Evaluation of Radiation Resistance of Polystyrene Using Molecular Dynamics Simulation

The scission rates of polystyrene and fluorinated polystyrene irradiated in an irradiation facility with Co-60 γ-rays were determined using molecular dynamics simulation and gel permeation chromatography (GPC) molecular weight distributions. The prediction was based on the assumption that γ-ray energy is transferred to the initial velocity of the primary knock-on atom. We employed a molecular dynamics simulation procedure to compute the changes in bond length between the connections for selected values of the absorbed dose and compared the calculated values with measurements made on the irradiated samples. The samples were exposed to four different absorbed doses of 25, 50, 75, and 100 kGy. The scission process and scission ratio were simulated with LAMMPS with ReaxFF potential for each bond, and we compared the simulation results with the experimental data especially measuring average molecular weight to evaluate the effect of fluorination on radiation enhancement.

Мобильный ускоритель на базе безжелезного импульсного бетатрона для радиографирования динамических объектов

The paper concerns the mobile accelerator based on the ironless pulsed betaron. The accelerator is aimed to radiograph dynamic objects with a large optical thickness. It has a possibility to obtain up to three γ-pulses in one cycle of the acceleration. The accelerator operation description and results of its testing powering in a single-pulse mode are provided. The estimated boundary energy of an electron beam is equal to 60 MeV at the capacitance value of 1.8 mF of the storage of the betatron electromagnet pulsed power system. The thickness of the lead test object examined with γ-rays is 140 mm at 4 m from the tantalum target. The full width of the output γ-pulse at half maximum is equal to 120 ns. The dimension of the radiation source is 3×6 mm. The application of these accelerators within the radiographic complex will allow increasing the investigation efficiency due to the optimization of the hydrodynamic experiments geometry and the cost reduction.

Physico-chemical properties of irradiated poly (vinyl alcohol)–Ethylene glycol blend films by γ-rays and ion beam

Poly (vinyl alcohol) is blended with ethylene glycol by casting method to form PVA-EG blend films. These films were irradiated by both N2 ion beam extracted from dc ion source at different ion fluences and γ-rays with various irradiation doses. The effects of ion beam and γ-rays irradiation on the thermal, micro-hardness, and gel fraction properties of PVA-EG blend films were investigated. The gel fraction % and micro-hardness increase with increasing the γ-rays doses up to 150 kGy and then decreased, where they increased at all fluences of ion beam irradiation. The improvement in the gel fraction percentage and micro-hardness suggest that PVA-EG blend films exhibited a crosslink density. The thermal behavior was examined by thermogravimetric analysis and it shows different thermal patterns depending on the type and dose of radiation. The thermal stability parameters of γ-rays- and ion beam-irradiated PVA-EG samples were evaluated using the Ti, Ts, T0.5, Tf temperatures, and activation energy (Ea) values. The thermal stability parameters were dependent on both the type and extent of irradiation dose and fluence. Finally, there is a good agreement between the obtained results from different measurement techniques.

A Validation Study on Immunophenotypic Differences in T-lymphocyte Chromosomal Radiosensitivity between Newborns and Adults in South Africa

Children have an increased risk of developing radiation-induced secondary malignancies compared to adults, due to their high radiosensitivity and longer life expectancy. In contrast to the epidemiological evidence, there is only a handful of radiobiology studies which investigate the difference in radiosensitivity between children and adults at a cellular level. In this study, the previous results on the potential age dependency in chromosomal radiosensitivity were validated again by means of the cytokinesis-block micronucleus (CBMN) assay in T-lymphocytes isolated from the umbilical cord and adult peripheral blood of a South African population. The isolated cells were irradiated with 60Co γ-rays at doses ranging from 0.5 Gy to 4 Gy. Increased radiosensitivities of 34%, 42%, 29%, 26% and 16% were observed for newborns compared to adults at 0.5, 1, 2, 3 and 4 Gy, respectively. An immunophenotypic evaluation with flow cytometry revealed a significant change in the fraction of naïve (CD45RA+) T-lymphocytes in CD4+ and CD8+ T-lymphocytes with age. Newborns co-expressed an average of 91.05% CD45RA+ (range: 80.80–98.40%) of their CD4+ cells, while this fraction decreased to an average of 39.08% (range: 12.70–58.90%) for adults. Similar observations were made for CD8+ cells. This agrees with previous published results that the observed differences in chromosomal radiosensitivity between newborn and adult T-lymphocytes could potentially be linked to their immunophenotypic profiles.

Radioactive nuclei for β + γ PET and theranostics: selected candidates

Positron emission tomography (PET) is an established medical diagnostic imaging method. Continuous improvements are aimed at refining image reconstruction, reducing the amount of radioactive tracer and combining with targeted therapy. Time-of-flight (TOF)-PET provides the localization of the tracer through improved time resolution, nuclear physics may contribute to this goal via selection of radioactive nuclei emitting additional γ-rays. This additional radiation, when properly detected, localizes the decay of the tracer at the line of response (LoR) determined by two detected 511 keV quanta. Selected candidates are presented. Some are particularly interesting, as they are strong candidates for theranostic applications.

γ-Ray Flux and Spectral Variability of Blazar Ton 599 during Its 2021 Flare

Blazars are known to emit exceptionally variable non-thermal emission over the wide range (from radio to γ-rays) of electromagnetic spectrum. We present here the results of our γ-ray flux and spectral variability study of the blazar Ton 599, which has been recently observed in the γ-ray flaring state. Using 0.1−300 GeV γ-ray data from the Fermi Gamma-ray Space Telescope (hereinafter Fermi), we generated one-day binned light curve of Ton 599 for a period of about one-year from MJD 59,093 to MJD 59,457. During this one year period, the maximum γ-ray flux detected was 2.24 ± 0.25 ×10−6 ph cm−2 s−1 at MJD 59,399.50. We identified three different flux states, namely, epoch A (quiescent), epoch B (pre-flare) and epoch C (main-flare). For each epoch, we calculated the γ-ray flux variability amplitude (Fvar) and found that the source showed largest flux variations in epoch C with Fvar∼ 35%. We modelled the γ-ray spectra for each epoch and found that the Log-parabola model adequately describes the γ-ray spectra for all the three epochs. We estimated the size of the γ-ray emitting region as 1.03 ×1018 cm and determined that the origin of γ-ray radiation, during the main-flare, could be outside of the broad line region.

Chapter 7 Solar and Heliospheric Physics and Interdisciplinary Research with LHAASO

In the following sub-sections, studies of solar-heliospheric effects on cosmic rays, investigating a possible link between cosmic ray flux and Earth’s climate, and detection of MeV-range γ-rays from thunderstorms with the data from LHAASO will be discussed; geophysical research with environmental neutrons will be introduced, and some Monte Carlo simulation results about effects of thunderstorm electric fields on LHAASO observations of cosmic rays will be given.

Evaluation the Safety and Security Procedures used In X-ray Clinics in Al-Harthiya-Baghdad

Radiation is a form of energy, its emitted either in the form of particles such as α-particles and β-particles (beta particles including the electron and the positron) or waves such as sunlight, X-rays and γ-rays. Radiation found everywhere around us and it comes from many different sources naturally or man-made sources. In this study a questionnaire was distributed to people working in the field of X-rays that used for a medical imaging (X-ray and CT-scan) to evaluate the extent of awareness and knowledge in estimate the damage of ionizing radiation as a result of wrong use. The questionnaire was distributed to medical clinics in Al-Harithiya in Baghdad, which it’s considered as one of the important areas in Iraq to attract and treat patients. It’s found that most of the commitment of radiography clinics by safety and security procedures. Most of the radiology clinics abide by most of the Iraqi Ministry of Health laws. However, some clinics did not implement some of the security and safety conditions

Quantitative modeling of carcinogenesis induced by single beams or mixtures of space radiations using targeted and non-targeted effects

Ionizing radiations encountered by astronauts on deep space missions produce biological damage by two main mechanisms: (1) Targeted effects (TE) due to direct traversals of cells by ionizing tracks. (2) Non-targeted effects (NTE) caused by release of signals from directly hit cells. The combination of these mechanisms generates non-linear dose response shapes, which need to be modeled quantitatively to predict health risks from space exploration. Here we used a TE + NTE model to analyze data on APC(1638N/+) mouse tumorigenesis induced by space-relevant doses of protons, 4He, 12C, 16O, 28Si or 56Fe ions, or γ rays. A customized weighted Negative Binomial distribution was used to describe the radiation type- and dose-dependent data variability. This approach allowed detailed quantification of dose–response shapes, NTE- and TE-related model parameters, and radiation quality metrics (relative biological effectiveness, RBE, and radiation effects ratio, RER, relative to γ rays) for each radiation type. Based on the modeled responses for each radiation type, we predicted the tumor yield for a Mars-mission-relevant mixture of these radiations, using the recently-developed incremental effect additivity (IEA) synergy theory. The proposed modeling approach can enhance current knowledge about quantification of space radiation quality effects, dose response shapes, and ultimately the health risks for astronauts.