1,859 research outputs found
Molecular ND Band Spectroscopy in the Divertor Region of Nitrogen Seeded JET Discharges
In this contribution we present OES measurements in the JET tokamak of the
deuterated NH (ND) radical and the correlation between results of those experiments and
measurement of ammonia production. The observation region covers most of the divertor and
its outer throat. Measurements are performed in different magnetic configurations. The results
include temporal and spatial dependence of the molecular emission intensity and study of the
emission band shape (vibrational and rotational temperatures) during different JET pulses, with
or without nitrogen seeding. Results are a step towards the understanding of nitrogen-containing
molecule creation and destruction in the divertor plasmaEURATOM 63305
Effect of toroidal field ripple on plasma rotation in JET
Dedicated experiments on TF ripple effects on the performance of tokamak plasmas have been carried out at JET. The TF ripple was found to have a profound effect on the plasma rotation. The central Mach number, M, defined as the ratio of the rotation velocity and the thermal velocity, was found to drop as a function of TF ripple amplitude (3) from an average value of M = 0.40-0.55 for operations at the standard JET ripple of 6 = 0.08% to M = 0.25-0.40 for 6 = 0.5% and M = 0.1-0.3 for delta = 1%. TF ripple effects should be considered when estimating the plasma rotation in ITER. With standard co-current injection of neutral beam injection (NBI), plasmas were found to rotate in the co-current direction. However, for higher TF ripple amplitudes (delta similar to 1%) an area of counter rotation developed at the edge of the plasma, while the core kept its co-rotation. The edge counter rotation was found to depend, besides on the TF ripple amplitude, on the edge temperature. The observed reduction of toroidal plasma rotation with increasing TF ripple could partly be explained by TF ripple induced losses of energetic ions, injected by NBI. However, the calculated torque due to these losses was insufficient to explain the observed counter rotation and its scaling with edge parameters. It is suggested that additional TF ripple induced losses of thermal ions contribute to this effect
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Tracer Tests in a Fractured Dolomite: 2. Controls on Mass-Recovery Rates for a Single-Porosity, Heterogeneous Conceptualization
A single-well injection-withdrawal (SWIW) test is evaluated as a tool to differentiate between single- and double-porosity conceptualizations of a system. Results from single-porosity simulations incorporating plume drift are also compared to observed data from a recent series of SWIW tests conducted in a fractured dolomite unit, for which a double-porosity conceptualization has been proposed. We evaluate the difficulty of differentiating the response for a double-porosity conceptualization from that for a heterogeneous, single-porosity conceptualization incorporating plume drift. Results of sensitivity studies on multiple, stochastically generated, heterogeneous transmissivity fields indicate that to simulate extremely slow mass-recovery rates for a SWIW test with a single-porosity conceptualization, the following conditions must be present: plume drift, extreme heterogeneities (high {sigma}InT), and an unusual configuration of the high and low transmissivity regions relative to the well location. A compilation of existing data suggests that the high degree of heterogeneity necessary is rare at the SWIW test scale.The observed data from the SWIW tracer tests cannot be matched to numerical simulation results when a single-porosity conceptualization is assumed. A signature of significant drift is less than 100% mass recovery with a zero derivative with respect to time of the late-time normalized cumulative mass curve indicating mass transported outside the capture zone of the withdrawal well. To minimize the risk of misinterpretation, an important design feature for SWIW tests is the collection of late-time data so that percent total mass recovery can be calculated
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Origin of faults, fissures and volcanic vent alignments at a structural triple junction, Newberry Volcano, central Oregon
Newberry Volcano in central Oregon formed at the intersection of extensional fault systems defining the Basin and Range extensional province, the Cascades Graben and the Brothers Fault Zone. A unique structural orientation characterizes each fault system. Basin and Range faults trend north, northeast and northwest. The Cascade Graben is defined by north-trending faults. The Brothers Fault Zone is defined by northwest trending faults. In this study we mapped faults, fissures, and vent alignments using LiDAR topographic data to investigate the stress regime of the volcanic edifice and surrounding environs. We seek to better understand the relationship between volcanic and tectonic signatures of stress regime and sites for proposed development of geothermal energy. Stress regime across a volcanic edifice reflects some combination of sources from plate motion, magma chambers at depth, and topography of the edifice itself. Orientation of faults, fissures and volcanic vent (cinder cones and volcanic vents typically parallel fault trend) alignments vary systematically around the volcanic edifice at Newberry. On the north side of the volcano, faults, fissures and volcanic vents generally trend north-northwest. Ring dikes, fractures and vents follow the rim defining the edge of the caldera. South of the caldera, faults, fissures and volcanic vents trend northeast. Whereas the ring dike and fault system around the caldera rim clearly reflect volcanic processes, the faults and volcanic features on the north side of the volcano parallel Basin and Range faults away from the edifice and apparently merge northward with the Cascade Graben fault system. Thus we conclude that these are tectonic faults formed in a stress regime controlled by plate motions. In contrast, the northeast trending faults in the south are enigmatic and unlike any other faults found regionally. One possible explanation is that these faults represent one arm of a radial fault system, the north arm of which has been reactivated as the result of overprinting by regional crustal extension. Geothermal prospects occur in the northern fault system, which reflects a tectonic rather than a volcanically or topographically controlled stress regime.Disclaimer: This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof
Flicker Light–Induced Retinal Vasodilation in Diabetes and Diabetic Retinopathy
10.2337/dc09-0075Diabetes Care32112075-2080DICA
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Debris flow initiation in proglacial gullies on Mount Rainier, Washington
Effects of climate change, retreating glaciers, and changing storm patterns on debris flow hazards concern
managers in the Cascade Range (USA) and mountainous areas worldwide. During an intense rainstorm in
November 2006, seven debris flows initiated from proglacial gullies of separate basins on the flanks of Mount
Rainier. Gully heads at glacier termini and widespread failure of gully walls imply that overland flow was transformed
into debris flow along gullies. We characterized gully change and morphology, and assessed spatial
distributions of debris flows to infer the processes and conditions for debris flow initiation. Slopes at gully
heads were greater than ~0.35 m m⁻¹ (19°) and exhibited a significant negative relationship with drainage
area. A break in slope–drainage area trends among debris flow gullies also occurs at ~0.35 m m⁻¹, representing
a possible transition to fluvial sediment transport and erosion. An interpreted hybrid model of debris flow initiation
involves bed failure near gully heads followed by sediment recruitment from gully walls along gully
lengths. Estimates of sediment volume loss from gully walls demonstrate the importance of sediment inputs
along gullies for increasing debris flow volumes. Basin comparisons revealed significantly steeper drainage
networks and higher elevations in debris flow-producing than non-debris flow-producing proglacial areas. The
high slopes and elevations of debris flow-producing proglacial areas reflect positive slope–elevation trends for
the Mount Rainier volcano. Glacier extent therefore controls the slope distribution in proglacial areas, and thus
potential for debris flow generation. As a result, debris flow activity may increase as glacier termini retreat
onto slopes inclined at angles above debris flow initiation thresholds.Keywords: Hazards, Cascade volcanoes, Debris flow, Glacier retreat, Climate change, In-gully debris flow initiatio
Role of Adiposity and Lifestyle in the Relationship Between Family History of Diabetes and 20-Year Incidence of Type 2 Diabetes in U.S. Women
OBJECTIVE - To evaluate to what extent the association between family history of diabetes and risk of type 2 diabetes can be explained by excess adiposity and lifestyle risk factors. RESEARCH DESIGN AND METHODS - We analyzed data from 73,227 women who participated in the Nurses' Health Study cohort. A family history of diabetes was defined as having at least one first-degree family member with diabetes. Lifestyle factors, weight, and height were assessed by using validated questionnaires, and BMI was calculated. The relative risk of type 2 diabetes was estimated using Cox proportional hazards analysis. RESULTS - We documented 5,101 cases of type 2 diabetes during 20 years of follow-up. The age-adjusted relative risk of type 2 diabetes in participants with a family history was 2.27 (95% CI 2.14-2.40) compared with the risk in those without a family history of diabetes. Participants with a family history of diabetes had a higher BMI and were more likely to have a parental history of obesity. BMI explained 21.1% (19.4-22.9) of the association between family history of diabetes and risk of type 2 diabetes. Intakes of red meat, alcohol, and sugar-sweetened beverages explained 1.1% (0.8-1.3), 4.8% (4.3-5.3), and 2.8% (2.4-3.2) of this association, respectively. CONCLUSIONS - These results suggest that excess adiposity and, to a lesser extent, specific dietary habits can explain a substantial part of the association between having a family history of diabetes and risk of type 2 diabetes. © 2010 by the American Diabetes Association
Preanalytical, Analytical, and Computational Factors Affect Homeostasis Model Assessment Estimates
OBJECTIVE—We investigated how β-cell function and insulin sensitivity or resistance are affected by the type of blood sample collected or choice of insulin assay and homeostatis model assessment (HOMA) calculator (http://www.dtu.ox.ac.uk)
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Design, modeling, and current interpretations of the H-19 and H-11 tracer tests at the WIPP site
Site-characterization studies at the Waste Isolation Pilot Plant (WIPP) site in southeastern New Mexico, US identified ground-water flow in the Culebra Dolomite Member of the Rustler Formation as the most likely geologic pathway for radionuclide transport to the accessible environment in the event of a breach of the WIPP repository through inadvertent human intrusion. The results of recent tracer tests, as well as hydraulic tests, laboratory measurements, and re-examination of Culebra geology and stratigraphy, have led to a significant refinement of the conceptual model for transport in the Culebra. Tracer test results and geologic observations suggest that flow occurs within fractures, and to some extent within interparticle porosity and vugs connected by microfractures. Diffusion occurs within all connected porosity. Numerical simulations suggest that the data from the tracer tests cannot be simulated with heterogeneous single-porosity models; significant matrix diffusion appears to be required. The low permeability and lack of significant tracer recovery from tracers injected into the upper Culebra suggest that transport primarily occurs in the lower Culebra
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