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排序方式: 共有87条查询结果,搜索用时 15 毫秒
1.
Joël Benoist 《Journal of Global Optimization》2003,25(3):321-335
In finite dimensional Euclidean space, we prove the contractibility of the efficient frontier of simply shaded sets. This work extends the result of Peleg [7], which confirms the contractibility of the efficient frontier in the convex case. 相似文献
2.
Let Δ0 be a group of finite type and FΔ0⊂Hom(Δ0,PGL(Rm)) be the subset of faithful representations for which there exists a properly convex Δ0-invariant open subset Ω in P(Rm) such that the quotient Δ0\Ω is compact. Koszul has proved in [J.L. Koszul, Déformation des connexions localement plates, Ann. Inst. Fourier 18 (1968) 103-114] that this subset FΔ0 is open. We describe the closure of FΔ0. As a consequence, we show that this subset FΔ0 is closed if and only if the virtual center of Δ0 is trivial. This condition is satisfied if and only if FΔ0 contains a strongly1 irreducible representation. 相似文献
3.
Catalytic wet air oxidation of oleic acid on ceria-supported platinum catalyst.effect of pH 总被引:1,自引:0,他引:1
Beno?t Levasseur Benoist Renard Jacques Barbier Jr. Daniel Duprez 《Reaction Kinetics and Catalysis Letters》2006,87(2):269-279
Summary Catalytic wet air oxidation (CWAO) of oleic acid was carried out in a batch reactor on platinum supported ceria catalyst (Pt/CeO2). Oleic acid is a water insoluble linear unsaturated fatty acid of 18 carbon atoms. To increase the homogeneity of the solution
by saponification, the influence of NaOH additions in oleic acid CWAO mechanism and catalyst performances have been investigated.
The oxidation of such molecule occurs by two types of mechanisms: successive carboxy-decarboxylation which leads essentially
to CO2and/or C-C bonds splitting in the alkyl chain inducing a high formation of acetic acid. With or without NaOH, the 5%Pt/CeO2catalyst is active in the conversion of oleic acid and selective to carbon dioxide. In alkaline medium, oleic acid is initially
saponified which increases the solubility of the reactant before it to be oxidized. Finally the oxidation is slightly delayed
by the presence of NaOH. The catalyst characterizations show no significant difference before and after reaction.</o:p> 相似文献
4.
Le Gal J Tisato F Bandoli G Gressier M Jaud J Michaud S Dartiguenave M Benoist E 《Dalton transactions (Cambridge, England : 2003)》2005,(23):3800-3807
Twelve novel oxo-technetium and oxo-rhenium complexes based on N2S2-, N2SO- or N3S-tetradentate semi-rigid ligands have been synthesised and studied herein. By reacting the ligands with a slight excess of suitable [MO]3+ precursor (ReOCl3(PPh3)2 or [NBu4][99gTcOCl4]), the monoanionic complexes of general formula [MO(Ph-XN2S)]- could be easily produced in high yield. The complexes have been characterized by means of IR, electrospray mass spectrometry, elemental analysis, NMR and conductimetry. The crystal structures of [PPh4][ReO(Ph-ON2S)] 1b and [NBu4][99gTcO(Ph-ON2S)] 1c have been established. The [MO]3+ moiety was coordinated via the two deprotonated amide nitrogens, the oxygen and the terminal sulfur atoms in 1b and 1c. In both compounds, the ON2S coordination set is in the equatorial plane, and the complexes adopted a distorted square-pyramidal geometry with an axial oxo-group. The chemical and structural identity of the different prototypic complexes (rhenium, 99gTc complexes and their corresponding 99mTc radiocomplexes) have been also established by a comparative HPLC study. 相似文献
5.
Alain Valla Benoist Valla Régis Le Guillou Dominique Cartier Laurent Dufossé Roger Labia 《Helvetica chimica acta》2007,90(3):512-520
Since the C15 β‐end‐group aldehyde 10 ((β‐ionylidene)acetaldehyde), an excellent intermediate in the syntheses of retinoids, can be synthesized in many ways from β‐ionone, and since the corresponding acyclic C15 ψ‐end‐group aldehyde 5 can easily be synthesized from citral ( 1 ) (Scheme 3), we applied the C15+C5 route to the syntheses of γ‐retinal ((all‐E)‐ 8 ) (Scheme 3) and retinal ((all‐E)‐ 13 ) (Scheme 4), and therefore, by coupling (2×C20→C40), to the preparation of lycopene ( 14 ) and β‐carotene ( 15 ) (Scheme 5). Our new syntheses of retinal ((all‐E)‐ 13 ) and γ‐retinal ((all‐E)‐ 8 use an extended aldol reaction with a C6 building block that incorporates a C5 unit after decarboxylation. 相似文献
6.
Alain Valla Nathalie Méheux Dominique Cartier Benoist Valla Laurent Dufossé 《合成通讯》2013,43(2):184-190
A synthesis of a new C-15 phosphorus ylide from a C-14 enaminone is reported. This reagent, which undergoes selective 1,2- or 1,4-additions with saturated and unsaturated aldehydes, may find some synthetic use for the preparation of β-end-group retinoid derivatives. 相似文献
7.
Polymer characterization has largely helped in the development of thermal analyzers and calorimeters, based mainly on the thermocouple technology, or more recently the semiconductor technology. With the use of an integrated silicon thermopile as a detector, a new thermal technique is appearing, to give more possibilities of investigations in the field of polymeric materials. Combining high sensitivity and use of small amount of sample, the originality of the new design comes from its low power consumption, giving rise to a portable version of the instrument. With such a concept, the thermal analysis technique is carried on the industrial site, to perform online measurements.Melting and crystallization, glass transition, control of reticulation are a promising field of applications for the characterization of polymeric materials on industrial sites.This revised version was published online in November 2005 with corrections to the Cover Date. 相似文献
8.
Carmen L. Huffman Melissa Lee Williams D. Michelle Benoist Richard E. Overstreet Emily E. Jellen‐McCullough 《Rapid communications in mass spectrometry : RCM》2011,25(16):2299-2306
In collision‐induced dissociation mass spectrometry experiments, the collision energy required for dissociation linearly depends on the degrees of freedom in the precursor ion. The magnitude of the slope of this relationship previously has been shown to qualitatively correlate to the relative binding strength of a noncovalently bound, monovalent complex. The goal of the work presented here is to determine if a similar methodology can be applied for assessing relative binding strengths in multivalent species. We have tested the method on complexes formed from 18‐crown‐6 and a variety of protonated, primary alkylamines, [CnH2n+1NH3]+ (n = 9, 12, 14, 16 and 18) and alkyldiamines, [H3NCnH2nNH3]2+ (n = 3, 5, 6, 9 and 12), and compared our results with dissociation energies calculated using density functional theory at the B3LYP/6‐31G* level. We found that the method correctly assessed the stronger crown ether/headgroup interaction in the two divalent species (1:1 and 2:1 complexes formed from the diaminoalkanes) compared with the weaker interaction in the monovalent species (1:1 complexes formed from mono‐aminoalkanes). However, the experimental method could not distinguish between the binding strengths of the two divalent complexes, perhaps because their calculated dissociation energies were quite similar. Our preliminary results suggest that this method could potentially be used for a quick and simple analysis of binding strengths in multivalent species if the binding strengths of the species are significantly different from one another. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
9.
Allali M Benoist E Gressier M Jaud J Habbadi N Souizi A Dartiguenave M 《Dalton transactions (Cambridge, England : 2003)》2004,(20):3178-3180
The title compound was synthesised via an unexpected intramolecular reduction of a nitro group in the oxo-Re(v) coordination sphere. 相似文献
10.
Le Gal J Latapie L Gressier M Coulais Y Dartiguenave M Benoist E 《Organic & biomolecular chemistry》2004,2(6):876-883
Synthetic pathways to a range of novel semi-rigid tetradentate ligands, with sulfur, amido or amino donor groups, designed to coordinate technetium 99m have been developed. The technetium-99m complexes have been prepared and their stabilities in serum and by metathesis reaction via cysteine exchange reactions were compared. HPLC comparison of two (99m)Tc-complexes and their rhenium analogues led to the first proof of the nature of our radioactive complexes. 相似文献