• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.2
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• pp.233-239
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• 2013

In this paper, a method of combining numerical analyses and experimental tests is used to evaluate fracture toughness of copper thin films of $15{\mu}m$ thickness. Far-field loadings of a global-local finite element model are inversely estimated by matching crack opening profiles in experiments with numerical results. The fracture toughness is then evaluated using the J-integral for cracks in thin films under far-field loadings. In experiments, Cu thin films attached to Aluminum sheets are loaded indirectly, and crack opening profiles are observed by microscope camera. Stress versus strain curves of Cu thin films are obtained through micro-tensile tests, and the grain size of Cu thin films is observed by TEM analysis. The results show that the fracture toughness of Cu thin films with $500nm{\sim}1{\mu}m$ sized grains is $6,962J/m^2$.

• Journal of Nutrition and Health
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• v.31 no.5
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• pp.906-913
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• 1998

This study an analyzes the effects of the P/S ratio of dietary lipids and antioxidant vitamin supplements on serum lipids level and fatty acid profile, the degree of lipid peroxidation, and the antioxidant enzyme activities in the liver of rats treated with 7,12-dimethylbenz($\alpha$) anthracene(DMBA). P/S ratio of dietary lipids was made into 0.5, 1 and 2 by mixing palm oil, soybean oil, sesame oil and perilla oil at 10%(w/w) fat level and n-6/n-3 ratio was fixed to 4. Antioxidant vitamin of $\alpha$-tocopherol or $\beta$-carotene was supplemented in addition to vitamin mixture which was given at 1 % of the standard diet. female Sprague-Dawley strain rats, about 60 days old, were divided into three groups(LP : low P/S ratio(0.5), MP : medium P/S ratio (1.0), HP , high P/S ratio(2.0)) and each group was sub-divided into three groups(S ; standard, T ; tocopherol supplemented, C : carotene supplemented): Two weeks after feeding experimental diets, all groups were treated with a single dose of DMBA(2mg/100g BW) by gastric intubation and fed experimental diet for 9 week. The results were as follows ; 1) Serum total cholesterol(TC) level was not significantly influenced by diet but tended to be lower in HP groups compared to LP and MP groups. Triglyceride level was the highest in LP groups and the lowest in $\alpha$-tocopherol supplemented groups. 2) Thiobarbituric acid reactive substance(TBARS) level, representing lipid peroxidation in hepatic microsome, tended to be increased as the unsaturation of dietary lipids increases. $\alpha$-Tocopherol supplement significantly decreased TBARS level. 3) The activities of superoxide dismutase(SOD) and glutathione peroxidase(GSHPx) in hepatic cytosol showed the tendency to be high with increasing P/S ratio of dietary lipids. SOD activity was not significantly influenced by antioxidant vitamin, but GSHPx activity was significantly increased in $\alpha$-tocopherol supplemented groups. In summary, high polyunsaturated fat diet was effective on reducing the serum level of total cholesterol and triglyceride, while it increased unsaturation and peroxidizability of serum fatty acid. With increasing P/S ratio of dietary lipids, lipid peroxidation was increased in the liver and antioxidant enzyme system was induced to inhibit lipid peroxidation against oxidative damage. $\alpha$-Tocopherol supplement was effective in lowering lipid peoxidation, but $\beta$-carotene supplement did not exhibit antioxidant effect. (Korean J Nutrition 31(5) 906~913, 1998)

• Applied Biological Chemistry
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• v.27 no.3
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• pp.180-186
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• 1984

For the study of glucose oxidase(GOD) and catalase(CAT) coimmobilization system, the enzymes were obtained from Penicillium spp., PS-8, and the strain itself was used as an immobilizing matrix. To separate glucose oxidase and catalase after the ammonium sulfate fractionation of the culture broth, DEAF-cellulose column was used and its activity yield was 54 and 34%, respectively. Both enzymes were immobilized on the cell matrix, followed crosslinking with 2.5% glutaraldehyde for 12hr. In the determination of efficiencies of GOD and CAT of dual, mixed and soluble enzyme systems, the dual immobilized one w-as superior to those of the soluble or mixed ones. In the comparison of pH profiles, the dual and mixed types showed broader maximum pH ranges than the soluble type. Varying CAT/GOD ratio of the dual system, the higher the ratio showed the broader activity profile. In the comparison of apparent $K_m$ of GOD only and CAT/GOD=10, they were $7.1{\times}10^{-2}$ and $5.1{\times}10^{-2}M$. Their activation energies showed 3.98kcal/mole/deg for GOD only and 2.98kcal/mole/deg for CAT/GOD=10.

• Korean Journal of Food Science and Technology
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• v.24 no.1
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• pp.42-48
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• 1992

The rate and extent of coagulation of milk using fast acidification with 0.1 N HCl were monitored by changes in viscosity and turbidity at various temperatures and pH. Also the gelation rate of milk using slow acidification with D-glucono-${\delta}$-lactone was measured in a small strain rheological scanner. Coagulation of milk casein occurred in a specific pH range and was accompanied by an abrupt increase in viscosity at pH 5.0. Acid coagulation rate was enhanced by increasing temperature from $20^{\circ}C{\sim}50^{\circ}C$, and the maximum rate was shown around pH 5.0. The addition of salt ($CaCl_{2}$) reduced the maximum coagulation rate at all temperature ranges and shifted the pH ranges for maximum coagulation rate and the onset pH of coagulation. The onset of gelation and the rate of network formation during slow acidification were facilitated by Cl ion, but suppressed by SCN-ion, as indicated by the rate of rigidity development. The susceptibility to syneresis was greater in the gel made at lower temperature and around pH 4.6, while preheated milk at $90^{\circ}C$ for 5 min prior to acidification showed the same syneresis profile at all heating temperatures ($60{\sim}90^{\circ}C$).

• Food Science of Animal Resources
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• v.30 no.4
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• pp.609-616
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• 2010

This study was conducted to determine the effects of dietary low grade soybean, fermented with Aspergillus oryzae (FSB 1) or Bacillus subtilis var. natto (FSB 2), on egg production and quality, fat and cholesterol content, and the fatty acid (FA) profile of eggs by lipid layer. A total of 18 Hi-Line strain layers, 22 wk of age, were randomly assigned to three dietary treatments: no fermented soybean (control), control with 15% FSB 1 (C + FSB 1), and control with 15% FSB 2 (C + FSB 2). The rate of egg production and egg weight were evaluated between two periods: one was from the 1st to 4th wk and the other was from the 5th to 8th wk. At the 8th wk, a total of 30 eggs were randomly selected from each treatment group and analyzed for physical quality, fat content, fatty acid composition and cholesterol content. The results showed that egg production was increased in hens fed with diets containing fermented soybeans from the 5th to 8th wk period (p<0.01). A similar tendency was observed through eight weeks' cumulative egg production (p<0.05). There were no significant differences in egg production between the C + FSB 1 and C + FSB 2 treatment groups (p>0.05). Egg weight and other physical properties did not vary between treatment groups (p>0.05). Egg yolks among different treatment groups were similar in fat content, but egg yolks in the C + FSB 1 and C + FSB 2 groups had lower oleic acid (p<0.05), higher linoleic, ${\alpha}$-linolenic, and arachidonic acids (p<0.01), and lower cholesterol content (p<0.05) than those in the control group. In conclusion, supplementation of fermented low grade soybeans might be useful as a functional feedstuff to improve egg production and quality for a healthy human diet.

• Journal of Korean Society of Steel Construction
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• v.26 no.4
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• pp.263-275
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• 2014

In this study, connection of steel reinforced concrete(SRC) column and composite beam which consists of H-section and U-section members were tested under cyclic loading. An essential point of the composite beam is the structural performance of welded joint between the H-section and the U-section members. To improve the structural performance of joint of two beam members, vertical stiffeners, trapezoidal stiffeners, and top bars were used. Five full-scaled specimens were designed to study the effect of a number of parameters on cyclic performance of connections such as H-section beam size($H-500{\times}200{\times}10{\times}16$, $H-600{\times}200{\times}11{\times}17$), the presence of stiffeners and top bars, and the presence of no weld access hole(WAH) method. Based on the test results, deformation capacity of the specimens with H-500 series beam and H-600 series beam were 4% and 3% rotation angle, which is the requirement for the Special Moment Frame and Intermediate Moment Frame(IMF), respectively. Test result showed that deformation capacity of connection with stiffeners and top bars is greater than that of connection without stiffeners and top bars. Finally, energy dissipation capacity and strain profile of specimens were summarized.

• Journal of Food Hygiene and Safety
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• v.27 no.1
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• pp.63-67
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• 2012

Antibiotic resistance in animal isolates of enterococci is a public health concern, because of the risk of transmission of antibiotic-resistant strains or resistance genes to humans through the food chain. This study investigated phenotypic and genotypic resistances profile of tetracycline in 245 $Enterococcus$ isolates from bovine milk. A total of 245 enterococci were isolated from 950 milk samples. The predominant strain was $E.$ $faecalis$ (n = 199, 81.2%) and $E.$ $faecium$ (n = 25, 10.2%). $E.$ $avium$ (n = 7, 2.9%), $E.$ $durans$ (n = 6, 2.5%), $E.$ $gallinarum$ (n = 4, 1.6%), and $E.$ $raffinosus$ (n = 4, 1.6%) were also isolated. Of the 245 enterococcal isolates 76.3% (n = 187) displayed tetracycline resistance (${\geq}16{\mu}g/ml$). Of the 187 tetracycline-resistant isolates, 83.4% (n = 156), 16.1% (n = 30), and 26.7% (n = 50) possessed the genes $tet$(M), $tet$(L), $tet$(S) respectively. While 3.2% (n = 6) of the tetracycline-resistant isolates possessed all three genes $tet$(M) + $tet$(L) + $tet$(S), 8.6% (n = 16), 16.0% (n = 30), and 2.7% (n = 5) of them possessed two genes $tet$(M) + $tet$(L), $tet$(M) + $tet$(S), and $tet$(L) + $tet$(S) respectively. The tetracycline resistance pattern investigated in this study was attributable mainly to the presence of $tet$(M).

• Journal of Life Science
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• v.25 no.2
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• pp.121-129
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• 2015

Alginates are found in marine brown seaweeds and in extracellular biofilms secreted by some bacteria. Previously, we reported an oligoalginate lyase from Sphingomonas sp. MJ-3 (MJ3-Oal) that had an exolytic activity and protein sequence homology with endolytic polymannuronate (polyM) lyase in the N-terminal region. In this study, the MJ3-Oal was tested for both exolytic and endolytic activity by homology modeling using the crystal structure of Alg17c from Saccharophagus degradans 2-40T. The tyrosine residue at the $426^{th}$ position, which possibly formed a hydrogen bond with the substrate, was mutated to phenylalanine. The FPLC profiles showed that MJ3-Oal degraded alginate quickly to monomers as a final product through the oligmers, whereas the Tyr426Phe mutant showed only exolytic alginate lyase activity. $^1H$-NMR spectra also showed that MJ3-Oal degraded the endoglycosidic bond of polyM and polyMG (polymannuronate-guluronate) blocks. These results indicate that oligoalginate lyase from Sphingomonas sp. MJ-3 probably catalyzes the degradation of both exo- and endo-glycosidic bonds of alginate.

• Journal of the Korea Concrete Institute
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• v.24 no.2
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• pp.205-214
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• 2012

Crack widths play an important role in the serviceability limit state. When crack widths are controlled sufficiently, the reinforcement corrosion can be reduced using only existing concrete cover thickness due to low permeability in the region of finely distributed hair-cracks. Thus, the knowledge about the tensile crack opening is essential in designing more durable concrete structures. Therefore, numerous researches related to the topic have been performed. Nevertheless accurate measurement of a crack width is not a simple task due to several reasons such as unknown potential crack formation location and crack opening damaging strain gages. In order to overcome these difficulties and measure precise crack widths, a displacement measurement system was developed using digital image correlation. Accuracy calibration tests gave an average measurement error of 0.069 pixels and a standard deviation of 0.050 pixels. Direct tensile test was performed using ultra high performance concrete specimens. Crack widths at both notched and unnotched locations were measured and compared with clip-in gages at various loading steps to obtain crack opening profile. Tensile deformation characteristics of concrete were well visualized using displacement vectors and full-field displacement contour maps. The proposed technique made it possible to measure crack widths at arbitrary locations, which is difficult with conventional gages such as clip-in gages or displacement transducers.

• Biomedical Science Letters
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• v.16 no.2
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• pp.75-82
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• 2010

The molecular epidemiological characteristics of methicillin-resistant Staphylococcus aureus (MRSA) isolates have demonstrated their genetic diversity and evolution. A total of 137 strains of MRSA clinical isolates was collected from Korean healthcare facility in 2007. The MRSA clinical isolates were analyzed by molecular typings (SCCmec element and agr locus typing), virule nce factor gene detections {(Panton-Valentine leukocidin (PVL), enterotoxin, exfoliative toxin and toxic shock syndrome toxin-1), and amplified fragment length polymorphism (AFLP)}. The MRSA clinical isolates were classified as SCCmec type II-agr type 1 (2 strains), type II-agr type 2 (79 strains), type III-agr type 1 (24 strains), type III-agr type 2 (2 strains), type IV-agr type 1 (27 strains), type IV-agr type 2 (2 strains), and non-typable (1 strain, agr type 3). Based on SCCmec types, SCCmec type II (95.1%) and III (88.5%) indicated higher multidrug resistance rate than SCCmec type IV (10.3%) (P<0.001). The most common enterotoxin genes were seg (83.8%), sei (83.1%), and sec (80.2%). The tst gene was present in 86 out of 137 (62.8%) MRSA isolates. All MRSA isolates were negative for PVL and exfoliative toxin genes. The combinations of toxin genes were observed in particular SCCmec types; 97.6% of SCCmec type II strains carried sec, seg, sei and tst genes, 73.0% of SCCmec type III strains carried sea gene, and 89.7% of SCCmec type IV strains carried sec, seg and sei genes. Each of the SCCmec types of MRSA isolates had distinct AFLP profile. In conclusion, SCCmec type II, agr type 1 and 2 have demonstrated to be the most common types in Korea, and the results indicated that the virulence factors are closely associated with their molecular types (SCCmec and agr types).