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Biomedical subjects

L K Hansen

Publications and source records attributed to L K Hansen.

97 records · Page 6Linked to original sources
PubMedDate not supplied

High prevalence of interatrial communications during the first three months of life.

The objective of this study was to analyze retrospectively the results of color Doppler echocardiographic (CDE) investigations performed for the first time on a child under circumstances where there was unrestricted access to CDE. The records were obtained from a tertiary referral center at a university hospital serving a population of about one million. The patients were children (n = 284) ages 0 days to 15 years 9 months referred for CDE over a 1-year period. Heart abnormalities were found in 119 children (42%). Among the children <3 months old, a heart abnormality was detected by CDE in 71%. The most prevalent diagnosis was atrial septal defect, particularly during the first 3 months of life, where the intraatrial communications accounted for 78% of the heart abnormalities. It is concluded that there is high prevalence of atrial communications during the first 3 months of life. The spectrum of diagnoses among newborns differs from the previously reported frequencies of congenital heart diseases. Better equipment (CDE) seems to diagnose abnormalities that might not be diagnosed otherwise.

Adolescent↗
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Preparation, analysis, and anticholinesterase properties of O,O-dimethyl phosphorothioate isomerides.

Previous studies have shown that impurities in commercial organophosphorus insecticides induce a variety of toxicological manifestations. Few studies have contrasted common impurity types and their comparative chemical and biochemical properties. In this study, five O,O-dimethyl phosphorothioate compounds were converted to their corresponding O,S-dimethyl phosphorothioates (isomerides) by a stepwise dealkylation-alkylation process (yields 58-76%). The O,S-isomerides and parent material were characterized by reverse-phase high-performance liquid chromatography (RPHPLC) and phosphorus (31P) nuclear magnetic resonance (NMR) spectroscopy. Methanol-water mixtures were found to adequately separate isomeride from parent structure with the isomeride eluting first. In general, the O,S-isomerides were found to be shifted about 40 ppm upfield relative to the O,O material. Isomerides were also determined to be significantly more potent as anticholinesterases (rat brain), with ki values approximating 1000-fold those of the parent material.

Animals↗
PubMedDate not supplied

Universal distribution of saliencies for pruning in layered neural networks.

A better understanding of pruning methods based on a ranking of weights according to their saliency in a trained network requires further information on the statistical properties of such saliencies. We focus on two-layer networks with either a linear or nonlinear output unit, and obtain analytic expressions for the distribution of saliencies and their logarithms. Our results reveal unexpected universal properties of the log-saliency distribution and suggest a novel algorithm for saliency-based weight ranking that avoids the numerical cost of second derivative evaluations.

Algorithms↗
PubMedDate not supplied

The Ojibwa Health Study: fish residue comparisons for Lakes Superior, Michigan, and Huron.

The Ojibwa Health Study is a descriptive epidemiology study of six Ojibwa reservations in the Upper Great Lakes. Fish consumption habits, contaminant (mercury [Hg], polychlorinated biphenyls [PCBs], and other organochlorines [OCs]) residues in dietary fish and humans, and chronic disease outcomes currently are being documented. Four hundred and fifty questionnaires and approximately 200 biological samples had been collected as of December 1994. Fish collections from reservations included lake trout, walleye, lake whitefish, and lake herring from Lakes Superior (three sites), Michigan, and Huron. Hg and OC residue analyses have been completed for the fish composite samples. A preliminary examination of the data has revealed regional differences in the contaminant burdens of the fish. Lake Michigan and Lake Huron whitefish composite samples had approximately twice the OC concentrations of Lake Superior whitefish samples. In general, the whitefish composite samples were far below the U.S. Food and Drug Administration or any state advisory limits for OC or Hg residues. Lake trout samples contained higher amounts of all residues than did the whitefish samples.

Body Burden↗