868 research outputs found
Computational convergence of the path integral for real dendritic morphologies
No full textNeurons are characterised by a morphological structure unique amongst biological cells, the core of which is the dendritic tree. The vast number of dendritic geometries, combined with heterogeneous properties of the cell membrane, continue to challenge scientists in predicting neuronal input-output relationships, even in the case of sub-threshold dendritic currents. The Green’s function obtained for a given dendritic geometry provides this functional relationship for passive or quasi-active dendrites and can be constructed by a sum-over-trips approach based on a path integral formalism. In this paper, we introduce a number of efficient algorithms for realisation of the sum-over-trips framework and investigate the convergence of these algorithms on different dendritic geometries. We demonstrate that the convergence of the trip sampling methods strongly depends on dendritic morphology as well as the biophysical properties of the cell membrane. For real morphologies, the number of trips to guarantee a small convergence error might become very large and strongly affect computational efficiency. As an alternative, we introduce a highly-efficient matrix method which can be applied to arbitrary branching structures
Neuronal computation on complex dendritic morphologies
No full textWhen we think about neural cells, we immediately recall the wealth of electrical
behaviour which, eventually, brings about consciousness. Hidden deep in the
frequencies and timings of action potentials, in subthreshold oscillations, and in
the cooperation of tens of billions of neurons, are synchronicities and emergent behaviours
that result in high-level, system-wide properties such as thought and cognition.
However, neurons are even more remarkable for their elaborate morphologies,
unique among biological cells. The principal, and most striking, component of neuronal
morphologies is the dendritic tree.
Despite comprising the vast majority of the surface area and volume of a
neuron, dendrites are often neglected in many neuron models, due to their sheer
complexity. The vast array of dendritic geometries, combined with heterogeneous
properties of the cell membrane, continue to challenge scientists in predicting neuronal
input-output relationships, even in the case of subthreshold dendritic currents.
In this thesis, we will explore the properties of neuronal dendritic trees, and
how they alter and integrate the electrical signals that diffuse along them. After
an introduction to neural cell biology and membrane biophysics, we will review
Abbott's dendritic path integral in detail, and derive the theoretical convergence
of its infinite sum solution. On certain symmetric structures, closed-form solutions
will be found; for arbitrary geometries, we will propose algorithms using various
heuristics for constructing the solution, and assess their computational convergences
on real neuronal morphologies. We will demonstrate how generating terms for the
path integral solution in an order that optimises convergence is non-trivial, and how a computationally-significant number of terms is required for reasonable accuracy.
We will, however, derive a highly-efficient and accurate algorithm for application to
discretised dendritic trees. Finally, a modular method for constructing a solution in
the Laplace domain will be developed
Manuel d’utilisation MACMA Salmo. Macro Excel d’Aide au Calcul de variables thermiques appliquées aux Milieux Aquatiques SALMOnicoles
No full textCet outil est une macro simple d’utilisation qui permet d’exploiter des données thermiques brutes sur les cours d’eau salmonicoles. La conception de cet outil de calcul a été initiée par la Fédération de Haute-Savoie pour la Pêche et la Protection des Milieux Aquatiques et l’INRA UMR CARRTEL de Thonon dans le cadre du programme INTERREG III « Truites autochtones » (2003-2006). Son but est de faciliter le traitement des données issues de suivis thermiques annuels de cours d’eau mis en place à partir de 2003
Manuel d’utilisation MACMA Salmo. Macro Excel d’Aide au Calcul de variables thermiques appliquées aux Milieux Aquatiques SALMOnicoles
No full textCet outil est une macro simple d’utilisation qui permet d’exploiter des données thermiques brutes sur les cours d’eau salmonicoles. La conception de cet outil de calcul a été initiée par la Fédération de Haute-Savoie pour la Pêche et la Protection des Milieux Aquatiques et l’INRA UMR CARRTEL de Thonon dans le cadre du programme INTERREG III « Truites autochtones » (2003-2006). Son but est de faciliter le traitement des données issues de suivis thermiques annuels de cours d’eau mis en place à partir de 2003
Lier pratiques démocratiques et efficacité économique : la rationalisation démocratique
No full textLe lien démocratie-efficacité constitue un objet de recherche au sein des sciences sociales, et des sciences de gestion en particulier. Mais du point de vue des organisations d’économie sociale, il n’apparaît pas pertinent de défendre l’existence d’un lien de causalité entre pratiques démocratiques et efficacité économique; pour l’auteur, la question importante porte sur la façon dont la définition de l’efficacité se construit dans ces organisations. L’article présente tout d’abord différentes approches établissant un lien entre démocratie et recherche d’efficacité. Puis, il montre la difficulté que cela représente d’introduire un concept des sciences politiques (la démocratie) dans l’univers de la gestion des entreprises. Il propose enfin une définition de l’efficacité comme construction sociale qui met en perspective un concept nouveau, la rationalisation démocratique, illustré par l’exemple des coopératives d’activité et d’emploi.The democracy/efficiency relationship is a research topic in the social sciences, particularly in management studies. However, from a social economy perspective, there is little point in arguing about the existence of a causal link between democratic practices and economic efficiency. For the author, the important question is how social-economy organizations define efficiency. The article first presents various approaches that establish a link between democracy and the pursuit of efficiency. He then shows the difficulty of introducing a concept from political science (democracy) into the world of business management. He concludes by suggesting a definition of efficiency as a social construct that puts into perspective a new concept—democratic rationalization—illustrated by the example of producer and worker cooperatives
Computational convergence of the path integral for real dendritic morphologies
No full textNeurons are characterised by a morphological structure unique among biological cells, the core of which is the dendritic tree. The vast number of dendritic geometries, combined with heterogeneous properties of the cell membrane, continue to challenge scientists in predicting neuronal input-output relationships, even in the case of subthreshold dendritic currents. The Green's function obtained for a given dendritic geometry provides this functional relationship for passive or quasi-active dendrites, and can be constructed by a sum-over-trips approach based on a path integral formalism. In this paper, we introduce a number of efficient algorithms for realisation of the sum-over-trips framework and investigate the convergence of these algorithms on different dendritic geometries. We demonstrate that the convergence of the trip sampling methods strongly depends on dendritic morphology as well as the biophysical properties of the cell membrane. For real morphologies, the number of trips to guarantee a small convergence error might become very large and strongly affect computational efficiency. As an alternative, we introduce a highly-efficient Matrix method which can be applied to arbitrary branching structures
In Search of Safety, Pleasure and Power: A Sensory Analysis onto the Themes of Spirituality, Nature and the Body in Jean Rhys’ Wide Sargasso Sea
No full textWritten by Jean Rhys and published in 1966, Wide Sargasso Sea narrates the tumultuous encounter of Antoinette Cosway –a creole woman born in the Caribbean- and Edward Rochester – a Victorian man from England. Since the publication of the novel, its tragic ending has inspired numerous interpretations. Yet a consensus seems to have been reached onto attributing the characters’ differences a major role in the developments of the story. Indeed describing the protagonists according to an othering process typical of postcolonial literature, - Edward for instance as a rational and Christian man belonging to the urban British world and coming from a cold, grey country; and Antoinette as a sensual and pagan woman belonging to the Caribbean wilderness and coming from a country of heat and sunshine-, the binary oppositions of the novel and their extension to the cultures both protagonists represent suggest that Antoinette and Edward are irreconcilably opposed to one another. But in their attempts at drawing the (anti-) hegemonic messages from the text by analysing these dichotomies, literary critics in postcolonial, ecofeminist and feminist studies have come up against oppositions presented in the novel concerning Westerners’ and Caribbean people’s relationships towards nature, corporeality and spirituality as presented in the novel. Indeed, and however several historical, cultural and anthropological facts now confirm the existence of such divergences between Westerners and Caribbean people, it is nevertheless important to note that these dichotomies were originally articulated as the ‘stereotype of the savage’ during the Hellenic period, and that under the influence of their propagandisation during the colonial era, these dichotomies have continued to influence Westerners’ perspectives onto non-European people. And it is still often in such a stereotypical manner that the differences between the protagonists of Jean Rhys’ novel are studied today. For indeed, it is perceptible that critics often omit to consider that the author herself deconstructs the dichotomies she draws upon by presenting both characters as capable of change –as a means of illustration, Edward will develop an actual sensitivity towards nature and Antoinette will discover sensuality without forasmuch always having embraced it. And it is thus with the purpose of explaining both protagonists’ relationship towards one another, while accounting not only for their capacity to transcend the expectations of their cultures, but also for the deeper origins of their divergences, that the following dissertation aims at deconstructing some of these stereotypes by demonstrating that both characters’ perspectives towards nature, corporeality and spirituality are determined by their changeable ways of drawing upon the senses and by the feelings of power, safety and pleasure that the natural world, corporeality and spirituality will as such provide them with or deprive them from.Master [120] en communication multilingue, Université catholique de Louvain, 2018La diffusion de ce mémoire n'est pas autorisée par l'institutio
Timing malaria transmission with mosquito fluctuations_data
No full textExcel file with all data used in our manuscript: Oocyst burden, bird parasitaemia and detrend parasitaemi
Timing malaria transmission with mosquito fluctuations
No full textInternational audienceTemporal variations in the activity of arthropod vectors can dramatically affect the epidemiology and evolution of vector-borne pathogens. Here, we explore the "Hawking hypothesis", which states that these pathogens may evolve the ability to time investment in transmission to match the activity of their vectors. First, we use a theoretical model to identify the conditions promoting the evolution of time-varying transmission strategies in pathogens. Second, we experimentally test the "Hawking hypothesis" by monitoring the within-host dynamics of Plasmodium relictum throughout the acute and the chronic phases of the bird infection. We detect a periodic increase of parasitemia and mosquito infection in the late afternoon that coincides with an increase in the biting activity of its natural vector. We also detect a positive effect of mosquito bites on Plasmodium replication in the birds both in the acute and in the chronic phases of the infection. This study highlights that Plasmodium parasites use two different strategies to increase the match between transmission potential and vector availability. We discuss the adaptive nature of these unconditional and plastic transmission strategies with respect to the time scale and the predictability of the fluctuations in the activity of the vector
Relationship between personality type and the ability to be a change agent
No full textPlan BThis descriptive study investigated the relationship between personality types as indicated on the Myer’s Briggs Type Indicator and the ability to be a change agent as measured by the Change Agent Inventory. The Myer’s Briggs Type Indicator (MBTI) Form G is a questionnaire designed to make Carl Jung’s theory of psychological types understandable and useful in everyday life. The author, Katharine Cook Briggs (1875-1968) and her daughter, Isabel Briggs Myers (1897-1980) were disciplined observers of human personality differences. They studied and elaborated the ideas of Jung, and applied them to human interaction. After more than 50 years of research and development, the current MBTI is the most widely used instrument for understanding normal personality differences. The Change Agent Inventory (CAI) provides a comprehensive assessment of the criteria and characteristics necessary to successfully implement key business changes in an organization. It can be used to assess individuals charged with the responsibility to make sure a change happens; and to select primary change agents for major change projects. The CAI was developed by Implementation Management Associates, Inc. of Brighton, Colorado. After these two instruments were taken by members of the College Operating Team (COT), a focus group was conducted with these questions asked of each member: What is your attitude toward change? Do you like or dislike change? Why? How effective are you as a change agent? The participants in this study were nine managers at a two-year technical college. The WITC - New Richmond COT has a variety of personality preferences. All the COT members demonstrated a higher than average capacity for change. There was a tendency for more intuitive managers to score higher on the change agent instrument. There was also a tendency for the higher the score on the change agent instrument the lower the MBTI Type S score. However, there did appear to be a positive relationship between the focus group responses and CAI scores
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