1,758 research outputs found
Most massive halos with Gumbel Statistics
We present an analytical calculation of the extreme value statistics for dark
matter halos - that is, the probability distribution of the most massive halo
within some region of the universe of specified shape and size. Our calculation
makes use of the counts-in-cells formalism for the correlation functions, and
the halo bias derived from the Sheth-Tormen mass function.
We demonstrate the power of the method on spherical regions, comparing the
results to measurements in a large cosmological dark matter simulation and
achieving good agreement. Particularly good fits are obtained for the most
likely value of the maximum mass and for the high-mass tail of the
distribution, relevant in constraining cosmologies by observations of most
massive clusters.Comment: Accepted to MNRA
The Neural Time Course of Semantic Ambiguity Resolution in Speech Comprehension.
Semantically ambiguous words challenge speech comprehension, particularly when listeners must select a less frequent (subordinate) meaning at disambiguation. Using combined magnetoencephalography (MEG) and EEG, we measured neural responses associated with distinct cognitive operations during semantic ambiguity resolution in spoken sentences: (i) initial activation and selection of meanings in response to an ambiguous word and (ii) sentence reinterpretation in response to subsequent disambiguation to a subordinate meaning. Ambiguous words elicited an increased neural response approximately 400-800 msec after their acoustic offset compared with unambiguous control words in left frontotemporal MEG sensors, corresponding to sources in bilateral frontotemporal brain regions. This response may reflect increased demands on processes by which multiple alternative meanings are activated and maintained until later selection. Disambiguating words heard after an ambiguous word were associated with marginally increased neural activity over bilateral temporal MEG sensors and a central cluster of EEG electrodes, which localized to similar bilateral frontal and left temporal regions. This later neural response may reflect effortful semantic integration or elicitation of prediction errors that guide reinterpretation of previously selected word meanings. Across participants, the amplitude of the ambiguity response showed a marginal positive correlation with comprehension scores, suggesting that sentence comprehension benefits from additional processing around the time of an ambiguous word. Better comprehenders may have increased availability of subordinate meanings, perhaps due to higher quality lexical representations and reflected in a positive correlation between vocabulary size and comprehension success
Extreme value statistics of smooth random Gaussian fields
We consider the Gumbel or extreme value statistics describing the
distribution function p_G(x_max) of the maximum values of a random field x
within patches of fixed size. We present, for smooth Gaussian random fields in
two and three dimensions, an analytical estimate of p_G which is expected to
hold in a regime where local maxima of the field are moderately high and weakly
clustered. When the patch size becomes sufficiently large, the negative of the
logarithm of the cumulative extreme value distribution is simply equal to the
average of the Euler Characteristic of the field in the excursion x > x_max
inside the patches. The Gumbel statistics therefore represents an interesting
alternative probe of the genus as a test of non Gaussianity, e.g. in cosmic
microwave background temperature maps or in three-dimensional galaxy catalogs.
It can be approximated, except in the remote positive tail, by a negative
Weibull type form, converging slowly to the expected Gumbel type form for
infinitely large patch size. Convergence is facilitated when large scale
correlations are weaker. We compare the analytic predictions to numerical
experiments for the case of a scale-free Gaussian field in two dimensions,
achieving impressive agreement between approximate theory and measurements. We
also discuss the generalization of our formalism to non-Gaussian fields.Comment: 10 pages, 2 figures, accepted for publication in MNRA
Clinical Study An Adaptive CBPR Approach to Create Weight Management Materials for a School-Based Health Center Intervention
properly cited. Purpose. From our previous clinical work with overweight/obese youth, we identified the need for research to create an effective weight management intervention to address the growing prevalence of adolescent metabolic syndrome. Formative assessment through an adaptive community-based participatory research (CBPR) approach was conducted toward the development of a nutritional and physical activity (DVD) and clinician toolkit for a school-based health center (SBHC) weight management intervention. Methods. We first conducted parent and adolescent interviews on views and experiences about obesity while convening a community advisory council (CAC) recruited from two participating urban New Mexico high schools. Thematic findings from the interviews were analyzed with the CAC to develop culturally and developmentally appropriate intervention materials. Results. Themes from the parent and adolescent interviews included general barriers/challenges, factors influencing motivation, and change facilitators. The CAC and university-based research team reached consensus on the final content of nutrition and physical activity topics to produce a DVD and clinician toolkit through six monthly sessions. These materials used in the SBHC intervention resulted in a greater reduction of body mass index when compared to adolescents receiving standard care. Conclusions. Formative assessment using an adaptive CBPR approach resulted in the creation of culturally and age appropriate weight reduction materials that were acceptable to study participants. This trial is registered with ClinicalTrials.gov NCT00841334
An Adaptive CBPR Approach to Create Weight Management Materials for a School-Based Health Center Intervention
Purpose. From our previous clinical work with overweight/obese youth, we identified the need for research to create an effective weight management intervention to address the growing prevalence of adolescent metabolic syndrome. Formative assessment through an adaptive community-based participatory research (CBPR) approach was conducted toward the development of a nutritional and physical activity (DVD) and clinician toolkit for a school-based health center (SBHC) weight management intervention. Methods. We first conducted parent and adolescent interviews on views and experiences about obesity while convening a community advisory council (CAC) recruited from two participating urban New Mexico high schools. Thematic findings from the interviews were analyzed with the CAC to develop culturally and developmentally appropriate intervention materials. Results. Themes from the parent and adolescent interviews included general barriers/challenges, factors influencing motivation, and change facilitators. The CAC and university-based research team reached consensus on the final content of nutrition and physical activity topics to produce a DVD and clinician toolkit through six monthly sessions. These materials used in the SBHC intervention resulted in a greater reduction of body mass index when compared to adolescents receiving standard care. Conclusions. Formative assessment using an adaptive CBPR approach resulted in the creation of culturally and age appropriate weight reduction materials that were acceptable to study participants. This trial is registered with ClinicalTrials.gov NCT00841334
The interplay of microscopic and mesoscopic structure in complex networks
Not all nodes in a network are created equal. Differences and similarities
exist at both individual node and group levels. Disentangling single node from
group properties is crucial for network modeling and structural inference.
Based on unbiased generative probabilistic exponential random graph models and
employing distributive message passing techniques, we present an efficient
algorithm that allows one to separate the contributions of individual nodes and
groups of nodes to the network structure. This leads to improved detection
accuracy of latent class structure in real world data sets compared to models
that focus on group structure alone. Furthermore, the inclusion of hitherto
neglected group specific effects in models used to assess the statistical
significance of small subgraph (motif) distributions in networks may be
sufficient to explain most of the observed statistics. We show the predictive
power of such generative models in forecasting putative gene-disease
associations in the Online Mendelian Inheritance in Man (OMIM) database. The
approach is suitable for both directed and undirected uni-partite as well as
for bipartite networks
Lagrangian circulation of Antarctic Intermediate Water in the subtropical South Atlantic
Author Posting. © The Authors, 2004. This is the author's version of the work. It is posted here by permission of Elsevier B. V. for personal use, not for redistribution. The definitive version was published in Deep Sea Research Part II: Topical Studies in Oceanography 52 (2005): 545-564, doi:10.1016/j.dsr2.2004.12.006.This study combines float data from different projects collected between 1991 and 2003 in the
South Atlantic to describe the flow of Antarctic Intermediate Water (AAIW). Velocity spacetime
averages are calculated for various grid resolutions and with cells deformed to match the
bathymetry, f/H or f/h (with H being the water depth and h being the thickness of the AAIW
layer). When judged by the degree of alignment between respective isolines and the resulting
average velocity fields, the best grid is based on a nominal cell size of 3º (latitude) by 4º
(longitude) with cell shapes deformed according to f/h. Using this grid, objectively estimated
mean currents (and their associated errors), as well as meridional and zonal volume transports are estimated. Results show an anticyclonic Subtropical Gyre centred near 36ºS and spanning
from 23º±1°S to 46° ± 1ºS. The South Atlantic Current meanders from 33ºS to 46ºS and
shows a mean speed of 9.6 ± 7.8 cm s-1 (8.5 Sv ± 3.5 Sv; 1 Sv = 1×106 m3 s-1). The northern
branch of the Subtropical Gyre is located between 22ºS and 32ºS and flows westward with a
mean speed of 4.7 ± 3.3 cm s-1 (9.3 Sv ± 3.4 Sv). Evidence of a cyclonic Tropical Gyre divided in two sub-cells is visible on the stream function.This work is supported through NSF-Grant no. OCE-0095647
and through the Alfred Wegener Institute for Polar and Marine Research
Scaling the laws of thermal imaging-based whale detection
Author Posting. © American Meteorological Society, 2020. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of the Atmospheric and Oceanic Technology 37(5), (2020): 807-824, doi:10.1175/JTECH-D-19-0054.1.Marine mammals are under growing pressure as anthropogenic use of the ocean increases. Ship strikes of large whales and loud underwater sound sources including air guns for marine geophysical prospecting and naval midfrequency sonar are criticized for their possible negative effects on marine mammals. Competent authorities regularly require the implementation of mitigation measures, including vessel speed reductions or shutdown of acoustic sources if marine mammals are sighted in sensitive areas or in predefined exclusion zones around a vessel. To ensure successful mitigation, reliable at-sea detection of animals is crucial. To date, ship-based marine mammal observers are the most commonly implemented detection method; however, thermal (IR) imaging–based automatic detection systems have been used in recent years. This study evaluates thermal imaging–based automatic whale detection technology for its use across different oceans. The performance of this technology is characterized with respect to environmental conditions, and an automatic detection algorithm for whale blows is presented. The technology can detect whales in polar, temperate, and subtropical ocean regimes over distances of up to several kilometers and outperforms marine mammal observers in the number of whales detected. These results show that thermal imaging technology can be used to assist in providing protection for marine mammals against ship strike and acoustic impact across the world’s oceans.This work was funded by the Office of Naval Research (ONR) under Award N000141310856, by the Environmental Studies Research Fund (ESRF; esrfunds.org) under Award 2014-03S and by the Alfred-Wegener-Institute Helmholtz Zentrum für Polar- und Meeresforschung. DPZ and OB declare competing financial interests: 1) Patent US8941728B2, DE102011114084B4: A method for automatic real-time marine mammal detection. The patent describes the ideas basic to the automatic whale detection software as used to acquire and process the data presented in this paper. 2) Licensing of the Tashtego automatic whale detection software to the manufacturer of IR sensor. The authors confirm that these competing financial interests did not alter their adherence good scientific practice. We thank P. Abgrall, J. Coffey, K. Keats, B. Mactavish, V. Moulton, and S. Penney-Belbin for data collection or IR image review. We thank S. Besaw, J. Christian, A. Coombs, P. Coombs, W. Costello, T. Elliott, E. Evans, I. Goudie, C. Jones, K. Knowles, R. Martin, A. Murphy, D. and J. Shepherd; and the staffs at the Irish Loop Express, the Myrick Wireless Interpretive Centre, the Mistaken Point Ecological Reserve, and the lighthouse keepers for logistical assistance at our remote field site. We thank D. Boutilier and B. McDonald (DFO) for assisting us in obtaining license to occupy permits for Cape Race. We thank D. Taylor (ESRF Research Manager) for his support
Doctors' learning habits: CME activities among Norwegian physicians over the last decade
<p>Abstract</p> <p>Background</p> <p>Coping with the increasing body of medical knowledge is a main challenge to all doctors. The aim of this study was to investigate self reported reading and learning habits among Norwegian doctors and their subjective ability to keep professionally updated.</p> <p>Methods</p> <p>A cross sectional survey among a randomised sample of Norwegian doctors was undertaken in 2004 (n = 1005, response rate 71%). A similar study with many identical questions was done in 1993 (n = 1041, response rate 71%) and a comparison of the results was made.</p> <p>Results</p> <p>Attending courses/congresses and reading medical literature were reported to be the most important sources of professional information in 2004, just like in 1993. Less time was spent on courses/congresses in 2004 than in 1993, and more time was spent on medical reading. The internet was regarded as useful for their professional life for three out of five, mostly among the younger and least among GPs.</p> <p>Two out of three doctors felt that they could obtain sufficient information for keeping updated in 2004, the same proportion as in 1993. A correlation was found between subjective coping with the information and a high level of continuing medical education (CME)-activities. The information copers had a higher level of job satisfaction than non-copers.</p> <p>Conclusion</p> <p>Over the last decade Norwegian doctors spend less time on attending courses/congresses and more time on medical reading, while the level of self perceived coping with information has been unchanged. The changing pattern of professional updating may reflect a more general individualistic trend in society. The consistent finding of a correlation between reading and attending courses, subjective coping and job satisfaction gives good reasons for recommending a high level of CME-activities among doctors.</p
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