Caffeine selectivity of divinylbenzene crosslinked polymers in aqueous media

The selective binding of caffeine to polymers is of interest in developing caffeine-specific sensors. The influence of the nature and quantity of crosslinking agents and functional monomers on the selectivity and binding affinity of a polymer to caffeine is reported. A high binding affinity and selectivity of divinylbenzene (DVB) crosslinked polymers toward caffeine was exhibited by the binding competition of caffeine with several dimethylated and chlorinated xanthines and N-methylated uric acids in aqueous media. To understand the nature of the caffeine–polymer interaction, we performed binding studies with solvents of different polarities and ionic strengths. The binding properties of DVB-based polymers containing different functional monomers were compared with Amberlite^® XAD resins. Analytes with hydrophilic and electron-withdrawing groups lowered their binding affinity with the polymer in comparison with caffeine and its dimethylated derivatives. The caffeine–polymer interaction appeared to be predominantly a hydrophobic π–π interaction but partly due to the presence of caffeine-specific sites. The reversibility of the caffeine–polymer binding was investigated, and the dissociation constants were approximated to be 27 and 6 mM. Dipole moments of caffeine and related molecules were estimated theoretically and were correlated with their corresponding B/T ratio, which is defined as the fraction of caffeine bound to the polymer. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 195–205, 2001     

如何建立流动人口综合治理工作机制

流动人口是一支较为活跃的社会群体,随着社会主义市场经济的迅速发展,流动人口的数量逐年增多,人口的频繁流动,给社会治安、计划生育、城市管理带来许多新情况、新问题、抓好流动人口综合治理与服务工作逐步成为一项重要工作内容.     

Multi-Criteria Decision Making support system for pancreatic islet transplantation

Pancreatic islet transplantation consists of replacing insulin-producing cells to restore normal glycemia in diabetic patients. This is a minimal invasive procedure that has been proved successful. Unfortunately unpredictability of islet transplant outcome remains a frustrating and costly issue limiting the clinical implementation of this procedure. Multiple variables are involved in the procedure and assessment is subjective to individual operators. The aim of this study was to generate a system expressing the probability of transplant success in relation to four classes of identified variables (donor, organ, isolation and recipient). We have proposed the utilization of Multi-Criteria Decision Making methods (MCDM) as a powerful tool for evaluating pancreatic islet transplant-related information with the goal to achieve optimal decision. Technique Ordered Preference by Similarity to the Ideal Solution (TOPSIS), one of the most widely used MCDM methods in decision support systems, was here utilized with modification to fit better in a medical system. In our modified method, we have utilized fuzzy logic in order to consider uncertain and vague data.     

Study on the interactions between soy and semolina proteins during pasta making

Spaghetti produced in a pilot plant were made from semolina and semolina blended with 10%, 15%, 25% or 50% of defatted soy flour (DSF) or toasted soy flour (TSF).Proteins of spaghetti were characterized by size exclusion-high-performance liquid chromatography (SE-HPLC). Results showed that soy globulins interact with semolina proteins during pasta making, forming polymers of high molecular weight. Of these, the sodium dodecyl sulphate-unextractable components were significantly higher (p < 0.001) (up to 49% unextractable polymeric proteins) (UPP) than that of spaghetti made of semolina (24.6% UPP). The decrease of S–S bonds and the increase of –SH free groups in the DSF–semolina spaghetti, with respect to that made of only semolina, suggest that polymerization among the different classes of proteins involves interaction by sulphydryl residues in blends with above 15% of DSF and that soy proteins tend to disrupt own gluten S–S interchange system. In the TSF–semolina spaghetti the increase of S–S bonds was higher with respect to that of –SH free, suggesting that the heat treatment, to which the TSF proteins were subjected, allowed them to cross link to semolina proteins by disulphide bonds.     

长距离、低成本采购可能会占用流动资金

据工信部日前最新消息：今年上半年，我国西部地区水泥产量为2．3亿吨，同比增长25．9％，增速远高于东部和中部地区。但西部地区水泥出厂价格则呈持续下降态势。     

Influence of electrodeposition parameters of Ni–W on Ni cathode for alkaline water electrolyser

In this study, different Ni–W coatings, obtained by cheap and technologically simple electrodeposition method, were examined as potential electrocatalysts for the hydrogen evolution reaction (HER). All electrodepositions were done on a Ni mesh substrate from ammoniacal-citrate bath containing different concentrations of Na₂WO₄. The influence of deposition parameters, such as deposition current density, pH and composition of ammoniacal-citrate bath on electrocatalytic activity of obtained Ni–W coatings toward HER was examined by polarization curve measurements in 6 M KOH at room temperature. The morphology and tungsten content of the Ni–W coatings were investigated by means of SEM and EDS analysis. All investigated electrodes have shown high electrocatalytic activity for the HER. The samples obtained at higher deposition current densities had the lowest overvoltage for the HER. It has been shown that the plating bath pH value is very important parameter in obtaining active coatings. Results of the analysis of polarization curves, morphology of deposited Ni–W coatings and the content of tungsten in the coatings, indicate that the surface roughness of the coatings is responsible for their catalytic activity towards HER.     

利用光栅实时测量激光波长的方法

探讨了利用光栅实时测量激光波长的理论依据，并进行了误差分析；尝试并实现了利用光栅实时测量激光波长的方法，预见到光栅是实时测量宽频带、脉冲激光波长的有效元件。     

燃油池窑改烧发生炉煤气池窑的设计

本文对燃油池窑改烧发生炉煤气池窑的设计进行了探讨，给出了一个实际冷修方案。