• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.3
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• pp.390-401
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• 2000

In this study, numerical calculation is carried out to investigate the influence of injection timing, fuel amount, intake $O_2$ concentration, and EGR on Nitric Oxide(NO) formation using a two-zone model in a diesel engine. Results can be summarized as follows. The NO formation is very sensitive to the burned gas temperature, so multi-zone model must be applied to combustion process to predict the burned gas temperature exactly. Since the burned gas temperature increases rapidly during the premixed combustion, most NO is formed within 20 crank angle degrees after ignition. As the injection timing is retarded, the combustion occurs later in the expansion process which causes the decrease of burned gas temperature and, as a result, NO formation decrease. The increase of fuel amount results in the increase of earlier formation of NO in the engine. As the intake $O_2$ concentration increases, the maximum pressure and burned gas temperature increase due to activate combustion. And, [O] mole fraction of equilibrium combustion products also increase. Therefore NO exponentially increases. If exhaust gas is recirculated, the burned gas temperature decreases which results in NO decrease. If exhaust gas is cooled, more NO can be decreased.

• Korean Journal of Materials Research
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• v.17 no.5
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• pp.244-249
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• 2007

The properties of anodized films on aluminum 6061 alloy in single electrolyte of sulfuric acid and mixed electrolyte of sulfuric-boric acid and sulfuric-boric-nitric acid have been studied. Polarization tests in NaC solution were used to investigate the corrosion performance. Characteristics of film formation and surface morphology were examined by optical microscopy, FE-SEM and EDS. The results obtained have indicated that oxide films growth have been promoted by nitric acid and anodized films in mixed electrolyte have superior corrosion resistance. In case of anodic films formed in mixed electrolyte, some grooves and numerous crazings were also observed at the surface.

• The Journal of Internal Korean Medicine
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• v.41 no.4
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• pp.553-562
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• 2020

Objective: To investigate the vasodilatory effect of Sipjeondaebo-tang by inhibiting RhoA activity in vascular cells during cold exposure. Methods: Human vascular endothelial cells and pericytes were pretreated with Sipjeondaebo-tang for 30 min, followed by incubation at 37 ℃ (control) or 25 ℃ (cold exposure) for 30 min. Activation of endothelin-1-mediated RhoA in pericytes was assessed by pretreating the cells with Sipjeondaebo-tang for 30 min, followed by incubation with endothelin-1 at 37 ℃ for 30 min. Western blotting was performed to measure the expression of active RhoA. Endothelin-1 and nitric oxide release from endothelial cells was examined with enzyme-linked immunosorbent assay kits. The formation of stress fibers and focal adhesion complexes was analyzed by immunocytochemistry. Results: Cold treatment activated RhoA in both pericytes and vascular endothelial cells, whereas Sipjeondaebo-tang treatment inhibited this activation. Sipjeondaebo-tang treatment also reversed the cold-mediated production of endothelin-1 and nitric oxide. Cold exposure promoted the formation of stress fibers and focal adhesion complexes by increasing the expression of phospho-focal adhesion complex kinase, whereas Sipjeondaebo-tang treatment suppressed this response. Conclusions: These findings suggested that Sipjeondaebo-tang inhibits cold-induced RhoA activation and its related pathway components, including endothelin-1 and nitric oxide, in vascular cells. Therefore, Sipjeondaebo-tang could be beneficial for the treatment of Raynaud's phenomenon.

• Natural Product Sciences
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• v.5 no.2
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• pp.80-84
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• 1999

Peroxynitrite is a cytotoxic intermediate produced by the reaction between the superoxide anion radical and nitric oxide. Flavonoids (afzelin, quercitrin and quercetin 3-O-sambubioside), and chlorogenic acid and its methyl ester obtained from leaves of loquat (Eriobotrya japonica) have recently been shown to scavenge 1,1-diphenyl-2-picrylhydrazyl radical and to inhibit lipid peroxidation in mouse liver homogenate. The aim of this study is to investigate the inhibitory effects of the above components on peroxynitrite produced stimulated by 3-morpholinosydnonimine (SIN-1) to produce superoxide anion radical and nitric oxide at the same time. In addition, the present study tests whether or not the components directly scavenge peroxynitrite itself. The results showed that the components with the aromatic ortho-dihydroxyl groups (catechol) were more potent inhibitors of peroxynitrite formation by SIN-1. In particular, the methyl ester form of chlorogenic acid showed the most potent inhibition. At $5\;{\mu}M$ concentration, the order of minimizing peroxynitrite formation were : methyl chlorogenic acid > quercitrin > quercetin 3-O-sambubioside > chlorogenic acid > afzelin. Authentic peroxynitrite was directly scavenged by the components in a manner similar to peroxynitrite formation by SIN-1. In particular, when compared with penicillamine as a positive control, methyl chlorogenate was as effective in inhibiting peroxynitrite formation and approximately 2 times more effective in scavenging an authentic peroxynitrite. These results demonstrate therefore, that components extracted from the leaves of Eriobotrya japonica effectively scavenged peroxynitrite.

• YAKHAK HOEJI
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• v.49 no.4
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• pp.347-354
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• 2005

Lipopolysaccharide (LPS) induces synthesis of several inflammatory cytokines and nitric oxide (NO). NO in brain is involved not only in the regulation of important metabolic pathways via intracellular cyclic GMP-dependent path­ways, but also in neurotoxic damage by reacting with superoxide ion leading to form peroxynitrite radical. Oxidative stress has suggested to be related to the inhibition of NO synthase/cyclic GMP pathway. OQ21 is a new fluorinated quinone compound that is recently known to have inhibitory effects on both NO synthase (NOS) and guanylyl cyclase (GC). In this study, we examined effects of OQ21, other known NOS or GC inhibitors, or an antioxidant, melatonin, on the oxidative stress produced by LPS in rat brain. Oxidative stress was observed by using the 2',7'-dichlorofluorescin diacetate to measure intra-cellular reactive oxygen species (ROS) production and by measuring the formation of thiobarbituric acid reactive substances to measure lipid peroxidation. LPS induced significant increase in both ROS produdction and lipid peroxidation in all brain regions tested (striatum, hippocampus and cortex), which were dissected 6hr after intraperitoneal administration of LPS to rats. Direct striatal injection of two NOS inhibitors, N-nitro-L-arginine methyl ester and diphenyleneiodonium, or a GC inhibitor, IH-[1,2,4]oxadiazolo[4,3-a]quinoxaline-l-one, produced no significant ROS increase. However, OQ21 enhanced ROS formation in striatal tissues from LPS-treated rats. Melatonin decreased LPS-induced ROS formation and decreased ROS formation increased by OQ21 in striatum of LPS-treated rats.

• The Journal of the Convergence on Culture Technology
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• v.8 no.6
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• pp.615-624
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• 2022

In this study, we assessed anti-oxidant activity, anti-microbial, inhibition of biofilm formation and inflammatory factors(nitric oxide, interleukin-6, interleukin-8) inhibitory effect of Perillae semen hydrothermal extract(PSW) and three kinds of Perillae semen supercritical fluid extract(PSSs) extracted by controlling temperature with no variation of pressure. Compared with PSW, PSSs had significantly lower minimal inhibitory concentrations(MICs) against Staphylococcus aureus(S. aureus) and the ability of PSSs to inhibit formation of biofilm was also superior. PSSs reduce the production of inflammatory mediator and inflammatory cytokines significantly compared to PSW. We suggest, therefore, Perillae semen supercritical fluid 45℃ extract which showed the best anti-microbial, inhibition of biofilm formation, and inhibition of inflammatory factors production among the supercritical fluid extracts could be used for protecting patients with atopic dermatitis from pruritus and transepidermal water loss as a functional ingredient from nature.

• Journal of the Korean institute of surface engineering
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• v.45 no.5
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• pp.198-205
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• 2012

The corrosion properties of anodized films on aluminium 6070 alloy in a sulfuric acid have been studied. Comparison to evaluate the anodized A6070 and pure 6070 specimen, corrosion tests in $HNO_3$ vapor environment of the 20 wt.% were performed up to 72 hours. Characteristics of film formation and surface morphology were examined by optical microscopy, FE-SEM, and EDS. The oxide film anodized in the sulfuric acid solution contained 5 to 10 wt.% of sulfur. In the initial stages of corrosion, anodized specimens exhibited corrosion resistance than the pure specimen. However, the corrosion conditions in 24 hours, corrosion was far more anodized specimen than pure specimen. Therefore, anodized films contained sulfur, nitric acid vapor in the environment is thought to stimulate corrosion.

• Journal of fish pathology
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• v.7 no.1
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• pp.63-70
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• 1994

Nitric oxide(NO) has recently been shown to play an important role on central nervous system(CNS) function in mammals. It is synthesized from L-arginine by the enzyme NO synthase. In this study, we examined this enzyme's existence in CNS of rainbow trout(Oncorhynchus mykiss) and described the forms of microglia. astrocytes. and oligodendrocytes. Two forms of microglia are distributed in CNS. one resembling their mammalian counterpart(large microglia : LM). and the other comprising small microglia(SM) with very little cytoplasm. CNS contained astrocytes of a distinct type which form reticular network, but lack connections to capillaries. The oligodendrocyte was generally a much denser cell than the astrocyte. We have detected NOS($1.04{\pm}0.12\;pg/min/mg$) from rainbow trout CNS. It could be inhibited reversibly or irreversibly by $N^{G}MMA$ and EGTA. These result suggest that the formation of NO from L-arginine in CNS is calcium-dependent and a pathway of early evolutionary orgin.

• Korean Journal of Materials Research
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• v.21 no.12
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• pp.639-643
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• 2011

Zinc oxide as an optoelectronic device material was studied to utilize its wide band gap of 3.37 eV and high exciton biding energy of 60 meV. Using anti-site nitrogen to generate p-type zinc oxide has shown a deep acceptor level and low solubility. To increase the nitrogen solubility in zinc oxide, group 13 elements (aluminum, gallium, and indium) was co-added to nitrogen. The effect of aluminum on nitrogen solubility in a $3{\times}3{\times}2$ zinc oxide super cell containing 72 atoms was investigated using density functional theory with hybrid functionals of Heyd, Scuseria, and Ernzerhof (HSE). Aluminum and nitrogen were substituted for zinc and oxygen sites in the super cell, respectively. The band gap of the undoped super cell was calculated to be 3.36 eV from the density of states, and was in good agreement with the experimentally obtained value. Formation energies of a nitrogen molecule and nitric oxide in the zinc oxide super cell in zinc-rich conditions were lower than those in oxygen-rich conditions. When the number of nitrogen molecules near the aluminum increased from one to four in the super cell, their formation energies decreased to approach the valence band maximum to some degree. However, the acceptor level of nitrogen in zinc oxide with the co-incorporation of aluminum was still deep.

• Archives of Pharmacal Research
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• v.21 no.6
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• pp.657-663
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• 1998

The enzyme responsible for the synthesis of nitric oxide (NO) from L-arginine in mammalian tissues is known as nitric oxide synthase (NOS) (EC.1.14.13.39). In the present study, the role of NO in the regulation of exocrine secretion was investigated in rat pancreatic acinar cells. Treatment of rat pancreatic acinar cells with cholecystokinin-octapeptide (CCK-OP) resulted in an increase in the arginine conversion to citrulline, the amount of $NO_X$, the release of amylase, and the level of CGMP. Especially, CCK-OP-stimulated increase of arginine to citrulline transformation, the amount of $NO_X$, and CGMP level were completely counteracted by the inhibitor of NOS, NG-monomethyl-L-arginine (MMA), by contrast, that of amylase release was partially reduced. Furthermore, MMA-induced decrease of NOS activity and amylase release showed dose-dependent pattern. The data on the time course of CCK-OP-induced citrulline formation and CGMP rise indicate that NOS and guanylate cyclase were activated by treatment of CCK-OP. However, the mechanism of agonist-stimulated guanylate cyclase activation in acinar cells remains unknown. Therefore, activation of NOS is one of the early events in receptor-mediated cascade of reactions in pancreatic acinar cells and NO, not completely, but partially mediate pancreatic enzyme exocrine secretion.