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Jinho Hwang,Aeran Kim,Jina Kim,Yunji Seol,Taegeon Oh,Jin-sol Shin,Hong Seok Jang,Yeon-Sil Kim,Byung Ock Choi,Young-nam Kang 한국물리학회 2018 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.73 No.10
During hyperthermia therapy, cancer cells are heated to a temperature in the range of 40 45 C for a defined time period to damage these cells while keeping healthy tissues at safe temperatures. Prior to hyperthermia therapy, the amount of heat energy transferred to the cancer cells must be predicted. Among various non-invasive methods, the thermal prediction method using the specific absorption rate (SAR) is the most widely used method. The existing methods predict the thermal distribution by using a single constant for the mass density in one organ through assignment. However, because the SAR and the bio heat equation (BHE) vary with the mass density, the mass density of each organ must be accurately considered. In this study, the mass density distribution was calculated using the relationship between the Hounsfield unit and the mass density of tissues in preceding research. The SAR distribution was found using a quasi-static approximation to Maxwell's equation and was used to calculate the potential distribution and the energy distributions for capacitive RF heating. The thermal distribution during exposure to RF waves was determined by solving the BHE with consideration given to the considering contributions of heat conduction and external heating. Compared with reference data for the mass density, our results was within 1%. When the reconstructed temperature distribution was compared to the measured temperature distribution, the difference was within 3%. In this study, the density distribution and the thermal distribution were reconstructed for the agar phantom. Based on these data, we developed an algorithm that could be applied to patients.
Jinho Hwang,Yunji Seol,Taegeon Oh,Na young An,Jaehyeon Lee,Chul-Seung Kay,Hong Seok Jang,Byung Ock Choi,Young-nam Kang 한국물리학회 2020 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.76 No.1
Prior to the hyperthermia, the amount of heat energy delivered to the tumors must be confirmed. If it cannot be confirmed before hyperthermia, normal tissues may also be heated, leading to possible necrosis. In a previous study, the thermal distribution was calculated using mass density distribution with CT image. The previous study was not performed various evaluations of accuracy for the developed thermal distribution prediction algorithm. In this study, the developed thermal distribution prediction algorithm was evaluated by comparing the phantom with the measured temperature and a commercial simulation software (Sim4Life) has been used as a reference data for hyperthermia studies. The difference between the measured temperature and the commercial simulation software (Sim4Life) was within 3%, and the difference between the measured temperature and the developed thermal distribution algorithm was also within 2%. The difference between the developed thermal distribution algorithm and the commercial simulation software was also within 3%. The thermal distribution algorithm developed in this study could predict the internal temperature of the patient before hyperthermia and increase the treatment accuracy by preventing necrosis from occurring in normal organs. In addition, it could easily predict the temperatures for hyperthermia without modeling CT images taken for the diagnosis of lesions.
Hwang, Jiseon,Kim, Kyung Mi,Chae, Junghyun,Chang, Jinho Pergamon Press 2018 Electrochimica acta Vol.291 No.-
<P><B>Abstract</B></P> <P>In this article, we report that electrochemically generated quaternary ammonium polybromide (QBr<SUB>2n+1</SUB>) droplets can act not only as electrochemical reactors for the electro-oxidation of Br<SUP>−</SUP>, but also as tiny reductants for Br<SUB>2</SUB> dissolved in an aqueous phase. We suggest two different theoretic models: <I>Cloud</I> and <I>Droplet</I>. In the <I>Cloud</I> model, we consider a cloud composed of small droplets located in the vicinity of a Pt ultramicroelectrode (UME). The positive feedback loop of the redox reaction is derived in the gap between the <I>Cloud</I> and the Pt UME, which leads to catalytic current enhancement, like the positive feedback mode of scanning electrochemical microscopy (SECM). In the <I>Droplet</I> model, a droplet adsorbed on the center of a Pt UME drives the catalytic feedback loop of the redox reaction. Next, we adopted the two theoretical models to explain the current amplification by QBr<SUB>2n+1</SUB> observed in our experimental systems. In the early potential region for electro-oxidation of Br<SUP>−</SUP>, we found the QBr<SUB>2n+1</SUB> droplets-<I>Cloud</I> model was a more reliable scenario for the catalytic current amplification. As the potential became more positively biased, stochastic collisions of QBr<SUB>2n+1</SUB> droplets occurred on the Pt UME, and in this stage, we determined that the QBr<SUB>2n+1</SUB>-<I>Droplet</I> model was the main catalytic mechanism for Br<SUP>−</SUP> electro-oxidation in the presence of QBr in the solution.</P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Hwang, Jiseon,Chang, Jinho The Electrochemical Society 2018 Journal of the Electrochemical Society Vol.165 No.7
<P>In this article, we account for the reduction pathway of quaternary ammonium polybromide (QBr(2n +/- 1)) droplets on Pt ultramicroelectrode (UME). In previous work, we electrochemically analyzed stochastic current spikes from Br -electrolysis in QBr(2n +/- 1) droplets by their particle impact on Pt UME. For electro-reduction of QBr 2n +/- 1 droplets through chronoamperometry, we found no evidence of stochastic current spikes, which are supposed to be evidence for direct electro-reduction (DR) of QBr(2n +/- 1) droplets to Br- and Q(+) through their particle impact on Pt UME. Instead, we suggest an indirect electro-reduction (IDR) mechanism for QBr(3) droplets via the following pathway based on a finite element analysis. The electrochemically generated QBr(3) droplets are mostly distributed in the vicinity of Pt UME within our experimental time scale due to their sizes. QBr(3) equilibrated with Q(+) and Bra(-) and the liberated Br3(-) from QBr(3) droplets are electrochemically reduced to Br until all the QBr(3) droplets in the vicinity of the Pt UME are depleted. We further found that QBr(2n +/- 1) species (n = 2 and 3) are not electro-reduced through IDR but are precipitated on Pt UME. In the chronoamperogram at each forward step of the fifty potential cycles, CA(forward-50 cycles), the potential was applied for 0.4 s where Br is oxidized on the Pt UME in an acidic solution containing QBr. In the CA(forward-50 cycles), the current spikes attributed to Br- -electrolysis in QBr(2n +/- 1) droplets by their particle-impact on Pt UME were observed. In the CA(reverse-50 cycles), the potential was applied for another 0.4 s, which is enough to drive the electro-reduction of Br3(-) on Pt UME. The frequency of the current spikes in the CA(forward-50 cycles) significantly declined as the potential-cycles increased. The chronoamperometric analyses indicated that the Pt surface is partially blocked by the reduction-inactive QBr(2n +/- 1 )species, which was confirmed to be mostly QBr(5) and QBr(7) by Raman spectroscopy. (C) 2018 The Electrochemical Society.</P>
High-mobility two-dimensional electron gas at the PbZr0.5Ti0.5O3/BaSnO3 heterostructure
Hwang Jaejin,Byun Jinho,Kim Hyejung,Lee Jaekwang 한국물리학회 2024 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.84 No.1
The two-dimensional electron gas (2DEG) formed at the oxide heterointerface between LaAlO3 (LAO) and SrTiO3 (STO) has gained signifcant attention due to its exotic physical properties and interfacial conductivity. However, the 2DEG resides in a weakly dispersive Ti-d band, resulting in relatively low mobility. This limitation hampers its practical applications in future oxide electronics. To enhance the mobility of the 2DEG, we propose the use of BaSnO3 (BSO) as a novel host material with a highly dispersive conduction Sn-5 s band. The s orbitals in BSO are signifcantly more delocalized than d orbitals, leading to a higher dispersion of the conduction band. Our frst-principles density functional theory (DFT) calculations reveal that a high-mobility n-type 2DEG can indeed be formed near the PbZr0.5Ti0.5O3/BSO interface. The polar feld of the ferroelectric PbZr0.5Ti0.5O3 generates an interfacial conducting state in BSO, resulting in a high-mobility n-type 2DEG within the highly dispersive Sn-5 s band.