Suppression of material transfer at contacting surfaces: The effect of adsorbates on Al/TiN and Cu/diamond interfaces from first-principles calculations

The effect of monolayers of oxygen (O) and hydrogen (H) on the possibility of material transfer at aluminium/titanium nitride (Al/TiN) and copper/diamond (Cu/C$_{\text{dia}}$) interfaces, respectively, were investigated within the framework of density functional theory (DFT). To this end the approach, contact, and subsequent separation of two atomically flat surfaces consisting of the aforementioned pairs of materials were simulated. These calculations were performed for the clean as well as oxygenated and hydrogenated Al and C$_{\text{dia}}$ surfaces, respectively. Various contact configurations were considered by studying several lateral arrangements of the involved surfaces at the interface. Material transfer is typically possible at interfaces between the investigated clean surfaces; however, the addition of O to the Al and H to the C$_{\text{dia}}$ surfaces was found to hinder material transfer. This passivation occurs because of a significant reduction of the adhesion energy at the examined interfaces, which can be explained by the distinct bonding situations.Comment: 27 pages, 8 figure

Die Welt 1000-1250: Globalgeschichte: die Welt von 1000 - 2000

Globalgeschichte ist kein Phänomen das erst im späten 15. Jahrhundert beginnt. Im vorliegenden Band wird der allmähliche Prozess der Entstehung einer umfassenden Globalgeschichte beschrieben. Obwohl man in der Zeit von 1000-1250 noch nicht von einem weltumspannenden Austausch sprechen kann, vor allem da der amerikanische Kontinent noch völlig eigenständig interagierte, gab es gut organisierte Handels- und Austauschbeziehungen, die Länder und sogar Kontinente umspannten. Wichtige Träger der Vermittlung zwischen verschiedenen Ländern und Regionen waren nicht nur wirtschaftliche und politische Interessen, die sich in Handelskontakten, diplomatischen Beziehungen und Gesandtschaften oder in Kriegen äußerten, sondern auch die Religionen, vor allem das Christentum, der Islam und der Buddhismus. Dabei war ein ausgebautes Verkehrswegenetz zu Lande und zu Wasser eine Voraussetzung. Die Verdichtung vielfältiger Interaktions- und Austauschprozesse seit der Jahrtausendwende schuf zwar nicht die "eine" Welt, sie bewirkte aber doch so folgenreiche "globale" Veränderungen in Wirtschaft, Gesellschaft, Politik und Kultur, dass sich die Phase nach 1250 mit einiger Berechtigung als "vormodernes Weltsystem" begreifen lässt

Feasibility studies for the measurement of time-like proton electromagnetic form factors from p¯ p→ μ+μ- at P ¯ ANDA at FAIR

This paper reports on Monte Carlo simulation results for future measurements of the moduli of time-like proton electromagnetic form factors, | GE| and | GM| , using the p¯ p→ μ+μ- reaction at P ¯ ANDA (FAIR). The electromagnetic form factors are fundamental quantities parameterizing the electric and magnetic structure of hadrons. This work estimates the statistical and total accuracy with which the form factors can be measured at P ¯ ANDA , using an analysis of simulated data within the PandaRoot software framework. The most crucial background channel is p¯ p→ π+π-, due to the very similar behavior of muons and pions in the detector. The suppression factors are evaluated for this and all other relevant background channels at different values of antiproton beam momentum. The signal/background separation is based on a multivariate analysis, using the Boosted Decision Trees method. An expected background subtraction is included in this study, based on realistic angular distributions of the background contribution. Systematic uncertainties are considered and the relative total uncertainties of the form factor measurements are presented