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41.
42.
The Debye screening length in degenerate non-parabolic bands is shown to have an oscillatory dependence on a quantizing magnetic field as in degenerate parabolic bands. The period of oscillations is, however, found to decrease with increasing non-parabolicity which also is observed to have no effect on the amplitude of the same.On leave of absence fromthe Department of Physics, B.N. College, Patna University, Patna 800004.The authors are indebted to Prof. J. N.Bhar for his keen interest in the work. 相似文献
43.
This paper presents anO(n
2) method for solving the parametric quadratic program
相似文献
44.
Pranav Chandrachood Tushar Gadkari Nirmala Deshpande Rajashree Kashalkar 《Journal of the Iranian Chemical Society》2012,9(1):47-51
The oxidation of 1,4-dihydropyridines has been carried out using catalytic quantity of transition metal nitrates supported on silica gel under IR irradiation. The C-4 de-alkylation is found to be minimal due to milder reaction conditions. The new protocol has been found to be economic and environment friendly. 相似文献
45.
Rajashree Hirlekar Vilasrao Kadam 《Journal of inclusion phenomena and macrocyclic chemistry》2009,63(3-4):219-224
Aim of the present work was to investigate the effect of methyl-β-cyclodextrin (MβCD) on the solubility and dissolution rate of carvedilol (CAR), a drug used orally for the treatment of hypertension. Phase solubility studies showed an AL-type diagram indicating the formation of inclusion complex in 1:1 molar ratio. Solid binary systems of the drug with MβCD were prepared by various methods. Physicochemical characterizations were performed using Fourier Transformation Infrared Spectroscopy, Differential Scanning Calorimetry and powder X-Ray Diffractometry. It could be concluded that CAR can form inclusion complex with MβCD. The dissolution profiles of inclusion complexes were determined and compared with those of CAR alone and the physical mixture. The dissolution rate of CAR was increased by MβCD inclusion complexation remarkably. 相似文献
46.
Nalawade Pravin Aware Babasaheb Dand Neha Kadam Vilasrao Hirlekar Rajashree 《Journal of inclusion phenomena and macrocyclic chemistry》2009,65(3-4):377-383
In this work, we illustrate the usefulness of cyclodextrins, namely, methyl-β-cyclodextrin (MβCD), an amorphous, methylated derivative of the natural β-cyclodextrin, as a tool to form an inclusion complex with Valsartan (VAL), a poorly water soluble drug. The phase solubility study showed AL type of curve with slope less than one indicating the formation of complexes in 1:1 molar ratio of drug and CD. The stability constant was found to be 538.14 ± 5.4 Mole?1. Solid binary systems between VAL and MβCD were prepared experimentally in a stoichiometry 1:1 by different techniques (physical mixing, kneading, co-evaporation). Afterward these products were characterized by Fourier transform infrared spectroscopy (FTIR), Differential scanning calorimetry (DSC), Scanning electron microscopy (SEM) and 1H Nuclear magnetic resonance study (1H NMR). The results obtained suggested that co-evaporation methods yield a higher degree of amorphous entities suggesting the formation of inclusion complex between VAL and MβCD. The dissolution of VAL from the binary systems was studied to select the most appropriate system for the formulation development. It was concluded that the preparation technique played an important role in the dissolution behavior of the drug and the inclusion complex between VAL and MβCD obtained by co-evaporation method allowed better performance. 相似文献
47.
G. Klopman S.K. Chakravarti N. Harris J. Ivanov R.D. SaiakHov 《SAR and QSAR in environmental research》2013,24(2):165-180
Computational screening is suggested as a way to set priorities for further testing of high production volume (HPV) chemicals for mutagenicity and other toxic endpoints. Results are presented for batch screening of 2484 HPV chemicals to predict their mutagenicity in Salmonella typhimurium (Ames test). The chemicals were tested against 15 databases for Salmonella strains TA100, TA1535, TA1537, TA97 and TA98, both with metabolic activation (using rat liver and hamster liver S9 mix test) and without metabolic activation. Of the 2484 chemicals, 1868 are predicted to be completely nonmutagenic in all of the 15 data modules and 39 chemicals were found to contain structural fragments outside the knowledge of the expert system and therefore suggested for further evaluation. The remaining 616 chemicals were found to contain different biophores (structural alerts) believed to be linked to mutagenicity. The chemicals were ranked in descending order according to their predicted mutagenic potential and the first 100 chemicals with highest mutagenicity scores are presented. The screening result offers hope that rapid and inexpensive computational methods can aid in prioritizing the testing of HPV chemicals, save time and animals and help to avoid needless expense. 相似文献
48.
A. N. Chakravarti K. P. Ghatak K. K. Ghosh S. Ghosh A. Dhar 《Zeitschrift für Physik B Condensed Matter》1982,47(2):149-153
An attempt is made to investigate the effects of size quantization on the effective mass in ultrathin films ofn-Cd3As2. It is found that the effective mass at the Fermi level depends on the size quantum number due to the effect of crystal-field splitting, resulting in different effective masses at the Fermi level corresponding to different electric subbands. It is also observed that the different effective masses closely approach each other, for a given film thickness, with increasing electron concentration and, for a given electron concentration, with increasing film thickness. 相似文献
49.
A. N. Chakravarti K. P. Ghatak A. Dhar K. K. Ghosh S. Ghosh 《Applied Physics A: Materials Science & Processing》1981,26(3):165-169
An attempt is made to investigate the effect of size quantization on the diffusivity-mobility ratio of the carriers in ultrathin films of semiconductors having Kane-type nonparabolic energy bands. It is shown, takingn-type InSb as an example, that the ratio oscillates both with increasing film thickness and with increasing carrier concentration under degenerate conditions and remains unaffected otherwise. The corresponding results for parabolic semiconductors are also obtained from the expressions derived. 相似文献
50.
Subhendu P. Chakravarti Utpal K. De Dipankar Ray 《General Relativity and Gravitation》1986,18(7):701-704
A simple approach for finding the exact solution of the matter dust distribution in the Brans-Dicke cosmology has been attempted. The condition for obtaining a complete exact solution is presented. 相似文献
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