5,730 research outputs found
Deep learning for inferring cause of data anomalies
Daily operation of a large-scale experiment is a resource consuming task,
particularly from perspectives of routine data quality monitoring. Typically,
data comes from different sub-detectors and the global quality of data depends
on the combinatorial performance of each of them. In this paper, the problem of
identifying channels in which anomalies occurred is considered. We introduce a
generic deep learning model and prove that, under reasonable assumptions, the
model learns to identify 'channels' which are affected by an anomaly. Such
model could be used for data quality manager cross-check and assistance and
identifying good channels in anomalous data samples. The main novelty of the
method is that the model does not require ground truth labels for each channel,
only global flag is used. This effectively distinguishes the model from
classical classification methods. Being applied to CMS data collected in the
year 2010, this approach proves its ability to decompose anomaly by separate
channels.Comment: Presented at ACAT 2017 conference, Seattle, US
Water in the Near IR spectrum of Comet 8P/Tuttle
High resolution spectra of Comet 8P/Tuttle were obtained in the frequency
range 3440.6-3462.6 cm-1 on 3 January 2008 UT using CGS4 with echelle grating
on UKIRT. In addition to recording strong solar pumped fluorescent (SPF) lines
of H2O, the long integration time (152 miutes on target) enabled eight weaker
H2O features to be assigned, most of which had not previously been identified
in cometary spectra. These transitions, which are from higher energy upper
states, are similar in character to the so-called 'SH' lines recorded in the
post Deep Impact spectrum of comet Tempel 1 (Barber et al., 2007). We have
identified certain characteristics that these lines have in common, and which
in addition to helping to define this new class of cometary line, give some
clues to the physical processes involved in their production. Finally, we
derive an H2O rotational temperature of 62+/- K and a water production rate of
(1.4+/-0.3)E28 molecules/s.Comment: Paper has been accepted for publication by MNRAS (11/06/09
Asymmetries observed in Saturn's magnetopause geometry
For over 10 years, the Cassini spacecraft has patrolled Saturn's magnetosphere and observed its magnetopause boundary over a wide range of prevailing solar wind and interior plasma conditions. We now have data that enable us to resolve a significant dawn-dusk asymmetry and find that the magnetosphere extends farther from the planet on the dawnside of the planet by 7 +/- 1%. In addition, an opposing dawn-dusk asymmetry in the suprathermal plasma pressure adjacent to the magnetopause has been observed. This probably acts to reduce the size asymmetry and may explain the discrepancy between the degree of asymmetry found here and a similar asymmetry found by Kivelson and Jia (2014) using MHD simulations. Finally, these observations sample a wide range of season, allowing the "intrinsic" polar flattening (14 +/- 1%) caused by the magnetodisc to be separated from the seasonally induced north-south asymmetry in the magnetopause shape found theoretically (5 +/- 1% when the planet's magnetic dipole is tilted away from the Sun by 10-17 degrees)
Internally driven large-scale changes in the size of Saturn’s magnetosphere
Saturn’s magnetic field acts as an obstacle to solar wind flow, deflecting plasma around the planet and forming a cavity known as the magnetosphere. The magnetopause defines the boundary between the planetary and solar dominated regimes, and so is strongly influenced by the variable nature of pressure sources both outside and within. Following from Pilkington et al. (2014), crossings of the magnetopause are identified using 7 years of magnetic field and particle data from the Cassini spacecraft and providing unprecedented spatial coverage of the magnetopause boundary. These observations reveal a dynamical interaction where, in addition to the external influence of the solar wind dynamic pressure, internal drivers, and hot plasma dynamics in particular can take almost complete control of the system’s dayside shape and size, essentially defying the solar wind conditions. The magnetopause can move by up to 10–15 planetary radii at constant solar wind dynamic pressure, corresponding to relatively “plasma-loaded” or “plasma-depleted” states, defined in terms of the internal suprathermal plasma pressure
Scalar models for the generalized Chaplygin gas and the structure formation constraints
The generalized Chaplygin gas model represents an attempt to unify dark
matter and dark energy. It is characterized by a fluid with an equation of
state . It can be obtained from a generalization of the
DBI action for a scalar, tachyonic field. At background level, this model gives
very good results, but it suffers from many drawbacks at perturbative level. We
show that, while for background analysis it is possible to consider any value
for , the perturbative analysis must be restricted to positive values
of . This restriction can be circumvented if the origin of the
generalized Chaplygin gas is traced back to a self-interacting scalar field,
instead of the DBI action. But, in doing so, the predictions coming from
formation of large scale structures reduce the generalized Chaplygin gas model
to a kind of quintessence model, and the unification scenario is lost, if the
scalar field is the canonical one. However, if the unification condition is
imposed from the beginning as a prior, the model may remain competitive. More
interesting results, concerning the unification program, are obtained if a
non-canonical self-interacting scalar field, inspired by Rastall's theory of
gravity, is imposed. In this case, an agreement with the background tests is
possible.Comment: Latex file, 25 pages, 33 figures in eps format. New section on scalar
models. Accepted for publication in Gravitation&Cosmolog
Observation and characterization of laser-driven Phase Space Electron Holes
The direct observation and full characterization of a Phase Space Electron
Hole (EH) generated by laser-matter interaction is presented. This structure
has been detected via proton radiography during the interaction between an
intense laser pulse (t=1ns temporally flat-top, I= 10^14W/cm^2) and a gold 26
micron thick hohlraum. This technique has allowed us the simultaneous detection
of propagation velocity, potential and electron density spatial profile across
the EH with fine spatial and temporal resolution providing an unprecedentedly
detailed experimental characterization
Gram-negative prosthetic joint infection: outcome of a debridement, antibiotics and implant retention approach. A large multicentre study
AbstractWe aim to evaluate the epidemiology and outcome of gram-negative prosthetic joint infection (GN-PJI) treated with debridement, antibiotics and implant retention (DAIR), identify factors predictive of failure, and determine the impact of ciprofloxacin use on prognosis. We performed a retrospective, multicentre, observational study of GN-PJI diagnosed from 2003 through to 2010 in 16 Spanish hospitals. We define failure as persistence or reappearance of the inflammatory joint signs during follow-up, leading to unplanned surgery or repeat debridement >30 days from the index surgery related death, or suppressive antimicrobial therapy. Parameters predicting failure were analysed with a Cox regression model. A total of 242 patients (33% men; median age 76 years, interquartile range (IQR) 68–81) with 242 episodes of GN-PJI were studied. The implants included 150 (62%) hip, 85 (35%) knee, five (2%) shoulder and two (1%) elbow prostheses. There were 189 (78%) acute infections. Causative microorganisms were Enterobacteriaceae in 78%, Pseudomonas spp. in 20%, and other gram-negative bacilli in 2%. Overall, 19% of isolates were ciprofloxacin resistant. DAIR was used in 174 (72%) cases, with an overall success rate of 68%, which increased to 79% after a median of 25 months' follow-up in ciprofloxacin-susceptible GN-PJIs treated with ciprofloxacin. Ciprofloxacin treatment exhibited an independent protective effect (adjusted hazard ratio (aHR) 0.23; 95% CI, 0.13–0.40; p <0.001), whereas chronic renal impairment predicted failure (aHR, 2.56; 95% CI, 1.14–5.77; p 0.0232). Our results confirm a 79% success rate in ciprofloxacin-susceptible GN-PJI treated with debridement, ciprofloxacin and implant retention. New therapeutic strategies are needed for ciprofloxacin-resistant PJI
Search for the standard model Higgs boson in the H to ZZ to 2l 2nu channel in pp collisions at sqrt(s) = 7 TeV
A search for the standard model Higgs boson in the H to ZZ to 2l 2nu decay
channel, where l = e or mu, in pp collisions at a center-of-mass energy of 7
TeV is presented. The data were collected at the LHC, with the CMS detector,
and correspond to an integrated luminosity of 4.6 inverse femtobarns. No
significant excess is observed above the background expectation, and upper
limits are set on the Higgs boson production cross section. The presence of the
standard model Higgs boson with a mass in the 270-440 GeV range is excluded at
95% confidence level.Comment: Submitted to JHE
Search for anomalous t t-bar production in the highly-boosted all-hadronic final state
A search is presented for a massive particle, generically referred to as a
Z', decaying into a t t-bar pair. The search focuses on Z' resonances that are
sufficiently massive to produce highly Lorentz-boosted top quarks, which yield
collimated decay products that are partially or fully merged into single jets.
The analysis uses new methods to analyze jet substructure, providing
suppression of the non-top multijet backgrounds. The analysis is based on a
data sample of proton-proton collisions at a center-of-mass energy of 7 TeV,
corresponding to an integrated luminosity of 5 inverse femtobarns. Upper limits
in the range of 1 pb are set on the product of the production cross section and
branching fraction for a topcolor Z' modeled for several widths, as well as for
a Randall--Sundrum Kaluza--Klein gluon. In addition, the results constrain any
enhancement in t t-bar production beyond expectations of the standard model for
t t-bar invariant masses larger than 1 TeV.Comment: Submitted to the Journal of High Energy Physics; this version
includes a minor typo correction that will be submitted as an erratu
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