http://hdl.handle.net/2027.42/21621 Sun, 26 May 2013 02:27:36 GMT 2013-05-26T02:27:36Z http://deepblue.lib.umich.edu:80/bitstream/id/98521/blockMlogo.jpg http://hdl.handle.net/2027.42/21621 http://hdl.handle.net/2027.42/97757 No Evidence for a Deglacial Intermediate Water Δ14C Anomaly in the Southwest Atlantic Sortor, Rachel The last deglaciation was characterized by an increase in atmospheric pCO2 and decrease in atmospheric radiocarbon activity. One hypothesis is that these changes were due to out-gassing of 14C-depleted carbon from the abyssal ocean. Reconstructions of foraminiferal Δ14C from the eastern tropical Pacific, Arabian Sea, and high latitude North Atlantic show that severe depletions in 14C occurred at intermediate water depths during the last deglaciation. It has been suggested that 14C-depleted water from the abyss upwelled in the Southern Ocean and was then carried by Antarctic Intermediate Water (AAIW) to these sites. However, locations in the South Pacific in the direct path of modern-day AAIW do not exhibit the Δ14C excursion and therefore cast doubt upon the AAIW mechanism (De Pol-Holz et al., 2010; Rose et al., 2010). Here we evaluate whether or not a deglacial 14C anomaly occurred at intermediate depths in the Southwest Atlantic. We find that the deglacial benthic Δ14C trend at our site is similar to the atmospheric Δ14C trend. Our results are also largely consistent with results from U/Th-dated corals at shallower water depths on the Brazil Margin (Mangini et al., 2010). We find no evidence in the southwestern Atlantic of a ~300‰decrease in intermediate water Δ14C from 18 to 14 kyr BP like that observed in the eastern tropical Pacific (Marchitto et al., 2007). When our results are paired with those from the South Pacific, it appears AAIW did not carry a highly 14C-depleted signal during the deglaciation. Another source of carbon is apparently required to explain the intermediate-depth Δ14C anomalies in the North Atlantic, Indian, and Pacific Oceans. Thesis submitted in partial fulfillment of the requirements for the degree of Master of Science in Geology, Department of Earth and Environmental Sciences Tue, 29 May 2012 00:00:00 GMT http://hdl.handle.net/2027.42/97757 2012-05-29T00:00:00Z http://hdl.handle.net/2027.42/97756 A New Paleothermometer for Forest Paleosols and its Implications for Cenozoic Climate Gallagher, Timothy Climate is a primary control on the chemical composition of paleosols, making them a potentially extensive archive applicable to problems ranging from paleoclimate reconstruction to paleoaltimetry. However, the development of an effective, widely-applicable paleosol temperature proxy has remained elusive. This is attributable to the fact that various soil orders behave differently due to their respective physical and chemical properties. Therefore, by focusing on an individual order or a subset of the twelve soil orders whose members exhibit similar process behavior, a better constrained paleothermometer can be constructed. Soil chemistry data were compiled for 158 modern soils in order to derive a new paleosol paleothermometry relationship between mean annual temperature and a paleosol weathering index (PWI) that is based on the relative loss of major cations (Na, Mg, K, Ca) from soil B horizons. The new paleothermometer can be applied to clay-rich paleosols that originally formed under forest vegetation, including Inceptisols, Alfisols, and Ultisols, and halves the uncertainty relative to previous approaches. A case study using Cenozoic paleosols from Oregon shows that paleotemperatures produced with this new proxy compare favorably with paleobotanical temperature estimates. Global climatic events are also evident in the Oregon paleosol record, 1 of 28 including a 2.8 °C drop across the Eocene-Oligocene transition comparable to marine records, and a Neogene peak temperature during the Mid-Miocene Climatic Optimum. Thesis submitted in partial fulfillment of the requirements for the degree of Master of Science in Geology, Department of Earth and Environmental Sciences Fri, 17 May 2013 00:00:00 GMT http://hdl.handle.net/2027.42/97756 2013-05-17T00:00:00Z http://hdl.handle.net/2027.42/97551 Impact of Critical Events in an Animated Classroom Story on Teacher Learners’ Online Comments Chieu, Vu-Minh; Aaron, Wendy; Herbst, Patricio We examined the effect of reference to critical events in an animated classroom story on the quality of teachers’ comments in an online learning experience. We analyzed data using systemic functional linguistics and logistic regression. We found statistically significant evidence that participants made more reflective and evaluative comments and proposed more alternative teaching moves when they referenced critical events than when they did not. The study contributes to validating a theoretical distinction between reference point and reference object in the literature on video assisted, online teacher education: While attached reference objects help learners be more focused and productive, those qualities differ depending on reference points included in those reference objects. This study also provides preliminary evidence to support the practice of selecting clips that deviate from instructional norms when designing video-based professional learning opportunities. Mon, 13 May 2013 00:00:00 GMT http://hdl.handle.net/2027.42/97551 2013-05-13T00:00:00Z http://hdl.handle.net/2027.42/97546 Trends in the incidence of noncardiogenic acute respiratory failure: the role of race Cooke, Colin; Erickson, Sara; Eisner, Mark; Martin, Greg Objective—We sought to examine trends in the race-specific incidence of acute respiratory failure in the United States. Design—Retrospective cohort study. Setting—We used the National Hospital Discharge Survey (NHDS) database (1992-2007), an annual survey of approximately 500 hospitals weighted to provide national hospitalization estimates. Patients—All incident cases of noncardiogenic acute respiratory failure hospitalized in the United States. Interventions—None Measurements and Main Results—We identified noncardiogenic acute respiratory failure by the presence of ICD–9 codes for respiratory failure or pulmonary edema (518.4, 518.5, 518.81, 518.82) and mechanical ventilation (96.7x), excluding congestive heart failure. Incidence rates were calculated using yearly census estimates standardized to the age and sex distribution of the 2000 census population. Annual cases of noncardiogenic acute respiratory failure increased from 86,755 in 1992 to 323,474 in 2007. Noncardiogenic acute respiratory failure among black Americans increased from 56.4 (95% CI 39.7 – 73.1) to 143.8 (95% CI 123.8 – 163.8) cases per 100,000 in 1992 and 2007, respectively. Among white Americans, the incidence of noncardiogenic acute respiratory failure increased from 31.2 (95% CI 26.2-36.5) to 94.0 (95% CI 86.7 – 101.2) cases per 100,000 in 1992 and 2007, respectively. The average annual incidence of noncardiogenic acute respiratory failure over the entire study period was 95.1 (95% CI 93.9 – 96.4) cases per 100,000 for black Americans compared to 66.5 (95% CI 65.8 – 67.2) cases per 100,000 for white Americans (rate ratio = 1.43, 95% CI 1.42-1.44). Overall in–hospital mortality was greater for other-race Americans, but only among patients with ≥ 2 organ failures (57% [95% CI 56-59%] for other-race, 51% [95% CI, 50-52%] for white, 50% [95% CI, 49-51%] for black). Conclusions—The incidence of noncardiogenic acute respiratory failure in the United States increased between 1992 and 2007. Black and other-race Americans are at greater risk of developing noncardiogenic acute respiratory failure compared to white Americans. Tue, 01 May 2012 00:00:00 GMT http://hdl.handle.net/2027.42/97546 2012-05-01T00:00:00Z