60Co Γ-radiation Research Articles

Characteristics and molecular mapping of a novel chlorophyll-deficient yellow-leaf mutant in rice

A yellow-leaf mutant (yl11) with chlorophyll-deficient in rice (Oryza sativa L.) was selected from the progeny of a japonica rice variety "Jiahua 1" treated with 60Co γ-radiation. In comparison with the wild-type parent, "Jiahua 1", the mutant had yellow-leaves at whole growth stages and displayed significantly decreased in chlorophyll content and net photosynthetic rate. Underdeveloped chloroplast and alterations of the major agronomic traits, such as plant-heights, were also observed in the mutant. Genetic analysis confirmed that the yellow-leaf mutant trait was controlled by a single recessive nuclear gene (yl11). Using SSR and In/Del molecular markers and 920 F2 and F3 plants from the cross of yl11 with the indica variety Peiai 64S, the yl11 was mapped between the molecular markers MM2199 and InDel21039 with a physical distance of 110 kb on the long arm of chromosome 11, in which no known functional genes for chlorophyll synthesis or chloroplast development in rice has been found. These findings will provide a foundation for the cloning and functional analysis of this gene in the future.

Effect of the γ-radiation on phenol fractions obtained from the leaves of Echinodorus macrophyllus Mich.

Echinodorus macrophyllus Mich. (Chapéu-de-couro) is popularly used as diuretic, anti-arrhythmic, anti-inflammatory, and anti-rheumatic agents. Leaves of this species are largely commercialized and show high level of microbiological contamination (bacteria and fungi). This work describes the effect of the 60Co γ-radiation on the phenol fractions obtained from the leaves of E. macrophyllus. trans-Ferulic acid, ( E)-caffeoyltartronic acid, 6- C-(1 -hexitol)-apigenin, and 6- C-(1 -hexitol)-luteolin were isolated by preparative HPLC. HPLC chromatograms showed concentration changes of some phenolic constituents, suggesting the formation of radiolytic products. The phenol fractions were active against Bacillus subitilis and Staphylococcus aureus and showed high antioxidant activity. However, the antibacterial and antioxidant activities reduced when the absorbed dose was increased.

Radioprotective efficacy of tocopherol succinate is mediated through granulocyte-colony stimulating factor

The purpose of this study was to elucidate the role of granulocyte colony-stimulating factor (G-CSF) induced by α-tocopherol succinate (TS) in protecting mice from total-body irradiation. CD2F1 mice were injected with a radioprotective dose of TS and the levels of cytokine in serum induced by TS were determined by multiplex Luminex. Neutralization of G-CSF was accomplished by administration of a G-CSF antibody and confirmed by cytokine analysis. The role of G-CSF on gastrointestinal tissue protection afforded by TS after irradiation (11Gy, 0.6Gy/min of 60Co γ-radiation) was determined by analysis of jejunum histopathology for crypt, villi, mitotic figures, apoptosis, and cell proliferation. Our results demonstrate that TS protected mice against high doses of radiation-induced gastrointestinal damage and TS also induced very high levels of G-CSF and keratinocyte-derived chemokine (KC) production in peripheral blood 24h after subcutaneous administration. When TS-injected mice were administered a neutralizing antibody to G-CSF, there was complete neutralization of G-CSF in circulating blood, and the protective effect of TS was significantly abrogated by G-CSF antibody. Histopathology of jejunum from TS-injected and irradiated mice demonstrated protection of gastrointestinal tissue, yet the protection was abrogated by administration of a G-CSF antibody. In conclusion, our current study suggests that induction of G-CSF resulting from TS administration is responsible for protection from 60Co γ-radiation injury.

Color center studies in KBr–NaI mixed crystals doped with gold

Abstract Mixed Alkali halide crystals containing KBr and NaI in different compositions were grown by slow evaporation technique. Obtained transparent crystals were doped with gold to study the role of dopant on the mixed crystals. Crystals were subjected to 60Co γ-radiation. The irradiated samples were subjected to Thermoluminescence, Optical Absorption and Electron Spin Resonance studies. Effect of Au + doping on TL intensity and absorption coefficient is discussed in the present paper.

In-situ preparation of poly(2-hydroxyethyl methacrylate)-titania hybrids using γ-radiation

Hybrids of titania and poly(2-hydroxyethyl methacrylate) were prepared using 60Co γ-radiation initiated polymerisation combined with sol–gel chemistry of titanium isopropoxide. Careful control of the rates of the sol–gel reaction was achieved with acetylacetone which ensured that the dispersion of titania nanoparticles remained stable and minimised aggregation during the polymerisation reaction. Essentially quantitative conversion was achieved with extremely few residual volatiles, as indicated by evolved gas FTIR and solid state NMR. The process yielded transparent orange hybrids, with titania loadings ranging from 3 wt.% to 15 wt.% (TGA). The pyrolysis onset temperatures increased by approximately 30 °C for the hybrids compared to the unfilled polymer. DSC indicated higher Tg’s compared with other pHEMA data in the literature, with a decrease in magnitude of the Tg occurring with increasing titania content. TEM shows high dispersion of particles in the 10–20 nm range, with modest aggregation. Equilibrium swelling showed that the hybrid hydrogels swelled less than half that of unfilled polymer, indicating that the titania is restricting the mobility of the chains through a cross-linking process.

Effect of alumina on the enhancement of hydrogen production and the reduction of hydrogen peroxide in the γ-radiolysis of pure water and 0.4 M H 2SO 4 aqueous solution

The H 2 and H 2O 2 produced by 60Co γ-radiation at room temperature were measured in pure water and 0.4 M H 2SO 4 aqueous solution with alumina powder. By increasing the addition of alumina powder, a strong reduction of H 2O 2 concentrations in the solutions was obtained, and the final product H 2 yields were correspondingly enhanced. These enhancement and reduction effects were diminished in the subsequent γ-radiation when irradiated alumina powder was used. The effects were reversibly restored by washing the irradiated powder with purified water. In 0.4 M H 2SO 4 solution with alumina powder, the H 2 yields increased by increasing the absorbed dose rate in the region of 1–5 kGy/h. The radiation-enhanced H 2 production correlated with the reduction of H 2O 2 concentration could be brought about by the reduction of H 2O 2 molecules and OH radicals in the solutions due to alumina powder.

Detection and investigation of oscillations of the rate of radiation-induced solid-state chain reactions at low temperatures

The data on the detection and investigation of rate oscillations of radiation-induced (60Co γ-radiation) cryochemical solid-state chain reactions are reviewed. Self oscillation regimes were observed for various reactions (ethylene hydrobromination, polymerization, and copolymerization) in the crystalline and glassy states both in the field of γ-radiation and as the post-effect recorded when the samples were warmed. The recent experimental data on the unusual oscillations of the polymerization rate of crystalline formaldehyde at 5–30 K are discussed. The mechanical factor (brittle disintegration) is proposed to be responsible for these oscillations.

Total body γ-irradiation decreases wound breaking strength during wound healing in rats

Objective To investigate the influence of total body irradiation with different doses of 60Coγ on wound breakingstrength during wound healing in rats. Methods Rats were exposed to 60Coγ radiation at dosages of 4,6,and 8 Gy. Within 30 min afterirradiation,full thickness skin wounds were made on the shaved back of rats to establish animal models of irradiated-trauma injury plusskin wounds ( n =20) ,and non-irradiated rats with pure incision injury were used as controls ( n =10) . The rats were sacrificed at day 10after treatment,and the full thickness skin wounds were harvested. Bio-mechanics method and histopathology examination were used toevaluate the wound breaking strength and histological features after healing. Results The wound breaking strength of model groups weregreatly retarded with the increase of irradiation doses. Statistical results showed that on day 10 the wound breaking strength values weresignificantly different between 4 Gy group ( [114. 26 ± 0. 29] g) and control group ( [117. 12 ± 1. 86] g,P 0. 05) ,and the woundbreaking strength values of 6 Gy group ( [91. 87 ±1. 96]g) and 8 Gy group ( [55. 26 ±2. 64]g) were significantly lower than that of thecontrol group ( P 0.05) . H-E staining showed that the wounds in the irradiation trauma groups had looser and disorder collagenous fiber andless fibroblast proliferation than control group. Conclusion Radiation injury may result in delayed wound healing,and the wound breakingstrength decreases with the increase of irradiation dose in model of irradiation injury plus full thickness skin wounds.

Effect of ionizing radiation field on CsI aerosols formed by condensation of supersaturated vapor

The effect of the ionizing radiation field on the behavior of CsI aerosols formed by condensation of supersaturated vapor was examined. Supersaturated CsI vapor was formed by evaporation from a metal surface ohmically heated to high temperatures. A study of the size distribution function of CsI particles showed that, both in the field of 60Co γ-radiation and in a stationary electron beam, three modes of particle size are observed with the mean sizes of 0.13, 0.57, and 0.76 μm. The amount of particles of size 0.13 μm is larger by a factor of ∼10–20 than the amount of particles of sizes 0.57 and 0.76 μm. Comparison of the distribution functions of CsI aerosol particles formed by supersaturated vapor condensation in an ionizing radiation field and without it showed that the ionizing radiation affected not only the size but also the amount of particles.

Estimation of relative biological effectiveness of tritium according to chromosome aberration frequency in human blood lymphocytes

The goal of this work was to determine the relative biological effectiveness (RBE) of tritium β-radiation according to the chromosome aberration frequency in the peripheral blood lymphocytes after in vitro and in vivo radiation exposures. The experimental RBE assessment of tritium β-radiation relative to 60Co γ-radiation according to unstable chromosome aberration frequency in the peripheral blood lymphocytes under particular conditions is described. It has been demonstrated that tritium β-radiation is, in general, more effective in the dose range of up to 1 Gy, which is most pronounced at low doses. The RBE value of tritium β-radiation at minimum doses reached 2.2 and decreased at higher doses (1 Gy) to 1.25. The data on comparative analysis of the frequency of stable chromosome aberrations in the blood lymphocytes of professional nuclear workers (Sarov, Russia) after long-term chronic exposure to tritium β-radiation, as compared with γ-irradiation, are reported for the first time. The higher biological effectiveness of tritium β-radiation was demonstrated and was estimated as 2.5.

Base resistance in Si unijunction transistor irradiated by 60Co γ-radiation

The change of base resistance in Si-UJT under irradiation of 60Co γ-ray is provided. Through multipoint measurement and real-time monitoring, it was shown that the base resistance decreased immediately and then increased slowly. Compared with domestic and foreign related research results, this proves that the displacement effect is the main effect of base resistance in Si-UJT irradiated by 60Co γ-ray, but it lags behind the ionization effect from microanalysis of the interaction between γ-ray and Si material. This is very important for the radiation hardened research.

Experimental determination of the mean ionization energy in nitrogen oxides in a 60Co γ-radiation field

The mean energy of ion pair formation in O2, N2, CO2, air, N2O, NO, and NO2 was experimentally determined. Verification of the procedure for determining the work of ionization from calculated stopping powers and ionization measurement data showed good agreement with published data. The mean energy of ion pair formation in NO (31.6 ± 0.1 eV) and NO2 (31.3 ± 0.2 eV) was determined for the first time.

Influence of γ-Radiation Dose Growth and Dose Rates on Luminescence Properties of Pure Silica Core Fibers with High-OH Group Content

Luminescence properties of pure silica core optical fibers (OFs) with a high-OH group content are studied in the visible region at different doses and dose rates of 60Co γ-radiation. It is shown that the γ-induced light emission (GLE) spectra consist of Cherenkov emission along the luminescence bands. Different increase rates of the luminescence bands at 450 and 650 nm and the absorption band at 610 nm with increasing γ-radiation dose are observed. The 450 nm luminescence band is caused by the recombination of holes with the trapped electrons of E'-centers. The dose dependence of the 650 nm luminescence band, caused by the nonbridging oxygen hole center (NBOHC), does not coincide with that of the 610 nm absorption band related to this center. It is shown that a considerable part of NBOHC participates in nonradiative relaxation. Also, there is an absorption band caused by color centers different from NBOHC, that contributes to the formation of the 610 nm absorption band. A linear dependence of GLE intensity (at wavelengths of 450 and 650 nm) on the dose rate increase is observed. Such a dependence is caused by a substantial increase in the Cherenkov emission intensity and comparatively small increases in luminescence band intensities at 450 and 650 nm.

Genetic Analysis and Mapping of a Thermo-sensitive White Stripe-Leaf Mutant at Seedling Stage in Rice ( Oryza sativa)

A thermo-sensitive white stripe-leaf mutant ( tws) was selected from the M 2 progeny of a japonica variety, Jiahua 1, treated by 60Co γ-radiation. In comparison with the wild type parent, the mutant displayed a phenotype of white stripe on the 3rd and 4th leaves, but began to turn normal green on the 5th leaf when grown at low temperatures (20°C and 24°C). Furthermore, the content of total chlorophyll showed an obvious decrease in the leaves with white stripe. These results suggest that the expression of the mutant trait was thermo-sensitive and correlated with the leaf age of seedlings. The genetic analysis indicated that the mutant trait was controlled by a single recessive nuclear gene, designated as tws. In addition, by using SSR markers and an F 2 segregating population derived from the cross between the tws mutant and 9311, tws was mapped between the markers MM3907 and MM3928 with a physical distance of 86 kb on rice chromosome 4.

Mathematical modelling of depth-dose response of polymer gel dosimeters

A dynamic partial differential equation (PDE) model is used to simulate the effects of radiation depth-doses on polymer formation in Polyacrylamide Gel (PAG) dosimeters. Depth-doses are simulated using different types of radiation including Co60 gamma and 6 and 15 MV X-ray photon beams, along with 6, 9, 12, 16 and 20 MeV electron beams. Effects of monomer diffusion (edge enhancement) and temperature are studied. Diffusion results in excess polymer formation at the position of maximum dose (4% for Co60 γ-radiation and less for other types of radiation studied). Temperature increases on the order of 2 °C increase the mass of polymer formed by approximately 2–3%. These results provide insight for calibrating dosimeters using depth-dose information.

A radiation-induced adaptive response prolongs the survival of prion-infected mice

Previously, it has been demonstrated that an "adaptive response" that includes the prevention, repair, and removal of oxidative damage can be evoked by radiation at dose rates substantially lower than those at which risks have been observed. The exact pathogenic mechanism of prion diseases is unknown, but circumstantial evidence suggests that oxidative stress plays a central role. Exposure of prion-infected mice to four 500 mGy/fraction doses of 60Co γ-radiation administered every other day at a low dose rate (0.5 mGy/min) starting at 2 days before infection, 7 days postinfection (dpi), or 50 dpi significantly prolonged the survival of infected mice. The 500-mGy radiation treatments started at 50 dpi also significantly prolonged the symptom-free period of the disease and caused a significant delay in the rise of the 8-hydroxydeoxyguanosine concentration observed in the urine of nonirradiated infected mice at 98 dpi. The duration of the reduction in oxidative stress achieved by the radiation treatments was similar in length to the prolonged survival of the irradiated mice. This suggests that the adaptive response induced by low-dose whole-body radiation treatments prolongs the survival of prion-infected mice by reducing oxidative stress.

Heterogeneous thermoradiation processes for hydrogen production from steam

A experimental flow unit for investigation of the radiation-catalytic decomposition of gases and liquids over the temperature range of 50–500°C in a 60Co γ-radiation field was designed and fabricated. The process of radiation-catalytic decomposition of steam in the presence of solids with different chemical compositions and structures was studied. The effect of the dose rate and the contact time of the reaction mixture with the solid on the rate of hydrogen formation was revealed. It was shown that the hydrogen formation efficiency decreases after cessation of irradiation.

Free volume and microstructural investigation of poly(ethylene terephthalate)-g -acrylic acid (PET-g-AA) copolymer films

Acrylic acid (AA) was grafted onto PET films by preirradiation method using a 60Co γ-radiation source. Microstructural investigation of the PET-g-AA copolymers has been carried out by wide angle X-ray diffraction (WAXD), dynamic mechanical analysis (DMA) and positron annihilation lifetime spectroscopy (PALS) techniques. The WAXD results showed only marginal variation in the crystallinity of the graft copolymers. Dynamic mechanical analysis showed an increase in the temperature of the α-relaxation and the tan δ value of subroom temperature secondary relaxations. From the PALS results, a complex variation of the free volume parameters, i.e. the o-positronium lifetime ( τ 3), its intensity ( I 3), fractional free volume ( f v ) and the intermediate lifetime component was observed for the graft copolymers. Multiple phenomena of the effect of secondary relaxations, additive behavior of the individual polymer free volume parameters and effects from interfacial defects have been invoked to understand the fluctuational nature of the free volume properties in the graft copolymers.

Effects of sterilization treatments on the analysis of TOC in water samples

Decomposition experiments conducted with and without microbial processes are commonly used to study the effects of environmental microorganisms on the degradation of organic pollutants. However, the effects of biological pretreatment (sterilization) on organic matter often have a negative impact on such experiments. Based on the principle of water total organic carbon (TOC) analysis, the effects of physical sterilization treatments on determination of TOC and other water quality parameters were investigated. The results revealed that two conventional physical sterilization treatments, autoclaving and 60Co γ-radiation sterilization, led to the direct decomposition of some organic pollutants, resulting in remarkable errors in the analysis of TOC in water samples. Furthermore, the extent of the errors varied with the intensity and the duration of sterilization treatments. Accordingly, a novel sterilization method for water samples, 0.45 μm micro-filtration coupled with ultraviolet radiation (MCUR), was developed in the present study. The results indicated that the MCUR method was capable of exerting a high bactericidal effect on the water sample while significantly decreasing the negative impact on the analysis of TOC and other water quality parameters. Before and after sterilization treatments, the relative errors of TOC determination could be controlled to lower than 3% for water samples with different categories and concentrations of organic pollutants by using MCUR.

The effect of gamma-radiation on polymer composites based on thermoplastic matrices

The effect of 60Co γ-radiation on polymer composite materials (PCMs) based on reinforcing glass cloth, polyethylene (PE), polyamide (PA) and polypropylene (PP) matrices has been studied. It has been found that PCMs based on more durable PP and PA matrices have a substantially lower radiation resistance as compared to their PE-matrix analogs. More stable carbon-reinforced plastics based on the PE matrix also have a lower radiation resistance as compared to fiberglass plastics. High-strength PE fiber, PE film, and PE-matrix composites behave in fundamentally different manners under the action of radiation.