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This work applies machine learning to holistically interrogate the influence of metallurgical factors, such as chemical composition, heat treatment, and mechanical properties, on the stress corrosion cracking resistance of corrosion-resistant alloys. In particular, we explored the effect of nickel in reducing the stress corrosion cracking susceptibility in boiling magnesium chloride, arguably a controversial topic since Copson’s 1959 seminal publication. This paper offers insights into the synergies of nickel with other alloying elements that ultimately impact the resistance to stress corrosion cracking. Furthermore, a more detailed description of statistical patterns in the so-called Copson curve is provided.

The production of methane (CH4) from natural-gas hydrate deposits via molecular replacement by injected, thermodynamically more favourable, carbon dioxide (CO2) is a promising method of energy prod...

Vamos usar a teoria de Corpos de Funções Algébricas em uma variável para estudar o grupo de automorfismos de curvas de Artin-Schreier, definidas sobre um corpo K algebricamente fechado de característica positiva. Nesse processo também estudaremos os subgrupos finitos de PGL(2;K). We use the theory of Algebraic Functions Fields in one variable to study the automorphism group of Artin-Schreier curves, defined over an algebraically closed field K of positive characteristic. In this process we also study the finite subgroups of PGL(2;K).

Parrots stand out among birds because of their poor conservation status and the lack of available information on their population sizes and trends. Estimating parrot abundance is complicated by the high mobility, gregariousness, patchy distributions, and rarity of many species. Roadside car surveys can be useful to cover large areas and increase the probability of detecting spatially aggregated species or those occurring at very low densities. However, such surveys may be biased due to their inability to handle differences in detectability among species and habitats. We conducted 98 roadside surveys, covering > 57,000 km across 20 countries and the main world biomes, recording ca. 120,000 parrots from 137 species. We found that larger and more gregarious species are more easily visually detected and at greater distances, with variations among biomes. However, raw estimates of relative parrot abundances (individuals/km) were strongly correlated (r = 0.86–0.93) with parrot densities (individuals/km2) estimated through distance sampling (DS) models, showing that variability in abundances among species (>40 orders of magnitude) overcomes any potential detectability bias. While both methods provide similar results, DS cannot be used to study parrot communities or monitor the population trends of all parrot species as it requires a minimum of encounters that are not reached for most species (64% in our case), mainly the rarest and more threatened. However, DS may be the most suitable choice for some species-specific studies of common species. We summarize the strengths and weaknesses of both methods to guide researchers in choosing the best–fitting option for their particular research hypotheses, characteristics of the species studied, and logistical constraints., This research was funded by Fundación Biodiversidad (Spanish Ministerio de Medio Ambiente, project 52I.CA2109), Fundación Repsol, Spanish Ministerio de Ciencia e Innovación (Project CGL2015-71378-P), and mostly by Loro Parque Fundación (Project SEJI/2018/024).

The state-space modelling process and validation of a generalized DC/DC/AC MMC structure is presented. This structure can be used to represent two different MMC topologies that are capable of performing simultaneous AC/DC and DC/DC conversions. The DC/DC/AC models enable controlled power exchanges between two DC systems and an AC system. The time-averaged model is developed in the $\alpha\beta0-$frame, and includes all dynamics in the converter structure, barring switching harmonics. The resulting model is validated against a switched converter model implemented in PLECS. The model can be used to perform time-domain studies of the multiport converters, at a much reduced simulation time than its switched model counterpart.

Establecer el perfil multidimensional de personas con intento de suicidio. Se estudiaron 116 personas reportadas con intento de suicidio en servicios de urgencias e instituciones educativas del departamento del Huila. Diseño descriptivo; con entrevista semi-estructurada, prueba de personalidad, inventario de depresión, evaluación de alcoholismo, evaluación de ideación e intento de suicidio. El perfil multidimensional se caracterizó: adolescentes rurales, adultos citadinos; son de consideración: ama de casa, con relación de pareja estable, y personas solas, divorciadas, desempleadas. La relación neuroticismo bajo y piscoticismo alto podría ayudar a explicar que el intento de suicidio haya sido realizado de "repente" sin existir ningún síntoma previo. La estructura y dinámica familiar disfuncional están altamente asociadas a la persona con intento de suicidio.

Mutually enhancing organisms can become reciprocal determinants of their distribution, abundance, and demography and thus influence ecosystem structure and dynamics. In addition to the prevailing view of parrots (Psittaciformes) as plant antagonists, we assessed whether they can act as plant mutualists in the dry tropical forest of the Bolivian inter-Andean valleys, an ecosystem particularly poor in vertebrate frugivores other than parrots (nine species). We hypothesised that if interactions between parrots and their food plants evolved as primarily or facultatively mutualistic, selection should have acted to maximize the strength of their interactions by increasing the amount and variety of resources and services involved in particular pairwise and community-wide interaction contexts. Food plants showed different growth habits across a wide phylogenetic spectrum, implying that parrots behave as super-generalists exploiting resources differing in phenology, type, biomass, and rewards from a high diversity of plants (113 species from 38 families). Through their feeding activities, parrots provided multiple services acting as genetic linkers, seed facilitators for secondary dispersers, and plant protectors, and therefore can be considered key mutualists with a pervasive impact on plant assemblages. The number of complementary and redundant mutualistic functions provided by parrots to each plant species was positively related to the number of different kinds of food extracted from them. These mutually enhancing interactions were reflected in species-level properties (e.g., biomass or dominance) of both partners, as a likely consequence of the temporal convergence of eco-(co)evolutionary dynamics shaping the ongoing structure and organization of the ecosystem. A full assessment of the, thus far largely overlooked, parrot-plant mutualisms and other ecological linkages could change the current perception of the role of parrots in the structure, organization, and functioning of ecosystems

The IUCN Red List is challenged with assessing the conservation status of species on which reliable demographic and distribution parameters are lacking. The hotly debated SAFE index, however, measures the “species’ ability to forestall extinction” and only requires information on population size. Nonetheless, both conservation assessment systems neglect the role of non-breeding population fractions in conservation. We conducted simple surveys to ascertain the spatial and population structure and conservation threats of the Endangered red-fronted macaw Ara rubrogenys, endemic to the Bolivian Andes. The area of occupancy (ca. 2600 Km2) encompassed eight breeding and six non-breeding areas, occupied by 807 individuals. By combining population-fraction censuses with the proportion of juveniles (8.6%), we inferred a breeding population of less than 100 pairs clumped in 38–40 nesting sites, with non-breeders representing ca. 80% of the population. While this increase in data quality raises questions as to whether the species should be upgraded to Critically Endangered, the SAFE index rendered questionable guidance for conservation triage. Conservation threats were spatially identified according to spatio-temporal and life-stage population structures and seasonal changes in habitat use. Several sources of habitat loss were widespread but, contrary to expectation, habitat-use models indicated that red-fronted macaws were not tied to forest remnants. Instead, they made use of agricultural lands resulting in conflicts with farmers. Awareness campaigns should focus on a few selected locations to resolve this conflict and reduce the uptake of individuals for use as pets, as the most effective way to increase population size in the medium-term

Se relevó la avifauna de 11 localidades en el Parque Nacional y Área Natural de Manejo Integrado Serranía del Aguaragüe, provincia Gran Chaco, departamento de Tarija, Bolivia. Fueron registradas en total 272 especies de aves, 5 de ellas amenazadas (Buteogallus coronatus, Ara militaris, Amazona tucumana, Vultur gryphus y Buteogallus solitarius). Se incluye el registro de 11 especies nuevas para el departamento de Tarija y de 14 que eran conocidas por pocos registros. Se registraron 29 especies endémicas zoogeográficas, 20 pertenecientes a la región Centro de América del Sur y 9 a la región Centro de los Andes. El Parque Nacional y Área Natural de Manejo Integrado Serranía del Aguaragüe es un área importante donde convergen elementos avifaunísticos propios de las selvas de montaña provenientes del oeste y del Chaco por el este, con el aporte de grupos de aves migrantes, principalmente australes. We studied the avifauna of 11 localities of the Serranía del Aguaragüe National Park and Natural Area of Integrated Management, Gran Chaco Province, Tarija Department, Bolivia. A total of 272 species were recorded, 6 of which were threatened (Buteogallus coronatus, Ara militaris, Amazona tucumana, Vultur gryphus y Buteogallus solitarius). This study includes 11 new species records for Tarija Department and 14 that were previously known by a few records. Twenty-nine species were zoogeographical endemisms: 20 for Central South America region and 9 for Central Andes region. The Serranía del Aguaragüe National Park and Natural Area of Integrated Management is an important area with convergent avifaunistic elements belonging to western mountain forests and eastern Chaco, along with several migrant species, especially austral ones.