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排序方式: 共有89条查询结果,搜索用时 31 毫秒
31.
Burchat PR King M Abrams GS Adolphsen CE Averill D Ballam J Barish BC Barklow T Barnett BA Bartelt J Bethke S Blockus D Bonvicini G Boyarski A Brabson B Breakstone A Bulos F Burke DL Cence RJ Chapman J Chmeissani M Cords D Coupal DP Dauncey P DeStaebler HC Dorfan DE Dorfan JM Drewer DC Elia R Feldman GJ Fernandes D Field RC Ford WT Fordham C Frey R Fujino D Gan KK Gatto C Gero E Gidal G Glanzman T Goldhaber G Gomez Cadenas JJ Gratta G Grindhammer G Grosse-Wiesmann P Hanson G Harr R Harral B 《Physical review D: Particles and fields》1990,41(11):3542-3545
32.
Abrams GS Adolphsen CE Averill D Ballam J Barish BC Barklow T Barnett BA Bartelt J Bethke S Blockus D Bonvicini G Boyarski A Brabson B Breakstone A Bulos F Burchat PR Burke DL Cence RJ Chapman J Chmeissani M Cords D Coupal DP Dauncey P DeStaebler HC Dorfan DE Dorfan JM Drewer DC Elia R Feldman GJ Fernandes D Field RC Ford WT Fordham C Frey R Fujino D Gan KK Gero E Gidal G Glanzman T Goldhaber G Gomez Cadenas JJ Gratta G Grindhammer G Grosse-Wiesmann P Hanson G Harr R Harral B Harris FA 《Physical review letters》1989,63(22):2447-2451
33.
C. B. Vicentini A. C. Veronese M. Guarneri M. Manfrini P. Giori S. Guccione 《Journal of heterocyclic chemistry》1994,31(6):1477-1480
Thiation of N-(1-tert-butyl-3-methylpyrazol-5-yl)carboxamides 2 with the Lawesson reagent afforded the corresponding thiocarboxamides 3 . Heating of 3 in formic acid gave the N-dealkylated thiocarboxamides 4 which were cyclized into 4H-pyrazolo[1,5-c][1,3,5]thiadiazine-4-thiones 5 by treatment with thiophosgene. 相似文献
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In this paper we study the well-known example of the ideal generated by all the r × r minors in the generic n × m matrix (Xij) from the point of view of Gröebner bases. 相似文献
36.
Jorge A. Guccione Juan J. Guccione 《Proceedings of the American Mathematical Society》2004,132(5):1241-1250
Let be a field, a finite-dimensional Frobenius -algebra and , the Nakayama automorphism of with respect to a Frobenius homomorphism . Assume that has finite order and that has a primitive -th root of unity . Consider the decomposition of , obtained by defining , and the decomposition of the Hochschild cohomology of , obtained from the decomposition of . In this paper we prove that and that if the decomposition of is strongly -graded, then acts on and .
37.
Abdullah?M?Asiri Harry?G?Heller David?S?Hughes Michael?B?HursthouseEmail author John?Kendrick Frank?JJ?Leusen Riccardo?Montis 《Chemistry Central journal》2014,8(1):70
Background
Derivatives of fulgides have been shown to have interesting photochromic properties. We have synthesised a number of such derivatives and have found, in some cases, that crystals can be made to change colour on crushing, a phenomenon we have termed “tribochromism”. We have studied a number of derivatives by X-ray crystallography, to see if the colour is linked to molecular structure or crystal packing, or both, and our structural results have been supported by calculation of molecular and lattice energies.Results
A number of 5-dicyanomethylene-4-diphenylmethylene-3-disubstitutedmethylene-tetrahydrofuran-2-one compounds have been prepared and structurally characterised. The compounds are obtained as yellow or dark red crystals, or, in one case, both. In two cases where yellow crystals were obtained, we found that crushing the crystals gave a deep red powder. Structure determinations, including those of the one compound which gave both coloured forms, depending on crystallisation conditions, showed that the yellow crystals contained molecules in which the structure comprised a folded conformation at the diphenylmethylene site, whilst the red crystals contained molecules in a twisted conformation at this site. Lattice energy and molecular conformation energies were calculated for all molecules, and showed that the conformational energy of the molecule in structure IIIa (yellow) is marginally higher, and the conformation thus less stable, than that of the molecule in structure IIIb (red). However, the van der Waals energy for crystal structure IIIa, is slightly stronger than that of structure IIIb – which may be viewed as a hint of a metastable packing preference for IIIa, overcome by the contribution of a more stabilising Coulomb energy to the overall more favourable lattice energy of structure IIIb.Conclusions
Our studies have shown that the crystal colour is correlated with one of two molecular conformations which are different in energy, but that the less stable conformation can be stabilised by its host crystal lattice.Graphical abstract Graphical representation of the structural and colour change in the tribochromic compound (III).
38.
利用螺旋波激发等离子体化学气相沉积(LPP-CVD)技术,以甲烷和氦气为反应气体产生等离子体.通过采集到甲烷的可见光到紫外发射光谱,对甲烷等离子体进行原位诊断,发现存在CH、Ha及Hβ等碎片粒子的光辐射,同时,分析了不同入射功率、气压下CH粒子以及Hβ、Hγ的相对强度变化情况.结果表明:CH粒子的相对强度随着射频功率是先增大而后减小,随工作气压的增大而逐渐减小;随气压及功率的增加,Hβ、Hγ相对强度变化的总体趋势都是先增加而后减小的. 相似文献
39.
Summary Evidence is given that in Y1−Ba2−Cu3−O7 single crystals a critical state is developed on increasing (or decreasing) the applied fieldH
0, only whenH
0 is parallel to the crystalc-axis. An ?irreversibility? line in the (H, T)-plane can be drawn where the irreversibility of the second-harmonic response sets in.
In honour of Prof. Fausto Fumi on the occasion of his retirement from teaching. 相似文献
40.