离子速度成像方法研究C8H17Br分子的光解动力学

用离子速度成像方法, 研究了长链C8H17Br分子在234 nm激光下的光解过程. 通过2+1共振增强多光子电离探测了两种光解产物Br*(2P1/2)和Br(2P3/2), 得到了它们的相对量子产率. 从光解产物Br*(2P1/2)和Br(2P3/2)的速度图像得到了能量和角度分布. 并根据相对量子产率和角度分布, 计算了不同解离通道的比例. 实验发现C8H17Br分子解离过程中大部分能量都转化为内能, 该能量分配可以较好地用软反冲模型来解释, 并分析了这种能量分配跟烷基大小的关系.     

离子速度影像法研究n-C7H15Br分子光解反应动力学

利用离子速度成像方法, 研究n-C7H15Br分子在231～239 nm范围内几个波长处的光解离动力学. 通过同一束激光经(2+1)共振多光子电离(REMPI)过程探测光解碎片Br(2P3/2)和Br*(2P1/2), 得到了不同激光波长处的离子速度分布图像, 从而获得C7H15Br光解产物的能量分配和角度分布. 结合各向异性参数和量子产率, 计算了n-C7H15Br分子在234 nm波长下不同解离通道的比例. 实验表明光解产物的能量分配可以用冲击模型中的软碰撞模型来解释. 实验还发现, 各向异性参数β(Br*)的值对光波长变化很敏感, 这是由电子激发态的绝热和非绝热过程决定的.     

F-(H2O)+CH3I Ligand Exchange Reaction Dynamics

Single hydration of the gas phase F\begin{document}$^-$\end{document}+CH\begin{document}$_3$\end{document}I\begin{document}$\rightarrow$\end{document} I\begin{document}$^-$\end{document}+CH\begin{document}$_3$\end{document}F reaction allows to probe solvent effects on a fundamental nucleophilic substitution reaction. At the same time, the addition of a solvent molecule opens alternative product channels. Here, we present crossed beam imaging results on the dynamics of the F\begin{document}$^-$\end{document}(H\begin{document}$_2$\end{document}O)+CH\begin{document}$_3$\end{document}I\begin{document}$\rightarrow$\end{document}[FCH\begin{document}$_3$\end{document}I]\begin{document}$^-$\end{document}+H\begin{document}$_2$\end{document}O ligand exchange pathway at collision energies between 0.3 and 2.6 eV. Product kinetic energies are constrained by the stability requirement of the weakly bound product complexes. This implies substantial internal excitation of the water molecule and disfavors efficient energy redistribution in an intermediate complex, which is reflected by the suppression of low kinetic energies as collision energy increases. At 0.3 eV, internal nucleophilic displacement is important and is discussed in light of the competing nucleophilic substitution pathways that form I\begin{document}$^-$\end{document} and I\begin{document}$^-$\end{document}(H\begin{document}$_2$\end{document}O).     

SSThread: Template‐free protein structure prediction by threading pairs of contacting secondary structures followed by assembly of overlapping pairs

Acquiring the three‐dimensional structure of a protein from its amino acid sequence alone, despite a great deal of work and significant progress on the subject, is still an unsolved problem. SSThread, a new template‐free algorithm is described here that consists of making several predictions of contacting pairs of α‐helices and β‐strands derived from a database of experimental structures using a knowledge‐based potential, secondary structure prediction, and contact map prediction followed by assembly of overlapping pair predictions to create an ensemble of core structure predictions whose loops are then predicted. In a set of seven CASP10 targets SSThread outperformed the two leading methods for two targets each. The targets were all β‐strand containing structures and most of them have a high relative contact order which demonstrates the advantages of SSThread. The primary bottlenecks based on sets of 74 and 21 test cases are the pair prediction and loop prediction stages. © 2014 Wiley Periodicals, Inc.     

离子速度成像方法研究溴代环己烷的紫外光解动力学

利用二维离子速度成像方法对C6H11Br分子在234 nm附近的光解动力学行为进行了研究. 通过(2+1)共振增强多光子电离探测了光解产物Br*(2P1/2)和Br(2P3/2), 得到它们的相对量子产率. 从光解产物Br*(2P1/2)和Br(2P3/2)的速度图像得到了能量和角度分布. 结果表明, Br*原子主要来自于S1态的直接解离, 而Br则绝大部分是从S2态向T3态的系间交叉跃迁得到, 并导致了两种解离通道能量分布的差别. 实验发现C6H11Br分子解离过程中大部分能量都转化为内能, 但与其它长链溴代烷烃分子相比, 可资用能更多地被分配到平动能中, 结合软反冲模型分析了这种能量分配跟环烷基的构象和稳定性的关系.     

CH2BrCl在265 nm光解产生的氯甲基自由基的振动内能

利用离子速度影像技术研究了CH2BrCl在265nm附近的激光光解.利用2+1共振增强多光子电离分别获得光解产物Br(2P1/2)和Br(2P3/2)的离子速度图像,从而得出Br(2P1/2)和Br(2P3/2)的速度分布,以及光解碎片的总平动能分布.据此,运用角动量守恒碰撞模型获得了解离氯甲基自由基(·CH2Cl)的振动内能分布.研究结果表明:CH2BrCl+hv→Br(2P1/2)+CH2Cl通道产生的氯甲基自由基中被激发的振动模主要是v4、v3+v4、v2+v4和v2+v6;CH2BrCl+hv→Br(2P3/2)+CH2Cl通道产生的氯甲基自由基中被激发的振动模主要是v2+v6、v1+v3、v2+v5、v2+v3+v5和v1+v5;母体分子CH2BrCl在吸收光解光子后除有v5(CBrstretch)振动模被激发外,还有v7(CH2a-stretch)等其它振动模也被激发.     

A Fréchet derivative-free cubically convergent method for set-valued maps

We introduce a new iterative method in order to approximate a locally unique solution of variational inclusions in Banach spaces. The method uses only divided differences operators of order one. An existence–convergence theorem and a radius of convergence are given under some conditions on divided difference operator and Lipschitz-like continuity property of set-valued mappings. Our method extends the recent work related to the resolution of nonlinear equation in Argyros (J Math Anal Appl 332:97–108, 2007) and has the following advantages: faster convergence to the solution than all the previous known ones in Argyros and Hilout (Appl Math Comput, 2008 in press), Hilout (J Math Anal Appl 339:53–761, 2008, Positivity 10:673–700, 2006), and we do not need to evaluate any Fréchet derivative. We provide also an improvement of the ratio of our algorithm under some center-conditions and less computational cost. Numerical examples are also provided.      

Monotone preimages of dendrites

A counterexample to a theorem of J.J. Charatonik and K. Omiljanowski giving sufficient conditions for a dendrite to be contained in all of its monotone preimages is given, and a corrected version of the theorem is presented. An alternative proof is provided for a characterization of dendrites monotonely equivalent to a universal dendrite that was originally proved using the erroneous result. Finally, in response to a question by J.J. Charatonik, it is shown that a dendrite contained in all of its monotone preimages must have a discrete set of ramification points.     

VANISHING THEOREMS FOR ACH KAHLER MANIFOLDS AND HARMONIC MAPS

We discuss a class of complete Kaihler manifolds which are asymptotically complex hyperbolic near infinity. The main result is vanishing theorems for the second L2 cohomology of such manifolds when it has positive spectrum. We also generalize the result to the weighted Poincare inequality case and establish a vanishing theorem provided that the weighted function p is of sub-quadratic growth of the distance function. We also obtain a vanishing theorem of harmonic maps on manifolds which satisfies the weighted Poincare inequality.