• Journal of Astronomy and Space Sciences
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• v.33 no.1
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• pp.1-11
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• 2016

Over the last few years, the data obtained using the Large Area Telescope (LAT) aboard the Fermi Gamma-ray Space Telescope has provided new insights on high-energy processes in globular clusters, particularly those involving compact objects such as MilliSecond Pulsars (MSPs). Gamma-ray emission in the 100 MeV to 10 GeV range has been detected from more than a dozen globular clusters in our galaxy, including 47 Tucanae and Terzan 5. Based on a sample of known gammaray globular clusters, the empirical relations between gamma-ray luminosity and properties of globular clusters such as their stellar encounter rate, metallicity, and possible optical and infrared photon energy densities, have been derived. The measured gamma-ray spectra are generally described by a power law with a cut-off at a few gigaelectronvolts. Together with the detection of pulsed γ-rays from two MSPs in two different globular clusters, such spectral signature lends support to the hypothesis that γ-rays from globular clusters represent collective curvature emission from magnetospheres of MSPs in the clusters. Alternative models, involving Inverse-Compton (IC) emission of relativistic electrons that are accelerated close to MSPs or pulsar wind nebula shocks, have also been suggested. Observations at >100 GeV by using Fermi/LAT and atmospheric Cherenkov telescopes such as H.E.S.S.-II, MAGIC-II, VERITAS, and CTA will help to settle some questions unanswered by current data.

• Journal of Plant Biotechnology
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• v.5 no.1
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• pp.51-57
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• 2003

Doubled haploids have long been recognized as a valuable tool in plant breeding since it not only offers the quickest method of advancing heterozygous breeding lines to homozygosity, but also increased the selection efficiency over conventional procedures due to better discrimination between genotypes within any one generation. Salt tolerant mutants were obtained in rice the variety, 'Hawsungbyeo', through in vitro mutagenesis of in vitro cultured anther-derived calli. Various doses (30, 50, 70 and 90 Gy) of gamma ray were applied to investigate the effect of radiation on callus formation on medium containing 1% NaCl, green plant regeneration, frequency of selected doubled haploid mutants and of the salt tolerant screen. It was demonstrated that the dose of 30 and 50 Gy gamma rays had significant effects on callus formation, regeneration and selection of salt tolerance. No tolerant lines were obtained from non-mutagenized cultures. From gamma ray irradiated cultures, five tolerant lines ($M_2$generation) at germination stage and 13 tolerant lines ($M_3$genoration) at seedling stage were obtained. The frequency of salt tolerant mutants indicates that anther culture applied in connection with gamma rays is an effective way to improve salt tolerance.

• Journal of Plant Biotechnology
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• v.46 no.2
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• pp.88-96
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• 2019

Terpenes constitute a large class of secondary metabolites in plants. The Oryza sativa terpene synthase is a vital gene in plant defense response. In this study, the molecular and physiological functions of Oryza sativa terpene synthase 30 (OsTPS30, LOC_Os08g07080) were investigated after exposure of the seeds and plants to gamma-rays. The OsTPS30 expression was slightly induced at 200 Gray (Gy), but was significantly induced at 400 Gy. The total terpenoid was synthesized more in OsTPS30-overexpressing (OX-OsTPS30) Arabidopsisthaliana plants than in wild-type (WT) plants. The OX-OsTPS30 plants exhibited resistance to gamma-rays, as compared to WT. The OX-OsTPS30 plants had significantly increased height and weight after gamma irradiation. Additionally, the activity of antioxidant enzymes was increased more in OX OsTPS30 plants than in WT plants after gamma irradiation. Furthermore, the OsTPS30-GFP fusion protein was mostly localized in the chloroplast, suggesting that OsTPS30 is putative MEP pathway-related terpene synthase.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.10
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• pp.2323-2328
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• 2012

Over the world, the development of critical technology for the safety and security of coastal distribution based on ubiquitous computing is being processed to meet the bottom lines of governmental regulations. Currently, 3D detectors using X-rays for freight search technology are being developed concerning U-based shipping security systems. In addition to that, there are increasing needs for developing portable radiation detector to detect gamma rays. The purpose of the thesis is to suggest the research of high speed portable gamma rays detector platform to prevent disorder caused to humans and public objects.

• Proceedings of the Korean Society of Medical Physics Conference
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• 2002.09a
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• pp.123-125
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• 2002

Blue light of Cherenkov radiation generated by electrons in transparent substances such as water and acrylic resin is well known generally. If students can easily observe the blue light at school, they may be impressed by the fascinating radiation. Four years ago, management of the Co-60 unit for radiotherapy was transferred to Nagoya University School of Health Sciences from a related hospital. We have examined whether or not the Cherenkov radiation in water from secondary electrons generated by Co-60 gamma-rays can be safely observed by eyes and photographs. First, the Cherenkov radiation in the water tank was led to the corridor outside the irradiation room by a mirror, and observed directly without any effect of the radiation exposure. Second, photographs of the Cherenkov radiation were taken under the conditions consisted of several irradiation fields and pass lengths of gamma-rays in water.

• Applied Chemistry for Engineering
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• v.5 no.2
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• pp.321-326
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• 1994

The water-soluble polyphosphazene possessing ether side groups was exposed to ${\gamma}-rays$ to prepare hydrogens with good water-swellability. The physical strength of these hydrogels could be controlled by irradiation dose of ${\gamma}-rays$. Trypsin and water-soluble polyphosphazene were irradiated together by ${\gamma}-rays$ for entrapment of enzymes into hydrogel networks. The activities of immobilized trypsin were examined spectrophotometrically after the reaction with N-${\alpha}$-benzoyl-1-arginine-p-nitroanilide in phosphate buffer. The immobilized trypsin was found to have good activity yield and suability after at least 500 hours.

• Polymer(Korea)
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• v.25 no.2
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• pp.270-278
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• 2001

Hydrogels for wound dressing were manufactured using poly(vinylalcohol)(PVA) and poly(N-vinylpyrrolidone)(PVP). The hydrogels were obtained by exposing to $^{60}$ Co${\gamma}$-rays after freezing and thawing of aqueous solutions of PVA and PVP to improve mechanical strength. Mechanical properties such as gelation, water absorptivity and gel strength were examined after repeating the \"freezing and thawing\" of PVA/PVP hydrogels, and then irradiating them at 40 kGy. The PVA/PVP ratio was in the range of 30:70 ~ 100:0, and the solid concentration of PVA/PVP was 20 wt%. The gelation and strength of hydrogels were much higher when \"freezing and thawing\" and the irradiation process were used than when only the irradiation process was utilized. In addition, the mechanical properties of PVA/PVP hydrogels after repetition of \"freezing and thawing\" are discussed. thawing\" are discussed.ssed.

• Nuclear Engineering and Technology
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• v.52 no.10
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• pp.2387-2393
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• 2020

In this study, a gradient material for shielding neutrons and gamma rays was developed, which consists of epoxy resin, boron carbide (B₄C), lead (Pb) and a little graphene oxide. It aims light weight and compact, which will be applied on the transportable nuclear reactor. The material is made up of sixteen layers, and the thickness and components of each layer were designed by genetic algorithm (GA) combined with Monte Carlo N Particle Transport (MCNP). In the experiment, the viscosities of the epoxy at different temperatures were tested, and the settlement regularity of Pb particles and B₄C particles in the epoxy was simulated by matlab software. The material was manufactured at 25 ℃, the Pb C and O elements of which were also tested, and the result was compared with the outcome of the simulation. Finally, the material's shielding performance was simulated by MCNP and compared with the uniformity material's. The result shows that the shielding performance of gradient material is more effective than that of the uniformity material, and the difference is most noticeable when the materials are 30 cm thick.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.12a
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• pp.87-90
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• 2006

Two SiC radiation detector samples were irradiated by Co-60 gamma rays. The irradiation was performed with dose rates of 5 kGy/hour and 15 kGy/hour for 8 hours, respectively. Metal/semiconductor contacts on the surface were fabricated by using a thermal evaporator in a high vacuum condition. The SiC detectors have metal contacts of Au(2000 ${\AA}$)/Ni(300 ${\AA}$) at Si-face and of Au(2000 ${\AA}$)/Ti(300 ${\AA}$) at C-face. I-V characteristics of the SiC semiconductor were measured by using the Keithley 4200-SCS parameter analyzer with voltage sources included. From the I-V curve, we analyzed the Schottky barrier heights(SBHs) on the basis of the thermionic emission theory. As a result, the 6H-SiC semiconductor showed- similar Schottky barrier heights independent to the dose rates of the irradiation with Co-60 gamma rays.

• Nuclear Engineering and Technology
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• v.54 no.1
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• pp.262-268
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• 2022

This paper introduces a novel concept of the pulsed neutron facility (PNF) for maximizing the production of the thermal neutrons and its application to medical use based on prompt gamma neutron activation analysis (PGNAA) using Monte Carlo simulations. The PNF consists of a compact D-T neutron generator, a graphite pile, and a detection system using Cadmium telluride (CdTe) detector arrays. The configuration of fuel pins in the graphite monolith and the design and materials for the moderating layer were studied to optimize the thermal neutron yields. Biological samples - normal and cancerous breast tissues - including chlorine, a trace element, were used to investigate the sensitivity of the characteristic γ-rays by neutron-trace material interactions and the detector responses of multiple particles. Around 90 % of neutrons emitted from a deuterium-tritium (D-T) neutron generator thermalized as they passed through the graphite stockpile. The thermal neutrons captured the chlorines in the samples, then the characteristic γ-rays with specific energy levels of 6.12, 7.80 and 8.58 MeV were emitted. Since the concentration of chlorine in the cancerous tissue is twice that in the normal tissue, the count ratio of the characteristic g-rays of the cancerous tissue over the normal tissue is approximately 2.