机械产品绿色设计结构体系研究

介绍了绿色设计的概念,探讨了绿色产品设计的结构体系。结构体系主要包括:材料选择,结构设计,装配和拆卸设计,回收设计,零部件分析,产品数据库的建立等。建立合适的产品绿色设计结构体系,是开展绿色机械产品设计工作的基础。     

Possible integration of upstream signals at Cdc42 in filamentous differentiation of S. cerevisiae

Various environmental stimuli (such as nitrogen starvation, short-chain alcohols and slowed DNA synthesis) induce filamentous differentiation in S. cerevisiae. Genetic mutations (such as deletion of the mitotic cyclin gene CLB2) cause constitutive filamentous differentiation. Although different stimulus-induced filamentous differentiation involves different signalling pathways, Cdc42 has been identified as a common regulator. We show here that Cdc42 is also required for hydroxyurea (HU)-induced and clb2Delta-caused filamentous growth. We show that the mitotic CDK Clb2/Cdc28 functions upstream of Cdc42 in regulating filamentous differentiation. This result points to possible existence of a Cdc42-MAPK-Clb2/Cdc28 positive feedback loop in the signalling of filamentous differentiation. We report isolation of a cdc42-Y40F allele that blocks HU-induced, but not nitrogen starvation-induced, short-chain alcohol-induced or clb2Delta-caused, filamentation. Based on these results, we propose a model in which Cdc42 functions as a possible integrator for the upstream signals of filamentous differentiation (from the filamentous growth MAPK pathway, the cAMP pathway and the Mec1/Rad53 checkpoint pathway). We also show evidence that the mitotic CDK inhibitor Swe1 may mediate the cross-talk between the cAMP and MAPK pathways.     

Perinatal lead and mercury exposure in Austria

Objective

The heavy metals lead (Pb) and mercury (Hg) are ubiquitous environmental pollutants with high neurotoxic potential. We aimed to compare perinatal Pb and Hg concentrations and to explore the potential association between Pb and Hg exposure and newborn anthropometry.

Study design

Pregnant women were recruited in 2005 at the General Hospital Vienna for participation in this longitudinal study. Pb and Hg concentrations were measured in maternal blood and hair, placenta, cord blood, meconium, and breast milk of 53 mother-child pairs by CV-AAS, GF-AAS, and HPLC-CV-ICPMS. We conducted bivariate analyses and categorical regression analysis (CATREG) to evaluate the determinants of Pb and Hg exposure, and of infant anthropometry.

Results

Median Pb and total Hg contents were low, i.e., 25 μg/L (maternal blood-Pb), 13 μg/L (cord blood-Pb), 0.7 μg/L (maternal blood-Hg), and 1.1 μg/L (cord blood-Hg). Hg levels in maternal and fetal tissues were frequently correlated (r > 0.3, P < 0.05, respectively). Regarding Pb, only maternal blood and cord blood concentrations correlated (P = 0.043). Cord blood levels indicated higher Hg exposure but lower Pb exposure relative to maternal blood contents. Adjusted CATREG models indicated the significant predictors of birth length (placenta-Pb, gestational length, meconium-Pb), birth weight (placenta-Pb, gestational length, maternal blood-Pb), and head circumference (maternal education, maternal height). Besides one significant correlation between maternal hair Hg and birth length, the mercury levels were not associated with newborn anthropometry.

Conclusions

Our data implicate that different modes of action may exist for placentar transfer of Pb and Hg as well as that low Pb exposure levels can result in lower birth weight. The findings related to newborn anthropometry need to be confirmed by the examination of larger study groups. Further research is needed to clarify the mechanisms of Pb and Hg transfer via the placenta, and to explore how prenatal Pb exposure is related to intrauterine growth.     

机电一体化及其教学探讨

本文从机电一体化的概念入手,根据其技术体系及我国的现状提出了对发展我国机电一体化教育的看法,对目前我国高校机电一体化教学改革具有一定的借鉴意义。     

粒铸EMCDB推进剂的力学性能研究

在国内首次用粒铸工艺制备出了力学性能好、具有燃烧平台的浇铸改性双基弹性体(EMCDB)推进剂.研究了燃烧催化剂、交联密度和耐寒增塑剂对粒铸EMCDB推进剂力学性能的影响,阐述了粒铸EMCDB推进剂的力学性能特点,分析了具有这些特点的原因,说明粒铸工艺在调节推进剂的性能方面有很大的优势.