Length Of Sheet Research Articles

Ankyrin-G regulated epithelial phenotype is required for mouse lens morphogenesis and growth

Epithelial cell polarity, adhesion, proliferation, differentiation and survival are essential for morphogenesis of various organs and tissues including the ocular lens. The molecular mechanisms regulating the lens epithelial phenotype however, are not well understood. Here we investigated the role of scaffolding protein ankyrin-G (AnkG) in mouse lens development by conditional suppression of AnkG expression using the Cre-LoxP recombination approach. AnkG, which serves to link integral membrane proteins to the spectrin/actin cytoskeleton, was found to distribute predominantly to the lateral membranes of lens epithelium with several isoforms of the protein being detected in the mouse lens. Conditional deficiency of AnkG impaired mouse lens morphogenesis starting from embryonic stage E15.5, with neonatal (P1) AnkG cKO lenses exhibiting overt abnormalities in shape, size, epithelial cell height, sheet length and lateral membrane assembly together with defective fiber cell orientation relative to lenses from littermate AnkG floxed or Cre expressing mice. Severe disruptions in E-cadherin/β-catenin-based adherens junctions, and the membrane organization of spectrin-actin cytoskeleton, ZO-1, connexin-50 and Na+-K+-ATPase were noted in AnkG deficient lenses, along with detection in lens epithelium of α-smooth muscle actin, a marker of epithelial to mesenchymal transition. Moreover, lens epithelial cell proliferation and survival were severely compromised while differentiation appears to be normal in AnkG deficient mouse lenses. Collectively, these results indicate that AnkG regulates establishment of the epithelial phenotype via lateral membrane assembly, stabilization of E-cadherin-based cell-cell junctions, polarity and membrane organization of transport and adhesion proteins and the spectrin-actin skeleton, and provide evidence for an obligatory role for AnkG in lens morphogenesis and growth.

Device design and flow scaling for liquid sheet jets

A design for and experimental study of microfluidic nozzles that generate thin liquid sheet jets is presented. A parametric study is conducted by varying nozzle geometry, flow rate, and fluid type, and scaling theories to scale and predict jet sheet thickness, width, and length are proposed.

Plasmoid instability in the semi-collisional regime

We investigate analytically and numerically the semi-collisional regime of the plasmoid instability, defined by the inequality $\unicode[STIX]{x1D6FF}_{\text{SP}}\gg \unicode[STIX]{x1D70C}_{s}\gg \unicode[STIX]{x1D6FF}_{\text{in}}$, where $\unicode[STIX]{x1D6FF}_{\text{SP}}$ is the width of a Sweet–Parker current sheet, $\unicode[STIX]{x1D70C}_{s}$ is the ion sound Larmor radius and $\unicode[STIX]{x1D6FF}_{\text{in}}$ is the width of the boundary layer that arises in the plasmoid instability analysis. Theoretically, this regime is predicted to exist if the Lundquist number $S$ and the length of the current sheet $L$ are such that $(L/\unicode[STIX]{x1D70C}_{s})^{14/9}<S<(L/\unicode[STIX]{x1D70C}_{s})^{2}$ (for a sinusoidal-like magnetic configuration; for a Harris-type sheet the lower bound is replaced with $(L/\unicode[STIX]{x1D70C}_{s})^{8/5}$). These bounds are validated numerically by means of simulations using a reduced gyrokinetic model (Zocco & Schekochihin, Phys. Plasmas, vol. 18 (10), 2011, 102309) conducted with the code Viriato. Importantly, this regime is conjectured to allow for plasmoid formation at relatively low, experimentally accessible, values of the Lundquist number. Our simulations obtain plasmoid instability at values of $S$ as low as ${\sim}250$. The simulations do not prescribe a Sweet–Parker sheet; rather, one is formed self-consistently during the nonlinear evolution of the initial tearing mode configuration. This proves that this regime of the plasmoid instability is realizable, at least at the relatively low values of the Lundquist number that are accessible to current dedicated experiments.

Performance enhancement of downwind sails due to leading edge flapping: A wind tunnel investigation

This work presents a wind tunnel experimental study on the effect of the leading edge flapping on the aerodynamic performance of a spinnaker. Four J80-class spinnaker models, combining two different assembling structures (panel layout) and two different sail materials are tested at various wind speeds and wind angles in a wind tunnel. Results show that, for the wind angle range the spinnaker is designed for, the sustained periodic flapping of the sail leading edge has a significant benefit on performance, with 10% increase in drive force. In these model-scale tests, the sail structural properties did not show significant differences in performance, but affect the point where flapping sets in: a model with a stiffer material and a cross-cut panel layout starts flapping for a longer sheet length, compared to a lighter cloth and a tri-radial layout. Finally, it is shown that the non-dimensional flapping frequency is rather constant ≃0.4 in the design range of wind angle, but it varies with the wind speed and sail structural properties on a smaller wind angle where the spinnaker is more stretched.

Behavior of macro synthetic fiber concrete beams strengthened with different CFRP composite configurations

Thirty-two normal-strength macro discontinuous structural synthetic fiber (DSSF) concrete beams were constructed and tested. In order to determine the optimum dosage of DSSF, eight of the beams were prepared with various dosages of DSSF, while the rest beams were prepared with an optimum DSSF dosage of 0.55% and with various carbon fiber reinforced polymer (CFRP) sheet lengths and widths. The tested parameters include mode of failure, load versus mid-span deflection response, ultimate deflection, ultimate load capacity, energy absorption, stiffness, performance factor, energy absorption ductility index, displacement ductility index, and concrete and CFRP sheet strains. The addition of DSSF and CFRP sheet enhanced most of the investigated parameters by providing internal and external crack arresting mechanisms, respectively, and enhancing the post-cracking ductility after reaching the extreme load capacity.

Light sheet microscopy with high spatial resolution based on polarized structured illumination beam modulated by the phase mask.

In this article, we present a method to improve axial resolution and expand the field of view of conventional light sheet fluorescence microscopy (LSFM) by phase modulation of the illumination beam. We added a bisected annular binary phase mask on the illumination path to modulate the radially polarized beam. The central spot of the modulated point spread function is narrower than that of Gaussian focus, although the sidelobe energy is increased. Then, a diffraction grating is used to produce multiple copies of this illumination pattern, and these pattern copies form the light sheet. By matching the numerical apertures of illumination lens and detection lens, the sidelobes on the detection axis can be suppressed in the captured data, although they do still contribute to photobleaching and phototoxicity in the sample. The simulation results show that the proposed method effectively reduces the thickness of the light sheet by 1.3 times, and increase the length of the light sheet by two times compared with conventional LSFM.

Improved shear strength design of cold-formed steel connection with single self-piercing rivet

In order to introduce self-piercing rivet (SPR) technique to component connections of thin-walled steel structures, 78 SPR joints were tested to evaluate their quality and the shear strength. Parameters included in this test program were the sheet thickness, and the rivet. Based on test results, the research developed an empirical formula between the combination thicknesses of sheet and rivet length, and proposed quality evaluation standard of SPR connections and a new design method of shear strength. The test results showed that sheet thickness and sheet thickness ratio had a great effect on failure mode, and rivet length was a key factor on shear properties of SPR connections. The proposed quality evolution standard and design calculation method of shear strength in this paper had certain reasonability and reliability.

Study of magnetic reconnection in large-scale magnetic island coalescence via spatially coupled MHD and PIC simulations

We study the process of magnetic reconnection in a coalescing magnetic island setup by means of numerical simulation. This process mimics flux tube merging which can take place in the solar corona, laboratory, and astrophysical objects. Simulations are performed with magnetohydrodynamics (MHD), Hall-MHD, and a newly developed Coupled MHD and Particle-In-Cell (PIC) model (CMAP). This model treats the global simulation domain with MHD, while the region around the reconnection zone is treated with PIC. This CMAP code allows us to simulate larger-scale domains with lesser computing power compared to fully PIC simulations. CMAP reproduces the dynamics of fully kinetic simulations which Hall-MHD does not capture, as seen in the Hall magnetic field and the reconnecting current sheet structure. For large islands in kinetic simulations, the current sheet does not form smoothly and shows chaotic behavior, and the magnetic islands also bounce and slosh. The current sheet thickness, length, and aspect ratios are calculated. They show that in the CMAP model, the thickness remains close to the ion skin depth, while the length changes weakly with the system size, giving a steady aspect ratio for the two largest system size simulations. The pressure tensor also shows large deviations from isotropy and gyrotropy near the current sheet. The CMAP simulations for smaller system sizes are compared to fully kinetic simulations, and we find that a minimum fraction of area has to be provided PIC feedback in the CMAP simulations in order to produce reconnection rates and dynamics similar to fully kinetic simulations. The reconnection rate reduces with the increasing island size. For the CMAP model, this reduction is steeper compared to MHD and Hall-MHD initially, but for larger system sizes, the reconnection rates in CMAP simulations show a steady behavior.

Flexural strength of steel I-beams reinforced with CFRP sheets at tension flange

The use of modern Carbon Fiber Reinforced Polymer (CFRP) to strengthen and repair steel beams in flexure has been rapidly increased within the past few years. This technique benefits from light-weight and extra-strong CFRP material to enhance the flexural capacity of cross section. To study the reinforcing effect of CFRP, one hundred and seventy-eight models were analyzed to cover six variables representing the common problem parameters; the variables were the slenderness ratio of web (hw/tw), the mono-symmetric ratio of I-beam (ψ), the area of CFRP (Acfrp), the modulus of elasticity of CFRP (Ecfrp), the tensile strength of CFRP (Fucfrp), and the length of CFRP sheet (Lcfrp). The adhesive properties used in parametric analysis were determined from experimental tests conducted for double-strap steel-to-CFRP joints with various bond lengths (50 to 200 mm), and the proposed model constructed using the general finite element program, ANSYS 17, was verified with experimental tests of full-scale steel beams reinforced with CFRP. The parametric study revealed that CFRP sheets were very efficient in reinforcing compact mono-symmetric sections, whereas the enhancement in beams with non-compact sections was very small. CFRP sheets were able to reach its ultimate strength provided that enough bond length was ensured. Analytical procedure to calculate the flexural strength of steel I-shaped beams reinforced with CFRP sheets at tension flange was presented.

Anisotropic radial basis function methods for continental size ice sheet simulations

In this paper we develop and implement anisotropic radial basis function methods for simulating the dynamics of ice sheets and glaciers. We test the methods on two problems: the well-known benchmark ISMIP-HOM B that corresponds to a glacier size ice and a synthetic ice sheet whose geometry is inspired by the EISMINT benchmark that corresponds to a continental size ice sheet. We illustrate the advantages of the radial basis function methods over a standard finite element method. We also show how the use of anisotropic radial basis functions allows for accurate simulation of the velocities on a large ice sheet, which was not possible with standard isotropic radial basis function methods due to a small ratio between the typical thickness and length of an ice sheet. Additionally, we implement a partition of unity method in order to improve the computational efficiency of the radial basis function methods.

Thermal Conductance along Hexagonal Boron Nitride and Graphene Grain Boundaries

We carried out molecular dynamics simulations at various temperatures to predict the thermal conductivity and the thermal conductance of graphene and hexagonal boron-nitride (h-BN) thin films. Therefore, several models with six different grain boundary configurations ranging from 33–140 nm in length were generated. We compared our predicted thermal conductivity of pristine graphene and h-BN with previously conducted experimental data and obtained good agreement. Finally, we computed the thermal conductance of graphene and h-BN sheets for six different grain boundary configurations, five sheet lengths ranging from 33 to 140 nm and three temperatures (i.e., 300 K, 500 K and 700 K). The results show that the thermal conductance remains nearly constant with varying length and temperature for each grain boundary.

Spray formation and atomization characteristics of non-Newtonian impinging jets at high Carreau numbers

Over the last two decades there has been a renewed interest in employing shear-thinning non-Newtonian liquids for use with liquid rocket engines due to a desire for greater safety and performance. Since the difficulty with producing quality atomization is the main disadvantage for using non-Newtonian liquid propellants, further understanding of the breakup physics and accurate measurement of the spray characteristics is needed. The atomization produced by the like-on-like jet impingement of three different non-Newtonian liquids was experimentally investigated in this work using shadowgraphy and Phase Doppler Anemometry (PDA) at high strain rates (105–106), which correspond closely to the strain rates used in practical rocket engines. The three water-based solutions tested were of two different grades of Carboxymethylcellulose (CMC): 0.5 wt.-% CMC-7HF, 0.8 wt.-% CMC-7MF, and 1.4 wt.-% CMC-7MF. The Bird–Carreau rheological model was used to characterize the non-Newtonian behavior and a generalized Carreau number was used as the primary parameter to characterize the liquid viscosity inside the orifice at injection. A generalized Bird–Carreau jet Reynolds number Rej,gen-BC and the jet Weber number Wej were used as primary parameters to characterize the spray formation, sheet breakup length, drop size, and drop velocity. The unique spray formation a behavior of the three non-Newtonian liquids was ascribed to the relative influence of the inertial vs. viscous forces, primarily expressed through Rej,gen-BC. At many relatively high inertial force test conditions, drops in the spray were near spherical and could be reliably measured using PDA. Spray characteristics of intact sheet length, drop diameter, and drop velocity were observed to be strong functions of Rej,gen-BC. In addition to providing fundamental understanding to aid with injector design for liquid rocket engine applications using non-Newtonian liquids, the measurements presented in this work could be used to validate a future closed-form analytical non-Newtonian atomization model, which remains an open problem in non-Newtonian impinging jets literature.

Vertically Oriented MoS2 with Spatially Controlled Geometry on Nitrogenous Graphene Sheets for High-Performance Sodium-Ion Batteries

Lithium-ion battery (LIB) has been a tremendous success for decades. As the demand for rechargeable batteries surges, a need has arisen for low-cost secondary batteries. Among various studies, sodium-ion battery (SIB) is the most promising secondary batteries due to its similar working principles and the abundance of sodium in the natural world. Among many anode materials for SIB, MoS­­2 has attracted attention because it can intercalate sodium ions in its layered structure. However, in the repeated intercalation of Na+ , MoS2 suffers from collapse of its layered structure. Herein, we present vertically grown MoS2 on nitrogenous reduced graphene oxides (N-RGO) with controlled sheet density and height of MoS2 sheets as SIB anode active material. The MoS2 materials are synthesized by gel-precursor based method. By adjusting the nucleation and growth processes, we controlled the height and density of MoS2 sheets to find optimal condition that show great performance and high stability. Control of the partial geometry can achieve these improved property because the high sheet density can prevent additional SEI layer and the shortened sheet length reduces the resistance of Na+ diffusion. It shows remarkably high reversible discharging capacity of 255mAh/g at 1C and 245mAh/g at 5C discharging with a capacity reduction of 5.35% after 1300 cycles. And closely packed MoS2 sheets shows specific capacity of 254, 243, 153, 86 mAh/g at 0.2, 2, 10, 50A/g current density, respectively. Furthermore, vertically grown MoS2 is paired with Na3V2(PO4)3 to fabricate SIB full cell, and the full cell shows a specific capacity of 262mAh/g (based on the mass of anode material) during 50 cycles. Figure 1

Determinants of the Eurosystem's Central Banks Provisions

AbstractCentral bank provisions may be used as a measure of the perceived risk of the balance sheet composition by a central bank. We identify three possible sources that may change the size of the provisions. These are: The length of the balance sheet, the central bank revenues, and measures of fiscal stress. Using data of the 11 founding members of the Eurosystem for the years 1999–2015, we are able to test each of the three determinants. We find that provisions are increased with the size of the balance sheet especially in the recent financial crisis. Moreover, provisions are increased at the cost of lower central bank revenues. While this holds for the pre‐crisis period this relationship seems to be less pronounced in the crisis period probably because of the more active collateral policy. Finally, central banks do not tend to lower provisions because of fiscal tensions. This is even more true in the crisis period.

Numerical and experimental study on multi-pass laser bending of AH36 steel strips

Laser bending is a process of bending of plates, small sized sheets, strips and tubes, in which a moving or stationary laser beam heats the workpiece to achieve the desired curvature due to thermal stresses. Researchers studied the effects of different process parameters related to the laser source, material and workpiece geometry on laser bending of metal sheets. The studies are focused on large sized sheets. The workpiece geometry parameters like sheet thickness, length and width also affect the bend angle considerably. In this work, the effects of width and thickness on multi-pass laser bending of AH36 steel strips were studied experimentally and numerically. Finite element model using ABAQUS® was developed to investigate the size effect on the prediction of the bend angle. Microhardness and flexure tests showed an increase in the flexural strength as well as microhardness in the scanned zone. The microstructures of the bent strips also supported the physical observations.

Size effect on interlayer shear between graphene sheets

Interlayer shear between graphene sheets plays an important role in graphene-based materials and devices, but the effect of in-plane deformation of graphene, which may depend on the graphene size, has not been fully understood. In this paper, the size effect on interlayer shear behavior between two graphene sheets is studied based on a non-linear shear-lag model with energy barrier analysis, in which both the lattice registry effect and the elastic deformation of graphene are taken into account, and molecular dynamics (MD) simulations are carried out to verify the model. Both theoretical prediction and MD simulations show that the maximum interlayer shear force of short graphene sheets increases with the graphene length and width. However, if the sheet length is beyond 20 nm, the maximum shear force cannot be further increased by increasing the graphene length due to the non-uniform relative displacement between graphene layers, which is caused by the in-plane deformation of graphene. The upper bound of the maximum shear force per unit graphene width is obtained analytically as a constant 5.6 N/m, suggesting that a small force can pull an infinite long graphene belt to slide on a graphene substrate. This study offers useful information for design and manufacture of graphene-based nano-devices and materials.

Fast Magnetic Reconnection: “Ideal” Tearing and the Hall Effect

Abstract One of the main questions in magnetic reconnection is the origin of triggering behavior with on/off properties that, once it is activated, accounts for the fast magnetic energy conversion to kinetic and thermal energies at the heart of explosive events in astrophysical and laboratory plasmas. Over the past decade, progress has been made on the initiation of fast reconnection via the plasmoid instability and what has been called “ideal” tearing, which sets in once current sheets thin to a critical inverse aspect ratio . As shown by Pucci & Velli, at , the timescale for the instability to develop becomes of the order of the Alfvén time and independent of the Lundquist number (here defined in terms of current sheet length L). However, given the large values of S in natural plasmas, this transition might occur for thicknesses of the inner resistive singular layer that are comparable to the ion inertial length d i . When this occurs, Hall currents produce a three-dimensional quadrupole structure of the magnetic field, and the dispersive waves introduced by the Hall effect accelerate the instability. Here we present a linear study showing how the “ideal” tearing mode critical aspect ratio is modified when Hall effects are taken into account, including more general scaling laws of the growth rates in terms of sheet inverse aspect ratio: the critical inverse aspect ratio is amended to , at which point the instability growth rate becomes Alfvénic and does not depend on either of the (small) parameters . We discuss the implications of this generalized triggering aspect ratio for recently developed phase diagrams of magnetic reconnection.

Ballistic thermophoresis of adsorbates on free-standing graphene

The textbook thermophoretic force which acts on a body in a fluid is proportional to the local temperature gradient. The same is expected to hold for the macroscopic drift behavior of a diffusive cluster or molecule physisorbed on a solid surface. The question we explore here is whether that is still valid on a 2D membrane such as graphene at short sheet length. By means of a nonequilibrium molecular dynamics study of a test system-a gold nanocluster adsorbed on free-standing graphene clamped between two temperatures [Formula: see text] apart-we find a phoretic force which for submicron sheet lengths is parallel to, but basically independent of, the local gradient magnitude. This identifies a thermophoretic regime that is ballistic rather than diffusive, persisting up to and beyond a 100-nanometer sheet length. Analysis shows that the phoretic force is due to the flexural phonons, whose flow is known to be ballistic and distance-independent up to relatively long mean-free paths. However, ordinary harmonic phonons should only carry crystal momentum and, while impinging on the cluster, should not be able to impress real momentum. We show that graphene and other membrane-like monolayers support a specific anharmonic connection between the flexural corrugation and longitudinal phonons whose fast escape leaves behind a 2D-projected mass density increase endowing the flexural phonons, as they move with their group velocity, with real momentum, part of which is transmitted to the adsorbate through scattering. The resulting distance-independent ballistic thermophoretic force is not unlikely to possess practical applications.

Effective thermal conductivity of carbon nanostructure based polyethylene nanocomposite: Influence of defected, doped, and hybrid filler

Thermal conductivity of polyethylene nanocomposite filled with graphene, carbon nanotube and hybrid graphene–carbon nanotube has been studied using micromechanical model. The effect of CNT volume fraction and graphene volume fraction, length of graphene sheet, length and radius of carbon nanotubes on the thermal conductivity of composite has been investigated. Thermal conductivity of graphene-PE nanocomposite and CNT-PE nanocomposite increases by increasing the length of CNT and length of graphene sheet respectively. Whereas increase in diameter of CNT contributes to the decreasing thermal conductivity of CNT-PE nanocomposite. Then, the effect of structure defect (single vacancy, stone-wales defect) and dopant (Boron-doped, Nitrogen-doped) in the structure of graphene and carbon nanotube on the thermal conductivity of CNT-PE and graphene-PE nanocomposites has been studied. The thermal conductivity of graphene -PE and CNT-PE nanocomposites decreases by increasing the concentration of defect and dopant in the structure of graphene and carbon nanotube, respectively.

Petahertz-frequency plasmons in graphene nanopore and their application to nanoparticle sensing

The Surface Plasmon Resonance (SPR) properties in the petahertz (1015 Hz) frequency range for monolayer graphene nanosheet and graphene nanopore are investigated using discrete dipole approximation method. We calculate graphene refractive indices by using rst-principle density functional theory. The near-fi eld enhancement made by plasmon in these structures is studied by employing nite-di erence-time-domain method. For graphene nanosheets, energy of the SPR peak drops with increase in the sheet length. Also, for graphene nanopores smaller than 5 nm in length, increasing the pore diameter decreases energy of the SPR peak and for some length values like 6 nm, this energy value is raised. For larger sheets (e.g., 8 nm), SPR peak is rather unchanged by variations of the pore diameter. The SPR is used to detect nanoscale objects such as gold, silver, copper, rhodium, and aluminium oxide. If nanoscale particles are inserted into the graphene nanopore, 0.195 to 0.474 eV shift in the SPR spectra appears. Type of the presented nanoparticle can be clearly determined by measuring the energy shifts in the SPR spectra. Our results show that petahertz-frequency plasmon in graphene nanopore can be used as a nanoscale-object detection methodology.