Biomedical subjects

M A Vorontsov

Publications and source records attributed to M A Vorontsov.

7 recordsLinked to original sources

PubMed2002

Chaotic free-space laser communication over a turbulent channel.

The dynamics of errors caused by atmospheric turbulence in a self-synchronizing chaos-based communication system that stably transmits information over an approximately 5 km free-space laser link is studied experimentally. Binary information is transmitted using a chaotic sequence of short-term pulses as a carrier. The information signal slightly shifts the chaotic time position of each pulse depending on the information bit. We report the results of an experimental analysis of the atmospheric turbulence in the channel and the impact of turbulence on the bit-error-rate performance of this chaos-based communication system.

Journal Article↗

PubMed2002

[Results of using the domestic vascular prosthesis "Ekoflon"].

The aim of the work was to study long-term results of application of a vascular transplant from modified polytetrafluoroethylene "Ekoflon". The investigation included 121 reconstructions performed during the last 6 year, 53 prostheses being implanted in the aorto-femoral position, 68--in the femoro-popliteal-tibial position. The long-term results have shown that the transplant "Ekoflon" in the position of the aorto-femoral shunt is not inferior to textile analogues and even has a number of advantages. When it is used below the inguinal fold the results of patency were worse than those with the autovenous one. But when there is no adequate autovein, under conditions of critical ischemia, prosthesis "Ekoflon" might be the material of choice for saving the lower extremity. The dynamic ultrasound duplex scanning and histological investigation of the prosthesis samples have shown an original morphogenesis of its "implantation".

Aged↗

PubMed2002

[Application of different textile vascular grafts in the aorto-femoral location and ways for their improvement].

A comparative analysis of 220 reconstructions of the aortofemoral segment with the application of vascular prostheses of firms "Sever" and "Vascutek" was made. It was established that in patients with obvious anemia and hemodilution (hematocrit less than 25%, hemoglobin less that 80 g/l) an important condition for less total blood loss was to impart the zero surgical porosity to the graft wall at the preoperative stage. However, the biological impregnation used for these purposes reinforces the inflammatory component in the implantation of the vascular graft. The authors propose to use a more inert polytetrafluoroethylene film to impart the zero surgical porosity to the graft wall.

Aorta↗

PubMed2001

Adaptive optics with advanced phase-contrast techniques. I. High-resolution wave-front sensing.

High-resolution phase-contrast wave-front sensors based on phase spatial light modulators and micromirror/ liquid-crystal arrays are introduced. Wave-front sensor performance is analyzed for atmospheric-turbulence-induced phase distortions described by the Kolmogorov and the Andrews models. A high-resolution phase-contrast wave-front sensor (nonlinear Zernike filter) based on an optically controlled liquid-crystal phase spatial light modulator is experimentally demonstrated. The results demonstrate high-resolution visualization of dynamically changing phase distortions within the sensor time response of approximately 10 ms.

Journal Article↗

PubMed2001

Adaptive optics with advanced phase-contrast techniques. II. High-resolution wave-front control.

A wave-front control paradigm based on gradient-flow optimization is analyzed. In adaptive systems with gradient-flow dynamics, the output of the wave-front sensor is used to directly control high-resolution wavefront correctors without the need for wave-front phase reconstruction (direct-control systems). Here, adaptive direct-control systems with advanced phase-contrast wave-front sensors are analyzed theoretically, through numerical simulations, and experimentally. Adaptive system performance is studied for atmospheric-turbulence-induced phase distortions in the presence of input field intensity scintillations. The results demonstrate the effectiveness of this approach for high-resolution adaptive optics.

Journal Article↗

PubMed2001

Anisoplanatic imaging through turbulent media: image recovery by local information fusion from a set of short-exposure images.

A wide-field-of-view white-light imaging experiment with artificially generated turbulence layers located between the extended object and the imaging system is described. Relocation of the turbulence sources along the imaging path allowed the creation of controllable anisoplanatic effects. We demonstrate that the recently proposed synthetic imaging technique [J. Opt. Soc. Am. A 16, 1623 (1999)] may result in substantial improvement in image quality for highly anisoplanatic conditions. It is shown that for multisource objects located at different distances the processing of turbulence-degraded short-exposure images may lead to a synthetic image that has an image quality superior to that of the undistorted image obtained in the absence of turbulence (turbulence-induced image quality enhancement).

Journal Article↗

PubMed1997

[Experimental and clinical research on the Russian Vitaflon blood vessel prosthesis].

The authors have performed an experimental and clinical assessment of a new graft. In 37 mongrel dogs 49 experiments were carried out with the implantation of grafts "Vitaflon" into different parts of the arterial and venous bed. It was shown that the domestic graft from modified polytetraftoroethylene had high biological inertia, good plastic properties, zero surgical porosity, strength and reliable "taking" by the recipient's organism. Following the experimental work the prosthesis "Vitaflon" (30-50 cm long and 8 mm diameter) was implanted in the femoro-popliteal-tibial position to 15 patients suffering from obliterating atherosclerosis of the lower extremity arteries. The period of follow-up observations was about 12 months. Thrombosis took place in two grafts in the early postoperative period. Other shunts were functioning well which was confirmed by the clinical picture and dopplerography.

Aged↗