• Environmental Analysis Health and Toxicology
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• 제31권
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• pp.2.1-2.4
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• 2016

Objectives In this study, we investigated the biodegradation features of 4 perfluorooctanesulfonate (PFOS) alternatives developed at Changwon National University compared to those of PFOS. Methods Biodegradation testing was performed with microorganisms cultured in the good laboratory practice laboratory of the Korea Environment Corporation for 28 days following the Organization for Economic Cooperation and Development guidelines for the testing of chemicals (Test No. 301 C). Results While $C_8F_{17}SO_3Na$, PFOS sodium salt was not degraded after 28 days, the 4 alternatives were biodegraded at the rates of 20.9% for $C_{15}F_9H_{21}S_2O_8Na_2$, 8.4% for $C_{17}F_9H_{25}S_2O_8Na_2$, 22.6% for $C_{23}F_{18}H_{28}S_2O_8Na_2$, and 23.6% for $C_{25}F_{17}H_{32}O_{13}S_3Na_3$. Conclusions $C_{25}F_{17}H_{32}S_3O_{13}Na_3$, $C_{23}F_{18}H_{28}S_2O_8Na_2$, and $C_{15}F_9H_{21}S_2O_8Na_2$ were superior to PFOS in terms of biodegradation rates and surface tension, and thus they were considered highly applicable as PFOS alternatives. Environmental toxicity, human toxicity, and economic feasibility of these compounds should be investigated prior to their commercialization.

• 대한화학회지
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• 제34권6호
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• pp.517-526
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• 1990

D-glucitol hexaacetate 와 xylitol pentaacetate의 결정구조를 단결정 X-선 회절법으로 연구하였다. D-glucitol hexaacetate 는 공간군 P2$_1$, 단위세포 상수는 a = 10.275 (2), b = 8.363 (1), c = 12.560 (5) $\AA$, $\beta$= 95.97 $(2)^{\circ}$; Z = 2이고, xylitol pentaacetate는 공간군이 P2$_1$/C이고, a = 18.126 (1), b = 11.422 (2), c = 8.649 (1) $\AA$, $\beta$ = 95.03 $(1)^{\circ}$이며 Z = 4이다. 회절세기는 diffractomerer로 얻었고, 분자구조는 직접법으로 밝혔으며, 최소자승법으로 정밀화하였다. 두 분자에 결쳐 결합의 평균길이는 C($sp^3)-C(sp^3$)가 1.514 (10), C($sp^3)-O: 1.444 (6),\; C(sp^2)-O: 1.347 (9),\; C(sp^2)=O: 1.197 (6),\; C(sp^2)-C(sp^3): 1.479(9){\AA}$이고, 평균 결합각도는 C($sp^3)-C(sp^3)-C(sp^3): 114.6 (17),\; O-C(sp^3)-C(sp^3): 109.4 (23),\; C(sp^2)-O-C(sp^3): 117.4 (6),\; O=C(sp^2)-O: 122.6 (6),\; C(sp^3)-C(sp^2)-O: 111.8 (7), C(sp^3)-C(sp^2)=O: 125.5 (4)${\circ}$이다. 두 분자내의 탄소 사슬들은 extended zigzag chain으로 되어 있어 D-glucitol과 xylitol 분자들의 conformation과는 다르다. Acetate group들의 각 원자들은 모두 한 평편상에 놓여있다.

• 한국지구과학회지
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• 제29권5호
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• pp.375-385
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• 2008

The relationship between two interannual climate variabilities and the frequency of tropical cyclone (TC) that landed over the Korean Peninsula (KP) has investigated for the period of 1951-2004. In the analysis of the relationship between KP-landfall TC frequency and the ENSO phase, most TCs of C-14 (TCs that do not pass through mainland China before landing the KP) and C-23 (TCs that pass through mainland China before landing the KP) tended to more land in the warm phase than normal and cold phases. However, TC intensity at landfall was stronger in the cold and normal phases. In the analysis of the relationship between KP-landfall TC frequency and Arctic Oscillation (AO) phase, the TCs of C-14 tended to more land in the positive (POS) phase of AO and the negative (NEG) phase of AO for C-23. It was found that AO index was negatively correlated with the Ni$\tilde{n}$o-3.4 index. And then the TCs of C-14 landed more frequently over the KP in the AO POS - Ni$\tilde{n}$o-3.4 NEG phases and in the AO NEG - Ni$\tilde{n}$o-3.4 POS phases for the TCs of C-23.

• Journal of Microbiology
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• 제35권4호
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• pp.300-308
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• 1997

The catechol 2,3-dioxygenase (C23O) encoded by the Pseudomonas putida xylE gene was over-produced in Escherichia coli and purified to homogeneity. The activity of the C23O required the reduced form of the Fe(II) ion since the enzyme was highly susceptible to inactivation with hydrogen perocide but reactivated with the addition of ferrous sulfate in conjunction with ascorbic acid. The C23O activity was abolished by treatment with the chemical reagents, diethyl-pyrocarbonate (DEPC), tetranitromethane (TNM), and 1-cyclohexy1-3-(2-morpholinoethyl) car-bodiimidemetho-ρ-toluenesulfontate (CMC), which are modifying reagents of histidine, tyrosine and glutamic acid, respectively. These results suggest that histidine, tyrosine and glutamic acid residues may be good active sites for the enzyme activity. These amino acid residues are conserved residues may be good active sites for the enzyme activity. These amino acid residues are conserved residues among several extradion dioxygenases and have the chemical potential to serveas ligands for Fe(II) coordination. Analysis of random point mutants in the C23O gene derived by PCR technique revealed that the mutated positions of two mutants, T179S and S211R, were located near the conserved His165 amd Hos217 residues, respectively. This finding indicates that these two positions, along with the conserved histidine residues, are specially effective regions for the enzyme function.

• 센서학회지
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• 제23권6호
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• pp.397-401
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• 2014

This paper describes the fabrication and characteristics of $C_2H_2$ gas sensor based on Ag-doped hierarchical ZnO nanostructures. In this work, a pure hierarchical ZnO structure was prepared using a simple hydrothermal method, and Ag nanoparticles doped the hierarchical ZnO structure were uniformly synthesized through photochemical route. The synthesized samples were characterized by SEM, TEM, EDS, XRD and PL spectra. Average size of prepared ZnO structures was around $2{\sim}3{\mu}m$ and showed highly uniform. The average size of Ag nanoparticles was 70 nm. The gas sensing properties of as-prepared products were investigated using resistivity-type gas sensors. 5 at% Ag-doped ZnO based sensors exhibited good performances for $C_2H_2$ gas in comparison with the un-doped one. The sensor based on Ag-doped hierarchical ZnO structures had linear response property from 5~1000 ppm of $C_2H_2$ concentration at working temperature of $200^{\circ}C$. The response values with 100 ppm $C_2H_2$ at $200^{\circ}C$ were 10% and 75% for pure and 5 at% Ag-doped hierarchical ZnO nanostructures, respectively. Moreover, the device showed excellent selectivity towards to $C_2H_2$ gas at optimal working temperature of $200^{\circ}C$.

• 한국환경보건학회지
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• 제42권2호
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• pp.112-117
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• 2016

Objectives: In this study, we investigated the biodegradation rates of 8 perfluorooctanesulfonate (PFOS) alternatives synthesized at the at Changwon National University in comparison to those of PFOS potassium salt and PFOS sodium salt. Methods: A biodegradability test was performed for 28 days with microorganisms cultured in the good laboratory practice laboratory at the Korea Environment Corporation following the OECD Guidelines for the testing of chemicals, Test No. 301 C Results: While $C_5H_8F_3SO_3K$, $C_8F_{17}SO_3K$ and $C_8F_{17}SO_3Na$ were not degraded after 28 days, the 3 alternatives were biodegraded at the rates of 31.4% for $C_8H_8F_9SO_3K$, 25.6% for $C_{10}H_8F_{13}SO_3K$, 23.6% for $C_{25}F_{17}H_{32}S_3O_{13}Na_3$, 20.9% for $C_{15}F_9H_{21}S_2O_8Na_2$, 15.5% for $C_{23}F_{18}H_{28}S_2O_8Na_2$, 8.5% for $C_{17}F_9H_{25}S_2O_8Na_2$ and 4.8% for $C_6H_8F_5SO_3K$. When the concentration was the same(500 mg/L), $C_{23}F_{18}H_{28}S_2O_8Na_2$ had the lowest tension with 20.94 mN/m, which was followed by $C_{15}F_9H_{21}S_2O_8Na_2$ (23.36 mN/m), $C_{17}F_9H_{25}S_2O_8Na_2$ (27.31 mN/m), $C_{25}F_{17}H_{32}S_3O_{13}Na_3$ (28.17 mN/m), $C_{10}H_8F_{13}SO_3K$ (29.77 mN/m) and $C_8H_8F_9SO_3K$ (33.89 mN/m). Having higher surface tension of 57.64 mN/m and 67.57 mN/m, respectively, than those of the two types of PFOS salts, $C_6H_8F_5SO_3K$ and $C_5H_8F_3SO_3K$ were found valueless as substitute for PFOS. Conclusion: The biodegradation test suggest that 6 compounds could be used as substitutes for PFOS. $C_{23}F_{18}H_{28}S_2O_8Na_2$ and $C_{15}F_9H_{21}S_2O_8Na_2$ were found to be the best substitutes based on biodegradation rate and surface tension, followed by $C_{25}F_{17}H_{32}S_3O_{13}Na_3$, $C_8H_8F_9SO_3K$ and $C_{10}H_8F_{13}SO_3K$. $C_{17}F_9H_{25}S_2O_8Na_2$ was found to have relatively low value as an alternative but it still had a potential to substitute the conventional PFOS.

• 한국전기전자재료학회논문지
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• 제23권5호
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• pp.368-373
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• 2010

In this study, we have investigated the effects of Cr dopant on the bulk trap levels and grain boundary characteristics of $Bi_2O_3$-based ZnO (ZB) varistor using admittance spectroscopy and dielectric functions (such as $Z^*,\;Y^*,\;M^*,\;{\varepsilon}^*$, and $tan{\delta}$). Admittance spectra show more than two bulk traps of $Zn_i$ and $V_o$ probably in different ionization states in ZnO-$Bi_2O_3-Cr_2O_3$ (ZBCr) system. Three kinds of temperature-dependant activation energies ($E_{bt}'s$) were calculated as 0.11~0.14 eV of attractive coulombic center, 0.16~0.17 eV of $Zn_{\ddot{i}}$, and 0.33 eV of $V_o^{\cdot}$ as dominant bulk defects. The grain boundaries of ZBCr could be electrochemically divided into two types as a sensitive to ambient oxygen i.e. electrically active one and an oxygen-insensitive i.e. electrically inactive one. The grain boundaries were electrically single type under 460 K (equivalent circuit as parallel $R_{gb1}C_{gb1}$) but separated as double one ($R_{gb1}C_{gb1}-R_{gb2}C_{gb2}$) over 480 K. It is revealed that the dielectric functions are very useful tool to separate the overlapped bulk defect levels and to characterize the electrical properties of grain boundaries.

• 한국자기공명학회논문지
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• 제23권2호
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• pp.40-45
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• 2019

The phase transition temperatures and thermodynamic properties of $(NH_4)_2MnCl_4{\cdot}2H_2O$ grown by the slow evaporation method were studied using differential scanning calorimetry and thermogravimetric analysis. A structural phase transition occurred at temperature $T_{C1}$ (=264 K), whereas the changes at $T_{C2}$ (=460 K) and $T_{C3}$ (=475 K) seemed to be chemical changes caused by thermal decomposition. In addition, the chemical shift and the spin-lattice relaxation time $T_{1{\rho}}$ were investigated using $^1H$ magic-angle spinning nuclear magnetic resonance (MAS NMR), in order to understand the role of $NH_4{^+}$ and $H_2O$. The rise in $T_{1{\rho}}$ with temperature was related to variations in the symmetry of the surrounding $H_2O$ and $NH_4{^+}$.

• Bulletin of the Korean Chemical Society
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• 제25권2호
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• pp.289-292
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• 2004

A trisaccharide, GlcNAcp- ${\beta}-(1{\to}3)-Galp-{\alpha}-(1{\to}2)$-6-deoxy-altroHepp- ${\alpha}-(1{\to}O$-propyl, as an O-antigenic repeating unit of C. jejuni serotype O:23 and O:36 was synthesized. Coupling of the GlcNPhth-(1${\to}$3)-Gal disaccharide donor with allyl 6-deoxy-altroHep acceptor in the presence of iodonium dicollidine perchlorate (IDCP) promoter afforded the ${\alpha}$-galactosidic trisaccharide with high stereoselectivities. Subsequent deacetalation, dephthaloylation, N-acetylation, and hydrogenolytic debenzylation furnished the title compound.

• 한국표면공학회지
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• 제23권2호
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• pp.18-23
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• 1990

Thin films of tin oxide were prepared by chemical vapor deposition (C.V>D) using the hydrolysis reaction of SnCl4, Deposition rate increased with the increase of temperature up to $500^{\circ}C$and then decreased at $700^{\circ}C$, Deposition rate with SnCl4 partial pressure showed RidealEley behavir. It was found that SnO2 thin film deposited at the temperature above $400^{\circ}C$ had(110) and (301) plane preferred orientation with crystallinity of rutite structure. Electrical resisvity of SnO2 thin film decreased with increase increase of deposition temperature and showed minimum value of 10-3 ohm at $500^{\circ}C$and than largely increased increased with further increase of deposition temperture.