关键词： density functional theory   excited states   fluorescence   ground states   molecular electronic states   molecule-photon collisions   organic compounds   quantum chemistry   solvent effects   water  

摘要： We present a combination of time-dependent density functional theory with the quantum mechanical/molecular mechanical approach which can be applied to study nonadiabatic dynamical processes in molecular systems interacting with the environment. Our method is illustrated on the example of ultrafast excited state dynamics of indole in water. We compare the mechanisms of nonradiative relaxation and the electronic state lifetimes for isolated indole, indole in a sphere of classical water, and indole + 3H(2)O embedded in a classical water sphere. In the case of isolated indole, the initial excitation to the S-2 electronic state is followed by an ultrafast internal conversion to the S-1 state with a time constant of 17 fs. The S-1 state is long living (> 30 ps) and deactivates to the ground state along the N-H stretching coordinate. This deactivation mechanism remains unchanged for indole in a classical water sphere. However, the lifetimes of the S-2 and S-1 electronic states are extended. The inclusion of three explicit water molecules opens a new relaxation channel which involves the electron transfer to the solvent, leading eventually to the formation of a solvated electron. The relaxation to the ground state takes place on a time scale of 60 fs and contributes to the lowering of the fluorescence quantum yield. Our simulations demonstrate the importance of including explicit water molecules in the theoretical treatment of solvated systems. (C) 2011 American Institute of Physics. [doi:10.1063/1.3622563]

关键词： Actins/genetics   Actins/metabolism   Animals   Biomechanics   Cells, Cultured   Cytoskeleton/metabolism   Fibroblasts/cytology   Fibroblasts/metabolism   Green Fluorescent Proteins/genetics   Green Fluorescent Proteins/metabolism   Immunohistochemistry   Immunohistochemistry   Rats   Recombinant Fusion Proteins/genetics   Recombinant Fusion Proteins/metabolism  

摘要： Mechanical forces can regulate various functions in living cells. The cytoskeleton is a crucial element for the transduction of forces in cell-internal signals and subsequent biological responses. Accordingly, many studies in cellular biomechanics have been focused on the role of the contractile acto-myosin system in such processes. A widely used method to observe the dynamic actin network in living cells is the transgenic expression of fluorescent proteins fused to actin. However, adverse effects of GFP-actin fusion proteins on cell spreading, migration and cell adhesion strength have been reported. These shortcomings were shown to be partly overcome by fusions of actin binding peptides to fluorescent proteins. Nevertheless, it is not understood whether direct labeling by actin fusion proteins or indirect labeling via these chimaeras alters biomechanical responses of cells and the cytoskeleton to forces. We investigated the dynamic reorganization of actin stress fibers in cells under cyclic mechanical loading by transiently expressing either egfp-Lifeact or eyfp-actin in rat embryonic fibroblasts and observing them by means of live cell microscopy. Our results demonstrate that mechanically-induced actin stress fiber reorganization exhibits very different kinetics in EYFP-actin cells and EGFP-Lifeact cells, the latter showing a remarkable agreement with the reorganization kinetics of non-transfected cells under the same experimental conditions.

关键词： 机械动力部件   实时监控   S7-300PLC   ET200  

摘要： 煤矿井下的特殊环境使得对机械动力部的检测一直处于相对简单和原始的状态,因此,设计了一种基于S7-300PLC煤矿井下机械动力部工况实时监控系统,并详细介绍了其工作原理、组成硬件的选择和软件的应用。经过定点实验证明,通过应用该系统工作人员数与检测时间都大大减少,检测效率提高29%。

关键词： Actuating device   Actuating force   Agricultural equipment   Agricultural machines   Control devices   Definitions   Layout   Manipulating devices   Operating devices   Operating forces   Operation   Specification (approval)   Tractors  

标准号: NF U02-101-2011

关键词： 机械动力学   研究生   课程改革   创新   案例教学  

摘要： 机械动力学是基础理论与实践应用紧密结合的研究生专业课程,属于力学与机械工程的交叉学科,既有基础理论高度的抽象性与严密的科学性,又具有实践应用的广泛性与深入性。针对研究生积极参与实际课题的浓厚兴趣与强烈愿望,通过对机械动力学课程内容和教学模式的改革,引入案例教学法,革新考核方式,使学生掌握解决问题的方法并应用到自己的科研课题中。同时,也引导学生从实际现象中发现和提出新问题,在培养"研究型"学生的实践过程中取得了良好效果。

关键词： 运动平台   运动学   动力学   ADAMS  

摘要： 应用机械系统动力学仿真分析软件ADAMS,对驾驶模拟器运动平台进行了运动学和动力学仿真研究.建立了6自由度Stewart型运动平台的虚拟样机模型,进行了仿真计算,得出支腿作动器行程和驱动力的变化曲线.仿真结果为运动平台的设计提供了依据.

关键词： 机械动筛跳汰机   分选效果   曲柄连杆机构   动力提升机构   急回特性  

摘要： 分析了影响动筛跳汰分选效果的主要原因,从研究动筛曲柄连杆机构急回特性入手,对机械式动筛跳汰机动力提升机构及动筛机构关键部位进行了改进和完善,设计了新型动力提升装置,为进一步研究及指导大型动筛跳汰机的设计开发奠定了基础。

关键词： 农业机械   劳动力   替代弹性   CES生产函数  

摘要： 基于CES生产函数,利用我国1978-2008年的统计数据,实证分析了粮食生产中农业机械总动力与劳动力投入之间的关系。结果表明:单位播种面积农业机械总动力与劳动力投入之间确实具有一定的替代关系,但目前农业劳动力投入量依然是影响我国粮食生产产量的重要因素,而农业机械替代劳动的作用不大。

关键词： 混合动力   工程机械   负荷特性  

摘要： 为了使工程机械取得更好的节能减排效果,通过对工程机械混合动力技术发展现状进行分析,并探讨了工程机械混合动力系统的关键技术,得出动力参数的匹配、能量的回收与控制及系统和关键元件的可靠性是影响混合动力系统性能的关键。