• 대한수의학회지
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• 제22권1호
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• pp.15-21
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• 1982

The biochemical properties of strains of Staphylococcus aureus isolated from cattle with peracute gangrenous mastitis, acute systemic mastitis and chronic mastitis were examined. Of 261 strains of Staphylococci isolated from quarters with clinical mastitis, 140 (53.6%) were classified as Staphylococcus aureus and 121 (46.4%) were coagulase-negative staphylococci. All the strains of Staphylococcus aureus isolated from quarters with peracute gangrenous mastitis and acute systemic mastitis showed production of alpha heamolysin, coagulase, lipase, phosphatase, nuclease and gelatinase, and fermentation of mannitol. However, of 114 strains of Staphylococcus aureus obtained from quarters with chronic mastitis, 64 (56.1%) possessed alpha lysin, and 43 (37.7%) produced lipase in egg yolk medium. The most common hemolytic pattern of the strains associated with chronic mastitis was ${\beta}{\delta}$ type.

• Transactions on Electrical and Electronic Materials
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• 제18권4호
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• pp.211-216
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• 2017

The dielectric properties of two polyurethanes (PUs) with different hard segments, i.e., aromatic methylene di-p-phenyl diisocyanate (MDI) and aliphatic hexamethylene diisocyanate (HDI), were investigated in the temperature range of -100 to $100^{\circ}C$ and in the frequency range of 1 Hz to 3 kHz. The ${\alpha}$-relaxations induced by the glass transition of the equivalent soft segments in the two PUs occurred at relaxation times of ${\tau}=3.46{\times}10^{-3}s$ for MDI-PU and ${\tau}=3.39{\times}10^{-2}s$ for HDI-PU at $-20^{\circ}C$, in accord with the temperature-frequency superposition principle, resulting in similar shifting factors. However, different I-relaxations were observed for the two PUs. The I-relaxation of MDI-PU occurred due to the mobility of the chain extenders near $80^{\circ}C$ with a slower shifting rate than the ${\alpha}$-relaxation. On the other hand, I-relaxation arising from both the extender and the unconstrained hard segments of HDI-PU occurred at $70{\sim}100^{\circ}C$, indicating complicated dielectric behavior due to partial interaction with the ${\alpha}$-relaxation at high frequencies. Thus, the I-relaxation of HDI-PU did not follow the superposition principle. The dielectric behaviors of the PUs were mainly influenced by their phase transitions, which were affected by the structure and components of the materials.

• 한국세라믹학회지
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• 제28권2호
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• pp.130-140
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• 1991

The powders of the system Si3N4-Y2O3-AlN were prepared using Si(OC2H5)4 and YCl3.6H2O together with commercial AlN powder. $\alpha$-Si3N4 was prepared by the carbothermal reduction and nitridation of the hydrolyzed gel at 135$0^{\circ}C$ for 10h in N2 atmosphere. YCl3.6H2O was observed to be changed to Y2O3 during the reaction. $\alpha$-Sialon(X=0.2, 0.4, 0.6) ceramics were obtained by hot-pressing the Si3N4-Y2O3-AlN mixture at 178$0^{\circ}C$ for 1h under 30 MPa. The content of $\alpha$-Sialon increased with increasing metal solubility(x value) and $\alpha$-Sialon single phase was obtained at the metal solubility of 0.6. With increasing metal solubility, flexural strength, fracture toughness and thermal shock resistence were decreased, while the microhardness was increased. Large elongated $\beta$-Si3N4 grains were mainly observed at lower metal solubility. Mechanical prorerties of the sintered ceramics with X=0.2 were measured as follows : flexural strength ; 650 MPa, fracture toughness ; 3.63 MN/m3/2, hardness ; 14.7 GPa, thermal shock resistence temperature ; 58$0^{\circ}C$.

• 대한화학회지
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• 제57권4호
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• pp.461-471
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• 2013

Optimized geometrical structure, atomic charges, molecular electrostatic potential, nonlinear optical (NLO) effects and thermodynamic properties of the title compound N-(2,5-methylphenyl)salicylaldimine (I) have been investigated by using ab initio quantum chemical computational studies. Calculated results showed that the enol form of (I) is more stable than keto form. The solvent effect was investigated for obtained molecular energies, hardneses and the atomic charge distributions of (I). Natural bond orbital and frontier molecular orbital analysis of the title compound were also performed. The total molecular dipole moment (${\mu}$), linear polarizability (${\alpha}$), and first-order hyperpolarizability (${\beta}$) were calculated by B3LYP method with 6-31G(d), 6-31+G(d,p), 6-31++G(d,p), 6-311+G(d) and 6-311++G(d,p) basis sets to investigate the NLO properties of the compound (I). The standard thermodynamic functions were obtained for the title compound with the temperature ranging from 200 to 450 K.

• Biomolecules & Therapeutics
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• 제19권4호
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• pp.438-444
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• 2011

The mushroom Coriolus versicolor contains biologically active polysaccharides, most of which belong to the ${\beta}$-glucan group. Diverse physicochemical properties, due to different sources and isolated types of ${\beta}$-glucans, can induce distinct biological activities. We investigated the effects of ${\beta}$-glucans from C. versicolor on phagocytic activity, nitric oxide (NO), TNF-${\alpha}$ production, and signaling of dectin-1, a well-known ${\beta}$-glucan receptor, in macrophages. ${\beta}$-Glucans increased phagocytic activity and TNF-${\alpha}$ and NO-iNOS/eNOS production. Laminarin, a specific inhibitor of dectin-1, showed strong inhibitory effects on phagocytosis and subsequent TNF-${\alpha}$, iNOS, and eNOS production increased by ${\beta}$-glucans, indicating that ${\beta}$-glucans reacts with dectin-1 receptors. We examined whether the aforementioned cytokines were involved in the signaling pathway from the dectin-1 receptor to phagocytosis, and found that the inhibition of iNOS, eNOS, and TNF-${\alpha}$ receptors significantly decreased ${\beta}$-glucan-induced phagocytosis. In conclusion, our study showed that dectin-1 signaling, triggered by ${\beta}$-glucans, subsequently elicited TNF-${\alpha}$ and NO-iNOS/eNOS production, and that these molecules seem to act as secondary molecules that cause eventual phagocytosis by macrophages. These findings suggest that C. versicolor could be used as a nutritional medicine that may be useful in the treatment of infectious disease.

• 대한수학회지
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• 제44권4호
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• pp.845-854
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• 2007

In this paper we investigate relationships between closure-type and convergence-type properties of hyperspaces over a space X and covering properties of X.

• 한국세라믹학회지
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• 제31권11호
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• pp.1396-1400
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• 1994

Electrical properties in the ZnO-Bi2O3-CoO-Zn7Sb2O12 system were investigated with Zn7Sb2O12 content (0.1~2 mol%). The increase of the Zn7Sb2O12 content inhibited the grain growth of ZnO, which showed a narrow grain size distribution of ZnO. The breakdown voltage (Vb) increased markedly with 1 mol% Zn7Sb2O12 addition due to the grain growth control behaviour of the Zn7Sb2O12 . The nonlinear I-V characteristic was significantly influenced by the Zn7Sb2O12 content (or Bi2O3/Zn7Sb2O12 ratio). Addition of 0.5 mol% Zn7Sb2O12 showed the highest nonlinear coefficient ($\alpha$) of 43. The leakage current in prebreakdown region was decreased with increasing Zn7Sb2O12 content.

• 한국미생물·생명공학회지
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• 제50권3호
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• pp.354-360
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• 2022

This research was designed to evaluate the possible anti-inflammatory effects of Carex scabrifolia Steud. extract using RAW264.7 cells. The assessments of these effects were based on cell viability assay, mRNA expression levels of interleukin-1 alpha (IL-1α), interleukin-1 beta (IL-1β), IL-6, tumor necrosis factor alpha (TNFα), and levels of nitric oxide (NO)/prostaglandin E2 (PGE₂) production. Quantitative real-time polymerase chain reaction showed that treatment with C. scabrifolia Steud. extract decreased the mRNA levels of iNOS, COX2, IL-1α, IL-1β, IL-6, and TNFα. Furthermore, from the production levels of PGE₂/NO, it can be inferred that C. scabrifolia Steud. extract exhibited anti-inflammatory properties. These results suggest that C. scabrifolia Steud. extract contains anti-inflammatory compound(s), and consequently, that it may have applications as a potent cosmeceutical material.

• 대한수학회논문집
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• 제27권1호
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• pp.69-76
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• 2012

Let R be a ring, and ${\alpha}$ be an endomorphism of R. An additive mapping H : R ${\rightarrow}$ R is called a left ${\alpha}$-multiplier (centralizer) if H(xy) = H(x)${\alpha}$(y) holds for all x,y $\in$ R. In this paper, we shall investigate the commutativity of prime and semiprime rings admitting left ${\alpha}$-multiplier satisfying any one of the properties: (i) H([x,y])-[x,y] = 0, (ii) H([x,y])+[x,y] = 0, (iii) $H(x{\circ}y)-x{\circ}y=0$, (iv) $H(x{\circ}y)+x{\circ}y=0$, (v) H(xy) = xy, (vi) H(xy) = yx, (vii) $H(x^2)=x^2$, (viii) $H(x^2)=-x^2$ for all x, y in some appropriate subset of R.

• 대한수학회논문집
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• 제21권2호
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• pp.293-320
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• 2006

Using calculus inequalities and embedding theorems in $R^1$, we establish $W^1_2$-estimates for the solutions of prey-predator population model with cross-diffusion and self-diffusion terms. Two cases are considered; (i) $d_1\;=\;d_2,\;{\alpha}_{12}\;=\;{\alpha}_{21}\;=\;0$, and (ii) $0\;<\;{\alpha}_{21}\;<\;8_{\alpha}_{11},\;0\;<\;{\alpha}_{12}\;<\;8_{\alpha}_{22}$. It is proved that solutions are bounded uniformly pointwise, and that the uniform bounds remain independent of the growth of the diffusion coefficient in the system. Also, convergence results are obtained when $t\;{\to}\;{\infty}$ via suitable Liapunov functionals.