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961.
Evgeniy V. Gromov Irene Burghardt James T. Hynes Horst Kppel Lorenz S. Cederbaum 《Journal of photochemistry and photobiology. A, Chemistry》2007,190(2-3):241-257
The excited electronic states of the p-coumaric acid thio-ester chromophore of the Photoactive Yellow Protein (PYP) are characterized in view of identifying the key factors determining the chromophore's isomerisation. These factors include the anionic nature of the chromophore, the presence of sulfur (rather than oxygen or nitrogen) in the ester moiety, and the presence of a hydrogen-bonding environment stabilizing the phenolate moiety. Two twisted stationary S1 structures are identified, corresponding to a twist around the double bond conjugated with the aromatic ring, and the single bond adjacent to the ring, respectively. The latter structure is accessed directly by relaxation from the Franck–Condon (FC) geometry. These structures are shown to entail a substantial polarization effect (increasing charge separation when moving towards the twisted geometry). Further, an inversion of charge character is observed for the double-bond twisted minimum, which can be accounted for by the vicinity of an S1–S0 conical intersection. The S1–S0 gap at the minimum geometries depends in a sensitive fashion on the -carbonyl heteroatom. Based upon these observations for the intrinsic properties of the chromophore, we further address the effect of the Arg52 residue, which acts as a counter-ion in the native protein environment. 相似文献
962.
随机环境中单边二重生灭链的常返性 总被引:1,自引:0,他引:1
随机环境中单边二重生灭链是随机环境中单边随机游动的推广,本文利用单边二重生灭链与依时分枝链的关系,分别给出了固定环境及随机环境中二重生灭链的常返,正常返和零常返的几个充要及充分条件,随机环境中的单边随机游动的常返性的相应结果可以作为本文的推论. 相似文献
963.
964.
Yuri Kifer 《Transactions of the American Mathematical Society》1998,350(4):1481-1518
I derive general relativized central limit theorems and laws of iterated logarithm for random transformations both via certain mixing assumptions and via the martingale differences approach. The results are applied to Markov chains in random environments, random subshifts of finite type, and random expanding in average transformations where I show that the conditions of the general theorems are satisfied and so the corresponding (fiberwise) central limit theorems and laws of iterated logarithm hold true in these cases. I consider also a continuous time version of such limit theorems for random suspensions which are continuous time random dynamical systems.
965.
为了研究强雷电电磁场(LEMP)对没有保护状态下无线电引信性能的影响,对LEMP进行了模拟。利用MARX发生器向宽带横电磁波(GTEM)室注入雷电电压波,在GTEM室内产生模拟的LEMP电场;利用浪涌发生器向亥姆霍兹线圈注入雷电电流波,在线圈内产生模拟的LEMP磁场。根据某型无线电引信可能遭遇的雷电电磁环境,对处于勤务处理状态的该型无线电引信进行了辐照效应实验,测试辐照前后引信的性能指标,对其差异进行比较,分析了LEMP对该型无线电引信性能指标的影响。结果表明,在强的雷电电磁场环境下LEMP电场会损坏该型无线电引信的高频组件,使其不能产生探测信号,导致引信不能正常发火;LEMP电场还会损坏检波电路,使检波直流电压不能达到正常指标,从而导致引信也不能正常发火;LEMP磁场对该型引信性能基本没有影响。 相似文献
966.
ZHU Guangwu LI Baoquan WANG Shijin LIN Hua''''an LIANG Jinbao SUN Yueqiang & WU Weiqi The Center for Space Science Applied Research Chinese Academy of Sciences Beijing China 《中国科学G辑(英文版)》2005,48(1):26-32
The space environment monitor (SEM) aboard FY-2 satellite consists of the high energy particle detector (HEPD) and the solar X-ray flux detector (SXFD). The SEM can provide real-time monitoring of flare and solar proton event for its operation at geostationary orbit and is also the first Chinese space system for monitoring and alerting solar proton event. During the 23rd solar maximum cycle, almost all the solar proton events that took place in this period are monitored and some of them are predicted successfully by analyzing the characteristics of X-ray flare monitored by the SEM. Some basic variation characteristics of particle at geostationary orbit are found such as day-night periodic variation of particle flux, the electron flux with energy >1.4 MeV in the scope from 10 to 200/cm2 s sr and the proton flux with energy >1.1 MeV in the scope from 600 to 8000/cm·s·sr during the time with no magnetic storm and solar eruption. 相似文献
967.
968.
V. V. Shumskii M. I. Yaroslavtsev 《Journal of Applied Mechanics and Technical Physics》2005,46(1):21-32
Gas dynamics of a low-pressure chamber in a double-chamber hotshot wind tunnel is considered. The time needed to fill the second chamber is in good agreement with the value obtained by examining the quasi-steady process of emptying and filling of the high-pressure and low-pressure chambers. The transitional process is strongly affected by wave processes in the channel between the chambers. By changing the place of the throttling grid in this channel, one can change the time of filling of the second chamber (decrease it severalfold). The examined schemes of air input into the second chamber ensure its complete deceleration. The Mach number at the exit of the second chamber (in the wind-tunnel nozzle throat) is almost constant over the cross section and close to unity.Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 46, No. 1, pp. 29–43, January–February, 2005. 相似文献
969.
纳米材料与技术在环保中的应用 总被引:1,自引:0,他引:1
本文介绍了纳米技术在大气、污水处理方面的实际应用 ,特别是在环境保护和环境治理方面的应用 .随着纳米材料和纳米技术在环保方面的应用更深入的研究 ,将会给我国乃至全世界在治理环境污染方面带来新的机会 相似文献
970.
HUANG Qing-Ming 《结构化学》2007,26(8):902-906
Fluorescence material of Sm doped Si-Ca-Mg system was synthesized by using the method of solid phase reaction at high temperature. The phase composition and crystal structure of this material were analyzed with XRD method for its composition and the existence form of Sm atom. We aimed to exactly determine the phase composition of this fluorescence material and the doping position and environment of rare-earth Sm atom in the system because these factors have significant effects on the properties. The analytical results show that the Sm atoms dope in Ca2O26Si6Sm8 lattice in the form of atomic site-occupation in three different space positions with different occupancy rates. Therefore, based on the XRD analytical results, the fluorescence material of Sm doped Si-Ca-Mg system with high performance can be synthesized. 相似文献