1,721,029 research outputs found
Ultra-short term HRV features as surrogates of short term HRV: A case study on mental stress detection in real life
Full text linkBackground: This paper suggests a method to assess the extent to which ultra-short Heart Rate Variability (HRV) features (less than 5 min) can be considered as valid surrogates of short HRV features (nominally 5 min). Short term HRV analysis has been widely investigated for mental stress assessment, whereas the validity of ultra-short HRV features remains unclear. Therefore, this study proposes a method to explore the extent to which HRV excerpts can be shortened without losing their ability to automatically detect mental stress. Methods: ECGs were acquired from 42 healthy subjects during a university examination and resting condition. 23 features were extracted from HRV excerpts of different lengths (i.e., 30 s, 1 min, 2 min, 3 min, and 5 min). Significant differences between rest and stress phases were investigated using non-parametric statistical tests at different time-scales. Features extracted from each ultra-short length were compared with the standard short HRV features, assumed as the benchmark, via Spearman's rank correlation analysis and Bland-Altman plots during rest and stress phases. Using data-driven machine learning approaches, a model aiming to detect mental stress was trained, validated and tested using short HRV features, and assessed on the ultra-short HRV features. Results: Six out of 23 ultra-short HRV features (MeanNN, StdNN, MeanHR, StdHR, HF, and SD2) displayed consistency across all of the excerpt lengths (i.e., from 5 to 1 min) and 3 out of those 6 ultra-short HRV features (MeanNN, StdHR, and HF) achieved good performance (accuracy above 88%) when employed in a well-dimensioned automatic classifier. Conclusion: This study concluded that 6 ultra-short HRV features are valid surrogates of short HRV features for mental stress investigation.Background: This paper suggests a method to assess the extent to which ultra-short Heart Rate Variability (HRV) features (less than 5 min) can be considered as valid surrogates of short HRV features (nominally 5 min). Short term HRV analysis has been widely investigated for mental stress assessment, whereas the validity of ultra-short HRV features remains unclear. Therefore, this study proposes a method to explore the extent to which HRV excerpts can be shortened without losing their ability to automatically detect mental stress. Methods: ECGs were acquired from 42 healthy subjects during a university examination and resting condition. 23 features were extracted from HRV excerpts of different lengths (i.e., 30 s, 1 min, 2 min, 3 min, and 5 min). Significant differences between rest and stress phases were investigated using non-parametric statistical tests at different time-scales. Features extracted from each ultra-short length were compared with the standard short HRV features, assumed as the benchmark, via Spearman's rank correlation analysis and Bland-Altman plots during rest and stress phases. Using data-driven machine learning approaches, a model aiming to detect mental stress was trained, validated and tested using short HRV features, and assessed on the ultra-short HRV features. Results: Six out of 23 ultra-short HRV features (MeanNN, StdNN, MeanHR, StdHR, HF, and SD2) displayed consistency across all of the excerpt lengths (i.e., from 5 to 1 min) and 3 out of those 6 ultra-short HRV features (MeanNN, StdHR, and HF) achieved good performance (accuracy above 88%) when employed in a well-dimensioned automatic classifier. Conclusion: This study concluded that 6 ultra-short HRV features are valid surrogates of short HRV features for mental stress investigation
Detection and Compensation of Inter-Channel Time Offsets in Indirect Fetal ECG Sensing
No full textNon-invasive fetal electrocardiogram (FECG) through multichannel maternal abdominal sensing requires a suitable signal processing in order to enhance the signal-to-noise ratio and produce a single FECG signal from which parameters of interest, such as fetal heart rate (FHR), can be determined. Several processing techniques have been presented in the literature, which can benefit from the number of channels involved in the processing. Among these, the recently presented spatio-temporal filtering (STF) performs a weighted sum of QRS complexes to produce the enhanced FECG signal, whose weighting coefficients are calculated on the basis of the quality of synchronization among different channels. After analyzing clinical FECG signals and proving that a deterministic time offset can affect abdominal FECG channels, the paper proposes an algorithm for the automatic compensation of such systematic effect, as a pre-processing block of STF-like techniques
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
A collaborative RESTful cloud-based tool for management of chromatic pupillometry in a clinical trial
No full textChromatic Pupillometry represents a novel approach for the assessment of Inherited Retinal Diseases. A multi-centric pilot study with a sample of 40 paediatric patients has been designed, involving physicians and engineers. In this paper, the Electronic Medical Record, named ORÁO and specifically developed to collect ophthalmologic and pupillometric data, is presented. The platform is a cloud- based application, with a RESTful and three-tier architecture. These features make it available via web for the ophthalmologists involved in the project and working in two different University centres. The platform has been designed by the whole team and developed by the Department of Information Engineering of the University of Florence. The interfaces of the medical record have been evaluated in term of Usability, according to standards. An Heuristic Evaluation has been performed in the first stage of the design of the platform and the main severe usability issues have been addressed. The outcome of the project is a customized software solution. Moreover, the physicians have an excellent attitude toward the use of ORÁO and they perceive it as a useful tool to gather the data they collect with the aim of evaluating the overall progression of the pilot study
Integration of loop gain measurement circuit for stability evaluation in DC/DC converters with time-based control
No full textThe crossover frequency of DC/DC converters is related to some key dynamic performances such as line and load transient response. In integrated converters, its experimental measurement using standard techniques requires the connection to internal nodes of the controller that are not always accessible to the user. This paper presents a novel integrated loop gain measurement circuit for DC/DC converters with time-based control. The proposed circuit requires only two current-controlled delay lines, a transconductor, and two flip-flops that can be easily integrated with limited area occupation. An analytic description that relates the circuit parameters with the loop gain transfer function is provided along with some design rules for the transistor-level implementation. A prototype of the loop gain measurement circuit has been embedded in a DC/DC boost converter with time-based control designed in a BCD technology with 180 nm CMOS. The circuit has an area occupation of 0.027 mm2 with a current consumption of a few tens of mu A
Studio dell'effetto della brefeldrina sulla moltiplicazione intracellulare di Legionella pneumophila
No full textAn automatic system supporting clinical decision for chronic obstructive pulmonary disease
No full textThis paper presents a system supporting clinical decisions for patients with Chronic Obstructive Pulmonary Disease (COPD). The system should partially fill the gaps highlighted during an analysis of the current state of the art of Clinical Decision Support Systems (CDSS) for telemonitoring patients affected by COPD. The first step taken was to replicate the performance of similar decision support systems found in the scientific literature. Using physiological parameters drawn from respiratory function tests on 414 patients, two predictive models were created using two machine-learning algorithms: neural network and support vector machine. Performance was comparable to that described in the literature. The results made it possible to affirm that the data available were sufficient to evaluate the extent of respiratory deficit. The next step was to create a new predictive model with better performance than previously obtained. The C5.0 Machine Learning Algorithm was chosen for the development of the model. The resulting performance on the data available was significantly better than with the two previous models. This new predictive model, called COPD, was then implemented in a user interface created using Java programming language. The new software developed, which enables the evaluation and classification of respiratory test results and which can be used in many clinical applications, provides excellent performance compared to the current state of the art
Variations on the Author
Full text link“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
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