Reproduction de : Thèse d'exercice : Chirurgie dentaire : Nantes : 2008. / Bibliogr.

Thèse de doctorat : Biomécanique : Paris 12 : 2007. / Titre provenant de l'écran-titre. Bibliogr. : 285 réf.

Thesis (M.S.)--University of Toledo, 2009. / Typescript. "Submitted as partial fulfillment of the requirements for the Master of Science in Biology." "A thesis entitled"--at head of title. Bibliography: leaves 48-55.

Thesis (M.P.E.)--Memorial University of Newfoundland, 2002. / Includes bibliographical references.

Recalcitrant soil carbon is a poorly understood component of total soil organic carbon (SOC). Although the turnover rate of the recalcitrant fraction is slow, warming temperatures are expected to speed the decomposition of recalcitrant SOC resulting in an increase of atmospheric CO₂ in the future. Several studies show that the oldest SOC is associated with the smallest mineral particles (clays), making direct spectroscopic analysis of old carbon difficult. To overcome the difficulty of analyzing natural samples, we created synthetic soils to examine the association between clay surfaces and specific biomolecules based on the hypothesis that clays with higher surface charge will more strongly bond organic molecules, and also that certain molecules will be better stabilized by clay. We used kaolinite, montmorillonite, or quartz (sand) as a synthetic soil inside 12 mL septum-capped vials, added either dissolved glucose or vanillic acid to each mineral, inoculated with soil microbes, and then purged the vials with a CO₂-free atmosphere. We incubated them and measured the concentration and [delta]¹³C of CO₂ that accumulated in the vials. Respiration rates were significantly higher in experiments containing vanillic acid than in those containing glucose. Respiration rates were lowest in experiments containing montmorillonite. We repeated the experiment using dilute H₂O₂ as an oxidant, and adding vanillic acid, glucose, or glycine. Vials with montmorillonite showed lower rates of CO₂ accumulation than kaolinite, and both glycine- and glucose-containing experiments had less CO₂ than vanillic acid-experiments. We conclude that the montmorillonite protected the organic matter from oxidation better than sand or kaolinite. Both clays protected organic matter better than sand. In all experiments with clay, the respired CO₂ had lower [delta]¹³C values than bulk substrate. This carbon isotope fractionation is likely due to preferential desorption, followed by oxidation, of 12C- as opposed to 13C- bearing organic molecules. The mineral-organic interaction is a strong bond that explains the old age of labile organic compounds in soils. These results indicate that the clay fraction of soils must be considered for accurate prediction of future land-atmosphere carbon fluxes. / text

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The present investigation was designed to elucidate the potential influence of age on speech breathing. Toward this end, 30 men representing three widely different age groups (25, 50, and 75 years) were studied. These individuals were carefully selected to meet stringent criteria, the most important of which related to health and physical characteristics. Speech breathing was studied via anteroposterior diameter changes of the rib cage and abdomen. Recordings were made during extemporaneous speaking and reading and during the performance of various chest wall maneuvers used in the measurement of the speech breathing data. In addition to speech breathing, selected measures of general respiratory function were obtained. These included measures of subdivisions of the lung volume and measures of resting tidal breathing. Results indicated that these 30 subjects were representative of other subjects studied with respect to measures of general respiratory function. Subdivisions of the lung volume were found to differ with age in the manner predicted by previous investigations. Age-related differences were most marked for measures of vital capacity and residual volume. By contrast, there were no age-related differences for measures of resting tidal breathing. Several speech breathing measures were found to differ with age. Age-related differences were usually between the 25- and 75-year-old subject groups and less commonly between the 25- and 50-year-old subject groups. For extemporaneous speaking, differences were found for lung volume excursion, rib cage volume initiation (referenced to the rib cage volume associated with the relaxed configuration of the chest wall), number of syllables per breath group, and lung volume expended per syllable (in percent vital capacity). For reading, differences were found for lung volume expended per syllable (in percent vital capacity). Age-related similarities and differences in general respiratory function and speech breathing are discussed in relation to possible underlying mechanisms. In addition, implications are drawn regarding evaluation and management of individuals with speech breathing disorders.

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