399 resultados para 1253


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高纯熔石英中掺杂TiO_2可使其具有低热膨胀或无膨胀性及特殊的紫外吸收,以实现能量转换,提高红外发射率,因而对其结构研究已受到关注,我们曾用Raman光谱研究了其结构与光谱特性,本文用光电子能谱(ESCA)探讨不同TiO_2含量的熔石英中网络缺陷与钛的配位结构变化。

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本文研究了聚乙烯吡啶(PVP)化学修饰电极预富集——石墨炉原子吸收法测定酒石酸锑钾的方法。结果表明,在 pH 为3.5的 HCl 介质中,酒石酸锑钾浓度在5.4×10~(-8)~2.2×10~(-6)g/ml 范围内,与吸光度值呈良好的线性关系。对1.1×10~(-6)g/ml 的酒石酸锑钾溶液平行测定9次,相对标准偏差为4.9%,最低检测限为1.6×10~(-8)g/ml。17种异离子及有机物不干扰测定,回收率在97~103%之间,结果令人满意。

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Berberine was abstracted from coptis chinensis and its inhibition efficiency on corrosion of mild steel in 1 M H2SO4 was investigated through weight loss experiment, electrochemical techniques and scanning electronic microscope (SEM) with energy disperse spectrometer (EDS). The weight loss results showed that berbefine is an excellent corrosion inhibitor for mild steel immersed in 1M H2SO4. Potentiodynamic curves suggested that berbefine suppressed both cathodic and anodic processes for its concentrations higher than 1.0 x 10(-4) M and mainly cathodic reaction was suppressed for lower concentrations. The Nyquist diagrams of impedance for mild steel in 1 M H2SO4 containing berbefine with different concentrations showed one capacitive loop, and the polarization resistance increased with the inhibitor concentration rising. A good fit to Flory-Huggins isotherm was obtained between surface coverage degree and inhibitor concentration. The surface morphology and EDS analysis for mild steel specimens in sulfuric acid in the absence and presence of the inhibitor also proved the results obtained by the weight loss and electrochemical experiments. The correlation of inhibition effect and molecular structure of berberine was then discussed by quantum chemistry study. (c) 2005 Elsevier B.V. All rights reserved.

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Two new benzochromone glycosides, rubrofusarin 6-O-alpha-L-rhamnosyl- (1 -> 6)-O-beta-D-glucopyranoside (1) and demethylflavasperone 10-O-beta-D-glucopyranoside (2), have been isolated from the stem of Berchemia racemosa Sieb. et Zucc. (Rhamnaceae). Their structures were elucidated on the basis of spectroscopic evidence.

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本文介绍了利用结构光实现三维信息获取和重建的方法。该方法是利用结构光和CCD摄像机构成的视觉系统对物体扫描,获取物体可视表面的相对三维坐标,建立不同视点下物体可视域的三维描述。通过对这些离散三维描述的拟合,获得完整的物体三维描述,建立该物体的几何模型。该技术对拟实制造、仿形加工等应用领域具有重要的意义。

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O trabalho apresenta as informações reunidas, tratadas e disponibilizadas na forma de um website, que pode ser visto como um instrumento de informação, com vistas à gestão ambiental do município. Ou seja, o website elaborado e disponibilizado pode ser uma ferramenta federadora das diversas iniciativas locais. O website faz parte do conjunto de instrumentos para subsidiar a elaboração da Agenda 21 do Município de Campinas-SP, e disponibilizar, de forma simples e transparente, informações sobre meio ambiente municipal para todos os cidadãos. Os dados numéricos, cartográficos e iconográficos apresentados no website têm sempre um caráter transitório, pois são passíveis de atualização, novas precisões e enriquecimentos. Portanto, devem ser considerados como documentos de trabalho, e que confere um caráter inovador de utilização da Internet.

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I wish to propose a quite speculative new version of the grandmother cell theory to explain how the brain, or parts of it, may work. In particular, I discuss how the visual system may learn to recognize 3D objects. The model would apply directly to the cortical cells involved in visual face recognition. I will also outline the relation of our theory to existing models of the cerebellum and of motor control. Specific biophysical mechanisms can be readily suggested as part of a basic type of neural circuitry that can learn to approximate multidimensional input-output mappings from sets of examples and that is expected to be replicated in different regions of the brain and across modalities. The main points of the theory are: -the brain uses modules for multivariate function approximation as basic components of several of its information processing subsystems. -these modules are realized as HyperBF networks (Poggio and Girosi, 1990a,b). -HyperBF networks can be implemented in terms of biologically plausible mechanisms and circuitry. The theory predicts a specific type of population coding that represents an extension of schemes such as look-up tables. I will conclude with some speculations about the trade-off between memory and computation and the evolution of intelligence.

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Bryant-Quinn, M. (2006). Waldo Williams: 'Holi'n Hir yn y Tir Tywyll'. In D. Walford Davies and J. Walford Davies(Eds.), Cof ac Arwydd: Ysgrifau Newydd ar Waldo Williams (pp.143-162). Abertawe: Cyhoeddiadau Barddas.

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Joern Fischer, David B. Lindermayer, and Ioan Fazey (2004). Appreciating Ecological Complexity: Habitat Contours as a Conceptual Landscape Model. Conservation Biology, 18 (5)pp.1245-1253 RAE2008

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126 hojas : ilustraciones.

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Betha Cholmáin maic Luacháin (BCh) is a key source of information about a small ecclesiastical community of the Irish midlands in the medieval period. BCh is one of the longest medieval Irish hagiographic texts. A sole copy exists. Scholarly concern with manuscript Rennes 598, and the Life of Colmán therein, diminished following the 1911 edition of BCh. The most attention paid to BCh in the following decades focused largely on its onomastic information. The necessary detailed study of the text has not been undertaken. The present work is an initial view of significant areas of interaction between the church of Lann and its ecclesiastical, social and political milieu. While social and cultural aspects of the text may constitute the focus of this study, linguistic data is also investigated, complementary to evidence regarding its social and political testimony. In this way, light is cast on a complex ecclesiastical microcosm in the twelfth-century Irish midlands. In keeping with recent methodological work in the field a variety of tools are used to aid investigation, and to show the Life within its genre and wider context. An interdisciplinary approach will bring together strands of literary, cultural, archaeological, onomastic, historical, geographical, genealogical and hagiographical information, with reference to linguistic evidence where appropriate. This thesis seeks to suggest a template for studies undertaken on smaller church communities, and is set out in two main sections. The first section investigates the figure of the saint, his life, church, the manuscript source and the combination of prose and verse in the text. The second section examines the testimony of the Life regarding the ecclesiastical and secular concerns of the community of Lann, and how these concerns are represented. Evidence regarding the members of this community and their interaction with the church and the wider world is also discussed.

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Focal segmental glomerulosclerosis (FSGS) is a histological lesion with many causes, including inherited genetic defects, with significant proteinuria being the predominant clinical finding at presentation. Mutations in COL4A3 and COL4A4 are known to cause Alport syndrome (AS), thin basement membrane nephropathy, and to result in pathognomonic glomerular basement membrane (GBM) findings. Secondary FSGS is known to develop in classic AS at later stages of the disease. Here, we present seven families with rare or novel variants in COL4A3 or COL4A4 (six with single and one with two heterozygous variants) from a cohort of 70 families with a diagnosis of hereditary FSGS. The predominant clinical finding at diagnosis was proteinuria associated with hematuria. In all seven families, there were individuals with nephrotic-range proteinuria with histologic features of FSGS by light microscopy. In one family, electron microscopy showed thin GBM, but four other families had variable findings inconsistent with classical Alport nephritis. There was no recurrence of disease after kidney transplantation. Families with COL4A3 and COL4A4 variants that segregated with disease represent 10% of our cohort. Thus, COL4A3 and COL4A4 variants should be considered in the interpretation of next-generation sequencing data from such patients. Furthermore, this study illustrates the power of molecular genetic diagnostics in the clarification of renal phenotypes.

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A numerical modelling method for the analysis of solder joint damage and crack propagation has been described in this paper. The method is based on the disturbed state concept. Under cyclic thermal-mechanical loading conditions, the level of damage that occurs in solder joints is assumed to be a simple monotonic scalar function of the accumulated equivalent plastic strain. The increase of damage leads to crack initiation and propagation. By tracking the evolution of the damage level in solder joints, crack propagation path and rate can be simulated using Finite Element Analysis method. The discussions are focused on issues in the implementation of the method. The technique of speeding up the simulation and the mesh dependency issues are analysed. As an example of the application of this method, crack propagation in solder joints of power electronics modules under cyclic thermal-mechanical loading conditions has been analyzed and the predicted cracked area size after 3000 loading cycles is consistent with experimental results.