AC conductivity in amorphous germanium

The ac conductivity in evaporated amorphous germanium films has been measured as a function of annealing and has been found to obey the ω^0.8 law, in accordance with the hopping model. The dc conductivity measurements on the same samples show a $\text{T}{}^{\mathrm{<mtext>1</mtext><mtext>4</mtext>}}$ law behaviour. The densities of localized states near the Fermi level g(E_F), obtained from both experiments are in reasonable agreement with each other. Both the measurements show a reduction by about a factor of 2 in g(E_F) when a freshly prepared film is fully annealed. High-temperature substrate films also show the ω^0.8 behaviour. This suggests that the frequency dependence of the ac conductivity is not caused by voids alone. Other possible explanations of our results are also discussed.     

Stimulated Brillouin Scattering of Whistler Waves by Electron-Acoustic Wave in a Two-Electron Temperature Plasma

Stimulated Brillouin Scattering has been investigated in a two-electron-temperature plasma and it is found that the growth rate can be controlled by injecting hot electrons in the plasma. For typical values of the magnetosphere plasmas the values of growth rates for different concentrations of hot to cold alectrons are calculated.     

Minerological studies on five plastic fire clays

Mineralogical studies on five plastic fire clays of India have been carried out by DTA, TG and electron microscopy. Studies were done on both as received and <1 fraction of clays. Results indicated that all the clays were predominantly kaolinite in nature and showed the main endothermic peak between 540° and 590°C and the exothermic peak between 920° and 985°C. A large exothermic peak at 810°C and a weight loss of 5.35% between 700° and 900°C in case of Barachatarma clay indicated the presence of graphitic carbon in the same. Both Neyveli and Badampahar clays contained illite and goethite. Electron micrographs of Mohuamilan and Neyveli clays showed hexagonal flakes of well-ordered kaolinite. Some tubular particles were seen in Chittorpur, Neyveli and Badampahar clays in addition to the kaolinite particles.The authors are thankful to Dr. B. K. Sarkar, director of the Institute for his kind permission to publish this paper.     

Parametric Excitation of Electron-Acoustic Mode in a Plasma of Two-Temperature Electrons

Using hydrodynamical model of the two-electron-temperatere plasma, the analytical investigation of parametric instability of electron-acoustic wave has been made. It is found that the growth rate decreases with increasing concentration ratio of the hot to the total electrons n_h0/n₀. The growth rate is found to be more for      

Subsolidus equilibria in the system BaO.TiO2.Al2O3

The subsolidus phase equilibrium relations in the system BaO.TiO₂.Al₂O₃ have been investigated using conventional solid state reaction techniques and X-ray powder diffraction. The existence of three known ternary compounds, BaTi₅Al₂O₁₄, BaTiAl₆O₁₂, and Ba₃TiAl₁₀O₂₀, was confirmed and their stability relations were studied. Various tie-lines existing between the ternary compounds and the binary titanates and aluminates of barium were established and a subsolidus phase diagram showing the phase assemblages compatible at 1200°C is presented.     

Ion Association and Solvation Behavior of Some 1-1 Electrolytes in 2-Ethoxyethanol Probed by a Conductometric Study

Precise measurements of the electrical conductances of solutions of potassium thiocyanate (KCNS), ammonium thiocyanate (NH₄CNS), sodium nitrate (NaNO₃) and ammonium nitrate (NH₄NO₃) in 2-ethoxyethanol (EE) at temperatures 35, 40, 45 and 50,^∘C are reported. The conductance data have been analyzed by the 1978 Fuoss conductance equation. A thermodynamic analysis of the ionic association processes has also been made and the Coulombic forces are found to play a major role in the association processes. The ionic contributions to the limiting equivalent conductances have been determined using the reference electrolyte method. Strong association was found for all these electrolytes in this solvent medium. The cations are found to be substantially solvated in 2-ethoxyethanol, whereas the anions appear to have only weak interaction with the solvent molecules.     

Direct calculation of the binding free energies of FKBP ligands

Direct calculations of the absolute free energies of binding for eight ligands to FKBP protein were performed using the Fujitsu BioServer massively parallel computer. Using the latest version of the general assisted model building with energy refinement (AMBER) force field for ligand model parameters and the Bennett acceptance ratio for computing free-energy differences, we obtained an excellent linear fit between the calculated and experimental binding free energies. The rms error from a linear fit is 0.4 kcal/mol for eight ligand complexes. In comparison with a previous study of the binding energies of these same eight ligand complexes, these results suggest that the use of improved model parameters can lead to more predictive binding estimates, and that these estimates can be obtained with significantly less computer time than previously thought. These findings make such direct methods more attractive for use in rational drug design.