• 한국재난정보학회 논문집
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• 제12권3호
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• pp.261-272
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• 2016

전 세계가 지구 온난화 현상에 의한 기상이변을 겪으면서 태풍이나 집중호우, 지진, 가뭄 등의 급증하는 자연재해로 인해 많은 피해를 입고 있다. 우리나라는 특히 대륙성 기후와 해양성 기후가 교차하는 국가로 국지성 집중호우 및 태풍의 강도가 심화되어 피해가 빈번하고 산사태, 폭풍, 홍수를 동반하여 피해 규모는 증가한다. 이에 본 연구는 태풍과 집중호우로 인한 피해가 특히 심하고 그에 따른 대책이나 기반시설이 제대로 마련되어 있지 않은 농촌마을로 한정하여 피해사례와 원인을 분석하였고, 외국의 자연재해 방지 대책 사례를 조사하였다. 이를 바탕으로 시설과 건축물, 공간계획 위주로 국내 농촌지역에 적용가능한 계획요소를 도출함으로써 재난안전마을을 구축하기 위한 방안을 제시하고자 하였다.

• 한국환경농학회지
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• 제30권4호
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• pp.395-401
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• 2011

BACKGROUND: Potassium (K) is one of the macronutrients which are essential for plant growth and development. Its deficiency in paddy soils is becoming one of the limiting factors for increasing rice yield in Asia. METHODS AND RESULTS: To investigate physiological symptoms under K-starvation (NP) compared with complete media (NPK) condition, we measured shoot/root length, weight, nutrients, and patterns of protein expression. The shoot growth was significantly reduced, but root growth was not affected by K-starvation. However, biomasses were decreased in both shoot and root. Uptake of K was reduced up to 85%, while total concentrations of P, Ca, Mg, Na were increased in root and shoot. To better understand the starved K mechanism of rice, comparative proteome analysis for proteins isolated from rice leaves was conducted using 2-DGE. Five spots of differentially expressed proteins were analyzed by MALDI-TOF MS. Analysis of these K-starvation response proteins suggested that they were involved in metabolism and defense. CONCLUSION(s): Physiological and 2-DGE based proteomics approach used in our study results in observation of morphology or nutrients change and identification of K-starvation responsive proteins in rice root. These results have important roles in maintaining nutrient homeostasis and would also be useful for further characterization of protein function in plant K nutrition.

• Journal of Plant Biotechnology
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• 제37권4호
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• pp.425-441
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• 2010

Forages are the backbone of sustainable agriculture. They includes a wide variety of plant species ranging from grasses, such as tall fescue and bermudagrass, to herbaceous legumes, such as alfalfa and white clover. Abiotic stresses, especially salinity, drought, temperature extremes, high photon irradiance, and levels of inorganic solutes, are the limiting factors in the growth and productivity of major cultivated forage crops. Given the great complexity of forage species and the associated difficulties encountered in traditional breeding methods, the potential from molecular breeding in improving forage crops has been recognized. Plant engineering strategies for abiotic stress tolerance largely rely on the gene expression for enzymes involved in pathways leading to the synthesis of functional and structural metabolites, proteins that confer stress tolerance, or proteins in signaling and regulatory pathways. Genetic engineering allows researchers to control timing, tissue-specificity, and expression level for optimal function of the introduced genes. Thus, the use of either a constitutive or stress-inducible promoter may be useful in certain cases. In this review, we summarize the recent progress made towards the development of transgenic forage plants with improved tolerance to abiotic stresses.

• 한국초지조사료학회지
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• 제37권3호
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• pp.231-236
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• 2017

Salt stress is one of the most limiting factors that reduce plant growth, development and yield. However, identification of salt-inducible genes is an initial step for understanding the adaptive response of plants to salt stress. In this study, we used an annealing control primer (ACP) based GeneFishing technique to identify differentially expressed genes (DEGs) in Italian ryegrass seedlings under salt stress. Ten-day-old seedlings were exposed to 100 mM NaCl for 6 h. Using 60 ACPs, a total 8 up-regulated genes were identified and sequenced. We identified several promising genes encoding alpha-glactosidase b, light harvesting chlorophyll a/b binding protein, metallothionein-like protein 3B-like, translation factor SUI, translation initiation factor eIF1, glyceraldehyde-3-phosphate dehydrogenase 2 and elongation factor 1-alpha. These genes were mostly involved in plant development, signaling, ROS detoxification and salt acclimation. However, this study provides new molecular information of several genes to understand the salt stress response. These genes would be useful for the enhancement of salt stress tolerance in plants.

• 환경생물
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• 제35권4호
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• pp.533-544
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• 2017

본 연구는 서해로 유입되는 전남과 전북의 24개 독립하천들을 대상으로 2016년 3월부터 10월까지 어류상을 조사하고, 생물 및 비생물 평가지수(BAc index)를 선정하여 수생태계 건강성 평가를 실시하였다. 출현 어류는 총 18과 44속 59종 4,127개체가 확인되었다. 우점종은 피라미 (Zacco platypus)로 확인되었다. 한국고유종은 각시붕어 (Rhodeus uyekii) 등 12종이었다. BAc index는 통계적으로 유의한(p<0.01 또는 0.05) 상관관계가 확인되었다. 수생태계 건강성 평가의 단계별 분포는 보통 단계(Fair)가 41.7%로 가장 높은 비율을 나타냈다. 양호 단계(Good)와 불량 단계(Poor)는 20.8%, 최적 단계(Excellent)는 16.7%로 각각 나타났다. 독립하천의 수생태계 건강성은 생물학적 평가지수보다 지형적 특성, 인위적 자연적 제한 요소에 따른 비생물학적 평가지수의 영향을 더 받는 것으로 확인되었다.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2009년 추계학술발표대회
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• pp.217-220
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• 2009

Conductive adhesives have been investigated for use in microelectronics packaging as a lead-free solder substitute due to their advantages, such as low bonding temperature. However, high resistivity and poor mechanical behavior may be the limiting factors for the development of conductive adhesives. The metal fillers and the polymer resins provide electrical and mechanical interconnections between surface mount device components and a substrate. As metal fillers used in conductive adhesives, silver is the most commonly used due to its high conductivity and the stability. However the cost of conductive adhesives with silver fillers is much higher than usual lead-free solders and silver has poor electro-migration performance. So, copper can be a promising candidate for conductive filler metal due to its low resistivity and low cost, but oxidation causes this metal to lose its conductivity. In this study, electrically conductive adhesives (ECAs) using surface modified copper fillers were developed. Especially, in order to overcome the problem associated with the oxidation of copper, copper particles were coated with silver, and the silver-coated copper was tested as a filler metal. Especially the effect of silver coating on the electrical resistance just after curing and after aging was investigated. As a result, it was found that the electrical resistance of ECA with silver-coated copper filler was clearly lower and more stable than that of ECA with pure copper filler after curing process. And, during high temperature storage test, the degradation rate of electrical resistance for ECA with silver coated copper filler was quite slower than that for ECA with pure copper filler.

• 한국어교육
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• 제28권4호
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• pp.63-86
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• 2017

This research aims to evaluate the effects and the shortcomings of strategies for teaching paraphrasing to foreign university students. For this study, the effects of teaching paraphrasing skills on student's academic writing was investigated through the assessment of pre- and post-test writing tasks and through a focus group interview. The teaching of paraphrasing was divided into 3 instructional sessions and the focus group interview was conducted at the end of the last session. After each instructional session three trained assessors evaluated the outcomes of pre and post task writings; the in-depth focus group interviews were conducted on seven of the students in order to define better positive effects as well as shortcomings. By comparing the scores of pre- and post-task assignments it is possible to affirm that there is a meaningful difference for overall scores; moreover, in an analysis conducted on each single sub-element of the paraphrasing skill, it emerged that except for "task completion", all other four elements of "structure", "understanding core content", "change of expression" and "academic expressions" showed a statistically significant improvement in performance. On the other hand, as a result of the focus group interview, it was possible to individuate as main shortcomings insufficient vocabulary knowledge, poor overall comprehension of the reference material, lack of practice and difficulty in connect sentences organically. It is possible to consider these elements as limiting factors in understanding the reference material and making correct citations by the students. Therefore, we suggest as supplementary instructional strategies a deeper attention to the difficulty level of the text, the introduction of devices to understand better the content of the reference material and an integrated practice of the paraphrasing skill.

• Bulletin of the Korean Chemical Society
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• 제19권6호
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• pp.661-666
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• 1998

Active reaction sites and electrochemical O2 reduction kinetics on La_{1-x}Sr_xMnO_{3+{\delta}} (x=0.1-0.4)/YSZ (yttria-stabilized zirconia) electrodes are investigated in the temperature range of 700-900 ℃ at $Po_2=10^{-3}$-0.21 atm. Results of the steady-state polarization measurements, which are formulated into the Butler-Volmer formalism to extract transfer coefficient values, lead us to conclude that the two-electron charge transfer step to atomically adsorbed oxygen is rate-limiting. The same conclusion is drawn from the $Po_2$-dependent ac impedance measurements, where the exponent m in the relationship of $I_o$ (exchange current density) ∝ $P_{o_{2}}^m$ is analyzed. Chemical analysis is performed on the quenched Mn perovskites to estimate their oxygen stoichiometry factors (δ) at the operating temperature (700-900 ℃). Here, the observed δ turns out to become smaller as both the Sr-doping contents (x) and the measured temperature increase. A comparison between the 8 values and cathodic activity of Mn perovskites reveals that the cathodic transfer coefficients $({\alpha}_c)$ for oxygen reduction reaction are inversely proportional to δ whereas the anodic ones $({\alpha}_a)$ show the opposite trend, reflecting that the surface oxygen vacancies on Mn perovskites actively participate in the $O_2$ reduction reaction. Among the samples of x= 0.1-0.4, the manganite with x=0.4 exhibits the smallest 8 value (even negative), and consistently this electrode shows the highest ${\alpha}_c$ and the best cathodic activity for the oxygen reduction reaction.

• 대한화장품학회지
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• 제28권1호
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• pp.135-149
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• 2002

To date, research on the regulation of melanogenesis has focused on factors which affect tyrosinase, the rate-limiting enzyme in the melanogenic pathway, by searching for chemicals which competitively inhibit tyrosinase function. Many types of tyrosinase inhibitors have been developed, but no satisfactory results have been made clinically until now, To find a new whitening agent, which effectively inhibits melanogenesis, we synthesized several compounds and selected compounds by cell-based assay system. Finally, 3, 4, 5-trimethoxy cinnamaie thymol ester(TCTE, Melasolv) was selected and the effects of TCTE on melanogenesis were investigated. Treatment of mouse-derived melanocyte melan-a cells with TCTE results in a marked down-regulation of tyrosinase activity. 80% decrease of tyrosinase activity occurs with 30uM TCTE treatment for 72 hours without affecting cell growth. The inhibition of tyrosinase activity is dose-dependent and melanin content was also decreased to 40%. From the in vitro tyrosinase assay using cell extract, TCTE does not act as a direct inhibitor of the enzyme. Treatment of melan-a cultures with TCTE blocks the increase in tyrosinase activity by either forskolin, 3-isobutyl-1-methtyl-xanthine. TCTE decreased the expression of tyrosinase, TRP-1 without effects on TRP-2 protein expression through the down regulation of tyrosinase and TRP-1 mRNA. From the results of cAMP immunoassays, intracellular levels of the cyclin nucleotide are unaffected in cells treated with TCTE. The inhibitory effects of melanin synthesis were also shown in reconstitute human epidermis model by topical application. These findings suggest that TCTE can be used for studying the regulation of melanogenesis and depigmenting agent.

• 한국환경농학회지
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• 제40권4호
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• pp.345-352
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• 2021

BACKGROUND: Salinity is one of the major limiting factors in agriculture that affect the growth and productivity of crops. It is economically difficult to artificially purify the soil affected by salt. Therefore, the use of plant growth-promoting bacteria (PGPB) in an effort to reduce stress caused by salt is emerging as a cost-effective and environment-friendly method. In this study, the purpose was to isolate the salt-tolerant bacteria from the rhizosphere soil and identify their ability to promote plant growth under salt stress condition. METHODS AND RESULTS: The isolates KST-1, KST-2, AST-3, and AST-4 that showed plant growth-promoting activity for barley in salt conditions were close to Bacillus cereus (KST-1, KST-2, and AST-4) and Bacillus thuringiensis (AST-3) and showed high salt tolerance up to 7% of additional NaCl to the media. When inoculated to barley, the strains had only minor effect on the length of the barley. However, the concentrations of chlorophyll in the barley leaves were found to be higher from the bacteria-inoculated pots than those from the uninoculated control. In particular, the chlorophyll concentration in Bacillus cereus AST-4 experiment was 5.45 times higher than that of the uninoculated control under the same experimental condition. CONCLUSION(S): The isolated salt-tolerant bacteria were found to influence on chlorophyll concentration of the barley. As represented by the strain AST-4, microbes may suggest a cost-effective and environmentally benign method to alleviate salt stress of crops cultivated in salt-accumulated soils such as reclaimed lands.