• FOCUS: LIFE SCIENCE
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• no.1
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• pp.3.1-3.7
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• 2024

The article discusses the critical role of chromatography in the analysis and purification of proteins in biopharmaceuticals, emphasizing the importance of comprehensive characterization for ensuring their safety and efficacy. It highlights the use of Avantor® ACE® HPLC columns for the separation and purification of proteins, focusing on the analysis of intact proteins using reversed-phase liquid chromatography (RPLC) with fully porous particles. This article also details the application of different mobile phase additives, such as TFA and formic acid, and emphasizes the advantages of using type B ultra-pure silica-based columns for efficiency and peak shape in biomolecule analysis. Additionally, it addresses the challenges of analyzing intact proteins due to slow molecular diffusion and introduces the concept of solid-core (or superficially porous) particles, emphasizing their benefits over traditional porous particles for the analysis of therapeutic proteins. Furthermore, it discusses the development of Avantor® ACE® UltraCore BIO columns, specifically designed for the high-efficiency separation of large biomolecules, such as proteins, and demonstrates their effectiveness in achieving high-resolution separations, even for higher molecular weight proteins like monoclonal antibodies (mAbs). In addition, it underscores the complexity of analyzing and characterizing intact protein biopharmaceuticals, requiring a range of analytical techniques and the use of wide-pore stationary phases, operated at elevated temperatures and with relatively shallow gradients. It highlights the comprehensive range of options offered by Avantor® ACE® wide pore columns, including both fully porous and solid-core particles, bonded with a variety of complementary stationary phase chemistries to optimize selectivity during method development. The use of ultrapure and highly inert base silica is emphasized for enabling the use of lower concentrations of mobile phase modifiers without compromising analyte peak shape, particularly beneficial for LC-MS applications. Then the article concludes by emphasizing the significance of reversed-phase liquid chromatography and its compatibility with mass spectrometry as a valuable tool for the separation and analysis of intact proteins and their closely related variants in biopharmaceuticals.

• Analytical Science and Technology
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• v.35 no.5
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• pp.189-196
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• 2022

When cationic basic compounds are chromatographed using hydro-organic mobile phase, the presence of anionic free silanols in the silica-based stationary phases results in broad and asymmetrical peaks. The addition of an ionic reagent to the mobile phase prevents analytes from accessing free silanols, improving peak shape. In this study, the chromatographic behavior of salbutamol sulfate as a basic compound was investigated under various conditions, including the use of different columns, mobile phases, and ion-pair reagents such as triethanolamine (TEA) and sodium heptane sulfonate (SHS). The retention and peak shape of chromatograms were both evaluated. The results show that pre-conditioning the column with TEA and including it in the mobile phase can prevent cationic analytes from accessing anionic silanols, resulting in improved peak shape. Furthermore, buffering the mobile phase is an important factor in keeping the pH constant throughout the process. The chosen method was validated in part. This study could be helpful for researchers and analyst to solve such problems with cationic basic components.

• Analytical Science and Technology
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• v.33 no.1
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• pp.1-10
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• 2020

Alpha lipoic acid, an antioxidant, is widely used for treatment of various diseases. It is a racemic mixture, with R-(+)-α lipoic acid exhibiting greater potency, bioavailability, and effectiveness than those of the S-form. Thus, selective R-(+)-α lipoic acid has been recently used in various applications, necessitating the development of a method to test the enantiomeric impurity in R-(+)-α lipoic acid. We developed a simple and fast high-performance liquid chromatography method using a new immobilized amylose-based chiral column (Chiralpak IA-3). Design of experiment was applied to accurately predict the effects and interactions among various factors affecting the analytical parameters and to optimize the chromatographic conditions. This optimized method could completely separate the two enantiomer peaks with a resolution > 1.8 within a short running time (9 min). Then, the optimized method was validated according to the guidelines of the International Conference on Harmonization and applied for quantification of S-(-)-α lipoic acid in some commercial R-(+)-α lipoic acid tromethamine raw material. Our results suggested that the developed method could be used for routine quality control of R-(+)-α lipoic acid products.

• Journal of Biomedical Engineering Research
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• v.30 no.1
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• pp.79-88
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• 2009

A harmonic quadrature demodulation method to extract the second harmonic component from focused ultrasound signals after a single transmit-receive event is proposed. In the proposed method, the focused ultrasound signal is converted into baseband inphase and quadrature components by multiplying with sine and cosine signals both having twice the center frequency of the transmitted signal and filtering the two modulated signals. The quadrature component is then passed through a Hilbert filter to be added to the inphase component, which leaves only the envelope of the second harmonic component. A novel phase estimation technique is employed in the proposed method to avoid the phase mismatch between the focused signal and the two modulating signals. The proposed method is verified through both theoretical analysis and computer simulations. It is shown that compared to the pulse inversion scheme the proposed method provides almost the same results for stationary targets and significantly improved harmonic to fundamental ratio for moving targets.

• Proceedings of the KIPE Conference
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• 2018.07a
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• pp.144-146
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• 2018

In order to meet the harmonics standards such as IEEE 519 and P1547 the output quality of a grid connected inverter should satisfy a certain level of Total Harmonic Distortion (THD) value. However, the output quality of an inverter gets degraded due to the grid voltage harmonics, the dead time effects and the nonlinearity of the switches, which all contributes to a higher THD value of the output. In order to meet the required THD value for the inverter output under the distorted grid condition the use of harmonic controller is essential. In this paper a novel feedforward harmonic compensation method is proposed in order to effectively eliminate the low order harmonics in the inverter current to the grid. In the proposed method, unlike the conventional harmonic control methods, the hamonic components are directly compensated by the feedforward terms generated by the PR controller with the grid current in the stationary frame. The proposed method is simple in implementation but powerful in eliminating the harmonics from the output. The effectiveness of proposed method is verified through the PSIM simulation and the experiments with a 5kW single phase grid connected inverter.

• The Transactions of the Korean Institute of Power Electronics
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• v.24 no.3
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• pp.215-227
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• 2019

Grid-connected inverters should satisfy a certain level of total harmonic distortion (THD) to meet harmonics standards, such as IEEE 519 and P1547. The output quality of an inverter is typically degraded due to grid voltage harmonics, dead time effects, and the device's turn-on/turn-off delay, which all contribute to increasing the THD value of the output. The use of a harmonic controller is essential to meet the required THD value for inverter output under a distorted grid condition. In this study, an improved feedforward harmonic compensation method is proposed to effectively eliminate low-order harmonics in the inverter current to the grid. In the proposed method, harmonic components are directly compensated through feedforward terms generated by the proportional resonant controller with the grid current in a stationary frame. The proposed method is simple to implement but powerful in eliminating harmonics from the output. The effectiveness of the proposed method is verified through simulation using PSIM software and experiments with a 5 kW single-phase grid-connected inverter.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.54 no.4
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• pp.201-207
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• 2005

This paper has investigated the sensorless vector control method of induction motor based on the stator flux oriented voltage equation and the digital low pass filter (LPF) with compensator of phase/gain. The Proposed vector control method is easy to decide the stator reference voltages and control of motor, since it is based on stator flux vector But this method has sensitive structure to excessive sensor noise and PWM pulsating components of stator currents because the measured stator currents are directly used to compensate the internal resistive voltage drop at the determination of stator reference voltages. To eliminate the noise sensitive of proposed vector drive, this paper propose the digital LPF with compensator of phase/gain base on orthogonal property of stator current vector in stationary $\alpha$, $\beta$ reference frame. The proposed methods have been simulated and implemented on a sensorless vector drive for 750W three-phase induction motor. The simulation and experimental results demonstrate effectiveness of the proposed methods.

• Korean Journal of Veterinary Research
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• v.38 no.2
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• pp.359-365
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• 1998

This study was conducted to isolate the protozoan parasite Babesia gibsoni by intraerythrocytic culture method of micoraerophilous stationary phase(MASP) and evaluate the possibility of application for the detection of B gibsoni in canine babesiosis. Also, indirect fluorescent antibody test(IFAT) and thick blood smear(giemsa stain), direct light microscopy (DLM), as control diagnostic tests, were conducted to compare diagnostic effects between MASP, IFAT and DLM. The results obtained from this study were summarized as follows. The protozoan parasite B gibsoni multiplied in 24-well polystyrene plate containing 1.2ml of canine red blood cell suspension in RPMI 1640 medium(pH 7.0) which is contained 20~40% normal canine serum(NCS) under the MASP condition of 5% $CO_2$ and 95% air at $37^{\circ}C$ incubator. Under the above MASP culturing system the percentage of parasitized erythrocytes(PPE) after incubation for 9 days reached the peak. The levels of PPE in MASP culture were shown more higher by exchanging the medium at 24 hour intervals. The parasite were purely isolated from MASP culture of canine red blood cells collected from dogs(pit bullterrier) infected with B gibsoni naturally. Among the total of 83 heads of pit bullterrier blood samples the positive rate was 32 heads(38.5%) in DLM, 45 heads(54.2%) in IFAT and 42 heads(50.6) in MASP culture. In negative cases of IFAT and DLM the isolation rates of B gibsoni by MASP culture were 16 heads(42.1%) of 38 heads and 16 heads(28.6%)% of 56 heads, respectively. From this study it was suggested that MASP culture method by RPMI 1640 medium was a reliable and useful diagnostic test for the diagnosis of B gibsoni infections in canine babesiosis.

• Proceedings of the Korean Society for Applied Microbiology Conference
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• 2000.04a
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• pp.53-60
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• 2000

Strain BH5 was isolated from naturally fermented Kimchi and identified as a bacteriocin producer, which has bactericidal activity against Micrococcus flavus ATCC 10240. Strain BH5 was identified tentatively as Lactococcus lactis by the API test and some characteristics. Lactococcus lactis BH5 showed a broad spectrum of activity against most of the non-pathogenic and pathogenic microorganisms tested by the modified deferred method. The activity of lacticin BH5, named tentatively as the bacteriocin produced by Lactococcus lactis BH5, was detected at the mid-log growth phase, reached its maximum during the early stationary phase, and decreased after the late stationary phase. Lacticin BH5 also showed a relatively broad spectrum of activity against non-pathogenic and pathogenic microorganisms as tested by the spot-on-lawn method. Its antimicrobial activity on sensitive indicator cells was completely disappeared by protease XIV or ${\alpha}$-chymotrypsin. The inhibitory activities of lacticin BH5 were detected during treatments up to 100$^{\circ}C$ for 30 min. Lacticin BH5 was very stable over a pH range of 2.0 to 9.0 and was stable with all the organic solvents examined. The cell concentration and bacteriocin production in strain BH5 were maximum when grown at 30$^{\circ}C$ in a modified MRS medium supplemented with 0.5% tryptone, 1.0% yeast extract, and 0.5% beef extract as nitrogen sources. It demonstrated a typical bactericidal mode of inhibition against Micrococcus flavus ATCC 10240. Lacticin BH5 was purified through ammonium sulfate precipitation, ethanol precipitation, and CM-Sepharose column chromatography. The apparent molecular mass of lacticin BH5 was estimated to be in the region of 3.7 kDa, by the direct detection of bactericidal activity after SDS-PAGE. Mutant strain NO141 which was isolated by nitrosoguanidine mutagenesis produced about 4 fold more bacteriocin than the wild type.

• Journal of IKEEE
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• v.7 no.1 s.12
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• pp.32-42
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• 2003

In this paper, radiation pattern of rectangular microstrip patch antenna with anisotropy substrates and superstrate is studied by using a rigorous full-wave approach and a moment method calculation. Dyadic Green's function is derived for selected anisotropy material by constitutive relation. From these results, integral equations of electric fields are formulated. The electric field integral equations are discretized into the matrix form by applying Galerkin's moment method and then the current coefficients are obtained.. After solving the current coefficients, the far-zone electric field in spherical coordinates can be obtained by using the stationary phase method. To verify the validity of numerical result, we compare our result with existing one and get a good agreement between them. From the numerical results, the radiation patterns for variation of uniaxial superstrate thickness, anisotropy ratio of substrate and superstrate layer are presented and analyzed.