Nearby Interface Research Articles

CO2 methanation over Ni nanoparticles inversely loaded with CeO2 and Cr2O3: Catalytic functions of metal oxide/Ni interfaces

Interfaces between active metal and metal oxide in a heterogenous catalyst often play an important role in catalysis. In this work, we intentionally synthesized a series of inverse CeO2-Cr2O3/Ni model catalysts with the formation of controlled CeO2-Ni and Cr2O3-Ni interfacial structures and investigated the roles of the oxide-metal interfaces in CO2 methanation performance through excluding the normal support effect. Experimental and DFT calculation results reveal that the formate pathway tends to occur on the catalyst with only CeO2-Ni interfaces. The Cr2O3-Ni interface formed after introducing Cr oxide alters the nearby CeO2-Ni interface by electron transfer through Ni, which brings an additional reaction pathway (CO pathway) on CeO2-Cr2O3/Ni. Furthermore, it shows a relatively lower CO2 absorption energy and activation energy barrier for CO2 dissociation to CO at the Cr2O3-Ni interface, favorable for CO2 activation and further hydrogenation, thus leading to excellent low-temperature activity.

Spectral multiplexing of telecom emitters with stable transition frequency.

In a quantum network, coherent emitters can be entangled over large distances using photonic channels. In solid-state devices, the required efficient light-emitter interface can be implemented by confining the light in nanophotonic structures. However, fluctuating charges and magnetic moments at the nearby interface then lead to spectral instability of the emitters. Here, we avoid this limitation when enhancing the photon emission up to 70(12)-fold using a Fabry-Perot resonator with an embedded 19-micrometer-thin crystalline membrane, in which we observe around 100 individual erbium emitters. In long-term measurements, they exhibit an exceptional spectral stability of <0.2 megahertz that is limited by the coupling to surrounding nuclear spins. We further implement spectrally multiplexed coherent control and find an optical coherence time of 0.11(1) milliseconds, approaching the lifetime limit of 0.3 milliseconds for the strongest-coupled emitters. Our results constitute an important step toward frequency-multiplexed quantum-network nodes operating directly at a telecommunication wavelength.

Single-side J-integral method for interfacial cracks

To evaluate the debonding failure behavior of the interface between two materials, such as a fiber reinforced polymer (FRP)–concrete interface, accurately and conveniently, a single-side J-integral method was proposed in which a path is only established on one side (concrete side) of an interfacial crack. A ΔJ criterion was established to identify the unstable propagation of an interfacial crack considering the influence of the nearby concrete cracks and interface mismatch phenomenon on the single-side J-integral. For validation, double-shear tests of fully bonded FRP–concrete specimens were carried out, with different pre-crack lengths (0, 20, 40, and 60 mm). The displacement field of the concrete surface was obtained by the digital image correlation (DIC) method. The single-side J-integral of the interfacial crack was calculated by a self-designed calculation program, and the J-integral–displacement curves were obtained. The calculation results of 14 integral paths for four kinds of specimens showed that the relative error was 15.8% between the mean absolute value of the critical ΔJ and the critical energy release rate Gside-C of the interfacial crack on the concrete side. Therefore, with the proposed method, not only the debonding failure of the interface and local crack propagation direction can be predicted, but the concrete cracks inside the J-integral paths can also be identified.

Transverse magnetic routing of light emission in hybrid plasmonic-semiconductor nanostructures: Towards operation at room temperature

We study experimentally and theoretically the temperature dependence of transverse magnetic routing of light emission from hybrid plasmonic-semiconductor quantum well structures where the exciton emission from the quantum well is routed into surface plasmon polaritons propagating along a nearby semiconductor-metal interface. In II-VI and III-V direct band semiconductors the magnitude of routing is governed by the circular polarization of exciton optical transitions, that is induced by a magnetic field. For structures comprising a (Cd,Mn)Te/(Cd,Mg)Te diluted magnetic semiconductor quantum well we observe a strong directionality of the emission up to 15% at low temperature of 20 K and magnetic field of 485 mT due to giant Zeeman splitting of holes mediated via the strong exchange interaction with Mn$^{2+}$ ions. For increasing temperatures towards room-temperature the magnetic susceptibility decreases and the directionality strongly decreases to 4% at T = 45 K. We also propose an alternative design based on a non-magnetic (In,Ga)As/(In,Al)As quantum well structure, suitable for higher temperatures. According to our calculations, such structure can demonstrate emission directionality up to 5% for temperatures below 200 K and moderate magnetic fields of 1 T.

Modified radiative lifetime of Eu3+ ions in Y2O3 thin films on Al2O3 substrates

The 5D0 – 7Fn fluorescence of Eu3+ ions in Y2O3 thin films grown on Al2O3 substrates was studied. The films were produced by laser molecular beam epitaxy. The spectral lines revealed small inhomogeneous broadening which evidences for small distortions of cubic lattice. The measurements of the fluorescence lifetimes provided an indication of photon density of states and local field effects due to a nearby dielectric interface on radiative transitions in impurity ions in thin crystalline films.

Anisotropic scaling lengths of colloidal monolayers near a water–air interface

Abstract

Strong Electronic Interaction of Amorphous Fe2O3 Nanosheets with Single‐Atom Pt toward Enhanced Carbon Monoxide Oxidation

AbstractPlatinum‐based catalysts are critical to several chemical processes, but their efficiency is not satisfying enough in some cases, because only the surface active‐site atoms participate in the reaction. Henceforth, catalysts with single‐atom dispersions are highly desirable to maximize their mass efficiency, but fabricating these structures using a controllable method is still challenging. Most previous studies have focused on crystalline materials. However, amorphous materials may have enhanced performance due to their distorted and isotropic nature with numerous defects. Here reported is the facile synthesis of an atomically dispersed catalyst that consists of single Pt atoms and amorphous Fe2O3 nanosheets. Rational control can regulate the morphology from single atom clusters to sub‐nanoparticles. Density functional theory calculations show the synergistic effect resulted from the strong binding and stabilization of single Pt atoms with the strong metal‐support interaction between the in situ locally anchored Pt atoms and Fe2O3 lead to a weak CO adsorption. Moreover, the distorted amorphous Fe2O3 with O vacancies is beneficial for the activation of O2, which further facilitates CO oxidation on nearby Pt sites or interface sites between Pt and Fe2O3, resulting in the extremely high performance for CO oxidation of the atomic catalyst.

Evidence of directivity during the earthquakes of 8 and 10 May 2014 (Mw 6.5, 6.1) in the Guerrero, Mexico seismic gap and some implications

We report on rupture directivity during 8 and 10 May 2014 earthquakes (Mw 6.5, 6.1), which occurred on the Mexican subduction thrust in the Guerrero seismic gap. The two events were located near each other and SE of the area that had ruptured in an Mw 7.2 earthquake on 18 April 2014. Near-source recordings show that the rupture during the 8 May propagated roughly along the strike towards ESE, while the directivity during the 10 May event was in the opposite direction. Analyses of the ground motions produced by the two earthquakes at regional distances (spectral ratios, ratios of peak ground accelerations and velocities, observed ground motion parameters, and radiated seismic energy) exhibit strong azimuthal variation, consistent with the directivity. As expected, the motions were enhanced in the forward direction. Since the attenuation of seismic waves from coastal earthquakes is slower along the inland path as compared to the coastal path, the ground motions during the 8 May earthquake at inland sites in the forward direction were exceptionally large. It follows that the combination of the two effects during future large/great earthquakes in the gap may lead to destructive ground motions at inland sites even at regional distances. The combined effect may have been one of the causes of the unprecedented number of deaths and injuries, and damage in Mexico City during the 1985 Michoacan earthquake (Mw 8.0) which ruptured a nearby subduction interface with a ESE directivity.

Surface swimmers, harnessing the interface to self-propel.

In the study of microscopic flows, self-propulsion has been particularly topical in recent years, with the rise of miniature artificial swimmers as a new tool for flow control, low Reynolds number mixing, micromanipulation or even drug delivery. It is possible to take advantage of interfacial physics to propel these microrobots, as demonstrated by recent experiments using the proximity of an interface, or the interface itself, to generate propulsion at low Reynolds number. This paper discusses how a nearby interface can provide the symmetry breaking necessary for propulsion. An overview of recent experiments illustrates how forces at the interface can be used to generate locomotion. Surface swimmers ranging from the microscopic scale to typically the capillary length are covered. Two systems are then discussed in greater detail. The first is composed of floating ferromagnetic spheres that assemble through capillarity into swimming structures. Two previously studied configurations, triangular and collinear, are discussed and contrasted. A new interpretation for the triangular swimmer is presented. Then, the non-monotonic influence of surface tension and viscosity is evidenced in the collinear case. Finally, a new system is introduced. It is a magnetically powered, centimeter-sized piece that swims similarly to water striders.

Evaluation of underground pipe-structure interface for surface impact load

Nuclear safety related buried pipelines need to be assessed for the effects of postulated surface impact loads. In published solutions, the buried pipe is often considered within an elastic half space without interference with other underground structures. In the case that a surface impact occurs in short distance from an underground pipe-structure interface, this boundary condition will further complicate the buried pipe evaluation. Neglecting such boundary effect in the assessment may lead to underestimating potential damage of buried pipeline, and jeopardizing safety of the nuclear power plant. Comprehensive analysis of such structure-pipe-soil system is often subjected to availability of state-of-art finite element tools, as well as costly and time consuming. Simple, but practical conservative techniques have not been established. In this study, a mechanics based solution is proposed in order to assess the magnitude of damage to a buried pipeline beneath a heavy surface impact considering the effect of a nearby pipe-structure interface. The proposed approach provides an easy to use tool in the early stage of evaluation before the decision of applying more costly technique can be made by owner of the nuclear facility.

Structure and Dynamics of Water at Carbon-Based Interfaces

Water structure and dynamics are affected by the presence of a nearby interface. Here, first we review recent results by molecular dynamics simulations about the effect of different carbon-based materials, including armchair carbon nanotubes and a variety of graphene sheets—flat and with corrugation—on water structure and dynamics. We discuss the calculations of binding energies, hydrogen bond distributions, water’s diffusion coefficients and their relation with surface’s geometries at different thermodynamical conditions. Next, we present new results of the crystallization and dynamics of water in a rigid graphene sieve. In particular, we show that the diffusion of water confined between parallel walls depends on the plate distance in a non-monotonic way and is related to the water structuring, crystallization, re-melting and evaporation for decreasing inter-plate distance. Our results could be relevant in those applications where water is in contact with nanostructured carbon materials at ambient or cryogenic temperatures, as in man-made superhydrophobic materials or filtration membranes, or in techniques that take advantage of hydrated graphene interfaces, as in aqueous electron cryomicroscopy for the analysis of proteins adsorbed on graphene.

Marangoni effect visualized in two-dimensions Optical tweezers for gas bubbles.

In the report we demonstrate how, using laser light, effectively trap gas bubbles and transport them through a liquid phase to a desired destination by shifting the laser beam position. The physics underlying the effect is complex but quite general as it comes from the limited to two-dimension, well-known, Marangoni effect. The experimental microscope-based system consists of a thin layer of liquid placed between two glass plates containing a dye dissolved in a solvent and a laser light beam that is strongly absorbed by the dye. This point-like heat source locally changes surface tension of nearby liquid-air interface. Because of temperature gradients a photo-triggered Marangoni flows are induced leading to self-amplification of the effect and formation of large-scale whirls. The interface is bending toward beam position allowing formation of a gas bubble upon suitable beam steering. Using various techniques (employing luminescent particles or liquid crystals), we visualize liquid flows propelled by the tangential to interface forces. This helped us to understand the physics of the phenomenon and analyze accompanying effects leading to gas bubble trapping. The manipulation of sessile droplets moving on the glass surface induced via controlled with laser light interface bending (i.e. “droplet catapult”) is demonstrated as well.

Cryo-EM Visualization of Nanobubbles in Aqueous Solutions.

The detection of nanobubbles on surfaces is well established (e.g., AFM and optical microscopy methods), but currently no methods exist for the direct detection of bulk nanobubbles. Here, cryo-electron microscopy (cryo-EM) has been employed to observe bubbles in aqueous solutions for the first time. Nitrogen bubbles generated by a chemical reaction were observed in amorphous ice trapped between two carbon films. The cryo-EM images of bubbles showed the same features as predicted by theory. The fact that no bubbles were observed near an air-water interface suggests that bubbles may diffuse to the nearby air-water interface and escape. The estimate of the bubble diffusion coefficient is about 30-250 μm2/s.

Effects of vertical obliquity on sonar images and elastic mechanisms for cylinders near a flat interface

The backscattered signal from targets located near a flat interface is highly dependent on the relative positions and orientations of the acoustic source/receiver, the interface, and the target. The acoustic backscattering spectrum versus aspect angle, also called the “acoustic color'' or “acoustic template,'' of solid cylinders was previously studied for the case where the cylinder axis was vertically oblique relative to a nearby water-air interface [D. Plotnick et al., J. Acoust. Soc. Am. 137, 470–480 (2015)]. The presence of the interface allows for multiple orientation-dependent paths by which sound is backscattered; this work examines the effects of vertical obliquity on these paths. Experimental data were on a solid cylinder at various obliquities near an air-water interface collected using a circular synthetic aperture sonar system. Emphasis will be placed on the effects of vertical obliquity on features in reconstructed sonar images. Several robust orientation dependent features are considered and the physical mechanisms identified through geometric arguments. Information about a target's 3-D orientation and size may be gleaned from these images, aiding the interpretation of features within the target's acoustic template. The coupling conditions for surface elastic waves are also considered. [Work supported by ONR.]

Photochemical tussue penetration via photosensitizer for the efficient penetration of drug into tumor tissue

Event Abstract Back to Event Photochemical tussue penetration via photosensitizer for the efficient penetration of drug into tumor tissue Jeongdeok Seo1 and Kun Na1 1 The Catholic University of Korea, Department of Biotechnology, Korea Introduction: A non-vascular drug eluting stent (DES) is a biomedical device that is implanted in the gastrointestinal (GI) tract for stabilizing the flow of body fluids when obstructive symptoms are shown due to tumor growth. Recently, gemcitabine (GEM) eluting membrane covered stents have been developed and highlighted because of the strong therapeutic effect of GEM in GI tumor therapy[1]. However, GEM has a low tissue penetration efficiency (PE%) in the GI tract because of its hydrophilicity and the epithelial barrier function. For this reason, some cells of a GEM treated tumor can continue to proliferate and allow tumor growth. We believe that an alteration of the epithelial layer is required for improving drug penetration[2]. Materials and Methods: To prepare the membranes, 200 mL of the above mixed solution(Gemcitabine(GEM), Photosensitizer(PS), Polyurethane(PU)) was poured into the polytetrafluorethylene (Teflon) mold and dried. The surface morphologies of each membrane were observed with Field emission-scanning electron microscopy (FE-SEM). To confirm the drug release behaviors, GEM-PU (PS absent membrane) and PS-GEM-PU were placed into conical tubes, and phosphate buffer saline was added. To confirm the generation of singlet oxygen, PS-GEM-PU was incubated in PBS for 0, 1 or 2 weeks. To confirm the PE% enhancing mechanism, CT-26 cells were cultured in a 6-well plate and Chang cells were cultured . To visualize the tissue penetration of the hydrophilic molecule, fluorescein was loaded instead of GEM in the drug eluting membrane. To evaluate in vivo tumor growth inhibition activity, CT-26 bearing Balb/c nude mice were used. Results: PS was uniformly spread in the membrane. GEM was located in the nearby abluninal side of the membrane. The releasing of GEM was not influenced by the addition of PS. Also, under the light exposure, the singlet oxygen was generated by PS at the membrane surface for 2 weeks. The PE% of GEM from PS-GEM with light was 30% higher than the others of in vitro penetration test. To visualize the tissue penetration test of the hydrophilic molecule, the intensity of the penetrated FITC in the PS-fluorescein with light group increased by approximately 200% compared to the others. To evaluate the tumor growth inhibition efficiency, the tumor with GEM-PU with or without light and PS-GEM-PU without light grew exponentially; almost 3 times larger tumor volumes were measured than in the PS-GEM-PU group. In TUNEL assay, apoptotic cells were detected at the nearby tumor-membrane interface in the case of GEM-PU with or without light and PS-GEM-PU without light. Discussion: To improve the tissue penetration efficiency of hydrophilic-drugs in non-vascular drug eluting stents(DES), we designed photochemical tissue penetration invested DES. Consequentially, tumor growth, when implanted with PS-GEM-PU, was effectively inhibited without significant side effects. Based on these results, we believe that the photochemical tissue penetration-DES system has great potential for improving the therapeutic effect of conventional DES. Conclusion: PS-GEM-PU was designed and prepared to increase both the tissue penetration and the therapeutic efficacy of a GEM loaded DES. In this study, we overcame this barrier using a PS-DES membrane. Thus, the membrane has a higher therapeutic effect than a conventional GEM eluting membrane. To improve the therapeutic potency of PS-DES system, further experiments were required to optimize drug content in DES membrane.

Increased hydrophobic surface exposure in the cataract-related G18V variant of human γS-crystallin

BackgroundThe objective of this study was to determine whether the cataract-related G18V variant of human γS-crystallin has increased exposure of hydrophobic residues that could explain its aggregation propensity and/or recognition by αB-crystallin. MethodsWe used an ANS fluorescence assay and NMR chemical shift perturbation to experimentally probe exposed hydrophobic surfaces. These results were compared to flexible docking simulations of ANS molecules to the proteins, starting with the solution-state NMR structures of γS-WT and γS-G18V. ResultsγS-G18V exhibits increased ANS fluorescence, suggesting increased exposed hydrophobic surface area. The specific residues involved in ANS binding were mapped by NMR chemical shift perturbation assays, revealing ANS binding sites in γS-G18V that are not present in γS-WT. Molecular docking predicts three binding sites that are specific to γS-G18V corresponding to the exposure of a hydrophobic cavity located at the interdomain interface, as well as two hydrophobic patches near a disordered loop containing solvent-exposed cysteines, all but one of which is buried in γS-WT. ConclusionsAlthough both proteins display non-specific binding, more residues are involved in ANS binding to γS-G18V, and the affected residues are localized in the N-terminal domain and the nearby interdomain interface, proximal to the mutation site. General significanceCharacterization of changes in exposed hydrophobic surface area between wild-type and variant proteins can help elucidate the mechanisms of aggregation propensity and chaperone recognition, presented here in the context of cataract formation. Experimental data and simulations provide complementary views of the interactions between proteins and the small molecule probes commonly used to study aggregation. This article is part of a Special Issue entitled Crystallin Biochemistry in Health and Disease.

Diffusion Bonding of Mg-AZ31B/Al-6061 and Characteristics with Pressure and with no Pressure

The study is diffusion bonding of Mg-AZ31 and Al-6061 under pressure and no pressure by using the direct bonding method. After bonding process, characteristics phase in interface and bonding boundaries of Mg-AZ31/Al-6061 were characterized . The diffusion formation was observed by SEM. Aluminum solid solution and Mg17Al12 alloy phase was proved by analysis of XRD. In the process of measurement, crystalline structure of nearby interface characteristics phase was analyzed in detail by TEM. Based on the above analysis, the crystal model of the magnesium alloy and aluminum alloys was established under pressure, and the bonding mechanism was discussed. The results show that the bonding materials could be bonded under no pressure and the structure of bonding interface is more optimized than pressure.

Interface-Mediated Photostimulation Effects on Diffusion and Activation of Boron Implanted into Silicon

Recent work has demonstrated the existence of nonthermal illumination effects on the diffusion of boron, arsenic, and isotopic silicon ion-implanted into silicon for ultra-shallow junction applications. In some cases, the degree of electrical activation is affected as well. The effects arise from super-bandgap light's direct action on bulk point defects via changes in their charge state. By contrast, the present work demonstrates the existence of a distinct mechanism whereby light acts indirectly on bulk defects via changes at a nearby interface. The changes occur in interfacial annihilation probability and/or electric potential, and affect the efficiency with which the interface absorbs point defects emitted by extended end-of-range defects during annealing.

Quantifying the Threat of Unsuppressed Wildfires Reaching the Adjacent Wildland-Urban Interface on the Bridger-Teton National Forest, Wyoming, USA

An important objective for many federal land management agencies is to restore fire to ecosystems that have experienced fire suppression or exclusion over the last century. Managing wildfires for resource objectives (i.e., allowing wildfires to burn in the absence of suppression) is an important tool for restoring such fire-adapted ecosystems. To support management decisions that allow wildfires to burn unsuppressed, land managers need a quantitative assessment of the potential for such wildfires to reach nearby fire-susceptible resources and assets. We established a study area on a portion of the Bridger-Teton National Forest near Jackson, Wyoming, USA, where land managers wish to restore fire by managing wildfires, but are concerned about the threat to residential buildings. We modeled the ignition and unsuppressed growth of wildfires starting in a remote portion of the study area using FSim, a fire occurrence, growth, and suppression simulation model. We then characterized annual area burned and the likelihood that wildfires would reach a nearby wildland-urban interface (WUI) defense zone. Early-season fires burned longer and grew larger than late-season fires, and thus had a higher likelihood of reaching the WUI zone (3 % of May fires compared to 0.1 % of October fires). Because fire managers do not anticipate managing all fire starts for resource objectives, we applied a simple rule set termed “RO rules,” indicating the fraction of starts by month to be managed for resource objectives. This reduced the expected number of fires reaching the WUI zone by 70 %, and the expected WUI zone area burned by 61 %. From 1990 to 2009, a mean of 207 ha yr−1 had been burned by wildfires starting in the remote portion of the study area. By contrast, we estimated that 14 431 ha yr−1 could burn if no fire starts were suppressed, and 4861 ha yr−1 after applying the RO rules. Our analysis approach can be extended to determine which parts of the landscape are most likely to produce fires that reach specific targets on the landscape.

Engineering domain fusion chimeras from I-OnuI family LAGLIDADG homing endonucleases

Although engineered LAGLIDADG homing endonucleases (LHEs) are finding increasing applications in biotechnology, their generation remains a challenging, industrial-scale process. As new single-chain LAGLIDADG nuclease scaffolds are identified, however, an alternative paradigm is emerging: identification of an LHE scaffold whose native cleavage site is a close match to a desired target sequence, followed by small-scale engineering to modestly refine recognition specificity. The application of this paradigm could be accelerated if methods were available for fusing N- and C-terminal domains from newly identified LHEs into chimeric enzymes with hybrid cleavage sites. Here we have analyzed the structural requirements for fusion of domains extracted from six single-chain I-OnuI family LHEs, spanning 40–70% amino acid identity. Our analyses demonstrate that both the LAGLIDADG helical interface residues and the linker peptide composition have important effects on the stability and activity of chimeric enzymes. Using a simple domain fusion method in which linker peptide residues predicted to contact their respective domains are retained, and in which limited variation is introduced into the LAGLIDADG helix and nearby interface residues, catalytically active enzymes were recoverable for ∼70% of domain chimeras. This method will be useful for creating large numbers of chimeric LHEs for genome engineering applications.