• Journal of the Korean institute of surface engineering
• /
• v.39 no.5
• /
• pp.235-239
• /
• 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 $5\;{\times}\;10^{17}\;ions/cm^2$.

• Journal of radiological science and technology
• /
• v.42 no.2
• /
• pp.131-135
• /
• 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.

• Journal of the Korean Society of Radiology
• /
• v.10 no.3
• /
• pp.153-159
• /
• 2016

This study investigated relationship between secondary electrons produced from single gold nanoparticle as a result of its interaction with radiation and particle size and incidence energy, provided basic data related to the dose enhancement effect based on gold nanoparticles. Monte Carlo simulation was applied by using MCNPX MC code, 50, 100, 150 kV and 6, 15 MV x-ray energy was used. In a water phantom, single gold nanoparticles that are 30, 50, 70, 90, and 110 nm in diameter were placed and the tally volume was designated at every 10 nm. Difference in electrons produced from gold nanoparticles was normalized based on absence of nanoparticle. When the X ray energy decreased and the diameter of gold particles increased, more electrons were produced. When the energy was lower, in the linear formula related to nanoparticle size and electron production, the gradient was higher. And, in comparison to the MV X-ray, at kV X-ray, significantly more electrons were produced. This study can be used as data to understand the dose enhancement effect based on gold nanoparticles, and further research related to various materials that dose enhancement including gold nanoparticles needs to be conducted.

• Korean Journal of Environmental Agriculture
• /
• v.21 no.3
• /
• pp.202-207
• /
• 2002

To establish the seed treatment method of the gamma radiation for germination enhancement of bottle gourd(Lagenaria siceraria Standl.) and pumpkin(Cucurbita ficifolia Bouche), seeds were irradiated with the dose of 1$\sim$20 Gy of the gamma radiation. The germination rate in irradiated group was higher than that of the control, depending on seed condition. In the case of bottle gourd, the germination rate of 70$\sim$80% germinative seed was increased at 4$\sim$20 Gy irradiated groups. Especially, it was the highest at 4 Gy irradiated group. The germination rate of 80$\sim$90% germinative seed was the highest at 4 Gy irradiated group. The germination rate of 70$\sim$80% and 80$\sim$90% germinative seed at 4 days after sowing was increased 66% and 26% at 4 Gy irradiated group, respectively. In the case of pumpkin, the germination rate of 70$\sim$80% and 80$\sim$90% germinative seed was increased at 2 Gy and 8 Gy irradiated group, respectively. Effect of the low-dose gamma radiation on the early growth was enhanced depending on their germination enhancement. Especially, it was the highest at 2 Gy irradiated group of 70$\sim$80% germinative seed of pumpkin. Catalase activity of bottle gourd was increased at 4 Gy irradiated group. Catalase and peroxidase activity of pumpkin were increased at 2 Gy and 8 Gy irradiated group. These results suggest that the germination, early growth and physiological activity of bottle gourd and pumpkin seeds could be promoted by the low dose gamma radiation.

• Radiation Oncology Journal
• /
• v.12 no.3
• /
• pp.285-293
• /
• 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.

• Korean Journal of Weed Science
• /
• v.32 no.3
• /
• pp.159-169
• /
• 2012

Hormesis is a dose-response phenomenon that is characterized by low-dose stimulation and high-dose inhibition. This biphasic dose-responses have had a long and extensive history in the fields of chemical toxicology, radiation biology and pharmacology. Hormesis has been found from bacteria, fungi, plants and animals, but hormesis in plants has received relatively little attention. Thus principles, occurrence, factors affecting the expression of hormetic responses, and their mechanisms in plants induced by herbicides are reviewed to provide the potentials for crop enhancement. Bromacil, bromoxynil, chloramben, propachlor, terbacil, EPTC, MSMA, and glyphosate at low doses showed stimulatory response in growth. Subtoxic dose of glyphosate increased sucrose content in sugarcane that is used worldwide in sugarcane production. Low dose of protoporphyrinogen-inhibiting herbicides induced increased pathogen defence, and low dose of triazine herbicides improved nitrogen metabolism and increased protein content in some crops. Further researches on potential benefits and risks of hormesis and its mechanism are needed for application of crop enhancement in agriculture.

• Progress in Medical Physics
• /
• v.18 no.4
• /
• pp.221-225
• /
• 2007

Monte Carlo calculations were performed to demonstrate the dose modulation with dynamic magnetic fields in phantom. The goal of this study is to obtain the uniform dose distributions at a depth region as a target on the central axis of photon beam under moving transverse magnetic field. We have calculated the depth dose curves for two cases of moving magnetic field along a depth line, constant speed and optimal speed. We introduced step-by-step shift and time factor of the position of the electromagnet as an approximations of continuous moving. The optimal time factors as a function of magnetic field position were calculated by least square methods using depth dose data for static magnetic field. We have verified that the flat depth dose is produced by varying the speed of magnetic field as a function of position as a results of Monte Carlo calculations. For 3 T magnetic field, the dose enhancement was 10.1% in comparison to without magnetic field at the center of the target.

• Journal of Photoscience
• /
• v.9 no.2
• /
• pp.197-200
• /
• 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
• /
• v.55 no.5
• /
• pp.1671-1676
• /
• 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
• /
• v.18 no.11
• /
• pp.1557-1563
• /
• 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.