723 research outputs found

    Sustainable Planning of Land Use Changes in farming areas under ecological protection

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    Land use has been changing in the last decades because of agricultural intensification and land abandonment which implies deterioration in the optimum habitat structure and quality. Habitat degradation and loss, resulting from changes in land use remain significant drivers of biodiversity loss. These trends are widely recognised and have forced national and international agencies to identify protected sites for natural areas with high biodiversity value. Special Protection Areas (SPAs) are natural zones particularly relevant for nature conservation. Regional planning is bound to play an increasing role in nature conservation policies because much biodiversity is located in farming areas outside natural parks. Agriculture in the Mediterranean Basin has always been highly dependent on rainfed crops, cereal, vine and olive. Vine growing plays an important role not only from the economic point of view, but also environmentally as a permanent plant cover in terms of preventing erosion, managing land and water resources in a sustainable way, defending against desertification an settling population in rural areas. A Geographic Information System (GIS) was used to implement a decision tool system to analyse the feasibility of new proposals to upgrade traditional vineyards in Castilla-La Mancha, Spain. The study focuses on the sustainability of current farming practices in Special Protection Areas for Steppe Land Birds. This paper presents a model to quantify the resulting habitat fragmentation basing on infrastructure facilities, leading to mapping areas where to apply restriction measures to prevent physical destruction of the habita

    Berezin Quantization of Gauged WZW and Coset Models

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    Gauged WZW and coset models are known to be useful to prove holomorphic factorization of the partition function of WZW and coset models. In this note we show that these gauged models can be also important to quantize the theory in the context of the Berezin formalism. For gauged coset models Berezin quantization procedure also admits a further holomorphic factorization in the complex structure of the moduli space.Comment: 15+1 pages, no figures, revte

    Measurements and modeling of Alfven eigenmode induced fast ion transport and loss in DIII-D and ASDEX Upgrade

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    Neutral beam injection into reversed magnetic shear DIII-D and ASDEX Upgrade plasmas produces a variety of Alfve´nic activity including toroidicity-induced Alfve´n eigenmodes and reversed shear Alfve´n eigenmodes (RSAEs). These modes are studied during the discharge current ramp phase when incomplete current penetration results in a high central safety factor and increased drive due to multiple higher order resonances. Scans of injected 80 keV neutral beam power on DIII-D showed a transition from classical to AE dominated fast ion transport and, as previously found, discharges with strong AE activity exhibit a deficit in neutron emission relative to classical predictions. By keeping beam power constant and delaying injection during the current ramp, AE activity was reduced or eliminated and a significant improvement in fast ion confinement observed. Similarly, experiments in ASDEX Upgrade using early 60 keV neutral beam injection drove multiple unstable RSAEs. Periods of strong RSAE activity are accompanied by a large (peak dSn=Sn 60%) neutron deficit. Losses of beam ions modulated at AE frequencies were observed using large bandwidth energy and pitch resolving fast ion loss scintillator detectors and clearly identify their role in the process. Modeling of DIII-D loss measurements using guiding center following codes to track particles in the presence of ideal magnetohydrodynamic (MHD) calculated AE structures (validated by comparison to experiment) is able to reproduce the dominant energy, pitch, and temporal evolution of these losses. While loss of both co and counter current fast ions occurs, simulations show that the dominant loss mechanism observed is the mode induced transition of counter-passing fast ions to lost trapped orbits. Modeling also reproduces a coherent signature of AE induced losses and it was found that these coherent losses scale proportionally with the amplitude; an additional incoherent contribution scales quadratically with the mode amplitude. VC 2011 American Institute of Physics.US Department of Energy DE-FC02-04ER54698, SC-G903402, DE-AC02-99CH11466, DE-FG03-97ER54415, DE-FG02-89ER53296, DE-FG02-08ER5499

    Beam ion losses due to energetic particle geodesic acoustic modes

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    We report the first experimental observations of fast-ion loss in a tokamak due to energetic particle driven geodesic acoustic modes (EGAMs). A fast-ion loss detector installed on the DIII-D tokamak observes bursts of beam ion losses coherent with the EGAM frequency. The EGAM activity results in a significant loss of beam ions, comparable to the first orbit losses. The pitch angles and energies of the measured fast-ion losses agree with predictions from a full orbit simulation code SPIRAL, which includes scattering and slowing-down.U.S. Department of Energy DE-FC02-04ER 54698, SC-G903402, DE-AC02-09CH1146

    Alfven eigenmode stability and fast ion loss in DIII-D and ITER reversed magnetic shear plasmas

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    Neutral beam injection into reversed-magnetic shear DIII-D plasmas produces a variety of Alfvenic activity including ´ toroidicity-induced Alfven eigenmodes (TAEs) and reversed shear Alfv ´ en eigenmodes (RSAEs). With measured ´ equilibrium profiles as inputs, the ideal MHD code NOVA is used to calculate eigenmodes of these plasmas. The postprocessor code NOVA-K is then used to perturbatively calculate the actual stability of the modes, including finite orbit width and finite Larmor radius effects, and reasonable agreement with the spectrum of observed modes is found. Using experimentally measured mode amplitudes, fast ion orbit following simulations have been carried out in the presence of the NOVA calculated eigenmodes and are found to reproduce the dominant energy, pitch and temporal evolution of the losses measured using a large bandwidth scintillator diagnostic. The same analysis techniques applied to a DT 8 MA ITER steady-state plasma scenario with reversed-magnetic shear and both beam ion and alpha populations show Alfven eigenmode instability. Both RSAEs and TAEs are found to be unstable ´ with maximum growth rates occurring for toroidal mode number n = 6 and the majority of the drive coming from fast ions injected by the 1 MeV negative ion beams. AE instability due to beam ion drive is confirmed by the non-perturbative code TAEFL. Initial fast ion orbit following simulations using the unstable modes with a range of amplitudes (δB/B = 10−5–10−3) have been carried out and show negligible fast ion loss. The lack of fast ion loss is a result of loss boundaries being limited to large radii and significantly removed from the actual modes themselves.US Department of Energy DE-FC02-04ER54698, DE-AC02-09CH11466, SC-G903402, DE-AC05-00OR22725, DE-FG03-97ER5441

    First principles of modelling the stabilization of microturbulence by fast ions

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    The observation that fast ions stabilize ion-temperature-gradient-driven microturbulence has profound implications for future fusion reactors. It is also important in optimizing the performance of present-day devices. In this work, we examine in detail the phenomenology of fast ion stabilization and present a reduced model which describes this effect. This model is derived from the high-energy limit of the gyrokinetic equation and extends the existing ‘dilution’ model to account for nontrivial fast ion kinetics. Our model provides a physicallytransparent explanation for the observed stabilization and makes several key qualitative predictions. Firstly, that different classes of fast ions, depending on their radial density or temperature variation, have different stabilizing properties. Secondly, that zonal flows are an important ingredient in this effect precisely because the fast ion zonal response is negligible. Finally, that in the limit of highly-energetic fast ions, their response approaches that of the ‘dilution’ model; in particular, alpha particles are expected to have little, if any, stabilizing effect on plasma turbulence. We support these conclusions through detailed linear and nonlinear gyrokinetic simulations

    Fast Mode Decision on H.264/AVC Baseline Profile for real-time performance

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    In this paper a new fast mode decision (FMD) algorithm is proposed for the recent H.264/AVC video coding standard, aiming to reduce its computational load without loosing coding efficiency. This algorithm identifies redundancy and selects the minimum sub-set of modes for each macroblock (MB) required to provide high rate-distortion (RD) efficiency. It is based on a fast analysis of the histogram of the difference image between frames which classifies the areas of each frame as active or non-active by means of an adaptive thresholding technique. More coding effort is devoted to active areas with the selection of a large sub-set of Modes, as these areas are expected to be the most relevant in terms of RD cost. Results show reduction values around 35–65% of motion estimation (ME) time, preserving the RD cost for the Baseline Profile, by using P-Slices and without needing B-Slices. Moreover, the strategy works as an intelligent tool for real-time applications with constrained number of operations per frame: it wisely uses the given operational resources distributing them among those MBs that need it

    Fast ion transport during applied 3D magnetic perturbations on DIII-D

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    Measurements show fast ion losses correlated with applied three-dimensional (3D) fields in a variety of plasmas ranging from L-mode to resonant magnetic perturbation (RMP) edge localized mode (ELM) suppressed H-mode discharges. In DIII-D L-mode discharges with a slowly rotating n = 2 magnetic perturbation, scintillator detector loss signals synchronized with the applied fields are observed to decay within one poloidal transit time after beam turnoff indicating they arise predominantly from prompt loss orbits. Full orbit following using M3D-C1 calculations of the perturbed fields and kinetic profiles reproduce many features of the measured losses and points to the importance of the applied 3D field phase with respect to the beam injection location in determining the overall impact on prompt beam ion loss. Modeling of these results includes a self-consistent calculation of the 3D perturbed beam ion birth profiles and scrape-off-layer ionization, a factor found to be essential to reproducing the experimental measurements. Extension of the simulations to full slowing down timescales, including fueling and the effects of drag and pitch angle scattering, show the applied n = 3 RMPs in ELM suppressed H-mode plasmas can induce a significant loss of energetic particles from the core. With the applied n = 3 fields, up to 8.4% of the injected beam power is predicted to be lost, compared to 2.7% with axisymmetric fields only. These fast ions, originating from minor radii ρ > 0.7, are predicted to be primarily passing particles lost to the divertor region, consistent with wide field-of-view infrared periscope measurements of wall heating in n = 3 RMP ELM suppressed plasmas. Edge fast ion Dα (FIDA) measurements also confirm a large change in edge fast ion profile due to the n = 3 fields, where the effect was isolated by using short 50ms RMP-off periods during which ELM suppression was maintained yet the fast ion profile was allowed to recover. The role of resonances between fast ion drift motion and the applied 3D fields in the context of selectively targeting regions of fast ion phase space is also discussed

    Laser-induced fluorescence detection at 266 nm in capillary electrophoresis Polycyclic aromatic hydrocarbon metabolites in biota

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    The separation of five phenolic polycyclic aromatic hydrocarbon metabolites (hydroxy-PAHs) has been performed by cyclodextrin-modified micellar electrokinetic chromatography (CD-MEKC) using a 30 mM borate buffer (pH 9.0) containing 60 mM sodium dodecyl sulfate and varying concentrations of γ-cyclodextrin (γ-CD). A concentration of 12.5 mM γ-CD was found to provide a baseline separation of the five hydroxy-PAHs. We applied conventional fluorescence and laser-induced fluorescence (LIF) detection, using a new, small-size, quadrupled Nd–YAG laser emitting at 266 nm. The best limits of detection, in the low ng/ml range, were achieved using LIF detection. For all analytes, linearity was observed up to ca. 100 ng/ml. As an application, conjugated pyrene metabolites in hepatopancreas samples from the terrestrial isopods Oniscus asellus and Porcellio scaber were separated and detected. Finally, flatfish bile samples from individuals exposed to polluted sediment or crude oil, which were part of an interlaboratory study, were analyzed by CD-MEKC with conventional fluorescence and LIF detection to determine the 1-hydroxypyrene concentrations.The authors wish to thank the Dutch Foundation for the Advancement of Science (NOW) for financial support and equipment (grant No. 344-006). Also, the technical assistance of Mr. J. Buijs is much appreciated
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