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        검색결과 3,152

        1941.
        2007.12 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        Here we analyze if the ionized shells associated with giant HII regions represent the progenitors of the larger neutral hydrogen supershells detected in the Milky Way and other spiral and dwarf irregular galaxies. We calculate the evolutionary tracks that 12 HII shells found by Relano et al. (2005, 2007) would have if they expanded into the interstellar medium because of multiple supernovae explosions occurring inside the cavity. We find, contrary to Relano et al. (2007), that the evolutionary tracks of these HII shells are inconsistent with the observed parameters of the largest and most massive neutral hydrogen supershells. Thus, an additional energy source to the multiple supernovae explosions is required in order to explain the origin of the most massive neutral hydrogen shells.
        4,000원
        1942.
        2007.12 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        It is well known that water vapor maser emission at 22.2 GHz is associated with the earliest stages of both low- and high-mass star formation and it can be considered a reliable diagnostic of their evolutionary state. Bright Rimmed Clouds (BRCs) are clouds that have been compressed by an external ionization-shock front which focuses the neutral gas into compact globules. The boundary layer between the neutral gas and the gas ionized by the incident photons is often called "bright rim" but the clumps are sometimes classified also as speck globules or cometary globules depending on their appearance. Small globules with bright rims have been considered to be potential sites of star formation and have been studied in several individual regions. We present results from high resolution VLA observations searching for new candidates of recent star formation in bright-rimmed clouds/globules associated with IRAS point sources.
        3,000원
        1943.
        2007.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Carbon materials of various morphologies were synthesized by pyrolysis of Soap-nut seeds (Sapindus mukorossi), Jack Fruit seeds (Artocarpus heterophyllus), Date-seeds (Phoenix dactylifera), Neem seeds (Azadirachta indica), Tea leaves (Ehretia microphylla), Bamboo stem (Bambusa bambus) and Coconut fiber (Cocos nucifera), without using any catalyst. Carbon materials thus formed were characterized by SEM XRD and Raman. Carbon thus synthesized varied in size (in μm) but all showed highly porous morphology. These carbon materials were utilized as the anode in Lithium secondary battery. Amongst the various precursors, carbon fibers obtained from Soap-nut seeds (Sapindus mukorossi) and Bamboo stem (Bambusa bambus), even after 100th cycles, showed the highest capacity of 130.29 mAh/g and 92.74 mAh/g respectively. Morphology, surface areas and porosity of carbon materials obtained from these precursors were analyzed to provide interpretation for their capacity to intercalate lithium. From the Raman studies it is concluded that graphitic nature of carbon materials assist in the intercalation of lithium. Size of cavity (or pore size of channels type structure) present in carbon materials were found to facilitate the intercalation of lithium.
        4,000원
        1944.
        2007.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Samples of active carbon of 1150 m2/g surface area were impregnated with ammoniacal salts of copper, chromium and silver, with and without triethylenediamine. The samples of impregnated carbon were aged at 50℃, with and without 90% RH (relative humidity), for a little more than one year and chemically evaluated periodically. Initially copper (II) and chromium (VI) reduced very fast in the samples in humid atmosphere to the extent of 30% and 60% respectively in four months. These values were found to be unaffected by the presence of triethylenediamine (TEDA) indicating that the chemical did not retard the reduction process of chromium (VI) and copper (II). However, in the absence of humidity the reduction of the impregnants was significantly less (10-12%, w/w) in four months. It was quite evident; therefore, that the moisture was mainly responsible for the reduction of chromium (VI) and copper (II) species in impregnated carbons. The prolonged ageing of the samples with and without triethylenediamme after four months with and without humid atmosphere showed that the extent of reduction of chromium (VI) was very low, i.e. 5-10% and of copper (II) was 2-25%. Silver is not reduced due to carbon, as it remained unchanged in concentration on storage. The impregnated carbon samples (100 g) without triethylenediamine, which were aged at room temperature for 5 years in absence of humidity and unaged when evaluated against cyanogen chloride (CNCl) at a concentration of 4 mg/L and airflow rate of 30 lpm showed a high degree of protection (80- 110 minutes).
        4,000원
        1945.
        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
        1946.
        2007.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Two experiments were conducted to determine the effect of wood vinegar (WV) on the fecal microbes and gas emission in weaned pigs. In Exp. 1, 224 weaned piglets (L×Y×D, 21 d-old, initial BW 6.02 ± 0.52 kg) were assigned to four treatments of different WV levels in randomized completely block design with four replicates (14 piglets/pen) for 28 days, including phases I (0-2 wk) and phase II (3-4 wk). The dietary treatments were 0, 0.1, 0.2 and 0.3% of WV added to a corn-soybean meal basal diet. The concentration of ammonia measured at 0 h and 24 h in feces did not differ among dietary treatments (p>0.05), but it was linearly decreased (p<0.05) in 0.2% and 0.3% addition level measured at 48 h and 72 h. The concentration of hydrogen sulfide had no significant change (p>0.05) within treatments measured at different time. The fecal total bacteria (TBC), Lactobacilli(LAB) and E. coli were measured on 14 d and 28 d. TBC were higher (p>0.05) in WV added treatments than the control. Similar results were obtained for LAB. But E. coli populations were decreased (p<0.05) in treatments added WV compared to control measured on 14 d and 35 d. In Exp. 2, 288 weaned piglets (L×Y×D, 21 d-old, initial BW 6.62 ± 0.31 kg) were assigned to four treatments in a randomized completely block design with four replicates (18 piglets/pen) for 28 days. The dietary treatments were basal diet (negative control, NC), 0.2% organic acid (positive control, PC), 0.2% antibiotic (AT) and 0.2% WV added to a corn-soybean meal basal diet. The fecal total bacteria (TBC), Lactobacilli(LAB) and E. coli were measured on 14 d and 28 d. TBC, LAB and E. coli showed lower counts in pigs fed AT diets than others. In conclusion, these results indicated that wood vinegar could reduce the NH3 concentration of feces and inhibited the growth of harmful bacteria.
        4,000원
        1947.
        2007.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        In this study 300 weaned pigs (Landrace × Yorkshire × Duroc, 23±3 d of age, 5.56± 1.21 kg initial body weight) were used to study the effect of fungal (Aspergillus oryzae, FSP-A) and fungal + bacteria (Aspergillus oryzae + Bacillus subtilis, FSP-B) fermented soya proteins on their blood hematology, enzymes and immune cell populations. Pigs were allotted to 5 treatments, each comprising of 4 pens with 15 pigs. Basal diets consisted of 15% soyabean meal (Control diet) while for treatment diets SBM was replaced with 3 and 6% of each FSP-A and FSP-B, respectively. The experimental diets were fed from 0 to 14 day after weaning and then a common commercial diet was fed from 15 to 35 day. Blood was collected on 14 and 35 day of experiment and analyzed for hematology, aspartate transaminase (AST), alanine transaminase (ALT) and immune cell populations. At d 14, lower RBC count, Hb and HCT values and higher AST values were noted in pigs fed FSP-A diets when compared with Control and FSP-B fed pigs.Also at d 14 pigs fed 6% FSP-A had lower NE (P<0.05) when compared with those fed 6% FSP-B. The level of FSP influenced the RDW on d 14 and MCHC, MO and MPV on d 35. In addition on d 35, pigs fed 3% FSP-A had lesser NE than those fed 6% FSP -A and Control diet, while pigs fed 6% FSP-B had the highest number of MO compared to other treatments. But there were no differences in the plasma AST and ALT values on d 35. Thus it may be concluded that the FSP either by fungal or fungal + bacterial sources had an influence on the blood hematological status and the populations of immune cells.
        4,000원
        1948.
        2007.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        A total of 240 weaned pigs (Landrace ×Yorkshire × Duroc, 22±3 d of age, 5.16±0.90 kg initial body weight) were used to study the effect of feeding level of microbial fermented soya protein on their blood hematology, enzymes and immune cell populations. The microbial (Aspergillus oryzae + Bacillus subtilis) fermented soya protein (FSP) was used. Pigs were allotted to four dietary treatments, each comprising of 4 pens with 15 pigs. Basal diets consisted of 15% soya bean meal (Control diet); while for treatment diets SBM was replaced with 3, 6 and 9% FSP. The experimental diets were fed from 0 to 14 day after weaning and then a common commercial diet was fed from 15 to 35 day. Blood was collected on 14 and 35 day of experiment and analyzed for hematology, plasma aspartate transaminase (AST), plasma alanine transaminase (ALT) and immune cell populations. Increasing the level of FSP in the diet of pigs linearly decreased distribution of red blood cells (P<0.01), MPV (P<0.05), MO (P<0.05), EO (P<0.05) and BA (P<0.05) on d 14. Linear and quadratic decrease in the RBC (P<0.05), Hb (P<0.05), HCT (P<0.01), PLT (P<0.001) and EO (P<0.05) and linear increase in the MCHC (P<0.001), MPV (P<0.05), WBC (P<0.05) and NE (P<0.05) on d 35 was noted. Pigs fed with 6% FSP had lower (P<0.05) levels of AST and ALT on d 14, while the levels of ALT and AST on d 35 did not differ among the dietary treatments. Thus the results suggest that microbial fermented soya protein affected the hematological indices, immune cell populations and plasma enzymes in weaned pigs.
        4,000원
        1949.
        2007.12 구독 인증기관 무료, 개인회원 유료
        To identify factors affecting the regeneration of Abies koreana, we examined environmental conditions on Mt. Halla. In three seedbed types (Sasa site, shade by rock, forest floor), we investigated temperature and soil moisture content. Stratified A. koreana seeds were placed on each seedbed types and counted germinated seedlings. Snow cover period in north-facing slope, 102±17 days, was significantly longer than that of southfacing slope, 94±14 days. Average temperature of May to July, the period of seed germination, was significantly lower in forest floor than around rocks and under Sasa quelpaertensis. Germination rate of on each seedbed types was not different. This study suggests that the proper environmental conditions of A. koreana's regeneration may be affected on more complex factors.
        4,000원
        1955.
        2007.10 구독 인증기관 무료, 개인회원 유료
        To design an efficient and acceptable indoor air environment in a badminton gymnasium, it is important to study the velocity and temperature field in the conditioned room. For diverse airflow patterns, the k- c models with wall function near solid boundaries are adopted to simulate airflow distribution in the gymnasium. The simulated result is analyzed in this paper, and it provides the important reference for the design of air condition system and optimization of the project. CFD is effective design tool for air flow in large space, for it can give the velocity and temperature values at any point quantitatively.
        3,000원
        1956.
        2007.10 구독 인증기관 무료, 개인회원 유료
        Correct air diffusion is essential for good air quality, comfortable conditions and energy efficiency in mechanical ventilation system. One general method to improve indoor air quality is to simply increase the ventilation rate. This approach, however, often conflicts with building energy efficiency requirement because conditioning outdoor air to the proper temperature, humidity level count for use as ventilation air consumes energy. Therefore, it is necessary for designers to predict the air movement properly. Successful predictions of room airflow yield such information as velocities and temperature distributions, which are useful to building design and analysis. In this paper, the application of computational fluid dynamic (CFD) techniques to large space design and analysis was investigated by comparing the results of CFD simulations and experimental results.
        3,000원