Morphology of multiscale defect structures and plastic strain localization during impact perforation of A6061 alloy targets

Mechanisms of plastic strain localization (PSL) and fracture localization (FL) during dynamic (impact) loading accompanied by “plug” formation are related to structural transitions in the ensemble of defects. A characteristic feature of these transitions in the A6061 alloy is the multiscale character of the resulting structures. It is established that two bands featuring multiscale invariance can exist, namely, the PSL and FL bands, the lengths of which depend on the impact velocity. The length of a deformed layer, in which strain is localized, has a clear tendency of growing toward the free surface of the target. The passage from the PSL to FL band is characterized by a sharp increase in the Hurst exponent.     

Peculiarities of the elastic-plastic transition and failure in polycrystalline vanadium under shock-wave loading conditions

Technical Physics Letters - Specific features in the deformation of polycrystalline vanadium under shock-wave loading conditions have been studied by experimental and theoretical methods. Analysis...     

Electroconductive properties of zirconia/carbon nanotube aerogel composite

Electroconductive properties of zirconia/multiwalled carbon nanotube aerogel composite are investigated. The composite exhibits bulk percolation cluster-like conductivity at wide range of spatial scales. Conductive atomic force microscopy reveals the localized nature of conductive properties of the composite on the micro(nano)scopic scale and the uniformity of current distribution in all conductive areas independently of their size. The presence of unlinked conductive chains and the possibility of their linking by dissociating ions are demonstrated in experiments on registration of I–V curves during the evacuation of the composite impregnated with distilled water. The experimental data make it possible to describe the electrical properties of the composite as the properties of a circuit formed by the parallel connections of numerous voltage dividers arranged in a bulk porous structure. These features make the synthesized composite a promising candidate for use in catalysis and water vapor sensors.     

Influence of grain size on the mechanism of fracture of the aluminum alloy V95

Mechanical behavior and mechanisms of fracture of the ultrafine-crystalline (UFC) and the coarse-crystalline (CC) aluminum alloy V95 (Al-6.0 Zn-2.3 Mg-2.0 Cu-0.4 Mn (wt %)) manufactured via using severe plastic deformation, namely, by dynamic equal-channel angular pressing (DCAP), have been studied. It has been demonstrated that the UFC material exhibits improved mechanical properties in comparison with the CC analog. A correlation analysis of fracture surfaces and the determination of the Hurst exponent have made it possible to perform a comparative estimation of the uniformity of the fracture structure and of the fractions of ductile and brittle fractures in the samples with the structure-scale characteristics different in value.     

Fat of the Gut: Epithelial Phospholipids in Inflammatory Bowel Diseases

Inflammatory bowel diseases (IBD) comprise a distinct set of clinical symptoms resulting from chronic inflammation within the gastrointestinal (GI) tract. Despite the significant progress in understanding the etiology and development of treatment strategies, IBD remain incurable for thousands of patients. Metabolic deregulation is indicative of IBD, including substantial shifts in lipid metabolism. Recent data showed that changes in some phospholipids are very common in IBD patients. For instance, phosphatidylcholine (PC)/phosphatidylethanolamine (PE) and lysophosphatidylcholine (LPC)/PC ratios are associated with the severity of the inflammatory process. Composition of phospholipids also changes upon IBD towards an increase in arachidonic acid and a decrease in linoleic and a-linolenic acid levels. Moreover, an increase in certain phospholipid metabolites, such as lysophosphatidylcholine, sphingosine-1-phosphate and ceramide, can result in enhanced intestinal inflammation, malignancy, apoptosis or necroptosis. Because some phospholipids are associated with pathogenesis of IBD, they may provide a basis for new strategies to treat IBD. Current attempts are aimed at controlling phospholipid and fatty acid levels through the diet or via pharmacological manipulation of lipid metabolism.     

Topological Relationships Cytoskeleton-Membrane Nanosurface-Morphology as a Basic Mechanism of Total Disorders of RBC Structures

The state of red blood cells (RBCs) and their functional possibilities depend on the structural organization of the membranes. Cell morphology and membrane nanostructure are compositionally and functionally related to the cytoskeleton network. In this work, the influence of agents (hemin, endogenous oxidation during storage of packed RBCs, ultraviolet (UV) radiation, temperature, and potential of hydrogen (pH) changes) on the relationships between cytoskeleton destruction, membrane nanostructure, and RBC morphology was observed by atomic force microscope. It was shown that the influence of factors of a physical and biochemical nature causes structural rearrangements in RBCs at all levels of organization, forming a unified mechanism of disturbances in relationships “cytoskeleton-membrane nanosurface-cell morphology”. Filament ruptures and, consequently, large cytoskeleton pores appeared. The pores caused membrane topological defects in the form of separate grain domains. Increasing loading doses led to an increase in the number of large cytoskeleton pores and defects and their fusion at the membrane nanosurfaces. This caused the changes in RBC morphology. Our results can be used in molecular cell biology, membrane biophysics, and in fundamental and practical medicine.