Technology played a crucial role in combating the COVID pandemic, both in the rapid development of vaccines and the early detection of the virus. Consequently, numerous studies in the medical field have focused on leveraging the power of artificial intelligence for COVID-19 detection. However, in the medical domain, it is essential to have a clear understanding of the processes and algorithms used in decision-making, as these directly impact people’s health. Therefore, efforts have been made to implement explainable artificial intelligence techniques, enabling humans to understand and explain the deep learning algorithms used in disease detection. In this work, we present a novel approach to detecting COVID-19 in chest X-rays using a Variational Autoencoder model to identify lung anomalies. This methodology aims to highlight critical areas of the image, allowing healthcare professionals to identify them more effectively. Additionally, it seeks to provide clearer explanations of the decisions made by the artificial i ntelligence, r educing the complexity of the "black boxes" generated by deep learning neural networks. With this methodology, we hope to improve the effectiveness and reliability of early COVID-19 detection through chest X-rays.

Recognizing variable stars is a task of interest in the astronomy community. Currently, this task has taken advantage of deep learning algorithms. However, these algorithms require a large amount of data to achieve high levels of precision. In this work, self-supervised learning is proposed to improve the classification of variable stars considering a reduced amount of data using recurrent networks. The experiments in Gaia dataset show that the proposed approach allows to improve performance, when compared with traditional initialization schemes, up to 7% and 13% in real databases in semi-supervised learning scenarios. In future work, we propose considering experiments with other variable star databases.

In recent years, air pollution has been a major concern for its implications on human health. Specifically, ozone ( $$\mathrm{O}_{3}$$ O 3 ) pollution is causing common respiratory diseases. In this paper, we illustrate the process of modeling and prediction hourly $$\mathrm{O}_ {3}$$ O 3 pollution measurements using wavelet transforms. We split the time series of $$\mathrm{O}_{3}$$ O 3 in daily intervals and estimate scale and wavelet coefficients for each interval by the discrete wavelet transform (DWT) with Haar filter. Subsequently we apply cumulated autoregressive integrated moving average (ARIMA) to estimate the coefficients and forecast their evolution in future intervals. Then the inverse discrete wavelet transform is implemented for the reconstruction of the time series and the forecast in the near future. In order to assess the performance of the proposed methodology, we compare the predictions obtained by the DWT–ARIMA with those obtained by the ARIMA model. Several theoretical results are shown through a simulation study.

This paper introduces an image denoising procedure based on a 2D scale-mixing complex-valued wavelet transform. Both the minimal (unitary) and redundant (maximum overlap) versions of the transform are used. The covariance structure of white noise in wavelet domain is established. Estimation is performed via empirical Bayesian techniques, including versions that preserve the phase of the complex-valued wavelet coefficients and those that do not. The new procedure exhibits excellent quantitative and visual performance, which is demonstrated by simulation on standard test images.