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This study aimed at assessing the value of heart rate variability (HRV) as a stress indicator before and after a final re-sit exam among healthy sixth grade medical students. Fifty participants were recruited for the study (test group, n = 30; control group, n = 20). Each participant was examined for 5 minutes pre and post exam periods using the Heartmath proprietary protocol. EmWave equipment was used to detect, record and analyze the HR and to plot out the variability in discrete percentages for low, medium and high coherences. Results indicated that mean percentage coherence score was significantly higher in the test group (p < 0.05) at low cardiac coherence domain, but lower (p < 0.05) at the high coherence domain, compared with the control. Coherence score was significantly higher (p < 0.05) after the exam indicating release from stress, as compared to before the examination when stress was observable among the exam candidates. There were no significant gender differences observed in cardiac coherence scores before and after examination. Our findings indicate that HRV is a reliable indicator of real-time exam stress and supports future clinical use of HRV as a non-invasive and simple stress test.

An enrichment procedure that exploits the difference in heat-sensitivity between exponentially growing and stationary phase cells has been developed for the isolation of yeast mutants. Enrichments of up to 12-fold for temperature-sensitive lethal mutants and of up to 15-fold for auxotrophs have been obtained with single cycles of selection. Still higher enrichments (to frequencies of greater than 90% and 80% for temperature-sensitive lethals and auxotrophs, respectively) have been obtained with multiple cycles of selection. The method requires no special parent strain, and seems adaptable to the selection of a wide variety of types of mutants.

The resistance of exponentially growing yeast cells to killing by exposure to 52 degrees C increase markedly as the growth temperature was increased. Identical killing curves were obtained for cells suspended in growth medium or in 0.9% saline. Cells resistant to killing at 52 degrees C were quite sensitive to killing at slightly higher temperatures. These results suggest a primary role for membrane damage in the mechanism of heat killing.