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  1. Liu, W. ; Wang, Y. ; Guo, B. ; Tang, X. ; Zeng, S. (Ed.)
    Sensitivity studies have shown that the 15 O(α, γ) 19 Ne reaction is the most important reaction rate uncertainty affecting the shape of light curves from Type I X-ray bursts. This reaction is dominated by the 4.03 MeV resonance in 19 Ne. Previous measurements by our group have shown that this state is populated in the decay sequence of 20 Mg. A single 20 Mg(βp α) 15 O event through the key 15 O(α, γ) 19 Ne resonance yields a characteristic signature: the emission of a proton and alpha particle. To achieve the granularity necessary for the identification of thismore »signature, we have upgraded the Proton Detector of the Gaseous Detector with Germanium Tagging (GADGET) into a time projection chamber to form the GADGET II detection system. GADGET II has been fully constructed, and is entering the testing phase.« less
    Free, publicly-accessible full text available January 1, 2023
  2. Liu, W. ; Wang, Y. ; Guo, B. ; Tang, X. ; Zeng, S. (Ed.)
    15 O( α , γ ) 19 Ne is regarded as one of the most important thermonuclear reactions in type I X-ray bursts. For studying the properties of the key resonance in this reaction using β decay, the existing Proton Detector component of the Gaseous Detector with Germanium Tagging (GADGET) assembly is being upgraded to operate as a time projection chamber (TPC) at FRIB. This upgrade includes the associated hardware as well as software and this paper mainly focusses on the software upgrade. The full detector set up is simulated using the ATTPCROOTv 2 data analysis framework for 20 Mgmore »and 241 Am.« less
    Free, publicly-accessible full text available January 1, 2023
  3. This interdisciplinary, inter-institutional research initiation project is motivated by the need to develop practical strategies for broadening the participation of African American students in engineering. The central objective of the project is to conduct a comparative study of the factors affecting the success and pathways to engineering careers of African American students at a Predominantly White Institution (PWI), the University of Toledo, and a Historically Black University (Alabama Agricultural and Mechanical University). Through this research we hope to gain insight into the factors affecting the social and academic well-being of students at PWIs and HBCUs from a psychological and anthropologicalmore »perspective. For students from underrepresented groups in STEM at both HBCUs and PWIs it is generally recognized that social capital in the form of familial, peer and mentor support is critical to persistence in their major field of study. However, the role that embedded networks within student groups in general, and minority engineering affinity groups in particular, play in engineering students’ identity formation and academic success is not well understood. It is also not clear how other factors including institutional support and the attitudes and beliefs of faculty and staff toward underrepresented minority students affect the ability of these students to integrate into the social and academic systems at their institutions and how these factors influence the formation and development of their identities as engineers. Here we report on the role of membership in organizations for underrepresented minority engineering students such as the National Society of Black Engineers (NSBE) in contributing to the interlinking of personal and professional identities, and to the career pathways of African American students enrolled in PWI and HBCU, respectively.« less
  4. Low enrollment, retention, and graduation rates of African American engineering students in the United States are a cause for concern [1]. Consequently, over the last decade there has been an upsurge of research identifying factors that have contributed to the problems encountered by African American students in higher education institutions in general, and in STEM fields in particular [2, 3]. The key factors identified as contributing to the attrition of minority African American students include perceptions of racism on campus, internalization of stereotypes, feelings of alienation and rejection, and inadequate support systems [4, 5]. In this context, considerations of institutionalmore »demographic characteristics, including the ethnic makeup of the student body is essential. Studies demonstrate that African American students at Historically Black Colleges and Universities (HBCUs) experience lower levels of isolation and overt racism, and higher levels of retention compared to African American students in Predominantly White Institutions (PWIs) [6, 7]. While some studies suggest that African American students experience lower levels of stereotype threat in HBCUs [8, 9], other studies indicate that there is little significant difference between students attending PWIs and HBCUs in their perceptions of stereotype threat. Based on qualitative and quantitative data from a national sample of engineering students, Brown, Morning, and Watkins report that students enrolled in HBCUs had more favorable perceptions of their college experience and that the higher graduation rate of African American students in HBCUs compared to their PWI counterparts could be attributed to lower perceptions of racism and discrimination [10]. It may be that the levels of stereotype threat experienced in the two types of institutions are different [11]. Based on the literature reviewed, the purpose of this study is to examine whether African American engineering students’ numerical majority status in HBCUs enhances the compatibility between their racial and professional identities and facilitates their integration; while their numerical minority status in PWIs diminishes the compatibility of the two social identities and stymies their integration. We examine this issue within the Social Identity and the Identity-focused Cultural Ecological Perspective theories. Before we turn to the two theoretical frameworks we describe the multiple context-dependent representations of majority-minority status with particular focus on African American college students in the United States.« less
  5. Abstract We search for signatures of gravitational lensing in the gravitational-wave signals from compact binary coalescences detected by Advanced Laser Interferometer Gravitational-wave Observatory (LIGO) and Advanced Virgo during O3a, the first half of their third observing run. We study: (1) the expected rate of lensing at current detector sensitivity and the implications of a non-observation of strong lensing or a stochastic gravitational-wave background on the merger-rate density at high redshift; (2) how the interpretation of individual high-mass events would change if they were found to be lensed; (3) the possibility of multiple images due to strong lensing by galaxies ormore »galaxy clusters; and (4) possible wave-optics effects due to point-mass microlenses. Several pairs of signals in the multiple-image analysis show similar parameters and, in this sense, are nominally consistent with the strong lensing hypothesis. However, taking into account population priors, selection effects, and the prior odds against lensing, these events do not provide sufficient evidence for lensing. Overall, we find no compelling evidence for lensing in the observed gravitational-wave signals from any of these analyses.« less
    Free, publicly-accessible full text available December 1, 2022
  6. Abstract We present a search for continuous gravitational-wave emission due to r-modes in the pulsar PSR J0537–6910 using data from the LIGO–Virgo Collaboration observing run O3. PSR J0537–6910 is a young energetic X-ray pulsar and is the most frequent glitcher known. The inter-glitch braking index of the pulsar suggests that gravitational-wave emission due to r-mode oscillations may play an important role in the spin evolution of this pulsar. Theoretical models confirm this possibility and predict emission at a level that can be probed by ground-based detectors. In order to explore this scenario, we search for r-mode emission in the epochsmore »between glitches by using a contemporaneous timing ephemeris obtained from NICER data. We do not detect any signals in the theoretically expected band of 86–97 Hz, and report upper limits on the amplitude of the gravitational waves. Our results improve on previous amplitude upper limits from r-modes in J0537-6910 by a factor of up to 3 and place stringent constraints on theoretical models for r-mode-driven spin-down in PSR J0537–6910, especially for higher frequencies at which our results reach below the spin-down limit defined by energy conservation.« less
    Free, publicly-accessible full text available November 1, 2022
  7. Free, publicly-accessible full text available November 1, 2022