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  1. Dr. Krishna Ganesh (Ed.)
    Nanoscale zero-valent iron nanoparticles (nZVIs) are known to boost biomass production and lipid yield in Fremyella diplosiphon, a model biodiesel-producing cyanobacterium. However, the impact of nZVI-induced reactive oxygen species (ROS) in F. diplosiphon has not been evaluated. In the present study, ROS in F. diplosiphon strains (B481-WT and B481-SD) generated in response to nZVI-induced oxidative stress were quantified and the enzymatic response determined. Lipid peroxidation as a measure of oxidative stress revealed significantly higher malondialdehyde content (p < 0.01) in both strains treated with 3.2, 12.8, and 51.2 mg L–1 nZVIs compared to untreated control. In addition, ROS in allmore »nZVI-treated cultures treated with 1.6–25.6 mg L–1 nZVIs was significantly higher than the untreated control as determined by the 2′,7′-dichlorodihydrofluorescein diacetate fluorometric probe. Immunodetection using densitometric analysis of iron superoxide dismutase (SOD) revealed significantly higher SOD levels in both strains treated with nZVIs at 51.2 mg L–1. In addition, we observed significantly higher (p < 0.001) SOD levels in the B481-SD strain treated with 6.4 mg L−1 nZVIs compared to 3.2 mg L–1 nZVIs. Validation using transmission electron microscopy equipped with energy-dispersive X-ray spectroscopy (EDS) revealed adsorption of nZVIs with a strong iron peak in both B481-WT and B481-SD strains. While the EDS spectra showed strong signals for iron at 4 and 12 days after treatment, a significant decrease in peak intensity was observed at 20 days. Future efforts will be aimed at studying transduction mechanisms that cause metabolic and epigenetic alterations in response to nZVIs in F. diplosiphon.« less
    Free, publicly-accessible full text available November 13, 2022
  2. With the urgent call for supporting science teachers to promote equity and justice through their daily work of teaching, there is a growing need for better understanding how science teachers come to engage in transformative teaching and learning that is equitably consequential. In this participatory design research project (Bang & Vossoughi, 2016), we created a professional learning context in which high school chemistry teachers engaged in a pedagogical imagining (Gutiérrez & Calabese Barton, 2015) by leveraging their teaching experiences, knowledge about students and communities, values, and concerns to create powerful learning contexts for Latinx and multilingual students from immigrant, low-incomemore »families. Drawing upon the perspective of learning as making and sharing of the world interwoven with making and sharing of selves (Warren et al, 2020), we analyzed teachers’ participations and discourses to examine teachers’ making and sharing that were equitably consequential. The findings illustrated three critical moments of teachers’ making and sharing where: (a) the teachers collectively developed shared pedagogical goals toward transformative learning while formulating agency, (b) the teachers and the researchers came to design a creative stoichiometry unit where students use chemistry to make their community better, and (c) the teachers came to be committed to being ‘intentional’ in their relational work to create a welcoming and safe learning environment using concrete pedagogical strategies. The analyses point out three design features of the professional learning context that were associated with the teachers’ consequential makings: (a) the use of a conceptual tool (i.e., ‘design principles’), (b) the power of “what if” discourses, and (c) creating a space for collective learning. Recommendations for designing professional learning context toward transformative teaching and learning are discussed.« less
  3. Despite increasing awareness about the role of classroom assessments in perpetuating educational inequities, the research community continues to struggle with how to support teachers to design and use classroom assessments for achieving equity. In response to recent calls to better connect learning theory to the design of classroom assessments, we explore the links among contemporary learning theories, classroom assessments, equity, and teachers’ professional learning. Building a conceptual argument that we should shift our attention from assessment tasks to a classroom activity system to better support minoritized students’ learning via classroom assessment, we examine how teachers participate in assessment codesign activitiesmore »in two research-practice partnerships (RPPs), and then identify emerging tensions in relation to promoting equity. Each RPP drew upon contemporary learning theories—sociocognitive and sociocultural learning theories, respectively—to create a coherent system of curriculum, instruction, and assessment. The examples show that the tensions emerging from each project are at least partially related to the learning theory that led the researchers to set up professional learning settings in a particular way. Our findings suggest that managing these tensions is an inherent part of the work as researchers seek to support equitable student learning. We discuss specific implications for the assessment community.« less
  4. Free, publicly-accessible full text available June 1, 2023
  5. The ratio of the electric to magnetic form factors of the proton, μpGEp/GMp, has been measured for elastic electron-proton scattering with polarized beam and target up to four-momentum transfer squared Q2=5.66(GeV/c)2 using double spin asymmetry for target spin orientation aligned nearly perpendicular to the beam momentum direction. This measurement of μpGEp/GMp agrees with the Q2 dependence of previous recoil polarization data and reconfirms the discrepancy at high Q2 between the Rosenbluth and the polarization-transfer method with a different measurement technique and systematic uncertainties uncorrelated to those of the recoil-polarization measurements. The form factor ratio at Q2=2.06(GeV/c)2 has been measured asmore »μpGEp/GMp=0.720±0.176stat±0.039sys, which is in agreement with an earlier measurement using the polarized target technique at similar kinematics. The form factor ratio at Q2=5.66(GeV/c)2 has been determined as μpGEp/GMp=0.244±0.353stat±0.013sys, which represents the highest Q2 measurement reached using double spin asymmetries with polarized target to date.« less
  6. Agent-based modeling (ABM) assumes that behavioral rules affecting an agent's states and actions are known. However, discovering these rules is often challenging and requires deep insight about an agent's behaviors. Inverse reinforcement learning (IRL) can complement ABM by providing a systematic way to find behavioral rules from data. IRL frames learning behavioral rules as a problem of recovering motivations from observed behavior and generating rules consistent with these motivations. In this paper, we propose a method to construct an agent-based model directly from data using IRL. We explain each step of the proposed method and describe challenges that may occurmore »during implementation. Our experimental results show that the proposed method can extract rules and construct an agent-based model with rich but concise behavioral rules for agents while still maintaining aggregate-level properties.« less
  7. null (Ed.)