Local Volume Effects in the Generalized Pseudopotential Theory

The generalized pseudopotential theory (GPT) is a powerful method for deriving real-space transferable interatomic potentials. Using a coarse-grained electronic structure, one can explicitly calculate the pair ion-ion and multi-ion interactions in simple and transition metals. Whilst successful in determining bulk properties, in central force metals the GPT fails to describe crystal defects for which there is a significant local volume change. A previous paper [PhysRevLett.66.3036 (1991)] found that by allowing the GPT total energy to depend upon some spatially-averaged local electron density, the energetics of vacancies and surfaces could be calculated within experimental ranges. In this paper, we develop the formalism further by explicitly calculating the forces and stress tensor associated with this total energy. We call this scheme the adaptive GPT (aGPT) and it is capable of both molecular dynamics and molecular statics. We apply the aGPT to vacancy formation and divacancy binding in hcp Mg and also calculate the local electron density corrections to the bulk elastic constants and phonon dispersion for which there is refinement over the baseline GPT treatment.Comment: 11 pages, 6 figure

Living with Living History: The Impact of Old Salem Museums and Gardens on the Quality of Life in Winston-Salem, North Carolina

History museums serve an important role in most communities throughout the United States as repositories of heritage and educational institutions. However, many museums neglect to consider the impact of the services they provide, especially in a holistic manner. Contemporary museum management demands better self-assessment tool than those currently in vogue. As museums struggle to survive in the twenty-first century, museum impact analysis is imperative to demonstrate their value to the communities they serve. This thesis tests the suitability of quality of life metrics for holistic evaluation of museum impacts. To do so, a pilot study was conducted at Old Salem Museums and Gardens (OSMG), an open-air living history museum located in Winston-Salem, North Carolina. OSMG demonstrates the adaptability of quality of life methods to evaluate the intricacies of the site and museum contributions to citizen well-being. Through this analysis of education, community, economic and physical character indicators, OSMG is informed to make more sustainable decisions and better demonstrate their value to the community of Winston-Salem. This thesis provides museum practitioners with an objective quality of life framework to measure museum impacts on the communities in which they are located

A GSD ESTIMATION OF THE RELATIVE WORTH OF COVER CROPS IN COTTON PRODUCTION SYSTEMS

Cover crops can help reduce the negative environmental impacts of cotton production. Using time series yield data, this study utilizes generalized stochastic dominance to evaluate the relative worth, via risk premiums, of three cover crop and two conventional production systems based on expected net returns of each system and decision maker risk attitude. Results indicate, within the limitation of the study, two cover crop regimes possess a high degree of dominance over conventional systems. Determination of the dominant regime depends upon the risk attitude of a specific decision maker. This research suggests cover crop production systems may be feasible alternatives to conventional practices.Crop Production/Industries, Environmental Economics and Policy,

Growth of Cowdria ruminantium, the causative agent of heartwater, in a tick cell line

The tick-borne rickettsia Cowdria ruminantium has been propagated continuously for over 500 days in the Ixodes scapularis tick cell line IDE8 by using the Gardel isolate from bovine endothelial cells as an inoculum. Infection of the tick cells was confirmed by PCR, karyotyping, electron microscopy, and reinfection of bovine cells

H ingestion into He-burning convection zones in super-AGB stellar models as a potential site for intermediate neutron-density nucleosynthesis

We investigate the evolution of super-AGB (SAGB) thermal pulse (TP) stars for a range of metallicities (Z) and explore the effect of convective boundary mixing (CBM). With decreasing metallicity and evolution along the TP phase, the He-shell flash and the third dredge-up (TDU) occur closer together in time. After some time (depending upon the CBM parametrization), efficient TDU begins while the pulse-driven convection zone (PDCZ) is still present, causing a convective exchange of material between the PDCZ and the convective envelope. This results in the ingestion of protons into the convective He-burning pulse. Even small amounts of CBM encourage the interaction of the convection zones leading to transport of protons from the convective envelope into the He layer. H-burning luminosities exceed 10⁹ (in some cases 10¹⁰) L⊙. We also calculate models of dredge-out in the most massive SAGB stars and show that the dredge-out phenomenon is another likely site of convective-reactive H-¹²C combustion. We discuss the substantial uncertainties of stellar evolution models under these conditions. Nevertheless, the simulations suggest that in the convective-reactive H-combustion regime of H ingestion the star may encounter conditions for the intermediate neutron capture process (i-process). We speculate that some CEMP-s/r stars could originate in i-process conditions in the H ingestion phases of low-Z SAGB stars. This scenario would however suggest a very low electron-capture supernova rate from SAGB stars. We also simulate potential outbursts triggered by such H ingestion events, present their light curves and briefly discuss their transient properties

In or out? Barriers and facilitators to refugee-background young people accessing mental health services

Refugee young people have been identified as a group with high risk for mental health problems, due to their experience of trauma, forced migration, and stressors associated with settlement. A high prevalence of mental health problems is reported in this group, however some research suggests refugee young people have low rates of mental health service access. There is little information available on barriers and facilitators to mental service delivery for this group. Using data from 15 focus groups and five key informant interviews with a total of 115 service providers from 12 agencies in Melbourne, Australia, this paper explores barriers and facilitators to engaging young people from refugee backgrounds with mental health services. Eight key themes emerged: cultural concepts of mental health, illness, and treatment; service accessibility; trust; working with interpreters; engaging family and community; the style and approach of mental health providers; advocacy; and continuity of care

Global Journalist: Covering two deadly viruses

On this April 22, 2020 program, interviewees discussed the reporting on the Zika virus and COVID-19. They also discussed the relationship between the press and public health officials when reporting on pandemics and epidemics. Host: Isabella Paxton. Guests: Donald G. McNeil Jr., Lynelle Phillips. Producers: Brendan Hall, Katharine Finnerty, Regan Mertz, Hannah France, Margo Wagner, Tom Kavanaugh, Jacob Faber, Caitlin King

Electronic structure and total energy of interstitial hydrogen in iron: Tight binding models

An application of the tight binding approximation is presented for the description of electronic structure and interatomic force in magnetic iron, both pure and containing hydrogen impurities. We assess the simple canonical d-band description in comparison to a non orthogonal model including s and d bands. The transferability of our models is tested against known properties including the segregation energies of hydrogen to vacancies and to surfaces of iron. In many cases agreement is remarkably good, opening up the way to quantum mechanical atomistic simulation of the effects of hydrogen on mechanical properties

Phoretic Motion of Spheroidal Particles Due To Self-Generated Solute Gradients

We study theoretically the phoretic motion of a spheroidal particle, which generates solute gradients in the surrounding unbounded solvent via chemical reactions active on its surface in a cap-like region centered at one of the poles of the particle. We derive, within the constraints of the mapping to classical diffusio-phoresis, an analytical expression for the phoretic velocity of such an object. This allows us to analyze in detail the dependence of the velocity on the aspect ratio of the polar and the equatorial diameters of the particle and on the fraction of the particle surface contributing to the chemical reaction. The particular cases of a sphere and of an approximation for a needle-like particle, which are the most common shapes employed in experimental realizations of such self-propelled objects, are obtained from the general solution in the limits that the aspect ratio approaches one or becomes very large, respectively.Comment: 18 pages, 5 figures, to appear in European Physical Journal

An Undergraduate Laboratory Manual for Analyzing a CRISPR Mutant with a Predicted Role in Regeneration

Exposing students to undergraduate research has reportedly improved students’ development of knowledge and skills in the laboratory, self-efficacy, satisfaction with their research, retention, and perseverance when faced with obstacles. Furthermore, utilizing authentic course-based undergraduate research experiences (CUREs) includes all students enrolled in the class, giving those who may not otherwise have access to an independent undergraduate research project an opportunity to engage in the scientific process in context of an original, unanswered question. In the fall of 2016, second semester introductory biology students conducted a semester-long research project on the transcription factor Lin28a to determine the effect of Lin28a on regeneration in a CRISPR mutant. During ten laboratory periods, students completed four experiments: 1) genotyping mutants by PCR and RFLP, 2) neuromast regeneration after copper sulfate treatment, 3) measuring changes in gene expression by RT-PCR after fin clipping, and 4) swimming behavior. In the context of this class, students were challenged to design their own experiments, interpret their own data, and make connections among the experiments to draft a final paper presenting their results and conclusions. Here, we present a student laboratory manual that can be adapted to other relevant CRISPR mutants. Overall, this coursework aligns with Vision and Change, and these experiments gave students a taste of the questions, techniques, and experimental design currently used in the field of regenerative biology