Time filter

Source Type

Saint-Sauveur-en-Rue, France

Maity P.,Indian Institute of Technology Kharagpur | Kumar K.,Indian Institute of Technology Kharagpur | Pal P.,Laboratoire Of Physique Statistique | Pal P.,National Institute of Technology Durgapur

We present results of direct numerical simulations on homoclinic gluing and ungluing bifurcations in a low-Prandtl-number (0 ≤ Pr ≤ 0.025) Rayleigh-Bénard system rotating slowly and uniformly about a vertical axis. We have performed simulations with stress-free top and bottom boundaries for several values of the Taylor number (5 ≤ Ta ≤ 50) near the instability onset. We observe a single homoclinic ungluing bifurcation, marked by the spontaneous breakingof a larger limit cycle into two limit cycles with the variation of the reduced Rayleigh number r for smaller values of Ta (< 25). A pair of homoclinic bifurcations, instead of one bifurcation, is Observed with the variation of r for slightly higher values of Ta (25 ≤ Ta ≤ 50) in the same fluid Dynamical system. The variation of the bifurcation threshold with Ta is also investigated. We Have also constructed a low-dimensional model which qualitatively captures the dynamics of the system near the homoclinic bifurcations for low rotation rates. The model is used to study the unfolding of bifurcations and the variation of the homoclinic bifurcation threshold with Pr. © EPLA, 2013. Source

Relaix F.,University Pierre and Marie Curie | Relaix F.,French Institute of Health and Medical Research | Relaix F.,Institute Of Myologie | Demignon J.,University of Paris Descartes | And 10 more authors.
PLoS Genetics

In mammals, several genetic pathways have been characterized that govern engagement of multipotent embryonic progenitors into the myogenic program through the control of the key myogenic regulatory gene Myod. Here we demonstrate the involvement of Six homeoproteins. We first targeted into a Pax3 allele a sequence encoding a negative form of Six4 that binds DNA but cannot interact with essential Eya co-factors. The resulting embryos present hypoplasic skeletal muscles and impaired Myod activation in the trunk in the absence of Myf5/Mrf4. At the axial level, we further show that Myod is still expressed in compound Six1/Six4:Pax3 but not in Six1/Six4:Myf5 triple mutant embryos, demonstrating that Six1/4 participates in the Pax3-Myod genetic pathway. Myod expression and head myogenesis is preserved in Six1/Six4:Myf5 triple mutant embryos, illustrating that upstream regulators of Myod in different embryonic territories are distinct. We show that Myod regulatory regions are directly controlled by Six proteins and that, in the absence of Six1 and Six4, Six2 can compensate. © 2013 Relaix et al. Source

Bustamante M.D.,University College Dublin | Brachet M.,Laboratoire Of Physique Statistique | Brachet M.,Universites Paris et I
Physical Review E - Statistical, Nonlinear, and Soft Matter Physics

Numerical simulations of the incompressible Euler equations are performed using the Taylor-Green vortex initial conditions and resolutions up to 40963. The results are analyzed in terms of the classical analyticity-strip method and Beale, Kato, and Majda (BKM) theorem. A well-resolved acceleration of the time decay of the width of the analyticity strip δ(t) is observed at the highest resolution for 3.7 Source

Habibi M.,Institute for Advanced Studies in Basic Sciences | Rahmani Y.,Institute for Advanced Studies in Basic Sciences | Rahmani Y.,University of Amsterdam | Bonn D.,University of Amsterdam | And 2 more authors.
Physical Review Letters

Under appropriate conditions, a column of viscous liquid falling onto a rigid surface undergoes a buckling instability. Here we show experimentally and theoretically that liquid buckling exhibits a hitherto unsuspected complexity involving three different modes-viscous, gravitational, and inertial-depending on how the viscous forces that resist bending of the column are balanced. We also find that the nonlinear evolution of the buckling exhibits a surprising multistability with three distinct states: steady stagnation flow, "liquid rope coiling," and a new state in which the column simultaneously folds periodically and rotates about a vertical axis. The transitions among these states are subcritical, leading to a complex phase diagram in which different combinations of states coexist in different regions of the parameter space. © 2010 The American Physical Society. Source

Aytouna M.,Soft Science | Paredes J.,Soft Science | Shahidzadeh-Bonn N.,Soft Science | Moulinet S.,Laboratoire Of Physique Statistique | And 5 more authors.
Physical Review Letters

We study the pinch-off dynamics of droplets of yield stress and shear thinning fluids. To separate the two non-Newtonian effects, we use a yield stress material for which the yield stress can be tuned without changing the shear thinning behavior, and a shear thinning system (without a yield stress) for which the shear thinning can be controlled over a large range, without introducing too much elasticity into the system. We find that the pinch-off remains very similar to that of constant viscosity Newtonian liquids, and consequently thinning in shear flow does not imply a thinning in elongational flow. © 2013 American Physical Society. Source

Discover hidden collaborations