Anomalous dissipation mechanism and Hall quantization limit in polycrystalline graphene grown by chemical vapor deposition

Ajuts: it has been performed within the EMRP (European Metrology Research Program), project SIB51, Graphohm. The EMRP is jointly funded by the EMRP participating countries within EURAMET (European association of national metrology institutes) and the European Union.We report on the observation of strong backscattering of charge carriers in the quantum Hall regime of polycrystalline graphene, grown by chemical vapor deposition, which alters the accuracy of the Hall resistance quantization. The temperature and magnetic field dependence of the longitudinal conductance exhibits unexpectedly smooth power-law behaviors, which are incompatible with a description in terms of variable range hopping or thermal activation but rather suggest the existence of extended or poorly localized states at energies between Landau levels. Such states could be caused by the high density of line defects (grain boundaries and wrinkles) that cross the Hall bars, as revealed by structural characterizations. Numerical calculations confirm that quasi-one-dimensional extended nonchiral states can form along such line defects and short circuit the Hall bar chiral edge states

Degenerate recognition of MHC class I molecules with Bw4 and Bw6 motifs by a killer cell Ig-like receptor 3DL expressed by macaque NK cells

The killer cell immunoglobulin-like receptors (KIRs) expressed on the surface of natural killer (NK) cells recognize specific major histocompatibility complex class I (MHC-I) molecules and regulate NK cell activities against pathogen-infected cells and neoplasia. In human immunodeficiency virus (HIV) infection, survival is linked to host KIR and MHC-I genotypes. In the simian immunodeficiency virus (SIV) macaque model, however, the role of NK cells is unclear due to the lack of information on KIR-MHC interactions. Here, we describe the first characterization of a KIR-MHC interaction in pig-tailed macaques (Macaca nemestrina). Initially, we identified three distinct subsets of macaque NK cells that stained ex vivo with macaque MHC-I tetramers loaded with SIV peptides. We then cloned cDNAs corresponding to 15 distinct KIR3D alleles. One of these, KIR049-4, was an inhibitory KIR3DL that bound MHC-I tetramers and prevented activation, degranulation and cytokine production by macaque NK cells after engagement with specific MHC-I molecules on the surface of target cells. Furthermore, KIR049-4 recognized a broad range of MHC-I molecules carrying not only the Bw4 motif but also Bw6 and non-Bw4/Bw6 motifs. This degenerate, yet peptide-dependent, MHC reactivity differs markedly from the fine specificity of human KIRs

Ezrin enhances line tension along transcellular tunnel edges via NMIIa driven actomyosin cable formation

Transendothelial cell macroaperture (TEM) tunnels control endothelium barrier function and are triggered by several toxins from pathogenic bacteria that provoke vascular leakage. Cellular dewetting theory predicted that a line tension of uncharacterized origin works at TEM boundaries to limit their widening. Here, by conducting high-resolution microscopy approaches we unveil the presence of an actomyosin cable encircling TEMs. We develop a theoretical cellular dewetting framework to interpret TEM physical parameters that are quantitatively determined by laser ablation experiments. This establishes the critical role of ezrin and non-muscle myosin II (NMII) in the progressive implementation of line tension. Mechanistically, fluorescence-recovery-after-photobleaching experiments point for the upstream role of ezrin in stabilizing actin filaments at the edges of TEMs, thereby favouring their crosslinking by NMIIa. Collectively, our findings ascribe to ezrin and NMIIa a critical function of enhancing line tension at the cell boundary surrounding the TEMs by promoting the formation of an actomyosin ring.Peer reviewe

Killer cell immunoglobulin-like receptor 3DL1-mediated recognition of human leukocyte antigen B [Letter]

Members of the killer cell immunoglobulin-like receptor (KIR) family, a large group of polymorphic receptors expressed on natural killer (NK) cells, recognize particular peptide-laden human leukocyte antigen (pHLA) class I molecules and have a pivotal role in innate immune responses1. Allelic variation and extensive polymorphism within the three-domain KIR family (KIR3D, domains D0–D1–D2) affects pHLA binding specificity and is linked to the control of viral replication and the treatment outcome of certain haematological malignancies1, 2, 3. Here we describe the structure of a human KIR3DL1 receptor bound to HLA-B*5701 complexed with a self-peptide. KIR3DL1 clamped around the carboxy-terminal end of the HLA-B*5701 antigen-binding cleft, resulting in two discontinuous footprints on the pHLA. First, the D0 domain, a distinguishing feature of the KIR3D family, extended towards β2-microglobulin and abutted a region of the HLA molecule with limited polymorphism, thereby acting as an ‘innate HLA sensor’ domain. Second, whereas the D2–HLA-B*5701 interface exhibited a high degree of complementarity, the D1–pHLA-B*5701 contacts were suboptimal and accommodated a degree of sequence variation both within the peptide and the polymorphic region of the HLA molecule. Although the two-domain KIR (KIR2D) and KIR3DL1 docked similarly onto HLA-C4, 5 and HLA-B respectively, the corresponding D1-mediated interactions differed markedly, thereby providing insight into the specificity of KIR3DL1 for discrete HLA-A and HLA-B allotypes. Collectively, in association with extensive mutagenesis studies at the KIR3DL1–pHLA-B*5701 interface, we provide a framework for understanding the intricate interplay between peptide variability, KIR3D and HLA polymorphism in determining the specificity requirements of this essential innate interaction that is conserved across primate species

The PROFOUND Database for evaluating vegetation models and simulating climate impacts on European forests

Process-based vegetation models are widely used to predict local and global ecosystem dynamics and climate change impacts. Due to their complexity, they require careful parameterization and evaluation to ensure that projections are accurate and reliable. The PROFOUND Database (PROFOUND DB) provides a wide range of empirical data on European forests to calibrate and evaluate vegetation models that simulate climate impacts at the forest stand scale. A particular advantage of this database is its wide coverage of multiple data sources at different hierarchical and temporal scales, together with environmental driving data as well as the latest climate scenarios. Specifically, the PROFOUND DB provides general site descriptions, soil, climate, CO2, nitrogen deposition, tree and forest stand level, and remote sensing data for nine contrasting forest stands distributed across Europe. Moreover, for a subset of five sites, time series of carbon fluxes, atmospheric heat conduction and soil water are also available. The climate and nitrogen deposition data contain several datasets for the historic period and a wide range of future climate change scenarios following the Representative Concentration Pathways (RCP2.6, RCP4.5, RCP6.0, RCP8.5). We also provide pre-industrial climate simulations that allow for model runs aimed at disentangling the contribution of climate change to observed forest productivity changes. The PROFOUND DB is available freely as a "SQLite" relational database or "ASCII" flat file version (at https://doi.org/10.5880/PIK.2020.006/; Reyer et al., 2020). The data policies of the individual contributing datasets are provided in the metadata of each data file. The PROFOUND DB can also be accessed via the ProfoundData R package (https://CRAN.R- project.org/package=ProfoundData; Silveyra Gonzalez et al., 2020), which provides basic functions to explore, plot and extract the data for model set-up, calibration and evaluation.Peer reviewe

Altered energy partitioning across terrestrial ecosystems in the European drought year 2018

Drought and heat events, such as the 2018 European drought, interact with the exchange of energy between the land surface and the atmosphere, potentially affecting albedo, sensible and latent heat fluxes, as well as CO(2)exchange. Each of these quantities may aggravate or mitigate the drought, heat, their side effects on productivity, water scarcity and global warming. We used measurements of 56 eddy covariance sites across Europe to examine the response of fluxes to extreme drought prevailing most of the year 2018 and how the response differed across various ecosystem types (forests, grasslands, croplands and peatlands). Each component of the surface radiation and energy balance observed in 2018 was compared to available data per site during a reference period 2004-2017. Based on anomalies in precipitation and reference evapotranspiration, we classified 46 sites as drought affected. These received on average 9% more solar radiation and released 32% more sensible heat to the atmosphere compared to the mean of the reference period. In general, drought decreased net CO(2)uptake by 17.8%, but did not significantly change net evapotranspiration. The response of these fluxes differed characteristically between ecosystems; in particular, the general increase in the evaporative index was strongest in peatlands and weakest in croplands. This article is part of the theme issue 'Impacts of the 2018 severe drought and heatwave in Europe: from site to continental scale'

Synthesis of 3-Azidopropyl-Functionalized GalNAc-β-(1→4)-Gal Natural Disaccharide

Oligosaccharides such as the GalNAc-β-(1→4)-Gal disaccharide are involved in host-pathogen interactions and their synthesis is a continuing challenge for organic chemists. Only a few reports have discussed the synthesis of functionalized GalNAc-β-(1→4)-Gal for its further conjugation and applications in glycobiology. The synthetic route described here is taking advantage of (1) a simple and affordable GlcNAc donor which is epimerized to the more expensive GalNAc donor and (2) a 1,6-anhydro-galactose acceptor exalting the reactivity at the 4-position of galactose. The allyloxycarbonyl (Alloc) protecting group used at the 2-position of the GalNAc residue was important (1) for a successful epimerization of the GlcNAc residue into the corresponding GalNAc donor but also (2) for the stereoselective β-glycosylation through anchimeric assistance. The key disaccharide intermediate was further transformed to a trichloroacetimidate donor which could then be glycosylated with any alcohol. The example chosen here is the 3-azidopropyl aglycon for the design of multivalent glycoclusters.<br /

Cooperative learning: a relevant instructional model for physical education pre-service teacher training?

Background: One of the key questions of physical education teacher educators (PETE) programmes refers to whether future teachers are prepared to build knowledge and skills to feel self-efficacious in teaching physical education (PE). This issue concerns the instructional model of teaching used to help PE pre-service teachers to master both pedagogical knowledge and motor skills. According to this twofold challenge, the direct instruction (DI) is mainly used for pre-service teacher training. Beyond this traditional model, other instructional models as cooperative learning (CL) approach arise in the initial PE teacher education. Nevertheless, surrounding attempts at innovation, little information related to the instructor’s role. Under the social cognitive perspective of self-efficacy and instructional competency building, more information is currently expected with regard to the strategies the instructor uses to scaffold the mastery of skills for PE pre-service teachers’ effective teaching. Purpose: The purpose of this article is to consider whether PE pre-service teachers are trained during short training sessions aimed to discover new physical activities. We examine the influence of a scaffolding procedure (CLS design) on PE pre-service teachers’ knowledge, skills and self-efficacy in comparison to a CL and a DI experience. This leads to consider to what extent this instructional support provided by the instructor would help pre-service teachers to perceive themselves as self-efficacious to teach contents in PE. Participants and design: After a pre-test, sixty-nine PE pre-service teachers were randomly assigned to one of the three following conditions: CL (14 males and 7 females); CLS (20 males and 8 females) or direct instruction condition (DI; 12 males and 8 females). For the training session a selected CL procedure (Jigsaw) [Aronson, Elliot, and Shelley Patnoe. 1997. The Jigsaw Classroom: Building Cooperation in the Classroom. 2nd ed. Wokingham: Addison-Wesley Educational]) was used to split CL and CLS participants into mixed-sex teams, whereas DI participants practiced the same exercises in dyads. According to the training conditions, the same instructor provided different information to participants along the three 2-hour instructional sessions with regard to: (a) warm-up (DI), (b) CL organization (CL), and (c) scaffolding integrated into a CL implementation (CLS). Data collection: A Pre-test/post-test design was used to consider PE pre-service teacher’s motor skill, knowledge for practice, and self-efficacy improvements. The post-test also examined participants’ pedagogical knowledge. Findings: The results showed that the participants in the three conditions progressed on performance, knowledge for practice, knowledge for teaching, and self-efficacy. Although no difference was found in self-efficacy between the three training conditions over time, significant differences appeared on pedagogical knowledge or/and motor skills with an advantage for the CL and CLS participants, respectively. Conclusion: Although short training sessions dedicated to discovering new sports stay problematic for teacher professional development, implementing CL pre-service teacher training designs would be a relevant alternative. Instructional knowledge would be developed mainly when they have explicitly access to information concerning the teacher intervention. Nevertheless, such a scaffolding procedure integrated into CL training designs would need to be applied repeatedly to various physical activities to have an impact on pre-service teachers’ self-efficacy

ICOS France

Les émissions mondiales de gaz à effet de serre ont augmenté jusqu’à atteindre en 2017 des niveaux sans précédent, plus de 400 ppm en CO2. Elles ont progressé plus rapidement entre 2000 et 2010 (+2,2% par an) qu’au cours des trois décennies précédentes. Maintenir un réchauffement inférieur à +2°C de température moyenne, comme le stipulent les engagements pris lors de la conférence de Paris, nécessite de réduire les émissions mondiales de GES de 40 à 70%. Mais comment mesurer les échanges de gaz à effet de serre, et vérifier les impacts des politiques de réduction adoptées sur l’atmosphère et le climat ? L’Infrastructure européenne ICOS répond à cette attente : elle est constituée de réseaux organisés de mesure du cycle du gaz à effet de serre dans l’atmosphère, les continents et les océans. ICOS est spécifiquement dédiée à la mesure des flux et des concentrations en dioxyde de carbone (écosystèmes, fuels fossiles et cimenteries), méthane (gaz naturel, agriculture et élevage), et oxyde nitreux (agriculture, fuels fossiles et feux) de 2016 à 2035. L’infrastructure ICOS mobilise plus de 500 chercheurs et ingénieurs de 17 pays européens ; c’est un élément clé de la feuille de route européenne des infrastructures de recherche (ESFRI) et elle constitue un Très Grand Instrument de Recherche (TGIR) de la stratégie nationale de recherche française

ICOS France

Les émissions mondiales de gaz à effet de serre ont augmenté jusqu’à atteindre en 2017 des niveaux sans précédent, plus de 400 ppm en CO2. Elles ont progressé plus rapidement entre 2000 et 2010 (+2,2% par an) qu’au cours des trois décennies précédentes. Maintenir un réchauffement inférieur à +2°C de température moyenne, comme le stipulent les engagements pris lors de la conférence de Paris, nécessite de réduire les émissions mondiales de GES de 40 à 70%. Mais comment mesurer les échanges de gaz à effet de serre, et vérifier les impacts des politiques de réduction adoptées sur l’atmosphère et le climat ? L’Infrastructure européenne ICOS répond à cette attente : elle est constituée de réseaux organisés de mesure du cycle du gaz à effet de serre dans l’atmosphère, les continents et les océans. ICOS est spécifiquement dédiée à la mesure des flux et des concentrations en dioxyde de carbone (écosystèmes, fuels fossiles et cimenteries), méthane (gaz naturel, agriculture et élevage), et oxyde nitreux (agriculture, fuels fossiles et feux) de 2016 à 2035. L’infrastructure ICOS mobilise plus de 500 chercheurs et ingénieurs de 17 pays européens ; c’est un élément clé de la feuille de route européenne des infrastructures de recherche (ESFRI) et elle constitue un Très Grand Instrument de Recherche (TGIR) de la stratégie nationale de recherche française