• Journal of Electrochemical Science and Technology
• /
• v.7 no.3
• /
• pp.199-205
• /
• 2016

We present the electrochemical performance of electric double layer capacitors (EDLCs) assembled with pyrrolidinium (Pyr)-based ionic liquid electrolytes at 55 ℃. Cations with various alkyl chain lengths were employed in Pyr-based ionic liquids to investigate the effect of cation structure on the cycling stability of EDLCs. The EDLCs exhibited initial specific capacitances ranging from 122.4 to 131.6 F g⁻¹ based on activated carbon material at 55 ℃. Cycling data and XPS results demonstrate that Pyr-based ionic liquid with longer alkyl chain is more effective for enhancing the cycling stability of EDLC by suppressing the reductive decomposition of pyrrolidinium cations during cycling at high temperatures.

• Asian-Australasian Journal of Animal Sciences
• /
• v.4 no.4
• /
• pp.407-410
• /
• 1991

The relationship between the possible structural change due to chemical modifications and functionality changes was studied in pigskin collagen. Amino groups in collagen were modified by succinylation and reductive alkylation. Carboxyl groups were modified using carbodiimide. Thermal denaturation temperature of collagen increased remarkably by carboxyl groups modification whereas decreased by succinylation and reductive alkylation. Emulsifying capacity was improved by reductive alkylation and carboxyl groups modification while emulsion stability was improved by succinylation. Chemical modifications increased solubility whereas decreased the foaming capacity of collagen. Viscosity of collagen at various pH varied with methods of modification.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2011.08a
• /
• pp.212-212
• /
• 2011

In addition to the catalysts' activity and selectivity, the deactivation of catalysts during use is of practical importance. It is crucial to understand the phenomena of the deactivation to predict the loss of activity during catalyst usage so that the high operational costs associated with catalyst replacement can be reduced. In this study, the activity of Ru catalysts, such as nanoparticles (3~6 nm) and polycrystalline thin film (50 nm), have been investigated under CO oxidation and oxidative/reductive reaction conditions at various temperatures with the ambient pressure X-Ray photoelectron spectroscopy (APXPS). With APXPS, the surface oxides on the catalyst are measured and monitored in-situ. It was found that the Ru film exhibited faster oxidation-and-reduction compared to that of nanoparticles showing mild oxidative-and-reductive characteristics. Additionally, the larger Ru nanoparticles showed a higher degree of oxide formation at all temperatures, suggesting a higher stability of the oxide. These observations are in agreement with the catalytic activity of Ru catalysts. The loss of activity of Ru films is correlated with bulk oxide formation, which is inactive in CO oxidation. The Ru nanoparticle, however, does not exhibit deactivation under similar conditions, suggesting that its surface is covered with a highly active ultrathin surface oxide. Since the active oxide is more stable as nanoparticles than as a film, the nanoparticles showed mild oxidative/reductive behavior, as confirmed by APXPS results. We believe these simultaneous observations of both the surface oxide of Ru catalysts and the reactivity in real time enable us to pinpoint the deactivation phenomena more precisely and help in designing more efficient and stable catalytic systems.

• Journal of Powder Materials
• /
• v.13 no.5 s.58
• /
• pp.360-365
• /
• 2006

The phase stability of tetragonal phase in Y-TZP was investigated in terms of the distribution of grain sizes and heat-treating atmosphere. Y-TZP with various grain sizes were prepared using duration time at $1600^{\circ}C$ as experimental parameter. Accumulated grain size distributions were built from the SEM micrographs and the amount of tetragonal phase were measured using XRD. Both results were compared to determine the critical grain size before and after heat-treatment in vacuum. The critical grain size drastically decreased compared with the small increase of average grain size due to the autocatalytic effect which critically affects the tetragonal to monoclinic phase transformation. After heat-treatment in reductive atmosphere critical grain size relatively increased due to the stabilization of tetragonal phase. The formation of oxygen vacancies during heat-treatment was ascribed to the increase of stability.

• Journal of Microbiology and Biotechnology
• /
• v.30 no.1
• /
• pp.146-154
• /
• 2020

With the advantages of biocatalytic method, enzymes have been excavated for the synthesis of chiral amino acids by the reductive amination of ketones, offering a promising way of producing pharmaceutical intermediates. In this work, a robust phenylalanine dehydrogenase (PheDH) with wide substrate spectrum and high catalytic efficiency was constructed through rational design and active-site-targeted, site-specific mutagenesis by using the parent enzyme from Bacillus halodurans. Active sites with bonding substrate and amino acid residues surrounding the substrate binding pocket, 49L-50G-51G, 74M,77K, 122G-123T-124D-125M, 275N, 305L and 308V of the PheDH, were identified. Noticeably, the new mutant PheDH (E113D-N276L) showed approximately 6.06-fold increment of k_cat/Km in the oxidative deamination and more than 1.58-fold in the reductive amination compared to that of the wide type. Meanwhile, the PheDHs exhibit high capacity of accepting benzylic and aliphatic ketone substrates. The broad specificity, high catalytic efficiency and selectivity, along with excellent thermal stability, render these broad-spectrum enzymes ideal targets for further development with potential diagnostic reagent and pharmaceutical compounds applications.

• YAKHAK HOEJI
• /
• v.39 no.5
• /
• pp.506-510
• /
• 1995

The 5-(2'-(N-(1-methyl-3'-carbamylphenyl)-n-propyl))aminoethyl)-8- hydroxy-4-methyl-carbostyril derivatives which have isoelectronic and isosteric structural similarity with dobutamine without having the Catechol-O-Methyltransferase (COMT) vulnerable m-hydroxy group were synthesized via 7 synthetic steps, and their stabilities in phosphate buffer solution(pH=7.4), human blood. 80% human plasma and 20% rat liver homogenate were determined in vitro condition.

• Journal of Life Science
• /
• v.24 no.1
• /
• pp.98-103
• /
• 2014

NAD(P)H quinone oxidoreductase 1 (NQO1) is a flavoprotein that catalyzes the two electron reduction of diverse substrates, including quinones. It uses NADH or NADPH as a cofactor for enzymatic machinery. In the metabolism of quinones, NQO1 has two conflicting functions because of the different stability of converted hydroquinones. The stable form of hydroquinone is excreted from cells by conjugation with glutathione or glucuronic acid. The unstable form of hydroquinone induces cell death by induction of oxidative stress and DNA damage. Certain quinones known as bio-reductive agents have a cytotoxic function following reduction by NQO1. Bio-reductive agents, such as ${\beta}$-lapachone or mitomycin C, induce the depletion of NAD(P)H and the generation of oxidative stress in an NQO1-dependent manner. NQO1 is highly expressed in several cancer tissues. Therefore, NQO1 is a good therapeutic target for cancer treatment with bio-reductive agents.

• Nuclear Engineering and Technology
• /
• v.54 no.6
• /
• pp.2329-2333
• /
• 2022

Base metal corrosion forms a significant issue during the chemical decontamination of the primary coolant loop in nuclear power plants as it is directly related to the economic and safety viability of decommissioning. In this technical note, potentiodynamic evaluations of several base metals (304 stainless steel, SA106 Grade B carbon steel, and alloy 600) were performed to determine their corrosion behavior during the hydrazine (N₂H₄)-based reductive ion decontamination (HyBRID) process. The results suggested that N₂H₄ protected the surface of the base metals in the HyBRID solution, which is primarily composed of H₂SO₄. The corrosion resistance of the carbon steel was further improved through the addition of CuSO₄ to the solution. The corrosion rate of carbon steel in the H₂SO₄-N₂H₄-CuSO₄ solution was lower than that exhibited in an oxalic acid solution, a commonly used reaction medium during commercial decontamination processes. These results indicate the superiority of the HyBRID process with respect to the base metal stability.

• Proceedings of the Korea Technical Association of the Pulp and Paper Industry Conference
• /
• 2006.06b
• /
• pp.337-347
• /
• 2006

Papers made from unbleached and bleached bagasse chemimechanical pulp were chemically modified by acetylation. The effects of irradiation on unbleached and bleached also reduced papers of bagasse chemimechanical pulp before and after acetylation were investigated in this study. Chemimechanical pulp was prepared from bagasse and then bleached with hydrogen peroxide. Unbleached and hydrogen bleached pulps were reduced by Sodium borohydride in different procedures. Paper sheets were prepared from pulps and then acetylated using a technical grade of acetic anhydride. Accelerated photo-aging was run on the samples using fluorescent lamps to verify photo-stability of paper sheets before and after pretreatments. Brightness reversion (as Post-color number) and other optical properties of the paper sheets were measured. Efficient inhibition of photo-yellowing of papers made from bagasse CMP was achieved by acetylation. The acetylated unbleached CMP was noticeably photo-bleached during irradiation. Sodium borohydride reduction followed by acetylation had the same effect as acetylation alone at the same degree of reaction time and reductive treatment did not affect the yellowing rate to any great extent. The pre-reduced, acetylated unbleached papers were, however, not brightened during irradiation. Calculation done by Kubelka-Munk equation showed that reductive treatment had little effect in reducing the photo-yellowing of paper made from CMP pulp; a small stabilization effect was observed in the case of bleached CMP, while unbleached CMP was slightly more prone to discolor in the later phase of photo-reversion. The improved stability towards light may was closely related to the decrease in the phenolic hydroxyl content as a result of blocking by acetyl groups during treatment with acetic anhydride. The results support the hypothesis that phenolic hydroxyl has an important role in the process of photo-reversion of high-yield pulps. The results obtained in this study demonstrate that the acetylation of paper manufactured from peroxide bleached Bagasse CMP significantly retards light-induced discoloration. The inhibition of yellowing is connected with a decrease in the phenolic hydroxyl content of both unbleached and peroxide bleached papers.

• Nuclear Engineering and Technology
• /
• v.55 no.6
• /
• pp.2256-2262
• /
• 2023

The electrochemical corrosion behaviors of SA106 Grade B (SA106B) carbon steel in H₂SO₄4-N₂H₄ and H₂SO₄-N₂H₄-CuSO₄ solutions at 95 ℃ have been investigated with the addition of commercial corrosion inhibitors (CI#30 and No. 570S), to determine the stability of SA106B in the hydrazine-based reductive metal ion decontamination (HyBRID) process. The potentiodynamic polarization experiment revealed that the corrosion inhibitors were capable of lowering the corrosion rate of SA106B in H₂SO₄-N₂H₄ solution. It was found that the corrosion inhibitors induced formation of fixed surface layer on the carbon steel upon the corrosion. This corrosion inhibition performance was reduced in the presence of CuSO₄ in the solution owing to the chemical reactions between organic compounds in the corrosion inhibitors and CuSO₄. CI#30 showed a better corrosion inhibition effect in the H₂SO₄-N₂H₄-CuSO₄ solution. Although the corrosion inhibitors can provide better stability to SA106B in the HyBRID solution, their application should be carefully considered because it may result in reduced decontamination performance and increased secondary waste generation.