• Volume 3, Issue 6

      December 1974,   pages  1-396

    • Errata

      Eric A Lord G A Shah

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    • Non-spherical magnetic moment in MnAlGe

      S K Paranjpe S R Tendulkar L Madhav Rao N S Satya Murthy

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      The magnetic structure factors of MnAlGe (space groupP4/nmm) measured with polarised neutrons have been expressed in terms of the magnetic moment of the Mn atom (site symmetry tetrahedral with tetragonal distortion), the Bessel transforms 〈jn〉 of the Mn radial functions and the fractional occupancies of the moment density in the various crystal field orbitals. The measured structure factors were least-squares fitted with the theoretical expression involving 〈jn〉 appropriate to the Mn0, Mn+ and Mn2+ atoms. The best fit was got using Mn0 transforms, yielding 1·45µB as the Mn magnetic moment. The fractional occupancies of the moment density in the crystal field orbitalsA1g,B1gEg andB2g were obtained. This analysis shows the magnetic moment to be highly non-spherical with a large fractional occupancy (38%) in theA1g orbital directed along the tetragonal axis while the fractional occupancies ofB1g andB2g are found to be 31% and 30% respectively. The fractional occupancy of the moment in theEg orbital directed towards the Ge and Al atoms is very low (1%). The spatially averaged moment density of Mn in MnAlGe is more diffuse than that of Mn I and Mn II in isostructural Mn2Sb.

    • On the decaying states and the transition rates

      N D Sen Gupta

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      The object of this paper is to point out that the hypothesis of decaying states,i.e., states with amplitude having a factor eγt (γ-real) is not compatible with the wave equation with a hermitian hamiltonian. An attempt has been made to obtain the expression for relative population density in general. It is shown that the usual expressions for the transition rates, which are proportional to time, may be obtained for a very restricted interval of time.

    • Effect of crystal and collimator misalignments on Bragg angle measurements

      V K Wadhawan

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      A mathematical analysis has been made of the combined effect of crystal and collimator misalignments on Bragg angles measured from zero-layer Weissenberg photographs. The results obtained here have been compared with those available for Bond’s method of measuring Bragg angles with diffractometers. The comparison shows that, for a given amount of crystal and collimator misalignments, Bond’s method and the 2 θ-method do not give identical results for small and intermediate Bragg angles.

    • An automatic technique for the measurement of thermoelectric power at high pressures

      T G Ramesh A S Reshamwala M T Srivatsa

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      We describe an automatic technique for direct recording of the themoelectric power of metals either as a function of temperature or pressure. This technique facilitates the process of measurement especially when one has to scan a wide temperature and pressure range. Typical experimental recordings of the γ-α electronic phase transition in cerium are also presented.

    • Measurement of effective specific heat of packed bed materials by the continuous flow electrical method

      P B Lal Chaurasia D R Chaudhary R C Bhandari

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      The theory of the continuous flow electrical method for the determination of specific heat of liquids has been extended to the measurements of effective specific heat of packed bed materials consisting of solid-liquid phase systems. Experimental data are reported showing the variation of effective specific heat with mass porosity and saturating liquid specific heat. The weighted arithmetic mean equation of constituent specific heats is in fair agreement with the measured values.

    • Application of holographic addition and subtraction to quadratic motion analysis

      P C Gupta K Singh

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      Hologram interferometry of objects moving with constant acceleration has been investigated with special reference to the techniques of holographic addition and subtraction, which results in an extension of the range of measurement of conventional time average holography. Distribution of intensity in the fringes has been plotted for some typical cases.

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