• Bulletin of the Korean Chemical Society
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• v.20 no.1
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• pp.35-41
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• 1999

Stability characteristics of hyperbolic reaction-diffusion equations with a reversible Brusselator model are investigated as an extension of the previous work. Intensive stability analysis is performed for three important parameters, Nrd, β and Dx, where Nrd is the reaction-diffusion number which is a measure of hyperbolicity, β is a measure of reversibility of autocatalytic reaction and Dx is a diffusion coefficient of intermediate X. Especially, the dependence on Nrd of stability exhibits some interesting features, such as hyperbolicity in the small Nrd region and parabolicity in the large Nrd region. The hyperbolic reaction-diffusion equations are solved numerically by a spectral method which is modified and adjusted to hyperbolic partial differential equations. The numerical method gives good accuracy and efficiency even in a stiff region in the case of small Nrd, and it can be extended to a two-dimensional system. Four types of solution, spatially homogeneous, spatially oscillatory, spatio-temporally oscillatory and chaotic can be obtained. Entropy productions for reaction are also calculated to get some crucial information related to the bifurcation of the system. At the bifurcation point, entropy production changes discontinuously and it shows that different structures of the system have different modes in the dissipative process required to maintain the structure of the system. But it appears that magnitude of entropy production in each structure give no important information related for states of system itself.

• Transactions of the Korean hydrogen and new energy society
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• v.34 no.5
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• pp.389-397
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• 2023

This study compares domestic and foreign research on renewable energy-based water electrolysis clean hydrogen. Domestic studies from 2010 to 2023 focused on technological efficiency, energy efficiency, and system efficiency, with few analyzing infrastructure and technology trends. Overseas research initially focused on technological efficiency and stability, but has since shifted to economic and environmental impact, policy effectiveness, industry-university-research cooperation, and sustainability. To improve water electrolysis technology production, this study suggests prioritizing technology stability over efficiency, resolving government regulations and resident acceptance issues, promoting industry-university-institute cooperation for rapid commercialization of research results, and developing a strategy for sustainable development of renewable energy-based water electrolysis technology.

• Microbiology and Biotechnology Letters
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• v.27 no.3
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• pp.184-190
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• 1999

To acquire an industrially useful biocatalyst for the enzymatic synthesis and production of various D-amino acid aminotransferase (D-AAT) activity. The enzyme activity was found from 110 strains of isolated thermophiles revealing its wide occurrence in thermophiles. Enzyme activity and thermal stability of the D-AAT producers were compared. Finally we have selected four thermophiles as producers of potent biocatalysts for the D-amino acid production; two thermophiles, Bacillus sp. Lk-1 and LK-2, having higher specific activity and two thermophiles, B. stearothermophilus KL-01 and Bacillus sp. KLS-01, having higher thermal stability than the D-AAT producers. Taxonomic and physiological characteristics of the four isolated thermophiles were described herein.

• Preventive Nutrition and Food Science
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• v.4 no.3
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• pp.175-179
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• 1999

To develop a production method for modified starches with less pollution, pH adjustment and gamma irradiation were applied to commerical corn starch. Blue values were significantly decreased , while alkali number, optical transmittance and solubility markedly increased when gamma irradiation was applied to pH 2 adjusted corn starch. Water binding capacity and swelling power at pH 5 were the highest among the samples. Gelatinization viscosity was considerably affected by gamma irradiation and pH of the starch. Gamma irradiation of pH 2 adjusted starch showed the lowest peak viscosity and the best cooling stability among the tested samples . Therefore, the production of modified starch with low viscosity as well as with sufficient viscosity stability seems feasible by controlling the pH of the starch and gamma irrdiation.

• The Journal of Korean Medicine
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• v.24 no.2
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• pp.166-178
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• 2003

Objectives : Nitric oxide (NO) plays an important role in normal and pathophysiological cells as a messenger molecule, neurotransmitter, microbiological agent, or dilator of blood vessels and arteriosclerosis, respectively. This study was undertaken to understand the mechanism of NO production and effect of Hyeolbuchukeo-tang (Xiefuzhuyu-tang) on NO production in cultured vascular smooth muscle cell (VSMC). Methods and Results : VSMC was isolated from aorta and cultured. Cultured primary cells were identified as VSMC with anti--smooth muscle actin antibody. A large amount of NO was produced in cultured VSMC treated with $IFN-{\gamma}$ plus TNF in a time- and dose-dependent manner. $TNF-{\alpha}$ was a more efficient stimulator than $IFN-{\gamma}$ in NO production of cultured VSMC. iNOS protein wasdetected within 3 hrs and it increased up to 12 hrs in a time-dependent manner. However, accumulated NO in cytokine-treated VSMC was not detected within 3 hrs. NO production in cytokine-treated VSMC showed the dose- and time-dependent manner, and increased up to 48 hrs. The activated VSMC produced a large amount of NO (about 60 uM). Hyeolbuchukeo-tang (Xiefuzhuyu-tang) alone did not induceNO production, but it potentiated the effect of $TNF-{\alpha}$ on NO production and increased NO production by about 20%. Hyeolbuchukeo-tang (Xiefuzhuyu-tang) did not affect the transcriptional activity of iNOS gene, but increased the accumulation of iNOS. These results indicate that Hyeolbuchukeo-tang (Xiefuzhuyu-tang) could modulate the translational level of iNOS. PKC did not modulate NO production, but calcium ionophore A23187 decreased NO production. However, Hyeolbuchukeo-tang (Xiefuzhuyu-tang) elevated the decreased NO production in A23187-treated VSMC by modulating the stability of iNOS transcripts. Half-life of the synthesized transcripts appeared to have about 6 hrs. PDTC, an $NF-{\kappa}B$ inhibitor, blocked the accumulation of iNOS mRNA, indicating that $NF-{\kappa}B$ served as an important modulator in the transcriptional regulation of iNOS. As Hyeolbuchukeo-tang (Xiefuzhuyu-tang) potentiated the effect of the $TNF-{\alpha}$ on NO production but had no additional effect on PDTC-modulated NO production, it is suggested that Hyeolbuchukeo-tang (Xiefuzhuyu-tang) enhances the $TNF-{\alpha}-mediated$ NO production of VSMC by modulating the iNOS activity and the stability of iNOS transcripts in activated VSMC having the elevated intracellular calcium ion. Conclusions : This study suggests that Hyeolbuchukeo-tang (Xiefuzhuyu-tang) has a potential capacity for preventing and treating diseases of the circulation system, including arteriosclerosis.

• Journal of Microbiology and Biotechnology
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• v.10 no.3
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• pp.321-326
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• 2000

To examine the feasibility of the long-term production of the human granulocyte colony stimulating factor (hG-CSF) using the $_{L}-arabinose$ promoter system of Escherichia coli, flask relay culture and cyclic fed-batch culture were performed. In the flask relay culture, it was found that the pismid was maintained stably up to about 170 generations in an uninduced condition, whereby the cells could also maintain the capability of expressing hG-CSF expression were maintained stably up to at least 100 generations. In contrast, in the cyclid fed-batch culture, segregational plasmid instability was observed within about 4 generations after induction, even though the cell growth and hG-CSF production reached their maximum balues, 78.0 g/l of dry cell weight and 7.0 g/l of hG-CSF, respectively. It would appear that, when compared to the flask relay culture, the high-cell density and high-level expression of hG-CSF in the cyclic fed-batch cultrure led to the segregational plasmid instability; in other words, a severe metabolic burden existe on the cells due to the high-level expression of hG-CSF. Accordingly, based on these long-term cultures, the segregational and structural plasmid instability was observed and a strategy to overcome such problems could be designed.

• KSBB Journal
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• v.7 no.2
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• pp.144-148
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• 1992

The purpose of this study is to develop a continuous process for sorbitol production using dried Zymomonas mobilis immobilized in K-carrageenan. The methods of glularaldehyde cross-linking of enzymes in CTAB (celyltrimetylammoniumbromide) treated cells immobilized in K-carrageenan showed stability for the production of sorbitol for 30 days of operation. K-carrageenan beads entrapping permeabilized cells were dried to Improve bead rigidity and storage stability. A semi-batch process with dry beads was carried out and only a small loss of enzyme activity (less than 8%) was observed during 72h. The value of Vmax for the dry K-carrageenan beads was found to be one half or that for free cells. It was shown that the productivities of the continuous process with wet K-carrageenan beads and dry beads at a dilution rate 0.1h-1 were 3.4g/L-h and 2.88h/L-h, respectively.

• Journal of Microbiology and Biotechnology
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• v.1 no.4
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• pp.274-280
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• 1991

Effects of IPTG induction on cell growth and production of ${\beta}$-galactosidase-preS2 fusion protein (${\beta}$gal-preS2) were studied in a defined medium using a recombinant Escherichia coli JM109/pCMHB30. IPTG was added (0.2 mM) to induce the cloned-gene expression in the early-, mid-, and late-log growth phases. The most serious decreases in growth rate and plasmid stability were observed for the induction in the early-log growth phase. The expression level of ${\beta}$gal-preS2 attained by the induction in the mid-log phase was about 0.51 mg fusion protein/mg total cellular protein, which was 2- and 5-fold improvement over the levels obtained with the inductions in the early- and late-log phases. Formation of acidic byproducts including acetate and pyruvate showed different profiles during the fermentation period for each cases of induction; pyruvate was the major byproduct for the induction in the early-log phase while acetate production became more significant for the cases of inductions in the mid- and late-log phases.

• Journal of the Korean Society for Precision Engineering
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• v.22 no.7 s.172
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• pp.155-163
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• 2005

Pressure heating rollers with temperature control were mounted to a flat cable laminating machine (FCLM). Pressure heating rollers should be heated up to the setting temperature $(175^{\circ}C)$ and kept on to producing good quality flexible flat cables (FFC). Existing Pressure heating rollers took more than 70minutes to the setting temperature and did not keep on the setting temperature in production. Temperature controller, electric power controller, material and diameter of rollers and heat capacities were changed to improve the temperature control of the pressure heat rollers for better production of the FFC. Thus, the reaching time to the setting temperature (RT), temperature stability time (TST) and temperature hunting (TH) were measured and compared with the existing pressure rollers case. The RT of A roller was shortened by 50minutes, and B roller was shortened by 15minutes. The TST of A roller was shortened by 13minutes, and B roller was shortened by 15minutes. The THs of both A and B rollers were settled up to ${\pm}5^{\circ}C$. Finally, the productivity of the FCLM and the quality of the FFC were increased.

• Archives of Pharmacal Research
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• v.23 no.4
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• pp.418-423
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• 2000

Oka strain VR-795 (Varicella Zoster Virus, VZV) of American Type Culture Collection (ATCC) has been used for chickenpox vaccine production. In order to use this strain for vaccine production, the strain must be identified and its stability must be confirmed. The identification of the Oka strain has been confirmed using Restriction Fragment Length Polymorphism (RFLP) and DNA sequence analysis of glycoprotein-II (gp-II). The amino acid sequences of Oka deduced from the DNA sequence of gp-II have changed at three amino acids against Ellen and at one amino acid against Webster. To prove the stability of the Oka strain during the passage, RFLP and DNA sequence analyses were also used with 11, 15 and 23 times of virus passage. We found that the Oka strain was stable at passages of up to 23 times, based on the RFLP and DNA sequence analyses. The confirmed Oka strain was renamed as BR-Oka for the purposes of chickenpox vaccine production.