Vladimir V. Berdnik

Characterization of optically soft spheroidal particles by multiangle light-scattering data by use of the neural-networks method.

A method for evaluating the size of optically soft spheroidal particles by use of the angular structure of scattered light is proposed. It is based on the use of multilevel neural networks with a linear activation function. The retrieval errors of radius R of the equivolume sphere and aspect ratio e are investigated. The ranges of the size of R, e, and the refractive index are 0.3-1.51 microns, 0.2-1, and 1.01-1.02, respectively. The retrieval errors of the equivolume radius and aspect ratio are 0.004 micron and 0.02, respectively, for a three-level neural network (at a precisely measured angular distribution of scattered light). The retrieval errors of R and e for a one-level neural network are 2-5 times greater. The errors for a multilevel neural network increase faster than those for a single-level network.

Light scattering and morphology of the lymphocyte as applied to flow cytometry for distinguishing healthy and infected individuals.

A simple optical model of single lymphocytes with smooth and nonsmooth surfaces has been developed for healthy and infected individuals. The model can be used for rapid (in the real-time scale) solution of the inverse light-scattering problem on the basis of optical data measured by label-free flow cytometry. Light scattering patterns have been calculated for the model developed. It has been shown that the smooth and nonsmooth cells can be resolved using the intensities of the sideward- and backward-scattered light. We have found by calculations and validated by the flow cytometer experiments that intensity distributions for the cells of lymphocyte populations can be used as a preliminary signatures of some virus infections. Potential biomedical applications of the findings for label-free flow cytometry detection of individuals infected with viruses of hepatitis B or C and some others viruses are presented.

Radiative transfer in a layer with oriented spheroidal particles

Abstract We present the results of numerical modeling of the angular distribution of radiation at the boundaries of and inside the layer with oriented spheroidal particles for the case of oblique incidence of a parallel beam of radiation upon the layer. The optical properties of particles controlling the elementary act of scattering are calculated in the Rayleigh–Gans approximation. To describe the propagation of radiation in the layer, we use the radiative transfer equation in which the medium characteristics depend on the direction of propagation. The influence of Fresnel reflections from the layer boundaries and the influence of a substrate are taken into account.

MODELLING OF RADIATIVE TRANSFER IN DISPERSE LAYERS OF A MEDIUM WITH A HIGHLY STRETCHED PHASE FUNCTION

Abstract We consider a method for solving the radiative transfer equation (RTE) based on the representation of the azimuth-averaged phase function as a combination of a smooth phase function and the Dirac delta function. Unlike the traditional transport approximation, the separation of delta anisotropy in the azimuth-averaged phase function leads to the necessity of solving the RTE with characteristics depending on the direction of radiation propagation. This makes it possible to achieve a better correspondence of the properties of the smoothed phase function to the potentialities of the quadrature formulas used to solve the RTE.

Multiple scattering in polymer dispersed liquid crystal films

A model to describe light transfer in polymer dispersed liquid crystal (PDLC) films has been developed. It takes into account the anisotropy of the nematic liquid crystal droplets, their polydispersity, multiple scattering, and Fresnel reflection at the film interfaces. The model is based on the solution of the radiative transfer equation by the adding method extended for anisotropic liquid crystal droplets. The anomalous diffraction approach was used for the description of light scattering on a single droplet. Calculations of the angular dependence of the intensity of light and contrast ratio on the morphology, illumination and observation conditions of PDLC films in the transmittance mode have been carried out. The results are in qualitative agreement with the published experimental data.

DETERMINATION OF THE ABSORPTION COEFFICIENT OF A DISPERSIVE MEDIUM

We consider the problem of the retrieval of the absorption coefficient from measurements at the boundaries of a finite-thickness layer of directly transmitted and scattered radiation as well as from measurements of scattered radiation alone. A method for rigorous solution to the first problem and an approximate method for solving the second problem at large optical thicknesses are proposed. The errors in the retrieved absorption coefficient have been investigated as a function of medium characteristics.

Retrieval of particle characteristics with high-order neural networks: application to scanning flow cytometry

The problem of retrieval of homogeneous spherical particles characteristics by the data on the intensity of scattered light is considered. To solve this problem the high-order neural networks method is used. The algorithms to determine radius and refractive index of particle using the multidot high-order neural networks are proposed. The nets to retrieve particles radius and refractive index by the data on the intensity of scattered light in a limiting range of available for measurement angles are constructed. The neural networks are trained in the range of radius from 0.5 up to 15.5 microns and refractive index from 1.02 to 1.2, respectively. Dependence of the retrieval errors on particle characteristics and the neural network structure is estimated.

Revealing some virus infections by lymphocyte laser scattering

Light scattering patterns have been calculated for a simple optical model constructed for single smooth and nonsmooth lymphocytes of healthy and infected individuals. It has been shown that the smooth and nonsmooth cells can be resolved using the intensities of the sideward and backward scattered light. We have found by calculations and validated by the flow-cytometer experiments that intensity distributions for the cells of lymphocyte populations can be used as a preliminary signatures of some virus infections. Potential biomedical applications of the findings for label-free flowcytometry detecting of individuals infected with viruses of hepatitises B or C and some others viruses are presented.

Characterization of size and refractive index of spherical particles with the neural networks by multi-angle light scattering data

A method to retrieve radius from 0.6 mkm up to 13.6 mkm and relative refractive index from 1.015 up to 1.28 of spherical homogeneous non-absorbing particles by multi-angle scattering is proposed. It is based on the formation of noise resistant functionals of the scattered intensity, which are invariant relatively linear homogeneous transformations of an intensity-based signal, and on the approximation of the retrieved parameters dependence on the functionals by a feed forward neural network. The values of intensity of light scattered in the interval of angles 10° - 60° are used. At 20% measurement errors the mean errors of the retrieval of radius and relative refractive index are 0.8% and 7%, respectively.

Sizing of spherical particles by multiangle light-scattering data: application of the high-order neural networks

The retrieval of size and refractive index of a spherical nonabsorbing particle by angular dependence of scattered light in application to the scanning flow cytometry is considered We consider the range of angles available for measurement from 10° to 60°. For the problem solution the high-order neural networks are used. The retrieval errors were investigated at the ranges of the radius and relative refractive index 0.6 - 10.6 microns, and 1.02 - 1.38, respectively.