An Instrumental Correction for the Determination of Mercury in Biological and Sediment Samples Using Cold Vapor Atomic Absorption Spectrophotometry

Low recovery rate and inconsistent measurements were found in the determination of mercury by method of cold vapor atomic absorption spectrophotometry using the hydride formation system (Hitachi HFS-2, Hitachi Ltd., Tokyo). To overcome this problem of insufficient reaction time we developed a simple T-joint device attaching to the commercial HFS-2 system for the determination of mercury in various biological tissues and sediment samples. The T-joint device was designed to combine sample and reductant injection which increased the reaction time of the sample allowing a complete formation of mercury vapor and speeding up the analysis process in comparison to the traditional cold vapor atomic absorption spectrometric method. Recoveries of mercury were in the range 95% - 100%. The corrected procedure gave precise and accurate readings with several certified reference materials: NIES No. 2 from the Japan Environment Agency; IAEA-356 from the International Atomic Energy Association, and DOLT-2, DORM-2, TORT-2, PACS-1 and MESS-2 from the National Research Council of Canada. Simple acid digestion methods were developed based on the sample Hg level and the nature of the sample. The sample detection limits were 0.0125 μg g⁻¹ fresh weight and 0.0625 μg g⁻¹ dry weight for biological samples, and as low as 0.0125 μg g⁻¹ dry weight for sediment samples. These analytical protocols we established met the general requirements in environmental research and monitoring of mercury pollution.     

悬浮体进样/氟化电热蒸发(ETV)/ICP-AES直接测定二氧化钛粉末中痕量钇

以聚四氟乙烯(PTFE)悬浮体为氟化剂,悬浮体制样/氟化辅助电热蒸发(ETV)/ICP-AES直接测定TiO₂陶瓷粉末中痕量杂质钇;考察了影响基体和待测元素的蒸发过程的各种因素;对比研究了待测元素和基体的氟化蒸发行为;实现了基体和待测元素的预分离,显着降低了基体效应。本法的检出限为0.26μg/L,相对偏差为3.8%(n=5,c=0.5mg/L).     

Truncation Error on Wavelet Sampling Expansions

We estimate the truncation error of sampling expansions on translationinvariant spaces, generated by integer translations of a single functionand on wavelet subspaces of L ₂(R). As a byproduct of themain result, we get the classical Jagerman's bound for Shannon's samplingexpansions. We also examine this error on certain wavelet sampling expansions.     

西藏雅鲁藏布江彭措林吊桥静动载试验

自从重庆綦江彩虹桥跨塌以来,人们对桥梁结构的工程质量越来越重视,桥梁建设单位纷纷提出进行静动载试验的要求。近来,我们进行了一些这方面的工作,本文主要介绍一座典型桥梁结构的静动载试验情况及结果,其目的是为桥梁的竣工验收提供依据。     

Rheological Properties of Nanosized AlN Powder Suspensions for Advanced Ceramics

The rheological properties (flow curves and viscoelastic behavior) of injection molding suspensions of a plasma-processed AlN nanosized powder (nanopowder) in paraffin are investigated over a broad range of shear rates (0.07–1350 s^–1). Two viscosity plateaux are observed on the flow curves and two values of the yield stress are obtained. The lower value of the strain amplitude (0.66%), exceeding the linearity limit of periodic shear, is restricted by the rheometer resolution. The ultrasound treatment and shear deformation of suspensions affect the structure of particle packing, which is responsible for the dependence of their rheological properties on the prehistory of mechanical actions.     

Scenarios for Multistage Stochastic Programs

A major issue in any application of multistage stochastic programming is the representation of the underlying random data process. We discuss the case when enough data paths can be generated according to an accepted parametric or nonparametric stochastic model. No assumptions on convexity with respect to the random parameters are required. We emphasize the notion of representative scenarios (or a representative scenario tree) relative to the problem being modeled.     

Accelerated Nuclear Magnetic Resonance Spectroscopy with Deep Learning

Nuclear magnetic resonance (NMR) spectroscopy serves as an indispensable tool in chemistry and biology but often suffers from long experimental times. We present a proof-of-concept of the application of deep learning and neural networks for high-quality, reliable, and very fast NMR spectra reconstruction from limited experimental data. We show that the neural network training can be achieved using solely synthetic NMR signals, which lifts the prohibiting demand for a large volume of realistic training data usually required for a deep learning approach.     

Untersuchungen der hepatischen Entgiftungskapazität klinisch gesunder Kindergartenkinder mit 15N-in-vivo-Tests

Es wird ein Vorschlag zur Systematik autoradiographischer Untersuchungen, verbunden mit dem Aufbau einer Datei Autoradiographie vorgestellt. Er sollte bei der Einschätzung von Möglichkeiten, Voraussetzungen und Leistungsgrenzen autoradiographischer Verfahren sowie bei der Planung autoradiographischer Versuche Hilfestellung geben und anregen, Ergebnisse autoradiographischer Untersuchungen nach einheitlichen Gesichtspunkten aufzubereiten und so einer Nachnutzung leichter zuzuführen. Die dargelegte Systematik wird kurz am Beispiel einer autoradiographischen Untersuchung zur Natriumdiffusion in Quarzglas erhlätert.     

A Routine Method for the Quantitative Determination of Polycyclic Aromatic Hydrocarbons (PAHs) in Urban Air

Abstract

We have developed a method for the quantitative determination of polycyclic aromatic hydrocarbons (PAHs) present in urban air, which can be performed rather quickly, and which uses a minimal amount of solvents.

Air samples were collected using a home-made low-volume air sampler equipped with glass fibre filter and polyurethane foam plugs. After Soxhlet extraction a liquid-liquid partition was carried out to isolate the PAH fraction. This liquid-liquid partition was performed in micro-scale, enabling us to use small quantities of the solvents and to separate the solution layers very rapidly using a centrifuge. Sample clean-up was accomplished on a high performance liquid chromatograph equipped with two normal phase silica columns. The losses of all investigated PAHs occurring during the various steps of sample clean-up have been determined. The qualitative and quantitative determination of the PAHs was carried out by capillary gas chromatography; the results were confirmed by GC/MS measurements.

The analytical procedure described was applied over a period of one year to measure the concentrations of 21 PAHs in the city of Vienna at a site with high traffic density. The concentrations of the four more volatile PAHs were determined on a semi-quantitative basis. The ratio of two selected PAHs was used to estimate the respective contribution of traffic and domestic heating to the total PAH level at the sampling site.