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141.
Jordi Bols Santiago Gubert Lluís Anglada Angel Prez Aurelio Sacristn Jos A. Ortiz 《Journal of heterocyclic chemistry》1994,31(6):1493-1496
The synthesis of the novel amino acid 6-(hydroxymethyl)-2-piperidinecarboxylic acid ( 1a ) and its ethyl ester 1b is reported. In the hydrogenation of 6-(hydroxymethyl)pyridine-2-carboxylates, hydrogenolysis of the alcohol group appeared as an unusual side reaction. Optimization of the reaction conditions allowed us to minimize hydrogenolysis and afforded pure 1 . 相似文献
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144.
It has been proposed that there are degrees of freedom intrinsic to quantum critical points that can contribute to quantum critical physics. We point out that this conclusion is quite general below the upper critical dimension. We show that in (2+1)D antiferromagnets Skyrmion excitations are stable at criticality and identify them as the critical excitations. We find exact solutions composed of Skyrmion and anti-Skyrmion superpositions, which we call topolons. We include the topolons in the partition function and renormalize by integrating out small size topolons and short wavelength spin waves. We obtain a correlation length exponent nu=0.690 666 and anomalous dimension eta=0.0166. 相似文献
145.
Alvarez S 《Dalton transactions (Cambridge, England : 2003)》2006,(17):2045-2051
The duality relationship between fullerenes and Frank-Kasper polyhedra suggests that these two families of polyhedra appear nested in solid state structures. Magic numbers, described by simple mathematical relationships, identify four families of fullerenes with tetrahedral and icosahedral symmetries. 相似文献
146.
Giner B Martín S Artigas H López MC Lafuente C 《The journal of physical chemistry. B》2006,110(35):17683-17690
The electron donor-acceptor abilities of some cyclic ethers (tetrahydropyran or tetrahydrofuran), benzene, and halobenzenes (fluorobenzene or chlorobenzene) and the molecular interactions between these compounds have been investigated through a wide set of thermodynamic mixing properties of their mixtures. The mixing properties have been derived from experimental measurements of density, speed of sound, refractive index, surface tension, heat of mixing, and vapor-liquid equilibrium at the temperature of 298.15 K. 相似文献
147.
We show that models of generalized modified gravity, with inverse powers of the curvature, can explain the current accelerated expansion of the Universe without resorting to dark energy and without conflicting with solar system experiments. We have solved the Friedmann equations for the full dynamical range of the evolution of the Universe and performed a detailed analysis of supernovae data in the context of such models that results in an excellent fit. If we further include constraints on the current expansion of the Universe and on its age, we obtain that the matter content of the Universe is 0.07相似文献
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N-Methyl trans-fused perhydroisoindolines substituted with a tributylstannyl group in the 2-position have been prepared and used as precursors of the corresponding alpha-aminoorganolithiums. The steric course of the reactions of these and other conformationally rigid organolithiums with various electrophiles is summarized and compared with the steric course of the unsubstituted analogs. A mechanistic rationale for the steric course of electrophilic substitutions of these organolithiums is discussed. Pathways involving both polar electrophilic substitutions and radical couplings were observed with different electrophiles. 相似文献
150.
Karbass N Sans V Garcia-Verdugo E Burguete MI Luis SV 《Chemical communications (Cambridge, England)》2006,(29):3095-3097
Long-term stable Pd(0) catalysts can be easily supported onto polymeric monoliths containing methyl-imidazole moieties and the corresponding reactors based on these materials can be applied for the continuous Heck reaction in near-critical EtOH. 相似文献