• 공업화학
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• 제8권1호
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• pp.49-58
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• 1997

고탄성, 고강도의 특성을 가지고 있는 열방성 액정고분자인 Vectra(LCP)와 무정형 poly(${\varepsilon}-caprolactam$) (PA)의 합금에서 LCP의 함량이 10parts 미만에서는 LCP의 네마틱 상의 유리전이온도가 $4{\sim}5^{\circ}C$ 정도 낮은 족으로 이동되나 그 이상의 함량에서는 유리전이온도의 이동을 볼 수 없는 것으로 보아 부분적인 상용성만 나타나게 됨을 확인하였다. PA/LCP 합금에서 LCP의 함량을 증가시켜 주기위해 N-g1ycinylmaleimide(GMI)를 합성한 다음 이를 methylmetacrylate(MMA)와 공중합시켜 poly(glycinylmaleimide-co-methylmetacrylate)[poly(GMI-co-MMA)]공중합체를 합성하고 이를 상용화제로 사용하였으며 이를 사용하는 경우 LCP 30parts 이상을 혼합하여도 혼화성이 있음을 알 수 있었고 이들 합금의 상용성은 합금의 각종 혼합비율에 따른 열적 특성과 rheological 특성을 측정하여 확인하고 고속충격특성과 굴곡강도 및 탄성율을 측정하였다.

• 한국주조공학회지
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• 제23권5호
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• pp.276-285
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• 2003

In the undercooled melt of $Pd_{40}Cu_{30}Ni_{10}P_{20}$ alloy, the solidification behavior including nucleation and growth of crystals at the micrometer level has been observed in-situ by use of a confocal scanning laser microscope combined with an infrared image furnace. The $Pd_{40}Cu_{30}Ni_{10}P_{20}$ alloy specimens were cooled from the liquid state to glass transition temperature. 575 K, at various cooling late under a helium gas flow. According to the cooling rate, the morphologies of the solidification front are changed among various types, irregular jog like front, columnar dendritic front, cellular grain, star like shape jog and fine grain, etc. The velocities of the solid-liquid interface are measured to be $10^{-5}{\sim}10^{-8}$ m/s which are at least two orders higher than the theoretical crystal growth rates. Combining the morphologies observed in terms of cooling rates and their solidification behaviors, we conclude that phase separation takes place in the undercooled molten $Pd_{40}Cu_{30}Ni_{10}P_{20}$ alloy. The continuous cooling transformation (CCT) diagram was constructed from solidification onset time at various linear cooling conditions with different rate. The CCT diagram suggests that the critical cooling rate for glassy solidification is about 1.5 K/s, which is in agreement with the previous calorimetric findings.

• Journal of Microbiology
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• 제38권4호
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• pp.239-244
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• 2000

The cats gene encodes the major catalase in Sreptomyces coelicolor, whose production increases upon H$_2$O$_2$treatment. Besides the previously identified primary promoter (catApl), a minor promoter (catAp2) was newly assigned by S1 nuclease mapping. The catAp2 transcript was observed transiently upon entry into the stationary phase in liquid culture and upon differentiation on solid plates, whereas the level of catApl transcription did not chance significantly during this growth transition. ThecatApl promoter was transcribed by the major vegetative RNA polymerase holoenzyme containing $\sigma$$\^$HrdB/, whereas the catAp2 was transcribed in vitro by the holoenzyme containing $\sigma$$\^$R/ that is activated under oxidative conditions. The cia-element regulating the H$_2$O$_2$-inducibility of catApl was identified within the 23 bp inverted repeat sequence located between -65 and -43 of the catApl promoter. We roamed this sequence HRE (H$_2$O$_2$-responsive Element). The distal half of the inverted repeat was more crucial for H$_2$O$_2$-dependent induction of the catApl transcript than the proximal half. HRE most likely serves as a binding site for the H$_2$O$_2$-responsive repressor CatR.

• 한국가축번식학회지
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• 제7권2호
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• pp.57-71
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• 1983

1. Diluted chicken semen can be preserved at 2 to 5$^{\circ}C$ for 24 to 48 hr with resultant fertility of greater than 90% of that of fresh semen. Turkey semen can be preserved at 10 to 15$^{\circ}C$ for 6 to 24 hr and provide economical fertility. 2. Frozen chicken semen has given variable results; a 21 to 93% fertility ranges as compared to 92 to 94% expected with fresh semen. Highest fertility levels obtained with frozen turkey semen intravaginally inseminated have been 61 and 63% using DMSO and glycerol, respectively, as cryoprotectants. 3. The use of glycerol as a cryoprotectant reauires that its concentration in semen be reduced to less than 2% either by dialysis or centrifugation after thawing and before intravaginal insemination if optimal fertility is to be obtained. 4. The temperature at which cryoprotectants are added to semen and the time allowed for equilibration are important for subsequent fertility pre- and post-freezing. 5. The type of container used for packaging the semen, freeze or cooling rates, thaw rates and level of cryoprotectant all interact in affecting cell survival. 6. Plastic freeze straws as a packaging device for semen offers the following advantages: easy to handle, require minimal storage space, offer a wide range of freeze and thaw rates, and insemination can be made directly from them upon thawing. 7. Controlled slow cooling rates of 1 to 8$^{\circ}C$/min have thus far provided the best results for cooling chicken semen throught the transition phase change (liquid to solid) or critical temperature range of ＋5 to -20 or -35$^{\circ}C$. 8. Highest fertilities have been achieved with frozen chicken semen where a slow thaw rate (2。 to 5$^{\circ}C$) has been used regardless of the freeze rate. 9. To maintain a constant high level of fertility throughout a breeding season with frozen semen, a higher absolute number of spermatozoa must be inseminated (2 to 3 times as many) as compared to fresh semen since a, pp.oximately 50% are destroyed during processing and freezing. 10. The quality of semen may vary with season and age of the male. Such changes in sperm quality could be accentuated by storage effects. Thus, the correct number of spermatozoa may very well vary during the course of a breeding period. 11. As to time of insemination, it is best to avoid inseminating chicken hens within 1-2 hr after or 3-5 hr before oviposition; and turkey hens during or 7-10 hr before oviposition. 12. The physiological receptiveness of the oviduct at the time of insemination is a very important biological factor influencing fertility levels throughout the breeding season.

• Elastomers and Composites
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• 제39권3호
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• pp.217-227
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• 2004

주사슬에 triad 메소겐 단위와 butylene terephthalate (BT) 단위를 갖는 새로운 액정 중합체를 중축합에 의해서 합성하였다. 합성된 중합체는 nematic 액정상을 보였으며 액정상으로의 전이온도는 $260^{\circ}C$를 보였다. PBT 용액에서 in-situ 중합에 의해서 제조된 TLCP/PBT 블렌드들의 특성 조사는 DSC, TGA, SEM, XRD 그리고 DMTA를 이용하여 이루어 졌다. 블렌드들은 PBT 매트릭스내에서 $0.05{\sim}0.2{\mu}m$ 사이즈를 갖는 잘 분산된 TLCP상들을 보여 주었다. TLCP 농도가 5에서 20wt%로 증가함에 따라서 블렌드내의 순수한 PBT의 ${\Delta}Hm$은 증가하였다. 이는 TLCP가 PBT 매트릭스 내에서 조핵제의 역할을 하였기 때문이다. 블렌드의 기계적 성질들은 TLCP의 농도에 의존하였는데 이 또한 TLCP가 블렌드 내에서 보강제 역할을 하였기 때문이다. 액정상과 PBT 매트릭스 상간에 좋은 계면 접착력을 보여 주었으며 in-situ 중합에 의해서 제조된 블렌드는 용융 블렌딩에 의해서 제조된 블렌드들보다 더욱더 높은 기계적 성질과 잘 분산된 TLCP 도메인들을 보여 주었다.