Monte carlo procedure for investigating light propagation and imaging of highly scattering media.

A Monte Carlo procedure has been developed to study photon migration through highly scattering nonhomogeneous media. When two scaling relationships are used, the temporal response when scattering or absorbing inhomogeneities are introduced can be evaluated in a short time from the results of only one simulation carried out for the homogeneous medium. Examples of applications to the imaging of defects embedded into a diffusing slab, a model usually used for optical mammography, are given.

A comparative analysis of fundamental frequency estimation methods with application to pathological voices.

One of the basic parameters characterising voiced phonation is the fundamental frequency, named pitch, which is the rate of vibration of the folds. In pathological voices. pitch variations within an utterance are indicative of the patient status.

Multiple scattering from Chebyshev particles: Monte Carlo simulations for backscattering in lidar geometry.

Lidar measurements are often interpreted on the basis of two fundamental assumptions: absence of multiple scattering and sphericity of the particles that make up the diffusing medium. There are situations in which neither holds true. We focus our interest on multiply-scattered returns from homogeneous layers of monodisperse, randomly oriented, axisymmetric nonspherical particles.

Parametric and non-parametric estimation of speech formants: application to infant cry.

The present paper addresses the issue of correctly estimating the peaks in the speech envelope (formants) occurring in newborn infant cry. Clinical studies have shown that the analysis of such spectral characteristics is a helpful noninvasive diagnostic tool. In fact it can be applied to explore brain function at very early stage of child development, for a timely diagnosis of neonatal disease and malformation.

Laboratory simulations of lidar returns from clouds.

The results of lidar measurements on laboratory-scaled cloud models are presented. The lidar system was based on a picosecond laser source and a streak camera. The cloud was simulated by a homogeneous aqueous suspension of calibrated microspheres.

Computerized cry analysis in infants affected by severe protein energy malnutrition.

A new method of computerized cry analysis has been utilized to evaluate the cries of infants affected by severe protein energy malnutrition. We studied 17 Kenian babies affected by severe malnutrition for more than four months (9 cases of marasmus and 8 of kwashiorkor) and a control group of 17 well-nourished babies. The cries of the malnourished children showed lower inter-utterance variability, formants' frequencies and cry score, assigned by the Infant Cry Modulation Assessment Scale.

Monte Carlo calculations of the modulation transfer function of an optical system operating in a turbid medium.

Using a Monte Carlo method, we investigate the effect of a turbid medium on image transmission by means of the modulation transfer function approach. We present results that refer to a medium that consists of a random distribution of water spherical particles in air. We analyze the effect of geometric conditions (medium width and position) and source characteristics (Lambertian, beam emission).

Transmission of a pulsed thin light beam through thick turbid media: experimental results.

Experimental results of light pulse transmission through thick turbid media are presented. Measurements have been carried out on polystyrene latex spheres by using a picosecond thin laser beam and a streak camera system. The results show that the shape of the received pulse depends mostly on the transport mean free path and on the absorption coefficient of the medium, indicating that both the absorption coefficient and the asymmetry factor of the scattering function can be obtained from the pulse shape.

Separation and analysis of forward scattered power in laboratory measurements of light beam transmittance through a turbid medium.

In laboratory measurements of the transmittance of a light beam through a diffusing medium (water plus latex spheres), a distinction between the attenuated beam power and the received forward scattered power was made possible by the use of a transmissometer whose receiver has a variable field of view. The dependence of the received scattered power on the FOV angle and on the medium optical depth was analyzed. The deduced separated contributions of first- and second-order scattering, as well as the total received scattered power, were compared to the results of calculations.