• Natural Product Sciences
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• v.22 no.2
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• pp.82-86
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• 2016

Six compounds were isolated from the secondary metabolites of the jellyfish-derived fungus Aspergillus fumigates, whose structures were identified by chemical methods and spectroscopic analysis as pseurotin F1 (1), azaspirofurans B (2), $(22E,\;24R)-24-methyl-5{\alpha}-cholesta-7,22-diene-3{\beta},5,6{\beta}-triol$ (3), $5{\alpha},8{\alpha}-epidioxyergosta-6,22-dien-3{\beta}-o1$ (4), $cyclo-({\small{L}}-Pro-{\small{L}}-Tyr)$ (5), fumitremorgin C (6). The compounds 1 - 5 were isolated from the fungus Aspergillus fumigates for the first time. The isolated compounds (1 - 6) were evaluated for antibiotic activity and cytotoxicity against six bacterial strains and ten human tumor cell lines, respectively.

• Korean Journal of Remote Sensing
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• v.23 no.5
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• pp.385-391
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• 2007

Subsurface Internal Waves(IWs) can be detected in satellite images as periodic alternating brighter/darker stripes. It is known that there are two types of IWs-depression type and elevation type-depending on the water depth in stratified oceans. In this study, we have quantitatively verified the process of converting polarity from depression waves to elevation waves using ERS-2 SAR image acquired over the northern South China Sea. We simulated the evolution of IWs near a turning point with a numerical model for internal wave propagation. The simulation results near the turning point clearly showed us not only a conversion process of IWs from depression to elevation waves, but also a similar wave pattern with the observed SAR image. We also simulated SAR intensity variation near the turning point. The upper layer currents were computed at regular intervals using the numerical model, as the IWs were passing through the turning point. Then, an integrated hydrodynamic-electromagnetic model was used for simulating SAR intensity profiles from the upper layer currents. The simulated SAR intensity profiles were compared with the observed SAR intensities.

• Ocean and Polar Research
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• v.35 no.2
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• pp.157-170
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• 2013

We investigated the seasonal succession of phytoplankton assemblages in the eastern part of the South Sea of Korea in relation to surface water masses. The study areas are under the direct influence of the Tsushima Warm Current (TCW) throughout the whole year, with its strength known to be seasonally variable. The region is also influenced by coastal waters (CW) driven from the South Sea of Korea and East China Sea, particularly in summer, as indicated by low salinity in the surface water. Nutrient property of the TCW can reveals whether the origin of the TCW is the nutrient-rich Kuroshio Current or the oligotropic Taiwan Warm Current. Surface chlorophyll-a (Chl-a) concentrations displayed a large seasonal variation for all stations, with high values found in spring and autumn and low values in summer and winter. At station M (offshore) and P (intermediate location between M and R), Chl-a concentrations in October were higher than those in March, when spring bloom normally occurs. This may be related to deeper mixed layer depths in October. Diatoms dominated under conditions of high nutrient supply in which Chaetoceros spp. and Skeletonema costatum-like spp. were abundant. S. costatum-like spp. dominated at stations R (onshore station) and P in December when there was greater nutrient supply, especially of phosphate. Flagellates and dinoflagellates dominated at all three stations after diatoms blooms. Dominant species were Scrippsiella trochoid in April and Ceratium furca in October at station R, and Gyrodinium spp. and Gymnodinium spp. at station M during summer, when the effect of the oligotropic Taiwan Warm Current and the oligotropic coastal water from East China Sea were strong. Redundancy analysis showed clear seasonal successions in the phytoplankton community and environmental conditions, in which both principal components 1 and 2 accounted for 69.6% of total variance. Our results suggested that environmental conditions seemed to be determined by the origin of the TCW and the relative seasonal strength of the water masses of the TCW and CW, which may affect phytoplankton growth and compositions in the study area.

• Maritime Security
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• v.5 no.1
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• pp.113-136
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• 2022

China has been pushing for a systematic strategy for territorialization over a long period of time to invade Korea's West Sea (Yellow Sea) in order to create China's territorial water. China's strategy for territorializing the West Sea is an activity in which China curbs the use of South Korea and enforces the illegal use of China in order to dominate the West Sea exclusively. China aided Chinese fishing boats that engaged in illegal fishing in Korea's jurisdiction as a means to territorialize the West Sea, and is opposed to combined exercise and training of Korea and the United States Naval Forces in the West Sea, while intentionally entering KADIZ(Korea Air Defense Identification Zone). In addition, Beijing used 'scientific exploration and research' measures as a pretext for its strategies in order to encroach on Korea's West Sea. China is carrying out such work to announce to the world that China is a systematic and organized country while consistently attempting to dominate the West Sea. China's activities in the West Sea seriously infringe South Korea's sovereignty. In order to respond to China's strategies of territorialization in the West Sea stated above, I analyzed the rejection effect of the ROK-US combined military training in the West Sea and presented a 'proportional response strategy centered on the ROK-US combined forces'. Korea should be able to respond proportionally to China's activities in the seas around the Korean peninsula, and Korea should be able to neutralize China's attempt to a Fait Accompli. In addition, just as China installs buoys in the Korea-China Provisional Measures Zone, Korea should be able to install and actively utilize some devices in the West Sea and for the use of free and open West Sea. Korea should not just wait for the tragic future to come without preparing for China's gradual and long-term strategy, and Seoul needs to respond to China's maritime policy in the West Sea with a more active attitude than it is now. China has historically taken a bold and aggressive response to neighboring countries that are consistent with a passive attitude, on the other hand, Beijing has taken a cautious approach to neighboring countries that respond with an active attitude. It should not be forgotten that Korea's passive response to the Chinese strategy in the name of a 'realistic approach' such as Korea's economic dependence on China for economy will result in China's success for territorialization of the West Sea.

• Journal of the Korean Society of Marine Environment & Safety
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• v.6 no.1
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• pp.99-109
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• 2000

The United Nations Convention on the Law of the Sea(hereinafter referred as "the Law") adopted in 1982 was enacted on November 16, 1994. South Korea, China, and Japan signed and ratified the Law, respectively. These three countries announced their domestic laws relating to Exclusive Economic Zone(EEZ) with reserving their applications. The enactment of the Law and announcement of EEZ inevitably brought new order on the seas. The New Fishery Agreement based on the Law with EEZ was concluded between South Korea and Japan and ratified by each country′s parliament. Another New Fishery Agreement between South Korea and China is also going to be concluded in near future. The New Fishery Agreements, however, do not include regulations relating to the marine scientific research, the protection of the marine environment, and so forth, which are essential for the States to fully implement the Law According to the New Fishery Agreements, it is impossible for the Coastal States to excercise their jurisdiction. Because the agreement of delimitation ocean boundaries among the three countries are not easy to settle, provisional agreements can only be concluded. Thus, many problems including the sovereignty over Dok-do between South Korea and Japan and delimitation of EEZ between South Korea and China can be arose anytime. This paper investigates the problems and possible counter measures in legal excercise on the seas by South Korean Government. The above mentioned problems introduced by the New Fishery Agreements include potential problems in the Middle Sea Zone, Provisional Zone, and so forth. In this paper, only the legal aspect of the Zones will be discussed excluding the law enforcement and the economic aspect of the Zones.

• Fisheries and Aquatic Sciences
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• v.20 no.4
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• pp.6.1-6.8
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• 2017

The objective of this research was to study the effect of astaxanthin (AST) on growth performance and antioxidant capacity in golden pompano (Trachinotus ovatus) both in vivo and in vitro. In the in vivo study, two diets were formulated with or without astaxanthin supplementation (D1 and D2; 0 and 200 mg/kg) to feed fish for 6 weeks. In the in vitro study, cells from hepatopancreas of golden pompano were isolated and four treatments with or without astaxanthin and $H_2O_2$ supplementation were applied (control group: without both astaxanthin and $H_2O_2$ treated; $H_2O_2$ group: just with $H_2O_2$ treated; $H_2O_2$ + AST group: with both astaxanthin and $H_2O_2$treated; AST group: just with AST treated). Results of the in vivo study showed that weight gain (WG) and special growth rate (SGR) significantly increased with astaxanthin supplemented (P < 0.05). Feed conversion ratio (FCR) of fish fed D2 diet was significantly lower than that of fish fed D1 diet (P < 0.05). Hepatic total antioxidant capacity (T-AOC) and the reduced glutathione (GSH) of golden pompano fed D2 diet were significant higher than those of fish fed D1 diet (P < 0.05). Superoxide dismutase (SOD) was significantly declined as astaxanthin was supplemented (P < 0.05). Results of the in vitro study showed that the cell viability of $H_2O_2$ group was 52.37% compared to the control group, and it was significantly elevated to 84.18% by astaxanthin supplementation ($H_2O_2$ + AST group) (P < 0.05). The total antioxidant capacity (T-AOC) and the reduced glutathione (GSH) of cell were significant decreased by oxidative stress from $H_2O_2$ (P < 0.05), but it could be raised by astaxanthin supplementation ($H_2O_2$ vs $H_2O_2$ + AST), and the malondialdehyde (MDA) was significant higher in $H_2O_2$ group (P < 0.05) and astaxanthin supplementation could alleviate the cells from lipid peroxidation injury. In conclusion, dietary astaxanthin supplementation can improve the growth performance of golden pompano. Moreover, astaxanthin can improve the golden pompano hepatic antioxidant capacity both in vivo and in vitro study by eliminating the reactive oxygen species.

• Journal of the Korean earth science society
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• v.25 no.1
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• pp.1-9
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• 2004

The clay minerals of thirty-four bottom sediments collected from the northwestern continental shelf of the East China Sea have been determined by X-ray diffraction analysis. The clay mineral distribution is mainly controlled by the sediment source and the dominant circulation pattern. The predominant clay mineral in our study area is illite comprising more-than 70% of whole clay fraction. The highest concentration of illite (>72%) is found in the southeastern offshore parts beyond the reach of terrigenous input from the Cheju Island. It means that these illites are largely transported by the Kuroshio Current from the South China Sea. Smectite is highly concentrated in the northwest middle part and in the outer-shelf mud patch. It seems to be due to the high supply of smectite transported from China where the fine-grained sediments are discharged from the modern and ancient Huanghe River. The relatively high abundance of kaolinite is likely derived from the Changjiang River via Taiwan ·Warm Current. In contrast, the large amounts of chlorite and high chlorite/kaolinite ratios occur in the northwestern are, reflecting the transportation by the Huanghai Sea Coastal Current from the southern Yellow Sea.

• Proceedings of the KSR Conference
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• 2005.05a
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• pp.1125-1131
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• 2005

This study is based on the assumption of surface transport linkages between Korea and China. Active economic cooperation between South Korea and North Korea are expected within the near future and Russia and China have interested in the land transport linkages in Korean peninsula. How much freight demands between the two countries that has been mainly dependent on air and sea transportation so far may convert the transport mode to surface transportation are estimated. Particularly, freight demands between South Korea and China's three northeast provinces are focused. The sensitivity analysis depends on transport time and transport cost changes is included. The modal shifts is estimated to be more sensitive to the changes in transport costs than those in transport time, suggesting the importance of transport costs of rail and road. Despite the dearth of data on the surface transport operation in North Korea, the attempts made in this study to estimate the demand conversion are hope to provide reference points for potential effects of the rail and road transport connections between China and the Korea peninsula before our discussions expand to the establishment of freight transport network of the northest Asia and, moreover, the Eurasian continent.

• Ocean and Polar Research
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• v.34 no.2
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• pp.201-218
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• 2012

The purpose of this study is to investigate climatological variations from the sea surface temperature (SST), chlorophyll-a concentration (Chl-a), and phytoplankton size class (PSC), using NOAA AVHRR, SeaWiFS, and MODIS data in the South Sea of Korea (SSK) and East China Sea (ECS). 26-year monthly SST and 13-year monthly Chl-a and PSC data, separated by whole and nine-different areas, were used to understand seasonal and inter-annual variations. SST and Chl-a clearly showed seasonal variations: higher SST and Chl-a were observed during the summer and spring, and lower values occurred during the winter and summer. The annual and monthly SST over 26 years increased by $0.2{\sim}1.0^{\circ}C$. The annual and monthly Chl-a concentration over 13 years decreased by $0.2{\sim}1.1mg/m^3$. To determine more detailed spatial and temporal variations, we used the combined data with monthly SST, Chl-a, and PSC. Between 1998 and 2010, the inter-annual trend of Chl-a decreased, with decreasing micro- and nano-size plankton, and increasing pico-size plankton. In regional analysis, the west region of the study area was spatially and temporally correlated with the area dominated by decreasing micro-size plankton; while the east region was less sensitive to coastal and land effects, and was dominated by increasing pico-size plankton. This phenomenon is better related to one or more forcing factors: the increased stratification of ocean driven by changes occurring in spatial variations of the SST caused limited contributions of nutrients and changed marine ecosystems in the study area.

• Proceedings of the KSRS Conference
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• v.2
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• pp.534-534
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• 2006