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중합방법에 따른 레진과 콤포머의 FTIR을 이용한 중합도 측정
배지명,김광만,김경남,김호철 대한치과기재학회 1998 대한치과재료학회지 Vol.25 No.2
The degree of conversion(DC) of composite resins are closely correlated with the mechanical properties. Fourier Transform Infrared(FTIR) Analysis is currently used to determine the DC for many advantages. In this study, three composite resins ; Aelitefil(AF; U.S.A.), VeridonFil-Photo(VF; Korea), Z-100(ZH; U.S.A.) and two compomers; Compoglass(CG; Lichtenstein), Dyract(DR; Germany) were used to make specimens with thickness of 0.1 ±0.02㎜. After one group of samples were light-cured for 20 second and those of the other group were Argon laser-cured with 0.23W continuous mode for 5 second, all the samples were kept dry at 37℃ for 24h. From the spectra acquired on an FTIR spectrometer(Bruker IFS 88, Germany), the aliphatic C=C absorbance peak at 1640㎝-¹ and the N-H reference peak at 3380㎝-¹ were measured using a standard baseline technique. The ratios of absorbance of C=C/N-H before polymerization to that of C=C/N-H after polymerization were used to calculate the residual C=C bonds. The results were as follows ; 1. The descending order of the degree of conversion was VF>AF>ZH, CG>DR in light cured group(p<0.05). 2. The descending order of the degree of conversion was VF>AF>CG>ZH, DR in laser cured group(p<0.05). 3. The degree of conversion of light-cured group was higher than laser-cured one only in ZH and not significantly different in other materials(p<0.05). In conclusion, the argon laser showed efficient curing capacity compared with light curing unit except ZH and the degree of conversion of compomer was inclined to be lower than that of composite resin.
배지명,김광만,김경남 대한치과기재학회 1997 대한치과재료학회지 Vol.24 No.1
The colors of composite resins are changed with time due to intrinsic and extrinsic factors. This study was aimed to characterize the effect of each factor. Specimens(dia.15mm×thic.2mm) were prepared from Z-100(ZH), Aelitefil(AF), Photo Clearfil Bright(PF), Bisfil-2B(BF) and Clearfil FⅡ(CF). One group of samples was exposed to a xenon arc of 1,000W with a total dose of 410kJ/㎡ for 228hrs in a weathering chamber and then immersed in filtered coffee for 7 days. The other group of samples was immersed in coffee first and then exposed to the xenon arc. The color were measured before and after each treatment with a spectrophotometr according to the C.I.E. L*a*b* color system. Ra values of surface roughness, contact angles and SEM observations before and after accelerated aging were compared. Results were as follows : 1. In the accelerated aging and subsequent staining group, the color changes of AF and PF after aging and all materials after subsequent staining, were greater than the upper limit of acceptibility(ΔE=3.3). 2. In the staining and subsequent accelerated aging group, the color changes of BF after staining and AF and PF after subsequent aging, were greater than the upper limit of acceptibility. 3. AF and PF were sensitive to intrinsic factors, BF to extrinsic factors, and extrinsic factors were activated by accelerated aging in ZH and, CF. 4. The color changes by accelerated aging showed consistent results regardles of pre-staining while those by staining were affected by pre-aging. 5. Ra values of roughness after aging did not change significantly and had no relation to the color changes after aging and subsequent staining(P<0.05). 6. Though the contact angles of AF, BF and CF after aging were reduced significantly, they had no relation to the color changes after aging and subsequent staining(P<0.05). It was concluded that each of the discoloration features by accelerated aging and staining was detectable and could be clinically used by considering the characteristics of the materials which are sensitive to intrinsic and/or extrinsic discoloration factors.
Identification of an Intermediate State as Spermatogonial Stem Cells Reprogram to Multipotent Cells
Kim, Hyung-Joon,Lee, Hyun-Jung,Lim, Jung-Jin,Kwak, Ki-Hoon,Kim, Jong-Soo,Kim, Ji-Hoon,Han, Yong-Mahn,Kim, Kye-Seong,Lee, Dong-Ryul Korean Society for Molecular and Cellular Biology 2010 Molecules and cells Vol.29 No.5
The aim of this study was to understand the mechanisms that allow mSSC lines to be established from SSCs. Small, multilayer clumps of SSCs formed during two to four weeks of in vitro culture and were then transferred to MEF feeders. Small, round, monolayer colonies containing cells destined to convert to mSSCs, designated as intermediate state SSCs (iSSCs), first appeared after two to three passages. During an additional nine passages (47-54 days) under the same culture conditions, iSSCs slowly proliferated and maintained their morphology. Ultimately, a cell type with an ES-like morphology (mSSC) appeared from the iSSC colonies, and two mSSC cell lines were established. The mSSCs had a high proliferative potential in serum-free ES culture medium and have been successfully maintained since their first establishment (> 12 months). We also compared the specific characteristics of iSSCs with those of SSCs and mSSCs using immunocytochemistry, FACS, RT-PCR, DNA methylation, and miRNA analyses. The results suggest that iSSCs represent a morphologically distinct intermediate state with characteristic expression patterns of pluripotency-related genes and miRNAs that arise during the conversion of SSCs into mSSCs. Our results suggest that iSSCs could be a useful model for evaluating and understanding the initiation mechanisms of cell reprogramming.