Higher depletion of lithium in planet host stars: no age and mass effect

Recent observational work by Israelian et al. has shown that sun-like planet host stars in the temperature range 5700K < Teff < 5850K have lithium abundances that are significantly lower than those observed for "single" field stars. In this letter we use stellar evolutionary models to show that differences in stellar mass and age are not responsible for the observed correlation. This result, along with the finding of Israelian et al., strongly suggest that the observed lithium difference is likely linked to some process related to the formation and evolution of planetary systems.Comment: 4 pages, 4 figures, letter accepted for publication in Astronomy & Astrophysic

Deep Learning Framework for Controlling Work Sequence in Collaborative Human–Robot Assembly Processes

project UIDB/EMS/00667/2020 (UNIDEMI)The human–robot collaboration (HRC) solutions presented so far have the disadvantage that the interaction between humans and robots is based on the human’s state or on specific gestures purposely performed by the human, thus increasing the time required to perform a task and slowing down the pace of human labor, making such solutions uninteresting. In this study, a different concept of the HRC system is introduced, consisting of an HRC framework for managing assembly processes that are executed simultaneously or individually by humans and robots. This HRC framework based on deep learning models uses only one type of data, RGB camera data, to make predictions about the collaborative workspace and human action, and consequently manage the assembly process. To validate the HRC framework, an industrial HRC demonstrator was built to assemble a mechanical component. Four different HRC frameworks were created based on the convolutional neural network (CNN) model structures: Faster R-CNN ResNet-50 and ResNet-101, YOLOv2 and YOLOv3. The HRC framework with YOLOv3 structure showed the best performance, showing a mean average performance of 72.26% and allowed the HRC industrial demonstrator to successfully complete all assembly tasks within a desired time window. The HRC framework has proven effective for industrial assembly applicationspublishersversionpublishe

Signatures of magnetic activity in the seismic data of solar-type stars observed by Kepler

In the Sun, the frequencies of the acoustic modes are observed to vary in phase with the magnetic activity level. These frequency variations are expected to be common in solar-type stars and contain information about the activity-related changes that take place in their interiors. The unprecedented duration of Kepler photometric time-series provides a unique opportunity to detect and characterize stellar magnetic cycles through asteroseismology. In this work, we analyze a sample of 87 solar-type stars, measuring their temporal frequency shifts over segments of length 90 days. For each segment, the individual frequencies are obtained through a Bayesian peak-bagging tool. The mean frequency shifts are then computed and compared with: 1) those obtained from a cross-correlation method; 2) the variation in the mode heights; 3) a photometric activity proxy; and 4) the characteristic timescale of the granulation. For each star and 90-d sub-series, we provide mean frequency shifts, mode heights, and characteristic timescales of the granulation. Interestingly, more than 60% of the stars show evidence for (quasi-)periodic variations in the frequency shifts. In the majority of the cases, these variations are accompanied by variations in other activity proxies. About 20% of the stars show mode frequencies and heights varying approximately in phase, in opposition to what is observed for the Sun.Comment: Accepted for publication in ApJS, 19(+86) pages, 11(+89) figures, 2(+87) table

Seismic signatures of magnetic activity in solar-type stars observed by Kepler

The properties of the acoustic modes are sensitive to magnetic activity. The unprecedented long-term Kepler photometry, thus, allows stellar magnetic cycles to be studied through asteroseismology. We search for signatures of magnetic cycles in the seismic data of Kepler solar-type stars. We find evidence for periodic variations in the acoustic properties of about half of the 87 analysed stars. In these proceedings, we highlight the results obtained for two such stars, namely KIC 8006161 and KIC 5184732.Comment: 4 pages, 1 figure, to appear in the Proceedings of the IAUS34

Population structure of Atlantic swordfish (Xiphias gladius L. 1758) (Teleostea, Xiphiidae) using mitochondrial DNA analysis: implications for fisheries management

Recent studies on Atlantic swordfish (Xiphias gladius L. 1758) genetic structure have demonstrated significant heterogeneity but the precise boundary between populations remains to be identified. In this context, genetic diversity was investigated by PCR–RFLP analysis at the control region of mitochondrial DNA (D–loop) from 274 swordfish specimens collected from five different areas of the Atlantic Ocean. The analysis of molecular variance (AMOVA) showed that genetic variation was mainly due to differences within rather than between the studied areas. Additionally, the phylogenetic analysis did not show evident relationships among haplotypes from all areas. However, low but significant FST values were recorded when comparing Equatorial samples with those from the north central and north tropical Atlantic. These results do not support a need for changing the current management boundary for the Atlantic fishery. Key words: Xiphiidae, Swordfish, Xiphias gladius, Mitochondrial DNA, Genetic variability, Atlantic Ocean.Estudios recientes sobre la estructura genética del pez espada del Atlántico (Xiphias gladius L. 1758) han demostrado una heterogeneidad significativa, pero los límites precisos entre poblaciones no han sido identificados. En este contexto, la diversidad genética se ha investigado mediante análisis PCR–RFLP en la región control de ADN mitocondrial (bucle D) de 274 peces espada recolectados en cinco zonas diferentes del océano Atlántico. El análisis de la varianza molecular (AMOVA) mostró que la variación genética se debía a diferencias en cada zona y no entre las zonas estudiadas. Además, los análisis filogenéticos no muestran relaciones evidentes entre los haplotipos de todas las zonas. A pesar de ello, al comparar las muestras ecuatoriales con las de zonas más al norte, se obtienen valores de FST bajos pero significativos. Estos resultados indican que no es necesario cambiar los límites de las zonas de gestión para la pesquería del Atlántico. Palabras clave: Xiphiidae, Pez espada, Xiphias gladius, ADN mitocondrial, Variabilidad genética, Océano Atlántico.Recent studies on Atlantic swordfish (Xiphias gladius L. 1758) genetic structure have demonstrated significant heterogeneity but the precise boundary between populations remains to be identified. In this context, genetic diversity was investigated by PCR–RFLP analysis at the control region of mitochondrial DNA (D–loop) from 274 swordfish specimens collected from five different areas of the Atlantic Ocean. The analysis of molecular variance (AMOVA) showed that genetic variation was mainly due to differences within rather than between the studied areas. Additionally, the phylogenetic analysis did not show evident relationships among haplotypes from all areas. However, low but significant FST values were recorded when comparing Equatorial samples with those from the north central and north tropical Atlantic. These results do not support a need for changing the current management boundary for the Atlantic fishery. Key words: Xiphiidae, Swordfish, Xiphias gladius, Mitochondrial DNA, Genetic variability, Atlantic Ocea

On the development of strong ridge episodes over the eastern North Atlantic

The occurrence of strong and persistent mid-latitude anticyclonic ridges over the Eastern North Atlantic is a major contributor to the occurrence of severe winter droughts over Western Iberia. We analyze the development of strong and persistent ridge episodes within 40–50°N; 40°W–5°E, which are defined as 300 hPa geopotential height anomalies above 50 gpm that persist for at least 10 consecutive days. Results suggest that the generation and maintenance of these episodes, with positive stratospheric geopotential anomalies over the North American continent and the adjacent North Pacific, are associated with an intensified polar jet. Such positive anomalies tend to detach from the main stratospheric anomaly and propagate eastwards and downwards as Rossby tropospheric waves. Furthermore, the Eastern North Atlantic ridge is generated and repeatedly reinforced until the stratospheric anomaly dissipates. Results also show evidence for waves breaking anticyclonically during the episodes, which is dynamically coherent with their persistency and quasi-stationarity

Efeito da concentração de zóosporos de Phytophthora palmivora na podridão do estipe da pupunheira.

Resumo 867