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71.
The model of dark matter featuring a component in the form of free particles and antiparticles (a, ā ) possessing self-interaction of the Coulomb type is considered. Darkmattermay form small-scale clumps where the annihilation of particles a and ā is enhanced. This annihilation may lead to observable effects (in cosmic rays, for example) and/or to the destruction of these clumps. However, there is an ambiguity in describing the annihilation (via recombination) of very slow particles, which may include a and ā in clumps. The effect of annihilation (in terms of the residual number of free particles a and ā in clumps) is estimated within two approaches (simplified quantum-mechanical and classical) at chosen parameter values. 相似文献
72.
The crystal structure of anosovite, (Ti1.69Al0.26Fe0.05)3+(Ti0.97Zr0.03)4+O5, prepared by carbothermal reduction of leucoxene under vacuum at 1450°C has been refined by Rietveld method using powder X‐ray diffraction data. It was found that it represents slightly monoclinically deformed pseudobrookite type structure with lattice parameters a = 9.8111 Å, b = 3.7509 Å, c = 9.9468 Å, β = 90.628°. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
73.
M. L. Levit O. V. Nazarova I. V. Moiseyuk A. V. Dobrodumov E. V. Didenko E. F. Panarin 《Polymer Science Series B》2012,54(1-2):41-49
On the basis of hydrophilic copolymers of N-vinylamides??N-vinylpyrrolidone and N-methyl-N-vinylacetamide??that contain carboxylic or activated ester groups, new polymeric ??-cyclodextrin derivatives are synthesized via polymer-analogous transformations. Their solubility in water depends on the content of ??-cyclodextrin and the types of hydrophilic and reactive comonomers. 相似文献
74.
The dependence of the Van Vleck component of the magnetic susceptibility of nanostructured cadmium sulfide CdS on the geometry and structure of CdS nanoparticles has been established by analyzing the data obtained from diffraction and magnetic measurements. It has been found that a decrease in the size of wurtzite CdS nanoparticles leads to an increase in the degree of distortion of the sp 3 orbitals (i.e., the degree of covalence), which reaches a limiting value for elongated particles with an average size of 9 nm. In particles with smaller sizes, the character of the orbital distortion sharply changes, and the Van Vleck contribution returns to the value typical of coarse-grained CdS. Nanoparticles less than 9 nm in size have a specific disordered close-packed structure and a centrosymmetric shape. The data obtained have made it possible to understand the reason of the dimensional phase transition from the crystalline state to a specific nanostate of cadmium sulfide. 相似文献
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Coastal erosion, accelerated by sea level rise, and subsidence are major Louisiana issues. With current sea-level-rise projections, coupled with the state's eroding barrier islands and coastal wetlands, the region's estuarine environments are in jeopardy of being lost, redefined, or permanently altered. As the coast erodes, Louisiana is endangered of losing valuable wetland's habitat. In addition, if the barrier islands disappear, the region's wetland-oriented oil and gas wells and associated infrastructure will be at risk to open Gulf conditions. If this should occur, each well, pipeline, and storage battery represents a potential environmental catastrophe. 相似文献
77.
CHEN Hong-jie LI Sheng LI Zhi-wei WU Zhi-shen ZHANG Ping-yu ZHANG Zhi-jun 《高等学校化学研究》2005,21(6):646-649
IntroductionMetal or alloy nanoparticles,because of their con-spicuous physicochemical properties,have been widelyapplied to various fields such as electronics,catalysis,magnetism,and corrosion-resistant materialsfields[1—4].It has been estimated that the particle sizeand the properties of nanoparticles depend strongly onthe specific method of fabrication and the applied ex-periment conditions,which makes the controlled syn-thesis of nanomaterials become an increasingly activeand important ar… 相似文献
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K. I. Belousov L. A. Nazarova A. V. Roiter V. V. Sergeichuk 《Ukrainian Mathematical Journal》1995,47(11):1661-1687
We prove that every finitely represented vectroid is determined, up to an isomorphism, by its completed biordered set. Elementary and multielementary representations of such vectroids (which play a central role for biinvolutive posets) are described.Translated from Ukrainskii Matematicheskii Zhurnal, Vol. 47, No. 11, pp. 1451–1477, November, 1995.The authors are indebted to P. Gabriel for discussions, in which the idea o f this paper emerged, and numerous remarks taken into account in the final version of the paper.This work was supported by the Foundation for Fundamental Research o f the Ukrainian State Committee on Science and Technology and the International Science Foundation (Grant No. U6E000). 相似文献