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排序方式: 共有1275条查询结果,搜索用时 15 毫秒
1.
Foda Omar Leclerc Bernard Okado Masato Thibon Jean-Yves Welsh Trevor A. 《Letters in Mathematical Physics》1998,43(1):31-42
A special family of partitions occurs in two apparently unrelated contexts: the evaluation of one-dimensional configuration sums of certain RSOS models, and the modular representation theory of symmetric groups or their Hecke algebras Hm. We provide an explanation of this coincidence by showing how the irreducible Hm-modules which remain irreducible under restriction to Hm_1 (Jantzen–Seitz modules) can be determined from the decomposition of a tensor product of representations sln. 相似文献
2.
The interaction between poly(methymethacrylate) (PMMA) and poly(vinyl chloride) (PVC) has been studied indilute urea solutions of dimethylformamide (DMF) at 28℃ using a dilute solution viscometry method. The results show thatthe polymer mixtures are compatible in DMF solution in the absence of urea. The influence of urea addition on the degree ofcompatibility of the polymer mixtures has been studied in terms of the compatibility parameters (△b_m and △[η]_m). It wasfound that the compatibility of the polymer mixtures is decreased with increasing urea addition, passing through a minimumat 0.5 M urea. 相似文献
3.
The enantiomers of 34 pharmaceutical weak-base analytes were separated by nonaqueous capillary electrophoresis in acidic methanol background electrolytes using the sodium salt of the new, single-isomer chiral resolving agent, octakis(2,3-O-dimethyl-6-O-sulfo)-gamma-cyclodextrin (ODMS). The effective mobilities, separation selectivities and peak resolution values of the weak-base analytes were determined as a function of the ODMS concentration in the 0-40 mM range and were found to follow the theoretical predictions of the charged resolving agent migration model (CHARM model) modified for ionic strength effects. Fast, efficient separations were achieved for both comparatively small and large enantiomers. 相似文献
4.
Two simple and sensitive spectrophotometric methods are described for the determination of six penicillin derivatives. The methods are based on the reaction of these drugs as n-electron donors with either 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ) or 7,7,8,8-tetracyanoquinodimethane (TCNQ) as pi-acceptors, to give a highly coloured radical anion. The coloured products are quantified spectrophotometrically at 460 and 842 nm for DDQ and TCNQ, respectively. The optimization of the different experimental conditions is described. The interference from streptomycin sulphate and common degradation products was also studied. The proposed methods were applied successfully to the determination of the different penicillins investigated, either in pure or dosage forms, with good accuracy and precision. The results were compared with those given by the official United States Pharmacopeial XXI method. 相似文献
5.
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
6.
7.
Omar Deeb Prof. Monika Leibscher Dr. Jörn Manz Prof. Wulf von Muellern Tamar Seideman Prof. 《Chemphyschem》2007,8(2):322-328
We propose an approach for separating nuclear spin isomers with coherent light and illustrate it by numerical calculations using fulvene as a model system. The scheme employs the equivalence of torsion and interchange of equivalent H-atoms in a class of molecules of which fulvene is a simple example. The exchange symmetry couples with the rotational symmetry to produce a spatial distinction between the two photo-excited nuclear spin isomers, and wavepacket interferometry is applied to separate the species. 相似文献
8.
Contrary to an earlier report, lithiation of tris(trimethylsilyl)methane followed by carbonation does not yield the acid (Me3Si)3CCO2H, (I), if an alkali extraction step is included in the work up; the product is actually the acid (Me3Si)2CHCO2H, (II). The acid (I) can be obtained if the alkali extraction is omitted. Separate experiments have confirmed that (I) is rapidly converted into (II) by aqueous or methanolic base. 相似文献
9.
Metal-organic frameworks with exceptionally high capacity for storage of carbon dioxide at room temperature 总被引:4,自引:0,他引:4
Metal-organic frameworks (MOFs) show high CO2 storage capacity at room temperature. Gravimetric CO2 isotherms for MOF-2, MOF-505, Cu3(BTC)2, MOF-74, IRMOFs-11, -3, -6, and -1, and MOF-177 are reported up to 42 bar. Type I isotherms are found in all cases except for MOFs based on Zn4O(O2C)6 clusters, which reveal a sigmoidal isotherm (having a step). The various pressures of the isotherm steps correlate with increasing pore size, which indicates potential for gas separations. The amine functionality of the IRMOF-3 pore shows evidence of relatively increased affinity for CO2. Capacities qualitatively scale with surface area and range from 3.2 mmol/g for MOF-2 to 33.5 mmol/g (320 cm3(STP)/cm3, 147 wt %) for MOF-177, the highest CO2 capacity of any porous material reported. 相似文献
10.