208 resultados para Igarapé-Açu - PA
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A unique reverse micelle method has been developed to prepare gold-coated iron (Fe@Au) nanoparticles. XRD, UV/vis, TEM, and magnetic measurements are utilized to characterize the nanocomposites. XRD only gives FCC patterns of gold for the obtained nanoparticles. The absorption band of the Fe@Au colloid shifts to a longer wavelength and broadens relative to that of the pure gold colloid. TEM results show that the average size of Fe@Au nanoparticles is about 10 nm, These nanoparticles are self-assembled into chains on micron scale under a 0.5 T magnetic field. Magnetic measurements show that the particles are superparamagnetic with a blocking temperature (T-B) of 42 K, At 300 K (above T-B), no coercivity (Hc) and remanence (M-r) is observed in the magnetization curve, while at 2K (below T-B) He and M, are observed to be 728 Oe and 4.12 emu/g, respectively, (C) 2001 Academic Press.
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Self-assembled monolayer of natural single-stranded DNA (ssDNA) from dl:natured plasmid DNA and pBR322/PstI marker was first observed on Au(111) by low-current STM (Lc-STM). The width of ssDNA stripe measured is 0.9 +/- 0.1 nm, which is just half of the theoretical width of double-stranded DNA (dsDNA). Each ssDNA stripe consists of bright and dark parts. alternatively; the period of two adjacent bright parts in the same ssDNA stripe measured is 0.4 +/- 0.1 nm, which is consistent with the theoretical distance between two adjacent base pairs in ssDNA. The stripe orientations in ssDNA domains are predominately at angles of 0 degrees, 60 degrees or 120 degrees relative to crystallographically faceted steps on the gold surface. The electrochemical experiment indicated that it was ssDNA but not dsDNA that was absorbed on Au(111)surface. (C) 2001 Elsevier Science B.V. All rights reserved.
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In situ electrochemical scanning tunneling microscopy (ECSTM) and an electrochemical quartz crystal microbalance (EQCM) have been employed to follow the adsorption/desorption processes of phenanthraquinone (PQ sat. in 0.1 mol l(-1) HClO4, solution) accompanied with an electrochemical redox reaction on the Au electrode. The result shows that: (1) the reduced form PQH(2) adsorbed at the Au electrode and the desorption occurred when PQH(2) was oxidized to PQ; (2) the adsorption process initiates at steps or kinks which provide high active sites on the electrode surface for adsorption, and as the potential shifts to negative, a multilayer of PQH(2) may be formed at the Au electrode; (3) the reduced PQH(2) adsorbed preferentially in the area where the tip had been scanned continually; this result suggests that the tip induction may accelerate the adsorption of PQH(2) on the Au(111) electrode. Two kinds of possible reason have been discussed; (4) high resolution STM images show the strong substrate lattice information and the weak monolayer adsorbate lattice information simultaneously. The PQH(2) molecules pack into a not perfectly ordered condensed physisorbed layer at potentials of 0.1 and 0.2 V with an average lattice constant a = 11.5 +/- 0.4 Angstrom, b = 11.5 +/- 0.4 Angstrom, and gamma = 120 +/- 2 degrees; the molecular lattice is rotated with respect to the substrate lattice by about 23 +/- 2 degrees. (C) 1997 Elsevier Science S.A.
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The modification of ethylene-propylene copolymer (EP) has been accomplished by radical EP-graft-acrylic acid (EP-g-AA) has been used to obtain ternary PA/EP/EP-g-AA blends by melt mixing. Different blend morphologies were observed by scanning electron microscopy; the domain size of the EP-dispersed phase in the polyamide 1010 matrix of compatibilized blends decreased compared with that of uncompatibilized blends. It is found that EP-g-AA used as the third component has a profound effect on the mechanical properties of the resulting blends. This behavior has been attributed to serious chemical interactions taking place between the two components. Thermal analysis shows that some thermal properties of PA in compatibilized PA/EP/EP-g-AA changed because of chemical reactions taken place during the blending process. Wide angle x-ray diffraction measurements also confirmed this result. (C) 1996 John Wiley & Sons, Inc.
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4-Aminophenol (4-AP), paracetamol (PRCT), norepinephrine (NE), and dopamine (DA) (all somewhat hydrophobic compounds) were HPLC electrochemically detected while the signals from uric acid (UA) and ascorbic acid (AA) (both hydrophilic compounds at the pH studied) were minimized, taking advantage of the permselectivity of the self-assembled n-alkanethiol monolayer (C-10-SAM)-modified Au electrodes based on solute polarity, The effects of various factors, such as the chain length of the n-alkanethiol modifier, modifying time, and pH value, on the permeability of C-10-SAM coatings were examined, The calibration curves, linear response ranges, detection limits, and reproducibilities of the EC detector for 4-AP, PRCT, NE, and DA were obtained, The result shows that the EC detector can be applied in the chromatographic detection of 4-AP, PRCT, NE, and DA in urine, effectively removing the influence of UA and AA in high concentrations existing in biological samples. As a result, a great improvement in the selectivity of EC detectors has been achieved by using Au electrodes coated with neutral n-alkanethiol monolayer.
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本文讨论了进口与国产PA—66经钴源辐射交联后,对机械物理性能产生的影响。发现适量经辐射的PA—66球压硬度、拉伸强度、Izod冲击强度都有较大幅度提高,并在100,000Gy剂量对达最大值,而断裂伸长率在100,000Gy剂量以下变化不大。国产PA—66辐射后在乙二醇中,在250℃时,2小时不起层,性能变化不大,可替代进口材料。
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I. INTRODUCTIONIn last decade, considerable attention was focused on polyacetylene. However, its practical application was affected considerably because of its poor strength and stability. Recently, Narrmann et al. reported that they could synthesize PA film with improved properties using modified Ziegler-Natta catalyst. However, no detailed
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The life cycle of seaweed Laminaria japonica involves a generation alternation between diploid sporophyte and haploid gametophte. The expression of foreign genes in sporophte has been proved. In this research, the recombinant expression in gametophyte was investigated by particle bombardment with the rt-PA gene encoding the recombinant human tissue-type plasminogen activator (Reteplase), which is a thrombolytic agent for acute myocardial infarction (AMI). Transgenic gametophytes were selected by their resistance to herbicide phosphiothricin (PPT), and proliferated in an established bubble column photo-bioreactor. According to the results from quantitative ELISA, Southern blotting, and fibrin agarose plate assay (FAPA) for bioactivity, it was showed that the rt-PA gene had been integrated into the genome of gametophytes of L. japonica, and the expression product showed the expected bioactivity, implying the proper post-transcript modification in haploid gametophyte.
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To evaluate the interactions between the atoms of An, Ag and Cu and clean Si(111) surface, two types of silicon clusters Si4H7 and Si16H20 together with their metal complexes were studied by using hybrid (U)B3LYP density functional theory method. Optimized geometries and energies on different adsorption sites indicate that: (1) the binding energies at different adsorption sites are large (ranging from similar to 1.2 to 2.6 eV depend on the metal atoms and adsorption sites), suggesting a strong interaction between metal atom and silicon surface; (2) the most favorable adsorption site is the on top (T) site. Mulliken population analysis indicated that in the system of on top (T) site, a covalent bond is formed between metal atom and dangling bond of surface Si atom. (c) 2006 Elsevier B.V. All rights reserved.
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概要介绍工业无线网络的标准化进程,详细介绍了用于过程自动化的工业无线网络WIA规范的网络构成、拓扑结构、协议体系和关键技术,并将WIA-PA与WirelessHART、ISASP100两大工业无线标准进行了比较分析。
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随着控制技术、计算机技术、通信技术的飞速发展,现场总线技术正逐渐取代集散控制技术。PROFIBUS现场总线技术作为应用最为广泛的现场总线技术之一,截止至2008年8月,其安装节点已经超过2500万个,市场份额超过20%。 本文首先深入研究了现场总线国际标准IEC61158-Type3(PROFIBUS标准),分析了PFOFIBUS 现场总线的层次结构模型、各层功能及层间通信关系,然后介绍了PROFIBUS PA的功能块模型,包括块的构成、分类、参数详解,以及把功能块模型映射到模块化DP从站设备的规则等。然后本文采用uC/OS-II嵌入式实时操作系统作为软件平台,应用瑞萨公司M16C/62P系列MCU与中科院沈阳自动化研究所自主研发的FBC0409现场总线通信控制器作为硬件平台,开发了支持PROFIBUS DPV0和DP V1的通信协议栈,并根据PA应用行规(V3.01)编写了相应的功能块程序,并且进行了验证。 本文给出了PROFIBUS DPV0、DPV1实现过程中的主要数据和功能定义,介绍了各层任务的创建初始化,处理过程,绘制了相关的软件流程图。本文给出了编写物理块、功能块、变换块和设备管理的参数定义和读写函数的方法。
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对海南二甲金矿和广东河台金矿形成的动力学条件进行了一系列的构造地球化学模拟实验。结果表明,动力变形中发生了明显的力学2化学耦合作用。云母矿物变形强烈,塑性变形,定向拉长显著。黑云母发生了褪色作用,从褐色变成浅褐色甚至无色;白云母干涉色从鲜艳的蓝色变为黄色,甚至无色。随试验温度、压力条件的升高,岩石、矿物从脆性变形向塑性变形演变。动力变形还使岩石和矿物中的元素呈现化学迁移和富集作用:云母矿物中的杂质容量降低,导致铁质释放;硫化物矿物的反射率增高,成矿元素特别是Au 在其不同部位发生一定的变化。自然金颗粒在析出过程中,与Si 、Fe 分离而纯化。动力变形中成矿元素(特别是Au)的迁移、富集等效应是通过压溶作用实现。
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对冬瓜山层控夕卡岩型铜矿床的矿物流体包裹体进行了深入研究,结果显示,主成矿阶段流体的温度高达350℃~400℃。成矿流体是一种高温、高盐度、高密度的流体,其中的稀土元素具轻稀土富集,Eu呈显著异常、轻重稀土分异明显的特征。由于其特殊的成矿环境,流体的输运过程是一种近于等温的过程,成矿作用发生于偏酸性且较还原的条件下。成矿流体由岩浆源和地层共同提供,是一个典型多成矿物质、多成矿阶段、多控矿因素的层控夕卡岩型矿床。
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扬子地块西南缘大面积低温成矿域的Au、Sb、Hg、As矿床,常出现共生分异的现象,在空间上形成Au、Sb、Hg、As矿床、矿带相伴出现而又相对独立的规律性分布。在详细研究Au、Sb、Hg、As矿床、矿带区域分布及其产出地质背景的基础上,从不同的角度,对制约Au、Sb、Hg、As矿床、矿带共生分异的因素进行了探讨。