• Asian-Australasian Journal of Animal Sciences
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• v.22 no.1
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• pp.82-89
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• 2009

Two in vitro experiments were conducted to examine the effects of propionate precursors in the dicarboxylic acid pathway on ruminal fermentatation characteristics, $CH_4$ production and degradation of feed by rumen microbes. Fumarate or malate as sodium salts (Exp. 1) or acid type (Exp. 2) were added to the culture solution (150 ml, 50% strained rumen fluid and 50% artificial saliva) to achieve final concentrations of 0, 8, 16 and 24 mM, and incubated anaerobically for 0, 1, 3, 6, 9 and 12 h at $39^{\circ}C$. For both experiments, two grams of feed consisting of 70% concentrate and 30% ground alfalfa (DM basis) were prepared in a nylon bag, and were placed in a bottle containing the culture solution. Addition of fumarate or malate in both sodium salt and acid form increased (p<0.0001) pH of culture solution at 3, 6, 9 and 12 h incubations. The pH (p<0.0001) and total volatile fatty acids (VFA, p<0.05) were enhanced by these precursors as sodium salt at 3, 6 and 9 h incubations, and pH (p<0.001) and total VFA (p<0.01) from fumarate or malate in acid form were enhanced at a late stage of fermentation (9 h and 12 h) as the addition level increased. pH was higher (p<0.001) for fumarate than for malate as sodium salt at 3 h and 6 h incubations. Propionate ($C_3$) proportion was increased (p<0.0001) but those of $C_2$ (p<0.05) and $C_4$ (p<0.01 - p<0.001) were reduced by the addition of sodium salt precursors from 3 h to 12 incubation times while both precursors in acid form enhanced (p<0.011 - p<0.0001) proportion of $C_3$ from 6h but reduced (p<0.018 - p<0.0005) $C_4$ proportion at incubation times of 1, 3, 9 and 12 h. Proportion of $C_3$ was increased (p<0.05 - p<0.0001) at all incubation times by both precursors as sodium salt while that of $C_3$ was increased (p<0.001) from 6h but $C_4$ proportion was decreased by both precursors in acid form as the addition level increased. Proportion of $C_3$ was higher (p<0.01 - p<0.001) for fumarate than malate as sodium salt from 6 h incubation but was higher for malate than fumarate in acid form at 9 h (p<0.05) and 12 h (p<0.01) incubation times. Increased levels (16 and 24 mM) of fumarate or malate as sodium salt (p<0.017) and both precursors in acid form (p<0.028) increased the total gas production, but no differences were found between precursors in both chemical types. Propionate precursors in both chemical types clearly reduced (p<0.0001 - p<0.0002) $CH_4$ production, and the reduction (p<0.001 - p<0.0001) was dose dependent as the addition level of precursors increased. The $CH_4$ generated was smaller (p<0.01 - p<0.0001) for fumarate than for malate in both chemical types. Addition of fumarate or malate as sodium type reduced (p<0.004) dry matter degradation while both precursors in both chemical types slightly increased neutral detergent fiber degradability of feed in the nylon bag.

• Journal of the Korean Ceramic Society
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• v.46 no.3
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• pp.242-248
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• 2009

Forsterite is a crystalline magnesium silicate with chemical formula $Mg_2SiO_4$, which has extremely low electrical conductivity that makes it an ideal substrate material for electronics. In this study, forsterite precursors were synthesized with magnesium silicate gels from the mixture of magnesium nitrate solution and various sodium silicate solution by the geopolymer technique. Precursors and heattreated powders were characterized by thermogravimetrical differential thermal analyzer(TG-DTA), X-ray diffractometer(XRD), scanning electron microscopy(SEM), Si magic angle spinning nuclear magnetic resonance(MAS-NMR), transmission electron microscopy(TEM). As the result of analysis about the crystallization behavior by DTA, the synthesized precursors were crystallized in the temperature range of $700^{\circ}C$ to $900^{\circ}C$. The XRD results showed that the gel composition began to crystallize at various temperature. Also, it was found that the sodium orthosilicate based precursors(named as 'FO') began to crystallize at above $550^{\circ}C$. The FO peaks were much stronger than sodium silicate solution based precursors(named as 'FW'), sodium metasilicate based precursors(named as 'FM') at $800^{\circ}C$. TEM investigation revealed that the 100nm particle sized sample was obtained from FO by heating up to $800^{\circ}C$.

• Electrical & Electronic Materials
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• v.28 no.2
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• pp.25-33
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• 2015

Ruthenium (Ru) thin films were grown on thermally-grown $SiO_2$ substrates by atomic layer deposition (ALD) using a sequential supply of four kinds of novel zero-valent Ru precursors, isopropyl-methylbenzene-cyclohexadiene Ru(0) (IMBCHDRu, $C_{16}H_{22}Ru$), ethylbenzen-cyclohexadiene Ru(0) (EBCHDRu, $C_{14}H_{18}Ru$), ethylbenzen-ethyl-cyclohexadiene Ru(0) (EBECHDRu, $C_{16}H_{22}Ru$), and (ethylbenzene)(1,3-butadiene)Ru(0) (EBBDRu, $C_{12}H_{16}Ru$) and molecular oxygen (O2) as a reactant at substrate temperatures ranging from 140 to $350^{\circ}C$. It was shown that little incubation cycles were observed for ALD-Ru processes using these new novel zero-valent Ru precursors, indicating of the improved nucleation as compared to the use of typical higher-valent Ru precursors such as cyclopentadienyl-based Ru (II) or ${\beta}$-diketonate Ru (III) metallorganic precursors. It was also shown that Ru nuclei were formed after very short cycles (only 3 ALD cycles) and the maximum nuclei densities were almost 2 order of magnitude higher than that obtained using higher-valent Ru precursors. The step coverage of ALD-Ru was excellent, around 100% at on a hole-type contact with an ultra-high aspect ratio (~32) and ultra-small trench with an aspect ratio of ~ 4.5 (top-opening diameter: ~ 25 nm). The developed ALD-Ru film was successfully used as a seed layer for Cu electroplating.

• Journal of the Korean Ceramic Society
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• v.45 no.5
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• pp.303-308
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• 2008

Mullite precursors were synthesized with aluminosilicate gels from mixture of aluminum nitrate and sodium orthosilicate by the geopolymer technique at ambient temperature. Then, the gel was heat-treated in air up to $1200^{\circ}C$ at intervals of $100^{\circ}C$. Raw and heat-treated gels were characterized by TG-DTA, XRD, FTIR, $^{29}Si$ MAS-NMR, TEM. The result to examine the crystallization of behavior though DTA, the synthesized precursors were crystallized in the temperature range from $950^{\circ}C$ to $1050^{\circ}C$. The XRD results showed that the gel compositions were begun to crystallize at various temperature. Also, it was found that the precursors of M-4 begun to crystallize at about $950^{\circ}C$. The M-4 XRD peaks were characterized better than $M-1{\sim}M-3$ at $1000^{\circ}C$. The formation temperature of mullite in this study is much lower than that of previous sol-gel methods, which crystallized at up of $1200^{\circ}C$. TEM investigations revealed that the sample with 10 nm particle size was obtained via heat-treated at $1000^{\circ}C$ for M-4.

• Bulletin of the Korean Chemical Society
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• v.11 no.2
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• pp.134-139
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• 1990

The hydrogenation catalyst precursors $[(L-L)Rh(NBD)]ClO_4\;(L-L=Fe({\eta}^5-C_5H_4PBu^t\;_2)_2,\;Fe({\eta}^5-C_5H_4PPhBu^t)_2$; NBD = norbornadiene) react with $H_2(1\;atm,\;30^{\circ}C$, MeOH) to yield $[(L-L)HRh({\mu}-H)_3RhH(L-L)]ClO_4$. These hydrido species are fluxional, and variable temperature NMR studies show the existence of a number of equilibria involving both fluxional and non-fluxional species. The synthesis, solution structures, and fluxional behaviors of these hydrides are described.

• Korean Journal of Materials Research
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• v.18 no.6
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• pp.302-306
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• 2008

Polycrystalline germanium (Ge) thin films were grown by metal organic chemical vapor deposition (MOCVD) using tetra-allyl germanium [$Ge(allyl)_4$], and germane ($GeH_4$) as precursors. Ge thin films were grown on a $TiN(50nm)/SiO_2/Si$ substrate by varying the growth conditions of the reactive gas ($H_2$), temperature ($300-700^{\circ}C$) and pressure (1-760Torr). $H_2$ gas helps to remove carbon from Ge film for a $Ge(allyl)_4$ precursor but not for a $GeH_4$ precursor. $Ge(allyl)_4$ exhibits island growth (VW mode) characteristics under conditions of 760Torr at $400-700^{\circ}C$, whereas $GeH_4$ shows a layer growth pattern (FM mode) under conditions of 5Torr at $400-700^{\circ}C$. The activation energies of the two precursors under optimized deposition conditions were 13.4 KJ/mol and 31.0 KJ/mol, respectively.

• Journal of Powder Materials
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• v.23 no.4
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• pp.287-296
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• 2016

$Ni_{1/3}Co_{1/3}Mn_{1/3}(OH)_2$ powders have been synthesized in a continuously stirred tank reactor via a co-precipitation reaction between aqueous metal sulfates and NaOH using $NH_4OH$ as a chelating agent. The co-precipitation temperature is varied in the range of $30-80^{\circ}C$. Calcination of the prepared precursors with $Li_2CO_3$ for 8 h at $1000^{\circ}C$ in air results in Li $Ni_{1/3}Co_{1/3}Mn_{1/3}O_2$ powders. Two kinds of obtained powders have been characterized by X-ray diffraction (XRD), scanning electron microscopy, particle size analyzer, and tap density measurements. The co-precipitation temperature does not differentiate the XRD patterns of precursors as well as their final powders. Precursor powders are spherical and dense, consisting of numerous acicular or flaky primary particles. The precursors obtained at 70 and $80^{\circ}C$ possess bigger primary particles having more irregular shapes than those at lower temperatures. This is related to the lower tap density measured for the former. The final powders show a similar tendency in terms of primary particle shape and tap density. Electrochemical characterization shows that the initial charge/discharge capacities and cycle life of final powders from the precursors obtained at 70 and $80^{\circ}C$ are inferior to those at $50^{\circ}C$. It is concluded that the optimum co-precipitation temperature is around $50^{\circ}C$.

• Journal of Microbiology and Biotechnology
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• v.3 no.4
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• pp.244-251
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• 1993

A novel system has been developed to produce ${\delta}-aminolevulinic$ acid (ALA) using the intact cells of late logarithmic phase of Rhodocyclus gelatinosus KUP-74. The system was shown optimum yield of extracellular ALA under a condition of anaerobic light irradiation (4 Klux) at $30^{\circ}C$ with no variation in cell mass. The rate of extracellular ALA formation was stimulated by low doses of either $C_4\;or\;C_5$ ALA biosynthetic precursors, where 5 mM ($C_4) and 3 mM ($C_5) of each precursors were appeared to generate the maximum rates of 3.3 and 4.0 nmoles of ALA per 0.35 mg cells per hr, respectively. Half-life of the system was 10 hr in a sense of an ability of portage transport of L-glutamate, and sequential dose of this compound was resulted in promising recovery of the ALA.

• Journal of the Korea Organic Resources Recycling Association
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• v.5 no.1
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• pp.25-32
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• 1997

The effect of levulinic acid (LA) and biosynthetic precursors of ${\delta}$-aminolevulinic acid (ALA) on the production of extracellular ALA was examined for the cells of soil derived Rhodospirillum rubrum N-1 belonged to the genus Rhodospirillaceae. The extracellular yield of ALA was increased to 23 fold (45 mg/l) from the basal condition (Lascelles' medium without L-glutamate) by successive addition of LA at initial (10 mM) and mid-log stage (30 mM) of cell cultivation. In addition to initial/mid-log mutual supplementations of LA (10 mM/30 mM) and glutamate (30/30 mM), respectively, by means of alternative feeding 10 mM $C_4$-precursors at mid-log phase of culture the extracellular ALA content was reached to 75 mg/l (40 fold).

• The Korean Journal of Ceramics
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• v.6 no.1
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• pp.32-36
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• 2000

Pyrolytic preparations of Ti-Al-N ceramics from three blended precursors were investigated. The precursors were prepared stirring ($HA1N^{i}Pr_m$ and an aminolysis product of $Ti(NMe_2)_4$ with $MeHNCH_2CH_2$NHMe in $C_6/H_6$ . IR and $^1H\;NMR $analyses suggested that essentially no Ti-N-Al bonds were present in the precursors. Pyrolysis of the precursors under $NH_3-N_2$led to the formation of brown solids with ceramic yields of about 30%, and the Ti-Al ratios in the pyrolyzed products were close to those of the precursors. XRD analysis of the pyrolyzed product from the precursor with Ti:Al=5:1 indicated the formation of a NaCl-type compound as the only crystalline phase. Pyrolysis of the precursor with Ti:Al=2:1 led to the formation of AlN besides the major NaCl-type compound. A ceramic composite containing AlN and the NaCl-type compound was formed by pyrolysis of the precursor with Ti:Al=1:2.