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A New Potential Atmospheric Accretion Mechanism: Acid-Catalyzed Hetero-Michael Addition Reactions
No full textThe mechanistic basis for the formation of low volatility secondary organic aerosol (SOA) commonly invokes the formation of larger molecules from two or more smaller molecules, which are generically termed as accretion reactions. The previously unconsidered acid-catalyzed hetero-Michael addition reaction (ACHMAR) is shown to be a potential accretion mechanism route for atmospherically relevant alpha,beta unsaturated carbonyls and alcohols, which are both common atmospheric constituents. The kinetics of ACHMARs for a series of carbonyls and alcohols were measured with bulk aqueous phase experiments using nuclear magnetic resonance (NMR) spectroscopy. The rates of these reactions are shown to be very sensitive to the structures of both the carbonyl (only ketones showed measured reactivity) and the alcohols, with both the less substituted carbonyl and alcohol species exhibiting faster rates of reaction. For example, these results suggest that the major isoprene primary oxidation product methyl vinyl ketone could undergo ACHMARs, while isoprene\u27s other major oxidation product, methacrolein, is not expected to be similarly reactive. Overall, these results indicate that ACHMARs involving atmospheric alpha,beta ketones are a plausible accretion mechanism in SOA
Baby Steps: What 3D Scans of the Pelvic Morphology in Ugandan Chimpanzee Populations Can Reveal About Our Bipedal Origins and the \u27Obstetrical Dilemma Hypothesis\u27
No full textWhy are humans, compared to other primates, born so helpless? My research tests aspects of the oldest and most widely accepted proposed explanation: The Obstetrical Dilemma (OD) hypothesis. The OD hypothesis postulates that slimmer pelvises result in more efficient bipedal movement, but with the evolutionary tradeoff that human babies must be born earlier to ensure that their heads fit through the pelvic outlet during birth. Using resources in Mary Church Terrell Main Library’s DigiLab, I created 3D scans and took obstetrically-relevant morphology measurements of pelvises of two populations of Ugandan chimpanzees, one fully quadrupedal and one whose members had frequently been observed moving bipedally. However, I found no statistically significant difference in the measured pelvic dimensions between the two populations. One explanation may be that there are confounding factors in my study, but another is that one of the central ideas of the OD hypothesis—that bipedalism is more efficient with a slimmer pelvis—is not sound
Comparing aboveground carbon storage in planted and self-recruited former farmland reverting to forest in NE Ohio
No full textIncreasing carbon storage in ecosystems is an important approach to mitigating rising atmospheric CO2 concentrations and the subsequent effects of climate change. Both tree planting and natural reforestation are proposed approaches for enhancing above- and below-ground carbon storage. This study aims to evaluate afforestation as a means to increase carbon accumulation. In 2013, four species of trees were planted on one section of abandoned farmland owned by Oberlin College. Adjacent sections were left to naturally reseed from the surrounding forest. We follow up on Wolfe and Schiff’s 2017 baseline carbon storage assessment for this site, which did not find significant differences between planted and unplanted sections. In 2024, our team measured aboveground carbon storage, and a second team assessed soil carbon. Unfortunately, the sites sampled in 2017 had been recently mowed without prior notice, so for comparison, we added a nearby, naturally reseeding third site that was unmowed. We hypothesized that planting would have increased aboveground carbon storage compared to natural regeneration due to the planted trees being older and larger, but that mowing would have a stronger negative impact because it removed lots of biomass from the ecosystem. Our results show significantly more aboveground carbon stored in the unmowed site than the other two, demonstrating the negative impact of mowing on carbon storage. Two planted species are currently out-performing the native red maple; however, this trend is likely to change over time, underscoring the importance of long-term studies to determine the best ecosystem management decisions for climate change mitigation
Moral Encroachment in Belief Formation: Balancing Evidence and Ethical Stakes
No full textBelief formation is often viewed as a process guided solely by evidential support, yet some philosophers argue that moral considerations also play a role in epistemic justification. Moral encroachment challenges the traditional evidentialist view by suggesting that the justification of a belief can depend on ethical concerns. This research project examines one form of epistemic risk – the tradeoff between seeking truth and avoiding error – and evaluates the competing frameworks of radical and moderate moral encroachment (RME and MME). The moderate approach holds that moral stakes influence evidential thresholds, requiring stronger justification for beliefs with serious ethical consequences. The radical approach, on the other hand, asserts that moral concerns can override evidential support, making some beliefs impermissible even when well-supported. This research project critiques RME for misplacing moral accountability in the belief’s content, for its impracticality in real-world decision-making, and for its potential to undermine rational inquiry by leading to inconsistent belief regulation. In contrast, MME provides a principled framework that integrates ethical considerations without compromising evidential rigor. By requiring more robust justification in morally sensitive contexts rather than outright rejecting beliefs, MME preserves epistemic integrity while addressing the ethical stakes of belief formation
L-Arabinose Alters the \u3ci\u3eE. coli\u3c/i\u3e Transcriptome to Favor Biofilm Growth and Enhances Survival During Fluoroquinolone Stress
No full textEnvironmental conditions, including nutrient composition and temperature, influence biofilm formation and antibiotic resistance in Escherichia coli. Understanding how specific metabolites modulate these processes is critical for improving antimicrobial strategies. Here, we investigated the growth and composition of Escherichia coli in both planktonic and biofilm states in the presence of L-arabinose, with and without exposure to the fluoroquinolone antibiotic levofloxacin, at two temperatures: 28 and 37 °C. At both temperatures, L-arabinose increased the growth rate of planktonic E. coli but resulted in reduced total growth; concurrently, it enhanced biofilm growth at 37 °C. L-arabinose reduced the efficacy of levofloxacin and promoted growth in sub-minimum inhibitory concentrations (25 ng/mL). Transcriptomic analyses provided insight into the molecular basis of arabinose-mediated reduced susceptibility of E. coli to levofloxacin. We found that L-arabinose had a temperature- and state-dependent impact on the transcriptome. Using gene ontology overrepresentation analyses, we found that L-arabinose modulated the expression of many critical antibiotic resistance genes, including efflux pumps (ydeA, mdtH,mdtM), transporters (proVWX), and biofilm-related genes for external structures like pili (fimA) and curli (csgA,csgB). This study demonstrates a previously uncharacterized role for L-arabinose in modulating antibiotic resistance and biofilm-associated gene expression in E. coli and provides a foundation for additional exploration of sugar-mediated antibiotic sensitivity in bacterial biofilms
Expanding Access to Previously Inaccessible 5-Membered N-Heteroarynes
No full textWe previously reported the synthesis of an inaccessible 7-aza-2,3-indolyne through the stabilization of interactions with nickel. This was achieved via intramolecular Suzuki coupling (i.e., oxidative addition and transmetalation) with ortho-borylaryl bromide derivatives of 7-azaindole. Many questions remained about the electronic structure of this complex, which herein we sought to answer through XPS studies. We also sought to expand the strategy to additional inaccessible five-membered heteroarynes and gain insights into factors that lead to successful aryne formation. Several new classes of heteroarynes derived from indole, pyrrolopyrimidine, and the remaining isomers of azaindole were accessed. Transmetalation studies show that aryne formation depends on the identity of the heteroarene. A borate complex of 4-azaindole was isolated and characterized via NMR spectroscopy and crystallographically. This complex could be promoted to undergo transmetalation through the installation of an electron-donating substituent, which was justified computationally. To demonstrate the utility of heteroarynes as a newly accessible functional group, a one-pot difunctionalization was achieved across these classes of heterocycles using newly accessible heteroaryne complexes