• Journal of the Korean Applied Science and Technology
• /
• v.31 no.4
• /
• pp.771-780
• /
• 2014

The antioxidative effects and component analysis of the Melaleuca quinquenervia leaf extracts were investigated. All experiments were performed with 50% ethanol extract, ethyl acetate fraction and aglycone fraction obtained from dried M. quinquenervia leaves. The DPPH (1,1-phenyl-2-picrylhydrazyl) scavenging activity ($FSC_{50}$) of ethyl acetate fraction ($10.05{\mu}g/mL$) of M. quinquenervia leaf extracts was similar to (+)-${\alpha}$-tocopherol($8.89{\mu}g/mL$) known as a typical antioxidant. Reactive oxygen species (ROS) scavenging activities ($OSC_{50}$) of the ethyl acetate fraction ($1.61{\mu}g/mL$) and aglycone fraction ($1.07{\mu}g/mL$) of leaf extracts of M. quinquenervia on ROS generated in $Fe^{3+}-EDTA/H_2O_2$ system using the luminol-dependent chemiluminescence assay were similar to that of L-ascorbic acid ($1.50{\mu}g/mL$). The cellular protective effect of the extracts on the rose bengal sensitized photohemolysis of human erythrocytes was increased in a concentration dependant manner ($1{\sim}50{\mu}g/mL$). Especially, the cellular protective effects of Aglycone fraction (${\tau}_{50}=158.80min$) and 50% Ethanol extract (${\tau}_{50}=50.1{\pm}0.2min$) on the $^1O_2$-induced cellular damage of human cells were exhibited the higher than (+)-${\alpha}$-tocopherol (${\tau}_{50}=38.0min$). TLC and HPLC were used to analyse active components in the ethylacetate fraction of the extracts. Results showed that avicularin and quercetrin were active components of the extracts. These findings suggest that the M. quinquenervia leaf extracts can be applied to new cosmetics products as an effective antioxidant ingradient.

• Journal of the Korean Applied Science and Technology
• /
• v.33 no.4
• /
• pp.647-657
• /
• 2016

In this study, the antioxidative effects and active component analysis of 50% ethanol extract, ethyl acetate fraction and aglycone fraction obtained from Prunella vulgaris L. were investigated. The free radical scavenging activities ($FSC_{50}$) was investigated at 50% ethanol extract ($15.25{\mu}g/mL$), ethyl acetate fraction ($8.68{\mu}g/mL$), and aglycone fraction ($8.25{\mu}g/mL$) respectively. Reactive oxygen species (ROS) scavenging activities ($OSC_{50}$) in $Fe^{3+}-EDTA/H_2O_2$ system using the luminol-dependent chemiluminescence assay was investigated at 50% ethanol extract ($4.68{\mu}g/mL$), ethyl acetate fraction ($1.00{\mu}g/mL$), and aglycone fraction($1.02{\mu}g/mL$) respectively. In the cellular protective effect against $^1O_2$ induced cellular damage of human erythrocytes, extract/fractions of P. vulgaris L. were increased in a concentration dependent manner($1{\sim}25{\mu}g/mL$). Especially, ${\tau}_{50}$ of aglycone fraction at concentrations of $25{\mu}g/mL$ showed the most protective effects at 337.9 min. It's showed nine times higher (+)-${\alpha}$-tocopherol (${\tau}_{50}=38.7min$) as typical antioxidant in the $^1O_2$-induced photohemolysis of human erythrocytes. TLC and HPLC were used to analyse active components in the ethyl acetate fraction and aglycone fraction of P. vulgaris L. In ethyl acetate fraction, caffeic acid, rosmarinic acid, quercetin 3-${\beta}$-D-glucoside, rutin, kaempferol-3-O-rutinoside, astragalin (kaempferol-3-O-glucoside) were identified. In aglycone fraction, caffeic acid, rosmarinic acid, quercetin, kaempferol were identified. These results indicated that extract/fraction of P. vulgaris L. is may be used in cosmetics industry as natural antioxidants by quenching and/or scavenging $^1O_2$ and other ROS, and protecting cellular membranes.

• Journal of computational fluids engineering
• /
• v.15 no.2
• /
• pp.35-40
• /
• 2010

In the present work, LES with new variational multiscale method is conducted on the fully developed channel flow with Reynolds number, 180 based on the friction velocity and the channel half width. Incompressible Navier-Stokes equations are integrated using finite element method with the basis function of NURBS. To solve space-time equations, Newton's method with two stage predictor multicorrector algorithm is employed. The code is parallelized using MPI. The computational domain is a rectangular box of size $2{\pi}{\times}2{\times}4/3{\pi}$ in the streamwise, wall normal and spanwise direction. Mean velocity profiles and velocity fluctuations are compared with the data of DNS. The results agree well with those of DNS and other traditional LES.

• Electrical & Electronic Materials
• /
• v.8 no.1
• /
• pp.64-70
• /
• 1995

We discussed the thermal analysis for a recording media with the variation of the laser pulse duration, the laser power and the temperature distribution in order to optimize the Te-based antireflection structure from the computer calculations. In the case that the radial heat diffusion is negligible, we can calculate the maximum temperature of the recording layer at the center of the spot by the Simple Model. The temperature profile of the recording layer is obtained from the Numerical Model by considering the total specific heat and the latent heat. As a result, the effect of the heat sinking acting as a thermal loss for the hole formation could be minimized by introducing the pulse with the hole formation duration(.tau.) below the thermal time constant(.tau.$_{D}$) of a dielectric layer. These requirments can be satisfied by using the dielectric thickness of the 2nd ART(Anti-Reflection Trilayer) condition or the dielectric materials with a low thermal diffusivity.y.

• Proceedings of the Korean Society of Applied Pharmacology
• /
• 2006.04a
• /
• pp.95-105
• /
• 2006

Alzheimer's disease (AD) is an irreversible, progressive brain disorder that is characterized by dementia. Amounts of p25 and cdk5 kinase activity are specifically upregulated in AD patient's brain samples. Considerable evidence now points importance of p25/cdk5 in generation of A$\beta$ peptides and hyperphosphorylation of tau linking amyloid plaques and neurofibrillary tangles, two major pathological hallmarks of AD. We demonstrated that P25/CDK5 phosphorylates BACE1, the first step protease to produce A$\beta$. P25/CDK5 inhibitors to reduce BACE1 phosphorylation and the secretion of A$\beta$ are screened through in silica, in vitro, and cell-based assays. Out of 4.3 million chemicals we finally selected two compounds to have IC50 of 10 microM in cell-based assays. The inhibitors block Tau phosphrorylation as well as BACE1 phosphorylation. In conclusion P25 should be one of the best targets for AD therapeutics.

• Journal of the Korean Mathematical Society
• /
• v.45 no.5
• /
• pp.1379-1391
• /
• 2008

Let k be an imaginary quadratic field, ${\eta}$ the complex upper half plane, and let ${\tau}{\in}{\eta}{\cap}k,\;q=e^{{\pi}{i}{\tau}}$. For n, t ${\in}{\mathbb{Z}}^+$ with $1{\leq}t{\leq}n-1$, set n=${\delta}{\cdot}2^{\iota}$(${\delta}$=2, 3, 5, 7, 9, 13, 15) with ${\iota}{\geq}0$ integer. Then we show that $q{\frac}{n}{12}-{\frac}{t}{2}+{\frac}{t^2}{2n}{\prod}_{m=1}^{\infty}(1-q^{nm-t})(1-q^{{nm}-(n-t)})$ are algebraic numbers.

• Honam Mathematical Journal
• /
• v.31 no.4
• /
• pp.463-478
• /
• 2009

Let k be an imaginary quadratic field, ℌ the complex upper half plane, and let ${\tau}{\in}k{\cap}$ℌ, q = exp(${\pi}i{\tau}$). And let n, t be positive integers with $1{\leq}t{\leq}n-1$. Then $q^{{\frac{n}{12}}-{\frac{t}{2}}+{\frac{t^2}{2n}}}{\prod}^{\infty}_{m=1}(1-q^{nm-t})(1-q^{nm-(n-t)})$ is an algebraic number [10]. As a generalization of this result, we find several infinite series and products giving algebraic numbers using Ramanujan's $_{1{\psi}1}$ summation. These are also related to Rogers-Ramanujan continued fractions.

• Journal of The Korean Astronomical Society
• /
• v.16 no.2
• /
• pp.31-42
• /
• 1983

Making use of a relation proposed by Wielen (1977), a new empirical relation between Call emission flux and stellar age is derived by analyzing Wilson and Woolley's spectroscopic data (1970) of late type main sequence stars (K0-M5) and kinematic properties of those stars given by Gliese (1969). The proposed relation shows that the emission flux excess of the Call H-K lines, $F_k'+F_k'$ introduced by Linsky et al. (1979) decreases with stellar age $\tau$ as $\tau^{-0.51}$, consistent with the inverse square law as noted by Skumanich (1972).

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2000.11a
• /
• pp.279-282
• /
• 2000

The displacement current measurement has been employed to study the dielectric properties of Langmuir films. A method for determining the dielectric relaxation time $\tau$ of floating monolayers on water surface is presented. The displacement current flowing across monolayers is analyzed using a rod-like molecular model. It's revealed that the dielectric relaxation time $\tau$ of monolayers in the isotropic polar orientational phase is determined using a liner relationship between the monolayers compression speed $\alpha$ and the molecular maximum area $A_{m}$. The compression speed $\alpha$ was about 30, 40, 50mm/minmm/min

• Journal of applied mathematics & informatics
• /
• v.37 no.5_6
• /
• pp.469-480
• /
• 2019

A generalized tiling is defined as a generalization of the properties of tiling a region of ${\mathbb{Z}}^2$ with dominoes, and comprises tiling with rhombus and any other tilings that admits height functions which can be ordered into a distributive lattice. By using properties of the distributive lattice, we prove that the Markov chain consisting of moving from one height function to the next by a flip is fast mixing and the mixing time ${\tau}({\epsilon})$ is given by ${\tau}({\epsilon}){\leq}(kmn)^3(mn\;{\ln}\;k+{\ln}\;{\epsilon}^{-1})$, where mn is the area of the grid ${\Gamma}$ that is a k-regular polycell. This result generalizes the result of the authors (T-tetromino tiling Markov chain is fast mixing, Theor. Comp. Sci. (2018)) and improves on the mixing time obtained by using coupling arguments by N. Destainville and by M. Luby, D. Randall, A. Sinclair.