Azadeh Samadani

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Because ocean water is typically resource-poor, bacteria may gain significant growth advantages if they can exploit the ephemeral nutrient patches originating from numerous, small sources. Although this interaction has been proposed to enhance biogeochemical transformation rates in the ocean, it remains questionable whether bacteria are able to efficiently(More)
Actin polymerization provides a powerful propulsion force for numerous types of cell motility. Although tremendous progress has been made in identifying the biochemical components necessary for actin-based motility, the precise biophysical mechanisms of force generation remain unclear. To probe the polymerization forces quantitatively, we introduce an(More)
We report for the first time that primary human neutrophils can undergo persistent, directionally biased movement away from a chemokine in vitro and in vivo, termed chemorepulsion or fugetaxis. Robust neutrophil chemorepulsion in microfluidic gradients of interleukin-8 (IL-8; CXC chemokine ligand 8) was dependent on the absolute concentration of chemokine,(More)
We present an experimental study of segregation of granular matter in a quasi-two-dimensional silo emptying out of an orifice. Size separation is observed when multisized particles are used with the larger particles found in the center of the silo in the region of fastest flow. We use imaging to study the flow inside the silo and quantitatively measure the(More)
It is generally assumed that single cells in an isogenic population, when exposed to identical environments, exhibit the same behavior. However, it is becoming increasingly clear that, even in a genetically identical population, cellular behavior can vary significantly among cells. Here we explore this variability in the gradient-sensing response of(More)
We report a novel morphological transition in a Bacillus subtilis colony initially growing under ambient conditions, after ultraviolet radiation exposure. The bacteria in the central regions of the colonies are observed to migrate towards the colony edge forming a ring during uniform spatial exposure. When the radiation is switched off, the colonies were(More)
We study the effect of fluids on the angle of repose and the segregation of granular matter poured into a silo. The experiments are conducted in two regimes where: (i) the volume fraction of the fluid (liquid) is small and it forms liquid bridges between particles thus giving rise to cohesive forces, and (ii) the particles are completely immersed in the(More)
Experimental systems that provide temporal and spatial control of chemical gradients are required for probing into the complex mechanisms of eukaryotic cell chemotaxis. However, no current technique can simultaneously generate stable chemical gradients and allow fast gradient changes. We developed a microfluidic system with microstructured membranes for(More)