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1.
2.
With the advances in pulsed laser systems, microscopic imaging techniques such as multiphoton and pump-probe fluorescence microscopy have developed into effective tools for investigating intensity and time-resolved phenomena inside biological systems. However, pulsed lasers used in these techniques usually are commercial systems with repetition frequencies of around 80 MHz. While these systems have proven to be adequate for multiphoton and pump-probe microscopic imaging applications, the temporal separation of the laser pulse train (around 12.5 ns) is long compared to the fluorescence lifetimes of many common fluorescence species. In this work, we present the designs of repetition rate multipliers based on passive optical components that can be used to increase the efficiency in multiphoton and pump-probe fluorescence microscopy. Depending on the lifetime of fluorescence molecules under investigation, the passive repetition rate multiplier can increase the duty cycle of multiphoton or pump-probe microscopy up to fourfold. 相似文献
3.
Ying‐Ling Liu Chuan‐Shao Wu Yie‐Shun Chiu Wen‐Hsuan Ho 《Journal of polymer science. Part A, Polymer chemistry》2003,41(15):2354-2367
A novel epoxy system was developed through the in situ curing of bisphenol A type epoxy and 4,4′‐diaminodiphenylmethane with the sol–gel reaction of a phosphorus‐containing trimethoxysilane (DOPO–GPTMS), which was prepared from the reaction of 9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide (DOPO) with 3‐glycidoxypropyltrimethoxysilane (GPTMS). The preparation of DOPO–GPTMS was confirmed with Fourier transform infrared, 1H and 31P NMR, and elemental analysis. The resulting organic–inorganic hybrid epoxy resins exhibited a high glass‐transition temperature (167 °C), good thermal stability over 320 °C, and a high limited oxygen index of 28.5. The synergism of phosphorus and silicon on flame retardance was observed. Moreover, the kinetics of the thermal oxidative degradation of the hybrid epoxy resins were studied. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2354–2367, 2003 相似文献
4.
Tandem cascade reactions of allylazides and olefinic dipolarophiles to give cis‐fused 2,3,7‐triazabicyclo [3.3.0]octenes ( 5, 6 or 7 ) are reported. Therein, an intermolecular dipolar cycloaddition of azide and alkene gave a triazoline which was followed by isomerization of the triazoline to a diazoester ( 4 ) and then an intramolecular dipolar cycloaddition from the diazo functional group and the double bond in 4 to give 5 . Compound 5 may further more undergo a Michael addition to give 7‐substituted‐ 2,3,7‐ triazabicyclo [3.3.0]oct‐2‐ene ( 6 ) or a tautomerization to give 2,3,7‐triazabicyclo[3.3.0]oct‐3‐ene ( 7 ). The reaction may be manipulated to stop at a particular stage by adopting a suit able solvent or an appropriate temperature. 相似文献
5.
Strachan JD Adler H Alling P Ancher C Anderson H Anderson JL Ashcroft D Barnes CW Barnes G Batha S Bell MG Bell R Bitter M Blanchard W Bretz NL Budny R Bush CE Camp R Caorlin M Cauffman S Chang Z Cheng CZ Collins J Coward G Darrow DS DeLooper J Duong H Dudek L Durst R Efthimion PC Ernst D Fisher R Fonck RJ Fredrickson E Fromm N Fu GY Furth HP Gentile C Gorelenkov N Grek B Grisham LR Hammett G Hanson GR Hawryluk RJ Heidbrink W Herrmann HW Hill KW Hosea J Hsuan H Janos A Jassby DL Jobes FC 《Physical review letters》1994,72(22):3526-3529
6.
Jian‐Hua Zhao Hsuan‐Liang Liu Hsin‐Yi Lin Chih‐Hung Huang Hsu‐Wei Fang Shau‐Wei Tsai 《中国化学会会志》2007,54(4):835-842
In this study, we present the results from the semiempirical molecular orbital calculations for the acylation step in the lipase‐catalyzed ester hydrolysis. The results reveal that the lowest energy path for the formation of the tetrahedral intermediate is for the serine residue of the catalytic triad to attack the substrate, followed by coupling heavy atom movement and proton transfer. The calculations of four active site models show that the cooperation of the aspartate group and the oxyanion hole is capable of lowering the activation energy by about 16 kcalmol?1. Our results further suggest that the lipase‐catalyzed ester hydrolysis adopts the single proton transfer mechanism. 相似文献
7.
Ching Hsuan Lin Zheng Rong Jiang Chun Shan Wang 《Journal of polymer science. Part A, Polymer chemistry》2002,40(22):4084-4097
A 2,6‐dimethyl phenol–dipentene adduct was synthesized from dipentene (DP) and 2,6‐dimethyl phenol, and then a 2,6‐dimethyl phenol–DP epoxy was synthesized from the reaction of the resultant 2,6‐dimethyl phenol–DP adduct and epichlorohydrin. The proposed structures were confirmed by Fourier transform infrared, elemental analysis, mass spectra, NMR spectra, and epoxy equivalent weight titration. The synthesized 2,6‐dimethyl phenol–DP adduct was cured with 4,4‐diamino diphenyl methane, phenol novolac, 4,4‐diamino diphenyl sulfone, and 4,4‐diamino diphenyl ether. The thermal properties of the cured epoxy resins were studied with differential scanning calorimetry, dynamic mechanical analysis, dielectric analysis, and thermogravimetric analysis. These data were compared with those for the bisphenol A epoxy system. The cured 2,6‐dimethyl phenol–DP epoxy exhibited a lower dielectric constant (ca. 3.1), a lower dissipation factor (ca. 0.065), a lower modulus, lower thermal stability (5% degradation temperature = 366–424 °C), and lower moisture absorption (1.21–2.18%) than the bisphenol A system but a higher glass‐transition temperature (ca. 173–222 °C) than that of bisphenol A system. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4084–4097, 2002 相似文献
8.
9.
Hou Chien Chang Ching Hsuan Lin Hung Tse Lin Shenghong A. Dai 《Journal of polymer science. Part A, Polymer chemistry》2012,50(5):1008-1017
Generally, protection and deprotection procedures of amino groups are required in preparing propargyl ether‐containing benzoxazines. In this study, we report a facile, deprotection‐free preparation of a propargyl ether‐containing phosphinated benzoxazine (2) from the nucleophilic substitution of a phenolic OH‐containing phosphinated benzoxazine (1) and propargyl bromide in the catalysis of potassium carbonate. The structure of (2) was characterized and confirmed by a high‐resolution mass spectrum, 1H, 13C, 1H‐1H, 1H‐13C nuclear magnetic resonance (NMR) spectra, and X‐ray single crystal diffractogram. infrared (IR) and differential scanning calorimetry were used to monitor the ring‐opening of benzoxazine and crosslinking of propargyl ether. The microstructure and the structure–property relationship of the resulting homopolymers and copolymers are discussed. The Tg of homopolymer of (2) is 208 °C by dynamic mechanical analysis, the coefficient of thermal expansion is 43 ppm/°C, and Td 5% (N2) is 393 °C, respectively, which are higher than those of the homopolymer of (1) . Similar trends were observed in the copolymerization system. The results demonstrate the beneficial effect of crosslinking afforded by the propargyl ether group is higher than that by the phenolic OH group. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012 相似文献