• Volume 29, Issue 2

      August 1987,   pages  1-223

    • Enhancement of thermopower in the highTc superconductor YBa2Cu3O7 and related compounds

      R Srinivasan V Sankaranarayanan N P Raju S Natarajan U V Varadaraju G V Subba Rao

      More Details Abstract Fulltext PDF

      The absolute thermopower of single phase YBa2Cu3O7 and Y0.8Er0.2Ba2Cu3O7 has been measured in the range 250 K to the superconducting transition temperature. It is found that these compounds show a large enhancement of thermopower in the range 150 K down toTc. This enhancement shows a steep exponential drop as the temperature increases from the transition temperature. The temperature variation of the enhancement is too steep to be accounted for by electron-phonon or electron-local structural excitation mechanisms.

    • Wave reflection from inhomogeneous media at normal incidence

      Philip D’Souza

      More Details Abstract Fulltext PDF

      Wave reflection from a medium with continuously varying refractive index is examined. A differential equation is developed, the solution of which yields the back-reflected part of a wave of unity amplitude incident on a non-homogeneous medium at normal incidence.

    • Adler-Bardeen theorem in path integral formulation

      Satish D Joglekar Anuradha Misra

      More Details Abstract Fulltext PDF

      The higher order contributions to Jacobian in Fujikawa’s path integral framework is considered and the form of anomaly equation in higher orders is established. An argument for the Adler-Bardeen theorem in this formulation is given.

    • A search for colour van der Waals interaction

      C V K Baba A Roy

      More Details Abstract Fulltext PDF

      It is suggested that the strength of nuclear colour van der Waals interaction, if present, can be determined by measuring deviations from Rutherford scattering of charged hadrons from nuclei, at energies well below the Coulomb barrier. Experimental limit on the strength of such a potential is obtained asλ<50, when the colour van der Waals potential is given byV(r)=λ(hc/r0)(r0/r)7, withr0, the scaling length, taken as 1 fm. This limit is obtained from an analysis of existing experiments and by performing scattering experiments of 3–4.6 MeV protons from a208Pb target.

    • Fluctuations in12C+24Mg elastic and inelastic scattering

      B Ghosh R Singh

      More Details Abstract Fulltext PDF

      The data on the ϑc.m.=180° excitation functions of12C+24Mg,12C* (4.43 MeV)+24Mg and12C+24Mg*(1.36 MeV) from 12.27 to 22.80 MeV, 16.53 to 27.47 MeV, and 11.33 to 26.40 MeV(c.m.) respectively have been subjected to statistical analysis. The effect of averaging interval, employed for data reduction, on the coherence widths as obtained from the autocorrelation function has been studied. The fluctuating features of the cross-sections turn out to be consistent with the statistical model expectations.

    • Laser optogalvanic spectrum of pure bromine discharge

      Vinod Kumar A K Rai D K Rai

      More Details Abstract Fulltext PDF

      Doppler limited laser optogalvanic (LOG) spectra are obtained by irradiating a bromine discharge with a cw dye laser. The discrete bands of the Br2B-X system appear superimposed on a strong continuum. The LOG spectrum is closely identical with the absorption/emission spectrum of Br2. Some extra bands and assigned in theB-X system are also observed and their vibrational quantum number assignment is given.

    • Holographic grating based Ebert spectrograph

      N C Das M V R K Murty

      More Details Abstract Fulltext PDF

      In this paper we discuss the aberration properties and design procedure of in-plane Ebert spectrograph using conventional as well as holographic diffraction gratings. In both cases the gratings are situated at the well-known √3-position so that the spectrum can be recorded on a flat surface. It has been found that the holographic grating system has better resolution than the conventional grating system. The design parameters of a medium sized holographic grating spectrograph in which a concave spherical mirror is mounted in the off-axis configuration have been specified. The performance of the spectrograph has been evaluated by plotting spot diagram.

    • On the valence instability in CeAl2

      T G Ramesh W B Holzapfel

      More Details Abstract Fulltext PDF

      This paper reports the observation of an isostructural electronic phase transition in CeAl2 near 77 Kbar pressure at ambient temperature. The present volume compression data obtained under truly hydrostatic pressure conditions gives a clear indication of the first order nature of this phase transformation.

    • Electrical second harmonic generation by (Pbx-Ba1−x)TiO3 and (Pbx-Sr1−x)TiO3 in the autostabilized state

      V M Jamadar T A Patil S H Chavan

      More Details Abstract Fulltext PDF

      The temperature autostabilizing nonlinear dielectric element (TANDEL) effect and second harmonic generation have been studied in the ferroelectric solid solutions of (Pbx-Ba1−x)TiO3 and (Pbx-Sr1−x)TiO3 near the Curie temperature used as TANDEL. The generated second harmonics are linear for low d.c. biasing fields with zero off-set while they decrease sharply at higher d.c. biasing fields. The results show that these solid solutions might be used as TANDEL elements.

    • Theoretical evaluation of the probability of success of the quasi-anomalous method

      K Chinnakali S Parthasarathy N Elango

      More Details Abstract Fulltext PDF

      Theoretical expressions for the probability of success of the quasi-anomalous method have been derived for triclinic, monoclinic and orthorhombic crystals containing a few (1, 2 or 3) heavy atoms per asymmetric unit besides a large number of light atoms. The results derived take into account data-truncation due to unobserved reflections. Using the theoretical expressions, tables of probability values for the success of the quasi-anomalous method are obtained as a function of the relevant parametersk andδ12. Corresponding results for triclinic crystals containing many heavy atoms (i.e.P = MN and MC cases) have also been obtained. It is seen that, using suitable heavy atoms to prepare the heavy-atom derivative, probability of success as high as 0.7 could be obtained in the case of proteins containing 1000 to 1500 atoms.

    • Dielectric polarization of the solutions of nitrotoluene and cyclohexane

      M Śliwińska-Bartkowiak B Szurkowski T Hilczer

      More Details Abstract Fulltext PDF

      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.

    • Effective medium in dispersed systems

      R N Pande D R Chaudhary F Gori

      More Details Abstract Fulltext PDF

      A structural analysis of effective medium formed by dispersed systems from the viewpoint of flux modification at large dispersions is presented. The effective medium coefficient is investigated for its parametric dependence and the effective properties are estimated through this dependence. This estimation covers all highly dispersed two-phase systems including the effect of container.

  • Pramana – Journal of Physics | News

    • Editorial Note on Continuous Article Publication

      Posted on July 25, 2019

      Click here for Editorial Note on CAP Mode

© 2017-2019 Indian Academy of Sciences, Bengaluru.