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Biodegradation of Medium-chain-length Polyhydroxyalkanoates by Pseudomonas sp. RY-1 (Pseudomonas sp. RY-1에 의한 Medium-chain-length Polyhydroxyalkanoates의 생분해)

  • 류강은;김영백;양영기;이영하
    • Korean Journal of Microbiology
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    • v.36 no.2
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    • pp.84-90
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    • 2000
  • Biodegradation of vanous medium-chain-length polyhydroxyalkanoates (MCL-PHAs) by an extracellular depolymerase system from Pseudomonas sp. RY-1 was investigated under laboratoly conditions. The degradation rate of the polymers was determined by quantitative clem zone technique, enzyme (turbidity) assay, and respirometry assay. Although the enzyme system secreted by Pscudomor~as sp. RY-1 was capable of degrading all MCL-PHAs tested. its secretion was influenced by the availability of secondary carbon sources. The rate of enzymatic degradation of MCL-PHAs was dependent upou the monomeric composition of the polyesters and reduced as the chain lengths of the monomer m t s in the polyesters increased. MCL-PHAs containing C-even monomer units showed faster degradation rate than MCL-PHAs containing C-odd monomer units. Respiration rates of MCL-PHAs with C-even monomer uuts were also much faster than those of MCL-PHAs with C-odd monomer units. The degmdation rate of MCL-PHAs bearing unsaturated substituents was faster than that of mcl-PHAs without functional substituents, which is suggesting the correlation between the degradation rate and the crystallinity of MCL-PHAs.

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Synthesis and Electrochemical Performance of Li2MnSiO4 for Lithium Ion Battery Prepared by Amorphous Silica Precusor (비정질 실리콘 산화물을 이용한 리튬망간실리콘산화물의 합성 및 전기화학적 특성 평가)

  • Jin, Yun-Ho;Lee, Kun-Jae;Kang, Lee-Seung;Jung, Hang-Chul;Hong, Hyun-Seon
    • Journal of Powder Materials
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    • v.19 no.3
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    • pp.210-214
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    • 2012
  • Mass production-capable $Li_2MnSiO_4$ powder was synthesized for use as cathode material in state-of-the-art lithium-ion batteries. These batteries are main powder sources for high tech-end digital electronic equipments and electric vehicles in the near future and they must possess high specific capacity and durable charge-discharge characteristics. Amorphous silicone was quite superior to crystalline one as starting material to fabricate silicone oxide with high reactivity between precursors of sol-gel type reaction intermediates. The amorphous silicone starting material also has beneficial effect of efficiently controlling secondary phases, most notably $Li_xSiO_x$. Lastly, carbon was coated on $Li_2MnSiO_4$ powders by using sucrose to afford some improved electrical conductivity. The carbon-coated $Li_2MnSiO_4$ cathode material was further characterized using SEM, XRD, and galvanostatic charge/discharge test method for morphological and electrochemical examinations. Coin cell was subject to 1.5-4.8 V at C/20, where 74 mAh/g was observed during primary discharge cycle.

Aflatoxin: Factors Affecting Aflatoxin Production (Aflatoxin과 그 생성(生成)에 관련되는 주요인(主要因))

  • Park, Kun-Young
    • Journal of the Korean Society of Food Science and Nutrition
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    • v.13 no.1
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    • pp.117-126
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    • 1984
  • Aflatoxins are toxic and carcinogenic secondary metabolites which are produced by trains of A. flavus and A. parasiticus during their growth on foods and feedstuffs. Aflatoxins are a group of closely related heterocyclic compounds of which $B_1$, $B_2$, and $G_2$ are the major members. Aflatoxins are synthesized via a polyketide pathway in which the general steps are acetate, an-thraquinones, xanthone and aflatoxins. Aflatoxin formation is favored by high moisture or high $a_w$(0.95${\sim}$0.99). The limiting $a_w$ for aflatoxin production on agricultural commodities is 0.83. Optimum temperature for aflatoxin production by the molds is $25{\sim}30^{\circ}C$ and the incubation time for the maximum production of the toxin is 7${\sim}$15 days. The limiting temperatures for aflatoxin production are ${\leq}7.5^{\circ}C\;and\;\geq40^{\circ}C$. Cycling temperatures may or may not stimulate aflatoxin production depending on the amplitude of cycling, substrate and strains of molds. Aflatoxin pro-ducing molds are aerobic organisms and thus have a requirement for oxygen. A decreasing $O_2$ concentration and/or increasing concentrations of $CO_2$ or $N_2$ depress the mold growth and aflatoxin formation. A. flavus grows competitively or associatively in the presence of other microorganisms and occasionally loses the competition with other microorganisms. Some lactic acid bacteria have been shown to reduce growth and aflatoxin production by A. parasiticus. Carbon source is the most important nutritional factors affecting aflatoxin formation by the molds. Sucrose, fructose and glucose are the most favorable carbon sources. Food substrates of plant derived products which have high carbohydrate content such as agricultural commodities and their products are most vulnerable to contamination by aflatoxins.

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Morphology of Arbuscular Mycorrhizal Roots and Effects of Root Age and Soil Texture on the Mycorrhizal Infection in Panax ginseng C.A. Meyer

  • Lee, Kyung-Joon;Park, Hoon;Lee, In-Sik
    • Journal of Ginseng Research
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    • v.28 no.3
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    • pp.149-156
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    • 2004
  • The objectives of this study were to investigate the morphology of mycorrhizal roots, and the effects of root age and soil texture on the mycorrhizal infection in ginseng (Panax ginseng C. A. Meyer) growing in Korea. Ginseng roots at ages of two to six years were collected from fields in late June. Their infection by arbuscular mycorrhizal fungi(AMF) was studied by clearing the roots and staining fungal hyphae with trypan blue. Root infection varied greatly depending on the developmental stages of young roots. Young tertiary roots, in diameter of smaller than 0.8 mrn, formed during the current growing season had root hairs and were frequently and in some cases heavily infected by AMF. Hyphal coils and arbuscules were abundant, while vesicles were rarely observed. Older secondary or tertiary roots in diameter of bigger than 1.0 mm with fully differentiated primary xylem formed during the previous growing season had no root hairs, and were not infected at all. The rates of mycorrhizal infection in the young tertiary roots were not affected by the age of the ginseng plants, suggesting that fungal populations might have not much changed during the aging of the cultivated fields up to six years. The differences in the infection rates among the different ages of ginseng were caused by differences in the amount of young tertiary roots in the samples. Soil texture, either sandy loam or clay loam, did not affect the rate of root infection. There were large variations in the infection rates among the different farms and locations within a farm. It strongly suggested that infection rates of the ginseng roots by AMF would be influenced by the practice of the farmers, possibly by avoiding consecutive planting, introduction of new topsoil, and the ways of handling the soil before transplanting the ginseng, such as fumigation or sterilization that might have affected indigenous inoculum sources of the AMF.

Science Teachers' Perception and Attitudes toward Nanotechnology (과학교사의 나노기술에 대한 인식과 태도)

  • Kim, Hyun-Jung;Hong, Hun-Gi
    • Journal of the Korean Chemical Society
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    • v.54 no.5
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    • pp.633-642
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    • 2010
  • In this study, science teachers' perception and attitude toward nanotechnology are examined through questionnaires gathered from 134 secondary science teachers. As a result, the study shows that science teachers have high perceptiveness. However, they do not understand specific information on nanotechnology correctly. Science teachers have positive attitudes toward nanotechnology and they have perceived risks of nanotechnology as well as benefits of nanotechnology. Science teachers show positive attitudes toward the application of nanotechnology, whereas they show negative attitudes toward personal information chip and nano-taste enhancer. Science teachers are exposed to nanotechnology via various sources such as TV and internet, whereas teachers rarely get information on nanotechnology-related concepts in textbooks and teaching resources. Science teachers have perceived many textbooks do not introduce enough nanotechnology-related concepts. Many teachers try to explain the nanotechnology when textbooks include nanotechnology-related concepts, whereas quite a few of teachers do not introduce the nanotechnology-related concepts in class.

Chartacteristics of Water-bottom Reflection Coefficients in Bransfield Strait, Antarctic Peninsula (남극 브랜스필드 해협의 해저면 반사계수 특성)

  • Jin, Yeong Geun;Hong, Jong Guk;Lee, Deok Gi
    • Journal of the Korean Geophysical Society
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    • v.2 no.4
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    • pp.241-250
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    • 1999
  • Reflection coefficients of the seafloor have been calculated from the amplitude ratio of secondary to primary water bottom reflection in seismic data obtained from Bransfield Strait, Antarctic Peninsula. Test processing for the coefficients shows that moving average is effective to reduce severe fluctuation of the coefficient measured at each point. Relationship between the coefficients and the properties of water bottom is analyzed to illuminate geological environment. In the central Bransfield Basin, the magnitude of reflection coefficients decreases as it is distant from the sedimentary sources. Reflection coefficients range from 0.12 to 0.2 near the continental slope of the basin, and from 0.1 to 0.12 in the basin floor. In the western Bransfield basin, reflection coefficients between 0.2 to 0.3 are obtained from the area eroded by glacial movement. On the volcanic structures near Deception Island, the coefficients show relatively high values more than 0.2. Paleo-geological structures uplifted by tectonic movement and outcropped by glacial erosion have relatively high coefficients.

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Beginnings of the Community Health Practitioner (CHP) System in Republic of Korea (한국 보건진료원 제도의 시작)

  • Yi, Ggod-Me
    • Journal of Korean Academy of Rural Health Nursing
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    • v.4 no.1
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    • pp.31-40
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    • 2009
  • Purpose: This research was done do identify and analyze the beginnings of the community health practitioner system in the Republic of Korea (ROK) around 1980. Method: Primary sources were collected and analyzed, mainly newspapers around 1980, the act for health service for rural areas, and other relative publications. Results: The government of the ROK was trying to solve the problem of doctorless villages and regarded the introduction of primary health care (PHC) services using registered nurses (RNs) to be an economic solution to this problem. The Korean Nurses' Association presented 'a plan for community health service' to the government party and medical association in 1976. In this plan, RNs would provide primary care at the sub-county (myun) level, and hospital would provide secondary care. The Korean Public Health Development Research Center was awarded the project 'RNs and nurse aids as CHP for primary care service and their training'. In 1977, 25 RNs began to work as PHC in 3 areas, and interim findings showed that RNs were very capable of doing PHC. The Ministry of Health and Welfare announced long term plans for health and welfare administration including a tertiary health care delivery system. RNs after training were posted to rural areas with no medical services to do medical treatment for mild cases. The Act for health services for rural areas was enacted on December 31, 1980. Enforcement Ordinance and Enforcement Regulations were enacted in 1981. In 1981, 257 CHP were selected, trained, and deployed. In 1983, the president of the ROK announced continuation of the CHP system for residents of medically vulnerable areas. The number of CHP increased from 257 in 1981 to 2038 in 1989.

Content of Rutin and Monacolin K in the Red Buckwheat Fermented with Monascus ruber (홍국균 발효 메밀에서의 rutin과 monacolin K의 함량 변화)

  • Kang, Dong-Zhou;Um, Joo-Bang;Lee, Song-Koo;Lee, Jong-Hoon
    • Korean Journal of Food Science and Technology
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    • v.35 no.2
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    • pp.242-245
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    • 2003
  • Buckwheat contains dietary rutin, a flavonol glycoside, which is able to antagonize hypertension in human and has antioxidant activity. Monacolin K, a secondary metabolite produced by fungi Monascus species, is an effective specific inhibitor of cholesterol biosynthesis. To develop functional health food, dehulled buckwheat was fermented with Manascus ruber to produce Anka, and contents of rutin and monacolin K and Anka were determined. The rutin content in dehulled buckwheat decreased slightly after germination, but increased with the growth of sprout. Growth of fungi had no influence on rutin content in dehulled buckwheat Anka, Monacolin K content in fermented dehulled buckwheat malt was lower than that in dehulled buckwheat Anka. Monacolin K content in dehulled buckwheat Anka decreased with increasing length of sprout in fermented dehulled buckwheat malt, probably due to consumption of nutrients, such as polysaccharides as carbon sources, during sprouting for growth of M. ruber.

A Diagnostic Study of Research Trends of School Library and Teaching Librarian (학교도서관·사서교사 주제 학술논문의 연구 성향 분석)

  • Yoo, Sarah
    • Journal of the Korean BIBLIA Society for library and Information Science
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    • v.28 no.4
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    • pp.181-201
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    • 2017
  • Even though the increasing number of researches of school libraries have grown for the last 36 years, the diverse and practical problems of school libraries and teaching librarians have not been addressed to the proper solutions. This article presents an overview of the characteristics and tendency of researches using the method of systematical review in order to check the assumptions and research consequences of school libraries and teaching librarians. Results show that survey study reviewing or comparing certain cases is the most common types of research methods, and that the majority of studies that relied only on prior studies or secondary data from other sources to make their claims and rarely specify the five criteria validating study process and methodological reliability. Some research questions for future study including necessity of change in problem-solving perspective are provided.

The Water Soluble Ionic Composition of PM2.5 at 1,100 m-Highland of Mt. Hallasan on Jeju Island, Korea (한라산 1,100 m 지역의 대기 중 PM2.5의 수용성 이온 조성)

  • Lee, Ki Ho;Hu, Chul Goo
    • Journal of Environmental Science International
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    • v.25 no.5
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    • pp.727-736
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    • 2016
  • The ambient mass concentration and chemical composition of the $PM_{2.5}$ were determined at the highland site with 1,100 m above sea level on Jeju Island from June 2013 to November 2014. Yearly averaged mass concentration of $PM_{2.5}$ was $11.97{\pm}8.63{\mu}g/m^3$. $PM_{2.5}$ concentrations were highest during the spring, while they tended to be lowest during the summer. Eight water soluble ionic species attributed 45.5% to $PM_{2.5}$ mass. $SO{_4}^{2-}$, $NO_3{^-}$ and $NH_4{^+}$ were major ions, which occupied to 27.9%, 3.7% and 12.3%, respectively. The greatest contributors to total mass concentration of water-soluble ions contained in $PM_{2.5}$ were sulfate, ammonium and nitrate. These three ions accounted for 96.6% in total ions mass concentration of $PM_{2.5}$. We could infer that these three secondary ions exist mostly in the form of $(NH_4)_2SO_4$ and $NH_4NO_3$. $Ca^{2+}$ and $Mg^{2+}$ had a good relationship and with r=0.9. The molar ratio of $Mg^{2+}/Ca^{2+}$ in this study was lower than the value observed in sea water and higher than that in soil dust, indicating that these two ions originated from other sources rather than ocean and soil dust in this study.