液相色谱-质谱/质谱法测定包装材料中的全氟辛酸及其盐类物质

全氟辛酸（PFOA）具有中等毒性的肝致癌性,并会影响生物体脂类物质的代谢及抑制生物体的免疫系统功能。本文对包装材料中PFOA及其盐类进行检测,所建立的方法可对包装材料的安全性评价提供技术支撑。     

气相色谱-质谱法测定包装材料中全氟辛酸及其盐类

快速溶剂萃取法萃取包装材料中的全氟辛酸(PFOA)及其盐类, 萃取液与乙酰化试剂反应后, 以全氟癸酸甲酯为内标物, 用内标法进行定量测定. 气相色谱质谱条件为: HP-Innowax毛细柱;柱温: 50 ℃ (5 min)30 ℃/min→240 ℃ (5 min);不分流进样;接口温度: 280 ℃;载气: 氦气, 0.8 mL/min;进样量: 1 μL;负化学源;反应气: 甲烷, 20%;选择离子扫描方式. 方法的线性范围1.0～105 μg/L, 线性相关系数r=0.999, 检出限0.1 μg/L, 不同浓度的PFOA的相对标准偏差分别为4.1%和3.2%, 回收率在87%～109%之间.     

磁力棒中心轴线上磁感应强度分布特点探讨

研究磁力棒中心轴线上磁场的磁感应强度分布特点,研究在轴线上排列数目不同的钢球（无磁性）,钢球被磁化后,对应的轴线上磁感应强度分布特点、变化规律和拟合公式,加深对轴线上磁场分布规律的深入理解。     

新型杀虫剂美加农(0.12%藻酸丙二醇酯可溶液剂)有效成分测定-称量法

介绍了称量法测定新型杀虫剂美加农(0.12%藻酸丙二醇酯可溶液剂)中有效成分的方法。该方法是基于水解藻酸丙二醇酯(propylene glycol alginate,PGA)所产生的藻酸不溶于水,因此可定量滤出。样品分析精密度为0.007%。     

镍改性ZSM-5催化剂及其SCR催化性能

采用液态离子交换法制备了不同负载量的镍改性ZSM-5分子筛催化剂,并考察了上述催化剂的微观结构和物理化学特性及其在NH3-SCR反应中的催化性能。结果表明:在负载量<10.9%时镍在分子筛中具有高度的分散性,而随着镍负载量的进一步增加,分子筛表面开始出现较大的NiO颗粒;镍元素只以+2价存在于分子筛催化剂中;在NH₃-SCR反应中,镍负载量低于14.9%时,增加镍负载量将提高催化剂的低温活性;当反应温度超过300℃时,高温催化中心开始起作用,但随镍负载量的增加,高温活性开始下降时的温度逐渐降低。     

Direct CP violation in B(s)→J/ψP(V)

In the framework of factorization, we study direct CP violation in the decays of B_(s)→J/ψP(V) (P(V) refer to the pseudoscalar (vector) meson). The CP violation depends strongly on Cabibbo-Kobayashi- Maskawa (CKM) matrix elements and the effective parameter, N_c. The recent experimental data for the branching ratios of B_(s)→J/ψP(V) are accurate enough and we can give a strong constraint on the range of N_c. We nd that the CP violating asymmetry is consistent with the available experiment values for the b→d transition, and a little smaller than the b→s transition. We also predict the CP violation of other decay channels for B_(s)→J/ψP(V). We expect our results can give valuable guidance for experiments.     

Protection-against-water-attack determined difference between strengths of backbone hydrogen bonds in kinesin's neck zipper region

Docking of the kinesin's neck linker(NL) to the motor domain is the key force-generation process of the kinesin.In this process, NL's β10 portion forms four backbone hydrogen bonds(HBs) with the motor domain. These backbone hydrogen bonds show big differences in their effective strength. The origins of these strength differences are still unclear.Using molecular dynamics method, we investigate the stability of the backbone HBs in explicit water environment. We find that the strength differences of these backbone HBs mainly arise from their relationships with water molecules which are controlled by arranging the surrounding residue sidechains. The arrangement of the residues in the C-terminal part of β10 results in the existence of the water-attack channels around the backbone HBs in this region. Along these channels the water molecules can directly attack the backbone HBs and make these HBs relatively weak. In contrast, the backbone HB at the N-terminus of β10 is protected by the surrounding hydrophobic and hydrophilic residues which cooperate positively with the central backbone HB and make this HB highly strong. The intimate relationship between the effective strength of protein backbone HB and water revealed here should be considered when performing mechanical analysis for protein conformational changes.     

自支撑聚酰亚胺/锆膜的制备及性能改善

 采用直流磁控溅射法制备自支撑锆(Zr)膜,采用二步法制备聚酰亚胺(PI)膜,在Zr膜表面沉积PI膜得到自支撑PI/Zr复合膜。均苯四甲酸酐(PMDA)和二甲基二苯醚(ODA)在二甲基乙酰胺(DMAC)中反应得到聚酰胺酸(PAA),然后PAA高温亚胺化得到PI;PI成膜时采用提拉法成膜。经国家同步辐射实验室计量线站测定,实际测量结果与理论分析一致,PI膜的引入虽然会导致自支撑薄膜透过率有所下降,但在类镍-银软X射线13.9 nm波段PI(200 nm)/Zr(300 nm)和PI(200 nm)/Zr(400 nm)自支撑薄膜的透过率仍然分别达到14.9%和7.5%。     

地震检波器弹性元件的强度计算和实验研究

本文分析研究了石油勘探用地震检波器弹性元件的断裂原因,对其在静载情况下的应力分布进行了有限元分析和光弹性实验研究,并对弹性元件做了改进。实验表明,改进后弹性元件的工作寿命较改进前有大幅度提高.     

液晶的历史

 液晶,是一种在一定温度范围内呈现不同于气态、液态,又不同于固态的特殊状态的物质。它既具有晶体所特有的双折射性,又具有液体的流动性。液晶最使人感兴趣的是:同一种液晶材料,在不同温度下可以处于不同的相,产生变化多端的相变现象。液晶系统分子间的作用力非常微弱,它的结构易受周围的机械应力、电磁场、温度和化学环境等变化的影响,因此在适度地控制周围的环境变化之下,液晶可以透光或反射光。由于只需很小的电场控制,因此液晶非常适合作为显示材料。从成分和呈现液晶相的物理条件来看,液晶可以分为热致液晶和溶致液晶两大类。热致液晶是指单一成分的纯化合物或均匀混合物在温度变化下出现的液晶相。