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Physique Théorique
(122) Production(s) de l'année 2017
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Physical modeling of active bacterial DNA segregation
Auteur(s): Walter J.-C.
Conference: Quantitative Methods in Gene Regulation IV (Cambridge, GB, 2017-12-18)
Texte intégral en Openaccess :
Ref HAL: hal-01881265_v1
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Résumé: Efficient bacterial chromosome segregation typically requires the coordinated action of a three-component, fueled by adenosine triphosphate machinery called the partition complex. We present a phenomenological model accounting for the dynamic activity of this system that is also relevant for the physics of catalytic particles in active environments. The model is obtained by coupling simplelinear reaction-diffusion equations with a proteophoresis, or “volumetric” chemophoresis, force field that arises from protein-protein interactions and provides a physically viable mechanism for complex translocation. This minimal description captures most known experimental observations: dynamic oscillations of complex components, complex separation and subsequent symmetricalpositioning. The predictions of our model are in phenomenological agreement with and provide substantial insight into recent experiments. From a non-linear physics view point, this system explores the active separation of matter at micrometric scales with a dynamical instability between static positioning and travelling wave regimes triggered by the dynamical spontaneous breaking ofrotational symmetry.
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Structuring polymer gels via catalytic reactions
Auteur(s): Hugouvieux Virginie, Kob W.
(Article) Publié:
Soft Matter, vol. 13 p.8706-8716 (2017)
Texte intégral en Openaccess :
Ref HAL: hal-01837825_v1
DOI: 10.1039/C7SM01814B
WoS: 000416556000005
Exporter : BibTex | endNote
2 Citations
Résumé: We use computer simulations to investigate how a catalytic reaction in a polymer sol can induce the formation of a polymer gel. To this aim we consider a solution of homopolymers in which freely-diffusing catalysts convert the originally repulsive A monomers into attractive B ones. We find that at low temperatures this reaction transforms the polymer solution into a physical gel that has a remarkably regular mesostructure in the form of a cluster phase, absent in the usual homopolymer gels obtained by a quench in temperature. We investigate how this microstructuring depends on catalyst concentration, temperature, and polymer density and show that the dynamics for its formation can be understood in a semi-quantitative manner using the interaction potentials between the particles as input. The structuring of the copolymers and the AB sequences resulting from the reactions can be discussed in the context of the phase behaviour of correlated random copolymers. The location of the spinodal line as found in our simulations is consistent with analytical predictions. Finally, we show that the observed structuring depends not only on the chemical distribution of the A and B monomers but also on the mode of formation of this distribution.
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Metamaterials modelling and design
Auteur(s): Bouchitté Guy, Felbacq D.
Ouvrage: PAN Stanford (2017)
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Trajectory formation principles are the same after mild or moderate stroke
Auteur(s): Mottet Denis, Van Dokkum E., Froger Jérôme, Gouaich Abdelkader, Laffont Isabelle
(Article) Publié:
Plos One, vol. 12 p.e0173674 (2017)
Texte intégral en Openaccess :
Ref HAL: hal-01773982_v1
PMID 28329000
DOI: 10.1371/journal.pone.0173674
WoS: 000399094700028
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10 Citations
Résumé: When we make rapid reaching movements, we have to trade speed for accuracy. To do so, the trajectory of our hand is the result of an optimal balance between feed-forward and feed-back control in the face of signal-dependant noise in the sensorimotor system. How far do these principles of trajectory formation still apply after a stroke, for persons with mild to moderate sensorimotor deficits who recovered some reaching ability? Here, we examine the accuracy of fast hand reaching movements with a focus on the information capacity of the sensorimotor system and its relation to trajectory formation in young adults, in persons who had a stroke and in age-matched control participants. We find that persons with stroke follow the same trajectory formation principles, albeit parameterized differently in the face of higher sensorimotor uncertainty. Higher directional errors after a stroke result in less feed-forward control, hence more feed-back loops responsible for segmented movements. As a consequence, movements are globally slower to reach the imposed accuracy, and the information throughput of the sensorimotor system is lower after a stroke. The fact that the most abstract principles of motor control remain after a stroke suggests that clinicians can capitalize on existing theories of motor control and learning to derive principled rehabilitation strategies.
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The experience of social exclusion in women with a history of suicidal acts: a neuroimaging study.
Auteur(s): Olié Emilie, Jollant Fabrice, Deverdun J., Menjot De Champfleur N., Cyprien Fabienne, Le Bars E., Mura Thibault, Bonafé Alain, Courtet Philippe
(Article) Publié:
Scientific Reports, vol. 7 p.89 (2017)
Texte intégral en Openaccess :
Ref HAL: hal-01727754_v1
PMID 28273888
DOI: 10.1038/s41598-017-00211-x
WoS: 000396942000006
Exporter : BibTex | endNote
29 Citations
Résumé: Suicidal behaviors result from a complex interaction between social stressors and individual vulnerability. However, little is known of the specific neural network supporting the sensitivity to social stressors in patients at risk of suicidal acts. Using functional Magnetic Resonance Imaging, we investigated brain processing of social rejection in suicide attempters. Thirty-six euthymic women with a history of depression and suicidal behavior were compared to 41 euthymic women with a history of depression but no suicidal attempt, and 28 healthy controls. The Cyberball Game was used as a validated social exclusion paradigm. Relative to healthy controls, both patient groups reported higher levels of social distress related to the task, without significant differences according to suicidal status. Compared to patients without any history of suicide attempt and healthy controls, suicide attempters showed decreased contrast in the left insula and supramarginal gyrus during the exclusion vs. inclusion condition, after controlling for number of depressive episodes, medication, mood disorder type or social phobia. Our study highlights impaired brain response to social exclusion in euthymic female suicide attempters in regions previously implicated in pain tolerance and social cognition. These findings suggest sustained brain dysfunctions related to social perception in suicide attempters.
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Kinematics in the brain: unmasking motor control strategies?
Auteur(s): van Dokkum Liesjet E H, Mottet Denis, Laffont I, Bonafé A, Menjot De Champfleur N., Froger J, Le Bars E.
(Article) Publié:
Experimental Brain Research, vol. 235 p.2639-2651 (2017)
Texte intégral en Openaccess :
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Interhypothalamic adhesion and multiple cerebral abnormalities in a 2-year-old boy.
Auteur(s): Loubet Antoine, Dargazanli Cyril, Joris Roux Charles, Rivier Francois, Menjot De Champfleur N., Leboucq Nicolas
(Article) Publié:
-Journal De Neuroradiologie / Journal Of Neuroradiology, vol. p.63-64 (2017)
Texte intégral en Openaccess :
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