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Influence of weir construction on chemical water quality, physical habitat, and biological integrity of fish in the Geum River, South Korea

100%

Lee S.-J. , An K.-G.

nr 4

The objectives of this study were to determine the long-term changes in water chemistry, physical habitat, and fish fauna/composition before and after construction of the Sejong Weir in Geum River, South Korea, during 2007–2014, and to evaluate the integrated ecological health based on chemical water quality, physical habitat, and biotic integrity using a star plot integration approach. As an indicator of water quality, the mean total phosphorus (TP) in the surface water decreased 2.6-fold after weir construction, indicative of P sedimentation from the water column due to structural changes from a lotic to a lentic system. The chlorophyll-a concentration decreased in response to P levels. Considering total nitrogen (TN), more than 91.7% of the total observations after weir construction (n = 96) had a TN:TP ratio >17, indicating potential P limitations on algal growth. The log-transformed TN:TP ratio had a weak positive correlation (p<0.005, R2 = 0.085, n = 96) with TN and a strong negative correlation (p<0.001, R2 = 0.575, n = 96) with TP. This indicated that the N:P ratio was regulated mainly by variations in P rather than N. After weir construction, the population of the lotic-type fish Zacco platypus decreased 13-fold, and the population of the lentic-type fish Pseudorasbora parva increased 3-fold. Overall, the integrated ecological health assessments revealed large degradations of >3-fold in biotic health, 2-fold in physical habitat health, and >5-fold in chemical health after weir construction.

Effects of PVA Polymer Type and Calcination Temperature on Synthesis of Nanocrystalline Yttria Powder by Polymer Solution Route

100%

Yang Y.-K. , Lee S.-J.

Archives of Metallurgy and Materials

2018

tom Vol. 63, iss. 3

1473--1476

Nano-sized yttria (Y2O3) powders were synthesized by a polymer solution route using polyvinyl alcohol (PVA) as an organic carrier. The PVA polymer affected the dispersion of yttrium ions in precursor sol. In this study, three kinds of PVA polymer (different molecular weight) were applied for synthesis of yttria powder. The PVA type as well as calcination temperature had a strongly influence on the particle morphology. Single crystal nano wire particles were observed at the temperature of polymer burn out range and the size was dependent on the PVA type. The stable, fully crystallized yttria powder was obtained through the calcination at 800°C for 1 h. The yttria powder prepared with the high weight PVA (MW: 153,000) revealed a particle size of 30 nm with a surface area of 18.8 m2/g.

Effect of Ni Content on the Austenite Stability and Mechanical Properties of Nanocrystalline Fe-Ni Alloy Fabricated by Spark Plasma Sintering

80%

Park D. , Oh S.-J. , Shon I.-J. , Lee S.-J.

nr 3

Alpha-Synuclein is localized in a subpopulation of rat brain synaptic vesicles

80%

Lee S.-J. , Jeon H. , Kandror K. V.

2008

tom 68

nr 4

Alpha-Synuclein is a neuronal protein implicated both in synaptic transmission and in neurodegenerative diseases. Although it is evident that this protein is enriched in the presynaptic terminals of neurons, localization in synaptic vesicles has not been conclusively determined. Here, we show that alpha-synuclein is present, but not enriched, in synaptic vesicles using highly purified synaptic vesicle preparations from rat brain homogenate. Immunoisolation of vesicles using antibodies against synaptophysin or synaptobrevin confirmed the presence of alpha-synuclein in synaptic vesicles. Additional separation of synaptic vesicles by sucrose velocity centrifugation showed that there are different subpopulations of synaptic vesicles and that alpha-synuclein is present only in a specific subpopulation, whereas synaptophysin and synaptobrevin were found in all the synaptic vesicles. Presence of alpha-synuclein only in a subset of synaptic vesicles suggests that this protein may have a specific function in synaptic vesicle cycling, hence in synaptic transmission.