Biomedical subjects

T Shinbrot

Publications and source records attributed to T Shinbrot.

9 recordsLinked to original sources

PubMed2001

Noise to order.

Patterns in natural systems abound, from the stripes on a zebra to ripples in a riverbed. In many of these systems, the appearance of an ordered state is not unexpected as the outcome of an underlying ordered process. Thus crystal growth, honeycomb manufacture and floret evolution generate regular and predictable patterns. Intrinsically noisy and disordered processes such as thermal fluctuations or mechanically randomized scattering generate surprisingly similar patterns. Here we discuss some of the underlying mechanisms believed to be at the heart of these similarities.

Journal Article↗

PubMed2001

Attraction of minute particles to invariant regions of volume preserving flows by transients.

We find that tracer material can be concentrated into invariant regions of flows due exclusively to transient effects, as are produced when tracers temporarily become more buoyant than the surrounding fluid. This can occur either as a single event, e.g., if the tracer is initially weakly buoyant, or under periodic forcing, e.g., when external effects (such as solar heating) change the tracer density periodically. We study both cases in experiments, in a model, and in direct numerical simulations of laminar flow in a stirred tank. Focusing occurs for very small tracer size and inertia in flows that are instantaneously strictly volume conserving.

Journal Article↗

PubMed2000

Does the granular matter?

Granular materials, such as sand, gravel, powders, and pharmaceutical pills, are large aggregates of macroscopic, individually solid particles, or "grains." Far from being simple materials with simple properties, they display an astounding range of complex behavior that defies their categorization as solid, liquid, or gas. Just consider how sand can stream through the orifice of an hourglass yet support one's weight on the beach; how it can form patterns strikingly similar to a liquid when vibrated, yet respond to stirring by "unmixing" of large and small grains. Despite much effort, there still is no comprehensive understanding of other forms of matter, like ordinary fluids or solids. In what way, therefore, is granular matter special, and what makes it so difficult to understand? An emerging interdisciplinary approach to answering these questions focuses directly on the material's discontinuous granular nature.

Journal Article↗

PubMed1999

Using variability to regulate long term biological rhythms.

We present a model for the generation of precise, long term rhythms from a collection of imprecise, short term oscillators. The model uses variability between oscillators in conjunction with simple coupling rules to produce long term rhythms that are independent of rate equations (e.g. Arrhenius). The rhythms generated by the model are controlled by only two independent parameters and exhibit several physiologically interesting properties, including ready entrainment to external signals and splitting in response to strong constant signals. The model provides several predictions that can be tested in future experiments.

Animals↗

PubMed1994