• Journal of Astronomy and Space Sciences
• /
• v.30 no.2
• /
• pp.83-85
• /
• 2013

Anomalous X-ray pulsars (AXPs) are thought to be magnetars which are young isolated neutron stars with extremely strong magnetic fields of > $10^{14}$ Gauss. Their tremendous magnetic fields inferred from the spin parameters provide a huge energy reservoir to power the observed X-ray emission. High-energy emission above 0.3 MeV has never been detected despite intensive search. Here, we present the possible Fermi Large Area Telescope (LAT) detection of ${\gamma}$-ray pulsations above 200 MeV from the AXP, 1E 2259+586, which puts the current theoretical models of ${\gamma}$-ray emission mechanisms of magnetars into challenge. We speculate that the high-energy ${\gamma}$-rays originate from the outer magnetosphere of the magnetar.

• Journal of the Korean Society of Tobacco Science
• /
• v.14 no.1
• /
• pp.12-23
• /
• 1992

This experiment was conducted to determine the optimum dosage of gamma rays for inducing artificial mutation of several mutant characters in the flue-cured tobacco. 1) In Hicks and BY 104, the gammarays irradiation has no significantly different effect on seed germination from the control. However, the average dosage for 50% growth inhibition was 25-30kr for all the varieties tested, which inhibition 46-52% and 43-57% of the seedling growths for Hicks and BY 104, respectively. 2) A mutant line 83H-5 was selected from Hicks by irradiation gamma ray at the level of 30kr. It has white flower, more resistance to bacterial wilt, Pssudomonas solanacearum, lower plant and stalk height, narrower leaf width, larger leaf shape index(lento width) and later days to flower when compared with the original variety Hicks. 3) White flower was recessive to pink flower in F, and Br (F1 X Hicks) progenies. F2 population of the cross gave segregation ratio of 3 pink flower:1 white flower, and B, (F1 X 83H-5) Population gave 1:1 ratio. Results showed that the white flower character is governed by a single recessive gene.

• Food Science and Preservation
• /
• v.7 no.1
• /
• pp.68-73
• /
• 2000

These experiments were performed to investigate the safety of two herbs-Houttuynia cordata Thunberg and Lycium chinese Miller-irradiated with gamma-rays in respect of genotoxicity. Water extracts from the 10 kGy gamma-irradiated herbs were examined in two short -term in vitro tests ; (1) Salmonella typhimurium reversion assay (Ames test) in strain TA 98 and Ta100 and (2) Micronuclues test on clutured Chinese hamster ovary(CHO) cells. No mutagenicity was detected in the two assays with or without metabolic activation . From these results , the safety of the herbs irradiated with gamma-rays at practical doses could be revealed in further tests of genotoxicity in vivo, chronic and reproductive toxicity.

• Journal of Radiation Protection and Research
• /
• v.42 no.1
• /
• pp.26-32
• /
• 2017

Background: Ionizing radiation is known to be harmful to human health. The shielding of ionizing radiation depends on the attenuation which can be achieved by three main rules, i.e. time, distance and absorbing material. Materials and Methods: The mass attenuation coefficient, linear attenuation coefficient, Half Value Layer (HVL) and Tenth Value Layer (TVL) of X-rays (32 keV, 74 keV) and gamma rays (662 keV) are measured in Barium compounds. Results and Discussion: The measured values agree well with the theory. The effective atomic numbers ($Z_{eff}$) and electron density (Ne) of Barium compounds have been computed in the wide energy region 1 keV to 100 GeV using an accurate database of photon-interaction cross sections and the WinXCom program. Conclusion: The mass attenuation coefficient and linear attenuation coefficient for $BaCO_3$ is higher than the $BaCl_2$, $Ba(No_3)_2$ and BaSO4. HVL, TVL and mean free path are lower for $BaCO_3$ than the $BaCl_2$, $Ba(No_3)_2$ and $BaSO_4$. Among the studied barium compounds, $BaCO_3$ is best material for x-ray and gamma shielding.

• Journal of Radiation Protection and Research
• /
• v.43 no.3
• /
• pp.85-96
• /
• 2018

Background: A variety of inorganic scintillators have been developed and improved for use in radiation detection and measurement, and in situ gamma-ray spectrometry in the environment remains an important area in nuclear safety. In order to verify the feasibility of promising scintillators in an actual environment, a performance test is necessary to identify gamma-ray peaks and calculate the radioactivity from their net count rates in peaks. Materials and Methods: Among commercially available scintillators, $LaBr_3(Ce)$ scintillators have so far shown the highest energy resolution when detecting and identifying gamma-rays. However, the intrinsic background of this scintillator type affects efficient application to the environment with a relatively low count rate. An algorithm to subtract the intrinsic background was consequently developed, and the in situ calibration factor at 1 m above ground level was calculated from Monte Carlo simulation in order to determine the radioactivity from the measured net count rate. Results and Discussion: The radioactivity of six natural radionuclides in the environment was evaluated from in situ gamma-ray spectrometry using an $LaBr_3(Ce)$ detector. The results were then compared with those of a portable high purity Ge (HPGe) detector with in situ object counting system (ISOCS) software at the same sites. In addition, the radioactive cesium in the ground of Jeju Island, South Korea, was determined with the same assumption of the source distribution between measurements using two detectors. Conclusion: Good agreement between both detectors was achieved in the in situ gamma-ray spectrometry of natural as well as artificial radionuclides in the ground. This means that an $LaBr_3(Ce)$ detector can produce reliable and stable results of radioactivity in the ground from the measured energy spectrum of incident gamma-rays at 1 m above the ground.

• Journal of Astronomy and Space Sciences
• /
• v.30 no.3
• /
• pp.145-152
• /
• 2013

Rotation-powered pulsars are excellent laboratories for studying particle acceleration as well as fundamental physics of strong gravity, strong magnetic fields and relativity. Particle acceleration and high-energy emission from the polar caps is expected to occur in connection with electron-positron pair cascades. I will review acceleration and gamma-ray emission from the pulsar polar cap and associated slot gap. Predictions of these models can be tested with the data set on pulsars collected by the Large Area Telescope on the Fermi Gamma-Ray Telescope over the last four years, using both detailed light curve fitting, population synthesis and phase-resolved spectroscopy.

• Electrical & Electronic Materials
• /
• v.4 no.2
• /
• pp.132-142
• /
• 1991

본 연구에서는 유기절연재료의 재방사선 재료개발을 위한다는 측면에서 두께 15[.mu.m]의 이축 연신 폴리프로필렌 필름을 시료로 선정하여 Co$^{60}$-.gamma.으로 조사시켜 온도 25-55[.deg.C], 전계 10-250[MV/m]사이에서 방사선 조사량 변화에 따른 전기전도현상을 연구하였다. 조사된 시료의 전기전도는 온도에 크게 의존하여 전계의 증가와 더불어 각기 다른 전도기구 특성을 갖는 4개의 영역으로 구분되었는데 각 영역별로 조사선량 변화에 따른 하전입자들의 거동상황을 규명하고 기초적인 제 물성정수를 결정하였다.

• Journal of Distribution Science
• /
• v.16 no.2
• /
• pp.53-65
• /
• 2018

Purpose - The purpose of this study is to investigate the effect of gamma - irradiation on the effluent from food distribution in the large agricultural and marine products market. This study will contribute to the distribution process as well as the agricultural and fishery distribution facilities. Research design, data, and methodology - In order to reduce the odor, the smell was examined in the anaerobic digestion process by irradiating gamma rays to the wastewater of mixed food discharged from a large restaurant. An odor determination panel list was constructed to determine if the odor was present in the air dilution drainage and the odor concentration was analyzed by instrumental analysis. Results - It was confirmed that the sulfur content increased gradually from 3 months. Ammonia decreased from 33.57ppm at the initial measurement to 4.12 ppm at the end of the experiment. Methane production was highest at 100kGy when exposed to gamma rays of 0-200kGy at pH 12. In other words, it is considered that gamma irradiation doses are most effective at 100kGy and are suitable for large capacity wastewater treatment facilities in terms of economic feasibility. Conclusions - In pre-treatment of compound food wastewater, gamma irradiation is most cost effective when examined at 100kGy. The economic efficiency of the pre-treatment method by gamma irradiation is much higher than the wastewater treatment in the large-scale agricultural and marine products distribution market.

• Journal of the Korean Society of Radiology
• /
• v.12 no.2
• /
• pp.133-138
• /
• 2018

The measurement of gamma-ray spectrum of $^{nat}W(p,xn)$ reaction with natural tungsten were performed by using a high energy proton generated from a 100-MeV proton linear accelerator of the Korea Multi-purpose Accelerator Complex (KOMAC). Gamma rays generated by various nuclides generated through the nuclide were measured using a gamma-ray spectroscopy system composed of HPGe detector. A gamma-ray standard source was used for energy calibration and efficiency measurement of the detector. Analysis of the gamma rays observed in the measured spectra showed that the radionuclides produced were $^{167}Re$, $^{178}Re$, $^{179}Re$, $^{180}Re$, $^{181}Re$, $^{182}Re$, $^{184}Re$, $^{172}Ta$, $^{174}Ta$, $^{178}Ta$, $^{182}Ta$, $^{184}Ta$, $^{175}W$, $^{176}W$, $^{177}W$ and $^{179}W$. Nuclides were generated. The results of this study will be applied to nuclear fusion, astrophysics, and nuclear medicine applications in the future.

• Korean Journal of Veterinary Research
• /
• v.56 no.1
• /
• pp.29-35
• /
• 2016

When exposed to gamma-rays, hair follicular cells immediately go through apoptosis, which hampers their rapid differentiation essential for the regeneration of hair. Phloroglucinol (PG) is a phenolic compound of Ecklonia cava, brown algae abundant in Jeju island, Korea. Containing plentiful polyphenols, PG is known for its instructive effects by inhibiting apoptosis, scavenging oxygen radicals, and protecting cells against oxidative stress. In this study, we demonstrate that PG rescues radiosensitive hair follicular cells from gamma radiation-induced apoptosis and DNA damage. To identify protective capacity of PG on hair follicles, we irradiated with 8.5 Gy (1.5 Gy/min) of gamma-rays to the whole body of C57BL/6 mice at day 6 after depilation with or without PG. In mice exposed to radiation, the expression of proapoptotic molecule p53 was downregulated in the skin of PG treated group. On immunohistochemical observation of the skin, PG inhibited the immunoreactivity of p53 and cleaved caspase-3. PG treatment protected hair follicular cells from cell death due to gamma-radiation. Our results suggest that PG presents radioprotective effects by inhibiting apoptosis of radiosensitive hair follicular cells and can protect hair follicular cells from gamma-ray induced damage.