用于放射性气溶胶在线富集进样的狭缝虚拟撞击器的研制

为满足环境气溶胶在线进样的要求,改善电感耦合等离子体质谱计(Inductively Coupled Plasma Mass Spectrometry,ICP蛳MS)对粒子中待测核素的探测限,研制出一套具有低流量、低压降特点的狭缝虚拟撞击器,可作为气溶胶在线富集进样系统的关键部件与ICPˉMS联用。本文介绍了该狭缝虚拟撞击器的研制情况:首先由ICP蛳MS的进样条件,根据经验公式完成了理论设计,确定进样流量为11L/min,强流与弱流的流量比为10,喷射狭缝宽度为1mm,长宽比为10;然后用计算流体动力学软件Fluent R对上述结构内部的流场和粒子运动径迹进行了数值模拟,考察了喷射狭缝与收集狭缝的间距G、收集狭缝的宽度Wc及其进口曲率半径的加工偏差对收集效率的影响,得到了较优化的取值范围:G取1.0～1.2mm,Wc取1.4～1.6mm,此时的切割粒径D50约2.5μm;加工出狭缝虚拟撞击器的原型装置,对其分别用室内空气气溶胶和荧光素钠标记的单分散油酸粒子进行富集性能测量。实测结果表明:空气动力学等效直径在2.5～5μm范围内的粒子浓度得到了明显富集,5μm的粒子的富集因子达到极大值7。     

原始成分组成对Ti(C,N)基金属陶瓷烧结性能的影响

采用真空烧结工艺制备了Ti(C,N)基金属陶瓷,研究了原始成分组成对材料烧结特性和力学性能的影响规律。结果表明:保持Mo/(Mo+Ni)为定值,随着硬质相成分的增加,烧结体抗弯强度降低,硬度增加;硬质相成分TiN含量超过一定阈值时,烧结体疏松导致硬度和抗弯强度同时大幅下降;TiN含量保持定值,硬质相成分含量增加,烧结体硬度增加,抗弯强度下降;粘结相成分用Co部分替代Ni,随Co含量的增加,烧结体硬度略有升高的基础上抗弯强度升高。     

镀W碳纳米管增强Al基复合材料的力学性能与导电率

以羰基钨为前驱体,采用羰基热分解法在碳纳米管表面镀覆了金属W.利用球磨混粉和放电等离子体烧结制备了镀W碳纳米管(W-CNTs)/Al复合材料,并研究了球磨时间和W-CNTs含量对材料力学性能和导电率的影响.结果表明:球磨6h粉体烧结后致密度高达99.5％,接近完全致密;随球磨时间延长,W-CNTs/Al复合材料抗拉强度...     

重轨钢铸坯热装影响因素分析和数值模拟

采用有限差分法建立了钢水从结晶器至二冷区和空冷区冷却过程以及280 mm ×380 mm连铸坯热装热送的温度模型,并分析了重轨钢U71Mn(%:0.66～0.76C、0.15～0.35Si、1.10～1.40Mn)和U75V(%:0.70～0.78C、0.50～0.70Si、0.75～1.05Mn、0.04～0.08V)中的氧、氮含量、铸坯低倍组织和加热炉人口处铸坯输送辊道等对该钢热装的影响。模拟结果表明,重轨钢铸坯热装可缩短加热时间40 min,铸坯输送辊道的工作温度为250℃。     

高强度低合金钢Q420N轧制工艺优化实践

试验高强度低合金钢Q420N(/％:0.16C,0.28Si,1.39Mn,0.015P,0.003S,0.11Cr,0.009N)的生产流程为120 t转炉-LF精炼-RH真空脱气-连铸300 mm×340 mm方坯-热连轧成Φ90 mm棒材.试验研究了普通轧制工艺(开轧1100～1150℃,终轧950～1000℃,...     

双重退火制度对TC21钛合金断裂韧性的影响

利用光学显微镜和扫描电镜等手段研究了双重退火工艺对TC21钛合金断裂韧性的影响。结果表明：不同退火制度下TC21钛合金试样断裂韧性均在100MPa·m1/2以上;第一次退火温度相同的条件下,随着第一次退火温度的升高,TC21钛合金断裂韧性都略有升高,而在第二次退火温度相同的条件下,第一次退火温度对TC21钛合金断裂韧性影响较小;经950℃×2h／AC＋590℃×411／AC双重热处理的TC21钛合金具有较崎岖的裂纹扩展路径和较好的塑性,故其断裂韧性最高,可达109．7MPa·m1/2。     

Role of ERAB/L-3-hydroxyacyl-coenzyme A dehydrogenase type II activity in Abeta-induced cytotoxicity

Endoplasmic reticulum-associated amyloid beta-peptide (Abeta)-binding protein (ERAB)/L-3-hydroxyacyl-CoA dehydrogenase type II (HADH II) is expressed at high levels in Alzheimer's disease (AD)-affected brain, binds Abeta, and contributes to Abeta-induced cytotoxicity. Purified recombinant ERAB/HADH II catalyzed the NADH-dependent reduction of S-acetoacetyl-CoA with a Km of approximately 68 microM and a Vmax of approximately 430 micromol/min/mg. The contribution of ERAB/HADH II enzymatic activity to Abeta-mediated cellular dysfunction was studied by site-directed mutagenesis in the catalytic domain (Y168G/K172G). Although COS cells cotransfected to overexpress wild-type ERAB/HADH II and variant beta-amyloid precursor protein (betaAPP(V717G)) showed DNA fragmentation, cotransfection with Y168G/K172G-altered ERAB and betaAPP(V717G) was without effect. We thus asked whether the enzyme might recognize alcohol substrates of which the aldehyde products could be cytotoxic; ERAB/HADH II catalyzed oxidation of a variety of simple alcohols (C2-C10) to their respective aldehydes in the presence of NAD+ and NAD-dependent oxidation of 17beta-estradiol. Addition of micromolar levels of synthetic Abeta(1-40) to purified ERAB/HADH II inhibited, in parallel, reduction of S-acetoacetyl-CoA (Ki approximately 1.6 microM), as well as oxidation of 17beta-estradiol (Ki approximately 3.2 microM) and (-)-2-octanol (Ki approximately 2.6 microM). Because micromolar levels of Abeta were required to inhibit ERAB/HADH II activity, whereas Abeta binding to ERAB/HADH II occurred at much lower concentrations (Km approximately 40-70 nM), the latter more closely simulating Abeta levels within cells, Abeta perturbation of ERAB/HADH II was likely to result from mechanisms other than the direct modulation of enzymatic activity. Cells cotransfected to overexpress ERAB/HADH II and betaAPP(V717G) generated malondialdehyde-protein and 4-hydroxynonenal-protein epitopes, which were detectable only at the lowest levels in cells overexpressing either ERAB/HADH II or betaAPP(V717G) alone. Generation of such toxic aldehydes was not observed in cells contransfected to overexpress Y168G/K172G-altered ERAB and betaAPP(V717G). We conclude that the generalized alcohol dehydrogenase activity of ERAB/HADH II is central to the cytotoxicity observed in an Abeta-rich environment.     

直接还原铁在电弧炉炼钢中的应用

对直接还原铁 (DRI)性能及其在电弧炉冶炼的特性作了较全面的论述。了解和掌握其特性是发挥其优越性的关键 ,是发展特殊钢和纯净钢的重要途径。     

Toxic Effect of Cd^2＋ on Potamogeton crispus Alleviated by Exogenous Nd^3＋

Cadmiumis non-nutrition element for the plantgrowth,it can cause potential threat to the environ-ment safety as it remains in the nature for a very longti me,and once its concentrations reach or exceed acertainthreshold value,it will interfere withthe met…