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171.
172.
R. Chen F. Chu C. Gauthier L. Chazeau I. Chaduc E. Bourgeat‐Lami M. Lansalot 《Journal of polymer science. Part A, Polymer chemistry》2010,48(11):2329-2339
Ethyl cellulose (EC) was incorporated into copolymer latexes via miniemulsion polymerization. The effects of EC viscosity and EC content on droplet size, particle size, and polymerization kinetics were investigated. The higher the EC content and viscosity, the larger the droplet size and the less stable the latex suspension. Small droplets that could be efficiently nucleated were formed for the lower‐viscosity EC but the latex still showed limited colloidal stability. This was attributed to some phase‐incompatibility between EC and the acrylic polymer. These stability issues were overcome by using an oil‐soluble initiator and a crosslinker. The later enabled to physically entrap EC inside the polymer particles, whereas the former allowed in situ grafting of the growing acrylic radicals to the EC backbone decreasing thereby the extent of phase separation. Thermal‐mechanical analyses evidenced that the films obtained from the hybrid latexes displayed better properties than the EC‐free latex films or the physical blends. This supports the hypothesis of formation of hybrid latexes that synergistically combine the properties of the acrylic matrix and the EC polymer. Interestingly, a significant increase of the elastic modulus was observed between 50 and 90 °C. This mechanical reinforcement was tentatively attributed to the formation of a percolating EC‐based hybrid phase. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2329–2339, 2010 相似文献
173.
Hon Kit Lee Yan Ping Heidi Iu Chi Chung Shek Helene Bendstrup Klinke 《Analytica chimica acta》2009,649(1):80-719
Withdrawal of the support for the REMEDi HS drug profiling system has necessitated its replacement within our laboratories with an alternative broad toxicological screening technique. To this end, a novel method, based on ultra-performance liquid chromatography (UPLC) and time-of-flight (TOF) mass spectrometry, was developed for the routine analysis of urine samples. Identification was achieved by comparison of acquired data to libraries containing more than 300 common drugs and metabolites, and was based on a combination of retention time, exact mass and fragmentation patterns. Validation data for the method is presented and comprised an evaluation of the following parameters: precision; transferability of the methodology between the six collaborating laboratories; specificity; extraction recovery and stability of processed samples; matrix effects and sensitivity.This paper presents the benefits of supplementary fragmentation data with particular regard to increasing specificity and confidence of identification and its usefulness with overdosed samples. The utility of the method was assessed by the parallel analysis of 30 authentic urine samples using the REMEDi HS and UPLC-TOF. The latter provided enhanced detection, leading to the identification of twice as many drugs. Furthermore it did not miss any compounds that were identified by REMEDi HS. The UPLC-TOF findings were further verified by a combination of data from three other conventional screening techniques, i.e., GC-MS, HPLC-DAD and UPLC-MS/MS. 相似文献
174.
Shear-flow induced detachment of Saccharomyces cerevisiae from stainless steel: influence of yeast and solid surface properties 总被引:5,自引:0,他引:5
Guillemot G Vaca-Medina G Martin-Yken H Vernhet A Schmitz P Mercier-Bonin M 《Colloids and surfaces. B, Biointerfaces》2006,49(2):126-135
The present study focused on the shear-induced detachment of Saccharomyces cerevisiae in adhesive contact with a 316L stainless steel surface using a shear stress flow chamber, with a view to determining the respective influence of the yeast surface properties and the support characteristics. The effect of cultivation of S. cerevisiae yeast cells on their subsequent detachment from the solid surface was particularly investigated. In order to elucidate the role of stainless steel, non-metallic supports were used as control, covering a broad range of surface properties such as surface free energy and roughness: polypropylene (hydrophobic), polystyrene (mildly hydrophobic, similar to stainless steel) and glass (hydrophilic). All materials were very smooth with respect to the size of yeast. First, experiments were carried out on two types of yeast cells, just rehydrated in saline solution, a biological model widely used in the literature. The influence of the ionic strength (1.5 and 150 mM NaCl) on glass and stainless steel was evaluated. Unlike on glass, no clear evidence was found for electrostatic repulsion with stainless steel since high adhesion was observed whatever the ionic strength. A lack of correlation in adhesion results was also obtained when considering the surface physico-chemical characteristics of type I (hydrophilic) and type II (hydrophobic) rehydrated cells and those of both polymers. It was postulated that unavoidable “sticky” compounds were present on the cell wall, which could not be completely removed during the successive washings of the rehydrated cell suspension before use. This could dramatically alter the yeast surface properties and modify the adhesion strength, thus clearly demonstrating the necessity to work with yeast coming from fresh cultures. Biologically active yeast cells were then used. Once cultured, type I- and type II-yeast cells were shown to exhibit the same hydrophilic properties. Regardless of the material used, for the same ionic strength (150 mM NaCl), yeast adhesion was drastically reduced compared to rehydrated yeast cells. Among all the materials tested, the specificity of 316L stainless steel was clearly established. Indeed, for glass and polymers, cell adhesion was substratum-dependent and driven by the balance between the Lifshitz-van der Waals and Lewis acid/base interactions. Despite nearly identical surface free energies for polystyrene and stainless steel, the metallic surface promoted a totally distinct behaviour which was characterized by a strong – although highly variable – yeast adhesion. 相似文献
175.
Chrétien JM Zammattio F Gauthier D Le Grognec E Paris M Quintard JP 《Chemistry (Weinheim an der Bergstrasse, Germany)》2006,12(26):6816-6828
The preparation of polymer-supported allyltin reagents was shown to be possible for both unfunctionalized and functionalized allyl units. These reagents were treated with aldehydes in the presence of cerium(III) or indium(III) salts to afford high yields of homoallylic alcohols, practically uncontaminated with organotin residues (less than 5 ppm). Some mechanism aspects are briefly discussed and the potential for regeneration and reuse of these supported reagents is pointed out. 相似文献
176.
Nanoring and nanocone arrays were prepared by conical openings of nanopores in as-prepared AAO film as a mold. 相似文献
177.
The elastic properties of a polycrystalline sample of invar Fe(64)Ni(36) have been investigated at ambient temperature by ultrasonic experiments up to 7 GPa. The pressure dependence of the bulk modulus is extracted without using any model and discussed in terms of invar anomaly models. 相似文献
178.
Micro-computed tomography (µCT) is a widely used imaging technique. Tomography has been used to study the distribution of magnetic nanoparticles within cancerous tissue after minimal-invasive cancer treatments such as magnetic drug targeting and magnetic hyperthermia. But not only the distribution is a relevant factor for the sucess of these therapeutic aproaches. The concentration of the magnetic nanoparticles within the respective tissue is also of great impact. In this paper we present a calibration procedure of a µCT-equipment for biological tissue samples enriched with magnetic nanoparticles developed to enable a semi-quantitative evaluation of 3-dimensional data sets. (© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
179.
We provide an improved version of the Darling–Erd?s theorem for sums of i.i.d. random variables with mean zero and finite variance. We extend this result to multidimensional random vectors. Our proof is based on a new strong invariance principle in this setting which has other applications as well such as an integral test refinement of the multidimensional Hartman–Wintner LIL. We also identify a borderline situation where one has weak convergence to a shifted version of the standard limiting distribution in the classical Darling–Erd?s theorem. 相似文献
180.
Sébastien Prévost Sébastien Gauthier Maria Cristina Caño de Andrade Céline Mordant Ali Rhida Touati Philippe Lesot Philippe Savignac Tahar Ayad Phannarath Phansavath Virginie Ratovelomanana-Vidal Jean-Pierre Genêt 《Tetrahedron: Asymmetry》2010,21(11-12):1436-1446
The dynamic kinetic resolution (DKR) of racemic α-chloro β-ketoesters and α-chloro β-ketophosphonates through ruthenium-mediated asymmetric hydrogenation is reported. The corresponding α-chloro β-hydroxyesters and α-chloro β-hydroxyphosphonates were obtained in good to high enantio- and diastereomeric excesses using, in particular, the atropisomeric ligand DIFLUORPHOS. This methodology allowed an efficient preparation of the anti phenylisoserine side chain of Taxotere® which has been used for the hemisynthesis of the cancer therapeutic agent itself. In addition, 13C NMR in chiral oriented solvents was used to investigate the DKR effect. 相似文献