• Asian Journal of Atmospheric Environment
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• 제4권2호
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• pp.106-114
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• 2010

By the application of novel double detector system of micro-PIXE that can detect light elements (Z<14), we made an attempt to provide a thorough discussion on the aging processes of Asian dust (hereafter called "AD") particle by reaction with sea-slat. The elemental spectra and maps obtained from the microbeam radiation of micro-PIXE to individual AD particles were useful for fractionating AD particles into both internally and externally mixed particles. A spatial distribution of elements in a minute domain of single particle obtained by scanning the microbeam irradiation enabled us not only to estimate the chemical mixing state of individual AD particles but also to presume their aging processes in both ambient air and cloud. By calculating the normalized micro-PIXE net count of elements, it was possible to classify individual AD particles into three distinct groups (i.e., (1) Aging type 1: AD particle coated by the gaseous Cl evaporated by the reaction between artificial acids and sea salt; (2) Aging type 2: AD particle mixed with sea salt but no additional reaction with artificial acids; and (3) Non-aged type) A relatively high transformation rate (63.3-75.9%) was shown in large particles (greater than $5.1\;{\mu}m$ in diameter).

• Maxillofacial Plastic and Reconstructive Surgery
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• 제12권2호
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• pp.21-33
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• 1990

This study was performed to evaluate the effects of preoperative and postoperative radiation on the healing of surgical wound and the relationship between surgery-radiation interaval histopathologically. Experimental animals were 64 rats of Sprague-Dawely strain weighing about 180grams. In postoperative radiation group, a single dose of 1000 rads irradiation was delivered on 1,2,3, weeks after incision and 24 animals were sacrificed on the 1st, 3rd, 7th, and 14th day after radiation. In preoperative radiation group incision was performed on 1,2,3,4 weeks after a single dose of 1000 rads and 32 animals were sacrificed on the 1st, 3rd, 7th, and 14th after incision. Tissue specimens were prepared as usual methods and stained with hematoxyline-eosin for ordinary light microscopy. Histopathologic study revealed the following favorable results : 1. In 2 and 3 weeks radiation group after incision, the healing process was unaffected by radiation. 2. In 1 week radiation group after incision, the healing process was slightly retarded, as compared with 2,3 weeks radiation group after incision. 3. In 1,2 and 3 weeks incision group after radiation, the healing process appeared about 7 days later than that of control group. 4. In 4 weeks incision after radiation, the healing process was unaffected by radiation.

• 한국초전도학회:학술대회논문집
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• 한국초전도학회 2000년도 High Temperature Superconductivity Vol.X
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• pp.45-50
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• 2000

We have investigated the influence of columnar defects (CD) on the vortex dynamics in pristine and iodine-intercalated Bi$_2$Sr$_2$CaCu$_2$O$_{8+{\delta}} single crystals from do SQUID magnetization measurements. Especially, the temperature dependence of the irreversibility fields, H$_{irr}$(T), were studied. Anisotropy ratio ${\gamma}$, estimated from the fitting to the 2-dimensional melting model (A. Schilling et al., Phys. Rev. Lett. 71 1899 (1993)) in higher fields than the matching field B$_{\phi}$ at low temperature region, turns out to be decreased by the iodine-intercalation and additionally by the heavy-ion irradiation.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2011년도 제40회 동계학술대회 초록집
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• pp.492-492
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• 2011

단일벽 탄소나노튜브(Single-Walled Carbon Nanotubes, SWCNTs)는 매우 우수한 전기적, 광전자적 특성을 가지고 있어 차세대 나노 전자소자 물질로 각광받고 있다. 특히, 이들의 전기적 특성은 직경과 카이랄리티(chirality)에 따라 금속성(metallic)과 반도체성(semiconducting)으로 구분된다. 각 특성에 따라 금속성은 투명전극, 반도체성은 전계효과 트랜지스터(CNT-FET)로 활용가능성이 높다. 하지만, 일반적으로 단일벽 탄소나노튜브는 이 두 가지의 특성이 혼재되어 합성되기 때문에, 그들의 선택적 분리는 나노튜브 기반 전자소자 응용을 위해 매우 중요한 과정 중 하나이다. 최근에는 반응 가스를 이용한 선택적 제거, 밀도차를 이용한 원심분리법(density gradient ultracentrifugation) 등 다양한 방법들이 보고된 바 있다. 본 연구는 대기 중에서 마이크로웨이브 조사하여 금속성 나노튜브만을 선택적으로 제거하였다. 마이크로웨이브 조사는 CVD 방법과 전기 방전법으로 성장된 단일벽 탄소나노튜브에 800W로 조사 시간을 변화하며 수행하였다. 실험 결과, 조사 시간이 증가할수록 두 종류의 나노튜브에서 반도체성 나노튜브는 남아있는 반면 금속성 나노튜브는 점차 제거되었다. 이러한 원인은 각 전기적 특성에 따른 유전상수 차이에 의하여 기인한 것이다. 전기적 특성과 결정성은 라만 분광법(Raman spectroscopy)을 통하여 분석하였으며, 직경 및 분산정도는 주사전자현미경(scanning electron microscope), 투과전자현미경(tunneling electron microscope)으로 관찰하였다.

• Animal cells and systems
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• 제7권2호
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• pp.159-164
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• 2003

The RAD3 gene of Saccharomyces cerevisiae is required for excision repair and is essential for cell viability. The RAD3 encoded protein possesses a single stranded DNA-dependent ATPase and DNA and DNA-RNA helicase activities. To examine the extent of conservation of structure and function of a S. pombe RAD3 during eukaryotic evolution, the RAD3 homolog gene was isolated by screening of genomic DNA library. The isolated gene was designated as HRD3 (homolog of RAD3 gene). Southern blot analysis confirmed that S. pombe chromosome contains the same DNA as HRD3 gene and this gene exists as a single copy in S. pombe. The transcript of 2.8 kb was detected by Northern blot analysis, The level of transcripts increased by ultraviolet (UV) irradiation, indicating that HRD3 is one of the UV-inducible genes in S. pombe. Furthermore, the predicted partial sequence of HRD3 protein has 60％ identity to S. cerevisiae RAD3 gene. This homology was particularly striking in the regions identified as being conserved in a group of DNA helicases. Gene deletion experiments indicate that the HRD3 gene is essential for viability and DNA repair function. These observations suggest evolutionary conservation of other protein components with which HRD3 might interact in mediating its DNA repair and viability functions.

• 전력전자학회논문지
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• 제25권2호
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• pp.118-126
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• 2020

A solar array simulator is a special power supply that regulates the output voltage and current to simulate the characteristics of a photovoltaic panel. The operating point of the panel is difficult to control with a single controller because of the non-linearity of the output curve, which is determined by the amount of irradiation, temperature, and panel material. In the conventional method, the output curve is divided into sections through the current and the voltage mode controls. It reduces the overall performance of the system due to the interchanging control mode. By using the single mode controller, the noise interference of the measured value and the stability of the control around the maximum power point were demonstrated. To solve these issues, this study proposes a new unified controller. The stability of the controller was analyzed along with operating principles, and performance improvement was experimentally verified.

• 한국전기전자재료학회논문지
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• 제29권9호
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• pp.576-580
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• 2016

Single-layered transition metal dichalcogenides (TMDs) exhibit more interesting physical properties than those of bulk TMDs owing to the indirect to direct bandgap transition occurring due to quantum confinement. In this research, we demonstrate that layer-by-layer laser etching of molybdenum diselenide ($MoSe_2$) flakes could be controlled by varying the parameters employed in laser irradiation (time, intensity, interval, etc.). We observed a dramatic increase in the photoluminescence (PL) intensity (1.54 eV peak) after etching the samples, indicating that the removal of several layers of $MoSe_2$ led to a change from indirect to direct bandgap. The laser-etched $MoSe_2$ exhibited the single $MoSe_2$ Raman vibration modes at ${\sim}239.4cm^{-1}$ and ${\sim}295cm^{-1}$, associated to out-of-plane $A_{1g}$ and in-plane ${E^1}_{2g}$ Raman modes, respectively. These results indicate that controlling the number of $MoSe_2$ layers by laser etching method could be employed for optimizing the performance of nano-electronic devices.

• Nuclear Engineering and Technology
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• 제54권6호
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• pp.2198-2203
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• 2022

As robotics become more sophisticated, there are a growing number of generic systems being used for routine tasks in nuclear environments to reduce risk to radiation workers. The nuclear sector has called for more commercial-off-the-shelf (COTS) devices and components to be used in preference to nuclear specific hardware, enabling robotic operations to become more affordable, reliable, and abundant. To ensure reliable operation in nuclear environments, particularly in high-gamma facilities, it is important to quantify the tolerance of electronic systems to ionizing radiation. To deliver their full potential to end-users, mobile robots require sophisticated autonomous behaviors and sensing, which requires significant computational power. A popular choice of computing system, used in low-cost mobile robots for nuclear environments, is the UP Core single board computer. This work presents estimates of the total ionizing dose that the UP Core running the Robot Operating System (ROS) can withstand, through gamma irradiation testing using a Co-60 source. The units were found to fail on average after 111.1 ± 5.5 Gy, due to faults in the on-board power management circuitry. Its small size and reasonable radiation tolerance make it a suitable candidate for robots in nuclear environments, with scope to use shielding to enhance operational lifetime.

• Journal of Microbiology and Biotechnology
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• 제33권9호
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• pp.1250-1256
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• 2023

Herein, different extracts of Scenedesmus deserticola JD052, a green microalga, were evaluated in vitro as a potential anti-aging bioagent. Although post-treatment of microalgal culture with either UV irradiation or high light illumination did not lead to a substantial difference in the effectiveness of microalgal extracts as a potential anti-UV agent, the results indicated the presence of a highly potent compound in ethyl acetate extract with more than 20% increase in the cellular viability of normal human dermal fibroblasts (nHDFs) compared with the negative control amended with DMSO. The subsequent fractionation of the ethyl acetate extract led to two bioactive fractions with high anti-UV property; one of the fractions was further separated down to a single compound. While electrospray ionization mass spectrometry (ESI-MS) and nuclear magnetic resonance (NMR) spectroscopy analysis identified this single compound as loliolide, its identification has been rarely reported in microalgae previously, prompting thorough systematic investigations into this novel compound for the nascent microalgal industry.

• Radiation Oncology Journal
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• 제23권3호
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• pp.161-168
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• 2005

목적: 강력한 항산화 효과를 지닌 melatonin을 전처치하였을 때 방사선유도성 섬유증 과정에서 중요한 사이토카인인 $TGF-{\beta}1$의 변화된 발현양상을 마우스 폐에서 연구하였다. 대상 및 방법: C57BL/6 마우스를 실험군에 따라 세 군(대조군, 방사선조사 단독군, melatonin 전처치군(방사선조사 1시간 전에 300 mg/kg 복강주사))으로 분류하고 양측 흉곽에 12 Gy의 선량을 단일조사하였다. 방사선조사 후 2주와 4주의 폐조직에서 $TGF-{\beta}1$ mRNA 발현수준을 측정하기 위해 semiquantitive RT-PCR를 시행하였고, $TGF-{\beta}1$ protein 발현의 수준과 위치를 보기 위해 면역조직화학염색을 시행하였다. 결과: 2주 후에 측정된 mRNA 발현은 방사선조사 단독군과 melatonin 전처치군에서 각각 대조군의 1.92배와 1.80배 증가된 수준을 보였고(p=0.064), 4주 후에는 각각 2.38배와 1.94배 수준의 증가된 발현을 보였다(p=0.004). $TGF-{\beta}1$ protein의 발현은 조직병리학적으로 방사선손상 영역에서 주로 관찰되었는데 폐포 대식세포와 폐포벽의 상피세포들이 주요 근원이었다. 발현수준은 2주완 4주 후에 각각 $15.8\%\;vs\;16.9\%$ (P=0.565), 그리고 $36.1\%\;vs\;25.7\%$ (p=0.009)이었다. 결론: Melatonin 전처치로 방사선조사에 의한 $TGF-{\beta}1$ mRNA와 protein의 발현이 4주 후에 유의하게 감소됨을 관찰하였다. 따라서 방사선으로 인한 폐손상 시에 항섬유증 약물로의 사용가능성을 확인하였다.