铝合金表面电偶腐蚀与电子功函数的关系

铝合金中经常会引入一些第二相来改善其性能,第二相由于和铝基体的电位差不同,将会对铝合金的局部腐蚀产生重大的影响.为了揭示铝合金腐蚀的物理本质,本文利用基于密度泛函理论第一性原理的计算方法,详细计算了铝合金中一些主要第二相(Al_2Cu、Al_3Ti和Al_7Cu_2Fe)的多种晶面的电子功函数,分析了电子从各个晶面逸出的难易,求得了第二相与Al基体的本征电势差,我们发现不同的晶面暴露在合金最外层,会显著地影响本征电势差;即便是同一晶面,暴露在最外层的原子种类和构型不同,对腐蚀的影响也不一样.从电子的层面解释了电偶腐蚀发生的原因.     

急性等容性血液稀释在脊柱手术中对血小板功能的影响

目的探讨急性等容性血液稀释（ANH）在脊柱手术中对患者血小板功能的影响。方法择期全麻下行脊柱手术患者20例,术前行颈内静脉穿刺采自体血,同时于外周静脉输入等量的胶体液（万汶）,术中连续监测HR,SPO2,Bp及尿量变化,分别于采血前（T0）,采血后15 min（T1）,输血前（T2）,输血后15 min（T3）,抽取桡动脉血查HB,HCT,LAC,并采用Sonoclot分析仪测定激活凝血酶原时间（ACT）,凝血速率（CR）,血小板功能（PF）。记录术中晶胶体液输入量,出血量和尿量。结果与T0相比,T1的HB,HCT显著下降（P〈0.01）,CR、PF显著下降（P〈0.01）,与T2相比,T3的HB,HCT显著回升,CR、PF显著升高（P〈0.01）,LAC,ACT变化无统计学意义。结论急性等容性血液稀释对脊柱手术患者血小板功能有一定的保护作用,对凝血功能无明显不良影响。     

Work function and negative electron affinity of ultrathin barium fluoride films

Thin films of barium fluorides with different thicknesses were deposited on GaAs substrate by electron beam evaporation. The aim of the work was to identify the best growth conditions for the production of coatings with a low work function suitable for the anode of hybrid thermionic-photovoltaic (TIPV) devices. The chemical composition and work function φ of the films with different thicknesses were investigated by X-ray photoelectron spectroscopy (XPS) and ultraviolet photoelectron spectroscopy (UPS). The lowest value of φ = 2.1 eV was obtained for the film with a thickness of ~2 nm. In the valence band spectra of the films at low kinetic energy, near the cutoff, a characteristic peak of negative electron affinity was present. This effect contributed to a further reduction of the film's work function.     

Effects of acid etching on the structure of PtNi catalyst and total exposed active sites

The integration technology of hydrogen preparation–hydrogen storage not only can utilize hydrogen energy efficiently but also can improve the selectivity of the electrode maximally. In the present work, the structure and composition of the PtNi catalyst was characterized by X-ray diffraction (XRD); and its electrochemical properties, morphology, and surface binding energy were analyzed by cyclic voltammetry (CV) and linear scanning voltammetry (LSV), scanning electron microscopy equipped with energy-dispersive spectrometry (SEM-EDS), and X-ray photoelectron spectroscopy (XPS), respectively. The effects of different acid etching treatments (e.g., etching time, etchant concentration, and etching temperature) on the structure and surface active sites were investigated by the orthogonal experiment. The experimental results reveal that after etching with 0.5 mol/L of perchloric acid for 0.5 h at 60°C, the electrode weight loss of the PtNi catalyst is mainly attributed to the large loss of Ni atoms in film layer. This results in the reduced alloy phase in film layer and the appearance of Pt characteristic diffraction peak. The relative content of Pt on the surface of the film electrode increases significantly, and the total number of active sites also increases correspondingly. The binding energy of Pt4f_7/2 decreases by 0.19 eV, and the number of active sites involved in hydrogen release decreases, indicative of the reduced promotion effect of the PtNi catalyst on hydrogen release.     

Taba: A Tool to Analyze the Binding Affinity

Evaluation of ligand-binding affinity using the atomic coordinates of a protein-ligand complex is a challenge from the computational point of view. The availability of crystallographic structures of complexes with binding affinity data opens the possibility to create machine-learning models targeted to a specific protein system. Here, we describe a new methodology that combines a mass-spring system approach with supervised machine-learning techniques to predict the binding affinity of protein-ligand complexes. The combination of these techniques allows exploring the scoring function space, generating a model targeted to a protein system of interest. The new model shows superior predictive performance when compared with classical scoring functions implemented in the programs Molegro Virtual Docker, AutoDock4, and AutoDock Vina. We implemented this methodology in a new program named Taba. Taba is implemented in Python and available to download under the GNU license at https://github.com/azevedolab/taba . © 2019 Wiley Periodicals, Inc.     

Distributed and multicore QuBiLS-MIDAS software v2.0: Computing chiral,fuzzy, weighted and truncated geometrical molecular descriptors based on tensor algebra

Advances to the distributed, multi-core and fully cross-platform QuBiLS-MIDAS software v2.0 ( http://tomocomd.com/qubils-midas ) are reported in this article since the v1.0 release. The QuBiLS-MIDAS software is the only one that computes atom-pair and alignment-free geometrical MDs (3D-MDs) from several distance metrics other than the Euclidean distance, as well as alignment-free 3D-MDs that codify structural information regarding the relations among three and four atoms of a molecule. The most recent features added to the QuBiLS-MIDAS software v2.0 are related (a) to the calculation of atomic weightings from indices based on the vertex-degree invariant (e.g., Alikhanidi index); (b) to consider central chirality during the molecular encoding; (c) to use measures based on clustering methods and statistical functions to codify structural information among more than two atoms; (d) to the use of a novel method based on fuzzy membership functions to spherically truncate inter-atomic relations; and (e) to the use of weighted and fuzzy aggregation operators to compute global 3D-MDs according to the importance and/or interrelation of the atoms of a molecule during the molecular encoding. Moreover, a novel module to compute QuBiLS-MIDAS 3D-MDs from their headings was also developed. This module can be used either by the graphical user interface or by means of the software library. By using the library, both the predictive models built with the QuBiLS-MIDAS 3D-MDs and the QuBiLS-MIDAS 3D-MDs calculation can be embedded in other tools. A set of predefined QuBiLS-MIDAS 3D-MDs with high information content and low redundancy on a set comprised of 20,469 compounds is also provided to be employed in further cheminformatics tasks. This set of predefined 3D-MDs evidenced better performance than all the universe of Dragon (v5.5) and PaDEL 0D-to-3D MDs in variability studies, whereas a linear independence study proved that these QuBiLS-MIDAS 3D-MDs codify chemical information orthogonal to the Dragon 0D-to-3D MDs. This set of predefined 3D-MDs would be periodically updated as long as new results be achieved. In general, this report highlights our continued efforts to provide a better tool for a most suitable characterization of compounds, and in this way, to contribute to obtaining better outcomes in future applications.     

Reduced eigensystem representation of the linear density-density response function

The linear density-density response function represents a formulation of the generalized density response of a molecular (or extended) system to arbitrary perturbing potentials. We have recently established an approach for reducing the dimension of the (in principle infinite) eigenspace representation (the moment expansion) and generalized it to arbitrary self-adjoint, positive-definite, and compact linear operators. Here, we present a modified representation—the reduced eigensystem representation—which allows to define a trivial criterion for the convergence of the approximation to the density response. By means of this novel eigensystem-like structure, the remarkable reduction of the dimensionality becomes apparent for the calculation of the density-density response function.     

初中化学教科书表格呈现方式及其教学功能价值的研究

以现行4个版本的义务教育化学教科书为研究对象,根据教科书中表格功能的不同,将其分为实验记录型表格、归纳总结型表格、习题型表格、资料卡片型表格等4类,对4类不同表格的教学功能价值进行了分析说明。并以沪教版为例,对当前初中化学教师使用教科书表格进行教学的情况进行了抽样调查与分析,由此提出3点教学建议。