• Natural Product Sciences
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• v.20 no.1
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• pp.39-43
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• 2014

Papenfussiella kuromo (PK) is a marine plant and an abundant ecological resource for the future; it is found in almost 80% of the terrestrial biosphere. The aim of this study was to investigate the antibacterial activity of PK against methicillin-resistant Staphylococcus aureus (MRSA), multidrug-resistant pathogen. The minimum inhibitory concentrations (MICs) of PK hexane fraction (PKH) against 7 strains of MRSA ranged from 1.0 to 2.0 mg/mL. In the checkerboard dilution method, a synergistic effect of the PKH and the antibiotics (oxacillin and norfloxacin) was seen. PKH markedly reduced the MIC of each of the 4 antibiotics against MRSA. The time-kill assay showed that the synergistic activity of PKH and an antibiotic reduced the bacterial counts below the lowest detectable limit after 24 h. These findings suggest that PKH has antibacterial activity, and may be important baseline data in future extensive studies of living marine resources as a source of compounds active against MRSA.

• Nuclear Engineering and Technology
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• v.49 no.8
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• pp.1752-1757
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• 2017

The aim of this study is to evaluate the radioactivity levels and radiological impacts of representative black sand samples collected from different locations in the Rashid area, Egypt. These samples were prepared and then analyzed using the high-resolution gamma ray spectroscopy technique with a high-purity germanium detector. The activity concentration ($A_c$), minimum detectable activity, absorbed gamma dose rate, external hazard index ($H_{ex}$), annual effective dose rate equivalent, radium equivalent, as well as external and internal hazard index ($H_{ex}$ and $H_{in}$, respectively) were estimated based on the measured radionuclide concentration of the $^{238}U$($^{226}Ra$) and $^{232}Th$ decay chains and $^{40}K$. The activity concentrations of the $^{238}U$, $^{232}Th$ decay series and $^{40}K$ of these samples varied from $45.11{\pm}3.1Bq/kg$ to $252.38{\pm}34.3Bq/kg$, from $64.65{\pm}6.1Bq/kg$ to $579.84{\pm}53.1Bq/kg$, and from $403.36{\pm}20.8Bq/kg$ to $527.47{\pm}23.1Bq/kg$, respectively. The activity concentration of $^{232}Th$ in Sample 1 has the highest value compared to the other samples; this value is also higher than the worldwide mean range as reported by UNSCEAR 2000. The total absorbed gamma dose rate and the annual effective dose for these samples were found to vary from 81.19 nGy/h to 497.81 nGy/h and from $99.86{\mu}Sv/y$ to $612.31{\mu}Sv/y$, which are higher than the world average values of 59 nGy/h and $70{\mu}Sv/y$, respectively. The $H_{ex}$ values were also calculated to be 3.02, 0.47, 0.63, 0.87, 0.87, 0.51 and 0.91. It was found that the calculated value of $H_{ex}$ for Sample 1 is significantly higher than the international acceptable limit of <1. The results are tabulated, depicted, and discussed within national and international frameworks, levels, and approaches.

• Biotechnology and Bioprocess Engineering:BBE
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• v.5 no.6
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• pp.418-421
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• 2000

A new direct colorimetric assay of microcystin in water and algal samples is proposed consisting of two procedures as follows: 1) the elimination of phosphorus in the sample and concentration of microcystin using a C(sub)18 cartridge, 2) the detection of the released phosphorus by the ascorbic acid method and determination of protein phosphatase (PP) inhibition by microcystin. The optimum amounts of phosphorylase ${\alpha}$ and PP-1 in 50 ${\mu}$L concentrated sample were 50$\mu\textrm{g}$/50${\mu}$L buffer and 1.0unit/50${\mu}$L buffer, respectively, for the best assay. The pH for the maximum activity of PP-1 was 8. The minimum detectable concentration for this method was about 0.02$\mu\textrm{g}$/L, which is sufficient to meet the proposed guideline level of 1$\mu\textrm{g}$ microcystin/L in drinking water. Consequently, it would seem that the proposed direct colorimetric assay using PP is a rapid, easy, and convenient method for the detection of microcystin in water and algal samples.

• Journal of Microbiology and Biotechnology
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• v.13 no.6
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• pp.853-858
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• 2003

Helicobacter pylori specifically adhere to host cells through a number of putative receptors and ligands, mainly based on carbohydrate-protein interactions. Polysaccharide fractions isolated from the leaves of Artemisia capillaris showed different inhibitory activities against H. pylori adhesion by using hemagglutination assay. Among these fractions, an acidic polysaccharide fraction FlA showed highly effective inhibitory activity, and its minimum inhibition concentration was 0.63 mg/ml. The inhibition results by the hemagglutination assay were consistent with those obtained by the enzymelinked glycosorbent assay, which was developed by the conjugation of horseradish peroxidase with fetuin, a sialic acid-containing glycoprotein which was specific to H. pylori adhesion. FlA contained the highest carbohydrate content among polysaccharide fractions, and no protein was detectable when further purified by gel filtration FPLC. Sugar composition analysis using GC revealed the highest amount of galacturonic acid among sugars, which suggests that FlA contains essentially acidic polysaccharides. Our data suggest that acidic polysaccharides may play an important role in the inhibition of H. pylori adhesion to host cells.

• Journal of the Korean Society of Radiology
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• v.5 no.1
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• pp.5-10
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• 2011

Based on basic concept of detection limit, sample measurement time & background measurement time was considered, and MDA values according to background measurement time and sample measurement time in land samples(river soil, surface soil, drinking water, underground water, surface water, pine leaf, mugwort) analysis among environmental samples were compared. Seeing the water sample analysis result, it was shown that most of the samples were not detected, and most of the samples in land specimen analysis showed to be below the detection limit of "Ministry of Education, Science and Technology Announcement Je-2008-28-ho", but $^{137}Cs$ which is one of artificial radioactive nuclide was detected in some samples. It can be traced back to 1950s and 1960s when nuclear tests were carried out in atmosphere and catastrophic Chernobyl atomic power station accident that caused fallouts in the sky, and this is common level of detection that can be observed worldwide. Seeing the result that the $^{134}Cs$(which is a isotope of $^{137}Cs$, and it has relatively short half life) was not detected in all samples, it can be considered it doesn't affect to the operation of atomic power station.

• Journal of the Korean Society of Radiology
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• v.6 no.1
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• pp.79-82
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• 2012

Iodine is one of important nuclides to be checked for radiation exposure after nuclear power facility accidents. After Chernobyl accident, it was observed that there is a greater amount of organic iodine in the atmosphere than inorganic iodine. In this study, we not only varied the amount of sample being exposed to $^{131}I$ and the duration of exposure to $^{131}I$ but also diluted the sample in distilled water and mixed the sample in kelp and liquid $^{131}I$ to measure and analyze the radiation detection levels. We concluded that the radiation levels were not high enough to be harmful to human body. The radiation from $^{131}I$ decreased over time, and we calculated the half life at 7-9 days. We found that the radiation from any sample containing $^{131}I$ was halved by up to 7days.

• Nuclear Engineering and Technology
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• v.52 no.10
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• pp.2361-2369
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• 2020

Compton cameras using large scintillators have been developed for high imaging sensitivity. These scintillator-based Compton cameras, however, mainly due to relatively low energy resolution, suffer from undesired background-radiation signals, especially when radioactive materials' activity is very low or their location is far from the Compton camera. To alleviate this problem for a large-size Compton camera, in the present study, a hybrid-type shielding system was designed that combines an active shield with a veto detector and a passive shield that surrounds the active shield. Then, the performance of the hybrid shielding system was predicted, by Monte Carlo radiation transport simulation using Geant4, in terms of minimum detectable activity (MDA), signal-to-noise ratio (SNR), and image resolution. Our simulation results show that, for the most cases, the hybrid shielding system significantly improves the performance of the large-size Compton camera. For the cases investigated in the present study, the use of the shielding system decreased the MDA by about 1.4, 1.6, and 1.3 times, increased the SNR by 1.2-1.9, 1.1-1.7, and 1.3-2.1 times, and improved the image resolution (i.e., reduced the FWHM) by 7-8, 1-6, and 3-5% for ¹³⁷Cs, ⁶⁰Co, and ¹³¹I point source located at 1-5 m from the imaging system, respectively.

• Nuclear Engineering and Technology
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• v.53 no.4
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• pp.1210-1217
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• 2021

The analysis of ⁴¹Ca in concrete generated from the nuclear facilities decommissioning is critical for ensuring the safe management of radioactive waste. An analytical method for the determination of ⁴¹Ca in concrete is described. ⁴¹Ca is a neutron-activated long radionuclide, and hence, for accurate analysis, it is necessary to completely extract Ca from the concrete sample where it exists as the predominant element. The decomposition methods employed were the acid leaching, microwave digestion, and alkali fusion. A comparison of the results indicated that the alkali fusion is the most suitable way for the separation of Ca from the concrete sample. Several processes of hydroxide and carbonate precipitation were employed to separate ⁴¹Ca from interferences. The method relies on the differences in the solubility of the generated products. The behavior of Ca and the interfering elements such as Fe, Ni, Co, Eu, Ba, and Sr is examined at each separation step. The purified ⁴¹Ca was measured by a liquid scintillation counter, and the quench curve and counting efficiency were determined by using a certified reference material of known ⁴¹Ca activity. The recoveries in this study ranged from 56 to 68%, and the minimum detectable activity was 50 mBq g^-1 with 0.5 g of concrete sample.

• Economic and Environmental Geology
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• v.38 no.6 s.175
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• pp.689-697
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• 2005

Mineralogical composition, $^{137}Cs$ activity, total organic carbon (TOC), and particle size of marine sediments near Wuljin Nuclear Powerplant were analyzed and the relationships among those components were investigated. The particle sizes of sediments were equivalent to sand size and in the range of $-0.48\~3.6\;Md\phi$. TOC contents and $^{137}Cs$ activities were in the range of $0.06\~1.75\%$ and minimum detectable activity (MDA) $\~4.0Bq/kg-dry$ with the average value of $1.15{\pm}0.62$ Bq/kg-dry, respectively. The sediments in study area were characterized by large particle size and small TOC contents, and $^{137}Cs$ activity compared with other marine sediments. The main mineral components were quartz and feldspar (albite, microcline, and small amount of orthoclase) with small amount of pyroxene, calcite, hornblende. Minerals with $10{\AA}$ XRD peak (mainly biotite) and chlorite were also identified. Among those minerals, biotite shows the linear relationship with $^{137}Cs$ content probably due to the frayed edge site (FES) on biotite or small amount of mixed illite. However, TOC content shows most linear relationship with $^{137}Cs$ content because no significant amount of clay minerals, which can adsorb significant amount of Cs, were observed in the study area, indicating that the distribution of $^{137}Cs$ in this study area was more significantly affected by the TOC content than mineral composition.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.9 no.3
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• pp.141-148
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• 2011

It is clarified in the radioactive waste transfer regulation that the concentration of radioactive waste for the major radio nuclide has to be examined when radioactive waste is guided to the radioactive waste stores. In case of the low level radioactive waste sample, the analytical results of radioactive waste concentration frequently show a value lower than minimum detectable activity (MDA). Since the MDA value basically depends on the amount of a sample, background value, measurement time, counting efficiency, and etc, it would be necessary to increase a sample amount with a intention of minimizing MDA. In order to measure a concentration of $^{129}I$ in low and medium level radioactive waste, $^{129}I$ was collected by using a distillation technique after leaching the simulated radioactive waste sample with a non-volatile acid. The recovery of $^{129}I$ measured was compared with that measured with column elution technique which is a conventional method using an anion-exchange resin. The recovery of inactive iodide by using the distillation method and column elution were found as $86.5{\pm}0.9%$ and $87.3{\pm}2.7%$, respectively. The recovery and MDA value calculated for distillation technique when 100 g of extracted solution of $^{129}I$ was taken, were found to be $84.6{\pm}1.6%$ and $1.2{\times}10^{-4}Bq/g$, respectively. Consequently, the proposed technique with simplified process lowered the MDA value more than 10 times compared to the column elution technique that has a disadvantage of limited sampling amount.