Wet-chemical synthesis of two-dimensional metal nanomaterials for electrocatalysis

Two-dimensional (2D) metal nanomaterials have gained ever-growing research interest owing to their fascinating physicochemical properties and promising application, especially in the field of electrocatalysis. In this review, we briefly introduce the recent advances in wet-chemical synthesis of 2D metal nanomaterials. Subsequently, the catalytic performances of 2D metal nanomaterials in a variety of electrochemical reactions are illustrated. Finally, we summarize current challenges and highlight our perspectives on preparing high-performance 2D metal electrocatalysts.     

国内旅游专题数据库建设情况调查与分析

随着国内旅游业的快速发展,旅游专题数据库的建设日益引起业界关注,本文调查分析了国内旅游专题数据库的建设现状,并从统一规划、协调发展;联合建设,提高数据库共享度;数据库选题及框架搭建;充分发挥高校图书馆的优势四个方面阐述了应采取的措施。     

重视医学论文中有关统计学分析的描述

完整和清晰的统计学分析描述将有助于读者理解并鉴别医学论文的结论与质量.针对中华医学会直接主办的18种期刊统计学分析描述方面存在的问题,提出改进建议.     

利用ASP技术实现图书馆主页上Web数据库的动态查询

介绍了利用ASP 技术在图书馆主页中的应用, 实现Web 数据库动态查询的整个实施过程。     

网络信息生态链效能的分析与评价

指出网络信息生态链效能是对网络信息生态链的运行效果及其对既定目标的实现程度的评价。网络信息生态链效能的评价是对网络信息生态链进行优化和对其效能进行提升的前提。从网络信息生态链的结构组成、信息流转、运行成本、功能价值和保障机制五大要素入手,构建网络信息生态链的评价指标体系,并基于层次分析法对网络信息生态链的效能进行评价,进而提出网络信息生态链效能的提升策略。     

大学图书馆规程的制订与思考——以《重庆大学图书馆规程》为例

“十四五”即将到来,图书馆需要在教育部颁布的《普通高等学校图书馆规程》的基础上,制订单馆的管理和服务流程规范,作为整个管理体制的纲,以《规程》为统领,梳理本馆的管理和服务模式,以利于图书馆治理能力的深化,在真正意义上提升图书馆效能,实现内涵式发展。文章以《重庆大学图书馆规程》为例,论述了整个编制过程和主要思想。     

Two decades of suspect evidence for adaptive molecular evolution—negative selection confounding positive-selection signals

There has been a large literature in the last two decades affirming adaptive DNA sequence evolution between species. The main lines of evidence are from (i) the McDonald-Kreitman (MK) test, which compares divergence and polymorphism data, and (ii) the phylogenetic analysis by maximum likelihood (PAML) test, which analyzes multispecies divergence data. Here, we apply these two tests concurrently to genomic data of Drosophila and Arabidopsis. To our surprise, the >100 genes identified by the two tests do not overlap beyond random expectation. Because the non-concordance could be due to low powers leading to high false negatives, we merge every 20–30 genes into a ‘supergene’. At the supergene level, the power of detection is large but the calls still do not overlap. We rule out methodological reasons for the non-concordance. In particular, extensive simulations fail to find scenarios whereby positive selection can only be detected by either MK or PAML, but not both. Since molecular evolution is governed by positive and negative selection concurrently, a fundamental assumption for estimating one of these (say, positive selection) is that the other is constant. However, in a broad survey of primates, birds, Drosophila and Arabidopsis, we found that negative selection rarely stays constant for long in evolution. As a consequence, the variation in negative selection is often misconstrued as a signal of positive selection. In conclusion, MK, PAML and any method that examines genomic sequence evolution has to explicitly address the variation in negative selection before estimating positive selection. In a companion study, we propose a possible path forward in two stages—first, by mapping out the changes in negative selection and then using this map to estimate positive selection. For now, the large literature on positive selection between species has to await reassessment.     

Web日志中用户存取模式的聚类研究

基于用户访问网页的不同序列反映了用户特定的兴趣,提出了Web日志中用户存取模式的聚类算法。利用传统的Leader算法只扫描数据集一遍的优点,以及粗糙理论在处理含有不确定信息问题上的优势,给出了结合粗糙理论的改进Leader算法对用户存取模式进行聚类方法,使得同一类中的用户存取模式尽可能的相近或相似,不同类中的模式尽可能的相异。实验结果表明,该算法在可承受的计算时间内可对Web日志中的用户存取模式进行有效聚类。     

用ISTP统计评估国际学术会议的等级

利用科技会议录索引ISTP,从会议主办机构、ISTP收录会议论文篇数和专家审定等三方面对ISTP收录的国际学术会议进行等级评估。评估结果为按学校学科专业、会议等级、会议名称等排列的EXCEL表。结果表明这种方法能定量与定性评估国际学术会议的等级。参考文献2.     

后手翻接团身后空翻三周技巧动作的运动学分析

团身后空翻三周动作是有加分因素的D级高难动作。该文通过查阅文献,专家座谈,结合拍摄到的我国优秀运动员完成的动作分析,认为后手翻动作不管是上肢或下肢摆动要快,制动也要快(制动角约为554),这样完成整个动作才能做到低、平、快。在团身后空翻起跳阶段脚着地前,髋、膝、踝关节应主动蹬伸,缩短踏跳时间;下肢蹬伸的同时,手臂和躯干快速向后摆动,并及时制动,形成较好的动量矩传递,脚离地时相髋未完全打开,有利于腾空后团身。