60Co Γ-rays Research Articles

Monte Carlo simulation of correction factors for IAEA TLD holders

The IAEA standard thermoluminescent dosimeter (TLD) holder has been developed for the IAEA/WHO TLD postal dose program for audits of high-energy photon beams, and it is also employed by the ESTRO-QUALity assurance network (EQUAL) and several national TLD audit networks. Factors correcting for the influence of the holder on the TL signal under reference conditions have been calculated in the present work from Monte Carlo simulations with the PENELOPE code for 60Co γ-rays and 4, 6, 10, 15, 18 and 25 MV photon beams. The simulation results are around 0.2% smaller than measured factors reported in the literature, but well within the combined standard uncertainties. The present study supports the use of the experimentally obtained holder correction factors in the determination of the absorbed dose to water from the TL readings; the factors calculated by means of Monte Carlo simulations may be adopted for the cases where there are no measured data.

Influence of γ-ray radiation on the structure and properties of paper grade bamboo pulp

Abstract Paper grade bamboo pulp with high molecular weight was irradiated in air by 60Co γ-ray to improve its dissolving property in N-methylmorpholine-N-oxide monohydrate (NMMO·H2O). The effects of γ-ray radiation on the structure and properties of the bamboo cellulose were investigated. The results showed that the bamboo cellulose with a G(s) value of 0.94 μmol J−1 was easily degraded by the 60Co γ-ray radiation. When the radiation dose increased, the average degree of polymerization ( DP ¯ ) of bamboo cellulose was decreased and its molecular weight distribution (MWD) became narrow, while its crystalline structure did not change obviously. Consequently, a spinning dope with high cellulose concentration and good spinnability was obtained in the range of absorbed dose from 5 to 10 kGy. This work presented an economic method to prepare regenerated bamboo cellulose fiber from paper grade bamboo pulp.

The impact of 60Co γ-ray on apoptosis to Hep-2 human laryngeal cancer cell in the condition of reoxygenation after hypoxia

Objective The aim of the study was to establish models of Hep-2 laryngeal cancer cell line of different oxygen supplying, trying to investigate the impact of normoxia, hypoxia, reoxygenation after hypoxia on apoptosis and expression of proteins HIF-1α and p53 to Hep-2 human laryngeal cancer cell line induced by 60Co γ-ray.

COMBINED APPROACH OF HEMATOLOGICAL BIOMARKERS AND PLASMA PROTEIN SAA FOR IMPROVEMENT OF RADIATION DOSE ASSESSMENT TRIAGE IN BIODOSIMETRY APPLICATIONS

Early treatment of populations exposed to ionizing radiation requires accurate and rapid biodosimetry with a precision as high as possible to determine an individual's exposure level and risk for morbidity and mortality. The purpose of this study was to evaluate the utility of multiple blood biomarkers for early-response assessment of radiation exposure using a murine (BALB/c, males) in vivo radiation model. Present results for mice exposed to whole-body Co gamma-rays (0.1 Gy min) over a broad dose range (0-7 Gy) demonstrate at 24 h after exposure: 1) dose-dependent increase in the acute phase protein serum amyloid A or SAA; 2) dose-dependent changes in blood cell counts (lymphocytes, neutrophils, and ratio of neutrophils to lymphocytes); 3) SAA results coupled with peripheral blood cell counts analyzed with use of multivariate discriminant analysis established very successful separation of irradiated animals; 4) an enhanced separation as the number of biomarkers increased. These results also demonstrate proof-in-concept that plasma protein SAA shows promise as a complimentary approach to conventional biodosimetry for early assessment of radiation exposures and, coupled with peripheral blood cell counts, provides early diagnostic information to effectively manage radiation casualty incidents.

Thermoluminescent properties of a Li 2O–B 2O 3–Al 2O 3 glass system doped with CaF 2 and Mn

A Li 2O–B 2O 3–Al 2O 3 glass system doped with CaF 2 and Mn was synthesized by fusion and its physical properties were investigated using thermoluminescence (TL) and differential thermal analysis (DTA) techniques. The TL glow curve peaks, resulting from this analysis, are characteristic of metastable levels intrinsic to CaF 2 crystals that have undergone γ-ray irradiation from a colbalt-60 ( 60Co) source. This provides evidence of CaF 2 crystal formation in the glass system. Furthermore, the TL glow peak at about 480 K was stable at room temperature, sensitive to 60Co γ-rays and showed good linearity with doses ranging from 3 Gy to approximately 100 Gy, and consequently could be used to quantify radiation doses. High quality synthesis of these crystals permits control of their thermoluminescent properties.

Structural transformation of multiwalled carbon nanotubes under γ-ray irradiation

Purified multiwalled carbon nanotubes (MWCNTs) were irradiated by 60Co γ-ray with different doses. The structural change of the MWCNTs was revealed by high-resolution transmission electron microscopy and Raman spectroscopy. It was found that under γ-ray irradiation some amorphous structure homogeneously covers the inner tube walls with graphite structure in irradiated MWCNTs. Moreover, the amorphous structure continuously proceeds and the graphite structure is reduced during the γ-ray irradiation till the irradiated MWCNTs become amorphous nanowires with a hollow structure. Based on the interaction between photons and carbon nanotubes, the structural transformation process and the corresponding mechanisms are discussed. In MWCNTs, the collision of a photon with a carbon atom will result in displacement of the atom, i.e. formation of a vacancy (single- or multi- vacancy) and a number of primary knock-on atoms which, if their energy is high, leave the tube or displace other atoms in the MWCNTs. If their energy is low, they can be adsorbed onto the tube walls. These adsorbed atoms play the role of interstitials. All the displaced atoms can be sputtered from the MWSNTs. The carbon atoms sputtered from the MWCNTs can further create some damage in a nearby MWCNTs or be absorbed onto its surface. Along with the simple defects, a number of more complex defects can be formed. The behavior of complex irradiation-induced defects is governed in part by annealing and diffusion of original defects-vacancies and interstitials. The γ-ray irradiation induced structural transformation of MWCNTs was a unique graphite to amorphous structural transition from the outer walls to the inner walls of the irradiated MWCNTs due to the removal of carbon atoms by knock-on displacements.

Sprouting and Rooting Inhibition of Garlic with Co-60 γ-rays

Effect of gamma-irradiation on sprouting and rooting of garlic was investigated. Sprouting and rooting of garlic were inhibited by irradiation of bulbs at 2 months after harvest with doses more than 30 Gy. Four weeks-later irradiation requires higher doses to complete sprouting/rooting inhibition.

Protective Effect of an Herbal Preparation (HemoHIM) on Radiation-Induced Intestinal Injury in Mice

The protective properties of an herbal preparation (HemoHIM) against intestinal damage were examined by evaluating its effects on jejunal crypt survival, morphological changes, and apoptosis in gamma-irradiated mice. The mice were whole-body irradiated with 12 Gy for the examination of jejunal crypt survival and any morphological changes and with 2 Gy for the detection of apoptosis and Ki-67 labeling. Irradiation was conducted using (60)Co gamma-rays. HemoHIM treatment was administered intraperitonially at a dosage of 50 mg/kg of body weight at 36 and 12 hours pre-irradiation and 30 minutes post-irradiation or orally at a dosage of 250 mg/kg of body weight/day for 7 or 11 days before necropsy. The HemoHIM-treated group displayed a significant increase in survival of jejunal crypts, when compared to the irradiation controls. HemoHIM treatment decreased intestinal morphological changes such as crypt depth, villus height, mucosal length, and basal lamina length of 10 enterocytes after irradiation. Furthermore, the administration of HemoHIM protected intestinal cells from irradiation-induced apoptosis. These results suggested that HemoHIM may be therapeutically useful to reduce intestinal injury following irradiation.

The RBE of 3.4 MeV -particles and 0.565 MeV neutrons relative to 60Co -rays for neoplastic transformation of human hybrid cells and the impact of culture conditions

The neoplastic transformation of human hybrid CGL1 cells is affected by perturbations from external influences such as serum batch and concentration, the number of medium changes during the 21-day expression period and cell seeding density. Nevertheless, for doses up to 1.5 Gy, published transformation frequencies for low linear energy transfer (LET) radiations (gamma-rays, MeV electrons or photons) are in good agreement, whereas for higher doses larger variations are reported. The (60)Co gamma-ray data here for doses up to 1.5 Gy, using a low-yield serum batch and only one medium change, are in agreement with published frequencies of neoplastic transformation of human hybrid cells. For 3.4 MeV alpha-particles (LET = 124 keV/mum) and 0.565 MeV monoenergetic neutrons relative to low doses of (60)Co gamma-rays, a maximum relative biological effectiveness (RBE(M)) of 2.8 +/- 0.2 and 1.5 +/- 0.2, respectively, was calculated. Surprisingly, at higher doses of (60)Co gamma-rays lower frequencies of neoplastic transformation were observed. This non-monotonic dose relationship for neoplastic transformation by (60)Co gamma-rays is likely due to the lack of a G2/M arrest observed at low doses resulting in higher transformation frequencies per dose, whereas the lower frequencies per dose observed for higher doses are likely related to the induction of a G2/M arrest.

The role of 60Co γ-ray irradiation on the interface states and series resistance in MIS structures

The effect of γ-ray exposure on the metal–insulator–semiconductor (MIS) structures has been investigated using the electrical characteristics at room temperature. The MIS structures are irradiated with 60Co γ-ray source. The energy distribution of interface states was determined from the forward bias I– V characteristics by taking into account the bias dependence of the effective barrier height and ideality factor. The value of series resistance decreases with increasing dose. Experimental results confirmed that γ-ray irradiation have a significant effect on electrical characteristics of MIS structures.

Radiation-induced point- and cluster-related defects with strong impact on damage properties of silicon detectors

This work focuses on the investigation of radiation-induced defects responsible for the degradation of silicon detector performance. Comparative studies of the defects induced by irradiation with 60Co-γ rays, 6 and 15 MeV electrons, 23 GeV protons and reactor neutrons revealed the existence of point defects and cluster-related centers having a strong impact on damage properties of Si diodes. The detailed relation between the “microscopic” reasons as based on defect analysis and their “macroscopic” consequences for detector performance is presented. In particular, it is shown that the changes in the Si device properties (depletion voltage and leakage current) after exposure to high levels of 60Co-γ doses can be completely understood by the microscopically investigated formation of two point defects, a deep acceptor and a shallow donor, both depending strongly on the oxygen concentration in the silicon bulk. Specific for hadron irradiation are the annealing effects which decrease (increase) the originally observed damage effects as seen by the changes of the depletion voltage and these effects are known as “beneficial” and “reverse” annealing, respectively. A group of three cluster-related defects, revealed as deep hole traps, proved to be responsible specifically for the reverse annealing. Their formation is not affected by the oxygen content or silicon growth procedure suggesting that they are complexes of multi-vacancies located inside extended disordered regions.

String-guided fast transport system and photoactivation of short-lived isomers 79mBr and 77mSe by 60Co γ-ray irradiation

A compact string-guided transport (SGT) system for samples irradiated by intense 60Co γ-rays has been developed for the study of resonance photoactivation of short-lived isomers. The path length from the irradiation port to the measuring port was 12.5 m and the transport time was within 3–4 s for samples up to 90 g. Results of half-life measurements of 79mBr and 77mSe were 5.06±0.44 and 17.4±0.8 s, respectively. The integral cross-sections of 79mBr and 77mSe were determined as 169±27 and 937±99 μb keV, respectively, on the basis of the 115mIn cross section.

Study of Resistance of Silicone Resin to Heat and Irradiation

Resistance of silicone resin to heat and irradiation was studied. The chemical structure of silicone resin before and after being heated and irradiated was analyzed by Fourier Transform Infrared Spectroscopy (FT-IR). The thermal stability of silicone resin was investigated by thermogravimetric analysis (TG) and differential thermogravimetry analysis (DTG), and its improvement was indicated by TG and DTG analyses of silicone resin after being irradiated by 60Co γ-ray under different fluence. The surface morphology, mechanical properties, corrosion resistance and chemical resistance of silicone resin clear paints before and after being heated and irradiated were studied by SEM, EIS et al.

Antagonistic effect of microwave on hematopoietic damage of mice induced by gamma-ray irradiation

To investigate antagonistic effect of microwave on hematopoietic damage of mice induced by gamma-ray irradiation. Male healthy Kunning mice were treated with low dose microwave radiation before exposure to (60)Co gamma-ray irradiation of 8.0 Gy. The 30-day survival rate and average survival time of the mice after the treatment were examined. Peripheral blood parameters and the organ indexes of thymus and spleen were also observed in the irradiated mice. After exposure to 5.0 Gy gamma irradiation, indexes of hematopoietic foci formation of bone marrow cells (CFU-GM) and the proliferation activity of BMNCs were examined. The serum concentration of hemopoietic factors (GM-CSF and IL-3) were detected by ELISA kits. Pre-exposure with 120 microW/cm(2) 900 MHz microwave increased the 30-day survival rate (P < 0.05) and the number of white blood cells of gamma-ray treated mice. The increases of the organ indexes of thymus and spleen, proliferation activity of BMNCs and CFU-GM hematopoietic foci numbers, as well as the higher serum concentration of GM-CSF and IL-3 were observed in the microwave pre-exposure group. Low dose microwave radiation may exert potential antagonistic effects on hematopoietic injuries induced by ionizing radiation. The underlying mechanisms might be related with stimulation of hematopoietic growth factors expression, promotion of HSCs/HPCs proliferation, suppression on the reduction of HSCs/HPCs caused by (60)Co gamma-ray, and enhanced construction of the hematopoietic system.

Measurements of neutron distribution in neutrons–γ-rays mixed field using imaging plate for neutron capture therapy

The imaging plate (IP) technique is tried to be used as a handy method to measure the spatial neutron distribution via the 157Gd(n,γ) 158Gd reaction for neutron capture therapy (NCT). For this purpose, IP is set in a water phantom and irradiated in a mixed field of neutrons and γ-rays. The Hiroshima University Radiobiological Research Accelerator is utilized for this experiment. The neutrons are moderated with 20-cm-thick D 2O to obtain suitable neutron field for NCT. The signal for IP doped with Gd as a neutron-response enhancer is subtracted with its contribution by γ-rays, which was estimated using IP without Gd. The γ-ray response of Gd-doped IP to non-Gd IP is set at 1.34, the value measured for 60Co γ-rays, in estimating the γ-ray contribution to Gd-doped IP signal. Then measured distribution of the 157Gd(n,γ) 158Gd reaction rate agrees within 10% with the calculated value based on the method that has already been validated for its reproducibility of Au activation. However, the evaluated distribution of the 157Gd(n,γ) 158Gd reaction rate is so sensitive to γ-ray energy, e.g. the discrepancy of the 157Gd(n,γ) 158Gd reaction rate between measurement and calculation becomes 30% for the photon energy change from 33 keV to 1.253 MeV.

Thermal and optical studies on unirradiated and γ-irradiated polyester track detector

Thermal and optical properties of unirradiated and γ-irradiated polyester track detector films in the dose range of 0–14.5 Mrad have been studied by thermogravimetry (TG) and UV-Visible spectroscopic technique. The samples were irradiated with 60Co γ-rays for doses of 4.7, 8.1 and 14.5 Mrad. The TG studies indicate that unirradiated and the γ-irradiated samples degrade in two steps. The kinetics of the two steps of degradation were also evaluated from the TG curves. Irradiation enhances the degradation rate and the effect increases further with increasing radiation dose. The optical band gaps of the unirradiated as well as the irradiated samples were also determined from the UV-Visible spectra. These studies can be used for the estimation of γ-dose using changes in absorbance and the activation energy due to γ-irradiation.

Differential radio-sensitivities of human chromosomes 1 and 2 in one donor in interphase- and metaphase-spreads after 60Co γ-irradiation

BackgroundRadiation-induced chromosome aberrations lead to a plethora of detrimental effects at cellular level. Chromosome aberrations provide broad spectrum of information ranging from probability of malignant transformation to assessment of absorbed dose. Studies mapping differences in radiation sensitivities between human chromosomes are seldom undertaken. Consequently, health risk assessment based on radio-sensitivities of individual chromosomes may be erroneous. Our efforts in this article, attempt to demonstrate differences in radio-sensitivities of human chromosome-1 and/or -2, both in interphase and metaphase spreads.MethodsUpon blood collection, dosimetry and irradiation were performed. Lymphocytes were isolated after whole-blood irradiation with 60Co γ-rays in the dose range of 0–5 Gy for both interphase, and metaphase aberration studies. Induction of premature chromosome condensation in interphase cells was accomplished using a phosphatase inhibitor, calyculin-A. Metaphase spreads were harvested from short-term peripheral blood lymphocyte cultures following colcemid arrest and using an automated metaphase harvester and spreader. Aberration analysis in both interphase and metaphase spreads were done using FISH.ResultsIn interphase, aberrant cell and aberration frequency involving chromosome 1 and/or 2 increased linearly with radiation dose. In metaphase, aberrations increased in a linear-quadratic manner with dose. Our studies ascertain that chromosome-2 is more radio-sensitive than chromosome-1 in both interphase and metaphase stages, albeit the DNA content of chromosome-2 is lesser than chromosome-1 by almost 10 million base pairs.ConclusionDifferences in radio-sensitivities of chromosomes have implications in genetic damage, chromosome organization, and chromosome function. Designing research experiments based on our vital findings may bring benefit to radiation-induced risk assessment, therapeutics and development of chromosome specific biomarkers.

Radioprotective activity of betalains from red beets in mice exposed to gamma irradiation

We investigated the radioprotective activity of betalains from red beets in mice irradiated by a 60Co gamma (γ) ray (6.0 Gy, at a dose of 1.5 Gy min − 1 ). Mice were randomly divided into five groups, namely the control group and four experimental groups which were given one of four concentrations of betalains from red beets (0, 5, 20 and 80 mg/kg, equivalent to betanin) for 30 days. The four experimental groups of mice were then exposed to the 60Co γ-rays and were given betalains from red beets for a further 3 days. The number of white blood cells, karyota of the femur and the number of micronuclei in polychromatophilic erythrocytes of bone marrow in mice were determined. The activity of superoxide dismutase, catalase, glutathione peroxidase, malondialdehyde, spleen index and thymus index were also determined. The results indicate that the administration of betalains from red beets is radioprotective in mice irradiated by 60Co in vivo. The underlying mechanism remains unclear but appears to be mediated by the antioxidant activity of the betalains from red beets and modulation of the immune system.

The usefulness of two-colour fluorescence in situ hybridization technique using chromosomal subset at metaphase and interphase stage in radiation biodosimetry

Peripheral bloods from healthy donors were irradiated by 60Co γ-rays and californium (252Cf) –neutron for 0.5 to 4 Gy and the frequencies of the translocations were detected by two colour fluorescence in situ hybridization (FISH). Chromosomes 1, 2 and 3 and chromosomes 6, 7 and 9 were labeled by rodamine-dUTP and fluorescein-dUTP as viewing red or green signal on metaphase chromosomes, respectively. In separate observation, translocation was detected on the interphase cells by the two color FISH method using whole chromosome painting probes of chromosomes 4 and 9. Detected translocations on the metaphase and interphase cells showed clear dose response relationships. Translocations induced by 60Co γ-rays, 252Cf neutrons, and those in atomic bomb survivors were able to detect easily by both interphase FISH and metaphase FISH using two colour of chromosome subsets. These results suggest that scoring of translocations by two colour FISH of chromosome subsets can serve as more sensitive and applicable biological dosimeter for short or long-term radiation effects. Keywords: Interphase FISH, biodosimetry, atomic bomb, neutron, γ rays

60Co γ-rays irradiation effect in DC performance of AlGaN/GaN high electron mobility transistors

Unpassivated/passivated AlGaN/GaN high electron mobility transistors (HEMTs) were exposed to 1.25 MeV 60Co γ-rays at a dose of 1 Mrad(Si). The saturation drain current of the unpassivated devices decreased by 15% at 1 Mrad γ-dose, and the maximal transconductance decreased by 9.1% under the same condition; moreover, either forward or reverse gate bias current was significantly increased, while the threshold voltage is relatively unaffected. By sharp contrast, the passivated devices showed scarcely any change in saturation drain current and maximal transconductance at the same γ dose. Based on the differences between the passivated HEMTs and unpassivated HEMTs, adding the C–V measurement results, the obviously parameter degradation of the unpassivated AlGaN/GaN HEMTs is believed to be caused by the creation of electronegative surface state charges in source–gate spacer and gate–drain spacer at the low dose (1 Mrad). These results reveal that the passivation is effective in reducing the effects of surface state charges induced by the 60Co γ-rays irradiation, so the passivation is an effective reinforced approach.