教育实证研究中研究工具开发与写作的品质要求

针对我国教育实证研究缺乏明确的质量追求和品质标准的问题,提炼了定量研究中成就测验、问卷、李克特量表等研究工具的品质要求,明确了研究工具开发的流程及品质要求,厘清了实证研究论文中研究工具写作的原则及内容要求。利用建构的品质指标分析了实证研究论文案例,指出了其优点及存在的问题。     

中学化学教师对实验装置研究现状分析与启示

实验装置研究一直是中学化学教师实验研究的重点,也是热点。通过文献分析的方法,对当前中学化学教师实验装置研究的现状进行了分析,从研究数量、研究内容、研究方法3个方面进行了探讨,指出了当前中学化学教师在实验装置研究中存在的问题,提出了建设性意见。     

教育实证研究中样本选择的原则及品质要求

我国教育研究领域大力倡导实证研究,却面临操作指南缺乏和品质标准不够明晰的问题,导致高质量的实证研究案例不多。研究样本的数量及其代表性或立意是保证实证研究品质的重要因素,讨论了定量研究和质性研究中选择研究样本的原则,明确了实证研究论文写作中研究样本部分的品质指标及内容要求,利用构建的品质指标及内容要求分析了4个教育实证研究论文案例。研究发现,提升我国教育实证研究质量的任务还是比较艰巨的。     

沸石类分子筛合成研究新进展

对当前国际上沸石和沸石类分子筛材料的合成研究进行了综述, 分析了合成研究动向, 指出了合成研究中值得注意的几点问题, 并提出了研究展望。     

蛋白质组学技术前沿进展

蛋白质组学是以生物体系整体蛋白质为研究对象的新的研究领域,已经成为后基因时代中生命科学最重要研究方向之一。 近年来,蛋白质组学研究取得了令人鼓舞的进展,一系列新技术与新方法得到了快速的发展。 本文总结了2013年以来蛋白质组学研究的有关新技术,并对其发展进行了展望。     

过氧化氢光化学的理论研究

介绍了研究过氧化氢光解离的重要意义及目前的理论研究现状,分析了存在的问题,并对今后该领域的理论研究进行了展望.     

星际分子微波波谱研究进展

介绍了星际分子研究的概况,对微波波谱作为研究星际分子的重要方法的特点、特殊方法和技术以及取得的进展进行了综述,特别对近年来的微波波谱星际分子研究进行了分类介绍,提出了目前研究的难点并展望了发展趋势.     

近20年国际化学教育研究的趋势和走向

本文介绍了近20年来国际化学教育研究的趋势和走向.从研究内容、研究方法及研究理论等方面进行了较为详细的阐述和评介.     

国内"化学概念教学"研究新进展

以国内化学概念学习研究为主要内容,从3个方面分析了国内对化学概念学习的研究：(1)关于化学概念教学的经验性研究;(2)关于化学概念教学的理论性研究;(3)关于化学概念教学的现代研究。本文也简单分析了国外化学概念教学的研究,并且通过对比国内外化学概念教学的研究,得到了一些启示。     

二氧化钛功能薄膜研究发展与应用

二氧化钛薄膜在紫外光照射下的光催化活性和亲水性吸引了许多科学工作者对其进行了大量的研究.本文对近年来二氧化钛功能薄膜的研究发展与应用作了简要介绍,同时也对研究中存在的问题和将来研究发展的方向进行了简单评述.     

Synthesis and Characterization of Water‐Soluble Conjugated Glycopolymer for Fluorescent Sensing of Concanavalin A

A neutral polyfluorene derivative that contains 20 mol % 2,1,3‐benzothiadiazole (BT) is synthesized by Suzuki cross‐coupling polymerization. A cationic conjugated polymer A and an α‐mannose‐bearing polymer B are subsequently obtained through different post‐polymerization methods. As a result of the charged pendant groups or sugar‐bearing groups attached to the polymer side chains, both A and B show good water‐solubility. The titration of Concanavalin A (Con A) into polymer aqueous solution leads to different fluorescent responses for polymers A and B . Polymer A does not show any obvious fluorescence change upon interaction with Con A, whereas polymer B shows fluorescence increase in BT emission intensity when Con A is added. This is because of the specific interaction between α‐mannose and Con A, which induces polymer aggregation, and then facilitates energy transfer from the phenylene–fluorene segments to the BT units. A practical calibration curve ranging from 1 nM to 250 nM is obtained by correlating the changes in BT emission intensity with Con A concentration. The advantage of polymer B ‐based Con A macromolecular probe is that it shows signal increase upon Con A recognition, which is significantly different from other conjugated polymer‐based fluorescence quenching assays.     

A New Interpretation of Apparent Induction Period in Ring‐Opening Polymerization of Octamethylcyclotetrasiloxane in Acid Emulsion

A following new interpretation of apparent induction period is proposed considering the experimental results obtained: octamethylcyclotetrasiloxane (D4) is activated by the reaction with acid to generate an activated derivative (A4). A4 reacts with D4 to generate A8, an active species containing eight dimethylsiloxane units. A8 backbites to generate mostly A4 and D4, which causes retardation in polymerization, but occasionally to form A3 and D5. A3 is highly reactive, and when the concentration of A3 exceeds a certain limit, much Ai where i is large enough is formed and promotes fast growth of chain at the interfacial area due to high concentration of D4. The interpretation assumes that A3 accelerates growth of chain faster than other species, and that A8 tends to backbite rather than grow. The interpretation is supported by the experimental results of polymerization conducted with D4 and D3, or D5 and D3 charged.     

Relationship between the broad OH stretching band of methanol and hydrogen-bonding patterns in the liquid phase

The OH stretching (nu(OH)) band of methanol observed in condensed phase has been analyzed in terms of hydrogen-bonding patterns. Quantum chemical calculations for methanol clusters have revealed that broadening of the nu(OH) envelope is reasonably reproduced by considering nearest and next-nearest neighbor interactions through hydrogen bonding. Because the hydrogen bond formed between donor (D) and acceptor (A) is cooperatively strengthened or weakened by a newly formed hydrogen bond at D or A, we have proposed the following notation for hydrogen-bonding patterns of monohydric alcohols: a(D)DAd(A)a(A), where a is the number of protons accepted by D (a(D)) or A (a(A)), and d(A) is the number of protons donated by A. The indicator of the hydrogen-bond strength, which is given by M(OH) = a(D) + d(A) - a(A), is correlated well with the nu(OH) wavenumber of the methanol molecule D participating in the a(D)DAd(A)a(A) pattern. The correlation between M(OH) and the hydrogen-bonding energy of the a(D)DAd(A)a(A) pattern has also been deduced from the calculation results for the clusters. The nu(OH) bands of methanol measured in the CCl4 solution and pure liquid have been successfully analyzed by the method proposed here.     

中成药中马兜铃酸A的HPLC/MS分析方法

建立了中成药中马兜铃酸A的高效液相色谱/质谱检测方法.测定结果表明,马兜铃酸A的质谱有较强的分子离子峰,最低检测限为5 ng(信噪比等于10),可以满足对中成药中马兜铃酸A测定之要求.     

Exploring molecular complexity: conical intersections and NH3 photodissociation

The role of conical intersections in the photodissociation of the A 1A2" state of NH3 is investigated using extended atomic basis sets and a configuration state function expansion of approximately 8.5 million terms. A previously unknown portion of the 1 1A-2 1A seam of conical intersections with only C(s) symmetry is located. This portion of the seam is readily accessible from the equilibrium geometry of the A 1A2" state. These conical intersections are expected to play a role in the competition between adiabatic and nonadiabatic pathways for NH3(A 1A2") photodissociation.     

PP2A in the regulation of cell motility and invasion

Cell motility is a very critical phenomenon that plays an important role in the development of eukaryotic organisms. One of the well studied cell motility phenomena is chemotaxis, which is described as a directional movement of cell in response to changes in external chemotactic gradient. Numerous studies conducted both in unicellular organism and in mammalian cells have demonstrated the importance of phosphatidylionositol-3 kinase (PI3K) in this process. In addition, it is now well established that although PI3K plays an activation role in chemotaxis, the role of phosphatases is also critical to maintain this dynamic cyclical process. Protein phosphatase 2A (PP2A) is a major serine/threonine phosphatase that is a key player in regulating PI3K signaling. PP2A is abundantly and ubiquitously expressed and has been highly conserved during the evolution of eukaryotes. PP2A is composed of three protein subunits, A, B, and C. Subunit 'A' is a 60-65 kDa structural component, 'C' is a 36-38 kDa catalytic subunit, and 'B' is a 54-130 kDa regulatory subunit. The core complex of PP2A is comprised of the A and C subunits, which are tightly associated and this dimeric core complexes with the regulatory B subunit. The B subunit determines the substrate specificity as well as the spatial and temporal functions of PP2A. PP2A plays an important role in regulating multiple signal transduction pathways, including cell-cycle regulation, cell-growth and development, cytoskeleton dynamics, and cell motility. This review focuses on the role of PP2A in regulating motility of normal and transformed cells.     

A2-rhodopsin: a new fluorophore isolated from photoreceptor outer segments

A2E and iso-A2E are fluorescent amphiphilic pyridinium bisretinoids involved in age-related macular degeneration (AMD). It is now shown that the presence of high exogenous concentrations of all-trans-retinal in photoreceptor outer segments leads to the formation of A2-rhodopsin (A2-Rh), an unprecedented fluorescent rhodopsin adduct which consists of bisretinoids (A2) linked to each of three lysine residues in rhodopsin (Rh) and which exhibits an emission spectrum similar to A2E. The fluorophore to protein ratio was determined by MALDI-TOF-MS and UV-VIS spectroscopy. Enzymatic degradation with thermolysin and cathepsin D showed that two of the A2 moieties were located in the region of the third cytoplasmic loop and 8th helix of Rh. Examination of A2-Rh and A2-PE (the precursor of A2E) fluorescence in relation to all-trans-retinal concentration indicated that whereas A2-PE formation is favored over that of A2-Rh, for a single rhodopsin molecule only one phosphatidylethanolamine molecule is available to react with all-trans-retinal; this phosphatidylethanolamine is probably tightly associated with the protein.     

Mechanism for the degradation of erythromycin A and erythromycin A 2'-ethyl succinate in acidic aqueous solution

A major drawback of the antibiotic erythromycin A is its extreme acid sensitivity, leading to rapid inactivation in the stomach. The accepted model for degradation in aqueous acidic solution has erythromycin A in equilibrium with erythromycin A enol ether and degrading to anhydroerythromycin A. We report a detailed kinetic study of the acidic degradation of erythromycin A and of erythromycin A 2'-ethyl succinate (the market-leading pediatric prodrug), investigating the reaction rates and degradation products via NMR. This reveals that the accepted mechanism is incorrect and that both the enol ether and the anhydride are in equilibrium with the parent erythromycin. By implication, both the anhydride and enol ether are antibacterially inactive reservoirs for the parent erythromycin. The actual degradation pathway is the slow loss of cladinose from erythromycin A (or erythromycin A 2'-ethyl succinate), which is reported here for the first time in a kinetic study. The kinetic analysis is based on global, nonlinear, simultaneous least-squares fitting of time course concentrations for all species across multiple datasets to integrated rate expressions, to provide robust estimates of the rate constants.     

Trapping rhodium carbenoids with aminoalkynes for the synthesis of diverse N-heterocycles

A convergent approach for the synthesis of diverse N-heterocycles is described. The reaction involves trapping of diazo-derived rhodium carbenoids with gold activated aminoalkynes, and accommodates both the donor/acceptor (D/A) as well as acceptor/acceptor (A/A) diazo carbonyls. Mechanistic investigations indicate that the Rh(II)/Au(I) catalyzed reaction of aminoalkynes with D/A diazos is concerted, while the reaction with A/A diazo is stepwise and proceeds with carbene N–H insertion and a subsequent Conia-ene cyclization.     

Reactions of substituted (methylthio)benzylidene Meldrum's acids with secondary alicyclic amines in aqueous DMSO. Evidence for rate-limiting proton transfer

The replacement of the methylthio group of substituted methylthiobenzylidene Meldrum's acids (2-SMe-Z) by secondary alicyclic amines occurs by a three-step mechanism. The first step is a nucleophilic attachment of the amine to 2-SMe-Z to form a zwitterionic intermediate T(+/-)(A); the second step involves deprotonation of T(+/-)(A) to form T(-)(A); while the third step represents general acid-catalyzed conversion of T(-)(A) to products. At high amine and/or high KOH concentration nucleophilic attachment is rate limiting. At low amine and low KOH concentration the reaction follows a rate law that is characteristic for general base catalysis which, in principle, is consistent with either rate-limiting deprotonation of T(+/-)(A) or rate-limiting conversion of T(-)(A) to products. A detailed structure-reactivity analysis indicates that for the reactions with piperazine, 1-(2-hydroxyethyl)piperazine, and morpholine it is deprotonation of T(+/-)(A) that is rate limiting, while for the reaction with piperidine, conversion of T(-)(A) to products is rate limiting.