RESUMO
The controlled creation, manipulation and detection of spin-polarized currents by purely electrical means remains a central challenge of spintronics. Efforts to meet this challenge by exploiting the coupling of the electron orbital motion to its spin, in particular Rashba spin-orbit coupling, have so far been unsuccessful. Recently, it has been shown theoretically that the confining potential of a small current-carrying wire with high intrinsic spin-orbit coupling leads to the accumulation of opposite spins at opposite edges of the wire, though not to a spin-polarized current. Here, we present experimental evidence that a quantum point contact -- a short wire -- made from a semiconductor with high intrinsic spin-orbit coupling can generate a completely spin-polarized current when its lateral confinement is made highly asymmetric. By avoiding the use of ferromagnetic contacts or external magnetic fields, such quantum point contacts may make feasible the development of a variety of semiconductor spintronic devices.
RESUMO
The submucosal connective tissue of the jejunum has been shown to be suitable for use as a vascular graft in preliminary dog studies. To partially characterize the mechanical properties of this new graft material, longitudinal stress (sigma)-strain (epsilon)-data were obtained on 13 specimens of canine jejunum, stripped of its mucosal and external smooth-muscle layers. The ratio of stress to strain is the modulus of elasticity (E). It was found that the stress sigma-strain epsilon-data fitted the expression sigma = K epsilon alpha very well. For a typical specimen sigma = 2.69 x 10(6) epsilon 2.33. The modulus of elasticity (E = sigma 1-1/alpha K1/alpha) was found to increase with increasing stress, ranging from about 2,000 to 9,000 mmHg. For the average specimen E = 573 sigma 0.57, where sigma is in mmHg, (1 mmHg = 133.3 Pascals).