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- Roy, Probir 4 (%)
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## The structure of bis-(L-threonine) copper (II). H2O

### Pramana (1975-04-01) 4: 198 , April 01, 1975

## K-capture probability in the decay of139Ce(137.5d)

### Pramana (1975-05-01) 4: 218-221 , May 01, 1975

The K-capture probability (*P*_{K}) in the decay of^{139}Ce (137.5d) has been determined from the analysis of the K x-ray gamma ray sum-peak observed with a Ge (Li) x-ray detector. Furthermore,*P*_{K} is estimated independently from the measurement of the K x-ray intensity in the decay, using the known conversion coefficients of the 165.8 keV transition. Using the weighted average of*P*_{K} measured as above, the mass difference between^{139}Ce and^{139}La is found to be 273
_{−13}^{+21}
keV.

## Lattice imaging of close-packed structures by high resolution electron microscopy: ABO3 perovskite polytypes

### Pramana (1975-11-01) 5: 274-283 , November 01, 1975

Lattice imaging technique of high resolution electron microscopy has been employed to examine 4H, 6H and 9R ABO_{3} perovskite polytypes. The lattice images can be correlated with the lattice periodicity and the stacking sequence of AO_{3} layers and BO_{6} octahedra. The study shows the utility and validity of the lattice imaging technique for the study of relatively close-packed systems.

## Fredholm approximants for potential scattering

### Pramana (1975-11-01) 5: 260-267 , November 01, 1975

An approximate method based on Fredholm approximants is used to solve Lippmann-Schwinger equation for*s*-and*p*-wave Yukawa and*s*-wave exponential potential scattering problems. The method is then applied to a problem of*π*-*π* scattering i nvolving the use of a well known equivalent potential. The equation for partial wave amplitudes is solved to generate the first three*π*-*π* resonances,*ρ, f*_{0}, and*g*, in a self-consistent manner.

## Anomalous absorption of intense electromagnetic radiation in a non-uniform overdense plasma

### Pramana (1975-04-01) 4: 184-191 , April 01, 1975

In this work, we present numerical computation of anomalous absorption of a powerful electromagnetic wave incident normally, on an isothermal plasma with a linear density gradient. We consider first, the “intensity” dependence of anomalous absorption treating two important cases: one that of a typical high temperature, high density fusion plasma occurring in a laser-pellet application and the other that of an ionospheric (F-layer) plasma. It is found that for low incident powers, reflection is almost constant, corresponding essentially, to classical electronion collisions. As we increase the incident power, however, we find that the reflection starts dropping and the absorption takes over. This result is interpreted in terms of the instability generated anomalous absorption of the incident wave. Next, we consider the “wavelength” dependence of anomalous absorption, wherein we observe that the effect of anomalous absorption is increasing for longer wavelengths of the incident laser radiation.

## A non-perturbative open-shell theory for atomic and molecular systems: Application to transbutadiene

### Pramana (1975-06-01) 4: 247-263 , June 01, 1975

A non-perturbative theory is proposed in this article in which an energy independent effective Hamiltonian is obtained for open-shell systems. We have given a diagrammatic version of theory to facilitate the analysis of the problem. The theory has been applied to a model 4-*π* electron problem, for calculating the lowest*π-π** singlet and triplet energy levels of transbutadiene. Comparison with full Cl calculation indicates the excellent workability of the theory.

## The crystal structure of bis-(L-threonine) copper(II).H2O

### Pramana (1975-02-01) 4: 83-94 , February 01, 1975

The crystal structure of bis-(L-threonine) copper (II).H_{2}O, Cu (C_{4}H_{8}NO_{3})_{2}.H_{2}O has been determined by heavy atom and Fourier methods and refined by least-squares using visually estimated three-dimensional x-ray data of 893 reflections. The blue crystals are monoclinic, space group*P*2_{1} with*α*=11·02,*b*=4·90,*c*=11·16Å and*β*=93·5°,*Z*=2. The final*R* is 0·10. Coordination of copper is distorted square pyramidal with ligands in*trans* configuration. The conformation of one of the aminoacid ligand is identical with L_{s}-Threonine while the other has a conformation with torsional angle*χ*^{1, 2}=−74(1)°.

## Characteristics of a high frequency ion source used in a low-energy accelerator

### Pramana (1975-05-01) 4: 229-241 , May 01, 1975

This work presents the characteristics of a high frequency ion source operating on a low energy, 150 keV accelerator. The latter is to be used as a neutron generator and its design is based on a theoretical analysis which shows that if the axial potential in an electrostatic electrode system is made to increase with four thirds the power of axial distance, inward electric forces will compensate space charge forces tending to blow up the beam. This results in a simplified acceleration tube much shorter and of higher gradient than the conventional acceleration columns. The ion source itself is an ordinary type using axial extraction of the beam, and its main properties investigated are the beam current and beam quality (or emittance). Dependence of the two on different parameters is investigated in a series of tests.

## Cylindrically symmetric matter distribution with a magnetic field in Einstein-Cartan theory

### Pramana (1975-11-01) 5: 289-293 , November 01, 1975

In this paper we have extended our earlier studies of solutions of Einstein-Cartan equations to the case where a magnetic field co-exists with the matter distribution. We have obtained an exact solution of Einstein-Cartan-Maxwell equations representing a static cylinder of perfect fluid with an axial magnetic field*H* and a non-zero spin density*K*, satisfying the equation of state*ρ*=*γ*(*p*_{r}+*p*_{s}−*H*^{2}/4*π*),*γ* being a constant. We notice that as a consequence of field equations there exists a direct relation between the pressure*p*, and the spin density*K*, indicating that an increase in pressure would enormously increase the spin density.

## On energy-momentum tensors as sourcesof spin-2 fields

### Pramana (1975-07-01) 5: 29-32 , July 01, 1975

The improvement terms in the generalised energy-momentum tensor of Callan, Coleman and Jackiw can be derived from a variational principle if the Lagrangian is generalised to describe coupling between ‘matter’ fields and a spin-2 boson field. The required Lorentz-invariant theory is a linearised version of Kibble-Sciama theory with an additional (generally-covariant) coupling term in the Lagrangian. The improved energy-momentum tensor appears as the source of the spin-2 field, if terms of second order in the coupling constant are neglected.