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        검색결과 560

        403.
        2001.01 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Composite adsorbents were prepared by mixing water plant sludge with phenolic resin having the ratio of 1 : 1, 1 : 2, and 1 : 3 respectively, curing from 100℃ to 170℃ under N2 atmosphere, and then activating with N2 at 700℃. Thermal property, specific surface area and morphology of the composite adsorbents as well as their precursors were measured by TGA, BET and SEM respectively. Removal efficiency of the composite adsorbents to NH4+ and TOC was compared with those of commercial zeolite and activated carbon. The adsorbents presented very promising TOC removal efficiency of 98%, which was identical level to that of commercial activated carbon while they displayed removal efficiency, only 32%, of NH4+. Therefore, this composite adsorbent considered as the alternative material of commercial activated carbon, used as an expensive removal agent of organic substances and THM in water treatment plant and it also suggested a possibility of practical application in other processes.
        3,000원
        404.
        2000.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Naphtha cracking bottom oil was reformed with heat treatment and then spun at 310℃. These pitch-based carbon fibers were carbonized at 1000℃ after oxidation at 280℃, for 90 min. These fibers were chemically activated with molar ratio of KOH/CF (1 : 1) at different temperatures (250~900℃) for 1 hr. The process of activation was characterized with DTA, TGA, BET surface area and pore size distribution. The activation of fibers by KOH was performed by several process. One is the reduction process that carbon fiber was reacted with K2O produced from dehydration process above 400℃. The other is the process that K2CO3 was directly reacted with carbon fiber. At 800℃, the activation was performed by catalyzed mechanism that K2O was obtained from the reaction of metal potassium with CO2, then was changed to K2CO3. At 870℃, the activation was also observed that activation mechanism was promoted by metal catalyst with CO2 from decomposition of K2CO3. The specific surface area of prepared activated carbon fibers was dependent on the activation mechanism. The specific surface area was in the range of 1519~2000 cm3/g and was the largest prepared at 870℃. The pores developed were mostly micropores which was very narrow and uniform. The total pore volume was 0.58~0.77 cm3/g.
        4,000원
        407.
        2000.06 KCI 등재 구독 인증기관 무료, 개인회원 유료
        There appeared enhancements of the conversion of methane by adding a small amount of CO in the aromatization reaction of methane using the Mo-zeolite catalyst. In case of adding CO2, CO2 changed to CO first, and then the conversion reaction occurred. It was observed by using isotopes as reactants that CO is related to the aromatization reaction of methane.
        4,000원
        408.
        2000.03 KCI 등재 구독 인증기관 무료, 개인회원 유료
        For decompose carbon dioxide, manganese oxide was synthesized with 0.25M-MnSO4·nH2O and 0.5M-NaOH by coprecipitation. We made magnetite deoxidized manganese oxide by hydrogen reduction for 1hour at 330℃. We investigated characteristics of catalyst, hydrogen reduction degree and decomposition rate of carbon dioxide. The structure of the hausmannite certified spinel type. The specific surface area of synthesized hausmannite and deoxidized hausmannite were 22.36m2/g, 33.56m2/g respectively. The decomposition rate of CO2 of deoxidized hausmannite was 57%.
        4,000원
        411.
        1998.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Platelet activation is originated by the intracellular or/and extracellular Ca^(2+). Agonist-induced Ca^(2+) entry through a plasma-membrane pathway has been reported repeatedly, but the mechanisms has proven harder to elucidate. Recently, a number of natural products have been isolated from medicinal plants and marine organisms and have proved to be useful chemical tools for resolving the mechanism of cellular functions. In an attempt to understand the mechanism of platelet activation in Bupleuri Radix, we have studied some aspects of the isolation of active components and their dependence of external Ca^(2+) on platelet activation. Acetone extract of Bupleuri Radix has the most activity on platelet activation and it's active components were identified as saikosaponin a and d. Their optimal concentration was respectively 20 ug/ml and 5 ug/ml and their platelet activation was not dependent on external Ca^(2+), whereas optimal concentration of each agonist was arachidonic acid (10 uM), collagen (10 ug/ml), thrombin (0.1 unit/ml), PAF (5 uM), PMA (5 uM), ionophore A23187 (2 uM) and their dependence of external Ca^(2+) on platelet activation appeared to thrombin$gt;collagen≥PAF$gt;PMA$gt;arachdonic acid$gt;ionophore A23187. These results suggest that saikosaponin is different from each agonists in the dependence of external Ca^(2+) on platelet activation.
        4,000원
        414.
        1998.10 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Unilateral neglect is a common neurological syndrome resulting from right-hemisphere strokes and has important prognostic value for functional outcome. The purpose of this study is to investigate the effectiveness of conventional and neurologically based treatment. As a result, right-himispheric activation approaches may reduce neglect. and may be more beneficial than conventional approach. For more beneficial effects, conventional approach combined with right-hemispheric activation approaches and cognitive skills remediation program.
        4,000원
        415.
        1998.04 KCI 등재 구독 인증기관 무료, 개인회원 유료
        This study was to determine the effect of ionomycin and 6-dimethylaminopurine (6-DMAP) and/or elcetrical stimulation on the oocyte activation and production of rabbit nuclear transplant embryos. The oocytes were collected from the oviduct of superovulated rabbits at 14 h post hCG injection and cultured in TCM-199 containing 10% FBS until 19 h post hCG injection. To determine the optimum concentration and exposure time of 6-DMAP, some oocytes were activated with 5 M ionomycin for 5 min and then in 2.0 mM 6-DMAP for 0.5 to 3.0 h, or in 1.0 to 3.0 mM 6-DMAP for 2.0 h. Other control oocytes were stimulated electrically(3X, 1.25 kV/cm, 60 sec) in 0.3 M mannitol solution supplemented with 100 M CaCl and MgCl. The nuclear donor embryos of 8-cell stage were synchronized to G phase of 16-cell stage, and the recipient cytoplasms were obtained from removal of the first polar body and a portion of membrane bound cytoplasm of the oocytes collected at 15 h post hCG injection. A separated blastomere was injected into the perivitelline space of the enucleated oocytes. The oocytes injected with nucleus were cultured until 19 h post hCG and then electrofused and activated by electrical stimulation with or without ionomycin and 6-DMAP. These nuclear transplant embryos were cultured in TCM-199 containing 10% FBS in 39˚C, 5% CO2 incubator for 120 h. For the oncytes activated parthenogenetically with electrical stimulation with or with-out ionomycin and the various concentration of exposure time of 6-DMAP, the highest cleavage(92.3%) and development to blastocyst stage(41.0%) were resulted from the oocytes activated by ionomycin and 2.0 mM 6-DMAP for 2.0 h, which were found to be significantly(P<0.05) higher than the cleavage(45.2%) and developement to blastocyst stage(14.3%) from the oocytes activated with electrical stimulation. The significantly(P<0.05) more oocytes(71.4%) developed to 4 cell stage at 24 h post activation by ionomycin and 6-DMAP than those by electrical stimulation(18.9%). For the nuclear transplant embryos, the cleavage rate was similarly high in oocyte activation by electrical stimulation with(79.4%) or without ionomycin and 6-DMAP(70.5%). However, the embryo development to blastocyst stage was significantly(P<0.05) higher in oocyte activation by electrical stimulation with ionomycin and 6-DMAP(44.4%) than by electrical stimulation only(25.0%). The significantly(P<0.05) more nuclear transplant embryos(45.6%) developed to 4 cell stage at 18 h post activation by electrical stimulation with ionomycin and 6-DMAP than those by electrical stimulation only(10.6%). These results indicated that the supplemental oocyte activation by ionomycin and 6-DMAP with electrical stimulation enhanced and accelerated the preimplanted in vitro development of the rabbit nuclear transplant embryos.
        4,000원
        416.
        1998.02 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        CO2gas중에서 산화된 활성탄소섬유를 77K에서 질소흡착에 의해 흡착등온곡선을 구하였다. 미세공부피와 외부표면적은 t-법으로 구하였으며, 평균기공크기와 기공분포는 Dubinin-Astakhov법으로 구하여 기공발당과정을 고찰하였다. 산화반응 초기(약 40% burn-off까지)에 섬유내부에 발달하는 미세공은 burn-off가 40%를 넘으면 서서히 큰 미세공으로 성장하며, burn-off가 약 60%이상되면 미세기공은 확대 또는 합체되어 점차 중기공으로 성장하는 것으로 관찰되었다. 또한 고온산화반응으로 발달한 기공은 저온에서 생성된 기공보다 크다.
        4,000원
        417.
        1998.02 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        등방성 피치계 탄소섬유를 Co2gas중에서 등온산화시켜 활성탄소섬유를 제조하였다. 산화된 섬유의 비표면적은 BET장치를 이용하여 측정하였다. Burn-off가 증가하여도 반응속도는 크게 감소하지 않았으며, 800˚C와 900˚C에서 산화된 섬유의 비표면적은 40%-60%의 burn-off에서 급격히 증가하다가 60%이상에서 감소하였다. 1100˚C에서 산화된 시편은 40%이상 burn-off되어도 비표면적은 크게 증가하지 않고 60%를 지나서도 계속해서 표면적이 증가하는 현상을 나타내었다. 1000˚C에서 60.4%의 burn-off가 일어난 산화섬유의 비표면적은 3,614m2/g로 가장 큰 값이 얻어졌다. 등방성 탄소섬유는 미세한 흑연결정립들이 무질서한 배향을 하고 있으며, 미세기공벽으로 작용할 수 있는 결정립층이 많기 때문에 활성탄소섬유 제조를 위한 원료로 적합하다고 판단된다.
        4,000원
        418.
        1997.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        In order to investigate the trace metals in Korean foods, the contents of Magnesium, Zinc, Manganese, Molybdenum and Selenium are studied in this paper. As show in the Table 1; a total of 250 samples of 25 species were analyzed by neutron activation analysis. The results obtained were as follows; 1. The overall ranges and mean (mg/100 g) were; Mg, 12.212-151.346 (55.164); Zn, 0.045-38.180 (2.473); Mn, 0.003-0.796 (0.225); Mo, ND-0.035 (0.007); Se, ND-0.069 (0.016). 2. The levels of all metals except Mo in shell fishes were high and the level of Mo in spices .was higher than that in other foods. 3. The levels of Zn and Mo in oyster were higher than another spcies.
        4,000원
        420.
        1997.09 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        6,000원