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H. Falk R. Geerling B. Hattendorf K. Krengel-Rothensee K. P. Schmidt 《Analytical and bioanalytical chemistry》1997,359(4-5):352-356
An ICP-MS method for the determination of ultra-traces of 24 Elements (Li, Be, Mg, Al, Cr, Mn, Co, Zn, Cu, Ga, As, Se, Rb, Sr, Mo, Ag, Cd, Sn, Sb, Ba, Tl, Pb, Bi, U) at ng/L to μg/L levels in highly saline solutions (up to 30 g/L NaCl) was developed. Calculated to the salt content of the samples, limits of detection at the sub-μg/kg level were obtained. This allows the measurement of samples like sea water, or clinical samples like urine, serum and whole blood, with few or without sample preparation and a drastic improvement to the limits of detection. Compared to the determination in solutions of 1 g/L NaCl the limits of detection in the original sample were improved by one order of magnitude. Improvements in instrumental stability are achieved by the use of an additional gas, that is introduced to the aerosol stream and avoids salt deposition in the aerosol tube of the torch, the use of High Matrix Content (HMC) cones, that show no clogging even at NaCl-concentrations up to 50 g/L. With this setup the long term stability for measurements with changing matrix concentrations is < 10% without and < 5% with use of an internal standard for the individual samples. Cleaning up is necessary after 2 days of operation. The direct analysis of the Nearshore Seawater Reference Material NRC-CNRC CASS3 showed a good agreement with the certified and measured concentrations. Elements, that do not suffer from an isobaric overlap of matrix compounds can be determined clearly at ng/L levels. Measurement of different matrix concentrations showed, that acceptable results can be achieved with a single calibration for concentrations from 5 g/L NaCl to 30 g/L NaCl, though matrix matching shows the best results. 相似文献
24.
W.G. Schmidt 《Applied Physics A: Materials Science & Processing》2002,75(1):89-99
There has been renewed interest in the structure of III-V compound semiconductor (001) surfaces caused by recent experimental
and theoretical findings, which indicate that geometries different from the seemingly well-established dimer models describe
the surface ground state for specific preparation conditions. I review briefly the structure information available on the
(001) surfaces of GaP, InP, GaAs and InAs. These data are complemented with first-principles total-energy calculations. The
calculated surface phase diagrams are used to explain the experimental data and reveal that the stability of specific surface
structures depends largely on the relative size of the surface constituents. Several structural models for the Ga-rich GaAs (001)(4×6)
surface are discussed, but dismissed on energetic grounds. I discuss in some detail the electronic properties of the recently
proposed cation-rich GaAs (001)ζ(4×2) geometry.
Received: 18 May 2001 / Revised version: 23 July 2001 / Published online: 3 April 2002 相似文献
25.
E. Casarejos P. Armbruster L. Audouin J. Benlliure M. Bernas A. Boudard R. Legrain S. Leray B. Mustapha S. Czajkowski T. Enqvist B. Fernandez J. Pereira M. Pravikoff F. Rejmund K. -H. Schmidt C. Stephan J. Taieb L. Tassan-Got C. Villagrasa C. Volant W. Wlazlo 《Physics of Atomic Nuclei》2003,66(8):1413-1420
The isotopic production cross sections of heavy residues in relativistic heavy-ion collisions have been investigated in inverse kinematics. The primary reaction products were fully identified in mass and atomic number prior to beta decay using the fragment separator FRS. The huge collection of data obtained helps in the understanding of the two main reaction mechanisms involved: fragmentation and fission. These data provide basic information for future radioactive ion beam facilities and for technical applications like intense neutron sources by means of spallation targets. 相似文献
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K. C. Nicolaou Dionisios Vourloumis Tianhu Li Joaquin Pastor Nicolas Winssinger Yun He Sacha Ninkovic Francisco Sarabia Hans Vallberg Frank Roschangar N. Paul King M. Ray V. Finlay Pareskevi Giannakakou Pascal Verdier-Pinard Ernest Hamel 《Angewandte Chemie (International ed. in English)》1997,36(19):2097-2103
28.
Patrick Mather Nino Grizzuti Glenn Heffner Mathias Ricker Willie E. Rochefort Markus Seitz Hans-Werner Schmidt Dale S. Pearson 《Liquid crystals》1994,17(6):811-826
In this paper, we report on the synthesis and detailed characterization of a new semiflexible nematic liquid crystalline polyester which could serve as a 'model' polyester for a variety of physical and physico-chemical investigations. The polymer is a nematic liquid over a wide temperature range-from the glass transition temperature at ∼95°C to the isotropic transition at ∼240°C. We expect this polyester to be particularly useful for studying the effect of flow on the orientation of liquid crystalline polymers, as well as the production and removal of disclinations. 相似文献
29.
O. Kindel F. J. Herrmann L. Schmidt 《Journal of Radioanalytical and Nuclear Chemistry》1994,183(2):219-224
By simulation experiments with a 10–5 mol/l solution of iodododecane labeled with131I in n-dodecane the influence of various materials and conditions, which are possible in nuclear fuel reprocessing, has been investigated. The formation of decomposition products was detected via HPLC with a radioactivity monitor. By means of252Cf plasma-desorption mass spectrometry (PDMS) the decomposition products were identified. It was found that a temperature of 100°C favored the formation of iodoalkanes with chain lengths of C1 to C11. The presence of TBP(tri-n-butyl-phosphate) accelerated the decomposition of iodododecane. In pure TBP only iodobutane was formed as a decomposition product. 相似文献
30.
Steven Schmidt Gü nter Lattermann Ralf Kleppinger Joachim H. Wendorff 《Liquid crystals》1994,16(4):693-702
Liquid crystalline complexes with chromium, molybdenum and with tungsten as metallic centres are reported. 1,4,7-Trisubstituted 1,4,7-triazacyclononane and three carbonyl groups are coordinated in an octahedral geometry. The observed mesophases are characterized as disordered rectangular columnar of a pyramidic type. 相似文献