Intrinsic background of the beta channel of the aerosol volumetric activity monitor

The work is devoted to the study of the features of generation of the intrinsic background of the measuring beta channel of the aerosol monitor in real conditions of measuring the volumetric activity of aerosols, caused by radionuclides of technogenic origin. The influence of external factors on the generation of the level of the intrinsic background of the measuring channel of the monitor and its metrological characteristics is investigated. The reliability of the results of measurements of the volumetric activity of air aerosols substantially depends on the correct accounting of external factors, parameters of the monitored environment and the specified operating mode of the monitor. Aerosol volumetric activity monitors, as a rule, operate in a continuous mode, in which the aspiration method of aerosol accumulation is implemented, followed by measuring the volumetric activity of aerosols by alpha radiation and (or) beta radiation generated by technogenic radionuclides. This article describes the results of experiments on measuring the iCAM aerosol monitor’s intrinsic beta channel background under real operating conditions, and its dependence on external factors. The studies were carried out on iCAM aerosol monitors (iCAM/D and iCAM/MF modifications) manufactured by Canberra Industries Inc. in a laboratory room in normal climatic conditions with a radon volumetric activity of 35±10 Bq·m-3 and an equivalent dose rate of gamma radiation of 0.13±0.02 μSv·h-1. In modern aerosol monitors, software and hardware solutions are implemented that allow to significantly reduce the background level and, as a result, to expand the measurement range of the volumetric activity of aerosols towards low values.

Improved Production of Recombinant Myrosinase in Pichia pastoris

The effect of the deletion of a 57 bp native signal sequence, which transports the nascent protein through the endoplasmic reticulum membrane in plants, on improved AtTGG1 plant myrosinase production in Pichia pastoris was studied. Myrosinase was extracellularly produced in a 3-liter laboratory fermenter using α-mating factor as the secretion signal. After the deletion of the native signal sequence, both the specific productivity (164.8 U/L/h) and volumetric activity (27 U/mL) increased more than 40-fold compared to the expression of myrosinase containing its native signal sequence in combination with α-mating factor. The deletion of the native signal sequence resulted in slight changes in myrosinase properties: the optimum pH shifted from 6.5 to 7.0 and the maximal activating concentration of ascorbic acid increased from 1 mM to 1.5 mM. Kinetic parameters toward sinigrin were determined: 0.249 mM (Km) and 435.7 U/mg (Vmax). These results could be applied to the expression of other plant enzymes.

Seismic process on the Krillon Peninsula (Sakhalin Island) after the earthquake on April 23, 2017

Research subject and methods. The seismicity of the Krilyon Peninsula (Sakhalin Island) after the earthquake on April 23, 2017 (M = 5.0) during the 2018–2021 period was investigated by the method of self-developing processes (SDP).Results. The seismic activity showed a damping trend after the earthquake (and several following aftershocks), with the activation of SDP seismicity observed in two cases. In the study area (40 km within the radius from the epicenter of the Krillon earthquake) and its immediate vicinity (up to 80 km), earthquakes with M = 3.9 and M = 4.3 were observed 74 and 26 days after seismic activations. These earthquakes are considered to be the strongest events occurred in the study area in the period under consideration. The results of the study were compared with the monitoring data of the Kamchatka branch of the Geophysical Survey Russian Academy of Sciences (KB GS RAS) on the volumetric activity of subsoil radon (OA Rn). It was revealed that the OA Rn anomalies detected in November 2018 and January 2020 had appeared several weeks after the identifed SDP. The anomalies were registered at observation points remote from the study area (as well as from the above-mentioned earthquakes) by no more than 50 km. Earthquakes in 2018 (M = 3.9) and 2020 (M = 4.3) occurred 19 and 32 days after the appearance of OA Rn anomalies. In general, the current situation can be assessed as calm, since, according to the analysis data, the seismic activity has no prerequisites for the transition from the decaying stage to the stage of stabilization. As shown in the work, this is a sign for preparing an earthquake with a magnitude higher than 5. Nevertheless, activation and (as a result) earthquakes of moderate strength (M < 5) are possible on a damping trend. Conclusion. It is proposed to take into account the self-developing processes of activation as a primary sign for a change in the geodynamic state of the environment, under which the appearance of OA Rn anomalies is possible. These anomalies are associated with the forecast of moderate seismicity during foreshock or aftershock activations.

Assessment of the radiation situation in the territory of the Saumalkol village, located near the mothballed uranium mine of the North Kazakhstan region

For the first time after the mothballing of the uranium mine, comprehensive studies were carried out to assess the radiation situation in the territory of the Saumalkol settlement in the North Kazakhstan region. On the territory of the Saumalkol settlement, pedestrian and automobile gamma surveys were carried out, the rates of the ambient equivalent dose of gamma radiation, the flux density of alpha and beta particles and the equivalent equilibrium volumetric activity of daughter products of 222Rn and 220Rn isotopes in residential premises were measured. Samples of soil, water and bottom sediments were taken for laboratory radio spectrometric and radiochemical analyzes. At all measurement points, geographic coordinates were determined using a satellite navigation device. On the territory of the abandoned mine and in some areas of the Saumalkol settlement, anomalous areas with a high value of gamma radiation power from 0.35 to 1.08 μSv/h were revealed. In the residential premises of the Saumalkol village, the equivalent equilibrium volumetric activity of daughter products of radon isotopes is up to 8 times higher than the norm (200 Bq/m3 ).

Radiation-Hygienic Monitoring in Potentially Radon-Hazardous Territories

Modern radioecological studies to assess the effect of natural radiation on the human body have shown that at the moment of development of society, the main contribution to the exposure of the population is made by natural sources of ionizing radiation, while from 50 to 90 % of the dose load are caused by the gas radon-222 (222Rn) and daughter products of its decay. This paper presents the results of radiation-hygienic monitoring of the potentially radon-hazardous territory of the city of Baley, Trans-Baikal Territory. The measurement of the volumetric activity of radon (OARn) was carried out in the premises of residential and public buildings by the integral method using track exposure meters REI-4. According to the indicator of the equivalent equilibrium volumetric activity of radon (EROARn), a radiation-hygienic assessment of the premises and the calculation of potential dose loads on the population living in this territory were carried out. Studies have shown that OARn in residential and public buildings depends on the geological characteristics of the territory, on the design and design of buildings and structures, and on the building materials used. It was found that the main criterion for assessing the potential radon hazard of territories is the value of OARn in rooms on the 1st floors of buildings. According to the degree of potential radon hazard, the territory of the city of Baley can be conditionally divided into 3 types: 1 type – the territory located on a geological fault; Type 2 – the southern part of the city, represented by sedimentary rocks; Type 3 – the northern part of the city, represented by rocks of the basic gabbroid group with a low content of natural radionuclides. The types of buildings and structures and the type of building materials affect the dose load, but do not determine it.

Bioprocess optimisation for high cell density endoinulinase production from recombinant Aspergillus niger

Endoinulinases gene was expressed in recombinant Aspergillus niger for selective and high-level expression using an exponential fed-batch fermentation. The effects of the growth rate (µ), glucose feed concentration, nitrogen concentration and fungal morphology, on enzyme production were evaluated. A recombinant endoinulinases with a molecular weight of 66 KDa was secreted. Endoinulinases production was growth associated at µ> 0.04 h -1 , which is characteristic of the constitutive gpd promoter used for the enzyme production. The highest volumetric activity (670 U/ml) was achieved at a growth rate of 93% of µ max (0.07 h -1 ), while enzyme activity (506 U/ml) and biomass substrate yield (0.043 g biomassDW /g glucose ) significantly decreased at low µ (0.04 h -1 ). Increasing the feed concentration resulted in high biomass concentrations and viscosity, which necessitated high agitation for improved mixing and oxygen. However, the high agitation and low DO levels (ca. 8% of saturation) led to pellet disruption and growth in mycelial morphology. Enzyme production profiles, product (Y p/s ) and biomass (Y x/s ) yield coefficients were not affected by feed concentration and morphological change. The gradual increase in the concentration of nitrogen sources showed that, a nitrogen limited culture was not suitable for endoinulinases production in recombinant A. niger. Moreover, the increase in enzyme volumetric activity was still directly related to an increase in biomass concentration. An increase in nitrogen concentration, from 3.8 to 12 g/L, resulted in volumetric activity increase from 393 to 670 U/ml, but the Y p/s (10053 U/g glucose ) and Y x/s (0.049 g biomasDWs /g glucose ) did not significantly change. The data demonstrated the potential of recombinant A. niger and high cell density fermentation for the development of largescale endoinulinases production system.

Radioactive Aerosols within Conditions of the New Safe Confinement in 2017–2020

The results of monitored behavior of radioactive aerosols within the conditions of the New Safe Confinement (NSC) in 2017–2020 are presented. Maximum “unorganized” flux of beta-emitting products of the Chornobyl accident from the Shelter object through the process openings and leakages of light roofing in the NSC basic volume observed in 2017 made 7.9 kBq/(m2 ∙day). Mean annual density of radionuclide deposition onto the light roofing during four years has been changing within the range of 1.7–2.2 kBq/(m2 ∙day). Over these years, mean annual volumetric activity of sum of long-lived beta-emitting nuclides coming in the “Bypass” system dropped from 0.84 to 0.17 Bq/m3 . Their carriers were aerosol particles with activity median aerodynamic diameter, mainly, from 4.3 to 10 μm. The data are given on radioactive contamination of near-surface air layer in the NSC basic volume.