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Chemistry is a central, practical and creative discipline. The development of chemistry plays an important role in the progress of science and society, as well as the improvement of the quality of human life. This paper introduces the chemical knowledge of stone, concrete, glass and other inorganic nonmetallic building materials by the anthropomorphically story. Taking nanomaterials as an example, the prospect of building materials development in the future is put forward. 相似文献
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《广东微量元素科学》2000,(3)
人体必需元素是人体健康之“友” ,不能缺乏 ,更不能没有 ,否则就使人患病 ;另一方面 ,也不能过多(从理论上来讲 ,任何必需元素都不能过多 ,但现实生活中 ,有一些元素并不存在由于过多而致病的问题 ) ,否则会化“友”为“敌” ,使人中毒 ,这类例子是很多的。例如食盐 ,井岗山时期 ,国民党反动派对红军实行封锁 ,把食盐也列为封资物资。电影《闪闪的红星》中潘冬子给红军送盐时 ,为了逃避敌人检查 ,把盐用水溶解浸湿棉衣 ,到达后再把棉衣中的盐水挤出来熬盐 ,可见食盐对于人体是多么必要。可是 ,过多吃食盐会导致高血压已是公认的事实 ,并为… 相似文献
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活性中间体和过渡态是两个不同的概念。在许多有机化学反应中,从反应物到产物往往不是一步完成,而是经历若干步骤。在这些多步骤反应中会形成一些极不稳定的反应中间体。例如,烷烃卤代反应过程中生成的碳游离基,烯烃与卤化氢加成过程中生成的碳正离子以及芳烃亲电取代反应中生成的σ络合物—碳正离子中间体等等都是非常活泼的中间体,它们一般称为有机活性中间体。有机活性中间体除碳游离基、碳正离子外,还有碳负离子、碳烯、苯炔等等。这些活性中间体都有着共同的特征:它们都非常活泼,生成后立即与其它物质反应,存在时间很短暂。 相似文献
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欧洲文艺复兴以后,早在拉丁语处于学术中心地位的时代,在法语、德语、英语等民族语言文献中就出现“炼金术”和“化学”2个不同的词语.但起初很长时间内这2个词语基本是同义语.18世纪以后,随着西方学术的“地方化”,欧洲民族语言逐渐取代拉丁语成为主要的学术语言.于此同时,“炼金术”与“化学”2个词有了明确的区别,并逐渐产生了2个不同的学科.本文简要考察了民族语言中“炼金术”与“化学”的起源和演变过程,并进一步说明,18世纪以后,现代化学与炼金术的分离是西方现代科学发展的一般特点:即与思辨哲学和神秘主义法术分离,走向学科的分化独立. 相似文献
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《广东微量元素科学》1999,(10)
先天性痴呆又叫先天愚型、白痴,是一种最常见的常染色体遗传病,患者智力低下,常呈伸舌样痴笑。这种患儿在新生中的发生率为15‰。统计表明,其发生率与婴儿母亲年龄有关;40岁以上孕妇新生婴儿,患儿出生率则上升到六十分之一,约为正常出生婴儿中患者的10倍。在细胞学上,除性... 相似文献
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Chlorhexidine (1,1-hexamethylene-bis-[5-(p-chlorophenyl)-biguanide]-digluconate; CHD) is one of the most frequently used antiseptics. In spite of this, its resorption and elimination has hardly been investigated. One of the main reasons for this is the lack of suitable procedures for its analysis in biological materials. Samples of CHD also may contain the carcinogen 4-chloroaniline which also may be formed as a degradation product in preparations.A HPLC method with end-capped stationary phase was developed which separates CHD, 4-chloroaniline and 1-chloro-4-nitrobenzene (a degradation product of 4-chloroaniline). Methods of solid-phase extraction and deproteinization for the purpose of isolating the analytes in serum and urine were also tested. In the latter process, isolation of all three compounds from the biological material using a single procedure was unsuccessful. Isolation of CHD, on the other hand, both from serum and from urine using solid-phase extraction with weak cation exchangers was successful and showed reliable retrieval rates. 相似文献
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Various substituted benzaldehydes were converted into benzoate esters with household bleach and sodium iodide in an alcohol solvent. The reaction works best with methanol. Only 4-chlorobenzaldehyde, 3-nitrobenzaldehyde, and 4-nitrobenzaldehyde reacted completely with 1-propanol under these conditions.
[Supplementary materials are available for this article. Go to the publisher's online edition of Synthetic Communications® for the following free supplemental resource(s): Full experimental and spectral details.] 相似文献
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Tian L Yang Q Jiang Z Zhu Y Pei Y Qiao M Fan K 《Chemical communications (Cambridge, England)》2011,47(21):6168-6170
In the challenging crotonaldehyde hydrogenation to crotyl alcohol, an Ag-In/SBA-15 catalyst fabricated by a modified "two solvents" strategy shows an unprecedentedly high yield of 86% at a selectivity of 87%, which exceeds the best results on Pt-, Au- and other Ag-based heterogeneous catalysts reported so far. 相似文献
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Gizelle A.B. Vieira Telma L.G. Lemos Marcos Carlos de Mattos Maria da Conceicão F. de Oliveira Vânia M.M. Melo Gonzalo de Gonzalo Vicente Gotor-Fernández Vicente Gotor 《Tetrahedron: Asymmetry》2009,20(2):214-219
Straightforward synthetic strategies for the preparation of optically active Mugetanol isomers have been developed through different independent chemoenzymatic routes implying the use of either alcohol dehydrogenases in aqueous media or lipases in organic solvents coupled with a catalytic hydrogenation process. Among the alcohol dehydrogenases tested, ADH RS1 showed the best activities in the bioreduction of 4-isopropylacetophenone. The lipase from Pseudomonas cepacia (PSL-C I) reached high activity values in the lipase-catalyzed transesterification of 4-isopropylphenyl)ethanol, while Candida antarctica lipase B showed the best stereopreference in the acetylation of 4-isopropylcyclohexylethanol. 相似文献
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Nitroxoline is a wide spectrum antibacterial and is one of the most important urinary antiseptics.The interaction between nitroxoline and human serum albumin(HSA)has been investigated systematically by fluorescence spectroscopy,synchronous fluorescence,three-dimensional fluorescence,CD spectroscopy and UV-Vis absorption spectroscopy.The results indicated that the quenching of HSA by nitroxoline was static.The corresponding thermodynamic parameters △H,△S and △G calculated according to van’t Hoff equation revealed that the intermolecular forces acting between nitroxoline and HSA were mainly hydrogen bonding and van der Waals forces.The conformational changes in the interaction were studied by synchronous fluorescence,CD spectroscopy and three-dimensional fluorescence spectra which showed changes in the microenvironment and conformation of HSA. 相似文献
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橡胶及橡胶制品中4种酚类防霉剂的高效液相色谱法测定 总被引:1,自引:0,他引:1
建立了橡胶及其制品中硝基苯酚(PNP)、2,3,5,6-四氯苯酚(TeCP)、五氯苯酚(PCP)、邻苯基苯酚(OPP)4种酚类防腐剂的高效液相色谱测定方法。样品冷冻粉碎后,经甲醇超声提取,在Venusil-XBP C18色谱柱(250 mm×4.6 mm,5μm)上以10 mmol/L醋酸铵和甲醇为流动相梯度洗脱,采用二极管阵列检测器,PCP、TeCP、OPP的检测波长为220 nm,PNP的检测波长为320 nm。4种酚类防霉剂的质量浓度在0.5~250mg/L范围内与峰面积呈良好的线性关系,相关系数大于0.999 4。丁苯橡胶、硅橡胶基体的加标回收实验结果表明:TeCP、PCP、OPP、PNP在不同基质中的平均加标回收率分别为82%~95%、68%~90%、85%~98%、87%~98%,相对标准偏差小于5%。 相似文献
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Kwong CK Huang R Zhang M Shi M Toy PH 《Chemistry (Weinheim an der Bergstrasse, Germany)》2007,13(8):2369-2376
A series of soluble, non-cross-linked polystyrene-supported triphenylphosphane and 4-dimethylaminopyridine reagents were prepared. Some of these polymeric reagents contained either alkyl alcohol or phenol groups on the polymer backbone. The use of these materials as organocatalysts in a range of Morita-Baylis-Hillman reactions indicated that hydroxyl groups could participate in the reactions and accelerate product formation. In the cases examined, phenol groups were more effective than alkyl alcohol groups for catalyzing the reactions. This article is one of the first reports of the synthesis and use of non-natural, bifunctional polymeric reagents for use in organic synthesis in which both functional groups can cooperatively participate in the catalysis of reactions. 相似文献
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Tuan Minh Nguyen Jean-Jacques Youte Angie Cheong Benjamin S.W. Tan Mark S. Butler 《Tetrahedron》2010,66(47):9270-9276
The synthesis of the chiral core structure of the lissoclimide class of anti-tumour agents containing three rings, including a chiral succinimide subunit and an exocyclic double bond, has been investigated. The compound 7 was obtained, without the use of any protecting groups for the alcohol at C-12, via an asymmetric boron-mediated aldol addition as the key step to install the chiral centres of the rare succinimido methanol moiety. This was followed by a sequence of lactonisation, microwave-assisted amidation and imidation reactions. 相似文献
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Complex formation between elemental iodine and polyvinyl alcohol was studied under flow conditions. The formation of substances with a weak hyperchromic effect in the UV and visible regions was detected. It was shown that this reaction could be used under flow conditions provided the gel-forming ability and viscosity of the polyvinyl alcohol solution were reduced by adding isopropanol and 6% dimethylsulfoxide. It was found that the reaction efficiency under flow conditions could be monitored using a new method for the determination of the dispersion coefficient of a sample based on comparison between standard and flow absorptivity coefficients. Because of the effect of nonequilibrium factors, it turns out that the best calibration function is a nonlinear one. The throughput capacity of the method is 140 samples per hour, and the limit of detection is 60 ng/mL. The high selectivity for chlorides allows one to determine iodine and its species in seawater and to monitor its concentration in white salt. 相似文献