• Journal of the Korean Chemical Society
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• v.64 no.1
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• pp.30-37
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• 2020

The purpose of this study was to identify the problems faced by students in sub-microscopic representation of acid-base reactions. Herein, we selected 30 students of 12^th grade science classes, who had studied various acid-base models. In order to investigate the sub-microscopic representation ability of the students, we developed nine items related to various contexts, such as one type of solute and solvent, two types of solutes and solvent, cases with water as solvent or with nonaqueous solvents. For all items, we consistently observed lack of concept of chemical change. In context of aqueous and nonaqueous solutions, the frequency of lack of concept of chemical bonding was high if ammonia was the solute or solvent. Moreover, the frequency of lack of concept related to the degree of electrolytic dissociation was high. Therefore, chemistry teachers should understand that students' ability to sub-microscopic representation of acid-base reactions can be enhanced by analyzing the difficulties faced by the students in solving diverse acid-base problems.

• Bulletin of the Korean Chemical Society
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• v.24 no.8
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• pp.1207-1210
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• 2003

The effect of solvent structure on the slope in the plot of ln K vs. solute carbon number was examined. It was found that the free energy of methylene group transfer from the gas phase into a solvent was always negative and that the absolute magnitude of interaction free energy between the methylene group and the solvent was always larger than the absolute magnitude of cavity formation free energy of the methylene group in the solvent. Thus, the slope in the plot of ln K vs. solute carbon number was always positive and its value decreases with increase of solvent polarity since the cavity formation energy of the CH₂ unit increases with increase of solvent polarity while the dispersive interaction energy of the CH₂ unit is virtually invariant. We also examined the effect of sequential addition of CH₂ unit to a solvent molecule upon ln K for three homologous series of solvents: n-alkanes, n-alcohols, and n-nitriles. Characteristic trends in the plots of ln K vs. solvent carbon number were observed for individual solvent groups. A decrease of ln K with solvent carbon number was observed for n-alkanes. An abrupt increase in ln K followed by levelling off was observed for n-alcohols while a final slight decrease in ln K after an abrupt increase followed by rapid levelling off was noted for n-nitriles. All of theses phenomena were found related to variation in cavity formation energy. It was clearly shown that a structural change of a polar solvent by sequential addition of CH₂ units causes an abrupt polarity decrease initially, then gradual levelling off, and finally, conversion to a virtually nonpolar solvent if enough CH₂ units are added.

• Journal of the Korean Chemical Society
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• v.45 no.1
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• pp.83-89
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• 2001

This study was to examine middle school students' understanding of dissolution. More than 75% students understood that dissolution was caused by small particles' filling the space between large particles due to the difference of size among particles. Some other students responded that solute disappeared or was absorbed in a solvent as the result of dissolution. Besides, they didn't know that space between particles was the reason of the volume's decreasing after the process of dissolution. Instead, they explained that space between particles caused dissolution. And they hardly understood the fact that solutes affect solubility. Students'misunderstanding about the concept of dissolution resulted from the lack of the explanation on the right concept of dissolution in science textbooks and the inappropriate use of the dissolution model by teachers. In conclusion, we need the appropriate explanation in middle school science textbooks that consider the students'level and the development of the appropriate model that demonstrates dissolution in the perspective of particles.

• KSBB Journal
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• v.21 no.5
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• pp.371-375
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• 2006

Frontal analysis(FA) and Pulsed input method(PIM) have been frequently utilized to measure isotherm of single solute, as well as non-competitive isotherms of two solutes in chromatography(1). FA and PIM were used in this study as complementary methods to measure adsorption isotherms of loxoprofen racemate in HPLC. Prior to FA and PIM experiments, measurements of loxoprofen solubility were made at hexane/ethanol=50/50, 80/20, 95/5(v/v) with acetic acid(0.5%) for adjusting pH. The last composition(95/5) of hexane/ethanol allows us to separate loxoprofen racemate into two forms(retentate, extract). PIM and FA were used to determine the isotherms of re-and ex-loxoprofen.

• Journal of Animal Reproduction and Biotechnology
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• v.34 no.3
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• pp.190-196
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• 2019

Tight junctions are constituents of the blood-epididymis barrier that play roles in regulating the unidirectional transcellular transport of ions, water, and solutes to maintain optimal conditions for sperm maturation and storage. Claudin 1 (Cldn1) and 4 (Cldn4) are known as tight junction proteins and are expressed in the basolateral membranes as well as tight junctions in the epididymis of rodents. Here, we examined the expression and localization of Cldn1 and 4 to determine the function of these proteins in the pig epididymis. Cldn1 was highly expressed in the basolateral membrane of epithelial cells in the caput and corpus regions of the epididymis. In the cauda region, however, Cldn1 labeling was significantly decreased in the basolateral membrane of epithelial cells. In contrast, labeling indicated that Cldn4 was expressed in the basolateral membrane in the cauda region of the epididymis and was present at punctate reactive sites in the caput and corpus regions. However, in no region of the epididymis did we detect colocalization of Cldn1 and 4 with labeled ZO-1, the distribution of which is restricted to the tight junctions. Our results indicate that Cldn1 and 4 were region-specifically expressed in the pig epididymis but not present in the tight junctions of epididymal epithelium. In addition, reciprocal regulation in specific regions of the epididymis between Cldn1 and 4 may play an important role in generating an optimal luminal environment for sperm maturation and storage in the pig epididymis.

• Journal of the Korean Society for Nondestructive Testing
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• v.20 no.3
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• pp.231-237
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• 2000

The commercial cermet cutting tools consist of multi-carbide and a binder metal of iron group, such as cobalt and nickel which are ferromagnetic. In this paper, a new approach to evaluate the mechanical properties of TiCN based cermet by magnetic properties were studied in relation to binder content and sintering conditions. The experimental cermet was prepared using commercial composition with the other binder contents by PM process. It was found that the magnetic properties of the sintered cermets remarkably depended on the microstructure and the total carbon content. The magnetic saturation was proportional to increment of coercive force. At high carbon content in sintered cermet, the magnetic saturation was increased by decreasing the concentration of solutes such as W, Mo, Ti in Co-Ni binder. As the coercive force increases, the hardness usually increases. The strength and toughness of the cermet also increased with increasing the magnetic saturation. The measurement of magnetic properties made it possible to evaluate the mechanical properties in the cermet cutting tools.

• Journal of Korean Society of Water and Wastewater
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• v.28 no.2
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• pp.235-248
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• 2014

The widespread occurrence of dissolved endocrine disrupting compounds(EDCs) and pharmaceutical active compounds(PhACs) in water sources is of concern due to their adverse effects. To remove these chemicals, adsorption of EDCs/PhACs on granular activated carbon(GAC) was investigated, and bisphenol A, carbamazepine, diclofenac, ibuprofen, and sulfamethoxazole were selected as commonly occurring EDCs/PhACs in the aquatic environment. Various adsorption isotherms were applied to evaluate compatability with each adsorption in the condition of single-solute. Removal difference between individual and competitive adsorption were investigated from the physicochemical properties of each adsorbate. Hydrophobicity interaction was the main adsorption mechanism in the single-solute adsorption with order of maximum adsorption capacity as bisphenol A > carbamazepine > sulfamethoxazole > diclofenac > ibuprofen, while both hydrophobicity and molecular size play significant roles in competitive adsorption. Adsorption kinetic was also controled by hydrophobicity of each adsorbate resulting in higher hydrophobicity allowed faster adsorption on available adsorption site on GAC. EDCs/PhACs adsorption on GAC was determined as an endothermic reaction resulting in better adsorption at higher temperature ($40^{\circ}C$) than lower temperature ($10^{\circ}C$).

• Journal of Ecology and Environment
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• v.35 no.4
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• pp.351-358
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• 2012

To investigate the environmental adaptation and ecophysiological characteristics of Suaeda maritima and S. asparagoides under saline conditions, plant growth and density were analyzed according to environmental changes of habitats. The total ion content of soil decreased with time, which was caused by the predominance of exchangeable $Na^+$ and $Cl^-$ in the upper layers. The population of S. maritima was more densely distributed in the region with higher ion contents of $Cl^-$, $Mg^{2+}$, $K^+$ and $Na^+$ than the population of S. asparagoides. Both species were showed a decreased population density according to increases in plant growth. Under the conditions of a salt field, S. maritima and S. asparagoides contained high inorganic ions to maintain low water potential, but low water soluble carbohydrate contents. In the case of free amino acid, S. maritima showed an especially high proline content, and contained rather large amounts of free amino acids, whereas S. asparagoides did not. Both species showed high inorganic ion contents in the leaves, which might be a mechanism of avoiding the ionic toxicity by diluting the accumulated ionic concentration with a high ratio of water content to dry weight. This result suggests that S. maritima seems to adapt to saline conditions by accumulating proline in addition to inorganic ions. S. asparagoides seems to adapt by osmoregulation processes, using inorganic ions rather than free amino acids.

• Journal of Nutrition and Health
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• v.29 no.10
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• pp.1059-1071
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• 1996

This study was performed to investigate the effect of dietary protein level on renal senescence. Male rats of 337.8$\pm$5.7g body weight were underlateral nephrectomy or shamoperation. The rats were divided into high protein(40% casein), normal protein(15% casein) and low protein(8% casein)diets and fed experimental diets ad libitum for 24 weeks. The results are summarized as follows. There was a hypertophy of the remnant kidney of uninephrectomized rats of 40% or 15% protein group, coming up to the comparable weights of both kidneys of sham-operated rats. However, the hypertrophic effect was not seen in uninephrectomized rats of 8% protein group. Serum albumin was lower in uninephrectomized rats. With increasing dietary protein level blood urea nitrogen was increased, whereas, urinary urea nitrogen excretion was decreased. Urinary solute excretion was higher in uninephrectomized group than in sham-operated group. However, effect of dietary protein level on urinary solute excretion varied dpending on th solutes tested. GFR and urinary protein excretion, throughout experiment, increased with feeding period and with dietary protein level. Proteinuria was most severe in uninephrectomized rats fed 40% casein diet. Maximum urine concentration ability measured after dehydration was not different among the experimental groups. Light microscopic examination showed focal segmental glomerulosclerosis and mild increas of glomerular mesangial matrix in uninephrectomized rats fed 40% and 15% protein diet, however, which was not observed in uninephrectomized rats fed 8% protein diet and in sham-operated rats fed 40% diet. Immunofluorescence studies revealed segmental deposits of albumin in the mesangium and capillary loops in high protein and uninephrectomized groups. Minimal granular deposition of IgG was noted in the mesangium of all experimental groups. In conclusion, high protein intake accelerated deterioration of renal function and it was correlated with morphological change. Low protein intake was effective in preventing these changes.

• Journal of Plant Biotechnology
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• v.7 no.2
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• pp.87-95
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• 2005

The tomato ripening associated membrane protein (TRAMP) (Fray et al., 1994) is a member of the major intrinsic protein (MIP) family, defined as channels facilitating the passage of water and small solutes through membranes. During normal fruit ripening the TRAMP mRNA levels were increased whereas the expression levels of TRAMP in low ethylene ACO1-sense suppressed lines, Nr and rin fruits, were lower than at the breaker stage of wild type fruit. TRAMP mRNA is inhibited by $LaCl_3$, which is an inhibitor of $Ca^{2+}$-stimulated responses, treatment but drought condition did not affect TRAMP expression. The levels of TRAMP mRNA transcripts were substantially higher in the dark treated seedlings and fruits. These suggest that TRAMP function as a water channel may be doubted because of several reasons; no water content was changed during ripening in wild type, antisense and overexpression lines, TRAMP expression under light condition was lower than dark condition and TRAMP expression was not changed in drought condition. Co-suppression plant, 3588 was one of sense suppression lines, which contain CaMV 35S promoter and sense pNY507 cDNA, produced small antisense RNA, approximately 21-25 nucleotides in length, mediated post-transcriptional gene silencing. Therefore, TRAMP expression was inhibited by small antisense and multiple copies might induce gene silencing without any production of double strand RNA. Total seven selected volatile productions, isobutylthiazole, 6-methyl-5-hepten-2-one, hexanal, hexenal methylbutanal, hexenol, and methylbutanol, were highly reduced in sense line whereas total volatile production was increased in TRAMP antisense line. These results suggested TRAMP might change volatile related compounds.