Induced astigmatism and concomitant high myopia correction with femtosecond laser-assisted intrastromal MyoRing implantation

Purpose. Analysis of the results of astigmatism correction after penetrating keratoplasty and concomitant high myopia using the MyoRing ring implantation, clinical case as an example.Material and methods. Patient G., 51 years old, underwent surgery to correct astigmatism and concomitant high myopia. MyoRing was implanted in the right eye within corneal transplant limits using femtosecond laser-assisted intrastromal MyoRing implantation. Before the surgery uncorrected visual acuity at the operated eye was 0.01; corrected visual acuity 0.06; spherical component of refraction was (-)6.0 D, cylindrical component was (-)8.0 D. Mean keratometry in the right eye was 43.96 D. Corneal hysteresis was 6.5 mm Hg, corneal resistance factor was 5.5 mm Hg, cornea thickness in center was 529 mkm. The patient was followed up for one year.Results. In 12 months after the surgery visual acuity of the right eye without correction was 0.7 and 0.8 with correction. Spherical component was (-)1.0 D, cylindrical component was (-)2.0 D. Mean keratometry in the right eye was 35.10 D. Corneal hysteresis was 7.2 mm Hg, corneal resistance factor was 6.3 mm Hg, cornea thickness in center was 533 mkm. The patient was satisfied with the result of operation.Conclusion. Femtosecond laser-assisted intrastromal MyoRing implantation for correction induced astigmatism after penetrating keratoplasty and concomitant high myopia is efficient, safe and provides strengthening of biomechanical properties of the cornea besides refractive and visual effect

The mathematical simulation of the temperature fields of building envelopes under permanent frozen soil conditions

The physical-mathematical model of the thermal state of the aired technical underground taking into account the air exchange and design features of construction under permanent frozen soil conditions has been suggested. The computational scheme of the temperature fields prediction of building envelopes of projected buildings and soil under and nearby buildings has been developed. The numerical simulation of the temperature fields of building envelopes changes was conducted during a year. The results of the numerical simulation showed that the heat coming from the technical undergrounds and through the walls does not influence the temperature field of the soil neither under a building nor at a distance from it

Automatic device for measuring of principal thermoelectric parameters of lead chalcogenides

The device intended for measuring of principal thermoelectric parameters of the narrow-gap lead chalcogenide semiconductors (the Seebeck coefficient, electrical conductivity and thermal conductivity) have been created. The device created can be controlled by personal computer. In the temperature range from 270K to 500K the  correctness of values of the thermoelectric parameters measured by the device are following: thermal conductivity – ±5,7%; electrical conductivity – ±3,5%; the Seebeck coefficient – ±4%

The measuring chamber of the device controlling the basic characteristics of the materials used in thermoelectric generators

The measuring chamber of a device intended for measuring of principal parameters of the thermoelectric materials (the Seebeck coefficient, electrical conductivity and thermal conductivity) is created. The design of the chamber unit (the cell for measuring of the parameters) allows one to perform the process of measuring of the parameters with the same set of details of the cell. In the volume of the chamber one can provide a vacuum to reduce a dispersion of a heat from the surface of the sample under investigation. To prevent any heat flow under the surface of the sample in a direction parallel to the sample axis the system of the conical mirrors is provided for the unit

CONCENTRATION AND TEMPERATURE DEPENDENCES IN EPR SPECTRA OD GD³⁺ PROBE CENTERS IN THE Pb_1-x Ag_xS и Pb_1-xCu_xS (0 ≤ x ≤ 0,011) THERMOELECTRIC CRYSTALS

Concentration and temperature dependences of parameters of the EPR spectra of Gd3+ centers introduced into the Pb1-xAgxS and Pb1-xCuxS thermoelectric semiconductor crystals (0 ≤ x ≤ 0,011) were investigated by means of EPR method. The crystals under investigation were grown from the melt containing lead sulfide, silver (or copper) sulfide, gadolinium and sulfur (the latter was used to provide stoichiometry). The investigations were performed in the 9320÷9340 MHz frequency range at temperatures of 4.2, 77, and 300 K. It was established that in the samples studied the silver and copper impurities did not create significant distortions in the structure of the base PbS crystal, but significantly affected the concentration of free carriers. Analysis of the obtained data on the concentration and temperature dependences of the spin-Hamiltonian parameters of the Gd3+ probe centers leads to the conclusion that silver and copper in the PbS crystal are acceptor like impurities, and also to determine their solubility and describe the distortions induced by them in the structure of the base crystal