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HG-ICP-AES法测定多金属矿区人发中的汞和砷 总被引:4,自引:2,他引:2
应用ICP-2070型等离子体发射光谱仪和氢化物发生技术,采用HNO3-HClO4酸消解体系,建立了生物样品中痕量汞和砷的氢化物发生-等离子体发射光谱检测法(HG-ICP-AES法)。在选定的实验条件下,Hg和As的检测限分别达到0.6和0.8 ng·mL-1,且分析稳定性较好,能满足生物样品中痕量Hg和As的检测要求。对人发、大米和茶叶等国家标准物质中Hg和As的含量进行对照测定,检测结果与推荐值一致,测定结果的RSD均在5%左右。与此同时,应用本法实测了湘西多金属矿区人发中Hg和As的含量,发现该矿区发Hg和发As平均含量为1.290和1.865 μg·g-1,分别为对照的3.59倍和2.44倍。表明湘西矿区人群Hg和As暴露危害严重,须引起相关部门重视。 相似文献
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Ⅲ族氮化物(又称GaN基)宽禁带半导体属于新兴的第三代半导体体系,在短波长光电子器件和功率电子器件领域具有重大应用价值。过去10多年,以蓝光和白光LED为核心的半导体照明技术和产业飞速发展,形成了对国家经济和人民生活产生显著影响的高技术产业。近年来GaN基功率电子器件受到了学术界和产业界的高度重视,形成了新的研发和产业化热点。首先介绍了半导体照明技术和产业的发展历程和现状,分析了当前GaN基LED芯片技术面临的关键科学和技术问题;然后重点介绍了GaN基微波功率器件和电力电子器件的发展历程和动态,包括微波功率器件已经取得的突破性进展和产业化现状,电力电子器件相对Si和SiC同类器件的优势和劣势,并对GaN基功率电子器件当前面临的关键科学和技术挑战进行了较详细的分析。 相似文献
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EAST中央控制系统 总被引:2,自引:0,他引:2
描述了EAST中央控制系统和EAST虚拟合作实验室系统的体系结构和各个部分的主要功能和设计思想。EAST中央控制系统主要功能是协调统一各个控制、诊断、采集子系统,为各个子系统提供统一的控制接口。EAST中央控制系统制定和规范了与各分控系统之间的通信协议,加强了对各分控系统的控制,统一和规范了控制数据的发布和控制参数的设置。系统按照功能模块设计和实施,有效地提高了系统的升级和扩展能力。 相似文献
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杉木综纤维素和木质素的近红外光谱法测定 总被引:16,自引:2,他引:14
用近红外光谱法对杉木中综纤维素和木质素含量进行了快速测定。用常规湿化学方法测定了48个杉木木材样品的综纤维素和木质素,用近红外光谱仪采集相应的光谱,进行二阶微分处理和平滑预处理后,用偏最小二乘法和完全交互验证方式建立相应预测模型。综纤维素校正模型和预测模型的相关系数分别为0.96和0.93;预测标准误差分别为0.39和0.50;木质素校正模型和预测模型的相关系数分别为0.99和0.90;预测标准误差分别为0.10和0.28。结果表明,近红外光谱法可以快速分析木材中综纤维素和木质素含量。 相似文献
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凸透镜成像规律这一重点和难点一直困扰着很多师生,对这个规律的理解和应用也较为生硬和枯燥.其实这规律中还有规律,焦点可分虚实像,二倍焦距可分像的大小,像的放大和缩小也是全方位的,物和像的移动是同方向的. 相似文献
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一、粒子物理和标准模型自从20世纪30年代物理学家建立了原子模型之后,人类对亚原子和更深层次物质结构、相互作用和自然规律的实验、理论的探索和研究揭示了自然界基本粒子的存在和他们的特性,以及由这些基本粒子组成的各类介子,重子,原子,分子和它们形成的丰富和多样的自然物质世界。 相似文献
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利用基于密度泛函理论的第一性原理方法计算TiCrTaV多组元合金中两种BCC结构的结构稳定性、力学性能、德拜温度、电子结构和布居分析.生成焓和内聚能结果表明BCC1的结构稳定性更好,更容易形成.弹性常数和模量表明BCC1的强度和韧性更强,BCC2的抗剪切能力和刚度更好,两种结构均具有弹性各向异性.德拜温度和Grüneisen参数结果表明BCC2的键合强度和热稳定性更好.电子结构和布居分析表明两种结构均包含共价键和金属键. Ta原子形成的共价键强度更大,金属键仅存在于Ti、Cr和V原子之间.元素成键后Ti和V原子失去电子,Cr和Ta原子得到电子. 相似文献
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María Pilar Chantada-Vázquez Antonio Moreda-Piñeiro María Carmen Barciela-Alonso 《应用光谱学评论》2017,52(2):145-174
Metalloproteins and metal–protein complexes play key roles in all organisms. For example, certain metalloproteins are involved in metal homeostasis and detoxification, or oxidative stress protection; whereas, metals serve as essential cofactors in a large number of metal–protein complexes. Advances in analytical instrumentation as well as informatics have allowed a complete characterization/assessment of both metalloproteins and metal–protein complexes. In some cases, the identification of the protein is a key factor for understanding its physiological function, such as when assessing protein corona in nanoparticles–protein assemblies. On other occasions, the identification of the binding sites in the peptide chain and conformational changes as a consequence of the metal–protein interaction, as well as the lability of this interaction, can explain the role of these metal-based biomolecules in living organisms. This article attempts to critically review the current state-of-the-art of the available analytical techniques for characterizing metalloproteins and metal–protein complexes. Methods for assessing the structure, characterization of the metal-binding sites, as well as the class of proteins involved in some metal (metallic nanoparticle)-binding proteins are discussed. Recent developments when assessing metalloproteins and metal–protein complexes in the clinical, environmental, and food fields, and pioneering research regarding nanoparticle–protein characterization, are also reviewed. 相似文献
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Hendrik Heinz Chandrani Pramanik Ozge Heinz Yifu Ding Ratan K. Mishra Delphine Marchon Robert J. Flatt Irina Estrela-Lopis Jordi Llop Sergio Moya Ronald F. Ziolo 《Surface Science Reports》2017,72(1):1-58
Nanostructures of diverse chemical nature are used as biomarkers, therapeutics, catalysts, and structural reinforcements. The decoration with surfactants has a long history and is essential to introduce specific functions. The definition of surfactants in this review is very broad, following its lexical meaning “surface active agents”, and therefore includes traditional alkyl modifiers, biological ligands, polymers, and other surface active molecules. The review systematically covers covalent and non-covalent interactions of such surfactants with various types of nanomaterials, including metals, oxides, layered materials, and polymers as well as their applications. The major themes are (i) molecular recognition and noncovalent assembly mechanisms of surfactants on the nanoparticle and nanocrystal surfaces, (ii) covalent grafting techniques and multi-step surface modification, (iii) dispersion properties and surface reactions, (iv) the use of surfactants to influence crystal growth, as well as (v) the incorporation of biorecognition and other material-targeting functionality. For the diverse materials classes, similarities and differences in surfactant assembly, function, as well as materials performance in specific applications are described in a comparative way. Major factors that lead to differentiation are the surface energy, surface chemistry and pH sensitivity, as well as the degree of surface regularity and defects in the nanoparticle cores and in the surfactant shell. The review covers a broad range of surface modifications and applications in biological recognition and therapeutics, sensors, nanomaterials for catalysis, energy conversion and storage, the dispersion properties of nanoparticles in structural composites and cement, as well as purification systems and classical detergents. Design principles for surfactants to optimize the performance of specific nanostructures are discussed. The review concludes with challenges and opportunities. 相似文献
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S. K. Chakarvarti 《Indian Journal of Physics》2009,83(6):737-749
Many techniques are being used in order to synthesize nano-micro materials falling under the realm of nanotechnology. It need
not be overemphasized that the miniaturization of devices and synthesis of new materials have a tremendous role in the development
of powerful electronics as well as material based technologies in other areas but for the laws of quantum mechanics posing
limitations besides the increasing cost and difficulties in manufacturing in such a small scale. The quest, therefore, for
the alternative technologies, have stimulated a surge of interest in nano-meter scale materials and devices in the recent
years. Metallic as well as semiconducting nano wires are the most attractive materials because of their unique properties
having myriad of applications like interconnects for nano-electronics, magnetic devices, chemical and biosensors, whereas
the hollow tubules are equally considered to be candidates for more potent applications — both in physical as well as biosciences.
Materials’ processing for nano-structured devices is indispensable to their rational design. The technique, known as “Template
Synthesis”, using electrochemical-electro less deposition is one of the most important processes for manufacturing nano-micro
structures, nano-composites and devices and is relatively inexpensive and simple. The technique involves using membranes —
ion crafted ones (popularly known as Particle Track-Etch Membranes or Nuclear Track Filters), alumite substrate membranes,
besides other types of membranes as templates. The parameters viz., diameter as well as length i.e., aspect ratio, shape and wall surface traits in these membranes are controllable.
In the present article a detailed review of this technique using track-etch membranes as templates in synthesis of nano-micro
materials including hybrid materials and devices like field-ion emitters, resonant tunneling diodes (RTDs) etc. is presented including most of the results obtained in our laboratory.
相似文献
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Physics of counterpropagating optical beams and spatial optical solitons is reviewed, including the formation of stationary states and spatiotemporal instabilities. First, several models describing the evolution and interactions between optical beams and spatial solitons are discussed, that propagate in opposite directions in nonlinear media. It is shown that coherent collisions between counterpropagating beams give rise to an interesting focusing mechanism resulting from the interference between the beams, and that interactions between such beams are insensitive to the relative phase between them. Second, recent experimental observations of the counterpropagation effects and instabilities in waveguides and bulk geometries, as well as in one‐ and two‐dimensional photonic lattices are discussed. A variety of different generalizations of this concept are summarized, including the counterpropagating beams of complex structures, such as multipole beams and optical vortices, as well as the beams in different media, such as photorefractive materials and liquid crystals. 相似文献
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The characteristics of radio-frequency (RF) plasma sheaths have been topics of much scientific study for decades, and have
also been of great importance in the manufacture of integrated circuits and fabricating microelectromechanical systems (MEMS),
as well as in the study of physical phenomena in dusty plasmas. The sheaths behave special properties under various situations
where they can be treated as collisionless or collisional, single-or dual-RF, one-or two-dimensional (1D or 2D) sheaths, etc.
This paper reviews our recent progress on the dynamics of RF plasma sheaths using a fluid method that includes the fluid equations
and Poission’s equation coupled with an equivalent circuit model and a hybrid method in which the fluid model is combined
with the Monte-Carlo (MC) method. The structures of RF sheaths behave differently in various situations and plasma parameters
such as the ion density, electron temperature, as well as the external parameters such as the applied frequency, power, gas
pressure, magnetic field, are crucial for determining the characteristics of plasma sheaths. 相似文献
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M. E. Elzain A. A. Yousif A. D. Al Rawas A. M. Gismelseed H. Widatallah K. Bouziani I. Al-Omari 《Hyperfine Interactions》2005,164(1-4):3-15
The electronic and magnetic structures of small FCC iron clusters in FCC Rh, Pd and Ag were calculated using the discrete
variational method as a function of cluster size and lattice relaxation. It was found that unrelaxed iron clusters, remain
ferromagnetic as the cluster sizes increase, while for relaxed clusters antiferromagnetism develops as the size increases
depending on the host metal. For iron in Rh the magnetic structure changes from ferromagnetic to antiferromagnetic for clusters
as small as 13 Fe atoms, whereas for Fe in Ag antiferromagnetism is exhibited for clusters of 24 Fe atoms. On the hand, for
Fe in Pd the transition from ferromagnetism to antiferromagnetism occurs for clusters as large as 42 Fe atoms. The difference
in the magnetic trends of these Fe clusters is related to the electronic properties of the underlying metallic matrix. The
local d densities of states, the magnetic moments and hyperfine parameters are calculated in the ferromagnetic and the antiferromagnetic
regions. In addition, the average local moment in iron-palladium alloys is calculated and compared to experimental results. 相似文献
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Tamara Basova Petr Semyannikov Vladimir Plyashkevich Aseel Hassan Igor Igumenov 《固体与材料科学评论》2009,34(3-4):180-189
The current review summarizes the data of saturated vapor pressure and thermodynamic parameters of the sublimation process of different phthalocyanines as reported in the literature as well as in our work. The volatility of phthalocyanines is analyzed from the standpoint of their molecular and crystal structure. The differences in the saturated vapor pressure value of the investigated phthalocyanines may reach some orders of magnitude and are determined by the Van der Waals and electrostatic interaction of the peripheral atoms of adjacent molecules, as well as to a specific interaction, the type and number of which depend on the type of molecules packing in the crystal. 相似文献
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快速的城市化进程使得当前城市普遍面临绿地面积减少、抗自然灾害能力下降等问题。针对城市资源与需求的矛盾,对现有屋顶绿化自动管理系统进行了研究,设计了一种基于无线传感器网络的屋顶绿化智慧管理系统。通过实时获取光照强度等植物生长环境参数;使用层次分析法对植物生长环境进行评估与分析,提出了量化环境适宜度指标,通过反馈控制系统,实现屋顶绿化植物的智慧管理。实验结果表明,与传统屋顶绿化方法相比较,系统可以提高24%的植物存活率,同时可实现屋顶降温20%的目标。系统具有成本低、自适应管理等优点,可以广泛应用于当前我国的城市屋顶绿化中,也可以为学界和业界的相关研究提供参考。 相似文献
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Xavier Carpentier Dominique Bazin Paul Jungers Solenn Reguer Dominique Thiaudière Michel Daudon 《Journal of synchrotron radiation》2010,17(3):374-379
At the surface of attached kidney stones, a particular deposit termed Randall's plaque (RP) serves as a nucleus. This structural particularity as well as other major public health problems such as diabetes type‐2 may explain the dramatic increase in urolithiasis now affecting up to 20% of the population in the industrialized countries. Regarding the chemical composition, even if other phosphate phases such as whitlockite or brushite can be found as minor components (less than 5%), calcium phosphate apatite as well as amorphous carbonated calcium phosphate (ACCP) are the major components of most RPs. Through X‐ray absorption spectroscopy performed at the Ca K‐absorption edge, a technique specific to synchrotron radiation, the presence and crystallinity of the Ca phosphate phases present in RP were determined ex vivo. The sensitivity of the technique was used as well as the fact that the measurements can be performed directly on the papilla. The sample was stored in formol. Moreover, a first mapping of the chemical phase from the top of the papilla to the deep medulla is obtained. Direct structural evidence of the presence of ACCP as a major constituent is given for the first time. This set of data, coherent with previous studies, shows that this chemical phase can be considered as one precursor in the genesis of RP. 相似文献