Search

Generally, brain angiogenesis is a tightly regulated process, which scarcely occurred in the absence of specific pathological conditions. Delivery of exogenous angiogenic factors enables the induction of desired angiogenesis by stimulating neovasculature formation. However, effective strategies of mimicking the angiogenesis process with exogenous factors have not yet been fully explored. Herein, we develop a 3D printed spatiotemporally compartmentalized cerebral angiogenesis inducing (SCAI) hydrogel patch, releasing dual angiogenic growth factors (GFs), using extracellular matrix-based hybrid inks. We introduce a new hybrid biomaterial-based ink for printing patches through dual crosslinking mechanisms: Chemical crosslinking with aza-Michael addition reaction with combining methacrylated hyaluronic acid (HAMA) and vascular-tissue-derived decellularized extracellular matrix (VdECM), and thermal crosslinking of VdECM. 3D printing technology, a useful approach with fabrication versatility with customizable systems and multiple biomaterials, is adopted to print three-layered hydrogel patch with spatially separated dual GFs as outer- and inner-layers that provide tunable release profiles of multiple GFs and fabrication versatility. Consequently, these layers of the patch spatiotemporally separated with dual GFs induce excellent neovascularization in the brain area, monitored by label-free photoacoustic microscopy in vivo. The developed multi-GFs releasing patch may offer a promising therapeutic approach of spatiotemporal drugs releasing such as cerebral ischemia, ischemic heart diseases, diabetes, and even use as vaccines. STATEMENT OF SIGNIFICANCE: : Effective strategies of mimicking the angiogenesis process with exogenous factors have not yet been fully explored. In this study, we develop a 3D printed spatiotemporally compartmentalized cerebral angiogenesis inducing (SCAI) hydrogel patch, releasing dual angiogenic growth factors (GFs) using extracellular matrix-based hybrid inks. We introduce a new hybrid biomaterial-based ink through dual crosslinking mechanisms: Chemical crosslinking with aza-Michael addition, and thermal crosslinking. 3D printing technology is adopted to print three-layered hydrogel patch with spatially separated dual GFs as outer- and inner-layers that provide tunable release profiles of multiple GFs and fabrication versatility. Consequently, these layers of the patch spatiotemporally separated with dual GFs induce excellent neovascularization in the brain area, monitored by photoacoustic microscopy in vivo.

Inflammation is a form of innate immune response of living organisms to harmful stimuli. In marine bivalves, inflammation is a common defense mechanism. Several studies have investigated the morphological features of inflammation in bivalves, such as hemocyte infiltration. However, the molecular and biochemical responses associated with inflammation in marine bivalves remain unexplored. Here, we investigated changes in nitric oxide (NO) levels, cyclooxygenase 2 (COX-2) activity, and allograft inflammatory factor-1 (AIF-1) gene expression levels in hemolymph samples collected from Manila clam (Ruditapes philippinarum) exposed to pro- and anti-inflammatory substances. These included the pro-inflammatory agent lipopolysaccharide (LPS), and the nonsteroidal anti-inflammatory drugs (NSAIDs) ibuprofen and diclofenac, all widely used in vertebrates. Our study showed that NO levels, COX-2 activity, and AIF-1 expression increased in response to the treatments with LPS and decreased in response to the treatments with NSAIDs in a concentration-dependent manner. These results suggest that the mechanism of inflammatory responses in bivalves is very similar to that of vertebrates, and we propose that inflammatory responses can be quantified using these techniques and used to determine the physiological status of marine bivalves exposed to biotic or abiotic stresses.

Hot corrosion behavior was evaluated by gadolinium monosilicate (Gd2SiO5) with volcanic ash for environmental barrier coatings (EBCs). Sintered Gd2SiO5 was prepared by the spark plasma sintering (SPS) method at 1400 °C for 20 min, and high-temperature corrosion resistance against of volcanic ash was evaluated at 1400 °C for 2 h, 12 h, and 48 h. The surface region of sintered Gd2SiO5 was partially dissolved in molten volcanic ash, creating a chemically reacted area. The formation of the elongated morphology of Ca2Gd8(SiO4)6O2 grains observed in the reaction area is thicker with increasing heat-treatment time as the volcanic ash dissolves. In addition, high-temperature X-ray diffraction was carried out to identify the dynamics of phase evaluation in the volcanic ash and Gd2SiO5. According to the results, corrosion occurs due to reaction of the Gd2SiO5 phase and the Ca component of volcanic ash at 1300 °C, and the Ca2Gd8(SiO4)6O2 phase is generated.

In the conventional experiment to assess the towing operations, the towing stability of the towed vessel has been evaluated under the condition without lateral motion of the tug-boat. However, the tug-boats may have a lateral force to change the direction of the towed vessel. In this study, experiments have been conducted considering unsteady conditions in the towing system. First, a towing test system in a Circular Water Channel (CWC) using the conventional experimental method is built. Second, the towing characteristics of the towed vessel are investigated using the conventional method, and they are compared with other research results and stability discriminant criteria. Third, the lateral motion of the tug-boat was modeled as a sinusoidal motion using a forced oscillation device changing frequency and amplitude. Finally, the discussion is given in terms of both towing- and course-stability of the towed vessel according to the lateral motion of the tug-boat.

Light-emitting diodes (LEDs) based on metal halide perovskite nanocrystals (MHP NCs) have been rapidly developed to reach external quantum efficiencies of up to 22% with their defect-tolerant nature and extremely high color purity (full width half maxima

Au/TiO2/GaN junctions with a TiO2 interlayer were deposited at various oxygen pressures from 5 mTorr to 80 mTorr, and their surface, microstructural, and electrical properties were investigated. Compared with a single 5 μm-Si-doped GaN film on an (0001) Al2O3 substrate, the 0.2 μm-Si-doped GaN film with an undoped GaN buffer layer demonstrated improved properties for the application to metal/semiconductor junctions. Atomic force microscope and tunneling electron microscope measurements suggested that the TiO2 interlayer deposited at room temperature exhibited a distinctive change above the oxygen deposition pressure of 40 mTorr. In contrast to the small rectification ratio of 101-102 for Au/GaN junctions, the Au/TiO2/GaN junctions with the TiO2 interlayers displayed a large rectification ratio of 106-107 when the oxygen pressure during the deposition of TiO2 interlayer was maintained at 40 mTorr. These results suggest that the leakage current and the rectification behavior in a metal/oxide/semiconductor junction can be effectively controlled using the oxygen deposition pressure for an oxide interlayer.

A mesh-type dimensionally stable anode (DSA) consisting of ruthenium and iridium with low catalyst loading was prepared as an oxygen evolution reaction catalyst in acidic and alkaline media. The electrodeposition (ED) conditions, i.e., applied current density and total cycle number, and ED solutions with different precursor ratios of ruthenium to iridium are examined to fabricate various DSAs with a uniform thickness, and the effect of the iridium content on the catalytic activity is investigated. Among various DSA electrodes, the DSA electrode without iridium exhibits the highest activity and stability in the acidic medium owing to the high ratio of ruthenium. Conversely, the DSA electrode obtained using the ED solution with the ratio of 8:2 exhibits the highest performance in the alkaline medium. This is because the DSA electrode without iridium showed low stability, which is attributed to the dissolution of ruthenium oxide in the alkaline medium. In addition, two large-scale DSA electrodes optimized in the acidic and alkaline electrolytes show excellent performance, indicating the feasibility of the application of this electrode in practical electrolysis.

Formic acid is a chemical with a simple molecular structure containing hydrogen. This liquid at room temperature is easy to handle and has a low toxicity, and is thus in the spotlight as a fuel. In particular, formic acid is an excellent fuel candidate because it can be operated at low temperatures when applied as a fuel in fuel cells with a high theoretical open-circuit voltage (1.48 V). However, it has a drawback in that the electrode catalyst is deactivated due to the generation of CO intermediates when formic acid is oxidized during cell operation. Therefore, to prevent this, an irreversibly adsorbed Bi on Pt catalyst is applied to a direct formic acid fuel cell (DFAFC) anode because it is easy to synthesize and economical. Physical analyses such as transmission electron microscopy (TEM), X-ray diffraction (XRD), and thermogravimetric analysis (TGA) were conducted, and electrochemical evaluations were performed through half-cell and single-cell level tests. The results revealed that the formic acid oxidation reaction activity of the Bi-modified Pt/C was 13 times higher than that of the conventional catalyst at 0.58 V. Further, a DFAFC stack was fabricated using the Bi-modified Pt/C, which yielded a power of 300 W. These results suggest that a simple synthesis method can be applied to fabricating industrially available DFAFC stacks.

In this study, we developed high-performance anion-exchange membrane water electrolysis (AEMWE) by investigating various parameters. To enhance AEMWE performance, the effects of the membrane-electrode assembly (MEA) fabrication method, operating conditions, and MEA parameters were examined. As a result of the optimization and the use of FAA-3-50 and FAA-3-Br as the AEM and anion-exchange ionomer, respectively, AEMWE showed the highest performance reported thus far. Single-cell tests and electrochemical impedance spectroscopy results indicate that optimized AEMWE minimized the ohmic, charge-transfer, and mass transport resistances. Overall, by examining the AEMWE parameters, we were able to improve the electrochemical reactions, namely, the oxygen evolution reaction and hydrogen evolution reaction, and achieved outstanding performance.

AlGaN/GaN heterostructures were successfully grown with the AlIn(Ga)N back barrier at 900 °C. However, the atomic composition of the AlIn(Ga)N layer was strongly dependent on the growth pressure, which resulted in a different lattice constant of the layer. The AlIn(Ga)N back barrier grown at 400 torr was almost lattice-matched to GaN layer. The AlGaN/GaN heterostructures with 10 and 15 nm-thick AlIn(Ga)N back barrier exhibited improved 2-DEG properties, compared to those of the conventional AlGaN/GaN heterostructure without the back barrier. The high electron mobility transistors (HEMTs) fabricated on the AlGaN/GaN heterostructure with a 15 nm-thick AlIn(Ga)N back barrier exhibited a very low off-state leakage current of ∼2 × 10−7 A/mm which is about 1 order lower in magnitude than the value of the device without the back barrier. The AlIn(Ga)N back barrier is a promising candidate as an alternative to conventional AlGaN and InGaN back barrier.

We made precipitated nano-ceria (∼5 nm) on the surface of the catalyst by heat treatment of Ce-supersaturated amorphous CeTiOx to improve the oxygen storage properties of CeO2. The catalysts were prepared by sol-gel methods and TiO2 nanoparticles were preferentially generated as a core material to form selective Ce-supersaturated structure on the catalyst surface. Reaction temperature and amount of doping element are optimized to induce selective crystallization of CeO2. Ce Ce (2nd shell) bond around 0.38 nm of Ce L3-edge extended X-ray absorption fine structure is reduced and nanostructure of precipitated ceria on the surface is observed by HREM. The catalyst is present as amorphous with precipitated nano-CeO2 on the surface. The de-NOx efficiency of the catalyst, which has precipitated CeO2, improves by ∼50% owing to the simultaneous reactions of the nano CeO2 and the amorphous CeTiOx.