Engineering the work function of armchair graphene nanoribbons using strain and surface functional species: a first principles study

First principles density-functional theory calculations were performed to study the effects of strain, edge passivation, and surface functional species on the structural and electronic properties of armchair graphene nanoribbons (AGNRs) with a particular focus on the work function. The work function was found to increase with uniaxial tensile strain while decreasing with compression. The variation of the work function under strain is primarily due to the shift of the Fermi energy with strain. In addition, the relationship between the work function variation and the core level shift with strain is discussed. Distinct trends of the core level shift under tensile and compressive strain were discovered. For AGNRs with the edge carbon atoms passivated by oxygen, the work function is higher than for nanoribbons with the edge passivated by hydrogen under a moderate strain. The difference between the work functions in these two edge passivations is enlarged (reduced) under a sufficient tensile (compressive) strain. This has been correlated to a direct-indirect band gap transition for tensile strains of about 4% and to a structural transformation for large compressive strains at about -12%. Furthermore, the effect of the surface species decoration, such as H, F, or OH with different covering density, was investigated. It was found that the work function varies with the type and coverage of surface functional species. F and OH decoration increase the work function while H decreases it. The surface functional species were decorated on either one side or both sides of AGNRs. The difference in the work functions between one-side and two-side decorations was found to be relatively small, which may suggest an introduced surface dipole plays a minor role.Comment: 10 pages, 9 figures, and 1 tabl

Engineering direct-indirect band gap transition in wurtzite GaAs nanowires through size and uniaxial strain

Electronic structures of wurtzite GaAs nanowires in the [0001] direction were studied using first-principles calculations. It was found that the band gap of GaAs nanowires experience a direct-to-indirect transition when the diameter of the nanowires is smaller than ~28 {\AA}. For those thin GaAs nanowires with an indirect band gap, it was found that the gap can be tuned to be direct if a moderate external uniaxial strain is applied. Both tensile and compressive strain can trigger the indirect-to-direct gap transition. The critical strains for the gap-transition are determined by the energy crossover of two states in conduction bands.Comment: 4 pages, 4 figure

Gene profiling of maternal hepatic adaptations to pregnancy

BACKGROUND: Maternal metabolic demands change dramatically during the course of gestation and must be co-ordinated with the needs of the developing placenta and fetus. The liver is critically involved in metabolism and other important functions. However, maternal hepatic adjustments to pregnancy are poorly understood. AIM: The aim of the study was to evaluate the influences of pregnancy on the maternal liver growth and gene expression profile. METHODS: Holtzman Sprague-Dawley rats were mated and sacrificed at various stages of gestation and post-partum. The maternal livers were analysed in gravimetric response, DNA content by PicoGreen dsDNA quantitation reagent, hepatocyte ploidy by flow cytometry and hepatocyte proliferation by ki-67 immunostaining. Gene expression profiling of non-pregnant and gestation d18.5 maternal hepatic tissue was analysed using a DNA microarray approach and partially verified by northern blot or quantitative real-time PCR analysis. RESULTS: During pregnancy, the liver exhibited approximately an 80% increase in size, proportional to the increase in body weight of the pregnant animals. The pregnancy-induced hepatomegaly was a physiological event of liver growth manifested by increases in maternal hepatic DNA content and hepatocyte proliferation. Pregnancy did not affect hepatocyte polyploidization. Pregnancy-dependent changes in hepatic expression were noted for a number of genes, including those associated with cell proliferation, cytokine signalling, liver regeneration and metabolism. CONCLUSIONS: The metabolic demands of pregnancy cause marked adjustments in maternal liver physiology. Central to these adjustments are an expansion in hepatic capacity and changes in hepatic gene expression. Our findings provide insights into pregnancy-dependent hepatic adaptations

Torts—Gross Negligence Under the Guest Statute

The first definitive interpretation of gross negligence within the meaning of the 1957 amendment to the Host-Guest Statute has been given by the Washington court in the case of Crowley v. Barto

Branching of the Falkner-Skan solutions for λ < 0

The Falkner-Skan equation f'" + ff" + λ(1 - f'^2) = 0, f(0) = f'(0) = 0, is discussed for λ < 0. Two types of problems, one with f'(∞) = 1 and another with f'(∞) = -1, are considered. For λ = 0- a close relation between these two types is found. For λ < -1 both types of problem allow multiple solutions which may be distinguished by an integer N denoting the number of zeros of f' - 1. The numerical results indicate that the solution branches with f'(∞) = 1 and those with f'(∞) = -1 tend towards a common limit curve as N increases indefinitely. Finally a periodic solution, existing for λ < -1, is presented.

Charting our Course: A Review of Stephen Andrew’s Searching for an Autoethnographic Ethic

This review critiques Stephen Andrew’s proposed method for applying ethical guidelines to autoethnographic research. Andrew argues that although extant autoethnographic literature attends to a variety of ethical considerations (i.e., relational ethics, reflexivity in research, tools for ethical writing), explicit analytical guidelines are lacking. Using excerpts from personal autoethnographies, Andrew illustrates his conception for an autoethnographic ethic leaving readers with practical tools and resonant narratives

Attraction and Adherence of Senior Adults to Exercise Programs

Older adults commonly hope to remain healthy and live independently until death. Lack of regular, sustained physical exercise results in a decline in physical functioning, impacting the elderly’s ability to perform activities needed for daily living. Previous research explored factors leading to attraction and adherence to senior exercise programs; however, few studies prioritize them. This study’s purpose was to better understand, via a prioritized list, what attracts and promotes adherence to physical exercise programs at the Treasure Valley (Boise, Idaho) YMCA. Study data collected will improve the YMCA’s ability to engage with seniors and better serve and improve community health

Chemical Tuning Enhances Both Potency Toward Nrf2 and In Vitro Therapeutic Index of Triterpenoids

The transcription factor Nrf2 protects against a number of experimental pathologies, and is a promising therapeutic target. The clinical investigation of a potent Nrf2-inducing agent, the triterpenoid (TP) bardoxolone methyl (BARD), was recently halted due to adverse cardiovascular events in chronic kidney disease patients, although the underlying mechanisms are yet to be resolved. The majority of small molecule Nrf2 inducers are electrophilic and trigger Nrf2 accumulation via the chemical modification of its redox-sensitive repressor Keap1. Therefore, it is pertinent to question whether the therapeutic targeting of Nrf2 could be hindered in many cases by the inherent reactivity of a small molecule inducer toward unintended cellular targets, a key mechanism of drug toxicity. Using H4IIE-ARE8L hepatoma cells, we have examined the relationship between (a) Nrf2 induction potency, (b) toxicity and (c) in vitro therapeutic index (ratio of b:a) for BARD and a number of other small molecule activators of Nrf2. We show that BARD exhibits the highest potency toward Nrf2 and the largest in vitro therapeutic index among compounds that have been investigated clinically (namely BARD, sulforaphane and dimethylfumarate). Through further examination of structurally related TPs, we demonstrate that an increase in potency toward Nrf2 is associated with a relatively smaller increase in toxicity, indicating that medicinal chemistry can be used to enhance the specificity of a compound as an inducer of Nrf2 signaling whilst simultaneously increasing its therapeutic index. These findings will inform the continuing design and development of drugs targeting Nrf