• Bulletin of the Korean Chemical Society
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• v.24 no.6
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• pp.739-743
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• 2003

New quaternary compounds $ANb_2PS_{10}$ (A = Na, Ag) and $AuNb_4P_2S_{20}$ were synthesized and characterized. The structures of three compounds consist of one-dimensional infinite chains built by [$Nb_2S_{12}$] and [$PS_4$] units. Cation atoms are occupied within the van der Waals gap of sulfur atoms between infinite chains to make -S…$M^+$…S- contacts. There is only one Au atom site and so crystallographically a unit cell contains four equivalent Au atoms in $AuNb_4P_2S_{20}$. This is only the half of the numbers of Na or Ag atoms in $NaNb_2PS_{10}$ or $AgNb_2PS_{10}$. The ratio between $Nb_2PS_{10}$ matrix vs the cation is, therefore, 1 : 1 for Ag and Na, but it is 2 : 1 for Au. Mixed valency in Au or Nb was expected to balance the charge in the latter compound. The electronic structures calculated based on the extended Huckel tight-binding method show that $ANb_2PS_{10}$ (A = Ag, Na) are semiconducting, while $AuNb_4P_2S_{20}$ is metallic, which is not consistent with the experimental results of these three compounds that all exhibit semiconducting property. The result of calculation suggests that $AuNb_4P_2S_{20}$ might be a magnetic insulator. Magnetic measurement experiment exactly proved that the compound is a Slater antiferromagnetic material with the Neels' temperature of 45 K. It is recognized, therefore, that electronic structure analysis is very useful to understand the properties of compounds.

• Journal of Environmental Science International
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• v.13 no.5
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• pp.479-488
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• 2004

Five sediment cores from the tidal flat of artificial Lake Shihwa are analyzed in terms of sedimentology and geochemistry to evaluate the heavy metal contamination and redox condition of surficial sediment following the Shihwa seawall construction. The variability of concentrations of various elements depends on the depositional environment, and reflects the various redox conditions and sediment provenances. The amounts of Ti and Al and their ratio of Ti/ Al with respect to Li clearly indicate that there is an anthropogenic contribution to the surficial sediment. The high concentrations of heavy metals suggest an anthropogenic contribution at ST. 34 and ST. 22. Concentrations of most elements (Cr, Cu, Zn and Pb) are higher near the Shihwa-Banwol industrial complex than in the central part of Lake Shihwa. Concentrations of heavy metal in surficial sediment near the Shihwa-Banwol industrial complex are two to eight times higher than in the center of Lake Shihwa. Enrichment factors (EF), which are normalized by the unpolluted shale, suggests a significant metallic contamination near the Shihwa-Banwol industrial complex (SBIC). The redox condition is divided into two anoxic and mixed oxi $c_oxic zones based on the carbon:sulfur (C/S) ratios of organic matter and elemental relationships. Correlations among geochemical elements Mn, U and Mo are significantly different from site to site, and may therefore be an indicator of the spatial redox condition. Controlling factors for switching anoxic/oxic conditions are thought to be water depth and the differences in industrial effluent supply. The variations of the Cu/Mn ratio in the sediments confirms above mentioned spatial differences of a redox condition in part, and therefore shows a location-dependence redox condition in sediments at four other sites. The redox condition of the surficial sediment characteristics of the Shihwa Lake are controlled by its geographic location and water depth.th.

• Journal of Oral Medicine and Pain
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• v.25 no.1
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• pp.41-51
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• 2000

This study was performed to investigate the effect of three modalities commonly used for reduction of oral malodor and to review the contributing factors for halitosis. For this study, 45 subjects of good general health in their third decades were selected, and they were divided into three groups by each modality, that is, tongue scraping, $ZnCl_2$ mouth rinse, and periodontal treatment. Subjective sense of halitosis, diets, Oral hygiene index based on tooth brushing and tongue brushing habit, resting salivary flow rate, gingival index, degree of tongue coating were recored in the Halito-Chart designed by the author. Oral malodor converted from volatile sulfur compound was measured by the Halimeter$^{(R)}$(Interscan Co., USA), and the correlation between the oral factors and pre-treatment halimeter score were analysed. Data obtained were analysed by the SPSS windows program and the results of this study were as follows : 1. There were no significant correlation between oral factors such as oral hygiene index, salivary flow rate, gingival index, degree of tongue coating and pre-treatment halimeter score. 2. Difference between pre- and post-treatment halimeter score by the three modalities were significant, but correlation between pre- and post-treatment score within group was most significant in the periodontal treatment group followed by the tongue scraping group and lowest in the $ZnCl_2$ mouth rinse group. 3. Reduction of halimeter score was significant only in subjects with relatively more tongue coating in the tongue scraping group, but in the $ZnCl_2$ mouth rinse group and in the periodontal treatment group, the modality applied to each group had same significant effects without regard to the degree of oral hygiene index or gingival index. 4. Men had more tongue coating than women, and reduction of halimeter score was significant in men, but not in women.

• KSBB Journal
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• v.15 no.3
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• pp.254-261
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• 2000

A bacterial leaching was conducted for pyrite with Thiobacillus ferrooxidans(ATcC 19859) and Thiobacillus KY isolated from acid mine water around Kwangyang area to characterize the surface of substrate as reaction progress at the optimum condition under 9K medium for 3- days. It was found that the surface crystallinity changes referred to hkl plane was observed for 20 days leached by T. ferrooxidans similar changes also observed for 10 days leached pyrite by Thiobacillus KY. Based on he results of SEM-EDS the atomic ratios of Fe, S and Si on the surface were changed to sulfur rich phase but exposed Si ratio decreased from 16.94% to 4.85% during 30days mainly due to reprecipitating of Fe and S as a mixed compound.

• Economic and Environmental Geology
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• v.23 no.1
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• pp.25-33
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• 1990

Gold-silver deposits of Deogheun and Beopjeon mines are composed of veins emplaced in Jurassic granite batholith. Based on ore structure and ore mineralogy, four distinct stages of mineral deposition are recognized in these ore deposits. Gold and silver minerals in Deogheun and Beopjeon-A ore deposits are precipitated in stage III and stage II, respectively. Mineral constituents of ores from these deposits are pyrite, sphalerite, arsenopyrite, pyrrhotite, chalcopyrite, galena, tetrahedrite, electrum, quartz and rhodochrosite. Cubanite, argentite and pyrargyrite occur only in Deogheun ore deposits. Ag content of electrum range from 42 to 66 atomic % in both ore deposits. Filling temperature of fluid inclusion from both ore deposits are as follows; stage I, $211-289^{\circ}$ ; stage II, $205-290^{\circ}$ ; stage III, $190-260^{\circ}$ ; stage IV, $136-222^{\circ}$ in Deogheun ore deposits. In Beopjeon-A ore deposits, stage I, $255-305^{\circ}$ ; stage II, $135-222^{\circ}$ ; stage III, $148-256^{\circ}$ ; stage IV, $103-134^{\circ}$. Salinities of fluid inclusions range from 1.6-8.5 wt. % equivalent NaCl in both ore deposits. Sulfur fugacities through stage II and III in Deogheun ore deposits inferred from data of mineral assemblage and fluid inclusion range from $10^{-11.0}-10^{-16.1}$1bars. Fluid pressure estimated from fluid inclusions which reveal boiling evidence range from 30-190 bars during mineralization in Deogheun ore deposits.

• Economic and Environmental Geology
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• v.29 no.2
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• pp.139-150
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• 1996

The Yucheon Bi deposits at Cheongha, Gyeongsangbugdo, is of a middle Paleogene (49 Ma) vein type, and is hosted in sandstone and shale of Banyawal formation in Cretaceous age. Based on mineral paragenesis, vein structure and mineral assemblages, two minera1ization stages were distinguished. The stage I consists of quartz with small amount of chlorite, pyrite, epidote, hal1oysite, vermiculite, serpentine and rutile associated with sericitization. The stage II is characterized by Bi minera1ization such as bismuthinite, Bi-Cu-Pb-S mineral, tetradymite, native gold, pyrite, pyrrhotite, arsenopyrite, wolframite, rutile, hematite, sphalerite, chalcopyrite, galena with alteration of sericite, chlorite, K-feldspar, albite and epidote. Fluid inclusion data indicate that fluid temperature and NaCl equivalent wt.% salinity range from 431 to $150^{\circ}C$ and from 19.2 to 0.18wt.% in the stage II. Evidence of boiling during the base-metal minera1ization indicates pressures 241 to 260 bars. Sulfur fugacity($-log\;f_{S2}$) deduced by mineral assemblages and compositions ranges from 5.1 to 5.7atm in early stage, from > 8.4 atm in middle stage and from 13.5 to 19.3 atm in late stage. It suggests that complex histories of progressive coo1ing, dilution and boiling were occurred by the mixing of the fluids. The ${\delta}^{34}S$, ${\delta}^{18}O$ and ${\delta}D$ data range from 2.5 to 3.9%, -0.5 to -4.1% and -29.7 to -47%, respectively. It indicated that hydrothermal fluids may be magmatic origin with boiling and mixing of meteoric water increasing paragenetic time.

• Environmental Analysis Health and Toxicology
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• v.15 no.4
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• pp.139-145
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• 2000

The Flavin-containing monooxygenase (FMOs) (EC1.14.13.8) are NADPH-dependent flavoenzymes that catalyze oxidation of soft nucleophilic heteroatom centers in a range of structurally diverse compounds, including foods, drugs, pesticides, and other xenobiotics. In humans, FMO3 is quantitatively a major human liver monooxygenase. In the present study, the baculovirus expression vector system was used to overexpress human FMO3 in insect cells for catalytic studies. Six commercially available organic selenium compounds were examined for substrate activity with microsomes isolated from Spodoptera frugiperda (Sf)9 cells infected with human FMO3 recombinant baculovirus. While none of the aromatic heterocyclic selenides tested showed detectable activity, all dialkyl- and alkylaryl-selenides free from ionic groups catalyzed the NADPH- and O$_2$-dependent oxidation. Kinetic constants demonstrate that (based on Km) dialkyl-and alkylaryl- selenides are better substrates for human FMO3 than analogous nitrogen or sulfur compounds .

• Journal of Microbiology and Biotechnology
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• v.11 no.6
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• pp.1046-1054
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• 2001

Bioleaching is the process in which insoluble metal sulfide is oxidized by specialized iron- and/or sulfur-oxidizing lithotrophic bacteria in acidic, metal-rich environments. Most of these processes are carried out by the genus Thiobacillus. Three novel Thiobacillus strains (Thiobacillus thiooxidans AZ11, Thiobacillus thiooxidans MET, and thiobacillus thiooxidans TAS) associated with bioleaching have been isolated from soil and sludge (Korean patent No. 1999-0073060 for T. thiooxidans AZ11, Korean patent No. 1999-0005798 for T. thiooxidans MET, and Korean patent No. 1999-0073059 for T. thiooxidans TAS). A partial sequence of 16S ribosomal RNA gene (16S rDNA) and the entire sequence of 16S/23S intergenic spacer region (ISR) were determined in the three above novel strains and in Thiobacillus ferrooxidans ATCC19859 as a reference strain. When phylogenetic analysis was performed based on G+C contents and sequence alignments, T. ferroxidans ATCC19859 was found to be closely related to previously registered T. ferrooxidans strains in a monophyletic manner, while the three novel T. thiooxidans strains were classified in a paraphyletic manner. Close examination on the base composition of 16S/23S ISR revealed that the 5\` part (nucleotide residues 21-200) was specific for the genus Thiobacillus. On the other end, the 3\` part (nucleotide residues 201-520) showed specificity in T. ferrooxidans strains, but not in T. thiooxidans strains. These results suggest that the proximal and distal halves of 16S/23S could be used as a genetic marker for the identification of the genus Thiobacillus and the species T. ferrooxidans, respectively.

• Journal of the Korean Society for Marine Environment & Energy
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• v.13 no.4
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• pp.249-262
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• 2010

Regulatory test method for Total Petroleum Hydrocarbons (TPHs) in the marine sediment and biota has not still been established even though TPHs are one of the major pollutants in marine environment. Based on the Korean Soil Standard Method (SSM) for TPHs, we considered a new treatment method for determining TPHs in marine environmental samples by using a Gas chromatography coupled with Mass spectrometric detector. We suggested an improved recovery test for quality control procedures and introduced analytical procedures of removing sulfur, polar organic materials, water and saponification for removing neutral lipids in marine bottom sediments and biota.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.5 no.1
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• pp.1-8
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• 2009

Nuclear hydrogen production using high temperature heat of a very high temperature reactor(VHTR) is one of the most attractive ways of mass hydrogen production without greenhouse gas emission. In many countries, sulfur-iodine(S-I) thermochemical process and high temperature steam electrolysis(HTSE) process are being investigated. In such processes, corrosion behavior of Intermediate heat exchanger materials are the most critical issues. Especially in a HTSE system, several heat exchangers will be facing hot steam conditions. In this paper, the status of high temperature corrosion researches in hot steam and supercritical water conditions are reviewed in view of the implication to HTSE conditions. Based on the review, test condition and plan of the hot steam corrosion of the candidate materials are formulated and described in some details along with the schematics of the test set-up. The test results and subsequent evaluation will be used in development of a interface system between the HTSE hydrogen production system and the VHTR.