Avian flu: isolation of drug-resistant H5N1 virus

The persistence of H5N1 avian influenza viruses in many Asian countries and their ability to cause fatal infections in humans have raised serious concerns about a global flu pandemic. Here we report the isolation of an H5N1 virus from a Vietnamese girl that is resistant to the drug oseltamivir, which is an inhibitor of the viral enzyme neuraminidase and is currently used for protection against and treatment of influenza. Further investigation is necessary to determine the prevalence of oseltamivir-resistant H5N1 viruses among patients treated with this drug.     

Cryptic boundaries in roof plate and choroid plexus identified by intersectional gene activation

The hindbrain roof plate and choroid plexus are essential organizing centers for inducing dorsal neuron fates and sustaining neuron function. To map the formation of these structures, we developed a broadly applicable, high resolution, recombinase-based method for mapping the fate of cells originating from coordinates defined by intersecting combinations of expressed genes. Using this method, we show that distinct regions of hindbrain roof plate originate from discrete subdomains of rhombencephalic neuroectoderm expressing Wnt1; that choroid plexus, a secretory epithelium important for patterning later-formed hindbrain structures and maintaining neuron function, derives from the same embryonic primordium as the hindbrain roof plate; and that, unlike the floor plate, these dorsal organizing centers develop in a patterned, segmental manner, built from lineage-restricted compartments. Our data suggest that the roof plate and choroid plexus may be formed of functional units that are capable of differentially organizing the generation of distinct neuronal cell types at different axial levels.     

新疆资源、人口与环境的可持续发展研究

本文阐述了新疆的自然条件和社会经济现状,分析了制约新疆经济可持续发展的诸多重要因素,并从区情出发,提出了新疆资源、人口与环境协调发展的构想.     

毛虫图的带宽

求出毛虫图的带宽的计算公式并给出一个较简洁的证明，讨论了此带公式的计算复杂性问题，提出一种更简单的算法。     

KOH/Al2O3固体碱催化酯交换合成生物柴油的研究

采用等体积浸渍法制备了KOH/Al_2O_3负载型固体碱催化剂,并将其用于菜籽油与甲醇酯交换法合成生物柴油的研究;分别考察了催化剂附载量、煅烧温度、醇油摩尔比、反应温度、反应时间等条件对生物柴油产率的影响;结果表明:用等体积浸渍法,在400℃煅烧5 h,制得负载量为20%(w)的KOH/Al_2O_3催化剂.当催化剂用量为5%(w),醇油摩尔比为12:1,在60℃下反应2 h后,生物柴油产率高达92.3%(w).运用X-射线衍射、比表面积测定等手段对催化剂结构进行了表征,结果表明催化剂的活性与其晶相和比表面积密切相关.     

基于盲数理论的机械稳健性优化设计

在机械稳健性优化设计中不确定变量常被假定为服从某种特定分布的随机变量,在随后的优化模型中丢掉了这些不确定变量的初始数据,这种对不确定变量的处理方式往往不能真切地反映不确定变量的本质,使得出的结论偏离事实. 为了更加真切地反映这些不确定变量,使用盲数表达机械设计中的不确定变量,运用盲数运算规则表达各不确定变量之间的关系,把盲数理论和稳健设计相结合,建立基于盲数理论的稳健设计优化模型. 使用该优化模型对一个气动换向装置进行了优化计算,优化结果好于传统的稳健设计结果. 基于盲数的方法是一种离散化的数值计算方法,算例充分展示了其灵活性,证明了该优化方法是合理的和实用的.     

稀井低勘探程度区块岩性圈闭预测方法分析——以准噶尔盆地阜东斜坡带石树沟群为例

在深入剖析阜东斜坡带岩性圈闭形成条件和分布规律的基础上,提出了适合于钻井稀少的低勘探程度区块的岩性圈闭预测方法.该方法主要包括如下5个要素:(1)层位标定技术(实现井震联合,确保层序地层学分析的可靠性和精度);(2)层序地层学分析法(确定岩性圈闭的有利发育层位及发育类型);(3)沉积相分析法(确定岩性圈闭的有利发育相带及具体位置);(4)叠后高分辨率处理技术(确保岩性圈闭识别的准确性);(5)波阻抗反演技术(岩性圈闭预测的核心技术).应用该方法对阜东斜坡带进行岩性圈闭预测取得了较好的效果.