PubMed Health⌕ Search

Biomedical subjects

M J Biggs

Publications and source records attributed to M J Biggs.

4 recordsLinked to original sources
PubMed2001

Small scale model for CFD validation in DAF application.

A laboratory model is used to measure the generic flow patterns in dissolved air flotation (DAF). The Perspex model used in this study allows the use of laser Doppler velocimetry (LDV), a non-invasive, high-resolution (+/- 2 mm s-1) laser technique of flow velocity measurement. Measurement of flow velocity in the single-phase situation was first carried out. Air-saturated water was then supplied to the tank and measurements of bubble velocity in the two-phase system were made. Vertical flow re-circulation was observed in the flotation zone. In the bottom of the flotation zone (near the riser) secondary flow re-circulation was observed, but only in the two-phase system. Another phenomenon was the apparent movement of flow across the tank width, which may be due to lateral dispersion of the bubble cloud. Data from preliminary computational fluid dynamics (CFD) models were compared against this measured data in the case of the single-phase system. The CFD model incorporating a k-epsilon model of turbulence was found to give closer agreement with the measured data than the corresponding laminar flow model. The measured velocity data will be used to verify two-phase computational fluid dynamics (CFD) models of DAF.

Air↗
PubMed2000

Characterization of a novel alanine-rich protein located in surface microdomains in Trypanosoma brucei.

Heterologous expression in COS cells followed by orientation-specific polymerase chain reaction to select and amplify cDNAs encoding surface proteins in Trypanosoma brucei resulted in the isolation of a cDNA ( approximately 1.4 kilobase) which encodes an acidic, alanine-rich polypeptide that is expressed only in bloodstream forms of the parasite and has been termed bloodstream stage alanine-rich protein (BARP). Analysis of the amino acid sequence predicted the presence of a typical NH(2)-terminal leader sequence as well as a COOH-terminal hydrophobic extension with the potential to be replaced by a glycosylphosphatidylinositol anchor. A search of existing protein sequences revealed partial homology between BARP and the major surface antigen of procyclic forms of Trypanosoma congolense. BARP migrated as a complex, heterogeneous series of bands on Western blots with an apparent molecular mass ( approximately 50-70 kDa) significantly higher than predicted from the amino acid sequence ( approximately 26 kDa). Confocal microscopy demonstrated that BARP was present in small discrete spots that were distributed over the entire cellular surface. Detergent extraction experiments revealed that BARP was recovered in the detergent-insoluble, glycolipid-enriched fraction. These data suggested that BARP may be sequestered in lipid rafts.

Amino Acid Sequence↗
PubMed1980

Electrically-evoked release of [3H]-histamine from the guinea-pig hypothalamus.

1 [3H]-histamine was taken up by slices of guinea-pig hypothalamus against a concentration gradient. 2 Electrical field stimulation of the superfused slices resulted in an increased efflux of radioactivity, the major part of which was shown to be associated with histamine by paper chromatography. 3 The evoked release of histamine was dependent on calcium ions in the superfusate and was increased by 56% when the frequency of stimulation was doubled from 5 to 10 Hz.

Animals↗