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排序方式: 共有211条查询结果,搜索用时 15 毫秒
1.
2.
Priya Jaiswal Vijaykumar Ijeri Ashwini Srivastava 《Journal of inclusion phenomena and macrocyclic chemistry》2004,49(3-4):219-224
This paper is a report on the complexation studies of silverions with certain water soluble crown ethers viz., 15-crown-5,18-crown-6, cyclam, diaza 15-crown-5 and certain water insolublecrown ethers viz., benzo 15-crown-5, dibenzodiaza 15-crown-4,dibenzyldiaza 18-crown-6 in some nonionic surfactants viz.,polyoxyethylated alkyl phenol (TX 100), polyoxyethylene (20)sorbiton monolaurate (Tween 20), polyoxyethylene (20) sorbitonmonoleate (Tween 80) and polyoxyethylated glyco monolaurylether (Brij 35) by potentiometry. In addition, conductometry wasalso used to study the complexation of oxa crown ethers to comparethe results obtained by potentiometry, which were found to be ingood agreement with each other. The complexation studies indicate1:1 complex formation between the silver ion and macrocycle, thelogML n+ values being in the range 1 to 9. 相似文献
3.
Ram C. Maurya Deen D. Mishra Surendra K. Jaiswal Sudipta Mukherjee 《Transition Metal Chemistry》1992,17(5):381-383
Some new low-spin hexacoordinated cyanonitrosyl complexes of Cr1 of the type [Cr(NO)(CN)2(L)2(H2)], where L is an aromatic aldehyde oxime or Mannich base, have been prepared by the interaction or K3[Cr(NO)(CN)5]· H2O with L in aqueous AcOH, and characterized by a range of physico-chemical techniques, I.r. data suggest that all the oxime
derivatives and Mannich bases act as monodentate ligands by coordinating through the aromatic nitrogen.
TMC 2564 相似文献
4.
The present paper describes various classification techniques like cluster analysis, principal component (PC)/factor analysis to classify different types of base stocks. The API classification of base oils (Group I-III) has been compared to a more detailed NMR derived chemical compositional and molecular structural parameters based classification in order to point out the similarities of the base oils in the same group and the differences between the oils placed in different groups. The detailed compositional parameters have been generated using and nuclear magnetic resonance (NMR) spectroscopic methods. Further, oxidation stability, measured in terms of rotating bomb oxidation test (RBOT) life, of non-conventional base stocks and their blends with conventional base stocks, has been quantitatively correlated with their NMR and elemental (sulphur and nitrogen) data with the help of multiple linear regression (MLR) and artificial neural networks (ANN) techniques. The MLR based model developed using NMR and elemental data showed a high correlation between the ‘measured’ and ‘estimated’ RBOT values for both training (R=0.859) and validation (R=0.880) data sets. The ANN based model, developed using fewer number of input variables (only NMR data) also showed high correlation between the ‘measured’ and ‘estimated’ RBOT values for training (R=0.881), validation (R=0.860) and test (R=0.955) data sets. 相似文献
5.
Solution properties of a drug and its partitioning into lipid bilayers were studied for drug extraction using several different techniques, such as surface tension, zeta potential, ultra filtration and UV-Vis spectroscopy. From the surface tension study it was found that the presence of salt makes the drug molecules more surface-active. Zeta potential revealed the adsorption of the drug into the liposome bilayers to be governed mostly by electrostatic forces. The drug retention volume was expressed as a capacity factor, K, and that was normalized with respect to the amount of the immobilized phospholipids. The K-values for the positively charged drug on the liposomes decreased in the presence of phosphate buffer due to the presence of the oppositely charged ions. The above methods can thus be used to understand the mechanism of drug-membrane interaction and quantification of drug absorption into liposomes. 相似文献
6.
Deo P Deo N Somasundaran P Jockusch S Turro NJ 《The journal of physical chemistry. B》2005,109(44):20714-20718
Structural changes of pyrene-labeled and unlabeled poly(maleic acid/octyl vinyl ether) (PMAOVE) and poly(maleic acid/methyl vinyl ether) (PMAMVE) with changes in pH have been investigated in this study. The changes in the photophysical properties of pyrene are interpreted to investigate uncoiling or swelling of the polymeric chains with pH. The vibrational fine structure of the pyrene fluorescence (I(3)/I(1)) and the ratio between excimer and monomer fluorescence (I(e)/I(m)) of both pyrene-labeled and unlabeled PMAMVE and PMAOVE suggest that, at pH 4, the polymers are in the coiled form and PMAOVE forms hydrophobic nanodomains. An increase in pH ionizes a number of COOH groups on both PMAMVE and PMAOVE, which leads to the stretching or swelling of the polymers. 相似文献
7.
Namita Singh Sana Ahmed Aliyah Fakim Somayah Qutub Othman Alahmed Omar El Tall Osama Shekhah Mohamed Eddaoudi Niveen M. Khashab 《Chemical science》2020,11(41):11280
Assembling well-defined MOF superstructures remains challenging as it requires easily removable hard templates or readily available immiscible solutions for an emulsion-based soft-template approach. In this work, a single-step emulsion-free soft templating approach is reported to spontaneously prepare hollow ZIF-8 and ZIF-67 colloidosomes with no further purification. These superstructures can load different enzymes regardless of the size and charge with a high encapsulation efficiency of 99%. We envisage that this work will expand the repertoires of MOF superstructures by the judicious selection of precursors and the reaction medium.An emulsion-free approach for the preparation of hollow ZIF-8 superstructures in a single step is established based on metal sulfate hydrates in methanol. 相似文献
8.
H. S. Dang H. B. Desai D. D. Jaiswal S. R. Kayasth S. Somasundaram 《Journal of Radioanalytical and Nuclear Chemistry》1983,77(1):65-70
A simple separation scheme for the analysis of As, Mn, Mo, Cu and Zn using neutron activation is described. It has been checked
using three standard reference materials, A-11 milk powder (IAEA) and bovine liver and orchard leaves (USNBS) and found to
give acceptable results. This scheme was applied for determination of these trace elements in mature human milk samples. The
concentrations of As, Mn, Mo, Cu in samples obtained from two socio-economic groups—low and middle incomes—were not significantly
different. However, Zn levels in samples obtained from the poor income group were significantly lower than in those obtained
from the other group.
Work carried out under Research Contract No. 2598/RB of International Atomic Energy, Vienna.
Health Physics Division.
Analytical Chemistry Division. 相似文献
9.
Angelika Basch Silvia Gross Namita Roy Choudhury Janis Matisons 《Journal of Sol-Gel Science and Technology》2005,33(1):39-45
New inorganic-organic hybrid materials were prepared by free-radical polymerization of methyl methacrylate (MMA) with methacrylate-substituted oxotantalum cluster [Ta4O4(OEt)8(OMc)4] and their properties evaluated. The cluster was prepared by the reaction of the parent alkoxide with methacrylic acid. Samples of the hybrid materials were produced with Ta-cluster to methyl methacrylate in the ratios of 1:50 and 1:100 and were characterized by thermal and spectroscopic techniques. The glass transition temperatures of the hybrid materials are shifted to higher temperatures than pure PMMA as a result of cross-linking of the polymer by the oxotantalum clusters. The increase in Tg is also observed from the dynamic mechanical analysis (DMA). Evidence of crosslinking between the Ta-cluster and PMMA is obtained from infrared spectroscopic study. Surface studies performed by X-ray photoelectron spectroscopy (XPS) provide information about the atomic concentrations of the surface and indicate tantalum bonded to oxygen. 相似文献
10.
Hassan Amirhashchi Anirudh Pradhan Rekha Jaiswal 《International Journal of Theoretical Physics》2013,52(8):2735-2752
Some new exact solutions of Einstein’s field equations have come forth within the scope of a spatially homogeneous and anisotropic Bianchi type-III space-time filled with barotropic fluid and dark energy by considering a variable deceleration parameter. We consider the case when the dark energy is minimally coupled to the perfect fluid as well as direct interaction with it. Under the suitable condition, the anisotropic models approach to isotropic scenario. We also find that during the evolution of the universe, the equation of state (EoS) for dark energy ω (de), in both cases, tends to ?1 (cosmological constant, ω (de)=?1), by displaying various patterns as time increases, which is consistent with recent observations. The cosmic jerk parameter in our derived models are in good agreement with the recent data of astrophysical observations under appropriate condition. It is observed that the universe starts from an asymptotic Einstein static era and reaches to the ΛCDM model. So from recently developed Statefinder parameters, the behaviour of different stages of the universe has been studied. The physical and geometric properties of cosmological models are also discussed. 相似文献