Spin-polarized Quantum Transport in Mesoscopic Conductors: Computational Concepts and Physical Phenomena

Mesoscopic conductors are electronic systems of sizes in between nano- and micrometers, and often of reduced dimensionality. In the phase-coherent regime at low temperatures, the conductance of these devices is governed by quantum interference effects, such as the Aharonov-Bohm effect and conductance fluctuations as prominent examples. While first measurements of quantum charge transport date back to the 1980s, spin phenomena in mesoscopic transport have moved only recently into the focus of attention, as one branch of the field of spintronics. The interplay between quantum coherence with confinement-, disorder- or interaction-effects gives rise to a variety of unexpected spin phenomena in mesoscopic conductors and allows moreover to control and engineer the spin of the charge carriers: spin interference is often the basis for spin-valves, -filters, -switches or -pumps. Their underlying mechanisms may gain relevance on the way to possible future semiconductor-based spin devices. A quantitative theoretical understanding of spin-dependent mesoscopic transport calls for developing efficient and flexible numerical algorithms, including matrix-reordering techniques within Green function approaches, which we will explain, review and employ.Comment: To appear in the Encyclopedia of Complexity and System Scienc

Rifampin in Experimental Endocarditis Due to Staphylococcus aureus in Rabbits

Rifampin possesses unique activity against Staphylococcus aureus. It is the most active antistaphylococcal antibiotic currently available and has been shown to be particularly effective in eradicating S. aureus from abscess cavities in experimental infections. However resistance develops rapidly in vitro and in vivo when large numbers of organisms (106-107) are present, and use of combination therapy has been recommended. The use of combination therapy is complicated by the finding that in vitro the addition of rifampin may reduce (antagonize) the bactericidal effect of the β-lactam antibiotics. This study examines the in vivo effect of treatment with a β-Iactam agent (cloxacillin), rifampin, or the combination on the eradication of S. aureus from cardiac vegetations in experimental endocarditis. Five different dosage combinations of the β-lactam agent and rifampin were administered for a three-day period, and an attempt was made to correlate peak serum bactericidal titers with results of quantitative cultures of vegetations after therapy. In two of five regimens the combination of rifampin and cloxacillin produced enhanced efficacy in vivo (synergism); in two regimens the effect was no greater than the effect of either drug alone (indifference), and in one regimen the combination was less effective than either single-drug regimen alone (antagonism). Peak serum bactericidal titers often were predictive of the in vivo effect when high doses of cloxacillin were used but were not consistently predictive of in vivo results when rifampin was the agent responsible for the major therapeutic effect. Rifampin-resistant strains did not emerge in animals receiving combination therapy but were isolated from vegetations from several animals receiving rifampin alon