670 research outputs found
Object Reuse and Exchange
The Open Archives Object Reuse and Exchange (OAI-ORE) project defines standards for the description and exchange of aggregations of Web resources. The OAI-ORE abstract data model is conformant with the Architecture of the World Wide Web and leverages concepts from the Semantic Web, including RDF descriptions and Linked Data. In this paper we provide a brief review of a motivating example and its serialization in Atom
A comparison of satellite- and ground-based measurements of SO2emissions from Tungurahua volcano, Ecuador
Satellite-measured SO2 mass loadings and ground-based measurements of SO2 emission rate are not directly comparable, with âŒ40% differences between mean emissions reported by each technique from Tungurahua volcano, Ecuador, during late 2007. Numerical simulations of postemission processing and dispersal of Tungurahua's SO2 emissions enable more effective comparison of ground- and satellite-based SO2 data sets, reducing the difference between them and constraining the impact of plume processing on satellite SO2 observations. Ground-based measurements of SO2 emission rate are used as the model input, and simulated SO2 mass loadings are compared to those measured by the Ozone Monitoring Instrument (OMI). The changing extent of SO2 processing has a significant impact on daily variation in SO2 mass loading for a fixed volcanic emission rate. However, variations in emission rate at Tungurahua are large, suggesting that overall volcanic source strength and not subsequent processing is more likely to be the dominant control on atmospheric mass loading. SO2 emission rate estimates are derived directly from the OMI observations using modeled SO2 lifetime. Good agreement is achieved between both observed and simulated mass loadings (âŒ21%) and satellite-derived and ground-measured SO2 emission rates (âŒ18%), with a factor of 2 improvement over the differences found by simple direct comparison. While the balance of emission source strength and postemission processing will differ between volcanoes and regions, under good observation conditions and where SO2 lifetime is âŒ24 hours, satellite-based sensors like OMI may provide daily observations of SO2 mass loading which are a good proxy for volcanic source strength
Transcatheter Aortic Valve Implantation in Dialysis Patients
Background/Aims: Transcatheter aortic valve implantation (TAVI) has emerged as a new therapeutic option for high-risk patients. However, dialysis patients were excluded from all previous studies. The aim of this study is to compare the outcomes of TAVI for dialysis patients with those for patients with chronic kidney disease (CKD) stages 3 and 4 and to compare TAVI with open surgery in dialysis patients. Methods: Part I: comparison of 10 patients on chronic hemodialysis with 116 patients with non-dialysis-dependent CKD undergoing TAVI. Part II: comparison of transcatheter (n = 15) with open surgical (n = 24) aortic valve replacement in dialysis patients. Results: Part I: dialysis patients were significantly younger (72.3 vs. 82.0 years; p < 0.01). Hospital stay was significantly longer in dialysis patients (21.8 vs. 12.1 days; p = 0.01). Overall 30-day mortality was 3.17%, with no deaths among dialysis patients. Six-month survival rates were similar (log-rank p = 0.935). Part II: patient age was comparable (66.5 vs. 69.5 years; p = 0.42). Patients in the surgical group tended to stay longer in hospital than TAVI patients (29.5 vs. 22.5 days; p = 0.35). Conclusion: TAVI is a safe procedure in patients on chronic hemodialysis. Until new data become available, we find no compelling reason to refuse these patients TAVI. Copyright (C) 2012 S. Karger AG, Base
Remarks on Stable and Quasi-stable k-Strings at Large N
We discuss k-strings in the large-N Yang-Mills theory and its supersymmetric
extension. Whereas the tension of the bona fide (stable) QCD string is expected
to depend only on the N-ality of the representation, tensions that depend on
specific representation R are often reported in the lattice literature. In
particular, adjoint strings are discussed and found in certain simulations. We
clarify this issue by systematically exploiting the notion of the quasi-stable
strings which becomes well-defined at large N. The quasi-stable strings with
representation-dependent tensions decay, but the decay rate (per unit length
per unit time) is suppressed as Lambda^2 F(N) where F(N) falls off as a
function of N. It can be determined on the case-by-case basis. The quasi-stable
strings eventually decay into stable strings whose tension indeed depends only
on the N-ality.
We also briefly review large-N arguments showing why the Casimir formula for
the string tension cannot be correct, and present additional arguments in favor
of the sine formula. Finally, we comment on the relevance of our estimates to
Euclidean lattice measurements.Comment: 40 pages, Latex. 10 figures. v2: final version accepted for
publication in Nucl.Phys.
Pathological completion in the intact visual field of hemianopia patients
We investigated figure segregation in the intact visual field (VF) of hemianopia patients. Three patients and matched controls performed a YesâNo figure detection task, where square or square fragments were embedded in a background of randomly oriented Gabor elements. We varied orientation and number of the fragment elements, stimulus eccentricity and background density (BD). Figure detection was impaired in all three patients in the entire intact VF, but potentially more pronounced in patients with cortical lesions. âPathological completionâ was most frequently observed for high BDs and for square fragments oriented towards the blind hemifield. Our findings confirm contour integration deficits in the intact VF of hemianopia patients. Further, our results indicate that (1) contour integration deficits are exacerbated by contextual interaction and (2) âpathological completionâ appears to be more likely associated with lesions of cortical rather than geniculo-striate origin. The deficits point to increased lateral suppressive inputs from background elements
Practice Makes Imperfect: Restorative Effects of Sleep on Motor Learning
Emerging evidence suggests that sleep plays a key role in procedural learning, particularly in the continued development of motor skill learning following initial acquisition. We argue that a detailed examination of the time course of performance across sleep on the finger-tapping task, established as the paradigm for studying the effect of sleep on motor learning, will help distinguish a restorative role of sleep in motor skill learning from a proactive one. Healthy subjects rehearsed for 12 trials and, following a night of sleep, were tested. Early training rapidly improved speed as well as accuracy on pre-sleep training. Additional rehearsal caused a marked slow-down in further improvement or partial reversal in performance to observed levels below theoretical upper limits derived on the basis of early pre-sleep rehearsal. This decrement in learning efficacy does not occur always, but if and only if it does, overnight sleep has an effect in fully or partly restoring the efficacy and actual performance to the optimal theoretically achieveable level. Our findings re-interpret the sleep-dependent memory enhancement in motor learning reported in the literature as a restoration of fatigued circuitry specialized for the skill. In providing restitution to the fatigued brain, sleep eliminates the rehearsal-induced synaptic fatigue of the circuitry specialized for the task and restores the benefit of early pre-sleep rehearsal. The present findings lend support to the notion that latent sleep-dependent enhancement of performance is a behavioral expression of the brain's restitution in sleep
Prognostic value of cardiac hybrid imaging integrating single-photon emission computed tomography with coronary computed tomography angiography
Aims Although cardiac hybrid imaging, fusing single-photon emission computed tomography (SPECT) myocardial perfusion imaging with coronary computed tomography angiography (CCTA), provides important complementary diagnostic information for coronary artery disease (CAD) assessment, no prognostic data exist on the predictive value of cardiac hybrid imaging. Hence, the aim of this study was to assess the prognostic value of hybrid SPECT/CCTA images. Methods and results Of 335 consecutive patients undergoing a 1-day stress/rest 99mTc-tetrofosmin SPECT and a CCTA, acquired on stand-alone scanners and fused to obtain cardiac hybrid images, follow-up was obtained in 324 patients (97%). Survival free of all-cause death or non-fatal myocardial infarction (MI) and free of major adverse cardiac events (MACE: death, MI, unstable angina requiring hospitalization, coronary revascularizations) was determined using the Kaplan-Meier method for the following groups: (i) stenosis by CCTA and matching reversible SPECT defect; (ii) unmatched CCTA and SPECT finding; and (iii) normal finding by CCTA and SPECT. Cox's proportional hazard regression was used to identify independent predictors for cardiac events. At a median follow-up of 2.8 years (25th-75th percentile: 1.9-3.6), 69 MACE occurred in 47 patients, including 20 death/MI. A corresponding matched hybrid image finding was associated with a significantly higher death/MI incidence (P < 0.005) and proved to be an independent predictor for MACE. The annual death/MI rate was 6.0, 2.8, and 1.3% for patients with matched, unmatched, and normal findings. Conclusion Cardiac hybrid imaging allows risk stratification in patients with known or suspected CAD. A matched defect on hybrid image is a strong predictor of MAC
Nernst branes in gauged supergravity
We study static black brane solutions in the context of N = 2 U(1) gauged
supergravity in four dimensions. Using the formalism of first-order flow
equations, we construct novel extremal black brane solutions including examples
of Nernst branes, i.e. extremal black brane solutions with vanishing entropy
density. We also discuss a class of non-extremal generalizations which is
captured by the first-order formalism.Comment: 44 pages, 3 figures, v2: added appendix B and references, minor
typographic changes, v3: added some clarifying remarks, version published in
JHE
Situated teaching-learning arrangements for the promotion of sustainability competencies in the in-company training of food professions
Der Modellversuch âNachhaltigkeit in den Lebensmittelberufen (NachLeben)â entwickelt und erprobt situierte betriebliche Lehr-Lernarrangements zur Förderung der Bewertungs-, Gestaltungs- und Systemkompetenz fĂŒr Ausbildungsberufe in der Lebensmittelindustrie und im Lebensmittelhandwerk. Ein Beispiel ist das Lehr-Lernarrangement âKunststoffe im Produktionsprozessâ, welches den Fokus des Artikels bildet. (DIPF/Orig.)The pilot project âSustainability in the food professions (NachLeben)â develops and tests situated in-company teaching-learning arrangements to promote assessment, design, and system competence for training occupations in the food industry and the food trade. One example is the teaching-learning arrangement âPlastics in the production processâ, which is the focus of the article. (DIPF/Orig.
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