Tamaz Medoidze

Photoplethysmography (PPG) is a photometric technique which is widely used in the detection of time-dependent blood volume changes in the peripheral tissues of the body. Despite the long history of research, the detailed mechanism of this phenomenon is still a matter of debates. This applies to such important body locations as the projection of the radial artery on the wrist. Based on the above, our goal is to determine the mechanism of the PPG-signal formation at this particular location. In this paper, we analyze a series of observations obtained using reflection-mode PPG. In our experiments, photoplethysmograms were recorded in the wavelength range of 400 – 1000 nm (with a step of 1 nm). Recordings were made for 10 s and the time step was 16.5 ms. Measurements were carried out in vivo on the projection of the radial artery of the wrist. The observed photoplethysmograms are described by modification of the physiological model of the interaction of light with living tissue proposed several years ago. This model provides a reasonable explanation for all observations. According to this model, it is the pulsating transmural pressure of the radial artery that increases/decreases the density of capillaries in the dermis, thereby modulating the volume of blood in the capillary bed. The photoplethysmogram observed in the green/blue range of the optical spectrum was due to modulation of the blood volume in the capillary bed. In the yellow-red and near infrared ranges, the PPG signal was a modulated blood volume in the capillary bed and artery. For these ranges, differences in the PPG signal shapes are not observed. Differences are observed only in intensities, which is proportional to the amount of blood in the area of interaction. The PPG signal is also modulated by the respiratory rate.

The goal of the present research is development and application of laser induced fluorescence excitation energy transfer method to donor–acceptor intercalator pair for quantitative and qualitative study of stability quality DNA double helix in solution, in real time. The approach is based on the example of acridine orange molecule (donor) and ethidium bromide (acceptor) intercalated in DNA. Fluorescence resonance energy transfer (FRET) radii were experimentally estimated in background electrolyte solution (0.01 M NaNO3) and proved to be 3.9 ± 0.3 nm and the data are in satisfactory agreement with the theoretically calculated value R0 = 3.5 ± 0.3 nm. Concentration of DNA sites, exposed to Cu(II), Cu(I), Ag(I) ions, AgNPs and temperature, which are applicable for intercalation, were estimated in relative units. FRET method allows estimating the concentration of double helix areas with high quality stability applicable for intercalation in DNA after it was subjected to stress effect. It gives the opportunity to compare DNAs of 1) different origin; 2) with various damage degrees; 3) being in various functional states.

The effect of addition of lead borate Pb(BO2)2 and boron oxide B2O3 on the phase evolution and superconducting properties of (Bi,Pb)-2223 high-temperature superconductor has been studied. Obtained results could enable us to develop a cheap and energy efficient fabrication technology for significant amount of high purity (Bi,Pb)-2223 superconducting materials via doping with boron-containing compounds.

1) Samples of the nominally pure and boron-added (Bi,Pb)-2223 high-temperature superconductor were prepared by the solid state reaction method and influence of B2O3 addition on the formation of (Bi,Pb)-2223 HTSs was investigated. Obtained results indicate that B2O3 additive drastically accelerates the formation of (Bi,Pb)-2223 superconductor; 2) Nominally pure and B2O3-added Eu-123 HTSs were prepared by the solid state reaction method. The decrease of the unit cell volume and Tc indicate a possibility of the added boron occupying the positions in the structure.

An effective way to obtain nanoparticles of solids (metal oxides) by microwave heating of samples is discussed.

An effective method of medical diagnosis based on the analysis of reduced form-factorization of fluorescence spectra in biological tissue with a sensitivity and specificity exceeding 90% is presented for turbid and fluorescent environment. Relevant device - laboratory optical / laser biospectrometer is described.

We present another point of view to the problem of randomness and chirality of the packed DNA. Our consideration related to the algorithms that generate the random distribution of equivalent polygons with zero volume and confined to spherical volumes, as well as Alexander polynomials, which does not distinguish completely among some kntted chains and so are not a good invariants. We present the new invariants based on Vassiliev polynomials, which are free of above mentioned constraints.

We present the homemade laser spectrometer. An important part of this spectroscopic system is ultraviolet coherent and non-coherent radiation. It is obtained by converting the fundamental mode of the YAG: Nd3 + laser radiation to the third (by mixing the basic and second harmonics) and the fourth (by doubling the 2nd harmonic) harmonics and the nitrogen laser, while the non-coherent source is YLiF4: Tm3 + system. This range of optical radiation allows to realize the laser-induced and / or non-coherent-source fluorescence of biological objects, which is the most informative method for studying electromagnetic interactions along with other methods of laser / optical spectroscopy. Therefore our UV system is very effective for medical diagnosis.

Absorption and fluorescence spectra, radiative lifetimes and manifold to manifold transitions branching ratios for 1I6, 3P2, and 3P1 multiplets in Tm3+:YLiF4 at the room temperature pointed out the following: 1I6 manifold can serve as upper laser level as effectively as the well known 1D2 and 1G4 levels.

A light scattering and laser-induced fluorescence device built in the laboratory of the Coherent Optics and Electronics Department of the Institute of Cybernetics is presented. The device can study the optical properties of bioobjects in a non-invasive, real-time mode.

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Scientific editor of monographs in foreign languages

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Research articles in high impact factor and local Scientific Journals

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