Contact Structure Research Articles

Dasatinib suppresses collective cell migration through the coordination of focal adhesion and E-cadherin in colon cancer cells

Collective cell migration is an important process in cancer metastasis. Unlike single-cell migration, collective cell migration requires E-cadherin expression in the cell cohort. However, the mechanisms underlying cellular contact and focal adhesions remain unclear. In this study, Src was hypothesized to coordinate focal adhesion and Rab11-mediated E-cadherin distribution during collective cell migration. This study primarily used confocal microscopy to visualize the 3D structure of cell-cell contacts with associated molecules. These results demonstrate that the clinical Src inhibitor dasatinib was less toxic to HT-29 colon cancer cells; instead, the cells aggregated. 3D immunofluorescence imaging showed that Rab11 was localized with E-cadherin at the adherens junctions of the apical cell-cell contacts. In the transwell assay, Rab11 colocalized with a broad range of E-cadherin proteins in collectively migrated cells, and dasatinib treatment significantly suppressed collective cell migration. Transmission electron microscopy demonstrated that dasatinib treatment increased cell membrane protrusion contacts and generated spaces between cells, which may allow epidermal growth factor receptor activity at the cell-cell contacts. This study suggests that dasatinib treatment does not inhibit cell survival but targets Src at different cellular compartments in the coordination of focal adhesions and cell-cell contacts in collective cell migration through E-cadherin dynamics in colon cancer cells.

From complex contact structures to real almost contact 3-structures

From complex contact structures to real almost contact 3-structures

On the space of null geodesics of a spacetime: the compact case, Engel geometry and retrievability

We compute the contact manifold of null geodesics of the family of spacetimes left{ left( mathbb {S}^2times mathbb {S}^1, g_circ -frac{d^2}{c^2}dt^2right) right} _{d,cin mathbb {N}^+text { coprime}}, with g_circ the round metric on mathbb {S}^2 and t the mathbb {S}^1-coordinate. We find that these are the lens spaces L(2c, 1) together with the pushforward of the canonical contact structure on STmathbb {S}^2cong L(2,1) under the natural projection L(2,1)rightarrow L(2c,1). We extend this computation to Ztimes mathbb {S}^1 for Z a Zoll manifold. On the other hand, motivated by these examples, we show how Engel geometry can be used to describe the manifold of null geodesics of a certain class of three-dimensional spacetimes, by considering the Cartan deprolongation of their Lorentz prolongation. We characterize the three-dimensional contact manifolds that are contactomorphic to the space of null geodesics of a spacetime. The characterization consists in the existence of an overlying Engel manifold with a certain foliation and, in this case, we also retrieve the spacetime.

Canonical curves and Kropina metrics in Lagrangian contact geometry

We present a Fefferman-type construction from Lagrangian contact to split-signature conformal structures and examine several related topics. In particular, we describe the canonical curves and their correspondence. We show that chains and null-chains of an integrable Lagrangian contact structure are the projections of null-geodesics of the Fefferman space. Employing the Fermat principle, we realize chains as geodesics of Kropina (pseudo-Finsler) metrics. Using recent rigidity results, we show that ‘sufficiently many’ chains determine the Lagrangian contact structure. Separately, we comment on Lagrangian contact structures induced by projective structures and the special case of dimension three.

In-Depth Analysis on Self Alignment Effect of the Fermi-Level Using Graphene on Both n- and p-Type Semiconductors.

Optimizing the contact structure while reducing the contact resistance in advanced transistors has become an extremely challenging problem. Because the existing techniques are limited to controlling only one semiconductor type, either n- or p-type, owing to their work function differences, significant challenges are encountered in the integration of a contact structure and metal suitable for both n- and p-type semiconductors. This is a formidable drawback of the complementary metal-oxide-semiconductor (CMOS) technology. In this paper, we demonstrate the effectiveness of a metal/graphene/semiconductor (MGrS) as a universal source/drain contact structure for both n- and p-type transistors. The MGrS contact structure significantly enhanced the reverse current density (JR) and reduced the Schottky barrier height (SBH) for both semiconductor types. From the analysis of the SBH values and their relationship with the metal work function, which refers to the S-parameter, the van der Waals contact of graphene (Gr) effectively alleviated the Fermi level (FL) pinning for both semiconductor types, reducing the metal-induced gap states (MIGS) at the Gr/semiconductor interface. Furthermore, Gr effectively modulated the work function of the contact metal to yield a position favorable for each semiconductor type. Consequently, a single MGrS contact structure on a Si substrate resulted in excellent Ohmic contacts in both n- and p-type Si, with SBH values reduced to 0.012 and 0.024 eV for n- and p-type Si, respectively. This new approach for integrating the contact structures of semiconductor types will lead to extended capabilities for high-performance device applications and CMOS logical circuitry.

Effect of Channel Shape on Performance of Printed Indium Gallium Zinc Oxide Thin-Film Transistors.

Printing technology will improve the complexity and material waste of traditional deposition and lithography processes in device fabrication. In particular, the printing process can effectively control the functional layer stacking and channel shape in thin-film transistor (TFT) devices. We prepared the patterning indium gallium zinc oxide (IGZO) semiconductor layer with Ga, In, and Zn molar ratios of 1:2:7 on Si/SiO2 substrates. And the patterning source and drain electrodes were printed on the surface of semiconductor layers to construct a TFT device with the top contact and bottom gate structures. To overcome the problem of uniform distribution of applied voltages between electrode centers and edges, we investigated whether the circular arc channel could improve the carrier regulation ability under the field effect in printed TFTs compared with a traditional structure of rectangular symmetry and a rectangular groove channel. The drain current value of the IGZO TFT with a circular arc channel pattern was significantly enhanced compared to that of a TFT with rectangular symmetric source/drain electrodes under the corresponding drain-source voltage and gate voltage. The field effect properties of the device were obviously improved by introducing the arc-shaped channel structure.

Geometry of non-standard Hamiltonian structures of Liénard equations and contact structure

We start with a self-contained brief review of the construction of non-standard Lagrangian and Hamiltonian structures for the Liénard equations satisfying Chiellini condition, we apply it to a special polynomial class of Liénard equation and explore the integrability structure. Then after a brief exposition of the contact geometry and its connection with the non-standard Hamiltonian structures, we describe the time evolution of the contact Hamiltonian and Liénard equation. We present the formulation of the Liénard equation in terms of General Equation for the Non-Equilibrium Reversible–Irreversible Coupling (GENERIC) method and also study the gradient-type flow. Finally, we describe the generalized Liénard equation by using the conformal Hamiltonian mechanics and illustrate our construction using spatio-temporal and autocatalysis systems.

Rotation-based schedules in elementary schools to prevent COVID-19 spread: a simulation study

Rotations of schoolchildren were considered as a non-pharmacological intervention in the COVID-19 pandemic. This study investigates the impact of different rotation and testing schedules.We built an agent-based model of interactions among pupils and teachers based on a survey in an elementary school in Prague, Czechia. This model contains 624 schoolchildren and 55 teachers and about 27 thousands social contacts in 10 layers. The layers reflect different types of contacts (classroom, cafeteria, etc.) in the survey. On this multi-graph structure we run a modified SEIR model of covid-19 infection. The parameters of the model are calibrated on data from the outbreak in the Czech Republic in spring 2020. Weekly rotations of in-class and distance learning are an effective preventative measure in schools reducing the spread of covid-19 by 75–81% . Antigen testing twice a week or PCR once a week significantly reduces infections even when using tests with a lower sensitivity. The structure of social contacts between pupils and teachers strongly influences the transmission. While the density of contact graphs for older pupils is 1.5 times higher than for younger pupils, the teachers’ network is an order of magnitude denser. Teachers moreover act as bridges between groups of children, responsible for 14–18% of infections in the secondary school compared to 8–11% in the primary school. Weekly rotations with regular testing are a highly effective non-pharmacological intervention for the prevention of covid-19 spread in schools and a way to keep schools open during an epidemic.

Nambu-Goto strings with a null symmetry and contact structure

Nambu-Goto strings with a null symmetry and contact structure

Finite Element Analysis of Nonlinear Contact Problems with Mixed Eulerian-Lagrangian Description

<p class="Abstract">This study deals with analysis of structures using mixed Eulerian-Lagrangian description. Apart from generally used Lagrangian description which uses initial configuration as reference, the newly proposed uses one of actual configuration as reference. Therefore, the total displacement is decomposed into two portions, i.e., the portion covering displacement from initial into referential configuration called Eulerian displacement, and the portion covering displacement from referential configuration into current configuration called Lagrangian displacement. The new technique is suitable to be applied to several classes of structures such as frictional contact and tensile structures. Eulerian displacement is used to represent relative displacements between material points paired in a nodal point in which slip mode occurs, while Lagrangian displacement is used to represent mutual displacement of material points paired in a nodal point in which stick mode occurs. The method was applied to certain contact problems, and the results obtained agreed fairly well with existing results found in references.</p>

“Circumbaltian space”: methodological priorities and regulatory grounds for delimitation

This paper outlines the methodological priorities for delimitating the Circumbaltian space as a unique geospatial form, namely: the geospatial approach, constructive modeling, the geohistorical paradigm, and the geotory concept. Based on the above, along with the theoretical and methodological ideas and algorithmic proposals outlined by the author in earlier works, as well as the regulatory prerequisites for delimitating the outer core of the Baltic naval civilization, the paper sets its land, water, and air boundaries. The author designs a three-step methodology for ranking coastal spaces and describes the basic land and water contact structure of the Baltic for urban planning purposes. The paper also draws legally compliant generalized boundaries of the Circumbaltian space and designs a basic digital model of this geospatial form.

Almost contact structures on the set of rational curves in a 4-dimensional twistor space

Almost contact structures on the set of rational curves in a 4-dimensional twistor space

A hybrid nanogenerator based on wind energy harvesting for powering self-driven sensing systems

The increase in energy demand makes it urgent to explore green energy sources. And wind energy is one of the most promising renewable energy sources. In this paper, a rotating hybrid nanogenerator with a combination of a direct-current triboelectric nanogenerator (DC-TENG) and an electromagnetic generator (EMG) is designed; the design concept is to harvest wind energy. First, an optimized ternary DC-TENG is designed based on the ternary dielectric triboelectrification effect. A soft contact structure is designed, which can effectively increase the frictional area as well as reduce the frictional resistance. Then, by introducing the EMG unit, the output power of the device and the speed of charging the capacitor are increased. The high output voltage of the DC-TENG and the high output current of the EMG complement each other to produce excellent power output. At 180 rpm/min, the output power of DC-TENG and EMG can reach 1.78 mW and 215 mW, respectively. With a simple power management circuit design, the device is successfully implemented to power small electronic devices. By charging a suitable capacitor, the device can be used as a power supply to power the sensor. Together with the sensor and power management circuit, it forms a self-powered sensing system that can drive the sensor for continuous operation. This work provides a simple, convenient, and reliable design that offers new insights into energy harvesting in nature.

An Environmental Evaluation of Ventilation Systems Aimed at Reducing Indoor Radon Concentration

The primary measures against radon in buildings are a tight contact structure or venting the subsoil beneath the building. In many cases, ventilation systems used in buildings to ensure good indoor air quality can also be used to reduce the radon concentration. This study aims to evaluate the environmental impacts of residential ventilation systems for their ability to lower the concentration of this gas. The life cycle assessment methodology was used to assess two kinds of ventilation systems. The results indicate that 95% of environmental impacts are associated with operational emissions, while 5% are associated with embodied ones. Moreover, an increase in radon supply rates resulted in an increase in energy consumption and related emissions, for example, the operational energy of an exhaust ventilation system aimed for a reduction to 200 Bq/m3 in a 9/15 cyclic mode range from 9.69 for a radon supply rate of 50 Bq/m3h to 32.27 for 200 Bq/m3h. These simulations show that ventilation systems cannot be considered universally suitable measures to reduce the radon concentration because they may become very energy demanding, and their environmental impact may be significant even considering the type of energy source. Based on this study, we can determine whether it makes sense for a given radon supply rate and energy source to use a ventilation system to reduce the radon concentration in residential buildings.

Compactifications of indefinite 3-Sasaki structures and their quaternionic Kähler quotients

We show that 3-Sasaki structures admit a natural description in terms of projective differential geometry. First we establish that a 3-Sasaki structure may be understood as a projective structure whose tractor connection admits a holonomy reduction, satisfying a particular non-vanishing condition, to the (possibly indefinite) unitary quaternionic group Sp(p,q)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\ ext {Sp}}(p,q)$$\\end{document}. Moreover, we show that, if a holonomy reduction to Sp(p,q)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\ ext {Sp}}(p,q)$$\\end{document} of the tractor connection of a projective structure does not satisfy this condition, then it decomposes the underlying manifold into a disjoint union of strata including open manifolds with (indefinite) 3-Sasaki structures and a closed separating hypersurface at infinity with respect to the 3-Sasaki metrics. It is shown that the latter hypersurface inherits a Biquard–Fefferman conformal structure, which thus (locally) fibers over a quaternionic contact structure, and which in turn compactifies the natural quaternionic Kähler quotients of the 3-Sasaki structures on the open manifolds. As an application, we describe the projective compactification of (suitably) complete, non-compact (indefinite) 3-Sasaki manifolds and recover Biquard’s notion of asymptotically hyperbolic quaternionic Kähler metrics.

Dynamic properties of sand with different contents of clay

In this study, a series of dynamic triaxial tests and corresponding simulations using discrete element method (DEM) were conducted on sand with different clay particle contents. The development of pore pressure, axial strain, stress path, and stress–strain curve were analyzed. The contact and pore structure characteristics were further examined through electron microscopy. Subsequently, the concept of a contact-to-particle ratio is proposed to describe the connection behavior. The results show that the influence of the clay particle content on the liquefaction resistance is not monotonous. With an increase in clay particle content, the effective stress of sand cannot reach zero. However, the increase in clay particles reduced the permeability coefficient of the sand, which resulted in weak liquefaction resistance of sand. When clay particle content reached 30–35%, the stress–strain curve failed at an early stage. The contact-to-particle ratio was the smallest when the clay particle content was 35%, that effective contact of the particles is only 15% of that in the pure sand sample. When clay content reached 40–50%, the sand sample gradually exhibited the characteristics of clay.

FINITE ELEMENT ANALYSIS OF THE STRESS-STRAIN STATE OF 3D COMPUTER GENERATED IMAGING OF REVERSE TOTAL SHOULDER ENDOPROSTHESES

Objective. To conduct a finite element analysis of the stress-strain state (STS) of the elements of the shoulder joint after implantation reverse shoulder endoprostheses. Material and methods. After 3Dscanning of the composite model of the scapula and humerus, geometric models of the shoulder joint were built in the SolidWorks 2019 SP 1.0 program, followed by mathematical modeling and FEA. For the comparative analysis of the STS of the «bone – reverse endoprosthesis» s ystem, t hree-dimensional m odels o f two types of reverse shoulder endoprostheses were created, which were then transformed into a finite-element model and implanted into the developed three-dimensional mathematical model of the shoulder joint without cement. The STS calculations of the elements of endoprostheses were carried out for two positions: abduction 90° and flexion 90° with a load of 5 kg. Results. Compared to the healthy shoulder joint, models with reverse shoulder endoprosthesis have significantly different contact stresses and contact areas. It was established that the maximum stress in the details of the contact parts of the endoprosthesis when retracted at an angle of 90° did not exceed +1.78 MPa, when bending +5.8 MPa. The maximum stresses on the liner during shoulder abduction are +8.6 MPa, the minimum –7.38 MPa, during flexion +2.3 MPa and –2.45 MPa, respectively. It has been proven that the contact areas of the hemisphere and inserts of both reverse endoprostheses during abduction and flexion of the limb by 90° are significantly larger (573 mm2 vs. 1809–2081 mm2) when compared with a healthy shoulder joint, while changes in the area between the endoprostheses are insignificant and equal to 2...3 %. Conclusions. Analysis of the STS load of elements of reverse shoulder endoprosthesis showed that the greatest stresses occur in the contact zones. It has been proven that the maximum stresses on the contact structures of endoprostheses are less than on the head of a healthy joint, but the contact area during implantation of a reversible endoprosthesis of the shoulder joint increases significantly (more than 3 times).

An L-Slot Frequency Reconfigurable Antenna Based on MEMS Technology.

Given the shortage of spectrum resources and the demand for communication systems of diminutive size, multi-function, and adaptive characteristics, this paper proposes an L-slot frequency reconfigurable antenna based on the MEMS switch. The antenna size is 4.07 × 5.27 mm2 and is suitable for the U-band. The antenna structure consists of two RF MEMS switches, a Rogers RT5880 dielectric substrate, an L-slot patch, and a full-coverage ground. The switch is of a series contact structure and is arranged at the corner of an L-slot. By controlling the on and off state of the switch, the antenna can switch between four states of 42.36, 47.65, 53.13, and 56.72 GHz. According to the simulation results in CST STUDIO SUITE 2018, the maximum gain of the antenna is 7.90 dB, the impedance bandwidth of each state is above 1 GHz, and the direction is mainly consistent. The antenna can meet the demand for multi-frequency millimeter wave communication.

Great circle fibrations and contact structures on odd-dimensional spheres

Great circle fibrations and contact structures on odd-dimensional spheres

Approximation of holomorphic Legendrian curves with jet-interpolation

We prove several interpolation results for holomorphic Legendrian curves lying in an odd dimensional complex Euclidean space with the standard contact structure. In particular, we show that an arbitrary countable set of points in C2n+1 lies on an injectively immersed isotropic surface with a prescribed complex structure. If the set has no accumulation points, the surface may be taken properly embedded. We also prove a Carleman-type theorem for holomorphic Legendrian curves with interpolation. Namely, a Legendrian curve, defined on a certain type of unbounded closed set in a given open Riemann surface R, may be approximated in the C0-topology by an entire Legendrian curve with prescribed finite-order Taylor polynomials at a closed discrete set of points in R. Under suitable conditions, the approximating map may be made into a proper embedding.