125 research outputs found
Background Estimation in a Gravitational Wave Experiment
The problem to estimate the background due to accidental coincidences in the
search for coincidences in gravitational wave experiments is discussed. The use
of delayed coincidences obtained by orderly shifting the event times of one of
the two detectors is shown to be the most correctComment: Latex file. 6 pages, 3 figures. Submitted to the proceeding of the 3
GWDAW workshop (Rome, dic 1999) (International journal of Modern physics D
Coherent search of continuous gravitational wave signals: extension of the 5-vectors method to a network of detectors
We describe the extension to multiple datasets of a coherent method for the
search of continuous gravitational wave signals, based on the computation of
5-vectors. In particular, we show how to coherently combine different datasets
belonging to the same detector or to different detectors. In the latter case
the coherent combination is the way to have the maximum increase in
signal-to-noise ratio. If the datasets belong to the same detector the
advantage comes mainly from the properties of a quantity called {\it coherence}
which is helpful (in both cases, in fact) in rejecting false candidates. The
method has been tested searching for simulated signals injected in Gaussian
noise and the results of the simulations are discussed.Comment: 9 pages, 2 figures. Journal of Physics: Conference Series, in pres
A method for narrow-band searches of continuous gravitational wave signals
Targeted searches of continuous waves from spinning neutron stars normally
assume that the frequency of the gravitational wave signal is at a given known
ratio with respect to the rotational frequency of the source, e.g. twice for an
asymmetric neutron star rotating around a principal axis of inertia. In fact
this assumption may well be invalid if, for instance, the gravitational wave
signal is due to a solid core rotating at a slightly different rate with
respect to the star crust. In this paper we present a method for {\it
narrow-band} searches of continuous gravitational wave signals from known
pulsars in the data of interferometric detectors. This method assumes source
position is known to high accuracy, while a small frequency and spin-down range
around the electromagnetic-inferred values is explored. Barycentric and
spin-down corrections are done with an efficient time-domain procedure.
Sensitivity and computational efficiency estimates are given and results of
tests done using simulated data are also discussed.Comment: 13 pages; 6 figures; accepted in PR
Novel directed search strategy to detect continuous gravitational waves from neutron stars in low- and high-eccentricity binary systems
We describe a novel, very fast and robust, directed search incoherent method
for periodic gravitational waves (GWs) from neutron stars in binary systems. As
directed search, we assume the source sky position to be known with enough
accuracy, but all other parameters are supposed to be unknown. We exploit the
frequency-modulation due to source orbital motion to unveil the signal
signature by commencing from a collection of time and frequency peaks. We
validate our pipeline adding 131 artificial continuous GW signals from pulsars
in binary systems to simulated detector Gaussian noise, characterized by a
power spectral density Sh = 4x10^-24 Hz^-1/2 in the frequency interval [70,
200] Hz, which is overall commensurate with the advanced detector design
sensitivities. The pipeline detected 128 signals, and the weakest signal
injected and detected has a GW strain amplitude of ~10^-24, assuming one month
of gapless data collected by a single advanced detector. We also provide
sensitivity estimations, which show that, for a single- detector data covering
one month of observation time, depending on the source orbital Doppler
modulation, we can detect signals with an amplitude of ~7x10^-25. By using
three detectors, and one year of data, we would easily gain more than a factor
3 in sensitivity, translating into being able to detect weaker signals. We also
discuss the parameter estimate proficiency of our method, as well as
computational budget, which is extremely cheap. In fact, sifting one month of
single-detector data and 131 Hz-wide frequency range takes roughly 2.4 CPU
hours. Due to the high computational speed, the current procedure can be
readily applied in ally-sky schemes, sieving in parallel as many sky positions
as permitted by the available computational power
HIV-Reverse Transcriptase Inhibition: Inclusion of Ligand-Induced Fit by Cross-Docking Studies
Nonnucleoside reverse transcriptase inhibitors (NNRTIs) have, in addition to the nucleoside reverse transcriptase inhibitors (NRTIs) and protease inhibitors (PIs), a definitive role in the treatment of HIV-1 infections. Since the appearance of HEPT and TIBO, more than 30 structurally different classes of compounds have been reported as NNRTIs, which are specific inhibitors of HIV-1 replication, targeting the HIV-1 reverse transcriptase (RT). Nevirapine and delavirdine are the first formally licensed for clinical use, and others have been licensed afterward, while several are in preclinical or clinical development. The NNRTIs interact with a specific site of HIV-1 RT (nonnucleoside binding site, NNBS) that is close to, but distinct from, the NRTI binding site. In this work we report the application of the Autodock program assessing its usability through reproduction of 41 NNRTI experimental bound conformations. Moreover, cross-docking experiments on the wild-type and mutated RT forms were conducted to take into account the enzyme flexibility as a valuable tool for structure-based drug design (SBDD) studies and to gain insight on the mode of action of new anti-HIV agents active against both wild-type and resistant strains
A method to search for long duration gravitational wave transients from isolated neutron stars using the generalized FrequencyHough
We describe a method to detect gravitational waves lasting
emitted by young, isolated neutron stars, such as those that could form after a
supernova or a binary neutron star merger, using advanced LIGO/Virgo data. The
method is based on a generalization of the FrequencyHough (FH), a pipeline that
performs hierarchical searches for continuous gravitational waves by mapping
points in the time/frequency plane of the detector to lines in the
frequency/spindown plane of the source. We show that signals whose spindowns
are related to their frequencies by a power law can be transformed to
coordinates where the behavior of these signals is always linear, and can
therefore be searched for by the FH. We estimate the sensitivity of our search
across different braking indices, and describe the portion of the parameter
space we could explore in a search using varying fast Fourier Transform (FFT)
lengths.Comment: 15 figure
Asteroseismology of solar-type stars with Kepler: III. Ground-based data
peer reviewedWe report on the ground-based follow-up program of spectroscopic and photometric observations of solar-like asteroseismic targets for the Kepler space mission. These stars constitute a large group of more than a thousand objects which are the subject of an intensive study by the Kepler Asteroseismic Science Consortium Working Group 1 (KASC WG-1). In the current work we will discuss the methods we use to determine the fundamental stellar atmospheric parameters using high-quality stellar spectra. These provide essential constraints for the asteroseismic modelling and make it possible to verify the parameters in the Kepler Input Catalogue (KIC)
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