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Biomedical subjects

M C Johnson

Publications and source records attributed to M C Johnson.

At least 145 records · Page 8Linked to original sources
PubMed1971

Extremely rapid visual search: the maximum rate of scanning letters for the presence of a numeral.

Subjects searched a rapid sequence of computer-produced letter arrays for the presence of a numeral in one of the arrays. The subjects' scanning rates were computed from their precentage of correct detections of the location of the numeral. Scanning rates were very high and approximately the same for a wide variety of conditions; the highest scanning rates (125 and 75 letters per second for two subjects) occurred when there were 9 or 16 letters in each of the arrays and when new arrays were presented every 40 to 50 milliseconds. Giving the subject advance knowledge of the numeral to be presented made little difference in the scores.

Computers↗
PubMed1971

Relation of lipid peroxidation to loss of cations trapped in liposomes.

Lipid peroxidation and alterations in cation loss have been induced in liposomes by ferrous ion, ascorbic acid, reduced and oxidized glutathione, and gamma radiation. Modifications of these effects by tocopherol and 2,6-di-tert-butyl-4-methylphenol (BHT) were studied when these antioxidants were either incorporated in the membrane or were added to already formed liposomes prior to the addition of the chemical agent or to irradiation. Lipid peroxidation, as indicated by the thiobarbituric acid test for malonic dialdehyde, did not correlate with alterations in cation loss. The largest amounts of lipid peroxidation induced by ascorbic acid and glutathione were associated with decreased cation loss. Inhibition of Fe(2+)- and radiation-induced lipid peroxidation by antioxidants did not inhibit the associated increase in cation loss. Tocopherol was a more effective antioxidant than BHT when it was incorporated in the membrane, whereas BHT was more effective when it was added to the liposomes after formation.

Antioxidants↗