2,605 research outputs found
Correlations and invariance of seismicity under renormalization-group transformations
The effect of transformations analogous to those of the real-space
renormalization group are analyzed for the temporal occurrence of earthquakes.
The distribution of recurrence times turns out to be invariant under such
transformations, for which the role of the correlations between the magnitudes
and the recurrence times are fundamental. A general form for the distribution
is derived imposing only the self-similarity of the process, which also yields
a scaling relation between the Gutenberg-Richter b-value, the exponent
characterizing the correlations, and the recurrence-time exponent. This
approach puts the study of the structure of seismicity in the context of
critical phenomena.Comment: Short paper. I'll be grateful to get some feedbac
Global Seismic Nowcasting With Shannon Information Entropy.
Seismic nowcasting uses counts of small earthquakes as proxy data to estimate the current dynamical state of an earthquake fault system. The result is an earthquake potential score that characterizes the current state of progress of a defined geographic region through its nominal earthquake "cycle." The count of small earthquakes since the last large earthquake is the natural time that has elapsed since the last large earthquake (Varotsos et al., 2006, https://doi.org/10.1103/PhysRevE.74.021123). In addition to natural time, earthquake sequences can also be analyzed using Shannon information entropy ("information"), an idea that was pioneered by Shannon (1948, https://doi.org/10.1002/j.1538-7305.1948.tb01338.x). As a first step to add seismic information entropy into the nowcasting method, we incorporate magnitude information into the natural time counts by using event self-information. We find in this first application of seismic information entropy that the earthquake potential score values are similar to the values using only natural time. However, other characteristics of earthquake sequences, including the interevent time intervals, or the departure of higher magnitude events from the magnitude-frequency scaling line, may contain additional information
Network of recurrent events for the Olami-Feder-Christensen model
We numerically study the dynamics of a discrete spring-block model introduced
by Olami, Feder and Christensen (OFC) to mimic earthquakes and investigate to
which extent this simple model is able to reproduce the observed spatiotemporal
clustering of seismicty. Following a recently proposed method to characterize
such clustering by networks of recurrent events [Geophys. Res. Lett. {\bf 33},
L1304, 2006], we find that for synthetic catalogs generated by the OFC model
these networks have many non-trivial statistical properties. This includes
characteristic degree distributions -- very similar to what has been observed
for real seismicity. There are, however, also significant differences between
the OFC model and earthquake catalogs indicating that this simple model is
insufficient to account for certain aspects of the spatiotemporal clustering of
seismicity.Comment: 11 pages, 16 figure
History of the Ile d\u27Orleans
This English translation of L.P. Turcotte\u27s Histoire de l\u27Ile d\u27Orleans, originally published in French in 1867, will give today\u27s English-speaking descendants of the early French colonists a peek into the lives of the 17th-century settlers of New France. This book focuses on the history of the Ile d\u27Orleans – a small island in the middle of the river just north of Québec City – where many early settlers established their homesteads.
Originally published in Québec: Atelier Typographique du Canadien, 21 rue de la Montagne, Basse-Ville, Québec City, 1867
Translated into English by Dr. Elizabeth Blood, Salem State University, Salem, Massachusetts, 2019https://digitalcommons.salemstate.edu/fchc/1000/thumbnail.jp
The effect of heavy element opacity on pre-main sequence Li depletion
Recent 3-D analysis of the solar spectrum data suggests a significant change
of the solar chemical composition. This may affect the temporal evolution of
the surface abundance of light elements since the extension of the convective
envelope is largely affected by the internal opacity value. We analyse the
influence of the adopted solar mixture on the opacity in the convective
envelope of pre-main sequence (PMS) stars and thus on PMS lithium depletion.
The surface Li abundance depends on the relative efficiency of several
processes, some of them still not known with the required precision; this paper
thus analyses one of the aspects of this ``puzzle''. Focusing on PMS evolution,
where the largest amount of Li burning occurs, we computed stellar models for
three selected masses (0.8, 1.0 and 1.2 Msun, with Z=0.013, Y=0.27, alpha=1.9)
by varying the chemical mixture, that is the internal element distribution in
Z. We analysed the contribution of the single elements to the opacity at the
temperatures and densities of interest for Li depletion. Several mixtures were
obtained by varying the abundance of the most important elements one at a time;
we then calculated the corresponding PMS Li abundance evolution. We found that
a mixture variation does change the Li abundance: at fixed total metallicity,
the Li depletion increases when increasing the fraction of elements heavier
than O.Comment: A&A accepted, 11 pages, 18 eps figure
Analysis of Self-Organized Criticality in the Olami-Feder-Christensen model and in real earthquakes
We perform a new analysis on the dissipative Olami-Feder-Christensen model on
a small world topology considering avalanche size differences. We show that
when criticality appears the Probability Density Functions (PDFs) for the
avalanche size differences at different times have fat tails with a q-Gaussian
shape. This behaviour does not depend on the time interval adopted and is found
also when considering energy differences between real earthquakes. Such a
result can be analytically understood if the sizes (released energies) of the
avalanches (earthquakes) have no correlations. Our findings support the
hypothesis that a self-organized criticality mechanism with long-range
interactions is at the origin of seismic events and indicate that it is not
possible to predict the magnitude of the next earthquake knowing those of the
previous ones.Comment: 5 pages, 3 figures. New version accepted for publication on PRE Rapid
Communication
The inter-rater reliability of the diagnosis of surgical site infection in the context of a clinical trial.
ObjectivesThe diagnosis of surgical site infection following endoprosthetic reconstruction for bone tumours is frequently a subjective diagnosis. Large clinical trials use blinded Central Adjudication Committees (CACs) to minimise the variability and bias associated with assessing a clinical outcome. The aim of this study was to determine the level of inter-rater and intra-rater agreement in the diagnosis of surgical site infection in the context of a clinical trial.Materials and methodsThe Prophylactic Antibiotic Regimens in Tumour Surgery (PARITY) trial CAC adjudicated 29 non-PARITY cases of lower extremity endoprosthetic reconstruction. The CAC members classified each case according to the Centers for Disease Control (CDC) criteria for surgical site infection (superficial, deep, or organ space). Combinatorial analysis was used to calculate the smallest CAC panel size required to maximise agreement. A final meeting was held to establish a consensus.ResultsFull or near consensus was reached in 20 of the 29 cases. The Fleiss kappa value was calculated as 0.44 (95% confidence interval (CI) 0.35 to 0.53), or moderate agreement. The greatest statistical agreement was observed in the outcome of no infection, 0.61 (95% CI 0.49 to 0.72, substantial agreement). Panelists reached a full consensus in 12 of 29 cases and near consensus in five of 29 cases when CDC criteria were used (superficial, deep or organ space). A stable maximum Fleiss kappa of 0.46 (95% CI 0.50 to 0.35) at CAC sizes greater than three members was obtained.ConclusionsThere is substantial agreement among the members of the PARITY CAC regarding the presence or absence of surgical site infection. Agreement on the level of infection, however, is more challenging. Additional clinical information routinely collected by the prospective PARITY trial may improve the discriminatory capacity of the CAC in the parent study for the diagnosis of infection.Cite this article: J. Nuttall, N. Evaniew, P. Thornley, A. Griffin, B. Deheshi, T. O'Shea, J. Wunder, P. Ferguson, R. L. Randall, R. Turcotte, P. Schneider, P. McKay, M. Bhandari, M. Ghert. The inter-rater reliability of the diagnosis of surgical site infection in the context of a clinical trial. Bone Joint Res 2016;5:347-352. DOI: 10.1302/2046-3758.58.BJR-2016-0036.R1
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