Microfluidic immunomagnetic multi-target sorting – a model for controlling deflection of paramagnetic beads

We describe a microfluidic system that uses a magnetic field to sort paramagnetic beads by deflecting them in the direction normal to the flow. Our experiments systematically study the dependence of the beads’ deflection on: bead size and susceptibility, magnet strength, fluid speed and viscosity, and device geometry. We also develop a design parameter that can aid in the design of microfluidic devices for immunomagnetic multi-target sorting

A simple portable somomicrometer, March - July 1966

Portable sonomicrometer for measuring heart dimension

An experimental and theoretical investigation of particle–wall impacts in a T-junction

Understanding the behaviour of particles entrained in a fluid flow upon changes in flow direction is crucial in problems where particle inertia is important, such as the erosion process in pipe bends.We present results on the impact of particles in a T-shaped channel in the laminar-turbulent transitional regime. The impacting event for a given system is described in terms of the Reynolds number and the particle Stokes number. Experimental results for the impact are compared with the trajectories predicted by theoretical particle tracing models for a range of configurations to determine the role of the viscous boundary layer in retarding the particles and reducing the rate of collision with the substrate. In particular a 2D model based on a stagnation point flow is used together with 3D numerical simulations. We show how the simple 2D model provides a tractable way of understanding the general collision behaviour, while more advanced 3D simulation can be helpful in understanding the details of the flow

Observer based feedback control of 3rd order LCC resonant converters

The paper considers specific issues related to the design and realisation of observer-based feedback of isolated output voltage for resonant power converters. To provide a focus to the study, a 3rd order LCC converter is employed as a candidate topology. It is shown that whilst resonant converters nominally operate at high switching frequencies to facilitate the use of small reactive components, by appropriate pre-conditioning of non-isolated resonant-tank voltages and currents, the resulting observer can be implemented at relatively low sampling frequencies, and hence, take advantage of low-cost digital hardware. Experimental results are used to demonstrate the accuracy of observer estimates under both transient and steady-state operating conditions, and to show operation of the observer as part of a closed-loop feedback system where the LCC resonant converter is used as a regulated power supply

The Magnetic Rayleigh-Taylor Instability in Three Dimensions

We study the magnetic Rayleigh-Taylor instability in three dimensions, with focus on the nonlinear structure and evolution that results from different initial field configurations. We study strong fields in the sense that the critical wavelength l_c at which perturbations along the field are stable is a large fraction of the size of the computational domain. We consider magnetic fields which are initially parallel to the interface, but have a variety of configurations, including uniform everywhere, uniform in the light fluid only, and fields which change direction at the interface. Strong magnetic fields do not suppress instability, in fact by inhibiting secondary shear instabilities, they reduce mixing between the heavy and light fluid, and cause the rate of growth of bubbles and fingers to increase in comparison to hydrodynamics. Fields parallel to, but whose direction changes at, the interface produce long, isolated fingers separated by the critical wavelength l_c, which may be relevant to the morphology of the optical filaments in the Crab nebula.Comment: 14 pages, 9 pages, accepted by Ap

Pump-induced Exceptional Points in Lasers

We demonstrate that the above-threshold behavior of a laser can be strongly affected by exceptional points which are induced by pumping the laser nonuniformly. At these singularities, the eigenstates of the non-Hermitian operator which describes the lasing modes coalesce. In their vicinity, the laser may turn off even when the overall pump power deposited in the system is increased. Such signatures of a pump- induced exceptional point can be experimentally probed with coupled ridge or microdisk lasers.Comment: 4.5 pages, 4 figures, final version including additional FDTD dat