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对科学方法和科学方法教育的再认识——祝贺《化学教育》30周年刊庆 总被引:1,自引:0,他引:1
科学方法是科学活动经验升华、程序化、规范化、强化的结果,是科学活动的过程规定性工具。方法的思维是科学方法的精髓。对具体的科学方法进行概括,形成科学方法的适用范围不同的层次。科学方法大体上可以分为经验方法、理性方法和具有补充、完善意义的"第三类方法"以及综合性方法。科学方法有局限性,需要关注方法的改进,注意创新。要搞好科学方法教育,必须以科学方法形成和发展的规律为基础,既要考虑科学方法的特点,也要考虑教育对象的特点。 相似文献
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《理化检验(化学分册)》2016,(7)
综述了近20年来。水体中铊的富集分离方法,如物理方法、化学方法、生物方法和电化学方法的研究现状,讨论了不同方法的优缺点,展望了水体中铊富集分离方法的发展方向(引用文献42篇)。 相似文献
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科学方法是科学素养的重要组成,本文结合近年高考试题着重分析了科学方法考查的主要方面:信息加工处理中的科学方法、化学中的守恒思维方法、化学实验中的科学方法、运用模型方法建立科学思维模式和科学发现史、化学发展史中所展现的科学方法等。 相似文献
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分别利用两种热力学方法(基于逸度相等的方法与基于活度相等的方法)预测了不同多孔介质中气体水合物的平衡分解条件, 对于非水合物相, 逸度方法采用Trebble-Bishnoi (TB)方程, 而活度方法则使用Soave-Redlich-Kwong (SRK)方程, 对于水合物相, 两种方法都利用了van der Waals-Platteeuw模型结合Llamedo等关于毛细管力作用模型来模拟. 两种方法的预测结果与实验结果吻合, 逸度方法的预测效果要好于活度方法. 相似文献
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提出了一种经济实用的价键计算方法VB-MP2方法.将体系的电子分为非活性电子和活性电子,应用MP2方法计算非活性电子的相关能效应,用VB方法处理活性电子.测试计算表明,该方法保持了价键方法的特点,且计算结果比传统的使用芯-价分离技术的价键方法有较大的改善. 相似文献
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用气相色谱-质谱法测定了水中6种有机含磷农药残留量,并比较了全自动固相萃取(方法1#)和全自动液-液萃取(方法2#)两种样品前处理方法。结果表明:从准确度方面,方法1#优于方法2#,所测得的方法1#的回收率在73.5%~92.0%之间,而方法2#的回收率在63.7%~89.7%之间;但方法2#耗时较方法1#少。 相似文献
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文章采用列表对比的方式,简要介绍了微孔吸附常用经典模型的出处、应用范围、发展历史和各自的特点。为了方便系统了解和掌握物理吸附中的微孔经典分析方法,文章将其分成三类:(1)由标准等温线发展出的方法,包括t-图法、αs-图法、n-图法和MP法;(2)基于微孔填充理论的方法,包括D-R方法、D-A方法和D-R-S方法;(3)目前普遍使用的方法,包括原始HK方法(狭缝型孔)、HK-SF方法(圆柱型孔)和HK-CY方法(球型孔)以及三种改进后的HK方法。 相似文献
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《Tetrahedron: Asymmetry》2005,16(16):2729-2747
We have developed practical synthetic routes to enantiopure d- and l-carba-β-altrose derivatives and all the possible stereoisomers via their divergent stereoconversions. Carba-β-d-altrose was prepared from 3-cyclohexene-1-carboxylic acid and converted to carba-β-d-mannose, carba-β-d-idose, and carba-β-d-talose derivatives via regio- and stereoselective oxidation/reduction of 3-OH and/or 4-OH. The four carbasugar stereoisomers were then transformed to the remaining 12 carbasugar stereoisomers and their 1,2-epoxides by regio- and stereoselective manipulation of hydroxyl groups in C1 and C2, which includes oxidation/reduction, Mitsunobu’s reaction, olefination/dihydroxylation, and epoxidation/ring-opening protocols. 相似文献
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Validamycin A is a member of microbial-derived C(7)N-aminocyclitol family of natural products that is widely used as crop protectant and the precursor of the antidiabetic drug voglibose. Its biosynthetic gene clusters have been identified in several Streptomyces hygroscopicus strains, and a number of genes within the clusters have been functionally analyzed. Of these genes, valB, which encodes a sugar nucleotidyltransferase, was found through inactivation study to be essential for validamycin biosynthesis, but its role was unclear. To characterize the role of ValB in validamycin biosynthesis, four carbasugar phosphate analogues were synthesized and tested as substrate for ValB. The results showed that ValB efficiently catalyzes the conversion of valienol 1-phosphate to its nucleotidyl diphosphate derivatives, whereas other unsaturated carbasugar phosphates were found to be not the preferred substrate. ValB requires Mg(2+), Mn(2+), or Co(2+) for its optimal activity and uses the purine-based nucleotidyltriphosphates (ATP and GTP) more efficiently than the pyrimidine-based NTPs (CTP, dTTP, and UTP) as nucleotidyl donor. ValB represents the first member of unsaturated carbasugar nucleotidyltransferases involved in natural products biosynthesis. Its characterization not only expands our understanding of aminocyclitol-derived natural products biosynthesis, but may also facilitate the development of new tools for chemoenzymatic synthesis of carbohydrate mimetics. 相似文献
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《Tetrahedron: Asymmetry》2000,11(19):3873-3877
Difluorinated carbasugar 3 has been synthesised from d-ribose via an intramolecular nitrone cycloaddition reaction with an overall yield of 22%. 相似文献
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Fructose was converted into C-1 diastereomeric carbocyclic building blocks resembling mannose using ruthenium-catalysed ring-closing metathesis as a key step. The potential use of the compounds in the synthesis of valienamine pseudodisaccharides is demonstrated using Mitsunobu coupling chemistry directly between a carbohydrate sulfonamide and the carbasugar C-1 alcohols. 相似文献
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Weiwu Ren Marco Farren-Dai Natalia Sannikova Katarzyna
widerek Yang Wang Oluwafemi Akintola Robert Britton Vicent Moliner Andrew J. Bennet 《Chemical science》2020,11(38):10488
Carbasugars are structural mimics of naturally occurring carbohydrates that can interact with and inhibit enzymes involved in carbohydrate processing. In particular, carbasugars have attracted attention as inhibitors of glycoside hydrolases (GHs) and as therapeutic leads in several disease areas. However, it is unclear how the carbasugars are recognized and processed by GHs. Here, we report the synthesis of three carbasugar isotopologues and provide a detailed transition state (TS) analysis for the formation of the initial GH-carbasugar covalent intermediate, as well as for hydrolysis of this intermediate, using a combination of experimentally measured kinetic isotope effects and hybrid QM/MM calculations. We find that the α-galactosidase from Thermotoga maritima effectively stabilizes TS charge development on a remote C5-allylic center acting in concert with the reacting carbasugar, and catalysis proceeds via an exploded, or loose, SN2 transition state with no discrete enzyme-bound cationic intermediate. We conclude that, in complement to what we know about the TS structures of enzyme-natural substrate complexes, knowledge of the TS structures of enzymes reacting with non-natural carbasugar substrates shows that GHs can stabilize a wider range of positively charged TS structures than previously thought. Furthermore, this enhanced understanding will enable the design of new carbasugar GH transition state analogues to be used as, for example, chemical biology tools and pharmaceutical lead compounds.Positive charge stabilized on remote C5-allylic center with catalysis occurring via a loose SN2 transition state. 相似文献
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A novel, concise, stereocontrolled approach to nine-membered carbasugar analogues (cyclononitols) from a bicyclo[4.3.1]deca-2,4-dien-10-one scaffold, harbouring a ‘locked’ cyclononane ring and latent functionalities, is described. 相似文献
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[reaction: see text] The synthesis of the carbasugar analogue of 1,4-anhydro-beta-d-galactopyranose, a proposed intermediate in the reaction catalyzed by uridine diphosphate-alpha-d-Galp mutase, in racemic form via Diels-Alder and Barton decarboxylation chemistry is reported. This compound was found not to inhibit the mutase from Mycobacterium tuberculosis, indicating that the enzyme does not possess a 1,4-anhydro-beta-d-galactopyranose binding pocket. 相似文献
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Cyclooctatetraene (COT) derived bicyclo[4.2.1]nona-2,4,7-trien-9-one has been recognized as a cyclooctane carbasugar equivalent and elaborated to a range of cyclooctane polyols (cyclooctitols) through a flexible strategy with moderate regio- and stereo-control. 相似文献
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《Tetrahedron: Asymmetry》2007,18(19):2326-2331
Our studies of the TIBAL-promoted Claisen rearrangement reaction and ring-closing metathesis (RCM) resulted in the development of an efficient synthetic route to polyfunctional seven-membered carbasugar synthons from d-arabinose. Moreover, the construction of 8-oxa-bicyclo[3.2.1]octane derivatives 10 and 13 was achieved by BCl3 or iodide-promoted intramolecular electrophilic addition reactions, which were regio- and stereoselective. 相似文献
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[reaction in text] A convergent strategy for the synthesis of beta-carba-galacto-disaccharides is illustrated by the preparation of 1 and 4, from a central "glycone" component 22, and the corresponding "aglycone" segments, monosaccharide alcohols, 23a or 23b. The key step is the formation of the carbasugar ring via an oxocarbenium ion-enol ether cyclization. 相似文献