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51.
Naumkin FY 《The journal of physical chemistry. A》2008,112(20):4660-4668
Small clusters consisting of a carbon diatom or triatom and several aluminum atoms are investigated ab initio, at an MP2 level of theory. The mainly ionic character of C-Al bonding predominantly leads to structures different from corresponding hydrocarbons (also if starting from analogous initial geometries), while still producing closed-shell ground states. It is found that in many cases stable geometries correspond to flat CAl(3) units. These include unique metal-framed dicarbon and tricarbon all-flat species with unusual planar tetra-coordination. Another frequent feature is a hyper-coordination of carbon atoms, supported by their high negative charges and critically examined via atom-in-molecule calculations. Also characterized are anionic states, electronic excitation and ionization, electron attachment and detachment, and charge distributions. 相似文献
52.
This paper using a geometric approach produces vanishing and nonvanishing results concerning the spaces of twisted symmetric
differentials on subvarieties , with k ≤ m. Emphasis is given to the case of k = m which is special and whose nonvanishing results on the dimensional range dim X > 2/3(N − 1) are related to the space of quadrics containing X and the variety of all tangent trisecant lines of X. The paper ends with an application showing that the twisted symmetric plurigenera, along smooth families of projective varieties Xt are not invariant even for α arbitrarily large.
Received: September 2006, Revision: May 2007, Accepted: June 2007 相似文献
53.
54.
We analyse one-loop radiative corrections to the inflationary potential in the theory, where inflation is driven by the Standard Model Higgs field. We show that inflation is possible provided the Higgs mass mH lies in the interval mmin<mH<mmax, where mmin=[136.7+(mt−171.2)×1.95] GeV, mmax=[184.5+(mt−171.2)×0.5] GeV and mt is the mass of the top quark. In the renormalization scheme associated with the Einstein frame the predictions of the spectral index of scalar fluctuations and of the tensor-to-scalar ratio practically do not depend on the Higgs mass within the admitted region and are equal to ns=0.97 and r=0.0034 correspondingly. 相似文献
55.
56.
Let X be a K3 surface over a number field K. We prove that there exists a finite algebraic field extension E/K such that X has ordinary reduction at every non-archimedean place of E outside a density zero set of places.
相似文献
57.
Alexey V. Varlamov Ekaterina V. Boltukhina Fedor I. Zubkov Eugenia V. Nikitina Konstantin F. Turchin 《Journal of heterocyclic chemistry》2006,43(6):1479-1495
58.
Fedor Skuban Svetlana R. Lukić Dragoslav M. Petrović Imre O. Gúth 《Journal of Non》2009,355(37-42):2059-2062
The bulk chalcogenide glasses in the pseudo-binary system (As2Se3)100?x(SbSI)x (with x = 20, 30, 50, 70 and 80 at.%) were prepared from high-purity elemental components by melt-quenching technique. It is a system with the variable ratio of classical amorphous compound As2Se3 and the molecule of antimony-sulphoiodide, SbSI, which in the monocrystal form is characterized as a ferroelectric. The refractive-index behaviour (magnitude and spectral dispersion) of investigated glasses was determined by the prism method and analyzed. To calculate and discuss the parameters of dispersion in the band gap region three different approaches were used (Cauchy, Sellmeier and Wemple–DiDomenico single-oscillator model). The comparison of the results shows good agreement between all applied models. It was found that the value of the refractive-index shows normal dispersion behaviour and increases with the increase of Sb (or SbSI) content in the investigated system, whereas the optical gap of these glasses Eg slightly decreases. 相似文献
59.
Dr. Yuzhou Wu Prof. Dr. Fedor Jelezko Prof. Dr. Martin B Plenio Prof. Dr. Tanja Weil 《Angewandte Chemie (International ed. in English)》2016,55(23):6586-6598
The currently available techniques for molecular imaging capable of reaching atomic resolution are limited to low temperatures, vacuum conditions, or large amounts of sample. Quantum sensors based on the spin‐dependent photoluminescence of nitrogen‐vacancy (NV) centers in diamond offer great potential to achieve single‐molecule detection with atomic resolution under ambient conditions. Diamond nanoparticles could also be prepared with implanted NV centers, thereby generating unique nanosensors that are able to traffic into living biological systems. Therefore, this technique might provide unprecedented access and insight into the structure and function of individual biomolecules under physiological conditions as well as observation of biological processes down to the quantum level with atomic resolution. The theory of diamond quantum sensors and the current developments from their preparation to sensing techniques have been critically discussed in this Minireview. 相似文献
60.
The hairpin ribozyme catalyzes a reversible phosphodiester cleavage reaction. We examined the roles of conserved nucleobases in catalysis using an abasic ribozyme rescue strategy. Loss of the active site G8 nucleobase reduced the cleavage rate constant by 350-fold while loss of A9 and A10 nucleobases reduced activity less than 10-fold. Certain heterocyclic amines restored partial activity when provided in solution to the variant lacking G8. Heterocyclic amines that were capable of rescue shared the exocyclic amine and cyclic amide in common with the Watson-Crick hydrogen bonding face of guanine. In contrast to the shallow pH dependence of unmodified ribozyme activity, rescue activity increased sharply with decreasing pH. These results support a novel model for RNA catalysis in which a cationic nucleobase contributes electrostatic stabilization to negative charge developing in the transition state. 相似文献