Tree-like graphings, wallings, and median graphings of equivalence relations

We prove several results showing that every locally finite Borel graph whose large-scale geometry is "tree-like" induces a treeable equivalence relation. In particular, our hypotheses hold if each component of the original graph either has bounded tree-width or is quasi-isometric to a tree. In the latter case, we moreover show that there exists a Borel quasi-isometry to a Borel forest, under the additional assumption of (componentwise) bounded degree. We also extend these results on quasi-treeings to Borel proper metric spaces. In fact, our most general result shows treeability of countable Borel equivalence relations equipped with an abstract wallspace structure on each class obeying some local finiteness conditions, which we call a proper walling. The proof is based on the Stone duality between proper wallings and median graphs, i.e., CAT(0) cube complexes.Comment: 38 page

Mechanical device or touchscreen widget: the effects of input device and task size on data entry on the primary flight display

ABSTRACT: Due to their customizability, touchscreens continue to advance as a device of choice when designing aircraft cockpits. Previous studies investigated the effect of turbulence on human performance when using touchscreens, but few have evaluated its performance for realistic aviation-specific tasks. In this study, we compared four touchscreen widgets and three mechanical devices during realistic data input on a primary flight display (PFD). Twenty participants took part in the experiment at a constant level of vibration, while simultaneously completing a secondary tracking task. Results indicated that virtual keypads lead to faster completion time for medium to large changes while keeping error rates low. Rotary knobs were fastest for small changes. Virtual keypads also had lower workload and discomfort compared to rotary knobs and drag-based widgets. We found the completion time to be the most important factor in tracking task performance, which translated in higher precision for keypads. These findings suggest that virtual keypads represent an efficient and secure option for numerical data input at low-to-medium vibration

Many-body Theory vs Simulations for the pseudogap in the Hubbard model

The opening of a critical-fluctuation induced pseudogap (or precursor pseudogap) in the one-particle spectral weight of the half-filled two-dimensional Hubbard model is discussed. This pseudogap, appearing in our Monte Carlo simulations, may be obtained from many-body techniques that use Green functions and vertex corrections that are at the same level of approximation. Self-consistent theories of the Eliashberg type (such as the Fluctuation Exchange Approximation) use renormalized Green functions and bare vertices in a context where there is no Migdal theorem. They do not find the pseudogap, in quantitative and qualitative disagreement with simulations, suggesting these methods are inadequate for this problem. Differences between precursor pseudogaps and strong-coupling pseudogaps are also discussed.Comment: Accepted, Phys. Rev. B15 15Mar00. Expanded version of original submission, Latex, 8 pages, epsfig, 5 eps figures (Last one new). Discussion on fluctuation and strong coupling induced pseudogaps expande

Novel in vitro and mathematical models for the prediction of chemical toxicity

The focus of much scientific and medical research is directed towards understanding the disease process and defining therapeutic intervention strategies. The scientific basis of drug safety is very complex and currently remains poorly understood, despite the fact that adverse drug reactions (ADRs) are a major health concern and a serious impediment to development of new medicines. Toxicity issues account for ∼21% drug attrition during drug development and safety testing strategies require considerable animal use. Mechanistic relationships between drug plasma levels and molecular/cellular events that culminate in whole organ toxicity underpins development of novel safety assessment strategies. Current in vitro test systems are poorly predictive of toxicity of chemicals entering the systemic circulation, particularly to the liver. Such systems fall short because of (1) the physiological gap between cells currently used and human hepatocytes existing in their native state, (2) the lack of physiological integration with other cells/systems within organs, required to amplify the initial toxicological lesion into overt toxicity, (3) the inability to assess how low level cell damage induced by chemicals may develop into overt organ toxicity in a minority of patients, (4) lack of consideration of systemic effects. Reproduction of centrilobular and periportal hepatocyte phenotypes in in vitro culture is crucial for sensitive detection of cellular stress. Hepatocyte metabolism/phenotype is dependent on cell position along the liver lobule, with corresponding differences in exposure to substrate, oxygen and hormone gradients. Application of bioartificial liver (BAL) technology can encompass in vitro predictive toxicity testing with enhanced sensitivity and improved mechanistic understanding. Combining this technology with mechanistic mathematical models describing intracellular metabolism, fluid-flow, substrate, hormone and nutrient distribution provides the opportunity to design the BAL specifically to mimic the in vivo scenario. Such mathematical models enable theoretical hypothesis testing, will inform the design of in vitro experiments, and will enable both refinement and reduction of in vivo animal trials. In this way, development of novel mathematical modelling tools will help to focus and direct in vitro and in vivo research, and can be used as a framework for other areas of drug safety science

Migratory Dermal Dendritic Cells Act as Rapid Sensors of Protozoan Parasites

Dendritic cells (DC), including those of the skin, act as sentinels for intruding microorganisms. In the epidermis, DC (termed Langerhans cells, LC) are sessile and screen their microenvironment through occasional movements of their dendrites. The spatio-temporal orchestration of antigen encounter by dermal DC (DDC) is not known. Since these cells are thought to be instrumental in the initiation of immune responses during infection, we investigated their behavior directly within their natural microenvironment using intravital two-photon microscopy. Surprisingly, we found that, under homeostatic conditions, DDC were highly motile, continuously crawling through the interstitial space in a Gαi protein-coupled receptor–dependent manner. However, within minutes after intradermal delivery of the protozoan parasite Leishmania major, DDC became immobile and incorporated multiple parasites into cytosolic vacuoles. Parasite uptake occurred through the extension of long, highly dynamic pseudopods capable of tracking and engulfing parasites. This was then followed by rapid dendrite retraction towards the cell body. DDC were proficient at discriminating between parasites and inert particles, and parasite uptake was independent of the presence of neutrophils. Together, our study has visualized the dynamics and microenvironmental context of parasite encounter by an innate immune cell subset during the initiation of the immune response. Our results uncover a unique migratory tissue surveillance program of DDC that ensures the rapid detection of pathogens

Dispersion et filage continu par coagulation de nanotubes de carbone

Cette thèse rapporte l'étude d'un procédé original de filage continu par coagulation de nanotubes de carbone afin d'obtenir une fibre composite aux propriétés balistiques remarquables. Elle s'intéresse à la caractérisation des fonctions chimiques de surface, de la morphologie et des dimensions des nanotubes aux différentes étapes du procédé. Y sont détaillées une étude quantitative des effets et cinétiques de scission des nanotubes par les ultrasons. Elle présente de plus des travaux relatifs au développement d'une ligne continue de filage des nanotubes de carbone en voie solvant. Des méthodes originales de caractérisation mécanique in-situ de fibre gel sont proposées, permettant notamment un meilleur contrôle des paramètres physicochimiques liés au procédé. Nous espérons que les résultats obtenus participeront à une meilleure compréhension des effets des traitements utilisés pour l'obtention de dispersion homogène de nanotubes de carbone et à un développement des procédés continus de filage textile.This thesis deals with an original continuous spinning process of carbon nanotubes by coagulation. It focuses on characterization of surface chemical functions, morphology and dimensions of carbon nanotubes at each stage of the process. We present a quantitative study about the effects and kinetics of nanotubes scission induced by ultrasound. We present also the development of a continuous wet-spinning line. We propose methods for in-situ mechanical characterization of gel fibers, which enable a better control of physico-chemical parameters of the process. We hope that these results will participate to a better global comprehension of the effects of treatments used to obtain homogeneous carbon nanotubes suspension and to the development of continuous spinning process of high performance textile fibers.BORDEAUX1-Bib.electronique (335229901) / SudocSudocFranceF

Diurnal variations of the optical properties of phytoplankton in a laboratory experiment and their implication for using inherent optical properties to measure biomass

© 2018 Optical Society of America Diurnal variations of phytoplankton size distributions, chlorophyll, carbon and nitrogen content, in vivo fluorescence and associated optical absorption and scattering properties were observed in the laboratory to help understand in situ and spatial observations. We grew triplicate semi-continuous cultures of T. pseudonana, D. tertiolecta, P. tricornutum and E. huxleyi under a sinusoidal light regime. We observed diurnal variations in the particulate absorption (ap), scattering (bp), attenuation (cp), and backscattering coefficients (bbp), which correlate with carbon and Chl concentrations. Relative variations from sunrise of bbp are slightly lower than those of cp, suggesting that bbp diurnal increases observed in nature are partly caused by phytoplankton. Non-concurrent changes of carbon and Chl-specific backscattering and scattering coefficients and optical cross-sections however indicates that using backscattering to infer scattering or biomass must be done with care

Le dessin et la psychothérapie d’enfants présentant des vulnérabilités de nature psychotique : illustration clinique

Le dessin est une expression graphique des capacités de représentation mentale de l’enfant. À travers ses dessins, l’enfant exprime ses craintes, ses angoisses et ses satisfactions de façon symbolique. L’emploi des dessins en contexte de psychothérapie s’avère particulièrement pertinent lorsque l’enfant utilise peu ou pas la parole pour s’exprimer. Le dessin permet d’établir un langage entre l’objet (contenu du dessin), le sujet (enfant) et l’observateur (psychologue), tout en offrant un support visuel sur lequel l’enfant peut coucher son monde fantasmatique. Ce dernier devient ainsi réel et tangible, sans pour autant représenter la réalité concrète de l’enfant. Cet article vise à montrer, à l’aide de quelques exemples, l’usage pouvant être fait des dessins dans les contextes d’une évaluation psychologique et d’une psychothérapie. Les dessins d’un jeune présentant des vulnérabilités de nature psychotique sont présentés et discutés à la lumière des éléments historiques et contextuels, des conflits intrapsychiques, des angoisses et des ressources psychologiques de l’enfant. Les auteurs illustrent également le travail thérapeutique réalisé autour des angoisses archaïques de morcellement, d’anéantissement et de persécution qui se sont manifestées massivement dans le transfert de l’enfant. Des considérations théoriques et cliniques relatives à la psychothérapie d’enfants présentant une organisation de la personnalité psychotique sont aussi exposées.Drawings constitute a graphic expression of the child’s mental representation capacity. Through their drawings, children express their fears, anxieties and satisfactions in a symbolic way. They are particularly useful when the child does not use speech to communicate with the clinician. Drawings establish a language between the object (content of the drawing), the subject (child) and the observer (psychologist), while providing a visual support through which the child can show his fantasy world. The latter thus becomes real and tangible, without representing the concrete reality of the child. This article aims to show how drawings can be used in the context of children’s psychological assessment and psychotherapy. The drawings of a child with some psychotic vulnerabilities are presented and discussed in the light of some historical and contextual elements as well as his intrapsychic conflicts, anxieties and psychological resources. The authors also illustrate the therapeutic work concerning the child’s primitive anxieties of fragmentation, annihilation, and persecution uncovered in the child’s transference. Theoretical and clinical considerations regarding psychotherapy with children with psychotic personality organization are discussed

Effect of follicle size and of the FecB booroola gene on oocyte function in sheep

International audienc