The electron impact fragmentation of 3- and 4-styrylpyridazine

The electron impact mass spectrometric fragmentation of trans-3- and trans-4-styrylpyridazine is reported in detail, including a comparison with other aza-stilbenes. With regard to a distinction between the two isomeric styrylpyridazines, the intensity ratio of the M⁺ and [M-1]⁺ ions, the general degree of fragmentation and the elimination pathways of nitrogen proved to be most characteristic.     

Cyclisierungen unter beteiligung von fluoridionen. 2. Mitteil. [1], [2]. 4.5-perfluor-1.3-dioxolane

4.5-Perfluoro-1.3-dioxolanes $\text{2}$ are available by reaction of 2(α-chloroalkoxy)perfluoro-carbonyl halides $\text{3}$ or -ketone $\text{9}$ with fluoride ions. A mechanism for the intramolecular ring- closure-reaction is proposed. Hydrogen atoms at C-2 in $\text{2}$ can be exchanged photochemically by chlorine. Starting from the 2-monochloro-derivatives $\text{16}$ the 2-monofluoro-4.5-perfluoro- 1.3-dioxolanes $\text{18}$ are formed by reaction with triethylamine- hydrofluoride.     

Double indication in catalytic-kinetic analysis: simultaneous photometric and thermometric indication of the iodine-azide reaction in closed and flow systems

The iodine—azide reaction catalyzed by sulphur-containing compounds is followed simultaneously by optical and thermometric measurements in closed and flowing systems. In the closed system, thiosulphate can be determined in the range 32.4–324 μg ml^-1, by observing the turbidity caused by the nitrogen formed during the reaction and the temperature changes. With the flow apparatus, thiosulphate can be determined in the range 112–1120 μg ml^-1 by continuously mixing the sample and reagent solutions. H₂S in nitrogen 5–100 ppm) is measured by sweeping the gas into the reaction Cuvette. In a third flow procedure, H₂S is liberated continuously from sodium sulphide solutions (0.1–10 μg S^2- ml^-1) by ascorbic acid, and swept to the measuring cuvette with nitrogen.     

Immunosensor for estrone with an equal limit of detection as common analytical methods

Immunoanalytical methods at a very low limit of detection (LOD) and a low limit of quantification (LOQ) are becoming more and more important for environmental analysis and especially for monitoring drinking water quality. Biosensors have suitable characteristics such as efficiency in allowing very fast, sensitive, and cost-effective detection. Here we describe a fully automated immunoassay for estrone with a LOD below 0.20 ng L^–1 and a LOQ below 1.40 ng L^–1. In contrast to common analytical methods such as GC-MS or HPLC-MS, the biosensor used requires no sample pre-treatment and pre-concentration. The basis of our sensitive assay is the antibody with a high affinity constant towards estrone. The very low amount of antibody per sample results in low validation parameters (LOD, LOQ, and IC50), but this assay for estrone represents the current device-related limitation of the River Analyser (RIANA).     

Arsenic biomethylation by the microorganism apiotrichum humicola in the presence of l-methionine-methyl-d3

The microorganism Apiotrichum humicola (previously known as Candida humicola) grown in the presence of either arsenate, arsenite, methylarsonic acid or dimethylarsinic acid, produces arsenic-containing metabolites in the growth medium. When L-methionine-methyl-d₃ is added to the cultures, the CD₃ label is incorporated intact into the metabolites to a considerable extent to form deuterated dimethylarsenic and trimethyl-arsenic species, indicating that S-adenosylmethionine, or some related sulphonium compound, is involved in the biological methylation. Conclusive evidence of CD₃ incorporation in the arsenicals found in the growth medium was provided by using a specially developed hydride generation-gas chromatography-mass spectrometry system (HG–GC–MS).     

热耦合型二级高频脉冲管制冷机实验研究

降低制冷温度至4 K温区是高频脉冲管制冷机的最新发展要求。本文介绍了一套热耦合型二级高频脉冲管制冷机的性能特性,它可以达到低于15 K以下的最低温度,是目前报道的高频二级脉冲管制冷机能获得的最低温度．通过对制冷机一级预冷、二级输入功率、二级冷量、室温条件等影响的分析,从实验角度揭示了该二级制冷系统的复杂影响,为进一步的深入分析和改进提供了基础。     

Singularity in the thermal boundary resistance between superfluid (4)He and a solid surface

We report new measurements in four cells of the thermal boundary resistance R between copper and (4)He below but near the superfluid-transition temperature T(lambda). For 10(-7)< or =t identical to 1-T/T(lambda))< or =10(-4) fits of R = R(0)t(-x(b))+R(B) to the data yielded x(b) approximately equal to 0.18, whereas a fit to theoretical values based on the renormalization-group theory yielded x(b) = 0.23. Alternatively, a good fit of the theory to the data could be obtained if the amplitude of the prediction was reduced by a factor close to 2. The results raise the question whether the boundary conditions used in the theory should be modified.     

Absolutbestimmung der austrittsarbeit von palladium mit einem röntgenphotoelektronenspektrometer

Based on the work of Ascarelli and Missoni⁴ and Evans¹ a method for absolute measurements of work-functions of electrically conductive samples is developed which is applicable to instruments without retarding field and with a spherical analyzer. The calibration of the instrument, as well as the determination of the onset of the secondary electron spectrum and the Fermi-level, are discussed. For a polycrystalline palladium platelet with an argon-ion cleaned surface, a work-function ofW′_Pd = 4.5(4) ± 0.2(0) eV has been obtained, which agrees with the literature value³ of 4.64 eV within the range of accuracy.