Lundberg, Micah, Krishan, Kapilanjan, Xu, Ning, O'Hern, Corey, Dennin, Michael
A fundamental difference between fluids and solids is their response to applied shear. Solids possess static shear moduli, while fluids do not. Complex fluids such as foams display an intermediate...
Viscoelastic shear banding in foam (2008)
Krishan, Kapilanjan, Dennin, Michael
Shear banding is an important feature of flow in complex fluids. Essentially, shear bands refer to the coexistence of flowing and non-flowing regions in driven material. Understanding the possible...
Discontinuous Jamming Transitions in Soft Materials (2008)
Many systems in nature exhibit transitions between fluid-like states and solid-like states, or "jamming transitions". There is a strong theoretical foundation for understanding equilibrium phase...
Combined macro- and micro-rheometer for use with Langmuir monolayers (2007)
Walder, Robert, Schmidt, Christoph, Dennin, Michael
A Langmuir monolayer trough that is equipped for simultaneous microrheology and standard rheology measurements has been constructed. The central elements are the trough itself with a full range of...
Statistics of microscopic yielding in sheared aqueous foams (2006)
Wang, Yuhong, Krishan, Kapilanjan, Dennin, Michael
We detail the statistical distribution of bubble rearrangements in a sheared two-dimensional foam. Such rearrangements, known as T1 events, are vital to mechanisms resulting in flow through...
Flow transitions in two-dimensional foams (2006)
Gilbreth, Christopher, Sullivan, Scott, Dennin, Michael
For sufficiently slow rates of strain, flowing foam can exhibit inhomogeneous flows. The nature of these flows is an area of active study in both two-dimensional model foams and three dimensional...
Bubble kinematics in a sheared foam (2006)
Wang, Yuhong, Krishan, Kapilanjan, Dennin, Michael
We characterize the kinematics of bubbles in a sheared two-dimensional foam using statistical measures. We consider the distributions of both bubble velocities and displacements. The results are...
Limits of the equivalence of time and ensemble averages in shear flows (2006)
Wang, Yuhong, Krishan, Kapilanjan, Dennin, Michael
In equilibrium systems, time and ensemble averages of physical quantities are equivalent due to ergodic exploration of phase space. In driven systems, it is unknown if a similar equivalence of time...
Asymmetric response of a jammed plastic bead raft (2006)
Twardos, Michael, Dennin, Michael
Fluctuation-dissipation relations have received significant attention as a potential method for defining an effective temperature in nonequilibrium systems. The successful development of an effective...
Impact of boundaries on velocity profiles in bubble rafts (2005)
Wang, Yuhong, Krishan, Kapilanjan, Dennin, Michael
Under conditions of sufficiently slow flow, foams, colloids, granular matter, and various pastes have been observed to exhibit shear localization, i.e. regions of flow coexisting with regions of...
Impact of noise on domain growth in electroconvection (2005)
Griffith, Mary, Dennin, Michael
The growth and ordering of striped domains has recently received renewed attention due in part to experimental studies in diblock copolymers and electroconvection. One surprising result has been the...
Early time evolution of Freedericks patterns generated from states of electroconvection (2005)
Funfschilling, Denis, Dennin, Michael
We report on the early time ordering in a nematic liquid crystal subjected to a sudden change in external ac electric field. We compare time evolution for two different initial states of...
Comparison between step strains and slow steady shear in a bubble raft (2004)
Twardos, Michael, Dennin, Michael
We report on a comparison between stress relaxations after an applied step strain and stress relaxations during slow, continuous strain in a bubble raft. A bubble raft serves as a model...
Slow Steady-Shear of Plastic Bead Rafts (2004)
Twardos, Michael, Dennin, Michael
Experimental measurements of the response of a two dimensional system of plastic beads subjected to steady shear are reported. The beads float at the surface of a fluid substrate and are subjected to...
Velocity Fluctuations in a Slowly Sheared Bubble Raft (2004)
A surprising feature of flow in slowly sheared model foam (bubble raft) is a measured discontinuity in the rate of strain as a function of position such that part of the system is ``flowing'' and the...
Statistics of Bubble Rearrangements in a Slowly Sheared Two-dimensional Foam (2004)
Many physical systems exhibit plastic flow when subjected to slow steady shear. A unified picture of plastic flow is still lacking; however, there is an emerging theoretical understanding of such...
Dislocation Dynamics in an Anisotropic Stripe Pattern (2004)
Kamaga, Carina, Ibrahim, Fatima, Dennin, Michael
The dynamics of dislocations confined to grain boundaries in a striped system are studied using electroconvection in the nematic liquid crystal N4. In electroconvection, a striped pattern of...
Velocity Profiles in Slowly Sheared Bubble Rafts (2003)
Lauridsen, John, Chanan, Greg, Dennin, Michael
Measurements of average velocity profiles in a bubble raft subjected to slow, steady-shear demonstrate the coexistence between a flowing state and a jammed state similar to that observed for...
Dependence of Striped Domain Growth on Background Wavenumber (2003)
Kamaga, Carina, Funfschilling, Denis, Dennin, Michael
We report on the growth of domains of standing waves in electroconvection in a nematic liquid crystal. An ac voltage is applied to the system, forming an initial state that consists of travelling...
Nonlinear Stress Fluctuation Dynamics of Sheared Disordered Wet Foam (2002)
Sheared wet foam, which stores elastic energy in bubble deformations, relaxes stress through bubble rearrangements. The intermittency of bubble rearrangements in foam leads to effectively stochastic...
Shear-Induced Stress Relaxation in a Two-Dimensional Wet Foam (2002)
Lauridsen, John, Twardos, Michael, Dennin, Michael
We report on experimental measurements of the flow behavior of a wet, two-dimensional foam under conditions of slow, steady shear. The initial response of the foam is elastic. Above the yield strain,...
Folding Langmuir Monolayers (2002)
Lu, Weixing, Knobler, Charles M., Bruinsma, Robijn F., Dennin, Michael, Twardos, Michael
The maximum pressure a two-dimensional surfactant monolayer is able to withstand is limited by the collapse instability towards formation of three-dimensional material. We propose a new description...
Modulation of Localized States in Electroconvection (2002)
Kamaga, Carina, Dennin, Michael
We report on the effects of temporal modulation of the driving force on a particular class of localized states, known as worms, that have been observed in electroconvection in nematic liquid...
Domain Coarsening in Electroconvection (2000)
Purvis, Lynne, Dennin, Michael
We report on experimental measurements of the growth of regular domains evolving from an irregular pattern in electroconvection. The late-time growth of the domains is consistent with the size of the...
I report on the effects of a periodic modulation of the control parameter on electroconvection in the nematic liquid crystal I52. Without modulation, the primary bifurcation from the uniform state is...
Direct observation of twist mode in electroconvection in I52 (2000)
I report on the direct observation of a uniform twist mode of the director field in electroconvection in I52. Recent theoretical work suggests that such a uniform twist mode of the director field is...
Reversible Random Sequential Adsorption of Dimers on a Triangular Lattice (1999)
Ghaskadvi, R. S., Dennin, Michael
We report on simulations of reversible random sequential adsorption of dimers on three different lattices: a one-dimensional lattice, a two-dimensional triangular lattice, and a two-dimensional...
Effect of Subphase Ca++ Ions on the Viscoelastic Properties of Langmuir Monolayers (1999)
Ghaskadvi, R. S., Carr, Sharon, Dennin, Michael
It is known that the presence of cations like Ca++ or Pb++ in the water subphase alters the pressure-area isotherms for fatty acid monolayers. The corresponding lattice constant changes have been...