Chiral ligand-protected gold nanoclusters: Considering the optical activity from a viewpoint of ligand dissymmetric field

Chirality is a geometric property of a physical, chemical, or biological object, which is not superimposable on its mirror image. Its significant presence has led to a strong demand in the development of chiral drugs, sensors, catalysts, and photofunctional materials. In recent years, chirality of nanoscale organic/inorganic hybrids has received tremendous attention owing to potential applications in chiral nanotechnology. In particular, with the recent progress in the syntheses and characterizations of atomically precise gold nanoclusters protected by achiral thiolates, atomic level origins of their chirality have been unveiled. On the other hand, chirality or optical activity in metal nanoclusters can also be introduced via the surface chiral ligands, which should be universal for the nanosystems. This tutorial review presents some optically-active metal (gold) nanoclusters protected by chiral thiolates or phosphines, and their chiroptical (or circular dichroism; CD) properties are discussed mostly from a viewpoint of the ligand dissymmetric field scheme. The examples are the gold nanoclusters protected by (R)-/(S)-2-phenylpropane-1-thiol, (R)-/(S)-mercaptosuccinic acid, phenylboronate-D/L-fructose complexes, phosphine sulfonate-ephedrinium ion pairs, or glutathione. Some methodologies for versatile asymmetric transformation and chiroptical controls of the nanocluster compounds are also described. In the dissymmetric field model as the origin of optical activity, the chiroptical responses of the gold nanoclusters are strongly associated with coupled oscillator and/or CD stealing mechanisms based on the concept of induced CD (ICD) derived from a perturbation theory, so on this basis, some characteristic features of the observed CD responses of chiral ligand-protected gold nanoclusters are presented in detail. We believe that various kinds of origins of chirality found in ligand-protected gold nanoclusters may provide models for understanding those of many related nanomaterials.     

液态保存血小板质量评价方法研究进展

对于液态保存血小板制品的质量评价,除了应符合血液和血液产品的常规检测项目标准外,主要限定在产品中的血小板收集量、白细胞混入量、红细胞混入量及pH值等指标,而缺乏对于血小板功能状态、临床输注效果指标的具体要求。随着对血小板功能状态、输注效果评价方法逐步完善和应用,必将建立起全面的血小板质量评价体系。     

计算机网络局域网技术及应用

本文介绍了局域网的基本概念以及局域网使用的传输媒体,目前企业组建局域网常用的局域网技术及其应用,包括CSMA/CD媒体访问控制、共享以太网、交换以太网、快速以太网、千兆以太网,对企业组建局域网提出了一些建议。     

原发性肝癌患者射频消融后外周血CD4+CD25+Foxp3+Treg细胞对预后的影响

目的研究射频消融术治疗原发性肝癌患者外周血CD4+CD25+Foxp3+调节性T细水平与预后的关系.方法回顾性分析102例原发性肝癌患者经射频消融治疗后外周血CD4+CD25+Foxp3+/CD4+比值与生存时间的关联.结果原发性肝癌患者射频术后CD4+CD25+Foxp3+细胞占CD4+T的比例显著降低,与临床分期、肿瘤大小、AFP水平相关.CD4+CD25+Foxp3+调节性T细胞数目与生存率相关.结论原发性肝癌患者射频消融治疗后外周血Treg水平是判断预后的独立预测指标.     

浅谈图书馆随书光盘的管理与利用

介绍了随书光盘文献的类型,分析了随书光盘文献的管理现状,探讨了如何加强随书光盘的管理。     

基于单片机的汽车刹车片实时温控系统

温度是影响刹车片性能的一个重要的环境变量,它直接制约着刹车片的制动性、耐磨性等各方面的性能。为了提高汽车行车制动安全,一方面可从材料上提高其制动性、耐磨性,另一方面也可利用现代电子技术引入刹车片实时温控的概念改善刹车片工作性能。文中提出了一个利用AT89C2051单片机对温度传感器MAX6577输出的信号频率进行计算处理,控制引自汽车水箱的冷却管线上的电磁阀开关,从而实现汽车刹车片温度实时监控的设计方案。该设计包括温度控制,水箱液位检测和报警等内容。     

浅议随书光盘的管理

介绍了随书光盘的概念、特点和常用的几种管理模式,分析了目前图书馆采用的随书光盘的管理方法和存在的不足,对随书光盘的管理模式提出了一些建议。     

深度学习中对比散度算法的有偏性分析

为了给对比散度算法的进一步优化提供理论指导,尝试从理论上分析对比散度算法的收敛性。首先从仅含4个结点的玻尔兹曼机入手,利用单纯形表征模型的概率空间,以及流形表征概率空间与模型参数的关系,形象地表示了对比散度算法和极大似然算法的收敛过程,并从理论上推导出对比散度算法的收敛集与极大似然算法的收敛集之差不为空,从而证明了对比散度算法的有偏性。基于该结论,设计了一种先利用对比散度算法进行预训练,再利用极大似然算法调优的训练策略。实验结果表明,在应用该策略获得同等收敛效果的条件下,训练迭代步骤降低了83.3%。     

延长双绞线的传输距离

在计算机网络布线中,双绞线是常用的一种传输介质,然而常会有传输距离超过了线缆允许的最大长度的情况,文章着重讨论了如何有效延长双绞线的最大传输距离.