Proceedings of the Indian Academy of Sciences - Section A

Raman, C.

doi: 10.1007/BF03049516pmid: N/A

Raman, C.

doi: 10.1007/BF03049517pmid: N/A

Dharmatti, S.; Govil, G.; Kanekar, C.; Khetrapal, C.; Virmani, Y.

doi: 10.1007/BF03049518pmid: N/A

The NMR spectra ofm-disubstituted benzenes, in which one of the substituents is kept constant and the other varied have been analysed. It has been shown that the proton-proton interactions in these molecules are not influenced by the inductive and resonance effects of the substituent but depend on its steric effect. A measure of the relative steric effects of different substituents is thus suggested. The results have been compared with other methods of measuring steric effects.

Katiyar, R.

doi: 10.1007/BF03049519pmid: N/A

Raman spectrum of a single crystal of ammonium sulphamate has been recorded for the two different orientations using λ 2537 resonance radiation of the mercury as the exciter. Thirty-four Raman lines have been observed of which eight belong to the lattice oscillations. Weak hydrogen bonding of NH2 group in the crystal was predicted. The infra-red absorption spectrum of the substance was taken in the powder form in potassium bromide disc, using Carl Zeiss UR10 IR spectrometer. Thirty-five absorption maxima could be identified.

Dweltz, N.; Ambady, G.; Radhakrishnan, T.

doi: 10.1007/BF03049520pmid: N/A

Small angle scattering patterns have been photographed from cotton (and viscose) fibres containing deposits of silver, mercuric sulphide, lead sulphide, lead chromate and lead iodide. These patterns have shown that deposits of the cubic crystals are nearly isodiametric and randomly oriented. On the other hand, particles of lead chromate and lead iodide are elongated, with the longer direction tending to be oriented along the fibre axis. These conclusions are in agreement with evidence on orientation secured from wide-angle diffraction. In the case of the randomly oriented deposits, extensive measurements have been made of the angular dependence of equatorial scattered intensity. Distributions of particle size have been computed which will synthesize back the scattered intensity. Some limitations of such calculations have been pointed out. It has been concluded, however, that the majority of particles are crystallites with dimensions of 200 Å or less. There are a few particles with very much larger dimensions. These may be polycrystalline aggregates which are lodged in the fibre lumen rather than in cellulosic substance.

Voisin, J.

doi: 10.1007/BF03049521pmid: N/A

Mackey’s theory of induced representations is used to construct the true irreducible representations of the universal covering group of the Galilei group. The invariant subgroup used in the present work is generated by the space translations and the accelerations. This treatment gives a deeper insight into the structure of the problem and is a useful footnote to the work of E. Inönü and E. P. Wigner and also to the work of A. S. Wightman. In the Appendix, we summarize the results obtained in applying Mackey’s theory to the projective representations and the reduction of their products.

Purushothama, C.

doi: 10.1007/BF03049522pmid: N/A

The possible modes of propagation of small disturbances in a homogeneous, incompressible initially unstressed, electrically conducting elastic medium at rest in the presence of a uniform external magnetic field are studied and it is found that if the medium is non-rigid (analogous to non-viscous fluids) and perfectly conducting, the disturbances propagate with Alfvén velocity. The effects of rigidity and finite conductivity on these transverse Alfvén waves have been investigated in some detail.