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排序方式: 共有697条查询结果,搜索用时 531 毫秒
41.
We study the viscoelastic behavior of aqueous foam mixed with solid noncolloidal particles. We show that adding a tiny amount of grains can enhance the elastic and loss shear moduli by more than 1 order of magnitude. The scaling of these moduli with solid volume fraction is in qualitative agreement with that predicted by an effective-medium rigidity percolation model. We present a simple model, based on capillary attraction, to explain the particle-size dependence of the threshold. 相似文献
42.
Xavier Cattoën Achraf Noureddine Jonas Croissant Nirmalya Moitra Kristýna Bürglová Jana Hodačová Olivia de los Cobos Martine Lejeune Fabrice Rossignol Delphine Toulemon Sylvie Bégin-Colin Benoît P. Pichon Laurence Raehm Jean-Olivier Durand Michel Wong Chi Man 《Journal of Sol-Gel Science and Technology》2014,70(2):245-253
The combination of the copper-catalyzed alkyne-azide cycloaddition (CuAAC) reaction with sol–gel processing enables the versatile preparation of sol–gel materials under different shapes with targeted functionalities through a diversity-oriented approach. In this account, the development of the CuAAC reaction under anhydrous conditions for the synthesis of sol–gel precursors and for the assembling of magnetic nanoparticles on self-assembled monolayers is related, as well as the use of the classical CuAAC methodologies for the functionalization of mesoporous silica nanoparticles and microdots arrays. Coupling CuAAC and Sol–Gel will result in simplified preparations of multifunctional materials with controlled morphologies. 相似文献
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Antoine Busseau Dr. Carmen Villegas Dr. Sylvie Dabos‐Seignon Dr. Clément Cabanetos Prof. Piétrick Hudhomme Dr. Stéphanie Legoupy 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(25):8452-8456
New penta(organo)fullerenes donor–acceptor systems bearing five tetrathiafulvalene recognition units have been synthesized to promote self‐assemblies similar in appearance to shuttlecocks nested into each other thanks to the conical host cavity created around the fullerene together with the π–π and electronic interactions. 相似文献
46.
Gehanne S Cecconi D Carboni L Righetti PG Domenici E Hamdan M 《Rapid communications in mass spectrometry : RCM》2002,16(17):1692-1698
We describe a simple approach for the relative quantification of individual proteins within a mixture. The method is based on the differential labelling of the mixtures by use of a commercially available acrylamide and deuterium-labelled [2,3,3'-d(3)]-acrylamide to alkylate proteins prior to two-dimensional (2-D) gel electrophoresis. The tryptic digests of the separated proteins were subjected to reflector matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) analysis and the relative peak heights of cysteine-containing peptides were used to quantify their precursor proteins. This approach was tested for the relative quantification of proteins within an artificial mixture of standard proteins and for proteins observed in a 2-D map of rat serum. A good correlation was found between the measured ratios derived from MALDI-TOF data and those theoretically calculated prior to 2-D analysis via known mixing ratios of the two alkylating reagents. The described procedure has proved to be effective for comparative measurements of protein abundances within the investigated mixtures. 相似文献
47.
Sylvie Condon Chunhai Zou Jean-Yves Nédélec 《Journal of organometallic chemistry》2006,691(15):3245-3250
Reduction of decyl dichloro- and trichloroacetate, under mild electrolysis conditions by using the sacrificial anode process, affords α-chlorocarbanions which readily react with trialkylboranes to give alkylated products in a one step reaction. 相似文献
48.
We have studied the slow linear viscoelastic response of wet aqueous foams by macroscopic creep compliance measurements, combined to a diffusing-wave spectroscopy investigation of the local dynamics. The data strongly suggest that this rheological response arises from two distinct relaxation mechanisms: The first is due to the coarsening induced bubble rearrangements and governs the steady-state creep; the second results from the interplay between surface tension and surface viscosity of the gas-liquid interfaces and gives rise to a transient relaxation. 相似文献
49.
Azotobacter vinelandii, a nitrogen-fixing soil bacterium, secretes in iron deficiency azotobactin delta, a highly fluorescent pyoverdin-like chromopeptidic hexadentate siderophore. The chromophore, derived from 2,3-diamino-6,7 dihydroxyquinoline, is bound to a peptide chain of 10 amino acids: (L)-Asp-(D)-Ser-(L)-Hse-Gly-(D)-beta-threo-HOAsp-(L)-Ser-(D)-Cit-(L)-Hse-(L)-Hse lactone-(D)-N(delta)-Acetyl, N(delta)-HOOrn. Azotobactin delta has three different iron(III) binding sites which are one hydroxamate group at the C-terminal end of the peptidic chain (N(delta)-Acetyl, N(delta)-HOOrn), one alpha-hydroxycarboxylic function in the middle of the chain (beta-threo-hydroxyaspartic acid), and one catechol group on the chromophore. The coordination properties of its iron(III) and iron(II) complexes were measured by spectrophotometry, potentiometry, and voltammetry after the determination of the acid-base functions of the uncomplexed free siderophore. Strongly negatively charged ferric species were observed at neutral p[H]'s corresponding to a predominant absolute configuration Lambda of the ferric complex in solution as deduced from CD measurements. The presence of an alpha-hydroxycarboxylic chelating group does not decrease the stability of the iron(III) complex when compared to the main trishydroxamate siderophores or to pyoverdins. The value of the redox potential of ferric azotobactin is highly consistent with a reductive step by physiological reductants for the iron release. Formation and dissociation kinetics of the azotobactin delta ferric complex point out that both ends of this long siderophore chain get coordinated to Fe(III) before the middle. The most striking result provided by fluorescence measurements is the lasting quenching of the fluorophore in the course of the protonation of the ferric azotobactin delta complex. Despite the release of the hydroxyacid and of the catechol, the fluorescence remains indeed quenched, when iron(III) is bound only to the hydroxamic acid, suggesting a folded conformation at this stage, around the metal ion, in contrast to the unfolded species observed for other siderophores such as ferrioxamine or pyoverdin PaA. 相似文献
50.
S-Alkyl dithioformates, generated by a cycloreversion process, react as 1,3-dipolarophiles with beta-lactam-based azomethine ylids to provide, after (net) elimination of MeSH, C(2)-unsubstituted penems. The overall cycloreversion/cycloaddition sequence was accelerated by microwave irradiation. [reaction: see text] 相似文献