Spin-current amplification by stimulated spin pumping

Stimulated emission is a process during which an atomic system gives away energy to create a coherent photon. It is fundamental to the operation of the optical amplifier. Here we propose two mechanisms for amplifying AC spin currents in a solid-state magnetic medium by a stimulated spin pumping process. The first is synchronous and consists of phase-locked pulses that perturb a precessing magnetic moment. The second is asynchronous and is driven by DC spin currents. The amplification relies on a non-adiabatic interaction taking place in a ferromagnetic medium in which the magnetic moment emits spin angular momentum in the form of spin current before equilibrating with the environment. The pumped spin current amplifies or absorbs the injected AC spin current mimicking the operation of the optical gain medium as readily seen from the gain saturation profiles. The mechanisms we propose are a first step towards a realistic spin current amplifier.Comment: 17 pages, 4 figure

The Ferris ferromagnetic resonance technique: principles and applications

Measurements of ferromagnetic resonance (FMR) are pivotal to modern magnetism and spintronics. Recently, we reported on the Ferris FMR technique, which relies on large-amplitude modulation of the externally applied magnetic field. It was shown to benefit from high sensitivity while being broadband. The Ferris FMR also expanded the resonance linewidth such that the sensitivity to spin currents was enhanced as well. Eventually, the spin Hall angle ({\theta}_SH) was measurable even in wafer-level measurements that require low current densities to reduce the Joule heating. Despite the various advantages, analysis of the Ferris FMR response is limited to numerical modeling where the linewidth depends on multiple factors such as the field modulation profile and the magnetization saturation. Here, we describe in detail the basic principles of operation of the Ferris FMR and discuss its applicability and engineering considerations. We demonstrated these principles in a measurement of the orbital Hall effect taking place in Cu, using an Au layer as the orbital to spin current converter. This illustrates the potential of the Ferris FMR for the future development of spintronics technology

Efficient generation of spin currents by the Orbital Hall effect in pure Cu and Al and their measurement by a Ferris-wheel ferromagnetic resonance technique at the wafer level

We present a new ferromagnetic resonance (FMR) method that we term the Ferris FMR. It is wideband, has significantly higher sensitivity as compared to conventional FMR systems, and measures the absorption line rather than its derivative. It is based on large-amplitude modulation of the externally applied magnetic field that effectively magnifies signatures of the spin-transfer torque making its measurement possible even at the wafer-level. Using the Ferris FMR, we report on the generation of spin currents from the orbital Hall effect taking place in pure Cu and Al. To this end, we use the spin-orbit coupling of a thin Pt layer introduced at the interface that converts the orbital current to a measurable spin current. While Cu reveals a large effective spin Hall angle exceeding that of Pt, Al possesses an orbital Hall effect of opposite polarity in agreement with the theoretical predictions. Our results demonstrate additional spin- and orbit- functionality for two important metals in the semiconductor industry beyond their primary use as interconnects with all the advantages in power, scaling, and cost

Ajout de kétamine dans les PCA d’opiacés: une revue systématique avec meta-analyses

La kétamine est souvent utilisée en postopératoire comme adjuvant d’opiacés dans l’antalgie contrôlée par le patient (PCA = patient controlled analgesia). Les bénéfices et risques de cette adjonction restent indéterminés. L’objectif de cette revue systématique et méta-analyse est de définir l’impact clinique de l’adjonction de kétamine sur l’intensité de la douleur, la consommation cumulée de morphine, l’incidence des nausées et vomissements postopératoires (NVPO), les évènements indésirables respiratoires et le risque d’hallucination. La recherche systématique dans les bases de données (Medline, Embase, Cochrane) a permis de sélectionner 19 études randomisées. Après méta-analyses, nos résultats mettent en évidence dans le groupe kétamine, un effet bénéfique sur l’intensité de la douleur, la consommation d’opiacés et l’incidence de NVPO. Le risque d’hallucination n’est pas augmenté et l’effet sur les évènements respiratoires indésirables reste incertain. La fiabilité de ces résultats est confirmée par les analyses « TSA » (trial sequential analyses)

Extracorporeal membrane oxygenation in COVID-19 associated acute respiratory distress syndrome: A narrative review

Venovenous extracorporeal membrane oxygenation (VV-ECMO) is an established rescue therapy in the management of refractory acute respiratory distress syndrome (ARDS). Although ECMO played an important role in previous respiratory viral epidemics, concerns about the benefits and usefulness of this technique were raised during the coronavirus disease 2019 (COVID-19) pandemic. Indeed, the mortality rate initially reported in small case series from China was concerning and exceeded 90%. A few months later, the critical care community published the findings from several observational cohorts on the use of extracorporeal membrane oxygenation (ECMO) in COVID-19-related ARDS. Contrary to the preliminary results, data from the first surge supported the use of ECMO in experienced centers because the mortality rate was comparable to those from the ECMO to Rescue Lung Injury in Severe ARDS (EOLIA) trial or other large prospective studies. However, the mortality rate of the population with severe disease evolved during the pandemic, in conjunction with changes in the management of the disease and the occurrence of new variants. The results from subsequent studies confirmed that the outcomes mainly depend on strict patient selection and center expertise. In comparison with non-COVID-related ARDS, the duration of ECMO for COVID-related ARDS was longer and increased over time. Clinicians and decision-makers must integrate this finding in the ECMO decision-making process to plan their ICU capacity and resource allocation. This narrative review summarizes the current evidence and specific considerations for ECMO use in COVID-19-associated ARDS

Extremely high-dose insulin requirement in a diabetic patient with COVID-19: a case report

Detailed description of hyperglycemia management in diabetic patients infected with SARS-CoV-2 remain limited, although patients with diabetes show higher complication and mortality rate than patients without diabetes. Transient non-severe increased insulin requirement in patients hospitalized for medical conditions such as sepsis or myocardial infarction is a well-known phenomenon. However, extremely high-dose insulin requirement remains a very rarely reported entity. Here, we report the case of an extreme and transitory insulin requirement episode in a type 2 diabetic patient presenting an acute respiratory distress syndrome caused by SARS-CoV-2