A census of Herbig Ae/Be stars: new candidates and analysis from a Gaia perspective

Herbig Ae/Be stars are pre-main sequence sources, canonically defined as having masses 2 Msun < M < 10 Msun, which are key to understanding the differences in formation mechanisms between low- and high-mass stars. The study of the general properties of these objects is hampered by the lack of a well-defined, homogeneous sample, and because few and mostly serendipitously discovered sources are known. As a consequence, many open problems involving high-mass star formation suffer from biases and lack of completeness. I study the general properties of the 252 known and proposed Herbig Ae/Be stars with parallaxes from Gaia DR2 at the start of this doctoral thesis. High-mass stars were found to have a much smaller infrared excess and optical variability compared to lower-mass stars, with the break at around 7 Msun. Different or differently acting (dust-) disc-dispersal mechanisms are proposed for this break. The variability indicator developed in this dissertation shows that approximately 25% of all Herbig Ae/Be stars are strongly variable. Evidence is provided to support the hypothesis that this variability is in most cases due to asymmetric dusty disc structures seen edge-on. Using that well-characterised sample of Herbig Ae/Be stars as a training sample for a bespoke machine learning algorithm, a homogeneous and well-defined catalogue of 8470 new pre-main sequence candidates was obtained. In parallel, a catalogue of 693 new classical Be candidates was produced. At least 1361 sources are potentially new Herbig Ae/Be stars according to their position in the Hertzsprung-Russell diagram. This increases the number of known objects of the class by an order of magnitude. In addition, I discuss the results of independent spectroscopic observations conducted for a selection of 145 new Herbig Ae/Be and 14 new classical Be stars. These independent observations further confirm the quality and the accuracy of the classification. I conclude with an analysis of the general properties of the new catalogues that validates the results and conclusions obtained for the set of previously known Herbig Ae/Be stars

Conditional Expression of RNase P in the CyanobacteriumSynechocystis sp. PCC6803 Allows Detection of Precursor RNAs

We have constructed a strain (CT1) that expresses RNase P conditionally with the aim to analyze the in vivotRNA processing pathway and the biological role that RNase P plays inSynechocystis 6803. In this strain, the rnpBgene, coding for the RNA subunit of RNase P, has been placed under the control of the petJ gene promoter (PpetJ), which is repressed by copper, cell growth, and accumulation of RNase P RNA is inhibited in CT1 after the addition of copper, indicating that the regulation by copper is maintained in the chimerical PpetJ -rnpB gene and that RNase P is essential for growth in Synechocystis. We have analyzed several RNAs by Northern blot and primer extension in CT1. Upon addition of copper to the culture medium, precursors of the mature tRNAs are detected. Furthermore, our results indicate that there is a preferred order in the action of RNase P when it processes a dimeric tRNA precursor. The precursors detected are 3′-processed, indicating that 3′ processing can occur before 5′ processing by RNase P. The size of the precursors suggests that the terminal CCA sequence is already present before RNase P processing. We have also analyzed other potential RNase P substrates, such as the precursors of tmRNA and 4.5 S RNA. In both cases, accumulation of larger than mature size RNAs is observed after transferring the cells to a copper-containing medium

Antioxidant and antiproliferative activities of the essential oils from Thymbra capitata and Thymus Species grown in Portugal

The antioxidant and antiproliferative activities of the essential oils from Thymbra capitata and Thymus species grown in Portugal were evaluated. Thymbra and Thymus essential oils were grouped into two clusters: Cluster I in which carvacrol, thymol, p-cymene, alpha-terpineol, and gamma-terpinene dominated and Cluster II in which thymol and carvacrol were absent and the main constituent was linalool. The ability for scavenging ABTS(center dot+) and peroxyl free radicals as well as for preventing the growth of THP-1 leukemia cells was better in essential oils with the highest contents of thymol and carvacrol. These results show the importance of these two terpene-phenolic compounds as antioxidants and cytotoxic agents against THP-1 cells.Fundacao para a Ciencia e Tecnologia (FCT) [Pest-OE/EQB/LA0023/2011

Cavity losses estimation in CSP applications

AIP Conference Proceedings, 2033, Nov. 2018, Article number 210007-1-210007-8Estimations of convection and radiation cavity losses in two common CSP applications have been analyzed; a cavity in a solar tower plant for high temperature (800 K) and in a down facing cavity in a Fresnel configuration for medium temperature (350 K) applications. An analysis regarding the effect of the configuration, geometry and the presence of wind has been also carried out.Ministerio de Ciencia e Innovación MTM2015-65608-PJunta de Andalucía Consejería de Economía y Conocimiento P12-FQM-1658Ministerio de Economía, Industria y Competitividad DPI2016-78887-C3-1-

Percepción del personal médico de atención primaria de salud acerca de sus funciones, formación y conocimientos en materia de salud laboral

ObjetivosEvaluar la percepción que el profesional médico de atención primaria de salud (PMAPS) tiene sobre sus funciones en prevención de riesgos laborales (PRL), así como sus conocimientos y habilidades en materia de salud laboral (SL).DiseñoEstudio descriptivo, transversal.EmplazamientoDepartamento de Salud 20 de la provincia de Alicante.ParticipantesTodos los PMAPS (n=104), con una participación del 80% (n=83).Mediciones principalesLos participantes autocumplimentaron un cuestionario específicamente desarrollado para el estudio. Se establecieron 16 cuestiones que abarcaban funciones en PRL y capacitación para desarrollarlas, así como cantidad y utilidad de formación recibidas en materia de SL.ResultadosEl PMAPS no percibe que tenga funciones en materia de PRL (mediana [Me], 2; rango intercuartílico [RI], 1-3). En mayor medida se consideró capacitado para identificar el origen laboral o no de una enfermedad atendida en su consulta (Me, 3; RI, 3-4). La formación en SL durante la licenciatura de medicina junto con la vía MIR se han identificado como las de menor cuantía (el 55,4 y el 60% de los entrevistados puntuaron en el valor 1 del cuestionario). EL PMAPS claramente ha considerado que una mayor formación en SL le ayudaría en su actividad diaria profesional; se obtuvieron puntuaciones de tipo alto (opciones de respuesta mayores o iguales a 4) en más del 70% de los entrevistados.ConclusionesEs necesario que se fomente la formación en SL para que el PMAPS se sienta parte integrante del personal sanitario con funciones en PRL y pueda adquirir los conocimientos y habilidades necesarios en materia de SL para su práctica médica habitual.ObjectivesTo evaluate the perception of primary health care medical staff (PHCMS) have on their functions in occupational risk prevention (ORP), as well as their knowledge and skills on the subject of occupational health (OH).DesignDescriptive cross-sectional study.SettingHealth Department 20 of Alicante province, Spain.ParticipantsAll PHCMS (N=104), with a participation of 80% (N=83).Primary MeasurementsThe participants self-completed a questionnaire specifically developed for the study. Sixteen questions were established and covered functions in ORP and skills for developing them, as well as the amount and usefulness of training received on the subject of OH.ResultsThe PHCMS did not perceive that they had functions as regards ORP (median [Me], 2; interquartile range [IR], 1-3). To a greater extent they considered themselves capable of identifying whether an illness seen in their clinic was of work origin or not (Me, 3; IR, 3-4).Training in OH as a medical student and in their medical internship (MIR) was identified as of minor importance (55.4% and 60%, respectively, of those surveyed scored a value of 1 in the questionnaire). The PHCMS obviously considered that better training in OH would help them in their daily professional activity. High scores were obtained for this (response options greater than or equal to 4) in more than 70% of the interviewees.ConclusionsTraining in OH must be encouraged so that PHCMS are seen to be health personnel with functions in ORP and are able to acquire the necessary knowledge and skills in OH for their routine medical practice

The M˙\dot{M}--MdiskM_{\rm{disk}} relationship for Herbig Ae/Be stars: a lifetime problem for disks with low masses?

The accretion of material from protoplanetary disks onto their central stars is a fundamental process in the evolution of these systems and a key diagnostic in constraining the disk lifetime. We analyze the relationship between the stellar accretion rate and the disk mass in 32 intermediate-mass Herbig Ae/Be systems and compare them to their lower-mass counterparts, T Tauri stars. We find that the $\dot{M}$--$M_{\rm{disk}}$ relationship for Herbig Ae/Be stars is largely flat at $\sim$10$^{-7}$ M$_{\odot}$ yr$^{-1}$ across over three orders of magnitude in dust mass. While most of the sample follows the T Tauri trend, a subset of objects with high accretion rates and low dust masses are identified. These outliers (12 out of 32 sources) have an inferred disk lifetime of less than 0.01 Myr and are dominated by objects with low infrared excess. This outlier sample is likely identified in part by the bias in classifying Herbig Ae/Be stars, which requires evidence of accretion that can only be reliably measured above a rate of $\sim$10$^{-9}$ M$_{\odot}$ yr$^{-1}$ for these spectral types. If the disk masses are not underestimated and the accretion rates are not overestimated, this implies that these disks may be on the verge of dispersal, which may be due to efficient radial drift of material or outer disk depletion by photoevaporation and/or truncation by companions. This outlier sample likely represents a small subset of the larger young, intermediate-mass stellar population, the majority of which would have already stopped accreting and cleared their disks.Comment: 16 pages, 3 figures, accepted to A

Clustering properties of intermediate and high-mass Young Stellar Objects

We have selected 337 intermediate and high-mass YSOs ($1.5$ to $20$ M$_{\odot}$) well-characterised with spectroscopy. By means of the clustering algorithm HDBSCAN, we study their clustering and association properties in the Gaia DR3 catalogue as a function of stellar mass. We find that the lower mass YSOs ($1.5-4$ M$_{\odot}$) have clustering rates of $55-60\%$ in Gaia astrometric space, a percentage similar to the one found in the T Tauri regime. However, intermediate-mass YSOs in the range $4-10$ M$_{\odot}$ show a decreasing clustering rate with stellar mass, down to $27\%$. We find tentative evidence suggesting that massive YSOs ($>10$ M$_{\odot}$) often appear $-$yet not always$-$ clustered. We put forward the idea that most massive YSOs form via a mechanism that demands many low-mass stars around them. However, intermediate-mass YSOs form in a classical core-collapse T Tauri way, yet they do not appear often in the clusters around massive YSOs. We also find that intermediate and high-mass YSOs become less clustered with decreasing disk emission and accretion rate. This points towards an evolution with time. For those sources that appear clustered, no major correlation is found between their stellar properties and the cluster sizes, number of cluster members, cluster densities, or distance to cluster centres. In doing this analysis, we report the identification of 55 new clusters. We present tabulated all the derived cluster parameters for the considered intermediate and high-mass YSOs.Comment: Accepted for publication in The Astronomical Journal on August 18th, 2023. Table 1 and the new clusters can be provided upon reques

Pro‑vegetarian food patterns and cardiometabolic risk in the PREDIMED‑Plus study: a cross‑sectional baseline analysis

Purpose We explored the cross-sectional association between the adherence to three diferent provegetarian (PVG) food patterns defned as general (gPVG), healthful (hPVG) and unhealthful (uPVG), and the cardiometabolic risk in adults with metabolic syndrome (MetS) of the PREDIMED-Plus randomized intervention study. Methods We performed a cross-sectional analysis of baseline data from 6439 participants of the PREDIMED-Plus rand omized intervention study. The gPVG food pattern was built by positively scoring plant foods (vegetables/fruits/legumes/ grains/potatoes/nuts/olive oil) and negatively scoring, animal foods (meat and meat products/animal fats/eggs/fsh and seafood/dairy products). The hPVG and uPVG were generated from the gPVG by adding four new food groups (tea and cof fee/fruit juices/sugar-sweetened beverages/sweets and desserts), splitting grains and potatoes and scoring them diferently. Multivariable-adjusted robust linear regression using MM-type estimator was used to assess the association between PVG food patterns and the standardized Metabolic Syndrome score (MetS z-score), a composed index that has been previously used to ascertain the cardiometabolic risk, adjusting for potential confounders. Results A higher adherence to the gPVG and hPVG was associated with lower cardiometabolic risk in multivariable models. The regression coefcients for 5th vs. 1st quintile were − 0.16 (95% CI: − 0.33 to 0.01) for gPVG (p trend: 0.015), and − 0.23 (95% CI: − 0.41 to − 0.05) for hPVG (p trend: 0.016). In contrast, a higher adherence to the uPVG was associated with higher cardiometabolic risk, 0.21 (95% CI: 0.04 to 0.38) (p trend: 0.019). Conclusion Higher adherence to gPVG and hPVG food patterns was generally associated with lower cardiovascular risk, whereas higher adherence to uPVG was associated to higher cardiovascular risk

The Radial Distribution and Excitation of H2 around Young Stars in the HST-ULLYSES Survey

The spatial distribution and evolution of gas in the inner 10 au of protoplanetary disks form the basis for estimating the initial conditions of planet formation. Among the most important constraints derived from spectroscopic observations of the inner disk are the radial distributions of the major gas phase constituents, how the properties of the gas change with inner disk dust evolution, and how chemical abundances and excitation conditions are influenced by the high-energy radiation from the central star. We present a survey of the radial distribution, excitation, and evolution of inner disk molecular hydrogen (H$_{2}$) obtained as part of the $HST$/ULLYSES program. We analyze far-ultraviolet spectroscopy of 71 (63 accreting) pre-main sequence systems in the ULLYSES DR5 release to characterize the H$_{2}$ emission lines, H$_{2}$ dissociation continuum emission, and major photochemical/disk evolution driving UV emissions (Ly$\alpha$, UV continuum, and C IV). We use the widths of the H$_{2}$ emission lines to show that most fluorescent H$_{2}$ arises between 0.1 - 1.4 au from the parent star, and show positive correlations of the average emitting radius with the accretion luminosity and with the dust disk mass. We find a strong correlation between H$_{2}$ dissociation emission and both the accretion-dominated Ly$\alpha$ luminosity and the inner disk dust clearing, painting a picture where water molecules in the inner 3 au are exposed to and dissociated by strong Ly$\alpha$ emission as the opacity of the inner disk declines with time.Comment: 19 pages, 11 figures. Accepted to the Astronomical Journa

Pro-vegetarian food patterns and cardiometabolic risk in the PREDIMED-Plus study: a cross-sectional baseline analysis

Purpose We explored the cross-sectional association between the adherence to three different provegetarian (PVG) food patterns defined as general (gPVG), healthful (hPVG) and unhealthful (uPVG), and the cardiometabolic risk in adults with metabolic syndrome (MetS) of the PREDIMED-Plus randomized intervention study. Methods We performed a cross-sectional analysis of baseline data from 6439 participants of the PREDIMED-Plus randomized intervention study. The gPVG food pattern was built by positively scoring plant foods (vegetables/fruits/legumes/grains/potatoes/nuts/olive oil) and negatively scoring, animal foods (meat and meat products/animal fats/eggs/fish and seafood/dairy products). The hPVG and uPVG were generated from the gPVG by adding four new food groups (tea and coffee/fruit juices/sugar-sweetened beverages/sweets and desserts), splitting grains and potatoes and scoring them differently. Multivariable-adjusted robust linear regression using MM-type estimator was used to assess the association between PVG food patterns and the standardized Metabolic Syndrome score (MetS z-score), a composed index that has been previously used to ascertain the cardiometabolic risk, adjusting for potential confounders. Results A higher adherence to the gPVG and hPVG was associated with lower cardiometabolic risk in multivariable models. The regression coefficients for 5th vs. 1st quintile were − 0.16 (95% CI: − 0.33 to 0.01) for gPVG (p trend: 0.015), and − 0.23 (95% CI: − 0.41 to − 0.05) for hPVG (p trend: 0.016). In contrast, a higher adherence to the uPVG was associated with higher cardiometabolic risk, 0.21 (95% CI: 0.04 to 0.38) (p trend: 0.019). Conclusion Higher adherence to gPVG and hPVG food patterns was generally associated with lower cardiovascular risk, whereas higher adherence to uPVG was associated to higher cardiovascular risk