709 research outputs found
Weyssenhoff fluid dynamics in general relativity using a 1+3 covariant approach
The Weyssenhoff fluid is a perfect fluid with spin where the spin of the
matter fields is the source of torsion in an Einstein-Cartan framework. Obukhov
and Korotky showed that this fluid can be described as an effective fluid with
spin in general relativity. A dynamical analysis of such a fluid is performed
in a gauge invariant manner using the 1+3 covariant approach. This yields the
propagation and constraint equations for the set of dynamical variables. A
verification of these equations is performed for the special case of
irrotational flow with zero peculiar acceleration by evolving the constraints.Comment: 20 page
Detection of sodium in the atmosphere of WASP-69b
Transit spectroscopy is one of the most commonly used methods to characterize
exoplanets atmospheres. From the ground, these observations are very
challenging due to the terrestrial atmosphere and its intrinsic variations, but
high-spectral resolution observations overcome this difficulty by resolving the
spectral lines and taking advantage of the different Doppler velocities of the
Earth, the host star and the exoplanet. We analyze the transmission spectrum
around the Na I doublet at 589 nm of the exoplanet WASP-69b, a hot Jupiter
orbiting a K-type star with a period of 3.868 days, and compare the analysis to
that of the well-know hot Jupiter HD 189733b. We also present the analysis of
the Rossiter-McLaughlin effect for WASP-69b. Two transits of WASP-69b were
observed with the HARPS-North spectrograph (R = 115 000) at the TNG telescope.
We perform a telluric contamination subtraction based on the comparison between
the observed spectra and a telluric water model. Then, the common steps of the
differential spectroscopy are followed to extract the transmission spectrum.
The method is tested with archival transit data of the extensively studied
exoplanet HD 189733b, obtained with the HARPS-South spectrograph at ESO 3.6m
telescope, and then applied to WASP-69b data. For HD 189733b, we spectrally
resolve the Na I doublet and measure line contrasts of (D2) and
(D1), and FWHMs of {\AA} (D2) and
{\AA} (D1), in agreement with previously published results. A net
blueshift of {\AA} is measured. For WASP-69b only the contrast of
the D2 line is measured (). Even if this corresponds to a
detection at the -level of excess absorption of in a
passband of {\AA}, more transits are needed to fully characterize the
lines profiles and retrieve accurate atmospheric properties.Comment: 15 pages, 14 figure
Analysis of unbounded operators and random motion
We study infinite weighted graphs with view to \textquotedblleft limits at
infinity,\textquotedblright or boundaries at infinity. Examples of such
weighted graphs arise in infinite (in practice, that means \textquotedblleft
very\textquotedblright large) networks of resistors, or in statistical
mechanics models for classical or quantum systems. But more generally our
analysis includes reproducing kernel Hilbert spaces and associated operators on
them. If is some infinite set of vertices or nodes, in applications the
essential ingredient going into the definition is a reproducing kernel Hilbert
space; it measures the differences of functions on evaluated on pairs of
points in . And the Hilbert norm-squared in will represent
a suitable measure of energy. Associated unbounded operators will define a
notion or dissipation, it can be a graph Laplacian, or a more abstract
unbounded Hermitian operator defined from the reproducing kernel Hilbert space
under study. We prove that there are two closed subspaces in reproducing kernel
Hilbert space which measure quantitative notions of limits at
infinity in , one generalizes finite-energy harmonic functions in
, and the other a deficiency index of a natural operator in
associated directly with the diffusion. We establish these
results in the abstract, and we offer examples and applications. Our results
are related to, but different from, potential theoretic notions of
\textquotedblleft boundaries\textquotedblright in more standard random walk
models. Comparisons are made.Comment: 38 pages, 4 tables, 3 figure
Glucose induced MAPK signalling influences NeuroD1-mediated activation and nuclear localization
AbstractThe helixâloopâhelix transcription factor NeuroD1 (also known as Beta2) is involved in ÎČ-cell survival during development and insulin gene transcription in adults. Here we show NeuroD1 is primarily cytoplasmic at non-stimulating glucose concentrations (i.e. 3 mM) in MIN6 ÎČ-cells and nuclear under stimulating conditions (i.e. 20 mM). Quantification revealed that NeuroD1 was in 40â45% of the nuclei at 3 mM and 80â90% at 20 mM. Treatment with the MEK inhibitor PD98059 or substitution of a serine for an alanine at a potential mitogen-activated protein kinase phosphorylation site (S274) in NeuroD1 significantly increased the cytoplasmic level at 20 mM glucose. The rise in NeuroD1-mediated transcription in response to glucose also correlated with the change in sub-cellular localization, a response attenuated by PD98059. The data strongly suggest that glucose-stimulation of the MEKâERK signalling pathway influences NeuroD1 activity at least partially through effects on sub-cellular localization
A feature-rich transmission spectrum for WASP-127b
WASP-127b is one of the lowest density planets discovered to date. With a
sub-Saturn mass () and super-Jupiter radius
(), it orbits a bright G5 star, which is about to
leave the main-sequence. We aim to explore WASP-127b's atmosphere in order to
retrieve its main atmospheric components, and to find hints for its intriguing
inflation and evolutionary history. We used the ALFOSC spectrograph at the NOT
telescope to observe a low resolution (, seeing limited) long-slit
spectroscopic time series during a planetary transit, and present here the
first transmission spectrum for WASP-127b. We find the presence of a strong
Rayleigh slope at blue wavelengths and a hint of Na absorption, although the
quality of the data does not allow us to claim a detection. At redder
wavelengths the absorption features of TiO and VO are the best explanation to
fit the data. Although higher signal-to-noise ratio observations are needed to
conclusively confirm the absorption features, WASP-127b seems to posses a
cloud-free atmosphere and is one of the best targets to perform further
characterization studies in the near future.Comment: Accepted for Publication A&A Letters, May 22nd, 201
A Novel Gabor Filtering and Adaptive Histogram Equalization Method for Improving Images
The correct information may only sometimes be effectively conveyed by images due to various factors, such as excessively bright or dark lighting and low or high contrast. As a result, picture improvement has become an essential part of digital image processing. This proposed method aims to develop an algorithm for improving photos captured in dark environments. This letter presents a new picture-enhancing approach that combines median and Gabor filtering using the wavelet domain with histogram equalization working over a spatial domain. The proposed method in this paper combines spatial and transformed domains for image enhancement and has been simulated using MATLAB. The simulation results of two different photos show that the suggested approach extends the histogram over a wide range of grayscale, offering a superior improvement to the original image. The novel proposed algorithm aims to improve image quality and visibility, making identifying essential details within the image easier. Further, the proposed technique's success is manifested by examining the produced photos' contrast and brightness. The findings reveal that the suggested technique beats the other strategies for improving low-contrast photos
The K2-ESPRINT Project VI: K2-105 b, a Hot-Neptune around a Metal-rich G-dwarf
We report on the confirmation that the candidate transits observed for the
star EPIC 211525389 are due to a short-period Neptune-sized planet. The host
star, located in K2 campaign field 5, is a metal-rich ([Fe/H] = 0.260.05)
G-dwarf (T_eff = 543070 K and log g = 4.480.09), based on
observations with the High Dispersion Spectrograph (HDS) on the Subaru 8.2m
telescope. High-spatial resolution AO imaging with HiCIAO on the Subaru
telescope excludes faint companions near the host star, and the false positive
probability of this target is found to be < using the open source
vespa code. A joint analysis of transit light curves from K2 and additional
ground-based multi-color transit photometry with MuSCAT on the Okayama 1.88m
telescope gives the orbital period of P = 8.2669020.000070 days and
consistent transit depths of or . The transit depth corresponds to a planetary radius of , indicating that EPIC 211525389 b is a
short-period Neptune-sized planet. Radial velocities of the host star, obtained
with the Subaru HDS, lead to a 3\sigma\ upper limit of 90 on the mass of EPIC 211525389 b, confirming its planetary nature.
We expect this planet, newly named K2-105 b, to be the subject of future
studies to characterize its mass, atmosphere, spin-orbit (mis)alignment, as
well as investigate the possibility of additional planets in the system.Comment: 11 pages, 9 figures, 4 tables, PASJ accepte
Na I and H absorption features in the atmosphere of MASCARA-2b/KELT-20b
We have used the HARPS-North high resolution spectrograph (=115
000) at TNG to observe one transit of the highly irradiated planet
MASCARA-2b/KELT-20b. Using only one transit observation, we are able to clearly
resolve the spectral features of the atomic sodium (Na I) doublet and the
H line in its atmosphere, measuring absorption depths of
0.170.03 and 0.590.08 for a 0.75 passband,
respectively. These absorptions are corroborated with the transmission measured
from their respective transmission light curves, which show a large
Rossiter-McLaughlin effect. In case of H, this absorption corresponds
to an effective radius of =1.200.04. While the S/N of the
final transmission spectrum is not sufficient to adjust different temperature
profiles to the lines, we find that higher temperatures than the equilibrium
are needed to explain the lines contrast. Particularly, we find that the Na I
lines core require a temperature of T=4210180K and that H requires
T=4330520K. MASCARA-2b, like other planets orbiting A-type stars, receives
a large amount of UV energy from its host star. This energy excites the atomic
hydrogen and produces H absorption, leading to the expansion and
abrasion of the atmosphere. The study of other Balmer lines in the transmission
spectrum would allow the determination of the atmospheric temperature profile
and the calculation of the lifetime of the atmosphere. In the case of
MASCARA-2b, residual features are observed in the H and H lines,
but they are not statistically significant. More transit observations are
needed to confirm our findings in Na I and H, and to build up enough
S/N to explore the presence of H and H planetary absorptions.Comment: 14 pages, 12 figure
On certain relationships between cosmological observables in the Einstein-Cartan gravity
We show that in the Einstein-Cartan gravity it is possible to obtain a
relation between Hubble's expansion and the global rotation (vorticity) of the
Universe. Gravitational coupling can be reduced to dimensionless quantity of
order unity, fixing the scalar mass density and the resulting negative
cosmological constant at spacelike infinity. Current estimates of the expansion
and rotation (see also astro-ph/9703082) of the Universe favour the massive
spinning particles as candidate particles for cold and hot dark matter. Nodland
and Ralston vorticity (Phys. Rev. Lett. 78 (1997) 3043) overestimates the value
favoured by the Einstein-Cartan gravity for three orders of magnitude.Comment: 7 pages, LaTeX styl
Permanent Neonatal Diabetes and Enteric Anendocrinosis Associated With Biallelic Mutations in NEUROG3
ArtĂculo de publicaciĂłn ISIOBJECTIVEâNEUROG3 plays a central role in the development
of both pancreatic islets and enteroendocrine cells. Homozygous
hypomorphic missense mutations in NEUROG3 have been recently
associated with a rare form of congenital malabsorptive diarrhea
secondary to enteroendocrine cell dysgenesis. Interestingly, the
patients did not develop neonatal diabetes but childhood-onset
diabetes. We hypothesized that null mutations in NEUROG3
might be responsible for the disease in a patient with permanent
neonatal diabetes and severe congenital malabsorptive diarrhea.
RESEARCH DESIGN AND METHODSâThe single coding
exon of NEUROG3 was amplified and sequenced from genomic
DNA. The mutant protein isoforms were functionally characterized
by measuring their ability to bind to an E-box element in the
NEUROD1 promoter in vitro and to induce ectopic endocrine cell
formation and cell delamination after in ovo chicken endoderm
electroporation.
RESULTSâTwo different heterozygous point mutations in
NEUROG3 were identified in the proband [c.82G.T (p.E28X)
and c.404T.C (p.L135P)], each being inherited from an unaffected
parent. Both in vitro and in vivo functional studies indicated
that the mutant isoforms are biologically inactive. In
keeping with this, no enteroendocrine cells were detected in intestinal
biopsy samples from the patient.
CONCLUSIONSâSevere deficiency of neurogenin 3 causes
a rare novel subtype of permanent neonatal diabetes. This finding
confirms the essential role of NEUROG3 in islet development and
function in humans
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