Edge Of Interface Research Articles

Albumin Alters the Conformational Ensemble of Amyloid-β by Promiscuous Interactions: Implications for Amyloid Inhibition.

Human serum albumin (HSA) is a key endogenous inhibitor of amyloid-β (Αβ) aggregation. In vitro HSA inhibits Aβ fibrillization and targets multiple species along the aggregation pathway including monomers, oligomers, and protofibrils. Amyloid inhibition by HSA has both pathological implications and therapeutic potential, but the underlying molecular mechanism remains elusive. As a first step towards addressing this complex question, we studied the interactions of an Aβ42 monomer with HSA by molecular dynamics simulations. To adequately sample the conformational space, we adapted the replica exchange with solute tempering (REST2) method to selectively heat the Aβ42 peptide in the absence and presence of HSA. Aβ42 binds to multiple sites on HSA with a preference to domain III and adopts various conformations that all differ from the free state. The β-sheet abundances of H14-E22 and A30-M33 regions are significantly reduced by HSA, so are the β-sheet lengths. HSA shifts the conformational ensemble towards more disordered states and alters the β-sheet association patterns. In particular, the frequent association of Q15-V24 and N27-V36 regions into β-hairpin which is critical for aggregation is impeded. HSA primarily interacts with the latter β-region and the N-terminal charged residues. They form promiscuous interactions characterized by salt bridges at the edge of the peptide-protein interface and hydrophobic cores at the center. Consequently, intrapeptide interactions crucial for β-sheet formation are disrupted. Our work builds the bridge between the modification of Aβ conformational ensemble and amyloid inhibition by HSA. It also illustrates the potential of the REST2 method in studying interactions between intrinsically disordered peptides and globular proteins.

Study on seismic and shock absorption performance of Yi Ci Hui stone pillar

The rigid block structure composed of multiple blocks of stones will sway during an earthquake. The rocking and rocking impact dissipates the seismic force and has good shock absorption performance. The seismic and seismic performance of Yi Ci Hui stone pillar with multi-layer block stones was studied. The results showed that: only the acceleration increases to a certain value, the rocking amplitude of the multi-layer stacked stone pillar occurs; with the continuous increase of the earthquake acceleration, the rocking amplitude of the stone pillar will rapidly decay or even be stationary. Stacking stone pillar can effectively take advantage of high compressive strength of block stone, and only produce compressive stress in the pillar root section to avoid stress failure of stone pillar. The energy reaction of the multi-layer stone pillar is mainly kinetic energy, which reaches the maximum when the stone pillar begins to shake, and then decreases rapidly. The total strain energy reaches the peak value when the stone pillar shakes, and then remains unchanged. The rocking and shaking of stacked stone pillars causes the impact of rock interface edge to dissipate seismic energy, which makes the rocking amplitude and kinetic energy of stone pillar gradually decrease, and the total strain energy is basically unchanged, which effectively plays the role of seismic shock absorption.

Dynamic Observation of Topological Soliton States in a Programmable Nanomechanical Lattice.

Topological soliton states, existing in the topological structures with edge defect or interface defect, are usually studied under steady state. Here, we experimentally observe the dynamic processes of the generation and the extinction of such soliton states in the Su-Schrieffer-Heeger model. The different topological structures are implemented on a programmable nanomechanical lattice, consisting of eight adjacent string resonators which are parametrically coupled by manipulation voltages. Moreover, the beating and localization behaviors at different topological interfaces are also observed in the same device. These results explicitly exhibit the dynamic processes of topological soliton states, which reveal real potential toward integrated multifunctional topological materials.

Study on time-dependent crack initiation law from Epoxy/SUS interface edges

Study on time-dependent crack initiation law from Epoxy/SUS interface edges

Edge effect and interface confinement modulated strain distribution and interface adhesion energy in graphene/Si system

In order to clarify the edge and interface effect on the adhesion energy between graphene (Gr) and its substrate, a theoretical model is proposed to study the interaction and strain distribution of Gr/Si system in terms of continuum medium mechanics and nanothermodynamics. We find that the interface separation and adhesion energy are determined by the thickness of Gr and substrate. The disturbed interaction and redistributed strain in the Gr/Si system induced by the effect of surface and interface can make the interface adhesion energy decrease with increasing thickness of Gr and diminishing thickness of Si. Moreover, our results show that the smaller area of Gr is more likely to adhere to the substrate since the edge effect improves the active energy and strain energy. Our predictions can be expected to be a guide for designing high performance of Gr-based electronic devices.

Comparison of Electropolishing of Aluminum in a Deep Eutectic Medium and Acidic Electrolyte

Research advances in electropolishing, with respect to the field of metalworking, have afforded significant improvements in the surface roughness and conductivity properties of aluminum polished surfaces in ways that machine polishing and simple chemical polishing cannot. The effects of a deep eutectic medium as an acid-free electrolyte were tested to determine the potential energy thresholds during electropolishing treatments based upon temperature, experiment duration, current, and voltage. Using voltammetry and chronoamperometry tests during electropolishing to supplement representative recordings via atomic force microscopy (AFM), surface morphology comparisons were performed regarding the electropolishing efficiency of phosphoric acid and acid-free ionic liquid treatments for aluminum. This eco-friendly solution produced polished surfaces superior to those surfaces treated with industry standard acid electrochemistry treatments of 1 M phosphoric acid. The roughness average of the as-received sample became 6.11 times smoother, improving from 159 nm to 26 nm when electropolished with the deep eutectic solvent. This result was accompanied by a mass loss of 0.039 g and a 7.2 µm change in step height along the edge of the electropolishing interface, whereas the acid treatment resulted in a slight improvement in surface roughness, becoming 1.63 times smoother with an average post-electropolishing roughness of 97.7 nm, yielding a mass loss of 0.0458 g and a step height of 8.1 µm.

Observations of symmetry-induced topological mode steering in a reconfigurable elastic plate

We experimentally investigate the valley-Hall effect for interfacial edge states, highlighting the importance of the modal patterns, between geometrically distinct regions within a structured elastic plate. These experiments, for vibration, are at a scale where detailed measurements are taken throughout the system and not just at the input/output ports; this exposes the coupling between geometrically distinct modes that underlie the differences between wave transport around gentle and sharp bends.

A new computational approach for three-dimensional singular stress analysis of interface voids

Defects in terms of three-dimensional voids are commonly encountered at bi-material interfaces. In the current study, the singular stress field near the circumferential corner line of a three-dimensional axisymmetric interfacial void is analyzed using our newly established singular interface edge elements. Under the premise that $$\rho {\ll }R$$ , the proposed singular element method does not depend on the size of the element; thereby, it is not necessary to use refined elements at the interface corner line. The numerical results reveal the intensity of the stress singularity at the interface line of the three-dimensional axisymmetric voids. The obtained stress intensity parameters can be used to judge the local fatigue crack initiation. The geometry effect of the void on the singular stress field at the circumferential interface corner line is studied and discussed in detail.

The transport of tungsten impurities induced by the intrinsic carbon during upper-single null discharge on EAST tokamak

• SOLPS-DIVIMP modeling is applied to the production and transport of W impurities on EAST. • High n e , s e p OMP suppresses W impurity, while higher input power enhances W concentration. • Strong correlation between T e at the outer target and W ion density at core is observed. • T e < 20 eV is required to maintain W concentration at CEI < 10 −5 in steady-state scenarios. The transport as well as accumulation of tungsten (W) impurity is one of the critical issues for the W divertor operation. The EAST tokamak with W and graphite divertor targets, provides a good platform for the investigation of W impurity behaviors. In this work, the production, transport and accumulation of W impurities are simulated via the SOLPS-DIVIMP modeling. The plasma background is obtained by the SOLPS simulations, while the W sputtering yield is calculated via empirical formula, and the following W transport is traced using the DIVIMP code. The W impurity source is mainly contributed by the incidence of carbon (C) impurity in this simulation. The distribution of W ions with different charge states is obtained and the transport of the W ions is analyzed by the net forces. The dependences of W impurity on the n e , s e p OMP and P SOL are illustrated, which show the divertor plasma has great impact on the W impurity distribution. The increase of n e , s e p OMP can suppress the W impurity in the core region with the fixed P SOL , while higher input power can enhance the W concentration significantly. The W impurity can lead to sufficient power radiation due to strong impurity source and high radiation rate in the core region during low density discharge, while the influence becomes weaker as n e , s e p OMP raises. The effects of self-sputtering on the W impurity accumulation are also discussed. With the increment of P SOL , the sputtering and self-sputtering of W increase remarkably, leading to the W ions concentration exceed 10 −5 in the core–edge interface (CEI). Moreover, the strong correlation between T e at the outer target and W ion density at CEI is observed, showing that T e < 20 eV is required to maintain W concentration at CEI below the acceptable limitation (10 −5 ) in steady-state scenarios in EAST (without ELMs).

Formation mechanism of hierarchical pattern fabricated by ultrasonic-assisted texturing: dynamic indentation induced pile-up

Ultrasonic-assisted surface texturing can produce surface textures with hierarchical micro/nano-scale structures on metal components. In this work, we prove that the formation of nano-scale structure originates from pile-up produced by ultrasonic dynamic indentation. Both quasi-static and dynamic indentations are performed on pure copper, 316 stainless steel, and pure titanium using an ultrasonic nanocrystal surface modification system. For the first time, it is revealed that ultrasonic dynamic indentation produces significant higher pile-up as compared with that of quasi-static indentation, making nanoscale structure possible. Finite element simulations demonstrate that dynamic indentation produces larger equivalent plastic strain, an indicator for work hardening, in the region close to the edge of the contact interface. It is conjectured that higher degrees of work hardening and dislocation density result in a higher dislocation resistance as compared with quasi-static indentation. The plastic deformation is confined at the contact interface and is then forced to move upward, leading to a significant pile-up.

Thickness-dependent electronic transport through epitaxial nontrivial Bi quantum films

In bismuth quantum films, a fascinating interplay between (bulk) quantum well and interface (edge) states is observed in this comprehensive study of DC magnetoconductance and Hall resistivity as a function of film thickness. While for thin layers (up to 40 bilayers, BL) conductance is governed by the surface states, strong contributions of a quantum well state dominate above 70 BL. Quantum corrections in a magnetic field normal to the surface, however, are dominated by the interface states for all thicknesses investigated for reasons discussed in the paper.

Development of a material model for predicting extreme deformation and grain refinement during cold spraying

Fusion-based additive manufacturing techniques such as selective laser melting, electron beam freeform fabrication cause solidification problems such as grain coarseness and high porosity. As a new technique, cold spraying (CS) can overcome such melting-induced drawbacks. In this study, a material model using dislocation dynamics was developed specifically for the CS process for describing the following five nanosecond-scale physical phenomena: strain hardening, normal-range strain rate hardening, ultra-high strain rate hardening, thermal softening and grain size evolution. A single Cu microparticle impact test was conducted, and a good agreement between experimental and model-predicted microparticle deformations was observed, indicating high model accuracy. The corresponding finite element model was established, and the individual effects of the above phenomena were discussed in detail to show that material deformation is mainly controlled by ultra-high strain rate hardening while jetting is controlled by thermal softening. Additionally, both simulated and actual grain size distributions indicated that grain refinement occurs only near the microparticle-substrate interface (mainly at the interface edge). Thus, the newly developed model could accurately reproduce the dynamic deformation behaviors of impacting particles and correctly predict grain refinement (particularly due to dynamic recrystallization).

Grazing-incidence X-ray diffraction investigation of the coincidence site lattice of the Ge/Si(001) system.

The Ge/Si(001) system has been analysed by grazing-incidence X-ray diffraction on a standard laboratory X-ray diffraction tool. A periodic array of interfacial edge dislocations forms a coincidence site lattice (CSL) which yields equidistantly spaced satellite peaks close to Bragg peaks of the Ge layer and Si substrate. The diffraction behaviour of the CSL was analysed using 2θ/φ scans along [100], [110] and [310] directions as well as azimuthal φ scans which revealed a 90° angular symmetry of the CSL. Additionally, different layer thicknesses, from 10 to 580 nm, were analysed, focusing on the dependence of layer thickness on the glancing angles of the satellite peaks. This method provides the ability to analyse whether or not epitaxially grown layers exhibit a periodic array of dislocations, and gain information about the orientation of the interfacial edge dislocations.

Dependence of bonding strength and variations in residual stress on interface wedge angles and bonding temperature conditions

AbstractResidual stress can considerably weaken systems with ceramics-to-metal joints. Herein, we investigate the dependence of bonding strength and residual stress variation of a ceramics-to-metal joint system on the interface wedge angle and bonding temperature condition. First, disparity between large-scale displacement models with varying work-hardening parameters was confirmed using thermal elastoplastic Finite Element Method (FEM) analysis. Each interface wedge shape was set to a plane surface to compare FEM results to experimental results related to the effect of the interface wedge angle on the practical bonding strength. The experimental results were specifically for a system consisting of Si3N4-WC/TiC/TaC bonded to Ni plate. The effects of the wedge angle of the metal side on residual stress near the interface edge were numerically predicted using FEM models. The interface wedge angles for this model, φ1 and φ2, were defined using the configuration angle between the interface and free surfaces of both materials. The numerical results showed that the stress σr on the free surface of the ceramic side was concentrated near the interface edge at which discontinuity in the stress state is generated. Dependence of the residual stress variation on both the wedge angle and temperature conditions can be predicted. It was confirmed that the bonding strength improves with decreasing residual stress in geometrical conditions. Therefore, residual stress appears to be a predominant factor affecting bonding strength. The observed fracture pattern showed that the fracture originated near the interface edges, after which small cracks propagated on the ceramic side. The residual stress is presumed to dominate bonding strength as the fracture occurred near the interface edge of the ceramic side. Results showed that the maximum bonding strength appears at the geometrical condition where the fracture pattern changes to φ2 lower than 90° of joint bonded at 980 °C. Therefore, the optimum interface wedge angle depends on a combination of materials and bonding temperature conditions, because the weak point of the bonded joint system will affect the stiffness balance of both materials and the adhesion power of the bonded interface.

Partially penalized IFE methods and convergence analysis for elasticity interface problems

In this paper, some partial penalized immersed finite element methods (PPIFEMs) are proposed and analyzed for solving elasticity interface problems. Through verifying the inverse trace inequality on the interface edges, the optimal convergence in the energy norm is derived. A new test function is constructed to obtain the discrete inf–sup condition of the penalty-free nonsymmetric PPIFEM and is utilized in the proof of the optimal convergence. Furthermore, the effect of the Lamé parameters on convergence is also studied. Various numerical examples and comparisons are provided to confirm the theoretical results.

Application of the Advanced Multi-Step Brazing for fabrication of the high heat flux component

A novel fabrication method for a divertor heat removal component with tungsten (W) armour and copper alloy heat sink was newly developed and named as the “Advanced Multi-Step Brazing (AMSB). The basic principle of multi-step brazing is to apply the “advanced brazing technique” repeatedly during the manufacturing process of the single divertor heat removal component. The advanced brazing technique was originally developed by our previous work for joining between oxide dispersion strengthened copper alloy (ODS-Cu) and W with BNi-6 (Ni–11%P) filler material. The applied ODS-Cu was GlidCop® (Cu-0.3wt%Al2O3). One of the possible examples of the AMSB fabrication process can be considered as follows. First, an appropriate cooling flow path channel is processed into a GlidCop® heat sink. Then, the flow path channel is sealed in a leak tightness condition with a lid made by GlidCop®. The leak tightness joint between GlidCop® (GlidCop®/GlidCop®) can be realized by application of the “advanced brazing technique.” Second, in order to facilitate the weldability to connect the other cooling pipe system, the sleeves made by stainless steel (SUS) are jointed on the interface edge of the flow path channel of the GlidCop® heat sink with a leak tightness condition by the “advanced brazing technique.” Finally, W armour is jointed on the GlidCop® heat sink also by the “advanced brazing technique.” In this study, the mechanical strength of the SUS/GlidCop® joint was confirmed by the three-point bending test. Then, AMSB divertor mock-up with leak tightness condition was successfully produced.

Evaluation of Shear Fatigue Delamination Strength of Porous Thermal Barrier Coatings by Torsion Pin-Test Method

The shear fatigue delamination strength of some porous thermal barrier coatings (TBCs) has been evaluated using the torsion pin-test method. The porosities of the tested TBCs were 0-5, 5-10, 15-20 and 25-35%. The shear delamination strength of the TBCs was evaluated and the shear fatigue delamination strength (S–N) curves were obtained under cyclic torsional loading. The Young’s modulus of the TBCs was evaluated by using indentation tests and the corresponding numerical analyses, and expressed as a function of coating porosity. Finite element analyses, using the commercial nonlinear finite element analysis software MARC, showed that almost the same stress distributions could be observed around the interface edge between the top coat and the bond coat when delamination occurred, regardless of the pin diameter. Therefore, only the specimens of 4-mm pin diameter were used in the fatigue test. The shearing fatigue delamination strength was investigated under cyclic torsion without tension. If combined torsion and tension were applied, fracture would occur inside the top coating instead of adhesively at the bond coat interface. It was found that the normalized S–N curves, divided by the critical delamination stress due to simple torsion, coincided with each other. Next, the stress intensity factor (K) of the singular shear stress field around the interface edge was determined for various porous coatings under simple torsion, and the relationships between K and porosity Pv were derived. The strength (K) of the shear stress singularity field was adopted as the fatigue delamination criterion for the porous TBCs under cyclic shearing. Finally, the S–N curves could be determined for porous TBCs with any value of porosity.

Actively controllable topological phase transition in phononic beam systems

Topological insulators, which allow edge or interface waves but forbid bulk waves, have revolutionized our scientific cognition of acoustic/elastic systems. Due to their nontrivial topological characteristics, edge (interface) waves are topologically protected against defects and disorders. This superior and unique characteristic could lead to a wealth of new opportunities in applications of quantum and acoustic/elastic information processing. However, current acoustic/elastic topological insulators are still at an infancy stage where the theory and prediction only work in laboratories and there are still many problems left open before promoting their practical applications. One of the apparent disadvantages is their narrow working frequency range, which is the main concern in this paper. We design a one-dimensional phononic beam system made of a homogeneous epoxy central beam sandwiched by two homogeneous piezoelectric beams, and covered with extremely thin electrodes, periodically and separately placed. These electrodes are connected to external electric circuits with negative capacitors. We show that a topological phase transition can be induced and tuned by changing the values of the negative capacitors. It follows that the working frequency of the topologically protected interface mode can be widely changed, such that the working frequency range of the topological insulator can be considerably ‘broadened’. This intelligent topological device may also find wide applications in intelligent technologies that need controllable information processing of high precision.

Transient Soldering Reaction Mechanisms of SnCu Solder on CuNi Nano Conducting Layer and Fracture Behavior of the Joint Interfaces

Soldering can be used in the connection of thin film solar cells, while the soldering quality is difficult to control as the conducting layer on the solar cells is nano-sized and can be consumed within a few seconds. In this study, the microstructure and fracture behavior of the Sn-0.7wt.%Cu/Cu-30wt.%Ni joint interfaces were investigated. The use of CuNi conducting layer deposited on the Al/Si film with about 150 nm thickness and a soldering time of a few seconds were investigated. The results reveal that dense rod-like (Cu,Ni)6Sn5 grains with a diameter of 100–200 nm are formed at the edge of the joint interface, which gradually transform into coarsely and loosely distributed rod-like (Cu,Ni)6Sn5 grains from the edge to the inner of the solder joint. The CuNi layer is completely consumed at the inner region, and the diameter of the (Cu,Ni)6Sn5 grain were constant at about 1 μm. With longer soldering time, the width of the transition region between the fine and coarse (Cu,Ni)6Sn5 grains decrease sharply from a few hundred micrometers to about 10 μm, and the coarse rod-like (Cu,Ni)6Sn5 grains distribute throughout all the joint interface. Tensile fracture of the Cu/SnCu/CuNi solder joints occurs around the (Cu,Ni)6Sn5/CuNi interface at the edge and along the solder/Al or Al/Si interfaces at the inner region. The longer reaction time results in exhaustion of the CuNi layer, weakening of the bonding between the Al/Si/SnO2 films, and decreased joint strength from over 40 MPa to lower than 35 MPa.

Influence of Additives on the Interfacial Width and Line Edge Roughness in Block Copolymer Lithography

The challenges of patterning next generation integrated circuits have driven the semiconductor industry to look outside of traditional lithographic methods in order to continue cost effective size scaling. The directed self-assembly (DSA) of block copolymers (BCPs) is a nanofabrication technique used to reduce the periodicity of patterns prepared with traditional optical methods. BCPs with large interaction parameters (χ eff), provide access to smaller pitches and reduced interface widths. Larger χ eff is also expected to be correlated with reduced line edge roughness (LER), a critical performance parameter in integrated circuits. One approach to increasing χ eff is blending the BCP with a phase selective additive, such as an Ionic liquid (IL). The IL does not impact the etching rates of either phase, and this enables a direct interrogation of whether the change in interface width driven by higher χ eff translates into lower LER. The effect of the IL on the layer thickness and interface width of a BCP are examined, along with the corresponding changes in LER in a DSA patterned sample. The results demonstrate that increased χ eff through additive blending will not necessarily translate to a lower LER, clarifying an important design criterion for future material systems.