Leading correction to the local density approximation for exchange in large-ZZ atoms

The large-$Z$ asymptotic expansion of atomic exchange energies has been useful in determining exact conditions for corrections to the local density approximation in density functional theory. We find that the necessary correction is fit well with a leading $Z \ln Z$ term, and find its coefficient numerically. The gradient expansion approximation also displays such a term, but with a substantially smaller coefficient. Analytic results in the limit of vanishing interaction with hydrogenic orbitals (a Bohr atom) are given, leading to the conjecture that the true coefficients for all atoms are precisely 2.7 times larger than their gradient expansion counterpart. Combined with the hydrogen atom result, this yields an analytic expression for the exchange-energy correction which is accurate to $\sim 5\%$ for all $Z$.Comment: 7 pages, 3 figure

Investigations of the exchange energy of neutral atoms in the large-Z limit

The non-relativistic large-$Z$ expansion of the exchange energy of neutral atoms provides an important input to modern non-empirical density functional approximations. Recent works report results of fitting the terms beyond the dominant term, given by the local density approximation (LDA), leading to an anomalous ZlnZ term that can not be predicted from naive scaling arguments. Here, we provide much more detailed data analysis of the mostly smooth asymptotic trend describing the difference between exact and LDA exchange energy, the nature of oscillations across rows of the periodic table, and the behavior of the LDA contribution itself. Special emphasis is given to the successes and difficulties in reproducing the exchange energy and its asymptotics with existing density functional approximations.Comment: 15 pages 11 figures + 4 pages supplemental informatio

Modeling the Treatment of Glioblastoma Multiforme and Cancer Stem Cells with Ordinary Differential Equations

Despite improvements in cancer therapy and treatments, tumor recurrence is a common event in cancer patients. One explanation of recurrence is that cancer therapy focuses on treatment of tumor cells and does not eradicate cancer stem cells (CSCs). CSCs are postulated to behave similar to normal stem cells in that their role is to maintain homeostasis. That is, when the population of tumor cells is reduced or depleted by treatment, CSCs will repopulate the tumor, causing recurrence. In this paper, we study the application of the CSC Hypothesis to the treatment of glioblastoma multiforme by immunotherapy. We extend the work of Kogan et al. (2008) to incorporate the dynamics of CSCs, prove the existence of a recurrence state, and provide an analysis of possible cancerous states and their dependence on treatment levels

Media Portrayal of GM Science and Citrus Greening in State and National Newspapers

Huanglongbing (HLB), commonly known as citrus greening, is a bacterial disease severely affecting the profitability and continuation of the citrus industry in Florida and is threatening the citrus industry in other states as well. Currently, the disease only can be managed, not cured. Gene-based therapies, such as GM science, have been identified as a viable long-term solution. However, consumer acceptance of genetically modified food is low and their understanding and acceptance of new technologies is largely dependent on what they receive through mass media. Therefore, the purpose of this research is to understand news coverage of both citrus greening and gene modification science. This content analysis studied news articles of either citrus greening or gene modification science in national and state-specific newspapers and identified that while citrus greening is not highly covered by newspapers, it is accurately described via appropriate terminology. Genetic modification science is more commonly a topic of news coverage and is somewhat neutral and balanced in coverage. This research shows that source use in media coverage of gene modification science is balanced, but sources are most commonly chosen from organizations with a directed opinion or position on the topic

The Effects of Caffeine on Jumping Performance and Maximal Strength in Female Collegiate Athletes

Introduction: Caffeine has long been used to enhance athletic performance. The research regarding caffeine’s effects on strength and power performance is lacking, especially in female athletes. Purpose: To analyze the acute effects of caffeine on jumping performance and maximal strength in female collegiate athletes. Methods: Eight female collegiate athletes performed two testing sessions separated by one week. Using a double-blind approach, athletes randomly received 6 mg/kg of body mass of caffeine (CAF) or a placebo (PLA). Following 60min of quiet sitting and a standardized warm-up, athletes were tested on measures of squat jump height (SJH) and peak power (SJPP), countermovement jump height (CMJH) and peak power (CMJPP), and isometric mid-thigh pull peak force (IPF) and rate of force development (RFD) on force platforms. Heart rate, systolic blood pressure, diastolic blood pressure, and tympanic temperature were measured at three time points across the testing session. A paired samples t-test with Hedge’s g effect size was used to compare performance results between conditions. A 2 x 3 (condition x time) repeated measures ANOVA was used to analyze changes in physiological measures between and within conditions. Alpha level for all analyses was set at pResults: There were small to moderate differences in SJH (p=0.08, g=0.26), SJPP (p=0.03, g=0.63), CMJH (p=0.004, g=0.27), CMJPP (p=0.18, g=0.20), IPF (p=0.08, g=0.25), and RFD (p=0.22, g=0.40) in favor of caffeine over placebo. Physiological measurements increased similarly across time for both conditions with the exception of SBP, which was greater following caffeine 3 administration compared to placebo (p=0.02). Conclusions: Caffeine ingestion produced small to moderate improvements in jumping performance; however, caffeine failed to significantly affect maximal strength when compared with the placebo. Nonetheless, there was a small increase in IPF and RFD compared to placebo. Therefore, caffeine appears to be an effective ergogenic aid when used to enhance jumping performance and possibly maximal strength in female collegiate athletes

Cognitive Ability, Cognitive Aging, and Debt Accumulation

In the past few decades, financial products target to consumers have become increasingly complex and recent evidence suggests that older adults are entering retirement with more debt than previous generations. We examine how cognitive ability is related to debt burdens among older adults and whether this relationship has changed over time with the increasingly complex financial landscape. Using data from the Health and Retirement Study spanning 1998 to 2014, we find that cognitive ability is an important predictor of debt burdens in older age and that, in more complex financial environments, individuals with higher cognitive ability have taken on higher debt levels than individuals with lower cognitive ability. In a complementary analysis using data from 2015 to 2019 drawn from the Understanding America Study, we find similar results and evidence that the relationship between cognitive ability and debt exposure is driven by financial sophistication. Our findings are broadly inconsistent with financial intermediaries pushing increasingly complicated financial products onto unsophisticated borrowers. However, we find that even higher cognitive ability individuals may have difficulty managing their debt burdens in more complex environments – they hold less total wealth, less liquid wealth, and are more likely to have debt levels that exceed half their assets than their counterparts prior to the expansion in complexity. All told, we find that individuals with higher cognitive ability disproportionately increased their debt burdens during the increase in financial product complexity, and that subsequently they were more financially fragile than similar individuals in previous cohorts.U.S. Social Security Administration, RDR18000002-02, UM20-11http://deepblue.lib.umich.edu/bitstream/2027.42/168222/1/wp411.pdfDescription of wp411.pdf : working paperSEL