Analytical ultracentrifugation (AUC) is a classical technique of physical biochemistry providing information on size, shape, and interactions of macromolecules from the analysis of their migration in centrifugal fields while free in solution. A key mechanical element in AUC is the centerpiece, a component of the sample cell assembly that is mounted between the optical windows to allow imaging a...

Recently, the steady sedimentation profile of a dilute suspension of chemically powered colloids was studied experimentally [J. Palacci et al., Phys. Rev. Lett. 105, 088304 (2010)]. It was found that the sedimentation length increases quadratically with the swimming speed of the active Brownian particles. Here we investigate theoretically the sedimentation of self-propelled particles undergoing...

The possible role of magnetic anomalies on Mars in gravitational enhancement of separation of charged dust is considered. It is known that charges become spatially separated by differential transport and gravitational sedimentation because the charge polarity of particles of dust depends on the particle size—where smaller particles are negatively charged and larger particles are positively char...

This article discusses the mechanisms of particle deposition onto cleanroom surfaces. The main mechanism for particles above about 0.5μm is gravitational settling. Turbulent deposition and electrostatic attraction can also occur at all particle sizes, and for particles below 0.5μm Brownian diffusion is important. Measurements of particle deposition rates (PDRs) were made of particles 10μm on wi...

The settling and packing properties of colloidal suspensions of large hard spheres in an effective gravitational field are investigated by a Monte Carlo constant-NPV simulation. The ratio of an effective gravitational potential to the repulsion/attraction potential in the hard sphere (G/ε) is a critical parameter that determines the surface coverage and packing properties of the system. The sur...

The actin cytoskeleton helps maintain structural organization within living cells. In large X. laevis oocytes, gravity becomes a dominant force and is countered by a nuclear actin network that prevents liquid-like nuclear bodies from immediate sedimentation and coalescence. However, nuclear actin's mechanical properties, and how they facilitate the stabilization of nuclear bodies, remain unknow...