• Membrane Journal
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• v.14 no.2
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• pp.173-184
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• 2004

For the application of direct methanol fuel cell (DMFC), sulfonated polystyrene/teflon (PS/PTFE) composite membranes were developed by changing monomer ratio of styrene and DVB. The composite membranes were prepared as follows: first, the monomer mixtures consisting of styrene, divinyl benzene and AIBN were impregnated in porous PTFE film and then, polymerized under 8$0^{\circ}C$ to give PS/PTFE membranes. Finally, the membranes were reacted with chlorosulfonic acid in 1,2-dichloroethane to give the sulfonated composite membranes. The measurements of ATR-FTIR, SEM, solvent uptake test and ion exchange capacity (IEC) were done for the resulting membranes before or after sulfonation, respectively, which showed the composite membranes with proper crosslinking degree and sulfonic acid content were prepared well as a function of styrene/DVB ratio. ion conductivity and methanol permeability were studied for the sulfonated membranes. It was found that with decreasing the ratio of styrene/DVB, methanol permeability decreased from $6.6{\times}10^{-7}∼1.3{\timas}10^{-7}$ $\textrm{cm}^2$/s, which are much lower values than that of Nafion$^{(R)}$117($1.02{\times}10^{-6}$ $\textrm{cm}^2$/s). Under the same monomer condition, ion conductivity decreased from 0.11 S/cm ($25^{\circ}C$) to 0.08 S/cm ($25^{\circ}C$), which are similar or a little higher values compared with $Nafion^{(R)}117 (1.02{\times}10^{-6}$ $\textrm{cm}^2$/s, 0.0824 S/cm). These two results confirmed the composite membranes prepared could be applied successfully to DMFC.C.

• Membrane Journal
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• v.16 no.3
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• pp.221-229
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• 2006

This study is about the preparation and characterization of sulfonated random copolymer membranes containing perfluorocyclobutane (PFCB), fluorenyl, and sulfonyl units. The polymers were prepared through three synthetic steps, that is, the synthesis of a trofluorovinylether-terminated monomer, its thermal polymerization, and post-sulfonation using chlorosulfonic acid. A series of sulfonated random copolymers with different ion exchange capacity (IEC) were prepared by changing contents of fluorenyl uints in polymers with fixed molar ratio of chlorosulfonic acid during the post-sulfonation reaction. All the synthesized compounds were characterized by FT-lR, $^1H-NMR$, $^{19}F-NMR$, and Mass spectroscopy. As the content of sulfonated fluorenyl units increased, the IEC, water uptake, and ion conductivity of the sulfonated random copolymer membranes increased. The sulfonated random copolymer S-1 and S-2 showed higher values of ion conductivity than the Nafion-115 in a wide range of temperatures ($25{\sim}80^{\circ}C$).

• Membrane Journal
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• v.16 no.1
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• pp.16-24
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• 2006

We report on the preparation and characterization of sulfonated polymer membranes containing perfluorocyclobutane (PFCB) units and fluorene units. The polymers were prepared through three synthetic steps, that is, the synthesis of a trifluorovinylether-terminated monomer, its thermal polymerization, and post-sulfonation using chlorosulfonic acid. A series of sulfonated polymers with different ion exchange capacity (IEC) were prepared by changing the content of chlorosulfonic acid during the post-sulfonation reaction. All the synthesized compounds were characterized by FT-IR, $^{1}H-NMR,\;^{19}F-NMR$, and Mass spectroscopy. As the content of chlorosulfonic acid increased, the SD, IEC, water uptake, and ion conductivity of the sulfonated polymer membranes increased. The sulfonated polymer 4 showed higher values of ion conductivity than the Nafion-$115^{\circledR}$ in a wide range of temperatures ($25{\sim}80^{\circ}C$).

• Membrane Journal
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• v.16 no.4
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• pp.241-251
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• 2006

In this study, crosslinked copolyimides with random (r-) and block (b-) structure were fabricated using N,N-bis(2-hydroxyethyl)-2-aminoethanesulfonic acid and pentanediol as crosslinkers. Linear r- and b-sulfonated copolyimides were also fabricated for comparison. Ion exchange capacities of r- and b-copolyimides were very similar to each other owing to their strong dependence of sulfonic acid content. The physical crosslinking via dimerization of carboxylic acid groups induced a reduced average interchain distance in b-copolyimide without crosslinkers. Consequently, its water uptake and methanol permeability were lower than those of r-sulfonated copolyimides. Simultaneously, the reduced interchain distance increased the content of fixed-charged ions per unit volume. The high fixed-charged ion density contributed to an enhancement of proton conductivity In the b-sulfonated copolyimide. Crosslinking caused the reduction of average interchain distance between polymer chains irrespective of types of crosslinker and polymer structure, leading to low methanol permeability. On the contrary, their proton conductivity was improved owing to formation of effective hydrophilic channels responsible for proton conduction. In particular, this trend was observed in r-copolyimide containing a fixed charged ion.

• Korean Journal of Soil Science and Fertilizer
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• v.18 no.3
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• pp.312-317
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• 1985

Growth response and nutrients uptake of tobacco grown on mulched and non mulched plots were investigated during the growing period. 1. The whole growing time was about 25 days shorter and relative growth rate was faster in the mulched plot than in the non mulched plot. 2. Nitrate content of leaf in the latter stage of tobacco grown on the non mulched plot was more continuously increased compared with mulched plot. As a result in the latter stage of tobacco leaf nitrate form of nitrogen level was much higher on non mulched plot than on mulched plot. 3. Reducing sugar content in cured leaves of tobacco grown on the non mulched plot was lower that of the mulched plot. This difference in reducing sugar content was remarkable in the bottom leaves that nitrate content was highest. 4. Tobacco growing on nonmulched soil may cause to be low quality owing to increasing of nitrogen compound and decreasing of reducing sugar content in cured leaves. 5. As distributions of nitrate and potassium content in leaves at different stalk position was similar each other, nitrate and potassium ion considered to be counter ion in absorption and translocation through the tobacco plant.

• Clean Technology
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• v.24 no.1
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• pp.55-62
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• 2018

The adsorbent used in water-adsorption cooling system utilizing low-temperature heat of below $90^{\circ}C$ is required to exhibit high water uptake capacity at a relative humidity ($P/P_0$) between 0.1 and 0.3. Mesoporous silica (MCM-41) and MOF(MIL-101) exhibit quite large water adsorption capacity under saturated water vapor at $35^{\circ}C$. However, these adsorbents show small water adsorption capacity ($0.027{g_{water}\;g_{ads}}^{-1}$, $0.074{g_{water}\;g_{ads}}^{-1}$, respectively) in the relative humidity ($P/P_0$) range of 0.1 to 0.3. In this study, the surface properties of mesoporous silica and MOF were modified by simple methods to develop an adsorbent having a higher water uptake than the conventional water adsorbents at a relative humidity ($P/P_0$) of 0.1 ~ 0.3. In the case of mesoporous silica (MCM-41) exhibiting mainly water adsorption at $P/P_0=0.5{\sim}0.7$, aluminum species was functionalized on the mesopore walls and then cations existing near the aluminum were exchanged with various cations (e.g., $Na^+$, ${NH_4}^+$, and $(C_2H_5)_4N^+$). In addition, 20 wt% (to total weight of the composites) of hygroscopic inorganic salt ($CaCl_2$) was impregnated on the MCM-41. In the case of the MIL-101 (MOF), 20 wt% of hygroscopic inorganic salt ($CaCl_2$) was impregnated on the MIL-101. The MCM-41 which was ion-exchanged with various cations has main adsorption branch around 0.5 of $P/P_0$ which was slightly shifted with low-pressure direction in comparison with pristine MCM-41. However, tiny increases were observed on the adsorption in the range of $P/P_0$ between 0.1 and 0.3. After salt impregnation on the MCM-41, the adsorption capacity under $P/P_0=0.1{\sim}0.3$ at $35^{\circ}C$ was increased from $0.027{g_{water}\;g_{ads}}^{-1}$ to $0.152{g_{water}\;g_{ads}}^{-1}$. In the case of MIL-101, the amount of water adsorption at $35^{\circ}C$ under $P/P_0=0.1{\sim}0.3$ was increased from $0.074{g_{water}\;g_{ads}}^{-1}$ to $0.330{g_{water}\;g_{ads}}^{-1}$ after the salt impregnation.

• Korean Journal of Soil Science and Fertilizer
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• v.2 no.1
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• pp.53-68
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• 1969

The nutriophysiological response of rice plant to root environment was investigated with eye observation of root development and rhizosphere in situation. The results may be summarized as follows: 1) The quick decomposition of organic matter, added in low yield soil, caused that the origainal organic matter content was reached very quickly, in spite of it low value. In high yield soil the reverse was seen. 2) In low yield soil root development, root activity and T/R value were very low, whereas addition of organic matter lowered them still wore. This might be contributed to gas bubbles around the root by the decomposition of organic matter. 3) Varietal difference in the response to root environment was clear. Suwon 82 was more susceptible to growth-inhibitine conditions on low-yield soil than Norin 25. 4) Potassium uptake was mostly hindered by organic matter, while some factors in soil hindered mostly posphorus uptake. When the organic matter was added to such soil, the effect of them resulted in multiple interaction. 5) The root activity showed a correlation coeffieient of 0.839, 0.834 and 0.948 at 1% level with the number of root, yield of aerial part and root yield, respectively. At 5% level the root-activity showed correlation-coefficient of 0.751, 0.670 and 0.769 with the uptake of the aerial part of respectively. N, P and K and a correlation-coefficient of 0.729, 0.742 and 0.815 with the uptake of the root of respectively N.P. and K. So especially for K-uptake a high correlation with the root-activity was found. 6) The nitrogen content of the roots in low-yield soil was higher than in high-yield soil, while the content in the upper part showed the reverse. It may suggest ammonium toxicity in the root. In low-yield soil Potassium and Phosphorus content was low in both the root and aerial part, and in the latter particularly in the culm and leaf sheath. 7) The content of reducing sugar, non-recuding sugar, starh and eugar, total carbohydrates in the aerial part of plants in low yield soil was higher than in high yield soil. The content of them, especially of reducing sugar in the roots was lower. It may be caused by abnormal metabolic consumption of sugar in the root. 8) Sulfur content was very high in the aerial part, especially in leaf blade of plants on low yield soil and $P_2O_5/S$ value of the leaf blade was one fifth of that in high yield soil. It suggests a possible toxic effect of sulfate ion on photophosphorization. 9) The high value of $Fe/P_2O_5$ of the aerial part of plants in low yield soil suggests the possible formation of solid $Fe/PO_4$ as a mechanical hindrance for the translocation of nutrients. 10) Translocation of nutrients in the plant was very poor and most nutrients were accumulated in the root in low yield soil. That might contributed to the lack of energy sources and mechanical hindrance. 11) The amount of roots in high yield soil, was greater than that in low yield soil. The in high-yield soil was deep, distribution of the roots whereas in the low-yield soil the root-distribution was mainly in the top-layer. Without application of Nitrogen fertilizer the roots were mainly distributed in the upper 7cm. of topsoil. With 120 kg N/ha. root were more concentrated in the layer between 7cm. and 14cm. depth. The amount of roots increased with the amount of fertilizer applied.

• Journal of the korean academy of Pediatric Dentistry
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• v.34 no.3
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• pp.408-419
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• 2007

In the child, it is very important that he/she will have the ability to suppress aesthetic restorative materials of secondary caries. With the representative preventive material against caries, the importance of fluoride is more emphasized. This study examined the differences in fluoride release and re-uptake among some restorative materials, following a treatment of APF gel and fluoride varnish. The surface roughness was observed under scanning electron microscope. Studying this will provide for the research to find effective restorative materials and fluoride type in tooth caries prevention. It is applied from presence at a clinic that restorative materials are resin, flowable resin, compomer and glass ionomer. Fluoride release was measured at 24-hour intervals for 7 days, 3-day intervals from 8th to 38th day using an ion-selective electrode and analyzer. Then, the materials were treated with the fluoride gel and fluoride varnish respectively, fluoride release was measured and specimens were evaluated under scanning electron microscope for 4 weeks. It was concluded that 1. Fluoride was released for 38 days from restorative materials under 1 ppm in case of flowable resin, 1-2 ppm in compomer and 2-8 ppm in glass ionomer, a few of fluoride was released after 45 days 2. Fluoride has more releasing after application of APF gel than fluoride varnish. Fluoride re-uptake was observed under 0.6-0.2 ppm in fluoride varnish and 0.6-2.6 ppm in APF gel after starting the procedure one day(p<0.05). For the remaining 4 weeks, they demonstrated a similar release. 3. Specimens were evaluated under scanning electron microscope. Applied fluoride in the experimental group surface was rougher than the control group that did not receive fluoride application. Fluoride varnish group had a smoother surface than both the APF gel group and the varnish APF gel group that received a fluoride application.

• Journal of the Korean Society for Marine Environment & Energy
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• v.7 no.1
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• pp.13-21
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• 2004

Temporal changes of Chl-α, physical and chemical factors were investigated by diurnal observation at 2-hour interval at three fixed stations in the western Chinhae Bay from 12 Aug. to 13 Aug. 1999. Difference of dissolved oxygen between surface and bottom layer was maximum when the thermocline were strong. Organic distribution such as COD was affected by the growth of phytoplankton. Limitting factor was nitrogen, that is, inorganic nitrogen plays a significant role on regulating the algal growth. Surface distribution of dissolved inorganic nitrogen was very low compared to bottom layer by uptake of organisms. Maximum value of Chl-α at station C2 and C11 were observed from subsurface layer, ranges of which exceeded possibility concentration of red tide outbreak, 10 mg/㎥. On the other hand, that of C15 exist at surface layer. In this area, DIN and DIP concentrations increased by input sources such as rainfall and benthic flux before the bloom of phytoplankton. Accumulation of phytoplankton occurred at subsurface layer by the rapid uptake of DIN, especially nitrate ion, when strong thermocline existed as approach to the afternoon, which led to the increase of organics in water column and oxygen deficiency water mass at bottom layer until late at evening. Since then, DIN increases gradually as water temperature decrease to minimum. The quantitative understanding of nitrogen of fluxed to and from the various sources is necessary for environmental management.

• The Korean Journal of Pharmacology
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• v.18 no.2
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• pp.89-102
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• 1982

The $Na^+-and\;K^+-induced\;Ca^{++}$ release was measured isotopically by millipore filter technique in pig heart mitochondria. With EGTA-quenching technique, the characteristics of mitochondrial $Ca^{++}-pool$ and the sources of $Ca^{++}$ released from mitochondria by $Na^+\;or\;K^+$ were analyzed. The mitochondrial $Ca^{++}-pool$ could be distinctly divided into two components: internal and external ones which were represented either by uptake through inner membrane, or by energy independent passive binding to external surface of mitochondria, respectively. In energized mitochondria, a large portion of $Ca^{++}$was transported into internal pool with little external binding, while in de-enerigzed state, a large portion of transported $Ca^{++}$ existed in the external pool with limited amount of $Ca^{++}$ in the internal pool which was possibly transported through the $Ca^{++}-carrier$ present in the inner membrane. $Na^+$ induced the $Ca^{++}$ release from both internal pool and external pool and external binding pool of mitochondria. In contrast, $K^+$ did not affect $Ca^{++}$ of the internal pool, but, displaced $Ca^{++}$ bound to external surface of the mitochondria. When the $Ca^{++}-reuptake$ was blocked by EGTA, the $Ca^{++}$ release from the internal pool by $Na^+$ was rapid; the rate of $Ca^{++}-efflux$ appeared to be a function of $[Na^+]^2$ and about 8mM $Na^+$ was required to elicit half-maximal velocity of $Ca^{++}-efflux$. So it was revealed that $Ca^{++}-efflux$ velocity was particulary sensitive to small changes of the $Na^+$ concentration in physiological range. Energy independent $Ca^{++}-binding$ sites of mitochondrial external surface showed unique characteristics. The total number of external $Ca^{++}-binding$ sites of pig heart mitochondria was 29 nmoles per mg protein and the dissociation constant(Kd) was $34{\mu}M$. The $Ca^{++}-binding$ to the external sites seemed to be competitively inhibited by $Na^+\;and\;K^+$; the inhibition constant(Ki) were 9.7 mM and 7.1 mM respectively. Considering the intracellular ion concentrations and large proportion of $Ca^{++}$ uptake in energized mitochondria, the external $Ca^{++}-binding$ pool of the mitochondria did not seem to play a significant role on the regulation of intracellular free $Ca^{++}$ concentration. From this experiment, it was suggested that a small change of intracellular free $Na^+$ concentration might play a role on regulation of free $Ca^{++}$ concentration in cardiac cell by influencing $Ca^{++}-efflux$ from the internal pool of mitochondria.