Biomedical subjects

J Munch

Publications and source records attributed to J Munch.

8 recordsLinked to original sources

PubMed2006

Compensation of strong thermal lensing in high-optical-power cavities.

In an experiment to simulate the conditions in high optical power advanced gravitational wave detectors, we show for the first time that the time evolution of strong thermal lenses follows the predicted infinite sum of exponentials (approximated by a double exponential), and that such lenses can be compensated using an intracavity compensation plate heated on its cylindrical surface. We show that high finesse approximately 1400 can be achieved in cavities with internal compensation plates, and that mode matching can be maintained. The experiment achieves a wave front distortion similar to that expected for the input test mass substrate in the Advanced Laser Interferometer Gravitational Wave Observatory, and shows that thermal compensation schemes are viable. It is also shown that the measurements allow a direct measurement of substrate optical absorption in the test mass and the compensation plate.

Journal Article↗

PubMed1996

Evaluation of photoscreener instruments in a childhood population. 1. Otago photoscreener and Dortmans videophotorefractor.

OBJECTIVE: To evaluate two photoscreeners in a childhood population. STUDY DESIGN: Double-masked study. SUBJECTS AND METHOD: One hundred and thirteen children aged between 11 and 44 months with either normal vision or known visual disorders were photoscreened without cycloplegia by the Otago and Dortmans (prototype) photoscreeners. Each child had a full ophthalmological examination either on the day of screening or in the proceeding six months. Photoscreen images were reviewed by an independent observer for indicators of amblyopiogenic risk factors, and compared to the full ophthalmological examination to determine sensitivity and specificity for each instrument. RESULTS: The Otago photoscreener returned a sensitivity of 70% and specificity of 82% for the detection of amblyopiogenic risk factors. The Dortmans photoscreener returned a sensitivity of 70% and specificity of 90%. Both photoscreeners were portable and easily operated. CONCLUSION: Children can be screened successfully for amblyopiogenic risk factors with these photoscreening systems. Further evaluation is required to determine specificity in a normal population. This would also provide information on the potential usefulness of photoscreeners in a cost effective childhood vision screening program.

Amblyopia↗

PubMed1984

Comparative carcinogenic and mutagenic activity of coal tar and petroleum asphalt paints used in potable water supply systems.

Coal tar and petroleum asphalt paints are among the products used as coatings for water pipes and storage tanks to retard corrosion. Formulations of these coatings were tested in the Ames mutagenesis and the mouse skin carcinogenesis bioassays. To test the mutagenicity of the paints, six doses ranging from 0.005 to 10 microliters per plate were assayed. In the mouse skin bioassay, doses of the coal tar paints ranging from 0.2 to 200 microliters were administered topically to 30 SENCAR mice per group. These initiating doses were followed by applications of 1.0 micrograms of 12-o-tetradecanoyl-phorbol-13-acetate (TPA) in 0.2 ml acetone topically, three times weekly for 20 weeks. Petroleum asphalt paints were tested in groups of 40 animals at 200 and 600 microliters doses. All coal tar paints showed mutagenic activity after metabolic activation with S-9, with the highest response being in strains TA 98 and TA 100. None of the petroleum asphalt paints gave mutagenic responses. Both types of coatings resulted in positive responses in the initiation/promotion study. The coal tar paints gave rise to 1000-1800 times the tumor response observed with petroleum asphalt products. One coal tar product was positive when tested as a complete carcinogen in the mouse at 2 microliters per application once weekly for 30 weeks, whereas the asphalt paint was negative at 100 times the dose. The biological responses to the products were greater than expected from their polycyclic aromatic hydrocarbon (PAH) content. These findings suggest that the hazard posed by these coatings may not be fully explained by their PAH contents.

Animals↗

PubMed1974