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Self-reported neurocognitive complaints in the Swiss HIV Cohort Study: a viral genome-wide association study
No full textInternational audienceAbstract People with HIV may report neurocognitive complaints, with or without associated neurocognitive impairment, varying between individuals and populations. While the HIV genome could play a major role, large systematic viral genome-wide screens to date are lacking. The Swiss HIV Cohort Study biannually enquires neurocognitive complaints. We quantified broad-sense heritability estimates using partial ‘pol’ sequences from the Swiss HIV Cohort Study resistance database and performed a viral near full-length genome-wide association study for the longitudinal area under the curve of neurocognitive complaints. We performed all analysis (i) restricted to HIV Subtype B and (ii) including all HIV subtypes. From 8547 people with HIV with neurocognitive complaints, we obtained 6966 partial ‘pol’ sequences and 2334 near full-length HIV sequences. Broad-sense heritability estimates for presence of memory loss complaints ranged between 1% and 17% (Subtype B restricted 1–22%) and increased with the stringency of the phylogenetic distance thresholds. The genome-wide association study revealed one amino acid (Env L641E), after adjusting for multiple testing, positively associated with memory loss complaints (P = 4.3 * 10−6). Other identified mutations, while insignificant after adjusting for multiple testing, were reported in other smaller studies (Tat T64N, Env *291S). We present the first HIV genome-wide association study analysis of neurocognitive complaints and report a first estimate for the heritability of neurocognitive complaints through HIV. Moreover, we could identify one mutation significantly associated with the presence of memory loss complaints. Our findings indicate that neurocognitive complaints are polygenetic and highlight advantages of a whole genome approach for pathogenicity determination
Dating the Solar System’s giant planet orbital instability using enstatite meteorites
No full textInternational audienceThe giant planets of the Solar System formed on initially compact orbits, which transitioned to the current wider configuration by means of an orbital instability. The timing of that instability is poorly constrained. In this work, we use dynamical simulations to demonstrate that the instability implanted planetesimal fragments from the terrestrial planet region into the asteroid main belt. We use meteorite data to show that the implantation occurred >=60 million years (Myr) after the Solar System began to form. Combining this constraint with a previous upper limit derived from Jupiter’s trojan asteroids, we conclude that the orbital instability occurred 60 to 100 Myr after the beginning of Solar System formation. The giant impact that formed the Moon occurred within this range, so it might be related to the giant planet instability
Fast Scrambling at the Boundary
No full textInternational audienceMany-body systems which saturate the quantum bound on chaos are attracting interest across a wide range of fields. Notable examples include the Sachdev-Ye-Kitaev model and its variations, all characterised by some form or randomness and all to all couplings. Here we study many-body quantum chaos in a quantum impurity model showing Non-Fermi-Liquid physics, the overscreened multichannel Kondo model. We compute exactly the low-temperature behavior of the out-of time order correlator in the limit of large and large number of channels , at fixed ratio . Due to strong correlations at the impurity site the spin fractionalizes in auxiliary fermions and bosons. We show that all the degrees of freedom of our theory acquire a Lyapunov exponent which is linear in temperature as , with a prefactor that depends on . Remarkably, for the impurity spin displays maximal chaos, while bosons and fermions only get up to half of the maximal Lyapunov exponent. Our results highlights two new features: a non-disordered model which is maximally chaotic due to strong correlations at its boundary and a fractionalization of quantum chaos
Kondo-Zeno crossover in the dynamics of a monitored quantum dot
No full text19 pages, 7 figuresWe study the dynamics of a quantum dot coupled to a metallic bath and subject to continuous monitoring of its charge density. The dynamics averaged over measurement noise is described by a dissipative Anderson impurity model with local Markovian dephasing, that we solve using an extension of the Non-Crossing Approximation in the vectorized Hilbert space. We show that the decay time scale of an initially polarised spin which is suddenly coupled to the bath and to the monitoring protocol displays a crossover from Kondo screening, with a lifetime controlled by interactions, to Quantum Zeno effect, with a lifetime which decreases with bare dissipation as the dephasing or monitoring rate is increased. Using a Schrieffer-Wolff transformation on the Lindbladian we derive an effective model for the long-time dynamics which is described at weak dissipation by a non-Hermitian Kondo model with complex-valued spin-spin exchange. As the dephasing is increased heating due to doublon production takes over and control the spin decay
Hybrid light-matter states in topological superconductors coupled to cavity photons
No full textInternational audienceWe consider a one-dimensional topological superconductor hosting Majorana bound states at its ends coupled to a single mode cavity. In the strong light-matter coupling regime, electronic and photonic degrees of freedom hybridize resulting in the formation of polaritons. We find the polariton spectrum by calculating the cavity photon spectral function of the coupled electron-photon system. In the topological phase the lower in energy polariton modes are formed by the bulk-Majorana transitions coupled to cavity photons and are also sensitive to the Majorana parity. In the trivial phase the lower polariton modes emerge due to the coupling of the bulk-bulk transitions across the gap to photons. Our work demonstrates the formation of polaritons in topological superconductors coupled to photons that contain information on the features of the Majorana bound states
Dynamics of spatial phase coherence in a dissipative Bose–Hubbard atomic system
No full textInternational audienc
CRISPR/Cas9-based somatic knock-in of reporters in the avian embryo in ovo
No full textGene editing and protein tagging are at the heart of modern developmental and cell biology. The advent of CRISPR/Cas9 based methods offers the possibility to develop customized approaches for genomic manipulations in non-classical experimental models. Here, we show that highly efficient somatic knock-ins of long DNA fragments can be achieved in the developing chick neural tube in ovo. We compare different types of repair matrices and different methods for the delivery of the CRISPR/Cas9 machinery, and find that an all plasmid-based approach and short arms of homology provide an easy and efficient method to achieve high frequencies of knock-in insertions with virtually no background signal. We use this method to target fluorescent reporters and dynamically monitor the subcellular distribution of endogenously expressed tagged proteins, as well as to insert the Gal4-VP16 transcription factor or the Cre recombinase at specific loci to label neural sub-populations in the chick embryonic spinal cord. Finally, we show that the method can also be applied to target the epiblast and somitic mesoderm
Ca 2+ regulation of Myosin II and Myosin VI during rupture of the Shigella -containing vacuole
No full textShigella , the causative agent of bacillary dysentery, invades epithelial cells to colonize the intestinal mucosa. Following invasion, Shigella is enclosed in a vacuole that needs to rupture for bacterial intra-cytosolic replication. We show here that rupture of the Shigella vacuole requires Ca 2+ influx leading to long lasting local Ca 2+ increases that regulate actin dynamics affecting the Shigella vacuole integrity. These Ca 2+ increases promote vacuolar rupture by activating myosin II associated with actin filaments in membrane ruffles distant from the vacuole, while tethering myosin VI at the actin coat-surrounded vacuole. Ca 2+ depletion and myosin II inhibition impair formation of the actin coat and vacuole rupture. Inhibition of myosin VI also delays rupture of vacuoles but lead to their tumbling. These findings highlight a role for Ca 2+ in coordinating actin–based forces and constraints during early rupture steps of bacterial vacuole, that pull on vacuolar membranes and tether them to the actin cortex via myosin II and VI, respectively, a process relevant to intracellular pathogen and endomembrane trafficking
Mastering the synthesis of high Na-content, moisture-stable layered oxide cathode for Na-ion batteries
No full textInternational audienceSodium layered oxides NaxMO2 (x ≤ 1 and M = transition metal) are of great interest for sodium-ion batteries due to their high energy density and cost-effectiveness. However, these materials, whether they are stoichiometric (Na/M 1 as in O3 NaMO2) or not (Na/M 0.7 as in P3/P2 NaxMO2), have certain disadvantages, namely sensitivity to humidity or inadequate capacity, respectively. Herein, we propose an intermediate composition Na0.85Ni0.38Zn0.04Mn0.48Ti0.1O2 that we succeed to stabilize in either O3 or a nanoscale mixture of O3-P3 or O3-P2 phases as proven by X-ray diffraction and transmission electron microscopy, through complex synthesis approaches including quenching, slow cooling and annealing in different atmospheres (Ar, air, O2 etc). We rationalize the stabilization of different phases and microstructure as a function of synthesis conditions and show how it influences the electrochemical performance. Through this study we identified a single phase O3 Na0.85Ni0.38Zn0.04Mn0.48Ti0.1O2 synthesized at 1000 °C in air, which exhibits a high capacity of ~170 mAh/g and good moisture stability. Furthermore, thanks to the synthesis- structure- electrochemical performance relationship identified here, we believe that this study will provide a reliable basis for optimizing the synthesis for best performing sodium layered oxides for commercialization
