Magnetogravitational instability of a rotating homogeneous gas cloud with radiation

Magnetogravitational instability of an infinite, homogeneous rotating hot plasma cloud associated with radiative processes has been studied with the help of relevant MHD equations using normal mode analysis. Rotation is taken parallel and perpendicular to the magnetic field for both, the longitudinal and transverse modes of propagation. The Jeans espression of instability is modified to give the stabilizing effect of radiation pressure. The stabilizing effect of magnetic field is observed only for transverse mode of propagation whereas rotation stabilizes only along the magnetic field for transverse mode. The stabilizing effect of rotation is comparatively more effective.D. S. Vaghela gratefully acknowledges the financial assistance for his minor research project given by University Grants Commission of India.     

Effect of doping on thermally stimulated discharge current in polystyrene

TSC spectra of PS exhibit one peak at 105°C. Doping with organic molecular compounds in PS lowers the peak temperature and enhances the peak current and activation energy. Doped samples show one more peak at higher temperature. The results are discussed on the basis of different theoretical models.     

Metal contact effect on the persistent internal polarization in pure and doped polystyrene

Photo-electrets of pure and copperphthalocyanine doped polystrrene films (thickness 20 μm) were formed by UV- radiation in an electric field with Al, Cu, Ni, Zn, Cd and Pb as electrode materials. The depolarization current and the released charge show a strong dependence on the material of the electrode. Two distinct regions in the current decay characteristic indicate that the polarization consists of trapped holes and electrons. The amount of charge injected increases with decreasing work function of the contact metal. Doping increases the stability of the charge.     

Energy minimum exciation in a ferromagnet

In a magnon-phonon interaction an energy minimum is obtained in the one-magnon ground-state dispersion. The magnon momentum at the minimum is half the product of the mass of the magnon and the sound velocity, $\text{h}\text{?}\text{k}{}_0\text{=}\text{1}\text{2}\text{h}\text{?}\text{ν × (cD)}{}^{-1}$.     

Light-charged-particle evaporation from hot 31P nucleus at E*∼ 60 MeV

The inclusive energy spectra of light charged particles, such as, α, p, d and t, evaporated from the hot ³¹P nucleus at an excitation energy E ^*∼ 60 MeV, have been measured at various angles. The compound nucleus ³¹P has been populated using two different entrance channel configurations; i.e., ⁷Li (47 MeV) + ²⁴Mg and ¹⁹F (96 MeV) + ¹²C reactions, leading to the same excitation energy of the compound system. It has been observed that the spectra obtained in the ⁷Li (47 MeV) + ²⁴Mg reaction follow the standard statistical-model prediction with a spherical configuration of the compound nucleus. But, the spectra obtained in the ¹⁹F (96 MeV) + ¹²C reaction deviate from similar predictions of the statistical model both on higher- as well as on lower-energy sides. Considerable deformation was required to be incorporated in the calculation in order to reproduce the measured-energy spectra in this case. Dynamical trajectory model calculations were not found to play any significant role in explaining the differences in behaviour between the two cases under study. The observed discrepancy has been attributed to the difference in the angular-momentum distributions of the compound nuclei formed in the two reactions.     

X-ray K-absorption edge shifts in transition elements

It has been found that a striking correlation exists between the plasman energy in solids and the chemical shifts of the X-ray K-absorption edges of the transition elements Cr, Cu, Ni, Co, Zn and their compounds. Fairly good agreement between the calculated values of the plasmon energies and the observed values of the chemical shifts has been obtained.     

Electrokinetic studies of cotton. Part IV.: Role of water in influencing surface charge density of cotton in electrolyte solution

Summary The streaming potentials are measured at the interface between cotton chemisorbed with different crosslinking agents and different electrolyte solutions. Data were obtained as a function of concentration of electrolytes.The zeta potentials are found to decrease with increasing electrolyte concentration. The rate of change of zeta potential is much smaller than the theoretical values calculated from the different models of double layer. The discrepancy between the observed and theoretical values has been discussed.The surface charge density,, on cotton at the interface has been calculated and found to increase with the electrolyte concentration. This functional relationship between -C is explained from the consideration of the modification of the structure of water in the vicinity of the ion. The increase in surface charge density with the increase in electrolyte concentration is in the order KCl> NaI> NaBr> NaCl which is in the structure breaking capacity.

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Zusammenfassung Das Strömungspotential an den Grenzflächen der aus mit verschiedenen Vernetzungsmitteln chemisorbierter Baumwolle und verschiedenen elektrolytischen Lösungen entstehenden Systeme wurde in Abhängigkeit von der Konzentration der Elektrolyten bestimmt.Es wurde festgestellt, daß die Zeta-Potentiale mit zunehmender Konzentration der Elektrolyte abfallen. Die Abnahme der Zeta-Potentiale war viel kleiner als der aus verschiedenen Doppelschichtmodellen theoretisch errechnete Wert. Die Ursachen dieses Unterschiedes zwischen beobachteten und berechneten Werten wurden erläutert.Die Flächenladungsdichte () für Baumwolle an der Grenzfläche nimmt mit zunehmender Elektrolytkonzentration (C) zu. Die funktionelle Beziehung zwischen undC wurde auf der Basis der Modifikation des in Ionennähe befindlichen Wassers erklärt. Die Erhöhung der Flächenladungsdichte mit zunehmender Elektrolytkonzentration wächst in der Reihenfolge KCl > NaI > NaBr > NaCl, was mit der Strukturbruchfähigkeit der Ionen übereinstimmt.

     

Overlap contribution to57Fe3+ isomer shifts in fluorides and oxides

We have calculated the overlap contribution to the contact charge density at the⁵⁷Fe³⁺ site in fluoride and oxide lattices, FeF₃, CaFe₂O₄, CaBaFe₄O₈ and KFeO₂. The trend in isomer shifts in going from one lattice to another is explained in terms of the overlap effects. The experimental values of the change in isomer shift from lattice to lattice is used to obtain the change in nuclear size. The values of r/r _N are found to lie between –0.81×10^–4 and –1.56×10^–4.