• The Journal of the Korea Contents Association
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• v.17 no.11
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• pp.588-599
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• 2017

This paper analyzes internet access model between ISP, CP and end users where CP uses various technologies to provide direct access to ISP owning subscribers to consume its own contents in low cost and high quality. The level of access charge depends on the competitiveness of CP market. When CP market is perfect competitive, the level of access charge is identical to that of social optimum while when CP market is monopoly, the level of access charge is influenced by the sensitivity of the contents price to access charge for CP. The dead weight loss due to monopoly market in CP can be removed by the regulation of access charge. Socially optimal access charge in monopoly market of CP is lower than that in competitive market. This is because the regulator wants to set access price to lower level to reduce welfare loss from monopoly in CP market where CP determines the price to over marginal cost.

• Korean Journal of Medicinal Crop Science
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• v.13 no.4
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• pp.138-140
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• 2005

This study was carried out to investigate the optimal conditions for efficient in vitro growth of Asparagus cochinchinensis (Lour.) Merr. shoot derived from shoot tip. Shoots were successfully cultured in MS medium. It was found that $23^{\circ}C{\sim}25^{\circ}C$ were suitable for shoot growth. The growth of shoot was greatly influenced by cytokinins. The shoots derived from shoot tip were well elongated on MS medium supplemented with BA and zeatin. In vitro shoots were very poor or no growing. Especially, 3.0 mg/l BA on MS medium was very effective in elongation of shoot. Root formation from in vitro growth of plant let was achieved on MS medium supplemented with 0.5 mg/l IBA. The results suggest that selection of plant growth regulator could be important factor to achieve an efficient in vitro growth.

• BMB Reports
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• v.42 no.6
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• pp.338-343
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• 2009

The Wnt/$\beta$-catenin signaling pathway alters adipocyte differentiation by inhibiting adipogenic gene expression. $\beta$-catenin plays a central role in the Wnt/$\beta$-catenin signaling pathway. In this study, we revealed that tumour necrosis factor-$\alpha$ (TNF-$\alpha$), a potential negative regulator of adipocyte differentiation, inhibits porcine adipogenesis through activation of the Wnt/$\beta$-catenin signaling pathway. Under the optimal concentration of TNF-$\alpha$, the intracellular $\beta$-catenin protein was stabilized. Thus, the intracellular lipid accumulation of porcine preadipocyte was suppressed and the expression of important adipocyte marker genes, including peroxisome proliferator-activated receptor-$\gamma$ (PPAR$\gamma$) and CCAAT/enhancer binding protein-$\alpha$ (C/EBP$\alpha$), were inhibited. However, a loss of $\beta$-catenin in porcine preadipocytes enhanced the adipogenic differentiation and attenuated TNF-$\alpha$ induced anti-adipogenesis. Taken together, this study indicated that TNF-$\alpha$ inhibits adipogenesis through stabilization of $\beta$-catenin protein in porcine preadipocytes.

• The Plant Pathology Journal
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• v.28 no.1
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• pp.40-48
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• 2012

$Potato$ $virus$ $X$ (PVX) replication is precisely regulated by regulatory viral sequences and by viral and/or host proteins. In a previous study, we identified a 54-kDa cellular tobacco protein that bound to a region within the first 46 nucleotides (nt) of the 5' non-translated region (NTR) of the viral genome. Optimal binding was dependent upon the presence of an ACCA sequence at nt 10-13. To identify host factors that bind to 5' NTR elements including AC-rich sequences as well as stemloop 1 (SL1), we used northwestern blotting and matrixassisted laser desorption/ionization time-of-flight mass spectrometry for peptide mass fingerprinting. We screened several host factors that might affect PVX replication and selected a candidate protein, $Nicotiana$ $tabacum$ WRKY transcription factor 1 (NtWRKY1). We used a $Tobacco$ $rattle$ $virus$ (TRV)-based virus-induced gene silencing (VIGS) system to investigate the role of NtWRKY1 in PVX replication. Silencing of $WRKY1$ in $Nicotiana$ $benthamiana$ caused lethal apical necrosis and allowed an increase in PVX RNA accumulation. This result could reflect the balancing of PVX accumulation in a systemic $N.$ $benthamiana$ host to maintain PVX survival and still produce a suitable appearance of mosaic and mottle symptoms. Our results suggest that PVX may recruit the WRKY transcription factor, which binds to the 5' NTR of viral genomic RNA and acts as a key regulator of viral infection.

• Korean Journal of Plant Tissue Culture
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• v.21 no.3
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• pp.145-150
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• 1994

This study was conducted to determine the effects of 3 cytokinins (BA,2iP and kinetin) and their concentrations (0, 0.1, 0.5, 1.0, and 2.0 mg/L) on multiple shoot production of Citrus spp. 'Sambokam' and 'Byungkyool' by nodal culture. Nodal explants were obtained from in vitro germinated seedlings of both cultivars. 'Sambokam' produced more multiple shoots than did 'Byungkyool' by nodal culture. Among the 3 cytokinins tested in this study BA supplemented in semi-solid MS basal medium was the most effective stimulator for multiple shoot production, and an optimal concentration was determined to be 1.0 mg/L. Shoot elongation and root formation were inhibited by increasing cytokinin concentration, regardless of cytokinin types. BA at 1.0 mg/L produced the most multiple shoots and the highest number of leaves in 'Sambokam', whereas any cytokinin and concentration studied in this experiment did not affect any scored variables such as shoot and leaf numbers, etc. in 'Byungkyool'.

• Journal of Plant Biotechnology
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• v.44 no.3
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• pp.335-342
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• 2017

Purple passion fruit (Passiflora edulis Sims) is one of the introduced tropical plants, an increasing interest has arisen due to its distinctive taste and attractive flavor. It is expected that passion fruit production and planted area will increase gradually in the years ahead because of high profitability and consumer's demands of healthful ingredients. So we tried to investigate the effect of plant growth regulators and antioxidants on in vitro plant regeneration and callus induction from leaf explants of passion fruit for an establishment of optimal mass propagation system. Young leaf explants of purple passion fruit were cultured in Murashige and Skoog (MS) medium containing different growth regulators and antioxidant additives to induce the shoot organogenesis. After 8 weeks, the highest embryogenic callus formation rate was obtained in MS medium supplemented with $1mg{\cdot}L^{-1}$ 6-benzylaminopurine (BAP) and $2mg{\cdot}L^{-1}$ 2,4-dichlorophenoxyacetic acid (2,4-D), furthermore, the shoot development via organogenesis was also observed. Silver nitrate ($AgNO_3$), which was added into the medium to minimize the adverse effects of leached phenolics, was effective for reduction of medium browning and sudden explant death. In the medium supplemented with $1mg{\cdot}L^{-1}$ BAP and $1mg{\cdot}L^{-1}$ gibberellic acid ($GA_3$), shoots were most vigorously regenerated and elongated. Most shoots rooted successfully in half strength medium with $1mg{\cdot}L^{-1}$ indol-3 acetic acid (IAA), and more than 90% of plantlets survived after 4-month acclimatization period.

• Environmental and Resource Economics Review
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• v.19 no.3
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• pp.459-483
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• 2010

This paper constructs the two-part tax-a combined form of output tax and entrance fee-for polluting oligopolists under endogenous entry. In the presence of external damage that varies exogenously with aggregate output, we show that the two-part tax produces the ex post Pigouvian rule and thus achieves the first-best optimum. We also examine a detailed analysis of the impact of the two-part tax on social welfare and government revenues. Finally, when estimation errors exist in the process of regulation, we identify the incentive conflicts between interest groups and analyze the effects of estimation errors on determining optimal tax. In particular, we show that if the regulator takes care of both welfare loss and revenue gain under the proposed two-part tax, not only over-estimation on the slope of external damage but also under-estimation on the slope of market demand should be taken into the policy consideration.

• Korean Journal of Microbiology
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• v.33 no.4
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• pp.237-241
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• 1997

Lipase (EC 3.1.1.3) in the culture filtrate of Streptomyces coelicolor A3(2) was active on ${\alpha}$-naphthyl-butyrate as well as on various triacylglycerols with different lengths of acyl chains. The extracellular lipase was purified 15-fold by ammonium sulfate fractionation, Sephadex G-100, DEAE-Cellulose and Phenyl-Sepharose CL4B column chromatography with overall yield of 16%. It showed an molecular weight of 34.7 kDa by SDS-polyacrylamide gel electrophoresis. The enzyme activity with tributyrin as substrate was optimal at pH 8.0~9.0 and at $37^{\circ}C$. The enzyme activity decreased when the chain length of acyl group of triacyglycerol increased. A-factor, a hormone-like regulator of Streptomyces differentiation inhibited the lipase activity, which might corelate with the low enzyme activity in early exponential growth phase.

• Korean Journal of Plant Tissue Culture
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• v.25 no.2
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• pp.119-123
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• 1998

In order to investigate the possibility of in vitro mass propagation via somatic embryogenesis from Sicyos angulatus L., effects of plant growth regulators and carbon sources on callus induction and somatic embryogenesis were evaluated. Optimal combinations of plant growth regulator for callus induction from cotyledon and inflorescence explants were 2,4-D 2.0 mg/L + BA 0.1 mg/L and 2,4-D 1.0 mg/L + BA 0.1 mg/L in MS basal medium supplemented with sucrose 30 g/L,, respectively. Somatic embryogenesis was observed from cultured inflorescence explants, but it could not be achieved from leaf or cotyledon explants. The most effective plant growth regulators for somatic embryogenesis from callus was NAA 1.0 mg/L + kinetin 10 mg/L in the half strength of MS basal medium supplemented with 20 g/L sucrose.

• Earthquakes and Structures
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• v.12 no.4
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• pp.425-436
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• 2017

Vibration control using a tuned mass damper (TMD) is an effective technique that has been verified using analytical methods and experiments. It has been applied in mechanical, automotive, and structural applications. However, the damping of a TMD cannot be adjusted in real time. An excessive mass damper stroke may be introduced when the mass damper is subjected to a seismic excitation whose frequency content is within its operation range. The semi-active tuned mass damper (SATMD) has been proposed to solve this problem. The parameters of an SATMD can be adjusted in real time based on the measured structural responses and an appropriate control law. In this study, a stiffness-controllable TMD, called a leverage-type stiffness-controllable mass damper (LSCMD), is proposed and fabricated to verify its feasibility. The LSCMD contains a simple leverage mechanism and its stiffness can be altered by adjusting the pivot position. To determine the pivot position of the LSCMD in real time, a discrete-time direct output-feedback active control law that considers delay time is implemented. Moreover, an identification test for the transfer function of the pivot driving and control systems is proposed. The identification results demonstrate the target displacement can be achieved by the pivot displacement in 0-2 Hz range and the control delay time is about 0.1 s. A shaking-table test has been conducted to verify the theory and feasibility of the LSCMD. The comparisons of experimental and theoretical results of the LSCMD system show good consistency. It is shown that dynamic behavior of the LSCMD can be simulated correctly by the theoretical model and that the stiffness can be properly adjusted by the pivot position. Comparisons of experimental results of the LSCMD and passive TMD show the LSCMD with less demand on the mass damper stroke than that for the passive TMD.