The neutron powder diffraction technique has been used for structural studies of Rb2UBr6 solid electrolyte as a function of temperature. The low-, room-, and high-temperature structures have been determined. At the temperature range of 4.2–80 K, the compound crystallizes in a monoclinic unit cell in the P21/c space group. At 80 K and 853 K, the compound crystallizes in a tetragonal unit cell in the P4/mnc space group. At 300 K, the lattice constants are a = b = 7.745(1) and c = 11.064(1) Å. At the temperature range of 853–960 K, a trigonal phase is observed in the Pʒ̄ml space group.
Research done on a set of simple fluidic (with the fluid used as the ionized medium being air under atmospheric pressure) alphavoltaic cells – small ionizing reactors or “nuclear batteries”, designed in the Faculty of Power and Aerospace Engineering of Warsaw University of Technology, Poland – has shown the possibility of accumulation of usable amount of electric charge. Two simple methods are proposed to describe the fluidic alphavoltaic cells in terms of their efficiency. The results of these methods are presented and compared with the efficiencies of other contemporary types of solid-body (semiconductor junction-based) alpha- and betavoltaic cells. The comparison showed that despite the far-reaching simplicity in design, the designed fluidic cells are still more efficient than some of the solid-body devices that use the alpha type of decay.
Background and objectives: This study describes the treatment planning and dose delivery methods of radiotherapy for patients undergoing bone marrow transplantation. The analysis was carried out in the context of the evolution of these methods over the last 60 years.
Materials and methods: A systematic literature search was carried out using the PubMed search engine. Overall, 90 relevant studies were included: 24 general studies, 10 describing isotopes usage, 24 related to conventional and 32 to advanced methods.
Results: The analysis of the evolution of radiotherapy methods shows how significantly the precision of dose planning methods and its delivery have changed. The atypical positioning caused by geometrical requirements for applications of isotopes or conventional techniques has been replaced by positioning on a therapeutic couch, which allows a more precise setup of the patient that is necessary for an exact delivery of the planned dose. The dose can be fully optimized and calculated on tomographic images by algorithms implemented in planning systems. Optimization process allows to reduce doses in organs at risk. The accuracy between planned and delivered doses can be checked by pretreatment verification methods, and the patient positioning can be checked by image guidance procedures.
Interpretation and conclusions: Current radiotherapy solutions allow a precise delivery of doses to the planning target volume while reducing doses to organs at risk. Nevertheless, it should be kept in mind that establishing radiotherapy as an important element of the whole therapeutic regimen resulted from the follow-up of patients treated by conventional techniques. To confirm the clinical value of new advanced techniques, clinical trials are required.
This study presented a self-designed prompt gamma neutron activation analysis (PGNAA) model and used Fluka simulation to simulate the heavy metals (Mn, Cu, Hg, Ni, Cr, Pb) in soil samples. The relationship between the prompt γ -ray yield of each heavy metal and soil thickness, content of heavy metals in the soil, and source distance was obtained. Simulation results show that the prompt γ -ray yield of each heavy metal increases with the increase in soil thickness and reaches saturation at 18 cm. The greater the proportion of heavy metals in the soil, the greater the prompt γ -ray yield. The highest content is approximately 3%, and the change in distance between the neutron source and soil sample does not affect the prompt γ -ray yield of heavy metals.
The triggering of a “dirty bomb” generates a complex scenario, with enormous challenges for the responders due to initial misinformation and the urgency to act quickly yet effectively. Normally, the first 100 h are decisive for perceiving the risk in a more realistic dimension, but the support of methodologies that rely on computational simulations can be valuable when making key decisions. This work seeks to provide support for the early decision-making process by using a Gaussian model for the distribution of a quantity of Cs-137 spread by a radiological dispersive device (RDD). By sequentially joining two independent programs, HotSpot Health Physics codes and RESidual RADiation (RESRAD)-RDD family of codes, we came up with results that suggest a segmented approach to the potentially affected population. These results advocate that (a) the atmospheric stability conditions represented by the Pasquill–Gifford classes and (b) the population subgroups defined by radiation exposure conditions strongly influence the postdetonation radiological effects. These variables should be taken into account in the elaboration of flexible strategies that include many climatic conditions and to priori-tize attention to different groups of public at risk. During the initial phases of such an event, it is believed that simulations using Gaussian models may be of value in anticipating the possible changes in key variables during the decision-making process. These variables may severely affect the effectiveness of the actions of responders and the general public’s safety.
The radon issue has been known worldwide for dozens of years. Many scientific (ICRP Publication No. 137), technical (ICRU Report No. 88), and legislative (Council Directive 2013/59/EURATOM (EU-BSS)) documents have been published in the last decade. More and more attention is being paid to precise quantification to determine the concentration and consequent effects of various pollutants on human health worldwide. The quality of measurement and the variety of measurement techniques increase the need to unify measurement procedures and metrology continuity. Countries around the world are beginning to unify metrological procedures for determining different quantities based on international recommendations and standards. Not only for these reasons, it became more actual a need for more accurate radon activity concentration measurement and radon metrology unification. This paper summarizes the main remarks and technical aspects to the historical development of radon metrology.
Clustering as a fundamental unsupervised learning is considered an important method of data analysis, and K-means is demonstrably the most popular clustering algorithm. In this paper, we consider clustering on feature space to solve the low efficiency caused in the Big Data clustering by K-means. Different from the traditional methods, the algorithm guaranteed the consistency of the clustering accuracy before and after descending dimension, accelerated K-means when the clustering centeres and distance functions satisfy certain conditions, completely matched in the preprocessing step and clustering step, and improved the efficiency and accuracy. Experimental results have demonstrated the effectiveness of the proposed algorithm.
A model for predator-prey interactions with herd behaviour is proposed. Novelty includes a smooth transition from individual behaviour (low number of prey) to herd behaviour (large number of prey). The model is analysed using standard stability and bifurcations techniques. We prove that the system undergoes a Hopf bifurcation as we vary the parameter that represents the efficiency of predators (dependent on the predation rate, for instance), giving rise to sustained oscillations in the system. The proposed model appears to possess more realistic features than the previous approaches while being also relatively easier to analyse and understand.