• Journal of Microbiology and Biotechnology
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• 제19권11호
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• pp.1348-1354
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• 2009

Bioconversion of the isoflavonoid genistein to 2'-hydroxygenistein (2'-HG) was performed using isoflavone 2'-hydroxylase (CYP81E1) heterologously expressed in yeast. A monohydroxylated product was analyzed by liquid chromatography-electrospray ionization-mass spectrometry (LC-ESI-MS) and NMR spectrometry and was identified as 2'-HG. An initial bioconversion rate of 6% was increased up to 14% under optimized conditions. After recovery, the biological activity of 2'-HG was evaluated. Bioconverted 2'-HG showed higher antioxidant activity against 1,1-diphenyl-2-picryl hydrazine (DPPH) and 2,2'-azino-bis (3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) radicals than did genistein. Furthermore, 2'-HG exhibited greater antiproliferative effects in MCF-7 human breast cancer cells than did genistein. These results suggest that 2'-hydroxylation of genistein enhanced its antioxidant activity and cell cytotoxicity in MCF-7 human breast cancer cells.

• 대한수의학회지
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• 제44권3호
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• pp.367-371
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• 2004

This report describes the determination of ceftiofur residues in milk from treatment of lactating dairy cattle by intramuscular injection of three consecutive daily doses of about 1 mg /kg BW, the recommended label dosing. The separation of ceftiofur was achieved on $C_1_8$ reverse phase column. The mobile phase consisted of 0.1% trifluoracetic acid in water (A) and 0.05% acetic acid in acetonitrile (B) and grediently flowed at the flow rate of 0.4 mL/min. As a result of analysis of blank raw bovine milk samples, matrix interference was not shown. Limit of detection and limit of quantitaion was 0.5 ng/mL and 1 ng/mL, respectively. The values of precision and recovery satisfied the guideline of National Veterinary Research and Quarantine Service (NVRQS, Korea). The mean residual concentration of ceftiofur in milk did not exceed 3.71 ng/mL when ceftiofur was administered intramuscularly to lactating dairy cattle for 3 consecutive days at 1 mg/kg of BW per day. It is much lower than the proposed MRL (100 ng/mL) of ceftiofur in milk.

• 한국추진공학회지
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• 제18권6호
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• pp.1-10
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• 2014

극초음속 흡입구를 직관적이며 체계적으로 설계할 수 있는 최적화된 방법을 제시한다. 마하 7의 이론식으로 계산된 극초음속 흡입구는 점성 조건의 전산수치해석을 수행하여 점성에 대한 오차를 보정한다. 전산수치해석을 통한 성능 비교에서 1단 쐐기에 비해 2단 쐐기를 가지는 흡입구 형상이 성능비교에서 좋은 결과를 보였다. 또한 비설계 조건에서 극초음속 흡입구의 성능은 설계 마하수 성능에 비해 손실이 크지 않았다.

• Membrane and Water Treatment
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• 제6권6호
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• pp.451-476
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• 2015

Membrane distillation (MD), which can utilize low-grade thermal energy, has been extensively studied for desalination. By incorporating solar thermal energy, the solar membrane distillation desalination system (SMDDS) is a potential technology for resolving the energy and water resource problems. Small-scale SMDDS (s-SMDDS) is an attractive and viable option for the production of fresh water for small communities in remote arid areas. The minimum-cost design and operation of s-SMDDS are determined by a systematic method, which involves a pseudo steady state approach for equipment sizing and the dynamic optimization using overall system mathematical models. The s-SMDDS employing three MD configurations, including the air gap (AGMD), direct contact (DCMD) and vacuum (VMD) types, are optimized. The membrane area of each system is $11.5m^2$. The AGMD system operated for 500 kg/day water production rate gives the lowest unit cost of $5.92/m^3$. The performance ratio and recovery ratio are 0.85 and 4.07%, respectively. For the commercial membrane employed in this study, the increase of membrane mass transfer coefficient up to two times is beneficial for cost reduction and the reduction of membrane heat transfer coefficient only affects the cost of the DCMD system.

• 한국수소및신에너지학회논문집
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• 제24권1호
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• pp.91-97
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• 2013

Recently a novel cycle named organic flash cycle (OFC) has been proposed which has improved potential for power generation from low-temperature heat sources. This study carries out thermodynamic performance analysis of OFC using various working fluids for recovery of low-grade heat sources in the form of sensible energy. Special attention is focused on the optimum flash temperature at which the exergy efficiency has the maximum value. Under the optimal conditions with respect to the flash temperature, the thermodynamic performances of important system variables including mass flow ratio, separation ratio, heat addition, specific volume flow rate at turbine exit, and exergy efficiency are thoroughly investigated. Results show that the exergy efficiency has a peak value with respect to the flash temperature and the optimum working fluid which shows the best exergy efficiency varies with the operating conditions.

• 방사성폐기물학회지
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• 제18권4호
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• pp.421-437
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• 2020

This study provides an assessment on a proposed method for separation of cesium, strontium, and barium using electrochemical reduction at a liquid bismuth cathode in LiCl-KCl eutectic salt, investigated via cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and scanning electron microscopy with energy dispersive X-ray spectrometry (SEM-EDS). CV studies were performed at temperatures of 723-823 K and concentrations of the target species up to 4.0wt%. Redox reactions occurring during potential sweeps were observed. Concentration of BaCl2 in the salt did not seem to influence the diffusivity in the studied concentration range up to 4.0wt%. The presence of strontium in the system affected the redox reaction of lithium; however, there were no distinguishable redox peaks that could be measured. Impedance spectra obtained from EIS methods were used to calculate the exchange current densities of the electroactive active redox couple at the bismuth cathode. Results show the rate-controlling step in deposition to be the mass transport of Cs+ ions from the bulk salt to the cathode surface layer. Results from SEM-EDS suggest that Cs-Bi and Sr-Bi intermetallics from LiCl-KCl salt are not thermodynamically favorable.

• 한국기계가공학회지
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• 제19권10호
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• pp.1-7
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• 2020

In this study, a multichannel gas-liquid microextraction system is designed by integrating the automatic elution of extraction line and multichannel gas-purging liquid phase microextraction. The system uses an injection pump and inert gas to push the extraction solvent to a sample bottle of a gas-phase color autosampler and then implements multichannel gas-liquid microextraction and gas chromatography-mass spectrometry. The system also employs a three-way integrated micro-high-temperature heater, syringe pump, and microflow controller to realize the simultaneous processing of multiple groups of samples, thus improving the sample pretreatment speed and reproducibility and reducing human error. Autoinjection experiments were implemented with polycyclic aromatic hydrocarbon standard samples. The experiments show that the average recovery rate of the system exceeds 70%, and the relative standard among the channels is less than 15%.

• Journal of Korean Neurosurgical Society
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• 제58권6호
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• pp.571-577
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• 2015

Direct removal of beak-type ossification of posterior longitudinal ligament at thoracic spine (T-OPLL) is a challenging surgical technique due to the potential risk of neural injury. Slipping off the cutting surface of a high-speed drill may result in entrapment in neural structures, leading to serious complications. Removal of T-OPLL with an ultrasonic osteotome, utilizing back and forth micro-motion of a blade rather than rotatory-motion of drill, may reduce such complications. We have applied the ultrasonic osteotome for posterior circumferential decompression of T-OPLL for three consecutive patients with beak-type OPLL and have described the surgical techniques and patient outcomes. The preoperative chief complaint was gait disturbance in all patients. Japanese orthopedic association scores (JOA) was used for functional assessment. Scores measured 2/11, 5/11, 2/11, and 4/11 for each patient. The ventral T-OPLL mass was exposed after posterior midline approach, laminotomy and transeversectomy. The T-OPLL mass was directly removed with an ultrasonic osteotome and instrumented segmental fixation was performed. The surgeries were uneventful. Detailed surgical techniques were presented. Gait disturbance was improved in all patients. Dural tear occurred in one patient without squeal. Postoperative JOA was 6/11, 10/11, 8/11, and 8/11 (recovery rate; 44%, 83%, 67%, and 43%) respectively at 18, 18, 10, and 1 months postoperative. T-OPLL was completely removed in all patients as confirmed with computed tomography scan. We hope that surgical difficulties in direct removal of T-OPLL might be reduced by utilizing ultrasonic osteotome.

• 한국수산과학회지
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• 제46권2호
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• pp.154-159
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• 2013

The AOAC Mouse Bioassay method (MBA) has been widely used for routine monitoring of paralytic shellfish poisoning (PSP) for more than 50 years. However, this method has low sensitivity and experiences interference from other components in the extract. Also, ethical issues have been raised against the continued use of this live-mouse assay. To establish an alternative method for PSP analysis, we attempted to develop PSP analysis conditions using liquid chromatography-tandem mass spectrometry (LC-MS/MS). The LC-MS/MS analysis of reference material showed very reasonable accuracy, and the analysis time was just 15 min. However, the recovery rate of toxin spike samples using the LC-MS/MS analysis was 59.4-91.0%. We also attempted to remove the matrix effect using shellfish extracts, but recoveries of C1 and C2 did not improve. A comparison between the results of MBA and LC-MS/MS analysis revealed good correlations, with values of 0.8878 and 0.9211 for oyster and mussel matrices, respectively.

• 환경위생공학
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• 제19권4호
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• pp.25-33
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• 2004

Acrylamide, difficult to analyze by GC and GC/MS due to the polarity and low volatility, was analyzed by LC/ESI/MS in the study. Acrylamide its(molecular weight 71amu) showed m/z=72 $(M+H)^+$ and high peak intensity at 22V in SIR mode. The mass spectrum ratios of acrylamide for qualitative identification had m/z=72 in precursor ion and m/z=55 in products ion, respectively. Those ratios at 30V in SIR mode ranged from 1: 1.4 to 1:1.17 despite various acrylamide concentrations. The ion intensity ratios of acrylamide $(m/z=72,\; [M+H]^+)$ to acrylamide isotopes $(m/z=73,\;[M+H]^+)$ ranged from 100 : 3.57 to 100 : 3.92. The results verified theoretical mass spectrum ratio that was 100:3.82. The linearity of standard calibration curve was y : 520.584x + 1815.26 with $r^2=0.99.$ In quality assurance and quality control, the recovery rate ranged from 81.64 percent to 90.97 percent and relative standard deviation was less than $10\%$ with 5 repeated injections at individual standard calibration solutions. The method was applied to analyze acrylamide in food at grocery stores. Snacks made of potatoes showed the highest acrylamide concentration followed by products made of French fries, wheat, and corn.