874 research outputs found

    Development of a Reference Design for a Cyber-Physical System

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    The purpose of this thesis is to develop a reference design to assist in the selection of security practices in power electronics design. A prototype will be developed from this reference design for evaluation. This evaluation will include a brief cost/benefit analysis to gauge the efficacy of implementing each layer of security throughout the power electronics design process. This thesis will also describe the obstacles and effectiveness of integrating a Trusted Platform Module (TPM) into a cyber-hardened grid-connected device. The TPM device is a secured crypto processor that assists in generating, storing, and restricting the use of cryptographic keys. The emphasis of this research is to establish integrity, authenticity, and confidentiality within a system by providing a baseline of security concerns for segments of the system. This research considers communication, control, and hardware level securities. The scope of this thesis will review the necessary security methods as well as consider the effects these methods have on the embedded system, to assess the desired security to responsiveness trade off. Applying this approach to a design process will alleviate various unknowns of appending security to a power electronics design. This thesis describes the specific vulnerabilities introduced within this grid-edge environment, and how the liabilities within the system can be mitigated. Initially, common security techniques will be considered to establish a guideline to benchmark performance and resource costs of the system. The foundation will be a non-hardened power electronic system platform with industry standard communication protocols. Several security techniques and attack vectors will then be evaluated to contribute to the base level platform. Other fail-safe features take place to gauge progress of the selected approach, non-inclusive to the TPM. Collectively, this investigation will determine a valid experiment by appraising and categorizing resource allocation, performance overhead, and monetary cost analysis results into a reference design. The prototype will then demonstrate methods to relieve common threats that are purposefully implemented into the design

    Diet of rainbow trout in Lake Rotoiti: an energetic perspective

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    We characterised seasonal and ontogenetic changes in diet and prey energy density of rainbow trout (Oncorhynchus mykiss) in Lake Rotoiti, New Zealand, to better understand the prey requirements of trout in central North Island lakes. Common smelt (Retropinna retropinna) was the dominant prey item of rainbow trout larger than 200 mm (77.8% of diet by weight), followed by kōura (freshwater crayfish Paranephrops planifrons; 6.3%), common bully (Gobiomorphus cotidianus; 5.5%), and kōaro (Galaxias brevipinnis; 3.4%). Juvenile rainbow trout (<200 mm) consumed amphipods, aquatic and terrestrial insects, oligochaetes, tanaid shrimps, and smelt. Trout consumed kōaro only in autumn and winter; consumption of other species did not vary seasonally. The maximum size of smelt consumed increased with increasing trout size, but trout continued to consume small smelt even as large adults. Consumption of larger prey items (kōaro and kōura) also increased with increasing trout size. This study indicates the importance of smelt for sustaining rainbow trout populations, as predation on other species was relatively low. These findings provide a basis for bioenergetic modelling of rainbow trout populations in lakes of the central North Island of New Zealand

    The ZEPLIN dark matter search: two phase xenon as a WIMP target

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    The existence of a significant non-baryonic component to the universe is widely accepted, with worldwide efforts underway trying to detect this so-called dark matter. The ZEPLIN detectors utilise liquid xenon as a target medium in the search of the expected rare interactions of Weakly Interacting Massive Particles, or WIMPs, with ordinary baryonic matter. The neutralino, arising in supersymmetric extensions to the standard model of particle physics, provides a particularly well-motivated candidate. The ZEPLIN-II and ZEPLIN-III experiments, operate in two-phase mode (liquid/gas), measuring both the scintillation and ionisation signatures produced during an interaction. These instruments form the basis of this thesis. The ZEPLIN-II experiment was operated underground at the Boulby Underground Laboratory, culminating in a WIMP search run lasting 57 days. Some key operational aspects are discussed, and a full description of the data analysis is given, which yielded a competitive upper limit on the spin-independent WIMP-nucleon scattering crosssection with a minimum of 6.6×10−7 pb for a 65 GeV/c2 WIMP with 90% confidence. Subsequently, a smaller collaboration proceeded with the commissioning and operation of ZEPLIN-III at Boulby. The detector was operated stably for 12 months, culminating in the first science run, which excluded a cross-section above 7.7 × 10−8 pb for a 55 GeV/c2 WIMP. This placed ZEPLIN-III as one of the world’s leading WIMP search experiments. Along with the WIMP search results, the data collected from these instruments have been exploited to extract information about the underlying xenon physics processes, which will play an important role in design of future systems. This includes the first quantitative measurements of single electron emission in a two-phase noble gas detector, studies of the field dependence of their response and of the anti-correlation between the scintillation and ionisation channels

    eHealth and the use of individually tailored information:a systematic review

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    Tailored messages are those that specifically target individuals following an assessment of their unique characteristics. This systematic review assesses the evidence regarding the effectiveness of tailoring within eHealth interventions aimed at chronic disease management. OVID Medline/Embase databases were searched for randomised control trials, controlled clinical, trials, before -after studies, and time series analyses from inception - May 2014. Objectively measured clinical processes/outcomes were considered. Twenty-two papers were eligible for inclusion: 6/22 used fully tailored messaging and 16/22 used partially tailored messages. Two studies isolated tailoring as the active component. The remainder compared intervention with standard care. In all, 12/16 studies measuring clinical processes and 2/6 studies reporting clinical outcomes showed improvements, regardless of target group. Study quality was low and design did not allow for identification of interventions’ active component. Heterogeneity precluded meta-analysis. This review has demonstrated that there is a lack of evidence to suggest that tailoring within an eHealth context confers benefit over non-tailored eHealth interventions. </jats:p

    Geomorphology from space: A global overview of regional landforms

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    This book, Geomorphology from Space: A Global Overview of Regional Landforms, was published by NASA STIF as a successor to the two earlier works on the same subject: Mission to Earth: LANDSAT views the Earth, and ERTS-1: A New Window on Our Planet. The purpose of the book is threefold: first, to serve as a stimulant in rekindling interest in descriptive geomorphology and landforms analysis at the regional scale; second, to introduce the community of geologists, geographers, and others who analyze the Earth's surficial forms to the practical value of space-acquired remotely sensed data in carrying out their research and applications; and third, to foster more scientific collaboration between geomorphologists who are studying the Earth's landforms and astrogeologists who analyze landforms on other planets and moons in the solar system, thereby strengthening the growing field of comparative planetology

    Transcriptional responses of soybean aphids to sublethal insecticide exposure

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    Insecticides are a key tool in the management of many insect pests of agriculture, including soybean aphids. The selection imposed by insecticide use has often lead to the evolution of resistance by the target pest through enhanced detoxification mechanisms. We hypothesised that exposure of insecticide-susceptible aphids to sublethal doses of insecticides would result in the up-regulation of genes involved in detoxification of insecticides, revealing the genes upon which selection might act in the field. We used the soybean aphid biotype 1 reference genome, version 6.0 as a reference to analyze RNA-Seq data. We identified multiple genes with potential detoxification roles that were up-regulated 12 h after sublethal exposure to esfenvalerate or thiamethoxam. However, these genes were part of a dramatic burst of differential gene expression in which thousands of genes were up- or down-regulated, rather than a defined response to insecticides. Interestingly, the transcriptional burst observed at 12 h s declined dramatically by 24-hrs post-exposure, suggesting a general stress response that may become fine-tuned over time. Includes Supplementary Materials

    Effects of Coumaphos and Imidacloprid on Honey Bee (Hymenoptera: Apidae) Lifespan and Antioxidant Gene Regulations in Laboratory Experiments

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    The main objective of this study was to test comparatively the effects of two common insecticides on honey bee Apis mellifera worker’s lifespan, food consumption, mortality, and expression of antioxidant genes. Newly emerged worker bees were exposed to organophosphate insecticide coumaphos, a neonicotinoid imidacloprid, and their mixtures. Toxicity tests were conducted along with bee midgut immunohistological TUNEL analyses. RT-qPCR assessed the regulation of 10 bee antioxidant genes linked to pesticide toxicity. We tested coumaphos at 92,600 ppb concentration, in combination with 5 and 20 ppb imidacloprid. Coumaphos induced significantly higher bee mortality, which was associated with down regulation of catalase compared to coumaphos and imidacloprid (5/20 ppb) mixtures, whereas, both imidacloprid concentrations independently had no effect on bee mortality. Mixture of coumaphos and imidacloprid reduced daily bee consumption of a control food patty to 10 mg from a coumaphos intake of 14.3 mg and 18.4 and 13.7 mg for imidacloprid (5 and 20) ppb, respectively. While coumaphos and imidacloprid mixtures induced down-regulation of antioxidant genes with noticeable midgut tissue damage, imidacloprid induced intensive gene up-regulations with less midgut apoptosis
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