• Journal of Ecology and Environment
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• 제43권4호
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• pp.376-384
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• 2019

Background: Nutrient release during litter decomposition was investigated in Vitex doniana, Terminalia avecinioides, Sarcocephallus latifolius, and Parinari curatellifolius in Makurdi, Benue State Nigeria (January 10 to March 10 and from June 10 to August 10, 2016). Leaf decomposition was measured as loss in mass of litter over time using the decay model W_t/W₀ = e-^{kd t}, while $Kd=-{\frac{1}{t}}In({\frac{Wt}{W0}})$ was used to evaluate decomposition rate. Time taken for half of litter to decompose was measured using T₅₀ = ln ²/k; while nutrient accumulation index was evaluated as $NAI=(\frac{{\omega}t\;Xt}{{\omega}oXo})$. Results: Average mass of litter remaining after exposure ranged from 96.15 g, (V. doniana) to 78.11 g, (S. lafolius) in dry (November to March) and wet (April to October) seasons. Decomposition rate was averagely faster in the wet season (0.0030) than in the dry season (0.0022) with P. curatellifolius (0.0028) and T. avecinioides (0.0039) having the fastest decomposition rates in dry and wet seasons. Mean residence time (days) ranged from 929 to 356, while the time (days) for half the original mass to decompose ranged from 622 to 201 (dry and wet seasons). ANOVA revealed highly significant differences (p < 0.01) in decomposition rates and exposure time (days) and a significant interaction (p < 0.05) between species and exposure time in both seasons. Conclusion: Slow decomposition in the plant leaves implied carbon retention in the ecosystem and slow release of CO₂ back to the atmosphere, while nitrogen was mineralized in both seasons. The plants therefore showed effectiveness in nutrient cycling and support productivity in the ecosystem.

• 한국조리학회:학술대회논문집
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• 한국조리학회 2001년도 하계정기학술세미나
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• pp.29-41
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• 2001

본 연구는 매실을 천연 항균물질로서의 이용 가능성을 검색하였다. 먼저 매실을 물과 methanol로 추출 한 extracts를 paper disc법으로 항균활성을 확인한 후 MeOH extract를 용매별로 분획한 각각의 fractions으로 paper disc법과 그 결과를 토대로 활성이 높은 fractions을 비탁법을 이용하여 농도별로 액체 배지 상에서 저해활성을 확인하였다. 변패균인 M. leteus는 매실의 EtOAc 획분과 BuOH 획분에 의해서 저해 되었고 또한 $H_2O$ 획분과 CHCl$_3$ 획분도 저해활성을 보였다. 한편 저해농도 시험에서는 BuOH 획분 100ppm 첨가 시 전혀 생육을 하지 못했다. 매실의 EtOAc 획분과 BuOH 획분은 B. cereus, B. subtilis와 S. epidrimidis에 대해서 강한 저해 활성을 보였다. 저해농도 시험에서는 B. cereus는 BuOH 획분 100ppm, B. subtilis는 EtOAc 획분 100ppm, S. epidrimidis는 EtOAc 획분 100ppm에서생육을 하지 못했다. G(-)세균은 매실성분에 의해서 저해를 받지만 G(+)세균에 비하여 저항성이 컸다. E. coli는 EtOAc 획분 500ppm에서 미약한 생육을 하엿으며 S. typhimurium는EtOAC 획분, BuOH 획분 모두 1,000ppm에서 생육을 전혀 하지 못했으며 P. vulgaris는 BuOH 획분 100ppm, V. parahaemolyticus는 BuOH 획분, EtOAc 획분 100ppm에서 전혀 생육을 하지 못하는 결과를 얻었다 한편, 효모중 S. cerevisiae IF1950은 EtOAc 획분 500ppm에서 50%의 저해를 받았으며 S. cerevisiae ATCC4105는 1,000pm의 EtOAc fr. 에서 50%의 저해를 하였다. 항곰팡이 실험에서는 A. niger에서만이 아주 미약한 저해를 보였다.

• 한국산림과학회지
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• 제19권1호
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• pp.25-31
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• 1973

1) 남서부(南西部) Mojave Desert의 식생관계(植生關係)를 동서남북(東西南北) 사면별(斜面別)로 1971년(年) 12월(月) 10일(日)부터 12일(日) 사이에 분석(分析) 비교(比較)하였다. 2) 조사지중(調査地中). Lycium andersonii가 우점종이고 다음으로 중요치(重要値)가 높은 종(種)들은 Larrea, Ephedra Franseria 등의 순서(順序)이었다. 3) 남사면(南斜面)에서의 Lycium의 중요치(重要値)는 다른 사면식물(斜面植物)보다 높아 약(約) 반(半)을 점유(占有)했다. 4) 식물상(植物相)은 지극(至極)히 단순(單純)하고 밀도(密度)가 낮아 35개(個) $1m^2$ 방형구(方形區) 중(中) 10종(種) 40개본(個本) 이내(以內)였다. 5) 사면별(斜面別) 식생(植生) 차이(差異)는 없었다. 6) 각(各) 사면별(斜面別) 중요치(重要値) 계수(係數)에 의한 군락계수(群落係數)의 비교(比較)에 의하면 87% 이상(以上)으로 거리(距離) 방향(方向)에 관계(關係)없이 이곳은 모두 같은 군총(群叢)에 속(屬)한다. 7) 본(本) 조사지(調査地)에서 공통(共通)으로 나타난 종(種)은 Lycium, Larrea, Ephedra, Franseria, Eriogonum, Yucca, Aster 등 7종(種)이다.

• 한국전기전자재료학회논문지
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• 제24권4호
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• pp.340-344
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• 2011

Thermoelectric bismuth telluride ($Bi_2Te_3$) films were deposited on $4^{\circ}$ off oriented (001) GaAs substrates using a modified metal organic chemical vapor deposition (MOCVD) system. The effects of substrate temperature on surface morphologies, crystallinity, electrical properties and thermoelctric properties were investigated. Two dimensional growth mode (2D) was observed at substrate temperature lower than $400^{\circ}C$. However, three dimensional growth mode (3D) was observed at substrate temperature higher than $400^{\circ}C$. Change of growth mechanism from 2D to 3D was confirmed with environmental scanning electron microscope (E-SEM) and X-ray diffraction analysis. Seebeck coefficients of all samples have negative values. This result indicates that $Bi_2Te_3$ films grown by modified MOCVD are n-type. The maximum value of Seebeck coefficient was -225 ${\mu}V/K$ and the power factor was $1.86{\times}10^{-3}\;W/mK^2$ at the substrate temperature of $400^{\circ}C$. $Bi_2Te_3$ films deposited using modified MOCVD can be used to fabricate high-performance thermoelectric devices.

• Journal of Ginseng Research
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• 제42권3호
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• pp.288-297
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• 2018

Background: The incidence of colorectal cancer (CRC) is increasing, with metastasis of newly diagnosed CRC reported in a large proportion of patients. However, the effect of Korean Red Ginseng extracts (KRGE) on epithelial to mesenchymal transition (EMT) in CRC is unknown. Therefore, we examined the mechanisms by which KRGE regulates EMT of CRC in hypoxic conditions. Methods: Human CRC cell lines HT29 and HCT116 were incubated under hypoxic (1% oxygen) and normoxic (21% oxygen) conditions. Western blot analysis and real-time PCR were used to evaluate the expression of EMT markers in the presence of KRGE. Furthermore, we performed scratched wound healing, transwell migration, and invasion assays to monitor whether KRGE affects migratory and invasive abilities of CRC cells under hypoxic conditions. Results: KRGE-treated HT29 and HCT116 cells displayed attenuated vascular endothelial growth factor (VEGF) mRNA levels and hypoxia-inducible $factor-1{\alpha}$ ($HIF-1{\alpha}$) protein expression under hypoxic conditions. KRGE repressed Snail, Slug, and Twist mRNA expression and integrin ${\alpha}V{\beta}6$ protein levels. Furthermore, hypoxia-repressed E-cadherin was restored in KRGE-treated cells; KRGE blocked the invasion and migration of colon cancer cells by repressing $NF-{\kappa}B$ and ERK1/2 pathways in hypoxia. Conclusions: KRGE inhibits hypoxia-induced EMT by repressing $NF-{\kappa}B$ and ERK1/2 pathways in colon cancer cells.

• 마이크로전자및패키징학회지
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• 제26권4호
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• pp.113-118
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• 2019

In this study, we investigated the growth of single-crystallinity α-Ga₂O₃ thin films on c-plane sapphire substrates using halide vapor pressure epitaxy. We also found the optimal growth conditions to suppress the phase transition of α-Ga₂O₃. Our results confirmed that the growth temperature and partial pressure of the reactive gas greatly influenced the crystallinity. The optimal growth temperature range was about 460~510℃, and the α-Ga₂O₃ thin films with the highest crystallinity were obtained at a III/VI ratio of 4. The thickness and surface morphology of the thin films was observed by scanning electron microscopy. The film thickness was 6.938 ㎛, and the full width at half maximum of the ω-2θ scan rocking curve was as small as 178 arcsec. The optical band gap energy obtained was 5.21 eV, and the films were almost completely transparent in the near-ultraviolet and visible regions. The etch pit density was found to be as low as about 6.0 × 10⁴ cm^-2.

• Bulletin of the Korean Chemical Society
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• 제25권1호
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• pp.59-62
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• 2004

The ammonium ion-selective electrodes ($NH^+_4$-ISEs) based on the tetrahydrofuran(THF)-containing-16-crown-4 derivatives,1,4,6,9,11,14,16,19-tetraoxocycloeicosane ($L^1$) and 5,10,15,20,-tetramethyl-1,4,6,9,11,14,16,19-tetraoxocycloeicosane ($L^2$), were prepared and the electrode characteristics were tested. The conditioned $NH_4^+$-ISEs (E1) based on $L^1$ with TEHP as a plasticising solvent mediator gave best results with near-Nernstian slope of 53.9 mV/decade of activity, detection limit of $10^{-4.9}$ M, and enhanced selectivity coefficients for the $NH^+_4$ ion with respect to an interfering $K^+$ ion (log $K^{pot}_{NH_4^+,K^+}$ = -1.84). This result was compared to other ammonium ionophores reported previously, for example, that of nonactin (log $K^{pot}_{NH_4^+,K^+}$ = -0.92). The proposed electrode showed no significant potential changes in the range of 3.0 < pH < 9.0.

• 한국전기전자재료학회논문지
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• 제12권1호
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• pp.44-49
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• 1999

In this study, microstructure and electrical conductivity of {(G $d_2$ $O_3$)$_{0.75}$( $Y_2$ $O_3$)$_{0.25}$}$_{x}$ (Ce $O_2$)$_{1-x}$ (0.01$\leq$x$\leq$0.25) was investigated as a function of composition x. GYO addition(x) increased the bulk density and G $d_2$ $O_3$ was found to be monoclinic at x>0.15. From the change of the lattice parameter with the addition(x), GYO solution limit for ceria was exceeded in the range of x=0.05 to 0.09. Thermal expansion coefficient(15~17$\times$10$^{-6}$ $^{\circ}C$) of GYC samples at x=0.01 to 0.07 was higher in value than that of 8YSZ(10.8$\times$10$^{-6}$ $^{\circ}C$). The electrical conductivity of GYC samples at x=0.05 showed the maximum(0.01S/cm) in value at 1073K which was 2 times higher than that of 8YSZ. The activation energy for the electrical conduction was determined to be 0.60eV in the temperature range of 1073K.3K..3K.

• 대한의용생체공학회:의공학회지
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• 제29권3호
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• pp.212-221
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• 2008

The total hip replacement (THR) has been used as the most effective way to restore the function of damaged hip joint. However, various factors have caused some side effects after the THR. Unfortunately, the success of the THR have been decided only by the proficiency of surgeons so far. Hence, It is necessary to find the way to minimize the side effect caused by those factors. The purpose of this study was to suggest the definite data, which can be used to design and choose the optimal hip implant. Using finite element analysis (FEA), the biomechanical condition of bone cement was evaluated. Stress patterns were analyzed in three conditions: cement mantle, procimal femur and stem-cement contact surface. Additionally, micro-motion was analyzed in the stem-cement contact surface. The 3-D femur model was reconstructed from 2-D computerized tomography (CT) images. Raw CT images were preprocessed by image processing technique (i.e. edge detection). In this study, automated edge detection system was created by MATLAB coding for effective and rapid image processing. The 3-D femur model was reconstructed based on anatomical parameters. The stem shape was designed using that parameters. The analysis of the finite element models was performed with the variation of parameters. The biomechanical influence of each parameter was analyzed and derived optimal parameters. Moreover, the results of FE A using commercial stem model (Zimmer's V erSys) were similar to the results of stem model that was used in this study. Through the study, the improved designs and optimal factors for clinical application were suggested. We expect that the results can suggest solutions to minimize various side effects.

• 한국표면공학회지
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• 제37권6호
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• pp.307-312
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• 2004

Extensive efforts have been made in an attempt to utilize photocatalytic properties of $TiO_2$ in visible range. $TiO_2$ and TiO-N thin films were made by the DC reactive magnetron sputtering method at $300^{\circ}C$. Various gases (Ar, $O_2$ and $N_2$) were used and Ti target was impressed by 0.6 kW-5.8 kW power range. The hysteresis phenomenon of the $TiO_2$ thin film as a function of the discharge voltage characteristic was observed to be higher as applied power increases. That of TiO-N thin film was occurred at the 5.8 kW power. The cross section and surface roughness of thin films were observed by FE-SEM and AFM. Average surface roughness of TiO-N thin film was observed as $15.9\AA$ and that of $TiO_2$ as $13.2\AA$. The crystal phases of both $TiO_2$ and TiO-N thin films were found to be anatase structure. The atomic $\beta$-N (396 eV peak in N 1s XPS) was shown in the rutile crystal of TiO-N and was considered acting as the origin of wavelength shift to the visible light.