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121.
Pankaj S. Joshi 《Pramana》2007,69(1):119-135
We consider here the genericity aspects of spacetime singularities that occur in cosmology and in gravitational collapse.
The singularity theorems (that predict the occurrence of singularities in general relativity) allow the singularities of gravitational
collapse to be either visible to external observers or covered by an event horizon of gravity. It is shown that the visible
singularities that develop as final states of spherical collapse are generic. Some consequences of this fact are discussed.
相似文献
122.
Nishant N. Patel K. B. Joshi 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,59(1):19-23
Using empirical pseudopotential method Γ-L crossover is found for
the Ga0.74Al0.26Sb. The conduction band minimum is observed to
switch at the (0.87, 0, 0) point for Ga0.51Al0.49Sb which shifts to
the X point for Ga0.21Al0.79Sb and remains at X leading finally to
indirect band gap in AlSb. Band structure calculations for a large number of
alloys are performed and bowing parameters bX and bL are proposed
for the EX and EL respectively. Our findings may serve as
directive to select the materials in a range of composition to examine the
bowing parameters and thereby effective mass experimentally for the
GaxAl1-xSb alloys. 相似文献
123.
A. Chaudhury R. Khatirkar N.N. Viswanathan V. Singal A. Ingle S. Joshi I. Samajdar 《Journal of magnetism and magnetic materials》2007
Commercial supply, from several steel manufacturers, of low-silicon non-grain-oriented electrical steel was monitored over a span of several years. A total of 51 samples were selected—selected from many hundreds on the basis of large differences in magnetic properties, but absence of significant variations in chemistry (other than differences in silicon percentage). The selected samples were analyzed for crystallographic texture and for grain size. 相似文献
124.
The structure of trans‐[Cr(Me2tn)2Cl2]2ZnCl4 (Me2tn = 2,2‐dimethylpropane‐1,3‐diamine) was determined by a single‐crystal X‐ray diffraction study at 173 K. The analysis reveals that there are three crystallographically independent chromium(III) complex cations in the title compound. The chromium(III) atoms are coordinated by four nitrogen atoms of Me2tn and two chlorine atoms in a trans arrangement, displaying a distorted octahedral geometry. The two six‐membered chelate rings in three complex cations are oriented in an anti chair–chair conformation with respect to each other. The Cr–N and Cr–Cl bond lengths average 2.0862(2) and 2.3112(6) Å, respectively. The ZnCl42– have slightly distorted tetrahedral arrangement with Zn–Cl lengths and the Cl–Zn–Cl angles are influenced by hydrogen bonding. The resolved absorption maxima in the electronic d–d spectrum were fitted with a secular determinant for a quartet energy state of the d3 configuration in a tetragonal field. It is confirmed that the nitrogen atoms of the Me2tn ligand are strong σ donors, but the chloro ligands have weak σ‐ and π donor properties toward the chromium(III) ion. 相似文献
125.
A. R. Joshi Abhay V. Patil U. M. Kasar 《Journal of Radioanalytical and Nuclear Chemistry》2010,286(1):67-69
Precipitation and solvent extraction methods have been investigated for the purification of plutonium from silver from the
solution generated during oxidative dissolution of plutonium oxide using Ag(II) ions. Initial experiments have been carried
out using thorium as representative of plutonium. Selecting the optimum conditions, the experiments were repeated with plutonium.
The results revealed that Pu can be purified from silver ions either by precipitating silver as silver chloride or silver
metal followed by Pu(IV) oxalate precipitation or by selective extraction of Pu(IV) into 20% Aliquat-336 or 30% TBP. 相似文献
126.
Sneha Karmarkar P. V. Khadikar Vijay K. Agrawal Keshav C. Mathur Manorama Mandloi Shobha Joshi 《Journal of Chemical Sciences》2000,112(1):43-49
Proton-ligand formation constants of salicylhydroxamic acids (SHA) and their nuclear substituted derivatives have been estimated
topologically using the normalized Wiener index, referred to as mean square Wiener index (Wms). Regression analysis of the
data indicates that Wms can be used successfully for estimating and monitoring proton-ligand formation constants. 相似文献
127.
AbstractGraphene is emerged as a highly sought after reinforcing filler for epoxy matrix in view of its superior electrical, mechanical and thermal properties. Dispersion of low concentration of graphene can significantly enhance the epoxy/graphene nanocomposites properties. Dispersion of graphene in epoxy matrix depends on processing protocols used, and interfacial interaction between epoxy matrix and graphene. Interfacial interaction between epoxy matrix and graphene can be achieved by covalent and non-covalent modification of graphene. This paper comprehensively review the influence of different processing protocols adopted for the processing of epoxy/graphene nanocomposites, and its effect on mechanical, thermal and electrical properties. In addition, covalent and non-covalent strategies adopted for modification of graphene, and its influence on mechanical, thermal and electrical properties of epoxy/graphene nanocomposites are extensively discussed. The future challenges associated with graphene reinforced epoxy nanocomposites processing have been discussed. 相似文献
128.
M. V. Kartikeyan A. K. Sinha H. N. Bandopadhyay S. N. Joshi E. Borie M. Thumm 《International Journal of Infrared and Millimeter Waves》2000,21(4):553-561
In this work, the field analysis of a cylindrical interaction structure, with helical grooves, and an inner dielectric lining for possible employment in high power TWT amplifiers in the conventional slow-wave regime, is presented. The Ohmic dominance of the microwave power on the walls of this propagating circuit is deduced. 相似文献
129.
The steady state and time domain spectroscopy of 9-aminoacridinium hydrochloride have been studied. 9-aminoacridine (I), 9-aminoacridinium
(II) and the double protonated ion (III) follow Waterman’s principle with respect to their spectra and lifetimes. It is established
that the excimer formation in (II) is from the ground state dimers which undergo either thermally-activated radiationless
excimer conversion or a geometrical rearrangement in the excited state at room temperature. The quenching of monomer emission
by dimers or foreign quenchers (KI) is found to be of transient nature as suggested by the continuum model.
The authors felicitate Prof. D S Kothari on his eightieth birthday and dedicate this paper to him on this occasion. 相似文献
130.
Energy migration and transfer from acriflavine to rhodamine B and malachite green in poly (methylmethacrylate) have been investigated using the decay function analysis. It is found that the influence of energy migration in energy transfer can be described quite convincingly by making use of the theories of Loring, Andersen and Fayer (LAF) and Huber. At high acceptor concentration direct donor-acceptor transfer occurs through Förster mechanism. 相似文献