• Korean Journal of Mineralogy and Petrology
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• v.35 no.3
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• pp.199-214
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• 2022

The Yeongnam Massif is one of representative basement provinces in the Korean Peninsula, which has experienced high-temperature, low-pressure (HTLP) regional metamorphism and partial melting. Here we reviewed recent developments in Paleoproterozoic (1.87-1.84 Ga) hot orogenesis of the Yeongnam Massif, typified by the granulite-facies metamorphism and partial melting recorded in the HTLP rocks. In particular, spatiotemporal linkage between the metamorphic and magmatic activities, including the Sancheong-Hadong anorthositic magma as a heat source, provides a key to understand the widespread HTLP metamorphism and partial melting in the Yeongnam Massif. Crustal anatexis, resulting from the fluid-present melting and muscovite/biotite dehydration melting, has yielded various types of leucosomes and leucogranites. Zircon and monazite petrochronology, using in-situ U(-Th)-Pb data from the secondary ion mass spectrometry, indicates that the HTLP metamorphism and anatexis lasted over a period of ~15 Ma at ca. 1870-1854 Ma. In addition, a fluid influx event at ca. 1840 Ma was locally recognized by the occurrence of incipient charnockite. Taken together, the Yeongnam Massif preserves a prolonged evolutionary record of the HTLP metamorphism, partial melting, and fluid influx diagnostic for a hot orogen. Such an orogen is linked to the Paleoproterozoic orogeny widespread in the North China Craton, and most likely represents the final phase of crustal evolution in the Columbia/Nuna supercontinent.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.47 no.4
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• pp.361-368
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• 2021

The objective of this study was to establish technology for removing bacteria with human- and eco-friendly material. Staphylococcus aureus as an important component for balanced equilibrium among microbiomes, was cultured under various concentrations of phosphate. Experimental observation relating to physical properties was performed in an addition of phosphate buffer. Statistically minimum value of size and hardness using atomic force microscope was observed on the matured biofilm at 5 mM concentration of phosphate. As a result of absorbance for the biofilm tagged with dye, concentration of biofilm was reduced with phophate, too. To identify whether this reduction by phosphate at the 5 mM is caused by counter ion or not, sodium chloride was treated to the biofilm under the same condition. To elucidate components of the biofilm counting analysis of the biofilm using time-of-flight secondary ion mass spectrometry was employed. The secondary ions from the biofilm revealed that alteration of physical properties is consistent to the change of extracellular polymeric substrate (EPS) for the biofilm. Viscoelastic characterization of the biofilm using a controlled shear stress rheometer, where internal change of physical properties could be detected, exhibited a static viscosity and a reduction of elastic modulus at the 5 mM concentration of phosphate. Accordingly, bacteria at the 5 mM concentration of phosphate are attributed to removing the EPS through a reduction of elastic modulus for bacteria. We suggest that the reduction of concentration of biofilm induces dispersion which assists to easily spread its dormitory. In conclusion, it is elucidated that an addition of phosphate causes removal of EPS, and that causes a function of antibiotic.

• Journal of Food Hygiene and Safety
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• v.34 no.3
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• pp.227-234
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• 2019

An analytical method was developed for the determination of oxytetracycline in agricultural products using the QuEChERS (Quick, Easy, Cheap, Effective, Rugged and Safe) method by liquid chromatography-tandem mass spectrometry (LC-MS/MS). After the samples were extracted with methanol, the extracts were adjusted to pH 4 by formic acid and sodium chloride was added to remove water. Dispersive solid phase extraction (d-SPE) cleanup was carried out using $MgSO_4$ (anhydrous magnesium sulfate), PSA (primary secondary amine), $C_{18}$ (octadecyl) and GCB (graphitized carbon black). The analytes were quantified and confirmed with LC-MS/MS using ESI (electrospray ionization) in positive ion MRM (multiple reaction monitoring) mode. The matrix-matched calibration curves were constructed using six levels ($0.001{\sim}0.25{\mu}g/mL$) and coefficient of determination ($r^2$) was above 0.99. Recovery results at three concentrations (LOQ, $10{\times}LOQ$, and $50{\times}LOQ$, n=5) were from 80.0 to 108.2% with relative standard deviations (RSDs) less than of 11.4%. For inter-laboratory validation, the average recovery was in the range of 83.5~103.2% and the coefficient of variation (CV) was below 14.1%. All results satisfied the criteria ranges requested in the Codex guidelines (CAC/GL 40-1993, 2003) and the Food Safety Evaluation Department guidelines (2016). The proposed analytical method was accurate, effective and sensitive for oxytetracycline determination in agricultural commodities. This study could be useful for safety management of oxytetracycline residues in agricultural products.