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971.
972.
Coasne B Haines J Levelut C Cambon O Santoro M Gorelli F Garbarino G 《Physical chemistry chemical physics : PCCP》2011,13(45):20096-20099
We report a molecular simulation study of the mechanical properties of microporous zeolites filled with guest molecules. We show that the adsorption of molecules in the micropores of the material increases its bulk modulus. These results provide a microscopic picture of the deactivation of pressure-induced amorphization by incorporation of molecules. 相似文献
973.
974.
We propose a strategy for optimizing distribution of flow in a microfluidic chamber for microreactor, lateral flow assay and immunocapture applications. It is aimed at maximizing flow throughput, while keeping footprint, cell thickness, and shear stress in the distribution channels at a minimum, and offering a uniform flow field along the whole analysis chamber. In order to minimize footprint, the traditional tree-like or "rhombus" design, in which distribution microchannels undergo a series of splittings into two subchannels with equal lengths and widths, was replaced by a design in which subchannel lengths are unequal, and widths are analytically adapted within the Hele-Shaw approximation, in order to keep the flow resistance uniform along all flow paths. The design was validated by hydrodynamic flow simulation using COMSOL finite element software. Simulations show that, if the channel is too narrow, the Hele-Shaw approximation loses accuracy, and the flow velocity in the chamber can fluctuate by up to 20%. We thus used COMSOL simulation to fine-tune the channel parameters, and obtained a fluctuation of flow velocity across the whole chamber below 10%. The design was then implemented into a PDMS device, and flow profiles were measured experimentally using particle tracking. Finally, we show that this system can be applied to cell sorting in self-assembling magnetic arrays, increasing flow throughput by a factor 100 as compared to earlier reported designs. 相似文献
975.
De K Legros J Crousse B Chandrasekaran S Bonnet-Delpon D 《Organic & biomolecular chemistry》2011,9(2):347-350
The synthesis of 8-aminoquinolines and 1,10-phenanthrolines with substituents in α of the nitrogen has been performed through an inverse-demanding aza-Diels-Alder (Povarov reaction) in the fluoroalcohols TFE or HFIP. This path involves simple starting materials: 1,2-phenylenediamines, enol ethers and aldehydes. 相似文献
976.
N-Vinyl ureas are emerging as a valuable class of compounds with both nucleophilic and electrophilic reactivity. They may be made by capturing the enamine tautomer of an imine with an isocyanate, a reaction which in general leads to the E isomer of the vinyl urea. Deprotonation of such a vinyl urea, or of an allyl urea, generates a dipole stabilized Z-allyl anion which may be protonated to return the Z-vinyl urea. Isomerization of an allyl urea with a Ru complex provides an alternative route to E-vinyl ureas. 相似文献
977.
The first trichromophoric sensitizer, consisting of covalently linked boradiazaindacene (BODIPY), zinc porphyrin (ZnP), and squaraine (SQ) units, has been synthesized by Heck alkynylation to obtain a panchromatic dye, for dye sensitized solar cells (DSSCs). Efficient intramolecular energy transfers (ET) were observed between all chromophoric subunits and enhance the overall conversion efficiency by 25%. The antenna effect is demonstrated by the photoaction spectrum which features all of a chromophore's absorption bands. 相似文献
978.
Functionalized alkylidene-cyclobutanes have been prepared from 2-fluoropyridinyl-6-oxy precursors derived from vinyl cyclobutanols by a radical addition-elimination process. A wide range of functional groups is tolerated, and the alkylidene-cyclobutanes can be further elaborated into cyclopentanones. The limitation of this approach resides in the competition with opening of the cyclobutane ring. 相似文献
979.
Badoud F Grata E Boccard J Guillarme D Veuthey JL Rudaz S Saugy M 《Analytical and bioanalytical chemistry》2011,400(2):503-516
The urinary steroid profile is constituted by anabolic androgenic steroids, including testosterone and its relatives, that
are extensively metabolized into phase II sulfated or glucuronidated steroids. The use of liquid chromatography coupled to
mass spectrometry (LC-MS) is an issue for the direct analysis of conjugated steroids, which can be used as urinary markers
of exogenous steroid administration in doping analysis, without hydrolysis of the conjugated moiety. In this study, a sensitive
and selective ultra high-pressure liquid chromatography coupled to quadrupole time-of-flight mass spectrometer (UHPLC-QTOF-MS)
method was developed to quantify major urinary metabolites simultaneously after testosterone intake. The sample preparation
of the urine (1 mL) was performed by solid-phase extraction on Oasis HLB sorbent using a 96-well plate format. The conjugated
steroids were analyzed by UHPLC-QTOF-MSE with a single-gradient elution of 36 min (including re-equilibration time) in the negative electrospray ionization mode.
MSE analysis involved parallel alternating acquisitions of both low- and high-collision energy functions. The method was validated
and applied to samples collected from a clinical study performed with a group of healthy human volunteers who had taken testosterone,
which were compared with samples from a placebo group. Quantitative results were also compared to GC-MS and LC-MS/MS measurements,
and the correlations between data were found appropriate. The acquisition of full mass spectra over the entire mass range
with QTOF mass analyzers gives promise of the opportunity to extend the steroid profile to a higher number of conjugated steroids. 相似文献
980.
Jérôme Julien Mihail Gărăjeu Jean-Claude Michel 《International Journal of Solids and Structures》2011,48(10):1485-1498
This paper presents a micromechanical model for a porous viscoplastic material containing two populations of pressurized voids of different sizes. Three scales are distinguished: the microscopic scale (corresponding to the size of the small voids), the mesoscopic scale (corresponding to the size of the large voids) and the macroscopic scale. It is assumed that the first homogenization step is performed at the microscopic scale, and, at the mesoscopic scale, the matrix is taken to be homogeneous and compressible. At the mesoscopic scale, the second homogenization step, on which the present study focuses, is based on a simplified representative volume element: a hollow sphere containing a pressurized void surrounded by a nonlinear viscoplastic compressible matrix. The nonlinear behavior of the matrix, which is expressed using the results obtained in the first homogenization step, is approached using a modified secant linearization procedure involving the discretization of the hollow sphere into concentric layers. Each layer has uniform secant moduli. The predictions of the model are compared with the more accurate numerical results obtained using the finite element method. Good agreement is found to exist with all the macroscopic stress triaxialities and all the porosity and nonlinearity values studied. 相似文献