Contact Borders Research Articles

Расчет движения подвижного состава по железнодорожному пути сеточно-характеристическим методом

The application of a grid-characteristic method is proposed for numerical simulation of the movement of rolling stock along a railway track laid on an earth and a bridge. In the study, the railway track is presented using a dynamic system of equations of the theory of elasticity of hyperbolic type. The grid-characteristic method relies on the characteristic properties of the system under consideration and uses finite-difference schemes of high order of accuracy to obtain a space-time solution. The features of railway structures are considered by changing the boundary conditions and conditions at the contact borders. To simulate the areas of contact of wheel pairs of rolling stock with the rail – the "wheel-rail" system – a previously developed pressure boundary condition is applied, modified so as to consider multi-element rolling stock. As a result of computer simulation of the movement of rolling stock along the railway track of various types, full-wave stress distribution in the track structure is obtained, which makes it possible to predict dangerous sections of rolling stock movement.

Effect of Polyvinylidene Fluoride Membrane Production Conditions on Its Structure and Performance Characteristics

Poly (vinylidene fluoride) membranes were prepared by freeze-casting. The effects of PVDF concentration, and freezing temperature on the morphology, crystallization, and performance of prepared membranes were examined. Polymer concentration was varied from 10 to 25 wt%. The freezing temperature was varied from -5 to -25 °C. Dimethyl sulfoxide (DMSO) and distilled water were used as solvents and non-solvents, respectively. The first step of this study was devoted to estimating the optimal concentration of PVDF solution in DMSO. Membranes prepared at different ratios were characterized using physical and mechanical characteristics and porosity. The second step was to optimize the time required for the production of the membranes. In the third step, it was shown that the freezing temperature had a remarkable effect on the morphology of the membranes: as the temperature decreases, there is a transition from spherulite structures to interconnected pores. It was shown that the diversity in the pore pattern for PVDF affects remarkably the water permeability through the polymer membrane. During the monitoring of the spread of crystallized areas during the formation of the membrane, it was found that the crystallization of the solvent begins at localized points of the microscale, further crystallized areas spread radially or unevenly along the surface of the solution, forming contact borders, which can lead to changes in the properties of the membrane in its area.

Chemogenic processes in the Azov paradynamic landscape system

The Azov paradynamic landscape system is characterized by an extraordinary variety of processes and phenomena of interaction between contact contrast media. One of the groups of such processes is chemogenic. Their diversity within the Priazov Paradynamic landscape system is extremely high on land, in the water area of the sea and in the “water-air”, “water-bottom”, “water-land” contact strips. In this regard, the role of chemogenic processes in the course of modern coastal processes and the formation of landscapes of the coastal zone of the sea is significant. They also determine the specifics of many parameters of the Priazov Paradynamic Landscape System.Purpose. The article discusses processes of chemogenic origin occurring in the coastal zone of the sea within boundaries of the Azov Sea paradynamic landscape system. Most of these processes are taking place at the main contact borders like “water-air”, “water-bottom”, and “water-land”. Results. The processes of salt exchange, migration of biogens and gas exchange are considered. It was revealed that chemogenic processes are an essential component of the entire variety of interactions in the coastal zone and are important for its functioning. The processes of aerosol transport of chemical elements and salts from the sea surface onto land and vice versa by atmospheric land-surface flows were analyzed. Characteristics of air saturation with marine salts from the surface of calm water and characteristics of aeolian transfer of salt crystals from the bottom of dried-up bodies of water were considered. The article also pays attention to the features of transfer of pollutants, in particular within seaport areas. Conclusions. Chemogenic processes in the coastal zone define its specific structure, functioning and the result thus being manifested in the development of characteristics of landscape systems such as humidification, salinity, chemogenic migration of substances, healing properties of sea air, high rates of biological productivity.

Cell geometry guides the dynamic targeting of apoplastic GPI-linked lipid transfer protein to cell wall elements and cell borders in Arabidopsis thaliana.

During cellular morphogenesis, changes in cell shape and cell junction topology are fundamental to normal tissue and organ development. Here we show that apoplastic Glycophosphatidylinositol (GPI)-anchored Lipid Transfer Protein (LTPG) is excluded from cell junctions and flat wall regions, and passively accumulates around their borders in the epidermal cells of Arabidopsis thaliana. Beginning with intense accumulation beneath highly curved cell junction borders, this enrichment is gradually lost as cells become more bulbous during their differentiation. In fully mature epidermal cells, YFP-LTPG often shows a fibrous cellulose microfibril-like pattern within the bulging outer faces. Physical contact between a flat glass surface and bulbous cell surface induces rapid and reversible evacuation from contact sites and accumulation to the curved wall regions surrounding the contact borders. Thus, LTPG distribution is dynamic, responding to changes in cell shape and wall curvature during cell growth and differentiation. We hypothesize that this geometry-based mechanism guides wax-carrying LTPG to functional sites, where it may act to “seal” the vulnerable border surrounding cell-cell junctions and assist in cell wall fortification and cuticular wax deposition.

Математическое моделирование упругих возмущений, распространяющихся из очага землетрясения

The goal of this article is the development of the research software for the mathematical modelling of elastic waves propagation originated in the earthquake hypocenter through heterogeneous media. As a source of the perturbation the geophysical focal mechanism model based on the slipping along the fault is used. For the description of dynamic behavior of media the hyperbolic system of equations of elastic media is used with the explicit allocation of contact borders of heterogeneities. It is solved using the grid-characteristic method on curvilinear structured 3D meshes. One feature of used numerical algorithm is its highscalability per core. The usage of curvilinear meshes allows describing a wide variety of geometries with high precision. Mathematical formulation of problem, development of the research software and a set of numerical experiments were done by authors. The results of modelling of propagation of seismic perturbation through geological multilayered medium and assessment of seismic resistivity of ground facility are described in this article. The estimation of software scalability per core was carried out.

Generalized Voronoi Tessellation as a Model of Two-dimensional Cell Tissue Dynamics

Voronoi tessellations have been used to model the geometric arrangement of cells in morphogenetic or cancerous tissues, however, so far only with flat hyper-surfaces as cell-cell contact borders. In order to reproduce the experimentally observed piecewise spherical boundary shapes, we develop a consistent theoretical framework of multiplicatively weighted distance functions, defining generalized finite Voronoi neighborhoods around cell bodies of varying radius, which serve as heterogeneous generators of the resulting model tissue. The interactions between cells are represented by adhesive and repelling force densities on the cell contact borders. In addition, protrusive locomotion forces are implemented along the cell boundaries at the tissue margin, and stochastic perturbations allow for non-deterministic motility effects. Simulations of the emerging system of stochastic differential equations for position and velocity of cell centers show the feasibility of this Voronoi method generating realistic cell shapes. In the limiting case of a single cell pair in brief contact, the dynamical nonlinear Ornstein-Uhlenbeck process is analytically investigated. In general, topologically distinct tissue conformations are observed, exhibiting stability on different time scales, and tissue coherence is quantified by suitable characteristics. Finally, an argument is derived pointing to a tradeoff in natural tissues between cell size heterogeneity and the extension of cellular lamellae.

Hermenêutica gestáltica de uma violência sexual intrafamiliar

This article shows the results of a qualitative research of orientation phenomenological-existential gestalt, which aimed to reveal some meanings attributed to the sexual violence inside family. It was configured as a case study in which the informant , from 9 to 11 years, was victimized by her father. The data were obtained in ONG Republica of Emaus, contemplating reading of documents, informal reports, participant observation and interview. The analysis conjugated, whenever possible, the theory of the interpretation of Ricoeur, concepts of the Gestalt-therapy (contact, figure-bottom and psychological nutrition) and of the Occupational Therapy (areas, components and acting contexts). Units of significance agglutinated meanings of the speech, that revealed positive aspects such as revelation of the experience, expansion of some contact borders and presentation of the weight of the lived experience sometimes as illustration other as bottom and negative aspects: repercussions own-contact without functionality, in the contact with the other and in some acting areas.

Analysis of the abnormal resistance in AlGaN/GaN heterostructure's ohmic contact tests

Ti/Al/Ti/Au and Ti/Al/Ni/Au ohmic contacts were fabricated on AlGaN/GaN heterostructure under different temperatures of rapid thermal processing (RTF). Since abnormal resistance values were observed during the contact resistance testing, the surface morphology and contact borders of the samples were analyzed to determine the physical mechanism. Such abnormal phenomenon is found to originate from cracking of the AlGaN layer during RTF, flowing of Ti/Al metallic liquid along the crevices, and continuous reaction of the metallic liquid with AlGaN/GaN. Such processes result in abnormal conduction channels. The possible mechanism of the crevice formation was discussed, and the possible solutions to avoid the crevices were proposed.

Blocking Wnt/LRP5 signaling by a soluble receptor modulates the epithelial to mesenchymal transition and suppresses met and metalloproteinases in osteosarcoma Saos-2 cells.

We previously reported the Wnt receptor low-density lipoprotein receptor-related protein 5 (LRP5) was frequently expressed in osteosarcoma (OS) tissue and correlated with metastasis and a lower disease-free survival. Subsequent in vitro analysis revealed that dominant-negative, soluble LRP5 (sLRP5) can reduce in vitro cellular invasion. In the current study, we examined the molecular mechanisms of blocking canonical Wnt signaling by sLRP5 in Saos-2 osteosarcoma cells. Transfection of sLRP5 caused a marked up-regulation of E-cadherin in this cell line. This increase in E-cadherin, seen primarily at the cell-cell contact borders, was associated with down-regulation of Slug and Twist, transcriptional repressors which mediate cancer invasion and metastasis. In contrast, N-cadherin, a mesenchymal marker, was reduced by sLRP5. In addition, blocking Wnt signaling by sLRP5 modulated other epithelial and mesenchymal markers (keratin 8 and 18, fibronectin), suggesting a reversal of epithelial-mesenchymal transition (EMT) seen during cancer progression. SLRP5 also reduced the expression of matrix metalloproteinase (MMP) 2 and 14, consistent with a decrease in invasive capacity. SLRP5 transfection decreased both Met expression and hepatocyte growth factor (HGF)-induced cell motility. Taken together, these results support a role for Wnt/LRP5 signaling in invasiveness of a subset of OS cells.

Colony specificity and chemotaxis in the compound ascidian Botryllus schlosseri

We re-investigated the behavior of hemocytes during the non-fusion (rejection) reaction between genetically incompatible colonies of the ascidian Botryllus schlosseri. In the course of the reaction, hemocytes - mainly morula cells - crowd inside the blind ends of marginal vascular vessels (known as ampullae) of the colonial leading edge (LE) facing the foreign colony which suggests the occurrence of chemotactic attraction of circulating hemocytes towards the ampullar lumen. Then, cells migrate, through the ampullar tips, into the partially fused tunics and contribute to the formation of the necrotic spots along the contact borders which characterize the reaction. Studies on histological sections clearly indicate that, although morula cell concentration is always higher in ampullae of the LE than in those of the lateral (L) part of the colony, their frequency significantly increases in LE ampullae of rejecting colonies with respect to LE ampullae of both fusing and isolated colonies. In addition, in vitro chemotaxis experiments demonstrated that blood plasma from incompatible colonies can stimulate morula cell migration through polycarbonate filters and this passage is inhibited by antibodies raised against mammalian pro-inflammatory cytokines. The possible nature and role of molecules recognized by anti-cytokine antibodies in hemocyte migration are discussed.

Numerical analysis of a 3D hydrodynamic contact

We study here the numerical analysis of a hydrodynamic contact in a particular configuration: the 3D incompressible viscous flow of a fluid dragged by a smooth plate over a rough surface. The mathematical model takes into account and discretizes the local topography of the rough profile. The simulation outcome will be the 3D velocity and pressure fields of the fluid film within the contact borders. This work is limited to the study of numerical resolution methods working solely in finite differences. The algorithms will be tested by analysing and comparing their results with analytically known flows.

Competitive dominance among sessile marine organisms in a high Arctic boulder community

In most hard substrate environments, space is a limiting resource for sessile organisms. Competition for space is often high and is a structuring force within the community. In the Beaufort Sea's Boulder Patch, crustose coralline red algae are major space occupiers. This research determined if coralline algae were com- petitively dominant over other sessile organisms. To test this hypothesis, overgrowth was documented in terms of ''winners'' and ''losers'' on the contact borders between different species. Crustose corallines occurred in over 80% of the observed interactions but were only winners in approximately half of them. Most frequently, bry- ozoans, tunicates, and sponges were superior competi- tors over crustose corallines, while at the same time these invertebrate groups were among the least abundant space occupiers.

Small-scale association measures in epibenthic communities as a clue for allelochemical interactions.

The small-scale associations in a rocky subtidal community in the northwestern Mediterranean were studied by a development of the continuous line transect method. This method allowed the overall measurement of non-randomness in interspecific contacts and the assignment of an association index to each species-pair, whose, significance was tested by Monte Carlo procedures. At the same time, the continuous recording allowed the study of the weakening of the interactions with increasing distances. Our purpose was to uncover evidence for allelochemical mechanisms of space occupation and maintenance. A strong non-randomness was found in the interspecific associations. This was mostly due to the interactions of the poecilosclerid sponge Crambe crambe (Schmidt) with its neighbours, especially its negative associations with other sponge species. The strength of the relationships fell drastically over the first few centimeters from the contact borders of the different species. The results pointed strongly to an allelochemical mechanism. The extracts of this sponge featured high bioactivity in laboratory assays, and field experiments demonstrated that the sponge can inhibit the growth of species in the community studied. Standard sampling techniques would have overlooked the spatial structure present in the data. The study emphasizes the need for both contact data and distance data in order to identify the underlying processes reliably. The line transect method provides both types of information easily and allows testing of models and identification of organisms likely to use chemical defenses in space competition. Its use as a preliminary step in studies of chemical ecology might help to detect presumptive allelochemical processes prior to experimental work on the potentially active species.

Stress and fatigue analysis of fretting on a stressed specimen under partial slip conditions

AbstractA new Fretting on a Stressed Specimen (FSS) device has been conceived to help evaluate the influence of static stress on cracking during fretting wear in a sphere‐on‐plane contact. The mechanical analysis of the stressing state induced by such a loading has been performed for elastic conditions. It is completed by the analytical determination of multiaxial Dang Van's fatigue crack nucleation criterion. The theoretical developments are confirmed by tests on a well‐known low alloy steel. Analysing the stressing state of the maximum loading condition at the critical surface contact borders, it is shown that a simple uniaxial approach can be used to define the crack nucleation risk in fretting wear and FSS. Comparing the classic fatigue descriptions that define the admitted alternated stress amplitude as a function of the mean stress value, the VDI approach is found to be the most relevant. Satisfying the linear relationships between stress components, specific FSS relationships are introduced to fit the experiments better. Because of this analytical description, all materials, surface, geometry, and contact parameters can be connected.

The role of integrins in the maintenance of endothelial monolayer integrity.

This paper shows that, in confluent human umbilical vein endothelial cell (EC) monolayers, the integrin heterodimers alpha 2 beta 1 and alpha 5 beta 1, but not other members of the beta 1 subfamily, are located at cell-cell contact borders and not at cellular free edges. Also the alpha v chain, but not its most common partner beta 3, that is widely expressed in EC cell-matrix junctions, is found at cell-cell borders. In EC monolayers, the putative ligands of alpha 2 beta 1 and alpha 5 beta 1 receptors, i.e., laminin, collagen type IV, and fibronectin, are also organized in strands corresponding to cell-cell borders. The location of the above integrin receptors is not an artifact of in vitro culture since it has been noted also in explanted islets of the native umbilical vein endothelium. The integrins alpha 2 beta 1 and alpha 5 beta 1 play a role in the maintenance of endothelial monolayer continuity in vitro. Indeed, specific antibodies to alpha 2 beta 1, alpha 5 beta 1, and the synthetic peptide GRGDSP alter its continuity without any initial cell detachment. Moreover, antibodies to alpha 5 beta 1 increase the permeation of macromolecules across confluent EC monolayers. In contrast beta 3 antibodies were ineffective. It is suggested that the relocation of integrins to cell-cell borders is a feature of cells programmed to form polarized monolayers since integrins have a different distribution in nonpolar confluent dermal fibroblasts. The conclusion is that some members of the integrin superfamily collaborate with other intercellular molecules to form lateral junctions and to control both the monolayer integrity and the permeability properties of the vascular endothelial lining. This also suggest that integrins are adhesion molecules provided with a unique biochemical adaptability to different biological functions.