• Biotechnology and Bioprocess Engineering:BBE
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• v.6 no.4
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• pp.301-305
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• 2001

The co-expression of the arg U gene in a double-vector expression system of recombi-nant Escherichia coli BL22(DE3)[pET-IEN2a+pAC-argU] significantly enhanced the production level of reconminant human interferon -$\alpha$2a(rhIFN-$\alpha$2a) in high cell density cultures, compared to a recombinant E. coli culture containing only the single expression vector, pET-IEN2a. The dry cell mass concentration increased to almost 100 g/L, and more than 4 g/L of rhIFN-$\alpha$2a was accumu-lated in the culture broth. Evidently, the synthesis of rhIFN-$\alpha$2a was strongly dependent on the pre-induction growtih rate and more efficient at a higher specific growth rate. The additional sup-ply of tRN $A^{Arg(AGG/AGA)}$ enhanced the expression level of the rhIFN-$\alpha$2a gene in the early stage of the post-induction phase, yet thereafter the specific production rate of rhIFN-$\alpha$2a rapidly de-creased due to severe segregational instability of plasmid vector pET-IEN2a. It would appear that the plasmid instability with only occurred to pET-IEN2a in the double vector system, was re-lated to the effect of translational stress due to the over expression of rhIFN-$\alpha$2a.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.37 no.3
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• pp.192-196
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• 2004

The in vitro effect of bisphenol A (BPA) on ovarian steroidogenesis of the longchin goby (Chasmichthys dolichognathus) was investigated. Oocytes taken during the maturing phase (vitellogenic, fully vitellogenic or germinal vesicle breakdown stage) were incubated with BPA (100 ng/mL) in the presence of exogenous precursor $^{3}H-17\alpha\;hydroxyprogesterone\;(^{3}H-17\alphaOHP).$ Steroids were extracted from the media and the isolated oocytes, and the extracts were separated and identified by thin layer chromatography and gas chromatography-mass spectrometry. The identities of the major metabolites were progestogens $[17{\alpha}-hydroxy,20{\alpha}-dihydroprogesterone\;(17{\alpha}20{\alpha}OHP)\;and\;17{\alpha}-hydrxy,20{\beta}-dihydroprogesterone\;(17{\alpha}20{\beta}OHP),$ androgens [androstenedione (A4) and testosterone (T)] and estrogens [estrone $(E_1)\;and\;estradiol-17{\beta}(E_2)].$ BPA treatment inhibited production of estrogens in all the maturing phases and progestogens in the germinal vesicle migrating stage. Percentage yield of estrogens was decreased with increased yield of androgens. In conclusion, BPA had an inhibitory effect on the conversion of $^3H-17\alphaOHP$ to estrogens and progestogens. These results demonstrate that BPA can act either estrogenic or anti-estrogenic effects.

• The Bulletin of The Korean Astronomical Society
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• v.38 no.2
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• pp.61.2-61.2
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• 2013

We present a study of optically emitting supernova remnants (SNRs) in M31 based on $H{\alpha}$ and [S II] images in the Local Group Survey. Using these images, we have selected objects that have [S II]:$H{\alpha}$ > 0.4 and morphology for typical SNRs. We find 76 new SNRs. We have also inspected 233 SNR candidates presented in previous studies, confirming that only 80 of them are SNRs. Combining these, we produce a master catalog of 156 SNRs in M31. We classify these SNRs according to two types of criteria: the SNR progenitor types (Type Ia and core-collapse (CC) SNRs) and the morphological types. Type Ia and CC SNRs are 23% and 77%, respectively, of the total sample. Most of CC SNRs are concentrated along the spiral arms, while Type Ia SNRs are rather spread over the entire galaxy including the inner region. CC SNRs are brighter in $H{\alpha}$ and [S II] than Type Ia SNRs. The cumulative size distribution of the SNRs with 15 < D < 50 pc is well fitted by a power law with an index, ${\alpha}=2.53{\pm}04$. It indicates that most SNRs in M31 are in Sedov-Taylor phase. Properties of these SNRs show little variation depending on the galactocentric distance. The $H{\alpha}$ and [S II] surface brightness shows a good correlation with X-ray luminosity for the SNRs that are center-bright.

• Journal of Korean Society for Atmospheric Environment
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• v.18 no.3
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• pp.183-192
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• 2002

Concentrations of $\alpha$- and ${\gamma}$-hexachlorocyclohexane (HCH) were measured in ambient air samples at a two week intervals between July 1999 and February 2000 at Ansung, Kyonggi province. Their concentration levels averaged at 78 ($\alpha$-HCH) and 18 pg/m$^3$(${\gamma}$-HCH). Although the use of HCHs was ceased in South Korea since 1979, their residues are still present in air even after nearly 20 years. Given the composition of the two main HCH pesticide formulation (technical HCH antral lindane), the $\alpha$/${\gamma}$-HCH ratio in air is a useful indicator on the regional scale. The moderately low $\alpha$/${\gamma}$-HCH ration in this study indicates previous usage of both technical HCH and lindane. The relationship of temperature with gas-phase partial pressures was also examined using the Clausius-Clapeyron equation. Slopes generated by linear regression analysis between partial pressure (In P) and 1/T were considerably steep thor HCHs. It is thus suggested that their concentrations are controlled by re-volatilization processes from surfaces in the local surroundings of the sampling site.

• Journal of Korean Ophthalmic Optics Society
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• v.5 no.1
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• pp.55-59
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• 2000

In this study, materials for spectacle lens cutting were fabricated by hot-pressing and annealing SiC powders with $Al_2O_3$ and $Y_2O_3$. A microstructure that consisted of uniformly distributed, large SiC grains and elongated SiC grains was developed by using ${\alpha}$-SiC powders. The microstructure was observed by scanning electron microscope(SEM). By hot-pressing and subsequent annealing, elongated ${\beta}$-SiC grains were grown via ${\beta}{\rightarrow}{\alpha}$ phase. This is caused the crack deflection as toughening mechanism. Typical hardness and fracture toughness of materials for spectacle lens cutting were 13.3 GPa and $4.8MPa{\cdot}m^{1/2}$, respectively.

• Journal of the Korean Ceramic Society
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• v.28 no.7
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• pp.561-567
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• 1991

Submicron ${\alpha}-SiC$ powder with $Al_2O_3$ addition was hot-pressed under the controlled heating and pressurizing schedule. $SiO_2$ layer on ${\alpha}-SiC$ powder was effective for the sintering of ${\alpha}-SiC$ powder when $Al_2O_3$ was used as an additive. Applying of pressure under the controlled schedule accelerated the rearrangment of SiC grains, yielding 98% of theoretical density of SiC even at $1900^{\circ}C$. Flexural strength of the specimen containing 2 wt% $Al_2O_3$ was increased as increasing the hot-pressing temperature up to $2050^{\circ}C$ and maximum value was 800 MPa, while the flexural strength of the specimen containing 10 wt% $Al_2O_3$ was decreased as increasing the hot-pressing temperature above $2000^{\circ}C$ due to the formation of continuous grain boundary phase. Fracture toughness of the specimens was in the range of $3.5~4.5\;MNm^{-3/2}$ regardless of the amount of $Al_2O_3$ addition.

• Journal of the Korean Ceramic Society
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• v.34 no.11
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• pp.1187-1197
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• 1997

Dry gel composed of primary particles more homogeneous than starting boehmite powder was prepared by dispersing and gelling the boehmite powder. The transformation temperatures of boehmite powder, dry gel seeded with 0, 1, 3, 5 wt% $\alpha$-Al2O3, and ball milled gel were 1192$^{\circ}C$, 1184$^{\circ}C$, 1141$^{\circ}C$, 1119$^{\circ}C$, 1117$^{\circ}C$, and 1106$^{\circ}C$, respectively. Sintering behavior of dry gel without seed was similar to that of boehmite powder, but the sintered density of dry gel was improved as much as 10%~15% than boehmite powder. In the case of dry gel seeded with 5 wt% $\alpha$-Al2O3, sintering behavior was much improved. The relative density of the gel seeded with 5 wt% $\alpha$-Al2O3 was 96% when sintered at 140$0^{\circ}C$ for 1h. On the other hand, ball milling of the non-seeded sol for 48h resulted in the relative density of 97% when sintered at 130$0^{\circ}C$ for 1h. The size and amount of $\alpha$-Al2O3 particles added by ball milling were 0.107 ${\mu}{\textrm}{m}$ and 0.5 wt%.

• Food Science and Biotechnology
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• v.15 no.2
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• pp.183-188
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• 2006

The tocopherol and tocotrienol contents of 39 vegetable oils, margarines, butters, and peanut butters typically consumed in the Korea diet were determined by direct solvent extraction method followed by normal phase liquid chromatography. All samples were locally obtained in the Cheongju area in 2003 and 2004. The study examined data on 19 vegetable oils, 10 margarines, 6 butters, and 4 peanut butters. ${\gamma}$-Tocopherol (${\gamma}$-T) and ${\alpha}$-tocopherol (${\alpha}$-T) were detectable in all products except butters and were usually present in the vitamin E form in greater quantity than the other isomers. Usually, ${\gamma}$-T content was higher than ${\alpha}$-T content in many samples. Tocotrienols were measurable in some samples but usually at levels less than the corresponding tocopherols. Three analytical method validation parameters, accuracy, precision, and specificity, were calculated to ensure the method's validity and were all confirmed to be reliable and satisfactory.

• Asian-Australasian Journal of Animal Sciences
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• v.8 no.4
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• pp.321-323
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• 1995

Observations were recorded regarding various fertility parameters on 26 Jersey donor cows following superovulation under tropical conditions. These cows, in their mid-luteal phase were treated with 2,500-3,000 i.u. PMSG or 28-40 mg FSH followed by $500{\mu}g$ $PGF_{2{\alpha}}$ injection 48-60 hours later, to induce oestrus. The cows were bred artificially twelve hours following standing oestrus. Embryo collection was carried out 7 days after oestrus. $PGF_{2{\alpha}}$ was injected to each donor cow after embryo recovery to regress the corpora lutea. Fertility data($PGF_{2{\alpha}}$-Oestrus interval, services per conception, days between embryo collection and successful service and any pathololgical condition) were recorded. $PGF_{2{\alpha}}$-Oestrus interval and correlation (r) between number of corpora lutea and $PGF_{2{\alpha}}$-Oestrus interval were $30.9{\pm}6.3$ and 0.17, respectively. Of 26 treated donors, 19 conceived within a period of $91.7{\pm}18.8$ days after embryo recovery. Average services per conception were $2.3{\pm}0.3$. Only two cows developed metritis which conceived after treatment with antibiotics. These observations indicated no profound adverse effect of superovulation on subsequent reproduction of donor cows, except some effect on services per conception, under tropical conditions.

• Journal of the Korean Chemical Society
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• v.35 no.6
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• pp.612-616
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• 1991

Metachromatic behavior of methylene blue (MB) in solutions of aqueous sodium dodecyl sulfate (SDS), chondroitin sulfate and L-${\alpha}$-lecithin vesicle at $18~52^{\circ}$C has been studied by absorption spectroscopy. MB was clustered in the matrix of the vesicle with high concentration of L-${\alpha}$-lecithin. The metachromasy of MB was found to be independent of phase transition temperature of vesicles. These results suggest that the dyes were aggregated on the hydrophilic surfaces of vesicle. In the vesicular system, the metachromatic effect of MB was dramatically decreased in the presence of hexadecyltrimethylammonium bromide (CTAB) than SDS. It is estimated that the intercalation site of these surfactants on vesicle surfaces was different, that is, the intercalation of CTAB was more effective than that of SDS.