Addressing Equity Asymmetries in General Chemistry Outcomes Through an Asset-Based Supplemental Course

Undergraduate first-semester general chemistry (GC1) functions as a gatekeeper to STEM degrees, asymmetrically impacting students who are nonwhite, from lower socioeconomic groups, non-native English speakers, two-year college transfers, and first-generation in college. Nationally, just under 30% of students earn grades of D, F, or withdraw (termed DFW) in GC1; however, DFW rates are much higher for subgroups underrepresented in STEM occupations. Socioeconomic inequalities tend to increase over an individual's lifetime due to the magnification of cumulative disadvantage. Because undergraduate degrees correlate with higher employment and STEM occupations correlate with higher earnings, GC1 represents a critical path point where disparities can be interrupted. The most common strategy employed for GC1 is deficit remediation for students determined to be at risk of DFW. Unfortunately, extensive evidence demonstrates that the use of remediation strategies for GC1 does not sustain benefits for students. In this work, an asset-based approach, less prevalent in higher education than preuniversity, was employed to stress test theories about interrupting disparities in STEM education. This causal-comparative study involving 1,807 observations reports on a 1-credit asset-based supplemental course in which DFW-potential students at a minority-serving institution coenrolled during six semesters. The study outlines this intervention, its impact on GC1 outcomes, and its potential residual impact on progression to the next course in the general chemistry sequence (GC2). Descriptive and hierarchical inferential analysis of the data revealed socially important patterns. The asset-based intervention successfully attracted students with greater cumulative disadvantage. The intervention closed asymmetries between students identified as DFW-potential and ABC-potential in GC1 when a nontraditional curriculum was used but not when a traditional curriculum was used. Mixed results and contingent effects were found for the intervention's impact on subsequent course outcomes. Taking at least 11 credits in the semester of taking GC1 provided an inoculate for participants in the asset-based intervention, increasing the likelihood of passing GC2.

van der Waals Solids from Self-Assembled Nanoscale Building Blocks

Traditional atomic van der Waals materials such as graphene, hexagonal boron-nitride, and transition metal dichalcogenides have received widespread attention due to the wealth of unusual physical and chemical behaviors that arise when charges, spins, and vibrations are confined to a plane. Though not as widespread as their atomic counterparts, molecule-based two-dimensional (2D) layered solids offer significant benefits; their structural flexibility will enable the development of materials with tunable properties. Here we describe a layered van der Waals solid self-assembled from a structure-directing building block and C60 fullerene. The resulting crystalline solid contains a corrugated monolayer of neutral fullerenes and can be mechanically exfoliated. The absorption spectrum of the bulk solid shows an optical gap of 390 ± 40 meV that is consistent with thermal activation energy obtained from electrical transport measurement. We find that the dimensional confinement of fullerenes significantly modulates the optical and electronic properties compared to the bulk solid.

Pulmonary fluid extraction and osmotic conductance, sigmaK, measured in vivo

The change in aortic blood density in an in vivo rabbit preparation was measured to assess fluid movement at the pulmonary capillaries caused by infusion of hypertonic solution (NaCl, urea, glucose, sucrose, or raffinose in isotonic saline) into the vena cava over 20 s. The hypertonic disturbance increased the plasma osmotic pressure by </=30 mosmol/l. The density change indicates that the fluid extraction from the lung tissue was completed within 10 s. It was followed by a fluid filtration into the lung tissue and then an extraction and filtration from peripheral organs. An exchange model with flow dispersion yields two equations to estimate the osmotic conductance (sigmaK; where sigma is the reflection coefficient of the test solute and K is the filtration coefficient including the total capillary surface area), and the tissue fluid volume from the area and first moment of the measured density change over the extraction phase. The values of sigmaK are 1.40 +/- 0.11, 1.00 +/- 0. 10, 1.71 +/- 0.10, 2.60 +/- 0.23, and 3.73 +/- 0.34 (SE) ml . h-1 . mosmol-1 . l . g-1 for NaCl, urea, glucose, sucrose, and raffinose, respectively. Consistent with the model prediction, the tissue fluid volume (0.28 +/- 0.04 ml/g wet lung tissue) was independent of the solute used. This value suggests that all fluid spaces in the alveolar septa participate in the process of fluid extraction due to an increase in plasma osmotic pressure.