Γ-ray Irradiation Research Articles

Penicillium oxalicum SL2-enhanced nanoscale zero-valent iron effectively reduces Cr(VI) and shifts soil microbiota

Most current researches focus solely on reducing soil chromium availability. It is difficult to reduce soil Cr(VI) concentration below 5.0 mg kg-1 using single remediation technology. This study introduced a sustainable soil Cr(VI) reduction and stabilization system, Penicillium oxalicum SL2–nanoscale zero-valent iron (nZVI), and investigated its effect on Cr(VI) reduction efficiency and microbial ecology. Results showed that P. oxalicum SL2–nZVI effectively reduced soil total Cr(VI) concentration from 187.1 to 3.4 mg kg–1 within 180 d, and remained relatively stable at 360 d. The growth curve of P. oxalicum SL2 and microbial community results indicated that γ-ray irradiation shortened the adaptation time of P. oxalicum SL2 and facilitated its colonization in soil. P. oxalicum SL2 colonization activated nZVI and its derivatives, and increased soil iron bioavailability. After restoration, the negative effect of Cr(VI) on soil microorganisms was markedly alleviated. Cr(VI), Fe(II), bioavailable Cr/Fe, Eh, EC and urease (SUE) were the key environmental factors of soil microbiota. Notably, Penicillium significantly stimulated the growth of urease-positive bacteria, Arthrobacter, Pseudarthrobacter, and Microvirga, synergistically reducing soil chromium availability. The combination of P. oxalicum SL2 and nZVI is expected to form a green, economical and long-lasting Cr(VI) reduction stabilization strategy.

Water Radiocatalysis for Selective Aqueous-Phase Methane Carboxylation with Carbon Dioxide into Acetic Acid at Room Temperature.

Methane (CH4) carboxylation with carbon dioxide (CO2) into acetic acid (CH3COOH) is an ideal chemical reaction to utilize both greenhouse gases with 100% atom efficiency but remains a great challenge under mild conditions. Herein, we introduce a concept of water (H2O) radiocatalysis for efficient and selective aqueous-phase CH4 carboxylation with CO2 into CH3COOH at room temperature. H2O radiolysis occurs under γ-ray radiation to produce ·OH radicals and hydrated electrons that efficiently react with CH4 and CO2, respectively, to produce ·CH3 radicals and ·CO2- species facilely coupling to produce CH3COOH. CH3COOH selectivity as high as 96.9 and 96.6% calculated respectively from CH4 and CO2 and a CH3COOH production rate of as high as 121.9 μmol·h-1 are acquired. The water radiocatalysis driven by γ-rays is also applicable to selectively produce organic acids from other hydrocarbons and CO2.

Tracing the antioxidant effect of vitamin E on ultra-high molecular weight polyethylene

The antioxidant effect of vitamin E on ultra-high molecular weight polyethylene (UHMWPE) during radiation oxidation and post-irradiation oxidation process was investigated using electron paramagnetic resonance spectroscopy (EPR) and fourier transform infrared microscopy (FTIR). EPR results showed that the free radical concentration of UHMWPE induced by γ-rays irradiation decreased with increasing vitamin E content both in air and nitrogen atmosphere. FTIR results indicated that the irradiated samples underwent a continuous oxidation reaction, and the higher the vitamin E content, the lower the oxidation reaction. However, radiation oxidation also occurred inevitably to the vitamin E-stabilized UHMWPE indicating vitamin E could only partially prevent oxidation. Further investigation suggested that ozone can rapidly oxidize the vitamin E-stabilized UHMWPE, that is, vitamin E cannot prevent ozone from oxidizing UHMWPE. Then radiation oxidation schematic presentation of vitamin E-stabilized UHMWPE was described. This work would provide more comprehensive understanding on the radiation oxidation and post-irradiation oxidation of vitamin E-stabilized UHMWPE.

Degradation behavior of DLC thin film under gamma-rays irradiation using molecular dynamics simulation

γ-rays have high energy, thus, when irradiated on the materials, lead to the degradation process of the materials which means the durability and efficiency of the system decrease. Therefore, analysis of the effect of γ-rays on the materials is important, despite this, little work has so far been undertaken to predict the irradiation effect. Furthermore, because the previous theoretical equations have many assumptions, the accuracy of the prediction is low. For these reasons, molecular dynamics simulation was used to analyze and predict the effect of γ-rays on the DLC thin film in this study. This study investigates the degradation process, bond distribution, and radical creation during γ-rays irradiated on the DLC thin film. The primary knock-on atoms (PKA) method was applied which can be mimicked first excited atoms by γ-rays. Also, to analyze the chemical change of the irradiated DLC, ReaxFF potential was selected. The dose rate condition covered various environments where the γ-rays were irradiated such as space, nuclear, medical, etc. The degradation mechanisms of DLC were different by the dose rate. For low dose rate conditions, the energy of excited atoms was converted by physical collisions between atoms. However, in the case of high dose rate conditions, radical production rapidly increased, resulting in physical and chemical energy dissipation. Within this paper, we present a fundamental numerical analysis of the degradation process that combines the PKA method and MD simulation to achieve improved accuracy. These findings could provide fundamental insight into the degradation phenomenon of surface-protective coatings for various applications with γ-ray irradiation environment.

RADIOPROTECTIVE PROTEIN OF TARDIGRADE DSUP (DAMAGE SUPPRESSOR) IS RESISTANT TO HIGH DOSES OF IONIZING RADIATION

The unique Dsup protein of the tardigrade Ramazzottiusvarieornatus increases resistance to radiation and oxidative stress in various species of organisms and in human cell culture. According to modeling data,Dsup forms a complex with DNA with an intermolecular distance of ∼4˚A, as a result of which DNA is lessdamaged by reactive oxygen species formed during exposure to radiation.However, the stability of the Dsupprotein itself under the in uence of ionizing radiation remains unclear, which is important for assessing its radioprotective potential and understanding the molecular mechanisms of the action of this protein under conditions of high doses of radiation. In this work, the radiation degradation of the Dsup protein after γ-ray irradiation by small-angle X-ray scattering (SAXS) and protein electrophoresis in polyacrylamide gel under denaturing conditions (SDS-PAGE) was studied for the rst time.It has been shown that, in contrast to the control bovine serum albumin, the spatial and structural characteristics of the Dsup protein remain almost unchanged even when exposed to high doses of radiation (5 and 10 kGy), which suggests its high radiation stability.

Single base substitution signatures 17a, 17b, and 40 are induced by γ-ray irradiation in association with increased reactive oxidative species

γ-Ray irradiation induces DNA double strand breaks (DSBs) and increases the risk of cancerization. Irradiated cells usually repair DSBs directly, but accumulate replication stress-associated DSBs, increasing the risk of structural variants (SVs). Although single nucleotide variants (SNVs) are also induced, it is still unclear which SNVs are induced by γ-ray irradiation. Here, we show that single base substitution (SBS) 17a, 17b, and 40 signatures were induced by γ-ray irradiation, which is mainly SNV induction in A-T bps. While SNVs induced by genomic instability were usually associated with SVs, SNVs induced by γ-ray irradiation and the associated signatures were not. As reactive oxygen species (ROS) are a possible cause of SBS17a and 17b, ROS were induced upon γ-ray irradiation (1–8 Gy), indicating the association of ROS for the SNV induction. Thus, our results reveal that ROS-associated SNVs are increased by irradiation, and that ROS-associated SNVs are induced independently of SVs.

Jet Mechanism and γ-Ray-emitting Region for Fermi Flat-spectrum Radio Quasars with Broad-line Emissions

Blazars are a subject of intense debate, specifically regarding their jet launch and emission mechanisms, and the origins of their γ-ray radiation. To explore these issues, we have built a comprehensive sample of flat-spectrum radio quasars (FSRQs), with well-characterized spectral energy distribution. This study aims to elucidate the dominant jet launch mechanism and the main processes behind the inverse Compton (IC) component. Additionally, we seek to pinpoint the location of the γ-ray dissipation region relative to the central black hole, denoted as R γ . Our approach involves a detailed analysis of broad-line region (BLR) emission, from which we derive robust estimates of the black hole masses using two distinct virial techniques. This enables us to constrain the jet power across a wide array of FSRQs. Our findings lead to several significant conclusions: (i) The correlation of jet power with black hole mass allows us to test the Blandford–Znajek, Blandford–Payne, and hybrid mechanisms. We find that the hybrid mechanism is most effective in explaining the jet power observed in the majority of FSRQs; (ii) The IC component of the γ-rays in FSRQs is predominantly due to the external Compton process. (iii) Through simulations, we determine the minimum and maximum values of R γ (the γ-ray dissipation region) and conclude it is located outside the BLR. This conclusion is derived from the variability timescale analysis.

Stochastic Wave Dark Matter with Fermi-LAT γ-Ray Pulsar Timing Array

Pulsar timing arrays (PTAs) can detect disturbances in the fabric of spacetime on a galactic scale by monitoring the arrival time of pulses from millisecond pulsars (MSPs). Recent advancements have enabled the use of γ-ray radiation emitted by MSPs, in addition to radio waves, for PTA experiments. Wave dark matter (DM), a prominent class of DM candidates, can be detected with PTAs due to its periodic perturbations of the spacetime metric. In response to this development, we perform in this Letter a first analysis of applying the γ-ray PTA to detect the ultralight axion-like wave DM, with the data of Fermi Large Area Telescope (Fermi-LAT). Despite its much smaller collecting area, the Fermi-LAT γ-ray PTA demonstrates a promising sensitivity potential. We show that the upper limits not far from those of the dedicated radio-PTA projects can be achieved. Moreover, we initiate a cross-correlation analysis using the data of two Fermi-LAT pulsars. The cross-correlation of phases, while carrying key information on the source of the spacetime perturbations, has been ignored in the existing data analyses for the wave DM detection with PTAs. Our analysis indicates that taking this information into account can improve the sensitivity to wave DM by ≳50% at masses below 10−23 eV.

Simulation studies of γ-ray radiation in laser-plasma interactions with structured targets

We studied the γ-ray emission from laser interactions with structured targets of Al and Au. Bremsstrahlung and Non-linear Compton Scattering (NCS) emission are considered for the γ-ray emission using the open source 2-D PIC code EPOCH. Different shapes of the target generated additional hot electrons, which helps to enhance the photon energy in individual cases. The enhancement of photon energy is due to the target's shape and the hot electrons. Hot electron generation and their dynamics, like refluxing behavior, are crucial phenomena in thin targets. This study uses four different shapes of Al and Au targets. The relative strength of emissions from both bremsstrahlung and NCS are compared. The shape of the target enhances the γ-ray energy, electron energy, and emitted photon number and improves the electron beam divergence. The effect of each target shape on hot electrons refluxing behavior and the role of the electric and magnetic fields are discussed in detail.

Investigating the effects of γ-ray irradiation on the mechanical and dielectric properties of poly(lactide)/poly(butylene adipate-co-terephthalate)/carbon nanotubes composites

Investigating the effects of γ-ray irradiation on the mechanical and dielectric properties of poly(lactide)/poly(butylene adipate-co-terephthalate)/carbon nanotubes composites

Evolution of the structure and tribological behavior of the organic coatings under gamma-ray irradiation

More reliable and long-term irradiation stability is essential for lubrication protection materials that served in nuclear energy equipment. In this paper, three typical commercially organic bonded solid lubricating coatings were chosen to investigate the influence of gamma (γ)-ray irradiation on microstructure and tribological behaviors. The evolution of microstructure and the changes of tribological properties for these coatings after irradiation were comparatively studied in detail. The results revealed that the crystallinity of the molybdenum disulfide (MoS2) lubricating phase was improved and were partial oxidized in the coatings after γ-ray irradiation, resulting in the surface roughness of the coating with MoS2 as the solid lubricating phase decreased significantly. The polytetrafluoroethylene (PTFE) lubricating phase was degraded from the long chains structure to smaller molecules after γ-ray irradiation. The results of tribological properties of the three coatings after γ-ray irradiation indicated that, for polyamide-imide-based lubricating coatings, the friction coefficient is decreased and the wear rate is increased after irradiation. For phenolic epoxy-based lubricating coating, the cross-linking effect of γ-ray irradiation predominated to improve the wear resistance and prolong the wear life of the coating. But overall, the influence of irradiation on tribological properties of three polymer-based coatings could almost be neglected duo to the changes of the microstructure in nanoscale. This work provides path and direction for design and preparation of the lubricating coatings that served in a nuclear reactor.

Nuclear mutagenesis and adaptive evolution improved photoautotrophic growth of Euglena gracilis with flue-gas CO2 fixation

To effectively improve biomass growth and flue-gas CO2 fixation of microalgae, acid-tolerant Euglena gracilis was modified with cobalt-60 γ-ray irradiation and polyethylene glycol (PEG) adaptive screening to obtain the mutant strain M800. The biomass dry weight and maximum CO2 fixation rate of M800 were both 1.47 times higher than that of wild strain, which was attributed to a substantial increase in key carbon fixation enzyme RuBisCO activity and photosynthetic pigment content. The high charge separation quantum efficiency in PSII reaction center, efficient light utilization and energy regulation that favors light conversion, were the underlying drivers of efficient photosynthetic carbon fixation in M800. M800 had stronger antioxidant capacity in sufficient high-carbon environment, alleviating lipid peroxidation damage. After adding 1 mM PEG, biomass dry weight of M800 reached 2.31 g/L, which was 79.1 % higher than that of wild strain. Cell proliferation of M800 was promoted, the apoptosis and necrosis rates decreased.

Synergistic Radiation Effects in PPD CMOS Image Sensors Induced by Neutron Displacement Damage and Gamma Ionization Damage.

The synergistic effects on the 0.18 µm PPD CISs induced by neutron displacement damage and gamma ionization damage are investigated. The typical characterizations of the CISs induced by the neutron displacement damage and gamma ionization damage are presented separately. The CISs are irradiated by reactor neutron beams up to 1 × 1011 n/cm2 (1 MeV neutron equivalent fluence) and 60Co γ-rays up to the total ionizing dose level of 200 krad(Si) with different sequential order. The experimental results show that the mean dark signal increase in the CISs induced by reactor neutron radiation has not been influenced by previous 60Co γ-ray radiation. However, the mean dark signal increase in the CISs induced by 60Co γ-ray radiation has been remarkably influenced by previous reactor neutron radiation. The synergistic effects on the PPD CISs are discussed by combining the experimental results and the TCAD simulation results of radiation damage.

Comparative studies of spectroscopic properties and surface structure of solid solutions of CaF2:SrF2:YbF3 crystals and ceramics

The optical properties of laser ceramics based on 65CaF2:30SrF2:5YbF3 have been studied and compared with a single crystal of the same composition when exposed to 60Co γ-rays. The spectral characteristics of the non-irradiated samples were similar. During and after γ-ray irradiation of the 65CaF2:30SrF2:5YbF3 crystal and ceramic samples, Yb3+→Yb2+ transformations occur as well as configurationally Yb3+→Yb3+ transitions between the different states of the Yb3+ ions with the participation of the interstitial Fi ions. Our analysis of the state of the surface of the single crystal and nanoceramics showed that the roughness on the surface of the ceramics was improved, while on the surface of the single crystal it worsened when compared to its initial state.

Assessment of Radiation Tolerance of Flash Memory by γ-Ray Irradiation

The radiation tolerance of a microcontroller (Raspberry Pi) required for the development of decommissioning robots was investigated. We found that the flash memory needed to boot the microcontroller had particularly low-radiation tolerance, significantly reducing the operation duration of the microcontroller in a radiation environment. We also found that certain high-performance flash memories have high radiation tolerance. Investigation of the process by which flash memory becomes inoperable revealed that internal memory information is rewritten owing to irradiation, leading to limited lifetime for memory.

Investigation of K2Cu(Cl,Br)3 crystalline scintillators

K2Cu(Cl,Br)3 crystals were prepared by the slow cooling method and evaluated for photoluminescence (PL) and scintillation properties. PL emission and scintillation peaks due to the recombination of excitons were observed at 400 nm. The PL quantum yields were estimated to be 61.0% for K2CuCl3, 72.7% for K2Cu(Cl0.5,Br0.5)3, and 75.8% for K2CuBr3, respectively. The scintillation decay curves were approximated by a single exponential function model, and the calculated decay time constants were 14–60 μs. The afterglow levels at 20 ms passed after X-ray irradiation were obtained to be 5–1225 ppm. The light yields of K2CuCl3 and K2Cu(Cl0.5,Br0.5)3 were 7700 and 9900 photons MeV−1 when calculated from the pulse height spectra under 137Cs γ-ray (662 keV) irradiation.

Hydrogen atom in γ-irradiated synthetic isopropylamine silica clathrate

Silica clathrates have polyhedral cage structures with guest molecules and are naturally found under various forms such as melanophlogite, chibaite, or bosoite. Although electron spin resonance (ESR) could be potentially used to date their formation, the evaluation of the thermal stability of the radiation-induced radicals is not simple, like in the case of chibaite. Decay mechanism of the radical should be understood to ensure reliable ESR dating results. To investigate the behavior of radiation-induced radical in silica clathrate, isopropylamine silica clathrate was synthesized from mixed solutions of orthosilicic acid and isopropylamine. Hydrogen atom and (CH3)2C·(NH2) radical are mainly formed by γ-ray irradiation at 77 K. Hydrogen atom decay around 230 K by following a first-order kinetics and its activation energy is 65 ± 4 kJ/mol. Since the amount of hydrogen atom decrease was similar to that of the (CH3)2C·(NH2) radical increase, it is hypothesized that hydrogen atom abstracts hydrogen from isopropylamine in the silica clathrate.

Designing a muon scattering scanner for nuclear debris measurement.

Removal of fuel debris is planned to start at Unit 2 of the Fukushima Daiichi Nuclear Power Plant. During the removal, it is desirable to distinguish fuel debris from radioactive wastes and to sort the fuel debris accordingly to the amounts of nuclear material contained. Muon scattering tomography invented at Los Alamos in the early 2000s is highly sensitivity to high-atomic-number materials such as uranium. A muon scanner to sort the debris is designed and currently in production. One of the challenges is to operate the muon scanner in the presence of high γ-ray radiations from the debris: muon-event-identification electronics and a muon-tracking algorithm in the presence of high γ-ray radiations were developed.

Gamma-ray-irradiated preparation and performance of magnetothermally responsive hybrid materials towards the tandem hydrogenation of halonitrobenzenes

Novel magneto-thermo dual responsive organic-inorganic hybrid materials (PdCu/Fe3O4@SiO2@PNIPAM) were successfully prepared under γ-ray irradiation in this work. The γ-ray irradiation simultaneously induced the grafting of the polymer PNIPAM, and the in-situ anchoring of metallic Pd and Cu via an irradiation reduction. The catalytic performance of the prepared PdCu/Fe3O4@SiO2@PNIPAM hybrid material (abbr. PdCu/FSP) was investigated for the dehydrogenation of ammonia borane (AB) and the tandem hydrogenation of halonitrobenzenes. The results showed that the as-prepared PdCu/FSP exhibited more excellent catalytic performance in the tandem hydrogenation reaction of halonitrobenzenes in comparison with a controlled sample by a traditional preparation method. Furthermore, the PdCu/FSP catalyst prepared at a radiation dose of 25 kGy achieved excess 99 % yield of m-chloroaniline (m-CAN) at room temperature within 5 min. The PdCu/FSP hybrid material could be easily recycled by simple magnetic separation, and increasing temperature led to obvious time-shortening behavior for facile magnetic separation. Owing to lack of the intrinsic drawbacks of conventional chemical reductants and radical initiators, the gamma-ray irradiation method provides an available strategy for the construction of hybrid catalytic materials towards the hydrogenated reduction of halonitrobenzenes.

Effects of high-dose gamma-ray irradiation on an In0.53Ga0.47As high electron mobility transistor

We investigate the effects of gamma-ray (γ-ray) irradiation on an In0.53Ga0.47As high electron mobility transistor (HEMT). After γ-ray radiation, the irradiated HEMT shows degradation of the maximum transconductance (g m,max ), the unity current gain cutoff frequency (f T ), and the maximum oscillation frequency (f max)—about 12.8%, 18.0%, and 16.9%, respectively—because of an increase in on-resistance (Ron) in In0.53Ga0.47As HEMTs exposed to high-dose γ-ray radiation. Moreover, we obtain a minimum noise figure (NFmin) of about 1 dB from 8 to 40 GHz for the irradiated HEMT, which is a lower value compared to a non-irradiated HEMT; this is because the gate leakage current is reduced after γ-ray irradiation.