• 생명과학회지
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• 제18권3호
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• pp.311-317
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• 2008

Pathophysiological oxidative stress results in neuronal cell death mainly due to the generation reactive oxygen species (ROS). In low oxygen situation such as hypoxia and ischemia, excessive ROS is generated. Coptidis Rhizoma (CR) is a traditional medicine used for the incipient stroke. In this report we show that CR water extracts $(1\;{\mu}g/ml)$ exhibited protective effects of neuronal cell death in a hypoxic model (2% $O_2/5%\;CO_2,\;37^{\circ}C,$ 3 hr) of cultured rat cortical cells. We further show that CR water extracts significantly reduced the intensity of green fluorescence after staining with $H_2DCF-DA$ on one hour and three days after hypoxic shock and in normoxia as well. Our results indicate that CR water extracts prevent neuronal death by suppressing ROS generation.

• The Plant Pathology Journal
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• 제40권1호
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• pp.1-15
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• 2024

The aim of this study was to isolate biocontrol bacteria that could antagonize brown rot of Dendrocalamus latiflorus, optimize the culture conditions, and develop an effective biocontrol preparation for brown rot of D. latiflorus. This study isolated a bacterium with an antagonistic effect on bamboo brown rot from healthy D. latiflorus rhizosphere soil. Morphology, molecular biology, and physiological biochemistry methods identified it as Bacillus siamensis. The following culturing media and conditions improved the inhibition effect of B. siamensis: the best culturing media were 2% sucrose, 1.5% yeast extract, and 0.7% potassium chloride; the optimal culturing time, temperature, pH, and inoculation amount were 48 h, 30℃, 6, and 20%. The optimum formula of the applying bacterial suspension was 14% sodium dodecyl benzene sulfonate emulsifier, 4% Na₂HPO₄·2H₂O, 0.3% hydroxypropyl methylcellulose thickener, and 20% B. siamensis. The pot experiment results showed the control effect of applying bacterial suspension, diluted 1,000 times is still better than that of 24% fenbuconazole suspension. The applying bacterial suspension enables reliable control of brown rot in D. latiflorus.

• Transactions on Electrical and Electronic Materials
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• 제6권6호
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• pp.245-248
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• 2005

The physical and electrical properties of polycrystalline $\beta$-SiC were studied according to different nitrogen doping concentration. Nitrogen-doped SiC films were deposited by LPCVD(1ow pressure chemical vapor deposition) at $900^{\circ}C$ and 2 torr using $100\%\;H_2SiCl_2$ (35 sccm) and $5 \%\;C_2H_2$ in $H_2$(180 sccm) as the Si and C precursors, and $1\%\;NH_3$ in $H_2$(20-100 sccm) as the dopant source gas. The resistivity of SiC films decreased from $1.466{\Omega}{\cdot}cm$ with $NH_3$ of 20 sccm to $0.0358{\Omega}{\cdot}cm$ with 100 sccm. The surface roughness and crystalline structure of $\beta$-SiC did not depend upon the dopant concentration. The average surface roughness for each sample 19-21 nm and the average surface grain size is 165 nm. The peaks of SiC(111), SiC(220), SiC(311) and SiC(222) appeared in polycrystalline $\beta$-SiC films deposited on $Si/SiO_2$ substrate in XRD(X-ray diffraction) analysis. Resistance of nitrogen-doped SiC films decreased with increasing temperature. The variation of resistance ratio is much bigger in low doping, but the linearity of temperature dependent resistance variation is better in high doping. In case of SiC films deposited with 20 sccm and 100 sccm of $1\%\;NH_3$, the average of TCR(temperature coefficient of resistance) is -3456.1 ppm/$^{\circ}C$ and -1171.5 ppm/$^{\circ}C$, respectively.

• 한국식품영양과학회지
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• 제35권2호
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• pp.231-237
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• 2006

알긴산을 선택적으로 분해하는 Bacillus licheniformis AL-577 균주가 생산하는 균체 외 효소를 정제하고 특성을 밝혔다. CM-Cellulose, DEAE-Sepharose 및 Gel 크로마토 그래프 등의 순서대로 정제하여 정제도가 약 98배 정도인 효소를 얻었다. 정제효소의 활성 최적 pH 및 온도는 5.0 및 $35^{\circ}C$이었고, pH 5.5이하와 pH 9.5이상의 반응조건에서는 불안정하였으며, $20^{\circ}C$이상의 온도에서는 불활성화가 쉽게 일어나는 효소였다. 얻어진 효소를 SDS-PAGE로 분자량을 측정한 결과 25,500 Da으로 추정되었다. NaCl 0.2 M 농도에서 최대의 활성을 나타내었고, 무첨가시에도 활성은 약간 나타내었다. $Cu^{2+},\;Fe^{2+},\;Mg^{2+},\;Zn^{2+}$ 등과 같은 2가 금속이 온에 의해서는 활성이 현저히 억제되었고, $K^+,\;Li^+$ 이온에 의해서 활성이 촉진됨을 알 수 있었다. 화학약품인 dithiothreitol 와 O-phenanthroline의 첨가로 인하여 약간의 활성 증가를 가져 왔으며 반면 EDTA, L-cysteine는 현저하게 감소하였다. 이 효소는 알긴산에만 특이적으로 작용함으로써 본 효소는 alginase 또는 alginate lyase인 것으로 판단되었다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2004년도 추계학술대회 논문집 Vol.17
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• pp.425-430
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• 2004

In this paper, in order to develop the low temperature sintering ceramics for multilayer piezoelectric transformer, PMN-PZT ceramics were manufactured with the variations of sintering times, and their microstructural, piezoelectric and dielectric properties were investigated. To manufacture multilayer piezoelectric transformer, the low temperature sintering composition is need, hence, $Li_2CO_3$ and $Bi_2O_3$ were used as sintering aids and the specimens were sintered during 30, 60, 90, 120, 150 and 180 minutes, respectively. At the specimen sintered during 90 minute, mechanical quality factor(Qm), electromechanical coupling factor(kp) and dielectric constant were showed the optimum values of 2356, 0.504 and 1266, respectively. All the specimens showed tetragonality phase, and pyrochlore phase was not shown.

• Environmental Engineering Research
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• 제23권1호
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• pp.21-27
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• 2018

Air pollution index (API) is used in Mainland China and includes only $SO_2$, $NO_2$ and $PM_{10}$. In 2016, air quality index (AQI) replaced API. AQI contains three more air pollutants (CO, $O_3$ and $PM_{2.5}$). Both the indices emphasize on the effect of a single pollutant, whereas the contributions of all other pollutants are ignored. Therefore, in the present work, a novel air quality index (NAQI), which emphasizes on all air pollutants, has been introduced for the first time. The results showed that there were 19 d (5.2%) in API, 28 d (7.7%) in AQI and 183 d (50.1%) in NAQI when the indices were more than 100. In API, $PM_{10}$ and $SO_2$ were regarded as the primary pollutants, whereas all five air pollutants in AQI were regarded as primary. Furthermore, four air pollutants (other than the CO) in NAQI were regarded as primary pollutants. $PM_{10}$, as being the primary pollutant, contributed greatly in these air quality indices, and accounted for 51.2% (API), 37.0% (AQI) and 52.6% (NAQI). The results also showed that particulate matter pollution was significantly high in Luzhou, where stricter pollution control measures should be implemented.

• Asian Journal of Atmospheric Environment
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• 제6권2호
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• pp.83-95
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• 2012

China has been a top producer and exporter of refined lead products in the world since the year 2000. After the phasing-out of leaded gasoline in the late 1990s, non-ferrous metallurgy and coal combustion have been identified as potential major sources of aerosol lead in China. This paper presents the single particle analytical results of ambient aerosol particles collected near a lead smelter using a scanning electron microscopy- energy dispersive x-ray spectroscopy (SEM-EDX). Aerosol particle samples were collected over a 24-hour period, starting from 8 pm on 31 May 2002, using a high volume TSP sampler. For this near source sample, 73 particles among 377 particles analyzed (accounting for 19.4%) were lead-containing particles mixed with other species (S, Cl, K, Ca, and/or C), which probably appeared to be from a nearby lead smelter. Lead-containing particles of less than $2{\mu}m$ size in the near source sample were most frequently encountered with the relative abundances of 42%. SEM-EDX analysis of individual standard particles, such as PbO, PbS, $PbSO_4$, $PbCl_2$, and $PbCO_3$, was also performed to assist in the clear identification of lead-containing aerosol particles. Lead-containing particles were frequently associated with arsenic and zinc, indicating that the smelter had emitted those species during the non-ferrous metallurgical process. The frequently encountered particles following the lead-containing particles were mineral dust particles, such as aluminosilicates (denoted as AlSi), $SiO_2$, and $CaCO_3$. Nitrate- and sulfate-containing particles were encountered frequently in $2-4{\mu}m$ size range, and existed mostly in the forms of $Ca(NO_3,SO_4)/C$, $(Mg,Ca)SO_4/C$, and $AlSi+(NO_3,SO_4)$. Particles containing metals (e.g., Fe, Cu, and As) in this near source sample had relative abundances of approximately 10%. Although the airborne particles collected near the lead smelter contained elevated levels of lead, other types of particles, such as $CaCO_3$-containing, carbonaceous, metal-containing, nitrates, sulfates, and fly-ash particles, showed the unique signatures of samples influenced by emissions from the lead smelter.

• 전기화학회지
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• 제5권2호
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• pp.52-56
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• 2002

졸-겔법을 이용하여 주석산화물을 흑연입자 표면에 도포하고 $400-600^{\circ}C$에서 열처리하여 미세결정구조를 갖는 리튬이온 전지용 주석산화물 전극을 제조하였다. 도포 된 주석산화물의 양은 $2.25 wt\%\~11.1 wt\%$로 조절하여 실험한 결과 주석산 화물의 함량에 따라 방전용량이 증가하고 또한 초기의 비가역 용랑도 증가함을 알 수 있었다. 싸이클에 따른 주석 산화물 전극의 방전용량은 propylene carbonate(PC) 계 전해액에서도 초기 싸이클에서 350mAh/g 이상, 30 싸이클 후 에서는 300mAh/g을 나타낸 반면, 표면개질이 되지 않은 흑연전극의 경우에는 140mAh/g의 방전용량을 나타내었다. 충방전 속도를 C/5에서 C/2로 빠르게 했을 때 주석산화물 전극과 흑연전극의 방전용량은 초기 용량의 $92\%,\;77\%$로 각각 나타났다. 이러한 전극 특성의 향상은 주석산화물이 리튬이온과 반응하여 형성된 리튬 옥사이드$(Li_2O)$부동태 피막이 흑연전극의 탈리 현상을 막고 또한 환원된 주석이 흑연입자간의 전기전도를 원활하게 하여 전극의 전류분포를 향상시키기 때문인 것으로 해석되었다.

• KEPCO Journal on Electric Power and Energy
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• 제6권2호
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• pp.173-179
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• 2020

전기자동차의 보급이 확대됨에 따라, 소비자의 고속충전에 요구가 높아지고 있으나 관련 연구는 미흡한 실정이다. 본 연구에서는 LiNi_0.5Co_0.2Mn_0.3O₂/Graphite 18650 실린더형 리튬이온전지를 이용하여, 정전류와 정출력 충전방식에 따른 전지 열화현상을 비교한다. 정전류모드의 충전속도를 1C, 2C, 3C, 4C로 설정하고, 각 충전속도에서의 에너지를 기반으로 정출력값을 산정하였다. 따라서, 동일 충전 에너지를 기반하여, 두 충전방식에 따른 전지 열화를 분석한 결과, 3C의 높은 율속에서 정출력 충전방식이 전지의 열화를 늦출 수 있음이 전압곡선, 용량유지율, 직류저항값으로 확인되었다. 그러나, 충전속도를 4C 이상 높이면, 충전방식보다 전지간 편차가 열화 거동을 지배하였다.

• 한국결정학회지
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• 제16권1호
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• pp.43-53
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• 2005

알칸화합물(alkanes)에서 탄소-수소결합을 활성화시켜서 더욱 값이 비싸고 더 유용한 알켄화합물(alkenes)로 만들 수 있는 촉매를 만들고자 지난 수 십 년간 많은 화학자들이 연구해왔다 이러한 목적의 하나로서 두개의 수소를 가지는 이리디움 P-C-P핀서(pincer) 착물 $(IrH_2{C_6H_3-2,6-(CH_2PBu_2^t)_2})$을 성공적으로 합성하였다. 이 착물은 알칸의 탈수소화반응(dehyrogenation)에 아주 효과적인 촉매로 알려졌다 알칸의 탈수소화반응에 촉매독으로 작용하는 질소, 물, 이산화탄소 및 일산화탄소와 같은 작은 화합물들과 직접 반응시켜서 어떻게 촉매독으로 작용하는지를 알아봤다. 촉매독으로 작용할 수 있는 화합물들을 합성하여 핵자기공명분광법(NMR)과 적외선분광법(IR)으로 확인하였고 분자구조를 알아보기 위해서 단결정X-ray 회절법을 통하여 확인하였다. 본 논문에서는 촉매 및 촉매독물질의 합성과 분자구조와 각각의 화합물의 반응성과 특이성을 알아보았다.