813 research outputs found
Ground Vibrational State SiO Emission in the VLA BAaDE Survey
Using a subsample of the Bulge Asymmetries and Dynamical Evolution (BAaDE)
survey of stellar SiO masers, we explore the prevalence and characteristics of
SiO emission. We identify 90 detections of maser, thermal,
or composite SiO emission out of approximately 13,000
candidate spectra from the NSF's Karl G. Jansky Very Large Array (VLA). We find
that the detected sources are likely asymptotic giant branch (AGB) stars
belonging to a bright, foreground Milky Way stellar disk population. For the 32
sources showing thermal components, we extract values for outflow velocity by
fitting thermal line profiles. We find a range of circumstellar envelope
expansion velocities, and compare to previously recorded OH and CO expansion
velocities. This preliminary survey is already the largest study of stellar
ground-vibrational-state SiO masers to date, and will be expanded to include
the entire VLA BAaDE dataset when data reduction for the 18,988 target sources
is completed.Comment: 23 pages, 8 figures, to be published in The Astronomical Journa
The Potential Role of Everlasting Flower (Helichrysum stoechas Moench) as an Antihypertensive Agent: Vasorelaxant Effects in the Rat Aorta
Helichrysum stoechas (L.) Moench (H. stoechas) is a medicinal plant traditionally used in the Iberian Peninsula to treat different disorders such as arterial hypertension. The aim of this study was to investigate the vascular effects of a polyphenolic methanolic extract of H. stoechas, which has high antioxidant activity, and its mechanism of action. Isometric myography studies were performed in an organ bath with rat aortic rings with intact endothelium. The H. stoechas extract produced vasorelaxation in the aortic rings that were precontracted by phenylephrine or KCl. L-NAME and Rp-8-Br-PET-cGMPS but not indomethacin or H-89; it also reduced the relaxant response evoked by H. stoechas extract on the phenylephrine-induced contractions. H. stoechas extract reduced the response to CaCl2 similar to verapamil and reduced the phenylephrine-induced contractions comparable with heparin. TRAM-34, apamin and glibenclamide reduced relaxation induced by the H. stoechas extract. The combination of L-NAME+TRAM-34+apamin almost completely inhibited the H. stoechas-induced effect. In conclusion, the relaxant effect of the H. stoechas extract is partially mediated by endothelium through the activation of the NO/PKG/cGMP pathway and the opening of Ca2+-activated K+ channels. Furthermore, the decrease in the cytosolic Ca2+ by the inhibition of Ca2+ influx through the L-type Ca2+ channels and by the reduction of Ca2+ release from the sarcoplasmic reticulum via the IP3 pathway is also involved. © 2022 by the authors. Licensee MDPI, Basel, Switzerland
New Superhard Phases for 3D C60-based Fullerites
We have explored new possible phases of 3D C60-based fullerites using
semiempirical potentials and ab-initio density functional methods. We have
found three closely related structures - two body centered orthorhombic and one
body centered cubic - having 52, 56 and 60 tetracoordinated atoms per molecule.
These 3D polymers result in semiconductors with bulk moduli near 300 GPa, and
shear moduli around 240 GPa, which make them good candidates for new low
density superhard materials.Comment: To be published in Physical Review Letter
One Star to Tag Them All (OSTTA): I. Radial velocities and chemical abundances for 20 poorly studied open clusters
Context: Open clusters are ideal laboratories to investigate a variety of
astrophysical topics, from the properties of the Galactic disc to stellar
evolution models. For this purpose, we need to know their chemical composition
in detail. Unfortunately, the number of systems with chemical abundances
determined from high resolution spectroscopy remains small. Aims: Our aim is to
increase the number of open clusters with radial velocities and chemical
abundances determined from high resolution spectroscopy by sampling a few stars
in clusters not studied previously. Methods: We obtained high resolution
spectra with the FIES spectrograph at NOT for 41 stars belonging to 20 open
clusters. These stars have high astrometric membership probabilities,
determined from the Gaia second data release. Results: We derived radial
velocities for all the observed stars, which were used to confirm their
membership to the corresponding clusters. For Gulliver\,37 we cannot be sure
the observed star is a real member. We derived atmospheric parameters for the
32 stars considered real cluster members. We discarded five stars because they
have very low gravity or atmospheric parameters were not properly constrained
due to low signal-to-noise ratio spectra. Therefore, detailed chemical
abundances were determined for 28 stars belonging to 17 clusters. For most of
them, this is the first chemical analysis available in the literature. Finally,
we compared the clusters in our sample to a large population of well studied
clusters. The studied systems follow the trends, both chemical and kinematical,
described by the majority of open clusters. Worth noticing that the three most
metal-poor studied clusters (NGC\,1027, NGC\,1750 and Trumpler 2) are enhanced
in Si but not in the other alpha-elements studied (Mg, Ca and Ti).Comment: 19 pages Accepted for publication on A&
Photometric AGN reverberation mapping - an efficient tool for BLR sizes, black hole masses and host-subtracted AGN luminosities
Photometric reverberation mapping employs a wide bandpass to measure the AGN
continuum variations and a suitable band, usually a narrow band (NB), to trace
the echo of an emission line in the broad line region (BLR). The narrow band
catches both the emission line and the underlying continuum, and one needs to
extract the pure emission line light curve. We performed a test on two local
AGNs, PG0003+199 (=Mrk335) and Ark120, observing well-sampled broad- (B, V) and
narrow-band light curves with the robotic 15cm telescope VYSOS-6 on Cerro
Armazones, Chile. In PG0003+199, H_alpha dominates the flux in the NB by 85%,
allowing us to measure the time lag of H_alpha against B without the need to
correct for the continuum contribution. In Ark120, H_beta contributes only 50%
to the flux in the NB. The cross correlation of the B and NB light curves shows
two distinct peaks of similar strength, one at lag zero from the autocorrelated
continuum and one from the emission line at tau_cent = 47.5 +/- 3.4 days. We
constructed a synthetic H_beta light curve, by subtracting a scaled V light
curve, which traces the continuum, from the NB light curve. The cross
correlation of this synthetic H_beta light curve with the B light curve shows
only one major peak at tau_cent = 48.0 +/- 3.3 days, while the peak from the
autocorrelated continuum at lag zero is absent. We conclude that, as long as
the emission line contributes at least 50% to the bandpass, the pure emission
line light curve can be reconstructed from photometric monitoring data so that
the time lag can be measured. For both objects the lags we find are consistent
with spectroscopic reverberation results. While the dense sampling (median 2
days) enables us to determine tau_cent with small (10%) formal errors, we
caution that gaps in the light curves may lead to much larger systematic
uncertainties. (Abstract shortened, see the manuscript.)Comment: 12 pages, 15 figures, accepted for publication in Astronomy and
Astrophysic
Nucleation of Brane Universes
The creation of brane universes induced by a totally antisymmetric tensor
living in a fixed background spacetime is presented, where a term involving the
intrinsic curvature of the brane is considered. A canonical quantum mechanical
approach employing Wheeler-DeWitt equation is done. The probability nucleation
for the brane is calculated taking into account both an instanton method and a
WKB approximation. Some cosmological implications arose from the model are
presented.Comment: 19 pages, 2 figure
Proteomic identification of novel cytoskeletal proteins associated with TbPLK, an essential regulator of cell morphogenesis in Trypanosoma brucei
Trypanosoma brucei is the causative agent of African sleeping sickness, a devastating disease endemic to sub-Saharan Africa with few effective treatment options. The parasite is highly polarized, including a single flagellum that is nucleated at the posterior of the cell and adhered along the cell surface. These features are essential and must be transmitted to the daughter cells during division. Recently we identified the T. brucei homologue of pololike kinase (TbPLK) as an essential morphogenic regulator. In the present work, we conduct proteomic screens to identify potential TbPLK binding partners and substrates to better understand the molecular mechanisms of kinase function. These screens identify a cohort of proteins, most of which are completely uncharacterized, which localize to key cytoskeletal organelles involved in establishing cell morphology, including the flagella connector, flagellum attachment zone, and bilobe structure. Depletion of these proteins causes substantial changes in cell division, including mispositioning of the kinetoplast, loss of flagellar connection, and prevention of cytokinesis. The proteins identified in these screens provide the foundation for establishing the molecular networks through which TbPLK directs cell morphogenesis in T. brucei
Cluster galaxies in XMMU J2235-2557: galaxy population properties in most massive environments at z~1.4
We present a multi-wavelength study of galaxy populations in the core of the
massive, X-ray luminous cluster XMMU J2235 at z=1.39, based on VLT and HST
optical and near-infrared photometry. Luminosity functions in the z, H, and Ks
bands show a faint-end slope consistent with being flat, and a characteristic
magnitude M* close to passive evolution predictions of M* of local massive
clusters, with a formation redshift z>2. The color-magnitude and color-mass
diagrams show evidence of a tight red sequence of massive galaxies, with
overall old stellar populations, generally early-type morphology, typically
showing early-type spectral features and rest-frame far-UV emission consistent
with very low star formation rates (SFR<0.2Msun/yr). Star forming spectroscopic
members, with SFRs of up to ~100Msun/yr, are all located at clustercentric
distances >~250kpc, with the central cluster region already appearing
effectively quenched. Massive galaxies in the core of this cluster appear to be
in an advanced evolutionary stage in terms of both star formation and mass
assembly. The high-mass end of the galaxy stellar mass function is essentially
already in place, and the stellar mass fraction estimated within r500 (~1%,
Kroupa IMF) is already similar to that of local massive clusters. On the other
hand, morphological analysis of the massive red sequence galaxies suggests that
they are smaller than similarly massive local early-types. While possibly
affected by systematics and biases, this result might imply that, in spite of
the overall early assembly of these sources, their evolution is not complete,
and processes like minor (and likely dry) merging might still shape their
structural properties to resemble those of their local counterparts, without
substantially affecting their stellar mass or host stellar
populations.[abridged]Comment: 14 pages, 9 figures, accepted for publication in Astronomy &
Astrophysic
Hepatobiliary phenotypes of adults with alpha-1 antitrypsin deficiency
OBJECTIVE: Alpha-1 antitrypsin deficiency (AATD) is a common, potentially lethal inborn disorder caused by mutations in alpha-1 antitrypsin (AAT). Homozygosity for the 'Pi*Z' variant of AAT (Pi*ZZ genotype) causes lung and liver disease, whereas heterozygous 'Pi*Z' carriage (Pi*MZ genotype) predisposes to gallstones and liver fibrosis. The clinical significance of the more common 'Pi*S' variant remains largely undefined and no robust data exist on the prevalence of liver tumours in AATD. DESIGN: Baseline phenotypes of AATD individuals and non-carriers were analysed in 482â380 participants in the UK Biobank. 1104 participants of a multinational cohort (586 Pi*ZZ, 239 Pi*SZ, 279 non-carriers) underwent a comprehensive clinical assessment. Associations were adjusted for age, sex, body mass index, diabetes and alcohol consumption. RESULTS: Among UK Biobank participants, Pi*ZZ individuals displayed the highest liver enzyme values, the highest occurrence of liver fibrosis/cirrhosis (adjusted OR (aOR)=21.7 (8.8-53.7)) and primary liver cancer (aOR=44.5 (10.8-183.6)). Subjects with Pi*MZ genotype had slightly elevated liver enzymes and moderately increased odds for liver fibrosis/cirrhosis (aOR=1.7 (1.2-2.2)) and cholelithiasis (aOR=1.3 (1.2-1.4)). Individuals with homozygous Pi*S mutation (Pi*SS genotype) harboured minimally elevated alanine aminotransferase values, but no other hepatobiliary abnormalities. Pi*SZ participants displayed higher liver enzymes, more frequent liver fibrosis/cirrhosis (aOR=3.1 (1.1-8.2)) and primary liver cancer (aOR=6.6 (1.6-26.9)). The higher fibrosis burden was confirmed in a multinational cohort. Male sex, age â„50âyears, obesity and the presence of diabetes were associated with significant liver fibrosis. CONCLUSION: Our study defines the hepatobiliary phenotype of individuals with the most relevant AATD genotypes including their predisposition to liver tumours, thereby allowing evidence-based advice and individualised hepatological surveillance
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