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Efficacy of Spectral Signatures for The Automatic Classification of Abnormal Ventricular Potentials in Substrate-Guided Mapping Procedures
No full textSeveral peculiar spectral signatures of post-ischaemic ventricular tachycardia (VT) electrograms (EGMs) have been recently published in the scientific literature. However, despite they were claimed as potentially useful for the automatic identification of arrhythmogenic targets for the VT treatment by trans-catheter ablation, their exploitation in machine learning (ML) applications has been not assessed yet. The aim of this work is to investigate the impact of the information retrieved from these frequency-domain signatures in modelling supervised ML tools for the identification of physiological and abnormal ventricular potentials (AVPs). As such, 1504 bipolar intracardiac EGMs from nine electroanatomic mapping procedures of post-ischaemic VT patients were retrospectively labelled as AVPs or physiological by an expert electrophysiologist. In order to assess the efficacy of the proposed spectral features for AVPs recognition, two different classifiers were adopted in a 10-time 10-fold cross-validation scheme. In both classifiers, the adoption of spectral signatures led to recognition accuracy values above 81%, suggesting that the use of the frequency-domain characteristics of these signals can be successfully considered for the computer-aided recognition of AVPs in substrate-guided mapping procedures
Automatic Recognition of Ventricular Abnormal Potentials in Intracardiac Electrograms
No full textVentricular abnormal potentials are low-amplitude electrical signals that appear in intracardiac electrograms during a QRS or with an unpredictable delay with respect to it. Their spatial localization can be exploited by cardiologists for the identification of the ablation targets in substrate-guided mapping and ablation procedures. In this work, an automatic approach for a reliable detection of such potentials in intracardiac electrograms is proposed.To this aim, 86 intracardiac electrograms from five patients with post-ischemic ventricular tachycardia, acquired by the CARTO3 System, were retrospectively annotated by an expert cardiologist, to be used for a supervised classifier training and test.The automatic detection was based on a non-linear denoising followed by a time-scale decomposition based on the continuous wavelet transform. Then, different morphological features were extracted from both the time-scale domain and the time domain, and used to feed a support vector machine trained to discriminate between physiological and abnormal potentials. The recognition accuracy exceeded 93%, paving the way to further developments and more extensive studies
Sustainable sparkling base wines obtained from waste matrices of the wine and honey supply chain
No full textThe present work was performed to improve the general quality characteristics of sparkling wines produced in Southern Italy (Sicily region) as well as the sustainability of the production process. To this purpose, two novel approaches were applied during experimental winemaking: (i), the use of raceme grapes (formed from the secondary shoots) of Grillo cultivar to improve the chemical characteristics of sparkling base wine; (ii), the technological selection of potential fructophilic Saccharomyces cerevisiae strains isolated from honey by-product to improve the alcoholic fermentations and the organoleptic features of bottled wines. The racemes are typical of Grillo cugrapes and mature 20 days after the primary production. The racemes, not reaching maturation, possess a high acidity, a low sugar content and pH values between 2.5-2.8. Thus, they represent a production scrap that can be enhanced through the production of base wines for sparkling wines in warm temperate climate areas, such as the Mediterranean Basin. The experimental vineyards were subjected to a topping operation to stimulate the production of racemes. The topping operation was carried out leaving a different number of buds in order to evaluate the incidence of the budding load on the quality of the grapes and musts. The yeasts used, previously isolated from honey by-products, were subjected to the genotypic identification and technologically characterization in order to select the strains with oenological potential. Four strains (SPF21, SPF42, SPF52 and SPF159) belonging to the species Saccharomyces cerevisiae have been used as starters to ferment raceme musts obtaining base wines characterized by a remarkable and significant sensation of acidity and flavour. This is the case with the Saccharomyces cerevisiae 'galactose –' yeasts: their fructophile index is generally higher than that of the standard S. cerevisiae yeasts (known as 'galactose +'). The SPF21, SPF42, SPF52 and SPF159 strains, which belongs to GAL- group, therefore has a naturally above-average propensity for fructose.
The experimental project was developed over two years at industrial level. The analysis of the chemical parameters of wines obtained through experimental vinifications showed the presence of high values of total acidity (10 g/l) and a low pH (<3). Furthermore, the base wines obtained at the end of fermentation were characterized by a discrete content of malic acid reaching a concentration of about 2.5 g/l. The presence of malic acid in the base wines is of considerable importance if a long-lasting sparkling wine has to be obtained and destined to a long aging. The present research has provided physicochemical and microbiological information on alcoholic fermentation conducted on must of Grillo racemes to produce base wines to be used for sparkling wine production. Fructophilic strains of S. cerevisiae, capable of regularly conducting alcoholic fermentation of a must with low pH and high quantity of organic acids, are of relevance for the application. At the same time, the physicochemical analyses of the base wines confirmed their suitability for the production of sparkling wine
Supervised Classification of Ventricular Abnormal Potentials in Intracardiac Electrograms
No full textVentricular abnormal potentials (VAPs) identification is a challenging issue, since they constitute the ablation targets in substrate-guided mapping and ablation procedures for ventricular tachycardia (VT) treatment. In this work, two approaches for the supervised classification of VAPs in bipolar intracardiac electrograms are evaluated and compared. To this aim, 954 bipolar electrograms were retrospectively annotated by an expert cardiologist. All signals were acquired from six patients affected by post-ischemic VT by the CARTO3 system at the San Francesco Hospital (Nuoro, Italy) during routine procedures. The first classification approach was based on a support vector machine trained and tested on four different features, extracted from both the time and time-scale domain, to identify physiological and abnormal potentials. Conversely, in order to assess the significance of the first approach and its features, in the second approach all the samples constituting a time-domain segment of each bipolar electrogram were given as input to a feed-forward artificial neural network. In both cases, the accuracy in VAPs and physiological potentials identification exceeded 79%, suggesting their efficacy and the possibility of VAPs automatic recognition without identifying peculiar features
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Use of selected indigenous yeasts from racemes of Grillo grape variety to improve the production of sparkling base wine
No full textThe production of sparkling wines in Sicily is increasing considerably. The most important oenological characteristics of high quality sparkling wines are high content of acidity and low pH. In Sicily, white grape varieties such as those of the cultivar Grillo are characterized by very low concentrations of malic and tartaric acids due to hot climate and reduced rainfall typical of the production area. On the other hand, a very large amount of raceme grapes, characterized by low pH and high content of tartaric and malic acids, is largely produced by Grillo varieties. Hence, the winemaking of racemes might represent a technological solution to increase the quality of the acids in the final wines. At the same time, the selection of yeast strains able to ferment grape must at very low pH is mandatory. With this in mind, the present research was carried out to isolate and selected novel yeast strains from racemes of Grillo cultivar and to set up an innovative ad hoc winemaking protocol to increase the acidity of sparkling base wine.
From spontaneous vinifications on Grillo grape racemes, 2873 yeasts were isolated and characterized at the phenotypic and genotypic level. A total of 493 Saccharomyces cerevisiae isolates were subject to intraspecific characterization by interdelta analysis. These strains were also screened on the basis of technological criteria (fermenting power and vigor, SO2 and alcohol tolerance and flocculence) and qualitative features (H2S production). Four strains of S. cerevisiae were selected and inoculated individually into must obtained from Grillo racemes at 12 and 16 % (w/v) of total sugars. All strains displayed a technological potential to drive the fermentation of must into wine at very low pH (2.5-2.8). The inoculation of the strains was performed after a pre-adaptation at pH 2.5. Thus, starters were able to successfully lead fermentation. For the first time an ecological investigation of yeast ecology of raceme grapes has been carried out and an innovative strategy to improve acidity of sparkling base wine in hot climate regions has been designed
Diversity of Saccharomyces cerevisiae strains associated to racemes of Grillo grape variety
No full textThe most important oenological characteristics of high-quality sparkling wines are high content of acidity and low pH. Racemes are late-maturing grapes of Grillo variety characterized by low pH and high content of tartaric and malic acids and, due to their intrinsic characteristics, might represent an interesting technological solution to increase acid quality of base sparkling wine. To this purpose, the use of yeasts able to ferment grape must at very low pH is mandatory for the success of the process. In this work, 261 Saccharomyces cerevisiae isolated from spontaneous vinifications of Grillo grape racemes were subject to intraspecific characterization by interdelta analysis which evidenced a total population consisting of 82 strains which were screened for their basis of technological traits including SO2 and alcohol tolerance, flocculence, growth at low temperatures and qualitative features such as H2S production. A total of 11 strains with interesting technological performance in vitro were inoculated into musts obtained from racemes of Grillo grape variety and microfermentation were monitored. For the first time an ecological investigation of yeast associated to raceme grapes has been carried out and provided an innovative strategy to improve the acidity of a Sicilian sparkling base wine from Grillo grape variety
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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