Physics of Atomic Nuclei最新文献

The structure of the compact X-ray source based on inverse Compton scattering designed at the National Research Nuclear University MEPhI as part of the project to create a gamma radiation source based on the electron storage ring is presented. The magnetic structure of the storage ring has been optimized using a genetic algorithm. Electron beam dynamics in a linac injector and the storage ring is discussed. The influence of collective effects in the storage ring on the possibility of obtaining the required parameters of the electron beam at the point of interaction with the laser pulse has been studied.

Several series of thin tantalum nanocluster films deposited on a quartz crystal are obtained. The masses of the films are measured using a quartz mass sensor. In each series, the films have characteristic particle sizes of 1.5 to 6.5 nm. Results from measuring mass show the ratio of the deposited mass to the incident volume of clusters differs for different sizes. A physical model of the particle deposition process is proposed and studied to explain the observed effect. According to modeling results, the focusing of particles does not change with size and is found to depend weakly on the initial velocity of the particles. It is concluded that the main reason for the above effect could be the difference between the coefficient of adhesion for particles of different sizes. It is proposed that this assumption be tested through additional experiments.

A comparative study of the structure of PM HIP compacts made using spherical particles (granules) of rapidly quenched PREP powder of a heat-resistant α+β Ti-based alloy and a similar product manufactured using traditional technology has been carried out. Multi-scale study of the microstructure of PM HIP compacts and an analogous product manufactured using traditional technologies has been performed by metallography, SEM, TEM, EDX, and OIM. The influence of vacuum heat treatment and temperature consolidation of HIP in the regions of (α+β) and β phases on the regularities of the structure formation of PM HIP compacts of the heat-resistant titanium-based alloy has been revealed. Features of microstructures such as lamellar, bimodal microstructure and grains have been detected and studied in detail in PM HIP compacts and in a product obtained by traditional technology. The extreme behavior of the partition ratio k_d of alloying elements between the α and β phases in the product obtained using traditional technology, in comparison with PM HIP compacts, has been discovered and studied in detail. Analysis of the obtained result, in comparison with the results of a comparative study of the structure and properties of PM HIP compacts obtained using rapidly quenched PREP powders and products obtained using traditional technology from stainless steels and Ni based superalloys, has allowed the following important conclusion. The cooling rate during solidification is the dominant factor in the formation of the final structural-phase state (composition of α and β phases in the Ti alloy) and, therefore, is a key hereditary technological parameter that determines the structural-phase state and the increased level of mechanical properties of PM HIP compacts compared to the product obtained using traditional technology.

Today, most scientific equipment designed to measure cosmic ray particle fluxes is located on the Earth’s surface. Those instruments record the intensities of secondary cosmic rays, which are created after the interaction of cosmic rays with the Earth’s atmosphere. With the advent of spectrometric equipment installed on space satellites, direct measurements of cosmic ray fluxes in a wide energy range have become possible. However, precise information on such measurements is not always available. Scientific equipment in outer space is subject to radiation wear, which manifests in a significant deterioration in the efficiency of particle registration. Neutron monitors have been stably measuring cosmic ray intensities for several decades. They are located on the Earth’s surface therefore they are not subject to radiation wear and. The paper discusses an algorithm for calibrating neutron monitors using satellite experiment data and the prospects for its application in analyzing cosmic ray particle fluxes during periods of minimum and maximum solar activity cycles, as well as during forbush decreases.

Radiopharmaceuticals (RPs) specific to prostate-specific membrane antigen (PSMA) are extremely promising for radioligand therapy of prostate cancer. The aim of this work was to study the general toxic properties of radiopharmaceutical ²²⁵Ac-DOTA-PSMA after its single intravenous administration to laboratory animals (“acute” toxicity). It was shown that the administration of  ²²⁵Ac-DOTA-PSMA to mice and rats (males and females) in doses of 100, 200, and 500 kBq/kg was satisfactorily tolerated by the animals. No significant signs of intoxication or death of animals were observed. No pathomorphological changes in internal organs and tissues were detected at autopsy of animals. In mice treated with ²²⁵Ac-DOTA-PSMA at doses of 200 and 500 kBq/kg, a decrease in the mass of salivary glands by 8–15% was observed compared to the control group (p > 0.05).

The paper considers the application of meteorological characterisation methodology to the regions recommended for NPP construction in Nigeria. Regions Geregu and Itu are considered as such, with significantly different meteorological characteristics, as they are located in different parts of the country (the former in the arid region, in the centre of the country, the latter—on the coast of the Gulf of Guinea in the Niger Delta). The methodology provides the mathematical apparatus for calculating the main characteristics of the surface layer of the atmosphere model. The use of this apparatus made it possible to estimate the general character of meteorological characteristics of the regions (longitudinal wind speed, turbulent diffusion coefficient, parameter characterising the transverse dispersion of impurity) and their averaged values used further as some parameters allowing to determine the characteristics of environmental radioactive contamination, which can include the air basin and the underlying surface. The use of a geophysical model of the surface layer of the atmosphere and the meteorological parameters obtained made it possible to answer a number of questions concerning the peculiarities of atmospheric transport of radioactive impurity characteristic of the regions of Nigeria in which the Government of Nigeria intends to build nuclear power plants. Therefore, the axial and transverse distributions of radioactive impurity as a function of atmospheric stability were obtained under hypothetical radiation accidents, which revealed the peculiarities of radioactive impurity distribution in these regions. The presented results of calculations should be taken into account when estimating the size of the buffer area around NPPs in one and another region and the necessary and sufficient number of environmental radiation monitoring stations when they are located within these zones.

The generation and dynamics of reverse electron flows in a high-power vacuum neutron tube leading to the intense heating of the elements of the discharge node up to their melting are analyzed. The contribution of each component of the reverse electron flow to the heating of the discharge node is considered.

A numerical model for calculating magnetic and mechanical stresses of the superconducting toroidal magnetic field superconducting system of a spherical tokamak is developed. Three configurations are considered: the Princeton-D solenoid and two different helical continuous solenoid configurations. The magnetic field distributions of the solenoids and the mechanical stress distributions to which they are subjected are calculated. It is demonstrated that the Princeton-D solenoid is the least favorable: the modulus of induction of the magnetic field on its windings is an order of magnitude greater than that of the continuous solenoids, resulting in a significantly lower—by 34%—maximum possible current throughput. The mechanical stresses in the first case are also noticeably higher. It is also shown that the two variants of the helical configuration differ insignificantly from each other.

The development of innovative fluorescence detection methods based on optically encoded microspheres of different colors and sizes is an important area of multiplexed detection and diagnosis of various diseases. For example, the xMAP technology of the American company Luminex employs polystyrene microspheres labeled with two or three organic fluorophores at different ratios, each with its unique spectral characteristics. Although xMAP can detect as many as 80 proteins or DNA sequences in a single test system, the need to use special equipment, produced only by the same company, for multiplexed analysis, as well as inherent disadvantages of organic fluorophores (a large Stokes shift and photobleaching under laser excitation) limit the applications of this technology. The objectives of this study were to design and fabricate microspheres encoded with semiconductor quantum dots. Carboxylated melamine-formaldehyde microspheres of three sizes were optically encoded with quantum dots of two colors immobilized between layers of oppositely charged polyelectrolytes on the surface of the microspheres. As a result, six populations of microspheres with different sizes and/or unique optical codes were obtained, characterized by a long-term stability and homogeneity in aqueous solutions. Analysis of the microspheres by the dynamic light scattering, epifluorescence microscopy, and flow cytometry methods showed their suitability for multiplexed analysis. At the same time, the use of quantum dots for optical encoding makes it possible to exclude photodegradation of the signal and to excite all quantum dot populations at the same wavelength of radiation, with effective separation of signals from the microspheres into different channels of a standard flow cytometer.

A method has been proposed to process and analyze the proximity by type-defining characteristics of large aggregations M > 10⁴ of various types Q > 10² of empirical discrete random frequency vectors RFV ≡ (nu ( cdot ) = {{nu }_{0}},~...~,{{nu }_{l}}) obtained from small volume samples (10 geqslant n = sumnolimits_{i = 1}^l {{{nu }_{i}}(k = i)} ) of random counts k = 0, 1, …, l with mean value (bar {k} < 5) over all samples. The method is based on a bijection between the RFV and its type-defining identifier (I(nu ,a) > 0) a) > 0, which is a linear statistic in the form of the scalar product of ν and the non-RFV a. The discrete multimodal empirical distributions (Cleft( {I(nu ,a)} right)) representing sequences of arranged by (I(nu ,a))and grouped peaks facilitate the analysis and prediction of the characteristics of peaks and the RFVs forming them with low frequencies of their occurrences at the given M value.