The kinetics of muon-catalyzed dt fusion

A main source of information about the muon-catalyzed fusion cycle in D-T mixtures are the cycling rates _c, which are characteristic for the kinetic equilibrium of states attained rapidly in dense targets. The measurement, analysis and interpretation of these rates will be discussed, concentrating on the extensive set of rates observed at PSI over the last decade in gaseous, liquid and solid targets.Invited talk presented by Peter Kammel.     

On sparse spanners of weighted graphs

Given a graphG, a subgraphG' is at-spanner ofG if, for everyu,v V, the distance fromu tov inG' is at mostt times longer than the distance inG. In this paper we give a simple algorithm for constructing sparse spanners for arbitrary weighted graphs. We then apply this algorithm to obtain specific results for planar graphs and Euclidean graphs. We discuss the optimality of our results and present several nearly matching lower bounds.The work of G. Das and D. Joseph was supported by NSF PYI Grant DCR-8402375. The work of D. Dobkin was supported by NSF Grant CCR-8700917. The work of J. Soares was supported by CNPq proc 203039/87.4 (Brazil) and NSF Grant CCR-9014562. This research was accomplished while G. Das was a student at the University of Wisconsin-Madison. A preliminary version was presented at the Second Scandinavian Workshop on Algorithm Theory, Bergen, Norway, 1990, under the title Generating Sparse Spanners for Weighted Graphs, and proceedings appear in the series Lecture Notes in Computer Science, Springer-Verlag. The preliminary version also appears as Princeton University Technical Report CS-TR-261-90, and as University of Wisconsin-Madison Computer Sciences Technical Report 882.     

Nanoclusters of Silicon and Germanium

Synthetic routes for the preparation of Si or Ge nanoclusters as gaseous species, colloids, supported composites, or as unsupported powders are reviewed along with selected characterization data. The optical properties of these and related materials, such as porous Si, are summarized with particular emphasis on photo- or electroluminescence phenomena. Research opportunities related to Si and Ge cluster chemistry are suggested.     

Zur Deutung der Ultraviolett-Absorptionsspektren der Edelgaskristalle

Zusammenfassung Die Anwendung des kürzlich zur Deutung der Ultraviolett-Absorptionsspektren der Alkalihalogenid-Kristalle vorgeschlagenen Anregungsmodells lokalisierter Exzitonen zur Interpretation der UV-Absorption fester Edelgase wird diskutiert.

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The application of the model of localized excitons, which has been recently suggested for the explanation of the ultra-violet absorption spectra of alkali halide crystals, to the interpretation of the uv-absorption of rare gas crystals is discussed.

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Résumé L'application du modèle d'excitons localisés qui était recemment proposé pour expliquer les spectres d'absorption ultraviolette des crystaux alcali-halogénures est discutée pour interpréter l'absorption u.v. des crystaux de gaz rares.

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Herrn Dr. G. Gliemann ist für zahlreiche Diskussionen und Durchsicht des Manuskripts sehr zu danken.     

LCAO-MO-berechnungen an schwefelhaltigen π-elektronensystemen—XXXIV : Nichtbindende S,S-wechselwirkung in polymethinfarbstoffen

Sulfur-containing polymethine dyes exhibit anomalous chromophoric properties. The vinylene shift of the first two homologues is often considerably larger or smaller than the shift between higher members of the series. Moreover, the absorption wavelengths of non-symmetrical dyes with sulfur-containing groups, as calculated by the mean value rule differ from the experimental data, but not in the predicted manner.This deviation is caused by an interannular no-bond SS-interaction in the monomethine ion. This conclusion is supported by the spectra of appropriately-substituted dyes and is substantiated by theoretical considerations. Starting from the well-known symmetry properties of polymethine MO's the simple PMO-method reproduces correctly the effects of the p_π-type overlap between atomic orbitals of adjacent S atoms at long wavelength absorptions: The SS-interactions lead to a hypsochromic shift in monomethines with (4N + 2)π-electrons (N = 1,2…) and to a bathochromic shift in monomethines with (4N)π-electrons.     

Die Bestimmung geringer Phosphatmengen neben gro?en Mengen Vanadat

Zusammenfassung Es wird ein neues Verfahren zur Bestimmung geringer P₂O₅-Mengen neben großen Mengen V₂O₅ beschrieben. Die Abtrennung des Vanadins geschieht dabei durch Ionenaustausch, während die Bestimmung des Phosphors in den vanadinfreien Eluaten colorimetrisch erfolgt. Das Verfahren wurde vorzugsweise an P₂O₅-haltigen Vanadinpentoxyden, Ammoniummetavanadaten und Natriumorthovanadaten erprobt und hat sich hierbei bestens bewährt.Herrn Ing.-Chem. G. Martens, der mir bei der Beschaffung der erforderlichen Vanadinverbindungen jederzeit in großzügiger Weise behilflich war, sei an dieser Stelle herzlichst gedankt.