METAL-FREE SELECTIVE SP3 C-H IMINATION AND COVALENT POSTSYNTHETIC MODIFICATION OF POLYSTYRENE BY DIRECT C-H AMINATION

Over the past two decades, there has been a high demand for methods enabling direct alkane C–H amination. Alkylamines are commonly found as natural products and bioactive compounds, and amino functionalization can improve the properties of commodity polymers. Transition-metal-catalyzed C–H amination has emerged as a powerful tool for C–N bond formation, but these reactions typically rely on nitrogen protecting groups such as sulfonamides, which limits substrate scope and requires multiple steps. My work focused on developing a metal-free C-H amination method, which offers new and useful amination scope and selectivity and avoids toxic or colored metal residues. Specifically, we developed a mild and selective protocol for preparing primary and secondary aliphatic amines in a single pot, based on intermolecular sp3 C-H imination. Our approach involves a unique hydrogen-atom transfer/radical addition mechanism, which differs from the more established Hoffman-Löffler-Freytag amination. From there, we have successfully transferred this method from small molecules to macromolecules, as the amino functional group is attractive for polymer modification. We developed a mild and selective simple amination of polystyrene without chain cleavage and cross linking by radical sp3 C-H imination, using a protocol we reported for the sp3 C-H imination of small molecules. This process incorporates primary amines, primary ammonium salts, and benzophenone ketimines in a straightforward manner, which will further inform future development of materials by the direct modification of polymer.Chemistry, Department o

Generalized Convergence for Multi-Step Schemes under Weak Conditions

We have developed a local convergence analysis for a general scheme of high-order convergence, aiming to solve equations in Banach spaces. A priori estimates are developed based on the error distances. This way, we know in advance the number of iterations required to reach a predetermined error tolerance. Moreover, a radius of convergence is determined, allowing for a selection of initial points assuring the convergence of the scheme. Furthermore, a neighborhood that contains only one solution to the equation is specified. Notably, we present the generalized convergence of these schemes under weak conditions. Our findings are based on generalized continuity requirements and contain a new semi-local convergence analysis (with a majorizing sequence) not seen in earlier studies based on Taylor series and derivatives which are not present in the scheme. We conclude with a good collection of numerical results derived from applied science problems

Building Bridges in STEM Education: Minoritized Secondary School Student Computer Science Pathways and Experiences

The experiences of underrepresented women and ethnic minorities in computer science (CS) fields are at the heart of understanding the factors that impact the critical transitions students face when entering into Science, Technology, Engineering, or Mathematics (STEM) careers. The research, conducted using a grounded theory approach, gauges student and teacher perspectives, specifically investigating minoritized student perspectives that influence their entrance and continuation into an educational pathway. The study’s outcomes underscore the crucial roles of (1) Student Family Encouragement, (2) School and Community Engagement, and (3) Professional/Teacher Mentorship as critical junctions that school districts should be aware of when creating student pathways into college and career, particularly for underrepresented groups

Carbon-Carbon Bonds Formed by Lewis Acid Catalysis or Photoactivation

Methods to generate C¬–C bonds are of great interest to synthetic organic chemists. Ideally, these reactions will be simple, robust, and catalytic. Herein is described the synthesis of tertiary and all-carbon quaternary centers from propargylic alcohols, organoboronates, and Lewis acids. Lewis acids can also be used to facilitate a mild Friedel-Crafts reaction between electron-rich aromatics and allylic or benzylic alcohols. Moreover, these methods can be applied to the synthesis of natural products. Finally, photoactivation of tosylhydrazones can allow for C–C bond formation when paired with organoboronates. This reaction was probed and the mechanism of photoactivation was elucidated

Enablers and Inhibitors to Implementing Tobacco Cessation Interventions within Homeless-Serving Agencies: A Qualitative Analysis of Program Partners’ Experiences

Despite the high tobacco use rates (~80%) and tobacco-related cancers being the second leading cause of death among people experiencing homelessness within the United States, these individuals rarely receive tobacco use treatment from homeless-serving agencies (HSAs). This qualitative study explored the enablers and inhibitors of implementing an evidence-based tobacco-free workplace (TFW) program offering TFW policy adoption, specialized provider training to treat tobacco use, and nicotine replacement therapy (NRT) within HSAs. Pre- and post-implementation interviews with providers and managers (n = 13) pursued adapting interventions to specific HSAs and assessed the program success, respectively. The organizational readiness for change theory framed the data content analysis, yielding three categories: change commitment, change efficacy and contextual factors. Pre- to post-implementation, increasing challenges impacted the organizational capacity and providers’ attitudes, wherein previously enabling factors were reframed as inhibiting, resulting in limited implementation despite resource provision. These findings indicate that low-resourced HSAs require additional support and guidance to overcome infrastructure challenges and build the capacity needed to implement a TFW program. This study’s findings can guide future TFW program interventions, enable identification of agencies that are well-positioned to adopt such programs, and facilitate capacity-building efforts to ensure their successful participation

A Geant4 Simulation Study Of A Xenon-Doped Liquid Argon, Full-Body, Time-of-Flight Positron Emission Tomography Scanner To Understand Its Performance And Noise Profile

Positron Emission Tomography (PET) is used to observe metabolic processes within living tissue. It works by reconstructing the annihilation origin of incident gamma rays produced by a positron emitting radiotracer. This field of nuclear imaging has seen a steady improvement of PET imaging largely due to the application of newer detection technologies and image reconstruction algorithms. However, current PET scanners possess a small field of view which limits the overall sensitivity. Increasing the sensitivity and using Time of Flight (TOF) information can help to improve the quality of PET scans. This thesis will outline a novel PET scanner design poised to expand the capabilities of PET imaging. 3Dπ is a Total-Body, TOF - PET scanner that uses Silicon Photomultipliers (SiPM) coupled with a Xenon-doped Liquid Argon (LAr+Xe) scintillator. This design was simulated using the Geant4 particle-matter monte carlo simulation tool-kit while following the National Electrical Manufacturers Association’s evaluation tests (2018) for performance assessment. The results presented here highlight a 20-fold increase in sensitivity compared to traditional scanners produces sub-centimeter spatial resolutions and can produce PET images from 15-30 second scans, faster than traditional non-full-body 30-35-minute scans. In addition to an evaluation of the performance, this thesis will cover the major sources of noise a detector such as this one experiences. Next, the noisy signals will be quantified by discriminating the energies of the incident gamma ray recorded by the scanner. Lastly, the datasets generated from the monte carlo simulation will be used to compare two image reconstruction algorithms in order to gauge the difference between an analytical algorithm and a noise driven iterative algorithm. With a LAr+Xe scintillator and solid-state photosensors, 3Dπ can use the precise TOF info of gamma rays to improve the localization of individual positron annihilations, and as one example benefit, provide low-dose PET scans for patients who may be at high risk for exposure to radiation such as expectant mothers and adolescent children

Spatiotemporal Variability of CO2, Solar-Induced Fluorescence, And Precipitation Over the Tropical Rainforests

Tropical rainforest ecosystems change forest dynamics during the dry/fire season, transitioning from an atmospheric CO2 sink to a CO2 source. The Amazon basin, Congo basin, and the tropical Indo-Pacific play vital roles in biospheric processes, which contribute to Earth’s atmospheric CO2 concentration. This investigation will use various space-based and ground-based datasets and empirical models to explore photosynthetic activity, spatiotemporal variability, and correlation among critical variables (e.g., Solar-induced chlorophyll fluorescence (SIF), CO2, precipitation, high vapor pressure deficit (VPD), and burned areas). Specifically, we use Orbiting Carbon Observatory 2 (OCO-2) SIF, OCO-2 CO2, Global Precipitation Climatology Project (GPCP) precipitation, Moderate Resolution Imaging Spectrometer (MODIS) burned area, and CarbonTracker Model. Over the entire Amazon basin from September 2014 to December 2019, we found a positive temporal correlation (0.94) between OCO-2 SIF and GPCP precipitation and a negative temporal correlation (–0.64) between OCO-2 SIF and OCO-2 CO2. These findings suggest that precipitation enhances photosynthesis, thus resulting in higher values for SIF and the rate of removal of atmospheric CO2 in the Amazon region. We also identify seasonal variations in the spatial distributions of these variables across the Amazon region. Over the Congo basin, during the same timeframe (Sep 2014-Dec 2019), we find that the atmospheric CO2 is ~2 ppm higher than the regional background during the boreal summer (June–August), primarily due to biomass burning and significantly reduced photosynthetic activities during the dry season. Over the tropical Indo-Pacific, we explore the spatial distributions of SIF, CO2, and precipitation during El Niño events verse other months. The CarbonTracker Model is employed to assess the impact of El Niño on atmospheric CO2. Various datasets of deseasonalized precipitation, deseasonalized SIF, and deseasonalized CO2 are analyzed in time series averaged over 10S-10N, 100E-160E. We have discovered that there is less precipitation, more sinking air, lower SIF, and higher CO2 over the Indo-Pacific region during the El Niño events. The CarbonTracker model can simulate the increase of atmospheric column CO2 during the El Niño event, although there are some difficulties in capturing the correct spatial distribution of CO2 anomalies. These findings suggest that improved seasonal fire management practices in these tropical regions are critical components needed to achieve successful and timely reductions in global carbon emissions, as set forth by international agreements.Earth and Atmospheric Sciences, Department o

"No Solider Left Behind": Gender Violence and Institutional Betrayal in the Case of Army Specialist Vanessa Guillén

Gender violence in the U.S. military remains alarmingly prevalent, as evidenced by the "129,000 service members (1 in 4 women, 1 in 15 men) [that] faced severe and persistent sexual harassment or gender discrimination in 2016"(Protect Our Defenders, 2018). Gender violence in the military is often characterized by layers of betrayal, rather than isolation to single or separable acts of explicit violence per se. This research investigates gender violence and betrayal in the 2020 case of Army Specialist Vanessa Guillén utilizing Barney Glaser and Anselm Strauss' methodological framework of Grounded Theory (1967) to examine five multimedia sources spanning 2020-2021. The three-step coding process (open, axial, and selective) was utilized to determine similarities/differences/trends within the textual accounts of her case and to ultimately generate two theories: the Negligence-Intentionality of Harm Spectrum and Identification as Trauma/Betrayal Antidote. The two theories address distinct parts of Vanessa's case. The Negligence-Intentionality Spectrum argues that for the onlooker, it can be difficult to determine whether actions taken by military officials regarding Vanessa were intentional/malicious, versus institutional inadequacies that result in harm. As for the Antidote to Betrayal, it comes in the form of social support which prompted the Guilléns forward following Vanessa's disappearance. Vanessa remains alive in people's hearts, demonstrating a potential immeasurable consequence to trauma and grief. This study is significant because it brings continued awareness and highlights how the military as an institution can better support their soldiers moving forward in the aftermath of Vanessa's case.Psychology, Department ofHonors Colleg

How Can Conflicts with Supervisors or Coworkers Affect Construction Workers’ Safety Performance on Site? Two Cross-Sectional Studies in North America

A safety plateau in the construction industry has been reported in the US and Canada, which has prompted researchers to seek new factors affecting construction safety performance. Tapping into advancements in the theory of human and organizational behaviors can yield valuable new perspectives. Therefore, by leveraging the advancement of the Job Demand Control Support model in the field of occupational safety and health, this paper firstly tested the impact of one newly added hindrance stressor (i.e., interpersonal conflicts on construction sites) by researchers on organizational behaviors on the safety performance of construction workers, based on two cross-sectional studies in the US and Canada. Differentiations were made between conflicts with supervisors and conflicts with coworkers. One personal resource factor, i.e., individual resilience, was also considered in this paper. A “causal” chain that shows the mitigation impact of individual resilience on conflicts with supervisors or coworkers, and the adverse impact of conflicts with supervisors or coworkers, on unsafe events were found to hold true for both US and Canadian construction sites, based on the results from measurement invariance tests and structural equation modelling. Recommendations regarding how to improve construction workers’ individual resilience and reduce interpersonal conflicts on site, thereby reducing safety incidents on site, are provided

Teacher Perceptions on Standards-Based Grading: How Standards-Based Grading Can Bring Equity to All

Background: The traditional grading system and practices have remained largely unchanged since the late 1800s, yet school districts have continued to implement these traditional numerical grading practices. Standards-based grading is an alternative non-traditional way of grading that has begun to make its way into some schools. Standards-based grading practices and systems focus on student mastery around a specific concept or skill, and also focuses on students’ product, process, and performance. It is essential that we explore different types of grading as our world continues to adapt and change. Purpose: This qualitative case-study learned about elementary school teachers’ perceptions of standards-based grading and how it considers equity for all students. The research question that guided this case-study was: What are elementary school teachers’ perceptions on standards-based grading and how does it consider equity for all students? Method: This qualitative case study consisted of data gathered from six elementary school teachers from a large suburban public school district in the southwest region of the United States outside of a major city in Texas who have used or are using standards-based grading in their instruction. The data sets were collected through semi-structured interviews and one focus group session. Questions were structured around the perceptions of equitable grading and the use of standards-based grading. In addition, the researcher kept a field journal for triangulation purposes. All sessions were recorded and transcribed using Microsoft Teams. Data collected through the interviews and focus groups were analyzed, coded, and triangulated for emerging themes. Results: There were three cycles of coding. The first cycle of coding was through hand coding of repeated phrases and words from these sessions that yielded eight emerging initial codes and 10 sub-codes. The second cycle of coding included 12 specific codes such as consistency, differentiation, multiple opportunities, feedback, and clarity. The third cycle of coding used in vivo coding triangulated with the first two cycles of coding and aligned to the Equity Framework from Feldman (2019). These results indicated that equitableness within standards-based grading is framed around clarity, tools, specific feedback, opportunities, the learning environment, and conversations. Participants shared their experiences in implementing standards-based grading on their campuses. Team planning around specific opportunities and student tools helped to bring clarity to the standards. Intentional feedback and multiple opportunities for mastery allowed for equitableness. Conclusion: School districts and administrations should consider the alignment and messaging around grading and reporting from district-level administrators to campus administrators, to classroom teachers and support staff. School districts and administration should also consider professional development opportunities to ensure calibration and understanding among campus leadership, campus level teams and campuses district-wide to have a broader impact on student learning and achievement.Curriculum and Instruction, Department o