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521.
Ring substituted α-bromoacetophenones undergo efficient photodecomposition upon ultraviolet irradiation in alcohol solvents. The process involves chain reactions mediated by the ketyl radicals derived by hydrogen abstraction from the alcohols. It is suggested that two chain reactions involving hydrogen and electron transfer may be taking place concurrently. Competitive studies lead to relative rate constants for the reactions of ketyl radicals with ring-substituted α-bromoacetophenones. 相似文献
522.
We have studied the nano-patterning of CoO film induced by misfit dislocation network at the interface with the Ag(0 0 1) substrate. Grazing incidence diffraction (GIXD), X-ray photoemission spectroscopy (XPS) and low energy electron diffraction (LEED) have been used to characterize chemistry and structure of the CoO layers. The XPS spectrum of the Co 2p core level permitted to establish the stoichiometric growth of CoO. The structure of the CoO film together with the absorption sites of cobalt and oxygen atoms was determined, thanks to GIXD measurements. Moreover we have followed the evolution of the in-plane lattice constant of the CoO as a function of the film thickness. It turns out that the CoO film growth starts with the same in-plane lattice constant of the Ag(0 0 1) substrate up to 3-4 ML; afterwards the in-plane parameter of CoO steadily increases before reaching a stable value of 2.98 Å at 23 ML. During the relaxation process, at about 8 ML of film thickness, we observe the formation of a buried misfit dislocation network. These dislocations, that have a period of 9.2 nm for a film thickness of 23 ML, induce mosaicity in the CoO film which then appears as a regular distribution of tilted domains. 相似文献
523.
P. A. Holstein M. Casanova A. Casner C. Cherfils E. Dattolo L. Disdier D. Galmiche J. Giorla M. Houry J. P. Jadaud S. Laffite S. Liberatore P. Loiseau L. Lours L. Masse M. C. Monteil O. Morice M. Naudy F. Philippe F. Poggi F. Renaud G. Riazuelo Y. Saillard P. Seytor M. Vandenboomgaerde F. Wagon 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,44(2):239-247
This article sums up the theoretical and experimental studies about
ignition. Three experiments are salient this year on the Omega laser in
collaboration with DOE laboratories (1) 3 cones of beams allow to mimic the
LMJ configuration and to get symmetry measurements. (2) We measured
perturbations due to hydro-instability in CHGe planar samples with face-on
and side-on radiographs. (3) We improved our nuclear diagnostics,
particularly the neutron image system tested on direct drive implosions. As far as LMJ target design is concerned, we defined
a preliminary domain
corresponding to the possible operation at 2ω. At 3ω we studied the low mode
instability effects on the DT deformation (due to the laser or to the
target) and on the yield. The stability is clearly improved with graded
doped CH for our nominal capsule L1215. 相似文献
524.
Renaud Lussier Yann Giroux Simon Thibault Denis Rodrigue Anna M. Ritcey 《先进技术聚合物》2020,31(6):1414-1425
Polydimethylsiloxane (PDMS)/iron oxide magnetic nanoparticle (NP) composites with tailored mechanical properties are prepared for use in magnetically actuated soft devices based on their controlled deformation by the application of an external magnetic field. This investigation reports the synthesis and functionalization of iron oxide NPs, the preparation of the PDMS/NP composites, the evaluation of NP dispersion using scanning electron microscopy (SEM) and optical microscopy, and the mechanical characterization of the composite films. Characterization includes rheological measurements as well as stress‐strain curves to obtain the Young modulus and elongation at break. SEM is used to probe individual NP dispersion, whereas optical microscopy provides rapid access to quantitative information about the size and distribution of particle aggregates. Results for nonfunctionalized (nf), oleic acid (OA)‐coated, and stearic acid (SA)‐coated iron oxide NPs and their blends are presented. PDMS elastomers containing both OA‐ and SA‐coated iron oxide NPs are found to have very low Young moduli with substantially higher resistance to failure than neat PDMS. For example, a formulation containing 2.5 wt% OA‐coated NPs and 2.5 wt% SA‐coated iron oxide NPs has a modulus of 0.15 MPa (compared with 0.24 MPa for neat PDMS), while it can withstand an elongation of about 1.5 times its initial length compared with only 0.3 times for neat PDMS. As a comparison, the modulus of the most commonly used commercial PDMS elastomer (Sylgard 184) is an order of magnitude higher than that of the composites prepared here, whereas maximum elongation is similar for the two. The formulations developed in this work could be used in applications where high deformability is required with limited magnetic field strength and/or NP loading. 相似文献
525.
Abstract Herein, we introduce one of the first examples of asymmetric organocatalyzed synthesis of 1,2-dihydropyridines, affording enantioselective access to and partially solving regioselectivity challenges in the synthesis of dihydropyridines. We demonstrate that through modification of organocatalysts both 1,2- and 1,4-dihydropyridines (1,2- and 1,4-DHPs) can be obtained with high regioselectivity (ratio of 1,2-DHP/1,4-DHP from 95/5 to 0/100) and enantioselectivity (33% ee for 1,2-DHPs and up to 98% ee for 1,4-DHPs) in good yields (up to 87%). 相似文献
526.
Bregiroux D Terra O Audubert F Dacheux N Serin V Podor R Bernache-Assollant D 《Inorganic chemistry》2007,46(24):10372-10382
On the basis of optimized grinding/heating cycles developed for several phosphate-based ceramics, the preparation of brabantite and then monazite/brabantite solid solutions loaded with tetravalent thorium, uranium, and cerium (as a plutonium surrogate) was examined versus the heating temperature. The chemical reactions and transformations occurring when heating the initial mixtures of AnO2/CeO2, CaHPO(4).2H2O (or CaO), and NH4H2PO4 were identified through X-ray diffraction (XRD) and thermogravimetric/differential thermal analysis experiments. The incorporation of thorium, which presents only one stabilized oxidation state, occurs at 1100 degrees C. At this temperature, all the thorium-brabantite samples appear to be pure and single phase as suggested by XRD, electron probe microanalyses, and micro-Raman spectroscopy. By the same method, tetravalent uranium can be also stabilized in uranium-brabantite, i.e., Ca0.5U0.5PO4, after heating at 1200 degrees C. Both brabantites, Ca0.5Th0.5PO4 and Ca0.5U0.5PO4, begin to decompose when increasing the temperature to 1400 and 1300 degrees C, respectively, leading to a mixture of CaO and AnO2 by the volatilization of P4O10. In contrast to the cases of thorium and uranium, cerium(IV) is not stabilized during the heating treatment at high temperature. Indeed, the formation of Ca0.5Ce0.5PO4 appears impossible, due to the partial reduction of cerium(IV) into cerium(III) above 840 degrees C. Consequently, the systems always appear polyphase, with compositions of CeIII1-2xCeIVxCaxPO4 and Ca2P2O7. The same conclusion can be also given when discussing the incorporation of cerium(IV) into La1-2xCeIIIx-yCeIVyCay(PO4)1-x+y. This incomplete incorporation of cerium(IV) confirms the results obtained when trying to stabilize tetravalent plutonium in Ca0.5PuIV0.5PO4 samples. 相似文献
527.
A concise synthesis of (±)-cylindricine C and its C(13)-epimer is described. Starting from 1-octyne, cylindricine C and 13-epi-cylindricine C were prepared in 11% and 15% yields, respectively. The synthesis involves the preparation of the central tricyclic moiety via a radical α-iodoketone carboazidation/bis-reductive amination sequence. Inversion of the stereochemistry at C(13) and C(5) was efficiently achieved on late stage intermediates. 相似文献
528.
Kuss S Cornut R Beaulieu I Mezour MA Annabi B Mauzeroll J 《Bioelectrochemistry (Amsterdam, Netherlands)》2011,82(1):29-37
Cancer cell multidrug resistance is a molecular signature that highly influences the outcome of chemotherapy treatment and for which there is currently no robust method to monitor in vitro its activity. Herein, we demonstrate that ferrocenemethanol (FcCH(2)OH) and its oxidized form ([FcCH(2)OH](+)) affect the redox state of cancer cells. Specifically, the interaction of FcCH(2)OH with the glutathione couple (GSH/GSSG) is shown in human adenocarcinoma cervical cancer cells HeLa and a multidrug resistant variant overexpressing the multidrug resistant associated protein 1 (MRP1) using bioanalytical techniques, such as flow cytometry and fluorescence microscopy. It is further demonstrated that the differential response to FcCH(2)OH in multidrug-resistant cells is in part due to MRP1's unspecific efflux. Scanning electrochemical microscopy confirmed the interaction between FcCH(2)OH and the cells, and the differential response was observed to depend on MRP1 expression. This newly established relation between FcCH(2)OH/[FcCH(2)OH](+), GSH/GSSG and multidrug resistance in human cancer cells enables than the acquisition of scanning electrochemical microscopy images. 相似文献
529.
Nechab M Besson E Campolo D Perfetti P Vanthuyne N Bloch E Denoyel R Bertrand MP 《Chemical communications (Cambridge, England)》2011,47(18):5286-5288
Mesoporous silica grafted with a tertiary amine was used as a basic nanocatalyst to promote in confined medium the enantioselective cascade rearrangement of enediynes based on the phenomenon of memory of chirality; the multi-substrates recyclable catalytic reagent could easily be recovered by simple filtration, and reused without any decrease in activity even when changing the solvent. 相似文献
530.
Oana?StanEmail author Renaud?Sirdey Jacques?Carlier Dritan?Nace 《4OR: A Quarterly Journal of Operations Research》2015,13(3):309-334
In this paper, we study the problem of joint placement and routing, both in the deterministic and stochastic cases, arising in the field of compilation of dataflow applications for manycore architectures. A GRASP algorithm is first proposed for solving the deterministic version and extended afterwards to treat the chance-constrained program with uncertainty affecting the weights of a dataflow process network. Extensive computational results, on representative synthetic benchmark and real data, illustrate the practical relevance of the approach, as well as the robustness of the obtained stochastic solutions. 相似文献