• Journal of Pharmaceutical Investigation
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• 제32권4호
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• pp.267-275
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• 2002

A self-microemulsifying drug delivery system (SMEDDS) was developed to increase the dissolution rate, solubility, and ultimately bioavailability of a poorly water soluble drug, lovastatin. SMEDDS was thε mixtures of oils, surfactants, and cosurfactants, which emulsify under conditions of gentle agitation, similar to those which would be encountered in the gastro-intestinal (GI) tract. Various types of self-emulsifying formulations were prepared using four types of oil (Capryol 90, Lauroglycol 90, Labrafil M 1944 CS and Labrafil M 2125), two surfactants (Cremophor EL and Tween 80), and three cosurfactants (Carbitol, PEG 400 and propylene glycol). Thε efficiency of emulsification was studied using a laser diffraction size analyzer to determine particle size distributions of the resultant emulsions. Optimized formulations selected for bioavailability assessment were Carpryol 90 (40%), Cremophor EL (30%) and Carbitol (30%). SMEDDS containing lovastatin (20 mg and 5 mg) were compared to a conventional lovastatin tablet $(Mevacor^{\circledR},\;20\;mg/tab)$ by the oral administration as prefilled hard gelatin capsules to fasted beagle dogs for in vivo study. The arεa under the serum concentration-time curve from time zero to the last measured time in serum, $AUC_{0{\rightarrow}24h}$, was significantly greater in SMEDDS, suggesting that bioavailability increase 130% and 192% by the SMEDDS, respectively. The self-emulsifying formulations of lovastatin afforded the improvement in absolute oral bioavailability relative to previous data of lovastatin tablet formulation. These data indicate the utility of dispersed self-emulsifying formulations for the oral delivery of lovastatin and potentially other poorly absorbed drugs.

• 한국결정성장학회지
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• 제6권2호
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• pp.238-246
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• 1996

$\beta$-SiC와 AIN의 혼합분말로부터 열간가압소결에 의하여 고밀도의 SiC-AIN 고용체가 $1870^{\circ}C$에서 $2030^{\circ}C$ 사이의 온도범위에서 제조되어졌다. 온도와 SiC/AIN의 비 및 seed의 존재에 따라 AIN과 $\beta$-SiC(3C) 분말의 반응은 2 H (wurzite) 구조로의 전이를 나타내었다. 결정상들은 SiC-rich 및 AIN-rich 고용체로 구성되었다. $2030^{\circ}C$, 1시간에서 5 wt%의 $\alpha$-SiC seed를 첨가한 50 % AIN/50% SiC의 조성에 대하여 완전한 고용체가 얻어졌으며, 미세구조가 비교적 균일한 2 H상의 결정립 크기를 가지고균일한 성장경향을 나타내었다. SiC-AIN 고용체에 있어서 $\alpha$-SiC seed의 변수가 전이기구 및 결정립의 크기와 모양을 비롯한 결정립 크기의 분포, 조성의 불균일성과 구조적 결함 등에 영향을 미칠 수 있었다.

• Journal of the Korean Wood Science and Technology
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• 제16권4호
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• pp.10-39
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• 1988

This study investigated the temperatures and relative humidities in the semi-greenhouse type solar dryer with a black rock-bed heat storage and without heat storage and outdoor temperature and relative humidity at 9 a.m. and 2 p.m.. A comparison was made of the drying rates, final moisture contents, moisture content distributions, casehardening stresses, drying defects, volumetric shrinkage of dried lumber for solar- and air-drying from the green condition of mixtures of Douglas-fir, lauan, taun, oak and sycamore 25mm- and 50 mm-thick lumber during the same period for four seasons, and heat efficiencies for solar dryer with and without the heat storage for saving of heat energy and the cost of lumber drying using the solar energy. The results from this study were summarized as follows: I. The mean weekly temperatures in the solar dryers were 3 to $6^{\circ}C$ at 9 a.m. and 9 to $13^{\circ}C$ at 2 p.m. higher than mean outdoor temperature during all the drying period. 2. The mean weekly relative humidities in the solar dryers were about 1 to 19% at 9 a.m. higher than the outdoor relative humidity. and the difference between indoor and outdoor relative humidity in the morning was greater than in the afternoon. 3. The temperatures and relative humidities in the solar dryer with and without the heat storage were nearly same. 4. The overall solar insolation during the spring months was highest and then was greater in the order of summer, atumm, and winter month. S. The initial rate of solar drying was more rapid than that of air drying. As moisture content decreased, solar drying rate became more rapid than that of air drying. The rates of solar drying with and without heat storage were nearly same. The drying rate of Douglas-fir was fastest and then faster in the order of sycamore, lauan, taun and oak. and the faster drying rate of species, the smaller differences of drying rates between thicknesses of lumber. The drying rates were fastest in the summer and slowest in the winter. The rates of solar drying during the spring were more slowly in the early stage and faster in the later stage than those during the autumn. 6. The final moisture contents were above 15% for 25mm-thick air dried and about 10% for solar dried lumber, but the mean final MCs for 50mm-thick lumber were much higher than those of thin lumber. The differences of final MC between upper and lower course of pile for solar drying were greater than those of pile for air drying. The differences of moisture content between the shell and the core of air dried lumbers were greater than those of solar dried lumber, smallest in the drying during summer and greatest in the drying during winter among seasons. 7. Casehardening stresses of 25mm- and 50mm-thick dried lumber were slight, casehardening stress of solar dried lumber was severer than that of air dried lumber and was similar between solar dried lumber with and without heat storage, Casehardening stresses of lumber dried during spring were slightest and then slighter in the order of summer, autumn, and winter. Casehardening stresses of Douglas -fir, sycamore and lauan were slight, comparing with those of taun and oak. 8. Maximum initial checks of 25mm-thick lumber occurred above and below fiber saturation point and those of 50mm-thick lumber occurred in the higher moisture content than thin lumber. As the moisture content decreased, most of checks were closed and didn't show distinct difference of the degree of checks among drying methods. The degree of checks were very slight in case of Douglas-fir and lauan, and severe in case of taun and oak. The degree of checks for 50mm-thick lumber were severer than those for 25mm-thick lumber. 9. The degree of warpage showed severe in case of oak and sycamore lumber, but no warping was found in case of Douglas-fir, lauan and taun. 10. The volumetric shrinkages of taun and oak were large and medium in case of Douglas-fir, lauan and sycamore. 11. Heat efficiencies of solar dryer with heat storage were 6.9% during spring, 7.7% during summer, 12.1% during autumn and 4.1% during winter season. Heat efficiency of solar dryer with heat storage was slightly greater than that of without heat storage. As moisture content of lumber decreased, heat efficiency decreased.

• 한국환경과학회:학술대회논문집
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• 한국환경과학회 1998년도 가을 학술발표회 프로그램
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• pp.2-4
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• 1998

Proliferation of Nocardia amarae cells in activated sludge has often been associated with the generation of nuisance foams. Despite intense research activities in recent years to examine the causes and control of Nocardia foaming in activated sludge, the foaming continued to persist throughout the activated sludge treatment plants in United States. In addition to causing various operational problems to treatment processes, the presence of Nocardia may have secondary effects on the fate of heavy metals that are not well known. For example, for treatment plants facing more stringent metal removal requirements, potential metal removal by Nocardia cells in foaming activated sludge would be a welcome secondary effect. In contrast, with new viosolid disposal regulations in place (Code o( Federal Regulation No. 503), higher concentration of metals in biosolids from foaming activated sludge could create management problems. The goal of this research was to investigate the metal sorption property of Nocardia amarae cells grown in batch reactors and in chemostat reactors. Specific surface area and metal sorption characteristics of N. amarae cells harvested at various growth stages were compared. Three metals examined in this study were copper, cadmium and nickel. Nocardia amarae strain (SRWTP isolate) used in this study was obtained from the University of California at Berkeley. The pure culture was grown in 4L batch reactor containing mineral salt medium with sodium acetate as the sole carbon source. In order to quantify the sorption of heavy metal ions to N amarae cell surfaces, cells from the batch reactor were harvested, washed, and suspended in 30mL centrifuge tubes. Metal sorption studies were conducted at pH 7.0 and ionlc strength of 10-2M. The sorption Isotherm showed that the cells harvested from the stationary and endogenous growth phase exhibited significantly higher metal sorption capacity than the cells from the exponential phase. The sequence of preferential uptake of metals by N. amarae cells was Cu>Cd>Ni. The specific surFace area of Nocardia cells was determined by a dye adsorption method. N.amarae cells growing at ewponential phase had significantly less specific surface area than that of stationary phase, indicating that the lower metal sorption capacity of Nocardia cells growing at exponential phase may be due to the lower specific surface area. The growth conditions of Nocardia cells in continuous culture affect their cell surface properties, thereby governing the adsorption capacity of heavy metal. The comparison of dye sorption isotherms for Nocardia cells growing at various growth rates revealed that the cell surface area increased with increasing sludge age, indicating that the cell surface area is highly dependent on the steady-state growth rate. The highest specific surface area of 199m21g was obtained from N.amarae cell harvested at 0.33 day-1 of growth rate. This result suggests that growth condition not only alters the structure of Nocardia cell wall but also affects the surface area, thus yielding more binding sites of metal removal. After reaching the steady-state condition at dilution rate, metal adsorption isotherms were used to determine the equilibrium distributions of metals between aqueous and Nocardia cell surfaces. The metal sorption capacity of Nocardia biomass harvested from 0.33 day-1 of growth rate was significantly higher than that of cells harvested from 0.5- and 1-day-1 operation, indicatng that N.amarae cells with a lower growth rate have higher sorpion capacity. This result was in close agreement with the trend observed from the batch study. To evaluate the effect of Nocardia cells on the metal binding capacity of activated sludge, specific surface area and metal sorption capacity of the mixture of Nocardia pure cultures and activated sludge biomass were determined by a series of batch experiments. The higher levels of Nocardia cells in the Nocardia-activated sludge samples resulted in the higher specific surface area, explaining the higher metal sorption sites by the mixed luquor samples containing greater amounts on Nocardia cells. The effect of Nocardia cells on the metal sorption capacity of activated sludge was evaluated by spiking an activated sludge sample with various amounts of pre culture Nocardia cells. The results of the Langmuir isotherm model fitted to the metal sorption by various mixtures of Nocardia and activated sludge indicated that the mixture containing higher Nocardia levels had higher metal adsorption capacity than the mixture containing lower Nocardia levels. At Nocardia levels above 100mg/g VSS, the metal sorption capacity of activate sludge increased proportionally with the amount of Noeardia cells present in the mixed liquor, indicating that the presence of Nocardia may increase the viosorption capacity of activated sludge.