球形刀三坐标曲面加工刀位计算及误差分析研究

针对三坐标数控编程及加工中的刀位计算问题，分析了计算球形刀在被加工曲面上任意一点刀具中心轨迹的坐标公式，讨论了采用球形刀加工而引起加工方法误差的原因及误差补偿方法，并给出了走刀步长与加工误差的关系式。     

α-生育酚在超临界CO_2中溶解度神经网络模型的建立

生育酚有很高的生理活性 ,油脂生产中得到的脱臭馏出物含有丰富的天然生育酚 作为萃取生育酚的基础 ,对甲酯化油脂脱臭馏出物中α -生育酚在超临界CO2 中的溶解度进行了测试 ,并用Chrastil分子缔合模型和RBF神经网络模型对溶解度数据进行了拟合 Chrastil分子缔合模型的相对误差为 2 5.36% 对于RBF神经网络模型 ,经过网络学习和训练 ,训练集平均误差仅为 0 .2 3% ,测试集误差为 6.4 8% ,效果比较理想     

Parallel bacterial evolution within multiple patients identifies candidate pathogenicity genes

Bacterial pathogens evolve during the infection of their human host(1-8), but separating adaptive and neutral mutations remains challenging(9-11). Here we identify bacterial genes under adaptive evolution by tracking recurrent patterns of mutations in the same pathogenic strain during the infection of multiple individuals. We conducted a retrospective study of a Burkholderia dolosa outbreak among subjects with cystic fibrosis, sequencing the genomes of 112 isolates collected from 14 individuals over 16 years. We find that 17 bacterial genes acquired nonsynonymous mutations in multiple individuals, which indicates parallel adaptive evolution. Mutations in these genes affect important pathogenic phenotypes, including antibiotic resistance and bacterial membrane composition and implicate oxygen-dependent regulation as paramount in lung infections. Several genes have not previously been implicated in pathogenesis and may represent new therapeutic targets. The identification of parallel molecular evolution as a pathogen spreads among multiple individuals points to the key selection forces it experiences within human hosts.     

Oral-facial-digital type I protein is required for primary cilia formation and left-right axis specification

The oral-facial-digital type I (OFD1) syndrome (OMIM 311200) is a human developmental disorder; affected individuals have craniofacial and digital abnormalities and, in 15% of cases, polycystic kidney. The disease is inherited as an X-linked dominant male-lethal trait. Using a Cre-loxP system, we generated knockout animals lacking Ofd1 and reproduced the main features of the disease, albeit with increased severity, possibly owing to differences of X inactivation patterns between human and mouse. We found failure of left-right axis specification in mutant male embryos, and ultrastructural analysis showed a lack of cilia in the embryonic node. Formation of cilia was defective in cystic kidneys from heterozygous females, implicating ciliogenesis as a mechanism underlying cyst development. In addition, we found impaired patterning of the neural tube and altered expression of the 5' Hoxa and Hoxd genes in the limb buds of mice lacking Ofd1, suggesting that Ofd1 could have a role beyond primary cilium organization and assembly.     

Low-density lipoprotein receptor-mediated endocytosis of PEGylated nanoparticles in rat brain endothelial cells

Poly(methoxypolyethyleneglycol cyanoacrylate-co-hexadecylcyanoacrylate) (PEG-PHDCA) nanoparticles have demonstrated their capacity to diffuse through the blood-brain barrier after intravenous administration. However, the mechanism of transport of these nanoparticles into brain has not yet been clearly elucidated. The development of a model of rat brain endothelial cells (RBEC) in culture has allowed investigations into this mechanism. A study of the intracellular trafficking of nanoparticles by cell fractionation and confocal microscopy showed that nanoparticles are internalized by the endocytic pathway. Inhibition of the caveolae-mediated pathway by preincubation with filipin and nystatin did not modify the cellular uptake of the nanoparticles. In contrast, chlorpromazine and NaN₃ pretreatment, which interferes with clathrin and energy-dependent endocytosis, caused a significant decrease of nanoparticle internalization. Furthermore, cellular uptake experiments with nanoparticles preincubated with apolipoprotein E and blocking of low-density lipoprotein receptors (LDLR) clearly suggested that the LDLR-mediated pathway was involved in the endocytosis of PEGPHDCA nanoparticles by RBEC. Received 1 September 2006; received after revision 4 December 2006; accepted 18 December 2006     

Homozygous mutation of AURKC yields large-headed polyploid spermatozoa and causes male infertility

The World Health Organization conservatively estimates that 80 million people suffer from infertility worldwide. Male factors are believed to be responsible for 20-50% of all infertility cases, but microdeletions of the Y chromosome are the only genetic defects altering human spermatogenesis that have been reported repeatedly. We focused our work on infertile men with a normal somatic karyotype but typical spermatozoa mainly characterized by large heads, a variable number of tails and an increased chromosomal content (OMIM 243060). We performed a genome-wide microsatellite scan on ten infertile men presenting this characteristic phenotype. In all of these men, we identified a common region of homozygosity harboring the aurora kinase C gene (AURKC) with a single nucleotide deletion in the AURKC coding sequence. In addition, we show that this founder mutation results in premature termination of translation, yielding a truncated protein that lacks the kinase domain. We conclude that the absence of AURKC causes male infertility owing to the production of large-headed multiflagellar polyploid spermatozoa.     

Sandwiched Renyi 量子相对熵单调性的另一证明

量子相对熵在保迹完全正定的映射作用下是单调递减的.此外,对于一种新提出的Sandwiched Renyi量子相对熵,当映射满足Schwarz不等式或映射保迹正定时,也有研究证明该量子相对熵的单调性也成立.本文利用复插值技巧给出当α∈[1/2,1)时Sandwiched Renyi量子相对熵单调性的另一证明.该技巧曾被用于证明α∈(1,∞)时量子相对熵在保迹正定映射的作用下满足单调性.     

基于Oracle的应用软件系统检索性能的优化

数据库的性能最终决定数据库实际的可用性。而对于一个设计成形并且已投入运行的大型数据库系统 ,通过改变应用程序的设计来进行调整优化是很复杂的。通过分析 Oracle服务器的特征 ,从最为关键的数据库逻辑结构、系统全局区、数据存储和磁盘I/ O4个方面阐述了在不改变应用程序的前提下提高系统性能的相应策略 ,通过一个基于 Oracle系统的试验 ,把数据的检索速度提高了 1 4倍     

阈值策略下带扰动的广义Erlang(n)对偶风险模型

在阈值分红策略下研究了带扰动的广义Erlang(n)对偶风险模型,在这个模型中得出了公司直到破产时刻为止的累积红利期望现值函数所满足的两个积分-微分方程,并求出了这种情况下的广义Lundberg基本方程,同时当模型中的利润额服从泊松分布的时候,得出方程的一般解。