Self-Dual Bending Theory for Vesicles

We present a self-dual bending theory that may enable a better understanding of highly nonlinear global behavior observed in biological vesicles. Adopting this topological approach for spherical vesicles of revolution allows us to describe them as frustrated sine-Gordon kinks. Finally, to illustrate an application of our results, we consider a spherical vesicle globally distorted by two polar latex beads.Comment: 10 pages, 3 figures, LaTeX2e+IOPar

Traffic Instabilities in Self-Organized Pedestrian Crowds

In human crowds as well as in many animal societies, local interactions among individuals often give rise to self-organized collective organizations that offer functional benefits to the group. For instance, flows of pedestrians moving in opposite directions spontaneously segregate into lanes of uniform walking directions. This phenomenon is often referred to as a smart collective pattern, as it increases the traffic efficiency with no need of external control. However, the functional benefits of this emergent organization have never been experimentally measured, and the underlying behavioral mechanisms are poorly understood. In this work, we have studied this phenomenon under controlled laboratory conditions. We found that the traffic segregation exhibits structural instabilities characterized by the alternation of organized and disorganized states, where the lifetime of well-organized clusters of pedestrians follow a stretched exponential relaxation process. Further analysis show that the inter-pedestrian variability of comfortable walking speeds is a key variable at the origin of the observed traffic perturbations. We show that the collective benefit of the emerging pattern is maximized when all pedestrians walk at the average speed of the group. In practice, however, local interactions between slow- and fast-walking pedestrians trigger global breakdowns of organization, which reduce the collective and the individual payoff provided by the traffic segregation. This work is a step ahead toward the understanding of traffic self-organization in crowds, which turns out to be modulated by complex behavioral mechanisms that do not always maximize the group's benefits. The quantitative understanding of crowd behaviors opens the way for designing bottom-up management strategies bound to promote the emergence of efficient collective behaviors in crowds.Comment: Article published in PLoS Computational biology. Freely available here: http://www.ploscompbiol.org/article/info%3Adoi%2F10.1371%2Fjournal.pcbi.100244

Dense matter with eXTP

In this White Paper we present the potential of the Enhanced X-ray Timing and Polarimetry (eXTP) mission for determining the nature of dense matter; neutron star cores host an extreme density regime which cannot be replicated in a terrestrial laboratory. The tightest statistical constraints on the dense matter equation of state will come from pulse profile modelling of accretion-powered pulsars, burst oscillation sources, and rotation-powered pulsars. Additional constraints will derive from spin measurements, burst spectra, and properties of the accretion flows in the vicinity of the neutron star. Under development by an international Consortium led by the Institute of High Energy Physics of the Chinese Academy of Science, the eXTP mission is expected to be launched in the mid 2020s.Comment: Accepted for publication on Sci. China Phys. Mech. Astron. (2019

Complex genetic patterns in human arise from a simple range-expansion model over continental landmasses

© 2018 Kanitz et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Although it is generally accepted that geography is a major factor shaping human genetic differentiation, it is still disputed how much of this differentiation is a result of a simple process of isolation-by-distance, and if there are factors generating distinct clusters of genetic similarity. We address this question using a geographically explicit simulation framework coupled with an Approximate Bayesian Computation approach. Based on six simple summary statistics only, we estimated the most probable demographic parameters that shaped modern human evolution under an isolation by distance scenario, and found these were the following: an initial population in East Africa spread and grew from 4000 individuals to 5.7 million in about 132 000 years. Subsequent simulations with these estimates followed by cluster analyses produced results nearly identical to those obtained in real data. Thus, a simple diffusion model from East Africa explains a large portion of the genetic diversity patterns observed in modern humans. We argue that a model of isolation by distance along the continental landmasses might be the relevant null model to use when investigating selective effects in humans and probably many other species

Rapid response to the M_w 4.9 earthquake of November 11, 2019 in Le Teil, Lower Rhône Valley, France

On November 11, 2019, a Mw 4.9 earthquake hit the region close to Montelimar (lower Rhône Valley, France), on the eastern margin of the Massif Central close to the external part of the Alps. Occuring in a moderate seismicity area, this earthquake is remarkable for its very shallow focal depth (between 1 and 3 km), its magnitude, and the moderate to large damages it produced in several villages. InSAR interferograms indicated a shallow rupture about 4 km long reaching the surface and the reactivation of the ancient NE-SW La Rouviere normal fault in reverse faulting in agreement with the present-day E-W compressional tectonics. The peculiarity of this earthquake together with a poor coverage of the epicentral region by permanent seismological and geodetic stations triggered the mobilisation of the French post-seismic unit and the broad French scientific community from various institutions, with the deployment of geophysical instruments (seismological and geodesic stations), geological field surveys, and field evaluation of the intensity of the earthquake. Within 7 days after the mainshock, 47 seismological stations were deployed in the epicentral area to improve the Le Teil aftershocks locations relative to the French permanent seismological network (RESIF), monitor the temporal and spatial evolution of microearthquakes close to the fault plane and temporal evolution of the seismic response of 3 damaged historical buildings, and to study suspected site effects and their influence in the distribution of seismic damage. This seismological dataset, completed by data owned by different institutions, was integrated in a homogeneous archive and distributed through FDSN web services by the RESIF data center. This dataset, together with observations of surface rupture evidences, geologic, geodetic and satellite data, will help to unravel the causes and rupture mechanism of this earthquake, and contribute to account in seismic hazard assessment for earthquakes along the major regional Cévenne fault system in a context of present-day compressional tectonics

Couches minces d'oxynitrure de titane : la réactivité comme moyen original de caractérisation physico - chimique

Titanium oxinitride thin films, TiNxOy, were elaborated on Si(100) by the MOCVD (Metal Organic Chemical Vapor Deposition) method, using titanium isopropoxide Ti(OCH(CH3)2)4 and ammonia NH3 as precursors. By varying the growth temperature, it is possible to modify the N/O ratio and change the conductivity of the films.The target of this work was to determine the composition and the structure of these TiNxOy thin films in order to understand the electrical properties. However, this study was difficult because classical characterization techniques (SEM, XRD, Raman, XPS...) were unable to describe the whole TiNxOy system. Indeed, only a structure which is isomorphic to TiN (NaCl structure) was detected in the samples elaborated at high temperature ( T > 550 °C) and quantitative analysis revealed relatively high oxygen content in all the samples. This study was broadened to TiN films in order to understand the importance of oxygen in this structure.Original characterization methods, based on the fact that it is possible to link the structure of a material to its reactivity, were carried out in order to complete previous characterizations. In particular, the study of the reactivity of thin films towards ion bombardment or thermal treatments allowed to determine and quantify the different phases which are present in TiNxOy thin films. For low synthesis temperatures (T L'objectif de ce travail était la détermination de la composition et de la structure des couches minces de TiNxOy de façon à en comprendre les propriétés électriques. Cependant, cette étude s'est rapidement avérée plus complexe que prévue, les techniques de caractérisation classiques (MEB, DRX, Raman, XPS...) étant insuffisantes pour décrire le système TiNxOy dans sa totalité. En effet, une seule phase cristallisée, isomorphe de TiN, a pu être mise en évidence dans les échantillons élaborés à haute température (T > 550 °C) tandis que des analyses quantitatives ont révélé des proportions d'oxygène relativement importantes dans tous les échantillons. Aussi, cette étude a été élargie à des films de TiN afin de comprendre l'importance de l'oxygène dans cette structure.Des méthodes de caractérisation originales, basées sur le fait qu'il est possible de relier la structure d'un matériau à sa réactivité, ont alors été mises en œuvre afin de compléter les analyses précédentes. Notamment, l'étude de la réactivité des couches minces vis-à-vis d'une irradiation ionique ou lors de traitements thermiques a permis de qualifier et quantifier les différentes phases des films minces de TiNxOy en réalité constitués d'une phase Ti(N,O) conductrice et d'une phase TiO2 isolante. Un modèle de percolation permettant la simulation des variations de conductivité des films à partir des proportions relatives de chacune de ces deux phases a alors pu être proposé

Pollution chimique de l'air intérieur

AIX-MARSEILLE2-BU Pharmacie (130552105) / SudocSudocFranceF

Determination of the vertical distribution of radioelements (K, U, Th, Cs) in soils from portable HP-Ge spectrometer measurements: A tool for soil erosion studies

International audienceSoil erosion studies, based on the 137Cs technique, require a lot of time-consuming cores to determine soil loss or gain. We show that portable HP-Ge spectrometer can be used to determine the content and the distribution in the soil of natural and artificial radionuclides. Simulations of gamma-rays transport throughout the soil profile used a Monte Carlo code. The methodology requires a unique undisturbed coring site to build the models, calibrate the spectrometer readings and derive soil denudation or accumulation thickness