The paper presents experimental research of the diffraction patterns of radiation reflected from the retroreflector spherical system of glass geodesic passive satellites of the Blitz-type created at the JSC "SPC "PSI". The Blitz-type satellites are used in the interests of the GLONASS for high-precision laser ranging and are a set of concentric layers with different refractive indices. The purpose of the study was to determine based on the experiment data the effective beam diameter forming the reflected radiation diffraction pattern in the far zone, which value was required to calculate the satellite energy parameter, i.e., the effective scattering surface. The effective beam diameter dimension for the indicated retroreflector spherical system was determined experimentally by installing various diaphragms that limited the radiation beam size. It is shown that alterations in the diffraction pattern in the far field started, when the diaphragm opening was smaller than the effective diameter. Experimental and calculated values of the satellite’s equivalent scattering surface were comparatively analyzed. According to the experimental results, the diffraction pattern is determined by the central zone of the retroreflector spherical system, where wave aberrations are less than a certain limit corresponding to the Fresnel diffraction with several active first zones

Experimental Research of the Diffraction Pattern of Radiation Reflected from the Retroreflector Spherical Glass Satellite

Aim . To improve the methods for assessing the state of the jaw bone tissue based on the use of ultrasonic shadow densitometry. Materials and methods . As a research method, there was used the latest development – velocimetric ultrasonic densitometer with an original software, ultrasonic sensors and an electronic positioner. The material of the experimental study were the macropreparations of the animal species "Domestic Pig", where the spongy and cortical substance of the bone tissue was isolated, and the speed of passage of ultrasound (SUS) through them was estimated. In the clinical part of the study, ultrasound diagnostics of bone tissue was performed in 38 people with physiological occlusion in various anatomical and functional areas. Results . Part of the study showed that the maximum SUS was observed through the cortical bone tissue from the oral side, and the minimum – through the spongy substance. In the clinical part of the study, the registration of SUS measurements through the bone tissue revealed statistically significant differences and showed that the highest bone density was determined in the anterior left and right parts of the mandible. The lowest bone density was determined in the lateral left and right sections of the upper jaw. Conclusions . Based on the conducted studies, there was developed a diagnostic map of the ultrasonic density of the periodontal bone tissue, which can complement the protocol of the patient's dental examination. The obtained results of SUS passage through the bone tissue in various anatomical and functional zones of the upper and lower jaws in examined persons with physiological occlusion can be taken as normalized indicators in assessing bone density. Ultrasound densitometry has proven to be a safe, non-invasive method that can be used to study jaw bone density in vivo. 

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The application of ultrasonic densitometry for assessing the state of periodontal bone tissue in persons with physiological occlusion (experimental clinical study)

Anna Andreevna Fokina

Papers

Experimental Research of the Diffraction Pattern of Radiation Reflected from the Retroreflector Spherical Glass Satellite

The application of ultrasonic densitometry for assessing the state of periodontal bone tissue in persons with physiological occlusion (experimental clinical study)