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51.
The addition of ethoxycarbonylnitrene to vinyl chlorides gives N-ethoxycarbonyl-α-chloroaziridines which undergo an easy rearrangement mainly or exclusively to N-ethoxycarbonyl-2-chloro-2-alkenylamines. 相似文献
52.
Oro LA Ciriano MA Tejel C Bordonaba M Graiff C Tiripicchio A 《Chemistry (Weinheim an der Bergstrasse, Germany)》2004,10(3):708-715
Treatment of the organoamido complexes [Rh(2)(mu-4-HNC(6)H(4)Me)(2)(L(2))(2)] (L(2) = 1,5-cyclooctadiene (cod), L = CO) with nBuLi gave solutions of the organoimido species [Li(2)Rh(2)(mu-4-NC(6)H(4)Me)(2)(L(2))(2)]. Further reaction of [Li(2)Rh(2)(mu-4-NC(6)H(4)Me)(2)(cod)(2)] with [Rh(2)(mu-Cl)(2)(cod)(2)] afforded the neutral tetranuclear complex [Rh(4)(mu-4-NC(6)H(4)Me)(2)(cod)(4)] (2), which rationalizes the direct syntheses of 2 from [Rh(2)(mu-Cl)(2)(cod)(2)] and Li(2)NC(6)H(4)Me. Reactions of [Li(2)Rh(2)(mu-4-NC(6)H(4)Me)(2)(CO)(4)] with chloro complexes such as [Rh(2)(mu-Cl)(2)(CO)(4)], [MCl(2)(cod)] (M = Pd, Pt), and [Ru(2)(mu-Cl)(2)Cl(2)(p-cymene)(2)] afforded the homo- and heterotrinuclear complexes PPN[Rh(3)(mu-4-NC(6)H(4)Me)(2)(CO)(6)] (5; PPN=bis(triphenylphosphine)iminium), [(CO)(4)Rh(2)(mu-4-NC(6)H(4)Me)(2)M(cod)] (M = Pd (6), Pt(7)) and [(CO)(4)Rh(2)(mu-4-NC(6)H(4)Me)(2)Ru(p-cymene)] (8), while the reaction with [AuCl(PPh(3))] gave the tetranuclear compound [(CO)(4)Rh(2)(mu--4-NC(6)H(4)Me)(2)[Au(PPh(3))](2)] (9). The structures of complexes 6, 8, and 9 were determined by X-ray diffraction studies. The anion of 5 reacts with [AuCl(PPh(3))] to give the butterfly cluster [[Rh(3)(mu-4-NC(6)H(4)Me)(2)(CO)(6)]Au(PPh(3))] (10), in which the Au atom is bonded to two rhodium atoms. Reaction of the anion of 5 with [Rh(cod)(NCMe)(2)](BF(4)) gave the tetranuclear complex [Rh(4)(mu-4-NC(6)H(4)Me)(2)(CO)(6)(cod)] (11) in which the Rh(cod) fragment is pi-bonded to one of the arene rings, while the reaction of the anion of 5 with [PdCl(2)(cod)] afforded the heterotrinuclear complex 6 through a metal exchange process. 相似文献
53.
Floris FM 《The journal of physical chemistry. B》2005,109(50):24061-24070
A new expression to compute the cavitation free energy has been derived by integrating a new model to fit its derivative with respect to the cavity radius. The derivatives were obtained from Monte Carlo simulations data of the contact values of distribution functions for hard-sphere solutes in TIP4P water at 298 K and 1 atm. The new expression, formulated in the framework of the thermodynamics of surfaces and unlike the classical simple models, gives good results also for very small cavities with a radius of approximately 1 A. The contribution to the free energy of a term, which depends on the excess number of molecules at the dividing surface, has been taken into account and discussed for the assumed dependence on r of the surface tension. The asymptotic behavior of the derivative has thus been considered, and a function t(r), which is 0 at r = 0 and 1 at infinity, has been introduced to describe the transition from small to large length regimes. The value of the surface tension obtained by fitting is in very good agreement with that obtained from a simulation of the liquid/vapor interface by using the TIP4P model. 相似文献
54.
Francesco Gasparrini Francesco Maggio Domenico Misiti Claudio Villani Franca Andreolini Gian Pietro Mapelli 《Journal of separation science》1994,17(1):43-45
Fast and efficient separations of chiral stereolabile compounds were obtained at very low temperature on a π-acid chiral stationary phase (R,R-DACH-DNB) using carbon dioxide-based mobile phases containing alcoholic polar modifiers. Furthermore, efficient separations of the newly discovered spherical carbon cluster buckminsterfullerene (C60) and the related higher fullerenes (C70, etc.) have been performed on the same stationary phase using eluents based on either n-hexane or carbon dioxide. 相似文献
55.
Giovanna Gasparri Fava Marisa Belicchi Ferrari Giorgio Pelosi Franca Zanardi Giovanni Casiraghi Gloria Rassu 《Journal of chemical crystallography》1996,26(7):509-513
The structure of 2,3-dideoxy-4-thio-d-arabino-heptonic acid 1,4-lactone has been determined by X-ray diffraction. Crystals of the compound are orthorhombic, space groupP212121, with cell dimensionsa=11.555(5),b=10.451(5),c=9.604(5) Å, andZ=4. The diffraction experiment has allowed to assign the absolute configuration (4R, 5R, 6R) to the chiral centers of the molecule. 相似文献
56.
Sandor Divenyi Marcelo A. Savi Hans I. Weber Luiz Fernando P. Franca 《Chaos, solitons, and fractals》2008,38(3):685-695
Non-smooth characteristics are, in general, the source of difficulties for the modeling and simulation of natural systems. These characteristics are usually related to either the friction phenomenon or the discontinuous behavior as intermittent contacts. This article develops an experimental investigation concerning non-smooth systems with discontinuous support. An experimental apparatus is developed in order to analyze the nonlinear dynamics of a single-degree of freedom system with discontinuous support. The apparatus is composed by an oscillator constructed by a car, free to move over a rail, connected to an excitation system. The discontinuous support is constructed considering mass–spring systems separated by a gap to the car position. This apparatus is instrumented to obtain all the system state variables. System dynamical behavior shows a rich response, presenting dynamical jumps, bifurcations and chaos. Different configurations of the experimental set up are treated in order to evaluate the influence of the internal impact within the car and also support characteristics in the system dynamics. 相似文献
57.
de Pasquale F Testa C Soldaini R Casieri C Podo F De Luca F 《Magnetic resonance imaging》2005,23(4):577-584
We propose an application of a Bayesian methodology to dynamic MR images of protons J-coupled to 13C nuclei for monitoring the in vivo 13C-glucose uptake of mouse brain. The very low population of these protons and the random noise make the analysis of these images extremely difficult. The proposed method restores the images and provides an "activation" map of the mouse brain by means of a hypothesis testing procedure. The restoration step is performed in the Bayesian framework so that among the other advantages of a stochastic approach, it is possible to model spatial and temporal information about neighboring pixels. This leads to a restoration procedure able to reduce the noise level while preserving the information about the edges of signal areas. Based on the restored images, the testing procedure provides us with a reliable map of pixels characterized by the 13C-glucose uptake. 相似文献
58.
Franca Graiff 《Annali di Matematica Pura ed Applicata》1971,89(1):65-84
Sunto Dopo aver definito le coordinate intrinseche in una generica varietà riemanniana viene costruita una variazione del tensore
fondamentale che lascia invariate le coordinate stesse. Viene quindi dimostrato che la conoscenza di questa deformazione rende
possibile la costruzione di un tensore doppio simmetrico avente data divergenza: cioè fornisce un integrale particolare delle
equazioni della statica dei continui comunque curvi a due e tre dimensioni, in presenza di forze di campo.
Viene inoltre mostrato che tale integrale particolare serve per costruire l’integrale generale delle equazioni stesse, e delle
analoghe in assenza di forze di campo. Si può ottenere così anche l’integrale generale delle equazioni della dinamica dei
continui negli spazi-tempo della Relatività generale.
Entrata in Redazione il 19 aprile 1971. 相似文献
59.
Bruno Lunelli Gabriele Cazzoli Franca Lattanzi 《Journal of Molecular Spectroscopy》1983,100(1):174-181
Contour simulation of the gas phase infrared fundamental bands of AsCl3 led to estimated values for the first-order Coriolis constants, the vibrational frequencies, and the relative values of the vibrational transition moments. Improved values of the six independent force constants of a general quadratic force field were determined on the basis of the observed frequencies, mean amplitudes of vibration, and Coriolis and centrifugal distortion constants. The potential energy distribution over the normal modes is reported. 相似文献
60.
Franca Busulini 《Annali dell'Universita di Ferrara》1959,9(1):71-117
Riassunto In questo lavoro si studia la geometria sopra una retta con riferimento al gruppo delle congruenze, supposto non transitivo
e con diverse ipotesi di rigidità.
Si perviene a strutture algebriche di tipo generale, che suggeriscono varie operazioni di immersione e contrazione, e ciò
mantenendo sempre vivo il legame con una intuizione che sia la più generale possibile della realtà empirica.
Lavoro fatto nel gruppo di ricerca n. 25 del C.N.R.: ?Strutture algebriche e loro legami con la geometria moderna?. 相似文献
Résumé Dans cet travail on étudie la géométrie sur une droite par rapport au groupe des congruences, supposé non transitif et avec des diverses hypothèses de rigidité. On arrive à des structures algébriques d'un type général suggérant diverses opérations d'immersion et de contraction, et cela en maintenant toujours la liaison par une intuition qui soit la plus générale que possible de la réalité empirique.
Lavoro fatto nel gruppo di ricerca n. 25 del C.N.R.: ?Strutture algebriche e loro legami con la geometria moderna?. 相似文献