Universal Rashba Spin Precession of Two-Dimensional Electrons and Holes

We study spin precession due to Rashba spin splitting of electrons and holes in semiconductor quantum wells. Based on a simple analytical expression that we derive for the current modulation in a broad class of experimental situations of ferromagnet/nonmagnetic semiconductor/ferromagnet hybrid structures, we conclude that the Datta-Das spin transistor (i) is feasible with holes and (ii) its functionality is not affected by integration over injection angles. The current modulation shows a universal oscillation period, irrespective of the different forms of the Rashba Hamiltonian for electrons and holes. The analytic formulas approximate extremely well exact numerical calculations of a more elaborate Kohn--Luttinger model.Comment: 7 pages, 2 eps figures included, minor change

Static polarizability of two-dimensional hole gases

We have calculated the density-density (Lindhard) response function of a homogeneous two-dimensional (2D) hole gas in the static (omega=0) limit. The bulk valence-band structure comprising heavy-hole (HH) and light-hole (LH) states is modeled using Luttinger's kdotp approach within the axial approximation. We elucidate how, in contrast to the case of conduction electrons, the Lindhard function of 2D holes exhibits unique features associated with (i) the confinement-induced HH-LH energy splitting and (ii) the HH-LH mixing arising from the charge carriers' in-plane motion. Implications for the dielectric response and related physical observables are discussed.Comment: 11 pages, 3 figures, IOP latex style, v2: minor changes, to appear in NJ

Impact of a split injection strategy on mixing, ignition and combustion behavior in Premixed Charge Compression Ignition combustion

Mixing, ignition and combustion behavior in a rapid compression and expansion machine operated under Premixed Charge Compression Ignition (PCCI) relevant conditions are investigated by combined passive optical and laser-optical high-speed diagnostics. The PCCI concept is realized using a split injection schedule consisting of a long base load injection and two closely separated short injections near top dead center. Previous studies of close-coupled double injections under constant ambient conditions showed an increased penetration rate of the subsequent fuel spray. However, the aerodynamic gain from the preceding injection is counteracted by the density rise during the compression stroke under transient engine conditions. The study confirms that the rate of mixing of the subsequent fuel spray is significantly increased. Regarding combustion behavior, the thermodynamic analysis exhibits contributions of low temperature oxidation reactions of more than 20 % to the total heat release, with a notable amount of unburnt fuel mass varying from 25 to 61 %. The analysis of the optical data reveals the multi-dimensional impact of changes in operating parameters on the local mixture field and ignition dynamics. The onset of low temperature reactivity of the first short injection is found to be dominated by the operating strategy, while the location is strongly related to the local mixing state. Low temperature ignition of the consecutive fuel spray is significantly promoted, when upstream low temperature reactivity of the preceding injection is sustained. Likewise, it is shown that high temperature ignition is accelerated by the entrainment of persistent upstream low temperature reactivity

Statistical process control for improving healthcare processes. A case study in an Italian teaching hospital

This study aims to investigate the utility and potentialities of statistical process control for monitoring performances of healthcare organizations. We retrospectively applied the statistical process control for monitoring perioperative system performance, represented in this study by the operating room turnaround time. The results showed that the control charts are able to identify the steady-state behavior of the process and to detect improvements or deteriorations in process performance over tim

Time-variable 3D ground displacements from High-Resolution Synthetic Aperture Radar (SAR). Application to La Valette landslide (South French Alps).

International audienceWe apply an image correlation technique to multi-orbit and multi-temporal High-Resolution (HR) SAR data. Image correlation technique has the advantage of providing displacement maps in two directions; e.g. the Line of Sight direction (LoS) and the Azimuth direction. This information, derived from the two modes of data acquisition (ascending and descending), can be combined routinely to infer the three dimensional surface displacement field at different epochs. In this study, a methodology is developed to characterize the displacement pattern of the large La Valette landslide (South French Alps) using TerraSAR-X images acquired in 2010. The results allow mapping the dynamics of different units of the La Valette landslide at high spatial resolution. The study demonstrates the potential of this new application of High Resolution SAR image correlation technique for landslide ground surface deformation monitoring

The European Scleroderma Trials and Research group (EUSTAR) task force for the development of revised activity criteria for systemic sclerosis: derivation and validation of a preliminarily revised EUSTAR activity index

Background Validity of European Scleroderma Study Group (EScSG) activity indexes currently used to assess disease activity in systemic sclerosis (SSc) has been criticised. Methods Three investigators assigned an activity score on a 0–10 scale for 97 clinical charts. The median score served as gold standard. Two other investigators labelled the disease as inactive/moderately active or active/very active. Univariate–multivariate linear regression analyses were used to define variables predicting the ‘gold standard’, their weight and derive an activity index. The cut-off point of the index best separating active/very active from inactive/moderately active disease was identified by a receiver-operating curve analysis. The index was validated on a second set of 60 charts assessed by three different investigators on a 0–10 scale and defined as inactive/moderately active or active/very active by other two investigators. One hundred and twenty-three were investigated for changes over time in the index and their relationships with those in the summed Medsger severity score (MSS). Results A weighted 10-point activity index was identified and validated: Δ-skin=1.5 (Δ=patient assessed worsening during the previous month), modified Rodnan skin score (mRss) \u3e18=1.5, digital ulcers=1.5, tendon friction rubs=2.25, C-reactive protein \u3e1 mg/dL=2.25 and diffusing capacity of the lung for CO (DLCO) % predicted \u3c70%=1.0. A cut-off ≥2.5 was found to identify patients with active disease. Changes in the index paralleled those of MSS (p=0.0001). Conclusions A preliminarily revised SSc activity index has been developed and validated, providing a valuable tool for clinical practice and observational studies

Nucleation of Ergodicity by a Single Mobile Impurity in Supercooled Insulators

We consider a disordered Hubbard model and show that, at sufficiently weak disorder, a single spin-down mobile impurity can thermalize an extensive initially localized system of spin-up particles. Thermalization is enabled by resonant processes that involve correlated hops of the impurity and localized particles. This effect indicates that Anderson localized insulators behave as “supercooled” systems, with mobile impurities acting as ergodic seeds. We provide analytical estimates, supported by numerical exact diagonalization, showing how the critical disorder strength for such mechanism depends on the particle density of the localized system. In the U→∞ limit, doublons are stable excitations, and they can thermalize mesoscopic systems by a similar mechanism. The emergence of an additional conservation law leads to an eventual localization of doublons. Our predictions apply to fermionic and bosonic systems and are readily accessible in ongoing experiments simulating synthetic quantum lattices with tunable disorder