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131.
132.
John M. Newsam Anthony K. Cheetham Bruce C. Tofield 《Journal of solid state chemistry》1985,60(2):214-229
The structure of anhydrous stoichiometric deuterium β-alumina, Dal11O17, has been determined at 4.2, 298, 573, and 720 K by profile refinement of powder neutron diffraction data. At each temperature the deuterium is found to lie in well-defined threefold sites close to the spacer oxygen, O(5). There is no evidence for delocalization of the deuterium away from O(5) and such a hydroxyl linkage is in accord with the low protonic conductivity observed in related materials. The effect of this unusual mirror-plane arrangement on the remainder of the structure and the variation with temperature of the lattice constants, bond lengths, and angles are discussed. 相似文献
133.
Non-resonant microwave absorption (NRMA) studies of superconducting MgB2 and a sample containing ∼10% by weight of MgO in MgB2 are reported. The NRMA results indicate near absence of intergranular weak links in the pure MgB2 sample. A linear temperature dependence of the lower critical field H
c1 is observed indicating a non-s wave superconductivity. However, the phase reversal of the NRMA signal which could suggest d wave symmetry is also not observed. In the MgB2 + MgO sample, much larger low field dependent absorption is observed indicating the presence of intergranular weak links.
The hysteretic behavior of NRMA is compared and contrasted in the two samples. In the pure MgB2 sample, a large hysteresis is observed between the forward and the reverse scans of the magnetic field indicating strong
pinning of flux lines. This hysteresis saturates a few degrees below T
c while in the MgB2 + MgO sample, a much slower increase of hysteresis with decreasing temperature is observed, a signature of weaker pinning. 相似文献
134.
Cheetham MR Bramble JP McMillan DG Krzeminski L Han X Johnson BR Bushby RJ Olmsted PD Jeuken LJ Marritt SJ Butt JN Evans SD 《Journal of the American Chemical Society》2011,133(17):6521-6524
Membrane proteins are key components of the plasma membrane and are responsible for control of chemical ionic gradients, metabolite and nutrient transfer, and signal transduction between the interior of cells and the external environment. Of the genes in the human genome, 30% code for membrane proteins (Krogh et al. J. Mol. Biol.2001, 305, 567). Furthermore, many FDA-approved drugs target such proteins (Overington et al. Nat. Rev. Drug Discovery 2006, 5, 993). However, the structure-function relationships of these are notably sparse because of difficulties in their purification and handling outside of their membranous environment. Methods that permit the manipulation of membrane components while they are still in the membrane would find widespread application in separation, purification, and eventual structure-function determination of these species (Poo et al. Nature 1977, 265, 602). Here we show that asymmetrically patterned supported lipid bilayers in combination with AC electric fields can lead to efficient manipulation of charged components. We demonstrate the concentration and trapping of such components through the use of a "nested trap" and show that this method is capable of yielding an approximately 30-fold increase in the average protein concentration. Upon removal of the field, the material remains trapped for several hours as a result of topographically restricted diffusion. Our results indicate that this method can be used for concentrating and trapping charged membrane components while they are still within their membranous environment. We anticipate that our approach could find widespread application in the manipulation and study of membrane proteins. 相似文献
135.
A detailed examination has been undertaken of the high field 13C-NMR spectrum of various acrylonitrile/vinyl acetate copolymers prepared by radical initiation in a heterogeneous aqueous batch reaction (taken to low conversion). It has been possible to establish the triad, tetrad and pentad sequences for copolymers employing sequence patterns and peak fractions as an aid to peak assignments. These results indicate that the copolymer cotacticity is virtually independent of the comonomer feed ratio. 相似文献
136.
The use of hexamethylphosphoramide as a single source of amine and phosphorus has made it possible to synthesize new three-dimensional zinc phosphate frameworks under solvothermal conditions. 相似文献
137.
138.
139.
W.T.A. Harrison U. Chowdhry C.J. Machiels A.W. Sleight A.K. Cheetham 《Journal of solid state chemistry》1985,60(1):101-106
Pure ferric tungstate, Fe2(WO4)3, has been prepared and characterized for the first time. Ferric tungstate has a structure very similar to that of ferric molybdate with a unit cell volume about 1.5% larger. Decomposition to Fe2WO6 and WO3 occurs at about 600°C. Ferric tungstate was tested as a catalyst for the selective oxidation of methanol and shown to have very different properties from ferric molybdate for this reaction. Whereas over the molybdate the predominant reaction is oxidation of methanol to formaldehyde, over the tungstate it is dehydration to dimethyl ether. 相似文献
140.
Adam V. Marsh Nathan J. Cheetham Dr. Mark Little Dr. Matthew Dyson Dr. Andrew J. P. White Dr. Peter Beavis Dr. Colin N. Warriner Dr. Anthony C. Swain Prof. Paul N. Stavrinou Prof. Martin Heeney 《Angewandte Chemie (International ed. in English)》2018,57(33):10640-10645
The synthesis of a highly twisted chrysene derivative incorporating two electron deficient o‐carboranyl groups is reported. The molecule exhibits a complex, excitation‐dependent photoluminescence, including aggregation‐induced emission (AIE) with good quantum efficiency and an exceptionally long singlet excited state lifetime. Through a combination of detailed optical studies and theoretical calculations, the excited state species are identified, including an unusual excimer induced by the presence of o‐carborane. This is the first time that o‐carborane has been shown to induce excimer formation ab initio, as well as the first observation of excimer emission by a chrysene‐based small molecule in solution. Bis‐o‐carboranyl chrysene is thus an initial member of a new family of o‐carboranyl phenacenes exhibiting a novel architecture for highly‐efficient multi‐luminescent fluorophores. 相似文献