https://pubs.kist.re.kr/handle/123456789/75357 2026-04-15T17:43:32Z https://pubs.kist.re.kr/handle/201004/138957 Title: Influence of a buried misfit dislocation network on the pyramid-to-dome transition size of Ge self-assembled quantum dots on Si(001) Authors: Kim, HJ; Chang, JY; Xie, YH Abstract: The critical sizes of the pyramid-to-dome transition of Ge self-assembled quantum dots (SAQDs) grown on relaxed SiGe buffer layers were investigated for the relationship between the misfit strain built in dots and nucleation sites. The strain field of arrays of buried dislocations in a relaxed SiGe buffer layer provided preferential nucleation sites for quantum dots. Burgers vector analysis using plan-view transmission electron microscopy verified that the preferential nucleation sites of Ge SAQDs depended on the Burgers vector direction of corresponding dislocations. The measurement of the lateral distance between SAQDs and dislocations clarified that the location of SAQDs was at the intersection of the dislocation slip plane and the top surface. The samples are fabricated to contain low dislocation densities. The average dislocation spacing is larger than the surface migration length of Ge adatoms, resulting in two groups of SAQDs, those that are located along the dislocations, and those that are not. Atomic force microscopy observations showed a distinctively larger critical size for Ge SAQDs grown over the intersection of the dislocation slip plane and the top surface than those grown in regions between dislocations. These experimental observations indicate that the critical size of the pyramid-to-dome transition is strongly dependent on misfit strain in SAQDs with lower strain being associated with a larger critical size. (C) 2002 Elsevier Science B.V. All rights reserved. 2003-01-01T00:00:00Z https://pubs.kist.re.kr/handle/201004/138956 Title: Extensive hepatic uptake of Pz-peptide, a hydrophilic proline-containing pentapeptide, into isolated hepatocytes compared with colonocytes and Caco-2 cells Authors: Shin, TH; Lee, PS; Kwon, OS; Chung, YB Abstract: The objective of the present study was to investigate the uptake process of 4-Phenylazobenzoxycarbonyl-Pro-Leu-Gly-Pro-D-Arg (Pz-peptide), a hydrophilic and collagenase-labile pentapeptide, by isolated hepatocytes. For comparison, the uptake of Pz-peptide by Caco-2 cells and colonic cells, two known paracellular routes of Pz-peptide, was also evaluated. A simple and sensitive reversed-phase HPLC assay method using UV detection has been developed. The coefficient of variation for all the criteria of validation were less than 15%. The method was, therefore, considered to be sutable for measuring the concentration of Pz-peptide in the biological cells. Pz-peptide was extensively uptaked into hepatocytes. The initial velocity of Pz-peptide uptake assessed from the initial slope of the curve was plotted as Eadie-Hofstee plots. The maximum velocity (V-max) and the Michaelis constant (K-m) were 0.190 +/- 0.020 nmol/min/10(6) cells and 12.1 +/- 3.23 muM, respectively. The permeability-surface area product (PSinflux) was calculated to be 0.0157 ml/min/10(6) cells. V-max and K-m values for Caco-2 cells were calculated to be 6.22 +/- 0.930 pmol/min/10(6) cells and 82.8 +/- 8.37 muM, respectively, being comparable with those of colonocytes (6.04 +/- 1.03 pmol/min/10(6) cells and 87.8 +/- 13.2 muM, respectively). PSinflux values for Caco-2 cells and colonocytes were calculated to be 0.0751 mul/min/10(6) cells and 0.0688 mul/min/10(6) cells, respectively. The more pronounced uptake of Pz-peptide by hepatocytes, when compared with Caco-2 cells and colonocytes, is probably due to its specific transporter. In conclusion, Pz-peptide, a paracellularly transported pentapeptide in the intestine and ocular epithelia, was uptaked into hepatocytes extensively. Although Pz-peptide is able to be uptaked into the Caco-2 cells and colonocytes, it is less pronounced when compared with hepatocytes. PSinflux values of Caco-2 cells and colonocytes for unbound Pz-peptide under linear conditions were less than 0.4% when compared with that of hepatocytes. 2003-01-01T00:00:00Z https://pubs.kist.re.kr/handle/201004/138955 Title: Shape and interband transition behavior of InAs quantum dots dependent on number of stacking cycles Authors: Kim, KM; Park, YJ; Roh, CH; Park, YM; Kim, EK; Hyon, CK; Park, JH; Kim, TW Abstract: InAs/GaAs multistacked quantum dot (QD) layers were grown by using molecular beam epitaxy with various numbers of stacking cycles to investigate the shape and the interband transition in the InAs QDs. The appearance of another photoluminescence (PL) peak on InAs/GaAs QDs with more than six stacking cycles originated from the change of the QDs from an isotropic pyramidal shape to an elongated anisotropic pyramidal shape. Dislocation lines along the [1 (1) over bar0] direction existing on. the InAs/GaAs QDs with more than six stacking cycles were attributed to the existence of excessive strain fields. Scanning transmission electron microscope and atomic force microscope images showed that the QD shape in the [1 (1) over bar0] direction was elongated without any remarkable change in the volume of the QDs. These results indicate that the shape of the InAs/GaAs QDs was strongly affected by the number of the stacking cycles and that the appearance of another PL peak is related to the change of the QD shape. 2003-01-01T00:00:00Z https://pubs.kist.re.kr/handle/201004/138954 Title: Deactivation and regeneration of titania catalyst supported on glass fiber in the photocatalytic degradation of toluene Authors: You, YS; Chung, KH; Kim, YM; Kim, JH; Seo, G Abstract: Two titania photocatalysts supported on glass fiber (GF) were prepared by using anatase-type crystalline P25 powder and dilute titanium isopropoxide solution (DTS). Chemical compositions and characteristics of the surface of the P25/GF and DTS/GF catalysts were examined with an XPS method, and their activities in the photocatalytic degradation of toluene under UV irradiation were discussed. Although a large amount of titania was stably impregnated on glass fiber on the DTS/GF catalyst, low-temperature calcination brought about insufficient oxidation of titanium atoms resulting in a heavy deposit of carbonaceous materials. Both catalysts (P25/GF and DTS/GF) were active in photocatalytic degradation, while their catalytic activity was lowered because of the accumulation of reactant and carbonaceous materials on the surface. Hydrogen peroxide completely regenerated the deactivated P25/GF catalyst by removing contaminants. However, the activity of the used DTS/GF catalyst was considerably enhanced by exposing it to hydrogen peroxide vapor to a level higher than the fresh catalyst due to the increase in the surface concentration of active oxidizing species as well as the removal of carbonaceous materials. 2003-01-01T00:00:00Z