Academic literature on the topic 'Biophysique – Modèles mathématiques'
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Journal articles on the topic "Biophysique – Modèles mathématiques":
Saint-Laurent, D., and L. Lavoie. "Les différentes approches méthodologiques de reconstitution des paléo-inondations : une revue de la littérature." Revue des sciences de l'eau 17, no. 1 (April 12, 2005): 91–115. http://dx.doi.org/10.7202/705524ar.
Dissertations / Theses on the topic "Biophysique – Modèles mathématiques":
Hugon, Julien. "Vers une modélisation biophysique de la décompression." Thesis, Aix-Marseille 2, 2010. http://www.theses.fr/2010AIX20691/document.
During a scuba diving decompression, a part of the gas that is dissolved in the body is eliminated throughbubbles that can generate potentially severe forms of decompression sickness (DCS). Known mathematicalmodels allow the determination of safe decompression procedures by stages but can only be applied for alimited range of diving configurations (pressure, duration, breathing gas). An extrapolation of these modelsto new expositions such as deep/short dives using mixtures is currently hazardous. In the presented work itis deemed that a biophysical modeling of the decompression mechanisms can produce safer preventivesolutions even for less explored expositions combining nitrogen and helium. Two models have beendeveloped for the prevention of articular and neurological DCS, which are the most frequent forms ofinjury. Existing database and risk analyses have been used to correlate the models. Both predict potentialdelays for the occurrence of DCS symptoms after a decompression. For the articular model it is shown that1/ the intratissular diffusion of inert gases between a target tendon and its neighborhood impacts theamplification dynamics of the generated gas phase 2/ the more the generated gas volume, the bigger theDCS risk 3/ stages of short and moderate durations have a low efficiency 4/ the efficiency of pure oxygenbreathing in order to reduce the risk during the shallow stages is moderated. For neurological DCS, theproposed global model allows estimation of the instantaneous volume of microbubbles that are formed intissues (muscles and adipose tissues) and that are transferred via the lymphatic system for instance in thevenous blood. The overload of the pulmonary filter by bubbles is assumed to be a primary event in the DCSpathogenesis. The original model correlation method uses in particular the recording of circulating bubblessignals through Doppler detections campaigns. One of these campaigns is dedicated to the presented thesiswork. The analysis leads to the following conclusions: I/ the DCS risk is linked to the total bubbles volumethat is transferred into the blood over a given period II/ the introduction of deep stages does not decreasethe risk III/ the breathing of pure oxygen during the shallow stages is very efficient in reducing this risk. Asecond neurological model is proposed: it is dedicated to the prevention of spinal cord DCS forms whichoccur early after the decompression and to the determination of the first required stops. The threedeveloped models give interesting prevention perspectives
Ladjimi, Mohamed Tahar. "Modélisation biophysique de la mort cellulaire en réponse au stress thermique." Thesis, Lille 1, 2019. http://www.theses.fr/2019LIL1R029/document.
The living cell is constantly exposed to various types of stress that can damage its components. When the induced damages are detected, defense mechanisms are activated to repair them while optimally managing the energy resources available and necessary for cell function. If the stress is too severe and the system can not defend itself, death will be inevitable. The cellular response to stress is orchestrated by intracellular signaling networks that are extraordinarily complex. The molecular species constituting these networks perform various tasks through biochemical reactions, forming synchronized biological process machineries. Our approach in this thesis for the study of these networks is to model them mathematically to reproduce an observed phenomenon and identify its key players, analyze their reactions in response to different signals, and possibly make precise enough and experimentally verifiable predictions that can be of an extreme utility for therapeutic applications. In our studies, we focus on thermal stress and on the resulting cellular response in terms of the dynamics of the molecular species involved, but also of cell fate (death or survival) at the end of the exposure, we adress those questions by dynamic models describing the biochemical kinetics of system variables as a consequence of temperature variation. In a first step, we demonstrate through simulations, followed by experimental validation, that the temporal form of heat stress significantly impacts cell survival. This first result highlights a mechanism of saturation of the repair species as a consequence of exposure to high temperatures. In a second step, we study the potential correlation between a variability introduced on the levels of two proteins in the heat shock response network and the phenomenon of fractional killing. According to our model predictions, experimentally measured chaperone proteins (repair species) variability alone is not sufficient to explain fractional killing, which must involve other sources of variability. Finally, an analysis of the isoeffect curves generated by a generic model of the cellular response to transient stress shows the existence of four sensitivity regimes depending on the duration-intensity parameters of the stress as well as on the parameters of the response network and its time scales. Our work highlights the potential and utility of dynamic network models in the characterization of dose-response curves
Parent, Benjamin. "Algorithmes d'optimisation et d'analyse des problèmes multidimensionnels non-linéaires en biologie et biophysique." Phd thesis, Ecole Centrale de Lille, 2007. http://tel.archives-ouvertes.fr/tel-00196740.
Pour cela, nous avons abordé le problème via deux aspects : le premier concerne la modélisation des interactions moléculaires en vue de prédire les modes de fixation et les affinités entre molécules. Puisque ces estimations nécessitent de considérer la flexibilité des acteurs, nous avons abordé, en premier lieu, la prédiction des conformations moléculaires qui reste un challenge majeur, caractérisé par ses aspects multimodal et de grandes dimensions. Nous avons alors développé une suite d'heuristiques autour d'un algorithme génétique central. Les paramètres de contrôle et les stratégies d'hybridation sont pilotés par un méta-algorithme permettant d'optimiser la recherche. En outre, des stratégies innovantes de parallélisation sur grilles d'ordinateurs ont été validées afin de réduire les temps de calculs. Enfin, pour entreprendre l'étude des conformations de plusieurs molécules, nous avons développé des algorithmes de criblage rapides basés sur la comparaison d'indices topologiques.
Nous avons également étudié un autre aspect en modélisant formellement certains graphes d'interactions, ceci à une toute autre échelle : celle des concentrations des molécules. Nous avons alors mis en évidence l'impact des modes d'interactions moléculaires sur la dynamique globale.
Chemla, Sandrine. "A biophysical cortical column model for optical signal analysis." Nice, 2010. http://www.theses.fr/2010NICE4004.
Voltage-sensitive dye imaging (VSDI) is a powerful modern neuroimaging technique whose application is expanding worldwide because it offers the possibility to monitor the neuronal activation of a large population with high spatial and temporal resolution. In this thesis, we investigate the biological sources of the voltage-sensitive dye signal (VSD signal), since this question remains unresolved in the literature. What does the voltage-sensitive dye imaging signal measures? This question is difficult to resolve at the physiological level as the signal is multi-component: The dye reflects the dynamics of the membrane potential of all membranes in the neuronal tissue, including all layers of the circuitry, all cell types (excitatory, inhibitory, glial) and all neuronal compartments (somas, axons, dendrites). To answer this question, we propose to use a biophysical cortical column model, at a mesoscopic scale, taking into account biological and electrical neural parameters of the laminar cortical structure. The model is based on a cortical microcircuit, whose synaptic connections are made between six specific populations of neurons, excitatory and inhibitory neurons in three main layers. Each neuron is represented by a reduced compartmental description with conductance-based Hodgkin-Huxley neuron model. The model is fed by a thalamic input with increasing activity, background activity and lateral connections. Isolated neurons and network behavior have been adjusted to fit data published in the literature. The so-calibrated model offers the possibility to compute the VSD signal with a linear formula. We validated the model by comparing the simulated and the measured VSD signal. Thanks to the compartmental construction of this model, we confirm and quantify the fact that the VSD signal is the result of an average from multiple components, with excitatory dendritic activity of superficial layers as the main contribution. It also suggests that inhibitory cells, spiking activity and deep layers are contributing differentially to the signal dependently on time and response strength. We conclude that the VSD signal has a dynamic multi-component origin and propose a new framework for interpreting VSD data
Amemou, Yago Ya Hilaire. "Modélisation biophysique de la dispersion et de la croissance des larves de sardinelles dans le Golfe de Guinée." Electronic Thesis or Diss., Sorbonne université, 2021. http://www.theses.fr/2021SORUS185.
The causes and dynamics of the ivoiro-ghanean upwelling have recently been investigated. The northern Gulf of Guinea zone supports a fishery of small pelagic fish where the most abundant the Sardinella. aurita (S. aurita). The success of the recruitment of the early stages of the larvae into juveniles is essentially conditioned by the local circulation which allows either to bring the eggs and larvae closer to the often coastal nurseries where the juveniles can develop, or either to disperse them offshore where they are subject to predation and lack of food. The mechanisms by which environmental conditions act to regulate the recruitment of S. aurita remain poorly understood in the northern Gulf of Guinea region, especially the potential interaction between dispersal, growth and mortality of larvae. The main objective of the thesis is to study the impact of food availability on the growth and the dispersion of sardinella larvae during their dispersal phase using a numerical modeling approach that allows to integrate fundamental hydrodynamic, biogeochemical and biological processes (CROCO-PISCES, ICHTHYOP). The results showed that coastal areas are the most favorable for retention because of the presence of eddies which act as barriers preventing eggs and larvae advection offshore. The most important spawning takes place during the small (February) and large (August) upwelling season. The maximum retention depths are the surface layers (0-25 m) and subsurface (25-50 m). These maximum laying depths associated with the maximum distribution of the simulated prey fields and the decrease in the intensity of the Guinea Current at depth
Karvouniari, Theodora. "Les ondes rétiniennes : théorie, numérique, expériences." Thesis, Université Côte d'Azur (ComUE), 2018. http://www.theses.fr/2018AZUR4014/document.
Retinal waves are spontaneous bursts of activity propagating in the developing retina, playing a fundamental role in shaping the visual system and retinal circuitry. They disappear completely upon maturation. Understanding how retinal waves are initiated and propagate in the retina could enable us to design protocols to trigger such retinal waves in the adult retina, expecting to reintroduce some plasticity in the retinal tissue and the projections in the brain. In my thesis, I have focused on a specific stage of development of waves, called stage II, induced by specific cells (SACs) and mediated by the neurotransmitter acetylcholine. Immature SACs exhibit a spontaneous bursting behavior due to intrinsic cellular mechanisms, which disappears completely upon maturation. Also, immature SACs are connected by excitatory connections, leading to propagating bursts of activity. The general spirit of this thesis work, is to propose a model for retinal waves (i) sufficiently close to biophysics to explain and propose experiments and (ii) suffciently well posed mathematically to analyse its dynamics upon varying biophysical parameters. In this context, we wanted to ellucidate the mechanisms causing immature SACs to burst and how retinal waves start, propagate and stop. We proposed a mathematical model, grounded on biophysics, and through bifurcations theory we explain the possible underlying cellular mechanisms of retinal waves, highlighting the relevant biophysical parameters controlling waves propagation and disparition. On top of that, we analyzed how the evolution of cholinergic conductance due to the maturation of nicotinic receptors dramatically changes the retinal wave characteristics. Especially, there is a very narrow interval of acetylcholine conductance where retinal waves size obey a power law distribution, suggesting a specific (homeostatic) mechanism stabilizing temporarily the SACs network in this specific range. To sum up, this thesis results are mainly theoretical, but they also lead to experimental predictions directly linked to biology
Teillet-Deborde, Jeffrey. "Intégration et optimisation de procédés de séparation d'ADN." Thesis, Toulouse 3, 2020. http://www.theses.fr/2020TOU30127.
This manuscript describes and discusses the integration of instrumentation hardware for the µLAS system, for the optimization of the analysis and separation of DNA molecules. First, we will discuss separation techniques, their approaches and strategies. And we will try to answer this question which is asked when a species migrates: how to characterize the competition between forced advection and natural diffusion? To optimize and improve the performance of the various separation technologies thus mentioned, it is necessary to introduce the issues inherent in each. Because there is indeed a wide range of actuation means that cause molecules to migrate in multiple ways: by hydrodynamics, by electrophoresis or even techniques combining the two approaches. Then we will introduce the µLAS technology and in what technological context it is placed. We will present the physical principles that govern the different stages of the technology's operation (concentration and separation). We will then approach the developments carried out during this thesis work on a temporal separation mode which involves a new chip model. Finally, we will show the development work, both in technological manufacturing and also in software intelligence, to set up slope engravings in silicon and thus enrich the µLAS system. Then we will introduce the instrumentation work carried out throughout these 3 years on a dedicated experimental bench. This chapter will be organized to introduce an uninformed reader to the basics and issues inherent in programming, instrumentation and automation of systems controlled by LabVIEW. We will use these bases to present the platform thus developed to pilot µLAS experiments. Finally, such a system needs to be characterized because it involves many players: computer and mechanical tools. Finally, we will present the separation results obtained using the fully integrated and automated µLAS platform. The analysis of these results raised questions and at the same time a study of the dynamic dispersion of DNA bands. We will end with some prospects for improvement, mentioned during the manuscript
Deslandes, François. "Modélisation de la dynamique des corps lipidiques chez Arabidopsis thaliana." Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLA042.
The aim of the PhD project is to dissect the mechanisms involved in the phenotype of lipid droplets both at the cellular level and the seed level. Studying a model of a lipid droplet embedded in the leaflets of a lipid bilayer reveals the existence of a critical volume at which the shape of the droplet breaks from a symmetrical elongated lens to a spherical protrusion. This budding mechanisms provides new insights in the formation of lipid droplets. Segmentation and tracking of lipid droplets from timelapse confocal microscopy images allows the detection of lipid droplets fusion events. A method based on the conservation of volume during the fusion event is developed and applied to detect fusion events for several embryos of A. thaliana. A model of the coalescence of lipid droplets during the development of early A. thaliana embryos is developed. The fusion rate is estimated and compared in different wild type and mutant embryos. The estimation is based on lipid droplets volumes measured from images at different stages of the development of the embryos
Azevedo, Carvalho Nathalie. "Un modèle informatique biologiquement réaliste des oscillations neuronales pathologiques observées dans la maladie de Parkinson." Electronic Thesis or Diss., Université de Lorraine, 2022. http://www.theses.fr/2022LORR0077.
My thesis is based on three axes: to develop a biophysical model, to propose a simulation tool, and exploit the model in simulation.We develop a biophysical model of the neuronal structure involved in Parkinson's disease, the basal ganglia. We simulate physiologically realistic neurons using the Hodgkin-Huxley formalism to incorporate specific ion channels present in different populations of GB neurons, including arkipallidal and proptotypic GPe, as well as dopaminergic D1 and D2 neurons in the striatum, whose cellular properties and connectivity appear to be prominent factors in the oscillatory behavior of the network. Our model is validated by experimental data in healthy conditions of the rat, collected by our biologist collaborators.We propose a simulation tool for impulse neural networks allowing realistic simulations on a large scale, > 1 million neurons, on a parallel machine i.e. Grid'5000, Explor, etc... SiReNe is a neural network simulator developed in the C language. This software is based on a hybrid simulation approach. It combines a numerical integration, Runge-Kutta 2, of the neuronal dynamics and an event-driven generation of the network connectivity during action potentials emissions. This approach, developed during the thesis, allows the simulation of large and very detailedneural networks of the Hodgkin-Huxley type.In the future, our model could be used in simulation to test some hypotheses on the pathological synchronization observed in Parkinson's disease. Like the role of GABAergic synaptic connections and the intrinsic neuronal properties of SK channels which control the precision of neuronal discharge. The simulation of large-scale models could be used to limit pathological synchronization and motor disorders through new neurostimulation methods, such as deep brain stimulation
Lavi, Ido. "Physical modeling of cell motility and morphodynamics." Thesis, Sorbonne université, 2019. http://www.theses.fr/2019SORUS237.
This thesis introduces a minimal hydrodynamic model of polarization, migration, and deformation of a biological cell confined between two parallel surfaces. Our model describes the cell cytoplasm as a viscous droplet that is driven by an active cytoskeleton force, itself controlled by a diffusive cytoplasmic solute. A linear stability analysis of this two-dimensional system reveals that solute activity first destabilizes a global polarization-translation mode, prompting cell motility through spontaneous-symmetry-breaking. At higher activity, the system crosses a series of Hopf bifurcations leading to coupled oscillations of droplet shape and solute concentration profiles. At the nonlinear level, we find traveling-wave solutions associated with unique polarized shapes that resemble experimental observations. In addition, we developed a numerical simulation of our moving-boundary problem based on the finite element method. The numerical study demonstrated the stability of our traveling-wave solutions, the existence of sustained oscillatory attractors, and the emergence of a finite-time pinch-off singularity. By incorporating mechanical interactions with the external environment, we explored cell scattering from stationary walls and obstacles, migration through imposed micro-geometries, and cell-cell collisions. These exercises capture a range of nontrivial patterns resulting from the intrinsic memory and deformability of the cell. Altogether, our work offers a mathematical paradigm of active deformable systems in which Stokes hydrodynamics are coupled to diffusive force-transducers
Books on the topic "Biophysique – Modèles mathématiques":
Pozrikidis, C. Computational hydrodynamics of capsules and biological cells. Boca Raton: Chapman & Hall/CRC, 2010.
Buchatsky, Leonid P., and Valery V. Stcherbic. Living Matter: Algebra of Molecules. Taylor & Francis Group, 2015.
Buchatsky, Leonid P., and Valery V. Stcherbic. Living Matter: Algebra of Molecules. Taylor & Francis Group, 2016.
Pozrikidis, C. Computational Hydrodynamics of Capsules and Biological Cells. Taylor & Francis Group, 2019.