605 resultados para 1321
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A systematic and quantitative research on the structure-property correlation has been carried out in KH2PO4 (KDP), NH4H2PO4 (ADP) and HIO3, based on the dielectric theory of complex crystals and the Levine bond charge model. We, for the first time, successfully solve the problems in the calculation of the nonlinearities of the complex inorganic nonlinear optical (NLO) crystals, which have O-H bonds in their crystal structures. We do this by introducing the bond-valence equation we have set up, calculating the nonlinear optical tensor coefficients d(ijk) of these three compounds, quantitatively determining the contributions of each type of bond to the total second-order NLO tensor coefficient (d(ijk)) of the crystal, and presenting the bond parameters and the linear properties of each kind of bond. For the first time, the NLO coefficient d(36) for ADP was calculated. All calculated results are in good agreement with experimental data. We found that O-H bonds also play an important role in these crystals, except for in the important anionic groups (PO4 groups and IO3 groups). All the results thus calculated show that our method is useful in evaluating the NLO coefficients of the inorganic NLO crystals containing O-H bonds in their structures, and should be a useful tool toward the future research into new nonlinear optical materials of this kind.
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Thymidylate synthase (TS), an essential enzyme for DNA de novo synthesis, is a critical therapeutic target in cancer therapy. Previous study has shown that TS was able to bind to its own mRNA in human and E.coli, resulting in translational repression. Zebrafish is the best animal model for vertebrate study. In order to study the regulatory mechanism of zebrafish TS, the enzyme were expressed in E. coli BL21 (DE3) and it was purified to homogeneity. Electrophoretic mobility shift assay (EMSA) was used to detect the interaction of zebrafish TS protein and its own TS transcript in vitro and the results showed that zebrafish TS could bound with its own mRNA specifically. Further study revealed that zebrafish TS was able to interact with its own mRNA in vivo using immunoprecipitation : RT-PCR technique. The results provide evidence that zebrafish may be developed as an useful model for studying the anti-metabolism agents.
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The conditional nonlinear optimal perturbation (CNOP), which is a nonlinear generalization of the linear singular vector (LSV), is applied in important problems of atmospheric and oceanic sciences, including ENSO predictability, targeted observations, and ensemble forecast. In this study, we investigate the computational cost of obtaining the CNOP by several methods. Differences and similarities, in terms of the computational error and cost in obtaining the CNOP, are compared among the sequential quadratic programming (SQP) algorithm, the limited memory Broyden-Fletcher-Goldfarb-Shanno (L-BFGS) algorithm, and the spectral projected gradients (SPG2) algorithm. A theoretical grassland ecosystem model and the classical Lorenz model are used as examples. Numerical results demonstrate that the computational error is acceptable with all three algorithms. The computational cost to obtain the CNOP is reduced by using the SQP algorithm. The experimental results also reveal that the L-BFGS algorithm is the most effective algorithm among the three optimization algorithms for obtaining the CNOP. The numerical results suggest a new approach and algorithm for obtaining the CNOP for a large-scale optimization problem.
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本文的研究内容是初级生产力模型计算方法以及活体叶绿素荧光测量方法在我国近海浮游植物光合作用研究中的应用。 论文对在我国近海实测的1321 组叶绿素垂直分布数据以及84 组初级生产力数据进行了非线性拟合分析,得出了描述叶绿素和初级生产力垂直变化规律的相应参数。结合光合参数——初始斜率α 的平面分布将我国近海分为9 个光合作用特征相对独立的分区。以光强和遥感叶绿素为输入变量,以各分区实测参数的平均值为模型参数,首次建立了分海区的时间-深度积分初级生产力计算模型。 对拟合参数的分析表明:我国近海深水叶绿素峰(DCM)在夏季最明显而在冬季则不明显,这与夏季温跃层的形成和冬季温跃层消失的规律相符合。最大光合速率参数主要受温度和营养盐状况的影响,但整体而言各个季节的变化不大。光合作用初始斜率参数主要受浮游植物光照条件和光照历史的影响,从春季到冬季持续增加,基本与光照强度的变化刚好相反。光抑制参数反映着浮游植物对高光强伤害的敏感性,它在夏、秋季较低而在冬季较高。 模型计算结果表明我国近海初级生产力规模约为6.4±1.0×108tC/a。总体来说我国近海海域初级生产力北方高于南方,西部高于东部。北方初级生产力高峰期大都出现在夏季而南方出现在冬季,中部则高峰期出现在春秋两季,与温跃层出现和消失的规律有一定的相关性。与由实测生产力推算的初级生产力相比,本模型的计算结果较高,误差产生的原因包括二类水体遥感叶绿素浓度偏高、地形因素等。与VGPM相比较,本模型的计算结果更接近于实测结果。模型中云覆盖度参数的变化可能引起计算结果约25%的变化,当取云覆盖度参数为0.5 时的计算结果与用实际天气状况数据的计算结果较为接近。制作了基于分区模型的水柱初级生产力计算软件,可在仅测量叶绿素浓度的情况下进行水柱初级生产力的计算。 模型准确度的进一步提高的途径主要包括实测参数数量的增加以及遥感叶绿素浓度准确性的提高。 与初级生产力相比,活体叶绿素荧光测量可以更快速、简便地跟踪浮游植光合作用动态。本研究首次将活体叶绿素荧光测量方法应用于野外浮游植物光合作用状态研究。通过暗驰豫实验,建立了使用OS5-AFM藻类荧光仪现场测定活体叶绿素荧光参数——Fv/Fm(光化学效率)的操作方法,并对胶州湾海域浮游植物光化学效率进行了高时空分辨率的调查,对相关因素进行了分析,并尝试通过Fv/Fm进行初级生产力计算。 结果表明,胶州湾海域表层Fv/Fm值的全年平均值约0.37,处于中等偏低水平。Fv/Fm值在秋季最高而春季最低,其平面分布在夏季较均匀而在春季则有较大的区域差异。湾东部Fv/Fm值变化幅度较大,一年中有4 个高峰期;而湾西部Fv/Fm值变化幅度较小,一年中有3 个高峰期。光合作用最活跃的海区随季节更替而变化,其年变化模式可能具有一定的重复性。不同深度上Fv/Fm值的海区平均值没有显著差异,但底层Fv/Fm值的空间差异较小。 通过对营养盐和Fv/Fm值时间变化的分析,首次发现了自然水体中Fv/Fm值变化对氮盐浓度变化响应的滞后效应,在不同的站点,影响Fv/Fm值的氮盐种类有所不同,湾西部海域与NH4+相关性较高而湾东部海域与NO3-的相关性较高,P、Si等则与Fv/Fm值基本无相关性。滞后期的长度并不稳定,1 旬和2 旬的滞后现象都可观察到。Fv/Fm值变化率与氮盐浓度变化率之间的相关性高于Fv/Fm值与氮盐浓度之间的相关性。这表明即使在胶州湾这样无机氮浓度很高、浮游植物生长基本不受氮源限制的水体,氮源浓度的变化仍然影响着浮游植物的光合作用状态。 初步建立了由Fv/Fm测量结果计算初级生产力的方法。模型的计算结果与文献资料中胶州湾水域初级生产力的时空分布趋势基本一致,但在数量上明显低于传统估算的结果。获得更多同步测量的初级生产力和Fv/Fm值数据可逐渐改善这一方法计算结果的准确性,并可籍次方法更快更方便地进行初级生产力的测算。
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In order to improve the production and accurately estimate response to selection, divergent selection for growth in shell height was conducted in a cultured population of the Japanese scallop Patinopecten yessoensis. Applying the same selection intensity +/- 1.756 in upward and downward directions, three groups including two selected groups of Fast and Slow and one non-selected Control group were created, which were reared under the same environmental conditions at any stage. Differences always significantly existed among the three groups (P < 0.05), except for larvae at day 1 and at day 5, and in the order of Fast > Control > Slow. The average standardized response to selection (SR), realized heritability (h(R)2) and genetic gain (GG) was 0.473%, 0.269% and 7.85% for the Fast group and 0.381%, 0.217% and 6.60% for the Slow group respectively. Moreover, significant differences (P < 0.05) were detected between the fast and the slow lines in both SR and h(R)2, providing evidence for an asymmetric response in two directions. Performance in shell height is improved by 7.85% in the fast line after one generation selection, suggesting that mass selection for faster growth in a cultured population of the Japanese scallop is effective.
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Survival of small mammals in winter requires proper adjustments in physiology, behavior and morphology. The present study was designed to examine the changes in serum leptin concentration and the molecular basis of thermogenesis in seasonally acclimatized root voles (Microtus oeconomus) from the Qinghai-Tibetan plateau. In January root voles had lower body mass and body fat mass coupled with higher nonshivering thermogenesis (NST) capacity. Consistently, cytochrome c oxidase activity and mitochondrial uncoupling protein-1 (UCP1) protein contents in brown adipose tissues were higher in January as compared to that in July. Circulating level of serum leptin was significantly lower in winter and higher in July. Correlation analysis showed that serum leptin levels were positively related with body mass and body fat mass while negatively correlated with UCP1 protein contents. Together, these data provided further evidence for our previous findings that root voles from the Qinghai-Tibetan plateau mainly depend on higher NST coupled with lower body mass to enhance winter survival. Further, fat deposition was significantly mobilized in cold winter and leptin was potentially involved in the regulation of body mass and thermogenesis in root voles. Serum leptin might act as a starvation signal in winter and satiety signal in summer.
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本文首先介绍了文献[1]给出的基于空值完全语义的五值逻辑(5VL),定义了基于5VL的比较运算和逻辑运算的运算规则,并以此为基础结出了一般条件表达式下选择运算的处理策略和实现算法。
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月表太阳辐射是深入研究月表温度分布的关键问题之一.本文根据月表有效太阳辐照度与太阳常数、太阳辐射入射角以及日月距离之间的关系,建立月表有效太阳辐照度的实时模型.该模型在1950-2050年的100年内的理论误差百分比小于0.28%,相对前人提出的模型在精度上有了很大程度的提高,能较为真实地反映月表有效太阳辐照度随时间的变化规律.计算结果表明2007年月表太阳辐照度的年变化范围在1321.5-1416.6 W·m^-2之间,平均为1368.0 W·m^-2.通过对月表太阳辐射入射角计算结果的分析,证实了月球的两极可能存在极昼极夜.
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利用被动微波遥感亮度温度数据反演月壤厚度是“嫦娥”探月工程的科学目标之一,也是人类探测月壤厚度的一种新的尝试。深入研究月表太阳辐射、月球内部热流以及月表温度的分布和变化规律,是解译遥感数据,反演月壤厚度的前提条件,也为进一步开展月球探测、开发利用月球资源乃至建立月球基地相关研究工作提供必要的参考。 本文根据月表有效太阳辐照度与太阳常数、日月距离和太阳辐射入射角的关系,建立了月表有效太阳辐照度的实时模型如下: (1) 其中, (2) (3) 通过对月表有效太阳辐照度实时模型的各个参数分析发现,影响月表有效太阳辐照度变化的主要因素是日地距离和太阳辐射入射角的变化。对模型的误差分析表明,从1950年到2050年的100年内,月表有效太阳辐照度计算结果的误差百分比小于0.28%,能更准确地反映月表有效太阳辐照度的变化情况。从2007年月表有效太阳辐照度的计算结果发现,该年内的月表有效太阳辐照度变化在1321.5~1416.6 W•m-2之间,平均为1368.0 W•m-2,一个月内的变化最小幅度为6.0 W•m-2,最大幅度为23.6 W•m-2。 在月表有效太阳辐照度的实时模型基础上,根据能量守恒和Stefan-Boltzmann定律,本文还得出了月表温度分布模型如下: (4) 其中,初始条件由下式决定, (5) 通过与月表温度实际观测结果的比较发现,当月表反射率、热发射率和热惯量分别取0.127、0.94和125 J•m-2•s-1/2•K-1时,模型的计算结果与实际观测值比较符合,能较好地预测理想条件下的月表温度。 月表热参数研究的一个重要应用就是解译对月被动微波遥感的亮度温度数据。在对月被动微波遥感探测中,辐射计获得的亮度温度反映了月球表层的热辐射特性。月球表层的热辐射与其自身的热状况紧密相关,结合文中建立的月表热参数模型,根据辐射传播理论进一步分析了对月微波遥感探测中,月球表层在不同情况下对亮度温度的贡献,确定了亮度温度随月表温度和月壤厚度的变化关系,对被动微波遥感探测月壤厚度的可能性和可能达到的精度进行了估算。 对月球表层的热辐射传播的分析发现,对月被动微波遥感探测获得的亮度温度受月球表层热辐射的控制,与月壤厚度具有指数相关性,并受到月表温度的影响。当月壤和月岩的复介电常数分别为2 + 0.005 j和9 + 1 j、相对磁导率均为1时,对应3.0GHz、7.8GHz、19.35GHz和37.0GHz四个频率的亮度温度与月壤厚度及月表温度的关系可分别近似表示为, 3.0GHz亮度温度: (6) 7.8GHz亮度温度: (7) 19.35GHz亮度温度: (8) 37.0GHz亮度温度: (9) 当月壤厚度和月表温度分别在0.5m~30m和100K~400K之间变化时,上述四个频率的亮度温度变化范围分别在212.5K~252.8K、207.4 K~266.7K、193.8 K~288.6K和174.0 K~310.9K之间。对于较低频率的被动微波遥感,亮度温度随月壤厚度的增大逐渐增大并趋于稳定;对较高频率的被动微波遥感,亮度温度随月壤厚度的增大会产生起伏波动,不利于用单波段反演月壤厚度。亮度温度梯度在频率较高时梯度较大,在很小的月壤厚度范围内很快就趋于0,不利于厚度较大时的月壤厚度反演,但对于厚度较小时的月壤厚度反演精度较高;同时,除3.0GHz外,7.8GHz、19.35GHz和37.0GHz三个频率的亮度温度梯度随月表温度的升高降幅较大,尤其是19.35GHz,适合在夜间对月壤厚度较小的地区进行更精确的探测。对于3.0GHz,其亮度温度梯度受月表温度变化的影响很小,能反映出较深层月壤厚度的信息,可以对月球进行全球全天时探测。若辐射计的分辨率为0.02K,3.0GHz频率对10m厚月壤的判别精度达到0.07m;对于20m厚月壤的精度为1.4m。当月壤厚度小于0.5m时,随着月壤厚度从0到0.5m增加,月球表层的亮度温度贡献呈先减小后增大的趋势,从而使某一亮度温度值可能对应存在两种不同的月壤厚度。因此,对于月壤厚度小于0.5m的区域,利用单波段被动微波遥感亮度温度反演月壤厚度是比较困难的。 在对月被动微波遥感探测中,可以利用月球夜晚时段的亮度温度数据判别月壤厚度是否小于0.5m。当月表温度为100K时,3.0GHz、7.8GHz、19.35GHz和37.0GHz四个频率的亮度温度判别参考值分别为212.9K、207.4K、193.5K和174.1K;月表温度为240K时,上述四个频率的亮度温度判别参考值分别为220.8K、226.8K、234.1K和237.2K。当亮度温度小于参考值时表示月壤厚度小于0.5m,反之,表示月壤厚度大于0.5m。更进一步地,可以根据月表温度的影响系数对月岩是否裸露于月表进行判断。当3.0GHz、7.8GHz、19.35GHz和37.0GHz四个频率的月表温度影响系数接近0.77、0.82、0.84和0.85时,可以认为月岩直接暴露于月表。
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Nkiruka, A., Multiple Principles and the Obligation to Obey the Law, Deakin Law Review. Vol. 10. No. 2. 2005. p. 524 RAE2008
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Sibona, Bruno, Le Cheval de Mazeppa, un cas d'intertextualit? franco-anglaise (L'Harmattan, 2006)