266 research outputs found
Pando: Personal Volunteer Computing in Browsers
The large penetration and continued growth in ownership of personal
electronic devices represents a freely available and largely untapped source of
computing power. To leverage those, we present Pando, a new volunteer computing
tool based on a declarative concurrent programming model and implemented using
JavaScript, WebRTC, and WebSockets. This tool enables a dynamically varying
number of failure-prone personal devices contributed by volunteers to
parallelize the application of a function on a stream of values, by using the
devices' browsers. We show that Pando can provide throughput improvements
compared to a single personal device, on a variety of compute-bound
applications including animation rendering and image processing. We also show
the flexibility of our approach by deploying Pando on personal devices
connected over a local network, on Grid5000, a French-wide computing grid in a
virtual private network, and seven PlanetLab nodes distributed in a wide area
network over Europe.Comment: 14 pages, 12 figures, 2 table
Mapping of the human visual cortex using image-guided transcranial magnetic stimulation
We describe a protocol using transcranial magnetic stimulation (TMS) to systematically map the visual sensations induced by focal and
non-invasive stimulation of the human occipital cortex. TMS is applied with a figure of eight coil to 28 positions arranged in a 232-cm
grid over the occipital area. A digitizing tablet connected to a PC computer running customized software, and audio and video recording
are used for detailed and accurate data collection and analysis of evoked phosphenes. A frameless image-guided neuronavigational device
is used to describe the position of the actual sites of the stimulation coils relative to the cortical surface. Our results show that TMS is able
to elicit phosphenes in almost all sighted subjects and in a proportion of blind subjects. Evoked phosphenes are topographically organized.
Despite minor inter-individual variations, the mapping results are reproducible and show good congruence among different subjects. This
procedure has potential to improve our understanding of physiologic organization and plastic changes in the human visual system and to
establish the degree of remaining functional visual cortex in blind subjects. Such a non-invasive method is critical for selection of suitable
subjects for a cortical visual prosthesis.This research has been carried out with financial support from the Commission of the European Communities, specific RTD programme âQuality of Life and Management of Living Resourcesâ, QLK6-CT-2001-00279 and by the Ministerio de Ciencia y Tecnologıa(MAT2000-1049)Fondo de Investigaciones de la Seguridad Social (FISS 01-0674)National Institute of Mental Health (MH60734, MH57980)National Eye Institute (EYEY12091)Harvard-Thorndike General Clinical Research Center at Beth Israel Deaconess Medical Center (NCRR MO1 RR01032).Medicin
Extreme quasars at high redshift
Context:Quasars radiating at extreme Eddington ratios (xA) are likely a prime
mover of galactic evolution and have been hailed as potential distance
indicators. Their properties are still scarcely known.
Aims:We test the effectiveness of the selection criteria defined on the 4D
Eigenvector 1 (4DE1) for identifying xA sources. We provide a quantitative
description of their UV spectra in the redshift range 2<z<2.9.
Methods:19 extreme quasar candidates were identified using 4DE1 selection
criteria applied to SDSS spectra: AlIII1860/SiIII]1892>0.5 and
CIII]1909/SiIII]1892<1. The emission line spectra was studied using
multicomponent fits of deep spectroscopic observations obtained with the
OSIRIS-GTC.
Results:Spectra confirm that almost all of these quasars are xA sources with
very similar properties. We provide spectrophotometric and line profile
measurements for the SiIV1397+OIV]1402, CIV1549+HeII1640, and the 1900A blend
composed by AlIII1860, SiIII]1892, FeIII and a weak CIII]1909. The spectra can
be characterized as very low ionization (logU~-3), a condition that explains
the significant FeIII emission. CIV1549 shows low equivalent width (<30 A for
the most sources), and high or extreme blueshift amplitudes (-5000<c(1/2)<-1000
kms-1). Weak-lined quasars appear as extreme xA quasars and not as an
independent class. The CIV1549 high amplitude blueshifts coexists in all cases
save one with symmetric and narrower AlIII and SiIII] profiles. Estimates of
the Eddington ratio using the AlIII FWHM as a virial broadening estimator are
consistent with the ones of a previous xA sample.
Conclusions:It is now feasible to assemble large samples of xA quasars from
the latest data releases of the SDSS. We provide evidence that AlIII1860 could
be associated with a low-ionization virialized sub-system, supporting previous
suggestions that AlIII is a reliable virial broadening estimator.Comment: 36 pages, 31 figures, 12 tables. Manuscript accepted for publication,
A&A. Corrected titl
Evaluation of rare earth doped silica sub-micrometric spheres as optically controlled temperature sensors
We report on the evaluation of rare earth (Er3ĂŸ, Eu3ĂŸ, and Tb3ĂŸ ions) SiO2 sub-micrometric
spheres as potential optically controllable temperature sensors. Details about fabrication, optical
manipulation and spectroscopic characterization of the sub-micrometric spheres are presented.
The fluorescence properties of the micros-spheres in the biological range (25â60 C) have been
systematically investigated. From this systematic study, the thermal resolution potentially
achieved in each case has been determined and compared to previous works
The Antares Collaboration : Contributions to the 34th International Cosmic Ray Conference (ICRC 2015, The Hague)
The ANTARES detector, completed in 2008, is the largest neutrino telescope in the Northern hemisphere. Located at a depth of 2.5 km in the Mediterranean Sea, 40 km off the Toulon shore, its main goal is the search for astrophysical high energy neutrinos. In this paper we collect the 21 contributions of the ANTARES collaboration to the 34th International Cosmic Ray Conference (ICRC 2015). The scientific output is very rich and the contributions included in these proceedings cover the main physics results, ranging from steady point sources, diffuse searches, multi-messenger analyses to exotic physics
Network metaâanalysis of postâexposure prophylaxis randomized clinical trials
Objectives: We performed a network metaâanalysis of PEP randomized clinical trials to evaluate the best regimen. /
Methods: After MEDLINE/Pubmed search, studies were included if: (1) were randomized, (2) comparing at least 2 PEP threeâdrug regimens and, (3) reported completion rates or discontinuation at 28 days. Five studies with 1105 PEP initiations were included and compared ritonavirâboosted lopinavir (LPV/r) vs. atazanavir (ATV) (one study), cobicistatâboosted elvitegravir (EVG/c) (one study), raltegravir (RAL) (one study) or maraviroc (MVC) (two studies). We estimated the probability of each treatment of being the best based on the evaluation of five outcomes: PEP nonâcompletion at day 28, PEP discontinuation due to adverse events, PEP switching due to any cause, lost to followâup and adverse events. /
Results: Participants were mostly men who have sex with men (n = 832, 75%) with nonâoccupational exposure to HIV (89.86%). Fourâhundred fiftyâfour (41%) participants failed to complete their PEP course for any reason. The Odds Ratio (OR) for PEP nonâcompletion at day 28 in each antiretroviral compared to LPV/r was: ATV 0.95 (95% CI 0.58â1.56; EVG/c: OR 0.65 95% CI 0.30â1.37; RAL: OR 0.68 95% CI 0.41â1.13; and MVC: OR 0.69 95% CI 0.47â1.01. In addition, the rankogram showed that EVG/c had the highest probability of being the best treatment for the lowest rates in PEP nonâcompletion at day 28, switching, lost to followâup or adverse events and MVC for PEP discontinuations due to adverse events. /
Conclusions: Our study shows the advantages of integrase inhibitors when used as PEP, particularly EVG as a SingleâTablet Regimen
Anisotropy and chemical composition of ultra-high energy cosmic rays using arrival directions measured by the Pierre Auger Observatory
The Pierre Auger Collaboration has reported evidence for anisotropy in the
distribution of arrival directions of the cosmic rays with energies
eV. These show a correlation with the distribution
of nearby extragalactic objects, including an apparent excess around the
direction of Centaurus A. If the particles responsible for these excesses at
are heavy nuclei with charge , the proton component of the
sources should lead to excesses in the same regions at energies . We here
report the lack of anisotropies in these directions at energies above
(for illustrative values of ). If the anisotropies
above are due to nuclei with charge , and under reasonable
assumptions about the acceleration process, these observations imply stringent
constraints on the allowed proton fraction at the lower energies
Advanced functionality for radio analysis in the Offline software framework of the Pierre Auger Observatory
The advent of the Auger Engineering Radio Array (AERA) necessitates the
development of a powerful framework for the analysis of radio measurements of
cosmic ray air showers. As AERA performs "radio-hybrid" measurements of air
shower radio emission in coincidence with the surface particle detectors and
fluorescence telescopes of the Pierre Auger Observatory, the radio analysis
functionality had to be incorporated in the existing hybrid analysis solutions
for fluoresence and surface detector data. This goal has been achieved in a
natural way by extending the existing Auger Offline software framework with
radio functionality. In this article, we lay out the design, highlights and
features of the radio extension implemented in the Auger Offline framework. Its
functionality has achieved a high degree of sophistication and offers advanced
features such as vectorial reconstruction of the electric field, advanced
signal processing algorithms, a transparent and efficient handling of FFTs, a
very detailed simulation of detector effects, and the read-in of multiple data
formats including data from various radio simulation codes. The source code of
this radio functionality can be made available to interested parties on
request.Comment: accepted for publication in NIM A, 13 pages, minor corrections to
author list and references in v
Search for First Harmonic Modulation in the Right Ascension Distribution of Cosmic Rays Detected at the Pierre Auger Observatory
We present the results of searches for dipolar-type anisotropies in different
energy ranges above eV with the surface detector array of
the Pierre Auger Observatory, reporting on both the phase and the amplitude
measurements of the first harmonic modulation in the right-ascension
distribution. Upper limits on the amplitudes are obtained, which provide the
most stringent bounds at present, being below 2% at 99% for EeV
energies. We also compare our results to those of previous experiments as well
as with some theoretical expectations.Comment: 28 pages, 11 figure
Renormalization of the QED of self-interacting second order spin 1/2 fermions
We study the one-loop level renormalization of the electrodynamics of spin
1/2 fermions in the Poincar\'e projector formalism, in arbitrary covariant
gauge and including fermion self-interactions, which are dimension four
operators in this framework. We show that the model is renormalizable for
arbitrary values of the tree level gyromagnetic factor g within the validity
region of the perturbative expansion, \alpha g^2 << 1. In the absence of tree
level fermion self-interactions, we recover the pure QED of second order
fermions, which is renormalizable only for |g|=2. Turning off the
electromagnetic interaction we obtain a renormalizable Nambu-Jona-Lasinio-like
model with second order fermions in four space-time dimensions.Comment: 32 pages, 9 figures. Published versio
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