Radiation effects on silver and zinc battery electrodes. V Interim report, Apr. - Jul. 1966

Gamma radiation effects determined on silver and zinc battery electrodes and silver-cadmium cell

Effects of high-energy protons on selected cells Final report, Jun. 1966 - Aug. 1966

Irradiation effects of high energy protons studied on silver-cadmium and nickel-cadmium cells containing battery electrodes and potassium hydroxide electrolyte

An Analysis of the Quasicontinuum Method

The aim of this paper is to present a streamlined and fully three-dimensional version of the quasicontinuum (QC) theory of Tadmor et al. and to analyze its accuracy and convergence characteristics. Specifically, we assess the effect of the summation rules on accuracy; we determine the rate of convergence of the method in the presence of strong singularities, such as point loads; and we assess the effect of the refinement tolerance, which controls the rate at which new nodes are inserted in the model, on the development of dislocation microstructures.Comment: 30 pages, 16 figures. To appear in Jornal of the Mechanics and Physics of Solid

Evolutionary relationships in Panicoid grasses based on plastome phylogenomics (Panicoideae; Poaceae)

Background: Panicoideae are the second largest subfamily in Poaceae (grass family), with 212 genera and approximately 3316 species. Previous studies have begun to reveal relationships within the subfamily, but largely lack resolution and/or robust support for certain tribal and subtribal groups. This study aims to resolve these relationships, as well as characterize a putative mitochondrial insert in one linage. Results: 35 newly sequenced Panicoideae plastomes were combined in a phylogenomic study with 37 other species: 15 Panicoideae and 22 from outgroups. A robust Panicoideae topology largely congruent with previous studies was obtained, but with some incongruences with previously reported subtribal relationships. A mitochondrial DNA (mtDNA) to plastid DNA (ptDNA) transfer was discovered in the Paspalum lineage. Conclusions: The phylogenomic analysis returned a topology that largely supports previous studies. Five previously recognized subtribes appear on the topology to be non-monophyletic. Additionally, evidence for mtDNA to ptDNA transfer was identified in both Paspalum fimbriatum and P. dilatatum, and suggests a single rare event that took place in a common progenitor. Finally, the framework from this study can guide larger whole plastome sampling to discern the relationships in Cyperochloeae, Steyermarkochloeae, Gynerieae, and other incertae sedis taxa that are weakly supported or unresolved.Fil: Burke, Sean V.. Northern Illinois University; Estados UnidosFil: Wysocki, William P.. Northern Illinois University; Estados UnidosFil: Zuloaga, Fernando Omar. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Botánica Darwinion. Academia Nacional de Ciencias Exactas, Físicas y Naturales. Instituto de Botánica Darwinion; ArgentinaFil: Craine, Joseph M.. Jonah Ventures; Estados UnidosFil: Pires, J. Chris. University of Missouri; Estados UnidosFil: Edger, Patrick P.. Michigan State University; Estados UnidosFil: Mayfield Jones, Dustin. Donald Danforth Plant Science Center; Estados UnidosFil: Clark, Lynn G.. Iowa State University; Estados UnidosFil: Kelchner, Scot A.. University of Idaho; Estados UnidosFil: Duvall, Melvin R.. Northern Illinois University; Estados Unido

The status of alien bamboos in South Africa

CITATION: Canavan, S. et al. 2021. The status of alien bamboos in South Africa. South African Journal of Botany, 138:33-40. doi:10.1016/j.sajb.2020.11.027.The original publication is available at https://www.sciencedirect.com/journal/south-african-journal-of-botanyThe growing interest in commercial cultivation of bamboos (Poaceae subfamily Bambusoideae) has led to the introduction of new alien species into South Africa. The rate at which bamboos are being planted in South Africa is a cause for concern because of the impacts of bamboo invasions in other parts of the world. To understand the risks associated with new introductions and new plantings, we assess the outcomes of past introductions of bamboos into South Africa. To this end we: (1) produce an inventory of alien bamboo taxa; (2) assess the distribution of bamboos; (3) determine the rate of spread of bamboo at a site with a high density of naturalised stands; and (4) evaluate the current regulatory status of alien bamboos in South Africa. We used a combination of expert opinion, literature, historical records of populations, and public participation to produce a species list and locate populations of alien bamboos. We also attempted to confirm species identities using DNA barcoding. We found that 28 currently-accepted species of bamboo have been recorded in South Africa. However, we have little confidence in this estimate, as 20 of the species could not be confirmed or identified as present in the country. Bamboos are an inherently challenging group to identify using vegetative material, and DNA barcoding was inconclusive. The distribution of bamboos across the country varied with the type or lineage (e.g. herbaceous, tropical or temperate) and the source of information (e.g. herbarium records, in-field observation or public contribution). Although alien bamboos are naturalised at several sites, we found no large invasive stands nor evidence of widespread negative environmental impacts. Nonetheless, we recommend caution regarding future introductions of bamboos for commercial cultivation, as the nature of the plantings will likely differ from the historical situation in both the location, configuration, and the scale of cultivation, and as new species are likely to be introduced. We propose several changes to the current listing of bamboo taxa in national legislation pertaining to alien and invasive species.https://www.sciencedirect.com/science/article/pii/S0254629920311868?via%3DihubPublisher’s versio

Three-dimensional molecular dynamics simulations of void coalescence during dynamic fracture of ductile metals

Void coalescence and interaction in dynamic fracture of ductile metals have been investigated using three-dimensional strain-controlled multi-million atom molecular dynamics simulations of copper. The correlated growth of two voids during the coalescence process leading to fracture is investigated, both in terms of its onset and the ensuing dynamical interactions. Void interactions are quantified through the rate of reduction of the distance between the voids, through the correlated directional growth of the voids, and through correlated shape evolution of the voids. The critical inter-void ligament distance marking the onset of coalescence is shown to be approximately one void radius based on the quantification measurements used, independent of the initial separation distance between the voids and the strain-rate of the expansion of the system. The interaction of the voids is not reflected in the volumetric asymptotic growth rate of the voids, as demonstrated here. Finally, the practice of using a single void and periodic boundary conditions to study coalescence is examined critically and shown to produce results markedly different than the coalescence of a pair of isolated voids.Comment: Accepted for publication in Physical Review

Prosthetic Knee

Amputations, specifically lower limb amputations, are common in Sub Saharan Africa and across the broader global community largely due to infection and disease. Our project, The Prosthetic Knee Team, partners with the orthopedic workshop at the CURE International Hospital in Kijabe, Kenya to create a prosthetic knee design for a specific type of amputation known as a Knee Disarticulation (also called through-knee). Currently, the orthopedic workshop is only able to provide one very expensive prosthetic knee option for these patients, and they often elect to undergo a second surgery, a trans-femoral amputation, because the cost of the second surgery and trans-femoral prosthesis combined is less than the currently available through-knee prosthetic. The goal of our project is to provide the orthopedic workshop with a manufacturable prosthetic knee design that provides through-knee amputees with a cheaper prosthetic option and removes the need to have a second amputation above the knee. Throughout the past two semesters, our focus was on organizing collected data, researching knee-disarticulations, and communicating with our client to more fully understand the scope of our project. After determining that moving forward our project will be manufacturing the prosthetic knees at Messiah College’s machine shop and shipping them to CURE Kenya to be fit on patients, we began to brainstorm potential design ideas. We are presently working on modifying and improving our chosen design to best meet all of the specifications laid out by our partner. Those specifications include minimized thigh-lengthening, low weight, maximized stability and durability, and aesthetically pleasing.https://mosaic.messiah.edu/engr2020/1017/thumbnail.jp

Neuroanatomic Predictors to Prodromal Psychosis in Velocardiofacial Syndrome (22q11.2 Deletion Syndrome): A Longitudinal Study

Background: Up to 30% of young adults with velocardiofacial syndrome (VCFS; 22q11.2 deletion syndrome) develop schizophrenia or psychosis. Identifying the neuroanatomic trajectories that increase risk for psychosis in youth with this genetic disorder is of great interest. Methods: We acquired high-resolution anatomic MR images and measures of psychiatric function on 72 youth with VCFS, 26 unaffected siblings and 24 age-matched community controls at two timepoints, between late childhood (mean age, 11.9 years) and mid-adolescence (mean age, 15.1 years). Results: With the exception of cranial gray matter and orbitofrontal prefrontal cortex, neuroanatomic trajectories in youth with VCFS were comparable to unaffected siblings and community controls during this developmental window. However, in youth with VCFS, longitudinal decreases in the volumes of cranial gray and white matter, prefrontal cortex, mesial temporal lobe, and cerebellum were associated with increased combined prodromal symptoms at Time 2. In contrast, only decreases in temporal lobe gray matter volumes (p \u3c .002) and verbal IQ (p \u3c .002) predicted specifically to positive prodromal symptoms of psychosis at Time 2. Conclusions: These findings are in line with studies of non-VCFS individuals at risk for schizophrenia, and suggest that early decrements in temporal lobe gray matter may be predictive of increased risk of prodromal psychotic symptoms in youth with VCFS

Simulations of energetic beam deposition: from picoseconds to seconds

We present a new method for simulating crystal growth by energetic beam deposition. The method combines a Kinetic Monte-Carlo simulation for the thermal surface diffusion with a small scale molecular dynamics simulation of every single deposition event. We have implemented the method using the effective medium theory as a model potential for the atomic interactions, and present simulations for Ag/Ag(111) and Pt/Pt(111) for incoming energies up to 35 eV. The method is capable of following the growth of several monolayers at realistic growth rates of 1 monolayer per second, correctly accounting for both energy-induced atomic mobility and thermal surface diffusion. We find that the energy influences island and step densities and can induce layer-by-layer growth. We find an optimal energy for layer-by-layer growth (25 eV for Ag), which correlates with where the net impact-induced downward interlayer transport is at a maximum. A high step density is needed for energy induced layer-by-layer growth, hence the effect dies away at increased temperatures, where thermal surface diffusion reduces the step density. As part of the development of the method, we present molecular dynamics simulations of single atom-surface collisions on flat parts of the surface and near straight steps, we identify microscopic mechanisms by which the energy influences the growth, and we discuss the nature of the energy-induced atomic mobility