Klaus G. Beuckers, Beate Johlen-Budnik (dir.), Das Gerresheimer Evangeliar. Eine spätottonische Prachthandschrift als Geschichtsquelle

Ce riche volume est consacré à un évangéliaire ottonien conçu pour l’abbaye Saint-Hippolyte de Gerresheim qui fait aujourd’hui partie du trésor de l’église paroissiale Sainte-Marguerite. Faisant suite au colloque organisé en 2015 à Gerresheim par Klaus Gereon Beuckers et Beate Johlen-Budnik, il présente l’état des recherches sur ce codex et l’étudie sous les angles paléographique, codicologique, artistique, politique et praxéologique. K. Gereon Beuckers discute d’abord l’historiographie depu..

CO2 Methanation over Rh/CeO2 Studied with Infrared Modulation Excitation Spectroscopy and Phase Sensitive Detection

Methane is a well-established fuel molecule whose production from CO2 through methanation garners increasing interest as an energy storage solution. While often produced with Ni based catalysts, other metals are of interest thanks to higher robustness and activity-selectivity numbers. The Rh/CeO2 catalyst has shown appreciable properties for CO2 methanation and its structural dynamics has been studied in situ. However, the reaction pathway is unknown. Here, we present infrared modulation excitation spectroscopy measurements with phase sensitive detection of a Rh/CeO2 catalyst adsorbate composition during H2 pulsing (0–2 vol.%) to a constant CO2 (0.5 vol.%) feed. Various carbonyl (CO) and carbonate (b-CO3 /p-CO3 ) ad-species clearly respond to the hydrogen stimulus, making them potential reaction intermediates. The different CO ad-species are likely intermediates for product CO and CH4 but their individual contributions to the respective formations are not unambiguously ascertained. As for the carbonate dynamics, it might be linked to the reduction/oxidation of the CeO2 surface upon H2 pulsing. Formate (HCOO) ad-species are clearly visible but appear to be, if not spectators, linked to slow side reactions possibly also affected by CeO2 redox processes

Endoskopie in der Handchirurgie: TeilI: Arthroskopie

Zusammenfassung: Die Arthroskopie zu diagnostischen und therapeutischen Zwecken ist in der Chirurgie der großen Gelenke nicht mehr wegzudenken. Mit der Entwicklung des entsprechenden feineren Instrumentariums ist es nicht verwunderlich, dass die Arthroskopie auch im Bereich der Handchirurgie zunehmend zum Zuge kommt. Insbesondere am Handgelenk hat sich die Arthroskopie durchgesetzt. Daneben werden auch zunehmend Verfahren für das Karpometakarpal-I (CMC-I)-Gelenk entwickelt, wobei hier die Behandlung der Rhizarthrose im Vordergrund steht. In der Diagnostik und Therapie von Pathologien der Metakarpo-Phalangeal- (MCP) sowie der proximalen und distalen Interphalangeal (PIP/DIP)-Gelenke spielt die Arthroskopie bisher eine eher untergeordnete Rolle. Dieser Artikel soll einen Überblick über die gängigsten arthroskopischen Verfahren am traumatisierten Handgelenk gebe

Why nitrogen oxide inhibits CO oxidation over highly dispersed platinum ceria catalysts

The influence of nitrogen oxide on the lean CO oxidation activity of highly dispersed Pt/ceria and reference Pt/alumina catalysts has been studied by kinetic measurements and infrared spectroscopic characterization. Co-feeding of nitrogen oxide leads to the formation of nitrates on the supports that induce a highly oxidized character of the Pt sites and in the case of Pt/ceria, inhibit ceria lattice oxygens to react with CO adsorbed on Pt rim sites via a Mars-van Krevelen mechanism below the ignition temperature. The build-up of nitrates below the light-off temperatures is faster when CO is present in the feed. Above the light-off temperatures, carbonates replace the nitrates while the catalytic activity remains high

Hampered PdO Redox Dynamics by Water Suppresses Lean Methane Oxidation over Realistic Palladium Catalysts

By use of operando spectroscopies under cycling reaction conditions, water is shown to hamper the redox dynamics of realistic palladium oxide nanoparticles dispersed onto alumina and hydrophobic zeolite supports thereby lowering the activity for total oxidation of methane. Water adsorption forms hydroxyl ad-species that block the methane and oxygen dissociation and seem to prevent lattice oxygen to take part in the methane oxidation. The main catalytic action is thus proposed to shift from the Mars-van Krevelen mechanism in dry conditions to a slower route that relies on Langmuir-Hinshelwood type of steps in wet conditions. This key finding has clear implications on catalyst design for low-temperature gas combustion emission control

The Complexity of Computing Minimal Unidirectional Covering Sets

Given a binary dominance relation on a set of alternatives, a common thread in the social sciences is to identify subsets of alternatives that satisfy certain notions of stability. Examples can be found in areas as diverse as voting theory, game theory, and argumentation theory. Brandt and Fischer [BF08] proved that it is NP-hard to decide whether an alternative is contained in some inclusion-minimal upward or downward covering set. For both problems, we raise this lower bound to the Theta_{2}^{p} level of the polynomial hierarchy and provide a Sigma_{2}^{p} upper bound. Relatedly, we show that a variety of other natural problems regarding minimal or minimum-size covering sets are hard or complete for either of NP, coNP, and Theta_{2}^{p}. An important consequence of our results is that neither minimal upward nor minimal downward covering sets (even when guaranteed to exist) can be computed in polynomial time unless P=NP. This sharply contrasts with Brandt and Fischer's result that minimal bidirectional covering sets (i.e., sets that are both minimal upward and minimal downward covering sets) are polynomial-time computable.Comment: 27 pages, 7 figure