• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 하계학술대회 논문집
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• pp.62-66
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• 2002

The conventional floating zone(FZ) crystal and Czochralski(CZ) silicon crystal have resistivity variations longitudinally as well as radially The resistivity variations of the conventional FZ and CZ crystal are not conformed to requirement of dopant distribution for power devices and thyristors. These resistivity variations in conventional cystals limits the reverse breakdown voltage that could be achieved and forced designers of high power diodes and thyristors to compromise the desired current-voltage characteristics. So to produce high Power diodes and thyristors, Neutron Transmutation Doping(NTD) technique is the one method just because NTD silicon provides very homogeneous distribution of doping concentration. This procedure involves the nuclear transmutation of silicon to phosphorus by bombardment of neutron to the crystal according to the reaction $^{30}$ Si(n,${\gamma}$)longrightarrow$^{31}$ Silongrightarrow(2.6 hr)$^{31}$ P+$\beta$$^{[-10]}$ . The radioactive isotope $^{31}$ Si is formed by $^{31}$ Si capturing a neutron, which then decays into the stable $^{31}$ P isotope (i.e., the donor atom), whose distribution is not dependent on the crystal growth parameters. In this research, neutron was irradiated on FZ silicon wafers which had high resistivity(1000~2000 Ω cm), for 26 and 8.3hours for samples of HTS-1 and HTS-2, and 13, 3.2, 2.0 hours for samples of IP-1, IP-2 and IP-3, respectively, to compare resistivity changes due to time differences. The designed resistivities were approached, which were 2.l Ωcm for HTS-1, 7.21 Ω cm for HTS-2, 1.792cm for IP-1, 6.83 Ωcm for IP-2, 9.23 Ωcm for IP-3, respectively. Point defects were investigated with Deep Level Transient Spectroscopy(DLTS). Four different defects were observed at 80K, 125K, 230K, and above 300K.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2010년도 하계학술대회 논문집
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• pp.313-313
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• 2010

$BiFeO_3$ (BFO), when forming a solid solution with $BaTiO_3$ (BTO), shows structural transformations over the entire compositional range, which not only gives a way to increase structural stability and electrical resistivity but also applies a means to have better ferromagnetic ordering. In this respect, we have prepared and studied 0.8 BFO-0.2 BTO thin films on Pt(111)/$TiO_2/SiO_2$/Si substrates by pulsed laser deposition. Various deposition parameters, such as deposition temperature and oxygen pressure, have been optimized to get better quality films. Based on the X-ray diffraction results, thin films were successfully deposited at the temperature of $700^{\circ}C$ and an oxygen partial pressure of 10mTorr and 330mTorr. The dielectric, ferroelectric, and magnetic properties have then been characterized. It was found that the films deposited under lower and higher oxygen pressure corresponded to lower leakage current. Magnetism measurement showed an induced ferromagnetism. The microstructures associated with the magnetic and dielectric properties of this mixed-perovskite solid solutions were observed by transmission electron microscopy, which revealed the existence of complicated ferroelectric domains, suggested that the weak spontaneous magnetization was closely associated with the decrease in the extent of rhombohedral distortion by a partial substitution of $BaTiO_3$ for $BiFeO_3$.

• JSTS:Journal of Semiconductor Technology and Science
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• 제15권5호
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• pp.526-532
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• 2015

We quantitatively investigated instability mechanisms under simultaneous positive gate and drain bias stress (SPGDBS) in self-aligned top-gate amorphous indium-zinc-oxide thin-film transistors. After SPGDBS ($V_{GS}=13V$and $V_{DS}=13V$), the parallel shift of the transfer curve into a negative $V_{GS}$ direction and the increase of on current were observed. In order to quantitatively analyze mechanisms of the SPGDBS-induced negative shift of threshold voltage (${\Delta}V_T$), we experimentally extracted the density-of-state, and then analyzed by comparing and combining measurement data and TCAD simulation. As results, 19% and 81% of ${\Delta}V_T$ were taken to the donor-state creation and the hole trapping, respectively. This donor-state seems to be doubly ionized oxygen vacancy ($V{_O}^{2+}$). In addition, it was also confirmed that the wider channel width corresponds with more negative ${\Delta}V_T$. It means that both the donor-state creation and hole trapping can be enhanced due to the increase in self-heating as the width becomes wider. Lastly, all analyzed results were verified by reproducing transfer curves through TCAD simulation.

• 한국과학교육학회지
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• 제23권2호
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• pp.176-188
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• 2003

자체 유도 현상은 고등학교의 모든 물리II 교과서에서 다뤄지고 있는 중요한 개념이다. 자체 유도 현상에 대한 설문 조사 결과, 코일로 구성된 회로에서 스위치를 열기만 하면 고압의 유도기전력이 발생한다는 과 일반화된 사고는 일반고등학교 학생뿐만 아니라 과학고등학교 학생들에서도 심각할 정도로 많이 나타난다. 자체 유도 현상에 대한 학생들의 일반화된 사고의 원인을 현행 물리II 교과서 분석을 통해 찾아볼 수 있었다. 그 결과, 특정 회로에서의 네온 전구의 점등 현상을 바탕으로 학생들의 직관적 사고에 의존한 막연한 설명이 주된 원인으로 나타났다. 자체 유도 현상에 대한 과학자적 이해를 돕기 위하여 정량적 해석을 시도 하였으며, 이를 바탕으로 학생들에게 자체 유도 현상을 효과적으로 이해시킬 수 있는 정상적인 접근 방법을 찾아보았다.

• BMB Reports
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• 제35권1호
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• pp.116-126
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• 2002

Nitric oxide (NO), synthesized from L-arginine by NO synthases, is a small, lipophilic, diffusible, highly reactive molecule with dichotomous regulatory roles in many biological events under physiological and pathological conditions. NO can promote apoptosis (pro-apoptosis) in some cells, whereas it inhibits apoptosis (anti-apoptosis) in other cells. This complexity is a consequence of the rate of NO production and the interaction with biological molecules such as metal ion, thiol, protein tyrosine, and reactive oxygen species. Long-lasting overproduction of NO acts as a pro-apoptotic modulator, activating caspase family proteases through the release of mitochondrial cytochrome c into cytosol, up-regulation of the p53 expression, and alterations in the expression of apoptosis-associated proteins, including the Bcl-2 family. However, low or physiological concentrations of NO prevent cells from apoptosis that is induced by the trophic factor withdrawal, Fas, $TNF{\alpha}$/ActD, and LPS. The anti-apoptotic mechanism is understood on the basis of gene transcription of protective proteins. These include: heat shock protein, hemeoxygenase, or cyclooxygenase-2 and direct inhibition of the apoptotic executive effectors caspase family protease by S-nitrosylation of the cysteine thiol group in their catalytic site in a cell specific way. Our current understanding of the mechanisms by which NO exerts both pro- and anti-apototic action is discussed in this review article.

• Molecules and Cells
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• 제40권12호
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• pp.906-915
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• 2017

Impairment of wound healing is a common problem in individuals with diabetes. Adiponectin, an adipocyte-derived cytokine, has many beneficial effects on metabolic disorders such as diabetes, obesity, hypertension, and dyslipidemia. C1q/TNF-Related Protein 9 (CTRP9), the closest paralog of adiponectin, has been reported to have beneficial effects on wound healing. In the current study, we demonstrate that CTRP9 regulates growth, differentiation, and apoptosis of HaCaT human keratinocytes. We found that CTRP9 augmented expression of transforming growth factor beta 1 ($TGF{\beta}1$) by transcription factor activator protein 1 (AP-1) binding activity and phosphorylation of p38 in a dose-dependent manner. Furthermore, siRNA-mediated suppression of $TGF{\beta}1$ reversed the increase in p38 phosphorylation induced by CTRP9. siRNA-mediated suppression of $TGF{\beta}1$ or p38 significantly abrogated the effects of CTRP9 on cell proliferation and differentiation while inducing apoptosis, implying that CTRP9 stimulates wound recovery through a $TGF{\beta}1$-dependent pathway in keratinocytes. Furthermore, intravenous injection of CTRP9 via tail vein suppressed mRNA expression of Ki67 and involucrin whereas it augmented $TGF{\beta}1$ mRNA expression and caspase 3 activity in skin of type 1 diabetes animal models. In conclusion, our results suggest that CTRP9 has suppressive effects on hyperkeratosis, providing a potentially effective therapeutic strategy for diabetic wounds.

• ALGAE
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• 제30권2호
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• pp.163-170
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• 2015

Tyrosinase inhibitors are an important component of cosmetic products. Our previous studies have proposed that eckol isolated from the brown alga Ecklonia cava, can be explored as a tyrosinase inhibitor. However, cellular activities and mechanism of action of eckol remain unknown. Therefore, the current study analyzed the eckol binding modes using the crystal structure of Bacillus megaterium tyrosinase. The effects of eckol on melanin synthesis induced by ${\alpha}$-melanocyte stimulating hormone in B16F10 melanoma cells were also investigated. We predicted the 3D structure of tyrosinase and used a docking algorithm to simulate binding between tyrosinase and eckol. These molecular modeling studies were successful (calculated binding energy value, $-115.84kcal\;mol^{-1}$) and indicated that eckol interacts with Asn205, His208, and Arg209. Furthermore, eckol markedly inhibited tyrosinase activity and melanin synthesis in B16F10 melanoma cells. We also found that eckol decreased the expression of tyrosinase, tyrosinase-related protein (TRP) 1, and TRP2. These results indicate that eckol is a potent inhibitor of melanogenesis, and this finding may be useful for the development of novel pharmaceutical and cosmetic agents.

• 대한의생명과학회지
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• 제20권3호
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• pp.156-161
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• 2014

It has been reported that safflower seeds have preventive effects against osteoporosis. Recently, safflower buds (SB) were found to have more useful functional ingredients than safflower seeds. In the current study, we evaluated the anti-osteoporosis effects of SB diet in ovariectomized (OVX) rats. The rats were divided into five groups; sham operated group, OVX alone group, OVX plus $17{\beta}$-estradiol ($E^2$ $10{\mu}g/kg$, i.p.) and OVX plus SB diet feeding group (0.3% or 1%). Feeding of SB diet (0.3% or 1%) to OVX rats markedly increased bone mineral density (BMD) of femurs, compared to the OVX group. The OVX rats exhibited a marked increase in trabecular separation (Tb.Sp) and this change was inhibited by the feeding of SB diet, similar to that seen with OVX+E2 group. Moreover, feeding of SB diet to OVX rats decreased the markers of bone turnover, including osteocalcin and alkaline phosphatase (ALP). These results suggest that SB extract has a bone sparing effect in OVX-induced trabecular bone loss and prevents deterioration of bone microarchitecture by suppressing the rate of bone turnover. Therefore, SB may be useful for preserving bone mass and structure in estrogen deficient women with a potential role in reducing postmenopausal osteoporosis.

• 동의생리병리학회지
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• 제23권4호
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• pp.799-804
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• 2009

Kamikaekyuk-tang(KMKKT), a formula of ten Oriental herbs, was orientally designed to promote vital energy, to remove blood stasis, and to decrease inflammation for treating cancers. KMKKT and its component had potent antiandrogen and androgen receptor activities in prostate cancer and also inhibited angiogenesis induced by basic fibroblast growth factor (bFGF) in human umbilical vein endothelial cells and suppressed the tumor growth in LLC-bearing mice, and liver metastasis of colon 26-L5 cancer cells, suggesting a potent cancer preventive agent. Nevertheless, there is no safety study of KMKKT before clinical trial so far. Thus, in the current study, we investigated the toxicity about ethanol-extracted KMKKT. Male and female Spraque Dawley (SD) rats were given orally by KMKKT at 250, 500, and 1000 mg/kg for 4 weeks. Mortality, clinical signs and measured change of body weight, food consumption and water consumption were observed. In addition, we performed ophthalmologic, urinary, hematological, blood serum biochemical and histopathological examination. Any general toxicity was not found in KMKKT treated group. Also, there were no significant differences in the parameters such as body weight, food consumption and water consumption, a lot of urine and blood factor levels except WBC, MCHC and Ca level compared with control group. Although WBC and MCHC were elevated in female rats and Ca level was decreased in male rats, these were within normal ranges. Finally, we determined that maximum tolerated dose (MTD) was 1000 mg/kg and no observed adverse effect level (NOAEL) was 500 mg/kg. Taken together, these results demonstrated that KMKKT is very safe to SD rats.

• Biomolecules & Therapeutics
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• 제24권2호
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• pp.171-177
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• 2016

Statins, HMG-CoA reductase inhibitors, are known to cause serious muscle injuries (e.g. myopathy, myositis and rhabdomyolysis), and these adverse effects can be rescued by co-administration of coenzyme $Q_{10}$ ($CoQ_{10}$) with statins. The goal of the current research is to assess the efficacy of combined treatment of $CoQ_{10}$ with Atorvastatin for hyperlipidemia induced by high-fat diet in SD rats. 4-week-old Sprague-Dawley male rats were fed normal diet or high-fat diet for 6 weeks. Then, rats were treated with either Statin or Statin with various dosages of $CoQ_{10}$ (30, 90 or 270 mg/kg/day, p.o.) for another 6 weeks. Compared to Statin only treatment, $CoQ_{10}$ supplementation significantly reduced creatine kinase and aspartate aminotransferase levels in serum which are markers for myopathy. Moreover, $CoQ_{10}$ supplementation with Statin further reduced total fat, triglycerides, total cholesterol, and low-density lipoprotein-cholesterol. In contrast, the levels of high-density lipoprotein-cholesterol and $CoQ_{10}$ were increased in the $CoQ_{10}$ co-treated group. These results indicate that $CoQ_{10}$ treatment not only reduces the side effects of Statin, but also has an anti-obesity effect. Therefore an intake of supplementary $CoQ_{10}$ is helpful for solving problem of obese metabolism, so the multiple prescription of $CoQ_{10}$ makes us think a possibility that can be solved in being contiguous to the obesity problem, a sort of disease of the obese metabolism.