Gamma Radiation Damage Research Articles

Determination of protective properties of some drug-active compounds against gamma radiation damage

Determination of protective properties of some drug-active compounds against gamma radiation damage

Low-Dose Gamma Radiation Fields Decrease Cell Viability, Damage DNA, and Increase the Expression of Hsp70 and p53 Proteins in Human Leukocytes

Low-Dose Gamma Radiation Fields Decrease Cell Viability, Damage DNA, and Increase the Expression of Hsp70 and p53 Proteins in Human Leukocytes

Localized strain relaxation effect on gamma irradiated AlGaN/GaN high electron mobility transistors

Strain localization in microelectronic devices commonly arises from device geometry, materials, and fabrication processing. In this study, we controllably relieve the local strain field of AlGaN/GaN HEMTs by milling micro-trenches underneath the channel and compare the device performance as a function of the relieved strain as well as radiation dosage. Micro-Raman results suggest that the trenches locally relax the strain in device layers, decreasing the 2DEG density and mobility. Intriguingly, such strain relaxation is shown to minimize the radiation damage, measured after 10 Mrads of 60Co-gamma exposure. For example, a 6-trench device showed only ∼8% and ∼6% decrease in saturation drain current and maximum transconductance, respectively, compared to corresponding values of ∼15% and ∼30% in a no-trench device. Negative and positive threshold voltage shifts are observed in 6-trench and no-trench devices, respectively, after gamma radiation. We hypothesize that the extent of gamma radiation damage depends on the strain level in the devices. Thus, even though milling a trench decreases 2DEG mobility, such decrease under gamma radiation is far less in a 6-trench device (∼1.5%) compared to a no-trench device (∼20%) with higher built-in strain.

Silicon Solar Cells for Post-Detonation Monitoring and Gamma-Radiation Effects

The feasibility of using solar cells for post-detonation monitoring, and more broadly, gamma-ray monitoring, is evaluated using Monte Carlo simulations and experiments in this work. We measured the short-circuit current Isc response of commercial silicon (Si) solar cells to 137Cs and 60Co gamma rays. A clear response of both mono- and polycrystalline Si solar cells to 137Cs and 60Co gamma rays was obtained in good agreement with the simulations. Radiation effects in solar cells due to accumulated gamma-ray dose were noticed as the drop in Isc and open-circuit voltage Voc. The atomic displacement cross section of the produced secondary fast electrons and nonionizing energy loss (NIEL) concepts were revisited to understand the principal gamma-radiation damage mechanism in solar cell devices. Analytical computations of and NIEL of electrons convoluted with simulated Compton electron distributions in Si enabled a fundamental understanding of the gamma-radiation effects and recovery mechanism in solar cells, further supporting the experimental results. Different from the ionization effects in the polymer and glass layers of a solar cell/panel, displacement damage in the Si p-n layer from gamma rays or fast electrons is much less than that from massive particles, which directly affects the charge collection performance fundamental to solar cell operation.

Nanoscale Stress Localization Effects on the Radiation Susceptibility of GaN High‐Mobility Transistors

Nanoscale localized mechanical stress fields develop unavoidably in microelectronic devices due to structural and processing aspects. Their global average is too small to influence bandgap or mobility, but it is proposed that stress localization can influence defect nucleation sites under radiation. This is investigated on gallium nitride high‐electron‐mobility transistors (GaN HEMTs). Using transmission electron microscopy, we spatially resolved the stress field in the AlGaN layer for both pristine and 10 Mrad gamma‐irradiated HEMTs. The quantitative nanobeam electron diffraction and geometric phase analysis indicate that tensile stressed localizations experience higher radiation‐induced strain. This finding is explained by the tensile stress dependence of the carrier concentration and mobility in the AlGaN layer. Since gamma radiation damage is inflicted by high‐energy electrons only, localized regions of higher tensile stress in the AlGaN layer are expected to be more susceptible to gamma rays.

Determination of the Protective Properties of Some Drug Active Compounds Against Gamma Radiation Damage

Determination of the Protective Properties of Some Drug Active Compounds Against Gamma Radiation Damage

Neutron Radiation Effects on Lubricants and O-Rings for Target and Accelerator Applications

Lubricants and O-rings are necessarily used for the construction of many accelerator-driven facilities as spallation sources or facilities for the production of radioactive isotopes. During operation, such component will absorb high doses of mixed neutron and gamma radiation, that can degrade their mechanical and structural properties. Experimental radiation damage tests of these components are mandatory for the construction of the facility. Methodologies for irradiation in nuclear reactor mixed fields and post-irradiation examination of lubricating oils, greases and O-rings were developed and are here presented. Samples were characterized with standard mechanical and physical-chemical tests. Parametric studies on the dose rate effects have been performed on O-rings. A case studies for a specific O-ring application in a gate valve has been developed. Some of the tested samples showed a dramatic change of their properties with dose, while others remain stable. Results were collected on nine commercial greases, on one oil and on four commercial elastomeric O-rings. The most radiation resistant among the selected products are now considered for application in facilities under construction. The main mechanisms of neutron and gamma radiation damage on these polymers were investigated at the mechanical and structural level.

Real-time, in situ probing of gamma radiation damage with packaged integrated photonic chips

Integrated photonics is poised to become a mainstream solution for high-speed data communications and sensing in harsh radiation environments, such as outer space, high-energy physics facilities, nuclear power plants, and test fusion reactors. Understanding the impact of radiation damage in optical materials and devices is thus a prerequisite to building radiation-hard photonic systems for these applications. In this paper, we report real-time, in situ analysis of radiation damage in integrated photonic devices. The devices, integrated with an optical fiber array package and a baseline-correction temperature sensor, can be remotely interrogated while exposed to ionizing radiation over a long period without compromising their structural and optical integrity. We also introduce a method to deconvolve the radiation damage responses from different constituent materials in a device. The approach was implemented to quantify gamma radiation damage and post-radiation relaxation behavior of SiO 2 -cladded SiC photonic devices. Our findings suggest that densification induced by Compton scattering displacement defects is the primary mechanism for the observed index change in SiC. Additionally, post-radiation relaxation in amorphous SiC does not restore the original pre-irradiated structural state of the material. Our results further point to the potential of realizing radiation-hard photonic device designs taking advantage of the opposite signs of radiation-induced index changes in SiC and SiO 2 .

Dynamics of gamma-radiation damage and recovery development in reproductive organs and sperm

Dynamics of gamma-radiation damage and recovery development in reproductive organs and sperm

Effects of minocycline and rapamycin in gamma-irradiated human embryonic stem cells-derived cerebral organoids.

Radiation induces DNA and protein damage and free radical formation, effectively establishing cellular senescence in a variety of models. We demonstrate the effects of two known pleiotropic drugs following gamma radiation damage in neurosphere/cerebral organoid system based on human embryonic stem cells. mTORC1 repression by rapamycin prior to irradiation, or metabolic activation by minocycline after irradiation, partially rescues neuroepithelium integrity, neurite-growing capacity, ventricle formation and extracellular acidification rate as an integral measure of metabolic output. Cerebral organoid model thus provides valid and robust readouts for radiation studies in a complex 3D setting.

EFFICIENCY OF FISH OIL IN PROTECTION OF PERIODONTAL LIGAMENT AND MANDIBULAR BONE OF RATS TREATED WITH CISPLATIN AND GAMMA RADIATION

Head and neck cancer is commonly treated with surgery, chemotherapy, radiotherapy either alone or in combination. The purpose of this study is to evaluate the efficiency of fish oil (FO) to preserve periodontal ligament and mandible in gamma irradiated albino rats treated with cisplatin (CP). Thirty male Albino rats were randomly divided into five groups; group C; served as control, group CP; rats were given a single dose of CP (10 mg/ kg body weight i.p), group R; rats were exposed to a single dose of 0.7 Gy γ-rays, group CP + R; rats were given CP and after 24 hours exposed to γ-rays, and group FO+ CP + R; similar to the previous group except for administration of FO (2 ml/ kg body weight) orally and daily for 12 consecutive days before CP injection. The mandibles were collected one day post irradiation and stained with hematoxylin and eosin for histological and histomorphometric analysis. CP and radiation alone or in combination induced bone resorption, degeneration of periodontal ligament fibers. Histomorphometric analysis revealed significant decrease of osteocyte number, fibroblastic and collagen area % and increase of periodontal ligament width. FO protected group showed normal histological appearance of both periodontal ligament and bone. In addition, histomorphometric data revealed normal values of all studied parameters. CP and/ or gamma radiation damage alveolar process and periodontal ligament probably due to osteocyte apoptosis, and supplementary treatment with FO may be potentially useful in protecting alveolar process and periodontal ligament during combined CP chemotherapy and radiotherapy.

Methodology trends on gamma and electron radiation damage simulation studies in solids under high fluency irradiation environments

The present work deals with the numerical simulation of gamma and electron radiation damage processes under high brightness and radiation particle fluency on regard to two new radiation induced atom displacement processes, which concern with both, the Monte Carlo Method based numerical simulation of the occurrence of atom displacement process as a result of gamma and electron interactions and transport in a solid matrix and the atom displacement threshold energies calculated by Molecular Dynamic methodologies. The two new radiation damage processes here considered in the framework of high brightness and particle fluency irradiation conditions are: 1) The radiation induced atom displacement processes due to a single primary knockout atom excitation in a defective target crystal matrix increasing its defect concentrations (vacancies, interstitials and Frenkel pairs) as a result of a severe and progressive material radiation damage and 2) The occurrence of atom displacements related to multiple primary knockout atom excitations for the same or different atomic species in an perfect target crystal matrix due to subsequent electron elastic atomic scattering in the same atomic neighborhood during a crystal lattice relaxation time. In the present work a review numeral simulation attempts of these two new radiation damage processes are presented, starting from the former developed algorithms and codes for Monte Carlo simulation of atom displacements induced by electron and gamma in

Post Situ neutron and gamma radiation damage tests on different quartz types

Post-Situ neutron and gamma radiation damage studies performed on seven types of quartz fibers are reported. All fibers contained quartz cores, some of which were UV enhanced. The fiber cladding was either polymer or quartz, while the buffer was either polymide or acrylite. Previous studies with electron and proton irradiation on numerous types of quartz fibers have shown different optical degradation levels. However, neutron and gamma irradiation has not been investigated for similar quartz fibers before. After 17.6 × 104 Gray of neutron and 73.5 × 104 Gray of gamma radiation, wavelength specific damage to each type of fibers was determined. It is seen that the FBP type quartz fiber by Polymicro shows the least damage due to neutron and gamma radiations.

Ellagic and ferulic acids alleviate gamma radiation and aluminium chloride-induced oxidative damage

AimIonizing radiation interacts with biological systems through the generation of free radicals, which induce oxidative stress. Aluminium (Al) can negatively impact human health by direct interaction with antioxidant enzymes. Ellagic acid (EA) and Ferulic acid (FA) are plant polyphenolic compounds, have gained attention due to their multiple biological activities. To date, no studies investigating the antioxidant effect of EA/FA in a model involving both γ radiation and aluminium chloride (AlCl3) have been reported. Herein, we investigated the protective effect of EA and FA against oxidative stress induced by γ radiation and AlCl3 in rats. MethodsRats were divided into thirteen groups: a negative control group, 3 positive control groups (γ-irradiated, AlCl3−treated and γ-irradiated+AlCl3−treated) and 9 groups (3 γ-irradiated, 3 AlCl3−treated and 3 γ-irradiated+AlCl3−treated) treated with EA and/or FA. Liver function and lipid profile were assessed. Levels of lipid peroxidation, protein oxidation and endogenous antioxidants as well as the concentrations of copper, iron and zinc were estimated in liver tissue homogenate. Furthermore, liver tissue sections were histologically examined. ResultsOral administration of EA and/or FA resulted in 1) amelioration of AlCl3 and/or γ-radiation-induced hepatic function impairment, dyslipidemia and hepatic histological alterations; 2) reduction in liver MDA and PCC levels; 3) elevation of liver CAT, GPx and SOD activity as well as GSH level; 4) elevation in liver Cu concentrations which was accompanied by a reduction in Fe and Zn concentrations. ConclusionsOral administration of EA and/or FA may be useful for ameliorating γ radiation and/or AlCl3-induced oxidative damage.

Photon interaction with semiconductor and scintillation detectors

Mass attenuation coefficients, effective atomic numbers, and electron densities for semiconductor and scintillation detectors have been calculated in the photon energy range 1 keV–100 GeV. These interaction parameters have been found to vary with detector composition and the photon energy. The variation in the parameters with energy is shown graphically for all the partial photon interaction processes. The effective atomic numbers of the detector were compared with the ZXCOM program, and the results were found to be comparable. Efficiencies of semiconductor and scintillation detectors are presented in terms of effective atomic numbers. The study should be useful for comparing the detector performance in terms of gamma spectroscopy, radiation sensitivity, radiation measurement, and radiation damage. The results of the present investigation should stimulate research work for gamma spectroscopy and radiation measuring materials.

Analytical modeling for gamma radiation damage on silicon photodiodes

Radiation-induced damage in PIN silicon photodiode induces degradation of the photodiode parameters. In this work, by presenting an analytical model, the effect of gamma dose on the dark current in a PIN photodiode array was investigated. Geant4 was used to obtain the damage constant as a result of primary incident particle fluence and NIEL distribution calculations. Experimental measurements as well as numerical simulation of the semiconductor with ATLAS were carried out to verify and parameterize the analytical model calculations. A reasonable agreement has been found between analytical results and experimental data for BPX65 silicon photodiodes irradiated by a Co-60 gamma source at total doses up to 500krad under different reverse voltages. Moreover, the results showed that the dark current of each photodiode array pixel has considerably increased by gamma dose irradiation.

Novel synthetic (S,S) and (R,R)-secoisolariciresinol diglucosides (SDGs) protect naked plasmid and genomic DNA From gamma radiation damage.

Secoisolariciresinol diglucoside (SDG) is the major lignan in wholegrain flaxseed. However, extraction methods are complex and are associated with low yield and high costs. Using a novel synthetic pathway, our group succeeded in chemically synthesizing SDG (S,S and R,R enantiomers), which faithfully recapitulates the properties of their natural counterparts, possessing strong antioxidant and free radical scavenging properties. This study further extends initial findings by now investigating the DNA-radioprotective properties of the synthetic SDG enantiomers compared to the commercial SDG. DNA radioprotection was assessed by cell-free systems such as: (a) plasmid relaxation assay to determine the extent of the supercoiled (SC) converted to open-circular (OC) plasmid DNA (pBR322) after exposure of the plasmid to gamma radiation; and (b) determining the extent of genomic DNA fragmentation. Exposure of plasmid DNA to 25 Gy of γ radiation resulted in decreased supercoiled form and increased open-circular form, indicating radiation-induced DNA damage. Synthetic SDG (S,S) and SDG (R,R), and commercial SDG at concentrations of 25-250 μM significantly and equipotently reduced the radiation-induced supercoiled to open-circular plasmid DNA in a dose-dependent conversion. In addition, exposure of calf thymus DNA to 50 Gy of gamma radiation resulted in DNA fragments of low-molecular weight (<6,000 bps), which was prevented in a dose-dependence manner by all synthetic and natural SDG enantomers, at concentrations as low as 0.5 μM. These novel results demonstrated that synthetic SDG (S,S) and SDG (R,R) isomers and commercial SDG possess DNA-radioprotective properties. Such properties along with their antioxidant and free radical scavenging activity, reported earlier, suggest that SDGs are promising candidates for radioprotection for normal tissue damage as a result of accidental exposure during radiation therapy for cancer treatment.

Hypothetical Proteins Present During Recovery Phase of Radiation Resistant Bacterium Deinococcus radiodurans are Under Purifying Selection

Deinococcus radiodurans has an unusual capacity to recover from intense doses of ionizing radiation. The DNA repair proteins of this organism play an important role in repairing the heavily damaged DNA by employing a novel mechanism of DNA double-strand break repair. An earlier report stated that genes of many of these repair proteins are under positive selection implying that these genes have a tendency to mutate, which in turn provides selective advantage to this bacterium. Several "hypothetical proteins" are also present during the recovery phase and some of them have also been shown for their roles in radiation resistance. Therefore, we tested the selection pressure on the genes encoding these poorly characterized proteins. Our results show that a number of "hypothetical proteins" present during the repair phase have structural adaptations compared to their orthologs and the genes encoding them as well as those for the DNA repair proteins present during this phase are under purifying selection. Evidence of purifying selection in these hypothetical proteins suggests that certain novel characteristics among these proteins are conserved and seem to be under functional constraints to perform important functions during recovery process after gamma radiation damage.

Nanomechanical Fingerprints of Gamma Radiation Damage to DNA

The exposure of cancer cells to ionizing radiation results in potentially lethal DNA lesions. For this reason, identification and quantification of various lesions have intensively been investigated. It has also been anticipated that DNA lesions may affect not only the chemical but also the mechanical integrity of the double helix. However, the relationship between DNA damage and mechanics has not been studied. Here, the mechanical properties of DNA damaged by ionizing radiation are examined at a single-molecule level by stretching lambda-phage DNA molecules that have been exposed to gamma-radiation. A simple-stretching method using Atomic Force Microscopy (AFM) not only identifies the types of DNA lesions but also provides information about the mechanical instability of damaged DNA against intact DNA. The results include the elastic properties of damaged DNA with single strand breaks (SSBs), double strand breaks (DSBs), and multiple-lesion clusters. The elasticity of irradiated DNA is changed compared to that of intact DNA. Specifically, consecutive stretching cycles of DNA containing multiple SSBs progressively shorten the width of the overstretching B-S transition. This originates from force-induced melting off of single-stranded DNA fragments, which upon consecutive stretching cycles converts the double helix into a hybrid structure with a growing number of single stranded gaps. Closely spaced SSBs on opposite strands, upon stretching, result in a rupture of the double helix at a decreased force of approximately 200 pN and other clustered lesions result in lowering the force at which force-induced melting of the double helix occurs. Taken together, our results suggest that single-molecule force spectroscopy may become a useful nanoscale DNA diagnostic tool.

In vivo role of Escherichia coli single-strand exonucleases in SOS induction by gamma radiation

Ionizing radiation causes different types of genetic damage, ranging from base modifications to single- and double-stranded DNA breaks, which may be deleterious or even lethal to the cell. There are different repair or tolerance mechanisms to counteract the damage. Among them is the Escherichia coli SOS system: a set of genes that becomes activated upon DNA damage to confer better opportunities for cell survival. However, since this response is triggered by single-stranded DNA regions, most lesions have to be processed or modified prior to SOS activation. Several genes such as recO, recB and recJ that seem to be required to induce the response have already been reported. The results of this work indicate that the four known E.coli single-strand exonucleases take part in processing gamma radiation damage, though RecJ and ExoI proved to be more important than ExoVII or ExoX. In addition, ExoV as well as glycosylases such as Nth and, to a lesser extent, Fpg are also required. A model intended to explain the role of all these genes in damage processing is presented.