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171 results on '"Varanini M"'

1. Deriving the respiratory sinus arrhythmia from the heartbeat time series using Empirical Mode Decomposition

Author

Balocchi, R., Menicucci, D., Santarcangelo, E., Sebastiani, L., Gemignani, A., Ghelarducci, B., and Varanini, M.

Subjects
Quantitative Biology - Tissues and Organs, Quantitative Biology - Quantitative Methods
Abstract

Heart rate variability (HRV) is a well-known phenomenon whose characteristics are of great clinical relevance in pathophysiologic investigations. In particular, respiration is a powerful modulator of HRV contributing to the oscillations at highest frequency. Like almost all natural phenomena, HRV is the result of many nonlinearly interacting processes; therefore any linear analysis has the potential risk of underestimating, or even missing, a great amount of information content. Recently the technique of Empirical Mode Decomposition (EMD) has been proposed as a new tool for the analysis of nonlinear and nonstationary data. We applied EMD analysis to decompose the heartbeat intervals series, derived from one electrocardiographic (ECG) signal of 13 subjects, into their components in order to identify the modes associated with breathing. After each decomposition the mode showing the highest frequency and the corresponding respiratory signal were Hilbert transformed and the instantaneous phases extracted were then compared. The results obtained indicate a synchronization of order 1:1 between the two series proving the existence of phase and frequency coupling between the component associated with breathing and the respiratory signal itself in all subjects., Comment: 12 pages, 6 figures. Will be published on "Chaos, Solitons and Fractals"

Published
2003
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9. Root exudates of grasses improve Fe uptake in a citrus rootstock sensitive to Fe-deficiency

Author

Cesco S., Varanini M., Pinton R., ROMBOLA', ADAMO DOMENICO, TAGLIAVINI, MASSIMO, C. J. LI ET AL., Cesco S., Rombolà A.D., Tagliavini M., Varanini M., and Pinton R.

Subjects
IRON DEFICIENCY, CITRUS, INTERCROPPING, PHYTOSIDEROPHORES, food and beverages, GRASSES
Abstract

Aim of the present work was to assess the capability of two perennial grasses (Poa pratensis L. and Festuca rubra L.) to improve Fe uptake by the highly-susceptible citrus rootstock citrumelo "Swingle". Citrus plants were unable to induce the physiological responses to Fe-deficiency; however, in these plants uptake of 59Fe from 59Fe-hydroxide could be increased by the presence of Fe-deficient grasses. No beneficial effect was observed with the use Fe-sufficient grasses. A progressive increase in 59Fe uptake by citrus plants was also evident after supplying increasing amounts of DMA, the major phytosiderofore (PS) released by grasses. Re-greening of Fe-deficient citrus plants was obtained by intercropping with grasses in rhizoboxes filled with a chlorosis-inducing calcareous soil; a concomitant increase in the amount of Fe in the leachates was also observed. Data indicate that Fe nutrition of a Fe-inefficient citrus rootstock can benefit from Fe mobilized by PS released by perennial graminaceous species.

Published
2005

12. Paradoxical response to an emotional task: Trait characteristics and heart-rate dynamics

Author

Balocchia, R., Varanini, M., Paoletti, G., Mecacci, G., Santarcangelo, E.L., Balocchia, R., Varanini, M., Paoletti, G., Mecacci, G., and Santarcangelo, E.L.

Abstract

Item does not contain fulltext, The present study evaluated the heart-rate dynamics of subjects reporting decreased (responders) or paradoxically increased relaxation (nonresponders) at the end of a threatening movie. Heart-rate dynamics were characterized by indices extracted through recurrence quantification analysis (RQA) and detrended fluctuation analysis (DFA). These indices were studied as a function of a few individual characteristics: hypnotizability, gender, absorption, anxiety, and the activity of the behavioral inhibition and activation systems (BIS/BAS). Results showed that (a) the subjective experience of responsiveness is associated with the activity of the behavioral inhibition system and (b) a few RQA and DFA indices are able to capture the influence of cognitive-emotional traits, including hypnotizability, on the responsiveness to the threatening task.

Published
2015

36. A multi-step approach for non-invasive fetal ECG analysis.

Author

Varanini, M, Tartarisco, G, Billeci, L, Macerata, A, Pioggia, G, and Balocchi, R

Abstract

Non-invasive monitoring of fetal cardiac activity is of great clinical interest to assess fetal health. To date, however, difficulties in detecting fetal beats from abdominal mother recordings prevented the possibility of obtaining reliable results. In this study a multi-step approach for the analysis of non-invasive fetal ECG is proposed. The first steps concern the pre-processing stages of baseline removal and power line interference canceling. The successive operations are: Independent Component Analysis (ICA) for maternal ECG extraction; mother QRS detection; maternal ECG canceling using a PQRST approximation obtained by weighted Singular Value Decomposition (SVD); second ICA applied to enhance the fetal ECG signal; fetal QRS detection. The results obtained in Physionet Challenge 2013 on the test sets are expressed as two scores (HRmse and RRrmse) measuring respectively the matching between the reference annotations of fetal HR and RR time series and those estimated with the developed software. The results obtained on the learning set are: sensitivity=99.4%, positive predictive accuracy=99.2% and HRmse=1.52 bpm2, RRrmse=2.11 ms. The scores for the open test set are: HRmse=34.0 bpm2, RRrmse=5.10 ms. The scores for the hidden test (open source section) are: HRmse=187 bpm2, RRrmse=21.0 ms. [ABSTRACT FROM PUBLISHER]

Published
2013

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