Enhanced Exciton-to-Trion Conversion by Proton Irradiation of Atomically Thin WS2.

Defect engineering of van der Waals semiconductors has been demonstrated as an effective approach to manipulate the structural and functional characteristics toward dynamic device controls, yet correlations between physical properties with defect evolution remain underexplored. Using proton irradiation, we observe an enhanced exciton-to-trion conversion of the atomically thin WS2. The altered excitonic states are closely correlated with nanopore induced atomic displacement, W nanoclusters, and zigzag edge terminations, verified by scanning transmission electron microscopy, photoluminescence, and Raman spectroscopy. Density functional theory calculation suggests that nanopores facilitate formation of in-gap states that act as sinks for free electrons to couple with excitons. The ion energy loss simulation predicts a dominating electron ionization effect upon proton irradiation, providing further evidence on band perturbations and nanopore formation without destroying the overall crystallinity. This study provides a route in tuning the excitonic properties of van der Waals semiconductors using an irradiation-based defect engineering approach.

Bismuth Nanoparticles Increase Effectiveness of Proton Therapy of Ehrlich Carcinoma.

We studied the antitumor activity of the combined use of local proton irradiation in two modes (10 and 31 Gy) with preliminary intra-tumoral injection of two types of bismuth nanoparticles differing in surface coating: coated with the amphiphilic molecule Pluronic-F127 or Silane-PEG (5 kDa)-COOH polymer. Nanoparticles were used in doses of 0.75 and 1.5 mg/mouse. In two independent series on experimental tumor model (solid Ehrlich carcinoma), bismuth nanoparticles of both modifications injected directly into the tumor enhanced the antitumor effects of proton therapy. Moreover, the radiosensitizing effect of bismuth nanoparticles administered via this route increased with the increasing the doses of nanoparticles and the doses of radiation exposure. In our opinion, these promising data obtained for the first time extend the possibilities of treating malignant neoplasms.

Comparative Analysis of Behavioral Reactions and Morphological Changes in the Rat Brain After Exposure to Ionizing Radiation with Different Physical Characteristics.

The aim of this research was to study behavioral reactions and morphological changes in the brain of adult female Sprague Dawley rats after exposure to 170 MeV and 70 MeV protons and gamma radiation (60Co) at a dose of 1 Gy. The analysis of the behavioral reactions in the T-maze showed that exposure to ionizing radiation with different LETs led to an increase in number of repeated entries into the arms of the maze in the spontaneous alternation test. In the Open Field test a decrease in overall motor activity in the group of irradiated animals (70 MeV protons at the Bragg peak) was observed. A decrease in the number of standing positions was seen in all groups of irradiated animals. Morphological analysis showed the development of early amyloidosis, autolysis of the ependymal layer, an increase in the number of neurodegenerative changes in various structures of the brain, and the development of neuronal hypertrophy on the 30th day after irradiation in the cerebellum and hippocampal hilus. Exposure to protons at a dose of 1 Gy leads to the development of structural and functional disorders of the central nervous system of animals on the 30th day after irradiation. These data indicate a damage of short-term memory, a decrease in motor activity and exploratory behavior of animals. With an increase in LET, there is an increase in the number of amyloid plaques in the forebrain of rats, autolysis of the ependymal layer of the ventricles, and the development of dystrophic changes. Investigations of behavioral reactions and morphological changes in various parts of the brain of adult rats on the 30th day after influence of ionizing radiation with different physical characteristics at a dose of 1 Gy. Various negative patho-morphological and cognitive-behavioral changes observed.

Effects of Hot Pixels on Pixel Performance on Backside Illuminated Complementary Metal Oxide Semiconductor (CMOS) Image Sensors.

Effects of hot pixels on pixel performance in light and dark environments have been investigated in pinned photodiode 0.18 µm backside illuminated CMOS image sensors irradiated by 10 MeV protons. After exposure to protons, hot pixels and normal pixels are selected from the whole pixel array, and their influences on key parameters are analyzed. Experimental results show that radiation-induced hot pixels have a significant impact on pixel performance in dark environments, such as dark signal nonuniformity, long integration time, and random telegraph signal. Hot pixels are caused by defects with complex structures, i.e., cluster defects. Furthermore, the dark current activation energy result confirms that the defects causing the hot pixels have defect energy levels close to mid-gap.

The ATR Inhibitor VE-821 Enhances the Radiosensitivity and Suppresses DNA Repair Mechanisms of Human Chondrosarcoma Cells.

To overcome the resistance to radiotherapy in chondrosarcomas, the prevention of efficient DNA repair with an additional treatment was explored for particle beams as well as reference X-ray irradiation. The combined treatment with DNA repair inhibitors-with a focus on ATRi VE-821-and proton or carbon ions irradiation was investigated regarding cell viability, proliferation, cell cycle distribution, MAPK phosphorylation, and the expression of key DNA repair genes in two human chondrosarcoma cell lines. Pre-treatment with the PARPis Olaparib or Veliparib, the ATMi Ku-55933, and the ATRi VE-821 resulted in a dose-dependent reduction in viability, whereas VE-821 has the most efficient response. Quantification of γH2AX phosphorylation and protein expression of the DNA repair pathways showed a reduced regenerative capacity after irradiation. Furthermore, combined treatment with VE-821 and particle irradiation increased MAPK phosphorylation and the expression of apoptosis markers. At the gene expression and at the protein expression/phosphorylation level, we were able to demonstrate the preservation of DNA damage after combined treatment. The present data showed that the combined treatment with ATMi VE-821 increases the radiosensitivity of human chondrosarcoma cells in vitro and significantly suppresses efficient DNA repair mechanisms, thus improving the efficiency of radiotherapy.

Radiation Hardness Study of Single-Photon Avalanche Diode for Space and High Energy Physics Applications.

The radiation hardness of 180 nm complementary metal-oxide-semiconductor (CMOS) and 55 nm bipolar-CMOS-double-diffused MOS single-photon avalanche diodes (SPADs) is studied using 10 MeV and 100 MeV protons up to a displacement damage dose of 1 PeV/g. It is found that the dark count rate (DCR) levels are dependent on the number and the type of defects created. A new stepwise increase in the DCR is presented. Afterpulsing was found to be a significant contributor to the observed DCR increase. A new model for DCR increase prediction is proposed considering afterpulsing. Most of the samples under test retain reasonable DCR levels after irradiation, showing high tolerance to ionizing and displacement damage caused by protons. Following irradiation, self-healing was observed at room temperature. Furthermore, high-temperature annealing shows potential for accelerating recovery. Overall, the results show the suitability of SPADs as optical detectors for long-term space missions or as detectors for high-energy particles.

Cellular and Molecular Biological Alterations after Photon, Proton, and Carbon Ions Irradiation in Human Chondrosarcoma Cells Linked with High-Quality Physics Data.

Chondrosarcomas are particularly difficult to treat due to their resistance to chemotherapy and radiotherapy. However, particle therapy can enhance local control and patient survival rates. To improve our understanding of the basic cellular radiation response, as a function of dose and linear energy transfer (LET), we developed a novel water phantom-based setup for cell culture experiments and characterized it dosimetrically. In a direct comparison, human chondrosarcoma cell lines were analyzed with regard to their viability, cell proliferation, cell cycle, and DNA repair behavior after irradiation with X-ray, proton, and carbon ions. Our results clearly showed that cell viability and proliferation were inhibited according to the increasing ionization density, i.e., LET, of the irradiation modes. Furthermore, a prominent G2/M arrest was shown. Gene expression profiling proved the upregulation of the senescence genes CDKN1A (p21), CDKN2A (p16NK4a), BMI1, and FOXO4 after particle irradiation. Both proton or C-ion irradiation caused a positive regulation of the repair genes ATM, NBN, ATXR, and XPC, and a highly significant increase in XRCC1/2/3, ERCC1, XPC, and PCNA expression, with C-ions appearing to activate DNA repair mechanisms more effectively. The link between the physical data and the cellular responses is an important contribution to the improvement of the treatment system.

Proton irradiation effects on mechanochemically synthesized and flash-evaporated hybrid organic-inorganic lead halide perovskites.

A hybrid organic-inorganic halide perovskite is a promising material for developing efficient solar cell devices, with potential applications in space science. In this study, we synthesized methylammonium lead iodide (MAPbI3) perovskites via two methods: mechanochemical synthesis and flash evaporation. We irradiated these perovskites with highly energetic 10 MeV proton-beam doses of 1011, 1012, 1013, and 4 × 1013protons cm-2and examined the proton irradiation effects on the physical properties of MAPbI3perovskites. The physical properties of the mechanochemically synthesized MAPbI3perovskites were not considerably affected after proton irradiation. However, the flash-evaporated MAPbI3perovskites showed a new peak in x-ray diffraction and an increased fluorescence lifetime in time-resolved photoluminescence under high-dose conditions, indicating considerable changes in their physical properties. This difference in behavior between MAPbI3perovskites synthesized via the abovementioned two methods may be attributed to differences in radiation hardness associated with the bonding strength of the constituents, particularly Pb-I bonds. Our study will help to understand the radiation effect of proton beams on organometallic halide perovskite materials.

Ductilization of Nanoporous Ceramics by Crystallinity Control.

Synthesizing ceramic materials with a significant amount of deformability is one of the most important engineering pursuits. In this study, we demonstrate the emergence of metal-like plasticity through the crystallinity control in the monolithic zirconia with the vertically aligned honeycomb-like periodic nanopore structures fabricated using the anodizing technique. The crystalline orders of the nanoporous zirconia films vary between monoclinic, tetragonal, and amorphous phases after the heat treatment and/or proton irradiation, whereas the vertical pore structures are maintained. The micropillar compression tests on those samples reveal a large amount of plasticity, more than 20% of total stains, in the as-anodized and proton-irradiated samples, both of which contain the amorphous phase. In contrast, the fully crystallized zirconia that resulted from annealing at 500 °C shows the brittle failure, the typical characteristic of conventional ceramic foams. These results offer a new opportunity for the nanoporous ceramic materials to be used in various applications, benefited from the tunable structural stability.

Proton Beam Induced Modification of Luminescence Properties of Polystyrene/Al2O3 Polymer Nanocomposites.

Polystyrene polymer (PS)/Al2O3 nanocomposite films were synthesized from PS:Al2O3 (1-x):x mixtures (x = 3 wt%) via solution casting method. These nanocomposite films were exposed to 5 MeV proton beam of different fluences. The proton beam induced changes in optical and luminescence properties of PS and PS:Al2O3 films have been investigated using FTIR, UV-visible, Photoluminescence and thermoluminescence studies. FTIR studies concede reduction in the peak intensity due to doping of Al2O3 and proton irradiation. The UV-visible spectra show shifting of absorption edge with increasing fluence. This can be attributed to creation of conjugated system of bonds. The band gap of PS and 3 wt% Al2O3 doped PS is observed to be 4.38 eV and 4.34 eV, respectively, whereas the band gaps of proton irradiated 3 wt% Al2O3 doped PS films are found to be 4.28 eV and 4.23 eV at the fluences of 1 × 1012 ions/cm2 and 1 × 1013 ions/cm2, respectively. The photoluminescence emission spectra show three peaks, wavelength at 411 nm, 435 nm and 462 nm corresponding to the PS in violet-blue region when excited with near UV wavelength of 380 nm. The intensity of emission peaks was found to increase with increasing fluence. The thermoluminescence curves of PS/Al2O3 were analysed using glow curve deconvolution method (GCD). The increase in TL peak intensity of the glow curve was observed as fluence increase.

Defining Processing Times for Accelerator Produced 225Ac and Other Isotopes from Proton Irradiated Thorium.

During the purification of radioisotopes, decay periods or time dependent purification steps may be required to achieve a certain level of radiopurity in the final product. Actinum-225 (Ac-225), Silver-111 (Ag-111), Astatine-211 (At-211), Ruthenium-105 (Ru-105), and Rhodium-105 (Rh-105) are produced in a high energy proton irradiated thorium target. Experimentally measured cross sections, along with MCNP6-generated cross sections, were used to determine the quantities of Ac-225, Ag-111, At-211, Ru-105, Rh-105, and other co-produced radioactive impurities produced in a proton irradiated thorium target at Brookhaven Linac Isotope Producer (BLIP). Ac-225 and Ag-111 can be produced with high radiopurity by the proton irradiation of a thorium target at BLIP.

Diffusion-weighted MRI treatment monitoring of primary hypofractionated proton and carbon ion prostate cancer irradiation using raster scan technique.

PURPOSE: To investigate parametric changes in the apparent diffusion coefficient (ADC) at multiple timepoints during and after completion of primary proton and carbon ion irradiation of prostate cancer (PCa) as compared with normal-appearing prostate parenchyma. MATERIALS AND METHODS: In all, 92 patients with histologically confirmed PCa received either proton or carbon ion hypofractionated radiotherapy (RT). All were prospectively evaluated with diffusion-weighted magnetic resonance imaging (DWI-MRI) at five timepoints: baseline, day 10 during therapy and 6 weeks, 6 months, and 18 months after treatment. Linear mixed models (LMM) were used to evaluate the effects of radiation, antihormonal therapy, time, and type of particle irradiation on manual ADC measurements. ADC differences related to prostate-specific antigen (PSA) relapse according to PSA thresholds and to Vancouver rules and Phoenix criteria were examined using LMM and unpaired Student's t-test. RESULTS: A measurable and continuous increase of tumor ADC measurements from baseline (1.194 × 10-3 mm2 /s) during (1.350 × 10-3 mm2 /s, day 10, P = 0.006) and after treatment (1.355/1.430/1.490 × 10-3 mm2 /s, week 6 / month 6 / month 18, P = 0.001/<0.001/<0.001) was found. ADC values of normal-appearing control tissue remained unchanged. Androgen deprivation (P ≥ 0.320), different PSA thresholds (P = 0.634), and PSA relapse criteria according to Vancouver rules (P ≥ 0.776) had no effect. A weak association between 18-month measurements and Phoenix criteria (P = 0.046) was found. CONCLUSION: ADC parametric changes were distinct in tumor tissue, highlighting the ability of diffusion MRI to evaluate different aspects of the microscopic pathophysiology. Although promising, their use as noninvasive imaging biomarkers requires further validation. LEVEL OF EVIDENCE: 1 Technical Efficacy: Stage 1 J. MAGN. RESON. IMAGING 2017;46:850-860.

Method of locating the visual axis objectively.

PURPOSE: To locate the visual axis of the eye objectively. METHOD: Based on three-beam scanning laser radar microprofilometry, a technique is proposed to objectively locate the visual axis of the eye. The laser beam consists of three components, two of them being shifted relatively to the central one by differing frequencies, filtered in spatially orthogonal directions. The centre of the foveola is defined as the crossing of steepest inclinations determined in the specific beam positions on the trajectory of scanning. The position of the cornea crossing by the visual axis is designated by the optical axis of the measuring instrument. RESULTS: Nanometer sensitivity was confirmed in a preliminary test. CONCLUSIONS: The proposed technique can be incorporated into any clinical wavefront sensing instrument and can be used for centration-sensitive vision correction, as well as for other instances when knowing the exact position of the fovea is important.

Proton irradiation induces persistent and tissue-specific DNA methylation changes in the left ventricle and hippocampus.

BACKGROUND: Proton irradiation poses a potential hazard to astronauts during and following a mission, with post-mitotic cells at most risk because they cannot dilute resultant epigenetic changes via cell division. Persistent epigenetic changes that result from environmental exposures include gains or losses of DNA methylation of cytosine, which can impact gene expression. In the present study, we compared the long-term epigenetic effects of whole body proton irradiation in the mouse hippocampus and left ventricle. We used an unbiased genome-wide DNA methylation study, involving ChIP-seq with antibodies to 5-methylcytosine (5mC) and 5-hydroxymethylcytosine (5hmC) to identify DNA regions in which methylation levels have changed 22 weeks after a single exposure to proton irradiation. We used DIP-Seq to profile changes in genome-wide DNA methylation and hydroxymethylation following proton irradiation. In addition, we used published RNAseq data to assess whether differentially methylated regions were linked to changes in gene expression. RESULTS: The DNA methylation data showed tissue-dependent effects of proton irradiation and revealed significant major pathway changes in response to irradiation that are related to known pathophysiologic processes. Many regions affected in the ventricle mapped to genes involved in cardiovascular function pathways, whereas many regions affected in the hippocampus mapped to genes involved in neuronal functions. In the ventricle, increases in 5hmC were associated with decreases in 5mC. We also observed spatial overlap for regions where both epigenetic marks decreased in the ventricle. In hippocampus, increases in 5hmC were most significantly correlated (spatially) with regions that had increased 5mC, suggesting that deposition of hippocampal 5mC and 5hmC may be mechanistically coupled. CONCLUSIONS: The results demonstrate long-term changes in DNA methylation patterns following a single proton irradiation, that these changes are tissue specific, and that they map to pathways consistent with tissue specific responses to proton irradiation. Further, the results suggest novel relationships between changes in 5mC and 5hmC.

Nuclear excitation functions of proton-induced reactions (Ep = 35 - 90 MeV) from Fe, Cu, and Al.

Fe, Cu, and Al stacked foils were irradiated by 90 MeV protons at the Los Alamos Neutron Science Center's Isotope Production Facility to measure nuclear cross sections for the production of medically relevant isotopes, such as 52gMn, 54Mn, 48Cr, 55Co, 58mCo and 57Ni. The decay of radioactive isotopes produced during irradiation was monitored using high-purity germanium gamma spectroscopy over the months following irradiation. Proton fluence was determined using the natAl(p,x)22Na, natCu(p,x)62Zn natCu(p,x)65Zn, and natCu(p,x)56Co monitor reactions. Calculated cross sections were compared against literature values and theoretical TALYS predictions. Notably this work includes the first reported independent cross section measurements of natCu(p,x)58mCo and natCu(p,x)58gCo.

Evaluation of low-dose proton beam radiation efficiency in MIA PaCa-2 pancreatic cancer cell line vitality and H2AX formation.

BACKGROUND AND OBJECTIVE: The aim of this study was to evaluate the efficiency of proton beam irradiation in pancreatic cancer cell line MIA PaCa-2 and its role in the cell cycle, apoptosis, and formation of histone γH2AX in different reparation times (72-h follow-up). MATERIAL AND METHODS: The MIA PaCa-2 pancreatic carcinoma cell line was irradiated with 1.6-Gy proton beam. After irradiation, cell viability was measured colorimetrically, and the cell cycle, apoptosis, and γH2AX expression were evaluated on a FACScan cytometer. RESULTS: Low-dose proton beam irradiation had an effect on the MIA PaCa-2 tumor cell line already 1h after exposure, but maximal lethality was reached after 72h postirradiation with a cell viability rate of 24%. The cell cycle went into partial G1/0 arrest, and was released after 72h. The expression of γH2AX was strong and its levels were significantly elevated as late as 48h post radiation. The apoptosis levels increased with post radiation incubation time to reach 79% after 72h. CONCLUSIONS: Our data demonstrate that low-doses proton beam irradiation had an effect on MIA PaCa-2 pancreatic carcinoma cell line. Full extent of irradiation had an impact only 24h postirradiation, triggering DNA arrested cell cycle in G1/0 phase. Formed DNA DSBs were found to be repaired via the NHEJ pathway mechanism within 72h. Unsuccessful repaired DSBs induced apoptotic cell death. After 72h reparation processes were completed, and cell cycle was released from arrest in G1/0 phase.

Proton-fluence dependent magnetic properties of exfoliable quasi-2D van der Waals Cr2Si2Te6magnet.

The discovery of long-range magnetic ordering in atomically thin materials catapulted the van der Waals (vdW) family of compounds into an unprecedented popularity, leading to potentially important technological applications in magnetic storage and magneto-transport devices, as well as photoelectric sensors. With the potential for the use of vdW materials in space exploration technologies it is critical to understand how the properties of such materials are affected by ionizing proton irradiation. Owing to their robust intra-layer stability and sensitivity to external perturbations, these materials also provide excellent opportunities for studying proton irradiation as a non-destructive tool for controlling their magnetic properties. Specifically, the exfoliable Cr2Si2Te6(CST) is a ferromagnetic semiconductor with the Curie temperature (TC) of ∼32 K. Here, we have investigated the magnetic properties of CST upon proton irradiation as a function of fluence (1 × 1015, 5 × 1015, 1 × 1016, 5 × 1016, and 1 × 1018H+/cm-2) by employing variable-temperature, variable-field magnetization measurements, and detail how the magnetization, magnetic anisotropy vary as a function of proton fluence across the magnetic phase transition. While theTCremains constant as a function of proton fluence, we observed that the saturation magnetization and magnetic anisotropy diverge at the proton fluence of 5 × 1016H+/cm-2, which is prominent in the ferromagnetic phase, in particular.This work demonstrates that proton irradiation is a feasible method for modifying the magnetic properties and local magnetic interactions of vdWs crystals, which represents a significant step forward in the design of future spintronic and magneto-electronic applications.

Characterization of fully-evaporated perovskite solar cells and photodetectors under high-intensity pulsed proton irradiation.

This study investigates the impact of proton irradiation on perovskite devices fabricated fully through vacuum deposition. Exposure to irradiation induces changes in both electrical and optical properties. The analysis reveals that the main factors influencing the observed performance changes in solar cells are a significant reduction in shunt resistance and a minor increase in series resistance, with minimal alterations in recombination dynamics. Remarkably, the devices maintain promising photodetector characteristics both before and after proton irradiation, particularly in a self-powered mode without a reverse bias. These findings provide valuable insights into the resilience of vacuum-deposited perovskite devices against ionizing radiation, highlighting their potential for applications in radiation-prone environments, such as the nuclear industry or space exploration.

Optical Thin Films in Space Environment: Investigation of Proton Irradiation Damage.

The present work reports a systematic study of the potential degradation of metals and dielectric thin films in different space environments. The mono- and bilayers selected are made of materials commonly used for the realization of optical components, such as reflective mirrors or building blocks of interferential filters. More than 400 samples were fabricated and irradiated with protons at different energies on ground-based facilities. The fluences were selected as a result of simulations of the doses delivered within a long-term space mission considering different orbits (Sun close, Jovian, and Geostationary orbits). In order to stress the samples at different depths and layer interfaces, experiments were carried out with a range of proton energies within 1 and 10 MeV values. An estimate of a safe maximum fluence has been provided for each type of sample at each energy. The damage mechanism, when present, has been investigated with different optical and structural techniques.

Proton induced activation studies in the carbon steel composites.

The number of accelerator installations has increased significantly in the last decade and requirements are consistently increasing. In these facilities neutrons and high energy charge particle induced reactions are possible with the metallic enclosures made up of natural Fe or steel composites used as structural components or shielding materials. Present study aims to generate a dose rate profile of the induced activations and quantify the induced radionuclide concentrations in the low carbon steel composites. A comparison of the radionuclide concentrations generated in the metallic Fe and SS-304 composite is also presented for a judicious material selection to minimise the radiation concerns.