Coupled 142Nd-143Nd evidence for a protracted magma ocean in Mars

Resolving early silicate differentiation timescales is crucial for understanding the chemical evolution and thermal histories of terrestrial planets. Planetary-scale magma oceans are thought to have formed during early stages of differentiation, but the longevity of such magma oceans is poorly constrained. In Mars, the absence of vigorous convection and plate tectonics has limited the scale of compositional mixing within its interior, thus preserving the early stages of planetary differentiation. The SNC (Shergotty-Nakhla-Chassigny) meteorites from Mars retain 'memory' of these events. Here we apply the short-lived 146Sm-142Nd and the long-lived 147Sm-143Nd chronometers to a suite of shergottites to unravel the history of early silicate differentiation in Mars. Our data are best explained by progressive crystallization of a magma ocean with a duration of approximately 100 million years after core formation. This prolonged solidification requires the existence of a primitive thick atmosphere on Mars that reduces the cooling rate of the interior.     

"校园一卡通"系统的设计

文章在对高校使用"校园一卡通"进行分析[1]的基础上,以IC卡为信息载体,对校园消费、管理系统的组成、硬件的构成及网络系统进行了设计.     

中国公共安全科技问题分析与发展战略规划研究

在给出公共安全系统性定义的基础上提出了公共安全综合指数的概念,讨论了不确定性的特点和系 统非优分析的方法,同时建立了公共安全运行体系。基于安全指数给出了公共安全控制能力指数,并且讨论了 不确定因素的分析方法。研究表明,公共安全科技贡献率是科技发展战略研究的关键,建立了科技投入与公共 安全目标函数,并且讨论了科技贡献增长率的投入产出关系。     

Operational properties and matrix representations of quantum measures

Denoted by M(A), QM(A) and SQM(A) the sets of all measures, quantum measures and subadditive quantum measures on a σ-algebra A, respectively. We observe that these sets are all positive cones in the real vector space F(A) of all real-valued functions on A and prove that M(A) is a face of SQM(A). It is proved that the product of m grade-1 measures is a grade-m measure. By combining a matrix M _μ to a quantum measure μ on the power set A _n of an n-element set X, it is proved that μ ≪ ν (resp. μ ⊥ ν) if and only if M _μ ≪ M _ν (resp. M _μ M _ν =0). Also, it is shown that two nontrivial measures μ and ν are mutually absolutely continuous if and only if μ·ν∈QM(A _n ). Moreover, the matrices corresponding to quantum measures are characterized. Finally, convergence of a sequence of quantum measures on A _n is introduced and discussed; especially, the Vitali-Hahn-Saks theorem for quantum measures is proved.     

信用攸关的利率互换的定价

在约化方法的框架下,针对实务界出现的一种新型信用衍生产品--信用攸关的利率互换(credit contingentinterest rate swap,CCIRS),以偏微分方程(partial differentialequation,PDE)为方法,利用对冲原理建立了定价模型.之后分别利用显式和隐式差分对模型进行数...     

S-nitrosylation of NADPH oxidase regulates cell death in plant immunity

Changes in redox status are a conspicuous feature of immune responses in a variety of eukaryotes, but the associated signalling mechanisms are not well understood. In plants, attempted microbial infection triggers the rapid synthesis of nitric oxide and a parallel accumulation of reactive oxygen intermediates, the latter generated by NADPH oxidases related to those responsible for the pathogen-activated respiratory burst in phagocytes. Both nitric oxide and reactive oxygen intermediates have been implicated in controlling the hypersensitive response, a programmed execution of plant cells at sites of attempted infection. However, the molecular mechanisms that underpin their function and coordinate their synthesis are unknown. Here we show genetic evidence that increases in cysteine thiols modified using nitric oxide, termed S-nitrosothiols, facilitate the hypersensitive response in the absence of the cell death agonist salicylic acid and the synthesis of reactive oxygen intermediates. Surprisingly, when concentrations of S-nitrosothiols were high, nitric oxide function also governed a negative feedback loop limiting the hypersensitive response, mediated by S-nitrosylation of the NADPH oxidase, AtRBOHD, at Cys 890, abolishing its ability to synthesize reactive oxygen intermediates. Accordingly, mutation of Cys 890 compromised S-nitrosothiol-mediated control of AtRBOHD activity, perturbing the magnitude of cell death development. This cysteine is evolutionarily conserved and specifically S-nitrosylated in both human and fly NADPH oxidase, suggesting that this mechanism may govern immune responses in both plants and animals.     

实时荧光定量PCR法检测环境假单胞菌属细菌丰度

应用实时荧光定量PCR法,建立了总细菌及假单胞菌属的标准曲线,并以环境样本中假单胞菌属与总细菌的比值反映其细菌丰度.应用该方法评价人工除藻反应器中组合填料、无纺布、弹性填料等介质对太湖水中溶藻细菌之一的假单胞菌属的富集情况.结果显示:该方法对总细菌的检测范围为103~108个基因拷贝/μL(R2=0.997);假单胞菌属的检测范围为1~105个基因拷贝/μL(R2=0.994).对除藻反应器溶藻细菌富集效果的评价显示,所建立的方法能有效检测反应器中填料对该类溶藻细菌的富集程度.初步证明所建立的方法可有效定量假单胞菌属在环境样本中的丰度.     

氧化铁纳米颗粒固定化溶藻菌的除藻作用

为了探讨氧化铁纳米颗粒固定化溶藻菌后对铜绿微囊藻的溶藻作用和降解微囊藻毒素LR(MC-LR)的作用,从太湖水体中分离获得一株属于芽孢杆菌属的溶藻菌,将其与氧化铁纳米颗粒固定化后,以普通Fe2O3作为实验对照,测定其溶藻作用和降解MC-LR作用.以激光粒度仪测定氧化铁纳米颗粒与溶藻菌两者单独和同时存在时的粒径大小及粒径分布,以获得氧化铁纳米颗粒固定化溶藻菌的证据.分析结果表明:在太湖水体中分离获得的一株芽孢杆菌具有较强的溶藻和降解MC-LR的作用,作用24 h后的溶藻率和MC-LR降解率分别达到44.3%和20.5%.同时加入氧化铁纳米颗粒后,溶藻率达到53.0%,MC-LR的降解率达到33.0%.激光粒度仪检测发现,氧化铁纳米颗粒与细菌混合后的颗粒物的平均直径增加到氧化铁纳米颗粒的12.3倍,同时氧化铁纳米颗粒和细菌单独存在时的粒径分布峰消失.氧化铁纳米颗粒是一种具有良好性能的生物固定化材料,可能通过其特有的途径有效地固定化溶藻菌,并增强溶藻菌的溶藻和降解藻毒素作用.     

实现平易建筑的设计方法

建筑单体的设计影响到城市整体的环境质量.文中在分析经典实例和具体工程实践的基础上指出:平易是中国传统文化中的一种价值取向,城市环境中的大量建筑需要平和简易以尊重地域文化和环境文脉.创造平易建筑需要在经济上采用限额设计、在功能上力求完善、在形式上有所制约,通过对适用、经济、美观三要素的合理综合进行优化设计,符合我国建筑发展的现状.     

基于泊位坐标的无人船自主靠泊仿真研究

针对神经网络自主靠泊控制器只能完成特定港口的靠泊,而无法拓展到其他没有训练数据的泊位这一问题,提出一种以泊位顶点为原点,岸线为y轴的坐标系(泊位坐标系)。采用泊位坐标系中相对位置来训练神经网络控制器,在V.Dragon-5000航海模拟器中选取集装箱船“银河号”,在大连港进行靠泊训练后,成功将靠泊控制器拓展到没有训练数据的深圳蛇口港与新加波樟宜港。仿真验证了采用新建立的坐标系可以拓展神经网络自主靠泊控制器适用范围,减小训练数据所需的成本。