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        검색결과 984

        382.
        2015.04 KCI 등재 구독 인증기관 무료, 개인회원 유료
        In this work, highly porous carbons were prepared by chemical activation of carbonized biomass-derived aerogels. These aerogels were synthesized from watermelon flesh using a hydrothermal reaction. After carbonization, chemical activation was conducted using potassium hydroxide to enhance the specific surface area and microporosity. The micro-structural properties and morphologies were measured by X-ray diffraction and scanning electron microscopy, respectively. The specific surface area and microporosity were investigated by N2/77 K adsorption-desorption isotherms using the Brunauer-Emmett-Teller method and Barrett-Joyner-Halenda equation, respectively. Hydrogen storage capacity was dependent on the activation temperature. The highest capacity of 2.7 wt% at 77 K and 1 bar was obtained with an activation temperature of 900°C.
        4,000원
        383.
        2015.04 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        We present observational results from optical long-slit spectroscopy of parsec-scale jets of DG Tau. From HH 158 and HH 702, the optical emission lines of H , [O i] 6300, 6363, [N ii] 6548, 6584, and [S ii] 6716, 6731 are obtained. The kinematics and physical properties (i.e., electron density, electron temperature, ionization fraction, and mass-loss rate) are investigated along the blueshifted jet up to 650′′ distance from the source. For HH 158, the radial velocity ranges from -50 to -250 km s-1. The proper motion of the knots is 0:′′196 - 0:′′272 yr-1. The electron density is 104 cm-3 close to the star, and decreases to 102 cm-3 at 14′′ away from the star. Ionization fraction indicates that the gas is almost neutral in the vicinity of the source. It increases up to over 0.4 along the distance. HH 702 is located at 650′′ from the source. It shows  -80 km s-1 in the radial velocity. Its line ratios are similar to those at knot C of HH 158. The mass-loss rate is estimated to be about  10-7 M⊙ yr-1, which is similar to values obtained from previous studies.
        4,200원
        384.
        2015.04 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Impact damages induced by a low-velocity impact load on carbon fiber reinforced polymer (CFRP) composite plates fabricated with various stacking sequences were studied experimentally. The impact responses of the CFRP composite plates were significantly affected by the laminate stacking sequences. Three types of specimens, specifically quasi-isotropic, unidirectional, and cross-ply, were tested by a constant impact carrying the same impact energy level. An impact load of 3.44 kg, corresponding to 23.62 J, was applied to the center of each plate supported at the boundaries. The unidirectional composite plate showed the worst impact resistance and broke completely into two parts; this was followed by the quasi-isotropic lay-up plate that was perforated by the impact. The cross-ply composite plate exhibited the best resistance to the low-velocity impact load; in this case, the impactor bounced back. Impact parameters such as the peak impact force and absorbed energy were evaluated and compared for the impact resistant characterization of the composites made by different stacking sequences.
        4,000원
        388.
        2015.04 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Carbon fibers (CFs) have a unique combination of properties which allow them to be widely used as reinforcing materials in advanced polymer composites. The mechanical properties of CF-reinforced polymer composites are governed mainly by the quality of interfacial adhesion between the CFs and the polymer matrix. Surface treatments of CFs are generally carried out to introduce chemical functional groups on the fiber surfaces, which provide the ability to control the surface characteristics of CFs. In this study, we review recent experimental studies concerning various surface treatment methods for CFs. In addition, direct examples of the preparation and properties of CF-reinforced thermosetting composites are discussed.
        4,200원
        393.
        2015.04 구독 인증기관·개인회원 무료
        Insect and natural enemy fauna were surveyed at conventional (CV) and organic-farming persimmon orchards (OF) at Jinju, Korea, using sweeping net and naked eyes in 2013 and 2014. Using sweeping net, 49 species at an OF and 18 species at a CV were observed in 2013. In 2014 too, more species were observed at OF (66 species, 33 families, 7 orders) than at a CV (25 species, 15 families, 5 orders). During both the years, dominant species were all hemipteran insects like Nysius plebejus (Lygaeidae) and Cletus punctiger (Coreidae) in both types of orchards, followed by Rhopalus maculatus (Rhopalidae), Riptortus pedestris (Alydidae). Similarly, naked eye inspection also found more species at OF (192 species, 72 families, 11 orders) than at CV (104 species, 52 families, 10 orders) in 2014. Dominant species in naked eye inspection were Lycorma emelianovi (Hemiptera: Fulgoridae), Apis mellifera (Hymenoptera: Apidae), Uroleucon cephalonopli (Hemiptera: Aphididae) at OF, and A. mellifera and R. maculatus at CV in 2014. Using naked eye inspection or sweeping net in 2014, more species of natural enemies were observed at OF (31 and 9 species, respectively) than at CV (18 and 5 species, respectively).
        394.
        2015.04 구독 인증기관·개인회원 무료
        The establishment of insect population in certain region is affected by three major characteristics, the host spectrum, the phenological plasticity and the overwintering strategy. The geographical distribution of insect population is directly affected by their successful establishment in local environment, thus, in case of development of potential geographical distribution models, three major characteristics should be considered carefully. In this study, we developed geographical distribution model using CLIMEX system with well-known insect species, Carposina sasakii. Its geographical distribution is limited to northeast Asia including Korea, Japan, China and the Soviet Far East. C. sasakii overwinters as a full-grown larva within spherical and compactly woven larval-cocoons in the soil. We calculated Diapause Index (DI) then incorporated DI into CLIMEX system to simulate Ecoclimatic Index (EI), which stands for ability of establishment in a certain area for further studies of geographical distribution of insect populations which have overwintering strategy in their life history.
        395.
        2015.03 구독 인증기관 무료, 개인회원 유료
        Shikonin, a major ingredient in the traditional Chinese herb Lithospermumerythrorhizon, exhibits multiple biological functions including antimicrobial, anti-inflammatory, and antitumor effects. It has recently been reported that shikonin displays antitumor properties in many cancers. This study was aimed to investigate whether shikonin could inhibit oral squamous carcinoma cell (OSCC) growth via mechanisms of apoptosis and cell cycle arrest. The effects of shikonin on the viability and growth of OSCC cell line, SCC25 cells were assessed by MTT assay and clonogenic assays, respectively. Hoechst staining and DNA electrophoresis indicated that the shikonin-treated SCC25 cells were undergoing apoptosis. Western blotting, immunocytochemistry, confocal microscopy, flow cytometry, MMP activity, and proteasome activity also supported the finding that shikonin induces apoptosis. Shikonin treatment of SCC25 cells resulted in a time- and dose-dependent decrease in cell viability, inhibition of cell growth, and increase in apoptotic cell death. The treated SCC25 cells showed several lines of apoptotic manifestation as follows: nuclear condensation; DNA fragmentation; reduced MMP and proteasome activity; decrease in DNA contents; release of cytochrome c into cytosol; translocation of AIF and DFF40 (CAD) onto the nuclei; a significant shift in Bax/Bcl-2 ratio; and activation of caspase-9, -7, -6, and -3, as well as PARP, lamin A/C, and DFF45 (ICAD). Shikonin treatment also resulted in down-regulation of the G1 cell cycle-related proteins and up-regulation of p27KIP1. Taken together, our present findings demonstrate that shikonin strongly inhibits cell proliferation by modulating the expression of the G1 cell cycle-related proteins, and that it induces apoptosis via the proteasome, mitochondria, and caspase cascades in SCC25 cells.
        4,200원
        396.
        2015.01 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Carbon aerogel is a porous carbon material possessing high porosity and high specific surface area. Nitrogen doping reduced the specific surface area and micropores, but it furnished basic sites to improve the CO2 selectivity. In this work, N-doped carbon aerogels were prepared with different ratios of resorcinol/melamine by using the sol-gel method. The morphological properties were characterized by scanning electron microscopy (SEM). Nitrogen content was studied by X-ray photoelectron spectroscopy (XPS) and the specific surface area and micropore volume were analyzed by N2 adsorption-desorption isotherms at 77 K. The CO2 adsorption capacity was investigated by CO2 adsorption-desorption isotherms at 298 K and 1 bar. Melamine containing N-doped CAs showed a high nitrogen content (5.54 wt.%). The prepared N-doped CAs exhibited a high CO2 capture capacity of 118.77 mg/g (at resorcinol/melamine = 1:0.3). Therefore, we confirmed that the CO2 adsorption capacity was strongly affected by the nitrogen moieties.
        4,000원
        397.
        2015.01 KCI 등재 구독 인증기관 무료, 개인회원 유료
        The process of oxidizing polyacrylonitrile (PAN)-based carbon fibers converts them into an infusible and non-flammable state prior to carbonization. This represents one of the most important stages in determining the mechanical properties of the final carbon fibers, but the most commonly used methods, such as thermal treatment (200°C to 300°C), tend to waste a great deal of process time, money, and energy. There is therefore a need to develop more advanced oxidation methods for PAN precursor fibers. In this review, we assess the viability of electron beam, gamma-ray, ultra-violet, and plasma treatments with a view to advancing these areas of research and their industrial application.
        4,000원
        398.
        2014.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        The boar sperm has more lipid droplets and specialty of seminal plasma compared with other species, causing difficulties of freezing sperm and decreases for the utilization of frozen semen into the artificial insemination. However, several studies reported significant results for the recovery of sperm motility and reproductive by addition of cryoprotectants and seminal plasma after thawing. This study was designed to investigate the effects of supplementation of trehalose or glycerol in the LEY (lactose and egg yolk in BTS) solution for the conventional freezing and vitrification process. Two boars aged 16 months were used to collect semen for 2 times in a week. The samples were allotted to 3 freezing solutions (LEY + glycerol 10.5% + OEP 1.5%, LEY + trehalose 1M + OEP 1.5%, and sucrose 1.5M + trehalose 1 M + OEP 1.5%) after centrifugation at 800 g for 10 minutes. Semen was equilibrated in freezing solutions for 10 minutes and injected into plastic straws with 2∼3 air bubbles to minimize freezing damages. Vitrification was performed to locate sperm in 5 cm above LN2 for 5 minutes, and the conventional freezing was conducted with an automatic freezer. Motility and survival rates were measured by CASA (Computer assisted sperm an alyzing system) and FITC (Fluorescein isothiocyanate), respectively after thawing semen at 50℃ for 12 seconds. The results were analyzed by ANOVA with STATVIEW statistical program. The vitrificatioin solution (LEY + 10.5% glycerol + 1.5% OEP) presented higher motility (20.9%) than other solutions while the solution (LEY + 1M trehalose + 1.5% OEP) showed the lowest (motility : 5.2%). However, survival rates of vitrified sperms detected by FITC showed 1~4% live sperms in almost of dead sperms at all vitrification solutions’ groups, but survival rate of freezing solution of LEY + 1M trehalose + 1.5% OEP LEY and LEY + 10.5% glycerol + 1.5% OEP were showed 49%, and 79%, respectively. There were differences (P<0.05) survival rate of conventional freezing in LEY + 10.5% glycerol + 1.5% OEP and LEY + 1M trehalose + 1.5% OEP and the remaining showed no differences. The results suggested that vitrified boar semen was not enough to be utilized for the artificial insemination, but it showed possibility to utilize for ICSI and conventional freezing with glycerol would be useful method for artificial insemination in pig while we choose the outstanding semen against tolerance to freezing damages.
        4,000원
        399.
        2014.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Objective of this study was to investigate the effect of nicotinic acid (NA) on the characteristics in fresh semen of miniature pig. We evaluated viability, acrosome reaction and mitochondrial integrity of sperm on 0, 3, 7 and 10 days during storage period with nicotinic acid. As results, the survival rate of sperm in 15 mM NA (day 3, 87.8 ± 1.2%; day 5, 84.0 ± 2.7%; day 7, 82.2 ± 0.9%) and 30 mM NA (day 3, 87.7 ± 0.3%; day 5, 84.4 ± 2.5%; day 7, 82.3 ± 0.7%) groups were higher than control and 5 mM NA groups in 3, 7 and 10 days of semen storage. The NA-treated sperm on 10 day was used day for observing acrosome integrity. The survival sperm with acrosome reaction was higher in 30 mM NA group (day 3, 2.7 ± 0.2%; day 5, 3.3 ± 0.6%; day 7, 11.4 ± 0.3%) than in the control, significantly (P<0.05). Moreover, the live sperm with mitochondrial integrity was higher in whole treatment groups of NA than control group, significantly (P<0.05). Specially, most mitochondrial integrity on 10 day of semen storage was significantly higher in 30 mM NA group (90.2 ± 1.6%) than other treatment groups (control, 81.8 ± 3.1%; 5 mM NA, 83.4 ± 3.0%; 15 mM NA, 89.1 ± 0.7%, P<0.05). In conclusion, supplement of NA in liquid semen of miniature pig can improve and maintain semen quality, such as viability, acrosome reaction, and mitochondria integrity.
        4,000원
        400.
        2014.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        To compensate for the critical shortage of human organs for allotransplantation, xenotransplantation studies using genetically modified pigs are being performed in Korea. Two types of pigs that are used are α1,3-galactosyltransferase gene knockout (GalT KO) pigs and GalT KO+hCD46 (human complement regulatory protein) pigs. The present study measured the gestation time, birth weight, daily growth rate, and heart weight of both kinds of transgenic minipigs. The gestation period for both types of pigs was 117∼119 days. There was no difference in the body weight of GalT KO (—/+) and GalT KO (—/—) piglets, but GalT KO+hCD46 (—hCD46+/+) pigs were significantly heavier at birth than were GalT KO+hCD46 (—hCD46+/—hCD46+) pigs. During the first 10 weeks of life, the daily weight gain of GalT KO+hCD46 (—hCD46+/—CD46+) piglets, which are considered the optimal type for xenotransplantation, was 0.19 kg. The weight of hearts from GalT KO piglets up to two months of age was affected more by body weight than by age. Transgenic pigs showed no differences in gestation period or reproductive ability compared with normal pigs. These results comprise basic data that may be used in xenotransplantation studies and transgenic animal production in Korea.
        4,000원