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1.
Lev Buhovsky 《Israel Journal of Mathematics》2004,143(1):181-187
In this paper we find homological restrictions on Lagrangians in cotangent bundles of spheres and Lens spaces.
This research was supported by the Israel Science Foundation (grand No. 205/02). 相似文献
2.
The main results of the paper are as follows: covering characterizations of wQN-spaces, covering characterizations of QN-spaces and a theorem saying that Cp(X) has the Arkhangel'ski?ˇ property (α1) provided that X is a QN-space. The latter statement solves a problem posed by M. Scheepers [M. Scheepers, Cp(X) and Arhangel'ski?ˇ's αi-spaces, Topology Appl. 89 (1998) 265-275] and for Tychonoff spaces was independently proved by M. Sakai [M. Sakai, The sequence selection properties of Cp(X), Preprint, April 25, 2006]. As the most interesting result we consider the equivalence that a normal topological space X is a wQN-space if and only if X has the property S1(Γshr,Γ). Moreover we show that X is a QN-space if and only if Cp(X) has the property (α0), and for perfectly normal spaces, if and only if X has the covering property (β3). 相似文献
3.
The relativistic correction to the triton binding energy approximated to the order (v/c)2 is calculated in the framework of relativistic Hamiltonian dynamics. We discuss the generator representation of the Poincaré group for three relativistic particles and its connection with the Feynman diagrams in the infinite-momentum frame (the light-front dynamics). The relativistic correction enhances the attraction in the three-nucleon system. The five-channel calculation with the Reid soft-core potential yeilds the result =–0.54 MeV, which is governed mainly by theD-wave contribution. TheS-wave contributions to are only –0.10 MeV. 相似文献
4.
S. V. Lev R. P. Zakirova Z. Saatov M. V. Gorovits N. K. Abubakirov 《Chemistry of Natural Compounds》1990,26(1):40-41
The possibility has been studied of obtaining ecdysteroids — ecdysterone and turkesterone — with the aid of a culture of the tissues and cells of the plantAjuga turkestanica. Conditions have been selected under which the yield of ecdysteroids in the culture of tissues and cells is comparable with amounts of the same substances in the organs of the whole plant.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 51–52, January–February, 1990. 相似文献
5.
6.
Polyethylene based composites are attractive materials for advanced circuit board applications because of their unique combination of properties: low dielectric constant and loss factor, light weight, high flexural modulus and low thermal expansion coefficient controlled in all spatial directions. This investigation describes a process to consolidate chopped fibers of ultra‐high molecular weight polyethylene concurrently with its bonding to a copper foil. Bonding is affected by a thin sheet of low‐density polyethylene, incorporating a crosslinking agent with a concentration gradient across the sheets thickness. In this single step process, the composite material is formed and bonded to the metal foil, achieving good adhesion without the use of extraneous glue. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
7.
Ryzhkov LR 《The Journal of organic chemistry》1996,61(8):2801-2808
Thermal decomposition of a primary alkyl diacyl peroxide 2 is investigated. Dependence of product yields on temperature, viscosity, and solvent polarity is examined in a variety of media. The excess of the alkene disproportionation product 4 and the presence of ester 3 and acid 5 is argued to demonstrate the existence of a discrete acyloxy-alkyl geminate radical pair. Stereoselective deuterium labeling of 2 and subsequent (1)H-NMR analysis of the resulting isotopomers of 4 confirm the radical nature of detected decomposition products. 相似文献
8.
In the two-photon visible dissociation of the iodobenzene cation, laser pulse shape is unimportant when collisional relaxation is slow compared to the time between pulses but becomes important when the relaxation rate is comparable to time between pulses. The dissociation can be simulated using an internal energy-governed computer model. 相似文献
9.
Crich D Mataka J Zakharov LN Rheingold AL Wink DJ 《Journal of the American Chemical Society》2002,124(21):6028-6036
A series of four S-allyl D-thiopyranosides, alpha- and beta-manno and xylo, were oxidized with MCPBA at low temperature to give seven of the eight possible sulfoxides, whose configuration at sulfur was determined either directly by X-ray crystallography or by correlation with closely related structures. For the axial thioglycosides oxidation leads very predominantly to the (R)(S)-diastereomer in the xylo series and exclusively so in the manno series; the configuration at C2 is of little importance in determining the stereoselectivity of oxidation of axial thioglycopyranosides. In the equatorial series the configuration at C2 has a significant effect on the outcome of the reaction as, although both series favored the (S)(S)-sulfoxide, selectivity was significantly higher in the case of the beta-mannoside than of the beta-xyloside. The two alpha-xylo sulfoxides have different conformations of the pyranoside ring with the (R)(S)-isomer adopting the (1)C(4) chair and the (S)(S)-diastereomer the (4)C(1). Each pair of diastereomeric sulfoxides was thermally equilibrated in C(6)D(6) and in CD(3)OD. In the mannose series the kinetic isomers are also thermodynamically preferred. In the xylose series, on the other hand, the nature of the thermodynamic isomer in both the alpha- and beta-anomers is a function of solvent with a switch observed on going from C(6)D(6) to CD(3)OD. The results are rationalized in terms of the exo-anomeric effect, steric shielding provided by H3 and H5 in the axial series, the interaction of the C2-O2 and sulfoxide dipoles, and increased steric interactions on hydrogen bonding of the sulfoxides to CD(3)OD. 相似文献
10.
The Incorporation of Titania into Modified Silicates for Solar Photodegradation of Aqueous Species 总被引:2,自引:0,他引:2
Lowell R. Matthews David Avnir Alexander D. Modestov Srinivasan Sampath Ovadia Lev 《Journal of Sol-Gel Science and Technology》1997,8(1-3):619-623
A new class of sol-gel-derived photocatalytic materials has been synthesized and used in solar-assisted photodegradation studies. The materials are comprised of a homogeneous dispersion of commercial TiO2 powder into silica and organically modified silicate (Ormosil) hosts. The efficiency of the photocatalytic properties of these TiO2-containing materials was determined by their relative performance in the solar photodecomposition of aqueous rhodamine B. The improved adsorption properties of the modified materials compared to commercial TiO2 increase the photodecomposition rate and the buoyancy properties, although excess hydrophobicity decreases the wetted section of the catalyst and its photocatalytic performance. These materials can be used as floatable catalysts for solar-assisted water purification. 相似文献