Sphere mass center determination by velocity modulation

This paper presents a new technique, called velocity modulation, for measuring the mass center location of a sphere, improving upon the accuracy of previous methods by at least a factor of 4. The sphere is rolled down a set of parallel rails. The offset of the sphere’s mass center with respect to its geometric center modulates the sphere’s velocity at the rolling frequency, which is detected by a series of differential optical shadow sensors. The measured times that the sphere crosses the sensors is compared with a simplified mechanics model in order to recover the sphere’s mass center location. The precision of the technique is demonstrated by the repeatability of independent measurements in one plane of a 50.8 mm (2 in.) stainless steel gage sphere. The best standard deviation achieved is 145 nm (95% confidence interval = 227 nm).     

Applications of mass spectrometry to the study of siRNA

RNA interference (RNAi) has quickly become a well‐established laboratory tool for regulating gene expression and is currently being explored for its therapeutic potential. The design and use of double‐stranded RNA oligonucleotides as therapeutics to trigger the RNAi mechanism and a greater effort to understand the RNAi pathway itself is driving the development of analytical techniques that can characterize these oligonucleotides. Electrospray (ESI) and MALDI have been used routinely to analyze oligonucleotides and their ability to provide mass and sequence information has made them ideal for this application. Reviewed here is the work done to date on the use of ESI and MALDI for the study of RNAi oligonucleotides as well as the strategies and issues associated with siRNA analysis by mass spectrometry. While there is not a large body of literature on the specific application of mass spectrometry to RNAi, the work done in this area is a good demonstration of the range of experiments that can be conducted and the value that ESI and MALDI can provide to the RNAi field. © 2010 Wiley Periodicals, Inc., Mass Spec Rev 30:979–998, 2011     

Consideration of the BDNF gene in relation to two phenotypes: Hoarding and obesity.

The gene coding for the brain derived neurotrophic factor (BDNF) has emerged as an interesting candidate for multiple brain and brain disorder-related phenomena. The primary aim of the present investigation was to consider the relationship between the BDNF Val66Met variant and two phenotypes: compulsive hoarding as a symptom dimension of obsessive–compulsive disorder (OCD), and body mass index (BMI). We examined the BDNF gene in a large (N = 301) clinical sample of probands with OCD. Participants were classified as hoarding or nonhoarding using a strict, multimeasure grouping approach. Results revealed that the Val/Val genotype was linked with hoarding classification and more severe hoarding behaviors, as well as greater BMI levels. Hoarding status was also associated with greater BMI scores, with individuals in the hoarding group being far more likely to be classified as obese compared with the nonhoarding group. Our findings may provide a distinct avenue through which hoarding and BMI could be linked. These findings are suggestive of a complex gene, body weight, and psychopathology relationship wherein a primitive, survival “thrifty gene” strategy may be conserved and represented in a subgroup of humans manifesting severe hoarding symptoms. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Investigating the chlorination of acidic pharmaceuticals and by-product formation aided by an experimental design methodology

The degradation of seven acidic drugs and two metabolites during chlorination was investigated by liquid chromatography-mass spectrometry (LC-MS). A triple-quadrupole (QqQ) system was used to follow the time course of the pharmaceuticals and by-products, while a quadrupole time-of-flight (Q-TOF) system was also used for the identification of the by-products. Under strong chlorination conditions (10 mg/L Cl₂, 24 h), only four of the target compounds were significantly degraded: salicylic acid, naproxen, diclofenac and indomethacine. The degradation kinetics of these four compounds were investigated at different concentrations of chlorine, bromide and pH by means of a Box-Behnken experimental design. Depending on these factors, measured pseudo-first order half-lives were in the ranges: 23-573 h for salicylic acid, 13-446 min for naproxen, 5-328 min for diclofenac and 0.4-13.4 min for indomethacine. Also, it was observed that chlorine concentration was the overall most significant factor, followed by the bromide concentration (except for indomethacine), resulting in increased degradation kinetics as they are increased. The degradation path of salicylic acid, naproxen and diclofenac consisted of aromatic substitution of one or two hydrogens by chlorine and/or bromide. Moreover, for diclofenac, two other by-products corresponding to a decarboxylation/hydroxylation pathway from the monohalogenated products were also identified. On the other hand, indomethacine degradation did not lead to halogenation products but to oxidation ones. The investigation of these by-products in real samples by LC-MS/MS (QqQ) showed that the halogenated derivates of salicylic acid occurred in all the drinking water and wastewater samples analysed.     

USB Mass Storage类设备的设计与实现

针对嵌入式系统与PC主机大量数据传输的需要,使用SD卡做为存储介质设计实现USB Mass Storage类设备。主机和存储设备之间的通讯严格按照USB20协议和USB Mass Storage类存储协议,该类存储设备构架于USB2．0协议之上,将存储命令嵌于USB协议之中。采用MAX3421作为USB外设控制器,MCF52233作为主控制器,通过SPI接口实现两者的通讯。试验结果表明,当MCF52233主频为60MHZ时,存储速度可以达到1．87Mbyte／s,满足了设备与主机数据交换速度的要求。     

红外光谱法对聚烯烃中抗氧剂1010的定性、定量研究

本文介绍了用红外光谱法定性、定量测定聚乙烯、聚丙烯中抗氧剂1010的情况。分析了抗氧剂1010和PE、PP粉料的FTIR图,确定了抗氧剂1010在聚烯烃中的特征吸收峰(1746cm-1),详细分析了用抗氧剂1010分别与定量的PE、PP所制样品对所测谱图和所制曲线的影响。根据抗氧剂1010的标准曲线可知,抗氧剂1010的含量与其特征峰的吸收强度呈良好的线性关系,相关系数达0．98以上,回收率最低为90．0％。该研究可以对聚乙烯、聚丙烯中的抗氧剂1010进行定性及定量,对分析抗氧剂在聚烯烃中的影响和改性有着重要的实际意义。     

基于跨模态空间匹配的多模态肺部肿块分割网络

现有多模态分割方法通常先对图像进行配准,再对配准后的图像进行分割。对于成像特点差异较大的不同模态,两阶段的结构匹配与分割算法下的分割精度较低。针对该问题,该文提出一种基于跨模态空间匹配的多模态肺部肿块分割网络(MMSASegNet),其具有模型复杂度低和分割精度高的特点。该模型采用双路残差U型分割网络作为骨干分割网络,以充分提取不同模态输入特征,利用可学习的空间变换网络对其输出的多模态分割掩膜进行空间结构匹配;为实现空间匹配后的多模态特征图融合,形变掩膜和参考掩膜分别与各自模态相同分辨率的特征图进行矩阵相乘,并经特征融合模块,最终实现多模态肺部肿块分割。为提高端到端多模态分割网络的分割性能,采用深度监督学习策略,联合损失函数约束肿块分割、肿块空间匹配和特征融合模块,同时采用多阶段训练以提高不同功能模块的训练效率。实验数据采用T2权重(T2W)磁共振图像和扩散权重磁共振图像(DWI)肺部肿块分割数据集,该方法与其他多模态分割网络相比,DSC (Dice Similarity Coefficient)和HD (Hausdorff Distance)等评价指标均显著提高。     

核阀密封面激光熔覆层稀释率控制研究

采用5KW横流CO2激光器对1Cr18Ni9Ti核阀密封面进行了Co基合金激光熔覆处理，测定了激光熔覆层的受基体成分稀释的稀释率，并将其微观组织形貌、稀释率与等离子喷焊处理的同种试件进行了对比分析，结果表明：在保证与基体良好冶金结构的条件下，激光熔覆层的稀释率远小于等离子喷焊层，激光熔覆层还具有组织细密、晶粒度高和硬度高的特点，进而分析探讨了对激光熔覆层的稀释率控制。     

苯和甲苯差分吸收光谱方法的实验室测量研究

本文介绍了差分光学吸收光谱法(DOAS)测量大气污染气体浓度的基本原理。DOAS方法就是利用氙灯发出的紫外—可见光，经望远镜准直后再经过一段距离的传输，由望远镜来接收．在传输中，由于各种不同的分子在不同的波段对光有不同的吸收特征，使光谱具有了污染物的特征，再通过与光源发出的光进行比较，反演这些气体在大气中浓度．我们将DOAS方法应用在监测有机物上，在分析光谱的过程中，应用多项式拟合和最小二乘法，从而精确地从测量光谱中来反演出大气中污染气体的浓度．文中用DOAS方法测量了苯和甲苯的样品，并分析了结果，结果和理论吻合．可为环境中有机污染物监测提供可靠的方法。     

Optical properties of CdSe quantum dots grown on ZnSe and ZnBeSe by molecular beam epitaxy

We report detailed studies of the optical properties of CdSe quantum dots (QDs) grown on ZnSe and ZnBeSe by molecular-beam epitaxy (MBE). We performed steady-state and time-resolved photoluminescence (PL) measurements and observe that nonradiative processes dominate at room temperature (RT) in the CdSe/ZnBeSe QDs structures, though these nonradiative processes do not dominate in the CdSe/ZnSe QDs structures up to RT. We performed secondary ion-mass spectrometry (SIMS) measurement and propose that the oxygen incorporation in the ZnBeSe layers (possibly caused by the reactivity of Be) may contribute to the dominant nonradiative processes at high temperatures in the QDs grown on ZnBeSe.