679 research outputs found

    Tectonic Controls on Taupo Volcanic Zone Geothermal Expression: Insights From Te Mihi, Wairakei Geothermal Field

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    Information on structure, stress, and their interrelationship is essential for understanding structurally controlled geothermal permeability. Active fault mapping, borehole image analysis, and well testing in the Te Mihi geothermal area, New Zealand, allows us to refine structural and fluid flow architecture of this resource. The Te Mihi area is structurally complex, comprising a set of NW dipping master faults containing pervasive SE dipping antithetic and splay structures in their hanging walls. These faults are also intersected by E-W striking faults. A localized, N-S striking structural trend is also observed at Te Mihi. In consideration with Global Navigation Satellite System velocity vectors, both active NE-SW and E-W striking faults create biaxial extension at Te Mihi, though the observed NE-SW SHmax direction suggests that contemporary extension is NW-SE dominated. Stress field perturbations coincide with structural complexities like fault splays and intersections and/or proximity to recently active E-W and NE-SW striking structures. Borehole fluid flow at Te Mihi is concentrated at NW dipping master fault intersections, travel time fractures on acoustic image logs, halo fractures on resistivity image logs, NE-SW and E-W striking fractures, intervals of high fracture density, and spatial concentrations of wide aperture fractures and recently active NE-SW and E-W striking fractures. This study suggests Te Mihi geothermal expression results from biaxial extension evident from active structural trend intersections and the predominance of NE-SW and E-W striking structures within permeable well zones. Biaxial extension is therefore an important control on crustal fluid flow within the Taupo Volcanic Zone and thus geothermal resource delineation

    Metabolic state alters economic decision making under risk in humans

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    Background: Animals' attitudes to risk are profoundly influenced by metabolic state (hunger and baseline energy stores). Specifically, animals often express a preference for risky (more variable) food sources when below a metabolic reference point (hungry), and safe (less variable) food sources when sated. Circulating hormones report the status of energy reserves and acute nutrient intake to widespread targets in the central nervous system that regulate feeding behaviour, including brain regions strongly implicated in risk and reward based decision-making in humans. Despite this, physiological influences per se have not been considered previously to influence economic decisions in humans. We hypothesised that baseline metabolic reserves and alterations in metabolic state would systematically modulate decision-making and financial risk-taking in humans. Methodology/Principal Findings: We used a controlled feeding manipulation and assayed decision-making preferences across different metabolic states following a meal. To elicit risk-preference, we presented a sequence of 200 paired lotteries, subjects' task being to select their preferred option from each pair. We also measured prandial suppression of circulating acyl-ghrelin (a centrally-acting orexigenic hormone signalling acute nutrient intake), and circulating leptin levels (providing an assay of energy reserves). We show both immediate and delayed effects on risky decision-making following a meal, and that these changes correlate with an individual's baseline leptin and changes in acyl-ghrelin levels respectively. Conclusions/Significance: We show that human risk preferences are exquisitely sensitive to current metabolic state, in a direction consistent with ecological models of feeding behaviour but not predicted by normative economic theory. These substantive effects of state changes on economic decisions perhaps reflect shared evolutionarily conserved neurobiological mechanisms. We suggest that this sensitivity in human risk-preference to current metabolic state has significant implications for both real-world economic transactions and for aberrant decision-making in eating disorders and obesity

    Atherosclerosis in young Brazilians suffering violent deaths: a pathological study

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    <p>Abstract</p> <p>Background</p> <p>Atherosclerosis is the leading cause of coronary heart disease and ischemic stroke, which can cause sudden death in adulthood. In general, the clinical manifestations of cardiovascular diseases are caused by atherosclerosis, which is a process that starts during middle age. More recent studies indicate that the atherosclerotic process begins during childhood.</p> <p>Methods</p> <p>To evaluate the extent of atherosclerotic disease in young Brazilians, we conducted a study of the pathological alterations in the major arteries of victims of violent death. Samples of the right carotid artery, left coronary artery, and thoracic aorta of young victims of violent death were analyzed and graded in accordance with the histological atherosclerotic lesion types proposed by the American Heart Association. Samples were collected from 100 individuals who had died from external causes, aged from 12 to 33 years.</p> <p>Results</p> <p>The majority of cases (83%) were male, and 66% of deaths were homicides caused by firearms. The median age was 20.0 years and mean body mass index was 20.9 kg/m<sup>2</sup>. Of the right carotid artery specimens, 3% were normal, 55% had type I, 40% had type II, 1% had type III, and 1% had type IV atherosclerotic lesions. Of the left coronary artery specimens, 5% were normal, 48% had type I, 41% had type II, 3% had type III, and 3% had type IV lesions. Of the thoracic aorta specimens, none were normal, 13% had type I, 64% had type II, 22% had type III, and 1% had type IV lesions. Overall, 97.34% of arteries examined had some degree of atherosclerosis. The most common histological type was type II (foam cells). No thoracic aorta specimens were normal, and the coronary artery specimens had the most atherosclerosis.</p> <p>Conclusions</p> <p>Our results show a high prevalence of atherosclerotic lesions among young people in Brazil. Intervention should be undertaken to decrease the rate of sudden cardiac death in the adult population.</p

    Ultraviolet radiation shapes seaweed communities

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    Analyzing the Impacts of Off-Road Vehicle (ORV) Trails on Watershed Processes in Wrangell-St. Elias National Park and Preserve, Alaska

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    Trails created by off-road vehicles (ORV) in boreal lowlands are known to cause local impacts, such as denuded vegetation, soil erosion, and permafrost thaw, but impacts on stream and watershed processes are less certain. In Wrangell-St. Elias National Park and Preserve (WRST), Alaska, ORV trails have caused local resource damage in intermountain lowlands with permafrost soils and abundant wetlands and there is a need to know whether these impacts are more extensive. Comparison of aerial photography from 1957, 1981, and 2004 coupled with ground surveys in 2009 reveal an increase in trail length and number and show an upslope expansion of a trail system around points of stream channel initiation. We hypothesized that these impacts could also cause premature initiation and headward expansion of channels because of lowered soil resistance and greater runoff accumulation as trails migrate upslope. Soil monitoring showed earlier and deeper thaw of the active layer in and adjacent to trails compared to reference sites. Several rainfall-runoff events during the summer of 2009 showed increased and sustained flow accumulation below trail crossings and channel shear forces sufficient to cause headward erosion of silt and peat soils. These observations of trail evolution relative to stream and wetland crossings together with process studies suggest that ORV trails are altering watershed processes. These changes in watershed processes appear to result in increasing drainage density and may also alter downstream flow regimes, water quality, and aquatic habitat. Addressing local land-use disturbances in boreal and arctic parklands with permafrost soils, such as WRST, where responses to climate change may be causing concurrent shifts in watershed processes, represents an important challenge facing resource managers

    Effects of body position on autonomic regulation of cardiovascular function in young, healthy adults

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    Background: Analysis of rhythmic patterns embedded within beat-to-beat variations in heart rate (heart rate variability) is a tool used to assess the balance of cardiac autonomic nervous activity and may be predictive for prognosis of some medical conditions, such as myocardial infarction. It has also been used to evaluate the impact of manipulative therapeutics and body position on autonomic regulation of the cardiovascular system. However, few have compared cardiac autonomic activity in supine and prone positions, postures commonly assumed by patients in manual therapy. We intend to redress this deficiency. Methods: Heart rate, heart rate variability, and beat-to-beat blood pressure were measured in young, healthy non-smokers, during prone, supine, and sitting postures and with breathing paced at 0.25 Hz. Data were recorded for 5 minutes in each posture: Day 1 - prone and supine; Day 2 - prone and sitting. Paired t-tests or Wilcoxon signed-rank tests were used to evaluate posture-related differences in blood pressure, heart rate, and heart rate variability. Results: Prone versus supine: blood pressure and heart rate were significantly higher in the prone posture (p &lt; 0.001). Prone versus sitting: blood pressure was higher and heart rate was lower in the prone posture (p &lt; 0.05) and significant differences were found in some components of heart rate variability. Conclusion: Cardiac autonomic activity was not measurably different in prone and supine postures, but heart rate and blood pressure were. Although heart rate variability parameters indicated sympathetic dominance during sitting (supporting work of others), blood pressure was higher in the prone posture. These differences should be considered when autonomic regulation of cardiovascular function is studied in different postures

    Search for new phenomena in final states with an energetic jet and large missing transverse momentum in pp collisions at √ s = 8 TeV with the ATLAS detector

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    Results of a search for new phenomena in final states with an energetic jet and large missing transverse momentum are reported. The search uses 20.3 fb−1 of √ s = 8 TeV data collected in 2012 with the ATLAS detector at the LHC. Events are required to have at least one jet with pT > 120 GeV and no leptons. Nine signal regions are considered with increasing missing transverse momentum requirements between Emiss T > 150 GeV and Emiss T > 700 GeV. Good agreement is observed between the number of events in data and Standard Model expectations. The results are translated into exclusion limits on models with either large extra spatial dimensions, pair production of weakly interacting dark matter candidates, or production of very light gravitinos in a gauge-mediated supersymmetric model. In addition, limits on the production of an invisibly decaying Higgs-like boson leading to similar topologies in the final state are presente

    Global gene expression analyses of bystander and alpha particle irradiated normal human lung fibroblasts: Synchronous and differential responses

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    <p>Abstract</p> <p>Background</p> <p>The existence of a radiation bystander effect, in which non-irradiated cells respond to signals from irradiated cells, is now well established. It raises concerns for the interpretation of risks arising from exposure to low doses of ionizing radiation. However, the regulatory mechanisms involved in the bystander response have not been well elucidated. To provide insight into the signaling pathways responding in bystanders, we have measured global gene expression four hours after bystander and direct alpha particle exposure of primary human lung fibroblasts.</p> <p>Results</p> <p>Although common p53-regulated radiation response genes like <it>CDKN1A </it>were expressed at elevated levels in the directly exposed cultures, they showed little or no change in the bystanders. In contrast, genes regulated by NFκB, such as <it>PTGS2 </it>(cyclooxygenase-2), <it>IL8 </it>and <it>BCL2A1</it>, responded nearly identically in bystander and irradiated cells. This trend was substantiated by gene ontology and pathway analyses of the microarray data, which suggest that bystander cells mount a full NFκB response, but a muted or partial p53 response. In time-course analyses, quantitative real-time PCR measurements of <it>CDKN1A </it>showed the expected 4-hour peak of expression in irradiated but not bystander cells. In contrast, <it>PTGS2, IL8 </it>and <it>BCL2A1 </it>responded with two waves of expression in both bystander and directly irradiated cells, one peaking at half an hour and the other between four and six hours after irradiation.</p> <p>Conclusion</p> <p>Two major transcriptional hubs that regulate the direct response to ionizing radiation are also implicated in regulation of the bystander response, but to dramatically different degrees. While activation of the p53 response pathway is minimal in bystander cells, the NFκB response is virtually identical in irradiated and bystander cells. This alteration in the balance of signaling is likely to lead to different outcomes in irradiated cells and their bystanders, perhaps leading to greater survival of bystanders and increased risk from any long-term damage they have sustained.</p
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