In this work, photodetectors with a built-in cooling system based on Peltier elements and with a cooling system based on a Dewar flask filled with liquid nitrogen are experimentally studied with the aim of practical estimation and comparison of capabilities of the photodetectors with different photosensitive element cooling types.
The regression model was applied to solve the problem of restoration of the concentration of components in a gas mixture using infrared absorption spectra. A solution to the problem of determining the concentrations of individual components of a multicomponent gas mixture is suggested and tested.
The paper presents the results of an in-vivo study of lymphedema tissue by optical coherent elastography in small animals. A lower limb lymphedema model in Wistar rats by lymph node resection was created. This article describes the application of the method of optical coherent elastography as a tool for in-vivo study of a model of lower limb lymphedema in small laboratory animals. Studies have shown that with the development of lymphedema, elastic properties change significantly.
Terahertz (THz) spectroscopy of skin pathologies associated with water migration and content were analyzed using the method of immersion optical clearing. It shows different behavior THz spectra for healthy and diabetic skin after application of an optical clearing agent. It method can be used to identify skin pathologies. There is a migration of water and contents from various layers of the skin and dehydration of the skin due to the application of the optical clearing agent.
This paper presents the design and radiation characteristics of compact THz molecular laser with optical pumping for photoacoustic spectroscopy are reported. As a pump source, the compact CO2 laser set in a pulse-periodic operation mode with radiation pulse power up of 100W is used. The wavelength tuning range of CO2 laser is from 9.17 to 10.93 μm on the 92 emission line of 12C16O2 molecule. Construction of the THz laser allows for switching between 3 different active mediums. Preliminary experiments showed the laser operating on 10 emission lines of methanol 12CH316OH with a wavelength range of 73-210 μm and a pulse power of up to 100 mW.
The optical parametric oscillator based on the first PPKTP crystal produced in Russia was created. This crystal has dimensions of 8×0.5×10 mm and polling period of Λ1=37.9 μm, Λ2=38.7 μm. The conversion efficiency of pump into idler at repetition rate 1 kHz is 7.5%, quantum efficiency 17.8% and slope efficiency 16.3%. The generation threshold was 110 μJ. The optical parametric oscillator based on the first PPKTA crystal was developed. Threshold for parametric generation was 130 μJ (14.4 MW/cm2), the quantum efficiency was 27% and the differential efficiency was 12%. The signal wavelength was 1.54 μm, and the idler wavelength corresponded to 3.31 μm.
In this paper, various designs of non-resonant photoacoustic cells with a different arrangement of microphones are investigated. It is demonstrated that it is possible to expand the dynamic range of measurement of gas concentration using the special configuration of cell cavities and the specific location of the microphone. The suppression of resonant acoustic effects occurring in the measuring photoacoustic cell is characteristic of this cell cavity design. Given this suppression, only the primary sound wave affects the microphone diaphragm. The implementation of a new cell design allows us to extend the range of measurement of SF6 gas impurity concentration in the atmosphere from 100 - 1000 ppm up to 10 - 10,000 ppm.
Low-level laser exposure is a non-invasive and less painful method, which is used as an alternative method to classical acupuncture with metal needles and could be applied in clinical medical practice. The study of the laser acupuncture effect on the electroencephalogram (EEG) characteristics was carried out. The electrodes were located on the surface of the subject's head according to the standard scheme 10-20. Experimental EEG data were obtained by standard digital 16-channel electroencephalograph with EEG18 V5.0.3 software. The EEG frequencies in each of the measurements have been analyzed. This work shows that low-level laser stimulation able to change the power of rhythms in the head areas, which corresponds to the stimulation of different brain regions.
The of multiphoton microscopy (MPM) based on two-photon fluorescence and second-harmonic generation is promising for diagnosing neoplastic transformation of tissues. The results of MPM studies of tissues with prostate adenocarcinoma embedded in paraffin blocks are presented. The tissue fluorescence was also analyzed using the fluorescence lifetime (Fluorescence-lifetime imaging microscopy - FLIM) option. The relationships between the fluorescence peculiarities and the second harmonic generation of the prostate gland tissues were obtained for different morphological images.
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