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Sommaires des Revues - Sciences

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Biases in forensic experts  Voir?

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News at a glance  Voir?

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NASA lander to probe interior of Mars  Voir?

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Department of State's air pollution sensors go global  Voir?

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Cannabis, opium use part of ancient Near Eastern cultures  Voir?

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Plan for 2020 U.S. census is fatally flawed, critics say  Voir?

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Ancient DNA untangles South Asian roots  Voir?

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Proposal to rescue postdocs from limbo draws darts  Voir?

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Omen in the blood  Voir?

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Risk-based reboot for global lab biosafety  Voir?

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Plant responses to CO2 are a question of time  Voir?

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On the quest for the strongest materials  Voir?

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Whispering neurons fuel cortical highways  Voir?

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Parkin function in Parkinson's disease  Voir?

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If two deletions don't stop growth, try three  Voir?

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A unifying concept in vascular health and disease  Voir?

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Reconsidering the Nobel Prize  Voir?

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Wielding new genomic tools wisely  Voir?

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Ivory crisis: Growing no-trade consensus  Voir?

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Ivory crisis: Role of bioprinting technology  Voir?

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Response--Ivory crisis  Voir?

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Insurance coverage for genomic tests  Voir?

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Megafaunal loss  Voir?

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A strongly oxidizing Paleoproterozoic era  Voir?

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Transient instruction changes migration  Voir?

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Inherited variation contributes to autism  Voir?

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An innovative approach for a rare disease  Voir?

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Taking an active interest in HIV latency  Voir?

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Reserving the right to stretch  Voir?

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Earlier detection of ovarian cancer  Voir?

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Recurring coherence  Voir?

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Trigenic interactions in yeast link bioprocesses  Voir?

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Continuing the resolution revolution  Voir?

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Large-scale integrated quantum optics  Voir?

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Light confined to a single atomic layer  Voir?

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Small, smooth, and bendable diamonds  Voir?

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Images frozen in time  Voir?

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A short-term trend reversed  Voir?

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The cellular composition of H3K27M gliomas  Voir?

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First steps of translocation elucidated  Voir?

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Conformation changes or cooperativity?  Voir?

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Restoring blood vessel stability  Voir?

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Estrogen accentuates autoimmunity  Voir?

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Potent platelets  Voir?

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Tuning the soil for growth  Voir?

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Tying genotype to phenotype, cell by cell  Voir?

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Weathering life after death  Voir?

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Explaining uneven mass loss  Voir?

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Manipulating an antiferromagnet  Voir?

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Reconfigurable metasurfaces  Voir?

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Even more genes control cell growth  Voir?

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Multidimensional quantum entanglement with large-scale integrated optics  Voir?

The ability to control multidimensional quantum systems is central to the development of advanced quantum technologies. We demonstrate a multidimensional integrated quantum photonic platform able to generate, control, and analyze high-dimensional entanglement. A programmable bipartite entangled system is realized with dimensions up to 15 x 15 on a large-scale silicon photonics quantum circuit. The device integrates more than 550 photonic components on a single chip, including 16 identical photon-pair sources. We verify the high precision, generality, and controllability of our multidimensional technology, and further exploit these abilities to demonstrate previously unexplored quantum applications, such as quantum randomness expansion and self-testing on multidimensional states. Our work provides an experimental platform for the development of multidimensional quantum technologies.

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Probing the ultimate plasmon confinement limits with a van der Waals heterostructure  Voir?

The ability to confine light into tiny spatial dimensions is important for applications such as microscopy, sensing, and nanoscale lasers. Although plasmons offer an appealing avenue to confine light, Landau damping in metals imposes a trade-off between optical field confinement and losses. We show that a graphene-insulator-metal heterostructure can overcome that trade-off, and demonstrate plasmon confinement down to the ultimate limit of the length scale of one atom. This is achieved through far-field excitation of plasmon modes squeezed into an atomically thin hexagonal boron nitride dielectric spacer between graphene and metal rods. A theoretical model that takes into account the nonlocal optical response of both graphene and metal is used to describe the results. These ultraconfined plasmonic modes, addressed with far-field light excitation, enable a route to new regimes of ultrastrong light-matter interactions.

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Capillarity-induced folds fuel extreme shape changes in thin wicked membranes  Voir?

Soft deformable materials are needed for applications such as stretchable electronics, smart textiles, or soft biomedical devices. However, the design of a durable, cost-effective, or biologically compatible version of such a material remains challenging. Living animal cells routinely cope with extreme deformations by unfolding preformed membrane reservoirs available in the form of microvilli or membrane folds. We synthetically mimicked this behavior by creating nanofibrous liquid-infused tissues that spontaneously form similar reservoirs through capillarity-induced folding. By understanding the physics of membrane buckling within the liquid film, we developed proof-of-concept conformable chemical surface treatments and stretchable basic electronic circuits.

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Ultralarge elastic deformation of nanoscale diamond  Voir?

Diamonds have substantial hardness and durability, but attempting to deform diamonds usually results in brittle fracture. We demonstrate ultralarge, fully reversible elastic deformation of nanoscale (~300 nanometers) single-crystalline and polycrystalline diamond needles. For single-crystalline diamond, the maximum tensile strains (up to 9%) approached the theoretical elastic limit, and the corresponding maximum tensile stress reached ~89 to 98 gigapascals. After combining systematic computational simulations and characterization of pre- and postdeformation structural features, we ascribe the concurrent high strength and large elastic strain to the paucity of defects in the small-volume diamond nanoneedles and to the relatively smooth surfaces compared with those of microscale and larger specimens. The discovery offers the potential for new applications through optimized design of diamond nanostructure, geometry, elastic strains, and physical properties.

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Five-dimensional imaging of freezing emulsions with solute effects  Voir?

The interaction of objects with a moving solidification front is a common feature of many industrial and natural processes such as metal processing, the growth of single crystals, the cryopreservation of cells, or the formation of sea ice. Interaction of solidification fronts with objects leads to different outcomes, from total rejection of the objects to their complete engulfment. We imaged the freezing of emulsions in five dimensions (space, time, and solute concentration) with confocal microscopy. We showed that the solute induces long-range interactions that determine the solidification microstructure. The local increase of solute concentration enhances premelting, which controls the engulfment of droplets by the front and the evolution of grain boundaries. Freezing emulsions may be a good analog of many solidification systems where objects interact with a solidification interface.

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Recurrences in an isolated quantum many-body system  Voir?

The complexity of interacting quantum many-body systems leads to exceedingly long recurrence times of the initial quantum state for all but the smallest systems. For large systems, one cannot probe the full quantum state in all its details. Thus, experimentally, recurrences can only be determined on the level of the accessible observables. Realizing a commensurate spectrum of collective excitations in one-dimensional superfluids, we demonstrate recurrences of coherence and long-range order in an interacting quantum many-body system containing thousands of particles. Our findings will enable the study of the coherent dynamics of large quantum systems even after they have reached a transient thermal-like state.

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Body size downgrading of mammals over the late Quaternary  Voir?

Since the late Pleistocene, large-bodied mammals have been extirpated from much of Earth. Although all habitable continents once harbored giant mammals, the few remaining species are largely confined to Africa. This decline is coincident with the global expansion of hominins over the late Quaternary. Here, we quantify mammalian extinction selectivity, continental body size distributions, and taxonomic diversity over five time periods spanning the past 125,000 years and stretching approximately 200 years into the future. We demonstrate that size-selective extinction was already under way in the oldest interval and occurred on all continents, within all trophic modes, and across all time intervals. Moreover, the degree of selectivity was unprecedented in 65 million years of mammalian evolution. The distinctive selectivity signature implicates hominin activity as a primary driver of taxonomic losses and ecosystem homogenization. Because megafauna have a disproportionate influence on ecosystem structure and function, past and present body size downgrading is reshaping Earth’s biosphere.

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Synaptic transmission from subplate neurons controls radial migration of neocortical neurons  Voir?

The neocortex exhibits a six-layered structure that is formed by radial migration of excitatory neurons, for which the multipolar-to-bipolar transition of immature migrating multipolar neurons is required. Here, we report that subplate neurons, one of the first neuron types born in the neocortex, manage the multipolar-to-bipolar transition of migrating neurons. By histochemical, imaging, and microarray analyses on the mouse embryonic cortex, we found that subplate neurons extend neurites toward the ventricular side of the subplate and form transient glutamatergic synapses on the multipolar neurons just below the subplate. NMDAR (N-methyl-d-aspartate receptor)–mediated synaptic transmission from subplate neurons to multipolar neurons induces the multipolar-to-bipolar transition, leading to a change in migration mode from slow multipolar migration to faster radial glial-guided locomotion. Our data suggested that transient synapses formed on early immature neurons regulate radial migration.

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Unexpected reversal of C3 versus C4 grass response to elevated CO2 during a 20-year field experiment  Voir?

Theory predicts and evidence shows that plant species that use the C4 photosynthetic pathway (C4 species) are less responsive to elevated carbon dioxide (eCO2) than species that use only the C3 pathway (C3 species). We document a reversal from this expected C3-C4 contrast. Over the first 12 years of a 20-year free-air CO2 enrichment experiment with 88 C3 or C4 grassland plots, we found that biomass was markedly enhanced at eCO2 relative to ambient CO2 in C3 but not C4 plots, as expected. During the subsequent 8 years, the pattern reversed: Biomass was markedly enhanced at eCO2 relative to ambient CO2 in C4 but not C3 plots. Soil net nitrogen mineralization rates, an index of soil nitrogen supply, exhibited a similar shift: eCO2 first enhanced but later depressed rates in C3 plots, with the opposite true in C4 plots, partially explaining the reversal of the eCO2 biomass response. These findings challenge the current C3-C4 eCO2 paradigm and show that even the best-supported short-term drivers of plant response to global change might not predict long-term results.

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Two-billion-year-old evaporites capture Earths great oxidation  Voir?

Major changes in atmospheric and ocean chemistry occurred in the Paleoproterozoic era (2.5 to 1.6 billion years ago). Increasing oxidation dramatically changed Earth’s surface, but few quantitative constraints exist on this important transition. This study describes the sedimentology, mineralogy, and geochemistry of a 2-billion-year-old, ~800-meter-thick evaporite succession from the Onega Basin in Russian Karelia. The deposit consists of a basal unit dominated by halite (~100 meters) followed by units dominated by anhydrite-magnesite (~500 meters) and dolomite-magnesite (~200 meters). The evaporite minerals robustly constrain marine sulfate concentrations to at least 10 millimoles per kilogram of water, representing an oxidant reservoir equivalent to more than 20% of the modern ocean-atmosphere oxidizing capacity. These results show that substantial amounts of surface oxidant accumulated during this critical transition in Earth’s oxygenation.

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Structure of a prehandover mammalian ribosomal SRP{middle dot}SRP receptor targeting complex  Voir?

Signal recognition particle (SRP) targets proteins to the endoplasmic reticulum (ER). SRP recognizes the ribosome synthesizing a signal sequence and delivers it to the SRP receptor (SR) on the ER membrane followed by the transfer of the signal sequence to the translocon. Here, we present the cryo–electron microscopy structure of the mammalian translating ribosome in complex with SRP and SR in a conformation preceding signal sequence handover. The structure visualizes all eukaryotic-specific SRP and SR proteins and reveals their roles in stabilizing this conformation by forming a large protein assembly at the distal site of SRP RNA. We provide biochemical evidence that the guanosine triphosphate hydrolysis of SRP·SR is delayed at this stage, possibly to provide a time window for signal sequence handover to the translocon.

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Paternally inherited cis-regulatory structural variants are associated with autism  Voir?

The genetic basis of autism spectrum disorder (ASD) is known to consist of contributions from de novo mutations in variant-intolerant genes. We hypothesize that rare inherited structural variants in cis-regulatory elements (CRE-SVs) of these genes also contribute to ASD. We investigated this by assessing the evidence for natural selection and transmission distortion of CRE-SVs in whole genomes of 9274 subjects from 2600 families affected by ASD. In a discovery cohort of 829 families, structural variants were depleted within promoters and untranslated regions, and paternally inherited CRE-SVs were preferentially transmitted to affected offspring and not to their unaffected siblings. The association of paternal CRE-SVs was replicated in an independent sample of 1771 families. Our results suggest that rare inherited noncoding variants predispose children to ASD, with differing contributions from each parent.

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Developmental and oncogenic programs in H3K27M gliomas dissected by single-cell RNA-seq  Voir?

Gliomas with histone H3 lysine27-to-methionine mutations (H3K27M-glioma) arise primarily in the midline of the central nervous system of young children, suggesting a cooperation between genetics and cellular context in tumorigenesis. Although the genetics of H3K27M-glioma are well characterized, their cellular architecture remains uncharted. We performed single-cell RNA sequencing in 3321 cells from six primary H3K27M-glioma and matched models. We found that H3K27M-glioma primarily contain cells that resemble oligodendrocyte precursor cells (OPC-like), whereas more differentiated malignant cells are a minority. OPC-like cells exhibit greater proliferation and tumor-propagating potential than their more differentiated counterparts and are at least in part sustained by PDGFRA signaling. Our study characterizes oncogenic and developmental programs in H3K27M-glioma at single-cell resolution and across genetic subclones, suggesting potential therapeutic targets in this disease.

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MFN2 agonists reverse mitochondrial defects in preclinical models of Charcot-Marie-Tooth disease type 2A  Voir?

Mitofusins (MFNs) promote fusion-mediated mitochondrial content exchange and subcellular trafficking. Mutations in Mfn2 cause neurodegenerative Charcot-Marie-Tooth disease type 2A (CMT2A). We showed that MFN2 activity can be determined by Met376 and His380 interactions with Asp725 and Leu727 and controlled by PINK1 kinase–mediated phosphorylation of adjacent MFN2 Ser378. Small-molecule mimics of the peptide-peptide interface of MFN2 disrupted this interaction, allosterically activating MFN2 and promoting mitochondrial fusion. These first-in-class mitofusin agonists overcame dominant mitochondrial defects provoked in cultured neurons by CMT2A mutants MFN2 Arg94->Gln94 and MFN2 Thr105->Met105, as demonstrated by amelioration of mitochondrial dysmotility, fragmentation, depolarization, and clumping. A mitofusin agonist normalized axonal mitochondrial trafficking within sciatic nerves of MFN2 Thr105->Met105 mice, promising a therapeutic approach for CMT2A and other untreatable diseases of impaired neuronal mitochondrial dynamism and/or trafficking.

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New Products  Voir?

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Academia's forgotten footnote  Voir?

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Observing the cell in its native state: Imaging subcellular dynamics in multicellular organisms  Voir?

True physiological imaging of subcellular dynamics requires studying cells within their parent organisms, where all the environmental cues that drive gene expression, and hence the phenotypes that we actually observe, are present. A complete understanding also requires volumetric imaging of the cell and its surroundings at high spatiotemporal resolution, without inducing undue stress on either. We combined lattice light-sheet microscopy with adaptive optics to achieve, across large multicellular volumes, noninvasive aberration-free imaging of subcellular processes, including endocytosis, organelle remodeling during mitosis, and the migration of axons, immune cells, and metastatic cancer cells in vivo. The technology reveals the phenotypic diversity within cells across different organisms and developmental stages and may offer insights into how cells harness their intrinsic variability to adapt to different physiological environments.

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Systematic analysis of complex genetic interactions  Voir?

To systematically explore complex genetic interactions, we constructed ~200,000 yeast triple mutants and scored negative trigenic interactions. We selected double-mutant query genes across a broad spectrum of biological processes, spanning a range of quantitative features of the global digenic interaction network and tested for a genetic interaction with a third mutation. Trigenic interactions often occurred among functionally related genes, and essential genes were hubs on the trigenic network. Despite their functional enrichment, trigenic interactions tended to link genes in distant bioprocesses and displayed a weaker magnitude than digenic interactions. We estimate that the global trigenic interaction network is ~100 times as large as the global digenic network, highlighting the potential for complex genetic interactions to affect the biology of inheritance, including the genotype-to-phenotype relationship.

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Erratum for the Report "A precise measurement of the magnetic field in the corona of the black hole binary V404 Cygni" by Y. Dallilar, S. S. Eikenberry, A. Garner, R. D. Stelter, A. Gottlieb, P. Gandhi, P. Casella, V. S. Dhillon, T. R. Marsh, S. P. Littlefair, L. Hardy, R. Fender, K. Mooley, D. J. Walton, F. Fuerst, M. Bachetti, A. J. Castro-Tirado, M. Charcos, M. L. Edwards, N. M. Lasso-Cabrera, A. Marin-Franch, S. N. Raines, K. Ackley, J. G. Bennett, A. J. Cenarro, B. Chinn, H. V. Donoso, R. Frommeyer, K. Hanna, M. D. Herlevich, J. Julian, P. Miller, S. Mullin, C. H. Murphey, C. Packham, F. Varosi, C. Vega, C. Warner, A. N. Ramaprakash, M. Burse, S. Punnadi, P. Chordia, A. Gerarts, H. de Paz Martin, M. Martin Calero, R. Scarpa, S. Fernandez Acosta, W. M. Hernandez Sanchez, B. Siegel, F. Francisco Perez, H. D. Viera Martin, J. A. Rodriguez Losada, A. Nunez, A. Tejero, C. E. Martin Gonzalez, C. Cabrera Rodriguez, J. Molgo, J. Esteban Rodriguez, J. I. Fernandez Caceres, L. A. Rodriguez Garcia, M. Huertas Lopez, R. Dominguez, T. Gaggstatter, A. Cabrera Lavers, S. Geier, P. Pessev, A. Sarajedini  Voir?

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Dernière mise à jour : 23/04/2018 : 05:08


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