Search

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.

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

Idiopathic pulmonary arterial hypertension is a progressive, incurable disease of unclear etiology; it is characterized by intensive remodeling of the pulmonary vascular bed with a predominant lesion of the distal pulmonary arteries and arterioles. A diagnostic criterion of the disease is an increase in the average pressure in the pulmonary artery more than 25 mm Hg. Arterial hypertension is difficult to diagnose, especially at the early stages due to non-specific clinical symptoms. The article describes the clinical case of diagnostics and treatment of a child with primary pulmonary hypertension of high degree.

Research objective: to assess the diagnostic significance of the pulse oximetry performed by the newborn for the 3rd hour of life to identify critical conditions and to justify the expediency of further introduction of this technology in the work of obstetric institutions. Results. In 5 maternity hospitals of the Republic of Tatarstan, from April 2016 to February 2017, 8358 88.4% of newborns were pulsometrically screened. Positive results were obtained in 95 (1.14%) patients. Because of screening, 13 newborns were diagnosed with congenital heart defects, not diagnosed in utero, in the first hours of life, five of them were critical. All newborns with critical congenital heart defects were successfully operated. Besides, 20 patients had persistent pulmonary hypertension, 30 had intrauterine pneumonia. Conclusions. The measurement of saturation at the 3rd hour of life of a newborn allows avoiding life-threatening complications in children with critical congenital heart defects and persistent pulmonary hypertension and in a stable state to transfer them to a further treatment stage.

The scattered field for a large faceted particle, that is, a particle bounded by a set of plane surfaces, is expanded in a series over multiplicity of reflection/ refraction events inside the particle. As a result, the scattered field is represented as a set of plane-parallel beams in the near zone of the particle. Then every beam is easy to describe analytically at an arbitrary distance from the particle. In particular, the beams undergo the Fraunhofer diffraction in the wave zone. In the far zone, a simple relationship between the geometric-optics and physicaloptics Mueller matrices is considered that allows one to use both of them. In the majority of problems of practical interest, only one or a small number of the beams makes the main contribution to the measured quantities. In these cases, the geometric-optics and physical-optics Mueller matrices can be calculated either analytically or numerically by means of appropriate fast codes. In particular, it is shown that for particles with a refractive index of about 1.3 such as ice crystals, the main contribution to the phase function for randomly oriented particles is caused by the beams with one internal reflection. This fact allows us to parameterize the phase function for ensembles of such particles. Furthermore, the nature of the backscattering peak well-known for ice crystal clouds is discussed in the framework of the geometric-optics Mueller matrix. Finally, an efficient algorithm for the calculation of diffraction near the forward-scattering direction for ensembles of faceted particles is developed which corresponds to the physical-optics approximation.