Pistons modeled by potentials

In this article we consider a piston modelled by a potential in the presence of extra dimensions. We analyze the functional determinant and the Casimir effect for this configuration. In order to compute the determinant and Casimir force we employ the zeta function scheme. Essentially, the computation reduces to the analysis of the zeta function associated with a scalar field living on an interval $[0,L]$ in a background potential. Although, as a model for a piston, it seems reasonable to assume a potential having compact support within $[0,L]$, we provide a formalism that can be applied to any sufficiently smooth potential.Comment: 10 pages, LaTeX. A typo in eq. (3.5) has been corrected. In "Cosmology, Quantum Vacuum and Zeta Functions: In Honour of Emilio Elizalde", Eds. S.D. Odintsov, D. Saez-Gomez, and S. Xambo-Descamps. (Springer 2011) pp 31

Molecular profiling of bark beetle mycobiota

No organism evolves in isolation; the symbiotic microorganisms associated with insects are key determinants of their hosts ecology and evolution. This thesis investigates the fungal communities found with bark and ambrosia beetles (Curculionidae: Scolytinae & Platypodinae) in an attempt to better understand the diversity and variability of this ecologically and economically important system. I start by assessing the efficacy of high throughput sequencing (HTS) and metabarcoding for the characterisation of fungal communities derived from whole arthropod DNA extracts (Chapter 2). I then apply this approach to understanding the biotic and abiotic determinants of beetle associated fungal taxa, and find that both beetle species identity and environmental conditions significantly predict community richness and composition (Chapter 3). In Chapter 4, I expand upon the beetle species level differences in microbial communities to show that they are driven by a relatively small subset of fungal taxa, predominantly belonging to the beetle associated Microascales, but also to the relatively unexplored Saccharomycetes. I further apply HTS to the recreation of beetle evolutionary histories using mitochondrial genomics, and test for correlations between beetle phylogenetic and mycobiotic similarities (Chapter 5). My investigations demonstrate the utility of recently developed sequencing technologies to the study of microbial symbioses and I conclude with a synthetic summary of my findings with suggestions for further research.Open Acces

Iatrogenic Electrocautery Damage and Cellular-Based Corrosion of Total Joint Arthroplasty Biomaterials

Introduction. The number of patients undergoing a Primary Total Knee Arthroplasty (PTKA) has been increasing steadily each year. Of those PTKA patients, 20% report long-term pain and/or some functional deficit. Cobalt-Chromium-Molybdenum (CoCrMo) alloy is one of the most used materials in Total Joint Arthroplasty (TJA) implants due the material’s high strength, high corrosion resistance, and biocompatibility. The release of metal ions and potential occurrence of metallosis in TJA has been shown to be detrimental to the longevity of the implant. The mechanisms leading to this increase in metal ion concentrations have been up for debate, with some believing it is caused by Electrocautery (EC) damage at the time of surgery and others believing it is caused by inflammatory cells attacking the implant surface. The purpose of this thesis is to identify to what degree Electrocautery damage can alter the implant surface and if inflammatory cells are able to alter the implant surface and ingest metal particles. Methodology. To better understand how EC damage can alter implant surfaces, three different types of femoral component bearing surfaces were selected and intentionally damaged in the operating room using the plasma arc from both monopolar (MP) (Bovie) and Bipolar (BP) (Aquamantys) sources. MP and BP EC damage was done at varying power levels using a 3-second hover method 3 mm from the implant surface. Scanning electron microscopy (SEM) (Zeiss, Oberkochen, Germany) was used to obtain a detailed microscopic analysis of the damaged areas. Energy-dispersive X-ray spectrometry (EDS) (Oxford, High Wycombe, UK) was utilized to assess the elements present in pits found in the corroded areas. Surface Topography was analyzed using a profilometer (DektakXT; Bruker, Tucson, AZ) in the central portion of the damaged area for each MP and BP energy setting. Each damaged area was evaluated with the aid of TalyMap (Mountains software; Digital Surf, Besançon, France) using ISO 4287 measurements for Arithmetic Average height (Ra), Kurtosis (Rk), Heighest Peak to Lowest Valley (Rz), and Skewness (Rsk). SEM, EDS, and Surface Topography were also used to look at undamaged areas of the implants. In a separate experiment, IC-21 ATCC murine peritoneal macrophages were cultured with RPMI 1640 growth medium of supplemented with 10% fetal bovine serum (FBS), L-glutamine, and gentamicin. Select groups of cells were then activated using Interferon Gamma (IFNγ) and Lipopolysaccharide (LPS). CoCrMo alloy disks were cut, polished, passivated, and placed into 96 well plates and a select number intentionally damaged in the operating room with a MP EC device. After the cells were allowed to attach to the surface for 24 hours, culture medium was replaced every 12 hours and supernatant fluid was collected every 4 days starting on the second day of the experiment. After 30 days, cells were removed from the surface, counted and digested. The metal concentrations found in the supernatant and digested cell mixture were assessed using inductively coupled plasma spectrometry (ICP-MS), conducted at Brooks Applied Labs (Bothwell, WA). Statistical analysis was conducted using SigmaPlot (Systat Software, Chicago, IL) and Microsoft Excel (Microsoft, Redmond, WA). Results. Surface Profilometry quantified the topographical changes due to the damage form the MP and BP EC devices. The median Ra and Rz measurements were larger for the BP damaged areas compared to the MP for all bearing surfaces. The Oxinium surface displayed the greatest increase in roughness parameters compared to the undamaged regions. The CoCr surface displayed the greatest Rsk for the BP damaged areas. The ZrN had the smallest differences in Rz and Ra for both MP and BP damage areas compared to undamaged areas. SEM imaging displayed pitting in the regions intentionally damage with a MP or BP EC device. Backscatter EDS analysis found significant changes in the elemental profile for the BP damage compared to the MP damage. Cellular corrosion of the CoCr disks was quantified by measuring the concentration of Co, Cr, and Mo in the supernatant fluid collected off of the culture over the course of the 30-day experiment. The Co supernatant concentration was higher in the Undamaged Disks with Activated Cells versus its control which contained medium with no cells. The Cr concentration was higher in the supernatant fluid of the EC Damaged Disks with Standard Cells versus its control which contained medium with no cells. Between experimental groups, higher concentrations of Co and Mo was found in the supernatant of the Undamaged Disks with Standard Cells versus the EC Damaged Disks with Standard Cells. There was also a higher Co supernatant metal concentration when comparing the Undamaged Disks with Activated Cells versus the EC Damaged Disks with Activated Cells. A higher Cr supernatant metal concentration was found in the EC Damaged Disks with Activated Cells versus the EC Damaged Disks with Standard Cells. Following the end of the 30-day experiment, cells were digested to determine their inner metal ion concentration. There was a significantly higher intracellular Co and Mo concentration in the Undamaged Disks with Activated Cells versus the Undamaged Disks with Standard Cells. As well as a higher intracellular Co concentration in the EC Damaged Disks with Activated Cells versus the EC Damaged Disks with Standard Cells. SEM imaging displayed microscopic pitting on the surface exposed to macrophages and EC damage. Backscatter EDS analysis found significant differences in the elemental concentration of Carbon, Oxygen, Iron and Nickel between the experimental groups. From the EDS Backscatter analysis, the disks with EC damage displayed a higher Fe/C ratio compared to the undamaged disks. Showing evidence that EC damage alters the chemical profile of the CoCr disk surface

Reconstructing the ecosystem context of a species: Honey-borne DNA reveals the roles of the honeybee

To assess a species’ impact on its environment–and the environment’s impact upon a species–we need to pinpoint its links to surrounding taxa. The honeybee (Apis mellifera) provides a promising model system for such an exercise. While pollination is an important ecosystem service, recent studies suggest that honeybees can also provide disservices. Developing a comprehensive understanding of the full suite of services and disservices that honeybees provide is a key priority for such a ubiquitous species. In this perspective paper, we propose that the DNA contents of honey can be used to establish the honeybee’s functional niche, as reflected by ecosystem services and disservices. Drawing upon previously published genomic data, we analysed the DNA found within 43 honey samples from Northern Europe. Based on metagenomic analysis, we find that the taxonomic composition of DNA is dominated by a low pathogenicity bee virus with 40.2% of the reads, followed by bacteria (16.7%), plants (9.4%) and only 1.1% from fungi. In terms of ecological roles of taxa associated with the bees or taxa in their environment, bee gut microbes dominate the honey DNA, with plants as the second most abundant group. A range of pathogens associated with plants, bees and other animals occur frequently, but with lower relative read abundance, across the samples. The associations found here reflect a versatile the honeybee’s role in the North-European ecosystem. Feeding on nectar and pollen, the honeybee interacts with plants–in particular with cultivated crops. In doing so, the honeybee appears to disperse common pathogens of plants, pollinators and other animals, but also microbes potentially protective of these pathogens. Thus, honey-borne DNA helps us define the honeybee’s functional niche, offering directions to expound the benefits and drawbacks of the associations to the honeybee itself and its interacting organisms

A dearth of data: fitting parasitoids into ecological networks

Studying parasitoids can provide insights into global diversity estimates, climate change impacts, and agroecosystem service provision. However, this potential remains largely untapped due to a lack of data on how parasitoids interact with other organisms. Ecological networks are a useful tool for studying and exploiting the impacts of parasitoids, but their construction is hindered by the magnitude of undescribed parasitoid species, a sparse knowledge of host ranges, and an under-representation of parasitoids within DNA-barcode databases (we estimate <5% have a barcode). Here, we advocate the use of DNA metabarcoding to construct the host-parasitoid component of multilayer networks. While the incorporation of parasitoids into network-based analyses has far ranging applications, we focus on its potential for assessing ecosystem service provision within agroecosystems

Writing autism inside-out autism and representation : a novel and critical essay.

M.A. University of KwaZulu-Natal, Durban 2014.The dissertation adopts both a creative and critical approach to exploring the representation of autism in literature. Much of the autism literature produced so far has arisen in first-world, developed contexts, characterised by a high degree of support and an extensive knowledge base. In this original novel, The Hum of the Sun, autism is presented in a contemporary South African context. Against a background of the rather narrow or limited representations of autism found in Western medical and popular literature, the novel intends to extend the range and focus of existing literary representation by exploring a condition of severely impaired communication in a developing world. The creation of Zuko, a character with autism, explores the extreme scenario of the classic form of the condition, where language is limited or non-existent. A third person narrative describes the experience of Zuko’s character through a visceral, sensory language that focuses on quality and immediate experience rather than cognitive processes. The theoretical component of this study discusses autism through a historical narrative from its emergence as a diagnosis, and the condition’s diversity but tendency to characterise as lack against a norm. The rise in popular representations of autism emerge from constructions in popular media, as well as the public’s fascination with and anxiety about the condition. Autism’s representation spans a variety of genres. Compared and contrasted here are the genres of psycho-medical, fiction and autobiography or life-writing. Such popular representations potentially both create awareness and simultaneously produce stereotypes about the condition. Here the question of the relationship between the different discourses examines the vexed notion of ‘truth’ in the epistemological value of literature. The value of literature as a source of knowledge, and a source of knowledge about autism, is discussed, which illuminates various ethical and aesthetic questions in writing. Representation might be viewed as construction, not reflection, and the role of discourse also determines how autism as a knowledge-object is constructed and shaped by a particular genre and its conventions. Literature is a construct and truth is complex, but literary texts can facilitate understanding and offer a form of truth and illumination about the condition. Within all three genres, attention is given to the use of language, the narrative arc and structure, common stereotypes, plot devices, the resolution and grounding assumptions in relation to the way autism is represented. Finally, the implications of this research for the writing of an autism narrative in the form of the novel, The Hum of the Sun, are examined, with reflection on the ways it is possible to extend the terms of the debate and avoid some of the pitfalls found in the examination of other texts

A topological approach to undefinability in algebraic extensions of Q\mathbb{Q}

For any subset $Z \subseteq \mathbb{Q}$, consider the set $S_Z$ of subfields $L\subseteq \overline{\mathbb{Q}}$ which contain a co-infinite subset $C \subseteq L$ that is universally definable in $L$ such that $C \cap \mathbb{Q}=Z$. Placing a natural topology on the set $\text{Sub}(\overline{\mathbb{Q}})$ of subfields of $\overline{\mathbb{Q}}$, we show that if $Z$ is not thin in $\mathbb{Q}$, then $S_Z$ is meager in $\text{Sub}(\overline{\mathbb{Q}})$. Here, thin and meager both mean "small", in terms of arithmetic geometry and topology, respectively. For example, this implies that only a meager set of fields $L$ have the property that the ring of algebraic integers $\mathcal{O}_L$ is universally definable in $L$. The main tools are Hilbert's Irreducibility Theorem and a new normal form theorem for existential definitions. The normal form theorem, which may be of independent interest, says roughly that every $\exists$-definable subset of an algebraic extension of $\mathbb Q$ is a finite union of single points and projections of hypersurfaces defined by absolutely irreducible polynomials.Comment: 24 pages. Introduction has been rewritte