• Journal of the Korean Society of Safety
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• v.12 no.4
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• pp.27-38
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• 1997

The effect of geometry factors on the combined mode stress intensity factor behaviors of a slant crack in a non-uniform thickness material was analysed by 2-dimensional theoretical analysis. The analysis is based on the Laurent's series expansions of complex potentials where the complex coefficients of the series are determined from the compatibility and the equilibrium conditions of the thickness interface and the stress free conditions of the crack surface. In numerical calculations the perturbation technique is employed. The expressions for the crack tip stress intensity factor are given in the form of power series of dimensionless crack length $\lamda$, and the function of crack slant angle $\alpha$ and thickness ratio $\beta$. The results of numerical calculations for each problems are represented as the correction factors F($\lamda$, $\alpha$, $\beta$). The results clearly show the following characteristics : The correction factors of the combined mode stress intensity factors for a non-uniform thickness material can be defined in the form of F($\lamda$, $\alpha$, $\beta$). The stress intensity factor values for a given crack length are decreased with increase of thickness ratio $\beta$.

• Electrical & Electronic Materials
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• v.14 no.12
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• pp.3-6
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• 2001

In common globular proteins, the native form is n its most stable state. However, the native form of inhibitory serpins (serine protease inhibitors) and some viral membrane fusion proteins is in a metastable state. Metastability in these proteins is critical to their biological functions. Our previous studies revealed that unusual interactions, such as side-chain overpacking, buried polar groups, surface hydrophobic pockets, ad internal cavities are the structural basis of the native metastability. To understand the mechanism by which these structural defects regulate protein functions, cavity-filling mutations of $\alpha$1-antitrypsin, a prototype serpin, were characterized. Increasing conformational stability is correlated with decreasing inhibitory activity. Moreover, the activity loss appears to correlate with the decrease in the rate of the conformational switch during complex formation with a target protease. We also increased the stability of $\alpha$1-antitrypsin greatly via combining various stabilizing single amino acid substitutions that were distributed throughout the molecule. The results showed that a substantial increase of stability, over 13 kcal/mol, affected the inhibitory activity with a correlation of 11% activity loss per kcal/mol. The results strongly suggest that the native metastability of proteins is indeed a structural design that regulates protein functions and that the native strain of $\alpha$1-antitrypsin distributed throughout the molecule regulates the inhibitory function in a concerted manner.

• Fibers and Polymers
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• v.1 no.2
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• pp.116-121
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• 2000

It has been considered that malic acid, $\alpha$-hydroky succinic acid, could not form crosslinks in the cellulosic materials unless activated by other polycarboxylic acids such as butanetetracarboxylic acid or citric acid because there are only two carboxylic acids per molecule available fur the formation of one anhydride intermediate. However we found that the dicarboxylic malic acid with sodium hypophosphite catalyst without the addition of other crosslinkers was able to improve wrinkle resistance of cotton up to $294^{\circ}$(dry WRA) and $285^{\circ}$ (wet WRA), which is a measure of crosslinking level in cotton. $^1$H FT-NMR, FT-IR and GPC analysis indicated the in-situ formation of an trimeric $\alpha$, $\beta$-rnalic acid with a composition of 1:3 through the esterification between hydroxyl group and one of carboxylic groups in malic acid during curing. The crosslinking of cotton was attributed to the trimeric $\alpha$, $\beta$-malic acid, a tetracarboxylic acid, which can form two anhydride rings during curing. The influence of crosslinking conditions such as concentrations of malic acid and catalyst, pH of the formulation bath, and curing temperature were investigated in terms of imparted wrinkle resistance and whiteness. The addition of reactive polyurethane resin in the formulation slightly increased the mechanical strength retention of crosslinked fabric coupled with additional increase in wrinkle resistance.

• The Korean Journal of Nuclear Medicine
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• v.36 no.2
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• pp.133-139
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• 2002

Purpose: Scintillation Proximity Assay (SPA) does not require the physical separation of receptor bound form from free form. SPA was applied to the study of interaction of human chorionic gonadotropin (hCG) and $anti-{\alpha}$ hCG in serum. Materials and methods: $Anti-{\alpha}$ hCG was biotinylated for the binding to streptavidin. The assay was based on the simple competitive binding method between $[^{125}I]hCG$ and the hCG in sample serum, with $anti-{\alpha}$ hCG-coated beads. Aliquots of biotinylated $anti-{\alpha}$ hCG were dispensed into scintillation vials containing $100{\mu}{\ell}\;[^125}I]hCG\;and\;200{\mu}{\ell}$ of either a standard concentration of hCG for preparation of standard curve or unknown sample, and incubated for 20 min. at room temperature. Then $20{\mu}{\ell}$ streptavidin-coated beads were added to vials, and finally incubated for 10 min at room temperature. Values for unknown samples were then calculated from the standard curve. Results: Optimal background counts were certificated using varied radioactivity of radionuclides. Appropriate standard curve was obtained from SPA method successively, and the concentration of hCG from unknown serum was determined by standard curve. The result from SPA assay was similar to that of RIA. Conclusion: This observation confirms that SPA method could be useful for clinical diagnosis.

• Biomedical Science Letters
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• v.16 no.4
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• pp.239-246
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• 2010

It is suggested that ovariectomy induces body weight gain primarily in the form of adipose tissue in rodents. Since liver peroxisome proliferator-activated receptor ${\alpha}$ (PPAR${\alpha}$) and uncoupling 2 (UCP2) are involved in the regulation of energy expenditure, it was investigated whether swim training regulates ovariectomy-induced adiposity and steatosis through liver PPAR${\alpha}$ and UCP2 activation in female ovariectomized mice, an animal model of postmenopausal women. Swim-trained mice had significantly decreased adipose tissue weights compared with sedentary control mice. Histological analysis showed that hepatic lipid accumulation was inhibited by swim training. Concomitantly, swim training significantly increased mRNA levels of PPAR${\alpha}$ and its target genes responsible for peroxisomal fatty acid ${\beta}$-oxidation, such as acyl-CoA oxidase, enoyl-CoA hydratase/3-hydroxyacyl-CoA dehydrogenase and thiolase in the liver. Moreover, swim training induced the mRNA expression of UCP2. These results suggest that swim training can effectively prevent adiposity and steatosis caused by ovariectomy, in part through activation of liver PPAR${\alpha}$ and UCP2 in female obese mice.

• Proceedings of the Korean Society for Applied Microbiology Conference
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• 1986.12a
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• pp.525.2-525
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• 1986

Cephalexin synthesizing enzyme (${\alpha}$ amino acid ester hydrolase) was partially purified from the culture broth of Acetobacter turbidans ATCC9325 through ammonium sulfate fractionation, DEAE, CM, and Sephacryl S-200 gel filtration. The enzyme has optimum pH 6.0 and temperature, 40$^{\circ}C$ respectively. From the analysis of reaction mixtures by thin layer chromatographic and high performance liquid chromatographic techniques, it was confirmed this enzyme catalyzed simultaneously the following reactions : 1) Synthesis of cephalexin from D-${\alpha}$-phenylglycine methylester (PGM) and 7-amino 3-deacetoxy-cetoxycephalosporanic acid (7-ADCA) 2) Hydrolysis of cephalexin to form 7-ADCA and phenylglycine (PG) 3) Hydrolysis of PGM to form PG and methanol. Base on the above experimental observations, the reaction model of this enzyme was identical with that of the enzyme from Xanthomonas citri.

• Bulletin of the Korean Mathematical Society
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• v.50 no.6
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• pp.1981-1988
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• 2013

We say a positive integer n satisfies the Lehmer property if ${\phi}(n)$ divides n - 1, where ${\phi}(n)$ is the Euler's totient function. Clearly, every prime satisfies the Lehmer property. No composite integer satisfying the Lehmer property is known. In this article, we show that every composite integer of the form $D_{p,n}=np^n+1$, for a prime p and a positive integer n, or of the form ${\alpha}2^{\beta}+1$ for ${\alpha}{\leq}{\beta}$ does not satisfy the Lehmer property.

• BMB Reports
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• v.37 no.6
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• pp.642-647
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• 2004

The lysine residues of Bacillus licheniformis $\alpha$-amylase (BLA) were chemically modified using citraconic anhydride or succinic anhydride. Modification caused fundamental changes in the enzymes specificity, as indicated by a dramatic increase in maltosidase and a reduction in amylase activity. These changes in substrate specificity were found to coincide with a change in the cleavage pattern of the substrates and with a conversion of the native endo- form of the enzyme to a modified exo- form. Progressive increases in the productions of $\rho$-nitrophenol or glucose, when para nitrophenyl-maltoheptaoside or soluble starch, respectively, was used as substrate, were observed upon modification. The described changes were affected by the size of incorporated modified reagent: citraconic anhydride was more effective than succinic anhydride. Reasons for the observed changes are discussed and reasons for the effectivenesses of chemical modifications for tailoring enzyme specificities are suggested.

• Proceedings of the KIEE Conference
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• 1994.07b
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• pp.1376-1378
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• 1994

Azobenzene derivative is so stiff that monolayer cannot be formed on the subphase. To form a monolayer on the subphase, azobenzene derivative was mixed arachidic acid. It didn't form a monolayer, either. The mixture of azobenzene derivative and L-${\alpha}$-phosphatidylcholine generated a monolayer on the wafer subphase. Thickness of LB film layered at 30 mN/m was about $70{\AA}$. The polarized UV-visible absorption spectra of the mixture exhibited a dichroic ratio of azobenzene derivative and L-${\alpha}$-phosphatidylcholine.

• Bulletin of the Korean Chemical Society
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• v.24 no.1
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• pp.19-22
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• 2003

For CHNO explosives, two new correlations of the form $P_{CJ}\;=\;8.7({\alpha}T_c')^{1/2}{\rho}_0^2-5\;and\;P_{CJ}\'=\'9.5({\alpha}T_c')^1/2{\rho}_0^2-9$ have been demonstrated, which relate detonation pressure, $P_{CJ}$; combustion temperature of the explosive in gas phase, $T_c$; combustion temperature of the explosive in crystalline state, $T_c'$; and the number of moles of gaseous products per unit weight of explosive, α; at initial density of the explosive, ${\rho}_0$. Experimental and semi-empirical PM3 procedures were used for the computation of $T_c$. Detonation pressures derived in this manner have a simple form without need to use computer code.