4,518 research outputs found
A Markov Chain Monte Carlo approach to the study of massive black hole binary systems with LISA
The Laser Interferometer Space Antenna (LISA) will produce a data stream
containing a vast number of overlapping sources: from strong signals generated
by the coalescence of massive black hole binary systems to much weaker
radiation form sub-stellar mass compact binaries and extreme-mass ratio
inspirals. It has been argued that the observation of weak signals could be
hampered by the presence of loud ones and that they first need to be removed to
allow such observations. Here we consider a different approach in which sources
are studied simultaneously within the framework of Bayesian inference. We
investigate the simplified case in which the LISA data stream contains
radiation from a massive black hole binary system superimposed over a (weaker)
quasi-monochromatic waveform generated by a white dwarf binary. We derive the
posterior probability density function of the model parameters using an
automatic Reversible Jump Markov Chain Monte Carlo algorithm (RJMCMC). We show
that the information about the sources and noise are retrieved at the expected
level of accuracy without the need of removing the stronger signal. Our
analysis suggests that this approach is worth pursuing further and should be
considered for the actual analysis of the LISA data.Comment: submitted to cqg as GWDAW-10 conference proceedings, 10 pages, 4
figures, some changes to plots and numerical detail
LISA Response Function and Parameter Estimation
We investigate the response function of LISA and consider the adequacy of its
commonly used approximation in the high-frequency range of the observational
band. We concentrate on monochromatic binary systems, such as white dwarf
binaries. We find that above a few mHz the approxmation starts becoming
increasingly inaccurate. The transfer function introduces additional amplitude
and phase modulations in the measured signal that influence parameter estmation
and, if not properly accounted for, lead to losses of signal-to-noise ratio.Comment: 4 pages, 2 figures, amaldi 5 conference proceeding
ESA, iron therapy and new drugs: Are there new perspectives in the treatment of anaemia?
Anemia is a well-known consequence of chronic kidney disease (CKD); it is mainly due to a relative insufficiency of erythropoietin synthesis by the failing kidneys. Over the years, the combination of erythropoiesis stimulating agents (ESA) and iron has become the standard of care of anemia. All ESAs effectively increase hemoglobin (Hb) levels in a substantial percentage of patients. However, in the last decade, their use has been surrounded by safety issues in increased cardiovascular risk, especially when used at high doses in inflamed and hyporesponsive patients. This has led to the definition of a more cautious Hb target. Iron deficiency is very frequent in CKD patients, with a higher frequency in non-dialysis patients. Traditionally, iron supplementation is mostly used as supportive therapy for anemia control. However, the concept is growing that intravenous iron therapy per se could be beneficial in the presence of heart failure. A new class of drugs, prolyl hydroxylase domain (PHD) inhibitors (PHD inhibitors) is becoming available for the treatment of anemia in CKD patients. Theoretically, these agents have a number of advantages, the main ones being that of stimulating the synthesis of endogenous erythropoietin and increasing iron avail-ability. The impact of their future use in clinical practice is still to be defined. Another possible strategy could be targeting serum hepcidin and its related pathways. This possibility is fascinating from the scientific point of view, but at present its development phase is still far from clinical application
The Effect of the LISA Response Function on Observations of Monochromatic Sources
The Laser Interferometer Space Antenna (LISA) is expected to provide the
largest observational sample of binary systems of faint sub-solar mass compact
objects, in particular white-dwarfs, whose radiation is monochromatic over most
of the LISA observational window. Current astrophysical estimates suggest that
the instrument will be able to resolve about 10000 such systems, with a large
fraction of them at frequencies above 3 mHz, where the wavelength of
gravitational waves becomes comparable to or shorter than the LISA arm-length.
This affects the structure of the so-called LISA transfer function which cannot
be treated as constant in this frequency range: it introduces characteristic
phase and amplitude modulations that depend on the source location in the sky
and the emission frequency. Here we investigate the effect of the LISA transfer
function on detection and parameter estimation for monochromatic sources. For
signal detection we show that filters constructed by approximating the transfer
function as a constant (long wavelength approximation) introduce a negligible
loss of signal-to-noise ratio -- the fitting factor always exceeds 0.97 -- for
f below 10mHz, therefore in a frequency range where one would actually expect
the approximation to fail. For parameter estimation, we conclude that in the
range 3mHz to 30mHz the errors associated with parameter measurements differ
from about 5% up to a factor of 10 (depending on the actual source parameters
and emission frequency) with respect to those computed using the long
wavelength approximation.Comment: replacement version with typos correcte
Media use during adolescence: the recommendations of the Italian Pediatric Society.
BACKGROUND: The use of media device, such as smartphone and tablet, is currently increasing, especially among the youngest. Adolescents spend more and more time with their smartphones consulting social media, mainly Facebook, Instagram and Twitter because. Adolescents often feel the necessity to use a media device as a means to construct a social identity and express themselves. For some children, smartphone ownership starts even sooner as young as 7 yrs, according to internet safety experts. MATERIAL AND METHODS: We analyzed the evidence on media use and its consequences in adolescence. RESULTS: In literature, smartphones and tablets use may negatively influences the psychophysical development of the adolescent, such as learning, sleep and sigh. Moreover, obesity, distraction, addiction, cyberbullism and Hikikomori phenomena are described in adolescents who use media device too frequently. The Italian Pediatric Society provide action-oriented recommendations for families and clinicians to avoid negative outcomes. CONCLUSIONS: Both parents and clinicians should be aware of the widespread phenomenon of media device use among adolescents and try to avoid psychophysical consequences on the youngest
Optical properties of V2O3 in its whole phase diagram
Vanadium sesquioxide V2O3 is considered a textbook example of Mott-Hubbard
physics. In this paper we present an extended optical study of its whole
temperature/doping phase diagram as obtained by doping the pure material with
M=Cr or Ti atoms (V1-xMx)2O3. We reveal that its thermodynamically stable
metallic and insulating phases, although macroscopically equivalent, show very
different low-energy electrodynamics. The Cr and Ti doping drastically change
both the antiferromagnetic gap and the paramagnetic metallic properties. A
slight chromium content induces a mesoscopic electronic phase separation, while
the pure compound is characterized by short-lived quasiparticles at high
temperature. This study thus provides a new comprehensive scenario of the
Mott-Hubbard physics in the prototype compound V2O3
Bayesian coherent analysis of in-spiral gravitational wave signals with a detector network
The present operation of the ground-based network of gravitational-wave laser
interferometers in "enhanced" configuration brings the search for gravitational
waves into a regime where detection is highly plausible. The development of
techniques that allow us to discriminate a signal of astrophysical origin from
instrumental artefacts in the interferometer data and to extract the full range
of information are some of the primary goals of the current work. Here we
report the details of a Bayesian approach to the problem of inference for
gravitational wave observations using a network of instruments, for the
computation of the Bayes factor between two hypotheses and the evaluation of
the marginalised posterior density functions of the unknown model parameters.
The numerical algorithm to tackle the notoriously difficult problem of the
evaluation of large multi-dimensional integrals is based on a technique known
as Nested Sampling, which provides an attractive alternative to more
traditional Markov-chain Monte Carlo (MCMC) methods. We discuss the details of
the implementation of this algorithm and its performance against a Gaussian
model of the background noise, considering the specific case of the signal
produced by the in-spiral of binary systems of black holes and/or neutron
stars, although the method is completely general and can be applied to other
classes of sources. We also demonstrate the utility of this approach by
introducing a new coherence test to distinguish between the presence of a
coherent signal of astrophysical origin in the data of multiple instruments and
the presence of incoherent accidental artefacts, and the effects on the
estimation of the source parameters as a function of the number of instruments
in the network.Comment: 22 page
A Case Study of Malignant Edema in Postpartum Mediterranean Buffaloes (Bubalus bubalis)
The paper describes for the first time four cases of postparturient malignant edema in water buffaloes due to Clostridium septicum (Cl. septicum). The study was carried out on four primiparous buffaloes that showed swelling of perineal and perivulvar areas, fever and agalactia a few hours after calving. Two of them died within 20 hours after calving. The other two developed edema in the skeletal muscles of one leg and were treated with sulfadiazine-trimethoprim for 10 days. The clinical signs completely resolved. Culture and molecular investigations identified the pathogen isolated from exudate taken from the vulva as Cl. septicum. The isolate showed multi-drug resistance. In the management of infection due to Cl. septicum, timely diagnosis and the chirurgic curettage, associated with a broad-spectrum antibiotic therapy, were found to be sufficient for the survival and recovery of the infected animals
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