Phase diagram of a graphene bilayer in the zero-energy Landau level

Bilayer graphene under a magnetic field has an octet of quasidegenerate levels due to spin, valley, and orbital degeneracies. This zero-energy Landau level is resolved into several incompressible states whose nature is still elusive. We use a Hartree-Fock treatment of a realistic tight-binding four-band model to understand the quantum ferromagnetism phenomena expected for integer fillings of the octet levels. We include the exchange interaction with filled Landau levels below the octet states. This Lamb-shift-like effect contributes to the orbital splitting of the octet. We give phase diagrams as a function of applied bias and magnetic field. Some of our findings are in agreement with experiments. We discuss the possible appearance of phases with orbital coherence

Edge structure of graphene monolayers in the {\nu} = 0 quantum Hall state

Monolayer graphene at neutrality in the quantum Hall regime has many competing ground states with various types of ordering. The outcome of this competition is modified by the presence of the sample boundaries. In this paper we use a Hartree-Fock treatment of the electronic correlations allowing for space-dependent ordering. The edge influence is modeled by a simple perturbative effective magnetic field in valley space. We find that all phases found in the bulk of the sample, ferromagnetic, canted antiferromagnetic, charge-density wave and Kekul$\'e$ distortion are smoothly connected to a Kekul$\'e$-distorted edge. The single-particle excitations are computed taking into account the spatial variation of the order parameters. An eventual metal-insulator transition as a function of the Zeeman energy is not simply related to the type of bulk order.Comment: 18 pages, 11 figures, corresponds to published versio

Effects on the motion of a body attracted by a rotating source, part 2 Progress report

Iterative method determining variation of any order of planned circular orbit about rotating gravitational sourc

Frequency correlations in reflection from random media

We present a theoretical study of frequency correlations of light backscattered from a random scattering medium. This statistical quantity provides insight into the dynamics of multiple scattering processes accessible both, in theoretical and experimental investigations. For frequency correlations between field amplitudes, we derive a simple expression in terms of the path length distribution of the underlying backscattering processes. In a second step, we apply this relation to describe frequency correlations between intensities in the regime of weak disorder. Since, with increasing disorder strength, an unexplained breakdown of the angular structure of the frequency correlation function has recently been reported in experimental studies, we explore extensions of our model to the regime of stronger disorder. In particular, we show that closed scattering trajectories tend to suppress the angular dependence of the frequency correlation function.Comment: 10 pages, 8 figure

Semimetallic features in quantum transport through a gate-defined point contact in bilayer graphene

We demonstrate that, at the onset of conduction, an electrostatically defined quantum wire in bilayer graphene (BLG) with an interlayer asymmetry gap may act as a 1D semimetal, due to the multiple minivalley dispersion of its lowest subband. Formation of a non-monotonic subband coincides with a near-degeneracy between the bottom edges of the lowest two subbands in the wire spectrum, suggesting an $8e^2/h$ step at the conduction threshold, and the semimetallic behaviour of the lowest subband in the wire would be manifest as resonance transmission peaks on an $8e^2/h$ conductance plateau.Comment: 9 pages, 8 figures (including appendices

A novel ex vivo model for investigation of fluid displacements in bone after endoprosthesis implantation

Tissue perfusion and mass transport in the vicinity of implant surfaces prior to integration or bonding may play a crucial role in modulating cellular activities associated with bone remodeling, in particular, at early stages of the integration process. Furthermore, fluid displacements have been postulated to transduct mechanical stress signals to bone cells via loading-dependent flow of interstitial fluid through the lacunocanalicular network of bone. Thus, an understanding and new possibilities for influencing these processes may be of great importance for implant success. An ex vivo model was developed and validated for investigation of fluid displacements in bone after endoprosthesis implantation. This model serves to explicate the effects of surgical intervention as well as mechanical loading of the implant-bone construct on load-induced fluid flow in the vicinity of the implant. Using this model, we intend to quantify perfusion and extravascular flow dynamics in the vicinity of implants and define optimal conditions for enhancing molecular transport of osteotropic agents from the implant surface to apposing bone as well as from the blood supply to the implant surface. Furthermore, the elucidation of main transport pathways may help in understanding the distribution of wear particles in bone surrounding implant, a process which has been postulated to cause osteolysis and implant loosenin

[Book Review:] Contact mechanics and friction: physical principles and applications

Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG geförderten) Allianz- bzw. Nationallizenz frei zugänglich.This publication is with permission of the rights owner freely accessible due to an Alliance licence and a national licence (funded by the DFG, German Research Foundation) respectively

Pharmacokinetics, in-vitro activity, therapeutic efficacy and clinical safety of aztreonam vs. cefotaxime in the treatment of complicated urinary tract infections

The minimal inhibitory concentrations (MICs) of aztreonam and cefotaxime were determined against 400 isolates from urological in-patients with complicated and/or hospital acquired urinary tract infections (UTI). Against the Gram-negative rods the activities of both antibiotics were comparable except for higher activity of aztreonam against Pseudomonas aeruginosa. The pharmacokinetic study in nine elderly patients showed a prolonged plasma half life of aztreonam (2.7 h) as compared to younger volunteers (1.6-1.9 h). In a prospective randomized study 39 urological patients with complicated and/or hospital acquired UTI were treated with 1 g aztreonam or cefotaxime iv twice daily for 4 to 15 days. Cure was obtained in 5 out of 18 patients in the aztreonam and 7 out of 20 patients in the cefotaxime group. There were 3 superinfections, 7 relapses and 3 reinfections in the aztreonam group and 1 failure, 1 superinfection, 6 relapses and 5 reinfections in the cefotaxime group. There was no significant difference in therapeutic efficacy between the two antibiotics. Both antibiotics were tolerated well and seem to be equally effective in the treatment of complicated UTI caused by sensitive organisms