High temperature piezoelectric properties of flux-grown α-GeO 2 single crystal

International audienceThe temperature-dependence of the piezoelectric properties of trigonal -GeO2 single-crystals obtained by the high-temperature flux method was measured by the resonance technique of the electrical impedance in the 20°C-600°C range. To approach the values of the two independent piezoelectric coefficients d11 and d14, we first measured as a function of temperature the elastic coefficients S11, S14 and S66 and the dielectric permittivity 11 which are involved in the coupling coefficient k of both the thickness shear mode and the transverse mode. A Y-cut plate with a simple +45°-rotation ((YXtwl) +45°/0°/0°) was used to measure the coupling coefficient of the thickness shear mode, and two X-turned plates ((XYtwl) +45°/0°/0° and (XYtwl)-45°/0°/0°) were prepared to characterize the coupling coefficient of two transverse modes. From the whole experimental measurements, the piezoelectric coefficients of -GeO2 were calculated up to 600 °C. They show that this crystal is one of the most efficient in regard of the -quartz-like family at room temperature, and that its thermal comportment retains large piezoelectric properties up to 600°C

Hidden magnetism at the pseudogap critical point of a high temperature superconductor

The mysterious pseudogap phase of cuprate superconductors ends at a critical hole doping level p* but the nature of the ground state below p* is still debated. Here, we show that the genuine nature of the magnetic ground state in La2-xSrxCuO4 is hidden by competing effects from superconductivity: applying intense magnetic fields to quench superconductivity, we uncover the presence of glassy antiferromagnetic order up to the pseudogap boundary p* ~ 0.19, and not above. There is thus a quantum phase transition at p*, which is likely to underlie highfield observations of a fundamental change in electronic properties across p*. Furthermore, the continuous presence of quasi-static moments from the insulator up to p* suggests that the physics of the doped Mott insulator is relevant through the entire pseudogap regime and might be more fundamentally driving the transition at p* than just spin or charge ordering.Comment: 26 pages, supplementary info include

Novel Loss of Function Variant in BCKDK Causes a Treatable Developmental and Epileptic Encephalopathy.

peer reviewedBranched-chain amino acids (BCAA) are essential amino acids playing crucial roles in protein synthesis and brain neurotransmission. Branched-chain ketoacid dehydrogenase (BCKDH), the flux-generating step of BCAA catabolism, is tightly regulated by reversible phosphorylation of its E1α-subunit. BCKDK is the kinase responsible for the phosphorylation-mediated inactivation of BCKDH. In three siblings with severe developmental delays, microcephaly, autism spectrum disorder and epileptic encephalopathy, we identified a new homozygous in-frame deletion (c.999_1001delCAC; p.Thr334del) of BCKDK. Plasma and cerebrospinal fluid concentrations of BCAA were markedly reduced. Hyperactivity of BCKDH and over-consumption of BCAA were demonstrated by functional tests in cells transfected with the mutant BCKDK. Treatment with pharmacological doses of BCAA allowed the restoring of BCAA concentrations and greatly improved seizure control. Behavioral and developmental skills of the patients improved to a lesser extent. Importantly, a retrospective review of the newborn screening results allowed the identification of a strong decrease in BCAA concentrations on dried blood spots, suggesting that BCKDK is a new treatable metabolic disorder probably amenable to newborn screening programs

Natural History of Liver Disease in a Large International Cohort of Children with Alagille syndrome:Results from The GALA Study

BACKGROUND: Alagille syndrome (ALGS) is a multisystem disorder, characterized by cholestasis. Existing outcome data are largely derived from tertiary centers and real-world data are lacking. This study aimed to elucidate the natural history of liver disease in a contemporary, international, cohort of children with ALGS.METHODS: Multicenter retrospective study of children with a clinically and/or genetically confirmed ALGS diagnosis, born Jan-1997 - Aug-2019. Native liver survival (NLS) and event-free survival rates were assessed. Cox models were constructed to identify early biochemical predictors of clinically evident portal hypertension (CEPH) and NLS.RESULTS: 1433 children (57% male) from 67 centers in 29 countries were included. 10 and 18-years NLS rates were 54.4% and 40.3%. By 10 and 18-years, 51.5% and 66.0% of ALGS children experienced ≥1 adverse liver-related event (CEPH, transplant or death). Children (&gt;6 and ≤12 months) with median total bilirubin (TB) levels between ≥5.0 and &lt;10.0 mg/dL had a 4.1-fold (95% CI 1.6 - 10.8) and those ≥10.0 mg/dL had an 8.0-fold (95% CI 3.4 - 18.4) increased risk of developing CEPH compared with those &lt;5.0 mg/dL. Median TB levels between ≥5.0 and &lt;10.0 mg/dL and &gt;10.0 mg/dL were associated with a 4.8 (95% CI 2.4 - 9.7) and 15.6 (95% CI 8.7 - 28.2) increased risk of transplantation relative to &lt;5.0 mg/dL. Median TB &lt;5.0 mg/dL were associated with higher NLS rates relative to ≥5.0 mg/dL, with 79% reaching adulthood with native liver (p&lt;0.001).CONCLUSIONS: In this large international cohort of ALGS, only 40.3% of children reach adulthood with their native liver. A TB &lt;5.0 mg/dL between 6-and-12-months of age is associated with better hepatic outcomes. These thresholds provide clinicians with an objective tool to assist with clinical decision-making and in the evaluation of novel therapies.</p

COVID-19 symptoms at hospital admission vary with age and sex: results from the ISARIC prospective multinational observational study

Background: The ISARIC prospective multinational observational study is the largest cohort of hospitalized patients with COVID-19. We present relationships of age, sex, and nationality to presenting symptoms. Methods: International, prospective observational study of 60 109 hospitalized symptomatic patients with laboratory-confirmed COVID-19 recruited from 43 countries between 30 January and 3 August 2020. Logistic regression was performed to evaluate relationships of age and sex to published COVID-19 case definitions and the most commonly reported symptoms. Results: ‘Typical’ symptoms of fever (69%), cough (68%) and shortness of breath (66%) were the most commonly reported. 92% of patients experienced at least one of these. Prevalence of typical symptoms was greatest in 30- to 60-year-olds (respectively 80, 79, 69%; at least one 95%). They were reported less frequently in children (≤ 18 years: 69, 48, 23; 85%), older adults (≥ 70 years: 61, 62, 65; 90%), and women (66, 66, 64; 90%; vs. men 71, 70, 67; 93%, each P &lt; 0.001). The most common atypical presentations under 60 years of age were nausea and vomiting and abdominal pain, and over 60 years was confusion. Regression models showed significant differences in symptoms with sex, age and country. Interpretation: This international collaboration has allowed us to report reliable symptom data from the largest cohort of patients admitted to hospital with COVID-19. Adults over 60 and children admitted to hospital with COVID-19 are less likely to present with typical symptoms. Nausea and vomiting are common atypical presentations under 30 years. Confusion is a frequent atypical presentation of COVID-19 in adults over 60 years. Women are less likely to experience typical symptoms than men

Conception d'une expérience de topographie aux rayons X : application à l'étude de défauts intrinsèques et extrinsèques dans les cristaux

X Rays Topography (XRT) is a characterization method based on diffraction contrast. Applicable to crystallized solids, it has ability to identify and study structural defects caused by material conception or forming. His development take place in laboratory source or synchrotron source in several geometry. Conception of XRT experience in Lang geometry require a special attention, in comparison with multiple possibility of this setting. We have design this experience, test and set it, at last we have demonstrate that it was possible to make XRT image on single crystalline samples.La topographie aux rayons X est une méthode de caractérisation basée sur le contraste de diffraction. Applicable aux solides cristallisés, elle permet l'identification et l'étude de défauts de structure engendrés par la conception et/ou la mise en forme d'un matériau. Sa mise en oeuvre est possible en source de laboratoire ou en source synchrotron selon plusieurs géométries. La conception d'une expérience de topographie en géométrie de Lang demande une attention particulière, en regard des multiples possibilités d'utilisation du montage. Nous avons conçu l'expérience, nous l'avons testée et réglée, enfin nous avons démontré qu'il était possible d'obtenir des clichés de topographie X sur des échantillons monocristallins

Détermination expérimentale du courant minimal d’inflammation de mélanges méthane/hydrogène contenant jusque 20 % d’hydrogène

The European Union aims to reduce its carbon emission by up to 80% until 2050. To reach this objective, a possible way consists in injecting hydrogen - produced from renewable energy - into the natural gas network, at a concentration of up to 20%. But hydrogen is more easily ignitable than natural gas. Therefore, use of such a hydrogen/natural gas blend in the existing natural gas network shall be carefully assessed. Especially, are the equipment already used in the natural gas network compatible with this type of blends? The applicable standard for classification of ignition sensitivity prescribes a classification of such hydrogen/methane blends in the same group as the natural gas for a concentration of hydrogen up to 25%. To investigate this issue, Ineris experimentally determined the Minimum Ignition Current (MIC) of hydrogen/methane blends, containing from 2% to 20% of hydrogen. The MIC is one of the two parameters used to classify a gas in its ignition sensibility group. This work demonstrates the need of a modification of the classification criteria defined in the applicable standard.A la suite de l’adoption du paquet Énergie- Climat 2030 en octobre 2014, l’Union européenne s’est fixé des objectifs ambitieux de diminution de ses émissions de gaz à effet de serre : • 40 % d’ici à 2030, • 80 % en 2050, • zéro émission nette en 2100. L’atteinte de ces objectifs implique la mise en oeuvre d’une véritable transition énergétique. Le procédé « Power-to-Gas » pourrait contribuer à cette transition. Il consiste à transformer l’énergie électrique en gaz (hydrogène ou méthane), afin de la stocker dans un objectif de recours croissant à des énergies renouvelables. Ainsi, dans les périodes de production excédentaire, l’électricité renouvelable est stockée sous forme de gaz, et peut donc être utilisée à tout moment. Le gaz ainsi généré peut être consommé de plusieurs façons. L’une d’entre elles consiste à injecter l’hydrogène obtenu directement dans le réseau de gaz naturel, jusqu’à une concentration de 20 %. L’hydrogène est un gaz bien plus facilement inflammable que le gaz naturel. L’ajout d’hydrogène dans le réseau de gaz naturel traditionnel soulève donc des questions relatives à la sécurité. En particulier, les équipements électriques déjà installés sur le réseau de gaz naturel en zone ATEX sont-ils compatibles avec la mise en oeuvre de ce mélange

Sensitivity analysis of atmospheric dispersion modeling in emergency situation

International audienceEach day, accidents involving hazardous materials are managed by Emergency Services. In order to bring the best adapted operational answer, it is necessary to determine with accuracy the concentrations of the gas to which people will be exposed. The expert in charge of modeling is facing a major difficulty: few (or no) information. Therefore, for a given situation, the generation of different effect distances is possible. A sensitivity analysis was carried out in order to determine the most influential parameters on the estimation of safety distances. The goal is to identify the parameters for which it is necessary to pay a very detailed attention. The first step of the study was to define the system to be analyzed. The second step consisted in working out a complete model of evaluation of safety distances in emergency situation. This was done by combining an existing dispersion model (SLAB) with a specifically developed application for the calculation of input parameters. The input data are operational data which can be collected from the accident site and the output data are safety distances. The third step consisted in selecting two test cases representative of an accident situation involving hazardous chemicals (leak on a wagon of ammonia and a wagon of propane). After that, it was characterizing the range of possible values of the whole input parameters. A fourth step consisted in applying two methods of sensitivity analysis: a screening method (MORRIS's method) and a local sensitivity analysis. Finally, the application of these methods, on the same case study, made it possible to highlight the points of convergence of the methods and their advantages. Finally, the parameters for which it is useless / useful to initiate considerable efforts to recover a reliable value were highlighted

Demonstration of site-selective angular-resolved absorption spectroscopy of the 4I15/2 - 4I13/2 erbium transition in the monoclinic crystal Y2SiO5

We study the angular dependence in polarized light of the optical absorption for the \er transition $^{4}I_{15/2} \rightarrow$$^{4}I_{13/2}$ in Y$_2$SiO$_5$, revealing thus the associated anisotropy and the orientation of the related absorption principal directions in the dielectric plan perpendicular to the monoclinic axis b. The measurements are performed at low temperature. This allows us to isolate the lowest crystal field levels in the ground and excited states. We spectrally resolve and independently characterize the two yttrium substitution sites in the Y$_2$SiO$_5$ matrix. The absorption tensor components cannot be unambiguously determined yet while only considering the investigated dielectric plane. Still, measurements remarkably demonstrate that this transition of interest for quantum optical memories is not only a magnetic-dipole allowed transition but indeed a hybrid electric-magnetic transition.Physics: Atoms, Light, MatterInterfaces microonde spin de terres rares pour le traitement quantique de l'informatio

Origin of Crazing in Deuterated KDP Crystals

International audienceThe H/D isotopic exchange between DKDP crystals [K(H(1-x)Dx)2PO4] and their environment causes a surface damage known as crazing. By studying crystals, grown under perfectly stationary conditions, with a combination of analysis techniques (surface microtopography, micro-Raman spectroscopy, X-ray diffraction topography, trace element analysis) we were able to determine the localization of the isotopic exchange, quantify it, and connect it with a preferential incorporation of impurity. This enables us to propose a direct correlation between the growth mechanisms governing the impurity incorporation, the increase of proton diffusion in the structure in that part of the crystal hence on the localization, and the magnitude of crazing upon aging of the DKDP crystals