• Proceedings of the Korean Society of Potoscience Conference
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• 2005.06a
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• pp.76-76
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• 2005

• Progress in Medical Physics
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• v.31 no.4
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• pp.135-144
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• 2020

Purpose: Gafchromic films for proton dosimetry are dependent on linear energy transfers (LETs), resulting in dose underestimation for high LETs. Despite efforts to resolve this problem for single-energy beams, there remains a need to do so for multi-energy beams. Here, a bimolecular reaction model was applied to correct the under-response of spread-out Bragg peaks (SOBPs). Methods: For depth-dose measurements, a Gafchromic EBT3 film was positioned in water perpendicular to the ground. The gantry was rotated at 15° to avoid disturbances in the beam path. A set of films was exposed to a uniformly scanned 112-MeV pristine proton beam with six different dose intensities, ranging from 0.373 to 4.865 Gy, at a 2-cm depth. Another set of films was irradiated with SOBPs with maximum energies of 110, 150, and 190 MeV having modulation widths of 5.39, 4.27, and 5.34 cm, respectively. The correction function was obtained using 150.8-MeV SOBP data. The LET of the SOBP was then analytically calculated. Finally, the model was validated for a uniform cubic dose distribution and compared with multilayered ionization chamber data. Results: The dose error in the plateau region was within 4% when normalized with the maximum dose. The discrepancy of the range was <1 mm for all measured energies. The highest errors occurred at 70 MeV owing to the steep gradient with the narrowest Bragg peak. Conclusions: With bimolecular model-based correction, an EBT3 film can be used to accurately verify the depth dose of scanned proton beams and could potentially be used to evaluate the depth-dose distribution for patient plans.

• Bulletin of the Korean Chemical Society
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• v.31 no.6
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• pp.1711-1714
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• 2010

• Journal of Plant Biology
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• v.30 no.4
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• pp.277-285
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• 1987

Undifferentiated suspension cells had the ability to transfer glucose and fructose actively, but the suspension culture cells were unable to transfer saccharide without previously splitting to monosccarides. The uptake of fructose showed the low- and high-affinity system compared to of glucose, which possessed only one saturable uptake system. In this paper, the low affinity system of the uptake of fructose has been studied intensively. Glucose did not inhibit the low affinity system of fructose competitively. The Km value was 47 mM for fructose, 7.4 mM for glucose and Vmax was 69 $\mu$mol/h.g fresh weight for fuctose, 9.8 $\mu$ mol/h.g fresh weight for glucose. Metabolizer inhibitors, both 50 $\mu$M of CCCP and DNP, inhibited 70% of the uptake of the low affinity system of fructose. The proton ions were accompanied by the uptake of fructose. The stoichiometry showed ratio of proton to fructose was 0.17. The mechanism ofthe uptake was fructose-proton-symport. The molecules of fructose accmululated inside 25 times more than outside. Therefore, the low affinity system of fructose was not mere diffusion, but depended on metabolic energy and thus transported actively. The importance of this system was discussed.

• Korean Journal of Metals and Materials
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• v.49 no.12
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• pp.977-982
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• 2011

Migration and interaction of multi-protons in a zinc-doped barium zirconate (Zn-doped $BaZrO_3$) super cell were investigated using a density functional theory. O ions in the super cell form interconnected octahedrons with Zr or Zn ions positioned in their centers and Ba ions positioned among the eight octahedrons. When one proton was added to the super cell, the energy barrier of 0.80 eV for proton transfer from the first to second nearest O ion sites from the Zn ion reached its highest value. When two protons were added to the super cell, the two protons preferred the first nearest O ions from the Zn ion. The two protons were accommodated by pushing the neighboring Zn ion further away from the center of the octahedron. Energy barriers for proton transfer from the Zn-octahedron to the neighboring Zr-octahedron were spread in the range of 0.36 ~ 1.02 eV.

• Journal of Life Science
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• v.17 no.8 s.88
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• pp.1100-1103
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• 2007

In proton therapy, the Bragg peak is spread out by modulating or degrading the energy of the particles to cover a well-defined target volume at a given depth. Proton transfer plays a key role in a variety of biological, the origin of the elements, tests of the standard model along with applications in medicine, industry and chemical phenomena such as water autoionization, fast proton diffusion, acid-base neutralization. We have studied the radiolysis of various natural resources and have evaluated the antioxidant activity of radiolysis products by proton beam. The most of antioxidant activities of natural resources were decreased with increasing proton fluence. Proton beam induced antioxidant activities both in 1,1-diphenyl-2-picrylhydrazyl radical (DPPH) assay and 2,2'-azinobis(3-ethylbenzot hialozinesulfonic acid) cation radical $(ABTS^{.+})$ assay by a dose dependent fashion.

• Proceedings of the KSME Conference
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• 2001.06d
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• pp.995-1000
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• 2001

Distributions of the parameters in proton exchange membrane fuel cell (PEMFC) has been analyzed numerically under steady-state and isothermal conditions. The distributions of the crucial parameters (e.g., temperature and pressure) in a PEMFC have a major impact on its safe and efficient operation. This paper predicts the performance of the model electrode plates by calculating the pressure and temperature distributions of working fluid. The calculated results of pressure and temperature at exit condition shows good agreement to experiments and gives details of flow pattern inside of electrode plates.

• Proceedings of the Korean Fiber Society Conference
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• 2003.10a
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• pp.27-28
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• 2003

Synthesis and properties of novel excited-state intramolecular proton transfer (ESIPT) materials recently developed in our group are described. Highly efficient ESIPT in polymeric system has been investigated theoretically and experimentally with a semi-rigid polyquinoline (PQH, PQDH) possessing an intramolecular tautomerizable hydrogen bond. Poly(aryl ether) dendrimers of three different generations that are cored with photo-tautomerizable quinoline (QGn, n=1,2,3) were also synthesized and characterized to investigate the effect of dendritic architecture on the ESIPT activity. Stimulated emission and amplified spontaneous emission in these organic materials system are discussed in terms of ESIPT activity.

• Proceeding of EDISON Challenge
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• 2015.03a
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• pp.91-98
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• 2015

Formamide의 중성가수분해 mechanism은 QM/MM (quantum mecahnics/molecular mechanics) molecular dynamics simulations 및 CPMD과 같은 방법으로 연구되어왔다. 본 연구에서는. Umbrella sampling을 이용한 QM/MM-MD simulation을 사용하여 4가지 반응의 free energy surface를 도출해냈다. 전체적으로, 가장 선호되는 메커니즘은 two step으로 구성된 water assisted stepwise mechanism이었으며 모든 mechanism은 ab-initio calculation과 QM/MM-MD simulation이 수행되었다. water assisted stepwise mechanism을 살펴보면, 첫 번째 step에서 formamide의 carbonyl group이 hydrate되면서 gem-diol intermediate를 형성한다. 다음 step에서, intermediate의 hydroxyl group으로부터 amino group으로 water-assisted proton transfer이 일어난다. 두 반응 모두에서 물이 proton transfer를 직접적으로 도와주는 것을 관찰할 수 있었다. 특히, ab-initio calculation과는 다르게 QM/MM-MD에서는 gem-diol intermediate가 안정화되는 것으로 solvent effect를 잘 보여준다.

• Bulletin of the Korean Chemical Society
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• v.31 no.4
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• pp.941-948
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• 2010

Ab initio and density functional theory methods have been employed to study all theoretically possible conformers of fluoroacetic acid. Molecular geometries and energetic of cis and trans monomers and cis dimers in gaseous phase have been obtained using HF, B3LYP and MP2 levels of theory, implementing 6-311++G(d,p) basis set. It was found that cis rotamers are more stable. In addition, it was found that in comparison with acetic acid the strength of hydrogen bonding in fluoroacetic acid decreased. The infrared spectrum frequencies and the vibrational frequency shifts are reported. Natural population and atom in molecule analysis performed to predict electrostatic interactions in the cyclic H-bonded complexes and charges. The proton transfer reaction is studied and activation energy is compared with acetic acid proton transfer reaction.