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Oil-Water Interface Transfer of Cefoperazone Pivaloyloxymethyl Ester
최영욱,김종갑,Choi, Young-Wook,Kim, Johng-Kap 한국약제학회 1989 Journal of Pharmaceutical Investigation Vol.19 No.1
Kinetic and thermodynamic aspects of the interface transfer of cefoperazone and its pivaloyloxymethyl ester were studied in a two-phase system composed of aqueous buffers and n-octanol by using the absolute reaction rate theory. In terms of the net thermodynamic parameters for the process, ${\Delta}S$ increased and ${\Delta}F$ decreased as the lipophilicity increased. With the increased ratio of forward $(k_f)$ to backward rate constants $(k_b)$, the ester was more lipophilic than cefoperazone, but the aqueous solubility was reduced.
Oral Absorption of Cefoperazone Pivaloyloxymethyl Ester
최영욱,박기배,최승호,김종갑,Choi, Young-Wook,Park, Gee-Bae,Choi, Seung-Ho,Kim, Johng-Kap 한국약제학회 1988 Journal of Pharmaceutical Investigation Vol.18 No.4
Pivaloyloxymethyl ester of cefoperazone was synthesized by treating sodium cefoperazone with chloromethyl pivalate and its chemical structure was determined by spectroscopic trials. The pharmaceutical properties of the ester were investigated to assess its potential as a prodrug of cefo perazone. Cefoperazone pivaloyloxymethyl ester was microbiologically inactive itself in vitro, but hydrolyzed into the parent drug in vivo. After a single oral dose of each drug to rabbits, serum concentrations of cefoperazone were determined by high performance liquid chromatographic assay. The ester showed higher and more sustained blood level than cefoperazone. Therefore, the total area under the serum concentration-time curve of the derivative was 16.8 times larger than that of the parent drug.
고분자 코팅을 이용한 경구용 리포좀의 개발 ( I ) : 다당체로 코팅된 리포좀의 담즙산염에 대한 안정성
최영욱(Young Wook Choi),한양희(Yang Hee Hahn) 한국약제학회 1992 Journal of Pharmaceutical Investigation Vol.22 No.3
Stabilization of liposomes against degradation by bile salts has been investigated in order to develop a liposomal model system for oral drug delivery. Two polysaccharides, amylopectin (AP) and chitin (CT), were employed to coat both empty liposomes and bromthymol blue (BTB)-encapsulated liposomes by adsorption-coating techniques. Turbidity changes and BTB-release characteristics in pH 5.6 buffer solutions with or without bile salts, sodium cholate and sodium glycocholate, were observed to compare the differences between uncoated liposomes and polysaccharide-coated liposomes. Initial turbidities of both uncoated and polysaccharide-coated liposomes in buffer solution were kept constant within 3% range during 4 hours of experiments. But they were decreased in a different manner in bile salts-containing buffer solutions, showing 10% or less decrease for polysaccharide-coated liposomes and 25% or more decrease for uncoated liposomes. BTB release from uncoated liposomes has been greatly increased upto 90% after 4 hours in bile salts-containing buffer solution, which is a clue for breakdown of liposomal vesicles. However, polysaccharide-coated liposomes showed the controlled-release pattern which is proportional to square-root of time, followed by around 50% release for the same time period. Consequently, it is possible to conclude that these polysaccharide-coated liposomes might be an available system for oral delivery of a drug which is unstable in gut environment.
崔永旭(Young-Wook Choi) 대한전기학회 2008 전기학회논문지 Vol.57 No.1
A hollow cathode which has extremely stable discharge characteristic has been developed. This is composed of the two separated lanthanum hexaboride (LaB6) of a disk type in the tube as the electron emitters. The way of design is of great advantage to extend the surface discharge area of the LaB6, which is also useful for optimal fixing of the LaB6. The hollow cathode is capable of producing 30 ㎾ (100 V, 300 A) of power continuously. Because the generated plasma beam with the high temperature (above 3000 ℃) from the hollow cathode passes through the center hole of the two intermediate electrodes, it is designed with the high temperature material of the tungsten and the suitable structure of the water cooling. The combinations of the hollow cathode and the two intermediate electrodes are practically useful for the ion plating plasma beam source.
Sputtering technique for magnessium oxide thin films
최영욱(Choi young wook) 대한전기학회 2006 대한전기학회 학술대회 논문집 Vol.2006 No.7
A high rate deposition sputtering process of magnesium oxide thin film in oxide mode has been developed using a 20 ㎾ unipolar pulsed power supply. The power supply was operated at a maximum constant voltage of 500 V and a constant current of 40 A. The pulse repetition rate and the duty were changed in the ranges of 10~50 ㎑ and 10~60%, respectively. The deposition rate increased with rising incident power to the target. Maximum incident power to the magnesium target was obtained by the control of frequency, duty and current. The deposition rate of a moving state was 9 ㎚ m/min at the average power of 1.5 ㎾.