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31.
K N Shrivastava 《Pramana》1985,25(4):491-496
We find that in the spin-polarized hydrogen, Bose condensation occurs for certain quantized values of the magnetic field.
Once the field is fixed, sweeping of the radio-frequency results in nuclear magnetic resonance so that condensation and NMR
occur simultaneously. We have found that nuclear self-induced transparency occurs. A new excitation designated by the present
author as superboojum, which is a discontinuity in the hydrodynamic equations in spin-polarized hydrogen having finite nuclear
as well as electronic spin is discovered. 相似文献
32.
The von Mises equivalent strain increment is derived for the case of large strain simple shear (torsion testing). This is used, in conjunction with the von Mises yield surface, to define the von Mises equivalent stress as well as the incremental work per unit volume. Integration of the equivalent strain increment leads to the definition of the von Mises equivalent strain for torsion. The Hencky equivalent strain increment is derived from the Hencky strain defined as the logarithm of the semi major and minor axes of the strain ellipse. This is then used, via the incremental work, to derive the ‘Hencky equivalent stress’. In the Onaka approach, the numerical values of the principal strain increments were integrated without taking into account the continuous rotation of the strain ellipse. This invalid operation leads to an expression for the equivalent strain increment that cannot be applied to the large strains considered by Onaka. Using the correct increments of the Hencky strain, it is shown that the shear strain increments turn negative and consequently, the incremental work becomes negative when the shear is large. 相似文献
33.
S. S. Umare R. S. Ningthoujam S. J. Sharma S. Shrivastava Sajith Kurian N. S. Gajbhiye 《Hyperfine Interactions》2008,184(1-3):235-243
NiFe2O4 nanoparticles have been synthesized by co-precipitation method at 145°C in N2 atmosphere using ethylene glycol as solvent and capping agent. This gives the promising synthesis route for nanoparticles at low temperature. The as-synthesized NiFe2O4 is subsequently heated at 400°C, 500°C, 700°C and 800°C. Crystallite size increases with the heat treatment temperature. The heat treatment temperature has direct effect on the electron paramagnetic resonance and intrinsic magnetic properties. The room temperature Mössbauer spectrum of the 800°C heated sample shows the two sextets pattern indicating that the sample is ferrimagnetic and Fe3?+? ions occupy both tetrahedral and octahedral sites of spinel structure. 相似文献
34.
Nor Aiyyuhal Jemali Hasan Abu Kassim V. Radhika Devi Keshav N. Shrivastava 《Journal of Non》2008,354(15-16):1744-1750
We have used the density functional theory to make the models of GexSe1?x glass for which the energy is a minimum. The clusters, Ge2Se2, Ge2Se3, Ge3Se, Ge3Se2, Ge4Se, GeSe3, GeSe4, chain mode zig-zag Ge4Se3, corner sharing GeSe4, and edge sharing Ge2Se6, have been made successfully and their vibrational spectra have been calculated from the first principles. We are able to optimize the bond distances as well as the bond angles. The calculated values of the frequencies of vibrations of the various clusters have been compared with those obtained from the experimental Raman spectra of actual glasses, GexSe1?x(0 < x < 0.3). The local concentration, x within 0.25 nm is nonuniform in the amorphous material. When the same cluster occurs in two stable configurations, low frequency vibrations of frequency, ν < 100 cm?1, are found. The corner sharing GeSe4 has low frequency modes at 54 cm?1 and 93 cm?1 whereas these modes disappear in the pyramidal configuration. The low frequency modes are therefore associated with the breaking of C4 symmetry of the pyramidal configuration. The computed vibrational frequencies of clusters Ge3, Ge4Se3, Ge2Se3, GeSe3 and Ge3Se2 are actually present in the Raman spectra of the glass, GexSe1?x(0 < x < 0.3). 相似文献
35.
Research on Chemical Intermediates - Diopside doped with various concentration (0.5, 1.0, 1.5, 2.0 and 2.5 mol%) of Dysprosium were prepared using solid-state reaction technique.... 相似文献
36.
The vibrational frequencies of GeS4, GeP4, Ge2S6, GeP3, Ge3P, Ge2P2, P2S2, P3S, P4S3, α-P4S4, β-P4S4, α-P4S5, β-P4S5, P4S7, P4S9 and P4S10 are theoretically computed from the first principles. The Raman frequencies of GexPxS1−2x glass are obtained for x varying from 0.05 to 0.019. The computed fundamental frequencies of clusters are compared with those experimentally found. In this way, we are able to identify the vibrating clusters in the real glass. The clusters identified in the real glass are found to be Ge2P2, P4S3, α-P4S4, β-P4S4, β-P4S5, P4S7, P4S9, β-P4S5, Ge2S6, Ge3P. 相似文献
37.
Saxena R Shrivastava S Chattopadhyay A 《The journal of physical chemistry. B》2008,112(38):12134-12138
The organization and dynamics of cellular membranes in the nervous system are crucial for the function of neuronal membrane receptors and signal transduction. Previous work from our laboratory has established hippocampal membranes as a convenient natural source for studying neuronal receptors. In this paper, we have monitored the organization and dynamics of hippocampal membranes and their modulation by cholesterol using pyrene fluorescence. The apparent dielectric constant experienced by pyrene in hippocampal membranes turns out to be approximately 20+/-3, depending on the experimental condition. Our results show that the polarity of the hippocampal membrane is increased upon cholesterol depletion, as monitored by changes in the ratio of pyrene vibronic peak intensities (I1/I3). This is accompanied by an increase in lateral diffusion, measured as an increase in the pyrene excimer/monomer ratio. These results are relevant in understanding the complex organization and dynamics of hippocampal membranes and could have implications in neuronal diseases characterized by defective cholesterol metabolism. 相似文献
38.
Srivastava Anshu Garg Gaurav Sharma Poojadevi Shah Nancy Sharma Sonal Shrivastava Neeta 《平面色谱法杂志一现代薄层色谱法》2016,29(3):203-208
JPC – Journal of Planar Chromatography – Modern TLC - Bacopa monnieri (L.) Pennell, commonly known as Brahmi, is an important medicinal plant of the Ayurvedic System of Medicine and is... 相似文献
39.
The results of measurements of substituent induced chemical shifts of carboxyl carbons (deltaCO) of dichloro- and difluorobenzoic acids, including the monosubstituted ones with substituents at meta- and/or ortho- positions, in chloroform-d and strengths of these acids (log K) in chlorobenzene show an anomalous reverse trend between deltaCO and log K, while the electron density at carboxyl carbons should influence similarly both deltaCO and log K. A detailed chemometric analysis of comparison of disubstituent effects between deltaCO and log K on the basis of Fujita-Nishioka's multiparameter approach and assumption of additivity of substituent effects shows a dominance of the localized pi-polarization mechanism relative to simple electrostatic effects upon deltaCO. Further, steric factors play a significant role in determining deltaCO whereas with respect to log K they were insignificant. The overall anomaly has been rationalized keeping in mind that, while log K is a gross measure of energy differences between the ionized and unionized forms of the acids, deltaCO is a very sensitive probe for determining changes in electron density at the carboxyl carbon of the unionized acid. 相似文献
40.
Pardasani D Kanaujia PK Gupta AK Tak V Shrivastava RK Dubey DK 《Journal of chromatography. A》2007,1141(2):151-157
Alkylphosphonic acids (APAs), particularly the methyl-, ethyl-, isopropyl- and n-propyl-phosphonic acids are important markers of extremely toxic nerve agents. Hence, their detection and identification is of vital importance to verification of chemical weapons convention (CWC). Verification analysis of CWC requires development of fast, reliable, simple and reproducible sample preparation methods of water and soil samples. Present investigation is focused on the optimization of alkylation of APAs in water with subsequent extraction of alkylated acids by hollow fiber liquid phase microextraction (HF-LPME). This simple and sensitive sample preparation of APAs from water offered better recoveries in comparison to conventionally used extraction technique. Under optimized conditions, the APAs were detected at the concentration of 0.5-0.75 microg/mL with S/N ratio > or = 5, whereas the LODs for alkyl APAs (monobasic APAs) were achieved up to 0.1 microg/mL. The developed method was finally tested with water samples supplied in 19th official proficiency test conducted by the OPCW. 相似文献