Barriers to front propagation in laminar, three-dimensional fluid flows.

We present experiments on one-way barriers that block reaction fronts in a fully three-dimensional (3D) fluid flow. Fluorescent Belousov-Zhabotinsky reaction fronts are imaged with laser-scanning in a laminar, overlapping vortex flow. The barriers are analyzed with a 3D extension to burning invariant manifold (BIM) theory that was previously applied to two-dimensional advection-reaction-diffusion processes. We discover tube and sheet barriers that guide the front evolution. The experimentally determined barriers are explained by BIMs calculated from a model of the flow.

Minocycline and generalized cutaneous pigmentation.

The recent literature contains sporadic mention of localized pigmentary accumulations in skin, bones, teeth, and thyroid tissue, presumably related to the use of systemic minocycline hydrochloride. It is our purpose to report the occurrence of generalized, cutaneous, dark blue-gray hyperpigmentation that developed in a woman while she was being treated with minocycline (Minocin) for acne vulgaris. We believe this pigmentary change to be minocycline-induced.