化学需氧量在线自动监测仪示值误差的检定

介绍化学需氧量(COD)在线自动监测仪示值误差的检定方法及注意事项。选取基准试剂邻苯二甲酸氢钾,依次配制零点溶液和质量浓度分别为50,150,500 mg/L的COD标准物质溶液,用于检定COD maxⅡ型在线监测仪的示值误差。直接配制溶液为100 mg/L的COD标准溶液,与相同浓度的标准物质溶液GBW(E)082219进行比较,结果符合检定规程JJG 1012–2006的要求。检定结果表明:以重铬酸钾为氧化剂时,邻苯二甲酸氢钾的COD氧化值呈线性关系,可直接配制100 mg/L的COD标准溶液;检定COD maxⅡ型在线监测仪,每次需要的标准溶液体积为100 m L,综合考虑,进行示值误差检定时,每种浓度至少配制500 m L。作为还原性标准物质用于检定仪器示值误差,邻苯二甲酸氢钾可能无法准确反映水体中有机物的真实还原情况,具有一定的局限性。     

取样量对润滑油中微量水分检测结果的影响

研究取样量对润滑油中微量水分测定结果的影响。基于卡尔·费休滴定法,在选定的测量条件下,用发生电极为有隔膜的自动库仑水分仪对基础油、有机热载体油、压缩机油、膨胀机油等新油和发动机油、汽轮机油、涡轮机油、压缩机油、齿轮油、液压油、导热油、船用油、电器绝缘油、风动工具油、金属加工油等在用油在0.1~2.0 g内各取9组不同质量的样品进行测定,得到了润滑油中微量水分准确测定所需的取样量。实验结果表明,新油取样量大于1.0 g,在用油取样量在1.0~1.5 g范围内,可以准确测定润滑油中微量水分含量。测定结果的相对标准偏差为0.83%~3.51%(n=10),样品加标回收率为95.0%~103.0%。在选择的取样量下,该方法具有良好的精密度、准确度,可连续测定多个样品,满足测定需求。     

Computer-assisted identification of multitrace electrophoretic patterns in differential display experiments

Modern multicapillary devices allow researchers to address increasingly complex biological questions involving comparisons of gene expression patterns across electrophoretic samples under various experimental conditions. As labor-intensive visual evaluation of the electrophoretic results is often the bottleneck of large-scale differential display (DD) studies, one way to further streamline this process is to focus only on a highly compressed list of the most potential patterns that are likely to provide reliable findings. To enable the identification of such candidate patterns, we present a computer-assisted method for objective ranking of multitrace peak patterns in DD experiments. The fundamental component of the multitrace pattern ranking method (MRANK) is the multiple alignment algorithm that allows for discovery of patterns involving sets of peak complexes from various electrophoretic samples. A score value is attached to each detected pattern which characterizes how accurately the pattern resembles the desired pattern query, freely defined by the researcher. The ranked pattern list produced by MRANK is validated against visual evaluation in terms of detecting and ranking a group of relevant patterns in a DD analysis of T-helper cell differentiation. We demonstrate high enrichment of the desired patterns on top of the score-ranked list (e.g., 90% of the visually selected patterns are discovered by looking through the first 3% of patterns in the ranked list of all patterns). The results suggest that a substantial amount of manual labor can be saved without compromising the accuracy of the findings by prioritizing the patterns according to MRANK output in the visual confirmation phase.     

基于多激光传感器装配的自由曲面法线找正方法研究

在国产化、技术自主化的大型飞机项目上,对孔位精度的标准正逐步升高,钻头的垂直度又是这一标准中最受关注的条件。机器人自动钻铆系统工作时,所产生的装配误差、磕碰、偏移等状况,不仅降低了制造及检测的准确度,还影响了整个结构件的疲劳性能。针对这一问题,提出了基于多激光传感器装配的自适应自由曲面法线检测技术,搭建了以该方法进行姿态找正的数学模型,并研究了检测装置的标定方法及流程。同时,着重讨论了在自适应方法检测时,利用电子经纬仪等装置进行误差补偿的相关技术。该方法的验证实验结果显示,多组实验数据均达到了法向精度<±0.5°的关键技术指标要求,找正后的法线平均偏差值为0.0667°。该方法能有效补偿在制孔工作中所产生的相关误差,进一步提高机器人的定位精度及法线方向检测精度。     

合肥光源基于束流准直系统的控制软件设计

束流位置监测器(BPM)和与其相邻的四极铁之间的电偏移对于电子储存环轨道校正十分重 要。改变四极铁的强度,并通过测量轨道变化就能够计算出该四极铁的磁中心相对于相邻的BPM的电中心 之间的偏差。基于NSRL储存环的BBA硬件系统和EPICS控制系统,采用Labview平台开发出了BBA测量 的软件控制程序。由计算机控制四极铁的强度,连续测量后拟合得到四极铁的磁中心与相邻BPM的相对偏 差,测量精度可以达到100μm。     

15N and 31P solid-state NMR study of transmembrane domain alignment of M2 protein of influenza A virus in hydrated cylindrical lipid bilayers confined to anodic aluminum oxide nanopores

This communication reports the first example of a high resolution solid-state 15N 2D PISEMA NMR spectrum of a transmembrane peptide aligned using hydrated cylindrical lipid bilayers formed inside nanoporous anodic aluminum oxide (AAO) substrates. The transmembrane domain SSDPLVVA(A-15N)SIIGILHLILWILDRL of M2 protein from influenza A virus was reconstituted in hydrated 1,2-dimyristoyl-sn-glycero-3-phosphatidylcholine bilayers that were macroscopically aligned by a conventional micro slide glass support or by the AAO nanoporous substrate. 15N and 31P NMR spectra demonstrate that both the phospholipids and the protein transmembrane domain are uniformly aligned in the nanopores. Importantly, nanoporous AAO substrates may offer several advantages for membrane protein alignment in solid-state NMR studies compared to conventional methods. Specifically, higher thermal conductivity of aluminum oxide is expected to suppress thermal gradients associated with inhomogeneous radio frequency heating. Another important advantage of the nanoporous AAO substrate is its excellent accessibility to the bilayer surface for exposure to solute molecules. Such high accessibility achieved through the substrate nanochannel network could facilitate a wide range of structure-function studies of membrane proteins by solid-state NMR.     

Destabilizing effect of a surface electric field generated by ionic adsorption on the molecular orientation of nematic liquid crystals

The destabilizing effect of a surface electric field, produced by selective ionic adsorption, on the molecular orientation of a nematic-liquid-crystal sample is analyzed for a cell in the shape of a slab of thickness d. The electric-field distribution considered in the analysis is the one obtained in the limit in which essentially all the positive ions are adsorbed. Because of the coupling of this surface field with the nematic director, the surface anchoring energy depends on the thickness of the sample as well as on the adsorption energy characterizing the surfaces. A relation connecting the threshold field for the destabilization of the homeotropic pattern to the adsorption energy and to the thickness of the sample is established in closed form, after solving a set of two coupled non-linear equations determining the electric-field distribution across the sample. It is shown that the values of surface electric field generated by adsorbed ions that can lead to a destabilization of the homeotropic alignment can be attained by real samples.     

一种新的基于多重液相色谱-质谱实验肽信号峰形相似性的校准算法

提出了一种基于多次重复液相色谱-质谱(LC-MS)实验,结合肽信号时间差校准的峰形相似性统计学习模型,解决了重复实验数据肽链校准匹配准确性与覆盖率低的问题。采用统计学习的方法,首先建立时间差统计模型,结果表明仅靠时间特征无法完全消除校准误差。因此,除了时间特征,引入了峰形相似性特征,即认为同一种肽链在多次重复实验谱图中会产生相似的LC峰形。通过选取训练数据集,提出了一种新的基于LC峰形相似性的肽信号校准算法,并通过测试序列完成模型测试。结果表明,改进算法的准确率达98. 3%;将该数学模型应用于校准匹配两个实验数据的所有LC-MS/MS肽链,其覆盖率达91. 0%。峰形相似性特征结合时间特征可以提升多次重复LC-MS实验中相关肽链信号的匹配校准的准确性与覆盖率。