关键词： Acclimation   C2H2 zinc finger protein   diameter growth   mechanical stimulus   Populus   TOUCH genes  

摘要： During their development, plants are subjected to repeated and fluctuating wind loads, an environmental factor predicted to increase in importance by scenarios of global climatic change. Notwithstanding the importance of wind stress on plant growth and development, little is known about plant acclimation to the bending stresses imposed by repeated winds. The time-course of acclimation of young poplars (Populus tremula ***. alba L.) to multiple stem bendings is studied here by following diameter growth and the expression of four genes PtaZFP2, PtaTCH2, PtaTCH4, and PtaACS6, previously described to be involved in the mechanical signalling transduction pathway. Young trees were submitted either to one transient bending per day for several days or to two bendings, 1-14 days apart. A diminution of molecular responses to subsequent bending was observed as soon as a second bending was applied. The minimum rest periods between two successive loadings necessary to recover a response similar to that observed after a single bending, were 7 days and 5 days for growth and molecular responses, respectively. Taken together, our results show a desensitization period of a few days after a single transitory bending, indicating a day-scale acclimation of sensitivity to the type of wind conditions plants experience in their specific environment. This work establishes the basic kinetics of acclimation to low bending frequency and these kinetic analyses will serve as the basis of ongoing work to investigate the molecular mechanisms involved. Future research will also concern plant acclimation to higher wind frequencies

关键词： calcium   hydration temperature dependence   QMCF MD   classical molecular dynamics  

摘要： Simulations using ab initio quantum mechanical charge field molecular dynamics (QMCF MD) and classical molecular dynamics using two-body and three-body potentials were performed to investigate the hydration of the Ca2+ ion at different temperatures. Results from the simulations demonstrate significant effects of temperature on solution dynamics and the corresponding composition and structure of hydrated Ca2+. Substantial increase in ligand exchange events was observed in going from 273.15 K to 368.15 K. resulting in a redistribution of coordination numbers to lower values. The effect of temperature is also visible in a red-shift of the ion-oxygen stretching frequencies, reflecting weakened ligand binding. Even the moderate increase from ambient to body temperature leads to significant changes in the properties of Ca2+ in aqueous environment. (C) 2009 Wiley Periodicals, Inc. J Cowin Chem 31: 1195-1200, 2010

关键词： Cells  

摘要： Mechanotactic cell motility has recently been shown to be a key player in the initial aggregation of crawling cells such as leukocytes and amoebae. The effects of mechanotactic signaling in the early aggregation of amoeboid cells are here investigated using a general mathematical model based on known biological evidence. We elucidate the hydrodynamic fundamentals of the direct guiding of a cell through mechanotaxis in the case where one cell transmits a mechanotactic signal through the fluid flow by changing its shape. It is found that any mechanosensing cells placed in the stimulus field of mechanical stress are able to determine the signal transmission direction with a certain angular dispersion which does not preclude the aggregation from happening. The ubiquitous presence of noise is accounted for by the model. Finally, the mesoscopic pattern of aggregation is obtained which constitutes the bridge between, on one hand, the microscopic world where the changes in the cell shape occur and, on the other hand, the cooperative behavior of the cells at the mesoscopic scale.

关键词： MOLECULAR rotation   ROTORS -- Dynamics   STATORS   ROTATIONAL motion   SOLID state electronics   X-ray diffraction   ACTIVATION (Chemistry)   TEMPERATURE effect  

摘要： Samples of 4,4'-bis(3,3,3-tri-d(5)-phenylpropynyl)biphenyl 2, 9,10-bis(3,3,3-tri-d(5)-phenylpropynyl)anthracene 3, 1,4-bis(3,3,3-tri-d(5)-phenylpropynyl)naphthalene 4, and 4,4'-bis(3,3,3-tri-d(5)-phenylpropynyl)-1, 1'-bi naphthyl 5 were prepared via a Sonogashira coupling of 3,3,3-tri-d(5)-phenylpropyne 7 and the appropriate aryl dibromide. Single crystal X-ray diffraction structures were obtained for an o-xylene clathrate of 2 and for solvent-free crystals of 3. All four molecular rotors were characterized by CPMAS C-13 NMR experiments with varying contact times in order to determine whether the carbon signals of the central rotator group could be selectively enhanced and studied without interference or overlap of signals from the deuterated stator, which is insensitive to the {H-1}-C-13 cross-polarization method. It was shown that the C-13 signals of the natural abundance rotator group can be selectively observed with short contact times (ca. 50 mu s) without interference from other C-13 signals in the molecule. Variable-temperature CPMAS C-13 NMR studies with a crystalline o-xylene solvate of biphenylene rotor 2 suggested a 2-fold flipping process in the fast exchange regime, even at temperatures as low as 199 K (-74 degrees C). Indirect support for this was obtained by studies carried out with a disordered, solvent-free solid, obtained by fast precipitation from hexanes and dichloromethane, which displayed slower dynamics within the same temperature range with an activation energy of 8.7 kcal/mol and a pre-exponential factor of 4.9 x 10(9) s(-1). Confirmation of an exchange process in the megahertz regime for the crystalline solvate was obtained by variable-temperature quadrupolar echo H-2 NMR data acquired with samples prepared with a deuterated biphenylene rotator and a natural abundance stator. Although rotational exchange occurs in the solvated samples with a slightly lower barrier of 7.4 kcal/mol, the main difference with the precipitated solid comes from t

关键词： morphological communication   morphological computation   tensegrity   robotics  

摘要： Traditional engineering approaches strive to avoid, or actively suppress, nonlinear dynamic coupling among components. Biological systems, in contrast, are often rife with these dynamics. Could there be, in some cases, a benefit to high degrees of dynamical coupling? Here we present a distributed robotic control scheme inspired by the biological phenomenon of tensegrity-based mechanotransduction. This emergence of morphology-as-information-conduit or 'morphological communication', enabled by time-sensitive spiking neural networks, presents a new paradigm for the decentralized control of large, coupled, modular systems. These results significantly bolster, both in magnitude and in form, the idea of morphological computation in robotic control. Furthermore, they lend further credence to ideas of embodied anatomical computation in biological systems, on scales ranging from cellular structures up to the tendinous networks of the human hand.

关键词： 机械支承系统   频谱分析   故障  

摘要： 针对2个典型动力机械支承系统故障案例,结合诊断原理,综合运用频谱分析、逆向推导、考虑运行史和检修史等多种诊断方法,准确地诊断出故障的根本原因,使设备隐患得以消除。

关键词： 结构阻尼   结合部   有限元   复特征值分析   模态试验  

摘要： 机械结合部的阻尼由连接界面之间的相对滑动产生,为结构阻尼,因此提出了一种基于结构阻尼的结合部动力学模型。该模型通过刚度和结构阻尼对机械结合部进行等效,模拟结合部的动力学特性。为了对模型进行验证,设计了一组试验进行研究。首先利用DASP系统对试验件进行模态试验,得到模态参数和模态振型,然后根据模态试验数据识别机械结合部动力学参数。基于新模型的有限元复特征值分析结果与模态试验分析结果误差较小,表明结合部动力学模型在设置适宜的参数时,能够模拟机械结合部的动力学特性,验证了模型的可行性。

关键词： 两相流   渣浆泵   密封   数值模拟  

摘要： 文章通过设计一种用于固液两相流泵的流体动力与机械组合密封的密封件,建立了较为完善的计算流体动力学分析模型。FLUENT计算选用标准k-ε湍流模型,对固液两相流泵密封件内部流场三维湍流流动进行了数值模拟。利用数值模拟的结果分析了固液两相在泵密封件内部流场三维湍内的流动状况。最后进行整机实验验证,结果表明:采用组合密封的液固两相流泵的泄露量减少,耐磨寿命大大提高。

关键词： 中国北方   装备制造业   技术展览会   基础零部件   国际化   动力传动   工业市场   东北老工业基地  

摘要： 中国北方市场奠定了国民经济重要的产业体系，汇集了众多领先的大型企业和特大型企业，是多产业、高价值、实力强、重要的工业基地。尤其是国家出台了一系列区域振兴政策和产业振兴政策，如东北老工业基地的振兴、京、津、冀环渤海经济圈的发展，以及汽车工业、装备制造业、轻工行业、钢铁行业等产业振兴规划后，该地区的发展速度和可持续性将得到极大提升。

关键词： 动力机械   山东省   发动机制造商   通用汽油机   高新技术开发区   公司简介   自主研发   制造企业  

摘要： 公司简介：山东华盛中天动力机械有限公司（原山东汽油机厂），是山东华盛中天机械集团有限公司的全资子公司，江北最大的四冲程通用发动机制造商，公司占地15万平米，位于山东省临沂市高新技术开发区，是一家集自主研发、制造检测、推广营销为一体的专业化制造企业。公司专业生产四冲程通用汽油机、柴油机、水泵、发电机组、舷外机等五大系列100多个品种。