The well-posedness of the Cauchy problem for self-interacting vector fields

We point out that the initial-value (Cauchy) problem for self-interactingvector fields presents the same well-posedness issues as for first-orderderivative self-interacting scalar fields (often referred to as $k$-essence).For the latter, suitable strategies have been employed in the last few years tosuccessfully evolve the Cauchy problem at the level of the infrared theory,without the need for an explicit ultraviolet completion. We argue that the verysame techniques can also be applied to self-interacting vector fields, avoidinga number of issues and "pathologies" recently found in the literature.<br

El uso de la realidad virtual y los videojuegos para el aprendizaje de las civilizaciones griega, egipcia y vikinga en el aula

This article presents a didactic proposal for third cycle of primary education that is built from a Final Degree Project and that has been put into practice. The proposal is related to the learning of different aspects of Greek, Viking and Egyptian cultures. The main objective of this article is to present a didactic planning for the learning of these civilizations from a playful and innovative perspective in which virtual reality and video games are used, including the most relevant results of its implementation. The methodology of the proposal is based on gamification and game-based learning (ABJ). The choice of this methodology is based on the facilities offered by both the expansion of technological development and the use of applications (apps) and video games in the daily life of students; supported by previous studies that show the benefits of the use of these technologies in teaching social sciences and history. The implementation is developed through a sequence of activities spanning several sessions in which, among other tasks, the video games Assassin's Creed: Discovery Tour, for exploration tasks, and Minecraft Education Edition, for representation tasks, are used. As for the results of the implementation, the proposal has been successful in its development, obtaining a high degree of achievement of the proposed didactic objectives and not encountering serious difficulties during the teaching-learning process.En el presente artículo se presenta una propuesta didáctica para tercer ciclo de educación primaria que se construye a partir de un Trabajo de Fin de Grado y que ha sido llevada a la práctica. La propuesta está relacionada con el aprendizaje de diferentes aspectos de las culturas griega, vikinga y egipcia. El objetivo central de este artículo es presentar una planificación didáctica para el aprendizaje de estas civilizaciones desde una perspectiva lúdica e innovadora en la cual se hace uso de la realidad virtual y los videojuegos; incluyendo además los resultados más relevantes de su puesta en práctica. La metodología de la propuesta está basada en la gamificación y el aprendizaje basado en juegos (ABJ). La elección de esta metodología se sustenta en las facilidades que ofrecen tanto la expansión del desarrollo tecnológico como el uso de las aplicaciones (app) y videojuegos en la vida cotidiana de los estudiantes; apoyándose en estudios previos que muestran los beneficios del uso de estas tecnologías en enseñanza de las ciencias sociales y de la historia. La puesta en práctica se desarrolla a través de una secuencia de actividades que abarca varias sesiones y en las que, entre otras tareas, se hace uso de los videojuegos Assassin’s Creed: Discovery Tour, para tareas de exploración, y Minecraft Education Edition, para tareas de representación. En cuanto a los resultados de la puesta en práctica, la propuesta ha sido exitosa en su desarrollo, obteniéndose un alto grado de consecución de los objetivos didácticos propuestos y no encontrando dificultades graves durante el proceso de enseñanza-aprendizaj

Exact, Born–Oppenheimer, and quantum-chemistry-like calculations in helium clusters doped with light molecules: The He2N2(X) system

9 pages, 2 figures, 4 tables.-- PACS nrs.: 34.20.-b; 31.50.-x; 31.15.A-; 33.15.Mt; 33.20.Vq; 36.40.-c.Helium clusters doped with diatomic molecules, He(N)–BC, have been recently studied by means of a quantum-chemistry-like approach. The model treats He atoms as “electrons” and dopants as “nuclei” in standard electronic structure calculations. Due to the large mass difference between He atoms and electrons, and to the replacement of Coulomb interactions by intermolecular potentials, it is worth assessing up to what extent are the approximations involved in this model, i.e., decoupling of the BC rotation from the He-atom orbital angular momenta and Born–Oppenheimer separation of the BC stretch versus the He motions, accurate enough. These issues have been previously tackled elsewhere for the 4He2–Br2(X) system, which contains a heavy dopant [Roncero et al., Int. J. Quantum Chem. 107, 2756 (2007)]. Here, we consider a similar cluster but with a much lighter dopant such as N2(X). Although the model does not provide the correct energy levels for the cluster, positions and intensities of the main detectable lines of the vibrotational Raman spectrum at low temperature are accurately reproduced.This work has been partially supported by the DGICYT Spanish Grant Nos. FIS2007-62006 and CTQ2004-02415/BQU. M.P.de L.-C. acknowledges the support of a MEC-CSIC Spanish Grant No. 2007501004. The calculations presented here were performed at Centro de Cálculo of IMAFF (CSIC).Peer reviewe

Expert-augmented machine learning.

Machine learning is proving invaluable across disciplines. However, its success is often limited by the quality and quantity of available data, while its adoption is limited by the level of trust afforded by given models. Human vs. machine performance is commonly compared empirically to decide whether a certain task should be performed by a computer or an expert. In reality, the optimal learning strategy may involve combining the complementary strengths of humans and machines. Here, we present expert-augmented machine learning (EAML), an automated method that guides the extraction of expert knowledge and its integration into machine-learned models. We used a large dataset of intensive-care patient data to derive 126 decision rules that predict hospital mortality. Using an online platform, we asked 15 clinicians to assess the relative risk of the subpopulation defined by each rule compared to the total sample. We compared the clinician-assessed risk to the empirical risk and found that, while clinicians agreed with the data in most cases, there were notable exceptions where they overestimated or underestimated the true risk. Studying the rules with greatest disagreement, we identified problems with the training data, including one miscoded variable and one hidden confounder. Filtering the rules based on the extent of disagreement between clinician-assessed risk and empirical risk, we improved performance on out-of-sample data and were able to train with less data. EAML provides a platform for automated creation of problem-specific priors, which help build robust and dependable machine-learning models in critical applications

Observational constraints to boxy/peanut bulge formation time

Boxy/peanut bulges are considered to be part of the same stellar structure as bars and both could be linked through the buckling instability. The Milky Way is our closest example. The goal of this letter is determining if the mass assembly of the different components leaves an imprint in their stellar populations allowing to estimate the time of bar formation and its evolution. To this aim we use integral field spectroscopy to derive the stellar age distributions, SADs, along the bar and disc of NGC 6032. The analysis shows clearly different SADs for the different bar areas. There is an underlying old (>=12 Gyr) stellar population for the whole galaxy. The bulge shows star formation happening at all times. The inner bar structure shows stars of ages older than 6 Gyrs with a deficit of younger populations. The outer bar region presents a SAD similar to that of the disc. To interpret our results, we use a generic numerical simulation of a barred galaxy. Thus, we constrain, for the first time, the epoch of bar formation, the buckling instability period and the posterior growth from disc material. We establish that the bar of NGC 6032 is old, formed around 10 Gyr ago while the buckling phase possibly happened around 8 Gyr ago. All these results point towards bars being long-lasting even in the presence of gas.Comment: Accepted for publication in MNRAS Letter

Energies and density distributions of (4He)N clusters doped with Br2(X): A Hartree-like approach

10 págs.; 8 figs.; 2 tabs.; PACS numberssd: 36.40.Mr, 31.15.Ar, 33.20.Fb, 33.80.GjEnergies and density distributions of the helium atoms in Br2(X) - (4He)N clusters are calculated using a quantum >Hartree-like> approach in which the dopant molecule and the 4He atoms play the role of the nuclei and electrons, respectively, of the original Hartree formulation. A detailed generalization of the methodology is presented. The validity of this treatment is assessed by comparing energies and density distributions for N =2 up to N=18 with those obtained by performing quantum diffusion Monte Carlo (DMC) calculations. The present Hartree model shows good agreement with the DMC calculations, the main difference being that the DMC density distributions of the He atoms are more isotropic than those generated via the model. The treatment is extended to larger (up to N=60) clusters and saturation effects are analyzed and discussed. ©2005 The American Physical Society.This work has been partially supported by the Italy-Spain Integrated Action Programme HI02-74, DGICYT Spanish Grant No. BFM2001-2179, European TMR network Grant No. HPRN-CT-1999-0005, and Cineca sGrant No. HPRI-CT- 1999-00048d. F.A.G. and C.DiP. thank the Research Committee of the University of Rome La Sapienza. M.P.deL.-C. was supported by the “Ramón and Cajal” Programme and J.J. by the Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences, and Biosciences, U.S. Department of Energy under Contract No. W-31-109-Eng-38.Peer Reviewe

Deep learning-based lung segmentation and automatic regional template in chest X-ray images for pediatric tuberculosis

Tuberculosis (TB) is still considered a leading cause of death and a substantial threat to global child health. Both TB infection and disease are curable using antibiotics. However, most children who die of TB are never diagnosed or treated. In clinical practice, experienced physicians assess TB by examining chest X-rays (CXR). Pediatric CXR has specific challenges compared to adult CXR, which makes TB diagnosis in children more difficult. Computer-aided diagnosis systems supported by Artificial Intelligence have shown performance comparable to experienced radiologist TB readings, which could ease mass TB screening and reduce clinical burden. We propose a multi-view deep learning-based solution which, by following a proposed template, aims to automatically regionalize and extract lung and mediastinal regions of interest from pediatric CXR images where key TB findings may be present. Experimental results have shown accurate region extraction, which can be used for further analysis to confirm TB finding presence and severity assessment. Code publicly available at https://github.com/dani-capellan/pTB_LungRegionExtractor.Comment: This work has been accepted at the SPIE Medical Imaging 2023, Image Processing conferenc

Structural control of the non-ionic surfactant alcohol ethoxylates (AEOs) on transport in natural soils

Surfactants, after use, enter the environment through diffuse and point sources such as irrigation with treated and non-treated waste water and urban and industrial wastewater discharges. For the group of non-ionic synthetic surfactant alcohol ethoxylates (AEOs), most of the available information is restricted to the levels and fate in aquatic systems, whereas current knowledge of their behavior in soils is very limited. Here we characterize the behavior of different homologs (C12-C18) and ethoxymers (E03, E06, and E08) of the AEOs through batch experiments and under unsaturated flow conditions during infiltration experiments. Experiments used two different agricultural soils from a region irrigated with reclaimed water (Guadalete River basin, SW Spain). In parallel, water flow and chemical transport were modelled using the HYDRUS-1D software package, calibrated using the infiltration experimental data. Estimates of water flow and reactive transport of all surfactants were in good agreement between infiltration experiments and simulations. The sorption process followed a Freundlich isotherm for most of the target compounds. A systematic comparison between sorption data obtained from batch and infiltration experiments revealed that the sorption coefficient (K-d) was generally lower in infiltration experiments, performed under environmental flow conditions, than in batch experiments in the absence of flow, whereas the exponent (beta) did not show significant differences. For the low clay and organic carbon content of the soils used, no clear dependence of K-d on them was observed. Our work thus highlights the need to use reactive transport parameterization inferred under realistic conditions to assess the risk associated with alcohol ethoxylates in subsurface environments. (C) 2020 The Authors. Published by Elsevier Ltd

Eliminating Error in the Chemical Abundance Scale for Extragalactic HII Regions

In an attempt to remove the systematic errors which have plagued the calibration of the HII region abundance sequence, we have theoretically modeled the extragalactic HII region sequence. We then used the theoretical spectra so generated in a double blind experiment to recover the chemical abundances using both the classical electron temperature + ionization correction factor technique, and the technique which depends on the use of strong emission lines (SELs) in the nebular spectrum to estimate the abundance of oxygen. We find a number of systematic trends, and we provide correction formulae which should remove systematic errors in the electron temperature + ionization correction factor technique. We also provide a critical evaluation of the various semi-empirical SEL techniques. Finally, we offer a scheme which should help to eliminate systematic errors in the SEL-derived chemical abundance scale for extragalactic HII regions.Comment: 24 pages, 9 Tables, 13 figures, accepted for publication in MNRAS. Updated considering minor changes during the final edition process and some few missing reference