关键词： PESTICIDES   MOLECULAR dynamics  

摘要： Nanoscale particles have the potential to modulate the transport, lifetimes, and ultimate uptake of pesticides that may otherwise be bound to agricultural soils. Engineered nanoparticles provide a unique platform for studying these interactions. In this study, we utilized discrete molecular dynamics (DMD) as a screening tool for examining nanoparticle-pesticide adsorptive interactions. As a proof-of-concept, we selected a library of 15 pesticides common in the United States and 4 nanomaterials with likely natural or incidental sources, and simulated all possible nanoparticle pesticide pairs. The resulting adsorption coefficients derived from DMD simulations ranged over several orders of magnitude, and in many cases were significantly stronger than pesticide adsorption on clay surfaces, highlighting the significance of specific nanoscale phases as a preferential media with which pesticides may associate. Binding was found to be significantly enhanced by the capacity to form hydrogen bonds with slightly hydroxylated fullerols, highlighting the importance of considering the precise nature of weathered nanomaterials as opposed to pristine precursors. Results were compared to experimental adsorption studies using selected pesticides, with a Pearson correlation coefficient of 0.97.

关键词： 农业机械化   产业结构演进   农村劳动力转移   VAR  

摘要： 本文在相关理论分析基础上,基于河南省1978-2014年的相关数据,构建了农业机械化、农村劳动力转移和产业结构多个指标,运用VAR模型将其纳入一个系统框架分析三者之间的动态影响关系。研究发现:(1)农业机械化、农村劳动力转移和产业结构演进之间存在长期动态均衡关系;(2)农业机械化和农村劳动力转移、产业结构演进和农村劳动力转移之间互不为Granger原因,但是存在产业结构演进到农业机械化、农村劳动力转移到产业结构演进的单向Granger原因。(3)脉冲函数分析表明,农业机械化、农村劳动力转移和产业结构演进之间的长期动态冲击响应为正,即农业机械化、农村劳动力转移和产业结构演进之间存在长期动态促进作用。(4)方差分解表明,农业机械化和产业结构演进对农村劳动力转移的贡献度分别达到16.15%和10.63%,产业结构演进变动来自农业机械化和农村劳动力转移解释力度分别为58.62%和13.20%,产业结构演进和农村劳动力转移对农业机械化的贡献度分别为12.28%和25.78%。

关键词： 颅脑损伤   机械通气   亚低温   神经功能   血流动力学  

摘要： 目的探讨亚低温(MHT)联合机械通气治疗对急性重度颅脑损伤(TBI)患者神经功能及血流动力学的影响。方法选取2015年8月至2016年11月收治的急性重度TBI患者90例,入院后均采取标准大骨瓣减压术进行治疗,根据术后治疗方式分为对照组和实验组,每组45例,对照组于术后6 h内进行早期气管插管机械通气,实验组在对照组的基础上联合MHT治疗。于治疗前后检测两组患者神经功能因子及血流动力学指标水平变化,采用Barthel指数积分、美国国立卫生研究院卒中量表(NIHSS)、精神状态评价量表(MMSE)评价两组治疗后神经功能恢复情况。结果治疗后两组神经胶质纤维酸性蛋白(GFAP)、神经元特异性烯醇化酶(NSE)、S100B蛋白(S-100B)、髓鞘碱性蛋白(MBP)均较治疗前下降(P<0.05,P<0.01),且实验组低于对照组(P<0.05,P<0.01)。治疗后两组平均血流速度(Vmean)、最大血流速度(V_(max))、最小血流速度(V_(min))、平均血流量(Qmean)均较治疗前上升,脑血管阻力(R)较治疗前下降(P<0.05,P<0.01),两组治疗后差异有统计学意义(P<0.05,P<0.01)。治疗后两组Barthel指数、MMSE评分显著高于治疗前,NIHSS评分显著低于治疗前(P均<0.01),实验组NIHSS评分显著高于对照组(P<0.05),其他评分组间比较无统计学差异(P>0.05)。结论 MHT联合机械通气治疗急性重度TBI疗效确切,可明显改善脑部血供状况,促进机体神经功能的恢复,对患者预后发挥重要作用。

关键词： Oxygen atom transfer   DFT   Kinetics  

摘要： The oxorhenium(V) dimer {MeReO(pdt)}(2) (where pdt = 1,2-propanedithiolate) catalyze the oxygen atom transfer (OAT) reaction from the pyridine oxide to triphenylarsine (Ph3As). The rate law is given by nu = k [Re-dimer][PyNO] and zero order dependence on Ph3As. The value of k at 25 degrees C in CHCl3 is 139 +/- 3 L mo(-1) s(-1). The activation parameters are Delta H-double dagger = 12.2 +/- 1.0 kcal mol(-1) and Delta S-double dagger = -7.9 +/- 3.24 cal K-1 mol(-1). According to the proposed mechanism, the rate determining step is the oxidation of Rev0 to (ReO2)-O-VII and the pyridine release. The triphenylarsine enters the catalytic cycle after the rate determining step. The reaction constant rho = -1.4 obtained from Hammett correlation with sigma for different substituted pyridine N -oxide. The computational study indicates that the oxidation of Re-V to Re-VII and release of the pyridine step is insensitive to the nature of the substituent on the pyridine with the average estimated activation barrier approximate to 11.5 kcal/mol from six different substituted pyridine oxide. It is proposed that electron donor substituent enrich the equilibrium of the first step of the proposed mechanism which is the coordination of the pyridine oxide with one rhenium atom to form I-1 (Scheme 2). The electron donor substituent on the pyridine increase the concentration of I-1 which will increase the rate of the reaction as the nu = k2[I-1]. (C) 2017 Elsevier B.V. All rights reserved.

关键词： 党建品牌   党员服务   实践服务  

摘要： 从搭建党员服务平台,丰富服务载体内容,发挥示范和辐射带动作用,对学生党员服务驿站建设进行实践探究。并通过党员服务项目支持党建工作品牌创建,激发党支部活力,促进基层党建品牌内涵式发展。

关键词： 工程机械   油电混合动力   节能   减排  

摘要： 随着全球化石能源的日益枯竭和环境污染的日益严重,如何改善工程机械的排放质量和实现工程机械的节能已经引起工程机械生产厂家和用户的广泛关注。油电混合动力技术近年来已经成为工程机械节能降耗的一个重要研究方向,受到工程机械领域的高度重视。根据研究工作积累和文献资料调研,总结了国内外主要研究机构对于油电混合动力工程机械的研究现状,分析了油电混合动力工程机械研制需要解决的关键技术,对油电混合动力工程机械的发展趋势进行了预测。

关键词： molecular dynamics   crack propagation   dislocations  

摘要： This study investigated the mechanical properties and crack propagation behavior of polycrystalline copper using a molecular dynamics simulation. The effects of temperature, grain size, and crack length were evaluated in terms of atomic trajectories, slip vectors, common neighbor analysis, the material's stress-strain diagram and Young's modulus. The simulation results show that the grain boundary of the material is more easily damaged at high temperatures and that grain boundaries will combine at the crack tip. From the stress-strain diagram, it was observed that the maximum stress increased as the temperature decreased. In contrast, the maximum stress was reduced by increasing the temperature. With regard to the effect of the grain size, when the grain size was too small, the structure of the sample deformed due to the effect of atomic interactions, which caused the grain boundary structure to be disordered in general. However, when the grain size was larger, dislocations appeared and began to move from the tip of the crack, which led to a new dislocation phenomenon. With regards to the effect of the crack length, the tip of the crack did not affect the sample's material when the crack length was less than 5 nm. However, when the crack length was above 7.5 nm, the grain boundary was damaged, and twinning structures and dislocations appeared on both sides of the crack tip. This is because the tip of the crack was blunt at first before sharpening due to the dislocation effect.

关键词： fission   fusion   bioenergetics   network   stiffness  

摘要： Mitochondria supply cells with energy in the form of ATP, guide apoptosis, and contribute to calcium buffering and reactive oxygen species production. To support these diverse functions, mitochondria form an extensive network with smaller clusters that are able to move along microtubules aided by motor proteins. Mitochondria are also associated with the actin network, which is involved in cellular responses to various mechanical factors. In this review, we discuss mitochondrial structure and function in relation to the cytoskeleton and various mechanical factors influencing cell functions. We first summarize the morphological features of mitochondria with an emphasis on fission and fusion as well as how network properties govern function. We then review the relationship between the mitochondria and the cytoskeletal structures, including mechanical interactions. We also discuss how stretch and its dynamic pattern affect mitochondrial structure and function. Finally, we present preliminary data on how extracellular matrix stiffness influences mitochondrial morphology and ATP generation. We conclude by discussing the more general role that mitochondria may play in mechanobiology and how the mechanosensitivity of mitochondria may contribute to the development of several diseases and aging.

ISBN: (纸本)9787568246637