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        검색결과 9,514

        5941.
        2008.03 구독 인증기관 무료, 개인회원 유료
        We have previously produced transgenic (TG) mice expressing the human lactoferrin (hLF), interleukin-10 (hIL-10), and thrombopoietin (hTPO) proteins in the milk. In this study, we examined whether simple crossbreeding between two kids of a single transgenic mouse can produce double transgenics co-expressing two human proteins.. The hLF male, and the hIL-10 male were crossbred with the hIL-10 and hTPO females, and the hTPO female, respectively. PCR analysis for genotyping showed 32%, 23% and 24% double transgenic rates for hLF/hIL-10, hLF/hTPO, and hIL-10/hTPO transgenes, respectively. We analyzed the expression levels of the human proteins from double transgenic mice and compared those with their single transgenic siblings. All double transgenic co-expressed two human proteins at comparable levels to singles', unless hTPO was not co-expressed: for hLF, 1.1 mg/ml in hLF/hIL-10, whereas 0.5 mg/ml in hLF/hTPO; for hIL-10, 4.1 mg/ml in hIL-10/hLF, whereas 1.4 mg/ml in hIL-10/hTPO. Ihe downregulation of hTPO to half level of singles' was observed in double transgenic mice. The possible reason why hTPO co-expressed might lead to down-regulation of another human protein was discussed. These results suggested that double transgenic generated by crossbreeding between two singles' could be useful system for bioreactor.
        4,000원
        5942.
        2008.03 구독 인증기관 무료, 개인회원 유료
        Most studies on transgenic bioreactors have focused on expression levels of interest genes. In this study we examined whether transgenic bioreactors would inherit expression level of the Oansgene to long-term generations independently of transgene sources. We employed three transgenic mice, which were separately reported, carrying different transgenes and copy numbers, 27 kb of hLF and 22 kb of hIL-10 genomic sequences, and 1.3 kb of hTPO cDNA, respectively. Three females of the transgenic lineages crossbred with a wild-type male up to 20 generations to test transgenic frequencies of their progenies and to determine expression levels of the transgenes. Ultimately, transmission rates of kLF, hIL-10, and hTPO were 64.3+-7.0, 59.3+-9.8, and 56.1+-9.7, respectively, appeared following Mendelian pattern of inheritance. Notably, we found that levels of expressions of hLF, hIL-10, and hTPO in milk were sustained to high numbers of generations. No transgene silencing of expression was observed in every generations of all transgenic mice. In conclusion, we suggest that once established animal bioreactors could consistently transmit the transgene to continual generations, without loss of expressional activity, independently of transgene sources.
        4,000원
        5943.
        2008.02 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        The present work was performed to investigate the effect of coiling temperature on the annealed texture in Cu/Nb-added ultra-low-carbon steels. The ultra-low-carbon steels were coiled at 650 and 720˚C, respectively. The result showed that the Cu-added ultra-low-carbon steel at a low coiling temperature produced a desirable annealed texture related to good formability. On the other hand, Nb-added ultra-low-carbon steel at a high coiling temperature also produced a desirable texture. This is attributed to the effect of Nb, which retards recrystallization during the coiling process.
        3,000원
        5944.
        2008.02 KCI 등재 구독 인증기관 무료, 개인회원 유료
        텐세그리티 구조물의 설계를 위한 다목적 최적화 기법이 제시되었다. 구조물의 기하가 먼저 주어지며, 설계변수는 부재력이다. 목적함수는 최대 강성매트릭스에 대한 최저 고유치와 찾고자 하는 목표값으로부터 가장 근접하게 일치하는 부재력이다. 복수의 목적함수 문제가 구속조건을 도입하여 일련의 단일 목적함수 문제로 전환되었다. 본 논문의 타당성을 알아보기 위해 텐세그리티 그리드에 대한 최적해를 구해 보았다.
        4,000원
        5945.
        2008.02 구독 인증기관 무료, 개인회원 유료
        This paper describes the traditional Ondol medical care, the specific combination of ancient and contemporary examples to be articulated. As a traditional Korean culture, to be extracted from the historical perspective, it described the relationship and origins between them, From a health perspective, in accordance with the logic and pharmacologyit introduced Ondol as the important principle of health care equipment. The modern architecture of some common harmful to the body, from the perspective of Ondol, it should be improved and based on scientific proof to the theory.
        4,000원
        5946.
        2007.12 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        The texture and microstructure in Cu/Nb added ultra low carbon steels through the different thickness layer were studied after hot rolling. It was found that the two ultra low carbon steels all show the inhomogeneity of hot rolling texture and the Cu-added ultra low carbon steel was far more inhomogeneous than Nb-added one. In the center layer, the strong α fibre, γ fibre textures and the shear textures including 001<110>, 111<112> were founded. Near the surface, the α fibre texture and the orientation texture caused by a typical plane-strain deformation condition of bcc metals were observed.
        3,000원
        5947.
        2007.12 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        5,800원
        5948.
        2007.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        This study was undertaken to determine the normal appearance of the postpartum uterine involution. Postpartum changes in uterine shape, architecture, echogenicity and diameter were monitored with ultrasonography in 8 Miniature Schnauzer dogs. Vaginal discharge was observed visually during the 3 weeks of postpartum. A large amount of viscous dark green discharge changed progressively to a small amount of transparent discharge. In the uterine shape, the transverse images were crescent or polygonal at the beginning, but became circular after 16 days. At postpartum day 24, the longitudinal images of placental and interplacental sites were similar to each other The echogenicity of uterine structure was clearly distinguishable among the hyperechoic serous membrane, hypochoic myometrium, hyperechoic endometrium, and anechoic uterine contents during the first week postpartum, but afterward the interluminal boundaries and echogenicity became obscure gradually. In addition, the anechoic substance of the endometrial cavity was not observed after postpartum day 28. In the uterine diameter, the diameter of placental sites decreased markedly from 24 mm at the first day postpartum to 13 mm at day 7, and the diameter of interplacental sites decreased from 15 mm at postpartum day 1 to 10 mm at day 7. At postpartum day 65, the uterus (6.4 mm) changed little and had a uniform homogenous echo, and thus it was confirmed that uterine involution was completed at that time in Miniature Schnauzer dogs.
        4,000원
        5949.
        2007.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Polypropylene (PP) composites with wood flour/wax/coupling agent were manufactured by melt compounding and injection molding. The influence of wood flour(WF), wax, and coupling agent on the mechanical and thermal properties of the composites was investigated. The addition of wood flour to neat PP has the higher tensile modulus and strength compared with neat PP. The presence of wax also improved the tensile modulus. At the same loading of PP and WF, the addition of coupling agent highly decreased the tensile modulus, and increased the tensile strength. From thermogravimetric analysis (TGA), the addition of wax improved the thermal stability of the composites in the later stages of degradation. The presence of MAPP and wood flour in turn decreased thermal stabilities of composites. From differential scanning calorimetry analysis (DSC), neither the loading of wax. nor the presence of MAPP has shown significant effect on the thermal transition of composites.
        4,200원
        5950.
        2007.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        In this study, graphite composites were fabricated by warm press molding method to realize commercialization of PEM fuel cells. Graphite composites have been considered as alternative economic materials for bipolar plate of PEM fuel cells. Graphite powder that enables to provide electrical conductivity was selected as the main substance. The graphite powder was mixed with phenolic resin and the mixture was pressed using a warm press method. First of all, the graphite powder was pulverized with a ball mill for the dense packing of composite. As the ball milling time increases, the average size of particles decreases and the size distribution becomes narrow. This allows for improvement of the uniformity of graphite composite. However, the surface electrical resistivity of graphite composite increases as the ball milling time increases. It is due to that graphite particles with amorphous phase are generated on the surface due to the friction and collision of particles during pulverizing. We found that the contact electrical resistivity of graphite particles increases as the particle size decreases. The contact electrical resistivity of graphite powders was reduced due to high molding pressure by warm press molding. This leads to improvement of the mechanical properties of graphite composite. Hydrogen gas impermeability was measured with the graphite composite, showing a possibility of the application for bipolar plate in fuel cell. And, I-V curves of the graphite composite bipolar plate exhibit a similar performance to the graphite bipolar plate.
        4,000원
        5951.
        2007.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        In the present study, electrospun PAN precursor webs and the stabilized and carbonized nanofiber webs processed under different heat-treatment conditions were characterized by means of weight loss measurement, elemental analysis, scanning electron microscopy (SEM), attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR), differential scanning calorimetry (DSC), thermogravimentric analysis (TGA), and X-ray diffraction (XRD) analysis. The result indicated that stabilization and carbonization processes with different temperatures and heating rates significantly influenced the chemical and morphological characteristics as well as the thermal properties of the stabilized and then subsequently carbonized nanofiber webs from PAN precursor webs. It was noted that the filament diameter and the carbon content of a carbonized nanofiber web as well as its weight change may be effectively monitored by controlling both stabilization and carbonization processes.
        4,000원
        5952.
        2007.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Poly(vinyl alcohol-co-ethylene) (PVA-co-PE)와 poly(styrene sulfonic acid-co-maleic acid) (PSSA-co-PMA)을 고분자 블렌딩 방법으로 50 : 50의 무게비율로써 수소이온 전도성 가교형 전해질막을 제조하였다. PSSA와 PMA이 3 : 1과 1 : 1의 몰 구성비로 되이 있는 두 가지 종류의 PSSA-co-PMA 고분자를 수소이온 전도성 고분자로 사용하였으며, PVA-co-PE 고분자는 에틸렌의 함량이 0, 27 그리고 44 mol%인 고분자를 사용하였다. 전해질 막은 PVA의 히드록실 그룹과 PMA의 카르복시릭 그룹 사이의 에스테르화 반응을 통한 열가교를 통해 제조하였고, FT-IR을 통하여 이를 확인하였다. PSSA-co-PMA의 몰비율이 3 : 1로 구성되어 제조된 전해질막은 몰비율 1 : 1로 구성되어 제조된 막보다 더 낮은 이온교환용량과 더 높은 함수율, 수소이온 전도도를 나타내었다. 또한, 전해질막에서 PE의 함량이 증가할수록 이온교환용량, 함수율, 수소이온 전도도가 계속해서 감소하는 경향성을 보였다. 전해질막의 이러한 물성들은 술폰산기의 함량과 친수성, 막의 가교구조 사이의 경쟁적인 효과로써 설명하였다.
        4,000원
        5953.
        2007.12 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        본 연구에서는 핵폐기물 매립장의 인공 방벽으로 사용되는 시멘트 물질들과 주변 지하수 반응 결과로 형성되는 강알칼리성 지하수와 주변 암과의 반응을 통해 변화되는 지하수 특성을 지구화학 모델링을 통해 예측하고자 하였다. 연구 결과 시멘트 수화반응을 통해서 pH는 13.3를 나타내었으며 이때 생성되는 광물들은 Brucite, Katoite, Calcium Silicate Hydrate(CSH 1.1), Ettringite, Hematitie, Portlandite였다. 이들 광물들과 경주 지역에서 채취된 지하수의 반응 모델링에서는 지하수의 pH가 12.4로 예측되었다. 이러한 강알칼리성 지하수와 주변 화강암과의 반응은 년 동안 반응속도 모델링을 통해 모사하였다. 그 결과 지하수의 최종 pH는 11.2였으며 pH는 규산염 광물과 CSH 광물들의 용해 침전에 의해 조절되고 있었다. 또한 지하수 수질도 이들 광물들과 점토광물 및 산화광물들의 용해 침전에 의해 결정되고 있었다. 본 연구 결과는 장기간 동안의 강알칼리성 지하수와 주변 암과의 반응 모델링을 통해 지구화학 및 수질 변화를 예측함으로서 인공 방벽의 안정성 평가에 기여할 수 있을 것으로 판단된다.
        4,000원
        5954.
        2007.12 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        RI 폐기물 내에 있는 낮은 방사능의 요오드의 함량을 결정하기 위해 산분해법과 BPGe 감마 선분광계를 이용하는 방법이 개발되었다. 분석에 앞서 모의시료인 제염지 내에 이 일정량 첨가되었으며, 100 mL의 0.4 N 와 100 mL의 9 M , 10 mL의 30% , 1 mL의 를 넣고 산분해과정을 거치면서 증류된 용액을 응축하여 포집하였다. 의 용매추출에 의한 화학 분리과정을 거친 후 를 첨가해서 얻은 AgI 침전물을 여과하고 건조하여 측정하였다. 산분해 과정, 화학 분리과정, 여과 및 침전과정 등 세 단계로 나눠 회수율을 측정한 결과, 각각 94% 이상의 회수율을 나타냈으며, 본 연구의 측정조건에서 최소검출방사능은 0.6 Bq/g이었다.
        4,000원
        5955.
        2007.12 구독 인증기관 무료, 개인회원 유료
        Human embryonic stem (ES) cells are derived from the inner cell mass of the preimplantation embryo and have the capacity to differentiate into various types of cells in the body. Hence, these cells may potentially be an indefinite source of cells for cell therapy in various degenerative diseases including neuronal disorders. For clinical applications of human ES cells, directed differentiation of these cells would be necessary. The objective of this study is to develop the culture condition for the expansion of neural precursor cells derived from human ES cells. Human ES cells were able to differentiate into neural precursor cells upon a stepwise culture condition. Neural precursor cells were propagated up to 5000-fold in cell numbers over 12-week period of culture and evaluated for their characteristics. Expressions of sox1 and pax6 transcripts were dramatically up-regulated along the differentiation stages by RT-PCR analysis. In contrast, expressions of oct4 and nanog transcripts were completely disappeared in neural precursor cells. Expressions of nestin, pax6 and sox1 were also confirmed in neural precursor cells by immunocytochemical analysis. Upon differentiation, the expanded neural precursor cells differentiated into neurons, astrocytes, and oligodendrocytes. In immunocytochemical analysis, expressions of type III β-tubulin and MAP2ab were observed. Presence of astrocytes and oligodendrocytes were also confirmed by expressions of GFAP and O4, respectively. Results of this study demonstrate the feasibility of long-term expansion of human ES cell-derived neural precursor cells in vitro, which can be a potential source of the cells for the treatment of neurodegenerative disorders.
        4,000원
        5956.
        2007.12 구독 인증기관 무료, 개인회원 유료
        The objective of this study was to determine the effect of administration of Prostaglandin F2α (PGF2α) on semen collection training and semen characteristics in sexually inexperienced boars. Boars were moved individually to a semen collection pen and were trained to mount dummy sow. During the first and second semen collection secessions, 4 out of 17 boars and 4 out of remaining 13 boars allowed collection of semen. The 9 boars that failed semen collection from first 2 attempts received immediately 15 mg of PGF2α i.m. (intramuscular injection) upon entering the collection pen for semen collection resulted in successful semen collection from all 9 boars. Total numbers of spermatozoa were higher in PGF2α treated boars but there was no significant difference in % motility kinematics characteristics between control and PGF2α treated groups during 72 hr period. Overall, administration of PGF2α in sexually inexperienced boars increased the sex drive and facilitated the mounting activity to the dummy sow for semen collection.
        3,000원
        5957.
        2007.12 구독 인증기관 무료, 개인회원 유료
        This study was conducted to examine the mRNA expression of apoptosis-related and imprinted genes and methylation pattern of the differentially methylated region (DMR) of H19 gene in day 35 of SCNT pig fetuses. The day 35 of natural mating (control) or cloned (clone) pig fetuses were recovered from uterus. Endometrium from dam and liver from fetus were obtained, respectively. mRNA expression was evaluated by real-time PCR and methylation pattern was analyzed by bisulfite sequencing method. The Bcl-2 mRNA expression in clone was significantly lower than that of control (p<0.05). The mRNA expression of H19 gene in both endometrium and liver was significantly higher in clone than that of control, respectively (p<0.05). The level of IGF-2 mRNA in liver of clone was significantly lower than that of control (p<0.05), whereas the mRNA expression of IGF2-R gene in liver of clone was significantly higher than that of control (p<0.05). The DMR of H19 was lower methylation pattern in clone than that of control. These results suggest that the aberrant mRNA expression of apoptosis-related and imprinted genes and the lower DMR methylation pattern of imprinted gene may be closely related to the inadequate fetal development of cloned fetus.
        4,000원
        5958.
        2007.12 구독 인증기관 무료, 개인회원 유료
        Embryonic stem (ES) cells are known to have an infinite proliferation and pluripotency that are associated with complex processes. The objective of this study was to examine expression of genes differentially regulated during differentiation of human ES cells by suppression subtractive hybridization (SSH). Human ES cells were induced to differentiate into neural precursor cells via embryoid body. Neural precursor cells were isolated physically based on morphological criteria. Immunocytochemical analysis showed expression of pax6 in neural precursor cells, confirming that the isolated cells were neural precursor cells. Undifferentiated human ES cells and neural precursor cells were subject to the SSH. TPX2 (Targeting Protein for Xklp2 (Xenopus centrosomal kinesin-like protein 2)) was identified, cloned and analyzed during differentiation of human ES cells into neural lineages. Expression of TPX2 was gradually down-regulated in embryoid bodies and neural precursor cells relative to undifferentiated ES cells. Targeting Protein for Xklp2 has been shown to be involved in cell division by interaction with microtubule development in cancer cells. Taken together, result of this study suggests that TPX2 may be involved in proliferation and differentiation of human ES cells.
        4,000원
        5959.
        2007.12 구독 인증기관 무료, 개인회원 유료
        The objective of this study was to prepare bioactive ginseng yogurts containing compound K, which is transformed from ginsenosides, and to investigate the compound’s cytotoxicity against tumor cells. Milk containng ginseng was fermented by Bifidobacteria KK-l and KK-2, and their activities for transforming ginsenosides to compound K were measured. Among the tested concentrations of ginseng in the milk, compound K was effectively produced in the 3% and 6% ginseng yogurts fermented for 48 hrs. These fermented ginseng yogurts were extracted with BuOH, and their cytotoxicities against tumor cells were examined. The BuOH extract of the yogurt made from the 3% ginseng milk showed cytotooxic activity against P388 and HeLa tumor cells. However, the nonfermented ginseng milk did not exhibit cytotoxicity against these cells. Therefore, we deem that the ginseng yogurt, which contained compound K, could be developed as a potential fermented drink product.
        3,000원
        5960.
        2007.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        This case study examined 10 Korean English teachers who were involved in small group work (SGW) for the purpose of improving their own English language proficiency. Their beliefs about and practices of SGW were closely observed as they actually went through a SGW. A total of 10 teachers (three groups) teaching at elementary or middle schools participated in the SGWs for one year. In the SGWs they were supposed to meet once a week in groups, give a presentation in English on a selected topic, and discuss the topics presented. Throughout the research period, they were interviewed and surveyed periodically. The result of the study showed that teachers generally had positive beliefs about SGWs and were very willing to go on with it in the same way they used to or in a little modified way. Especially, the teachers revealed strong conviction that the most powerful aspect of SGW was that it kept them motivated to continue learning, which has rarely been the case when they tried to study individually.
        6,300원