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  1. Free, publicly-accessible full text available June 1, 2025
  2. Transfer students, who are disproportionately URM and first-generation, are a target population for boosting engineering representation. Transfer students in mechanical, aerospace and civil engineering at [the institution] take thermodynamics, a required gateway course, in their first or second term. This paper outlines the results from an observational study to determine how students interact in a peer-led learning environment. The PEERSIST (Peer-led, Student Instructed, Study group) model promotes academic competence through peer dialogue, in which disciplinary knowledge is socially co-constructed and refined over successive sessions. In order to help demonstrate that student interactions are the main source of learning in Peer-Led Study Groups (PLSGs), interactions between students were recorded and compared to those in traditional TA-led recitations using the observation protocol. Results show that students in PLSGs interact with their peers significantly more than students in the TA-led control group. The study also compares peer interactions by incoming course preparedness and finds a non-significant relationship between incoming GPA and peer-to-peer interactions. In contrast, the study finds a negative relationship between the rate at which students ask for and receive help and incoming GPA. 
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  3. Transfer students, who are disproportionately URM and first-generation, are a target population for boosting engineering representation. Transfer students in mechanical, aerospace and civil engineering at [the institution] take thermodynamics, a required gateway course, in their first or second term. This paper outlines the results from an observational study to determine how students interact in a peer-led learning environment. The PEERSIST (Peer-led, Student Instructed, Study group) model promotes academic competence through peer dialogue, in which disciplinary knowledge is socially co-constructed and refined over successive sessions. In order to help demonstrate that student interactions are the main source of learning in Peer-Led Study Groups (PLSGs), interactions between students were recorded and compared to those in traditional TA-led recitations using the observation protocol. Results show that students in PLSGs interact with their peers significantly more than students in the TA-led control group. The study also compares peer interactions by incoming course preparedness and finds a non-significant relationship between incoming GPA and peer-to-peer interactions. In contrast, the study finds a negative relationship between the rate at which students ask for and receive help and incoming GPA. 
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  4. Abstract The generation of broadband wave energy frequency spectra from narrowband wave forcing in geophysical flows remains a conundrum. In contrast to the long-standing view that nonlinear wave–wave interactions drive the spreading of wave energy in frequency space, recent work suggests that Doppler-shifting by geostrophic flows may be the primary agent. We investigate this possibility by ray tracing a large number of inertia–gravity wave packets through three-dimensional, geostrophically turbulent flows generated either by a quasigeostrophic (QG) simulation or by synthetic random processes. We find that, in all cases investigated, a broadband quasi-stationary inertia–gravity wave frequency spectrum forms, irrespective of the initial frequencies and wave vectors of the packets. The frequency spectrum is well represented by a power law. A possible theoretical explanation relies on the analogy between the kinematic stretching of passive tracer gradients and the refraction of wave vectors. Consistent with this hypothesis, the spectrum of eigenvalues of the background flow velocity gradients predicts a frequency spectrum that is nearly identical to that found by integration of the ray tracing equations. 
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  5. Free, publicly-accessible full text available February 1, 2025
  6. ABSTRACT

    Extragalactic fast X-ray transients (FXTs) are a class of soft (0.3–10 keV) X-ray transients lasting a few hundred seconds to several hours. Several progenitor mechanisms have been suggested to produce FXTs, including supernova shock breakouts, binary neutron star mergers, or tidal disruptions involving an intermediate-mass black hole and a white dwarf. We present detailed host studies, including spectroscopic observations of the host galaxies of seven XMM-Newton-discovered FXTs. The candidate hosts lie at redshifts 0.0928 <z < 0.645 implying peak X-ray luminosities of 1043 erg s−1<LX < 1045 erg s−1 and physical offsets of 1 kpc < rproj < 22 kpc. These observations increase the number of FXTs with a spectroscopic redshift measurement by a factor of 2, although we note that one event is re-identified as a Galactic flare star. We infer host star formation rates and stellar masses by fitting the combined spectroscopic and archival photometric data. We also report on a contemporaneous optical counterpart search to the FXTs in Pan-STARRS and ATLAS by performing forced photometry at the position of the FXTs. We do not find any counterpart in our search. Given our constraints, including peak X-ray luminosities, optical limits, and host properties, we find that XRT 110 621 is consistent with an supernova shock breakout (SN SBO) event. Spectroscopic redshifts of likely host galaxies for four events imply peak X-ray luminosities that are too high to be consistent with SN SBOs, but we are unable to discard either the binary neutron star or white dwarf–intermediate-mass black hole tidal disruption event scenarios for these FXTs.

     
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  7. Karunakaran, S. ; Higgins, A. (Ed.)
    In this report, we characterize seven of twenty-five students’ responses to a single written homework assignment from the Spring 2021 academic semester. The homework was designed to incorporate the Vector Unknown 2D digital game to investigate how students answered questions about span and linear independence after playing various levels of the game. We present our modification of the roles and characteristics framework of Zandieh et al. (2019), our identification of students’ grammatical use of game language and math language, as well as the results of analyzing students’ homework responses using our framework. 
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  8. Abstract

    On 8 July 2021 a M6.0 normal faulting earthquake rocked the community of Walker and the surrounding region near the California‐Nevada border. In the 1990s, field surveys of nearby Meadowcliff Canyon identified numerous precarious rocks deemed likely to topple in the event of strong shaking. Despite their proximity (∼6 km) to the 2021 earthquake, the precarious rocks still remain standing. In this work, we combine advanced source and ground motion characterization techniques to help unravel this mystery. High‐precision hypocentral locations reveal a clear north/south‐striking, east‐dipping rupture plane along the southern extension of the Slinkard Valley fault. The mainshock nucleated near the base of the fault, triggering thousands of aftershocks. Bayesian source spectral analyses indicate that the mainshock had a moderately‐high stress drop (∼17 MPa), and that aftershocks with deeper hypocenters have higher stress drops. Peak Ground Acceleration (PGA) recordings at regional stations agree well with existing ground motion models, predicting PGA of ∼0.3 g in Meadowcliff Canyon, a level sufficient to topple precarious rocks based on PGA‐derived stability criteria. We demonstrate that despite these large ground accelerations, the pulse duration in Meadowcliff Canyon is too short to supply the impulse necessary to damage these features, observations which support the application of dynamic toppling models that account for the joint effects of pulse amplitude and duration when assessing rock fragility. This study provides a unique vantage point from which to interpret rarely‐observed strong‐motion recordings from close to an active normal fault, one of many that dominate hazard along the eastern Sierra.

     
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