Ferroelectric control of the spin texture in germanium telluride

The electrical manipulation of spins in semiconductors, without magnetic fields or auxiliary ferromagnetic materials, represents the holy grail for spintronics. The use of Rashba effect is very attractive because the k-dependent spin-splitting is originated by an electric field. So far only tiny effects in two-dimensional electron gases (2DEG) have been exploited. Recently, GeTe has been predicted to have bulk bands with giant Rashba-like splitting, originated by the inversion symmetry breaking due to ferroelectric polarization. In this work, we show that GeTe(111) surfaces with inwards or outwards ferroelectric polarizations display opposite sense of circulation of spin in bulk Rashba bands, as seen by spin and angular resolved photoemission experiments. Our results represent the first experimental demonstration of ferroelectric control of the spin texture in a semiconductor, a fundamental milestone towards the exploitation of the non-volatile electrically switchable spin texture of GeTe in spintronic devices.Comment: 18 pages, 4 figure

Cycle-based Symbolic Simulation of Gate Level Synchronous Circuits

Symbolic methods are often considered the state-of-the-art technique for validating digital circuits. Due to their complexity and unpredictable run-time behavior, however, their potential is currently limited to small-to-medium circuits. Logic simulation privileges capacity, it is nicely scalable, flexible, and it has a predictable run-time behavior. For this reason, it is the common choice for validating large circuits. Simulation, however, typically visits only a small fraction of the state space: The discovery of bugs heavily relies on the expertise of the designer of the test stimuli. In this paper we consider a symbolic simulation approach to the validation problem. Our objective is to trade-off between formal and numerical methods in order to simulate a circuit with a "very large number" of input combinations and sequences in parallel. We demonstrate larger capacity with respect to symbolic techniques and better efficiency with respect to cycle-based simulation. We show that it is possible to symbolically simulate very large trace sets in parallel (over 100 symbolic inputs) for the largest ISCAS benchmark circuits, using 96Mbytes of memory. 1

Cycle-based Symbolic Simulation of Synchronous Circuits

Symbolic methods are often considered the state-of-the-art technique for validating digital circuits. Due to their complexity and unpredictable run-time behavior, however, their potential is currently limited to small-to-medium circuits. Logic simulation privileges capacity, it is nicely scalable, flexible, and it has a predictable run-time behavior. For this reason, it is the common choice for validating large circuits. Simulation, however, typically visits only a small fraction of the state space. The discovery of bugs heavily relies on the expertise of the designer of the test stimuli. In this paper we consider a symbolic simulation approach to the validation problem. Our objective is to trade-off between formal and numerical methods in order to simulate a circuit with a "very large number" of input combinations and sequences in parallel. We demonstrate larger capacity with respect to symbolic techniques and better efficiency with respect to cycle-based simulation. We show that it is possible to symbolically simulate very large trace sets in parallel (over 100 symbolic inputs) for the largest ISCAS benchmark circuits, using 96 Mbytes of memor

Erdosteine enhances airway response to salbutamol in patients with mild-to-moderate COPD

Background: Oxidative stress is presumed to impair β-adenoceptor function and airway patency. Erdosteine (E), a mucomodulatory compound, has shown important antioxidant properties. Methods: The objective was to assess the effect of antioxidant interventions on short-term airway response to salbutamol in non-reversible mild-to-moderate COPD patients. Thirty COPD patients (GOLD class 1—2), current smoker (≥10 pack/year), randomly received E 300 mg, N-acetylcysteine (NAC) 600 mg, or placebo, twice daily for ten days. Reversibility to salbutamol 200 μg was tested in baseline, after four and ten days of each treatment. ROS and 8-isoprostane blood levels were measured on the same days. Between-treatment comparison was performed by ANOVA and t-test or Wilcoxon test, and p<0.05 assumed. E enhanced FEV1 reversibility after four and ten days significantly (+5.1% and +5.0%; both p<0.01 vs. placebo), while NAC only showed a transient effect at day 4 (+3.0%, p<0.05), but not at day 10 (+1.3%, p = ns). Results: E and NAC caused significant drops in ROS blood levels after four and ten days (p<0.001 and p<0.0001 vs. placebo). In contrast to NAC, E lowered 8-isoprostane levels substantially for ten days (p = 0.017 and p = 0.0004 vs. placebo, respectively). Only E restored significantly short-term reversibility in COPD patients previously unresponsive to β 2 -adrenergics. Conclusions: This effect seems more related to the peculiar protection against lipid peroxidation rather than to the scavenging activity, which proves equal to that of NAC. E provides a sort of indirect bronchodilation through 're-sensitisation' of β 2 -adrenoceptors. Once confirmed in further controlled studies, it may be useful in long-term treatment of COPD

Investigation of charge-to-spin conversion in GeTe

Spin-orbit coupling effects in materials with broken inversion symmetry are responsible for peculiar spin textures. Among them, ferroelectric materials allow for non-volatile control of the spin degree of freedom through the non-volatile electrical inversion of the spin texture, through to their reversible spontaneous polarization. Such functionality holds potential for technological applications exploiting spin effects controlled by electric fields. The ferroelectric Rashba semiconductor Germanium Telluride stands out as material for Spin-Orbitronics: its ferroelectricity provides a nonvolatile state variable able to generate and drive a giant bulk Rashba-type spin splitting of the electronic bands, while its semiconductivity would allow for the realization of spin-based transistors. The ferroelectric control of the bands topology and of the spin texture is expected to reflect in the tunability of the spin transport properties. Here we exploit the unidirectional spin Hall magnetoresistance of Fe/GeTe heterostructures to characterize charge-to-spin conversion in GeTe. Our preliminary results indicate a sizable conversion efficiency at low temperature (120 K), which promotes ferroelectric Rashba semiconductors as promising candidates for the implementation of non-volatile electrically reconfigurable computing devices based on spin transport in semiconductors

Ferroelectric Control of the Spin Texture in GeTe

The electric and nonvolatile control of the spin texture in semiconductors would represent a fundamental step toward novel electronic devices combining memory and computing functionalities. Recently, GeTe has been theoretically proposed as the father compound of a new class of materials, namely ferroelectric Rashba semiconductors. They display bulk bands with giant Rashba-like splitting due to the inversion symmetry breaking arising from the ferroelectric polarization, thus allowing for the ferroelectric control of the spin. Here, we provide the experimental demonstration of the correlation between ferroelectricity and spin texture. A surface-engineering strategy is used to set two opposite predefined uniform ferroelectric polarizations, inward and outward, as monitored by piezoresponse force microscopy. Spin and angular resolved photoemission experiments show that these GeTe(111) surfaces display opposite sense of circulation of spin in bulk Rashba bands. Furthermore, we demonstrate the crafting of nonvolatile ferroelectric patterns in GeTe films at the nanoscale by using the conductive tip of an atomic force microscope. Based on the intimate link between ferroelectric polarization and spin in GeTe, ferroelectric patterning paves the way to the investigation of devices with engineered spin configurations

Myeloid calcifying cells promote atherosclerotic calcification via paracrine activity and allograft inflammatory factor-1 overexpression

Several cell types contribute to atherosclerotic calcification. Myeloid calcifying cells (MCCs) are monocytes expressing osteocalcin (OC) and bone alkaline phosphatase (BAP). Herein, we tested whether MCCs promote atherosclerotic calcification in vivo. We show that the murine spleen contains OC(+)BAP(+) cells with a phenotype similar to human MCCs, a high expression of adhesion molecules and CD11b, and capacity to calcify in vitro and in vivo. Injection of GFP(+) OC(+)BAP(+) cells into 8- or 40-week ApoE(-/-) mice led to more extensive calcifications in atherosclerotic areas after 24 or 4 weeks, respectively, compared to control OC(-)BAP(-) cells. Despite that OC(+)BAP(+) cells had a selective transendothelial migration capacity, tracking of the GFP signal revealed that presence of injected cells within atherosclerotic areas was an extremely rare event and so GFP mRNA was undetectable by qPCR of lesion extracts. By converse, injected OC(+)BAP(+) cells persisted in the bloodstream and bone marrow up to 24 weeks, suggesting a paracrine effect. Indeed, OC(+)BAP(+) cell-conditioned medium (CM) promoted calcification by cultured vascular smooth muscle cells (VSMC) more than CM from OC(-)BAP(-) cells. A genomic and proteomic investigation of MCCs identified allograft inflammatory factor (AIF)-1 as a potential candidate of this paracrine activity. AIF-1 stimulated VSMC calcification in vitro and monocyte-specific (CD11b-driven) AIF-1 overexpression in ApoE(-/-) mice increased calcium content in atherosclerotic areas. In conclusion, we show that murine OC(+)BAP(+) cells correspond to human MCCs and promote atherosclerotic calcification in ApoE(-/-) mice, through paracrine activity and modulation of resident cells by AIF-1 overexpression