• 대한화학회지
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• 제35권4호
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• pp.397-404
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• 1991

역상 액체크로마토그래피에서, 간접 분광광도법으로 비발색단 물질인 지방족산, 지방족알코올 및 tetraalkylammonium 염들을 검출할 수 있었다. Benzyltriethylammonium bromide(BTEAB)를 검출시약으로 사용하였다. 또한 시료들의 머무름 기구와 시료들의 머무른 시간에 영향을 미치는 여러 가지 인자 즉, 검출시약의 농도, 메탄올의 농도, 이동상에 첨가한 화합물의 종류와 농도, 이동상의 온도와 pH, 시료분자에 있는 작용기의 종류에 대하여 알아보았다. 그리고 최적조건하에서 몇 가지 혼합시료들을 분리할 수 있었다.

• KSBB Journal
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• 제16권4호
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• pp.327-331
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• 2001

전라남도 보성산 녹차로부터 유용성분인 카테킨 화합물을 초임계 이산화 탄소와 첨가제를 사용하여 추출하고 역상 고성능 액체 크로마토그래피(RP-HPLC)를 사용하여 분석하였다. LiChrospher 100RP-18(15 $\mu$m)로 충진된 column을 이용하여 0.05% phosphoric acid가 포함된 물과 acetonitrile을 이동상으로 사용하였으며 구배용매 조성법을 적용하였다. 이동상의 조성에 따른 체류인자의 조절을 통해 EGCG를 분리하였다. 각각의 초임계 추출법에 따른 EGCG의 추출량을 비교한 결과, 초임계 유체에 극성물질을 포함하는 경우가 녹차의 유용 성분인 EGCG의 추출량이 가장 많았다. 그러나 ethanol에 의한 용매 추출법은 초임계 유체에 의한 추출법보다 EGCG에 대해 많은 추출양과 선택적인 고순도 분리가 가능하였다.

• Archives of Pharmacal Research
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• 제22권1호
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• pp.86-88
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• 1999

An advance d and sensitive high-performance liquid chromatographic (HPLC) method for determination of omeparzole in human plasma has been developed. After omeprazole was extracted from plasma with diethylether, the organic phase was transferred to another tube and trapped back with 0.1 N NaOH solution. The alkaline aqueous layer was injected into a reversed-phase C8 column. Lansoprazole was used as an internal standard. The mobile phase consisted of 30% of acetonitrile and 70% of 0.2 M $ KH_{2}PO_{4}$, pH 7.0. Recoveries of the analytes and internal standard were >75.48%. The coefficients of variation of intra- and inter-day assay were <5.78 and 4.59% for plasma samples. The detection limit in plasma was 2 ng/ml. The clinical applicability of this assay method was evaluated by determining plasma concentration-time courses of the respective analytes in 24 healthy volunteers after oral administration 40 mg of omeprazole. The present assay is considered to be simple, accurate, economical and suitable for the study of the kinetic disposition of omeprazole in the body.

• 열처리공학회지
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• 제34권5호
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• pp.218-225
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• 2021

In this study, damping capacities were comparatively investigated for Mg-9%Al alloy with as-cast (AC) and fully discontinuous precipitates (DPs) microstructures, respectively. The DPs microstructure was obtained by solution treatment at 678 K for 24 h, followed by furnace cooling to RT. The AC microstructure was typically characterized by partially divorced eutectic β(Mg₁₇Al₁₂) phase particles distributed along the α-(Mg) matrix cell boundaries. The DPs microstructure showed lamellar morphology consisting of α and β thin layers with various interlamellar spacings. The DPs microstructure had better damping capacity than the AC microstructure in the strain-amplitude independent region, while in the strain-amplitude dependent region, the damping behavior was reversed. In view of the microstructural features of AC and DPs, the lower concentration of Al in the α-(Mg) phase for the DPs microstructure and the lower β phase number density for the AC microstructure would be responsible for the higher damping capacities in the strain-amplitude independent and strain-amplitude dependent regions, respectively.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제15권3호
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• pp.1140-1155
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• 2021

Up to now, many state-of-arts have been proposed for two-way relaying system with linear modulations. The performances of antenna selection (AS) at both transmit and relay nodes need to be investigated in some two-way relaying multiple-input multiple-output (TWRM) systems. In this paper, the goal is focused on the study of nonlinear modulations, i.e., continuous phase modulation (CPM) in TWRM systems. Firstly, the joint phase trellis are simplified by reversed Rimoldi processing so as to reduce the systems' complexity. Then the performances of joint transmit and receive antenna selection (JTRAS) with CPM modulations in two-way relaying MIMO systems are analyzed. More exactly, the pair wise probability (PEP) is used to evaluate the error performance based on the CPM signal matrix, which is calculated in terms of Laurent expression. Since the channels subject to two terminal nodes share common antennas at relay node R in multiple-access scheme, we revise the JTRAS algorithm and compare it to existing algorithm via simulation. Finally, the error performances for various schemes of antenna selection are simulated and compared to the analysis in this paper.

• Journal of Audiology & Otology
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• 제25권1호
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• pp.43-48
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• 2021

Background and Objectives: Conflicting mechanisms have been reported about spontaneous reversal of positional nystagmus during head-roll maneuver in patients with benign paroxysmal positional vertigo (BPPV). The objective of this study is to review the reports about the characteristics and possible mechanisms of reversing positional nystagmus and to present seven new cases. Subjects and Methods: Seven cases (5 males, 2 females; 4 left-sided, 3 right-sided) were recruited among 732 patients with BPPV seen outpatient clinic between 2009 and 2019. Diagnosis of lateral canal canalolithiasis was confirmed when transient geotropic nystagmus was documented during head-roll test. Reversing positional nystagmus was analyzed in each case and clinical characteristics of the patients were documented. Results: The age of patients was ranging between 30 to 64 years (46.44±10.91). Duration of symptoms was short (21.34±19.74). Six of them had a story of head trauma. Initial latency was short. First, intense geotropic nystagmus was observed following provocative head-roll position on the affected side. There was short "silent phase". Then, a longer second-phase of reversed nystagmus was noted. Total duration of nystagmus was 78.40±6.82 seconds. Maximal slow phase velocity was 24.05±6.34 deg/sec. All patients were cured with barbeque maneuver. Conclusions: Ipsilateral reversing positional nystagmus during head-roll maneuver is due to lateral canal canalolithiasis. Mechanism is likely to be due to endolymphatic double flow. Bilateral cases may be due to simultaneous co-existence of canalolithiasis and cupulolithiasis. Longer recording of nystagmus is recommended not to miss the cases with spontaneous direction-changing positional nystagmus.

• 대한청각학회지
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• 제25권1호
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• pp.43-48
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• 2021

Background and Objectives: Conflicting mechanisms have been reported about spontaneous reversal of positional nystagmus during head-roll maneuver in patients with benign paroxysmal positional vertigo (BPPV). The objective of this study is to review the reports about the characteristics and possible mechanisms of reversing positional nystagmus and to present seven new cases. Subjects and Methods: Seven cases (5 males, 2 females; 4 left-sided, 3 right-sided) were recruited among 732 patients with BPPV seen outpatient clinic between 2009 and 2019. Diagnosis of lateral canal canalolithiasis was confirmed when transient geotropic nystagmus was documented during head-roll test. Reversing positional nystagmus was analyzed in each case and clinical characteristics of the patients were documented. Results: The age of patients was ranging between 30 to 64 years (46.44±10.91). Duration of symptoms was short (21.34±19.74). Six of them had a story of head trauma. Initial latency was short. First, intense geotropic nystagmus was observed following provocative head-roll position on the affected side. There was short "silent phase". Then, a longer second-phase of reversed nystagmus was noted. Total duration of nystagmus was 78.40±6.82 seconds. Maximal slow phase velocity was 24.05±6.34 deg/sec. All patients were cured with barbeque maneuver. Conclusions: Ipsilateral reversing positional nystagmus during head-roll maneuver is due to lateral canal canalolithiasis. Mechanism is likely to be due to endolymphatic double flow. Bilateral cases may be due to simultaneous co-existence of canalolithiasis and cupulolithiasis. Longer recording of nystagmus is recommended not to miss the cases with spontaneous direction-changing positional nystagmus.

• 전기학회논문지
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• 제66권2호
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• pp.315-322
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• 2017

This study presents a novel two­phase eight stator poles and six rotor poles (8/6) switched reluctance machine (SRM) that can compensate for the vibration and noise problems of two­phase 6/3 SRM and compare the characteristics of two SRMs. In the case of two­phase 6/3 SRM, the short flux path and the flux direction inside the stator are not reversed, so they have high efficiency characteristics. However, the use of three rotor poles causes problems of vibration and noise because the radial force applied to the rotor poles is not balance. The proposed two­phase 8/6 SRM has advantages of 6/3 SRM such as the flux­reversal­free stator and it can improve vibration and noise by using six rotor poles due to balanced radial force acting on the rotor poles. In order to make a reasonable comparison between two SRMs, the electromagnetic field structure of 8/6 SRM is designed to have equivalent torque characteristic to 6/3 SRM and then the copper loss and core loss are compared and analyzed. Finally, we compare the effieicney of two SRMs using finite element analysis and compare the distribution of radial force acting on the rotor poles based on Maxwell's stress method.

• Journal of Pharmaceutical Investigation
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• 제21권1호
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• pp.33-41
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• 1991

A high-performance liquid chromatographic (HPLC) method was developed for the simultaneous determination of theophylline(TP) and its metabolites, 1-methyluric acid (1-MU) and 1,3-dimethyluric acid (1,3-DMU), in rat plasma and urine. An $100\;{\mu}l$ aliquot of a plasma or urine sample was mixed with $250\;{\mu}l$ of acetonitrite and vortexed. After centrifugation, $200\;{\mu}l$ (plasma) or $20\;{\mu}l$ (urine) aliquot of the supernatant was dried by $N_2$ stream and redissolved in $100\;{\mu}l$ (plasma) or $200\;{\mu}l$ (urine) of the mobile phase. A $20\;{\mu}l$ of the mobile phase solution was injected onto a $C_{18}$ reversed-phase column. The column was maintained at $45^{\circ}C$ by the aid of electric heating jacket. The mobile phase was a 3%(v/v) methanol solution in deionized water which contains sodium acetate (100 mM) and tetrabutyl ammonium hydroxide (4 mM). pH of the mobile phase was adjusted 4.5 by the addition of acetic acid. Detection limits for TP, 1-MU, and 1,3-DMU in plasma were 0.2, 0.1 and $0.1\;{\mu}/ml$, respectively and the corresponding values in urine were all $5\;{\mu}g/ml$. Inter- and intra-day variability of the assay for all compounds in the plasma samples was less than 5.5 and 3.8%, respectively. The retention times for 1-MU, 1,3-DMU, and TP were approximately 7, 8.5 and 18 min, respectively. Sample preparation procedure used in this method was simple, rapid and reproducible. Renal clearance of TP and its metabolites in rats showed plasma concentration dependency indicating renal tubular secretion and reabsorption of them.

• Bulletin of the Korean Chemical Society
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• 제32권10호
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• pp.3597-3602
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• 2011

A simple and rapid analytical method was developed for the determination of eight isoquinoline alkaloids in Corydalis species. Eight isoquinoline alkaloids, including 2 aporphine alkaloids (isocorydine and glaucine) and 6 protoberberine alkaloids (coptisine, palmatine, berberine, canadine, corydaline, and tetrahydrocoptisine) were used as chemical markers which have a various biological activity and determined for quality control of Corydalis (C.) species (C. ternata, C. yanhusuo, and C. decumbens). To evaluate the quality of these herbal medicines, LC chromatographic separation of alkaloids were preferentially investigated on reversed-phase C18 column with pH variation and composition of mobile phase. In addition, the separation of these alkaloids in herbal extracts was found to be significantly affected on mobile phase composition using gradient elution. Especially for C. yanhusuo extract, berberine was seriously interfered with other alkaloid extracted from sample matrix when mobile phase composition was not optimized. As results, these compounds were successfully separated within 28 min using 10 mM ammonium acetate containing 0.2% triethylamine (adjusted at pH 5.0) as a mobile phase with gradient elution. On the basis of optimized HPLC conditions, 23 different Corydalis species samples were analyzed for the determination of alkaloid levels. In addition, principal component analysis (PCA) combined with the chromatographic data could be successfully classified the different geographic origin samples.