993 resultados para 742


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固体化合物(NH_4)_6Mo_7O_(24)·4H_2O和(PPh_3)_2CuCl与饱和液体NH_4HS反应获得桔红针状标题晶体。晶体空间群为P2_1/c,晶胞参数a=11.742(2),b=28.186(7),c=19.304(3),β=100.57(2)°,V=6280.4(?)~3,D_c=1.46g/cm~3,Z=4,F(000)=2816。在3≤2θ≤45°范围内收集到8414个独立衍射强度数据,其中3856个I≥1.5σ(I)强度数据参加结构计算。标题化合物分子是以{MoCu_3S_3Cl}类立方烷型簇为核心的分子,Mo—Cu的平均距离为2.716。

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CaF_2 single crystal is very useful as optical host materials. It has been systematically studied and widely used in thermoluminescence that rare earth ions were doped into CaF_2 single crystal with chemical methods. However, the ion implan-

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本文采用批次培养和半连续培养的方法,研究了中国近海的主要赤潮生物之一尖刺菱形藻的营养盐吸收动力学和营养盐限制下的生长进行了研究。1)中国近海的尖刺菱形藻为尖刺型,不能形成软骨藻酸;2)尖刺菱形藻是一种典型的广温广盐的近岸型海洋浮游硅藻,其适应不同环境的能力较强;3)尖刺菱形藻的营养盐吸收动力学符合米氏酶动力学方程V=V_mXS/(Ks+S);4)在稳定状态下,米氏方程与Droop方程一起,与Mond方程一样,都可以很好地描述尖刺菱形藻的生长率与外界环境中限制性营养盐浓度之间的关系 ;5)与其他浮游植物相比较,尖刺菱形藻吸收无机氮的能力较强,而吸收无机磷的能力相对较弱。

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通过分析一氧化氮(nitric oxide,NO)、活性氧(reactive oxygen species,ROS)和干旱胁迫对小麦根氧化还原状态和叶片脱落酸(abscisic acid,ABA)积累的影响,探讨了干旱胁迫下NO和H2O2调节ABA合成的可能机制。结果表明:干旱胁迫处理初期小麦根还原型谷胱甘肽含量降低、抗氧化酶活性发生振荡变化,细胞氧化还原状态向氧化型转变。NO和H2O2能模拟干旱胁迫的作用使细胞状态向氧化型转变,还可以使小麦叶片ABA积累量上升。干旱胁迫下NO和H2O2对ABA合成的调节作用可能是通过调节细胞氧化还原状态进行。

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通过野外控制实验,研究了高寒矮嵩草草甸群落植物多样性、初级生产力对模拟降雨条件的响应.结果表明:(1)在植物生长期(6月),增加降雨20%、增加降雨40%,植物群落物种多样性指数(H)和均匀度指数(J)分别比对照提高了0.188和0.011、0.735和0.076,生长期(7月)增加降雨20%物种H和J提高了0.409和0.07;(2)禾草类:增加降雨20%处理的地上生物量与对照相比没有明显的显著性差异(P>0.05),增加降雨40%处理的地上生物量与对照相比差异显著(P<0.05),说明过多增加降雨会抑制禾草的生长发育.杂类草:减少降雨50%处理的地上生物量与对照相比差异显著(P<0.05),其地上生物量对减少降雨的反映比较敏感.莎草类:其地上生物量对增加和减少降雨都没有显著变化;(3)0~10 cm和0~30 cm土层地下生物量均在增加降雨20%时最高,地下生物量的总量也在增加降雨20%时最高;(4)矮嵩草草甸地下生物量与地上生物量、总生物量的比值接近于生长季末时最大,且在模拟增加降雨20%的水平时,7、8、9月份地下和地上生物量较其它处理组高.

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Emodin, a natural anthraquinone compound isolated from the rhizome of rhubarb, is reported to suppress the growth of tumor in many clinical situations. In this study, we focused on the effect of emodin in human breast cancer BCap-37 cells and further understand the underlying molecular mechanism in treating breast cancer. Using MTT assay and flow cytometry, we demonstrated the critical role of emodin in the suppression of the proliferation of BCap-37 cells based on a concentration- and time-dependent manner. The increase of apoptotic rate was also observed after incubation of BCap-37 cells on emodin at 20 mu M and 50 mu M for 48 h. The cells exhibited typical apoptotic features including cellular morphological change, chromatin condensation and membrane blebbing. The results of the study further showed that Bcl-2 level decreased, while Bax and cytosolic cytochrome c levels in sample cells increased after the emodin treatment by using Western blot. The decline in the Bcl-2/Bax ratio and the increase of cytosolic cytochrome c concentration were consistent with the increase of the apoptotic ratio. The results strongly suggest that the disruption of the mitochondrial signaling pathway was involved in emodin-induced apoptosis in BCap-37 cells.

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根据工程实际需要,提出了一种基于点对应的三维测量数据融合新方法。该方法可利用不同测量过程中得到的点集数据之间部分点的对应关系,求解出两次测量数据坐标系之间的坐标变换关系,进而将两部分数据统一在一个坐标系中。在坐标变换求取过程中采用旋动理论,将带约束的多变量函数的非线性优化问题转化为线性方程组的求解问题,不但大大降低了计算的复杂性,而且算法稳定性好,具有很高的求解精度,完全可以满足工程需要。

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如何快速可靠地获取空间目标深度信息是计算机视觉领域中的一个关键问题。本文主要论述了利用立体视觉原理快速精确获取空间目标深度信息的方法。本系统是为测量落在多合相机有效视场内的炸点深度信息而设计的。其首先对各相机抽取出的特征点进行快速匹配处理,找到所有匹配点对;然后再利用已找到的匹配点对来恢复该空间目标的深度信息。系统所使用的特征点快速匹配算法是作者提出的一种新的算法,具有很好的效果,且对应用范围没有特殊要求,并给出了仿真结果。作者所做工作大致分成下面几部份:1、提出了一种基于熵算子的目标特征提取的平滑滤波器参数的自适应选取方法,即让计算机根据输入图象固有特性自动选择其平滑滤波器的参数,摆脱人为因素的影响,并给出了实例。2、提出了一种基子图象特征点的尘标约束的特征点快速匹配算法,该算法既保留了epipolar线约束快速匹配的优点,又解决了实际测量中epipolar无法解决的问题。这对于从硬件上实现本系统在理论上提供了可能。同时给出了由多相机特征点对来恢复该空间目标点深度信息的公式。3、对上述结果进行了误差分析,指出影响结果精度的主要因素,对提交实际测量精度提供了理论依据,并给出了仿真结果。4、为摄象机建立了成象几何模型,并对摄象机内部永外部参数进行了标定处理,介绍了一种简单快速标定摄象机内部和外部参数的方法。

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云南会泽超大型铅锌矿床明显受北东向构造带控制,构造带中的脉状方解石为富碳酸盐流体活动的产物。文章通过对这种脉状方解石的稀土元素地球化学研究,探讨构造流体的来源及其与成矿流体的关系。结果显示,矿区北东向构造带中脉状方解石的稀土含量范围较宽(∑REE:5.47l×10^—6~56.788×10^—6)、稀土配分模式为相似的轻稀土富集型、存在较强的铕负异常(δEu:0.439~0.742)。结合地层、矿石中脉石矿物方解石、蛾眉山玄武岩的稀土元素含量和碳、氧同位素组成,认为控矿构造带中方解石稀土为同源构造流体的结晶产物,构造流体稀土元素地球化学特征明显受成矿流体的控制。

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A new mesoporous sphere-like SBA-15 silica was synthesized and evaluated in terms of its suitability as stationary phases for CEC. The unique and attractive properties of the silica particle are its submicrometer particle size of 400 nm and highly ordered cylindrical mesopores with uniform pore size of 12 nm running along the same direction. The bare silica particles with submicrometer size have been successfully employed for the normal-phase electrochromatographic separation of polar compounds with high efficiency (e.g., 210 000 for thiourea), which is matched well with its submicrometer particle size. The Van Deemeter plot showed the hindrance to mass transfer because of the existence of pore structure. The lowest plate height of 2.0 mu m was obtained at the linear velocity of 1.1 mm/s. On the other hand, because of the relatively high linear velocity (e.g., 4.0 mm/s) can be generated, high-speed separation of neutral compounds, anilines, and basic pharmaceuticals in CEC with C-18-modified SBA-15 silica as stationary phases was achieved within 36, 60, and 34 s, respectively.

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This thesis is presented in two parts. Data for this research is from the Cork BASELINE (Babies after SCOPE, Evaluating Longitudinal Impact using Neurological and Nutritional Endpoints) Birth Cohort Study (n = 2137). In this prospective birth cohort study, pediatric follow-up with in-person appointments were repeated from the time of birth through to 2, 6 and 12 months, and at 2 years. Body composition was measured by air displacement plethysmography at birth and at 2 months using the PEA POD Infant Body Composition Tracking System. This thesis provides the first extensive report on the study’s 2 year assessment. In part one, the aims were to investigate potential early-life risk factors for childhood overweight and obesity, including rapid growth and body composition in infancy and umbilical cord concentrations of leptin and high molecular weight (HMW) adiponectin. This research is the first to describe rapid growth in early infancy in terms of changes in direct measures of body composition. These are also the first data to examine associations between umbilical cord leptin and HMW adiponectin concentrations and changes in fat and lean mass in early infancy. These data provide additional insight into characterising the growth trajectory in infancy and into the role of perinatal factors in determining infant growth and subsequent overweight/obesity risk. In part two of this thesis, the aims were to quantify vitamin D intake and status at 2 years and to investigate whether 25-hydroxyvitamin D [25(OH)D] concentrations in early pregnancy and in umbilical cord blood are associated with infant growth and body composition. There was a low prevalence of vitamin D deficiency among Irish 2 year olds (n = 742) despite a high prevalence of inadequate intakes and high latitude (51°N). Maternal 25(OH)D concentrations at 15 weeks gestation and cord 25(OH)D concentrations at delivery were not associated with infant growth or adiposity.

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The shared-memory programming model can be an effective way to achieve parallelism on shared memory parallel computers. Historically however, the lack of a programming standard using directives and the limited scalability have affected its take-up. Recent advances in hardware and software technologies have resulted in improvements to both the performance of parallel programs with compiler directives and the issue of portability with the introduction of OpenMP. In this study, the Computer Aided Parallelisation Toolkit has been extended to automatically generate OpenMP-based parallel programs with nominal user assistance. We categorize the different loop types and show how efficient directives can be placed using the toolkit's in-depth interprocedural analysis. Examples are taken from the NAS parallel benchmarks and a number of real-world application codes. This demonstrates the great potential of using the toolkit to quickly parallelise serial programs as well as the good performance achievable on up to 300 processors for hybrid message passing-directive parallelisations.