3,617 research outputs found
Liberia v. Bickford: the Continuing Problem of Recognition of Governments and Civil Litigation in the United States
Bidirectional ventricular tachycardia in cardiac sarcoidosis.
A 73-year-old man with history of pulmonary sarcoidosis was found to have runs of non-sustained bidirectional ventricular tachycardia (BVT) with two different QRS morphologies on a Holter monitor. Cardiac magnetic resonance delayed gadolinium imaging revealed a region of patchy mid-myocardial enhancement within the left ventricular basal inferolateral myocardium. An 18-fluorodeoxyglucose positron emission tomography (FDG-PET) showed increased uptake in the same area, consistent with active sarcoid, with no septal involvement. Follow-up FDG-PET one year later showed disease progression with new septal involvement. Cardiac sarcoidosis, characterized by myocardial inflammation and interstitial fibrosis that can lead to conduction system disturbance and macro re-entrant arrhythmias, should be considered in differential diagnosis of BVT. BVT may indicate septal involvement with sarcoidosis before the lesions are large enough to be detected radiologically
The use (and misuse) of sediment traps in coral reef environments : theory, observations, and suggested protocols
© The Authors, 2010. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Coral Reefs 30 (2011): 23-38, doi:10.1007/s00338-010-0705-3.Sediment traps are commonly used as standard tools for monitoring “sedimentation” in coral reef environments. In much of the literature where sediment traps were used to measure the effects of “sedimentation” on corals, it is clear from deployment descriptions and interpretations of the resulting data that information derived from sediment traps has frequently been misinterpreted or misapplied. Despite their widespread use in this setting, sediment traps do not provide quantitative information about “sedimentation” on coral surfaces. Traps can provide useful information about the relative magnitude of sediment dynamics if trap deployment standards are used. This conclusion is based first on a brief review of the state of knowledge of sediment trap dynamics, which has primarily focused on traps deployed high above the seabed in relatively deep water, followed by our understanding of near-bed sediment dynamics in shallow-water environments that characterize coral reefs. This overview is followed by the first synthesis of near-bed sediment trap data collected with concurrent hydrodynamic information in coral reef environments. This collective information is utilized to develop nine protocols for using sediment traps in coral reef environments, which focus on trap parameters that researchers can control such as trap height (H), trap mouth diameter (D), the height of the trap mouth above the substrate (z o ), and the spacing between traps. The hydrodynamic behavior of sediment traps and the limitations of data derived from these traps should be forefront when interpreting sediment trap data to infer sediment transport processes in coral reef environments
Local dependence of ion temperature gradient on magnetic configuration, rotational shear and turbulent heat flux in MAST
Experimental data from the Mega Amp Spherical Tokamak (MAST) is used to show
that the inverse gradient scale length of the ion temperature R/LTi (normalized
to the major radius R) has its strongest local correlation with the rotational
shear and the pitch angle of the magnetic field (or, equivalently, an inverse
correlation with q/{\epsilon}, the safety factor/the inverse aspect ratio).
Furthermore, R/LTi is found to be inversely correlated with the
gyro-Bohm-normalized local turbulent heat flux estimated from the density
fluctuation level measured using a 2D Beam Emission Spectroscopy (BES)
diagnostic. These results can be explained in terms of the conjecture that the
turbulent system adjusts to keep R/LTi close to a certain critical value
(marginal for the excitation of turbulence) determined by local equilibrium
parameters (although not necessarily by linear stability).Comment: 6 pages, 3 figures, submitted to PR
A Numerical Relativity Waveform Surrogate Model for Generically Precessing Binary Black Hole Mergers
A generic, non-eccentric binary black hole (BBH) system emits gravitational
waves (GWs) that are completely described by 7 intrinsic parameters: the black
hole spin vectors and the ratio of their masses. Simulating a BBH coalescence
by solving Einstein's equations numerically is computationally expensive,
requiring days to months of computing resources for a single set of parameter
values. Since theoretical predictions of the GWs are often needed for many
different source parameters, a fast and accurate model is essential. We present
the first surrogate model for GWs from the coalescence of BBHs including all
dimensions of the intrinsic non-eccentric parameter space. The surrogate
model, which we call NRSur7dq2, is built from the results of numerical
relativity simulations. NRSur7dq2 covers spin magnitudes up to and mass
ratios up to , includes all modes, begins about orbits
before merger, and can be evaluated in . We find the
largest NRSur7dq2 errors to be comparable to the largest errors in the
numerical relativity simulations, and more than an order of magnitude smaller
than the errors of other waveform models. Our model, and more broadly the
methods developed here, will enable studies that would otherwise require
millions of numerical relativity waveforms, such as parameter inference and
tests of general relativity with GW observations.Comment: 10 pages, 5 figures; Added report numbe
Wave- and tidally-driven flow and sediment flux across a fringing coral reef : southern Molokai, Hawaii
This paper is not subject to U.S. copyright. The definitive version was published in Continental Shelf Research 24 (2004): 1397-1419, doi:10.1016/j.csr.2004.02.010.The fringing coral reef off the south coast of Molokai, Hawaii is currently being studied as part of a US Geological Survey (USGS) multi-disciplinary project that focuses on geologic and oceanographic processes that affect coral reef systems. For this investigation, four instrument packages were deployed across the fringing coral reef during the summer of 2001 to understand the processes governing fine-grained terrestrial sediment suspension on the shallow reef flat (h=1 m) and its advection across the reef crest and onto the deeper fore reef. The time–series measurements suggest the following conceptual model of water and fine-grained sediment transport across the reef: Relatively cool, clear water flows up onto the reef flat during flooding tides. At high tide, more deep-water wave energy is able to propagate onto the reef flat and larger Trade wind-driven waves can develop on the reef flat, thereby increasing sediment suspension. Trade wind-driven surface currents and wave breaking at the reef crest cause setup of water on the reef flat, further increasing the water depth and enhancing the development of depth-limited waves and sediment suspension. As the tide ebbs, the water and associated suspended sediment on the reef flat drains off the reef flat and is advected offshore and to the west by Trade wind- and tidally- driven currents. Observations on the fore reef show relatively high turbidity throughout the water column during the ebb tide. It therefore appears that high suspended sediment concentrations on the deeper fore reef, where active coral growth is at a maximum, are dynamically linked to processes on the muddy, shallow reef flat
Comprehensive system models: Strategies for evaluation
The task of evaluating comprehensive earth system models is vast involving validations of every model component at every scale of organization, as well as tests of all the individual linkages. Even the most detailed evaluation of each of the component processes and the individual links among them should not, however, engender confidence in the performance of the whole. The integrated earth system is so rich with complex feedback loops, often involving components of the atmosphere, oceans, biosphere, and cryosphere, that it is certain to exhibit emergent properties very difficult to predict from the perspective of a narrow focus on any individual component of the system. Therefore, a substantial share of the task of evaluating comprehensive earth system models must reside at the level of whole system evaluations. Since complete, integrated atmosphere/ ocean/ biosphere/ hydrology models are not yet operational, questions of evaluation must be addressed at the level of the kinds of earth system processes that the models should be competent to simulate, rather than at the level of specific performance criteria. Here, we have tried to identify examples of earth system processes that are difficult to simulate with existing models and that involve a rich enough suite of feedbacks that they are unlikely to be satisfactorily described by highly simplified or toy models. Our purpose is not to specify a checklist of evaluation criteria but to introduce characteristics of the earth system that may present useful opportunities for model testing and, of course, improvement
Book Review: Christopher Darnton. Rivalry and Alliance Politics in Cold War Latin America
This document includes Dr. Field\u27s review of Christopher Darnton\u27s Rivalry and Alliance Politics in Cold War Latin America. Baltimore: Johns Hopkins University Press, 2014. ISBN: 9781421413617 (paperback, $44.95). It is part of H-Diplo | ISSF, Roundtable, Volume VIII, No. 8 (2016)
Hanford A and AX-Farm Leak Assessments Report: 241-A-103, 241-A-104, 241-A-105, 241-AX-102, 241-AX-104 and Unplanned Waste Releases
This report summarizes information on historical waste loss events associated with tanks and piplines in the 241-A and 241-AX tank farms
Hyperalkaline speleothem from Derbyshire: new observations on morphology and growth crystallisation
- …