关键词： amyloid   inhibitor   peptide fibrils   peptide interactions   NMR structure  

摘要： The misfolding and aggregation of proteins to form amyloid fibrils is a characteristic feature of several common age-related diseases. Agents that directly inhibit formation of amyloid fibrils represent one approach to combating these diseases. We have investigated the potential of a cyclic peptide to inhibit fibril formation by fibrillogenic peptides from human apolipoprotein C-II (apoC-II). Cyc[60-70] was formed by disulfide cross-linking of cysteine residues added to the termini of the fibrillogenic peptide comprising apoC-II residues 60-70. This cyclic peptide did not self-associate into fibrils. However, substoichiometric concentrations of cyc[60-70] significantly delayed fibril formation by the fibrillogenic, linear peptides apoC-II[60-70] and apoC-II[56-76]. Reduction of the disulfide bond or scrambling the amino acid sequence within cyc[60-70] significantly impaired its inhibitory activity. The solution structure of cyc[60-70] was solved using NMR spectroscopy, revealing a well-defined structure comprising a hydrophilic face and a more hydrophobic face containing the Met60, Tyr63,Ile66 and Phe67 side chains. Molecular dynamics (MD) studies identified a flexible central region within cyc[60-70], while MD simulations of "scrambled" cyc[60-70] indicated an increased formation of intramolecular hydrogen bonds and a reduction in the overall flexibility of the peptide. Our structural studies suggest that the inhibitory activity of cyc [60-70] is mediated by an elongated structure with inherent flexibility and distinct hydrophobic and hydrophilic faces, enabling cyc[60-70] to interact transiently with fibrillogenic peptides and inhibit fibril assembly. These results suggest that cyclic peptides based on amyloidogenic core peptides could be useful as specific inhibitors of amyloid fibril formation. (C) 2012 Elsevier Ltd. All rights reserved.

关键词： PLC控制   变频器   PID运算   压缩机节能  

摘要： 利用PLC和变频器对传统设计的空调系统进行改造,使用变频交流无级调速和PLC的PID功能来自动调节控制压缩机电机,可实现冷库稳恒温度,改善压缩机组工作品质,节约能源,也为常见机械设备动力节能的改造,提供了一个普遍的方法。

关键词： 柴油   生物能源   市场调查  

摘要： 介绍生物柴油生产技术进展,我国的开发潜力及市场前景。

关键词： 非光滑系统   振动   冲击   拍频激励  

摘要： 考虑系统的振动和钻进运动,建立了能够将高频低幅激励转化为低频高幅响应的冲击钻进机械系统的力学模型。分析了系统部件在碰撞以后出现"同步"和"非同步"运动的条件。采用了具有低频调制激励与振动系统固有频率(所期望的低频)吻合以及只用调制波正值部分激励质量块M2这两种特征的拍频运动激励,结果表明,该激励能够产生有效的冲击力,即锤击效应。给出了两种能够获得稳定钻进运动的途径。

关键词： 混合动力工程机械   驱动电机   永磁同步电机系统  

摘要： 分析了混合动力工程机械所采用的电机系统控制关键技术及研究现状,以最具有应用前景的永磁同步电机系统为例进行了电机驱动系统的控制系统设计,并进行了试验研究。

关键词： 机械通气   吸痰负压   吸痰效果   血流动力学  

摘要： 目的探讨不同吸痰负压对机械通气患者吸痰效果和血流动力学的影响,以寻找适合机械通气患者的安全有效的吸痰负压。方法选取某三级甲等医院综合性ICU行机械通气治疗的成年患者20例,均由培训合格后的注册护士采用3种负压(-75 mmHg,-150 mmHg,-300 mmHg)(1 mmHg=0.133 kPa)行密闭式吸痰,由2名注册护士共同评估吸痰效果(痰鸣音改善状况及吸痰间隔时间);并于吸痰前2 min,吸痰后5 min、10 min,测定并记录动态的血流动力学变化。结果吸痰负压为-150mmHg时吸痰间隔时间(76.0±33.3)min明显长于吸痰负压为-75 mmHg及-300 mmHg时(34.5±17.3)min、(55.5±16.7)min,同时吸痰后痰鸣音改善状况明显优于吸痰负压为-75 mmHg时(P<0.05)。不同负压组不同时间点的舒张压与平均动脉压差异具有统计学意义(P<0.05)。并且在吸痰负压为-300 mmHg时,吸痰后5 min舒张压与平均动脉压相对于吸痰前明显增高(P<0.05)。结论-150mmHg是安全、有效的适合机械通气患者的吸痰负压。

关键词： carbon nanotube   molecular dynamics   X-junction   stiffness  

摘要： The mechanical behavior of seven different carbon nanotube(CNT)X-junctions with a varying number of bonds was investigated through molecular dynamics *** X-junctions are composed of two(6,0)single-walled carbon nanotubes(SWNTs)created via vibration-assisted heat *** junctions,containing anywhere between one and seven bonds,are subject to uniaxial tensile,shear and torsional strain,and then the stiffness values are determined for each *** subjected to tensile and shear strain,both the arrangement and orientation of bonds are found to affect the stiffness of junctions more substantially than the number of bonds,bond length or bond ***,anisotropic shear behavior is observed in the X-junctions,which can be attributed to the junction’s bond ***,the stiffness of X-junctions tested under an applied torque(torsion)differs from the stiffness under tensile and shear strain,however,in that it is more substantially affected by the number of bonds present in the junction than by any other property.

关键词： 动力性能   农业机械   合理利用   作业机械   农业生产   作业项目   机组   拖拉机  

摘要： 根据农业生产的需要，将拖拉机与作业机械编成各种机组，以完成不同的农业作业项目。农机化作业一般是以机组的形式进行的，因此，研究农业机械的动力性能首先要研究机组的动力性能。

关键词： 工程机械   发动机   公司  

摘要： 由莱恩（中国）动力有限公司生产的LN2110G型发动机具有以下特点：

关键词： conclusive mathematical modeling   core prediction   insulin signaling   mechanistic explanation   rat adipocytes  

摘要： Insulin signaling through insulin receptor (IR) and insulin receptor substrate-1 (IRS1) is important for insulin control of target cells. We have previously demonstrated a rapid and simultaneous overshoot behavior in the phosphorylation dynamics of IR and IRS1 in human adipocytes. Herein, we demonstrate that in murine adipocytes a similar overshoot behavior is not simultaneous for IR and IRS1. The peak of IRS1 phosphorylation, which is a direct consequence of the phosphorylation and the activation of IR, occurs earlier than the peak of IR phosphorylation. We used a conclusive modeling framework to unravel the mechanisms behind this counter-intuitive order of phosphorylation. Through a number of rejections, we demonstrate that two fundamentally different mechanisms may create the reversed order of peaks: (i) two pools of phosphorylated IR, where a large pool of internalized IR peaks late, but phosphorylation of IRS1 is governed by a small plasma membrane-localized pool of IR with an early peak, or (ii) inhibition of the IR-catalyzed phosphorylation of IRS1 by negative feedback. Although (i) may explain the reversed order, this two-pool hypothesis alone requires extensive internalization of IR, which is not supported by experimental data. However, with the additional assumption of limiting concentrations of IRS1, (i) can explain all data. Also, (ii) can explain all available data. Our findings illustrate how modeling can potentiate reasoning, to help draw nontrivial conclusions regarding competing mechanisms in signaling networks. Our work also reveals new differences between human and murine insulin signaling.