Nonlinear optics of graphene in a strong magnetic field

Graphene placed in a magnetic field possesses an extremely high mid/far-infrared optical nonlinearity originating from its unusual band structure and selection rules for the optical transitions near the Dirac point. Here we study the linear and nonlinear optical response of graphene in strong magnetic and optical fields using quantum- mechanical density-matrix formalism. We calculate the power of coherent terahertz radiation generated as a result of four-wave mixing in graphene. We show that even one monolayer of graphene gives rise to appreciable nonlinear frequency conversion efficiency and Raman gain for modest intensities of incident infrared radiation.Comment: 16 pages, 6 figure

Semiconductor-enriched single wall carbon nanotube networks applied to field effect transistors

Substantial progress on field effect transistors "FETs" consisting of semiconducting single wall carbon nanotubes "s-SWNTs" without detectable traces of metallic nanotubes and impurities is reported. Nearly perfect removal of metallic nanotubes is confirmed by optical absorption, Raman measurements, and electrical measurements. This outstanding result was made possible in particular by ultracentrifugation (150 000 g) of solutions prepared from SWNT powders using polyfluorene as an extracting agent in toluene. Such s-SWNTs processable solutions were applied to realize FET, embodying randomly or preferentially oriented nanotube networks prepared by spin coating or dielectrophoresis. Devices exhibit stable p-type semiconductor behavior in air with very promising characteristics. The on-off current ratio is 10^5, the on-current level is around 10 $\mu$A, and the estimated hole mobility is larger than 2 cm2 / V s

Pharmacokinetic analysis after implantation of everolimus-eluting self-expanding stents in the peripheral vasculature

Background: A novel self-expanding drug-eluting stent was designed to release everolimus 225 mu g/cm(2) to prevent restenosis following peripheral arterial intervention. The purpose of this study was to measure the pharmacokinetic profile of everolimus following stent implantation. Methods: One hundred four patients with symptomatic peripheral arterial disease underwent implantation of everolimus-eluting stents in the femoropopliteal arteries. In a prespecified subset of 26 patients, blood samples for assay of everolimus content were collected prior to stent implantation, at 1, 4, and 8 hours postprocedure, prior to discharge, and at 1 month postproccdure. Results: A total of 39 stents, ranging from 28 mm to 100 mm in length, were implanted in 26 patients, resulting in a total delivered everolimus dose range of 3.0 to 7.6 mg. Following the procedure, the maximum observed everolimus blood concentrations (C-max) varied from 1.83 +/- 0.05 ng/mL after implantation of a single 80-mm stent to 4.66 +/- 1.78 ng/mL after implantation of two 100-mm stents. The mean time to peak concentration (T-max) varied from 6.8 hours to 35 hours. The pharmacokinetics of everolimus were dose-proportional in that dose-normalized C-max and area under the curve values were constant over the studied dose range. Conclusions: After implantation of everolimus-eluting self-expanding stents in the femoropopliteal arteries, systemic blood concentrations of everolimus are predictable and considerably lower than blood concentrations observed following safe oral administration of everolimus

Total Angular Momentum Conservation During Tunnelling through Semiconductor Barriers

We have investigated the electrical transport through strained p-Si/Si_{1-x}Ge_x double-barrier resonant tunnelling diodes. The confinement shift for diodes with different well width, the shift due to a central potential spike in a well, and magnetotunnelling spectroscopy demonstrate that the first two resonances are due to tunnelling through heavy hole levels, whereas there is no sign of tunnelling through the first light hole state. This demonstrates for the first time the conservation of the total angular momentum in valence band resonant tunnelling. It is also shown that conduction through light hole states is possible in many structures due to tunnelling of carriers from bulk emitter states.Comment: 4 pages, 4 figure

Bodenerosionsminderung in bergigen Regionen am Beispiel des Landkreises Mansfeld-Südharz - BebeR

Die Auswirkungen des Klimawandels werden derzeit intensiv erforscht. Dabei werden insbesondere auch für die Böden Veränderungen prognostiziert, die weitreichende ökonomische, soziale und ökologische Folgen haben werden. Dabei wird eine Zunahme der Erosionsproblematik aufgrund von Starkniederschlägen und aufgrund der Veränderungen im Bodenwasser- und Stoffhaushalt prognostiziert. Vor allem bestimmen aber Landnutzung, Bodenbearbeitung und -bei ackerbaulicher Nutzung- die Wahl der Feldfrucht über das Ausmaß der Erosion. Besonders der zunehmende Versiegelungsgrad führt langfristig dazu, dass weniger Wasser versickert und mehr oberflächlicher Abfluss entsteht. In den Regionen des Mittelgebirges und deren Vorländern spielen daher sowohl die flächenhafte Erosion als auch die Gewässerbetterosion eine große Rolle. Maßnahmen zur Minderung der Erosion sind bereits in Handbüchern und Beratungsleitfäden veröffentlicht worden. In der Praxis werden diese Lösungen jedoch selten gesamtheitlich und unter Einbeziehung verschiedener Akteure durchgeführt. Ziel des Projektes ist es daher zu demonstrieren, wie ein Planungs- und Abwägungsprozess zur Minderung der Bodenerosion (Flächen- und Gewässerbetterosion) unter Einbeziehung unterschiedlicher Akteursgruppen (Kommune, Bevölkerung, Landwirtschaft, Naturschutz) im vorrangig ländlichen Raum in einer bergigen Region im Südharz (Sachsen-Anhalt) erfolgen kann. Hierbei fugiert das Gebiet um den Regenbeek, mit einer hauptsächlich gewässerbettbezogenen Erosion und der Bereich des Vietzbach, welcher von flächenhafter Erosion betroffen ist, als Beispielregion. Vor allem am Regenbeek wird deutlich, dass die vom Oberlieger durch zunehmende Versiegelung verursache erhöhte Abflussmenge, zu massiven Erosionen führt. Diese wirken sich auf den Unterlieger in Form von größeren Schlammablagerungen aus. Im BebeR-Projekt sollen vereinfachte Methoden entwickelt werden, mit denen die Erosion abgeschätzt und auf deren Grundlage Anpassungsmaßnahmen in Zusammenarbeit der Akteure aus verschiedenen Bereichen entworfen und bewertet werden

International development volunteering: An instrument for promoting education in line with the Sustainable Development Goals?

Education is one of the central tenets of the United Nations 2030 Agenda for Sustainable Development. International volunteer services (IVS) in development often aim to provide volunteers with knowledge and skills needed in a globalized world. We use the case of the German weltwärts programme, one of the largest IVS worldwide, to investigate how far IVS can be viewed as an instrument promoting education in line with the Sustainable Development Goals (SDGs). First, we discuss how weltwärts aligns conceptually with the principles and contents of the SDGs. Second, we present empirical evidence on how far the envisioned principles and education outcomes are achieved on the implementation level. We conclude with a discussion of the potentials and limitations of weltwärts in promoting education in line with the SDGs

Towards a tidal loading model for the Argentine-German Geodetic Observatory (La Plata)

We present a regionalized model of ocean tidal loading effects for the Argentine-German Geodetic Observatory in La Plata. It provides the amplitudes and phases of gravity variations and vertical deformation for nine tidal constituents to be applied as corrections to the observatory’s future geodetic observation data. This model combines a global ocean tide model with a model of the tides in the Río de la Plata estuary. A comparison with conventional predictions based only on the global ocean tide model reveals the importance of the incorporation of the regional tide model. Tidal loading at the observatory is dominated by the tides in the Atlantic Ocean. An additional contribution of local tidal loading in channels and groundwater is examined. The magnitude of the tidal loading is also reviewed in the context of the effects of solid earth tides, atmospheric loading and non-tidal loadsFacultad de Ciencias Naturales y Muse

Towards a tidal loading model for the Argentine-German Geodetic Observatory (La Plata)

We present a regionalized model of ocean tidal loading effects for the Argentine-German Geodetic Observatory in La Plata. It provides the amplitudes and phases of gravity variations and vertical deformation for nine tidal constituents to be applied as corrections to the observatory’s future geodetic observation data. This model combines a global ocean tide model with a model of the tides in the Río de la Plata estuary. A comparison with conventional predictions based only on the global ocean tide model reveals the importance of the incorporation of the regional tide model. Tidal loading at the observatory is dominated by the tides in the Atlantic Ocean. An additional contribution of local tidal loading in channels and groundwater is examined. The magnitude of the tidal loading is also reviewed in the context of the effects of solid earth tides, atmospheric loading and non-tidal loadsFacultad de Ciencias Naturales y Muse

Horizontal and vertical deformation rates linked to the Magallanes‐Fagnano Fault, Tierra del Fuego: Reconciling geological and geodetic observations by modeling the current seismic cycle

We integrate geodetic, geological and seismological observations in Tierra del Fuego,into a consistent and quantitative analysis, to better understand the current crustaldeformation associated to the Magallanes-Fagnano Fault, i.e., the transform boundarybetween the South American and Scotia plates at the southern tip of Patagonia. Toobtain reliable geodetic estimates of the thickness of the seismogenic layer, we modelthe current seismic cycle from the great 1949 Mw 7.7 earthquake to the present,including the lasting effects of postseismic relaxation. The model parameters are con-strained by GNSS velocities obtained by reprocessing 24 years of observations in theisland with up-to-date models and satellite products. We combine the observed de-formation rates with long-term geological estimates of the slip rate in this transformsystem during the Holocene. The modeling results point to a seismogenic layer thick-ness of 15 ± 3 km and to fault planes inclined 63◦ ± 4◦ , dipping to the South. Alongthe sections of the Magallanes-Fagnano Fault in the island these results are consistentwith a seismic moment deficit rate, per unit of length, of 3.2±0.8×1012 N m a−1 km−1,and a cumulative seismic moment, to date, equivalent to an earthquake of magnitudeMw ´7. The postseismic viscoelastic relaxation, probably related to viscous flow inthe mantle, affects the entire region up to ∼ 200 km away from the Magallanes-FagnanoFault, and more than 60 years after the earthquake.Fil: Mendoza, Luciano Pedro Oscar. Universidad Nacional de la Plata. Facultad de Cs.astronomicas y Geofisicas. Laboratorio Maggia.; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Departamento de Astrometría; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; ArgentinaFil: Richter, Andreas Jorg. Universidad Nacional de la Plata. Facultad de Cs.astronomicas y Geofisicas. Laboratorio Maggia.; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Departamento de Astrometría; Argentina. Technische Universität Dresden; AlemaniaFil: Marderwald, Eric Rodolfo. Universidad Nacional de la Plata. Facultad de Cs.astronomicas y Geofisicas. Laboratorio Maggia.; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Departamento de Astrometría; ArgentinaFil: Hormaechea, José Luis. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; Argentina. Estación Astronómica Río Grande; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas; ArgentinaFil: Connon, Gerardo Claudio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; Argentina. Estación Astronómica Río Grande; ArgentinaFil: Scheinert, M.. Technische Universität Dresden; AlemaniaFil: Dietrich, R.. Technische Universität Dresden; AlemaniaFil: Perdomo, Raul Anibal. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas; Argentin