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The production of the radioisotope molybdenum-99 in the WWR-K research reactor is achieved through the activation method 98Mo(n,γ)99Mo, utilizing a target of natural molybdenum trioxide irradiated under standard conditions (thermal neutron spectra and water environment). Under such conditions, the maximum specific activity of molybdenum-99 reaches (2.3 ± 0.3) Ci/g Mo after 7 d of irradiation. However, the escalating demand for molybdenum-99 and the need to reduce its production cost, necessitates urgent and increased productivity. This study aims to optimize the irradiation conditions for molybdenum powder in the WWR-K reactor to increase the specific activity of molybdenum-99. For this purpose, we evaluated various irradiation capsule designs comprised various neutron moderator materials and thicknesses. Through extensive modeling calculations, we obtained an optimal capsule design that increases the specific activity of molybdenum-99 to 3.31 Ci per 1 g of Mo.

Background: Catheter ablation (CA) for ventricular tachycardia (VT) can be a useful treatment strategy, however, few studies have compared CA to medical therapy (MT) in the sarcoidosis population. Objective: To assess in-hospital outcomes and unplanned readmissions following CA for VT compared to MT in patients with sarcoidosis. Methods: Data was obtained from the Nationwide Readmissions Database between 2010 and 2019 to identify patients with sarcoidosis admitted for VT either undergoing CA or MT during elective and non-elective admission. Primary endpoints were a composite endpoint of inpatient mortality, cardiogenic shock, cardiac arrest and 30-day hospital readmissions. Procedural complications at index admission and causes of readmission were also identified. Results: Among 1581 patients, 1217 with sarcoidosis and VT underwent MT compared to 168 with CA during non-elective admission. 63 patients admitted electively underwent CA compared with 129 managed medically. There was no difference in the composite outcome for patients undergoing catheter ablation or medical therapy during both non-elective (9.0 % vs 12.0 %, p = 0.312) and elective admission (3.2 % vs. 7.8 %, p = 0.343). The most common cause of readmission were ventricular arrhythmias (VA) in both groups, however, those undergoing elective CA were less likely to be readmitted for VA compared to non-elective CA. The most common complication in the CA group was cardiac tamponade (4.8 %). Conclusion: VT ablation is associated with similar rates of 30-day readmission compared to MT and does not confer increased risk of harm with respect to inpatient mortality, cardiogenic shock or cardiac arrest. Further research is warranted to determine if a subgroup of sarcoidosis patients admitted with VT are better served with an initial conservative management strategy followed by VT ablation.

Background. The central element in a software-defined network (SDN) is a controller that plays a key role in the management and control of network devices. There was a need to research and develop a conceptual model of the SDN controller as the most important part of the network. The purpose of the study is to develop a conceptual model of SDN controller in the AnyLogic program to evaluate the efficiency of data transmission. Materials and methods. This paper examined the performance, resource management efficiency and security of the simulation model. The physical components of the network such as device resource, switching and control nodes are briefly described. An algorithm for traffic distribution, resource management, and control and security functions is developed. The operation of the circuit with the SDN controller is debugged, data is measured, and network performance shortcomings are found. The solution to these shortcomings is to increase the network throughput by increasing the capacity of network equipment. Various tests and evaluation of the performance, efficiency, and stability of SDN controllers and their impact on the network infrastructure were carried out. Results. Setup, configuration of SDN controller network was done. Network with different bandwidths were investigated. Delays and overflows with a set number of incoming packets were identified. Due to the software-defined network with separate control, control and fast configuration of components is possible, it was shown in the experiments. Conclusions. The conceptual model of the SDN controller circuit was considered. But on its basis the positive and negative sides of the scheme with SDN controller have been revealed, and the solution for increasing the network capacity has been revealed.

Technologies associated with using concentrated energy flows are increasingly used in industry due to the need to manufacture products made of hard alloys and other difficult-to-process materials. This work is devoted to expanding knowledge about the processes accompanying the impact of laser pulses on material surfaces. The features of these processes are reflected in the acoustic emission signals, the parameters of which were used as a tool for understanding the accompanying phenomena. The influence of plasma formations above the material surface on self-oscillatory phenomena and the self-regulation process that affects pulse productivity were examined. The stability of plasma formation over time, its influence on the pulse performance, and changes in the heat flux power density were considered. Experimental data show the change in the power density transmitted by laser pulses to the surface when the focal plane is shifted. Experiments on the impact of laser pulses of different powers and durations on the surface of a hard alloy showed a relationship between the amplitude of acoustic emission and the pulse performance. This work shows the data content of acoustic emission signals and the possibility of expanding the research of concentrated energy flow technologies.

We utilized a blend of replica exchange and event-chain Monte Carlo techniques to generate candidate configurations, aiming for a maximal packing fraction of hard disks within a circular enclosure. Our investigation encompassed systems comprising N particles, with N ranging from 300 to 720. Through our analysis, we identified 108 novel maximal packings, with some surpassing existing configurations by over 0.001 in packing fraction. As such, Monte Carlo methods demonstrate their efficacy in tackling optimization challenges of this nature. [ABSTRACT FROM AUTHOR]

A brief review of methods for increasing the diffraction efficiency of optical elements synthesized by direct laser writing is done. It is noted that the previously proposed methods for recording the topology of similar elements using volumetric or surface contour masks do not provide an ultimate solution to a problem of increasing the diffraction efficiency. The performed model and physical experiments on the fabrication of structures of surface-relief phase optical elements by recording zone profiles using oblique laser beams show the fundamental possibility of forming steep side walls of the reverse zone slopes and the feasibility of developing this technology based on laser image generators.

During the last years, the interest in the application of the additive manufacturing (AM), also known as 3D printing, becomes extremely popular in the various fields of the medicine including the dentistry. Currently, metal and ceramic materials are most often used for dental prosthetics manufactured by 3D printing. The yttria-stabilized zirconia (YSZ) ceramics has become the best alternative for metal-based dental restorations. In this regard, the main goal of this review deals with studying the effect of the 3D printing parameters on the macro- and microstructure and, accordingly, on the mechanical properties of the sintered YSZ, and on this basis, to give the practical recommendations to clinical dentistry and further prospects. As most researched in recent years, the 3D printing methods of such ceramics are the Laser-Stereolithography (Laser-SL) and the Stereolithography-Digital Light Processing (SL-DLP) based on the vat-photopolymerization technology and are discussed here. The physical foundations and the technological parameters of these AM technologies are considered. The main attention focuses on the effects of the thermal conditions during the 3D printing on the solidification microstructure (density, grain size, and crystalline phase composition), which is controlled by the manufacturing technologies. In addition, the true hardness and the biaxial flexural strength of the 3D printed YSZ samples are discussed. At last, the advantages of 3D printing ceramics in dentistry are mentioned.

The article is aimed at solving the problem of parametric identification of non-linear object models using the example of a mathematical model of the micro-arc oxidation process. An algorithm for parametric identification, based on an experiment in the micro-arc oxidation process, the results of which form a training and control sample is proposed; sequential training of neural networks and calculation of the parameters estimates of the nonlinear model according to experimental data are performed. Experimental testing of the proposed method of neural network parametric identification on the example of the micro-arc oxidation process confirmed that the standard deviation of current and voltage from the nominal values does not exceed ±4%. The obtained results were used in the development of an intelligent hardware-software complex for the production of protective coatings by the micro-arc oxidation method.

Background. The study is devoted to the issue of improving the accuracy of automated measuring instruments for the electrical parameters of oxide coatings. In measuring instruments, integrating circuits based on an operational amplifier, which is a universal amplifying device, are used to perform linear mathematical operations on analog signals. The disadvantage of the integrating circuit is the use of an operational amplifier, when using which it is necessary to take into account many parameters and factors that can affect the output signal, and hence the accuracy of the measured value. Materials and methods. Methods of indirect measurement of voltage and current on the studied sample with an oxide coating using the proposed structures of measuring channels are presented. It is shown that the parameters of operational amplifiers have a significant influence on the additive and multiplicative errors of measurement results, for the analysis of which a linear model of an operational amplifier is considered. Results. Based on the metrological analysis of the voltage measurement channel on the test sample, formulas for estimating additive, multiplicative and nonlinear error components are obtained. The contribution of multiplicative and additive parameters of the operational amplifier to the error of measurement results is analyzed in detail. Conclusions. Metrological analysis of the equivalent circuit of an operational amplifier with feedback has been performed, which can be used to estimate additive and multiplicative errors of circuits based on operational amplifiers widely used in instruments and measuring systems. It is shown that the total relative error of the developed channels for measuring current and voltage does not exceed 0.5%, which makes it possible to measure these values of the studied oxide coatings with guaranteed accuracy.

The representation of temperature measurement methods is worldwide, as is the number of industries that use them. Their utilization allows one to assess the object’s temperature relatively accurately and further according to the defined dependencies to evaluate its condition. In the medical sector, non-invasive temperature measurement methods are increasingly gaining ground. In our work, we focus on the design of a system for measuring skin temperature using digital DS18B20 thermometers. The technical design consists of the mechanical design of the sensor housing based on the requirements of healthcare professionals, the design of a 1-wire bus active pull-up driver with improved features, and the user software, allowing for the future implementation in various, not necessarily medical environments. The main contribution lies in optimizing the hardware design concerning the components’ parameters and surge protection. In the medical field, the aim was to compare changes in skin temperature in the shoulder region depending on the type of muscle contraction during static and dynamic components of movement and to record the thermal work of the muscle during activity in real-time. We experimented by applying temperature sensors to the deltoid muscle of the dominant limb in a temperature environment of 25.76 °C. In the experimental measurements, we demonstrated that during the three selected muscle work movements, there was a temperature change in the respective regions of the deltoid muscle for each of the three, which the temperature sensors could capture. Our results were statistically significant when comparing the baseline values, and the highest temperature reached. The level of significance $\alpha \leqslant 0.05$ and a low percentage of errors were valid.

The world has experienced a decline in maternal and child mortality in the last few decades, increase in global health expenditure over the years was the major factor responsible for that. But in Africa and other developing countries, the rate of maternal and child mortality has been soaring. The objective of this paper is to investigate the impact of health expenditure on maternal and child mortality in African countries at different income level. On this note, the paper was based on the panel data covering the period of 2000 to 2017 for 39 African countries. After a cross sectional dependence test and panel unit root test, fixed effect results showed that, government health expenditure has no significant impact on reducing child mortality in African countries at all income level. Whereas, it has an impact on reducing the maternal mortality in low-income and lower middle income countries. It was also found that Private health expenditure has significant impact on reducing child and maternal mortality at all income level. Based on this, the paper recommends that governments at different level especially from low-income and lower middle income countries should provide quality health care services and regular immunization for women and children in order to reduce maternal and child mortality in Africa region.

The need to create monitoring systems to equip the technological machinery of automated production determines the relevance of searching for parameters of acoustic signals that carry information about the course of treatment processes. The study of acoustic signals in various types of material processing allowed the identification of general features of changes in their spectral composition associated with variations in the power density of energy impact on processed material. The results of experimental work on various technological equipment, including blade processing and processing with concentrated energy flows, are presented in this work. It is shown that changes in the quality of processing in the form of increased tool wear, the concentration of erosion products during WEDM (wire electrical discharge machining), focal plane displacement during laser processing, etc., lead to a natural change in the ratio of acoustic signal amplitudes in the low frequency and high frequency ranges. This property can be used in monitoring systems for automatic equipment.

The review analyses the microstructure of the commercial Co–Cr–(Mo, W) dental alloys fabricated by 3D digital selective laser melting (SLM), which is the most promising technique among the emerging additive fabrication technologies used for metal products manufacturing in dentistry. In this regard, the main goal is to compare the microstructures of the metal dental products produced by two currently used technologies, namely, conventional casting and SLM. We consider the latest research published from 2013 to 2022. The microstructures are evaluated using optical microscopy (OM), scanning electron microscopy with energy-dispersive x-ray spectroscopy (SEM–EDS), x-ray diffractometry (XRD), electron backscatter diffraction (EBSD) pattern analysis, and atomic force microscopy (AFM). The microstructure analysis allows concluding whether the SLM fabrication process is suitable for dental applications. As shown, the microstructure of the Co–Cr dental alloys depends on both the chemical composition of the samples and the parameters of the manufacturing technique used. Experimental results have proven that, in contrast to the conventional casting, the SLM-fabricated specimens display superior microstructure due to complete local melting and rapid solidification. Additionally, the SLM process minimizes residual flaws and porosity. As a result, SLM allows producing the dense material comprising homogeneous fine-grain microstructure.

Subject and Purpose. The problems under consideration concern selection and focusing of higher-order modes in a waveguide-based dielectric laser. The purpose is to clarify the physics underlying the behavior of, and permitting control over, continuous terahertz-frequency laser beams of various spatial polarizations. Methods and Methodology. The mode parameters of the waveguide-based laser resonator involving an inhomogeneous phase-stepped mirror were calculated in a matrix technique. To analyze the propagation and focusing of the laser beams that can be excited in a variety of diffraction zones by the wave modes of a waveguide-based quasi-optical resonator, a vectorial Rayleigh–Sommerfeld theory was used. The pertinent experimental studies were performed with the use of known measurement methods suitable for the terahertz frequency range. Results. A method for selecting the higher-order EH12q-mode of a terahertz-range laser resonator has been suggested, substantiated theoretically and approbated in experiment. It envisages placing an additional element to perform control over the system’s modal structure, namely a (2.3…2.8) λ-wide groove on the surface of one of the resonator mirrors. This measure can significantly increase losses for all undesirable modes. At the same time, the losses for the higher EH12q-mode remain practically unchanged, which creates conditions for its predominant excitation. Theoretical and experimental studies of moderate and ‘sharp’ focusing in free space of higher-order modes with different spatial polarizations of a dielectric waveguide-based resonator have been carried out. Conclusion. As has been shown, the proposed phase-stepped mirror with a groove can effectively select the higher-order transverse modes that may be required. The linearly polarized EH12q-mode has maximum field intensity in the focal region of the lens employed. For azimuthally polarized TE02q- and TE03q-modes the central lobes, noticeably shifted from the focus of the lens, have a field maximum. An increase in the axial intensity is observed upon ‘sharp’ focusing in the field distribution of the radially polarized TM02q- and TM03q-modes. In this case their central lobes, like those of the higher TE0nq-modes, are noticeably shifted from the lens focus.