Avances en espectrometría de masas con fuente de plasma: Análisis simultáneo de elementos mayores y trazas mediante Q-ICP-MS y análisis isotópicos de Sm-Nd mediante HR-MC-ICP-MS. Aplicación en estudios geoquímicos

186 p. : il.

Retratos das periferias urbanas nos raps dos Racionais MC's

Este trabalho tem por objetivo verificar, a partir do recorte de um dado discurso musical (rap), como os jovens das periferias urbanas brasileiras têm representado discursivamente o social. Sob esse aspecto, a representação dos atores sociais no discurso é o principal foco analítico, tendo como perspectivas teóricas de estudo a Análise Crítica do Discurso (doravante ACD), e a lingüística funcional sistêmica (doravante LFS) no que diz respeito a questões de linguagem. O trabalho apresenta uma introdução na qual são apontadas características de grupos musicais diretamente afetados por conflitos sociais, destacando-se como corpus de trabalho o discurso musical dos Racionais MCs e seguindo-se de uma contextualização histórica do grupo e do movimento hip- hop. Em seguida, apresentam-se, no capítulo teórico, as matérias ligadas diretamente ao objeto de estudo (discurso, ideologia e tipos de significado), ao mesmo tempo em que é feita uma apresentação da linha teórica utilizada e da orientação assumida pelos autores de referência para o trabalho (Fairclough e Halliday). Logo depois, no capítulo metodológico, são descritas as etapas de construção da pesquisa, observando-se os seguintes aspectos: 1) apresentação dos critérios de constituição do corpus, destacando o interesse pelo estilo rap, através de suas principais características, até delimitar as músicas do grupo Racionais MCs para análise; 2) descrição do corpus, a partir de uma característica particular (gangstar rap), com posterior explicação da metodologia criada aqui para sua análise; 3) explicação da categoria analítica utilizada (a representação dos atores sociais), através de exemplos dados pelo seu autor (van Leeuwen, 1996) e outros encontrados no próprio corpus. A análise volta-se, inicialmente, para a observação do significado representacional enfocando as estratégias de representação dos atores sociais utilizadas pelo discurso rap; e, num segundo momento, revela uma prática de polarização, a partir da qual se traça a identidade discursiva do grupo Racionais MCs e sua alteridade (significado identificacional). Com os resultados obtidos, foi possível refletir sobre uma forma de representar o mundo, realizada atualmente por alguns jovens oriundos de comunidades periféricas. Dessa forma, foi possível perceber como os sentidos produzidos por eles podem revelar aspectos significativos de uma nova ordem social brasileira

不同光源下TiO_2膜对MC-RR光催化降解的比较研究

通过溶胶-凝胶法制备了纳米级的锐钛矿型TiO2膜,利用纯化的MC-RR分别研究了该膜在太阳光、UVA和UVC三种光源下对MC-RR的催化降解行为。结果表明,太阳光下TiO2膜对MC-RR的催化降解反应符合一级反应动力学,而在UVA和UVC下符合二级反应。不同光源下TiO2膜的催化效果差别较大,在太阳光下催化效果最为明显,反应速率常数由5.12×10-5·min-1增加到5.49×10-3·min-1,增加了两个数量级;UVA次之,由6.0×10-4L·mg-1·min-1增加到1.55×10-3L·mg-

Implementation of multi-group cross-section methodology in BGCore MC-depletion code

BGCore is a software package for comprehensive computer simulation of nuclear reactor systems and their fuel cycles. The BGCore interfaces Monte Carlo particles transport code MCNP4C with a SARAF module - an independently developed code for calculating in-core fuel composition and spent fuel emissions following discharge. In BGCore system, depletion coupling methodology is based on the multi-group approach that significantly reduces computation time and allows tracking of large number of nuclides during calculations. In this study, burnup calculation capabilities of BGCore system were validated against well established and verified, computer codes for thermal and fast spectrum lattices. Very good agreement in k eigenvalue and nuclide densities prediction was observed for all cases under consideration. In addition, decay heat prediction capabilities of the BGCore system were benchmarked against the most recent edition of ANS Standard methodology for UO2 fuel decay power prediction in LWRs. It was found that the difference between ANS standard data and that predicted by the BGCore does not exceed 5%.

Determinations of MC-LR and [Dha(7)] MC-LR Concentrations and Physicochemical Properties by Liquid Chromatography-Tandem Mass Spectrometry

A liquid chromatography electrospray mass spectrometry (LC/ESI/MS) method working in multiple reactions monitoring mode for the determination of trace amounts of microcystin variants (MC-LR and [Dha(7)] MC-LR) in waters was developed. The limit of quantification was 0.05 mu g/L and the limit of detection was 0.015 mu g/L for MC-LR and [Dha(7)] MC-LR, respectively. Recoveries for MCs were in the range of 68%-81%. MC-LR and [Dha(7)] MC-LR were chemically stable with similar physiochemical behavior.

A novel chemiluminescent immunoassay for microcystin (MC) detection based on gold nanoparticles label and its application to MC analysis in aquatic environmental samples

A novel chemiluminescent immunoassay method based on gold nanoparticles was developed for the detection of microcystins (MCs). The immunoassay included three main steps: indirect competitive immunoreaction, oxidative dissolution of gold nanoparticles, and indirect determination for MCs with Au3+-catalysed luminol chemiluminesent system. The method has a wide working range (0.05-10 mu g L-1, r(2) = 0.9914), the limit of detection was determined to be 0.024 mu g L-1, which is much lower than the World Health Organization's proposed guidelines (1 mu g L-1) for drinking-water. The proposed method was applied to MC analysis in natural water and fish tissue samples, and most results in the proposed method were in agreement with the conventional indirect competitive enzyme-linked immunosorbent assay method, which indicated that the new chemiluminescent immunoassay was sensitive, reliable, and suitable for MC analysis in natural water and fish tissue samples.

mc-Si : H/c-Si solar cell prepared by PECVD

Hetero-junction solar cells with an me-Si: H window layer were achieved. The open voltage is increased while short current is decreased with increasing the mc-Si:H layer's thickness of emitter layer. The highest of V-oc of 597 mV has obtained. When fixed the thickness of 30 nm, changing the N type from amorphous silicon layer to micro-crystalline layer, the efficiency of the hetero-junction solar cells is increased. Although the hydrogen etching before deposition enables the c-Si substrates to become rough by AFM images, it enhances the formation of epitaxial-like micro-crystalline silicon and better parameters of solar cell can be obtained by implying this process. The best result of efficiency is 13.86% with the V-oc of 549.8 mV, J(sc) of 32.19 mA center dot cm(-2) and the cell's area of 1 cm(2).

改性剂对Mc尼龙－6等温结晶动力学的影响

用差示扫描量热法测定了Ⅲ型改性剂对ＭＣ尼龙－６等温结晶行为的影响。结果表明，Ａｖｒａｍｉ指数ｎ、成核机理、晶体生长方式及结晶晶型基本不受改性剂的影响，Ⅲ型改性剂使ＭＣ尼龙－６熔体等温结晶条件下结晶速率变慢，结晶度χｃ略有降低，平衡熔点升高６℃，有利于改善ＭＣ尼龙－６的韧性及耐热性。

利用MC-ICP-MS测定硼同位素及其在西藏地热和盐湖中的初步应用

Based on previous studies, boron can be separated from aqueous samples with Amberlite IRA-743 resin. Experiments on the elute temperature, elute volume and the dynamic resin exchange capacity have been performed in this study. Results show that the dynamic exchange capacity of the resin is 4.2mg B/g and at room temperature, boron fixed on the resin within this capacity level can be extracted quantitatively by using 5ml 2%HNO3. A new procedure has been developed for the measurement of boron isotope ratios in water samples using a Neptune MC-ICP-MS, after resolving the memory effect, which is a key problem, and investigating the impacts of mass bias and Si matrix effect. Using this method, it usually takes 20 min to perform one measurement on 0.1ppm boron solution with a precision of 0.23‰ (SD). If the relative deviation between a sample and the standard is large, the washout time needs to be doubled to achieve a higher precision. δ11B values of water samples from Yangbajing geothermal field vary from -10.53 to -9.13‰. Owing to the large difference B concentration and the small B isotope difference between deep geothermal water and surface water, B isotope ratios of the shallow geothermal fluids are dominated by the deep end member rather than the shallower one in the mixing process. As a consequence, δ11B-B relation is indicative basically of a dilution process. Vapor-liquid separation and calcite scaling also greatly influence B isotope fractionation. δ11B values of water samples from Dagejia geothermal field are from -15.98‰ to -11.67‰. Boron in Changma River near the field has two sources, freshwater lakes (Dajiamang Lake and Canke Lake) and geothermal waters. Finally, a preliminary discussion is included on boron geochemical characteristics of the salt lakes in Shuanghu area and other geothermal fields, to provide information for future studies on boron isotope geochemistry of geothermal systems and salt lakes in Tibet.

Lu-Hf同位素的MC-ICP-MS实验方法及其在华北克拉通典型火山岩研究中的应用

Over past ten years, a great development has been made in the Lu-Hf isotopic system with the advent of MC-ICP-MS. Based on a comprehensive review of available references in the related field, a novel analytical protocol of three exchange chromatographies after one mixed acid attacking geological samples was developed in this work, which not only avoids common multiple sample treatments for natural inhomegeneous samples, but also is useful for Rb-Sr, Sm-Nd and Lu-Hf isotopic system simultaneously, especially for the garnet- and apatite-bearing rocks for the Sm-Nd and Lu-Hf geochronology. An analytical procedure for the Lu and Hf concentration in geological samples determined by by ID-MC-ICP-MS was detailedly investigated. The Hf yield is > 90 % and total procedural blank is less than. 50 pg for Hf and 10 pg for Lu, respectively. The developed method was successfully applied to the determination of Lu and Hf concentrations for USGS geological materials. A one-column procedure for Hf purification in geological samples using common anion exchange chromatography and its isotopic analyses by MC-ICP-MS were also established. Multiple analyses of Standard Reference Materials demonstrate that this method was simple, time-saving, cheap and efficient, especially suitable for the Hf isotopic compositions of young samples. Finally, the measurements of Sr and Nd isotopic compositions using Neptune MC-ICP-MS were described briefly, which indicates that Neptune MC-ICP-MS can precisely measure Sr and Nd isotopic compositions as the TIMS does, even more efficient and less time-consuming than the TIMS method. The Hf isotopic characteristics of typical volcanic rocks (Cenozoic Changle-Linqu basalts, Mesozoic Fangcheng basalts, Mesozoic Jianguo basalts, Mesozoic Wulahada high-Mg andesite, Cenozoic Fanshi, Zuoquan and Xiyang-Pingding basalts of the Taihang Mountains, Paleozoic diamondiferous Menyin and Fuxian Kimblites) from the North China Craton were firstly studied in this work. Coupled with Nd isotopic compositions, it shows that the Hf isotopes could be a better tracer for mantle sources than the Nd isotopes. Individual kimberlite fields from both the Mengyin and Fuxian regions have quite uniform Hf isotopic compositions, similar to the situation for the Nd isotopes.

硒、锌同位素MC-ICP-MS分析方法研究及其在生物和环境样品中的应用

一定元素的同位素组成被认为是该元素特有的“指纹”，同位素组成测量是地球化学、生命科学、环境化学、地质科学和核科学等领域重要的研究手段。利用同位素技术开展生命过程，地球系统中的物理、化学、生物过程及其资源、环境与灾害效应，资源勘探，污染物溯源等方面的研究，既是该技术的前沿研究主题，也使相关领域的研究更加“精细量化”，从而在新的科学纵深揭示出更加清晰的规律。 1992年多接收电感耦合等离子体质谱仪(MC-ICP-MS)的问世，为同位素分析提供了一种强有力的技术手段，与传统的热电离同位素质谱相比，MC-ICP-MS具有测量速度快、操作简便、灵敏度高等优点。而且，由于等离子体源产生的高温，在理论上能测量所有的金属元素和一些非金属元素，并已很好地解决了一些高电离电位元素同位素测量的难题（如Se, Zn, Hf等），用MC-ICP-MS准确、精密测量各种元素同位素组成的方法正在逐渐得到发展和完善。目前，MC-ICP-MS比较成熟的方法主要是针对核和地质科学研究中应用较多的U, Pb, Sm, Nd, Sr, Hf, B, Li等，在硒和锌同位素测量方法学的研究还相对较少（尤其是硒），对一些测量中受各种干扰较为严重的、原子量小于80 的元素同位素的测量技术还有待进一步深入探索和研究。锌、硒元素不仅与人类健康息息相关，而且随着质谱分析技术的发展，使其在环境地球化学、生命科学等领域有着广泛的应用前景。准确测量生物、食品、环境、地质等样品中的锌、硒元素含量、各种形态及其同位素组成受到越来越多的关注。锌、硒同位素准确测量的方法学研究，不仅可以广泛应用于各相关领域，也为锌和硒同位素基、标准物质研制奠定技术基础，从而为锌、硒元素含量和同位素测量提供量值溯源保障。 本工作针对锌和硒元素同位素组成以及生物、环境等样品中成分量准确测量存在的问题，通过使用六极杆碰撞室MC-ICP-MS进行准确测量锌和硒元素同位素的技术研究，结合在化学计量研究中的长期实践及相关文献，从方法学角度和应用方面得出以下结论： 1.MC-ICP-MS仪器测量主要参数，如炬管轴向位置、载气流量、碰撞气流量、仪器稳定性等对测量结果影响很大，要获得高精度的测量结果，须优化和固定参数设置，保持仪器的稳定状态。在六极杆碰撞室MC-ICP-MS测量锌同位素时，高纯氩气碰撞气模式是较为理想的模式，64Zn/66Zn、67Zn/66Zn、68Zn/66Zn同位素丰度比测量精度达到0.002－0.008％，70Zn/66Zn 测量精度达到0.01％；在高纯氢气和氩气碰撞气按一定比例混合的模式下， 76Se/80Se、77Se/80Se、78Se/80Se、82Se/80Se同位素丰度比测量精度达到0.004－0.005%。 2.采用高纯、高浓缩64Zn和66Zn配制了8个校正样品 (64Zn/66Zn：0.6－2.2)；用高纯、高浓缩同位素76Se和82Se配制了16个校正样品（76Se/82Se： 0.05－11.8），用这些样品分别测量并计算了仪器系统误差校正系数K，这些校正样品的K64/66 和 K76/82的相对标准偏差分别为0.034％和0.03％，均在仪器的测量不确定度范围内，说明在校正样品同位素变化范围内，仪器测量同位素丰度比的校正系数没有发生明显变化。 3.在硒同位素丰度比值测量中，氢气碰撞气的使用是SeH产生的重要原因之一，Ar/H在2－7之间都可以满足硒同位素比值测量的要求，即保证较高的硒灵敏度、较小的SeH生成比例、稳定的同位素比值测量结果。本工作建立了SeH的校正计算公式，在对测量结果的质量歧视进行校正时，77Se和78Se的校正更为复杂，因为它们除自身产生的SeH外，还分别受到了来自76SeH和77SeH的影响，故校正质量偏移时应首先对SeH进行校正。对于不同的SeH生成比例，经过校正后，硒的同位素丰度比校正值是一致的，并不受SeH生成比例变化影响。 4.通过对IDMS过程中的关键技术研究，明确了如何正确使用该方法以获得准确测量结果。IDMS方法在测量步骤中引入的不确定度影响因素相对于其它化学分析方法较少，并且可以被明确地表达出来，测量结果可直接溯源到国际单位，因此，该方法对化学计量学研究具有十分重要的意义。 5.建立了适用于ICP-MS测量血清、大豆粉、金枪鱼等多种复杂基体中锌和硒元素的样品前处理方法，建立了锌和硒的ICP-IDMS测量方法。将建立的方法应用于人血清标准物质研制、国家计量院之间的国际比对和合作研究中，取得的优异成绩验证了所建方法的可靠性和可比性。IDMS方法在样品前处理上不怕样品损失和高精度同位素丰度比测量的优点，使其在复杂基体中硒、锌的准确测量方面较其它分析方法具有独特的优势，可在生物、临床、环境、食品等方面的分析研究中广泛应用。