Design and performance evaluation of a large field-of-view dual-particle time-encoded imager based on a depth-of-interaction detector

Time-encoded imaging is useful for identifying potential special nuclear materials and other radioactive sources at a distance.In this study,a large field-of-view time-encoded imager was developed for gamma-ray and neutron source hotspot imaging based on a depth-of-interaction(DOI)detector.The imager primarily consists of a DOI detector system and a rotary dual-layer cylindrical coded mask.An EJ276 plastic scintillator coupled with two SiPMs was designed as the DOI detector to increase the field of view and improve the imager performance.The difference in signal time at both ends and the log of the signal amplitude ratio were used to calculate the interaction position resolution.The position resolution of the DOI detector was calibrated using a collimated Cs-137 source,and the full width at half maximum of the reconstruction position of the Gaussian fitting curve was approximately 4.4 cm.The DOI detector can be arbitrarily divided into several units to independently reconstruct the source distribution images.The unit length was optimized via Am-Be source-location experiments.A multidetector filtering method is proposed for image denoising.This method can effectively reduce image noise caused by poor DOI detector position resolution.The vertical field of view of the imager was(-55°,55°)when the detector was placed in the center of the coded mask.A DT neutron source at 20 m standoff could be located within 2400 s with an angular resolution of 3.5°.

The role of crm-1 in ionizing radiation-induced nervous system dysfunction in Caenorhabditis elegans

Ionizing radiation can cause changes in nervous system function.However,the underlying mechanism remains unclear.In this study,Coenorhabditis elegans(C.elegans)was irradiated with 75 Gy of ^(60)Co whole-body γ radiation.Behavioral indicators(head thrashes,touch avoidance,and foraging),and the development of dopaminergic neurons related to behavioral function,were evaluated to assess the effects of ionizing radiation on nervous system function in C.elegans.Various behaviors were impaired after whole-body irradiation and degeneration of dopamine neurons was observed.This suggests that 75 Gy of γ radiation is sufficient to induce nervous system dysfunction.The genes nhr-76 and crm-1,which are reported to be related to nervous system function in human and mouse,were screened by transcriptome sequencing and bioinformatics analysis after irradiation or sham irradiation.The expression levels of these two genes were increased after radiation.Next,RNAi technology was used to inhibit the expression of crm-1,a gene whose homologs are associated with motor neuron development in other species.Downregulation of crm-1 expression effectively alleviated the deleterious effects of ionizing radiation on head thrashes and touch avoidance.It was also found that the expression level of crm-1 was regulated by the nuclear receptor gene nhr-76.The results of this study suggest that knocking down the expression level of nhr-76 can reduce the expression level of crm-1,while down-regulating the expression level of crm-1 can alleviate behavioral disorders induced by ionizing radiation.Therefore,inhibition of crm-1 may be of interest as a potential therapeutic target for ionizing radiation-induced neurological dysfunction.

Application of microdosimetry on biological physics for ionizing radiation

Stochastic characterization of radiation interaction is of importance to cell damage. Microdosimetry is to investi- gate the random structures of particle tracks in order to understand the dose-effect in cellular scales. In the review, we introduced the basic concepts of microdosimetry as well as the experimental methods （TEPC） and Monte Carlo simula- tions. Three basic biophysical models are interpreted and compared, including the target model, linear-quadratic model, and microdosimetric-kinetic model. The bottlenecks in the current microdosimetry research are also discussed, which need the interdisciplinary contributions from biology, physics, mathematics, computer science and electric engineering.

Synergistic impact of cocatalysts and hole scavenger for promoted photocatalytic H2 evolution in mesoporous TiO2–NiSx hybrid

Photocatalytic solar energy conversion to hydrogen is sustainable and attractive for addressing the global energy and environmental issue. Herein, a novel photocatalytic system (NiS/Ni3S4 cocatalysts modified mesoporous TiO2) with superior photocatalytic hydrogen evolution capability through the synergistic impact of NiS/Ni3S4 (NiSx) cocatalyst and efficient hole scavenger has been demonstrated. The photocatalytic hydrogen evolution of TiO2-NiSx hybrids with the different content of NiSx and upon different organic hole scavengers was both investigated. The hybrid of TiO2 decorated with 3%(mole ratio of Ni^2+) NiSx cocatalyst in methanol solution showed the optimal photocatalytic hydrogen evolution rate of 981.59 μmol h^-1 g^-1 which was about 20 times higher than that of bare mesoporous TiO2. Our results suggested that the boosted hydrogen production performance is attributed to both the improved photoinduced electrons migration between NiS and Ni3S4 in cocatalyst and the high hole captured efficiency by hole scavengers of methanol.

A method for direct conversion of EPID images to incident fluence for dose reconstruction

A direct incident fluence measurement method based on amorphous silicon electronic portal imaging device(a-Si EPID) has been developed for pretreatment verification of intensity-modulated radiation therapy(IMRT).The EPID-based incident fluence conversion method deconvolves EPID images to the primary response distribution based on measured lateral scatter kernels in the EPID detector using Conjugate Gradient algorithm.The primary response is converted to the incident fluence based on measured fluence conversion matrix which corrects for off-axis position dependence of the a-Si EPID response and the "horn" beam profile caused by flatting filter. To verify feasibility and accuracy of this method, square fields of various sizes and two IMRT plans were delivered. The dose distributions computed based on EPID-derived incident fluence were compared with the measurement data. For all square field sizes except the smallest field(2 cm), the mean dose differences in cross-line dose profiles were within 1% excluding the penumbra region, and gamma passing percentages with a 2%/2 mm criterion were about 99%. For two IMRT plans, the least gamma passing percentage for all eight IMRT fields was 98.14% with 2%/3 mm criteria. It can be concluded that our direct EPID-based incident fluence conversion method is accurate and capable of being applied to pretreatment dose verification in clinical routines.

Determination of thickness of wax deposition in oil pipelines using gamma-ray transmission method

Wax deposition in pipelines is a crucial problem in the oil industry.An approach that combines the gammaray transmission method with scanning technology is proposed to detect the thickness of wax deposition.The performance of the method is validated through simulations with MCNP code.An experiment is also carried out with a 300 mCi ^(137)Cs source and a LaBr_3 detector.A good correspondence is observed between the simulation and experimental results.The results indicate that the approach is efficient for detecting the thickness of wax deposition in oil pipelines.

Experimental study on fragmentation behaviors of molten LBE and water contact interface

Based on the design of CLEAR(China LEAd-based Reactor), it is important to study the molten LBE(LeadBismuth Eutectic)/water interaction following an incidental steam generator tube rupture(SGTR) accident.Experiments were carried out to investigate the fragmentation behavior of the molten LBE/water contacting interface, with a high-speed video camera to record the fragmentation behavior of 300–600?C LBE at 20?C and 80?C of water temperature. Violent explosion phenomenon occurred at water temperature of 20?C, while no explosion occurred at 80?C. Shapes of the LBE debris became round at 80?C of water temperature, whereas the debris was of the needle-like shape at 20?C. For all the molten LBE and water temperatures in the present study,the debris sized at 2.8–5.0 mm had the largest mass fraction. The results indicate that the dominant physical mechanism of the molten LBE fragmentation was the Kelvin-Helmholtz instability between LBE/water direct contact interface.

An algorithm for Monte Carlo simulation of bremsstrahlung emission by electrons

An algorithm for Monte Carlo simulation of bremsstrahlung emission by electrons based on the framework of Super MC is presented in this paper with efficient and accurate methods to sample the angular distribution and energy of bremsstrahlung photons. The photon energy is sampled according to scaled energy-loss differential cross sections tabulated by Seltzer and Berger. A novel hybrid model for photon angular distribution by low-and high-energy incident electrons is developed. The model uses Tsai's full form of angular distribution function with atomic form factors for high-energy incident electrons. For electrons o\500 ke V, a simple efficient and accurate analytical distribution function is developed, using adjustable parameters determined from the fitting of numerical values of the shape functions tabulated by Kissel et al. The efficiency of sampling photon energy is 80%. Our angular sampling algorithm for high-energy electron bremsstrahlung based on Tsai distribution function is very efficient(sampling efficiency*70%) in the useful photon energy range.

Detection of heavy metals in aqueous solution using PGNAA technique

A prompt gamma neutron activation analysis setup was developed for heavy metal detection in aqueous solutions with a 300 m Ci241Am-Be neutron source and a4 4 inch(diameter height) BGO detector. In the present work, heavy metals, including Mn, Cu, Ni, Cr and Zn, were measured by the setup. The minimum detectable concentrations of Mn, Cu, Ni, Cr and Zn were 246.6, 391.2, 218.1,301.5 and 2804.1 ppm, respectively. The minimum detectable concentration of each element and the linearity response between the characteristic peak counts and elements concentrations have been studied. And the results showed that all heavy metals had a good linear relationship between characteristic peak counts and concentrations.

Role of non-coding RNAs in pancreatic cancer: The bane of the microworld

Our understanding of the mechanisms underlying the development of pancreatic cancer has been greatly advanced.However,the molecular events involved in the initiation and development of pancreatic cancer remain inscrutable.None of the present medical technologies have been proven to be effective in significantly improving early detection or reducing the mortality/morbidity of this disease.Thus,a better understanding of the molecular basis of pancreatic cancer is required for the identification of more effective diagnostic markers and therapeutic targets.Non-coding RNAs(ncRNAs),generally including microRNAs and long non-coding RNAs,have recently been found to be deregulated in many human cancers,which provides new opportunities for identifying both functional drivers and specific biomarkers of pancreatic cancer.In this article,we review the existing literature in the field documenting the significance of aberrantly expressed and functional ncRNAs in human pancreatic cancer,and discuss how oncogenic ncRNAs may be involved in the genetic and epigenetic networks regulating functional pathways that are deregulated in this malignancy,particularly of the ncRNAs’role in drug resistance and epithelialmesenchymal transition biological phenotype,with the aim of analyzing the feasibility of clinical application of ncRNAs in the diagnosis and treatment of pancreatic cancer.

Radiation-induced one-pot synthesis of grafted covalent organic frameworks

Post-synthetic functionalization of covalent organic frameworks(COFs)is an alternative way to enhance and broaden their properties and potential applications.However,the chemical functionalization of COFs is a great challenge because traditional procedures are often time-and energy-consuming,while the crystallinity of COFs can be damaged under harsh conditions.Here we report the in-situ introduction of functional graft chains onto the skeleton of COFs during the synthesis process through the combination of radiation-induced synthesis and graft polymerization techniques under ^(60)Co gamma-ray radiation.The synthesis and functionalization of COFs are simultaneously accomplished in a chemical system under ambient conditions yielding a large number of different functionalized COFs.The obtained carboxyl-functionalized COFs exhibit excellent radioactive uranium removal capabilities from aqueous solution with fast uptake dynamics,high adsorption capacity,and excellent selectivity over other competing metal ions.

The role of bacteria and its derived biomaterials in cancer radiotherapy

Bacteria-mediated anti-tumor therapy has received widespread attention due to its natural tumor-targeting ability and specific immune-activation characteristics.It has made significant progress in breaking the limitations of monotherapy and effectively eradicating tumors,especially when combined with traditional therapy,such as radiotherapy.According to their different biological characteristics,bacteria and their derivatives can not only improve the sensitivity of tumor radiotherapy but also protect normal tissues.Moreover,genetically engineered bacteria and bacteria-based biomaterials have further expanded the scope of their applications in radiotherapy.In this review,we have summarized relevant researches on the application of bacteria and its derivatives in radiotherapy in recent years,expounding that the bacteria,bacterial derivatives and bacteria-based biomaterials can not only directly enhance radiotherapy but also improve the anti-tumor effect by improving the tumor microenvironment(TME)and immune effects.Furthermore,some probiotics can also protect normal tissues and organs such as intestines from radiation via anti-inflammatory,anti-oxidation and apoptosis inhibition.In conclusion,the prospect of bacteria in radiotherapy will be very extensive,but its biological safety and mechanism need to be further evaluated and studied.

Fully conversing and highly selective oxidation of benzene to phenol based on MOFs-derived CuO@CN photocatalyst

Developing highly efficient photocatalysts for selective oxidation of benzene to phenol is of great significance. However, it is still challenging to simultaneously achieve high conversion rate and selectivity.Herein, we demonstrate 99.9% of benzene photoconversion and 99.1% of phenol selectivity under the illumination of AM 1.5 for 12 h. For this purpose, an advanced CuO@CN photocatalyst has been fabricated by loading tubular carbon nitride(CN) with CuO nanoparticles thermally polymerized from Cu-based metal-organic frameworks(MOFs). The sluggish photocharge carrier recombination rate and the excellent stability indicate that the as-prepared nanocomposite is an ideal photocatalyst for benzene oxidation application. This work paves a new avenue for designing novel photocatalyst based on MOFs and carbon nitride materials.

PIG3 downregulation enhances the radiosensitivity of NSCLC cells by promoting G_(2)/M cell cycle arrest and apoptosis

Objective:To investigate the mechanism of p53-induced gene 3(PIG3)-regulation of radioresistance in human non-small cell lung cancer(NSCLC)cells,in order to explore new biomarkers and therapeutic targets to combat radioresistance and improve the 5-year survival rate.Methods:The PIG3 gene was knocked down in A549 cells using siRNA,and was overexpressed in H1299 cells using a PIG3 expression plasmid.After confirming PIG3 knockdown and overexpression through the Western blot analysis,the radiosensitivity,DNA damage,cell cycle distribution,and apoptosis in these cells were analyzed using colony formation assay,immunofluorescence staining forγH2AX,and flow cytometry,respectively.Results:PIG3 silencing markedly increased the radiosensitivity of NSCLC cells,with radiosensitization ratios of 1.12 and 1.25.Compared with the corresponding negative control,PIG3 knockdown significantly enhanced G2/M phase arrest(siNC:26.12±2.50,siPIG3#1:34.98±4.19,siPIG3#2:37.79±3.53,P<0.05),promoted radiation-induced apoptosis(siNC:14.61±1.85,siPIG3#1:17.26±1.14,siPIG3#2:20.70±2.04,P<0.05),and reduced the number ofγ-H2AX foci 0.5,1,and 2 h after radiation(P<0.05).Conversely,PIG3 overexpression markedly decreased the radiosensitivity of NSCLC cells,as evidenced by the reduction of G2/M phase arrest(NC:33.18±2.11 vs.PIG3:24.21±3.09,P<0.05)and apoptosis(NC:15.49±0.56 vs.PIG3:12.79±0.29,P<0.05),and increased DNA damage(P<0.05).Conclusions:PIG3 downregulation increases the radiosensitivity of NSCLC cells,and PIG3-upregulation leads to the progression in radioresistance.Therefore,PIG3 is a potential target for radiotherapy for NSCLC.

An Appreciation for the Rabbit Ladderlike Modeling of Radiation-induced Lung Injury with High-energy X-Ray

Background：To evaluate the utility of rabbit ladderlike model of radiation-induced lung injury （RILI） for the future investigation of computed tomography perfusion.Methods：A total of 72 New Zealand rabbits were randomly divided into two groups：36 rabbits in the test group were administered 25 Gy of single fractionated radiation to the whole lung of unilateral lung;36 rabbits in the control group were sham-radiated.All rabbits were subsequently sacrificed at 1,6,12,24,48,72 h,and 1,2,4,8,1 6,24 weeks after radiation,and then six specimens were extracted from the upper,middle and lower fields of the bilateral lungs.The pathological changes in these specimens were observed with light and electron microscopy;the expression of tumor necrosis factor-α （TNF-a） and transforming growth factor-βl （TGF-β1） in local lung tissue was detected by immunohistochemistry.Results：（1） Radiation-induced lung injury occurred in all rabbits in the test group.（2） Expression of TNF-a and TGF-β1 at 1 h and 48 h after radiation,demonstrated a statistically significant difference between the test and control groups （each P 〈 0.05）.（3） Evaluation by light microscopy demonstrated statistically significant differences between the two groups in the following parameters （each P 〈 0.05）：thickness of alveolar wall,density of pulmonary interstitium area （1 h after radiation）,number offibroblasts and fibrocytes in interstitium （24 h after radiation）.The test group metrics also correlated well with the time ofpostradiation.（4） Evaluation by electron microscopy demonstrated statistically significant differences in the relative amounts of collagen fibers at various time points postradiation in the test group （P 〈 0.005）,with no significant differences in the control group （P 〉 0.05）.At greater than 48 h postradiation the relative amount of collagen fibers in the test groups significantly differ from the control groups （each P 〈 0.05）,correlating well with the time postradiation （r =0.99318）.Conclusions：A consistent and reliable rabbit model of RILI can be generated in gradient using 25 Gy of high-energy X-ray,which can simulate the development and evolution of RILI.

Synergy of first-and second-sphere interactions in a covalent organic framework boosts highly selective platinum uptake

Platinum recovery from waste electrical and electronic equipment(WEEE) in highly acidic solutions is significant to the electronics industry and environmental remediation. However, the lack of ingenious design and synergetic coordination gives rise to unsatisfied PtCl_(4)^(2-)extraction capacities and selectivities in most previously reported adsorbents(e.g., polymeric and inorganic materials). Herein, we proposed a synergistic strategy that realizes highly selective PtCl_(4)^(2-)uptake through first-and second-sphere coordinations. The proof-of-concept imine-linked covalent organic framework(SCU-COF-3) was found to chelate Pt Cl42-via the direct N…Pt coordination and the synergistically interlaminar N–H…Cl hydrogen bonds, which was disclosed by the comprehensive analysis of extended X-ray adsorption fine structure(EXAFS) characterizations and density functional theory(DFT) calculations. The unique adsorption mechanism imparts a superior adsorption capacity(168.4 mg g-1)and extraordinary Pt(II) selectivity to SCU-COF-3 under static conditions. In addition, SCU-COF-3 exhibits an upgraded distribution coefficient of 1.62 × 10^(5)mL· g^(-1), one order of magnitude higher than those of reported natural adsorbents. Specifically, SCU-COF-3 can extract PtCl_(4)^(2- )quantitatively from a simulated acidic waste solution coexisting with other 12 competitive ions, suggesting its promising application in practical scenarios.

Effects of SWI/SNF complex on DNA damage repair in heterochromatin of embryonic fibroblast cells

Objective:To investigate the impact of SWI/SNF complex on heterochromatin DNA damage repair after exposure to X-ray irradiation,in order to explore the underlying mechanism.Methods:NIH3T3 and MRC5 cells were treated with 50 nmol/L siRNA targeting SWI/SNF complex subunits(BRM,ARID1A,BRG1 and SNF5),and YAP/TAZ.At 24 h after transfection,the cells were irradiated with 0.5 and 1 Gy of X-rays.At 20,60 and 240 min post-irradiation,γH2AX assay was performed to evaluate the radiation response in total or heterochromatin.Comet assay was used to determine the role of YAP/TAZ in DNA damage when the cells were irradiated with 4 Gy of X-rays.NIH3T3 were treated with 50 nmol/L siRNA targeting BRM/BRG1 and YAP/TAZ to determine their relationship on heterochromatin DNA damage repair.Results:In NIH3T3,SWI/SNF complex subunits(BRM,ARID1A and BRG1)knock-down increasedγH2AX in total and heterochromatin at 1 Gy 60 min post-irradiation(P<0.05),while SNF5 knock-down decreased heterochromatinγH2AX at 1 Gy 20 min post-irradiation(P<0.05).In MRC5,BRM and BRG1 knock-down increasedγH2AX in total and heterochromatin at 1 Gy 60 min post-irradiation(P<0.05).Inconsistently,ARID1A knockdown did not affect it,and SNF5 knock-down increased heterochromatinγH2AX at 1 Gy 60 min post-irradiation(P<0.05).Moreover,YAP/TAZ knock-down decreased heterochromatinγH2AX in NIH3T3 and MRC5(P<0.05).Meanwhile,YAP/TAZ knock-down decreased Tail Moment in comet assay at 4 Gy 60 min post-irradiation(P<0.05).BRM/BRG1 combining with YAP/TAZ knock-down significantly decreased heterochromatinγH2AX compared with single BRM/BRG1 knock-down at 0.5 Gy 60 min post-irradiation(P<0.05).Conclusions:The SWI/SNF complex subunits exhibited varying effects on DNA damage repair.BRM/BRG1 knockdown promotedγH2AX accumulation in heterochromatin through YAP/TAZ.This study provides a novel direction for DNA damage repair and sheds light on the role of SWI/SNF complex in response to DNA damage repair in heterochromatin.

Superior Iodine Uptake Capacity Enabled by an Open Metal-Sulfide Framework Composed of Three Types of Active Sites

Efficient adsorption of gaseous radioiodine is pivotal for the sustainable development of nuclear energy and the long-termradiation safety of the ecological system.However,state-of-the-art adsorbents(e.g.metal-organic frameworks and covalent-organic frameworks)currently under exploration suffer severely from limited adsorption capacity,especially under a real-world scenariowith extremely lowradioiodine concentration and elevated temperature.This mostly originates from the relatively weak sorption driving forces mainly determinedby the iodine-adsorbent interaction consistingof noncovalent interactionswith a small fraction of strong chemical bonding.Here,we document the discovery of an open metal-sulfide framework((NH_(4))_(2)(Sn_(3)S_(7)),donated as SCU-SnS)constructed by three different types of active sites as a superior iodine adsorbent.Benefiting from the ability of iodine for pre-enrichment into the framework by charge-balancing NH_(4)^(+)through N-H···I interaction,the efficient reduction of I^(2)affording I^(-)by S^(2-),and extremely high binding affinity between Sn_(4)^(+)and I^(-),SCU-SnS exhibit a record-breaking iodine adsorption capacity(2.12 g/g)under dynamic breakthrough conditions and the highest static capacity(6.12 g/g)among all reported inorganic adsorbents,both at 348 K.Its facile synthesis and low cost endow SCU-SnS with powerful application potential for the nuclear industry.

Approaches to Nanoparticle Labeling:A Review of Fluorescent,Radiological,and Metallic Techniques

Nanomaterials are widely used in commercial products,resulting in the release of nanoscale particles into the environment.This raises concerns about their potential exposure risks in complex biological matrices.Most attempts use engineered nanomaterials(ENMs)to mimic the biological behavior of nanoparticles in the environment,and labeling of ENMs by sensors is a commonly used approach for sensitive detection and tracking of ENMs in organisms.However,due to the distinct physicochemical properties of nanoparticles,different labeling approaches have been developed,each with varying applicability.In this Review,we summarize the three main types of labeling methods used for nanoparticles:fluorescent,radiological,and metallic labeling.We discuss their labeling mechanisms,efficiency,stability,target nanoparticles,and applicability in different organism models.Finally,we propose a labeling scheme for specific nanoparticles.Overall,this Review provides a comprehensive overview of the advances in nanoparticle labeling techniques and their potential applications in environmental and health studies.