2,148 research outputs found
De l’art de nager à la science de la natation
La natation a beaucoup évolué au cours des deux derniers siècles. Essentiellement pratique sociale (bains et loisirs) jusqu’à la fin du XIXe siècle, elle a ensuite acquis le statut de sport au début du XXe siècle bien avant d’atteindre le niveau de professionnalisme qu’elle possède aujourd’hui. Mais quel a été le rôle de la recherche dans cette évolution ? C’est ce qu’explique Patrick Pelayo dans cet article en prenant notamment comme exemple la spectaculaire évolution des techniques du crawl. Il montre comment «l’art de nager » s’est progressivement transformé en science de la natation.Swimming has considerably changed over the last two centuries. Mainly a social practice (baths and leisure) until the end of the 19th century, it then acquired the status of sport in the early 20th Century well before reaching the level of professionalism it benefits from today. What was the role of research in this development? Patrick Pelayo explains it in this article by using as an example the spectacular evolution of the crawl techniques. He shows how "the art of swimming" has gradually turned into a science of swimming
Patterns of helminth infection in Kenyan elephant populations
Background: The dynamics of helminth infection in African elephant populations are poorly known. We examined
the efects of age, sex, social structure and the normalized diference vegetation index (NDVI) as primary drivers of
infection patterns within and between elephant populations.
Methods: Coprological methods were used to identify helminths and determine infection patterns in distinct
elephant populations in Maasai Mara National Reserve, Tsavo East National Park, Amboseli National Park and LaikipiaSamburu Ecosystem. Gaussian fnite mixture cluster analyses of egg dimensions were used to classify helminth eggs
according to genera. Generalized linear models (GLM) and Chi-square analyses were used to test for variation in
helminth infection patterns and to identify drivers in elephant populations.
Results: Helminth prevalence varied signifcantly between the studied populations. Nematode prevalence (96.3%)
was over twice as high as that of trematodes (39.1%) in elephants. Trematode prevalence but not nematode prevalence varied between populations. Although we found no associations between helminth infection and elephant
social groups (male vs family groups), the median helminth egg output (eggs per gram, epg) did vary between social
groups: family groups had signifcantly higher median epg than solitary males or males in bachelor groups. Young
males in mixed sex family groups had lower epg than females when controlling for population and age; these differences, however, were not statistically signifcant. The average NDVI over a three-month period varied between
study locations. Cluster analyses based on egg measurements revealed the presence of Protofasciola sp., Brumptia
sp., Murshidia sp., Quilonia sp. and Mammomonogamus sp. GLM analyses showed that the mean epg was positively
infuenced by a three-month cumulative mean NDVI and by social group; female social groups had higher epg than
male groups. GLM analyses also revealed that epg varied between elephant populations: Samburu-Laikipia elephants
had a higher and Tsavo elephants a lower epg than Amboseli elephants.
Conclusions: Elephants had infection patterns characterized by within- and between-population variation in prevalence and worm burden. Sociality and NDVI were the major drivers of epg but not of helminth prevalence. Gastrointestinal parasites can have a negative impact on the health of wild elephants, especially during resource scarcity. Thus,
our results will be important when deciding intervention strategies.This research was funded by the Kenya Wildlife Service and the Department of Animal Pathology, Veterinary Faculty, University of Santiago de Compostela, Lugo, SpainS
e-INEBRIA special interest group roadmap to best practices for practice and research on brief digital interventions for problematic alcohol and illicit drug use
Background: There is huge potential for scaling up the delivery of brief interventions for alcohol and illicit drug use, given the increasing coverage and technologies of e-digital interventions, including applications for smartphones and tablets. However, while the quantity of digital interventions is increasing rapidly, the involvement of brief-intervention researchers and the development of good practices has just begun. Roadmap: In 2018, the Special Interest Group on digital interventions from the International Network on Brief Interventions for Alcohol & Other Drugs (e-INEBRIA SIG) initiated a conversation on possible avenues of future research, which subsequently turned into a roadmap for digital interventions during further discussions. This roadmap consists of points considered relevant for future research, ongoing technological developments, and their implementation across a continuum of prevention and care. Moreover, it outlines starting points for the diversification of brief digital interventions, as well as next steps for quality improvement and implementation in public health and clinical practice. Conclusions: The roadmap of the e-INEBRIA SIG on digital interventions is a starting point that indicates relevant next steps and provides orientation for researchers and interested practitioners in the ambiguous literature and complexity of current digital interventions
Measurement of the cosmic ray spectrum above eV using inclined events detected with the Pierre Auger Observatory
A measurement of the cosmic-ray spectrum for energies exceeding
eV is presented, which is based on the analysis of showers
with zenith angles greater than detected with the Pierre Auger
Observatory between 1 January 2004 and 31 December 2013. The measured spectrum
confirms a flux suppression at the highest energies. Above
eV, the "ankle", the flux can be described by a power law with
index followed by
a smooth suppression region. For the energy () at which the
spectral flux has fallen to one-half of its extrapolated value in the absence
of suppression, we find
eV.Comment: Replaced with published version. Added journal reference and DO
Energy Estimation of Cosmic Rays with the Engineering Radio Array of the Pierre Auger Observatory
The Auger Engineering Radio Array (AERA) is part of the Pierre Auger
Observatory and is used to detect the radio emission of cosmic-ray air showers.
These observations are compared to the data of the surface detector stations of
the Observatory, which provide well-calibrated information on the cosmic-ray
energies and arrival directions. The response of the radio stations in the 30
to 80 MHz regime has been thoroughly calibrated to enable the reconstruction of
the incoming electric field. For the latter, the energy deposit per area is
determined from the radio pulses at each observer position and is interpolated
using a two-dimensional function that takes into account signal asymmetries due
to interference between the geomagnetic and charge-excess emission components.
The spatial integral over the signal distribution gives a direct measurement of
the energy transferred from the primary cosmic ray into radio emission in the
AERA frequency range. We measure 15.8 MeV of radiation energy for a 1 EeV air
shower arriving perpendicularly to the geomagnetic field. This radiation energy
-- corrected for geometrical effects -- is used as a cosmic-ray energy
estimator. Performing an absolute energy calibration against the
surface-detector information, we observe that this radio-energy estimator
scales quadratically with the cosmic-ray energy as expected for coherent
emission. We find an energy resolution of the radio reconstruction of 22% for
the data set and 17% for a high-quality subset containing only events with at
least five radio stations with signal.Comment: Replaced with published version. Added journal reference and DO
Measurement of the Radiation Energy in the Radio Signal of Extensive Air Showers as a Universal Estimator of Cosmic-Ray Energy
We measure the energy emitted by extensive air showers in the form of radio
emission in the frequency range from 30 to 80 MHz. Exploiting the accurate
energy scale of the Pierre Auger Observatory, we obtain a radiation energy of
15.8 \pm 0.7 (stat) \pm 6.7 (sys) MeV for cosmic rays with an energy of 1 EeV
arriving perpendicularly to a geomagnetic field of 0.24 G, scaling
quadratically with the cosmic-ray energy. A comparison with predictions from
state-of-the-art first-principle calculations shows agreement with our
measurement. The radiation energy provides direct access to the calorimetric
energy in the electromagnetic cascade of extensive air showers. Comparison with
our result thus allows the direct calibration of any cosmic-ray radio detector
against the well-established energy scale of the Pierre Auger Observatory.Comment: Replaced with published version. Added journal reference and DOI.
Supplemental material in the ancillary file
Precise measurement of the W-boson mass with the CDF II detector
We have measured the W-boson mass MW using data corresponding to 2.2/fb of
integrated luminosity collected in proton-antiproton collisions at 1.96 TeV
with the CDF II detector at the Fermilab Tevatron collider. Samples consisting
of 470126 W->enu candidates and 624708 W->munu candidates yield the measurement
MW = 80387 +- 12 (stat) +- 15 (syst) = 80387 +- 19 MeV. This is the most
precise measurement of the W-boson mass to date and significantly exceeds the
precision of all previous measurements combined
Optimasi Portofolio Resiko Menggunakan Model Markowitz MVO Dikaitkan dengan Keterbatasan Manusia dalam Memprediksi Masa Depan dalam Perspektif Al-Qur`an
Risk portfolio on modern finance has become increasingly technical, requiring the use of sophisticated mathematical tools in both research and practice. Since companies cannot insure themselves completely against risk, as human incompetence in predicting the future precisely that written in Al-Quran surah Luqman verse 34, they have to manage it to yield an optimal portfolio. The objective here is to minimize the variance among all portfolios, or alternatively, to maximize expected return among all portfolios that has at least a certain expected return. Furthermore, this study focuses on optimizing risk portfolio so called Markowitz MVO (Mean-Variance Optimization). Some theoretical frameworks for analysis are arithmetic mean, geometric mean, variance, covariance, linear programming, and quadratic programming. Moreover, finding a minimum variance portfolio produces a convex quadratic programming, that is minimizing the objective function ðð¥with constraintsð ð 𥠥 ðandð´ð¥ = ð. The outcome of this research is the solution of optimal risk portofolio in some investments that could be finished smoothly using MATLAB R2007b software together with its graphic analysis
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