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排序方式: 共有593条查询结果,搜索用时 15 毫秒
1.
The instability of the plane interface between two uniform, superposed, electrically conducting and counter-streaming fluids through a porous medium is considered in the presence of a horizontal magnetic field. In the absence of surface tension, perturbations transverse to the direction of streaming are found to be unaffected by the presence of streaming if perturbations in the direction of streaming are ignored. For perturbations in all other directions there exists instability for a certain wavenumber range. The instability of this system is postponed by the presence of magnetic field. The magnetic field and surface tension are able to suppress this Kelvin-Helmholtz instability for small wavelength perturbations and the medium porosity reduces the stability range given in terms of a difference between the streaming velocities and the Alfvén velocity.This research forms a part of the research project awarded to the first author (R.C.S.) by the University Grants Commission. 相似文献
2.
The carrier technique has been used to concentrate Cr(VI) radiometrically by studying the carrying efficiency as a function of pH of aqueous medium, added ions, carrying capacity, amount of carrier and subsequent desorption of the activity adsorbed under optimum experimental conditions. The study shows that under optimum experimental conditions, 0.15 g of ZrO2 and 0.25 g of TiO2 carry 0.01 mg and 0.001 mg of chromium respectively. Further, the activity carried under the specified conditions can be recovered more or less quantitatively by leaching the carrier. 相似文献
3.
Triorganotin(IV) and triorganolead(IV) derivatives of the types Me3Sn(SCZ) and Ph3Pb(SCZ) (where SCZ? is the anion of a semicarbanzone ligand) have been synthesized by substitution reactions of trimethyltin chloride and triphenyl-lead chloride with semicarbazones derived from heterocyclic ketones. The resulting complexes have been characterized by elemental analyses, molecualr weight determinations and conductivity measurements. The mode of bonding has been established on the basis of infrared and 1H, 13C and 119Sn NMR spectroscopic studies. Some respresentative complexes have also been evaluated for their antimicrobial effects on different species of pathogenic fungi and bacteria; the results of these investigations have been reported in the present paper. 相似文献
4.
A theoretical study of π-electron spin density distributions has been made for a series of fluoro-substituted hydrocarbon radical cations using unrestricted Hartree-Fock theory. Although some of the predicted proton splittings are not in very good agreement with experiment, the overall agreement with experiment can be passed as fairly satisfactory considering the approximate nature of the theory used. The experimental fluorine splittings can be well predicted by using a one-parameter relationship between the isotropic fluorine splitting (aF) and the π-electron spin density (ρCC) on the attached carbon. It has been further shown that both ρCC and the proportionality constant (Qeff) in the linear relation, are fairly insensitive to the parameter choice. 相似文献
5.
Soot deep oxidation catalyzed by molybdena and molybdates: a thermogravimetric investigation 总被引:2,自引:0,他引:2
Molybdena (MoO3) and molybdates of bismuth (Bi2Mo3O12), chromium (Cr2Mo3O12), barium (BaMoO4), manganese (MnMoO4) and copper (Cu3Mo2O9) were synthesized and characterized by X-ray powder diffractometry and infrared spectroscopy. They were then assessed as ‘loose contact' catalysts for soot deep oxidation (combustion) in air by thermogravimetry. A similar assessment was carried out on commercial chromia (Cr2O3) and tungsta (WO3). Observed high oxidation activity of MoO3, as compared to both Cr2O3 and WO3, is attributed to the higher volatility (mobility) of MoOx species. On similar grounds, observed high activity of MoO3 and Cu3Mo2O9, as compared to the other test molybdates, is explained. Relatively speaking, however, a higher activity was observed for Cu3Mo2O9 than MoO3, whereby soot ignition temperature decreased from 571°C (uncatalyzed oxidation) to 430°C, to occur within the temperature range of diesel exhaust (200–450°C). This observation is ascribed to copper-promoted redox conduct of Mo(VI) in the oxidation reaction of soot. Kinetics of the reaction was studied non-isothermally, and the kinetic parameters (A, k, ΔE and the reaction order) were calculated. 相似文献
6.
Chu I Liu F Soares A Kumari P Nomeir AA 《Rapid communications in mass spectrometry : RCM》2002,16(15):1501-1505
Rapid, generic gradient liquid chromatography/tandem mass spectrometry (LC/MS/MS) assays, designed to accelerate sample analyses, have been developed to keep pace with the productivity of advanced synthetic procedures. In this study, LC/MS/MS was combined with an in vitro, cell-based, blood-brain barrier (BBB) model to evaluate the potential of new chemical entities (NCEs) to cross the BBB. This in vitro assay provides the permeability of discovery compounds across a monolayer of a primary culture of bovine brain microvessel endothelial cells in a fraction of the time that is required for in vivo studies (brain/plasma concentrations), using only 2 mg of the compound. The results are consistent with in vivo brain/plasma concentration ratio data. 相似文献
7.
Santosh Kumari Suvarcha Chauhan Kuldeep Singh Ahmad Umar Hassan Fouad Mohammad Shaheer Akhtar 《Molecules (Basel, Switzerland)》2022,27(24)
This study aims to understand how glycyl dipeptide affected the compressibility, volumetric behavior and viscometric behavior of the cationic surfactants CTAB (Cetyltrimethylammonium bromide) and DTAB (dodecyltrimethylammonium bromide). Information on solute–solute, solute–solvent, and solvent–solvent interactions has been inferred using the quantification of density (ρ), speed of sound (u) and viscosity in aqueous media containing glycyl dipeptide in the temperature range 293.15–313.15 K at an interval of 5 K. The data from the aforementioned research have been used to enumerate numerous volumetric and compressibility metrics that aid in the collection of information about the interactional behavior of the system under consideration. The study suggests that CTAB interacts strongly compared to DTAB with dipeptide, and it also significantly dehydrates glycyl dipeptide. The difference in water–water interactions caused by the loss of hydrophobic hydration of the surfactant molecules upon the addition of cationic surfactants may be the cause of the variation in determined parameters with surfactant concentration. Consideration of the structural rearrangement of molecules that may occur in the system has been used to explain the results of viscosity and computed factors related to viscosity. The patterns of competitive intermolecular interactions in the ternary (dipeptide + water + surfactant) system have been used to analyze the trends of all the parameters. The study may be helpful to understand the stability and structural changes in protein–surfactant systems mediated through various interactions that may be present in the system. 相似文献
8.
Mondal Imdadul Hoque Rangan Latha Uppaluri Ramagopal V. S. 《Journal of Thermal Analysis and Calorimetry》2021,145(5):2389-2403
Journal of Thermal Analysis and Calorimetry - Drying characteristics of horticultural produce often target studies on the process parameters so as to derive useful data for the development of... 相似文献
9.
Roul Pradip Kumari Trishna Goura V. M. K. Prasad 《Journal of mathematical chemistry》2021,59(9):1977-1993
Journal of Mathematical Chemistry - This paper is concerned with the development of a collocation method based on the Bessel polynomials for numerical solution of a general class of nonlinear... 相似文献
10.
Rajan Patel Meena Kumari Abbul Bashar Khan 《Applied biochemistry and biotechnology》2014,172(8):3701-3720
Room temperatures ionic liquids are considered as miraculous solvents for biological system. Due to their inimitable properties and large variety of applications, they have been widely used in enzyme catalysis and protein stability and separation. The related information present in the current review is helpful to the researchers working in the field of biotechnology and biochemistry to design or choose an ionic liquid that can serve as a noble and selective solvent for any particular enzymatic reaction, protein preservation and other protein based applications. We have extensively analyzed the methods used for studying the protein–IL interaction which is useful in providing information about structural and conformational dynamics of protein. This can be helpful to develop and understanding about the effect of ionic liquids on stability and activity of proteins. In addition, the affect of physico-chemical properties of ionic liquids, viz. hydrogen bond capacity and hydrophobicity on protein stability are discussed. 相似文献