An experimental documentation of a hypersonic shock-wave turbulent boundary layer interaction flow: With and without separation

An experiment, thoroughly documenting the flow field resulting from the interaction of a shock wave with a nonadiabatic hypersonic turbulent boundary layer, is described. Detailed mean flow and surface data are presented for two shock strengths resulting in attached and separated flows, respectively. The surface measurements include continuous pressure, shear and heat-flux distributions upstream, in, and downstream of the interaction regions. At closely spaced intervals along the surface, boundary-layer profiles of static and pitot pressure and total temperature were obtained from which velocity, density and static temperature profiles were derived. The data are presented in both graphical and tabular form. These data are of sufficient detail to validate advanced computer codes and their associated turbulence models

Aggregation of chemotactic organisms in a differential flow

We study the effect of advection on the aggregation and pattern formation in chemotactic systems described by Keller-Segel type models. The evolution of small perturbations is studied analytically in the linear regime complemented by numerical simulations. We show that a uniform differential flow can significantly alter the spatial structure and dynamics of the chemotactic system. The flow leads to the formation of anisotropic aggregates that move following the direction of the flow, even when the chemotactic organisms are not directly advected by the flow. Sufficiently strong advection can stop the aggregation and coarsening process that is then restricted to the direction perpendicular to the flow

On-Demand Electrically Induced Decomposition of Thin-Film Nitrocellulose Membranes for Wearable or Implantable Biosensor Systems

Implantable or subcutaneous biosensors used for continuous health monitoring have a limited functional lifetime requiring frequent replacement and therefore may be highly discomforting to the patient and become costly. One possible solution to this problem is use of biosensor arrays where each individual reserve sensor can be activated on-demand when the previous one becomes inoperative due to biofouling or enzyme degradation. Each reserve biosensor in the array is housed in an individual Polydimethylsiloxane (PDMS) well and is protected from exposure to bodily fluids such as interstitial fluid ( ISF) by a thin-film nitrocellulose membrane. Controlled activation is achieved by decomposing over an individual sensor well. Electrically activated thermal decomposition of the nitrocellulose membrane is caused by passing an electric current through an Au/Ti filament placed on top of the membrane. By applying an energy of as low as 7 mJ to the Au/Ti filament with cross-sectional area of 8 x 107 cm2, a current density of ≈ 105 – 106 A/cm2 causes explosive decomposition of thin-film Au/Ti filaments. Having a thermal decomposition temperature of ≈200°C, nitrocellulose is locally heated directly under the Au/Ti filament. This leads to opening of the nitrocellulose membrane within 50 ms allowing for exposure of biosensor to biofluids. 50 ms is sufficiently short to prevent local heating of surrounding tissues and therefore is not a danger to a potential patient