• Journal of the korean academy of Pediatric Dentistry
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• v.31 no.4
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• pp.555-563
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• 2004

The pH of beverages is known to be low and have, therefore, been implicated in the increasing incidence of erosion. Erosion is believed to be the predominant cause of teeth wear in children and young adults, although there will always be a contribution from attrition and abrasion. The aim of the present study was to evaluate the effect of yogurt on the progression of erosive demineralization in human enamel using demineralization model in vitro. In 4 yogurts, available on the market, pH, buffering capacity and the concentrations of calcium, phosphate and fluoride were determined. The buffering effect was determined by titration with NaOH. 50 milliliters of each drink was then titrated with 1M sodium hydroxide, added in 0.5 milliliters increments, until the pH reached about 7. Human deciduous enamel(n=40) samples were divided into four groups and exposed to 80ml of the yogurt for 30,60, 90 and 120min. Enamel surface microhardness(VHN) was examined before and after each exposure. 1. The average PH of fermented milk was 3.77 and this pH value was acidic enough to cause tooth erosion. 2. All of the fermented milks were found to be erosive(p<0.05) 3. The teeth exposed to the fermented milk all showed erosion like lesions and microhardness measurements showed that enamel surface hardness decreased proportionately with increased time of immersion in all tooth specimen groups. 4. After immersion for 30 and 60 minutes, reduction rate of microhardness values was not significantly different between the groups(p>0.05). However, after 90 and 120 minutes, reduction rate of each group was significantly different(p<0.05).

• Journal of Animal Science and Technology
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• v.46 no.2
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• pp.273-282
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• 2004

Composting animal manure is one of feasible treatments that reserves some portion of nutrients of manure. Although the application of compost to arable land has many advantages, the repeated cultivation of the agriculture land will accumulate the level of heavy metals in the soil which is potentially hamful to people and animals. Therefore it is important to know the characteristics concentration and species of heavy metals in a variety of chemical fonns than just total content of the metal. Because the metals in different forms have different mobilities and bioavailabilites. The aim of this study was to examine the total content and the chemical forms of the heavy metals; Cr, Ni, Cu, Zn, As, Cd and Pb in the animal manure composted with sawdust or rice hull as a bulking agent. A total of 75 compost samples were collected throughout the country and classified into the three groups in accordance with the characteristics of raw materials: swine manure, poultry manure, and mixed(swine + poultry + cattle)manure. The compost samples were analyzed for total metal content and fractionated by sequential chemical extractions to estimate the quantities of metals: exchangeable, adsorbed, organically bound, carbonate and residual. The results showed that the heavy metal concentrations in all compost samples were lower than the maximum acceptable limits by the Korea Compost Quality Standards. The concentrations of heavy metals in the swine manure compost were higher than those of both the poultry and the mixed manure compost except for Cr. Zn and Cu concentrations of three different compost ranged from 157 to 839 mg Zn/kg DM(dry matter) and from 47 to 458 mg Cu/kg DM, depending on the composition of animal manures. The predominant forms for extracted metals were Cr, Ni, Zn, As and Ph, residual; Cu, organic; and Cd, carbonate. The results suggested that the legal standards for composts should be reexamined to revise the criteria on the total metal content as well as metal speciation.

• Korean Journal of Microbiology
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• v.40 no.1
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• pp.29-36
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• 2004

The purpose of this work was to investigate the relationships between acrylamide degradation by Pseudomonas sp. JK-7 and several relevant physicochemical environment parameters. In initial experiments, the bacterial culture, strain JK-7 isolated from paddy soil sample was developed to grow aerobically with acrylamide as the sole source of carbon and nitrogen. The bacterium was identified as genus Pseudomonas in the basis of use BIOLOG test, and designated as Pseudomunas sp. JK-7. Strain JK-7 could degrade 50 mM acrylamide completely within 72 hours of incubation. Major intermediates resulting from acrylamide degradation were not detected with the HPLC methodology except acrylic acid which appeared to accumulate transiently in the growth medium. The pH increased from 7.0 to 8.7 with complete degradation of the initial 50 mM acrylamide within 72 hours of incubation. pH control in the range of 5 to 9 influenced the growth of JK-7 and acrylamide degradation, whereas it was not examined the growth and degradation at pH 3 or pH 11, respectively. The effect of supplemented carbons (e.g., glucose, fructose, citrate, succinate) on the acrylamide degradation by the test culture of JK-7 was evaluated. The results indicated that the addition of carbons accelerated the bacterial growth and acrylamide degradation compared to those in the absence of supplemented carbons. The effect of supplemented nitrogens on the degradation was monitored. Increasing concentrations of yeast extract resulted in higher growth yield, based on the turbidity measurement, and complete degradation of acrylamide. However, acrylamide degradation was essentially uninfluenced by the addition of $(NH_{4})_{2}SO_{4}$, $NH_4Cl$ or urea. Addition of $AgNO_3$, $CuSO_4$ or $HgCl_2$ except $ZnSO_4$ in the test culture inhibited the degradation of acrylamide and growth of JK-7.

• The Korean Journal of Mycology
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• v.23 no.1 s.72
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• pp.92-104
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• 1995

Ten species of Cordyceps species were collected throughout Kangwon province including Chuncheon Dongsanmyun KNU forest experiment from June to September, 1993. Collected Cordyceps species were identified as Cordyceps militaris, C. roseostromata, C. kyushuensis, C. scarabaeicola, Phytocordyceps ninchukiospora, C. nutans, Paecilomyces tenuipes, C. sphecocephala, Hymenostilbe odonatae, Torrubiella sp.. C. militaris, type species of Cordyceps species, was mainly formed on pupae of Lepidoptera and found after the rainy season around July. Fruiting body of C. roseostromata was morphologically similar to those of C. militaris, but relatively small in size and they were also found on lawn or pupa of Lepidoptera. Fruiting body of C. scarabaeicola was found on adult Scarabaeidae specifically and collect fruiting bodies of C. kyushuensis were on larva of moth. C. nutans and C. sphecocephala had host specificity on Hemiptera and Hymenoptera, respectively. Each species formed elliptical fertile part attach to the slim and carneous stalk and they were collected the most in specimen number through whole season of the summer. Ascospore of Phytocordyceps ninchukiospora on seed was characterized by two viable, multiseptate, fusiform units linked end-to-end by a long, filiform connective. Paecilomyces tenuipes, imperfect stage of the genus Cordyceps is multi-infective fungi that attack all stages of all groups of insects. Hymenostilbe odonatae attacks only adult Odonata and Torrubiella sp. formed on spider was difficult to collect because it was found the back side of leaf. As results of cultural test PDA medium showed the best mycelial growth. In the experiment of effect of the acidity inside of the media, C. militaris was good on pH 5, C. nutans and Phytocordyceps ninchukiospora were good on pH 6 and Paecilomyces tenuipes was on pH 7 and C. scarabaeicola was on pH 9. All isolates tested showed the best mycelial growth at $20^{\circ}C$. Morphologically similar isolates were used to analyze protein banding pattern among and within species. As a result, C. militaris, C. roseostromata and C. kyushuensis were clustered into close species and C. scarabaeicola and Phytocordyceps ninchukiospora were relatively distant from those species.

• Journal of Life Science
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• v.23 no.2
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• pp.197-206
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• 2013

The present study investigated whether leukemia-maintaining cells reside in a differentiation-resistant fraction using a megakaryocytic differentiation model of K562 cells. Treatment with phorbol-12-myristate-13-acetate (PMA) significantly inhibited the colony-forming efficiency of the K562 cells. At a PMA concentration of 1 nM or higher, colony was not formed, but approximately 40% of K562 cells still survived in soft agar. Approximately 70% of colony-forming cells that were isolated following the removal of PMA after exposure to the agent were differentiated after treatment with 10 nM PMA for 3 days. The differentiation rate of the colony-forming cells was gradually increased and reached about 90% 6 weeks after colony isolation, which was comparable to the level of a PMA-treated K562 control. Meanwhile, imatinib-resistant variants from the K562 cells, including K562/R1, K562/R2, and K562/R3 cells, did not show any colony-forming activity, and most imatinib-resistant variants were CD44 positive. After 4 months of culture in drug-free medium, the surface level of CD44 was decreased in comparison with primary imatinib-resistant variants, and a few colonies were formed from K562/R3 cells. In these cells, Bcr-Abl, which was lost in the imatinib-resistant variants, was re-expressed, and the original phenotypes of the K562 cells were partially recovered. These results suggest that leukemia-maintaining cells might reside in a differentiation-resistant population. Differentiation therapy to eliminate leukemia-maintaining cells could be a successful treatment for leukemia if the leukemia-maintaining cells were exposed to a differentiation inducer for a long time and at a high dose.

• Journal for History of Mathematics
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• v.22 no.2
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• pp.27-52
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• 2009

This article discusses the contributions of the leader Oswald Veblen, who was the president of AMS during 1923-1924. In 2006, Korea ranked 12th in SCIE publications in mathematics, more than doubling its publications in less than 10 years, a successful model for a country with relatively short history of modern mathematical research. Now there are 192 four-year universities in Korea. Some 42 of these universities have Ph.D. granting graduate programs in mathematics and/or mathematical education in Korea. Rapid growth is observed over a broad spectrum including a phenomenal performance surge in International Mathematical Olympiad. Western mathematics was first introduced in Korea in the 17th century, but real significant mathematical contributions by Korean mathematicians in modern mathematics were not much known yet to the world. Surprisingly there is no Korean mathematician who could be found in MaC Tutor History Birthplace Map. We are at the time, to have a clear vision and leadership for the 21st century. Even with the above achievement, Korean mathematical community has had obstacles in funding. Many people thinks that mathematical research can be done without funding rather unlike other science subjects, even though they agree fundamental mathematical research is very important. We found that the experience of early American mathematical community can help us to give a vision and role model for Korean mathematical community. When we read the AMS Notice article 'The Vision, Insight, and Influence of Oswald Veblen' by Steve Batterson, it answers many of our questions on the development of American mathematics in early 20th century. We would like to share the story and analyze its meaning for the development of Korean Mathematics of 21st century.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.32 no.4
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• pp.385-390
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• 1999

HPLC method usually has been used for the determination of ATP and its related compounds in fish muscle and fish sauce. But, total amount of ATP related compounds in fish sauce is determined less than that of fish muscle. In order to establish the extract analysis method for ATP related compounds in fish sauce, a new enzymatic method was developed and compared with existing HPLC method. Fish sauce was extracted with chilled perchloric acid and neutralized to Ph 7.0 with potassium hydroxide solution, the extract was used as sample analyzed by HPLC as usual. On the other hand, for sample analyzed by enzymatic method, 1 ml extract solution was pipetted into test tube. To the tube, 0.5ml of mixed suspension adenosinedeaminase (4U), nucleosidephosphorylase (0.02U) and xanthineoxidase (0.03U) suspended in 2.0ml of 1/15 M sodium phosphate buffer solution pH 7.6 and 1.5ml deionized water wereadded for the decomposition of IMP, HxR and Hx to uric acid at $37^{\circ}C$ for 40 minutes. Total uric acid was determined by measuring optical density at 290nm. In HPLC method, salt decreased the total amount of ATP related compounds by $13.6\~16.2\%$ at $2.5\%$ concentration, but no effect in enzymatic method. IMP, HxR and Hx were detected at 254nm, while uric acid at only 290nm. The ratio of the total amount of ATP related compounds by HPLC method was about $45\%$ of that by enzymatic method in fish sauce. Form these results, enzymatic method is more accurate and simple than HPLC method for analysis of ATP related compounds in fish sauce.

• Cross-Cultural Studies
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• v.25
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• pp.679-694
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• 2011

La langue est un des ${\acute{e}}l{\acute{e}}ments$ $privil{\acute{e}}gi{\acute{e}}s$ de la $r{\hat{e}}verie$ chez Bachelard. La langue est une force fondamentale de l'imagination. D'une part, elle garde son propre valeur dans le processus de l'imagination, et d'autre part elle forme sa propre image. La $priorit{\acute{e}}$ de langue chez Bachelard a, en effet, quelque liaison avec la notion de Logos qui avait ${\acute{e}}t{\acute{e}}$ $trait{\acute{e}}$ depuis longtemps comme $v{\acute{e}}rit{\acute{e}}$ ${\acute{e}}ternelle$ dans la $m{\acute{e}}taphysique$ occidentale. Cependant, la notion de logos de Bachelard se $diff{\grave{e}}re$ de celle de $m{\acute{e}}taphysique$ occidentale. Tandis que la $m{\acute{e}}taphysique$ traditionnelle traite le logos comme un but ${\acute{e}}ternel$ de sa $m{\acute{e}}ditation$, Bachelard donne l'importance sur la $capacit{\acute{e}}$ linguistique et imaginaire du logos. Le $logosph{\grave{e}}re$ est un des exemples qui montre bien la $diff{\acute{e}}rence$ entre la notion de logos de Bachelard et celle de $m{\acute{e}}taphysique$ traditionnelle. Le $logosph{\grave{e}}re$ est un $n{\acute{e}}ologisme$ de Bachelard qui est fait pour $d{\acute{e}}signer$ $l^{\prime}atmosph{\grave{e}}re$ verbal de la $soci{\acute{e}}t{\acute{e}}$ contemporaine $gr{\hat{a}}ce$ ${\grave{a}}$ l'emission de radio. Bachelard comprend le $ph{\acute{e}}nom{\grave{e}}ne$ de radio en tant que $r{\acute{e}}alisation$ de $Psych{\acute{e}}$ dans la vie quotidienne. C'est $gr{\hat{a}}ce$ ${\grave{a}}$ la technologie moderne que nous pouvons avoir l'univers de langue plus facilement par rapport aux $si{\grave{e}}cles$ $pr{\acute{e}}c{\acute{e}}dents$. Selon Bachelard, la radio n'est pas un simple instrument de communication. C'est une porte pour entrer dans la $r{\hat{e}}verie$ universelle. La radio est une voix du monde qui exprime notre inconscient. Quand un $r{\hat{e}}veur$ $r{\hat{e}}ve$, son $r{\hat{e}}verie$ se $d{\acute{e}}veloppe$ en se discutant avec le monde. Alors, quand nous $r{\hat{e}}vons$, nous parlons au monde et nous ${\acute{e}}coutons$ du monde, de sorte que nous devenons les citoyens du $logosph{\grave{e}}re$. Dans son oeuvre Sur la Grammatologie, J. Derrida critique la $m{\acute{e}}taphysique$ occidentale en la intitulant logocentrisme. Derrida pense que la philosophie occidentale a comme le but final la $pr{\acute{e}}sence$ de logos. Cette $pr{\acute{e}}sence$ de logos ne peut ${\hat{e}}tre$ $r{\acute{e}}alis{\acute{e}}e$ que par la langue de la voix, non pas par la langue de $caract{\grave{e}}re$. $D^{\prime}o{\grave{u}}$ vient le logocentrisme ou le phonocentrisme de $m{\acute{e}}taphysique$ occidental. Mais Derrida pense que le logocentrisme n'est qu'un autre aspect de l'ethnocentrisme ${\acute{e}}troit$ de l'occident. La notion de $logosph{\grave{e}}re$ de Bachelard a quelques ressemblances avec logocentrisme par ses apparences. Cependant, elles ont une $diff{\acute{e}}rence$ fondamentale depuis leur $d{\acute{e}}part$. Tandis que logocentrisme $tra{\hat{i}}te$ la parole en tant que $mani{\grave{e}}re$ d'expression de raison qui est une puissance fondamentale de l'homme, Bachelard pense que la parole est un $r{\acute{e}}sultat$ d'une opposition et fusion de notre raisons et parole. Bachelard pense que la parole est une $r{\acute{e}}alisation$ de l'image qui est l'essence de notre $psych{\acute{e}}$. Pour lui, la parole, la quintessence de $logosph{\grave{e}}re$, est le champ de l'imagination $d^{\prime}o{\grave{u}}$ jaillissent les images. C'est pour cela que $logosph{\grave{e}}re$ se situe ${\grave{a}}$ l'antipode de logocentrisme. $Logosph{\grave{e}}re$ nous fournit un espace de $r{\hat{e}}verie$ de langue. Notre $soci{\acute{e}}t{\acute{e}}$ contemporaine $fourr{\acute{e}}e$ des images visuelles creuses est $d{\acute{e}}pouill{\acute{e}}e$ de plus en plus des espaces de $r{\hat{e}}veries$. C'est une des raisons que le $logosph{\grave{e}}re$ de Bachelard doit ${\hat{e}}tre$ $r{\acute{e}}activ{\acute{e}}$ aujourd'hui.

• Korean Journal of Legislative Studies
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• v.22 no.2
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• pp.113-156
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• 2016

Media scholars take a lion stake in power circle. Not only do they take a part in media policies but seize prestigious positions like board members in Korea Communication Commission(KCC). Unfortunately, though, little has been known about who they are, what qualifications they have, and whether they meet public interests. This paper attempts to unveil the mechanism of those politicized intellectuals who are specialized on the media. Two categories divided into 'representative' and 'expertise' are employed for this purpose. On the one hand, the representative means the degree of committment into such public services as participation in conferences or non-profit organizations. On the other hand, the number of research articles, books and projects belong to the expertise. Evaluation levels consist of 'excellence, good and average' were allocated to those scholars who are(were) in 'Power Hole,' where decision makings come into being. Some interesting observations were made though this study. First of all, such criteria as representative and expertise vaguely suggested by the laws were hardly fit into those intellectuals, Rarely did they commit into public service let alone showing vigilance in academic activities. Secondly, both ideological loyalty and political activities in line with the government had much to do with taking such positions. Thirdly, not surprisingly, it showed that to graduate from Seoul National University and have Ph.D. degree from U.S.A. was one of the most essential factors. In final, most of them were very good at taking advantage of the press in way of boosting their publicity. To attend at policy making processes either in form of board members or advisers is inevitable for media experts. However, as shown in this study, such qualification of public service and academic eagerness shouldn't be underestimated. Academic integrity not selling intelligence solely for private interests needs to be protected as well. The authors hope this study to provide a valuable opportunity to establish a kind of ethical standards in participating into politics.

• Journal of Soil and Groundwater Environment
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• v.14 no.4
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• pp.23-32
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• 2009

The sorption of europium (Eu (III)) onto kaolinite and the influence of humic acids over a range of pH 3 ~ 11 has been studied by batch adsorption experiment (V/m = 250 : 1 mL/g, $C_{Eu(III)}\;=\;1\;{\times}\;10^{-5}\;mol/L$, $C_{HA}\;=\;5{\sim}50\;mg/L$, $P_{CO2}=10^{-3.5}\;atm$). The concentrations of HA and Eu(III) in aqueous phase were measured by UV absorbance at 254nm (e.g., $UV_{254}$) and ICP-MS after microwave digestion for HA removals, respectively. Results showed that the HA sorption onto kaolinite was decreased with increasing pH and their sorption isotherms fit well with the Langmuir adsorption model (except pH 3). Maximum amount ($q_{max}$) for the HA sorption at pH 4 to 11 was ranged from 4.73 to 0.47 mg/g. Europium adsorption onto the kaolinite in the absence of HA was typical, showing an increases with pH and a distinct adsorption edge at pH 3 to 5. However in the presence of HA, Eu adsorption to kaolinite was significantly affected. HA was shown to enhance Eu adsorption in the acidic pH range (pH 3 ~ 4) due to the formation of additional binding sites for Eu coming from HA adsorbed onto kaolinite surface, but reduce Eu adsorption in the intermediate and high pH above 6 due to the formation of aqueous Eu-HA complexes. The results on the ternary interaction of kaolinte-Eu-HA are compared with those on the binary system of kaolinite-HA and kaolinite-Eu and adsorption mechanism with pH was discussed.