635 research outputs found

    Simulation of river flow in the Thames over 120 years: evidence of change in rainfall-runoff response?

    Get PDF
    Study region: The Thames catchment in southern England, UK. Study focus: Modelling with 124 years of rainfall, potential evaporation (PE), temperature and naturalised flow data. Daily rainfall-runoff flow simulation using current and three historic land cover scenarios to determine the stationarity of catchment response examined through three time-frames of analysis – annual, seasonal and flow extremes. The criterion of response stationarity is often assumed in climate change impact studies. New hydrological insights: The generally close correspondence between observed and simulated flows using the same model parameter values for the whole period is indicative of the temporal stability of hydrological processes and catchment response, and the quality of the hydrometric data. Changes that have occurred are a decrease in flood peak response times, typically two to three days pre and post the early 1940s, from change in agricultural practices and channel conveyance, and an increase of about 15% in summer flow from increase in urban land cover between the first decade of the 20th and 21st centuries. The water balance was found to be sensitive to the PE data used, with care needed to avoid discontinuity between two parts of the data record using different methods for calculation. Long-term mean annual rainfall shows little change but contrasting patterns of variation in seasonal rainfall demonstrate a variable climate for which simulated flow is similar to observed flow

    An investigation of the effect of transient climate change on snowmelt, flood frequency and timing in northern Britain

    Get PDF
    Climate change is almost certain to affect snow and ice processes. Even at lower latitudes, changes in snow cover at high altitudes can significantly affect catchment hydrology. This paper uses data from a transient Regional Climate Model projection (HadRM3Q0) for 1950-2099 (A1B emissions) to drive hydrological models for three nested catchments on the river Dee in north-east Scotland, to assess potential changes in flood frequency and timing using annual maxima and moving-window analyses. Some results are also shown for an upland catchment in northern England. Modelling is performed both with and without a snow module, to demonstrate the effects of snowfall/melt and how these change through time and vary between catchments. Modelled changes in flood magnitude and timing are non-linear, with most changes for daily mean flows not significant. For longer duration (30-day) flows with snow there are significant decreases in peak magnitude, particularly for the smaller higher altitude Dee catchments, with peaks occurring months earlier in future (changes without snow are generally not significant). There is a general convergence in results with and without snow later in the period, as snow processes become less important, but convergence occurs at different times for different catchments and occurs differently for daily and 30-day peak flows due to the differential effects of snow at different durations. This highlights the importance of including snow processes for such catchments, particularly for longer duration flows, but also highlights the complexity of interactions: Physical catchment properties, the balance between precipitation occurrence and temperature, and how this balance alters as the climate changes will each be critical in determining the impact on the magnitude and timing of peak flows, making it hard to generalise results

    Regionalisation of climate impacts on flood flows to support the development of climate change guidance for Flood Management

    Get PDF
    Current Defra / Environment Agency guidance (FCDPAG3 supplementary note: http://www.defra.gov.uk/environ/fcd/pubs/pagn/climatechangeupdate.pdf) requires all flood management plans to allow for climate change by incorporating, within a sensitivity analysis, an increase in river flows of up 20% over the next 50 years, and beyond. This guidance is the same for all of England and Wales, making no allowance for regional variation in climate change or catchment type. This reflects the lack of scientific evidence to resolve the spatial distribution of potential impacts on flood flows with enough confidence to set such policy regionally. The 20% allowance was first raised in 1999 for MAFF and subsequently reviewed following the release of the UKCIP02 scenarios. Although the 20% figure is a memorable precautionary target, there is the risk that it leads to a significant under- or over-estimation of future flood risk in individual catchments. Defra and the Environment Agency procured project FD2020 (Regionalisation of climate change impacts on flood flows) to provide a more rigorous science base for refreshing the FCDPAG3: supplementary note guidance. The FD2020 approach is exploring the relationships between catchment characteristics and climate change impacts on peak flows in a “scenario neutral” way. This is done by defining a regular set of changes in climate that encompass all the current knowledge from the new scenarios available from the IPCC Fourth Assessment Report. For each of the 155 catchments included in the research, this broad approach will provide multiple scenarios to produce a “vulnerability surface” for change in the metrics of peak flows (e.g. the 20-year flood flow). Some of the UKCP09 products have also been used to understand what these projections may mean for changes to peak flow. The catchment-based analysis will be used to generalise to other gauged sites across Britain, using relationships with catchment characteristics, providing the scientific evidence for the development of regional guidance on climate change allowances. Specifically the project is: Investigating the impact of climate change on peak river flows in over 150 catchments across Britain to assess the suitability of the FCDPAG3 20% climate change allowance. Investigating catchment response to climate change to identify potential similarities such that the FCDPAG3 nationwide allowance could be regionalised. Investigating the uncertainty in changes to future peak river flows from climate change. Developing an approach that has longevity beyond the project timeframe and the lifetime of the latest generation of climate model results

    Proteomic profiling of bovine M. longissimus lumborum from Crossbred Aberdeen Angus and Belgian Blue sired steers varying in genetic merit for carcass weight

    Get PDF
    Bovine skeletal muscle is a tissue of significant value to the beef industry and global economy. Proteomic analyses offer the opportunity to detect molecular mechanisms regulating muscle growth and intramuscular fat accumulation. The current study aimed to investigate differences in protein abundance in skeletal muscle tissue of cattle from two breeds of contrasting maturity (early vs. late maturing), adiposity, and muscle growth potential, namely, Belgian Blue (BB) × Holstein Friesian and Aberdeen Angus (AA) × Holstein Friesian. Twenty AA (n = 10) and BB (n = 10) sired steers, the progeny of sires of either high or low genetic merit, expressed as expected progeny difference for carcass weight (EPDcwt), and bred through AI, were evaluated as 4 genetic groups, BB-High, BB-Low, AA-High, and AA-Low (n = 5 per treatment). Chemical composition analysis of M. longissimus lumborum showed greater protein and moisture and decreased lipid concentrations for BB-sired compared with AA-sired steers. To investigate the effects of both sire breed and EPDcwt on M. longissimus lumborum, proteomic analysis was performed using 2-dimensional difference gel electrophoresis followed by mass spectrometry. Proteins were identified from their peptide sequences, using the National Center for Biotechnology Information (NCBI) and Swiss-prot databases. Metabolic enzymes involved in glycolysis (glycogen phosphorylase, phosphoglycerate mutase) and the citric acid cycle (aconitase 2, oxoglutarate dehydrogenase) were increased in AA- vs. BB-sired steers. Expression of proteins involved in cell structure, such as myosin light chain isoforms and troponins I and T, were also altered due to sire breed. Furthermore, heat shock protein β-1 and peroxiredoxin 6, involved in cell defense, had increased abundance in muscle of AA-sired relative to BB-sired steers. Protein abundance of glucose-6-phosphate isomerase, enolase-3, and pyruvate kinase was greater in AA-sired animals of High compared with Low EPDcwt. Changes in the expression of these proteins were supported by gene expression analysis using quantitative real-time PCR. This information will aid in our understanding of genetic infl uences controlling muscle growth and fat accumulation and could contribute to future breeding programs to increase lean tissue gain of beef cattle

    Learning to rank from medical imaging data

    Get PDF
    Medical images can be used to predict a clinical score coding for the severity of a disease, a pain level or the complexity of a cognitive task. In all these cases, the predicted variable has a natural order. While a standard classifier discards this information, we would like to take it into account in order to improve prediction performance. A standard linear regression does model such information, however the linearity assumption is likely not be satisfied when predicting from pixel intensities in an image. In this paper we address these modeling challenges with a supervised learning procedure where the model aims to order or rank images. We use a linear model for its robustness in high dimension and its possible interpretation. We show on simulations and two fMRI datasets that this approach is able to predict the correct ordering on pairs of images, yielding higher prediction accuracy than standard regression and multiclass classification techniques

    El Acaparamiento de Tierras en América Latina y el Caribe Visto Desde una Perspectiva Internacional más Amplia

    Get PDF
    Introducción y mensajes claves Este documento se basa en la investigación empírica que fue encomendada por la Organización de las Naciones Unidas para la Alimentación y la Agricultura (FAO) sobre las condiciones y tendencias del ―acaparamiento de tierras‖ en 17 países de América Latina y el Caribe (véase el Anexo para una lista completa de los estudios, así como el documento síntesis correspondiente; FAO, 2011). Los 17 estudios se concluyeron a mediados de 2011. El marco analítico común de los estudios es amplio, pero a la vez focalizado. Por un lado es amplio porque analiza los procesos generales de las tierras rurales y la concentración de capital en el contexto de la globalización neoliberal. Por el otro, es focalizado porque analiza el fenómeno del ―acaparamiento de tierras‖ basándose estrictamente en tres dimensiones específicas, a saber: i) el gran alcance de las adquisiciones de tierra a gran escala; ii) la participación de los gobiernos extranjeros en estos tratos sobre tierras; y iii) el impacto negativo de dichas inversiones recientes en tierras sobre la seguridad alimentaria del país receptor. Es en gran medida debido a este tipo de marco analítico que la mayoría de los estudios pudieron desentrañar y recopilar gran cantidad de material empírico relacionado con la dinámica de las tierras en la región; sin embargo, dado que el enfoque de su análisis y conclusiones se basó en la definición y la dimensión angostas del acaparamiento de tierras, la conclusión obtenida fue que el ―acaparamiento de tierras‖ se da únicamente en dos países de la región: Argentina y Brasil. ..

    Acaparamiento de tierras y acumulación capitalista: aspectos clave en América Latina

    Get PDF
    __Abstract__ We introduce this special issue by explaining seven characteristics of land grabbing in Latin America. These features are not unique to the region. By highlighting them – arguing, for instance, that a key aspect in Latin America is intra-regional land grabbing driven by (trans)Latina companies – we hope to inspire new cross-regional comparisons to understand the dynamics of “global” land grabbing. Our focus on Latin America challenges some problematic generalisations in the literature, for instance, that land grabs occur mainly in fragile states. We interrogate the relationship between land grabbing and the “foreignisation” narrative, and the need to revisit the broader question of land concentration. Thus we build upon the literature locating land grabs and the land question within the political economy of global capitalism

    Nutrient concentration relationships between the fourth petiole and upper-stem of potato plants

    Get PDF
    Successfully evaluating the nutritional status of a crop during growth and development is dependent upon sampling an identifiable plant part. Consistently sampling a petiole of the same maturity in potatoes (Solanum tuberosum L.) is difficult. We evaluated the nutrient relationships between the upper-stem and the fourth petiole from Russet Burbank plants in field studies having N, P, K, Zn or Mn variables. The upper-stem was obtained by excising the stem below the sixth leaf and removing all leaves and the terminal meristem. Petole NO3-N, P, K, Zn and Mn concentrations were from deficient to sufficient. The NO 3-N, P and K concentrations were similar in the fourth petiole and upper-stem, while the Zn concentration was 40% higher in the upper-stem. Calcium, Mg and Mn concentrations were lower in the upper-stem than in the fourth petiole. Copper and S relationships were not adequately defined. The fourth petiole's NO 3-N, P and K diagnostic concentrations now used to monitor plant nutrient status can also be used for upper-stem samples. Zinc diagnostic concentrations should be increased, while Ca, Mg and Mn concentrations should be adjusted downward in the upper-tem. Additional data are needed to refine the Ca and Mg relationships, and to establish relationships for Cu, S and other essential nutrients. A significant advantage of using the upper-stem is the elimination of the petiole selection problem when sampling
    corecore