The oxide responsible for high-temperature superconductivity (onset ∼100 K, zero resistance above liquid N₂ temperature) is found to be YBa₂Cu₃O₇±δ.

The concept of the Pauli-Lubanski vector is generalized for classical relativistic massless spinning particles to arbitrary space-time dimensions. The properties of this generalized Pauli-Lubanski “vector” are studied and used to set up a Hamiltonian description of such particles in a compact way.

Nonsingular cosmological models with reducing torsion induced by vacuum quantum effects are constructed. The metric of the models described corresponds to the inflationary universe. Moreover, anisotropic nonsingular cosmological model with constant torsion is constructed.

Phase-shift-equivalent potentials are used to study the sensitivity of triton binding energy (E_T) to the off-shell behaviour of two-nucleonT matrix in a translationally-invariant basis of harmonic oscillator wavefunction. For a smaller value of inverse range parameterλ (1.95 fm⁻¹), which is close to the attractive range of our model potential, a 21% variation in the triton binding energy is obtained. For the other value ofλ an off-shell variation of about 28% inE_T is obtained.

Design details of a 100 MeV proton linear accelerator (Alvarez system) operating at a resonating frequency of 400 MHz have been studied. Increase in the linac operating frequency has become feasible with the possibility of injecting protons from a radio frequency quadrupole accelerator with energies higher than the conventional pre-injectors. Various electrical parameters of such a system have been calculated and compared with the existing linac injectors operating at 200 MHz.

The electrical capacitance of the binary liquid mixturen. heptane + methanol at its critical composition is studied in both one-phase and two-phase regions. The two-phase capacitance data are used with the known functional forms for the order parameter and the diameter to obtainT_c andc_c with greater precision. This helps in reducing the number of unknown parameters in the functional form for the one-phase capacitance. The data show consistency with an alpha (α) exponent for dc/dt in the one phase region.

The effects of various ambients on the non-chopped and chopped films of cryolite, MgF₂ and mixed cryolite-MgF₂, as measured by ellipsometer, are reported. The moisture decreases the refractive index whereas an increase is observed in air and other ambients. In all the ambient-aging the chopped films show smaller changes (nearly half) in refractive index than non-chopped films. Aging seems to be due to three main processes, a long-term adsorption-like surface reaction and two short-term reactions.

The general tensor force model has been modified by incorporating separately the electron-ion interactions. The model satisfies the translational symmetry requirements of the lattice and is used to obtain the phonon dispersion curves of chromium, molybdenum and tungsten. The agreement between the theoretical and experimental frequencies is very good.

Semiconducting materials are employed in the fabrication of a number of semiconductor devices and opto-electronic detectors etc depending on their properties, state of purity and perfection and energy band gap values. In the present study, a latest and novel photoacoustic spectroscopic technique has been employed for the determination of energy band gap of some semiconductors namely CdS, CdSe, CdTe, ZnS, ZnO, Se and Si in the powder form. Values obtained have been compared with those reported by conventional methods.

The collision-generated hybridization which has been found responsible for the on-site mixing of the atomic-likef-state and the band-liked states in mixed valence solids has been studied for the cerium solid. A practical expression which depends on the lattice constant and temperature has been obtained for the collision-generated hybridization. Numerical calculations show that the valence varies continuously with lattice constant and that temperature makes the transition smoother. The collision-generated hybridization is found to be of significant strength in the intermediate valence regime; but over a wide range of the valence near 3.5 it varies rather slowly without preferring a particular valence. Factors which can assist the collision-generated hybridization in stabilizing the mixed valence phase at a particular lattice constant are discussed.