Competing spin transfer and dissipation at Co/Cu(001) interfaces on femtosecond timescales

By combining interface-sensitive non-linear magneto-optical experiments with femtosecond time resolution and ab-initio time-dependent density functional theory, we show that optically excited spin dynamics at Co/Cu(001) interfaces proceeds via spin-dependent charge transfer and backtransfer between Co and Cu. This ultrafast spin transfer competes with dissipation of spin angular momentum mediated by spin-orbit coupling already on sub 100 fs timescales. We thereby identify the fundamental microscopic processes during laser-induced spin transfer at a model interface for technologically relevant ferromagnetic heterostructures.Comment: 5 pages, 4 figure

Does Cosmic-Ray-Induced Heterogeneous Chemistry Influence Stratospheric Polar Ozone Loss ?

Cosmic-ray (CR) -induced heterogeneous reactions of halogenated species have been suggested to play the dominant role in causing the Antarctic ozone hole. However, measurements of total ozone in Antarctica do not show a compact and significant correlation with CR activity. Further, a substantial CR-induced heterogeneous loss of chlorofluorocarbons is incompatible with multiyear satellite observations of N2O and CFC-12. Thus, CR-induced heterogeneous reactions cannot be considered as an alternative mechanism causing the Antarctic ozone hole

Schlaf und Nachtfluglärm: subjektive Wirkungen der Kernruhezeit am Frankfurter Flughafen im Längsschnittvergleich

Im Rahmen des Forschungsverbundprojekts NORAH untersuchte das DLR Institut für Luft- und Raumfahrtmedizin im Modul „Auswirkungen von Fluglärm auf den nächtlichen Schlaf“ in drei Messkampagnen die subjektiven Wirkungen des Fluglärms auf den Schlaf vor und nach Eröffnung der Landebahn Nordwest am Frankfurter Flughafen im Oktober 2011 und der damit einhergehenden Kernruhezeit von 23 bis 5 Uhr. Die Studien wurden im Auftrag des Umwelt- und Nachbarschaftshauses im Forum Flughafen und Region (FFR) erstellt. Sie wurden mit insgesamt 202 Probanden zu Hause im durch Nachtfluglärm belasteten Rhein-Main Gebiet durchgeführt. Die subjektiven Wirkungen des nächtlichen Fluglärms vor und nach Einführung der Kernruhezeit wurden durch Einschätzungen der schlafbezogenen psychologischen Parameter „Schlafdauer“, „Schlaftiefe“ und „Schlaferholung“ mit visuellen Analogskalen (VAS) erfasst. Als weitere Indikatoren einer durch Fluglärm schlafgestörten Nacht dienten Müdigkeits- und Schläfrigkeitsbewertungen morgens nach dem Aufstehen mittels eines Fatigue-Fragebogens (FAT) und der Karolinska Sleepiness Scale (KSS). Für alle subjektiven Variablen wurden Expositions-Wirkungskurven in Abhängigkeit vom energieäquivalenten fluglärmbezogenen Dauerschallpegel LAeq sowie der Anzahl an nächtlichen Überfluggeräuschen mittels logistischer Regression mit Zufallseffekt berechnet. Nicht-akustische Moderatoren und das Studienjahr wurden bei der Modellbildung berücksichtigt. Im Längsschnittvergleich zeigt sich für die Schlaftiefe und Schlaferholung sowie die Müdigkeit und Schläfrigkeit eine statistisch signifikante Zunahme im dreijährigen Studienverlauf, was einer Verschlechterung des Schlaferlebens der Anwohner entspricht. Danach hat die Einführung der Kernruhezeit am Frankfurter Flughafen subjektiv zu keiner statistisch signifikanten Verbesserung des Schlafs im Vergleich zur Basiserhebung im Jahr 2011 mit durchgängigem Nachtflugbetrieb geführt. Dieses Ergebnis ist allerdings unabhängig von der Fluglärmbelastung und auf den Einfluss nicht erhobener Parameter zurückzuführen

Structure prediction based on ab initio simulated annealing for boron nitride

Possible crystalline modifications of chemical compounds at low temperatures correspond to local minima of the energy landscape. Determining these minima via simulated annealing is one method for the prediction of crystal structures, where the number of atoms per unit cell is the only information used. It is demonstrated that this method can be applied to covalent systems, at the example of boron nitride, using ab initio energies in all stages of the optimization, i.e. both during the global search and the subsequent local optimization. Ten low lying structure candidates are presented, including both layered structures and 3d-network structures such as the wurtzite and zinc blende types, as well as a structure corresponding to the beta-BeO type

Intra- and interbrain synchronization and network properties when playing guitar in duets

To further test and explore the hypothesis that synchronous oscillatory brain activity supports interpersonally coordinated behavior during dyadic music performance, we simultaneously recorded the electroencephalogram (EEG) from the brains of each of 12 guitar duets repeatedly playing a modified Rondo in two voices by C.G. Scheidler. Indicators of phase locking and of within-brain and between-brain phase coherence were obtained from complex time-frequency signals based on the Gabor transform. Analyses were restricted to the delta (1–4 Hz) and theta (4–8 Hz) frequency bands. We found that phase locking as well as within-brain and between-brain phase-coherence connection strengths were enhanced at frontal and central electrodes during periods that put particularly high demands on musical coordination. Phase locking was modulated in relation to the experimentally assigned musical roles of leader and follower, corroborating the functional significance of synchronous oscillations in dyadic music performance. Graph theory analyses revealed within-brain and hyperbrain networks with small-worldness properties that were enhanced during musical coordination periods, and community structures encompassing electrodes from both brains (hyperbrain modules). We conclude that brain mechanisms indexed by phase locking, phase coherence, and structural properties of within-brain and hyperbrain networks support interpersonal action coordination (IAC)

COMPLETE SOLUTION OF THE XXZ-MODEL ON FINITE RINGS. DYNAMICAL STRUCTURE FACTORS AT ZERO TEMPERATURE.

The finite size effects of the dynamical structure factors in the XXZ-model are studied in the euclidean time $(\tau)$-representation. Away from the critical momentum $p=\pi$ finite size effects turn out to be small except for the large $\tau$ limit. The large finite size effects at the critical momentum $p=\pi$ signal the emergence of infrared singularities in the spectral $(\omega)$-representation of the dynamical structure factors.Comment: PostScript file with 12 pages + 11 figures uuencoded compresse

Identification and characterization of a novel extracellular matrix protein nephronectin that is associated with integrin alpha8beta1 in the embryonic kidney.

The epithelial-mesenchymal interactions required for kidney organogenesis are disrupted in mice lacking the integrin alpha8beta1. None of this integrin's known ligands, however, appears to account for this phenotype. To identify a more relevant ligand, a soluble integrin alpha8beta1 heterodimer fused to alkaline phosphatase (AP) has been used to probe blots and cDNA libraries. In newborn mouse kidney extracts, alpha8beta1-AP detects a novel ligand of 70-90 kD. This protein, named nephronectin, is an extracellular matrix protein with five EGF-like repeats, a mucin region containing a RGD sequence, and a COOH-terminal MAM domain. Integrin alpha8beta1 and several additional RGD-binding integrins bind nephronectin. Nephronectin mRNA is expressed in the ureteric bud epithelium, whereas alpha8beta1 is expressed in the metanephric mesenchyme. Nephronectin is localized in the extracellular matrix in the same distribution as the ligand detected by alpha8beta1-AP and forms a complex with alpha8beta1 in vivo. Thus, these results strongly suggest that nephronectin is a relevant ligand mediating alpha8beta1 function in the kidney. Nephronectin is expressed at numerous sites outside the kidney, so it may also have wider roles in development. The approaches used here should be generally useful for characterizing the interactions of novel extracellular matrix proteins identified through genomic sequencing projects

Mechanical properties of Li-Sn alloys for Li-ion battery anodes: A first-principles perspective

© 2016 Author(s). Fracture and pulverization induced by large stress during charging and discharging may lead to the loss of electrical contact and capacity fading in Sn anode materials. A good understanding of mechanical properties is necessary for their optimal design under different lithiation states. On the basis of first-principles calculations, we investigate the stress-strain relationships of Li-Sn alloys under tension. The results show that the ideal tensile strengths of Li-Sn alloys vary as a function of Li concentration, and with the increase of Li+ concentration, the lowest tensile strength decreases from 4.51 GPa (Sn) to 1.27 GPa (Li7Sn2). This implies that lithiation weakens the fracture resistance of Li-Sn alloys