• Korean Journal of Fisheries and Aquatic Sciences
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• v.30 no.2
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• pp.216-224
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• 1997

In order to investigate the osmoregulation capability of grey mullet, Mugil cephalus with the different salinities, juvenile fish $(13.6{\pm}0.2\;TL)$ stocked in seawater (SW) were abruptly transferred to each experimental group $0\%SW(0\%_{\circ}),\;25\%SW(7.7\%_{\circ}),\;50\%SW(16.1\%_{\circ})\;and \;100\%SW(32.8\%_{\circ})$ and reared for 60 days. Blood samples were taken by the time schedule after the transfer. Plasma $Na^{+},\;K^{+},\;Cl^{-}$ and osmolality, muscle water content, and the electron microscopical observations of chloride cells were analyzed and made by the time schedule. In $100\%SW$, the maintainable levels of plasma $Na^{+},\;K^{+},\;Cl^{-}$ and osmolality were $167.1{\pm}7.7mM/l,\;9.1{\pm}2.1mM/l,\;137.8{\pm}5.6mM/l\;and\;351{\pm}18\;mOsm/kg$, respectively. These values were significantly changed at $6h\~1\;day$ after the beginning of the experiment with four different salinities. Fish from $0\%\;and\;25\%SW$ had lower osmolalities than those of fish from $50\%\;and\;100\%SW$, and showed the hyposmotic regulation pattern. At the end of the experiment (60 days after transfer), however, no significant difference was found in the concentrations of plasma $Na^{+},\;K^{+}\;and\;Cl^{-}$ among four experimental groups. Hematocrit was increased with salinity (P<0.01). After 10 days, fish from $0\%\;and\;25\%SW$ showed the hypertrophy, fusion and edema of epithelial layer in gill lamella. However, at the 15th day, epithelial layer in gill lamella was back to the normal status. On gill of fish from $0\%SW$, one apical pit held two or three chloride cells in common. Muscle water content was subsequently regulated to near the normal levels within 4 days, and there was no significant difference among four different salinities at the end of the experiment.

• Journal of the Korean Chemical Society
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• v.37 no.8
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• pp.711-716
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• 1993

The mechanism for electrochemical oxidation of natural alkaloid, ${\iota}$-sparteine (SP) was studied in acetonitrile solvent. The cyclic voltammogram of SP shows two irreversible anodic peaks at +0.75 V and +1.45 V vs. Ag/AgCl (0.1M AgNO$_2$ in acetonitrile) electrode. Coulometry reveals that the number of electrons involved in each oxidation peaks is in the range of 1.2∼1.3 respectively. Neutral imine radical was produced by fast deprotonation of SP radical cation formed by oxidation of one nitrogen atom in SP. Two pathways are possible for the reaction of the neutral radical: Due to the disproportionation of the radical, SP and enamine were mainly produced. Also, the 1,2-dehydrosparteinium cation was formed as minor product through the second one electron transfer oxidation of this radical. The (+)-lupanine was produced by treatment of sparteinium cation with potassium hydroxide. We have isolated and confirmed the electrolysis products using IR, GC-MS, UV-Vis, and thin-layer spectroelectrochemical method.

• Journal of the Korean Vacuum Society
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• v.14 no.4
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• pp.207-214
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• 2005

This paper presents a channel structure for promising high performance pseudomorphic high electron mobility transistor(pHEMT) switching device for design and fabricating of microwave control circuits, such as switches, phase shifters, attenuators, limiters, for application in personal mobile communication systems. Using the designed epitaxial channel layer structure and ETRI's $0.5\mu$m pHEMT switch process, single pole double throw (SPDT) Tx/Rx monolithic microwave integrated circuit (MMIC) switch was fabricated for 2.4 GHz and 5 GHz band wireless local area network (WLAN) systems. The SPDT switch exhibits a low insertion loss of 0.849 dB, high isolation of 32.638 dB, return loss of 11.006 dB, power transfer capability of 25dBm, and 3rd order intercept point of 42dBm at frequency of 5.8GHz and control voltage of 0/-3V These performances are enough for an application to 5 GHz band WLAN systems.