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        검색결과 9,514

        5861.
        2008.06 KCI 등재 구독 인증기관 무료, 개인회원 유료
        The commercial activated carbons are typically prepared by activation from coconut shell char or coal char containing lots of inorganic impurities. They also have pore structure and pore size distribution depending on nanostructure of precursor materials. In this study, two types of commercial activated carbons were applied for EDLC electrode by removing impurities with acid treatments, and controlling pore size distribution and contents of functional group with heat treatment. The effect of the surface functional groups on electrochemical performance of the activated carbon electrodes was investigated. The initial gravimetric and volumetric capacitance of coconut based activated carbon electrode which was acid treated by HNO3 and then heat treated at 800℃ were 90 F/g and 42 F/cc respectively showing 94% of charge-discharge efficiency. Such a good electrochemical performance can be possibly applied to the medium capacitance of EDLC.
        4,000원
        5862.
        2008.06 KCI 등재 구독 인증기관 무료, 개인회원 유료
        폴리비닐리덴플로라이드(PVDF) 지지체 위에 빗살모양의 술폰화된 공중합체를 코팅하여 나노 분리막을 제조하였다. 빗살모양의 공중합체는 원자전달 라디칼 중합법(ATRP)에 의해 제조하였으며, 폴리비닐클로라이드의 주사슬과 폴리스티렌 술폰산(PSSA)의 곁사슬로 구성되어 있다. 핵자기 공명법(1 H-NMR), FT-IR분광학 그리고 WAXS 분석법에 의해 공중합체가 성공적으로 합성되었음을 확인하였다 PVC-g-PSSA로 구성된 복합 나노 분리막은 PSSA의 함량이 증가함에 따라 플럭스와 배제율 모두 증가하였다. 이러한 성능 향상은 분리막의 술폰산의 함량의 증가로써 설명할 수 있다. PSSA가 71wt%첨가된 나노 복합막의 배제율은 Na2SO4 88%, NaCl 33%을 나타내었고, 플럭스는 Na2SO4 26, NaCl 34 L/m 2 h을 각각 나타내었다.
        4,000원
        5863.
        2008.06 KCI 등재 구독 인증기관 무료, 개인회원 유료
        This study aims to find a correlation between XRD and Raman result of the activated carbon fibers as a function of its activation degrees. La of the isotropic carbon fiber prepared by oxidation in carbon dioxide gas have been observed using laser Raman spectroscopy. The basic structural parameters of the fibers were evaluated by XRD as well, and compared with Raman result. The La of the carbon fibers were measured to be 25.5 a from Raman analysis and 23.6 a from XRD analysis. La of the ACFs were 23.6 a and 20.4 a, respectively, representing less ordered through activation process. It seems that the ID/IG of Raman spectra were related to crystallite size(La). Raman spectroscopy has demonstrated its unique ability to detect structural changes during the activation of the fibers. There was good correlation between the La value obtained from Raman and XRD.
        3,000원
        5864.
        2008.06 구독 인증기관 무료, 개인회원 유료
        The objective of this study was to determine the potential hazardous effects of sorting process by flowcytometry on the quality of boar spermatozoa by flowcytometer. Freshly collected boar semen was diluted and divided into two groups; control none sorted and sorted. Sperms in sorted group were processed with flowcytometer for cell sorting with 100 uM nozzle under the 20 psi pressure. Measurements on each parameter were made at two time points, 0hr (right after sorting) and 24 hr post sorting. Although there was a tendency of lower viability in sorted group than none sorted control group, the percentage of live cells in control(75.83+-6.92 & 59.53+-10.34) was not significantly different from sorted (59.7+-7.34 & 43.97+-3.76) at both 0 and 24 hr post sorting. However, sorted sperm showed significantly lower mitochondrial function compared to the control at both 0 h (79.37+-3.22 vs. 63.50+-10.05) and 24hr(67.27+-3.22 vs. 46.97+-5.37) time points (p<0.007). Sperm DNA fragmentation rate was significantly lower in control (22.0+-7.04) than that of sorted (32.27+-7.49) at 24 hr time point (p<0.0002). Taken together, these data suggested thatsorting process by flowcytometer may have influenced sperm motility rather than viability. Also high speed sperm sorting by flowcytometer has significant effects on DNA fragmentation on elapsed time after sorting.
        3,000원
        5865.
        2008.06 KCI 등재 구독 인증기관 무료, 개인회원 유료
        High modulus pitch based carbon fibers (HM) were exposed to isothermal oxidation using tube furnace in carbon dioxide gas to study the oxidation kinetics under the temperature of 800-1100℃. The kinetic equation f=1--(-atb) was introduced and the constant b was obtained in the range of 1.02~1.42. The oxidation kinetics were evaluated by the reaction-controlling regime (RCR) depending upon the apparent activation energies with the conversion increasing from 0.2 to 0.8. The activation energies decrease from 24.7 to 21.0 kcal/mole with the conversion increasing from 0.2 to 0.8, respectively. According to the RCR, the reaction was limited by more diffusion controlling regime for the HM fibers with the conversion increasing. Therefore, it seems that the oxidation which is under the diffusion controlling regime takes place continuously from the skin to the core of the fiber.
        4,000원
        5866.
        2008.06 KCI 등재 구독 인증기관 무료, 개인회원 유료
        A 3-month-old American Cocker spaniel was presented at the Veterinary Teaching Hospital, Chungbuk National University, for examination of urinary tract after dissection of vaginal mass at local clinic before 10 days. Clinical examination of the affected bitch revealed a normal sized vulva in a normal anatomical position with a grossly enlarged clitoris, which contained an os clitoris. On examinations of the genital gland, there were testis, epididymis, ductus deferens and uterus. The histology of both gonads was primarily testis. Seminiferous tubules were divided into many parts by fibrous connective tissue. A small number of spermatogonia was present, but large numbers of Leydig's cells were existed. A normal female karyotype (78, XX) was detected in metaphase spreads obtained from cultured peripheral lymphocytes. Y chromosome specific sequences were not detected in genomic DNA by PCR. After 27 months, the os clitoris was larger than 3-month-old dog and os bone was more calcified than young age. Combining the results of cytogenetic, molecular genetic and histological examinations, the dog was diagnosed as a female hermaphrodite with Sry-negative XX sex reversal.
        4,000원
        5867.
        2008.06 KCI 등재 구독 인증기관 무료, 개인회원 유료
        폴리스티렌-블록-폴리히드록에틸 메타크릴레이트(PS-b-PHEMA), 술포석시닉산(SA), 인텅스텐산(PWA)으로 구성된 수소 이온 전도성 나노복합 고분자 전해질막을 제조하였다. 폴리히드록에틸 메타크릴레이트(PHEMA) 블록의 히드록실그룹(-OH)와 술포석시닉산(SA)의 -COOH 그룹과의 에스테르 반응에 의하여 전해질막을 가교시켰다. 폴리헤테로산(PWA)을 도입했을 때, SO3 - 그룹의 신축 밴드가 1187 cm -1에서 1158 cm -1로 낮아졌으며, 이는 PWA 입자가 전해질막의 술폰산 그룹과 상호작용함을 나타낸다. PWA 함량이 30wt%가 되었을 때, 상온 전도도는 0.045에서 0.062S/cm로 증가되었으며, 이는 PWA 입자의 고유 전도도 특성과 전해질막의 술폰산기의 산도가 증가했기 때문이다. 또한 30wt%를 함유한 복합 전해질막은 100℃에서는 최대 0.126 S/cm의 수소 이온 전도도를 나타내었다 PWA가 첨가됨에 따라 복합 전해질막의 열적특성 또한 증가하였다.
        4,000원
        5868.
        2008.06 KCI 등재 구독 인증기관·개인회원 무료
        The caterpillar-shaped Chinese medicinal mushroom (DongChongXiaCao) looks like a worm in the winter and likes a grass in the summer. The fruiting bodies of Cordyceps species have demonstrated various biological activities and used as traditional medicines in Asian countries. The price of wild Cordyceps have been ascending every year as their demand increase. Recently, the artificial cultivation of these fungi has been successfully established and they are currently produced on a rice or pupae media. This study was carried out to investigate the soluble sugar, amino acid and fatty acid profiles in the fruiting-bodies of Cordyceps militaris, C. pruinosa and Paecilomyces. tenuipes formed on the living silkworm (Bombyx mori) host. Soluble sugars such as glycerol, glucose, mannitol and sucrose were found in the fruiting bodies of Cordyceps militaris, C. pruinosa and P. tenuipes. Total soluble sugar content was 29.23 ㎎g-1in C. militaris, 8.61㎎g-1 in C. pruinosa and 24.00 ㎎g-1in P. tenuipes on dry weight basis. Total free amino acid content was 14.09 ㎎g-1in C. militaris, 34.60㎎g-1 in C. pruinosa and 17.09 ㎎g-1 in P. tenuipes. The content of oleic acid in fatty acids was above high more than 30% regardless of species.
        5869.
        2008.06 KCI 등재 구독 인증기관·개인회원 무료
        Agaricus blazei is well known as a traditional medicinal mushroom and it has been shown to exhibit immunostimulatory and anti-cancer activity. However, the cellular and molecular mechanism of apoptosis of cancer cells is poorly understood. In this study, we have investigated whether A. blazei extract (ABE) exerts anti-proliferative and apoptotic effects on human leukemia THP-1 cells. It was found that ABE induced a time- and dose-dependent increase in leukemia cells apoptosis through caspase-3 activation and PARP cleavage. Activation of caspase- 9 induced by ABE suggested that ABE-induced signaling was mediated through a mitochondrial death pathway. In addition, we observed an elevation of ROS and a consequent loss of mitochondrial membrane potential, further suggesting that ABE-induced death signaling was mediated through a mitochondrial oxygen stress pathway. The antioxidant Nacetylcysteine, however, opposed ABE-mediated mitochondrial dysfunction, caspase activation, and apoptosis, supporting the role of ROS in the apoptotic process. We conclude that ABE induces apoptosisin human leukemia cells through a reactive oxygen species and caspase-dependent mitochondrial pathway.
        5870.
        2008.06 KCI 등재 구독 인증기관·개인회원 무료
        This study was carried out to investigate amino acid contents of golden mushroom and pink mushroom. The amino acid analysis was followed by AccQ-Tag method and HPLC on gradient conditions. Seventeen amino acids were analyzed and sixteen amino acids were found in golden mushroom ; fifteen amino acids in pink mushroom respectively. Among total amino acid in golden mushroom, cystein content was the highest and glycine, glutamic acid, proline were followed. Among total amino acid in pink mushroom, cystein was the highest and glycine, lysine, methionine were followed. As shown in Fig.1, 2, concerning amino acids, cystein was dominant. and alanine was detectied in golden mushroom but pink mushroom.
        5871.
        2008.06 KCI 등재 구독 인증기관·개인회원 무료
        Mushroom is the only microorganism cultivated as the crop, and Plerotus ostreatus is one of the most important edible mushrooms. Efficient production of edible mushrooms relies on the precise control of fruiting body development, and an identification of the molecular mechanism of fruiting body development has commercial and scientific importance. In order to identify the developmentally regulated genes during fruiting body development, cDNA libraries were constructed from eight developmental stages of the P. ostreatus. From these libraries, 11,761 expressed sequence tags (ESTs) were generated. Based on these results, we performed macroarray analysis using 1,528 unigene clones at three developmental stages of mycelium, fruiting body and basidiospores. Plasmids isolated from these clones were blotted on the nylon membrane. The isotope-labelled cDNA probes for hybridization of the northern blot were prepared from total RNAs isolated from three developmental stages of mushroom. The 33, 14, 10 unigenes were very highly expressed in mycelia, fruit body and basidiospores, respectively. To confirm expression pattern of these genes, RT-PCR was performed using the total RNA isolated from three developmental stages. Seven genes were successfully amplified in RT-PCR. The expression patterns of the genes were similar with that in macroarray. One of seven genes was identified as a 12kDa heat shock protein and its expression level was very highly at fruiting stage, but not detected at mycelium stage.
        5872.
        2008.06 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        고준위 방사성폐기물 처분장으로부터 유출된 핵종에 의한 선량률을 계산하기 위한 생태계평가 코드 ACBIO를 일반적인 구획모델링도구인 AMBER를 이용하여 BIOMASS 방법론을 적용하여 개발하였다. ACBIO의 유용성을 보이고, 구획의 변화나 일부 파라미터값의 변화에 따른 구획 내 농도와 방사능, 그리고 구획간의 플럭스의 민감도도 검토하였다. 지하매질-생태계 경계(GBI)를 통해 넘어오는 핵종의 유출플럭스에 따른 선량환산인자를 각 핵종별로 구하여 결정집단내 개인의 최대피폭선량율을 선량환산인자로 얻는 계산을 수행하였다. 또한 생태계 요소의 구획모델링이나 가능한 피폭집단의 설정, 그리고 GBI의 인지 등이 생태계평가에 중요한 요소가 되는 것을 확인하였다.
        6,700원
        5873.
        2008.06 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        We have investigated the optical properties of the global haze on Titan from spectra recorded between 7100 and 9200Åwhere CH4 absorption bands of various intensities occur. The Titan spectra were obtained on Feb. 23, 2005 (UT), near the times of the Cassini T3 flyby and Huygens probe, using an optical echelle spectrograph (BOES) on the 1.8-m telescope at Bohyunsan Observatory in Korea. In order to derive the optical properties of the haze as a function of altitude, we developed an inversion radiative-transfer program using an atmospheric model of Titan and laboratory CH4 absorption coefficients available from the literature. The derived extinction coefficients of the haze increase toward the surface, and the coefficients at shorter wavelengths are greater than those at longer wavelengths for the 30 - 120 km altitude range, indicating that the Titanian haze becomes optically thin toward the longer wavelength range. Total optical depths of the haze are estimated to be 1.4 and 1.2 for the 7270 -7360Åand 8940 -9150Å ranges, respectively. Based on the Huygens/DISR data set, Tomasko et al. (2005) reported total optical depths of 2.5 - 3.5 at 8290Å depending on the assumed fractal aggregate particle model. The total optical depths based on our results are smaller than those of Tomasko et al., but they partially overlap with their results if we consider a large uncertainty from possible variations of the CH4 mixing ratio over Titan's disk. We also derived the single scattering albedo of the haze particles as a function of altitude: it is less than 0.5 at altitudes higher than ~150Km the average particle radius is smaller than the wavelengths, whereas near the surface, it becomes comparable or greater.
        4,300원
        5874.
        2008.06 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        To detect exoplanets and study pulsation of K giant stars, we have observed precise RV (radial velocity) of about 55 early K giant (K0 - K4) stars brighter than V = 5 magnitude since 2003 by using BOES, a high resolution Echelle spectrograph attached to the 1.8 m telescope at BOAO (Bohyunsan Optical Astronomy Observatory). We detected periodic RV variation of KO III star β Gem (HD 62509) with a period P=596.6 ± 2.3 days and a semi-amplitude K=44.8 ± 0.7 ms-1 If we adopt 1.7 M⊙ for the mass of β Gem, this yields the minimum mass of the companion m sin i = 2.64 M Jupiter results agree well with Hatzes et al. (2006) and Reffert et al. (2006), and confirm their discovery of a planetary object around β Gem. We also confirmed about 192 minutes short period stellar oscillation found by Hatzes and Zechmeister (2007). This is the first report of exoplanet detection using BOES and demonstrates that the RV observation using BOES is accurate and stable enough to detect exoplanets around bright K giant stars.
        4,000원
        5875.
        2008.06 구독 인증기관 무료, 개인회원 유료
        Phytic acid (PA) is a naturallu occurring polyphosphorylated carbohydrate that is present in substantial amounts in almost all plants and mammalian cells. Recently PA has received much attention for its role in anticancer activity. We investigated the preventive effect of PA on the formation of colonic aberrant crypt foci (ACF), a preneoplastic lesion, induced by azoxymethane (AOM). After acclimation for one week, six-week old male ICR mice were fed on the AIN-93G purified diet and PA (0.5% or 2% PA in water) for 8 weeks. The animals were treated with azoxymethane (AOM, 10 mg/kg b.w.) three times (0, 1, and 2 weeks) to induce colonic aberrant crypt foci (ACF). After sacrifice, the total numbers of aberrant crypts (AC) and ACF in colonic mucosa were counted after staining with methylene blue. Blood and serum were analyzed with a blood cell differential counter and an automatic serum analyzer. AOM treatment without PA induced the total numbers of 85.7 ± 12.9 and 115.2 ± 19.9, respectively. PA at the dose of 2% AC/colon by PA at the dose of 0.5% were 73.4 ± 12.9 and 115.2 ± 19.9, respectively. PA at the dose of 2% significantly decreased the ACF and AC numbers to 56.5 ± 14.6 and 95.4 ± 17.2, respectively (p<0.01). PA at the doses of 0.5 and 2% decreased the numbers of ACF and AC/colon in a dose-dependent manner. Although some parameters in blood counts and serum chemistry were changed compared with the control, no specific toxicity was found. Theses findings suggest that phytic acid can be a chemopreventive agent for colon carcinogenesis resulting from inhibition of the development of ACF in ICR mice.
        4,000원
        5877.
        2008.06 구독 인증기관 무료, 개인회원 유료
        In this study, consumer acceptance and sensory intensity evaluations were performed on sponge cakes prepared with domestic and imported cake flours. Specific volume data as well as cross-sectional photograph observations confirmed that the imported flour sample group had greater volume than the domestic flour groups. The imported flour sample group also had a significantly (p<0.05) higher mean overall acceptability score at 5.82; however, it was not significantly different from the domestic white flour sample group (5.40). There was no significant difference in overall texture acceptance between samples prepared with imported and domestic white flours; however, their scores were significantly higher than that of the domestic whole flour group (p<0.05). Consumer acceptances of color significantly decreased as the orders of cake group prepared using the imported, domestic white, and domestic whole flours with the values of 6.48, 5.72 and 4.61, respectively (p<0.05). Acceptance of the air cell and the acceptance and intensity of sweetness did not show significant differences between the imported and domestic white flour group.
        4,000원