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41.
Jean-Luc Decout Alain Lablache-Combier Claude Loucheux 《Journal of polymer science. Part A, Polymer chemistry》1980,18(7):2371-2390
Vinylpyridine-N-oxide units were introduced in polymeric chains in order to study their photocrosslinking. Copolymers of styrene and 4-vinylpyridine-N-oxide were especially synthesized and studied. The methods used for characterization of photocrosslinked films were a “photoresist test” or the measurement of the insolubility and of the swelling ratio. The Cleavage of the N-oxide bond was responsible for the photocrosslinking. The competitive formation of carbonyl compounds took place and decreased the rate of photocrosslinking. This last reaction is favored by triplet-state quenchers. The photosensitivity of the copolymers was determined as a function of the wavelength of the radiation used. When the photocrosslinking proceeded, a film of the copolymeric material became transparent in the 280–320-nm range. Thick films could therefore be completely photocrosslinked when irradiated in this range of wavelength. 相似文献
42.
Spadini L Schindler PW Charlet L Manceau A Vala Ragnarsdottir K 《Journal of colloid and interface science》2003,266(1):1-18
The surface properties of ferrihydrite were studied by combining wet chemical data, Cd(K) EXAFS data, and a surface structure and protonation model of the ferrihydrite surface. Acid-base titration experiments and Cd(II)-ferrihydrite sorption experiments were performed within 3<-log[H(+)]<10.5 and 0.5<[Cd(t)]<12 mM in 0.3 M NaClO(4) at 25 degrees C, where [Cd(t)] refers to total Cd concentration. Measurements at -5.5triple bond Fe-OH(-1/2),logk((int))=-8.29, assuming the existence of a unique intrinsic microscopic constant, logk((int)), and consequently the existence of a single significant type of acid-base reactive functional groups. The surface structure model indicates that these groups are terminal water groups. The Cd(II) data were modeled assuming the existence of a single reactive site. The model fits the data set at low Cd(II) concentration and up to 50% surface coverage. At high coverage more Cd(II) ions than predicted are adsorbed, which is indicative of the existence of a second type of site of lower affinity. This agrees with the surface structure and protonation model developed, which indicates comparable concentrations of high- and low-affinity sites. The model further shows that for each class of low- and high-affinity sites there exists a variety of corresponding Cd surface complex structure, depending on the model crystal faces on which the complexes develop. Generally, high-affinity surface structures have surface coordinations of 3 and 4, as compared to 1 and 2 for low-affinity surface structures. 相似文献
43.
Alain J.P. Alix 《Journal of Molecular Structure》1976,33(1):137-139
Microwave spectra of CH18 OCOOH, CHOC18 OOH, CHOCO18 OH, 13 CHOCOOH and CHO13 COOH are reported and have been used in combination with data on CHOCOOH and CHOCOOD to determine the molecular structure as r(C=O)ald. = 1.174 ± 0.006 Å, r(C=O)acid = 1.203 ±0.006 Å, r(C—O) = 1.313 ± 0.010 Å, r(C—C) = 1.535 ± 0.005 Å, r(O—H) = 0.948 ± 0.004 Å, r(C—H) = 1.104 ±0.010 Å, ald. = 123.7 ± 0.4<, 相似文献
44.
This paper is concerned with persistency properties which allow the evaluation of some variables at all maximizing points of a quadratic pseudo-Boolean function. Hammer, Hansen and Simeone (1984) have proposed to determine these variables using a procedure described by Balinski for computing a strongly complementary pair of optimal primal and dual solutions for arbitrary linear programs. We propose a linear time algorithm for determining these variables from a best roof off, i.e. from a lowest upper linear bound off. 相似文献
45.
Alain Gioan 《Applied Mathematics and Optimization》1982,8(1):59-67
LetV andW be two Banach spaces, withV reflexive, a bounded convex set ofV, A a linear mapping fromV intoW, and letF be a convex functional onW. We minimizeJ(v)=F(Av) on using hypotheses about particular sequences in IfV is uniformly convex, we prove existence and uniqueness of a solution of minimal norm minimizingJ. In the Hilbert space case, withF defined byF(w)=w–f
2,f given inW, we get existence and uniqueness of the projection off on A(), which generalizes the case where A() is a closed set ofW (taking closed andA continuous). Finally, we give examples, and we study an unbounded operator case. 相似文献
46.
Alain Glangetas Fazil O. Gülacar Jean M. J. Tronchet Armand Buchs 《Helvetica chimica acta》1980,63(6):1740-1747
Electron Impact Mass Spectrometry of the 3-Desoxy-1,2: 5,6-di-O-isopropylidene-3-methylidene-δ-D -hexofuranose and Some C(3′)-Substituted Analogues The mass spectra of the 3-desoxy-1,2:5, 6-di-O-isopropylidene-3-methylidene- α-D -ribo-hexofuranose and of some C(3′)-mono- and -disubstituted derivatives have been investigated. Deuterium labelled molecules allow fragmentation modes to be proposed. 相似文献
47.
Philippe Andrianary Gérard Jenner Alain Kiennemann 《Journal of organometallic chemistry》1983,252(2):209-220
The CO/H2 homologation of methanol to acetaldehyde and subsequently to its dimethyl acetal in the presence of cobalt acetate promoted by iodine was examined under various conditions. Temperature and pressure were found as critical parameters. High pressures (140 MPa) and low temperatures (160–170°C) give optimal yields and selectivity to acetaldehyde. According to pressure, temperature, contact time, gas ratio and ligand/catalyst ratio, the reaction is oriented towards acetaldehyde, its dimethyl acetal or methyl acetate. 相似文献
48.
Claude Aslangul Alain Veillard Raymond Daudel Fernand Gallais 《Theoretical chemistry accounts》1971,23(3):211-225
Résumé On propose un exemple quantitatif de la distinction entre une liaison de covalence et une liaison de coordination; cette différenciation, fondée sur les propriétés de la molécule une fois formée, semble très nette pour les énergies de liaison, les populations de recouvrement et les charges des groupes; en particulier, un critère récent, proposé par deux des auteurs, est remarquablement vérifié. Enfin, on essaie de préciser la signification des symboles chimiques traditionnels.
Les auteurs tiennent à remercier très vivement M. M. Berthier et Millié d'avoir mis à leur disposition le programme de localisation indispensable à ce travail, ainsi que Mademoiselle Le Guen et le C.I.R.C.E. pour la réalisation des calculs sur l'ordinateur IBM 360-75. 相似文献
Quantitative studies of the difference between a covalence and a coordination bond: The molecules of amine-borane and aminoborane
An illustration of the distinction between these two types of chemical bonds is proposed, which is based on the properties of the molecule once built. Bond energies, overlap populations and group charges vary considerably from one compound to the other; more, a recent criterion given by two of the authors seems to be particularly suitable for describing the character of the bond. Lastly, one tries to give an explicit signification to the usual chemical symbols.
Zusammenfassung Es wird ein quantitatives Beispiel der Unterscheidung zwischen einer kovalenten und einer koordinativen Bindung angegeben, die auf den Eigenschaften des vorliegenden Moleküls beruht. Sie erscheint sehr günstig für die Bindungsenergien, die Überlagerungspopulationen und die Gruppenladungen. Insbesondere wird ein Kriterium, das kürzlich von zwei der Autoren angegeben wurde, gut verifiziert. Schließlich wird versucht, die üblichen chemischen Symbole zu präzisieren.
Les auteurs tiennent à remercier très vivement M. M. Berthier et Millié d'avoir mis à leur disposition le programme de localisation indispensable à ce travail, ainsi que Mademoiselle Le Guen et le C.I.R.C.E. pour la réalisation des calculs sur l'ordinateur IBM 360-75. 相似文献
49.
Burel-Deschamps L Giamarchi P Stephan L Lijour Y Le Bihan A 《Journal of fluorescence》2006,16(2):177-183
The absorption and fluorescence spectra of carbaryl (CB), carbofuran (CF) and carbendazim (MBC) have been studied. Fluorescence lifetime and fluorescence quantum yields are also reported as well as the influence of pH, solvent and presence of humic acids on fluorescence. The limit of detection (LD) of the three compounds has been measured by direct analysis by laser-induced fluorescence (LIF) using a pulsed YAG laser with an Optical Parametric Oscillator (OPO) as excitation source and an Intensified Charged Coupled Device (ICCD) camera for the fluorescence detection. Instrumental LD found for CB, for MBC and for CF are respectively 4, 50 and 1000 ng L−1. In tap water, the LD obtained is 800 ng L−1 for MBC and 20,000 ng L−1 for CF. For CB, the use of a time shift between excitation and emission allows to reach a LD of 20 ng L−1 in tap water. 相似文献
50.