• Korean Journal of Materials Research
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• v.9 no.10
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• pp.1006-1011
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• 1999

B-doped hydrogenated amorphous silicon carbide (a-SiC:H) thin films were prepared by plasma-enhanced chemical-vapor deposition in a gas mixture of $SiH_4$, $CH_4$ and $B_2H_6$. Microstructures and chemical properties of a-SiC:H films grown with varing the volume ratio of $CH_4$ to $SiH_4$ were characterized with various analysis methods including scanning electron microscopy(SEM), X-ray diffractometry(XRD), Raman spectroscopy, Fourier-transform infrared (FTIR) spectroscopy. X-ray photoelectron spectroscopy(XPS), UV absorption spectroscopy and photoconductivity measurements. While Si:H films grown without $CH_4$ showed amorphous state, the addition of $CH_4$ during deposition enhanced the development of a microcrystalline phase. By introducing C atoms into the film, Si-Si and Si--$\textrm{H}_{n}$ bonds of a -Si:H films were gradually replaced by Si-C, C-C, and Si--$\textrm{C}_{n}\textrm{H}_{m}$ bonds. Consequently, the electrical resistivity and optical bandgap of a-SiC:H films were increased with the C concentration in the film.

• Fisheries and Aquatic Sciences
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• v.2 no.1
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• pp.1-7
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• 1999

Antioxidant activity of a methanol extract of Symphyocladia latiuscula was evaluated by the thiocyanate method in the linoleic acid system. The methanol extract inhibited the peroxidation of linoleic acid in a dose-dependent manner. The MeOH extract was then sequentially partitioned with n-hexane, $CH_2Cl_2$, EtOAc, n-BuOH and H20. The antioxidant activity of the fractions increased in order of $CH_2Cl_2$, n-hexane, EtOAc, and n-BuOH. There was no activity found in $H_2O$ partitoned fraction by the thiocyanate method. Especially, the activities of the fractions of n-hexane and $CH_2Cl_2$ were comparable to that of 2,6-di-tert­butylhydroxytoluene (BHT). Column chromatography of the $CH_2Cl_2$ fraction over silica gel yielded cholesterol (1) and 2,3,6-tribromo 4,5-dihydroxybenzyl methyl ether (2) which were identified by instrumental analysis of MS and $^1H-$ and $^{13}C-NMR$. The latter (2) demonstrated significant antioxidant activity.

• Bulletin of the Korean Chemical Society
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• v.20 no.1
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• pp.65-68
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• 1999

Novel mononuclear group 13 metal complexes with the formula (R2M){NC5H4C(CH3)NNC(S)NH(C6H5)} (M=Al, R=iC4H9 (1); M=Ga, R=iC4H9 (2); M=Al, R=CH2SiMe3 (3); M=Ga, R=CH2SiMe3 (4)) result when 2-acetyl pyridine 4-phenyl-thiosemicarbazone ligand is mixed with trialkyl aluminum or trialkylgallium. These compounds 1-4 are characterized by microanalysis, NMR (1H, 13C) spectroscopy, mass spectra, and singlecrystal X-ray diffraction. X-ray single-crystal diffraction analysis reveals that 1 is mononuclear metal compound with coordination number of 5 and N, N, S-coordination mode.

• Carbon letters
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• v.8 no.1
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• pp.12-16
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• 2007

Molecular sieving carbon (MSC) for separating $O_2-N_2$ and $CO_2-CH_4$ has been prepared through chemical vapor deposition (CVD) of methane and benzene on activated carbon spheres (ACS) derived from polystyrene sulfonate beads. The validity of the material for assessment of molecular sieving behavior for $O_2-N_2$ and $CO_2-CH_4$ pair of gases was assessed by the kinetic adsorption of the corresponding gases at $25^{\circ}C$. It was observed that methane cracking on ACS lead to deposition of carbon mostly in whole length of pores rather than in pore entrance, resulting in a reduction in adsorption capacity. MSC showing good selectivity for $CO_2-CH_4$ and $O_2-N_2$ separation was obtained through benzene cracking on ACS with benzene entrantment of $0.40{\times}10^{-4}\;g/ml$ at cracking temperature of $725^{\circ}C$ for a period of 90 minutes resulting in a selectivity of 3.31:1.00 for $O_2-N_2$ and 8.00:1.00 for $CO_2-CH_4$ pair of gases respectively.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.132-132
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• 2010

In the nano-scale Si processing, patterning processes based on multilevel resist structures becoming more critical due to continuously decreasing resist thickness and feature size. In particular, highly selective etching of the first dielectric layer with resist patterns are great importance. In this work, process window for the infinitely high etch selectivity of silicon oxynitride (SiON) layers and silicon nitride (Si3N4) with EUV resist was investigated during etching of SiON/EUV resist and Si3N4/EUV resist in a CH2F2/N2/Ar dual-frequency superimposed capacitive coupled plasma (DFS-CCP) by varying the process parameters, such as the CH2F2 and N2 flow ratio and low-frequency source power (PLF). It was found that the CH2F2/N2 flow ratio was found to play a critical role in determining the process window for ultra high etch selectivity, due to the differences in change of the degree of polymerization on SiON, Si3N4, and EUV resist. Control of N2 flow ratio gave the possibility of obtaining the ultra high etch selectivity by keeping the steady-state hydrofluorocarbon layer thickness thin on the SiON and Si3N4 surface due to effective formation of HCN etch by-products and, in turn, in continuous SiON and Si3N4 etching, while the hydrofluorocarbon layer is deposited on the EUV resist surface.

• YAKHAK HOEJI
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• v.38 no.4
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• pp.455-461
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• 1994

Each nitrogen and oxygen site isotope enriched the cyclophosphamide metabolite phosphoramide mustard was synthesized. Reaction of N,N-bis(2-chloroethyl)phosphoramidic dichloride$[Cl_2P(O)N(CH_2CH_2Cl)_2]$ with benzyl alcohol and ammonia gave N,N-bis(2-chloroethyl)phosphorodiamidic acid phenylmethyl ester $[BzO(H_2N)P(O)N(CH_2CH_2Cl)_2]$. Catalytic hydrogenation of this benzyl ester followed by the addition of cyclohexylamine provided PM. Incorporation of $^{15}NH_3$ into this general scheme gave PM with a $^{15}NH_2$ moiety. Glycine-$^{15}N$ was converted to bis(2-chloroethyl)amine-$^{15}N$ hydrochloride which, in turn, provided for N,N-bis(2-chloroethyl)phosphorodiamidic-$^{15}N$ dichloride. Use of this compound in the general synthetic pathway yielded PM CHA with $^{15}N$ in the mustard moiety. $^{17}O$-Enriched PM was generated through the use of benzyl alcohol-$^{17}O$. To obtain the alcohol, labelled benzaldehyde was made by exchange with $^{17}OH_2$ and was then reduced with sodium borohydride.

• Animal Bioscience
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• v.34 no.8
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• pp.1415-1424
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• 2021

Objective: Portable laser methane detectors (LMDs) may be an economical means of estimating CH₄ emissions from ruminants. We validated an LMD-based approach and then used that approach to evaluate CH₄ emissions from indigenous dairy cows in a dryland area of Ethiopia. Methods: First, we validated our LMD-based approach in Simmental crossbred beef cattle (n = 2) housed in respiration chambers and fed either a high- or low-concentrate diet. From the results of the validation, we constructed an estimation equation to determine CH₄ emissions from LMD CH₄ concentrations. Next, we used our validated LMD approach to examine CH₄ emissions in Fogera dairy cows grazed for 8 h/d (GG, n = 4), fed indoors on natural-grassland hay (CG1, n = 4), or fed indoors on Napier-grass (Pennisetum purpureum) hay (CG2, n = 4). All the cows were supplemented with concentrate feed. Results: The exhaled CH₄ concentrations measured by LMD were linearly correlated with the CH₄ emissions determined by infrared-absorption-based gas analyzer (r² = 0.55). The estimation equation used to determine CH₄ emissions (y, mg/min) from LMD CH₄ concentrations (x, ppm m) was y = 0.4259x+38.61. Daily CH₄ emissions of Fogera cows estimated by using the equation did not differ among the three groups; however, a numerically greater milk yield was obtained from the CG2 cows than from the GG cows, suggesting that Napier-grass hay might be better than natural-grassland hay for indoor feeding. The CG1 cows had higher CH₄ emissions per feed intake than the other groups, without significant increases in milk yield and body-weight gain, suggesting that natural-grassland hay cannot be recommended for indoor-fed cows. Conclusion: These findings demonstrate the potential of using LMDs to valuate feeding regimens rapidly and economically for dairy cows in areas under financial constraint, while taking CH₄ emissions into consideration.

• Fisheries and Aquatic Sciences
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• v.4 no.1
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• pp.47-49
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• 2001

Nitrite scavenging activity of a methanol extract of Symphyocladia latiuscula was studied. The methanol extract scavenged the nitrite in a dose-dependent manner. The MeOH extract was then sequentially partitioned with n-hexane, $CH_2Cl_2$, EtOAc, n-BuOH and $H_2O$. The scavenging activity of the fractions increased in order of $CH_2Cl_2$, n-hexane, EtOAc, n-BuOH, and $H_2O$. Especially, the activity of the $CH_2Cl_2$ fraction was comparable to that of L-ascorbic acid. Column chromatography of the most active $CH_2Cl_2$ fraction over silica gel yielded three active bromophenol congeners (1-3) which were identified as (2R)-2-(2,3,6-tribromo 4,5-dihydro­xybenzyl) cyclohexanone (1), 2,3,6-tribromo 4,5-dihydroxybenzyl methyl ether (2), and 2,3,6­tribromo 4,5-dihydroxybenzyl alcohol (3) respectively.

• Journal of the Korean Chemical Society
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• v.54 no.5
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• pp.541-550
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• 2010

A new $N_4O_3$ heptadentate ligand, N,N'-Bis(2-hydroxybenzyl)-1,3-bis[(2-aminoethyl)amino]-2-propanol(H-BAP 4HCl)was synthesized. The hydrochloric acid salts of Br-BAP 4HCl, Cl-BAP 4HCl, $CH_3O$-BAP 4HCl and $CH_3$-BAP 4HCl containing Br-, Cl-, H-, $CH_3O-$ and $CH_{3^-}$ groups at the para-site of the phenol group of the H-BAP were synthesized. The structures of the ligands were confirmed by C. H. N. atomic analysis and $^1H$ NMR, $^{13}C$ NMR, UV-visible and mass spectra. The elemental stepwise protonation constants(${logK_n}^H$) of the synthesized $N_4O_3$ ligands showed six steps of the proton dissociation. The orders of the overall dissociation constants($log{\beta}_p$) of the ligands were Br-BAP < Cl-BAP < H-BAP < $CH_3O$-BAP < $CH_3$-BAP. The orders agreed well with that of Hammett substituent constants($\sigma_p$). The calculated stability constants($logK_{ML}$) between the ligands and transition metal ions agreed well with the order of the overall proton dissociation constants of the ligands but they showed a reverse order in Hammestt substituent constants($\sigma_p$). The order of the stability constants between the transition metal ions with the ligands were Co(II) < Ni(II) < Cu(II) > Zn(II) > Cd(II) > Pb(II).

• Membrane and Water Treatment
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• v.8 no.2
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• pp.171-184
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• 2017

This study presents the effect of hydraulic retention time (HRT) on the characteristics of emission of three major greenhouse gases (GHGs) including $CH_4$, $CO_2$ and $N_2O$ during operation of a sequencing batch reactor for aerobic oxidation of methane with denitrification (AeOM-D SBR). Dissolved $N_2O$ concentration increased, leveled-off and slightly decreased as the HRT increased from 0.25 to 1d. Concentration of the dissolved $N_2O$ was higher at the shorter HRT, which was highly associated with the lowered C/N ratio. A longer HRT resulted in a higher C/N ratio with a sufficient carbon source produced by methanotrophs via methane oxidation, which provided a favorable condition for reducing $N_2O$ formation. With a less formation of the dissolved $N_2O$, $N_2O$ emission rate was lower at a longer HRT condition due to the lower C/N ratio. Opposite to the $N_2O$ emission, emission rates of $CH_4$ and $CO_2$ were higher at a longer HRT. Longer HRT resulted in the greater total GHGs emission as $CO_2$ equivalent which was doubled when the HRT increased from 0.5d to 1.0 d. Contribution of $CH_4$ onto the total GHGs emission was most dominant accounting for 98 - 99% compared to that of $N_2O$ (< 2%).