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Proton Conducting Membrane based on Crosslinked Sulfonated Polyimide for Direct Methanol Fuel Cell
성경아,김완근,오근환,주민주,박정기 한국전기화학회 2009 한국전기화학회지 Vol.12 No.3
Crosslinked membrane based on sulfonated polyimide was prepared by the introduction of crosslinkable monomer in polymerization process and crosslinking during membrane casting. Crosslinked membranes showed different properties from non-crosslinked membranes. Crosslinking decreased methanol crossover and therefore unit cell using crosslinked membrane showed increased open circuit voltage, 0.81 V, in comparison with unit cell using noncrosslinked membrane, 0.71 V. In addition, water uptake of crosslinked membrane, 40.5%, was lower than that of non-crosslinked membrane, 57.0%, and this resulted in improved dimensional stability. However, proton conductivity of crosslinked membranes showed rather low relative to non-crosslinked membrane due to reduced water uptake.
Interactions between marine bacteria and red tide organisms in Korean waters
성경아,정해진 한국조류학회I 2013 ALGAE Vol.28 No.4
There is increasing interest in the relationships between marine bacteria and red tide organisms. Some bacteria are known to kill red tide organisms, and may be responsible for accelerating the termination of red tides. Thus, certain algicidal bacteria have been proposed for the control of red tides. Meanwhile, many red tide organisms are known to feed on marine bacteria. The roles of marine bacteria and red tide organisms are therefore reversible. In Korean waters, the killing of red tide organisms by algicidal bacteria, and also the feeding of red tide organisms on marine bacteria have been extensively investigated. The findings of such studies may influence the conventional view of red tide dynamics, and also planktonic food webs. Here, we review the species and concentrations of algicidal bacteria that kill red tide organisms in Korean waters, as well as the ingestion rate and grazing impact of red tide organisms on marine bacteria. Furthermore, we offer an insight into the ecological roles of these 2 components in marine planktonic food webs.
Interactions Between the Pathogenic Bacterium Vibrio parahaemolyticus and Red-tide Dinoflagellates
성경아,정해진 한국해양과학기술원 2011 Ocean science journal Vol.46 No.2
Vibrio parahaemolyticus is a common pathogenic bacterium in marine and estuarine waters. To investigate interactions between V. parahaemolyticus and co-occurring redtide dinoflagellates, we monitored the daily abundance of 5 common red tide dinoflagellates in laboratory culture; Amphidinium carterae, Cochlodinium ploykrikoides, Gymnodinium impudicum, Prorocentrum micans, and P. minimum. Additionally, we measured the ingestion rate of each dinoflagellate on V. parahaemolyticus as a function of prey concentration. Each of the dinoflagellates responded differently to the abundance of V. parahaemolyticus. The abundances of A. carterae and P. micans were not lowered by V. parahaemolyticus, whereas that of C. polykrikodes was lowered considerably. The harmful effect depended on bacterial concentration and incubation time. Most C. polykrikoides cells died after 1 hour incubation when the V. parahaemolyticus concentration was 1.4×10^7 cells ml^(-1), while cells died within 2 days of incubation when the bacterial concentration was 1.5×10^6 cells ml^(-1). With increasing V. parahaemolyticus concentration, ingestion rates of P. micans, P. minimum, and A. carterae on the prey increased, whereas that on C. polykrikoides decreased. The maximum or highest ingestion rates of P. micans, P. minimum, and A. carterae on V. parahaemolyticus were 55, 5, and 2 cells alga^(-1) h^(-1), respectively. The results of the present study suggest that V. parahaemolyticus can be both the killer and prey for some red tide dinoflagellates.
성경아,명금옥,정해진,이원호,김형섭,Hyun Jung Jo,박재연,유영두 한국조류학회I 2017 ALGAE Vol.32 No.1
We explored feeding by the mixotrophic ciliate Mesodinium rubrum, heterotrophic nanoflagellates (HNFs), and small ciliates (<30 μm in cell length) on natural populations of heterotrophic bacteria in Masan Bay, Keum River Estuary, and in the coastal waters of the Saemankeum area, Korea when M. rubrum red tides occurred. We also measured ingestion rates of M. rubrum on cultured heterotrophic bacteria as a function of bacterial concentration in the laboratory. The ingestion rates of M. rubrum on natural populations of heterotrophic bacteria (2.3–16.8 bacteria grazer−1 h−1) were comparable to or lower than those of co-occurring HNFs (10.7–41.7 bacteria grazer−1 h−1), but much lower than those of co-occurring small ciliates (76.0–462.2 bacteria grazer−1 h−1). However, the maximum grazing coefficient of M. rubrum (0.245 d−1) on natural populations of heterotrophic bacteria was much higher than that of small ciliates (0.089 d−1), and slightly higher than that of HNFs (0.204 d−1). With increasing bacterial concentrations, ingestion rates of M. rubrum on cultured heterotrophic bacteria continuously increased, but became saturated at higher prey concentrations over 1–5 × 106 cells mL−1. The maximum ingestion rate of M. rubrum on cultured heterotrophic bacteria was 34.4 bacteria grazer−1 h−1. Based on the present study, it is suggested that M. rubrum may be an important grazer of heterotrophic bacteria and sometimes have considerable grazing impact on natural populations of heterotrophic bacteria.