置换空间PBBs中的两个凸性

在全函数空间有有限逼近的条件下,置换空间中弱*局部完全k-凸、弱*中点局部一致凸的表现形式是对每个s∈S,Bs有相应的性质,推广了文[3]的结果。     

Species-specific differences in the mitogenic activity of heparin-binding growth factors in the sera of various mammals

Sera from different mammalian species displayed great differences in mitogenic activity, as measured by stimulation of DNA synthesis in BALB/c 3T3 cells (3T3 cells). Among the sera examined, fetal bovine serum was least active, and increasing activity was detected in calf serum, human serum, rat serum and mouse serum, in that order. Rat and mouse sera exhibited extremely high mitogenic activity with 3T3 cells, but when TIG-1 human fetal lung fibroblasts were used for the DNA assay instead, the activity levels of all of the sera were lower, and the differences between them were smaller. To determine the reasons for these differences, the heparin-binding growth factors in each serum were separated on a heparin affinity column. Five peaks of DNA-stimulating activity were obtained. Three of these were found in all sera examined, with both 3T3 cells and TIG-1 cells. Two other peaks were found only with 3T3 cells; one was peculiar to rat and mouse sera, with extremely high activity in the rat, and the other was specific to fetal serum. The dependence of the activity of these peaks on the cells used for the test was confirmed using normal rat lung fibroblasts and immortalized rat kidney cells. These findings adequately explain the species-specific differences in mitogenic activity of whole sera, and the variation in activity depending on the cells used for assay of DNA synthesis.     

钝化304不锈钢单晶在硫酸含氯介质中的孔蚀

采用交流阻抗技术,研究钝化304不锈钢单晶体在pH1.0,0.25mol/lNa_2SO_4含氯介质中的孔蚀行为。对孔蚀过程中的阻抗频谱特征进行了分析,提出孔蚀的发生和发展过程中都有复合物(MOHC1)形成。复合物进一步吸附更多的氯离子,导致溶解反应发生。并提出一个孔蚀的的反应机理模型,它与304不锈钢多晶体在硫酸含氯介质中的孔蚀机理没有本质的差别。     

平面上一种Denjoy型积分

在文[7]的基础上定义了一种新的Denjoy型积分,并讨论它的简单性质.     

一类特殊完全正多重线性映射

研究了C~*-代数上某类完全正多重线性映射与算子内积,C~*-代数表示的关系以及纯完全正多重线性映射的刻画,特别证明了纯性与不可约表示的等价性。     

Compensatory caspase activation in MPP+-induced cell death in dopaminergic neurons

Many have hypothesized that cell death in Parkinsons disease is via apoptosis and, specifically, by the mitochondrial-mediated apoptotic pathway. We tested this hypothesis using a mouse dopaminergic cell line of mesencephalic origin, MN9D, challenged with the Parkinsonism-causing neurotoxin MPP⁺ (1-methyl-4-phenylpyridinium ion). Apoptosis was the main mode of cell death when the cells were subjected to MPP⁺ treatment under serum-free conditions for 24 h. Caspase-3 and caspase-9, however, were not activated, thus indicating the existence of alternate or compensatory cell death pathway(s) in dopaminergic neuronal cells. Using caspase inhibitors, we demonstrated that these pathways involve caspase-2, –8, –6 and –7. A time-course study indicated that activation of caspase-2 and –8 occurred upstream of caspase-6 and caspase-7. Upon MPP⁺ challenge, the apoptosis-inducing factor was translocated from the mitochondria into the MN9D cytosol and nucleus. These results suggest the existence of alternative apoptotic pathways in dopaminergic neurons.Received 20 September 2004; received after revision 5 November 2004; accepted 22 November 2004     

关于σ—点有限CS^＊—网^＊

证明了具有σ-点有限cs-网的空间,可以刻划为度量空间在某确定映射下的像.     

固相挤出自增强聚丙烯的性能与结构研究

通过优化口模流场的拉伸应变速率,利用柱塞式挤出机（名义拉伸比为18.48）,在低于聚丙烯（PP）熔点的145~155 ℃区间,固相挤出了自增强PP片材,拉伸强度大幅度提高,在挤出温度155 ℃时达到最大值378 MPa,比熔融挤出试样的强度提高了10倍多.研究了挤出工艺的影响,在155 ℃时固相挤出平均速率最高,试样的真实拉伸比也最大.采用DSC、XRD、SEM表征了自增强聚丙烯地微观结构和断口形貌,结果表明,自增强PP的结晶度明显提高,155 ℃固相挤出的PP结晶度提高了1倍,具有更高的热稳定性,片材中