Nearest-neighbor based wavelet entropy rate measures for intrapartum fetal heart rate variability.

The interpretation and analysis of intrapartum fetal heart rate (FHR), enabling early detection of fetal acidosis, remains a challenging signal processing task. The ability of entropy rate measures, amongst other tools, to characterize temporal dynamics of FHR variability and to discriminate non-healthy fetuses has already been massively investigated. The present contribution aims first at illustrating that a k-nearest neighbor procedure yields estimates for entropy rates that are robust and well-suited to FHR variability (compared to the more commonly used correlation-integral algorithm). Second, it investigates how entropy rates measured on multiresolution wavelet and approximation coefficients permit to improve classification performance. To that end, a supervised learning procedure is used, that selects the time scales at which entropy rates contribute to discrimination. Significant conclusions are obtained from a high quality scalp electrode database of nearly two thousands subjects collected in a French public university hospital.

Universal intermittent properties of particle trajectories in highly turbulent flows.

We present a collection of eight data sets from state-of-the-art experiments and numerical simulations on turbulent velocity statistics along particle trajectories obtained in different flows with Reynolds numbers in the range R{lambda}in[120:740]. Lagrangian structure functions from all data sets are found to collapse onto each other on a wide range of time lags, pointing towards the existence of a universal behavior, within present statistical convergence, and calling for a unified theoretical description. Parisi-Frisch multifractal theory, suitably extended to the dissipative scales and to the Lagrangian domain, is found to capture the intermittency of velocity statistics over the whole three decades of temporal scales investigated here.

Discrepancy between subcritical and fast rupture roughness: a cumulant analysis.

Rough crack fronts in a sheet of paper, obtained during a creep experiment, do not follow true scaling laws. Local roughness exponents are estimated using the first order cumulant, a quantity recently introduced in the turbulence literature [J. Delour, J. F. Muzy, and A. Arneodo, Eur. Phys. J. B 23, 243 (2001)10.1007/s100510170074]. Using a large data set (102 fronts), we find a significant difference in local roughness between the slow (subcritical) and the fast growth regime.

Intermittency of velocity time increments in turbulence.

We analyze the statistics of turbulent velocity fluctuations in the time domain. Three cases are computed numerically and compared: (i) the time traces of Lagrangian fluid particles in a (3D) turbulent flow (referred to as the dynamic case); (ii) the time evolution of tracers advected by a frozen turbulent field (the static case); (iii) the evolution in time of the velocity recorded at a fixed location in an evolving Eulerian velocity field, as it would be measured by a local probe (referred to as the virtual probe case). We observe that the static case and the virtual probe cases share many properties with Eulerian velocity statistics. The dynamic (Lagrangian) case is clearly different; it bears the signature of the global dynamics of the flow.

Lagrangian velocity statistics in turbulent flows: effects of dissipation.

We use the multifractal formalism to describe the effects of dissipation on Lagrangian velocity statistics in turbulent flows. We analyze high Reynolds number experiments and direct numerical simulation data. We show that this approach reproduces the shape evolution of velocity increment probability density functions from Gaussian to stretched exponentials as the time lag decreases from integral to dissipative time scales. A quantitative understanding of the departure from scaling exhibited by the magnitude cumulants, early in the inertial range, is obtained with a free parameter function D(h) which plays the role of the singularity spectrum in the asymptotic limit of infinite Reynolds number. We observe that numerical and experimental data are accurately described by a unique quadratic D(h) spectrum which is found to extend from h(min) approximately 0.18 to h(max) approximately 1.

Comparison of the rates of adverse drug reactions. Ionic contrast agents, ionic agents combined with steroids, and nonionic agents.

The influence of ionic agents alone, of diatrizoate plus two oral doses of methylprednisolone premedication, and of a nonionic agent (iohexol) upon the frequency and severity of adverse drug reactions (ADRs) was compared in ten hospitals during three separate time periods from 1985 to 1989. Nonionic agents were found to reduce significantly total ADRs; 52 of 8857 patients receiving nonionic agents experienced reactions, versus 263 of 6006 patients for ionics (P less than .0001). The frequency of reactions classed as mild (2.9% for ionic agents versus 0.476 for nonionic agents: P less than .001), moderate (1.2% versus 0.1%; P less than .001), or severe (0.37% versus 0.01%; P less than .001), also favored nonionic agents. Steroid premedication provided some protection, but iohexol was significantly better with respect to mild reactions (2.9% versus 0.4%, P less than .001), moderate reactions (0.9% versus 0.1%, P less than .01), and severe reactions (0.25% versus 0.01%, P less than .01). The contrast medium was the greatest risk factor for adverse reaction (odds ratio 7.3), while prior contrast reaction (odds ratio 6.25), and hay fever (odds ratio 2.3) were found to be significant independent risks. We conclude that nonionic agents are safer for intravenous use than ionic agents given alone or with corticosteroid premedication.