超声波/零价铁协同降解氯代芳香化合物定量结构与性质关系的研究

在相同条件下,测得超声波/零价铁(US/Fe~0)协同降解18种氯代芳香化合物的准一级速率动力学常数(logk)。以SIM- CA-P软件的PLS回归分析法,研究反应降解速率常数与物质定量结构的关系(QSPR),得到最佳QSPR模型,并经验证。模型的分析结果表明:在US/Fe~0体系中,物质的亨利常数H、最终生成热HOF、最高占据轨道能E_(homo)和疏水性常数logK_(ow),是影响氯代芳香有机物降解的主要因素。但E_(lumo)-E_(homo),极化率α,总电子能量TE和分子的双中心电子推斥能EE_2的影响也不可忽视。     

电位滴定的某些进展

离子选择电极直接电位法的基础是能斯特方程式。一般说来,电池电位是三个电位项之和 E_(电池)=E_(指示)-E_(参比) E_(接界)E_(指示)和E_(参比)分别是指示电极和参比电极电位,E接界是液接界电位。将指示电极电位的能斯特方程代入则可得     

仪表工问答

60.测温仪表的允许基本误差如何计算? 答测温仪表的允许基本误差常用公式有配热电偶仪表和配热电阻仪表两种。这两种公式的符号和单位不同,但符号意义相同。 (1)配热电偶测温仪表的基本误差以毫伏(mv)表示,不应超过仪表的允许基本误差δE_允=±K(E_终-E_始)% 式中δE_允——仪表的允许基本误差,mv; E_终、E_始——与标尺终点、始点标度线上示值相对应的电压值,mv; K——仪表精确度等级。例1 设有一台精确度等级K为0.5、分度号为EU2、测量范围为0～1100℃(相应热电势为0～45.10 mv)的电子电位差计,其允许基本误差: δE_允=±K(E_终-E_始)%=±0.5×(45.10-0)%=±0.23mv 例2 设有一台精确度等级K为1.0、分度号为LB3、测量范围为0～1600℃(相应热电势0～16.688mv)的XCT-101动圈式指示调节仪,其允许基本误差δE_允=±K(E_终-E_始)%=±1.0×(16.688-0)%=±0.167 mv     

基于GRA-IBAS-BP网络的短期配电网负荷预测

针对城市配电网负荷非线性、易受多种因素影响的特点,提出一种基于灰色关联分析(GRA,Grey Relational Analysis)和改进天牛须搜索算法优化的BP网络(IBAS-BP,Improved Beetle Antennae Search-Back Propagation)的短期负荷预测模型.本文首先通过灰色关联分析选取了与待测日特征高度相关的相似日样本,然后改进了标准天牛须搜索算法参数的更新策略,并将其运用于BP网络参数的寻优过程.最后,对某市2018年夏季网供负荷数据进行实验表明,相对于传统BP神经网络,该组合方法能有效提高负荷预测精度.     

基于决策粗糙集的多属性灰色关联聚类方法

针对多属性灰色关联聚类的阈值确定问题,利用决策粗糙集方法,通过引入两个阈值参数定义决策对象间的可能关系和集合;将其代替基于灰色关联聚类的非此即彼关系,构建基于决策粗糙集的多属性灰色关联聚类方法,并采用贝叶斯推理探讨多属性灰色关联聚类的阈值计算机理;最后以案例验证所提方法的有效性和合理性.结果表明,所提出的方法是经典灰色关联聚类的拓展和泛化,能够客观、科学地确定多属性灰色关联聚类阈值.     

基于灰色关联支持向量机的粮食产量预测

研究粮食准确预测问题,由于粮食产量受到多种高维非线性、随机性和有限样本等因素的影响,单一模型不能全面描述其变化趋势,预测精度较低。为了提高粮食产量预测精度,提出一种将灰色关联支持向量机的粮食产量预测模型。首先采用灰色关联分析确定粮食产量变化主要影响因子,然后通过支持向量机学习建立粮食产量与因子之间的非线性映射关系,最后为避免人为选择参数的盲目性,采用遗传算法确定支持向量机参数并对将来粮食产量进行预测。利用1978-2011年我国粮食产量进行仿真,并将预测结果与单一机模型进行对比。结果表明,灰色关联支持向量机提高了粮食产量的预测精度,可以较好地应用于粮食产量预测中。     

常压下Ag-TiO2纳米管制备及光催化反应动力学研究

首次在常压下,以试剂TiO2、NaOH和AgNO3为原料,碱熔温度为700℃,水热法制备了Ag-TiO2复合纳米管光催化剂。TEM和XRD用于纳米管组织与形貌表征。研究了纳米管制备以及用于模拟污染物甲基橙(MO)光催化降解的实验条件。结果表明,原料是否碱熔,水热温度高低和时间长短,对光催化剂性能影响明显;当MO溶液初始浓度Co为4mg/L、光催化降解反应持续4h,光催化降解率达到99%。降解反应的速率常数k与Co呈0.9966级的动力学关系。     

方酸菁染料结构与电子性质的分子轨道法研究

采用改进的半经验分子轨道法(PPP—SCF—MO)计算了8种吲哚方酸菁染料分子的电子结构和电子光谱,计算得到的最大吸收峰波长与实验值较好的一致,计算得到的荧光跃迁能ΔE_(fl)与荧光峰波数υ_(fl)存在如下关系:υ_(fl)=10.664ΔE_(fl)-3.1299(k·cm~(-1)),r=0.9721。计算得到的前线轨道能量E_(HOMO)和电子跃迁能E_(abs)与氧化电位E_(1/2,OX)存在如下关系:E_(1/2,OX)=0.520(-E_(HOMO))+4.291E_(abs)-11.100,r=0.909。并讨论了电子结构与光谱性能的关系。     

面板数据的灰色矩阵关联模型及在 旱灾脆弱性风险中的应用

针对现有面板数据灰色关联模型中存在样本(指标)的排列顺序影响关联序问题,构建面板数据下新的灰色关联模型.考虑到多指标面板数据的动态发展特征,在其矩阵表征中增加各指标对应的变化增量和变化速度,并用均方根距离(RMSD)对指标矩阵的相似性进行测度,提出灰色矩阵关联模型,讨论其规范性和保序性.通过算例验证该模型的关联度不受多指标样本排列顺序的影响,并将其应用于旱灾脆弱性风险因子的识别中,理清了区域农业旱灾脆弱性及其影响因素的关联关系,为区域农业旱灾风险管理提供了理论支持.     

乙二胺缩3,5-二氯水杨醛的合成、表征及量子化学计算

本文用乙二胺与水杨醛衍生物在非水相中合成了一种新的双希夫碱配体,并通过元素分析、核磁、质谱和红外等方法进行了表征。采用Gaussian 03在DFT/B3LYP水平下进行理论研究。计算出分子总能量TE、分子最高占据轨道能E_(HOMO)、分子最低空轨道能E_(LUMO)、标准焓H~θ、标准自由能G~θ、恒容热熔Cv~θ、标准熵S~θ、零点能E_0、分子偶极矩μ、前线轨道能量差△E等热力学参数。优化了几何构型模拟出分子的部分重要键长((?))、键角(°)、二面角(°)等结构参数。经过Mulliken布居分析得到了原子的净电荷分布。计算出原子轨道对前线分子轨道的贡献(%)。通过对热力学参数、结构参数、原子净电荷布局和原子轨道对前线分子轨道贡献的总体探讨,表明目标分子具有较好的空间结构和较强的配位能力,是一个良好的配体;并且,它的生物活性很强,可以进一步进行抑菌性能和抗氧化性能等研究并且应用到各个领域。     

磺酰脲类除草剂定量结构-生物降解性关系(QSBR)研究

选取了分子量、熔点、蒸气压、溶解度、LogKOW pKa,MCI,ELUMO和几个代表性原子所带的电荷等具有代表性的参数,结合化合物好氧生物降解作用的半衰期(HL),通过多元线性回归方法对磺酰脲类除草剂的生物降解性进行了定量结构一生物降解性(QSBR)研究,建立了相应的QSBR模型,R^2=0．941。并利用该模型对氯磺隆进行预测,结果表明,该模型对氯磺隆的好氧生物降解性具有良好的预测能力。     

二烷氧基喹唑啉类PDGFR抑制剂的定量构效关系及分子设计

用量子化学密度泛函、分子力学及统计方法,对二烷氧基喹唑啉衍生物进行定量构效关系(QSAR)研究.由计算所得的化合物分子的几何结构、电子结构参数和分子性质为广义描述符(变量),通过逐步回归分析,筛选出主要因素,建立QSAR方程.结果表明化合物的偶极距(μ),A环C1和C3原子的净电荷(QC1和QC3)以及取代基R7的立体参数(MR7)是影响化合物抑制活性的主要因素.方程的拟合相关系数(r2)和交叉验证系数(q2)分别为0.874和0.8093,表明方程具有良好的预测能力,可用于预测未知化合物的活性.基于此QSAR方程,设计了4个具有较高抑制活性的新的化合物并有待实验的验证.     

Estimation of aircraft component production cost using knowledge based engineering techniques

A comprehensive method is presented to estimate aircraft component production costs using Knowledge Based Engineering (KBE) techniques. A suite of parametrical cost estimation blocks are treated as Cost Primitives (CPs), which contain attributes such as cost types, cost driving parameters, and cost estimation relationships. A CP is associated with a parameterized geometry and a set of specific design parameters including part/assembly types, materials and production methods. Production cost is estimated by aggregating the cost of different CPs within a tree structure integrating both product breakdown and cost breakdown structures. The cost analysis tool is integrated into a KBE application by building Capability Modules (CMs), which provide manufacturable geometric representations for cost estimation and can be used to summarize output reports for further optimization. Case studies concerning stiffened panels are carried out, verifying the accuracy of the cost estimation method and illustrating the applicability of this method together with the integrated KBE application for various aircraft components. The main contribution of this research is automating the cost integration in the design process to improve the fidelity, repeatability and traceability of cost analysis.     

Carboxypeptidases in disease: Insights from peptidomic studies

Carboxypeptidases (CPs) perform many diverse physiological functions by removing C-terminal amino acids from proteins and peptides. Some CPs function in the degradation of proteins in the digestive tract while other enzymes play biosynthetic roles in the formation of neuropeptides and peptide hormones. Another set of CPs modify tubulin by removing amino acids from the C-terminus and from polyglutamyl side chains, thereby altering the properties of microtubules. This review focuses on three CPs: carboxypeptidase E, carboxypeptidase A6, and cytosolic carboxypeptidase 1. Naturally occurring mutations in all three of these enzymes are associated with disease phenotypes, ranging from obesity to epilepsy to neurodegeneration. Peptidomics is a useful tool to investigate the relationship between these mutations and alterations in peptide levels. This technique has also been used to define the function and characteristics of CPs. Results from peptidomics studies have helped to elucidate the function of CPs and clarify the biological underpinnings of pathologies by identifying peptides altered in disease states. This review describes the use of peptidomic techniques to gain insights into the normal function of CPs and the molecular defects caused by mutations in the enzymes.     

Capillary pumps with constant flow rate

This paper unambiguously derives, ab initio starting from the Navier–Stokes and Laplace equations, the geometric parameters defining capillary pumps (CPs) with rectangular cross section with constant volumetric flow rate and steady velocity profile. The parametric formulation of the channel shape is derived using Taylor series approximations of the capillary pressure and the hydrodynamic flow resistance with negligible error. First, the design parameters are derived for a CP consisting of a single channel and illustrated with an example. Thereafter, the design parameters for multichannel and for micropillar array CPs are derived. Finally, the design of CPs for multistep constant flow rates derived and those for arbitrarily varying flow rates are discussed.     

3D-QSAR and molecular docking studies of selective agonists for the thyroid hormone receptor beta

Three-dimensional quantitative structure-activity relationship (3D-QSAR) models were developed using comparative molecular field analysis (CoMFA) and comparative molecular similarity analysis (CoMSIA) on a series of agonists of thyroid hormone receptor beta (TRbeta), which may lead to safe therapies for non-thyroid disorders while avoiding the cardiac side effects. The reasonable q(2) (cross-validated) values 0.600 and 0.616 and non-cross-validated r(2) values of 0.974 and 0.974 were obtained for CoMFA and CoMSIA models for the training set compounds, respectively. The predictive ability of two models was validated using a test set of 12 molecules which gave predictive correlation coefficients (r(pred)(2)) of 0.688 and 0.674, respectively. The Lamarckian Genetic Algorithm (LGA) of AutoDock 4.0 was employed to explore the binding mode of the compound at the active site of TRbeta. The results not only lead to a better understanding of interactions between these agonists and the thyroid hormone receptor beta but also can provide us some useful information about the influence of structures on the activity which will be very useful for designing some new agonist with desired activity.     

Comparison of homology models and X-ray structures of the nuclear receptor CAR: assessing the structural basis of constitutive activity

The constitutive androstane receptor (CAR) possesses an intrinsic basal activity whose structural basis has been analysed during the last decade. Recently, we published a homology model of the CAR ligand binding domain (LBD) based on the X-ray structures of the closely related pregnane X (PXR) and vitamin D (VDR) receptor. A detailed analysis of the homology model and molecular dynamics (MD) simulations afforded us to propose a potential mechanism underlying the constitutive activity of CAR. Almost simultaneously, X-ray structures of human and mouse CAR LBD were released. In the present study, a detailed analysis and comparison of homology model and X-ray structures is carried out in order to evaluate the quality and reliability of our homology modelling procedure. The hypothesis of the constitutive activity which we proposed on the basis of our modelling results was tested for consistency with the crystal structures. In addition, the features stated to be essential for the basal activity based on the X-ray data were investigated by means of molecular dynamics simulations. Our results show that the homology modelling procedure was able to predict the CAR LBD structure with high accuracy. Structural features that have been revealed as critical for constitutive activity in the model are also observed in the X-ray structures. Furthermore, the MD simulations of the CAR X-ray structures and a detailed analysis of other NRs clarify the role of distinct structural features that have been assigned an important role for the constitutive activity.     

分子顶点相关指数用于卤代苯lgKow的预估

为寻找卤代苯类化合物分子结构与正辛醇/水分配系数(lgK_(ow))的关系,通过定义分子顶点原子特征值,构建了1种分子顶点相关指数(molecular vertexes correlative index,MVCI),并用于卤代苯类化合物的结构表征。再分别利用多元线性回归(MLR)和偏最小二乘回归(PLSR)建模,同时采用内、外双重验证的办法深入分析和检验所得模型的稳定性和预测能力,模型拟合的复相关系数(R)分别为0.9945和0.9940;留一法(LOO)交互校验(CV)的复相关系数(R_(CV))分别为0.9913和0.9925。结果表明该相关指数具有较强的分子结构表达能力,所建模型具有良好的稳定性和预测能力,可用于卤代苯类化合物正辛醇/水分配系数(lgK_(ow))的预测。