Effects of solar evolution on finite acquisition time of Fabry-Perot-Interferometers in high resolution solar physics

The imaging spectro-polarimeter VTF (Visible Tunable Filter) will be operated at the Daniel K. Inouye Solar Telescope (DKIST). Due to its capability of resolving dynamic fine structure of smaller than 0.05'', the finite acquisition time of typically 11 s affects the measurement process and potentially causes errors in deduced physical parameters. We estimate those errors and investigate ways of minimising them. We mimic the solar surface using a magneto-hydrodynamic simulation with a spatially averaged vertical field strength of 200 G. We simulate the measurement process scanning through successive wavelength points with a temporal cadence of 1 s. We synthesise FeI 617.3 nm. Besides the classical composition of the line profile, we introduce a novel method in which the intensity in each wavelength point is normalised using the simultaneous continuum intensity. Milne-Eddington inversions are used to infer the line-of-sight velocity, v(los), and the vertical (longitudinal) component of the magnetic field, B(los). We quantify systematic errors, defining the temporal average of the simulation during the measurement as the truth. We find that with the classical composition of the line profiles, errors exceed the sensitivity for v(los) and in filigree regions also for B(los). The novel method that includes normalisation reduces the measurement errors in all cases. Spatial binning without reducing the acquisition time decreases the measurement error slightly. The evolutionary time-scale in inter-granular lanes, in particular in areas with magnetic features (filigree), is shorter than the time-scale within granules. Hence less accumulations could be used for strong magnetic field in inter-granular lanes and more accumulations could be used for the weak granular magnetic fields. As a key result, we suggest to include the novel method of normalisation in corresponding data pipelines.Comment: 11 pages, 11 figures, accepted for publication in A&

Dipolar Evolution in a Coronal Hole Region

Using observations from the SOHO, STEREO and Hinode, we investigate magnetic field evolution in an equatorial coronal hole region. Two dipoles emerge one by one. The negative element of the first dipole disappears due to the interaction with the positive element of the second dipole. During this process, a jet and a plasma eruption are observed. The opposite polarities of the second dipole separate at first, and then cancel with each other, which is first reported in a coronal hole. With the reduction of unsigned magnetic flux of the second dipole from 9.8*10^20 Mx to 3.0*10^20 Mx in two days, 171 A brightness decreases by 75% and coronal loops shrink obviously. At the cancellation sites, the transverse fields are strong and point directly from the positive elements to the negative ones, meanwhile Doppler red-shifts with an average velocity of 0.9 km s-1 are observed, comparable to the horizontal velocity (1.0 km s-1) derived from the cancelling island motion. Several days later, the northeastern part of the coronal hole, where the dipoles are located, appears as a quiet region. These observations support the idea that the interaction between the two dipoles is caused by flux reconnection, while the cancellation between the opposite polarities of the second dipole is due to the submergence of original loops. These results will help us to understand coronal hole evolution.Comment: 23 pages, 9 figures. accepted by Ap

Más interculturalidad en tiempos de crisis

Presentación del número por parte de sus editores

A preliminary evaluation of a low-cost multispectral sensor for non-destructive evaluation of olive fruits’ fat content

[Abstract] This study presents a preliminary evaluation of a low-cost multispectral device for the non-destructive assessment of olive fruits’ fat content. The developed device integrates a multispectral sensor, with a spectral response of 18 channels falling in a range from 410 to 940 nm, a calibrated light source, and a programmable board, in a ‘gun’-shaped device whose trigger activates sample reading. The device was used to measure 50 intact olive samples, which were subsequently chemically analysed to determine their actual fat content. Then, the multispectral readings from the 18 channels were used as input variables to train a neural network, using the actual fat content registers as reference data. The measured results, in terms of root-mean-square-error and coefficient of determination, shows promising capabilities of the developed low-cost device in the prediction of fat content of intact olives, what stands up for further development and experimentation.This work was supported by grant PID2020- 119217RA-I00 funded by MCIN/AEI/ 10.13039/501100011033, and grant IJC2019-040114-I funded by MCIN/AEI/ 10.13039/501100011033, and also by project TIColiVA with grant P18-RTJ-4539 funded by the Regional Government of Andalusia through the “PAIDI, Plan Andaluz de Investigación, Desarrollo e Innovación”. The authors would also like to thank “Cooperativa Nuestra Señora de la Oliva”, for generously providing the olive samples with which this research was conducted.Ministerio de Ciencia e Innovación; 10.13039/501100011033Junta de Andalucía; P18-RTJ-453

Automatic detection of crohn disease in wireless capsule endoscopic images using a deep convolutional neural network

The diagnosis of Crohn’s disease (CD) in the small bowel is generally performed by observing a very large number of images captured by capsule endoscopy (CE). This diagnostic technique entails a heavy workload for the specialists in terms of time spent reviewing the images. This paper presents a convolutional neural network capable of classifying the CE images to identify those ones affected by lesions indicative of the disease. The architecture of the proposed network was custom designed to solve this image classification problem. This allowed different design decisions to be made with the aim of improving its performance in terms of accuracy and processing speed compared to other state-of-the-art deep-learning-based reference architectures. The experimentation was carried out on a set of 15,972 images extracted from 31 CE videos of patients affected by CD, 7,986 of which showed lesions associated with the disease. The training, validation/selection and evaluation of the network was performed on 70%, 10% and 20% of the total images, respectively. The ROC curve obtained on the test image set has an area greater than 0.997, with points in a 95-99% sensitivity range associated with specificities of 99-96%. These figures are higher than those achieved by EfficientNet-B5, VGG-16, Xception or ResNet networks which also require an average processing time per image significantly higher than the one needed in the proposed architecture. Therefore, the network outlined in this paper is proving to be sufficiently promising to be considered for integration into tools used by specialists in their diagnosis of CD. In the sample of images analysed, the network was able to detect 99% of the images with lesions, filtering out for specialist review 96% of those with no signs of disease.Funding for open access charge: Universidad de Huelva / CBUA This work was part of a project funded under the 2014-2020 Andalusia ERDF Operational Programme (Project Reference: UHU-1257810- PO FEDER 2014-2020

Un hasta pronto, un saludo y un adiós

Artículo en dos idiomas: español y alemánPresentación del número por parte de sus editores

Models and Observations of Sunspot Penumbrae

The mysteries of sunspot penumbrae have been under an intense scrutiny for the past 10 years. During this time, some models have been proposed and refuted, while the surviving ones had to be modified, adapted and evolved to explain the ever-increasing array of observational constraints. In this contribution I will review two of the present models, emphasizing their contributions to this field, but also pinpointing some of their inadequacies to explain a number of recent observations at very high spatial resolution. To help explaining these new observations I propose some modifications to each of them. These modifications bring those two seemingly opposite models closer together into a general picture that agrees well with recent 3D magneto-hydrodynamic simulations.Comment: 9 pages, 1 color figure. Review talk to appear in the proceedings of the International Workshop of 2008 Solar Total Eclipse: Solar Magnetism, Corona and Space Weather--Chinese Space Solar Telescope Scienc

Acústica de una pista polideportiva multiusos con cubierta en membrana textil tensionada.

The acoustic study of a sports court of the High Performance Centre of La Cartuja (Seville) is presented. This is an area covered with a tensional textile structure. On-site measurements of impulse responses using sinusoidal sweeps and acoustic simulation with CATT-Acoustic are performed. In both cases, the spectral behaviour of each acoustic parameter value and its spatial distribution are analysed. The model used in the simulation is calibrated using an iterative process to adjust simulated reverberation times that differ by no more than 5% of those measured. Proposals are then made for the adaptation of the acoustic behaviour of the sports courtSe presenta el estudio acústico de una pista polideportiva del Centro de Alto Rendimiento de La Cartuja (Sevilla). Se trata de un espacio cubierto con una estructura textil tensionada. Se ha realizado la medición in-situ de las respuestas al impulso mediante barridos sinusoidales y una simulación acústica con CATT-Acoustic. En ambos casos se analiza el comportamiento espectral de cada parámetro acústico y se valora su distribución espacial. El modelo utilizado en la simulación se ha calibrado, usando un procedimiento iterativo, de modo que los tiempos de reverberación simulados y medidos no difieran en más de un 5%. Finalmente se hacen propuestas de adecuación de su comportamiento acústic