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排序方式: 共有117条查询结果,搜索用时 15 毫秒
1.
The capability of double focussing magnetic sector inductively coupled plasma mass spectrometry (HR-ICP-MS) for the determination
of trace elements in different body fluids was investigated in commercially available control materials. The elements included
in this study were: Al, As, Cd, Cr, Co, Cu, Hg, Mn, Ni, Pb, Sb, Se, Tl and Zn. Sample preparation, instrument stability and
the results, which are in very good agreement to the given values, are presented and discussed.
Received: 27 August 1997 / Revised: 19 November 1997 / Accepted: 23 November 1997 相似文献
2.
H. Mahdjour C. Pappa R. Wendler K. Baberschke 《Zeitschrift für Physik B Condensed Matter》1986,63(3):351-364
The ESR of the spin glassAgMn (2.7 and 9.6 at %) has been investigated below and aboveT
g(0.1T
g<T<5T
g) at various microwave frequencies. The analysis yields:1) No explicit frequency dependence but strong magnetic field effects, inherent with ESR-experiments.2) Part of the excess line width is identified as critical spin fluctuations, following a power law. However, because of the presence of the applied field, the reduced temperaturet is not a good scaling variable. We choose the non-linear susceptibility X
s
divided byH
2, which scales as the order parameter susceptibility. The experiment yieldsW
ex(X
s
/H
2)
p
,p=0.42. From this we deduce z3. 相似文献
3.
Total digestion of silicate containing matrices (plants,soil, sludges) using a pressure ashing device with PFA-vessels 总被引:1,自引:0,他引:1
A digestion procedure for silicate containing matrices like soil, sludge, etc. by using a commercially available pressure ashing device (Seif-Aufschlutechnik, Germany) with PFA (perfluoroalkoxy) sample vessels is described at the results for different matrix- and trace elements in different suitable certified standard reference materials. The advantages of this technique compared with the use of Teflon®-(PTFE, polytetrafluoroethylene) vessels and the open treatment in Pt-crucibles will be discussed. 相似文献
4.
5.
Wijkens P Jastrzebski JT van Der Schaaf PA Kolly R Hafner A van Koten G 《Organic letters》2000,2(11):1621-1624
A general method for the functionalization of Si-Cl terminated carbosilane dendritic molecules via organolithium or organomagnesium reagents is described. Quantitative exchange of the bromine atoms of 4-bromophenyl-functionalized dendrimers affords polylithiated species that are valuable starting materials for further functionalization, e.g., into pyridyl alcohols. The latter were successfully applied as catalyst precursors in a ruthenium-mediated ring-closure metathesis reaction. 相似文献
6.
The capability of double focussing magnetic sector inductively coupled plasma mass spectrometry (HR-ICP-MS) for the determination
of trace elements in different body fluids was investigated in commercially available control materials. The elements included
in this study were: Al, As, Cd, Cr, Co, Cu, Hg, Mn, Ni, Pb, Sb, Se, Tl and Zn. Sample preparation, instrument stability and
the results, which are in very good agreement to the given values, are presented and discussed.
Received: 27 August 1997 / Revised: 19 November 1997 / Accepted: 23 November 1997 相似文献
7.
Calculation of regulating index r from M̄W values determined by experiments is proposed. The calculation is based on the assumption that the M̄W values only depend on the conversion and the regulating index in emulsion polymerization. On this basis the calculation of regulator concentration in the latex particles was also possible. M̄W values calculated in this way and experimental M̄W values show good agreement. 相似文献
8.
We investigate analytically and numerically the energy bands, persistent currents and the magnetic moment in a thin hollow cylinder in the presence of a magnetic field including the spin. Two different cases are considered systematically, an Aharonov-Bohm flux threading the hole of a cylinder and a magnetic field penetrating the whole cylinder. It is shown that the halving of the fundamental period of the magnetic moment can be attributed to the coupling of the azimuthal and paraxial electron motions caused by the impurity scattering. The influence of the virtual channels, resulting from evanescent states, on the energy bands and persistent currents is examined in detail. The virtual channels assure a continuous reconstruction of the energy bands immediately under the thresholds of the channels. 相似文献
9.
Gordeev SN Zhukov AA de Groot PA Jansen AG Gagnon R Taillefer L 《Physical review letters》2000,85(21):4594-4597
We report on transport measurements of YBa 2Cu 3O (7-delta) single crystals with different oxygen contents in the geometry B, J ||ab (J perpendicularB). Our data show that the vortices become confined between the Cu-O planes below a well-defined temperature at which the effective size 2xi of the vortex core is approximately equal to the period of the Cu-O layers. This confinement strongly increases the vortex liquid freezing temperature. A new melting line is found separating a vortex liquid and a smectic phase, which shows an oscillatory field dependence reflecting differences between commensurate and incommensurate smectic states. 相似文献
10.
ICP-MS (inductively coupled plasma mass spectrometry) is shown as a very sensitive method for quantitative determination of Th and U concentration and excretion analysis in urine without any sample pretreatment. The current standard method for incorporation monitoring applies alpha-spectrometry, a very tedious and time consuming technique. ICP-MS offers an attractive alternative for monitoring of thorium and uranium body burdens in occupationally exposed subjects and also larger groups of the general population. A limit of determination of 0.5 ng/L in aqueous solutions and 1 ng/L in urine samples for both elements was achieved, with a precision of about ± 10% in the concentration range of appr. 10 ng/L. Due to the lack of a suitable reference material, the accuracy of the method was tested by comparing some of the results with those obtained by -spectrometry, especially for U. There was a sufficient agreement on both results. 相似文献