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991.
992.
Luigi Lay Francesco Nicotra Luigi Panza Giovanni Russo Guido Sello 《Journal of carbohydrate chemistry》2013,32(8):1269-1281
Abstract The use of epoxides obtained by dimethyldioxirane epoxidation of 2,3-anhydro-1,3-dideoxy-4,5:7,8-di-O-isopropylidene-D-manno-oct-1-enitol as glycosyl donors is described. This method offers a simple and stereoselective access to precursors of Kdo glycosides. The stereochemical outcome of the reaction is rationalized by means of semiempirical calculations of the transition states leading to glycosides formation. 相似文献
993.
A method based on the analytical evaluation of residual unsaturations and on the knowledge of the cyclization ratios is presented for the determination of the cyclopolymer composition in terms of structural units. The application of this method to the products of the free radical polymerization of vinyl-transcrotonate and of divinyl ether is described. 相似文献
994.
We classify Walker structures, self-dual and anti-self-dual metrics among the invariant metrics of four-dimensional generalized symmetric spaces. 相似文献
995.
996.
Giuseppe Bruno Archimede Rotondo Giovanni Grassi Francesco Foti Francesco Risitano Francesco Nicol 《Acta Crystallographica. Section C, Structural Chemistry》2004,60(7):o496-o497
The title compound, C18H15BrN2O5, a promising N‐protected α‐amino acid, was synthesized directly from an unusual bromo dipole and a 4‐(arylmethylene)oxazolone. The crystal packing of the title compound is a racemic mixture. Peculiar graph‐set motifs driven by the most important hydrogen bonds are described. 相似文献
997.
Giovanni A. Longo 《Experimental Thermal and Fluid Science》2009,33(2):284-291
This paper presents the heat transfer coefficients and the pressure drop measured during HFC-410A condensation inside a commercial brazed plate heat exchanger: the effects of saturation temperature, refrigerant mass flux and vapour super-heating are investigated. The heat transfer coefficients show weak sensitivity to saturation temperature and great sensitivity to refrigerant mass flux and vapour super-heating. At low refrigerant mass flux (<20 kg/m2 s) the saturated vapour condensation heat transfer coefficients are not dependent on mass flux and are well predicted by Nusselt [W. Nusselt, Die oberflachenkondensation des wasserdampfes, Energy 60 (1916) 541–546, 569–575] analysis for vertical surface: the condensation process is gravity controlled. For higher refrigerant mass flux (>20 kg/m2s) the saturated vapour condensation heat transfer coefficients depend on mass flux and are well predicted by Akers et al. [W.W. Akers, H.A. Deans, O.K. Crosser, Condensing heat transfer within horizontal tubes, Chem. Eng. Prog. Symp. Series 55 (1959) 171–176] equation: forced convection condensation occurs. In the forced convection condensation region the heat transfer coefficients show a 30% increase for a doubling of the refrigerant mass flux. The condensation heat transfer coefficients of super-heated vapour are 8–10% higher than those of saturated vapour and are well predicted by Webb [R.L. Webb, Convective condensation of superheated vapor, ASME J. Heat Transfer 120 (1998) 418–421] model. A simple linear equation based on the kinetic energy per unit volume of the refrigerant flow is proposed for the computation of the frictional pressure drop. 相似文献
998.
999.
1000.
Sandro Cacchi Cosmin L. Cotet Giovanni Forte Laura Martín Elies Molins Francesco Petrucci Adelina Vallribera 《Tetrahedron》2007,63(11):2519-2523
Electron-rich and electron-poor aryl iodides are converted, in high to excellent yields, into the corresponding carboxylic acids through a hydroxycarboxylation reaction catalyzed by a recoverable and reusable phosphine free palladium-carbon aerogel catalyst using lithium formate and acetic anhydride as an internal condensed source of carbon monoxide. The catalyst system can be reused several times without any appreciable loss of activity. 相似文献