Effective suppression of deactivation by utilizing Ni-doped ordered mesoporous alumina-supported catalysts for the production of hydrogen and CO gas mixture from methane

Several different kinds of ordered mesoporous alumina (OMA)-supported and Ni-doped OMA-supported Ni catalysts have been prepared for catalytic partial oxidation of methane (CPOM) to produce hydrogen and CO gas mixture. The Ni metal was incorporated in various ways of the impregnation, the doping, and the partial doping followed by impregnation. The prepared OMA-supported catalysts showed a wormhole-like, pseudo-hexagonal structure. By incorporating Ni in the OMA matrix during synthesis of supports, the resulting catalysts showed better-distributed and less-sintered nanocrystals even after CPOM at elevated temperature for over 100 h. By employing the partial doping of Ni followed by impregnation of Ni, the prepared CPOM catalyst was found more productive due to the well-distributed and well-anchored Ni nanocrystals inside the OMA matrix and the confined ordered mesopores as well. Through the test under non-stoichiometric feed ratio, the catalyst prepared only by impregnation was found vulnerable to carbon deposition and deactivated more rapidly. Even worse, the formation rate of carbon deposition was so fast that the test could not be conducted due to the increased pressure difference. In contrast, the highly distributed Ni nanocrystals partially or fully utilizing doping were found to have stronger resistance to carbon deposition.     

An impulse-time perturbation approach for enhancing the robustness of extra-insensitive input shapers

In this paper, perturbation-based extra-insensitive input shapers (PEI-ISs) are proposed to enhance the robustness of the input shaping technique. The extra-insensitive input shaper (EI-IS) has been known to be more robust than the so-called derivative input shapers such as ZVD, ZVDD, and ZVDDD shapers. However, the robustness of the known EI-IS is restricted by the symmetric property in the sensitivity curve. To address this, the PEI-IS is devised by multiplying a series of input shapers in the Laplace domain, of which the impulse times are slightly perturbed from those of the zero vibration (ZV) shaper. For a single-hump case, a closed-form solution to the PEI-IS is provided. For two- and three-hump cases, the approximate solutions are presented. The robustness is evaluated by simulations and assessed by means of the insensitivity. It will be shown that the proposed PEI-IS does improve the robustness and that it can be easily designed.     

Preparation and evaluation of poly(2-hydroxyethyl aspartamide)-hexadecylamine-iron oxide for MR imaging of lymph nodes

The purpose of this study was to synthesize biocompatible poly(2-hydroxyethyl aspartamide)–C₁₆-iron oxide (PHEA-C₁₆-iron oxide) nanoparticles and to evaluate their efficacy as a contrast agent for magnetic resonance imaging of lymph nodes. The PHEA-C₁₆-iron oxide nanoparticles were synthesized by coprecipitation method. The core size of the PHEA-C₁₆-iron oxide nanoparticles was about 5 to 7 nm, and the overall size of the nanoparticles was around 20, 60, and 150 nm in aqueous solution. The size of the nanoparticles was controlled by the amount of C₁₆. The 3.0-T MRI signal intensity of a rabbit lymph node was effectively reduced after intravenous administration of PHEA-C₁₆-iron oxide with the size of 20 nm. The in vitro and in vivo toxicity tests revealed the high biocompatibility of PHEA-C₁₆-iron oxide nanoparticles. Therefore, PHEA-C₁₆-iron oxide nanoparticles with 20-nm size can be potentially useful as T2-weighted MR imaging contrast agents for the detection of lymph nodes.     

CHIR99021 Augmented the Function of Late Endothelial Progenitor Cells by Preventing Replicative Senescence

Endothelial progenitor cells (EPCs) are specialized cells in circulating blood, well known for their ability to form new vascular structures. Aging and various ailments such as diabetes, atherosclerosis and cardiovascular disease make EPCs vulnerable to decreasing in number, which affects their migration, proliferation and angiogenesis. Myocardial ischemia is also linked to a reduced number of EPCs and their endothelial functional role, which hinders proper blood circulation to the myocardium. The current study shows that an aminopyrimidine derivative compound (CHIR99021) induces the inhibition of GSK-3β in cultured late EPCs. GSK-3β inhibition subsequently inhibits mTOR by blocking the phosphorylation of TSC2 and lysosomal localization of mTOR. Furthermore, suppression of GSK-3β activity considerably increased lysosomal activation and autophagy. The activation of lysosomes and autophagy by GSK-3β inhibition not only prevented replicative senescence of the late EPCs but also directed their migration, proliferation and angiogenesis. To conclude, our results demonstrate that lysosome activation and autophagy play a crucial role in blocking the replicative senescence of EPCs and in increasing their endothelial function. Thus, the findings provide an insight towards the treatment of ischemia-associated cardiovascular diseases based on the role of late EPCs.     

Optical design of a static solar concentrator using Fresnel lenses

We present an optical design for a static solar concentrator for a photovoltaic cell (SCPV). The concentrator consists of two Fresnel lenses, one concave and one convex. The SCPV was designed and optimized using ray-tracing computer simulations. The performance of the SCPV was demonstrated using two settings: static mode and periodic mode with passive bi-yearly angle adjustments. Even without an active tracking system, the SCPV achieved an average Concentration ratio (CR) in the range of 1.94-2.86. The CR was distributed non-uniformly throughout the year, and the value and season of the highest CR were different for the two settings. The optimal mode for SCPV use can be chosen by balancing specific preferences regarding the target season for peak performance, maximum average CR, and maintenance frequency.

     

Effect of polymers on the nanostructure and on the carbonation of calcium silicate hydrates: a scanning transmission X-ray microscopy study

This study investigated the effects of organic polymers (polyethylene glycol and hexadecyltrimethylammonium) on structures of calcium silicate hydrates (C–S–H) which is the major product of Portland cement hydration. Increased surface areas and expansion of layers were observed for all organic polymer modified C–S–H. The results from attenuated total reflectance–Fourier transform infrared (ATR–FTIR) spectroscopic measurements also suggest lowered water contents in the layered structures for the C–S–H samples that are modified by organic polymers. Scanning transmission X-ray microscopy (STXM) results further supports this observation. We also observed difference in the extent of C–S–H carbonation due to the presence of organic polymers. No calcite formed in the presence of HDTMA whereas formation of calcite was observed with C–S–H sample modified with PEG. We suggest that the difference in the carbonation reaction is possibly due to the ease of penetration and diffusion of the CO₂. This observation suggests that CO₂ reaction strongly depends on the presence of organic polymers and the types of organic polymers incorporated within the C–S–H structure. This is the first comprehensive study using STXM to quantitatively characterize the level of heterogeneity in cementitious materials at high spatial and spectral resolutions. The results from BET, XRD, ATR–FTIR, and STXM measurements are consistent and suggest that C–S–H layer structures are significantly modified due to the presence of organic polymers, and that the chemical composition and structural differences among the organic polymers determine the extent of the changes in the C–S–H nanostructures as well as the extent of carbonation reaction.     

Improved electrochemical performance of a cyclic ultracapacitor using slurry electrodes under various flow conditions

A cyclic ultracapacitor is a promising energy storage device that can be used for grid energy storage. The cyclic ultracapacitor combines the advantages of both ultracapacitors and flow batteries, enabling rapid charging and large‐scale energy use. To improve the electrochemical performance under the flow condition, it is necessary to find a more electrical active material and design a flow cell that minimizes the resistance. In this study, we investigate the effects of changing the ratio of the active material in a slurry electrode under various operating conditions. Slurry electrodes were prepared with different ratios of active material and conductive additive but with a fixed electrolyte amount. Voltage–time curves of both a single and a stack‐flow cell in the constant‐current mode were obtained to analyze the relationship between the active materials ratio and the cell performance. Having more adsorption sites according to the active material amount is more important than increasing the electric conductivity by the conductive additive amount with regard to cell performance capabilities in a low resistance condition such as a non‐flow mode. However, higher electrical conductivity on a slurry electrode is more beneficial to improve the electrochemical performance in the stack‐flow mode, which has harsh resistance levels. Copyright © 2017 John Wiley & Sons, Ltd.     

Pd coated one-dimensional Ag nanostructures: Controllable architecture and their electrocatalytic performance for ethanol oxidation in alkaline media

One-dimensional (1D) metal-coated Pd structures are efficient catalysts for the ethanol electro-oxidation and promising strategy for minimizing the Pd-loading toward commercialization of direct ethanol fuel cells (DEFCs). Herein, the decorated and core-shell architectures of a novel Pd coating on Ag nanowires (PdAg-NWs) are controllable by a two-step polyol method based on the galvanic replacement reaction. The integration of uniform shell with a low Pd concentration and partial hollow structure onto 1D PdAg-NWs exhibits the highest efficiency for ethanol oxidation reaction (EOR) in alkaline solution. In comparison with Pd nanoparticles (PdNPs/C), the PdAgNWs/C performes 11 times superior EOR activity, and the onset potential shifts 80 mV negatively. The presence of Ag in PdAg-NWs enhances the absorption capacity of ethanol molecules and hydroxyl ions on the active sites, and improves the catalyst tolerance to CO-like intermediates, making them a potential anodic catalyst for DEFCs.