• 대한전기학회:학술대회논문집
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• 대한전기학회 1997년도 추계학술대회 논문집 학회본부
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• pp.311-313
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• 1997

The effects of porosity on the pressureless sintered $\beta$-SiC-$ZrB_2$ composites with $Al_2O_3$ additions(4, 8, 12wt.%) under argon atmosphere were investigated. Relative density of $\beta$-SiC-$ZrB_2$ composites were decreased with the $Al_2O_3$ content. The relative density and fracture toughness of $\beta$-SiC-$ZrB_2$ with 4wt% $Al_2O_3$ are 93.2%, $1.323MPa{\cdot}m^{1/2}$ respectively. The Vicker's hardness and flexural strength of $\beta$-SiC-$ZrB_2$ with 12wt.% $Al_2O_3$ are 0.492GPa, 261MPa respectively. Fracture toughness of $\beta$-SiC-$ZrB_2$ composites are directly proportional to relative density.

• 농업과학연구
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• 제46권2호
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• pp.369-379
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• 2019

Alzheimer's disease (AD) is the most common neurodegenerative disease associated with age, and amyloid beta ($A{\beta}$) is known to cause Alzheimer's disease. In the present study, we investigated the protective effects of Cirsium japonicum var. maackii extract and its fractions against $A{\beta}$-induced neurotoxicity in C6 glial cells. The cells treated with $A{\beta}_{25-35}$ showed a decrease in cell viability and an increase in reactive oxygen species (ROS) production compared with the non-treated cells. However, the cells treated with the C. japonicum var. maackii extract and its fractions increased the cell viability and inhibited the $A{\beta}$-induced ROS production. These results demonstrate the neuroprotective effects of C. japonicum var. maackii against $A{\beta}$. To further examine the protective mechanism, we measured inflammation and apoptosis related protein expressions. The cells treated with extract and fractions from C. japonicum var. maackii down-regulated inflammatory related proteins such as cyclooxygenase-2, interleukin $(IL)-1{\beta}$, and IL-6, and attenuated apoptosis related proteins including B-cell lymphoma-2 (Bcl-2) associated X protein/Bcl-2 ratio. In particular, the ethanol and ethylacetate fraction exhibited higher inhibitory effect against ROS production and apoptosis-related protein expressions among the extract and the other fractions. Therefore, this study demonstrated the protective effects of C. japonicum var. maackii extract and its fractions against $A{\beta}$-induced neurotoxicity in C6 glial cells through the regulation of oxidative stress, inflammation, and apoptosis, suggesting that it might have potential as a therapeutic for AD.

• Nuclear Medicine and Molecular Imaging
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• 제41권2호
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• pp.112-117
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• 2007

Imaging distribution of ${\beta}-amyloid$ plaques in Alzheimer's disease is very important for early and accurate diagnosis. Early trial of the ${\beta}-amyloid$ plaques includes using radiolabeled peptides which can be only applied for peripheral ${\beta}-amyloid$ plaques due to limited penetration through the blood brain barrier (BBB). Congo red or Chrysamine G derivatives were labeled with Tc-99m for imaging ${\beta}-amyloid$ plaques of Alzheimer patient's brain without success due to problem with BBB penetration. Thioflavin T derivatives gave breakthrough for ${\beta}-amyloid$ imaging in vivo, and a benzothiazole derivative [C-11]6-OH-BTA-1 brought a great success. Many other benzothiazole, benzoxazole, benzofuran, imidazopyridine, and styrylbenzene derivatives have been labeled with F-18 and I-123 to improve the imaging quality. However, [C-11]6-OH-BTA-1 still remains as the best. However, short half-life of C-11 is a limitation of wide distribution of this agent. So, it is still required to develop an Tc-99m, F-18 or I-123 labeled agent for ${\beta}-amyloid$ imaging agent.

• 한국환경보건학회:학술대회논문집
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• 한국환경보건학회 2005년도 국제학술대회
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• pp.341-344
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• 2005

The expression of the glutathione S-transferase (GST), whose induction accounts for antioxidant defense system, is regulated by activation of CCAAT/enhancer binding protein ${\beta}$ ($C/EBP{\beta}$), Sick house syndrome (SHS) presents healthy damage owing to the indoor environment of a building. Toluene has been implicated in one of the important causes of SHS. The present study investigated the effects of toluene treatment on the induction of GSTA2 gene and its mechanism. H411E cells treated with toluene, and GSTA2 expression was determined by immunoblot analysis. The translocation of $C/EBP{\beta}$ was assessed by immunocytochemical assays. $C/EBP{\beta}$ DNA binding activity was determined by electrophoretic mobility shift assays. The role of the C/EBP binding site in the induction of the GSTA2 gene was assessed by luciferase reporter-gene activity. Toluene induced GSTA2 protein expression. In toluene-treated cells, $C/EBP{\beta}$ translocated to the nucleus and bound to the consensus sequence of C/EBP (TTGCGCAA). Toluene treatment increased luciferase reporter-gene activity in cells transfected with the C/EBP-containing regulatory region of the GSTA2 gene. Oxidative stress is believed to play an important role in the induction of GSTA2 gene by toluene This study shows that toluene-induced GSTA2 gene expression is dependent upon nuclear translocation and binding of $C/EBP{\beta}$ to the C/EBP response element in the GSTA2 gene promoter.

• Food Science and Biotechnology
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• 제15권3호
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• pp.437-440
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• 2006

To explore the possible usefulness of ${\beta}$-glucans as natural antioxidants, the antioxidant profiles of ${\beta}$-glucan, extracted from Saccharomyces cerevisiae KCTC 7911, and water soluble and insoluble mutant ${\beta}$-glucan, isolated from yeast mutant S. cerevisiae IS2, were examined by five different in vitro evaluation methods: lipid peroxidation value (POV), nitric oxide (NO), 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical, reducing power, and ${\beta}$-carotene diffusion assay. The antioxidant activities of all ${\beta}$-glucans evaluated in POV test were comparable to or better than that of the known antioxidant, vitamin C. Remarkably, the ${\beta}$-glucan and water insoluble mutant ${\beta}$-glucan possessed 2.5-fold more potent activity than vitamin C at a dosage of 2 mg. Although vitamin C showed 100-fold greater activity than all ${\beta}$-glucans in NO and DPPH tests for measuring the radical scavenging capacity, all ${\beta}$-glucans revealed higher radical scavenging activity than the known radical scavenger, N-acetyl-L-cysteine (NAC), in DPPH test. The water insoluble mutant ${\beta}$-glucan had 2.6- and 5-fold greater antioxidative activity than water soluble ${\beta}$-glucan in NO and DPPH tests, respectively, showing that all ${\beta}$-glucans were able to scavenge radicals such as NO or DPPH. While all ${\beta}$-glucans revealed lower antioxidant profiles than vitamin C in both reducing power activity and ${\beta}$-carotene agar diffusion assay, the ${\beta}$-glucan and water insoluble mutant ${\beta}$-glucan did show a marginal reducing power activity as well as a considerable ${\beta}$-carotene agar diffusion activity. These results confirmed the potential usefulness of these ${\beta}$-glucans as natural antioxidants.

• 한국세라믹학회지
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• 제30권1호
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• pp.46-54
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• 1993

$\beta$-SiC was chemically vapor deposited by pyrolysis of MTS＋H2 gas mixture. The experiments were conducted in the temperature range of 1100~150$0^{\circ}C$ with a r.f. induction furnace under atmospheric pressure. The IR, XRD, EDS and AES analysis revealed that the free Si was always codeposited with SiC below 140$0^{\circ}C$, regardless of the total flow rate and MTS concentration, whereas $\beta$-SiC single phase was deposited at 150$0^{\circ}C$. C3H8 or CH2Cl2 as an excess C sources, was supplied with MTS in order to obtain stoichiometric SiC at low temperature. With the addition of C3H8 or CH2Cl2, the deposition rate was increased and $\beta$-SiC single phase could be deposited even at temperature as low as 110$0^{\circ}C$. In the absence of C3H8 or CH2Cl2, the microhardness of the layer was quite low (

• 한국식품영양과학회지
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• 제21권1호
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• pp.54-59
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• 1992

Lactobacillus acidophilus를 이용한 배추김치 제조 연구의 일환으로 이 균이 생성하는, 김치의 연화와 밀접한 관련이 있는 효소의 하나인 ${\beta}-galactosidase\;({\beta}-Galase)$의 성질을 균체내외 효소로 구분하여 조사하였다. Gel여과법에 의하여 측정한 균체내외 ${\beta}-Galase$의 개략적인 분자량은 각각 550,000 및 740,000 dalton이었으며 $K_{m}$값은 각각 1.67mg/ml 및 1.33mg/ml $V_{max}$은 각각 $8.5{\mu}mol/mg/30min$ 및 $2.65{\mu}\;mol/ml/30min$이었다. 최적 pH는 균체내 효소의 경우는 7, 균체외 효소는 8이었으며 최적온도는 다같이 $30^{\circ}C$ 최적 소금농도는 $4{\sim}5%$이었다. ${\beta}-Galase$의 열에 대한 안정성은 $60^{\circ}C$에서 $90^{\circ}C$로 온도가 높아질수록 그리고 열처리 시간이 길어질수록 감소하였는데 최초 열처리 2분간의 감소율이 가장 높았다.

• Natural Product Sciences
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• 제2권1호
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• pp.9-13
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• 1996

Three new withanolides, designated as withatatulins B, C, and D, were isolated from the fresh flowers of Datura tatula Linn. Detailed spectral analysis of these compounds permitted advancement of their structures respectively, as $5{\beta},6{\beta}-epoxy-12{\beta}$,21-dihydroxy-1-oxo-witha-2,24-dienolide (2), $6{\beta},12{\beta},21-trihydroxy-1-oxowitha$ 2, 4,24-trienolide (3) and $5{\beta},6{\beta},12{\beta}$,21-tetrahydroxy-1-oxo-witha-2,24-dienolide (4a). Withanolides with oxygen functions both at 12 and 21-positions are rare and first reported from Datura species.

• Biomolecules & Therapeutics
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• 제24권6호
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• pp.623-629
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• 2016

(1S,2S,3E,7E,11E)-3,7,11,15-cembratetraen-17,2-olide (LS-1), a marine cembrenolide diterpene, has anticancer activity against colon cancer cells such as HT-29, SNU-C5/5-FU (fluorouracil-resistant SNU-C5) and SNU-C5. However, the action mechanism of LS-1 on SNU-C5 human colon cancer cells has not been fully elucidated. In this study, we investigated whether the anticancer effect of LS-1could result from apoptosis via the modulation of $Wnt/{\beta}$-catenin and the TGF-${\beta}$ pathways. When treated with the LS-1, we could observe the apoptotic characteristics such as apoptotic bodies and the increase of sub-G1 hypodiploid cell population, increase of Bax level, decrease of Bcl-2 expression, cleavage of procaspase-3 and cleavage of poly (ADP-ribose) polymerase in SNU-C5 cells. Furthermore, the apoptosis induction of SNU-C5 cells upon LS-1 treatment was also accompanied by the down-regulation of $Wnt/{\beta}$-catenin signaling pathway via the decrease of GSK-$3{\beta}$ phosphorylation followed by the decrease of ${\beta}$-catenin level. In addition, the LS-1 induced the activation of TGF-${\beta}$ signaling pathway with the decrease of carcinoembryonic antigen which leads to decrease of c-Myc, an oncoprotein. These data suggest that the LS-1 could induce the apoptosis via the down-regulation of $Wnt/{\beta}$-catenin pathway and the activation of TGF-${\beta}$ pathway in SNU-C5 human colon cancer cells. The results support that the LS-1 might have potential for the treatment of human colon cancer.

• 대한수학회논문집
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• 제33권3호
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• pp.787-798
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• 2018

For $1{\leq}p{\leq}{\infty}$, let $H^p$ be the usual Hardy space on the unit circle. When ${\alpha}$ and ${\beta}$ are bounded functions, a singular integral operator $S_{{\alpha},{\beta}}$ is defined as the following: $S_{{\alpha},{\beta}}(f+{\bar{g}})={\alpha}f+{\beta}{\bar{g}}(f{\in}H^p,\;g{\in}zH^p)$. When p = 2, we study the hyponormality of $S_{{\alpha},{\beta}}$ when ${\alpha}$ and ${\beta}$ are some special functions.