• 한국표면공학회지
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• 제39권5호
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• pp.235-239
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• 2006

The aluminum nitride(AlN) layer on Al7075 substrate has been formed through nitrogen ion implantation process. The implantation process was performed under the conditions : 100 keV energy, total ion dose up to $2{\times}10^{18}\;ions/cm^2$. XRD analysis showed that aluminum nitride layers were formed by nitrogen implantation. The formation of Aluminum nitride enhanced surface hardness up to 265HK(0.02 N) from 150HK(0.02 N) for the unimplanted specimen. Micro-Knoop hardness test showed that wear resistance was improved about 2 times for nitrogen implanted specimens above $5\;{\times}\;10^{17}\;ions/cm^2$. The friction coefficient was measured by Ball-on-disc type wear tester and was decreased to 1/3 with increasing total nitrogen ion dose up to $1\;{\times}\;10^{18}ions/cm^2$. The enhancement of mechanical properties was observed to be closely associated with AlN formation. AES analysis showed that the maximum concentration of nitrogen increased as ion dose increased until $5\;{\times}\;10^{17}\;ions/cm^2$.

• 대한방사선기술학회지:방사선기술과학
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• 제42권2호
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• pp.131-135
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• 2019

The purpose of this study was to evaluate the efficacy of brachytherapy of breast cancer by dose assessment which a steady increased in Korea women. The dose assessment was performed using the MCNPX program, a MonteCarlo simulation technique. The sources used for brachytherapy was 192Ir. And nanoparticle which used for dose enhancement was gold. The density of nanoparticle was 7, 18 and 30 mg. Evaluation of absorbed dose according to distance is measured at a distance of 30, 50, 100 and 200 cm from the patient. As a result, The breast absorbed dose results increased in proportion to the density of nanoparticle. And the surrounding organs were not significantly different according to the density. But, in some organs, the absorbed dose decreased as the density of nanoparticles increased. Absorbed dose according to the distance was in inverse proportion to distance.

• 한국방사선학회논문지
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• 제10권3호
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• pp.153-159
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• 2016

방사선과 상호작용으로 단일 금 나노입자로부터 나타나는 2차 전자의 발생과 입자 크기, 입사 에너지 간의 관계를 확인하였으며, 금 나노입자를 이용한 선량 증가 효과에 대한 기초 자료를 제공하고자 하였다. MCNPX MC code를 이용하여 Monte Carlo 시뮬레이션 기법을 적용하였으며, X선 에너지는 50, 100, 150 kV와 6, 15 MV를 사용하였다. 물 팬텀 내부에 30, 50, 70, 90, 110 nm 직경의 단일 금 나노입자를 위치시켜 10 nm 간격으로 계수 체적을 지정하였다. 금 나노입자로부터 발생하는 전자의 차이는 입자가 없을 때를 기준으로 표준화하여 나타내었으며, X선의 에너지가 낮을수록, 금 입자의 직경이 클수록 많은 전자의 발생을 보였다. 에너지가 낮을수록 나노입자의 크기와 전자 발생 간 선형식에서 높은 기울기 값을 나타내었으며, MV X선에 비해 kV X선에서 현저히 많은 전자의 발생을 보였다. 금 나노입자를 이용한 선량 증가 현상을 이해하기 위한 자료로 활용할 수 있을 것으로 생각되며, 추후 금 나노입자를 포함한 다양한 선량 증가 물질에 대한 추가 연구가 필요할 것으로 사료된다.

• 한국환경농학회지
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• 제21권3호
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• pp.202-207
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• 2002

참박과 호박 채종종자의 발아율을 증진시킬 수 있는 종자처리 방법을 확립하고자 저선량 감마선을 1$\sim$20 Gy 까지 조사하여 발아와 초기생육 및 생리활성을 관찰하였다. 저선량 조사한 참박과 호박종자의 발아율은 대조구보다 증가하는 경향을 보였는데 그 효과는 종자상태에 따라 다르게 나타났다. 참박 70$\sim$80% 발아율종자의 발아는 4$\sim$20 Gy에서 증가하였는데 특히 4 Gy조사에서 가장 높았고, 80$\sim$90% 발아율종자도 4 Gy 조사에서 효과를 보였다. 파종 4일 후의 발아율은 참박 70$\sim$80%와 80$\sim$90% 발아율 종자의 경우는 4 Gy조사에서 대조구보다 각각 66%와 26% 증가하였고, 호박의 70$\sim$80% 발아율종자는 2 Gy 조사에서, 80$\sim$90% 발아율종자는 8 Gy 조사에서 향상되었다. 저선량 조사한 유묘생육은 발아율이 증가한 선량에서 증가하였는데 특히 호박 70$\sim$80% 종자의 2 Gy 조사에서 가장 높았다. 파종 6일 후에 조사한 참박의 효소활성은 4 Gy 조사시에 단백질과 catalase 활성이, 호박의 경우는 catalase와 peroxidase 활성이 2 Gy와 8 Gy 조사에서 증가하였다. 참박과 호박종자의 발아와 유묘생육 및 생리활성은 저선량 감마선 조사에 의해 촉진됨을 확인할 수 있었다.

• Radiation Oncology Journal
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• 제12권3호
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• pp.285-293
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• 1994

Purpose : The study was designed to investigate the effect of cis-dichlorodiammineplatinum(II)(cis-DDP) on the radiation-induced cardiomyopathy in the rat. Materials and Methods : The myocardial damage was assessed by histopathologic changes. In radiation alone group, radiation dose ranged from 10-40 Gy X-ray in a single dose and in combined group, cis-dichlorodiammineplatinum(II) at a dose of 6 mg/kg was given intraperitoneally immediately after irradiation of same dose with X-ray alone group. Results : The early changes by radiation included congestion, inflammatory cell infiltrations and fibrosis in myocardial interstitium with focal myocardial necrosis, which was noted in 10 Gy group, Myocardial fibrosis was increased by increasing dose of radiation but myocardial necrosis was not Proportional to radiation dose. cis-DDP alone group showed minimal degeneration of myocardium with surrounded by inflammatory cell infiltrations. In combined group, myocardial fibrosis in 10 Gy group were similar to radiation alone group, but 30 Gy and 40 Gy groups showed severer changes. Electron microscopic examination showed disruption of Z-band and edema of mitochondria with decreased matrix density in 20 Gy radiation group which were severer in 40 Gy radiation group. Combined group showed endothelial changes and disruption of Z-band worse than radiation alone group as well as increased connective tissue, which was considered as a hallmark of late change in radiation-induced heart disease. Conclusion : This results showed minimal enhancement of the radiation-induced cardiomyopathy in rats by cis-DDP.

• 한국잡초학회지
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• 제32권3호
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• pp.159-169
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• 2012

일부 화학물질은 고농도에서 독성을 나타내지만 낮은 농도에서는 촉진되거나 유익하게 이용될 수 있는데 이와 같은 양방향 농도반응 현상을 양면성이라고 하며, 많은 제초제와 식물독소에서 볼 수 있다. 양면성 농도반응은 동물, 식물, 미생물을 포함하는 모든 생물체에서 일반적으로 볼 수 있다. 이 현상은 동물과 포유동물에서 가장 관심이 많았으나 식물에서는 관심이 적었다. 2,4-D, metribuzin, bromacil, bromoxynil, chloramben, propachlor, terbacil, EPTC, MSMA, glyphosate, metsulfuron, acifluorfen, terbuthylazine는 저농도에서 양면성 촉진반응을 나타냈다. Metsulfuron과 glyphosate는 아미노산 생합성에 양면성 반응을 나타냈고, terbacil과 simazine은 단백질 함량을 증가시켰다. 그리고 acifluorfen과 terbuthylazine의 양면성 반응은 직접 혹은 간접적으로 아미노산 생합성과 관련된 기작에 의하여 유도 혹은 증대되었다. Sulfentrazone과 lactofen을 처리하면 식물독소 생산을 증가시켜 균핵병 발생을 감소시켰다. 사탕수수에서 glyphosate 저농도 처리에 의한 설탕생산 증가효과는 설탕산업에서 상용화되어 활용되고 있다. 제초제의 생장촉진 반응을 나타내는 요인들에 대하여는 많이 밝혀졌으나 양면성의 작용기작에 관한 연구는 극히 제한되었고, 생장촉진을 화학적으로 유기하는 기작은 아직 완전히 밝혀지지 않았다.

• 한국의학물리학회지:의학물리
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• 제18권4호
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• pp.221-225
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• 2007

움직이는 자기장을 이용한 팬텀 속 선량 변조에 관한 몬테칼로 계산을 수행하였다. 본 연구의 목적은 빔 축을 따라 이동하는 횡 자기장을 이용하여 특정감이 영역에 균일한 선량을 얻는 것이다. 이를 위해 두 가지 구성 즉, 깊이 방향으로 일정한 속도 그리고 점차 감소하는 속도를 가지는 자기장에 대해 깊이 선량율을 구하였다. 연속적 움직임에 대한 근사로서 단계별 이동과 시간인자를 도입하였다. 위치별 정지한 자기장 대한 김이 선량율 자료에 최소제곱법을 적용하여 자기장 위치에 따른 최적의 시간인자를 구하였다. 몬테칼로 계산결과를 통하여 자기장의 속도를 변화시킴으로써 평탄한 선량 분포를 얻을 수 있음을 확인하였다. 이 때 3 T 자기장 세기에 대한 계산결과 평탄 영역의 선량은 자기장이 없을 때에 비해 약 10.1% 증가하는 것으로 나타났다.

• Journal of Photoscience
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• 제9권2호
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• pp.197-200
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• 2002

UVR-induced immunosuppression contributes to skin cancer. The aim was to construct accurate dose response curves for primary and secondary contact sensitivity for solar-simulated UVR (ssUVR; 290-400nm), UVA and UVB as the role of UVA in immunosuppression is controversial. We used a xenon arc source. The mice were immobilised, enabling accurate dosing. C57BL/6 mice were immunosuppressed at half the dose of ssUVR required to cause sunburn but not by higher doses (up to the sunburn dose). Thus, ssUVR causes systemic immunosuppression only over a narrow, low dose range. UVA caused suppression at low but not high doses whereas UVB induced immunosuppression at all doses tested. 8 weeks later the mice were resensitised to assess tolerance. Mice exposed to the minimum immunosuppressive dose of ssUVR prior to primary sensitisation were tolerant to re-sensitisation. However, at higher doses of ssUVR, these mice were protected from tolerance. Interestingly, while low doses of UV A caused immunosuppression, even lower doses enhanced the response to the second sensitisation. Higher doses of UVA had no affect. UVB induced tolerance in a dose related manner. Thus, ssUVR only induces immunosuppression and tolerance over a narrow dose range. Both UVA and UVB are immunosuppressive at this dose, while higher doses of UVA protect from the suppressive effects of UVB. Surprisingly very low doses of UVA enhanced memory development. Thus UVR has complex effects on the immune system depending on dose and spectrum.

• Nuclear Engineering and Technology
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• 제55권5호
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• pp.1671-1676
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• 2023

The influence of adding iodine as a contrast substance to elevate radiation in a tumor is studied using simulation techniques of Monte-Carlo. The study is carried on a brain cancer by adopting an unsophisticated head phantom. The ionizing radiation source is an external beam of x-rays with energy range of a few tens of keV. The expected radiation dose increment due to adding the iodine is investigated by comparing the radiation in the tumor after and before adding the iodine and calculating the ratio between the two doses. Several concentrations of the contrast substance are used to quantify its impact. The change of the dose increment with the source energy is also examined. It is found that the radiation elevation in the tumor tends to saturate with increasing the iodine concentration, and for the studied domain of energies (30 keV-100 keV), the radiation dose enhancement factors (RDEF) for the different iodine concentrations (1%-9%) show peaked curves, with the peak occurring between 60 keV and 70 keV. For the highest concentration studied, 9%, the peak value is almost 7.

• Asian-Australasian Journal of Animal Sciences
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• 제18권11호
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• pp.1557-1563
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• 2005

Ovarian follicular fluid contains both stimulatory and inhibitory agents that influence the growth and maturation of oocyte. In the present study, an attempt was made to isolate and study the biological properties of ovarian follicular fluid peptide(s) in buffaloes. Bubaline ovarian follicular was made steroid- and cell-free. A protein fraction was obtained by saturation (30-35% level) of the follicular fluid with ammonium sulfate. The protein fraction was purified with Sephadex-G 50 gel filtration chromatography and a single peak was obtained in the eluant volume, which was lyophilized. SDS-PAGE of the lyophilized fraction revealed a single band and the molecular weight of the peptide was 26.6 kDa. The peptide stimulated the cumulus cell expansion and in vitro maturation rate of oocytes in buffaloes in a dose dependent manner when it was incorporated at different dose levels (0, 10, 25, 50, 100 and 1,000 ng $ml^{-1}$ of maturation medium). The basic culture medium consisted of TCM 199 with Bovine serum albumin (0.3%). The in vitro maturation rates were comparable to those obtained with a positive control medium (TCM 199+20 ng EGF $ml^{-1}$+steer serum (20%)). Further purification and biological assays may throw more light on the nature and functions of this peptide.