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Hydroxyapatite 비드에 부착한 [^3H] - 표지된 세균의 씬틸레이션 측정에 관한 연구
이시영,이장희,최선진 대한구강생물학회 1989 International Journal of Oral Biology Vol.13 No.2
This study investigated the possible involvement of sample self absorption when [^3H]-labeled Streptococcus mutans cells that adhered to spheroidal hydroxyapatite beads were counted by scintillation spectrophotometer. To determine whether or not the beads cause self absorption of the energy of β particles, the beads-adhered bacterial cells were removed and counted alone. Two procedures were employed to remove bacterial cells from the beads. First, bacteria-adhered beads were dissolved with 0.33 N HCl, the dissolved solution was filtered to collect bacteria, and the filter was counted. Second, the bacteria adhered to beads were desorbed with potassium phosphate buffer, bacteria were collected on filter, and the filter was counted. Whatman glass microfibre filters GF/A and GF/F were used and filtration was carried out either with suction or without suction (i.e., by blotting). When the radioactivity was counted by blotting on GF/F filter, the count rate was increased to 280% in HA and 240% in SHA as compared with CPM of the control. Count rate of the bacteria was lower when filtered with suction than without suction. However, there was no difference in count rate when intact cell suspensions filtered either with suction of without were counted. Though HCl-treated cells were observed as intact by Gram staining, the above results seem to indicate that cells were damaged when treated with HCl, thus some of the DNA leaked out of the cells when filtered with suction. When the buffer-desorbed bacterial cells were filtered by blotting and counted, the count rate was increased to 290% in HA and 350% in SHA as compared with CPM of the control. The results of the present study mean that a high count rate is obtainable when the sample self absorption is removed. Therefore, the sample self absorption should be considered in order to measure the correct number of bacteria adhered to HA beads.
Choe, Young-Son,Kim, Min-Young,Kim, Won-Ho The Polymer Society of Korea 2003 Macromolecular Research Vol.11 No.4
The isothermal cure reactions of blends of epoxy (DGEBA, diglycidyl ether of bisphenol A)/anhydride resin with polyamide copolymer (poly(dimmer acid-co-alkyl polyamine)) or PEI were studied using differential scanning calorimetry (DSC). Rheological measurements have been made to investigate the viscosity and mechanical relaxation behavior of the blends. The reaction rate and the final cure conversion were decreased with increasing the amount of thermoplastics in the blends. Lower values of final cure conversions in the epoxy/thermoplastic blends indicate that thermoplastics hinder the cure reaction between the epoxy and the curing agent. Complete miscibility was observed in the uncured blends of epoxy/thermoplastics up to $120^{\circ}C$ but phase separations occurred in the early stages of the curing process at higher temperatures than $120^{\circ}C$. According to the rheological measurement results, a rise of G' and G" at the onset of phase separation is seen. A rise of G' and G" is not observed for neat epoxy system since no phase separation is seen during cure reaction. At the onset of phase separation the rheological behavior was influenced by the amount of thermoplastics in the epoxy/thermoplastic blends, and the onset of phase separation can be detected by rheological measurements.