Characterization of gelatin nanofiber prepared from gelatin-formic acid solution

Gelatin, well known as a biocompatible polymer, was dissolved in formic acid and gelatin nanofiber was successfully prepared by the electrospinning using gelatin-formic acid dope solution. Stability of the dope solution was evaluated by measuring viscosity change with time. Even though the viscosity dropped markedly after 5 h, the spinnability and morphology of gelatin nanofiber were not affected at all. The parameters, such as electric field, spinning distance, and concentration of dope solution, were examined for studying the effects on electrospinnability and morphology (size, size distribution, uniformity, bead formation, etc.) of gelatin nanofiber web. The gelatin nanofibers, in the mean size of 70-170 nm, could be prepared by controlling the dope concentration under proper conditions. The electrospun gelatin nanofiber exhibited a mixture of α-helical and random coil conformation, which was amorphous structure with very low crystallinity. The structural transformation, from a helical (α-helix and triple-helix) to random coil conformation, might occur when formic acid was used for the dissolution of gelatin in electrospinning.     

Performance of a micro-thermophotovoltaic power system using an ammonia-hydrogen blend-fueled micro-emitter

The potential of ammonia (NH₃)-hydrogen (H₂) blends as a carbon-free, green fuel in a 1–10 W micro-thermophotovoltaic (micro-TPV) device is evaluated experimentally. When NH₃–H₂ blends are used directly (without any modification) in a heat-recirculating micro-TPV configuration that has an installation of gallium antimonide (GaSb) photovoltaic cells and was developed for hydrocarbon fuel, low temperature on the micro-emitter outer surface is observed, generating a secondary flame at the micro-emitter outlet. Thus, the micro-TPV device has been modified to eliminate the secondary flame by enhancing the residence time of fed NH₃–H₂–air mixtures and uniform burning: a cyclone adapter for a fuel-air mixture supply system and a helical adapter for the fuel-air mixture upstream of the micro-emitter. Under optimized design and operating conditions, the micro-TPV device produces 5.2 W with an overall efficiency of 2.1% and an emitter efficiency of 37%, indicating the maximum temperature of the micro-emitter outer surface up to 1408 K. Thus, the feasibility of using NH₃–H₂ blends in practical micro power-generation devices has been demonstrated, implying the potential of partial NH₃ substitution to improve the safety of pure H₂ use with no carbon generation.     

Production of cellulases and β-glucosidase in Trichoderma reesei mutated by proton beam irradiation

To obtain mutant strains producing high levels of cellulases (FPase and CMCase) and ??-glucosidase, Trichoderma reesei KCTC 6950 was mutated by proton beam irradiation. Five mutants were selected out of 1,000 mutants of T.reesei treated with proton beam irradiation, based on their ability for enzyme production on a plate screening medium. In submerged cultures containing Mandel??s fermentation medium, the mutant strain T-2 (MT-2) demonstrated a 165% increase in the activity of FPase, a 146% increase in the activity of CMCase, and a 313% increase in the activity of ??-glucosidase, compared with the wild type strain. Additionally, the properties of high level ??-glucosidase produced by MT-2 were the same as those of the wild type strain, e.g., an optimum pH of 4.8, and an optimum temperature of 65 °C. Moreover, the protein concentrations of ??-glucosidase produced by the wild type strain and MT-2 were measured by SDS-PAGE, and then ??-glucosidase activities were detected by the MUG-zymogram assay.     

Development and characterization of tubular direct methanol fuel cells for use in in situ NMR analysis

The present study developed a tubular direct methanol fuel cell (tubular DMFC) for use in in situ Nuclear Magnetic Resonance (NMR) that could monitor various electrochemical reactions in real time. The tubular DMFC was fabricated in such a way as to prevent corrosion of cell components and to facilitate a supply of the reactants and removal of the products. The cell showed improved performance and durability sufficient for its use in an in situ NMR test, but problems with rapid performance decay persisted. Detailed reasons for the performance degradation were investigated through rigorous analytical work using various techniques. The tubular DMFC was also installed in an NMR probe to test signal sensitivity and resolution of ²D NMR spectra for deuterated methanol (CD₃OH) and deuterated water (D₂O). The spectral resolutions of both species were high, and their signal intensities were strong enough to realize an acceptable spectra.     

Numerical investigation and optimization of the thermal performance of a brushless DC motor

A computational study of a brushless DC motor is presented to determine the thermo-flow characteristics in the windings and bearings under the effects of heat generation. The rotation of the rotor blades drives an influx of ambient air into the rotor inlet. The predicted inflow rates were higher at the front inlet than at the rear inlet due to non-uniform pressure distribution. A recirculation zone appeared in the tiny interfaces between windings. The poor cooling performance was caused by flow separation near the groove threshold by the inclination angle of the bearing groove and by a relatively slow velocity near the bearing and between windings. Based on these results, design parameters for the inlet location and geometry, and for the bearing groove geometry, were determined and optimized to enhance the cooling performance up to 24%.     

Muddy water animation with different details

Muddy water is an example of suspension, which is a mixture containing particles that separate into distinct layers if left undisturbed. When stirred, however, the mud substance flows like a liquid and again begins settling out. Mud is composed of various sized particles, and they produce different effects when it is blended with water. This paper classifies the mud particles into three types and proposes different simulation methods for the types. The experimental results demonstrate that the proposed methods effectively produce visually plausible muddy water effects. Copyright © 2015 John Wiley & Sons, Ltd.     

Acceleration effect of sericin on shear-induced β-transition of silk fibroin

Although silk sericin (SS) occupies 25% of silk protein, its importance has often been overlooked in the natural silk spinning process and in the formation of the crystalline structure of silk fibroin (SF). In this study, we elucidated the role of SS in the crystallization process of SF under shear using SF/SS blend solutions. In order to apply shear stress to the blend solution, a rotating glass rod was inserted into a glass tube filled with the solution and the shear rate was determined to be in the range of 598–724 s⁻¹. After shearing, SF aggregates were formed and the amount of the aggregates increased with shearing time. Additionally, it was observed that the aggregate formation and β-sheet transition of SF were enhanced when a proper amount of SS was in the blend solution. Consequently, the SS considerably contributes to the structural transition of SF under shear. The SS can improve the shear-induced β-sheet transition and crystallization of SF.     

Rapid synthesis of Pt-based alloy/carbon nanotube catalysts for a direct methanol fuel cell using flash light irradiation

We synthesized Pt, Pt–Ru alloy and Pt–Ru–Mo alloy nanoparticles on the multi-walled carbon nanotubes (MWCNTs) using flash light irradiation and characterized these catalysts. Pt₁₀₀, Pt₅₀-Ru₅₀ alloy and Pt₄₃-Ru₄₃-Mo₁₄ alloy are coated onto MWCNTs followed by flash light irradiation to facilitate the formation of nanoparticle-alloys. The fabricated pure Pt and Pt-based alloy nanoparticle/MWCNTs were characterized by X-ray diffraction (XRD), raman spectroscopy and scanning electron microscopy (SEM). Cyclic voltammetry (CV) studies and electrochemical impedance spectroscopy (EIS) results revealed that the Pt₄₃-Ru₄₃-Mo₁₄/MWCNT catalyst has higher activity and stability with regard to methanol electro-oxidation than the Pt₁₀₀/MWCNT and Pt₅₀-Ru₅₀/MWCNT catalysts.     

Optical properties of post-annealed ZnO:Al thin films studied by spectroscopic ellipsometry

In this paper, effects of the thermal annealing on the structural, electrical, and optical properties of Al-doped ZnO (ZnO:Al) thin films prepared by reactive radio-frequency sputtering were investigated. From the X-ray diffraction observations, the orientation of ZnO:Al films was found to be a c-axis in the hexagonal structure. The optical properties of the films were investigated by optical transmittance and spectroscopic ellipsometry characterization. Based on Tauc–Lorentz model, the optical constants of ZnO:Al films were extracted in the photon energy ranging from 1.0 to 4.5 eV. Our result showed that the refractive index and extinction coefficient of the films changed consistently with annealing temperature.