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  1. Within chemistry education, there are various curricular and pedagogical approaches that aim to improve teaching and learning in chemistry. Efforts to characterize these transformations have primarily focused on student reasoning and performance, and little work has been done to explore student perceptions of curricular and pedagogical transformations and whether these perceptions align with the transformational intent. To complement our previous work on the Organic Chemistry, Life, the Universe, and Everything (OCLUE) curriculum, we developed this exploratory study to determine if students had perceived the goals of the transformation. As in our previous research on OCLUE, we compared perceptions between OCLUEmore »and a more traditional organic chemistry course. Using inductive and deductive qualitative methodologies, we analyzed student responses to three open-eneded questions focused on how students perceived they were expected to think, what they found most difficult, and how they perceived they were assessed. The findings were classified into three superodinate themes: one where students perceived they were expected to learn things as rote knowledge, such as memorization (“Rote Knowledge”), another where students perceived they were expected to use their knowledge (“Use of Knowledge”), and responses that used vague, generalized language, were uninformative, or did not address the questions asked (“Other”). Students in these two courses responded very differently to the open-ended questions with students in OCLUE being more likely to perceive they were expected to use their knowledge, while students in the traditional course reported rote learning or memorization more frequently. As the findings evolved, our interpretations and discussions were influenced by sociocultural perspectives and other cultural frameworks. We believe this approach can provide meaningful insights into transformational intent and certain features of classroom cultures.« less
    Free, publicly-accessible full text available March 4, 2023
  2. ABSTRACT As the Milky Way and its satellite system become more entrenched in near field cosmology efforts, the need for an accurate mass estimate of the Milky Way’s dark matter halo is increasingly critical. With the second and early third data releases of stellar proper motions from Gaia, several groups calculated full 6D phase-space information for the population of Milky Way satellite galaxies. Utilizing these data in comparison to subhalo properties drawn from the Phat ELVIS simulations, we constrain the Milky Way dark matter halo mass to be ∼1–1.2 × 1012 M⊙. We find that the kinematics of subhaloes drawn from more- ormore »less-massive hosts (i.e. >1.2 × 1012 M⊙ or <1012 M⊙) are inconsistent, at the 3σ confidence level, with the observed velocities of the Milky Way satellites. The preferred host halo mass for the Milky Way is largely insensitive to the exclusion of systems associated with the Large Magellanic Cloud, changes in galaxy formation thresholds, and variations in observational completeness. As more Milky Way satellites are discovered, their velocities (radial, tangential, and total) plus Galactocentric distances will provide further insight into the mass of the Milky Way dark matter halo.« less
    Free, publicly-accessible full text available May 23, 2023
  3. Free, publicly-accessible full text available January 1, 2023
  4. Abstract We report the discovery of MAGAZ3NE J095924+022537, a spectroscopically confirmed protocluster at z = 3.3665 − 0.0012 + 0.0009 around a spectroscopically confirmed UVJ -quiescent ultramassive galaxy (UMG; M ⋆ = 2.34 − 0.34 + 0.23 × 10 11 M ⊙ ) in the COSMOS UltraVISTA field. We present a total of 38 protocluster members (14 spectroscopic and 24 photometric), including the UMG. Notably, and in marked contrast to protoclusters previously reported at this epoch that have been found to contain predominantly star-forming members, we measure an elevated fraction of quiescent galaxies relative to the coeval field ( 73.3more »− 16.9 + 26.7 % versus 11.6 − 4.9 + 7.1 % for galaxies with stellar mass M ⋆ ≥ 10 11 M ⊙ ). This high quenched fraction provides a striking and important counterexample to the seeming ubiquitousness of star-forming galaxies in protoclusters at z > 2 and suggests, rather, that protoclusters exist in a diversity of evolutionary states in the early universe. We discuss the possibility that we might be observing either “early mass quenching” or nonclassical “environmental quenching.” We also present the discovery of MAGAZ3NE J100028+023349, a second spectroscopically confirmed protocluster, at a very similar redshift of z = 3.3801 − 0.0281 + 0.0213 . We present a total of 20 protocluster members, 12 of which are photometric and eight spectroscopic including a poststarburst UMG ( M ⋆ = 2.95 − 0.20 + 0.21 × 10 11 M ⊙ ). Protoclusters MAGAZ3NE J0959 and MAGAZ3NE J1000 are separated by 18′ on the sky (35 comoving Mpc), in good agreement with predictions from simulations for the size of “Coma”-type cluster progenitors at this epoch. It is highly likely that the two UMGs are the progenitors of Brightest Cluster Galaxies seen in massive virialized clusters at lower redshift.« less
    Free, publicly-accessible full text available February 1, 2023
  5. This study is a follow up to two earlier studies characterizing student real-time use of mechanistic arrows. In these previous studies, students were asked to predict a product by drawing a curved arrow mechanism using an interface that allowed recording and replay of student actions. In the present study two different student cohorts responded to the same tasks as the original studies: a cohort who were enrolled in a traditional organic course, and a cohort who were part of a transformed organic course (Organic Chemistry, Life, the Universe and Everything, OCLUE). Both cohorts improved in their ability to predict anmore »appropriate product over the two semesters, and we found little meaningful difference in the ability of students from either cohort to predict the outcome of a familiar reaction. However, students in the OCLUE cohort were more likely to draw mechanistic arrows than the students from the traditional course. In contrast, when the task involved predicting the product of an unfamiliar reaction, OCLUE students were over three times more likely to draw mechanistically reasonable steps and produce a plausible product than students from the traditional cohort. We propose that the differences between the two cohorts emerge from the following: (1) explicit attempts in the OCLUE course to link drawing reactions mechanisms using the electron pushing formalism to the scientific practice of constructing explanations. It is our contention that this approach changes the arrow pushing mechanism from a skill to the construction of a model which students can use to predict and explain outcomes; and (2) the numerous opportunities in the OCLUE course to try out ideas without penalty, leading to a willingness to try to determine outcomes in unfamiliar situations.« less
  6. Abstract We present spatially resolved Hubble Space Telescope grism spectroscopy of 15 galaxies at z ∼ 0.8 drawn from the DEEP2 survey. We analyze H α +[N ii ], [S ii ], and [S iii ] emission on kiloparsec scales to explore which mechanisms are powering emission lines at high redshifts, testing which processes may be responsible for the well-known offset of high-redshift galaxies from the z ∼ 0 locus in the [O iii ]/H β versus [N ii ]/H α Baldwin—Phillips—Terlevich (BPT) excitation diagram. We study spatially resolved emission-line maps to examine evidence for active galactic nuclei (AGN), shocks,more »diffuse ionized gas (DIG), or escaping ionizing radiation, all of which may contribute to the BPT offsets observed in our sample. We do not find significant evidence of AGN in our sample and quantify that, on average, AGN would need to contribute ∼25% of the H α flux in the central resolution element in order to cause the observed BPT offsets. We find weak (2 σ ) evidence of DIG emission at low surface brightnesses, yielding an implied total DIG emission fraction of ∼20%, which is not significant enough to be the dominant emission line driver in our sample. In general we find that the observed emission is dominated by star-forming H ii regions. We discuss trends with demographic properties and the possible role of α -enhanced abundance patterns in the emission spectra of high-redshift galaxies. Our results indicate that photoionization modeling with stellar population synthesis inputs is a valid tool to explore the specific star formation properties which may cause BPT offsets, to be explored in future work.« less
    Free, publicly-accessible full text available November 1, 2022
  7. Every year new safety features and regulations are employed within the process industry to reduce risks associated with operations. Despite these advancements chemical plants remain hazardous places, and the role of the engineer will always involve risk mitigation through real time decision making. Results from a previous study by Kongsvik et al., 2015 indicated that there were three types of decisions in major chemical plants: strategic decisions, operational decisions, and instantaneous decisions. The study showed the importance for improving upon engineers’ operational and instantaneous choices when tasked with quick solutions in the workforce. In this research study, we dive deepermore »to understand how senior chemical engineering students’ prioritize components of decision making such as budget, productivity, relationships, safety, and time, and how this prioritization may change as a result of participation in a digital immersive training environment called Contents Under Pressure. More specifically, we seek to address the following two research questions: (1) How do senior chemical engineering students prioritize safety in comparison to criteria such as budget, personal relationships, plant productivity, and time in a process safety context, and (2) How does senior chemical engineering students’ prioritization of decision making criteria (budget, personal relationships, plant productivity, safety, and time) change after exposure to a virtual process safety decision making environment? As part of this study, 187 senior chemical engineering students from three separate institutions completed a pre- and post-reflection survey around their engagement with Contents Under Pressure and asked them to rank their prioritizations of budget, productivity, relationships, safety, and time. Data was analyzed using descriptive statistics, and Friedman and Wilcoxon-sign-rank post hoc analyses were completed to determine any statistical differences between the rankings of decision making factors before and after engagement with Contents Under Pressure. Simulating process safety decision making with interactive educational supports may increase students’ understanding of genuine workplace environments and factors that contribute to process safety, without the real world hazards that result from poor decision making. By understanding how students prioritize these factors, chemical engineering curricula can be adapted to focus on the areas of process safety decision making where students need the largest improvement, thereby better preparing them to enter the engineering workforce.« less
  8. ABSTRACT Observations suggest that satellite quenching plays a major role in the build-up of passive, low-mass galaxies at late cosmic times. Studies of low-mass satellites, however, are limited by the ability to robustly characterize the local environment and star formation activity of faint systems. In an effort to overcome the limitations of existing data sets, we utilize deep photometry in Stripe 82 of the Sloan Digital Sky Survey, in conjunction with a neural network classification scheme, to study the suppression of star formation in low-mass satellite galaxies in the local Universe. Using a statistically driven approach, we are able tomore »push beyond the limits of existing spectroscopic data sets, measuring the satellite quenched fraction down to satellite stellar masses of ∼107 M⊙ in group environments (Mhalo = 1013−14 h−1 M⊙). At high satellite stellar masses (≳1010 M⊙), our analysis successfully reproduces existing measurements of the quenched fraction based on spectroscopic samples. Pushing to lower masses, we find that the fraction of passive satellites increases, potentially signalling a change in the dominant quenching mechanism at M⋆ ∼ 109 M⊙. Similar to the results of previous studies of the Local Group, this increase in the quenched fraction at low satellite masses may correspond to an increase in the efficacy of ram-pressure stripping as a quenching mechanism in groups.« less