• Journal of Pharmaceutical Investigation
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• v.30 no.1
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• pp.51-54
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• 2000

A column-switching high performance liquid chromatographic method has been developed for the determination of a fluconazole in human plasma. Each plasma sample was centrifuged for 10 min at 5000 g. After an aliqout of the supernatant was taken to nylon microcentrifuge filter, these samples were centrifuged for 10 min at 5000 g. An aliqout of the supernatant was injected directly onto the HPLC column. Deionized water was run for 2 min at a flow rate of 1.0 ml/min to retain fluconazole in an extration column, while proteins and endogenous interferences were eluted to the waste. The analyte was then back-flushed onto an analytical column, $C_{18}$ reversed-phase column. The mobile phase for analytical column, 0.01 M sodium acetate (pH 5.0)-methanol (65:35, v/v), was run at a flow rate of 1.0 ml/min. The column effluent was monitored by ultraviolet detection at 261 nm. The retention time for fluconazole was 11.76 min in human plasma. The detection limit for fluconazole in human plasma was $0.2\;{\mu}g/ml$. No interference from endogenous substances was observed.

• Proceedings of the KIEE Conference
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• 2001.11b
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• pp.106-108
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• 2001

As 3V cathode material, a new doping spinel material, LiMn1.6Se0.4O4 powder with a phase-pure polycrystalline was synthesized by a sol-gel method. In spite of Jahn-teller distortion in 3V region($2.4{\sim}3.5V$), the LiMn1.6Se0.4O4 electrode shows no capacity loss. The material in the 3V region initially delivers a discharge capacity of 100mAh/g which increase with cycling to reach 105mAh/g after 90cycles. And 5V cathode material LiNi0.5-xMxMn1.5O4(M=Cr, V, Fe) compounds have been synthesized by sol-gel method. a series of electroactive spinel compounds, LiNi0.5-xMxMn1.5O4(M=Cr, V, Fe) has been studied by crystallographic and electrochemical methods. The material presents only one plateau at around 4.5 V vs. Li/Li+ with a large discharge capacity of 152mAh/g and fairly good cyclability.

• Food Science and Preservation
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• v.4 no.2
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• pp.181-187
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• 1997

New HPLC method was developed for determination of some flavonoids such as naringin, hesperidin, neohesperidin, rutin, quercitrin, naringenin, hesperetin and apigenin and their contents in citrus juice and citrus peel from citrus varieties Brown in Cheju. Detection was at 280nm and reverse phase ${\mu}$-Bondapak C-18 column was used. Water/methanol/acetic acid as the mobile phase was better than water/acetonitrile/acetic acid. Flavonoids were more stable in 20% n,n-dimethylformamide in methanol(20% DMF) than methanol and pH 12 adjusted by 1N-sodium hydroxide solution. Standard flavonoid solutions were injected three times consecutively and the reproduciability was 0.236 to 3.550%, Correlation coefficient of the calibration curve was 0.9946 to 0.9999. The exiraction efficiency of hesperidin from citrus peel was evaluated with different extraction method such as reflux, ultra-sonicating method, using three solvents (aqueous solutions with pH12 adjusted by 1N-sodium hydroxide, methanol and 20% DMF), respectively. The reflux for 4 hour in 20% DMF was the most efficient of the tested methods and solvents, and recovery percentage were 78.0∼130.0%. Flavonoids were determined in citrus juice. Naringin was 68.2mg/100$m\ell$ in Natsudaidai, Hesperidin were 85.6mg/100$m\ell$ in Sankyool and Neohesperidin was 25.3mg/100$m\ell$ in Dangyooja. Flavonoids were determined in citrus peel. Naringin was 110mg/g in Dangyooja, Hesperidin was 242mg/g in Hungjin and Neohesperidin was 87.9mg/g in Dangyooja.

• Journal of Pharmaceutical Investigation
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• v.30 no.4
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• pp.283-288
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• 2000

The purpose of the present study was to investigate the topical bioavailability of retinol (vitamin A) after its transdermal administration. For this purpose, we developed the convenient HPLC method to measure the retinol concentration in the biological fluids such as plasma and skin tissues. The low detection limit was $0.1\;{\mu}g/ml$ using a gradient HPLC system of UV detection. The initial plasma concentration of retinol was about $20\;{\mu}g/ml$ after its i.v. bolus administration (4.32 mg/kg). The half life $(t_{1/2{\alpha}})$ in the distributive phase was 1.3 min, while retinol was slowly disappeared in the post-distributive phase. On the other hand, the maximum plasma concentration $(C_{max})$ was about 776 ng/ml after appling to rat skin at a dose of 43.2 mg/kg. Furthermore, the concentration of retinol in the skin tissues was about 600 ng/g tissue at 12 hr after its transdermal administration. In conclusion, the initial plasma concentration of retinol was comparable with the skin concentration after its cutaneous absorption, followed by being decreased with the passage of the time.

• Communications for Statistical Applications and Methods
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• v.29 no.2
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• pp.251-261
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• 2022

As AI has a wide range of influence on human social life, issues of transparency and ethics of AI are emerging. In particular, it is widely known that due to the existence of historical bias in data against ethics or regulatory frameworks for fairness, trained AI models based on such biased data could also impose bias or unfairness against a certain sensitive group (e.g., non-white, women). Demographic disparities due to AI, which refer to socially unacceptable bias that an AI model favors certain groups (e.g., white, men) over other groups (e.g., black, women), have been observed frequently in many applications of AI and many studies have been done recently to develop AI algorithms which remove or alleviate such demographic disparities in trained AI models. In this paper, we consider a problem of using the information in the sensitive variable for fair prediction when using the sensitive variable as a part of input variables is prohibitive by laws or regulations to avoid unfairness. As a way of reflecting the information in the sensitive variable to prediction, we consider a two-stage procedure. First, the sensitive variable is fully included in the learning phase to have a prediction model depending on the sensitive variable, and then an imputed sensitive variable is used in the prediction phase. The aim of this paper is to evaluate this procedure by analyzing several benchmark datasets. We illustrate that using an imputed sensitive variable is helpful to improve prediction accuracies without hampering the degree of fairness much.

• Microbiology and Biotechnology Letters
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• v.42 no.1
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• pp.73-81
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• 2014

Salsola collina, also known as Russian thistle, is widely distributed in and around waste facilities, roadsides, and drought and semi-drought areas, and is used as a traditional folk remedy in Chinese medicine for the treatment of hypertension. In this study, we have evaluated the anti-oxidative and anti-cancer activities of the ethanol extract of S. collina Pall. (EESC), and the molecular mechanisms of its anti-cancer effects on human colon carcinoma HT29 cells. EESC exhibited anti-oxidative activity through DPPH radical scavenging capacity and showed cytotoxic activity in a dose-dependent manner in HT29 cells. After EESC treatment, HT29 cells altered their morphology, becoming smaller and irregular in shape. EESC also induced cell accumulation in the G2/M phase in a dose-dependent manner, accompanied by a decrease of cell population in the G1 phase. The G2/M arrest by EESC was associated with the increased expression of cyclin-dependent kinase (CDK) inhibitor p21 and Wee1 kinase, which phosphorylates, or inactivates, Cdc2. EESC treatment induced the phosphorylation of Cdc2 and Cdc25C, and inhibited cyclin A and Cdc25C protein expression. In addition, S arrest was induced by the highest concentration of EESC treatment, associated with a decrease of cyclin A and Cdk2 expression. These findings suggest that EESC may possess remarkable anti-oxidative activity and exert an anti-cancer effect in HT29 cells by cell cycle regulation.

• Journal of the Korean Electrochemical Society
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• v.3 no.2
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• pp.109-114
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• 2000

The relation between the phase-shift profile fur the intermediate frequencies and the Langmuir adsorption isotherm at the poly-Ir/0.1 M $H_2SO_4$ aqueous electrolyte interface has been studied using ac impedance measurements, i.e., the phase-shift methods. The simplified interfacial equivalent circuit consists of the serial connection of the electrolyte resistance $(R_s)$, the faradaic resistance $(R_F)$, and the equivalent circuit element $(C_P)$ of the adsorption pseudoca-pacitance $(C_\phi)$. The comparison of the change rates of the $\Delta(-\phi)/{\Delta}E\;and\;\Delta{\theta}/{\Delta}E$ are represented. The delayed phase shift $(\phi)$ depends on both the cathode potential (E) and frequency (f), and is given by $\phi=tan^{-1}[1/2{\pi}f(R_s+R_F)C_P]$. The phase-shift profile $(-\phi\;vs.\;E)$ for the intermediate frequency (ca. 1 Hz) can be used as an experimental method to determine the Langmuir adsorption isotherm $(\theta\;vs.\;E)$. The equilibrium constant (K) for H adsorption and the standard free energy $({\Delta}G_{ads})$ of H adsorption at the poly-Ir/0.1 M $H_2SO_4$ electrolyte interface are $2.0\times10^{-4}$ and 21.1kJ/mol, respectively. The H adsorption is attributed to the over-potentially deposited hydrogen (OPD H).

• The Bulletin of The Korean Astronomical Society
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• v.43 no.1
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• pp.51.2-51.2
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• 2018

Polarimetry is a powerful technique to investigate the physical properties of surface materials on airless bodies in the solar system. It is known that the degree of linear polarization changes as a function of the phase angle (the angle between Sun-target-Observer). Especially, the dependency of the polarization degree at large phase angle allows us to obtain information related to the particle size and porosity, which is difficult to be determined via other observation techniques (i.e., photometry and spectroscopy). However, despite the advantage, only a few asteroids were observed with polarimetric devices at large phase angles. Here, we present our new polarimetric research of Near-Earth Asteroids (NEAs) observed at the large phase angles. Among the NEAs, we focus on S- and Q-type asteroids, which include: (331471) 1984 QY1, (90075) 2002 VU94, and (66391) 1999 KW4. The observation was conducted using the Pirka 1.6-m Telescope at the Nayoro Observatory of Hokkaido University at the phase angles ${\alpha}{\sim}100degree$, which provides us the maximum polarization degrees of these objects. Considering the observational results together with two objects ((1566) Icarus and (4179) Toutatis) in reference papers [1], [2], we will discuss the implication of the regolith size on their surfaces.

• Natural Product Sciences
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• v.14 no.1
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• pp.68-72
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• 2008

A simple reversed phase HPLC method was developed for extracting pharmacologically active compounds coptisine, palmatine, berberine, and epiberberine from the roots of Coptis chinensis using a binary gradient of acetonitrile : 10 mM hexanesulfonic acid-Na monohydrate with UV detection at 254 nm. The coptisine (1), palmatine (2), berberine (3), and epiberberine (4) contents of the roots of C. chinensis collected from sixteen district markets in Korea and China were $6.79\;{\sim}\;24.63\;{\mu}g/g$, $5.40\;{\sim}\;20.75\;{\mu}g/g$, $21.40\;{\sim}\;81.21\;{\mu}g/g$, and $3.45\;{\sim}\;12.04\;{\mu}g/g$, respectively.

• Polymer(Korea)
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• v.31 no.6
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• pp.461-468
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• 2007

In order to understand the structure of the existing aggregate in the nanocomposite, which has been prepared with polyester and trisilanolisobutyl polyhedral oligomeric silsesquioxane(TBPOSS), laser light scattering(LLS) and SEM-EDS were applied to its 1,1,1,3,3,3-hexafluoro-2-propanol solution and original sample, respectively. Although aggregate particles appeared as spherical shape of the average diameter of 120 nm in SEM image, they were not microgels but almost linear copolymer chains ($M_w=2.3{\times}10^6\;g/mol$) alternating 320 molecules of TBPOSS with polyester subchains. It has been microphase-separated from the matrix polyester due to the difference of chemical composition. As the matrix, polyester chain of $M_w=4.0{\times}10^4\;g/mol$ had averagely 2.5 molecules of TBPOSS per chain. It is also found that about 93% of total TBPOSS molecules existed in matrix phase and the residual 7% in spherically aggregated phase.