• Archives of Pharmacal Research
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• v.17 no.3
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• pp.182-189
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• 1994

The effect of lipophilicity on the mechanisms of drug absorption through biomembranes was investigated empolying HPLC system and the fluorescence technique. Human erythrocyte ghost membranes were used as a model biomembrane. A series of four parabens (methyl, ethyl, rpopyl, and butyl) and p-hydroxybenzoic acid were used as the model drugs for lipophilicities and their partition coefficients were measured in Sorensen's phosphate buffer solution (pH 5)/octanol system. Absorption amount of parabens through erythrocyte ghost membranes increased with an increase of lipophilicity resulted from the addition of methylene group to the n-alkyl chain of parabens. And the effect of parabens on the fluidity of ghost membrane also increased with an increase of their lipophilicities.

• Journal of the Korea Society of Computer and Information
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• v.8 no.3
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• pp.47-52
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• 2003

In this paper. a new wavelet packet image coder is proposed for images that include many high-frequency components using the relation between subbands. The new algorithm presents parent-child relationship for reducing image reconstruction error using relations between individual frequency subbands. By parent-child relationship, every coefficient is partitioned and encoded for the zerotree structure. It demonstrates higher PSNR under the same bit rate. These results show that the encoding process of the proposed coder is more accurate than the conventional ones for images that include many high-frequency elements.

• Journal of the Korean Society for Precision Engineering
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• v.23 no.8 s.185
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• pp.89-99
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• 2006

In this paper a new shape reconstruction method that allows us to construct surface models from very large sets of points is presented. In this method the global domain of interest is divided into smaller domains where the problem can be solved locally. These local solutions of subdivided domains are blended together according to weighting coefficients to obtain a global solution using partition of unity function. The suggested approach gives us considerable flexibility in the choice of local shape functions which depend on the local shape complexity and desired accuracy. At each domain, a quadratic polynomial function is created that fits the points in the domain. If the approximation is not accurate enough, other higher order functions including cubic polynomial function and RBF(Radial Basis Function) are used. This adaptive selection of local shape functions offers robust and efficient solution to a great variety of shape reconstruction problems.

• Textile Coloration and Finishing
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• v.2 no.2
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• pp.33-38
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• 1990

Nitrocellulose [NC]-Poly(vinylamine) [PVAm] blended membranes with the change of amino group contents were prepared. The sorption and permeation of a mono-sulfonic acid dye, Orange II, in the membranes were investigated by the steady-state permeation method at $50^{\circ}C$ and pH 2.2. The results were discussed in the framework of dual sorption and diffusion theory. It was found that thesorption isotherms comprise a partition and two Langmuir type adsorption having similar binding constants. One of the latter sorption modes is due to unknown adsorption sites in NC and the other is due to the amino groups in PVAm. Apparent diffusion coefficients for collective P and L dye species, $D_P\; and D_L$, were obtained. Interpretation of $D_P$ values leads to two modes of partitions; one is such that dye is immobilized in NC and the other is the dissolution of the dye into the internal water phase.

• Bulletin of the Korean Chemical Society
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• v.11 no.2
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• pp.95-99
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• 1990

The dioxygen transfer reaction from $N^5$-ethyl-4a-hydroperoxy-3-methyllumiflavin anion (4a-FlEtOO-) has been extended to isomeric aminophenol systems (1a-4a). O-aminophenol (o-AP, 1a & 2a) and p-aminophenol(p-AP, 3a & 4a) were turned out to be good substrates, whereas m-aminophenol(m-AP, 5a) was not. This is due to the charge location which is not on the carbon bearing the amino group. o-AO's react with 4a-FlEtOO- to give isophenoxazine derivatives (6 & 7) and with p-AP's to produce p-benzoquinone derivatives (8 & 9). The partition coefficients $(k_2/k_3)$ of 1a & 2a were $4.84{\times}10^{-4}\;&\;1.66{\times}10^{-5}M$, respectively and those of methylated aminophenolates, 2a & 4a were 4-10 times greater than nonmethylated substrates, 1a & 3a.

• Microbiology and Biotechnology Letters
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• v.20 no.1
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• pp.61-67
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• 1992

The synthesis of N-benzyloxycarbonyl-L-aspartyl-L-phenylalanine methyl ester(ZAPM), a precursor of aspartame, from N-benzyloxycarbonyl-L-aspartic acid(Z-Asp) and L-phenylalanine methyl ester hydrochloride(L-PM-HCl) was investigated in ethylacetate-MES buffer two-phase system using thermolysin. In organic two-phase system, the degree of spontaneous hydrolysis of L-PM. HCl was significantly reduced with increasing the volume ratio of organic to aqueous phase. Stability of thermolysin in organic two-phase system was found to be higher than that in MES buffer solution. More than 90% of initial enzyme activity was maintained after 10 days of incubation in case that the volume of organic phase was equal to that of buffer phase, while the half life of thermolysin was about 2 days in aqueous buffer solution. The results of partitioning of substrates and product in organic two-phase system showed that the difference in partition coefficients between substrates and product was maximum at pH 5.5. The optimal pH for 2-APM synthesis in organic two-phase system was found to be 5.5-5.8, which is consistent with the value expected from the partition experiments. As the concentration of substrates was increased the conversion yield of Z-APM was increased with concomitant reduction of L-PMqHC1 hydrolysis. In case that the concentration of L-PM-HCl and Z-Asp were 160 mM and 80 mM respectively, the conversion yield of Z-APM reached 90% after 28 hrs of reaction. The yield obtained at different volume ratio of organic phase compares well with the predicted equilibrium constant in biphasic system.

• Journal of Pharmaceutical Investigation
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• v.31 no.3
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• pp.143-150
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• 2001

Butyrolactone ester of ceftezole (CFZ-BL) was synthesized by esterification of ceftezole (CFZ) with ${\alpha}-bromo-{\gamma}-butyrolactone$. The synthesis was confirmed by spectroscopic analysis. CFZ-BL was more lipophilic than CFZ when the lipophilicity was assessed by partition coefficients between n-octanol and water at various pH. CFZ-BL itself did not show any microbiological activity in vitro, but serums taken after oral administration of CFZ-BL showed substaintial microbiological activity indicating that CFZ-BL is converted to microbiologically active metabolite, probably CFZ, in the body. The conversion was confirmed by in vitro incubation study, in which CFZ-BL was incubated in some body tissues of rabbit. Liver homogenate showed fastest conversion of CFZ-BL among the tissues tested (blood and intestine). Thus, CFZ-BL appeares to be rapidly metabolized in the liver to CFZ following oral administration. The metabolism process appears to be hydrolysis of the ester to CFZ, the parent drug of CFZ-BL. In vivo metabolism of CFZ-BL to CFZ was confirmed by analying CFZ by HPLC. CFZ concentration in the serum samples taken after oral administration of CFZ-BL were higher than those in the serum samples taken after oral administration of equivalent amount of CFZ. Oral bioavailability of CFZ-BL, a prodrug of CFZ, was 1.45-fold higher than that of CFZ in rabbits possibly due to enhanced lipophility and absorption of the prodrug.

• The Transactions of the Korea Information Processing Society
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• v.4 no.12
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• pp.3185-3199
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• 1997

This paper suggests techniques to reduce coding time which is a problem in traditional fractal compression and to improve fidelity of reconstructed images by determining fractal coefficient through adaptive selection of block approximation formula. First, to reduce coding time, we construct a linear list of domain blocks of which characteristics is given by their luminance and variance and then we control block searching time according to the first permissible threshold value. Next, when employing three-level block partition, if a range block of minimum partition level cannot find a domain block which has a satisfying approximation error, we choose new approximation coefficients using a non-linear approximation of luminance term. This boosts the fidelity. Our experiment employing the above methods shows enhancement in the coding time more than two times over traditional coding methods and shows improvement in PSNR value by about 1-3dB at the same com- pression rate.

• Proceedings of the KSME Conference
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• 2001.11b
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• pp.22-29
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• 2001

The present study investigates the effects of various rib arrangements and rotating on heat/mass transfer in the cooling passage of gas turbine blades. The cooling passage has very complex flow structure, because of the rib turbulator and rotating effect. Experiments and numerical calculation are conducted to investigate the complex flow structures and heat transfer characteristics; the numerical computation is performed using a commercial code, FLUENT ver.5, to calculate the flow structures and the experiments are conducted to measure heat/mass transfer coefficients using a naphthalene sublimation technique. For the rotating duct tests, the test duct, which is the cross section of is $20mm\times40mm$ (the hydraulic diameter, $D_h$, of 26.7 mm, has two-pass with $180^{\circ}$ turning and the rectangular ribs on the wall. The rib angle of attack is $70^{\circ}$ and the maximum radius of rotation is $21.63D_h$. The partition wall has 10 mm thickness, which is 0.5 times to the channel width, and the distance between the tip of the partition wall and the outer wall of the turning region is 26.7 mm $(1D_h)$. The turning effect of duct flow makes the very complex flow structure including Dean type vortex and high turbulence, so that the heat/mass transfer increases in the turning region and at the entrance of the second pass. The Coriolis effect deflects the flow to the trailing surface, resulting in enhancement of the heat/mass transfer on the trailing surface and reduction on the leading surface in the first pass. However, the opposite phenomena are observed in the second pass. The each rib arrangement makes different secondary flow patterns. The complex heat/mass transfer characteristics are observed by the combined effects of the rib arrangements, duct rotation and flow turning.

• Journal of the Korean Society of Radiology
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• v.8 no.1
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• pp.19-26
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• 2014

This paper suggests techniques to enhance coding time which is a problem in traditional fractal compression and to improve fidelity of reconstructed images by determining fractal coefficient through adaptive selection of block approximation formula. First, to reduce coding time, we construct a linear list of domain blocks of which characteristics is given by their luminance and variance and then we control block searching time according to the first permissible threshold value. Next, when employing three-level block partition, if a range block of minimum partition level cannot find a domain block which has a satisfying approximation error, we choose new approximation coefficients using a non-linear approximation of luminance term. This boosts the fidelity. Our experiment employing the above methods shows enhancement in the coding time more than two times over traditional coding methods and shows improvement in PSNR value by about 1-3dB at the same compression rate.