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Dan, Kyung-Sik,Kim, Byoung-Chul,Han, Yang-Kyoo The Polymer Society of Korea 2009 Macromolecular Research Vol.17 No.5
The side chain liquid crystal triblock copolymers (TBCs), which underwent phase transitions below their decomposition temperature, were prepared by copolymerization of poly(n-butyl acrylate) and a comonomer containing the mesogenic azobenzene group. The physical properties of TBCs in the distinctive transition temperature ranges were investigated in terms of the liquid crystal (LC) content in the copolymers. The phase transition temperatures traced optically, thermally and rheologically were well coincided one another and clearly exhibited the phase transition of smectic-nematic-isotropic with increasing temperature. In the smectic phase, increasing temperature made the liquid crystal system more elastic, but viscosity (${\eta}'$) remained almost constant. In the nematic phase, increasing temperature abruptly decreased ${\eta}'$ and G', ultimately leading to isotropic phase. Both smectic and nematic phases exhibited Bingham viscosity behavior but the former gave much greater yield stress at the same LC content.
Cho, Yong-Han,Dan, Kyung-Sik,Kim, Byoung-Chul The Korean Society of Rheology 2008 Korea-Australia rheology journal Vol.20 No.2
The rheological properties of polar solutions are very sensitive to preparative methods as well as measuring conditions. The effects of dissolution temperature on the rheological properties of the solutions of polyvinyl alcohol (PVA) in dimethyl sulfoxide were investigated over the range of dissolution temperatures $70-130^{\circ}C$. Viscosity was increased as dissolution temperature was increased. PVA solutions prepared at 120 and $130^{\circ}C$ showed Bingham behavior, which became less noticeable with decreasing dissolution temperature. The modified Cole-Cole plot of the solutions gave slope less than 2, suggesting the solutions were a heterogeneous system irrespective of optical transparency. Further, the slope was decreased with increasing dissolution temperature, indicating that the solid character got more prominent as dissolution temperature was increased. However, the relaxation time of the solutions was little dependent on dissolution temperature.
Yong Han Cho,Kyung Sik Dan,Byoung Chul Kim 한국유변학회 2008 Korea-Australia rheology journal Vol.20 No.2
The rheological properties of polar solutions are very sensitive to preparative methods as well as measuring conditions. The effects of dissolution temperature on the rheological properties of the solutions of polyvinyl alcohol (PVA) in dimethyl sulfoxide were investigated over the range of dissolution temperatures 70 - 130 ℃. Viscosity was increased as dissolution temperature was increased. PVA solutions prepared at 120 and 130℃ showed Bingham behavior, which became less noticeable with decreasing dissolution temperature. The modified Cole-Cole plot of the solutions gave slope less than 2, suggesting the solutions were a heterogeneous system irrespective of optical transparency. Further, the slope was decreased with increasing dissolution temperature, indicating that the solid character got more prominent as dissolution temperature was increased. However, the relaxation time of the solutions was little dependent on dissolution temperature.
Effects of Propylene Glycol on the Physical Properties of Poly(vinyl alcohol) Solutions and Films
Cho, Yong-Han,Kim, Byoung-Chul,Dan, Kyung-Sik The Polymer Society of Korea 2009 Macromolecular Research Vol.17 No.8
To trace the plasticizing effects of propylene glycol (PG) on poly(vinyl alcohol) (PVA), the rheological properties of PVA solutions in dimethyl sulfoxide (DMSO) and the physical properties of PVA films were discussed in terms of PG content. Both properties were closely related to the hydrogen bond breaking effects of PG The 6 and 12 wt% PVA solutions containing PG exhibited Bingham behavior, which was more noticeable at lower plasticizer content and higher polymer concentration. The 6 wt% PVA solutions containing more than 30 wt% PG showed a sudden decrease of viscosity over the frequency range of 0.08 and 0.2 rad/s. However, the 12 wt% PYA solutions showed no viscosity reduction even at a PG content up to 40 wt%. The glass transition temperature of the PVA/PG films was almost linearly decreased with increasing PG content but an abrupt reduction was observed at a plasticizer content 30 wt%, suggesting that the hydrogen bond breaking effects of PG on PVA became dominant between 20 and 30 wt%. This effect was further supported by the similar tendency of the tensile properties.
건강인의 비인강내 MRSA 보균율과 methicillin 내성 포도구균에서의 mecA와 femA 유전자의 검출
김신무 ( Shin Moo Kim ),송남경 ( Nam Kyung Song ),신상희 ( Sang Hee Shin ),정재옥 ( Jae Ok Chung ),이규식 ( Gyu Sik Lee ),김유현 ( Yoo Hyun Kim ),오재세 ( Jae Se Oh ),차정단 ( Chong Dan Cha ),문상은 ( Sang Eun Moon ),김강주 ( Kang 대한임상검사과학회 1999 대한임상검사과학회지(KJCLS) Vol.31 No.2
Nasal carriage rate and methici11in resistance of Staphνlococcus aureus in healthy adults are not well known in Korea. In this study, nasal specimens collected from college students during March to June, 1998 were cultured for S. aureus and the susceptibility of the isolates was determined by agar di1ution method and the relationship of methici11in resistance level and 서 -lactamase production was analyzed. Also, presence of mecA and femA was detected from the isolates by PCR. Isolation rate of S. aureus from the 339 subjects was 20%, and the rate was higher in female (21%) than in male (12%). Among the isolates, 2.1% were MRSAs. Against MSSA, clindamycin, fusidic acid, mupirocin and vancomycin were most active (MICso50 ≤1 μgjml and MIC90 2 μgj ml) and the resistancerates to cephalothin, eηthromycin , gentamicin and tetracyc1ine 20% and to chloramphenicol and penicillin G, were 73%. The MIC range of oxacillin against MRSA was 16-≥ 128 μgj ml, while MICso and MIC90 were 32 μgjml and 128 μgjml, respectively. Fusidic acid, mupirocin and vancomycin were most active against MRSA (both MICso and MIC90 were 1 μgjml). Resistance rate of MRSA to c1indamycin was 18%, but they were ~59% to 6 other antibiotics. ß -lactamase-producing strains were more prevalent among the low level methicillin-resistant isolates. mecA was detected from all MRSAs, but none from MSSAs. femA was detected from all of the MRSAs and MSSAs and none in coagulase-negative staphylococcus. In conc1usion, hea1thy adults occasiona11y carη MRSAs, but they may have acquired them in hospitals. Fusidic acid and vancomycin should be useful to treat MRSA infection, while mupirocin should be useful to control nasal carriage. me때 and femA may be used to differentiate MRSA from MSSA, and S. aureus from coagulsae-negative staphylococcus, respectively.
Evaluation of Mosquito Repellents Prepared with Natural Plants
Seong Ik Park,Jeong Ju Park,Dan Bi Kim,Na Young Moon,Ji Yoon Shin,Sun Kyung Cha,Sa Ra Kim,Jong-Sik Kim,Dong Cheol Shon 한국식품영양과학회 2021 한국식품영양과학회 학술대회발표집 Vol.2021 No.10
In this study, we prepared 5 different kinds of the mosquito repellents using methanol extracts of natural plants and evaluated their effective dose and duration time as a mosquito repellent against to Aedes albopictus in nude mice model. And also, the volatile flavor components of natural plants were analyzed. The effective dose was the highest in Nepeta cataria. Among mosquito repellents prepared with natural plant extracts, repellents prepared with Nepeta cataria, Actinidia polygama, and Artemisia Linne extracts were the most effective for duration time. As a result of analyzing the volatile flavor components of each natural plant, a total of 28 components in Mentha suaveolens and 19 components in Actinidia polygama were detected. A total of 27 components in Artemisia Linne, a total of 26 components in Nepeta cataria, and a total of 19 components in Taraxacum platycarpum were detected. Especially, nepetalactone was identified with one of volatile flavor components of Nepeta cataria. Overall, the results indicate that 5 kinds of natural plants have efficacy as a mosquito repellent and natural plants can be useful resources for developing natural mosquito repellents.