• Korean Journal of Plant Resources
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• v.23 no.6
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• pp.519-525
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• 2010

Chlorogenic acid, formed of an ester of caffeic acid and quinic acid, which is naturally abundant in many plant species, was used as a model O-dihydoxy phenolic compound. In the previous study, we have reported that the isolated constituent from Apocynum venetum leaves has an inhibitory effect on $Cu^{2+}$-induced oxidative modification of low-density lipoprotein (LDL). Among them, chlorogenic acid showed the most potent anti-LDL oxidative activity than other compounds. For the reason, we investigated the inhibitory effect of the chlorogenic acid on $Cu^{2+}$-induced oxidative modification of LDL, monitored a lag time in the conjugated-diene formation and TBARS formation, and measured TNBS free amino acid group, and form cell formation in vitro system. The TBARS- and diene- formation were strongly inhibited by chlorogenic acid ($0{\sim}100\;{\mu}g/ml$) with dose dependent manner. On the other hand, TNBS reactive lysine amino groups on LDL oxidation were protected by chlorogenic acid- treated cell group. Therefore, chlorogenic acid inhibited to cholesterol accumulation in the isolated peritoneal macrophage.

• Transactions of Materials Processing
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• v.20 no.7
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• pp.518-523
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• 2011

The three dimensional geometries of an aluminum open cell foam before and after uniaxial compressive loading were investigated using the X-ray micro CT(computed tomography). Aluminum 6101-T6 open cell foams of 10, 20, 40 ppi (pore per inch) were considered in this work. After the serial sectioning CT images of aluminum foams were obtained from non-destructive X-ray images, the exact 3D structure were reproduced and visualized with commercial image processing program. The relative density ratio was around the 7.0 to 9.0 range, the unit cells showed anisotropic shapes having the different dimensional ratios of 1.1 to 1.3 between the rise and the transverse directions. The yield stress increased with the relative density ratio and the volumetric strain increased proportionally with compressive strain. The plateau stress in the compressive stress-strain curve was caused by the buckling of ligaments.

• Journal of Electrochemical Science and Technology
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• v.7 no.2
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• pp.91-96
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• 2016

Oxidation behaviours of ash free coal (AFC), carbon, and H₂ fuels were investigated with a coin type molten carbonate fuel cell. Because AFC has no electrical conductivity, its oxidation occurs via gasification to H₂ and CO. An interesting behaviour of mass transfer resistance reduction at higher current density was observed. Since the anode reaction has the positive reaction order of H₂, CO₂ and H₂O, the lack of CO₂ and H₂O from AFC results in a significant mass transfer resistance. However, the anode products of CO₂ and H₂O at higher current densities raise their partial pressure and mitigate the resistance. The addition of CO₂ to AFC reduced the resistance sufficiently, thus the resistance reduction at higher current densities did not appear. Electrochemical impedance results also indicate that the addition of CO₂ reduces mass transfer resistance. Carbon and H₂ fuels without CO₂ and H₂O also show similar behaviour to AFC: mass transfer resistance is diminished by raising current density and adding CO₂.

• Journal of Korean Academy of Oral and Maxillofacial Radiology
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• v.24 no.2
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• pp.403-410
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• 1994

The purpose of this study was to investigate the irradiation effects on the secretory granules of the rat submandibular gland acinar cell. For this study, Sprague-Dawley strain rats were irradiated to their neck region with the dose of 5Gy and l0Gy by 6MV X-radiation, and sacrificed on the experimental periods after irradiation. The authors observed the ultrastructural changes of the secretory granules of the rat submandibular gland acinar cell under a trasmission electron microscope. The results were as follows: In the transmission electron microscopic examination, secretory granules were blurred in limiting membrane on the 3hours groups after irradiation. And they showed decrease in number, irregularities in shape and distributional pattern, and inhomogeneous internal electron density on the Iday and 3days groups. After then, these changes were recovered in shape and distributional pattern on the 14days groups, and changes of internal electron density and limiting membrane were recovered on the 28days groups after irradiation. Among the intracellular organelles, rough endoplasmic reticulum was scattered, but golgi complex was not changed. And such pathologic changes were earlier and more prominent in 10Gy irradiated groups than in 5Gy irradiated groups.

• Biotechnology and Bioprocess Engineering:BBE
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• v.2 no.2
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• pp.132-135
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• 1997

We prepared capsules containing Saccharomyces cerevisiae and Zoogloea ramigera cells for the removal of lead(II) and cadmium ions. Microbial cells were encapsulated and cultured in the growth medium. The S.cerevisiae cells grown in the capule did not leak through the capsule membrane. The dried cell density reached to 250 g/l on the basis of the inner volume of the 2.0 mm diameter capsule after 36 hour cultivation. The dry whole cell expolymer density of encapsulated Z.ramigera reached to 200 g/L. The capsule was crosslinked with triethylene tetramine and glutaric dialdehyde solutions. The cadmium uptake of encapsulated whole cell expolymer of Z.ramigera was 55mg Cd/g biosorbent. The adsorption line followed well Langmuir isotherm. The lead uptake of the encapsulated S. cerevisiae was about 30 mg Pb/g biomass. The optimum pH of the lead uptake using encapsulated S. cerevisiae was found to be 6. Freundlich model showed a little better fit to the adsorption data than Langmuir model 95 percent of the lead adsorbed on the encapsulated biosorbents was desorbed by the 1 M HCl solution. The capsule was reused 50 batches without loosing the metal uptake capacity. And the mechanical strength of the crosslinked capsule was retained after 50 trials.

• Electrical & Electronic Materials
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• v.10 no.9
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• pp.930-937
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• 1997

Polycrystalline CdTe thin films have been studied for photovoltaic application because of their high absorption coefficient and optimal band energy(1.45 eV) for solar energy conversion. In this study CdTe thin films were deposited on CdS(chemical bath deposition)/ITO(indium tin oxide) substrate by rf-magnetron sputtering under various conditions. Structural optical and electrical properties are investigated with XRD UV-Visible spectrophotometer SEM and solar simulator respectively. The fabricated CdTe/CdS solar cell exhibited open circuit voltage( $V_{oc}$ ) of 610 mV short circuit current density( $J_{sc}$ ) of 17.2 mA/c $m^2$and conversion efficiency of about 5% at optimal sputtering conditions.

• Membrane Journal
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• v.20 no.3
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• pp.173-184
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• 2010

Microbial fuel cell (MFC) is a promising renewable energy source that can generate electrical energy from organic wastes using microbe. This technology has been regarded as a future green alternative energy in that MFC makes use of organic-rich wastewater and also reduces waste sludges as well as produces electricity. To be practically realized, however, achieving higher power density than now is demanded, which may be possible by eliminating various negative factors to act as resistances in MFC operations. For instance, highly activated microbes, highly conductive electrode materials, and fast electron transfer between microbes and electrodes can lead to MFC with high power density. In particular, polymer electrolyte membranes are also a key component for improved MFC performance.

• Journal of the Korean Ceramic Society
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• v.42 no.12 s.283
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• pp.816-820
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• 2005

The doped-ceria is a strong candidate material for an intermediate temperature SOFC. However, the mechanical strength and the magnitude of electrical conductivity need to be increased at low sintering temperature. In this study, to improve both properties, $1at\% $ of Mg, Ca, Cr, Fe, Co, Ni, Cu, Ga, and Zr were added to the GDC20 ($20at\%$ Gd-doped Ceria) and sintered at $1350^{\circ}C$ that is $250^{\circ}C$ lower than $1600^{\circ}C$. With addition, the relative density of the sintered sample increased. Fe, Co, Ni, Cu, Ga doped-GDC20 showed high relative density over $92\%$. Among them, Ga doped-GDC20 showed the most improved sinterability. The conductivity of doped­GDC20 increased by $\~10$ times at $300\~700^{\circ}C$.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.21 no.4
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• pp.300-304
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• 2008

A novel characterization method was investigated to estimate the trap generation during the program /erase cycles in nand flash memory cell. Utilizing Fowler-Nordheim tunneling current, floating gate potential and oxide electric field, we established a quantitative model which allows the knowledge of threshold voltage (Vth) as a function of either program or erase operation time. Based on our model, the derived results proved that interface trap density (Nit) term is only included in the program operation equation, while both Nit and oxide trap density (Not) term are included in the erase operation equation. The effectiveness of our model was tested using 50 nm nand flash memory cell with floating gate type. Nit and Not were extracted through the analysis of Program/Erase speed with respect to the endurance cycle. Trap generation and cycle numbers showed the power dependency. Finally, with the measurement of the experiment concerning the variation of cell Vth with respect to program/erase cycles, we obtained the novel quantitative model which shows similar results of relationship between experimental values and extracted ones.

• Korean Journal of Veterinary Pathology
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• v.5 no.1
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• pp.1-4
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• 2001

Squamous cell carcinoma was diagnosed in a 4.5-year-old male African hedgehog (Atelerix albiventris). The patient was referred to Seoul National University, Veterinary Medical Teaching Hospital after 5 days history of left eye exophthalmos and corneal trauma. He had enlarged upper and lower jaw at the left part of the face and endophthalmitis of the left eye. On radiographic examinations, loss of bone density at the left zygomatic arch and sun-burst type periosteal reaction of left mandible with decreased bone density was noted. Histologically, the neoplastic mass consisted of markedly invasive, cords of nests of squamous epithelial cells. Intercellular bridges and keratin pearl formation were also noted.