Does the frequency of stochastic convergence in per capita ecological footprint matter?

Among the environmental economics research issues, the issue of convergence has received quite a lot of attention, which is also known as stationary analysis. In this research strand, whether shocks to the time series variable are permanent or temporary is tested via the unit root tests. In this study, based on the theory and empirical works of stochastic convergence, we evaluate the convergence for the BASIC member countries, including Brazil, South Africa, India, and China. We use a variety of methodologies to see whether the convergence of ecological footprint holds for these countries or not. We first use the wavelet decomposition technique to decompose the series into the short run, middle run, and long run, and then we run several unit root tests to confirm the stationarity property of the series. The methodologies implemented in this study allow us to apply econometric tests to the original series as well as to the decomposed series. The results of panel CIPS test demonstrate that the null hypothesis of unit root could be rejected for the short run but not for the middle and long run, implying that long-lasting impact might prevail due to any shocks to the ecological footprint in the middle and long run. The results for individual countries varied.

Seasonal dynamics of influenza in Brazil: the latitude effect.

BACKGROUND: Influenza is a global transmissible disease. Its dynamics is far better understood in temperate climates than in the tropics. We aim to close this knowledge gap between tropical and temperate regions by showing how the influenza seasonality evolves in Brazil, a tropical country that encompasses a wide range of latitudes and six climatic sub-types. METHODS: We analyzed a state-level, weekly Syndrome of Acute Respiratory Disease (SARI) incidence data ranging from 2010 to 2016. We combined two techniques hierarchically: first the wavelet decomposition technique to detect annual periodicity and then circular statistics to describe seasonal measures of the periodic states. RESULTS: We found significant annual periodicity in 44% of the states. For these, we calculated several seasonal measures such as the center of gravity or mean timing of activity. The relationship between the seasonal signatures and latitude was clear and statistically significant. States with seasonal signature are clustered along the coast. Most Amazonian and Central West states exhibit no seasonal behavior. Among the seasonal states, influenza starts in Northeast region, spreading southbound. CONCLUSIONS: Our study advances the comprehension of influenza seasonality in tropical areas and could be used to design more effective prevention and control strategies.

A wavelet-based method for power-line interference removal in ECG signals

Abstract Introduction The analysis of electrocardiogram (ECG) signals allows the experts to diagnosis several cardiac disorders. However, the accuracy of such diagnostic depends on the signals quality. In this paper it is proposed a simple method for power-line interference (PLI) removal based on the wavelet decomposition, without the use of thresholding techniques. Methods This method consists in identifying the ECG and noise frequency range for further zeroing wavelet detail coefficients in the subbands with no ECG coefficients in the frequency content. Afterward, the enhanced ECG signal is obtained by the inverse discrete wavelet transform (IDWT). In order to choose the wavelet function, several experiments were performed with synthetic signals with worse Signal-to-Noise Ratio (SNR). Results Considering the relative error metrics and runtime, the best wavelet function for denoising was Symlet 8. Twenty synthetic ECG signals with different features and eight real ECG signals, obtained in the Physionet Challenge 2011, were used in the experiments. Results show the advantage of the proposed method against thresholding and notch filter techniques, considering classical metrics of assessment. The proposed method performed better for 75% of the synthetic signals and for 100% of the real signals considering most of the evaluation measures, when compared with a thresholding technique. In comparison with the notch filter, the proposed method is better for all signals. Conclusion The proposed method can be used for PLI removal in ECG signals with superior performance than thresholding and notch filter techniques. Also, it can be applied for high frequencies denoising even without a priori frequencies knowledge.