infection by m. tuberculosis can be demonstrated by tuberculin testing. on sequential ppd some person show a marked increase in the size of their skin reactions which may not be due to recent or past tuberculous infection. this phenomenon (booster effect) can occur as soon as a week after the initial test and persist for as long as a year. methods and materials: the purpose of this research is ...

Spin transport properties of a coupled bilayer electron gas with Rashba spin-orbit coupling are studied. The definition of the spin currents in each layer as well as the corresponding continuitylike equations in the bilayer system are given. The curves of the spin Hall conductivities obtained in each layer exhibit sharp cusps around a particular value of the tunneling strength and the conductiv...

Low-temperature, electronic transport in Landau levels N > 1 of a twodimensional electron system is strongly anisotropic. At half-filling of either spin level of each such Landau level the magnetoresistance either collapses to form a deep minimum or is peaked in a sharp maximum, depending on the in-plane current direction. Such anisotropies are absent in the N = 0 and N = 1 Landau level, which ...

The shape of an electronic droplet in the quantum Hall effect is sensitive to gradients of the magnetic field, even if they are placed outside the droplet. Magnetic impurities cause a fingering instability of the edge of the droplet, similar to the Saffman-Taylor fingering instability of an interface between two immiscible phases. We discuss the fingering instability and some algebraic aspects ...

The current state of the theory of the Fractional Quantum Hall Effect is critically analyzed, especially the generally accepted concept of composite fermions. It is argued that there is no sound theoretical foundation for this concept. A simple one-dimensional model is proposed, which presumably has an energy spectrum similar to that of the FQHE system. —————————————————————