Bestimmung von Fremdfett in Kakaoerzeugnissen

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Bestimmung von Fremdfett in Kakaoerzeugnissen

Ohne Zusammenfassung     

青蒿素研究进展

青蒿素是目前治疗疟疾的特效药。本文对自青蒿素发现以来的最新研究进展进行了比较详尽的综述。内容包括: 青蒿素的发现及历史, 青蒿素的来源, 青蒿素的全合成,青蒿素的生物合成, 青蒿素衍生物以及植物组织培养生产青蒿素。     

国内光催化研究进展简述

分1975~1985, 1985~1995和1995~2012三个时期简要介绍了国内光催化研究进展, 主要侧重于光催化材料及其改性、应用和反应机理方面的研究进展, 并指出了当前光催化领域存在的一些重要问题和未来的发展趋势, 涉及到光解水、CO₂还原、环境净化和选择性有机合成等方面.     

Interpretation of inorganic arsenic metabolism in humans in the light of observations made in vitro and in vivo in the rat

The toxicity of inorganic trivalent arsenic for living organisms is reduced by in vivo methylation of the element. In man, this biotransformation leads to the synthesis of monomethylarsonic (MMA) and dimethylarsinic (DMA) acids, which are efficiently eliminated in urine along with the unchanged form (As_i). In order to document the methylation process in humans, the kinetics of As_i, MMA and DMA elimination were studied in volunteers given a single dose of one of these three arsenicals or repeated doses of As_i. The arsenic methylation efficiency was also assessed in subjects acutely intoxicated with arsenic trioxide (As₂O₃) and in patients with liver diseases. Several observations in humans can be explained by the properties of the enzymic systems involved in the methylation process which we have characterized in vitro and in vivo in rats as follows: (1) production of As_i metabolites is catalyzed by an enzymic system whose activity is highest in liver cytosol; (2) different enzymic activities, using the same methyl group donor (S-adenosylmethionine), lead to the production of mono- and di-methylated derivatives which are excreted in urine as MMA and DMA; (3) dimethylating activity is highly sensitive to inhibition by excess of inorganic arsenic; (4) reduced glutathione concentration in liver moderates the arsenic methylation process through several mechanisms, e.g. stimulation of the first methylation reaction leading to MMA, facilitation of As_i uptake by hepatocytes, stimulation of the biliary excretion of the element, reduction of pentavalent forms before methylation, and protection of a reducing environment in the cells necessary to maintain the activity of the enzymic systems.     

Use of NAA in marine environment and in archaeology in Greece

Neutron activation analysis (NAA) is a very sensitive and accurate multielement analytical method that is widely applied to the investigation of environmental and archaeological problems. The first part of this paper is a review of pollution studies of toxic trace elements in sediments, seawater and marine organisms of Saronikos Gulf, Greece by NAA. The second part of this paper is a review of provenance studies based on minor and trace element research in ancient ceramics, obsidian, flint, limestone, marble and lead by Instrumental NAA, performed at the NCSR Demokritos.     

Electrolysis in nanochannels for in situ reagent generation in confined geometries

In situ generation of reactive species within confined geometries, such as nanopores or nanochannels is of significant interest in overcoming mass transport limitations in chemical reactivity. Solvent electrolysis is a simple process that can readily be coupled to nanochannels for the electrochemical generation of reactive species, such as H(2). Here the production of hydrogen-rich liquid volumes within nanofluidic structures, without bubble nucleation or nanochannel occlusion, is explored both experimentally and by modeling. Devices comprised of multiple horizontal nanochannels intersecting planar working and quasi-reference electrodes were constructed and used to study the effects of confinement and reduced working volume on the electrochemical reduction of H(2)O to H(2) and OH(-). H(2) production in the nanochannel-embedded electrode reactor output was monitored by fluorescence emission of fluorescein, which exhibits a pH-dependent emission intensity. Initially, the fluorescein solution was buffered to pH 6.0 prior to stepping the potential cathodic of E(0)' for the generation of OH(-) and H(2). Because the electrochemical products are obtained in a 2:1 stoichiometry, local measurements of pH during and after the cathodic potential steps can be converted into H(2) production rates. Independent experimental estimates of the local H(2) concentration were then obtained from the spatiotemporal fluorescence behavior and current measurements, and these were compared with finite element simulations accounting for electrolysis and subsequent convection and diffusion within the confined geometry. Local dissolved H(2) concentrations were correlated to partial pressures through Henry's Law and values as large as 8.3 atm were obtained at the most negative potential steps. The downstream availability of electrolytically produced H(2) in nanochannels is evaluated in terms of its possible use as a downstream reducing reagent. The results obtained here indicate that H(2) can easily reach saturation concentrations at modest overpotentials.     

Verunreinigungen in Tetrachlorkohlenstoff und in Benzol

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钙与人体及临床

钙是宏量元素，是人体中含量较高的元素之一，体内99％的钙构成骨骼和牙齿以及维持骨骼结构，1％的钙调节人体重要生理功能。钙的含量过高或过低都与许多疾病有关，只有保持一种平衡状态，才能使机体处于正常环境。     

美国化学教育中的科学道德教育

介绍了近年来美国科学界维护科学道德的行动及美国某些大学化学系开设科学道德教育课程的情况     

Lipoproteine in Humanserum und in Ultrazentrifugaten

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Trends in education in analytical chemistry

Summary At the session of the WPAC of Fechem on education in analytical chemistry it was concluded that it is now essential to include chemometrics and basic knowledge of computers in all courses on analytical chemistry.

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Tendenzen in der analytisch-chemischen Ausbildung

Zusammenfassung Bei einer Tagung der WPAC über die Lehre auf dem Gebiet der analytischen Chemie wurde bei der Betrachtung neuer Aspekte festgestellt, daß vor allem Chemometrie und Grundkenntnisse in Computertechnik in die Ausbildung aufgenommen werden sollten.

     

Gemini表面活性剂合成进展

系统总结了近百种Gemini表面活性剂的合成路线和方法,并且按照其结构特点分门别类地进行比较和归纳,对今后Gemini表面活性剂的合成发展方向提出了一些看法,这对促进此类新颖表面活性剂的工业化进程将具有指导意义。     

Recent Advances in in situ multi-spectroelectrochemistry

To consider the past, present and future of in situ spectroelectrochemistry, a review on the recent state of modern spectroelectrochemistry and trends in the development of spectroelectrochemcial techniques is presented for the combined application of different in situ spectroelectrochemcial methods like ESR spectroelectrochemistry, NMR spectroelectrochemistry, Raman spectroelectrochemistry or IR spectroelectrochemistry to electrode systems. Starting with a discussion of the first steps in spectroelectrochemistry in the past, the main part of this review is focused on the advantages of the combined application of spectroelectrochemical techniques in the analysis of electrode reactions. The spectroelectrochemical methods are demonstrated to be successful in electrode reactions both for solid structures like polymers or carbon nanotubes and for molecular structures like fullerenes and oligothiophenes. The final outlook is attributed to future developments in spectroelectrochemistry.     

Styrol in Polystyrol und in Styrol-Methylmethacrylat-Copolymeren

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Recent Advances in Analytical Methodology for in vivo Electrochemistry in Mammals

Electrochemistry is one of the most advanced techniques for monitoring neurochemical activities in the living brain because electrochemical approaches bear the advantageous features of high spatial and temporal resolutions, which facilitate its tremendous potential in investigating the highly spatially heterogeneous brain system and the fast dynamics of neurochemical activities. On the other hand, since brain is the most complicated organ in the sense of its numerous kinds of neurochemical species, high selectivity is always required for any analytical methods that approach the brain. In this review, we will discuss various electrochemical methodologies to achieve selective detection of neurochemicals in mammalian brain and the strategies developed mainly by our group towards selective monitoring of both electrochemically active and inactive neurochemicals. At the end, we will discuss possible solutions towards brain mapping of neurochemical species and combination of neurochemical detection strategy with electrophysiology as the direction of future development of electroanalysis in living brain.