• Volume 19, Issue 1

      July 1982,   pages  1-115

    • An analytical algorithm for the evaluation of two-electron integrals in diatomics: A test calculation with an elliptical basis set

      Dhiman Sinha Rama Basu

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      A purely analytical method designed to compute the two-electron integrals that appear in anab-initio calculation of the electronic structures of diatomic molecules using elliptical basis set is presented. Test calculations are successfully carried out on LiH molecule.

    • The effect of longitudinal-transverse coupling and medium temperature on Cerenkov radiation

      D Nageswar Patro

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      The effect of medium properties on the energy loss suffered by a relativistic charged particle in a dielectric medium generating Cerenkov radiation is discussed. Here we have taken into account the effect of the coupling of the longitudinal (σ) mode with the transverse (λ) mode in the electromagnetic interaction. Calculation shows that the inclusion of λ-σ coupling in the transverse interaction affects significantly the radiation output. However the modification of the radiation due to the thermal state of the system becomes important at very high temperatures such as one finds in astrophysical situations. This temperature effect is negligible at ordinary temperatures and thus is undetectable in laboratory experiments.

    • Linearization stability of coupled gravitational and scalar fields in asymptotically flat space-times

      R V Saraykar

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      Using the methods of Choquet-Bruhat, Fischer and Marsden and using weighted Sobolev spaces developed recently by Christodoulou and Choquet-Bruhat, it is proved that the Einstein field equations coupled with self-gravitating scalar fields are linearization stable in asymptotically flat space-times.

    • Fractional order phase transition in lipid bilayer: dipalmitoyllecithin

      R C Agnihotri C Mehrotra V D Gupta Vandana Srivastava

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      Dipalmitoyllecithin (DPL) shows an order ← → disorder pressure transition which is neither of first order nor of second order but can be treated as a fractional order (3/2 order) transition. The Ising model formalism is adopted for the study of such a system. A suitable equilibrium constant is defined which generates a 3/2 order transition. Transition curves are obtained and compared with the experimental curves of Liu and Kay. Reverse transition curves are also obtained and the system exhibits hysteresis effect. An approximate expression connecting transition pressures at different temperatures is obtained and the calculated and the experimental values are in good agreement.

    • The crystal structure of (L-proline-L-alanine) copper (II)·2·5 H2O

      V Amirthalingam K V Muralidharan

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      The crystal and molecular structure of (L-proline-L-alanine) Cu·2·5 H2O has been determined by the heavy atom method with 583 visually estimated reflexions and refined by full matrix least squares toR=0·101. The crystals are monoclinic witha=16·47 (3),b=7·74 (2),c=9·51 (3) Å andβ=109·7 (5)°; space groupC2;Z=4. The copper coordination is nearly square pyramidal with one water in the basal plane and another occupying the apical together with the aminoN, peptideN and the carboxylO of the dipeptide in the coordination. The Cu-peptide-Cu linkage isvia the hydrogen bonding between the water in the basal plane and the carbonyl O atom of the proline residue. One water is on the 2-fold axis.

    • X-ray energy levels: Deviations between experimental and theoretical values

      Amar Nath Nigam Om Prakash Rajput

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      Energy values ofK, LII andLIII levels calculated by the relativistic self consistent field method have been used to compute the energies of1, 2 lines. These values deviate considerably from the experimental values due to Bearden and Burr. The deviations are discussed and given an empirical fit.

    • An AC magnetic susceptibility bridge and cryostat for the temperature range 2–300 K

      R Ranganathan G Rangarajan

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      A mutual inductance bridge to measure low frequency magnetic susceptibilities of magnetic materials has been constructed. Salient features of the bridge, which uses a variable mutual inductance simulated using operational amplifiers, the cryostat and the coil assembly are described in this paper. The apparatus has been employed for accurate measurement of superconducting transition temperatures and for sensitive detection of magnetic ordering transitions in liquid helium and liquid nitrogen temperature ranges respectively. The bridge has been calibrated to determine the static susceptibility of magnetic materials as a function of temperature.

    • General relations among observables in a large class of neutral-current processes mediated by one, two, or threeZ bosons

      C C Hazra M K Parida

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      Without assuming any symmetry amongμ, e andτ leptons, we consider several neutral current processes involving 73 physical parameters and deduce general relations among them implied by different classes of gauge models with one, two and three neutralZ bosons. In the single-Z boson model there are 60 general relations while the two (three)-boson model leads to 48 (36) relations. If onlyμ-e universality is imposed, the physical parameters reduce to 41 and the single (two)-Z boson model yields 31 (22) relations, while only 13 relations exist for the threeZ boson model. Imposingμ-e-τ universality decreases the number of physical parameters to 18, while the number of relations in the single- and two-Z boson models reduces to 11 and 5, respectively. In these relations are contained those obtained by Hung and Sakurai and Parida and Rajasekaran in the corresponding cases. In addition we obtain some new inequalities among the observable parameters which are to be satisfied by all gauge models.

    • Some comments on quark masses and baryon magnetic moments

      K Babu Joseph M N Sreedharan Nair

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      The suggestion made by Lipkin regarding the quark masses and magnetic moments of baryons is examined in the context of the variable pressure bag model. We find that the exact agreement obtained by Lipkin between theory and experiment in the case ofμ(Λ) cannot be considered accidental, contrary to the scepticism expressed by Minami.

    • Magnetic domain behaviour of MgFe2O4-CoFe2O4 system

      Venkatesh Rao H V Keer

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      Ferrites with the composition Mg1−xCOxFe2O4(0<x≤0·33) were synthesized by solid state reaction between MgO,α-Fe2O3 and CoFe2O4 at 1300°C. The compounds were analyzed from the results of x-ray diffraction, magnetic hysteresis and initial susceptibility (χ) studies. All the compounds of the series were found to be monophasic with no appreciable change in their lattice parameter. The saturation magnetization and coercive field (Hc) values increased with increasing cobalt ferrite content. Similarly, the shapes of theχ-T curves and temperature variations ofHc values indicated that the magnetic behaviour changes from multi-domain to single domain with increasing cobalt content. The results are similar to those observed for the (MgFe2O4)1−x (Co3O4) system.

    • Electronic structure of disordered BCC alloys

      V K Srivastava A Mookerjee

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      This paper describes and analyses a self-consistent cluster coherent potential approximation calculation of the electron density of states of a random, binary alloy on abcc lattice.

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