HeH+体系光缔合反应的动力学研究

采用含时量子波包方法研究基电子态HeH⁺体系优化的光缔合几率,即He+H⁺→HeH⁺随碰撞粒子对初始动量的变化,并研究伴随该过程的多光子跃迁和解离.选取v=6振动能级为目标态,通过优化激光场参数得到碰撞粒子对的最优光缔合几率.结果表明：随着碰撞粒子对初始动量的增加,光缔合所用的最优激光场的持续时间逐渐减少,但光场的强度和失谐逐渐增加.在某些初始碰撞动量附近,由于共振多光子跃迁过程的存在,最优的光场不能严格地将碰撞粒子对缔合到目标态.此外,研究表明随着初始动量的增加,系统的超阈值解离几率近似线性地增加到一个最大值,直至饱和强度.并且,在碰撞粒子对的初始动量较大时,超阈值解离主导解离过程.     

PELE贯穿薄靶后外壳破片径向速度计算方法与影响因素分析

基于横向效应增强型弹丸(PELE)侵彻金属薄靶板过程分析,将弹体前端在撞击作用下的变形过程分解为轴向一维压缩和径向自由膨胀两个变形阶段;依据冲击波理论,给出了弹体前端的冲击波压缩势能,由功能转化原理,给出了PELE前端外壳在靶后形成破片的最大径向飞散速度计算公式。计算结果在多种工况下均与文献的实验结果较为一致。计算结果表明:PELE靶后外壳破片的最大径向飞散速度与外壳和内芯材料的体积模量和泊松比有关,且随二者的增大而增大;PELE外壳破片的最大径向飞散速度是壳体和内芯在冲击波压缩作用下共同径向膨胀的结果,且外壳膨胀能在弹体整体膨胀能中所占比例较大,计算中应当同时考虑弹体外壳和内芯材料的横向膨胀效应对弹体破片径向飞散速度的影响。     

25MeV/u 40)Ar+209Bi裂变反应研究

实验对25MeV/u ⁴⁰Ar+²⁰⁹Bi体系的裂变反应,利用线性动量转移的分窗选择不同的激发能,研究裂变动能分布和质量分布与热核初始激发能的关系.实验证实激发能小于380MeV时裂变总动能分布与低激发能复合核相似.激发能大于380MeV时,最可几动能呈现出随激发增加而增加,并出现高能非对称性,而且质量分布宽度随激发能增加而迅速增大.     

In Silico Structure-Based Approach for Group Efficiency Estimation in Fragment-Based Drug Design Using Evaluation of Fragment Contributions

The notion of a contribution of a specific group in an organic molecule’s property and/or activity is both common in our thinking and is still not strictly correct due to the inherent non-additivity of free energy with respect to molecular fragments composing a molecule. The fragment- based drug discovery (FBDD) approach has proven to be fruitful in addressing the above notions. The main difficulty of the FBDD, however, is in its reliance on the low throughput and expensive experimental means of determining the fragment-sized molecules binding. In this article we propose a way to enhance the throughput and availability of the FBDD methods by judiciously using an in silico means of assessing the contribution to ligand-receptor binding energy of fragments of a molecule under question using a previously developed in silico Reverse Fragment Based Drug Discovery (R-FBDD) approach. It has been shown that the proposed structure-based drug discovery (SBDD) type of approach fills in the vacant niche among the existing in silico approaches, which mainly stem from the ligand-based drug discovery (LBDD) counterparts. In order to illustrate the applicability of the approach, our work retrospectively repeats the findings of the use case of an FBDD hit-to-lead project devoted to the experimentally based determination of additive group efficiency (GE)—an analog of ligand efficiency (LE) for a group in the molecule—using the Free-Wilson (FW) decomposition. It is shown that in using our in silico approach to evaluate fragment contributions of a ligand and to estimate GE one can arrive at similar decisions as those made using the experimentally determined activity-based FW decomposition. It is also shown that the approach is rather robust to the choice of the scoring function, provided the latter demonstrates a decent scoring power. We argue that the proposed approach of in silico assessment of GE has a wider applicability domain and expect that it will be widely applicable to enhance the net throughput of drug discovery based on the FBDD paradigm.     

Applying characteristic fragment filtering for rapid detection and identification of ingredients in rhubarb by HPLC coupled with linear ion trap–Orbitrap mass spectrometry

Chemical characteristic fragment filtering in MSⁿ chromatograms was proposed to detect and identify the components in rhubarb rapidly using high‐performance liquid chromatography coupled with linear ion trap–Orbitrap mass spectrometry. Characteristic fragments consist of diagnostic ions and neutral loss fragments. Characteristic fragment filtering is a postacquisition data mining method for the targeted screening of groups with specific structures, including three steps: first, in order to comprehensively summarize characteristic fragments for global identification of the ingredients in rhubarb, representative authentic standards of dominant chemical categories contained in rhubarb were chosen, from which fragmentation rules and a characteristic fragments schedule were proposed; second, characteristic fragment filtering was used to rapidly recognize analogous skeletons; finally, combined with retention time, accurate mass, characteristic fragments, and previous literature, the structures of the filtered compounds were identified or tentatively characterized. As a result, a total of 271 compounds were detected and identified in rhubarb, including 34 anthraquinones, 83 anthrones, 46 tannins, 17 stilbenes, 24 phenylbutanones, 26 acylglucosides, 26 chromones, and 15 other compounds, 69 of which are potentially new compounds. The proposed characteristic fragment filtering strategy would be a reference for the large‐scale detection and identification of the ingredients of herbal medicines.     

Electromagnetic dissociation of 3.7 A GeV^16O in nuclear emulsion

The electromagnetic dissociation (ED) of 3.7 A GeV {}^{16}O in nuclear emulsion is investigated with high statistics. It is found that the electromagnetically dissociated cross section increases with increasing beam energy, the charge distribution of projectile fragments is the same as the results at 60 and 200 A GeV, and the production probability of projectile fragments with charge 3≤Z≤5 is less than that of the other projectile fragments. These results can be well explained by use of Weizsacker and Williams method for calculating the ED contributions. The percentile abundance of various decay modes for ED at 3.7 A GeV is close to the result at 60 and 200 A GeV, but it is different from the result at 14.6 A GeV. The ED of 3.7 A GeV is mainly caused by the giant dipole and quadrupole resonance of E1 and E2, which can be qualitatively explained by the multiplicity distribution of projectile proton in ED. The multiplicity distribution of the α fragments in ED and nuclear events have different functional forms. This difference may be a consequence of the different reaction mechanism involved.     

Automated site-directed drug design: Searches of the Cambridge Structural Database for bond lengths in molecular fragments to be used for automated structure assembly

Summary In this paper a database of small frequently occurring molecular fragments is used for the determination of fragment bond lengths from the Cambridge Structural Database. A large number of bond types are described that have not been reported previously.     

30MeV/u 40Ar+159Tb反应中前角区复杂碎片的来源

在前角测量了30MeV/u ⁴⁰Ar+¹⁵⁹Tb反应中两裂片符合下的轻粒子和复杂碎片,利用线性动量转移和总横向动量方法对三体符合事件进行了碰撞参数分类. 实验结果表明,在中心碰撞中复杂碎片主要来自于平衡类靶核的统计发射,并伴随有非平衡中途成份;而周边碰撞中前角区复杂碎片主要来自于弹核碎裂成份. 在半中心碰撞中则存在类弹、类靶和中途三种成份.