Rotation of an immersed cylinder sliding near a thin elastic coating

It is known that an object translating parallel to a soft wall in a viscous fluid produces hydro- dynamic stresses that deform the wall, which, in turn, results in a lift force on the object. Recent experiments with cylinders sliding under gravity near a soft incline, which confirmed theoretical arguments for the lift force, also reported an unexplained steady-state rotation of the cylinders [Saintyves et al. PNAS 113(21), 2016]. Motivated by these observations, we show, in the lubrication limit, that an infinite cylinder that translates in a viscous fluid parallel to a soft wall at constant speed and separation distance must also rotate in order to remain free of torque. Using the Lorentz reciprocal theorem, we show analytically that for small deformations of the elastic layer, the angular velocity of the cylinder scales with the cube of the sliding speed. These predictions are confirmed numerically. We then apply the theory to the gravity-driven motion of a cylinder near a soft incline and find qualitative agreement with the experimental observations, namely that a softer elastic layer results in a greater angular speed of the cylinder.Comment: 16 pages, 4 figure

Charting the Topography of the Neural Network Landscape with Thermal-Like Noise

The training of neural networks is a complex, high-dimensional, non-convex and noisy optimization problem whose theoretical understanding is interesting both from an applicative perspective and for fundamental reasons. A core challenge is to understand the geometry and topography of the landscape that guides the optimization. In this work, we employ standard Statistical Mechanics methods, namely, phase-space exploration using Langevin dynamics, to study this landscape for an over-parameterized fully connected network performing a classification task on random data. Analyzing the fluctuation statistics, in analogy to thermal dynamics at a constant temperature, we infer a clear geometric description of the low-loss region. We find that it is a low-dimensional manifold whose dimension can be readily obtained from the fluctuations. Furthermore, this dimension is controlled by the number of data points that reside near the classification decision boundary. Importantly, we find that a quadratic approximation of the loss near the minimum is fundamentally inadequate due to the exponential nature of the decision boundary and the flatness of the low-loss region. This causes the dynamics to sample regions with higher curvature at higher temperatures, while producing quadratic-like statistics at any given temperature. We explain this behavior by a simplified loss model which is analytically tractable and reproduces the observed fluctuation statistics.Comment: 7 pages, 4 figure

Measuring the impact of forest management on the structure and composition of moth communities using automatic and manual light traps

International audienceHuman-induced environmental impacts threaten global biodiversity, including temperate forestswhich have been highly altered and reduced. Despite these disturbances, temperate forests serveas biodiversity hotspots and play an important role in the conservation of declining species. Insectdecline, often overlooked, is of significant concern due to its consequences on ecosystems andhuman health. To reverse insect decline, we first need to understand the influence our activitieshave on their populations. In this regard, our study focused on the impact of the French «futaierégulière» forest management method on moth communities.First, we chose to evaluate the effect of forest management on species richness and diversity.Sampling took place using two types of automatic light traps (T-traps LepiLED and SkinnerActinic) in the forest of Tours-Larçay-les Hâtes, focusing on two contrasting plots : a naturallyevolving plot and a managed plot. Contrary to our hypothesis, we found that forest managementdoes not appear to have a significant impact on the moth communities we studied.However, to confirm our results, we first had to improve upon our current biomonitoring protocol,focusing on increasing the sampling effort of micro moths which was initially insufficient. Thiswas our second step. To do so we chose to use Bioform towers along with our automatic traps.By doing so, we concluded that the “futaie régulière” forest management method has no effect onthe richness and diversity of both the macro moth and the micro moth communities located in theforest of Tours-Larçay-les Hâtes

Den interkulturella blicken i pedagogik : Inte bara goda föresatser

Med ”interkulturell blick” avses i denna antologi ett speciellt förhållningssätt. Perspektivet är gränsöverskridande och kosmopolitiskt. Det handlar om en ”inkluderande globalism”, en strävan att frigöra sig från etnocentriska synsätt för att i stället skapa en inkluderande, jämlik och demokratisk pedagogik. Det rör sig inte om någon kompenserande ”specialpedagogik för invandrare”. Snarare gäller det att med pedagogikens hjälp bidra till att göra det annorlunda normalt, till att skapa en ”diversifierad normalitet”. Boken är indelad i två delar: Interkulturalitet och samhälle samt Interkulturalitet och lärande. De flesta bidragen har skrivits av forskare och lärare vid Södertörns högskola och är baserade på författarnas forskning om interkulturell pedagogik. Bland bidragsgivarna finns också lärare som främst skriver utifrån sina praktiska yrkeserfarenheter av pedagogik och interkulturalitet

Les gabapentinoïdes : une revue de la littérature

International audienceThe objective of this review is to produce a synthesis of the state of knowledge regarding the epidemiology, pharmacology, clinical and analytical toxicology of gabapentinoids. The pharmacological class of gabapentinoids is mainly represented by gabapentin and pregabalin, which were marketed around the 2000s. Soon after their marketing, cases of misuse were documented and related to abuse and dependence. Gabapentinoids are well-tolerated and acute poisonings are most often benign, except in cases of poly-intoxication, particularly with opiates. Pregabalin increases the risk of death due to opioid overdose. To date, there is no specific treatment, management is based on symptomatic treatment. Numerous analytical methods allowing the detection and determination of pregabalin and gabapentin in blood, urine and hair have been published, the analyzes are mainly carried out in liquid chromatography coupled to tandem mass spectrometry. Testing for gabapentinoids should be done routinely in death related to substance abuse.L’objectif de cette revue de la littérature est de réaliser une synthèse de l’état des connaissances concernant l’épidémiologie, la pharmacologie, la toxicologie clinique et analytique des gabapentinoïdes. La classe pharmacologique des gabapentinoïdes est principalement représentée par la gabapentine et la prégabaline, qui ont été commercialisées autour des années 2000. Rapidement après leur commercialisation, des cas de mésusage ont été documentés dans des contextes d’abus et de dépendance. Ce sont des médicaments bien tolérés et les intoxications aiguës sont le plus souvent bénignes, sauf en cas de poly-intoxication en particulier avec des opiacés. La prégabaline augmente le risque de décès par overdose aux opiacés. En l’absence d’antidote spécifique, la prise en charge repose sur un traitement symptomatique. De nombreuses méthodes analytiques permettant la détection et le dosage de la prégabaline et de la gabapentine dans le sang, les urines et les cheveux ont été publiées, aujourd’hui les analyses sont le plus souvent effectuées en chromatographie liquide couplée à la spectrométrie de masse en tandem. La recherche des gabapentinoïdes devrait être effectuée systématiquement dans les cas de décès liés à l’usage de substances