Application of an ePix100 detector for coherent scattering using a hard X‐ray free‐electron laser

A prototype ePix100 detector was used in small‐angle scattering geometry to capture speckle patterns from a static sample using the Linac Coherent Light Source (LCLS) hard X‐ray free‐electron laser at 8.34 keV. The average number of detected photons per pixel per pulse was varied over three orders of magnitude from about 23 down to 0.01 to test the detector performance. At high average photon count rates, the speckle contrast was evaluated by analyzing the probability distribution of the pixel counts at a constant scattering vector for single frames. For very low average photon counts of less than 0.2 per pixel, the `droplet algorithm' was first applied to the patterns for correcting the effect of charge sharing, and then the pixel count statistics of multiple frames were analyzed collectively to extract the speckle contrast. Results obtained using both methods agree within the uncertainty intervals, providing strong experimental evidence for the validity of the statistical analysis. More importantly it confirms the suitability of the ePix100 detector for X‐ray coherent scattering experiments, especially at very low count rates with performances surpassing those of previously available LCLS detectors.     

傅里叶变换红外光谱诊断地中海贫血症

为建立简单快速的地中海贫血诊断方法,本研究探讨了以傅里叶变换红外光谱结合水平衰减全反射(FTIR-HATR)技术在地中海贫血诊断中的制样方法及光谱的数据处理方法.在制样预处理中,通过对样品进行稀释并干燥成膜消除水分子对光谱吸收干扰,保持ATR光谱中各波长对样品的穿透深度一致.结果表明,当1652 cm-1吸收度小于1.5时(即透射率T小于4%时),各波峰强度与血红蛋白浓度呈良好的线性关系(r>0.995)及实验重复性(RSD<4%).在数据处理上,改进的相对强度方法用于800～1780 cm-1和2480～3600 cm-1区间的分析.通过与常规的傅里叶去卷积谱及差谱方法相比,本方法可消除样品浓度所带来的影响因素,灵敏地揭示群体数据中组分与结构在不同组间的显著差异,如1638 cm-1处重叠的蛋白二级结构峰,1172 cm-1、1440 cm-1表征脂类物质的吸收峰,1064 cm-1表征磷酸化合物峰位及表征SH的2553 cm-1附近的吸收峰在正常组与地中海贫血组间存在显著差异.从而避免了几个峰位的相对强度所反映的信息不足及选择参比峰的困扰,对揭示整体的差异变化规律有着重要的作用.     

Simultaneous determination of bromide and nitrate in contaminated waters by ion chromatography using amperometry and absorbance detectors

This study describes a new ion chromatography method using a low-capacity anion exchange column with amperometric and absorbance detection for rapid and simultaneous determination of Br⁻ and NO₃⁻ in contaminated waters where one of these ions is present in excess compared to other. The use of two detectors overcomes the problem of baseline separation for Br⁻ and NO₃⁻ for accurate quantification, which was commonly encountered when using a low-capacity anion exchange column and suppressed conductivity detection mode. The method achieved accurate quantification of these two ions without requirement of baseline separation. The accuracy of 2.8% for NO₃⁻ was determined using a quality control sample obtained from UN GEMS/Water PE Study No. 6. The detection limits for Br⁻ and NO₃⁻ were 20 and 6 μg l⁻¹ (25 μl sample), respectively. Linearity of these two ions was over three orders of magnitude with a correlation coefficient >0.998. The influence of potential interfering ions was also studied followed by the determination of Br⁻ and NO₃⁻ in seawater, unsaturated zone water, soil extract and groundwater.     

顶空固相微萃取与气相色谱-火焰热离子检测器联用测定白酒中吡嗪类化合物

应用顶空固相微萃取(HS-SPME)与气相色谱-火焰热离子检测器(GC-FTD)联用技术,建立了快速检测白酒中吡嗪类化合物的方法。本实验对吸附温度、时间及离子强度对萃取效果的影响进行了优化;在优化条件下,吡嗪类化合物在所测范围内具有良好的线性关系(R2>0.99),酒样重复测定的相对标准偏差小于13.6%,检测限小于0.20μg/L,回收率大于80.2%。用该方法测定了茅台酒、郎酒中的吡嗪类化合物。     

高纯气体中痕量水的LiAlH4柱间接法测量

采用氢化铝锂反应柱在一定条件下将气体中的痕量水转化成氢气,利用氧化锆为检测器的气相色谱法测定转化的氢气,从而间接得出高纯气体中痕量水的含量.此方法选择性好,常温下反应快速、完全且稳定,重复性很好.同时,气相色谱法测定氢气干扰因素少、进样量少、样品消耗少、分析快速而准确.     

A Comparison of the Properties of Contactless Conductivity and Diode‐Array Photometric Detectors in Analyses of Low‐Molecular,Biologically Active Substances by Capillary Electrophoresis in Acetic Acid Solutions

The performance of the contactless conductivity (C⁴D) and diode array photometric (DAD) detectors has been compared for CE separations of creatinine, arginine and 3‐methylhistidine in acetic acid background electrolytes. The contactless conductivity detector response has also been modeled. It has been found that the two detectors provide similar responses and can readily be used for dual CE detection. Changes in the acetic acid concentration affect the C⁴D noise less than the DAD noise, but their effect on the C⁴D response to the analytes is greater than with DAD. In general, C⁴D provides better detection results at higher acetic acid concentrations, while DAD is more sensitive and reliable at very low ones. Capillaries with greater internal diameters are preferable for both detectors, provided that the separation efficiency is not adversely affected. Acetic acid is a suitable background electrolyte for CE separations of small, basic organic molecules.     

Polyketide analysis using mass spectrometry,evaporative light scattering,and charged aerosol detector systems

In this study, a mass spectrometer (MS), an evaporative light scattering detector (ELSD), and a charged aerosol detector (CAD) were used to analyze an erythromycin precursor (termed 6-deoxyerythronolide B). The work highlights the capabilities of each detector to analyze a representative polyketide compound that does not possess a natural chromophore, and presents the first comparison to include a charged aerosol system. Each detector was evaluated based upon limit of detection (LOD), dynamic range, and precision in the context of polyketide analysis. Due to its low LOD, wide dynamic range, and ability to provide molecular weight information, the MS was deemed the best detection option for the analysis of low-concentration, poorly identified polyketide compounds. Alternatively, both the CAD and ELSD systems studied showed better precision and accuracy. The ELSD demonstrated the best precision at 3%, but its LOD was limited to concentrations primarily greater than or equal to 1 mg/L. The Corona CAD demonstrated a LOD (0.012 mg/L) and dynamic range comparable to mass spectroscopy and therefore serves as a more cost-efficient alternative for polyketide production schemes with low titers.     

Certification and uncertainty evaluation of the certified reference materials of poly(ethylene glycol) for molecular mass fractions by using supercritical fluid chromatography

Poly(ethylene glycol) (PEG) is a useful water-soluble polymer that has attracted considerable interest in medical and biological science applications as well as in polymer physics. Through the use of a well-calibrated evaporative light-scattering detector coupled with high performance supercritical fluid chromatography, we are able to determine exactly not only the average mass but also all of the molecular mass fractions of PEG samples needed for certified reference materials issued by the National Metrology Institute of Japan. In addition, experimental uncertainty was determined in accordance with the Guide to the expression of uncertainty in measurement (GUM). This reference material can be used to calibrate measuring instruments, to control measurement precision, and to confirm the validity of measurement methods when determining molecular mass distributions and average molecular masses. Especially, it is suitable for calibration against both masses and intensities for matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Figure Comparison between the molecular mass fractions of PEG 1000 before calibration (si) (○) and after calibration (wi) (⧫). The error bar shows the expanded uncertainty of k = 2 of each mass fraction     

水平井筒压降重要性的判别新方法研究

以前许多关于水平井的研究,都没有涉及到井筒压降,通过建立数学模型,提出了简单的解析式,来确定井筒压降对水平井流入的相对影响.用两个无量纲数的简单作用来说明水平井筒中的压降的相对重要性,一个是井筒中流动的雷诺数,另一个是被称为水平井数的新无量纲数.用这一相对关系,优化设计井筒的直径和长度来保证井筒压降不影响产能.     

A full Nesterov–Todd step infeasible-interior-point algorithm for Cartesian P*(κ) horizontal linear complementarity problems over symmetric cones

Euclidean Jordan algebra is a commonly used tool in designing interior-point algorithms for symmetric cone programs. In this paper, we present a full Nesterov–Todd (NT) step infeasible interior-point algorithm for horizontal linear complementarity problems over Cartesian product of symmetric cones. Since the algorithm uses only full-NT feasibility and centring steps, it has the advantage that no line searches are needed. The complexity result obtained here for symmetric cones using NT directions coincides with the best bound obtained for horizontal linear complementarity problems.