• Mass Spectrometry Letters
• /
• 제2권3호
• /
• pp.73-75
• /
• 2011

In the collisionally-activated dissociation of the proton-bound cluster ions of DNA base guanine (G) and cytosine (C), $G{\bullet}{\bullet}H^+{\bullet}{\bullet}C$, the abundance of [$CH^+$] ions was found to be higher than that of [$GH^+$] despite the fact that G has a higher proton affinity than C. This unexpected observation seems to demonstrate another example that the simple kinetic method scheme does not work. We suggest that a kinetic factor or detailed dynamics governing the proton transfer and dissociation should be carefully considered in the applications of the kinetic method to the proton affinity measurements.

• 한국연소학회:학술대회논문집
• /
• 한국연소학회 2004년도 제28회 KOSCO SYMPOSIUM 논문집
• /
• pp.75-82
• /
• 2004

The conditional moment closure(CMC) model has been implemented in context with the unstructured-grid finite-volume method which efficiently handle the physically and geometrically complex turbulent reacting flows. The validation cases include a turbulent nonpremixed $CO/H_2/N_2$ Jet flame and a turbulent nonpremixed $H_2/CO$ flame stabilized on an axisymmetric bluff-body burner. In terms of mean flame field, minor species and NO formation, numerical results has the overall agreement with expermental data. The detailed discussion has been made for the turbulence-chemistry interaction and NOx formation characteristics as well as the comparative performance for CMC and flamelet model.

• Bulletin of the Korean Chemical Society
• /
• 제34권3호
• /
• pp.759-762
• /
• 2013

Four prominent features of Titan's haze are found within the '3.4-${\mu}m$' absorption to be uniform with recent vertically resolved Cassini/VIMS spectra. These are absorptions at 2998 $cm^{-1}$ (3.34 ${\mu}m$), 2968 $cm^{-1}$ (3.37 ${\mu}m$), 2927 $cm^{-1}$ (3.42 ${\mu}m$), and 2882 $cm^{-1}$ (3.47 ${\mu}m$). A detailed fitting suggests that the 2998 $cm^{-1}$ feature could originate from amorphous acetonitrile ($CH_3CN$) carrying about 25% of integrated optical depth; the remaining features, which account for 75% of the integrated optical depth, could arise from a distinct triplet (C-H stretching) structure of radiolyzed hydrocarbons. An additional feature was possibly evidenced at altitudes higher than 300 km and attributable to 'polymer-capped' methane ($CH_4$), significantly constraining the chemical composition of organic haze layers under Titan's active radiation field.

• 대한기계학회논문집B
• /
• 제27권4호
• /
• pp.440-446
• /
• 2003

Steady-state structure and acoustic pressure responses of GH$_2$-LOx diffusion flames in stagnation-point flow configuration have been studied numerically with a detailed chemistry to investigate the acoustic instabilities. The Rayleigh criterion is adopted to judge the instability of the GH$_2$-LOx flames from amplification and attenuation responses at various acoustic pressure oscillation conditions for near-equilibrium to near-extinction regimes. Steady state flame structure showed that the chain branching zone is embedded in surrounding two recombination zones. The acoustic responses of GH$_2$-LOx flame showed that the responses in near-extinction regime always have amplification effect regardless of realistic acoustic frequency. That is, GH$_2$-LOx flame near-extinction is much sensitive to pressure perturbation because of the strong effect of a finite-chemistry.

• Bulletin of the Korean Chemical Society
• /
• 제23권2호
• /
• pp.262-266
• /
• 2002

Computations are presented for the ortho- and para-substituted benzyl alcohol-$H_2O$ clusters. A variety of conformers are predicted, and their relative energies are compared. Binding energies of the clusters are computed, and detailed analysis is presented on the effects of substitution on the strength of the hydrogen bond in the clusters. F- and $NH_2-$ substituted clusters are studied to analyze the effects of electron-withdrawing and electron-pushing groups. In para-substituted clusters, the inductive effects are dominant, affecting the binding energies in opposite way depending on whether the hydroxyl group is proton-donating or -accepting. For ortho-substituted clusters, more direct involvement of the substituting group and the resulting geometry change of the hydrogen bond should be invoked to elucidate complicated pattern of the binding energy of the clusters.

• 한국자기공명학회논문지
• /
• 제20권2호
• /
• pp.41-45
• /
• 2016

Chemical investigation of a marine-derived fungus, Penicillium sp. 108YD020, resulted in the discovery of six bile acid derivatives, glycocholic acid (1), glycocholic acid methyl ester (2), cholic acid (3), glycochenodeoxycholic acid (4), glycodeoxycholic acid methyl ester (5), and cholic acid methyl ester (6). The structures of six bile acid derivatives 1-6 were determined by the detailed analysis of 1D, 2D NMR and LC-MS data, along with chemical methods and literature data analysis.

• 한국진공학회:학술대회논문집
• /
• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
• /
• pp.176.1-176.1
• /
• 2014

Graphene has attracted an increasing attention due to its extraordinary electronic, mechanical, and thermal properties. Especially, the two dimensional (2D) sheet of graphene with an extremely high surface to volume ratio has a great potential in the preparation of multifunctional nanomaterials, as 2D supports to host metal nanoparticles (NPs). Copper oxide is widely used in various areas as antifouling paint, p-type semiconductor, dry cell batteries, and catalysts. Although the copper oxide(II) has been well known for efficient catalyst in C-N cross-coupling reaction, copper oxide(I) has not been highlighted. In this research, CuO and Cu2O nanoparticles (NPs) dispersed on the surface of grapehene oxide (GO) have been synthesized by impregnation method and their morphological and electronic structures have been systemically investigated using TEM, XRD, and XAFS. We demonstrate that both CuO and Cu2O on graphene presents efficient catalytic performance toward C-N cross coupling reaction. The detailed structural difference between CuO and Cu2O NPs and their effect on catalytic performance are discussed.

• 한국연소학회지
• /
• 제14권2호
• /
• pp.10-17
• /
• 2009

The present study numerically investigate the effects of the Syngas chemical kinetics on the basic flame properties and the structure of the Syngas nonpremixed flames. In order to realistically represent the turbulencechemistry interaction and the spatial inhomogeneity of scalar dissipation rate, the Eulerian Particle Flamelet Model (EPFM) with multiple flamelets has been applied to simulate the combustion processes and NOx formation in the syngas turbulent nonpremixed flames. Validation cases include the Syngas turbulent nonpremixed jet and swirling flames. Based on numerical results, the detailed discussion has been made for the effects of the chemical kinetics, the flame structure, and NOx formation characteristics in the turbulent Syngas nonpremixed flames.

• Natural Product Sciences
• /
• 제2권1호
• /
• pp.9-13
• /
• 1996

Three new withanolides, designated as withatatulins B, C, and D, were isolated from the fresh flowers of Datura tatula Linn. Detailed spectral analysis of these compounds permitted advancement of their structures respectively, as $5{\beta},6{\beta}-epoxy-12{\beta}$,21-dihydroxy-1-oxo-witha-2,24-dienolide (2), $6{\beta},12{\beta},21-trihydroxy-1-oxowitha$ 2, 4,24-trienolide (3) and $5{\beta},6{\beta},12{\beta}$,21-tetrahydroxy-1-oxo-witha-2,24-dienolide (4a). Withanolides with oxygen functions both at 12 and 21-positions are rare and first reported from Datura species.

• Natural Product Sciences
• /
• 제9권2호
• /
• pp.105-108
• /
• 2003

During our research program to find DNA strand-scission agents from higher plants, the MeOH extracts of the stems of Mucuna birdwoodiana Tutcher. (Leguminosae) exhibited the most potent activity with an $IC_{50}$ value of $4.9\;{\mu}g/ml$. Thus, detailed laboratory investigation was performed, and led to the isolation of known compounds, $({\pm})$-catechin (1) and (-)-epicatechin(2) as active principles. Compounds 1 and 2 showed significant activity of DNA strand-scission with $IC_{50}$ values of 10.8 and $7.5\;{\mu}g/ml$, respectively (positive control, bleomycin: $IC_{50}\;3.3\;{\mu}g/ml$.