• Earthquakes and Structures
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• v.15 no.5
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• pp.565-581
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• 2018

This paper proposes a new analytical formulation for computing the seismic input at various levels of a structure in terms of floor response spectra. The approach, which neglects the dynamic interaction between primary structure and secondary element, is particularly useful for the seismic assessment of secondary and non-structural elements. The proposed formulation has a robust theoretical basis and it is based on few meaningful dynamic parameters of the main building. The method has been validated in the linear and nonlinear behavior of the main building through results coming from both experimental tests (available in literature) and parametric numerical analyses. The conditions, for which the Floor Spectrum Approach and its simplified assumptions are valid, have been derived in terms of specific interval ratios between the mass of the secondary element and the participant mass of the main structure. Finally, a practice-oriented formulation has been derived, which could be easily implementable also at code level.

• Korean Journal of Food Science and Technology
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• v.32 no.6
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• pp.1437-1441
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• 2000

Acycloretinoic acid was prepared from acycloretinal by oxidation with Tollens reagent. Acycloretinoic acid was separated with Silica-HPLC and analyzed by ODS-HPLC with a photodiode array detector and by GC-MS. Lycopene was solubilized in toluene and aqueous Tween 40, and then oxidized by incubating at $37^{\circ}C$ under atmospheric oxygen. Acidic compound was produced by autoxidation of lycopene. Retention time, UV-Vis spectra and mass spectra of the acidic compound were identical to the standard acycloretinoic acid. Thus, acycloretinoic acid was confirmed to occur in vitro under oxidation condition of lycopene.

• The Bulletin of The Korean Astronomical Society
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• v.44 no.2
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• pp.50.2-50.2
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• 2019

We present the results of high-resolution (R ≥ 30,000) optical and near-infrared spectroscopic monitoring observations of a FU Orionis-type object, 2MASS J06593158-0405277. We have monitored 2MASS J06593158-0405277 with the Bohyunsan Optical Echelle Spectrograph (BOES) and the Immersion GRating INfrared Spectrograph (IGRINS) since December 2014. Various features produced by wind, disk, and outflow/jet were detected. The wind features varied over time and disappeared about a year after the outburst occurred. The double-peaked line profiles were detected in the optical and near-infrared, and the line widths decrease with increasing wavelength. The disk features in the optical spectra are fit well with G2-type or G5-type stellar spectra convolved with a disk rotational profile of about 45 km s^-1, which corresponds to a disk radius of about 71 R_⊙for a central mass of 0.75 M_⊙. Disk features in near-infrared spectra are fit well with a K1-type stellar spectrum convolved with a disk rotational profile of about 35 km s^-1, which corresponds to a disk radius of about 117 R_⊙ for a central mass of 0.75 M_⊙. We also detected [S II] and H2 emission lines, which are rarely found in FUors but are usually found in the earlier stage of young stellar objects. Therefore, we suggest that 2MASS J06593158-0405277 is in the relatively earlier part of Class II stage.

• Bulletin of the Korean Chemical Society
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• v.29 no.11
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• pp.2237-2240
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• 2008

• Bulletin of the Korean Chemical Society
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• v.30 no.9
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• pp.2061-2065
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• 2009

Two simple algorithm modifications are made to the THRASH data retrieval program with the aim of improving analysis speed for complex Fourier transform ion cyclotron resonance (FTICR) mass spectra. Instead of calculating the least-squares fit for every charge state in the backup charge state determination algorithm, only some charge states are pre-selected based on the plausibility values obtained from the FT/Patterson analysis. Second, a modification is made to skip figure-of-merit (FOM) calculations in the central m/z region between two neighboring peaks in isotopic cluster distributions, in which signal intensities are negligible. These combined modifications result in a significant improvement in the analysis speed, which reduces analysis time as much as 50% for ubiquitin (8.6 kDa, 76 amino acids) FTICR MS and MS/MS spectra at the reliability (RL) value = 0.90 and five pre-selected charge states with minimal decreases in data analysis quality (Table 3).

• Toxicological Research
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• v.29 no.2
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• pp.107-114
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• 2013

Mass spectrometry (MS) is a very powerful instrument that can be used to analyze a wide range of materials such as proteins, peptides, DNA, drugs, and polymers. The process typically involves either chemical or electron (impact) ionization of the analyte. The resulting charged species or fragment is subsequently identified by the detector. Usually, single mass uses source-induced dissociation (SID), whereas mass/mass uses collision-induced dissociation (CID) to analyze the chemical fragmentations Each technique has its own advantages and disadvantages. While CID is most effective for the analysis of pure substances, multiple-step MS is a powerful technique to get structural data. Analysis of veterinary drugs ampicillin, chloramphenicol, ciprofloxacin, and oxytetracycline serves to highlight the slight differences between SID and CID. For example, minor differences were observed between ciprofloxacin and oxytetracycline via SID or CID. However, distinct fragmentation patterns were observed for ampicllin depending on the analysis method. Both SID and CID showed similar fragmentation spectra but different signal intensities for chloramphenicol. There are several factors that can influence the fragmentation spectra, such as the collision energy, major precursor ion, electrospray mode (positive or negative), and sample homogeneity. Therefore, one must select a fragmentation method on an empirical and case-by-case basis.

• Korean Journal of Pharmacognosy
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• v.41 no.4
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• pp.303-307
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• 2010

To overcome the limit of morphological method for classification of herbal drug, a novel method to discriminate its origin using pyrolysis mass spectrometry-multivariate analysis was developed. This method was applied successfully to Scutellaria baicalensis Georgi, one of the most popular herbal drug in oriental countries. The ethylacetate soluble fractions were prepared by sonication from pulverized roots of S. baicalensis which were collected from various regions including Korea and China, and subjected to direct insertion probe (DIP) mass spectrometry to achieve mass spectra of pyrolizates of extracts. The probe temperature was elevated from $30^{\circ}C$ to $320^{\circ}C$ at increasing rate $64^{\circ}C/min$, and the average mass spectrum calculated from total ion chromatography (TIC) was obtained. The relative peak intensities versus m/z were subjected to SAS program, and the training set (9 from Korea origin and 22 from China origin) was clustered two groups as its origin. In the test set, 11 samples among total 13 test sample were successfully classified according to their origin by developed method with accuracy of 85%.

• Macromolecular Research
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• v.16 no.2
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• pp.108-112
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• 2008

Matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) analysis of nonpolar polymeric materials is affected by the sample preparation as well as the matrix and cationizing agent. This study examined the influence of silver salt types on the MALDI analysis of polybutadiene (PB). Silver trifluoroacetate (AgTFA), silver benzoate (AgBz), silver nitrate ($AgNO_3$), and silver p-toluenesulfonate (AgTS) were used as the silver salts to compare the MALDI mass spectra of PB. The mixture solution of PB and 2,5-dihydroxybenzoic acid (DHB), as a matrix dissolved in THF, was spotted on the sample plate and dried. A droplet of the aqueous silver salt solution was placed onto the mixture. The mass spectrum with AgBz showed the clear $[M+Ag]^+$ ion distribution of PB while the mass spectrum with AgTFA did not show $[M+Ag]^+$ ions but only silver cluster ions. The mass spectra with $AgNO_3$ and AgTS did not show a clear $[M+Ag]^+$ ion distribution. The difference in the formation of $[M+Ag]^+$ ions of PB depending on the silver salts was attributed to the silver cation transfer reaction between the silver salt and the matrix (DHB). The mass spectrum showed a clear $[M+Ag]^+$ ion distribution of PB when the conjugate acid of the silver salt was less acidic than the matrix.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.29 no.4 s.235
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• pp.453-459
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• 2005

In this paper, we are proposing a robust tool which is capable of measuring the size and elemental composition of submicron particles from twenty to several hundreds nanometers at the same time, i.e., named Single Particle Mass Spectrometer (SPMS). The home-made SPMS employs a laser ablation/multi-photon ionization method to tear a nanoparticle into the constituent elemental ions. One thing different from the conventional Aerosol Time-of-Flight Mass Spectrometer (ATOFMS) is the power of the ionization laser. Much strong laser used in this work makes it possible to generate elemental ions rather than molecular ions from a nanoparticle. Also the use of high power laser may guarantee a complete ionization of a particle, which was confirmed by the existence of multiple charged ions. If a particle is evaporated/ionized completely and detected through electric field-free TOF tube without any loss, we can extract the original particle volume from the measured total ion numbers. Collecting a number of particles mass spectra, we get a database of size and elemental composition of nanoparticles, with which we may take a took into any kinds of chemical reaction occurring at nanoscale. Several issues related to size estimation by SPMS will be discussed.

• Mass Spectrometry Letters
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• v.5 no.3
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• pp.89-93
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• 2014

Lincomycin is one of the major species among the Pharmaceuticals and Personal Care Products (PPCPs) detected from the four major rivers in Korea. The structure characterization was performed of six degradation products of lincomycin formed under the irradiation of electron beam, and the degradation efficiency as a function of the various irradiation dose and sample concentration was investigated. Electron beam (10 MeV, 0.5 mA and 5 kW) experiments for the structural characterization of degradation products that are fortified with lincomycin, were performed at the dose of 10 kGy. The separation of degradation products and lincomycin was carried out using a C18 column ($2.1{\times}100$ mm, $3.5{\mu}m$), using gradient elution with 20 mM ammonium acetate and acetonitrile. The structures of six degradation products of lincomycin were proposed by interpretation of mass spectra and chromatograms by LC-MS/MS. The mass fragmentation pathways of mass spectra in tandem mass spectrometry were also proposed. Experiments were performed of the degradation efficiency as a function of the irradiation dose intensity and the initial concentration of lincomycin in an aqueous environment. In addition, increased degradation efficiency was observed with a higher dose of electron beam and lower concentration.