• Volume 7, Issue 3

      September 1976,   pages  141-222

    • Ion acoustic solitary wave in an inhomogeneous plasma with non-uniform temperature

      B N Goswami Mukul Sinha

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      A modifiedK-dV equation, which describes the propagation of an ion acoustic solitary wave in an inhomogeneous plasma with both density and temperature gradients, is derived. It is shown that, the velocity of a solitary wave increases as it propagates towards regions of increasing temperature.

    • Temperature dependence of chlorine NQR in 2-chloro 5-nitrobenzoic acid and 4-chloro 3-nitrobenzoic acid

      V S S Sastry J Ramakrishna

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      Temperature dependence of chlorine nuclear quadrupole resonance in 2-chloro 5-nitrobenzoic acid and 4-chloro 3-nitrobenzoic acid has been investigated in the region 77° K to room temperature. No phase transition has been observed. The results are analysed to obtain the torsional frequencies and their temperature dependence. A nonlinear temperature dependence is obtained for the torsional frequencies.

    • The x-ray anomalous dispersion and optical rotation in the crystalline solid solution NaClO3: NaBrO3

      K S Chandrasekaran S K Mohanlal

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      Sodium chlorate and sodium bromate crystals of thes ame structural configuration have opposite senses of optical rotation. It is also known that these halates exhibit continuous miscibility in solid solution. In the present work, the conjecture of Bijvoet that in the solid solution of these halates, the crystalline configuration would continue itself, has been directly verified by two approaches: (i) by optical rotation measurements on single crystals which show an annulling trend in proportion with composition and (ii) by measuremerts of Bijvoet inequality for several reflections from a single crystal (rich in chlorate) which shows an agreeable trend with the calculated values for chlorate.

    • A spectroscopic study of the Scorpio-Centaurus association

      R Rajamohan

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      Rotational velocities as well as hydrogen and helium line intensities of one hundred and twelve members of the Scorpio-Centaurus association have been derived. For stars withMv<0·0, the distribution of rotational velocities of both the upper Scorpius subgroup and the upper Centaurus -Lupus subgroup are similar and closely resemble those of the field stars. Stars withMv>0·0, all of which are found in the dense upper Scorpius region, rotate much faster than their counter-parts amongst field stars, the Pleiades and Alpha-Persei cluster members.

      The measured equivalent width ofHγ for 77 stars provide a distance modulus of 6·0 ± 0·09 magnitudes for the association. Evolutionary effects in the derived hydrogen line intensities are found between the two subgroups. The hydrogen-line intensities at all spectral types in the upper Centaurus-Lupus subgroup are systematically smaller than those of members in the upper Scorpius subgroup.

      Analysis of high dispersion spectra of five members of the association yield a helium abundance ofNHe/NH=0·096 ± 0·004. Along with data available in the literature, the mean helium abundance of thirteen stars of this association is found to be 0·098 ± 0·004 by number. For the two main subgroups of this association, we derive a value of 0·105 ± 0·001 for the upper Centaurus-Lupus group from three stars and 0·096 ± 0·005 for the upper Scorpius group from ten stars.

      Within the capabilities of our present methods, there seems to be no difference between the two subgroups as far as rotational velocities and initial helium abundance are concerned, a fact that must be borne in mind in the interpretation of the difference found between the two subgroups from photoelectric photometry.

    • Multiple scattering of muons in beryllium

      S D Sharma S Mukherjee

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      The defocussing and the depolarization of a high energy muon beam in a beryllium filter, often used to eliminate accompanying pions, have been studied. The quantum mechanical transport equation of Waldmann, which can also be used to describe the multiple scattering of Dirac particles, is solved with a distorted wave Born approximation. Calculations are done for both the Thomas-Fermi and the Hartree-Fock potential of the beryllium atom. It is shown that the Hartree-Fock potential leads to a less divergent beam. The depolarization of a longitudinally polarized muon beam in passage through a thin beryllium foil is also studied.

    • Theg-factor of the 659 keV level in117In

      R G Pillay S H Devare P N Tandon

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      We have measured theg-factor of the 659 keV, 3/2+, state in117In, using time differential perturbed angular correlation technique. The spin precession of this state was measured in an external field of 20·2 kG. The values of the Larmor precession frequencyω and theg-factor are obtained to be (60·1±0·3)106 rads/sec and 0·625±0·007 respectively.

    • General bounds on the isovector coupling constants of the weak neutral current

      G Rajasekaran K V L Sarma

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      We show that experimental data on inclusive neutrino reactions can be used to obtain general bounds on the coupling constants of the isovector part of the hadronic weak neutral current provided this isovector current is related to the charged current by isospin rotation. These bounds are free from the assumption of a specific model for the neutral current as well as any dynamical assumption on the hadronic structure functions. We derive upper bounds on the coupling constants which involve only the cross sections for isospin-averaged nucleon target as well as lower bounds which require a knowledge of the cross sections for proton and neutron separately.

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