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Biomedical subjects

D C Montgomery

Publications and source records attributed to D C Montgomery.

8 recordsLinked to original sources
PubMed2005

Numerical study of dynamo action at low magnetic Prandtl numbers.

We present a three-pronged numerical approach to the dynamo problem at low magnetic Prandtl numbers P(M). The difficulty of resolving a large range of scales is circumvented by combining direct numerical simulations, a Lagrangian-averaged model and large-eddy simulations. The flow is generated by the Taylor-Green forcing; it combines a well defined structure at large scales and turbulent fluctuations at small scales. Our main findings are (i) dynamos are observed from P(M)=1 down to P(M)=10(-2), (ii) the critical magnetic Reynolds number increases sharply with P(M)(-1) as turbulence sets in and then it saturates, and (iii) in the linear growth phase, unstable magnetic modes move to smaller scales as P(M) is decreased. Then the dynamo grows at large scales and modifies the turbulent velocity fluctuations.

Journal Article↗
PubMed2001

Velocity field distributions due to ideal line vortices.

We evaluate numerically the velocity field distributions produced by a bounded, two-dimensional fluid model consisting of a collection of parallel ideal line vortices. We sample at many spatial points inside a rigid circular boundary. We focus on "nearest-neighbor" contributions that result from vortices that fall (randomly) very close to the spatial points where the velocity is being sampled. We confirm that these events lead to a non-Gaussian high-velocity "tail" on an otherwise Gaussian distribution function for the Eulerian velocity field. We also investigate the behavior of distributions that do not have equilibrium mean-field probability distributions that are uniform inside the circle, but instead correspond to both higher and lower mean-field energies than those associated with the uniform vorticity distribution. We find substantial differences between these and the uniform case.

Journal Article↗
PubMed1975

Effect of oral contraceptives on factor VIII clotting activity and factor VIII related antigen in normal women.

The factor VIII clotting activity (VIIIc1 and factor VIII related antigen (VIIIRAg) were determined repeatedly in 24 pairs of age-matched normal women, one of each pair being on oral contraceptives. No significant differences in either parameter or in the VIIIc/VIIIRAg ration were found between the two groups ,although the mean factor VIII clotting activity and VIIIc/VIIIRAg ratios for women on oral contraceptives were very slightly higher than for those not on oral contraceptives.

Adult↗
PubMed1973

Follicular contact dermatitis due to coloured permanent-pressed sheets.

A delayed hypersensitivity type of allergic contact dermatitis was observed following exposure to certain brands of 50% cotton, 50% polyester coloured permanent-pressed sheets produced by a particular manufacturer. The dermatitis presented as an extremely pruritic follicular eczema of the body and vesicular edema of the ears and face. Patch testing excluded formalin as the allergen but suggested permanent-pressing chemicals as a possibility. Several washings of the sheets did not prevent the development of the dermatitis. The removal of sheets did not immediately result in improvement: the condition could persist for up to eight weeks after their discontinuance.

Bedding and Linens↗