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排序方式: 共有898条查询结果,搜索用时 31 毫秒
51.
Self-assembled,deterministic carbon nanotube wiring networks 总被引:4,自引:0,他引:4
52.
Viornery L Saliba C Daskiewicz JB Bayet C Comte G Fenet B Gutierrez G Barron D 《Chemical & pharmaceutical bulletin》2000,48(11):1768-1770
Phytochemical investigation of the leaves of Umbilicus pendulinus afforded in addition to 2-O-caffeoyl malate, isoquercitrin and Z-venusol, the new isomer E-venusol. Special NMR experiments were carried out to elucidate the configuration of the two latter compounds. 相似文献
53.
Mauricio G. Constantino Paulo M. Donate Nicola Petragnani 《Tetrahedron letters》1982,23(10):1051-1054
A short synthesis of racemic natural product (1) from the known compound (7) is described. A model study, using cyclochexanone as starting material, is also reported. 相似文献
54.
55.
Sergio?del?CampoEmail author Mauricio?Cataldo Francisco?Pe?a 《General Relativity and Gravitation》2005,37(4):675-683
We study a model in which a closed universe with dust and quintessence matter components may look like an accelerated flat Friedmann–Robertson–Walker (FRW) universe at low redshifts. Several quantities relevant to the model are expressed in terms of observed density parameters,
M
and , and of the associated density parameter
Q
related to the quintessence scalar field Q. 相似文献
56.
Christian DC Felix J Gottschalk EE Gutierrez G Hartouni EP Knapp BC Kreisler MN Moreno G Reyes MA Sosa M Wang MH Wehmann A 《Physical review letters》2005,95(15):152001
We report the results of a high-statistics, sensitive search for narrow baryon resonances decaying to Xi-pi-, Xi-pi+, Xi+pi-, and Xi+pi+. The only resonances observed are the well known Xi0(1530) and Xi0(1530). No evidence is found for the states near 1862 MeV, previously reported by NA49 [Phys. Rev. Lett. 92, 042003 (2003)]. At the 95% confidence level, we find the upper limit for the production of a Gaussian enhancement with sigma=7.6 MeV in the Xi-pi- effective mass spectrum to be 0.3% of the number of observed Xi0(1530)-->Xi-pi+. We find similarly restrictive upper limits for an enhancement at 1862 MeV in the Xi-pi+, Xi+pi-, and Xi+pi+ mass spectra. 相似文献
57.
Using a simple model it is shown that the cost of constraining a hydrated potassium ion inside a narrow nanopore is smaller than the cost of constraining the smaller hydrated sodium ion. The former allows for a greater distortion of its hydration shell and can therefore maintain a better coordination. We propose that in this way the larger ion can go through narrow pores more easily. This is relevant to the molecular basis of ion selective nanopores and since this mechanism does not depend on the molecular details of the pore, it could also operate in all sorts of nanotubes, from biological to synthetic. 相似文献
58.
59.
Mauricio Gomes Constantino Valquiria Aragão Gil Valdo José da Silva 《Tetrahedron letters》2008,49(8):1393-1395
The core structure of the natural sesquiterpene lactones furanoheliangolides, an 11-oxabicyclo[6.2.1]undecane system, was synthesized through a pathway involving two Diels-Alder reactions. 相似文献
60.
Karla Calfumán María Jesus Aguirre Diego Villagra Claudia Yañez Carmen Arévalo Betty Matsuhiro Leonora Mendoza Mauricio Isaacs 《Journal of Solid State Electrochemistry》2010,14(6):1065-1072
In this work, the modification of a glassy carbon electrode with tetraruthenated porphyrins electrostatically assembled onto
a Nafion film, previously adsorbed on the electrode surface, is reported. This modified electrode was characterized by scanning
electron microscopy–energy-dispersive X-ray, Raman spectroscopy, UV-Vis spectroelectrochemistry, and cyclic voltammetry. The
Nafion film onto the glassy carbon electrode shows a smooth disposition; when the tetraruthenated porphyrin is incorporated
on the Nafion film, the complex is adsorbed in a homogeneous way. The modified electrode catalyzes HSO3− oxidation in water–ethanol solutions and shows an enhanced stability compared with the electrode modified with the dip coating
method. Rotating disk electrode experiments showed a kinetic limitation to the electron transfer controlled by charge propagation
in the film. I/E curves show a Tafel slope of 120 mV/decade corresponding to a first electron-transfer reaction, depending on the potential,
as the determining step. Spectroelectrochemical experiments demonstrated that Ru(II) is the active site for the electrocatalysis. 相似文献