432 research outputs found
A source-free integration method for black hole perturbations and self-force computation: Radial fall
Perturbations of Schwarzschild-Droste black holes in the Regge-Wheeler gauge
benefit from the availability of a wave equation and from the gauge invariance
of the wave function, but lack smoothness. Nevertheless, the even perturbations
belong to the C\textsuperscript{0} continuity class, if the wave function and
its derivatives satisfy specific conditions on the discontinuities, known as
jump conditions, at the particle position. These conditions suggest a new way
for dealing with finite element integration in time domain. The forward time
value in the upper node of the ) grid cell is obtained by the linear
combination of the three preceding node values and of analytic expressions
based on the jump conditions. The numerical integration does not deal directly
with the source term, the associated singularities and the potential. This
amounts to an indirect integration of the wave equation. The known wave forms
at infinity are recovered and the wave function at the particle position is
shown. In this series of papers, the radial trajectory is dealt with first,
being this method of integration applicable to generic orbits of EMRI (Extreme
Mass Ratio Inspiral).Comment: This arXiv version differs from the one to be published by Phys. Rev.
D for the use of British English and other minor editorial difference
Postseismic deformation and body forces shaping the Apennines and adjacent sedimentary basins in Umbria-Marche
The geodynamic complexity of the Apennines and adjacent sedimentary basins in Umbria-Marche (North-Central
Italy) makes the dynamics of the present day deformation and its relationships with the seismicity less well understood.
In this paper, we argue that, further to buoyancy forces, postseismic deformation of earthquakes taking place
on the Apennines contributes to the regional deformation. We investigate the interaction between the normal faulting
system responsible of the 1997 Umbria-Marche earthquake sequence (Colfiorito fault) and the low angle normal
faulting system bordering the sedimentary basins, namely the Altotiberina fault. We set-up a 2D finite element
model of the lithosphere-asthenosphere accounting for lateral heterogeneities and investigate how this heterogeneous
structure is capable of localizing strain under the Umbria-Marche sedimentary basins, providing a way for
the Colfiorito fault to influence the evolution of the Altotiberina fault. We show how the two different length and
time scale processes, namely postseismic deformation and buoyancy, are complementary in shaping the Apennines
and adjacent sedimentary basins. The high resolution deformation patterns modeled in this study can hardly be reproduced
by a model accounting only for external forces such as a rotating or subducting or retreating Adria
Modeling of Kashmir Aftershock Decay Based on Static Coulomb Stress Changes and Laboratory-Derived Rate-and-State Dependent Friction Law
We model the spatial and temporal evolution of October 8, 2005 Kashmir earthquake\u2019s aftershock activity using the rate-and-state dependent friction model incorporating uncertainties in computed coseismic stress perturbations. We estimated the best possible value for frictional resistance \u2018\u2018Arn\u2019\u2019, background seismicity rate \u2018\u2018r\u2019\u2019 and coef\ufb01cient of stress variation \u2018\u2018CV\u2019\u2019 using maximum log-likelihood method. For the whole Kashmir earthquake sequence, we measure a frictional resistance Arn * 0.0185 MPa, r * 20 M3.7? events/year and CV = 0.94 \ub1 0.01. The spatial and temporal forecasted seismicity rate of modeled aftershocks \ufb01ts well with the spatial and temporal distribution of observed aftershocks that occurred in the regions with positive static stress changes as well as in the apparent stress shadow region. To quantify the effect of secondary aftershock triggering, we have re-run the estimations for 100 stochastically declustered catalogs showing that the effect of aftershock-induced secondary stress changes is obviously minor compared to the overall uncertainties, and that the stress variability related to uncertain slip model inversions and receiver mechanisms remains the major factor to provide a reasonable data \ufb01t
Analysis of iatrogenic risk related to anticholinergic effects using two scales in acute geriatric inpatient unit
Anticholinergic medications are responsible for most frequent adverse drug effects. Two scales have been elaborated as tools for prescribers: the Anticholinergic Drug Scale (ADS) of Carnahan et al., and the Anticholinergic Risk Scale (ARS) of Rudolph et al. The objective of this study was to analyze the diagnostic performance of both scales for predicting signs related to an anticholinergic effect. Method: Medical records of 1379 patients aged 75 years or older hospitalized in a geriatric acute care unit between 2002 and 2005 were studied. The analyze was made retrospectively, but data were collected prospectively. Results: Risk of appearance of total anticholinergic signs (ADS : OR 1,45, CI 95% [1,03-2,03], p=0,037 and ARS : OR 1,98, CI 95% [1,19-3,28] p<0,01) and peripheral signs (ADS: OR 1,66, CI 95% [1,22-2,26], p<0,01 and ARS : OR 1,81, CI 95% [1,19-2,75], p<0,01) increased when score was >= 3 with both scales, which wasn\u27t the case for central signs. Conclusion: Both scales permitted to detect an increased risk of appearance of total and peripheral anticholinergic signs, but not the centrals as delirium. Interest of total anticholinergic burden remains to be demonstrated, especially for delirium risk assessment
Fourth order indirect integration method for black hole perturbations: even modes
On the basis of a recently proposed strategy of finite element integration in
time domain for partial differential equations with a singular source term, we
present a fourth order algorithm for non-rotating black hole perturbations in
the Regge-Wheeler gauge. Herein, we address even perturbations induced by a
particle plunging in. The forward time value at the upper node of the
grid cell is obtained by an algebraic sum of i) the preceding node values of
the same cell, ii) analytic expressions, related to the jump conditions on the
wave function and its derivatives, iii) the values of the wave function at
adjacent cells. In this approach, the numerical integration does not deal with
the source and potential terms directly, for cells crossed by the particle
world line. This scheme has also been applied to circular and eccentric orbits
and it will be object of a forthcoming publication.Comment: This series of papers deals with EMRI for LISA. With the respect to
the v1 version, the algorithm has been improved; convergence tests and
references have been added; v2 is composed by 23 pages, and 6 figures. Paper
accepted by Class. Quantum Gravity for the special issue on Theory Meets Data
Analysis at Comparable and Extreme Mass Ratios (Capra and NRDA) at Perimeier
Institute in June 201
Avoiding selection bias in gravitational wave astronomy
When searching for gravitational waves in the data from ground-based
gravitational wave detectors it is common to use a detection threshold to
reduce the number of background events which are unlikely to be the signals of
interest. However, imposing such a threshold will also discard some real
signals with low amplitude, which can potentially bias any inferences drawn
from the population of detected signals. We show how this selection bias is
naturally avoided by using the full information from the search, considering
both the selected data and our ignorance of the data that are thrown away, and
considering all relevant signal and noise models. This approach produces
unbiased estimates of parameters even in the presence of false alarms and
incomplete data. This can be seen as an extension of previous methods into the
high false rate regime where we are able to show that the quality of parameter
inference can be optimised by lowering thresholds and increasing the false
alarm rate.Comment: 13 pages, 2 figure
Antimicrobial Resistance of Escherichia coli Isolated from Chickens in West of Algeria
Modern poultry flocks undergo strong microbial pressure. Antibiotics can contribute to reduce bacterial infections. Their use increased these last years. Studies performed in Morocco and Algeria highlighted the importance of antibioresistance after excessive use of antibiotics in poultry breeding. In western Algeria, 240 strains of enterobacteriaceae were isolated according to usual bacteriological procedures. In order to assess antimicrobial resistance, the disc diffusion method for antibiotic susceptibility (tetracycline (TE), enrofloxacin (ENR), trimethoprim+sulfamethoxazole (SXT), amoxicillin+clavulanic acid (AMC), ceftiofur (KF), colistin (CT), neomycin (N), gentamicin (GN) and chloramphenicol (C) was applied (Antibioresistance Committee of the French Microbiology Society, 2010). All enterobacteriaceae strains isolated presented at least one resistance to those antibiotics. Escherichia coli counted for 47.5% of these strains (N=114). By omitting intermediate resistances, 28% of E. coli presented a resistance to at least 6 antibiotics and 31.6% to 5 antibiotics. In general, 90.35%, 79.82%, 70.17%, 92.10%, 62.28%, 31.57% and 21.05% of E. coli were resistant to, respectively, TE, ENR, SXT, AMC, KF, CT and N. Considering such a high resistance rate, it is strongly advised to implement epidemiological survey of bacterial resistances at the regional level
Advanced VIRGO: detector optimization for gravitational waves by inspiralling binaries
For future configurations, we study the relation between the abatement of the
noise sources and the Signal to Noise Ratio (SNR) for coalescing binaries. Our
aim is not the proposition of a new design, but an indication of where in the
bandwidth or for which noise source, a noise reduction would be most efficient.
We take VIRGO as the reference for our considerations, solely applicable to the
inspiralling phase of a coalescing binary. Thus, only neutron stars and small
black holes of few solar masses are encompassed by our analysis. The
contributions to the SNR given by final merge and quasi-normal ringing are
neglected. It is identified that i) the reduction in the mirror thermal noise
band provides the highest gain for the SNR, when the VIRGO bandwidth is divided
according to the dominant noises; ii) it exists a specific frequency at which
lies the potential largest increment in the SNR, and that the enlargement of
the bandwidth, where the noise is reduced, produces a shift of such optimal
frequency to higher values; iii) the abatement of the pendulum thermal noise
provides the largest, but modest, gain, when noise sources are considered
separately. Our recent astrophysical analysis on event rates for neutron stars
leads to a detection rate of one every 148 or 125 years for VIRGO and LIGO,
respectively, while a recently proposed and improved, but still conservative,
VIRGO configuration would provide an increase to 1.5 events per year. Instead,
a bi-monthly event rate, similar to advanced LIGO, requires a 16 times gain. We
analyse the 3D (pendulum, mirror, shot noises) parameter space showing how such
gain could be achieved.Comment: Change of title (Virgo detector optimization for gravitational waves
by coalescing binaries) and partially of text. 6 figure
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