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  • DNA  (1)
  • INSTRUMENTATION AND PHOTOGRAPHY  (1)
  • population dynamics  (1)
  • 1
    ISSN: 1573-6822
    Keywords: DNA ; flow cytometry ; genotoxicology ; largemouth bass ; red blood cells
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Analysis of cellular DNA content by flow cytometry has been used to detect genetic changes associated with exposure to environmental contaminants. In lower vertebrates, nucleated red blood cells can be collected for analysis without harm to the animal. Because erythrocytes sampled from an individual should have identical amounts of DNA, the coefficient of variation (CV) around the G0/G1 peak should be small. Increases in CV can indicate genetic aberrations, but may also be caused by sample handling and preparation or problems with instrumentation. To increase confidence in associating increases in CV with external causes, artifactual changes in CV due to sample treatment and instrument parameters should be identified and minimized. We assessed the effects of various sampling and handling protocols on the CV of nucleated blood cells collected from largemouth bass (Micropterus salmoides). We also compared the distribution of cells among the G0/G1, S, and G2/M phases of the cell cycle to see whether these were affected by sampling or treatment protocols. Groups of 7 fish were bled on 7 consecutive days, and blood from each fish was analyzed by flow cytometry when freshly collected, and after freezing for 1 hour or 10 days. The same fish were bled again over a consecutive 7-day period, and the experiment was repeated. CV and cell cycle distribution were not affected by our freezing protocol. Repeat sampling from the same individual did not affect CV, but altered the distribution of cells in the cell cycle, suggesting increased hemopoiesis in response to blood sampling. Day-to-day variation in the CV occurred in both fresh and frozen samples, probably as the result of small variations in instrument adjustments. These results demonstrate the suitability of this freezing protocol for these blood samples, and illustrate the importance of assessing sources of variation when using flow cytometry to screen wild populations in genotoxicological studies.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1572-9761
    Keywords: Sigmodon hispidushabitat mosaic ; sex-age cohorts ; survivorship ; density decline ; landscape ; population dynamics ; electromorphs
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract This study describes the demographic features of a population of Sigmodon hispidus utilizing the habitat mosaic provided by a Carolina Bay on the Atlantic coastal plain of South Carolina. A total of 71 cotton rats were captured 160 times on a 4 ha grid during a winter decline from 25/ha to less that 1/ha. Body weights of adults declined until early February and then increased; those of subadults grew very slowly until February followed by a spurt in growth. Weight gain did not differ between survivors and non-survivors for males, but female survivors gained 1.5 g per week more than non-survivors. Female subadults exhibited higher mortality early in the decline and males later. Adult females were randomly distributed across 8 microhabitats, whereas adult males were almost exclusively confined to heavy Rubus cover. Subadult males used wet sites more than any other cohort; subadult females were widely distributed using drier sites most frequently. By the end of the decline, all survivors were localized in Rubus-dominated patches. No statistically significant changes in electromorph genotypes or allele frequencies were detected, but survivors had a higher frequency of the F-allele at the adenylate kinase locus than did non-survivors (42.3% vs. 16.7%). Our findings affirm the importance of a landscape perspective in understanding the population dynamics of cotton rats, and show how a habitat mosaic influences survival differentially among sex-age cohorts.
    Type of Medium: Electronic Resource
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  • 3
    Publication Date: 2019-06-28
    Description: The need for a validation technique for computational fluid dynamics (CFD) codes in STOVL applications has led to research efforts to apply infrared thermal imaging techniques to visualize gaseous flow fields. Specifically, a heated, free-jet test facility was constructed. The gaseous flow field of the jet exhaust was characterized using an infrared imaging technique in the 2 to 5.6 micron wavelength band as well as conventional pitot tube and thermocouple methods. These infrared images are compared to computer-generated images using the equations of radiative exchange based on the temperature distribution in the jet exhaust measured with the thermocouple traverses. Temperature and velocity measurement techniques, infrared imaging, and the computer model of the infrared imaging technique are presented and discussed. From the study, it is concluded that infrared imaging techniques coupled with the radiative exchange equations applied to CFD models are a valid method to qualitatively verify CFD codes used in STOVL applications.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: AIAA PAPER 91-0675
    Format: text
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