This article revisits a reduced model of cardiac electro-physiology which was proposed to understand the genesis of unidirectional block pathology and of ectopic foci. We underline some specificities of the model from the viewpoint of dynamical systems and bifurcation theory. We point out that essentially the same properties are shared by a simpler system more accessible to analysis. With this simpler system, it becomes possible to give a new presentation of the phenomenon in a phase plane with time moving slow (...) manifolds. This presentation can be of interest both for cardiac electro-physiologists and for mathematicians. (shrink)
WHO II low grade glioma evolves inevitably to anaplastic transformation. Magnetic resonance imaging is a good non-invasive way to watch it, by hemodynamic and metabolic modifications, thanks to multinuclear spectroscopy 1H/31P. In this work we study a multi-scale minimal model of hemodynamics and metabolism applied to the study of gliomas. This mathematical analysis leads us to a fast-slow system. The control of the position of the stationary point brings to the concept of domain of viability. Starting from this system, the (...) equations bring to light the parameters that push glioma cells out of their domain of viability. Four fundamental factors are highlighted. The first two are cerebral blood flow and the rate of lactate transport through monocarboxylate transporters, which must be reduced in order to push glioma out of its domain of viability. Another factor is the intra arterial lactate, which must be increased. The last factor is pH, indeed a decrease of intra cellular pH could interfere with glioma growth. These reflections suggest that these four parameters could lead to new therapeutic strategies for the management of low grade gliomas. (shrink)
This work presents a mathematical model describing the interactions between the cross-shore structure of small pelagic fish population an their exploitation by coastal and offshore fisheries. The complete model is a system of seven ODE’s governing three stocks of small pelagic fish population moving and growing between three zones. Two types of fishing fleets are inter-acting with the fish population, industrial boats, constrained to offshore area, and artisanal boats, operating from the shore. Two time scales were considered and we use (...) aggregation methods that allow us to reduce the dimension of the model and to obtain an aggregated model, which is a four dimension one. The analysis of the aggregated model is performed. We discuss the possible equilibriums and their meaning in terms of fishery management. An interesting equilibrium state can be obtained for which we can expect coexistence and a stable equilibrium state between fish stocks and fishing efforts. Some identification parameters are also given in the discussion part of the model. (shrink)
We investigate a system of two species exploiting a common resource. We consider both abiotic and biotic resources. We are interested in the asymmetric competition where a given consumer is the locally superior resource exploiter and the other is the locally inferior resource exploiter. They also interact directly via interference competition in the sense that LIE individuals can use two opposite strategies to compete with LSE individuals: we assume, in the first case, that LIE uses an avoiding strategy, i.e. LIE (...) individuals go to a non-competition patch to avoids competition with LSE individuals, and in the second one, LIE uses an aggressive strategy, i.e. being very aggressive so that LSE individuals have to go to a non-competition patch. We further assume that there is no resource in the non-competition patch so that individuals have to come back to the competition patch for their maintenance, and the migration process acts on a fast time scale in comparison with demography and competition processes. The models show that being aggressive is efficient for LIE’s survival and even provoke global extinction of the LSE and this result does not depend on the nature of resource. (shrink)
Blood coagulation is regulated through a complex network of biochemical reactions of blood factors. The main acting enzyme is thrombin whose propagation in blood plasma leads to fibrin clot formation. Spontaneous clot formation is normally controlled through the action of different plasma inhibitors, in particular, through the thrombin binding by antithrombin. In the current study we develop a mathematical model of clot formation both in quiescent plasma and in blood flow and determine the analytical conditions on the antithrombin concentration corresponding (...) to different regimes of blood coagulation. (shrink)
The French school of theoretical biology has been mainly initiated in Poitiers during the sixties by scientists like J. Besson, G. Bouligand, P. Gavaudan, M. P. Schützenberger and R. Thom, launching many new research domains on the fractal dimension, the combinatorial properties of the genetic code and related amino-acids as well as on the genetic regulation of the biological processes. Presently, the biological science knows that RNA molecules are often involved in the regulation of complex genetic networks as effectors, e.g., (...) activators, inhibitors or hybrids. Examples of such networks will be given showing that there exist RNA “relics” that have played an important role during evolution and have survived in many genomes, whose probability distribution of their sub-sequences is quantified by the Shannon entropy, and the robustness of the dynamics of the networks they regulate can be characterized by the Kolmogorov–Sinaï dynamic entropy and attractor entropy. (shrink)
The present work is a contribution to the understanding of the sempiternal problem of the “burden of factor two” implied by sexual reproduction versus asexual one, as males are energy consumers not contributing to the production of offspring. We construct a deterministic mathematical model in population dynamics where a species enjoys both sexual and parthenogenetic capabilities of reproduction and lives on a limited resource. We then show how polygamy implies instability of a parthenogenetic population with a small number of sexually (...) born males. This instability implies evolution of the system towards an attractor involving both populations. We also exhibit the analogy with a parasite/host system. (shrink)
This article describes new aspects of hysteresis dynamics which have been uncovered through computer experiments. There are several motivations to be interested in fast-slow dynamics. For instance, many physiological or biological systems display different time scales. The bursting oscillations which can be observed in neurons, β-cells of the pancreas and population dynamics are essentially studied via bifurcation theory and analysis of fast-slow systems (Keener and Sneyd, 1998; Rinzel, 1987). Hysteresis is a possible mechanism to generate bursting oscillations. A first part (...) of this article presents the computer techniques (the dotted-phase portrait, the bifurcation of the fast dynamics and the wave form) we have used to represent several patterns specific to hysteresis dynamics. This framework yields a natural generalization to the notion of bursting oscillations where, for instance, the active phase is chaotic and alternates with a quiescent phase. In a second part of the article, we emphasize the evolution to chaos which is often associated with bursting oscillations on the specific example of the Hindmarsh–Rose system. This evolution to chaos has already been studied with classical tools of dynamical systems but we give here numerical evidence on hysteresis dynamics and on some aspects of the wave form. The analytical proofs will be given elsewhere. (shrink)
We provide a mathematical study of a model of energy metabolism and hemodynamics of glioma allowing a better understanding of metabolic modifications leading to anaplastic transformation from low grade glioma.This mathematical analysis allows ultimately to unveil the solution to a viability problem which seems quite pertinent for applications to medecine.
: Françoise Dastur describes her efforts to practice history of philosophy in a (paradoxically) non-historical fashion. She discusses her concept of the historical, and argues that the only true way to be of one's time is to be against one's time.
Françoise Dastur describes her efforts to practice history of philosophy in a (paradoxically) non-historical fashion. She discusses her concept of the historical, and argues that the only true way to be of one's time is to be against one's time.
Françoise Dastur describes her efforts to practice history of philosophy in a non-historical fashion. She discusses her concept of the historical, and argues that the only true way to be of one's time is to be against one's time.
In a recent paper – Lesbian motherhood and mitochondrial replacement techniques: reproductive freedom and genetic kinship – we argued that lesbian couples who wish to have children who are genetically related to both of them should be allowed access to mitochondrial replacement techniques. Françoise Baylis wrote a reply to our paper –‘No’ to lesbian motherhood using human nuclear genome transfer– where she challenges our arguments on the use of MRTs by lesbian couples, and on MRTs more generally. In this (...) reply we respond to her claims and further clarify our position. (shrink)
Dialogue d'amitié, ce livre à deux voix témoigne d'un long travail commun. Les deux chapitres, « Ulysse en personne » et « Au miroir de Pénélope » qui ouvrent et ferment le livre, sont rédigés par Jean-Pierre Vernant qui écrit là quelques unes de ses pages les plus abouties, récit et analyse mêlés, au service du questionnement toujours neuf d'un texte cent fois relu. Le but de ce questionnement, c'est aussi celui des chapitres rédigés par Françoise Frontisi-Leroux sous le (...) titre « L'.. (shrink)
Dan ZAHAVI, Husserl and Transcendental Intersubjectivity. A Response to the Linguistic-Pragmatic Critique ; Françoise DASTUR, Chair et langage. Essais sur Merleau-Ponty ; Jean GREISCH, Michel Henry et l’épreuve de la vie ; Elisabeth STRÖKER, The Husserlian Foundations of Science ; John McCUMBER, Metaphysics and Oppression, Heidegger’s Challenge to Western Philosophy ; Marc RICHIR, Phénoménologie en esquisses. Nouvelles fondations ; Raphaël GÉLY, La genèse du sentir. Essai sur Merleau-Ponty ; John SALLIS, Force of Imagination: The Sense of the Elemental ; (...) Bin KIMURA, L’entre. Une approche phénoménologique de la schizophrénie ; Dermot MORAN, Tim MOONEY, The Phenomenology Reader ; Ion COPOERU, Structuri ale constituirii ; Fabio CIARAMELLI, La distruzione del’desiderio. Il narcisismo nell’epoca di consumo di massa ; Pierre KELLER, Husserl and Heidegger on Human Experience. (shrink)
Ce livre réunit douze articles publiés dans différentes revues entre 1979 et 1993 qui, tous, abordent sous un angle un peu différent une question qui taraude l'auteur : quel est le fondement de la hiérarchie entre les sexes ? Françoise Héritier, anthropologue, observe tout d'abord celle-ci chez les Samo, ethnie du Burkina Faso qui fut son premier terrain, mais elle la repère également dans tous les systèmes de parenté. C'est en effet en tant qu'anthropologue de la parenté qu'elle pours..
Dans cet ouvrage de 430 pages – dont neuf consacrées à un index des auteurs anciens et modernes – Geneviève Clerico, Bernard Colombat et Jean Soubiran ont réuni 22 textes écrits par Françoise Desbordes de 1981 à 2000 et généralement publiés antérieurement dans des revues scientifiques ou actes de colloques. Ces études ne concernent pas la rhétorique, domaine privilégié de l’activité scientifique de F.D., ni les analyses textuelles, les contributions de F.D. à ces disciplines ayant fait l’obje..
Françoise Proust’s essential points of reference are Kant and Walter Benjamin. Alain Badiou ignores the extraordinary and sometimes beautiful dark power of Proust’s work on Benjamin. As is clear, however, from both Daniel Bensaïd’s interview with Proust and the title of Élizabeth Lemirre and Catherine Perret’s memorial volume (Une philosophie de la résistance: Françoise Proust), the concept of Proust that is most likely to become the dominant one is not Badiou’s, but rather the concept of her as above (...) all a philosopher of `resistance’. (shrink)
L'ouvrage rassemble les contributions de trois célèbres antiquisants : Paul Veyne, dont les contributions à la pensée contemporaine excèdent largement ses travaux sur l'histoire et la littérature latine, accompagné de François Lissarague, spécialiste en iconographie grecque, et de Françoise Frontisi-Ducroux, iconographe et actuellement sous-directrice au Collège de France. La différence de leurs approches et la variété de leurs champs de recherche présentent ces trois études comme comp..
Health Care Ethics is another addition to the growing number of texts that attempt to provide a much-needed Canadian perspective on many of the issues that arise in the delivery of health care. The readings are divided into three parts: “The Nature and Context of Health Care Ethics”; “Decision-Making in Health Care”; and “Decisions Near the Beginning and End of Life.” Collectively, they cover a variety of different issues—pluralism and multiculturalism, resource allocation and rationing, consent, research involving human subjects, genetics, (...) abortion, assisted reproductive technologies, euthanasia, and assisted suicide. The editorial introductions to these issues, while well written, readable, and clear, are general and deliberately non-committal in assessing the different and competing approaches and arguments reflected in the selected articles in which these issues are discussed. (shrink)
Aucun historien sérieux ne pourrait prétendre le contraire, une histoire sans les femmes n'est plus possible. Et pourtant la question, certes provocatrice, ne semblait pas incongrue en 1997, lorsqu'elle fut retenue pour intituler le colloque qui s'est tenu à Rouen, ainsi que l'ouvrage paru l'année suivante. Très tôt, l'histoire des femmes a dû s'exercer à dresser des bilans. Portée par l'engagement et la quête identitaire, il lui fallut périodiquement tenir un discours de justificatio..
As a feminist bioethicist, I have frequently wondered why the exclusion of pregnant women has been the default position for most clinical research and how social values have influenced this decision. Relatedly, I wonder what responsible research involving pregnant women would look like. As a theorist who conducts research on the concept of vulnerability, I have often wanted to know why there has been so little research into the harmful effects of the routine exclusion of pregnant women, including questions such (...) as: What do pregnant women actually think about participating in research? How should we treat pregnant women and their fetuses for the purposes of consent (are they two separable persons or one complex... (shrink)
This fascinating anthology focuses on the question of how we make families, and how bionormative assumptions shape or distort our collective thinking about parenting, children’s welfare, and state obligations to parents and children. The editors are primarily interested in the question of whether parents’ moral responsibilities toward children differ for children produced through assistive reproductive technologies compared to children brought into the family via adoption. As the editors point out, in the realm of ART, most of the philosophical literature has (...) been focused on parental autonomy and rights to assistance in reproducing, while the adoption literature is almost entirely focused on the... (shrink)
Il y a comme un hiatus entre le titre et le sous-titre de ce livre. Le titre, Aux origines de l'action sociale, annonce une intention modeste ; en effet l'ouvrage, composé de touches successives, ne se présente pas comme une synthèse historique organisée. Par contre le sous-titre indique un projet précis et construit, un projet d'histoire : L'invention des services sociaux aux chemins de fer. Dans le texte tout se passe comme si les auteurs n'avaient pas voulu (pas su ?) (...) choisir entre .. (shrink)