• Korean Journal of Materials Research
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• v.16 no.5
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• pp.323-328
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• 2006

In situ electrical conductivity measurements on $V_2O_5WO_3/TiO_2$ catalysts were carried out at between 100 and $300^{\circ}C$ under pure oxygen, NO and $NH_3$ to investigate the reaction mechanism for ammonia SCR (selective catalytic reduction) de NOX. The electrical conductivity of catalysts changed irregularly with supply of NO. It was, however, found that the electrical conductivity change with ammonia supply was regular and the increase of electrical conductivity was mainly caused by reduction of the labile surface oxygen. The electrical conductivity change of catalysts showed close relationship with the conversion rate of NOx. Variation of conversion rate in atmosphere without gaseous oxygen also showed that labile lattice oxygen is indispensable in the initial stage of the de NOx reaction. These results suggest that liable lattice oxygen acts decisive role in the de NOx mechanism. They also support that de NOx reaction occurs through the Eley?Rideal type mechanism. The amount of labile oxygen can be estimated from the measurement of electrical conductivity change for catalysts with ammonia supply. This suggests that measurement of the change can be used as a measure of the de NOx performance.

• Biomolecules & Therapeutics
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• v.31 no.1
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• pp.89-96
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• 2023

Uric acid produced by guanine deaminase (GDA) is involved in photoaging and hyperpigmentation. Reactive oxygen species (ROS) generated by uric acid plays a role in photoaging. However, the mechanism by which uric acid stimulates melanogenesis in GDA-overexpressing keratinocytes is unclear. Keratinocyte-derived paracrine factors have been identified as important mechanisms of ultraviolet-induced melanogenesis. Therefore, the role of paracrine melanogenic growth factors in GDA-induced hypermelanosis mediated by uric acid was examined. The relationships between ROS and these growth factors were examined. Primary cultured normal keratinocytes overexpressed with wild type or mutant GDA and those treated with xanthine or uric acid in the presence or absence of allopurinol, H₂O₂, or N-acetylcysteine (NAC) were used in this study. Intracellular and extracellular bFGF and SCF levels were increased in keratinocytes by wild type, but not by loss-of-function mutants of GDA overexpression. Culture supernatants from GDA-overexpressing keratinocytes stimulated melanogenesis, which was restored by anti-bFGF and anti-SCF antibodies. Allopurinol treatment reduced the expression levels of bFGF and SCF in both GDA-overexpressing and normal keratinocytes exposed to exogenous xanthine; the exogenous uric acid increased their expression levels. H₂O₂-stimulated tyrosinase expression and melanogenesis were restored by NAC pretreatment. However, H₂O₂ or NAC did not upregulate or downregulate bFGF or SCF, respectively. Overall, uric acid could be involved in melanogenesis induced by GDA overexpression in keratinocytes via bFGF and SCF upregulation not via ROS generation.

• Journal of Internet Computing and Services
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• v.7 no.1
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• pp.17-30
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• 2006

With the wide acceptance of the Internet and the Web, volumes of information and related users have increased and companies have become to need security mechanisms to effectively protect important information for business activities and security problems have become increasingly difficult. This paper proposes a improved access control model for access control enforcement in enterprise environments through the integration of the temporal constraint character of the GT-RBAC model. sub-role hierarchies concept and PBDM(Permission Based Delegation Model). The proposed model. called Extended GT-RBAC(Extended Generalized Temporal Role Based Access Control) delegation Model. supports characteristics of GTRBAC model such as of temporal constraint, various time-constrained cardinality, control flow dependency and separation of duty constraints (SoDs). Also it supports conditional inheritance based on the degree of inheritance and business characteristics by using sub-roles hierarchies and supports permission based delegation, user to user delegation, role to role delegation, multi-step delegation and temporal delegation by using PBDM.

• Animal Bioscience
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• v.37 no.2_spc
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• pp.323-336
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• 2024

Molecular hydrogen (H₂) and formate (HCOO^-) are metabolic end products of many primary fermenters in the rumen ecosystem. Both play a vital role in fermentation where they are electron sinks for individual microbes in an anaerobic environment that lacks external electron acceptors. If H₂ and/or formate accumulate within the rumen, the ability of primary fermenters to regenerate electron carriers may be inhibited and microbial metabolism and growth disrupted. Consequently, H₂- and/or formate-consuming microbes such as methanogens and possibly homoacetogens play a key role in maintaining the metabolic efficiency of primary fermenters. There is increasing interest in identifying approaches to manipulate the rumen ecosystem for the benefit of the host and the environment. As H₂ and formate are important mediators of interspecies interactions, an understanding of their production and utilization could be a significant starting point for the development of successful interventions aimed at redirecting electron flow and reducing methane emissions. We conclude by discussing in brief ruminant methane mitigation approaches as a model to help understand the fate of H₂ and formate in the rumen ecosystem.

• Advances in nano research
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• v.9 no.1
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• pp.15-24
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• 2020

Iron has a crucial role in growth as part of metalo-proteins like haemoglobin or myoglobin, enzymes; they are also involved in energetic reactions. Iron plays a vital role in fertility. At high doses, Iron has a harmful consequence on the reproductive system, which can be strongly reflected the final stage of spermatogenesis. Nutritional products are claiming to use nanotechnology and it is important to recognize the potential toxicity of nano-sized nutrients. Recently iron nanoparticles were proposed as a food additive for poultry. The objective of this study was to investigate the effects of L-cystein coated iron oxide nanoparticles on reproductive performance in male quails. The results of Fourier Transform Infrared Spectrometer, Alternating Gradient Force Magnetometer and Scaning Electron Microscopy showed that iron oxide nanoparticles was produced and have been coated with L-cycstein (Fe₃O₄-Cys NPs). A total of 100 one-week-old quail chicks were randomly placed to five groups of five replicates. Four quails (two male and two females) were raised in an individual cage for each replicate. The five experimental treatment diets consisted; negative control diet, with no Iron supplementation; positive control diet supplemented with 60 mg/kg of Fe₃O₄; treatment diets supplemented with 0.6, 6 and 60 mg/kg of L-cystein coated iron oxide nanoparticles. The hemoglobin, Red blood cell, mean corpuscular volume, mean corpuscular hemoglobin, mean corpuscular hemoglobin concentration, gonadal somatic index, daily sperm production, total testicular sperm and sperm viability of the male quails that were fed with diet supplemented by 0.6 mg/kg of Fe₃O₄-Cys NPs were improved as compare with negative control. This study showed that not only the use of the Fe₃O₄-Cys nanoparticles had no side effects but also it can be used as a feed additive to improve the reproductive performance in male quails.

• Journal of the Chungcheong Mathematical Society
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• v.32 no.4
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• pp.383-391
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• 2019

For a DM stack 𝓧, Chen, Marcus and Úlfarsson ([3]) constructed a stack 𝓖_𝓧 of gerbes in 𝓧 that plays a key role in their setting up the theory of very twisted stable maps to 𝓧. This stack is realized as a rigidification of the stack S_𝓧 of subgroups of the inertia stack of 𝓧. In this article, we show that when 𝓧 is a quotient stack, the stacks 𝑺_𝓧 and 𝓖_𝓧 are also quotient stacks.

• Journal of Korean Ophthalmic Optics Society
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• v.6 no.2
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• pp.23-29
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• 2001

In the SP series of glasses, the formation of droplet is well done with increasing PbO. But in the case SP-1, droplet could not be observed in low concentration PbO. These results are considered that PbO does the role of a network modifier, so the crosslinking break down by $SiO_2$. But, in the glasses contained PbO above 50 mol%, glasses are formeddue to $Pb^{4+}$ ion does the role of a network former. As a result of electrical conductivity analysis for SP series of glasses, the electrical conduction is due to bipolaron at high temperature, and it is due to single polaron hopping at low temperature. In the SP series of glasses, electrical conduction mechanism coincide with the correlated-barrier hopping(CBH) model.

• Journal of Applied Biological Chemistry
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• v.63 no.2
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• pp.137-145
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• 2020

Oxidative stress is one of the pathogenic mechanisms of various neurodegenerative diseases, such as Alzheimer's disease. Neuroglia, the most abundant cells in the brain, is thought to play an important role in the antioxidant defense system and neuronal metabolic support against neurotoxicity and oxidative stress. We investigated the protective effect of paeoniflorin (PF) against oxidative stress in C6 glial cells. Exposure of C6 glial cells to hydrogen peroxide (H₂O₂, 500 μM) significantly decreased cell viability and increased amounts of lactate dehydrogenase (LDH) release, indicating H₂O₂-induced cellular damage. However, treatment with PF significantly attenuated H₂O₂-induced cell death as shown by increased cell survival and decreased LDH release. The H₂O₂-stimulated reactive oxygen species production was also suppressed, and it may be associated with improvement of superoxide dismutase activity by treatment with PF. In addition, an increase in ratio of Bcl-2/Bax protein expression was observed after treatment with PF. In particular, the down-stream of the apoptotic signaling pathway was inhibited in the presence of PF, mostly by reduction of cleaved-poly ADP ribose polymerase, cleaved caspase-3, and -9 protein expression. Furthermore, H₂O₂-induced phosphorylation of c-Jun N-terminal kinase and extracellular signal-regulated kinase 1/2 was attenuated by treatment with PF. Taken together, neuroprotective effect of PF against oxidative stress probably result from the regulation of apoptotic pathway in C6 glial cells. In conclusion, our findings suggest that PF may be a potent therapeutic agent for neurodegenerative disorders.

• Molecules and Cells
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• v.44 no.12
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• pp.893-899
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• 2021

BLT2 is a low-affinity receptor for leukotriene B₄, a potent lipid mediator of inflammation generated from arachidonic acid via the 5-lipoxygenase pathway. The aim of this study was to investigate whether BLT2 plays any role in sepsis, a systemic inflammatory response syndrome caused by infection. A murine model of cecal ligation and puncture (CLP)-induced sepsis was used to evaluate the role of BLT2 in septic inflammation. In the present study, we observed that the levels of ligands for BLT2 (LTB₄ [leukotriene B₄] and 12(S)-HETE [12(S)-hydroxyeicosatetraenoic acid]) were significantly increased in the peritoneal lavage fluid and serum from mice with CLP-induced sepsis. We also observed that the levels of BLT2 as well as 5-lipoxygenase (5-LO) and 12-LO, which are synthesizing enzymes for LTB₄ and 12(S)-HETE, were significantly increased in lung and liver tissues in the CLP mouse model. Blockade of BLT2 markedly suppressed the production of sepsis-associated cytokines (IL-6 [interleukin-6], TNF-α [tumor necrosis factor alpha], and IL-1β [interleukin-β] as well as IL-17 [interleukin-17]) and alleviated lung inflammation in the CLP group. Taken together, our results suggest that BLT2 cascade contributes to lung inflammation in CLP-induced sepsis by mediating the production of inflammatory cytokines. These findings suggest that BLT2 may be a potential therapeutic target for sepsis patients.

• Bulletin of the Korean Chemical Society
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• v.32 no.8
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• pp.2571-2576
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• 2011

Surface film formation on $Li(Ni_{1/3}Co_{1/3}Mn_{1/3})O_2$ cathodes upon oxidation of electrolyte during electrochemical cycling was investigated. Information on the important factors for film formation on the cathode can facilitate the design of additives that improve the properties of the cathode. Pyrazole is added to the electrolyte because it is readily oxidized to form a surface film on the cathode. The results of differential scanning calorimetry and Fourier transform infrared spectroscopy (FTIR) showed that the active material played a dominant role in the interfacial film formation with the electrolyte. Carbon black played a negligible role in the surface film formation.