Comunidades de carroñeros en el Neotrópico: patrones ecológicos y comportamentales

Programa de Doctorado Medio Ambiente y SostenibilidadUnderstanding the processes that allow several species depending on the same resource to coexist are fundamental in the maintenance of biodiversity, ultimately affecting ecosystem functions, and being a key issue in community ecology. The non-random structure of natural communities is driven by multiple biological, ecological, and evolutionary forces, and can be described by habitat utilization, resource availability, and the activity and interactions of the organisms that compose them. These interactions can be antagonistic (e.g., competition) or facilitative (e.g., mutualistic plant-pollinator). However, not all species within a network play the same ecological role or perform it with the same importance, since they will have different ecological traits. Competition between species that coexist within the same guild is particularly interesting because the similarity of their ecological niches increases competition strength. However, positive co-occurrence patterns within guilds may also emerge from facilitation processes, reducing competition and playing an important role in community structure. Carrion is an ephemeral and unpredictable resource in time and space. These characteristics allow a multitude of species to feed on the resource, even forming temporary mixed aggregations with high levels of competitive and facilitative interactions. Such dynamics make scavenger systems an ideal model for studying positive and negative processes across scales using diverse methodological approaches. This thesis focuses on describing the ecological factors and behavioral patterns that govern a scavenger community in the Neotropics, by the placement and monitoring of two carcass sizes in the field by using camera-trapping. Specifically this thesis aims to assess the following objectives: describe for the first time the scavenger community and identify the factors affecting scavenging efficiency in the Brazilian Cerrado (Chapter 3); infer interspecific processes of competition and facilitation through the study of species co-occurrence patterns in this Neotropical guild (Chapter 4); analyze possible information transmission cascades within this Neotropical scavenger community (Chapter 5); and determine factors driving temporal dynamics of scavenging successions (Chapter 6). In Chapter 3, we describe the vertebrate scavenger community composition of the Brazilian Cerrado, a biodiversity hotspot. In addition, we analyzed the effects of vegetation cover, time of carcass placement and carcass weight, on different variables related to community composition and efficiency. We documented a total of 19 vertebrate scavenging species, four species of vultures and 15 facultative scavengers. Carcass size was the most important factor affecting the scavenger assemblage and consumption patterns, while we did not find an effect of habitat or timing of carrion placement on scavenging patterns. The results show a highly diverse and efficient scavenging vertebrate community in the Brazilian Cerrado, and the need to preserve them in the face of the significant habitat transformations suffered by this biodiversity hotspot. In Chapter 4, we analyzed patterns of spatial and temporal co-occurrence between species, both qualitatively and quantitatively, and determined the activity patterns of the different scavenger species. Our results show complex competitive and facilitative relationships among scavenging species in the Brazilian Cerrado that are influenced by carcass size, and change depending on the spatial and temporal scale at which they are analyzed. The scavenger assemblages that consumed large and small carcasses were different, evidencing resource partitioning between obligate and facultative scavengers. Furthermore, as an alternative to reduce competition levels, most species showed differences in their scavenging patterns, in addition to a strong temporal segregation during carcass consumption. Regarding New World vultures, our results suggest a strong interference competition between species with clear differences in their ecological traits (e.g., size, social behavior). However, we also found evidence of facilitation processes between vulture species in the location and access to the interior of the carcasses. Our findings highlight the role of obligate scavengers both in competition and facilitation processes in this vertebrate scavenger community. To clarify the processes that result in associations between vulture species with different foraging efficiencies, in Chapter 5, we apply a survival-modelling strategy to determine the transmission of social information among different species during carrion location. The use of different senses (smell and sight) within this guild facilitates carcass location through the transmission of social information between species with different carrion foraging efficiencies. Vultures with a highly developed sense of smell play a key role in this process, as they are the first ones to arrive at the carcasses and their presence seems to serve as a visual cue for other species to locate the resource. Our study supports the local enhancement hypothesis within scavengers, whereby individuals locate carcasses by following foraging heterospecifics, also suggesting the importance of the sense of smell in the maintenance of the community structure. In Chapter 6, we perform the first in-depth analysis of the factors driving temporal dynamics of scavenging successions by using interspecific aggressions as a behavioral proxy of competition intensity. The results show that resource availability shapes behavioral interactions between species. Furthermore, facilitation was related to moments of higher tolerance (i.e., lower aggressiveness), thus reducing competition intensity and affecting community structure and dynamics. Our study highlights the importance of monitoring behaviors that are directly transferable to community function (e.g., those related to foraging and resource consumption), also considering the dynamics of succession over time. This novel framework evidences complex ephemeral successional processes characterized by a fluctuation in facilitation and competition intensity during the consumption of an unpredictable resource linked to key ecosystem processes. Finally, the general discussion (Chapter 7) addresses the implications of the findings obtained in the previous chapters, its contribution to the study of communities from a general perspective, and for scavenger assemblages, including conservation implications. Furthermore, we examine the limitations identified and outline avenues for future research aimed at comprehending the determinants of the balance between positive and negative processes among coexisting species.Comprender los procesos que permiten la coexistencia de varias especies que dependen de un mismo recurso es fundamental para el mantenimiento de la biodiversidad, lo que en última instancia afecta a las funciones ecosistémicas, siendo una cuestión clave en la ecología de comunidades. La estructura no aleatoria de las comunidades está impulsada por múltiples fuerzas biológicas, ecológicas y evolutivas, pudiendo describirse mediante la utilización del hábitat, la disponibilidad de recursos y la actividad e interacciones de los organismos que las componen. Estas interacciones pueden ser antagónicas (por ejemplo, competencia) o positivas (por ejemplo, mutualismo planta-polinizador). Sin embargo, no todas las especies de una red desempeñan el mismo papel ecológico, ni lo hacen con la misma importancia, ya que pueden tener rasgos ecológicos diferentes. La competencia entre especies que coexisten dentro del mismo gremio es especialmente interesante porque cuanto más similares son sus nichos ecológicos mayor es la competencia. Sin embargo, los patrones positivos de co-ocurrencia dentro de los gremios también pueden ser debidos a procesos de facilitación, reduciendo la competencia y desempeñando un papel fundamental en la estructura de la comunidad. La carroña es un recurso efímero e impredecible en el tiempo y el espacio. Estas características permiten que multitud de especies se alimenten de este recurso, llegando a formar agregaciones mixtas temporales con altos niveles de interacciones competitivas y de facilitación. Estas dinámicas hacen de los sistemas carroñeros un modelo ideal para estudiar procesos positivos y negativos a distintas escalas, y utilizando diversos enfoques metodológicos. Esta tesis se centra en describir los factores ecológicos y patrones de comportamiento que gobiernan una comunidad de carroñeros en el Neotrópico, mediante la colocación y seguimiento de carroñas de dos tamaños en el campo mediate fototrampeo. En concreto, esta tesis pretende evaluar los siguientes objetivos: describir por primera vez la comunidad de carroñeros e identificar los factores que afectan a la eficiencia carroñera en el Cerrado brasileño (Capítulo 3); inferir procesos interespecíficos de competencia y facilitación a través del estudio de los patrones de co-ocurrencia de especies en este gremio neotropical (Capítulo 4); analizar posibles cascadas de transmisión de información dentro de esta comunidad de carroñeros (Capítulo 5); y determinar los factores que impulsan la dinámica temporal de las sucesiones carroñeras (Capítulo 6). En el Capítulo 3 describimos la composición de la comunidad de vertebrados carroñeros del Cerrado brasileño, un punto caliente de biodiversidad. Además, analizamos los efectos de la cobertura vegetal, el momento de colocación de la carroña y su peso, sobre diferentes variables relacionadas con la composición y eficiencia de la comunidad. Documentamos un total de 19 especies de vertebrados carroñeros, cuatro especies de buitres y 15 carroñeros facultativos. El tamaño de las carroñas fue el factor más importante que afectó a la composición de la comunidad de carroñeros y a los patrones de consumo, mientras que no se observó ningún efecto del hábitat o del momento de la deposición de la carroña. Los resultados muestran una comunidad de vertebrados carroñeros altamente diversa y eficiente en el Cerrado brasileño, y la necesidad de preservarlos frente a las significativas transformaciones del hábitat que se están dando en este punto caliente de biodiversidad. En el Capítulo 4, analizamos los patrones de co-ocurrencia espacial y temporal entre especies, tanto cualitativa como cuantitativamente, y determinamos los patrones de actividad de las diferentes especies carroñeras. Nuestros resultados muestran complejas relaciones competitivas y facilitadoras entre las especies carroñeras en el Cerrado brasileño que están influenciadas por el tamaño de la carroña, y cambian dependiendo de la escala espacial y temporal a la que se analicen. Los grupos de carroñeros que consumieron carroñas grandes y pequeñas fueron diferentes, evidenciando la partición de recursos entre carroñeros obligados y facultativos. Además, como alternativa para reducir los niveles de competencia, la mayoría de las especies mostraron diferencias en sus patrones de actividad, además de una fuerte segregación temporal durante el consumo de la carroña. En cuanto a los buitres del Nuevo Mundo, nuestros resultados sugieren una fuerte competencia por interferencia entre especies, con claras diferencias en base a sus rasgos ecológicos (p. ej., tamaño, comportamiento social). Sin embargo, también encontramos evidencias de procesos de facilitación entre especies de buitres en la localización y acceso al interior de las carroñas. Nuestros hallazgos destacan el papel de los carroñeros obligados tanto en los procesos de competencia como de facilitación en esta comunidad de vertebrados carroñeros. Para entender los procesos que dan lugar a asociaciones entre especies de buitres con distintas eficiencias de búsqueda de alimento, en el Capítulo 5 aplicamos una estrategia de modelado de supervivencia para determinar la transmisión de información social entre distintas especies durante la localización de la carroña. El uso de diferentes sentidos (olfato y vista) dentro de este gremio facilita la localización de las carroñas mediante la transmisión de información social entre especies con diferentes eficiencias de forrajeo. Los buitres con un sentido del olfato muy desarrollado desempeñan un papel clave en este proceso, ya que son los primeros en localizar y llegar a las carroñas y su presencia parece servir de pista visual para que otras especies localicen el recurso. Nuestro estudio apoya la hipótesis de la “mejora local” dentro de los carroñeros, según la cual los individuos localizan las carroñas siguiendo a los heteroespecíficos que buscan alimento, sugiriendo también la importancia del sentido del olfato en el mantenimiento de la estructura de la comunidad. En el Capítulo 6, realizamos el primer análisis en profundidad de los factores que determinan la dinámica temporal de las sucesiones de carroñeros utilizando las agresiones interespecíficas como indicador conductual de la intensidad de competencia. Los resultados muestran que la disponibilidad de recursos determina las interacciones conductuales entre especies. Además, la facilitación se relacionó con momentos de mayor tolerancia (es decir, menor agresividad), reduciendo así la intensidad de la competencia y afectando a la estructura y dinámica de la comunidad. Nuestro estudio destaca la importancia de monitorizar los comportamientos que son directamente transferibles a la función de la comunidad (por ejemplo, los relacionados con la búsqueda de alimento y el consumo de recursos), considerando también la dinámica de la sucesión a lo largo del tiempo. Este novedoso marco evidencia complejos procesos dinámicos caracterizados por una fluctuación en la facilitación y la intensidad de la competencia durante el consumo de un recurso impredecible vinculado a procesos ecosistémicos clave. Finalmente, la discusión general (Capítulo 7) aborda las implicaciones de los hallazgos obtenidos en los capítulos anteriores, su contribución al estudio de las comunidades desde una perspectiva general, y para el gremio de carroñeros en particular, incluyendo las implicaciones para la conservación. Además, se examinan las limitaciones identificadas y se esbozan vías para futuras investigaciones encaminadas a comprender los determinantes del equilibrio entre procesos positivos y negativos entre especies que coexisten

On the hot interstellar medium of high-redshift galaxies

Tese de mestrado, Física (Astrofísica e Cosmologia) Universidade de Lisboa, Faculdade de Ciências, 2017At high redshift, galaxies are very different from the ones in the local Universe. They present several high ionization ultraviolet emission lines such as Civ, Oiii] and Ciii], besides Heii which is associated with young and massive stars. The energy required for the production of emission lines like Civ was once only associated to Active Galactic Nuclei (AGNs). However, photoionization models have shown that these lines can be produced by star forming galaxies (SFGs) holding very hot and young stellar populations with a low metal content. The properties of high-redshift galaxies are not fully understood and the discrimination between these galaxies and AGNs is essential for their understanding. Recently, diagnostic diagrams using ultraviolet emission lines started being developed, however they are based on single stellar populations, which cannot reproduce the spectral energy distribution of these galaxies. In this work we produce and present three sets of models of nebular emission that allow to interpret and distinguish SFGs and AGNs, using the photoionization simulation code cloudy. We created a set of cloudy models using black bodies with a broad range of temperatures (20000 - 150000 K), densities (102 - 105 cm-3) and metallicities (1 – 10-5 Zʘ), which span from ionization parameters logU ~ -1 to -4.5. This provides a set of models with well known input parameters. Models below ~ 70000K can reproduce SFGs while the ones with higher temperature go into the classical AGN regime. To simulate AGNs we create another set of models based on power laws with slopes from -1.2 to -2.0 within the same range of densities and metallicities. Thirdly, for SFGs we used the state-of-the-art binary stellar evolutionary models bpass.v2 (Binary Population And Spectral Synthesis code). It is thought that at least ~ 70% of stars live in binary systems. Binary interactions which account for rotation effects are extremely important to understand the spectral energy distribution of these galaxies. In particular, for low metallicity systems, at which binary interactions promote dynamically mass transfer between the stars contrarily to high metallicity systems where the binary tends to become a wide structure. We present emission-line ratios diagnosis diagrams based on Ciii], Oiii], Civ and Heii] using our photoionization models. These diagrams allow to discriminate between SFGs and AGNs and at the same time provide a tool for unveiling the physical properties of these sources. We apply the modelling results to a population of 10 analogues of high redshift galaxies at z ~2 - 3 selected by their UV continuum. We found that these galaxies are better described by our bpass models holding young stellar populations with ages ~ 106:4 - 106:8 yrs, ionization parameters ~ logU = -2.21 , low stellar metallicities ~ 0.2 - 0.1 Z_ and very low gas metallicities ~ 0.004 Zʘ. We used the results obtained for these galaxies to calculate optical emission lines fluxes for [Oiii], [Oii], Hα and Hβ. These emission line fluxes can probe metal poor SFGs at high redshift to be observed with upcoming telescopes such as the James Webb Space telescope, and further test the validity of bpass models to explain these sources. We then analyse 6 bright Lyα emitters at the same range of redshifts, and we found that 3 of these systems are also better described by our bpass models. They are consistent with being analogues of high redshift galaxies, in particular 2 galaxies which present young ages (~ 106:3 - 106:5 yrs), higher ionization parameter (logU = -1.84 to -1.74) and lower stellar metallicity (< 0.1 Zʘ) than the previous UV continuum selected galaxies. We then use our models to understand the absence of metal lines in bright LAEs at redshifts up to z = 6 - 7, and we conclude that most of these sources require deeper observations. Lastly, we analyse galaxies from the HiZELS survey, selected with narrow band filters by their bright H_ emission line. We analyse a total of 425 spectra obtained with follow-up VIMOS (VLT) spectroscopy and we calculated the spectroscopic redshifts of 87 galaxies and AGNs. We found bright ionization ultraviolet lines in 2 of these galaxies at z ~ 1.5 and we estimate that these galaxies present extreme properties similar to the z ~ 2 - 3 bright LAEs analysed before. Our models provide a tool to discriminate between the nature of the galaxies, and estimate their physical properties. Our results are highly important to understand the properties of young galaxies now being found at the epoch of reionization. We aim to make all our modelling results fully public so it can benefit a wider community

Towards the cross-identification of radio galaxies with machine learning and the effect of radio-loud AGN on galaxy evolution

It is now well established that active galactic nuclei (AGN) play a fundamental role in galaxy evolution. On cosmic scales, the evolution over cosmic time of the star-formation rate density and black hole accretion rate appear to be closely related, and on galactic scales, the mass of the stellar bulge is tightly correlated to the mass of the black hole. In particular, radio-loud AGN, which are characterised by powerful jets extending hundreds of kiloparsecs from the galaxy, make a significant contribution to the evolution of the most massive galaxies. There exists a correlation between the prevalence of radio-loud AGN and the stellar and black hole masses, with the stellar mass being the stronger driver of AGN activity. Furthermore, essentially all of the most massive galaxies host a radio-loud AGN. AGN feedback is the strongest candidate for driving the quenching of star-formation activity, in particular at galaxies at the highest masses, as it is capable of maintaining these galaxies as "red and dead". However, the precise mechanisms by which AGN influence galaxy evolution remain poorly understood. The anticipation of the Square Kilometre Array (SKA) brought radio astronomy into a revolutionary new era. New-generation radio telescopes have been built to develop and test new technologies while addressing different scientific questions. These have already detected a large number of sources and many previously unknown galaxies. One of these telescopes is the Low Frequency Array (LOFAR), which has been conducting an extensive survey across the entire northern sky called the LOFAR Two-Metre Sky Survey (LoTSS). In LoTSS, the source density is higher than in any existing large-area radio survey, and in less than a third of the survey, LoTSS already detected more than 4 million radio sources. The large size of the LoTSS samples already allows the separation of the AGNs into bins of stellar mass, environment, black hole mass, star formation rate, and morphology independently, thus enabling the breaking of degeneracies between the different parameters. The radio, long used to identify and study AGNs, is a powerful tool when radio sources are matched to their optically identified host galaxies. This "cross-matching" process typically depends on a combination of statistical approaches and visual inspection. For compact sources, cross-matching is traditionally achieved using statistical methods. The task becoms significantly more difficult when the radio emission is extended, split into multiple radio components, or when the host galaxy is not detected in the optical. In these cases, sources need to be inspected, radio components need to be eventually associated together into physical sources, and then radio sources need to be cross-matched with their optical and/or infrared counterparts. With recent radio continuum surveys growing massively in size, it is now extremely laborious to visually cross-match more than a small fraction of the total sources. The new high-sensitivity radio telescopes are also better at detecting complex radio structures, resulting in an increase in the number of radio sources whose radio emission is separated into different radio components. In addition, due to a higher density of objects, more compact sources can be randomly positioned close enough to resemble extended sources. Consequently, the cross-matching of radio galaxies with their optical counterparts is becoming increasingly difficult. It is crucial to minimise the extent of unnecessary inspection, with the present cross-matching systems demanding improvement. In this thesis, I use Machine Learning (ML) to investigate solutions to improve the cross-matching process. ML is a rapidly evolving technique that has recently benefited from a vast increase in data availability, increased computing power, and significantly improved algorithms. ML is gaining popularity in the field of astronomy, and it is undoubtedly the most promising technique for managing the large radio astronomy datasets, while having available at the same time the amount of data required to train ML algorithms. Part of the work in this thesis was indeed focused on creating a dataset based on visual inspections of the first data release of the LoTSS survey (LoTSS DR1) in order to train and cross-validate the ML models, and apply the results to the second data release (LoTSS DR2). I trained tree-based ML models using this dataset to determine whether a statistical match is reliable. In particular, I implemented a classifier to identify the sources for which a statistical match to optical and infrared catalogues by likelihood ratio is not reliable in order to select radio sources for visual inspection. I used the properties of the radio sources, the Gaussians that compose a source, the neighbouring radio sources, as well as the optical counterparts. The best model, a gradient boosting classifier, achieves an accuracy of 95% on a balanced dataset and 96% on real unbalanced data after optimising the classification threshold. The results were incorporated in the cross-matching of LoTSS DR2. I further present a deep learning classifier for identifying sources that require radio component association. In order to improve spatial and local information about the radio sources, I create a multi-modal model that makes use of different types of input data, with a convolutional network component of the model receiving radio images as input and a neural network component using parameters measured from the radio source and its near neighbours. The model helps to recover 94% of the sources with multiple components in balanced dataset and has an accuracy of 97% on real unbalanced data. The method has already been applied with success to properly identify sources that require component association in order to get the correct radio fluxes for AGN population studies. The ML techniques used in this work can be adapted to other radio surveys. Furthermore, ML will be crucial to dealing with the next radio surveys, in particular for source detection, identification and cross-matching, where only with reliable source identification is it possible to combine radio data with other data at different wavelengths and maximally exploit the scientific potential of the radio data. The use of deep learning, in particular testing ways of combining different data types, can bring further advantages, as it may help with the comprehension of data with different origins. This is particularly important for any upcoming data integration within the SKA. Finally, I used the results of cross-matching the LoTSS DR2 data to understand the interaction between radio-loud AGN, the host galaxy, and the surrounding environment. Specifically, the investigation focused on the properties of the hosts of radio-loud AGN, such as stellar mass, bulge mass, and black hole mass, as well as morphology and environmental factors. The results consistently support the significant influence of stellar mass on radio-AGN activity. It was found that galaxy morphology (i.e. ellipticals vs. spirals) has a negligible dependence on AGN activity unless at higher masses, but those correlate with stellar mass as well as with the environment. The most relevant factor for radio AGN prevalence, after controlling for stellar mass, emerged as higher-density environments, in particular on a global scale. These outcomes provide valuable insights into the triggering and fuelling mechanisms of radio-loud AGN, aligning with cooling flow models and improving our understanding of the phenomenon

Behavioral interactions are modulated by facilitation along a heterotrophic succession

Competition and facilitation drive ecological succession but are often hard to quantify. In this sense, behavioral data may be a key tool to analyze interaction networks, providing insights into temporal trends in facilitation and competition processes within animal heterotrophic succession. Here, we perform the first in-depth analysis of the factors driving temporal dynamics of carcass consumption by analyzing behavioral patterns (i.e., interactions) and community dynamics metrics (i.e., species richness, abundance, turnover, and diversity) in a Neotropical scavenger guild. For this purpose, we monitored goat carcasses using automatic cameras. From 573 reviewed videos, we registered 1784 intraspecific and 624 interspecific interactions, using intraspecific and interspecific aggressions (n = 2048) as a behavioral proxy of competition intensity. Our results show that resource availability shapes behavioral interactions between vultures, with a specific effect of the different species on behavioral and competition dynamics, showing the existence of a hierarchy between species. Furthermore, behavioral processes linked to carcass opening tended to be facilitative, related to moments of higher tolerance (i.e., lower aggressiveness), thus reducing competition intensity and also affecting community structure and dynamics. This novel framework demonstrates complex ephemeral successional processes characterized by a fluctuation in facilitation and competition intensity during the consumption of an unpredictable resource linked to key ecosystem processes.Lara Naves-Alegre, and Esther Sebastián-González were supported by the Generalitat Valenciana and the European Social Fund (ACIF/2019/056, SEJI/2018/024, respectively). Esther Sebastián-González also received the grant RYC2019-027216-I funded by MCIN/AEI/ 10.13039/501100011033 and by ESF Investing in Your Future

Scavenger assemblages are structured by complex competition and facilitation processes among vultures

Understanding the factors that allow multiple species to coexist and share resources is an outstanding question in community ecology. Animals that share resources tend to use different strategies to decrease potential competition, through morphological adaptations, establishment of hierarchies, behavioral adaptations or spatial or temporal segregation. The main objective of this study was to infer interspecific processes of competition and facilitation through the study of species co-occurrence patterns in a vertebrate scavenger guild in de Brazilian cerrado. We analyzed patterns of spatial and temporal co-occurrence between species pairs, both qualitatively and quantitatively, and determined the activity patterns of the different scavenger species. For this purpose, we placed and monitored 11 large (i.e. goat) and 45 small (i.e. chicken) carcasses by camera-trapping, obtaining a total of 27 448 images. Our results show complex competitive and facilitative relationships among scavenging species in the Brazilian cerrado that are influenced by carcass size and change depending on the spatial and temporal scale at which they are analyzed. The scavenger assemblages that consumed large and small carcasses were different, evidencing resource partitioning between obligate and facultative scavengers. Furthermore, as an alternative to reduce competition levels, most species showed differences in their scavenging patterns, in addition to a strong temporal segregation during carcass consumption. Regarding New World vultures, our results suggest a strong interference competition between species with clear differences in their ecological traits (e.g. size, social behavior). However, we also found evidence of facilitation processes between vulture species in the location and access to the interior of the carcasses. Our findings highlight the role of obligate scavengers both in competition and facilitation processes in this vertebrate scavenger community. Future research should focus on investigating which species play the most important role in the structure and dynamics of this community, also considering intraspecific and behavioral patterns.LNA, ZMR and ESG were supported by the Generalitat Valenciana and the European Social Fund (ACIF/2019/056, APOSTD/2019/016, SEJI/2018/024, respectively), and JASZ by funds from the Spanish Ministry of Science, Innovation and Universities and the European Regional Development Fund (RTI2018-099609-B-C21). ESG received the grant RYC2019-027216-I funded by MCIN/AEI/10.13039/501100011033 and by ESF Investing in your future. ZMR was also supported by a postdoctoral contract funded by the Junta de Andalucía (POSTDOC_21_00353)

Biomecànica de l’arquitectura muscular i potència mecànica de salt en joves

Objectiu: Analitzar les relacions i diferències en potència mecànica en salt i l’arquitectura de la musculatura extensora de les extremitats inferiors en subjectes joves segons el sexe i el nivell d’activitat física. Metodologia: S’han realitzat 3 estudis: 2 de metodològics i 1 d’aplicat. Al Primer es van comparar 2 mètodes d’avaluació de la potència de curta durada basats en salt i en pedaleig. Al Segon es va comparar el mesurament de la potència en salt mitjançant un mètode directe davant d’alguns d’indirectes. Al Tercer es va analitzar la potència de salt i l’arquitectura de la musculatura extensora d’extremitats inferiors en una població d’homes i de dones distribuïts cada un en 3 subgrups amb diferent condició física. Hi van participar 244 subjectes: 9 universitaris; 161 homes aspirants a una Facultat de Ciències de l’Esport; 12 jugadores de voleibol de la Selecció Espanyola; 12 dones i 7 homes jugadors de voleibol de Primera Divisió Nacional; 10 dones i 10 homes de Ciències de l’Esport; 12 dones i 11 homes universitaris sedentaris. Resultats i discussió:  A l’Estudi 1 les potències obtingudes amb tots dos mètodes correlacionaven entre si, però amb el salt es van obtenir valors gairebé 3 vegades superiors. A l’Estudi 2 la punta de potència amb equacions correlacionava amb l’obtingut amb plataforma de forces. No obstant això, totes les equacions han subestimat la potència respecte a la plataforma. A l’Estudi 3, la variable d’arquitectura que millor ha correlacionat amb el salt ha estat el gruix muscular del vast lateral (VL). La població d’homes ha mostrat potències més grans en salt, majors gruixos i longituds de fascicles en VL, i angles de penniació en VL i gastrocnemi lateral (GL) que no pas la de dones. Les dones han mostrat majors longituds de fascicles en GL i gastrocnemi medial (GM) que no pas els homes. Entre subgrups de diferent sexe els d’homes han mostrat més capacitat de salt que els respectius de dones. Entre els subgrups del mateix sexe s’han trobat diferències en potència de salt, però no en arquitectura muscular. Homes i dones semblen presentar diferències de partida en algunes variables d’arquitectura, que els podrien condicionar diferències en el rendiment físic en algunes activitats. Les majors potències dels homes sobre les dones al costat de les diferències en gruix i longitud de fascicles del VL entre els dos i les correlacions trobades fan pensar que l’arquitectura d’aquest ventre condiciona la potència de salt i explica el major rendiment dels homes davant les dones en el salt, però no explicaria les diferències entre subgrups del mateix sexe. Conclusions: Les diferents arquitectures dels subjectes explicarien les diferències en la capacitat de salt entre homes i dones, però no les diferències entre subgrups del mateix sexe. El VL és el ventre que major implicació ha mostrat amb la potència en salt

A large Hαα survey of star formation in relaxed and merging galaxy cluster environments at z∼0.15−0.3z\sim0.15-0.3

We present the first results from the largest H$\alpha$ survey of star formation and AGN activity in galaxy clusters. Using 9 different narrow band filters, we select $>3000$ H$\alpha$ emitters within $19$ clusters and their larger scale environment over a total volume of $1.3\times10^5$ Mpc$^3$. The sample includes both relaxed and merging clusters, covering the $0.15-0.31$ redshift range and spanning from $5\times10^{14}$ $M_{\odot}$ to $30\times10^{14}$ $M_{\odot}$. We find that the H$\alpha$ luminosity function (LF) for merging clusters has a higher characteristic density $\phi^*$ compared to relaxed clusters. $\phi^*$ drops from cluster core to cluster outskirts for both merging and relaxed clusters, with the merging cluster values $\sim0.3$ dex higher at each projected radius. The characteristic luminosity $L^*$ drops over the $0.5-2.0$ Mpc distance from the cluster centre for merging clusters and increases for relaxed objects. Among disturbed objects, clusters hosting large-scale shock waves (traced by radio relics) are overdense in H$\alpha$ emitters compared to those with turbulence in their intra-cluster medium (traced by radio haloes). We speculate that the increase in star formation activity in disturbed, young, massive galaxy clusters can be triggered by interactions between gas-rich galaxies, shocks and/or the intra-cluster medium, as well as accretion of filaments and galaxy groups. Our results indicate that disturbed clusters represent vastly different environments for galaxy evolution compared to relaxed clusters or average field environments

Unravelling the vertebrate scavenger assemblage in the Gobi Desert, Mongolia

Despite the essential role that vertebrate scavengers play in ecosystems, most studies have been conducted in Europe and North America, and there is a lack of information on vertebrate scavengers in vast regions of the world. Our aim was to describe the functioning and composition of the unknown vertebrate scavenger assemblage in the Gobi Desert, Mongolia, and determine how carcass size and habitat type affect species composition and carrion use. We monitored carcasses with camera traps and we also conducted observation points to survey the raptor community and identify the proportion of raptor species making use of the carcasses. We recorded eight vertebrate scavenger species (five birds and three mammals) by camera trap and seven raptors at observation points. Over half of the raptor species recorded at the observation points were also found feeding on carrion. The two most threatened species were only recorded in the mountain habitat. Furthermore, scavenger abundance and consumption rates were higher at large carcasses. This study highlights the importance of scavenging by raptors and other vertebrate scavengers for carrion elimination in ecosystems with extreme climatic conditions.AOT, JMPG, ZMR, LNA and ESG were supported by Generalitat Valenciana (SEJI/2018/024), ZMR and LNA also by contracts co-funded by the Generalitat Valenciana and the European Social Fund (APOSTD/2019/016 and ACIF/2019/056, respectively), and JASZ by funds from the Spanish Ministry of Science, Innovation and Universities and the European Regional Development Fund (RTI 2018-099609-B-C21)

CAPAS: A context-aware system architecture for physical activities monitoring

Attribute grammars are widely used by compiler-generators since it allows complete specifications of static semantics. They can also be applied to other fields of research, for instance, to human activities recognition. This paper aims to present CAPAS, a Context-aware system Architecture to monitor Physical ActivitieS. One of the components that is present in the architecture is the attribute grammar which is filled after the prediction is made according to the data gathered from the user through the sensors. According to some predefined rules, the physical activity is validated after an analysis on the attribute grammar, if it meets those requirements. Besides that it proposes an attribute grammar itself which should be able to be incorporated in a system in order to validate the performed physical activity.This work has been supported by FCT – Fundação˜ para a Ciência e Tecnologia within the Project Scope: ˆ UID/CEC/00319/2019

The nature of luminous Ly α emitters at z ∼ 2–3: maximal dust-poor starbursts and highly ionizing AGN

Deep narrow-band surveys have revealed a large population of faint Ly α emitters (LAEs) in the distant Universe, but relatively little is known about the most luminous sources ( LLyα≳1042.7  erg s−1; LLyα≳L∗Lyα ). Here we present the spectroscopic follow-up of 21 luminous LAEs at z ∼ 2–3 found with panoramic narrow-band surveys over five independent extragalactic fields (≈4 × 106 Mpc3 surveyed at z ∼ 2.2 and z ∼ 3.1). We use WHT/ISIS, Keck/DEIMOS, and VLT/X-SHOOTER to study these sources using high ionization UV lines. Luminous LAEs at z ∼ 2–3 have blue UV slopes ( β=−2.0+0.3−0.1 ) and high Ly α escape fractions ( 50+20−15  per cent) and span five orders of magnitude in UV luminosity (MUV ≈ −19 to −24). Many (70 per cent) show at least one high ionization rest-frame UV line such as C IV, N V, C III], He II or O III], typically blue-shifted by ≈100–200 km s−1 relative to Ly α. Their Ly α profiles reveal a wide variety of shapes, including significant blue-shifted components and widths from 200 to 4000 km s−1. Overall, 60 ± 11  per cent appear to be active galactic nucleus (AGN) dominated, and at LLyα > 1043.3 erg s−1 and/or MUV < −21.5 virtually all LAEs are AGNs with high ionization parameters (log U = 0.6 ± 0.5) and with metallicities of ≈0.5 − 1 Z⊙. Those lacking signatures of AGNs (40 ± 11  per cent) have lower ionization parameters ( logU=−3.0+1.6−0.9 and log ξion = 25.4 ± 0.2) and are apparently metal-poor sources likely powered by young, dust-poor ‘maximal’ starbursts. Our results show that luminous LAEs at z ∼ 2–3 are a diverse population and that 2×L∗Lyα and 2×M∗UV mark a sharp transition in the nature of LAEs, from star formation dominated to AGN dominated