5,192 research outputs found
Chemical fingerprints of hot Jupiter planet formation
The current paradigm to explain the presence of Jupiters with small orbital
periods (P 10 days; hot Jupiters) that involves their formation beyond the
snow line following inward migration, has been challenged by recent works that
explored the possibility of in situ formation. We aim to test whether stars
harbouring hot Jupiters and stars with more distant gas-giant planets show any
chemical peculiarity that could be related to different formation processes.
Our results show that stars with hot Jupiters have higher metallicities than
stars with cool distant gas-giant planets in the metallicity range +0.00/+0.20
dex. The data also shows a tendency of stars with cool Jupiters to show larger
abundances of elements. No abundance differences between stars with
cool and hot Jupiters are found when considering iron peak, volatile elements
or the C/O, and Mg/Si ratios. The corresponding -values from the statistical
tests comparing the cumulative distributions of cool and hot planet hosts are
0.20, 0.01, 0.81, and 0.16 for metallicity, , iron-peak, and
volatile elements, respectively. We confirm previous works suggesting that more
distant planets show higher planetary masses as well as larger eccentricities.
We note differences in age and spectral type between the hot and cool planet
hosts samples that might affect the abundance comparison. The differences in
the distribution of planetary mass, period, eccentricity, and stellar host
metallicity suggest a different formation mechanism for hot and cool Jupiters.
The slightly larger abundances found in stars harbouring cool Jupiters
might compensate their lower metallicities allowing the formation of gas-giant
planets.Comment: Accepted by Astronomy & Astrophysic
Connecting substellar and stellar formation. The role of the host star's metallicity
Most of our current understanding of the planet formation mechanism is based
on the planet metallicity correlation derived mostly from solar-type stars
harbouring gas-giant planets. To achieve a far more reaching grasp on the
substellar formation process we aim to analyse in terms of their metallicity a
diverse sample of stars (in terms of mass and spectral type) covering the whole
range of possible outcomes of the planet formation process (from planetesimals
to brown dwarfs and low-mass binaries). Our methodology is based on the use of
high-precision stellar parameters derived by our own group in previous works
from high-resolution spectra by using the iron ionisation and equilibrium
conditions. All values are derived in an homogeneous way, except for the M
dwarfs where a methodology based on the use of pseudo equivalent widths of
spectral features was used. Our results show that as the mass of the substellar
companion increases the metallicity of the host star tendency is to lower
values. The same trend is maintained when analysing stars with low-mass stellar
companions and a tendency towards a wide range of host star's metallicity is
found for systems with low mass planets. We also confirm that more massive
planets tend to orbit around more massive stars. The core-accretion formation
mechanism for planet formation achieves its maximum efficiency for planets with
masses in the range 0.2 and 2 M. Substellar objects with higher
masses have higher probabilities of being formed as stars. Low-mass planets and
planetesimals might be formed by core-accretion even around low-metallicity
stars.Comment: Accepted by A&
Searching for signatures of planet formation in stars with circumstellar debris discs
(Abridged) Tentative correlations between the presence of dusty debris discs
and low-mass planets have been presented. In parallel, detailed chemical
abundance studies have reported different trends between samples of planet and
non-planet hosts. We determine in a homogeneous way the metallicity, and
abundances of a sample of 251 stars including stars with known debris discs,
with debris discs and planets, and only with planets. Stars with debris discs
and planets have the same [Fe/H] behaviour as stars hosting planets, and they
also show a similar -Tc trend. Different behaviour in the -Tc
trend is found between the samples of stars without planets and the samples of
planet hosts. In particular, when considering only refractory elements,
negative slopes are shown in cool giant planet hosts, whilst positive ones are
shown in stars hosting low-mass planets. Stars hosting exclusively close-in
giant planets show higher metallicities and positive -Tc slope. A
search for correlations between the -Tc slopes and the stellar
properties reveals a moderate but significant correlation with the stellar
radius and as well as a weak correlation with the stellar age. The fact that
stars with debris discs and stars with low-mass planets do not show neither
metal enhancement nor a different -Tc trend might indicate a
correlation between the presence of debris discs and the presence of low-mass
planets. We extend results from previous works which reported differences in
the -Tc trends between planet hosts and non hosts. However, these
differences tend to be present only when the star hosts a cool distant planet
and not in stars hosting exclusively low-mass planets.Comment: Accepted for publication in Astronomy and Astrophysic
The metallicity signature of evolved stars with planets
We determine in a homogeneous way the metallicity and individual abundances
of a large sample of evolved stars, with and without known planetary
companions. Our methodology is based on the analysis of high-resolution echelle
spectra. The metallicity distributions show that giant stars hosting planets
are not preferentially metal-rich having similar abundance patterns to giant
stars without known planetary companions. We have found, however, a very strong
relation between the metallicity distribution and the stellar mass within this
sample. We show that the less massive giant stars with planets (M < 1.5 Msun)
are not metal rich, but, the metallicity of the sample of massive (M > 1.5
Msun), young (age < 2 Gyr) giant stars with planets is higher than that of a
similar sample of stars without planets. Regarding other chemical elements,
giant stars with and without planets in the mass domain M < 1.5 Msun show
similar abundance patterns. However, planet and non-planet hosts with masses M
> 1.5 Msun show differences in the abundances of some elements, specially Na,
Co, and Ni. In addition, we find the sample of subgiant stars with planets to
be metal rich showing similar metallicities to main-sequence planet hosts. The
fact that giant planet hosts in the mass domain M < 1.5 Msun do not show
metal-enrichment is difficult to explain. Given that these stars have similar
stellar parameters to subgiants and main-sequence planet hosts, the lack of the
metal-rich signature in low-mass giants could be explained if originated from a
pollution scenario in the main sequence that gets erased as the star become
fully convective. However, there is no physical reason why it should play a
role for giants with masses M < 1.5 Msun but is not observed for giants with M
> 1.5 Msun.Comment: Accepted for publication by A&A, 34 pages, 15 figures, abstract
abridge
The Cyber Aggression in Relationships Scale: A New Multidimensional Measure of Technology-Based Intimate Partner Aggression
The purpose of this study was to develop and provide initial validation for a measure of adult cyber intimate partner aggression (IPA): the Cyber Aggression in Relationships Scale (CARS). Drawing on recent conceptual models of cyber IPA, items from previous research exploring general cyber aggression and cyber IPA were modified and new items were generated for inclusion in the CARS. Two samples of adults 18 years or older were recruited online. We used item factor analysis to test the factor structure, model fit, and invariance of the measure structure across women and men. Results confirmed that three-factor models for both perpetration and victimization demonstrated good model fit, and that, in general, the CARS measures partner cyber aggression similarly for women and men. The CARS also demonstrated validity through significant associations with in-person IPA, trait anger, and jealousy. Findings suggest the CARS is a useful tool for assessing cyber IPA in both research and clinical settings
The Cyber Aggression in Relationships Scale: A New Multidimensional Measure of Technology-Based Intimate Partner Aggression
The purpose of this study was to develop and provide initial validation for a measure of adult cyber intimate partner aggression (IPA): the Cyber Aggression in Relationships Scale (CARS). Drawing on recent conceptual models of cyber IPA, items from previous research exploring general cyber aggression and cyber IPA were modified and new items were generated for inclusion in the CARS. Two samples of adults 18 years or older were recruited online. We used item factor analysis to test the factor structure, model fit, and invariance of the measure structure across women and men. Results confirmed that three-factor models for both perpetration and victimization demonstrated good model fit, and that, in general, the CARS measures partner cyber aggression similarly for women and men. The CARS also demonstrated validity through significant associations with in-person IPA, trait anger, and jealousy. Findings suggest the CARS is a useful tool for assessing cyber IPA in both research and clinical settings
Proteomic identification and characterization of hepatic glyoxalase 1 dysregulation in non-alcoholic fatty liver disease
Background: Non-alcoholic fatty liver disease (NAFLD) is the most common liver disease worldwide. However, its
molecular pathogenesis is incompletely characterized and clinical biomarkers remain scarce. The aims of these
experiments were to identify and characterize liver protein alterations in an animal model of early, diet-related,
liver injury and to assess novel candidate biomarkers in NAFLD patients.
Methods: Liver membrane and cytosolic protein fractions from high fat fed apolipoprotein E knockout (ApoE−/−)
animals were analyzed by quantitative proteomics, utilizing isobaric tags for relative and absolute quantitation
(iTRAQ) combined with nano-liquid chromatography and tandem mass spectrometry (nLC-MS/MS). Differential
protein expression was confirmed independently by immunoblotting and immunohistochemistry in both murine
tissue and biopsies from paediatric NAFLD patients. Candidate biomarkers were analyzed by enzyme-linked
immunosorbent assay in serum from adult NAFLD patients.
Results: Through proteomic profiling, we identified decreased expression of hepatic glyoxalase 1 (GLO1) in a
murine model. GLO1 protein expression was also found altered in tissue biopsies from paediatric NAFLD patients. In
vitro experiments demonstrated that, in response to lipid loading in hepatocytes, GLO1 is first hyperacetylated then
ubiquitinated and degraded, leading to an increase in reactive methylglyoxal. In a cohort of 59 biopsy-confirmed adult
NAFLD patients, increased serum levels of the primary methylglyoxal-derived advanced glycation endproduct,
hydroimidazolone (MG-H1) were significantly correlated with body mass index (r = 0.520, p < 0.0001).
Conclusion: Collectively these results demonstrate the dysregulation of GLO1 in NAFLD and implicate the
acetylation-ubquitination degradation pathway as the functional mechanism. Further investigation of the role
of GLO1 in the molecular pathogenesis of NAFLD is warranted.
Keywords: Non-alcoholic fatty liver disease, Glyoxalase, Methylglyoxal, Proteomics, iTRA
Silica stable isotopes and silicification in a carnivorous sponge Asbestopluma sp.
The stable isotope composition of benthic sponge spicule silica is a potential source of palaeoceanographic information about past deep seawater chemistry. The silicon isotope composition of spicules has been shown to relate to the silicic acid concentration of ambient water, although existing calibrations do exhibit a degree of scatter in the relationship. Less is known about how the oxygen isotope composition of sponge spicule silica relates to environmental conditions during growth. Here, we investigate the vital effects on silica, silicon and oxygen isotope composition in a carnivorous sponge, Asbestopluma sp., from the Southern Ocean. We find significant variations in silicon and oxygen isotopic composition within the specimen that are related to unusual spicule silicification. The largest variation in both isotope systems was associated with the differential distribution of an unconventional, hypersilicified spicule type (desma) along the sponge body. The absence an internal canal in the desmas suggests an unconventional silicification pattern leading to an unusually heavy isotope signature. Additional internal variability derives from a systematic offset between the peripheral skeleton of the body having systematically a higher isotopic composition than the internal skeleton. A simplified silicon isotope fractionation model, in which desmas were excluded, suggests that the lack of a system for seawater pumping in carnivorous sponges favours a low replenishment of dissolved silicon within the internal tissues, causing kinetic fractionation during silicification that impacts the isotope signature of the internal skeleton. Analysis of multiple spicules should be carried out to "average out" any artefacts in order to produce more robust downcore measurements
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