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Biomedical subjects

H Lam

Publications and source records attributed to H Lam.

At least 73 records · Page 4Linked to original sources
PubMed1991

Static and dynamic stresses during valve closure of a bileaflet mechanical heart valve prosthesis.

The effect of contact geometry and component compliance on the magnitude, distribution, and state of various types of stresses on a bileaflet mechanical heart valve prosthesis during valve closure was analyzed using an Edwards-Duromedics mitral valve as example. Static and dynamic stresses developing on both the leaflet and pivot ball during valve closure were modeled using finite element analysis (FEA). Uniform contact between the leaflet and housing as well as between the pivot ball and pivot slot can significantly reduce both static and dynamic stresses around the contact area. The level of the dynamic flexural stresses can be an order of magnitude higher than that of the static stresses. When both the radial and axial compliance of the housing are taken into consideration, peak dynamic stress was more than 40% less than that generated through the impact between a moving leaflet and a non-compliant rigid housing.

Compliance↗
PubMed1985

Mutagenic metabolites in rat urine after dermal exposure to 1,3-diaminobenzene.

Amberlite XAD-2 purified urine extracts from rats treated dermally with 1,3-diaminobenzene were fractionated by HPLC and the metabolites were identified by GC-MS. Mutagenic activity in Salmonella typhimurium TA 98 was equally distributed between the two fractions, none of which contained the parent amine. The first fraction, eluted between 2-7 minutes, contained only a very small amount of presently unidentified metabolites, while the second fraction eluted between 14-19 minutes contained N,N'-diacetyl-1,3-diaminobenzene. Both fractions showed minor, but still significant activity even without metabolic activation. A non-mutagenic fraction, eluted between 10-12 minutes contained N-acetyl -acetyl-1,3-diaminobenzene and N,N'-diacetyl-2,4-diaminophenol.

Animals↗
PubMed1984

Hemoglobin Hamilton or alpha 2 beta 2 11(A8)Val leads to Ile: a silent beta-chain variant detected by Triton X-100 acid-urea polyacrylamide gel electrophoresis.

A silent beta-chain hemoglobin variant, not detectable by starch gel or agar gel electrophoresis was found using Triton X-100 acid-urea polyacrylamide gel electrophoresis. The abnormal beta-X chain had a more anodic electrophoretic mobility; 38% of the total beta chain was of the abnormal type. Structural analysis using high-performance liquid chromatography and microsequencing procedures indicated a valine to isoleucine substitution at position beta 11(A8). This anomaly did not change the functional properties of the hemoglobin molecule. A mild reticulocytosis was observed in the propositus.

Electrophoresis, Polyacrylamide Gel↗