• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 한국전기전자재료학회 2003년도 제5회 영호남 학술대회 논문집
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• pp.93-93
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• 2003

Photoluminescence(PL) properties of Silicon nanocrystals (nc-Si) as a function of temperature is reported to consider the mechanism of PL. Nc-Si has been made by $Si^+$ ion-implantation into thermal $SiO_2$ and subsequent annealing. And after gold had been diffused at the same samples above, the resultant PL spectra has been compared to the PL spectra from the non-gold doped nc-Si. PL peak energy variation from nc-Si is same with the variation of energy bandgap of bulk silicon as temperature changes from 6 K to room temperature. This result may mean nc-Si is still indirect transition material like bulk silicon. Gold doped nc-Si reveals short peak wavelength of PL spectrum than gold undoped one. PL peak shift through gold doing process shows clearly the PL mechanism is not from defect or interface states. PL intensity increases from 6K to a certain temperature and then decrease to room temperature. This characteristic with temperature shows that phonon have a role for the luminescence as theory explains that electron and hole can be recombined radiatively by phonon's assist in nc-Si, which is almost impossible in bulk silicon. Therefore luminescence is observed in nc-Si constructed less than a few of unit cell and the peak energy of luminescence can be higher than the bulk bandgap energy by the bandgap widening effect occurs in nanostructure.

• Journal of architectural history
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• 제17권6호
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• pp.87-98
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• 2008

The purpose of this study is ultimately subjected to the Orientalism, even though this deals with some positive effects in the realm of art and architecture as the scope of study, because through which the relationship between two different cultures will be discussed. That is to say, this research focused not only on how the presentation of 'avant-garde' visual art, which is explained as formal 'purity' and 'abstraction' as the characteristics of modern arts, could be made in the transition to the 20th's World, but also on what is the role and meaning of Eastern thoughts, which is popular in that time, for the new philosophical background of the artistic revolution. As a result, this study found that a lot of 'avant-garde' architects such as F. L. Wright, M. Mahony in Prairie School and L. Sullivan, D. Burnham, J. Root in Chicago School, and Lauweriks, H. P. Berlage who introduced Wright's works into the Europe, had possessed the 'Universal Philosophy' including Unitarianism, Transcendentalism, Deism, and Theosophy which are all influenced by Oriental religions and thoughts through historic western philosophers, although it is generally well-known that W. Kandinsky and P. Mondrian were belong to that. Furthermore, they gave attention to the Oriental religions and thoughts in that time, eventually made a historical progressive process of unification of thoughts between East and West. In a word, the new universalism was the philosophical background that made the artist's idea and presentation on 'from Being into Becoming'.

• Bulletin of the Korean Chemical Society
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• 제35권1호
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• pp.177-181
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• 2014

Pseudo-first-order rate constants ($k_{obsd}$) have been measured spectrophotometrically for the reactions of Y-substituted-phenyl benzoates (5a-j) with potassium ethoxide (EtOK) in anhydrous ethanol at $25.0{\pm}0.1^{\circ}C$. The plots of $k_{obsd}$ vs. [EtOK] curve upward regardless of the electronic nature of the substituent Y in the leaving group. Dissection of $k_{obsd}$ into the second-order rate constants for the reactions with the dissociated $EtO^-$ and ion-paired EtOK (i.e., $k_{EtO^-}$ and $k_{EtOK}$, respectively) has revealed that the ion-paired EtOK is more reactive than the dissociated $EtO^-$. The Br${\phi}$nsted-type plots for the reactions with the dissociated $EtO^-$ and ion-paired EtOK exhibit highly scattered points with ${\beta}_{lg}$ = -$0.5{\pm}0.1$. The Hammett plots correlated with ${\sigma}^o$ constants result in excellent linear correlations, indicating that no negative charge develops on the O atom of the leaving Y-substituted-phenoxide ion in transition state. Thus, it has been concluded that the reactions with the dissociated $EtO^-$ and ion-paired EtOK proceed through a stepwise mechanism, in which departure of the leaving group occurs after the RDS, and that $K^+$ ion catalyzes the reactions by increasing the electrophilicity of the reaction center through a four-membered cyclic TS structure.

• Bulletin of the Korean Chemical Society
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• 제28권8호
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• pp.1265-1272
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• 2007

A solid acid catalyst, NiSO4/CeO2-ZrO2 was prepared simply by promoting ZrO2 with CeO2 and supporting nickel sulfate on CeO2-ZrO2. The support of NiSO4 on ZrO2 shifted the phase transition of ZrO2 from amorphous to tetragonal to higher temperatures because of the interaction between NiSO4 and ZrO2. The surface area of 10-NiSO4/1-CeO2-ZrO2 promoted with CeO2 and calcined at 600 oC was very high (83 m2/g) compared to that of unpromoted 10-NiSO4/ZrO2 (45 m2/g). This high surface area of 10-NiSO4/1-CeO2-ZrO2 was due to the promoting effect of CeO2 which makes zirconia a stable tetragonal phase as confirmed by XRD. The role of CeO2 was to form a thermally stable solid solution with zirconia and consequently to give high surface area and acidity of the sample, and high thermal stability of the surface sulfate species. 10-NiSO4/1- CeO2-ZrO2 containing 1 mol% CeO2 and 10 wt% NiSO4, and calcined at 600 oC exhibited maximum catalytic activities for both reactions, 2-propanol dehydration and cumene dealkylation.

• Korean Journal of Materials Research
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• 제8권6호
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• pp.484-492
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• 1998

The formation mechanism of the epitaxial cobalt silicide from Co/Ti/OOO) Si structure has been investigated. The transition temperature of CoSi to CoSi, was found to increase with increasing the Ti interlayer thickness, which may be owing to the occupation of the tetrahedral sites by Ti atoms in the CoSi crystal structure as well as the blocking effect of the Ti interlayer on the diffusion of Co. Also, the Co- Ti-O ternary compound formed at the metal! Si interface at the begining of silicidation, which seems to play an important role in epitaxial growth of Co silicide. The final layer structures obtained after a rapid thermal annealing of the Cot Ti/( 100) Si bi-layer structure turned out to be Ti oxide/Co- Ti-Si/epi-$CoSi_2$/OOO)

• Journal of Microbiology
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• 제45권5호
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• pp.418-421
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• 2007

The nucleotide at position 791(G791) of E. coli 16S rRNA was previously identified as an invariant residue for ribosomal function. In order to characterize the functional role of G791, base substitutions were introduced at this position, and mutant ribosomes were analyzed with regard to their protein synthesis ability, via the use of a specialized ribosome system. These ribosomal RNA mutations attenuated the ability of ribosomes to conduct protein synthesis by more than 65%. A transition mutation (G to A) exerted a moderate effect on ribosomal function, whereas a transversion mutation (G to C or U) resulted in a loss of protein synthesis ability of more than 90%. The sucrose gradient profiles of ribosomes and primer extension analysis showed that the loss of protein-synthesis ability of mutant ribosomes harboring a base substitution from G to U at position 791 stems partially from its inability to form 70S ribosomes. These findings show the involvement of the nucleotide at position 791 in the association of ribosomal subunits and protein synthesis steps after 70S formation, as well as the possibility of using 16S rRNA mutated at position 791 for the selection of second-site revertants in order to identify ligands that interact with G791 in protein synthesis.

• Journal of Microbiology and Biotechnology
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• 제23권7호
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• pp.1031-1040
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• 2013

Candida albicans is a dimorphic fungus that commensally colonizes human mucosal surfaces. The aim of this study was to assess the role of different C. albicans morphologies in inducing pattern recognition receptors (PRRs) and cytokines in macrophages. Macrophages may respond to pathogen-associated molecular patterns via TLR2 and TLR4 by expressing cytokines. The hyphal transition of C. albicans was induced by 20% serum (S), RPMI-1640 (R), or $39^{\circ}C$ culture (H). Macrophages were then challenged with either yeast (Y) or different hyphae cultures of C. albicans, followed by RT-PCR and FACS analysis of PRRs expression. In addition, macrophages were stimulated with either yeast or different hyphae cultures of C. albicans used by RT-PCR and Bio-Plex analysis of cytokines production. Macrophages expressed high levels of TLR4 and dectin-1 after stimulation with Y cells. In contrast, stimulation with H or R cells strongly increased the expression of TLR2 and dectin-2. Stimulation with Y cells significantly enhanced the expression of IL-$1{\beta}$ and weakly increased the expression of IL-6 and IL-12. Stimulation with hyphal cells (S, R, and H) strongly increased IL-10 expression, but weakly reduced IL-$1{\beta}$ expression. The phagocytosis activity and NO production of macrophages were decreased upon treatment with hyphal cells compared with yeast, and depended on the length of hyphae. In summary, the yeast and hyphae forms of C. albicans resulted in an induction of different PRRs, with accompanying differences in immune cell cytokine profiles.

• Journal of Haehwa Medicine
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• 제14권1호
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• pp.201-211
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• 2005

Cdc2 kinase is a prototypical cyclin-dependent kinase critical for G2 to M phase cell cycle transition. Yet, its function in the nervous system is largely unknown. Here, we investigated possible role of Cdc2 in axonal regeneration using sciatic nerve system in rat. Cdc2 protein levels and activity were increased in the injured sciatic nerves 3 and 7 days after crush injury and then decreased to basal level 14 days later. Administration of Cdc2 kinase inhibitor roscovitine in vivo at the time of crush injury significantly inhibited axonal regeneration when regrowing axons were analyzed using retrograde tracers. Cdc2 protein levels in cultured Schwann cells which were prepared from sciatic nerves 7 days after crush injury were much higher compared with those from uninjured sciatic nerves, suggesting that Cdc2 protein expression was primarily induced in the Schwann cells. To further investigate Cdc2 function in Schwann cell, we examined changes in cultured Schwann cell proliferation and migration in culture system. Both the number of proliferating Schwann cells and the extent of neurite outgrowth from co-cultured DRG neurons were significantly decreased by Cdc2 inhibitor roscovitine treatment in DRG culture which was prepared from animals with sciatic nerve injury for 7 days. Also, Schwann cell migration in the injured sciatic nerve explant was significantly inhibited by roscovitine treatment. Taken together, the present data suggest that Cdc2 may be involved in peripheral nerve regeneration via Schwann cell proliferation and migration.

• Bulletin of the Korean Chemical Society
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• 제27권12호
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• pp.1989-1996
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• 2006

The $NiSO_4/CeO_2-ZrO_2 $catalysts containing different nickel sulfate and $CeO_2$ contents were prepared by the impregnation method, where support, $CeO_2-ZrO_2$was prepared by the coprecipitation method using a mixed aqueous solution of zirconium oxychloride and cerium nitrate solution followed by adding an aqueous ammonia solution. No diffraction line of nickel sulfate was observed up to 20 wt %, indicating good dispersion of nickel sulfate on the surface of $CeO_2-ZrO_2$. The addition of nickel sulfate (or $CeO_2$) to $ZrO_2$ shifted the phase transition of $ZrO_2$ from amorphous to tetragonal to higher temperatures because of the interaction between nickel sulfate (or $CeO_2$) and $ZrO_2$. A catalyst (10-$NiSO_4/1-CeO_2-ZrO_2$) containing 10 wt % $NiSO_4$ and 1 mole % $CeO_2$, and calcined at $600{^{\circ}C}$ exhibited a maximum catalytic activity for ethylene dimerization. The catalytic activities were correlated with the acidity of catalysts measured by the ammonia chemisorption method. The role of $CeO_2$was to form a thermally stable solid solution with zirconia and consequently to give high surface area, thermal stability and acidity of the sample.

• Journal of IKEEE
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• 제15권4호
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• pp.299-304
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• 2011

In this paper, the circular polarized horn antenna composed of circular polarizer and impedance transformer is designed, and fabricated. For the circular polarizer, two types of the polarizer are designed and the electrical performance of them is compared; rectangular waveguide polarizer with $45^{\circ}$-inclined dielectric slab and oval shaped one. Straight type mode converter has a stepped impedance structure and plays a role of converting waveguide TE mode into coaxial TEM mode, and the proposed antenna is designed to directly connect with active components using the feed-through in the input port of the mode converter. Fabricated antenna has the wideband performance, VSWR<1.5 and Axial ratio < 1.0dB, ranging from 30.085 to 30.885 GHz, and the antenna gain is 6.7~7.0 dBi.