• Ocean and Polar Research
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• 제26권1호
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• pp.51-58
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• 2004

We isolated and identified culturable Arctic bacteria that had inhabited soils around the Korean Arctic Research Station Dasan located at Ny-Alsund, Svalbard, Norway $(79^{\circ}N,\;12^{\circ}E)$. The collected soils were diluted in distilled water; the diluted soil-water was spread on 3M petri-films at Dasan Station. The petri-films were transported to the laboratory at KORDI, and cultured at $4^{\circ}C$. Colonies grown on the petri-films were subsequently cultured on nutrient agar plates at $4^{\circ}C$ every 7 days. The pure colonies were inoculated into nutrient liquid media, genomic DNA was extracted, and phylogenetic analysis was performed on the basis of 165 rDNA sequences. A total of 227 strains of bacteria were isolated. Among them, 16S rDNA sequences of 185 strains were identical with those of known strains isolated in this study, and 42 strains were finally identified. Phylogenetic analysis using 16S rDNA indicated that the 30 strains belonged to Pseudomonas, 7 strains to Arthrobacter, two strains to Flavobacterium, and the remaining to Achromobacter, Pedobacter, and Psychrobacter. Among the 42 strains, 14 bacteria produced protease: they were 6 strains of Pseudomonax, 4 strains of Arthrobater, an Achromobacter strain, 2 strains of Flavobacterium, and a Pedohacter strain. We expect these Arctic bacteria can be used for screening to develop new industrial enzymes that are active at low temperatures.

• Ocean and Polar Research
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• 제37권1호
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• pp.23-35
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• 2015

A 450 m-long sediment section was recovered from Hole U1359D located at the eastern levee of the Jussieau submarine channel on the Wilkes Land continental rise (East Antarctica) during IODP Expedition 318. The age model for Hole U1359D was established by paleomagnetic stratigraphy and biostratigraphy, and the ages of core-top and core-bottom were estimated to be about 5 Ma and 13 Ma, respectively. Biogenic opal content during this period varied between 3% and 60%. In the Southern Ocean, high biogenic opal content generally represents warm climate characterized by the increased light availability due to the decrease of sea-ice distribution. The surface water productivity change in terms of biogenic opal content at about 10.2 Ma in the Wilkes Land continental rise was related to the development of Northern Component Water. After about 10.2 Ma, more production of Northern Component Water in the North Atlantic caused to increase heat transport to the Southern Ocean, resulting in the enhanced diatom production. Miocene isotope events (Mi4~Mi7), which are intermittent cooling intervals during the Miocene, appeared to be correlated to the low biogenic opal contents, but further refinement was required for precise correlation. Biogenic opal content decreased abruptly during 6 Ma to 5.5 Ma, which most likely corresponds to the Messinian salinity crisis. Short-term variation of biogenic opal content was related to the extent of sea-ice distribution associated with the location of Antarctic Polar Front that was controlled by glacial-interglacial paleoclimate change, although more precise dating and correlation will be necessary. Diatom production in the Wilkes Land continental rise increased during the interglacial periods because of the reduced sea-ice distribution and the southward movement of Antarctic Polar Front.

• 한국초등과학교육학회지:초등과학교육
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• 제33권2호
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• pp.401-414
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• 2014

The purpose of this study is to investigate the elementary preservice teachers' conceptions about 'plastics' focusing on non-polar property from a National University of Education. For the study, the views about plastics, relative shapes of a water droplet on plastic or glass material, and relative shapes of water surface in the plastic or glass measuring cylinder were surveyed from the preservice teachers. And the responses were analyzed based on the patterns. The results from the study are as follows: First, most preservice teachers were well aware of the plastic products which are used in daily life. Second, the responses concerning the reason why plastics can be used commonly were divided into 2 categories with 14 sub-level groups. However relatively few preservice teachers mentioned regarding 'chemical stability' and 'conductivity', which are associated with the plastics' non-polar property. Third, it was found that 50 participants (30.1%) had 'Scientific conception (Sc)', 38 (22.9%) had 'Partial-scientific conception (Ps)', 66 (39.8%) had 'Misconception (Mc)', and 12 (7.2%) had 'No conception (Nc)' on the subject of the relative shapes of a water droplet. Fourth, the distribution patterns and the ratio of the preservice teachers' conception on the survey question 3 concerning the relative shapes of water surface were quite similar to those of the survey question 2. So it was concluded that overall understanding level of the preservice teachers was pretty low on the subjects of the relative polarities of the plastic, glass, and water as well as their interactions. Fifth, the distribution percentile of 'Sc'/'Ps'/'Mc'/'Nc' was not related with the gender but highly correlated with preservice teachers' academic field and their science subjects taken in high school. Based on the results from the study, some educational guidelines were suggested.

• Ocean and Polar Research
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• 제24권3호
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• pp.249-253
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• 2002

There is a great deal evidence concerning crustal uplift, after deglaciation, in the vicinity of Syowa Station $(69^{\circ}S,\;39^{\circ}E)$ from tide gauge data, seismic evidence, raised beaches, marine terraces, etc. The geomorphological and tide gauge data show that the crustal uplift is going on around Syowa Station. Seismic observations at Syowa Station started in 1959. Phase readings of the earthquakes have been published by National Institute of Polar Research once a year since 1968, as one of the Data Report Series. Eighteen local earthquakes were detected on short period seismograms at Syowa Station in 1990-2000. The seismicity during the period from 1990 to 2000 was lower than that from 1987 to 1989 when epicenters of local earthquakes were determined by tripartite seismic array. Local earthquake activity corroborates the crustal uplif4 which is an intermittent phenomenon. Sea level falling of 4.5 mm/y was found using data in 1975-1992. This felling rate is consistent with the geomorphological data. A route for repeat leveling survey was established in East Ongul Island. No appreciable change of sea level was observed for the last 14 years. A dynamics of the crustal uplift around Syowa Station has been discussed using geomorphological data, ocean tide, and seismic and leveling data, which is estimated to be an intermittent phenomenon. When local seismic activity is high, the crustal uplift is estimated to be going on. On the contrary, the crustal uplift is in dormancy when the local seismicity is low. Repeated leveling measurements suggest no significant changes, which further supports the idea that the crustal uplift in offshore is not a tilt trend movement but a block movement.

• Ocean and Polar Research
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• 제38권4호
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• pp.339-345
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• 2016

Stable water vapor isotopes have been utilized as a tracer for studying atmospheric global circulations, climate change and paleoclimate with ice cores. Recently, since laser spectroscopy has been available, water vapor isotopes can be measured more precisely and continuously. Studies of water vapor isotopes have been conducted over the world, but it is the early stage in south Korea. For vapor isotopes study, a cryogenic sampling device for water vapor isotopes has been developed. The cryogenic sampling device consists of the dewar bottle, filled with extremely low temperature material and impinger connected with a vacuum pump. Impinger stays put in the dewar bottle to change the water vapor which passes through the inside of impinger into the solid phase as ice. The fact that water vapor has not sampled completely leads to isotopic fractionation in the impinger. To minimize the isotopic fractionation during sampling water vapor, we have tested the method using a serial connection with two sets of impinger device in the laboratory. We trapped 98.02% of water vapor in the first trap and the isotopic difference of the trapped water vapor between two impinger were about 20‰ and 6‰ for hydrogen and oxygen, respectively. Considering the amount of water vapor trapped in each impinger, the isotopic differences for hydrogen and oxygen were 0.33‰ and 0.06‰, respectively, which is significantly smaller than the precision of isotopic measurements. This work can conclude that there is no significant fractionation during water vapor trapping.

• Journal of Ecology and Environment
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• 제46권4호
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• pp.282-291
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• 2022

Background: The Arctic permafrost stores enormous amount of carbon (C), about one third of global C stocks. However, drastically increasing temperature in the Arctic makes the stable frozen C stock vulnerable to microbial decomposition. The released carbon dioxide from permafrost can cause accelerating C feedback to the atmosphere. Soil organic matter (SOM) composition would be the basic information to project the trajectory of C under rapidly changing climate. However, not many studies on SOM characterization have been done compared to quantification of SOM stocks. Thus, the purpose of our study is to determine soil properties and molecular compositions of SOM in four different Arctic regions. We collected soils in different soil layers from 1) Cambridge Bay, Canada, 2) Council, Alaska, USA, 3) Svalbard, Norway, and 4) Zackenberg, Greenland. The basic soil properties were measured, and the molecular composition of SOM was analyzed through pyrolysis-gas chromatography/mass spectrometry (py-GC/MS). Results: The Oi layer of soil in Council, Alaska showed the lowest soil pH and the highest electrical conductivity (EC) and SOM content. All soils in each site showed increasing pH and decreasing SOC and EC values with soil depth. Since the Council site was moist acidic tundra compared to other three dry tundra sites, soil properties were distinct from the others: high SOM and EC, and low pH. Through the py-GC/MS analysis, a total of 117 pyrolysis products were detected from 32 soil samples of four different Arctic soils. The first two-axis of the PCA explained 38% of sample variation. While short- and mid-hydrocarbons were associated with mineral layers, lignins and polysaccharides were linked to organic layers of Alaska and Cambridge Bay soil. Conclusions: We conclude that the py-GC/MS results separated soil samples mainly based on the origin of SOM (plants- or microbially-derived). This molecular characteristics of SOM can play a role of controlling SOM degradation to warming. Thus, it should be further investigated how the SOM molecular characteristics have impacts on SOM dynamics through additional laboratory incubation studies and microbial decomposition measurements in the field.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1993년도 한국자동제어학술회의논문집(국제학술편); Seoul National University, Seoul; 20-22 Oct. 1993
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• pp.480-485
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• 1993

A method for obtaining optimal orbital maneuvers of a space vehicle has been developed by combining feedback linearization method with the elegance of the Lambert's theorem. To obtain solutions to nonlinear orbital maneuver problems. The full nonlinear equations of motion for space vehicle in polar coordinate system are transformed exactly into a controllable linear set in Brunovsky canonical form by using feedback linearization by choosing position vector as fully observable output vector. These equations are used to pose a linear optimal tracking problem with a solutions to Lambert's problem and a linear analytical solution of continuous low thrust problem as reference trajectories.

• 한국고분자학회:학술대회논문집
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• 한국고분자학회 2006년도 IUPAC International Symposium on Advanced Polymers for Emerging Technologies
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• pp.123-124
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• 2006

Ionic liquids (ILs) are collecting keen interests as an advanced substituent of electrolyte solution as well as novel solvents. In the present talk, I will introduce some strategies to fix IL structure on polymer chains to prepare polar polymers with low glass transition temperature. Namely, cationic, anionic, and zwitterionic monomers have been prepared, and they have been homopolymerized or copolymerized to prepare polymer electrolytes with different properties. The polymers themselves showed very poor ionic conductivity, but it was improved by suitable spacer between charged site and main chain. Other unique characteristics of functional ILs and new polymerized ionic liquids will also be mentioned.

• Bulletin of the Korean Chemical Society
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• 제6권4호
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• pp.183-186
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• 1985

The lattice vibrational calculation of orthorhombic hydrogen chloride is performed using physically realistic potential function which can reproduce the X-ray structure and heat of sublimation of the low temperature phase. The polar coordinates representation is introduced in order to describe the intermolecular interactions in a molecular crystal. The splitting in internal modes is calculated as 49 $cm^{-1}$ and the other modes are in good agreement with experimental results.

• 미생물학회지
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• 제54권1호
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• pp.60-68
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• 2018

남극 해양세균 Pseudoalteromonas arctica PAMC 21717로부터 저온활성 alkaline protease (Pro21717)를 부분정제하였다. Pro21717 효소 추출액은 skim milk를 포함하는 zymogram gel 상에서 약 37 kDa (낮은 활성)과 74 kDa (높은 활성) 위치에서 두 개의 뚜렷한 투명밴드(clear zone)를 형성하였다. 단백질 분해활성을 나타내는 두 개의 효소단백질은 동일한 N-말단 아미노산 서열을 가지고 있었으며, 하나의 유전자에서 발현된 미성숙 단백질(precursor)이 37 kDa 크기의 단백질분해효소로 성숙화과정을 거친 후 74 kDa 크기로 이량체화됨으로써 좀 더 높은 활성을 가지는 것으로 판단된다. Pro21717은 $0-40^{\circ}C$ (최고활성 온도 $40^{\circ}C$) 온도 범위에서 단백질분해활성을 나타내었고 pH 5.0-10.0 (최적 pH 9.0) 범위에서 효소활성을 유지하였다. 주목할만한 특성으로써, Pro21717은 $40^{\circ}C$에서의 최고 효소활성(100%) 대비, $0^{\circ}C$와 $10^{\circ}C$에서 각각 30%와 45%의 높은 저온활성을 나타내었다. 또한 다양한 합성 펩타이드류에 대해 분해활성을 나타내는 Pro21717은 $Cu^{2+}$에 의해 활성이 증가하였으며, 시판용 세탁세제(commercial detergent formulation)에 포함되어 있는 다양한 종류의 계면활성제, 화학성분, 금속이온에 의해 활성이 감소되지 않았다. 전반적으로 저온활성 Pro21717은 글로벌 상업용효소 생산회사 Novozymes이 시판하고 있는 중온성 효소 Subtilisin Carlsberg (trademark Alcalase)에 버금가는 유용한 효소학적 특성이 있는 동시에 상대적으로 더 높은 저온활성을 보여주고 있다. 위의 실험결과들은, Pro21717은 $15^{\circ}C$ 이하의 차가운 수돗물에서도 세척력을 유지하는 새로운 세탁세제 효소첨가제로서의 개발 가능성을 보여주고 있다.