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111.
D. Greig M. J. Hall C. Hammond B. J. Hickey H. P. Ho M. A. Howson M. J. Walker N. Wiser D. G. Wright 《Journal of magnetism and magnetic materials》1992,110(3):L239-L246
We report the first observation of a giant magnetoresistance (MR) in Co/Cu superlattices grown by MBE. The maximum value of the MR is - 26% and this is found in a specimen for which the copper layers are about 7 Å thick and which includes a thin 10 Å layer of gold in the buffer region between the substrate and the superlattice. From RHEED and X-ray diffraction it is shown that the metallic layers in the specimens grown in this way are extremely flat and that the orientation of the copper is (111). 相似文献
112.
Accurate comparative measurements have been made of the X-ray diffraction pattern of a bulk arsenic sulphide glass prepared from the melt and a 250 μm film prepared by vapour deposition of the evaporated bulk. By using Ag Kα radiation, measurements have been made up to so as to give good spatial resolution. Significant differences are found between bulk and film specimens, and in particular a shoulder is found on the high r side of the first peak in the distribution function for the film. Also, the film is richer in arsenic than the parent bulk. The results are compared in detail with a number of models, all of which involve covalent bonding requirements being fully satisfied, and it is concluded that there are more AsAs bonds in the film than the minimum required by stoichiometry and that a significant fraction () of these are unusually long ( compared to the more usual 2.5 Å). The most probable explanation is that the vapour contains a significant fraction of As4S4 species (in which the AsAs distances are ) and that the film contains a mixture of molecular species which have undergone considerable polymerization. The extent to which this results in a sheet-like structure similar to that proposed for the bulk glass remains unclear. 相似文献
113.
Thomas R. Puleo Stephen J. Sujansky Shawn E. Wright Prof. Dr. Jeffrey S. Bandar 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(13):4216-4229
Organic superbases are a distinct and increasingly utilized class of Brønsted base that possess properties complementary to common inorganic bases. This Concept article discusses recent applications of commercial organic superbases in modern synthetic methodologies. Examples of the advantages of organic superbases in three areas are highlighted, including the discovery of new base-catalyzed reactions, the optimization of reactions that require stoichiometric Brønsted base, and in high-throughput experimentation technology. 相似文献
114.
A key contact in the active site of an aminoglycoside phosphotransferase enzyme (APH(3')-IIIa) is a pi-pi stacking interaction between Tyr42 and the adenine ring of bound nucleotides. We investigated the prevalence of similar Tyr-adenine contacts and found that many different protein systems employ Tyr residues in the recognition of the adenine ring. The geometry of these stacking interactions suggests that electrostatics play a role in the attraction between these aromatic systems. Kinetic and calorimetric experiments on wild-type and mutant forms of APH(3')-IIIa yielded further experimental evidence of the importance of electrostatics in the adenine binding region and suggested that the stacking interaction contributes approximately 2 kcal/mol of binding energy. This type of information concerning the forces that govern nucleotide binding in APH(3')-IIIa will facilitate inhibitor design strategies that target the nucleotide binding site of APH-type enzymes. 相似文献
115.
Bearman KR Blackmore DC Carter TJ Colin F Wright JD Ross SA 《Chemical communications (Cambridge, England)》2002,(9):980-981
Encapsulation of Amberlyst A-26 supported tribromide in a 10,000 MW polyethylene glycol matrix gives a robust colour-sensitive reagent matrix which can be deposited on indium-tin oxide coated polyvinylidene fluoride (PVDF) piezoelectric film for the detection of styrene (and other alkene) vapours. 相似文献
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Tripathi S Armstrong DS Christy ME Clark JH Gorringe TP Hasinoff MD Kovash MA Wright DH Zołnierczuk PA 《Physical review letters》2002,89(25):252501
We report the first observation of double radiative capture on pionic hydrogen. The experiment was conducted at the TRIUMF cyclotron using the RMC spectrometer and detected gamma-ray coincidences following pi(-) stops in liquid hydrogen. We found the branching ratio for double radiative capture to be [3.05+/-0.27(stat)+/-0.31(syst)]x10(-5). The measured branching ratio and angle-energy distributions support the theoretical prediction of a dominant contribution from the pipi-->gammagamma annihilation mechanism. 相似文献
119.
We develop a variational theory of the crossover from the one-dimensional (1D) regime to the 3D regime for ultracold Bose gases in thin waveguides. Within the 1D regime we map out the parameter space for fermionization, which may span the full 1D regime for suitable transverse confinement. 相似文献
120.