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The paper studies the interaction between surgical catgut and silver nanoparticles depending on the fiber surface treatment and time of exposure (1 and 24 hours) in Ag-containing gels. After a 24-hour exposure, the maximum sorption capacity is observed on polished catgut for silver nanoparticles ranging in size from 1 to 10 nm. After this time period, the sorption capacity of silver nanoparticles on unpolished catgut occurs in Agcontaining gel within the whole size range, mainly from 1 to 5 nm, when silver nanoparticles are obtained by cavitation and diffusion photoreduction. At the same time, the incubation period of 1 hour in Argogel does not provide the potentially effective concentration of silver nanoparticles on the fiber surface.

The aggregate stability of silver nanoparticles (Ag – NPs) in a gel composition is estimated. It is established that during long-term storage (for 3 years), a decrease in the number of nanoparticles with sizes of 1–5 and 5–10 nm and a significant increase in the number of nanoparticles with sizes of 10–15 nm are observed. At the same time, the fraction of silver nanoparticles with sizes greater than 30 nm is less than 5%.

The method of modifying suture material with silver nanoparticles was tested. The paper presents the results nanoparticle sorption on the surface of different types of polymer fibers. The expediency of processing suture threads for intraoperative prophylaxis of purulent-septic complications in surgery is shown.

The results of our study of the size, optical properties, and aggregate stability of silver nanoparticles in aqueous solutions 1, 2, and 12 months after their synthesis are reported. It has been shown that nanoparticles synthesized using a combined application of physical factors, such as ultraviolet radiation, ultrasound, and uniform mixing (providing conditions of isolation from the atmospheric air) are smaller in size (from 1 to 10 nm) and have more homogenous distribution of the diameter of nanoparticles. A lower aggregation has been noted compared with particles prepared without observing the synthesis algorithm that was developed and conditions given above. The results of studying antimicrobial antiseptic properties based on a colloidal nanosilver solution prepared using the technology of diffusion-cavitation photochemical reduction of silver nitrate are also reported. A high antimicrobial activity of the resulting colloidal solution with silver nanoparticles against clinical isolates of P. aeruginosa, A. baumanii, and E. coli has been demonstrated as compared with the original silver nitrate and the ligand (polyvinylpyrrolidone) used in the synthesis of the colloid at the same concentration. At a concentration of 10 μg/mL, a colloidal solution with silver nanoparticles has been found to possess bactericidal activity against two isolates of P. aeruginosa, three isolates of A. baumanii, and five isolates of E. coli. At a concentration of 1 μg/mL, the colloidal solution of silver nanoparticles has possessed only bacteriostatic activity against all isolates of the bacteria. The minimum bacteriostatic inhibitory concentration of nanosilver has determined to be 3 μg/mL.

The paper presents the results of research and development of concentrated type p—i—n-diodes switches providing the switching time at the level of a few nanoseconds. To increase lock losses of (~40 dB) the authors use a cascade connection of diodes into waveguide and microstrip transmission line of q = p/2 electric length. Investigation results of creation of switching devices using longitudinally and transversely-distributed p—i—n-structures in the shortwave part of the millimeter wavelength range (f = 300 GHz) are presented. When developing switching devices intended to control the level of microwave power in the millimeter wavelength range, a number of special features arise limiting the achievement of optimal parameters. The dimensions of the metal ceramic packaged p—i—n-diodes and the mounting elements of semiconductor structures become comparable with the wavelength. As a result, package cannot be considered in the calculations and in the design as the capacity of the concentrated type. In our case the diode package is considered in the form of radial line which is able to transform the input impedance of the transmission line to the terminals of the diode structures, and realize high-impedance state (parallel resonance) in the device circuit in the mode of microwave power transmission. Engineering calculations for the given parameters of the silicon mesostructures showed the possibility of creating high-speed devices for switching microwave power with good characteristics. For diode assembling industrial clockwork ruby jewels with high quality of surface finish, strength and appropriate dimensions are applied as dielectric bushings. Suffice it to say that in the frequency range of 150 GHz, we used the bushings with dimensions of external diameter D = 0.4 mm and a height of h = 0.15 mm. The switches created provide transient units of nanoseconds, isolation more than 40 dB at relative frequency bandwidth of 30-40%. Evaluating progress in the development of millimeter wavelength devices, it should be noted that at frequencies greater than 200 GHz, the application of the concentrated type diodes is problematic. In this range it would seem to be promising to use bulk semiconductors. In this case surface-oriented p—i—n-structures can be applied as unified elements of the control devices in the shortwave part of the millimeter range, as well as in quasi-optical transmission lines.

Transmitting devices for small radars in the millimeter wavelength range with high resolution on range and noise immunity. The work presents the results of research and development of compact pulse oscillators with digital frequency switching from pulse to pulse. The oscillator consists of a frequency synthesizer and a synchronized amplifier on the IMPATT diode. Reference oscillator of synthesizer is synchronized by crystal oscillator with digital PLL system and contains a frequency multiplier and an amplifier operating in pulse mode. Small-sized frequency synthesizer of 8 mm wave lengths provides an output power of ~1.2 W per pulse with a frequency stability of no worse than 2•10–6. Radiation frequency is controlled by three-digit binary code in OOL levels. Synchronized amplifier made on IMPATT diodes provides microwave power up to 20 W in oscillator output with microwave pulse duration of 100—300 ns in an operating band. The oscillator can be used as a driving source for the synchronization of semiconductor and electro-vacuum devices of pulsed mode, and also as a transmitting device for small-sized radar of millimeter wave range.

Present-day technology allows manufacturing of GaAs/AlGaAs heterostructures with layers width down to a nanometer. Time of electron tunneling through AlGaAs potential barrier with such width and height of a few tenths of electron volt is less than a picosecond. It makes possible to create microwave diode on base of the single-barrier nanostructure with electron tunnel injection through AlGaAs potential barrier and electron drift in GaAs transit layer with comparable time delays of electron tunneling and transit. Microwave impedance of the diode we study in framework of small-signal theory but with considering electron injection delay along with transit delay as for resonant-tunneling diode.

A model of small-signal impedance of semiconductor transit-time diode with injection time of electron negligible less than its transit time had been developed by Sze [1]. Modification of the model with consideration of injection delay has been applied on studying of semiconductor [2] and vacuum [3] resonant-tunneling diodes impedance. We apply the modification to investigate impedance of a diode on AlGaN micro-cathode with electron field emission and transit in vacuum layer with comparable emission and transit time delays.