A comment on free-fermion conditions for lattice models in two and more dimensions

We analyze free-fermion conditions on vertex models. We show --by examining examples of vertex models on square, triangular, and cubic lattices-- how they amount to degeneration conditions for known symmetries of the Boltzmann weights, and propose a general scheme for such a process in two and more dimensions.Comment: 12 pages, plain Late

An Open Governor’s Seat, Open Constitutional Question, and the Need for an Answer

Another election cycle always means a renewal of fresh lawsuits and legal questions, and 2022 is no exception. the announcement of Sarah Huckabee Sanders’s run for Governor of Arkansas reignites an interesting aspect of Arkansas’s Constitution: must a candidate for Governor live in the State of Arkansas for seven consecutive years, immediately preceding taking office? A final ruling by the Arkansas Supreme Court will give clarity and stability going forward for the most important elected position in the state

Examining race differences in cardiovascular health among young men: The role of residential segregation

Background: Racial residential segregation (RRS) is a fundamental cause of racial disparities in cardiovascular disease (CVD) risk and prevalence. While the effects of RRS on Black-White disparities in CVD have been well documented, knowledge about the effect of RRS on CVD disparities among men is limited. Cardiovascular health (CVH) is inversely associated with CVD risk and may prevent CVD disparities in later adult years if better understood. Thus, the goal of this dissertation is to examine whether RRS influences the emergence of race differences in CVH among young Black and White men in the US. Methods: Data for aims 1 and 2 were drawn from the National Longitudinal Study of Adolescent to Adult Health (Add Health). In aim 1, we used logistic regression to examine whether RRS influenced the association between race and CVH among young men (ages 24-32; N=5,080). In aim 2, we used mixed effects latent growth modeling to examine whether RRS during adolescence contributed to alternative body mass index (BMI), sleep, and cigarette use male trajectories by race from adolescence to young adulthood (ages 13-31; (N=8,612). Lastly, aim 3 used concept mapping data collected from a community sample of 30 young Black men residing in two southern Black communities to understand their conceptualizations of how CVH is linked to residential context. Results: In aim 1,we observed race disparities in ideal CVH when young Black and White men reside in neighborhoods comprised of 55% or more White residents. In aim 2, BMI, sleep, and cigarette use trajectories differed by neighborhood RRS during adolescence for White males. However, adolescent RRS caused different trajectories only for BMI among Black males. In aim 3, the final concept map depicted eight conceptual domains classified into two overarching domains of neighborhood features that were either protective or harmful to Black men’s CVH. Conclusion: Overall, study findings advance knowledge of the extent that RRS influences Black-White differences in CVH among young men. Taken together, findings from this dissertation have the potential to inform research, healthcare delivery, and policy solutions to better serve young men within their residential contexts and attenuate racial disparities in CVD.Doctor of Philosoph

Control of thermal expansion, behavior on compression, and guest loading in framework materials

Each chapter in this thesis focuses on open framework systems found to display anomalous properties relating to their unique structures. The systems investigated were chosen for their open framework form, flexibility, and modifiability. These three key factors can allow for the structural control necessary for tunable thermal expansion and phase stability to be achieved in materials that inherently display large negative thermal expansion (NTE). Concepts necessary for the understanding of thermal expansion research will be covered in sufficient detail as well as examples from the different materials classes being investigated in this thesis. Definitions, mechanisms, applications, and real examples of thermal expansion, behavior upon compression, and composite research are reviewed in chapter 1. Chapters 2, 3 and 4 examine the control of thermal expansion in ReO3-type metal fluoride systems. ReO3-type materials exhibit the simplest crystalline structure found to exhibit strong NTE. Because of its inherent simplicity, modification and analysis of these structures is relatively straightforward. This being the case, the coefficients of thermal expansion (CTEs) of ReO3-type materials have been found to range from strongly positive to strongly negative. This fact reveals deeper complications involving the ionicity, bond strength, and general flexibility of these structures that lead to diverse thermodynamic behavior. In these chapters certain metal fluorides were chosen that have previously been found to exhibit both structural tunability and large NTE. The structural tunability allows for certain flexible structural components to be replaced by more rigid counterparts (systematically) to control the properties related directly to flexibility, such as thermal behavior. Specifically, Mg1-xZr1+xF6+2x and Sc1-xZrxF3+x solid solutions were found to display tunable thermal expansion and phase stability upon the introduction of edge-sharing polyhedra within their structures. The introduction of this specific defect is mediated by the metal ratio within these systems. The use of defects to control thermodynamic behavior is a common theme in this thesis, but the work in chapter 4 shows that the techniques involved in behavioral control must be modified specifically for each system they are being applied to. In chapter 4, Ca[Zr(IV)1-xNb(V)x]F6+x solid solutions are investigated using the same general technique applied successfully to the materials of chapters 1 and 2. Interestingly, it is shown that this specific variation of the technique does not appear to introduce the same defect that was found in the previous two systems. This new defect introduced leads to changes in the structural behavior that are non-ideal for application but demonstrates the importance of developing a diverse toolkit when approaching thermodynamic behavioral modification. Chapters 5 and 6 investigate an even broader range of thermal behavior control techniques, which span from structural scaffold modification to guest inclusion. A comparison of how effective these techniques are for a diverse set of metal organic frameworks (MOFs) is drawn and previously unexplored routes of structural control are introduced for these systems. While some techniques facilitated direct tunability of thermal expansion from positive to negative within a measured temperature range, others simply showed non-systematic changes in the thermal expansion or just the controlled inhibition of pronounced NTE. Insights into the origin of these differences in thermal behavior are obtained through an in-depth analysis of synchrotron‐radiation total scattering and diffraction experiments, as well as complementary molecular simulations performed by collaborators. The implications of these works on the prospects for MOFs as an emergent material class for NTE-related applications are also discussed. While several metal–organic frameworks are known to display negative thermal expansion, there have been no reports where the thermal expansion of a MOF has been tuned continuously from negative to positive through the formation of single-phase solid solutions. In the system Zn-DMOF-TMx, Zn2[(bdc)2–2x(TM-bdc)2x][dabco], the introduction of increasing amounts of TM-bdc, with four methyl groups decorating the benzene dicarboxylate linker, leads to a smooth transition from negative to positive thermal expansion in the a–b plane of this tetragonal material. The temperature at which zero thermal expansion occurs evolves from ∼186 K for the Zn-DMOF parent structure (x = 0) to ∼325 K for Zn-DMOF-TM (x = 1.0). The formation of mixed linker solid solutions is likely a general strategy for the control of thermal expansion in MOFs and its prospects are also discussed. Finally, Chapter 7 expands upon the recent discovery of a new class of hybrid ReO3-type fluoride perovskites that contain a neutral molecule (He) in the perovskite A-site. These experiments involve taking a prototypical NTE metal fluoride, ScF3, and exposing it to high pressure helium at high temperature. The pore aperture and activation barriers for diffusion are compared to that of the first known hybrid fluoride perovskite with the formula [He]CaZrF6. Evidence for the inclusion of He in ScF3 is reviewed and future directions for the project are discussed.Ph.D

Coffee and Caffeine Ingestion Have Little Effect on Repeated Sprint Cycling in Relatively Untrained Males

The present study investigated the effect of ingesting caffeine-dose-matched anhydrous caffeine or coffee on the performance of repeated sprints. Twelve recreationally active males (mean ± SD age: 22 ± 2 years, height: 1.78 ± 0.07 m, body mass: 81 ± 16 kg) completed eighteen 4 s sprints with 116 s recovery on a cycle ergometer on four separate occasions in a double-blind, randomised, counterbalanced crossover design. Participants ingested either 3 mg·kg−1 of caffeine (CAF), 0.09 g·kg−1 coffee, which provided 3 mg·kg−1 of caffeine (COF), a taste-matched placebo beverage (PLA), or a control condition (CON) 45 min prior to commencing the exercise protocol. Peak and mean power output and rating of perceived exertion (RPE) were recorded for each sprint. There were no significant differences in peak power output (CAF: 949 ± 199 W, COF: 949 ± 174 W, PLA: 971 ± 149 W and CON: 975 ± 170 W; p = 0.872; η P 2 = 0.02) or mean power output (CAF: 873 ± 172 W, COF: 862 ± 44 W, PLA: 887 ± 119 W and CON: 892 ± 143 W; p = 0.819; η P 2 = 0.03) between experimental conditions. Mean RPE was similar for all trials (CAF: 11 ± 2, COF: 11 ± 2, PLA: 11 ± 2 and CON: 11 ± 2; p = 0.927; η P 2 = 0.01). Neither the ingestion of COF or CAF improved repeated sprint cycling performance in relatively untrained males

Communicating new knowledge on previously reported genetic variants

Genetic tests often identify variants whose significance cannot be determined at the time they are reported. In many situations, it is critical that clinicians be informed when new information emerges on these variants. It is already extremely challenging for laboratories to provide these updates. These challenges will grow rapidly as an increasing number of clinical genetic tests are ordered and as the amount of patient DNA assayed per test expands; the challenges will need to be addressed before whole-genome sequencing is used on a widespread basis. Information technology infrastructure can be useful in this context. We have deployed an infrastructure enabling clinicians to receive knowledge updates when a laboratory changes the classification of a variant. We have gathered statistics from this deployment regarding the frequency of both variant classification changes and the effects of these classification changes on patients. We report on the system's functionality as well as the statistics derived from its use. Genet Med 2012:14(8):713–71

Racial Residential Segregation and Race Differences in Ideal Cardiovascular Health among Young Men

Background: Race disparities in cardiovascular disease (CVD) related morbidity and mortality are evident among men. While previous studies show health in young adulthood and racial residential segregation (RRS) are important factors for CVD risk, these factors have not been widely studied in male populations. We sought to examine race differences in ideal cardiovascular health (CVH) among young men (ages 24–34) and whether RRS influenced this association. Methods: We used cross-sectional data from young men who participated in Wave IV (2008) of the National Longitudinal Survey of Adolescent to Adult Health (N = 5080). The dichotomous outcome, achieving ideal CVH, was defined as having ≥4 of the American Heart Association’s Life’s Simple 7 targets. Race (Black/White) and RRS (proportion of White residents in census tract) were the independent variables. Descriptive and multivariate analyses were conducted. Results: Young Black men had lower odds of achieving ideal CVH (OR = 0.67, 95% CI = 0.49, 0.92) than young White men. However, RRS did not have a significant effect on race differences in ideal CVH until the proportion of White residents was ≥55%. Conclusions: Among young Black and White men, RRS is an important factor to consider when seeking to understand CVH and reduce future cardiovascular risk