CzSL: Learning from citizen science, experts, and unlabelled data in astronomical image classification

Citizen science is gaining popularity as a valuable tool for labelling large collections of astronomical images by the general public. This is often achieved at the cost of poorer quality classifications made by amateur participants, which are usually verified by employing smaller data sets labelled by professional astronomers. Despite its success, citizen science alone will not be able to handle the classification of current and upcoming surv e ys. To alleviate this issue, citizen science projects have been coupled with machine learning techniques in pursuit of a more robust automated classification. Ho we v er, e xisting approaches have neglected the fact that, apart from the data labelled by amateurs, (limited) expert knowledge of the problem is also available along with vast amounts of unlabelled data that have not yet been exploited within a unified learning framework. This paper presents an innov ati ve learning methodology for citizen science capable of taking advantage of expert- and amateur-labelled data, featuring a transfer of labels between experts and amateurs. The proposed approach first learns from unlabelled data with a convolutional auto-encoder and then exploits amateur and expert labels via the pre-training and fine-tuning of a convolutional neural network, respectively. We focus on the classification of galaxy images from the Galaxy Zoo project, from which we test binary, multiclass, and imbalanced classification scenarios. The results demonstrate that our solution is able to impro v e classification performance compared to a set of baseline approaches, deploying a promising methodology for learning from different confidence levels in data labelling.Center of Excellence Severo Ochoa’ award to the Instituto de Astrof ´ısica de Andaluc ´ıa (grant no. SEV-2017-0709)A-TIC-434-UGR20 and PID2020-119478GB-I00NVIDIA Corporatio

Kubo formula for Floquet states and photoconductivity oscillations in a 2D electron gas

The recent discovery of the microwave induced vanishing resistance states in a two dimensional electron system (2DES) is an unexpected and surprising phenomena. In these experiments the magnetoresistance of a high mobility 2DES under the influence of microwave radiation of frequency $\omega$ at moderate values of the magnetic field, exhibits strong oscillations with zero-resistance states (ZRS) governed by the ratio $\omega /\omega_c$, where $\omega_c$ is the cyclotron frequency. In this work we present a model for the photoconductivity of a two dimensional electron system (2DES) subjected to a magnetic field. The model includes the microwave and Landau contributions in a non-perturbative exact way, impurity scattering effects are treated perturbatively. In our model, the Landau-Floquet states act coherently with respect to the oscillating field of the impurities, that in turn induces transitions between these levels. Based on this formalism, we provide a Kubo-like formula that takes into account the oscillatory Floquet structure of the problem. We study the effects of both short-range and long-range disorder on the photoconductivity. Our calculation yields a magnetoresistance oscillatory behavior with the correct period and phase. It is found that, in agreement with experiment, negative dissipation can only be induced in very high mobility samples. We analyze the dependence of the results on the microwave power and polarization. For high-intensity radiation multi-photon processes take place predicting new negative-resistance states centered at $\omega / \omega_c=1/2$, and $\omega / \omega_c= 3/2$.Comment: Final version, accepted for publication in Phys. Rev.

Foeniculum sanguineum Triano y A. Pujadas (Apiaceae) nueva especie del suroeste de la Región Mediterránea

Foeniculum sanguineum Triano & A. Pujadas, sp. nov., from the south western Mediterranean Region (Spain & Morocco) is described. Its characterization and a comparative study with the related species Foeniculum vulgare Mill., has been carried out through morphological, cytological, chemical and molecular analysis. F. sanguineum is distinguished primarily for its red petals, pink pollen in fresh, and red stylopod. It is a diploid species (2n= 22). A high proportion of limonene and piperitenone oxide (absent in F. vulgare) has been found in the essential oil composition of the dry fruits of F. sanguineum and a high amount (about 50 %) of α-phellandrene in its roots and stems. Phylogenetic analyses were performed using the internal transcribed spacer sequences of nuclear ribosomal DNA (ITS) and the chloroplast rbcL gene sequences. ITS analysis supports the existence of the new species, while revealing sequence divergence both at the intraspecific and at the interspecific levels. A Single-nucleotide-polymorphism (SNP) sequence divergence found in the slow evolving chloroplast gene provided additional support for the novel species characterization, for which the name Foeniculum sanguineum is proposed

Surface mechanomyography and electromyography provide non-invasive indices of inspiratory muscle force and activation in healthy subjects

The current gold standard assessment of human inspiratory muscle function involves using invasive measures of transdiaphragmatic pressure (Pdi) or crural diaphragm electromyography (oesEMGdi). Mechanomyography is a non-invasive measure of muscle vibration associated with muscle contraction. Surface electromyogram and mechanomyogram, recorded transcutaneously using sensors placed over the lower intercostal spaces (sEMGlic and sMMGlic respectively), have been proposed to provide non-invasive indices of inspiratory muscle activation, but have not been directly compared to gold standard Pdi and oesEMGdi measures during voluntary respiratory manoeuvres. To validate the non-invasive techniques, the relationships between Pdi and sMMGlic, and between oesEMGdi and sEMGlic were measured simultaneously in 12 healthy subjects during an incremental inspiratory threshold loading protocol. Myographic signals were analysed using fixed sample entropy (fSampEn), which is less influenced by cardiac artefacts than conventional root mean square. Strong correlations were observed between: mean Pdi and mean fSampEn |sMMGlic| (left, 0.76; right, 0.81), the time-integrals of the Pdi and fSampEn |sMMGlic| (left, 0.78; right, 0.83), and mean fSampEn oesEMGdi and mean fSampEn sEMGlic (left, 0.84; right, 0.83). These findings suggest that sMMGlic and sEMGlic could provide useful non-invasive alternatives to Pdi and oesEMGdi for the assessment of inspiratory muscle function in health and disease.Peer ReviewedPostprint (published version

Noninvasive assessment of inspiratory muscle neuromechanical coupling during inspiratory threshold loading

Diaphragm neuromechanical coupling (NMC), which reflects the efficiency of conversion of neural activation to transdiaphragmatic pressure (Pdi), is increasingly recognized to be a useful clinical index of diaphragm function and respiratory mechanics in neuromuscular weakness and cardiorespiratory disease. However, the current gold standard assessment of diaphragm NMC requires invasive measurements of Pdi and crural diaphragm electromyography (oesEMGdi), which complicates the measurement of diaphragm NMC in clinical practice. This is the first study to compare invasive measurements of diaphragm NMC (iNMC) using the relationship between Pdi and oesEMGdi, with noninvasive assessment of NMC (nNMC) using surface mechanomyography (sMMGlic) and electromyography (sEMGlic) of lower chest wall inspiratory muscles. Both invasive and noninvasive measurements were recorded in twelve healthy adult subjects during an inspiratory threshold loading protocol. A linear relationship between noninvasive sMMGlic and sEMGlic measurements was found, resulting in little change in nNMC with increasing inspiratory load. By contrast, a curvilinear relationship between invasive Pdi and oesEMGdi measurements was observed, such that there was a progressive increase in iNMC with increasing inspiratory threshold load. Progressive recruitment of lower ribcage muscles, serving to enhance the mechanical advantage of the diaphragm, may explain the more linear relationship between sMMGlic and sEMGlic (both representing lower intercostal plus costal diaphragm activity) than between Pdi and crural oesEMGdi. Noninvasive indices of NMC derived from sEMGlic and sMMGlic may prove to be useful indices of lower chest wall inspiratory muscle NMC, particularly in settings that do not have access to invasive measures of diaphragm function.Peer ReviewedPostprint (published version

A review and classification of heuristics for permutation flow-shop scheduling with makespan objective

Makespan minimization in permutation flow-shop scheduling is an operations research topic that has been intensively addressed during the last 40 years. Since the problem is known to be NP-hard for more than two machines, most of the research effort has been devoted to the development of heuristic procedures in order to provide good approximate solutions to the problem. However, little attention has been devoted to establish a common framework for these heuristics so that they can be effectively combined or extended. In this paper, we review and classify the main contributions regarding this topic and discuss future research issues.Ministerio de Ciencia y Tecnología DPI-2001-311

Symmetry breaking as the origin of zero-differential resistance states of a 2DEG in strong magnetic fields

Zero resistance differential states have been observed in two-dimensional electron gases (2DEG) subject to a magnetic field and a strong dc current. In a recent work we presented a model to describe the nonlinear transport regime of this phenomenon. From the analysis of the differential resistivity and the longitudinal voltage we predicted the formation of negative differential resistivity states, although these states are known to be unstable. Based on our model, we derive an analytical approximated expression for the Voltage-Current characteristics, that captures the main elements of the problem. The result allow us to construct an energy functional for the system. In the zero temperature limit, the system presents a quantum phase transition, with the control parameter given by the magnetic field. It is noted that above a threshold value ($B>B_{th}$), the symmetry is spontaneously broken. At sufficiently high magnetic field and low temperature the model predicts a phase with a non-vanishing permanent current; this is a novel phase that has not been observed so far.Comment: 6 pages, 2 figure

Crónicas de una derrota. La vista del águila

Difícilmente se podría calificar de crisis de la cultura la actual sobreabundancia de ofertas culturales, la exigencia también creciente de la demanda o el mismo interés de los programadores en acertar con su público. Sin embargo, no siempre un aumento del consumo implica satisfacción. Cabría preguntarse, por supuesto, si ese cierto pesimismo que empieza a prender en los gestores culturales por los dudosos resultados, digamos educativos, de su trabajo, sólo lo padecen ellos y la general opinión es que, por el contrario, estamos en el buen camino de podar la cultura de cualquier voluntad social. Si así fuera, estas crónicas de una derrota, que todavía quiero creer provisional, serían más bien una necrológica. Y este tipo de iniciativas periféricas de poner en valor, y en cuestión, las ideas de cada gestor voluntarioso, una perfecta reserva india que se extinguirá sola por la degeneración de esas especies animales que sólo se cruzan con parientes. Pero tiempo habrá de hablar de nosotros.   Chronicles of a defeat. The view of the Eagle   Abstract: The current overabundance of cultural offerings, the also growing demand for demand or the same interest of programmers in hitting their audience could hardly be described as a cultural crisis. However, an increase in consumption does not always imply satisfaction. One might wonder, of course, if that certain pessimism that is beginning to ignite in cultural managers due to the dubious results, let's say educational, of their work, only they suffer and the general opinion is that, on the contrary, we are on the right track to prune the culture of any social will. If so, these chronicles of a defeat, which I still want to believe provisional, would be rather an obituary. And this type of peripheral initiatives to put in value, and in question, the ideas of each willful manager, a perfect Indian reservation that will become extinct by itself due to the degeneration of those animal species that only interbreed with relatives. But time will have to talk about us.    Artículo recibido: 07/04/2008. Aceptado: 09/06/2008      

The closing lemma and the planar general density theorem for Sobolev maps

We prove that given a non-wandering point of a Sobolev-(1,p) homeomorphism we can create closed trajectories by making arbitrarily small perturbations. As na application, in the planar case, we obtain that generically the closed trajectories are dense in the non- wandering set.The first and fourth authors were partially supported by the Research Centre of Mathematics of the University of Minho with the Portuguese Funds from the "Fundacao para a Ciencia e a Tecnologia", through the Project UID/MAT/00013/2013. The third and fourth authors were partially supported by the Project "New trends in Lyapunov exponents" (PTDC/MAT-PUR/29126/2017)

Optimizing algorithms for thresholding segmentation applied to weed detection on UAV remote images.

En este trabajo se ha buscado la implementación de una alternativa al método de Otsu (1979) desarrollada por Hui-Fuang Ng (2006), el cual maximiza la diferencia entre varianzas espectrales y realiza una búsqueda multiumbral. En el estudio se emplearon imágenes procedentes de vehículos aéreos no tripulados (UAVs) tomadas en cultivos de maíz y girasol. Con una única ejecución del algoritmo en un entorno de análisis orientado a objetos, se discriminan aquellos objetos correspondientes a la fracción vegetal del suelo desnudo y se estima un umbral diferenciador entre cultivo y malas hierbas que contribuya a un subsiguiente proceso de clasificación. La técnica de Hui-Fuang detectó un mayor porcentaje de vegetación en todos los casos estudiados, oscilando el incremento entre un 3% y un 20%.This works aimed to implement an alternative to Otsu’s method (1979) developed by Hui- Fuang Ng (2006), which maximizes the difference between spectral variances and performs a multithreshold seeking. Unmanned aerial images taken in maize and sunflower crops were used in the research. In a single algorithm execution applied to an Object Based Image Analysis environment, the objects corresponding to both the vegetation fraction and bare soil are discriminated and a threshold to separate crop from weeds was also estimated, making easier a subsequent classification process. Fui-Huang’s technique provides a higher percentage of vegetation detection in all the cases, with an improvement which ranges from 3% to 20%