Biomedical subjects

J R de Bruyn

Publications and source records attributed to J R de Bruyn.

3 recordsLinked to original sources

PubMed2001

Behavior of sink and source defects in a one-dimensional traveling finger pattern.

We present the results of an experimental study of sink and source defects in a one-dimensional pattern of traveling fingers that form at a driven fluid-air interface. We find that sinks and sources behave differently: Sinks separate regions of differing wave number and move smoothly so as to keep the phase difference across the sink fixed. They are transient objects which are eventually destroyed at the boundaries of the experiment or by collision with a source. Sources, on the other hand, are long lived. They are symmetric and stationary on average, although individual sources move erratically and do not display the phase-matching behavior of the sinks.

Journal Article↗

PubMed2001

Spiral patterns in oscillated granular layers.

Cell-filling spiral patterns are observed in a vertically oscillated layer of granular material when the oscillation amplitude is suddenly increased from below the onset of pattern formation into the region where stripe patterns appear for quasistatic increases in amplitude. These spirals are transients and decay to stripe patterns with defects. A transient spiral defect chaos state is also observed. We describe the behavior of the spirals, and the way in which they form and decay. Our results are compared with those for similar spiral patterns in Rayleigh-Bénard convection in fluids.

Journal Article↗

PubMed2000

Development and geometry of isotropic and directional shrinkage-crack patterns.

We have studied shrinkage-crack patterns which form when a thin layer of an alumina/water slurry dries. Both isotropic and directional drying were studied. The dynamics of the pattern formation process and the geometric properties of the isotropic crack patterns are similar to what is expected from recent models, assuming weak disorder. There is some evidence of a gradual increase in disorder as the drying layer become thinner, but no sudden transition, in contrast to what has been seen in previous experiments. The morphology of the crack patterns is influenced by drying gradients and front propagation effects, with sharp gradients having a strong orienting and ordering effect.

Journal Article↗