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21.
R. E. Bollen S. Je. Kossolapow M. I. Jagnjatinski A. A. Ashworth und D. K. Below 《Fresenius' Journal of Analytical Chemistry》1942,123(5-6):226-227
Ohne Zusammenfassung 相似文献
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A variety of parameters affecting the determination of iodide in biological materials by ion-pair chromatography and electrochemical detection were examined in detail. It became apparent that the pH value, the ion-pair concentration, the proportion of organic solvent and of organic bases as a component of the buffer solution, as well as the salt concentration in the eluent system could effectively influence the retention characteristics of iodide in the chromatographic system, resulting in the separation of potential interfering substances. The presence of other anions in the sample matrix has to be taken into consideration, particularly thiocyanate because of its long retention time. Investigations of the electrochemical detection mechanism revealed that the reaction hitherto assumed to be responsible for detector signal generation (formation of AgI) is incorrect. In addition, a much more sensitive detection of iodide than that cited in the literature to date is possible if the detector potential is optimally selected and any anticipated interfering substances are removed by chromatography. Use of a gold electrode rather than a silver electrode also considerably enhances the reliability of the procedure. 相似文献
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A characteristic equation for the spectrum of an eigenvalue problem on c2-networks is deduced, and those special cases are investigated in which the spectrum depends mainly on the structure of the abstract graph belonging to the c2-network. 相似文献
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A. Below U. Brehm J. A. De Loera and J. Richter-Gebert 《Discrete and Computational Geometry》2000,24(1):35-48
This paper addresses three questions related to minimal triangulations of a three-dimensional convex polytope P .
• Can the minimal number of tetrahedra in a triangulation be decreased if one allows the use of interior points of P as vertices?
• Can a dissection of P use fewer tetrahedra than a triangulation?
• Does the size of a minimal triangulation depend on the geometric realization of P ?
The main result of this paper is that all these questions have an affirmative answer. Even stronger, the gaps of size produced
by allowing interior vertices or by using dissections may be linear in the number of points.
Received August 16, 1999, and in revised form February 29, 2000. Online publication May 19, 2000. 相似文献
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In this paper we compare the spectral radius of a weighted additive mean L of order t involving Hadamard powers of nonnegative matrices with the corresponding mean R of the respective spectral radii especially, when all matrices are row stochastic, we obtain L≥R for t≥1 and L≤R for 0 ≤ t ≤ 1. 相似文献
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A. A. Kaminskii S. E. Sarkisov F. Below H. -J. Eichler 《Optical and Quantum Electronics》1990,22(Z1):S95-S105
The luminescence and absorption properties of Ba(Y1–x
Er
x
)2F8 (x=0.001, 0.01, 0.05, 0.1, 0.2 and 0.3) and the Er3+-ion decay kinetics of luminescent transitions from three initial laser states, the4S3/2,4F.9/2 and4I11/2 manifolds, were measured. The crystal-field splitting schemes for allJ-manifolds which are involved in (J J)-luminescence transitions and stimulated emission parameters of Er3+ -ions in BaY2F8 were determined. A comparison of laser powers and efficiencies of BaY2F8 and Y3Al5O12, Lu3Al5O12 and LiYF4 single crystals doped with Er3+-ions shows the similar performance of these materials. 相似文献
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Joachim von Below Helmut Kaul 《Calculus of Variations and Partial Differential Equations》1998,7(1):41-51
We consider semilinear elliptic equations with a principal part degenerating on a boundary hyperplane. Weak existence, uniqueness
and regularity of solutions are established by variational methods and by reduction to uniformly elliptic equations. An important
application arises in the mathematical treatment of the rotating star problem in general relativity, where the axial symmetry
admits the reduction of one of the Einstein equations to a problem of the above form on a meridian half plane.
Received February 12, 1997 / Accepted May 15, 1997 相似文献
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