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451.
Santiago Tainta María J. Erro María J. Garde Miguel A. Muriel 《Fiber and Integrated Optics》2013,32(5-6):324-335
Abstract An electrically reconfigurable time-domain spectral amplitude encoding/decoding scheme is proposed herein. The setup is based on the concept of temporally pulse shaping dual to spatial arrangements. The transmitter is based on a short pulse source and uses two conjugate dispersive fiber gratings and an electro-optic intensity modulator placed in between. Proof of concept results are shown for an optical pulse train operating at 1.25 Gbps using codes from the Hadamard family with a length of eight chips. The system is electrically reconfigurable, compatible with fiber systems, and permits scalability in the size of the codes by modifying only the modulator velocity. 相似文献
452.
Mixtures of maleic anhydride and thiophene were polymerized to alternating copolymers under the influence of azobisisobutyronitrile. The yield and molecular weight were highest when equimolar amounts of both monomers were used. Through comparison of the NMR spectrum of the copolymer with the NMR spectra of 2,3-dihydrothiophene and 2,5-dihydrothi-ophene, the copolymer proposed consists mainly of the following structure: It is believed that polymerization occurs via a charge-transfer complex. 相似文献
453.
Corbierre MK Cameron NS Lennox RB 《Langmuir : the ACS journal of surfaces and colloids》2004,20(7):2867-2873
A series of polymer-coated Au nanoparticles have been prepared using the "grafting-to" approach. Thiol-terminated polystyrene and poly(ethylene oxide) ligands are found to form dense brushes on the faceted gold nanoparticle surfaces. Depending on the polymer, the ligand grafting densities on the gold nanoparticles are 1.2- to 23.5-fold greater than those available via self-assembled monolayer formation of the corresponding two-dimensional gold surfaces. 相似文献
454.
In the case of poly(lactic acid) stereocopolymers, it has been shown that the hydrolytic degradation of derived devices depends very much on whether zinc lactate or tin octoate was used to polymerize lactides. In contrast, no effect was found in the case of nanoparticles derived from poly(dl-lactic acid)-block-poly(ethylene glycol) copolymers obtained by anionic polymerization of dl-lactide initiated by the sodium salt of monomethoxypoly(ethylene glycol) or by coordination-insertion polymerization of dl-lactide initiated by monomethoxypoly(ethylene glycol) in the presence of tin octoate as catalyst. To understand the difference of behaviour, in vitro hydrolytic degradation of thick plates made of the same copolymers but under different conditions was investigated. Changes were monitored by 1H Nuclear Magnetic Resonance, Size Exclusion Chromatography, Electrospray Mass Spectrometry and Capillary Zone Electrophoresis. It is shown that chain cleavage occurred from the very beginning of degradation and that plates disintegrated after 13 weeks. In all cases, degradation proceeded faster inside than at the surface, in contrast to what was observed for nanoparticles. Tin-type copolymer plates degraded more slowly than sodium macroalcoholate-type ones and were sensitive to purification conditions, in contrast to the latter. 相似文献
455.
Mass spectra of four tetrahydrotetrabenzo[b,d,h,j] [1,6]diazacyclododecines are reported. Loss of phenan-threne gives 2,2′-diaminobiphenyl or the appropriate substituted diamine as the base peak in three cases. Substituents ortho to the biphenyl link substantially modify the fragmentation pattern. Mass spectra of the four 2,2′-diaminobiphenyls have been determined for comparison. 相似文献
456.
Epidermal reconstructs: a new tool to study topical and systemic photoprotective molecules 总被引:2,自引:0,他引:2
Cario-André M Briganti S Picardo M Nikaido O Gall Y Ginestar J Taïeb A 《Journal of photochemistry and photobiology. B, Biology》2002,68(2-3):79-87
In this study, we compared the effects of sunscreens and antioxidants on reconstructed epidermis made with or without melanocytes 24 h after UVB, UVA or UVA+B irradiation. For this purpose, we studied sunburn cells and cyclobutane pyrimidine dimer formation, protein and lipid oxidation, catalase and superoxide dismutase activities and vitamin E levels. Topical sunscreens protected against direct cell death and thymine dimer formation whereas their protective effect against protein and lipid oxidation and antioxidant depletion was less marked partly due to the difficulty of spreading the cream. Antioxidant molecules protected against direct cell death and protein oxidation but not against thymine dimer formation. Since topical sunscreens and systemic antioxidant protected the skin differently, we speculate that their association might protect more efficiently against UV-induced damage. This model is relevant to study systemic molecules but is less practical, due to the technical limitations of studying topical molecules. 相似文献
457.
Herman Gershon Donald D. Clarke Muriel Gershon 《Monatshefte für Chemie / Chemical Monthly》2002,133(11):1437-1442
Summary. 6-Fluoro-8-quinolinol was prepared from 2-amino-5-fluorophenol by a Skraup synthesis. No synergism was observed between 5-fluoro- and 6-fluoro-8-quinolinols or between 6-fluoro- and 7-fluoro-8-quinolinols
against any of the six fungi in our test system (Aspergillus niger, A. oryzae, Myrothecium verrucaria, Trichoderma viride, Mucor cirinelloides, and Trichophyton mentagrophytes) in Sabouraud dextrose broth. Unlike the fluoro-8-quinolinols, the 8-quinolinols comparably substituted with chlorine or bromine did form
synergistic mixtures. This is attributed to steric factors.
Corresponding author. E-mail: clarke@fordham.edu
Received May 23, 2002; accepted May 29, 2002 相似文献
458.
The opening pathway of wobble pairs dG.T and rG.U has been investigated in four DNA and two RNA duplexes. Using NMR spectroscopy, we measured the imino proton exchange of both G(H1) and T/U(H3), catalyzed by ammonia, tris, and OH(-), and we calculated the free energy surface related to G.T/U opening by molecular dynamics simulations. Taken together the experimental and theoretical results, we suggest that wobble pairs open through a coupled rotation of the bases toward the major groove where exchange of both imino protons takes place with the surrounding water. 相似文献
459.
Yoann Marsac Stéphanie Legoupy Muriel Pipelier Anne-Marie Aubertin Rachid Benhida 《Tetrahedron》2005,61(32):7607-7612
Enantiomerically enriched cyclobutene compounds 13 and 24 are good precursors of several cyclobutane nucleoside analogs. The synthetic ways involve, in the key step, either hydroboration or dihydroxylation. 相似文献
460.
Nonglaton G Benitez IO Guisle I Pipelier M Léger J Dubreuil D Tellier C Talham DR Bujoli B 《Journal of the American Chemical Society》2004,126(5):1497-1502
A new approach to oligonucleotide arrays is demonstrated that utilizes zirconium phosphonate-derivatized glass slides. The active slides are prepared by binding Zr(4+) to surfaces terminated with organophosphonate groups previously deposited using either Langmuir-Blodgett or self-assembled monolayer methods. Oligonucleotide probes modified with a terminal phosphate bind strongly to the active zirconium phosphonate monolayer, and arrays for detecting fluorescent targets have been prepared using commercial spotting and scanning instruments. Preferred binding to the surface of the terminal phosphate of the modified probes instead of the internal phosphate diester groups is demonstrated and shown to yield increased fluorescence intensity after hybridization with labeled targets. A significant decrease in background signal is achieved by treating the slides with bovine serum albumin after spotting and before hybridization. A further increase in fluorescence after hybridization is observed when using a poly-guanine spacer between the probe oligomer and the terminal phosphate. Combining these modifications, an intensity ratio of nearly 1000 is achieved when comparing 5'-phosphate-modified 33-mer probes with unmodified probes upon hybridization with fluorescent targets. 相似文献