Solving the Pulsar Equation using Physics-Informed Neural Networks

In this study, Physics-Informed Neural Networks (PINNs) are skilfully applied to explore a diverse range of pulsar magneto-spheric models, specifically focusing on axisymmetric cases. The study successfully reproduced various axisymmetric models found in the literature, including those with non-dipolar configurations, while effectively characterizing current sheet features. Energy losses in all studied models were found to exhibit reasonable similarity, differing by no more than a factor of three from the classical dipole case. This research lays the groundwork for a reliable elliptic Partial Differential Equation solver tailored for astrophysical problems. Based on these findings, we foresee that the utilization of PINNs will become the most efficient approach in modelling three-dimensional magnetospheres. This methodology shows significant potential and facilitates an effortless generalization, contributing to the advancement of our understanding of pulsar magnetospheres.Comment: 9 pages, 8 figures, version

Modelling Force-Free Neutron Star Magnetospheres using Physics-Informed Neural Networks

Using Physics-Informed Neural Networks (PINNs) to solve a specific boundary value problem is becoming more popular as an alternative to traditional methods. However, depending on the specific problem, they could be computationally expensive and potentially less accurate. The functionality of PINNs for real-world physical problems can significantly improve if they become more flexible and adaptable. To address this, our work explores the idea of training a PINN for general boundary conditions and source terms expressed through a limited number of coefficients, introduced as additional inputs in the network. Although this process increases the dimensionality and is computationally costly, using the trained network to evaluate new general solutions is much faster. Our results indicate that PINN solutions are relatively accurate, reliable, and well-behaved. We applied this idea to the astrophysical scenario of the magnetic field evolution in the interior of a neutron star connected to a force-free magnetosphere. Solving this problem through a global simulation in the entire domain is expensive due to the elliptic solver's needs for the exterior solution. The computational cost with a PINN was more than an order of magnitude lower than the similar case solved with classical methods. These results pave the way for the future extension to 3D of this (or a similar) problem, where generalised boundary conditions are very costly to implement.Comment: 11 pages, 10 figures, submitted for publication in MNRA

Songbird dynamics under the sea : acoustic interactions between humpback whales suggest song mediates male interactions

© The Author(s), 2018. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Royal Society Open Science 5 (2018): 171298, doi:10.1098/rsos.171298.The function of song has been well studied in numerous taxa and plays a role in mediating both intersexual and intrasexual interactions. Humpback whales are among few mammals who sing, but the role of sexual selection on song in this species is poorly understood. While one predominant hypothesis is that song mediates male–male interactions, the mechanism by which this may occur has never been explored. We applied metrics typically used to assess songbird interactions to examine song sequences and movement patterns of humpback whale singers. We found that males altered their song presentation in the presence of other singers; focal males increased the rate at which they switched between phrase types (p = 0.005), and tended to increase the overall evenness of their song presentation (p = 0.06) after a second male began singing. Two-singer dyads overlapped their song sequences significantly more than expected by chance. Spatial analyses revealed that change in distance between singers was related to whether both males kept singing (p = 0.012), with close approaches leading to song cessation. Overall, acoustic interactions resemble known mechanisms of mediating intrasexual interactions in songbirds. Future work should focus on more precisely resolving how changes in song presentation may be used in competition between singing males.D.M.C. was supported by an EPA Science to Achieve Results (STAR) Fellowship for PhD research

Dynamic habitat models reflect interannual movement of cetaceans within the California current ecosystem

This modeling project was funded by the Navy, Commander, U.S. Pacific Fleet (U.S. Navy), the Bureau of Ocean Energy Management (BOEM), and by the National Oceanic and Atmospheric Administration (NOAA), National Marine Fisheries Service (NMFS), Southwest Fisheries Science Center (SWFSC). The 2018 survey was conducted as part of the Pacific Marine Assessment Program for Protected Species (PacMAPPS), a collaborative effort between NOAA Fisheries, the U.S. Navy, and BOEM to collect data necessary to produce updated abundance estimates for cetaceans in the CCE study area. BOEM funding was provided via Interagency Agreement (IAA) M17PG00025, and Navy funding via IAA N0007018MP4C560, under the Mexican permit SEMARNAT/SGPA/DGVS/013212/18. The methods used to derive uncertainty estimates were developed as part of “DenMod: Working Group for the Advancement of Marine Species Density Surface Modeling” funded by OPNAV N45 and the SURTASS LFA Settlement Agreement, and managed by the U.S. Navy’s Living Marine Resources (LMR) program under Contract No. N39430-17-C-1982. Other permits included INEGI: Oficio núm. 400./331/2018, INEGI.GMA 1.03 SAGARPA de Oficio B00.02.04.1530/2018 NMFS Permit No. 19091.The distribution of wide-ranging cetacean species often cross national or jurisdictional boundaries, which creates challenges for monitoring populations and managing anthropogenic impacts, especially if data are only available for a portion of the species’ range. Many species found off the U.S. West Coast are known to have continuous distributions into Mexican waters, with highly variable abundance within the U.S. portion of their range. This has contributed to annual variability in design-based abundance estimates from systematic shipboard surveys off the U.S. West Coast, particularly for the abundance of warm temperate species such as striped dolphin, Stenella coeruleoalba, which increases off California during warm-water conditions and decreases during cool-water conditions. Species distribution models (SDMs) can accurately describe shifts in cetacean distribution caused by changing environmental conditions, and are increasingly used for marine species management. However, until recently, data from waters off the Baja California peninsula, México, have not been available for modeling species ranges that span from Baja California to the U.S. West Coast. In this study, we combined data from 1992–2018 shipboard surveys to develop SDMs off the Pacific Coast of Baja California for ten taxonomically diverse cetaceans. We used a Generalized Additive Modeling framework to develop SDMs based on line-transect surveys and dynamic habitat variables from the Hybrid Coordinate Ocean Model (HYCOM). Models were developed for ten species: long- and short-beaked common dolphins (Delphinus delphis delphis and D. d. bairdii), Risso’s dolphin (Grampus griseus), Pacific white-sided dolphin (Lagenorhynchus obliquidens), striped dolphin, common bottlenose dolphin (Tursiops truncatus), sperm whale (Physeter macrocephalus), blue whale (Balaenoptera musculus), fin whale (B. physalus), and humpback whale (Megaptera novaeangliae). The SDMs provide the first fine-scale (approximately 9 x 9 km grid) estimates of average species density and abundance, including spatially-explicit measures of uncertainty, for waters off the Baja California peninsula. Results provide novel insights into cetacean ecology in this region as well as quantitative spatial data for the assessment and mitigation of anthropogenic impacts.Publisher PDFPeer reviewe

Microplastic occurrence and phthalate ester levels in neuston samples and skin biopsies of filter-feeding megafauna from La Paz Bay (Mexico)

The impacts of microplastics on filter feeders megafauna have recently received increased attention. These or-ganisms are potentially exposed to plastic ingestion and the release of added/sorbed contaminants during feeding activities. An assessment of microplastic abundance and the chemical impact of Phthalates esters (PAEs) were performed in neustonic samples and skin biopsies of Balaenoptera physalus and Rhincodon typus inhabiting the Gulf of California (Mexico). Sixty-eight percent of the net tows contained plastics with a maximum of 0.24 items/ m3 mainly composed of polyethylene fragments. PAE levels were detected both in environmental and skin biopsy samples, with the highest values in the fin whale specimens (5291 ng/g d.w). Plasticizer fingerprint showed a similar distribution pattern between neustonic samples and filter-feeding species, with DEHP and MBP having the highest concentrations. The detection of PAE levels confirmed their potential role as plastic tracers and give preliminary information about the toxicological status of these species feeding in La Paz Bay

Biotecnologías reproductivas en el ganado bovino: cinco décadas de investigación en México

The main bovine reproductive biotechnologies are recapitulated herein in five sections, and their historical development and current status are analyzed, including the results generated in Mexico. In the 1970s, estrus synchronization and ovulation induction began; thus, the reproductive cycle started to be controlled with the resources available at that time, based on the knowledge of bovine reproductive physiology. Over the years, hormone therapy evolved as new compounds were discovered, refining methods to standardize the effect and generating new methods for the release of hormones. The most widely used biotechnology in the world, artificial insemination, owes its expansion to advances in semen processing, among which the development of diluents, cryopreservation, semen sexing, and computer-assisted sperm analysis stand out. The embryonic era began with the development of multi-ovulation and methods for collecting, evaluating, transferring, and cryopreserving embryos. The second embryonic era came with the fully in vitro production of embryos from immature eggs and frozen sperm, known as in vitro embryo production. Great research and material resources have been invested in this procedure, rendering it a pillar of genetic improvement and productivity, in combination with two other tools: sexed semen and genomic evaluations. A golden age of in vitro embryo production is on the horizon, with the possibility to produce accurate modifications in the embryo genome, thanks to gene editing technology.A lo largo de cinco secciones, se recapitulan las principales biotecnologías reproductivas en el bovino, se analiza su desarrollo histórico, estado actual, y se incluyen resultados generados en México. En la década de 1970, se inició la sincronización estral e inducción de la ovulación donde, basados en el conocimiento de la fisiología reproductiva bovina, se empezó a controlar el ciclo reproductivo con recursos disponibles en aquel entonces. Con los años, la terapia hormonal evolucionó conforme se descubrieron nuevos compuestos, refinando métodos para estandarizar el efecto y generar nuevos métodos de liberación de las hormonas. La biotecnología más usada en el mundo, la inseminación artificial, debe su expansión a los avances en el procesamiento del semen, donde destaca el desarrollo de diluyentes, la criopreservación, el sexado del semen y el análisis espermático asistido por computadora. La era embrionaria inició con el desarrollo de la multiovulación y los métodos para colectar, evaluar, transferir y criopreservar los embriones. La segunda era embrionaria llegó con la producción de embriones completamente in vitro, partiendo de óvulos inmaduros y semen congelado, en lo que se denominó la producción in vitro de embriones. En ésta, se han invertido grandes recursos de investigación, y materiales, para hacerla un pilar del mejoramiento genético y la productividad, en combinación con otras dos herramientas, el semen sexado y las evaluaciones genómicas. Se vislumbra una época de oro de la producción in vitro de embriones con la posibilidad de modificar el genoma de embriones con precisión, gracias a la tecnología de edición de genes

Fin whale (Balaenoptera physalus) mitogenomics: A cautionary tale of defining sub-species from mitochondrial sequence monophyly

The advent of massive parallel sequencing technologies has resulted in an increase of studies based upon complete mitochondrial genome DNA sequences that revisit the taxonomic status within and among species. Spatially distinct monophyly in such mitogenomic genealogies, i.e., the sharing of a recent common ancestor among con-specific samples collected in the same region has been viewed as evidence for subspecies. Several recent studies in cetaceans have employed this criterion to suggest subsequent intraspecific taxonomic revisions. We reason that employing intra-specific, spatially distinct monophyly at non-recombining, clonally inherited genomes is an unsatisfactory criterion for defining subspecies based upon theoretical (genetic drift) and practical (sampling effort) arguments. This point was illustrated by a re-analysis of a global mitogenomic assessment of fin whales, Balaenoptera physalus spp., published by Archer et al. (2013), which proposed to further subdivide the Northern Hemisphere fin whale subspecies, B. p. physalus. The proposed revision was based upon the detection of spatially distinct monophyly among North Atlantic and North Pacific fin whales in a genealogy based upon complete mitochondrial genome DNA sequences. The extended analysis conducted in this study (1676 mitochondrial control region, 162 complete mitochondrial genome DNA sequences and 20 microsatellite loci genotyped in 380 samples) revealed that the apparent monophyly among North Atlantic fin whales reported by Archer et al. (2013) to be due to low sample sizes. In conclusion, defining sub-species from monophyly (i.e., the absence of para- or polyphyly) can lead to erroneous conclusions due to relatively 'trivial' aspects, such as sampling. Basic population genetic processes (i.e., genetic drift and migration) also affect the time to the most recent common ancestor and hence the probability that individuals in a sample are monophyletic

Measurement of the cross-section and charge asymmetry of WW bosons produced in proton-proton collisions at s=8\sqrt{s}=8 TeV with the ATLAS detector

This paper presents measurements of the $W^+ \rightarrow \mu^+\nu$ and $W^- \rightarrow \mu^-\nu$ cross-sections and the associated charge asymmetry as a function of the absolute pseudorapidity of the decay muon. The data were collected in proton--proton collisions at a centre-of-mass energy of 8 TeV with the ATLAS experiment at the LHC and correspond to a total integrated luminosity of 20.2~\mbox{fb^{-1}}. The precision of the cross-section measurements varies between 0.8% to 1.5% as a function of the pseudorapidity, excluding the 1.9% uncertainty on the integrated luminosity. The charge asymmetry is measured with an uncertainty between 0.002 and 0.003. The results are compared with predictions based on next-to-next-to-leading-order calculations with various parton distribution functions and have the sensitivity to discriminate between them.Comment: 38 pages in total, author list starting page 22, 5 figures, 4 tables, submitted to EPJC. All figures including auxiliary figures are available at https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/STDM-2017-13

Observation of associated near-side and away-side long-range correlations in √sNN=5.02 TeV proton-lead collisions with the ATLAS detector

Two-particle correlations in relative azimuthal angle (Δϕ) and pseudorapidity (Δη) are measured in √sNN=5.02  TeV p+Pb collisions using the ATLAS detector at the LHC. The measurements are performed using approximately 1  μb-1 of data as a function of transverse momentum (pT) and the transverse energy (ΣETPb) summed over 3.1<η<4.9 in the direction of the Pb beam. The correlation function, constructed from charged particles, exhibits a long-range (2<|Δη|<5) “near-side” (Δϕ∼0) correlation that grows rapidly with increasing ΣETPb. A long-range “away-side” (Δϕ∼π) correlation, obtained by subtracting the expected contributions from recoiling dijets and other sources estimated using events with small ΣETPb, is found to match the near-side correlation in magnitude, shape (in Δη and Δϕ) and ΣETPb dependence. The resultant Δϕ correlation is approximately symmetric about π/2, and is consistent with a dominant cos⁡2Δϕ modulation for all ΣETPb ranges and particle pT

Search for direct production of charginos and neutralinos in events with three leptons and missing transverse momentum in √s = 7 TeV pp collisions with the ATLAS detector

A search for the direct production of charginos and neutralinos in final states with three electrons or muons and missing transverse momentum is presented. The analysis is based on 4.7 fb−1 of proton–proton collision data delivered by the Large Hadron Collider and recorded with the ATLAS detector. Observations are consistent with Standard Model expectations in three signal regions that are either depleted or enriched in Z-boson decays. Upper limits at 95% confidence level are set in R-parity conserving phenomenological minimal supersymmetric models and in simplified models, significantly extending previous results