Γ-irradiated Samples Research Articles

Effect of γ-rays irradiation on the structural, magnetic, and electrochemical properties of ZnMn2O4 nanoparticles

The study explored the effect of gamma-ray irradiation on the physical, magnetic, and electrochemical properties of ZnMn2O4 synthesized by the burning method. On the physical characterization side, the study utilized multiple metrology techniques to determine the impact of radiation dosage on bond lengths, density, crystallite size, micro strain, lattice constant, and dislocation density. No irradiation impact on the sample's tetragonal spinel structure was observed up to 250 kGy doses. However, the lattice parameters increased post-γ-irradiation and were apparent in the morphology change of irradiated samples compared to control spinel. Conversely, the magnetic parameters decreased post-irradiation based on the vibrating-sample magnetometry (VSM) testing of control and γ-irradiated samples. Changes in parameters like saturation magnetization (Ms) and magneton number (nB) can be attributed to ion-induced disorder and cation distribution in irradiated samples. Finally, the electrochemical testing showed supercapacitor behavior for all ZnMn2O4 samples, with a positive impact of radiation on electrical capacitance and stability. While the γ-irradiated sample with a 250 kGy dose showed a capacitance (Csp) of 515 F/g with 87.6% stability, the control sample had a Csp of 123 F/g and 78% stability. ZnMn2O4 material meets the needs of energy storage devices operating at high ionizing radiation doses.

Gamma-induced stress, strain and p-type doping in MBE-grown thin film MoTe2.

A thorough examination of the stability of a 2D MoTe2 thin film exposed to high-dose gamma radiation (γ) is addressed in this study. This study compares the film before and after irradiation (10-600 kGy dosage) to report the impact of γ radiation on the surface morphology, work function, tensile strain and charge redistribution in the MoTe2 thin film. The radiation damage to the film is monitored by optical micrographs (OM) and with atomic force microscopy (AFM) and conceptualized by thermal strain in the film. Raman spectroscopy has been used to analyze the shifting and to address the strain that arises due to irradiation in its vibrational mode. Kelvin probe force microscopy (KPFM) has been performed to evaluate the work function of the film, which increases by 0.14 eV for the 600 kGy γ-irradiated sample, implying shifting of the Fermi-level to the valence band of the spectrum and thus it results in p-type doping in the film. Owing to the reduced atomic mass and high energy of tellurium atoms, γ-irradiation causes tellurium vacancies, which lead to the formation of dangling bonds at unoccupied sites. When oxygen is adsorbed at these reactive spots, a charge-transfer mechanism takes place. This mechanism involves the transfer of electrons from the thin MoTe2 film to the adsorbed oxygen, forming oxides and causing p-type doping. Furthermore, p-doping is verified by the valence band shifting by 1.27 eV in 600 kGy in γ-irradiated samples in X-ray photoelectron spectroscopy. This comprehensive study shows how γ irradiation affects the chemical and physical characteristics of the MoTe2 thin film. Consequently, it shows that if devices integrating MoTe2 thin films are meant to be used in high-dose radiation conditions, the adsorbate concentrations, radiation shielding and required lifetimes must be carefully evaluated.

Modification of thermal and electrical characteristics of hybrid polymer nanocomposites through gamma irradiation for advanced applications

In this article, we present a straightforward in-situ approach for producing Ag NPs incorporated in graphene oxide (GO) blended with glutaraldehyde (GA) cross-linked polyvinyl alcohol (PVA) matrix. Samples are γ-irradiated by doses of 2, 5, and 10 kGy and in comparison with the pristine films, the thermal conductivity (‘k’) and effusivity are measured. ‘k’ decreases with irradiation doses up to 5 kGy and further increase in the dosage results increase in ‘k’. We performed FDTD modeling to verify the effect of polarization and periodicity on the absorptivity and emissivity spectra that are correlated to the ‘k’ and effusivity, empirically. Hence, we can confess that the structural properties of the prepared hybrid nanocomposite are manipulated by γ-irradiation. This attests that the PVA/GO-Ag/GA nanocomposite is radiation-sensitive and could be employed for thermal management systems. Moreover, their strong electrical insulation, as the measured dc conductivity of the γ-irradiated samples is found to be in the range of 2.66 × 10−8–4.319 × 10−7 Sm−1, which is below the percolation threshold of 1.0 × 10−6 Sm−1, demonstrates that they are excellent candidates for the use of thermal management materials. The low ‘k’ values allow us to use this promising material as thermal insulating substrates in microsensors and microsystems. They are also great choices for usage as wire and cable insulation in nuclear reactors due to their superior electrical insulation.Graphical

Effects of gamma-irradiation on the superconducting properties of FeTe0.55Se0.45 single crystals grown by self-flux method

We have investigated the effect of gamma (γ)-irradiation on the structural and superconducting properties of FeTe0.55Se0.45 single crystals grown by the self-flux method. The impact of γ-irradiation on the superconducting transition temperature (TC), critical current density (JC), and vortex pinning mechanism has been systematically studied. The x-ray diffraction study reveals the growth of single crystals along the c-axis. The superconductivity has been confirmed in pristine and γ-irradiated samples through temperature-dependent resistivity (ρ(T)) and magnetization [M(T)] measurements. After irradiation, a slight improvement is observed in the upper critical field Hc2(0) values. The values of thermally activated energy have been calculated and a crossover from a single to collective vortex pinning regime is observed. Additionally, we have analyzed the vortex phase diagrams, revealing a transition from vortex liquid to vortex glass state. Furthermore, the presence of second magnetization peak (SMP) or fishtail effect has been noticed in the M(H) loops, and with increasing temperature, the position of SMP (Hsp) shifts toward lower magnetic field regions. The critical current density has been estimated by Bean's critical state model at different magnetic fields [JC(H)] and temperatures [JC(T)]. The defects through gamma-irradiation lead to a significant threefold increase in JC compared to pristine samples in self-field and at 2 K. The pinning mechanisms have been explained using collective pinning theory and the Dew-Hughes model by analyzing the normalized pinning force density. Our analysis indicates that δl-pinning is dominant and point defects are present in all the samples.

The Influence of Ionizing Radiation on Paclitaxel-Loaded Nanoparticles Based on PLGA

The effect of ionizing radiation (γ-rays and electron beam) on anticancer drug delivery systems (DDSs) properties was evaluated concerning potential sterilization. For this purpose, paclitaxel (PTX)-loaded nanoparticles were obtained using a biodegradable, self-developed copolymer of l-lactide and glycolide (PLGA), synthesized in the presence of bismuth 2-ethylhexanoate catalyst. The nanoparticles were obtained with a high encapsulation efficiency of PTX (EE = 94.2%). The average size of the nanoparticles was 253.5 nm. The influence of irradiation (sterilization dose, 25 kGy) on the microstructure and the physicochemical and thermal properties of the polymer matrix was investigated, as well as the effect of irradiation on the morphology and physicochemical properties of the pharmaceutical formulations of the nanoparticles. Additionally, an in vitro drug release study was conducted regarding any alterations in the kinetic profiles of drug release. It was confirmed that the irradiation with both types of ionizing radiation, i.e., γ-rays and electron-beam (EB), slightly decreased the average molecular weight of the polymer matrix. While only negligible changes in the microstructure and thermal properties of PLGA were observed after irradiation with EB, the average length of lactidyl blocks (lLL) in the copolymer chains irradiated with γ-rays decreased from 4.33 to 3.35. Moreover, the contribution of crystalline phase (Xc) in γ-irradiated samples decreased significantly from 35.1% to 22.7%, suggesting a dominant mechanism of chain scission over cross-linking in PLGA samples irradiated with γ-rays. In vitro drug release results demonstrate a sustained and controlled release of PTX from the nanoparticles based on PLGA. The kinetics of drug release was defined as first order with non-Fickian diffusion. Only negligible differences in the kinetic profiles of PTX release from PLGA drug carriers were observed after irradiation. The overall results suggest good resistance of PLGA nanoparticles to irradiation within the conditions used and the great potential of EB in the sterilization process of the polymeric DDSs.

Assessment of the impact of γ-irradiation on the piperine content and microbial quality of black pepper

Abstract The major bioactive component of black pepper (Piper nigrum) is piperine which has demonstrated beneficial therapeutic properties. The purpose of this research was to investigate the effects of different irradiation doses on the content of piperine in black pepper. Samples were irradiated with 60Co γ-rays (at absorbed doses of 0.5, 1, 3, 5, 7, 10, and 12 kGy). Thin-layer chromatography (TLC) and UV–Vis spectrophotometry methods were used for measuring the piperine content in the samples. TLC was performed using three mobile phases (1. toluene:ethyl acetate, 7:3 v/v; 2. acetone:n-hexane, 6:4 v/v; 3. toluene:methanol, 8.5:1.5 v/v) and the retention factor (R f) value for piperine was equal to 0.66, 0.94, and 0.67, respectively. The content of piperine in γ-irradiated samples of black pepper was found to be between 0.04 and 1.05% w/w from the spectrophotometry analyses. Irradiation slightly decreased the piperine content of black pepper. It was found that piperine crude yield from black pepper was from 1.10 (the unirradiated sample) to 1.69, 1.07, 0.60, 0.90, 0.30, 1.20, 0.80% for irradiated samples, respectively. Microbiological analyses were performed with standard plate count method, which resulted in a decreasing number of the total cell count of microbial cells with increasing the radiation dose. Treatment with irradiation reduced the population of bacteria by 4 logs.

Surface Properties of Gamma-Irradiated Polypropylene

polypropylene (PP) has been studied as a function of the absorbed dose. It has been established that γ-irradiation leads to an increase in the free surface energy of the polymer, its acid–base component, and the surface polarity. An analysis of the IR spectra of γ-irradiated PP samples indicated the formation of oxygen-containing groups in the composition of PP macromolecules, which was confirmed by the values of the surface acidity parameter. An increase in the dose led to an increase in the concentration of products of radiation-induced conversion. A significant increase in the melt flow index (MFI) of polypropylene up to an absorbed dose of 150 kGy also evidenced the occurrence of oxidation and destruction processes. The MFI decreased at radiation doses above 150 kGy, and this fact indicates that such doses of ionizing radiation lead to the predominance of the processes of polymer structuring or crosslinking.

Optical spectroscopy assessment of the impact of γ-ray irradiation on Gd3+-doped phosphate glass

The effects of γ-ray irradiation (10, 100 kGy) on Gd3+-doped phosphate glass were evaluated. Glass irradiated at 100 kGy was characterized alongside the pristine by differential scanning calorimetry, Fourier transform-infrared spectroscopy and Raman scattering, wherein a lack of alteration in thermal and structural properties was supported. Yet, absorption bands developed around 500 nm with γ-ray dose indicating phosphorus oxygen hole center defects. Optical band gap and Urbach energies exhibited decreasing and increasing trends, respectively, reflecting the influence of trapped electrons and increased disorder/defects. By exciting γ-irradiated samples at 265 nm, blue radio-photoluminescence was observed where intensity increased with dose. Decay curves measured monitoring 415 nm emission showed first-order kinetics suggested to arise from phosphorus electron centers. Emission from Gd3+ was quenched with gamma-ray dose while the 6P7/2 emitting state lifetimes decreased. Correlations between Gd3+ emission intensities and lifetimes with optical band gaps suggest electron center defects perform as ‘energy sinks’.

Investigating into physical properties of composites of polymer blends and cobalt chloride irradiated by gamma ray for optical devices development

The present work studies the influence of cobalt chloride (CoCl2) and γ-irradiation dose on the optical, thermal properties, and dynamic mechanical analysis (DMA) of different blends of (PVA/PEG /PVP). Different optical parameters were deduced before and after γ-irradiation with different doses (5, 10, and 15 kGy). The optical conductivity (σoptical) values for the prepared blends and composites indicate their importance for optical energy applications, especially after γ-irradiation. Modifying and enhancing the refractive index of γ-irradiated samples enables their use in various optical devices. Linear optical susceptibility (χ(1)) and the third nonlinear susceptibility (χ(3)) increased by decreasing the PVA amount in the blend and composites. Thermogravimetric analysis TGA confirmed that by adding CoCl2 to the hosting blends, the thermal oxidative degradation energy Ea became much higher than unirradiated samples. The DMA results show that the storage modulus was significantly improved after adding CoCl2 and after irradiating the samples by 5 and 10 kGy. Also, all the samples exhibited two relaxation temperatures and were greatly affected by adding the filler.

Assessment of changes in microbiological, physicochemical, and sensory qualities of γ‐irradiated strawberries ( Fragaria × ananassa Duch. “Maehyang”) during storage

In this study, the effects of γ-irradiation at 0.15–0.9 kGy on the quality attributes of ‘Maehyang’ strawberries were evaluated. Both the irradiation dose and storage period affected the physicochemical properties of the fruit, such as pH, total soluble solids, and titratable acidity in the γ-irradiated samples compared with those in the control, but the difference was not significant (p < 0.05). The irradiation samples showed dose-dependent decreases in decay incidence, weight loss, microbial burden, hydrogen peroxide, and malondialdehyde levels. Although total phenolic content, ellagic acid, catechin, pelargonidin, and antioxidant activity increased gradually during storage regardless of irradiation, these parameters changes were delayed in strawberries irradiated at 0.9 kGy; furthermore, they had the highest overall acceptance sensory scores after storage and lowest rates of firmness loss and color-change deterioration. γ-irradiation at 0.9 kGy is thus sufficient for phytosanitary purposes, as it extends shelf life and maintains sensory qualities of strawberries.

Modulation of the optoelectronic properties of polyimide (Kapton-H) films by gamma irradiation for laser attenuation and flexible space structures

polyimide (PI or Kapton-H) has proven its potential in the field of optoelectronic, nuclear technology and space industry due to its excellent electric insulation, transparency and flexibility. The present study focuses the effect of γ-irradiation (0, 25, 50 and 100 Mrd) on the structural, optical, AC electrical conductivity and dielectric properties of PI film samples. In the results, the crystallite size was shown to be increased from 37.77 to 73.42 Å in the X-ray diffraction XRD study. Certain variations in assignment bands like (O–H) stretching and carbonyl (CO) symmetric stretching were observed in FTIR spectrum. A shift in the absorption edge is observed in the UV–vis spectroscopy to higher wavelengths and consequently a decrease in both direct and indirect band gap energy Egopt. The calculated values of the refractive index n is also increased upon γ-irradiation. The parameters of Wemple - DiDomenico (WDD) are calculated for pristine and γ-irradiated film samples. The dependence of the dissipation factor tanδ and optical conductivity σopt are studied as a function of the photon energy (hν) at different γ-doses. Moreover, the 3rd order non-linear susceptibility χ(3) and non-linear index of refraction n2 were also studied. Optical limiting measurements indicate that irradiation of PI samples with high γ-dose (100 Mrd) highly attenuated the laser beams (532 and 632.8 nm) which may be useful for use in optoelectronic laser limiters and filters. The AC electrical conductivity σac, dielectric constant ε′ and dielectric loss ε″ are also investigated in the range of frequency (100 Hz - 1 MHz). The values of σAC are enhanced by irradiation with γ-rays and the behaviors of the frequency exponent s indicates that the AC conduction in PI samples is governed by the correlated barrier hopping (CBH) mechanism.

Effects of Radiation sterilization Dose on the Molecular Weight and Gelling Properties of Commercial Alginate Samples

To estimate the molecular weight (Mw) and gelling properties, a total of 26 alginate samples consisting of control (n = 13) and 15 kGy γ-irradiated (n = 13) samples were characterized through viscometric and gel permeation chromatography (GPC-MALLS) methods. Based on the observations, a remarkable decrease in the intrinsic viscosity of all samples of alginates was evident due to the effects of radiation, with a linear relationship between viscosity and concentration in 0.01 M NaCl solution. The correlation among the Mw, percentage mass recovery, radii of gyration (Rz/Rg), and percentage reduction of Mw assessed by GPC was significant. The Mw decreased dramatically (from 3.1 × 105 to 0.49 × 105 mole/g in sample no. 12) by the effect of radiation with momentous relation to the % reduction of the molecular weight. The highest molecular weight reduction (84%), which is the most sensitive to γ-radiation, and the average reduction rate was ≥50%. The mass recovery was 100% obtained from samples no. 1,3,4,5,7,12, and 13, while the rest of the samples’ recovery rate was significantly higher. The reduction rate of mass molecular weight (Mw) is higher than the average molecular weight (Mv), but they showed a sensitivity towards radiation, consequently their performance are different from each other. The stability test was performed as a critical behaviour in the control, recurrently same as in the irradiated samples. Thus, the sterilization dose of 15 kGy for the Mw distribution, and subsequently for the characterization, was significantly effective.

Impact of γ-rays Irradiation on Hybrid TiO2-SiO2 Sol-Gel Films Doped with RHODAMINE 6G.

In the present paper, we investigate how the optical and structural properties, in particular the observed photoluminescence (PL) of photocurable and organic-inorganic TiO2-SiO2 sol-gel films doped with Rhodamine 6G (R6G) are affected by γ-rays. For this, four luminescent films, firstly polymerized with UV photons (365 nm), were submitted to different accumulated doses of 50 kGy, 200 kGy, 500 kGy and 1 MGy while one sample was kept as a reference and unirradiated. The PL, recorded under excitations at 365 nm, 442 nm and 488 nm clearly evidences that a strong signal peaking at 564 nm is still largely present in the γ-irradiated samples. In addition, M-lines and Fourier-transform infrared (FTIR) spectroscopies are used to quantify the radiation induced refractive index variation and the chemical changes, respectively. Results show that a refractive index decrease of 7 × 10−3 at 633 nm is achieved at a 1 MGy accumulated dose while a photo-induced polymerization occurs, related to the consumption of CH=C, Si-OH and Si-O-CH3 groups to form Ti-O and Si-O bonds. All these results confirm that the host matrix (TiO2-SiO2) and R6G fluorophores successfully withstand the hard γ-ray exposure, opening the way to the use of this material for sensing applications in radiation-rich environments.

Gamma-irradiation of common biological samples for stable carbon and nitrogen isotope and elemental analyses.

Around the world biosecurity measures are being strengthened to prevent the spread of pests and diseases across national and international borders. Quarantine protocols that involve sample sterilisation have potential effects on sample integrity. The consequences of sterilisation methods such as gamma (γ)-irradiation on the elemental and chemical properties of biological samples have not been widely examined. We tested the effect of γ-irradiation (50 kGy) on the stable carbon and nitrogen isotope compositions (δ13 C and δ15 N values) and elemental concentrations (C % and N %) of common biological samples (fish, plants and bulk soils). The analysis used a continuous flow system consisting of a Delta V Plus isotope ratio mass spectrometer connected with a Thermo Flash 1112 elemental analyser via a ConFlo IV interface. Results were compared using two one-sided tests (TOST) to test for statistical similarity between paired samples. There was no change in the δ15 N values or N % of γ-irradiated samples, and only small changes to the δ13 C values of consumers (range: 0.01‰ to 0.04‰), producers (-0.02‰ to 0.04‰) and sediments (0‰ to 0.07‰). The magnitude of change in δ13 C values was greatest at low carbon concentrations but appeared negligible when measured against replicated sample analysis and the combined analytical uncertainty (i.e., 0.10‰). The C % values of irradiated samples were higher for consumers (0.23%) and lower for producers and sediments (0.04% and 0.05%, respectively) which may have implications for certain types of biological material. Routine γ-irradiation has little effect on the stable carbon and nitrogen isotope compositions of common biological samples and marginal effects on carbon elemental concentrations. This is unlikely to warrant concerns since the observed difference is typically of a magnitude lower than other sources of potential uncertainty.

Transfusion of γ-irradiated blood components to individuals does not compromise the cytogenetic dose assessment

Most blood components for transfusions are irradiated ex vivo to prevent transfusion-associated graft-versus-host disease (TA-GvHD); this irradiation can potentially affect the cytogenetic dose assessment of patients showing acute radiation syndrome (ARS) with bone marrow suppression or acute anaemia. Whole blood samples from five donors were irradiated with 0, 10 or 25 Gy γ-rays. The mitotic activity of each cultured blood sample was measured by calculating the mitotic index. A dicentric chromosome assay was used to evaluate the chromosomal aberrations and absorbed dose of blood lymphocytes. Mitogenic activity and scorable metaphase spreads were significantly decreased in the blood samples irradiated with 10 and 25 Gy (p < 0.001). Moreover, a significant increase in the mean scores of all types of chromosomal aberrations in the 10 Gy γ-irradiated samples was observed, with the estimated dose being 11.3 Gy (95% CI: 10.67–11.95 Gy); however, we were unable to estimate the exposure dose in the 25 Gy γ-irradiated samples due to a limited number of scorable metaphase spreads. The mitotic index of the 25 Gy γ-irradiated whole blood samples was significantly suppressed by more than 4-log fold. Thus, in the present study, we evaluated the effects of recommended radiation doses in γ-irradiated transplantation blood components using cytogenetic dosimetry. These results suggest that the partial transfusion of blood components to patients with ARS or acute anaemia did not compromise the estimation of the exposure dose using cytogenetic dosimetry.

IMPROVEMENT OF DIATOMITE CHARACTERISTICS AND ITS APPLICATION FOR WINE FILTRATION

Diatomite is widely used as a filtering material in spirit-containing systems industry. In the presented paper, different types of treatment of diatomite from the Jradzor deposit, and the effectiveness of application of the modified samples for filtering the home-made wine have been studied. It is shown that due to the treatment of the raw diatomite sample, the surface characteristics and filtration (sorption) parameters of raw diatomite are improved. At first, raw diatomite from Jradzor deposit was water treated to remove the clay additives, then thermally treated at 900 0C and after it some samples were γ-irradiated by 500 Gr- a dose, which is acceptable for foods. Based on nitrogen adsorption-desorption isotherms, the values of the specific surface by the methods of BET and BJH have been determined. Also, the values of microporous and total pore volume, humidity and bulk density have been determined for the treated samples of diatomite. The effectiveness of home-made wine filtration capability for two modified samples of diatomite have been studied. The effect of the filtering material amount and the filtering material-filtrate shaking time on the effectiveness of filtration has been studied by the photocolorimetric method. It is established that the γ-irradiated samples, which pass the water and thermal treatments at 900 0C, are more effective than the filtering materials

Preliminary study of linearity response of γ-irradiated graphene oxide as a novel dosimeter using the Raman spectroscopy

In this experimental study, graphene oxide (GO) nanopowder was prepared and irradiated by the 60Co γ-rays in different absorbed doses of 0, 10, 30, 50, 80, 100, 120 and 150 kGy at dose rate of 1.62 Gy s−1 at room temperature. Field emission scanning electron microscope and high-resolution transmission electron microscopy analyses were used to investigate structural defects in GO material. Then, using Raman spectroscopy, the ratio of ID/IG related to D- and G-bands in the wavenumbers of 1350 and 1586 cm−1 was, respectively, measured in terms of absorbed dose to determine the dose–response of GO material. The results showed that the dose–response of γ-irradiated samples at the dose range of 0–50 kGy was linear. There was a decline in dose–response after 100 kGy due to graphitization of carbon nanostructure material or annealing the defects in the sample. The results of this study showed that the linearity response of γ-irradiated GO as a novel passive dosimeter is suitable for the dosimetry of γ-rays at the radiation processing level.

Using prediction models to identify miRNA-based markers of low dose rate chronic stress

Robust biomarkers of exposure to chronic low dose stressors such as ionizing radiation, particularly following chronic low doses and dose-rates, are urgently needed. MicroRNAs (miRNA) have emerged as promising markers of exposure to high dose and dose-rate. Here, we evaluated the feasibility of classifying γ-radiation exposure at different dose rates based on miRNA expression levels. Our objective was to identify miRNA-signatures discriminating between exposure to γ-radiation or not, including exposure to chronic low dose rates.We exposed male CBA/CaOlaHsd and C57BL/6NHsd wild-type mice to 0, 2.5, 10 and 100 mGy/h γ-irradiation (3 Gy total-dose). From an initial screening of 576 miRNAs, a set of 21 signature-miRNAs was identified based on differential expression (>± 2-fold or p < 0.05). This 21-signature miRNA panel was investigated in 39 samples from 4/5 livers/group/mouse strain. A set of significantly differentially expressed miRNAs was identified in all γ-irradiated samples. Most miRNAs were upregulated in all γ-irradiated groups compared to control, and functional analysis of these miRNAs revealed involvement in several cancer-related signaling pathways.To identify miRNAs that distinguished exposed mice from controls, nine prediction methods; i.e., six variants of generalized regression models, random-forest, boosted-tree and nearest-shrunken-centroid (PAM) were used. The generalized regression methods seem to outperform the other prediction methods for classification of irradiated and control samples.Using the 21-miRNA panel in the prediction models, we identified sets of candidate miRNA-markers that predict exposure to γ-radiation. Among the top10 miRNA predictors, contributing most in each of the three γ-irradiated groups, three miRNA predictors (miR-140-3p, miR-133a-5p and miR-145a-5p) were common. Three miRNAs, miR-188-3p/26a-5p/26b-5p, were specific for lower dose-rate γ-radiation. Similarly, exposure to the high dose-rates was also correctly predicted, including mice exposed to X-rays. Our approach identifying miRNA-based signature panels may be extended to classify exposure to environmental, nutritional and life-style-related stressors, including chronic low-stress scenarios.

Characterization of radiolytically synthesized feroxyhyte and oxidized magnetite nanoparticles

Iron(III) chloride deaerated alkaline aqueous colloidal solutions in the presence of 2-propanol and DEAE-dextran (diethylaminoethyl-dextran hydrochloride) were γ-irradiated with doses of 36 and 130 kGy. The dose rates were ~7 and ~31 kGy h−1. The extremely stable aqueous suspension of substoichiometric Fe2.83O4 magnetite nanoparticles ~4.7 nm in size were formed at a dose rate of ~7 kGy h−1 and at a dose of 36 kGy. At a dose of 130 kGy the anisotropic δ-FeOOH magnetic discs with a diameter of ~256 nm and thickness of ~40 nm were formed. Each disc has a substructure consisting of approximately eighteen laterally stacked thin nanodiscs of about 2.2 nm in thickness. At a higher dose rate of ~31 kGy h−1and at a dose of 36 kGy, XRD revealed the presence of highly substoichiometric Fe2.75O4 magnetite, whereas TEM analysis revealed the presence of ~4.3 nm magnetite nanoparticles along with rod-shaped γ-Fe2O3 nanoparticles. The values of isomer shift in Mössbauer spectra of about 0.33 mm s−1 showed that all Fe(II) in substoichiometric magnetites oxidized to Fe(III) one month after synthesis. At high dose and dose rate, the rolled rod-like δ-FeOOH magnetic nanoparticles were formed having the diffraction patterns with streaks, which are characteristic of tubular structures. The magnetic measurements showed exceptional intrinsic room-temperature magnetic properties of both δ-FeOOH nanostructures with the Curie temperature above 300 K. In order to ascertain the formation of Fe(II) intermediate products prior to their oxidation, γ-irradiated samples were isolated by admixing glycerol. The amounts of Fe(II) in glycerol-isolated solid samples were determined using Mössbauer spectroscopy. Carbonate Green Rust I [GR(CO32−)] and Fe(OH)2 intermediate phases were confirmed by XRD and Mössbauer spectroscopy. The amounts of Fe2+ in the acidified solutions containing dissolved γ-irradiation ferrous products were determined using the potassium permanganate titration. The amounts of Fe2+ were 68.9% and 96.1% at doses of 36 and 130 kGy, respectively. Thus, at a dose of 130 kGy the radiolytically generated Fe(OH)2, after coming in contact with oxygen and CO2 from the air, topotactically oxidized to GR(CO32−) and further to δ-FeOOH without any structural changes. The lower dose rate (~7 kGy h−1) favored the δ-FeOOH nanodisc morphology, whereas the higher dose rate (~31 kGy h−1) favored the formation of tubular rod-like δ-FeOOH nanoparticles.

A COMPARATIVE STUDY OF THE RADIOLYSIS OF USED TRANSFORMER OIL AND OIL CONTAINING 1, 2, 4-TRICHLORBENZENE UNDER THE INFLUENCE OF GAMMA-RADIATION

A comparative study of the radiolysis of used transformer oil and oil containing 1, 2, 4-trichlorbenzene (TCB) under the influence of gamma-radiation was carried out. Dependence of concentration of H2, H2O2, pH-indicator and IR-spectra of γ-irradiated samples from absorbed doses in the range of 4…136 kGy was studied. The pH-value dependence and concentration of hydrogen peroxide as a function of the absorbed dose is studied. Irradiation leads to increasing of acidity, related with dechlorination of TCB molecules. It is found that during the radiolysis of transformer oil containing TCB in the presence of dissolved oxygen, radiation-initiated oxidation of the oil takes place (formation of H2O2, CO2).