Search PubMed⌕ Search

Biomedical subjects

J D Thomas

Publications and source records attributed to J D Thomas.

At least 343 records · Page 19Linked to original sources
PubMed1981

A model of schistosomiasis incorporating the searching capacity of the miracidium.

This paper describes a modification of the model for the transmission of schistosomiasis proposed by Macdonald (1965), which allows the snail host-locating efficiency of the miracidium to be taken into account. The modified model allows for a choice of miracidia efficiency. If it is assumed that the miracidia are inefficient hunters than the resulting model is very sensitive to perturbations; relatively small changes in small numbers not only cause appreciable changes in the percentage of snails infected but resulted in attainment of the threshold (the point at which schistosomiasis ceases to be endemic). If, however, the miracidia are efficient snail hunters then the model is much less sensitive to perturbations; here the percentage of snails infected is much less affected by changing snail numbers, and the threshold is much more difficult to reach by reducing snail numbers. It is argued that, on the whole, the empirical data give more support to the latter model, although there are some circumstances under which the former model might apply. However, even with these modifications it is considered that the Macdonald model does not provide a satisfactory explantation of field observations.

Animals↗
PubMed1981

A zero-base approach to medical school planning and budgeting.

The University of Michigan Medical School has concluded that the traditional budgeting process used by it and other academic institutions fails to discriminate adequately among programs, particularly in times of level or declining resources, and that this failure could result in mediocrity. As a result, the school decided to develop a new system for managing resources and chose to explore an approach that utilizes the principles of zero-base budgeting. An important reason for selecting this technique was its requirement that managers plan, evaluate, and set priorities for all programs, existing as well as new. After a feasibility study that produced encouraging results, a test implementation of the newly developed system was carried out in all six of the school's basic science departments and in two clinical departments. While some difficulties were encountered, including those normally associated with the introduction of a new and complex system, the results of the test implementation were encouraging, and the process is undergoing further development to broaden its application in the clinical departments.

Budgets↗
PubMed1978

Sweat testing for cystic fibrosis. Diagnostic screening with a combination chloride ion-selective electrode.

Screening of sweat chloride in newborn infants with the Orion Skin Chloride Measuring System and incorporating some procedural innovations is described. The results indicate that while diagnostic screening for cystic fibrosis can be readily undertaken, the test with the chloride ion-selective electrode is best left at least to the second day of life or later because of insufficient sweating in very young babies. Measurements on 2 babies with cystic fibrosis are also discussed.

Age Factors↗
PubMed1978

Natural rates of teacher approval and disapproval in grade-7 classrooms.

The natural rates of teacher verbal approval and disapproval in ten grade-seven classrooms were determined and compared with those described by White (1975). Although there were differences in the observation techniques used and the behavioral, cultural, and ethnic groups sampled, the results were similar. The majority of the teachers displayed individual rates of disapproval that were higher than their individual approval rates. The correlations between levels of on-task behavior and approval and disapproval rates were low. The issues raised by these findings are discussed in terms of directions for further research.

Journal Article↗
PubMed1977

Sweat testing for cystic fibrosis: errors associated with the in-situ sweat test using chloride ion selective electrodes.

The in-situ sweat test is prone to errors from various sources. This paper examines errors due to evaporation, absorption of water into the skin, and pressure of the electrode on the skin. Only evaporation caused serious errors. The accuracy and precision when measuring small chloride/sweat samples on the skin are not significantly worse than when measuring bulk solutions.

Chlorides↗
PubMed1977

Sweat testing for cystic fibrosis: characteristics of a combination chloride ion-selective electrode.

Filling solution leakage, reproducibility, stability, interferences and temperature effects have been studied in relation to the use of the Orion 96-17-01 combination chloride ion-selective electrode in sweat testing for cystic fibrosis. While stability and reproducibility is good, certain antiseptic systems and especially Hibitaine (chlorhexidine gluconate) interfere with the electrode and therefore need to be absent during sweat testing. Temperature conditions during calibration and sweat testing need to be controlled in view of the extent of response variations for even modest temperature differences between sensor-skin interface and electrode stem.

Chemistry, Clinical↗
PubMed1976

The chemical ecology of Biomphalaria glabrata: the effects of ammonia on the growth rate of juvenile snails.

When juvenile specimens of Biomphalaria glabrata were subjected to concentrations of ammonia ranging from 1-100 mug/ml in various media the following effects were observed: the addition of ammonia to borate buffered media caused mortality. Both borate and tris-buffered media caused a decrease in the growth rate of snails when compared with controls in SSW. The growth rates of the snails could be enhanced by increasing the concentration of ammonia to critical thresholds, but further increases beyond these thresholds resulted in growth inhibition. The toxicity of ammonia in ambient water was augmented by an an increase in pH. The possible causation and ecological significance of these effects are discussed. There are indications that the snails are physiologically well-adapted to utilize ammonia when required and also to control its excretion and uptake from the medium.

Ammonia↗