警惕儿童铅中毒

儿童玩具和学习用品的含铅量普遍较高。有报告表明 ,7种玩具表面油漆中含的可溶性铅已超过国际最高允许量。学生常用的铅笔 ,有 6类超标 ,含铅量最高的超标 4 12倍 ;课桌、椅的棕黑色油漆层超标 36 7倍 ;彩色蜡笔足以引起儿童铅中毒。有关专家指出 :正常人血液中不应含铅 ;儿童铅中毒诊断标准为血铅水平超过或等于 0 4 83μｍｏｌ/Ｌ。铅主要通过消化道和呼吸道进入人的体内 ,而铅往往最容易被儿童吸收。除了前面提到的那些铅污染源 ,还有含铅汽油的燃烧、含铅油漆的风化、工业污染等 ,都是铅尘的重要来源。一旦发生铅中毒 ,会有以下表现…     

广州市天河区1000例城区与工业区儿童发铅分析

抽样调查了天河城区及工业区３￣６岁托幼儿童的发铅,进行分组对照比较。结果表明,生活在城区儿童的发铅异常者占抽样人数的３４．４％,而生活在工业区儿童的发铅异常者则占总抽样人数的５２．２％,把两组儿童的发铅平均含量作比较发现,城区组显著低于工业区组儿童（Ｐ〈０．０１）,提示,生活在工业区的儿童是铅暴露的高危人群。     

铅污染对幼儿健康影响的调查研究

对调查区和对照区共２０３名￣６岁幼儿进行了血铅汪洋的调查。结果显示，生活在不同环境下的幼儿，已受到程度不同的铅污染。工业相对集中的城镇（调查区）幼儿血铅含量为５．１５μｇ／ｄＬ，大于郊区（对照区）幼儿的血铅含量３．５４μｇ／ｄＬ，交通和工矿企业对周围环境的污染是幼儿体内铅的主要来源。     

顺德市大良城区与顺峰山工业区800例儿童发铅分析

对大良城区及顺峰山工业区８００例０－６岁托幼儿童进行了健康检查及发铅测定。并分组对照比较。结果表明，生活在城区儿童的发铅异常占抽样的３３．５％，而生活在工业区儿童的发铅异常者则占抽样人数的４３．８％，对两组不同年龄组儿童的发铅比较发现，低年龄组儿童发铅异常显著高于高年龄组儿童。     

铅对作业工人健康及其子代智商的影响

为了研究铅的作用,对１１６名铅作用工人做了健康检查,测定了其３１名４￣６岁子女的智商,并测定了６８名父母为非铅作业工人的儿童智商,以作对照。神经衰弱是工人最常见的症状,其次是消化系统症状。车间空气铅浓度与尿铅、尿δ－ＡＬＡ、神经衰弱有相关关系。铅作业者子女的平均智没为８４．８２,显著低于对照组的９８．３０。铅作业女子中有３２．３％的人智商≤８５,而对照组仅１１．８％,;铅作业子女中有６．５％的人智     

清洁工艺生产铅

一种新的湿法炼铅方法——碳酸化转化法，铅转化率达９０％以上，元素硫生成率为８０％以上。ＰｂＣＯ３可电解成金属铅或制成１０种铅化工产品。元素硫便于储存和运输。矿石中的ＦｅｘＳｙ对转化有催化作用。该方法彻底消除了火法炼铅过程中铅蒸气和二氧化硫对环境的污染，实现了清洁生产。     

68例智力低下儿童发病原因与发铅含量关系探讨

对本院遗传优生门诊１９９４年以来确诊为６８例智力低下儿童进行了发铅测定。其中１２人发铅明显超过正常值,占总数的１７．６％。发铅增高的１２人中,有５人为神经系统病变,１人为射材矮小,另外６例无明显医学原因。本组病例显示,铅对儿童的神经系统损害较明显。讨论了防止胎儿和儿童受铅毒害的措施。     

深圳地区正常儿童尿液微量元素的测定

以电位溶出法检测了４３７例３个月～１２岁正常儿童的尿液锌、铜、铅、镉含量，结果显示：（１）在所有儿童尿中均未检出铜和镉，铅在部分尿中可检出，但含量低微，而尿锌的含量相对较高，且正常波动范围较大，相差几倍～十几倍，（２）尿液锌、铅含量在正常男女儿童间无明显性别差异（Ｐ＜０．０５）；（３）尿液锌、铅含量在３～１２个月、１岁～、３岁～组间无显著差异，但它们均高于７～１２岁组（Ｐ＜０．００１～０．０５）．     

环境铅暴露对儿童智能与行为的影响

环境铅暴露对儿童的危害已成为世界范围内一种严重的公共卫生问题。既往的研究表明环境铅暴露对儿童的智力发育将产生不良影响 ,尤其是对于婴儿 ,铅暴露是影响其精神发育的决定因素之一 ;长期的铅暴露具有累加作用 ,其毒害作用也是累加的 ;铅暴露又是导致儿童行为异常的因素之一 ;大量研究显示儿童多动症与儿童铅暴露水平有关。此外 ,铅暴露还可能影响部分儿童运动功能的发育。     

中国城市儿童百分之五十铅中毒

铅是一种严重的环境毒和神经毒，一旦被人吸收则在人体内长期积累而不易排出，它将严重损伤人的神经系统和造血系统。来自中国科技大学“重金属铅对儿童学习记忆的影响及其细胞和分子机制”的研究成果表明：随着环境污染加重，每人每天从空气、水和食物中吸收大约２０至４０微克的铅，它不但影响婴幼儿和儿童的智力发育，甚至直接影响到儿童身高与体重。据这项由中科大神经生物学系阮迪云教授主持的国家自然科学基金“九五”重点项目统计，我国城市中有一半左右的儿童血铅水平超过每分升１０微克的铅中毒标准。大脑边缘系统海马结构是学习记…     

二氧化碳和丙烯直接合成甲基丙烯酸的NiPMo/TiO2催化剂的研究

用溶胶-凝胶法以磷钼酸(MPA)的镍盐溶液水解钛酸四丁酯制备了NiPMo/TiO2催化剂.使用ICP、 XRD、 TG-DTA、 IR、 TPD-MS和微反应技术研究了催化剂的化学组成、热稳定性、化学吸附性质和催化反应性能.杂多钼酸盐与TiO2通过O2-在TiO2表面发生了键合.在623 K下,杂多阴离子仍保持原有的Keggin结构.CO2在Lewis酸位Ni(Ⅱ)和Lewis碱位Ni-O-Mo的桥氧协同作用下生成CO2卧式吸附态Ni(Ⅱ)←O-(CO)←(O--Ni).丙烯有多种吸附态在催化剂上吸附.在563 K、 1 MPa和空速1500 h-1的反应条件下,丙烯的摩尔转化率为3.2%,产物MAA选择性为95%.     

Synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives

Different approaches for the synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives from simple amino acids have been investigated. A library of 33 precursors for the preparation of N-hydroxy pyrazinones was obtained in moderate to good yields.     

α-Amino acid derived enaminones and their application in the synthesis of N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates and other heterocycles

A new and simple synthesis of novel N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates, which exist in equilibrium with their 4-oxo tautomers, has been developed in two steps starting from N-protected α-amino acids. The key intermediates are enaminones, which can also be isolated, characterized, and used for the construction of other functionalized heterocycles, before they spontaneously decompose to pyrrole products. 4-Hydroxypyrroles are prone to partial aerial oxidation but can be efficiently alkylated or reduced to stable polysubstituted pyrrolidine derivatives.     

Specific intramolecular aromatic CH insertion of diazosulfonamides

The chemoselectivity in the intramolecular CH insertion of various diazosulfonamides has been experimentally studied. The results reveal that the aliphatic 1,4-, 1,5-, or 1,6-C(sp³)?H insertions of diazosulfonamides are not accessible, while the aromatic 1,5-C(sp²)?H insertion can be realized specifically by adjusting the diazo-adjacent group. In addition, the general chemoselectivities in the intramolecular CH insertions of diazosulfonyl compounds are summarized. Generally, diazosulfones undergo both aromatic 1,5-C(sp²)?H and aliphatic 1,5- and 1,6-C(sp³)?H insertions, while diazosulfonates undergo aliphatic 1,5- and 1,6-C(sp³)?H insertions. However, diazosulfonamides only undergo aromatic 1,5-C(sp²)?H insertion.     

A general and convenient synthesis of 4-(tosylmethyl)semicarbazones and their use in amidoalkylation of hydrogen,heteroatom, and carbon nucleophiles

A general synthesis of previously unknown semicarbazone-based α-amidoalkylating reagents, 4-(tosylmethyl)semicarbazones, has been developed. The synthesis involved three-component condensation of semicarbazones of aliphatic or aromatic aldehydes with the same or other aldehydes and p-toluenesulfinic acid. The scope and limitations of this reaction were investigated. The compounds obtained were demonstrated to be an efficient α-(4-semicarbazono)alkylating agents. They were reacted with H- (sodium borohydride), O- (sodium methylate), S- (sodium phenylthiolate), N- (pyrrolidine, sodium succinimide), P- (trialkyl phosphites), and C-nucleophiles (sodium diethyl malonate) to give the corresponding products of the tosyl group substitution, 4-substituted semicarbazones, including analogues of nitrofurazone. Among the prepared compounds tested in vitro for antibacterial and antifungal activity, three nitrofuryl-containing semicarbazones exhibited high biological activities with minimum inhibitory concentration (MIC) values of 8–32 μg/mL.     

Synthesis of novel chiral bidentate hydroxyalkyl-N-heterocyclic carbene ligands and their application in palladium-catalyzed Mizoroki–Heck couplings and asymmetric addition of diethylzinc to benzaldehyde

A small library of new chiral bidentate hydroxyalkyl-imidazolium salts 1 is conveniently synthesized on multi-gram scale from inexpensive and commercially available chiral pool amino acids. The corresponding carbenes, generated by deprotonation of imidazolium salts 1, in combination with palladium(II) chloride were tested in the Mizoroki–Heck coupling reaction. The most significant results in terms of yields and reactivities were achieved with low catalyst loading. The catalytic activities of these imidazolium salts were also investigated in the asymmetric addition of diethylzinc to benzaldehyde. The use of MgO nanoparticles as an additive in conjunction with these ligands played a crucial role in increasing the efficiency of these reactions.     

Toward new camptothecins. Part 6: Synthesis of crucial ketones and their use in Friedländer reaction

In the context of the preparation of camptothecin and luotonin A analogs, the synthesis of some key keto-precursors and their use in Friedländer condensation are described. This paper also focuses on the stability of these keto intermediates and emphasizes the major differences between indolizinones and pyrroloquinazolinones series. Noteworthy is also the report of some original structures isolated as by-products of some experiments.     

N-Heterocyclic carbene-palladacyclic complexes: synthesis,characterization and their applications in the C-N coupling and α-arylation of ketones using aryl chlorides

N-Heterocyclic carbene-palladacyclic complexes 3 were successfully achieved in a one-pot procedure under mild conditions. The structure of 3a was unambiguously confirmed by X-ray single crystal diffraction and it was an active catalyst in the Buchwald-Hartwig amination and α-arylation of ketones even at very low catalyst loadings (0.01?mol%).     

Iodine-mediated oxidative Pictet-Spengler reaction using terminal alkyne as the 2-oxoaldehyde surrogate for the synthesis of 1-aroyl-β-carbolines and fused-nitrogen heterocycles

An efficient iodine-mediated oxidative Pictet-Spengler reaction in dimethyl sulphoxide (DMSO) using terminal alkynes as the 2-oxoaldehyde surrogate for the synthesis of aryl (9H-pyrido[3,4-b]indol-1-yl)methanones is described. The scope of the protocol includes the total synthesis of Fascaplysin, Eudistomins Y₁ and Y₂. The methodology is extended for preparing pyrrolo[1,2-a]-quinoxaline and indolo[1,5-a]quinoxaline derivatives. The utility of 1-aroyl-β-carbolines was demonstrated by performing palladium-catalyzed β-carboline directed ortho-C(sp2)-H functionalization of the phenyl ring with thiomethyl (SMe) group using DMSO as source and for accessing 4-aryl-canthin-6-ones.     

CoFe2O4自形成磁性液体场致结构化对磁化的影响

The Langevin paramagnetic theory can’t describe the relation between magnetization of ferrofluids and applied magnetic field. The structuralization of ferrofluids, which is considered the main influence factor of the magnetization, is regarded. The part of magnetization works is deposited when the structure is forming. This action influences the magnetization of ferrofluids directly or indirectly. On the base of the “compressing” model, the Langevin function that usually describes the magnetization of ferrofluid is modified, and a well-fitted curve is obtained. An equation of the relation between the equivalent volume fraction after being “compressed” and the intensity of magnetic field is discovered, which approximately describes the process of magnetization. The relation between the approximate initial susceptibility and the volume fraction can be obtained from modified formula.