• Ocean and Polar Research
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• 제36권2호
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• pp.145-156
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• 2014

Macrobenthic biodiversity in the rocky intertidal areas of the Tae-an region, Republic of Korea, has decreased since the Hebei Spirit oil spill in December 2007. We aimed to investigate ecological roles of Pacific oyster (Crassostrea gigas) because recruitment and growth of oysters are critical to the recovery of damaged rocky shore ecosystem. We surveyed two sites monthly: natural rocky substrate and farming substrate, from July 2012 to January 2013 to identify and compare the changes in macrobenthic fauna. The abundance of young oysters was higher at the natural site. On the other hand, the mean height of oyster on the farming substrate was more than twice as great. The abundance of oyster at the natural site increased until October and then continuously decreased until end of study period. However, the abundance of oyster at the farming site constantly decreased from the beginning of study period. These different growth patterns might be attributable to spatial competition between oyster and a barnacle species (Balanus albicostatus) and environmental factors. At the natural site, physical stress factors including dramatic temperature changes and desiccation a few of the major factors limiting growth during aerial exposure. In addition, motile macrobenthos could be detrimental to oysters because they interrupt filter-feeding activities and hence hamper the growth of oysters. We show the higher recruitment of oysters at the natural site and healthy growth in the farming substrate are due to complicated differences in physical and biological stress factors.

• Ocean and Polar Research
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• 제28권3호
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• pp.225-236
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• 2006

Seagrass meadows are considered as critical habitats for a wide variety of marine organisms in coastal and estuarine ecosystems. In many cases, studies on the spatial/temporal distribution of seagrass have depended on direct observations using SCUBA diving. As an alternative method fur studying seagrass distribution, an application of hydroacoustic technique has been assessed for mapping seagrass distribution in Dongdae Bay, on the south coast of Korea, in September 2005. Data were collected using high frequency transducer (420 kHz split-beam), which was installed with towed body system. The system was linked to DGPS to make goo-referenced data. Additionally, in situ seagrass distribution has been observed using underwater cameras and SCUBA diving at four stations in order to compare with acoustic data. Acoustic survey was conducted along 23 transects with 3-4 blot ship speed. Seagrass beds were vertically limited to depths less than 3.5m and seagrass height ranged between 55 and 90cm at the study sites. Dense seagmss beds were mainly found at the entrance of the bay and at a flat area around the center of the bay. Although the study area was a relatively small, the vertical and spatial distributions of the seagrass were highly variable with bathymetry and region. Considering dominant species, Zostera marina L., preliminary estimation of seagrass biomass with acoustic and direct sampling data was approximately $56.55g/m^2$, and total biomass of 104 tones (coefficient variation: 25.77%) was estimated at the study area. Hydroacoustic method provided valuable information to understand distribution pattern and to estimate seagrass biomass.

• Ocean and Polar Research
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• 제30권2호
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• pp.181-191
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• 2008

This study aims at assessment of spatio-temporal distribution of demersal fish aggregations near the west coast of Jeju Island using hydroacoustic survey. A 200 kHz split beam transducer attached to a small towed body was used for all acoustic investigations. The received acoustic data were in situ acoustic target strength (TS, dB) for all pings and nautical area scattering coefficient(NASC, $m^2/mile^2$) for 0.1 mile along 12 acoustic transects. Demersal fish aggregations are distributed around the coastal slope having 20 to 30 m depth throughout all seasons. The concentration is higher during the summer season. With regard spatial distribution, higher demersal fish aggregations have been detected near the West coast of Shinchang and especially near Chagwi-do. Pelagic fish aggregations were higher to the south of Chagwi-do during the spring season. Additionally, standing stock of demersal fish aggregations from the NASC data, TS function, and length-weight function of dominant species was estimated as follows: 3.2 ton (CV 21.8%) in December 2006, 17.9 ton (CV 21.6%) in April 2007, 30.8 ton (CV 17.8%) in June 2007, and 22.5 ton (CV 24.2%) in October 2007. The application of hydroacoustic methods offers a new approach to understanding spatiotemporal structure and estimate the biomass of demersal fish aggregations in the coastal area. And the results can be made up limitations of qualitative analysis through net and diving for fisheries resources survey in coastal area.

• 한국응용과학기술학회지
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• 제29권4호
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• pp.599-609
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• 2012

이 연구의 목적은 버려진 굴 패각을 재활용하여 감소시키는 것으로 굴 패각과 해조펄프를 이용하여 식품의 보존에 대한 항산화비드를 활용하는데 있다. 이 연구는 두 부분으로 나누었다. 첫 번째는 파일럿 규격조건으로 설계하고 제조하였다. 둘째는 [A],[B],[C-a],[C-b]화합물에 대한 최적제조 조건을 다루어 확립하고 이들 생성물을 분석하였다. 파일럿 규격 제조는 해조펄프의 분자수식합성과/Cl-전분 그리고 그의 다양한 비드 형태들이 극성용매에서 다양한 중량비율로 액상 혼합하여 제조되었다. 부가적으로, 혼합과정에서 해조펄프의 비율이 증가함으로서, 해조펄프/Ag-굴 패각을 섞인 것의 항균성은 감소되었으나 항산화와 비드의 견고성 성질은 증가되었다. 파일럿 규격의 생성라인은 해조 펄프와 Cl-전분을 분자수식으로 합성하였다. 그리고 극성용매를 사용하여 여러 가지 중량비율로 다양한 형태의 비드를 제조하였다.

• 대한지리학회지
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• 제42권1호
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• pp.1-14
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• 2007

본 연구에서는 우리나라 육상 국지 예보 구역을 대상으로 예보 정확도를 분석하였다. 연구 기간 동안 평가 요소별 정확도는 강수 유무가 가장 낮았고 하늘 상태가 가장 높았다. 지역적으로 예보 정확도는 강원도에서 가장 낮았으며 경상남도와 경상북도에서 높았다. 계절별 예보 정확도의 만점 빈도는 겨울에 가장 높았고 여름에 가장 낮았다. 예보 정확도가 낮은 날의 기압 배치형을 분석했을 때 여름철에는 정체전선형 기압 배치에서 강수 유무의 예보 정확도가 낮았다. 가을과 겨울에는 한대 고기압 확장형 기압 배치에서 기온 예보의 정확도가 크게 낮아지는 경우가 많았다. 봄과 가을의 이동성 고기압형 기압 배치에서는 날씨가 급격하게 변하여 예보 정확도가 낮았다. 예보 정확도가 가장 낮은 지역인 영동 지역의 상층 850hPa 고도의 풍향 자료와 예보 정확도를 비교하여 분석한 결과, 최저 및 최고 기온은 서풍일 때, 강수 유무의 경우 동풍일 때 예보 정확도가 낮았다.

• Ocean and Polar Research
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• 제38권1호
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• pp.1-19
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• 2016

Recently, there has been a growing interest in physical-biological ocean-modeling systems by communities in the fields of science and business. In this paper, we present preliminary results from a coupled physical-biological model for the Northwestern Pacific marginal seas. The ocean circulation component is an implementation of the Regional Ocean Modeling System (ROMS), and the lower trophic level ecosystem component is a Nutrient-Phytoplankton-Zooplankton-Detritus (NPZD) model. The ROMS-NPZD coupled system, with a 25 km resolution, is forced by climatological atmospheric data and predicts the physical variables and concentrations of nitrate, phytoplankton, zooplankton, and detritus. Model results are compared with remote-sensed sea surface temperature and chlorophyll, and with climatological sea surface salinity and nitrate. Our model adequately reproduces the observed spatial distribution and seasonal variability of nitrate and chlorophyll concentrations as well as physical variables, showing a high correlation in the East Sea (ES) and Kuroshio/Oyashio Extension (KOE) region but relatively low correlation in the Yellow Sea (YS) and East China Sea (ECS). Although some deficiencies were found in the biological components, such as the over/underestimation of the intensity of phytoplankton blooms in the ES and KOE/the YS and ECS, our system demonstrates the capability of the model to capture and record dominant seasonal variability in physical-biological processes and this holds out the promise of coming to a better understanding of such processes and making better predictions .

• Ocean and Polar Research
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• 제29권4호
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• pp.349-366
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• 2007

Seasonal variations of various physicochemical components (temperature, salinity, pH, DO, COD, DOC, nutrients-silicate, DIN, DIP) and potential limiting factor for phytoplankton primary production were studied in the surface water of semi-enclosed Masan Bay. Seasonal variations of nutrient concentrations, with lower values in summer and winter, and higher in fall, are probably controlled by freshwater loadings to the bay, benthic flux and magnitude of occurrence of phytoplankton communities. Their spatial distributional patterns are primarily dependent on physical mixing process between freshwater and coastal seawater, which result in a decreasing spatial gradient from inner to outer part of the bay. In the fall season of strong wave action, the major part of nutrient inputs (silicate, ammonium, dissolved inorganic phosphorus) comes from regeneration (benthic flux) at sediment-water interface. During the summer period, high Si:DIN and Si:DIP and low DIN:DIP relative to Redfield ratios suggest a N- and secondarily P-deficiency. During other seasons, however, silicate is the potential limiting factor for primary production, although the Si-deficiency is less pronounced in the outer region of the bay. Indeed, phytoplankton communities in Masan Bay are largely affected by the seasonal variability of limiting nutrients. On the other hand, the severe depletion of DIN (relatively higher silicate level) during summer with high freshwater discharge probably can be explained by N-uptake of temporary nanoflagellate blooms, which responds rapidly to pulsed nutrient loading events. In Masan Bay, this rapid nutrient consumption is considerably important as it can modify the phytoplankton community structures.

• Journal of Radiation Protection and Research
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• 제41권3호
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• pp.185-190
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• 2016

Background: In order to measure neutron energy spectra, the conventional Bonner Sphere Spectrometers (BSS) are widely used. In this spectrometer, several measurements with different size Bonner spheres are required. Operators should, therefore, place these spheres in several times to a measurement point where radiation dose might be relatively high. In order to reduce this effort, novel neutron energy spectrometer using an onion-like single Bonner sphere was proposed in our group. This Bonner sphere has multiple sensitive spherical shell layers in the single sphere. In this spectrometer, a band-shaped thermal neutron detection medium, which consists of a LiF-ZnS mixed powder scintillator sheet and a wavelength-shifting (WLS) fiber readout, was looped to each sphere at equal angular intervals. Amount of LiF neutron converter is reduced near polar region, where the band-shaped detectors are concentrated, in order to uniform the directional sensitivity. The LiF-ZnS mixed powder has an advantage of extremely high light yield. However, since it is opaque, scintillation photons cannot be collect uniformly. This type of detector shows no characteristic shape in the pulse height spectrum. Subsequently, it is difficult to set the pulse height discrimination level. This issue causes sensitivity fluctuation due to gain instability of photodetectors and/or electric modules. Materials and Methods: In order to solve this problem, we propose to replace the LiF-ZnS mixed powder into a flexible and Transparent RUbber SheeT type $LiCaAlF_6$ (TRUST LiCAF) scintillator. TRUST LiCAF scintillator can show a peak shape corresponding to neutron absorption events in the pulse height spectrum. Results and Discussion: We fabricated the prototype detector with five sensitive layers using TRUST LiCAF scintillator and conducted basic experiments to evaluate the directional uniformity of the sensitivity. Conclusion: The fabricated detector shows excellent directional uniformity of the neutron sensitivity.

• BMB Reports
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• 제33권6호
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• pp.493-498
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• 2000

Aquifex pyrophilus, a hyperthermophilic bacterium, has a serine-type protease that is located at the cell wall fraction with a mature size of 43 kDa. Molecular cloning of the protease gene revealed that it has an ORF of 619 amino acids with homologous catalytic site of serine-type proteases [Choi, I.-G., Bang, W.-K., Kim, S.-H., Yu, G. Y., J. Biol. Chem. (1999), Vol. 274, pp. 881-888]. Constructs containing different regions of the protease gene, including a alanine-substituted mutant at the active site serine, were constructed, and the factors affecting the expression level of the cloned protease gene in E. coli were examined. The presence of the C-terminus hydrophobic region of the protease hindered over-expression in E. coli. Also, the proteolytic activity of the expressed protein appeared to toxic to E. coli. An inactive form that deleted both of the N-terminal signal sequence and the C-terminal polar residues was over-expressed in a soluble form, purified to homogeneity, and its thermostability examined. The purified protein showed three disulfide bonds and three free sulfhydryl group. The thermal denaturation temperature of the protein was measured around $90^{\circ}C$ using a differential scanning calorimeter and circular dichroism spectrometry. The disulfide bonds were hardly reduced in the presence of reducing agents, suggesting that these disulfide bonds were located inside of the protein surface.

• 대한화학회지
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• 제35권1호
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• pp.85-89
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• 1991

한국 남해안 소흑산도에서 채집한 해면 V.japonica H.로부터 통상적인tetradecanoic 및 hexadecanoic methyl ester 이외에 탄소가 홀수인 pentadecanoic, heptadecanoic methyl ester와 가지달린 12-methyltetradecanoic, 14-methylpentadecanoic, 15-methylhexadecanoic 및 14-methylhexadecanoic methyl ester가 발견되었으며, 주 sterol 성분으로는 cholesterol과 소량의 ergost-25-ene-3,5,6-triol이 검출되었다. 한편, 여수 돌산도에서 채집한 해면 H.sinapium의 주 sterol성분은 5${\alpha}$-cholestan-3${\beta}$-ol이었고 cholesterol은 소량으로 얻어졌다. 지방산으로는 팔미틴산, 팔미토레인산, 올레인산, 스테아린산 및 리놀레인산 에틸에스터 이외에 상당량의 arachidonic산 에틸에스터가 함유되어 있었다. 상기 지역에서 채집한 또 다른 해면에서는 상당량의 tetradecanoic tetradecyl 및 hexadecyl ester와 sterol 성분으로 cholesteryl acetic 및 fatty acid ester가 함유되어 있었다.