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Dynamique des fluides biologiques
No full textBiological flows develop in complex geometries characterized by deformable walls and unsteady conditions. A multiplicity of physiological/biological functions occurring at very different scales, i. e., from macroscopic to microscopic scales, closely depend on local and/ or global flow characteristics. Depending on tube sizes, inertial effects related to local acceleration combined with convective and even centrifugal acceleration can deeply modify flow characteristics, the latter being advantageously described by non dimensional numbers based on local geometrical dimensions, fluid properties, velocity and acceleration of fluid : e. g., number of Reynolds, Womersley, Dean, time varying Strouhal. Special attention is put on some flow characteristics such as velocity profile, pressure drop, which are specific of biological flows such as unsteadiness, boundary layer development, secondary or swirling flows as well as transition phenomena between steady and unsteady flow. Applications are extracted from airway flow and vascular system.Les écoulements biologiques se développent dans des géométries complexes présentant des parois déformables, et pour des conditions rarement stationnaires. Une multitude de fonctions physiologiques/ biologiques se réalisant à des échelles différentes allant du macroscopique au microscopique, dépendent de façon étroite des caractéristiques locales ou globales de l’écoulement. Dépendant de la taille des conduits, les effets d’inertie liés à l’accélération locale combinés à ceux liés à l’accélération convective voire centrifuge peuvent modifier fortement les caractéristiques de l’écoulement lesquelles peuvent être décrites par des nombres sans dimension spécifiques de la géométrie locale, du fluide considéré, de sa vitesse moyenne et de son accélération : notamment nombres de Reynolds, Womersley, Dean, de Strouhal au cours du cycle. L’attention est portée sur certaines caractéristiques (en terme de profils de vitesse et pertes de charge) spécifiques des écoulements biologiques comme l’instationnarité, le développement de la couche limite, les écoulements secondaires ou tourbillonnaires, les phénomènes de transition stationnaires instationnaires. Les applications sont issues de résultats obtenus dans l’arbre aérien et le système vasculaire.Isabey Daniel, Fodil Redouane, Louis Bruno. Dynamique des fluides biologiques. In: L'eau et le monde vivant. 28èmes Journées de l'Hydraulique. Congrès de la Société Hydrotechnique de France. Paris, 12 et 13 octobre 2004. 2004
Exploration et modélisation de l'écoulement inspiratoire au passage des fosses nasales
No full textIn clinical routine the exploration of the obstructive disorders in the nose is done primarily using techniques (tomodensitometry, endoscopic clinical examination) giving only one static image of the nose. Here we present two noninvasive investigation methods allowing to have a functional image of the nasal fossae. The posterior rhinomanometry gives an index of the resistance of each nasal fossae. The acoustic rhinometry gives the longitudinal cross-sectional area along the airways. A model with individualized compliant elements was associated with these methods in order to better understanding the fluid-structure coupling in the nasal fossae during inspiration. The proposed model, used in steady state conditions, allowed to simulate the pressure flow relationship in vivo observed in normal conditions as well as in pathological conditions. Our results suggest that the wall compliance is an essential parameter to understand the inspiratory flow limitation phenomenon well known by physiologists. This model, by predicting the functional pressure flow relationship, could be a useful tool for the clinician to evaluate the potential effects of treatments.En routine l'exploration des troubles obstructifs du nez se fait essentiellement à l'aide de techniques ne donnant qu'une image très statique du nez (tomodensitométrie, examen clinique endoscopique, ...). Ici, nous présentons deux méthodes d'investigation non-invasives permettant d'avoir une image fonctionnelle de la fosse nasale. La rhinomanométrie postérieure donne un index de la résistance globale de chaque fosse nasale. La rhinométrie acoustique apporte une visualisation du calibre des voies aériennes sous forme de l'évolution longitudinale de l'aire des sections droites de ce conduit. Un modèle à éléments individualisés compliants a été associé à ces 2 méthodes dans le but de mieux comprendre le couplage fluide structure se développant dans la fosse nasale à l'inspiration. Ce modèle, utilisé en conditions statiques, permet de simuler la relation pression débit observée in vivo chez le sujet sain comme chez le sujet pathologique. Nos résultats suggèrent que la compliance des fosses nasales est un paramètre essentiel pour comprendre les phénomènes de limitation de débit observés par les physiologistes à l'inspiration. Ce model par sa faculté de prédire la relation fonctionnelle entre pression et débit pourrait devenir un outil pour le clinicien dans le but d'évaluer les effets potentiels du traitement envisagé.Louis Bruno, Fodil Redouane, Isabey Daniel. Exploration et modélisation de l'écoulement inspiratoire au passage des fosses nasales. In: L'eau et le monde vivant. 28èmes Journées de l'Hydraulique. Congrès de la Société Hydrotechnique de France. Paris, 12 et 13 octobre 2004. 2004
Multiscale and age-dependant biophysical characterization of a pre-clinical rat model in the context of Duchenne muscular dystrophy
No full textDepuis les récentes avancées en biophysique, les scientifique ont constaté que l’organisation du cytosquelette d'une cellule influence les propriétés mécaniques des cellules et des tissus résultants. Il a été également noté que le tissu musculaire avait une structure complexe à plusieurs échelles et que la dystrophine est un élément clé du cytosquelette des cellules le composant. En l'absence de dystrophine, une maladie grave et progressive qui affecte tous les muscles squelettiques, connue sous le nom de dystrophie musculaire de Duchenne, se développe. Enfin, dans notre équipe, nous avons identifié un modèle de rat pertinent pour l'étude de cette maladie dans notre laboratoire, appelé RDMD-del52. Nos questions scientifiques sont donc : Quel est l’impact de l’absence de la dystrophine sur les propriétés mécaniques du muscle, à quelle échelle cette réponse apparait et à quelle étape de la maladie cette réponse est-elle la plus prononcée. Afin de répondre à ces questions, nous avons décidé d’effectuer une caractérisation des propriétés mécaniques, essentiellement le module de Young, la viscosité et les propriétés de prolifération et de migration, sur différentes échelles du muscle, c’est-à-dire, les myoblastes et les myotubes mis en culture, les fibres musculaires isolées et les muscles en entier. Afin de réaliser cette caractérisation, nous avons choisi le modèle rat RDMD-del52 appartenant à notre équipe pour sa pertinence et sa disponibilité. Cette caractérisation du modèle dystrophique a été comparée à une caractérisation que nous avons faite sur un modèle WT de la même lignée. La DMD étant une maladie progressive, nous avons pensé qu’il serait pertinent de suivre cette comparaison de façon temporelle et 3 time points ont été choisi, 1 mois, 6 mois et 10 mois, ce qui équivaut à l’âge de 10 ans, 18 ans et 26 ans pour l’humain. De ce fait, 1 mois est l’âge de début d’apparition des symptômes, 6 mois est l’âge où ces symptômes s’accentuent et 10 mois est l’âge à partir duquel le rat DMD risque de décéder. En résumé, une étude étude qu’on peut désigner comme une caractérisation en 3D a été effectuée.Since recent advances in biophysics, scientists have found that the organization of a cell’s cytoskeleton influences the mechanical properties of cells and resulting tissues. It was also noted that muscle tissue has a complex structure at several scales and that dystrophin is a key component of the cytoskeleton of the cells making it up. In the absence of dystrophin, a serious and progressive disease that affects all skeletal muscles, known as Duchenne muscular dystrophy, develops. Finally, in our team, we identified a rat model relevant to the study of this disease in our laboratory, called RDMD-del52.Our scientific questions are therefore: What is the impact of the absence of dystrophin on the mechanical properties of the muscle, on what scale this response appears and at what stage of the disease this response is most pronounced.In order to answer these questions, we decided to perform a characterization of the mechanical properties, essentially the Young module, the viscosity and the proliferation and migration properties, on different scales of the muscle, that is, cultured myoblasts and myotubes, isolated muscle fibres and whole muscles. In order to achieve this characterization, we chose the RDMD-del52 rat model belonging to our team for its relevance and availability. This characterization of the dystrophic model was compared to a characterization we did on a WT model of the same lineage. As DMD is a progressive disease, we thought it would be relevant to follow this comparison over time and 3 time points were chosen, 1 month, 6 months and 10 months, which is equivalent to the age of 10 years, 18 years and 26 years for humans.Thus, 1 month is the age of onset of symptoms, 6 months is the age at which these symptoms worsen and 10 months is the age at which the DMD rat is likely to die. In summary, a study that can be described as a 3D characterization was conducted
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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