预处理条件对Ag/SBA-15催化剂上甲苯催化氧化反应性能的影响

甲苯是一种典型的挥发性有机污染物.近年来,催化氧化法是一种广泛使用并具有开发潜力的有效去除挥发性有机污染物的方法,而贵金属催化剂一直是首选.介孔二氧化硅材料SBA-15具有规则孔道和较高的比表面积因而在催化领域中具有较大的应用潜力.本课题组已对一系列的SBA-15负载的纳米银催化剂的制备和低温催化氧化性能进行了研究,本文则通过研究不同预处理处理气氛对Ag/SBA-15催化剂结构以及甲苯催化氧化性能的系统研究,获得纳米银催化剂结构与甲苯催化氧化性能间的构效关系,对新催化剂的结构优化以及甲苯催化净化的低温催化剂开发具有重要的科学意义.研究表明,处理气氛明显影响了银物种和氧物种的状态,进而影响了催化剂的催化活性,先氧气(500℃)后氢气(300℃)处理的O500-H300催化剂对甲苯的反应活性明显优于在500℃氧气处理样品O500及氢气处理样品H500.由X-射线衍射和O2-程序升温脱附(TPD)可知,氧气500 oC处理使催化剂上形成大颗粒银粒子和氧化银粒子,以及大量次表层氧物种.氢气处理使催化剂形成较大的银粒子,由于未经过氧气处理,该催化剂上并没有次表层氧的生成.先氧气处理再氢气处理后催化剂上形成高分散的小粒径银粒子以及次表层氧物种,这表明低温氢气处理可以降低银粒子的尺寸并使催化剂上的银粒子得到再分散,同时不会影响次表层氧物种的形成.从催化剂的甲苯吸附和TPD实验中看出,大尺寸银粒子对甲苯具有较强的吸附性能,从而有利于甲苯在低温的催化氧化,但是在高温反应中没有优势;小尺寸银粒子虽然对甲苯的吸附能力不强,但是对分子氧有较好的吸附作用,进而增强自身与甲苯的相互作用,而且也促进了分子氧的活化,预处理中形成的次表层氧有效增强了甲苯和银粒子的相互作用,因此,先氧气后氢气处理的O500-H300样品在反应中显示出最好的甲苯催化活性.     

近红外光谱法定性描述酵母菌的生长过程

提出了一种基于近红外光谱分析技术的酵母菌生长过程描述方法.利用Antaris Ⅱ型傅里叶变换近红外光谱仪获取酵母菌培养过程中,发酵物样本在10000~4000 1范围内的光谱数据,同时采用光电比浊法测定各样本的光密度(Optical density, OD)值;运用竞争性自适应重加权采样(Competitive adaptive reweighted sampling, CARS)算法优选特征光谱,再利用极限学习机(Extreme learning machine, ELM)建立酵母菌生长过程4个阶段的分类模型.研究结果显示,参与CARS-ELM模型建立的波长个数为30,其10次运行在训练集和测试集中的平均识别率分别为98.68%和97.37%.研究结果表明,利用近红外光谱分析技术结合适当的化学计量学方法描述酵母菌生长过程是可行的.     

Rapid protein expression analysis with an interferometric biosensor for monitoring protein production

The concentration of a recombinantly expressed protein has to be monitored to select optimal expression conditions throughout the protein production process. Today this is usually achieved semiquantitatively with sodium dodecyl sulfate polyacrylamide gel electrophoresis/western blotting or with ELISAs, which are time- and labor-intensive methods. In this paper the applicability of a label-free sensor system based on a Young interferometer is presented as an alternative for the monitoring of recombinant protein production. Once a protein is successfully produced, the interferometric biosensor allows any protein–protein interaction to be characterized in a label-free manner. This is demonstrated with an antibody/antigen pair, where the antibody is directed against a four-amino-acid tag used for protein expression analysis as well as purification during recombinant protein production. Label-free detection of the tagged protein is shown both in buffer and in bacterial cell lysate as a sample matrix. The system exhibiting a low limit of detection, low drift and reliable operation is compared with a commercial surface plasmon resonance sensor and a competitive ELISA. Figure 1 Waveguide sensor chip; grating (green) illuminated by a red light source. Image courtesy of Unaxis Optics Electronic supplementary material Supplementary material is available in the online version of this article at and is accessible for authorized users.     

光谱分析法研究八羧酸酞菁铝配合物与牛血清白蛋白的结合作用

以八羧酸酞菁铝配合物(AlPc(COOH)8)为红区荧光探针,用紫外光谱和荧光光谱分析方法研究了(AlPc(COOH)8)与牛血清白蛋白(BSA)的结合作用,测定了八羧酸酞菁铝与牛血清白蛋白(BSA)的结合位置数和结合常数,结果分别为n=5.7,K=5.74×105和K=3.51×105,两种分析方法结果基本一致.以氯血红素(HE)、布洛芬(IB)、L-色氨酸(TRP)为分子探针,用络合竞争法研究了它们对AlPc(COOH)8-BSA体系紫外光谱的影响,结果表明,往体系中加入HE后,AlPc(COOH)8的单体吸收峰增强,体系由结合态往游离态"转变",而加入TRP和IB后,吸收光谱未观察到明显的变化,由此确定AlPc(COOH)8与BSA的结合点为SiteⅠ.     

敬告读者——《光谱学与光谱分析》已全文上网

从2008年第7期开始在《光谱学与光谱分析》网站(www.gpxygpfx.com)“在线期刊”栏内发布《光谱学与光谱分析》期刊全文,读者可方便地免费下载摘要和PDF全文,欢迎浏览、检索本刊当期的全部内容;并陆续刊出自2004年以后出版的各期摘要和PDF全文内容。2009年起《光谱学与光谱分析》每期出版日期改为每月1日。     

Evolutionary consequences of harvesting for a two-zooplankton one-phytoplankton system

Considering the impact of harvesting on the coexistence and competitive exclusion of competitive predators, a two-zooplankton one-phytoplankton model with harvesting is proposed and investigated. First, stability criteria of the model is analyzed both from local and global point of view. Second, two types of zooplankton will competitively exclude each other in the absence of harvesting with the zooplankton with the larger threshold persisting. If harvest rates are discriminate, then a dominant zooplankton may occur depending on the harvesting level. Thus, for some harvesting levels, the zooplankton one may persist while for other harvesting levels zooplankton two may persist. Furthermore, the value of the harvesting level and coexistence line are obtained when coexistence occur. Finally, the impact of harvesting is mentioned along with numerical results to provide some support to the analytical findings.     

Sequential competitive location on networks

We present a survey of recent developments in the field of sequential competitive location problems, including the closely related class of voting location problems, i.e. problems of locating resources as the result of a collective election. Our focus is on models where possible locations are not a priori restricted to a finite set of points. Furthermore, we restrict our attention to problems defined on networks. Since a line, i.e. an interval of one-dimensional real space, may be interpreted as a special type of network and because models defined on lines might contain ideas worth adopting in more general network models, we include these models as well, yet without describing them in detail for the sake of brevity.     

Competitive facility location and design with reactions of competitors already in the market

A new retail facility is to locate and its service quality is to determine where similar facilities of competitors offering the same goods are already present. The market share captured by each facility depends on its distance to customers and its quality, which is described by a probabilistic Huff-like model. In order to maximize the profit of the new facility, a two-stage method is developed, which takes into account the reactions of the competitors. In the quality decision stage, the competitive decision process occurring among facilities is modelled as a game, whose solution is given by its Nash equilibrium. The solution, which can be represented as functions of the location of the new facility, is obtained by analytical resolution of a system of equations in the case of one facility in the market or by polynomial approximation in the case of multiple facilities. In the location decision stage, an interval based global optimization method is used to determine the best location of the new facility. Numerical experiments on randomly generated instances demonstrate the effectiveness of the method.