• Journal of Microbiology and Biotechnology
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• v.19 no.11
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• pp.1301-1305
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• 2009

The evolution of living organisms occurs via a combination of highly complicated processes that involve modification of various features such as appearance, metabolism and sensing systems. To understand the evolution of life, it is necessary to understand how each biological feature has been optimized in response to new environmental conditions and interrelated with other features through evolution. To accomplish this, we constructed contents-based trees for a two-component system (TCS) and metabolic network to determine how the environmental communication mechanism and the intracellular metabolism have evolved, respectively. We then conducted a comparative analysis of the two trees using ARACNE to evaluate the evolutionary and functional relationship between TCS and metabolism. The results showed that such integrated analysis can give new insight into the study of bacterial evolution.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.8-8
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• 2011

During the last half decade, chemically modified graphene (CMG) has been studied in the wide range of applications, such as polymer composites, energy-related materials, sensors, 'paper'-like materials, field-effect transistors (FET), inks, actuators, and biomedical applications due to its excellent electrical, mechanical, and thermal properties. Chemical modification of graphene oxide, which is generated from graphite oxide, which is produced by simple oxidation of graphite, has been a promising route to achieve mass production of CMG platelets via their colloidal suspensions. Graphene oxide contains a range of reactive oxygen functional groups, which renders it a good candidate for use in the aforementioned applications (among others) through chemical functionalizations. In this presentation, I will discuss my recent research activities on the fundamental chemistry of graphite oxide, as well as novel applications based on CMGs. Topics will include the chemical structure of CMGs and colloidal suspensions of CMG platelets, as well as a wide variety of applications.

• 한국정보디스플레이학회:학술대회논문집
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• 2000.01a
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• pp.197-198
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• 2000

A surface-assisted photo-control of the liquid crystal (LC) alignment has been achieved by modifying the topmost surface of the polyimide film with photo-reactive molecules. Recently, photo-alignment technique using a thin film of poly(vinyl cinnamates) have been reported. However their commercial potentiality is limited by their low thermal stability. To enhance thermal stability, we synthesized the chalcone derivatives as the photo-reactive molecules and introduced the materials on the surface-modified polyimide film.. We identified that the photo-chemical reaction of the chalcone derivatives occur in few minutes with irradiation of UV light. The photo-alignment characteristics of the modified polyimide films treated by polarized UV light and their LC cells are investigated as a function of exposure dose.

• Bulletin of the Korean Chemical Society
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• v.23 no.8
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• pp.1057-1061
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• 2002

The Hafnia alvei aspartase activity with acetic anhydride treatment gradually increased and reached 7.5-fold that of the native one. The activity of the acetylated aspartase was a little higher than that of the native enzyme, indicating that the cooperativity between a substrate and enzyme is increased. The optimum temperature of the native asparatse was $45^{\circ}C$, and that of the acetylated enzyme shifted to $40^{\circ}C.$ The pH vs. the activity profile of the acetylated asparatse was also different from that of the native enzyme. The initial velocity pattern of the acetylated aspartase intersects to the left of the ordinate, indicating the sequential kinetic mechanism other than a rapid equilibrium ordered one. The reciprocal plots for aspartate of the native aspartase were curved, but those of the acetylated aspartase were linear, indicating the Michaelis-Menten kinetics. The helical content of the acetylated aspartase was rather decreased to $9{\textperthousand}$ than that $(63{\textperthousand})$ of the native one.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.17 no.2
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• pp.156-161
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• 2004

We investigated the effects of oxidizer additive on the performance of Cu-CMP process using commonly used tungsten slurry. In order to compare the removal rate and non-uniformity as a function of oxidizer contents, we used alumina-based tungsten slurry and copper blanket wafers deposited by DC sputtering method. According to the CMP removal rates and particle size distribution, and the microstructures of surface layer by SEM image as a function or oxidizer contents were greatly influenced by the slurry chemical composition of oxidizers. The difference in removal rate and roughness of copper surface are believed to cause by modification in the mechanical behavior of $Al_2$O$_3$abrasive particles in CMP slurry.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2006.11a
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• pp.111-114
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• 2006

This paper is to investigate the chemical composition and physical properties of cements collected at different crushing process line of ordinary portland cement to verify the possibility for producing special purpose cement based on the particle distribution technique. According to test results, six different cement samples with different blaine were gathered. loss on ignition and chemical composition of cements gathered were satisfied with KS L 5201. Cement collected at line 5 had the lowest blaine value while cement at line 4 had the highest blaine value. The coarser the cement particle is, the larger the fluidity of cement is. The compressive strength of cement was highly affected by the blaine value of cement. It is confirmed that the use of cement produced by the process of particle distribution control may be applied for special purpose cement without modification of chemical composition.

• Korean Chemical Engineering Research
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• v.46 no.1
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• pp.7-14
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• 2008

Carbon nanotubes are considered as the most ideal nano filler in the field of composites with their excellent electrical, mechanical, and thermal properties. Therefore carbon nanotubes composites are increasingly utilized in conductive materials, structural material with high strength and low weight and multifunctional material. This review article describes recent research trend of carbon nanotubes synthesis, modification, various properties of the carbon nanotubes composites and their application. Furthermore the future development direction for the commercialization of carbon nanotubes composites is proposed.

• Journal of the Semiconductor & Display Technology
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• v.18 no.3
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• pp.47-51
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• 2019

The three different polymer compounds were manufactured with the three different fire retardant (silane coated magnesium dihydroxide) contents, 180, 200, 220 phr, for making cable sheath for ship industry. In the research, ethylene-vinylacetate, polyethylene as matrix polymers and ethylene-vinylacetate grafted maleic anhydride as coupling agent were selected for compounding with fire retardant, closslinking agent, plasticizer, and other additives. In the evaluation. ΔT, Mooney viscosity, and tensile strength increased with the content of fire retardant. But it was found that too much fire retardant damaged aging resistance and cold resistance of the polymer compound.

• Bulletin of the Korean Chemical Society
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• v.34 no.1
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• pp.149-153
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• 2013

The chemical functionalization of carboxylated multi-walled carbon nanotubes (MWCNT-COOH) by creatinine (MWCNT-Amide) and latter modification with 2-aminobenzophenone for producing 1-methyl-9-phenyl-1H-imidazo[4,5-b]quinolin-2-amine (MWCNT-quino) have been investigated. All products were characterized by Fourier transform infrared spectroscopy, Raman spectroscopy, scanning electron microscope, elemental analysis, thermogravimetric analysis, derivative thermogravimetric and cellular investigations. The interesting point is that MWCNT-quino can be homogeneously dispersed in dimethylformamide and to some extent in ethyl alcohol without sonication. Also, MTT assay was used to examine the behavior of cell proliferation after 48 h of cell culture experiments. Cellular results showed high toxicity of MWCNT-quino on the cancer cells. These functionalizations have been chosen due to active sites of carbonyl and methylene groups in MWCNT-Amide and the creating quinoline derivative on the MWCNTs for future application.

• Bulletin of the Korean Chemical Society
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• v.27 no.11
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• pp.1815-1818
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• 2006

Imogolite which has chemical composition, $(HO)_3Al_2O_3SiOH$, was synthesized with orthosilicate acid and aluminium chloride at low pH solution. It has extremely large aspect ratio with an external diameter of 2nm and the length of a few micrometers. The high aspect ratio of the imogolite could make the material as the filler for the high strength fiber and as the wire for the electronic applications. Here, Imogolite that derives considerable microporosity from a nanometer-sized tubular structure has been modified with a conducting polymer, polypyrrole. Its bonding and wiring structure were confirmed by IR and TEM. The measured conductivity after modification with polypyrrole increased with polypyrrole thickness at various voltage conditions.