• Journal of the Korean Ceramic Society
• /
• v.38 no.5
• /
• pp.412-417
• /
• 2001

본 연구는 습식법으로 수산화 알루미늄과 티타니아를 출발물질로 하여 $Al_2$O$_3$-TiO$_2$복합분체를 제조하였으며, 2 mol의 Al(OH)$_3$분말에 대하여 TiO$_2$분말량을 1, 3, 5, 7, 9, 11 wt%로 첨가하여 $Al_2$O$_3$-TiO$_2$복합분체의 특성을 조사하였다. 제조된 $Al_2$O$_3$-TiO$_2$계 복합분체는 $700^{\circ}C$~140$0^{\circ}C$까지 하소하여 XRD 분석을 한 결과 100$0^{\circ}C$까지는 TiO$_2$(rutile)상과 η-Al$_2$O$_3$상이 공존하다가 110$0^{\circ}C$부터 130$0^{\circ}C$까지는 η-Al$_2$O$_3$에서 $\alpha$-Al$_2$O$_3$로의 상전이가 일어나서 $\alpha$-Al$_2$O$_3$상과 TiO$_2$(rutile)상이 나타났으며 하소온도 140$0^{\circ}C$, TiO$_2$첨가량이 5 wt%일 때부터 $Al_2$TiO$_{5}$가 생성되기 시작하였다. TiO$_2$첨가량에 따른 비표면적값은 첨가량이 7 wt%까지는 감소하였으나 그 이상 첨가시 증가하였다. 입도분석 결과 평균입경은 15.74~23.21$mu extrm{m}$로서 TiO$_2$첨가량이 3 wt%일 때 가장 작은 값을 가졌으며 TiO$_2$첨가량은 5 wt% 이상부터 점차 감소하였다.

• Proceedings of the SCSK Conference
• /
• 2003.09b
• /
• pp.32-43
• /
• 2003

UV irradiation on a skin brings about the qualitative and quantitative alterations of the extracellular matrix. Repeated-UV irradiation suppressed the synthesis of collagen and activated the expression of the matrix metalloprotease (MMP). In this paper, on the purpose of development of novel anti-aging agents from natural sources, effects of several natural products on in vitro MMP-1 activity and UVA induced MMP-1 synthesis in human dermal fibroblast (HDF) culture were studied. We measured MMP-1 activities by fluorescence assay using gelatin as substrates. As a result, the extract of Dicentra spectabilis, and flower buds of Tussilago farfara showed strong inhibitory effect. Among them, the extract of flower buds of Tussilago fartara and Dicentra spectabilis inhibited MMP-1 activity by 92% and 87% at 0.05% (w/v). And UVA induced MMP-1 expression were analyzed by enzyme-linked immunosorbent assay (ELISA) and gelatin-based zymography in HDF culture. The extract of flower buds of Tussilago farfara and Dicentra spectabilis suppressed the UVA induced expression of MMP-1 by similar level of Vitamin C 200$\mu$M at 0.1% (w/v). These results suggest that the extract of Dicentra spectabilis, and flower buds of Tussilago farfara effectively prevent skin from the UV-induced photoaging. So the extracts are thought to have potential as effective raw materials for anti-aging cosmetics.

• Archives of Pharmacal Research
• /
• v.26 no.6
• /
• pp.471-477
• /
• 2003

Three phospholipids (4-6) and three aromatic amines (1-3) were obtained from the methanol extract of Bombycis corpus. Based on spectral data, their structures have been elucidated as nicotiamide (1), cytidine (2), adenine (3), 1-Ο-(9Z-octadecenoyl)-2-Ο-(8Z,11Z-octadecadienoyl)-sn-glycero-3-phosphorylcholine (4), 1,2-di-Ο-hexadecanoyl-sn-glycero-3-phosphorylcholine (5) and 1,2-di-Ο-9Z-octadecenoyl-sn-glycero-3-phosphorylcholine (6). We examined the effects of compounds on synthesis of NGF in cultured astrocytes. By RT-PCR analysis, expresison of NGF mRNA in astrocytes cultured in serum-starvation increased after the addition of phospholipid (10 $\mu$M). The NGF content in the culture medium was significantly increased by compound 5, compared with the control value. These results suggest that three phospholipid compounds isolated from the methanol extract of Bombycis corpus may exert neurotrophic effects by stimulation of NGF synthesis in astrocytes.

• Journal of the Korean Ceramic Society
• /
• v.35 no.11
• /
• pp.1171-1181
• /
• 1998

$SrZr_{0.95}$$Y_{0.05}$$O_{2.975}$ powder was synthesized by ultrasonic spray pyrolysis using a solution that Sr carbonate and Zr and Y nitrates were dissolved in a citric acid solution. The processes of particle formation were in-vestigated with respect to solution properties and pyrolysis temperature. With changing the solution con-centration form 0.1M to 0.01M there was a tendency that average sizes of droplets and particles were de-creased and their size distributions were narrowed. Citrate functional groups converted the droplets into gel particles which prevented an inhomogeneous precipitation of the metal ions and facilitated the diffusion of gases during thermal decomposition. As a result the powder having spherical particles without hollow par-ticles could be prepared. Low pyrolysis temperature led to amorphous particles due to incomplete pyrolysis and made the particles difficult to maintain spherical shape due to retarded gelation of the droplets. Whereas higher pyrolysis temperature produced hollow and broken particles because the droplets un-derwent rapid gelationand decomposition. The particles obtained at two pyrolysis temperature $500^{\circ}$and $1000^{\circ}C$ consisted of a perovskite phase and a very small amount of $SrCO_3$ However after calcination at $1000^{\circ}C$ the particles contained a single perovskite phase having an average particle size of 0.63${\mu}{\textrm}{m}$ and an apparent density near to the theoretical density.

• Resources Recycling
• /
• v.5 no.3
• /
• pp.50-55
• /
• 1996

The synthesis of Ca,,(PO,),(OH), by adding (NFIa)J),HPO, to lhe solution of Ca(NO,), dlssolvad CaO in HNO, and contmlled pH with NH,OH was carried out for certain time at room temperahire and atmosphere. Ca,,(PO,),(OH), was rorrned at the range from pN 10 to pH 13. The particle s~zeof Ca,,(PO,),(OH)i was 0.1-0.5 &In. Thc optimum reaction lime was 30 min, and the temperature was 40-70$^{\circ}$C. the shape also was not changed in spite of heating to iDVC hr 1 hour the c~ystalliratian temperature was 90$^{\circ}$C Ca,,(PO,),(OH), was calcinatcd and the shape also was not changzd, in spile of hcaling to 500$^{\circ}$C for 1 hour. But Ca,,(PO,),(OH), calcinated for lhour al 800$^{\circ}$C was changed to the spheric particle of Ca,,,(PO,),(OH),, CaO and Ca,(PO,),.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.57 no.4
• /
• pp.625-628
• /
• 2008

Ba-Zn ferrite powders for electromagnetic insulator were synthesized by self-propagating high-temperature synthesis(SHS) with a reaction of $xBaO_2+(1-x)ZnO+0.5Fe_2O_3+Fe{\rightarrow}Ba_xZn_{1-x}Fe_2O_4$. In this study, phase indentification of SHS products was carried out by using x-ray diffractometry and quasi-nano sized Ba-Zn powders were prepared by a pulverizing process. SHS mechanism was studied by thermodynamical analysis about oxidation reaction among $BaO_2,\;ZnO,\;Fe_2O_3$, and Fe. As oxygen pressure increases from 0.25 MPa to 1.0 MPa, the SHS reactions occur well and make clearly the SHS products. X-ray analysis shows that final SHS products formed with the ratio of $BaO_2/ZnO$ of 0.25, 1.0 and 4.0, are mainly $Ba_xZn_{1-x}Fe_2O_4$. Based on thermodynamical evaluation, the heat of formation increases in the order of $ZnFe_2O_4,\;BaFe_2O_4$, and $Ba_xZn_{1-x}Fe_2O_4$. This supports that $Ba_xZn_{1-x}Fe_2O_4$ phase is predominately formed during SHS reaction. The SHS reactions to form $Ba_xZn_{1-x}Fe_2O_4$ depends on oxygen partial pressure, and the heat of formation during the SHS reaction. The SHS reactions tends to occur well with increasing the oxygen partial pressure and BaO2/ZnO ratio in the reactants This means that the SHS reaction for the formation of Ba-Zn ferrite includes the reduction of BaO2/ZnO and the oxidation of Fe. $Ba_xZn_{1-x}Fe_2O_4$ powders after pulverizing is agglomeratedwith a size of about $50{\mu}m$, in which quasi-nano sized particles with about 300nm are present.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2006.06a
• /
• pp.286-287
• /
• 2006

Barium titanate ($BaTiO_3$) glycolate particles were synthesized at temperature as low as $100^{\circ}C$ through glycothermal reaction by using $Ba(OH)_2{\cdot}8H_2O$ and amorphous titanium hydrous gel as precursors and ethylene glycol as solvent. The particle size and morphology of $BaTiO_3$ glycolate powders can be controlled by varying the reaction conditions such as the reaction temperature and Ba:Ti molar ratio of starting precursors. After glycothermal treatment at $220^{\circ}C$ for 24 h in 1.25:1(Ba:Ti), the average particle size of the $BaTiO_3$ glycolate powder was about 200-400 nm and low agglomeration. $BaTiO_3$ powders were formed by heat-treating the glycolate powder in air at $500-1000^{\circ}C$. As a result, the size of $BaTiO_3$ crystallites changed from around 50-300 nm. It is also demonstrated that the size and shape of $BaTiO_3$ particles investigated as a function of calcination temperature. The $BaTiO_3$ particles obtained from optimum synthesis condition were pressed, sintered and measured for the dielectric property. The $BaTiO_3$ ceramics sintered at $1250^{\circ}C$ for 2 h had 98 % of theoretical density. The ceramics have an average grain size of about $1\;{\mu}m$ and displays the high dielectric constant (~3100) and low dielectric loss (<0.1) at room temperature.

• Journal of Microbiology
• /
• v.43 no.4
• /
• pp.375-380
• /
• 2005

Autonomous ultradian metabolic oscillation (T$\simeq$50 min) was detected in an aerobic chemostat culture of Saccharomyces cerevisiae. A pulse injection of GSH (a reduced form of glutathione) into the culture induced a perturbation in metabolic oscillation, with respiratory inhibition caused by $H_2S$ burst pro-duction. As the production of $H_2S$ in the culture was controlled by different amino acids, we attempted to characterize the effects of GSH on amino acid metabolism, particularly with regard to branched chain and sulfur-containing amino acids. During stable metabolic oscillation, concentrations of intra-cellular glutamate, aspartate, threonine, valine, leucine, isoleucine, and cysteine were observed to oscil-late with the same periods of dissolved $O_2$ oscillation, although the oscillation amplitudes and maximal phases were shown to differ. The methionine concentration was stably maintained at 0.05 mM. When GSH (100 $\mu$M) was injected into the culture, cellular levels of branched chain amino acids increased dramatically with continuous $H_2S$production, whereas the cysteine and methionine concentrations were noticeably reduced. These results indicate that GSH-dependent perturbation occurs as the result of the promotion of branched chain amino acid synthesis and an attenuation of cysteine and methionine synthesis, both of which activate the generation of $H_2S$. In a low sulfate medium containing 2.5 mM sulfate, the GSH injections did not result in perturbations of dissolved $O_2$ NAD(P)H redox oscillations without burst $H_2S$ production. This suggests that GSH-dependent perturbation is intimately linked with the metabolism of branched-chain amino acids and $H_2S$ generation, rather than with direct GSH-GSSG redox control.

• Korean Journal of Materials Research
• /
• v.24 no.5
• /
• pp.255-258
• /
• 2014

Zirconium boride is an artificial or which is rarely found in the nature. $ZrB_2$ is popular in the hard material industry because it has a high melting point, excellent mechanical properties and chemical stability. There are two known methods to synthesize $ZrB_2$. The first involves direct reaction between Zr and B, and the second is by reduction of the metal halogen. However, these two methods are known to be unsuitable for mass production. SHS(Self-propagating High-temperature Synthesis) is an efficient and economic method for synthesizing hard materials because it uses exothermic reactions. In this study, $ZrB_2$ was successfully synthesized by subjecting $ZrO_2$, Mg and $B_2O_3$ to SHS. Because of the high combustion temperature and rapid combustion, in conjunction with the stoichiometric ratio of $ZrO_2$, Mg and $B_2O_3$; single phase $ZrB_2$ was not synthesized. In order to solve the temperature problem, Mg and NaCl additives were investigated as diluents. From the experiments it was found that both diluents effectively stabilized the reaction and combustion regime. The final product, made under optimum conditions, was single-phase $ZrB_2$ of $0.1-0.9{\mu}m$ particle size.

• Journal of Radiation Industry
• /
• v.7 no.2_3
• /
• pp.127-134
• /
• 2013

Bombesin receptors are overexpressed in many kinds of human tumors. In particular, the gastrin releasing peptide receptor (GRPR) which is also called bombesin receptor subtype 2, has been identified in prostate cancer. In the present study, we developed a bombesin antagonist-based $^{177}Lu$-labeled peptide, $^{177}Lu$-DOTA-$Ala(SO_3H)$-Aminooctanoyl-Gln-Trp-Ala-Val-N methyl Gly-His-Statine-Leu-$NH_2$ (DOTA-sBBNA). DOTA-sBBNA was prepared using a solid phase synthesis method. It was labeled with $^{177}Lu$ by a high radiolabeling yield (>98%), and its Log P value was -2.05. The radiolabeled peptide was highly stable in serum incubation at $37^{\circ}C$ for 48 hr. A competitive displacement of $^{125}I-[Tyr^4]$-Bombesin on the PC-3 human prostate carcinoma cells revealed that the $IC_{50}$ value of the peptide was 6.76 nM indicating a highly nanomolar binding affinity for GRPR. These results suggest that $^{177}Lu$-DOTA-sBBNA can be a potential candidate for targeting prostate cancer, and further studies to evaluate its biological characteristics are needed.