Correlation between geometrical parameters of electrical tree and corresponding partial discharge parameters in XLPE

This paper deals with the experimental study on the correlation between the geometrical parameters of electrical tree and corresponding partial discharge (PD) characteristic parameters in the course of electrical tree aging within cross linked polyethylene (XLPE) insulation. The electrical tree aging tests were performed on specimens removed from a section of 220 kV transmission cable. The PD macroscopic characteristic parameters were found to be significantly dependent on the corresponding geometrical parameters of electrical tree channels in the course of aging of XLPE, and different kind of electrical tree has different characteristics, and there is obvious correlation between the type of electrical tree and the pre-applied power-frequency stress. Beside, using regression analysis, the expression of the relation between them were obtained, and from which it can be seen that there is significant nonlinear correlation between geometrical parameters of electrical tree and corresponding PD characteristic parameters in the course of aging of XLPE. Therefore, the aging degree of XLPE can be effectively evaluated by recognizing the changing regularity of the PD rnacroscopic characteristic parameters.     

CTS及M-CTS与Men+的配位

进行了ＣＴＳ的降解,研究了ＣＴＳ及Ｍ－ＣＴＳ与Ｍｅｎ＋的配位．用光谱分析ＣＴＳ及Ｍ－ＣＴＳ与Ｍｅｎ＋的配位结果,提出ＣＴＳ及Ｍ—ＣＴＳ的配位规律．即不同分子量ＣＴＳ的配位能力,低分子量大于高分子量;不同基团的配位能力：－ＮＨ２＞＞—ＯＨ＞—Ｃ＝Ｏ不同金属离子与相同分子量的ＣＴＳ配位,基本遵循与游离氨配位规律．     

Culture in low levels of oxygen enhances in vitro proliferation potential of satellite cells from old skeletal muscles

The proliferation ability of satellite cells (considered the 'stem cells' of mature myofibers) declines with increasing age when cultured under standard cell culture conditions of 21% oxygen. However, actual oxygen levels in the intact myofiber in vivo are an order of magnitude lower. No studies to date have addressed the issue of whether culturing satellite cells from old muscles under more 'physiologic' conditions would enhance their proliferation and/or differentiation ability. Therefore, we analyzed satellite cells derived from 31-month-old rats in standard cultures with 21% O₂ and in lowered (∼3%) O₂. Under the lowered O₂ conditions, we noted a remarkable increase in the percentage of large-sized colonies, activation of cell cycle progression factors, phosphorylation of Akt, and downregulation of the cell cycle inhibitor p27^Kip1. These data suggest that lower O₂ levels provide a milieu that stimulates proliferation by allowing continued cell cycle progression, to result ultimately in the enhanced in vitro replicative life span of the old satellite cells. Such a method therefore provides an improved means for the ex vivo generation of progenitor satellite cell populations for potential therapeutic stem cell transplantation. Received 20 April 2001; received after revision 28 May 2001; accepted 31 May 2001     

4-Hydroxynonenal-modified amyloid-beta peptide inhibits the proteasome: possible importance in Alzheimer's disease

The amyloid β-peptide (Aβ) is a 4-kDa species derived from the amyloid precursor protein, which accumulates in the brains of patients with Alzheimer’s disease. Although we lack full understanding of the etiology and pathogenesis of selective neuron death, considerable data do imply roles for both the toxic Aβ and increased oxidative stress. Another significant observation is the accumulation of abnormal, ubiquitin-conjugated proteins in affected neurons, suggesting dysfunction of the proteasome proteolytic system in these cells. Recent reports have indicated that Aβ can bind and inhibit the proteasome, the major cytoslic protease for degrading damaged and ubiquitin-conjugated proteins. Earlier results from our laboratory showed that moderately oxidized proteins are preferentially recognized and degraded by the proteasome; however, severely oxidized proteins cannot be easily degraded and, instead, inhibit the proteasome. We hypothesized that oxidatively modified Aβ might have a stronger (or weaker) inhibitory effect on the proteasome than does native Aβ. We therefore also investigated the proteasome inhibitory action of Aβ _1–40 (a peptide comprising the first 40 residues of Aβ) modified by the intracellular oxidant hydrogen peroxide, and by the lipid peroxidation product 4-hydroxynonenal (HNE). H₂O₂ modification of Aβ _1–40 generates a progressively poorer inhibitor of the purified human 20S proteasome. In contrast, HNE modification of Aβ _1–40 generates a progressively more selective and efficient inhibitor of the degradation of fluorogenic peptides and oxidized protein substrates by human 20S proteasome. This interaction may contribute to certain pathological manifestations of Alzheimer’s disease Received 26 September 2000; accepted 26 September 2000     

中国西北干旱区土地退化与生态建设问题

本文阐述了西北干旱区自然环境的基本特点，讨论了土地退化中土地沙漠化、土地盐渍化和草地退化问题。指出生态建设应当尊重自然,不宜大面积植树造林，采取生态修复措施和建立自然保护区有助于环境整治与生态建设。在区域发展中应当重视土地与水资源的合理开发利用以及区域间环境与发展协调等问题。     

纳米ZnO光催化有机磷农药降解的研究

研究纳米氧化锌对三种有机磷农药的降解情况，考查了催化剂及其用量、光照时间、pH值的影响，结果表明纳米氧化锌能使有机磷农药发生降解。实验结果还表明不同形貌的氧化锌在降解有机磷农药时其效果不一样，网状比粒状所需要时间要短，这可能因为网状的粒径比较小，与降解体系接触空间更大。     

电催化氧化水中苯酚的循环伏安特性研究

采用循环伏安法考察了水中有机污染物苯酚在电极上的电催化氧化行为,并介绍了苯酚在不同介质中的电催化氧化降解途径.     

Fe0对活性艳兰K-3R的还原降解效果

研究了活性染料活性艳兰K-3R在Fe0-H2O/O2,Fe0-H2O/N2,Fe0-H2O3种实验体系中被Fe0还原降解的效果.结果表明:氧气对Fe0活性艳兰K-3R的还原降解有促进作用;Fe0与活性艳兰K-3R的最佳反应条件是在Fe0-H2O/O2体系中,体系的pH值为碱性,反应时间为10~15 min;增大转速、染料初始质量浓度以及Fe粉加入量,染料的还原降解效率提高,且Fe粉重复使用3~4次不影响处理效果.     

纳米Ag/TiO2对溴虫腈的光催化降解

用紫外杀菌灯为光源,Ag/TiO2,SDS/Ag/TiO2和TiO2作光催化剂对悬浮液中溴虫腈进行光催化降解,并采用高效液相色谱、液-质联用仪和紫外-可见分光光度计对降解过程浓度变化进行分析。研究结果表明:在100mL混合中性溶液中,当溴虫腈质量浓度为100mg/L、催化剂质量浓度为1.0g/L、温度为室温条件下,溴虫腈5h的降解率分别为78%,65%和55%(空白实验为32%)。用上述3种催化剂为光降解源和空白实验制备4种纳米农药水乳剂,于玻璃上涂膜后在相同条件下进行太阳光降解实验,各制剂中溴虫腈降解率分别为62%,53%,34%和13%;在酸性条件下,溴虫腈分子和催化剂的吸附及氢键的形成十分有利,这有利于溴虫腈的降解;紫外光、太阳光下溴虫腈分解的主要中间产物为氯苯,其他中间产物含量较少。     

Fe3+/UV光催化降解活性染料X3B的研究

为考察活性染料X3B在Fe3 /UV(λ≥320nm)体系中的降解行为,研究了Fe3 浓度对X3B降解的影响.结果表明:X3B在Fe3 /UV体系中能有效降解,且降解速率常数随着Fe3 浓度的增加而增大;通过光谱比较、X3B降解过程中的光谱特征以及羟基猝灭实验等,推测了X3B的降解机理.研究结果支持羟基自由基机理,而非配合物降解机理.