Search results for "Serie"

Linear and nonlinear parametric model identification to assess granger causality in short-term cardiovascular interactions

2008

We assessed directional relationships between short RR interval and systolic arterial pressure (SAP) variability series according to the concept of Granger causality. Causality was quantified as the predictability improvement (PI) of a time series obtained when samples of the other series were used for prediction, i.e. moving from autoregressive (AR) to AR exogenous (ARX) prediction. AR and ARX predictions were performed both by linear and nonlinear parametric models. The PIs of RR given SAP and of SAP given RR, measuring baroreflex and mechanical couplings, were calculated in 15 healthy subjects in the resting supine and upright tilt positions. Using nonlinear models we found a bilateral i…

Need of causal analysis for assessing phase relationships in closed loop interacting cardiovascular variability series

2003

The phase spectra obtained by the classical closed loop autoregressive model (2AR) and by an open loop autoregressive model (ARXAR) were compared to shed light on the need of introducing causality in the assessment of the delay between RR and arterial pressure oscillations. The reliability of the two approaches was tested in simulation and real data setting. In simulation, the coupling strength of a bivariate closed loop process was adjusted to obtain a range of working conditions from open to closed loop. In open loop condition, 2AR and ARXAR phases were comparable and in agreement with the imposed delay. In closed loop condition, ARXAR model returned the imposed delays, while 2AR showed a…

A new Framework for the Spectral Information Decomposition of Multivariate Gaussian Processes

2021

: Different information-theoretic measures are available in the literature for the study of pairwise and higher-order interactions in multivariate dynamical systems. While these measures operate in the time domain, several physiological and non-physiological systems exhibit a rich oscillatory content that is typically analyzed in the frequency domain through spectral and cross-spectral approaches. For Gaussian systems, the relation between information and spectral measures has been established considering coupling and causality measures, but not for higher-order interactions. To fill this gap, in this work we introduce an information-theoretic framework in the frequency domain to quantify t…

Analysis of neuronal networks in the visual system of the cat using statistical signals--simple and complex cells. Part II.

1978

Superimposing additively a two-dimensional noise process to deterministic input signals (bars) the neurons of area 17 show a class-specific reaction for the task of signal extraction. Moving both parts of the signals simultaneously and varying the signal to noise ratio (S/N) the simple cells achieve the same performance as resulted from the psychophysical experiment. Type I complex cells extract moving deterministic signals (i.e. bars) from the stationary noise, whereas in the answers of Type II complex cells the statistical parts of the signals predominate. Considering the different cell types each as a series of a linear and a nonlinear system one obtains the cell specific space-time freq…

ChemInform Abstract: A Series of Calix(4)arenes, Having Two Opposite Para Positions Connected by an Aliphatic Chain.

1989

On the use of fractional calculus for the probabilistic characterization of random variables

2009

In this paper, the classical problem of the probabilistic characterization of a random variable is re-examined. A random variable is usually described by the probability density function (PDF) or by its Fourier transform, namely the characteristic function (CF). The CF can be further expressed by a Taylor series involving the moments of the random variable. However, in some circumstances, the moments do not exist and the Taylor expansion of the CF is useless. This happens for example in the case of $\alpha$--stable random variables. Here, the problem of representing the CF or the PDF of random variables (r.vs) is examined by introducing fractional calculus. Two very remarkable results are o…

A method for the probabilistic analysis of nonlinear systems

1995

Abstract The probabilistic description of the response of a nonlinear system driven by stochastic processes is usually treated by means of evaluation of statistical moments and cumulants of the response. A different kind of approach, by means of new quantities here called Taylor moments, is proposed. The latter are the coefficients of the Taylor expansion of the probability density function and the moments of the characteristic function too. Dual quantities with respect to the statistical cumulants, here called Taylor cumulants, are also introduced. Along with the basic scheme of the method some illustrative examples are analysed in detail. The examples show that the proposed method is an a…

Radiolanthanides in Nuclear Medicine

2004

ELECTROCHEMICAL CONVERSION OF DICHLOROACETIC ACID TO CHLOROACETIC ACID IN A MICROFLUIDIC STACK AND IN A SERIES OF MICROFLUIDIC REACTORS

2015

The electrochemical conversion of dichloroacetic acid to chloracetic acid was performed in three different micro devices: a simple micro fluidic cell; a microfluidic stack equipped with various electrode chambers in series and three micro fluidic cells in series. The electrochemical synthesis of chloracetic acid was performed successfully with high yields and selectivity under a single-pass mode without supporting electrolyte at low cell voltages. An increase of the productivity and of the final concentration of the target product was achieved by using a stack with two or three electrode chambers in series. The utilization of three micro reactors in series open interesting new perspectives,…

Sicilian Chinese art collections and Chinoiserie

L'Europa ha creato uno stile unico di design decorativo nei secoli XVII-XVIII che è stato profondamente ispirato allo stile orientale di Cina, Giappone e India. Lo stile europeo è rimasto sconosciuto alla Cina in quel momento, ed è anche raramente menzionato nella storia dell'arte moderna e del design cinese. Tuttavia, la Chinoiserie ha rappresentato un tema ricorrente all'interno degli stili artistici europei, che non si presenta come una moda regionale, ma bensì come un movimento d'arte complesso e variabile in tutta Europa. La significativa ricerca sul design Chinoiserie è stata intrapresa nei XX-XXI secoli, con centinaia di monografie e articoli pubblicati in inglese, francese, tedesco …