3,778 research outputs found

    Hydro-economic modeling with aquifer-river interactions for sustainable basin management

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    Water demands for irrigation, urban and environmental uses in many arid and semiarid regions continue to grow, while freshwater supplies from surface and groundwater resources are becoming scarce and are expected to decline because of climate change. Policymakers in these regions are faced with hard choices on water management and policies. Hydro-economic modeling is the state-of-the arts tool to assist policymakers in the design and implementation of sustainable water management policies in basins. The strength of hydro-economic modeling lies in its capacity to integrate key biophysical and socio-economic components within a coherent framework. A major gap in developments of hydro-economic models to date has been the difficulty of integrating surface and groundwater flows based on the theoretically correct Darcy equations used by the hydrogeological community. The hydro-economic model presented here specifies a spatially-explicit groundwater flow element. The methodological contribution to previous modeling efforts is the explicit specification of the aquifer-river interactions, which are important when aquifer systems make a sizable contribution to basin resources. This advanced framework is applied to the Jucar basin (Spain) for the assessment of different climate change scenarios and policy choices, specially the hydrologic, land use and economic outcomes. The response to scenarios integrates the multiple dimensions of water resources, allowing results to provide valuable information on the basin scale climate change adaptation paths to guide alternative policy choices using sound science.The research has been supported by projects INIA RTA2010-00109-C04 and RTA2014-00050-00-00 from the Spanish Ministry of Economy and Competitiveness, and BIL13MA072 from the MAPFRE Foundation.Publishe

    Structural Characterization of the Enzymes Composing the Arginine Deiminase Pathway in Mycoplasma penetrans

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    The metabolism of arginine towards ATP synthesis has been considered a major source of energy for microorganisms such as Mycoplasma penetrans in anaerobic conditions. Additionally, this pathway has also been implicated in pathogenic and virulence mechanism of certain microorganisms, i.e. protection from acidic stress during infection. In this work we present the crystal structures of the three enzymes composing the gene cluster of the arginine deiminase pathway from M. penetrans: arginine deiminase (ADI), ornithine carbamoyltransferase (OTC) and carbamate kinase (CK). The arginine deiminase (ADI) structure has been refined to 2.3 Å resolution in its apo-form, displaying an "open" conformation of the active site of the enzyme in comparison to previous complex structures with substrate intermediates. The active site pocket of ADI is empty, with some of the catalytic and binding residues far from their active positions, suggesting major conformational changes upon substrate binding. Ornithine carbamoyltransferase (OTC) has been refined in two crystal forms at 2.5 Å and 2.6 Å resolution, respectively, both displaying an identical dodecameric structure with a 23-point symmetry. The dodecameric structure of OTC represents the highest level of organization in this protein family and in M.penetrans it is constituted by a novel interface between the four catalytic homotrimers. Carbamate kinase (CK) has been refined to 2.5 Å resolution and its structure is characterized by the presence of two ion sulfates in the active site, one in the carbamoyl phosphate binding site and the other in the β-phosphate ADP binding pocket of the enzyme. The CK structure also shows variations in some of the elements that regulate the catalytic activity of the enzyme. The relatively low number of metabolic pathways and the relevance in human pathogenesis of Mycoplasma penetrans places the arginine deiminase pathway enzymes as potential targets to design specific inhibitors against this human parasite

    New VME indicator species (excluding corals and sponges) and some potential VME elements of the NAFO Regulatory Area

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    A review of over 500 taxa known to occur in the NRA revealed three additional faunal groups (additional to NAFO 2008a) that meet the criteria for a VME indicator based on traits related to functional significance, fragility, and the life-history traits of component species that produce a slow recovery to disturbance. These are crinoids, erect bryozoans and large sea squirts. For each group it is the dense aggregations (beds/fields) that are considered to be VME in order to establish functional significance. Although each group is present in the NRA, data to date have not revealed any concentrations of note with the exception of one catch of the stalked tunicate Boltenia ovifera (large sea squirt). Black corals were considered to be VME indicators by NAFO based on what was then known of their distribution. These were included based on the uniqueness/rarity criterion of habitats of rare, threatened or endangered species that occur only in discrete areas, however evaluation of their distribution using trawl survey, rock dredge and underwater video has indicated that they have widespread occurrence at low densities in the NRA and along the continental slopes off Labrador. However, because they are thought to be extremely long-lived and therefore ‘iconic’ if not rare, we have identified where the highest frequency of occurrence is for this taxon. Lastly, based on NEREIDA multibeam bathymetry we have identified more canyon heads, steep flanks and new seamounts in the NRA as possible VME elements

    PERCIVAL: Open-source posit RISC-V core with quire capability

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    The posit representation for real numbers is an alternative to the ubiquitous IEEE 754 floating-point standard. In this work, we present PERCIVAL, an application-level posit RISC-V core based on CVA6 that can execute all posit instructions, including the quire fused operations. This solves the obstacle encountered by previous works, which only included partial posit support or which had to emulate posits in software. In addition, Xposit, a RISC-V extension for posit instructions is incorporated into LLVM. Therefore, PERCIVAL is the first work that integrates the complete posit instruction set in hardware. These elements allow for the native execution of posit instructions as well as the standard floating-point ones, further permitting the comparison of these representations. FPGA and ASIC synthesis show the hardware cost of implementing 32-bit posits and highlight the significant overhead of including a quire accumulator. However, results show that the quire enables a more accurate execution of dot products. In general matrix multiplications, the accuracy error is reduced up to 4 orders of magnitude. Furthermore, performance comparisons show that these accuracy improvements do not hinder their execution, as posits run as fast as single-precision floats and exhibit better timing than double-precision floats, thus potentially providing an alternative representation

    How does a cadaver model work for testing ultrasound diagnostic capability for rheumatic-like tendon damage?

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    To establish whether a cadaver model can serve as an effective surrogate for the detection of tendon damage characteristic of rheumatoid arthritis (RA). In addition, we evaluated intraobserver and interobserver agreement in the grading of RA-like tendon tears shown by US, as well as the concordance between the US findings and the surgically induced lesions in the cadaver model. RA-like tendon damage was surgically induced in the tibialis anterior tendon (TAT) and tibialis posterior tendon (TPT) of ten ankle/foot fresh-frozen cadaveric specimens. Of the 20 tendons examined, six were randomly assigned a surgically induced partial tear; six a complete tear; and eight left undamaged. Three rheumatologists, experts in musculoskeletal US, assessed from 1 to 5 the quality of US imaging of the cadaveric models on a Likert scale. Tendons were then categorized as having either no damage, (0); partial tear, (1); or complete tear (2). All 20 tendons were blindly and independently evaluated twice, over two rounds, by each of the three observers. Overall, technical performance was satisfactory for all items in the two rounds (all values over 2.9 in a Likert scale 1-5). Intraobserver and interobserver agreement for US grading of tendon damage was good (mean κ values 0.62 and 0.71, respectively), with greater reliability found in the TAT than the TPT. Concordance between US findings and experimental tendon lesions was acceptable (70-100 %), again greater for the TAT than for the TPT. A cadaver model with surgically created tendon damage can be useful in evaluating US metric properties of RA tendon lesions

    Coping with environmental eukaryotes; identification of pseudomonas syringae genes during the interaction with alternative hosts or predators

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    Understanding the molecular mechanisms underpinning the ecological success of plant pathogens is critical to develop strategies for controlling diseases and protecting crops. Recent observations have shown that plant pathogenic bacteria, particularly Pseudomonas, exist in a range of natural environments away from their natural plant host e.g., water courses, soil, non-host plants. This exposes them to a variety of eukaryotic predators such as nematodes, insects and amoebae present in the environment. Nematodes and amoeba in particular are bacterial predators while insect herbivores may act as indirect predators, ingesting bacteria on plant tissue. We therefore postulated that bacteria are probably under selective pressure to avoid or survive predation and have therefore developed appropriate coping mechanisms. We tested the hypothesis that plant pathogenic Pseudomonas syringae are able to cope with predation pressure and found that three pathovars show weak, but significant resistance or toxicity. To identify the gene systems that contribute to resistance or toxicity we applied a heterologous screening technique, called Rapid Virulence Annotation (RVA), for anti-predation and toxicity mechanisms. Three cosmid libraries for P. syringae pv. aesculi, pv. tomato and pv. phaseolicola, of approximately 2000 cosmids each, were screened in the susceptible/non-toxic bacterium Escherichia coli against nematode, amoebae and an insect. A number of potential conserved and unique genes were identified which included genes encoding haemolysins, biofilm formation, motility and adhesion. These data provide the first multi-pathovar comparative insight to how plant pathogens cope with different predation pressures and infection of an insect gut and provide a foundation for further study into the function of selected genes and their role in ecological success
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