• Steel and Composite Structures
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• v.45 no.3
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• pp.409-423
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• 2022

Nowadays, there is a high demand for great structural implementation and multifunctionality with excellent mechanical properties. The porous structures reinforced by graphene platelets (GPLs) having valuable properties, such as heat resistance, lightweight, and excellent energy absorption, have been considerably used in different engineering implementations. However, stiffness of porous structures reduces significantly, due to the internal cavities, by adding GPLs into porous medium, effective mechanical properties of the porous structure considerably enhance. This paper is relating to vibration analysis of fluidconveying cantilever porous graphene platelet reinforced (GPLR) pipe with fractional viscoelastic model resting on foundations. A dynamical model of cantilever porous GPLR pipes conveying fluid and resting on a foundation is proposed, and the vibration, natural frequencies and primary resonant of such a system are explored. The pipe body is considered to be composed of GPLR viscoelastic polymeric pipe with porosity in which Halpin-Tsai scheme in conjunction with the fractional viscoelastic model is used to govern the construction relation of nanocomposite pipe. Three different porosity distributions through the pipe thickness are introduced. The harmonic concentrated force is also applied to the pipe and the excitation frequency is close to the first natural frequency. The governing equation for transverse motions of the pipe is derived by the Hamilton principle and then discretized by the Galerkin procedure. In order to obtain the frequency-response equation, the differential equation is solved with the assumption of small displacement, damping coefficient, and excitation amplitude by the multiple scale method. A parametric sensitivity analysis is carried out to reveal the influence of different parameters, such as nanocomposite pipe properties, fluid velocity and nonlinear viscoelastic foundation coefficients, on the primary resonance and linear natural frequency. Results indicate that the GPLs weight fraction porosity coefficient, fractional derivative order and the retardation time have substantial influences on the dynamic response of the system.

• Anatomy and Cell Biology
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• v.56 no.4
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• pp.494-507
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• 2023

Vascular dementia (VaD) is characterized by progressive memory impairment, which is associated with microglia-mediated neuroinflammation. Polyphenol-rich natural plants, which possess anti-inflammatory activities, have attracted scientific interest worldwide. This study investigated whether Rubus fruticosus leaf extract (RFLE) can attenuate VaD. Sprague-Dawley rats were separated into five groups: SO, sham-operated and treated with vehicle; OP, operated and treated with vehicle; RFLE-L, operated and treated with low dose (30 mg/kg) of RFLE; RFLE-M, operated and treated with medium dose (60 mg/kg) of RFLE; and RFLE-H, operated and treated with high dose (90 mg/kg) of RFLE. Bilateral common carotid artery and hypotension were used as a modeling procedure, and the RFLE were intraorally administered for 5 days (preoperative 2 and postoperative 3 days). The rats then underwent memory tests including the novel object recognition, Y-maze, Barnes maze, and passive avoidance tests, and neuronal viability and neuroinflammation were quantified in their hippocampi. The results showed that the OP group exhibited VaD-associated memory deficits, neuronal death, and microglial activation in hippocampi, while the RFLE-treated groups showed significant attenuation in all above parameters. Next, using BV-2 microglial cells challenged with lipopolysaccharide (LPS), we evaluated the effects of RFLE in dynamics of proinflammatory mediators and the upstream signaling pathway. RFLE pretreatment significantly inhibited the LPS-induced release of nitric oxide, TNF-α, and IL-6 and upregulation of the MAPKs/NF-κB/iNOS pathway. Collectively, we suggest that RFLE can attenuate the histologic alterations and memory deficits accompanied by VaD, and these roles are, partly due to the attenuation of microglial activation.

• The Journal of Natural Sciences
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• v.4
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• pp.143-159
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• 1991

In order to investigate the micropropagation of Pelargonium, 2 cultivars of P. peltatum 'Pouletta' and P. zonale 'Pinto Red' were cultured in vitro on the MS basal medium supplemented with various concentrations of growth regulators. It attempted to study the induction of callus and the differentiation of organs from leaf disc, petiole segments, stem segments. hypocotyle segments and flower stalk segments. The results are summarized as follows; A. As for the initiation of callus, stem explant was proved to be the most suitable one among various explants of P. zonale 'Pinto Red'. The medium was supplemented with 1.0mg/1 BAP and 1.0mg/1 NAA. As NAA concentration increased, callus formation was enhanced, but higher concentration of NAA inhibited callus fromation. Leaf and hypocotyle explants showed less callus formation than stem and petiole explants. B. In P. zonale 'Pinto Red' petiole culture, the condition of cullus culture such as hormone concentration resulted in affecting shoots differentiation. The best result of shoots formation from the callus reculture were obtained from the combination of 0.5-1.0mg/1 BAP and 0.1-1.0mg/1 NAA when the callus was cultured in 1.0mg/1 BAP and 0.05mg/1 NAA. When the callus was cultured in medium without BAP, the shoot was not differentiated in subculture regardless to BAP and NAA concentration. and only callus was formed. C. Poly-phenol substance was observed in MS medium supplemented without PVP, in which callus was not formed from the leaf of P. peltatum 'Rouletta'. Polyphenol substance was not observed in MS medium supplemented with PVP, in which callus formation was increased. D. The callus formation of P. peltatum 'Rouletta' showed the stem explant being best result. The best result particularly in the stem explant among others. The optimal hormonal concentration was 0.1mg/1 NAA and 5.0mg/1 BAP. The shoot formation was observed at 0.05mg/1 NAA and 1.0mg/1 BAP, 0.1mg/1 NAA and 5.0mg/1 BAP. The shoot was malformed and the tissue recultured turned necrotic.

• KSBB Journal
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• v.11 no.3
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• pp.303-310
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• 1996

The marine microalga Isochrysis galbana Parke was studied to optimize its growth conditions in flask culture. Important medium components studied include nitrogen source, buffer, trace elements and vitamins. Environmental conditions include pH, temperature, light intensity, mixing extent and working volume. The medium prepared from natural sea-waters gave a higher final cell density than the medium prepared from synthetic sea-water Nitrate was a better source than ammonium. In the range of 0.4∼2mM, the final cell density was proportional to the initial nitrate concentration and the cell yield was estimated to be 8.5g dry cell wt/g N. For phosphate, optimal growth was observed in 0.1∼1.0mM but a considerable variation in pH was resulted. The addition of Tris at 5mM or 7mM could stabilize the medium pH, but this significantly reduced both growth rate and final cell density, The effect of trace elements and vitamins was negligible. Optimal temperature and initial pH were $20^{\circ}C$ and 8. When the intensity of incident light was varied in the range of 400∼2100 lux, the growth rate increased from 10mL to 70mL, the final cell density decreased although the initial growth rate did not change. Optimal agitation speed was 100rpm when working volume was 30mL. With optimal conditions, the maximum specific growth rate obtained was 0.021hr-1 and the final cell density was 1.1g/L.

• Microbiology and Biotechnology Letters
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• v.10 no.2
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• pp.133-144
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• 1982

The distribution of acid phosphatase activity was investigated with 141 microorganisms from the type culture collection of Chong Kun Dang laboratory and the 41 strains isolated from natural sources. The phytase activity was detected mainly with fungal strains. A fungus isolated from soil and identified as Aspergillus niger had shown the highest phytase activity. The environmental conditions for the enzyme formation by the isolate and some properties of the enzyme were also studied. The results obtained were as follows: (1) The highest phytase production was observed when the fungus was cultivated at 28$^{\circ}C$ for 5 days in the corn starch based medium using the cells incubated at 34$^{\circ}C$ for 3 days as a seed. (2) The optimal initial pH of the culture medium was found to around 2 for the formation of phytase. (3) Sucrose was proved to be one of the most effective carbon sources tested for the enzyme production. (4) As an inorganic nitrogen source, potassium nitrate was found to give a good result in the production of phytase. (5) Synthesis of phytase was significantly increased by the supplement with 0.2 % corn steep liquor to the basal medium as an organic nitrogen source. (6) At the concentration of 40-80 mg inorganic phosphate per liter of the culture medium, the enzyme formation revealed the highest level. But as the phosphate was increased above this optimum concentration the phytase activity was drastically decreased although the cell density showed to be still increasing

• The Journal of Industrial Distribution & Business
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• v.9 no.11
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• pp.93-104
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• 2018

Purpose - For small and medium sized firms, CEO characteristics are main factor influencing firms' prosperity as well as performance. So it is quite natural that many people are interested in factors of CEO that matters. In this research, CEO characteristics in terms of capabilities and skill or special knowledge necessary to run the business are invested for manufacturing firms. Precedent studies reveal that CEO characteristics such as psychological factors including desire to succeed, tendency to take risks, personal factors including age, year of running business, and task related factors including managing capability, communication skills, network influence firm performance for manufacturing firms. However, these studies simply verify whether or not those factors affect firm's managing performance. This study, however, goes further to investigate how is the affecting process from CEO's capabilities and organization characteristics to firm's core competence, and from core competence to advantages, and from advantages to managing performance. Research design, data, and methodology - We make a questionnaire and surveyed manufacturing firm CEO's in Gyeonggi-do area. General characteristics analysis, factor analysis, regression analysis, and control effect analysis was conducted. SPSS 2.0 Win, version was used. Results - The CEO characteristics including basic capability, task capability, leadership, and organization characteristics affect core competence at the statistically significant level. And, core competence affect both price advantage and differentiation advantage at the significant level. Some unique finding is that while differentiation advantage affects both financial achievement and non-financial achievement, price advantage does not affect both financial and non-financial achievement. And firm characteristics mainly measured by CEO characteristics of skills has control effects on the trace from core competence to price advantage. Conclusions - For small and medium sized firms CEO characteristics is the most important factor influencing firm's prosperity. For manufacturing firms, whether CEO has the skill or special knowledge to run the firm is critical factor. The study results show that CEO's for manufacturing firms put importance on price and price advantage which seems to be familiar to them. However, the price advantage does not influential to financial and non-financial achievement. This result suggests that small and medium sized manufacturing firms' CEO's should make effort to improve other aspects of advantages to be more competitive.

• Journal of Ginseng Research
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• v.12 no.2
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• pp.104-113
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• 1988

Effect of the purified ginsenoside $-Rb_1$ and $-Rb_2$ on LDL receptor biosynthesis of CHO cell cultured in a high cholesterol medium was investigated . Cholesterol uptake by CHO cell cultured in a medium containing various amounts of cholesterol was traced and found that the cholesterol uptake was proportional to the concentration of cholesterol in the medium, and the population of LDL receptors were proportionally decreased as the increasing cholesterol level in the cell. However, when the CHO cells were cultured in the medium containing ginsenosides, no significant decrease of LDL receptor population occured. The biosynthesis of protein and RNA of the above cells was higher than that of CHO cells cultured in the absence of the ginsenosides, suggesting that the ginsenosides might stimulate LDL receptor bio-synthesis. It was also observed that the ginsenosides stimulated the biosynthesis of estradiol and progesterone from cholesterol in the CHO cell. From the above results, it seemed that the ginsenosides lowers the cholesterol level by stimulating the cholesterol metablism including steroid hormone biosynthesis, resulting in the lowering of inhibitory action of cholesterol on LDL receptor biosynthesis.

• Journal of Life Science
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• v.17 no.6 s.86
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• pp.831-835
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• 2007

This study was carried out to obtain information about the valuable combination and concentration to produce good plants of cut gerbera flowers of 19 domestically - bred gerbera cultivars. BA and kinetin combination is more effective than NAA and BA combination to produce good plants and mass propagation of domestically - bredgerbera cultivars. Normally almost of 19 cultivars, mass propagation was more effective on the medium containing 1.0 mg/L BA + 0.5, 1.0 mg/L kinetin. But some cultivars, 'Sunnyeo', 'Oksaem','Piny', and 'Pink Light', vitrified plants were induced on MS medium high level of BA concentration(BA 1.0 mg/L), in comparison with those on the medium with low level of BA(0.1 mg/L).Fresh and dry weight, more effective on the medium containing BA 0.5 mg/L . Kinetin 0.1, 0.5 mg/L. Anatomical investigation of vitrified leaf, stomata of vitrified leaves were circular and inflated, where-as those of normal leaves.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.3B
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• pp.303-310
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• 2009

Natural zeolite is widely used as sorbents and bio-media materials because it is cheap as well as it has efficient porous structures and large cation exchange. In this study, the effect of metal cations $(Na^+,\;Ca^{2+},\;Mg^{2+},\;Al^{3+})$ adsorbed to natural zeolite on the microorganism attachment was investigated. Metal-modified zeolites (MMZ) were prepared with 0.01 M, 0.02 M and 0.1 M NaCl, $CaCl_2$, $MgCl_2$ and $AlCl_3$ solutions respectively, which concentrations were equivalent to 10%, 20% and 100% of cation exchange capacity (CEC) of natural zeolite. Pseudomonas putida was used as microorganism which was cultivated in Beef Extract Medium at $26^{\circ}C$. The microorganism attachment to MMZ was increased more than natural zeolite. The amount of bacterial adhesion to MMZ and natural zeolite were $Mg^{2+}>natural>Na^+>Al^{3+}>Ca^{2+}$ under 10% of CEC, $Mg^{2+}>Ca^{2+}>Al^{3+}>natural>Na^+$ under 20% of CEC and $Ca^{2+}>Mg^{2+}>natural>Al^{3+}>Na^+$ under 100% of CEC. Especially, Mg-modified zeolite (Mg-MZ) showed the highest amount of bacterial adhesion, which increased the microorganism attachment 60% higher than natural zeolite under 10% of CEC. However, the amount of bacterial adhesion was decreased as the concentration of metal cations modified to zeolite were increased, showing that the increased amounts were 60% under 10% of CEC, 50% under 20% of CEC and 10% under 100% of CEC in Mg-MZ. Additionally, the effect of $Mg^{2+}$ in solution on the bacterial adhesion was investigated in order to compare it with the effect of $Mg^{2+}$ adsorbed to zeolite. The maximum quantity of bacterial adhesion to Mg-MZ was not different from the amount of microorganism attachment to the natural zeolite when $Mg^{2+}$ solution was added.

• Journal of Korea Society of Digital Industry and Information Management
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• v.11 no.2
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• pp.167-179
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• 2015

Recently the small and medium sized companies are more difficult to find people than large companies. So it is natural that having a great interest in leadership and its effects in organizations. This study examines how transformational leaders influence on empowerment, self-efficacy and job satisfaction in IT company. Investigating the effect between transformational leadership and job satisfaction in IT company may also be a tip of an understanding of how to manage employee turnover. Samples of 387 employees in IT companies were analyzed by structural equation modeling using Lisrel 8.7 and it showed acceptable data-fit of proposed model and supported all of research hypotheses. The empirical results indicated that transformational leadership significantly influences empowerment, self-efficacy and job satisfaction and also it confirmed that empowerment and self-efficacy are effective mediators linking job satisfaction. That is the findings reveal that transformational leaders boost employee's job satisfaction indirectly.