MUSE observations of a changing-look AGN I: The re-appearance of the broad emission lines

Optical changing-look Active Galactic Nuclei (AGN) are a class of sources that change type within a short timescale of years or decades. This change is characterised by the appearance or disappearance of broad emission lines, often associated with dramatic AGN continuum flux changes that are orders of magnitude larger than those expected from typical AGN variability. In this work we study for the first time the host galaxy of a changing-look AGN, Mrk 590, using high spatial resolution optical and near-infrared observations. We discover that after ~ 10 yr absence, the optical broad emission lines of Mrk 590 have reappeared. The AGN optical continuum flux however, is still ~ 10 times lower than that observed during the most luminous state in the 1990s. The host galaxy shows a 4.5 kpc radius star-forming ring with knots of ionised and cold molecular gas emission. Extended ionised and warm molecular gas emission are detected in the nucleus, indicating that there is a reservoir of gas as close as 60 pc from the black hole. We observe a nuclear gas spiral between radii r ~ 0.5 - 2 kpc, which has been suggested as a dynamical mechanism able to drive the necessary gas to fuel AGN. We also discover blue-shifted and high velocity dispersion [O III] emission out to a radius of 1 kpc, tracing a nuclear gas outflow. The gas dynamics in Mrk 590 suggest a complex balance between gas inflow and outflow in the nucleus of the galaxy.Comment: Accepted for publication in MNRA

Hole concentration in a diluted ferromagnetic semiconductor

We consider a mean-field approach to the hole-mediated ferromagnetism in III-V Mn-based semiconductor compounds to discuss the dependence of the hole density on that of Mn sites in Ga_{1-x}Mn_xAs. The hole concentration, p, as a function of the fraction of Mn sites, x, is parametrized in terms of the product m*J_{pd}^2 (where m* is the hole effective mass and J_{pd} is the Kondo-like hole/local-moment coupling), and the critical temperature Tc. By using experimental data for these quantities, we have established the dependence of the hole concentration with x, which can be associated with the occurrence of a reentrant metal-insulator transition taking place in the hole gas. We also calculate the dependence of the Mn magnetization with x, for different temperatures (T), and found that as T increases, the width of the composition-dependent magnetization decreases drammatically, and that the magnetization maxima also decreases, indicating the need for quality-control of Mn-doping composition in diluted magnetic semiconductor devices.Comment: 4 pages, 3 figures, RevTeX 3; Fig. 1 changed, new references adde

The impact of the COVID-19 pandemic on airlines’ passenger satisfaction

This study aims to understand airline passengers' satisfaction trends by analyzing the most influential factors on satisfaction before and during the COVID-19 pandemic. The sample consists of a dataset with 9745 passenger reviews published on airlinequality.com. The reviews were analyzed with a sentiment analysis tool calibrated for the aviation industry for accuracy. Machine learning algorithms were then implemented to predict review sentiment based on airline company, travelers' type and class, and country of origin. Findings show passengers were unhappy before the pandemic, aggravated after the COVID-19 outbreak. The staff's behavior is the main factor influencing passengers' satisfaction. Predictive modeling showed that it is possible to predict negative review sentiments with satisfactory performance rather than positive reviews. The main takeaway is that passengers, after the pandemic, are most worried about refunds and aircraft cabin cleanliness. From a managerial standpoint, airline companies can benefit from the created knowledge to adjust their strategies in agreement and meet their customers' expectations.info:eu-repo/semantics/publishedVersio

Revisión crítica de los estudios sobre biogeografía de macroalgas marinas del Mediterráneo.

Revisión crítica de los estudios sobre biogeografía de macroalgas marinas del Mediterráneo. Teniendo en cuenta los procedimientos metodológicos que se siguen en los estudios biogeográficos, se reconocen tres tipos básicos de aproximaciones: biogeografía descriptiva, biogeografía narrativa y biogeografía analítica. En este trabajo se analizan las aportaciones realizadas a la ficogeografía de las macroalgas marinas del mar Mediterráneo, atendiendo a cada una de las tres aproximaciones posibles. Existen escasas floras del Mediterráneo oriental y la costa africana, además de un estancamiento metodológico en los estudios narrativos y analíticos, impidiendo el avance de la ficogeografía. Se discuten las posibles líneas futuras de investigación con el objeto de incentivar un avance significativo en los conocimientos ficogeográficos del Mediterráneo

Variação sazonal e influência de fatores meteorológicos na incidência de descolamentos regmatógenos da retina na zona centro de Portugal e na Madeira

Objetivos: Analisar a variação sazonal e a influência de fatores meteorológicos na incidência a 5 anos de descolamento regmatógeno da retina (DRR), na região centro do país e região autónoma da Madeira (RAM). Métodos: Série de casos consecutiva, retrospetiva e multicêntrica. Incluíram-se doentes submetidos a cirurgia de DRR no Centro Hospitalar e Universitário de Coimbra e Hospital Doutor Nélio Mendonça entre Janeiro’10 e Dezembro’14. A seleção de casos foi feita através codificação ICD-9-CM e os critérios de inclusão foram: 1)idade ≥18 anos; 2)DRR de novo; 3)reparação cirúrgica do DRR. Consideraram-se critérios de exclusão: 1)DR tracional, exsudativo ou misto; 2)DR antigo ou re-descolamento; 3)soluções de continuidade ou lesões regmatógenas tratadas apenas com laser. Os dados meteorológicos diários das estações de Coimbra, Leiria, Aveiro, Viseu, Guarda, Castelo Branco e Funchal, foram utilizados na análise estatística. Resultados: Foram incluídos 1013 olhos (914 da região centro e 99 da RAM), com idade média 61,84±14,00 anos. Através de um modelo cronológico de regressão linear constatou-se a presença de sazonalidade com picos nos meses de Maio e Setembro. A temperatura média apresentou uma associação marginalmente significativa com a incidência de DRR num modelo biológico de regressão linear considerando os mais fortes preditores de DRR da amostra. Conclusões: Os nossos resultados demonstram que a incidência de DRR se associa a um padrão sazonal significativo que parece ser explicado pela temperatura. Este estudo alerta para a necessidade de um eficaz planeamento em saúde que deverá passar por uma gestão harmoniosa de recursos humanos em épocas de maior incidência

Luttinger liquid superlattices

We calculate the correlation functions and the DC conductivity of Luttinger liquid superlattices, modeled by a repeated pattern of interacting and free Luttinger liquids. In a specific realization, where the interacting subsystem is a Hubbard chain, the system exhibits a rich phase diagram with four different phases: two metals and two compressible insulators. In general, we find that the effective low energy description amalgamates features of both types of liquids in proportion to their spatial extent, suggesting the interesting possibility of `engineered' Luttinger liquids.Comment: RevTeX, 5 pages, 3 figure

Conjectures of Mathematical Logic and Educational Games for Basic Education Based on the Guidelines of NCP, NCG and NBC

Current technological advances allow us to create, adapt or simply use numerous resources to achieve improvements in teaching-learning. The purpose of this article is to show the result of an analysis of the current normative documents and recommendations for national education in Brazil (National Curricular Guidelines - National Curricular Parameters and National Common Curricular Base), primary and secondary education, regarding the contents recommended in mathematical logic, complementing with the analysis of a pedagogical political project of the fundamental education of a public school, to verify the existence of this content, in it. From this analysis and reflection on the importance of educational games in teaching, the article proposes the development of an educational game especially to assist in teaching the functionalities on the symbols of logic. It highlights the contribution of this game to the teaching-learning of these rules and symbols and, finally, concludes by showing the importance of this activity in the educational process

Radio propagation measurements and modeling for standardization of the site general path loss model in International Telecommunications Union recommendations for 5G wireless networks

The International Telecommunications Union Radiocommunication Sector (ITU‐R) Study Group 3 identified the need for a number of radio channel models in anticipation of the World Radiocommunications Conference in 2019 when the frequency allocation for 5G will be discussed. In response to the call for propagation path loss models, members of the study group carried out measurements in the frequency bands between 0.8 GHz up to 73 GHz in urban low rise and urban high rise as well as suburban environments. The data were subsequently merged to generate site general path loss models. The paper presents an overview of the radio channel measurements, the measured environments, the data analysis and the approach for the derivation of the path loss model adopted in Recommendation ITU‐R P.1411‐10

Automation of a plane grating spectrograph

A Zeiss model PGS-2 plane grating spectrograph was automated by replacing its photograph film detection system with an EGG-Reticon 1024S photodiode array (PDA) and by controlling the main instrument functions through the use of a home-made interface connected to a microcomputer. The array was cooled by four Peltier elements to allow integration of the emitted light for up to 40 s. The interface performs data acquisition from the sensor array, controls the grating position and the excitation source. A QuickBasic 4.5 program manages the interface, for data storage and treatment, and allows a graphical display and user-friendly interaction. Results show an absolute standard deviation for the wavelength localization of +/- 0.036 nm, and a spectral resolution of 0.05 nm at 443 nm when a 651 grooves/mm grating is employed. In each scan, the sensor array can collect data in a 18.7 nm wide window. Sensitivity was inferred from experimental data that showed an accurate localization of emission lines for Sn and Cu present in metal alloys at 0.006 and 0.03%, respectively. Quantitative results obtained for determination of Mn in steel samples and Ph in aqueous solution are also presented.18171