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1.
ABSTRACTQM(UB3LYP)/MM(AMBER) calculations were performed for the locations of the transition structure (TS) of the oxygen–oxygen (O–O) bond formation in the S4 state of the oxygen-evolving complex (OEC) of photosystem II (PSII). The natural orbital (NO) analysis of the broken-symmetry (BS) solutions was also performed to elucidate the nature of the chemical bonds at TS on the basis of several chemical indices defined by the occupation numbers of NO. The computational results revealed a concerted bond switching (CBS) mechanism for the oxygen–oxygen bond formation coupled with the one-electron transfer (OET) for water oxidation in OEC of PSII. The orbital interaction between the σ-HOMO of the Mn(IV)4–O(5) bond and the π*-LUMO of the Mn(V)1=O(6) bond plays an important role for the concerted O–O bond formation for water oxidation in the CaMn4O6 cluster of OEC of PSII. One electron transfer (OET) from the π-HOMO of the Mn(V)1=O(6) bond to the σ*-LUMO of the Mn(IV)4–O(5) bond occurs for the formation of electron transfer diradical, where the generated anion radical [Mn(IV)4–O(5)]-? part is relaxed to the ?Mn(III)4?…?O(5)- structure and the cation radical [O(6)=Mn(V)1]+ ? part is relaxed to the +O(6)–Mn(IV)1? structure because of the charge-spin separation for the electron-and hole-doped Mn–oxo bonds. Therefore, the local spins are responsible for the one-electron reductions of Mn(IV)4->Mn(III)4 and Mn(V)1->Mn(IV)1. On the other hand, the O(5)- and O(6)+ sites generated undergo the O–O bond formation in the CaMn4O6 cluster. The Ca(II) ion in the cubane- skeleton of the CaMn4O6 cluster assists the above orbital interactions by the lowering of the orbital energy levels of π*-LUMO of Mn(V)1=O(6) and σ*-LUMO of Mn(IV)4–O(5), indicating an important role of its Lewis acidity. Present CBS mechanism for the O–O bond formation coupled with one electron reductions of the high-valent Mn ions is different from the conventional radical coupling (RC) and acid-base (AB) mechanisms for water oxidation in artificial and native photosynthesis systems. The proton-coupled electron transfer (PC-OET) mechanism for the O–O bond formation is also touched in relation to the CBS-OET mechanism. 相似文献
2.
Michael R. Caputo 《Natural Resource Modeling》1989,3(2):241-259
This paper analyzes the extent to which standard dynamic renewable resource models possess refutable implications. Both the steady state comparative static and local comparative dynamic properties of the standard model are studied. A unified framework is developed which enables one to analyze the qualitative properties of any standard renewable resource model. This is achieved by explicitly linking the local stability, steady state comparative static, and local comparative dynamic properties of the model. 相似文献
3.
Fiber-optic reflex sensor for in-line production measurement 总被引:1,自引:0,他引:1
The paper describes experiments concerning distance measurement with fiber-optic sensor and improvement of the measurement principle. The sensor probe was well-designed with a small structure and multi-function. The novel optical fiber probe arrangement as well as the possibilities of use for complex measurement problems are explained using the measurement of an internal screw thread as an example. The experimental results show that the measurement uncertainty of the thread minor diameter can reach ±10 μm, and the stability of the measurement system is better than 0.07%. 相似文献
4.
Zi‐Niu Wu 《国际流体数值方法杂志》2005,48(5):541-564
The widely used locally adaptive Cartesian grid methods involve a series of abruptly refined interfaces. In this paper we consider the influence of the refined interfaces on the steady state errors for second‐order three‐point difference approximations of flow equations. Since the various characteristic components of the Euler equations should behave similarly on such grids with regard to refinement‐induced errors, it is sufficient enough to conduct the analysis on a scalar model problem. The error we consider is a global error, different to local truncation error, and reflects the interaction between multiple interfaces. The steady state error will be compared to the errors on smooth refinement grids and on uniform grids. The conclusion seems to support the numerical findings of Yamaleev and Carpenter (J. Comput. Phys. 2002; 181: 280–316) that refinement does not necessarily reduce the numerical error. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
5.
网络股泡沫大小测度研究 总被引:1,自引:0,他引:1
网络股泡沫是最能反映网络泡沫本质的表现形式,本文利用理性预期理论,构建了网络股泡沫大小的测度模型,说明网络股泡沫的存在,在此基础上确定了网络股泡沫大小的测度指标,并以雅虎公司股票为例对泡沫的大小进行了测度,结果符合网络泡沫的实际情况。 相似文献
6.
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8.
光纤传感振动检测系统及其实验研究 总被引:3,自引:0,他引:3
实际工程结构中的振动检测是十分重要的,也是十分复杂的,常用的结构振动检测传感器易受工程现场恶劣环境的影响.而光纤传感器具有小巧、抗电磁干扰、灵敏度高、适合长期监测等优点。本文建立了基于马赫—曾德(Mech-Zehnder)干涉原理的光纤传感振动检测系统.研制了运用先进的数字信号处理技术采集和处理数据的专用软件,并在典型结构件——钢制悬臂梁结构上进行了外加信号作用下的强迫振动检测和冲击载荷作用下的自由衰减振动检测,测量了该结构件的频率及振幅,其结果与同时进行的成熟的电测结果相近,说明光纤传感器用于结构件的振动测量是可靠的。本文为光纤传感器应用于实际工程的振动检测提供了新的技术装置,具有工程应用前景。 相似文献
9.
L. A. Utracki 《Journal of Polymer Science.Polymer Physics》2004,42(15):2909-2915
The Simha and Somcynsky (S–S) statistical thermodynamics theory was used to compute the solubility parameters as a function of temperature and pressure [δ = δ(T, P)], for a series of polymer melts. The characteristic scaling parameters required for this task, P*, T*, and V*, were extracted from the pressure–temperature–volume (PVT) data. To determine the potential polymer–polymer miscibility, the dependence of δ versus T (at ambient pressure) was computed for 17 polymers. Close proximity of the δ versus T curves for four miscible polymer pairs: PPE/PS, PS/PVME, and PC/PMMA signaled the usefulness of this approach. It is noteworthy, that the tabulated solubility parameters (derived from the solution data under ambient conditions) propounded the immiscibility of the PVC/PVAc pair. The computed values of δ also suggested miscibility for polymer pairs of unknown miscibility, namely PPE/PVC, PPE/PVAc, and PET/PSF. In recognizing the limitations of the solubility parameter approach (the omission of several thermodynamic contributions), these preliminary results are auspicious because they indicate a new route for estimating the miscibility of any polymeric material at a given temperature and pressure. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 2909–2915, 2004 相似文献
10.
汪更生 《数学物理学报(B辑英文版)》2005,25(1):7-22
This paper deals with maximum principle for some optimal control problem governed by some elliptic variational inequalities. Some state constraints are discussed. The basic techniques used here are based on those in [1] and a new penalty functional defined in this paper. 相似文献