An effective mode selection method for square waveguides is proposed. One has to cut up the waveguide and turn the parts around optical axis. Nearly round fundamental mode is almost indifferent to such asymmetry while the minor modes suffer great losses. The "turn" losses evaluation through the mode overlap integral confirms the method effectiveness. Lasing experiments were performed for an RF-pumped CO2 laser with a folded U-type resonator. To introduce asymmetry, waveguide channels were shifted so that the waveguide end fold mirrors image is turned axially.The laser beam quality was tested with "ModeMaster" coherent beam propagation analyzer. M2 value equal to one within the device tolerance is measured.

Effects of successive exposure to ionizing irradiation and low-intensity broadband red light on electrical activity of the heart and myocardium microstructure were studied in rats. Lowintensity red light corrected some ECG parameters, in particular, it normalized QT and QTc intervals and voltage of R and T waves. Changes in ECG parameters were followed by alterations in microstructure of muscle fi laments in the myocardium of treatment group animals comparing to control group.

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The introduction of technologically advanced methods of lithotripsy into medical practice changes the nature of postoperative complications. Among them, the main complications are inflammatory infections. This largely determines the search for new, improved methods of stone fragmentation avoiding small stone fragments and dissemination of the pelvicalyceal system of the kidney with stoneassociated infection. The authors have developed a method for controlled stone fragmentation using a continuous-wave diode laser with a hot-spot effect at the optical fiber end.The aim of the study was to evaluate the efficacy of controlled urinary stone fragmentation using a continuous-wave diode laser with a highly heated distal end of the optical fiber light guide as a method of preventing inflammatory infections in clinical practice.Materials and Methods. We analyzed 1666 case histories of urolithiasis patients who underwent percutaneous nephrolithotripsy/ nephrolithoextraction and contact ureterolithotripsy/ureteroextraction, we also performed a prospective analysis of complications based on the Clavien-Dindo classification in 90 patients who underwent fine fragmentation of stones with various lithotripters: ultrasonic, pneumatic, and holmium laser. The method of controlled stone fragmentation by a diode laser with a hot-spot effect was tested on postoperative samples of 26 renal calculi. For the first time in clinical practice, this method was tested in the bladder cavity (n=10).Results. In the percutaneous nephrolithotripsy group, postoperative infectious and inflammatory complications occurred in 34.1% of cases, in the percutaneous nephrolithoextraction group -in 24.6%, in the contact ureterolithotripsy group -in 7.8%, in the ureterolithoextraction group -in 2.5%. The analysis made it possible to identify factors promoting the development of infectious and inflammatory complications. For the first time in clinical practice, there were successfully performed ten operations of stone fragmentation using a continuous-wave diode laser with a hot-spot effect. Controlled coarse fragmentation of stones providing the possibility to reduce the number of infectious and inflammatory complications was performed in the bladder as a model for testing the method.Conclusion. The method of laser-induced controlled coarse fragmentation of stones with a hot-spot effect, developed and tested in clinical practice, is promising for the prevention of infectious and inflammatory complications in patients with potentially infected stones since their fine fragmentation and, consequently, spread of stone-associated toxins and microflora within the urinary system is avoided.