Bulk Spin-Hall Effect

We show that a two-dimensional spin-orbit-coupled system in the presence of a charge/spin-density wave with a wave-vector perpendicular to an applied electric field supports bulk manifestations of the direct/inverse spin-Hall effect. We develop a theory of this phenomenon in the framework of the spin diffusion equation formalism and show that, due to the inhomogeneity created by a spin-grating, an anomalous bulk charge-density wave is induced away from sample boundaries. The optimal conditions for the observation of the effect are determined. The main experimental manifestation of the bulk spin-Hall effect, the induced charge/spin-density-wave, is characterized by a pi/2-phase shift relative to the initial non-homogeneous spin/charge-polarization profile and has a non-monotonic time-varying amplitude.Comment: 4 pages, 4 figure

Non-equilibrium spin dynamics in a trapped Fermi gas with effective spin-orbit interaction

We consider a trapped atomic system in the presence of spatially varying laser fields. The laser-atom interaction generates a pseudospin degree of freedom (referred to simply as spin) and leads to an effective spin-orbit coupling for the fermions in the trap. Reflections of the fermions from the trap boundaries provide a physical mechanism for effective momentum relaxation and non-trivial spin dynamics due to the emergent spin-orbit coupling. We explicitly consider evolution of an initially spin-polarized Fermi gas in a two-dimensional harmonic trap and derive non-equilibrium behavior of the spin polarization. It shows periodic echoes with a frequency equal to the harmonic trapping frequency. Perturbations, such as an asymmetry of the trap, lead to the suppression of the spin echo amplitudes. We discuss a possible experimental setup to observe spin dynamics and provide numerical estimates of relevant parameters.Comment: 5 pages, 4 figures; published versio

Nearest-neighbour Attraction Stabilizes Staggered Currents in the 2D Hubbard Model

Using a strong-coupling approach, we show that staggered current vorticity does not obtain in the repulsive 2D Hubbard model for large on-site Coulomb interactions, as in the case of the copper oxide superconductors. This trend also persists even when nearest-neighbour repulsions are present. However, staggered flux ordering emerges {\bf only} when attractive nearest-neighbour Coulomb interactions are included. Such ordering opens a gap along the $(\pi,0)-(0,\pi)$ direction and persists over a reasonable range of doping.Comment: 5 pages with 5 .eps files (Typos in text are corrected

Spin relaxation in a generic two-dimensional spin-orbit coupled system

We study the relaxation of a spin density injected into a two-dimensional electron system with generic spin-orbit interactions. Our model includes the Rashba as well as linear and cubic Dresselhaus terms. We explicitly derive a general spin-charge coupled diffusion equation. Spin diffusion is characterized by just two independent dimensionless parameters which control the interplay between different spin-orbit couplings. The real-time representation of the diffuson matrix (Green's function of the diffusion equation) is evaluated analytically. The diffuson describes space-time dynamics of the injected spin distribution. We explicitly study two regimes: The first regime corresponds to negligible spin-charge coupling and is characterized by standard charge diffusion decoupled from the spin dynamics. It is shown that there exist several qualitatively different dynamic behaviors of the spin density, which correspond to various domains in the spin-orbit coupling parameter space. We discuss in detail a few interesting phenomena such as an enhancement of the spin relaxation times, real space oscillatory dynamics, and anisotropic transport. In the second regime, we include the effects of spin-charge coupling. It is shown that the spin-charge coupling leads to an enhancement of the effective charge diffusion coefficient. We also find that in the case of strong spin-charge coupling, the relaxation rates formally become complex and the spin/charge dynamics is characterized by real time oscillations. These effects are qualitatively similar to those observed in spin-grating experiments [Weber et al., Nature 437, 1330 (2005)].Comment: 18 pages, 7 figure

Surface states, Friedel oscillations, and spin accumulation in p-doped semiconductors

We consider a hole-doped semiconductor with a sharp boundary and study the boundary spin accumulation in response to a charge current. First, we solve exactly a single-particle quantum mechanics problem described by the isotropic Luttinger model in half-space and construct an orthonormal basis for the corresponding Hamiltonian. It is shown that the complete basis includes two types of eigenstates. The first class of states contains conventional incident and reflected waves, while the other class includes localized surface states. Second, we consider a many-body system in the presence of a charge current flowing parallel to the boundary. It is shown that the localized states contribute to spin accumulation near the surface. We also show that the spin density exhibits current-induced Friedel oscillations with three different periods determined by the Fermi momenta of the light and heavy holes. We find an exact asymptotic expression for the Friedel oscillations far from the boundary. We also calculate numerically the spin density profile and compute the total spin accumulation, which is defined as the integral of the spin density in the direction perpendicular to the boundary. The total spin accumulation is shown to fit very well the simple formula S ~(1 - m_L/m_H)^2, where m_L and m_H are the light- and heavy-hole masses. The effects of disorder are discussed. We estimate the spin relaxation time in the Luttinger model and argue that spin physics cannot be described within the diffusion approximation.Comment: 22 pages, 8 color figure

New oral anticoagulants and their reversal agents

Atrial fibrillation is a commonly encountered pathology in medical practice, and its prevalence has shown a continuous rise over the past years. Atrial fibrillation has a significant impact on patients\u27 quality of life, not only due to the standard anticoagulant treatment with vitamin K antagonists that require close monitoring and dose adjustment, but also due to the fragile equilibrium between hemorrhagic and thrombotic risks. The introduction of new oral anticoagulants (NOACs) in the treatment guidelines for atrial fibrillation has improved the quality of life, as NOACs do not require close monitoring or dose adjustments. However, even if the safety profile of the NOACs regarding the hemorrhagic risk is superior to vitamin K antagonists, the problem raised by an unexpected hemorrhage (e.g. severe hemorrhage after an accident) and the need for efficient hemostasis in a chronic anticoagulated patient has remained unsolved. To find a solution for this problem, reversal agents for NOACs have been developed and tested, and two of them, idarucizumab and andexanet-alpha, have already been approved by the FDA, thus making NOACs increasingly appealing as a choice of anticoagulation treatment

Approaches and Directions for the Physiotherapeutic Management of Patients with “Duchenne” Muscular Dystrophy

Duchenne muscular dystrophy (DMD) affects cardiac and skeletal muscles but represents a condition that causes numerous secondary pathologies. Although there is no curative treatment available, multidisciplinary approaches, centered on the needs of the patient, improve the quality and duration of life. Therapies such as physiotherapy, occupational therapy, physical activities, and respiratory physiotherapy, but also the management of cardiac, osteo-muscular, and neuro-psychiatric manifestations, are continuously developing, (as new data becomes available) and are the key to DMD management today. These multidisciplinary approaches can lead to good long-term outcomes by helping patients with muscular dystrophy reduce muscle damage, early detect and treat heart failure, and manage cognitive impairment as best they can

Serious Games in Formal Education: Discussing Some Critical Aspects

International audienceInnovation in technology together with evolution in pedagogical approaches is encouraging increased integration of technology-supported interventions in mainstream teaching practices. One area attracting particularly close attention in this respect is Serious Games (SGs), which offer considerable potential for facilitating both formal and informal learning experiences in supported and standalone contexts. Advances in technology and in technology enhanced learning are raising learners' expectations for immersive and engaging game-based experiences. This trend is underpinned by the emergence of young learners adept at using digital technologies and the internet; there is an attendant risk that, as students, they may be alienated by traditional education and its failure to engage them fully in a lifelong learning process and prepare them adequately for the challenges of the 21st Century. SGs would appear to offer an attractive solution in this regard. However, there are a number of inhibitors preventing their wider take-up in mainstream education, with the result that the considerable potential on offer has yet to be fully exploited. This situation is the background for the joint efforts of partners in the Games and Learning Alliance (GALA), an EC-funded Network of Excellence on SGs, especially the sub-group dedicated to the pedagogical dimension of SGs. In its discussions on the key challenges for more wide-scale and effective SG use, the group has focused in particular on aspects related to the central role played by the educator in formal education settings. Specifically, discussion has focused on the challenges posed when educators are called on to modify their practice, adopting the new roles and approaches demanded for effective SG deployment. This paper presents the outcome of the group's exploration. It frames the question of the educator's central role by drawing on research work that, in the view of the different authors, embodies the major references for shedding light on this multi-faceted aspect. As well as the new role that the educator assumes in games-based learning environments, particular attention is also dedicated to the innovative pedagogical approaches that can be applied to SG deployment, especially those inspired by peer collaboration

Doppler velocimetry of spin propagation in a two-dimensional electron gas

Controlling the flow of electrons by manipulation of their spin is a key to the development of spin-based electronics. While recent demonstrations of electrical-gate control in spin-transistor configurations show great promise, operation at room temperature remains elusive. Further progress requires a deeper understanding of the propagation of spin polarization, particularly in the high mobility semiconductors used for devices. Here we report the application of Doppler velocimetry to resolve the motion of spin-polarized electrons in GaAs quantum wells driven by a drifting Fermi sea. We find that the spin mobility tracks the high electron mobility precisely as a function of T. However, we also observe that the coherent precession of spins driven by spin-orbit interaction, which is essential for the operation of a broad class of spin logic devices, breaks down at temperatures above 150 K for reasons that are not understood theoretically