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排序方式: 共有234条查询结果,搜索用时 15 毫秒
31.
Julien P.A. Makongo Dinesh K. Misra James R. Salvador Nathan J. Takas Guoyu Wang Michael R. Shabetai Aditya Pant Pravin Paudel Ctirad Uher Kevin L. Stokes Pierre F.P. Poudeu 《Journal of solid state chemistry》2011,184(11):2948-2960
Bulk Zr0.25Hf075NiSn half-Heusler (HH) nanocomposites containing various mole fractions of full-Heusler (FH) inclusions were prepared by solid state reaction of pre-synthesized HH alloy with elemental Ni at 1073 K. The microstructures of spark plasma sintered specimens of the HH/FH nanocomposites were investigated using transmission electron microscopy and their thermoelectric properties were measured from 300 K to 775 K. The formation of coherent FH inclusions into the HH matrix arises from solid-state Ni diffusion into vacant sites of the HH structure. HH(1–y)/FH(y) composites with mole fraction of FH inclusions below the percolation threshold, y∼0.2, show increased electrical conductivity, reduced Seebeck coefficient and increased total thermal conductivity arising from gradual increase in the carrier concentration for composites. A drastic reduction (∼55%) in κl was observed for the composite with y=0.6 and is attributed to enhanced phonon scattering due to mass fluctuations between FH and HH, and high density of HH/FH interfaces. 相似文献
32.
Pravin G. Bhuta 《Zeitschrift für Angewandte Mathematik und Physik (ZAMP)》1964,15(6):647-652
Zusammenfassung Für einen beidseitig eingespannten schlanken Stab, dessen Enden sich auf einem Kreis verschieben können, wird die exakte Lösung entwickelt. Die Reaktionen sowie die elastische Linie lassen sich mit Hilfe von elliptischen Integralen erster und zweiter Gattung bestimmen. Ein numerisches Beispiel zeigt die Anwendung der behandelten Methode, die bei der Konstruktion gewisser drehbarer Einspannung von Interesse ist. 相似文献
33.
In the past two decades a large initiative has been put forth to understand the biological and pathogenic properties of the human T-cell lymphotropic virus type 1 (HTLV-1); this has ultimately led to the development of various experimental vaccination and therapeutic strategies to combat HTLV-1 infection. The focus of this work is to outline key targets for the design of therapeutics for HTLV-1, such as fusion mediated by the envelope glycoprotein, and to discuss reports of novel vaccines or therapeutics. These strategies include peptide, recombinant protein, DNA, and viral vectors. The final focus of this review is to acquaint the reader with vaccine approaches developed in our laboratory over the last decade. These strategies include the development of envelope glycoprotein derived B-cell epitopes for the induction of neutralizing antibodies, as well as a strategy to generate a multivalent cytotoxic T-lymphocyte (CTL) response against the HTLV-1 Tax antigen. 相似文献
34.
Consider a tandem queue model with a single server who can switch instantaneously from one queue to another. Customers arrive according to a Poisson process with rate λ . The amount of service required by each customer at the ith queue is an exponentially distributed random variable with rate μi. Whenever two or more customers are in the system, the decision as to which customer should be served first depends on the optimzation criterion. In this system all server allocation policies in the finite set of work conserving deterministic policies have the same expected first passage times (makespan) to empty the system of customers from any initial state. However, a unique policy maximizes the first passage probability of empty-ing the system before the number of customers exceeds K, for any value of K, and it stochastically minimizes (he number of customers in the system at any time t > 0 . This policy always assigns the server to the non empty queue closest to the exit 相似文献
35.
We demonstrate, analytically and experimentally, a simple, but effective method to determine the topological charge of an optical vortex by using a spherical bi-convex lens, a ubiquitous optical element found in any optics laboratory. Just by tilting the lens and recording the intensity distribution of a propagating vortex at a predicted position past the lens, we have been able to measure both the sign and the magnitude of the topological charge m up to m=±14. Our experimental results are in excellent agreement with analytical predictions. 相似文献
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The CuSO4/ascorbate-mediated ‘click’ reaction of 2-(2-azidophenyl)-4,5-diaryloxazoles and arylacetylenes proceeded through an alternate pathway whereby reduction of the azide predominated over formation of the 1,2,3-triazole-forming cycloaddition. The unimolecular product, 2-(2-aminophenyl)-4,5-diphenyloxazole, was isolated which appears to be a formal reduction of the arylazide to the corresponding arylamine. A series of oxazoles which possessed various substituents (F, Cl, Br, OCH3) on the 4,5-diaryl rings and having the 2-azido group on the 2-oxazolylphenyl position were submitted to the same ‘click’ conditions and gave the corresponding arylamine products (73–99%). The reaction appears to be specific toward the ortho-azido substitution of the polycyclic system, as the corresponding azidomethyl-substituted phenyl oxazoles do not give the ‘reduction’ products but gave the expected click products with the acetylenic co-reactants. 相似文献
39.
An efficient copper-aluminum hydrotalcite catalyst for asymmetric hydrosilylation of ketones at room temperature 总被引:1,自引:0,他引:1
Kantam ML Laha S Yadav J Likhar PR Sreedhar B Jha S Bhargava S Udayakiran M Jagadeesh B 《Organic letters》2008,10(14):2979-2982
A catalyst system consisting of a copper-aluminum hydrotalcite-chiral diphosphine ligand effects asymmetric hydrosilylation of several ketones, using polymethylhydrosiloxane (PMHS) as the stoichiometric reducing agent at room temperature, with moderate-to-excellent enantioselectivities. The catalyst is recovered by simple centrifugation, and the efficiency of the catalyst remains almost unaltered even after several cycles. 相似文献
40.
Pravin Shende Renuka Chaphalkar Kiran Deshmukh R. S. Gaud 《Journal of Dispersion Science and Technology》2016,37(4):504-511
Lansoprazole is a proton-pump inhibitor used in treatment of gastric ulcers, gastroesophageal reflux disease (GERD), and Zollinger–Ellison syndrome. The objective of the study was physicochemical investigation and comparative characterization of nanosuspensions of lansoprazole by complexing with β-cyclodextrin and β-cyclodextrin-based nanosponges to enhance its solubility and stability. Inclusion complexes of lansoprazole with β-cyclodextrin and nanosponges were prepared by physical method and polymer condensation method, respectively. Particle size, zeta potential, encapsulation efficiency, in vitro release, FTIR, and Differential Scanning Calorimeter (DSC) studies were used as characterization parameters. The average particle size of lansoprazole nanoparticles was found to be in the range of 178.7 ± 6.39 nm to 204.9 ± 2.91 nm. The high zeta potential values were attained to ensure a high-energy barrier and favor a good stability of nanosuspensions. In vitro release study showed the controlled release of lansoprazole, which was more satisfactory than individual drug. FTIR spectroscopy showed that there was interaction of cyclodextrin and its nanosponges with drug. DSC study revealed that drug was involved in complexion with cyclodextrin and nanosponges. Solubility and stability of lansoprazole were remarkably improved by inclusion complexation. Based on these findings, it can be concluded that engineered nanosuspension of lansoprazole is a promising carrier for nanoparticulate drug delivery in gastric ulcer. 相似文献