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71.
Recently, special attention has been paid to the development of active wound dressing materials based on biopolymers. Collagen is a natural polymer, which meets the requirements of modern materials for medical applications. However, despite its unique properties, collagen has no antimicrobial activity. In this work thymol was incorporated into collagen films to meet antimicrobial properties of the material. Thymol is a naturally occurring phenolic compound recognized as an antimicrobial agent. Collagen/thymol thin films were obtained through solvent evaporation using collagen solutions containing different amounts of thymol. The structure of the obtained materials was studied using FTIR-ATR spectroscopy. The inhibition ability on the growth of several strains of microorganisms was tested. The standard ISO 22196:2007 was used to define the bactericidal properties of the material. The growth of the following bacteria on the collagen/thymol films was studied: Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, Bacillus subtilis, Enterobacter aerogenes, Candida albicans. The results showed that the growth of Staphylococcus aureus was the most inhibited compared to the other tested strains. Collagen/thymol material is more efficient against pathogens through direct contact compared to the diffusion of thymol from the material. In general, the thymol addition inhibits biofilm formation on the collagen surface. 相似文献
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Yun-an Yan 《化学物理学报(中文版)》2017,30(3):277-286
A wide range of quantum systems are time-invariant and the corresponding dynamics is dictated by linear differential equations with constant coefficients.Although simple in mathematical concept,the integration of these equations is usually complicated in practice for complex systems,where both the computational time and the memory storage become limiting factors.For this reason,low-storage Runge-Kutta methods become increasingly popular for the time integration.This work suggests a series of s-stage sth-order explicit RungeKutta methods specific for autonomous linear equations,which only requires two times of the memory storage for the state vector.We also introduce a 13-stage eighth-order scheme for autonomous linear equations,which has optimized stability region and is reduced to a fifth-order method for general equations.These methods exhibit significant performance improvements over the previous general-purpose low-stage schemes.As an example,we apply the integrator to simulate the non-Markovian exciton dynamics in a 15-site linear chain consisting of perylene-bisimide derivatives. 相似文献
74.
Qing-yao Wang Jia-qi Fang Lu-lu Deng Xiao-jiang Hao Shu-zhen Mu 《Chemistry Central journal》2017,11(1):138
The regioselective demethoxylation and dehalogenation of dihalogenated dibenzocyclooctadiene lignans derivatives were realized in a one-step reaction with excellent yields in the sodium and t-butanol reaction system. 相似文献
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In this paper, we analyze finite time stability for a class of differential equations with finite delay. Some sufficient conditions for the finite time stability results are derived based on delayed matrix exponential approach and Jensen’s and Coppel’s inequalities. Finally, we demonstrate the validity of designed method and make some discussions by using a numerical example. 相似文献
77.
为了解西南某典型山地煤矿区周边农田土壤、农作物重金属的富集情况及对当地人群健康的影响程度,采集矿区周边农田土壤样品和对应的农作物样品,测定重金属Cr、Mn、Zn、As、Pb的含量。运用Nemero指数法、潜在风险指数法对土壤重金属的污染程度进行评价;采用靶标危害系数法(THQ)评价农作物重金属对人体的健康风险。结果显示,Cr、Mn、Zn、As、Pb分别是背景值的1.81、1.90、2.89、1.30、0.86倍,处于轻度污染级别,轻微危害程度。农作物重金属Cr、Pb和As含量的超标情况较严重,Zn的含量超标相对较小。各农作物富集的重金属对人体的健康风险大小为:高粱>玉米>白菜>葱>辣椒。农作物重金属对儿童健康的危害均达到了慢性中毒;对成人健康的影响,高粱处于慢性中毒,其它农作物重金属处于产生较大影响的危害程度。农作物重金属与土壤重金属的相关性分析表明,农作物重金属的含量与土壤重金属全量并无线性关系;各重金属在农作物中的转移能力不同;Pb,As在农作物中的转移能力较大,而Cr相对较小。鉴于矿区重金属的富集情况,应尽快采取修复治理措施,为保证当地人群健康,建议当地居民不再食用和种植富集重金属严重的高粱、玉米农作物。 相似文献
78.
Sulfone derivatives, an important synthetic strategy in drug discovery, are acquiring more importance in plant protection field in recent years because of their pesticide activities, such as antifungal, antibacterial, acaricidal, insecticidal, herbicidal, and antiviral activity. Introduction of different pharmacophores into sulfone framework can afford a series of sulfone derivatives to build some sulfone derivatives as novel active molecules. The purpose of this review was to collate literature work reported by researchers on sulfone derivatives for their various pesticidal activities from year 2010 to 2020. 相似文献
79.
咔咯是由四个吡咯共轭相连而形成的具有芳香性的新型卟啉类大环化合物,但咔咯分子中存在一个直接连结两个吡咯环的C?C键,与卟啉相比,仅仅是少了一个“meso”位置的C原子.因此,在结构上,咔咯含有三个“吡咯型”氮原子和一个“吡啶型”氮原子,当咔咯失去三个内氢原子后变成了三价阴离子,易与金属形成高价态的稳定配合物.氮杂咔咯是一种咔咯的meso位上的C被取代为N的咔咯衍生物.与正常的咔咯相比,它更易于与过渡金属形成稳定配合物.正是由于这些独特的结构特点,使其在金属催化、染料敏化太阳能电池、光敏剂、金属传感器、甚至在医学上都有很好的应用前景.金属有机大环均相催化剂的非均相化,是改进反应产物分离和实现催化剂循环使用的最简单有效方法之一.环境友好的Mn氮杂咔咯催化剂,在温和条件下可以利用氧气直接将有机底物氧化.本文选用Mn氮杂咔咯催化剂作为基本构建单元,通过理论计算,构建了一种新型的具有高催化活性的含Mn氮杂咔咯环结构单元的二维纳米催化材料.我们分别使用高斯软件(Gaussian 09)和维也纳从头算模拟软件包(VASP)对孤立分子和周期性体系进行结构优化以及性质的计算.在这种二维材料中,每一个Mn原子作为相对独立的金属单原子中心(SAC),保留了单环中Mn金属中心的高催化活性.在温和的光照条件下,Mn金属中心可以直接活化氧气生成类自由基[Mn]-O-O中心,随后[Mn]-O-O中心可以有效地通过夺取有机底物中的H和紧接着新生自由基的偶合反应,选择性氧化C?H键为C?OH键.另外,通过沿[Mn]-O-O反应轴施加不同强度的外电场,可对此二维纳米材料的催化反应活性进行精细调控.本文为实验上制备基于Mn氮杂咔咯的非均相催化剂以及单原子Mn基催化剂提供了理论依据. 相似文献
80.