• Applied Biological Chemistry
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• v.48 no.4
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• pp.352-357
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• 2005

The optimization of extraction conditions of phytoestrogen from pomegranate by hot water was conducted by analyzing the extraction characteristics. The purpose of this study was effective utilization of bioactive components of pomegranate, and the analyzing was performed with response surface methodology (RSM). This study established 10 sections based on the central composite design with the independent variables of extraction temperature (60, 70, 80, 90, $100^{\circ}C$) and extraction time (1, 2, 3, 4, 5 hr) to predict the optimal conditions for extraction of the effective components. The dependent variables were measured for extracted materials, those were, the major components such as chlorogenic acid, kaempferol, $17-{\alpha}-estradiol\;and\;17-{\beta}-estradiol$ content, and regression analysis was performed by SAS program, and optimal conditions for each characteristics were predicted, and the characteristics of extraction were analyzed by response surface methodology. It was found that chlorogenic acid, kaempferol, and $17-{\alpha}-estradiol$ content were greatly affected by extraction temperature. However, $17-{\beta}-estradiol$ content was affected significantly by extraction time. Regression formulas for each variable were elicited from this study, and the chlorogenic acid, kaempferol, $17-{\alpha}-estradiol\;and\;17-{\beta}-estradiol$ content depending on response surface methodology factor were superimposed. It was shown that optimal temperature and extraction time were $98{\sim}100^{\circ}C\;and\;3{\sim}5$ hrs, respectively.

• Journal of Soil and Groundwater Environment
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• v.9 no.2
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• pp.20-27
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• 2004

Kinetic characteristics dependent on several factors such as iron mineral and organic solvents were investigated. When F $e^{0}$ , FeS and Fe $S_2$ were used as mediators, minerals affecting reaction rate were in the following order : $Fe_{0}$ 0/ ＞ FeS ＞ $FeS_2$ when in contact $C_2$C $l_{6}$ . The more chloride substituted, the higher reaction rate were observed. The reaction rates were dependent on pH, shaking rate, temperature and specific surface area. 1, 10-phenanthroline and EDTA degradation rates were fast, indicating that they adsorbed on the surface of the iron which makes the electron transfer reaction easy. Nitrate which has $\pi$＊ orbital of molecular can increase electron transfer rate because it is delocalized in its entity. The reaction rates were not affected by hydroquinone. Degradation rates were much enhanced with naturally occurring kaolinite because of the surface corrosion of Fe mineral. However, The reaction rate was not affected by F $e^{2+}$ or S $O_4$$^{2-}$ presented in solution.n.

• Proceedings of the Materials Research Society of Korea Conference
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• 2012.05a
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• pp.68.1-68.1
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• 2012

The best part of graphene is - charge-carriers in it are mass less particles which move in near relativistic speeds. Comparing to other materials, electrons in graphene travel much faster - at speeds of $10^8cm/s$. A graphene sheet is pure enough to ensure that electrons can travel a fair distance before colliding. Electronic devices few nanometers long that would be able to transmit charge at breath taking speeds for a fraction of power compared to present day CMOS transistors. Many researches try to check a possibility to make it a perfect replacement for silicon based devices. Graphene has shown high potential to be used as interconnects in the field of high frequency electrical devices. With all those advantages of graphene, we demonstrate characteristics of electrical and optical properties of graphene such as the effect of graphene geometry on the microwave properties using the measurements of S-parameter in range of 500 MHz - 40 GHz at room temperature condition. We confirm that impedance and resistance decrease with increasing the number of graphene layer and w/L ratio. This result shows proper geometry of graphene to be used as high frequency interconnects. This study also presents the optical properties of graphene oxide (GO), which were deposited in different substrate, or influenced by oxygen plasma, were confirmed using different characterization techniques. 4-6 layers of the polycrystalline GO layers, which were confirmed by High resolution transmission electron microscopy (HRTEM) and electron diffraction analysis, were shown short range order of crystallization by the substrate as well as interlayer effect with an increase in interplanar spacing, which can be attributed to the presence of oxygen functional groups on its layers. X-ray photoelectron Spectroscopy (XPS) and Raman spectroscopy confirms the presence of the $sp^2$ and $sp^3$ hybridization due to the disordered crystal structures of the carbon atoms results from oxidation, and Fourier Transform Infrared spectroscopy (FTIR) and XPS analysis shows the changes in oxygen functional groups with nature of substrate. Moreover, the photoluminescent (PL) peak emission wavelength varies with substrate and the broad energy level distribution produces excitation dependent PL emission in a broad wavelength ranging from 400 to 650 nm. The structural and optical properties of oxygen plasma treated GO films for possible optoelectronic applications were also investigated using various characterization techniques. HRTEM and electron diffraction analysis confirmed that the oxygen plasma treatment results short range order crystallization in GO films with an increase in interplanar spacing, which can be attributed to the presence of oxygen functional groups. In addition, Electron energy loss spectroscopy (EELS) and Raman spectroscopy confirms the presence of the $sp^2$ and $sp^3$ hybridization due to the disordered crystal structures of the carbon atoms results from oxidation and XPS analysis shows that epoxy pairs convert to more stable C=O and O-C=O groups with oxygen plasma treatment. The broad energy level distribution resulting from the broad size distribution of the $sp^2$ clusters produces excitation dependent PL emission in a broad wavelength range from 400 to 650 nm. Our results suggest that substrate influenced, or oxygen treatment GO has higher potential for future optoelectronic devices by its various optical properties and visible PL emission.

• Korean Chemical Engineering Research
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• v.51 no.2
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• pp.285-291
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• 2013

The effects of sensing materials, coating methods, diluent gases, and temperature have been studied in detail to make a quartz crystal microbalance based adsorption sensor system for detecting gases. In particular, sensor elements for detecting $NO_2$ and $SO_2$, that are known as major air pollutants, have been prepared by coating two different polymers, polypyrrole and poly(3,4-ethylenedioxythiophene). The sensor elements prepared in this work have high sensitivity and selectivity for $NO_2$ and $SO_2$ at ppm level concentrations. It was proven that the sensing characteristics and response rate of the sensing elements are highly dependent on the coating method and the loading mass of sensing materials.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.42 no.12
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• pp.27-34
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• 2005

We have investigated the correlation between the active-layer uniformity and reliability of InGaN/GaN blue LEDs. According to initial characteristics, the devices are classified into two groups: group I devices of uniform light-emission and group II devices of non-uniform light-emission. The group II devices are more dependent on temperature and we have found two degradation mechanisms through reliability test. One is bulk degradation in which the degradation occurred over the entire chip and another one is edge degradation in which the degradation occurred from the edge of the chip. Bulk degradation caused by the nonradiative defects is found to be faster in group II devices while there is no difference in the rate of the much faster edge degradation, where darkening starts from the n-Ohmic contact edge. Therefore, more uniform active layer, more uniform current spreading, and the passivation of the dry-etched side-wall are essential for the high reliability of InGaN/GaN LEDs.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.11
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• pp.1297-1303
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• 2012

In this paper, the standard procedures for measuring the moisture sorption properties of thin polymeric materials such as polyethylene terephthalate (PET) by using the thermo-gravimetric method to characterize the moisture diffusion in the polymer are presented, and the sorption properties are quantified. The moisture diffusivity and solubility are characterized to investigate the effect of temperature and humidity on the moisture sorption properties according to the Arrhenius equation. The validation of the obtained sorption properties using thermogravimetry is discussed with the measured permeability based on Fickian diffusion. The nonlinear behavior of the concentration dependent moisture diffusion is investigated experimentally, and the nonlinearity is characterized numerically for the case of having an interface with an inorganic material such as a metal. The Fickian/Non-Fickian model based on the obtained moisture sorption properties is compared and discussed.

• Journal of Microbiology and Biotechnology
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• v.24 no.8
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• pp.1096-1104
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• 2014

$\small{L}$-Asparaginase from gram-positive bacteria has been poorly explored. We conducted recombinant overexpression and purification of $\small{L}$-asparaginase from Staphylococcus sp. OJ82 (SoAsn) isolated from Korean fermented seafood to evaluate its biotechnological potential as an antileukemic agent. SoAsn was expressed in Escherichia coli BL21 (DE3) with an estimated molecular mass of 37.5 kDa, determined using sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Consistent with asparaginases in gram-negative bacteria, size-exclusion chromatography determined SoAsn as a homodimer. Interestingly, the optimal temperature of SoAsn was $37^{\circ}C$ and over 90% of activity was retained between $37^{\circ}C$ and $50^{\circ}C$, and its thermal stability range was narrower than that of commercial E. coli $\small{L}$-asparaginase (EcAsn). Both SoAsn and EcAsn were active between pH 9 and 10, although their overall pH-dependent enzyme activities were slightly different. The $K_m$ value of SoAsn was 2.2 mM, which is higher than that of EcAsn. Among eight metals tested for enzyme activity, cobalt and magnesium greatly enhanced the SoAsn and EcAsn activity, respectively. Interestingly, SoAsn retained more than 60% of its activity under 2 M NaCl condition, but the activity of EcAsn was reduced to 48%. Overall, the biochemical characteristics of SoAsn were similar to those of EcAsn, but its kinetics, cofactor requirements, and NaCl tolerance differed from those of EcAsn.

• Journal of Microbiology and Biotechnology
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• v.24 no.6
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• pp.781-787
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• 2014

2-Ketogluconic acid production by Klebsiella pneumoniae is a pH-dependent process, strictly proceeding under acidic conditions. Unfortunately, cell growth is inhibited by acidic conditions, resulting in low productivity of 2-ketogluconic acid. To overcome this deficiency, a two-stage fermentation strategy was exploited in the current study. During the first stage, the culture was maintained at neutral pH, favoring cell growth. During the second stage, the culture pH was switched to acidic conditions favoring 2-ketogluconic acid accumulation. Culture parameters, including switching time, dissolved oxygen levels, pH, and temperature were optimized for the fed-batch fermentation. Characteristics of glucose dehydrogenase and gluconate dehydrogenase were revealed in vitro, and the optimal pHs of the two enzymes coincided with the optimum culture pH. Under optimum conditions, a total of 186 g/l 2-ketogluconic acid was produced at 26 h, and the conversion ratio was 0.98 mol/mol. This fermentation strategy has successfully overcome the mismatch between optimum parameters required for cell growth and 2-ketogluconic acid accumulation, and this result has the highest productivity and conversion ratio of 2-ketogluconic and produced by microorganism.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.12
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• pp.7283-7286
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• 2014

SiOC films were prepared as insulators for displays by sputtering at low temperatures, and the relationship with the electrical properties waaas examined. The electrical properties of SiOC films were affected by the annealing process, and SiOC films annealed at 100oC showed a significant increase in thickness and a decrease in the reflective index. XRD revealed an increase in the degree of the amorphous structure. Moreover, the capacitance and leakage current of the SiOC films annealed at 100oC decreased. These characteristics of SiOC films highlight their potential as ideal insulators. Amorphous SiOC films by the reduction of polarization are dependent on the elongation effect of the bonding lengths in the structure and the thickness. The properties of these SiOC films are suitable for low temperature displays.

• Current Research on Agriculture and Life Sciences
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• v.30 no.1
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• pp.51-59
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• 2012

Fresh oyster mushrooms (Pleurotus ostreatus) were gamma-irradiated at 0, 1, 2, and 3 kGy. The effects on various quality attributes were determined during storage at $5{\pm}1^{\circ}C$. Color changes were more prominent in the cap region than the stem part. At the start of storage increase of Hunter's L-value (lightness) was observed in the caps of 2 and 3 kGy-irradiated samples. The L-value was higher in the all irradiated samples during storage. The trend was different in the case of stem region, where L-value decreased upon irradiation, but remained high throughout storage. The ${\alpha}$-value declined, whereas the b-value increased following irradiation. Irradiation showed a dose-dependent effect on the firmness, which was clearer during storage, but the samples irradiated at 1 kGy maintained an overall better texture than other irradiated samples. The weight loss was also higher in the all irradiated samples during storage. The samples irradiated at 1 kGy showed good physical appearance without any fungal attack at the end of storage; however color change in cap region was quite apparent. The ultra-structural drastic effect of irradiation was understandable using scanning electron microscopy. E-nose analysis demonstrated a clear change in the volatile profiles of all irradiated samples. Although the effect of irradiation on quality characteristics was quite clear but the all irradiated samples were free from fungal attack that was observed in the case of control sample.