Chiral damping of magnetic domain walls

Structural symmetry breaking in magnetic materials is responsible for a variety of outstanding physical phenomena. Examples range from the existence of multiferroics, to current induced spin orbit torques (SOT) and the formation of topological magnetic structures. In this letter we bring into light a novel effect of the structural inversion asymmetry (SIA): a chiral damping mechanism. This phenomenon is evidenced by measuring the field driven domain wall (DW) motion in perpendicularly magnetized asymmetric Pt/Co/Pt trilayers. The difficulty in evidencing the chiral damping is that the ensuing DW dynamics exhibit identical spatial symmetry to those expected from the Dzyaloshinskii-Moriya interaction (DMI). Despite this fundamental resemblance, the two scenarios are differentiated by their time reversal properties: while DMI is a conservative effect that can be modeled by an effective field, the chiral damping is purely dissipative and has no influence on the equilibrium magnetic texture. When the DW motion is modulated by an in-plane magnetic field, it reveals the structure of the internal fields experienced by the DWs, allowing to distinguish the physical mechanism. The observation of the chiral damping, not only enriches the spectrum of physical phenomena engendered by the SIA, but since it can coexists with DMI it is essential for conceiving DW and skyrmion devices

Randomly organized and self-assembled Na0.5Bi0.5TiO3 nanodots elaborated by sol-gel and pulsed laser deposition routes

International audienceThis work reports for the first time on the elaboration, by both chemical (sol-gel) and physical (pulsed laser deposition) routes, of lead-free ferroelectric Na0.5Bi0.5TiO3 nanodots deposited on bare c-sapphire single crystal substrates presenting a 5° miscut angle along the [110] direction. Prior to any deposition, the sapphire substrates were treated at 1350 °C, during 24 h in air, in order to increase the height of the surface steps, reaching by this way ~8 nm. The experimental parameters adjusted for the growth of Na0.5Bi0.5TiO3 dots were the concentration of sols and the number of laser pulses (50 and 100) for the sol-gel and pulsed laser deposition routes, respectively. Whereas the sol-gel route leads to randomly organized Na0.5Bi0.5TiO3 nanodots in respect to the surface steps, the pulsed laser deposition route provokes the self-assembly for some important proportion of these dots along the same surface steps. Despite the lack of organization for the sol-gel dots, the latter present a much more regular distribution in size (~100 and ~10-20 nm as an average lateral dimensions and height, respectively) compared to dots deposited by laser ablation, where three different populations of grains can be observed. In each case, the dots do not seem to be epitaxially grown

Performance prediction and assessment of reusability and recycling of refractory materials using the NDT sensoring approach and Machine Learning

Refractory materials are necessary for the Iron and Steel (I&S) sector to endure the demanding conditions of its manufacturing processes. These materials' brief service lives, which can range from a few minutes to several months, create substantial problems for consumption, disposal, and environmental effect. There is a rising need for sustainable solutions that are compliant with the European Green Deal's standards for reduced greenhouse gas emissions, increased energy efficiency, and life cycle assessments. The Concerted European Activity on Sustainable Applications of REFractories (Doctoral Network CESAREF), which aims to enhance research and practices linked to refractory material in the Iron & Steel industry, was founded in 2022 to address these concerns

Epitaxial growth and properties of lead-free ferroelectric Na0.5Bi0.5TiO3 thin films grown by pulsed laser deposition on various single crystal substrates

International audienceThe epitaxial growth of lead-free ferroelectric Na0.5Bi0.5TiO3 (NBT) thin films on various single crystal substrates was successfully achieved, using the pulsed laser deposition technique (PLD). The present work is divided in two parts, focused on: (i) the growth of NBT layers on c- and r-sapphire (Al2O3) substrates, with and without introducing a CeO2 buffer layer, and (ii) the growth of NBT layers on bare (001)SrTiO3 substrates, with and without introducing a LaNiO3 layer, that could be used as a bottom electrode. In the first part, it was shown that the introduction of a CeO2 buffer layer completely modifies the out-of-plane growth orientation of the NBT films, as well as their microstructure. Indeed, (001)NBT films epitaxially grow only on r-Al2O3 substrates buffered with epitaxial (001)CeO2 layers, while, growing simply NBT on top of bare c or r-Al2O3 substrates, or on top of CeO2/c-Al2O3 heterostructures leads to polycrystalline or textured films. In the second part, we demonstrate that (001)-oriented NBT layers deposited on either bare (001)SrTiO3 or (001)SrTiO3 substrates (STO) covered with (001)LaNiO3 (LNO) are systematically epitaxially grown. Furthermore, the microstructure of the samples is strongly affected by the introduction of the LaNiO3 layer

Mechanical response of UO2 single crystals submitted to low-energy ion irradiation

International audience{111}- and {100}-oriented UO2 single crystals were irradiated with 500-keV Ce3+ ions in the 1014 - 9x1014 cm-2 fluence range. The irradiation-induced strain was monitored using high-resolution X-ray diffraction. A mechanical modelling dedicated to thin irradiated layers was applied to account for the reaction of the unirradiated part of the crystals. The elastic strain, which is confined along the surface normal of the samples, increases with ion fluence until it is dramatically relieved. This behaviour is observed for both orientations. While the measured elastic strain depends on the crystallographic direction, the strain due to irradiation defects only is found to be equal for both directions, with a maximum value of ∼0.5%. Strain relaxation takes place at the damage peak, but the in-plane lattice parameter of the irradiated layer remains unchanged and equal to that of the pristine material. Meanwhile, the strain at the damaged/pristine interface continues to increase

Relationship between ventilator-associated pneumonia and mortality in COVID-19 patients: a planned ancillary analysis of the coVAPid cohort

Background Patients with SARS-CoV-2 infection are at higher risk for ventilator-associated pneumonia (VAP). No study has evaluated the relationship between VAP and mortality in this population, or compared this relationship between SARS-CoV-2 patients and other populations. The main objective of our study was to determine the relationship between VAP and mortality in SARS-CoV-2 patients. Methods Planned ancillary analysis of a multicenter retrospective European cohort. VAP was diagnosed using clinical, radiological and quantitative microbiological criteria. Univariable and multivariable marginal Cox's regression models, with cause-specific hazard for duration of mechanical ventilation and ICU stay, were used to compare outcomes between study groups. Extubation, and ICU discharge alive were considered as events of interest, and mortality as competing event. Findings Of 1576 included patients, 568 were SARS-CoV-2 pneumonia, 482 influenza pneumonia, and 526 no evidence of viral infection at ICU admission. VAP was associated with significantly higher risk for 28-day mortality in SARS-CoV-2 group (adjusted HR 1.65 (95% CI 1.11-2.46), p = 0.013), but not in influenza (1.74 (0.99-3.06), p = 0.052), or no viral infection groups (1.13 (0.68-1.86), p = 0.63). VAP was associated with significantly longer duration of mechanical ventilation in the SARS-CoV-2 group, but not in the influenza or no viral infection groups. VAP was associated with significantly longer duration of ICU stay in the 3 study groups. No significant difference was found in heterogeneity of outcomes related to VAP between the 3 groups, suggesting that the impact of VAP on mortality was not different between study groups. Interpretation VAP was associated with significantly increased 28-day mortality rate in SARS-CoV-2 patients. However, SARS-CoV-2 pneumonia, as compared to influenza pneumonia or no viral infection, did not significantly modify the relationship between VAP and 28-day mortality

a retrospective multicenter study

Funding This study was supported in part by a grant from the French government through the « Programme Investissement d’Avenir» (I-SITE ULNE) managed by the Agence Nationale de la Recherche (coVAPid project). Prof. Ignacio Martin-Loeches has been supported by SFI (Science Foundation Ireland), Grant number 20/COV/0038. The funders of the study had no role in the study design, data collection, analysis or interpretation, writing of the report or deci sion to submit for publication.BACKGROUND: Ventilator-associated pneumonia (VAP) is common in patients with severe SARS-CoV-2 pneumonia. The aim of this ancillary analysis of the coVAPid multicenter observational retrospective study is to assess the relationship between adjuvant corticosteroid use and the incidence of VAP. METHODS: Planned ancillary analysis of a multicenter retrospective European cohort in 36 ICUs. Adult patients receiving invasive mechanical ventilation for more than 48 h for SARS-CoV-2 pneumonia were consecutively included between February and May 2020. VAP diagnosis required strict definition with clinical, radiological and quantitative microbiological confirmation. We assessed the association of VAP with corticosteroid treatment using univariate and multivariate cause-specific Cox's proportional hazard models with adjustment on pre-specified confounders. RESULTS: Among the 545 included patients, 191 (35%) received corticosteroids. The proportional hazard assumption for the effect of corticosteroids on the incidence of VAP could not be accepted, indicating that this effect varied during ICU stay. We found a non-significant lower risk of VAP for corticosteroid-treated patients during the first days in the ICU and an increased risk for longer ICU stay. By modeling the effect of corticosteroids with time-dependent coefficients, the association between corticosteroids and the incidence of VAP was not significant (overall effect p = 0.082), with time-dependent hazard ratios (95% confidence interval) of 0.47 (0.17-1.31) at day 2, 0.95 (0.63-1.42) at day 7, 1.48 (1.01-2.16) at day 14 and 1.94 (1.09-3.46) at day 21. CONCLUSIONS: No significant association was found between adjuvant corticosteroid treatment and the incidence of VAP, although a time-varying effect of corticosteroids was identified along the 28-day follow-up.publishersversionpublishe

a planned ancillary analysis of the coVAPid cohort

Funding: This study was supported in part by a grant from the French government through the «Programme Investissement d’Avenir» (I-SITE ULNE) managed by the Agence Nationale de la Recherche (coVAPid project). The funders of the study had no role in the study design, data collection, analysis, or interpreta tion, writing of the report, or decision to submit for publication.BACKGROUND: Patients with SARS-CoV-2 infection are at higher risk for ventilator-associated pneumonia (VAP). No study has evaluated the relationship between VAP and mortality in this population, or compared this relationship between SARS-CoV-2 patients and other populations. The main objective of our study was to determine the relationship between VAP and mortality in SARS-CoV-2 patients. METHODS: Planned ancillary analysis of a multicenter retrospective European cohort. VAP was diagnosed using clinical, radiological and quantitative microbiological criteria. Univariable and multivariable marginal Cox's regression models, with cause-specific hazard for duration of mechanical ventilation and ICU stay, were used to compare outcomes between study groups. Extubation, and ICU discharge alive were considered as events of interest, and mortality as competing event. FINDINGS: Of 1576 included patients, 568 were SARS-CoV-2 pneumonia, 482 influenza pneumonia, and 526 no evidence of viral infection at ICU admission. VAP was associated with significantly higher risk for 28-day mortality in SARS-CoV-2 (adjusted HR 1.70 (95% CI 1.16-2.47), p = 0.006), and influenza groups (1.75 (1.03-3.02), p = 0.045), but not in the no viral infection group (1.07 (0.64-1.78), p = 0.79). VAP was associated with significantly longer duration of mechanical ventilation in the SARS-CoV-2 group, but not in the influenza or no viral infection groups. VAP was associated with significantly longer duration of ICU stay in the 3 study groups. No significant difference was found in heterogeneity of outcomes related to VAP between the 3 groups, suggesting that the impact of VAP on mortality was not different between study groups. INTERPRETATION: VAP was associated with significantly increased 28-day mortality rate in SARS-CoV-2 patients. However, SARS-CoV-2 pneumonia, as compared to influenza pneumonia or no viral infection, did not significantly modify the relationship between VAP and 28-day mortality. CLINICAL TRIAL REGISTRATION: The study was registered at ClinicalTrials.gov, number NCT04359693.publishersversionpublishe

DxTools: Processing large data files recorded with the Bruker D8 diffractometer

International audienceData processing is the daily reality for crystallographers who often seek to automate this repetitive task. With modern commercial diffractometers allowing for more elaborate experiments to be performed, the use of commercial software is almost unavoidable to process the data which is often provided in a manufacturer-specific format. This is especially the case when the intensity is recorded as a function of more than one single scanning motor, and/or when recording data with a one-dimensional detector. A simple, free and open-source alternative is here presented to process that type of diffraction data recorded with the Bruker D8 diffractometer. It allows handling of data files (in uxd and brml format) corresponding to reciprocal space maps [in the (Q x , Q z) and (Q x , Q y) planes], temperature-dependent scans, spatial scans, sin²ψ measurements and pole figures. The program is easy to use and can be extended to any file format. It can be downloaded from https://aboulle.github.io/DxTools