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- Genre: Academic theses
- Creators: Herckes, Pierre
A Meta-Analysis of Experimental Examinations of Racism in U.S. Pre-K-12th Grade Educational Contexts
Description
Racism primarily has been examined in United States (U.S.) educational contexts via survey and qualitative investigations, which reveal Black, Indigenous, and People of Colors’ (BIPOCs’) self-reported experiences of individual racism. Missing from this research is a focus on the perpetrators of racism and the institutional nature of racism in U.S. education. Experimental examinations of racism in U.S. education are efficacious in identifying perpetrators of racism and offer objective evidence of racism, which can underscore the importance of qualitative and survey findings. However, experimental examinations of racism in educational contexts are infrequent, examine a wide array of perpetrators (e.g., peers, teachers, principals) and educational domains (grading, diagnoses, liking), and reveal mixed findings. Thus, I utilized meta-analytic techniques to explore the magnitude of the effect of racism in pre-K-12th grade contexts as demonstrated by experimental examinations. In addition, I explore moderation of the effect of racism by 1) the type of experimental technique, 2) the specific perpetrator, 3) the BIPOC target, 4) the region of the US, and 5) the design of treatment assignment. Using 71 effect sizes from 57 studies, I found evidence that racism is present in U.S. pre-K-12th grade education for BIPOC [Cohen’s d=0.15, 95% CI(0.05, 0.25)]. Heterogeneity existed in the overall effect, and moderators included the U.S. region, and the level of racism (e.g., individual versus institutional) explained the heterogeneity of the effects. The findings are discussed in terms of theoretical and methodological implications and future directions for research.
ContributorsJanssen, Jayley (Author) / Seaton, Eleanor (Thesis advisor) / Miller, Cindy F (Committee member) / Causadias, Jose (Committee member) / Jager, Justin (Committee member) / Arizona State University (Publisher)
Created2023
Description
Banded iron formations (BIFs) are among the earliest possible indicators for oxidation of the Archean biosphere. However, the origin of BIFs remains debated. Proposed formation mechanisms include oxidation of Fe(II) by O2 (Cloud, 1973), photoferrotrophy (Konhauser et al., 2002), and abiotic UV photooxidation (Braterman et al., 1983; Konhauser et al., 2007). Resolving this debate could help determine whether BIFs are really indicators of O2, biological activity, or neither.
To examine the viability of abiotic UV photooxidation of Fe, laboratory experiments were conducted in which Fe-bearing solutions were irradiated with different regions of the ultraviolet (UV) spectrum and Fe oxidation and precipitation were measured. The goal was to revisit previous experiments that obtained conflicting results, and extend these experiments by using a realistic bicarbonate buffered solution and a xenon (Xe) lamp to better match the solar spectrum and light intensity.
In experiments reexamining previous work, Fe photooxidation and precipitation was observed. Using a series of wavelength cut-off filters, the reaction was determined not to be caused by light > 345 nm. Experiments using a bicarbonate buffered solution, simulating natural waters, and using unbuffered solutions, as in prior work showed the same wavelength sensitivity. In an experiment with a Xe lamp and realistic concentrations of Archean [Fe(II)], Fe precipitation was observed in hours, demonstrating the ability for photooxidation to occur significantly in a simulated natural setting.
These results lead to modeled Fe photooxidation rates of 25 mg Fe cm-2 yr-1—near the low end of published BIF deposition rates, which range from 9 mg Fe cm-2 yr-1 to as high as 254 mg Fe cm-2 yr-1 (Konhauser et al., 2002; Trendall and Blockley, 1970). Because the rates are on the edge and the model has unquantified, favorable assumptions, these results suggest that photooxidation could contribute to, but might not be completely responsible for, large rapidly deposited BIFs such those in the Hamersley Basin. Further work is needed to improve the model and test photooxidation with other solution components. Though possibly unable to fully explain BIFs, UV light has significant oxidizing power, so the importance of photooxidation in the Archean as an environmental process and its impact on paleoredox proxies need to be determined.
To examine the viability of abiotic UV photooxidation of Fe, laboratory experiments were conducted in which Fe-bearing solutions were irradiated with different regions of the ultraviolet (UV) spectrum and Fe oxidation and precipitation were measured. The goal was to revisit previous experiments that obtained conflicting results, and extend these experiments by using a realistic bicarbonate buffered solution and a xenon (Xe) lamp to better match the solar spectrum and light intensity.
In experiments reexamining previous work, Fe photooxidation and precipitation was observed. Using a series of wavelength cut-off filters, the reaction was determined not to be caused by light > 345 nm. Experiments using a bicarbonate buffered solution, simulating natural waters, and using unbuffered solutions, as in prior work showed the same wavelength sensitivity. In an experiment with a Xe lamp and realistic concentrations of Archean [Fe(II)], Fe precipitation was observed in hours, demonstrating the ability for photooxidation to occur significantly in a simulated natural setting.
These results lead to modeled Fe photooxidation rates of 25 mg Fe cm-2 yr-1—near the low end of published BIF deposition rates, which range from 9 mg Fe cm-2 yr-1 to as high as 254 mg Fe cm-2 yr-1 (Konhauser et al., 2002; Trendall and Blockley, 1970). Because the rates are on the edge and the model has unquantified, favorable assumptions, these results suggest that photooxidation could contribute to, but might not be completely responsible for, large rapidly deposited BIFs such those in the Hamersley Basin. Further work is needed to improve the model and test photooxidation with other solution components. Though possibly unable to fully explain BIFs, UV light has significant oxidizing power, so the importance of photooxidation in the Archean as an environmental process and its impact on paleoredox proxies need to be determined.
ContributorsCastleberry, Parker (Author) / Anbar, Ariel D (Thesis advisor) / Herckes, Pierre (Committee member) / Lyons, James (Committee member) / Arizona State University (Publisher)
Created2017