• 한국정보디스플레이학회:학술대회논문집
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• 2006.08a
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• pp.906-909
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• 2006

The secondary electron emission coefficient $({\gamma})$ of the cathode is an important factor for improving the discharge characteristics of AC-PDPs because of its close relationship to discharge voltage. In AC-PDPs, MgO is most widely used as a surface protective layer. In this experimental, we have investigated the electronic structure of the energy band structure of the MgO layer responsible for the high ${\gamma}$. The MgO layers have been deposited by electron beam evaporation method, where the $O_2$ partial pressures have been varied as 0, $5.2{\times}10^{-5}$ torr, $1.0{\times}10^{-4}$ torr, and $4.1{\times}10^{-4}$ torr, in this experiment. It is noted that work function that is energy gap between surface and first defect level of MgO layer has the lowest value for the highest O2 partial pressure of $4.1^{\ast}10^{-4}$ Torr.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.1
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• pp.32.2-32.2
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• 2012

Gamma Ray Bursts (GRBs) are the most energetic events in the universe, and are known to arise from the death of massive stars in many cases. Their extreme brightness makes it possible to detect them at very high redshift (z > 6.5), well into the epoch of re-ionization, providing us with an opportunity to investigate the deaths of the first stars when the universe was much younger than 1 Gyr. Here, we report the discovery of GRB 100905A, a GRB at $z$ - 7.5 (age of the universe at 700 Myr). Our observation revealed a strong spectral break between z and J band, allowing us to estimate its photometric redshift. Its gamma-ray light curve shows a very short duration of about 0.7 sec, the shortest duration event at z > 5. Investigation of this and three other known GRBs at z > 6.5 reveals that they are all short duration bursts. This is puzzling, considering that GRBs from death of massive stars do not show short duration. We suggest two possible explanations for this: (i) the BAT light curves of the high redshift GRBs suffered from observational selection effect where we are only observing the very tip of the light curve; (ii) the stars in the early universe had a peculiar nature that are different from ordinary stars at lower redshifts.

• Korean Journal of Biological Psychiatry
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• v.22 no.4
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• pp.205-215
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• 2015

Objectives Sex hormones exposure during the prenatal period has an effect on cerebral lateralization. Male brains are thought to be more lateralized than female brains. Bipolar disorder was known to show abnormalities in cerebral laterality whose characteristics could be estimated by electroencephalography (EEG) coherences. We studied sex-related differences of EEG coherences between healthy controls and patients with bipolar disorder to examine the sex effects in the genesis of bipolar disorder. Methods Participants were 25 patients with bipolar disorder (11 male, 14 female) and 46 healthy controls (23 male, 23 female). EEG was recorded in the eyes closed resting state. To examine dominant EEG coherence associated with sex differences in both groups within five frequency bands (delta, theta, alpha, beta, and gamma) across several brain regions, statistical analyses were performed using analysis of covariance. Results Though statistically meaningful results were not found, some remarkable findings were noted. Healthy control females showed more increased interhemispheric coherences than control males in gamma frequency band. There were no differences in the intrahemispheric coherences between the healthy control males and females. In patients with bipolar disorder, female dominant pattern in interhemispheric coherences was attenuated compared with healthy control. Conclusions Sex differences of EEG coherences, which could be a marker for cerebral laterality, were attenuated in patients with bipolar disorder compared with healthy controls. These results imply that abnormal sex hormone exposure during early development might play some role in the pathogenesis of bipolar disorder.

• Asian-Australasian Journal of Animal Sciences
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• v.26 no.10
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• pp.1406-1415
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• 2013

The study was conducted to correlate the periparturient immune status in terms of neutrophil functions and cytokine expression in peripheral blood mononuclear cell culture with impending postpartum reproductive disorders in buffaloes. Forty pregnant buffaloes were observed for occurrence of postpartum reproductive disorders (PRD), i.e., metritis, endometritis and delayed uterine involution etc., during one week prepartum to four weeks postpartum period. A representative number (n = 6) of buffaloes that did not develop any PRD were included in group I (healthy, control), while the animals which experienced PRD were assigned into group II (PRD, n = 8). The blood samples were collected at weekly interval from one week prepartum to four weeks postpartum period considering the day of calving as 'd 0'. Differential leucocytes counts, superoxide and hydrogen peroxide production activity in isolated neutrophils and the mRNA expression profile of cytokines i.e., IL-2, IL-4 and IFN-${\gamma}$ in PBMC culture were studied in all the samples. A higher total leucocytes, neutrophil and band cells count along with impaired neutrophil functions i.e., lowered level of production of superoxide and hydrogen peroxide before parturition and during early postpartum period were observed in buffaloes developing PRD. Further, a lower expression of IL-2, IFN-${\gamma}$ and IL-4 mRNA in PBMC culture was observed at calving in buffaloes that subsequently developed PRD at later postpartum. Thus, suppression in neutrophil function and cytokine expression at prepartum to early postpartum period predisposes the buffaloes to develop postpartum reproductive disorders. Hence, monitoring of neutrophils function and cytokine expression profile would be effective to predict certain reproductive disorders at late pregnancy or immediately after parturition in buffaloes. In future, this may be a novel approach for determining suitable management and therapeutic decisions for prevention of commonly occurring reproductive disorders in farm animals.

• Proceedings of the Korean Society of Applied Pharmacology
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• 1995.04a
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• pp.113-113
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• 1995

본 연구는 표고버섯에서 분리정제한 렉틴 성분(LEL)을 말초혈액 단핵세포(PBMC)에 반응시켜 사이토카인 유도능을 지질다당류(LPS)와 비교하여 역전사효소 중합반응법(RT-PCR)으로 측정하였다. 측정 대상 사이토카인은 IL-1, IL-2, IL-6, TNF$\alpha$ 및 IFN${\gamma}$의 다섯가지였으며 이들을 대상으로 PBMC에 렉틴을 적용하여 1, 8, 24, 48, 72, 96, 120분 등의 시간대에서 반응시켜 사이토카인의 유전자 발현 유도에 관한 다음의 결과를 얻었다. LEL의 사용 농도에 따른 편도선 림프구(tonsillar lymphocyte)의 TNF$\alpha$ 유전자 발현 양상은 반응 1시간의 경우 LEL의 일부 농도와 LPS 전농도에서 관찰되었으나 반응 40시간째에는 LEL 전농도와 LPS 전농도에서 TNF$\alpha$ 유전자 발현 양상을 관찰할 수 없었다. RT-PCR 결과 원액이나 회석액 재료로부터 관찰된 TNF$\alpha$유전자 band의 강 약 차이는 나타나지 않았다. LEL의 자극에 의한 반응 시간대 별 PBMC에 의한 사이토카인 유전자 발현 양상은 위에서 언급된 다섯가지 사이토카인을 유도, 생성할 수 있다는 것이 확인되었는데, IL-2, IL-6 및 IFN${\gamma}$는 120시간까지 장시간 지속되는 유전자 발현이 가능한 반면 TNF $\alpha$의 생성 양상은 이들 사이토카인의 생성 양상과는 판이하게 반응 1, 8 및 24 시간대까지만 TNF$\alpha$ 유전자 발현을 관찰할 수 있었고 IL-1은 72 시간까지 반응을 나타내는 등 특이적 양상을 보였다. 한편 LPS는 실험에 사용된 전 사이토카인의 유전자 발현을 120시간대까지 반응이 유지됨을 관찰하였기에 LPS가 PBMC의 강력한 사이토카인 유도체임을 입증할 수 있었으며 LEL과 다소 상이한 결과를 보였으나 LEL 또한 PBMC로부터 사이토카인을 생성 유지시킬 수 있는 유도체로 작용함을 확인할 수 있었다.

• Journal of Korea Foundry Society
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• v.24 no.6
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• pp.356-365
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• 2004

Mechanical properties and microstructures of the Ni-AI-Fe and Ni-AI-Fe-(B, Zr) alloys which containing $10{\sim}30at$.%Fe, 0.1at.%B and/or 0.1at.%Zr have been investigated. The experimental results showed that the microstructures of Ni25Al were changed from a single phase ${\gamma}$ to dual phase ${\gamma}$ and ${\beta}$ by addition of 27at.%Fe. Ni45Al, however, kept the single ${\beta}$ phase even though Fe was added upto 30at.%. The hardness of Ni25Al were increased from $H_RB$ 70 to $H_RC$ 39 by addition of 27at.%Fe. In the case of Ni45Al which have $H_RC$ 37, the hardness was decreased by lOat.%Fe addition, but increased with 30at.%Fe. The yield strength and ultimate compressive strength in the compressive test have showed a similar trend with the hardness change. The strain to fracture was 14% at maximum and achieved in Ni25Al-27at.%Fe and Ni25Al-27at.%Fe-0.1 at.%B alloys. The Ni45Al showed a relatively low strain to fracture as 4%. The impact absorption energy of Ni25Al increased from 0.74 kg-m to 1.81 kg-m by addition of 27at.%Fe. In case of Ni45Al, the addition of lOat.%Fe and lOat.%Fe with small amounts of Band Zr did not change significantly the impact absorption energy of 0.60 kg-m, whereas the addition of 30at.%Fe with small amounts of B and Zr increased it slightly. In fracture tests, both of two basic materials showed the same intergranular fracture but by adding Fe it changed to the cleavage fracture mode or co-existing of cleavage and intergranular fractures.

• Journal of Radiation Protection and Research
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• v.15 no.2
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• pp.87-100
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• 1990

For the quantitative evaluation and assessment of radiation exposure from terrestrial component of natural environmental radiation, successive thermoluminescence dosimetry and periodical in-situ gamma ray spectrometry were carried out for a period of 24 months. LiF PTFE dise TLDs and $3&{\phi}{\times}3'$cylindrical NaI(Tl)scintill ation detector in association of portable multichannel analyzer (4096 ch) were used in this study. The doses measured were evaluated and assessed in terms of effective dose equivalent. As a concomitant output, the dose equivalent due to ionizing component of cosmic ray was able to be evaluated. According to the results obtained in terms of variance weighted mean, the annual effective dose equivalents of terrestrial gamma ray and cosmic ray ionizing component in Taejeon area came out to be $564{\pm}4\;{\mu}Sv(64.8{\pm}0.5nSv{\cdot}h^{-1}$ and $300{\pm}2\;{\mu}Sv(34.3{\pm}0.2nSv{\cdot}h^{-1}$, respectively, which are reasonable comparably with that appeared in UNSCEAR Report[28]as per caput annual effective dose equivalent in 'areas of normal background radiation'.

• Analytical Science and Technology
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• v.20 no.5
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• pp.406-412
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• 2007

The formation of inclusion complexes between ${\beta}$-cyclodextrin and diethylenetriamine substituted-pyridine copper(II) perchlorate; [Cu(dien)(sub-py)] $(ClO_4)_2$, were studied by spectrophotometric methods. On account of charge-transfer band(MLCT) and $^2T_2{\rightarrow}^2E$, the two high peaks were observed as an inclusion complex for the [${\beta}$-CD]$[Cu(dien)(p-Cl-py)]^{2+}$ in the ultraviolet region of the spectrum. The ${\beta}$-CD and $[Cu(dien)(sub-py)]^{2+}$ ion formed a 1:1 complex, and the formation constants were decreased with the increasing temperatures, due to weak binding energy between ${\beta}$-CD and $[Cu(dien)(sub-py)]^{2+}$ ion. This reaction was controlled by enthalpy. In a correlation of the Hammett substituent constants and formation constants for the reaction, formation constants were increased by strong binding energy in the inclusion complexes when electron donating groups were substituted in pyridine ring.

• Nuclear Engineering and Technology
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• v.56 no.9
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• pp.3804-3811
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• 2024

The study focuses on creating new boro-silicate glasses doped with SnO₂ for radiation shielding. It examines how substituting Na₂O with SnO₂ affects their structural, optical, and shielding properties. Density increases from 2.406 to 2.488 g/cm³ with rising SnO₂, measured via the Archimedes Method. The examination for the glassy phase was performed using the XRD diffractometer. UV/Vis spectrophotometer analysis reveals reduced refractive index (2.412-1.976) and increased optical absorption-band gap (direct: 3.648-5.662 eV; indirect: 2.994-5.163 eV) with SnO₂ concentrations of 0-9 mol.%). The effectiveness of the radiation shielding was assessed over the 0.059-1.408 MeV gamma-ray energy interval. The analysis demonstrates that when the concentration of SnO₂ increases, the synthesized glasses' linear attenuation coefficient improves. As the SnO₂ content was raised between 0 and 9 mol%, the linear attenuation coefficient rose between 0.489 and 2.892 cm^-1 (at energy of 0.059 MeV) and between 0.126 and 0.128 cm^-1 (at energy of 1.408 MeV), respectively. As the SnO₂ content was raised between 0 and 9 mol%.

• The Bulletin of The Korean Astronomical Society
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• v.38 no.2
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• pp.68.2-68.2
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• 2013

Camera for QUasars in EArly uNiverse (CQUEAN) is an optical CCD camera system made by Center for Exploration of the Origin of the Universe (CEOU). CQUEAN is developed for follow-up observation of red sources such as high-redshift quasar candidates ($z{\geq}5$), gamma-ray bursts (GRB), brown dwarfs and young stellar objects. The CQUEAN is composed of a science camera with deep-depletion CCD chip which is sensitive at around $1{\mu}m$, a set of custom-made wide-band filters for detection of quasar candidates at z~5, and a guide camera. A focal reducer was developed to secure $4.8^{\prime}{\times}4.8^{\prime}$ field of view, and an in-house user software for efficient data acquisition. CQUEAN was attached to 2.1m Otto Struve Telescope in McDonald Observatory, USA, in August 2010. About 1000 quasar candidates including 3 confirmed with follow-up spectroscopy, have been observed so far, and many high-z galaxy cluster candidates, GRBs and supernovae were also observed. And monitoring of HBC 722, a young stellar object, is under way since 2011. Further enhancement of CQUEAN including the introduction of narrow-band filters is planned.