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关键词： Blue copper sites   Pseudoazurin   Type 1 copper   275 GHz EPR   Absorption spectrum   Plastocyanin  

摘要： We report on a high-frequency electron-paramagnetic-resonance study of the type 1 copper site of pseudoazurin. The spectra fully resolve the contribution of a nearly axial spectrum besides the rhombic spectrum, which unequivocally proves the existence of two conformations of the copper site. Pseudoazurins have been considered from Achromobacter cycloclastes including eight mutants and from Alcaligenes faecalis. The two conformations are virtually the same for all pseudoazurins, but the rhombic/axial population varies largely, between 91/9 and 33/67. These observations are discussed in relation to optical absorption spectra and X-ray diffraction structures. A similar observation for fern plastocyanin from Dryopteris crassirhizoma suggests that dual conformations of type 1 copper sites are more common. (C) 2014 Elsevier Inc. All rights reserved.

关键词： Little Auk   Alle alle   brood enlargement   incubation   single-egg layer  

摘要： Initial reproductive investments in birds are energy-demanding. Amount of energy allocated to egg production and incubation may have an important role in determining parental fitness and evolution of clutch size. Here, we investigated whether the Little Auk (Alle alle (L., 1758)), a small alcid with one-egg clutch but two brood patches (probably remnant of the original two-egg clutch), is capable of incubating two eggs and rearing two chicks. We performed an experiment with removing the egg from 20 nests and transferring it to 20 experimental nests (EN). In 25% of EN, both eggs failed to hatch;in 75% of EN, only one egg hatched successfully. Hatching success in EN was 2.5 times lower than in control nests (CN). In EN, chicks hatched only from eggs warmed during >90% of inspections. Owing to the prolonged incubation, the chicks in EN hatched 2 days later than in CN. However, due to the shorter period spent in the nest in EN, fledging dates in both types of nests were similar. The similar body mass and survival of chicks from EN and CN suggest that these traits were influenced mainly by the rearing conditions. Our study emphasize the importance of the incubation phase as a constraint on clutch size.

关键词： maximum power point tracking   photovoltaic system   power benefit prediction   semiconductor theory   sun-tracking type system   system installation  

摘要： Photovoltaic (PV) systems incorporated with sun-tracking technology have been proposed and verified to effectively increase the power harvest. However, the actual power generated from a PV module has not been investigated and compared with that analyzed from theoretical models of the PV material. This study proposes a novel method for estimating the power benefit harvested by a two-axis sun-tracking type (STT) PV system. The method is based on semiconductor theory and the dynamic characteristics, including maximum power point tracking of PV modules that can be integrated with the database of annual solar incidences to predict the power harvested by any STT PV system. The increment of annual energy provided by an STT PV system installed at any arbitrary latitude, compared with that by a fixed-type system, can be accurately estimated using the proposed method. To verify the feasibility and precision performance of this method, a fixed-type and a two-axis STT PV system were installed at 24.92 degrees north latitude in northern Taiwan and tested through long-term experiments. The experimental results show that the energy increments estimated by the theoretical model and actual measurement are 19.39% and 16.74%, respectively. The results demonstrate that the proposed method is capable of predicting the power benefit harvested by an STT PV system with high accuracy. Using our method, a PV system installer can evaluate beforehand the economic benefits of different types of PV systems while taking different construction locations into consideration, thereby obtaining a better installation strategy for PV systems. Copyright (C) 2012 John Wiley & Sons, Ltd.

关键词： CLUTCHES (Machinery)   HYDRAULIC control   TAPS & dies   HYDRAULIC engineering  

摘要： The article offers information on clutches that were used 25 years ago as of August 2014 that engage and disengage power transmission in hydraulic systems. Topics discussed include utility of clutches for power system loading and unloading, the views of mechanical engineer Joseph A. Montaine on the efficiency of clutches, and the role of clutches in reducing system cost by tapping into a pressurized hydraulic system.

关键词： CXCR4 receptor   endothelial cells   SDF-1 alpha  

摘要： Objective-Although stromal cell-derived factor (SDF)-1 alpha is well known to modulate the mobilization of hematopoietic stem cells and endothelial progenitor cells, its effects on some pre-existing vascular functions remain unknown. We have investigated here the role of SDF-1 alpha signaling in endothelial barrier function. Approach and Results-Treatment with SDF-1 alpha elevated transendothelial electrical resistance and inhibited the dextran hyperpermeability elicited by thrombin in bovine aortic endothelial cells, both indicating an increase in endothelial barrier function. SDF-1 alpha binds to 2 receptors, C-X-C chemokine receptor types 4 and 7 (CXCR4 and CXCR7). Pretreatment with a CXCR4 antagonist or CXCR4 gene depletion by small interfering RNA (siRNA) eliminated SDF-1 alpha- induced endothelial barrier enhancement. In contrast, CXCR7 antagonist or CXCR7 gene depletion by siRNA did not influence SDF-1 alpha-induced barrier enhancement. Pretreatment with a Gi-protein inhibitor, a phosphoinositide 3-kinase (PI3K) inhibitor, or PI3K p110 gamma subunit gene depletion by siRNA also inhibited SDF-1 alpha-induced barrier enhancement significantly. Western blot analysis revealed that SDF-1 alpha phosphorylated Akt(Ser473) in endothelial cells, suggesting PI3K activation. Immunostaining showed that treatment with SDF-1 alpha formed a cortical actin rim, which was accompanied by Rac1 activation. In vivo, SDF-1 alpha inhibited croton oil-induced vascular leakage indexed by dye extravasation, which is attenuated by a pretreatment with a CXCR4 antagonist. Conclusions-We have identified SDF-1 alpha as a novel suppressor of endothelial permeability. Specifically, SDF-1 alpha stimulates the CXCR4/PI3K/Rac1 signaling pathway and the subsequent cytoskeletal rearrangement.

标准号: QB/T 4684-2014

摘要： 本标准规定了波轮式全自动洗衣机配用的减速离合器的术语和定义、产品分类及基本参数、要求、试验方法、标志、包装、运输及贮存。本标准适用于波轮式全自动洗衣机配用的减速离合器。

关键词： 拖拉机   离合器   发动机   故障排除  

摘要： 农机在现代农业生产中的普及应用,大大提高了生产力和工作效率。在农机长期使用中,常有一定的损耗,产生故障,在排除故障时,可以拆机进行,但有些故障完全可以避免拆机麻烦,通过观察听音等方法,找到故障的原因进而排除。本文主要针对拖拉机的几种故障的原因进行分析,以供农机维修者参考。

关键词： 机械产品   设计缺陷   辨识   约束关系网   最优修正  

摘要： 提出了机械产品装配设计参数与其约束判定函数的关联方法,研究了装配约束关系网中节点的数据结构,给出了装配约束关系网的构建方法,描述了装配约束关系网的禁忌表访问方式,在此基础上提出了基于装配约束关系网的装配设计缺陷的辨识模型与方法。从装配约束关系网中的设计缺陷节点出发,以约束路径的权值之和为目标函数,采用蚁群算法对装配设计缺陷的修正路径进行了优化。以膜片离合器的装配设计为实例进行了装配设计缺陷的辨识与修正,结果表明,提出的装配设计缺陷辨识模型与修正方法不仅能够快速辨识出装配设计缺陷,而且能够有效地提高装配设计缺陷的修正质量和效率。

关键词： 起步品质   模糊控制  

摘要： AMT车辆的起步品质直接影响车辆的驾驶舒适性。对离合器的接合过程进行合理控制,能有效改善车辆的起步效果。在MATLAB上,以油门开度、油门开度变化率、离合器主从动盘转速差比、起步阻力作为模糊控制器的输入量,制定了接合过程中离合器接合速度控制规则,设计了离合器模糊控制算法,建立了离合器接合模型并进行仿真。仿真结果表明,以四参数作为控制系统的输入量,能真实的反映驾驶员起步意图和道路条件的变化,有效的控制离合器的接合速度,改善离合器的接合质量。