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71.
France RR Compton RG Davis BG Fairbanks AJ Rees NV Wadhawan JD 《Organic & biomolecular chemistry》2004,2(15):2195-2202
Electrochemical glycosylation of a selenoglycoside donor proceeds efficiently in an undivided cell in acetonitrile to yield beta-glycosides. Measurement of cyclic voltammograms for a selection of seleno-, thio-, and O-glycosides indicates the dependence of oxidation potential on the anomeric substituent allowing the possibility for the rapid construction of oligosaccharides by selective electrochemical activation utilising variable cell potentials in combination with reactivity tuning of the glycosyl donor. A variety of disaccharides are readily synthesised in high yield, but limitations of the use of selenoglycosides as glycosyl donors for selective glycosylation of thioglycoside acceptors are exposed. The first electrochemical trisaccharide synthesis is described. 相似文献
72.
A technique has been developed to reduce the ?OH content of multicomponent glasses. The glasses were treated with perfluoropropane and the linear absorption coefficient of ?OH reduced from typically 0.08 to as low as 0.01 cm?1, which corresponds to a reduction of ?OH content to approximately 2 ppm. A fibre pulled from treated glasses had a reduced loss at 1.3 μm, and a loss of 2.9 dB km?1 at 1.12 μm which is the lowest reported loss for a fibre prepared by a double crucible technique. 相似文献
73.
The automotive industry more and more frequently uses composite materials such as molded compounds (sheet‐molded compounds, SMC, or bulk‐molded compounds, BMC). Bonding is then the only way of assembling two pieces. Consequently, and in order tentatively to predict the adhesive behavior of such materials, it is necessary to have a good knowledge of their surface properties. Here, different complementary techniques of surface analysis allowed us, on the one hand, to reach this aim for BMCs prepared by compression molding and, on the other hand, to show the influence on the surface properties of the concentration and composition of the internal release agent added to the blend. The surface heterogeneity and the organic nature of the surface of the compounds are shown and no phase separation occurs there as in the bulk. Mold release agents remain in the surface layer and induce some acid–base character to the surface material which depends on the type of stearate introduced in the blend. Copyright © 1999 John Wiley & Sons, Ltd. 相似文献
74.
Blank B Chartier M Czajkowski S Giovinazzo J Pravikoff MS Thomas J de France G de Oliveira Santos F Lewitowicz M Borcea C Grzywacz R Janas Z Pfutzner M 《Physical review letters》2000,84(6):1116-1119
In an experiment at the SISSI/LISE3 facility of GANIL, we used the projectile fragmentation of a primary 58Ni26+ beam at 74.5 MeV/nucleon with an average current of 3 &mgr;A on a natural nickel target to produce very neutron-deficient isotopes. In a 10-day experiment, 287 42Cr isotopes, 53 45Fe isotopes, 106 49Ni isotopes, and 4 48Ni isotopes were unambiguously identified. The doubly magic nucleus 48Ni, observed for the first time, is the most proton-rich isotope ever identified with an isospin projection T(z) = -4. It is probably the last doubly magic nucleus with "classical" shell closures accessible for present-day facilities. Its observation allows us to deduce a lower limit for the half-life of 48Ni of 0.5 &mgr;s. 相似文献
75.
A drawing induced loss has been found to exist in multicomponent glass optical fibres, and has been shown to be due to absorption. Two loss peaks were identified at 580 and 360 nm with peak heights of 340 and 490 dBkm?1, respectively. The 580 nm peak was believed to be due to silicon oxygen hole centres formed during fibre drawing. The induced loss could be partially removed by annealing, and the behaviour of the induced loss under various heat treatments was investigated. It was also found that the loss could be completely eliminated by the addition of 0.1 wt% As2O3 to the glass melt. 相似文献
76.
[reaction: see text]. We describe a superior procedure for the catalytic, asymmetric synthesis of beta-lactams using a bifunctional catalyst system consisting of a chiral nucleophile and an achiral Lewis acid. 相似文献
77.
G. Prange E. O. Whittier C. S. Trimble E. Pijanowski R. Lucentini Elsa Drago S. Bezzi S. Sacconi J. Großfeld B. W. Hammer C. R. Barnicoat M. Baumann A. Iwanowa A. Ljutenberg T. Dudkina H. Schmalfuß O. Benecke A. Koss Ciusa Waller H. Toms R. T. M. Haines J. C. Drummond N. Evers A. G. Jones W. Smith I. Tveraaen Alf Klem W. Leithe R. Strohecker A. F. H. Ward und G. D. France 《Fresenius' Journal of Analytical Chemistry》1937,108(7-8):292-304
Ohne Zusammenfassung 相似文献
78.
G. Duchêne C. M. Petrache C. W. Beausang F. A. Beck T. Byrski D. Curien P. J. Dagnall S. Flibotte P. D. Forsyth G. de France B. Haas B. Kharraja J. C. Merdinger D. Prévost C. Schück C. Theisen P. J. Twin J. P. Vivien 《Zeitschrift für Physik A Hadrons and Nuclei》1994,350(1):39-44
Excited states in the nucleus150Tb have been investigated up to spin 39? and 13 MeV excitation energy using the130Te(27Al, 7n) reaction and the EUROGAM array. The theoretical interpretation of the observed states has been performed in the framework of the deformed independent particle model. The analysis of the decay out of the yrast superdeformed band indicates that normal-deformed states with spins between 24? and 28? are fed. 相似文献
79.
Heat transfer was studied to two-phase flow in the post-CHF dispersed flow regime under swirl conditions. Data were used for post-CHF water flow at high pressure, 15.9 MPa, inside a vertical tube with twisted-tape inserts. Data used were obtained under test conditions typical of heat exchanger operation with low wall superheats of 5-40°C. The mass flux range of the data was 910-1878 kg/m2 s, and three tape-twist ratios were used: 2.55, 5.03, and 7.52. The low wall superheat and the relatively high mass fluxes resulted in higher than predicted drop-wall heat transfer. The only existing heat transfer correlation for this flow situation was modified to include this heat exchanger parameter range. 相似文献
80.