• Journal of the Korean Magnetic Resonance Society
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• v.4 no.2
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• pp.91-102
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• 2000

The photoproduced cation radical of N-methylphenothiazine doped in the different kind of matrices of phenyltriethoxysilane (PhiTEOS), vinyltriethoxysilane (VTEOS), and methyloiethoxysilane (METOS) was comparatively studied with electron spin resonance (ESR) and electron nuclear double resonance (ENDOR). The photoinduced charge separation efficiency was determined by integration of ESR spectra which correspond to the amount of photoproduced cation radical in the matrices. This was correlatively studied with the polarity and pore size of the gel matrices. The polarity of the matrices was comparatively determined by measuring λ$\sub$max/ values of PC$_1$ in the different matrices. The relative pore size among the matrices was determined by measuring relative proton matrix ENDOR line widths of the photoproduced cation radical of PCI. The decay kinetic constants of the cation radical of PCI in the different matrices was relatively studied with fitting the biexponential decay curves after exposure into the ambient condition. This is correlatively interpreted with the polarity and pore size of the matrices.

• Bulletin of the Korean Chemical Society
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• v.30 no.3
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• pp.608-612
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• 2009

The local structures of the boron and vanadium sites in the ternary glass $xV_2O_5-B_2O_3-yNa_2O$ were studied by $^{11}B\;and\;^{51}V$ magic angle spinning (MAS) nuclear magnetic resonance (NMR). With increasing x, the mole ratios of the $BO_3\;and\;BO_4$ structures were enhanced, as were the quadrupole asymmetry parameters for the $BO_3$ structures, while the quadrupole coupling constants for the sites were reduced. However, the opposite trends were observed with increasing y, implying that $V_2O_5$ and $Na_2O$ play opposite roles. The $VO_4,\;VO_5\;and\;VO_6$ structures with all oxygens bonded to the vanadium neighbors were identified. Vanadiums bonded to the greater number of oxygens were more populated at higher contents of $Na_2O\;and\;V_2O_5$. In addition, the $VO_4$ structures with at least one oxygen bonded to boron instead of vanadium were detected at low $Na_2O$ contents. The electron densities of various vanadium oxide structures were affected by the weight densities and vanadium ion densities. The $VO_4$ structures were more likely to be vanadium oxide structures right next to $V4^{+}$ ions.

• Korean Journal of Radiology
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• v.20 no.5
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• pp.801-811
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• 2019

Objective: To determine whether diffusion kurtosis imaging (DKI) is effective in monitoring tumor response to neoadjuvant chemotherapy in patients with osteosarcoma. Materials and Methods: Twenty-nine osteosarcoma patients (20 men and 9 women; mean age, 17.6 ± 7.8 years) who had undergone magnetic resonance imaging (MRI) and DKI before and after neoadjuvant chemotherapy were included. Tumor volume, apparent diffusion coefficient (ADC), mean diffusivity (MD), mean kurtosis (MK), and change ratio (ΔX) between pre-and post-treatment were calculated. Based on histologic response, the patients were divided into those with good response (≥ 90% necrosis, n = 12) and those with poor response (< 90% necrosis, n = 17). Several MRI parameters between the groups were compared using Student's t test. The correlation between image indexes and tumor necrosis was determined using Pearson's correlation, and diagnostic performance was compared using receiver operating characteristic curves. Results: In good responders, MD_post, ADC_post, and MK_post values were significantly higher than in poor responders (p < 0.001, p < 0.001, and p = 0.042, respectively). The ΔMD and ΔADC were also significantly higher in good responders than in poor responders (p < 0.001 and p = 0.01, respectively). However, no significant difference was observed in ΔMK (p = 0.092). MD_post and ΔMD showed high correlations with tumor necrosis rate (r = 0.669 and r = 0.622, respectively), and MD_post had higher diagnostic performance than ADC_post (p = 0.037) and MK_post (p = 0.011). Similarly, ΔMD also showed higher diagnostic performance than ΔADC (p = 0.033) and ΔMK (p = 0.037). Conclusion: MD is a promising biomarker for monitoring tumor response to preoperative chemotherapy in patients with osteosarcoma.

• Biotechnology and Bioprocess Engineering:BBE
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• v.6 no.4
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• pp.293-300
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• 2001

A polyrotaxane-biotin conjugate was synthesized and its interaction with streptavidin measured using surface plasmon resonance(SPR) detection. A biodegradable polyrotaxane in which ca, 22 molecules of ${\alpha}$-cyclodextrina(${\alpha}$-CDs) were threaded onto a poly(ethylene oxide) chain(M$\sub$n:4,000) capped with benzyloxycarbonyl-L-phenylalanine was conjugated with a biotin hydorazide and 2-aminoethanol after activing the hydroxyl groups of ${\alpha}$-CDs in the polyrotaxane using N, N'-carbonyldiimidazole. The results of the high-resolution $^1$H-nyclear lmagnetic resonance($^1$H-NMR)spectra and gel permeation chromatography of the conjugate showed that ca, 11 biotin molecules were actually introduced to the polyrotaxane scaffold. An SPR analysis showed that the binding curves of the biotin molecules in the conjugate on the streptavidin-deposited surface changed in a concentration dependent manner, indicating that the biotin in the conjugate was ac-tually recognized by streptavidin. The association equilibrium constant(K$\sub$a/) of the interaction be-tween the conjugate and steptavidin tetramer was of the order 10$\^$7/. These results suggest that polyrotaxane is useful for scaffolds as a polymeric ligand in biomedical fields.

• Structural Engineering and Mechanics
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• v.76 no.2
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• pp.163-173
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• 2020

As a vehicle moves on multiple equal-span beams at constant speed, the running vehicle would be subjected to repetitive excitations from the beam vibrations under it. Once the exciting frequency caused by the vibrating beams coincides with any of the vehicle's frequencies, resonance would take place on the vehicle. A similar resonance phenomenon occurs on a beam subject to sequential moving loads with identical axle-intervals. To reduce both resonant phenomena of a vehicle moving on guideway girders, this study proposed an additional feedback controller based the condensed virtual dynamic absorber (C-VDA) scheme. This condensation scheme has the following advantages: (1) the feedback tuning gains required to adapt the control currents or voltages are directly obtained from the tuning forces of the VDA; (2) the condensed VDA scheme does not need additional DoFs of the absorber to control the vibration of the maglev-vehicle/guideway system. By decomposing the maglev vehicle-guideway coupling system into two sub-systems (the moving vehicle and the supporting girders), an incremental-iterative procedure associated with the Newmark method is presented to solve the two sets of sub-system equations. From the present studies, the proposed C-VDA scheme is a feasible approach to suppress the interaction response for a maglev vehicle in resonance moving on a series of guideway girders.

• Journal of the Korean Magnetics Society
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• v.13 no.4
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• pp.171-175
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• 2003

Electron paramagnetic resonance (EPR) of Fe$^{3+}$ in LiTaO$_3$ single crystal, grown by Czochralski method, has been studied by employing an X-band spectrometer. Resonance spectra of Fe$^{3+}$ ion on the crystallographic principal axes were obtained with 9.447 ㎓ at room temperature. The spectroscopic splitting parameter g and zero-field splitting (ZFS) parameter D (= 3 B$_{2}$sup 0/) are calculated with effective spin Hamiltonian. Fe$^{3+}$ center in stoichometric single crystal turns out to be different with that in congruent single crystal reported previously. From the analysis of temperature dependence of resonance fields for Fe$^{3+}$ ion, there is no any phase transition at the temperature range (from -160 $^{\circ}C$ to 20 $^{\circ}C$).

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.21 no.4
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• pp.143-148
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• 2021

A systematic study of Bloch surface wave (BSW), which is created by guided mode resonance (GMR) of dielectric multilayer structures with a grating profile, is presented to analyze the sensing performance of bio-sensors. The effect of structural parameters on optical behavior is evaluated by using Babinet's principle and modal transmission-line theory. The sensitivity of designed bio-sensors is proportional to the grating constant at wavelength spectrum, and inversely proportional to the normal wave vector of incident electromagnetic wave at angular spectrum. Numerical results for two devices with SiO/SiO₂ and TiO₂/SiO₂ multilayer dielectric stacks are presented, showing that BSW can be exploited for the realization of efficient diffraction-based bio-sensors from infrared to visible-band range.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.35 no.4
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• pp.392-397
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• 2022

We present the structural and optical properties of Au@TiO₂ core-shell microsphere structure prepared by a hydrothermal synthesis method. As a way to improve the efficiency of organic solar cells, the Au@TiO₂ core-shell microsphere was synthesized to use the local surface plasmon resonance (LSPR) phenomenon. The synthesized results were confirmed to have the Au@TiO₂ core-shell structure using a high-resolution transmission electron microscopy. An absorption was observed to occur at 527 nm belonging to the visible light region using a visible light spectroscopy, which supports the LSPR phenomenon. We suggest that the Au@TiO₂ core-shell microsphere is highly likely to be applied to organic solar cells including dye-sensitized solar cells. In addition, we expect it to be widely used not only in the energy but also in the bio as well as in the environmental fields.

• Applied Chemistry for Engineering
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• v.33 no.1
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• pp.113-118
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• 2022

Multifunctional nanomaterials based on mesoporous silica nanoparticles (MSN) and metal oxide nanocrystals are among the most promising materials for theragnosis because of their ease of modification and high biocompatibility. However, the preparation of multifunctional nanoparticles requires time-consuming multistep processes. Herein, we report a simple one-pot synthesis of multifunctional Mn₃O₄/mesoporous silica core/shell nanoparticles (Mn₃O₄@mSiO₂) involving the temporal separation of core formation and shell growth. This simple procedure greatly reduces the time and effort required to prepare multifunctional nanoparticles. Despite the simplicity of the process, the properties of nanoparticles are not markedly different from those of core/shell nanoparticles synthesized by a previously reported multistep process. The Mn₃O₄@mSiO₂ nanoparticles are biocompatible and have potential for use in optical imaging and magnetic resonance imaging.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.34 no.5
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• pp.342-347
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• 2021

Phase evolution, sintering behavior, microstructure, and microwave dielectric properties of (1-x) mol Ba₃V₄O₁₃ - (x) mol BaV₂O₆ system were investigated. The sintered specimens of all compositions consisted of Ba₃V₄O₁₃ and BaV₂O₆, and no secondary phase was observed. As x increased, the linear shrinkage decreased to the composition of x=0.5, and then increased again, implying that Ba₃V₄O₁₃ and BaV₂O₆ phases interfered mutually with each other during sintering. All compositions showed a dense microstructure with a large grain growth. Cracks were observed in some compositions because of the relatively high sintering temperature of 620~640℃. As x increased, the dielectric constant increased, while the quality factor was maintained from about 50,000 GHz to about 70,000 GHz up to the composition of x=0.9, and then decreased to 20,987~27,180 GHz at the composition of x=1.0. As x increased, the temperature coefficient of the resonance frequency showed a (+) value from a (-) value. The dielectric constant, the quality factor, and the temperature coefficient of resonant frequency of x=0.7 composition sintered at 640℃ for 4 hours were 10.61, 71,126 GHz, and -4.9 ppm/℃, respectively. This composition showed a good chemical compatibility with Al powder, indicating that the Ba₃V₄O₁₃-BaV₂O₆ ceramics are a candidate material for ULTCC (Ultra-Low Temperature Co-fired Ceramics) applications.