Black-hole horizons as probes of black-hole dynamics I: post-merger recoil in head-on collisions

The understanding of strong-field dynamics near black-hole horizons is a long-standing and challenging prob- lem in general relativity. Recent advances in numerical relativity and in the geometric characterization of black- hole horizons open new avenues into the problem. In this first paper in a series of two, we focus on the analysis of the recoil occurring in the merger of binary black holes, extending the analysis initiated in [1] with Robinson- Trautman spacetimes. More specifically, we probe spacetime dynamics through the correlation of quantities defined at the black-hole horizon and at null infinity. The geometry of these hypersurfaces responds to bulk gravitational fields acting as test screens in a scattering perspective of spacetime dynamics. Within a 3 + 1 approach we build an effective-curvature vector from the intrinsic geometry of dynamical-horizon sections and correlate its evolution with the flux of Bondi linear momentum at large distances. We employ this setup to study numerically the head-on collision of nonspinning black holes and demonstrate its validity to track the qualita- tive aspects of recoil dynamics at infinity. We also make contact with the suggestion that the antikick can be described in terms of a "slowness parameter" and how this can be computed from the local properties of the horizon. In a companion paper [2] we will further elaborate on the geometric aspects of this approach and on its relation with other approaches to characterize dynamical properties of black-hole horizons.Comment: final version published on PR

Microscopic and Macroscopic Signatures of Antiferromagnetic Domain Walls

Magnetotransport measurements on small single crystals of Cr, the elemental antiferromagnet, reveal the hysteretic thermodynamics of the domain structure. The temperature dependence of the transport coefficients is directly correlated with the real-space evolution of the domain configuration as recorded by x-ray microprobe imaging, revealing the effect of antiferromagnetic domain walls on electron transport. A single antiferromagnetic domain wall interface resistance is deduced to be of order $5\times10^{-5}\mathrm{\mu\Omega\cdot cm^{2}}$ at a temperature of 100 K.Comment: 3 color figure

Biological evidence supports an early and complex emergence of the Isthmus of Panama.

The linking of North and South America by the Isthmus of Panama had major impacts on global climate, oceanic and atmospheric currents, and biodiversity, yet the timing of this critical event remains contentious. The Isthmus is traditionally understood to have fully closed by ca. 3.5 million years ago (Ma), and this date has been used as a benchmark for oceanographic, climatic, and evolutionary research, but recent evidence suggests a more complex geological formation. Here, we analyze both molecular and fossil data to evaluate the tempo of biotic exchange across the Americas in light of geological evidence. We demonstrate significant waves of dispersal of terrestrial organisms at approximately ca. 20 and 6 Ma and corresponding events separating marine organisms in the Atlantic and Pacific oceans at ca. 23 and 7 Ma. The direction of dispersal and their rates were symmetrical until the last ca. 6 Ma, when northern migration of South American lineages increased significantly. Variability among taxa in their timing of dispersal or vicariance across the Isthmus is not explained by the ecological factors tested in these analyses, including biome type, dispersal ability, and elevation preference. Migration was therefore not generally regulated by intrinsic traits but more likely reflects the presence of emergent terrain several millions of years earlier than commonly assumed. These results indicate that the dramatic biotic turnover associated with the Great American Biotic Interchange was a long and complex process that began as early as the Oligocene-Miocene transition

Recent and Rapid Radiation of the Highly Endangered Harlequin Frogs (Atelopus) into Central America Inferred from Mitochondrial DNA Sequences

Populations of amphibians are experiencing severe declines worldwide. One group with the most catastrophic declines is the Neotropical genus Atelopus (Anura: Bufonidae). Many species of Atelopus have not been seen for decades and all eight Central American species are considered “Critically Endangered”, three of them very likely extinct. Nonetheless, the taxonomy, phylogeny, and biogeographic history of Central American Atelopus are still poorly known. In this study, the phylogenetic relationships among seven of the eight described species in Central America were inferred based on mitochondrial DNA sequences from 103 individuals, including decades-old museum samples and two likely extinct species, plus ten South American species. Among Central American samples, we discovered two candidate species that should be incorporated into conservation programs. Phylogenetic inference revealed a ladderized topology, placing species geographically furthest from South America more nested in the tree. Model-based ancestral area estimation supported either one or two colonization events from South America. Relaxed-clock analysis of divergence times indicated that Atelopus colonized Central America prior to 4 million years ago (Ma), supporting a slightly older than traditional date for the closure of the Isthmus. This study highlights the invaluable role of museum collections in documenting past biodiversity, and these results could guide future conservation efforts

Win-Win for Dairy Farms: Heifers Raised on Pasture Reduce Cost and Produce More Milk at First Lactation

Pastures under good management promote environmental, economic, and animal welfare advantages. However, comparisons of animal performance for pasture-raised dairy heifers versus confinement-raised dairy heifers are scarce. A study was conducted to evaluate the performance of dairy heifers raised on pasture or in confinement. Heifers raised on pasture had similar body weight and age at calving and greater dry matter intake in the end of 2nd grazing season. Cost of heifers raised on pasture was 26.7% less in the first grazing season and 58.4% less in the second grazing season compared to heifers raised in confinement. Heifers raised on pasture had greater dry matter intake and milk yield through first lactation. Physiological adaptation and nutritional benefits are involved in those benefits through lactation. Mammary gland development before breeding and increased feed intake before calving might be the main drivers for the advantages found for heifers raised on pasture compared to heifers raised in confinement. However, further studies are needed to evaluate nutritional and physiological differences of heifers raised on pasture compared to heifers raised in confinement

Managing Interspecies Competition to Improve Spring Pasture

Orchardgrass (Dactylis glomerata L.) is one of the earliest maturing pasture grasses utilized in the northeastern United States. However, wet springs can delay forage harvesting resulting in advanced forage maturity and reduction in nutritive value. Chicory (Cichorium intybus L.) is a tall, upright-growing forb that shows promise as a high-energy companion crop to orchardgrass and may delay orchardgrass maturity through shading effects on plant morphology. The objective of this study was to evaluate monocultures and mixtures of orchardgrass, chicory, and white clover (Trifolium repens L.) over two consecutive springs to determine the effects of species diversity on plant maturity, nutritive characteristics, and botanical composition of forage mass. Forage monocultures and mixtures were planted in central Pennsylvania in August 2018 and were observed for two years with three harvests occurring each year (one each in spring, summer, and fall). In the first spring, orchardgrass demonstrated nine days delay in maturity when grown with chicory as compared to when grown in monocultures or in orchardgrass-white clover mixtures. Although orchardgrass was at an earlier developmental stage, fiber concentrations were similar when grown with or without chicory. Additionally, in the first spring, orchardgrass mixtures containing chicory had 1.5x greater forage mass than orchardgrass monocultures and orchardgrass-white clover mixtures. Chicory biomass was low in the second spring, likely due to winterkill following a late fall harvest the previous year, resulting in a negligible effect on orchardgrass. However, orchardgrass-chicory-white clover mixtures (even with low amounts of chicory in the second year) had the greatest forage mass and nutritive value yield over both years, indicating that these mixtures can provide greater agronomic benefits than orchardgrass monocultures

Networking the Flight of the Monarchs: An audiovisual telematic performance

Networking the Flight of the Monarchs\u27 is an audi-Networking the Flight of the Monarchs\u27 is an audi- \u27Networking the Flight of the Monarchs\u27 is an audiovisual telematic performance. Soundscapes from monarch butterfly reserves in Canada, Mexico and the USA are live-streamed from open microphones installed by Rob Mackay in 2018 and 2019, and blended with improvised performances networked in real-time from California (David Blink - hand- pan/trumpet); Mexico (Rolando Rodriguez - poetry); Canada (Jessica Rodriguez - video); and the United Kingdom (Rob Mackay - flutes and computer). Inspired by Teresa Connors’ creative practice, “ecological performativity” enacts a non- anthropocentric model, characterised as the dance of agency between living and non-living systems, human and non-human actors, and the complexity within which they are entangled [1]. This model stems from the premise that artistic practice enables different perspectives of the world and becomes an apparatus for change, promoting what Welsby considers “a long overdue ontological shift in the way we exist in the world” [2]. In this performance, multiple spatialities and temporalities are layered together, creating connections between past, present, and future, as well as multiple webs between human and non-human participants, weaving together in a dance of agency [3]. The intended effect is a kind of ‘telephenomenology’, building a sense of connectedness, embodied knowing, and empathy. ovisual telematic performanc e. Soundscapes frommonarch butterfly reserves in Canada, Mexico andthe USA are live-streamed from open microphonesinstalled by Rob Mackay in 2018 and 2019, andblended with improvised performances networked inreal-time from California (David Blink - hand-pan/trumpet); Mexico (Rolando Rodriguez - poetry);Canada (Jessica Rodriguez - video); and the UnitedKingdom (Rob Mackay - flutes and computer).Inspired by Teresa Connors’ creative practice,“ecological performativity” enacts a non-anthropocentric model, characterised as the danceof agency between living and non-living systems,human and non-human actors, and the complexitywithin which they are entangled [1]. This modelstems from the premise that artistic practice enablesdifferent perspectives of the world and becomes anapparatus for change, promoting what Welsby con-siders “a long overdue ontological shift in the waywe exist in the world” [2].In this performance, multiple spatialities and tem-poralities are layered together, creating connectionsbetween past, present, and future, as well as multi-ple webs between human and non-human partici-pants, weaving together in a dance of agency [3].The intended effect is a kind of ‘telephenomenolo-gy’, building a sense of connectedness, embodiedovisual telematic performanc e. Soundscapes frommonarch butterfly reserves in Canada, Mexico andthe USA are live-streamed from open microphonesinstalled by Rob Mackay in 2018 and 2019, andblended with improvised performances networked inreal-time from California (David Blink - hand-pan/trumpet); Mexico (Rolando Rodriguez - poetry);Canada (Jessica Rodriguez - video); and the UnitedKingdom (Rob Mackay - flutes and computer).Inspired by Teresa Connors’ creative practice,“ecological performativity” enacts a non-anthropocentric model, characterised as the danceof agency between living and non-living systems,human and non-human actors, and the complexitywithin which they are entangled [1]. This modelstems from the premise that artistic practice enablesdifferent perspectives of the world and becomes anapparatus for change, promoting what Welsby con-siders “a long overdue ontological shift in the waywe exist in the world” [2].In this performance, multiple spatialities and tem-poralities are layered together, creating connectionsbetween past, present, and future, as well as multi-ple webs between human and non-human partici-pants, weaving together in a dance of agency [3].The intended effect is a kind of ‘telephenomenolo-gy’, building a sense of connectedness, embodie

Networking the Flight of the Monarchs

\u27Networking the Flight of the Monarchs\u27 is an audiovisual telematic performance. Soundscapes from monarch butterfly reserves in Canada, Mexico and the USA are live-streamed from open microphones installed by Rob Mackay in 2018 and 2019, and blended with improvised performances networked in real-time from California (David Blink - handpan/trumpet); Mexico (Rolando Rodriguez - poetry); Canada (Jessica Rodriguez - video); and the United Kingdom (Rob Mackay - flutes and computer). Inspired by Teresa Connors’ creative practice, “ecological performativity” enacts a non- anthropocentric model, characterised as the dance of agency between living and non-living systems, human and non-human actors, and the complexity within which they are entangled [1]. This model stems from the premise that artistic practice enables different perspectives of the world and becomes an apparatus for change, promoting what Welsby considers “a long overdue ontological shift in the way we exist in the world” [2]. In this performance, multiple spatialities and temporalities are layered together, creating connections between past, present, and future, as well as multiple webs between human and non-human participants, weaving together in a dance of agency [3]. The intended effect is a kind of ‘telephenomenology’, building a sense of connectedness, embodied knowing, and empathy

Protocolo de telemedicina para la consulta psiquiatrica

En Colombia existen diversas poblaciones en zonas aisladas que no tienen acceso a servicios de salud especializados, entre ellos salud mental. La telemedicina es una herramienta que permite proporcionar estos servicios, llevando medicina especializada a un menor costo y similar calidad a través de tecnologías de la información y las comunicaciones. Como una solución a esta problemática se propuso la estructuración de un protocolo de teleconsulta psiquiátrica y la implementación de una aplicación web, con el fi n de proveer servicios de diagnóstico y control a pacientes con incidencia de enfermedades mentales. Para la realización de este proyecto se analizaron lineamientos clínicos y operacionales en servicios de telepsiquiatría, se realizó un análisis de algunas patologías de interés, se hizo un desarrollo del proceso de ingeniería de software, y por último se diseñó una evaluación técnica y clínica de la aplicación para así obtener una retroalimentación del sistema.Colombia had are several isolated populations in areas without access to specialized health services, much less on mental health. Telemedicine is a tool that allows to provide these services, bringing specialized medicine at lower costs and similar quality through information and communication technologies. As a solution to this problem, a psychiatric tele-consultation protocol and the implementation of a web application was proposed in order to provide diagnosis and follow up to patients with mental diseases. For the development of this project; clinical and operational guidelines in Telepsychiatry services were reviewed, diseases of interest were analyzed, a software engineering process was implemented, and fi nally a clinical and technical evaluation were designed in order to have a feedback for the system