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.

Detection of Low-Energy X-rays Using YSO Scintillation Crystal Arrays for GRB Experiments

We developed an X-ray detector using 36 arrays, each consisting of a 64-pixellated yttrium oxyorthosilicate (YSO) scintillation crystal and a 64-channel multi-anode photomultiplier tube. The X-ray detector was designed to detect X-rays with energies lower than 10 keV, primarily with the aim of localizing gamma-ray bursts (GRBs). YSO crystals have no intrinsic background, which is advantageous for increasing low-energy sensitivity. The fabricated detector was integrated into UBAT, the payload of the Ultra-Fast Flash Observatory (UFFO)/Lomonosov for GRB observation. The UFFO was successfully operated in space in a low-Earth orbit. In this paper, we present the responses of the X-ray detector of the UBAT engineering model identical to the flight model, using 241Am and 55Fe radioactive sources and an Amptek X-ray tube. We found that the X-ray detector can measure energies lower than 5 keV. As such, we expect YSO crystals to be good candidates for the X-ray detector materials for future GRB missions.

Methodological improvements for fluorescence recordings in Xenopus laevis oocytes

Xenopus laevis oocytes are a widely used model system because of their capacity to translate exogenous mRNA, but their high intrinsic background fluorescence is a disadvantage for fluorescence recordings. Here, we developed two distinct methods for improving fluorescence recordings from oocytes. One was a pharmacological method in which a small-molecule salt-inducible kinase inhibitor was co-injected with the mRNA of interest to stimulate melanin production. We interrogated the oocytes using cut-open voltage clamp with simultaneous fluorescence recording and found that by increasing the amount of light-absorbing melanin in these oocytes, we decreased their intrinsic background fluorescence. The treated oocytes produced fluorescence signals that were approximately four times larger. The second method consisted of direct injection of synthetic melanin. This method also significantly improved (doubled) fluorescence signals and allowed any oocyte to be used for fluorescence recording. These two methods provide significant improvements of the signal quality for fluorescent oocyte recordings and allow all healthy oocytes to be used for high-sensitivity recordings.

Observer-Biased Analysis of Gene Expression Profiles

Microarray generated gene expression data are characterized by their volume and by the intrinsic background noise. The main task of revealing patterns in gene expression data is typically carried out using clustering analysis, with soft clustering leading the more promising candidate methods. In this chapter, Fuzzy C-Means with a variable Focal Point (FCMFP) is exploited as the first stage in gene expression data analysis. FCMFP is inspired by the observation that the visual perception of a group of similar objects is (highly) dependent on the observer position. This metaphor is used to provide a new analysis insight, with different levels of granularity, over a gene expression dataset.