• 폴리머
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• 제29권4호
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• pp.380-384
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• 2005

Sodium montmoillonite 혹은 sodium montmorillonite가 삽입된 macromer의 존재 하에서 fluoroalkyl methacrylate와 아크릴산을 라디칼 공중합하여 불소화 아크릴계 이온성 고분자/sodium montmorillonite 복합재료를 제조하고, 이들의 X-선 회절 특성, 인장물성, 수분흡수율 등 물리적 성질을 조사하였다. 또, 이들을 이용하여 이온성 고분자-백금 복합재료(IPMC)를 제조하여 수 볼트의 외부 전위에 의한 전류 흐름 및 변위 거동을 측정한 결과, sodium montmorillonite가 이온의 이동을 방해하여 전류 및 변위량의 감소를 초래함을 관찰하였다.

• Ocean and Polar Research
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• 제34권3호
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• pp.275-286
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• 2012

Over the last 20 years there have been more than 3000 peer-reviewed papers relating to climate change and biodiversity published, and still the numbers are increasing. However, most studies focused on the impacts of climate change at population or community levels, and the results invariably reveal that there has been, or will be, a negative effect on the structure and pattern of biodiversity. Moreover, the climate change models and statistical analyses used to test the impacts are only newly developed, and the analyses or predictions can often be misled. In this review, I ask why an individual's life history is considered in the study how climate change affects biodiversity, and what ecological factors are impacted by climate change. Using evidence from a range of species, I demonstrate that diverse life history traits, such as early growth rate, migration/foraging behaviour and lifespan, can be shifted by climate change at individual level. Particularly I discuss that the optimal decision under unknown circumstance (climate change) would be the reduction of the ecological fitness at individual level, and hence, a shift in the balance of the ecosystem could be affected without having a critical impact on any one species. To conclude, I summarize the links between climate changes, ecological decision in life history, the revised consequence at individual level, and discuss how the finely-balanced relationship affects biodiversity and population structure.

• 한국콘텐츠학회:학술대회논문집
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• 한국콘텐츠학회 2013년도 춘계 종합학술대회 논문집
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• pp.361-362
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• 2013

As one of the steps toward understanding how the plant is well adapted to strongly saline habitats, the purple pigment compound that is accumulated in Suaeda japonica was extracted and characterized. The extracted pigment compound exhibited typical characteristics of betacyanin that were represented by water solubility, pH- and temperature-dependent color changes, sensitivity to light, UV-Vis spectra, and gel electrophoretic migration pattern. LC-MS of the extracted pigment compound showed the presence of two major protonated molecular ions ($[M+H]^+$) at m/z 651.1 and m/z 827.1. According to the DPPH assay, it was found to have an antioxidant activity that is linearly increased in proportion to the reaction time for up to 30 min, and the activity was comparable to that of control BHA at 9.0 mg/ml. The cytotoxic activity against several tumor cell lines was also examined following the MTT assay. The significant growth inhibitory effect was observed on two tumor cell lines, SW-156 (human kidney carcinoma) and HEC-1B (human endometrial adenocarcinoma). Probably, the pigment compound may function as an osmolyte to uphold halotolerant physiological processes in saline environment.

• Animal Systematics, Evolution and Diversity
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• 제32권2호
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• pp.105-111
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• 2016

The genetic structure of marine animals that inhabit the seashore is affected by numerous factors. Of these, gene flow and natural selection during recruitment have strong influences on the genetic structure of seashore-dwelling species that have larval periods. Relative contributions of these two factors to the genetic structure of marine species would be determined mainly by the duration of larval stage. The relationship between larval period and genetic structure of population has been rarely studied in Korea. In this study, genetic variations of cytochrome oxidase subunit I (COI) were analyzed in two dominant species on rocky shore habitats in the Korean peninsula: periwinkle Littorina brevicula and acorn barnacle Fistulobalanus albicostatus. Both species are not strongly structured and may have experienced recent population expansion. Unlike periwinkle, however, barnacle populations have considerable genetic variation, and show a bimodal pattern of mismatch distribution. These results suggest that barnacle populations are more affected by local adaptation rather than gene flow via larval migration. The bimodal patterns of barnacle populations observed in mismatch distribution plots imply that they may have experienced secondary contact. Further studies on seashore-dwelling species are expected to be useful in understanding the evolution of the coastal ecosystem around Korean waters.

• 자원환경지질
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• 제33권4호
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• pp.261-271
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• 2000

In order to evaluate the environmental impact of U anormaly in the drainage system around the Shinbo talc mine area, U contents, their distribution patterns, bioaccumulation and a-radioactivity in stream water, stream sediments and aquatic organisms were investigated. The U contents of stream water attenuated with increasing distance from the mine area. The same attenuation pattern is shown in stream sediments from mine to 0.75 km downstream, although these contain highly enriched U contents (24~83 mg/kg) comparing with the international average concentration of surface soils (0.79~11 mg/kg). However, U content increases abruptly in sediment at 1.5 km downstream, probably due to detrital migration and rediposition of U enriched sediments. Futhermore, enriched U in downstream sediments occur in high proportions of carbonate and Fe-Mn oxide bounded forms, which show high potential of a secondary pollution source. For aquatic organisms, bio accumulation degree of U are in the order: aquatic larvae>black snail>mountain frog>crawfish. Cultured trout by the U enrich groundwater (387 ${\mu}g$/l) shows U accumulation in the part of branchia (CRs 5.25) and bones (CRs 11.2) but not in flesh (CRs 0.03). Total a-radioactivity have been measured in the level as 0.47 nCi/l for groundwater, 2.94~18 nCi/kg${\cdot}$DW for organisms and 93~328 nCi/kg${\cdot}$DW for sediments.

• 한국동물학회지
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• 제35권2호
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• pp.161-172
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• 1992

In the short-term treahent of 12-0-tetradecanoylphorbol-13-acetate (TPA) or platelet-derived growth factor (PDGF), the'Wh and PDGF induced the Protein Kinase C (PKC) activation and migration from the cytoplasm to the peripheral nulcear membrane. And the activated PKC which was directly or indirectly stimulated by TPA or PDGF Phosphorylated many kinds of PKC's targeting proteins and induces various biological responses. Especially, the cytoplasmic PKC was phosphorylated within 1 hr and 10 min by TPA-and PDGF-treahent respectivelv. In the long-term treatment of TPA or PDGF, both of them induced the down-regulation and translocation of PKC in the mvoblasts. The down-regulation of PKC isozyrnes, the pattern of PKC I and ll was similar to the PKC 111 isozpnes in the cytoplasm. But in the nucleolus, the TPA did not induce and down-regulation or the inhibition of the immunoreactivity of PKC III antibody. This investigation indicates that each isozvmes of PKC mal be performed the different effects to the down-regulation of the cytoplasm or nucleolus. And douvn-regulated myoblasts contained low immunoreactivity of PKC antibodies.

• Toxicological Research
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• 제12권1호
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• pp.21-27
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• 1996

Vitamin C has been well known to be a potential chemopreventive agent for several toxic compounds. It reduced the mutation frequencies of 6-sulfooxymethylbenzo[a]pyrene (SMBP) and 6hydroxymethylbenzo[a]pyrene (HMBP) in Salmonella typhimurium TA98 and TA100, indicating that corbic acid affects both frameshift and base-pair substitution mtltations. A similar type of dose-response relationship was shown in the V79 cells, although the inhibitory effect was less dramatic compared with that in S. typhimurium. However, SMBP or HMBP binding to calf thymus DNA was not affected by the presence of vitamin C, suggesting that SMBP seems to be much more reactive to calf thymus DNA than vitamin C. This was supported by migration pattern and fluorescence intensity of SMBP-modified plasmid on the gel. These restilts were not correlated with mutation tests in bacterial and mammalian cell systems. It has been already reported that vitamin C inactivates SMBP through the formation of covalently bound addact. It was found from HPLC analysis that the reaction between vitamin C and SMBP was accomplished within just 5 min and then produced the several products. These findings indicate that the beneficiary of vitamin C is not merely derived from the covalent adducts. On the other hand, the addition of DNA to incubation mixture reduced the amounts of vitamin C adducts while the magnitude of HMBP peak increased, suggesting that DNA accelerates the SMBP hydrolysis to intercept the interaction between SMBP and vitamin C or forms rapidly complex with SMBP.

• 한국자원식물학회지
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• 제31권4호
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• pp.342-354
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• 2018

Suaeda japonica is a halophytic plant that lives in mudflat at intertidal zone of western and southern coastal areas of Korea. The seawater-living plants showed a purple color during their whole life. In contrast, freshwater-living plants displayed a green color in leaves. When seawater-living plants were transferred to potting soil, the purple color was gradually changed to green in the leaves. The extracted purple pigment compound exhibited typical characteristics of betacyanin that were represented by water solubility, pH- and temperature-dependent color changes, sensitivity to light, UV-Vis spectra, and gel electrophoretic migration pattern. The LC-MS analysis of the extracted pigment compound showed the presence of two major protonated molecular ions ($[M+H]^+$) at m/z 651.1 and m/z 827.1. Antioxidant activity of the pigment compound was determined using stable free radical DPPH assay. It was found to have an antioxidant activity that is linearly increased in proportion to the reaction time for up to 30 min, and the activity was comparable to that of control BHA at 9.0 mg/ml. The anticancer activity against several tumor cell lines was also examined following the MTT assay. The significant growth inhibitory effect was observed on two tumor cell lines, SW-156 (human kidney carcinoma) and HEC-1B (human endometrial adenocarcinoma). Probably, the pigment compound may function as an osmolyte to uphold halotolerant physiological processes in saline environment.

• Geomechanics and Engineering
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• 제17권1호
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• pp.19-30
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• 2019

Recent research on the behavior of silty sand tends to advocate the use of equivalent skeleton void ratio to characterize the density state of this type of soil. This paper presents an investigation to explore the physical meaning of the equivalent skeleton void ratio by means of DEM simulations for assemblies of coarse and fine particles under biaxial shear. The simulations reveal that the distribution pattern of fine particles in the soil skeleton plays a crucial role in the overall macroscopic response: The contractive response observed at the macro scale is mainly caused by the movement of fine particles out of the force chains whereas the dilative response is mainly associated with the migration of fine particles into the force chains. In an assembly of coarse and fine particles, neither all of the fine particles nor all of the coarse ones participate in the force chains to carry the external loads, and therefore a more reasonable definition for equivalent skeleton void ratio is put forward in which a new parameter d is introduced to take into account the fraction of coarse particles absent from the force chains.

• 한국수산과학회지
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• 제56권2호
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• pp.259-264
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• 2023

Day-night vertical euphausiid distribution was investigated at three stations in the East Sea using a Multiple Opening/Closing Net and Environmental Sensing System (MOCNESS). Three euphausiid species were recognized. Euphausia pacifica was more dominant than Thysanoessa longipes. Euphausiids were collected at Station 1 at night, Station 2 at sunset, and Station 3 during the daytime. At Station 1, calyptopis and furcilia stages were concentrated from the surface to 30 m and 20-40 m, respectively. Juveniles and E. pacifica were distributed in strata shallower than 30 m. At Station 2, calyptopis and furcilia stages were dominant in strata from the surface to 40 m. Juveniles were not recorded in strata at 30-100 m. However, E. pacifica occurred in these strata. At Station 3, calyptopis and furcilia stages occurred in the upper 40 m of strata. E. pacifica was distributed deeper than 100 m and rarely occurred above 100 m. The furcilia stages weakly migrated, whereas the calyptopis stages did not. Juveniles and E. pacifica showed a clear migration pattern. Vertical distribution of euphausiids in the northern East Sea varied by life stage and time of day.