• Bulletin of the Korean Chemical Society
• /
• v.31 no.9
• /
• pp.2479-2482
• /
• 2010

Using a pinhole-type glass nozzle equipped for a corona-excited supersonic expansion (CESE), precursor 2,6-dichlorotoluene seeded in a large amount of inert carrier gas helium was discharged to produce jet-cooled but electronically excited benzyl-type radicals. The visible vibronic emission spectrum was recorded with a long-path monochromator to observe vibronic bands in the $D_1{\rightarrow}D_0$ electronic transition of benzyl-type radicals. The spectral analysis revealed the generation of not only the 2,6-dichlorobenzyl radical as a typical product, but also the o-chlorobenzyl radical as an unexpected species, which indicates the possible molecular rearrangement in eliminating a chlorine atom from the benzene ring. A possible mechanism is proposed for the formation of the o-chlorobenzyl radical from the precurs or in the gas phase.

• 한국초전도학회:학술대회논문집
• /
• v.10
• /
• pp.285-288
• /
• 2000

The effect of the initial BSCCO 2212 grain size on the final gain size and the formation of the BSCCO 2223 was studied using a powder precursor synthesized by two-powder method. 2212 and CaCuO$_2$ tapes were prepared by dip coating and joined by pressing and then followed by the repeated thermo mechanical treatment. The samples were characterized by XRD and SEM analysis. The formation and grain size of the BSCCO 2223 depended on the initial BSCCO 2212 grain size.

• Mass Spectrometry Letters
• /
• v.9 no.2
• /
• pp.56-60
• /
• 2018

In this study, matrix-assisted laser desorption/ionization (MALDI) was applied to the TEMPO-assisted FRIPS for the first time. We found that 3-HPA is the optimal matrix for the analysis of p-TEMPO-Bz-Sc-peptides, which gives minimal precursor fragmentations. MALDI-TOF/TOF experiments on p-TEMPO-Bz-Sc-peptides yielded mainly $[a_n+H]^+$, $[z_n+H]^+$, and $[y_n]^+-type$ products, indicating that radical-driven peptide fragmentation occurs in MALDI-TOF/TOF-MS.

• Journal of the Korean Ceramic Society
• /
• v.30 no.1
• /
• pp.17-24
• /
• 1993

Sol-gel spin-coating technique was used to produce Nb2O5 thin films on silicon substrates from Nb(OC2H5)5 precursor. The films were heat-treated at temperatures between $600^{\circ}C$ and 100$0^{\circ}C$ in oxygen atmosphere and their crystalline phases, chemical states, and dielectric characteristics were investigated by X-ray diffractometry (XRD), Auger electron spectroscopy (AES), and C-V measurements, respectively. After 1 hour heat-treatment at 80$0^{\circ}C$, T-type Nb2O5 was formed, and its chemical composition was homogeneous with no appreciable SiO2 oxide at interfaces between the films and substrates. The films heat-treated at temperatures between $600^{\circ}C$ and 80$0^{\circ}C$ exhibit dielectric constant of less than 20 while the films heat treated at 100$0^{\circ}C$ show dielectric constant of 28.

• The Korean Journal of Ceramics
• /
• v.4 no.3
• /
• pp.240-244
• /
• 1998

The analytical method was developed to calculate efficiency of densifying carbon/carbon (C/C) composites using coal tar pitch as a matrix precursor at each cyle. Three factors were defined in analyzing the densification process: impregnation efficiency, retention efficiency, and overall densification efficiency. The relationships developed were applied to the experimental results for three densification cycles of C/C composites with pitches as an impregnant to evaluate the factors which may depend on the impregnant and on the route of carbonization. The impregnation efficiency increased with the repeated process cycles whereas the retention efficiency decreased irrespective of the impregnant and carbonization route. Carbonization route P+A+G, in which pressure carbonizationl (P) and graphitization (G) were done before after atmospheric pressure carboniztion (A) respectively, using impregnant of high carbon yields was the most effective method in densifying C/C composites.

• The Korean Journal of Ceramics
• /
• v.4 no.3
• /
• pp.199-203
• /
• 1998

$Pb(Zr, Ti)O_3$ (Pb:Zr:Ti=1:0.52:0.48) thin films were prepared on single crystal MgO(100) substrates by dipping-pyrolysis process using a solution of constituent metal naphthenates as starting materials. The solution was spin-coated onto substrate and the precursor films were pyrolyzed at $200^{\circ}C$ in air or at $200^{\circ}C$ in argon for 1, 2, 5 and 24h, followed by final heat treatment at $750^{\circ}C$. For all the films, highly (h00)/(00l)-oriented Pb$Pb(Zr, Ti)O_3$ thin films with smooth surfaces and crack-free were obtained, whereas thin film pyrolyzed in air for 24 h exhibited polycrystalline character. According to the pole-figure analysis, epitaxy of the product films was found to depend on pyrolysis atmosphere.

• Carbon letters
• /
• v.2 no.2
• /
• pp.91-98
• /
• 2001

Porous carbons have been prepared from different parts of banana stems using two different routes, viz., by pyrolysing the mass at different temperatures as well as by treating the dried mass with chemicals followed by pyrolysis. The pyrolysis behaviour of all these materials has been studied up to $1000^{\circ}C$. Samples treated with acids exhibit more increase in surface area as compared to those treated with alkalies or salts. Analysis of BET surface area shows that the carbon prepared at low temperature shows mixed porosity, i.e., micro and mesopores. Samples heated to high temperature above $700^{\circ}C$ show decrease in macroporosity and increase in microporosity. Liquid adsorption studies have been made using methylene blue and heavy oil. The activated carbons so prepared exhibit higher oil adsorption mainly in the macro and mesopores.

• Proceedings of the Korea Air Pollution Research Association Conference
• /
• 2000.11a
• /
• pp.345-347
• /
• 2000

최근 대도시 지역의 오존농도가 환경 규제기준을 초과하는 빈도가 증가하고 있는 실정이다. 이들은 대부분 탄화수소로 이루어진 유기화합물로 구성되어 있다. 따라서 이러한 물질들은 오존의 생성과 관련 있는 전구체(precursor)로 작용을 하기 때문에 집중적인 모니터링이 요구되고 있다.(한국대기보전학회 측정분석분과위원회, 1998). 오존은 산화제인 $H_2O$$_2$, O2, OH와 더불어 대기중 수분과 NOx, SOx가 반응을 하여 황산, 질산을 포함하는 산성비, 산성안개등의 생성에 중요한 역할을 한다고 알려져 있다. (이기원 외, 1993). 중략)

• BMB Reports
• /
• v.46 no.12
• /
• pp.582-587
• /
• 2013

Adipocyte differentiation is a complex developmental process forming adipocytes from various precursor cells. The murine 3T3-L1 preadipocyte cell line has been most frequently used in the studies of adipocyte differentiation. Differentiation of 3T3-L1 preadipocytes includes a medium containing fetal bovine serum (FBS) with hormonal induction. In this study, we observed that differentiation medium containing adult bovine serum (ABS) instead of FBS did not support differentiation of preadipocytes. Impaired adipocyte differentiation was due to the presence of a serum protein factor in ABS that suppresses differentiation of preadipocytes. Using a proteomic analysis, alpha-2-macroglobulin and paraoxonase/arylesterase 1, which were previously shown to suppress differentiation of preadipocytes, were identified as anti-adipogenic proteins. Although their functional mechanisms have not yet been elucidated, the anti-adipogenic effects of these proteins are discussed.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.26 no.3
• /
• pp.410-416
• /
• 2002

The fluid flow, heat transfer and the local mass fraction of chemical species in the chemical vapor deposition(CVD) manufacturing process are studied numerically. Flow with a dilute precursor concentration of silane in hydrogen as the carrier gas enters to the reactor and deposits silicon onto the heated surface. The silicon deposition rate using silane is calculated in the horizontal or vertical, axisymmetric reactor. The effects of inlet carrier gas velocity, mass fraction of silane, susceptor angle and rotation of surface on the deposition rate are described.