886 resultados para the overlapping distribution analysis.
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IEECAS SKLLQG
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新生代以来,全球气候经历了一系列的冷暖交替,呈现总体变冷的趋势。对该时期不同区域气候变化过程的深入研究有助于我们更好地理解现今全球气候变化规律。中新世是新生代古气候与古环境演变的一个重要转折时期,定量重建山东山旺中新世气候是认识和理解中国东部与东亚新近纪气候演变的一个关键环节。 将化石植物作为气候代用指标,用于研究过去全球气候变化,已经广为国际科学界接纳。国际上,定量研究第三纪气候的植物学方法按照不同原理可以划分为两大类,其各自代表分别为基于化石的现存最近亲缘类群生态适应度推演古气候参数值的共存分析法(Coexistence Approch, CA )和基于叶片形态特征与气候相关关系的叶缘分析(Leaf Margin Analysis, LMA )与气候叶片多变量程序(Climate Leaf Analysis Multivariate Program, CLAMP)。两大主流方法各有优势,也各有局限性。前人运用两大主流方法对山旺中新世植物群相同地层,同套数据的分析结果表明:LMA 和CLAMP 所估测年均温数值要显著低于CA 所估测的数值。其差异的原因既可能是LMA 和CLAMP 由于埋藏因素的影响造成估测值偏低,也可能由于CA 数据库数据主要来自于欧洲和北美而缺乏东亚的资料所致。 本论文提出了一种新的方法——分布区叠加分析(Overlapping Distribution Analysis, ODA )对山旺中新世古气候进行定量重建。ODA 采用最近亲缘类群在叠加区间的气候参数来重建化石植物所生活的当时当地的气候。其详细步骤如下:1. 鉴定化石植物和认定它们的最近亲缘类群(尽量到种级水平)。2. 调查这些最近亲缘类群的分布数据(包括经度、纬度和海拔数据)。某些类群可能会有不止一个最近亲缘类群,须将这些最近亲缘类群的分布数据合并。3. 对分布数据分析,得出包含最多类群的最大叠加区间。4. 调查在最大叠加区间中气象站点的气候数据。5. 按照公式(1)和(2)来转换年均温数据TU=T0 - (HU -H0)×Γ (1); TL=T0 - (HL -H0)×Γ (2) 其中HU (m) 是海拔叠加区间的上界; HL (m) 是海拔叠加区间的下界; H0 (m) 气象站的实测海拔; T0 (ºC) 气象站的实测年均温; TU (ºC) 在海拔叠加区间气温的下界; TL (ºC) 在海拔叠加区间气温的上界; 系数Γ 为大气垂直直减率,年均温为0.5ºC/100m,最冷月均温为 0.45ºC/100m,最热月均温为 0.6ºC/100m。同样的方法,在海拔叠加范围内最冷月均温与最热月均温范围也可以确定,而降水量则采用气象台站的原始数据。6. 在这些转换数据的基础上,得出年均温,最冷月均温,最热月均温,年较差和年平均降水量波动范围。 ODA 分析结果表明:山旺中新世时期年均温为10.9-14.5oC,年较差为21.1-22.7oC,最冷月均温为-0.5-3.3oC,最热月均温为21.9-25.0oC,年平均降水量为1107.3-1880.0mm 。同时本论文还定量恢复了山旺硅藻土矿各层的古气候参数,其所估测的古气候参数数值与CLAMP 和LMA 的结果一致,而与CA 不同。对山旺气候参数的恢复表明,虽然其中新世年均温与现在相似,但最冷月均温要高于现在。 本项研究的创新之处是选择同一个研究地点(山东山旺),依据同一套数据(化石植物的类群资料),采用国际上以不同原理为基础的主流方法,同时加入我们自己提出的新方法,进行的古气候重建,对所获得气候参数值进行对比和验证,并对其存在的差异进行分析和探讨。
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The catalytic action of putrescine specific amine oxidases acting in tandem with 4-aminobutyraldehyde dehydrogenase is explored as a degradative pathway in Rhodococcus opacus. By limiting the nitrogen source, increased catalytic activity was induced leading to a coordinated response in the oxidative deamination of putrescine to 4-aminobutyraldehyde and subsequent dehydrogenation to 4-aminobutyrate. Isolating the dehydrogenase by ion exchange chromatography and gel filtration revealed that the enzyme acts principally on linear aliphatic aldehydes possessing an amino moiety. Michaelis-Menten kinetic analysis delivered a Michaelis constant (KM=0.014mM) and maximum rate (Vmax=11.2μmol/min/mg) for the conversion of 4-aminobutyraldehyde to 4-aminobutyrate. The dehydrogenase identified by MALDI-TOF mass spectrometric analysis (E value=0.031, 23% coverage) belongs to a functionally related genomic cluster that includes the amine oxidase, suggesting their association in a directed cell response. Key regulatory, stress and transport encoding genes have been identified, along with candidate dehydrogenases and transaminases for the further conversion of 4-aminobutyrate to succinate. Genomic analysis has revealed highly similar metabolic gene clustering among members of Actinobacteria, providing insight into putrescine degradation notably among Micrococcaceae, Rhodococci and Corynebacterium by a pathway that was previously uncharacterised in bacteria.
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In a supersonic chemical oxygen-iodine laser (COIL) operating without primary buffer gas, the features of flowfield have significant effects on the Laser efficiency and beam quality. In this paper three-dimensional, multi-species, chemically reactive CFD technology was used to study the flowfield in mixing nozzle implemented with a supersonic interleaving jet configuration. The features of the flowfield as well as its effect on the spatial distribution of small signal gain were analyzed.
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We describe the use of a Wigner distribution function approach for exploring the problem of extending the depth of field in a hybrid imaging system. The Wigner distribution function, in connection with the phase-space curve that formulates a joint phase-space description of an optical field, is employed as a tool to display and characterize the evolving behavior of the amplitude point spread function as a wave propagating along the optical axis. It provides a comprehensive exhibition of the characteristics for the hybrid imaging system in extending the depth of field from both wave optics and geometrical optics. We use it to analyze several well-known optical designs in extending the depth of field from a new viewpoint. The relationships between this approach and the earlier ambiguity function approach are also briefly investigated. (c) 2006 Optical Society of America.
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MS-based proteomic methods were utilised for the first time in the discovery of novel penile cancer biomarkers. MALDI MS imaging was used to obtain the in situ biomolecular MS profile of squamous cell carcinoma of the penis which was then compared to benign epithelial MS profiles. Spectra from cancerous and benign tissue areas were examined to identify MS peaks that best distinguished normal epithelial cells from invasive squamous epithelial cells, providing crucial evidence to suggest S100A4 to be differentially expressed. Verification by immunohistochemistry resulted in positive staining for S100A4 in a sub-population of invasive but not benign epithelial cells.
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To assess the quality of school education, much of educational research is concerned with comparisons of test scores means or medians. In this paper, we shift this focus and explore test scores data by addressing some often neglected questions. In the case of Brazil, the mean of test scores in Math for students of the fourth grade has declined approximately 0,2 standard deviation in the late 1990s. But what about changes in the distribution of scores? It is unclear whether the decline was caused by deterioration in student performance in upper and/or lower tails of the distribution. To answer this question, we propose the use of the relative distribution method developed by Handcock and Morris (1999). The advantage of this methodology is that it compares two distributions of test scores data through a single distribution and synthesizes all the differences between them. Moreover, it is possible to decompose the total difference between two distributions in a level effect (changes in median) and shape effect (changes in shape of the distribution). We find that the decline of average-test scores is mainly caused by a worsening in the position of all students throughout the distribution of scores and is not only specific to any quantile of distribution.
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The spatial distribution of Rotylenchulus reniformis on cotton cultivated in crop rotation with sorghum-peanut-velvetbean was studied using geostatistics. The experimental field, which had been continuously cropped with cotton for 20 years, comprised two 32 x 48 m-grids, each divided in sixty-four 4 x 6 in sampling plots. For all crops, 300 cm(3) soil samples were taken at the center of each plot at crop germination (Pi) and again at harvest (Pf), from which the numbers of nematodes were determined. The results revealed that the spatial distribution of R. reniformis was highly aggregated and with the aid of geostatistical techniques the nematode intensities were mapped and the risk areas accurately identified. Consequently, geostatistics is here considered a useful tool for planning nematode control strategies, particularly in precision agriculture.
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Objective: The non-homogenous aspect of periodontal ligament (PDL) has been examined using finite element analysis (FEA) to better simulate PDL behavior. The aim of this study was to assess, by 2-D FEA, the influence of non-homogenous PDL on the stress distribution when the free-end saddle removable partial denture (RPD) is partially supported by an osseointegrated implant. Material and Methods: Six finite element (FE) models of a partially edentulous mandible were created to represent two types of PDL (non-homogenous and homogenous) and two types of RPD (conventional RPD, supported by tooth and fibromucosa; and modified RPD, supported by tooth and implant [10.00x3.75 mm]). Two additional FE models without RPD were used as control models. The non-homogenous PDL was modeled using beam elements to simulate the crest, horizontal, oblique and apical fibers. The load (50 N) was applied in each cusp simultaneously. Regarding boundary conditions the border of alveolar ridge was fixed along the x axis. The FE software (Ansys 10.0) was used to compute the stress fields, and the von Mises stress criterion (sigma vM) was applied to analyze the results. Results: The peak of sigma vM in non-homogenous PDL was higher than that for the homogenous condition. The benefits of implants were enhanced for the non-homogenous PDL condition, with drastic sigma vM reduction on the posterior half of the alveolar ridge. The implant did not reduce the stress on the support tooth for both PDL conditions. Conclusion: The PDL modeled in the non-homogeneous form increased the benefits of the osseointegrated implant in comparison with the homogeneous condition. Using the non-homogenous PDL, the presence of osseointegrated implant did not reduce the stress on the supporting tooth.
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