• Applied Chemistry for Engineering
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• v.7 no.4
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• pp.794-801
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• 1996

$TiO_2$ fine powders were synthesized via hydrolysis reaction of titanium isopropoxide in isopropanol solvent and the reaction rates were studied by use of UV spectroscopic method. The reactions were controlled to proceed to pseudo-first-order reaction in the presence of excess water in isopropanol solvent. The rate constants which varied with temperature and concentration of water were calculated by Guggenheim method. Reactions using $D_2O$ were also carried out to determine the catalytic character of water. n value of water molecules in transition state and the thermodynamic parameters showed that the reaction proceeded by $S_N2$ mechanism. $TiO_2$ powders synthesized in this reaction were almost spheric forms and had average particle size of $0.3{\mu}m$ diameter.

• Journal of the Korean Ceramic Society
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• v.41 no.1
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• pp.62-68
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• 2004

In this study, SHS process has been employed to fabricate porous $MoSi_2$ material with electric-resistive heating capability through the control of pore size. The preform for SHS reaction was consisted of molybdenum powder with different sizes and silicon powder with different contained quantity. The size of the $MoSi_2$ particles thus formed was determined by the generated heat of combustion, not by the size of molybdenum powder. However, the pore size of $MoSi_2$ composite was proportional to the particle size of molybdenum powder. that is the coarser the molybdenum powder used, the larget the formed pore size. Based on these results, the porous $MoSi_2$ composite could be fabricated with a desired pore size. By orienting the porous molybdenum disilicide-based material in the form of pore size gradient, porous materials used for filters with improved dirt-holding capacity can be manufactured.

• Journal of the Korean Ceramic Society
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• v.34 no.10
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• pp.1083-1091
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• 1997

As one of the chemical powder fabrication methods, the powder preparation method by using oxalate has the following advantages; (1) easy to control the chemical stoichiometry, (2) easy to fabricate homogeneous and fine particles, and (3) easy to be thermaly decomposed at low temperature. In the present study, the initial morphology and size distribution of the powder were controlled and the homogeniaty was improved. By carefully controlling the pH with NH4OH, the Bi(Pb)-Sr-Ca-Cu-O superconducting powders were prepared and investigated for their properties. The microstructures and the superconducting properties of the pelletized samples were investigated. Also, the microstructures and electrical properties of the samples prepared by tape casting method were investigated. The fabricated powders were spherical with less than 400 nm, but most of them were agglomerated to be 1~3 ${\mu}{\textrm}{m}$ in size. The critical temperature of the pelletized sample annealed at 84$0^{\circ}C$ for 72 hours in air was 110K. And the critical currents of annealed samples in air prepared by tape casting process for 24 hours and 72 hours were 0.6 A (Jc=600A/$\textrm{cm}^2$) and 1.9A (Jc=1, 900A/$\textrm{cm}^2$) respectively.

• Polymer(Korea)
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• v.30 no.2
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• pp.162-167
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• 2006

Polyamic acid (PAA) was prepared from cyclobutane-1,2,3,4-tetracarboxylic dianhydride (CBDA) and 4,4'-fiaminodiphenyl ether (DDE). In order to impart a photosensitivity to the PAA, diazonaphthoquinone (DNQ) derivative (DI) was added. However, the addition of the DI was not enough to inhibit the dissolution of the PAA for a aqueous alkal solution. Therefore, we had synthesized poly(amic acid ester)s by an adding 1,2-epoxy-3-phenoxypropane to the PAA. That is, an acidity of the PAA could be controlled by an esterification reaction of 1,2-epoxy-3-phenoxypropane with the PAA. Significant difference of a dissolution rate of the poly(amic acid ester) between an o(posed and unexposed area was observed at an acid content of 60% and less. Resolution of the positively patterned film showed about $25{\mu}m$ at the exposure dose of $200mJ/cm^2$.

• The Journal of Korean Medicine Ophthalmology and Otolaryngology and Dermatology
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• v.16 no.3
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• pp.129-144
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• 2003

Recently many efforts were focused to understand the mechanical insights of melanogenesis to develop the agents for hyper-pigmentation and hypo-pigmentation. In the melanin biosynthetic pathway, tyrosinase is the rate limiting enzyme, and ${\alpha}$-melanocyte stimulating hormone(MSH) or cAMP-elevating agents stimulate melanogenesis and enhance the melanin synthesis and the tyrosinase activity. The author has analyzed the effects of Rhizoma Bletillae on the basal melanogenic activities of B16／F10 mouse melanoma cells, and on the ${\alpha}$-MSH or forskolin-induced melanogenesis. Rhizoma Bletillae alone markedly suppressed melanin content and tyrosinase activity in a dose-dependent manner. Pretreatment of the cells with Rhizoma Bletillae also suppressed the increase of ${\alpha}$-MSH (100 nM) or forskolin (20 ${\mu}M$)-induced melanin content and tyrosinase activity. The decrease in the tyrosinase activity was paralled by a decrease in the abundance of tyrosinase protein and tyrosinase promoter activity. Pretreatment of the cells with Rhizoma Bletillae also inhibited the increase of forskolin(20${\mu}M$) induced the amount of tyrosinase protein and tyrosinase promoter activity. The results of DOPA staining revealed that pretreatment of the cells with Rhizoma Bletillae showed less intensity than B16 melanoma cells stimulated with ${\alpha}$-MSH or forskolin. These results suggest that Rhizoma Bletillae inhibits melanogenesis and abrogates ${\alpha}$-MSH and cAMP-induced melanogenesis in B16 melanoma cells.

• Journal of Sasang Constitutional Medicine
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• v.22 no.4
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• pp.77-84
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• 2010

1. Objectives Yanggyuksanhwa-tang for Soyangin was applied to investigate the immunological activities on antigen (Ag)-specific or Ag-non-specific immune responses on murine macrophage cell line (RAW 264.7) and ovalbumin/aluminium (OVA/Alum)-immunized mice. 2. Methods This study were carried out in nitric oxide (NO) synthesis on RAW 264.7 cells and cellular proliferation on mouse splenocytes. C57BL/6 mice were immunized intraperitonially with OVA/Alum (100 ${\mu}g$/200 ${\mu}g$) on day 1, 8, and 15. Yanggyuksanhwa-tang was administrated to mice orally for 3 weeks from day 1. On day 22, OVA-, lipopolysaccharide (LPS)-, and concanavalin A (Con A)-stimulated splenocyte proliferation and antibodies (OVA-specific antibodies of the IgG, IgG1, and total IgM classes) in plasma were measured. 3. Results Yanggyuksanhwa-tang significantly enhanced cellular proliferation by LPS and Con A on splenocytes from OVA/Alum-immunized mice (p<.001). Yanggyuksanhwa-tang also significantly enhanced plasma OVA-specific IgG (p<.001), IgG1 (p<.001), and total IgM (p<.01) levels compared with the OVA/Alum group. 4. Conclusions These results suggested that Yanggyuksanhwa-tang for Soyangin could be used as immunopotent.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.24 no.3
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• pp.51-58
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• 1998

Generally pigment differs from dye stuff because it cannot be melted in water but also because it is stable physically and chemically. In this study you will discover the function, properties and effects of Micai-TiO$_2$-SiO$_2$pigment as abase material pigment. But until now used Mica of the base material is about 7-l5${\mu}{\textrm}{m}$ with an average diameters of 15${\mu}{\textrm}{m}$. A new characteristic superficial pigment was obtained from covering the TiO$_2$ and SiO$_2$ with the adsorption result of isoelectric point of a Mica flake, TiO$_2$ and SiO$_2$In the composition reaction study of adsorption was done as well as the physical characteristics of the superficial texture of the obtained material. L,a,b of color change as oil was absorbed, optical nature and change of reflection according to direct and diffused reflection. In the composition of Mica slurry the best result obtained was in a solution with pH 2.0 to 2.3. Following this result, we can come to the idea that electrical attraction was done during the change of electrical charge of the Mica and TiO$_2$ deposit. Also this pigment shows a big scale between the direct reflection and diffused reflection light. Using this characteristic in cosmetic, it was obtained a natural but a contrast between light and shadow making possible a sculptured make-up. Color change due to oil adsorption was insignificant which improved the last of make up.

• Archives of Pharmacal Research
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• v.27 no.5
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• pp.512-517
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• 2004

The structural relationship of 16 asiatic acid (AA) derivatives, including AA and asiaticoside (AS) to cytotoxicity and anti-hepatofibrotic activity in HSC-T6 cells, were investigated. Cytotoxicities of AA derivatives varied from 5.5 $\mu$M to over 2000 $\mu$M of $IC_{50}$/ depending on AA functional group modifications. Substituting the hydroxyl group at the C(2) to N≡C and substituting bulky groups for dihydroxyl groups at (3), (23) of the A-ring increased the cytotoxicity, but keto group at C(11) and benzoyl ester at C(2) were greatly reduced it. Modification of the carboxylic acid group at C28 also reduced the cytotoxicity. The collagen synthesis determined by hydroxyproline content in the cells was inhibited from a maximum of 48% (Zlx-i-85 and 87) to 15% (AS) by AA derivatives. The anti-hepatofibrotic effect of these compounds might be due to the reduced expression of prolyl 4-hydroxylase $\alpha$ and $\beta$ subunits and TIMP2. However, the inhibition of collagen by asiaticoside derivatives did not show any structural-activity relationship.

• Journal of the Korean Chemical Society
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• v.35 no.3
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• pp.275-279
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• 1991

Ultra-fine alumina, ${\alpha}-Al_2O_3$, with ${\phi}$ = 0.1∼0.5 ${\mu}$m was obtained from pure ammonium aluminum sulfate(alum) as the thermal decomposition product. Pure alum(> 99.7%) could be prepared by the precepitation and the successive recrystallization in an acidic aqueous solution at pH = 1.5∼2.5, which was theoretically predicted by only considering the concentrations of hydroxide and carbonate for aluminum and sodium in the solution, and also experimentally confirmed as the optimum precepitation condition for alum without forming any impurities like aluminum hydroxide or sodium one.

• Bulletin of the Korean Chemical Society
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• v.34 no.10
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• pp.3017-3021
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• 2013

Coumaroyl dipeptide amide, Coumaric acid-LG-$NH_2$, was prepared successfully using the solid-phase method, and its efficacy as a skin whitening agent was studied. Coumaric acid-LG-$NH_2$ was prepared with Rink-amide resin, and 96.354% of purity was obtained. Using MTT assay and LDH release assay, we found that it exhibited very low cytotoxicity. And, we found that Coumaric acid-LG-$NH_2$ inhibited tyrosinase activity dose-dependently and showed superior tyrosinase inhibitory activity to well-known whitening agent, arbutin. $IC_{50}$ value of Coumaric acid-LG-$NH_2$ was 182.4 ${\mu}M$, and $IC_{50}$ value of arbutin was 384.6 ${\mu}M$. Also, in measurement of melanin contents using B16F1 melanoma cell lines, Coumaric acid-LG-$NH_2$ reduced melanin production induced by ${\alpha}$-MSH statistically significant, and showed superior melanin inhibitory activity to p-coumaric acid or arbutin. In addition, Coumaric acid-LG-$NH_2$ reduced MC1R mRNA expression level. Thus, we concluded that MC1R pathway is the significant pathway of Coumaric acid-LG-$NH_2$, and Coumaric acid-LG-$NH_2$ has great potential to be used as novel whitening agents.