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Examination of radiation effects on Cs2LiYCl6:Ce3+ scintillators using a 100 MeV proton beam
Nam Uk-won,윤석원,Park Won-Kee,Pyo Jeonghyun,Sohn Jongdae,Moon Bongkon,예성준,Kim Sunghwan 한국물리학회 2022 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.80 No.5
Cs2LiYCl6:Ce3+ scintillator is worthwhile to study, since it has good pulse shape discrimination capability which lead to thermal or fast neutron detection based on the reactions of the constituent elements of Li and Cl. In this study, the effects of proton dose on the scintillation performance of CLYC were measured to check its feasibility for space exploration. A 100 MeV proton beam generated by the Korean Multi-Purpose Accelerator Complex (KOMAC) was used for irradiation of the crystal. The pulse shape discrimination (PSD) for gamma-rays and thermal neutrons as a function of protons dose was used as a standard method for evaluation. After removing gamma-rays background from neutron signal by PSD, we examined the effect of the proton dose on the scintillator based on the electron equivalent energy induced by thermal neutron. When a proton beam was irradiated on the CLYC scintillator at 1 krad, we found a decrease in the light yield by approximately 50% and a rapid increase in the background radiations. Therefore, the detector for gamma-ray measurements was considered unsuitable in high-level proton fields, such as in a low-Earth orbit, owing to the activation problem in CLYC scintillators. However, given that the neutrons can be separated from gamma-rays by the PSD, conducting in situ calibrations using the peaks of the thermal neutron channels up to the maximum dose of the order of several krad through a neutron spectrometer is possible.
Computational Drug Discovery Approach Based on Nuclear Factor-κB Pathway Dynamics
Nam, Ky-Youb,Oh, Won-Seok,Kim, Chul,Song, Mi-Young,Joung, Jong-Young,Kim, Sun-Young,Park, Jae-Seong,Gang, Sin-Moon,Cho, Young-Uk,No, Kyoung-Tai Korean Chemical Society 2011 Bulletin of the Korean Chemical Society Vol.32 No.12
The NF-${\kappa}B$ system of transcription factors plays a crucial role in inflammatory diseases, making it an important drug target. We combined quantitative structure activity relationships for predicting the activity of new compounds and quantitative dynamic models for the NF-${\kappa}B$ network with intracellular concentration models. GFA-MLR QSAR analysis was employed to determine the optimal QSAR equation. To validate the predictability of the $IKK{\beta}$ QSAR model for an external set of inhibitors, a set of ordinary differential equations and mass action kinetics were used for modeling the NF-${\kappa}B$ dynamic system. The reaction parameters were obtained from previously reported research. In the IKKb QSAR model, good cross-validated $q^2$ (0.782) and conventional $r^2$ (0.808) values demonstrated the correlation between the descriptors and each of their activities and reliably predicted the $IKK{\beta}$ activities. Using a developed simulation model of the NF-${\kappa}B$ signaling pathway, we demonstrated differences in $I{\kappa}B$ mRNA expression between normal and different inhibitory states. When the inhibition efficiency increased, inhibitor 1 (PS-1145) led to long-term oscillations. The combined computational modeling and NF-${\kappa}B$ dynamic simulations can be used to understand the inhibition mechanisms and thereby result in the design of mechanism-based inhibitors.
Calibration of TEPC for CubeSat Experiment to Measure Space Radiation
Uk-Won Nam,Won-Kee Park,Jaejin Lee,Jeonghyun Pyo,Bong-Kon Moon,Dae-Hee Lee,Sunghwan Kim,Ho Jin,Seongwhan Lee,Jungho Kim,Hisashi Kitamura,Yukio Uchihori 한국우주과학회 2015 Journal of Astronomy and Space Sciences Vol.32 No.2
A newly designed Tissue Equivalent Proportional Counter (TEPC) has been developed for the CubeSat mission, SIGMA (Scientific cubesat with Instruments for Global Magnetic field and rAdiation) to investigate space radiation. In order to test the performance of the TEPC, we have performed heavy ion beam experiments with the Heavy Ion Medical Accelerator in Chiba (HIMAC), Japan. In space, human cells can be exposed to complex radiation sources, such as X-ray, Gamma ray, energetic electrons, protons, neutrons and heavy charged particles in a huge range of energies. These generate much a larger range of Linear Energy Transfer (LET) than on the ground and cause unexpected effects on human cells. In order to measure a large range of LET, from 0.3 to 1,000 keV/μm, we developed a compact TEPC which measures ionized particles produced by collisions between radiation sources and tissue equivalent materials in the detector. By measuring LET spectra, we can easily derive the equivalent dose from the complicated space radiation field. In this HIMAC experiment, we successfully obtained the linearity response for the TEPC with Fe 500 MeV/u and C 290 MeV/u beams and demonstrated the performance of the active radiation detector.
Nam, Hyo-Jin,Jang, Seong-Soo,Kim, Young-Sik,Lee, Caroline-Sunyong,Jin, Won-Hyeog,Cho, Il-Joo,Bu, Jong-Uk The Institute of Electronics and Information Engin 2005 Journal of semiconductor technology and science Vol.5 No.1
Silicon nitride cantilevers integrated with silicon heaters and piezoelectric sensors were developed for the scanning probe microscope (SPM) based data storage application. These nitride cantilevers are expected to have better mechanical stability and uniformity of initial bending than the previously developed silicon cantilevers. Data bits of 40 nm in diameter were recorded on PMMA film and the sensitivity of the piezoelectric sensor was 0.615 fC/nm, meaning that indentations less than 20 nm in depth can be detected. For high speed operation, $128{\times}128$ cantilever array was developed.
Nam Hyo-Jin,Kim Young-Sik,Lee Caroline Sunyong,Jin Won-Hyeog,Jang Seong-Soo,Cho Il-Joo,Bu Jong-Uk The Society of Information Storage Systems 2005 정보저장시스템학회논문집 Vol.1 No.1
In this paper, a new silicon nitride cantilever integrated with silicon heater and piezoelectric sensor has been firstly developed to improve the uniformity of the initial bending and the mechanical stability of the cantilever array for thermo-piezoelectric SPM(scanning probe microscopy) -based data storages. This nitride cantilever shows thickness uniformity less than $2\%$. Data bits of 40 nm in diameter were recorded on PMMA film. The sensitivity of the piezoelectric sensor was 0.615 fC/nm after poling the PZT layer. For high speed operation, 128${\times}$128 probe array was developed.
Calibration of TEPC for CubeSat Experiment to Measure Space Radiation
Nam, Uk-Won,Park, Won-Kee,Lee, Jaejin,Pyo, Jeonghyun,Moon, Bong-Kon,Lee, Dae-Hee,Kim, Sunghwan,Jin, Ho,Lee, Seongwhan,Kim, Jungho,Kitamura, Hisashi,Uchihori, Yukio The Korean Space Science Society 2015 Journal of Astronomy and Space Sciences Vol.32 No.2
A newly designed Tissue Equivalent Proportional Counter (TEPC) has been developed for the CubeSat mission, SIGMA (Scientific cubesat with Instruments for Global Magnetic field and rAdiation) to investigate space radiation. In order to test the performance of the TEPC, we have performed heavy ion beam experiments with the Heavy Ion Medical Accelerator in Chiba (HIMAC), Japan. In space, human cells can be exposed to complex radiation sources, such as X-ray, Gamma ray, energetic electrons, protons, neutrons and heavy charged particles in a huge range of energies. These generate much a larger range of Linear Energy Transfer (LET) than on the ground and cause unexpected effects on human cells. In order to measure a large range of LET, from 0.3 to $1,000keV/{\mu}m$, we developed a compact TEPC which measures ionized particles produced by collisions between radiation sources and tissue equivalent materials in the detector. By measuring LET spectra, we can easily derive the equivalent dose from the complicated space radiation field. In this HIMAC experiment, we successfully obtained the linearity response for the TEPC with Fe 500 MeV/u and C 290 MeV/u beams and demonstrated the performance of the active radiation detector.
Nam Ji Won,Lee Jong Min,Lyo In Uk,Kwon Soon Chan,Sim Hong Bo 대한말초신경학회 2021 The Nerve Vol.7 No.1
Posterior lumbar interbody fusion (PLIF) is a well-known method for treating spinal diseases in which adjacent segment disease (ASD) is a representative complication. To correct ASD, posterior fusion is extended to the upper or lower segment, and the previous instruments are removed. However, there have been a few reports of complications after instrument removal. Here, we report on a case of compression fracture that occurred without history of trauma after ASD revision and instrument removal surgery. A 68-year-old woman underwent PLIF at L3-5 and was hospitalized for treatment of ASD. She underwent oblique lumbar interbody fusion at L2-3 after removal of the previous screws. One month later, she visited the hospital with sudden lower back pain. Plain radiography revealed a compression fracture of L4. The patient’s pain was relieved after conservative treatment. Our findings show that instrument removal during revision operations should be performed carefully because it can lead to compression fracture without a history of trauma.