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排序方式: 共有113条查询结果,搜索用时 15 毫秒
1.
G. Date T. R. Govindarajan P. Sankaran R. Shankar 《Communications in Mathematical Physics》1990,132(2):293-313
We compute the homotopy groups
0 and
1 of the classical configuration space of anO(3) invariant field theory on
×, where
is a compact two dimensional manifold for arbitrary genusg and- denotes the time coordinate. We also present the finite dimensional, unitary, irreducible, inequivalent representations of the appropriate fundamental groups and comment on some of their implications. 相似文献
2.
3.
Tetsuro Shimo Shinichi Yamasaki Kenichi Date Hisako Uemura Kenichi Somekawa 《Journal of heterocyclic chemistry》1993,30(2):419-423
Photosensitized cycloaddition of 4,6-dimethyl-2-pyrone ( 1 ) with methacrylonitrile ( 3b ) afforded two types of [2 + 2]cycloadducts, 4b and 6b , across the C5-C6 and C3-C4 double bonds in 1 , respectively. Photosensitized reactions of 1 with dimethyl maleate and dimethyl cyclobutene-1,2-dicarboxylate gave [2 + 2]cycload-ducts 4d, 4e across the C5-C6 double bond, in addition to [4 + 2]cycloadduct 9d or bicyclo[4.2.0]octadiene 10e . The photoreactions of methyl 2-pyrone-5-carboxylate ( 2 ) with 3b and 2-chloroacrylonitrile ( 3c ) gave [4 + 2]cycloadducts 5b, 5c in addition to [2 + 2]cycloadducts 11b and 11c across the C5-C6 double bond in 2 . The photocycloaddition mechanism was explained from results calculated by means of PM3-CI method. Namely, the site- and/or regio-selective products, 4, 5, 8, 9 and 10 were thought to come from the same site-selective radical intermediates in the case of electron-poor olefins. Pyrolysis and/or hydrolysis of the cycload-ducts 4e, 5b, 5c gave 5,6-dihydro-2-pyrone 12 or benzene derivatives. 相似文献
4.
5.
A combined ion chromatography (IC) with inductively coupled plasma mass spectrometry (ICP—MS) system as an element-selective detector has been used for the determination of arsenic compounds. Seven arsenic compounds were separated by cation-exchange chromatography. Subsequently, the separated arsenic compounds were directly introduced into the ICP—MS and were detected at m/z =75. Detection limits for the seven arsenic compounds ranged from 0.8 to 3.8 μg As/l. The IC–ICP–MS system was applied to the determination of arsenic compounds in the urine of dimethylarsinic acid (DMAA)-exposed rats. DMAA was the most abundant arsenic compound detected. Arsenous acid, monomethylarsonic acid and trimethylarsine oxide were also detected. 相似文献
6.
The spinel FeCoCrO4 has been studied between 4.2 and 538°K. Characteristic Mossbauer spectra of paramagnetic, magnetic and electronic relaxation types have been observed. The Mossbauer parameters for Fe3+ ions situated at tetrahedral (A) and octahedral (B) sites have been calculated. The cation distribution in magnetic and paramagnetic phases is found to be approximately Fe0.53+Co0.52+[Co0.52+Fe0.53+Cr3+]O4. The Neel temperature been determined by the temperature scanning method to be 310±5°K. 相似文献
7.
A space-time filled with the self-gravitating charged fluid with constant electric permitivity and constant magnetic permeability is investigated. On expressing the stress-energy tensor in terms of an orthonormal tetrad, the equations of motion and Maxwell equations are formulated. In case of the geodesic flow, the conditions for divergence-free electric and magnetic fields are obtained. It is shown that the space-time permeated by the charged fluid with the electric field orthogonal to the magnetic one is embedded in 5-dimensional flat class-one space-time if and only if the electromagnetic energy flux vector vanishes. 相似文献
8.
H. Suematsu K. Ohmatsu K. Sugiyama T. Sakakibara M. Motokawa M. Date 《Solid State Communications》1981,40(3):241-243
The whole magnetization curve of the first stage compound C6Eu has been measured by using pulsed fields up to 400 kG below 40 K. For H ⊥ c, c being the crystal c-axis, four regions are observed in the magnetization curve; I) the initial magnetization region with an apparent moment of ~ 0.6microB per Eu ion (H < 12 kG), II) the intermediate region with nearly constant moment of 2.2 – 2.7 microB, which corresponds to the full moment of Eu2+ ion (22 < H < 82 kG), III) the region of a linear field dependence (82 < H < 205 kG), and IV) the saturation region above 205 kG, where the saturation moment is found as 6.2 microB. For H//c, the magnetization increases monotonically and approaches to a saturation value corresponding to 6 microB above 240 kG. 相似文献
9.
10.
Nonperturbative corrections from loop quantum cosmology (LQC) to the scalar matter sector are already known to imply inflation. We prove that the LQC modified scalar field generates exponential inflation in the small scale factor regime, for all positive definite potentials, independent of initial conditions and independent of ambiguity parameters. For positive semidefinite potentials it is always possible to choose, without fine-tuning, a value of one of the ambiguity parameters such that exponential inflation results, provided zeros of the potential are approached at most as a power law in the scale factor. In conjunction with the generic occurrence of bounce at small volumes, particle horizon is absent, thus eliminating the horizon problem of the standard big bang model. 相似文献