Cavitation erosion behaviour of 20SiMn low alloy steel in Na2SO4 and NaHCO3 solutions

Most of the former studies on cavitation erosion (CE) in corrosive media were carried out in NaCl solutions. In contrast, the effects of and ions, which are dominant anions in most rivers of China, on cavitation erosion have not been investigated systematically. In this paper, the cavitation erosion behaviour of 20SiMn low alloy steel in Na₂SO₄ and NaHCO₃ solutions was investigated by using a magnetostrictive-induced CE facility. The micrographs of damaged surfaces were observed by scanning electron microscope (SEM). It was found that the CE rate of 20SiMn low alloy steel in 0.003% Na₂SO₄ solution was higher than that in 0.003% NaCl solution, but in 0.03%, 0.3%, and 3% solutions their CE rate was almost the same. The CE rate of 20SiMn low alloy steel in 0.003-3% NaHCO₃ solutions was higher than that in the equivalent 0.003-3% Na₂SO₄ and 0.003-3% NaCl solutions, which may be related to stress corrosion cracking or corrosion fatigue mechanism in NaHCO₃ solutions. The role of corrosion was analyzed by using polarization curves, electrochemical impedance spectroscopy (EIS), linear polarization resistance and the corrosion potential with or without cavitation. Independent of the test media, cavitation shifted the corrosion potential in the positive direction and strongly enhanced the cathodic current density in the polarization curves. In the interaction of cavitation erosion and corrosion, the corrosion-induced erosion component was predominant. Cavitation also greatly reduced the magnitude of impedance though the initial impedance under cavitation conditions in 3% NaHCO₃ solution was almost one order larger than that in 3% Na₂SO₄ solution.     

基于小波理论的便携式振动监测系统设计

针对传统的机械振动监测系统复杂,价格昂贵、识别率不高等特点,提出一种基于小波理论的便携式振动监测系统。该系统采用OMAP-L138为嵌入式处理核心,具有强大的数据处理能力。通过对模拟转矩试验台的振动信号进行分析,结果表明,小波分析能够对故障诊断达到了精确、实用的效果。     

Multisim10仿真软件在数字电子技术实验教学中的应用

为了提高数字电子技术实验教学质量,加强学生的学习技能和创新能力,文章提出了将Multisim10软件与传统实验教学相结合,通过对74LS138D功能的讲解介绍仿真软件在数字电路实验中的应用.研究表明,运用Multisim10的仿真功能可以提高实验的效率和学生的学习积极性,对于帮助学生加深对理论知识的理解和自主思考问题、...     

Analysis of miR-9-5p,miR-124-3p,miR-21-5p,miR-138-5p,and miR-1-3p in Glioblastoma Cell Lines and Extracellular Vesicles

Glioblastoma (GBM), the most common primary brain tumor, is a complex and extremely aggressive disease. Despite recent advances in molecular biology, there is a lack of biomarkers, which would improve GBM’s diagnosis, prognosis, and therapy. Here, we analyzed by qPCR the expression levels of a set of miRNAs in GBM and lower-grade glioma human tissue samples and performed a survival analysis in silico. We then determined the expression of same miRNAs and their selected target mRNAs in small extracellular vesicles (sEVs) of GBM cell lines. We showed that the expression of miR-21-5p was significantly increased in GBM tissue compared to lower-grade glioma and reference brain tissue, while miR-124-3p and miR-138-5p were overexpressed in reference brain tissue compared to GBM. We also demonstrated that miR-9-5p and miR-124-3p were overexpressed in the sEVs of GBM stem cell lines (NCH421k or NCH644, respectively) compared to the sEVs of all other GBM cell lines and astrocytes. VIM mRNA, a target of miR-124-3p and miR-138-5p, was overexpressed in the sEVs of U251 and U87 GBM cell lines compared to the sEVs of GBM stem cell line and also astrocytes. Our results suggest VIM mRNA, miR-9-5p miRNA, and miR-124-3p miRNA could serve as biomarkers of the sEVs of GBM cells.     

基于MQ138传感器的甲醛检测仪设计

甲醛是一种无色,有强烈刺激性气味的剧毒气体,在各类装饰材料、家具均含有甲醛.为了能够快速准确测量室内和厂矿等一些特殊环境甲醛浓度,系统以单片机STC89S51为主控核心,采用半导体MQI38甲醛传感器为数据采集模块,设计了一种甲醛浓度测量装置,完成了该装置的硬件电路和软件部分设计,经测试表明:系统的相对误差小于3％,量程为1～10×10-6,具有精度高、性能稳定、反应迅速、性价比高,而且结构简单、使用简洁方便,可广泛应用于室内及厂矿等一些特殊环境中甲醛浓度检测.     

妊娠期糖尿病中患者miR-138-5p通过调控缺氧诱导因子1α保护β细胞功能

目的:探讨在妊娠期糖尿病(GDM)患者中miR-138-5p对胰岛β细胞功能的影响及其相关作用机制。方法:通过RT-qPCR对比15例GDM患者与15例的正常健康孕妇外周血中miR-138-5p的表达差异;miR-138-5p mimic及inhibitor分别转染入β细胞系INS-1细胞中,过表达或抑制其在该细胞中的表达水平,并通过RT-qPCR验证转染效率;利用MTT增殖实验、Annexin V-FITC凋亡实验及胰岛素释放实验分别检测miR-138-5p对INS-1细胞的增殖、凋亡和胰岛素释放能力的影响;通过miRNA靶基因预测软件TargetScan筛选miR-138-5p的目标靶基因,并利用双荧光素酶基因报告及Western blot实验进行验证;功能挽救实验证实miR-138-5p是否通过靶向调控其目标基因而发挥对INS-1细胞的增殖、凋亡及胰岛素释放能力影响;Western blot实验检测miR-138-5p在INS-1细胞中作用的分子信号通路。结果:与正常健康孕妇相比,GDM患者外周血中miR-138-5p的表达显著低表达;在INS-1细胞中转染miR-138-5p mimic及inhibitor后可显著促进或抑制miR-138-5p的表达;过表达miR-138-5p可明显促进INS-1细胞的增殖,抑制其发生凋亡并促进细胞对胰岛素的释放能力;而下调miR-138-5p的表达,可显著抑制INS-1细胞的增殖,促进其发生凋亡及抑制细胞的胰岛素释放能力;通过miRNA靶基因预测软件TargetScan筛选缺氧诱导因子1α(hypoxia-inducible factor-1α, HIF-1α)为miR-138-5p的目标靶基因,双荧光素酶基因报告实验及Western blot实验提示miR-138-5p可抑制INS-1细胞中HIF-1α的表达;功能挽救实验证实miR-138-5p通过调控HIF-1α的表达,影响INS-1细胞的增殖、凋亡及胰岛素释放能力;Western blot实验明确miR-138-5p可能通过靶向调控HIF-1α的表达,影响PI3K/AKT信号通路中PI3K、AKT及其磷酸化后的p-PI3K、p-AKT蛋白而发挥对INS-1细胞的作用。结论:在GDM患者中,miR-138-5p可能通过靶向调控HIF-1α的表达,进而影响PI3K/AKT信号通路,促进β细胞的增殖、抑制其凋亡,并促进其胰岛素释放能力从而保护β细胞的功能。     

Development of a Device for Detecting Fuel Failure in a Pool-Type Reactor Effective Extraction of Fission Rare Gases by Introducing Gas Bubbles

Studies have been made for developing a sensitive device for monitoring possible release of fission products from fuel elements of a pool-type research reactor. Gas bubbles were introduced into the reactor-coolant water to extract dissolved fission rare gases, ⁸⁹Kr and ¹³⁸Xe, and their daughter nuclides, ⁸⁹Rb and ¹³⁸Cs, were counted with high efficiency. Various causes that influence the efficiency of extracting the rare gases and of collecting the daughter nuclides were studied by two methods: (1) a “filter method”, in which the air covering water was sucked and the daughter nuclides were caught onto a filter paper, and (2) a “bottle method”, in which the bubbled gas was sampled into a bottle, and the gas was later washed with water, and the activities on the filter or of the water were counted. The items affecting the efficiency of extraction include the flow rate of gas introduced, the position (the depth and the radial direction) of the gas exit in the reactor water, and whether the coolant was circulated or not. Analysis was made of the effect of the depth on the extraction efficiency of dissolved gas into bubbles. On the basis of these results, a fuel-monitoring device for routine use was tentatively designed, both in the filter and in the bottle methods, and tests were made. The filter method was found to be unsatisfactory for practical use. The bottle method enabled an automatic system which functions well enough to be used as a fuel-failure monitoring device.     

基于51单片机的电镀废水处理控制系统设计

设计了电镀废水处理控制系统,本系统采用MCS-51系列单片机为控制核心,完成电镀废水处理控制系统的设计。详细介绍了利用A/D转换芯片TLC2543进行模数转换,三八译码器74HC138与89S51的接口电路设计,对硬件原理图和程序框图作了简洁的描述。     

Photocatalysis of 2,2',3,4,4',5'-hexachlorobiphenyl and its intermediates using various catalytical preparing methods

Four etching solutions used on support materials and two coating methods of TiO(2) were conducted to investigate the effects of catalytical preparing methods on the photocatalysis of 2,2',3,4,4',5'-hexachlorobiphenyl (PCB congener 138). The results of XRD analyses confirmed that various etching solutions used on support substrates did not influence the characteristics of titanium(IV) oxide. The XRD patterns of crystallization for the catalysts before and after purification remained unchanged. Hydrofluoric acid used as an etching solution for the support substrates provided the best adhesion stability for the catalysts that demonstrated the highest photocatalytic efficiency for congener 138. Xenon and ultraviolet lamps were used to compare the irradiation effect on photocatalysis. The shortest half-lives of congener 138 were 7.4 and 12.2 h using xenon and UV reactors, respectively. Lower chlorinated biphenyls (lower congener numbers) were identified through the continuous dechlorination of congener 138. PCB congeners 99, 87, 66, 49, 28, 17, 9, and 7 were detected as a result of dechlorination from higher chlorinated congeners to lower chlorinated congeners along with the extension of exposure times. The concentrations of chloride ion were increased with increasing exposure time through dechlorination, while the concentrations of organic chlorine of congener 138 were decreased. Meta-dechlorination was the most commonly found mechanism for the photocatalysis of PCB 138. The activation energy of the photocatalysis of congener 138 was 70.8 kJ mol(-1).     

Production of the Isomeric State of 138Cs in the Thermal Neutron Capture Reaction 137Cs(n, γ)138Cs

In order to obtain precise data of the neutron capture cross section of the reaction ¹³⁷Cs(n, γ)¹³⁸Cs, the production probability of isomer state ^138mCs was measured in this work. Targets of about 0.37MBq ¹³⁷Cs were irradiated for 3 min in. the pneumatic tube facility (Pn-3) of Kyoto University Reactor (KUR). The 1,436 keV gamma;-ray emitted from both of ^138gCs and ^138mCs was measured. A ratio of the production probability between ^138gCs and ^138mCs was deduced from time dependence of peak counts of 1,436 keV γ-ray by making use of difference of half-lives of ^138gCs (33.41 min) and ^138mCs (2.91 min). The production probability of ^138mCs was obtained as 0.75plusmn;0.18 and this value revised the effective cross section upwards by 9plusmn;2percnt;. The effective cross section ô and the thermal neutron capture cross section σo were obtained as ô=0.29±0.02 b and σ=0.27±0.03b with taking into account the production of ^138mCs.