The control of protein release from poly(DL-lactide co-glycolide) microparticles by variation of the external aqueous phase surfactant in the water-in oil-in water method

A unique feature of p21 that distinguishes it from the other cyclin-dependent kinase (CDK) inhibitors is its ability to associate with the proliferating cell nuclear antigen (PCNA), an auxiliary factor for DNA polymerases delta and epsilon. While it is now well established that inhibition of cyclin/CDK complexes by p21 can result in G1 cell cycle arrest, the consequences of p21/PCNA interaction on cell cycle progression have not yet been determined. Here, we show, using a tetracycline-regulated system, that expression of wild-type p21 in p53-deficient DLD1 human colon cancer cells inhibits DNA synthesis and causes G1 and G2 cell cycle arrest. Similar effects are observed in cells expressing p21CDK-, a mutant impaired in the interaction with CDKs, but not in cells expressing p21PCNA-, a mutant deficient for the interaction with PCNA. Analysis of cells treated with a p21-derived PCNA-binding peptide provides additional evidence that the growth inhibitory effects of p21 and p21CDK result from their ability to bind to PCNA. Our results suggest that p21 might inhibit cell cycle progression by two independent mechanisms, inhibition of cyclin/CDK complexes, and inhibition of PCNA function resulting in both G1 and G2 arrest.     

基于AT89C52单片机的智能温控器

介绍一种以单片机AT89C52为基础、采用电压/频率转换技术、具有计算机通讯功能的智能温控表.     

建筑外窗气密性检测实验室的建立

在东华大学能源与环境检测中心建立的背景下,搭建了建筑外窗气密性检测的试验台并进行了实地检测,给出了外窗气密性定级检测的要点,分析了气密性检测对建筑节能的意义,并提出加强气密性的可行性措施。     

压电换能器底座ANSYS有限元分析

压电换能器是超声无损检测中的一个重要的组成环节,然而,有许多因素影响压电换能器的性能。文章运用有限元ANSYS软件,模拟出压电换能器的模型,分析其底座对压电换能器性能的影响。结果发现,金属基座不仅具有保护压电材料的作用,解决电极引出问题,而且还能增大压电换能器的输出电压,有效地提高其压电性能。     

Complicated resistivity‐temperature behavior in polymer composites

The resistivity of different polymer composites is investigated in different temperature‐changing processes, which demonstrates more complicated changing behaviors than that usually reported in literatures. The complicated resistivity‐temperature (R‐T) behaviors cannot be explained by current theories, and the contradictions of them with current theories are presented in this article. With the experiments, a new viewpoint on the R‐T behaviors of polymer composites is proposed, i.e., the resistivity changes are attributed to internal stress generated when the morphology and structure of the composites undergo great changes. Based on this speculation, the complicated R‐T behaviors of polymer composites can be well explained. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2217–2221, 2002     

Aging Behavior of xPb(Fe2/3W1/3)O3· (1 –x)Pb(Fe1/2Nb1/2)O3 Ceramic

The aging behavior of a series of lead perovskite dielectrics with the compositions x Pb(Fe_2/3W_1/3)O₃·(1 – x )Pb(Fe_1/2-Nb_1/2)O₃, where 0 ≤ x ≤ 1, and the effect of dopants were studied. Below the Curie temperature ( T _c), the capacitance and the dissipation factor (tan δ) decrease approximately linearly with logarithmic time. The aging rate depends on the temperature difference, Δ T , between the aging temperature and T _c, and on the dopant concentration, but is independent of the measurement frequency between 1 and 1000 kHz. The maximum aging rate is about 3% per decade of time for capacitance and 5% per decade for tan δ at 1 mol% dopant concentration, and increases to 6.3% for capacitance and 8.5% for tan δ at 0.7 mol% dopant concentration. These results are consistent with an aging mechanism caused by changing ferroelectric domain structure with time, as proposed for BaTiO₃.     

Improving Properties of Poly(vinylidene fluoride) by Adding Expanded Graphite without Surface Modification via Water‐Assisted Mixing Extrusion

Expanded graphite (EG) is introduced into poly(vinylidene fluoride) (PVDF) by melt mixing extrusion with water injection. The results demonstrate that the unfunctionalized EG in composite prepared with water injection exbibits better dispersion than that in the one prepared without water injection due to the promoting role of water during extrusion. Thus, the PVDF/EG composite with loading of 4 wt% prepared by water‐assisted mixing extrusion (WAME) exhibits electrical conductivity of about three orders of magnitude higher than the neat PVDF and one order of magnitude higher than the one prepared without water injection. Comparing to the neat PVDF, the thermal conductivity of the composites prepared with and without water injection is increased by 101.5% and 75.0%, respectively. The introduced EG leads to increased Young’s modulus and tensile strength especially for the composite prepared by WAME. The present work indicates that WAME can promote the dispersion of EG in PVDF matrix without any extra functionalization.     

棉籽的综合利用及深加工技术

棉籽是棉花加工的副产品,综合利用棉籽对节约资源、提高经济效益、促进农业生态系统良性循环有着重要意义.介绍了棉籽油制备生物柴油、棉籽粕脱毒的方法,以及利用棉籽制备高附加值产品棉酚、棉子糖、维生素E、木糖醇的技术,并对棉籽的深加工及利用技术应用前景进行了展望.     

反胶束体系增溶水量对棉籽粕蛋白的萃取研究

棉籽粕中蛋白质含量约为50%。讨论了阳离子CTAB/正辛烷(正辛醇或正戊醇)、阴离子AOT/异辛烷两种反胶束体系在不同条件下的W0与萃取率之间的关系。通过调整助表面活性剂、助溶剂的种类和加入量,从而改变萃取率的主要影响因素——增溶水的量(W0),并得出最佳萃取率(84%)时,W0取值范围是30～40。     

真菌融合子R201纤维素酶的纯化及性质研究

采用两株真菌康宁木霉3.2774和白腐真菌5.776融合产生的融合菌株R201对秸秆进行液态发酵,发酵粗酶液经硫酸铵盐析,SephadexG-100柱层析2次后酶活可提纯8.89倍。经SDS-PAGE测得3种纤维素酶的分子量约为66.3、52.7ku和37.0ku。酶作用的最适温度为50℃,最适pH值为5.0,在40℃以下,pH值4～6之间酶活较稳定。浓度为5mmol/L的Fe2 对酶反应有明显促进作用。