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21.
R. Keil 《Fresenius' Journal of Analytical Chemistry》1979,297(1):44-48
Zusammenfassung Die nachstehend beschriebene Untersuchung zeigt, daß manche Metallionenzusätze Empfindlichkeitsverbesserungen bei der Bestimmung des Urans durch Flammen-AAS ergeben. Als wirksamster Zusatz wurde Gallium gefunden, das die Empfindlichkeit gegenüber reiner Uranlösung etwa um den Faktor 5 steigern kann. Durch die Anwendung der sogenannten Injektionsmethode kann mit kleinsten Probevolumen die zur Analyse notwendige Absolutmenge des Urans bis zur Nachweisgrenze von 0,5 g vermindert werden. Zusätzlich wurde die bewährte Uran-Extraktions-Aufkonzentrierungsmethode mit Triphenylarsinoxid in CHCl3 für die AAS modifiziert, womit in vielen Fällen eine weitere Erniedrigung der Nachweisgrenze erzielt werden kann.Für die Überprüfung des Manuskriptes möchte ich den Herren Dr. P. Baertschi und O. Antonsen herzlich danken. 相似文献
22.
23.
Kurt Egger und Manfred Keil 《Fresenius' Journal of Analytical Chemistry》1965,210(3):201-208
Zusammenfassung Durch Anwendung lipophiler Lösungsmittel (z. B. Chloroform— Methanol— Methyl-äthyl-keton = 942) werden Flavonverbindungen auf Polyamid nach vorwiegend verteilungschromatographischen Gesetzmäßigkeiten getrennt. Dadurch kommen gegenüber den bisher verwendeten Fließmitteln neuartige Aufspaltungen zustande. Es erfolgt eine Trennung auch jener Aglykone und Glykoside, die in den bisher beschriebenen Gemischen identische Rf-Werte hatten. Durch Kombination von polarer und lipophiler Entwicklung im zweidimensionalen Chromatogramm sind weitgehende Rückschlüsse auf die Struktur der Verbindungen zu gewinnen. Die Rf-Werte zahlreicher Flavonverbindungen in einer chloroformhaltigen und einer wäßrigen Fließmittelfolge werden vergleichend diskutiert.
Wertvolle Testsubstanzen wurden uns in dankenswerter Weise von Herrn Prof. Dr. Hörhammer, München (K-3-rham. gluc.) und Herrn Prof. Dr. Beckmann, Stuttgart-Hohenheim (K-3-rham. gluo.-7-gluo.) zur Verfügung gestellt. — Die Deutsche Forschungsgemeinschaft hat die Untersuchung durch Sachmittel gefördert. 相似文献
Summary Flavone compounds are separated on polyamide by lipophilic solvent mixtures in a partition-chromatographic way. In contrast to solvent systems used so far, new separations were obtained. Aglycones and glycosides difficultly to resolve hitherto can be easily differentiated now. Combination of polar and lipophilic development in a 2-dimensional chromatogram helps to identify the structure of the compounds. The Rf-values of a number of flavones obtained with solvents containing CHCl3 are compared with those obtained with solvents containing water.
Wertvolle Testsubstanzen wurden uns in dankenswerter Weise von Herrn Prof. Dr. Hörhammer, München (K-3-rham. gluc.) und Herrn Prof. Dr. Beckmann, Stuttgart-Hohenheim (K-3-rham. gluo.-7-gluo.) zur Verfügung gestellt. — Die Deutsche Forschungsgemeinschaft hat die Untersuchung durch Sachmittel gefördert. 相似文献
24.
R. Keil 《Fresenius' Journal of Analytical Chemistry》1971,257(5):349-350
25.
We study the self-diffusion of simple gases inside single-walled carbon nanotubes at the zero-loading limit by molecular dynamics simulations. The host-framework flexibility influence is taken into account. In particular, we study the influences of nanotube size and temperature. For the carbon-nanotube radius-dependent self-diffusivities, a maximum is observed, which resembles the so-called levitation effect. This occurs for pores having a radius comparable to the position of the interaction-energy minimum. Surprisingly, the temperature influence is not uniform throughout different pore sizes. Diffusivities are expected to increase with temperature. This effect is observed for carbon nanotubes distinctly larger than the guest molecules. Remarkably, for smaller pores, the self-diffusivities decrease with increasing temperature or exhibit a maximum in the temperature dependence. This effect is caused by competing influences of collision frequency and temperature. 相似文献
26.
Geert Keil 《Metaphysica》2013,14(2):149-164
The article introduces a special issue of the journal Metaphysica on vagueness and ontology. The conventional view has it that all vagueness is semantic or representational. Russell, Dummett, Evans and Lewis, inter alia, have argued that the notion of “ontic” or “metaphysical” vagueness is not even intelligible. In recent years, a growing minority of philosophers have tried to make sense of the notion and have spelled it out in various ways. The article gives an overview and relates the idea of ontic vagueness to the unquestioned phenomenon of fuzzy spatiotemporal boundaries and to the associated “problem of the many”. It briefly discusses the question of whether ontic vagueness can be spelled out in terms of “vague identity”, emphasizes the often neglected role of the difference between sortal and non-sortal ontologies and suggests a deflationary answer to the ill-conceived question of whether the “ultimate source” of vagueness lies either in language or in the world. 相似文献
27.
Philip M. Keil Ademola Soyemi Kilian Weisser Prof. Tibor Szilvási Prof. Christian Limberg Dr. Terrance J. Hadlington 《Angewandte Chemie (International ed. in English)》2023,62(19):e202381961
The open-shell cationic stannylene-iron(0) complex 4 ( 4 =[PhiPDippSn⋅Fe⋅IPr]+; PhiPDipp={[Ph2PCH2Si(iPr)2](Dipp)N}; Dipp=2,6-iPr2C6H3; IPr=[(Dipp)NC(H)]2C:) cooperatively and reversibly cleaves dihydrogen at the Sn−Fe interface under mild conditions (1.5 bar, 298 K), in forming bridging hydrido-complex 6 . The One-electron oreduction of the related GeII−Fe0 complex 3 leads to oxidative addition of one C−P linkage of the PhiPDipp ligand in an intermediary Fe−I complex, leading to FeI phosphide species 7 . One-electron reduction reaction of 4 gives access to the iron(−I) ferrato-stannylene, 8 , giving evidence for the transient formation of such a species in the reduction of 3 . The covalently bound tin(II)-iron(−I) compound 8 has been characterised through EPR spectroscopy, SQUID magnetometry, and supporting computational analysis, which strongly indicate a high localization of electron spin density at Fe−I in this unique d9-iron complex. 相似文献
28.
J?RG?FELDVOSSEmail author SALVATORE?SICILIANO THOMAS?WEIGEL 《Transformation Groups》2016,21(2):377-398
In this paper it is shown that the projective cover of the trivial irreducible module of a finite-dimensional solvable restricted Lie algebra is induced from the one dimensional trivial module of a maximal torus. As a consequence, the number of the isomorphism classes of irreducible modules with a fixed p-character for a finite-dimensional solvable restricted Lie algebra L is bounded above by p MT(L), where MT(L) denotes the maximal dimension of a torus in L. Finally, it is proved that in characteristic p > 3 the projective cover of the trivial irreducible L-module is induced from the one-dimensional trivial module of a torus of maximal dimension, only if L is solvable. 相似文献
29.
A novel algorithm for modeling the influence of the host lattice flexibility in molecular dynamics simulations is extended to chain-like molecules and mixtures. This technique, based on a Lowe-Andersen thermostat, maintains the advantages of both simplicity and efficiency. The same diffusivities and other properties of the flexible framework system are reproduced. Advantageously, the computationally demanding flexible host lattice simulations can be avoided. Using this methodology we study the influence of flexibility on diffusion of n-alkanes inside single-walled carbon nanotubes. Furthermore, results are shown for diffusion of two mixtures (methane-helium and ethane-butane). Using these results we investigate the accuracy of theories describing diffusion in the Knudsen regime. For the dynamics in carbon nanotubes the Knudsen diffusivities are much too low. The Smoluchowski model gives better results. Interestingly, the extended Smoluchowski model can reproduce our simulation results obtained with a rigid host lattice. We modify this model to also treat collisions with a flexible interface correctly. As the tangential momentum accommodation coefficient is needed for the theoretical models, we introduce a simple concept to calculate it. 相似文献
30.
In sonochemical reactors the effect of emerging cavitation bubbles has significant influence on the amplitude and structure of the developing sound field. Calculations show that the damping parameter and the phase velocity may, depending on the pressure amplitude, change by several orders of magnitude. For example, the sound velocity in water comes to 1500 ms−1, whereas in a bubbly liquid it may decrease to 20 ms−1, which is much below the velocity of sound in air (about 340 ms−1). In this paper, a method of calculating the time dependent three-dimensional pressure field in sonochemical reactors of various shapes is presented. It takes into account inhomogeneous distributed wave parameters which are a function of the spatial depending pressure amplitude. The modeled results are then compared with experimentally measured values of a certain kind of reaction vessel. The agreement is found to be satisfactory. 相似文献