890 resultados para MC-VIEW


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Natural hazards and human activities in the coastal zone are threatening the integrity of the coastal resource system. Conflicts of interest between short term economic benefits and long term ecologic assets should be identified and solved by means of a balanced CZM approach. Systems analysis, supported by mathematical modelling tools are the appropriate instruments to assist the coastal zone manager. The paper presents a general system description of the coastal zone, and focuses on the modelling of the natural subsystem components of this system as a first step towards a model for Integrated Coastal Management (ICM).

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Maps of surface chlorophyllous pigment (Chl a + Pheo a) are currently produced from ocean color sensors. Transforming such maps into maps of primary production can be reliably done only by using light-production models in conjuction with additional information about the column-integrated pigment content and its vertical distribution. As a preliminary effort in this direction. $\ticksim 4,000$ vertical profiles pigment (Chl a + Pheo a) determined only in oceanic Case 1 waters have been statistically analyzed. They were scaled according to dimensionless depths (actual depth divided by the depth of the euphotic layer, $Z_e$) and expressed as dimensionless concentrations (actual concentration divided by the mean concentration within the euphotic layer). The depth $Z_e$ generally unknown, was computed with a previously develop bio-optical model. Highly sifnificant relationships were found allowing $\langle C \rangle_tot$, the pigment content of the euphotic layer, to be inferred from the surface concentration, $\bar C_pd$, observed within the layer of one penetration depth. According to their $\bar C_pd$ values (ranging from $0.01 to > 10 mg m^-3$), we categorized the profiles into seven trophic situations and computed a mean vertical profile for each. Between a quasi-uniform profile in eutrophic waters and a profile with a strong deep maximum in oligotrophic waters, the shape evolves rather regularly. The wellmixed cold waters, essentially in the Antarctic zone, have been separately examined. On average, their profiles are featureless, without deep maxima, whatever their trophic state. Averaged values their profiles are featureless, without deep maxima, whatever their trophic state. Averaged values their profiles are featureless, without deep maxima, whatever their trophic state. Averaged values of $ρ$, the ratio of Chl a tp (Chl a + Pheo a), have also been obtained for each trophic category. The energy stored by photosynthesizing algae, once normalized with respect to the integrated chlorophyll biomass $\langle C \rangle _tot $ is proportional to the available photosythetic energy at the surface via a parameter $ψ∗$ which is the cross-section for photosynthesis per unit of areal chlorophyll. By tanking advantage of the relative stability of $ψ∗.$ we can compute primary production from ocean color data acquired from space. For such a computation, inputs are the irradiance field at the ocean surface, the "surface" pigment from which $\langle C \rangle _tot$ can be derived, the mean $ρ value pertinent to the trophic situation as depicted by the $\bar C_pd or $\langle C \rangle _tot$ values, and the cross-section $ψ∗$. Instead of a contant $ψ∗.$ value, the mean profiles can be used; they allow the climatological field of the $ψ∗.$ parameter to be adjusted through the parallel use of a spectral light-production model.

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The macroscopic mechanical properties of polyaniline (PANI) lie mainly on two factors, the structure of molecular aggregations of polymers and the mechanical properties of a single polymer chain. The former factor is swell revealed; however, the latter is rarely studied. In this article, we have employed atomic force microscopy-based single-molecule force spectroscopy to investigate the mechanical properties of a kind of water-soluble PANI at a single-molecular level. We have carried out the study comparatively on single-chain-stretching experiments of oxidized, reduced, and doped PANI and obtained a full view of the single-chain elasticity of PANI in all these states. It is found that oxidized and reduced PANI chains are rigid, and the oxidized PANI is more rigid than the reduced PANI. Such a difference in single-chain elasticity can be rationalized by the molecular structures that are composed of benzenoid diamine and quinoid diimine its different proportions. The doped PANI has been found to be more flexible than the oxidized and reduced PANI, and the modified freely jointed chain parameters of doped PANI are similar with those of a common flexible-chain polymer.

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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。

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A global wavenumber-3 dipole SST mode is showed to exist in the Southern Hemisphere subtropical climate variability in austral summer. A positive (negative) phase of the mode is characterized by cool (warm) SST anomalies in the east and warm (cool) SST anomalies in the southwest of the south Indian, Pacific, and Atlantic Oceans, respectively. This coherent dipole structure is largely a response of ocean mixed layer to the atmospheric forcing characterized by migration and modulation of the subtropical high-pressures, in which the latent heat flux play a leading role through wind-induced evaporation, although ocean dynamics may also be crucial in forming SST anomalies attached to the continents. Exploratory analyses suggest that this mode is strongly damped by the negative heat flux feedback, with a persistence time about three months and no spectral peak at interannual to decadal time scales. As the subtropical dipole mode is linearly independent of ENSO and SAM, whether it represents an additional source of climate predictability should be further studied. Citation: Wang, F. (2010), Subtropical dipole mode in the Southern Hemisphere: A global view, Geophys. Res. Lett., 37, L10702, doi: 10.1029/2010GL042750.

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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.

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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.

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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。

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自然界锂同位素分馏强烈,这使得它在很多方面都得到了应用,如地球化学、天体化学和核工业等。所有这些领域都要求精确的测定6Li/7Li的比值。但由于锂是微量元素,而且在测试过程中还存在明显的干扰,因此在进行锂同位素比值测定之前必须对样品进行分离和富集。本文以锂元素标准样品和钾、钠、钙、镁元素标准样品的混合溶液为主要研究对象,采用阳离子交换树脂AG-50W-X8来分离富集锂,探索在不同淋洗介质条件下锂分离纯化的最佳介质条件。初步得出以下结论: 1、本次研究建立了相对简单、高效的锂同位素分离方法。用单一的柱子分离、提纯样品锂;用低浓度的盐酸(0.15M HCl)直接作为淋洗介质,操作过程简单。 2、对锂同位素比值测定产生潜在影响因素,如基体效应、回收率、流程空白等进行了实验研究,证实这些影响因素对于本次研究所建立的方法来说都是可以忽略不计的。 3、用MC-ICP-MS测定样品的锂同位素组成,分析结果的准确度和精度与现阶段所报道数据相同。测定海水的锂同位素组成(+31.6±1.0‰,2σ)与Tomoscak 等(+31.8±1.9‰,2σ)的分析值相近。 4、该方法也适用于低含量的样品。我们分离并测定了不同类型样品的锂同位素组成,样品锂含量在0.064µg/g和132µg/g之间,说明该方法也同样适用于低含量地质样品的分析测定。

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We explore representation of 3D objects in which several distinct 2D views are stored for each object. We demonstrate the ability of a two-layer network of thresholded summation units to support such representations. Using unsupervised Hebbian relaxation, we trained the network to recognise ten objects from different viewpoints. The training process led to the emergence of compact representations of the specific input views. When tested on novel views of the same objects, the network exhibited a substantial generalisation capability. In simulated psychophysical experiments, the network's behavior was qualitatively similar to that of human subjects.

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This paper describes the main features of a view-based model of object recognition. The model tries to capture general properties to be expected in a biological architecture for object recognition. The basic module is a regularization network in which each of the hidden units is broadly tuned to a specific view of the object to be recognized.