大气电场倒转与突发钠层及突发E层的相关性

突发钠层(Sporadic Sodium Layer, Na_S)是中高层大气金属层最为显著的一种现象,其发生机制目前尚无定论。突发E层(Sporadic E layer, E_S)是等离子体密度异常增大的薄层,被认为与Na_S密切相关。为进一步研究Na_S及E_S事件之间相关性及影响因素,利用中国科学院“子午工程”2010～2018年合肥科大站宽带钠荧光共振激光雷达观测结果,并结合武汉左岭镇站数字测高仪及九峰站大气电场仪数据,分析大气电场倒转(即北向电场)对Na_S以及E_S事件的影响。在统计的91例Na_S事件中,发生于大气电场倒转时的比例为20/91; 同时,在发生Na_S事件的事例中,E_S消失或中断的比例较大(14/20),表明E_S可能以提供钠源的形式转化为Na_S。此外,在分析武汉左岭镇站数字测高仪数据的同时进行概率统计,结果表明:当大气电场倒转时,E_S临界频率减小甚至消失的概率较大(187/242),少数情况下可能造成临界频率增大甚至激发E_S生成(55/242); E_S虚高消失比例为179/242,E_S不变比例为27/242,E_S上升比例为23/242。综上所述,大气北向电场在一定程度上对E_S事件的发生有抑制作用,并对E_S事件的发生高度有明显影响。最后,对一种与电场倒转相关的突发钠层机制也进行了讨论。     

微量元素Al和Mn对银带材性能的影响

为解决银材自然时效软化的问题，存99．999％Ag中添加0.004％A1和0．003％Mn(按质量)制成纯度为99．99％的Ag材，实验表明，采用变形率为90．90％所制备的银材，在25℃温度下，自然时效365d，其强度σb=370MPa，硬度HV=1030MPa保持稳定不变，有效地抑制了纯银材自然时效80d，其力学性能便大幅度下降的问题。     

金属大气腐蚀实验技术进展

综述了金属大气腐蚀的实验方法和分析手段及各种方 法的优缺点，探讨了金属大气腐蚀研究的发展趋势.     

EFFECT OF AGING ON HYDROGEN EMBRITTLEMENT SUSCEPTIBILITY OF STEEL Cr21Ni6Mn9N

Effects of 650℃ aging for 1—1000 h on structure and hydrogen embrittlement susceptibility(HES)of steel Cr21Ni6Mn9N have been investigated.The results show that M_(23)C_6 typecarbide precipitates at grain boundaries and Cr-depletive region appears beside them duringaging.The precipitates grow and connect each other as the aging time prolongs.Meanwhile,the degree of Cr-depletion aggravates first and then recovers gradually while the aging time isvery long,i.e.,1000 h.The HES of the steel increases with increasing aging time but does notreduce with the recovery of Cr content at the Cr-depletive region.That implies that the ex-isting of carbides at grain boundaries might be the main reason which promotes the HES ofsteel during aging.     

热氧老化EPR电缆绝缘局部放电特性及劣化机理

为了探究热氧老化后乙丙橡胶电缆绝缘的局部放电特性及劣化机理,文中通过典型柱–板电极对不同老化程度的乙丙橡胶试样进行了局部放电试验,并对其放电发展特性和材料理化性质进行了分析。结果表明:放电起始电压和闪络电压均随绝缘老化程度的提高而降低;根据放电过程中放电特征量的变化规律,可将放电过程划分为4个阶段:起始阶段、发展阶段、持续阶段、预闪络阶段,且不同老化程度试样的PRPD谱图在各阶段呈现出特定形状;老化后的试样表面气化或气体解吸附、内部添加剂成分析出导致试样表面出现"沟壑区"、白色块状物和"微孔",分子结构中的羰基等含氧基团、聚乙烯和聚丙烯等自由基数量的增加是乙丙橡胶绝缘在热氧老化后更易出现局部放电的关键原因。     

生物质硅炭增强改性氢化丁腈橡胶的性能及老化规律

以生物质硅炭(Si/CB)取代部分N550炭黑为补强剂、HNBR为基体制备了生物质硅炭改性的HNBR复合材料。研究了硅炭对HNBR的补强行为,高温真空介质中橡胶的热老化行为及主链老化结构的演变。与传统炭黑的增强效果相比,生物质硅炭增强的HNBR表现出更好的韧性、撕裂强度、较低的永久变形及高温力学性能。160℃下老化20 d,材料的拉伸强度保持率大于100%,生物质硅炭表现出较好的耐老化能力。链接-CN官能团的α-碳原子高温下易均裂氢原子生成自由基,连续加氢还原使-C■N转化为-C■NH,直至形成化学交联结构,导致橡胶的玻璃化转变温度升高。氢化丁腈的CN含量越低,耐老化能力越突出。依据分子主链老化的结构演变信息,提出了HNBR的可能老化机理。     

干式接地变压器的故障分析

本文介绍两台干式接地变压器相继故障,通过事故象征,进行全面分析,由于制造工艺欠佳等原因,造成运行中高压侧绕组匝间短路,确定了产品故障的根本原因。     

Nicotinamide Phosphoribosyltransferase as a Key Molecule of the Aging/Senescence Process

Aging is a phenomenon underlined by complex molecular and biochemical changes that occur over time. One of the metabolites that is gaining strong research interest is nicotinamide adenine dinucleotide, NAD⁺, whose cellular level has been shown to decrease with age in various tissues of model animals and humans. Administration of NAD⁺ precursors, nicotinamide mononucleotide (NMN) and nicotinamide riboside (NR), to supplement NAD⁺ production through the NAD⁺ salvage pathway has been demonstrated to slow down aging processes in mice. Therefore, NAD⁺ is a critical metabolite now understood to mitigate age-related tissue function decline and prevent age-related diseases in aging animals. In human clinical trials, administration of NAD⁺ precursors to the elderly is being used to address systemic age-associated physiological decline. Among NAD⁺ biosynthesis pathways in mammals, the NAD⁺ salvage pathway is the dominant pathway in most of tissues, and NAMPT is the rate limiting enzyme of this pathway. However, only a few activators of NAMPT, which are supposed to increase NAD⁺, have been developed so far. In this review, we will focus on the importance of NAD⁺ and the possible application of an activator of NAMPT to promote successive aging.     

A New Tool to Study Parkinsonism in the Context of Aging: MPTP Intoxication in a Natural Model of Multimorbidity

The diurnal rodent Octodon degus (O. degus) is considered an attractive natural model for Alzheimer’s disease and other human age-related features. However, it has not been explored so far if the O. degus could be used as a model to study Parkinson’s disease. To test this idea, 10 adult male O. degus were divided into control group and MPTP-intoxicated animals. Motor condition and cognition were examined. Dopaminergic degeneration was studied in the ventral mesencephalon and in the striatum. Neuroinflammation was also evaluated in the ventral mesencephalon, in the striatum and in the dorsal hippocampus. MPTP animals showed significant alterations in motor activity and in visuospatial memory. Postmortem analysis revealed a significant decrease in the number of dopaminergic neurons in the ventral mesencephalon of MPTP animals, although no differences were found in their striatal terminals. We observed a significant increase in neuroinflammatory responses in the mesencephalon, in the striatum and in the hippocampus of MPTP-intoxicated animals. Additionally, changes in the subcellular expression of the calcium-binding protein S100β were found in the astrocytes in the nigrostriatal pathway. These findings prove for the first time that O. degus are sensitive to MPTP intoxication and, therefore, is a suitable model for experimental Parkinsonism in the context of aging.     

Polyphenol Supplementation Reverses Age-Related Changes in Microglial Signaling Cascades

Microglial activity in the aging neuroimmune system is a central player in aging-related dysfunction. Aging alters microglial function via shifts in protein signaling cascades. These shifts can propagate neurodegenerative pathology. Therapeutics require a multifaceted approach to understand and address the stochastic nature of this process. Polyphenols offer one such means of rectifying age-related decline. Our group used mass spectrometry (MS) analysis to explicate the complex nature of these aging microglial pathways. In our first experiment, we compared primary microglia isolated from young and aged rats and identified 197 significantly differentially expressed proteins between these groups. Then, we performed bioinformatic analysis to explore differences in canonical signaling cascades related to microglial homeostasis and function with age. In a second experiment, we investigated changes to these pathways in aged animals after 30-day dietary supplementation with NT-020, which is a blend of polyphenols. We identified 144 differentially expressed proteins between the NT-020 group and the control diet group via MS analysis. Bioinformatic analysis predicted an NT-020 driven reversal in the upregulation of age-related canonical pathways that control inflammation, cellular metabolism, and proteostasis. Our results highlight salient aspects of microglial aging at the level of protein interactions and demonstrate a potential role of polyphenols as therapeutics for age-associated dysfunction.