• Membrane and Water Treatment
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• 제6권4호
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• pp.263-276
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• 2015

This paper deals with the influence of chemical oxygen demand to nitrogen ratio ((COD/N) ratio) on the performance of an membrane bioreactor. We aim at establishing relations between COD/N ratio, organisms' distribution and sludge properties (specific resistance to filtration (SRF) and membrane fouling). It is also essential to define new criteria to characterize the autotrophic microorganisms, as the measurements of apparent removal rates of ammonium seem irrelevant to characterize their specific activity. Two experiments (A and B) have been carried on a 30 L lab scale membrane bioreactor with low COD/N ratio (2.3 and 1.5). The obtained results clearly indicate the role of the COD/N ratio on the biomass distribution and performance of the membrane bioreactor. New specific criteria for characterising the autotrophic microorganisms activity, is also defined as the ratio of maximum ammonium rate to the specific oxygen uptake rate in the endogenous state for autotrophic bacteria which seem to be constant whatever the operating conditions are. They are about 24.5 to 23.8 $gN-NH_4{^+}/gO_2$, for run A and B, respectively. Moreover, the filterability of the biological suspension appear significantly lower, specific resistance to filtration and membrane fouling rate are less than $10^{14}m^{-2}$ and $0.07\;10^{12}m^{-1}.d^{-1}$ respectively, than in conventional MBR confirming the adv < antage of the membrane bioreactor functioning under low COD/N ratio.

• 한국임상약학회지
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• 제18권2호
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• pp.120-123
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• 2008

The purpose of this study was to investigate the effect of naringin, one of flavonoids, on the pharmacokinetics and bioavailability of nimodipine in rabbits. Pharmacokinetic parameters of nimodipine were determined in rabbits after oral administration of nimodipine (16 mg/kg) with or without naringin (1, 5 or 15 mg/kg). Nimodipine was analyzed by high performance liquid chromatography using Hypersil ODS column. Naringin significantly (p<0.05) increased the area under the plasma concentration-time curve (AUC) and the peak concentration ($C_{max}$) of nimodipine at 5 and 15 mg/kg. The absolute bioavailability (AB%) of nimodipine by prescence of naringin (5 or 15 mg/kg) increased from 32.2-36.9% (p<0.05) compared to the control (22.0%). However, presence of naringin had no significant effect on the elimination rate constant ($K_{el}$) of nimodipine. There were no apparent changes of the time of peak concentration ($T_{max}$) of nimodipine by coadministration. These results suggest that the increased bioavailability and the significant changes of these pharmacokinetic parameters of nimodipine by naringin may be attributed to the potential of narigin to inhibit cytochrome P450 (CYP) 3A4 and P-glycoprotein efflux pump in the liver and intestinal mucosa.

• 대한화학회지
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• 제37권5호
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• pp.527-536
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• 1993

Chitin을 강알칼리로 탈아세틸화시켜 합성한 chitosan을 증류수에 팽윤시킨 다음 글리세린을 가하여 교반하였다. 이 고분자 용액에 약물인 silver sulfadiazine을 가하여 경피흡수용 고분자 matrix을 제조하였다. 이렇게 제조된 고분자 matrix로부터 약물의 방출거동과 고분자 matrix 변수와의 상관관계 등을 조사함으로써 지속적이고 조절된 경피흡수제형으로서의 사용 가능성과 특성을 조사하였다. 고분자 matrix 내의 약물의 함유량과 matrix의 두께가 증가할수록 약물의 방출시간은 더 지연되었다. 그러나 글리세린의 함유량이 증가함에 따라 약물의 방출시간은 오히려 감소하였다. 약물의 함유량, 글리세린의 함유량 및 matrix의 두께가 증가할수록 겉보기 방출속도상수(K)값도 증가하였다.이상과 같이 chitosan은 의약의 방출조절형제제로서 가능성을 나타냈으며, 약물로 사용된 silver sulfadiazine의 방출거동은 Higuchi model에 따른 확산으로 생각되었다.

• Design & Manufacturing
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• 제2권6호
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• pp.43-48
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• 2008

Magnesium alloys have given high attention to the industry of light-weigh as automobile and electronics with aluminium, titanium and composite alloys due to their high strength, low specific density and good damping characteristics. But the magnesium contained structures under high temperature have the problems related to creep deformation and rupture life, which is a reason of developing the new material against creep deformation to use them safely. The purpose of this study is to predict the creep deformation mechanism and rupture time of AZ31 magnesium alloy. For this, creep tests of AZ31 magnesium alloy were done under constant creep load and temperature with the equipment including automatic temperature controller with acquisition computer. The apparent activation energy Qc, the applied stress exponent n and rupture life have been determined over the temperature range below 0.5Tm and stress range of 109~187MPa, respectively, in order to investigate the creep behavior. AZ31 Magnesium alloy identify the activation energy for creep deformation and the stress dependence to creep rate at below 0.5Tm, and then investigate the mechanism for creep deformation and creep rupture life of AZ31 Magnesium alloy.

• 약학회지
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• 제38권2호
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• pp.114-122
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• 1994

A study on the absorption mechanism of cefixime(CF), an oral ${\alpha}-amino$ group deficient cephalosporin antibiotic, has been undertaken through the rat jejunum and nasal cavity using an in situ simultaneous perfusion technique developed in our laboratory. CF was well absorbed in the jejunum and nasal cavity of rats at pH 5.0, but not at pH 7.0. CF absorption was studied over four orders of magnitude in concentration to determine saturability. Disappearance of CF in the perfusate followed first-order kinetics at all tested concentrations. The apparent first-order absorption rate constant was found to be dependent on the concentration over the range of $0.1\;mM{\sim}3\;mM$ in the jejunum and nasal cavity of rats. Inhibitors were added to determine the competitive inhibition of CF absorption. The presence of L-tyrosine, L-phenylalanine, alanine-alanine, glycine-glycine and cefadroxil produced the significant inhibition of CF absorption in the nasal cavity and jejunum. However, there was no evidence of the inhibition in the presence of cefazolin. In addition, The CF absorption in the nasal cavity and jejunum was inhibited significantly by ouabain and 2,4-dinitrophenol(DNP). This study suggested that CF is absorbed across the rat nasal cavity and jejunum by carrier-mediated transport mechanism and energy consuming system.

• 대한기계학회논문집A
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• 제21권5호
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• pp.735-745
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• 1997

In this study, the compressibility of resin was considered in filling analysis to account for the possible packing type flow. A numerical simulation program employing a hybrid finite element/finite difference scheme was developed to solve Hele-Shaw flow of the compressible viscous fluid at non-isothermal conditions. To advance the melt front, a control volume approach was adopted. Thin complex 3-D shapes of cavities, runners, and sprues were discretized by employing triangular, cylindrical and/or rectangular strip elements. Mass conservation was applied to each control volume to solve for the pressure distribution. Directly applying a constant mass flow rate at the inlet removes calculation of the apparent pressure boundary conditions, resulting in better simulation condition. The Cross model was used to model viscosity and the Tait equation was employed to represent density as a function of temperature and pressure. The validity of the developed program was verified through comparisons with available data in the literature and the effect of compressibility on the pressure distribution was discussed. To reduce computation time, 1-D and 2-D elements were used instead of applying triangular elements and the numerical results were compared to each other.

• 한국응용약물학회:학술대회논문집
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• 한국응용약물학회 2003년도 Annual Meeting of KSAP : International Symposium on Pharmaceutical and Biomedical Sciences on Obesity
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• pp.107-107
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• 2003

The purpose of this study is to examine that the efflux transport system for choline from brain to blood is present at the blood-brain barrier (BBB) using brain efflux index (BEI) method. ［$^3$H］Choline was microinjected into parietal cortex area 2 (Par2) region of rat brain, and was eliminated from the brain with an apparent elimination half life of 45 min. The BBB efflux clearance of ［$^3$H］choline was 0.12 $m\ell$/min/g brain, which was calculated from the efflux rate constant (1.5${\times}$10$\^$-2/ min$\^$-1/) and the distribution volume in the brain slice (8.1 $m\ell$/g brain). This process was saturable and significantly inhibited by various organic cationic compounds including hemicholinium-3, tetraethylammonium chloride (TEA) and verapamil, by antioxidant, ${\alpha}$-phenyl-n-tert-butyl nitrone (PBN), and by Alzheimer's disease therapeutics, such as acetyl $\ell$-carnitine and tacrine. In conclusion, this finding is the first direct in vivo evidence that choline is transported from brain to the blood across the BBB via a carrier-mediated efflux transport process.

• Bulletin of the Korean Chemical Society
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• 제23권11호
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• pp.1513-1518
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• 2002

Kinetic studies on the water-gas shift reaction catalyzed by magnetite/chromium oxide and copper/zinc oxide were carried out by using an in situ photoacoustic spectroscopic technique. The reactions were performed in a closed-circulation reactor system using a differential photoacoustic cell at total pressure of 40 Torr in the temperature range of 100 to $350^{\circ}C.$ The CO2 photoacoustic signal varying with the concentration of CO2 during the catalytic reaction was recorded as a function of time. The time-resolved photoacoustic spectra obtained for the initial reaction stage provided precise data of CO2 formation rate. The apparent activation energies determined from the initial rates were 74.7 kJ/mol for the magnetite/chromium oxide catalyst and 50.9 kJ/mol for the copper/zinc oxide catalyst. To determine the reaction orders, partial pressures of CO(g) and H2O(g) in the reaction mixture were varied at a constant total pressure of 40 Torr with N2 buffer gas. For the magnetite/chromium oxide catalyst, the reaction orders with respect to CO and H2O were determined to be 0.93 and 0.18, respectively. For the copper/zinc oxide catalyst, the reaction orders with respect to CO and H2O were determined to be 0.79 and 0, respectively.

• 약학회지
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• 제44권3호
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• pp.245-250
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• 2000

Because nonsteroidal anti-inflammatory drugs are reported to cause fluid retention and hypertension by inhibition of prostaglandin synthesis, the effects of piroxicam on pharmacodynamics and pharmacokinetics of nifedipine were studied in male spontaneously hypertensive rats. They received nifedipine (0.5 mg/kg) alone or combined with piroxicam (5 mg/kg) intravenously. Plasma levels norepinephrine, an index of sympathetic stimulation, were measured prior to each treatment and 5 min after drug administration. Changes in blood pressure were examined serially and blood samples for analysis of nifedipine were also taken for 6 hr following drug administration. Plasma nifedipine concentration were assayed by HPLC and pharmacokinetic parameters were calculated. Blood pressure was reduced (p<0.01), but plasma norepinephrine level was increased (p<0.05) by nifedipine administration. Anti-hypertensive effect of nifedipine was potentiated (p<0.05) by piroxicam coadministration, but effect of nifedipine on plasma norepinephrine level was not affected. In case of rats received nifedipine and piroxicam, plasma nifedipine concentrations were higher (p<0.05) than those from rats received nifedipine alone at 2,3,4,5 and 6 hours following drug administration. The area under the plasma concentration vs. time curve was increased (p<0.05), while the elimination rate constant was decreased (p<0.01) by piroxicam coadministration. No significant differences were observed in the plasma clearance, apparent volume of distribution and elimination half-life. Thus, piroxicam not only potentiated antihypertensive effect of nifedipine, but also altered nifedipine pharmacokinetics in the rats. It is concluded that the potentiation of nifedipine antihypertensive effect might correlate with the increment of its plasma concentration by piroxicam coadministration.

• 한국수소및신에너지학회논문집
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• 제26권4호
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• pp.308-317
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• 2015

To investigate the effect of microstructure on the formation of the desorption peak, the volumetric thermal analysis technique (VTA) was applied to the Mg-13.5 wt% Ni hydride system. The sample made by the HCS (hydriding combustion synthesis) process had two kinds of Mg microstructures. Linear heating was started with various constant heating rates. Only one peak was appeared in the case of the small initial hydrogen wt% (0.83 wt%). Yet, two peaks were appeared with increasing initial hydrogen wt% (1.85 and 3.73 wt%) when only Mg was hydrogenated. The first peak was formed through the evolution of hydrogen from $MgH_2$, made by eutectic Mg. The second peak was formed through the evolution of hydrogen from $MgH_2$, made by primary Mg. Therefore, this result shows that the microstructure also has a considerable effect on forming the desorption peak. We have also derived the hydrogen desorption equations by VTA to get apparent activation energy when the rate-controlling step for the desorption of the hydrided system is the diffusion of hydrogen through the ${\alpha}$ phase and the chemical reaction ${\beta}{\rightarrow}{\alpha}$.