Inverse dose protraction effects of low-LET radiation: evidence and significance.

Biological effects of ionizing radiation vary not merely with total dose but also with temporal dose distribution. Sparing dose protraction effects, in which dose protraction reduces effects of radiation have widely been accepted and generally assumed in radiation protection, particularly for stochastic effects (e.g.

Reply to Comments on 'Modeling for predicting survival fraction of cells after ultra-high dose rate irradiation'.

Liew and Mairani (2024.248001) commented on our previous reply to comments on our paper, 'Modeling for predicting survival fraction of cells after ultra-high dose rate irradiation'. We appreciate their comments on the choice of experimental data on DNA damage for cell survival and agree that the estimate of the dose-response curve on cell survival depends on the selection of DNA damage data.

Dynamics of plastic debris and its density change between river compartments in the Tuul River system, Mongolia.

Plastic pollution in river environments has become an emerging global concern. However, the migration of plastic and changes in its properties between river compartments are less understood. This study demonstrates the plastic debris aging and the dynamics between floodplain, surface water, and sediment compartments of the Tuul River, Mongolia.

ESR measurement of carbonated hydroxyapatite for dosemeter.

We have examined a dosimetry characteristic of carbonate hydroxyapatite (CO3HAp), which is a dental bone graft material. The purpose of this work is to investigate the reproducibility and stability of radiation-induced radicals on CO3HAp samples and assess the feasibility of using these materials as dosemeters. CO3HAp samples were exposed to gamma rays with dose range from 10 to 10 000 Gy.

Evaluation of materials for developing a new individual dosemeter using electron spin resonance spectroscopy.

Alanine dosemeters are widely used as solid dosemeters; however, evaluating doses in the mGy order of radiation is difficult because of their lower sensitivity for low doses. We applied the electron spin resonance dosimetry technique to investigate whether hydroxyapatite, the main component of teeth, is a suitable material for a new dosemeter to detect radiation from mGy to Gy. Commercially available synthetic hydroxyapatite possesses the essential characteristics required for a dosemeter material and has been demonstrated to accurately measure doses in the mGy to Gy range.

Geant4 Monte Carlo simulation of human exposure to indoor Rn from building materials.

The present study aimed to develop a Monte Carlo model to estimate the annual effective dose due to radon exposure sourced by radon gas in the walls and floor of a standard model room. With the purpose of developing a tool for radon level assessment in dwellings and workplaces, Geant4 toolkit was used to simulate the energy deposited by gamma rays emitted by radioactive radon progeny in a water phantom positioned at three different locations within the model room. The energy deposition was then used to estimate the annual effective dose through a deterministic approach.

Significant role of secondary electrons in the formation of a multi-body chemical species spur produced by water radiolysis.

Scientific insights into water photolysis and radiolysis are essential for estimating the direct and indirect effects of deoxyribonucleic acid (DNA) damage. Secondary electrons from radiolysis intricately associated with both effects. In our previous paper, we simulated the femtosecond (1 × 10 s) dynamics of secondary electrons ejected by energy depositions of 11-19 eV into water via high-energy electron transport using a time-dependent simulation code.

Effect of neutron beam properties on dose distributions in a water phantom for boron neutron capture therapy.

From the viewpoints of the advantage depths (ADs), peak tumor dose and skin dose, we evaluated the effect on the dose distribution of neutron beam properties, namely the ratio between thermal and epithermal neutron fluxes (thermal/epithermal ratio), fast neutron component and γ-ray component. Several parameter surveys were conducted with respect to the beam properties of neutron sources for boron neutron capture therapy assuming boronophenylalanine as the boron agent using our dose calculation tool, called SiDE. The ADs decreased by 3% at a thermal/epithermal ratio of 20-30% compared with the current recommendation of 5%.

Biofilm-mediated interactions between plastics and radiocesium in coastal environments.

A ubiquitous distribution of plastic debris has been reported in aquatic and terrestrial environments; however, the interactions between plastics and radionuclides and the radioactivity of environmental plastics remain largely unknown. Here, we characterize biofilms developing on the surface of plastic debris to explore the role of plastic-associated biofilms as an interaction medium between plastics and radiocesium (Cs) in the environment. Biofilm samples were extracted from plastics (1-50 mm in size) collected from two contrasting coastal areas in Japan.

Dose-rate coefficients for external exposure to radionuclides uniformly distributed in soil to an infinite depth.

Using a database on external exposures to environmental sources provided by the International Commission on Radiological Protection, monoenergetic and nuclide-specific dose-rate coefficients have been evaluated for volumetric sources with a uniform distribution to an effectively infinite depth in soil. Organ equivalent and effective dose rates for the public (newborns; 1-, 5-, 10-, and 15-year-old children; and adults), ambient dose equivalent rates, and air kerma free-in-air rates at 1 m above the ground were computed. This was performed using the weighted-integral method for monoenergetic photon and electron sources in an energy region of 10-2 to 8 MeV with 25 energy points to obtain the respective monoenergetic dose-rate coefficients.

Validating the application of the revised ICRP's biokinetic models for organicC and organically bound tritium to members of the public.

In 2016, the International Commission on Radiological Protection (ICRP) has revised the biokinetic models for carbon and tritium in Publication 134 to calculate the dose coefficients of these radionuclides for workers. The following publication for members of the public is now in the process of revising by the ICRP. According to the draft manuscript published for consultation in 2023, the same models will be adopted for members of the public, although the parameters in these models are not corroborated by the metabolic data of radionuclides in foods.

Liquid water radiolysis induced by secondary electrons generated from MeV-energy carbon ions.

Fast ion beams induce damage to deoxyribonucleic acid (DNA) by chemical products, including secondary electrons, produced from interaction with liquid water in living cells. However, the production process of these chemical products in the Bragg peak region used in particle therapy is not fully understood. To investigate this process, we conducted experiments to evaluate the radiolytic yields produced when a liquid water jet in vacuum is irradiated with MeV-energy carbon beams.

First-principles calculations on dislocations in MgO.

While ceramic materials are widely used in our society, their understanding of the plasticity is not fully understood. MgO is one of the prototypical ceramics, extensively investigated experimentally and theoretically. However, there is still controversy over whether edge or screw dislocations glide more easily.

LET-based approximation of the microdosimetric kinetic model for proton radiotherapy.

Background: Phenomenological relative biological effectiveness (RBE) models for proton therapy, based on the dose-averaged linear energy transfer (LET), have been developed to address the apparent RBE increase towards the end of the proton range. The results of these phenomenological models substantially differ due to varying empirical assumptions and fitting functions. In contrast, more theory-based approaches are used in carbon ion radiotherapy, such as the microdosimetric kinetic model (MKM).

Dynamics and functions of microbial communities in the plastisphere in temperate coastal environments.

Microbial attachment and biofilm formation on microplastics (MPs <5 mm in size) in the environment have received growing attention. However, there is limited knowledge of microbial function and their effect on the properties and behavior of MPs in the environment. In this study, microbial communities in the plastisphere were explored to understand microbial ecology as well as their impact on aquatic ecosystems.

Compact and transportable system for detecting lead-shielded highly enriched uranium using Cf rotation method with a water Cherenkov neutron detector.

The global challenge of on-site detection of highly enriched uranium (HEU), a substance with considerable potential for unauthorized use in nuclear security, is a critical concern. Traditional passive nondestructive assay (NDA) techniques, such as gamma-ray spectroscopy with high-purity germanium detectors, face significant challenges in detecting HEU when it is shielded by heavy metals. Addressing this critical security need, we introduce an on-site detection method for lead-shielded HEU employing a transportable NDA system that utilizes the Cf rotation method with a water Cherenkov neutron detector.

Cell-cycle dependence on the biological effects of boron neutron capture therapy and its modification by polyvinyl alcohol.

Boron neutron capture therapy (BNCT) is a unique radiotherapy of selectively eradicating tumor cells using boron compounds (e.g., 4-borono-L-phenylalanine [BPA]) that are heterogeneously taken up at the cellular level.

Advances in understanding cesium retention on calcium silicate material.

Retention or trapping of cesium, one of the radiologically important fission products, in the nuclear reactor becomes a great concern as the occurrence may affect radioactivity in the long term or its environmental fate. Herein the chemical compound of cesium that had been largely trapped on the nuclear reactor structural material of (calcium silicate) thermal insulator in a simulated nuclear accident condition was investigated. A combined pre- and post-water dissolution analysis through infrared (IR) spectroscopy and optical emission spectroscopy (OES) was explored to resolve the characterization difficulty encountered in conventional X-ray diffraction analysis reported in the previous works.

Analysis of particles containing alpha emitters in stagnant water in Fukushima Daiichi Nuclear Power Station's Unit 3 reactor building.

Particles containing alpha (α) nuclides were identified from sediment in stagnant water in the Unit 3 reactor building of the Fukushima Daiichi Nuclear Power Station (FDiNPS). We analyzed different concentrations of α-nuclide samples collected at two sampling sites, the torus room and the main steam isolation valve (MSIV) room. The solids in the stagnant water samples were classified, and the uranium (U) and total alpha concentrations of each fraction were measured by dissolution followed by inductively coupled plasma mass spectrometry and α-spectrometry.

Evaluation of relative biological effectiveness for diseases of the circulatory system based on microdosimetry.

In the next decade, the International Commission on Radiological Protection (ICRP) will issue the next set of general recommendations, for which evaluation of relative biological effectiveness (RBE) for various types of tissue reactions would be needed. ICRP has recently classified diseases of the circulatory system (DCS) as a tissue reaction, but has not recommended RBE for DCS. We therefore evaluated the mean and uncertainty of RBE for DCS by applying a microdosimetric kinetic model specialized for RBE estimation of tissue reactions.

Uncovering the characteristics of plastic-associated biofilm from the inland river system of Mongolia.

The occurrence and characteristics of plastic debris in aquatic and terrestrial environments have been extensively studied. However, limited information exists on the properties and dynamic behavior of plastic-associated biofilms in the environment. In this study, we collected plastic samples from an inland river system in Mongolia and extracted biofilms to uncover their characteristics using spectroscopic, isotopic, and thermogravimetric techniques.

Consideration of the dielectric response for radiation chemistry simulations.

The spur reaction, a spatially nonhomogeneous chemical reaction following ionization, is crucial in radiolysis or photolysis in liquids, but the spur expansion process has yet to be elucidated. One reason is the need to understand the role of the dielectric response of the solvating molecules surrounding the charged species generated by ionization. The dielectric response corresponds to the time evolution of the permittivity and might affect the chemical reaction-diffusion of the species in a spur expansion process.

The impact of dose rate on responses of human lens epithelial cells to ionizing irradiation.

The knowledge on responses of human lens epithelial cells (HLECs) to ionizing radiation exposure is important to understand mechanisms of radiation cataracts that are of concern in the field of radiation protection and radiation therapy. However, biological effects in HLECs following protracted exposure have not yet fully been explored. Here, we investigated the temporal kinetics of γ-H2AX foci as a marker for DNA double-strand breaks (DSBs) and cell survival in HLECs after exposure to photon beams at various dose rates (i.

Records of the riverine discharge of I in riverbank sediment after the Fukushima accident.

Although I discharge from watersheds is fundamental for assessing long-term radiation effects on aquatic ecosystems, I originating from the Fukushima nuclear accident is yet be evaluated. This study investigated the transport behavior of I by riverbank surveys conducted from 2013 to 2015 in a watershed where the I/Cs activity ratio is low in the mountainous area and high in the plain as of 2011. Until 2015, the I/Cs activity ratio of the levee crown in the studied watershed was similar to that of the surrounding area in 2011.