The analysis of the wavelength-dependent albedo of exoplanets represents a direct way to provide insight into their atmospheric composition and to constrain theoretical planetary atmosphere modeling. ...Wavelength-dependent albedo can be inferred from the exoplanet's reflected light of the host star, but this is not a trivial task. In fact, the planetary signal may be several orders of magnitude lower (10−4 or below) than the flux of the host star, thus making its extraction very challenging. Successful detection of the planetary signature of 51 Peg b has been recently obtained by using cross-correlation function or autocorrelation function techniques. In this paper we present an alternative method based on the use of Independent Component Analysis (ICA). In comparison to the above-mentioned techniques, the main advantages of ICA are that the extraction is "blind" i.e., it does not require any a priori knowledge of the underlying signals, and that our method allows us not only to detect the planet signal but also to estimate its wavelength dependence. To show and quantify the effectiveness of our method we successfully applied it to both simulated data and real data of an eclipsing binary star system. Eventually, when applied to real 51 Peg + 51 Peg b data, our method extracts the signal of 51 Peg but we could not soundly detect the reflected spectrum of 51 Peg b mainly due to the insufficient signal-to-noise ratio of the input composite spectra. Nevertheless, our results show that with "ad hoc" scheduled observations an ICA approach will be, in perspective, a very valid tool for studying exoplanetary atmospheres.
The strong intervening absorption system at redshift 1.15 towards the very bright quasar HE 0515−4414 is the most studied absorber for measuring possible cosmological variations in the fine-structure ...constant,
α
. We observed HE 0515−4414 for 16.1 h with the Very Large Telescope and present here the first constraint on relative variations in
α
with parts-per-million (ppm) precision from the new ESPRESSO spectrograph: Δ
α
/
α
= 1.3 ± 1.3
stat
± 0.4
sys
ppm. The statistical uncertainty (1
σ
) is similar to the ensemble precision of previous large samples of absorbers and derives from the high signal-to-noise ratio achieved (≈105 per 0.4 km s
−1
pixel). ESPRESSO’s design, and the calibration of our observations with its laser frequency comb, effectively removed wavelength calibration errors from our measurement. The high resolving power of our ESPRESSO spectrum (
R
= 145 000) enabled the identification of very narrow components within the absorption profile, allowing a more robust analysis of Δ
α
/
α
. The evidence for the narrow components is corroborated by their correspondence with previously detected molecular hydrogen and neutral carbon. The main remaining systematic errors arise from ambiguities in the absorption profile modelling, effects from redispersing the individual quasar exposures, and convergence of the parameter estimation algorithm. All analyses of the spectrum, including systematic error estimates, were initially blinded to avoid human biases. We make our reduced ESPRESSO spectrum of HE 0515−4414 publicly available for further analysis. Combining our ESPRESSO result with 28 measurements, from other spectrographs, in which wavelength calibration errors have been mitigated yields a weighted mean Δ
α
/
α
= −0.5 ± 0.5
stat
± 0.4
sys
ppm at redshifts 0.6−2.4.
ABSTRACT
The gravitationally lensed quasar J014516.6-094517 at z = 2.719 has been observed with the ESPRESSO instrument at the ESO VLT to obtain high-fidelity spectra of the two images A and B with a ...resolving power R = 70 000. At the redshifts under investigation (2.1 ≲ z ≲ 2.7), the Lyman forests along the two sightlines are separated by sub-kiloparsec physical distances and exhibit a strong correlation. We find that the two forests are indistinguishable at the present level of signal-to-noise ratio and do not show any global velocity shift, with the cross-correlation peaking at Δv = 12 ± 48 $\rm m~s^{-1}$. The distribution of the difference in velocity of individual Ly α features is compatible with a null average and a mean absolute deviation of 930 $\rm m~s^{-1}$. Significant differences in NH i column density are not detected, putting a limit to the RMS fluctuation in the baryon density on ≲1 proper kpc scales of Δρ/ρ ≲ 3 per cent. On the other hand, metal lines show significant differences both in velocity structure and in column density. A toy model shows that the difference in velocity of the metal features between the two sightlines is compatible with the motions of the baryonic component associated with dark matter haloes of typical mass M ≃ 2 × 1010 M⊙, also compatible with the observed incidence of the metal systems. The present observations confirm the feasibility of the Sandage test of the cosmic redshift drift with high-fidelity spectroscopy of the Lyman forest of distant, bright quasars, but also provide an element of caution about the intrinsic noise associated with the usage of metal features for the same purpose.
Abstract
We analyze the oxygen abundances of a stellar sample representative of the two major Galactic populations: the thin and thick disks. The aim is to investigate the differences between members ...of the Galactic disks and contribute to the understanding of the origin of oxygen chemical enrichment in the Galaxy. The analysis is based on the O
i
= 6300.30 Å oxygen line in high-resolution spectra (
R
∼ 52,500) obtained from the Gaia-ESO public spectroscopic Survey (GES). By comparing the observed spectra with a theoretical data set computed in LTE with the SPECTRUM synthesis and ATLAS12 codes, we derive the oxygen abundances of 516 FGK dwarfs for which we have previously measured carbon abundances. Based on kinematic, chemical, and dynamical considerations, we identify 20 thin and 365 thick disk members. We study the potential trends of both subsamples in terms of their chemistry (O/H, O/Fe, O/Mg, and C/O versus Fe/H and Mg/H), age, and position in the Galaxy. The main results are that (a) O/H and O/Fe ratios versus Fe/H show systematic differences between thin and thick disk stars with an enhanced O abundance of thick disk stars with respect to thin disk members and a monotonic decrement of O/Fe with increasing metallicity, even at metal-rich regime; (b) there is a smooth correlation of O/Mg with age in both populations, suggesting that this abundance ratio can be a good proxy of stellar ages within the Milky Way; and (c) thin disk members with Fe/H ≃ 0 display a C/O ratio smaller than the solar value, suggesting a possibly outward migration of the Sun from lower Galactocentric radii.
Abstract
This paper focuses on carbon, which is one of the most abundant elements in the universe and is of high importance in the field of nucleosynthesis and galactic and stellar evolution. The ...origin of carbon and the relative importance of massive and low- to intermediate-mass stars in producing it is still a matter of debate. We aim at better understanding the origin of carbon by studying the trends of C/H, C/Fe, and C/Mg versus Fe/H and Mg/H for 2133 FGK dwarf stars from the fifth
Gaia
–ESO Survey internal data release (GES iDR5). The availability of accurate parallaxes and proper motions from
Gaia
DR2 and radial velocities from GES iDR5 allows us to compute Galactic velocities, orbits, absolute magnitudes, and, for 1751 stars, Bayesian-derived ages. Three different selection methodologies have been adopted to discriminate between thin- and thick-disk stars. In all the cases, the two stellar groups show different C/H, C/Fe, and C/Mg and span different age intervals, with the thick-disk stars being, on average, older than the thin-disk ones. The behaviors of C/H, C/Fe, and C/Mg versus Fe/H, Mg/H, and age all suggest that C is primarily produced in massive stars. The increase of C/Mg for young thin-disk stars indicates a contribution from low-mass stars or the increased C production from massive stars at high metallicities due to the enhanced mass loss. The analysis of the orbital parameters
R
med
and
supports an “inside–out” and “upside–down” formation scenario for the disks of the Milky Way.
Observations of metal absorption systems in the spectra of distant quasars allow one to constrain a possible variation of the fine-structure constant throughout the history of the Universe. Such a ...test poses utmost demands on the wavelength accuracy and previous studies were limited by systematics in the spectrograph wavelength calibration. A substantial advance in the field is therefore expected from the new ultra-stable high-resolution spectrograph E
SPRESSO
, which was recently installed at the VLT. In preparation of the fundamental physics related part of the E
SPRESSO
GTO program, we present a thorough assessment of the E
SPRESSO
wavelength accuracy and identify possible systematics at each of the different steps involved in the wavelength calibration process. Most importantly, we compare the default wavelength solution, which is based on the combination of Thorium-Argon arc lamp spectra and a Fabry-Pérot interferometer, to the fully independent calibration obtained from a laser frequency comb. We find wavelength-dependent discrepancies of up to 24 m s
−1
. This substantially exceeds the photon noise and highlights the presence of different sources of systematics, which we characterize in detail as part of this study. Nevertheless, our study demonstrates the outstanding accuracy of E
SPRESSO
with respect to previously used spectrographs and we show that constraints of a relative change of the fine-structure constant at the 10
−6
level can be obtained with E
SPRESSO
without being limited by wavelength calibration systematics.
Following a similar approach on carvacrol-based derivatives, we investigated the synthesis and the microbiological screening against eight strains of
, and the cytotoxic activity against human ...gastric adenocarcinoma (AGS) cells of a new series of ether compounds based on the structure of thymol. Structural analysis comprehended elemental analysis and
H/
C/
F NMR spectra. The analysis of structure-activity relationships within this molecular library of 38 structurally-related compounds reported that some chemical modifications of the OH group of thymol led to broad-spectrum growth inhibition on all isolates. Preferred substitutions were benzyl groups compared to alkyl chains, and the specific presence of functional groups at
position of the benzyl moiety such as 4-CN and 4-Ph endowed the most anti-
activity toward all the strains with minimum inhibitory concentration (MIC) values up to 4 µg/mL. Poly-substitution on the benzyl ring was not essential. Moreover, several compounds characterized by the lowest minimum inhibitory concentration/minimum bactericidal concentration (MIC/MBC) values against
were also tested in order to verify a cytotoxic effect against AGS cells with respect to 5-fluorouracil and carvacrol. Three derivatives can be considered as new lead compounds alternative to current therapy to manage
infection, preventing the occurrence of severe gastric diseases. The present work confirms the possibility to use natural compounds as templates for the medicinal semi-synthesis.
Processes of development during fetal life profoundly transform tendons from a plastic tissue into a highly differentiated structure, characterised by a very low ability to regenerate after injury in ...adulthood. Sheep tendon is frequently used as a translational model to investigate cell‐based regenerative approaches. However, in contrast to other species, analytical and comparative baseline studies on the normal developmental maturation of sheep tendons from fetal through to adult life are not currently available. Thus, a detailed morphological and biochemical study was designed to characterise tissue maturation during mid‐ (2 months of pregnancy: 14 cm of length) and late fetal (4 months: 40 cm of length) life, through to adulthood. The results confirm that ovine tendon morphology undergoes profound transformations during this period. Endotenon was more developed in fetal tendons than in adult tissues, and its cell phenotype changed through tendon maturation. Indeed, groups of large rounded cells laying on smaller and more compacted ones expressing osteocalcin, vascular endothelial growth factor (VEGF) and nerve growth factor (NGF) were identified exclusively in fetal mid‐stage tissues, and not in late fetal or adult tendons. VEGF, NGF as well as blood vessels and nerve fibers showed decreased expression during tendon development. Moreover, the endotenon of mid‐ and late fetuses contained identifiable cells that expressed several pluripotent stem cell markers Telomerase Reverse Transcriptase (TERT), SRY Determining Region Y Box‐2 (SOX2), Nanog Homeobox (NANOG) and Octamer Binding Transcription Factor‐4A (OCT‐4A). These cells were not identifiable in adult specimens. Ovine tendon development was also accompanied by morphological modifications to cell nuclei, and a progressive decrease in cellularity, proliferation index and expression of connexins 43 and 32. Tendon maturation was similarly characterised by modulation of several other gene expression profiles, including Collagen type I, Collagen type III, Scleraxis B, Tenomodulin, Trombospondin 4 and Osteocalcin. These gene profiles underwent a dramatic reduction in adult tissues. Transforming growth factor‐β~1 expression (involved in collagen synthesis) underwent a similar decrease. In conclusion, these morphological studies carried out on sheep tendons at different stages of development and aging offer normal structural and molecular baseline data to allow accurate evaluation of data from subsequent interventional studies investigating tendon healing and regeneration in ovine experimental models.
We present a high-resolution synthetic spectral library, INTRIGOSS, designed for studying FGK stars. The library is based on atmosphere models computed with specified individual element abundances ...via ATLAS12 code. Normalized SPectra (NSPs) and surface Flux SPectra (FSP) in the wavelength range 4830-5400 were computed with the SPECTRUM code. INTRIGOSS uses the solar composition of Grevesse et al. and four /Fe abundance ratios, and consists of 15,232 spectra. The synthetic spectra are computed with astrophysical gf-values derived by comparing synthetic predictions with a solar spectrum of very high signal-to-noise ratio and the UVES-U580 spectra of five cool giants. The validity of the NSPs is assessed by using the UVES-U580 spectra of 2212 stars observed in the framework of the Gaia-ESO (European Southern Observatory) survey and characterized by homogeneous and accurate atmospheric parameter values and by detailed chemical compositions. The greater accuracy of NSPs with respect to spectra from the synthetic spectral libraries AMBRE, GES_Grid, PHOENIX, C14, and B17 is demonstrated by evaluating the consistency of the predictions of the different libraries for stars in the UVES-U580 sample. The validity of the FSPs is checked by comparing their prediction with both the observed spectral energy distribution (SED) and spectral indices. The comparison of FSPs with SEDs derived from the libraries ELODIE, INDO-U.S., and MILES indicates that the former reproduce the observed flux distributions within a few per cent and without any systematic trend. The good agreement between observational and synthetic Lick/SDSS (Sloan Digital Sky Survey) indices shows that the predicted blanketing of FSPs well reproduces the observed one, thus confirming the reliability of INTRIGOSS FSPs.
The design of tendon biomimetic electrospun fleece with Amniotic Epithelial Stem Cells (AECs) that have shown a high tenogenic attitude may represent an alternative strategy to overcome the ...unsatisfactory results of conventional treatments in tendon regeneration.
In this study, we evaluated AEC-engineered electrospun poly(lactide-co-glycolide) (PLGA) fleeces with highly aligned fibers (ha-PLGA) that mimic tendon extracellular matrix, their biocompatibility, and differentiation towards the tenogenic lineage. PLGA fleeces with randomly distributed fibers (rd-PLGA) were generated as control.
Optimal cell infiltration and biocompatibility with both PLGA fleeces were shown. However, only ha-PLGA fleeces committed AECs towards an Epithelial-Mesenchymal Transition (EMT) after 48 h culture, inducing their cellular elongation along the fibers' axis and the upregulation of mesenchymal markers. AECs further differentiated towards tenogenic lineage as confirmed by the up-regulation of tendon-related genes and Collagen Type 1 (COL1) protein expression that, after 28 days culture, appeared extracellularly distributed along the direction of ha-PLGA fibers. Moreover, long-term co-cultures of AEC-ha-PLGA bio-hybrids with fetal tendon explants significantly accelerated of half time AEC tenogenic differentiation compared to ha-PLGA fleeces cultured only with AECs.
The fabricated tendon biomimetic ha-PLGA fleeces induce AEC tenogenesis through an early EMT, providing a potential tendon substitute for tendon engineering research.
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