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41.
N-salicyloyl-(L)-phenylalanine was prepared by a simple, two-step process from (L)-phenylalanine benzyl ester and acetylsalicyloyl chloride followed by hydrolysis and catalytic hydrogenation in an overall yield of 85%. 相似文献
42.
The local topological zeta function is a rational function associated to a germ of a complex holomorphic function. This function can be computed from an embedded resolution of singularities of the germ. For functions that are nondegenerate with respect to their Newton polyhedron it is also possible to compute it from the Newton polyhedron. Both ways give rise to a set of candidate poles of the topological zeta function, containing all poles. For plane curves, W. Veys showed how to filter the actual poles out of the candidate poles induced by the resolution graph. In this Note we show how to determine from the Newton polyhedron of a nondegenerate plane curve which candidate poles are actual poles. To cite this article: A. Lemahieu, L. Van Proeyen, C. R. Acad. Sci. Paris, Ser. I 347 (2009). 相似文献
43.
Abécassis B Testard F Arleth L Hansen S Grillo I Zemb T 《Langmuir : the ACS journal of surfaces and colloids》2006,22(19):8017-8028
The ternary catanionic system octylammoniumoctanoate/octane/water is studied by combined SANS, light scattering, conductivity, and phase diagram approach in the water-poor microemulsion region. The sphere-to-cylinder growth and branching depends on the concentration, the water-to-surfactant ratio, and the temperature. The unidimensional growth leads to a network of interconnected wormlike micelles. Like most studied linear nonionic surfactants, in this true catanionic system at equimolarity of anionic and cationic surfactant, the curvature toward water increases with temperature, making connections between cylinders less frequent. 相似文献
44.
A short synthetic strategy for preparation of the conduritols is described. The key step employs a zinc-mediated fragmentation of protected methyl 5-deoxy-5-iodo-d-pentofuranosides followed by an allylation of the intermediate aldehyde in the same pot. The allylation is performed with 3-bromopropenyl benzoate and occurs with good diastereoselectivity. An amino group can be introduced in the product by trapping the intermediate aldehyde as the imine prior to the allylation. The functionalised 1,7-octadienes, thus obtained, are converted into protected conduritols by ring-closing olefin metathesis. 相似文献
45.
Lise Baiget Jean Escudié Gabriela Cretiu Nemes Luminita Silaghi-Dumitrescu 《Journal of organometallic chemistry》2005,690(2):307-312
Dechlorofluorination of ArSb(F)-C(Cl)CR2 (CR2 = fluorenylidene, Ar = 2,4,6-tri-tert-butylphenyl) by tert-butyllithium afforded a 3,4-bis(fluorenylidene)-1,2-distibacyclobutane. The formation of the latter probably involves the transient stibaallene ArSbCCR2 followed by a head-to-head dimerization via two SbC double bonds. Molecular orbital calculations at the ab initio and DFT levels support the head-to-head dimerization of ArSbCCR2 with the formation of a 1,2-distibacyclobutane. 相似文献
46.
Zhendi Wang Merv Fingas Michael Landriault Lise Sigouin Bill Castle David Hostetter Dachung Zhang Brad Spencer 《Journal of separation science》1998,21(7):383-395
During January and February 1996, a significant number of tarball/patty incidents occurred along the coasts of Vancouver Island, Washington, Oregon, and California. Samples of the tarballs were collected from the affected beaches and analyzed by gas chromatography/mass spectrometry (GC/MS) and gas chromatography/flame ionization detector (GC/FID) using a tiered analytical approach developed for determining the origin of oils. Selected samples were further analyzed using a carbon isotopic technique. Also, the relative abundances of a large number of “source-specific marker” compounds, in particular alkylated series of polycyclic aromatic hydrocarbons within the same alkylation isomeric groups, were compared. Results of the analysis revealed that (1) California/Oregon samples were chemically similar and consistent with the same source. They were identified to be bunker type fuel; (2) The tarball samples collected from British Columbia and Ocean Shores, Washington were chemically similar and consistent with the same source (also bunker type fuel). They were found to be similar to but may have a source different than the California/Oregon samples; (3) The source of the tarball/patty samples was neither Alaska North Slope oil nor California Monterrey Miocene oil; (4) The spilled oil samples have been highly weathered since release, and the California samples were more heavily weathered than the British Columbia samples. 相似文献
47.
Lise Nygaard Dines Christen J.Tormod Nielsen E.Jonas Pedersen Ole Snerling Erik Vestergaard G.Ole Sørensen 《Journal of Molecular Structure》1974,22(3):401-413
Microwave spectra of the complete set of monosubstituted isotopic pyrazoles have been investigated and the complete rs structure of pyrazole determined. The deuterated and 15N species of pyrazole were prepared, while the 13C species were examined in natural abundance. The spectrum of the parent compound was remeasured yielding rotational and centrifugal distortion constants.The mutual position of the hydrogen atoms and the direction of the dipole moment in the pyrazole principal axis system has been unambiguously established.The 14N quadrupole hyperfine structure was resolved and the quadrupole coupling constants derived by Blackman et al. [8] were confirmed.An estimated rz structure is compared to crystal structures derived by X-ray and neutron diffraction showing the N-H bond in the crystal to be prolonged. But, otherwise no significant differences seem to develop when bringing the molecule from its isolated state into the crystal with its strong hydrogen bonds. 相似文献
48.
Lise Meitner 《Applied Scientific Research》1955,4(1):68-72
Zusammenfassung Es werden einige Beispiele für die Anwendung der Tracer-methode angeführt, die nicht so allgemein bekannt sind wie ihre Ausnutzung
für Probleme der Biologie oder der reinen Chemic. 相似文献
49.
Charruault L Michelet V Taras R Gladiali S Genêt JP 《Chemical communications (Cambridge, England)》2004,(7):850-851
This paper describes the asymmetric version of highly atom-economical alkoxycyclization of 1,6-enynes, using a combination of silver salts with the Pt(II)/(R)-Ph-BINEPINE system. 相似文献
50.
We numerically investigate the Olami-Feder-Christensen model on a quenched random graph. Contrary to the case of annealed random neighbors, we find that the quenched model exhibits self-organized criticality deep within the nonconservative regime. The probability distribution for avalanche size obeys finite size scaling, with universal critical exponents. In addition, a power law relation between the size and the duration of an avalanche exists. We propose that this may represent the correct mean-field limit of the model rather than the annealed random neighbor version. 相似文献