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        검색결과 392

        241.
        2010.12 KCI 등재 구독 인증기관·개인회원 무료
        Four Ganoderma lucidum strains, Chizhi 05, Jingda, Huizhou and Xinzhou, were screened out as hybrid parent in order to establish G. lucidum cross breeding system that based on protoplast monokaryogenesis method. Monokaryotic strains of each parental strains were obtained and mating type of each monokaryotic strains were determined. One to three monokaryotic strains that have different mating types were mated, and hybrids were identified by clamp connection observation and antagonist response. The results showed that the number of monokaryon came from Chizhi 05, Jingda, Huizhou and Xinzhou was 9, 14, 40 and 38, respectively. Only one mating type was obtained from Jingda, and two mating types were obtained from the other three strains, Chizhi 05, Huizhou and Xinzhou, respectively. Chi-square test showed that the ratio of two mating types of the three strains was 1:1. Fourteen monokaryotic strains of different mating types from 4 parental strains were select as a cross- breeding materia, and 17 hybrids were obtained, which were identified by clamp connection observation and antagonist response. This study proclaimed that the practicality of the hybridization breeding of G. lucidum by protoplast monokaryogenesis method.
        244.
        2010.06 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Thirteen species of mealybugs were intercepted in quarantine at Korean ports of entry on plant materials from China over the past 9 years (2000-2009). Of these, Phenacoccus madeirensis Green has been newly reported in China through this study. This list and key are provided to assist in identifying intercepted specimens of mealybugs from China.
        3,000원
        245.
        2010.03 구독 인증기관 무료, 개인회원 유료
        Prostatic calculi are common finding in radiographic examination, however, the true incidence and the clinical significance are not clearly known. We investigated the prevalence of prostatic calculi and the relationship between prostatic calcification and urolithiasis. From a database, 305 consecutive subjects older than 30 years of age who had undergone regular health checks in our hospital from January 2007 to July 2009 were enrolled in this study. Prostatic calculi and urinary stones were confirmed by non-enhanced CT. According to the presence of prostatic calculi, they were divided into two groups and the relationship with urolithiasis was determined using statistical analysis. Among 305 male subjects, prostatic calculi were found in 97 (31.9%), which revealed a linear trend with aging (r=0.928, p=0.023), while asymptomatic upper urinary tract stones were found in 45 subjects (14.9%). A significant difference was observed in mean age (p<0.001), however, no difference was observed in prevalence of diabetes mellitus (DM), hypertension (HT), and body mass index (BMI). In the prostatic calculi group, 24 (24.7%) subjects had previously unknown urolithiasis, while only 21 subjects (10.1%) in the non-prostatic calculi group had urinary stones. The prevalence of urolithiasis was significantly higher in men with prostatic calcification than in those without prostatic calcification (OR=2.92, 95% CI: 1.53-5.58, p=0.001). No significant differences in serum chemistry were observed between the two groups. Among the 45 patients with urolithiasis, no significant differences were observed in the mean stone size according to the presence of prostatic calcification. Our data showed that prostatic calcification was prevalent up to approximately 31.9% and was frequently combined with upper urinary tract stones. These results indicate that evaluation for urolithiasis might be needed in patients with incidentally detected prostatic calcification.
        4,000원
        247.
        2009.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        5,800원
        248.
        2009.08 구독 인증기관·개인회원 무료
        Chemical investigation of the aerial parts of Lespedaza hedysaroides resulted in the isolation of 8 flavonoids:orientin (1), isoorientin (2), vitexin (3), isovitexin (4), Isomyricitrin (5), meletin-3-O-β-d-glucoside (6), luteolin-7-O-glucoside (7), 6-Xylopyranosylluteolin (8), The result showed t㏊t Lespedeza hedysaroides was rich in flavonoid glycosides, espically of C-glycosylflavones which have good Pharmacia and bioactive. So Lespedeza hedysaroides was concluded that it has vast prospect for exploitation and utilization.
        252.
        2008.10 구독 인증기관·개인회원 무료
        To understand geographic genetic variation of the species and relationships among populations of the bumble bee, Bombus ardens, that is utilized as green house pollinator we expanded our investigation by sequencing somewhat longer mitochondrial DNA (mtDNA) fragment, covering some uninvestigated regions within the species distribution, and analyzing the sequence data in terms of population genetic structure. For the purpose of study, a portion of mitochondrial COI gene, corresponding to "DNA Barcode" region (658 bp) was sequenced from 160 individuals of B. ardens collected over 15 localities in Korea. The sequence data revealed overall relatively low genetic diversity within species, with a maximum sequence divergence of 0.3%. Geographically, one haplotype (BARBA01) was found in all localities surveyed, with the frequency of 91% (145 among 160 individuals), whereas other haplotypes were found in a locality mostly as a single individual, suggesting that haplotype distribution can be summarized as coexistence of widespread, one dominant haplotype and regionally restricted, other haplotypes. Overall, very high rate of per generation female migration (Nm = 4.6 ~ infinite) and very low level of geographic substitution (FST = 0 ~ 0.099) among localities were characteristic. Although some populations were genetically subdivided from the remaining localities in the hierarchical analysis, there was regional polarity on this subdivision. Taken together with gene flow estimates, the nature of genetic divergence of the bumble bee populations is characterized as one that possessing low genetic diversity, high gene flow, and wide spread of one dominant haplotype, consistent with the previous finding. To have further detailed information of this valuable genetic resource, further longer and variable molecular portion is under investigating.
        253.
        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
        254.
        2007.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Carbon/silicon composites were synthesized by mixing silicon powders with petroleum pitch and subsequent heat-treatment. The resultant composites were composed of carbon and nano-size crystalline silicon identified by XRD and EDX. FIB images and SEM images were taken respectively to detect the existence of silicon impregnated in carbon and the distribution of silicon on the carbon surface. The obtained carbon/silicon materials were assembled as half cell anodes for lithium ion secondary battery and their electrochemical properties were tested. The pitch/silicon composite (3 : 1 wt. ratio) heat treated at 1000℃ and mixed with 55.5 wt.% of graphite showed relatively good electrochemical properties such as the initial efficiency of 78%, the initial discharge capacity of 605 mAh/g, and the discharge capacity of 500 mAh/g after 20 cycles.
        4,000원
        255.
        2007.09 KCI 등재 구독 인증기관 무료, 개인회원 유료
        As a part of enhancing the performance of wood-plastic composites (WPC), polypropylene (PP)/ nanoclay (NC)/ wood flour (WF) nanocomposites were prepared using melt blending and injection molding process to evaluate their thermal stability. Thermogravimetric analysis (TGA) was employed to investigate thermal degradation kinetics of the nanocomposites both dynamic and isothermal conditions. Dynamic scans of the TGA showed an increased thermal stability of the nanocomposites at moderate wood flour concentrations (up to 20 phr, percentage based on hundred percent resin) while it decreased with the addition of 30 phr wood flour. The activation energy (Ea) of thermal degradation of nanocomposites increased when nanoclay was added and the concentration of wood flour increased. Different equations were used to evaluate isothermal degradation kinetics using the rate of thermal degradation of the composites, expressed as weight loss (%) from their isothermal TGA curves. Degradation occurred at faster rate in the initial stages of about 60 min., and then proceeded in a gradual manner. However, nanocomposites with wood flour of 30 phr heated at 300℃ showed a drastic difference in their degradation behavior, and reached almost a complete decomposition after 40 min. of the isothermal heating. The degree of decomposition was greater at higher temperatures, and the residual weight of isothermal degradation of nanocomposites greatly varied from about 10 to 90%, depending on isothermal temperatures. The isothermal degradation of nanocomposites also increased their thermal stability with the addition of 1 phr nanoclay and of wood flour up to 20 phr. But, the degradation of PP100/NC1/MAPP3/WF30 nanocomposites with 30 phr wood flour occurs at a faster rate compared to those of the others, indicating a decrease in their thermal stability.
        4,000원
        256.
        2007.06 구독 인증기관 무료, 개인회원 유료
        Poly(imide p-alkoxycinnamate)s of various alkyl chain lengths were synthesized by esterifying chloromethylated polyimide (CMPI), a synthetic platform for functionalized polyimides. Soluble CMPI, obtained by chloromethylation of soluble polyimide from diaminodiphenylether and 4,4’-(hexafluoroisopropylidene) diphthalic anhydride, was esterified with various p-alkoxycinnamic acids in the presence of base and phase transfer catalyst. The reaction underwent almost quantitatively. The structure of resulting polymer was characterized by 1H-NMR and FT-IR spectroscopic methods. Thin polymer film on a glass substrate was irradiated with polarized UV light, inducing a homogeneous liquid crystal alignment.
        4,000원
        259.
        2006.09 구독 인증기관·개인회원 무료
        The precipitation behaviors of γ″(Ni3Nb) in four Ni-base alloys were investigated. The four alloys were forged Ni20Cr20Fe5Nb alloy, mechanically alloyed Ni20Cr20Fe5Nb alloy, IN 718 alloy and ECAPed(equal channel angular pressing) IN 718 alloy. Aging treatment was employed at either 600℃ or 720℃ for 20 hrs. The TEM observation and hardness test were performed to identify the formation of γ″. The precipitation of γ″ was noticed after aging at 600℃ for 20 hrs in the mechanically alloyed Ni20Cr20Fe5Nb alloy and ECAPed IN 718 alloy, while it was observed after aging at 720℃ for 20 hrs in the forged Ni20Cr20Fe5Nb alloy and IN 718 alloy before ECAP. The lower aging temperature for γ″ precipitation in the mechanically alloyed Ni20Cr20Fe5Nb alloy and ECAPed IN 718 alloy than in the forged Ni20Cr20Fe5Nb alloy and IN 718 alloy before ECAP appeared to be due to the severe plastic deformation which occurred during mechanical alloying or ECAP.
        260.
        2006.09 구독 인증기관·개인회원 무료
        The microstructures of Ni-containing P/M steels produced by admixed powders or diffusion alloyed powders are usually heterogeneous. To improve the microstructure homogeneity, the effects of Mo and Cr additions in the prealloyed powder form were examined. The results showed that the microstructural homogeneity was improved and superior mechanical properties were achieved with increases in the alloy content, particularly for the Cr. Such a beneficial effect was attained due to the reduction of the repelling effect between Ni and C, as was demonstrated through thermodynamic analysis using the Thermo-Calc software.