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Active solution processed nanomaterials have emerged as a very high promising candidates for photonic applications. The reason of this arises from the facts that they exhibit high quantum yield emission at room temperature and wavelength tunability, other than their processing involves easy and cheap fabrication techniques and a versatile integration on different substrates. In this way, active properties...
We show an enlargement in the free spectral range (FSR) of the emission spectra of a L7 photonic crystal microcavity (PCM). The FSR enlargement is achieved by the selective modal suppression of the second cavity mode. The selective suppression is made by introducing two nano-inclusions in specific sites within the defect region that forms the cavity. We have demonstrated the suppression of the second...
This paper presents a user-friendly interface in Matlab??, called BioSigBrowser, that aims to facilitate the use of algorithms in biomedical signal processing. It includes methods related with cardiovascular signal processing, namely some multimodal analysis. This platform can treat a single signal or work in a batch mode on a given database as is usual in research. Furthermore, its modular characteristic...
In this research, we propose an evolving neuro-fuzzy recurrent network (ENFRN). The network is capable to perceive the change in the actual system and adapt (self organize) itself to the new situation. The network generates a new hidden neuron if the smallest distance between the new data and all the existing hidden neurons (the winner neuron) is more than a given radius. We propose a new pruning...
In this work we studied the evolution of increased ventricular repolarization dispersion (VRD) in the ECG during ischemia induced by percutaneous transluminal coronary angioplasty (PTCA). T-wave duration is measured by an automatic delineator and proposed as a index to quantify increased VRD. Moreover, spatial complexity of repolarization is measured by singular value decomposition (SVD) related indexes...
QT interval is a surface ECG measure which has been the subject of great research interest. Usually, a prolongation of the QT interval beyond the normal value is associated with bad cardiac prognosis. In this paper we revisit the wavelet transform based method. Rather than using a threshold related or the highest inflection point of the derivative, we use the extreme on the second derivative which...
T-wave alternans (TWA) is considered as an index of susceptibility of sudden cardiac death. The Physionet/CinC challenge 2008 encourages teams to automatically detect and quantify the magnitude of TWA in every record of a given database. A reference ordering based on all entries submitted to the challenge is used for evaluation of algorithms. We participated in the challenge using a multilead analysis...
In a previous study, we presented a new approach to characterize heart rate turbulence (HRT). An HRT detector was developed which involved a HRT test statistic T (x), being based on Karhunen-Loeve (KL) basis functions. The purpose of the present study is to evaluate the performance of T (x) on simulated data and compare to that of turbulence onset (TO) and turbulence slope (TS). Three different simulations...
Several methods have been proposed to automatically detect and estimate T-wave alternans (TWA) in the ECG, all of them operating on a single-lead basis. In this study a multilead detection scheme is proposed. It combines principal component analysis with the Laplacian likelihood ratio method to improve the detection results. A simulation is carried out to evaluate the effect of different types of...
The objective of this work is to develop a model for ECG classification based on multilead features. The MIT-BIH Arrhythmia database was used following AAMI recommendations and class labeling. We used for classification classical features as well as features extracted from different scales of the wavelet decomposition of both leads integrated in an RMS manner. Step-wise and a randomized method were...
Electrogram (EGM) delineation is an increasingly important task to be performed in implantable cardiac devices such as pacemakers and defibrillators. Reliable detection and of EGM components might help to minimize the risk of false detections. Efforts are therefore undertaken to examine whether existing ECG delineators can be adapted for the delineation of EGMs. One issue to be solved is the low sampling...
Component tolerances and mismatches due to process variations severely degrade the performance of bandgap reference (BGR) circuits. In this paper, the authors describe the design of a BGR considering the Pelgrom's mismatch model. The main purpose of our methodology is to convey the design to reach a good trade-off between area and mismatch. Implemented in standard 0.35mum CMOS technology, the circuit...
The purpose of this study is to assess QT interval measurements from the EASI 12-lead ECG as compared to the standard 12-lead ECG. The QT interval was automatically measured in simultaneously recorded standard and EASI 12-lead ECGs, using a validated wavelet-based delineator. The agreement between the two sets of measurements was quantified both on a lead-by-lead basis and a multilead basis. The results...
In this work a multilead (ML) algorithm for ECG delineation was validated against the CSE and the PTB databases (DB). This algorithm is based on a previously validated single-lead (SL) algorithm, which is also used as reference in this work. For both DB a set of manual reference annotations made by experts is available. The algorithm performance was assessed by the measurement of QRS onset (QRSon)...
In this work we analyzed the T wave width evolution on an ECG database containing 27 records coming from diabetic patients performing the Valsalva Maneuver (VM). The objective is to assess whether the maneuver is accompanied with early signs of ischemia and if those are measurable by T wave shortening. The hypothesis for this T wave shortening is that endocardial action potentials reduce their duration...
Prolonged QT interval is considered as an index of propensity to dangerous ventricular tachyarrhythmias. The Physionet/CinC challenge 2006 encourages teams to automatically measure the QT interval of lead Il's first representative beat in every record of the PTB database. A "median self-centering approach" based on manual entries to the challenge is used for evaluation of algorithms. We...
The precision of QT interval measures depends on the correct location of QRS and T boundaries and also on the analysing lead. The usual automatic strategy to deal with multiple leads is to apply post-processing decision rules for selecting one of the single-lead (SL) measures. We proposed a multilead VCG strategy that locates the onset and the end of the QT interval, attending to an optimal transformed...
In this work we studied the evolution of ventricular repolarization dispersion (VRD) in the ECG during ischemia induced by Percutaneous Transluminal Coronary Angioplasty (PTCA). We hypothesized that at early ischemia stages the endocardium action potential duration (APD) is slightly reduced or unchanged while the epicardium one is reduced in a larger proportion and afterwards the APD at the epicardium...
In this work we evaluate the joint robustness of a multilead delineation and a parametric approach to study the relations between HRV and QTV. The performance of the automatic system is studied over simulated 3-lead ECG signals in order to quantify the improvement allowed by the multilead delineation. Respiratory effect and contamination with realistic noise extracted from a real ECG, rescaled to...
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