• Nuclear Engineering and Technology
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• 제51권3호
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• pp.860-866
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• 2019

The lead element or its salts are good radiation shielding materials. However, their toxic effects are high. Due to less toxicity of bismuth salts, the radiation shielding properties of the bismuth salts have been investigated and compared to that of lead salts to establish them as a better alternative to radiation shielding material to the lead element or its salts. The transmission geometry was utilized to measure the mass attenuation coefficient (${\mu}/{\rho}$) of different salts containing lead and bismuth using a high-resolution HPGe detector and different energies (between 81 and 1333 keV) emitted from point sources of $^{133}Ba$, $^{57}Co$, $^{22}Na$, $^{54}Mn$, $^{137}Cs$, and $^{60}Co$. The experimental ${\mu}/{\rho}$ results are compared with the theoretical values obtained through WinXCOM program. The theoretical calculations are in good agreement with their experimental ones. The radiation protection efficiencies, mean free paths, effective atomic numbers and electron densities for the present compounds were determined. The bismuth fluoride ($BiF_3$) is found to have maximum radiation protection efficiency among the selected salts. The results showed that present salts are more effective for reducing the intensity of gamma photons at low energy region.

• 한국재료학회지
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• 제18권4호
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• pp.169-174
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• 2008

The structural and electrical properties of amorphous $BaSm_2Ti_4O_{12}$ (BSmT) films on a $TiN/SiO_2/Si$ substrate deposited using a RF magnetron sputtering method were investigated. The deposition of BSmT films was carried out at $300^{\circ}C$ in a mixed oxygen and argon ($O_2$ : Ar = 1 : 4) atmosphere with a total pressure of 8.0 mTorr. In particular, a 45 nm-thick amorphous BSmT film exhibited a high capacitance density and low dissipation factor of $7.60\;fF/{\mu}m2$ and 1.3%, respectively, with a dielectric constant of 38 at 100 kHz. Its capacitance showed very little change, even in GHz ranges from 1.0 GHz to 6.0 GHz. The quality factor of the BSmT film was as high as 67 at 6 GHz. The leakage current density of the BSmT film was also very low, at approximately $5.11\;nA/cm^2$ at 2 V; its conduction mechanism was explained by the the Poole-Frenkel emission. The quadratic voltage coefficient of capacitance of the BSmT film was approximately $698\;ppm/V^2$, which is higher than the required value (<$100\;ppm/V^2$) for RF application. This could be reduced by improving the process condition. The temperature coefficient of capacitance of the film was low at nearly $296\;ppm/^{\circ}C$ at 100 kHz. Therefore, amorphous BSmT grown on a TiN substrate is a viable candidate material for a metal-insulator-metal capacitor.

• Journal of Pharmaceutical Investigation
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• 제34권3호
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• pp.161-168
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• 2004

5-Fluorouracil (5-FU) is an antimetabolite anticancer agent active against many types of solid tumors. Tegafur (TF), a prodrug of 5-FU, is frequently used in combination with uracil as dihydropyrimidine dehydrogenase (DPD) inhibitory fluoropyrimidine. We studied the stability of 5-FU and TF in biological fluids of rats and determined their bioavailability (BA) and excretion into bile, and urine. The drug concentrations were analyzed by an HPLC method. At room temperature, there was a 14-30% decrease in the concentration of 5-FU and TF in bile, urine, and plasma specimen at 10 and $100\;{\mu}g/ml$ over 240 min. No significant difference was noted among the sample types or between two different concentrations of 10 and $100{\mu}g/ml$. The decrease in drug concentration was significantly less in samples kept on ice (6-12%) for both drugs. These data indicate that biological fluid samples containing 5-FU or TF in plasma, urine, or bile should be placed on ice during the sample collection. Following these storage guidelines, samples were collected after administration 50 mg/kg of each drug via i.v. or oral route. BA was 1.5 folds greater for TF (60%) than that of 5-FU (42%). Approximately 0.52 and 3.3% of the i.v. doses of 5-FU and TF was excreted into bile, respectively. Renal clearance of 5-FU was about 16% of its total body clearance. These results suggest that instability of 5-FU and TF in biological fluids should be considered in pharmacokinetic or pharmacogenomic studies.

• Computers and Concrete
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• 제13권3호
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• pp.361-375
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• 2014

The moisture transport in underground concrete was experimentally investigated and the nonlinear model of moisture transport considering the effects of water diffusion, hydration of cementicious materials and water permeability was proposed. The consumed moisture content by self-desiccation could be firstly calculated according to evolved hydration degree of cement and mineral admixtures. Furthermore, the finite differential method was adopted to solve the moisture transport model by linearizing the nonlinear moisture diffusion coefficient. The comparison between experimental and calculated results showed a good agreement, which indicated that the proposed moisture model could be used to predict moisture content evolution in underground concrete members with drying-wetting boundaries.

• 열처리공학회지
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• 제13권4호
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• pp.217-223
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• 2000

The boronizing effects of STD 61 steel have been studied on the micro structure and hardness. The STD 61 Steel was soaked in molten salt, consisted of KCl, $BaCl_2$, NaF, $B_2O_3$, FeB, and Ce, at various temperatures and times. The boronizing conditions for the peak hardness were the temperature range of $900^{\circ}C$ to $950^{\circ}C$ for 5 hr and that of $1000^{\circ}C$ for 3 hr, respectively. Four boride layers such as FeB, $Fe_2B$, ${\alpha}$ and matrix layer surface were observed from the microscopic surface examination. The thickness of boride layer was increased by increasing the boronizing time and the temperature. The structure of boride layer was tooth shape.

• 한국동물위생학회지
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• 제42권2호
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• pp.93-112
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• 2019

Calf diarrhea is a common disease in young claves and is still a major cause of productivity and economic loss in livestock farms. Fecal samples from Korean native cattle (n=100) with diarrhea from 64 farms in Gwangju area, Korea from september 2017 to December 2018 were examined for shedding of important protozoan parasitic, viral and bacterial pathogens using culture, rapid test kit and PCR methods. Of 57 (89.1%) of the 64 Korean native cattle farms examined had samples infected with at least one of the investigated pathogens. Among 100 fecal samples, 88 samples were positive for at least one the twelve pathogens and 51 samples were simultaneously positive for two or more pathogens by culture and PCR assay. Bovine group A rotavirus (BRV) was the most common pathogen, found in 43/100 (43.0%) samples on 32/64 (50.0%) farms. Subsequently, kobuvirus (30.0%), pathogenic E. coli (29.0%), bovine parvovirus (17.0%), Giardia spp. (13.0%), Eimeria spp. (10.0%), Clostridium perfringens type A (8.0%), bovine torovirus (8.0%), bovine viral diarrhea virus (6.0%), bovine coronavirus (5.0%), bovine norovirus (2.0%) and Cryptosporidium spp. (2.0%) were detected. Nebovirus, kırklareli virus, bovine adenovirus, Salmonella spp. and intestinal parasites were not detected. Of the 72 calves sampled in this age group, 64 (88.9%) samples were positive for at least one enteropathogen. BRV was identified in 34/72 (47.2%) samples from 27/48 (56.3%) farms. Subsequently, pathogenic E. coli (30.6%), kobuvirus (29.2%), BPaV (22.2%), Giardia spp. (15.3%), Eimeria spp. (9.7%), BVDV (6.9%), Cl. perfringens type A (6.9%), BCoV (4.6%) and Cryptosporidium spp. (2.8%) were detected in fecal samples. A total of ninety-six strains of E. coli were isolated from one hundred fecal samples collected from Korean native cattle with diarrhea. The presence of stx1, stx2, eaeA, LT, STa, STb, ehxA, saa, F4, F5(K99), F6, F17, F18 and F41 genes in the isolates was investigated by PCR. Out of ninety-six E. coli isolates screened for specific genes, 30 strains E. coli were identified to harbor shiga toxin-producing E. coli (STEC) 7 (7.3%), enterohemorrhagic E. coli (EHEC) 8 (8.3%), enteropathogenic E. coli (EPEC) 6 (6.3%), enterotoxigenic E. coli (ETEC) 2 (2.1%) and STEC/ETEC hybrid 7 (7.3%). This study provides epidemiological estimates of the prevalence of Korean native cattle's enteropathogens in Gwangju area, Korea, which would be used for cattle farmers and veterinarians to select appropriate therapeutic method.

• 한국자원식물학회지
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• 제34권2호
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• pp.156-165
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• 2021

바이오에너지작물의 중요한 소재를 제공하는 화본과 식물인 홍띠(Imperata cylindrica 'Rubra')의 기내재생 식물체의 유전적 안정성을 조사하고자 생장점 부위를 기내배양하여 재분화시킨 녹색 재생식물체의 변이성을 ISSR 마커로 조사하였다. MS(Murashige and Skoog, 1962) 배지에 식물체 기부의 생장점 부위를 적출하여 캘러스를 유도하고(0.1 mg/L 2,4-D와 2 mg/L BA), 캘러스 증식(0.1 mg/L 2,4-D와 0.05 mg/L BA), 신초 재분화(0.01 mg/L NAA와 2 mg/L BA) 후 MS 배지에서 발근시켜 재분화 식물체를 유도하고 100% 활착시켰다. 대조구인 모식물체 홍띠 8개체, 1년간 노지 포장에서 재배중인 재분화 녹색 식물체 10개체와 실험실 내 화분에서 재배중인 재분화 녹색 식물체 10개체, 총 28개체에 대하여 ISSR 분석한 결과 유전적 다형성은 재분화 식물체가 실내포트 재배식물체 4.1% 및 노지 재배식물체 3.1%로 0%인 대조구보다 높게 나타났다. 또한, 총 28개체들 간의 유전적 유사도를 평가한 결과, 유전적 유사도 지수는 0.919~1.0 사이에 분포하며, 평균 0.972로 유전적 충실도가 높게 나타났다. 군집분석 결과 노지에서 재배한 재분화 식물체와 모식물체(대조군)가 독립적으로 유집되었다.

• 미생물학회지
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• 제23권3호
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• pp.177-183
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• 1985

20-80%로 황산암모늄 분획한 효소액을 사용하여 Arthrobacter sp. JH-13균주가 생산하는 세포외 cytosme deaminase의 성질을 검토하였다. 검토한 기질 중, 본 효소는 cytosine과 5- f1uorocytosine을 기질로 이용하였으며, 효소의 활성에 대한 최적 pH는 8.0부근이었고, 최적 온도는 $40^{\circ}C$부근으로 나타났다. 본 효소는 0.2M의 p potassium phosphate 완충액 (pH 8.0) 보다 0.2M의 tris-HCl 완충액 (pH 8. 0) 에서 더욱 안정하였다. 온도에 대한 안정성을 검토한 결과. $50^{\circ}C$ 부근까지는 대체로 안정하였으나, $70^{\circ}C$에서는 완전히 활성을 잃었다. 또한 ImM의 $Fe^{3+},\;K^+\;Na^+$ 이온은 효소의 활성을 증가시켰으나 0.01mM의 $Co^{2+},\;Cu^{2+},\;Ni^{2+},\;Hg^{2+},\;Ag^{2+},\;Zn^{2+},\;Ba^{2+},\;Mg^{2+}$ 이온들은 효소의 활성올 강력하게 저해하였다. O.lmM의 p-mercuribenzoate, trichloroacetic acid, N-ethylmaleim mide등은 효소의 활성을 완전히 저해하였으며. O.lmM의 2-mercaptoethanol은 효소의 활성올 약간 증가시키는 것으로 나타났다.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2007년도 하계종합학술대회 논문집
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• pp.437-438
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• 2007

In this paper a embedded decoupling capacitor design with gap structure will be discussed. A novel structure is modeling and analization by High Frequency Structure Simulator (HFSS). Proposed capacitor have $2m{\times}2m$ in rectangular shape. The film thickness of copper/dielectric film/substrate is respectively 35um/20um/35um. A dielectric layer of BaTiO3/epoxy has the relative permittivity of 25. Compare of the planar decoupling capacitor, capacitance densities of this structure in the range of $55{\mu}F$/mm2 have been obtained with 50um gap while capacitance densities of planar structure $55{\mu}F$/mm2 in the same size. The frequency dependent behavior of capacitors is numerically extracted over a wide frequency bandwidth 500MHz-7GHz. The decoupling capacitor can work at high frequency band increasing the gap size.

• Journal of Microbiology and Biotechnology
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• 제25권7호
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• pp.1070-1083
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• 2015

A gene (GT-SM3B) encoding a thermostable secreted oligoendopeptidase (GT-SM3B) was cloned from the thermophile Geobacillus thermoleovorans DSM 15325. GT-SM3B is 1,857 bp in length and encodes a single-domain protein of 618 amino acids with a 23-residue signal peptide having a calculated mass of 67.7 kDa after signal cleavage. The deduced amino acid sequence of GT-SM3B contains a conservative zinc metallopeptidase motif (His⁴⁰⁰-Glu⁴⁰¹-X-XHis⁴⁰⁴). The described oligopeptidase belongs to the M3B subfamily of metallopeptidases and displays the highest amino acid sequence identity (40.3%) to the oligopeptidase PepF_Ba from mesophilic Bacillus amyloliquefaciens 23-7A among the characterized oligopeptidases. Secretory production of GT-SM3B was used, exploiting successful oligopeptidase signal peptide recognition by Escherichia coli BL21 (DE3). The recombinant enzyme was purified from the culture fluid. Homodimerization of GT-SM3B was determined by SDS-PAGE. Both the homodimer and monomer were catalytically active within a pH range of 5.0–8.0, at pH 7.3 and 40℃, showing the K_m, V_max, and k_cat values for carbobenzoxy-Gly-Pro-Gly-Gly-Pro-Ala-OH peptidolysis to be 2.17 ± 0.04 × 10^-6 M, 2.65 ± 0.03 × 10^-3 µM/min, and 5.99 ± 0.07 s^-1, respectively. Peptidase remained stable at a broad pH range of 5.0–8.0. GT-SM3B was thermoactive, demonstrating 84% and 64% of maximum activity at 50℃ and 60℃, respectively. The recombinant oligopeptidase is one of the most thermostable M3B peptidase, retaining 71% residual activity after incubation at 60℃ for 1 h. GT-SM3B was shown to hydrolyze a collagenous peptide mixture derived from various types of collagen, but less preferentially than synthetic hexapeptide. This study is the first report on an extracellular thermostable metallo-oligopeptidase.