5,960 research outputs found
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
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
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
The growing (good) bubbles: insights into US consumers of sparkling wine
Purpose The purpose of this paper is to investigate sparkling wine consumption behavior and preferences of a large sample of US consumers (n=1,096) exploring the differences among genders and generational cohorts. Design/methodology/approach The sample has been drawn from Wine opinions, a specialized market research company with a large online panel of US wine consumers. Data were collected through a survey mailing model, administering a structured questionnaire. Findings Findings reveal that consumption frequency between genders is not statistically different and women generally prefer sparkling wines priced below 15\u201310\u2013$14.99 one. Originality/value The study sheds light on the changing consumer attitudes to create competitive advantages for wineries. Specifically, it provides valuable marketing insights into the peculiarities of sparkling wine consumption for each generation (e.g. price-point preferences and type of wine)
Observing the dynamics of super-massive black hole binaries with Pulsar Timing Arrays
Pulsar Timing Arrays are a prime tool to study unexplored astrophysical
regimes with gravitational waves. Here we show that the detection of
gravitational radiation from individually resolvable super-massive black hole
binary systems can yield direct information about the masses and spins of the
black holes, provided that the gravitational-wave induced timing fluctuations
both at the pulsar and at the Earth are detected. This in turn provides a map
of the non-linear dynamics of the gravitational field and a new avenue to
tackle open problems in astrophysics connected to the formation and evolution
of super-massive black holes. We discuss the potential, the challenges and the
limitations of these observations.Comment: 5 pages, 1 figur
Eccentric double white dwarfs as LISA sources in globular clusters
We consider the formation of double white dwarfs (DWDs) through dynamical
interactions in globular clusters. Such interactions can give rise to eccentric
DWDs, in contrast to the exclusively circular population expected to form in
the Galactic disk. We show that for a 5-year Laser Interferometer Space Antenna
(LISA) mission and distances as far as the Large Magellanic Cloud, multiple
harmonics from eccentric DWDs can be detected at a signal-to-noise ratio higher
than 8 for at least a handful of eccentric DWDs, given their formation rate and
typical lifetimes estimated from current cluster simulations. Consequently the
association of eccentricity with stellar-mass LISA sources does not uniquely
involve neutron stars, as is usually assumed. Due to the difficulty of
detecting (eccentric) DWDs with present and planned electromagnetic
observatories, LISA could provide unique dynamical identifications of these
systems in globular clusters.Comment: Published in ApJ 665, L5
Revealing the nature of magnetic shadows with numerical 3D-MHD simulations
We investigate the interaction of magneto-acoustic waves with magnetic
network elements with the aim of finding possible signatures of the magnetic
shadow phenomenon in the vicinity of network elements. We carried out
three-dimensional numerical simulations of magneto-acoustic wave propagation in
a model solar atmosphere that is threaded by a complexly structured magnetic
field, resembling that of a typical magnetic network element and of
internetwork regions. High-frequency waves of 10 mHz are excited at the bottom
of the simulation domain. On their way through the upper convection zone and
through the photosphere and the chromosphere they become perturbed, refracted,
and converted into different mode types. We applied a standard Fourier analysis
to produce oscillatory power-maps of the line-of-sight velocity. In the power
maps of the upper photosphere and the lower chromosphere, we clearly see the
magnetic shadow: a seam of suppressed power surrounding the magnetic network
elements. We demonstrate that this shadow is linked to the mode conversion
process and that power maps at these height levels show the signature of three
different magneto-acoustic wave modes.Comment: Astronomy & Astrophysics Letters, in print 4 pages, 4 figure
Ambulatory surgery for perianal Crohn’s disease. Study of feasibility
Background. One-third of Crohn’s disease (CD) patients present perianal fistula. The gold standard in the diagnosis and treatment of symptomatic perianal disease (PAD) in CD is the exploration of the anal canal and distal rectum under anesthesia (EUA). This procedure is mainly conducted as a day case surgery. Unfortunately, it is not always possible to proceed within the ideal timing and any delay may well represent a relevant clinical issue. The aim of this study was to evaluate the feasibility of outpatient treatment of symptomatic perianal fistulas in CD patients. Methods. All CD patients under regular follow-up at our inflammatory bowel disease referral center, presenting with symptomatic perianal fistulas, were offered surgical consultation. The data of patients were prospectively collected for three years (February 2014 to February 2017) for the purpose of the study. All clinical information, including previous EUA and/or records from MRI and endoscopic ultrasound, was included. Outpatient anal canal and distal rectum exploration and treatment (OE) were undertaken during the specialist surgical consultation. Fistulas were classified according to Parks’s classification; the type of outpatient treatment and compliance of patients were recorded. Pain was assessed by VAS at the time of the procedure and during the first control. Patients were followed up in the surgical clinic in relation to the study. Results. Ninety-two CD patients with symptomatic perianal fistulas had surgical consultation during the study period. OE was offered to all but 18 patients who fulfilled the exclusion criteria or had an extremely severe disease; six patients refused the OE (8.11%). Of the 68 patients undergoing OE, eleven (16.18%) had previous surgery for perianal disease. The OE was accomplished in sixty-one patients (89.71%), while in 7 patients, it was abandoned for scarce compliance. Nine patients (14.75%) underwent drainage of perianal abscess; in 3 of them, it was possible to probe the fistula tract, find the internal orifice, and pass a loose seton. Overall, setonage was performed in 50 patients (81.97%). Rectovaginal setons were placed in 3 patients and more than one seton (up to 3) in 6 cases. Fistulotomy was performed in 4 simple subcutaneous fistulous tracts. Concordance with the preoperative findings was found in 54 out of 61 patients. EUA was scheduled at the time of OE for the 7 patients who did not complete the procedure. All sixty-one patients who had the OE were followed up for a minimum of 12 months. Conclusions. This preliminary study indicates that OE in CD patients with symptomatic perianal fistulas is safe and feasible in a high-volume referral center. It might provide several benefits, including patients’ logistics, reduce or remove patients’ symptoms and discomfort, allow for a timely start of medical therapy, and avoid further complications
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