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The purpose of this study is to investigate and quantify the influence of nanoparticle composition, size, and concentration on the difference between dose enhancement values derived from Monte Carlo simulations with homogeneous and structured geometrical representations of the target region in metal nanoparticle-enhanced photon brachytherapy. Values of the dose enhancement factor (DEF) were calculated for Pd-103, I-125, and Cs-131 brachytherapy sources with gold, silver, or platinum nanoparticles acting as targeting agents. Simulations were performed using the Geant4 toolkit with condensed history models of electron transport. Stringent limits were imposed on adjustable parameters that define secondary electron histories, so that simulations came closest to true event-by-event electron tracking, thereby allowing part of the nanoparticle-laden volume used for calculating the dose to be represented as a structured region with uniformly distributed discrete nanoparticles. Fine-tuned physical models of secondary radiation emission and propagation, along with the discrete geometrical representation of nanoparticles, result in a more realistic assessment of dose enhancement. The DEF correction coefficient is introduced as a metric that quantifies the absorption of secondary radiation inside the nanoparticles themselves, a phenomenon disregarded when the target region is treated as a homogeneous metal–tissue mixture, but accounted for by discrete nanoparticle representation. The approach applied to correcting DEF values both draws from and expands upon several related investigations published previously. Comparison of the obtained results to those found in relevant references shows both agreement and deviation, depending on nanoparticle properties and photon energy. © 2020, China Science Publishing & Media Ltd. (Science Press), Shanghai Institute of Applied Physics, the Chinese Academy of Sciences, Chinese Nuclear Society and Springer Nature Singapore Pte Ltd.

Composite hydrogels capable of controlled drug delivery via ion exchange are an interesting group of materials for the construction of implantable drug reservoirs for electrically charged drugs. In this study, we synthesized composite poly(DL-lactide-co-glycolide)/poly(acrylic acid) (PLGA-PAA) hydrogels by sequential application of UV or gamma irradiation and traditional phase inversion. Physicochemical properties of the composite PLGA-PAA hydrogels were investigated using Fourier transform infrared spectroscopy with attenuated total reflectance (FTIR-ATR), scanning electron microscopy (SEM), and differential scanning calorimetry (DSC). We examined the ion exchange capacity (IEC) and swelling behavior of these materials to determine their potential as drug reservoirs. Composite PLGA-PAA hydrogel synthesized using UV irradiation (UV-PLGA-PAA) exhibited a porous microstructure with submicron-sized hydrogel-rich aggregates and homogeneous chemical composition. Swelling behavior and IEC of this material were highly reproducible. Composite PLGA-PAA hydrogels synthesized using gamma irradiation (G-PLGA-PAAs) had a less uniform microstructure with larger pores and micron-sized hydrogel-rich aggregates while exhibiting rather inhomogeneous chemical composition. These materials showed superior swelling properties, but a more variable IEC, compared to the material fabricated using UV irradiation. Results of DSC analysis showed a dose-dependent decrease in glass transition temperature for G-PLGA-PAAs indicating the effects of PLGA chain scission. Our findings indicate that gamma irradiation is a possible alternative to UV irradiation in the synthesis of composite PLGA-PAA hydrogels which can modify or control important material properties. However, the synthesis protocol using gamma irradiation should be further optimized to improve the IEC reproducibility. In our future research, we will investigate the in vitro release of charged drugs from synthesized composite PLGA-PAA hyd

In recent years, water pollution and contamination had become a major threat to the ecosystem. However, the use of nanostructured materials has been proven as a very promising approach in the treatment of polluted water. The present study reports the results of the gamma ray-assisted modification of hydrophobic carbon quantum dot (hCQD)/polyurethane nanocomposites for photocatalytic degradation of organic dyes. Different characterization methods were applied to investigate the influence of the different doses of gamma irradiation (1, 10 and 200 kGy) on the physical and chemical properties of nanocomposites (morphology, chemical content, mechanical properties, wettability, and potential for singlet oxygen generation). Surface morphology and mechanical properties analyses showed that gamma rays induced insignificant changes in the structure of nanocomposites, but the potential for singlet oxygen generation increased significantly. Here we also explore, in detail, the photocatalytic properties of gamma-ray modified hCQDs/polyurethane nanocomposites. UV-vis analysis showed that the removal efficiency of the rose bengal dye reached up to 97% for the nanocomposite irradiated with the dose of 200 kGy.

This paper deals with the flash memory reliability in terms of the ionizing radiation effects. In fact, the reliability of flash memory depends on physico-chemical restrictions of electrostatic nature due to the effects of ionizing radiation. The presented results are actual as a high degree of integrated components miniaturization affects the memory sensitivity, while the role of memories in the solar cells management system for space flights is increasing, so that the effects of ionizing radiation may cause changes in the stored data or the physical destruction of the flash memory components.

Effects of exposing several insulators, commonly used for various purposes in integrated circuits, to beams of protons have been investigated. Materials considered include silicon dioxide, silicon nitride, aluminium nitride, alumina, and polycarbonate (Lexan). The passage of proton beams through ultrathin layers of these materials has been modeled by Monte Carlo simulations of particle transport. Parameters that have been varied in simulations include proton energy and insulating layer thickness. Materials are compared according to both ionizing and nonionizing effects produced by the passage of protons.

This paper examines the effects of irradiating indium oxide films of nanoscale thickness by ion beams, when these films are in the Cooper-pair insulator state. Radiation effects are predicted on the basis of Monte Carlo simulations of ion transport. Results of numerical experiments are interpreted within the theoretical model of a Cooper-pair insulator. The study suggests that radiation-induced changes in InOx films exposed to ion beams could significantly alter their current-voltage characteristics and that a transition to a metallic state is possible, due to radiation-induced perturbation of the fine-tuned granular structure. Furthermore, incident and displaced ions can break up enough Cooper pairs in InOx films to cause dissolution of this specific insulating state.

Cooper-pair insulators are materials that exhibit superconducting behavior, but under specific conditions, regarding film thickness, bias voltage, applied magnetic field, and presence of magnetic impurities, act as insulators with thermally activated Cooper pairs as charge carriers. This paper investigates possible radiation effects in thin films of such materials. Radiation effects are predicted on the basis of Monte Carlo simulations, using 2D Josephson junction array as a model of material structure. Results of a combined theoretical and numerical analysis suggest that radiation-induced change of the Josephson junction charging energy could significantly affect the current-voltage characteristics of a Cooper-pair insulator, and that a transition to a metallic state is possible, due to radiation-induced disruption of the fine-tuned granular structure. The breaking of Cooper pairs, caused by incident and displaced ions, can also destroy the conditions for this specific insulating state to exist.

This paper investigates possible radiation effects in the Cooper-pair insulator state of indium oxide films. Radiation effects are predicted on the basis of Monte Carlo simulations. Results of a combined theoretical and numerical analysis suggest that radiation-induced changes in the investigated films could significantly affect their current-voltage characteristics, and that a transition to a metallic state is possible, due to radiation-induced disruption of the fine-tuned granular structure. Dissociation of Cooper pairs, caused by both the incident radiation and the ions displaced within InOx films, can also destroy the conditions for this specific insulating state to subsist.

This paper investigates the conditions for the applicability of the geometrical similarity law to impulse breakdown in gases, using statistical methods necessitated by the stochastic nature of the impulse breakdown voltage. Theoretical analysis in the paper is accompanied by experimental results obtained for geometrically similar systems, i.e. for systems with equal shapes of the macroscopic and microscopic electrical field. The experiments were conducted in controlled laboratory conditions, for a wide range of gas pressure and inter-electrode gap values. Two-electrode systems were used, with both homogeneous and non-homogeneous electrical fields, utilizing SF(6), N(2) and He gases as insulators. Standard lightning and switching voltage impulses were applied, as well as ramp-shaped impulses with different slopes. On the basis of the statistical processing of the obtained experimental results, conclusions regarding the conditions for the applicability of the geometrical similarity law to impulse breakdown in gases are drawn.

20 kV distribution networks with all its components, such as transformers, switches, cables etc., have existed and been operating safely for many decades. From an economic point of view, it would be convenient to replace the transformer-motor combination by just a single 20 kV asynchronous motor, even if the motor itself were more expensive. The cost of a transformer, facilities and maintenance gained in this way would easily cover the extra costs of a motor. Efficiency considerations also make elimination of the step-down transformer desirable. Furthermore, modern technological advances make the production of 20 kV asynchronous motors possible, which is proved by the existence of 32 kV generators. The main problem lies in overcoming the differences between the construction of the aforementioned network equipment and the high-voltage asynchronous motor. This paper analyzes the weak points in the insulation system of an asynchronous motor, and proposes improvements allowing motor supply voltage to be increased to 20 kV.

The wide-spread use of semiconductor and gas-filled diodes for non-linear over-voltage protection results in a variety of possible working conditions. It is therefore essential to have a thorough insight into their reliability in exploitation environments which imply exposure to ionizing radiation. The aim of this paper is to investigate the influence of irradiation on over-voltage diode characteristics by exposing the diodes to californium-252 combined neutron/gamma radiation field. The irradiation of semiconductor over-voltage diodes causes severe degradation of their protection characteristics. On the other hand, gas-filled over-voltage diodes exhibit a temporal improvement of performance. The results are presented with the accompanying theoretical interpretations of the observed changes in over-voltage diode behaviour, based on the interaction of radiation with materials constituting the diodes.

This paper discusses the influence of radiation energy and angle of incidence as possible sources of uncertainties in measurements performed by GM counters. Based on the detection efficiency of GM counters, it has been concluded that the energy of incident radiation does not contribute to the overall uncertainty The angle of incident radiation does contribute to overall uncertainty, but only in the case of gamma radiation detection. In that case, the uncertainty should be determined by using geometrical probability.

In this paper we expound on the procedure of determining the pulse tolerable voltage characteristic in the voltage-versus-time frame, by applying the time enlargement law to the breakdown time random variable, and using a single statistical sample for this variable, obtained through experiments with a predefined shape of the voltage load. The suggested algorithm has been experimentally tested for Ar, N(2), and SF(6) gases, in the pat product (pressure x interelectrode gap) range from 10(-4) to 300 bar mm. The testing was performed by comparing the pulse tolerable voltage characteristic of a two-electrode configuration obtained by applying a particular shape of the pulse voltage load with the values corresponding to other pulse voltage shapes, covering a wide range of frequencies. Satisfactory results have been obtained concerning the applicability of the procedure, with certain minor limitations, which are pointed out. [DOI: 10.1143/JJAP.47.8928]

This paper investigates, through theory and experiment, the applicability of the results obtained in laboratory tests of relatively short duration performed on model structures, as a part of the process of designing high-voltage equipment intended for lasting exploitation. Possibilities and limititions of applying these results to practical structures are examined using the methods of mathematical statistics. Special attention is devoted to the influence of electrode surface enlargement and pulse load (overvoltage) prolongation on the statistical behaviour of the pulse breakdown voltage random variable, expressed in the form of the enlargement law. In the theoretical part of the paper, the general four-dimensional (space-time) enlargement law is derived, along with its simplified three-dimensional (surface-time) variant. In the part of the paper related to the experiment, performed with the aim of testing the applicability of the derived surface-time enlargement law to SF6 gas-insulated two-electrode systems, a description of the experimental equipment and procedure is provided, along with the details of measurement data processing. Comparison of experimental results with those predicted by the surface-time enlargement law proved its validity for a two-electrode configuration with a homogenous and radial electric field, insulated by SF6 gas under pressure (with gas pressure as a parameter).

In this paper we expound on the procedure of determining the pulse tolerable voltage characteristic in the voltage-versus-time frame, by applying the time enlargement law to the breakdown time random variable, and using a single statistical sample for this variable, obtained through experiments with a predefined shape of the voltage load. The suggested algorithm has been experimentally tested for Ar, N(2), and SF(6) gases, in the pat product (pressure x interelectrode gap) range from 10(-4) to 300 bar mm. The testing was performed by comparing the pulse tolerable voltage characteristic of a two-electrode configuration obtained by applying a particular shape of the pulse voltage load with the values corresponding to other pulse voltage shapes, covering a wide range of frequencies. Satisfactory results have been obtained concerning the applicability of the procedure, with certain minor limitations, which are pointed out. [DOI: 10.1143/JJAP.47.8928]