On Lithium-6 as diagnostic of the lithium-enrichment mechanism in red giants

High lithium-7 ($\mathrm{^7Li}$) abundances in giants are indicative of non-standard physical processes affecting the star. Mechanisms that could produce this signature include contamination from an external source, such as planets, or internal production and subsequent mixing to the stellar surface. However, distinguishing between different families of solutions has proven challenging, and there is no current consensus model that explains all the data. The lithium-6 ($\mathrm{^6Li}$) abundance may be a potentially important discriminant, as the relative $\mathrm{^6Li}$ and $\mathrm{^7Li}$ abundances are expected to be different if the enrichment were to come from internal production or from engulfment. In this work, we model the $\mathrm{^6Li}$ and $\mathrm{^7Li}$ abundances of different giants after the engulfment of a substellar mass companion. Given that $\mathrm{^6Li}$ is more strongly affected by Galactic chemical evolution than $\mathrm{^7Li}$, $\mathrm{^6Li}$ is not a good discriminant at low metallicities, where it is expected to be low in both star and planet. For modeled metallicities ([Fe/H]$>-0.5$), we use a "best case" initial $\mathrm{^6Li/^7Li}$ ratio equal to the solar value. $\mathrm{^6Li}$ increases significantly after the engulfment of a companion. However, at metallicities close to solar and higher, the $\mathrm{^6Li}$ signal does not last long in the stellar surface. As such, detection of surface $\mathrm{^6Li}$ in metal-rich red giants would most likely indicate the action of a mechanism for $\mathrm{^6Li}$-enrichment other than planet engulfment. At the same time, $\mathrm{^6Li}$ should not be used to reject the hypothesis of engulfment in a $\mathrm{^7Li}$-enriched giant or to support a particular $\mathrm{^7Li}$-enhancement mechanism

Safety evaluation of the food enzyme pullulanase from genetically modified Bacillus subtilis strain NZYM-AK

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Lithium abundance patterns of late-F stars: an in-depth analysis of the lithium desert

We address the existence and origin of the lithium (Li) desert, a region in the Li - T_eff plane sparsely populated by stars. Here we analyze some of the explanations that have been suggested for this region, including mixing in the late main sequence, a Li dip origin for stars with low Li abundances in the region, and a possible relation with the presence of planets. To study the Li desert, we measured the atmospheric parameters and Li abundance of 227 late-F dwarfs and subgiants, chosen to be in the T_eff range of the desert and without previous Li abundance measurements. Subsequently, we complemented those with literature data to obtain a homogeneous catalog of 2318 stars, for which we compute masses and ages. We characterize stars surrounding the region of the Li desert. We conclude that stars with low Li abundances below the desert are more massive and more evolved than stars above the desert. Given the unexpected presence of low Li abundance stars in this effective temperature range, we concentrate on finding their origin. We conclude that these stars with low Li abundance do not evolve from stars above the desert: at a given mass, stars with low Li (i.e., below the desert) are more metal-poor. Instead, we suggest that stars below the Li desert are consistent with having evolved from the Li dip, discarding the need to invoke additional mixing to explain this feature. Thus, stars below the Li desert are not peculiar and are only distinguished from other subgiants evolved from the Li dip in that their combination of atmospheric parameters locates them in a range of effective temperatures where otherwise only high Li abundance stars would be found (i.e., stars above the desert).Comment: Accepted for publication in A&

Evidence of extra-mixing in field giants as traced by lithium and carbon isotope ratio

Although not predicted by standard stellar evolution, it is known that the surface abundance of light elements changes during the red giant branch (RGB) as a result of extra-mixing. This is associated usually with thermohaline mixing acting after the RGB bump. Peculiar lithium-enriched RGB stars might also be related to either enhanced extra-mixing or pollution from external sources. We measure the lithium (Li) abundance and carbon isotopic ratio C12/C13 in a sample of 166 field red giants with -0.3<[Fe/H]<0.2, targeted by the EXPRESS radial velocity program to analyze the effects of extra-mixing. The Li abundance pattern is complicated to interpret, but the comparison between RGB and core-He burning giants shows the effects of extra-mixing consistent with thermohaline. The most Li-enriched giant in the sample was classified as a RGB star close to the luminosity function bump with low C12/C13. Given that the C12/C13 should not be affected by external mechanisms, contamination by an external source, such as a planet, does not seem to be the source of the high Li. The C12C13 presents new clues to describe the extra-mixing. There is a decreasing correlation between mass and C12/C13 in the RGB and an increasing correlation in the horizontal branch, which, once again, is consistent with thermohaline mixing. Our data also shows a correlation between C12/C13 and [Fe/H]. There is no evident impact of binarity either on Li or C12/C13. Our sample shows behavior that is consistent with additional mixing acting after the RGB bump. Li, which is heavily affected by rotational mixing and other processes, does not show a clear trend. Instead, the C12/C13 could be the best tool to study mixing in red giants. Additional measurements of C12/C13 in field stars would greatly improve our ability to compare with models and understand the mixing mechanisms.Comment: 15 pages, 12 figures, submitted to A&A, comments welcom

Safety evaluation of the food enzyme β-amylase from genetically modified Bacillus licheniformis strain NZYM-JA

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Afectación del sistema cardiovascular en la infección por SARS-CoV-2

Introduction: COVID-19 is an emerging disease with global incidence, which exhibits a greater number of complications in patients with comorbidities, mainly in those with a history of cardiovascular disease.Objective: to describe the implications of COVID-19 in the cardiovascular system.Method: A review of the literature was conducted in the MEDLINE, SciELO, JAMA and Elsevier databases, recovering 35 articles, which were taken as the basis for the present review. The combination of terms using search formulas was used to retrieve articles.Development: COVID-19 can be variable in correspondence with the presentation form and accompanying symptoms, as well as the recipient's immune response. SARS-CoV-2 binds to cells through the viral spike structural protein that binds to the angiotensin-converting enzyme 2 receptor from viral receptors; therefore, hypertensive patients or those with other cardiovascular conditions have a higher risk of developing severe forms of COVID-19. Among the cardiovascular diseases associated with infection by a coronavirus, myocarditis, arrhythmias, acute myocardial infarction and heart failure stand out.Conclusions: the main cardiovascular implications in patients with COVID-19 are arrhythmia, thromboembolic disease, myocarditis, heart failure of acute onset and myocardial infarction, which condition a more serious picture of the disease. The inflammatory response, hemodynamic changes secondary to the viral process, as well as hypoxemia, constitute mechanisms of negative impact on cardiovascular health, leading to the development of acute cardiac injury.Introducción: la COVID-19 es una enfermedad emergente con incidencia global, que exhibe mayor número de complicaciones en pacientes con comorbilidades, principalmente en aquellos con antecedentes de enfermedades cardiovasculares.Objetivo: describir las implicaciones de la COVID-19 en el sistema cardiovascular.Método: Se realizó una revisión de la literatura en las bases de datos MEDLINE, SciELO, JAMA y Elsevier, recuperándose 35 artículos, los cuales se tomaron de base para la presente revisión. Se empleó la combinación de términos mediante fórmulas de búsqueda para recuperar los artículos.Desarrollo: la COVID-19 puede ser variable en correspondencia con la forma de presentación y síntomas acompañantes, así como la respuesta inmunitaria del receptor. El SARS-CoV-2  se une a las células a través de la proteína estructural viral de espiga que se une al receptor de la enzima convertidora de angiotensina 2 a partir de receptores virales; por ello, los pacientes hipertensos o  con  otras  afecciones cardiovasculares tienen un mayor riesgo de desarrollar formas severas de COVID-19.  Dentro de las afectaciones cardiovasculares asociados a la infección por un coronavirus destacan la miocarditis, arritmias, infarto agudo de miocardio e insuficiencia cardíaca.Conclusiones: Las principales implicaciones cardiovasculares en los pacientes con COVID-19 son arritmia, enfermedad tromboembólica, miocarditis, insuficiencia cardiaca de inicio agudo e infarto de miocardio, las cuales condicionan un cuadro más grave de la enfermedad. La respuesta inflamatoria, los cambios hemodinámicos secundarios al proceso viral, así como la hipoxemia, constituyen mecanismos de repercusión negativa sobre la salud cardiovascular, llevando al desarrollo de lesión cardiaca aguda.

Accretion of Planetary Material onto Host Stars

Accretion of planetary material onto host stars may occur throughout a star's life. Especially prone to accretion, extrasolar planets in short-period orbits, while relatively rare, constitute a significant fraction of the known population, and these planets are subject to dynamical and atmospheric influences that can drive significant mass loss. Theoretical models frame expectations regarding the rates and extent of this planetary accretion. For instance, tidal interactions between planets and stars may drive complete orbital decay during the main sequence. Many planets that survive their stars' main sequence lifetime will still be engulfed when the host stars become red giant stars. There is some observational evidence supporting these predictions, such as a dearth of close-in planets around fast stellar rotators, which is consistent with tidal spin-up and planet accretion. There remains no clear chemical evidence for pollution of the atmospheres of main sequence or red giant stars by planetary materials, but a wealth of evidence points to active accretion by white dwarfs. In this article, we review the current understanding of accretion of planetary material, from the pre- to the post-main sequence and beyond. The review begins with the astrophysical framework for that process and then considers accretion during various phases of a host star's life, during which the details of accretion vary, and the observational evidence for accretion during these phases.Comment: 18 pages, 5 figures (with some redacted), invited revie

Conozcamos lo mejor de la flora y fauna de la región del Ariari en el municipio de Granada, departamento del Meta. “Catarsis turística”

Esta propuesta tiene como principal objetivo dar a conocer las riquezas turísticas de la región del Ariari en el departamento del Meta en cuanto a la sensibilización de visitantes y habitantes en general, iniciando por los estudiantes de los grados décimos y undécimos de la institución Educativa General Santander del municipio de Granada, como principales promotores y gestores del cuidado y disfrute de los tesoros invaluables que ofrece la regió

Assembling a high-precision abundance catalogue of solar twins in GALAH for phylogenetic studies

Stellar chemical abundances have proved themselves a key source of information for understanding the evolution of the Milky Way, and the scale of major stellar surveys such as GALAH have massively increased the amount of chemical data available. However, progress is hampered by the level of precision in chemical abundance data as well as the visualization methods for comparing the multidimensional outputs of chemical evolution models to stellar abundance data. Machine learning methods have greatly improved the former; while the application of tree-building or phylogenetic methods borrowed from biology are beginning to show promise with the latter. Here we analyse a sample of GALAH solar twins to address these issues. We apply The Cannon algorithm to generate a catalogue of about 40,000 solar twins with 14 high precision abundances which we use to perform a phylogenetic analysis on a selection of stars that have two different ranges of eccentricities. From our analyses we are able to find a group with mostly stars on circular orbits and some old stars with eccentric orbits whose age-[Y/Mg] relation agrees remarkably well with the chemical clocks published by previous high precision abundance studies. Our results show the power of combining survey data with machine learning and phylogenetics to reconstruct the history of the Milky Way.Comment: Accepted in MNRAS journal. Associated catalog of high precision, Cannon-rederived abundances for GALAH solar twins to be made publicly available upon publication and available now upon request. See Manea et al. 2023 for a complementary, high precision, Cannon-rederived abundance catalog for GALAH red giant star