• Journal of Microbiology
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• 제40권1호
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• pp.82-85
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• 2002

The aerobic batch growth of Issatchenkia orientalis DY252 with glucose and fructose medium was investigated at 32$\^{C}$ and pH 5.0. Aerobic ethanol production was evident with yeast I, orientalis. A diauxic lag of about 1 h between growth on glucose and growth on ethanol during batch culture was observed. However, no diauxic growth occurred with fructose. As the incubation temperature was increased from 32 to 39$\^{C}$, viability at the end of each batch culture declined significantly, from 93 to 43%, Unlike the effect of temperature, viability was not greatly affected by incubation pH, and cell yield values in a range of 0.45-0.48 were obtained. In order to overcome overflow metabolism, a fedbatch culture under glucose limitation was carried out. Compared with aerobic batch culture, about 10% improvement in cell yield was achieved with a fed-batch culture in optimal conditions.

• Journal of Microbiology and Biotechnology
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• 제12권1호
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• pp.162-165
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• 2002

With the objective of identifying the commercial potential of new direct-fed microbials, several temperature-tolerant strains were isolated from cane molasses at $39^{\circ}C$ and tested for their tolerance to pH, bile salts, and a mixture of volatile fatty acids (acetic acid:propionic acid:butyric acid=6.5:2.0:1.5). It was found that the isolated strain DY 252 grew very well up to pH 2.0 and was resistant to relatively high concentrations of bile salts. Among the strains tested, DY 252 was least inhibited by the addition of volatile fatty acids to the growth medium at $39^{\circ}C$. Accordingly, it would appear that strain DY 252, identified as yeast Issatchenkia orientalis, may be a potential candidate for use as a microbial feed additive.

• The Plant Pathology Journal
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• 제15권3호
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• pp.168-171
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• 1999

Crude extracts of pathogenic Streptomyces turgidiscabies isolates produced necrotic reaction on potato slices. Necrosis was first visible 24 hr after application and increased in severity over several days. However, necrosis was not observed when crude extracts of nonpathogenic strains were applied onto tuber slices. Presence of thaxtomin A from crude extracts of pathogenic S. turgidiscabies was identified by thin layer chromatography and high performance liquid chromatography. Nonpathgenic strains did not produce thaxtomin A in oatmeal broth. Inoculation of potato tuber slices with thaxtomin A partially purified from crude extract of a pathogenic S. turgidiscabies ST5 reproduce necrotic reaction suggesting that thaxtomin A is a pathogenicity determinant in S. turgidiscabies.

• 한국세라믹학회지
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• 제46권5호
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• pp.515-519
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• 2009

Carbon layers were fabricated on silicon carbide by chlorination reaction at temperatures between $1000^{\circ}C$ and $1500^{\circ}C$ with $Cl_2/H_2$ gas mixtures. The effect of reaction temperature on the micro-structures and tribological behavior of SiC derived carbon layer was investigated. Tribological tests were carried out ball-on-disk type wear tester. Carbon layers were characterized by X-ray diffractometer, Raman spectroscopy and surface profilometer. Both friction coefficients and wear rates were maintained low values at reaction temperature up to $1300^{\circ}C$ but increased suddenly above this temperature. Variation of surface roughness as a function of reaction temperature was dominant factor affecting tribological transition behavior of carbon layer derived from silicon carbide at high temperature.

• 한국세라믹학회지
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• 제44권7호
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• pp.375-380
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• 2007

Tribological properties of carbon layers produced by high temperature chlorination of SiC ceramic and DLC (diamond-like carbon) coatings produced by ion plating method were investigated and compared. Carbon coatings were produced by exposure of ball and disc type SiC in chlorine and hydrogen gas mixtures at $1200^{\circ}C$. After treatment for 10 h, dense carbon films up to $180{\mu}m$ in thickness were formed. Tribological behavior of newly developed carbon films were compared with that of DLC films. Wear resistance and frictional coefficient of the surface modified ball and disc type SiC were significantly improved compared to an untreated SiC specimen, and also the modified carbon layer had better performance than DLC coatings. Therefore, in this study, the newly developed carbon films have several advantages over existing carbon coatings such as DLC coatings and showed superior tribological performances.

• Macromolecular Research
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• 제17권8호
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• pp.603-608
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• 2009

Novel ultra-high molecular weight polyethylene (UHMWPE)/zirconia composites were previously prepared by the in situ polymerization of ethylene using a Ti-based Ziegler-Natta catalyst supported on to the surface of zirconia, as a bearing material for artificial joints. Tribological tests revealed that a uniform dispersion of zirconia in UHMWPE markedly increased the wear resistance. The effects of zirconia content on the oxidation behavior of the ${\gamma}$-ray-treated UHMWPE/zirconia composite surfaces were examined. The oxidation index that estimates the oxidation degree as the content of total carbonyl compounds was monitored using Fourier transform infrared spectroscopy-attenuated total reflectance. The changes in the surface composition due to the oxidation were confirmed by electron spectroscopy for chemical analysis. The extent of oxidation decreased with increasing zirconia content, which was attributed to the increased crystallinity as well as the decreased polymer portion of the UHMWPE/zirconia composites.

• Tribology and Lubricants
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• 제25권1호
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• pp.20-24
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• 2009

TiC-derived carbon coatings have been synthesized at $600^{\circ}C$ temperature treatment with $H_2/Cl_2$ mixture gases. From Raman spectroscopy measurements, the modified layer was covered with carbon and the thick-ness of the layer was increased with increasing reaction time. And $I_D/I_G$ ratio was decreased with increasing reaction time. The superior tribological property was obtained from TiC reacted with $Cl_2$ gas for 2 hrs. And the tribological property measurements indicate that TiC-derived carbon layer has $0.9{\times}10_{-6}mm^3/Nm$ in wear coefficient and 0.13 in friction coefficient.

• 국제학술발표논문집
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• The 3th International Conference on Construction Engineering and Project Management
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• pp.487-492
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• 2009

A large-scaled research project titled "Intelligent Excavating System (IES)" sponsored by Korean government has launched in 2006. An issue of real-time 3D terrain modeling has become a crucial point for successful implementation of IES due to many application limitations of state-of-the-art techniques developed in various high-technology fields. Many feasible technologies such as laser scanning, structured lighting and so on were widely reviewed by professionals and researchers for one year. Various efforts such as literature reviews, interviews, and indoor experiments make us select a structural light technique and stereo vision technique as appropriate techniques for accomplishment of real-time 3D terrain modeling. It, however, revealed that off-the-shelf products of structural light and stereo-vision technique had many technical problems which should be resolved for practical applications in IES. This study introduces diverse methods modifying off-the-shelf package of the structural light method, one of feasible techniques and eventually allowing this technique to be successfully utilized for achieving fundamental research goals. This study also presents many efforts to resolve practical difficulties of this technique considering basic characteristics of excavating operations and particular environment of construction sites. Findings showed in this study would be beneficial for other researchers to conduct new researches for application of vision techniques to construction fields by provision of detail issues about practical application and diverse practical methods as solutions overcoming these issues.

• 대한수의학회지
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• 제33권3호
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• pp.513-524
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• 1993

mechanisms for the hypocholesterolemic effects of $\beta$-glucan remain unclear. Rats were divided into 3 groups ; normal control group, atherogenic group(oral administration of cholesterol 40 mg/kg/day plus vit. $D_2$ 320,000 IU/kg/day), $\beta$-glucan treatment group(atherogenic treatment plus $\beta$-glucan 0.135 g/kg/day). The $\beta$-glucan treatment group showed moderate increases of serum lipids concentration compared with atherogenic group. In histopathological examination, aortas showed no critical lesions. The total fecal neutral sterols and bile acids excreted for 6 days was increased compared with both normal and atherogenic group. To compare effects of soluble fiber and insoluble fiber extracted from barley on postprandial lipemia, 5 healthy male adults ingested on separate days a low-fiber(total dietary fiber 2.61g) control meal or dietary fiber-enriched(12.61g) meals. Fasting and postprandial blood samples were obtained for 6.5h and serum lipids were analyzed. The serum total lipids, total cholesterols, LDL & VLDL-cholesterol were markedly reduced with soluble fiber-enriched meals, but no decrease with insoluble fiber-enriched meals. These results suggest that mechanisms for the hypocholesterolemic effect of $\beta$-glucan on rats were due to the inhibition of cholesterol absorption in the intestinal lumen and acceleration of cholesterol catabolism in the liver. And the soluble dietary fiber($\beta$-glucan) has the hypocholesterolemic effect by dropping serum LDL & VLDL-cholesterol in the clinical study.

• Parasites, Hosts and Diseases
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• 제47권4호
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• pp.381-386
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• 2009

A survey to determine the geographical distribution and relative abundance of potential vectors of scrub typhus was conducted from October to November 2006 at 13 localities throughout the Republic of Korea. Apodemus agrarius accounted for 97.6% (80/82) of all rodents, while only 2 Myodes regulus (2/82) were collected. A total of 10,860 chiggers were collected from A. agrarius belonging to 4 genera and 8 species, while only Walehia fragilis (40) was collected from Myodes regulus. Leptotrombidium pallidum (8,137; 74.9%), a vector of scrub typhus, was the predominant species collected from A. agrarius followed by Leptotrombidium scutellare (2,057, 18.9%), Leptotrombidium palpale (279; 2.7%), Leptotrombidium orientale (232; 2.1%), and Leptotrombidium zetum (79; 0.7%), Neotrombicula tamiyai (58; 0.5%), Euschoengastica koreaensis (16; 0.1%), and Cheladonta ikaoensis (2; < 0.1 %). L. pallidum was the predominant chigger collected at collection sites in Gangwon (100%), Gyeonggi (87.2%), Chungnam (100%), Chungbuk (100%), Jeonbuk (73.9%), Jeonnam (77.0%), and Gyeongbuk (66.1%) provinces, whereas L. scutellare was the predominant chigger collected in Gyeongnam province (77.9%) and Jeju Island (62.3%). Data suggest a correlation between chigger population abundance and human cases of scrub typhus in Korea.