135 research outputs found
An adaptive perception-based image preprocessing method
The aim of this paper is to introduce an adaptive preprocessing procedure based on human perception in order to increase the performance of some standard image processing techniques. Specifically, image frequency content has been weighted by the corresponding value of the contrast sensitivity function, in agreement with the sensitiveness of human eye to the different image frequencies and contrasts. The 2D Rational dilation wavelet transform has been employed for representing image frequencies. In fact, it provides an adaptive and flexible multiresolution framework, enabling an
easy and straightforward adaptation to the image frequency content. Preliminary experimental results show that the proposed preprocessing allows us to increase the performance of some standard image enhancement algorithms in terms of visual quality and often also in terms of PSNR
Red-channel (6000-8000 {\AA}) nuclear spectra of 376 local galaxies
We obtained long-slit optical spectra of the nuclear regions of 376 galaxies
in the local Universe using the 1.5m Cassini telescope of Bologna Observatory.
Of these spectra, 164 were either never taken before by the Sloan Digital Sky
Survey (SDSS), or given by the Nasa Extragalactic Database (NED). With these
new spectra, we contribute investigating the occurrence of active galactic
nuclei (AGNs). Nevertheless, we stress that the present sample is by no means
complete, thus, it cannot be used to perform any demographic study. Following
the method presented in Gavazzi et al. (2011), we classify the nuclear spectra
using a six bin scheme: SEY (Seyfert), sAGN (strong AGN), and wAGN (weak AGN)
represent active galactic nuclei of different levels of activity; HII accounts
for star-forming nuclei; RET (retired) and PAS (passive) refer to nuclei with
poor or no star-formation activity. The spectral classification is performed
using the ratio of 6584 {\lambda} [NII] to H{\alpha} lines and the equivalent
width (EW) of H{\alpha} versus [NII]/H{\alpha} (WHAN diagnostic introduced by
Cid Fernandes and collaborators) after correcting H{\alpha} for underlying
absorption. The obtained spectra are made available in machine readable format
via the Strasbourg Astronomical Data Center (CDS) and NED.Comment: 8 pages, 6 Figures, 4 Tables, accepted for publication in Astronomy &
Astrophysic
Una nuova interfaccia utente per il controllo del telescopio cassini di loiano
A causa delle regole per il contenimento della pandemia, per diverso tempo i ricercatori non hanno potuto effettuare le osservazioni in presenza presso il Telescopio Cassini e le ormai consolidate modalità di lavoro notturno hanno dovuto subire un radicale cambiamento. Allo stato attuale il controllo del Telescopio e della strumentazione di piano focale non sono maturi a tal punto per consentire osservazioni remote e la presenza del personale tecnico è ancora necessaria. Tuttavia, per alcune tipologie di ricerche, come quelle che richiedono misure fotometriche e astrometriche, è possibile osservare in parziale autonomia da remoto lasciando al personale tecnico presente in Osservatorio il compito di risolvere i problemi tecnici nel caso questi insorgano. In questo rapporto tecnico viene descritta la nuova interfaccia di controllo del Telescopio e dello strumento BFOSC sviluppata per semplificare la gestione delle osservazioni remote
SiFAP: A New Fast Astronomical Photometer
A fast photometer based on SiPM technology was developed and tested at the University of Rome "La Sapienza" and at the Bologna Observatory. In this paper we present the improvements applied to our instrument, concerning new cooled sensors, a new version of the electronics and an upgraded control timing software
SiFAP: A New Fast Astronomical Photometer
A fast photometer based on SiPM technology was developed and tested at the University of Rome "La Sapienza" and at the Bologna Observatory. In this paper we present the improvements applied to our instrument, concerning new cooled sensors, a new version of the electronics and an upgraded control timing software
M31 Pixel Lensing PLAN Campaign: MACHO Lensing and Self Lensing Signals
We present the final analysis of the observational campaign carried out by
the PLAN (Pixel Lensing Andromeda) collaboration to detect a dark matter signal
in form of MACHOs through the microlensing effect. The campaign consists of
about 1 month/year observations carried out during 4 years (2007-2010) at the
1.5m Cassini telescope in Loiano ("Astronomical Observatory of BOLOGNA", OAB)
plus 10 days of data taken in 2010 at the 2m Himalayan Chandra Telescope (HCT)
monitoring the central part of M31 (two fields of about 13'x12.6'). We
establish a fully automated pipeline for the search and the characterization of
microlensing flux variations: as a result we detect 3 microlensing candidates.
We evaluate the expected signal through a full Monte Carlo simulation of the
experiment completed by an analysis of the detection efficiency of our
pipeline. We consider both "self lensing" and "MACHO lensing" lens populations,
given by M31 stars and dark matter halo MACHOs, in the M31 and the Milky Way
(MW), respectively. The total number of events is compatible with the expected
self-lensing rate. Specifically, we evaluate an expected signal of about 2
self-lensing events. As for MACHO lensing, for full 0.5 (0.01) solar mass MACHO
halos, our prediction is for about 4 (7) events. The comparatively small number
of expected MACHO versus self lensing events, together with the small number
statistics at disposal, do not enable us to put strong constraints on that
population. Rather, the hypothesis, suggested by a previous analysis, on the
MACHO nature of OAB-07-N2, one of the microlensing candidates, translates into
a sizeable lower limit for the halo mass fraction in form of the would be MACHO
population, f, of about 15% for 0.5 solar mass MACHOs.Comment: ApJ accepted, 13 pages, 5 figures, 2 table
Discovery of a Nova-Like Cataclysmic Variable in the Kepler Mission Field
We announce the identification of a new cataclysmic variable star in the
field of the Kepler Mission, KIC J192410.81+445934.9. This system was
identified during a search for compact pulsators in the Kepler field.
High-speed photometry reveals coherent large-amplitude variability with a
period of 2.94 h. Rapid, large-amplitude quasi-periodic variations are also
detected on time scales of ~1200 s and ~650 s. Time-resolved spectroscopy
covering one half photometric period shows shallow, broad Balmer and He I
absorption lines with bright emission cores as well as strong He II and Bowen
blend emission. Radial velocity variations are also observed in the Balmer and
He I emission lines that are consistent with the photometric period. We
therefore conclude that KIC J192410.81+445934.9 is a nova-like variable of the
UX UMa class in or near the period gap, and it may belong to the rapidly
growing subclass of SW Sex systems. Based on 2MASS photometry and companion
star models, we place a lower limit on the distance to the system of ~500 pc.
Due to limitations of our discovery data, additional observations including
spectroscopy and polarimetry are needed to confirm the nature of this object.
Such data will help to further understanding of the behavior of nova-like
variables in the critical period range of 3-4 h, where standard cataclysmic
variable evolutionary theory finds major problems. The presence of this system
in the Kepler mission field-of-view also presents a unique opportunity to
obtain a continuous photometric data stream of unparalleled length and
precision on a cataclysmic variable system.Comment: Accepted for publication in the Astronomical Journal. 8 pages, 7
figures, uses emulateapj
A fetal wave of human type 3 effector gamma delta cells with restricted TCR diversity persists into adulthood
Accumulating evidence suggests that the mouse embryonic thymus produces distinct waves of innate effector gamma delta T cells. However, it is unclear whether this process occurs similarly in humans and whether it comprises a dedicated subset of innate-like type 3 effector gamma delta T cells. Here, we present a protocol for high-throughput sequencing of TRG and TRD pairs that comprise the clonal gamma delta TCR. In combination with single-cell RNA sequencing, multiparameter flow cytometry, and TCR sequencing, we reveal a high heterogeneity of gamma delta T cells sorted from neonatal and adult blood that correlated with TCR usage. Immature gamma delta T cell clusters displayed mixed and diverse TCRs, but effector cell types segregated according to the expression of either highly expanded individual V delta 1(+) TCRs or moderately expanded semi-invariant V gamma 9V delta 2(+) TCRs. The V gamma 9V delta 2(+) T cells shared expression of genes that mark innate-like T cells, including ZBTB16 (encoding PLZF), KLRB1, and KLRC1, but consisted of distinct clusters with unrelated V gamma 9V delta 2(+) TCR clones characterized either by TBX21, FCGR3A, and cytotoxicity-associated gene expression (type 1) or by CCR6, RORC, IL23R, and DPP4 expression (type 3). Effector gamma delta T cells with type 1 and type 3 innate T cell signatures were detected in a public dataset of early embryonic thymus organogenesis. Together, this study suggests that functionally distinct waves of human innate-like effector gamma delta T cells with semi-invariant V gamma 9V delta 2(+) TCR develop in the early fetal thymus and persist into adulthood
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