S. Yu. Nikitin

Study of laser beam scattering by inhomogeneous ensemble of red blood cells in a shear flow

Laser ektacytometry is a technique widely used for measuring the deformability of red blood cells (erythrocytes) in blood samples in vitro. In ektacytometer, a flow of highly diluted suspension of erythrocytes in variable shear stress conditions is illuminated with a laser beam to obtain a diffraction pattern. The diffraction pattern provides information about the shapes (shear-induced elongations) of the cells under investigation. This paper is dedicated to developing the technique of laser ektacytometry so that it would enable one to measure the distribution of the erythrocytes in deformability. We discuss the problem of calibration of laser ektacytometer and test a novel data processing algorithm allowing to determine the parameters of the distribution of erythrocytes deformability. Experimentally, we examined 12 specimens of blood of rats under the action of 4 shear stresses. Analysis of the data shows that in conditions of a limited range of digitizing the diffraction patterns, the measurement errors for the mean deformability, deformability scatter and the skewness of erythrocytes distribution in deformability by our method are respectively 15%, 20% and 20%.

Scattering of a laser beam on a wet blood smear and measurement of red cell size distribution

We report an automated laser system that allows the red cell size distribution to be measured. Experiments are performed on laser light scattering by a suspension of oriented red blood cells (a wet blood smear). Based on an analysis of the angular distribution of light intensity in the diffraction pattern, we have restored the red cell size distribution. The average diameter of a red blood cell is determined with an error of less than 1%, and the spread of red blood cells in size – with an error of about 20%. We discuss the problems of photometry and processing of diffraction patterns, preparing blood samples and data processing algorithms, including methods for solving the inverse scattering problem.

Analysis of laser beam scattering by an ensemble of particles modeling red blood cells in ektacytometer

Using a simple theoretical model, we have obtained approximate relations between the characteristics of particles, modeling red blood cells, and the parameters of the diffraction pattern, produced by a laser beam diffracted in the ektacytometer. We have estimated, in particular, the effect of the particles size dispersion on the diffraction pattern visibility. The estimate shows, that relation of light intensities in the first minimum and the first maximum in the diffraction pattern is a parameter, which is rather sensitive to the particles size dispersion.

Evaluation of a molecule size using data of the time-domain coherent anti-Stokes Raman spectroscopy

Thermal velocity correlation function for a gas medium molecule is calculated. The velocity correlation time is found to be three times of the molecule mean free run time. The hydrogen molecule diameter is evaluated using data of the time-domain coherent anti-Stokes Raman spectroscopy.

Time-Domain Coherent Polarization Spectroscopy of Inhomogeneously Broadened Transitions: Theory and Experimental Possibilities

Time-domain Coherent Antistokes Raman Spectroscopy (CARS) provides valuable information about interaction of particles in gaseous media [1]. Here we present brief outline of our theoretical models and give some quantitative parameters, relating to Hydrogen, Nitrogen Ammonia and Methane molecules, as well as to Thallium and Thulium atoms.