• Bulletin of the Korean Chemical Society
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• v.14 no.6
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• pp.692-696
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• 1993

Prediction of retention times in transition metal-mandelate and transition metal-tartrate complex systems were studied on the cation exchanger. Plots of k' vs [mandelate] and k' vs [tartrate] were obtained under the condition of a constant competing cation concentration. The equation to predict the retention time of transition metal ion was derived from the ion exchange equilibria. Individual capacity factors (${k_1}',\;{k_2}'$) and stability constants ($K_1,\;K_2$) of the complexes were calculated from the non-linear least square method. Good resolution of the transition metals was predicted by the stepwise equation in the gradient method. The values of retention times from the calculation and the experiment agreed well each other.

• Bulletin of the Korean Chemical Society
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• v.17 no.12
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• pp.1109-1111
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• 1996

The Podand Ⅰ (Figure 1) has been studied as cation carrier in a bulk liquid membrane system. Ag+ and some other transition metal ions (M2+=Cu, Ni, Co, Zn, and Cd) have been transported using the podand as carrier in a bulk liquid membrane system. Studies on the transport of equimolar mixtures of two or three competing components have also been carried out with the same system. Ag+ exhibited a higher transport rate than the other M2+ in the competitive experiments. Ligand structure and the equilibrium constant for complex formation are important parameters in the transport of the metal ions.

• Korean Journal of Environmental Agriculture
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• v.16 no.2
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• pp.142-148
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• 1997

This study was performed to develop the biological treatment technology of wastewater polluted with heavy metals. Heavy metal-tolerant microorganisms, such as Pseudomonas putida, P. aeruginosa, P. chlororaphis and P. stutzeri possessing the ability to accumulate cadmium, lead, zinc and copper, respectively, were isolated from industrial wastewaters and mine wastewaters polluted with various heavy metals. The effect of competing ions and metabolic inhibitors on heavy metal accumulation in the cells was investigated. Heavy metal accumulation into cells was drastically decreased in the presence of competing cation, $Al^{3+}$, and also decreased, at a lesser extent, in the presence of competing anions, $CO_3\;^{2-}$ and $PO_4\;^{2-}$. But heavy metal accumulation was not influenced generally in the presence of the other rations and anions. The accumulation of Cd, Zn or Cu by Cd-, Zn- or Cu-tolerant microorganism was remarkably decreased in the presence of metabolic inhibitors, but the accumulation of Pb by Pb-tolerant microorganism was little affected in the presence of metabolic inhibitors. These results suggested that the accumulation of Cd, Zn or Cu by Cd-, Zn- or Cu-tolerant microorganism was concerned with the biological activity depending on energy, and the accumulation of Pb by Pb-tolerant microorganism depended on not the biological activity but the physical adsorption on the cell surface. Each heavy metal-tolerant microorganism also exhibited some ability to accumulate the other heavy metals in solution containing equal concentrations of cadmium, lead, zinc and copper, when measured at 48 hours after inoculation of the microorganisms, but the accumulation rates were somewhat low as compared to the accumulation rates of heavy metal fitting to each tolerance. These results suggested that the accumulation of each heavy metal by each heavy metal-tolerant microorganism was a selective accumulation process.

• Bulletin of the Korean Chemical Society
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• v.35 no.3
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• pp.833-838
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• 2014

The energy- and time-dependent branching to the competing dissociation paths are studied by theory for coupled unimolecular dissociations of the o-, m-, and p-chlorotoluene radical cations to $C_7{H_7}^+$ (benzylium and tropylium). There are four different paths to $C_7{H_7}^+$, three to the benzylium ion and one to the tropylium ion, and all of them are coupled together. The branching to the multiple paths leads to the multiexponential decay of reactant with the branching ratio depending on both internal energy and time. To gain insights into the multipath branching, we study the detailed kinetics as a function of time and internal energy on the basis of ab inito/RRKM calculations. The number of reaction steps to $C_7{H_7}^+$ is counted for each path. Of the three isomers, the meta mostly goes through the coupling, whereas the para proceeds with little or no coupling. In the beginning, some reactants with high internal energy decay fast to the benzylium ion without any coupling and others rearrange to the other isomers. Later on all three isomers dissociate to the products via long-lived intermediates. Thus, the reactant shows a multiexponential decay and the branching ratio varies with time as the average internal energy decreases with time. The reciprocal of the effective lifetime is taken as the rate constant. The resulting rate-energy curves are in line with experiments. The present results suggest that the coupling between the stable isomers is thermodynamically controlled, whereas the branching to the product is kinetically controlled.

• Bulletin of the Korean Chemical Society
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• v.33 no.11
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• pp.3625-3628
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• 2012

Fluorescent organic molecules that respond to changes in the $Fe^{2+}$ concentration with selectivity to other abundant di-valent metal ions will offer the ability to understand the dynamic fluctuations of the $Fe^{2+}$ ion in interesting media. The use of 6-Br-ppmbi, derived from 2-pyridin-2-yl-benzimidazole, for metal ion-selective fluorescence recognition was investigated. Screening of the main group and transition metal ions showed exclusive selectivity for $Fe^{2+}$ ions even in the presence of competing metal ions. In addition, the requirement for low concentrations of probe molecules to detect certain amounts of $Fe^{2+}$ ions make this sensor unique compared to previously reported $Fe^{2+}$ ion sensors.

• Applied Chemistry for Engineering
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• v.4 no.2
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• pp.365-372
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• 1993

$CO_2$ methanation was performed over Ni supported on cation-exchanged Y zeolites under atmospheric pressure at $250{\sim}550^{\circ}C$ and $H_2/CO_2$ mole ratio of 4. Adsorption strength between carbon dioxide and nickel was found to be Influenced by the cation exchanged in the zeolite. TPD(Temperature-programmed desorption) results show that the adsorption strength decreases in the order of Ni/NaY>Ni/MaY>Ni/HY. TPSR(Temperature-programmed surface reaction) results indicate that enhanced methanation activity is obtained when the adsorption strength between carbon dioxide and nickel is stroing. As the reduction temperature increases, the methantion activity of the catalyst increase. From this result the larger size nickel particle seems advantageous for $CO_2$ methanation reaction. The maximum activity is obtained when nickel loading is 3.3wt%. Carbon monoxide is produced as a by-product throughout the reaction temperature range, and as the contact time increases, the selectivity to methane increases and the selectivity to carbon monoxide decreases steadily. Thus methane seems to be produced from $CO_2$ via CO as an intermediate species. In the temperature range of $410{\sim}450^{\circ}C$, the methane production rate is found to be dependent on the orders of 3.3~-0.5 and 1.4~3.6 with respect to $CO_2$ and $H_2$ partial pressures, respectively. This clearly shows that $CO_2$ and $H_2$ are competing for adsorption sites and as the reaction temperature increases, it becomes increasingly difficult for $H_2$ to be adsorbed on the catalyst surface.

• Economic and Environmental Geology
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• v.56 no.5
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• pp.515-532
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• 2023

Bentonite, predominantly consists of expandable clay minerals, is considered to be the suitable buffering material in high-level radioactive waste disposal repository due to its large swelling property and low permeability. Additionally, the bentonite has large cation exchange capacity and specific surface area, and thus, it effectively retards the transport of leaked radionuclides to surrounding environments. This study aims to review the thermodynamic sorption models for four radionuclides (U, Am, Se, and Eu) and eight bentonites. Then, the thermodynamic sorption models and optimized sorption parameters were precisely analyzed by considering the experimental conditions in previous study. Here, the optimized sorption parameters showed that thermodynamic sorption models were related to experimental conditions such as types and concentrations of radionuclides, ionic strength, major competing cation, temperature, solid-to-liquid ratio, carbonate species, and mineralogical properties of bentonite. These results implied that the thermodynamic sorption models suggested by the optimization at specific experimental conditions had large uncertainty for application to various environmental conditions.

• Journal of Korean Society for Atmospheric Environment
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• v.14 no.5
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• pp.479-490
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• 1998

The concentrations of ten inorganic (sodium, chloride, sulfate, ammonia, etc.) and three organic (acetate, formate, and MSA) ions associated with airborne particulate matter were measured from Cheju Island, Korea during the three field intensive campaigns conducted in (1) Sept./oct. 1997 (fall), (2) Dec. 1997 (winter), and (3) April 1998 (spring). The results of our measurements indicated that the concentration levels of most ionic species were decreasing significantly across the three experimental periods. The patterns of concentration reduction were clear as the sum of all cation and anion species changed dramatically across those periods such as 294> 144 > 65 and 193 >96>74 nequiv/m3, respectively. The changes were best explained in terms of the wind rose patterns of the study site. Since our sampling spot is located on the western-end point of Cheju Island, it is likely to reflect the effects of diverse sources such as natural, marine processes during NW and local non-maritime ones during SE winds. .Hence, the periodical changes in ionic concentrations may be accounted for by the comparable changes in wind direction. To further investigate environmental characteristics of these ionic components, correlation analysis was conducted not only between meteorological and ion data but between different ion-pairs. The results of these analyses confirm that the concentration levels of ionic species are strongly affected by wind speed and temperature and that there are certain patterns between ion species to which such effects apply. In light of the significance of the wind rose patterns in the area, we further extended these analyses into four data groups that were divided on the basis of wind direction. The results of these analyses showed that the strength of correlations between important pairs (e.g.:. between windspeed and most of major inorganic species including sodium and chloride) can be ranked on the distribution of major ions are very diverse, depending on data grouping scheme for such analysis. The results of this study thus suggest that environmental behavior of chemical components be analyzed in various respects, rather than simple standard, especially if measurements are made in complex environmental condition under which both natural and anthropogenic effects are competing each other.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.7 no.1
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• pp.50-58
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• 2004

The aim of this study was to characterize the forest vegetation structure and site of Quercus serrata forest for ecological forest management and ecological niche. The results are as follows : The chemical properties of Q. serrata forest soil were 0.24% of total nitrogen, 8.27 of organic matter, 74ppm of available phosphorous, 1.64(me/100g) of Ca, 0.22(me/100g) of Mg, 0.74(me/100g) of K and 9.3(me/100g) of cation exchangeable capacity. The dominant species in Quercus serrata forest were Quercus serrata, Quercus acutissima, Quercus variabilis, Quercus mongolica, Styrax obassia, Fraxinus rhynchophylla and Styrax japonica. DBH analysis showed that Quercus serrata seems to remain as a dominant species for the present because they had random distribution based on few of big individuality, many of small and middle individuality. But the Q. serrata community is competing with Q. mongolica and F. rhynchophylla, whose density of small individuality has increased. With the classification of TWINSPAN, Q. serrata forest was classified three groups, such as Q. serrata-Acer mono, Q. serrata, Q. serrata-Q. acutissima communities. The results of the correlation analysis of Q. serrata major communities and environment factors are as follows; Q. serrata-A. mono community was found relatively in high elevated and eastern and northern area that has relatively high percentage organic matter. Also Q. serrata community was found in high elevated and eastern and northern area that has high percentage organic matter. Q. serrata-Q. acutissima community was found in low elevated and southern and western area that has low percentage organic matter.

• Molecules and Cells
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• v.40 no.10
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• pp.787-795
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• 2017

Avoiding ingestion of excessively salty food is essential for cation homeostasis that underlies various physiological processes in organisms. The molecular and cellular basis of the aversive salt taste, however, remains elusive. Through a behavioral reverse genetic screening, we discover that feeding suppression by $Na^+$-rich food requires Ionotropic Receptor 76b (Ir76b) in Drosophila labellar gustatory receptor neurons (GRNs). Concentrated sodium solutions with various anions caused feeding suppression dependent on Ir76b. Feeding aversion to caffeine and high concentrations of divalent cations and sorbitol was unimpaired in Ir76b-deficient animals, indicating sensory specificity of Ir76b-dependent $Na^+$ detection and the irrelevance of hyperosmolarity-driven mechanosensation to Ir76b-mediated feeding aversion. Ir76b-dependent $Na^+$-sensing GRNs in both L- and s-bristles are required for repulsion as opposed to the previous report where the L-bristle GRNs direct only low-$Na^+$ attraction. Our work extends the physiological implications of Ir76b from low-$Na^+$ attraction to high-$Na^+$ aversion, prompting further investigation of the physiological mechanisms that modulate two competing components of $Na^+$-evoked gustation coded in heterogeneous Ir76b-positive GRNs.