Study of NBT-Pluronic F-127 Gels as 1D UV Radiation Dosimeters for Measurement of Artificial Light Sources.

This work reports on radiochromic dosimeters for 1D UV light measurements. The dosimeter is composed of a 25% Pluronic F-127 that forms a physical gel matrix and nitro blue tetrazolium chloride (NBT) as a radiation-sensitive compound. This dosimeter was exposed to UVA, UVB and UVC radiation, and the radiochromic reactions were followed with reflectance spectrophotometry including changes in light reflectance and color coordinates in the CIELAB color system. The exposition of dosimeters to all UV radiation caused color changes from pale yellow to dark violet, and its intensity increased with increasing absorbed dose. The effects of NBT concentration and UV radiation type on the dose-response of the dosimeters were also examined. The results obtained reveal that the dosimeters are the least sensitive to irradiation with UVC and the most sensitive to irradiation with UVB (e.g., dosimeter with 2 g/dm3 of NBT was characterized by the following parameters: the threshold dose 0.1 J/cm2; the dose sensitivity -5.97 ± 0.69 cm2/J; the linear dose range 0.1-2.5 J/cm2; the dynamic dose range was equal to 0.1-3 J/cm2). The results obtained reveal that the NBT-Pluronic F-127 dosimeters can be potentially useful as 1D sensors for artificial UV radiation sources measurements.

212Pb: Production Approaches and Targeted Therapy Applications.

Over the last decade, targeted alpha therapy has demonstrated its high effectiveness in treating various oncological diseases. Lead-212, with a convenient half-life of 10.64 h, and daughter alpha-emitter short-lived 212Bi (T1/2 = 1 h), provides the possibility for the synthesis and purification of complex radiopharmaceuticals with minimum loss of radioactivity during preparation. As a benefit for clinical implementation, it can be milked from a radionuclide generator in different ways. The main approaches applied for these purposes are considered and described in this review, including chromatographic, solution, and other techniques to isolate 212Pb from its parent radionuclide. Furthermore, molecules used for lead's binding and radiochemical features of preparation and stability of compounds labeled with 212Pb are discussed. The results of preclinical studies with an estimation of therapeutic and tolerant doses as well as recently initiated clinical trials of targeted radiopharmaceuticals are presented.

Photothermal conversion of Ti2O3 film for tuning terahertz waves.

Dynamic tuning of terahertz (THz) wave is vital for the development of next generation THz devices. Utilization of solar energy for tuning THz waves is a promising, eco-friendly, and sustainable way to expand THz application scenarios. Ti2O3 with an ultranarrow bandgap of 0.1eV exhibits intriguing thermal-induced metal-insulator transition (MIT), and possesses excellent photothermal conversion efficiency. Herein, Ti2O3 film was fabricated by a two-step magnetron sputtering method, and exhibited an excellent photothermal conversion efficiency of 90.45% and demonstrated temperature-dependent THz transmission characteristics with a wideband at 0.1-1 THz. We supposed to combine photothermal conversion characteristics with temperature-dependent THz transmission properties of Ti2O3 film, which could introduce solar light as the energy source for tuning THz waves. Our work will provide new sight for investigating MIT characteristics of Ti2O3 at THz regime and exhibit huge potential in the application of tuning terahertz waves in outdoor scenarios in the future.

NuSTAR Observation of Energy Release in 11 Solar Microflares.

Solar flares are explosive releases of magnetic energy. Hard X-ray (HXR) flare emission originates from both hot (millions of Kelvin) plasma and nonthermal accelerated particles, giving insight into flare energy release. The Nuclear Spectroscopic Telescope ARray (NuSTAR) utilizes direct-focusing optics to attain much higher sensitivity in the HXR range than that of previous indirect imagers. This paper presents 11 NuSTAR microflares from two active regions (AR 12671 on 2017 August 21 and AR 12712 on 2018 May 29). The temporal, spatial, and energetic properties of each are discussed in context with previously published HXR brightenings. They are seen to display several "large flare" properties, such as impulsive time profiles and earlier peak times in higher-energy HXRs. For two events where the active region background could be removed, microflare emission did not display spatial complexity; differing NuSTAR energy ranges had equivalent emission centroids. Finally, spectral fitting showed a high-energy excess over a single thermal model in all events. This excess was consistent with additional higher-temperature plasma volumes in 10/11 microflares and only with an accelerated particle distribution in the last. Previous NuSTAR studies focused on one or a few microflares at a time, making this the first to collectively examine a sizable number of events. Additionally, this paper introduces an observed variation in the NuSTAR gain unique to the extremely low livetime (<1%) regime and establishes a correction method to be used in future NuSTAR solar spectral analysis.

Accelerated Electrons Observed Down to <7 keV in a NuSTAR Solar Microflare.

We report the detection of emission from a nonthermal electron distribution in a small solar microflare (GOES class A5.7) observed by the Nuclear Spectroscopic Telescope Array, with supporting observation by the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI). The flaring plasma is well accounted for by a thick-target model of accelerated electrons collisionally thermalizing within the loop, akin to the "coronal thick-target" behavior occasionally observed in larger flares. This is the first positive detection of nonthermal hard X-rays from the Sun using a direct imager (as opposed to indirectly imaging instruments). The accelerated electron distribution has a spectral index of 6.3 ± 0.7, extends down to at least 6.5 keV, and deposits energy at a rate of ~2 × 1027 erg s-1, heating the flare loop to at least 10 MK. The existence of dominant nonthermal emission in X-rays down to <5 keV means that RHESSI emission is almost entirely nonthermal, contrary to what is usually assumed in RHESSI spectroscopy. The ratio of nonthermal to thermal energies is similar to that of large flares, in contrast to what has been found in previous studies of small RHESSI flares. We suggest that a coronal thick target may be a common property of many small microflares based on the average electron energy and collisional mean free path. Future observations of this kind will enable understanding of how flare particle acceleration changes across energy scales, and will aid the push toward the observational regime of nanoflares, which are a possible source of significant coronal heating.

Laue diffraction and time-resolved crystallography: a personal history.

A personal, historical view is presented of Laue X-ray diffraction and its application to time-resolved studies of dynamic processes, largely in light-sensitive biological systems. In Laue diffraction, a stationary crystal is illuminated by a polychromatic X-ray source. Laue diffraction has inherent complications largely absent in monochromatic diffraction, and consequently fell into disuse for quantitative structure determination. However, the advent of naturally polychromatic, intense, pulsed storage ring X-ray sources in the 1970s led to re-examination at Daresbury and elsewhere of its underlying principles. Laue diffraction has been successfully applied at storage ring sources to time-resolved, pump-probe crystallographic studies, whose exposure time and time resolution were progressively reduced from minutes to seconds, milliseconds, nanoseconds and 100 ps. Most recently, hard X-ray free electron laser sources have been used to generate narrow bandpass Laue diffraction patterns. The femtosecond X-ray pulses from such sources are completely destructive, generate only one diffraction pattern per tiny crystal and have unusual properties. However, they too are being applied to time-resolved crystallography to explore, for example, isomerization and rapid tertiary structural changes on the chemical, femtosecond timescale. This article is part of the theme issue 'Fifty years of synchrotron science: achievements and opportunities'.

Determination of isotopes activity ratio using gamma ray spectroscopy based on neural network model.

The uranium isotopes activity-ratio was determined using in-situ γ-ray spectroscopic measurements and an artificial neural network model. The method was developed to use forward-learn multilayer algorithm. Each layer consists of a perceptron, that controls the forward-learn process, and a mean-square-error mapping for the spectral data from the set of fired perceptrons. The set of output parameters should represent a vector of coefficients for double logarithmic polynomial that distinguish the instrumental efficiency. The forward-learn is controlled by a rejection function which is based on an input set Ψ of parameters that tells the neural layer to accept or reject data points. Each layer maps to the next layer by reducing chi-square-difference with the experimental uncertainty as weight. There are two supervised controls to the network, the maximum deviation from interpolated curve and the assumed initial set of rejection parameters (Ψ0). The model was tested on spectra of known enrichments and gave an excellent agreement with low enriched uranium samples ((1.38 ±â€¯0.14)% and (20 ±â€¯1.55)%). The use of the algorithm on natural uranium ore and association with radium-226 daughters causes increase of uncertainty and deviation of the results from the certified value. The current algorithm provides a practical solution to a wide range of gamma-ray measurement problems encountered for in-situ characterization of uranium-containing materials. These include security, safeguards, fuel assessment, decontamination and decommissioning operations with no collimation or special setup. It is also applicable for large-scale installations.

SPS technique for ionizing radiation source fabrication based on dense cesium-containing core.

The work presents a novel method for fabrication of the high-quality ionizing radiation source (IRS), which is promising to replace unsafe commercial products based on 137CsCl prohibited by IAEA. Spark plasma sintering (SPS) technique has been applied to produce dense ceramic and glass-ceramic matrixes from Cs-containing (˜13.5 wt.%) zeolite yielding in non-dispersible cores sealed in the container of radiation-resistant steel (J93503, US standard). One-stage SPS regimes to provide high-quality product have been optimized: sintering temperature <1000 °C, heating and holging duration 13 and 5 min, respectively, pressure 24.5 MPa. XRD, SEM, EDX, BET, XFS and solid-state MAS NMR 133Cs methods prove exceptional physico-chemical and mechanical characteristics of the obtained materials, namely: density 99.8% from theoretical, compressive strength ˜477 MPa, leaching rate 10-4-10-6 g cm-2 day-1. Results of the investigation can be promising for fabrication of the IRS cores on a large scale as done for similar Russian products RSL, IGI-C, M37C, GID-C.

Deciphering Residual Emissions: Time-dependent Models for the Nonthermal Interstellar Radiation from the Milky Way.

Cosmic rays (CRs) in the Galaxy are an important dynamical component of the interstellar medium (ISM) that interact with the other major components (interstellar gas and magnetic and radiation fields) to produce broadband interstellar emissions that span the electromagnetic spectrum. The standard modeling of CR propagation and production of the associated emissions is based on a steady-state assumption, where the CR source spatial density is described using a smoothly varying function of position that does not evolve with time. While this is a convenient approximation, reality is otherwise, where primary CRs are produced in and about highly localized regions, e.g., supernova remnants, which have finite lifetimes. In this paper, we use the latest version of the galprop CR propagation code to model time-dependent CR injection and propagation through the ISM from a realistic 3D discretized CR source density distribution, together with full 3D models for the other major ISM components, and make predictions of the associated broadband nonthermal emissions. We compare the predictions for the discretized and equivalent steady-state model, finding that the former predicts novel features in the broadband nonthermal emissions that are absent for the steady-state case. Some of the features predicted by the discretized model may be observable in all-sky observations made by WMAP and Planck, the recently launched eROSITA, the Fermi-LAT, and ground-based observations by HESS, HAWC, and the forthcoming CTA. The nonthermal emissions predicted by the discretized model may also provide explanations of puzzling anomalies in high-energy γ-ray data, such as the Fermi-LAT north/south asymmetry and residuals like the so-called "Fermi bubbles."

THE MODERN STATE OF PROBLEM OF PROVIDING RADIO PROTECTION OF UKRAINE'S POPULATION FROM NATURAL RELEASE SOURCES (review of literature). / PROBLEMY RADIATsIINOÏ BEZPEKY NASELENNIa, IaKE ZAZNAIe OPROMINENNIa VID PRYRODNYKh DZhEREL (ogliad literatury).

The article focuses on a scientific literature review connected with data summarizing of long-term studies of pop-ulation exposure to natural ionizing radiation sources. In order to assess the current state of the problem ofensuring radiation protection of the population of Ukraine from natural sources of radiation, the author analyzesthe scientific approaches and principles of the theory of anti-radiation protection by examining the recommen-dations of leading international organizations and the domestic specifics of limiting irradiation from naturalsources. Moreover, it highlights the main historical stages of the introduction of national regulations for limit-ing population exposure to certain natural radiation sources. Besides, the author presents research results of for-eign and national scientists towards the natural radioactivity of environmental compartments and area of humanhabitation.According to the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR), an averageannual effective radiation dose per capita from natural sources is 2.4 mSv that is 46 % of the total dose of humanexposure. In Ukraine, a dose from natural radiation sources is 3.5 mSv per year that determines 60% of the total doseof human exposure.Reported by UNSCEAR an average annual dose of human exposure to all factors is 5.2 mSv, while the natural com-ponent with the technogenic enhanced background contributes 4.2 mSv per year to the total dose where there isradon-222 - 1.5 mSv per year. In Ukraine, the total dose of population exposure is rather more and is 5.9 mSv peryear, while the natural component ratio with the technogenic enhanced background is notably higher and up to 5.1mSv per year. Part of radon-222 is 2.4 mSv per year in it.Attention is paid to the reassessment of the magnitude of radiation risks caused by radon, which served as thebasis for improving approaches aimed at ensuring radon safety for the population. Radon is the most determiningradiation factor for the population that requires careful regulatory control by government programs.

Robust Radiation Sources Localization Based on the Peak Suppressed Particle Filter for Mixed Multi-Modal Environments.

This paper addresses a detection problem where sparse measurements are utilized to estimate the source parameters in a mixed multi-modal radiation field. As the limitation of dimensional scalability and the unimodal characteristic, most existing algorithms fail to detect the multi-point sources gathered in narrow regions, especially with no prior knowledge about intensity and source number. The proposed Peak Suppressed Particle Filter (PSPF) method utilizes a hybrid scheme of multi-layer particle filter, mean-shift clustering technique and peak suppression correction to solve the major challenges faced by current existing algorithms. Firstly, the algorithm realizes sequential estimation of multi-point sources in a cross-mixed radiation field by using particle filtering and suppressing intensity peak value, while existing algorithms could just identify single point or spatially separated point sources. Secondly, the number of radioactive sources could be determined in a non-parametric manner as the fact that invalid particle swarms would disperse automatically. In contrast, existing algorithms either require prior information or rely on expensive statistic estimation and comparison. Additionally, to improve the prediction stability and convergent performance, distance correction module and configuration maintenance machine are developed to sustain the multimodal prediction stability. Finally, simulations and physical experiments are carried out in aspects such as different noise level, non-parametric property, processing time and large-scale estimation, to validate the effectiveness and robustness of the PSPF algorithm.

Erratum: Reconstructing three-dimensional protein crystal intensities from sparse unoriented two-axis X-ray diffraction patterns. Corrigendum.

[This corrects the article DOI: 10.1107/S1600576717006537.].

Reconstructing three-dimensional protein crystal intensities from sparse unoriented two-axis X-ray diffraction patterns.

Recently, there has been a growing interest in adapting serial microcrystallography (SMX) experiments to existing storage ring (SR) sources. For very small crystals, however, radiation damage occurs before sufficient numbers of photons are diffracted to determine the orientation of the crystal. The challenge is to merge data from a large number of such 'sparse' frames in order to measure the full reciprocal space intensity. To simulate sparse frames, a dataset was collected from a large lysozyme crystal illuminated by a dim X-ray source. The crystal was continuously rotated about two orthogonal axes to sample a subset of the rotation space. With the EMC algorithm [expand-maximize-compress; Loh & Elser (2009). Phys. Rev. E, 80, 026705], it is shown that the diffracted intensity of the crystal can still be reconstructed even without knowledge of the orientation of the crystal in any sparse frame. Moreover, parallel computation implementations were designed to considerably improve the time and memory scaling of the algorithm. The results show that EMC-based SMX experiments should be feasible at SR sources.

Protein crystal structure from non-oriented, single-axis sparse X-ray data.

X-ray free-electron lasers (XFELs) have inspired the development of serial femtosecond crystallography (SFX) as a method to solve the structure of proteins. SFX datasets are collected from a sequence of protein microcrystals injected across ultrashort X-ray pulses. The idea behind SFX is that diffraction from the intense, ultrashort X-ray pulses leaves the crystal before the crystal is obliterated by the effects of the X-ray pulse. The success of SFX at XFELs has catalyzed interest in analogous experiments at synchrotron-radiation (SR) sources, where data are collected from many small crystals and the ultrashort pulses are replaced by exposure times that are kept short enough to avoid significant crystal damage. The diffraction signal from each short exposure is so 'sparse' in recorded photons that the process of recording the crystal intensity is itself a reconstruction problem. Using the EMC algorithm, a successful reconstruction is demonstrated here in a sparsity regime where there are no Bragg peaks that conventionally would serve to determine the orientation of the crystal in each exposure. In this proof-of-principle experiment, a hen egg-white lysozyme (HEWL) crystal rotating about a single axis was illuminated by an X-ray beam from an X-ray generator to simulate the diffraction patterns of microcrystals from synchrotron radiation. Millions of these sparse frames, typically containing only ∼200 photons per frame, were recorded using a fast-framing detector. It is shown that reconstruction of three-dimensional diffraction intensity is possible using the EMC algorithm, even with these extremely sparse frames and without knowledge of the rotation angle. Further, the reconstructed intensity can be phased and refined to solve the protein structure using traditional crystallographic software. This suggests that synchrotron-based serial crystallography of micrometre-sized crystals can be practical with the aid of the EMC algorithm even in cases where the data are sparse.

Biostructural Science Inspired by Next-Generation X-Ray Sources.

Next-generation synchrotron radiation sources, such as X-ray free-electron lasers, energy recovery linacs, and ultra-low-emittance storage rings, are catalyzing novel methods of biomolecular microcrystallography and solution scattering. These methods are described and future trends are predicted. Importantly, there is a growing realization that serial microcrystallography and certain cutting-edge solution scattering experiments can be performed at existing storage ring sources by utilizing new technology. In this sense, next-generation sources are serving two distinct functions, namely, provision of new capabilities that require the newer sources and inspiration of new methods that can be performed at existing sources.

Acondicionamiento de las fuentes de radio 226 en Cuba / Conditioning of radium 226 sources in Cuba

RESUMEN Debido al riesgo que representa el empleo del Ra-226, a nivel internacional se ha recomendado suspender la producción y uso de fuentes radiactivas selladas de este radionúclido. Consecuente con esto, las fuentes de Ra-226 en Cuba fueron recogidas, caracterizadas y acondicionadas. El trabajo describe los aspectos operacionales y de seguridad relacionados con el acondicionamiento de las fuentes radiactivas de Ra-226, para lo cual se requirió de una autorización de la Autoridad Reguladora, otorgada en forma de un Permiso Especial. Una evaluación radiológica de todas las operaciones, el informe de seguridad, así como el plan de emergencia se elaboraron y aprobaron antes de las operaciones. Se estableció un sistema integral de gestión de la calidad que demostró la confiabilidad del trabajo. Como resultado de estas operaciones, se encapsularon y acondicionaron 188,5 GBq de Ra-226 contenidos en diferentes tipos de fuentes radiactivas (agujas y tubos de braquiterapia, fuentes de control, etc.). Las cápsulas con las fuentes se acondicionaron para su almacenamiento prolongado dentro de cinco bultos, de manera que se puedan recuperar.

ABSTRACT The production and use of Ra-226 sealed sources was internationally recommended to be halted for health and safety reasons. Consequently, all Ra-226 sources in Cuba were collected, characterized and conditioned. The paper describes the safety and operational aspects related to the Ra-226 conditioning. For this, a Special Permission was granted by the Regulatory Body, as required. A radiological assessment, a safety report as well as an emergency plan were prepared and approved before the operations. The work was accomplished with due reliability following an established comprehensive Quality Management System. As a result of these operations, 188.5 GBq of Ra-226, contained in different types of radiation sources (brachytherapy needles and tubes, standard sources for calibration, etc.) were encapsulated and conditioned. The capsules with the sources were conditioned in a retrievable form within fi ve waste packages intended for long term storage.

Desmantelamiento de un irradiador de neutrones / Disassembly of a neutron irradiator

En el trabajo se describe el proceso de desmantelamiento de un irradiador neutrónico de 4,44·1011 Bq empleado en la radiomutagénesis vegetal. Se reporta el procedimiento desarrollado para dicho proceso. La importancia de estas experiencias está dada por tratarse de una instalación no estándar, atípica.

The disassembly of 4.44·1011 Bq neutron irradiator used in vegetable radio mutagenesis is described. The procedure developed for such purpose is reported. This irradiator is a non standard installation therefore, the disassembly experience is unique.

On the use of high dose rate Ir192 and Yb169 sources with the MammoSite® radiation therapy system.

Ample literature exists on the dose overestimation by commercially available treatment planning systems in MammoSite® applications using high dose rate Ir192 sources for partial breast brachytherapy as monotherapy, due to their inability to predict the dose reduction caused by the radiographic contrast solution in the balloon catheter. In this work Monte Carlo simulation is used to verify the dose rate reduction in a balloon breast applicator which does not vary significantly with distance and it is 1.2% at the prescription distance for the reference simulated geometry of 10% diluted radiographic contrast media and 2.5cm balloon radius. Based on these findings and the minimal hardening of the initially emitted photon spectrum for Ir192, a simple analytical method is proposed and shown capable for correcting dosimetry planning in clinical applications. Simulations are also performed to assess the corresponding dose reduction in applications of balloon breast applicators using high dose rate Yb169 sources that have recently become available. Results yield a far more significant and distance dependent dose reduction for Yb169 (on the order of 20% at the prescription distance for the abovementioned reference simulation geometry). This dose reduction cannot be accounted for using simple analytical methods as for Ir192 due to the significant hardening of the initially emitted Yb169 photons within the diluted radiographic contrast media. Combined with results of previous works regarding the effect of altered scatter conditions (relative to treatment planning system assumptions) on breast treatment planning accuracy, which is more pronounced for Yb169 relative to Ir192, these findings call for the amendment of dose treatment planning systems before using Yb169 high dose rate sources in balloon breast applicators.