Dose Rates Of Ionizing Radiation Research Articles

Evaluation of Low-dose Radiation-induced DNA Damage and Repair in 3D Printed Human Cellular Constructs.

DNA double-strand breaks (DSBs) induced by ionizing radiation (IR) are considered to be the most critical lesion that when unrepaired or misrepaired leads to genomic instability or cell death depending on the radiation exposure dose. The potential health risks associated with exposures of low-dose radiation are of concern since they are being increasingly used in diverse medical and non-medical applications. Here, we have used a novel human tissue-like 3-dimensional bioprint to evaluate low-dose radiation-induced DNA damage response. For the generation of 3-dimensional tissue-like constructs, human hTERT immortalized foreskin fibroblast BJ1 cells were extrusion printed and further enzymatically gelled in a gellan microgel-based support bath. Low-dose radiation-induced DSBs and repair were analyzed in the tissue-like bioprints by indirect immunofluorescence using a well-known DSB surrogate marker, 53BP1, at different post-irradiation times (0.5 h, 6 h, and 24 h) after treatment with various doses of γ rays (50 mGy, 100 mGy, and 200 mGy). The 53BP1 foci showed a dose dependent induction in the tissue bioprints after 30 min of radiation exposure and subsequently declined at 6 h and 24 h in a dose-dependent manner. The residual 53BP1 foci number observed at 24 h post-irradiation time for the γ-ray doses of 50 mGy, 100 mGy, and 200 mGy was not statistically different from mock treated bioprints illustrative of an efficient DNA repair response at these low-dose exposures. Similar results were obtained for yet another DSB surrogate marker, γ-H2AX (phosphorylated form of histone H2A variant) in the human tissue-like constructs. Although we have primarily used foreskin fibroblasts, our bioprinting approach-mimicking a human tissue-like microenvironment-can be extended to different organ-specific cell types for evaluating the radio-response at low-dose and dose-rates of IR.

Dose rate effect on mortality from ischemic heart disease in the cohort of Russian Mayak Production Association workers

For improvement of the radiation protection system it is crucial to know the factors that modify the radiation dose–response relationship. One of such key factors is the ionizing radiation dose rate. There are, however, very few studies that examine the impact of the dose rate on radiogenic risks observed in human cohorts exposed to radiation at various dose rates. Here we investigated the impact of the dose rate (in terms of the recorded annual dose) on ischemic heart disease (IHD) mortality among Russian nuclear workers chronically exposed to radiation. We observed significantly increased excess relative risks (ERR) of IHD mortality per unit of external gamma-ray absorbed dose accumulated at higher dose rates (0.005–0.050 Gy/year). The present findings provide evidence for the association between radiation dose rate and ERRs of IHD mortality in occupationally chronically exposed workers per unit total dose. IHD mortality risk estimates considerably increased with increasing duration of uninterrupted radiation exposure at high rates. The present findings are consistent with other studies and can contribute to the scientific basis for recommendations on the radiation protection system.

Changes in ionizing radiation dose rate affect cell cycle progression in adipose derived stem cells.

Biomedical use of radiation is utilized in effective diagnostic and treatment tools, yet can introduce risks to healthy tissues. High energy photons used for diagnostic purposes have high penetration depth and can discriminate multiple tissues based on attenuation properties of different materials. Likewise, the ability to deposit energy at various targets within tumors make the use of photons effective treatment for cancer. Radiation focused on a tumor will deposit energy when it interacts with a biological structure (e.g. DNA), which will result in cell kill should repair capacity of the tissue be overwhelmed. Likewise, damage to normal, non-cancerous tissues is a consequence of radiation that can lead to acute or late, chronic toxicity profiles. Adipose derived stem cells (ADSCs) are mesenchymal stem cells that have been proven to have similar characteristics to bone marrow derived stem cells, except that they are much easier to obtain. Within the body, ADSCs act as immunomodulators and assist with the maintenance and repair of tissues. They have been shown to have excellent differentiation capability, making them an extremely viable option for stem cell therapies and regenerative medicine applications. Due to the tissue ADSCs are derived from, they are highly likely to be affected by radiation therapy, especially when treating tumors localized to structures with relatively high ADSC content (eg., breast cancer). For this reason, the purpose behind this research is to better understand how ADSCs are affected by doses of radiation comparable to a single fraction of radiation therapy. We also measured the response of ADSCs to exposure at different dose rates to determine if there is a significant difference in the response of ADSCs to radiation therapy relevant doses of ionizing radiation. Our findings indicate that ADSCs exposed to Cesium (Cs 137)-gamma rays at a moderate dose of 2Gy and either a low dose rate (1.40Gy/min) or a high dose rate (7.31Gy/min) slow proliferation rate, and with cell cycle arrest in some populations. These responses ADSCs were not as marked as previously measured in other stem cell types. In addition, our results indicate that differences in dose rate in the Gy/min range typically utilized in small animal or cell irradiation platforms have a minimal effect on the function of ADSCs. The potential ADSCs have in the space of regenerative medicine makes them an ideal candidate for study with ionizing radiation, as they are one of the main cell types to promote tissue healing.

Comparative study of radioactivity levels and radionuclide fingerprints in typical marine ecosystems of coral reefs, mangroves, and hydrothermal vents

As a key environmental parameter to induce radiation dose and effect on non-human species, radioactivity level is rarely evaluated in typical ecosystems of coral reefs, mangroves, and hydrothermal vents. In this study, naturally occurring radionuclides (238U, 226Ra, 228Ra, and 40K) in carbonate, silicate, and sulfide sediments collected from coral reefs, mangroves, and hydrothermal vents were simultaneously measured using high purity germanium (HPGe) γ spectrometry. Radioactivity levels and radionuclide fingerprints (226Ra/238U and 228Ra/226Ra) were interpreted and explored for tracking sources and formation processes of marine sediments in distinct marine ecosystems. Additionally, ionizing radiation dose rate on representative marine biotas (mollusc-bivalve, crustacean, polychaete worm, benthic fish, and pelagic fish) was evaluated using the ERICA tool with an increasing rank in coral reefs < mangroves < hydrothermal vents. Polychaete worm received the highest radiation dose relative to other marine biotas. We also emphasized the dominant contribution of 210Po to total radiation dose rate on marine biotas.

X-ray radiation effects on thin film nanocomposites of functionalized and copper coated multi-walled carbon nanotube and poly(methyl methacrylate)

Multi-walled carbon nanotube (MWCNT) and poly(methyl methacrylate) (PMMA) nanocomposites have the potential to be deployed as sensing elements for various applications including ionizing radiation detection. In this work, a 160 kV x-ray ionizing radiation source has been used to study the ionizing radiation dose rate effects on Ferrocene doped MWCNTs, MWCNTs functionalized with - carboxylic acid (COOH), hydrogen peroxide, amine, and MWCNTs coated/ modified with copper. Solution blending method was used in synthesizing the nanocomposites and the synthesized composites were cast on interdigitated electrodes (IDEs) to perform radiation sensing experiments by monitoring changes in the films’ resistance. We have observed a clear, repeatable and proportionate response curve for radiation dose rate measurements with Ferrocene doped MWCNT/PMMA thin film composites. A weaker response is observed for functionalized MWCNT/PMMA films. Ferrocene doped MWCNT/PMMA composite showed the most increased sensitivity to x-ray radiation when compared to all other functional groups reported here and as compared to unfunctionalized MWCNT/PMMA composites. Ferrocene doped MWCNT/PMMA films’ resistance changed over 18% compared to changes observed for unfunctionalized MWCNT/PMMA films of about 6%. Accelerated post radiation recovery of Ferrocene doped MWCNT/PMMA composites using a heat treatment technique is presented. The results of this study suggest that simple sensor elements based on relatively economical MWCNTs could be useful for the detection of ionizing radiation.

Power lines and ionizing radiation.

The magnetic field and ionizing radiation dose rate were measured near ground level in the vicinity of a utility power line. The dose rate was monitored using thermoluminescence detectors. Measurements were made at distances up to about 100 m from the main transmission line from the Kewaunee Nuclear Power Plant while the plant was in operation and while the plant was shut down for refueling. No evidence was found that the dose rate is significantly different in the presence of the magnetic field from the power line than in its absence.

Field and laboratory measurements of low-level thorium, uranium and potassium

Abstract Thermoluminescence, photoluminescence and electron-spin resonance dating require the accurate determination of the ionizing radiation dose rate experienced by the sample. The availability of portable multichannel analysers with calculation and storage facilities, gives an immediate read-out of total γ-ray dose rate, potassium, thorium and uranium concentrations and provides storage for spectra. Extensive measurements have been made for sites at which disequilibrium is not expected and the results agree very closely with those obtained by XRF and neutron activation. For potassium and thorium, the field measurement is accurate and precise and for uranium the measurement is also accurate if there is no disequilibrium. Any discrepancy with a non-radiometric determination of uranium suggests disequilibrium and the necessity for further investigation.

Superhot electron model for ionizing radiation dose rate response of GaAs junction field-effect transistors

The ionizing radiation dose rate response of GaAs junction field-effect transistors (JFETs) cannot be explained by the usual photocurrent model. A model is proposed in which superhot electrons from a region of many tens of microns are collected ballistically over the repulsive built-in P+ gate barrier of irradiated n-JFETs providing a gate current of polarity opposite to that of the ordinary junction photocurrent. Steady state is established by inflow of thermal electrons from the source which increases the bulk electron concentration and causes a drift velocity saturated drain current through the substrate at positive drain voltages. Since collection range of holes is much shorter than of electrons, p-JFETs do not exhibit this effect.

Channel and Substrate Currents in GaAs FETS Due to Ionizing Radiation

Measurements of photocurrents due to pulsed ionizing radiation are reported and analyzed for planar, ion implanted GaAs junction field-effect transistors fabricated on semi-insulating GaAs substrates. With the help of various device geometries and contact arrangements, it will be shown that the primary photocurrent of the pn-junction gate of the JFET is much smaller than the additional photocurrent originating in the semi-insulating substrate by electron hole pair generation. For a 3 ?m contact separation the substrate photocurrent in amperes is empirically given by Ips = 6 × 10-11 VAW?, where VA is the applied voltage in volts, W the width of the contacts in cm and ? the dose rate in rad(GaAs)/s. The relation for Ips has also been theoretically assessed in good agreement with the experimental results. Since the primary photocurrent Ipp, is much smaller than Ips, the prediction of logic upset due to ionizing radiation dose rate has to be expanded to include this induced substrate photocurrent.

Dynamic extraction of recoil products from complex-ions adsorbed on an ion-exchanger application to the hexammine- and trisethylenediamine-cobalt ions

A continuous extraction of recoil products from the Szilard-Chalmers reaction on a complex ion adsorbed on an ion-exchange resin has been proposed for obtaining a high yield and specific activity. The method was tested using hexamminecobalt and trisethylenediaminecobalt ions, the recoiling radioactive aquocobaltous ion being continuously eluted with 0·5% ammonium citrate solution (pH 5·0). When the concomitant ionizing radiation dose rate was high the method gives a lower retention.