On the impedance of a high-frequency capacitive discharge with different excitation methods

Consideration is given to a low-pressure ( << ) capacitive high-frequency discharge with large-area electrodes when it is excited by an electromagnetic field with a frequency from 13 to 900 MHz. General analytical formulas are obtained for the amplitudes of natural waves and the impedance of the discharge. It is taken into account that the excitation of surface waves and higher nonpropagating modes occurs both due to the axial inhomogeneity of the plasma-metal layer structure and due to edge effects at the electrode cut. The higher ampli-tude of the resonance modes in this case (in comparison with the excitation of the discharge by a TEM wave) leads to a greater irregularity in the dependence of the discharge impedance on the electron density. This conclusion is confirmed by the direct calculation of impedance using the Comsol Multiphysics® software.

Efficacy of myopia control by combination of orthokeratology and instillation of low-concentration atropine

Majority of reports regarding methods of myopia control are devoted to the use of orthokeratology lens¬es (OKL) or atropine. The purpose of the study was to estimate the efficacy and safety of using OKL in com¬bination with instillation of 0.01% atropine drops for myopia control in children. Material and methods. Prospective cohort study in¬cluded 34 patients (68 eyes) aged 8 to 14 years old with acquired myopia. Groups with low (17 patients, 34 eyes), moderate (12 patients, 24 eyes) and high (5 patients, 10 eyes) myopia were identified and examined prior to and 6, 12 and 18 months after adding 0.01% atropine instillations to OKL wearing. To assess the degree of pro¬gression of myopia in dynamics the following parameters were evaluated: refraction (by Huvitz MRK 3100P, axial length (AL) by IOL-Master, “Carl Zeiss”, (Germany), ampli¬tude of accommodation (AA) by Grand Seiko WRK-5100K, positive-relative accommodation (PRA), pseudoaccom¬modation (PA) and annual gradient of progression (AGP). Results. The most noticeable effect was observed in patients with low myopia. In patients with low myopia, the rate of annual progression gradient decreased by 3.4 times by 18th month of atropine use; therefore a condition close to stabilization of myopia progression occurred. The data is statistically significant. In patients with moderate myopia, despite the de¬crease of the AGP within 6-month period of atropine use by 3.7 times, the increase of APG was observed by 12th month of atropine use, which continued until 18th month of observation. In spite of this, in comparison with baseline indices, the decrease in the rate of myo¬pia progression was obtained. The data is statistically significant. In patients with high myopia, change in the AGP was not ob¬served within the 6-month period of atropine use; afterwards, a gradual decrease in the rate of myopia progression was noted: AGP decreased by 1.2 times by 12th month. By 18th month of atropine use, AGP decreased by 1.5 times compared to its initial level. The data is statistically significant. Evidently, the inhibitory effect of OKL, which is de¬termined by optical factors such as peripheral myopic defocus, even in combination with atropine, is not suf¬ficient to halt the progression of high myopia, because of structural and biomechanical changes of the sclera. Conclusion. Based on the preliminary results ob¬tained, 100% efficacy of a long-term instillation of low-concentration atropine cannot be claimed, howev¬er, the positive effect does exist and therefore the study continues.

Simulation of electromagnetic waves interaction with dispersed particles on the surface layer of the liquid medium.

Numerical simulation of the interaction of laser light with dispersed particles at different temper-atures of the surface layer of the oceans and seas. We were obtained shape and amplitude of the acoustic signal formed during this interaction and assess the pressure amplitudes of the acoustic signals at different temperatures of the surface layer of the liquid. The evaluation of the ampli-tude of the acoustic pressure has built its dependence on the surface temperature of the liquid.