• Bulletin of the Korean Chemical Society
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• 제32권6호
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• pp.2003-2007
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• 2011

We report a highly sensitive surface-enhanced Raman scattering (SERS) platform for the selective trace analysis of mercury (II) ions in drinkable water using aptamer-conjugated silver nanoparticles. Here, an aptamer designed to specifically bind to $Hg^{2+}$ ions in aqueous solution was labelled with a TAMRA moiety at the 5' end and used as a Raman reporter. Polyamine spermine tetrahydrochloride (spermine) was used to promote surface adsorption of the aptamer probes onto the silver nanoparticles. When $Hg^{2+}$ ions are added to the system, binding of $Hg^{2+}$ with T-T pairs results in a conformational rearrangement of the aptamer to form a hairpin structure. As a result of the reduced of electrostatic repulsion between silver nanoparticles, aggregation of silver nanoparticles occurs, and the SERS signal is significantly increased upon the addition of $Hg^{2+}$ ions. Under optimized assay conditions, the concentration limit of detection was estimated to be 5 nM, and this satisfies a limit of detection below the EPA defined limit of 10 nM in drinkable water.

• Bulletin of the Korean Chemical Society
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• 제32권10호
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• pp.3561-3565
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• 2011

A rapid and inexpensive method was developed for the determination of trace silver in geological samples by using sulfhydryl cotton coupled with ICP-MS. The interferences such as $^{90}Zr$, $^{92}Mo$ and $^{93}Nb$ on silver were investigated in detail. Sulfhydryl cotton was found to be an effective adsorbent for separation of interferences for Ag in the solutions. Excellent agreements with the certified values were obtained for all the certified reference materials. The memory effects of Ag by ICP-MS were examined by using different agents, including water, nitric acid, and HCl-thiourea to all standards/samples. The agents also acted as cleansing solutions. A combination of HCl with thiourea gave the minimum memory effect. For comparison of results, a proposed Chinese Geology Survey procedure DC-ARC-AES and a direct determination pretreatment method of ICP-MS (water bath- auqa regia digestion) were studied. Under optimal conditions, the detection limits of our method for $^{107}Ag$ and $^{109}Ag$ were 1.2 ng/g and 1.3 ng/g, which offered much better accuracy for some difficult analysis geological samples such as GBW07604, GBW07605.

• Bulletin of the Korean Chemical Society
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• 제7권1호
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• pp.55-58
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• 1986

Analytical capability of surface-enhanced Raman scattering has been evaluated. Silver films prepared by homogeneous chemical reduction were used as the substrate. Detection limits for p-nitrobenzoic acid, thiophenol and rhodamine 6G were around $10{\sim}100\;pg$.

• Restorative Dentistry and Endodontics
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• 제15권2호
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• pp.1-16
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• 1990

This study was to evaluate the cytotoxic effect in vitro and the tissue response within the rat peritoneal cavity to high copper amalgam and glass ionomer-silver cement, suggested for use as a retrograde endodontic filling material. In the cytotoxicity experiment, the radioactively ($^{51}Cr$) labeled L929 mouse fibroblasts were employed to determine the relative cytotoxicity of two experimental materials. Those materials were evaluated immediately after set and after one and seven days setting. In the tissue response experiment, two experimental materials were to evaluate mean peritoneal cellular count, differential cell count and the content of silver and copper in pooled packed cells and eluate samples taken by peritoneal lavage technique, and compared with surgical control after one day. two, four and six weeks of implantation. The results were as following: 1. High copper amalgam exhibited significant cytotoxicity immediately after set but showed no sign of toxicity after one day and seven days setting materials. 2. Glass ionomer-silver cement showed no sign of toxicity immediately after set and after one day and seven days setting. 3. High copper amalgam and glass ionomer-silver cement groups produce no significant difference in the mean peritoneal cell count when compared with the surgical control group after one day, two and four weeks of implantation. Surgical control group exhibited significantly a greater cell count when compared with the High copper amalgam group after six weeks. 4. High copper amalgam group increased significantly in the percentage macrophages after four and six weeks of implantation when compared with surgical control group. 5. The trace metal analysis involved an increased silver content in the elutes and an increased copper content in the packed cells of high copper amalgam group, and an increased silver content in the packed cells and elutes of glass ionomer-silver cement group.

• The Journal of Korean Academy of Prosthodontics
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• 제27권1호
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• pp.31-47
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• 1989

The purpose of this study was to evaluate the chemical bond strength of successively recast Pd-Ag ceramic alloys with porcelain and to investigate changes of quantity of trace elements at the metal-porcelain interface. Porcelain was fired as usual manner on the each successively recast specimen. Rectangular planar shear test was performed and bond strength was measured by Instron universal testing machine. Diffusion of trace elements at the each interface was observed by ESCA (Electron Spectroscopy for Chemical Analysis). The obtained results were as follows : 1. Chemical bond strength was significantly decreased after second recasting. But in case of first recasting, there was no significant decrease of bond strength statistically (p<0.05). 2. Bond strength was not significantly decreased in each generation, when fifty percents new alloy was added (p<0.05). 3. Ag, Sn and In were observed at the porcelain interface. But Pd was not observed. 4. The quantity of Ag, In ions were progressively increased at the metal-porcelain interface as the casting was repeated. Silver ion was most significantly increased.

• The Journal of Natural Sciences
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• 제17권1호
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• pp.65-77
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• 2006

This study aims at providing suitable outdoor spaces for physical, social, and psychological condition of Korea elderly, examining design characteristics and presenting design guideline of outdoor space for elderly. To do this, this study examined previous research papers and scholastic writings, related to elderly housing, and analyzed existing outdoor space for elderly. Additionally evaluation of usage pattern and physical trace carried out four silver towns. As a result, first, the study showd that characteristics of outdoor space are related to safety, amenity, recognition and efficiency. Second, types of outdoor space in elderly related facilities are very limited in verity, just facilitating with rest space, sport space, and garden space. Third, from a standpoint of barrier-free-design, four silver town cases are not carefully concerning about outdoor space for elderly. These spaces should be designed for both neighborhood and elderly people.

• Acta Via Serica
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• 제3권2호
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• pp.73-90
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• 2018

The Silk Road tied the globe together for the first time by producing an early globalization phenomenon. Some consider that the ancient Silk Road disintegrated around the $18^{th}$ century CE due to the fall of the Muslim empires and the kingdoms between Asia and Europe. However, the maritime trade among East Asia and the Spanish dominion on the American continent reactivated the ancient Silk Road on some levels, and maintained trade dynamics until the $19^{th}$ century. This was possible because of Mexican silver and trade spots. Notwithstanding its historical background, Mexico seems so far away from the new Silk Road, or the Belt and Road Initiative in the $21^{st}$ century. Thus, this paper analyzes Mexico's historic and current role concerning the Silk Road. First, I conceptualize and compare the ancient Silk Road and Belt and Road Initiative through the lens of complex interdependence theory. I propose that, unlike the ancient Silk Road, the Belt and Road Initiative is a case of an induced complex interdependence. Second, I study the Manila Galleons' dynamics in order to trace the ancient ties with the Silk Road. I emphasize Mexican silver's contribution to East Asian economies and the importance of Mexico's role in the East Asia-Spanish trade. Consequently, I analyze Mexico's position in the Belt and Road Initiative. Finally, I present some concluding remarks about Mexico's role in the Silk Road.

• Economic and Environmental Geology
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• 제19권spc호
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• pp.193-206
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• 1986

A number of auriferous veins occur in the Precambrian metamorphic terrain from Chungju to Mugeug district. These gold (-silver) deposits consist mainly of the fissure-filling quartz veins intruding the Precambrian gneiss or schist and Jurassic or Cretaceous granite. These gold (-silver) deposits can be 'divided into two mineralization epochs, (a) gold-rich veins related to Daebo igneous activity, and (b) gold-silver veins related to Bulgugsa igneous activity. These two groups of ore deposits with different generation can be characterized by the mode of occurrence of ore vein and the ore mineral associations. The auriferous quartz veins of Taechang and Boryeon mines associated with late Jurassic igneous activity are massive in character, and show the simple mineral assemblages and low Ag/Au ratio in the ores, representing a single mineralization system. The ore minerals are predominantly quartz containing minor or trace amonts of pyrrhotite, sphalerite, galena, pyrite, chalcopyrite and electrum. Electrum is closely associated with pyrrhotite and has chemical compositions from 61.4 to 78.5 atomic % Au. Fluid inclusion data suggest that ore minerals were deposited at temperatures between 238 and $390^{\circ}C$ from $CO_2$-rich fluids. The gold and/or silver-bearing quartz veins of Geumwang mine related to middle Cretaceous igneous activity are characterized by the multistage history, diverse mineral assemblages with high Ag/Au ratio in the ores. The ores of Geumwang mine have two contrasting mineral assemblages (1) pyrite+galena+sphalerite+arsenopyrite+electrum+argentite, representing the higher gold mineralization, and (2) pyrite+chalcopyrite+ galena +sphalerite+ arsenopyrite+silver sulfosalts+ electrum+ native silver+argentite, representing the higher silver mineralization. Electrum is closely associated with pyrite and has chemical compositions from 11.2 to 49.9 atomic % Au. The depositional environment during the higher gold mineralization can be estimated as the range of both temperature and sulfur fugacity, T= $200{\sim}300^{\circ}C$, log f ($S_2$) = $10^{-10}{\sim}10^{-15}$. The higher silver mineralization may be interpreted to have formed a range of falling temperature ($150{\sim}200^{\circ}C$) and low sulfur fugacity($10^{-10}{\sim}10^{-15}$). These temperature data are consistent with homogenization temperatures of fluId inclusions in quartz. Thus, the gold veins related to the Daebo igneous activity may be formed by the environment of higher temperature and pressure than the gold-silver veins associated with the Bulgugsa igneous activity.

• Economic and Environmental Geology
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• 제45권6호
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• pp.623-641
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• 2012

The Janggun lead-zinc-silver deposit is hydrothermal-metasomatic deposit. We have sampled wallrock, hydrother-maly-altered rock and lead-zinc-silver ore vein to study the element dispersion during wallrock alteration. The hydrothermal alteration that is remarkably recognized at this deposit consists of rhodochrositization and dolomitization. Wallrock is dolomite and limestone that consisit of calcite, dolomite, quartz, phlogopite and biotite. Rhodochrosite zone occurs near lead-zinc-silver ore vein and include mainly rhodochrosite with amounts of calcite, dolomite, kutnahorite, arsenopyrite, pyrite, chalcopyrite, sphalerite, galena and stannite. Dolomite zone occurs far from lead-zinc-silver ore vein and is composed of mainly dolomite and minor calcite, rhodochrosite, pyrite, sphalerite, chalcopyrite, galena and stannite. The correlation coefficients among major, trace and rare earth elements during wallrock alteration show high positive correlations(dolomite and limestone = $Fe_2O_3(T)$/MnO, Ga/MnO and Rb/MnO), high negative correlations(dolomite = MgO/MnO, CaO/MnO, $CO_2$/MnO, Sr/MnO; limestone = CaO/MnO, Sr/MnO). Remarkable gain elements during wallrock alteration are $Fe_2O_3(T)$, MnO, As, Au, Cd, Cu, Ga, Pb, Rb, Sb, Sc, Sn and Zn. Remarkable loss elements are CaO, $CO_2$, MgO and Sr. Therefore, elements(CaO, $CO_2$, $Fe_2O_3(T)$, MgO, MnO, Ga, Pb, Rb, Sb, Sn, Sr and Zn) represent a potential tools for exploration in hydrothermal-metasomatic lead-zinc-silver deposits.

• The Journal of Asian Finance, Economics and Business
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• 제8권1호
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• pp.81-91
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• 2021

This paper investigates the long run hedging ability of precious metals against the risks associated with adverse conditions of economic and financial variables for Pakistan, the USA, China, and India. Monthly data of gold, silver, platinum, stock returns, exchange rate, industrial production, and inflation was collected for the selected economies. Saikkonen and Lutkepohl (2002) unit root test was employed to access the unit root properties of the data series and identify the break dates. Furthermore, this study used the Johansen cointegration test with and without structural breaks to identify the long-run relationship between metals prices and different financial and economic variables. The findings suggest that the time series under study have unit root problem at level with and without structural breaks. Without considering structural breaks, the Johansen trace test indicates that in Pakistan and China, gold, silver, and platinum hold a cointegrating relationship with macroeconomic and financial variables. For the US, gold indicates cointegration which supports the hedging ability of gold against inflation, stock, and industrial production in the long run. The results of the cointegration test after incorporating the structural breaks provide even stronger evidence of the long-run relationship of precious metals and consumer prices, exchange rate, and stock prices.