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21.
The surface heat transfer coefficient for In, Sn, and Pb films is obtained from the investigation of the hysteresis in the magnetic field-voltage characteristics of these films in He I and He II. This hysteresis is caused by the heating-induced formation of normal hotspots in the resistive state of the films. The experiments demonstrate the influence of the thermal boundary resistance and of the thermal conductivity of the substrate and helium bath on the hysteresis. 相似文献
22.
Summary The paper deals with mixed boundary value problems and transmission problems for elliptic differential and pseudo-differential operators. These problems are considered as elements of an algebra (where is the considered domain, x=, YX a submanifold of codimension 1, where the conditions have a jump, and x is a certain compactification of X/Y), the elements of which are described on a symbolic level. By means of additional conditions (of trace and potential type, with respect to Y) a given mixed problem is extended to an operator, and the Fredholm property of is established under an ellipticity condition, the parametrix is constructed on symbolic level and ind is expressed. In the second part the authors also study classes of special cases, namely differential operators of second and higher order with mixed boundary conditions for dim 2, where explicit index expressions are derived. 相似文献
23.
Elsholz O Frank C Matyschok B Steiner F Wurl O Stachel B Reincke H Schulze M Ebinghaus R Hempel M 《Fresenius' Journal of Analytical Chemistry》2000,366(2):196-199
A monitor is described which provides the on-line determination of mercury in river water at concentrations from 20 to 1000 ng/L. The measurement includes an on-line digestion with Br-/BrO3- and UV-radiation. Each determination is controlled by an on-line addition of 50 and 100 ng/L mercury carried out by pre-dilution of a 500 and 1000 ng/L stock solution using sequential injection analysis (SIA). One cycle of analysis takes 20 min and results in nine signals. A five days stand-alone operation has been performed successfully. Details are also published at web page: "http/www.rzbd.fh-hamburg.de/-prmercol". 相似文献
24.
Marita Hohmann Luise Krauth-Siegel K. Weidenhammer Wolfgang Schulze Manfred L. Ziegler 《无机化学与普通化学杂志》1981,481(10):95-106
Molecular and Crystal Structures of (CO)4W(μ-S-t-C4H9)2W(CO)4, η7-C7H7W(μ-SC6H4CH3)3W(CO)3 and η7-C7H7W(μ-S-n-C4H9)3W(CO)(μ-S-n-C4H9)2W(CO)4 The molecular structures of the two binuclear complexes (CO)4W(μ-S-t-C4H9)2W(CO)4 and η7-C7H7W(μ-SC6H4CH3)3W(CO)3 and of the tungsten cluster η7-C7H7W(μ-S-n-C4H9)3W(CO)-(μ-S-n-C4H9)2W(CO)4 respectively are described. In the nonlinear trinuclear cluster the central tungsten atom is connected to the two tungsten atoms by two and three μ-S-n-C4H9 bridges respectively and additionally by one W? W bond each. The coordination sphere of the W atoms is completed by a η7-C7H7 ring and four CO groups respectively; the central tungsten carries an additional CO group. 相似文献
25.
26.
Summary Using a two-step liquid chromatographic separation on normalphase cartridges, crude extracts of diesel particulate matter
can be separated without time-consuming sample handling into special fractions which mainly contain slightly-polar oxygenated
polycyclic aromatic hydrocarbons (oxy-PAH) and nitrated polycyclic aromatic hydrocarbons (nitro-PAH). Subsequent analysis
was by fused-silica capillary gas chromatography on a SE54 column along with flame-ionisation (GC/FID) and positive-ion electron-impact
mass spectrometric detection (GC/MS) respectively. A number of individual oxy-PAH belonging to four different chemical classes
(ketones, quinones, anhydrides and aldehydes) and several individual nitro-PAH were characterized by their retention times
and mass spectra.
Presented at the 15th International Symposium on Chromatography, Nürnberg, October 1984 相似文献
27.
The preparation and properties of K2MoOS3 and K2WOS3 are reported. During the reaction of these salts in aqueous solution with H2Se in the presence of Cs+ the compounds Cs2MoOS2Se and Cs2WOS2Se are formed. (For X-Ray-data see “Inhaltsübersicht”). 相似文献
28.
29.
Gerhard Schulze Edzard Han Wolfgang Frenzel 《Fresenius' Journal of Analytical Chemistry》1989,332(8):844-848
Summary The interferences caused by inorganic ions, organic anions and Triton X-100 in the determination of lead by flow injection potentiometric and voltammetric stripping analysis at a mercury film electrode were investigated. The experiments were performed in the concentration range of 1–10 mg/l Pb2+. For both methods linear calibration plots were obtained in the presence of an excess of nitrate, chloride, perchlorate and sulphate. Iodide strongly interferes due to mercury complexation.Metal ion interference caused by formation of irreversible amalgams (as in the case of codeposition of Ni, Co, Fe and Cr) is avoided by proper choice of deposition potential. No effect of water soluble reduced species, i.e. Fe(II) and Cr(II), on the stripping signals was observed. The presence of acetate, citrate and tartrate does not limit the determination of lead by potentiometric stripping analysis (PSA) but has a marked effect on anodic stripping voltammetric (ASV) signals. No influence of Triton X-100 on the determination of lead by PSA was found. In ASV 10–3% Triton X-100 diminished the peak current by 15%.
Herrn Prof. Dr. Rolf Neeb aus Anlaß seines 60. Geburtstags gewidmet 相似文献
Herrn Prof. Dr. Rolf Neeb aus Anlaß seines 60. Geburtstags gewidmet 相似文献
30.
High-modulus carbon fibers are used as working electrodes in differential-pulse stripping voltammetry and potentiometric stripping analysis. Different types of electrodes (particularly single-fiber and brush electrodes) are compared with regard to reproducibility, sensitivity, and practical aspects. Zinc, cadmium, and lead are determined in the 100 μg 1?1 to 1 mg l?1 range and optimum experimental parameters are described. The cut single-fiber electrode has the best general characteristics. 相似文献