Adsorbing behavior of polycarboxylate superplasticizer in the presence of the ester group in side chain

The effect of the ester group in side chain on adsorbing behavior and dispersion of polycarboxylate superplasticizer (PC) was studied by comparing the performance of two types of PC. The fluidity of cement paste was tested to discuss the dispersing ability and dispersing retention ability of PC. The total organic carbon analyzer was used to measure the adsorption amount, and the adsorption layer was obtained by x-ray photoelectron spectroscopy. Fourier-transform infrared spectroscopy, nuclear magnetic resonance, and pH value were used to verify the stability of the ester group, and the electrokinetic properties of cement particle were confirmed using the zeta potential measurement. The results show that the ester group in side chain reduces the initial dispersing ability while it increases the dispersing retention ability. The dispersing retention ability depends on the increase of adsorption amount and adsorption layer in 5–60 minutes, and the greater increase leads to the better dispersing retention ability. The ester group can be decomposed to release carboxyl group to enhance the adsorbing ability of PC under the condition of cement hydration, which is the main reason for the greater increase of adsorption amount and adsorption layer and the improvement in dispersing retention ability. It suggests that grafting the ester group is a good way to enhance the dispersing retention ability.     

高校化学类专业课程思政建设目标与实现途径刍议——以物理化学课程教学为例

课程思政建设是当前专业课程教学改革的重要内容。课程思政建设应以专业人才培养目标为指引,基于"以学生为中心""以产出为导向"的理念进行系统设计和实施。本文以物理化学课程教学为例,介绍如何围绕课程教学目标,对课程思政进行系统设计,深入挖掘课程育人功能,突出世界观和方法论教学,突出学生综合评价能力、学科思维能力和批判创新能力的培养,推动专业教学由知识导向型向能力和素质导向型转变。     

ISOLATION OF MUTANTS OF THE FUNGUS Cercospora nicotianae ALTERED IN THEIR RESPONSE TO SINGLET-OXYGEN-GENERATING PHOTOSENSITIZERS

Fungi in the genus Cercospora produce a singlet-oxygen-generating photosensitizing toxin cercosporin, which plays an important role in the ability of these fungi to parasitize plants. Previous studies demonstrated that resistance to cercosporin was associated with the ability of the fungus to reduce and detoxify cercosporin transiently. In order to characterize the mechanism of cercosporin resistance further, two types of mutants were isolated. One set of mutants was selected directly for sensitivity to cercosporin. Six cercosporin-sensitive mutants were isolated. Five of the mutants were totally inhibited by cercosporin as well as by five other photosensitizers, methylene blue, toluidine blue, eosin Y, rose bengal and hematoporphyrin. These five mutants were also deficient in cercosporin-reducing ability. The sixth cercosporin-sensitive mutant was only partially inhibited by cercosporin. This mutant was unaltered in cercosporin-reducing ability and in its response to the other photosensitizers. In order to test hypotheses concerning the mechanism of cercosporin reduction, a second set of mutants was selected for general deficiency in cell surface-reducing capability by screening for the inability to reduce two tetrazolium dyes (p-tolyltetrazolium red and 2,3,5-triphenyltetrazolium chloride) of similar redox potential to cercosporin. Dye-reduction-deficient mutants were unaltered in their resistance to cercosporin and in cercosporin-reducing ability. We conclude that cercosporin resistance of these fungi is strongly correlated with the ability to reduce cercosporin. However, cercosporin-reducing ability is separable from the general ability to reduce external electron acceptors.     

口诀教学对高一学生氧化还原反应分析能力的影响

探讨在高一年级氧化还原反应新课教学中,使用口诀教学对学生氧化还原反应分析能力的影响,涉及简单氧化还原反应的分析广度和速度、不同复杂程度氧化还原反应的分析深度.结果显示:口诀教学对实验组学生氧化还原反应分析能力的形成和发展,起到良好的即时效果和保持效果;实验组和对照组学生的分析能力在教学过程中均获得显著提高,但表现出不同...     

维生素C磷酸酯镁的稳定性及其清除超氧离子自由基的动力学

维生素C磷酸酯镁(magnesium ascorbyl phosphate,MAP)是维生素C(VC)的替代品,由于其特有的性质而广泛应用在食品添加剂中.对比测定了MAP和VC清除超氧阴离子自由基(O2-·)的能力,研究了VC和MAP在不同温度和不同保存时间后清除O2-·自由基的能力和稳定性;并拟合了不同温度下储存不同时间后MAP的抗氧化能力.结果表明,MAP在20℃下保存20d对O2-·的清除能力仅减弱20%左右,半衰期为53d;但VC在20℃下保存10d后清除O2-·的能力几乎完全消失.与此同时,不同温度下储存不同时间后MAP清除超氧阴离子自由基的反应为一级反应,采用拟合方程计算的抗氧化能力理论值和实验值基本相符.     

电解质溶液界面结构的分子动力学模拟研究

电解质溶液界面结构的研究不仅具有重要的理论意义, 而且具有一定的实用价值. 采用分子动力学模拟研究了LiCl, LiBr, LiI, NaI, KI, CsI水溶液中阴阳离子在1×105 Pa和300 K下的气液界面分布情况, 探讨离子水化与电解质溶液界面结构的关系, 并分析阳离子水化能力的强弱对共存阴离子在界面富集分布的影响. 通过对模拟结果的分析发现, 离子的水化能力越强, 就越能形成稳定的水化结构而处于本体相中, 水化能力越弱, 则越易在界面富集. 该机理合理地解释了离子在界面的分布现象, 阳离子水化能力一般较其共存阴离子强而处于本体相, 阴离子则趋向在界面处富集; 不同阴离子在界面的密度分布也与阴离子的水化能力相关, 阴离子水化能力越弱, 其在界面富集程度越高, 不同阴离子在界面的富集趋势为Cl－＜Br－＜I－; 阳离子水化能力的强弱也影响其共存阴离子在界面的富集程度, 阳离子的水化能力越弱, 其共存阴离子在界面的富集程度就越低.     

A novel terpyridine/benzofurazan hybrid fluorophore: metal sensing behavior and application

Terpyridine/benzofurazan conjugation results in a new hybrid fluorophore of the colorimetric sensing ability for Fe(2+) and fluorimetric sensing ability for XII group cations. The improved emission properties and cell imaging ability imply it is a suitable platform to construct a fluorescent sensor for metal imaging in biological systems.     

环糊精高分子

环糊精以其独特的包合特性而引入注目，已被广泛地应用于化学分离及分析、药物控制释放、食品加工和环境保护等领域。环糊精高分子亦被证实具有包含、缓释及催化的能力，以及良好的机械强度和化学稳定性。本文综述了国内外关于环糊精高分子的类型、合成方法及实际应用的最新研究进展。     

提高化学师范学生实践与创新能力的实践探索

师范生教育实践和创新能力是教师培养的薄弱环节,为此,西北师范大学化学化工学院通过实施教师教育能力和科研创新能力提升计划等举措,着重加强对学生教学实践和创新能力的培养,主要采用实践环节教学与中学教学实际相结合、专业学习与科研创新有效结合等方法,有效提高了化学师范生的实践与创新能力。     

以大型仪器为依托构建本科生科研素质培养的新模式

本文以江汉大学高分子材料与工程专业本科教学为例,提出以大型仪器为依托构建本科生科研素质培养的新模式。借助于大型仪器在本科生科研素质培养中的优势作用,采用建立在线资料库、大型仪器模拟仿真、大型仪器操作实训、组建学生科研团队和建立多元化考核评价体系等措施,进一步激发学生的学习兴趣,培养学生的自主学习能力、独立思考能力、团队协作能力和创新能力。通过转变学习方式和方法,提升学生的学习和科学研究等方面的综合能力,为高素质、有特色的应用型技术人才的培养提供一定的参考。     

环糊精聚合物在药物研究中的应用

环糊精聚合物既保持了环糊精包结、缓控释、催化和识别的能力,又兼具高聚物良好的机械强度、较好的稳定性和化学可调性,是一类很有潜力的功能高分子材料,引起了越来越多的关注。本文在概述了国内外关于环糊精高分子的类型及合成方法的基础上,重点综述了环糊精高聚物在药物的手性分离、分子印迹技术、给药系统以及在提高药物溶解度等方面的最新的研究进展。     

Antioxidant and photo-antioxidant abilities of catechins

Catechins are studied vigorously, in particular, concerning the antioxidant ability as polyphenol, which is generally considered responsible for photo-antioxidant natures of catechins. In this study, the antioxidant and photo-antioxidant abilities of (+)-catechin, (−)-epicatechin, and epigallocatechin have been investigated kinetically and discussed in detail. As a result, this study clarifies that a strong antioxidant is not always a good photo-antioxidant as well as that catechins show a high antioxidant ability in an initial oxidation process and acquire a photo-antioxidant ability with the progress of photo-oxidation. In particular, (+)-catechin and (−)-epicatechin convert into quercetin to show a remarkable photo-antioxidant ability almost comparable to quercetin. In this case, (−)-epicatechin has a higher photo-antioxidant ability than (+)-catechin, although they differ only in the configurations. These facts are explained by the direct conversion of the catechins into quercetin.     

Investigation of the peel test for measuring self-cleanable characteristic of fluorine-modified coatings

The self-cleanable ability of coatings is important to prevent or remove polluting fingerprints, dust, water and oils for a number of applications. Fluorocarbon polymers have been used to provide self-cleanable ability due to their low surface energy. The efficiency of fluorine-modified coatings has been evaluated by measuring surface free energy using a contact angle measurement. However, this method is not sufficient to define the polluting-preventive ability or removability of fluorine-modified coatings due to the amount of fluorine content.A peel test can be used to determine the self-cleanable characteristics of fluorine-modified coatings by evaluating adhesion between the coating surface and pressure sensitive adhesives (PSAs). In addition, adhesion can be used to predict the amount of polluting-preventive ability or removability of coatings by comparing the peel strength of commercial PSAs. We designed fluorine-modified acrylic resins with different fluorine contents for a new testing method. Comparing the contact angle measurement with the peel test results, the peel test for the self-cleanable characteristic of coatings was more suitable than the contact angle measurement to predict the polluting-preventive ability and removability of coatings.     

分子模拟方法考察泡沫生成能力

采用分子模拟的方法研究表面活性剂的泡沫生成能力, 以界面形成能作为考察泡沫体系中液膜界面积的量化依据, 研究了泡沫液膜厚度、表面活性剂分子界面密度以及表面活性剂类型对泡沫液膜界面形成能计算的影响. 通过与实验结果相对应, 建立了界面形成能和泡沫生成能力之间的联系.     

Sequence-selective and hydrolytic cleavage of DNA by zinc finger mutants

We have reported the successful conversion of the structural zinc site in zinc finger peptides to a functional zinc site. A series of resulting zinc finger mutants exhibit the hydrolytic ability of the activated ester depending on the coordination geometry and acidity of the zinc ions. In this study, we explored the hydrolytic ability of DNA by the H4 mutant since the mutant showed the highest hydrolytic ability of the activated ester among the series of mutant peptides. The zinc-bound form of the H4 mutant peptide exhibited the hydrolytic ability of activated phosphoesters and even converted the supercoiled plasmid to the nicked circular form. An increasing ionic strength leads to a loss in the nuclease ability of the zinc finger mutants due to the nonspecific interaction between the zinc finger peptide and DNA. In sharp contrast, the three-tandem H4-type zinc finger protein performed the specific DNA hydrolysis at the GC box even at a high ionic strength. Thus, the present study demonstrated that converting the native zinc site to the hydrolytic zinc site in the zinc finger protein is a novel approach for creating artificial nucleases with sequence selectivity.     

有机化学专业核心课程群教学质量提升改革实践

针对当前有机化学专业核心课程群教学中存在的问题,开展了相应的教学质量提升改革。通过细化课堂教学实施方案,引导学生课前主动预习;通过分段式课堂教学,提高学生课堂参与度;通过多层次的课后练习,提高学生的综合能力;通过提高考题的高阶性,引导学生注重思考能力和综合能力的发展。经过这样的教学质量提升改革,学生学习的主动性、思考能力和综合能力得到了显著的提高,为培养知识、能力和思维全面协调发展的创新人才奠定了坚实的基础。     

表面活性剂亲水-亲油能力对动态界面张力的影响

当两个不互溶的液相接触时 ,如果其中一相或两相含有表面活性物质 ,就可能产生动态界面张力 .两相间的界面张力随时间连续变化 ,直到平衡为止 .在到达平衡的过程中 ,经常通过一个最低值 .酸 性油 /碱水体系也会出现类似现象 .England和 Berg[1]把动态界面张力解释为表面活性物质在界面上累积的结果 ,并观察到 1,5-戊二醇由白油向水 中传质时存在明显的吸附-脱附位垒 .Rubin和 Radke[2]首次给出了解释酸性原油与碱水溶液接触时产生动态界面张力的物理模型 ,他们提出在油水界面上存在一个表面活性物质的脱附位垒 ,原油中的酸性物质与氢氧化…     

PtFe掺杂石墨烯抗CO中毒性能的理论研究

基于密度泛函理论第一性原理研究了以单空位缺陷(SV)石墨烯为载体的Pt,Fe及PtFe二元金属催化剂的抗CO中毒能力.结果表明,对于单金属原子Pt和Fe,Fe更易吸附在SV石墨烯上;而对于PtFe二元金属催化剂,SV石墨烯对其固定能力明显好于Pt-SV,即Pt催化剂中掺杂Fe大大增加了SV石墨烯对金属催化剂的稳定性.Pt,Fe及PtFe二元金属催化剂抗CO中毒能力的研究结果表明,PtFe-6结构的抗CO中毒能力明显强于Pt-SV,接近于Fe-SV的抗CO中毒能力,在所有二元金属催化剂中PtFe-6的稳定性最好,明显优于Pt在SV石墨烯上的稳定性.通过在Pt中加入非贵金属Fe既可提高DMFC中阳极Pt催化剂的抗CO中毒能力,又可提高其催化活性.     

THE EFFECTS OF GROWTH-INHIBITING TREATMENTS ON PHOTOREPAIR IN CULTURED FISH CELLS

Abstract Goldfish cells (RBCF-1) cultured at different cell densities were harvested and their photorepair (PR) abilities were examined in terms of survival. Photorepair ability gradually increased during the phase of logarithmic growth, reaching a maximum in cells at the confluent state. This enhancement of PR ability disappeared 12 h after replating of cells in fresh medium. A number of growth-inhibiting treatments (serum depletion, UVC, hydroxyurea [HU], change in incubation temperature) were tested for their ability to induce PR. The treatment of cells with HU and serum depletion induced PR while the other treatments did not. The increase in the ability to perform PR after treatment with HU or serum depletion returned to normal levels more rapidly than that after fluorescent light treatment.     

基于专业课程培养本科生创新精神和科研能力——以无机合成化学为例

以无机合成化学为例进行了基于专业课程培养本科生创新精神和科研能力的教学方法改革,探索以专业课程为载体加强本科生创新精神和科研能力的培养,提高学生在学习中的主体地位,培养勤于思考、敢于怀疑、勇于创新的素质和精神,提升科研能力,形成终身学习的能力和习惯。教学改革取得了一定的成效。