Dissertations / Theses on the topic 'Correction de la diffusion cellulaire'
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Yang, Ning. "Online monitoring of bioreactors by Raman spectroscopy and machine learning." Electronic Thesis or Diss., université Paris-Saclay, 2024. http://www.theses.fr/2024UPAST083.
Full textThis thesis presents a novel and reproducible modeling strategy for online monitoring of bioreactors using Raman spectroscopy and Machine Learning. The main aim of this study is to develop simplified models using the Raman spectra of standards in solution. It consists of three key parts.The first part involves optimizing Raman acquisition parameters and developing a PLS regression model using pure standards. Subsequently, a preliminary validation was carried out using mixed standards to mimic changes in the composition of different molecules in the medium during the alcoholic fermentation process. The second part defined a nonlinear expression to interpret the Raman attenuation induced by the presence of microorganisms in a real bioreactor, allowing the correction of cell--scattered spectra. For model evaluation, numerous batches and one fed--batch bioreactor were launched to validate the working performance and predictive robustness of the obtained correction strategy and regression model. The third part highlights the advantages of our proposed modeling methodology over the traditional way that uses the spectra from bioreactors to train the regression model.Overall, the innovative approach demonstrated an excellent prediction performance on all validation and testing datasets, presenting significant potential for bioprocess engineering. It enables more accurate and efficient monitoring of multiple compounds in real time, as well as enhances process control and optimization. The proposed strategy is expected to have an extended application in the bioproduction industry
Buvat, Irène. "Correction de la diffusion en imagerie scintigraphique." Paris 11, 1992. http://www.theses.fr/1992PA112310.
Full textStinson, Eric. "Distortion correction for diffusion weighted magnetic resonance images." Thesis, McGill University, 2009. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=32587.
Full textL'imagerie par résonance magnétique (IRM) de diffusion est utile dans l'étude du cerveau humain, tant en santé que dysfonctionnel ou atteint de maladie. Malheureusement, cette technique est susceptible à des distortions géometriques qui diminuent la précision et la valeur des données. Un algorithme de correction de ces distortions doit être utilisé pendant le traitement des données. Le but de ce mémoire est de développer, d'implementer et de tester une méthode de correction des distortions pour l'IRM de diffusion. Un algorithme de correction des distortions fut developé et implémenté, puis évalué sur des ensembles de données cérébrales humaines simulées et réelles. L'algorithme fonctionne bien pour des données simulées avec des valeurs b jusqu'à b=2000 s/(mm*mm). La cause des échecs de la correction de distortion fut également étudiée. Les échecs sont attribués à une combinaison de la réduction du rapport signal sur bruit (SNR, pour signal-to-noise ratio) et de l'augmentation des différences de contraste, dans les ensembles de données avec des valeurs-b plus élevées.
Schnell, Sondre Kvalvåg, Thijs J. H. Vlugt, Jean-Marc Simon, Signe Kjelstrup, and Dick Bedeaux. "Direct calculation of the thermodynamic correction factor, gamma, from molecular dynamics simulations." Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-185607.
Full textSchnell, Sondre Kvalvåg, Thijs J. H. Vlugt, Jean-Marc Simon, Signe Kjelstrup, and Dick Bedeaux. "Direct calculation of the thermodynamic correction factor, gamma, from molecular dynamics simulations." Diffusion fundamentals 16 (2011) 72, S. 1-2, 2011. https://ul.qucosa.de/id/qucosa%3A13814.
Full textIyombe, Jean-Paul. "Correction du gène de la dystrophine avec les nucléases à doigts de zinc." Thesis, Université Laval, 2013. http://www.theses.ulaval.ca/2013/30298/30298.pdf.
Full textGene therapy without gene transfer using specific restriction endonucleases is a therapeutic approaches aimed at the development of a cure for Duchenne muscular dystrophy (DMD). To correct the dystrophin gene with zinc finger nucleases (ZFNs) targeting exon 50of DYS gene, we produced ZFNs proteins in bacteria and purified them. The results obtained after in vitro assays show that ZFNs produced specifically recognize a target sequence located in exon 50 of the gene DYS and can be generated in a precise manner the double strand breaks. They also show that ZFNs produced proteins can be transduced with or without agent transduction, in cultured myoblasts of patients’ Duchenne dystrophy.
Suissa, Michaël Freyssingeas Eric Place Christophe. "Dynamique interne du noyau d'une cellule vivante étude par diffusion dynamique de la lumière /." [S.l.] : [s.n.], 2006. http://tel.archives-ouvertes.fr/tel-00091487.
Full textJia, Jieshuang. "Study of molecules with nonsense mutation correction capacity." Thesis, Lille 2, 2015. http://www.theses.fr/2015LIL2S009/document.
Full textNonsense mutations represent approximately 10% of mutations found in the inherited geneticdiseases. mRNAs harboring a nonsense mutation are rapidly degraded by a quality-controlmechanism called nonsense-mediated mRNA decay (NMD) to prevent the synthesis of toxic or nonfunctionaltruncated proteins. Some stratégies have been developed to correct nonsense mutations.In our lab, we study 2 of them which are (i) the NMD inhibition and (ii) the PTC-readthroughactivation which is a mechanism leading to the incorporation of an amino-acid at the PTC position. Todesign new therapeutic tools for the inherited genetic diseases, our lab tested molecules byscreening to find ones with the capacity of NMD inhibition. For each molecules selected in thescreen, we measure the efficiency of NMD inhibition and PTC-readthrough activation of thesemolecules in cell lines harboring a nonsense mutation. We have shown that amlexanox not onlyinhibits NMD but also activâtes PTC readthrough. But the efficacy of amlexanox is still low. Wewanted to find other families of molecules capable of rescuing the expression of nonsense mutationcontainingmRNA with a higher efficacy or with some specificity. In my study, I found two spécialfamilies, one is the family of apoptosis inducers and the other is the family of cytoskeleton inhibitors.I found that apoptosis inducers can inhibit NMD by activating caspase pathway and cleave NMDfactors (UPF1 and UPF2). I also found that cytoskeleton inhibitors can inhibit NMD and some of themcan activate PTC-readthrough by inducing NMD factors (UPF1 or/and UPF3X) to concentrate in Pbodiesor in other cytoplasmic foci. The efficiencies of these molecules on NMD inhibition are similaror higher than amlexanox. Apoptosis inducers and cytoskeleton inhibitors demonstrated thatmolecules which can inhibit NMD or/and activate PTC-readthrough can be found and candemonstrate a higher correction of nonsense mutation efficiency than the existing molecules(ataluren or amlexanox for example)
Valon, Léo. "Contrôle Optogénétique de la Polarité Cellulaire." Thesis, Paris, Ecole normale supérieure, 2014. http://www.theses.fr/2014ENSU0008/document.
Full textIn this thesis we focus on the mechanisms that establish cell polarization, particularly during cell migration. Despite latest developments that enable visualization of RhoGTPases activity, the underlying principles dictating the cell’s ability to coordinates multiple signaling modules is still unclear. Optogenetic methods have been recognized as promising tools to dissect these intracellular signaling networks by allowing perturbations to be spatially and temporally controlled. We established the quantitative relationship between illumination patterns and the corresponding gradients of induced signaling activity through the characterization of the biophysical properties of CRY2/CIBN. We determined that it is possible to create subcellular gradients of recruited proteins of different shapes of choice up to spatial resolutions of 5μm and temporal ones of ca. 3 minutes.We applied the aforementioned optogenetic approach as a means to perturb the activity of cdc42, Rac1 and RhoA. We characterized the effects of subcellular activation of those RhoGTPases using membrane activity, cell shape changes and cell displacement as reporters of cell polarization and migration. We show that localized activation of RhoGTPases can trigger cellular organization and drive the cell into a migrating state.We also characterized the effects of local activation of RhoA on different cellular effectors as focal adhesion complexes, actin filaments and myosin molecular motors. We measured the dynamics of the newly formed focal adhesion complexes and the acto-myosin complex during retraction events.Altogether, our optogenetic methodology enables simultaneous measurement of the imposed perturbation and the cell response in a straightforward and reproducible way. It provides a quantitative way to control cell polarity and a step forward in the dissection of subcellular signaling networks
RICA, CHARLES. "Correction de la diffusion compton en scintigraphie a l'aide de reseaux neuro-mimetiques." Paris 7, 1996. http://www.theses.fr/1996PA077272.
Full textMas, Jacky. "Amélioration de la résolution et correction de la diffusion Compton en imagerie isotopique." Besançon, 1989. http://www.theses.fr/1989BESA2047.
Full textAlhamud, Alkathafi Ali. "Implementation of anatomical navigators for real time motion correction in diffusion tensor imaging." Doctoral thesis, University of Cape Town, 2012. http://hdl.handle.net/11427/10052.
Full textProspective motion correction methods using an optical system, diffusion-weighted prospective acquisition correction, or a free induction decay navigator have recently been applied to correct for motion in diffusion tensor imaging. These methods have some limitations and drawbacks. This article describes a novel technique using a three-dimensional-echo planar imaging navigator, of which the contrast is independent of the b-value, to perform prospective motion correction in diffusion weighted images, without having to reacquire volumes during which motion occurred, unless motion exceeded some preset thresholds. Water phantom and human brain data were acquired using the standard and navigated diffusion sequences, and the mean and whole brain histogram of the fractional anisotropy and mean diffusivity were analyzed.
Leguebe, Michael. "Modélisation de l'électroperméabilisation à l'échelle cellulaire." Thesis, Bordeaux, 2014. http://www.theses.fr/2014BORD0169/document.
Full textCell permeabilization by intense electric pulses, called electropermeabilization, is a biological phenomenon involved in recent anticancer therapies. It allows, for example, to increase the efficacy of chemotherapies still reducing their side effects, to improve gene transfer, or to proceed tumor ablation. However, mechanisms of electropermeabilization are not clearly explained yet, and the mostly adopted hypothesis of the formation of pores at the membrane surface is in contradiction with several experimental results.This thesis modeling work is based on a different approach than existing electroporation models. Instead of deriving equations on membranes properties from hypothesis at the molecular scale, we prefer to write ad hoc laws to describe them, based on available experimental data only. Moreover, to be as close as possible to these data, and to ease the forthcoming work of parameter calibration, we added to our model equations of transport and diffusion of molecules in the cell. Another important feature of our model is that we differentiate the conductive state of membranes from their permeable state.Numerical methods, as well as a 3D parallel C++ code were written and validated in order to solve the partial differential equations of our models. The modeling work was validated by showing qualitative match between our simulations and the behaviours that are observed in vitro
Malherbe, Godefroy. "Modélisation de la diffusion dans le noyau et application à l'activation cellulaire." Paris 6, 2010. http://www.theses.fr/2010PA066481.
Full textDumeur, Axel. "Planification d'un réseau de diffusion pour des services convergents avec le cellulaire." Paris, ENST, 2004. http://www.theses.fr/2004ENST0047.
Full textDigital Television, which corresponds to DVB-T and DVB-H, enables new uses: in indoor and mobile reception and the engineering get closer to the cellular one. The first part of the work carried out deals with the deployment of digital broadcast network for mobile and indoor reception. One goal is to have a total coverage close to GSM. In addition to the classic MFN (Multi Frequency Network), one can consider SFN (Single Frequency Network) and mix MFN/SFN. A study is carried out on SFN network that relies on a statistical analysis of signal over interference ratio. The results enable the determination of possible inter-site distances. An approach is then developped for mix MFN/SFN networks. The second part deals with the joint management of the spectral ressource in the case of a coordinated deployment of a braodcast and a cellular network that use the same frequency band. Two points are discussed: a geographical reused of the spectrum and a temporal one. Concerning the geographical reuse, the reuse of frequency bands dedicated to digital broadcasting by system using UMTS air interface type is studied. The results show a notably degraded relative UMTS (downlink) capacity compared to a single UMTS network. A trade off between the quality of each network and the cost of such deployment has to be found. Concerning the dynamic and temporal reuse, the works carried out is related to the DSA (Dynamic Spectrum Allocation) approaches, developped in the European project DRIVE. An analytical model based on queueing theory is proposed; it uses MAP process
Beauvier, Edouard. "Propagation d'un front de réaction-diffusion dans un écoulement cellulaire multi-échelle." Thesis, Aix-Marseille, 2013. http://www.theses.fr/2013AIXM4728/document.
Full textThe propagation of a reaction-diffusion front is experimentally studied in a multi-scale cellular flow. The front is produced by an autocatalytic chemical reaction in an aqueous solution. The flow is generated by electroconvection and its multi-scale nature is induced by overlaying magnets of different scales. This enables an independent tune of the flow intensity at each scale. The geometry and the mean velocity of the front have been determined over a large range of scale intensities. These features are confirmed by a numerical simulation based on a burnt and fresh domain dynamics, the burnt domain expanding across the fresh one. The effect of the multi-scale nature of the flow on the mean front velocity is recovered by a renormalisation method validated by a collapse of the data onto a single curve
Brion, Véronique. "Towards real-time diffusion imaging : noise correction and inference of the human brain connectivity." Thesis, Paris 11, 2013. http://www.theses.fr/2013PA112058/document.
Full textMost magnetic resonance imaging (MRI) system manufacturers propose a huge set of software applications to post-process the reconstructed MRI data a posteriori, but few of them can run in real-time during the ongoing scan. To our knowledge, apart from solutions dedicated to functional MRI allowing relatively simple experiments or for interventional MRI to perform anatomical scans during surgery, no tool has been developed in the field of diffusion-weighted MRI (dMRI). However, because dMRI scans are extremely sensitive to lots of hardware or subject-based perturbations inducing corrupted data, it can be interesting to investigate the possibility of processing dMRI data directly during the ongoing scan and this thesis is dedicated to this challenging topic. The major contribution of this thesis aimed at providing solutions to denoise dMRI data in real-time. Indeed, the diffusion-weighted signal may be corrupted by a significant level of noise which is not Gaussian anymore, but Rician or noncentral chi. After making a detailed review of the literature, we extended the linear minimum mean square error (LMMSE) estimator and adapted it to our real-time framework with a Kalman filter. We compared its efficiency to the standard Gaussian filtering, difficult to implement, as it requires a modification of the reconstruction pipeline to insert the filter immediately after the demodulation of the acquired signal in the Fourier space. We also developed a parallel Kalman filter to deal with any noise distribution and we showed that its efficiency was quite comparable to the non parallel Kalman filter approach. Last, we addressed the feasibility of performing tractography in real-time in order to infer the structural connectivity online. We hope that this set of methodological developments will help improving and accelerating a diagnosis in case of emergency to check the integrity of white matter fiber bundles
Lagny, Thibaut. "Myosine 1b – Mécanique membranaire et dynamique cellulaire." Thesis, Paris Sciences et Lettres (ComUE), 2018. http://www.theses.fr/2018PSLET007.
Full textThe unconventional motor protein myosin 1b is involved in a variety of cellular processes, controlling, e.g. endomembrane shape, axon development, and cell segregation. The mechanism by which myosin 1b is able to fulfil its functions in a variety of cellular locations remains unknown to date, yet the described phenotypes suggest a role of myosin 1b at the interface between membranes and actin. Notably, it is required for efficient cell segregation after activation of the EphB2 receptor which induces cell contraction.This thesis presents a detailed characterization of the effects of myosin 1b on (1) the mechanical properties of the cell membrane, studied by membrane tether pulling with an optical tweezer, and (2) the dynamics of the actin cytoskeleton and transmembrane proteins, studied by a variety of microscopy-based methods.Here we show that class 1 myosins do not generally change effective membrane tension in adherent cells, likely due to efficient compensation mechanisms. Furthermore, we show that friction between the actin cortex and the plasma membrane depends on the total density of membrane-cortex linkers and the relative fraction of bound proteins. The observed deficiency in cell contraction in absence of myosin 1b is thus independent of a persistent, global change in effective membrane tension.In the second part of this thesis, we show that myosin 1b likely does not change EphB2’s receptor dynamics in the plasma membrane, i.e. its diffusion and clustering behavior.Finally, using TIRF-SIM imaging and quantitative description of actin flows, we reveal that myosin 1b has an intriguing yet non-intuitive effect on actin dynamics at the cellular ventral surface.In conclusion, even if the mechanism by which myosin 1b changes cellular response to EphB2 stimulation still remains unknown, we have finally been able to pinpoint its function to a well-defined and quantifiable observation, i.e. changed actin flow dynamics. Future experiments will be able to address this observation and dissect its underlying mechanism. This will allow concluding on whether myosin 1b has a common effect that governs all its described biological roles
Birkby, Paul. "Numerical studies of reacting and non-reacting underexpanded sonic jets." Thesis, Loughborough University, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.297581.
Full textLaurens, Marina. "Etude des conséquences de l'ischémie-reperfusion sur le processus de mort cellulaire et de leurs correction." Nice, 2004. http://www.theses.fr/2004NICE4040.
Full textEtchegaray, Christèle. "Modélisation mathématique et numérique de la migration cellulaire." Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLS428/document.
Full textCollective or individual cell displacements are essential in fundamental physiological processes (immune response, embryogenesis) as well as in pathological developments (tumor metastasis). The intracellular processes responsible for cell motion have a complex self-organized activity spanning different time and space scales. Highlighting general principles of migration is therefore a challenging task.In a first part, we build stochastic particular models of migration. To do so, we describe key intracellular processes as discrete in space by using stochastic population models. Then, by a renormalization in large population, infinitesimal size and accelerated dynamics, we obtain continuous stochastic equations for the dynamics of interest, allowing a relation between the intracellular dynamics and the macroscopic displacement.First, we study the case of a leukocyte carried by the blood flow and developing adhesive bonds with the artery wall, until an eventual stop. The binding dynamics is described by a stochastic Birth and Death with Immigration process. These bonds correspond to resistive forces to the motion. We obtain explicitly the mean stopping time of the cell.Then, we study the case of cell crawling, that happens by the formation of protrusions on the cell edge, that grow on the substrate and exert traction forces. We describe this dynamics by a structured population process, where the structure comes from the protrusions' orientations. The limiting continuous model can be analytically studied in the 1D migration case, and gives rise to a Fokker-Planck equation on the probability distribution for the protrusion density. For a stationary profile, we can show the existence of a dichotomy between a non motile state and a directional displacement state.In a second part, we build a deterministic minimal migration model in a discoïdal cell domain. We base our work on the idea such that the structures responsible for migration also reinforce cell polarisation, which favors in return a directional displacement. This positive feedback loop involves the convection of a molecular marker, whose inhomogeneous spatial repartition is characteristic of a polarised state.The model writes as a convection-diffusion problem for the marker's concentration, where the advection field is the velocity field of the Darcy fluid that describes the cytoskeleton. Its active character is carried by boundary terms, which makes the originality of the model.From the analytical point of vue, the 1D model shows a dichotomy depending on a critical mass for the marker. In the subcritical and critical cases, it is possible to show global existence of weak solutions, as well as a rate-explicit convergence of the solution towards the unique stationary profile, corresponding to a non-motile state. Above the critical mass, for intermediate values, we show the existence of two additional stationary solutions corresponding to polarised motile profiles. Moreover, for asymmetric enough initial profiles, we show the finite time apparition of a blowup.Studying a more complex model involving activation of the marker at the cell membrane permits to get rid of this singularity.From the numerical point of vue, numerical experiments are led in 2D either in finite volumes (Matlab) or finite elements (FreeFem++) discretizations. They allow to show both motile and non motile profiles. The effect of stochastic fluctuations in time and space are studied, leading to numerical simulations of cases of responses to an external signal, either chemical (chemotaxis) or mechanical (obstacles)
Bastien, Guérin. "Nouvelle méthode spatio-spectrale de correction de la diffusion en tomographie à émission de positons." Phd thesis, Université Pierre et Marie Curie - Paris VI, 2010. http://tel.archives-ouvertes.fr/tel-00488904.
Full textBrion, Véronique. "Imagerie de diffusion en temps-réel : correction du bruit et inférence de la connectivité cérébrale." Phd thesis, Université Paris Sud - Paris XI, 2013. http://tel.archives-ouvertes.fr/tel-00821493.
Full textHering, Jan [Verfasser], and Bernd [Akademischer Betreuer] Jähne. "Robust Motion and Distortion Correction of Diffusion-Weighted MR Images / Jan Hering ; Betreuer: Bernd Jähne." Heidelberg : Universitätsbibliothek Heidelberg, 2016. http://d-nb.info/1180737466/34.
Full textGuérin, Bastien. "Nouvelle méthode spatio-spectrale de correction de la diffusion en tomographie à émission de positons." Paris 6, 2010. http://www.theses.fr/2010PA066129.
Full textPizzolato, Marco. "IRM computationnelle de diffusion et de perfusion en imagerie cérébrale." Thesis, Université Côte d'Azur (ComUE), 2017. http://www.theses.fr/2017AZUR4017/document.
Full textDiffusion and Perfusion Magnetic Resonance Imaging (dMRI & pMRI) represent two modalities that allow sensing important and different but complementary aspects of brain imaging. This thesis presents a theoretical and methodological investigation on the MRI modalities based on diffusion-weighted (DW) and dynamic susceptibility contrast (DSC) images. For both modalities, the contributions of the thesis are related to the development of new methods to improve and better exploit the quality of the obtained signals. With respect to contributions in diffusion MRI, the nature of the complex DW signal is investigated to explore a new potential contrast related to tissue microstructure. In addition, the complex signal is exploited to correct a bias induced by acquisition noise of DW images, thus improving the estimation of structural scalar metrics. With respect to contributions in perfusion MRI, the DSC signal processing is revisited in order to account for the bias due to bolus dispersion. This phenomenon prevents the correct estimation of perfusion metrics but, at the same time, can give important insights about the pathological condition of the brain tissue. The contributions of the thesis are presented within a theoretical and methodological framework, validated on both synthetical and real images
Rinkel, Jean. "Correction du diffusé pour la reconstruction tomographique quantitative avec un capteur plan numérique." Grenoble 1, 2006. http://www.theses.fr/2006GRE10117.
Full textCone Bearn Computed Tomography has the advantage of mechanical simplicity in that full 3D information can be acquired by a single rotation of the source-detector system and used to obtain isotropic reconstructed volumes. However, detection is performed by a flat panel detector and one of the main drawbacks of such detectors is that the amount of scatter reaching them is much higher than that observed in fan beam systems. The scattered radiation induces artefacts that result in under-estimates of the attenuation coefficients in reconstructed images. The aim of this thesis is to develop data pre-processing and scatter correction methods to be used in quantitative three-dimensional imaging with a flat-panel detector and to evaluate these methods in a medical context. The first part of the study describes the experimental bench set-up and defines the protocol used to ensure that data acquisitions are reproducible. Next, pre-processing methods used to correct the artefacts due to the detector are described. These methods concern the correction of defective pixels, image darkness and the spatial non-uniformity of detector response. Original methods are also proposed to correct detector non-linearity and scattering, including X-ray scatter and optical diffusion within the detector. These methods are validated experimentally on thorax phantoms. The last part of the study proposes a new method to correct the scattered radiation generated within the examined object. The method is based on an estimation of the scattered radiation images associated with each tomographic angle of view. Estimation is performed by a calibration of scattering on reference objects combined with analytical modelling of the first-order scattering process. This method is validated on thorax phantoms in a configuration of the experimental bench that has no anti-scatter grid. An adaptation of the method using an anti-scatter grid is also proposed and evaluated experimentally
Donner, Quentin. "Correction de l'atténuation et du rayonnement diffusé en tomographie d'émission à simples photons." Université Joseph Fourier (Grenoble), 1994. http://www.theses.fr/1994GRE10155.
Full textThe aim of single photon emission tomography is to compute a functional picture of an organ. This is done by administering to the patient a radiopharmaceutical which is fixing in the organ. Then, one computes the distribution of the radiopharmaceutical from the measurement of the emitted gamma-rays. However, an important part of these gamma-rays are interacting with the matter inside the body. The aim of this work is to take these interactions into account so as to reconstruct more accurately. .
Mallet, François. "Cohérence quantique, diffusion magnétique et effets topologiques." Grenoble 1, 2006. https://theses.hal.science/tel-00546850.
Full textIn this thesis are reported experimental results centered on the thematic of the electronic quantum coherence at very low temperatures, obtained by very precise measurements of the quantum correction to the classical electronic transport in metallic nanostructures. We have first studied the coherence effects in network of metallic one-dimensional wires. We have shown the influence on the coherence itself of the diffusion dimensionality. By going from a macroscopic conductor to a purely mesoscopic one, we measured a crossover in the scaling of the quantum corrections amplitudes when the phase coherence length exceed the typical size of the system. This has allowed us to really precise what the ensemble averaging is in Mesoscopic Physics. In the second part of this work, we have shown the temperature dependence of the phase coherence length in metallic wire with magnetic impurities. These samples were fabricated in a very new and controlled way, by using a new technics with a focus ion beam. We have measured a universal behavior over 2 decades in temperature for the dephasing due to one magnetic impurity. This was the direct prove that this added decoherence belongs to the physics of the generic many body problem named « Kondo Physics ». We have finally shown that the measured dephasing rate was in excellent agreement with recent theoretical calculations based one the numerical renormalization group technics. More precisely we have shown that the magnetic impurities screening induces a linear desaturation of the phase coherence time above 0,1 TK
Kraft, Sandra. "Routine Development for Artefact Correction and Information Extraction from Diffusion Weighted Echo Planar Images of Rats." Thesis, KTH, Skolan för teknik och hälsa (STH), 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-190993.
Full textBiologer och läkare studerar komplexa biologiska processer för vilket de använder avancerade bildgivande metoder. De samlar bilder som innehåller mycket information vilken måste extraheras på ett korrekt sätt. Detta kräver god datorvana och kunskaper inom bildprocessning, vilket de sällan har. För att komma runt problemet, syftade den här masteruppsattsen till att utveckla en rutin för artefaktkorrigering och informationsextrahering från bilder tagna i ett forskningsprojekt vid Karolinska Institutet i Stockholm. Genom att utveckla rutinen, visar uppsattsen hur mjukvaror utvecklade för bilder av människa kan appliceras på bilder av råtta. Rutinen hanterar formatteringsproblem och artefaktkorrigering, beräknar diffusionsmått, och utför statistiska tester på spatiellt matchade magnetresonansavbildningar tagna med diffusionsviktade ekoplana metoder. Rutinen verifierades genom att analysera bilder som den processat och det konstaterades att den skapar korrekta bilder. Framtida studier inom området bör fokusera på att utveckla atlaser av råttor och fortsätta identifieringen av hur mjukvaror utvecklade för bilder av människa kan appliceras på bilder av råtta.
Ali, Olivier. "Etude théorique de la transduction mécano-chimique dans l'adhérence cellulaire." Grenoble 1, 2010. http://www.theses.fr/2010GRENY022.
Full textComplex systems observed in molecular biology are subject of major interest for statistical physic out of equilibrium. This is the case in particular of the focal adhesions which has been the center of theoretical investigation. The descriptions of this system have been limited to the understanding of mature focal adhesions that have a life-span superior to ten minutes. However, the understanding of what happen at the early stage remains fully open. The goal of this PhD is to propose a model of bidirectional mecano-chemical transduction process, from the Inside to the outside and reciprocally, based on the allosteric character of the interaction between integrins (sensing the extracellular matrix) and an activable cytoplasmic Partner, talin. This work is divided in three parts : i) a modelisation of the cell border based on the calculation of the chemical potential of the activable Partner and on its cycle of activation, ii) the numerical and analytical resolution of the equations proposed before and iii) an update of the previous model where the integrins have been allowed to diffuse and present in this case the ability to cluster in high constraints regions
Gerin, Chloé. "Modélisation et études histologiques de gliomes diffus de bas grade." Paris 7, 2012. http://www.theses.fr/2012PA077066.
Full textDiffuse low-grade gliomas (LGG) are primary brain tumors. After a slow growth, they evolve to high-grade gliomas, resulting into death. These tumors are very diffuse, thus diffîcult to treat. A better knownledge of them could allow to cure them or, failing that, to optimize treatments. We studied the growth of LGG with a simple mathematical model, which led us to speculate (i) that they arise in adolescence, (ii) that the age of the tumor at diagnosis can be calculated easily, and (iii) that the growth rate is an important prognostic factor. This last prediction is consistent with clinical observations. To test this spatial model, we have quantitatively characterized biopsy tissues of human LGG, particularly the presence of edema. The microscopic analysis of these data underpins the idea that edema is the cause of the abnormality seen on T2-weighted MR imaging. To take this new result into account, we have incorporated edema into the initial model as a consequence of the presence of tumor cells. This model helps explain the long decay of the tumor radius for tens of months after radiation therapy: as tumor cells become less numerous, drainage of the edema becomes predominant. This model, which has only three free parameters, has been validated thanks to clinical data from twenty patients
Suissa, Michaël. "Dynamique interne du noyau d'une cellule vivante : étude par diffusion dynamique de la lumière." Phd thesis, Ecole normale supérieure de lyon - ENS LYON, 2006. http://tel.archives-ouvertes.fr/tel-00091487.
Full textBien que l'étude de cette dynamique soit devenue l'un des enjeux majeurs de la recherche en biologie cellulaire, la dynamique globale du noyau est encore peu comprise. Pour étudier cette dynamique nous avons mis au point un montage expérimental original de diffusion dynamique de la lumière. Il est à noter que si la diffusion dynamique de la lumière est une technique « classique » pour l'étude des propriétés dynamiques des systèmes moléculaires organisés (i.e. systèmes colloïdaux, surfactants, polymères en solution, gels, cristaux liquides), elle n'avait, encore, jamais été utilisée pour étudier les propriétés dynamiques du noyau d'une cellule vivante. Grâce à ce montage, nous avons étudié la dynamique globale du noyau de cellules neuroblastomes de la lignée SHEP, au cours du cycle cellulaire. Nous avons ainsi pu observer que la dynamique interne du noyau est très riche et très complexe, avec un très grand nombre de temps caractéristiques s'étalant de quelques millisecondes à quelques dizaines de secondes. Par l'analyse des fonctions d'autocorrélation de l'intensité diffusée, < I(0)I(t) >, nous avons, plus particulièrement, sondé la dynamique interne du noyau entre la milliseconde et la seconde. Nous avons mis en évidence deux distributions indépendantes de temps caractéristiques. La première est une distribution de temps rapides compris entre 5 et 70 ms. La deuxième est une distribution de temps plus lent compris entre 0,5 et 2 s. Nous avons montré que ces distributions étaient dépendantes de la phase du cycle dans laquelle se trouvaient les cellules.
Le montage expérimental que nous avons construit nous a également permis de mettre en évidence et d'étudier un processus de transmission de la mort par apoptose d'une cellule vers ses plus proches voisines.
Tang, Chengyong. "Parameter estimation and bias correction for diffusion processes and a nonparametric approach to census population size estimation." [Ames, Iowa : Iowa State University], 2008.
Find full textAhmadou, Mohamed Diaa. "Contribution au développement d'un dispositif robuste de détection-diffusion d'huiles essentielles à concentration contrôlée." Thesis, Université de Lorraine, 2015. http://www.theses.fr/2015LORR0187/document.
Full textControlThis work contributes to the design of a gas diffusion-sensing system controlling in real time the essential oil concentration in a confined atmosphere. The objective is to create reproducible exposure conditions of olfactory stimuli on living beings to test their neurosensory impacts. The main constraint is to measure with good accuracy and rapidity the odor concentration of a global atmosphere. We decided to use a gaseous detection device (electronic nose) based on commercial resistive metal oxide sensors coupled to a prior learning at fixed concentrations of pine essential oil. Experimental equipment was first developed in order to study, characterize and especially optimize the device performances to be achieved. Initially, the study of time gas sensor responses was used to optimize working measurement conditions: cycle of 75s gas exposure phase, followed by 350s pure air regeneration phase. First results allowed the classification of our sensors in terms of rapidity, sensitivity and drift levels. A systematic characterization measurement was made under various concentration variations: increasing, decreasing or random ones taking account of all possible forms of response drifts. To reduce errors due to the drifts, an original pretreatment was initiated by normalizing each sensor response value in relation with its corresponding conductance value at the end of regeneration phase. Two normalized features and also the maximum value of the derivative curve were defined for each time sensor response. The analysis by ACP and AFD classification methods of the database created using these three features show the difficulty in differentiating high concentrations, even by eliminating the two least efficient sensors. So, a completely new approach was proposed by combining the orthogonal signal correction technique (OSC) allowing to remove irrelevant information, and the Partial Linear Square regression method PLS, adapted in case of multi-collinearity and a large number of parameters. Using these two methods yields a much better discrimination of the high concentrations, maintaining the concentration prediction accuracy with a maximum stability of the regression model. Finally, the concentration prediction has been optimized by substituting representative parameters with the full response signal, the calculation time remaining low. A very good assessment of the gas concentration in all the used range was obtained. So we have developed a robust and accurate model for the calibration of our system thanks to a combination of original processing and analysis methods, allowing to achieve a reliable detection-diffusion prototype
Bonneau, Stéphanie. "Dynamique d'interaction de tétrapyrroles avec des membranes et des lipoprotéines : conséquences sur la localisation cellulaire." Paris 6, 2003. https://tel.archives-ouvertes.fr/tel-00193125.
Full textAassine, Saadia. "Couplage de type prediction - correction d'un automate cellulaire et d'un modele localise pour un probleme de dynamique de vegetation." Perpignan, 1999. http://www.theses.fr/1999PERP0340.
Full textHozé, Nathanaël. "Modélisation et méthodes d'analyse de la diffusion et agrégation au niveau moléculaire pour l'organisation sous-cellulaire." Paris 6, 2013. http://www.theses.fr/2013PA066695.
Full textIn the present PhD thesis, we study diffusion and aggregation in the context of cellular biology. Our goal is to obtain physical laws of several processes such as particle assembly or laws of diffusion in microdomains, in order to determine how subcellular processes are constructed from elementary molecular organization. This change of scale can be formulated and analyzed using several tools such as partial differential equations, statistical physics, stochastic processes and numerical simulations. We present here several methods and we apply them to study questions in biophysics, neurobiology and cellular biology. Examples are receptors trafficking on cellular membrane, nuclear organization and the dynamics of viral assembly. In the first part, to obtain an estimation of the effective diffusion coefficient of a Brownian particle moving in between obstacles, we compute the mean time for a Brownian particle to arrive to a narrow opening defined as the region of minimal distance between two disks of identical radius. The method relies on M\"obius conformal transformation applied to the Laplace equation. Using this result, we develop statistical methods to solve a reverse engineering problem which consists in recovering parameters of a stochastic equation from a large number of short trajectories. Applying this method to superresolution data of receptor trafficking, we identify novel molecular organization, which are described as potential wells (deterministic part of the SDE). We next solve a different question: how is it possible to reconstruct surfaces from a large sample of short stochastic trajectories? By using Ito's formula, we derive a new class of nonlinear partial differential equations that allow us to reconstruct the surface. This section is illustrated with numerical examples. In the second part, we focus on an aspect of nuclear organization and our goal is to model and analyze telomere dynamics (ends of the chromosomes) in the cell nucleus. Early experimental findings reveal that yeast telomeres organize dynamically in a small numbers of clusters, yet this process remains poorly understood. Thus, we use a statistical physics approach to study the joint dynamics of the 32 telomeres, that we model as independent Brownian particles that can also form aggregates. We estimate the number of clusters and the number of telomeres per cluster using exact formula that we derive from our model. We identify the relevant parameters by comparing our results with experimental data. In particular, we show that a single parameter - the ratio of the association to the dissociation rate - is sufficient to account for telomere clustering in various conditions. Finally, we develop an empirical model to study particle aggregation to a single nucleation site. The distribution of particles in small clusters before arriving is a key ingredient to derive kinetic laws. We derive these laws using first a deterministic model and then a stochastic jump process, which allows us to obtain also an explicit expression for the mean time that the nucleation site is filled. We discuss some applications to HIV capsid formation
Schram, Vincent. "Approche par la diffusion translationnelle de la structuration latérale de milieux modèles membranaires." Toulouse 3, 1993. http://www.theses.fr/1993TOU30186.
Full textDib, Carla. "développement d'approches de correction des myoblastes issus de patients atteints de la dystrophie facio-scapulo-humérale." Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLS224.
Full textFacio-Scapulo-Humeral dystrophy is characterized by progressive and asymmetrical muscle weakness. It mainly affects the facial, scapular and humeral muscles. The association of several epigenetic events with three genetic factors of the subtelomeric region of chromosome 4 results in a chromatin organization modification making it permissive to the aberrant expression of genes in the 4q35 region. FSHD myoblasts exhibit differentiation defects in vitro and dysregulations in major pathways such as the cellular response to oxidative stress and myogenic differentiation. The limitations of cell therapy and the complex genetic and epigenetic interplay in FSHD leave it, till now, incurable. However advances in cellular and genetic therapies of myopathies open up new horizons for future applications in the FSHD context. The thesis work is structured around three themes. First, we demonstrate the feasibility of phenotypic and functional correction of FSHD myotubes in vitro by fusing 50% of normal myoblasts with FSHD myoblasts. Next, we evaluate two genomic editing approaches. In the first one, we target the site of attachment of chromosome 4 to the nuclear matrix, FR-MAR with the CTCF protein using the CRISPR / dCas9 system for the purpose of restoring the chromatin organization and the insulating function of FR-MAR. In the second one, we exchange the homologous regions 4q35 and 10q26 by translocation in order to correct the FSHD myoblasts as the three genetic factors of the 4q35 locus are pathogenic only on a genetic background linked to chromosome 4. Finally, we study the role of the oxidative stress in the FSHD
Sarr, Fatima Seydou. "Modélisation du mécanisme de diffusion d'une série de statines à travers la membrane cellulaire : approche biochromatographique et thermodynamique." Besançon, 2010. http://www.theses.fr/2010BESA0018.
Full textThe xenobiotic cell membrane passage studies such as statins is needed to assess their bioavailability and pharmacokinetics. It is done through three types of stationary phases filling a chromatographic column : an Immobilized Artificial Membrane (IAM) to study passive diffusion, an Oatp2 stationnary phase (Organic anion transporting polypeptide 2) and cell membrane stationary phases (CMSP) (i. E. Constituted with extracts membrane of rat hepatocytes Oatp2 overexpressed or not to study facilitated diffusion). These studies will analyze and better understand the physical and chemical processes involved in the xenobiotic diffusion mechanism. The results showed that the interactions governing the statin association with biological membranes or transporters are Van der Waals, hydrogen and electrostatic bonds. The hydrophobic effect plays a major role in this association. We have also shown that magnesium increases the station passive diffusion but decreases their facilitated diffusion. The Oatp2 stationary phase models the statin diffusion optimal and similar to the CMC. This new Oatp2 stationary phase easier to develop experimentally, coupled with an analytical column separate classic (type C18) and a mass spectrum (i. E. , CLHP-Oapt2/CLHP-C18/SM) should serve to make studies such as " screening " to find and develop new and specific inhibitors for each member of the Oatp subfamily
Le, Bars Anne-Lise. "Développements méthodologiques pour l’IRM de diffusion cardiaque." Electronic Thesis or Diss., Université de Lorraine, 2021. http://www.theses.fr/2021LORR0089.
Full textDiffusion magnetic resonance imaging (MRI) is a non-invasive imaging modality that allows the assessment of microarchitecture in biological tissues. Knowing the arrangement of myocardial fiber is important to fully understand cardiac electrophysiology in patients, and therefore to improve the treatment of complex arrythmia such as ventricular tachycardia. Nevertheless, efforts have to be made to apply diffusion MRI to moving organs because of the various artefacts created by displacements. Macroscopic motion, including cardiac contraction and breathing is in the range of a few millimeters, whereas diffusion motion is at the micrometer scale. To deal with cardiac motion, a cardiac-triggered diffusion-weighted spin-echo echo planar imaging sequence can be used with first and second order motion-compensated diffusion-encoding gradients. However, these sequences are very sensitive to the phase of the cardiac cycle chosen to perform the acquisition. Moreover, the ventricle coverage is often limited to a few slices due to the long scan time required to have sufficient SNR. Considering these limitations, the thesis has been separated in two parts with the following objectives: to implement a subject-specific cardiac synchronization and to set up an efficient protocol that performs a full coverage of the left-ventricle with isotropic resolution. The subject-specific cardiac synchronisation has been implemented using a real-time phase contrast (RTPC) sequence which is sensitive to motion. RTPC sequence provides knowledge on the variability in duration of cardiac phases. By modelling the cardiac variability, it was possible to study the quality of the diffusion measurement as a function of the cardiac phase. In regards of the results, the sequence can be valuable to optimize and/or adapt the trigger delay to target the diastasis. This phase is the quiescent phase of the cardiac cycle but also the most variable as a function of heart-rate. The online reconstruction of RTPC sequence has been successfully implemented to facilitate the deployment of the sequence to adapt the trigger delay for future clinical research, possibly with other applications. The focus of the second part of the work was to retrieve tri-dimensional information about myocardial fiber organisation with a full coverage of left ventricle. This full coverage is mandatory to simulate cardiac electrophysiology. A bulk motion-corrected super-resolution approach to cDTI has been proposed to improve spatial resolution without significant cost on SNR. Therefore, the total scan time can be reduced by this method. Evaluation in a numerical heart phantom and in a physical helicoidal phantom, have shown the improvement of spatial resolution and diffusion tensor estimation in a general case (except when the underlying geometry is highly favorable to low resolution images). This is of particular interest when there are significant changes in orientation of principal diffusion direction along the slice direction, according to the global geometry of the heart. The feasibility of super-resolution in-vivo cDTI on healthy volunteers has shown the applicability of the approach
Ahmadou, Mohamed Diaa. "Contribution au développement d'un dispositif robuste de détection-diffusion d'huiles essentielles à concentration contrôlée." Electronic Thesis or Diss., Université de Lorraine, 2015. http://www.theses.fr/2015LORR0187.
Full textControlThis work contributes to the design of a gas diffusion-sensing system controlling in real time the essential oil concentration in a confined atmosphere. The objective is to create reproducible exposure conditions of olfactory stimuli on living beings to test their neurosensory impacts. The main constraint is to measure with good accuracy and rapidity the odor concentration of a global atmosphere. We decided to use a gaseous detection device (electronic nose) based on commercial resistive metal oxide sensors coupled to a prior learning at fixed concentrations of pine essential oil. Experimental equipment was first developed in order to study, characterize and especially optimize the device performances to be achieved. Initially, the study of time gas sensor responses was used to optimize working measurement conditions: cycle of 75s gas exposure phase, followed by 350s pure air regeneration phase. First results allowed the classification of our sensors in terms of rapidity, sensitivity and drift levels. A systematic characterization measurement was made under various concentration variations: increasing, decreasing or random ones taking account of all possible forms of response drifts. To reduce errors due to the drifts, an original pretreatment was initiated by normalizing each sensor response value in relation with its corresponding conductance value at the end of regeneration phase. Two normalized features and also the maximum value of the derivative curve were defined for each time sensor response. The analysis by ACP and AFD classification methods of the database created using these three features show the difficulty in differentiating high concentrations, even by eliminating the two least efficient sensors. So, a completely new approach was proposed by combining the orthogonal signal correction technique (OSC) allowing to remove irrelevant information, and the Partial Linear Square regression method PLS, adapted in case of multi-collinearity and a large number of parameters. Using these two methods yields a much better discrimination of the high concentrations, maintaining the concentration prediction accuracy with a maximum stability of the regression model. Finally, the concentration prediction has been optimized by substituting representative parameters with the full response signal, the calculation time remaining low. A very good assessment of the gas concentration in all the used range was obtained. So we have developed a robust and accurate model for the calibration of our system thanks to a combination of original processing and analysis methods, allowing to achieve a reliable detection-diffusion prototype
Seigneur, Alain. "Cytométrie en flux : conception d'un appareil et validation expérimentale." Paris 11, 1987. http://www.theses.fr/1987PA112025.
Full textThe flow cytometry techniques allow the analysis and sorting of living biologic cells at rates above five for then thousand events per second. After a short review, we present in this report the design and development of a "high-tech" apparatus intended for research laboratories and the experimental results. The first part deals with the physical principles allowing morphologic and functional analysis of cells or cellular components. The measured parameters are as follows: electrical resistance pulse sizing, light scattering and fluorescence. Hydrodynamic centering is used, and in the same way, the division of a water-stream into droplets leading to electrostatic sorting of particules. The second part deals with the apparatus design at the "Commissariat à l'Energie Atomique" (C. E. A. ) and industrialised by "ODAM" (ATC 3000). The last part of this thesis work is the performance evaluations of this cytometer. The difference between the two size measurement methods are analyzed: electrical resistance pulse sizing versus small-angle light scattering. By an original optics design, high sensitivity has been reached in the fluorescence measurement: the equivalent noise corresponds to six hundred fluorescein isothiocyanate (FITC) molecules. The sorting performances have also been analyzed and the cell viability proven
Dos, Santos Ferreira Jorge. "Identification des mécanismes en boucle fermée dans le comportement cellulaire." Compiègne, 2008. http://www.theses.fr/2008COMP1734.
Full textThe aim of this work is to try to use observed global changes to understand interactions between individual nodes inside biochemical networks. We have worked on the determination of the essential interactions in the auto regulatory process that describes the cell cycle of Xenopus frog eggs. The results make possible an assessment of the effect of each protein on the biochemical network stability. The technique was applied also to a dynamical analysis of a uterine cell electrical activity model with view to study the impact of physiological parameters on the response of the model and identify the main subsystems generating the electrical activity. We also present a model developed for understanding an enzymatic diffusion-reaction system. The objective is to analyze the dynamic behavior of three different chemical species, the modification of enzymatic kinetic properties and the existence of sophisticated behaviors resulting of the catalytic activity induced by immobilization of Acetylcholinesterase enzyme into an artificial membrane enzymatically inactive. The results make possible the characterization and prediction of system behavior as well as a qualitative analysis of the system stability via bifurcation diagrams. The model is then extrapolated to a distributed system in order to analyze its spatio-temporal behavior. Numerical results make possible the assessment of the concentration profile of the chemical species on space and time, what is not directly observable by biochemists. Finally, we study a model developed for a network of Sinorhizobium meliloti bacterium and propose an algorithm for intracellular fluxes estimation
Taljan, Kyle Andrew Ignatius. "Investigations of Anatomical Connectivity in the Internal Capsule of Macaques with Diffusion Magnetic Resonance Imaging." Cleveland State University / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=csu1311093061.
Full textAmorino, Chiara. "Bias correction for drift and volatility estimation of jump diffusion processes and non - parametric adaptive estimation of the invariant measure." Thesis, université Paris-Saclay, 2020. https://www.biblio.univ-evry.fr/theses/2020/2020UPASE006.pdf.
Full textThe thesis deal with the parametric and non-parametric inference in jump process models.It consists of 3 parts which gather 4 chapters.The first part, which contains 2 chapters, focuses on the estimation of the drift and volatility parameters via some contrast function methods starting from a discretely observed process.The main goal is to minimise the conditions on the discretization step so that it can go to $0$ arbitrarily slowly.The second part of the thesis regards some asymptotic developments, and bias correction, for the estimation of the integrated volatility.The third part of the thesis is about the adaptive estimation of the invariant measure for jump processes
Bouchard-Gilanton, Véronique. "Modélisation et correction de l'effet Compton dans la reconstruction d'images tomoscintigraphiques." Grenoble 1, 1997. http://www.theses.fr/1997GRE10003.
Full textCaré, Bertrand. "Modèles individu-centrés de l'impact fonctionnel des hétérogénéités de diffusion et de distribution spatiale des protéines de signalisation cellulaire." Phd thesis, INSA de Lyon, 2012. http://tel.archives-ouvertes.fr/tel-00858499.
Full textSune, Albert. "Diffusion transverse de phospholipides dans la membrane plasmique de cellules sanguines : étude par résonance paramagnétique et microscopie électronique." Montpellier 1, 1987. http://www.theses.fr/1987MON13513.
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