Long-length ultrafine-grained (UFG) Ti rods are produced by equal-channel angular pressing via the conform scheme (ECAP-C) at 200°C, which is followed by drawing at 200°C. The evolution of ...microstructure, macrotexture, and mechanical properties (yield strength, ultimate tensile strength, failure stress, uniform elongation, elongation to failure) of pure Ti during this thermo-mechanical processing is studied. Special attention is also paid to the effect of microstructure on the mechanical behavior of the material after macrolocalization of plastic flow. The number of ECAP-C passes varies in the range of 1–10. The microstructure is more refined with increasing number of ECAP-C passes. Formation of homogeneous microstructure with a grain/subgrain size of 200nm and its saturation after 6 ECAP-C passes are observed. Strength properties increase with increasing number of ECAP passes and saturate after 6 ECAP-C passes to a yield strength of 973MPa, an ultimate tensile strength of 1035MPa, and a true failure stress of 1400MPa (from 625, 750, and 1150MPa in the as-received condition). The true strain at failure failure decreases after ECAP-C processing. The reduction of area and true strain to failure values do not decrease after ECAP-C processing. The sample after 6 ECAP-C passes is subjected to drawing at 200¯C resulting in reduction of a grain/subgrain size to 150nm, formation of (101¯0) fiber texture with respect to the rod axis, and further increase of the yield strength up to 1190MPa, the ultimate tensile strength up to 1230MPa and the true failure stress up to 1600MPa. It is demonstrated that UFG CP Ti has low resistance to macrolocalization of plastic deformation and high resistance to crack formation after necking.
The influence of ischemia–reperfusion (I/R) action on pancreatic blood flow (PBF) and the development of acute pancreatitis (AP) in laboratory rats is evaluated in vivo by using the laser speckle ...contrast imaging (LSCI). Additionally, the optical properties in norm and under condition of AP in rats were assessed using a modified integrating sphere spectrometer and inverse Monte Carlo (IMC) software. The results of the experimental study of microcirculation of the pancreas in 82 rats in the ischemic model are presented. The data obtained confirm the fact that local ischemia and changes in the blood flow velocity of the main vessels cause and provoke acute pancreatitis.
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The choice of a radiation high-speed non-contact method for measuring the surface temperature of an object under the influence of a hydrogen plasma jet is substantiated. A theoretical assessment ...was made of the contribution of the intensity of recombination and bremsstrahlung plasma radiation to the pyrometer readings. It is shown that under certain conditions hydrogen plasma can be considered transparent to the thermal radiation of the material in the mid-IR wavelength (MWIR) range of 3–5 μm. An infrared spectral ratio pyrometer based on an uncooled two-spectral MIR photodiode with a sandwich structure, designed to control the temperature of an object under study in an experimental setup of a hydrogen plasma gun, is considered. The experimental results of monitoring the surface temperature of some composite material samples in the process of pulsed plasma exposure are presented.
Aim
. To identify land and water areas for inclusion in the regional ecological framework of Sevastopol City and to define the core areas for ensuring the representative character of the nature ...protection network and the ecological stability of the region.
Material and Methods
. Based on field surveys, archival and published data, the structure of the ecological framework of Sevastopol was specified as a part of the Crimean ecological network, developed in 2008. A schematic map of the protected areas and ecological framework elements was developed and calculation of their area carried out using the QGIS‐3.10.10. The index of environmental significance was calculated according to Guryevskikh and a scale for its gradation was suggested. For ecological centres and corridors, the ratio of key areas of the first and second order was analyzed.
Results
. The creation of 34 protected areas was proposed and their conservation value was shown. The boundaries of the core areas and 11 structural elements of the ecological framework were specified, its representativeness was characterized and problems of its implementation were discussed. As a result of optimization of the nature protection network of Sevastopol, the share of the protected areas and ecological framework of the total area of the city will be increased to 37.1 and 66%, respectively. A complex of conservational measures has been proposed for the protection of populations and biotopes of rare species included in the Red Data Book of Sevastopol.
Conclusions
. The creation of new core areas and the optimisation of the nature conservation network will ensure the maintenance of the sustainability of the ecological framework and the ecological stability of the region but will not make significant changes to the previously formed disproportion due to the impossibility of creating large objects with a high category of protection. The implementation of the ecological framework project will help to reduce the risk of losing the biological and landscape diversity of the region.
Extended dark matter (DM) substructures may play the role of microlenses in the Milky Way and in extragalactic gravitational lens systems (GLSs). We compare microlensing effects caused by point ...masses (Schwarzschild lenses) and extended clumps of matter using a simple model for the lens mapping. A superposition of the point mass and the extended clump is also considered. For special choices of the parameters, this model may represent a cusped clump of cold DM, a cored clump of self-interacting dark matter (SIDM) or an ultra-compact minihalo of DM surrounding a massive point-like object. We built the resulting micro-amplification curves for various parameters of one clump moving with respect to the source in order to estimate differences between the light curves caused by clumps and by point lenses. The results show that it may be difficult to distinguish between these models. However, some region of the clump parameters can be restricted by considering the high amplification events at the present level of photometric accuracy. Then we estimate the statistical properties of the amplification curves in extragalactic GLSs. For this purpose, an ensemble of amplification curves is generated yielding the autocorrelation functions (ACFs) of the curves for different choices of the system parameters. We find that there can be a significant difference between these ACFs if the clump size is comparable with typical Einstein radii; as a rule, the contribution of clumps makes the ACFs less steep.
An ultrafine-grained (UFG) austenite Cr-Ni stainless steel was produced by equal-channel angular pressing. The UFG samples were irradiated in a research nuclear reactor up to damaging doses of 12 and ...15dpa at 350°C and 450°C, respectively. The post-irradiation examination featured in this work covers microstructural and mechanical property changes at test temperatures of 20–650°C. Microstructural studies showed that the concentration of Frank loops was considerably lower in the UFG steel compared to in the coarse-grained material. It was also found that irradiation resulted in precipitation of α-phase in triple junctions of the UFG steel. The post-irradiation examination of mechanical properties testified that the UFG steel exhibited lower irradiation hardening and higher strength compared to the coarse-grained material in the entire testing temperatures range, and improved ductility when tested at 500–650°C. In summary, we testified that microstructure refinement of an austenite stainless steel down to UFG scale led to enhancement of its resistance to neutron irradiation at elevated temperatures.
In continuation of a preclinical study of the new alkylating anticancer drug chlonisol {2-3-(2-chloroethyl)-3-nitrosoureido-1,3-propanediol} created by us, its activity was assessed after ...intracranial transplantation of Ehrlich carcinoma and HER2-positive breast cancer into mice. Temozolomide, which is used in the treatment of malignant gliomas, was selected as an alkylating reference drug. Chlonisol significantly increased the median lifespan of tumor-bearing animals, surpassing temozolomide in activity for both tumor models. A comparison of survival curves of mice with HER2-positive breast cancer tumor transplants revealed no therapeutic effect of temozolomide, unlike an obvious increase in the survival of mice in the chlonisol group. Chlonisol can be a potential cytostatic agent in the chemotherapy of neoplastic lesions of the nervous system, which is extremely important in the treatment of HER2-positive breast cancer, which often metastasizes to the brain.
The results of large-scale radiation, genetic, cytogenetic, and molecular genetic studies on the nature and frequency of heritable mutations of two sex-linked and three autosomal genes of
Drosophila ...melanogaster
after exposure to
60
Co γ-rays and 0.85 MeV neutrons are presented. Regularities were established for the studied genes and radiations in the induction of five different types of recessively inherited mutations, which can be combined into two main classes—the class of chromosomal mutations in one way or another affecting the gene under study (changes leading to sterility of F
1
mutants, multilocus deletions, inversion or translocation breakpoint chromosome in the region of gene localization) and a class of “point” gene mutations with a complex spectrum of DNA changes detected by PCR and sequencing. In this report, the results of classical genetic and cytogenetic analysis of these classes of mutations are considered in detail and the frequency of their induction by γ-rays or neutrons is estimated per locus per dose unit (1 Gy). An important and unexpected result of the assessment was the fact that the frequency of “point” mutations turned out to be invariant (on average, 1.15 E-06/locus/Gy) for the studied genes and radiation, in contrast to chromosomal mutations, where a pronounced locus-specificity is observed for individual types of mutations. At the same time, neutrons are two or more times more effective than γ-rays in inducing this class of mutations. It is significant that the average frequency of “point” mutations induction correlates with the average cDNA length of these genes (1.62 kb), but not with their average size (6.07 kb), indicating that the target for “point” mutations is, obviously, not the entire DNA of the gene, but only the informational part of its exons. The dependence of the frequency of chromosomal mutations of one type or another on the position of the gene on the chromosome and in the three-dimensional space of the genome is discussed.
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