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This paper explores the possibility of using dual representation of geometry to speed up ray tracing and ensure robustness of light propagation simulation in complex optical systems with freeform surfaces defined by high-degree polynomials (up to order 34) or Jacobi polynomials. Traditional methods for representing this geometry both as a triangular mesh and as an analytical expression are analyzed. The analysis demonstrates the disadvantages of the traditional approaches due to the insufficient accuracy of calculating coordinates of the point at which the ray intersects the triangular mesh, as well as the non-robustness of the conventional procedures for finding the point of intersection between the tangent ray and the analytical surface. Thus, it is proposed to use a dual representation of geometry as a rough approximation of the surface by a triangular mesh, which is subsequently used as an initial approximation to find the point at which the ray intersects the surface defined by an analytical expression. This approach significantly speeds up convergence of the analytical methods and improves robustness of their solutions. The use of the Intel® Embree library to quickly find the point of intersection between the ray and the rough triangular mesh, as well as a vector model to refine the coordinates of the point of intersection between the ray and the analytically represented geometry, allows us to develop and implement a ray tracing algorithm for an optical system that has surfaces with dual representation of geometry. Experiments carried out using the developed algorithm show a significant speedup of ray tracing while preserving computational accuracy and high robustness of the results. The results are demonstrated by evaluating the point spread function and glare for two lenses with freeform surfaces defined by Jacobi polynomials. In addition, for these two lenses, an image formed by an RGB-D object that simulates a real scene is calculated. [ABSTRACT FROM AUTHOR]

This paper presents an approach to 3D model reconstruction from point cloud data using modern neural network architectures. The method is based on PointNet++ and Transformer. PointNet++ plays a key role, providing efficient feature extraction and encoding of complex geometries in 3D scenes. This is achieved by recursively applying PointNet++ to nested partitions of the input point set in a metric space. Convex decomposition, which is an important step in the proposed approach, transforms complex 3D objects into sets of simpler convex shapes. This facilitates data processing and makes the reconstruction process more manageable. Then, Transformer trains the model on the extracted features, which enables the generation of high-quality reconstructions. It should be noted that Transformer is used only to determine positions of the walls and detect object boundaries. This combination of technologies allows us to achieve high accuracy of 3D model reconstruction. The main idea of the method is to segment the point cloud into small fragments, which are then reconstructed as polygon meshes. To restore missing points in point cloud data, a method based on the L1-median algorithm and local features of the point cloud is used. This approach can adapt to different geometric structures and correct topological connectivity errors. The proposed method is compared with several modern approaches, demonstrating its potential in various fields, including architecture, engineering, digitalization of cultural heritage, as well as augmented and mixed reality systems. This confirms its wide applicability and great perspectives for further development. [ABSTRACT FROM AUTHOR]

The features of hydrogen trapping under the irradiation of zirconium alloys E110 and E635 with an electron beam (400 eV, 0.8 mA/cm2) in various gaseous ambient containing oxygen and hydrogen (Ar + O2 + H2; Ar + H2O) are studied. The effect of surface temperature on the hydrogenation of zirconium alloys under electron irradiation is studied. It is shown that neither exposure nor electron irradiation in a gaseous ambient containing a mixture of H2 and O2 at 700 K for 20 h leads to a change in the hydrogen level in the E110 alloy, while hydrogen partially escapes from the E635 alloy during the experiment. The amount of hydrogen in zirconium alloys after exposure in a gaseous ambient containing H2O in a similar temperature–time regime also changes insignificantly; however, if the alloys are irradiated with electrons under these conditions, then they contain 1.5–2 times more hydrogen. When temperature of the samples is raised to 900 K, electron irradiation in the presence of water vapor, on the contrary, reduces the trapping of hydrogen in the E110 and E635 alloys, compared with exposure in the same gaseous ambient without irradiation. It is concluded that electron irradiation affects the balance of surface reactions of formation of hydroxyl groups from adsorbed water molecules and reverse reactions of formation of water molecules from surface hydroxyls. The direction of shifting the balance of these reactions depends on the surface temperature. [ABSTRACT FROM AUTHOR]

In this paper, we analyze realistic rendering methods in terms of their efficiency in calculating caustic and indirect illumination. As the basic approach to realistic rendering, we choose bidirectional progressive ray tracing with backward photon maps. The main factors that reduce the efficiency of this method are analyzed. It is shown that the main factor that affects its performance is slow access to photon map data. Different techniques for construction of spatial acceleration structures are considered, their advantages and disadvantages are investigated. As the main approaches, we select the regular spatial grid and binary kd-tree. The spatial grid provides high-speed access to photon data at low adaptability of photon map partitioning. The kd-tree is characterized by high spatial adaptability of photon map partitioning but slow access to photon data. We propose a combined solution that takes advantage of the adaptability of the kd-tree and the fast data access of the spatial grid. For this purpose, the regular grid is superimposed on the kd-tree constructed based on the principle of space partitioning of a photon region into geometrically identical halves. To reduce memory consumption, we propose, first, to use multilevel spatial grids superimposed on the selected nodes of the kd-tree and, second, to store spatial grids in the form of hash tables in order to reduce the size of the acceleration structure. Thus, a spatial acceleration structure of a new type—a tree of hash tables—is proposed and implemented. For the spatial structure developed, we implement methods for finding the nearest photons the integration spheres of which cover the illumination point, as well as methods for finding the intersection between a ray segment and photon integration spheres. The proposed software solutions are implemented in the Lumicept software package; for some scenes, the proposed method is compared with the Lumicept method based on the binary tree. The comparison shows that our method can increase the overall speed of the rendering process by more than 40%. [ABSTRACT FROM AUTHOR]

Mixed reality systems are a promising direction of research that opens up great opportunities for interaction with virtual objects in the real world. Like any promising direction, mixed reality has a number of unresolved problems. One of these problems is the synthesis of natural lighting conditions for virtual objects, including the correct light interaction of virtual objects with the real world. Since virtual and real objects are located in different spaces, it is difficult to ensure their correct interaction. To create digital copies of real-world objects, machine learning tools and neural network technologies are employed. These methods are successfully used in computer vision for space orientation and environment reconstruction. As a solution, it is proposed to transfer all objects into the same information space: virtual space. This makes it possible to solve most of the problems associated with visual discomfort caused by the unnatural light interaction of real and virtual objects. Thus, the basic idea of the method is to recognize physical objects from point clouds and replace these objects with virtual CAD models. In other words, it implies semantic analysis of a scene and classification of objects with their subsequent transformation into polygonal models. In this study, we use competitive neural network architectures, which can provide state-of-the-art results. The test experiments are carried out on Semantic3D, ScanNet, and S3DIS, which are currently the largest datasets with point clouds that represent indoor scenes. For semantic segmentation and classification of 3D point clouds, we use the PointNeXt architecture based on PointNet, as well as modern methods of data augmentation in the process of learning. For geometry reconstruction, the Soft Rasterizer differentiable rendering method and the Total3Understanding neural network are considered. [ABSTRACT FROM AUTHOR]

The possibility of implementing physically correct rendering of scenes with caustic illuminance using the DirectX Raytracing API with its subsequent integration into the real-time rendering pipeline is studied. The proposed method is based on the use of additional visibility maps for forward caustic illuminance and visibility maps for backward caustics, which are created for light sources and a virtual camera, respectively. The paper considers the possibility of using backward photon mapping by means of the DirectX Raytracing API and presents an algorithm for calculating the caustic illuminance and the results of testing the software implementation of the proposed algorithm with various method parameters. The dependence of the rendering speed on the scene parameters and characteristics that determine the quality of the caustic luminance calculation—the number of rays emitted by the light source, the maximum depth of the specular ray path, and the number of light sources in the scene is studied. The test results showed that the developed algorithm and its software implementation can provide high-quality calculation of caustic illuminance in real-time and can be used in the gaming industry to increase the realism of visual perception when rendering scenes with complex lighting conditions. [ABSTRACT FROM AUTHOR]

We studied the effect of quercetin on ovarian adenocarcinoma SKOV-3 cell line and isogenic subline SKOV-3/CDDP resistant to the anticancer drug cisplatin. It was found that in resistant cells, quercetin in a concentration of 100 μM that causes a decrease in the cell viability suppressed the expression of genes encoding the key antioxidant enzymes (SOD2, CAT, GPX1, and HO-1), transcription factor Nrf2, and kinases of the PI3K/Akt/mTOR signaling pathway. In parental cells, quercetin, on the contrary, increased the expression of these genes. The results confirm the redox-dependent regulation induced by quercetin and its opposite nature in cisplatin-sensitive and cisplatin-resistant cancer cells. [ABSTRACT FROM AUTHOR]

Regulatory T cells CD4+CD25+FoxP3+СD127low (Tregs) play a key role in the maintenance of tolerance to autoantigens, inhibit the function of effector T and B lymphocytes, and provide a balance between effector and regulatory arms of immunity. Patients with autoimmune diseases are characterized by decreased Treg numbers and impaired suppressive activity. Replacement therapy with autologous Tregs transformed ex vivo could restore the destroyed balance of the immune system. We developed a method for the cultivation of Treg precursor cells. Using this method, we were able to grow up to 300−400 million Treg cells from 50 mL of peripheral blood during a week. In this study, we demonstrated that 90−95% of ex vivo-transformed Tregs had the phenotype CD4+CD25+FoxP3+СD127low and increased the transcription of the FoxP3 and Helios genes. Ex vivo-transformed Tregs were characterized by increased demethylation of the FoxP3 promoter and activation of the proliferation gene markers cyclin B1, Ki67 and LGALS 1. Ex vivo-transformed Tregs had increased suppressive activity, and up to 80–90% of these cells secreted the cytokines TNFα and IFNγ. Our data suggest that ex vivo-transformed autologous Tregs have genetic, immunophenotypic and functional characteristics of regulatory T cells. In the future, they can be used for adoptive immunotherapy of autoimmune diseases and inhibition of transplantation immunity. [ABSTRACT FROM AUTHOR]

Asparaginase is one of the most important chemotherapeutic agents against acute lymphoblastic leukemia, the most common form of blood cancer. To date, both asparaginases from E. coli and Dickeya dadantii (formerly known as Erwinia chrysanthemi), used in hematology, induce chemoresistance in cancer cells and side effects in the form of hypersensitivity of immune reactions. Leukemic cells may be resistant to asparaginase due to the increased activity of asparagine synthetase and other mechanisms associated with resistance to asparaginase. Therefore, the search for new sources of L-asparaginases with improved pharmacological properties remains a promising and prospective study. This article discusses the mechanisms of development of resistance and drug resistance to L-asparaginase, as well as possible ways to overcome them. [ABSTRACT FROM AUTHOR]

The effect of curcumin on the resistance of SKOV-3 human ovarian adenocarcinoma cells to cisplatin was studied. It was found that curcumin induced "reversal" of cancer cells resistance, which was associated with suppression of the expression of genes encoding the key antioxidant enzymes (SOD1, SOD2, CAT, GPX1, and HO-1) and transcription factor Nrf2 and a decrease in the expression of genes encoding kinases of the PI3K/Akt/mTOR signaling pathway. The obtained results confirm the role of redox-dependent regulation in the "reversal" of cancer cells resistance to cisplatin. [ABSTRACT FROM AUTHOR]

This work is devoted to the study of photon mapping methods applied to realistic rendering. In distinction from the conventional rendering methods, the calculation of the indirect and caustic luminance is based on backward photon maps (which are also called observation maps). The main advantages of this method are described. These advantages are the natural distribution of the photons in the regions forming the image luminance and the reduction of the number of photons formed on the trace of one ray. The main algorithmic difficulty of the backward photon mapping method is discussed, which is the necessity to synchronize data access during the calculations and accumulate the luminance due to indirect and caustic illuminance. To resolve this difficulty, it is proposed to use intermediate photon maps of the indirect and caustic illumination distributed over the computation threads that render the corresponding parts of the image. Based on this analysis, the method of progressive backward photon mapping is introduced, and an algorithm of realistic rendering based on this method is described. The proposed algorithm does not require additional synchronization during the accumulation of luminance at the image points, which makes it possible to efficiently implement it not only on the central processor but also on graphics processors (GPUs). Results of the qualitative and quantitative comparison of the rendering results produced by the methods of progressive forward and backward photon mapping are presented. [ABSTRACT FROM AUTHOR]

One of the main problems of mixed reality devices is the lack of universal methods and algorithms for the visualization of virtual world objects in real space. The key point of natural perception of virtual objects in the real world is the creation of natural lighting conditions for virtual world objects by light sources located in the real world, i.e. the formation of natural glares on virtual objects and shadows cast by these objects in the real world. The paper proposes a method for adequately determining the position of the main light sources of the real world in mixed reality systems. Modern technologies that combine the capability of forming 2.5D images created by depth cameras and their subsequent computer processing using neural networks make it possible to identify real-world objects, recognize their shadows, and correctly restore the light sources that create these shadows. The results of the proposed method are presented, the accuracy of restoring the position of the light sources is estimated, and the visual difference between the image of the scene with the original light sources and the same scene with the restored parameters of the light sources is demonstrated. [ABSTRACT FROM AUTHOR]

The activity of novel uncharacterized extremophilic L-asparaginases from the psychrophilic fungi Sclerotiniaborealis, the thermoacidophilic crenarchea Acidilobus saccharovorans, and the thermophilic bacteria Melioribacter roseus were studied. Active enzymes were produced via the expression of the native L-asparaginase gene from M. roseus (MrA) and synthetic genes encoding fungal S.borealis (SbA) and archeal A. saccharovorans (AsA) L-asparaginases after codon optimization in Escherichia coli cells. In the study, the maximum specific activity at different temperatures and pH was observed for MrA. The activity of MrA crude extract was highest at 75°С and a pH of 9.0. Metal ions (1 mM) differed in their effects on enzyme activity. Сu2+ and Zn2+ ions completely abolished enzyme activity. Changes in the specific activity of MrA crude extract in the presence of Fe3+, Ni2+, Ca2+, and Mg2+ varied within 5–28%. Our findings show that L-asparaginase of M. roseus may be a promising object for the further study of enzymatic properties and biotechnological applications. [ABSTRACT FROM AUTHOR]

Juvenile common carp were treated with Cd2+ at a sublethal concentration for Cyprinidae (6.4 mg/L). The expression of N-methyl-D-aspartate receptor subunit genes (NR2A, NR2B) and ATP-binding cassette subfamily C member 1 gene (ABCC1) was compared between treated and untreated fish. In addition, cadmium accumulation in the fish tissues was assessed. NR2A was 18.9-fold upregulated by Cd2+ in the eyes (choroid + retina), which accumulated Cd, and was not upregulated in brain, which didn't accumulate Cd. This may have been caused by the blocking of calcium channels by Cd2+, which has a very similar ionic radius to that of Ca2+. ABCC1 was 2.6-fold upregulated in gills and was not upregulated in liver; both tissues accumulated high levels of Cd. This difference may have been caused by the accumulation of predominantly previously inactivated Cd in liver or by some difference in the mechanisms of self-detoxification from Cd2+ in fish gills and liver. [ABSTRACT FROM AUTHOR]

The importance of the topic of this paper is caused by the rapid development of virtual, mixed, and augmented reality systems. A problem in designing virtual reality (VR), augmented reality (AR) and mixed reality (MR) systems is the assessment of the visual perception of the result, in particular, the assessment of discomfort caused either by differences in the illumination conditions of objects in the real and virtual worlds or by the conflict of the vergence and accommodation of vision of the device user. The standard optical characteristics, such as aberration, frequency and contrast characteristic, and others are not applicable to evaluating the discomfort of visual perception. On the other hand, the discomfort can be assessed using a real proptotype; however, its fabrication can be labor consuming and expensive. We propose methods for virtual prototyping of visual optical systems that can be used in designing AR, VR, and MR devices for the analysis of discomfort caused, for example, by the vergence–accommodation conflict in virtual and augmented reality systems or by differences in the illumination conditions of real and virtual scene objects in mixed reality systems. [ABSTRACT FROM AUTHOR]

Abstract: Stochastic ray tracing is used for rendering photorealistic images formed by augmented reality optical systems that combine the image generated by an optoelectronic device with the image of the environment. Methods for improving the efficiency of stochastic ray tracing that preserve the physical correctness of the simulation are proposed. Using a head-up display (HUD) as an example, it is shown that the forward stochastic ray tracing methods are sometimes more efficient than backward stochastic ray tracing methods for the visual simulation of augmented reality images. Approaches making it possible to combine the forward, backward, and bidirectional ray tracing in a unified simulation procedure are proposed. The results are illustrated by synthesized images produced by the optical system of head-up display. [ABSTRACT FROM AUTHOR]

In the process of optimization of heterologous expression of thermostable chemotaxis proteins CheW and CheY as industrially useful polypeptides, their direct influence on the cell growth kinetics and morphology of Escherichia coli was observed. CheW and CheY of bacteria of the genus Thermotoga, being expressed in recombinant form in E. coli cells, are involved in the corresponding signal pathways of the mesophilic microorganisms. The effects of such involvement in the metabolism of "host" cells are extremely diverse: from rapid aging of the culture to elongation of the stationary growth phase. We also discuss the mechanisms of the influence of the heterologous chemotaxis proteins on cells, their positive and negative effects, as well as potential applications in industry and biomedicine. [ABSTRACT FROM AUTHOR]

Using genetic engineering methods we have developed expression vectors for synthesis of recombinant proteins TnaCheY and TnaCheY-mut, the homologues of the chemotaxis protein CheY from the hyperthermophilic organism Thermotoga naphthophila in Escherichia coli BL21(DE3) cells. The cultivation conditions of transformed cell strains were optimized. The influence of episomal expression of the heterologous chemotaxis protein CheY on growth kinetics parameters of the culture of mesophilic bacteria E. coli was investigated. The optimal purification flowchart of the obtained proteins using thermolysis has been proposed. Based on the data obtained, we discuss potential areas of application of recombinant variants of the CheY thermostable chemotactic protein. Using the E. coli BL21(DE3) laboratory strain as an example, the possibility of employment of the episomal expression of such proteins to control the cultivation and production time of pharmaceutically and industrially valuable metabolites due to the impact on some stages of the bacterial chemotaxis has been experimentally proven. [ABSTRACT FROM AUTHOR]

Normal human CD4+ T-lymphocytes can undergo malignant transformation during prolong cultivation in conditions of high endonuclease G (EndoG) expression or after DNA damage. The aim of this work was to study biochemical and cytogenetic features of transformed ex vivo human malignant CD4+ T- lymphocytes, as well as biochemical and morphological characteristics of tumors that develop in athymic mice after transplantation of these cells. The telomerase activity was higher and telomere length was shorter in tumor cells than in control cells. Transformed malignant cells exhibited a high level of chromosomal aberrations. Expression of genes regulating the cell cycle changed in transformed malignant CD4+ T-lymphocytes and tumor cells. The tumors that developed were classified as multicomponent Т-cell lymphomas and panniculitis-like T-cell lymphomas. Thus, transformed CD4+ T-lymphocytes can generate malignant tumors of various histogenesis. [ABSTRACT FROM AUTHOR]

Mutant homologues of small chemotactic and DNA-binding proteins from thermophilic bacteria Thermotoga petrophila RKU-1 and Thermotoga naphthophila were obtained. These proteins can be expressed in the recombinant form in E. coli cells. A wide range of properties and parameters that are important for isolation of these proteins were revealed: stability in a wide temperature and pH range, high level of expression, solubility, and the possibility of using simple purification schemes with low number of successive steps. The positive effect of proteins on in vitro fibroblasts growth was demonstrated. The described properties of the target proteins indicate the possibility of their use in different biotechnology industries as an inexpensive source of L-amino acids. [ABSTRACT FROM AUTHOR]

It is known that apoptotic endonuclease G (EndoG) induces alternative splicing (AS) of telomerase catalytic subunit TERT (telomerase reverse transcriptase) mRNA and inhibits telomerase activity in tumor cells and activated human T cells. The aim of this study was to investigate the possibility of TERT mRNA AS induction and inhibition of telomerase activity by EndoG in activated mouse and rat lymphocytes. To induce EndoG expression, mouse and rat CD4+, CD8+ T cells, B cells, and NK cells were transfected with the pEndoG-GFP plasmid or incubated with the DNA-damaging agent cisplatin in vitro. The increase in the EndoG expression resulted in decreased expression of full-length active TERT variant, enhanced synthesis of the truncated splicing variant, and decreased telomerase activity. An increase in the EndoG expression, a change in the mRNA pool of TERT splicing variants, and inhibition of telomerase activity were observed in mouse and rat lymphocytes after cisplatin administration in vivo. Thus, EndoG is capable of inducing TERT mRNA AS and regulating telomerase activity in mouse and rat lymphocytes. [ABSTRACT FROM AUTHOR]

In this work, a recombinant chemotaxis CheW protein from Thermotoga petrophila RKU-1 (TpeCheW) and its mutant homologue (TpeCheW-mut) have been obtained. Despite the low homology with the CheW protein of the Escherichia coli bacteria, these proteins do not cause metabolic overload and are well expressed by E. coli laboratory strains. A wide range of features and parameters important for isolation of the TpeCheW-mut protein, such as stability over a wide range of temperatures and pH values, high level of expression, solubility, and the possibility of using simple low-stage purification schemes, including heat pretreatment, has been recognized. Possible directions of using this protein in the practice of scientific and applied research have been formulated and justified. [ABSTRACT FROM AUTHOR]

Activity of the telomerase catalytic subunit hTERT (human Telomerase Reverse Transcriptase) can be regulated by alternative splicing of its mRNA. At the present time, the exact mechanism of hTERT splicing is not fully understood. Apoptotic endonuclease EndoG is known to participate this process. EndoG expression is induced by DNA damages. The aim of this work was to investigate the ability of DNA-damaging agents with different mechanism of action to induce EndoG expression and to inhibit telomerase activity due to the activation of hTERT alternative splicing in normal activated human CD4+ and CD8+ Т lymphocytes. All investigated DNA-damaging agents were able to induce EndoG expression. Cisplatin, a therapeutic compound, producing DNA cross-links induced the highest level of DNA damages and EndoG expression. Incubation of CD4+ and CD8+ Т cells with cisplatin caused the changes in proportion of hTERT splice variants and inhibition of telomerase activity. [ABSTRACT FROM AUTHOR]

The effect of apoptotic endonuclease EndoG on alternative splicing of mRNA of human telomerase catalytic subunit hTERT (human telomerase reverse transcriptase) and telomerase activity in normal human lymphocytes were studied. Human CD4+, CD8+, B, and NK cells were transfected with a plasmid pEndoG-GFP containing EndoG gene or control plasmid pGFP. The levels of mRNA of EndoG or hTERT splicing variants were analyzed by real-time PCR. Protein content was assessed by Western blotting. Telomerase activity was measured by the telomere repeats amplification protocol. EndoG overexpression reduced the expression of active full-length hTERT and increased the expression of inactive splice variant. Shifted balance of hTERT splice variants in cells led to a significant decrease in telomerase activity within 72 h after transfection. [ABSTRACT FROM AUTHOR]

Apoptotic endonuclease EndoG plays a key role in the alternative splicing of mRNA of human TERT telomerase catalytic subunit. The aim of this work was to test the ability of EndoG to induce alternative splicing of mRNA of other genes and in other organisms. To determine new mRNA splice-variants, EndoG overexpression was induced in human, mouse and rat CD4+-T-lymphocytes followed by sequencing of total RNA of these cells. Sequencing results showed that besides TERT, EndoG induced alternative splicing of deoxyribonuclease I (DNase I), caspase-2 (Casp-2) and BCL-x. The expression level of EndoG strongly correlated with mRNA splicing-variants of TERT, DNase I, Casp-2, and BCL-x in intact CD4+-T cells of healthy donors as well as different lines of mice and rats. EndoG overexpression induced down-regulation of fulllength mRNAs of TERT, DNase I, Casp-2, and BCL-x and up-regulation of their short-length mRNAs. Alternative splicing of studied mRNAs resulted in down-regulation of enzymatic activity of proteins in vitro and in vivo. The results of this work confirm the ability of endonuclease EndoG to induce alternative splicing of several mRNAs in human, mice and rats. [ABSTRACT FROM AUTHOR]