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Biomedical subjects

T Bohr

Publications and source records attributed to T Bohr.

At least 19 recordsLinked to original sources
PubMed2001

Stability balloon for two-dimensional vortex ripple patterns.

Patterns of vortex ripples form when a sand bed is subjected to an oscillatory fluid flow. Here we describe experiments on the response of regular vortex ripple patterns to sudden changes of the driving amplitude a or frequency f. A sufficient decrease of f leads to a "freezing" of the pattern, while a sufficient increase of f leads to a supercritical secondary "pearling" instability. Sufficient changes in the amplitude a lead to subcritical secondary "doubling" and "bulging" instabilities. Our findings are summarized in a "stability balloon" for vortex ripple pattern formation.

Journal Article↗
PubMed2001

Breakdown of universality in transitions to spatiotemporal chaos.

We show that the transition from laminar to active behavior in extended chaotic systems can vary from a continuous transition in the universality class of directed percolation with infinitely many absorbing states to what appears as a first-order transition. The latter occurs when finite lifetime nonchaotic structures, called "solitons," dominate the dynamics. We illustrate this scenario in an extension of the deterministic Chaté-Manneville coupled map lattice model and in a soliton including variant of the stochastic Domany-Kinzel cellular automaton.

Journal Article↗
PubMed1995

Death certificates: an efficient source for ascertainment of Creutzfeldt-Jakob disease cases.

Case ascertainment for an epidemiologic study of Creutzfeldt-Jakob disease (CJD) can be difficult. This report investigates the efficiency of various sources of case ascertainment for CJD. Cases were identified utilizing neuropathologists, hospitals and death certificates from 11 targeted states. For the period of 1986-1988, 247 death certificates indicating a diagnosis of CJD were obtained. Only 26 potential cases were identified without death certificates. The proportion of neuropathologically confirmed cases identified by death certificates only, i.e., which were not identified through any other source, was 42%. Furthermore, 80% of all the neuropathologically confirmed cases were ascertained utilizing death certificates as a source. Of the remaining 20%, 7% were ascertained through neuropathologists only, 10% through hospitals only, 1.5% through a combination of hospitals and neuropathologists, and 1.5% through another source. The false-positive rate for death certificates with neuropathology (which may have been performed after the death certificate was filled out) was estimated to be 8.3%. The results indicate that death certificates were by far the most efficient source for initial ascertainment of potential CJD cases to be followed by verification of diagnosis.

Creutzfeldt-Jakob Syndrome↗