• Tribology and Lubricants
• /
• v.18 no.5
• /
• pp.324-332
• /
• 2002

In order to enhance the thermal stability of binder materials of bonded type solid lubricants, several metal-alkoxide based sol-gel materials such as methyltrimethoxysilane(MTMOS), titaniumisopropoxide$(Ti(Opr^i)_4),$ zirconiumisopropoxide $(Zr(Opr^i)_4)$ and aluminumbutoxide$(Al(Obu^t)_4)$ were chemically modified by epoxy-, acrylic- and fluoro-silane compounds, respectively. Friction and wear characteristics of these hybrid ceramic materials were tested with a micro tribo-tester, and evaluated with respect to both heat-curing temperature and the time. Test results generally showed that hybrid ceramic materials modified by epoxy-silane compounds had a low friction compared to others. And the higher het-curing temperature and the longer heat treatment time resulted in the higher friction and the lower wear. IR spectroscopic analyses revealed that these results were caused mainly by the increased metal oxide content in hybrid ceramics when the heat-curing temperature was over $320^{\circ}C.$

• Korean Journal of Veterinary Research
• /
• v.39 no.2
• /
• pp.338-342
• /
• 1999

Twenty three strains of Escherichia (E) coli O157 : H7 isolated from Korea, Japan, USA were analyzed by pulsed-field gel electrophoresis (PFGE) of XbaI-digested chromosomal DNA and multiplex polymerase chain reaction. Various PFGE patterns of E. coli O157 : H7 were found on the same farm. Most of the E, coli O157 : H7 strains had shiga-like toxin (slt) II gene only (43.5%) or both slt I and slt II genes(30.4%). eaeA gene was highly conserved in the E. coli O157 : H7. There was no correlation between PFGE and slt gene patterns. The results indicate that various genotypes of E. coli O157 : H7 have spread throughout the country and genomic DNA patterns generated by PFGE are highly specific for different strains and have significant value in epidemiologic investigations of infectious disease outbreaks.

• Journal of the Korean Ceramic Society
• /
• v.31 no.9
• /
• pp.1060-1068
• /
• 1994

Stable zirconia sol was prepared from zirconium butoxide Zr(OC4O9)4 as a precursor and ethylacetoacetate(EAcAc) or diethylene glycol(DEG) as a chelating agent under ambient agent under ambient atmosphere by Sol-Gel process. The sythesized sol was coated on 304 stainless steel substrate by dip coating, thereafter zirconia film could be obtained by heat-treatment at $600^{\circ}C$. The characteristics of coating film were determined by FT-IR, XRD, and ellipsometion peak represented Zr-O-Zr bonding of tetragonal phase was shown at 470cm-1. Crystallization of zirconia gel and film from amorphous state to tetragonal phase started at 40$0^{\circ}C$, and then transformed into monoclinic phase around $700^{\circ}C$. Zirconia film coated on 304 stainless steel substrate showed relatively low porosity of 16% when it was coated with 0.4M zirconia sol and thereafter heat-treated at 80$0^{\circ}C$ and the film was densified continuously up to 90$0^{\circ}C$. The zirconia film of 10 nm thick acted as a protective layer against oxidation up to $700^{\circ}C$.

• Journal of Korea Technical Association of The Pulp and Paper Industry
• /
• v.43 no.1
• /
• pp.11-16
• /
• 2011

This study was carried out in order to elucidate the effect of latex dosage and properties on aging behavior of coated paper. The coated paper with five different coating formulations were prepared and also four different latices were used. The coated paper were thermally aged at $105^{\circ}C$ for 14 days and the optical properties were measured. Increasing latex content increased the magnitude of reduction in brightness and whiteness. In addition, the variations in CIE a$^*b^*$ were larger with increasing latex dosage. Latex which has the lower gel content and the higher Tg showed the higher reduction in brightness and whiteness and much variation in CIE a$^*b^*$. However the particle size of latex didn't affect to thermal behavior of coated paper. These results indicate that latex which has higher Tg and lower gel content is the one of the main factors affecting aging behavior of coated paper.

• Microbiology and Biotechnology Letters
• /
• v.9 no.4
• /
• pp.185-190
• /
• 1981

1. $\alpha$-amylase from B. circulans F-2 was purified with specific activity 55.0 u/mg. protein (about 23 times of the original specific activity) and the yield of 25.5%, by means of corn starch absorption, salting out with ammonium sulfate (80% saturation), gel filtration on Bio-Gel P-100 and DE-32 column chromatography. 2 The purified enzyme showed two closely migrated protin bands on polyacrylamide disc gel electrophoresis, both of which have amylase activity judging from the activity staining of the gel. On SDS-polyacrylamide disc gel electrophoresis, however, the purified enzyme showed a single band suggesting that those two bands are the charge isomers of an amlyase having the slightly different charge. 3. Plot of log mobility of two bands versus polyacrylamide gel concentration according to Hedrick and Smith gave the parallel lines indicating them to be charge isomers. 4. To confirm the action pattern of two enzyme protein bands, each band was separated and was eluted from the gel and eluates were incubated with soluble starch. Oligosaccharide pattern produced by each eluate was examined by paper chromatography. The eluates of two bands showed the same action pattern. 5. The maltohexaose was the only hydrolysis product of soluble starch in the early stage of hydrolysis.

• Journal of the Korean Ceramic Society
• /
• v.26 no.6
• /
• pp.795-801
• /
• 1989

The polycrystalline mullite fiber was synthesized from various combination of starting materials including metal alkoxides and colloidal sol by the sol-gel process. The best spinnability was observed in the sol which showed shear thinning and hysteresis (i.e., thixotropic flow), indicating that the network structure was broken down as the shear rate increased. The mullite fiber was polycrystalline after firing and characterized by thermal analysis, XRD, FT-IR spectroscopy, rheological measurements, and SEM.

• The Korean Journal of Ceramics
• /
• v.6 no.4
• /
• pp.390-395
• /
• 2000

Silicon, titanium, zirconium phosphates were synthesized by starting with appropriate chemical precursors in a solution. The synthetic procedure, chemical and physical structures were examined by FT-IR, liquid and solid state NMR, TGA, SEM, XRD, etc. The phosphates were examined for thermal and electrical properties. Advantages of the synthesis technique and the data on unique structures and thermal properties are reported.

• Journal of Plant Biology
• /
• v.33 no.1
• /
• pp.73-80
• /
• 1990

Subcellular distribution of arginase activity was measured in leaves of Canavalia lineata. Both mitochondrial and cytosolic fraction were found to contain the arginase activity. It was noticible that cytosolic fraction contained a substantial amount of arginase activity. Different mobility of arginase from these two fractions was showed on DEAE-Sephacel chromatography and polyacrylamide gel electrophoresis. Also different pI value was showed 6.3 in cytosolic and 6.7, 7.1 in mitochondiral fraction on IEF gel electrophoresis. However, canavaine-dependent-activity (CDA) of arginase in these two fractions were not different. These results indicate that heterogenity of arginase occurs in leaves of C. lineata.

• Journal of the East Asian Society of Dietary Life
• /
• v.10 no.5
• /
• pp.439-444
• /
• 2000

호알칼리성 방선균 Streptomyes sp. B-2를 Glucose Isomerse 생성을 위해 토양에서 분리했다. Glucose Isomerase(G.I)는 high fructose glucose syrup과 fructose의 생산을 위해서 식품 공업에서 아주 중요시되고 있는 효소이다. 호알칼리성 방선균 Streptomyces sp. B-2가 생성하는 glucose isomerase(G.I.)를 정제하였다. G.I.는 (NH$_4$)$_2$So$_4$분획, DEAE-cellulose, Sephadex G-200 chromatography하여 순수 분리 하였다. 순수분리된 G.I.는 electrophoresis에 의해 확인을 했다. SDS-acrylamide gel electrophoresis에 의해 정제된 효소는 single band를 보여주었다.

• Journal of Life Science
• /
• v.6 no.4
• /
• pp.241-249
• /
• 1996

A collagenase was isolated from the culture filtrate of Vibrio mimicus (ATCC 33658). The enzyme was purified to homogeneity by ammonium sulfate precipitation and DEAE-Sephadex A-50 chromatography, which an activity recovery of 22%. The molecular weight of the purified enzyme was estimated to be 42 kDa by SDS-polyacrylamide gel electrophoresis and gel filtration, indication a monomer structure. The optimum pH and temperature od the enzyme for insoluble collagen (Type I) were around 7.75 and 28$\circ$C, respectively. Some chelating agents and serine protease inhibitor inactivated the enzyme, but L-cysteine and histidine did not affect the activity. The amino acid composition indicated that the collagenase contained high amounts of amino acid residues of glycine and alanine. The K$_{m}$ and R$_{cat}$/K$_{m}$ values for the collagenase, using insoluble collagen (type I) as substrate, were 2.86 mg/ml and 972.28 U/mg-protein, respectively.