An iterative warping and clustering algorithm to estimate multiple wave-shape functions from a nonstationary oscillatory signal

Nonsinusoidal oscillatory signals are everywhere. In practice, the nonsinusoidal oscillatory pattern, modeled as a 1-periodic wave-shape function (WSF), might vary from cycle to cycle. When there are finite different WSFs, $s_1,\ldots,s_K$, so that the WSF jumps from one to another suddenly, the different WSFs and jumps encode useful information. We present an iterative warping and clustering algorithm to estimate $s_1,\ldots,s_K$ from a nonstationary oscillatory signal with time-varying amplitude and frequency, and hence the change points of the WSFs. The algorithm is a novel combination of time-frequency analysis, singular value decomposition entropy and vector spectral clustering. We demonstrate the efficiency of the proposed algorithm with simulated and real signals, including the voice signal, arterial blood pressure, electrocardiogram and accelerometer signal. Moreover, we provide a mathematical justification of the algorithm under the assumption that the amplitude and frequency of the signal are slowly time-varying and there are finite change points that model sudden changes from one wave-shape function to another one.Comment: 39 pages, 11 figure

Enhancing Missing Data Imputation of Non-stationary Signals with Harmonic Decomposition

Dealing with time series with missing values, including those afflicted by low quality or over-saturation, presents a significant signal processing challenge. The task of recovering these missing values, known as imputation, has led to the development of several algorithms. However, we have observed that the efficacy of these algorithms tends to diminish when the time series exhibit non-stationary oscillatory behavior. In this paper, we introduce a novel algorithm, coined Harmonic Level Interpolation (HaLI), which enhances the performance of existing imputation algorithms for oscillatory time series. After running any chosen imputation algorithm, HaLI leverages the harmonic decomposition based on the adaptive nonharmonic model of the initial imputation to improve the imputation accuracy for oscillatory time series. Experimental assessments conducted on synthetic and real signals consistently highlight that HaLI enhances the performance of existing imputation algorithms. The algorithm is made publicly available as a readily employable Matlab code for other researchers to use

Procesamiento, análisis y modelado de señales biomédicas: un enfoque integrador

Este proyecto se centra en el estudio, desarrollo y aplicación de técnicas de procesamiento, modelado y análisis de señales que permitan abordar los casos de señales biomédicas. Abordaremos métodos adaptativos de análisis de señales, principalmente la descomposición empírica en modos y sus variantes. Se avanzará en el desarrollo de modelos de las señales relacionadas con el aparato fonador. Se continuará el estudio de modelos en espacio de estados que permiten extraer información sobre el estado instantáneo del tracto vocal y de la fuente glótica. Se estudiará la factibilidad de extraer nuevos parámetros acústicos de utilidad clínica. Investigaremos técnicas y herramientas provenientes de la teoría de la información estudiando medidas basadas en la integral de correlación asistida por ruido y la integral de correlación U, propuestas por nuestro grupo, para la estimación de los invariantes dimensión, entropía y ruido, en sistemas simulados y reales de variadas dimensiones. Finalmente, se continuará con la formación de recursos humanos, a través de la realización de becas postdoctorales y doctorales CONICET, y el fortalecimiento de un grupo de investigación en el área de las TICs en el procesamiento de señales biomédicas, en el contexto del Instituto de Bioinformática y Bioingeniería en vías de creación. ARK/CAICYT: http://id.caicyt.gov.ar/ark:/s22504559/rd18ww2h

Oxidative status and stress during highly energetic life-history stages of Chinstrap Penguins: breeding versus molting

Life-history stages such as reproduction and molt are energetically costly. Reproductive costs include those associated not only with offspring production, but also protecting and provisioning young. Costs typically associated with molting include decreased thermoregulatory and locomotive performance, and increased metabolic and nutritional costs. Energetic demands may disrupt homeostasis, particularly in terms of its maintenance (e.g., oxidative stress and immunity). Few investigators have explored the relationship between effort (increased metabolic rate) and oxidative status and stress by comparing life-history stages with different energetic demands. However, comparative studies are crucial for understanding the processes of energy allocation and their consequences for different physiological functions. Our objective was to determine how two highly demanding life-history stages, breeding and molting, affected oxidative balance in Chinstrap Penguins (Pygoscelis antarcticus), a species where these two activities do not overlap. We found that the heterophil/lymphocyte (H/L) ratio was significantly higher during breeding than molting; oxidative damage was also higher during breeding. In contrast, we found no significant differences between these stages in total antioxidant capacity. We also found sex differences, with males having greater oxidative damage than females. Our results suggest that breeding is more stressful and more demanding for Chinstrap Penguins than molting, and provide further support for the relationship between effort, in terms of increased metabolic rate, and oxidative balance.Fil: Colominas Ciuró, Roger. Consejo Superior de Investigaciones Cientificas. Museo Nacional de Ciencias Naturales; EspañaFil: Masero, José A.. Universidad de Extremadura; EspañaFil: Benzal, Jesús. Consejo Superior de Investigaciones Científicas. Estación Experimental de Zonas Aridas; EspañaFil: Bertellotti, Néstor Marcelo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Centro para el Estudio de Sistemas Marinos; ArgentinaFil: Barbosa, Andrés. Consejo Superior de Investigaciones Cientificas. Museo Nacional de Ciencias Naturales; Españ

On the use of short-time Fourier transform and synchrosqueezing-based demodulation for the retrieval of the modes of multicomponent signals

Short communicationInternational audienceIn this paper, our goal is to compare different recent time-frequency (TF) approaches to retrieve the modes of multicomponent signals (MCSs). While it is acknowledged that the synchrosqueezing transform (SST) improves the readability of the time-frequency representation (TFR) of the modes of MCSs, and that SST-based demodulation (DSST) is more efficient than SST itself for mode retrieval (MR), it is unclear whether DSST outperforms downsampled short-time Fourier transform (STFT) in that matter. The goal of the present paper is to answer this question and to propose a variant of DSST that reduces mode-mixing. The focus is put on the sensitivity of the different techniques to frequency modulation for the modes and frequency resolution

First record of Babesia sp. in Antarctic penguins

This is the first reported case of Babesia sp. in Antarctic penguins, specifically a population of Chinstrap penguins (Pygoscelis antarctica) in the Vapour Col penguin rookery in Deception Island, South Shetlands, Antarctica. We collected peripheral blood from 50 adult and 30 chick Chinstrap penguins. Examination of the samples by microscopy showed intraerythrocytic forms morphologically similar to other avian Babesia species in12 Chinstrap penguinadults and sevenchicks. The estimated parasitaemias ranged from 0.25 × 10−2%to 0.75 × 10−2%. Despite the low number of parasites found inblood smears, semi-nested PCR assays yielded a 274 bp fragment in 12 of the 19 positive blood samples found by microscopy. Sequencing revealed that the fragment was 97% similar to Babesia sp. 18S rRNA from Australian Little Penguins (Eudyptula minor) confirming presence of the parasite. Parasite prevalence estimated by microscopy in adults and chicks was higher (24% vs. 23.3%, respectively) than found by semi-nested PCR (16% vs. 13.3% respectively).Although sampled penguins were apparently healthy,the effect of Babesia infection in these penguins is unknown. The identification of Babesia sp. inAntarctic penguins is an important finding. Ixodes uriae, as the only tick species present in the Antarctic Peninsula, is the key to understanding the natural history of this parasite. Future work should address the transmission dynamics and pathogenicity of Babesia sp. in Chinstrap penguin as well as in other penguin species, such as Gentoo penguin (Pygoscelis papua) and Adélie penguin (Pygoscelis adeliae), present within the tick distribution range in the Antarctic Peninsula.Fil: Montero, Estrella. Instituto de Salud Carlos III; EspañaFil: González, Luis Miguel. Instituto de Salud Carlos III; EspañaFil: Chaparro, Alberto. Instituto de Salud Carlos III; EspañaFil: Benzal, Jesus. Consejo Superior de Investigaciones Científicas. Estación Experimental de Zonas Aridas; EspañaFil: Bertellotti, Néstor Marcelo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico; ArgentinaFil: Masero, Jose A.. Universidad de Extremadura; EspañaFil: Colominas Ciuró, Roger. Museo Nacional de Ciencias Naturales; EspañaFil: Vidal Burgos, Virginia. Museo Nacional de Ciencias Naturales; EspañaFil: Barbosa, Andres. Museo Nacional de Ciencias Naturales; Españ

Incubation increases oxidative imbalance compared to chick rearing in a seabird, the Magellanic penguin (Spheniscus magellanicus)

It is expected that activities which require a high use of energy could generate higher oxidative stress. In the present study, we have compared two breeding periods (incubation and chick rearing) with different energetic demands in the Magellanic penguin, predicting a higher oxidative unbalance during chick rearing since involves higher demanding activities such as chick feeding and greater nest protection than during incubation. Specifically, we predicted higher oxidative damage and lower antioxidant defences during chick rearing than during incubation. Fieldwork was conducted in a Magellanic penguin colony located in Estancia San Lorenzo (42°05′S, 63°49′W), Peninsula Valdes, Argentina, during the breeding season of 2014–2015. Surprisingly, our results did not support our initial prediction. Incubating adults had their oxidative status unbalanced showing significantly lower antioxidant levels than those rearing chicks. Moreover, oxidative damage did not show any significant variation between both breeding periods. Further, we did not find differences in oxidative status between sexes. Our results suggest that incubation is a highly demanding activity compared to chick rearing in terms of oxidative balance since the lower presence of antioxidants can be explained as they have probably depleted to limit oxidative damage by ROS. Differential foraging effort could explain such results as Magellanic penguins adjust their foraging location to prey availability performing longer foraging trips during incubation than during chick rearing which increases the energy costs and therefore imbalance penguins oxidative status. Our results show the importance of examining physiological markers such as oxidative stress to assess differences during the breeding cycle and how the behaviour at sea could explain such differences in seabirds.This study was funded by the Spanish Ministry of Economy and Competitiveness (CTM2011-24427). RCC received financial aid from an FPI and a mobility grant from the Spanish Ministry of Economy and Competitiveness (BES2012-059299 and EEBB-I-14-078877),Peer Reviewe