Possibility of controlling the temperature of the vein wall during endovasal laser treatment (EVLT) is investigated. The desired medical effect is achieved by the coagulation of the vein wall at the temperature of 80 °C. Heating of the vein wall is mainly due to the efficient conversion of laser radiation into heat in an optothermal fiber converter (OTFC) located at the output end of the optical fiber placed inside the vein. Titanium-containing optothermal fiber converter (TOTFC) is very promising for EVLT application due to its high efficiency in converting laser energy into thermal energy and its smooth shape that excludes perforation of the vein wall when the fiber moves inside the vein. During the endovasal laser treatment heated by laser radiation TOTFC emits an IR signal which can be used for controlling the temperature on the vein wall during endovasal laser treatment. At present study, a computer thermophysical model of the EVLT with TOTFC has been developed in the COMSOL Multiphysics 5.4 program (COMSOL Inc., Burlington, MA, USA). In the EVLT model, a laser radiation wavelength of 980 nm with an average laser power of 8–14 W to the traction speed of the optical fiber in range of 1–7 mm/s is applied. The dependence of the TOTFC temperature and the temperature on the vein wall has been numerically investigated. In accordance with Planck’s formula, the dependence of the spectral luminosity density of a blackbody simulating IR signal from TOTFC on its temperature has been determined. The spectral luminosity density in a wide range the wavelength of 0.4–20 μm, as well as in spectral ranges limited by the transmission of the quartz fiber and the sensitivity of Ge and PbS photodetectors was defined. The possibility of controlling the average power of the laser radiation depending on the magnitude of the change in the spectral luminosity density of TOTFC during EVLT is demonstrated. The results obtained can be useful in developing laser medical equipment and materials for use in vascular surgery at endovasal laser treatment.

The possibility of active laser delivery of a modern chlorine-containing photosensitizing drug Chloderm (Chloderm, Russia) under the nail plate by laser radiation with a wavelength of 450 nm for the purpose of photodynamic therapy of onychomycosis is studied. In an in vitro experiment, sequential laser microporation of the nail plate and active delivery of the drug under the nail plate by this laser radiation with an intensity of up to 200 W/cm2 were investigated. The results of studying the absorption spectra of an aqueous solution of Chloderm in the range of 400-900 nm before and after exposure to 450 nm laser radiation are presented. It is demonstrated that sequential laser microporation and active laser drug delivery under the nail plate is possible at laser radiation intensity greater than 178 W/cm2. It is shown that the maximum rate and efficiency of nail plate ablation by 450 nm laser radiation is achieved at an intensity of 200 W/cm2 and is 2750± 30 μm/s and 1.47 ± 0.05 μm/mJ, respectively. The delivery rate of Chloderm under the nail plate is 1.15± 0.1 mg/s. It is shown that exposure to 450 nm laser radiation at the intensity of 200 W/cm2 for a time sufficient to deliver the drug under the nail plate does not change the extinction coefficient of the drug at the laser wavelength and slightly changes the conformational state of Chloderm. Keywords: laser delivery, ablation, wavelength, absorption coefficient, chlorine-containing photosensitizing drug, laser radiation.

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The paper presents the results of a study of the extinction spectra (350-900 nm) of aqueous solutions of modern chlorine-containing photosensitizing drugs for photodynamic therapy "Chloderm" (Chloderm, Russia) and "Chloderm with hyaluronic acid" (Chloderm, Russia) before and after irradiation by visible light with wavelengths of 405 nm, 450 nm, and 656±10 nm, with exposure time 0-20 min and intensity 0-200 mW/cm 2 . It is demonstrated that the addition of hyaluronic acid does not deform the shape of the extinction spectrum of the photosensitizing drug but reduces its absorption in proportion to the drop in the concentration of the photosensitizer in the drug. Photodynamic light action in the investigated range of parameters leads to a slight decrease in the extinction coefficient of both drugs at the wavelengths of the exposure, but significantly reduces extinction and deforms the Qy 00 absorption band (600-700 nm), thereby changing the ratio of monomers and tetramers in the drugs. This band is most significantly deformed after exposure to light with a wavelength of 656±10 nm, the least -with a wavelength of 450 nm.

Some issues of the determination of agriculture-induced nutrient load upon watercourses including nitrogen and phosphorous carryover from agricultural lands, as well as the said elements accumulation on the catchment area due to cattle-breeding development have been considered with the Kama River basin as a study case. Measures on mitigation of this load upon watercourses have been proposed.