• Bulletin of the Korean Chemical Society
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• v.9 no.4
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• pp.198-202
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• 1988

Several new palladium(II) complexes of aminophosphines, $(Pd(L)X_2)$, (L = $Ph_2PNH$ ++ $NR_2$; R = $CH_3(L_1)$, $C_2H_5(L_2)$ : X = Cl, Br, I, and NCS) that contain two different donor atoms of nitrogen and phosphorus as ${\pi}$-electron acceptor, were synthesized and characterized by conductivity measurement, ir, and UV/Vis-spectra. For the dithiocyanatopalladium(II) complexes with aminophosphines, it was confirmed that the thiocyanate group trans to phosphorus is coordinated as Pd-NCS mode and the one trans to nitrogen as Pd-SCN mode, and the aminophosphines form six-membered chelate ring. The spectra of dihalogenopalladium(II) complexes with aminophosphines show that the band maxima are shifted to the short wavelengths as the concentration is decreased.

• Journal of Korean Society of Environmental Engineers
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• v.28 no.3
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• pp.292-299
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• 2006

Batch experiments were performed to evaluate the effects of the electron donor dosage and the initial biomass on the reductive dechlorination of perchloroethene(PCE) with benzoate as an electron donor. When benzoate was added less than the theoretical requirement for dechlorination(electron donor/acceptor ratio=0.5 and 1), the dechlorination efficiency increased from 71% to 94.3% with the increase in benzoate dosage, but the fraction of electron equivalent utilized for dechlorination decreased from 92.7% to 79.6%. Methane production was observed when the hydrogen concentration was higher than the threshold value(10 nM) after PCE and trichloroethene (TCE) were reduced to cis-1,2-dichloroethene(cDCE). When benzoate was added more than the theoretical requirement, the residual hydrogen converted into methane after the completion of dechlorination. The increase in the seeding biomass shortened the lag time for dechlorination, but it did not affect the maximum dechlorination rate as it was mainly governed by the benzoate fermentation rate. When the seeding biomass concentration was high, active dechlorination during the early period increased dechlorination efficiency while decreasing methane production.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.19 no.2
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• pp.75-78
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• 2009

Si-doped GaAs single crystals were grown by vertical gradient freeze using PBN crucibles. The amount of oxide layer $B_{2}O_{3}$ in PBN crucible was changed($0{\sim}0.2wt%$) and measured the concentration of carriers. The segregation coefficients of Si in GaAs melt decreased rapidly from initial 0.1 to 0.01 as the amount of $B_{2}O_{3}$ increases. At the same time, concentration of carriers was shown to decrease. It is likely that the reaction between dopant Si and $B_{2}O_{3}$ in GaAs melt results in the reduction of Si dopants(donor) while increase in the amount of boron(acceptor). The thin layer of $B_{2}O_{3}$ glass in PBN crucible was proved to be a better way to reduce defect formation rather than the total amount of $B_{2}O_{3}$.

• Journal of Soil and Groundwater Environment
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• v.21 no.6
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• pp.192-203
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• 2016

A field investigation was conducted on an aquifer contaminated with trichloroethylene (TCE) for application of in situ reactive zone treatment using nanosized zero-valent iron (NZVI). The aquifer was an unconfined aquifer with a mean hydraulic conductivity of $5.14{\times}10^{-4}cm/sec$, which would be favorable for NZVI injection. Seasonal monitoring of TCE concentration revealed a presence of non-aqueous phase liquid form of TCE near IW (injection well). The hydrochemical data characterized the site groundwater to be a $Ca-HCO_3$ type. The average value of Langelier Saturation Index of the groundwater was -1.33, which implied that the site was favorable for corrosion of NZVI. Dissolved oxygen (DO) concentration varied between 2.5~11.5 mg/L, which indicated that DO would greatly compete with TCE as an electron acceptor. The hydrogeological and hydrochemical characterization reveals that the time around November would be appropriate for NZVI injection when water level and temperature are relatively high and DO concentration is low.

• Microbiology and Biotechnology Letters
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• v.27 no.3
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• pp.252-259
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• 1999

Anoxic sediments collected from Shiwha-ho area were used to find the relationship between the heavy-metal, organic content and anaerobic respiration bacteria by most probable number (MPN) method. Analysis of the sediments showed that COD content was higher in the sediments collected from Ansan-cheon and Shiwha-ho than those collected from sea area nearby. Particularly noticeable was the fact that heavy metal concentration was much higher in the sediments of Shiwha-ho area contaminated by heavy-metal, although they were rich in electron donor and electron acceptor for Fe(III)-reducing bacteria using lactate as an electron donor was in the range of 1.1$\times$106-4.6$\times$107MPNs/ml in the sediments collected from the sea-side of the lake, which were lower in heavy-methal concentration and higher in Fe-Mn content than those from other region. The number of Fe(III)-reducing bacteria using acetate as an electron donor was in the rang eof 4.3$\times$102-8.1$\times$105MPNs/ml in the same sediments. Chromate-reducing bacteria were more populated(4.6$\times$104-8.1$\times$105MPNs/ml) in the sediments contaminated by heavy metals. The number of sulfate-reducing bacteria wee counted in the sediments collected from the more contaminate inner-side than those from the sea-side of the lake.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.171-171
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• 2010

GaN 기반 Light emitting diodes(LEDs)의 p-type doping layer는 일반적으로 hole을 발생시키는 acceptor로 Mg이 사용하되고 있다. 보통 Mg이 도핑된 p-type GaN은 >$1\;{\Omega}{\cdot}cm$의 저항이 존재하는데 그 이유는 Mg의 열적 이온화를 위한 activation 에너지가 높아서 상온에서 valence band의 hole concentration는 전체 억셉터 농도의 1%가 되지 않기 ��문이다. 본 논문에서는 높은 hole 농도를 얻기 위해서 metalorganic chemical-vapor deposition (MOCVD)를 장비를 사용하여 사파이어 기판의 misorientation-angle에 따른 p-type a-plane(11-20) GaN 특성을 분석하였다. misorientation-angle은 c축 방향으로 $+0.15^{\circ}$, $-0.15^{\circ}$, $-0.2^{\circ}$, $-0.4^{\circ}$ off된 r-plane(1-102) 사파이어 기판 을 사용하였다. p-type 도핑물질로 bis-magnesium (Cp2Mg) 소스를 사용하였고 성장 과정중 발생하는 hydrogen passivation으로 인한 Mg-H complexes현상을 해결하기위해 conventional furnace annealing (CFA)와 rapid thermal annealing (RTA)를 이용하여 열처리 공정을 진행하였다. 열처리 공정은 Air와 N2 분위기에서 $650^{\circ}C$에서 $900^{\circ}C$ 사이의 다양한 온도에서 수행하였고 Hall 측정을 위해 Ni을 전극 물질로 사용하였다. 상온에서 Accent HL5500IU Hall system을 사용하여 hole concentration, mobility, specific resistance을 측정하였다. 열처리 공정 후 Hall측정 결과 $+0.15^{\circ}$, $-0.15^{\circ}$, $-0.2^{\circ}$, $-0.4^{\circ}$ off된 각 샘플들은 온도, 시간, 분위기에 따라 hole concentration ($7.4{\times}10^{16}cm^{-3}{\sim}6{\times}10^{17}cm^{-3}$), mobility(${\mu}h=\;1.72\;cm^2/V-s\;{\sim}15.2\;cm^2/V-s$), specific resistance(4.971 ohm-cm ~8.924 ohm-cm) 가 변화됨을 확인 할 수 있었다. 또한 광학적 특성을 분석하기 위해 Photoluminescence (PL)을 측정하였다.

• Korean Journal of Materials Research
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• v.34 no.7
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• pp.321-329
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• 2024

In this work, a series of BaTiO₃-based ceramic materials, Ba(Al_0.5Nb_0.5)_xTi_1-xO₃ (x = 0, 0.04, 0.06, 0.08), were synthesized using a standard solid-state reaction technique. X-ray diffraction profiles indicated that the Al+Nb co-doping into BaTiO₃ does not change the crystal structure significantly with a doping concentration up to 8 %. The doping ions exist in Al³⁺ and Nb⁵⁺ chemical states, as revealed by X-ray photoelectron spectroscopy. The frequency-dependent complex dielectric properties and electric modulus were studied in the temperature range of 100~380 K. A colossal dielectric permittivity (>1.5 × 10⁴) and low dielectric loss (<0.01) were demonstrated at the optimal dopant concentration x = 0.04. The observed dielectric behavior of Ba(Al_0.5Nb_0.5)_xTi_1-xO₃ ceramics can be attributed to the Universal Dielectric Response. The complex electric modulus spectra indicated the grains exhibited a significant decrease in capacitance and permittivity with increasing co-doping concentration. Our results provide insight into the roles of donor and acceptor co-doping on the properties of BaTiO₃-based ceramics, which is important for dielectric and energy storage applications.

• Journal of Microbiology and Biotechnology
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• v.16 no.1
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• pp.64-67
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• 2006

To enhance the stability of ascorbic acid, the glycosylation of ascorbic acid was studied using the transfructosylation activity of levan fructotransferase. When levan was used as glycosyl donor, a novel fructoside (ascorbic acid 2-ffuctoside) was formed by the transfructosylation activity of the levan fructotransferase. The production of ascorbic acid 2-fructoside was highly affected by the concentration of the fructosyl acceptor (ascorbic acid). When $35\%$ of ascorbic acid and $2\%$ of levan were incubated with LFTase of 0.5 unit/glevan at $37^{\circ}C$ for 85 h, a maximum 52 g/l of AA-2F was produced.

• Microbiology and Biotechnology Letters
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• v.27 no.4
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• pp.304-310
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• 1999

We have developed a new process for the production of new structure oligosaccharides using the mixed-culture fementation of Lipomyces starkeyi KSM22 and leuconostoc mesenteroides B-512FMCM.L.starkeyi KSM22 produces a novel DXAMase(an enzyme containing both dextranase and amylase activities). It hydrolyzes the soluble starch and dextran. The hydrolyzates were used as acceptors for dextransucrase of L.mesenteroides to synthesize the new oligosaccharides(NOS). In fermentation, as the concentration of sucrose was increased from 9%(w/v) to 15%(w/v), the yields of dextran(sum of dextran I, MW=66kD, and dextran II, MW=21kD) was increased from 12.7% to 42.5%, and NOS was increased from 3.9% to 5.2% of the theoretical, respectively. The NOS of dp(degree of polymerization) 5 and over was increased from 33.1% to 58.3% of the total NOS. The NOS showed heat resistant up to 12$0^{\circ}C$ and was stable at pHs ranged from 2 to 6. The NOS decreased the pH changes in the culture of S. mutans, and also showed inhibitory effects on the growth of S. aureus or S. typhimurium.

• Bulletin of the Korean Chemical Society
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• v.32 no.9
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• pp.3261-3266
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• 2011

The interaction of bilobalide (BB) and ginkgolides B (GB) with bovine serum albumin (BSA) was investigated by fluorescent technique and UV/vis absorption spectroscopy. The results showed that BB and GB could intensively quench the fluorescence of BSA through a static quenching procedure. The binding constants (Ka) and the average binding distance between the donor (BSA) and the acceptor (ginkgolides) were obtained ($r_{BB}$ = 5.33 nm and $r_{GB}$ = 4.20 nm) by the theory of non-radiation energy transfer, and then the thermodynamic parameters such as ${\Delta}S^0$ (0.17-0.32 kJ/mol), ${\Delta}G^0$ (-20.76 ~ -17.79 kJ/mol) and ${\Delta}H^0$ (32.47-76.52 kJ/mol) could be calculated, respectively. All these results revealed that the interaction of BB and GB with BSA were driven mainly by hydrophobie force. The synchronous fluorescence spectroscopy was applied to examine the effect of two ginkgolides on the configuration of BSA. The configuration alteration of BSA could be induced by the hydrophobicitv environment of tyrosine with the increase of the drug concentration.