18 research outputs found
Effective Viscosity of Dilute Bacterial Suspensions: A Two-Dimensional Model
Suspensions of self-propelled particles are studied in the framework of
two-dimensional (2D) Stokesean hydrodynamics. A formula is obtained for the
effective viscosity of such suspensions in the limit of small concentrations.
This formula includes the two terms that are found in the 2D version of
Einstein's classical result for passive suspensions. To this, the main result
of the paper is added, an additional term due to self-propulsion which depends
on the physical and geometric properties of the active suspension. This term
explains the experimental observation of a decrease in effective viscosity in
active suspensions.Comment: 15 pages, 3 figures, submitted to Physical Biolog
Dynamics of electrostatically-driven granular media. Effects of Humidity
We performed experimental studies of the effect of humidity on the dynamics
of electrostatically-driven granular materials. Both conducting and dielectric
particles undergo a phase transition from an immobile state (granular solid) to
a fluidized state (granular gas) with increasing applied field. Spontaneous
precipitation of solid clusters from the gas phase occurs as the external
driving is decreased. The clustering dynamics in conducting particles is
primarily controlled by screening of the electric field but is aided by
cohesion due to humidity. It is shown that humidity effects dominate the
clustering process with dielectric particles.Comment: 4 pages, 4 fig
Diabetes increases mortality after myocardial infarction by oxidizing CaMKII
Diabetes increases oxidant stress and doubles the risk of dying after myocardial infarction, but the mechanisms underlying increased mortality are unknown. Mice with streptozotocin-induced diabetes developed profound heart rate slowing and doubled mortality compared with controls after myocardial infarction. Oxidized Ca(2+)/calmodulin-dependent protein kinase II (ox-CaMKII) was significantly increased in pacemaker tissues from diabetic patients compared with that in nondiabetic patients after myocardial infarction. Streptozotocin-treated mice had increased pacemaker cell ox-CaMKII and apoptosis, which were further enhanced by myocardial infarction. We developed a knockin mouse model of oxidation-resistant CaMKIIδ (MM-VV), the isoform associated with cardiovascular disease. Streptozotocin-treated MM-VV mice and WT mice infused with MitoTEMPO, a mitochondrial targeted antioxidant, expressed significantly less ox-CaMKII, exhibited increased pacemaker cell survival, maintained normal heart rates, and were resistant to diabetes-attributable mortality after myocardial infarction. Our findings suggest that activation of a mitochondrial/ox-CaMKII pathway contributes to increased sudden death in diabetic patients after myocardial infarction