The study of cooperation has been extensively studied in game theory. Especially, two-player two-strategy games have been categorized according to their equilibrium strategies and fully analysed. ...Recently, a grand unified game covering all types of two-player two-strategy games, i.e., the weightlifting game, was proposed. In the present study, we extend this two-player weightlifting game into an n-player game. We investigate the conditions for pure strategy Nash equilibria and for Pareto optimal strategies, expressed in terms of the success probability and benefit-to-cost ratio of the weightlifting game. We also present a general characterization of n-player games in terms of the proposed game. In terms of a concrete example, we present diagrams showing how the game category varies depending on the benefit-to-cost ratio. As a general rule, cooperation becomes difficult to achieve as group size increases because the success probability of weightlifting saturates towards unity. The present study provides insights into achieving behavioural cooperation in a large group by means of a cost–benefit analysis.
Context. Stars are born together from giant molecular clouds and, if we assume that the priors were chemically homogeneous and well-mixed, we expect them to share the same chemical composition. Most ...of the stellar aggregates are disrupted while orbiting the Galaxy and most of the dynamic information is lost, thus the only possibility of reconstructing the stellar formation history is to analyze the chemical abundances that we observe today. Aims. The chemical tagging technique aims to recover disrupted stellar clusters based merely on their chemical composition. We evaluate the viability of this technique to recover co-natal stars that are no longer gravitationally bound. Methods. Open clusters are co-natal aggregates that have managed to survive together. We compiled stellar spectra from 31 old and intermediate-age open clusters, homogeneously derived atmospheric parameters, and 17 abundance species, and applied machine learning algorithms to group the stars based on their chemical composition. This approach allows us to evaluate the viability and efficiency of the chemical tagging technique. Results. We found that stars at different evolutionary stages have distinct chemical patterns that may be due to NLTE effects, atomic diffusion, mixing, and biases. When separating stars into dwarfs and giants, we observed that a few open clusters show distinct chemical signatures while the majority show a high degree of overlap. This limits the recovery of co-natal aggregates by applying the chemical tagging technique. Nevertheless, there is room for improvement if more elements are included and models are improved.
MicroRNAs (miRNAs) are promising drug targets for obesity and metabolic disorders. Recently, miRNA mimics are providing a unique mechanism of action that guides the process for drug development and ...sets out the context of their therapeutic application. miRNA (miR)-21 expression in white adipose tissue (WAT) has been associated with obesity. We aimed to analyze miR-21 expression levels in relation to diabetes and obesity to determine the effect that miR-21 mimic has on processes involved in WAT functionality, to dissect the underlying molecular mechanisms, and to study the potential therapeutic application of the miR-21 mimic against obesity. We found higher miR-21 levels in WAT from non-diabetic obese compared to normoweight humans and mice. Moreover, in 3T3-L1 adipocytes, miR-21 mimic affect genes involved in WAT functionality regulation and significantly increase the expression of genes involved in browning and thermogenesis. Interestingly, in vivo treatment with the miR-21 mimic blocked weight gain induced by a high-fat diet in obese mice, without modifying food intake or physical activity. This was associated with metabolic enhancement, WAT browning, and brown adipose tissue (AT) thermogenic programming through vascular endothelial growth factor A (VEGF-A), p53, and transforming growth factor β1 (TGF-β1) signaling pathways. Our findings suggest that miR-21 mimic-based therapy may provide a new opportunity to therapeutically manage obesity and consequently, its associated alterations.
Display omitted
miR-21 mimic could serve as a potential therapeutic tool to control obesity by delaying energy storage and promoting energy expenditure in adipose tissue.
Microalgae: Fast-Growth Sustainable Green Factories Forján, Eduardo; Navarro, Francisco; Cuaresma, María ...
Critical reviews in environmental science and technology,
08/2015, Volume:
45, Issue:
16
Journal Article
Peer reviewed
Microalgae are definitely on the way to become a sustainable, fast-growing natural green source for highly demanded market products. Research is currently looking at promising outstanding ...applications of microalgae among which are the production of biofuels from the fatty acids present in biomass, functional foods enriched with microalgae healthy bioactive molecules, and greenhouse gas mitigation (CO
2
consuming) based on high cell density microalgae cultures technology. Besides, other traditional microalgae applications are currently increasing in competitiveness in a growing market demand for green biomass, in which microalgae are widely recognized as a healthy, sustainable, and biological renewable resource. Among these traditional applications, microalgae are being used to improve the nutritional quality in animal feed, particularly in aquaculture, therapeutic agent source, and antioxidant activity. In addition, microalgae also show to be functional in waste effluents treatment to remove N and P, thus preventing eutrophication, heavy metals, and others contaminants. This review intends to offer a comprehensive overview of basic aspects of microalgae physiology, massive production of biomass, and current fields of applications at industrial scale.
ABSTRACT We report on the detection, from observations obtained with the Apache Point Observatory Galactic Evolution Experiment spectroscopic survey, of a metal-poor (Fe/H = −1.3 dex) field giant ...star with an extreme Mg-Al abundance ratio (Mg/Fe = −0.31 dex; Al/Fe = 1.49 dex). Such low Mg/Al ratios are seen only among the second-generation population of globular clusters (GCs) and are not present among Galactic disk field stars. The light-element abundances of this star, 2M16011638-1201525, suggest that it could have been born in a GC. We explore several origin scenarios, studying the orbit of the star in particular to check the probability of its being kinematically related to known GCs. We performed simple orbital integrations assuming the estimated distance of 2M16011638-1201525 and the available six-dimensional phase-space coordinates of 63 GCs, looking for close encounters in the past with a minimum distance approach within the tidal radius of each cluster. We found a very low probability that 2M16011638-1201525 was ejected from most GCs; however, we note that the best progenitor candidate to host this star is GC Centauri (NGC 5139). Our dynamical investigation demonstrates that 2M16011638-1201525 reaches a distance from the Galactic plane and minimum and maximum approaches to the Galactic center of Rmin < 0.62 kpc and Rmax < 7.26 kpc in an eccentric (e ∼ 0.53) and retrograde orbit. Since the extreme chemical anomaly of 2M16011638-1201525 has also been observed in halo field stars, this object could also be considered a halo contaminant, likely to have been ejected into the Milky Way disk from the halo. We conclude that 2M16011638-20152 is also kinematically consistent with the disk but chemically consistent with halo field stars.
ABSTRACT
Investigating the chemical homogeneity of stars born from the same molecular cloud at virtually the same time is very important for our understanding of the chemical enrichment of the ...interstellar medium and with it the chemical evolution of the Galaxy. One major cause of inhomogeneities in the abundances of open clusters is stellar evolution of the cluster members. In this work, we investigate variations in the surface chemical composition of member stars of the old open cluster M67 as a possible consequence of atomic diffusion effects taking place during the main-sequence phase. The abundances used are obtained from high-resolution UVES/FLAMES spectra within the framework of the Gaia-ESO Survey. We find that the surface abundances of stars on the main sequence decrease with increasing mass reaching a minimum at the turn-off. After deepening of the convective envelope in subgiant branch stars, the initial surface abundances are restored. We found the measured abundances to be consistent with the predictions of stellar evolutionary models for a cluster with the age and metallicity of M67. Our findings indicate that atomic diffusion poses a non-negligible constraint on the achievable precision of chemical tagging methods.
Space-based transit surveys such as K2 and the Transiting Exoplanets Survey Satellite (TESS) allow the detection of small transiting planets with orbital periods greater than 10 days. Few of these ...warm Neptunes are currently known around stars bright enough to allow for detailed follow-up observations dedicated to their atmospheric characterization. The 21-day period and 3.95 R⊕ planet HD 106315c has been discovered by K2 based on the observation of two of its transits. We observed HD 106315 using the 1.2 m Euler telescope equipped with the EulerCam camera on two occasions to confirm the transit using broadband photometry and refine the planetary period. Based on two observed transits of HD 106315c, we detect its ~1 mmag transit and obtain a precise measurement of the planetary ephemerides, which are critical for planning further follow-up observations. We used the attained precision together with the predicted yield from the TESS mission to evaluate the potential for ground-based confirmation of Neptune-sized planets found by TESS. We find that one-meter class telescopes on the ground equipped with precise photometers could substantially contribute to the follow-up of 162 TESS candidates orbiting stars with magnitudes of V ≤ 14. Of these candidates, 74 planets orbit stars with V ≤ 12 and 12 planets orbit V ≤ 10, which makes them high-priority objects for atmospheric characterization with high-end instrumentation.
Gaia Data Release 2 Holl, B.; Audard, M.; Nienartowicz, K. ...
Astronomy and astrophysics (Berlin),
10/2018, Volume:
618
Journal Article
Peer reviewed
Open access
Context.
The
Gaia
Data Release 2 (DR2) contains more than half a million sources that are identified as variable stars.
Aims.
We summarise the processing and results of the identification of variable ...source candidates of RR Lyrae stars, Cepheids, long-period variables (LPVs), rotation modulation (BY Dra-type) stars,
δ
Scuti and SX Phoenicis stars, and short-timescale variables. In this release we aim to provide useful but not necessarily complete samples of candidates.
Methods.
The processed
Gaia
data consist of the
G
,
G
BP
, and
G
RP
photometry during the first 22 months of operations as well as positions and parallaxes. Various methods from classical statistics, data mining, and time-series analysis were applied and tailored to the specific properties of
Gaia
data, as were various visualisation tools to interpret the data.
Results.
The DR2 variability release contains 228 904 RR Lyrae stars, 11 438 Cepheids, 151 761 LPVs, 147 535 stars with rotation modulation, 8882
δ
Scuti and SX Phoenicis stars, and 3018 short-timescale variables. These results are distributed over a classification and various Specific Object Studies tables in the
Gaia
archive, along with the three-band time series and associated statistics for the underlying 550 737 unique sources. We estimate that about half of them are newly identified variables. The variability type completeness varies strongly as a function of sky position as a result of the non-uniform sky coverage and intermediate calibration level of these data. The probabilistic and automated nature of this work implies certain completeness and contamination rates that are quantified so that users can anticipate their effects. Thismeans that even well-known variable sources can be missed or misidentified in the published data.
Conclusions.
The DR2 variability release only represents a small subset of the processed data. Future releases will include more variable sources and data products; however, DR2 shows the (already) very high quality of the data and great promise for variability studies.
ABSTRACT We investigate the radial velocity (RV) variability and spectroscopic binarity of 19 Galactic long-period ( 10 days) classical Cepheid variable stars whose trigonometric parallaxes are being ...measured using the Hubble Space Telescope and Gaia. Our primary objective is to constrain possible parallax error due to undetected orbital motion. Using over 1600 high-precision RVs measured between 2011 and 2016, we find no indication of orbital motion on 5 year timescales for 18 Cepheids and determine upper limits on allowed configurations for a range of input orbital periods. The results constrain the unsigned parallax error due to orbital motion to <2% for 16 stars, and <4% for 18. We improve the orbital solution of the known binary YZ Carinae and show that the astrometric model must take into account orbital motion to avoid significant error (∼ 100 arcsec). We further investigate long-timescale ( > 10 years) variations in pulsation-averaged velocity vγ via a template fitting approach using both new and literature RVs. We discover the spectroscopic binarity of XZ Car and CD Cyg, find first tentative evidence for AQ Car, and reveal KN Cen's orbital signature. Further (mostly tentative) evidence of time-variable vγ is found for SS CMa, VY Car, SZ Cyg, and X Pup. We briefly discuss considerations regarding a vetting process of Galactic Leavitt law calibrators and show that light contributions by companions are insignificant for most distance scale applications.
Context. We present the transit and follow-up of a single transit event from Campaign 14 of K2, EPIC248847494b, which has a duration of 54 h and a 0.18% depth. Aims. Using photometric tools and ...conducting radial velocity follow-up, we vet and characterise this very strong candidate. Methods. Owing to the long, unknown period, standard follow-up methods needed to be adapted. The transit was fitted using Namaste, and the radial velocity slope was measured and compared to a grid of planet-like orbits with varying masses and periods. These used stellar parameters measured from spectra and the distance as measured by Gaia. Results. Orbiting around a sub-giant star with a radius of 2.70 ± 0.12 RSol, the planet has a radius of 1.11−0.07+0.07 RJup 1.11 − 0.07 + 0.07 R Jup $ 1.11_{-0.07}^{+0.07}R_\mathrm{Jup} $ and a period of 3650−1130+1280 3650 − 1130 + 1280 $ 3650_{-1130}^{+1280} $ days. The radial velocity measurements constrain the mass to be lower than 13 MJup, which implies a planet-like object. Conclusions. We have found a planet at 4.5 AU from a single-transit event. After a full radial velocity follow-up campaign, if confirmed, it will be the longest-period transiting planet discovered.
PDF
