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排序方式: 共有502条查询结果,搜索用时 31 毫秒
1.
D. Amutha Rani Y. Yamamoto S. Mohri M. Sivakumar Y. Tsujita H. Yoshimizu 《Journal of Polymer Science.Polymer Physics》2003,41(3):269-273
In this study, a novel stepwise extraction method has been examined. The guest molecules housed between the helices of the clathrate δ form of syndiotactic polystyrene can be removed completely with this method. A systematic study of the preparation of a solvent‐free mesophase (emptied clathrate) membrane, its helical and residual solvent contents, and its structural transformations has been performed. In this first attempt, an enhancement in the TTGG helical content has been observed in the extracted membrane, and a conceptual mechanism is proposed. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 269–273, 2003 相似文献
2.
S. Mohri D. Amutha Rani Y. Yamamoto Y. Tsujita H. Yoshimizu 《Journal of Polymer Science.Polymer Physics》2004,42(2):238-245
Syndiotactic polystyrene (sPS) has various crystalline forms such as α, β, γ, and δ forms, and a mesophase depending on the preparation method. In this study, we focused on the mesophase with the molecular cavity of sPS, which is obtained by step‐wise extraction of the guest molecules from the sPS δ form. To prepare the mesophase containing different shapes and sizes of the cavity, two kinds of the sPS δ form membrane cast from either toluene or chloroform solution were first prepared and then the guest molecules were removed by a step‐wise extraction method using acetone and methanol. We could succeed in the preparation of two kinds of mesophase with different shapes and sizes of the molecular cavity. Either toluene or chloroform vapor sorption to the sPS mesophase membranes was examined at 25 °C. Sorption analysis indicates that the mesophase with large molecular cavities can mainly sorb large molecules; on the other hand, the mesophase with small cavities can sorb only the small molecules, and is unable to sorb a large amount of large molecule because the cavity was too small to sorb the large molecules. Therefore, the sPS mesophase membrane has sorption selectivity based on the size of the molecular cavity. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 238–245, 2004 相似文献
3.
Prakash O Kaur H Batra H Rani N Singh SP Moriarty RM 《The Journal of organic chemistry》2001,66(6):2019-2023
The combination reagent (dichloroiodo)benzene and lead(II) thiocyanate in dichloromethane effects oxidation of various enol silyl ethers, ketene silyl acetals, and beta-dicarbonyl compounds, thereby providing an efficient and convenient method for alpha-thiocyanation of carbonyl and beta-dicarbonyl compounds. 相似文献
4.
Perchloric acid supported on silica gel acts as an excellent reagent system in converting glucals into 2,3-unsaturated-O-glucosides in good to excellent yields in short reaction time with good alpha selectivity. Primary, secondary, and allylic alcohols, phenols, and thiols react with 3,4,6-tri-O-acetyl glucal with equal ease. In addition to this, a chiral furan diol is obtained from unprotected D-glucal or D-galactal in good yields. 相似文献
5.
On the mechanism of nanopore filling of SAPO-5 molecular sieve by nitrogen molecules 总被引:1,自引:0,他引:1
Boddenberg B Radha Rani V Grosse R 《Langmuir : the ACS journal of surfaces and colloids》2004,20(25):10962-10969
SAPO-5 molecular sieve was synthesized according to patent literature and characterized with X-ray diffraction, electron microscopy (SEM, TEM), and solid state magic angle spinning NMR spectroscopy. The material of particles in the micrometer region was found to consist of ca. 20 nm microcrystallites packed in mostly parallel orientation to ca. 200 nm sized agglomerates. The nitrogen adsorption isotherm was measured at 77.6 K over ca. 7 decades of pressure up to pore saturation. The course of the isotherm is interpreted to consist of filling of the nanopores (diameter, 0.73 nm) up to 2N(2)/unit cell, subsequent multilayer adsorption on the outer surface of the agglomerates, and, finally, pore condensation in the interparticle adsorption space. The nanopore adsorption can be quantitatively reproduced with the statistical mechanical model of a quasi one-dimensional lattice gas taking intermolecular interactions into account. The evaluated energy parameters are of physically reasonable magnitude and agree with literature data. The multilayer part of the adsorption isotherm can be well represented by the Brunauer-Emmett-Teller model yielding a specific outer space area (63 m(2) g(-)(1)) which is consistent with estimated geometrical and pore size analysis data. 相似文献
6.
A silver selective electrode based on TEPQA‐MCM‐41 material was developed and used for the selective determination of Ag+ ion in various samples. The effect of various plasticizers i. e. dimethyl phthalate (DMP), Tris(ethylhexyl)phosphate (TEP), bis‐(2‐ethylhexyl)sebacate (BEHS), bis‐(2‐ethylhexyl)adipate (BEHA) was investigated. The electrode of the composition of 2 : 1 : 77 : 12 : 8 (w/w, %) of TEPQA‐MCM‐41 : NaTPB : Graphite powder : paraffin oil : DMP respectively, works satisfactorily in a wide concentration range of 1.3×10?9 M–1.0×10?1 M for Ag+ ion with a lower detection limit (LOD) of 1.0×10?9 M and has Nernstian slope of 63.4 1 mV/decay. The electrode can be used in a pH range of 2.3 to 6.7 for a period of 3 months without any divergence in potential response. The selectivity coefficient calculated by fixed interference method indicates the high selectivity of the electrode towards Ag+ ion over other tested cations. 相似文献
7.
Moriarty RM Rani N Enache LA Rao MS Batra H Guo L Penmasta RA Staszewski JP Tuladhar SM Prakash O Crich D Hirtopeanu A Gilardi R 《The Journal of organic chemistry》2004,69(6):1890-1902
A general and novel solution to the synthesis of biologically important stable analogues of prostacyclin PGI(2), namely benzindene prostacyclins, has been achieved via the stereoselective intramolecular Pauson-Khand cyclization (PKC). This work illustrates for the first time the synthetic utility and reliability of the asymmetric PKC route for synthesis and subsequent manufacture of a complex drug substance on a multikilogram scale. The synthetic route surmounts issues of individual step stereoselectivity and scalability. The key step in the synthesis involves efficient stereoselection effected in the PKC of a benzoenyne under the agency of the benzylic OTBDMS group, which serves as a temporary stereodirecting group that is conveniently removed via benzylic hydrogenolysis concomitantly with the catalytic hydrogenation of the enone PKC product. Thus the benzylic chiral center dictates the subsequent stereochemistry of the stereogenic centers at three carbon atoms (C(3a), C(9a), and C(1)). 相似文献
8.
A simple, rapid, and highly sensitive method for the detection of micro amounts of nitro compounds has been developed. Nitro compounds are reduced into corresponding hydroxylamines with zinc dust and acetic acid and coupled with diazonium chloride to give hydroxytriazines which give an intense pink to violet color with diphenylamine in acetic acid medium. Quantities of 0.1 μg or less of nitro compounds can be detected in 0.25 ml of total solution by this method. The method is free from the common interference. 相似文献
9.
Dinesh Kumar Ashu Rani D. S. N. Prasad K. S. Gupta 《Reaction Kinetics and Catalysis Letters》1991,43(1):133-141
The kinetics of the oxidation of 2-furancarboxaldehyde by thallic perchlorate at 50°C obeys the rate law
相似文献
10.
Dharmendra Kashyap Manushree Tanwar Chanchal Rani Pranit Hemant Bagde Siddharth Singh Nidhi Varshney Vaishali Saini Amit Mishra Rajesh Kumar Hem Chandra Jha 《Journal of Raman spectroscopy : JRS》2024,55(5):549-565
Helicobacter pylori and Epstein–Barr Virus (EBV) are Group 1 carcinogens that can enhance gastric cancer progression. Bioactive substances extracted from plants can be effective therapeutic agents in cancer treatment. For example, Withania somnifera extract-WSE reduces the Gankyrin oncoprotein, which is upregulated in the presence of H. pylori and EBV. The various biochemical and metabolic changes upon 24 hrs post-infection followed by W. somnifera extract (WSE) treatment on gastric epithelial cells (AGS) can be studied using spectroscopic techniques. In the biomedical sciences, Raman and NMR spectroscopy have been extensively employed to interpret cellular alterations contributing to the onset of infection and the severity of gastric cancer. More specifically, alterations in cellular biochemical homeostasis are linked to the moieties of cholesterol, collagen, choline, carbohydrate, lipids, tyrosine, and phenylalanine. Further, we have found significantly elevated FWHM for carbohydrates, tumor associated protein, collagen, cholesterol, and cholesterol ester in the co-infection model. We also looked into the potential correlation between these molecules using molecular network analysis and found several related factors that can be modulated through biomolecular levels. These molecules are crucial in several physiological functions, including cell division, cell proliferation, apoptosis, necrosis, cell migration, and lipid transport. Our study paves the pathway to study H. pylori and EBV co-infection in human gastric epithelial cells and the therapeutic interventions of WSE in this scenario and highlights specific biomolecular alterations, which can be focused for further mechanistic investigations. 相似文献
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