96 research outputs found
Investigating the Optical Counterpart Candidates of Four INTEGRAL Sources localized with Chandra
We report on the optical spectroscopic follow up observations of the
candidate counterparts to four INTEGRAL sources: IGR J04069+5042, IGR
J06552-1146, IGR J21188+4901 and IGR J22014+6034. The candidate counterparts
were determined with Chandra, and the optical observations were performed with
1.5-m RTT-150 telescope (T\"{U}B\.{I}TAK National Observatory, Antalya, Turkey)
and 2.4-m Hiltner Telescope (MDM Observatory, Kitt Peak, Arizona). Our
spectroscopic results show that one of the two candidates of IGR J04069+5042
and the one observed for IGR J06552-1146 could be active late-type stars in RS
CVn systems. However, according to the likelihood analysis based on Chandra and
INTEGRAL, two optically weaker sources in the INTEGRAL error circle of IGR
J06552-1146 have higher probabilities to be the actual counterpart. The
candidate counterparts of IGR J21188+4901 are classified as an active M-type
star and a late-type star. Among the optical spectra of four candidates of IGR
J22014+6034, two show H\alpha emission lines, one is a late-type star and the
other is a M type. The likelihood analysis favors a candidate with no
distinguishing features in the optical spectrum. Two of the candidates
classified as M type dwarfs are similar to some IGR candidates claimed to be
symbiotic stars. However, some of the prominent features of symbiotic systems
are missing in our spectra, and their NIR colors are not consistent with those
expected for giants. We consider the IR colors of all IGR candidates claimed to
be symbiotic systems and find that low resolution optical spectrum may not be
enough for conclusive identification.Comment: 24 pages, 12 figures; accepted for publication in Ap
Assessing the capacity of a denoising diffusion probabilistic model to reproduce spatial context
Diffusion models have emerged as a popular family of deep generative models
(DGMs). In the literature, it has been claimed that one class of diffusion
models -- denoising diffusion probabilistic models (DDPMs) -- demonstrate
superior image synthesis performance as compared to generative adversarial
networks (GANs). To date, these claims have been evaluated using either
ensemble-based methods designed for natural images, or conventional measures of
image quality such as structural similarity. However, there remains an
important need to understand the extent to which DDPMs can reliably learn
medical imaging domain-relevant information, which is referred to as `spatial
context' in this work. To address this, a systematic assessment of the ability
of DDPMs to learn spatial context relevant to medical imaging applications is
reported for the first time. A key aspect of the studies is the use of
stochastic context models (SCMs) to produce training data. In this way, the
ability of the DDPMs to reliably reproduce spatial context can be
quantitatively assessed by use of post-hoc image analyses. Error-rates in
DDPM-generated ensembles are reported, and compared to those corresponding to a
modern GAN. The studies reveal new and important insights regarding the
capacity of DDPMs to learn spatial context. Notably, the results demonstrate
that DDPMs hold significant capacity for generating contextually correct images
that are `interpolated' between training samples, which may benefit
data-augmentation tasks in ways that GANs cannot.Comment: This paper is under consideration at IEEE TM
Unsupervised Medical Image Translation with Adversarial Diffusion Models
Imputation of missing images via source-to-target modality translation can
improve diversity in medical imaging protocols. A pervasive approach for
synthesizing target images involves one-shot mapping through generative
adversarial networks (GAN). Yet, GAN models that implicitly characterize the
image distribution can suffer from limited sample fidelity. Here, we propose a
novel method based on adversarial diffusion modeling, SynDiff, for improved
performance in medical image translation. To capture a direct correlate of the
image distribution, SynDiff leverages a conditional diffusion process that
progressively maps noise and source images onto the target image. For fast and
accurate image sampling during inference, large diffusion steps are taken with
adversarial projections in the reverse diffusion direction. To enable training
on unpaired datasets, a cycle-consistent architecture is devised with coupled
diffusive and non-diffusive modules that bilaterally translate between two
modalities. Extensive assessments are reported on the utility of SynDiff
against competing GAN and diffusion models in multi-contrast MRI and MRI-CT
translation. Our demonstrations indicate that SynDiff offers quantitatively and
qualitatively superior performance against competing baselines.Comment: M. Ozbey and O. Dalmaz contributed equally to this stud
The regulation of animal behavior by cellular stress responses
Cellular stress responses exist to detect the effects of stress on cells, and to activate protective mechanisms that promote resilience. As well as acting at the cellular level, stress response pathways can also regulate whole organism responses to stress. One way in which animals facilitate their survival in stressful environments is through behavioral adaptation; this review considers the evidence that activation of cellular stress responses plays an important role in mediating the changes to behavior that promote organismal survival upon stress
Optical variabilities in Be/X-ray binary system:GRO J2058+42
We present an analysis of long-term optical monitoring observations and
optical spectroscopic observations of the counterpart to CXOU J205847.5+414637
(high mass X-ray binary system). We search for a variability in the light curve
of Be star. We used differential magnitudes in the time series analysis. The
variability search in the optical light curve was made by using different
algorithms. The reduction and analysis of spectra were done by using MIDAS and
its suitable packages. We have performed a frequency search which gave us the
value 2.404 1/day. This value is attributed to the non-radial pulsation of Be
star. H alpha emission line profiles always show double-peaked emissions with a
mean equivalent width of 2.31 \pm 0.19 \AA ~and a peak separation of 516 \pm 45
km/s. This suggests that Be star disk is still present. CXOU J205847.5+414637
is in X-ray quiescent state.Comment: 8 pages, 9 figures. To appear at Astronomy and Astrophysic
Distorted cyclotron line profile in Cep X-4 as observed by NuSTAR
We present spectral analysis of NuSTAR and Swift observations of Cep X-4
during its outburst in 2014. We observed the source once during the peak of the
outburst and once during the decay, finding good agreement in the spectral
shape between the observations. We describe the continuum using a powerlaw with
a Fermi-Dirac cutoff at high energies. Cep X-4 has a very strong cyclotron
resonant scattering feature (CRSF) around 30 keV. A simple absorption-like line
with a Gaussian optical depth or a pseudo-Lorentzian profile both fail to
describe the shape of the CRSF accurately, leaving significant deviations at
the red side of the line. We characterize this asymmetry with a second
absorption feature around 19 keV. The line energy of the CRSF, which is not
influenced by the addition of this feature, shows a small but significant
positive luminosity dependence. With luminosities between (1-6)e36 erg/s, Cep
X-4 is below the theoretical limit where such a correlation is expected. This
behavior is similar to Vela X-1 and we discuss parallels between the two
systems.Comment: 6 pages, 4 figure, accepted for publication in ApJ letter
Localizing INTEGRAL Sources with Chandra: X-Ray and Multi-Wavelength Identifications and Energy Spectra
We report on Chandra observations of 18 hard X-ray (>20 keV) sources
discovered with the INTEGRAL satellite near the Galactic plane. For 14 of the
INTEGRAL sources, we have uncovered one or two potential Chandra counterparts
per source. These provide soft X-ray (0.3-10 keV) spectra and sub-arcsecond
localizations, which we use to identify counterparts at other wavelengths,
providing information about the nature of each source. Despite the fact that
all of the sources are within 5 degrees of the plane, four of the IGR sources
are AGN (IGR J01545+6437, IGR J15391-5307, IGR J15415-5029, and IGR
J21565+5948) and four others are likely AGN (IGR J03103+5706, IGR J09189-4418,
IGR J16413-4046, and IGR J16560-4958) based on each of them having a strong IR
excess and/or extended optical or near-IR emission. We compare the X-ray and
near-IR fluxes of this group of sources to those of AGN selected by their 2-10
keV emission in previous studies and find that these IGR AGN are in the range
of typical values. There is evidence in favor of four of the sources being
Galactic (IGR J12489-6243, IGR J15293-5609, IGR J16173-5023, and IGR
J16206-5253), but only IGR J15293-5609 is confirmed as a Galactic source as it
has a unique Chandra counterpart and a parallax measurement from previous
optical observations that puts its distance at 1.56+/-0.12 kpc. The 0.3-10 keV
luminosity for this source is 1.4e32 erg/s, and its optical/IR spectral energy
distribution is well described by a blackbody with a temperature of 4200-7000 K
and a radius of 12.0-16.4 Rsun. These values suggest that IGR J15293-5609 is a
symbiotic binary with an early K-type giant and a white dwarf accretor. We also
obtained likely Chandra identifications for IGR J13402-6428 and IGR
J15368-5102, but follow-up observations are required to constrain their source
types.Comment: 17 pages, accepted by Ap
Ion source and LEBT of KAHVELab proton beamline
The KAHVE Laboratory, at Bo\u{g}azi\c{c}i University, Istanbul, Turkey is
home to an educational proton linac project. The proton beam will originate
from a 20 keV H+ source and will be delivered to a two module Radio Frequency
Quadrupole (RFQ) operating at 800 MHz via a low energy beam transport (LEBT)
line. Currently, the design phase being over, commissioning and stability tests
are ongoing for the proton beamline which is already produced and installed
except the RFQ which is being manufactured. This work summarizes the design,
production and test phases of the ion source and LEBT line components
The External Exposome and Allergies: From the Perspective of the Epithelial Barrier Hypothesis
IntroductionIn the last decades, we have seen a rapid increase in the prevalence of allergic diseases such as asthma, allergic rhinitis, atopic dermatitis, and food allergies. The environmental changes caused by industrialization, urbanization and modernization, including dramatic increases in air pollutants such as particulate matter (PM), diesel exhaust, nitrogen dioxide (NO2), ozone (O3), alarming effects of global warming, change and loss of biodiversity, affect both human health and the entire ecosystem.ObjectiveIn this review, we aimed to discuss the effects of the external exposome on epithelial barriers and its relationship with the development of allergic diseases by considering the changes in all stakeholders of the outer exposome together, in the light of the recently proposed epithelial barrier hypothesis.MethodTo reach current, prominent, and comprehensive studies on the subject, PubMed databases were searched. We included the more resounding articles with reliable and strong results.ResultsExposure to altered environmental factors such as increased pollution, microplastics, nanoparticles, tobacco smoke, food emulsifiers, detergents, and household cleaners, and climate change, loss and change in microbial biodiversity, modifications in the consumption of dietary fatty acids, the use of emulsifiers, preservatives and the decrease in the antioxidant content of the widely consumed western diet may disrupt the epithelial barriers of the skin, respiratory and gastrointestinal tracts, making us more vulnerable to exogeneous allergens and microbes. Epithelial cell activation, microbial dysbiosis and bacterial translocation disrupt the immune balance and a chronic Th2 inflammation ensues.ConclusionDramatic increases in air pollution, worrisome effects of global warming, dysbiosis, changing dietary habits and the complex interactions of all these factors affect the epithelial barriers and local and systemic inflammation. We want to draw attention to the emerging health effects of environmental changes and to motivate the public to influence government policies for the well-being of humans and the nature of the earth and the well-being of future generations
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