9,142 research outputs found
LISA observations of massive black holes binaries using post-Newtonian wave-forms
We consider LISA observations of in-spiral signals emitted by massive black
hole binary systems in circular orbit and with negligible spins. We study the
accuracy with which the source parameters can be extracted from the data
stream. We show that the use of waveforms retaining post-Newtonian corrections
not only to the phase but also the amplitude can drastically improve the
estimation of some parameters.Comment: Latex 2 pages, 1 figure. To appear in: "Third Amaldi Conference on
Gravitational Waves". Edt. S. Meshkov; American Institute of Physic
Sol–gel synthesis and thermal behavior of bioactive ferrous citrate–silica hybrid materials
Imbalance of the iron level in the body causes several diseases. In particular, the low level of iron, during pregnancy, is
responsible for the iron deficiency anemia, and even of neurodegenerative diseases. Although the treatment of iron
deficiency anemia with oral iron supplements has been known, this problem still afflicts many people. The aim of this work
was the development of a system able to release ferrous ions in a controlled manner. Controlled drug release for medical
applications, indeed, appears to be a very interesting alternative to a systemic therapy because it is assurance of treatment
continuity and drug stability and optimizes drug absorption. For this purpose, ferrous citrate (Fe(II)C) was synthesized by a
redox reaction between iron powder and citric acid. Fourier transform infrared spectroscopy (FTIR), 1,10-phenanthroline
and sodium thiocyanate colorimetric assays confirmed that only Fe(II)C was obtained by redox reaction. Afterward,
obtained Fe(II)C was embedded within a SiO2 matrix in different mass percentage, by means of a sol–gel route. FTIR
spectroscopy and simultaneous thermogravimetry/first-order derivative of thermogravimetry were used to confirm the
Fe(II)C presence in the silica matrix and to investigate the thermal behavior of the sol–gel materials, respectively. The
bioactivity test carried out by soaking the synthesized drug delivery systems in a simulated body fluid showed that the
biological properties of the silica matrix are not modified by the presence of Fe(II)C
Data Processing for LISA's Laser Interferometer Tracking System (LITS)
The purpose of this paper is twofold. First, we will present recent results
on the data processing for LISA, including algorithms for elimination of clock
jitter noise and discussion of the generation of the data averages that will
eventually need to be telemetered to the ground. Second, we will argue, based
partly on these results, that a laser interferometer tracking system (LITS)
that employs independent lasers in each spacecraft is preferable for reasons of
simplicity to that in which the lasers in two of the spacecraft are locked to
the incoming beam from the third.Comment: 5 pages, Proceedings of the Third LISA Symposium (Golm, Germany,
2000
Characterising gravitational wave stochastic background anisotropy with Pulsar Timing Arrays
Detecting a stochastic gravitational wave background, particularly radiation
from individually unresolvable super-massive black hole binary systems, is one
of the primary targets for Pulsar Timing Arrays. Increasingly more stringent
upper limits are being set on these signals under the assumption that the
background radiation is isotropic. However, some level of anisotropy may be
present and the characterisation of the power at different angular scales
carries important information. We show that the standard analysis for isotropic
backgrounds can be generalised in a conceptually straightforward way to the
case of generic anisotropic background radiation by decomposing the angular
distribution of the gravitational wave power on the sky into multipole moments.
We introduce the concept of generalised overlap reduction functions which
characterise the effect of the anisotropy multipoles on the correlation of the
timing residuals from the pulsars timed by a Pulsar Timing Array. In a search
for a signal characterised by a generic anisotropy, the generalised overlap
reduction functions play the role of the so-called Hellings and Downs curve
used for isotropic radiation. We compute the generalised overlap reduction
functions for a generic level of anisotropy and Pulsar Timing Array
configuration. We also provide an order of magnitude estimate of the level of
anisotropy that can be expected in the background generated by super-massive
black hole binary systems.Comment: 12 pages plus 5 page Appendix. Accepted to PR
Analysis of the first IPTA Mock Data Challenge by the EPTA timing data analysis working group
This is a summary of the methods we used to analyse the first IPTA Mock Data
Challenge (MDC), and the obtained results. We have used a Bayesian analysis in
the time domain, accelerated using the recently developed ABC-method which
consists of a form of lossy linear data compression. The TOAs were first
processed with Tempo2, where the design matrix was extracted for use in a
subsequent Bayesian analysis. We used different noise models to analyse the
datasets: no red noise, red noise the same for all pulsars, and individual red
noise per pulsar. We sampled from the likelihood with four different samplers:
"emcee", "t-walk", "Metropolis-Hastings", and "pyMultiNest". All but emcee
agreed on the final result, with emcee failing due to artefacts of the
high-dimensionality of the problem. An interesting issue we ran into was that
the prior of all the 36 (red) noise amplitudes strongly affects the results. A
flat prior in the noise amplitude biases the inferred GWB amplitude, whereas a
flat prior in log-amplitude seems to work well. This issue is only apparent
when using a noise model with individually modelled red noise for all pulsars.
Our results for the blind challenges are in good agreement with the injected
values. For the GWB amplitudes we found h_c = 1.03 +/- 0.11 [10^{-14}], h_c =
5.70 +/- 0.35 [10^{-14}], and h_c = 6.91 +/- 1.72 [10^{-15}], and for the GWB
spectral index we found gamma = 4.28 +/- 0.20, gamma = 4.35 +/- 0.09, and gamma
= 3.75 +/- 0.40. We note that for closed challenge 3 there was quite some
covariance between the signal and the red noise: if we constrain the GWB
spectral index to the usual choice of gamma = 13/3, we obtain the estimates:
h_c = 10.0 +/- 0.64 [10^{-15}], h_c = 56.3 +/- 2.42 [10^{-15}], and h_c = 4.83
+/- 0.50 [10^{-15}], with one-sided 2 sigma upper-limits of: h_c <= 10.98
[10^{-15}], h_c <= 60.29 [10^{-15}], and h_c <= 5.65 [10^{-15}].Comment: 10 pages, 5 figure
Exploration of Gifted Subtypes Differentiated Across Standardized Cognitive Variables
The field of gifted education has evolved through the 20th century, with legislative efforts by the federal government providing the framework necessary to highlight the needs of gifted learners. Gifted and talented learners are not a homogeneous group, to the contrary, they are varied and unique (Reis & Sullivan, 2010). Ideally, researchers and educators could collaborate to compile a conclusive list of characteristics of gifted learners, which could guide identification, teaching strategies, and curriculum selection for this population (Reis & Sullivan, 2010). Little is known about the cognitive profiles of gifted children. This study will review the utilization of the WISC-IV in defining the highest levels of intelligence as evidenced in the gifted learner. In doing so, it is hoped that the construct of giftedness will be explored, highlighting the vast heterogeneity evident in this population
The information content of gravitational wave harmonics in compact binary inspiral
The nonlinear aspect of gravitational wave generation that produces power at
harmonics of the orbital frequency, above the fundamental quadrupole frequency,
is examined to see what information about the source is contained in these
higher harmonics. We use an order (4/2) post-Newtonian expansion of the
gravitational wave waveform of a binary system to model the signal seen in a
spaceborne gravitational wave detector such as the proposed LISA detector.
Covariance studies are then performed to determine the ultimate accuracy to be
expected when the parameters of the source are fit to the received signal. We
find three areas where the higher harmonics contribute crucial information that
breaks degeneracies in the model and allows otherwise badly-correlated
parameters to be separated and determined. First, we find that the position of
a coalescing massive black hole binary in an ecliptic plane detector, such as
OMEGA, is well-determined with the help of these harmonics. Second, we find
that the individual masses of the stars in a chirping neutron star binary can
be separated because of the mass dependence of the harmonic contributions to
the wave. Finally, we note that supermassive black hole binaries, whose
frequencies are too low to be seen in the detector sensitivity window for long,
may still have their masses, distances, and positions determined since the
information content of the higher harmonics compensates for the information
lost when the orbit-induced modulation of the signal does not last long enough
to be apparent in the data.Comment: 13 pages, 5 figure
Recognizable neonatal clinical features of aplasia cutis congenita
Background: Aplasia cutis congenita (ACC), classified in nine groups, is likely to be underreported, since milder isolated lesions in wellbeing newborns could often be undetected, and solitary lesions in the context of polymalformative syndromes could not always be reported. Regardless of form and cause, therapeutic options have in common the aim to restore the deficient mechanical and immunological cutaneous protection and to limit the risk of fluid leakage or rupture of the exposed organs. We aimed to review our institutional prevalence, comorbidities, treatment and outcome of newborns with ACC. Methods: We conducted a retrospective study including all newborns affected by ACC and admitted at the University Mother-Child Department from October 2010 to October 2019. Anthropometric and clinical characteristics of ACC1 versus a non-isolated ACC group were analyzed. Results: We encountered 37 newborns, 16 with ACC1 versus 21 with non-isolated ACC. The incidence rate of 0.1% in ACC1 was higher than expected, while 19% of cases showed intrafamilial autosomal dominant transmission. Higher birth weight centile, though lower than reference population, being adequate for gestational age, normal Apgar score and euglycemia characterizing ACC1 resulted associated to a rapid tissue regeneration. Non-isolated ACC, in relation to concomitant congenital anomalies and higher prematurity rate, showed more surgical and medical complications along with the risk of neonatal death. Specifically, newborns with ACC4 were characterized by the frequent necessity of abdominal wall defect repair, responsible for the occurrence of an abdominal compartment syndrome. Conclusion: Prompt carefully assessment of the newborn with ACC in order to exclude concomitant other congenital malformations, provides clues to the underlying pathophysiology, and to the short-term prognosis. Family should be oriented toward identification of other family members affected by similar pathology, while obstetric history should exclude initial multiple pregnancy with death of a co-twin, placental anomalies and drug assumption. Molecular-genetic diagnosis and genetic counseling are integrative in individualized disease approach
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
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