1,398 research outputs found
Adaptive Noise Reduction of Scintigrams with a Wavelet Transform
The aim of this study was to eliminate the effect of Poisson noise in scintigrams with a wavelet thresholding method. We developed a new noise reduction method with a wavelet transform. The proposed method was a combination of the translation-invariant denoising method and our newly introduced denoising filter which was applicable for Poisson noise. To evaluate the validity of our proposed method, phantom images and scintigrams were used. The results with the phantom images showed that our method was better than conventional methods in terms of the peak signal-to-noise ratio by 3 dB. Quality of the scintigrams processed with our method was better than that with the conventional methods in terms of reducing Poisson noise while preserving edge components. The results demonstrated that the proposed method was effective for the reduction of Poisson noise in scintigrams
Variation of Inner Radius of Dust Torus in NGC4151
The long-term optical and near infrared monitoring observations for a type 1
act ive galactic nucleus NGC 4151 were carried out for six years from 2001 to
2006 b y using the MAGNUM telescope, and delayed response of flux variations in
the band to those in the band was clearly
detected. Based on cross correlation analysis, we precisely measured a lag time
for eight separate periods, and we found that is not
constant changing be tween 30 and 70 days during the monitoring period. Since
is the ligh t travel time from the central energy source out to the
surrounding dust torus, this is the first convincing evidence that the inner
radius of dust torus did ch ange in an individual AGN. In order to relate such
a change of with a change of AGN luminosity , we presented a
method of taking an average of th e observed -band fluxes that corresponds
to the measured value of , and we found that the time-changing track
of NGC 4151 in the versus diagram during the monitoring period
deviates from the relation of expected from dust
reverberation. This result, combined with t he elapsed time from period to
period for which was measured, indicat es that the timescale of dust
formation is about one year, which should be taken into account as a new
constraint in future studies of dust evolution in AGNs.Comment: 5 pages, 3 figures, To appear in the ApJ Lette
Arbitrary shape surface Fresnel diffraction
Fresnel diffraction calculation on an arbitrary shape surface is proposed.
This method is capable of calculating Fresnel diffraction from a source surface
with an arbitrary shape to a planar destination surface. Although such
calculation can be readily calculated by the direct integral of a diffraction
calculation, the calculation cost is proportional to in one
dimensional or in two dimensional cases, where is the number of
sampling points. However, the calculation cost of the proposed method is in one dimensional or in two dimensional cases using
non-uniform fast Fourier transform
Superconducting gap and pair breaking in CeRu2 studied by point contacts
The superconducting gap in a CeRu single crystal is investigated by
point contacts. BCS-like behavior of the gap in the temperature range
below TT, where T is the critical temperature, is
established, indicating the presence of a gapless superconductivity region
(between T and T). The pair-breaking effect of paramagnetic
impurities, supposedly Ce ions, is taken into consideration using the
Scalski-Betbeder-Matibet-Weiss approach based on Abrikosov-Gorkov theory. It
allows us to recalculate the superconducting order parameter (in the presence of paramagnetic impurities) and the gap (in
the pure case) for the single crystal and for the previously studied
polycrystalline CeRu. The value 2(0)2 meV, with
2(0)kT3.75, is found in both cases,
indicating that CeRu is a ``moderate'' strong-coupling superconductor.Comment: 4 pages incl. 3 figs., publ. in Fiz. Nizk. Temp.
(http://fnte.ilt.kharkov.ua/list.html
Cav2.3 (α1E) Ca2+ channel participates in the control of sperm function
AbstractTo know the function of the Ca2+ channel containing α12.3 (α1E) subunit (Cav2.3 channel) in spermatozoa, we analyzed Ca2+ transients and sperm motility using a mouse strain lacking Cav2.3 channel. The averaged rising rates of Ca2+ transients induced by α-D-mannose–bovine serum albumin in the head region of Cav2.3−/− sperm were significantly lower than those of Cav2.3+/+ sperm. A computer-assisted sperm motility assay revealed that straight-line velocity and linearity were greater in Cav2.3−/− sperm than those in Cav2.3+/+ sperm. These results suggest that the Cav2.3 channel plays some roles in Ca2+ transients and the control of flagellar movement
Complex sequencing rules of birdsong can be explained by simple hidden Markov processes
Complex sequencing rules observed in birdsongs provide an opportunity to
investigate the neural mechanism for generating complex sequential behaviors.
To relate the findings from studying birdsongs to other sequential behaviors,
it is crucial to characterize the statistical properties of the sequencing
rules in birdsongs. However, the properties of the sequencing rules in
birdsongs have not yet been fully addressed. In this study, we investigate the
statistical propertiesof the complex birdsong of the Bengalese finch (Lonchura
striata var. domestica). Based on manual-annotated syllable sequences, we first
show that there are significant higher-order context dependencies in Bengalese
finch songs, that is, which syllable appears next depends on more than one
previous syllable. This property is shared with other complex sequential
behaviors. We then analyze acoustic features of the song and show that
higher-order context dependencies can be explained using first-order hidden
state transition dynamics with redundant hidden states. This model corresponds
to hidden Markov models (HMMs), well known statistical models with a large
range of application for time series modeling. The song annotation with these
models with first-order hidden state dynamics agreed well with manual
annotation, the score was comparable to that of a second-order HMM, and
surpassed the zeroth-order model (the Gaussian mixture model (GMM)), which does
not use context information. Our results imply that the hierarchical
representation with hidden state dynamics may underlie the neural
implementation for generating complex sequences with higher-order dependencies
Reverberation measurements of the inner radius of the dust torus in 17 seyfert galaxies
We present the results of a dust reverberation survey for 17 nearby Seyfert 1 galaxies, which provides the largest homogeneous data collection for the radius of the innermost dust torus. A delayed response of the K-band light curve after the V-band ligh
The Lick AGN Monitoring Project: Photometric Light Curves and Optical Variability Characteristics
The Lick AGN Monitoring Project targeted 13 nearby Seyfert 1 galaxies with
the intent of measuring the masses of their central black holes using
reverberation mapping. The sample includes 12 galaxies selected to have black
holes with masses roughly in the range 10^6-10^7 solar masses, as well as the
well-studied AGN NGC 5548. In conjunction with a spectroscopic monitoring
campaign, we obtained broad-band B and V images on most nights from 2008
February through 2008 May. The imaging observations were carried out by four
telescopes: the 0.76-m Katzman Automatic Imaging Telescope (KAIT), the 2-m
Multicolor Active Galactic Nuclei Monitoring (MAGNUM) telescope, the Palomar
60-in (1.5-m) telescope, and the 0.80-m Tenagra II telescope. Having
well-sampled light curves over the course of a few months is useful for
obtaining the broad-line reverberation lag and black hole mass, and also allows
us to examine the characteristics of the continuum variability. In this paper,
we discuss the observational methods and the photometric measurements, and
present the AGN continuum light curves. We measure various variability
characteristics of each of the light curves. We do not detect any evidence for
a time lag between the B- and V-band variations, and we do not find significant
color variations for the AGNs in our sample.Comment: 16 pages, 20 figures, 8 tables, accepted for publication in ApJ
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