Interferometric Investigation of Liquid Thin Film Meniscus

Indagine interferometrica per misurare il profilo di curvatura di un sottile menisco di ottano su una superficie liscia di silicone. Progettazione di una camera per studiare microscopicamente la curvatura dell’interfaccia liquido-solido, con l'obiettivo di verificare sperimentalmente l’accuratezza e la ripetibilità dell’analisi interferometrica per raggiungere risultati consistenti nelle misurazioni di curvatura.openEmbargo temporaneo per motivi di segretezza e/o di proprietà dei risultati e/o informazioni sensibil

History of migraine and volume of brain infarcts: The italian project on stroke at young age (IPSYS)

BACKGROUND AND PURPOSE: Migraine has been shown to increase cerebral excitability, promote rapid infarct expansion into tissue with perfusion deficits, and result in larger infarcts in animal models of focal cerebral ischemia. Whether these effects occur in humans has never been properly investigated. METHODS: In a series of consecutive patients with acute ischemic stroke, enrolled in the setting of the Italian Project on Stroke at Young Age, we assessed acute as well as chronic infarct volumes by volumetric magnetic resonance imaging, and compared these among different subgroups identified by migraine status. RESULTS: A cohort of 591 patients (male, 53.8%; mean age, 37.5±6.4 years) qualified for the analysis. Migraineurs had larger acute infarcts than non-migraineurs (median, 5.9 cm3 [interquartile range (IQR), 1.4 to 15.5] vs. 2.6 cm3 [IQR, 0.8 to 10.1], P<0.001), and the largest volumes were observed in patients with migraine with aura (median, 9.0 cm3 [IQR, 3.4 to 16.6]). In a linear regression model, migraine was an independent predictor of increased log (acute infarct volumes) (median ratio [MR], 1.64; 95% confidence interval [CI], 1.22 to 2.20), an effect that was more prominent for migraine with aura (MR, 2.92; 95% CI, 1.88 to 4.54). CONCLUSION: s These findings reinforce the experimental observation of larger acute cerebral infarcts in migraineurs, extend animal data to human disease, and support the hypothesis of increased vulnerability to ischemic brain injury in people suffering migraine

High Risk of Secondary Infections Following Thrombotic Complications in Patients With COVID-19

Background. This study’s primary aim was to evaluate the impact of thrombotic complications on the development of secondary infections. The secondary aim was to compare the etiology of secondary infections in patients with and without thrombotic complications. Methods. This was a cohort study (NCT04318366) of coronavirus disease 2019 (COVID-19) patients hospitalized at IRCCS San Raffaele Hospital between February 25 and June 30, 2020. Incidence rates (IRs) were calculated by univariable Poisson regression as the number of cases per 1000 person-days of follow-up (PDFU) with 95% confidence intervals. The cumulative incidence functions of secondary infections according to thrombotic complications were compared with Gray’s method accounting for competing risk of death. A multivariable Fine-Gray model was applied to assess factors associated with risk of secondary infections. Results. Overall, 109/904 patients had 176 secondary infections (IR, 10.0; 95% CI, 8.8–11.5; per 1000-PDFU). The IRs of secondary infections among patients with or without thrombotic complications were 15.0 (95% CI, 10.7–21.0) and 9.3 (95% CI, 7.9–11.0) per 1000-PDFU, respectively (P = .017). At multivariable analysis, thrombotic complications were associated with the development of secondary infections (subdistribution hazard ratio, 1.788; 95% CI, 1.018–3.140; P = .043). The etiology of secondary infections was similar in patients with and without thrombotic complications. Conclusions. In patients with COVID-19, thrombotic complications were associated with a high risk of secondary infections

Dépasser la limite de stabilité thermique avec des alliages chalcogénure innovants pour les applications des mémoires à changement de phase embarquées

La présente thèse vise à explorer les propriétés et à évaluer le potentiel de films minces innovants à base de chalcogénures pour de futures applications de mémoire à changement de phase (PCM) embarquée nécessitant une rétention des données à haute température. Les films étudiés, déposés par pulvérisation cathodique, sont les alliages GeSe1-xTex, situés sur la ligne pseudo-binaire GeSe-GeTe. Le manuscrit est divisé en cinq chapitres. Le chapitre 1 présente les technologies et le marché des mémoires et les limites actuelles et décrit le contexte pour le développement des mémoires émergentes. Le principe de fonctionnement des PCM est décrit en détail, en mettant l'accent sur le lien entre les performances des dispositifs et les propriétés des matériaux à changement de phase. Une attention particulière est accordée aux exigences des applications PCM embarquées. Les matériaux à changement de phase les plus connus, à savoir GeTe et Ge2Sb2Te5 (GST225), leur structure cristalline et leurs propriétés en relation avec les performances des dispositifs mémoire sont présentés. Le mécanisme de la liaison métavalente et les propriétés des matériaux métavalents sont ensuite présentés. L'utilisation d'alliages GST riches en Ge comme stratégie pour améliorer la stabilité thermique dans les applications PCM embarquées est décrite, ainsi que le rôle bénéfique du dopage N dans ces alliages. Un état des lieux de la littérature sur les alliages de GeSe1-xTex est ensuite présenté, avec un accent particulier sur la structure de leur phase cristalline. Le chapitre 2 présente les techniques expérimentales utilisées pour caractériser les couches minces de GeSe1-xTex. Elles sont regroupées en fonction du mécanisme physique sur lequel elles sont basées: mesures de résistivité électrique en fonction de la température, techniques de caractérisation optique, microscopie électronique à balayage, analyse par diffraction des rayons X et techniques de mesures de composition par faisceaux d'ions. Le chapitre 3 présente tout d'abord le principe de la méthode de dépôt par pulvérisation cathodique. Cette technique de dépôt offre la possibilité d'explorer facilement une large gamme de compositions et de produire des films d'épaisseur nanométrique, de l'ordre de grandeur de l’épaisseur des films intégrés dans les mémoires. Plusieurs films minces GeSe1-xTex, avec x variant de 0 à 1, ont été déposés par co-pulvérisation magnétron de cibles GeTe et GeSe pures dans des outils de pulvérisation industriels. De l'azote a également été incorporé dans les films GeSe1-xTex. Les équipements de pulvérisation, les paramètres de dépôt et le processus d'élaboration sont décrits dans ce chapitre. Une liste des échantillons déposés et de leur composition est également fournie. Le chapitre 4 est consacré à la caractérisation expérimentale des films minces de GeSe1-xTex. L'évolution de leurs propriétés physiques et de leur structure cristalline avec la concentration en Te est étudiée. Leur stabilité thermique, leur comportement résistif, ainsi que le contraste optique et électrique entre les états cristallin et amorphe sont étudiés. La phase cristalline des films minces GeSe1-xTex est analysée par diffraction des rayons X (XRD) à température ambiante et en fonction de la température, ainsi que par des mesures de spectroscopie RAMAN à température ambiante. Les résultats obtenus sont discutés et comparés à l'état de l'art et aux résultats de la littérature publiés au cours de la thèse. L'étude de l'incorporation d'azote dans les films minces GeSe1-xTex est présentée dans le chapitre 5, en se concentrant sur l'influence de N sur les propriétés de changement de phase et la structure des films. La première intégration de films GeSe1-xTex dopés à l'azote et non dopés dans des véhicules de test PCM industriels du CEA-LETI est présentée dans la deuxième partie du chapitre. Quelques caractérisations électriques préliminaires dans le dispositif sont également rapportées.The present thesis aims at exploring the properties and evaluate the potential of innovative chalcogenide thin films for future embedded phase-change memory (PCM) applications requiring high-temperature data retention. The investigated films, deposited by sputtering technique, are the GeSe1-xTex alloys, located on the GeSe-GeTe pseudo-binary line. The manuscript is structured in 5 chapters. Chapter 1 presents the memory technology market and its current limitations, providing the context for the development of emerging memories. The working principle of a PCM is described in details, focusing on the link between device performance and phase-change material properties. Particular attention is given to the embedded PCM application requirements. The most known phase-change materials, i.e. GeTe and Ge2Sb2Te5 (GST225), their crystalline structure and properties in relation to device performances are presented. The mechanism of metavalent bonding (MVB) and the properties of MVB materials are then introduced. The use of Ge-rich GST alloys as a strategy to improve thermal stability in embedded PCM applications is discussed, together with the beneficial role of N doping in these alloys. A state of the art of the literature on chalcogenide GeSe1-xTex alloys is then provided, with particular emphasis on the structure of their crystalline phase. In chapter 2, the experimental techniques used to characterize GeSe1-xTex thin films are presented. They are grouped according to the physical mechanism on which they are based: electrical resistivity measurements as a function of temperature, optical characterization techniques, scanning electron microscopy, X-ray analysis and composition measurements by ion beam techniques. Chapter 3 is devoted to the sample synthesis. It first presents the principle of the sputtering deposition method. This deposition technique offers the possibility to easily explore a wide range of compositions and produce films with nanometer thicknesses on the order of those integrated in memory devices. Several GeSe1-xTex thin films, with x varying from 0 to 1, were deposited by magnetron co-sputtering of pure GeTe and GeSe targets in industrial sputtering tools. Nitrogen was also incorporated in GeSe1-xTex films. The sputtering equipment, the deposition parameters and the elaboration process are described in this chapter. A list of the deposited samples and their composition is also provided. Chapter 4 is devoted to the experimental characterization of GeSe1-xTex thin films. The evolution of their physical properties and crystalline structure with Te concentration is investigated. The study of their thermal stability and resistive behavior is reported, as well as the optical and electrical contrast between the crystalline and amorphous states. The crystalline phase of GeSe1-xTex thin films is analyzed by room temperature and temperature-resolved X-ray diffraction (XRD), as well as room-temperature RAMAN spectroscopy measurements. The obtained results are discussed and compared with the state of the art and literature results published during the thesis. The study of nitrogen incorporation in GeSe1-xTex thin films is provided in chapter 5, focusing on the influence of N on the phase-change properties and structure of the films. The first integration of N-doped and undoped GeSe1-xTex films in PCM memory test vehicles of CEA-LETI is presented in the second part of the chapter. The choice of compositions to be integrated is discussed and the issues encountered during the integration process are highlighted. Some preliminary electrical characterizations in device are also reported. Finally, the Conclusions and the Perspectives of this work are presented

Interferometric Investigation of Liquid Thin Film Meniscus

Indagine interferometrica per misurare il profilo di curvatura di un sottile menisco di ottano su una superficie liscia di silicone. Progettazione di una camera per studiare microscopicamente la curvatura dell’interfaccia liquido-solido, con l'obiettivo di verificare sperimentalmente l’accuratezza e la ripetibilità dell’analisi interferometrica per raggiungere risultati consistenti nelle misurazioni di curvatura

Overcoming the Thermal Stability Limit of Chalcogenide Phase‐Change Materials for High‐Temperature Applications in GeSe 1− x Te x Thin Films

International audienceThe electrical, optical, and structural properties of GeSe1−xTex phase‐change materials thin films with 0.16 ≤ x ≤1 prepared by cosputtering of GeSe and GeTe targets are studied. The crystallization temperature of the films increases significantly when the Te content decreases. Se‐rich films show an extremely large electrical contrast between their amorphous and crystalline states. A high polarizability of the crystalline phase is observed in the entire x range and is related to the presence of metavalent bonds. This is explained by the persistence of a rhombohedral crystalline phase, isostructural to GeTe, in the GeSe1−xTex films down to x = 0.16. Hence, the substitution of only 16 at% of the Se atoms by Te atoms transforms the covalent GeSe into a phase‐change material with a huge and unprecedented contrast of resistivity (up to 11 orders of magnitude) and a very high thermal stability (up to 10 years at 272 °C) for an alloy exhibiting no phase separation upon crystallization. This outstanding combination of properties makes Se‐rich GeSe1−xTex thin films extremely promising for integration in memory devices requiring a very high data retention such as automotive and embedded applications

Robot-assisted stair climbing training and conventional physiotherapy in chronic stroke patients. A preliminary comparison

Introduction: Stair-climbing up and down is an essential part of everyday\u2019s mobility. Physiotherapy focuses on strengthening, real in terms of intensity stair-climbing practice. The present work aims at a comparison whether an intensive robot-assisted stair climbing training (RASCT) is more effective than conventional physiotherapy (CP) for improving stair climbing ability and gait in stroke patients. Material and Methods: Ten patients were randomly assigned to RASCT(n = 5) or CP(n = 5) group. Patients underwent ten - utive weeks either RASCT or CP. The primary outcome was the Berg Balance Scale (BBS), Time Up and Go Test (TUG), 10-Meter - muscles were also assessed before and after treatment. Results: At enrolment no differences were found between RASCT and CP for all outcomes. After the intervention improvements were found for in the RASCT group, but not for the CP group. Improvements were more physiological muscle activation in RASCT group (5 lower - served. Conclusion: RASCT may reduce the time required to climbing up and down the stairs. A larger sample is required to reveal the superiority of one approach rather than another one

Optical Properties of GeSe 1 −x Te x Chalcogenide Materials Promising for on‐Chip Low and Ultra‐Low Loss Reconfigurable Photonics and Nonlinear Devices

International audienceThe highly promising linear and nonlinear optical properties of innovative thin films of GeSe 1– x Te x chalcogenide materials in the amorphous as‐deposited state, and after crystallization, are revealed here. These innovative alloys bridge the gap between two families of materials: chalcogenide glasses (GeSe) and phase‐change materials (GeTe). Their unique optical properties make them attractive candidates for reconfigurable and nonlinear photonic applications in the infrared. In this context, it is shown how, by varying the Te content of GeSe 1– x Te x thin films, it is possible to tailor their linear and nonlinear optical properties to optimize them for a wide range of innovative applications

Training robot-assistito dell \u2019esecuzione delle scale e del cammino per il recupero dell\u2019 abilit\ue0 ad eseguire le scale e del cammino in pazienti affetti da ictus cronico: studio pilota randomizzato controllato

Introduction. Stair-climbing up and down is an essential part of everyday\u2019s mobility. Physiotherapy focuses on strengthening, stress in terms of intensity stair-climbing practice. Objectives. To compare whether an intensive robot-assisted stair climbing train- (CP) for improving stair climbing ability and gait in stroke patients. Materials and methods. A pilot randomized clinical trial. Patients received RASCT or CP, ten 45-minute treatment sesup and down time to accomplish 9 stairs, Berg Balance Scale (BBS), Time Up and Go Test (TUG), 10-Meter Walking Test - worth Scale, and the electromyography of eight lower limb muscles were assessed before and after treatment. Results. Ten patients were randomly assigned to the RASCT (n=5) or were found in both groups in TUG (P=0.04; P=0.04), 10MWT (P=0.04; P=0.04) and Gait speed (p=0.04; 0.04). After treatment the 6MWT(P= 0.04) and a greater improvements in stair climbing up and down ability (P=0.06). After training, more physiological muscles activation was found. Conclusions. RASCT protocol is feasible and might improve gait and stair climbing ability in chronic stroke patients. A larger sample is required to reveal the superiority of one approach rather than with another on

Nanocomposites of chalcogenide phase-change materials: from C-doping of thin films to advanced multilayers

International audienceEngineering of chalcogenide phase-change materials at the nanoscale is required to improve the performances of ultimate size memory devices and reduce their power consumption. Amorphous C-doped GeTe thin films and innovative multilayers consisting of periodic stacks of a few nm thick GeTe, or Ge$_2$Sb$_2$Te$_5$, and C layers with a thickness between 0.5 and 2 nm are deposited by magnetron sputtering at room temperature. The phase-change material is then crystallized by heat treatment. In C-doped GeTe films, the phase separation of C and GeTe during the GeTe crystallization leads to the spontaneous formation of a nanocomposite, consisting of amorphous C located at the grain boundaries of GeTe crystallites, but the resulting nanostructure is highly disordered. In contrast, the deposition of multilayers allows control of the nanostructure and the interfaces between the phase-change material and the C phase. Transmission electron microscopy and X-ray diffraction at room temperature and as a function of temperature during annealing show that the multilayer structure is maintained after crystallization of the phase-change material, even when the thickness of the C layer is as low as 0.5 nm. GeTe and Ge$_2$Sb$_2$Te$_5$ crystallites are anisotropic, their size in the direction perpendicular to the layers being determined by the design of the multilayer. The crystallisation temperature of the GeTe and Ge2Sb2Te5 layers depends on the structure of the stack, revealing scaling and stress effects. The results presented show that GeTe/C and Ge$_2$Sb$_2$Te$_5$/C MLs are promising for applications in memory devices and also in photonic and thermoelectric devices