• Journal of Microbiology and Biotechnology
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• v.30 no.2
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• pp.196-205
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• 2020

In this study, the acidic lipase from Aspergillus niger (ANL) was homologously expressed in A. niger. The expression of ANL was significantly improved by the expression of the native ANL with the introns, the addition of the Kozak sequence and the optimization of the signal sequences. When the cDNA sequence of ANL fused with the glaA signal was expressed under the gpdA promoter in A. niger, no lipase activity could be detected. We then tried to improve the expression by using the full-length ANL gene containing three introns, and the lipase activity in the supernatant reached 75.80 U/ml, probably as a result of a more stable mRNA structure. The expression was further improved to 100.60 U/ml by introducing a Kozak sequence around the start codon due to a higher translation efficiency. Finally, the effects of three signal sequences including the cbhI signal, the ANL signal and the glaA signal on the lipase expression were evaluated. The transformant with the cbhI signal showed the highest lipase activity (314.67 U/ml), which was 1.90-fold and 3.13-fold higher than those with the ANL signal and the glaA signal, respectively. The acidic lipase was characterized and its highest activity was detected at pH 3.0 and a temperature of 45℃. These results provided promising strategies for the production of the acidic lipase from A. niger.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.11a
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• pp.120-120
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• 2006

탄소나노튜브는 nm급의 크기에 높은 전기전도도, 열전도 효율, 감한 기계적 강도 등의 장점을 가지며, FED(Field Emission Display), 극미세 전자 스위칭 소자, SET(Single Electron Transistor), AFM(Atomic Force Microscope) tip등 여러 분야로의 응용을 연구하고 있다. 본 연구에서는 탄소나노튜브를 Si 웨이퍼 위에 Ni/Ti 금속층을 촉매층으로 사용하고, 암모니아($NH_3$)가스와 아세틸렌 ($C_2H_2$)가스를 각각 희석가스와 성장원으로 사용하여 합성하였다. 탄소나노튜브의 성장은 Hot filament 화학기상증측(HFPECVD) 방식을 사용하였으며, 이 방법은 다량의 합성, 높은 균일성, 좋은 정렬 특성등의 장점을 가진다. 성장 온도는 탄소나노튜브의 성장 특성을 변화시키는 중요한 요소이다. 성장 온도에 따라 수직적 성장, 성장 밀도등의 특성 변화를 관찰하였다. 성장된 탄소나노튜브층 성분 분석은 에너지 분산형 X-선 측정기(EDS)를 통해 관찰하였고, 끝단에 촉매층이 존재하는 30~50 nm 폭을 가진 다중벽 탄소나노튜브를 고배율 투과전자현미경(HRTEM) 분석을 통해 관찰하였다. 전계방사 주사전자현미경(FESEM) 분석을 동해 1~3${\mu}m$의 길이를 가진 탄소나노튜브가 높은 밀도로 성장된 것을 확인하였다.

• Journal of Radiation Protection and Research
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• v.41 no.2
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• pp.81-86
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• 2016

Background: For positron emission tomography (PET) application, cadmium zinc telluride (CZT) has been investigated by several institutes to replace detectors from a conventional system using photomultipliers or Silicon-photomultipliers (SiPMs). The spatial and energy resolution in using CZT can be superior to current scintillator-based state-of-the-art PET detectors. CZT has been under development for several years at the Korea Atomic Energy Research Institute (KAERI) to provide a high performance gamma ray detection, which needs a single crystallinity, a good uniformity, a high stopping power, and a wide band gap. Materials and Methods: Before applying our own grown CZT detectors in the prototype PET system, we investigated preliminary research with a developed discrete type data acquisition (DAQ) system for coincident events at 128 anode pixels and two common cathodes of two CZT detectors from Redlen. Each detector has a $19.4{\times}19.4{\times}6mm^3$ volume size with a 2.2 mm anode pixel pitch. Discrete amplifiers consist of a preamplifier with a gain of $8mV{\cdot}fC^{-1}$ and noise of 55 equivalent noise charge (ENC), a $CR-RC^4$ shaping amplifier with a $5{\mu}s$ peak time, and an analog-to-digital converter (ADC) driver. The DAQ system has 65 mega-sample per second flash ADC, a self and external trigger, and a USB 3.0 interface. Results and Discussion: Characteristics such as the current-to-voltage curve, energy resolution, and electron mobility life-time products for CZT detectors are investigated. In addition, preliminary results of gamma ray imaging using 511 keV of a $^{22}Na$ gamma ray source were obtained. Conclusion: In this study, the DAQ system with a CZT radiation sensor was successfully developed and a PET image was acquired by two sets of the developed DAQ system.

• Bulletin of the Korean Chemical Society
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• v.25 no.5
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• pp.687-693
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• 2004

Composite membranes with a titania layer were prepared by soaking-rolling method with the titania sol of nanoparticles formed in the sol-gel process and investigated regarding the vapor permeation of various organic mixtures. The support modification was conducted by pressing $SiO_2$ xerogel of 500 nm in particle size under 10 MPa on the surface of a porous stainless steel (SUS) substrate and designed the multi-layered structure by coating the intermediate layer of ${\gamma}-Al_2O_3$. Microstructure of titania membrane was affected by heat-treatment and synthesis conditions of precursor sol, and titania formed at calcination temperature of 300$^{\circ}C$ with sol of [$H^+$]/[TIP]=0.3 possessed surface area of 210 $m^2$/g, average pore size of 1.25 nm. The titania composite membrane showed high $H_2/N_2$ selectivity and water/ethanol selectivity as 25-30 and 50-100, respectively. As a result of vapor permeation for water-alcohol and alcohol-alcohol mixture, titania composite membrane showed water-permselective and molecular-sieve permeation behavior. However, water/methanol selectivity of the membrane was very low because of chemical affinity of permeants for the membrane by similar physicochemical properties of water and methanol.

• Journal of the Korean Ceramic Society
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• v.40 no.12
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• pp.1170-1176
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• 2003

We developed an evolutionary optimization process involving a genetic algorithm and combinatorial chemistry (combi-chem), which was tailored exclusively for tile development of LED phosphors with a high luminescent efficiency, when excited by soft ultra violet irradiation. The ultimate goal of our study was to develop oxide red phosphors, which are suitable for three-band white Light Emitting Diodes (LED). To accomplish this, a computational evolutionary optimization process was adopted to screen a Eu$^{3+}$-doped alkali earth borosilicate system. The genetic algorithm is a well-known, very efficient heuristic optimization method and combi-chem is also a powerful tool for use in an actual experimental optimization process. Therefore the combination of a genetic algorithm and combi-chem would enhance the searching efficiency when applied to phosphor screening. Vertical simulations and an actual synthesis were carried out and promising red phosphors for three-band white LED applications, such as Eu$_{0.14}$Mg$_{0.18}$Ca$_{0.07}$Ba$_{0.12}$B$_{0.17}$Si$_{0.32}$O$_{\delta}$, were obtained.

• Korean Membrane Journal
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• v.8 no.1
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• pp.21-30
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• 2006

A faujasite NaY zeolite membrane was prepared on a tubular ${\alpha}-Al_2O_3$ support by the secondary growth process, and effects of permeation test conditions on the $CO_2/N_2$ separation were investigated. A NaY zeolite membrane with good $CO_2/N_2$ separation was successfully synthesized by using the hydrothermal solution ($Al_2O_3:SiO_2:Na_2O:H_2O$ = 1:6:14:840 in a molar base): at a permeation temperature of $30^{\circ}C$, its $CO_2$ permeance and $CO_2/N_2$ separation factor were $2.5{\times}10^{-7}mol/m^2secPa$ and 34, respectively. The $CO_2$ and $N_2$ permeations were highly dependent on permeation test conditions (feed composition, feeding rate, feed pressure, He sweeping rate and permeation temperature). The results indicated that (i) $CO_2$ and $N_2$ permeations through NaY zeolite membrane are governed by surface and micropore diffusions, respectively, (ii) the preparation of NaY zeolite membrane with a large permeating area is one of the most difficult hurdles for its real applications, and (iii) the retardation of $N_2$ permeation is an effective key to improve $CO_2/N_2$ separation factor in NaY zeolite membrane.

• Journal of Science Education
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• v.33 no.1
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• pp.111-121
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• 2009

The purpose of this research is to survey elementary pre-service teachers' in understand the legal Units, focusing on seven basic unit such a 'm', 'm2', 'L', 'kg', 'K', 'cd', 's'. This study specifically investigates whether the students understand the legal units. The subjects were 1096 students from the University of Education in Jinju, Gyeongnam. Data was collected through a questionnaire which was designed by this research and checked by authority, and the frequency and percentage of responses to each question were obtained and analysed. The survey was the legal units on interesting, using the experience of confusing and understanding of elementary pre-service teachers. The Korea Government is regulating using traditional measures such as 'pyeong' or 'don' in commercial transactions change to adopt the metric system for as a subsidiary the first of July, 2007. The interesting of the legal units dose not exceed a positive answer to the question 52.1%. Their were answered that the experience of the confused of 60.1% in the life. How to do efforts for the settle down of the legal units that answered broadcasting>in class>a campaign>study and training by an academic year in oder. Findings show regardless of academic year, gender and from the department of liberal arts or the science department all the students knew very well that 'm' '$m^2$', 'L', 'kg' are included in the legal units, compared to the others low percentage of 'K', 'cd' and 's' the legal units. In case of time(s), women has correct answered 2.7 times than man. In case of academic year, except for the third-year students was not to exceed 50%. In case of from the department of liberal arts or the science department contrary to one's expectations increase of 50% or more correct answer while half the students scored in science. The elementary pre-service teachers are seems to thinking separate the legal units with their in university life. Also elementary pre-service teachers are the lack of interest on society. Their should be for settle down of the legal units through learning to class in university, newspapers, strengthen publicity activities of broadcast media's further more by maintenance efforts of the government.

• Economic and Environmental Geology
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• v.50 no.4
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• pp.257-266
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• 2017

Batch experiments were performed to develop the method for the pH reduction of recycled aggregate by using $scCO_2$ (supercritical $CO_2$), maintaining the pH of extraction water below 9.8. Three different aggregate types from a domestic company were used for the $scCO_2$-water-recycled aggregate reaction to investigate the low pH maintenance of aggregate during the reaction. Thirty five gram of recycled aggregate sample was mixed with 70 mL of distilled water in a Teflon beaker, which was fixed in a high pressurized stainless steel cell (150 mL of capacity). The inside of the cell was pressurized to 100 bar and each cell was located in an oven at $50^{\circ}C$ for 50 days and the pH and ion concentrations of water in the cell were measured at a different reaction time interval. The XRD and SEM-EDS analyses for the aggregate before and after the reaction were performed to identify the mineralogical change during the reaction. The extraction experiment for the aggregate was also conducted to investigate the pH change of extracted water by the $scCO_2$ treatment. The pH of the recycled aggregate without the $scCO_2$ treatment maintained over 12, but its pH dramatically decreased to below 7 after 1 hour reaction and maintained below 8 for 50 day reaction. Concentration of $Ca^{2+}$, $Si^{4+}$, $Mg^{2+}$ and $Na^+$ increased in water due to the $scCO_2$-water-recycled aggregate reaction and lots of secondary precipitates such as calcite, amorphous silicate, and hydroxide minerals were found by XRD and SEM-EDS analyses. The pH of extracted water from the recycled aggregates without the $scCO_2$ treatment maintained over 12, but the pH of extracted water with the $scCO_2$ treatment kept below 9 of pH for both of 50 day and 1 day treatment, suggesting that the recycled aggregate with the $scCO_2$ treatment can be reused in real construction sites.

• Journal of the Mineralogical Society of Korea
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• v.20 no.3
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• pp.193-201
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• 2007

We used $^6Li$ and $^7Li$ MAS NMR to investigate the fate and local environments of Li in the interlayer of clay minerals such as hectorite, Woming-montmorillonite, beidellite, and lepidollite at room and high ($250^{\circ}C$) temperature. Although $^6Li$ NMR spectra show narrower peaks than those of $^7Li$ NMR, S/N ratio is low and there are no obvious differences in chemical shifts suggesting that it is difficult to apply $^6Li$ NMR to have information on the local environments of Li in the clay interlayers. $^7Li$ NMR spectra, however, show changes in the peak width and quadrupole patterns providing information on the local environments of Li in the interlayer even though changes in the chemical shift are not observed. In montmorillonite, two different local environments of Li are observed; one has a narrow peak with typical quadrupole patterns whereas another has a broad peak without those of the patterns. Changes in the peak width is also observed from broad to narrow in the $^7Li$ NMR spectra for beidellite but not for hectorite at high temperature. Our results suggest that the peak width change in the broad peak is attributed to the coordination changes in the water molecules around Li which is tightly bonded on the basal oxygen of Si tetrahedra as inner-sphere complexes. The narrow peak in montmorillnoite can be assigned to the Li bended as outer-sphere complexes.

• Journal of Food Hygiene and Safety
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• v.39 no.2
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• pp.72-82
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• 2024

This study aimed to develop a scientifically and systematically standardized xylooligosaccharide analytical method that can be applied to products with various formulations. The analysis method was conducted using HPLC with Cadenza C₁₈ column, involving pre-column derivatization with 1-phenyl-3-methyl-5-pyrazoline (PMP) and UV detection at 254 nm. The xylooligosaccharide content was analyzed by converting xylooligosaccharide into xylose through acid hydrolysis. The pre-treated methods were compared and evaluated by varying sonication time, acid hydrolysis time, and concentration. Optimal equipment conditions were achieved with a mobile phase consisting of 20 mM potassium phosphate buffer (pH 6)-acetonitrile (78:22, v/v) through isocratic elution at a flow rate of 0.5 mL/min (254 nm). Furthermore, we validated the advanced standardized analysis method to support the suitability of the proposed analytical procedure such as specificity, linearity, detection limits (LOD), quantitative limits (LOQ), accuracy, and precision. The standardized analysis method is now in use for monitoring relevant health-functional food products available in the market. Our results have demonstrated that the standardized analysis method is expected to enhance the reliability of quality control for healthy functional foods containing xylooligosaccharide.