• Journal of Life Science
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• v.27 no.1
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• pp.100-121
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• 2017

The sexual reproduction of the unicellular green alga Chlamydomonas is reviewed for a comprehensive understanding of the complex processes. The sexual life cycle of C. reinhardtii is distinguished into five main stages: gametogenesis, gamete activation, cell fusion, zygote maturation, and meiosis and germination. Gametogenesis is induced by nitrogen starvation in the environment. C. reinhardtii has two mating types: mating type plus ($mt^+$) and mating type minus ($mt^-$), controlled by a single complex mating type locus ($MT^+$ or $MT^-$) on linkage group VI. In the early gametogenesis agglutinins are synthesized. The $mt^+$ and $mt^-$ agglutinins are encoded by the autosomal genes SAG1 (Sexual AGglutination1) and SAD1 (Sexual ADhesion1), respectively. The agglutinins are responsible for the flagellar adhesion of the two mating type of gametes. The flagellar adhesion initiates a cAMP mediated signal transduction pathways and activates the flagellar tips. In response to the cAMP signal, mating structures between two flagella are activated. The $mt^+$ and $mt^-$ gamete-specific fusion proteins, Fus1 and Hap2/Gcs1, are present on the plasma membrane of the two mating structures. Contact of the two mating structures leads to develop a fertilization tubule forming a cytoplasmic bridge between the two gametes. Upon fusion of nuclei and chloroplasts of $mt^+$ and $mt^-$ cells, the zygotes become zygospores. It is notable that the young zygote shows uniparental inheritance of chloroplast DNA from the $mt^+$ parent and mitochondrial DNA from the $mt^-$ parent. Under the favorable conditions, the zygospores divide meiotically and germinate and then new haploid progenies, vegetative cells, are released.

• Korean Journal of Environmental Biology
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• v.17 no.4
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• pp.439-448
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• 1999

To investigate the population dynamics and survival of Genus Vibrio, population densities of aerobic saprophytic bacteria and Vibrio groups were measured 4 times in the intertidal waters of the Yellow Sea near Kunsan from November, 1997 to June, 1998. The distribution of heterotrophic bacteria during the survey periods by plate count and direct count method ranged from 1.2$\pm$0.6$\times$10$^3$~2.0$\pm$1.5$\times$10$^4$CFU ml­$^1$and from 6.0$\pm$4.0$\times$10$^{5}$ ~1.9$\pm$1.5$\times$10$^{7}$ cells ml­$^1$, respectively. Vibrio groups were distributed in the range of 1$\times$10 and 6$\pm$2.2$\times$10$^2$CFU ml­$^1$. The proportion of Vibrio groups to total heterotrophic bacteria was between 0.1 and 6% during the survey periods. A total of 51 isolates was obtained from TCBS agar plates and identified to species level by Biolog Identification System$^{TM}$. As a result, dominant genera were V, mediterranei, V aitguillarum, tr metschnikovii, and V. parahaemolyticus, and isolates were clustered into 26 groups based on the relatedness of average linkage clustering method at 70% level. As for the susceptibility of 51 isolates to 7 kinds of antibacterial agents (gentamicin, ampicillin, chlorarnphenicol, streptomycin, kanamycin, tetracycline, carbenicillin), 96% of isolates showed high resistance to more than one antibiotics and 65% of isolates contained a plasmid, of which size was observed greater than 12 kb, The number of cells of 3 tested strains (V. anguillarum, V. vulnificus, and V. metschnikovii) in filtered aged seawater decreased by approximately 1 to 5 orders of magnitude during 30-d incubation. In most cases, the numbers of cells decreased rapidly until day 3, then decreased slowly by day 30. The number of cells incubated at 15$^{\circ}C$ showed higher survival than those at 4$^{\circ}C$ and $25^{\circ}C$. These results may be considered for the basic supporting data in the risk assessment of vibriosis in summer.r.

• Strategy21
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• s.32
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• pp.222-270
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• 2013

서구 근대 국제관계학의 태동은 "전쟁의 원인"을 밝혀내려고 했던 유럽 지식인들의 학문적 도전에서부터 비롯되었다고 할 수 있다. 1, 2차 세계대전의 잔혹함을 겪으면서 이들은 전쟁(특히 전쟁의 원인)에 대한 좀 더 과학적인 연구를 통해 어떻게 하면 국가들 간의 전쟁을 예방할 수 있을까에 집중해 왔다. 이러한 학문적 경향을 반영한 것이 잘 알려진 미국 미시간 대학의 "전쟁 상관성 연구 프로젝트(Correlates of War Project)"이다. 이는 나폴레옹 전쟁이 끝나고 비엔나체제가 시작된 1815년 이후 국가들 간 발생한 모든 전쟁 관련 자료를 데이터베이스화하여,국제관계학자들이 전쟁(Interstate War)이나 군사분쟁(Militarized Interstate Disputes)을 정량 또는 정성적으로 연구할 수 있도록 다양한 정보들을 제공하고 있다. 최근 Paul F. Diehl, William R. Thompson과 같은 학자들은 전쟁을 분석단위로 하는 전쟁의 원인(Causes of War)을 연구하는 학풍에서 벗어나, 국가들 간의 분쟁과 전쟁을 연구하기 위해 숙적관계(Rivalry)라는 새로운 분석의 단위를 제시하였다. 숙적관계는 국제관계에 있어서 지속적으로 분쟁 또는 전쟁을 일으키는, 즉 무력분쟁의 긴 역사를 가지고 있는, 두 국가를 일컫는다. 국가들 간의 숙적관계는 학자들에 따라 Interstate Rivalry, Enduring Rivalry, Strategic Rivalry 등 다양한 정의와 성격을 갖고 있다. 이러한 국가들의 사례로는 2차대전 이전까지 프랑스-독일 관계, 2차대전 이후 중동지역 이스라엘과 아랍국가들 간의 관계, 냉전기 미소관계, 인도-파키스탄 및 남북한 관계 등을 예로 들 수 있다. 이렇게 널리 알려진 숙적관계 외에도 남미의 칠레-아르헨티나, 에콰도르-페루와 아프리카의 소말리아-에티오피아 등 학자들에 따라 1815년 이후 약 200개의 숙적관계를 제시하고 있다. 숙적관계에 대한 연구는 기존의 전쟁의 원인 중심이었던 정량적 국제분쟁 연구에 두 국가의 분쟁역사를 포함시키는 정성적 연구를 접합시키고 있다. 본 연구는 1945년 이후 숙적관계 국가들의 관계종식과 관련하여, 거시론적이고 전체론적 접근방법(Macro - level Holistic Approach)을 제시하고 있다. 먼저 1945년 이후 발생한 국가들 간의 숙적관계 종식(Rivalry Termination)을 이해하기 위해, 거시적 관점에서 숙적관계를 발생시키게 된 역사적 원인을 살펴보고 있다. 특히 1945년 이후 숙적관계와 관련된 중요한 요인들 중에서 전쟁, 영토분쟁, 그리고 근대국가 형성에 대해 살펴보고 다음과 같은 두 가지 명제(proposition)를 제시한다. 첫째, 1945년 이후의 숙적관계 형성과 지속에는 2차대전 이후 독립국가 형성, 헌팅턴이 주장한 제3의 물결(민주화), 그리고 냉전기 미소경쟁 등의 역사적 배경이 영향을 주었다는 것이다. 둘째, 이러한 역사적 배경에 더하여 1945년 이후 숙적관계는 전쟁에 의해 시작된 숙적관계와 전쟁 없이 시작된 숙적관계 등 2가지로 나눌 수 있으며, 전쟁에 의해 시작되고 영토분쟁과 근대국가 형성 문제를 내포하고 있는 숙적관계가 그렇지 않은 숙적관계에 비해 오랫동안 지속되며 관계해결이 어렵다는 것이다. 앞서 제시된 2가지 명제들과 관련하여 본문에서는 다양한 학자들이 제시한 숙적관계 정의들에 일치하는 23개의 숙적관계(Consensus Rivalries)를 선정하여 이들에 대한 비교분석(Descriptive Analysis)을 실시하였다. 이들 사례들을 1945년 이전과 이후로 나누어, 숙적관계 형성과 종식에 있어 핵심요소인 국가들 간 힘의 차이(Power Relations), 분쟁의 주요 원인(Primary Conflict Issue), 숙적관계에 있어 다른 국가들과의 연계성(Rivalry Linkage), 전쟁의 횟수와 시기 등을 통해 비교하였다. 숙적관계의 종식과 관련하여 약소국 간의 숙적관계(Minor Dyad)가 오래 지속되고, 영토분쟁(Territorial Disputes)이 숙적관계를 지속시키는 주요인이며, 다른 숙적관계와의 연계성이 적은 숙적들이 오래 지속된다는 비교분석 결과가 나왔다. 또한 전쟁의 횟수는 숙적관계 종식에 큰 영향을 미치지 못하지만 전쟁으로 인해 시작된 숙적관계가 그렇지 않은 경우보다 더욱 오래 지속되는 것으로 확인되었다. 끝으로 2차대전 이전의 숙적관계는 대부분 전쟁을 통해 종식되었지만, 1945년 이후에는 전쟁 없이도 숙적관계가 종식된 경우가 많았음을 보여 주고 있다. 본 연구의 주목적은 "1945년 이후 형성된 숙적관계를 어떻게 종식시킬 수 있을 것인가?"라는 규범적 논제를 통해, 23개의 주요 숙적관계를 발굴하여 거시적, 역사적 관점에서 비교분석함에 있다. 이는 특히 우리나라가 처한 현실과 관련하여 중요한 시사점을 갖는다. 남북관계가 갖는 특수성보다는 1945년 이후 국제정치 역사속에서 발생한 숙적관계 현상이라는 일반성의 틀에서 남북관계를 이해하고자 했다. 남북관계를 베트남, 예멘, 독일 등 분단국가의 사례들과만 비교 연구하는 제한된 시각에서 벗어나, 인도-파키스탄, 그리스-터키, 에콰도르-페루 등 유사한 숙적들 간의 관계들과 비교하는 새로운 연구의 장을 제시하고자 한다. 따라서 앞으로 숙적관계 종식에 대한 더욱 다양화된 사례연구를 통해 한반도 분쟁해결에 필요한 새로운 교훈을 얻을 수 있을 것이다. 예를 들면 2차대전 이후 발생한 국경을 접하고 있는 비강대국들의 평화적인 숙적관계 종식에 대한 사례연구는 남북한이 앞으로 지향해야 할 방향을 제시해 줄 수 있을 것이다. 끝으로 본 연구는 특정한 정책적 함의를 도출하기 보다는 숙적관계와 관련된 하나의 거시적 이론를 제시하고, 주요 숙적관계 국가들에 대한 비교설명을 통해 현존하는 숙적관계 해결을 위한 하나의 분석의 틀을 제시하는 것으로 국제분쟁 연구에 기여하고자 하였다.

• Applied Chemistry for Engineering
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• v.9 no.2
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• pp.207-213
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• 1998

On the basis of the previous study[1], miscibility were investigated and intermolecular interaction strength for the miscibility were relatively compared for the blends poly{2,2-(m-phenylene)-5,5'-bibenzimidazole}(PBI) with two aromatic polyimides (PIs) synthesized by another dianhydride. Aromatic PAAs were prepared by the reaction of condensation of two diamines, 4,4'-methylene dianiline(4,4'-MDA) and 4,4'-oxydianiline(4,4'-ODA) with 3,3',4,4'-diphenylsulfone tetracarboxylic dianhydride(DSDA) using DMAc, and then converted into PIs after curing. PBI/PAA blends were prepared by solution blending. Cast films or precipitated powders of the PBI/PAA blends were cared at a high temperature to transform into PBI/PIs blends. Miscibility and specific intermolecular interaction for miscibility in the blends were investigated, and compared with previous polyimide structures of PBI/PIs blends [1]. Two blends, PBI/DSDA+4,4'-MDA(Blend-V) and PBI/DSDA+4,4'-ODA(Blend-VI), were found miscible : the evidences were optically clear films, synergistic single composition dependent $T_g{\prime}s$, and frequency shifts of N-H stretching band as much as $39{\sim}40cm^{-1}$, and of C=O stretching band near 1730 and $1780cm^{-1}$, 5~6 and $3{\sim}4cm^{-1}$, respectively. The specific intermolecular interactions existing between PBI and PIs were relatively analyzed with the area(A) formed between the $T_g{\prime}s$ of the measured and that of the calculated by the Fox equation at all compositions, the ${\kappa}$ values in Gordon-Taylor equation obtained from the measured $T_g{\prime}s$, and differences of the frequency shifts in the functional N-H and carbonyl stretching band. From the results, the area(A) and the ${\kappa}$ values for Blend-V and VI were smaller than those for Blend-III and IV used in previous study[1]. Differences of the frequency shifts in the functional groups(N-H and C=O) also showed similar tendency. Thus, specific intermolecular interaction strength in terms of hydrogen bonding of PBI/PI blends is dependent upon chemical structures of PIs, that is, PIs it seems that $SO_2$ group in dianhydride(DSDA) has weaker hydrogen bond strength than those of C=O in BTDA. In other words, it implies that the former occupied bulk space than the latter due to the sterric effect.

• Korean Journal of Psychosomatic Medicine
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• v.10 no.2
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• pp.142-153
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• 2002

The authors intended to investigate personality characteristics and those influence on the outcome of cognitive behavioral therapy in patients with panic disorder. 167 patients who met DSM-IV criteria for panic disorder were assessed by the PDQ-R(Personality Disorder Questionnaire-Revision) and various self-report tools for assessing symptoms of panic disorder. The effect of therapy was measured by the changes of scores and the end state functioning before and after 12-sessions of CBT. The patients with panic disorder were more likely showed obsessive-compulsive, avoidant and paranoid personality disorder and also Cluster C. If is needed when patients were divided into two groups according to total scores of PDQ-R(high or low personality disorder groups), high personality disorder group showed many evidences for increased psychopathology at the start of treatments, this suggested the close linkage between panic disorder and personality disorder. Interestingly, there were no significant differences between both groups in scores of clinical variables and the end state functioning. In conclusion, although patients with high tendency of personality disorder had more generalized problems at the beginning of treatments, they could improve as much as the patients with low tendency of personality disorder. They can be helped by cognitive behavioral therapy for panic disorder and seem to profit as much as patients with low tendency of personality disorder. If is needed to seek other factors in poor responders for cognitive behavioral therapy.

• Journal of Intelligence and Information Systems
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• v.17 no.4
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• pp.305-316
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• 2011

Recommender system is the system which, by using automated information filtering technology, recommends products or services to the customers who are likely to be interested in. Those systems are widely used in many different Web retailers such as Amazon.com, Netfix.com, and CDNow.com. Various recommender systems have been developed. Among them, Collaborative Filtering (CF) has been known as the most successful and commonly used approach. CF identifies customers whose tastes are similar to those of a given customer, and recommends items those customers have liked in the past. Numerous CF algorithms have been developed to increase the performance of recommender systems. However, the relative performances of CF algorithms are known to be domain and data dependent. It is very time-consuming and expensive to implement and launce a CF recommender system, and also the system unsuited for the given domain provides customers with poor quality recommendations that make them easily annoyed. Therefore, predicting in advance whether the performance of CF recommender system is acceptable or not is practically important and needed. In this study, we propose a decision making guideline which helps decide whether CF is adoptable for a given application with certain transaction data characteristics. Several previous studies reported that sparsity, gray sheep, cold-start, coverage, and serendipity could affect the performance of CF, but the theoretical and empirical justification of such factors is lacking. Recently there are many studies paying attention to Social Network Analysis (SNA) as a method to analyze social relationships among people. SNA is a method to measure and visualize the linkage structure and status focusing on interaction among objects within communication group. CF analyzes the similarity among previous ratings or purchases of each customer, finds the relationships among the customers who have similarities, and then uses the relationships for recommendations. Thus CF can be modeled as a social network in which customers are nodes and purchase relationships between customers are links. Under the assumption that SNA could facilitate an exploration of the topological properties of the network structure that are implicit in transaction data for CF recommendations, we focus on density, clustering coefficient, and centralization which are ones of the most commonly used measures to capture topological properties of the social network structure. While network density, expressed as a proportion of the maximum possible number of links, captures the density of the whole network, the clustering coefficient captures the degree to which the overall network contains localized pockets of dense connectivity. Centralization reflects the extent to which connections are concentrated in a small number of nodes rather than distributed equally among all nodes. We explore how these SNA measures affect the performance of CF performance and how they interact to each other. Our experiments used sales transaction data from H department store, one of the well?known department stores in Korea. Total 396 data set were sampled to construct various types of social networks. The dependant variable measuring process consists of three steps; analysis of customer similarities, construction of a social network, and analysis of social network patterns. We used UCINET 6.0 for SNA. The experiments conducted the 3-way ANOVA which employs three SNA measures as dependant variables, and the recommendation accuracy measured by F1-measure as an independent variable. The experiments report that 1) each of three SNA measures affects the recommendation accuracy, 2) the density's effect to the performance overrides those of clustering coefficient and centralization (i.e., CF adoption is not a good decision if the density is low), and 3) however though the density is low, the performance of CF is comparatively good when the clustering coefficient is low. We expect that these experiment results help firms decide whether CF recommender system is adoptable for their business domain with certain transaction data characteristics.

• Journal of The Korean Association For Science Education
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• v.37 no.4
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• pp.565-575
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• 2017

This study analyzes the epistemic considerations and the argumentation level revealed in the discourse of the key concept of natural selection for science-gifted elementary students. The paper analyzes and discusses the results of a three-student focus group, drawn from a cohort of twenty gifted sixth-grade elementary students. Nature, generality, justification, and audience were used to analyze epistemic consideration. Learning progression in scientific argumentation including argument construction and critique was used to analyze students' scientific argumentation level. The findings are as follows: First, Epistemic considerations in discourse varied between key concepts of natural selection discussed. The nature aspect of epistemic considerations is highly expressed in the discourse for all natural selection key concepts. But the level of generality, justification and audience was high or low, and the level was not revealed in the discourse. In the heredity of variation, which is highly expressed in terms of generality of knowledge, the linkage with various phenomena against the acquired character generated a variety of ideas. These ideas were used to facilitate engagement in argumentation, so that all three students showed the level of argumentation of suggestions of counter-critique. Second, students tried to explain the process of speciation by using concepts that were high in practical epistemic considerations level when explaining the concept of speciation, which is the final natural selection key concept. Conversely, the concept of low level of epistemic considerations was not included as an explanation factor. The results of this study suggest that students need to analyze specific factors to understand why epistemological decisions are made by students and how epistemological resources are used according to context through various epistemological resources. Analysis of various factors influencing epistemological decisions can be a mediator of the instructor who can improve the quality and level of the argumentation.

• Journal of the Korean earth science society
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• v.42 no.3
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• pp.311-324
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• 2021

Recently, ten geosites have been considered in Hwaseong for endorsement as national geoparks, including the Jebudo, Gojeongri Dinosaur Egg Fossils, and Ueumdo geosites. The Jebudo geosite in the southern part of the Seoul metropolitan area has great potential for development as a new geoscience educational site because it has geological, geographical (landscape), and ecological significance. In this study, we described the geological characteristics through field surveys in the Jebudo geosite. We evaluated its potential as a geo-education site based on comparative analysis with other geosites in Hwaseong Geopark. In addition, we reviewed the practical effect of field education at geosites on the essential concepts and critical competence-oriented education emphasized in the current 2015 revised science curriculum. The Jebudo Geosite is geologically diverse, with various metamorphic rocks belonging to the Precambrian Seosan Group, such as quartzite, schist, and phyllite. Various geological structures, such as clastic dikes, faults, joints, foliation, and schistosity have also been recorded. Moreover, coastal geological features have been observed, including depositional landforms (gravel and sand beaches, dunes, and mudflats), sedimentary structures (ripples), erosional landforms (sea cliffs, sea caves, and sea stacks), and sea parting. The Jebudo geosite has considerable value as a new geo-education site with geological and geomorphological distinction from the Gojeongri Dinosaur Egg Fossils and Ueumdo geosites. The Jebudo geosite also has opportunities for geo-education and geo-tourism, such as mudflat experiences and infrastructures, such as coastal trails and viewing points. This geosite can help develop diverse geo-education programs that improve key competencies in the science curriculum, such as critical thinking, inquiry, and problem-solving. Furthermore, by conducting optimized geo-education focused on the characteristics of each geosite, the following can be established: (1) the expansion of learning space from school to geopark, (2) the improvement of understanding of specific content elements and linkage between essential concepts, and (3) the extension of the education scope throughout the earth system. There will be positive impacts on communication, participation, and lifelong learning skills through geopark education.

• Journal of The Korean Association For Science Education
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• v.41 no.2
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• pp.145-154
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• 2021

This study aims to investigate teachers' perceptions of the composition of high school science elective courses ahead of the 2022 curriculum revision, and to derive implications for the organization of the 2022 revised science curriculum in preparation for the full implementation of the high school credit system. To this end, a survey was conducted by randomly sampling high schools across the country. A total of 192 science teachers responded to the questionnaire. In addition, 12 high school science teachers were selected as a focus group, and in-depth interviews were conducted to investigate opinions on the restructuring of elective courses in science. Main research results include 129 (67.2%) science teachers in the survey answered that the current 2015 curriculum's science and elective courses system should be maintained. In the next curriculum, when reconstructing science elective subjects, it is necessary to provide an opportunity to experience the entire contents of each science field through Science I·II system as before, and to ensure student choice in preparation for the credit system. In addition, the opinion that general elective subjects should be organized to include all the contents of science I and II subjects was the highest. Through in-depth interviews, science teachers emphasized that the current science I subject system allows access to the content areas of science as much as possible as the number of subjects is small, and that subjects, such as physics, where the hierarchy of concepts is important, should deal with important content within one subject rather than divided by area. On the other hand, in the current I subject system, there is no subject for liberal arts students to choose from, so teachers suggested that science electives should be organized by subdividing each content area. Based on the research results, the necessity of organizing high school science elective courses in consideration of the purpose of the high school credit system, ways to organize science-convergence elective courses as subjects for all students regardless of career aptitude, ways to organize science-career elective courses, and ways to organize science elective courses in connection with the college admission system were proposed.