Systemic advantage has a meaningful relationship with grade outcomes in students' early STEM courses at six research universities.

Background: Large introductory lecture courses are frequently post-secondary students' first formal interaction with science, technology, engineering, and mathematics (STEM) disciplines. Grade outcomes in these courses are often disparate across student populations, which, in turn, has implications for student retention. This study positions such disparities as a manifestation of systemic inequities along the dimensions of sex, race/ethnicity, income, and first-generation status and investigates the extent to which they are similar across peer institutions. Results: We examined grade outcomes in a selected set of early STEM courses across six large, public, research-intensive universities in the United States over ten years. In this sample of more than 200,000 STEM course enrollments, we find that course grade benefits increase significantly with the number of systemic advantages students possess at all six institutions. The observed trends in academic outcomes versus advantage are strikingly similar across universities despite the fact that we did not control for differences in grading practices, contexts, and instructor and student populations. The findings are concerning given that these courses are often students' first post-secondary STEM experiences. Conclusions: STEM course grades are typically lower than those in other disciplines; students taking them often pay grade penalties. The systemic advantages some student groups experience are correlated with significant reductions in these grade penalties at all six institutions. The consistency of these findings across institutions and courses supports the claim that inequities in STEM education are a systemic problem, driven by factors that go beyond specific courses or individual institutions. Our work provides a basis for the exploration of contexts where inequities are exacerbated or reduced and can be used to advocate for structural change within STEM education. To cultivate more equitable learning environments, we must reckon with how pervasive structural barriers in STEM courses negatively shape the experiences of marginalized students. Supplementary Information: The online version contains supplementary material available at 10.1186/s40594-024-00474-7.

Thermodynamics and Kinetics for the Free Radical Oxygen Protein Oxidation Pathway in a Model for ß-Structured Peptides.

Oxidative stress plays a role in many biological phenomena, but involved mechanisms and individual reactions are not well understood. Correlated electronic structure calculations with the MP2, MP4, and CCSD(T) methods detail thermodynamic and kinetic information for the free radical oxygen protein oxidation pathway studied in a trialanine model system. The pathway includes aerobic, anaerobic and termination reactions. The course of the oxidation process depends on local conditions and availability of specific reactive oxygen species (ROS). A chemical mechanism is proposed for how oxidative stress promotes ß-structure formation in the amyloid diseases. The work can be used to aid experimentalists as they explore individual reactions and mechanisms involving oxygen free radicals and oxidative stress in ß-structured proteins.

Carboxylic acid catalyzed hydration of acetaldehyde.

Electronic structure calculations of the pertinent stationary points on the potential energy surface show that carboxylic acids can act effectively as catalysts in the hydration of acetaldehyde. Barriers to this catalyzed process correlate strongly with the pKa of the acid, providing the potential to provide the predictive capacity of the effectiveness of carboxylic acid catalysts. Transition states for the acid-catalyzed systems take the form of pseudo-six-membered rings through the linear nature of their hydrogen bonds, which accounts for their relative stability compared to the more strained direct and water-catalyzed systems. When considered as a stepwise reaction of a dimerization followed by reaction/complexation, it is likely that collisional stabilization of the prereactive complex is more likely than reaction in the free gas phase, although the catalyzed hydration does retain the potential to proceed on water surfaces or in droplets. Lastly, it is observed that postreactive diol-acid complexes are significantly stable (∼12-17 kcal/mol) relative to isolated products, suggesting the possibility of long-lived hygroscopic species that could act as a seed molecule for condensation of secondary organic aerosols.

Atmospheric oxidation of peroxyacetic acid.

The full reactive atmospheric oxidation profile of peroxyacetic acid under high NO conditions was examined using electronic structure calculations at various levels of theory. The three pathways resulting from the reaction of peroxyacetic acid with the hydroxyl radical were (1) addition of OH to the central carbon, (2) abstraction of the acidic hydrogen, and (3) abstraction of the methyl hydrogen. These pathways were followed to terminal product steps, the major products being acetic acid for pathway 1 and formaldehyde for pathways 2 and 3.

Nature of the chemical bond in transition: dissection of radical-molecule reactivity.

A complete method for quantifying the Born-Oppenheimer barriers of radical--molecule abstraction reactions is derived from first principles with the dual objectives of analytical prediction and conceptual understanding. Expanding upon the work of Donahue et al. (J. Phys. Chem. A 1998, 102, 3923-3933) this treatment uses the strategic construction of reactant-like and product-like wave functions to evaluate the coupling between crossing diabatic states. The overall reaction coordinate is evaluated in a modular fashion, whereby each region is analyzed within the context of its governing physics.