41 research outputs found
Overabundance of alpha-elements in exoplanet host stars
We present the results for a chemical abundance analysis between
planet-hosting and stars without planets for 12 refractory elements for a total
of 1111 nearby FGK dwarf stars observed within the context of the HARPS GTO
programs. Of these stars, 109 are known to harbour high-mass planetary
companions and 26 stars are hosting exclusively Neptunians and super-Earths. We
found that the [X/Fe] ratios for Mg, Al, Si, Sc, and Ti both for giant and
low-mass planet hosts are systematically higher than those of comparison stars
at low metallicities ([Fe/H] < from -0.2 to 0.1 dex depending on the element).
The most evident discrepancy between planet-hosting and stars without planets
is observed for Mg. Our data suggest that the planet incidence is greater among
the thick disk population than among the thin disk for mettallicities bellow
-0.3 dex. After examining the [alpha/Fe] trends of the planet host and non-host
samples we conclude that a certain chemical composition, and not the Galactic
birth place of the stars, is the determinating factor for that. The inspection
of the Galactic orbital parameters and kinematics of the planet-hosting stars
shows that Neptunian hosts tend to belong to the "thicker" disk compared to
their high-mass planet-hosting counterparts.We also found that Neptunian hosts
follow the distribution of high-alpha stars in the UW vs V velocities space,
but they are more enhanced in Mg than high-alpha stars without planetary
companions. Our results indicate that some metals other than iron may also have
an important contribution to planet formation if the amount of iron is low.
These results may provide strong constraints for the models of planet
formation, especially for planets with low mass.Comment: 10 pages, 8 figures, 3 tables, accepted for publication in Astronomy
& Astrophysic
Double-blind test program for astrometric planet detection with Gaia
We use detailed simulations of the Gaia observations of synthetic planetary
systems and develop and utilize independent software codes in double-blind mode
to analyze the data, including statistical tools for planet detection and
different algorithms for single and multiple Keplerian orbit fitting that use
no a priori knowledge of the true orbital parameters of the systems. 1) Planets
with astrometric signatures times the single-measurement error
and period yr can be detected reliably, with a very
small number of false positives. 2) At twice the detection limit, uncertainties
in orbital parameters and masses are typically . 3) Over 70% of
two-planet systems with well-separated periods in the range
yr, , and eccentricity are
correctly identified. 4) Favorable orbital configurations have orbital elements
measured to better than 10% accuracy of the time, and the value of the
mutual inclination angle determined with uncertainties \leq 10^{\degr}. 5)
Finally, uncertainties obtained from the fitting procedures are a good estimate
of the actual errors. Extrapolating from the present-day statistical properties
of the exoplanet sample, the results imply that a Gaia with = 8
as, in its unbiased and complete magnitude-limited census of planetary
systems, will measure several thousand giant planets out to 3-4 AUs from stars
within 200 pc, and will characterize hundreds of multiple-planet systems,
including meaningful coplanarity tests. Finally, we put Gaia into context,
identifying several areas of planetary-system science in which Gaia can be
expected to have a relevant impact, when combined with data coming from other
ongoing and future planet search programs.Comment: 32 pages, 24 figures, 6 tables. Accepted for pubolication in A&
Secondary prevention of venous thromboembolism: Predictors and outcomes of guideline adherence in a long-term prospective cohort study.
Background
Prevention of recurrent venous thromboembolism (VTE) is considered a main goal of VTE management. However, the extent to which physicians adhere to the recommendations from evidence-based guidelines is unknown.
Aim
From a large, prospective clinical cohort, we aimed to (1) quantify the adherence of treatment recommendations to evidence-based guidelines and establish its predictors, and (2) estimate its impact on clinical outcomes and costs in patients with VTE.
Methods
We included 6'243 consecutive patients with VTE treated at the university outpatient unit. Detailed clinical characteristics and treatment recommendations were recorded. Adherence of treatment recommendations to evidence-based guidelines at risk assessment was assessed in terms of duration of anticoagulant treatment. Data on death were obtained from the Swiss Central Compensation Office. Health care claims data recorded between 2014 and 2019 were retrieved from Helsana, one of the largest Swiss health insurance companies.
Results
The adherence to evidence-based guidelines was 36.1%. Among patients with non-adherence, overtreatment was present in 70.1%. Significant patient-related predictors of guideline adherence were (a) age above 50 years, (b) male sex, (c) pulmonary embolism, (d) unprovoked VTE, (e) multiple VTE, (f) laboratory tests not ordered, and (g) various cardiovascular comorbidities. Non-adherence was not significantly associated with mortality, hospitalization, admission to nursing home, and costs.
Conclusions
The adherence to evidence-based guidelines was low, and several unrelated predictors appeared. Although these results need to be confirmed in other settings, they highlight the need for implementation of evidence-based guidelines in clinical practice
Chemical abundances of 1111 FGK stars from the HARPS GTO planet search program.Galactic stellar populations and planets
We performed a uniform and detailed abundance analysis of 12 refractory
elements (Na, Mg, Al, Si, Ca, Ti, Cr, Ni, Co, Sc, Mn and V) for a sample of
1111 FGK dwarf stars from the HARPS GTO planet search program. 109 of these
stars are known to harbour giant planetary companions and 26 stars are hosting
exclusively Neptunians and super-Earths. The main goals of this paper are i) to
investigate whether there are any differences between the elemental abundance
trends for stars of different stellar populations; ii) to characterise the
planet host and non-host samples in term of their [X/H]. The extensive study of
this sample, focused on the abundance differences between stars with and
without planets will be presented in a parallel paper. The equivalent widths of
spectral lines are automatically measured from HARPS spectra with the ARES
code. The abundances of the chemical elements are determined using a LTE
abundance analysis relative to the Sun, with the 2010 revised version of the
spectral synthesis code MOOG and a grid of Kurucz ATLAS9 atmospheres. To
separate the Galactic stellar populations we applied both a purely kinematical
approach and a chemical method. We found that the chemically separated (based
on the Mg, Si, and Ti abundances) thin and thick discs are also chemically
disjunct for Al, Sc, Co and Ca. Some bifurcation might also exist for Na, V,
Ni, and Mn, but there is no clear boundary of their [X/Fe] ratios. We confirm
that an overabundance in giant-planet host stars is clear for all the studied
elements.We also confirm that stars hosting only Neptunian-like planets may be
easier to detect around stars with similar metallicities as non-planet hosts,
although for some elements (particulary alpha-elements) the lower limit of
[X/H] are very abrupt.Comment: 14 pages, 12 figures, 6 tables. accepted for publication in Astronomy
& Astrophysic
Small molecule activators of SIRT1 replicate signaling pathways triggered by calorie restriction in vivo
<p>Abstract</p> <p>Background</p> <p>Calorie restriction (CR) produces a number of health benefits and ameliorates diseases of aging such as type 2 diabetes. The components of the pathways downstream of CR may provide intervention points for developing therapeutics for treating diseases of aging. The NAD<sup>+</sup>-dependent protein deacetylase SIRT1 has been implicated as one of the key downstream regulators of CR in yeast, rodents, and humans. Small molecule activators of SIRT1 have been identified that exhibit efficacy in animal models of diseases typically associated with aging including type 2 diabetes. To identify molecular processes induced in the liver of mice treated with two structurally distinct SIRT1 activators, SIRT501 (formulated resveratrol) and SRT1720, for three days, we utilized a systems biology approach and applied Causal Network Modeling (CNM) on gene expression data to elucidate downstream effects of SIRT1 activation.</p> <p>Results</p> <p>Here we demonstrate that SIRT1 activators recapitulate many of the molecular events downstream of CR <it>in vivo</it>, such as enhancing mitochondrial biogenesis, improving metabolic signaling pathways, and blunting pro-inflammatory pathways in mice fed a high fat, high calorie diet.</p> <p>Conclusion</p> <p>CNM of gene expression data from mice treated with SRT501 or SRT1720 in combination with supporting <it>in vitro </it>and <it>in vivo </it>data demonstrates that SRT501 and SRT1720 produce a signaling profile that mirrors CR, improves glucose and insulin homeostasis, and acts via SIRT1 activation <it>in vivo</it>. Taken together these results are encouraging regarding the use of small molecule activators of SIRT1 for therapeutic intervention into type 2 diabetes, a strategy which is currently being investigated in multiple clinical trials.</p
The PLATO 2.0 mission
PLATO 2.0 has recently been selected for ESA's M3 launch opportunity (2022/24). Providing accurate key planet parameters (radius, mass, density and age) in statistical numbers, it addresses fundamental questions such as: How do planetary systems form and evolve? Are there other systems with planets like ours, including potentially habitable planets? The PLATO 2.0 instrument consists of 34 small aperture telescopes (32 with 25 s readout cadence and 2 with 2.5 s candence) providing a wide field-of-view (2232 deg 2) and a large photometric magnitude range (4-16 mag). It focusses on bright (4-11 mag) stars in wide fields to detect and characterize planets down to Earth-size by photometric transits, whose masses can then be determined by ground-based radial-velocity follow-up measurements. Asteroseismology will be performed for these bright stars to obtain highly accurate stellar parameters, including masses and ages. The combination of bright targets and asteroseismology results in high accuracy for the bulk planet parameters: 2 %, 4-10 % and 10 % for planet radii, masses and ages, respectively. The planned baseline observing strategy includes two long pointings (2-3 years) to detect and bulk characterize planets reaching into the habitable zone (HZ) of solar-like stars and an additional step-and-stare phase to cover in total about 50 % of the sky. PLATO 2.0 will observe up to 1,000,000 stars and detect and characterize hundreds of small planets, and thousands of planets in the Neptune to gas giant regime out to the HZ. It will therefore provide the first large-scale catalogue of bulk characterized planets with accurate radii, masses, mean densities and ages. This catalogue will include terrestrial planets at intermediate orbital distances, where surface temperatures are moderate. Coverage of this parameter range with statistical numbers of bulk characterized planets is unique to PLATO 2.0. The PLATO 2.0 catalogue allows us to e.g.: - complete our knowledge of planet diversity for low-mass objects, - correlate the planet mean density-orbital distance distribution with predictions from planet formation theories,- constrain the influence of planet migration and scattering on the architecture of multiple systems, and - specify how planet and system parameters change with host star characteristics, such as type, metallicity and age. The catalogue will allow us to study planets and planetary systems at different evolutionary phases. It will further provide a census for small, low-mass planets. This will serve to identify objects which retained their primordial hydrogen atmosphere and in general the typical characteristics of planets in such low-mass, low-density range. Planets detected by PLATO 2.0 will orbit bright stars and many of them will be targets for future atmosphere spectroscopy exploring their atmosphere. Furthermore, the mission has the potential to detect exomoons, planetary rings, binary and Trojan planets. The planetary science possible with PLATO 2.0 is complemented by its impact on stellar and galactic science via asteroseismology as well as light curves of all kinds of variable stars, together with observations of stellar clusters of different ages. This will allow us to improve stellar models and study stellar activity. A large number of well-known ages from red giant stars will probe the structure and evolution of our Galaxy. Asteroseismic ages of bright stars for different phases of stellar evolution allow calibrating stellar age-rotation relationships. Together with the results of ESA's Gaia mission, the results of PLATO 2.0 will provide a huge legacy to planetary, stellar and galactic science
Walking parallel paths or taking the same road? : The effect of collaborative incentives in innovation contests
All rights rerserved. We examine the role of participants’ interactions in innovation contests. In contrast to the dominant view of a competitive organisation of innovation contests, we suggest that, especially for ideation projects, a collaborative setting may be beneficial in terms of the amount of ideation activity and the quality of the generated ideas. Using two experiments, we show the usefulness of a collaborative approach when two particular conditions are met: first, the overall effort must be compensated according to performance criteria in such a way that participants are aware of the impact of their actions. Thus, the reward mechanism has to ensure that all contributors to a specific idea benefit from their involvement. Second, the host has to provide feedback throughout the contest to make it clear for participants what idea(s) to focus on. Our results show that, while the elaboration effort can be increased by introducing a collaborative reward mechanism alone, the best results are achieved when both conditions are met
Walking parallel paths or taking the same road? The effect of collaborative incentives in innovation contests
We examine the role of participants’ interactions in innovation contests. In contrast to the dominant view of a competitive organisation of innovation contests, we suggest that, especially for ideation projects, a collaborative setting may be beneficial in terms of the amount of ideation activity and the quality of the generated ideas. Using two experiments, we show the usefulness of a collaborative approach when two particular conditions are met: first, the overall effort must be compensated according to performance criteria in such a way that participants are aware of the impact of their actions. Thus, the reward mechanism has to ensure that all contributors to a specific idea benefit from their involvement. Second, the host has to provide feedback throughout the contest to make it clear for participants what idea(s) to focus on. Our results show that, while the elaboration effort can be increased by introducing a collaborative reward mechanism alone, the best results are achieved when both conditions are met