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There is a well-documented relationship between academic match and bachelor’s degree completion; students who undermatch are less likely to complete a BA than those who match or overmatch, net of academic qualifications and demographic characteristics. Little is known, however, about whether this association has changed over time. I argue that recent trends in U.S. higher education may have altered this association. Thus, while prior research has documented gaps in outcomes between undermatched, matched, and overmatched students, it is important to understand how these gaps may be evolving. The present study uses nationally representative data from three cohorts of first-time college students—students who began college in 1995, 2003, and 2011—to examine this question. Findings show that, in some ways, the association between academic match and BA completion has remained stable over time; across all three cohorts, undermatched students are less likely to graduate than matched and overmatched students, after controlling for academic qualifications and demographic characteristics. In other ways, the association may be evolving; overall, overmatched students’ odds of graduation have increased over time, while matched and undermatched students’ have not. There are multiple possible explanations for this, including the fact that graduation rates in recent years have become increasingly stratified by college selectivity. The study concludes with recommendations for policy and practice, as well as suggestions for future research.

Fast radio bursts (FRBs) last for milliseconds and arrive at Earth from cosmological distances. Although their origins and emission mechanisms are unknown, their signals bear similarities with the much less luminous radio emission generated by pulsars within our Miky Way Galaxy 1 , with properties suggesting neutron star origins 2 , 3 . However, unlike pulsars, FRBs typically show minimal variability in their linear polarization position angle (PA) curves 4 . Even when marked PA evolution is present, their curves deviate significantly from the canonical shape predicted by the rotating vector model (RVM) of pulsars 5 . Here we report on FRB 20221022A, detected by the Canadian Hydrogen Intensity Mapping Experiment Fast Radio Burst project (CHIME/FRB) and localized to a nearby host galaxy (about 65 Mpc), MCG+14-02-011. This FRB shows a notable approximately 130° PA rotation over its about 2.5 ms burst duration, resembling the characteristic S-shaped evolution seen in many pulsars and some radio magnetars. The observed PA evolution supports magnetospheric origins 6 , 7 – 8 over models involving distant shocks 9 , 10 – 11 , echoing similar conclusions drawn from tempo-polarimetric studies of some repeating FRBs 12 , 13 . The PA evolution is well described by the RVM and, although we cannot determine the inclination and magnetic obliquity because of the unknown period or duty cycle of the source, we exclude very short-period pulsars (for example, recycled millisecond pulsars) as the progenitor. FRB 20221022A, detected by the Canadian Hydrogen Intensity Mapping Experiment Fast Radio Burst project, shows a pronounced change in polarization during the burst, providing important clues into the nature of the source.

The precise origins of fast radio bursts (FRBs) remain unknown. Multiwavelength observations of nearby FRB sources can provide important insights into the enigmatic FRB phenomenon. Here we present results from a sensitive, broadband X-ray and radio observational campaign of FRB 20200120E, the closest known extragalactic repeating FRB source (located 3.63 Mpc away in an ~10-Gyr-old globular cluster). We place deep limits on the persistent and prompt X-ray emission from FRB 20200120E, which we use to constrain possible origins for the source. We compare our results with various classes of X-ray sources, transients and FRB models. We find that FRB 20200120E is unlikely to be associated with ultraluminous X-ray bursts, magnetar-like giant flares or an SGR 1935+2154-like intermediate flare. Although other types of bright magnetar-like intermediate flares and short X-ray bursts would have been detectable from FRB 20200120E during our observations, we cannot entirely rule them out as a class. We show that FRB 20200120E is unlikely to be powered by an ultraluminous X-ray source or a young extragalactic pulsar embedded in a Crab-like nebula. We also provide new constraints on the compatibility of FRB 20200120E with accretion-based FRB models involving X-ray binaries. These results highlight the power of multiwavelength observations of nearby FRBs for discriminating between FRB models. Deep X-ray limits are placed on the source of the closest fast radio burst, FRB 20200120E, ruling out an ultraluminous X-ray source or a young extragalactic pulsar embedded in a Crab-like nebula as its origin.

In this thesis I describe three statistical studies of fast radio bursts (FRBs), focusing on constraining the Milky Way’s (MW's) ionized halo, developing new spatial point process methodology for the identification of repeating FRBs, and performing (and maximizing the utility of) multi-wavelength observations of a nearby, active FRB. My FRB sample mainly comes from the revolutionary dataset from the FRB project of the Canadian Hydrogen Intensity Mapping Experiment (CHIME/FRB).The first project places upper limits on the total Galactic electron column as a function of Galactic latitude using FRB dispersion measures (DMs). By applying four different boundary models, I set observation-based constraints of the total Galactic DM contribution for |b| ≥ 30°, depending on the Galactic latitude and selected model, that span 87.8 − 141 pc cm−3. These results suggest that some commonly used MW halo models overestimate the halo’s gas density, especially when assuming high halo masses. This work highlights the impact of feedback mechanisms in shaping the halo.The second project introduces a novel approach to inference on noisy nonhomogeneous Poisson processes (NHPPs), in particular describing the k-contact distribution for events in a noisy NHPP. Using a hierarchical Bayesian model, I first estimate hyperparameters that govern the intensity of the NHPP that describes CHIME/FRB's detection of independent FRBs on the sky. I then leverage the posterior distribution to infer the probability of detecting a given number of events within a certain radius in observation space. This approach has significantly increased sensitivity for identifying repeating FRB sources, increasing detection significance in 86% of cases and decreasing the computed probability, the `probability of chance coincidence', by a median factor of around 3000 compared to the previous methodology.The third project focuses on searching for high-energy emission associated with an FRB, using contemporaneous X-ray and radio observations of the hyperactive and nearby repeating FRB source FRB 20220912A. Utilizing data from XMM-Newton, NICER, Effelsberg, CHIME/Pulsar, and CHIME/FRB, I place stringent upper limits on the X-ray to radio fluence ratio (η x/r) at the time of radio bursts from the source. Despite detecting 30 radio bursts during the simultaneous X-ray observations, no significant X-ray emission was observed. Using a new Bayesian methodology that I developed, I set a 99.7% credible interval upper limit on η x/r of < 2 × 106 , the most stringent such limit for any FRB to date. These limits approach the level expected from proposed FRB emission mechanisms and observed phenomena from Galactic magnetars, especially when adopting an X-ray spectrum similar to that observed from the Galactic magnetar SGR 1935+2154 during its FRB-like emission.This thesis contributes to the field of FRB science by improving our understanding of the Milky Way’s halo and hence its co-evolution with the Galaxy and intergalactic medium, by developing novel statistical tools for identifying repeating FRBs and associations between other poorly-localized phenomena, and by placing deep limits on any associated X-ray emission of these enigmatic sources.

Objective:Pediatric cancer and cancer-related treatments may disrupt brain development and place survivors at risk for long term problems with cognitive functions. Processing efficiency has been operationalized as a nuanced cognitive skill that reflects both processing speed (PS) and working memory (WM) abilities and is sensitive to neurobiological disruption. Pediatric cancer survivors are at risk for processing efficiency deficits; however, a thorough characterization of processing efficiency skills across pediatric primary central nervous system (CNS) tumor and non-CNS cancer survivors has not yet been reported.Participants and Methods:Participants were selected from a mixed retrospective clinical database of pediatric cancer survivors (Total n=160; primary CNS tumor n=33; Non-CNS n=127). Univariate analyses were conducted to examine differences in processing efficiency mean scores (t-tests) and percent impairment (scores >1 SD below mean; chi-squared tests) between the total sample and normative sample, and across groups (CNS vs. Non-CNS). Multiple linear regressions were utilized to evaluate the relationships between additional risk factors, including biological sex, age at diagnosis, time since treatment, and socioeconomic status, and processing efficiency outcomes.Results:The total sample obtained lower scores on WM (M=90.83, SD=13.35) and PS (M=88.86, SD=14.38) measures than normative samples (M=100, SD=15), p < 0.001. Greater percentage of pediatric cancer survivors demonstrated impairment across all processing efficiency measures (24.8-38.1%) than normative samples (15.9%), p < 0.001. Regarding group differences, the CNS group obtained lower mean WM (M=84.85, SD =11.77) and PS (M=80, SD=14.18) scores than the Non-CNS group (WM M=92.39, SD=13.32; PS M=91.16, SD=13.56), p < 0.001. Rates of impairment between groups only differed for PS scores, with 63.6% of the CNS group and 31.5% of the non-CNS group demonstrating impairment, p < 0.001. Primary CNS tumor cancer type and male biological sex emerged as the only significant risk factors that predicted processing efficiency skills, with male sex predicting lower scores on PS (ß=8.91 p<.001) and semantic fluency (ß=7.59, p=.007).Conclusions:These findings indicate that both pediatric primary CNS tumor and non-CNS cancer survivors exhibit substantial weaknesses in processing efficiency skills after treatment. While both groups demonstrated deficits compared to normative samples, the CNS group was more susceptible to PS impairments than non-CNS group. A basic initial study of the relationships between risk factors and processing efficiency skills revealed that primary CNS cancer was a predictor of lower performance on working memory and processing speed measures, while male biological sex was a significant risk factor for worse performance on processing speed and semantic fluency measures. Continued focus on the construct of processing efficiency in pediatric cancer survivors is warranted. Applying a standardized approach to assessing and communicating this nuanced cognitive skill could contribute to advancing both clinical practice and outcomes research of pediatric cancer survivors.

Lackluster BA completion rates have made it clear that improving postsecondary outcomes in the U.S. is not simply a matter of raising college enrollment rates. In addition to increasing the number of people who attend college, it is also important to increase the number of people who graduate. Over the years, scholars have identified many factors that help and hinder students as they make their way through college. One of these factors, and the focus of this three-study dissertation, is college choice. By college choice, I mean students’ decisions about where to attend college. One way to think about college choice is to think about it in terms of academic match. Academic match refers to the alignment between a student’s academic qualifications and the selectivity of the college they attend. Students “match” when they attend colleges that are well-aligned with their academic qualifications. Conversely, they “undermatch” when they attend colleges that are less selective than we might expect, and they “overmatch” when they attend colleges that are more selective than we might expect. A consistent finding from the existing research on academic match is that students who match or overmatch are more likely to complete a BA than those who undermatch. Little is known, however, about whether this association has changed over time. In Study 1, I use nationally representative data from three cohorts of first-time college students—students who began college in 1995, 2003, and 2011—to examine this question. Findings from this descriptive study show that, in some ways, the association between academic match and BA completion has remained stable over time; across all three cohorts, matched and overmatched students are more likely to graduate than undermatched students. In other ways, however, the association may be evolving; overall, overmatched students’ odds of graduation have increased over time, while matched and undermatched students’ have not. Study 1 highlights the continued importance of programs and interventions that seek to improve BA completion rates by reducing the prevalence of undermatch. By connecting these findings to broader trends in higher education, it also provides some working hypotheses for why academic match continues to be a strong predictor of student success. This sets the stage for future, hypothesis-testing research with additional implications for policy and practice. In Study 2, I contribute to the literature on college choice by evaluating the plausibility of the “cost hypothesis,” as it relates to college proximity and college choice. Existing research has found that college proximity plays an important role in the college choice process. While it is true that some students are eager to attend colleges that are far from their hometowns, the more common scenario is for students to attend colleges that are close to home. Many scholars have argued that this is because it can be more costly to attend a far-away college. I refer to this as the “cost hypothesis.” If it is more costly to attend a far-away college, then people who live in areas where colleges are few and far between—areas with low geographic access to higher education—may find it especially challenging to pay for college, as they have no choice but to attend colleges that are relatively far away. Study 2 assesses the plausibility of this line of reasoning by examining the association between geographic access to higher education, distance traveled to college, and college costs, as indicated by student debt. Using data from the High School Longitudinal Study of 2009, I find that people with lower levels of geographic access tend to travel longer distances to attend college. In addition, I find that people who travel longer distances tend to accumulate more student debt. Finally, I find suggestive evidence that people with lower levels of geographic access tend to accumulate more student debt. These descriptive insights pave the way for future research on this topic. Additional research in this area could be one of the keys to understanding, and ultimately remedying, geographic inequalities in postsecondary outcomes. In Study 3, I contribute to the literature on college choice by investigating whether, for some students, there may be important drawbacks to attending a match college or, more generally, a more selective college. Several studies have highlighted the fact that, for students from low-income, first-generation, and minoritized backgrounds, selective colleges can be socially isolating and difficult to navigate. Given this, some have wondered whether less selective colleges may offer more welcoming and engaging environments for students from these backgrounds. Study 3 uses data from the 2012/17 Beginning Postsecondary Students Longitudinal Study to examine whether this might be the case. Specifically, this descriptive study examines the association between college selectivity and affective engagement (feeling socially and emotionally connected to school), as well as the association between college selectivity and behavioral engagement (engaging in schooling-related activities). Findings show that students from a wide range of backgrounds report higher levels of affective and behavioral engagement at more selective, as opposed to less selective, colleges. This pattern is robust to several potential confounding factors, including college type, college size, and students’ pre-college academic qualifications. However, although the association between selectivity and affective engagement is positive for most subgroups, it is relatively flat for Black students. Overall, Study 3 lends additional support to the argument that selective colleges, though far from perfect, have important advantages over their less selective counterparts. This study has implications for ongoing debates about college choice, including debates about the extent to which prospective college students should prioritize things like selectivity and prestige during the college search process. That said, more research is needed to fully understand the link between college selectivity and student engagement, as well as the link between college selectivity and other indicators of student wellbeing.

Education is essential for successful transition from hospital to home, for both persons with stroke and their caregivers. Guided by Orem's self-care deficit nursing theory, this article identifies self-care needs about which physical and occupational therapists believe caregivers most frequently want information. The therapists (N=113), who responded to a mailed survey, were mostly White women prepared at the graduate educational level in the eastern United States. Descriptive statistics revealed that demonstrating safe transfer techniques was the most frequently chosen information need (82%) identified by physical and occupational therapists surveyed.

To determine whether ultrasound guidance improves the quality of continuous popliteal block when compared with a nerve stimulator after major foot and ankle surgery. Prospective, randomized, double-blinded clinical trial. Operating room, Postanesthesia Care Unit (PACU), and hospital wards of a university-affiliated hospital. 45 ASA physical status 1, 2, and 3 patients undergoing elective major foot and ankle surgery. Placement of a popliteal sciactic nerve catheter using either nerve stimulator or ultrasound guidance. In the PACU, a continuous infusion of ropivacaine 0.2% was started at a basal rate of 4 mL/hr and adjusted in a standardized fashion to maintain visual analog scale (VAS) pain scores < 4. All patients also received intravenous (IV) patient-controlled analgesia with hydromorphone and oral opioids. VAS pain scores at rest and with physical therapy, ropivacaine use, opioid use, and opioid-related side effects were recorded. Cummulative ropivacaine use was lower in patients whose catheter was placed by ultrasound than by nerve stimulator guidance (mean 50 vs 197 mL, P < 0.001). Pain scores at rest and during activity were similar between groups. Cumulative opioid consumption (mean 858 vs 809 mg oral morphine equivalents) and daily frequencies of nausea (5% to 33% vs 0 to 24%) and pruritus (0 to 21% vs 0 to 24%) were similar between groups. Length of hospital stay was similar between groups (3.5 vs 3.7 days). Ultrasound guidance was associated with less local anesthetic consumption than with the nerve stimulator; however, there was little clinical benefit, as all other outcomes were similar between groups.

We use the Canadian Hydrogen Intensity Mapping Experiment (CHIME) Fast Radio Burst (FRB) Project to search for FRBs that are temporally and spatially coincident with gamma-ray bursts (GRBs) occurring between 2018 July 7 and 2023 August 3. We do not find any temporal (within 1 week) and spatial (within overlapping 3 sigma localization regions) coincidences between any CHIME/FRB candidates and all GRBs with 1 sigma localization uncertainties <1 deg. As such, we use CHIME/FRB to constrain the possible FRB-like radio emission for 27 short gamma-ray bursts (SGRBs) that were within 17 deg. of CHIME/FRB's meridian at a point either 6 hrs prior up to 12 hrs after the high-energy emission. Two SGRBs, GRB 210909A and GRB 230208A, were above the horizon at CHIME at the time of their high-energy emission and we place some of the first constraints on simultaneous FRB-like radio emission from SGRBs. While neither of these two SGRBs have known redshifts, we construct a redshift range for each GRB based on their high-energy fluence and a derived SGRB energy distribution. For GRB 210909A, this redshift range corresponds to z = [0.009, 1.64] with a mean of z=0.13. Thus, for GRB 210909A, we constrain the radio luminosity at the time of the high-energy emission to L <2 x 10e46 erg s-1, L < 5 x 10e44 erg s-1, and L < 3 x 10e42 erg s-1 assuming redshifts of z=0.85, z=0.16, and z=0.013, respectively. We compare these constraints with the predicted simultaneous radio luminosities from different compact object merger models.

We present an extensive contemporaneous X-ray and radio campaign performed on the repeating fast radio burst (FRB) source FRB 20220912A for eight weeks immediately following the source's detection by CHIME/FRB. This includes X-ray data from XMM-Newton, NICER, and Swift, and radio detections of FRB 20220912A from CHIME/Pulsar and Effelsberg. We detect no significant X-ray emission at the time of 30 radio bursts with upper limits on \\(0.5-10.0\\) keV X-ray fluence of \\((1.5-14.5)\\times 10^{-10}\\) erg cm\\(^{-2}\\) (99.7% credible interval, unabsorbed) on a timescale of 100 ms. Translated into a fluence ratio \\(\\eta_{\\text{ x/r}} = F_{\\text{X-ray}}/F_{\\text{radio}}\\), this corresponds to \\({\\eta}_{\\text{ x/r}} < 7\\times10^{6}\\). For persistent emission from the location of FRB 20220912A, we derive a 99.7% \\(0.5-10.0\\) keV isotropic flux limit of \\(8.8\\times 10^{-15}\\) erg cm\\(^{-2}\\) s\\(^{-1}\\) (unabsorbed) or an isotropic luminosity limit of 1.4\\(\\times10^{41}\\) erg s\\(^{-1}\\) at a distance of 362.4 Mpc. We derive a hierarchical extension to the standard Bayesian treatment of low-count and background-contaminated X-ray data, which allows the robust combination of multiple observations. This methodology allows us to place the best (lowest) 99.7% credible interval upper limit on an FRB \\({\\eta}_{\\text{ x/r}}\\) to date, \\({\\eta}_{\\text{ x/r}} < 2\\times10^6\\), assuming that all thirty detected radio bursts are associated with X-ray bursts with the same fluence ratio. If we instead adopt an X-ray spectrum similar to the X-ray burst observed contemporaneously with FRB-like emission from Galactic magnetar SGR 1935+2154 detected on 2020 April 28, we derive a 99.7% credible interval upper limit on \\({\\eta}_{\\text{ x/r}}\\) of \\(8\\times10^5\\), which is only 3 times the observed value of \\({\\eta}_{\\text{ x/r}}\\) for SGR 1935+2154.