1,673 research outputs found

    Life expectancy of shingle beaches: measuring in situ abrasion

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    In situ abrasion of shingle beach material is a neglected area of study in coastal geomorphology, with reduction in beach volumes normally attributed to longshore and offshore drift. Results from field abrasion experiments conducted on flint shingle beaches on the East Sussex coast, southern England, show that in situ reductions in volume of beach material may be more significant than has been thought. Two beaches composed almost entirely of flint shingle were seeded with hard quartzite from a Devon beach and less resistant limestone from a South Wales beach that are readily distinguishable from the flint. The seeding commenced in January 2001. The pebbles, similar in size and shape to the natural flint shingle, were left in the surf zone at two sites. Prior to exposure the pebbles were engraved with a code number and weighed. At regular intervals those that could be re-found were re-weighed and returned to the beach. Abrasion rates were calculated for each pebble as percentage weight loss per tide. By the end of October 2001, more than 700 measurements of abrasion rates had been made from a total of 431 pebbles. Average limestone abrasion rates (0.0266% loss of weight per tide) were three times greater than those of quartzite (0.0082% per tide). Measurable abrasion rates were recorded over just a few tidal cycles, not only in severe wave conditions but also in much calmer weather. The maximum abrasion rates recorded exceeded 1% per tide for limestone

    Global Spinors and Orientable Five-Branes

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    Fermion fields on an M-theory five-brane carry a representation of the double cover of the structure group of the normal bundle. It is shown that, on an arbitrary oriented Lorentzian six-manifold, there is always an Sp(2) twist that allows such spinors to be defined globally. The vanishing of the arising potential obstructions does not depend on spin structure in the bulk, nor does the six-manifold need to be spin or spin-C. Lifting the tangent bundle to such a generalised spin bundle requires picking a generalised spin structure in terms of certain elements in the integral and modulo-two cohomology of the five-brane world-volume in degrees four and five, respectively.Comment: 18 pages, LaTeX; v2: version to appear in JHE

    Black Hole Masses in Three Seyfert Galaxies

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    We analyze published reverberation mapping data for three Seyfert galaxies (NGC 3227, NGC 3516, and NGC 4593) to refine the mass estimate for the supermassive black hole in the center of each object. Treatment of the data in a manner more consistent with other large compilations of such masses allows us to more securely compare our results to wider samples of data, e.g., in the investigation of the M_bh-sigma relationship for active and quiescent galaxies.Comment: 14 pages, 4 figures. Accepted for publication in Ap

    Predicting climate change impacts on maritime Antarctic soils: A space-for-time substitution study

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    We report a space-for-time substitution study predicting the impacts of climate change on vegetated maritime Antarctic soils. Analyses of soils from under Deschampsia antarctica sampled from three islands along a 2,200 km climatic gradient indicated that those from sub-Antarctica had higher moisture, organic matter and carbon (C) concentrations, more depleted δ13C values, lower concentrations of the fungal biomarker ergosterol and higher concentrations of bacterial PLFA biomarkers and plant wax n-alkane biomarkers than those from maritime Antarctica. Shallow soils (2 cm depth) were wetter, and had higher concentrations of organic matter, ergosterol and bacterial PLFAs, than deeper soils (4 cm and 8 cm depths). Correlative analyses indicated that factors associated with climate change (increased soil moisture, C and organic matter concentrations, and depleted δ13C contents) are likely to give rise to increases in Gram negative bacteria, and decreases in Gram positive bacteria and fungi, in maritime Antarctic soils. Bomb-14C analyses indicated that sub-Antarctic soils at all depths contained significant amounts of modern 14C (C fixed from the atmosphere post c. 1955), whereas modern 14C was restricted to depths of 2 cm and 4 cm in maritime Antarctica. The oldest C (c. 1,745 years BP) was present in the southernmost soil. The higher nitrogen (N) concentrations and δ15N values recorded in the southernmost soil were attributed to N inputs from bird guano. Based on these analyses, we conclude that 5–8 °C rises in air temperature, together with associated increases in precipitation, are likely to have substantial impacts on maritime Antarctic soils, but that, at the rates of climate warming predicted under moderate greenhouse gas emission scenarios, these impacts are likely to take at least a century to manifest themselves

    Translation of findings from laboratory studies of food and alcohol intake into behavior change interventions : the experimental medicine approach.

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    Objectives: Laboratory studies have contributed important information about the determinants of food and alcohol intake, and they have prompted the development of behavior change interventions that have been evaluated in randomized controlled trials conducted in the field. In this article we apply a recent experimental medicine (EM) framework to this body of research. Method: A conceptual review and focused discussion of the relevant literature is presented. Results: We illustrate how it is possible to translate findings from studies of food and alcohol intake in the laboratory into interventions that are effective for changing behavior in the real world. We go on to demonstrate how systematic failures can occur at different stages within the EM framework, and how these failures ultimately result in interventions that are ineffective for changing behavior. We also consider methodological issues that may constrain the external validity of findings from laboratory studies including demand effects, participant characteristics, and the timing and dose of behavioral interventions. Throughout, we make recommendations to improve the translation of findings from laboratory studies into behavior change interventions that are effective in the field. Conclusions: Consideration of the EM framework will help to ensure that promising candidate interventions for eating and drinking that are identified in laboratory studies can fulfill their translational promise

    Filling the gap between chemical carcinogenesis and the hallmarks of cancer: a temporal perspective

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    Background Cancer is believed to arise through the perturbation of pathways and the order of pathway perturbation events can enhance understanding and evaluation of carcinogenicity. This order has not been examined so far, and this study aimed to fill this gap by attempting to gather evidence on the potential temporal sequence of events in carcinogenesis. Design The methodology followed was to discuss first the temporal sequence of hallmarks of cancer from the point of view of pathological specimens of cancer (essentially branched mutations) and then to consider the hallmarks of cancer that one well‐known carcinogen, benzo(a)pyrene, can modify. Results Even though the sequential order of driving genetic alterations can vary between and within tumours, the main cancer pathways affected are almost ubiquitous and follow a generally common sequence: resisting cell death, insensitivity to antigrowth signals, sustained proliferation, deregulated energetics, replicative immortality and activation of invasion and metastasis. The first 3 hallmarks can be regarded as almost simultaneous while angiogenesis and avoiding immune destruction are perhaps the only hallmarks with a varying position in the above sequence. Conclusions Our review of hallmarks of cancer and their temporal sequence, based on mutational spectra in biopsies from different cancer sites, allowed us to propose a hypothetical temporal sequence of the hallmarks. This sequence can add molecular support to the evaluation of an agent as a carcinogen as it can be used as a conceptual framework for organising and evaluating the strength of existing evidence

    Association of FCGR3A and FCGR3B haplotypes with rheumatoid arthritis and primary Sjögren's syndrome [POSTER PRESENTATION]

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    Background Rheumatoid arthritis (RA) is an autoimmune disease that is thought to arise from a complex interaction between multiple genetic factors and environmental triggers. We have previously demonstrated an association between a Fc gamma receptor (FcγR) haplotype and RA in a cross-sectional cohort of RA patients. We have sought to confirm this association in an inception cohort of RA patients and matched controls. We also extended our study to investigate a second autoanti-body associated rheumatic disease, primary Sjögren's syndrome (PSS). Methods The FCGR3A-158F/V and FCGR3B-NA1/NA2 functional polymorphisms were examined for association in an inception cohort of RA patients (n = 448), and a well-characterised PSS cohort (n = 83) from the United Kingdom. Pairwise disequilibrium coefficients (D') were calculated in 267 Blood Service healthy controls. The EHPlus program was used to estimate haplotype frequencies for patients and controls and to determine whether significant linkage disequilibrium was present. A likelihood ratio test is performed to test for differences between the haplotype frequencies in cases and controls. A permutation procedure implemented in this program enabled 1000 permutations to be performed on all haplotype associations to assess significance. Results There was significant linkage disequilibrium between FCGR3A and FCGR3B (D' = -0.445, P = 0.001). There was no significant difference in the FCGR3A or FCGR3B allele or genotype frequencies in the RA or PSS patients compared with controls. However, there was a significant difference in the FCGR3A-FCGR3B haplotype distributions with increased homozygosity for the FCGR3A-FCGR3B 158V-NA2 haplotype in both our inception RA cohort (odds ratio = 2.15, 95% confidence interval = 1.1–4.2 P = 0.027) and PSS (odds ratio = 2.83, 95% confidence interval = 1.0–8.2, P = 0.047) compared with controls. The reference group for these analyses comprised individuals who did not possess a copy of the FCGR3A-FCGR3B 158V-NA2 haplotype. Conclusions We have confirmed our original findings of association between the FCGR3A-FCGR3B 158V-NA2 haplotype and RA in a new inception cohort of RA patients. This suggests that there may be an RA-susceptibility gene at this locus. The significant increased frequency of an identical haplotype in PSS suggests the FcγR genetic locus may contribute to the pathogenesis of diverse autoantibody-mediated rheumatic diseases

    Geothermal Energy Challenge Fund: the Guardbridge Geothermal Technology Project

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    GEOTHERMAL ENERGY CHALLENGE EXECUTIVE SUMMARY This feasibility study investigates whether a geothermal district heating system, which accesses Hot Sedimentary Aquifer (HSA) resources underlying a brownfield site at Guardbridge in northeast Fife, can be developed in a cost-effective manner. This project’s scope is to assess the available geological information and estimate the hot saline aquifer heat supply, calculate the current heat demand at the Guardbridge site, Guardbridge village, and the nearby towns of Leuchars and Balmullo, and to incorporate future Guardbridge development plans (provided by the University of St Andrews) and anticipated growth in housing stock (from Fife Council) to estimate future heat demand. The capital, maintenance and repair costs for the geothermal well and designed district heating network are used to develop economic models for a number of district heat network scenarios. A key aspect of this study is an evaluation of the opportunities to cost effectively de-risk deep geothermal exploration in Central Scotland, and to outline the potential for developing geological heat storage systems. The study identifies the key legislative and environmental issues, risks and uncertainties associated with any exploration and production, involves stakeholder engagement, and makes recommendations for a Phase 2 stage for geothermal heat development at Guardbridge. Two of the key outputs from this feasibility study will be an economic model and business case based on different heat demand options, and an optimised model of well design based on different exploration strategies. Both are transferable to similar operations at other geothermal sites. The key objectives are therefore to: (a)design a geothermal well that will be drilled in Phase 2 of the project, and secure valuable information on Fife regional sub-surface geology and geothermal properties of the primary aquifer, (b)explore how advanced drilling techniques, such as directional drilling, can be deployed to improve geothermal recovery, (c) demonstrate how a geothermal system can integrate with an existing biomass heating installation to optimise both schemes and provide a district heat network for on-site industries and the local community, (d)evaluate the potential for storage of seasonal heat energy in the subsurface (a first in Scotland), and (e)assess the relative merits of water treatment and on-site recycling, reinjection or disposal to sea. A regional geological model was constructed using available data from the British Geological Survey, published data and academic theses. The sub-surface geology was interpreted from surface geology and extrapolating the local behaviour of geological structures into the Guardbridge area. Modelling the geology involved defining the orientation and width of a natural fault zone, which could be a significant influence on the behaviour of the Hot Sedimentary Aquifers. The rock units of interest in this study are the Upper Devonian Scone Sandstone, Glenvale Sandstone, Knox Pulpit and Kinnesswood formations, and the latter two units are previously identified as having the highest potential to be highly productive aquifers. The presence of a major fault near the Guardbridge site means that the target aquifers are at very different depths on either side of the fault. The report therefore investigates and evaluates three well options to target the different aquifers at the varying depths on either side of the fault. Hydrogeological modelling was conducted using FEFLOW® to evaluate the behaviour of the fault on fluid flow rates, and to predict the necessary conductivities to produce reasonable, economic and sustainable rates of fluid extraction. Although not an accurate model of the Guardbridge site, and limited by a significant lack of data constraining the important parameters, the flow simulations suggest that fracture permeability in the aquifers and underlying rocks is needed to sustain the flows recommended by this study, and re-injection would be required if a producing well was to be sustainable over many decades. Regionally developed rock quality predictors have been used to estimate the permeability and temperature of the target aquifer intervals in the three selected well options at, or near, Guardbridge. Oil field well simulation tools have been used to estimate water flow rates, temperature profiles, and circulating rates from different geological models of the wells. Two of the wells, GB-1 and ES-1, are not expected to penetrate enough high permeability sandstone to support the minimum water flow rates of 5 l/s and so are ruled out as viable aquifer producers. GB-2 is a deviated well that penetrates the Kinnesswood and Knox Pulpit formations, the best quality regional aquifers, in a zone where the fault may enhance the permeability even more, and has potential to supply 5 to 20 l/s of water at a surface temperature of 25 oC (± 2 oC). Such a well will be produced using an electric submersible pump which will require 20 - 40 kw of power to deliver 15 l/s of flow (although the volumetric rate will vary with the rock quality). GB-2 is taken forward and drilling designs are provided with three outcomes: 1) a dry hole scenario; 2) a 5 l/s scenario; and, 3) a 15 l/s scenario. The vertical wells have been modelled as heat pump circulating wells, and therefore would not produce any aquifer water at the surface. Only deeper wells, up to 2500 m, have the potential to give surface temperature increase of 5 oC at reasonable circulation rates (e.g. 8 l/s). A deep GB-1 well as a heat pump could be taken forward in Phase 2 as an alternative heat source. The proposed GB-2 deviated well can be drilled across the fault from the Guardbridge site to a depth of 1200 m. A casing string set will isolate the shallow geology and a slotted liner used to prevent hole collapse of the target intervals. Such a well will require a 100 tonne conventional drilling rig and well control, logging and coring tools will assess the aquifer quality. In the most likely case, the drilling phase will take 24 days, including rig mobilisation and demobilisation. If coring and logging demonstrate that the well will not flow adequately, then the well will be suspended. Low cost options have been investigated that would allow exploratory wells to be drilled and this could result in the recovery of regionally significant data on the performance of the aquifers at depth, although none of the boreholes could be completed to production stage due the drilling technology employed. The drilling scenarios investigated do not include a re-injection well, in order to create an economically viable district heating network project, even though very preliminary hydrogeological modelling demonstrates that re-injection is required if the geothermal well is to be sustainable over 30+ years. Alternative management of produced water investigated in this report are: water disposal-tosea and partial-full water recycling and re-use on site. The first option could have environmental consequences on the adjacent Eden Estuary, which is part of the Tay River and Eden Estuary Special Protection Area, and these potential impacts would need formal assessment by a competent authority (Fife Council and SNH) as part of a Habitat Regulations Appraisal, and an Environmental Impact Assessment is most likely required. The second option reduces the environmental impacts on the estuary, but has additional CAPEX and OPEX costs which are estimated. The opportunity to be innovative about partial water recycling and resale should be investigated in Phase 2. The heat demand is based on preliminary district heating network layouts at different scales, based on the demand analysis. Demand has been assessed at Guardbridge and the nearby towns of Leuchars and Balmullo, using the Scotland Heat Map and future development data provided by the University of St Andrews and the Fife Development Plan. These various options provide an indication of the potential annual and peak heating demands that can then be compared against the geothermal heating potential, and an economic modelling tool was developed to analyse the performance of the overall system, including key performance indicators to evaluate the financial viability. This analysis leads to a preliminary network design and an economic model of the potential scheme. The District Heating Opportunity Assessment Tool (DHOAT) designed for the Danish Energy Agency analyses the Heat Map data and preliminary network designs and provides peak and annual demands and key performance indicators, namely total heat demand and indicative CAPEX, OPEX, REPEX and heat sales. All input parameters are modelled with an uncertainty of ±10%. Based on this analysis, the proposed development of one well and estimated heat supply is not sufficient capacity to provide heat outside of the Guardbridge site itself. All district heating network designs and economic models were therefore based on the aggregated customer base of the Guardbridge site. The economic model assumes that geothermal heat can supply 50% of the Guardbridge site needs (2,867 MWh/a), with a capacity of 0.42 MW, and the other 50% would be provided by the biomass plant. Revenues from heat sales are based on a heat sale price scaling (MWh and p/kWh) and costs of heat from the biomass plant. An Excel model calculates the profitability of the scheme based on a CAPEX of £530,000 for the heating network and £1,517,000 for the well completion, flow tests and water treatment. OPEX and REPEX costs are principally power consumption for the heat and distribution pumps (£280,000), and a ESP and heat pump replacement after 10 years (£250,000). NPV and IRR are used to demonstrate viability for potential investors over a 21-year period; the best case scenario shows that the scheme might achieve a 10% IRR and a positive NPV. However, the heat sale price is too low to create sufficient margin to make the economic performance attractive. This is principally due to the cost of the geothermal heat. The capital cost of the geothermal well is a significant portion of the project CAPEX and does not vary with the well heat potential, which is a relatively modest value given the temperature and flow rate estimates presented. Flow rate is highly uncertain, while temperature is better constrained and low due to the shallow depth of the proposed well. The district heating network requires higher temperatures and the addition of a heat pump increases the capital costs and adds a relatively high operating cost for the electricity to run the pump. The carbon emissions reductions are compared to an individual gas boiler alternative (business as usual [BAU]) and the geothermal-biomass heat network shows an 84% reduction in carbon emissions, assuming that the biomass boilers and geothermal heat pumps each supply 50% of the network demand. About 58% of the emissions reduction (13,878 tonnes CO2/kWh relative to BAU) is attributed to heat generation from the biomass plant and the remaining 42% (9,812 tonnes CO2/kWh relative to BAU) is attributed to the geothermal well and the heat pump. These figures are based on a model lifetime of 20 years. The value of this carbon saving has not been included in the economic model, however it could be considered to represent an additional savings compared to the business-as-usual alternative. The heating network can be enhanced at a subsequent stage to provide combined heating and cooling for the site. This would increase the utilisation of the heat pump by operating in combined heating and cooling mode during interseasonal periods. Although not explored in any extensive technical or economic sense, the system could also potentially be used to fill separate hot and cold seasonal heat stores. Requirements for Phase 2 would begin with a non-invasive geophysical survey to provide imaging of the fault and the target aquifers in the subsurface. This could be completed in three months. Phase 2 would most likely require the preparation of an Environmental Statement before any drilling could commence on site, particularly addressing the viability of disposal of water to the sea. However, current developments at Guardbridge have required Environmental Statements (i.e. since 2014) and much baseline data already exists. The time required to complete an EIA range from 12 weeks to prepare the report, or up to one year of time if SNH and Fife Council require additional new data. A benefit of the Guardbridge site is therefore its status as an industrial site with a pre-existing history in terms of Environmental Statements. Ideally, Phase 2 would culminate in revised well designs, procurement of the drilling rig, and test drilling to intercept the fault and target aquifers. The time and costs are estimated and depend on the choice of drilling option. A positive outcome from a test borehole would lead to the design of a full production well and progression of the project as a Technology Demonstrator. Regardless of whether the test borehole proves that the Guardbridge District Heating Network project is viable, the data recovered as part of the test drilling (core samples, flow tests and water chemistry) will be highly significant for de-risking hot sedimentary aquifer exploration across central Scotland. The economic feasibility of the Guardbridge geothermal heat project is dependent on the best case scenario for flow rates, along with a large number of other poorly constrained variables. It could be economic, but there is a very large uncertainty in the geothermal heat estimates. However, the additional value in the potential research that can be achieved at Guardbridge in de-risking hot sedimentary aquifer exploration in the Central Belt of Scotland, as well as integrating low carbon heat source exploration with other technologies, including dual heating and cooling and water recycling, should be considered when deciding to progress this project
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