Towards robust regional estimates of CO2 sources and sinks using atmospheric transport models

Information about regional carbon sources and sinks can be derived from variations in observed atmospheric CO2 concentrations via inverse modelling with atmospheric tracer transport models. A consensus has not yet been reached regarding the size and distribution of regional carbon fluxes obtained using this approach, partly owing to the use of several different atmospheric transport models. Here we report estimates of surface-atmosphere CO2 fluxes from an intercomparison of atmospheric CO2 inversion models (the TransCom 3 project), which includes 16 transport models and model variants. We find an uptake of CO2 in the southern extratropical ocean less than that estimated from ocean measurements, a result that is not sensitive to transport models or methodological approaches. We also find a northern land carbon sink that is distributed relatively evenly among the continents of the Northern Hemisphere, but these results show some sensitivity to transport differences among models, especially in how they respond to seasonal terrestrial exchange of CO2. Overall, carbon fluxes integrated over latitudinal zones are strongly constrained by observations in the middle to high latitudes. Further significant constraints to our understanding of regional carbon fluxes will therefore require improvements in transport models and expansion of the CO2 observation network within the tropics.     

几种绣线菊叶片表皮形态的扫描电镜研究

用扫描电镜对几种绣线菊叶片的表皮结构进行了比较观察，结果表明，所观察的几种绣线菊叶片上表皮均呈波纹网状结构，而下表皮存在着较显著的差别，其细胞的形状，大小和排列方式不甚相同，此外气孔的大小，形态及密度亦存在差异。     

Electric-field-induced capillary attraction between like-charged particles at liquid interfaces

Nanometre- and micrometre-sized charged particles at aqueous interfaces are typically stabilized by a repulsive Coulomb interaction. If one of the phases forming the interface is a nonpolar substance (such as air or oil) that cannot sustain a charge, the particles will exhibit long-ranged dipolar repulsion; if the interface area is confined, mutual repulsion between the particles can induce ordering and even crystallization. However, particle ordering has also been observed in the absence of area confinement, suggesting that like-charged particles at interfaces can also experience attractive interactions. Interface deformations are known to cause capillary forces that attract neighbouring particles to each other, but a satisfying explanation for the origin of such distortions remains outstanding. Here we present quantitative measurements of attractive interactions between colloidal particles at an oil-water interface and show that the attraction can be explained by capillary forces that arise from a distortion of the interface shape that is due to electrostatic stresses caused by the particles' dipolar field. This explanation, which is consistent with all reports on interfacial particle ordering so far, also suggests that the attractive interactions might be controllable: by tuning the polarity of one of the interfacial fluids, it should be possible to adjust the electrostatic stresses of the system and hence the interparticle attractions.     

Linkage of high-density lipoprotein-cholesterol concentrations to a locus on chromosome 9p in Mexican Americans.

High-density lipoproteins (HDLs) are anti-atherogenic lipoproteins that have a major role in transporting cholesterol from peripheral tissues to the liver, where it is removed. Epidemiologic studies have shown that low levels of high-density lipoprotein-cholesterol (HDL-C) are associated with an increased incidence of coronary heart disease and an increased mortality rate, indicating a protective role of high concentrations of HDL-C against atherogenesis and the development of coronary heart disease. HDL-C level is influenced by several genetic and nongenetic factors. Nongenetic factors include smoking, which has been shown to decrease the HDL-C level. Exercise and alcohol have been shown to increase HDL-C levels. Decreased HDL-C is often associated with other coronary heart disease risk factors such as obesity, hyperinsulinemia and insulin resistance, hypertriglyceridemia and hypertension. Although several genes have been identified for rare forms of dyslipidemia, the genes accounting for major variation in HDL-C levels have yet to be identified. Using a multipoint variance components linkage approach, we found strong evidence of linkage (lod score=3.4; P=0.00004) of a quantitative trait locus (QTL) for HDL-C level to a genetic location between markers D9S925 and D9S741 on chromosome 9p in Mexican Americans. A replication study in an independent set of Mexican American families confirmed the existence of a QTL on chromosome 9p.     

仿人机器人支撑转换期振动分析

支撑转换期的冲击产生的振动是影响机器人实现稳定、快速的仿人步行的一个重要原因。该文分析了振动对仿人机器人步行性能的影响,运用三维有限元模态分析理论,采用ANSYS软件技术对THBIP- 双足机器人系统结构的振动特性进行了研究,建立了精确的有限元弹性力学模型,计算出结构的固有频率和振型,并结合静力学分析结果和频率测试实验结果,研究刚度、间隙和接触对振动特性的影响。频率测试、比较、分析结果说明,该模型能够正确分析出THBIP- 样机结构的力学特性。     

一种C-RAN架构下载波迁移的调度策略

在云无线电接入网络(cloud-radio access network,RAN)架构的基础上,为提高载波迁移后虚拟多模基站的资源利用率和负载均衡度,把CPU资源适度分离成基带CPU资源和协议CPU资源,并提出一种基于负载特征的载波迁移调度策略.针对物理层主机的触发类型和虚拟多模基站的负载特征,采用双阈值上下触发方式触发迁移,根据9种负载状态并采用最小资源代价策略,完成对需要迁移的虚拟多模基站以及目标主机的选择.实验结果表明,基带资源利用率方差均值降低0.04左右,协议资源利用率方差均值降低0.03左右,实现了虚拟基站迁移的自主管理,并且达到了节约资源的目的.迁移前后,虚拟基站的状态没发生太大的改变,具有良好的一致性.     

毛细力驱动自组装定位模型

毛细力驱动自组装的定位是利用微元件及基片表面之间的毛细力作用实现的。为了研究微元件及组装区的形状对自组装定位的影响,在分析毛细力驱动自组装机理的基础上,利用能量法建立了毛细力驱动自组装系统的定位解析模型,预测了不同形状微元件的自组装结果,并对一些不合理的组装设计进行了修正。结果表明:通过计算自组装表面能量可以预测组装结果,并设计合理的粘合区形状。