• Volume 26, Issue 4

      April 1986,   pages  301-377

    • On the axiomatic approach to the maximum entropy principle of inference

      S N Karbelkar

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      Recent axiomatic derivations of the maximum entropy principle from consistency conditions are critically examined. We show that proper application of consistency conditions alone allows a wider class of functionals, essentially of the form ∝ dxp(x)[p(x)/g(x)]s, for some real numbers, to be used for inductive inference and the commonly used form − ∝ dx p(x)ln[p(x)/g(x)] is only a particular case. The role of the prior densityg(x) is clarified. It is possible to regard it as a geometric factor, describing the coordinate system used and it does not represent information of the same kind as obtained by measurements on the system in the form of expectation values.

    • Supersymmetric preon models with three-fermion generations

      V Gupta H S Mani U Sarkar

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      A class of supersymmetric preon models is considered in which the hypercolour groupGHC and the unbroken flavour groupGf anomalies are zero without needing spectators. It is shown that forGHC=SU(2) and SU(3) quarks and leptons as composites can be obtained satisfying ’t Hooft’s anomaly matching conditions. For the case ofGHC=SU(3),Gf can accommodate a horizontal symmetry group to describe just three generations.

    • Zeros of the helicity amplitudes of Σ+-p elastic scattering

      S Mohanty J K Mohapatra

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      Optimally exploiting the analytic structure of the helicity amplitudes of Σ+-p scattering we locate their zeros by making a fit to the differential cross-section curves at 40, 100 and 150 MeV energies. Minute changes in the positions of the zeros produced detectable noises in the fit. It was observed that quite reliable predictions for the phase shifts can also be obtained from this analysis.

    • Differential incoherent scattering of 279.2 keV photons by Zr, Sn, Ta, Pb and U

      G K Raju K Venkataramaniah M S Prasad K Narasimhamurty V A Narasimhamurty

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      Differential incoherent scattering cross-section ratios of 279.2 keV photons by zirconium, tin, tantalum, lead and uranium elements are experimentally determined by comparing the peak areas under the degraded photon energy with that of an equivalent aluminium foil employing a high resolution 35 c.c. coaxial Ge(Li) detector. Studies have been made in single configuration in an angular range of 20° to 115°. The results are compared with theoretical values obtained from the non-relativistichfs model of Hubbell and co-workers. The cross-section ratios decrease as the atomic number increases for a given scattering angle.

    • Inelastic scattering of pions on7Li

      S B Patangi G Ramachandran

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      The recent experimental results of Gibson and coworkers, for inelastic scattering of pions on7Li, leading to the first five excited states of7Li are analyzed using a shell model description including configuration admixtures and representing the transition nucleon densities following Helm model, used extensively in the context of inelastic scattering of electrons. With the transition radii for protons and neutrons chosen to be 3.9 fm and 4.1 fm respectively, good fits to the experimental cross sections are obtained. In contrast to the distorted wave Born approximation (dwba) calculations using optical model codes, we find the present work is able to reproduce the observed maxima and minima precisely. Moreover this analysis reveals the importance of considering the configuration admixtures especially in the transitions to24P5/2 (7.48 MeV) and24D7/2 (9.67 MeV) levels.

    • Magnetic symmetry and transport properties in crystals

      V Appalanarasimham

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      The number of non-vanishing independent tensor components in respect of the known transport properties for the magnetic variants of the crystallographic point groups are obtained by adopting a different procedure. This method fulfils the orthogonality conditions of group theory.

    • Molecular orbital studies on the CO/Ni chemisorption system in presence of alkali additives and steps

      S K Saha B C Khanra

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      The atom superposition and electron delocalization molecular orbital theory has been used to study the effect of alkali additives and steps on the dissociative chemisorption of CO molecule on Ni(001) surface. We have found that with increasing concentration of alkali atoms the CO bond length increases, the CO bond strength weakens and the CO dissociation barrier decreases. The results are in qualitative agreement with experimental results. The steps have also been found to reduce the dissociation barrier quite significantly compared with the reduction by alkali additives.

    • Electron paramagnetic resonance study of free radicals inγ-irradiated single crystal of tris(glycine) calcium(II) dibromide

      P Subramanian N Hariharan J Sobhanadri

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      Tris(glycine) calcium(II) dibromide single crystal has been irradiated with aγ-source to produce free radicals and the irradiated sample has been subjected toepr studies. The observed spectra reveal that an NH4 radical is formed by rupturing glycine molecule due to irradiation. The unpaired electron is localized on the C-N bond. The proton hyperfine interaction on the unpaired spin shows orthorhombic symmetry and the spectroscopic splitting factor remains isotropic.

    • Microscopic theory of soliton propagation in4He films

      A C Biswas C S Warke

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      A microscopic theory has been provided for propagation of solitons in superfluid4He films at temperatureT=0°K.

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