The influence of geostrophic force on the stability of an heterogeneous conducting fluid with a radial gravitional force

The linear and nonlinear stability of a heterogeneous incompressible inviscid perfectly conducting fluid between two cylinders is investigated in the presence of a radial gravitational force and geostrophic force. The stability for linear disturbances is investigated using the normal mode method, while the nonlinear stability is investigated by applying the energy method. In the case of linear theory, it is found that a necessary condition for in stability is that the algebraic sum of hydrodynamic, hydromagnetic and rotation Richardson number is less than one quarter somewhere in the fluid. A semi-circle theorem similar to that of Howard is also obtained. In the case of nonlinear disturbances a universal stability estimate namely a stability limit for motions subject to arbitrary nonlinear disturbances is obtained in the form $$E \leqslant E_0 \exp ( - 2M\tau ).$$ The motion is asymptotically stable if $$\delta \leqslant 1 + J_m + J_H $$ somewhere in the fluid. This asymptotic stability limit is improved using the calculus of variation technique. We also find that whenδ=1/4, andJ _R=1, both the linear and nonlinear stability criteria coincide and in that particular case, we have a necessary and sufficient condition for stability.     

Time structure of the hadronic component of extensive air showers

Proceedings - Mathematical Sciences - A detailed study of the time structure of hadrons of energy > 5 GeV in extensive air showers has been carried out at Ootacamund (8·00 gm/cm2) using...     

Doubly ortho-linked quinoxaline/triarylamine hybrid as a bifunctional, dipolar electroluminescent template for optoelectronic applications

The titled hybrid (Q-H) works as a clippable optoelectronic unit. Q-spacer-Q systems function as efficient orange emitters reaching EL intensities (L) of up to 6840 cd m-2 with etaext of 0.77% and operation efficiencies of 1.60 cd A-1 and 0.8 lm W-1. Notably, Q-An acts as a (bluish) green emitter, reaching L of 12347 cd m-2 with similar operational efficiency.     

Steady flow generated by the differential rotation of a porous disk of finite thickness

When a body of fluid bounded by a porous disk of finite thickness is disturbed from a state of rigid rotation by an enhanced (or reduced) angular velocity of the disk, a few authors followed Darcys model and observed that the centrifugal pumping occurs through the entire porous layer regarded as a convection zone. The shear stress can develop only at the edge of the porous layer. We use a porous disk of high permeability that allows the fluid in the porous disk to deform in response to the changing angular velocity. Based on the Birkmans model, we solve for the steady non-linear flow and observe that there arises (i) a convection zone of nearly uniform angular velocity at the boundary (within the porous layer) and (ii) a transition zone adjacent to the convection zone which provides a smooth transition to the interior. This makes the model relevant to some astrophysical situations as described by some authors [1, 3]. The two point boundary value problem is solved subject to the boundary conditions, the far field conditions, and the matching conditions at the fluid-porous medium interface. The solution is obtained using a numerical procedure known as the method of Adjoints.Received: June 13, 2002; revised: July 7, 2003     

Comparative study of recent phenomenological potentials for the NaCl-type alkali halides derived from elastic and dielectric data

A comparative study is presented of various phenomenological potentials for the NaCl-type alkali halides-based on elastic and dielectric data and on a “combination” of the Born model with a deformable ion mode-reported in recent years by Catlow, Diller and Norgett, by Corish, Parker and Jacobs, by Sangster et al. and by Hardy and Karo. First a critical analysis is made of the models adopted by the various AA and of the procedures to determine the pertinent parameters, emphasizing the different, often crude approximations used and the thermodynamic inconsistencies present in them. The quality of the fits achieved, and of the predictions made with the different models is then discussed. Finally, one compares directly the resulting effective pair potentials for the short-range interactions cation-anion, anion-anion and cation-cation, as well as the various types of parameters (specifically the potential parameters (Born repulsive parameters and van der Waals coefficients) and the shell-model parameters). One finds that the effective short-range potentials for each pair interaction in a given salt reported by the various AA-taken as a whole-have a sizeable indeterminacy, due both to the Born repulsive and vdW contributions.     

Interferons

Interferons are proteins which bring about a nonspecific and nonimmunological defence reaction against virus infections in vertebrates. Interferon formation is induced in vivo and in vitro by viruses and other agents, e.g. endotoxins, nucleic acids, synthetic anionic copolymers, and phytohemagglutinins. All attempts to produce pure interferons have so far been unsuccessful. Interferons can only exert an antiviral action when the cellular RNA and protein synthesis is intact.     

New methods for the Preparation of Nitrosyl Chloride

A pure sample of nitrosyl chloride has been prepared either by reaction of phosphorus trichloride with concentrated nitric acid or by reaction of phosphorus trichloride with sodium nitrate in presence of water. The nitrosyl chloride gas has been characterized by i.r. spectral data and elemental analysis.     

Studies of mass and energy correlations in thermal neutron fission of U-235 accompanied by long range alpha particles

Several characteristics of fission accompanied by long range alpha particles (LRA) have been studied in the thermal neutron induced fission of²³⁵U. The kinetic energies of fission fragments and the LRA were measured with a back-to-back ionization chamber and semiconductor detectors respectively. The kinetic energies of the two fragments and the LRA in LRA fission, along with the energies of pair fragments in the normal binary fissions, were recorded event by event on a magnetic tape by means of a four-parameter data acquisition system. The data were analysed to study the dependence of different quantities in LRA fission on the fragment mass ratio, LRA energy and the total kinetic energy of the fission fragments. It is seen that the most probable energy of LRA increases significantly for near symmetric mass divisions. The total kinetic energy for all mass ratios in LRA fission is found to be (2.6±0.7) MeV larger than that in binary fission. The difference in the total kinetic energies in LRA and binary fissions is seen to be dependent on mass ratio. This result may suggest that the scission configuration in LRA fission is different for different mass ratios. Correlations between the fission fragment and LRA energies have been studied for several mass ratios. It is seen that the most probable fragment kinetic energyĒ _k varies nearly linearly with the LRA energyE _a for various mass divisions but the variation of the most probable LRA energyĒ _a with fragment kinetic energyE _k is found to deviate from linearity for several mass ratios. From a least square fit to the variation ofĒ _k withE _a it is found that the slope (dĒ _k/dE_a) increases with the increase in mass ratio. The present results are discussed to arrive at a better understanding of the scission configuration in the fission accompanied by LRA emission.