Fukui函数和局域软度应用于亲电加成反应的区位选择性的研究

Fukui函数、局域软度、广义Fukui函数以及广义软度通常被称为反应描述符。使用它们研究和探讨了HCl与不对称烯烃以及溴苯硒与不对称苯乙烯的亲电加成反应的区位选择性。在MP2/6-311++G(d, p)理论水平下,采用有限差分方法计算这些反应描述符,同时也使用ABEEMσπ方法进行了计算。ABEEMσπ模型下的局域软度和广义局域软度,分别结合局域硬-软酸碱(HSAB)原理,得出亲电试剂氯化氢与溴苯硒,更容易进攻不对称乙烯和苯乙烯中的马氏碳原子,符合马氏规则。而有限差分方法不能完全地解释该系列反应的区位选择性。此外,主要产物所对应的马氏碳原子的广义局域软度值,就能够预测出此类反应的活性序列,所得结果与速率常数有很好的关联。     

The degradation and local tissue effects of collagen hydrogel and sponge implants in muscle

Collagen products will degrade and evoke certain local tissue reaction after being implanted. ISO 10993.6 is the international standard to evaluate local tissue reaction for biomaterials. However, even in the present version, it does not define the specific view fields for scoring local tissue reaction in the sections, which may influence the fair evaluation for the degradable polymer, such as collagen. In this study, 4 kinds of collagens and 2 kinds of bio-inert products were implanted into the rabbit muscle for 26 weeks, and two different scoring methods (uniform distribution scoring method and area locating scoring method) were applied to evaluate the local tissue reaction for each implant. The results showed that the tissue reaction on the interface was active, but the various scores in the implant and surrounding areas could help us to understand the differences of the degradation process. An area locating scoring method which selected the fields in the implant, interface and surroundings respectively showed a higher total score and offered more detailed information compared to the uniform distribution scoring method. Since the degradation and tissue reaction degree in the different areas are ever changing for the degradable implants, this area locating scoring method is sensitive, effective and applicable for the semi-quantitative evaluating system of ISO 10993.6.     

Local electrochemical impedance spectroscopy: A window into heterogeneous interfaces

The ability to probe surface reactivity on a local scale has led to a new insight into the comprehension of the electrochemical reactivity in relation with the microstructure of the surface. Among the different techniques developed in recent years, local electrochemical impedance spectroscopy has the advantage of using a transient approach to locally characterize a stationary electrochemical system without the need to add any redox mediator in solution, which is a great advantage for the study of different systems.In this review, particular attention is paid to the different ways of measuring the local impedance, and the technique implementing a local current measurement in solution is deeply discussed. This local electrochemical impedance spectroscopy journey also encompasses a discussion about technical and experimental limitations.