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71.
Rodríguez-Muñiz GM Marin ML Lhiaubet-Vallet V Miranda MA 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(26):8024-8027
DNA damage: The reactivity of HO(.) with silylated 2'-deoxyribonucleosides was investigated in acetonitrile by means of a time-resolved technique. The obtained rate constants were in general slightly lower than those reported for the natural nucleosides in water. Analysis of the reaction mixture by UPLC-MS revealed that HO(.) attack occurred at the nucleobase (see scheme). 相似文献
72.
73.
Montaignac B Praveen C Vitale MR Michelet V Ratovelomanana-Vidal V 《Chemical communications (Cambridge, England)》2012,48(52):6559-6561
Enantioselective metallo-organocatalyzed carbocyclizations of formyl-alkynes have been developed. The cooperation between aminocatalysis and a chiral copper(I) complex granted access to enantio-enriched cyclopentanes through the challenging formation of all-carbon quaternary stereocenters. 相似文献
74.
The title materials exist as stable phases in the MgO—MgCl2—H2O system at 120 °C. 相似文献
75.
Efficient Csp(3)-Csp(3) Suzuki couplings have been developed with both potassium cyclopropyl- and alkoxymethyltrifluoroborates. Moderate to good yields have been achieved in the cross-coupling of potassium cyclopropyltrifluoroborate with benzyl chlorides possessing electron-donating or electron-withdrawing substituents. Benzyl chloride was also successfully cross-coupled to potassium alkoxymethyltrifluoroborates derived from primary, secondary, and tertiary alcohols. 相似文献
76.
77.
We consider the region of closed time-like curves (CTCs) in three-dimensional flat Lorentz space–times. The interest in this global geometrical feature goes beyond the purely mathematical one. Such space–times are lower-dimensional toy models of sourceless Einstein gravity or cosmology. In three dimensions all such space–times are known: they are quotients of Minkowski space by a suitable group of Poincaré isometries. The presence of CTCs would indicate the possibility of “time machines”, a region of space–time where an object can travel along in time and revisit the same event. Such space–times also provide a testbed for the chronology protection conjecture, which suggests that quantum back reaction would eliminate CTCs. In particular, our interest in this note will be to find the set free of CTCs for
, where
is modeled on Minkowski space and γ is a Poincaré transformation. We describe the set free of CTCs where γ is hyperbolic, parabolic, and elliptic. 相似文献
78.
79.
Virginie Charette 《Geometriae Dedicata》2006,118(1):173-183
The Margulis invariant of an affine hyperbolic element measures the signed Lorentzian displacement along the unique closed geodesic in its class.
Given a group of affine transformations of Minkowski spacetime whose linear part is Schottky, the Margulis invariant is a
useful tool in determining properness of its action. This paper, based on a presentation given at CGG IV Oostende 2005, describes
the affine deformation space of a rank two Schottky group. Several illustrations are included, contrasting the difference
between the case of a three-holed sphere and that of a one-holed torus.
Paper based on a presentation given at CGG IV Oostende 2005. Attendance of the conference and the subsequent writing of this
paper was made possible by an NSERC Discovery Grant. 相似文献
80.
Niel V Muñoz MC Gaspar AB Galet A Levchenko G Real JA 《Chemistry (Weinheim an der Bergstrasse, Germany)》2002,8(11):2446-2453
Low-spin, high-spin and spin-transition behaviours have been observed for the doubly interpenetrating three-dimensional bimetallic compounds (FeII(pz)[Ag(CN)2]2).pz (pz = pyrazine), (FeII(4,4'-bipy)2[Ag(CN)2]2) (4,4'-bipy = 4,4'-bipyridine), and (FeII(bpe)2[Ag(CN)2]2) (bpe = bispyridylethylene), respectively. The single crystals of the bpe derivative undergo a spin transition with a large hysteresis loop at about 95 K. After several warming and cooling cycles, the single crystals become a microcrystalline powder with 50% spin transition. Influence of pressure--as well as light-induced excited spin-state trapping (LIESST) on the thermal 50% spin transition of the microcrystalline sample has also been investigated. Thermal spin-transition behaviour has also been induced at pressures higher than 1 bar for the 4,4'-bipy derivative. Both the 4,4'-bipy and bpe derivatives show strong pressure dependence of the spin state at 300 K. 相似文献