• Proceedings of the Materials Research Society of Korea Conference
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• 2012.05a
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• pp.105.1-105.1
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• 2012

고온가압소결으로 제조된 SiCf/SiC 복합체는 부식과 침식에 강하고 우수한 열적 성질과 고온에서의 높은 기계적 강도를 유지하는 장점을 가진 복합체다. 복합체의 파괴인성은 섬유와 기지 사이에 존재하는 열분해탄소 (PyC) 계면층에 의해 큰 영향을 받는데, 고온가압소결중 첨가되는 소결조제 ($Y_2O_3$, MgO, $Al_2O_3$)와 반응하여 계면이 손상되어 복합체의 기계적 특성치가 낮아지는 결과를 보였다. 본 연구에서는 계면의 손상을 보호하고자 PyC 계면상 위에 SiC 층을 증착하였는데 계면층과 SiC 층의 증착은 화학기상 증착법(CVD)을, 기지채움 공정은 전기영동법(EPD)과 고온가압소결방법(Hot Pressing)을 이용하여 복합체를 제조하였다. Tyranno-SA 섬유에 소스가스인 메탄을 열분해 하여 200nm 두께로 PyC 계면상을 증착하고, 두께를 달리하여 보호층으로써의 SiC 층을 single 과 double layer로 증착하였다. SiC 나노분말과 소결 첨가제인 $Y_2O_3$, $Al_2O_3$, MgO를 첨가한 슬러리를 전기영동법(EPD)을 이용하여 섬유내부에 슬러리를 함침시켰고, 이러한 프리폼을 $1750^{\circ}C$/20MPa의 조건으로 고온 가압소결 하여 $SiC_f$/SiC 복합체를 제조하였다. 이렇게 single layer와 double layer로 제조된 $SiC_f$/SiC 복합체에 대해 밀도와 미세구조를 관찰하였고, 기계적 특성을 비교하여 보호층으로써의 SiC 증착효과를 고찰하고자 하였다.

• Journal of the Korean Society of Food Science and Nutrition
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• v.15 no.2
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• pp.158-164
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• 1986

Polyphenol oxidase in apple (Golden Delicious) was extracted, partially purified and its properties were found as follows; Polyphenol oxidase showed optimum pH for activity at 6.5 and optimum temperature at $30^{\circ}C$ and high affinity to o-diphenol compounds. Cysteine, ascorbic acid and sodium metabisulfite appeared to be most effective inhibitors. EDTA showed a slight inhibition. During the enzyme was kept in test tube at $4^{\circ}C\;and\;20^{\circ}C$ for a week, polyphenol oxidase activity decreased sharply during the first four days at $20^{\circ}C$, then decreased slowly as the storage was prolonged. At $4^{\circ}C$, the polyphenol oxidase activity appeared to be relatively stable during the first two days before activity began to decline sharply. Polyacrylamide disc gel electrophoresis indicated four bands with polyphenol oxidase activity. Three bands and one band of the active bands were observed after heating for 1hr at $60^{\circ}C\;and\;70^{\circ}C$ respectively. The enzyme activity was observed 40% after treatment at $60^{\circ}C$ and 5% after treatment at $70^{\circ}C$. Therefore, no difference in the thermal stability was observed between active bands and the enzyme activity.

• Korean Journal of Food Science and Technology
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• v.53 no.1
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• pp.1-11
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• 2021

In this review, recent foodborne outbreaks caused by viruses in the Republic of Korea (2010-2019) were analyzed. The human norovirus was found to be the major foodborne virus causing an average of 94.9% of the viral outbreaks. Reverse-transcription polymerase chain reaction (PCR) with electrophoresis has been widely used to detect viruses, but several rapid detection methods, including real-time PCR, multiplex PCR, and quantum dot assay, have also been suggested. For norovirus inactivation studies, surrogates such as murine norovirus and feline calicivirus have been widely used to identify the reduction rate owing to the limitations in laboratory cultivation. Conversely, direct cell infection studies have been conducted for other foodborne viruses such as adenovirus, astrovirus, rotavirus, and hepatitis A or E virus. Moreover, virucidal mechanisms using various physical and chemical treatments have been revealed. These recent studies suggest that rapid in situ detection and effective control are valuable for ensuring food safety against viral infections.

• Journal of Animal Science and Technology
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• v.49 no.1
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• pp.129-136
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• 2007

This study was performed to determine the protein profiles using sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and Angiotensin-I-converting enzyme(ACE) inhibitory activity (IC50) as affected by the various meat cuts, digestion times with pepsin. Hydrolysates having the protein concentration of 10 ug/mL had approximately 36∼39% ACE inhibitory activities, regardless of meat cut and digestion time. Protein concentration and ACE inhibitory activity of the diluted hydrolysate increased after 1-hr digestion. In original hydrolysates, ACE inhibitory activities of loin had higher than those of round (P<0.05). In addition, non-heated hydrolysates had higher ACE inhibitory activities than heated counterparts. When myosin B was digested by pepsin more than 1 hr, improved ACE inhibitory activities were observed as compared to the non-digested control.

• Applied Biological Chemistry
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• v.35 no.6
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• pp.479-484
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• 1992

This study was undertaken to determine the effects of cultural conditions on cell growth and casein hydrolysis for cell production in order to add Micrococcus sp. LL3 as a potential agent for industrial application with aim of shortening ripening period and improving flavor. Optimum temperature for cell growth and caseinolysis was $30^{\circ}C$ and $37{\circ}C$, respectively, and optimum pH was 7.0. The enzyme remained stable up to $50^{\circ}C$. Hydrolysis patterns of casein were also observed on SDS-PAGE. Both ${\alpha}-casein$ and ${\beta}-casein$ were totally hydrolysed by enzymes from Micrococcus sp. LL3 during culture. A preferential attack on ${\beta}-casein$ was observed. Production of aminopeptidase which cleaved polypeptides was the highest in early stationary phase during cell growth.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.162-162
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• 2010

InAs 는 광전자 및 광통신 소자에 널리 이용되는 $In_xGa_{1-x}As_yP_{1-y}$ 화합물의 endpoint 로서, Heterojunction Field-Effect Transistors (HEMTs), Heterojunction Bipolar Transistor (HBT) 등에 중요하게 이용되고, 다양한 소자의 기판으로도 폭넓게 사용되는 물질이다. InAs 의 반도체 소자로의 응용을 위해서는 정확한 광 특성과 밴드갭 값들이 필수적이며, 분광타원편광분석법(ellipsometry) 을 이용한 상온 InAs 유전율 함수는 이미 정확히 알려져 있다. 그러나 상온에서는 $E_2$ 전이점 영역에서 여러 개의 밴드갭들이 중첩되어 있어, 밴드구조계산 등에 필수적인 InAs의 전이점을 정확히 정의하기 어렵다. 또한, 현재의 산업계에서 중요하게 여겨지는 실시간 모니터링을 위해서는 증착온도에서의 유전율 함수 데이터베이스가 필수적이다. 이와 같은 필요성에 의해, 22 K - 700 K 의 온도범위에서 InAs 의 유전율 함수와 밴드갭 에너지에 대한 연구를 수행하였다. InAs bulk 기판을 methanol, acetone, DI water 등으로 세척 한 뒤, 저온 cryostat 에 부착하였다. 분광타원분석법은 표면의 오염에 매우 민감하기 때문에, 저온에서의 응결 방지를 위해 고 진공도를 유지하며, 액체 헬륨으로 냉각하였다. 0.7 - 6.5 eV 에너지 영역에서 측정이 가능한 분광타원편광분석기로 측정한 결과, 온도가 증가함에 따라 열팽창과 phonon-electron 상호작용효과의 증가에 의해, 밴드갭 에너지 값의 적색 천이와 밴드갭들의 중첩을 관찰 할 수 있었다. 정확한 밴드갭 에너지 값의 분석을 위하여 2계 미분을 통한 표준 밴드갭 해석법을 적용하였으며, 22 K 의 저온에서는 $E_2$ 전이점 영역에서 중첩된 여러 개의 밴드갭들을 분리 할 수 있었다. 또한 고온에서의 연구를 통해, 실시간 분석을 위한 InAs 유전함수의 데이터베이스를 확립하였다. 본 연구의 결과는 InAs 를 기반으로 한 광전자 소자의 개발 및 적용분야와 밴드갭 엔지니어링 분야에 많은 도움이 될 것으로 예상한다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.9
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• pp.641-646
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• 2016

Soot particles generated by fossil fuel combustion normally have fractal morphology with aggregates consisting of small spherical particles. Thus, Rayleigh or Mie elastic light scattering theory is not feasible for determining the fractal properties of soot aggregates. This paper describes a detailed process for applying Rayleigh-Debye Gans (RDG) scattering theory to effectively extract the morphological properties of any nano-scale particles. The fractal geometry of soot aggregates produced from an isooctane diffusion flame was observed using ex situ transmission electron microscopy (TEM) after thermophoretic sampling. RDG scattering theory was then used to analyze their fractal morphology, and various properties were calculated, such as the diameter of individual soot particles, number density, and volume fraction. The results show indiscernible changes during the soot growth process, but a distinct decreasing trend was observed in the soot oxidation process. The fractal dimension of the soot aggregates was determined to be around 1.82, which is in good agreement with that produced for other types of fuel. Thus, it can be concluded that the value of the fractal dimension is independent of the fuel type.

• Journal of fish pathology
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• v.11 no.2
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• pp.129-136
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• 1998

In March 1997, a new rhabdovirus was isolated from moribund cultured Japanese flounder Paralichthys olivaceus in sea water tank and cage culture systems in Kyung-Nam and Chun-Nam province, Korea. At temperature $15^{\circ}C$ the virus replicated and induced cytopathic effects (CPE), which progressed to eventual cytolysis, in susceptible cell lines, including RTG-2 and EPC. The CHES-214 cell line was refractory. Virus particles were bullet-shaped and measured $70nm{\times}100$ to 150 nm in size. The isolate was sensitive to pH 3, to diethyl ether, and to heat ($50^{\circ}C$ 5 min, $60^{\circ}C$ 1 min). Viral replication was not inhibited by $10^{-4}$ M 5-iododeoxyuridine. Virus infectivity was reduced by anti-HRV (8401-H) rabbit serum, but can not reduced by antisera against infectious hematopoietic necrosis virus (IHNV), chum salmon reovirus (CSV), retrovirus of salmonid (RVS) and infectious pancreatic necrosis virus (IPNV). HRV virus antigen was detected by fluorescent antibody test (FAT) in the cytoplasm of infected EPC cell. Purified isolates virions were composed of: polymerase (L), glycoprotein (G), nucleoprotein (N) and 2 matrix proteins (M1 and M2). Based upon their relative mobilities, the estimated molecular weights of the proteins were: L, 160 kDa; G, 55 kDa; N, 45 kDa; M1, 26 kDa; and M2, 22 kDa.

• The Korean Journal of Mycology
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• v.24 no.1 s.76
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• pp.8-16
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• 1996

The ${\alpha}-amylase$ of Alternaria alternata was purified through ammonium sulfate precipitation, dialysis and Sephadex G-100 column chromatography. One single band was obtained in SDS-polyacrylamide gel electrophoresis. The optimum pH for enzyme activity was 5.0 and the enzyme activity was maintained at $3.6{\sim}7.0$pH range. The optimum temperature for ${\alpha}-amylase$ activity was $40^{\circ}C$ and 71% of the activity was still maintained until 30 min after heating at $80^{\circ}C$. The ${\alpha}-amylase$ was slightly activated by $Mn^{2+},\;Zn^{2+}\;and\;Sn^{2+}$, but inhibited by $Ba^{2+},\;Pb^{2+},\;Co^{2+}\;and\;Ag^{1+}$. The $Hg^{2+}\;and\;Ag^{2+}$ slightly inhibited the activity of the enzyme at concentrations of $10^{-3}\;and\;10^{-4}M$. The Michaelis constant $(K_m)$ to soluble starch was $6.50{\times}10^{-2}M$ and inhibition constant $(K_i)$ by the 1mM EDTA was $8.0{\times}10^{-2}M$. The inhibition of this enzyme by EDTA was competitive one.

• Journal of Food Hygiene and Safety
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• v.29 no.1
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• pp.31-39
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• 2014

Norovirus causes acute gastroenteritis in all age groups and its food poisoning outbreaks are rapidly increasing in Korea. Reverse transcription-polymerase chain reaction (RT-PCR) is most widely used for the rapid detection of foodborne viruses due to high sensitivity. However, the false positive results of RT-PCR obtained against already inactivated viruses could be a serious drawbacks in food safety area. In this study, we investigated a method to yield true positive RT-PCR results only with alive viruses. To decompose the RNA genes from dead viruses, the enzymatic treatments composed of proteinse K and Ribonuclease A were applied to the sanitized and inactivated virus particles. Another aim of this study was to quantify the efficiencies of several major sanitizing treatments using real-time RT-PCR. Feline calicivirus (FCV) that belongs to the same Caliciviridae family with norovirus was used as a surrogate model for norovirus. The initial level of virus in control suspension was approximately $10^4$ PFU/mL. Most of inactivated viruses treated with the enzymatic treatment for 30 min at $37^{\circ}C$ were not detected in RT-PCR, Quantification results to verify the inactivation efficiencies of sanitizing treatments using real-time RT-PCR showed no false positive in most cases. We could successfully develope a numerical quantification process for the inactivated viruses after major sanitizing treatments using real-time RT-PCR. The results obtained in this study could provide a novel basis of rapid virus quantification in food safety area.