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Based on traditional alpha radiation detection technology for detecting nearby distances，using the principle of alpha radiation particles inducing air fluorescence，remote measurement of alpha radiation activity can be achieved. By establishing a model for alpha activity measurement based on point sources，and using photomultiplier tubes to measure the photons induced by alpha radiation，an empirical formula relating the source activity to the net photon counting rate of the photomultiplier tube was developed. The study investigated the factors influencing fluorescence conversion efficiency by changing radiation sources of different energies，altering media，and varying pressures. The results showed that the fluorescence conversion efficiency of 241Am source in air to be 3.24×10−6 -7.83×10−6. Sources with higher energy exhibit higher fluorescence conversion efficiency. Pressure shows a linear positive correlation with fluorescence conversion efficiency. Among air，nitrogen，and argon，argon gas was found to effectively enhance the fluorescence efficiency The empirical formula can be used for calculating the activity of radioactive sources. Investigating the factors influencing fluorescence conversion efficiency provides data references for improving the efficiency and accuracy of remote α radiation detection.

Abstract Astronauts travelling in space will be exposed to mixed beams of particle radiation and photons. Exposure limits that correspond to defined cancer risk are calculated by multiplying absorbed doses by a radiation-type specific quality factor that reflects the biological effectiveness of the particle without considering possible interaction with photons. We have shown previously that alpha radiation and X-rays may interact resulting in synergistic DNA damage responses in human peripheral blood lymphocytes but the level of intra-individual variability was high. In order to assess the variability and validate the synergism, blood from two male donors was drawn at 9 time points during 3 seasons of the year and exposed to 0–2 Gy of X-rays, alpha particles or 1:1 mixture of both (half the dose each). DNA damage response was quantified by chromosomal aberrations and by mRNA levels of 3 radiation-responsive genes FDXR, CDKN1A and MDM2 measured 24 h post exposure. The quality of response in terms of differential expression of alternative transcripts was assessed by using two primer pairs per gene. A consistently higher than expected effect of mixed beams was found in both donors for chromosomal aberrations and gene expression with some seasonal variability for the latter. No synergy was detected for alternative transcription.

Astronauts travelling in space will be exposed to mixed beams of particle radiation and photons. Exposure limits that correspond to defined cancer risk are calculated by multiplying absorbed doses by a radiation-type specific quality factor that reflects the biological effectiveness of the particle without considering possible interaction with photons. We have shown previously that alpha radiation and X-rays may interact resulting in synergistic DNA damage responses in human peripheral blood lymphocytes but the level of intra-individual variability was high. In order to assess the variability and validate the synergism, blood from two male donors was drawn at 9 time points during 3 seasons of the year and exposed to 0–2 Gy of X-rays, alpha particles or 1:1 mixture of both (half the dose each). DNA damage response was quantified by chromosomal aberrations and by mRNA levels of 3 radiation-responsive genes FDXR, CDKN1A and MDM2 measured 24 h post exposure. The quality of response in terms of differential expression of alternative transcripts was assessed by using two primer pairs per gene. A consistently higher than expected effect of mixed beams was found in both donors for chromosomal aberrations and gene expression with some seasonal variability for the latter. No synergy was detected for alternative transcription. [ABSTRACT FROM AUTHOR]

Irradiated epoxy thick films are important for optical properties and may be used in many optical applications. This study aims to evaluate the effect of alpha irradiation on the optical and structural properties of epoxy thick films. Epoxy resin films were prepared by mixing epoxy resin (A) with hardener (B) at a mixing ratio of 3:1. Thus, specific thick films with thicknesses of 0.7 mm, 0.8 mm and 1 mm were manufactured. Using visible and ultraviolet spectroscopy is one of the most important methods for studying polymers band gaps and electrical properties. The absorbance and transmittance spectra were used to investigate the optical properties of epoxy coatings of different thicknesses over a wavelength range of 300 nm-900 nm. Optical properties, such as absorption coefficient, refractive index, extinction coefficient, real dielectric constant, imaginary dielectric and optical band gap, were measured. The results show that the epoxy thick films have good optical transparency in the low-wavelength region. The results showed that increasing the thickness of the resin films decreased the optical energy gap and refractive index while increasing the absorption and extinction coefficients. In comparison, the effect of irradiation on an epoxy film of thickness 1 mm leads to an increase in the transmittance spectrum and energy gap and a decrease in the optical constants. The Fourier-transform infrared (FTIR) spectrum of the films was examined and showed the types of chemical bonds of the epoxy films before and after irradiation. [ABSTRACT FROM AUTHOR]

Recycled agricultural wastes are being used in the building and construction sector as cement additives as a result of the environmental impact of cement production. Agricultural byproducts, on the other hand, are naturally occurring radioactive elements that could expose people and the environment to radiation dangers. As a result, this research assesses the radiological characteristics of agricultural byproducts utilized as building and construction materials with special attention to their activity concentrations (226Ra series, 232Th series, and 40K isotopes). The levels of alpha and gamma radiation were measured via the activity concentrations. Alpha and gamma radiation (output data) and activity concentrations (input data) were trained using artificial intelligence techniques, and the model's effectiveness was evaluated. In terms of the metrics of the model, the linear regression algorithm outperformed other algorithms. Finally, none of the agricultural byproducts studied are at risk from alpha and gamma radiation. Thus, the findings provide the reference information needed to build a framework for radiation monitoring of surveyed agricultural byproducts.

Different alpha exposure setups are often used to study the relation between biological responses and LET. This study aimed to estimate the dose heterogeneity and uncertainty in four exposure setups using Geant4 and PARTRAC codes. The importance of the irradiation system characteristics was shown in the context of reporting experimental results, especially in radiobiological studies at the molecular level. Geant4 was used to estimate the dose distributions in cells grown on a disk exposed to alpha particles penetrating from above and below. The latter setup was simulated without and with a collimator. PARTRAC was used for the validation of Geant4 simulations based on distributions of the number of alpha particles penetrating a round nucleus and the deposited energy. The LET distributions obtained for simulated setups excluding the collimator were wide and non-Gaussian. Using a collimator resulted in a Gaussian LET distribution, but strongly reduced dose rate and dose homogeneity. Comparison between PARTRAC and Geant4 calculations for the cell nucleus exposed to alpha radiation showed an excellent agreement. The interpretation of results from radiobiological experiments with alpha particles should always cover the characteristics of the experimental setup, which can be done precisely with computational methods. [ABSTRACT FROM AUTHOR]

Radon is a carcinogenic factor, but the effects of the potential carcinogenicity of radon progeny on the human body during the prenatal period have not yet been explored. Based on data regarding the half-lives of radon-222 and radon-220 and their progeny, this paper considers their potential effects on the human body in the prenatal period. Radon-220 represents a small fraction of the total radon concentration in the air, but the dose of radon-220 progeny may have a significant effect in the prenatal period, as the precursors of polonium-212 exhibit substantially longer half-lives than the corresponding precursors of polonium-214. Theoretically, it is possible that radon-220 decay products, particularly polonium-212, are the predominant emitters of alpha particles in the prenatal period. Studies aiming to establish a relationship between exposure to radon during pregnancy and the subsequently observed incidence of childhood neoplasms should consider this observation. [ABSTRACT FROM AUTHOR]

The present work describes the procedure for testing the suitability of a polyethylene terephthalate film (after irradiation with heavy ions it is widely used in various fields) as an alpha-track detector. The test was carried out in order to determine the prospects for the use of this film in studies evaluating the indoor and outdoor radon concentrations. The study was conducted using a radionuclide source of alpha particles Am-241. Irradiated film samples were chemically treated. In order to further compare the results, unirradiated film samples were also chemically etched under the same conditions. To determine the presence of tracks, compare and analyze their parameters, all samples were examined using a scanning electron microscope. SEM images of the investigated samples are shown. The results obtained showed the unsuitability of using these films for registration of alpha particles. Currently, studies of the indoor and outdoor radon concentrations are being carried out using solid-state nuclear detector LR-115 based on cellulose nitrate.

This study focuses on a CMOS sensing system for Radon and alpha radiation, which is based on a semiconductor device that is integrated monolithically on a single chip with the Readout Circuitry, thus allowing fabrication of a low-power and low-cost sensing system. The new sensor is based on a new mosaic design of an array of Floating Gate non-volatile memory-like transistors, which are implemented in a standard CMOS technology, with a single polysilicon layer. The transistors are electrically combined in parallel and are operated at subthreshold, thus achieving very high sensitivity and reduced noise. The sensing system’s architecture and design is presented, along with key operation concepts, characterization, and analysis results. Alpha and radon exposure results are compared to commercial radon detectors. The new sensor, dubbed TODOS-Radon sensor, measures continuously, is battery operated and insensitive to humidity.

Radon is a carcinogenic factor, but the effects of the potential carcinogenicity of radon progeny on the human body during the prenatal period have not yet been explored. Based on data regarding the half-lives of radon-222 and radon-220 and their progeny, this paper considers their potential effects on the human body in the prenatal period. Radon-220 represents a small fraction of the total radon concentration in the air, but the dose of radon-220 progeny may have a significant effect in the prenatal period, as the precursors of polonium-212 exhibit substantially longer half-lives than the corresponding precursors of polonium-214. Theoretically, it is possible that radon-220 decay products, particularly polonium-212, are the predominant emitters of alpha particles in the prenatal period. Studies aiming to establish a relationship between exposure to radon during pregnancy and the subsequently observed incidence of childhood neoplasms should consider this observation.

The paper presents the results of the analysis of long-term series of monitoring data on the radon flux density. They were produced using a accumulation chamber of our own design, which allows, in terms of the readings of alpha radiation counters, to obtain the values of the radon flux density. The main results and the most illustrative examples of the behavior of the investigated characteristic of radon are present in the work. As a result, conclusions were drawn about the features of radon release rate from the soil into the surface atmosphere at different time scales and under different meteorological conditions, which can be used in the future to monitor the radon flux density using ionizing radiation detectors, and is also fundamental for the development new models.

The optical properties of Makrofol samples are investigated under various fluences of alpha exposure (2 MeV at 5 × 10 2 , 10 3 , 5 × 10 3 , 10 4 , 5 × 10 4 , 10 5 , 5 × 10 5 and 10 6 alphas.cm2 alongside the unirradiated ones (pristine). Several analyses, including UV–visible, diffused reflectance spectroscopy (DRS), photoluminescence (PL), Fourier transform infrared/attenuated total reflectance (FTIR-ATR), X-ray photoelectron spectroscopy (XPS) and sessile drop technique, are carried out to reveal the subsequent variations in the optical features of the irradiated polymer foils. The optical transmittance of the irradiated samples notably increases against the pristine ones, while it undergoes a+ plateau over various fluences. Additionally, the scattering events are more prominent in pristine samples over UV (240–400 nm) and IR (900–1040 nm) compared to the irradiated ones. While there are negligible physical alterations on the polymer surface, the photoluminescence emission gradually decreases with increasing alpha fluences in the irradiated samples mainly due to the reduction in the population of the aromatic rings. The latter is also verified by means of the surface chemical analyses such as XPS, FTIR-ATR and sessile drop/contact angle measurements. XPS reveals that the alpha particles give rise to the successive scissions of C–C and C O bonds and the consequent recombination events in the form of C–O bonds, evidenced by the changes in their abundance percentages. Concurrently, the surface hydrophilicity initially elevates up to a certain fluence and then reduces at higher fluences, indicating a couple of competitive mechanisms are involved in the context of the interactions of the alpha particles with the Makrofol polycarbonate (PC). • The optical properties of Makrofol samples are investigated under alpha exposure. • The variations in the optical features of the irradiated polymer foils are studied. • UV–Visible reveals a drastic increase of spectral transmission in favor of irradiated PC. • XPS spectra demonstrate a reduction of carbonyl abundance in terms alpha fluences. • The contact angle levels down against alpha fluence. [ABSTRACT FROM AUTHOR]

Introduction : Radon (Rn) is a chemically inert gas with no odor, color, and taste. It is created from the decay of uranium in the soil and can penetrate the building through the interiors. As a result, Rn can enter the human body with the release of alpha radiation along with airborne dust and cause chronic illnesses such as lung cancer and multiple sclerosis. The Multiple Sclerosis disease, as a complex multifactor disease, is the most common widespread neurotic disorder among the young people. The purpose of this study was to collect and review the past studies published in this field since 1996. Materials and Methods: In this review, the related articles were searched and studied using key words such as "Radon, Action, Thoron, MS, MS Disseminated, and Sclerosis" using the PRISMA statement. Results: After reviewing the studies, several effective factors in the prevalence of MS were identified. Some of these factors were a result of the exposure to high levels of radon gas. Penetrations from the building cracks of floor, soil bed, and dwelling materials as well as the water resources are among the most important sources of Rn. Conclusion: According to the results, the amount of Rn and it’s daughters in the environment are recognized as the risk factors for the MS prevalence.

Remote detection of alpha radiation by optical means is a widely accepted alternative to the more traditional detection methods that typically rely on direct contact with the radiation itself. Optical detection operates by collecting the light, the radioluminescence that is produced when alpha particles are being stopped in a medium. Each medium creates radioluminescence with a distinct spectral pattern and intensity. To properly design the detection optics, the radioluminescence's spectral shape and the number of photons generated per alpha event have to be known. Those properties are well known for some stopping media like air, and remote detection has been successfully implemented. However, the radioluminescence properties for the stopping media nitric acid and water are not well known, which prevents the application of the technique in relevant areas like spent nuclear fuel processing. In this contribution, we determine the light yield of alpha particles emitted by 241Am dissolved in a well characterized weak nitric acid solution. It was found to be 0.31 ± 0.007 photons per alpha event. [ABSTRACT FROM AUTHOR]

• Using 211At to study α radiation's impact on Th(Ⅳ) and U(Ⅵ) extraction by TiAP. • The effects of α and γ radiation on Th(Ⅳ) and U(Ⅵ) extraction by TiAP are similar. • The modified extraction behavior mainly stems from the radiolysis product HDiAP. Tri- iso -amyl phosphate (TiAP) is considered as a promising alternative to tri-butyl phosphate (TBP) for the reprocessing of spent nuclear fuels. However, how radiation alters the extraction properties of the extractant and what is the mechanism causing this phenomenon has not been determined, especially under alpha radiation. This study investigates the extraction of Th(IV) and U(VI) by 36 % TiAP - n-dodecane (n-DD) after exposure to alpha radiation from 211At, and compared with gamma radiation at an equivalent dose. The results indicate that the effect of alpha radiation on TiAP has a similar trend to gamma radiation, and the concentration of HNO 3 plays a crucial role in the extraction of Th(IV) and U(VI) by irradiated TiAP. Even at low doses (10 kGy), radiolysis of the extractants remains observable. In addition, the stripping of extracted Th(Ⅳ) from the irradiated organic phase is more difficult than U(VI), which is consistent with previous investigations on gamma radiation. Theoretical calculations suggest that the [DiAP]− ligand formed by HDiAP as a radiolysis product of TiAP is closely related to the strong extraction ability of Th(Ⅳ) in the extraction system after radiation at low acidity, since the [DiAP]− ligand exhibits a higher coordination ability than TiAP and HDiAP, especially with Th(IV). The outcomes of this work not only provide a procedure for exploring the alpha radiation of extractions based on a short half-life nuclide, but also demonstrate the connection between the radiolysis products and the change of extraction performance, which are helpful for us to gain a better understanding of the potential of TiAP to be used in the separation and purification of Th(Ⅳ) and U(Ⅵ) in reprocessing plants. [ABSTRACT FROM AUTHOR]

There is still no consensus regarding the ultimate cause of the famous 3–4-year population cycles of lemmings. According to the plant stress hypothesis, herbivore population peaks are caused by stress factors that force plants to reallocate stored defensive proteins to transportable and easily digestible N-compounds. One possible plant stress factor is ionization caused by exhalation of the radioactive noble gas radon, which is enhanced after spring tides, i.e., tides at new or full Moon. I hypothesized that increased ionization caused by radon accumulation in the subnivean space after peak spring tides, which occur close to perihelion (31 December–05 January, when the Earth–Sun distance is shortest), and at 3.8-year intervals, results in increased protein digestibility of mosses, which are important food for lemmings. Population outbreaks of Norway lemming Lemmus lemmus occurred two years after peak spring tides during 1871–1910, when also perigee (the time when the Earth–Moon distance is shortest) coincided with spring tides and perihelion. Thereafter this relationship weakened, and lemming peaks became less pronounced and more related to plant seed indices. As we have now entered a new 30-year period with coincidence of spring tide, perihelion and perigee, I predict more regular and pronounced lemming outbreaks in the next decades, unless radon accumulation is prevented by frequent lack of a stable snow cover due to global warming. • Population cycles of lemmings follow the 3.8-year cycle in peak spring tides close to perihelion, i.e., peak spring tides. • Radon exhalation is enhanced at peak spring tides. • Ionization caused by radon accumulation beneath the snowpack is a possible plant stress factor that favor lemmings. • Populations of Norway lemming peaked after peak spring tides, in particular when peak spring tides coincided with perigee. [ABSTRACT FROM AUTHOR]

Introduction: Smokers and non-smokers are at the risk of developing lung cancer when exposed to alpha rays as a result of the relatively low levels of radium and radon that may be present in different tobacco species. There is a great interest in studies and research on the radionuclides in narghile tobacco emitting alpha particles to know the relationship between smoking narghile and cancer, especially lung cancer. Material and Methods: This study was conducted to measure the alpha rays in 30 different narghile samples in the markets of Iraq. Radon concentrations were determined using time-tested passive radio doses containing CR-39 solid-state pathway detectors. Results: The radon concentrations in samples varied from27.44±4.4 Bq/m3 to 214.61±18.1 Bq/m3 with the mean value of 65.60±41.04 Bq/m3. The annual effective dose varies from 0.69±0.09 mSv/y to 5.41±2.20 mSv/y with the mean value of 1.64±1.03 mSv/y. The lung cancer risk cases per year vary from 12.46±2.11 to 97.45±7.34 with the mean value of 29.77±18.63 per million people. The effective radium content ranged between 0.054Bq/kg and 0.425Bq/kg with the mean value of 0.131 of Bq/kg, while the radon emission values for the mass and surface units ranged from 0.410 to 3.212 with the mean of 0.996 mBq/kg.h and 9.040 to 70.703 with the mean value of 21.943mBq/m2.h, respectively. Conclusion: The results of the study showed that alpha rays are within the internationally accepted limits and presently do not pose a threat to human health and life in terms of the radiation activity of the investigated narghile tobacco species in this study.

Uncertainties regarding the magnitude of health effects following exposure to low doses of ionizing radiation remain a matter of concern both for professionals and for the public. There is consensus within the international radiation research community that more research is required on biological effects of radiation doses below 100 mGy applied at low dose rates. Moreover, there is a demand for increasing education and training of future radiation researchers and regulators. Research, education and training is primarily carried out at universities but university-based radiation research is often hampered by limited access to radiation sources. The aim of the present report is to describe small and cost-effective low activity gamma and alpha sources that can easily be installed and used in university laboratories. A gamma radiation source was made from an euxenite-(Y) rock (Y,Ca,Ce,U,Th)(Nb,Ta,Ti)2O6) that was found in an abandoned mine in Sweden. It allows exposing cells grown in culture dishes to radiation at a dose rate of 50 µGy/h and lower. Three alpha sources were custom-made and yield a dose rate of 1 mGy/h each. The construction, dosimetry and cellular effects of the sources are described. We hope that the report will stimulate research and training activities in the low dose field by facilitating access to radiation sources. [ABSTRACT FROM AUTHOR]

High LET including alpha radiation-based approaches have been proved as a promising mode for cancer therapy owing to their biophysical and radiobiological advantages compared to photon beams. Studies pertaining to effect of α-radiation on cancer cells are limited to cytotoxic high doses. In this study, human lung adenocarcinoma (A549) cells were α-irradiated using 241Am α-irradiator and effects of low dose of alpha radiation on these cells was studied under in vitro and in vivo conditions. Clonogenic and other assays showed increased cellular proliferation at lower doses (1.36 and 6.8 cGy) but killing at higher doses (13.6–54.4 cGy). Further studies at low dose of alpha (1.36 cGy) showed increased TGF-β1 in the conditioned medium (CM) at early time point (24 h) but CM replacement did not affect the clonogenic survival. In these cells, increased phosphorylation of connexin 43 was correlated with decrease in gap-junction communication observed by dye transfer co-culture experiment. A decrease in caveolin-1 but increase in survivin expression was observed in low dose α-irradiated cells. An increase in cyclinD1 and decrease in Bcl-2, the target proteins of survivin, was observed in these cells. Low dose α-irradiated cancer cells transplanted in SCID mice showed significantly higher tumor volume, which was accompanied with an increased fraction of mitotic and PCNA/Ki67 positive cells in these tumor tissues. Taken together, our results suggest an increase in proliferation and tumor volume at in vitro and in vivo levels, respectively, when A549 cells were irradiated with low dose of α-radiation. These findings may be relevant for a better understanding of radiobiological processes during high LET-based cancer radiotherapy. [ABSTRACT FROM AUTHOR]

Diffusing alpha-emitting radiation therapy (DaRT) employs intratumoral Ra-224-coated seeds that efficiently destroy solid tumors by slowly releasing alpha-emitting atoms inside the tumor. In immunogenic tumor models, DaRT was shown to activate systemic antitumor immunity. Agonists of the membrane-bound toll-like receptors (TLRs) enhanced these effects and led to tumor rejection. Here, we examined the combination of DaRT with agents that activate a different type of pattern recognition receptors, the cytoplasmatic RIG1-like receptors (RLRs). In response to cytoplasmatic viral dsRNA, RLRs activate an antiviral immune response that includes the elevation of antigen presentation. Thus, it was postulated that in low-immunogenic tumor models, RLR activation in tumor cells prior to the induction of their death by DaRT will be superior compared to TLR activation. Intratumoral cytoplasmatic delivery of the dsRNA mimic polyIC by polyethylenimine (PEI), was used to activate RLR, while polyIC without PEI was used to activate TLR. PolyIC(PEI) prior to DaRT synergistically retarded 4T1 triple-negative breast tumors and metastasis development more efficiently than polyIC and rejected panc02 pancreatic tumors in some of the treated mice. Splenocytes from treated mice, adoptively transferred to naive mice in combination with 4T1 tumor cells, delayed tumor development compared to naïve splenocytes. Low-dose cyclophosphamide, known to reduce T regulatory cell number, enhanced the effect of DaRT and polyIC(PEI) and led to high long-term survival rates under neoadjuvant settings, which confirmed metastasis clearance. The epigenetic drug decitabine, known to activate RLR in low doses, was given intraperitoneally prior to DaRT and caused tumor growth retardation, similar to local polyIC(PEI). The systemic and/or local administration of RLR activators was also tested in the squamous cell carcinoma (SCC) tumor model SQ2, in which a delay in tumor re-challenge development was demonstrated. We conclude that RIG-I-like activation prior to intratumoral alpha radiation may serve as a potent combination technique to reduce both tumor growth and the spread of distant metastases in low-immunogenic and metastatic tumor models.

Abstract Background While alpha microdosimetry dates back a couple of decades, the effects of localized energy deposition of alpha particles are often still unclear since few comparative studies have been performed. Most modern alpha microdosimetry studies rely for large parts on simulations, which negatively impacts both the simplicity of the calculations and the reliability of the results. A novel microdosimetry method based on the Fluorescent Nuclear Track Detector, a versatile tool that can measure individual alpha particles at sub-micron resolution, yielding accurate energy, fluence and dose rate measurements, was introduced to address these issues. Methods Both the detectors and U87 glioblastoma cell cultures were irradiated using an external Am241 alpha source. The alpha particle tracks measured with a Fluorescent Nuclear Track Detector were used together with high resolution 3D cell geometries images to calculate the nucleus dose distribution in the U87 glioblastoma cells. The experimentally obtained microdosimetry parameters were thereafter applied to simulations of 3D U87 cells cultures (spheroids) with various spatial distributions of isotopes to evaluate the effect of the nucleus dose distribution on the expected cell survival. Results The new experimental method showed good agreement with the analytically derived nucleus dose distributions. Small differences (

Diffusing alpha-emitting radiation therapy (DaRT) employs intratumoral Ra-224-coated seeds that efficiently destroy solid tumors by slowly releasing alpha-emitting atoms inside the tumor. In immunogenic tumor models, DaRT was shown to activate systemic antitumor immunity. Agonists of the membrane-bound toll-like receptors (TLRs) enhanced these effects and led to tumor rejection. Here, we examined the combination of DaRT with agents that activate a different type of pattern recognition receptors, the cytoplasmatic RIG1-like receptors (RLRs). In response to cytoplasmatic viral dsRNA, RLRs activate an antiviral immune response that includes the elevation of antigen presentation. Thus, it was postulated that in low-immunogenic tumor models, RLR activation in tumor cells prior to the induction of their death by DaRT will be superior compared to TLR activation. Intratumoral cytoplasmatic delivery of the dsRNA mimic polyIC by polyethylenimine (PEI), was used to activate RLR, while polyIC without PEI was used to activate TLR. PolyIC(PEI) prior to DaRT synergistically retarded 4T1 triple-negative breast tumors and metastasis development more efficiently than polyIC and rejected panc02 pancreatic tumors in some of the treated mice. Splenocytes from treated mice, adoptively transferred to naive mice in combination with 4T1 tumor cells, delayed tumor development compared to naïve splenocytes. Low-dose cyclophosphamide, known to reduce T regulatory cell number, enhanced the effect of DaRT and polyIC(PEI) and led to high long-term survival rates under neoadjuvant settings, which confirmed metastasis clearance. The epigenetic drug decitabine, known to activate RLR in low doses, was given intraperitoneally prior to DaRT and caused tumor growth retardation, similar to local polyIC(PEI). The systemic and/or local administration of RLR activators was also tested in the squamous cell carcinoma (SCC) tumor model SQ2, in which a delay in tumor re-challenge development was demonstrated. We conclude that RIG-I-like activation prior to intratumoral alpha radiation may serve as a potent combination technique to reduce both tumor growth and the spread of distant metastases in low-immunogenic and metastatic tumor models. [ABSTRACT FROM AUTHOR]

The main obstacle to applying aluminum oxide doped with carbon and magnesium (Al 2 O 3 :C,Mg)-based fluorescent nuclear track detectors (FNTDs) in radionuclide therapy with alpha emitters is that it has not been known how to achieve an accurate and in situ dose assessment for in vitro cellular experiments. In this study, we developed an automatic 3D track reanalysis algorithm (ATRA) to analyze the alpha energy spectra in FNTDs. The algorithm provides an excellent track identification rate and an excellent track linking rate (0.961) without significant variations in various track densities. The algorithm also achieves a reliable track detection rate exceeding 0.927 for track densities at the level of in situ measurement, and it successfully measures the alpha energy spectra for obtaining the absorbed dose. We also confirmed that the track overlap clearly interferes with accurate track reconstruction for track densities beyond 1.5 × 106 tracks cm−2. We provided a correction equation that can be used to obtain the actual alpha tracks for high track densities; the equation may also correct estimations of absorbed doses due to alpha particles. • Automatic 3D track reanalysis algorithm (ATRA) was developed. • The track detection rates of ATRA exceeded 0.927 at in situ measurement level. • The effect of track overlap on ATRA was quantified with various track densities. • Correction equation was provided for correcting absorbed dose due to alpha particle. [ABSTRACT FROM AUTHOR]

The delivery of radiation therapy (RT) for cancer with intent to cure has been optimized and standardized over the last 80 years. Both preclinical and clinical work emphasized the observation that radiation destroys the tumor and exposes its components to the immune response in a mode that facilitates the induction of anti-tumor immunity or reinforces such a response. External beam photon radiation is the most prevalent in situ abolition treatment, and its use exposed the “abscopal effect”. Particle radiotherapy (PRT), which has been in various stages of research and development for 70 years, is today available for the treatment of patients in the form of alpha particles, proton, or carbon ion radiotherapy. Charged particle radiotherapy is based on the acceleration of charged species, such as protons or carbon-12, which deposit their energy in the treated tumor and have a higher relative biological effectiveness compared with photon radiation. In this review, we will bring evidence that alpha particles, proton, or carbon ion radiation can destroy tumors and activate specific anti-tumor immune responses. Radiation may also directly affect the distribution and function of immune cells such as T cells, regulatory T cells, and mononuclear phagocytes. Tumor abolition by radiation can trigger an immune response against the tumor. However, abolition alone rarely induces effective anti-tumor immunity resulting in systemic tumor rejection. Immunotherapy can complement abolition to reinforce the anti-tumor immunity to better eradicate residual local and metastatic tumor cells. Various methods and agents such as immunoadjuvants, suppressor cell inhibitors, or checkpoint inhibitors were used to manipulate the immune response in combination with radiation. This review deals with the manifestations of particle-mediated radiotherapy and its correlation with immunotherapy of cancer.

Compact chromatin is linked to a poor tumour prognosis and resistance to radiotherapy from photons. We investigated DNA damage induction and repair in the context of chromatin structure for densely ionising alpha radiation as well as its therapeutic potential. Chromatin opening by histone deacetylase inhibitor trichostatin A (TSA) pretreatment reduced clonogenic survival and increased γH2AX foci in MDA-MB-231 cells, indicative of increased damage induction by free radicals using gamma radiation. In contrast, TSA pretreatment tended to improve survival after alpha radiation while γH2AX foci were similar or lower; therefore, an increased DNA repair is suggested due to increased access of repair proteins. MDA-MB-231 cells exposed to fractionated gamma radiation (2 Gy × 6) expressed high levels of stem cell markers, elevated heterochromatin H3K9me3 marker, and a trend towards reduced clonogenic survival in response to alpha radiation. There was a higher level of H3K9me3 at baseline, and the ratio of DNA damage induced by alpha vs. gamma radiation was higher in the aggressive MDA-MB-231 cells compared to hormone receptor-positive MCF7 cells. We demonstrate that heterochromatin structure and stemness properties are induced by fractionated radiation exposure. Gamma radiation-exposed cells may be targeted using alpha radiation, and we provide a mechanistic basis for the involvement of chromatin in these effects.

Charge coupled devices (CCDs) have been shown to have potential for detecting charged particles and other forms of ionising radiation. In particular, the clusters in the pixel images produced are distinctive for α and β radiations, with α particles causing large, symmetrical clusters or long, vertical tracks often referred to as blooming, and β particles causing long, curved tracks. The size and shape of these tracks are also related to the energy of the incident radiation, giving the potential for spectroscopy of these types of radiation. This could be used, for example, to realise a hand-held, portable device for in-situ detection and identification of radioactive contamination. Images have been taken of exposures to a 210Po α-particle source using Sony ICX825AL interline transfer CCDs, covered with a thin, aluminised Mylar film to prevent inadvertent exposure to light. Both vertical streaks and round clusters have been observed in each of the three CCDs used. Increased levels of noise have been seen after several hours of exposure to the 210Po source, found to be caused by damage from α radiation. Three methods have been investigated to reduce this noise: 1) Annealing at 100°C for 24 hours repairs a significant proportion of the damage caused by the α radiation, though the effectiveness is reduced with each subsequent exposure and annealing cycle; 2) Cooling is performed during exposures by using a heat pipe to move heat away from the back of the CCD and a fan to cool the heat pipe and electronics associated with the CCD.This reduces the dark current during CCDmeasurements, and the method of cooling used allows thedevice to retain its small, hand-held size; 3) Anyremaining noise can be removed later using imageprocessing. These techniques are combined to extend thelifetime of the device. The rate of damage from the 210Posource is similar whether the device is cooled or not,however the noise evident in the images produced whencooled is significantly less, allowing the CCD to be usedfor a longer time between annealing operations.

Abstract In order to test the delayed effect of radiation on the progeny of irradiated survivors, the human keratinocyte cell line HaCaT and the fish common bluegill embryonic cell line CHSE/F were exposed to low-dose high-LET α-radiation from Ra-226 or γ-rays. The clonogenic survival fraction, mitochondrial membrane polarization (MMP) and reproductive ability of the descendants of the surviving cells were measured. For progeny of irradiated HaCaT survivors, no delayed cell death occurred. On the contrary, progeny at about 47 cell doublings after Ra-226 irradiation and progeny at about 14 cell doublings after γ-irradiation showed increased clonogenic survival. However the total cell number was reduced for progeny of Ra-226-treated cells up to about 47 cell doublings after irradiation and for progeny of γ-irradiated cells up to about 28 doublings after irradiation, which means low reproductive ability had appeared. In addition, α-radiation from Ra-226 had greater impact on the MMP of the HaCaT progeny than γ-rays. MMP of progeny of Ra-226-treated cells decreased at 5 cell doublings after irradiation and increased dose-dependently at 19 cell doublings after treatment, and then decreased dose-dependently at 47 cell doublings, while there was no significant effect on MMP in progeny of γ irradiated cells. The progeny of Ra-226-irradiated CHSE/F survivors showed more serious damage than the offspring of γ-irradiated CHSE/F cells. Significant, dose-dependent delayed cell death occurred in progeny of surviving cells up to about 61 cell doublings after Ra-226 treatment, and the reproductive ability was also significantly reduced. But the MMP increased, which might be because of the increased removal of dead cells. For progeny of CHSE/F cells surviving γ-rays radiation, no significant change in clonogenic survival occurred, except for offspring of cells surviving low dose (0.1 Gy and 0.5 Gy) irradiation, which had higher survival than control up to about 28 cell doublings after irradiation. But the number of cells which were the progeny of γ-irradiated survivors decreased dose-dependently up to about 28 cell doublings after γ-irradiation. Highlights • Chronic low-dose high-LET α-radiation from Ra-226 is effective in inducing lethal mutations. • Decreased clonogenic survival did not occur in descendants of irradiated HaCaT survivors, and hormesis may be induced. • Mitochondrial membrane depolarization may be involved in the induction of lethal mutation. [ABSTRACT FROM AUTHOR]

Due to its ability to induce DNA damage in a space and time controlled manner, ionising radiation is a unique tool for studying the mechanisms of DNA repair. The biological effectiveness of ionising radiation is related to the ionisation density which is defined by the linear energy transfer (LET). Alpha particles are characterised by high LET, while X-rays by low LET values. An interesting question is how cells react when exposed to a mixed beam of high and low LET radiation. In an earlier study carried out with human peripheral blood lymphocytes (PBL) we could demonstrate that alpha radiation X-rays interact in producing more chromosomal aberrations than expected based on additivity. The aim of the present investigation was to look at the mechanism of the interaction, especially with respect to the question if it is due to an augmented level of initial damage or impaired DNA repair. PBL were exposed to various doses of alpha particles, X-rays and mixed beams. DNA damage and the kinetics of damage repair was quantified by the alkaline comet assay. The levels of phosphorylated, key DNA damage response (DDR) proteins ATM, p53 and DNA-PK were measured by Western blotting and mRNA levels of 6 damage-responsive genes were measured by qPCR. Alpha particles and X-rays interact in inducing DNA damage above the level predicted by assuming additivity and that the repair of damage occurs with a delay. The activation levels of DDR proteins and mRNA levels of the studied genes were highest in cells exposed to mixed beams. The results substantiate the idea that exposure to mixed beams presents a challenge for the cellular DDR system. [ABSTRACT FROM AUTHOR]

Summary: Structured illumination microscopy (SIM) for the imaging of alpha particle tracks in fluorescent nuclear track detectors (FNTD) was evaluated and compared to confocal laser scanning microscopy (CLSM). FNTDs were irradiated with an external alpha source and imaged using both methodologies. SIM imaging resulted in improved resolution, without increase in scan time. Alpha particle energy estimation based on the track length, direction and intensity produced results in good agreement with the expected alpha particle energy distribution. A pronounced difference was seen in the spatial scattering of alpha particles in the detectors, where SIM showed an almost 50% reduction compared to CLSM. The improved resolution of SIM allows for more detailed studies of the tracks induced by ionising particles. The combination of SIM and FNTDs for alpha radiation paves the way for affordable and fast alpha spectroscopy and dosimetry. [ABSTRACT FROM AUTHOR]

This paper presents the remote detection of alpha contamination in a nuclear facility. Alpha-active material in a shielded nuclear radiation containment chamber has been localized by optical means. Furthermore, sources of radiation danger have been identified in a staged crime scene setting. For this purpose, an electron-multiplying charge-coupled device camera was used to capture photons generated by alpha-induced air scintillation (radioluminescence). The detected radioluminescence was superimposed with a regular photograph to reveal the origin of the light and thereby the alpha radioactive material. The experimental results show that standoff detection of alpha contamination is a viable tool in radiation threat detection. Furthermore, the radioluminescence spectrum in the air is spectrally analyzed. Possibilities of camera-based alpha threat detection under various background lighting conditions are discussed. [ABSTRACT FROM AUTHOR]

223Radium (223Ra) is widely used in nuclear medicine to treat patients with osseous metastatic prostate cancer. In clinical practice 223Ra cannot be imaged directly; however, gamma photons produced by its short‐lived daughter nuclides can be captured by conventional gamma cameras. In this work, we show that 223Ra and its short‐lived daughter nuclides can be detected with optical imaging techniques. The light emission of 223Ra was investigated in vitro using different setups in order to clarify the mechanism of light production. The results demonstrate that the luminescence of the 223Ra chloride solution, usually employed in clinical treatments, is compatible with Cerenkov luminescence having an emission spectrum that is almost indistinguishable from CR one. This study proves that luminescence imaging can be successfully employed to detect 223Ra in vivo in mice by imaging whole body 223Ra biodistribution and more precisely its uptake in bones. [ABSTRACT FROM AUTHOR]

In this study, the design, simulation and construction of three micro pattern gas-detectors, THGEM, with different geometric dimensions are presented. Moreover, their ability of operation in SQS mode to determine the incident rays position without using any conventional imaging system is investigated. In the presence of UV absorbing gas mixtures, the proportional mode of the gas detector operation is followed by SQS mode as soon as the visible light column appears at the ray entrance location. In the method employed, each THGEM hole as an image pixel independent of other holes can operate in SQS mode with emerging a light column. As a consequence, it can be used for alpha beam imaging since the brightness of each hole at a certain voltage is proportional to the number of primary electrons entering the hole. [ABSTRACT FROM AUTHOR]

The Alpha-Gamma device at the National Institute of Standards and Technology utilizes the interaction of neutrons with a totally absorbing l0B target to precisely measure the flux of a monochromatic neutron beam. This apparatus has been used to calibrate the 6Li(n,a)3H based flux monitor which the NIST neutron beam lifetime experiment BL2 used in its measurement of the most precise neutron beta decay lifetime to date. The unique geometry and measurement technique of Alpha-Gamma allows for a competitive measurement of neutron interaction cross sections, such as the uranium-235 fission cross section (n,f). A description of Alpha-Gamma design and preliminary results pertaining to this application will be discussed. [ABSTRACT FROM AUTHOR]

When exposed to air, alpha particles cause the production of light by exciting the molecules surrounding them. This light, the radioluminescence, is indicative of the presence of alpha radiation, thus allowing for the optical sensing of alpha radiation from distances larger than the few centimeters an alpha particle can travel in air. While the mechanics of radioluminescence in air and other gas compositions is relatively well understood, the same cannot be said about the radioluminescence properties of liquids. Better understanding of the radioluminescence properties of liquids is essential to design methods for the detection of radioactively contaminated liquids by optical means. In this article, we provide radioluminescence images of Am-241 dissolved in aqueous nitric acid ( HNO 3 ) solution and present the recorded radioluminescence spectrum with a maximum between 350 nm and 400 nm , and a steep decrease at the short wavelength side of the maximum. The shape of the spectrum resembles a luminescence process rather than Cerenkov light, bremsstrahlung, or other mechanisms with broadband emission. We show that the amount of light produced is about 150 times smaller compared to that of the same amount of Am-241 in air. The light production in the liquid is evenly distributed throughout the sample volume with a slight increase on the surface of the liquid. The radioluminescence intensity is shown to scale linearly with the Am-241 concentration and not be affected by the HNO 3 concentration.

This work presents a comparison of three autoradiography techniques for imaging biological samples contaminated with actinides: emulsion-based, plastic-based autoradiography and a quantitative digital technique, the iQID camera, based on the numerical analysis of light from a scintillator screen. In radiation toxicology it has been important to develop means of imaging actinide distribution in tissues as these radionuclides may be heterogeneously distributed within and between tissues after internal contamination. Actinide distribution determines which cells are exposed to alpha radiation and is thus potentially critical for assessing absorbed dose. The comparison was carried out by generating autoradiographs of the same biological samples contaminated with actinides with the three autoradiography techniques. These samples were cell preparations or tissue sections collected from animals contaminated with different physico-chemical forms of actinides. The autoradiograph characteristics and the performances of the techniques were evaluated and discussed mainly in terms of acquisition process, activity distribution patterns, spatial resolution and feasibility of activity quantification. The obtained autoradiographs presented similar actinide distribution at low magnification. Out of the three techniques, emulsion autoradiography is the only one to provide a highly-resolved image of the actinide distribution inherently superimposed on the biological sample. Emulsion autoradiography is hence best interpreted at higher magnifications. However, this technique is destructive for the biological sample. Both emulsion- and plastic-based autoradiography record alpha tracks and thus enabled the differentiation between ionized forms of actinides and oxide particles. This feature can help in the evaluation of decorporation therapy efficacy. The most recent technique, the iQID camera, presents several additional features: real-time imaging, separate imaging of alpha particles and gamma rays, and alpha activity quantification. The comparison of these three autoradiography techniques showed that they are complementary and the choice of the technique depends on the purpose of the imaging experiment. [ABSTRACT FROM AUTHOR]

Children are at risk for adverse health outcomes from occupant-controllable indoor airborne contaminants in their homes. Data are needed to design residential interventions for reducing low-income children's pollutant exposure. Using customized air quality monitors, we continuously measured fine particle counts (0.5 to 2.5 microns) over a week in living areas of predominantly low-income households in San Diego, California, with at least one child (under age 14) and at least one cigarette smoker. We performed retrospective interviews on home characteristics, and particle source and ventilation activities occurring during the week of monitoring. We explored the relationship between weekly mean particle counts and interview responses using graphical visualization and multivariable linear regression (base sample n = 262; complete cases n = 193). We found associations of higher weekly mean particle counts with reports of indoor smoking of cigarettes or marijuana, as well as with frying food, using candles or incense, and house cleaning. Lower particle levels were associated with larger homes. We did not observe an association between lower mean particle counts and reports of opening windows, using kitchen exhaust fans, or other ventilation activities. Our findings about sources of fine airborne particles and their mitigation can inform future studies that investigate more effective feedback on residential indoor-air-quality and better strategies for reducing occupant exposures. [ABSTRACT FROM AUTHOR]

• Chemical durability of nuclear glass was studied by considering combined effects of vapor hydration and radiation. • No significant impact of ionizing effect was observed on the leaching behavior of hydrated glass. • The presence of pre-hydrated layer, especially the secondary phases, showed major impacts on glass chemical durability. During the long-term disposal of high-level nuclear waste glass in the geological disposal facility, the nuclear glass could be exposed to an unsaturated vapor environment prior to the direct contact with groundwater. Additionally, glass will experience damages due to self-irradiation. In this study, experiments were performed to investigate the chemical durability of glass after being hydrated and irradiated. This study proposes an attempt to investigate the impact of ionizing effect by applying alpha or gamma radiations to the pre-hydrated glass. The impact on chemical durability is evaluated by leaching the hydrated and irradiated glass samples. With the studied doses, 8 Giga Gy of alpha radiation or 100 kGy of gamma radiation, no significant modification of chemical durability is observed upon irradiation. On the other hand, leaching of pre-hydrated glass shows the increase of the initial release of Si, which is considered to be related to the dissolution of secondary phases. Furthermore, the total dissolution of hydrated layer is observed, which would result in the release of radionuclides at the same rate as Si does and thus needs further investigation. [ABSTRACT FROM AUTHOR]