• Proceedings of the Korean Environmental Sciences Society Conference
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• 2003.11a
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• pp.113-118
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• 2003

An investigation has been carried out on collision-induced dissociation (CID) in the development of an analytical protocol for the determination of polycyclic aromatic hydrocarbons (PARs) by ion trap tandem mass spectrometry. Two different considerations were used to choose the optimal CID conditions for complex matrix environmental samples, namely, to determine the highest signal-to-noise (SIN) ratio and the other to eliminate the background interferences originated from complex matrix samples. The PAR content of agricultural soil was measured to estimate overall distribution of PAR in throughout the country, we collected and analyzed 226 soil samples from paddy and upland soil. The average content of total PAR in all samples was 236 ${\mu}g$ $kg^{-1}$, and the range was from 23.3 to 2, 834 ${\mu}g$ $kg^{-1}$. The overall distribution of PAR was found to be closely related to the pollution sources, the size of city and the type of industry.

• Mass Spectrometry Letters
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• v.11 no.1
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• pp.6-9
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• 2020

Matrix-assisted laser desorption/ionization-mass spectrometry (MALDI-MS) analysis of ionic liquid matrices (ILMs) prepared using pyridine and dihydroxybenzoic acid (DHB), such as 2,3-DHB and 2,5-DHB, displayed an unconventional peak at m/z 232.0, which was regarded as [DHB+pyridine-H]⁺. The peak at m/z 232.0 was not observed from other ILMs prepared using other DHB isomers, such as 2,4-DHB, 2,6-DHB, 3,4-DHB, and 3,5-DHB. Two requirements to observe the peak at m/z 232.0 in a DHB/pyridine ILM are suggested. First, carboxyl and hydroxyl groups must be located ortho to each other. Second, the secondary hydroxyl group must be located at a carbon with a high electron density. Based on these two requirements, a potential mechanism for the generation of the peak at m/z 232.0 is suggested.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.05a
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• pp.689-694
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• 2003

An iterative modal analysis approach is developed to determine the effect of transverse open cracks on the dynamic behavior of simply supported pipe conveying fluid subject to the moving mass. The equation of motion is derived by using Lagrange's equation. The influences of the velocity of moving mass and the velocity of fluid flow and a crack have been studied on the dynamic behavior of a simply supported pipe system by numerical method. The presence of crack results in higher deflections of pipe. The crack section is represented by a local flexibility matrix connecting two undamaged beam segments i.e. the crack is modelled as a rotational spring. Totally, as the velocity of fluid flow and the crack severity are increased, the mid-span deflection of simply supported pipe conveying fluid is increased. The time which produce the maximum dynamic deflection of the simply supported pipe is delayed according to the increment of the crack severity.

• Bulletin of the Korean Chemical Society
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• v.24 no.9
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• pp.1308-1312
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• 2003

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) was used to observe folic acid and its derivatives such as tetrahydrofolate and 5-methyltetrahydrofolate in a vitamin tablet and in foods. Folic acid in a vitamin tablet was determined using angiotensin I as an internal reference. Tetrahydrofolic acid, 5-methyltetrahydrofolic acid, and an oxygenated folate were observed from a human blood sample using graphite plate. The results show that these mass spectrometric methods are useful for quickly obtaining a profile of folates.

• Bulletin of the Korean Chemical Society
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• v.20 no.11
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• pp.1299-1302
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• 1999

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) was used to demonstrate cross-linking of peptides induced by transglutaminase. The presence of ε-( Υ-glutamyl)lysine isopeptide cross-link in the acid hydrolysate of the cross-linking reaction mixture was also demonstrated by MALDI-TOF-MS without prior separation. MALDI-TOF-MS quickly provided peptide mass maps after pronase digestion of the cross-linked peptide adduct, which enabled us to monitor the hydrolytic sequence. Pronase appears to preferentially hydrolyze peptide bonds distant from the cross-link before hydrolyzing peptide bonds around the cross-link. The results suggest that pronase digestion followed by MALDI-TOF-MS could be used for determination of amino acid sequence around a modification site.

• Translational and Clinical Pharmacology
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• v.25 no.2
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• pp.67-73
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• 2017

Glimepiride, a third generation sulfonylurea, is an antihyperglycemic agent widely used to treat type 2 diabetes mellitus. In this study, an untargeted urinary metabolomic analysis was performed to identify endogenous metabolites affected by glimepiride administration. Urine samples of twelve healthy male volunteers were collected before and after administration of 2 mg glimepiride. These samples were analyzed by liquid chromatography-tandem mass spectrometry (LC-MS/MS), and then subjected to multivariate data analysis including principal component analysis and orthogonal partial least squares discriminant analysis. Through this metabolomic profiling, we identified several endogenous metabolites such as adenosine 3', 5'-cyclic monophosphate (cAMP), quercetin, tyramine, and urocanic acid, which exhibit significant metabolomic changes between pre- and posturine samples. Among these, cAMP, which is known to be related to insulin secretion, was the most significantly altered metabolite following glimepiride administration. In addition, the pathway analysis showed that purine, tyrosine, and histidine metabolism was affected by pharmacological responses to glimepiride. Together, the results suggest that the pharmacometabolomic approach, based on LC-MS/MS, is useful in understanding the alterations in biochemical pathways associated with glimepiride action.

• Proceedings of the Korean Vacuum Society Conference
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• 1999.07a
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• pp.167-167
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• 1999

In laser ionisation mass spectrometry (LIMS) atoms and molecules which are desorbed from solid surfaces are ionised by an intense laser beam. The photoions which are created are then mass analysed in a time-of-flight mass spectromenter. In best situations, 10% of the ejected particles can be detected, giving the technique^g , pp b sensitivity. Since the ionisation and desorption steps are separated, matrix effects are minimised, in contrast to competitor techniques like SIMS, so quantitation is improved. The talk will illustrate the application of LIMS to basic studies in sputtering in Sr, Cu3Au(100) and Ni3Al(100) as well as ultratrace analysis of Zr in Si.

• Korean Journal of Clinical Laboratory Science
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• v.55 no.4
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• pp.244-252
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• 2023

The timeliness and accuracy of test results are crucial factors for clinicians to decide and promptly administer effective and targeted antimicrobial therapy, especially in life-threatening infections or when vital organs and functions, such as sight, are at risk. Further research is needed to refine and optimize matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS)-based assays to obtain accurate and reliable results in the shortest time possible. MALDI-TOF MS-based bacterial identification focuses primarily on techniques for isolating and purifying pathogens from clinical samples, the expansion of spectral libraries, and the upgrading of software. As technology advances, many MALDI-based microbial identification databases and systems have been licensed and put into clinical use. Nevertheless, it is still necessary to develop MALDI-TOF MS-based antimicrobial-resistance analysis for comprehensive clinical microbiology characterization. The important applications of MALDI-TOF MS in clinical research include specific application categories, common analytes, main methods, limitations, and solutions. In order to utilize clinical microbiology laboratories, it is essential to secure expertise through education and training of clinical laboratory scientists, and database construction and experience must be maximized. In the future, MALDI-TOF mass spectrometry is expected to be applied in various fields through the use of more powerful databases.

• Preventive Nutrition and Food Science
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• v.10 no.1
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• pp.40-45
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• 2005

Age-related changes in bone metabolism are well established by biochemical markers of bone matrix in serum and urine, but analysis of the residual bone matrix, which is still turning over, has not been investigated. In the present study, we measured in vivo rates of bone protein synthesis using a precursor-product method based on the exchange of ²H from ²H₂O into amino acids. Four percent ²H₂O was administered to mice in drinking water after intraperitonial (i.p) bolus injection of 99.9% ²H₂O. Mice were divided into the two groups: growing young mice were administered 4% ²H₂O for 12 weeks after an i.p bolus injection at 5 week of age, whereas weight stable adult mice started drinking 4% ²H₂O 8 weeks later than the growing group and continued 4% ²H₂O drinking for 8 weeks. Mass isotopomer abundance in alanine from bone protein was analyzed by gas chromatography/mass spectrometry. Body ²H₂O enrichments were in the range of 1.88-2.41% over the labeling period. The fractional synthesis rates (ks) of bone protein were 2.000±0.071%/d for growing mice and 0.243±0.014%/d for adult mice. These results demonstrate that the bone protein synthesis rate decreases with age and present direct evidence of age-related changes in bone protein synthesis.

• Journal of Advanced Marine Engineering and Technology
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• v.28 no.3
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• pp.482-492
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• 2004

Recently. the market trend for marine diesel engine has involved the lower running speeds. larger stroke/bore ratio and higher combustion pressure. Consequently, because of the flexible engine shafting system due to the larger mass. inertia and the more elasticity, the complicated coupled torsional-axial vibrations have occurred in the operating speed range. Also, the vibrations act as an excitation on the hull-structural vibration. To predict the vibration behavior with more accuracy and reliability. many studies have proposed the several kinds of method to calculate the stiffness matrix of crankshaft. However, most of these methods have a weak point to spend much time on three dimensional modeling and meshing work for crankshaft. Therefore. in this work. the stiffness matrix for the crankthrow is calculated using the energy method (Influence Coefficient Method, ICM) with the each mass having 6 degree of freedom. Its effectiveness is verified through the comparison with the stiffness matrix obtained by using the finite element method (FEM) and measured results for actual ships propulsion system.