The Non-Orientable Four-Genus of Ten-Crossing Knots

We perform a detailed and complete computation of the non-orientable smooth 4-genus gamma4 for all 165 prime knots with crossing number equal to ten. Prior to this work, this important knot invariant was only known for knots with up to 9 crossings, and our work substantially expands on this body of knowledge. Our results have been published in the peer-reviewed Journal of Knot Theory and its Ramifications, and have been entered into the online database of knot invariants for low-crossing knots - KnotInto

Post-translational phosphorylation dynamics in Arabidopsis and Physcomitrella

Phosphorylation is the most abundant post-translational modification that involves the chemical addition of a phosphate group onto serine, threonine, or tyrosine residues of substrate proteins. Phosphorylation is utilized to regulate protein activity, stability, or localization to respond to cellular needs. This dissertation starts in Chapter Two by discussing the phospho-regulation of the Arabidopsis plant cellulose synthase complex and cellulose synthase-like proteins. Chapter Three discusses protein-protein complex dynamics in the model moss plant Physcomitrella patens. This chapter demonstrates that Physcomitrella convergently evolved to contain hetero-oligomeric cellulose synthase complexes similar to land plants like Arabidopsis. Chapter Four investigates how the loss-of-function of a secretory pathway protein can suppress the near-sterile phenotype of a calcium-dependent protein kinase in Arabidopsis pollen, providing the first genetic connection between a calcium kinase and the secretory pathway. Lastly, Chapter Five utilizes quantitative phospho-proteomics to identify two proteins with heat-stress-dependent phosphorylation sites with implications on pollen fitness. To conclude, this dissertation describes a phosphorylation-dependent link between the topics covered in each chapter and a concluding perspective on how this work could contribute to the future of plant phosphorylation research

ELECTRONIC NICOTINE PRODUCTS AS A HARM REDUCTION INTERVENTION FOR CIGARETTE CESSATION AMONG PEOPLE WITH SUBSTANCE USE DISORDERS (PWSUDs)

BackgroundThe prevalence of cigarette smoking in the US has continued to decline over the past two decades. However, the prevalence of cigarette smoking remains high among certain population groups, including people with substance use disorders (PWSUDs), compared to estimates in populations without substance use disorders. Due to the high rates of smoking among PWSUDs, they are disproportionately affected by tobacco-related illnesses compared to the general population. Therefore, identifying interventions that can reduce the harm of tobacco use and promoting the health of this population has the potential to save lives and promote health in the wider US population. Purpose The aims of my dissertation include the following: 1. to compare the uptake of cigarette smoking cessation aids (e.g., Food and Drug Administration (FDA)-approved cessation products or e-cigarettes) among US adults (18+ years) with substance use problems (PWSUPs) who currently smoke to people without substance use problems (SUPs) who currently smoke cigarettes in a nationally representative US sample; 2. to examine the effect of e-cigarette use with instructions as a switching tool on daily cigarette consumption among US adults (21+ years) with substance use disorders; and 3. to understand the experience of US adults (21+ years) with substance use disorders regarding the use of e-cigarettes for switching away from cigarettes and its acceptance within their social network following a brief intervention using e-cigarettes to switch to cigarettes. Methods In the first paper, I used a cross-sectional design with a nationally representative sample of US adults to investigate the differences in past year uptake of FDA-approved cessation aids (i.e., nicotine replacement therapies (NRTs), cessation medications (i.e., varenicline, bupropion)), e-cigarettes for cigarette cessation, and e-cigarettes for cigarette reduction among individuals with substance use problems compared to those without. The study sample was obtained from the US Population Assessment of Tobacco and Health (PATH) Study Wave 6, which was collected in 2021. Weighted multivariable logistic regression models were used to identify the uptake of cessation aids and e-cigarettes for cessation and reduction between individuals with high-severity SUPs and those without SUPs. In the second paper, I used an intensive longitudinal design with a sample of US adults enrolled in outpatient substance use treatment. The population provided daily diaries of number of cigarettes smoked per day (CPD) over a baseline period (days 1-7), and then received e-cigarette devices, guided instructions on how to switch from cigarettes to e-cigarettes, and four pods of tobacco-flavored nicotine e-liquids. Participants then provided daily records on CPD and daily e-cigarette puff times over a period of two weeks. Linear fixed effect models were used to estimate the change in CPD by e-cigarette puff times. For the third paper, I conducted in-depth qualitative interviews with participants who completed a two-week period of e-cigarette use for switching. I used an inductive approach to explore themes relating to the experience of switching to e-cigarettes on nicotine cravings, social relationships, and fit with substance use treatment among adults in outpatient treatment for substance use disorders. Results Study One My results showed that among adults who smoke cigarettes, a higher proportion of those with high SUP severity used NRTs, cessation medications, and e-cigarettes for cigarette cessation, respectively (12.3%, 8.4%, 15.7%), compared to those with no/low SUP severity (9.8%, 6.0%, 8.9%). I also found that respondents with high SUPs had 63% (95% CI:1.16-2.29) higher odds of using e-cigarettes for cessation than those without SUPs. Study Two My study sample comprised 25 eligible adults who had a median age of 40 years. Following the switch to e-cigarettes on day-8, the number of cigarettes smoked per day (CPD) reduced on average by 21 cigarettes (β: -20.58; 95% CI: -22.10, -19.07). For every one time a participant used e-cigarettes above their personal average, they smoked 0.12 fewer cigarettes (95% CI: -0.20, -0.04), and as the days progressed following e-cigarette use, daily CPD decreased on average (β: -0.20; 95% CI: -0.32, -0.08). Study Three The study sample comprised 30 adults in outpatient treatment for substance use disorders. I identified six main lines of inquiry from descriptions participants provided about their experience using e-cigarettes to switch from cigarettes with multiple themes within each line of inquiry, namely: 1. Facilitators and barriers during switching experience; 2. Moments of persistent craving and smoking lapses; 3. Strategies and adaptation among PWSUDs using e-cigarettes to switch away from cigarettes; 4. Navigating e-cigarette use as a switching tool during substance use treatment; 5. Intentions on future e-cigarette use after switching. A common facilitator was the convenience of e-cigarettes based on their sensory and physical attributes, which simulate cigarettes. A common barrier was lack of satisfaction from e-cigarettes. Participants also indicated perceived health benefits, social opportunities were facilitators for switching; and moments of persistent cravings occurred in the mornings after waking, after meals, and during stressful situations. Notably, participants described tapering down their cigarette use rather than making an abrupt switch, as a more practical strategy. There were mixed intentions on whether to continue using e-cigarettes after quitting cigarettes or to quit e-cigarettes as well. Conclusions Research on smoking cessation among individuals with substance use disorders is crucial for saving lives and improving health outcomes in the US, as it has the potential to impact more than half of the 48.5 million US adults affected by SUDs who smoke cigarettes. This thesis contributes to the broader scientific literature by demonstrating that individuals with SUDs have higher odds of using e-cigarettes for cigarette cessation and reduction than those without SUDs. The research also suggests that nicotine e-cigarettes could be effective for reducing cigarette consumption when interpreted alongside other studies, with these findings extending to populations with problematic psychoactive substance use outside of residential treatment settings, using standardized devices with guided instructions. Importantly, I found that the experience of using e-cigarettes as a smoking harm reduction tool—and switching from cigarettes to e-cigarettes—is multifaceted, with multiple individual-level factors (e.g., perceived satisfaction, motivation from health benefits) and social factors (e.g., familial or peer support) contributing to the potential success of cessation or reduction. Overall, these findings suggest that guided e-cigarette use may be an acceptable, effective, and practical cessation intervention for adults with SUDs who are interested in quitting or reducing cigarette smoking. Future studies can explore how evidence-based counseling and behavioral management strategies might be deployed to support cessation with e-cigarettes. Policy measures can also be developed to integrate e-cigarettes as smoking harm reduction tools for adults in SUD treatment who are motivated and interested in using them to quit or reduce cigarette smoking

Density Demonstration Projects: Strategies for Improving Asphalt Pavement Density

Knowing that in-place density is key for building cost effective and durable asphalt pavements, the Federal Highway Administration (FHWA) initiated the "Enhanced Durability of Asphalt Pavements through Increased In-place Pavement Density" demonstration project. The aim was to support State Departments of Transportation (DOTs) with evaluation of their existing density requirements for acceptance. It was anticipated that the results may aid State DOTs in reviewing and updating, as needed, their current field density acceptance criteria.United States Department of TransportationFederal Highway Administratio

Leveraging Fourier Transform Infrared Spectroscopy to Elucidate Post-Fire Chemical Changes

Vegetation fires are a natural and common occurrence in forest ecosystems of the Sierra Nevada, resulting in changes to soils, vegetation, and hydrology. To successfully manage challenges of increased severity and frequency of fire and ensure the long-term health and sustainability of Sierra Nevada landscapes, continuous monitoring, and adaptive management efforts are needed. Land management strategies in fire-affected ecosystems require novel approaches that address soil water repellency (SWR), enhance water retention, and support vegetation recovery while acknowledging impacts on ecosystem resilience. This dissertation examined the relationships among temperature, charcoal, and SWR. First, laboratory methods of charcoal production in a controlled muffle furnace were compared with replicated fire conditions in a combustion facility. The heat-related chemical transformations of the produced charcoal were also compared using Fourier Transform Infrared (FTIR) spectroscopy and statistical analysis using Modern Analogue Technique (MAT). Mixed responses were observed when using FTIR spectra to infer fire temperature and vegetation species by measuring temperature changes in charcoal chemistry. Then, field-based data were collected to examine the relationships between burn severity, hydrophobic compound ratios, and infiltration rates for historic vegetation fire sites in the Sierra Nevada. An inverse relationship was found between hydrophobiccompound ratios, measured using FTIR, and soil water infiltration, emphasizing SWR in influencing post-fire soil hydrology. Finally, changes in the chemistry of vegetation fire collected charcoal to infer fire temperature using FTIR spectra were combined with infiltration measurements to examine temperature thresholds of SWR. Results showed that the relationship between charcoal temperatures collected from SWR soils needed to be clarified. Most charcoals had inferred temperatures above the threshold shown for SWR soils to occur, suggesting that charcoals could have been deposited from tree crowns and do not necessarily represent temperatures reached during fire for local soil microsite conditions. This study enhances our understanding of charcoal pyrolysis temperatures through FTIR analysis from a chemical standpoint. These findings have important implications for land management in fire-impacted ecosystems, highlighting the need forstrategies that mitigate soil erosion, improve water retention, and promote vegetation recovery, all while considering the role of SWR in ecosystem resilience