Active Learning for Computationally Efficient Distribution of Binary Evolution Simulations

Binary stars undergo a variety of interactions and evolutionary phases, critical for predicting and explaining observed properties. Binary population synthesis with full stellar-structure and evolution simulations are computationally expensive requiring a large number of mass-transfer sequences. The recently developed binary population synthesis code POSYDON incorporates grids of MESA binary star simulations which are then interpolated to model large-scale populations of massive binaries. The traditional method of computing a high-density rectilinear grid of simulations is not scalable for higher-dimension grids, accounting for a range of metallicities, rotation, and eccentricity. We present a new active learning algorithm, psy-cris, which uses machine learning in the data-gathering process to adaptively and iteratively select targeted simulations to run, resulting in a custom, high-performance training set. We test psy-cris on a toy problem and find the resulting training sets require fewer simulations for accurate classification and regression than either regular or randomly sampled grids. We further apply psy-cris to the target problem of building a dynamic grid of MESA simulations, and we demonstrate that, even without fine tuning, a simulation set of only $\sim 1/4$ the size of a rectilinear grid is sufficient to achieve the same classification accuracy. We anticipate further gains when algorithmic parameters are optimized for the targeted application. We find that optimizing for classification only may lead to performance losses in regression, and vice versa. Lowering the computational cost of producing grids will enable future versions of POSYDON to cover more input parameters while preserving interpolation accuracies.Comment: 20 pages (16 main text), 10 figures, submitted to Ap

The impact of mass-transfer physics on the observable properties of field binary black hole populations

We study the impact of mass-transfer physics on the observable properties of binary black hole populations formed through isolated binary evolution. We investigate the impact of mass-accretion efficiency onto compact objects and common-envelope efficiency on the observed distributions of $\chi_{eff}$, $M_{chirp}$ and $q$. We find that low common envelope efficiency translates to tighter orbits post common envelope and therefore more tidally spun up second-born black holes. However, these systems have short merger timescales and are only marginally detectable by current gravitational-waves detectors as they form and merge at high redshifts ($z\sim 2$), outside current detector horizons. Assuming Eddington-limited accretion efficiency and that the first-born black hole is formed with a negligible spin, we find that all non-zero $\chi_{eff}$ systems in the detectable population can come only from the common envelope channel as the stable mass-transfer channel cannot shrink the orbits enough for efficient tidal spin-up to take place. We find the local rate density ($z\simeq 0.01$) for the common envelope channel is in the range $\sim 17-113~Gpc^{-3}yr^{-1}$ considering a range of $\alpha_{CE} \in [0.2,5.0]$ while for the stable mass transfer channel the rate density is $\sim 25~Gpc^{-3}yr^{-1}$. The latter drops by two orders of magnitude if the mass accretion onto the black hole is not Eddington limited because conservative mass transfer does not shrink the orbit as efficiently as non-conservative mass transfer does. Finally, using GWTC-2 events, we constrain the lower bound of branching fraction from other formation channels in the detected population to be $\sim 0.2$. Assuming all remaining events to be formed through either stable mass transfer or common envelope channels, we find moderate to strong evidence in favour of models with inefficient common envelopes.Comment: 26 pages, 13 figures, accepted for publication in A&

La Montología Global 4D: Hacia las Ciencias Convergentes y Transdisciplinarias de Montaña a través del Tiempo y el Espacio

With mountain studies we use integrative approaches for geoliteracy about productive socioecological landscapes, and motivate further transdisciplinary research in montology. We conceived this white paper as a confluence of individual expertise and collective reasoning towards forming synergistic research clusters dealing with convergent mountain science, to advance montology to a new level, whereby innovative thinking about sustainability science and regenerative development incorporates alternative propositions for maintenance, improvement, or regeneration of living conditions of mountainscapes. We seek to use this contemporary framing of sustainability and ecological restoration as the impetus to better understand nature-culture relations, framed on lived-in mountains that operate in four dimensions (length, width, depth, and time) oriented at maximizing the cross-cutting of themes around mountains as productive socioecological systems, in a new academic institutionalized convergent unit. We conclude with a call for consilient, sustainable, regenerative development in the world’s mountains.La utilización de los estudios de montaña requiere de narrativas integradoras para la geoalfabetización sobre paisajes socioecológicos productivos y motiva más investigaciones transdisciplinares en el campo de la montología. Concebimos este artículo como la confluencia de la experiencia individual y el razonamiento colectivo hacia la formación de grupos de investigación sinérgicos que se ocupan de la ciencia de montaña convergente, para hacer avanzar la montología a un nuevo nivel, mediante el cual el pensamiento innovador sobre la ciencia de la sustentabilidad y el desarrollo regenerativo incorpora propuestas alternativas para el mantenimiento, la mejora, o regeneración de las condiciones de vida de los paisajes de montaña. Buscamos utilizar este marco contemporáneo de sustentabilidad y restauración ecológica como el ímpetu para comprender mejor las relaciones de la naturaleza y la cultura, desde una perspectiva transdisciplinar, en montañas habitadas que operan en cuatro dimensiones (largo, ancho, alto y tiempo). El artículo está orientado a potenciar la transversalidad de temáticas en torno a las montañas como sistemas socioecológicos productivos, en una nueva disciplina académica institucionalizada y convergente. Concluimos con un llamado a un desarrollo regenerativo, sustentable y consiliente en las montañas del mundo

Amazonian Amphibian Diversity Is Primarily Derived from Late Miocene Andean Lineages

The Neotropics contains half of remaining rainforests and Earth's largest reservoir of amphibian biodiversity. However, determinants of Neotropical biodiversity (i.e., vicariance, dispersals, extinctions, and radiations) earlier than the Quaternary are largely unstudied. Using a novel method of ancestral area reconstruction and relaxed Bayesian clock analyses, we reconstructed the biogeography of the poison frog clade (Dendrobatidae). We rejected an Amazonian center-of-origin in favor of a complex connectivity model expanding over the Neotropics. We inferred 14 dispersals into and 18 out of Amazonia to adjacent regions; the Andes were the major source of dispersals into Amazonia. We found three episodes of lineage dispersal with two interleaved periods of vicariant events between South and Central America. During the late Miocene, Amazonian, and Central American-Chocoan lineages significantly increased their diversity compared to the Andean and Guianan-Venezuelan-Brazilian Shield counterparts. Significant percentage of dendrobatid diversity in Amazonia and Chocó resulted from repeated immigrations, with radiations at <10.0 million years ago (MYA), rather than in situ diversification. In contrast, the Andes, Venezuelan Highlands, and Guiana Shield have undergone extended in situ diversification at near constant rate since the Oligocene. The effects of Miocene paleogeographic events on Neotropical diversification dynamics provided the framework under which Quaternary patterns of endemism evolved

Home and Online Management and Evaluation of Blood Pressure (HOME BP) using a digital intervention in poorly controlled hypertension: randomised controlled trial

Objective: The HOME BP (Home and Online Management and Evaluation of Blood Pressure) trial aimed to test a digital intervention for hypertension management in primary care by combining self-monitoring of blood pressure with guided self-management. Design: Unmasked randomised controlled trial with automated ascertainment of primary endpoint. Setting: 76 general practices in the United Kingdom. Participants: 622 people with treated but poorly controlled hypertension (&gt;140/90 mm Hg) and access to the internet. Interventions: Participants were randomised by using a minimisation algorithm to self-monitoring of blood pressure with a digital intervention (305 participants) or usual care (routine hypertension care, with appointments and drug changes made at the discretion of the general practitioner; 317 participants). The digital intervention provided feedback of blood pressure results to patients and professionals with optional lifestyle advice and motivational support. Target blood pressure for hypertension, diabetes, and people aged 80 or older followed UK national guidelines. Main outcome measures: The primary outcome was the difference in systolic blood pressure (mean of second and third readings) after one year, adjusted for baseline blood pressure, blood pressure target, age, and practice, with multiple imputation for missing values. Results: After one year, data were available from 552 participants (88.6%) with imputation for the remaining 70 participants (11.4%). Mean blood pressure dropped from 151.7/86.4 to 138.4/80.2 mm Hg in the intervention group and from 151.6/85.3 to 141.8/79.8 mm Hg in the usual care group, giving a mean difference in systolic blood pressure of −3.4 mm Hg (95% confidence interval −6.1 to −0.8 mm Hg) and a mean difference in diastolic blood pressure of −0.5 mm Hg (−1.9 to 0.9 mm Hg). Results were comparable in the complete case analysis and adverse effects were similar between groups. Within trial costs showed an incremental cost effectiveness ratio of £11 ($15, €12; 95% confidence interval £6 to £29) per mm Hg reduction. Conclusions: The HOME BP digital intervention for the management of hypertension by using self-monitored blood pressure led to better control of systolic blood pressure after one year than usual care, with low incremental costs. Implementation in primary care will require integration into clinical workflows and consideration of people who are digitally excluded. Trial registration: ISRCTN13790648

#IranVotes: Political Discourse on Iranian Twitter during the 2016 Parliamentary Elections

In this study, we map and analyze the content and structural features of the Iranian Twittersphere as exhibited over the course of the 2016 legislative elections in order to identify the communities that developed around various political, social, and cultural issues and to assess the influence of online political campaigning that emerged on the platform over the course of the election campaign. Given Iran’s ongoing efforts to control and restrict freedom of expression around numerous political, social, and cultural issues in public spaces, we are interested to assess how users make use of the uncensored space provided by Twitter to speak out about various contentious issues. We achieve this by engaging in network analysis and content analysis of tweets and media content posted over the course of the election period. Although Twitter remains blocked by the Iranian authorities, the widespread use of circumvention tools by Iranian citizens has allowed them to make use of it as a free and open space for public engagement around contentious and divisive political and social issues. Using a mixed-methods approach combining social network analysis with qualitative content analysis of election-related content of the Iranian Twittersphere during the elections, we identify and analyze 46 clusters of users ranging from human rights activists through to reformist and conservative political commentators, technology advocates, and literature enthusiasts. In addition to these interest-bound clusters, we also observe that the network is home to extensive networks of everyday users, who share jokes, idle chatter, and flirtatious messages. Although the Twittersphere hosts a significant volume of political content, it is by no means a purely political space. The intense online activity of the Iranian diaspora and the extent of its engagement with digital networks of activists and journalists inside the Islamic Republic is another major feature of the Iranian Twittersphere that we explore in this study—we observe that the level of interconnectedness between diasporic and domestic networks is remarkably high, indicating that the Iranian Twittersphere offers more than just an uncensored space for activists inside Iran, but provides Iranians in exile with the opportunity to engage with the development of political and social discourses inside the country. We find that the scale of Twitter activity amongst diaspora Iranians and more liberal segments of Iranian society has had two major impacts upon the political makeup of the Twittersphere: firstly, a general politicization of the Twittersphere; and secondly, the squeezing out of politically divergent voices—especially from conservative factions, who appear to have found their home on alternative (unblocked) social networking sites. Although it does not necessarily hold a hugely politically diverse or representative chunk of Iranian netizens, the Iranian Twittersphere does function as an important bridge to connect the country’s vast diaspora networks to politically engaged, reformist-leaning citizens living inside Iran

Alteration of volcanic deposits in the ANDRILL AND-1B core: Influence of paleodeposition, eruptive style, and magmatic composition

Alteration minerals, assemblages, and textures were studied in a 175-m-thick volcanic sequence found between 759.32 and 584.19 m below seafloor within the 1285-m-long ANDRILL (Antarctic Geological Drilling project) McMurdo Ice Shelf core (MIS AND-1B). Three main alteration zones were identified through the application of different analytical methods (optical and scanning electron microscopy, electron microprobe, and X-ray diffraction). Alteration zoning is guided by the texture of the volcanic deposits, which is in turn determined by the eruptive style, transport mechanisms, and paleodepositional conditions. In particular, alteration reflects the evolution of paleodepositional conditions from submarine or shallow water to subaerial due to the growth of a nearby volcanic edifice. The general alteration trend is also influenced by the contribution of volcanogenic sediments derived from the reworking of silica-rich pyroclasts from earlier volcanic activity

Active learning for computationally efficient distribution of binary evolution simulations

Binary stars undergo a variety of interactions and evolutionary phases, critical for predicting and explaining observations. Binary population synthesis with full simulation of stellar structure and evolution is computationally expensive, requiring a large number of mass-transfer sequences. The recently developed binary population synthesis code POSYDON incorporates grids of MESA binary star simulations that are interpolated to model large-scale populations of massive binaries. The traditional method of computing a high-density rectilinear grid of simulations is not scalable for higher-dimension grids, accounting for a range of metallicities, rotation, and eccentricity. We present a new active learning algorithm, psy-cris, which uses machine learning in the data-gathering process to adaptively and iteratively target simulations to run, resulting in a custom, high-performance training set. We test psy-cris on a toy problem and find the resulting training sets require fewer simulations for accurate classification and regression than either regular or randomly sampled grids. We further apply psy-cris to the target problem of building a dynamic grid of MESA simulations, and we demonstrate that, even without fine tuning, a simulation set of only ∼1/4 the size of a rectilinear grid is sufficient to achieve the same classification accuracy. We anticipate further gains when algorithmic parameters are optimized for the targeted application. We find that optimizing for classification only may lead to performance losses in regression, and vice versa. Lowering the computational cost of producing grids will enable new population synthesis codes such as POSYDON to cover more input parameters while preserving interpolation accuracies