWOs, etc. In this paper, we give a simulated result for transport of electron beams with velocity $V_{b} = 5.23 \times 10^{8}$ cm s-1 , relativistic factor $\gamma = 1.16$, and beam voltage = ∼80 kV in notched wiggler magnet array. The calculation includes self-consistent effects of beam-generated fields. Our results show that the notched wiggler configuration with ∼6.97 kG magnetic field strength can provide vertical and horizontal confinements for a sheet electron beam with 0.3 cm thickness and 2 cm width. The feasibility calculation addresses to a system expected to drive for 13–20 GHz BWO with rippled waveguide parameters as width $w = 3.0$ cm, thickness $t = 1.0$ cm, corrugation depth $h = 0.225$ cm, and spatial periodicity $d = 1.67$ cm.

    • Drift wave in pair-ion plasma

      Samiran Ghosh Nikhil Chakrabarti Manoranjan Khan M R Gupta

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      The conditions for the existence of low-frequency electrostatic drift wave in pair-ion plasma are discussed. It is shown that the temperature and/or mass difference of both species could produce drift wave in a pair-ion plasma. The results are discussed in the context of the fullerene pair-ion plasma experiment.

    • Plasma excitations in a single-walled carbon nanotube with an external transverse magnetic field

      K A Vijayalakshmi T P Nafeesa Baby

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      The effect of different uniform transverse external magnetic fields in plasma frequency when propagated parallel to the surface of the single-walled metallic carbon nanotubes is studied. The classical electrodynamics as well as Maxwell’s equations are used in the calculations. Equations are developed for both short- and long-wavelength limits and the variations are studied graphically.

    • Dust-acoustic solitons in quantum plasma with kappa-distributed ions

      Mehran Shahmansouri

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      Arbitrary amplitude dust-acoustic (DA) solitary waves in an unmagnetized and collisionless quantum dusty plasma comprising cold dust particles, kappa (𝜅)-distributed ions and degenerate electrons are investigated. The influence of suprathermality and quantum effects on the linear dispersion relation of DA waves is investigated. Then, the effect of 𝜅-distributed ions and degenerate electrons on the existence domain of solitons is discussed in the space of ($M, f$). The comparison of the existence domain for higher and lower values of 𝜅 shows that suprathermality results in propagation of solitons with lower values of Mach number, and the quantum effects, lead to a higher values of Mach number. The existence domain of solitons for nondegenerate 𝜅-distributed electrons is considered for comparison with effect of degenerate electrons. Also, we found that the Sagdeev potential well becomes deeper and wider as $\varepsilon_{F-i}$ decreases, as for lower 𝜅 values, the influence of quantum effects on the Sagdeev pseudopotential profile is smaller.

    • A tentative model for estimating the compressibility of rock-salt AgCl$_{x}$ Br$_{1−x}$ alloys

      Vassiliki Katsika-Tsigourakou Efthimios S Skordas

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      Ab initio detailed calculations of the elastic properties of AgCl$_{x} Br$_{1−x}$ alloys were recently made using density-functional perturbation theory and by employing the virtual crystal approximation or by means of the full potential linearized augmented plane wave method. Here, we suggest a simple theoretical model that enables estimation of isothermal compressibility of these alloys in terms of the elastic data of end-members alone. The calculated values are in satisfactory agreement with the experimental ones. The present model makes use of an early suggestion that interconnects Gibbs energy for the formation and/or migration of defects in solids with bulk properties.

    • Effect of Al doping on microstructure and optical band gap of ZnO thin film synthesized by successive ion layer adsorption and reaction

      S Mondal S R Bhattacharyya P Mitra

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      Thin films of pure and aluminum-doped zinc oxide (AZO) were deposited on glass substrates from ammonium zincate bath following a chemical dipping technique called successive ion layer adsorption and reaction (SILAR). Characterization techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive X-rays (EDX) were used to investigate the effect of Al doping on the microstructure of AZO films. Particle size analysis using X-ray line broadening shows marginally increasing trend with increasing Al impurity. The average particle size for pure ZnO is 22.75 nm. It increases to 24.26 nm for 1% AZO film and 25.13 nm for 2% AZO film. Incorporation of Al was confirmed from elemental analysis using EDX. SEM micrograph shows that pure ZnO particles are spherical shaped. However, AZO films show particles with off-spherical shape with compact interconnected grains. The value of band gap for pure ZnO is 3.229 eV and it increases to 3.29 eV for 1% AZO indicating a blue-shift for 1% AZO film. However, for 2% AZO film, a decrease in band gap compared to pure ZnO is observed indicating a red-shift of fundamental absorption edge. Electrical resistance shows an initial decrease with increasing Al content. With further enhancement of Al incorporation, the resistance increases.

    • Spin-dependent rectification in the C59N molecule

      Mahvash Arabi Darehdor Nasser Shahtahmasebi

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      Coherent spin-dependent electron transport is investigated in three conditions: (1) a C60 molecule is connected to two ferromagnetic (FM) electrodes symmetrically, (2) a C59N molecule is connected to two FM electrodes symmetrically and (3) a C59N molecule is connected to two FM electrodes asymmetrically. This work is based on a single-band tight-binding model Hamiltonian and the Green’s function approach with the Landauer–Buttiker formalism. Electrodes used in this study are semi-infinite FM electrodes with finite cross-section. Obvious rectification effect is observed in the C59 N molecule which is connected to the FM electrodes asymmetrically. This effect is more in the P alignment of FM electrodes than in AP alignment of FM electrodes. This study indicates that the rectification behaviour is due to the asymmetry in molecule and junctions. Also in this investigation tunnel magnetoresistance (TMR) is calculated for these molecules. Asymmetry is observed in TMR of C59N which is coupled to the electrodes asymmetrically due to asymmetric junctions, but TMR of C60 is symmetric.

    • Complex network perspective on structure and function of Staphylococcus aureus metabolic network

      L Ying D W Ding

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      With remarkable advances in reconstruction of genome-scale metabolic networks, uncovering complex network structure and function from these networks is becoming one of the most important topics in system biology. This work aims at studying the structure and function of Staphylococcus aureus (S. aureus) metabolic network by complex network methods. We first generated a metabolite graph from the recently reconstructed high-quality S. aureus metabolic network model. Then, based on `bow tie' structure character, we explain and discuss the global structure of S. aureus metabolic network. The functional significance, global structural properties, modularity and centrality analysis of giant strong component in S. aureus metabolic networks are studied.

    • Studying the cosmological apparent horizon with quasistatic coordinates

      Rui-Yan Yu Towe Wang

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      This article aims at a natural generalization of the static coordinates to the $(n + 1)$-dimensional Friedmann–Lemaître–Robertson–Walker (FLRW) Universe. After demonstrating a no-go theorem, we put forward the quasistatic coordinates for the FLRW Universe. Then, the quasistatic coordinates are utilized to study the unified first law and the scalar-type perturbations on the cosmological apparent horizon.

    • Particle–particle Tamm–Dancoff approximation and particle–particle random phase approximation calculations for 18O and 18F nuclei

      Alih Taqi Al-Bayati

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      The nuclear structures of 18O and 18F nuclei are studied using particle–particle Tamm–Dancoff approximation (pp TDA) and particle–particle random phase approximation (pp RPA). All possible single-particle states of the allowed angular momenta are considered in the 0p and 1s–0d shells. The Hamiltonian is diagonalized in the presence of Warburton and Brown interactions. The results containing energy-level schemes and transition strength $B(E2)$ are compared with the available experimental data.

    • Soliton solutions of some nonlinear evolution equations with time-dependent coefficients

      Hitender Kumar Anand Malik Fakir Chand

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      In this paper, we obtain exact soliton solutions of the modified KdV equation, inho-mogeneous nonlinear Schrödinger equation and $G(m, n)$ equation with variable coefficients using solitary wave ansatz. The constraint conditions among the time-dependent coefficients turn out as necessary conditions for the solitons to exist. Numerical simulations for dark and bright soliton solutions for the mKdV equation are also given.

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