• Korean Journal of Ecology and Environment
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• v.50 no.4
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• pp.452-458
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• 2017

The nitrogen isotope value in both ammonium and nitrate ion were determined at 9 stations during both June and August 2016, in order to understand the origin of DIN at the Han river. ${\delta}^{15}N-NO_3$ and ${\delta}^{15}N-NH_4$ values in 8 stations (CP, SB, MHC, P4, SJ, SBC, P2, SC) were no significant variation. However ${\delta}^{15}N-NO_3$ and ${\delta}^{15}N-NH_4$ values in KK (Kyeongan stream) showed significant different in comparison with 8 stations, with an apparent increase of nitrogen isotope values. These results indicate that antropogenic nitrogen source influence on KK station. Also the ${\delta}^{13}C$ and ${\delta}^{15}N$ isotope ratio of phytoplankton (Diatom and Cyanobacteria) in KK (Kyeongan stream) showed heavier values, compared to other study stations. These results indicate that nitrogen isotope value in phytoplankton effects by different nitrogen source in study sites. These results suggest that the analysis of stable isotope ratios is a simple but useful tool for the identification of dissolved inorganic nitrogen origin in aquatic environments.

• Journal of Yeungnam Medical Science
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• v.16 no.1
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• pp.101-107
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• 1999

We evaluated the results of sequential SPECT dual-isotope imaging with Tl-201 and Tc-99m MIBI in 24 patients. all of whom also had coronary angiography within the past one month. Coronary angiography showed that 12 patients had no CAD, 4 patients had one-vessel CAD, 7 patients had two-vessel CAD and 1 patient had three-vessel CAD. Serial studies of resting Tl-201 and dipyridamole stress Tc-99m MIBI were completed within 2 hours. When more than 50% of coronary artery narrowing was considered significant, the overall sensitivity and specificity of CAD detection were 91.7%. The sensitivity of CAD detection in patients with one-vessel and multi-vessel diseases was 75% and 100%. respectively. Therefore, sequential dual-isotope SPECT demonstrated high sensitivity and specificity for CAD detection. In conclusion, sequential dual-isotope imaging is feasible and can be completed in a short time and may therefore enhance laboratory throughput and patient convenience.

• Economic and Environmental Geology
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• v.46 no.6
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• pp.495-508
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• 2013

Recently, stable isotopes (${\delta}^{18}O$ and ${\delta}D$) of water are increasingly analyzed using laser-based technologies. These methods have advantages over Isotope Ratio Mass Spectrometry (IRMS) in that they can be used for in-situ measurements and require much less maintenance and preparation work. Two types of laser-based methods are currently available, which have different analytical principles; OA-ICOS (off-axis integrated cavity output spectroscopy) and WS-CRDS (wavelength-scanned cavity ring-down spectroscopy). In the WS-CRDS instrument, water is vaporized at controlled environment and transferred to an optical cavity by nitrogen carrier gas, and stable isotopic compositions of water vapor are measured using the degree of absorbance of specific wavelengths and the ratios of attenuation time of the laser intensity with the sensitivity of ppb to tens of ppt level. In this study, we introduce the principle of the WS-CRDS technology and the performance results including stability and comparisons with Isotope Ratio Mass Spectrometry (IRMS) and suggest possible applications of various topics in isotope hydrology.

• Laboraroty Animal Research
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• v.34 no.4
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• pp.248-256
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• 2018

O-2-$^{18}F$-fluoroethyl-l-tyrosine ($[^{18}F]FET$) has been widely used for glioblastomas (GBM) in clinical practice, although evaluation of its applicability in non-clinical research is still lacking. The objective of this study was to examine the value of $[^{18}F]FET$ for treatment evaluation and prognosis prediction of anti-angiogenic drug in an orthotopic mouse model of GBM. Human U87MG cells were implanted into nude mice and then bevacizumab, a representative anti-angiogenic drug, was administered. We monitored the effect of anti-angiogenic agents using multiple imaging modalities, including bioluminescence imaging (BLI), magnetic resonance imaging (MRI), and positron emission tomography-computed tomography (PET/CT). Among these imaging methods analyzed, only $[^{18}F]FET$ uptake showed a statistically significant decrease in the treatment group compared to the control group (P=0.02 and P=0.03 at 5 and 20 mg/kg, respectively). This indicates that $[^{18}F]FET$ PET is a sensitive method to monitor the response of GBM bearing mice to anti-angiogenic drug. Moreover, $[^{18}F]FET$ uptake was confirmed to be a significant parameter for predicting the prognosis of anti-angiogenic drug (P=0.041 and P=0.007, on Days 7 and 12, respectively, on Pearson's correlation; P=0.048 and P=0.030, on Days 7 and 12, respectively, on Cox regression analysis). However, results of BLI or MRI were not significantly associated with survival time. In conclusion, this study suggests that $[^{18}F]FET$ PET imaging is a pertinent imaging modality for sensitive monitoring and accurate prediction of treatment response to anti-angiogenic agents in an orthotopic model of GBM.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.27 no.3
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• pp.144-157
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• 2022

Noble gases, which are chemically inert and behave conservatively in marine environments, have been used as tracers of physical processes such as air-sea gas exchange, mixing of water masses, and distribution of glacial meltwater in the ocean. For precise measurements of Ne, Ar, and Kr, we developed a mass spectrometric system consisting of a quadrupole mass spectrometer (QMS), a high vacuum preparation line, an activated charcoal cryogenic trap (ACC), and a set of isotope standard gases. The high vacuum line consists of three sections: (1) a sample extraction section that extracts the dissolved gases in the sample and mixes them with the standard gases, (2) a gas preparation section that removes reactive gases using getters and separates the noble gases according to their evaporation points with the ACC, and (3) a gas analysis section that measures concentrations of each noble gas. The ACC attached to the gas preparation section markedly lowered the partial pressures of Ar and CO₂ in the QMS, which resulted in a reduced uncertainty of Ne isotope analysis. The isotope standard gases were prepared by mixing ²²Ne, ³⁶Ar, and ⁸⁶Kr. The amounts of each element in the mixed standard gases were determined by the reverse isotope dilution method with repeated measurements of the atmosphere. The analytical system achieved precisions for Ne, Ar, and Kr concentrations of 0.7%, 0.7%, and 0.4%, respectively. The accuracies confirmed by the analyses of air-equilibrated water were 0.5%, 1.0%, and 1.7% for Ne, Ar, and Kr, respectively.

• Korean Journal of Ecology and Environment
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• v.56 no.4
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• pp.339-347
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• 2023

Dissolved organic matter (DOM) is a key component in the biogeochemical cycling in freshwater ecosystem. However, it has been rarely explored, particularly complex river watershed dominated by natural and anthropogenic sources, such as various effluent facility and livestock. The current research developed a new analytical method for TOC/TN (Total Organic Carbon/Total Nitrogen) stable isotope ratio, and distinguish DOM source using stable isotope value (δ¹³C-DOC) and spectroscopic indices (fluorescence index [FI] and biological index [BIX]). The TOC/TN-IR/MS analytical system was optimized and precision and accuracy were secured using two international standards (IAEA-600 Caffein, IAEA-CH-6 Sucrose). As a result of controlling the instrumental conditions to enable TOC stable isotope analysis even in low-concentration environmental samples (<1 mgC L^-1), the minimum detection limit was improved. The 12 potential DOM source were collected from watershed, which includes top-soils, groundwater, plant group (fallen leaves, riparian plants, suspended algae) and effluent group (pig and cow livestock, agricultural land, urban, industry facility, swine facility and wastewater treatment facilities). As a result of comparing characteristics between 12 sources using spectroscopic indices and δ¹³C-DOC values, it were divided into four groups according to their characteristics as a respective DOM sources. The current study established the TOC/TN stable isotope analyses system for the first time in Korea, and found that spectroscopic indices and δ¹³C-DOC are very useful tool to trace the origin of organic matter in the aquatic environments through library database.

• Archives of Pharmacal Research
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• v.19 no.4
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• pp.302-306
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• 1996

The $^1H- and^{13}C-NMR$ spectra of alaternin, aurantio-obtusin, chryso-obtusin, obtusin and 2-glucosyl obtusifolin isolated from the seeds of Cassia tora have been assigned based on HMBC, long-range HETCOR, fully $^1H-coupled {13}^C-NMR$, deuterium isotope experiment, and by comparison with the model compounds.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2005.10a
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• pp.261-262
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• 2005

• Bulletin of the Korean Chemical Society
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• v.35 no.3
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• pp.753-757
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• 2014

The nucleophilic substitution reactions of Y-aryl N,N-dimethyl phosphoroamidochloridates with substituted anilines and deuterated anilines are kinetically investigated in acetonitrile at $65.0^{\circ}C$. A stepwise mechanism with a rate-limiting leaving group departure from the intermediate is proposed based on the positive ${\rho}_{XY}$ value. The deuterium kinetic isotope effects involving deuterated anilines show secondary inverse with all the nucleophiles, rationalized by a dominant backside nucleophilic attack.

• 전기의세계
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• v.13 no.1
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• pp.30-33
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• 1964

최근 우리나라의 isotope사용은 의학 및 농학을 비롯하여 여러 분야에서 활발히 움직이고 있으나 공업면의 응용에는 아직 거의 없는 실정에 놓여있는 것이다. 그것은 계측기의 성능이 종래의 다른 방식과 비교할 때 대단히 우수하여 계측만으로의 목적으로는 좋은 평가를 받았든 것이나 process공업의 목적으로는 측정 절단 그리고 제어를 하는 복잡한 체계로서 시작하여야 되는 고로 다소 고도의 기술을 요하는 난점이 있었기 때문이었다. 따라서 본지에서는 실제 isotope가 process공업에 응용될때 문제되는 점 즉 process제어 정밀도의 우려를 가려내는 검출단의 성능과 각 공업에서 사용할 수 있는 계측기의 제어계를 간단히 해설하여 보기로 한다.