Infrared Emission by Dust Around lambda Bootis Stars: Debris Disks or Thermally Emitting Nebulae?

We present a model that describes stellar infrared excesses due to heating of the interstellar (IS) dust by a hot star passing through a diffuse IS cloud. This model is applied to six lambda Bootis stars with infrared excesses. Plausible values for the IS medium (ISM) density and relative velocity between the cloud and the star yield fits to the excess emission. This result is consistent with the diffusion/accretion hypothesis that lambda Bootis stars (A- to F-type stars with large underabundances of Fe-peak elements) owe their characteristics to interactions with the ISM. This proposal invokes radiation pressure from the star to repel the IS dust and excavate a paraboloidal dust cavity in the IS cloud, while the metal-poor gas is accreted onto the stellar photosphere. However, the measurements of the infrared excesses can also be fit by planetary debris disk models. A more detailed consideration of the conditions to produce lambda Bootis characteristics indicates that the majority of infrared-excess stars within the Local Bubble probably have debris disks. Nevertheless, more distant stars may often have excesses due to heating of interstellar material such as in our model.Comment: 10 pages, 5 figures, 4 tables, accepted by ApJ, emulateap

Exotic tree plantations and avian conservation in northern Iberia: a view from a nest–box monitoring study

Plantaciones de árboles exóticos y conservación de la avifauna en el norte de la península ibérica: perspectiva de un estudio de seguimiento de cajas nido La expansión de plantaciones de árboles exóticos en la costa cantábrica de la península ibérica suscita preocupación por la conservación de la biodiversidad de aves, puesto que las tendencias actuales sugieren que esta región podría convertirse en un monocultivo de especies de eucalipto australiano. Para arrojar más luz sobre los factores que promueven las diferencias en las comunidades de aves entre y dentro de las plantaciones de árboles exóticos (pino de Monterrey Pinus radiata y Eucalyptus spp.) y los bosques nativos de la zona de Urdaibai (norte de España), el objetivo del presente estudio consistió en analizar (1) la forma en que el tipo de hábitat y las características de la vegetación afectan a la riqueza de especies de aves y el asentamiento de determinadas especies durante el período de cría; (2) si algunos parámetros reproductivos (p.ej. la fecha o el tamaño de puesta) varían entre los hábitats en una especie de ave generalista (el carbonero común, Parus major); y (3) la existencia de diferencias entre hábitats por lo que hace a la abundancia de una fuente clave de alimento de la que se prevé que las aves insectívoras dependan para la cría (las orugas). Nuestros resultados confirmaron que las poblaciones de eucalipto albergan las comunidades más pobres de aves y establecieron el desarrollo del sotobosque como un factor importante para el establecimiento de las especies de páridos. Asimismo, hallamos que los árboles exóticos presentaban una abundancia de orugas menor que la de los robles nativos (Quercus robur), lo que podría contribuir a explicar las diferencias observadas entre los hábitats en cuanto a la abundancia y la riqueza de aves de esta región. No obstante, no se hallaron diferencias entre los hábitats por lo que concierne a la fecha y el tamaño de puesta para el carbonero común, lo que sugiere que los posibles costes de criar en plantaciones de árboles exóticos se producirían en etapas posteriores del periodo reproductivo (p.ej. el número de pollos emplumados), una circunstancia que habrá que seguir investigando.Plantaciones de árboles exóticos y conservación de la avifauna en el norte de la península ibérica: perspectiva de un estudio de seguimiento de cajas nido La expansión de plantaciones de árboles exóticos en la costa cantábrica de la península ibérica suscita preocupación por la conservación de la biodiversidad de aves, puesto que las tendencias actuales sugieren que esta región podría convertirse en un monocultivo de especies de eucalipto australiano. Para arrojar más luz sobre los factores que promueven las diferencias en las comunidades de aves entre y dentro de las plantaciones de árboles exóticos (pino de Monterrey Pinus radiata y Eucalyptus spp.) y los bosques nativos de la zona de Urdaibai (norte de España), el objetivo del presente estudio consistió en analizar (1) la forma en que el tipo de hábitat y las características de la vegetación afectan a la riqueza de especies de aves y el asentamiento de determinadas especies durante el período de cría; (2) si algunos parámetros reproductivos (p.ej. la fecha o el tamaño de puesta) varían entre los hábitats en una especie de ave generalista (el carbonero común, Parus major); y (3) la existencia de diferencias entre hábitats por lo que hace a la abundancia de una fuente clave de alimento de la que se prevé que las aves insectívoras dependan para la cría (las orugas). Nuestros resultados confirmaron que las poblaciones de eucalipto albergan las comunidades más pobres de aves y establecieron el desarrollo del sotobosque como un factor importante para el establecimiento de las especies de páridos. Asimismo, hallamos que los árboles exóticos presentaban una abundancia de orugas menor que la de los robles nativos (Quercus robur), lo que podría contribuir a explicar las diferencias observadas entre los hábitats en cuanto a la abundancia y la riqueza de aves de esta región. No obstante, no se hallaron diferencias entre los hábitats por lo que concierne a la fecha y el tamaño de puesta para el carbonero común, lo que sugiere que los posibles costes de criar en plantaciones de árboles exóticos se producirían en etapas posteriores del periodo reproductivo (p.ej. el número de pollos emplumados), una circunstancia que habrá que seguir investigando.The spread of exotic tree plantations on the North Atlantic coast of the Iberian peninsula raises concern regarding the conservation of avian biodiversity as current trends suggest this region might become a monoculture of Australian Eucalyptus species. To shed more light on the factors promoting differences in avian communities between and within exotic tree (Monterey Pine Pinus radiata and Eucalyptus spp.) plantations and native forests in the Urdaibai area (northern Spain), this study aimed to explore (1) how the type of habitat and vegetation characteristics affect bird species richness and the settlement of some particular species during the breeding period, (2) if some reproductive parameters (i.e. egg–laying date and clutch size) vary among habitats in a generalist bird species (the Great Tit Parus major), and (3) the existence of differences among habitats in the abundance of a key food resource on which some insectivorous birds are expected to rely upon for breeding (i.e. caterpillars). Our results confirmed that Eucalyptus stands house the poorest bird communities, and identified understory development as an important determinant for the establishment of titmice species. Furthermore, we found that exotic trees showed lower caterpillar abundance than native Oak trees (Quercus robur), which might contribute to explain observed differences among habitats in bird abundance and richness in this region. However, we did not find differences among habitats in egg–laying date and clutch size for the Great Tit, suggesting that the potential costs of breeding in exotic tree plantations would occur in later stages of the reproductive period (e.g. number of nestlings fledged), a circumstance that will require further research

Online Optimization of LTI Systems Under Persistent Attacks: Stability, Tracking, and Robustness

We study the stability properties of the interconnection of an LTI dynamical plant and a feedback controller that generates control signals that are compromised by a malicious attacker. We consider two classes of controllers: a static output-feedback controller, and a dynamical gradient-flow controller that seeks to steer the output of the plant towards the solution of a convex optimization problem. We analyze the stability of the closed-loop system under a class of switching attacks that persistently modify the control inputs generated by the controllers. The stability analysis leverages the framework of hybrid dynamical systems, Lyapunov-based arguments for switching systems with unstable modes, and singular perturbation theory. Our results reveal that under a suitable time-scale separation, the stability of the interconnected system can be preserved when the attack occurs with "sufficiently low frequency" in any bounded time interval. We present simulation results in a power-grid example that corroborate the technical findings

Metabolic Syndrome: An Overview on Its Genetic Associations and Gene-Diet Interactions

Metabolic syndrome (MetS) is a cluster of cardiometabolic risk factors that includes central obesity, hyperglycemia, hypertension, and dyslipidemias and whose inter-related occurrence may increase the odds of developing type 2 diabetes and cardiovascular diseases. MetS has become one of the most studied conditions, nevertheless, due to its complex etiology, this has not been fully elucidated. Recent evidence describes that both genetic and environmental factors play an important role on its development. With the advent of genomic-wide association studies, single nucleotide polymorphisms (SNPs) have gained special importance. In this review, we present an update of the genetics surrounding MetS as a single entity as well as its corresponding risk factors, considering SNPs and gene-diet interactions related to cardiometabolic markers. In this study, we focus on the conceptual aspects, diagnostic criteria, as well as the role of genetics, particularly on SNPs and polygenic risk scores (PRS) for interindividual analysis. In addition, this review highlights future perspectives of personalized nutrition with regard to the approach of MetS and how individualized multiomics approaches could improve the current outlook

Characterizing Cosmic-Ray Propagation in Massive Star-forming Regions: The Case of 30 Doradus and the Large Magellanic Cloud

Using infrared, radio, and γ-ray data, we investigate the propagation characteristics of cosmic-ray (CR) electrons and nuclei in the 30 Doradus (30 Dor) star-forming region in the Large Magellanic Cloud (LMC) using a phenomenological model based on the radio-far-infrared correlation within galaxies. Employing a correlation analysis, we derive an average propagation length of ~100-140 pc for ~3 GeV CR electrons resident in 30 Dor from consideration of the radio and infrared data. Assuming that the observed γ-ray emission toward 30 Dor is associated with the star-forming region, and applying the same methodology to the infrared and γ-ray data, we estimate a ~20 GeV propagation length of 200-320 pc for the CR nuclei. This is approximately twice as large as for ~3 GeV CR electrons, corresponding to a spatial diffusion coefficient that is ~4 times higher, scaling as (R/GV)δ with δ ≈ 0.7-0.8 depending on the smearing kernel used in the correlation analysis. This value is in agreement with the results found by extending the correlation analysis to include ~70 GeV CR nuclei traced by the 3-10 GeV γ-ray data (δ ≈ 0.66 ± 0.23). Using the mean age of the stellar populations in 30 Dor and the results from our correlation analysis, we estimate a diffusion coefficient D_R ≈ (0.9-1.0) × 10^(27)(R/GV)0.7 cm^(2) s^(–1). We compare the values of the CR electron propagation length and surface brightness for 30 Dor and the LMC as a whole with those of entire disk galaxies. We find that the trend of decreasing average CR propagation distance with increasing disk-averaged star formation activity holds for the LMC, and extends down to single star-forming regions, at least for the case of 30 Dor

FGF21 serum levels are related to insulin resistance, metabolic changes and obesity in Mexican people living with HIV (PLWH).

Antiretroviral therapy has significantly improved prognosis in treatment against HIV infection, however, prolonged exposure is associated to cardiovascular diseases, lipodystrophy, type 2 diabetes, insulin resistance, metabolic alteration, as obesity which includes the accumulation of oxidative stress in adipose tissue. FGF21 is a peptide hormone that is known to regulate glucose and lipid metabolism. FGF21 is expressed and secreted primarily in the liver and adipose tissue, promoting oxidation of glucose/fatty acids and insulin sensitivity. Alterations in FGF21 may be associated with the development of insulin resistance, metabolic syndrome and cardiovascular disease. We hypothesized that FGF21 protein levels are associated with metabolic abnormalities, placing special attention to the alterations in relation to the concurrence of overweight/obesity in people living with HIV (PLWH)