Spin Reversal of a Quantum Hall Ferromagnet at a Landau Level Crossing.

When Landau levels (LLs) become degenerate near the Fermi energy in the quantum Hall regime, interaction effects can drastically modify the electronic ground state. We study the quantum Hall ferromagnet formed in a two-dimensional hole gas around the LL filling factor ν=1 in the vicinity of a LL crossing in the heave-hole valence band. Cavity spectroscopy in the strong-coupling regime allows us to optically extract the spin polarization of the two-dimensional hole gas. By analyzing this polarization as a function of hole density and magnetic field, we observe a spin flip of the ferromagnet. Furthermore, the depolarization away from ν=1 accelerates close to the LL crossing. This is indicative of an increase in the size of skyrmion excitations as the effective Zeeman energy vanishes at the LL crossing.

Interaction-Induced Shubnikov-de Haas Oscillations in Optical Conductivity of Monolayer MoSe_{2}.

We report polarization-resolved resonant reflection spectroscopy of a charge-tunable atomically thin valley semiconductor hosting tightly bound excitons coupled to a dilute system of fully spin- and valley-polarized holes in the presence of a strong magnetic field. We find that exciton-hole interactions manifest themselves in hole-density dependent, Shubnikov-de Haas-like oscillations in the energy and line broadening of the excitonic resonances. These oscillations are evidenced to be precisely correlated with the occupation of Landau levels, thus demonstrating that strong interactions between the excitons and Landau-quantized itinerant carriers enable optical investigation of quantum-Hall physics in transition metal dichalcogenides.

[Telemedicine in acute stroke care--a health economics view]. / Telemedizin in der Schlaganfall-Akutversorgung--eine gesundheitsökonomische Bestandsaufnahme.

Specialized stroke units offer optimal treatment of patients with an acute stroke. Unfortunately, their installation is limited by an acute lack of experienced neurologists and the small number of stroke patients in sparsely populated rural areas. This problem is increasingly being solved by the use of telemedicine, so that neurological expertise is made available to basic and regular care. It has been demonstrated by national and international pilot studies that solidly based and rapid decisions can be made by telemedicine regrading the use of thrombolysis, as the most important acute treatment, but also of other interventions. So far studies have only evaluated improvement in the quality of care achieved by networking, but not of any lasting effect on any economic benefit. Complementary to a medical evaluation, the qualitative economic assessment presented here of German and American concepts of telemetric care indicate no difference in efficacy between various ways of networking. Most noteworthy, when comparing two large American and German studies, is the difference in their priorities. While the American networks achieved targeted improvements in efficacy of care that go beyond the immediate wishes of the doctors involved, this was of only secondary importance in the German studies. Also, in contrast to several American networks, the German telemetry networks have not tended to be organized for future growth. In terms of economic benefits, decentralized organized networks offer a greater potential of efficacy than purely local ones. Furthermore, the integration of inducements into the design of business models is a fundamental factor for achieving successful and lasting existence, especially within a highly competitive market.