Search

The purpose of this study — to represent a detailed description of the procedure for creating and training a neural network mapping on the example of the dynamics modeling of a neural oscillator of the Hodgkin–Huxley type; to show that the neural network mappings trained for single oscillators can be used as elements of a coupled system that simulate the behavior of coupled oscillators. Methods. Numerical method is used for solving stiff systems of ordinary differential equations. Also a procedure for training neural networks based on the method of back propagation of error is employed together with the Adam optimization algorithm, that is a modified version of the gradient descent supplied with an automatic step adjustment. Results. It is shown that the neural network mappings built according to the described procedure are able to reproduce the dynamics of single neural oscillators. Moreover, without additional training, these mappings can be used as elements of a coupled system for the dynamics modeling of coupled neural oscillator systems. Conclusion. The described neural network mapping can be considered as a new universal framework for complex dynamics modeling. In contrast to models based on series expansion (power, trigonometric), neural network mapping does not require truncating of the series. Consequently, it allows modeling processes with arbitrary order of nonlinearity, hence there are reasons to believe that in some aspects it will be more effective. The approach developed in this paper based on the neural network mapping can be considered as a sort of an alternative to the traditional numerical methods of modeling of dynamics. What makes this approach topical is the current rapid development of technologies for creating fast computing equipment that supports neural network training and operation.

The paper describes in brief the functional capabilities of a computer code for optimizing the neutronics model parameters (neutron data, technological parameters, and their covariance matrices) based on results of reactor physics experiments using conditional nonlinear multi-parameter optimization algorithms. The code’s application scope includes adjustment of neutron constants, technological parameters and their covariance matrices based on integral measurement results, formulation of requiremen117198ts with respect to the neutron data uncertainties for achieving the target accuracies in calculation of the reactor functionals, and estimation of the reactor performance prediction accuracy, as well as the informativity and similarity metrics of reactor physics experiments with respect to each other and in relation to the target reactor system. The paper also considers some examples of using the code to refine the neutronics models of nuclear reactor and fuel cycle systems based on results of reactor physics experiments.

A novel method was proposed for the experimental investigation of wavefront distortion introduced to amplified radiation by pumped active elements in high-power laser amplifiers. The method is based on the simultaneous measurement of temperature distribution and the distribution of population density of the excited laser level in active elements. The underlying theory of the technique was presented; various factors affecting the accuracy of wavefront distortion determination were analyzed. The method was tested to study the wavefront distortion and the depolarization of radiation introduced by the Yb:YAG active element of a cryogenically cooled laser amplifier with high-power diode pumping. The focal length of the thermal lens was 0.40 ± 0.03 and 0.47 ± 0.05 m for the horizontal and vertical planes, respectively. The focal length of the electron lens was two orders of magnitude larger. The maximum value of losses induced by depolarization was 8.5%.

Our study explores the integration of three-dimensional (3D) virtual reality (VR) and 3D printing in neurosurgical preoperative planning. Traditionally, surgeons relied on two-dimensional (2D) imaging for complex neuroanatomy analyses, requiring significant mental visualization. Fortunately, nowadays advanced technology enables the creation of detailed 3D models from patient scans, utilizing different software. Afterwards, these models can be experienced through VR systems, offering comprehensive preoperative rehearsal opportunities. Additionally, 3D models can be 3D printed for hands-on training, therefore enhancing surgical preparedness. This technological integration transforms the paradigm of neurosurgical planning, ensuring safer procedures.

The paper provides a brief description of the functionality of the nuclear energy system modelling application package (NESAPP), including a list of modelling objects, key assumptions and areas of application. NESAPP consists of the following main modules: NUDAPS (a module for calculating thermal neutron cross-sections, resonance integrals and one-group neutron cross-sections, and associated uncertainties), NUCLEX (a module for calculating the evolution of the nuclide composition and characteristics of nuclear fuel in reactors and at the nuclear fuel cycle front-end and back-end steps), NUCAB (a module for adjusting isotopic composition and blending), FANES (a module for analysing material flows and integrating data in nuclear energy evolution scenarios), ECNES (a module for assessing economic performance metrics for the nuclear energy evolution scenarios). Each of the modules is a calculation tool that can be used as independent or integrated into the software for technical and economic modelling of nuclear energy systems. Various calculation models are implemented in the modules, allowing users to evaluate the methodological component of the calculation uncertainty in scenario modelling studies and the functionality for assessing the impact of initial data uncertainties on the resulting indicators. The authors also provide some examples of applying NESAPP.

The objective was to explore possibilities with reconstruction of opposable digital stump of the hand transplanted with microvascular anastomoses in frostbite patients. Material and methods Medical histories and long-term results of treatment of two frostbite patients with finger stumps of both hands were reviewed. The triphalangeal finger and the thumb were reconstructed by transplanting the opposable finger stump together with the metacarpophalangeal joint using microvascular and microneural anastomoses. The stumps were mobilized and transplanted to the distal ulnar artery with the venous drainage performed using the dorsal saphenous vein of the hand. Long-term results were examined at 10 years and 2.5 years of surgery. Clinical, radiological, biomechanical and biophysical investigations were produced. Results The bilateral gripping function was restored in recipient stumps without functional damage to the donor stumps. Discriminatory sensitivity of reconstructed fingers was 6mm and 8 mm, the range of active motion in the transplanted joint was 55 and 66 degrees. Discussion Opposable digital stump transplantation with microvascular anastomoses has significant advantages over the classical surgery. The technique allows for one-stage restoration of a finger to have sufficient length, function, adequate blood supply and innervation due to a short digital stump being transplanted with the metacarpophalangeal joint. The advantage over a toe transplant consists of the use of digital structures of the hand that are identical in functionality and the anatomy reducing the need for secondary interventions. Conclusion The method of management can be successfully applied for frostbite patients with hand stumps according to indications.

The paper presents the results from a multi-criteria comparative evaluation of potential deployment scenarios for Russian nuclear power with thermal and sodium-cooled fast reactors in a closed nuclear fuel cycle (the so-called two-component nuclear energy system). The comparison and the ranking were performed taking into account the recommendations and using the IAEA/INPRO software tools for comparative evaluation of nuclear energy systems, including tools for sensitivity/uncertainty analysis with respect to weighting factors. Ten potential Russian nuclear power deployment scenarios with different shares of thermal and sodium-cooled fast reactors were considered, including options involving the use of MOX fuel in VVER reactors. Eight key indicators were used, estimated as of 2100 and structured into a three-level objectives tree. The comparative evaluation and the ranking were carried out based on the multi-attribute value theory. The model for assessing the key indicators was developed using the IAEA/INPRO MESSAGE-NES energy system planning software tool. The information base for the study was formed by publications of experts from JSC SSC RF-IPPE, NRC Kurchatov Institute and NRNU MEPhI. The presented results show that it is possible to enhance significantly the sustainability of the Russian nuclear energy system, when considering multiple performance indicators, through the intensive deployment of sodium-cooled fast reactors and the transition to a closed nuclear fuel cycle. Tasks have been outlined for the follow-up studies to make it possible to obtain more rigorous conclusions regarding the preferred options for the evolution of a two-component nuclear energy system.

Analysis of record achievements in athletics has almost a century of history. The leading method during the study was the ergometric measurement method. Ergometric analysis of the results was performed proceeding from the relationship between the length of the distance and the limit time to overcome it. Analysis of record curves at different running distances was performed on the basis of the technique proposed by N.I. Volkov. To analyse the growth of record achievements, we also applied the logarithmic transformation of exponential dependence. Ergometric analysis of record curves displayed that with each new exponential spike in the improvement of results, an increase in the endurance coefficient is noted. It was established that athletes who train to overcome long running distances have better ergometric indicators characterizing aerobic performance: they are characterized by a higher coefficient of "critical speed" and a less pronounced decrease in the curve of the dependence "speed – time". And middle-distance athletes were characterized by large values of power factor, which gives clear advantages upon performing intense muscular work. The data obtained by us in the analysis of record achievements in short distances and the forecast of records for these distances allowed to distinguish four stages throughout the history of record achievements in athletics, within each of which occurred a radical reorganization of the training methodology used.

The work is aimed at the investigation of the influence of nonlinear active ions concentration profiles in Yb:YAG laser elements on temperature distribution and wavefront distortions during amplification using sub-kilowatt level diode pumping. A mathematical model is presented for the theoretical study of the amplification process in crystals with cubic crystal system. A detailed comparison of Yb:YAG active elements with the same thickness and absorbed pumping power, but with various concentration profiles of Yb3+, ions is carried out. It is shown that the use of active elements with an increasing dopant concentration in the pump beam direction allows one to optimize the temperature profile inside the active element and, thus, reduce the thermal-induced wavefront distortions of the amplified radiation. Modeling is carried out for the experimentally grown crystal with linear concentration gradient profile. It is shown that the linear doping profile with a gradient of 0.65 at.%/mm allows increasing the small-signal gain up to 10% and decreasing the thermal-induced wavefront distortions by ~15%.

Purpose To determine the effect of biometrical parameters of the radial bone and due to edge defect formed on the radius strength properties using calculation methods. Materials and methods The study of bone strength affecting factors was conducted with the aid of experimental and calculation methods. Biometrical parameters were studied in 10 pairs of the human cadaveric radius as an intact bone initially and after the formation of rectangular or triangle-shaped edge cuts. To determine the stress-strain behaviour, mathematical calculations were performed based on the beam flexural theory for isotropic materials. Computation study were conducted using the finite element method with the NX Siemens software package. Based on assumed mathematical models, the actual areas of safe loads in the presence of cuts and values of destructive loads depending on the depth and shape of a cut taking into account the initial curvature of the bone as well as the criteria of a required residual strength in variation of influencing parameters were identified by means of calculations. Results It was established that an increase in bone curvature results in the reduction of longitudinal destructive loads and in increasing values of the normal strength. The 0.05 bone curvature combined with the 0.5 cut causes a decrease in the ultimate load by 20 times (up to 4.8 % for a rectangular cut and to 5.4 % for a triangular cut). A 0.5-deep cut in the bone which curvature is 0.05 enhances the normal stress by 6.9 times for a triangular cut and by 7.8 times for a rectangular one as compared to a bone without curvature. The critical values for the curvature and depth of the cut were established which permit to avoid additional bone reinforcement. Conclusion The strength of the radius with a maginal defect depends not only on the depth of a cut but on its location, shape and on the radius curvature.

The purpose of this review is to present in a unified manner the latest results on mathematical modeling of rough hyperbolic chaos in systems of various physical nature. Main research Methods are the numerical solution of systems of differential equations and partial differential equations, numerical extraction of the phase of oscillatory processes or spatial patterns, calculating of Lyapunov exponents, and studying the mutual arrangement of the stable and unstable manifolds of chaotic trajectories, the calculation of Gaussian curvature of surfaces. These procedures allow to reveal the typical attributes of rough hyperbolic chaos. Results reproduce the studies of already known phenomena, however, their qualitative explanation and quantitative confirmation are given in in a more detailed form, in accordance with the development of ideas about them. Conclusion. Methodologically the proposed review article may be interesting for undergraduate and graduate students in terms of studying the principles of construction and analysis of systems with chaotic behavior.

Phage therapy is now seen as a promising way to overcome the current global crisis in the spread of multidrug-resistant bacteria. However, phages are highly strain-specific, and in most cases one will have to isolate a new phage or search for a phage suitable for a therapeutic application in existing libraries. At an early stage of the isolation process, rapid screening techniques are needed to identify and type potential virulent phages. Here, we propose a simple PCR approach to differentiate between two families of virulent Staphylococcus phages (Herelleviridae and Rountreeviridae) and eleven genera of virulent Klebsiella phages (Przondovirus, Taipeivirus, Drulisvirus, Webervirus, Jiaodavirus, Sugarlandvirus, Slopekvirus, Jedunavirus, Marfavirus, Mydovirus and Yonseivirus). This assay includes a thorough search of a dataset comprising S. aureus (n = 269) and K. pneumoniae (n = 480) phage genomes available in the NCBI RefSeq/GenBank database for specific genes that are highly conserved at the taxonomic group level. The selected primers showed high sensitivity and specificity for both isolated DNA and crude phage lysates, which permits circumventing DNA purification protocols. Our approach can be extended and applied to any group of phages, given the large number of available genomes in the databases.

It seems to be of current interest to consider and analyse possible electrical and non-electrical applications of small and medium sized reactors for both the nearest and more distant future. The paper presents the results of a comparative analysis of the economic attractiveness of nuclear power plant (NPP) designs based on small and medium-sized reactor modules and a large-sized reactor in order to identify conditions for increasing the investment attractiveness of NPP modular design concept. The analysis is based on the evaluation of such economic performance metrics as net present value, present value, internal rate of return, discounted payback period, and levelized cost. It was shown that, in terms of the present value and levelized costs, the NPP modular design concept is less economically attractive in comparison with the NPP design based on a large-sized reactor. In terms of the net present value, internal rate of return and payback period, the NPP modular design concept can be considered economically attractive if only the predicted learning effect is observed when the modules are constructed and the scale factor is not less than 0.5. In this case, it will be economically feasible to construct an NPP based on a small number of medium sized reactor modules. If the scale factor is not less than 0.6, one may talk about the economic attractiveness of NPP designs based on reactor modules of lower power. The impact of various debt financing schemes was analysed and it was demonstrated that, in relative terms, changes in the economic performance indicators are comparable in the implementation of the NPP modular design and a large sized reactor.

Coagulase-negative staphylococci (CNS), in particular Staphylococcus haemolyticus, play an important role in the etiology of nosocomial infections. Most CNS are resistant to beta-lactam antibiotics, which is realized through the production of the second penicillin-binding protein. This protein is encoded by the mecA gene and, together with the genes of recombinases (ccr), is part of the mobile element of staphylococci - the staphylococcal cassette chromosome. During the study, the mecA and ccr genes were analyzed using a collection of 142 genomes of S.haemolyticus. The mecA gene was detected in 117 genomes (82.4%) and had a pronounced conservation. Based on the analysis of recombinase gene sequences, it was established that 118 samples (83%) contain ccr, and 22 different combinations of the mecA and recombinase genes presence are described. The combination of ccrA4B4 was the most common for S.haemolyticus (25%). Type-specific primers were proposed, to assess the variability of recombinase genes, their performance was validated on 54 clinical isolates.