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Tunable gratings in a hollow-core photonic bandgap fiber based on acousto-optic interaction
Yeom, Dong-Il,Park, Hyun Chul,Hwang, In Kag,Kim, Byoung Yoon The Optical Society 2009 Optics express Vol.17 No.12
<P>We demonstrate a coherent intermodal coupling in a hollow-core photonic bandgap fibers (PBGF) using an acoustic grating. A theoretical study on the properties of acoustic and optical wave propagating the PBGF is performed indicating that the applied frequency higher than 10 MHz is required to obtain the acousto-optic interaction at the wavelength around 1550 nm. Wavelength-tunable coupling from fundamental mode to higher-order core modes is achieved with more than 90% coupling efficiency at the applied frequency of 11.54 MHz. The low dispersive properties and the mode filed distributions of the higher-order guided modes of the air-core PBGF in the experiment show reasonable agreement with the simulation results.</P>
조직학과 효소활성 방법을 이용한 순 타이타늄과 타이타늄 합금의 상대적인 생체적합성 평가
염동선(Dong Sun Yeom),김병일(Byung Il Kim),이유미(Yu Mi Lee),이은정(Eun Jung Lee),이성태(Sung Tae Yee),성치남(Chi Nam Seong),서권일(Kwon Il Seo),조현욱(Hyun Wook Cho) 한국독성학회 2007 Toxicological Research Vol.23 No.2
Titanium or titanium alloy is a widely used implant material according to its certified biocompatibility, sufficient strength and ready availability. The purpose of this study was to evaluate the relative biocompatibility of titanium and titanium alloy specimens (Ti-29Nb-13Ta, TiNb and Ti-6Al-4V, Ti64) using in vivo and in vitro methods. For in vivo experiment, the specimens were implanted in the abdominal subcutaneous region of female mice for 2 and 4 weeks. The reaction of connective tissue to specimens was evaluated histologically. The specimens were encapsulated by fibrous connective tissue consisting of fibroblast, fibrocyte and other cells including neutrophil, macrophage, giant multinucleated cell and unidentified cells. Some newly formed blood vessels were located in the fibrous capsule surrounding the implant. Cell types and the thickness of fibrous capsules were examined quantitatively. Most of cell types located in the fibrous capsule were fibroblasts and fibrocytes. The average thickness of fibrous capsules for the TiNb specimens was much thinner than that of the titanium alloy, Ti64. The thickness of the fibrous capsule around all titanium specimens decreased at 4 weeks compared to 2 weeks post-implantation. The biocompatibility of titanium and titanium alloy specimens were also investigated in in vitro method using alkaline phosphatase from MG-63 cells. Alkaline phosphatase activity of the TiNb specimen showed higher activity than the titanium alloy, Ti64. In conclusion, the TiNb alloy with thin capsule thickness in vivo and high alkaline phosphatase activity in vitro will be of considerable use in biomedical applications.
Responses of the Brans–Dicke field due to gravitational collapses
Hwang, Dong-il,Yeom, Dong-han Institute of Physics 2010 Classical and quantum gravity Vol.27 No.20
<P>We study responses of the Brans–Dicke field due to gravitational collapses of scalar field pulses using numerical simulations. Double-null formalism is employed to implement the numerical simulations. If we supply a scalar field pulse, it will asymptotically form a black hole via dynamical interactions of the Brans–Dicke field. Hence, we can observe the responses of the Brans–Dicke field by two different regions. First, we observe the late time behaviors <I>after</I> the gravitational collapse, which include formations of a singularity and an apparent horizon. Second, we observe the fully dynamical behaviors <I>during</I> the gravitational collapse and view the energy–momentum tensor components. For the late time behaviors, if the Brans–Dicke coupling is greater (or smaller) than −1.5, the Brans–Dicke field decreases (or increases) during the gravitational collapse. Since the Brans–Dicke field should be relaxed to the asymptotic value with the elapse of time, the final apparent horizon becomes time-like (or space-like). For the dynamical behaviors, we observed the energy–momentum tensors around ω ∼ −1.5. If the Brans–Dicke coupling is greater than −1.5, the <I>T<SUB>uu</SUB></I> component can be negative at the outside of the black hole. This can allow an instantaneous inflating region during the gravitational collapse. If the Brans–Dicke coupling is less than −1.5, the oscillation of the <I>T<SUB>vv</SUB></I> component allows the apparent horizon to shrink. This allows a combination that violates weak cosmic censorship. Finally, we discuss the implications of the violation of the null energy condition and weak cosmic censorship.</P>
김동은 ( Dong Eun Kim ),유덕선 ( Deok Seon Yu ),정일민 ( Il Min Jung ),이정한 ( Jeong Han Lee ),염승룡 ( Seung Ryong Yeom ),권영달 ( Young Dal Kwon ) 한방재활의학과학회 2009 한방재활의학과학회지 Vol.19 No.2
Objectives: The aim of this study is to suggest approach of oriental medical management and necessity by research of eastern and western medical literatures for Complex Regional Pain Syndrome(CRPS). Methods: We reviewed the clinical and experimental literatures of eastern and western concerned with CRPS which is related causation, signs and symptoms, diagnosis, etiology and management. Results: 1. CRPS is divided into type 1 and 2 by nerve injury. Two types of CRPS have been recognized: type 1, corresponds to RSD and occurs without a definable nerve lesion, and type 2, formerly called causalgia refers to cases where a definable nerve lesion is present. These conditions can be charaterized clinically by the sensory abnormalities, vascular abnormalities, oedema, sweating abnormalities, motor or trophic changes. 2. CRPS are well known to patients and physicians relatively, but the pathophysiology, causation and treatments are still unclear. 3. CRPS is needed to take the early diagnosis and multidisciplinary approach for significant effect. 4. CRPS can be regarded for obstruction syndrome of Ki and blood(痺證), blood stasis(瘀血), Wei symptom(痺證), numbness(痲木) in the oriental medical management of CRPS. Conclusions: Above the results, it is suggested that further studies and active approach of management of CRPS will be conducted precisely in oriental medicine.
Kim, Dong Joon,Park, Young Soo,Kim, Nam Doo,Min, Sang Hyun,You, Yeon-Mi,Jung, Yuri,Koo, Han,Noh, Hanmi,Kim, Jung-Ae,Park, Kyung Chan,Yeom, Young Il Korean Society for Molecular and Cellular Biology 2015 Molecules and cells Vol.38 No.4
Pyruvate kinase M2 isoform (PKM2), a rate-limiting enzyme in the final step of glycolysis, is known to be associated with the metabolic rewiring of cancer cells, and considered an important cancer therapeutic target. Herein, we report a novel PKM2 activator, PA-12, which was identified via the molecular docking-based virtual screening. We demonstrate that PA-12 stimulates the pyruvate kinase activity of recombinant PKM2 in vitro, with a half-maximal activity concentration of $4.92{\mu}M$, and effectively suppresses both anchorage-dependent and -independent growth of lung cancer cells in non-essential amino acid-depleted medium. In addition, PA-12 blocked the nuclear translocalization of PKM2 in lung cancer cells, resulting in the inhibition of hypoxia response element (HRE)-mediated reporter activity as well as hypoxia-inducible factor 1 (HIF-1) target gene expression, eventually leading to the suppression of cell viability under hypoxia. We also verified that the effects of PA-12 were dependent on PKM2 expression in cancer cells, demonstrating the specificity of PA-12 for PKM2 protein. Taken together, our data suggest that PA-12 is a novel and potent PKM2 activator that has therapeutic implications for lung cancer.
Numerical Modeling of in-Band Pumped Ho-Doped Silica Fiber Lasers
Wang, Jiachen,Yeom, Dong-il,Simakov, Nikita,Hemming, Alexander,Carter, Adrian,Lee, Sang Bae,Lee, Kwanil IEEE 2018 Journal of Lightwave Technology Vol.36 No.24
<P>A theoretical model to describe in-band pumped holmium doped silica fiber lasers is presented. The model is established based upon theory and parameters obtained from published research works. Both core-pumped system and cladding-pumped system are simulated with the model. The simulation results agree well with most experimental results, and for the cases in which the simulation results show discrepancy with the experimental results the disagreement can be reasonably explained. Through numerical analysis it is found that besides common negative factors such as non-radiative decay, fiber loss, and non-optimized resonator configuration, energy transfer upconversion plays a deleterious role in the performance of in-band pumped holmium doped silica fiber lasers. In particular, inhomogeneous upconversion associated with ion clustering is found to cause significant degradation of slope efficiencies of lasers, a fact that is useful to understand the unsolved problem regarding the lower-than-expected slope efficiencies observed in previous studies of in-band pumped holmium doped fiber lasers.</P>