The principal aim of a spectral observer is twofold: the reconstruction of a signal of time via state estimation and the decomposition of such a signal into the frequencies that make it up. A spectral observer can be catalogued as an online algorithm for time-frequency analysis because is a method that can compute on the fly the Fourier transform (FT) of a signal, without having the entire signal available from the start. In this regard, this paper presents a novel spectral observer with an adjustable constant gain for reconstructing a given signal by means of the recursive identification of the coefficients of a Fourier series. The reconstruction or estimation of a signal in the context of this work means to find the coefficients of a linear combination of sines a cosines that fits a signal such that it can be reproduced. The design procedure of the spectral observer is presented along with the following applications: (1) the reconstruction of a simple periodical signal, (2) the approximation of both a square and a triangular signal, (3) the edge detection in signals by using the Fourier coefficients, (4) the fitting of the historical Bitcoin market data from 2014-12-01 to 2018-01-08 and (5) the estimation of a input force acting upon a Duffing oscillator. To round out this paper, we present a detailed discussion about the results of the applications as well as a comparative analysis of the proposed spectral observer vis-à-vis the Short Time Fourier Transform (STFT), which is a well-known method for time-frequency analysis.

The purpose of this paper is to provide a structural review of the progress made on detection and localization of leaks in pipelines by using approaches based on the Kalman filter. This is, to the best of our knowledge, the first review on the t opic. In particular, it is the first to try to draw the attention of the leak detection community to the important contributions that use the Kalman filter as the core of a computational pipeline monitoring system. Without being exhaustive, we try to gather the results from different research groups and present them in a unified fashion. For this reason, we propose a classification of the current approaches based on the Kalman filter. For each of the existing approaches within this classification, the basic concepts, fundamental results, and relations with the other approaches are discussed in detail. The review starts from a short summary of basic concepts about state observers. Then, a brief history of the use of the Kalman filter for diagnosing leaks is described by mentioning the most outstanding approaches. At last, we briefly discuss some emerging research problems, such as the leak detection in pipelines transporting heavy oils, and we discuss the main challenges and some open problems.

Starch is a biopolymer with wide potential for the generation of new biodegradable packages due to its high availability and low price. However, due to its weak functional properties, it is necessary to limit the interaction of some hydroxyl, and to evaluate blends with other polymers to improve their performance. Glycerol plasticized acetylated corn starch films were developed by the casting method, and the impact of incorporating chitosan (TPS:CH) at various proportions (75:25, 50:50, and 25:75 v/v) was studied. The effect of the chitosan ratios on the films' physical, mechanical, water vapor barrier, and thermal properties was evaluated. Chitosan protonated amino groups promote the formation of intermolecular bonds, improving the tensile strength, the thermal stability, the water adsorption capacity, and the gas barrier of starch films. Where the film composed of TPS25-CH75 was the one that presented the best barrier to water vapor. These composite films are a good option for development of biodegradable packaging.

Background: There is limited data on gender-based differences in atrial fibrillation (AF) treatment and prognosis. Our aim was to examine gender-related differences in medical attention in emergency department (ED) and follow-up (FU) among patients diagnosed with an AF episode and to determine whether there are gender-related differences in clinical characteristics, therapeutic strategies and long-term adverse events in this population. Methods: We performed a retrospective observational study of patients who presented to a tertiary hospital ER for AF from 2010-2015, with a minimum FU of one year. Data on medical attention received, mortality and other adverse outcomes were collected and analyzed. Results: Among the 2 013 patients selected, 1232 (60%) was female. Women were less likely than men to be evaluated by a cardiologist during the ED visit (11.5% vs. 16.6%, p=0.001) and were less likely to be admitted (5.9% vs. 9.5%, p<0.05). Electrical cardioversion was performed more frequently in men, both during the first episode (3.4% vs. 1.2%, p=0.001) and during FU (15.9% vs. 10.6%, p<0.001), in spite of a lower AF recurrence rate in women (9.9% vs 18.1%). During FU, women had more hospitalizations for heart failure (26.2% vs. 16.1%, p<0.001). Conclusions: In patients with AF, although no gender differences in mortality, there were significant differences in clinical outcomes, medical attention received, and therapeutic strategies. Women underwent fewer attempts at cardioversion, had a lower probability of being evaluated by cardiologists and showed a higher probability of hospitalization for heart failure. Being alert to these iniquities should facilitate to adopt measures to correct them.