Actinium Abundance in the Atmospheres of Three Red Supergiants in the Magellanic Clouds

The actinium abundance in the atmospheres of red supergiants PMMR23 and PMMR144 in the Small Magellanic Cloud and RM_1-667 in the Large Magellanic Cloud was estimated. The results of spectral observations with the ESO 3.6-m telescope with resolving power R = 30000 were used. Since actinium was not found in the atmospheres of PMMR23 and PMMR144, only the upper limits were set on its abundance: logN(Ac/H) <–15.1 and–15.0, respectively. The estimated abundance of actinium in the atmosphere of RM_1-667 varied with parameters of the atmospheric model from–14.1 to–13.3. The lines of ionized actinium λ 616.475 nm and λ 581.085 nm were used in this analysis.     

Field application of freezing technology for social infrastructures

There are numerous methods to prevent seepage flow and ground improvement methodologies such as cement grouting, sheet piling, and the membrane method. In this paper, we present case histories of freezing technology applications in the construction of a deep tunnel sewerage system, undersea highway tunnel, and liquefied natural gas tank. Heaving pressure measurements for various soil types around a liquefied natural tank are compared with existing data. In this paper, we present temperature variations at the bottom and side of a liquefied natural gas tank. Our findings show that ground-freezing technology is very effective in controlling ground water infiltration into underground structures as well providing soil reinforcement in the soft ground.     

Recent Primary Production and Small Phytoplankton Contribution in the Yellow Sea during the Summer in 2016

The high nutrient concentration associated with the mixing dynamics of two warm and cold water masses supports high primary production in the Yellow Sea. Although various environmental changes have been reported, no recent information on small phytoplankton contribution to the total primary production as an important indicator for marine ecosystem changes is currently available in the Yellow Sea. The major objective of this study is to determine the small (< 2 μm) phytoplankton contribution to the total primary production in the Yellow Sea during August, 2016. In this study, we found relatively lower chlorophyll a concentrations in the water column than those previously reported in the central waters of the Yellow Sea. Moreover, the overall contribution of small phytoplankton (53.1%) to the total chlorophyll a concentration was considerably higher in this study than that (10.7%) observed previously. Based on the N/P ratio (67.6 ± 36.6) observed in this study, which is significantly higher than the Redfield ratio (16), we believe that phytoplankton experienced P-limiting conditions during the study period. The average daily carbon uptake rate of total phytoplankton in this study was 291.1 mg C m^-2 d^-1 (± 165.0 mg C m^-2 d^-1) and the rate of small phytoplankton was 205.7 mg C m^-2 d^-1 (± 116.0 mg C m^-2 d^-1) which is 71.9% (± 8.8%) of the total daily carbon uptake rate. This contribution of small phytoplankton observed in this study appears to be higher than that reported previously. Our recent measured primary production is approximately 50% lower than the previous values decades ago. The higher contributions of small phytoplankton to the total chlorophyll a concentration and primary production might be caused by P-limited conditions and this resulted in lower chlorophyll a concentration and total primary production in this study compared to previous studies.     

Antioxidant efficacy of extracts from a variety of seaweeds in a cellular system

As a part of an ongoing search for antioxidants frodm marine sources, antioxidant activities of 24 kinds of seaweeds (4 green algae, 8 brown algae, and 12 red algae) were investigated. The seaweeds were extracted by acetone/ dichloromethane and methanol, respectively. The antioxidant properties of both extracts were evaluated using four different activity tests, including degree of occurrence of intracellular reactive oxygen species (ROS), NO, lipid peroxidation, and GSH (glutathione) in mouse macrophage Raw 264.7 cells. The levels of intracellular reactive oxygen species (ROS) and GSH were measured using 2’,7’-dichlorofluorescin diacetate (DCF-DA) and monobromobimane as fluorescence probe, respectively. Moreover, the generation of NO and lipid peroxidation products were determined by each method based on the Griess reaction and TBARS assay. Solvent extracts from seaweeds such asScytosiphon lomentaria, Prionitis cornea, Laruencia okamurae,Callophyllis japonica, Sargassum horneri, Dictyopteris divaricat a,Lomentaria catenata, Corallina confuse, Ishige okamurae, andAhnfeltiopsis flabelliformi exhibited high antioxidant activities in cellular oxidizing systems.     

Hydroelastic vibration of a cantilever cylindrical shell partially submerged in a liquid

The dynamic characteristics of a circular cylindrical shell in contact with a liquid are theoretically studied. The cantilevered cylindrical shell with open ends is partially submerged in a liquid which is unbounded in the radial direction, but bounded by a rigid and flat bottom. Since the liquid is assumed to be incompressible and inviscid, the liquid motion can be described as the velocity potentials written in terms of the appropriate Bessel functions for both the inner and the outer liquid regions. The compatibility of the dynamic displacement along the contacting surfaces between the shell and liquid leads the resulting equations, satisfying both the shell and liquid motions, which are solved by using the collocation method. Finally, the Rayleigh–Ritz method is applied to extract the wet natural frequencies and the mode shapes of the liquid-coupled system. The validity of the theoretical method is established with the aid of a commercial finite element computer code. In order to evaluate the dynamic characteristics of the liquid-coupled system, the effects of the submerged depth and the axial gap between the bottom end of the shell and the bottom surface of the liquid are demonstrated.     

Abundance of epiphytic dinoflagellates from coastal waters off Jeju Island,Korea During Autumn 2009

The occurrence of harmful epiphytic dinoflagellates is of concern to scientists, the aquaculture industry, and government due to their toxicity not only to marine organisms but also to humans. There have been no studies on the abundance of the epiphytic dinoflagellates in Korean waters. We explored the presence of epiphytic dinoflagellates in the coastal waters off Jeju Island, southwestern Korea. Furthermore, we measured the abundance of epiphytic dinoflagellates on the thalli of 24 different macroalgae, collected from five different locations in October 2009. Five epiphytic dinoflagellate genera Amphidinium, Coolia, Gambierdiscus, Ostreopsis, and Prorocentrum were found. These five genera were observed on the thalli of the macroalgae Chordaria flagelliformis, Martensia sp., Padina arborescens, and Sargassum sp., while none were observed exceptionally on Codium fragile. The abundance of Ostreopsis spp. was highest on Derbesia sp. (8,660 cells/g wet weight), while that of Gambierdiscus spp. was highest on Martensia sp. (4,870 cells/g-ww). The maximum abundances of Amphidinium spp., Coolia spp., and Prorocentrum spp. were 410, 710, and 300 cells/g-ww, respectively. The maximum abundance of Coolia spp., Gambierdiscus spp., and Ostreopsis spp. obtained in the present study was lower than for other locations reported in literature. The results of the present study suggest that the presence and abundance of epiphytic dinoflagellates may be related to the macroalgal species of the coastal waters of Jeju Island.     

First record of three barracudina fishes (Aulopiformes: Teleostei) in Korean waters

Three barracudina fishes (Paralepididae) were newly recorded from the southern sea of Korea. Lestidium prolixum is characterized by a single band of luminous ducts on the midventral line and absence of a papilla anterior to the eye. Lestrolepis intermedia and L. japonica are similar in having a black papilla immediately in front of the eye and two bands of luminous ducts on the midventral line. However, the dorsal fin of L. intermedia is located more posterior along the body than that of L. japonica, and L. intermedia have larger number of anal fin rays 42 (vs. 36–40) and vertebrae 95 (vs. 86–87) than L. japonica.     

Why did the copepod Calanus sinicus increase during the 1990s in the Yellow Sea?

Recent field and retrospective data were combined to investigate variations from 1984 to 1998 in the spring abundance of dominant copepods in the Yellow Sea. A calanoid copepod, Calanus sinicus, was chosen to assess the long-term changes in abundance associated with temperature, salinity, chlorophyll-a and predator abundance. Average anomalies of sea surface temperature (SST), salinity, and the abundance of C. sinicus were positive in the 1990s and negative in the 1980s. The average abundances of C. sinicus in the study area in the 1990s were also significantly higher than those in the 1980s (p<0.01). Catches of the anchovy Engraulis japonicus, a predator of C. sinicus, showed a decreasing trend during the study period. The higher abundances of C. sinicus in the 1990s may have been affected by an increase in water temperature and a decrease in predators, without distinctive changes in chlorophyll-a concentrations during the study period.     

The First Record of Long Headed Eagle Ray,Aetobatus flagellum (Pisces: Myliobatidae) from Korea

A specimen ofAetobatus flagellum was collected at Uljin in June 2005 for the first time in Korea. This specimen is characterized by the cephalic fin, the long snout, the dorsal fin between pelvic fins, spiracles on the dorsal side of the disc, the deeply notched nasal curtain and the one row of the teeth in the lower and the upper jaws. And unlikeAetobatus narinari, it does not have any spots on the its dorsal side of the disc. We report this specimen as the first record from Korea and name it ‘Bak-jui-ga-o-ri’ in Korean.