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The complicated reaction pathway of the water–gas shift reaction (WGSR) hinders understanding the overall reaction mechanism and extracting the factors to design better performing catalysts. Here, we use density functional theory to study the mechanism of WGSR catalyzed by Au single atoms stabilized at the CeOx–TiO2interfaces on TiO2particles (ACT catalyst). We constructed two energetic landscapes of the WGSR (redox and associative mechanisms), concurrently presenting the H2formation as a rate-determining step. Electronic analysis data showed that the charge state of the oxygen ions participating in WGSR strongly correlates with the oxygen vacancy formation energy (OVF) and hydrogen binding energy (ΔEH), directly scaling the CO oxidation power and the H2production ability. Further expansion toward various Au on oxide–oxide combinations confirmed that the delicate control of metal-oxide-oxide interfaces with optimized local electronic structures expresses the rational design of a WGSR catalyst.

Valence change-type resistance switching behaviors in oxides can be understood by well-established physical models describing the field-driven oxygen vacancy distribution change. In those models, electroformed residual oxygen vacancy filaments are crucial as they work as an electric field concentrator and limit the oxygen vacancy movement along the vertical direction. Therefore, their movement outward by diffusion is negligible. However, this situation may not be applicable in the electroforming-free system, where the field-driven movement is less prominent, and the isotropic oxygen vacancy diffusion by concentration gradient is more significant, which has not been given much consideration in the conventional model. Here, we propose a modified physical model that considers the change in the oxygen vacancies’ charged state depending on their concentrations and the resulting change in diffusivity during switching to interpret the electroforming-free device behaviors. The model suggests formation of an hourglass-shaped filament constituting a lower concentration of oxygen vacancies due to the fluid oxygen diffusion in the thin oxide. Consequently, the proposed model can explain the electroforming-free device behaviors, including the retention failure mechanism, and suggest an optimized filament configuration for improved retention characteristics. The proposed model can plausibly explain both the electroformed and the electroforming-free devices. Therefore, it can be a standard model for valence change memristors.

The order – disorder transition temperature of the PtCo bulk alloy and the effect of heat treatment on an as-sputtered disordered PtCo thin film have been investigated using Monte Carlo simulations coupled with a modified embedded atom method. From the long-range order curve combined with atomistic configurations, the order – disorder transition temperature is estimated between 1000 K and 1200 K. It has also been confirmed that the heat treatment at 900 K on the as-sputtered PtCo thin film induced ordering. The Pt segregation at the top surface of the thin film resulted in ordering of the whole thin film, except for four or five bottom layers probably because of the influence of the substrate.

Two-dimensional (2D) materials are promising components for defect passivation of metal halide perovskites. Unfortunately, commonly used polydisperse liquid-exfoliated 2D materials generally suffer from heterogeneous structures and properties while incorporated into perovskite films. We introduce monodisperse multifunctional 2D crystalline carbon nitride, poly(triazine imide) (PTI), as an effective defect passivation agent in perovskite films via typical solution processing. Incorporation of PTI into perovskite film can be readily attained by simple solution mixing of PTI dispersions with perovskite precursor solutions, resulting in the highly selective distribution of PTI localized at the defective crystal grain boundaries and layer interfaces in the functional perovskite layer. Several chemical, optical, and electronic characterizations, in conjunction with density functional theory calculations, reveal multiple beneficial roles from PTI: passivation of undercoordinated organic cations at the surface of perovskite crystal, suppression of ion migration by blocking diffusion channels, and prevention of hole quenching at perovskite/SnO2interfaces. Consequently, a noticeably improved power conversion efficiency is achieved in perovskite solar cells, accompanied with promoted stability under humid air and thermal stress. Our strategy highlights the potential of judiciously designed 2D materials as a simple-to-implement material for various optoelectronic devices, including solar cells, based on hybrid perovskites.

In an aging society in the world, dementia that leads to pain in patients and their families has become a common disease in our lives. Among dementia, Alzheimer's disease (AD) is the most commonly shown disease. Various causes of the disease have been proposed and amyloid hypothesis insists that the toxic amyloid‐β (Aβ) species could be the major risk factor of the onset and progression of AD. In this perspective, clearance of Aβ species from the brain by regulating the activity of amyloid degrading enzymes (ADE), including neprilysin and matrix metalloproteinases, could be a potent treatment for AD. Therefore, the structures and functions of these enzymes along with biological molecules in the brain would be important to understand the pathogenesis of AD and develop an effective medication for the disease. In this review, multiple ADE with biological molecules which could affect the activities and/or expression of the enzymes are summarized. The amyloid degrading enzymes (ADE) could control the levels of amyloidogenic proteins in brain consequently affect the pathogenesis of Alzheimer's disease (AD). Therefore, understanding the expression and activity of ADE along with other biological molecules in the brain is essential to develop therapeutic agents to treat AD.

AMOLED pixel circuit was proposed to compensate for reduced luminance by both the stretching and IR drop on power line. In addition, the proposed circuit keeps compensation function for both the positive and negative shift. The proposed circuit was verified by the simulation for the negative shift of threshold voltages, IR drop at power bus line and the stretching induced luminance change.

Low voltage oxide thin film transistor (TFT) was developed using high dielectric gate insulator by thermal oxidation of tantalum metal. Thermal oxidation was carried out after deposition of tantalum layer by sputtering. Thermal grown tantalum oxide was analyzed by HR‐TEM and XPS. Through XPS analysis, it was confirmed that the binding energy of Ta4f indicates the formation of tantalum oxide. And the clear O1s peak has good Ta‐O bond. The transfer characteristic of the developed oxide transistor showed mobilities over 10 cm2/V·s and the inverter circuit operating below 1 V was achieved.

Hybridization of low-dimensional components with diverse geometrical dimensions should offer an opportunity for the discovery of synergistic nanocomposite structures. In this regard, how to establish a reliable interfacial interaction is the key requirement for the successful integration of geometrically different components. Here, we present 1D/2D heterodimensional hybrids via dopant induced hybridization of 2D Ti3C2TxMXene with 1D nitrogen-doped graphene nanoribbon. Edge abundant nanoribbon structures allow a high level nitrogen doping (∼6.8 at%), desirable for the strong coordination interaction with Ti3C2TxMXene surface. For piezoresistive pressure sensor application, strong adhesion between the conductive layers and at the conductive layer/elastomer interface significantly diminishes the sensing hysteresis down to 1.33% and enhances the sensing stability up to 10 000 cycles at high pressure (100 kPa). Moreover, large-area pressure sensor array reveals a high potential for smart seat cushion-based posture monitoring application with high accuracy (>95%) by exploiting machine learning algorithm.

An effective pathway to build macroscopic scale functional architectures bearing diverse structural dimensions is one of the critical challenges in the two-dimensional (2D) MXene research area. Unfortunately, assembling MXene without adhesive binder is largely limited due to its innate brittle nature and the relatively weak inter-flake van der Waals contact, in contrast to other mechanically compliant 2D materials such as graphene. Herein, an electrochemical self-assembly of pure Ti3C2TxMXenes is presented for functional multidimensional MXene structures, effectively driven by layer-by-layer spontaneous interfacial reduction at metal template surfaces and subsequent defunctionalization. A three-dimensional open porous aerogel as well as 2D highly stacked thin film structures could be readily obtained in this approach, along with largely enhanced electrical properties induced by spontaneous removal of charge-trapping oxygen functional groups. Accordingly, supercapacitors and electromagnetic interference shielding films based on the multidimensional assembly demonstrate excellent performances.

Multiscale and multimodal imaging of material structures and properties provides solid ground on which materials theory and design can flourish. Recently, KAIST announced 10 flagship research fields, which include KAIST Materials Revolution: Materials and Molecular Modeling, Imaging, Informatics and Integration (M3I3). The M3I3 initiative aims to reduce the time for the discovery, design and development of materials based on elucidating multiscale processing–structure–property relationship and materials hierarchy, which are to be quantified and understood through a combination of machine learning and scientific insights. In this review, we begin by introducing recent progress on related initiatives around the globe, such as the Materials Genome Initiative (U.S.), Materials Informatics (U.S.), the Materials Project (U.S.), the Open Quantum Materials Database (U.S.), Materials Research by Information Integration Initiative (Japan), Novel Materials Discovery (E.U.), the NOMAD repository (E.U.), Materials Scientific Data Sharing Network (China), Vom Materials Zur Innovation (Germany), and Creative Materials Discovery (Korea), and discuss the role of multiscale materials and molecular imaging combined with machine learning in realizing the vision of M3I3. Specifically, microscopies using photons, electrons, and physical probes will be revisited with a focus on the multiscale structural hierarchy, as well as structure–property relationships. Additionally, data mining from the literature combined with machine learning will be shown to be more efficient in finding the future direction of materials structures with improved properties than the classical approach. Examples of materials for applications in energy and information will be reviewed and discussed. A case study on the development of a Ni–Co–Mn cathode materials illustrates M3I3’s approach to creating libraries of multiscale structure–property–processing relationships. We end with a future outlook toward recent developments in the field of M3I3.

Achieving historically anticipated improvement in the performance of integrated circuits is challenging, due to the increasing cost and complexity of the required technologies with each new generation. To overcome this limitation, the exploration and development of novel interconnect materials and processes are highly desirable in the microelectronics field. Molybdenum (Mo) is attracting attention as an advanced interconnect material due to its small resistivity size effect and high cohesive energy; however, effective processing methods for such materials have not been widely investigated. Here, we investigate the electrochemical behavior of ions in the confined nanopores that affect the electrical properties and microstructures of nanoscale Mo and Mo–Co alloys prepared via template-assisted electrodeposition. Additives in an electrolyte allow the deposition of extremely pure metal materials, due to their interaction with metal ions and nanopores. In this study, boric acid and tetrabutylammonium bisulfate (TBA) were added to an acetate bath to inhibit the hydrogen evolution reaction. TBA accelerated the reduction of Mo at the surface by inducing surface conduction on the nanopores. Metallic Mo nanowires with a 130 nm diameter synthesized through high-aspect-ratio nanopore engineering exhibited a resistivity of (63.0 ± 17.9) μΩ·cm. We also evaluated the resistivities of Mo–Co alloy nanowires at various compositions toward replacing irreducible conventional barrier/liner layers. An intermetallic compound formed at an Mo composition of 28.6 at%, the resistivity of the Mo–Co nanowire was (58.0 ± 10.6) μΩ·cm, indicating its superior electrical and adhesive properties in comparison with those of conventional barriers such as TaN and TiN. Furthermore, density functional theory and non-equilibrium Green’s function calculations confirmed that the vertical resistance of the via structure constructed from Mo-based materials was 21% lower than that of a conventional Cu/Ta/TaN structure.

Two-dimensional (2D) MXene has shown enormous potential in scientific fields, including energy storage and electromagnetic interference (EMI) shielding. Unfortunately, MXene-based material structures generally suffer from mechanical fragility and vulnerability to oxidation. Herein, mussel-inspired dopamine successfully addresses those weaknesses by improving interflake interaction and ordering in MXene assembled films. Dopamine undergoes in situpolymerization and binding at MXene flake surfaces by spontaneous interfacial charge transfer, yielding an ultrathin adhesive layer. Resultant nanocomposites with highly aligned tight layer structures achieve approximately seven times enhanced tensile strength with a simultaneous increase of elongation. Ambient stability of MXene films is also greatly improved by the effective screening of oxygen and moisture. Interestingly, angstrom thick polydopamine further promotes the innate high electrical conductivity and excellent EMI shielding properties of MXene films. This synergistic concurrent enhancement of physical properties proposes MXene/polydopamine hybrids as a general platform for MXene based reliable applications.

Perovskite crystal grain size control, grain boundary passivation, and grain bridging are the keys to obtaining high efficiency in perovskite solar cells. A small amount of semiconducting single-walled carbon nanotubes added to a perovskite active layer can achieve this. In particular, the surfactants attached to the semiconducting single-walled carbon nanotubes a crucial role. In this work, we synthesized a new surfactant, 4,6-di(anthracen-9-yl)-1,3-phenylene bis(dimethylcarbamate), which has a polyaromatic group on one end and a urea-analogue carbamate group on the other end. The polyaromatic anthracene end functions as a nanotweezer clenching the carbon nanotubes strongly via π–π interaction while the carbamate end interacts with Pb2+, functioning as a strong Lewis base. In addition, the new surfactant has conjugated double bonds with a suitable bandgap, resulting in enhanced charge mobility in the perovskite film. Overall, the new surfactant-clenched semiconducting carbon nanotubes showcase superior effectiveness as passivators and charge bridges in perovskite solar cells as compared to the conventional deoxycholate surfactant-wrapped semiconducting single-walled carbon nanotubes. The new surfactant-attached semiconducting carbon nanotube-added NH3CH3PbI3-based perovskite solar cells exhibited a power conversion efficiency of 20.7%, which is higher than that of the reference devices with no additives (18.4%) and the previously reported semiconducting single-walled carbon nanotube-added devices (19.7% in this work and 19.5% in the literature).

Multiple pathogenic elements, including reactive oxygen species, amyloidogenic proteins, and metal ions, are associated with the development of neurodegenerative disorders. We report minimalistic redox-based principles for preparing compact aromatic compounds by derivatizing the phenylene moiety with various functional groups. These molecular agents display enhanced reactivities against multiple targets such as free radicals, metal-free amyloid-β (Aβ), and metal-bound Aβ that are implicated in the most common form of dementia, Alzheimer’s disease (AD). Mechanistic studies reveal that the redox properties of these reagents are essential for their function. Specifically, they engage in oxidative reactions with metal-free and metal-bound Aβ, leading to chemical modifications of the Aβ peptides to form covalent adducts that alter the aggregation of Aβ. Moreover, the administration of the most promising candidate significantly attenuates the amyloid pathology in the brains of AD transgenic mice and improves their cognitive defects. Our studies demonstrate an efficient and effective redox-based strategy for incorporating multiple functions into simple molecular reagents.

The development of catalysts for the electrochemical N2reduction reaction (NRR) with a low limiting potential and high Faradaic efficiency is highly desirable but remains challenging. Here, to achieve acceleration, we develop and report a slab graph convolutional neural network (SGCNN), an accurate and flexible machine learning (ML) model that is suited for probing surface reactions in catalysis. With a self-accumulated database of 3040 surface calculations at the density-functional-theory (DFT) level, SGCNN predicted the binding energies, ranging over 8 eV, of five key adsorbates (H, N2, N2H, NH, NH2) related to NRR performance with a mean absolute error (MAE) of only 0.23 eV. SGCNN only requires the low-level inputs of elemental properties available in the periodic table of elements and connectivity information of constituent atoms; thus, accelerations can be realized. Via a combined process of SGCNN-driven predictions and DFT verifications, four novel catalysts in the L12crystal space, including V3Ir(111), Tc3Hf(111), V3Ni(111), and Tc3Ta(111), are proposed as stable candidates that likely exhibit both a lower limiting potential and higher Faradaic efficiency in the NRR, relative to the reference Mo(110). The ML work combined with a statistical data analysis reveals that catalytic surfaces with an average d-orbital occupation between 4 and 6 could lower the limiting potential and potentially overcome the scaling relation in the NRR.

Peripheral nerve injuries represent a significant problem in public health, constituting 2–5% of all trauma cases1. For severe nerve injuries, even advanced forms of clinical intervention often lead to incomplete and unsatisfactory motor and/or sensory function2. Numerous studies report the potential of pharmacological approaches (for example, growth factors, immunosuppressants) to accelerate and enhance nerve regeneration in rodent models3–10. Unfortunately, few have had a positive impact in clinical practice. Direct intraoperative electrical stimulation of injured nerve tissue proximal to the site of repair has been demonstrated to enhance and accelerate functional recovery11,12, suggesting a novel nonpharmacological, bioelectric form of therapy that could complement existing surgical approaches. A significant limitation of this technique is that existing protocols are constrained to intraoperative use and limited therapeutic benefits13. Herein we introduce (i) a platform for wireless, programmable electrical peripheral nerve stimulation, built with a collection of circuit elements and substrates that are entirely bioresorbable and biocompatible, and (ii) the first reported demonstration of enhanced neuroregeneration and functional recovery in rodent models as a result of multiple episodes of electrical stimulation of injured nervous tissue.

The polarizable charge equilibration (PQEq) method was developed to provide a simple but accurate description of the electrostatic interactions and polarization effects in materials. Previously, we optimized four parameters per element for the main group elements. Here, we extend this optimization to the 24 d-block transition-metal (TM) elements, columns 4–11 of the periodic table including Ti–Cu, Zr–Ag, and Hf–Au. We validate the PQEq description for these elements by comparing to interaction energies computed by quantum mechanics (QM). Because many materials applications involving TM are for oxides and other compounds that formally oxidize the metal, we consider a variety of oxidation states in 24 different molecular clusters. In each case, we compare interaction energies and induced fields from QM and PQEq along various directions. We find that the original χ and Jparameters (electronegativity and hardness) related to the ionization of the atom remain valid; however, we find that the atomic radius parameter needs to be close to the experimental ionic radii of the transition metals. This leads to a much higher spring constant to describe the atomic polarizability. We find that these optimized parameters for PQEq provide accurate interaction energies compared to QM with charge distributions that depend in a reasonable way on the coordination number and oxidation states of the transition metals. We expect that this description of the electrostatic interactions for TM will be useful in molecular dynamics simulations of inorganic and organometallic materials.

To overcome the limited feasibility of various refractory high-entropy alloys (HEAs) due to the presence of (i) very dense elements (W and Ta), (ii) costly elements (Hf and Ta), and (iii) oxidation prone elements (V) in them, AlxCryMozNbTiZr HEAs were prepared via arc-melting. Considering the critical nature of oxidation resistance in high-temperature applications, HEAs were characterized to form a combinatorial library of microstructural and oxidation behavior. AlxCryMozNbTiZr HEAs revealed multiphase microstructures consisting of intermetallic phases along with BCC matrices. Mass loss and porous microstructures were obtained in Mo-rich HEAs after oxidation at 1000 °C for 1 h. The presence of Al enhanced the oxidation resistance and developed a protective oxide layer on the HEAs. Al30Cr10-NTZ exhibited promising potential for use in high temperature applications, as it showed an oxidation time exponent of ∼0.5 and a dense and continuous oxide layer.

Lithium–sulfur batteries (Li–S) are considered the most promising systems for next-generation energy storage devices due to their high theoretical energy density and relatively low cost. However, the practical applications of Li–S batteries are hindered by the poor electronic conductivity of sulfur and capacity degradation resulting from the shuttle effect of lithium polysulfides (LiPSs). Herein, we demonstrate use of a tin-sulfide (SnS2) modified separator to facilitate the redox reaction involving LiPS intermediates and realize improved electrochemical performance in a Li–S battery. Density functional theory (DFT) calculations revealed that SnS2exhibits a strong affinity with LiPSs and induces a rapid conversion of trapped polysulfides. As a result, Li–S batteries with a SnS2-modified separator exhibited an enhanced specific capacity of 1300 mA h g−1at 0.2C (corresponding to a high areal capacity of 4.03 mA h cm−2), which was maintained at 1040 mA h g−1after 150 cycles. Furthermore, an excellent rate capability is achieved with a capacity of 700 mA h g−1(2.17 mA h cm−2) at 5C. Additionally, the modified separator exhibited excellent cycling performance up to 500 cycles at 2C, with a low capacity decay rate of 0.0710% per cycle. The excellent performance of the sulfur electrode is mainly attributed to the incorporation of the SnS2coating layer on the separator, which effectively confines polysulfides viaboth chemical and physical interaction and rapidly improves lithium ion diffusion. Moreover, the SnS2coating layer greatly improves sulfur utilization and efficiently accelerates the kinetic conversion of trapped polysulfides.

Recently, Pt3M (M = Fe, Ni, Co, Cu, etc.) intermetallic compounds have been highlighted as promising candidates for oxygen reduction reaction (ORR) catalysts. In general, to form those intermetallic compounds, alloy phase nanoparticles are synthesized and then heat-treated at a high temperature. However, nanoparticles easily agglomerate during the heat treatment, resulting in a decrease in electrochemical surface area (ECSA). In this study, we synthesized Pt–Fe alloy nanoparticles and employed carbon coating to protect the nanoparticles from agglomeration during heat treatment. As a result, Pt3Fe L12structure was obtained without agglomeration of the nanoparticles; the ECSA of Pt–Fe alloy and intermetallic Pt3Fe/C was 37.6 and 33.3 m2gPt–1, respectively. Pt3Fe/C exhibited excellent mass activity (0.454 A mgPt–1) and stability with superior resistances to nanoparticle agglomeration and iron leaching. Density functional theory (DFT) calculation revealed that, owing to the higher dissolution potential of Fe atoms on the Pt3Fe surface than those on the Pt–Fe alloy, Pt3Fe/C had better stability than Pt–Fe/C. A single cell fabricated with Pt3Fe/C showed higher initial performance and superior durability, compared to that with commercial Pt/C. We suggest that Pt3M chemically ordered electrocatalysts are excellent candidates that may become the most active and durable ORR catalysts available.

The complexity of Alzheimer’s disease (AD) stems from the inter-relation of multiple pathological factors upon initiation and progression of the disease. To identify the involvement of metal-bound amyloid-β (metal-Aβ) aggregation in AD pathology, among the pathogenic features found in the AD-affected brain, small molecules as chemical tools capable of controlling metal–Aβ aggregation were developed. Herein, we report a new class of 2,2′-bipyridine (bpy) derivatives (1–4) rationally designed to be chemical modulators toward metal–Aβ aggregation over metal-free Aβ analogue. The bpyderivatives were constructed through a rational design strategy employing straightforward structural variations onto the backbone of a metal chelator, bpy: (i) incorporation of an Aβ interacting moiety; (ii) introduction of a methyl group at different positions. The newly prepared bpyderivatives were observed to bind to metal ions [i.e., Cu(II) and Zn(II)] and interact with metal–Aβ over metal-free Aβ to varying degrees. Distinguishable from bpy, the bpyderivatives (1–3) were indicated to noticeably modulate the aggregation pathways of Cu(II)–Aβ and Zn(II)–Aβ over metal-free Aβ. Overall, our studies of the bpyderivatives demonstrate that the alteration of metal binding properties as well as the installation of an Aβ interacting capability onto a metal chelating framework, devised via the rational structure-based design, were able to achieve evident modulating reactivity against metal–Aβ aggregation. Obviating the need for complicated structures, our design approach, presented in this work, could be appropriately utilized for inventing small molecules as chemical tools for studying desired metal-related targets in biological systems.

Objective To investigate a potential correlation between changes in voice and changes in nasal volume.Methods The endoscopic endonasal transsphenoidal approach (EETSA) was performed on 120 patients between February 2009 and August 2016 by using the bilateral modified nasoseptal rescue flaps method. All the patients were subjected to pre- and postoperative paranasal computed tomography (CT) and voice evaluations by using acoustic analyses, a nasometer to measure the nasalance, and determination of the voice handicap index (VHI). Paranasal CT and the medical image processing software were used to calculate changes in nasal cavity volume in three nasal sections.Results Enlargement of the nasal cavity after surgery was evident in all three areas (anteronasal, p < 0.001; midnasal, p = 0.005; postnasal, p = 0.025). In addition, EETSA resulted in significantly higher mean nasalance scores for the oronasal passage (p < 0.001) and nasal passage (p < 0.001); more frequency perturbation (jitter) (p < 0.001) and amplitude perturbation (shimmer) (p < 0.001); and higher grade, roughness, breathiness, asthenia, and strain scores (p < 0.001), and VHI (p = 0.01). However, only changes in the nasal volume after EETSA correlated with postnasal hypernasality (r = 0.2; p = 0.029).Conclusion Although changes in nasal volume, voice, and speech may develop after EETSA, we found that changes in nasal volume were not correlated with changes in any voice-quality measure. However, the postnasal cavity was the region most dramatically affected by EETSA, and postnasal volume changes after surgery may be associated with hypernasal speech.

As a route to the production of organic–inorganic hybrid multilayers, the growth behavior of molecular layer deposited (MLD) alucone and atomic layer deposited (ALD) Al2O3films on top of each other was examined. MLD alucone films were prepared using trimethyl aluminum and diethylene glycol precursors, the latter resulting in faster growth rates than ethylene glycol precursors. The sensitivity of individual alucone films with respect to ambient exposure was found to be related to moisture permeation and hydration reactions, of which the mechanism is studied by density functional theory calculations. Deleterious effects such as thickness reduction over time could be suppressed by applying a protective Al2O3layer on top of alucone. A preliminary nucleation period was required in the ALD process of Al2O3films on alucone surfaces, prior to reaching a linear regime where the thickness increases linearly with respect to the number of ALD cycles. The same behavior was observed for alucone growing on Al2O3. The protective Al2O3films were found to effectively suppress moisture permeation, thus isolating the underlying alucone from the surrounding environment. The water vapor transmission rate was greatly reduced when an Al2O3/alucone/Al2O3multilayer stack was formed, which suggests that proper combinations of organic/inorganic hybrid structures may provide chemically stable platforms, especially for mechanically flexible applications.

Understanding the size-dependent oxygen affinity of small Au nanoparticles (NPs) and nanoclusters (NCs) is central to the rational design of Au oxidation catalysts. However, relevant complete experimental or computational information on the intrinsic catalytic nature of Au NPs/NCs is scarce. Here, to provide fundamental insights into the intrinsic size- and coordination-dependent catalytic nature of free-standing small Au NPs/NCs for oxidation reactions, we constructed small unsupported Aun(n= 1–10, 13, 19, 20, 25, 38, and 55) NCs and scrutinized their oxygen-adsorption chemistry and corresponding CO oxidation activity using density functional theory (DFT) calculations. Strong oxygen binding to AunNCs is essential for facile CO oxidation. Among our studied Au NCs, only the tiny Au3, Au5, and Au7NCs strongly bound O2and CO. The subsequent CO oxidation pathways studied by DFT confirmed that Au5exhibited the highest CO oxidation rate among the studied Au NCs. We observed that only highly limited, tiny Au NCs with a specific structural motif can catalyze CO oxidation themselves. We observed that a delicate balance between the energy of CO adsorption and that of O2adsorption is required to maximize the catalytic activity of Au NCs with respect to CO oxidation.

Copper nanowires (Cu NWs) are promising materials for transparent electrode applications. However, their growth mechanism during water-based synthesis remains unclear. The steric hindrance of a surfactant, which has been considered in previous studies, is insufficient to explain the suppression of Cu oxide formation during water-based synthesis. In this paper, we suggest that ethylenediamine (EDA, C2H4(NH2)2), which is commonly used as a structure-directing agent (SDA), may play an important role as an oxidation inhibitor in water-based synthesis of Cu NWs. High-resolution transmission electron microscopy (HR-TEM) analysis indicated that the Cu NWs grow from icosahedral seeds. Additionally, energy-dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS) suggested that EDA affects the oxidation state of the as-prepared Cu NW surface. Finally, density functional theory (DFT) calculations revealed that the adsorption of EDA effectively hinders the adsorption of oxidizing species and prevents the oxidation of the Cu seeds. This effect is attributed to a filling of the antibonding states and an increase in the electrostatic repulsion between the Cu seeds and the oxidizing species.

Optimizing synthesis parameters is crucial in fabricating an ideal cathode material; however, the design space is too vast to be fully explored using an Edisonian approach. Here, by clustering eleven domain-expert-derived-descriptors from literature, we use an inverse design surrogate model to build up the experimental parameters-property relationship. Without struggling with the trial-and-error method, the model enables design variables prediction that serves as an effective strategy for cathode retrosynthesis. More importantly, not only did we overcome the data scarcity problem, but the machine learning model has guided us to achieve cathode with high discharge capacity and Coulombic efficiency of 209.5 mAh/g and 86%, respectively. This work demonstrates an inverse design-to-device pipeline with unprecedented potential to accelerate the discovery of high-energy-density cathodes.

When Alzheimer’s disease (AD) progresses, several pathological features arise including accumulation of misfolded protein aggregates [e.g., amyloid- (A) plaques], metal ion dyshomeostasis, and oxidative stress. These characteristics are recently suggested to be interconnected through a potential factor, metal-associated A (metal−A) species. The role of metal–A species in AD pathogenesis remains unclear, however. To elucidate the contribution of metal–A species to AD pathology, as well as to develop small molecules as chemical tools and/or theranostic (therapeutic and diagnostic) agents for this disease, curcumin (Cur), a natural product from turmeric, and its derivatives have been studied towards both metal-free and metal-induced A aggregation. Although Cur has indicated anti-amyloidogenic activities and antioxidant properties, its biological use has been hindered due to low solubility and stability in physiologically relevant conditions. Herein, we report the reactivity of Cur and its derivatives (Gd-Cur, a potential multimodal A imaging agent; Cur-S, a water soluble derivative of Cur that has substitution at the phenolic hydroxyls) with metal-free A and metal−A species. Our results and observations indicate that Gd-Cur could modulate Cu(II)-triggered A aggregation more noticeably over metal-free or Zn(II)-induced analogues; however, Cur-S was not observed to noticeably modulate A aggregation with and without metal ions. Overall, our studies present information that could aid in optimizing the molecular scaffold of Cur for the development of chemical tools or theranostics for metal−A species.

A simple oleylamine-based thermal decomposition process using different time steps for precursor injection was used to obtain bimetallic Ag–Cu nanoparticles with a narrow size distribution. Experimental and theoretical studies were carried out to demonstrate that these bimetallic nanoparticles are less prone to oxidation. The calculated energy trends for O2adsorption on the nanoparticles show that the adsorption energy declines rapidly when more than six O2molecules are present, indicating that O2is rarely adsorbed on Ag–Cu nanoparticles. Electron transfer from Cu to Ag within these bimetallic nanoparticles allows far better resistance to oxidation than monometallic Cu nanoparticles.

Catalytic decomposition of ammonia (NH3) is a promising chemical reaction in energy and environmental applications. Density functional theory (DFT) calculations were performed to clarify the detailed catalytic mechanism of NH3decomposition on an Fe(100) surface. Specifically, the elementary steps of the mechanism were calculated for the general dehydrogenation pathway of NH3. The adsorption of two types of ammonia dimers (2NH3), locally adsorbed NH3and hydrogen-bonded NH3, were then compared, revealing that locally adsorbed NH3is more stable than hydrogen-bonded NH3. By contrast, the dehydrogenation of dimeric NH3results in a high energy barrier. Moreover, the catalytic characteristics of NH3decomposition on a nitrogen (N)-covered Fe surface must be considered because the recombination of nitrogen (N2) and desorption have an extremely high energy barrier. Our results indicate that the catalytic characteristics of the NH3decomposition reaction are altered by N coverage of the Fe surface. This study primarily focused on energetic and electronic analysis. Finally, we conclude that Fe is an alternative catalyst for the decomposition of NH3in COx-free hydrogen production.

Uvular necrosis after long-term endotracheal intubation has been previously reported, but there have been no reports regarding soft palate necrosis after endotracheal intubation. Recently, we encountered 2 patients who had a high degree of soft palate necrosis following endotracheal intubation during long-term care in the intensive care unit. This study reports noncongenital soft palate cleft caused by endotracheal intubation. Two patients, aged 30 and 38 years, with noncongenital cleft palate were treated with pharyngeal flap andor palatoplasty at our institution from March 2011 to May 2013. Initially, the patients complained of acquired speech disorder and severe oronasal regurgitation caused by a palatal defect. Speech ability was evaluated preoperatively and postoperatively by a perceptual language test and nasopharyngoscopy. The cleft soft palates of both patients were completely repaired, and the aforementioned symptoms improved after surgery. Postoperative courses were uneventful in both of the cases, and neither patient experienced a recurrence. Although rare, long-term intensive care unit care with endotracheal intubation can cause noncongenital soft palate cleft. In cases with iatrogenic cleft palate that does not heal with conservative treatment, surgical procedures such as pharyngeal flap and palatoplasty can be helpful.

Abstract

Utilizing density functional theory calculations and a modified kinetic model, we report the CO oxidation reactivity of negatively and positively charged isolated cuboctahedron (COh) and icosahedron (Ih) Ag13nanoparticles. Charging the nanoparticles modifies the electron distribution in the core and shell atoms as well as the structural stability of the Ag nanoparticles. During the reaction, Ih Ag13nanoparticles can be easily deformed into an amorphous or COh structure, which is more stable than the Ih structure. However, it does not function well as a renewable catalyst. Although a neutral COh Ag13nanoparticle exhibits relatively poor reactivity, the reactivity is enhanced significantly by excess electrons. This study provides fundamental insight into how the electronic and structural interaction between an oxide support and the supported nanoparticle affects the catalytic activity of the general nanocatalyst.

We report the geometric and electronic effects of amine (with one lone pair electron) and thiol (with two lone pair electrons) ligands on the structural transformation of Pt55nanoparticles (NPs) by first-principles calculation. Although a cuboctahedral (COh) structure is less stable than an icosahedral (Ih) structure by 1.36 eV for a bare Pt55NP, the activation barrier from the COh to the Ih structure is very high, by 1.97 eV, indicating that it would be difficult to observe the structural evolution of a COh structure to an Ih structure for a bare Pt55NP at ambient temperature. However, with the help of the adsorption of methylamine, the structural evolution from a COh structure to an Ih structure is accomplished by the Mackay transformation. This transformation is driven by a combination of both the external forces resulting from the adsorption of the ligand, which pull out the Pt atoms on the face sites of NPs in a radial direction, and the contraction forces in a tangential direction. As more methylamine is added, the Ih structure is observed to return to the original COh structure owing to the directional orbital hybridization that occurs between the Pt NPs and the methylamine. In contrast, such structural evolutions are not observed in the case of methylthiol because the sulfur (S) in the ligand has two lone pair electrons, leading to two Pt–S bonds. As a result, the radial-directed external force that the NPs experience because of the adsorption of methylthiols is much lower than that found in methylamine-ligated NPs. Furthermore, the adsorption of methylthiol leads to an expansion (not contraction) in the tangential direction, which does not qualify as a Mackay transformation. Thus, the Pt NPs ligated with methylthiol do not have a driving force strong enough to cause structural change. The methylthiol-stabilized Pt NPs retain their initial COh structure despite an abundance of ligand adsorption. From these results, we suggest that the NP structure can be controlled by varying the amount and species of ligands.

We scrutinized the reaction mechanism of CO2methanation catalyzed by a Pd-MgO/SiO2catalyst. Density functional theory studies showed that MgO and Pd nanoparticles play completely different roles. We found that MgO initiates the reaction by binding a CO2molecule, forming a magnesium carbonate species on the surface, and that a supply of atomic H is essential for further hydrogenation of magnesium carbonate to methane. A CO2temperature-programmed desorption study gives credence to our findings on the role of MgO. Our results confirm the bifunctional mechanism of CO2methanation by a Pd-MgO/SiO2catalyst.

CO oxidation is a very useful reference reaction in catalysis by nanoparticles (NPs). Two reaction modelsan association mechanism (AM) and a carbonate-mediated mechanism (CMM)have been suggested for CO oxidation catalyzed by small NPs. It is still unclear, however, when and why these mechanisms preferentially operate. With the Ag13 crystalline NPs and the Ag12Pd1 core−shell NP, using a density functional theory calculation and a microkinetic reaction model, we found that the different reaction mechanisms can operate with different reaction intermediates accompanied by a balance in the adsorption energy of reactants. Variations in the adsorption energy of adsorbates can result from the interchange of two reaction mechanisms, even in a single NP. An AM operates when both reactants interact strongly with a NP, whereas the contribution of the CMM in CO oxidation increases when a CO molecule interacts weakly or not at all with a NP.

We present a new approach to retard undesirable cluster aggregation. Using molecular dynamics simulations, we found that a large Au cluster that collides with a small cluster of metals other than Au has a locally distorted structure. Because of the lattice mismatch with a graphite surface, the distorted region of the Au cluster acts as a pinning center during the cluster diffusion process. Through the pivotal rotation caused by the pinning center, the Au cluster significantly reduces lateral diffusion. We also found that the most effective factor in the distortion of the structure is the difference in atomic size. The results of an AuNi system which has a large difference in atomic size confirm that a collision with a small Ni cluster reduces the diffusion of the large Au cluster. On the basis of these results, we expect that the use of cluster collision leads us to promising applications in the production of immobilized clusters.

We use density functional theory to examine some of the important aspects of methanol oxidation to formaldehyde catalyzed by isolated MO3(M = V, Mo, and Cr) clusters supported on rutile, TiO2(110). Thermodynamic analysis led us to conclude that in the presence of oxygen, the M (M = V, Mo, and Cr) atom takes three oxygen atoms from the gas phase and this MO3species is the oxidant in the catalyst. We calculate the structure of these clusters, their Bader charge, the structure of the methoxide formed by methanol adsorption, and the activation energy for the dehydrogenation of the methyl group in the methoxide. We find that VO3is a substantially better catalyst than MoO3or CrO3.

Density functional theory calculations and a modified reaction model confirm that the initial high CO oxidation reactivity of a 13Ag-Ih nanoparticle from an icosahedron (Ih) structure is immediately diminished as the nanoparticle is transformed to an amorphous state by a reaction-driven structural change. The adsorption of O2and the formation of a four-center intermediate metastable state from coadsorbed CO and O2positively charge the 13Ag-Ih nanoparticle, and the repulsive force between the Ag atoms causes the reaction-driven structural change of the 13Ag-Ih nanoparticle. When one central Ag atom is substituted with a solute atom, a core−shell type of 12Ag−1X-Ih (X = Pd, Pt, Au, Ni, or Cu) bimetallic nanoparticle is stabilized. Among them, we propose the 12Ag−1Pd nanoparticle as a robust and reactive Ag-based bimetallic nanoparticle for CO oxidation. The results show that the structural fluxionality accounts for the catalytic activity of small nanoparticles.

The diffusive nature of Au and the Pt clusters supported on various carbon nanotubes (CNTs) is studied through molecular dynamics simulation. We found out that the cluster−CNT interface is essential and the matching between the diffusion pathways on the CNT and the linear atomic arrangements of the bottom layer of the clusters controls the diffusion behavior of the clusters. The atomic arrangement of the cluster bottom layer is independent of the kind of CNTs. The direction and the gap of the diffusion pathways on the CNTs were however quite dependent on the chirality and radius of the CNTs. Based on careful investigations, we propose a strategy for minimizing the aggregation of CNT-supported nanoclusters that worsen the catalytic properties.

This report on the overstabilization of the metastable structure of isolated Ag−Pd catalyst composed of 135 Ag and 16 Pd atoms is based on a combination of several computational methods such as molecular dynamics, a density functional theory, transition-state calculation, and a modified basin hopping Monte Carlo simulation. With Pd atoms pinned at the metastable position up to the melting point, the overstabilization essentially originated from the systematic interaction of several factors, the high kinetic energy barrier of Pd movement, the low melting temperature of the 135Ag−16Pd cluster, the specific surface morphology, and the low solute concentration. Our results suggest that not only thermodynamics but additional kinetic or structural factors should be considered systematically in deciding the structure of bimetallic clusters for the given conditions.

We used density functional theory to study CO oxidation catalyzed by TiO 2(110), in which some Ti atoms on the surface are replaced with V, Cr, Mo, W, or Mn. We find that in the presence of O, V, Cr, Mo, and W dopants at the surface bind an oxygen atom so that the dopant has formula MO (M = V, Cr, Mo, W). Rutile doped with Mn does not take an oxygen atom from the gas phase. We find that these materials oxidize CO by a Mars−van Krevelen mechanism in which the role of the dopant is to facilitate the formation of oxygen vacancies. The energy of CO reaction with an oxygen atom from the surface layer decays linearly with the energy of vacancy formation Δ Ev, whereas the energy of adsorption of O 2at a vacancy is a linear function of Δ Ev. These are the only two reactions in the mechanism whose energy varies from one doped oxide to another. Because they both depend on the energy of oxygen vacancy formation, the latter quantity is a good descriptor of catalytic activity. In deciding which intermediate reactions are most likely from an energetic point of view, we impose a “spin conservation” rule: a reaction that requires “flipping a spin” is too slow for catalysis. Because of this, we only consider reactions that conserve spin. We find that all the dopants studied here lower the energy of vacancy formation; therefore, the doped oxides are better oxidants than the undoped ones.

This study reported the fabrication of tin oxide (SnO2) nanostructures on Co-coated Si substrates by the thermal heating of Sn powders. The microstructures and morphologies of the resultant nanostructures were studied by means of X-ray diffraction (XRD), transmission electron microscopy (TEM), selected area electron diffraction (SAED), and scanning electron microscopy (SEM). The product mainly comprised the tangled nanowires with average diameters in the range of 50-180 nm. The nanostructures were single-crystalline rutile structure of SnO2. The PL measurement with the Gaussian fitting exhibited visible light emission bands centered at 576 nm and 638 nm, respectively. We have discussed the possible growth mechanism of the nanostructures.

We analyze the effect of the geometrical shape and size of the cross section on the spin-polarized transport and the giant magnetoresistance (GMR) by a finite element method, and evaluate the stability and the physical properties of nano-scale spin valves. We calculate the transmission coefficients in the ballistic regime by using a transfer-matrix method, and evaluate the GMR of the current perpendicular to the plane (CPP) by using a circuit theory. The conduction-band structure is simplified to the potential step, which is determined by combining the interfacial parameters calculated by first-principles with the free electron model. The geometrical shapes of the cross section are line and square. As a result, the cross sectional shape has a significant effect on the spin-polarized transport and the GMR. The square-shaped cross section has an advantage of the large GMR, which is contrary to the line-shaped cross section. These phenomena result from the difference of the cut-off energies with the transverse modes and, consequently, the different spin-down transmission coefficients.

Phytosphingosine-1-phosphate (PhS1P) was found to stimulate an intracellular calcium increase via phospholipase C but not pertussis toxin (PTX)- sensitive G-proteins in L2071 mouse fibroblasts. PhS1P also activated ERK and p38 kinase, and these activations by PhS1P were inhibited by PTX. Moreover, PhS1P stimulated the chemotactic migration of L2071 cells via PTX-sensitive Gi protein(s). In addition, the PhS1P-induced chemotactic migration of L2071 cells was also dramatically inhibited by LY294002 and SB203580 (inhibitors of phosphoinositide 3-kinase and p38 kinase, respectively). L2071 cells are known to express four S1P receptors, i.e., S1P1, S1P2, S1P3, and S1P4, and pretreatment with an S1P1 and S1P3 antagonist (VPC 23019) did not affect on PhS1P-induced chemotaxis. This study demonstrates that PhS1P stimulates at least two different signaling cascades, one is a PTX-insensitive but phospholipase C dependent intracellular calcium increase, and the other is a PTX-sensitive chemotactic migration mediated by phosphoinositide 3-kinase and p38 kinase.

Permanent mold and semi-liquid die A356 cast alloys were used to examine the roles of microstructures and aging conditions on fatigue crack growth. HIP treatment to the A356 alloy generates substructure like dendritic arm boundaries as well as reduction of pores, which improves fracture elongation and fatigue fracture toughness. The similar substructure occur at primary α-Al and inter Si particles of semi-liquid die cast, too. Fracture elongation of HIPed permanent mold cast is comparable to that semi-liquid die cast, the fatigue crack growth is faster than in semi-liquid die cast. Plastic hardening occurs around fatigue crack flank, which decreases fatigue crack growth rate, and such effect appears highly in under aged alloy.

The molecular dynamics (MD) simulation employing the embedded atom method (EAM) has been performed to examine the phase stability of Pt nanoclusters, Ptn (n=38, 147, 309 and 561 atoms) with size and temperature. From heating and freezing curves of the nanoclusters, the clusters (Pt147, Pt309 and Pt561) larger than 1 nm in size showed an icosahedral morphology near 460 ~ 660 K during freezing, where the formation energy of the icosahedral phase is 0.051 eV/atom for Pt147, 0.056eV/atom for Pt309 and 0.067 eV/atom for Pt561. We also investigated coalescence between two Pt nanoclusters and observed that the minimum size of the coalescent one is around 1 nm at 673 K.

In spite of frequent defect in industrial boilers, life assessment or diagnostic method for them has not been studied. In this research, SB410 carbon steel used in industrial boilers is simulated with artificial aging heat treatment. To do qualitative life assessment, differences in micro-structures and hardness of SB410 by the degradation time are studied. In addition, variation in material properties by aging was observed with the tensile test at room temperature and 179 °C and changes in ductile to brittle transition temperature was observed with the charpy impact test performed at several test temperature.

Abstract.It has been claimed that a focused word may project its focus to a syntactic constituent larger than the focused item, under what are known as Focus Projection principles (Selkirk 1995; Rochemont 1998). Engdahl and Vallduvi (1996) rejected this purely syntax-based approach and proposed considering the interactions between the grammatical function and the types of an argu-ment. Chung, Kim, and Sells (to appear) applied Engdahl and Valduvi's theory to Korean and claimed that in Korean only a theme argument, but not an oblique argument (1.O or Locative PP), can project its focus to the Verb Phrase. This paper examines how VP focus is realized in Korean and tests Chung et al.'s claim that the types and the order of arguments can affect the focus projec-tion (especially 'VP focus'). The results show that there is no sensitivity to argument type, word order, or the length of VP in projecting the domain of focus to VP in Korean. Regardless of these factors, VP focus was prosodically marked by boosting the prominence of all words inside the VP, with the VP-initial word being the most prominent. Our data suggest that focus projection rules can be eliminated as proposed in Buring (2003).

Exchange-bias (Hex) of NiFe/NiO bilayers grown epitaxially on MgO(100) and MgO(111) have been measured in order to understand exchange biasing phenomena more clearly. According to HRXRD, the separate reflections of MgO and NiO were observed, which implied that NiO layers grew epitaxially on MgO substrates. The rms roughness (Rrms) of NiO on MgO(100) measured by AFM was 1.79 Å while that of NiO on MgO(111) was 17.85 Å. Despite a higher Rrms, the value of Hex, 85 Oe in the case of NiFe/NiO on MgO(111) was larger than that of NiFe/NiO on MgO(100), 47 Oe, probably due to stronger effect of (111) texture of NiO surface. But low Hex of NiFe/NiO on MgO(111) implied that exchange biasing was generated by not only upcompensated spins but also compensated spins of NiO. Hex of NiFe/NiO bilayer grown on Si(100) was 118 Oe. According to SEM, grain size of NiO surface grown on Si(100) was very small, which mean its domain size was also very small. The explanation of the effect of domain size was consistent with random field model.