18,424 research outputs found
Lightning-induced ventricular fibrillation
We present a case of a previously healthy 17 year-old white male boy scout who collapsed after
a lightning strike, and was found to be in ventricular fibrillation when emergency medical
services arrived. The ventricular fibrillation was defibrillated into sinus rhythm after a single
direct current (DC) countershock. However, the patient has remained in coma. Commotio
cordis, sudden cardiac death from low-energy chest wall impact, is a phenomenon in which an
exactly timed and located blow on the chest during the cardiac cycle results in ventricular
fibrillation. Commotio cordis and electrical shock can both result in ventricular arrhythmias.
We speculate that in this patient, ventricular fibrillation began immediately after the lightning,
which probably struck at the peak of the T wave. (Cardiol J 2007; 14: 91–94
Boulder Bands on Lobate Debris Aprons: Does Spatial Clustering Reveal Accumulation History for Martian Glaciations?
Glacial landforms such as lobate debris aprons (LDA) and Concentric Crater Fill (CCF) are the dominant debris-covered glacial landforms on Mars. These landforms represent a volumetrically significant component of the Amazonian water ice budget, however, because small craters (diameter D 0.5-1 km) are poorly retained glacial brain terrain surfaces, and, since the glacial landforms are geologically young, it is challenging to reliably constrain either individual glacial deposit ages or formational sequences in order to determine how quickly the glaciers accumulated. A fundamental question remaining is whether ice deposition and flow that formed LDA occurred episodically during a few, short instances, or whether glacial flow was quasi-continuous over a long period (~108 yr). Because glaciation is thought to be controlled largely by obliquity excursions, a larger question is whether glacial deposits on Mars exhibit regional to global characteristics that can be used to infer synchronicity of flow or degradation
Constraining the initial temperature and shear viscosity in a hybrid hydrodynamic model of =200 GeV Au+Au collisions using pion spectra, elliptic flow, and femtoscopic radii
A new framework for evaluating hydrodynamic models of relativistic heavy ion
collisions has been developed. This framework, a Comprehesive Heavy Ion Model
Evaluation and Reporting Algorithm (CHIMERA) has been implemented by augmenting
UVH 2+1D viscous hydrodynamic model with eccentricity fluctuations,
pre-equilibrium flow, and the Ultra-relativistic Quantum Molecular Dynamic
(UrQMD) hadronic cascade. A range of initial temperatures and shear viscosity
to entropy ratios were evaluated for four initial profiles, and
scaling with and without pre-equilibrium flow. The model results
were compared to pion spectra, elliptic flow, and femtoscopic radii from 200
GeV Au+Au collisions for the 0--20% centrality range.Two sets of initial
density profiles, scaling with pre-equilibrium flow and
scaling without were shown to provide a consistent description of all three
measurements.Comment: 21 pages, 32 figures, version 3 includes additional text for
clarification, division of figures into more manageable units, and placement
of chi-squared values in tables for ease of viewin
The temperature dependence of the isothermal bulk modulus at 1 bar pressure
It is well established that the product of the volume coefficient of thermal
expansion and the bulk modulus is nearly constant at temperatures higher than
the Debye temperature. Using this approximation allows predicting the values of
the bulk modulus. The derived analytical solution for the temperature
dependence of the isothermal bulk modulus has been applied to ten substances.
The good correlations to the experiments indicate that the expression may be
useful for substances for which bulk modulus data are lacking
Upper respiratory tract infections and general anaesthesia in children
Conflicting reports regarding the hazards of anaesthesia in children presenting for surgery with an upper respiratory tract infection have appeared in the literature. In the present study 130 children undergoing general anaesthesia with face mask for myringotomy and grommet insertion were graded as having either an acute or recent upper respiratory tract infection or were asymptomatic according to predetermined clinical symptoms and signs. The severity of respiratory and related complications were scored during induction, emergence and recovery. The peripheral oxygen saturation was recorded during induction, emergence, transfer to the recovery ward and in the recovery ward itself. There were no significant differences (p > 0.05) in the complication scores between the three groups of children. However, the incidence of hypoxaemia (oxygen saturation ± 93%) was significantly greater during transfer in the acute infection group (p = 0.001) and the recent infection group (p = 0.02), as well as during recovery in the acute group (p = 0.03) compared with asymptomatic children.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/75689/1/j.1365-2044.1992.tb02389.x.pd
Volatility clustering and scaling for financial time series due to attractor bubbling
A microscopic model of financial markets is considered, consisting of many
interacting agents (spins) with global coupling and discrete-time thermal bath
dynamics, similar to random Ising systems. The interactions between agents
change randomly in time. In the thermodynamic limit the obtained time series of
price returns show chaotic bursts resulting from the emergence of attractor
bubbling or on-off intermittency, resembling the empirical financial time
series with volatility clustering. For a proper choice of the model parameters
the probability distributions of returns exhibit power-law tails with scaling
exponents close to the empirical ones.Comment: For related publications see http://www.helbing.or
-NMR of Isolated Li Implanted into a Thin Copper Film
Depth-controlled -NMR was used to study highly spin-polarized Li
in a Cu film of thickness 100 nm deposited onto a MgO substrate. The positive
Knight Shifts and spin relaxation data show that Li occupies two sites at
low temperatures, assigned to be the substitutional () and octahedral ()
interstitial sites. Between 50 to 100 K, there is a site change from to
. The temperature dependence of the Knight shifts and spin-lattice
relaxation rates at high temperatures, i.e. when all the Li are in the
site, is consistent with the Korringa Law for a simple metal.Comment: Accepted for publication in Phys. Rev.
Carbon Free Boston: Technical Summary
Part of a series of reports that includes:
Carbon Free Boston: Summary Report;
Carbon Free Boston: Social Equity Report;
Carbon Free Boston: Buildings Technical Report;
Carbon Free Boston: Transportation Technical Report;
Carbon Free Boston: Waste Technical Report;
Carbon Free Boston: Energy Technical Report;
Carbon Free Boston: Offsets Technical Report;
Available at http://sites.bu.edu/cfb/OVERVIEW:
This technical summary is intended to argument the rest of the Carbon Free Boston technical reports
that seek to achieve this goal of deep mitigation. This document provides below: a rationale for carbon
neutrality, a high level description of Carbon Free Boston’s analytical approach; a summary of crosssector strategies; a high level analysis of air quality impacts; and, a brief analysis of off-road and street
light emissions.Published versio
Impact of Investor's Varying Risk Aversion on the Dynamics of Asset Price Fluctuations
While the investors' responses to price changes and their price forecasts are
well accepted major factors contributing to large price fluctuations in
financial markets, our study shows that investors' heterogeneous and dynamic
risk aversion (DRA) preferences may play a more critical role in the dynamics
of asset price fluctuations. We propose and study a model of an artificial
stock market consisting of heterogeneous agents with DRA, and we find that DRA
is the main driving force for excess price fluctuations and the associated
volatility clustering. We employ a popular power utility function,
with agent specific and
time-dependent risk aversion index, , and we derive an approximate
formula for the demand function and aggregate price setting equation. The
dynamics of each agent's risk aversion index, (i=1,2,...,N), is
modeled by a bounded random walk with a constant variance . We show
numerically that our model reproduces most of the ``stylized'' facts observed
in the real data, suggesting that dynamic risk aversion is a key mechanism for
the emergence of these stylized facts.Comment: 17 pages, 7 figure
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