手性金属配合物Δ,Λ-[Ru(IP)_2dppz]~(2 )对含G:T错配的环丁烷嘧啶二聚体识别和部分构型修复的分子力学研究

环丁烷嘧啶二聚体(CyclobutanePyrimidineDimer,CPD)是紫外线对DNA损伤导致皮肤癌的首要环节,XPC-hHR23B是最早作为对CPD的损伤识别剂的,但其识别效率很低.本文首次采用分子力学方法模拟了一种新的手性金属配合物?,Λ-[Ru(IP)2dppz]2 对含G:T错配的CPD双螺旋DNA的识别作用.模拟结果显示:金属配合物[Ru(IP)2dppz]2 的两个手性异构体都对含G:T错配的CPD双螺旋DNA具有识别作用,识别的过程体现了很强的手性选择性、沟选择性和位点特异性.同时,我们发现:在Λ-[Ru(IP)2dppz]2 插入到CPD后,形成CPD的两个T碱基由原来的敞口形状部分地转为近平行状,使其在构型上得到初步的修复.     

Work function of metals: Relation between theory and experiment

Theoretical approaches to calculation of work function within jellium model and the problem of extension of this model to include the lattice corrections to the work function are briefly discussed. Lattice corrections to the work function obtained from the experiment are estimated and compared with those calculated theoretically.

It is found that the mean value of the experimental lattice correction <δψ_hkl>_hkl compared to the mean work function is negligible. It is stated that the mean work function can be treated as a material constant characterizing a given metal, such as, e.g., binding energy.An expression for the dependence of jellium work function on r_s, valid in a metallic range of r_s, is given. A comparison between then theoretical and experimental results is presented and the role of correlation energy is examined. It is shown that more accurate approximations of the correlation energy than that given by Wigner's formula lead to a better agreement with experiment. A simple model is presented for explanation of work function changes on single crystal planes. Some recent results concerning the thermal dependence of work function are given. The dependence of the work function on the degree of coverage is discussed both for alkali and non-alkali atoms adsorption. Theoretical models are briefly reviewed and comparison between theory and experiment is made. A simple model is presented for explanation of the work function variation on rough planes in metallic non-alkali atoms chemisorption.     

High resolution imaging of contact potential difference using a novel ultrahigh vacuum non-contact atomic force microscope technique

An ultrahigh vacuum scanning Kelvin probe force microscope (UHV SKPM) based on the gradient of electrostatic force was developed using the technique of a UHV non-contact atomic force microscope (NC-AFM) capable of atomic level imaging, and used for simultaneous observation of contact potential difference (CPD) and NC-AFM images. The CPD images with a potential resolution of less than 10 meV were observed in the UHV SKPM, demonstrating an atomic level resolution. The change of potential corresponding to the charges on the insulated surface of polypropylene have been observed in UHV SKPM. We also demonstrated a reliable method to obtain the CPD from the bias voltage dependence curves of the frequency shift in all of the scanning area. The results are consistent with comparing the barrier height images in that the work functions of adatoms are greater than the work function of corner holes.     

热可逆共价交联反应及其研究进展

梗概评述了环戊二烯（ＣＰＤ）与双环戊二烯（ＤＣＰＤ）之间Ｄｉｅｌｓ－Ａｌｄｅｒ反应的特点,以及将其引作大分子间交联键的思路;以此为基础详细讨论了热可逆共价交联聚合物的分析方法。制备路线,以及利用这一反应目前所达到的研究水平和成就 。     

Contamination inspection on wafer with oxide or nitride film by using a vibrating contact potential difference probe

Contamination inspection on the oxide and nitride films deposited on silicon wafer surface by using vibrating contact potential difference (CPD) probe is presented in this paper. Contaminants induce the variation of the CPD between a dielectric layer and the probe material. However, the screening effect of the charges on the surface, interface and in the dielectric layer overwhelms the contamination signals when using the vibrating CPD monitor. This obstacle can be overcome using the signal characteristic diagnosis by which most of the charge signals can be filtered out. The validity of this approach was verified by means of the vapor phase decomposition coupling with inductively coupled plasma mass spectrometry (VPD‐ICP‐MS), and we found that the filtrated contamination signals were correlated closely with the metallic concentration. Moreover, the proper annealing process could enhance the response signals of contaminants, especially for Ni and Cu, in the nitride film monitoring. This inspection method was effectively applied in the trace metallic contamination routine monitor and the contamination source tracing of the furnace tools. Copyright © 2010 John Wiley & Sons, Ltd.     

Predicting kinetic parameters for coal devolatilization by means of Artificial Neural Networks

The chemical percolation devolatilization (CPD) model has been shown to represent the devolatilization process of different coals and heating conditions with good accuracy. However, its use in computational fluid dynamics is limited because of its relatively high computational cost. Here, an Artificial Neural Network (ANN) based model for predicting coal devolatilization kinetics is developed based on a database constructed with the CPD model for a wide range of coals and heating rates. The heating rates and the information of ultimate and proximate analysis are chosen as inputs of the ANN model to consider the effects of coal types and heating conditions on coal devolatilization; the outputs are the kinetic parameters for the two-step kinetic model. The learning, validation, and application results show that the proposed ANN model has a competitive prediction capability on both the total volatile release and release rates when compared with the CPD model, but has obvious computational efficiency advantages. Furthermore, the relative impact of the coal type and heating rate on each kinetic parameter for coal devolatilization is quantitatively evaluated through the Garson equation. It is found that the heating rate has the strongest effect on the pre-exponential factor, while the coal types show significant influence on the activation energy and final yield of the two reactions in the two-step model.     

β-二酮亚胺钛化合物催化乙烯和环戊二烯共聚合反应机理的密度泛函理论研究

运用密度泛函理论（DFT）对β-二酮亚胺钛化合物[PhNC（CH3）CHC（CF3）O]2TiCl2催化乙烯（E）和环戊二烯（CPD）共聚合反应的反应机理进行了理论研究.计算结果表明：乙烯和CPD的共聚反应中,CPD插入反应可以通过1,2插入和2,1插入两种路径进行,1,2插入能垒略低于2,1插入,因此我们预测两种路径...     

D,L-[Ru(phen)_2dppz]~(2+)对含G:T错配的环丁烷嘧啶二聚体识别和修复的理论研究

环丁烷嘧啶二聚体(Cyclobutane Pyrimidine Dimer,CPD)是紫外线对DNA损伤导致皮肤癌的首要环节,XPC-hHR23B是最早作为对CPD的损伤识别剂的,但其识别效率很低.首次采用分子力学方法模拟了手性金属配合物D,L-[Ru(phen)2dppz]2+(phen=1,10phenanthroline,dppz=dipyrido[3,2-a∶2’,3’-c]phenazine)对含G∶T错配的CPD双螺旋DNA的识别作用.模拟结果显示:该配合物的左手异构体优先从小沟方向识别与G∶T错配相邻的A4T5/T7G6区域,而右手异构体则优先从大沟方向识别与G∶T错配相邻的另一区域T6A7/G5T4.由于CPD的形成,该DNA螺旋高度扭曲,使得识别过程体现了手性选择性和位点特异性,左手异构体更占优势.详细的能量分析发现:在配合物插入碱基堆积过程中的空间位阻状况决定了识别作用的结果,静电相互作用也在一定程度上产生了影响.此外,我们还发现,金属配合物插入CPD相邻的区域后,能将形成CPD的两个T碱基由原来的敞口形状部分地转为近平行状,使其得到构型上的部分修复.     

D，L-[-Ru（phen）2dppz-]^2＋对含G：T错配的环丁烷嘧啶二聚体识别和修复的理论研究

环丁烷嘧啶二聚体（Cyclobutane Pyrimidine Dimer,CPD）是紫外线对DNA损伤导致皮肤癌的首要环节,XPC-hHR23B是最早作为对CPD的损伤识别剂的,但其识别效率很低．首次采用分子力学方法模拟了手性金属配合物D,L-[Ru（phen）2dppz]^2＋（phen=1,10phenanthroline,dppz—dipyrido[3,2-a：2’,3＇-c]phenazine）对含G：T错配的CPD双螺旋DNA的识别作用．模拟结果显示：该配合物的左手异构体优先从小沟方向识别与G：T错配相邻的4T5／T7G6区域,而右手异构体则优先从大沟方向识别与G：T错配相邻的另一区域T6A7／C5T4．由于CPD的形成,该DNA螺旋高度扭曲,使得识别过程体现了手性选择性和位点特异性,左手异构体更占优势．详细的能量分析发现：在配合物插入碱基堆积过程中的空间位阻状况决定了识别作用的结果,静电相互作用也在一定程度上产生了影响．此外,我们还发现,金属配合物插入CPD相邻的区域后,能将形成CPD的两个T碱基由原来的敞口形状部分地转为近平行状,使其得到构型上的部分修复．     

Effect of substrate atomic structure on intersolubility and alloying in Pd/Nb adsorption system

In order to investigate to what extent the crystallographic structure of the substrate affects the process of interdiffusion and surface alloy formation in the case of the same components, adsorption systems of Pd on Nb(0 1 1), Nb(0 0 1) and Nb(1 1 1) have been studied by means of low-energy electron diffraction, Auger electron spectroscopy, and contact potential measurement. For all the systems, Pd dissolves in the substrate, when its population on the surface exceeds 1 ML. Kinetics of the mutual solution depends on the amount of deposited Pd, and increases with increasing amount of the adsorbate. Independent of the substrate structure, there was no evidence for a mixing of Pd and Nb in the top-most layer. For the Pd/Nb(0 1 1) system, the lateral interactions inside the Pd adlayer surpass the adsorbate–substrate interaction. The adsorbate–substrate interaction is dominant for the Pd/Nb(0 0 1) and Pd/Nb(1 1 1) systems, and results in the formation of a sandwich-like laminar surface alloy with a Pd layer on top.