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## Ratios ofB andD meson decay constants with heavy quark symmetry

### Pramana (1996-09-01) 47: 261 , September 01, 1996

## Magnetized cylindrically symmetric universe in general relativity

### Pramana (1996-07-01) 47: 25-31 , July 01, 1996

A magnetized cylindrically symmetric universe with two degrees of freedom in which the free gravitational field is Petrov type I degenerate, is obtained. The magnetic field is due to an electric current produced along the x-axis. The distribution consists of an electrically neutral perfect fluid with an infinite electrical conductivity. The behaviour of the model when magnetic field tends to zero and other physical aspects of the model are also discussed.

## The chemical compositions and ages of globular clusters

### Journal of Astrophysics and Astronomy (1996-06-01) 17: 1-6 , June 01, 1996

Recent technological advances have led to a dramatic improvement in the quality of photometric and spectroscopic data obtainable on stars in globular clusters. Evidence from CCD-based colour magnitude diagrams points to clear differences in age between some clusters. High dispersion spectra show that abundance variations cannot explain the observed differences. In particular, it seems that NGC 288 must be 2–3 Gyr older than NGC 362. The same spectra show that although there is a spread in some molecular band strengths in NGC 362, the total C+N+O abundance remains constant, indicating that the material has undergone varying amounts of nuclear processing. No variations are seen in the abundances of iron group elements. Lower dispersion spectra for a large sample of faint stars in 47 Tucanae, obtained with a multi-object optical fibre system, show that unevolved main sequence stars in that cluster share the same CNO variations as the bright giants. The conclusion from all these data is that the intra-cluster CNO variations are neither truly primordial nor due to evolutionary mixing. It may be that there was a sufficiently extended period of star formation for material from first generation stars to be used in later generations, or that some pollution has occurred due to mass loss. Finally, it is noted that if ‘prehistoric’ clusters exist with ages of around 50 Gyr, as hypothesised in some cosmological models, these should probably still be rather obvious and readily recognised.

## Neutron stars before 1967 and my debt to Chandra

### Journal of Astrophysics and Astronomy (1996-12-01) 17: 77-79 , December 01, 1996

## Higher order elastic constants and generalized Gruneisen parameters of elastic waves and low temperature thermal expansion of gadolinium

### Pramana (1996-12-01) 47: 435-445 , December 01, 1996

Expressions for the higher order elastic constants are derived using the sublattice displacements to the second degree in strains. These expressions are used to obtain the higher order elastic constants and their pressure derivatives in gadolinium. The higher order elastic constants are used to find out the generalized Gruneisen parameters of the elastic waves propagating in different directions in gadolinium. The Brugger gammas are evaluated and the low temperature limit of the Gruneisen gamma is obtained. The results are compared with the available reported values.

## Depopulation of Na(8s) colliding with ground state He: Study of collision dynamics

### Pramana (1996-05-01) 46: 373-380 , May 01, 1996

A systematic study of the collison dynamics associated with depopulation of Na(8*s*) atom colliding with ground state He has been made by applying the semi-classical impact parameter method using molecular orbital (MO) basis sets of different sizes. The cross-sections for total depopulation of the parent atom as well as those for individual transitions have been calculated. It is shown that the basis set must be large enough so as to include not only the immediate adjacent states coupling with the parent state but also other nearby states, which can affect the overall flux distribution in the reaction.

## Static and dynamic properties of heavy light mesons in infinite mass limit

### Pramana (1996-05-01) 46: 349-355 , May 01, 1996

We summarize the consequences of the infinite limit of heavy quark mass in the results of form factors, charge radii and decay constants of heavy light mesons within a QCD inspired quark model recently reported.

## Self-interacting one-dimensional oscillators

### Pramana (1996-03-01) 46: 203-211 , March 01, 1996

Energy eigenvalues and 〈*x*^{2}〉_{n} for the oscillators having potential energy*V*(*x*)=(*ω*^{2}*x*^{2}/2)+*λ*<*x*^{2r}>*x*^{2s} have been determined for various values of*λ, r, s* and*n* using renormalized hypervirial-Padé scheme. In general, the results show an improvement over the findings of earlier workers. Variation of the evaluated quantities and of the renormalization parameter with*λ, r, s* and*n* has been discussed. In addition, this potential has been employed as an illustrative example of the applicability of alternative formalism of perturbation theory developed by Kim and Sukhatme (*J. Phys.**A25* 647 (1992)).

## Quantum motion over a finite one-dimensional domain: With and without dissipation

### Pramana (1996-11-01) 47: 371-377 , November 01, 1996

Quantum motion of a single particle over a finite one-dimensional spatial domain is considered for the generalized four parameter infinity of boundary conditions (GBC) of Carreau*et al* [1]. The boundary conditions permit complex eigenfunctions with nonzero current for discrete states. Explicit expressions are obtained for the eigenvalues and eigenfunctions. It is shown that these states go over to plane waves in the limit of the spatial domain becoming very large. Dissipation is introduced through Schrödinger-Langevin (SL) equation. The space and time parts of the SL equation are separated and the time part is solved exactly. The space part is converted to nonlinear ordinary differential equation. This is solved perturbatively consistent with the GBC. Various special cases are considered for illustrative purposes.

## Perturbation theory of polar hard Gaussian overlap fluid mixtures

### Pramana (1996-02-01) 46: 75-89 , February 01, 1996

A perturbation theory of polar hard Gaussian overlap fluid mixture is discussed. Explicit analytic expressions for the second and third varial coefficients are given. Numerical results are estimated for the thermodynamic properties of quadrupolar hard Gaussian overlap fluid and fluid mixture. It is found that the excess free energy and internal energy depend on concentrations*c*_{1},*c*_{2}, molecular diameter ratio*R*, shape parameter*K* and the quadrupole moments*Q**_{1},*Q**_{2}.