• Proceedings of the Korean Vacuum Society Conference
• /
• 2013.08a
• /
• pp.210.2-210.2
• /
• 2013

현재 국내의 상용화된 디지털 방식 X-선 영상장치에서 간접변환방식은 대부분 CsI를 사용하고 있으며, X-선 흡수에 의해 전기적 신호를 발생시키는 직접변환방식은 Amorphous Selenium(a-Se)을 사용한다. a-Se은 진공 중에 녹는점이 낮아 증착시 substrate의 온도에 따라 민감한 변화를 보인다. 본 연구에서는 간접변환방식에 비해 높은 영상의 질을 획득할 수 있는 직접변환방식의 a-Se기반 X-선 검출기 제작 시 substrate에 인가된 온도에 따른 특성을 연구하여 최적화 된 substrate의 온도를 알고자 한다. 본 실험에서는 glass에 투명한 전극물질인 Indium Tin Oxide (ITO)가 electrode로 형성된 substrate를 사용하였으며 그 상단에 a-Se을 Physical Vapor Deposition (PVD)방식을 거쳐 X-선 검출기 샘플을 제작하였다. PVD 공정 시 네 개의 보트에 a-Se 시료를 각각 100g씩 총 400g을 넣고, $5{\times}10-5Torr$까지 진공도를 낮추었다. 보트의 온도는 $270^{\circ}C$에서 40분 $290^{\circ}C$에서 90분으로 온도를 인가하여 a-Se을 기화시켜 증착하였다. 증착 시 substrate 온도를 각각 $20^{\circ}C$, $40^{\circ}C$, $60^{\circ}C$, $70^{\circ}C$ 네 종류로 나누어 실험을 진행하였다. 끝으로 증착된 a-Se 상단에 Au를 PVD방식으로 electrode를 형성시켜 a-Se기반의 X-선 검출기 샘플 제작을 완료하였다. 제작된 a-Se기반의 X-선 검출기 샘플의 두께는 80에서 $85{\mu}m$로 온도에 따른 차이가 없었다. 이후에 전기적 특성을 평가하기위해 electrometer와 oscilloscope를 이용하여 Dark current와 Sensitivity를 측정하여 Signal to Noise Ratio(SNR)로 도출하였으며 Scanning Electron Microscope(SEM) 표면 uniformity를 관찰하였다. 또한 제작된 a-Se기반 X-선 검출기 샘플의 hole collection 성능을 확인하고자 mobility를 측정하였다. 측정결과 a-Se의 work function을 고려한 $10V/{\mu}m$기준에서 70kV, 100mA, 0.03sec의 조건의 X-선을 조사 하였을 때 Sensitivity는 세 종류의 검출기 샘플이 15nC/mR-cm2에서 18nC/mR-cm2으로 비슷한 양상을 나타내었지만, substrate온도가 $70^{\circ}C$때의 샘플은 10nC/mR-cm2이하로 저감됨을 알 수 있었다. 그리고 substrate온도 $60^{\circ}C$에서 제작된 검출기 샘플의 전기적 특성이 SNR로 환산 시, 15.812로 가장 우수한 전기적 특성을 나타내어 최적화 된 온도임을 알 수 있었다. SEM촬영 시 온도상승에 따라 표면 uniformity가 우수하였으며, Mobility lifetime에서는 $60^{\circ}C$에서 제작된 검출기 샘플이 deep trap 수치가 높아 hole이 $0.04584cm2/V{\cdot}sec$로 $0.00174cm2/V{\cdot}sec$의 electron보다 26.34배가량 빠른 것을 확인하였다. 본 연구를 통해 a-Se증착 시, substrate에 인가된 온도는 균일한 박막의 형성 및 표면구조에 영향을 미치며 온도가 증가할수록 안정적인 전기적 특성을 나타내지만 $70^{\circ}C$이상일 시, a-Se층의 결정화가 생겨 deep trap을 발생시켜 전기적 특성이 저하됨을 확인 할 수 있었다. 따라서 증착 시의 substrate의 온도 최적화는 a-Se기반 X-선 검출기의 안전성 및 성능향상을 위해 불가피한 요소가 된다고 사료된다.

• Journal of Life Science
• /
• v.29 no.2
• /
• pp.191-197
• /
• 2019

Parkinson's disease (PD) is a progressive neurodegenerative disease that mainly affects motor system with clinical features such as bradykinesia, rigidity, tremor and abnormal posture. PD is characterized by the death of dopaminergic neurons in the substantia nigra pars compacta, which is associated with accumulation of oxidative stress and dysregulation of intracellular signaling pathway. Quercetin-3-O-glucuronide (Q3GA), a major metabolite of quercetin, has been reported to have neuroprotective effects. In this study, we examined the neuroprotective effect of Q3GA against 1-methyl-4-phenyl pyridinium ($MPP^+$)-induced neurotoxicity of PD and the underlying molecular mechanisms in SH-SY5Y cells. MTT and LDH assay showed that Q3GA significantly decreased $MPP^+$-induced cell death, which is accompanied by a reduction in poly (ADP-ribose) polymerase (PARP) cleavage. Furthermore, it attenuated $MPP^+$-induced intracellular reactive oxygen species (ROS) with the reduction of Bax/ Bcl-2 ratio. Moreover, Q3GA significantly increased the phosphorylation of Akt and cAMP response element binding protein (CREB), but it has no effects on the phosphorylation of extracellular signal-regulated kinase (ERK). Taken together, these results demonstrate that Q3GA significantly attenuates $MPP^+$-induced neurotoxicity through ROS reduction and Akt/CREB signaling pathway in SH-SY5Y cells. Our findings suggest that Q3GA might be one of the potential candidates for the prevention and/or treatment of PD.

• Journal of Applied Biological Chemistry
• /
• v.63 no.4
• /
• pp.421-428
• /
• 2020

This study investigated a mixture of Astragalus membranaceus (AM) and Lithospermum erythrorhizon (LE) extracts (ALM16), exerts anti-inflammatory effects in lipopolysaccharide (LPS)-induced RAW264.7 macrophage cells, and its underlying mechanism. ALM16 was prepared by mixing AM and LE extracts in a ratio of 7:3 (w/w). Cytotoxicity of ALM16 in RAW264.7 cells was not shown up to 200 ㎍/mL of ALM16. The results of this study showed that ALM16 does-dependently inhibits the production of nitric oxide, prostaglandin E2 and pro-inflammatory cytokines (interleukin-1β, interleukin-6, and tumor necrosis factor-α) in LPS-induced RAW264.7 cells. ALM16 not only markedly reduced the protein expression levels of inducible nitric oxide synthase and cyclooxygenase-2 (COX-2) in LPS-stimulated RAW264.7 cells, but also inhibited the nuclear translocation and DNA-binding activity of nuclear factor-kappa B (NF-κB). In addition, ALM16 specifically inhibited the phosphorylation of c-Jun N-terminal kinase and extracellular signal-regulated kinases in LPS-stimulated RAW264.7 cells. In conclusion, these results suggest that ALM16 may exert anti-inflammatory effect by modulating mitogen-activated protein kinase and NF-κB signaling pathways.

• Korean Journal of Radiology
• /
• v.20 no.5
• /
• pp.854-861
• /
• 2019

Objective: To evaluate quantitative magnetic resonance imaging (MRI) parameters for differentiation of cysts from and solid masses in the anterior mediastinum. Materials and Methods: The development dataset included 18 patients from two institutions with pathologically-proven cysts (n = 6) and solid masses (n = 12) in the anterior mediastinum. We measured the maximum diameter, normalized T1 and T2 signal intensity (nT1 and nT2), normalized apparent diffusion coefficient (nADC), and relative enhancement ratio (RER) of each lesion. RERs were obtained by non-rigid registration and subtraction of precontrast and postcontrast T1-weighted images. Differentiation criteria between cysts and solid masses were identified based on receiver operating characteristics analysis. For validation, two separate datasets were utilized: 15 patients with 8 cysts and 7 solid masses from another institution (validation dataset 1); and 11 patients with clinically diagnosed cysts stable for more than two years (validation dataset 2). Sensitivity and specificity were calculated from the validation datasets. Results: nT2, nADC, and RER significantly differed between cysts and solid masses (p = 0.032, 0.013, and < 0.001, respectively). The following criteria differentiated cysts from solid masses: RER < 26.1%; nADC > 0.63; nT2 > 0.39. In validation dataset 1, the sensitivity of the RER, nADC, and nT2 criteria was 87.5%, 100%, and 75.0%, and the specificity was 100%, 40.0%, and 57.4%, respectively. In validation dataset 2, the sensitivity of the RER, nADC, and nT2 criteria was 90.9%, 90.9%, and 72.7%, respectively. Conclusion: Quantitative MRI criteria using nT2, nADC, and particularly RER can assist differentiation of cysts from solid masses in the anterior mediastinum.

• Investigative Magnetic Resonance Imaging
• /
• v.12 no.2
• /
• pp.115-122
• /
• 2008

Purpose : To evaluate the correlation between the radiological non-invasive hepatic fibrosis index (RNHFI), as determined by SPIO-enhanced MRI, and the laboratory non-invasive hepatic fibrosis index. Materials and Methods : Patients (99 total: 61 men and 38 women; mean age: 58 years) who underwent SPIO-enhanced MRI (1.5T) during 5 years included. These patients were subdivided into a liver cirrhosis group (LCG) and a non-liver cirrhosis group (non-LCG). Using PACS view, we measured the RNHFI (mean standard deviation of hepatic signal intensity (SD), noise-corrected coefficient of variation (CV)) of three ROIs in the liver parenchyma by SPIO-enhanced MRI. The laboratory non-invasive hepatic fibrosis index (AST-platelet ratio index (APRI)) of all patients was calculated from the laboratory data. We compared the RNHFI and APRI of LCG with those of non-LC group using Student's t-test. A bivariate correlation was performed to investigate the relationship between the RNHFI and APRI in the LCG. Results : For the LCG, mean values of SD and CV by SPIO-enhanced MRI were $10.3{\pm}3.7$ and $0.19{\pm}0.08$, respectively. For the non-LCG, mean values of SD and CV were $6.5{\pm}1.6$ and $0.08{\pm}0.05$, respectively. The mean APRI of the LCG and the non- LCG were $2.04{\pm}1.7$ and $0.32{\pm}0.32$, respectively. The RNHFI and APRI were significantly different between both groups (p<0.05). For the LCG, the bivariate correlation between SD and APRI revealed a statistically significant positive correlation (r=0.5, p<0.001). In both groups, there was no statistically significant correlation between CV and APRI. Conclusion: A measurement of SD can be a simple and useful method for the evaluation of hepatic fibrosis.

• Korean Journal of Biological Psychiatry
• /
• v.23 no.4
• /
• pp.148-156
• /
• 2016

Objectives According to previous studies, the cannabinoid receptor 1 (CNR1) gene could be an important candidate gene for schizophrenia. Some studies have linked the (AAT)n trinucleotide repeat polymorphism in CNR1 gene with the risk of schizophrenia. Meanwhile, smooth pursuit eye movement (SPEM) has been regarded as one of the most consistent endophenotypes of schizophrenia. In this study, we investigated the association between the (AAT)n trinucleotide repeats in CNR1 gene and SPEM abnormality in Korean patients with schizophrenia. Methods We measured SPEM function in 167 Korean patients with schizophrenia (84 male, 83 female) and they were divided according to SPEM function into two groups, good and poor SPEM function groups. We also investigated allele frequencies of (AAT)n repeat polymorphisms on CNR1 gene in each group. A logistic regression analysis was performed to find the association between SPEM abnormality and the number of (AAT)n trinucleotide repeats. Results The natural logarithm value of signal/noise ratio (Ln S/N ratio) of the good SPEM function group was $4.34{\pm}0.29$ and that of the poor SPEM function group was $3.21{\pm}0.70$. In total, 7 types of trinucleotide repeats were identified, each containing 7, 10, 11, 12, 13, 14, and 15 repeats, respectively. In the patients with $(AAT)7$ allele, the distributions of the good and poor SPEM function groups were 18 (11.1%) and 19 (11.0%) respectively. In the patients with $(AAT)_{10}$ allele, $(AAT)_{11}$ allele, $(AAT)_{12}$ allele, $(AAT)_{13}$ allele, $(AAT)_{14}$ allele and $(AAT)_{15}$ allele, the distributions of good and poor SPEM function groups were 13 (8.0%) and 12 (7.0%), 4 (2.5%) and 6 (3.5%), 31 (19.8%) and 35 (20.3%), 51 (31.5%) and 51 (29.7%), 36 (22.2%) and 45 (26.2%), 9 (5.6%) and 4 (2.3%) respectively. As the number of (AAT) n repeat increased, there was no aggravation of abnormality of SPEM function. Conclusions There was no significant aggravation of SPEM abnormality along with the increase of number of (AAT)n trinucleotide repeats in the CNR1 gene in Korean patients with schizophrenia.

• Investigative Magnetic Resonance Imaging
• /
• v.8 no.1
• /
• pp.32-41
• /
• 2004

Purpose : To measure the NMR relaxation properties of MnPC, to observe the characteristics of liver enhancement patterns on MR images in experimentally implanted rabbit VX2 tumor model, and to estimate the possibility of tissue specific contrast agent for MnPC in comparison with the hepatobiliary agent. Materials and Methods : Phthalocyanine (PC) was chelated with paramagnetic ions, manganese (Mn). 2.01 g (5.2 mmol) of phthalocyanine was mixed with 0.37 g (1.4 nlmol) of Mn chloride at $310^{\circ}C$ for 36 hours and then purified by chromatography ($CHCl_3:\;CH_3OH=98:2$, volume ratio) to obtain 1.04 g $(46\%)$ of MnPC (molecular weight = 2000 daltons). The T1/T2 relaxivity (R1/R2) for MnPC were determined at a 1.5 T (64 MHz) MR spectrometer. VX2 tumor model was experimentally implanted in the liver parenchyma of rabbits. All MR studies were performed on 1.5 T. The human extremity radio frequency coil of a bird cage type was employed. MR images were acquired at 17 to 24 days after VX2 carcinoma implantation.4 mmol/kg MnPC and 0.01 mmol/kg Mn-DPDP were injected via the ear vein of rabbits. T1-weighted images were obtained with spin-echo (TR/TE=516/14 msec) and fast multiplanar spoiled gradient recalled (TR/TE : 80/4 msec, $60^{\circ}$ flip angle) pulse sequence. Fast spin-echo (TR/TE=1200/85 msec) was used to obtain the T2-weighted images. Results : The value of T1/T2 relaxivity (R1/R2) of MnPC was $7.28\;mM^{-1}S^{-1}$ and $55.56\;mM^{-1}S^{-1}$ respectively at 1.5 T (64 MHz). Because the T2 relaxivity of MnPC that bonded strongly, covalently manganese with phthalocyanine was very high, the signal intensity of liver parenchyma was decreased on postcontrast T2-weighted images and we could easily distinguish the VX2 carcinoma within the liver parenchyma. When MnPC was administrated intravenously, the tumor margin delineation was more remarkable than Mn-DPDP-enhanced images. The enhancement of liver parenchyma with MnPC persisted at relatively high levels over at least one hour after injection of the contrast agents. Conclusion : The hepatic uptake and biliary excretion of MnPC, which are similar to Mn-DPDP, suggest that this agent is a new liver-specific agent. Also, MnPC seems to be used as a dual contrast agent (T1 and T2) with high T2 relaxivity. However, it is warranted that MnPC needs further investigation as a potential contrast agent for MR imaging of the liver. That is, further characterizations of MnPC are needed in vivo and in vitro before clinical trials. The diagnostic potential of MnPC will also have to be examined more in the animal models of additional types.

• Progress in Medical Physics
• /
• v.22 no.4
• /
• pp.216-223
• /
• 2011

Recently PTW developed a MicroLion liquid ionization chamber which is water_equivalent and has a small sensitive volume of $0.002cm^3$. The aim of this work is to investigate such dosimetric characteristics as dose linearity, dose rate dependency, spatial resolution, and output factors of the chamber for the external radiotherapy photon beam. The results were compared to those of Semiflex chamber, Pinpoint chamber and Diode chamber with the sensitive volumes of $0.125cm^3$, $0.03cm^3$ and $0.0025cm^3$, respectively and evaluated to be suitable for small fields. This study was performed in the 6MV photon energy from a Varian 2300 C/D linac accelerator and the MP3 water phantom (PTW, Freiburg) was used. Penumbras in the varios field sizes ranged from $0.5{\times}0.5cm^2$ to $10{\times}10cm^2$ were used to evaluate the spatial resolution. Output factors were measured in the field sizes of $0.5{\times}0.5$ to $40{\times}40cm^2$. Readings of the chamber was linearly proportional to dose. Dose rate dependency was measured from 100 MU/min to 600 MU/min, showed a maximum difference of 5.0%, and outputs decreased with dose rates. The spatial resolutions determined with comparing profiles for the field sizes of $0.5{\times}0.5cm^2$ to $10{\times}10cm^2$ agreed between every detector except the Semiflex chamber to within 2%. Outputs of detectors were compared to that of Semiflex chamber and showed good agreements within 2% for every chamber. This study shows that MicroLion chamber characterized by a high signal-to-noise ratio and water equivalence could be suitable for the small field dosimetry.

• Proceedings of the Materials Research Society of Korea Conference
• /
• 2011.05a
• /
• pp.5-5
• /
• 2011

The research and development of hybrid electric vehicle (HEV), plug-in hybrid electric vehicle (PHEV) and electric vehicle (EV) are intensified due to the energy crisis and environmental concerns. In order to meet the challenging requirements of powering HEV, PHEV and EV, the current lithium battery technology needs to be significantly improved in terms of the cost, safety, power and energy density, as well as the calendar and cycle life. One new technology being developed is the utilization of composite cathode by mixing two different types of insertion compounds [e.g., spinel $LiMn_2O_4$ and layered $LiMO_2$ (M=Ni, Co, and Mn)]. Recently, some studies on mixing two different types of cathode materials to make a composite cathode have been reported, which were aimed at reducing cost and improving self-discharge. Numata et al. reported that when stored in a sealed can together with electrolyte at $80^{\circ}C$ for 10 days, the concentrations of both HF and $Mn^{2+}$ were lower in the can containing $LiMn_2O_4$ blended with $LiNi_{0.8}Co_{0.2}O_2$ than that containing $LiMn_2O_4$ only. That reports clearly showed that this blending technique can prevent the decline in capacity caused by cycling or storage at elevated temperatures. However, not much work has been reported on the charge-discharge characteristics and related structural phase transitions for these composite cathodes. In this presentation, we will report our in situ x-ray diffraction studies on this mixed composite cathode material during charge-discharge cycling. The mixed cathodes were incorporated into in situ XRD cells with a Li foil anode, a Celgard separator, and a 1M $LiPF_6$ electrolyte in a 1 : 1 EC : DMC solvent (LP 30 from EM Industries, Inc.). For in situ XRD cell, Mylar windows were used as has been described in detail elsewhere. All of these in situ XRD spectra were collected on beam line X18A at National Synchrotron Light Source (NSLS) at Brookhaven National Laboratory using two different detectors. One is a conventional scintillation detector with data collection at 0.02 degree in two theta angle for each step. The other is a wide angle position sensitive detector (PSD). The wavelengths used were 1.1950 ${\AA}$ for the scintillation detector and 0.9999 A for the PSD. The newly installed PSD at beam line X18A of NSLS can collect XRD patterns as short as a few minutes covering $90^{\circ}$ of two theta angles simultaneously with good signal to noise ratio. It significantly reduced the data collection time for each scan, giving us a great advantage in studying the phase transition in real time. The two theta angles of all the XRD spectra presented in this paper have been recalculated and converted to corresponding angles for ${\lambda}=1.54\;{\AA}$, which is the wavelength of conventional x-ray tube source with Cu-$k{\alpha}$ radiation, for easy comparison with data in other literatures. The structural changes of the composite cathode made by mixing spinel $LiMn_2O_4$ and layered $Li-Ni_{1/3}Co_{1/3}Mn_{1/3}O_2$ in 1 : 1 wt% in both Li-half and Li-ion cells during charge/discharge are studied by in situ XRD. During the first charge up to ~5.2 V vs. $Li/Li^+$, the in situ XRD spectra for the composite cathode in the Li-half cell track the structural changes of each component. At the early stage of charge, the lithium extraction takes place in the $LiNi_{1/3}Co_{1/3}Mn_{1/3}O_2$ component only. When the cell voltage reaches at ~4.0 V vs. $Li/Li^+$, lithium extraction from the spinel $LiMn_2O_4$ component starts and becomes the major contributor for the cell capacity due to the higher rate capability of $LiMn_2O_4$. When the voltage passed 4.3 V, the major structural changes are from the $LiNi_{1/3}Co_{1/3}Mn_{1/3}O_2$ component, while the $LiMn_2O_4$ component is almost unchanged. In the Li-ion cell using a MCMB anode and a composite cathode cycled between 2.5 V and 4.2 V, the structural changes are dominated by the spinel $LiMn_2O_4$ component, with much less changes in the layered $LiNi_{1/3}Co_{1/3}Mn_{1/3}O_2$ component, comparing with the Li-half cell results. These results give us valuable information about the structural changes relating to the contributions of each individual component to the cell capacity at certain charge/discharge state, which are helpful in designing and optimizing the composite cathode using spinel- and layered-type materials for Li-ion battery research. More detailed discussion will be presented at the meeting.

• Journal of the Korean Society of Radiology
• /
• v.11 no.1
• /
• pp.27-35
• /
• 2017

The purpose of this study was to investigate the features of CsI:Tl and $Gd_2O_2S$ detectors with an indirect conversion method using phantom in the DR (digital radiography) system by obtaining images of thick chest phantom, medium thickness thigh phantom, and thin hand phantom and by analyzing the SNR and CNR. As a result of measuring the SNR and CNR according to the thickness change of the subject, the SNR and CNR were higher in CsI:Tl detector than in $Gd_2O_2S$ detector when the medium thickness thigh phantom and thin hand phantom were scanned. However, when the thick chest phantom was used, for the SNR at 80~125 kVp and the CNR at 80~110 kVp in the $Gd_2O_2S$ detector, the values were higher than those of CsI:Tl detector. The SNR and CNR both increased as the tube voltage increased. The SNR and CNR of CsI:Tl detector in the medium thickness thigh phantom increased at 40~50 kVp and decreased as the tube voltage increased. The SNR and CNR of $Gd_2O_2S$ detector increased at 40~60 kVp and decreased as the tube voltage increased. The SNR and CNR of CsI:Tl detctor in the thin hand phantom decreased at the low tube voltage and increased as the tube voltage increased, but they decreased again at 100~110 kVp, while the SNR and CNR of $Gd_2O_2S$ detector were found to decrease as the tube voltage increased. The MTF of CsI:Tl detector was 6.02~90.90% higher than that of $Gd_2O_2S$ detector at 0.5~3 lp/mm. The DQE of CsI:Tl detector was 66.67~233.33% higher than that of $Gd_2O_2S$ detector. In conclusion, although the values of CsI:Tl detector were higher than those of $Gd_2O_2S$ detector in the comparison of MTF and DQE, the cheaper $Gd_2O_2S$ detector had higher SNR and CNR than the expensive CsI:Tl detector at a certain tube voltage range in the thick check phantom. At chest X-ray, if the $Gd_2O_2S$ detector is used rather than the CsI:Tl detector, chest images with excellent quality can be obtained, which will be useful for examination. Moreover, price/performance should be considered when determining the detector type from the viewpoint of the user.