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991.
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993.
Takao Mori Fuxiang Zhang Andreas Leithe-Jasper 《Journal of solid state chemistry》2004,177(2):444-448
Physical properties of a series of homologous RE-B-C(N) B12 cluster compounds REB17CN, REB22C2N, and were investigated. The structures of the compounds are layer-like along the c-axis, with rare earth and B6 octahedral layers separated by B12 icosahedral and C-B-C chain layers whose number increases successively from two B12 layers for the REB17CN compound to four for the REB28.5C4 compound. The rare earth atoms are configured in two triangular flat layers which are stacked on top of one another in AB stacking where the nearest-neighbor rare earth directions are the three atoms forming a triangle in the adjacent layer. The series of homologous compounds exhibit a spin glass transition with Tf shifting in correspondence with variations of the basal plane lattice constants, consistent with the magnetic interaction being effective in the basal planes. The isothermal remanent magnetization shows a stretched exponential decay . Exponents determined for the different homologous compounds were scaled as a function of Tr=T/Tf and found to follow the empirical dependency determined for typical spin glasses. It is indicated that a mixture of disorder originating from the partial occupancy of the rare earth sites and frustration of interactions due to the unique configuration is responsible for the manifestation of spin glass transitions in these homologous systems. 相似文献
994.
Asano Y Murakami A Kobayashi T Goldberg A Guillaumont D Yabushita S Irie M Nakamura S 《Journal of the American Chemical Society》2004,126(38):12112-12120
The mechanism of the photochromic cycloreversion reactions is theoretically examined in a model system of dithienylethenes by means of the CASSCF and CASPT2 methods. The structures of its conical intersections (CIs), which are the branching points of the internal conversions, were obtained. The analyses of the minimum energy paths from the Franck-Condon states and the CI points suggest that the cycloreversion reaction occurs during the intramolecular vibrational energy redistribution (IVR) toward the quasi-equilibrium on the 2A state. The current study of the model system will provide a basic insight for the photochromic molecular design. 相似文献
995.
The ratio of the Tamagawa measure and a certain invariant measure on the group GLn() is computed, where is the adèle of a division algebra D over a global field. An explicit formula of the ratio is described in terms of the special values of the zeta function of D. This formula yields (i) an explicit lower bound of the Hermite–Rankin constant n,m(D) of D and (ii) an explicit asymptotic behavior of the distribution of rational points on Brauer–Severi variety.Mathematics Subject Classification (2000): Primary 11R52, Secondary 11H50 相似文献
996.
997.
The sequential coupling and cyclization reactions between aryl halides and methyl propiolate were investigated. The electron-withdrawing groups on the aromatic ring are essential for producing the methyl indole-2-carboxylate derivatives. On the other hand, the presence of an extra methyl propiolate and Pd(PPh3)4 were required to provide an efficient catalytic system for the cyclization reactions. This reaction was used for the total synthesis of duocarmycin SA. 相似文献
998.
Motoyoshi Baba Masayuki Suzuki Hiroto Kuroda Takao Hamakubo Masahiro Hayashi Tatsuhiko Kodama 《Journal of luminescence》2007,127(2):355-361
We improved an ultrafast time-resolved fluorescence resonance energy transfer (FRET) spectroscopy system and measured directly the decrease in the fluorescence decay time of the FRET signal, without any entanglement of components in the picosecond time scale from the donor-acceptor protein pairs (such as cameleon protein for calcium ion indicator, and ligand-activated GRIN-Go proteins pair). The drastic decrease in lifetime of the donor protein fluorescence under the FRET condition (e.g. a 47.8% decrease for a GRIN-Go protein pair) proves the deformation dynamics between donor and acceptor fluorescent proteins in an activated state of a mixed donor-acceptor protein pair. This study is the first clear evidence of physical contact of the GRIN-Go proteins pair using time-resolved FRET system. G protein-coupled receptors (GPCRs) are the most important protein family for the recognition of many chemical substances at the cell surface. They are the targets of many drugs. Simultaneously, we were able to observe the time-resolved spectra of luminous proteins at the initial stage under the FRET condition, within 10 ns from excitation. This new FRET system allows us to trace the dynamics of the interaction between proteins at the ligand-induced activated state, molecular structure change and combination or dissociation. It will be a key technology for the development of protein chip technology. 相似文献
999.
Let C1,···,Cd be Mumford curves defined over a finite extension of and let X=C1×···×Cd. We shall show the following: (1) The cycle map CH0(X)/n → H2d(X, μn⊗d) is injective for any non-zero integer n. (2) The kernel of the canonical map CH0(X)→Hom(Br(X),) (defined by the Brauer-Manin pairing) coincides with the maximal divisible subgroup in CH0(X). 相似文献
1000.