992 resultados para 588


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Isopolymolybdate (VI) anion transfer across the water/nitrobenzene (w/n) interface was studied by cyclic voltammetry. The effect of pH and responsed kinetics of isopolymolybdate anion's formation in the water phase on the transfer behavior have been studi

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General equations of the electrocatalytic reaction at an ultramicroelectrode modified with redox species have been described according to the Andrieux Saveant model. The electrocatalytic kinetic process has been discussed for the whole set of cases, ie (R), (R + S), (SR) (SR + E), (E), (R + E), (ER), (S), (ER + S) and (S + E) limiting situations. The effect of gamma on the catalytic steady state current shows that the higher the value of gamma, the lower the catalytic current. The kinetic process shifts rapidly from R to E with increasing values of gamma. It is favorable for catalysis only when gamma is very low. Therefore, the redox species modified ultramicroelectrode with thin film is utilized for electrocatalysis, and the larger the radius of ultramicroelectrode, the higher the catalytic efficiency.

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本文详细地研究了泡沫塑料静态吸附金的条件及用硫代米蚩酮光度法测定金时 Tl、Hg、Ag、Pd 等干扰离子的分离及消除干扰的方法,并提出了定量解脱金的简便方法。拟定了快速测定矿石中金的分析方法。

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Heat shock protein 22 (HSP22) is an important member of small heat shock protein (sHSP) subfamily which plays a key role in the process of protecting cells, facilitating the folding of nascent peptides, and responding to stress. In the present study, the cDNA of HSP22 was cloned from Argopecten irradians (designated as AiHSP22) by rapid amplification cDNA end (RACE) based on the expressed sequence tags (ESTs). The full-length cDNA of AiHSP22 was of 1,112 bp, with an open reading frame of 588 bp encoding a polypeptide of 195 amino acids. The deduced amino acid sequence of AiHSP22 showed high similarity to previously identified HSP22s. The expression patterns of AiHSP22 mRNA in different tissues and in haemocytes of scallops exposed to Cd2+, Pb2+ or Cu2+ were investigated by real-time quantitative RT-PCR. The mRNA of AiHSP22 was constitutively expressed in all examined tissues, including haemocyte, muscle, kidney, gonad, gill and heart. The expression level in heart and muscle was higher than that in other tissues. The mRNA level of AiHSP22 in haemocytes was up-regulated after a 10 days exposure of scallops to Cu2+, Pb2+ and Cd2+. However, the expression of AiHSP22 did not increase linearly along with the rise of heavy metal concentration. Different concentrations of the same metal resulted in different effects on AiHSP22 expression. The sensitive response of AiHSP22 to Cu2+, Pb2+ and Cd2+ stress indicated that it could be developed as an indicator of exposure to heavy metals for the pollution monitoring programs in aquatic environment.

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Genetic differentiation of the shrimp Penaeus chinensis in the Yellow Sea and Bohai Sea was investigated using the mitochondrial control region (CR). RFLP of a partial CR segment (613 bp) shows that 106 out of 122 (86.9%) individuals from six sampling localities along the coast of northern China and the west coast of the Korean Peninsula share the same haplotype, and the haplotype frequencies among localities are not significantly different. The findings are further confirmed by sequencing the complete CR. Divergence of the complete CR (992 bp) is less than 1.6% in 14 individuals from the six localities. F-statistics based on RFLP data and the TCS network of sequencing data suggest little genetic differentiation of P. chinensis in the Yellow Sea and Bohai Sea. Mismatch analysis suggests a rapid expansion of P. chinensis population to the Yellow Sea and the Bohai Sea, which probably occurred with the rapid rise in sea level after the last glacial maximum. Despite the lack of genetic heterogeneity, we propose that P. chinensis populations in this region should be treated as separate management units, as fishery management programs have to be applied on a local basis by different governments.

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Transglutaminase can catalyze the cross-linking reaction between soluble clotting protein molecules from the plasma for prevention of excess blood loss from a wound and obstructing micro-organisms from invading the wound in crustaceans. A novel transglutaminase (FcTG) gene was cloned from hemocytes of Chinese shrimp Fenneropenaeus chinensis by 3' and 5' rapid amplification of cDNA ends (RACE) PCR. The full-length cDNA consists of 2972 bp, encoding 757 amino acids with a calculated molecular mass of 84.96 kDa and a theoretical isoelectric point of 5.61. FcTG contains a typical transglutaminase-like homologue (TGc domain: E-value = 1.94e-38). Three catalytic sites (Cys-324, His-391 and Asp-414) are present in this domain. The deduced amino acid sequence of FcTG showed high identity with black tiger shrimp TG, kuruma shrimp TG and crayfish TG. Transcripts of FcTG mRNA were mainly detected in gill, lymphoid organ and hemocytes by RT-PCR. RNA in situ hybridization further confirmed that FcTG was constitutively expressed in hemocytes both in the circulatory system and lymphoid organ. The variation of mRNA transcription level in hemocytes and lymphoid organ following injection of killed bacteria or infection with white spot syndrome virus (WSSV) was quantified by RT-PCR. The up-regulated expression of FcTG in shrimp lymphoid organ following injection of bacteria indicates that it is inducible and might be associated with bacterial challenge. (c) 2006 Elsevier Ltd. All rights reserved.

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摘 要 矿物是沉积物的主要成分,其陆源组分经过地表径流或风带到海洋,直接或间接地沉积下来。海洋中陆源矿物的多寡反映了物源供给和输送动力的强弱,从长尺度看受构造活动和地貌演化所控制,因此大的构造运动必然在相邻边缘海沉积的陆源组分和通量变化中留下烙印。 新生代南海海盆经历了两次扩张,第二次扩张发生在32~15.5 Ma,这次扩张使东北巴拉望地块向南漂移,形成了南海中央海盆。青藏高原的隆升具有分阶段不均匀性,目前研究认为渐新世以来青藏高原快速隆升的时代有25~17 Ma,13~8 Ma 和3.4 Ma~现今。为了探明青藏高原加速隆升和南海构造扩张在南海沉积中的响应,我们对ODP 184 航次在中国南海1148站取得的沉积物进行了矿物学分析。通过化学提纯分离方法获得陆源矿物,粘土矿物,长石矿物、石英的含量以及它们的通量;通过X射线衍射分析获得粘土矿物的组成并估算了各组分的沉积通量;用激光粒度仪分析了陆源物质的粒度。 利用以上分析的结果和本航次的年代数据获得33 Ma以来的沉积矿物的含量、通量和陆源物质粒度随时间变化曲线。在此基础上讨论了33 Ma来南海陆源矿物含量和通量对南海构造扩张及青藏高原隆升的响应。结果发现南海28.5 Ma之前的沉积矿物组成与沉积通量同南海海底构造扩张的开始和脊跳跃有关;23.5 Ma之后的沉积受青藏高原隆升影响,青藏高原在25~17 Ma,13~8 Ma 和3.4~present的加速隆升南海沉积物中均有反映,尤其是3.4 Ma以来的快速隆升,在沉积矿物中的反映非常明显。从23.5 Ma开始,1148 站陆源矿物的源区从东南变到西北,这是因为随着南海海底扩张,南部物源远离沉积站位从而影响减弱;同时,青藏高原隆升导致地表剃度增加,河流转向与侵蚀加强并开始影响到南海。

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通过对健骨胶囊及实验大鼠股骨中的微量元素铜、锌、铁、锰的分析,阐述了健骨胶囊中微量元素对实验大鼠股骨中的微量元素铜、锌、铁、锰的影响以及骨质疏松症的改善,具有重要的营养学、药理功效学作用.

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于2006年10月对乌江干流梯级水库(乌江渡水库、东风水库、洪家渡水库、引子渡水库和普定水库)中微微型浮游生物(聚球藻、微微型真核浮游生物和异养细菌)的分布特征进行了调查.温度、溶解氧、pH、叶绿素等用YSI 6920进行原位测定.

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胶北煌斑岩分别采自龙口、烟台和威海地区,包括拉辉煌斑岩、斜闪正煌岩和角闪煌斑岩,煌斑岩K—Ar全岩年龄变化于89.3~169.5Ma,为晚中生代岩浆活动的产物。在岩石化学组成上,SiO2=42.02%~54.95%,以钙碱性系列为主.岩石以富集大离子亲石元素(LILE)(Ba,U,K,Th)和LREE,亏损高场强元素(HFSE)(Nb,Ta和Ti)为特征,Mg^#=33.9~53.9,Eu/Eu^*=0.71~0.89,^87Sr/^86Sr初始比值0.707642~0.709791,εNd(t)为-17.6~-10.4,^206Pb/^204Pb=37.588~38.431,^207Pb/^204Pb=15.423~15.531,^206Pb/^204Pb=17.204~18.179。表明煌斑岩源自俯冲陆壳(扬子下地壳)在地幔源区发生交代作用时形成的富集型地幔的部分熔融体.考虑到煌斑岩具有大陆边缘弧玄武岩的特征,我们认为煌斑岩在成因上同样与古大洋板块的俯冲作用有关,为碰撞后弧岩浆作用形成的脉岩。

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本文系统地研究了黔西南晴隆锑矿床中萤石的稀土元素地球化学,表面不同颜色,不同矿物组合的萤石的稀土元素含量变化较大,但具有固定的REE分配模式,以明显的负Ce异常,富MREE,分配曲线相平缓为特征;这种配分模式主要是受其晶体化学因素的控制,而与溶液中REE络合物的稳定性关系不大。萤石的稀土元素组成与其矿物共生组合的关系不大,但与其颜色关系较密切。萤石的Ce,Eu异常主要是受氧逸度的控制,流体源区的氧逸度较高,矿物沉淀场所的氧逸度相对较低,从而导致该矿中萤石呈明显的负Ce异常,或正或负的Eu异常。晴隆锑矿床形成于开放体系条件下,水/岩反应很可能是导致萤石发生沉淀的主要机制。萤石中的Ca部分来自茅口组灰岩,部分来自大厂层玄武岩;而矿化剂F及要来自外部。

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汞是一种毒性极强的环境污染物。由于汞能在大气中存在并能长距离迁移,因此汞已经被定义为全球性污染物。研究表明有色金属锌的冶炼是大气汞的一个重要的人为汞污染源。西方发达国家在炼锌过程中由于有严格的污染物控制措施,使得这个问题得到有效的控制。由于经济和技术的原因我国大多数锌冶炼企业在冶炼过程中没有进行烟气汞的回收,从而使得我们不能借鉴国外的相关研究成果。我国2005年精锌总产量占到了世界的1/4,是全世界最大的锌锭生产国家,但相关的研究却非常滞后。近年来我国锌冶炼向大气排汞的问题已经引起了国际争议,而且冶炼过程中排放的汞对局部生态系统会产生重要影响,因此锌冶炼过程中释放汞所造成的环境问题已经越来越受到人们的关注和重视。 本研究的目的是通过对不同锌矿山的锌矿石和浮选锌精矿以及冶炼厂不同源锌精矿的研究从而了解我国的矿石汞含量,及矿石浮选过程中汞的分配;通过对冶炼过程向大气排汞的研究,认识锌精矿中汞在锌冶炼过程中的分配,估算不同冶炼方式汞的释放因子。如A、B和C冶炼厂是用不同的工艺来炼锌的,其汞的释放因子也不同。通过对土法炼锌区和工业炼锌区水体、土壤、大气和植物中汞的分布、迁移转化规律的研究,认识锌冶炼对局部生态系统产生的影响。 1.矿石和锌精矿中汞的研究 成因和分类不同的铅锌矿床锌矿石和浮选锌精矿中汞的测定结果表明:凡口矿的矿石和浮选的锌精矿中汞含量比兰坪矿矿石和浮选锌精矿高了2个数量级。凡口矿锌矿石和锌精矿中汞的含量分别是64.5-107 mg∙kg-1,588-602 mg∙kg-1;对应兰坪矿锌矿石和锌精矿中汞的含量分别是0.23~0.40 mg∙kg-1,1.91-3.33 mg∙kg-1。不同冶炼厂不同矿源的锌精矿中汞含量测定结果表明:不同源锌精矿中汞含量在0.10-1100 mg∙kg-1之间,变动范围非常大。而冶炼厂冶炼所用的混合锌精矿中汞含量差别不大,冶炼所用的混和锌精矿汞含量在37-105 mg∙kg-1之间变动。 2.锌精矿中汞在冶炼过程中的分配和汞释放因子的研究 对采用不同炼锌工艺的冶炼厂和有除汞工艺的A、B冶炼厂所用的锌精矿中的汞在冶炼过程分配的质量平衡对比表明,A冶炼厂和B冶炼厂锌精矿中的汞在冶炼过程中的分配显著不同,主要制约因素是是否对烟气中汞进行回收。在烟气到达除汞设备前,A和B冶炼厂在焙砂和尘、酸洗、电除雾等流程对烟气中汞的去除效果相近。不同的是,A厂要进行烟气汞回收,烟气经过汞回收后,50%以上烟气中的汞在这一流程被去除。这使得A、B冶炼厂后续的流程制酸吸收汞和排向大气汞所占的比例有较大的差异。 不同冶炼方式的汞释放因子表明,无任何环保措施的土法炼锌活动的释汞因子为113 g·t-1,不对烟气汞进行回收的B厂和C冶炼厂汞的释放因子分别为49 g·t-1和243 g·t-1,对烟气汞回收的A冶炼厂汞的释放因子为5.7 g·t-1。综合各种不同炼锌方式的汞释放因子及其精锌产量,得出了锌冶炼过程中汞的综合释放因子,从而估算出我国锌冶炼向大气排汞量约61.3-178 t·y-1。 3.锌冶炼对局部生态系统的影响 炼锌区的冶炼废渣是冶炼过程中的主要废弃物,随意堆放的废渣是当地农田土壤的重要汞污染源,大气汞中活性汞和颗粒态汞的沉降也是当地农田土壤另一个汞污染源。土法炼锌区和工业炼锌区土壤分析结果表明,工业炼锌对局部环境的影响更为严重。土壤汞含量对比如下:A冶炼厂周边环境污染土壤汞含量259-2990 μg·kg-1,远高于威宁土法炼锌点污染土壤汞含量72-355 μg·kg-1。威宁土法炼锌点土壤中甲基汞含量的分析表明,在冶炼点附近的土壤中甲基汞绝对含量和甲基汞/总汞的比例都高于其它样点,说明冶炼点附近土壤中汞的甲基化水平提高。A冶炼厂污水处理渣亦没有得到妥善的处理,成为当地潜在的汞污染源。 土法炼锌区水体汞的含量明显受到冶炼渣的影响。工业炼锌过程产生的废水经处理后的水汞含量100%超过国家工业废水排放标准,这些处理后的水的排放是当地重要的汞污染源。A冶炼厂周边稻田水分析表明,溶解态甲基汞占溶解态总汞的的平均比率(5%)远高于一般自然水体(<1%),可能与稻田特殊环境有关。 土法炼锌区大气汞含量测定表明,冶炼点附近大气汞浓度剧增,高达5220 ng·m-3,锌冶炼是当地主要的大气汞污染源。大气汞浓度的提升,是导致农作物玉米叶部位汞含量增高的原因。植物体的地上绿色部分通过叶片吸收大气汞是植物体内汞富集的重要途径之一。 土法炼锌区和工业炼锌区农作物果实中汞含量的测定结果对比如下:A冶炼厂附近稻田产出的部分大米样品中总汞含量已经超过了国家食品限量卫生标准(20 µg·kg-1),所有辣椒中总汞含量全部超出了国家蔬菜卫生限量标准(10 µg·kg-1)。土法炼锌区所取农作物样品未出现果实汞含量超标现象。食用这些汞含量超标的食物将对当地居民带来潜在的危害。

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A Pd-Ag (24 wt%) alloy composite membrane was prepared by the magnetron sputtering. A gamma-Al2O3 membrane was synthesized by the sol-gel method and used as substrate of the Pd-Ag alloy film. The process parameters of the magnetron sputtering were optimized as a function of the compactness of the Pd-Ag alloy film. The best membrane with a thickness of 1 mu m was produced with a sputtering pressure of 2.7 Pa and a substrate temperature of 400 degrees C. The membrane had an H-2/N-2 permselectivity of 51.5-1000 and an H-2 permeation rate of 0.036-1.17 x 10(-5)cm(3)/cm(2).s. Pa, depending on operating conditions.