On the Sparsest Representation of Electrocardiograms

In recent years, telecardiology has been growing in significance, due to the shortage of local caregivers in various parts of the world. As the cardiac data volume grows, compact representation becomes imperative in view of bandwidth, storage, power and other constraints. In this backdrop, we present empirical studies on electrocardiogram (ECG) signal representation using a wide variety of wavelet bases. Specifically, we arrange the transform coefficients in decreasing order of magnitude, and count the number of coefficients accounting for 99% of the signal energy (a sparser representation requires less number). We observe that 'Symlet' and 'Daubechies' families generally offer more compact representation compared to Meyer wavelet as well as biorthogonal and reverse biorthogonal families. In particular, the sparsest representation is provided by the 'sym4' (closely followed by the 'db4') wavelet basis for a broad class of ECG signals. Interestingly, this behavior is observed quite consistently across all fifteen (twelve standard and three Frank) leads. Our study assumes significance in the context of basis selection for various ECG signal processing applications, including compression, denoising and compressive sensin

On the Sparsest Representation of Electrocardiograms

In recent years, telecardiology has been growing in significance, due to the shortage of local caregivers in various parts of the world. As the cardiac data volume grows, compact representation becomes imperative in view of bandwidth, storage, power and other constraints. In this backdrop, we present empirical studies on electrocardiogram (ECG) signal representation using a wide variety of wavelet bases. Specifically, we arrange the transform coefficients in decreasing order of magnitude, and count the number of coefficients accounting for 99% of the signal energy (a sparser representation requires less number). We observe that 'Symlet' and 'Daubechies' families generally offer more compact representation compared to Meyer wavelet as well as biorthogonal and reverse biorthogonal families. In particular, the sparsest representation is provided by the 'sym4' (closely followed by the 'db4') wavelet basis for a broad class of ECG signals. Interestingly, this behavior is observed quite consistently across all fifteen (twelve standard and three Frank) leads. Our study assumes significance in the context of basis selection for various ECG signal processing applications, including compression, denoising and compressive sensin

Synthesis and preliminary biological profile of new NO-donor tolbutamide analogues.

We describe a new class of NO-donor hypoglycemic products obtained by joining tolbutamide, a typical hypoglycemic sulfonylurea, with a NO-donor moiety through a hard link. As NO-donors we chose either furoxan (1,2,5-oxadiazole 2-oxide) derivatives or the classical nitrooxy function. A preliminary biological characterization of these compounds, including stimulation of insulin release from cultured rat pancreatic β-cells and in vitro vasodilator and anti-aggregatory activities, is reported

Objective quality evaluation of an angularly-continuous light-field format

With the rapid advances in light-field display and camera technology, research in light-field content creation, visualization, coding and quality assessment has gained momentum. While light-field cameras are already available to the consumer, light-field displays need to overcome several obstacles in order to become a commonplace. One of these challenges is the unavailability of a light-field visualization format which can be used across various light-field displays. Existing light-field representations are optimized for specific displays and converting them for visualization on a different display is a computationally expensive operation, often resulting in the degradation of perceptual quality. To this end, an intermediate, display-independent and angularly-continuous light-field representation format has been proposed recently, targeted towards large-field-of-view light-field displays. In this paper, we evaluate the said data format in terms of degradation in objective quality under three compression methods. We found that, while offering display-independence, the intermediate light-field format maintains the same objective quality in general and achieves higher objective quality in some cases compared to the conventional linear camera representation

The viewing conditions of light-field video for subjective quality assessment

At the time of this paper, research on the quality of light-field visualization is continuously gaining momentum, as the excellence in visual performance shall be one of the key enablers of the emergence and long-Term presence of this technology on the consumer market. Experiments on perceived quality began in parallel with the appearance of commercially available light-field displays. As the techniques of subjective quality assessment on these displays are not standardized yet, certain parameters may greatly vary, such as viewing conditions. Although most of the current research efforts in this area address forms of static visualization, light-field video is also an essential target of quality evaluation. In this paper, we introduce the results of an experiment investigating the viewing conditions of light-field video quality assessment. The tests directly compare the perceived horizontal motion parallax of static viewing positions with motion patterns. The visual quality of the test conditions was degraded by the reduction of content spatial and angular resolution, as they both affect the smoothness of the horizontal motion parallax