有机合成反应选择性及其控制策略

有机合成是化学研究领域中最具有魅力的。结构复杂、性质多元、应用广泛的有机物及其合成方法学,让人赞叹与探求。文章用科学方法论总结了有机合成中的化学选择性、区域选择性和立体选择性的规律及其热力学和动力学控制策略,提出了综合利用其控制原理解释或预测竞争性反应产物的基本方法。     

A fast and versatile cross-linking strategy via o-phthalaldehyde condensation for mechanically strengthened and functional hydrogels

Fast and catalyst-free cross-linking strategy is of great significance for construction of covalently cross-linked hydrogels. Here, we report the condensation reaction between o-phthalaldehyde (OPA) and N-nucleophiles (primary amine, hydrazide and aminooxy) for hydrogel formation for the first time. When four-arm poly(ethylene glycol) (4aPEG) capped with OPA was mixed with various N-nucleophile-terminated 4aPEG as building blocks, hydrogels were formed with superfast gelation rate, higher mechanical strength and markedly lower critical gelation concentrations, compared to benzaldehyde-based counterparts. Small molecule model reactions indicate the key to these cross-links is the fast formation of heterocycle phthalimidine product or isoindole (bis)hemiaminal intermediates, depending on the N-nucleophiles. The second-order rate constant for the formation of phthalimidine linkage (4.3 M⁻¹ s⁻¹) is over 3000 times and 200 times higher than those for acylhydrazone and oxime formation from benzaldehyde, respectively, and comparable to many cycloaddition click reactions. Based on the versatile OPA chemistry, various hydrogels can be readily prepared from naturally derived polysaccharides, proteins or synthetic polymers without complicated chemical modification. Moreover, biofunctionality is facilely imparted to the hydrogels by introducing amine-bearing peptides via the reaction between OPA and amino group.     

Emotional reactions and coping responses of employees to a cyber-attack: A case study

Cybersecurity is a serious threat to information technology (IT) systems, with most organisations now relying on their IT systems to function day-to-day. Therefore, it is crucial that organisations ensure they are protected. This research investigates the emotional and coping responses of employees towards a cyber-attack. Data was collected through an in-depth case study approach (24 semi-structured interviews) conducted at a global manufacturing company, along with primary observations and a corpus of secondary materials. Our data analysis applied a grounded approach which was then refined using an emotion theoretic lens with the application of Technology Threat Avoidance Theory (TTAT). Drawing on structural appraisal theory, our findings indicate the IT security team in the case study oscillated between positive problem-focused coping and negative emotion-focused coping. A key explanatory feature or turnaround mechanism that mediated this oscillation was senior management empathy and resource mobilization. Building on the analyses, a conceptual model is developed called the Transformation of Coping through Empathic Leadership (T-CEL). The research suggests the crucial role that senior management play in transforming the emotional and coping capabilities of employees through their intervention and support. The study extends the IS Security theoretical background through a TTAT-lens for the analysis of cyber-attack incidents.     

901型视觉动作反应仪在体育训练中的应用

训练运动员、飞行员视觉动作反应的响应速度和准确性,避免由视觉动作障碍造成的失误,对提高运动成绩和战斗力有重要意义。901型视觉动作反应仪是将计算机高科技应用于体育领域的新产品,实现对人体视觉动作反应能力的定量测试和分析,并可对人体视觉动作反应能力进行强化训练,使训练科学化。文章旨在介绍该仪器在体育训练方面的应用。     

论运动动机冲突及其对动作反应的影响

运动动机冲突是运动员在运动中产生动作迟缓反应和降低动作目标的矛盾心理现象。合理解决运动动机冲突，有利于运动员运动成绩的提高。     

中学化学中的离子反应与高考中的离子反应方程式

This thesis discusses the judgment of the ionic reaction and ionic reaction representation.     

维生素E在生体中的抗氧化作用

讨论维生素E对生体中脂质氧化作用的抑制,及其化学反应过程机理与动脉硬化的关系.     

化学振荡在无机实验中的增设

本文介绍了在传统的无机经典实验中引进化学振荡实验，以求促进无机化学实验的改革．     

谈高职英语口语教学的重心

英语作为世界通用的语言工具,越来越为人们所重视。而能否真正有效地进行英语会话交流,还依赖于讲话者的语音语调是否“通用”及可接受。针对我国高职学生的英语现状,从语音、词汇、句型等方面进行简单剖析,提出英语口语教学中教师应注意的问题与解决的方法。     

机械合金化诱发固态燃烧反应机理研究进展

本文简要介绍了机械合金化原理和特点，着重讨论了几种机械合金化诱发固态燃烧反应机理，并提出今后努力的方向。