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Abstract In this work, the problem of radiation scattering by ice crystals typical for cirrus clouds is solved for a 94-GHz radar (wavelength 3189 µm) and a lidar (wavelength 0.355 µm); the ice refractive indices are 1.7864 + 0.0032i and 1.3249 + 0i, respectively. The scattering matrices are calculated within the physical optics approximation and the discrete dipole approximation for the case of randomly oriented particles with sizes from 4 to 1000 µm. The ratio of the radar and lidar backscattering signals in the backward direction (the so-called radar–lidar ratio) is calculated for a wide range of the particle size for typical shapes of cirrus cloud ice crystals. It is shown that this ratio can be used for estimating the size of ice crystals in cirrus clouds.

Background. Gastroesophageal reflux disease (GERD) is an urgent problem of modern gastroenterology as well as the most common pathology of the upper gastrointestinal tract; it is a chronic disease that significantly reduces the patient's quality of life, increases the risk of developing Barrett's esophagus and esophageal adenocarcinoma. Objective. To assess the potentials of multichannel intraluminal pH impedance monitoring in the diagnosis of esophageal diseases. Material and methods. In 3 patients with clinical and endoscopic signs of GERD esophageal multichannel intraluminal pH-impedance monitoring was performed using the diagnostic equipment Digitrapper pH-Z from Given Imaging (USA). Results. 24-hour esophageal pH monitoring enabled to verify the diagnosis of GERD, to reveal a hypersensitive esophagus and manifestations of nocturnal acid breakthrough. Conclusions. Multichannel intraluminal pH-impedance monitoring is the "gold standard" for the diagnosis of esophageal diseases; it significantly expands opportunities of gastroenterologists in the treatment of GERD.

Aim. To investigate the specific features of the expression of second-type melatonin receptors (MTNR1B) by epithelial cells of the distal esophagus in gastroesophageal reflux disease (GERD), depending on the severity of endoscopic changes in the mucous membrane.Materials and methods. The study included 48 GERD patients, out of whom 37 and 11 people were suffering from non-erosive reflux disease (NERD) and erosive reflux disease (ERD), respectively. The control group consisted of 18 patients without GERD, comparable with the main groups by gender, age and body mass index. In order to determine the expression of MTNR1B, esophagogastroduodenoscopy with the collection of biopsy material from the mucous membrane of the distal esophagus was performed. The quantification of the MTNR1B expression intensity was carried out using the Aperio ImageScope_v9.1.19.1567 software. The level of melatonin metabolite, 6-sulphatehydroxymelatonin (6-SOMT), was determined in daily urine, as well as separately in daytime and nighttime portions.Results. The intensity of MTNR1B expression by esophageal epithelial cells in patients with NERD demonstrated no difference with the control group (0.436 (0.123, 0.668) and 0.437 (0.202, 0.692), respectively; p> 0.05). A significant decrease in the expression of MTNR1B receptors was noted in patients with ERD compared to NERD patients (0.127 (0.059, 0.156) and 0.436 (0.123, 0.668), respectively; p = 0.017) and patients in the control group (0.437 (0.202, 0.692); p = 0.033). The low intensity of MTNR1B expression was associated with more pronounced endoscopic changes in the mucous membrane of the esophagus (r = –0.40; p = 0.0015). A statistically significant relationship was found between the expression intensity of MTNR1B and the level of melatonin in the daytime (r = 0.42; p = 0.018), as well as the night/day index reflecting the daily rhythm of melatonin synthesis (r = –0.43; p = 0.016).Conclusions. The obtained data indicate that a decrease in the intensity of MTNR1B expression by esophageal epithelial cells can be considered as a prognostically unfavourable sign of the GERD course. The low intensity of MTNR1B expression is associated with a more severe (erosive) form of GERD and more pronounced endoscopic changes in the mucous membrane of the esophagus.

Light backscattering matrices are calculated within the physical optics approximation for hexagonal atmospheric ice particles distorted in different ways for the case of arbitrary spatial orientation and single scattering. A hexagonal prism with a height of 31.62 mu m and an external diameter of 22.14 mu m, which is typical for column-type particles observed in cirrus clouds, is chosen as a basic geometric shape. Three shape distortion methods for the particles are used: tilt, convexity and concavity; the angle of distortion varies from 0 degrees to 50 degrees for every particle type. The wavelength of incident radiation is 1.064 mu m. The calculation has shown a sharp decrease in the backscattering cross section with an increase in the angle of distortion for all particle types under study.

An Erratum to this paper has been published: https://doi.org/10.1134/S1024856023330023

Aim. To evaluate the features of melatonin cyrcadian production in patients with gastroesophageal reflux disease associated with obstructive sleep apnea/hypopnea syndrome. Methods. We examines 29 patients with gastroesophageal reflux disease were examined (group 1), 29 patients with gastroesophageal reflux disease associated with obstructive sleep apnea/hypopnea syndrome (group 2), and 22 patients with obstructive sleep apnea/hypopnea syndrome (group 3). The comparison group included 21 people without gastroesophageal reflux disease and obstructive sleep apnea/hypopnea syndrome (group 4). The content of 6-sulfatoxymelatonin was determined in 24-hour urine and separately in its daytime and night portions by enzyme immune assay. The night/day index was calculated. The compared groups were comparable by gender but the patients with obstructive sleep apnea/hypopnea syndrome and gastroesophageal reflux disease associated with this syndrome differed from the patients from comparison group by older age, which is consistent with epidemiology of sleep apnea. The analysis of the data obtained was performed using the program Statistica 10.0. When comparing quantitative indicators between four independent samples, KruskelWallis test was used. In order to study the relationship between the phenomena, the Spearman rank correlation coefficient was calculated. Results. A significantly increased level of 6-sulfatoxymelatonin in 24-hour urine was determined in group 2 (p=0.0000), as well as in day (0.0000) and night portions (0.015) compared to group 1, in 24-hour urine (p=0.0007) and its day portion (p=0.0001) compared to group 3, in day portion of urine compared to group 4 (p=0.029). In group 2 compared to group 4 a significant shift in melatonin synthesis peak during daytime hours was observed, which is expressed in a statistically significant decrease in the night/day index (p=0.0003). Correlation analysis revealed statistically significant relations between the level of 6-sulfatoxymelatonin in urine and the severity of sleep apnea (in 24-hour urine: r=0.64, p=0.0000; in daytime portion: r=0.62, p=0.0000; in night portion: r=0.40, p=0.003), as well as respiratory monitoring indicators indicating sleep fragmentation due to apnea (the number of awakenings associated with respiratory events: r=0.58; p=0.00001; activation of the central nervous system associated with respiratory efforts: (r=0.50; p=0.0002). Conclusion. The patients with gastroesophageal reflux disease associated with obstructive sleep apnea/hypopnea syndrome have an increased level of 6-sulfatoxymelatonin in urine associated with the shift of its peak synthesis to daytime hours; the identified changes correlate with apnea/hypopnea index reflecting the severity of apnea and sleep disturbance.

Results of analyzing the numerical calculation of light scattering matrices for ice crystals of arbitrary shape with allowance for absorption are presented. The matrices are obtained within the framework of the geometrical optics approximation. The effect of absorption on properties of light backscattering is estimated for problems of laser sounding of the atmosphere. The results demonstrate that taking into account the absorption when the wavelength is shifted inward the IR range leads to a decrease in the scattered radiation intensity. The effect of absorption for wavelengths of 0.355 and 0.532 μm does not exceed hundredths of a percent; for 1.064 μm, several percent; and for the near IR range, it can exceed tens of percent.

An algorithm for interpreting light backscattering matrices (LBSMs) obtained experimentally on the unique high-altitude polarization lidar of the National Research Tomsk State University in the process of cirrus cloud sounding is described. In terms of the database of LBSMs calculated theoretically within the framework of the physical optics approximation, microphysical characteristics of cirrus clouds such as the particle size, orientation, and shape, as well as the percentage of particles with different shapes, are estimated.

The technique and results of the study of optical and microphysical characteristics of contrails with the use of the unique high-altitude polarization lidar of the National Research Tomsk State University are described. The microstructure parameters of ensembles of crystalline particles were estimated by comparing elements of light backscattering matrices calculated theoretically and obtained experimentally. It is shown that the condensation trail appearing in the atmosphere behind the plane 30–40 min after the emission of fuel combustion products from the engines consists of small chaotically oriented ice particles, mostly of the column shape.

The extinction matrix for an ensemble of hexagonal ice plates and columns is presented. The extinction matrix for droxtal and bullet crystals has been estimated. The calculations have been carried out for particles with characteristic dimensions from 10 to 100 μm and wavelengths from 0.3 to 10 μm assuming a gamma distribution of particle size with a width parameter μ < 4. It has been found that the extinction matrix of an ensemble of atmospheric ice crystals in the visible wavelength region is a unit matrix with a coefficient equal to the doubled area of the particle projection. The error of this representation does not exceed tenths of a percent and does not depend on the type of crystals and their spatial orientation. It has also been found that such a representation of the extinction matrix in the IR region is possible only for hexagonal columns, bullets, and similar crystals with a characteristic size greater than 20 μm for wavelengths less than 8 μm.

Background. In recent years growing evidence has suggested the potential role of obstructive sleep apnoea- hypopnoea (OSAH) in the genesis of atrial fibrillation (AF), but the precise mechanisms linking these two conditions are currently unknown. The aim. To assess the prevalence of OSAH in a sample of non-valvular AF patients and evaluate the clinical profile of non-valvular AF patients depending on the severity of sleep-disordered breathing. Material and methods. We enrolled into the study 172 patients with non-valvular AF (mean age 55.54±8.43 years; 68.02% males). The study subjects were divided into 4 groups according to the results of clinical laboratory evaluation (typical complaints, clinical markers, the Epworth scale scores and cardiorespiratory monitoring). Results. OSAH patients had higher body mass index, greater waist and neck circumference than non-OSAH patients (p

The technique for solving the problem of light backscattering by the physical optics method is considered. Recommendations on carrying out a preliminary estimation of the contribution of geometrical optics beams are given to reduce the list of beams that are necessary for the calculation by a factor of hundreds. The presented empirical estimating formulas and recommendations on choosing the optimum step of numerical integration make it possible to considerably reduce the resource intensity of the physical optics method for specified microphysical models of hexagonal crystalline particles. The obtained results of solving the light scattering problem are freely available in the form of a databank of Mueller matrices.

Results of the study of microphysical characteristics of cirrus clouds in Hefei, China, with a multiwavelength polarization lidar are presented. Measurements were carried out from December 2010, to February 2013. In this work, we consider the only dependable parameter of lidar signals, i.e., the linear depolarization ratio measured at a wavelength of 532 μm. The dependences of depolarization ratios on both the size of ice crystals and the distribution of their distortion angles were calculated in this work for the first time. These results were used for retrieving, with some uncertainty, the microphysical parameters of cirrus clouds observed in Hefei during that period.