The relationship of graphite/AsF5 intercalation compounds to Cx+AsF6− salts

Graphite intercalated by AsF₅ has been reported to give compounds of formula C_8nAsF₅ where n is the stage. It is doubtful however if materials of exact composition C_8nAsF₅ have ever been obtained. The intercalation of graphite by AsF₅ is associated with electron oxidation of the graphite according to the equation: 3AsF₅ + 2e^? → 2AsF₆^? + AsF₃. Because of the easy removal or displacement of AsF₃ the As:F ratio is readily increased beyond 5. By treating graphite with excess AsF₅, removing volatiles under vacuum and repeating the cycle seven times a first stage salt C₁₀⁺AsF₆^? (C_o = 7.96 ā) is made. Interaction of graphite with AsFs in the molar ratio 8:1, within a small volume reactor, yields a material of approximate composition C₈AsF₅. The major component of the volatiles at the onset of their removal is AsF₅,, but, at a composition close to C₁₀AsF₅, is AsF₃. ‘Graphite AsF₅’ can be prepared by adding AsF₃ to C_xAsF₆ salts. The electrical conductivities of ‘AsF₅’ and AsF₆ relatives will be compared and discussed.     

Base-catalyzed polymerization of acryloyl- and methacryloyl-α-amino acid amides

N-Acryloylglycinamide, N-methacryloylglycinamide, N-acryloyl-DL - and L -alaninamide, and N-methacryloyl-DL - and -L -alaninamide were polymerized by basic catalysts. Polymers with low viscosities were obtained. Automatic amino acid analyses of the hydrolyzates of these polymers indicated that a hydrogen transfer from the terminal amide group took place along with vinyl polymerization. Hydrogen transfer from the secondary amide group was also observed. The ratio of the hydrogen transfer and the vinyl polymerizations was determined by results of automatic amino acid analyses.     

Structure-property relationship in py-hexahydrocinchonidine diastereomers: ab initio and NMR study

Two py-hexahydrocinchonidine diastereomers were selectively obtained in the heterogeneous catalytic hydrogenation of cinchonidine over supported Pt catalyst. The two isolated compounds when used as chiral base catalysts in the Michael addition of a beta-keto ester to methyl vinyl ketone gave products of opposite configuration in excess. To trace the reason of this behavior, in the present study, the structures of the two diastereomers were fully optimized by ab initio quantum chemical calculation. These results were then compared with several nuclear Overhauser enhancement spectroscopy (NOESY) signal intensities from the spectra of the two compounds. Further we performed a conformational search on all the optimized geometries independently for the two flexible torsional angles, which are linking the quinuclidine and tetrahydroquinoline moieties present in these molecules. This study allowed us to propose the configuration of the C(4)(') chiral center. Thus, the product mixture resulted in the hydrogenation of cinchonidine containing the 4'-(S)-diastereomer in excess (de = 20%). According to the computation results the 4'-(S)-diastereomer is more stable than the 4'-(R)-diastereomer. The 4'-(S)-conformer obtained by computation has lower electronic energy than the structures obtained for the 4'-(R)-diastereomer, which may explain the excess formation of the first one. The results of the Michael addition catalyzed by these diastereomers were interpreted on the basis of these conclusions.     

Quantitative microarray analysis of intact glycolipid-CD1d interaction and correlation with cell-based cytokine production

The protein CD1d binds self and foreign glycolipids for presentation to CD1-restricted T cells by means of TCR recognition and activates T(H)1 and T(H)2 chemokine release. In this study, a variety of glycolipid ligands were attached to a microarray surface and their binding with dimeric CD1d was investigated. An alpha-galactosyl ceramide (alpha-GalCer) bearing a carbamate group at the 6'-OH position was tethered to the surface, and the dissociation constant on surface with CD1d was determined to reflect the multivalent interaction. Competition assays were then used to determine the dissociation constants (Ki) of new and intact glycolipids in solution. The 4-fluorophenyloctanoyl-modified alpha-GalCer (18) was found to bind most strongly with CD1d (Ki 0.21 microM), 2 orders of magnitude stronger than alpha-GalCer and more than three times more selective than alpha-GalCer for IFN-gamma release from NKT cells. Various alpha-GalCer analogues were analyzed, and the results showed that the binding affinity of glycolipids to CD1d correlates well with IFN-gamma production but poorly with IL-4 secretion by NKT cells, suggesting that tighter binding ligands could bias cytokine release through the T(H)1 pathway.     

Organozeolite materials and their properties

Attempts in developing organozeolites, namely microporous and mesoporous crystalline inorganic-organic composites with a zeolite-like three-dimensional framework and organic moieties covalently connected to the framework, are briefly reviewed. MCM-41 type mesoporous materials modified by organic functional groups have been prepared by use of organosiloxane as a part of Si sources and by post-modification of the purely inorganic materials using organosiloxane. Also, the incorporation of organic moieties into the zeolite frameworks has been tried. Recently, several novel metal organophosphonates with a three-dimensional framework, which can be regarded as organozeolites, have been prepared. Along with these new attempts, the authors' studies in preparation, structural analysis and gas adsorption properties of microporous aluminomethylphosphonates are introduced.     

Lattice locations of 8Li in Cu

The dipolar broadening of the NMR on short-lived β-emitter ⁸Li implanted in single crystal Cu has been observed as a function of crystal orientation at several temperatures. From the orientation angle dependence of the line width, it was found that the main component of the ⁸Li occupies substitutional site, while about 30% of ⁸Li occupies octahedral interstitial site at temperatures below 300 K. This revised version was published online in August 2006 with corrections to the Cover Date.     

牙鲆群体Idh-1基因座位杂合型个体选择性优势

利用淀粉凝胶水平电泳法分析了人工牙鲆种苗群体的异柠檬酸脱氢酶同工酶 (IDH) .对牙鲆材料分析得知 Idh- 1基因座位只存在 A、B两个等位基因 ,而且在 2 3个样品群中 ,有 19个样品群呈现 A、B这两个等位基因所决定的基因型的杂合型个体过剩现象 ,表现出杂合基因型的选择性优势 .设定这 19个呈杂合型过剩样品群的死亡率为零 ,即以杂合型 A/ B的成活率为 10 0 %来计算其纯合型的成活率 ,得到纯合型个体 A/ A和 B/ B的成活率分别为 6 9.2 %和 75 .2 % ;从个体的标准体长上看 ,在表现为杂合型个体过剩的 19个样品群中 ,15个样品群的杂合型个体 (A/ B)大于纯合型个体 (B/ B) .其结果反映了牙鲆人工养殖放流群体的 Idh- 1的基因型与成活率及生长存在相关性 .     

Separation and enzymatic degradation of blend films of poly(L-lactic acid) and cellulose

Blend films of poly(L -lactic acid) (PLLA) and cellulose with various composition was prepared by casting from trifluoroacetic acid solution. One hydroxyl group per each glucose unit was esterified by trifluoroacetic acid. The trifluoroacetyl group was hydrolyzed completely during the degradation. Weight losses for 90/10 and 75/25 PLLA/cellulose blends by proteinaze K were greatly increased compared with pure PLLA sample due to the large depression of the crystallinity of PLLA component, while cellulase was effective only for the degradation of pure cellulose film. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1861–1864, 1998     

A Local Thermal Non-Equilibrium Solution Based on the Brinkman–Forchheimer-Extended Darcy Model for Thermally and Hydrodynamically Fully Developed Flow in a Channel Filled with a Porous Medium

Transport in Porous Media - A general analytical solution procedure for the Brinkman–Forchheimer-extended Darcy model has been proposed to obtain local thermal non-equilibrium solutions for...