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- Author or Editor: T. H. Kim x
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Abstract
Radioaactive samples in cylindrical beakers have been measured using a high purity Ge spectrometer. Self-attenuation effects at various densities of the radioactive samples filled in cylindrical beakers were studied by experimenal and theoretical methods. Coincidence summing effects for specific nuclides were also determined from the measurements of full-energy peak efficiencies in a given source-to-detector geometry.
Abstract
Monochromatic MeV-energy neutron source for secondary reaction was developed utilizing tritium embedded titanium (Ti-3H) thin film via 3H(p,n)3He reaction. We have measured the neutron energies and the energy spread by resonance reactions of 12C(n,tot) and 28Si(n,tot). The available energy was within the range from 0.6 to 2.6 MeV. Energy spread was 1.6% at energy of 2.077 MeV. The flux in the beam direction was determined to be 3.76·107 n/s/sr by irradiating 197Au by about 2 MeV neutrons. This source was shown to be useful for measurements of nuclear data by measuring the total cross sections of neutrons on Fe and comparing these data to the data of ENDF-6.
Summary In this study, the thermal properties of agro-flour-filled polybutylene succinate (PBS) bio-composites were investigated. PBS is one of the biodegradable polymers made from the condensation reaction of glycols and dicarboxylic acid and is naturally degraded by natural soil burial system. The thermal properties of the bio-composites were analyzed according to the agro-flour content and mesh size. On increasing agro-flour content, the thermal stability, degradation temperature and derivative thermogravimetric curve (DTGmax) temperature of the bio-composites decreased while the ash content increased. The thermal degradation of the bio-composites was not affected by agro-flour mesh size. The glass transition (T g) and melting (T m) temperatures of the bio-composites were not significantly changed. The storage modulus (E’) of the bio-composites was higher than that of neat PBS, because the incorporation of agro-flour increased the stiffness of the bio-composites. At higher temperatures, E’ of the bio-composites decreased due to the increasing viscosity and chain mobility of neat PBS. The thermal properties of bio-composites have an important effect on the manufacturing system and application methods.
Abstract
Neutron capture cross sections on 63Cu and 186W were measured by fast neutron activation method at neutron energies from 1 to 2 MeV. Monoenergetic fast neutrons were produced by 3H(p,n)3He reaction. Neutron energy spread by target thickness, which was assumed to be the main factor of neutron energy spread, was estimated to be 1.5% at neutron energy of 2.077 MeV. Neutron capture cross sections on 63Cu and 186W were calculated by reference comparison method on those of 197Au(n,γ). Not only statistical errors of gamma-counts from samples but also systematic errors in the counting efficiency for HP Ge detector and the uncertainty of areal density of samples were considered in calculating neutron capture cross section. Estimated neutron capture cross sections on 63Cu and 186W were also compared with ENDF-6 data.
A simple, rapid, and sensitive liquid chromatography–tandem mass spectrometry (LC–MS/MS) method was developed and validated for the determination of zinc pyrithione (ZnPT) and pyrithione (PT) in shampoos. The method consisted of a liquid–liquid extraction for sample preparation. The mass spectrometer was operated in multiple reaction monitoring (MRM) mode via the positive electrospray ionization interface. A linear regression (weighted 1/x) was used to fit calibration curves over the concentration range of 50–2000 ng/mL for both ZnPT and PT. Excellent linearity (r 2 ≥ 0.9996) was achieved for all. The method was validated and found to be accurate (95.9–108.2% for ZnPT and 94.9–110.4% for PT), precise, and selective. Analytes in shampoos were found to be stable in the autosampler (6 °C for 6 h), in room temperature (for 6 h), and after three freeze–thaw cycles, and recovery of analytes was reproducible (90.8–94.6% for ZnPT and 90.2–96.3% for PT).
Summary
Capsaicin has been reported to exhibit an inhibitory effect on the P-glycoprotein (P-gp) function in vitro. To investigate its concentration-dependent effect in vivo, a sensitive assay that can characterize the absorption and disposition of capsaicin needs to be developed. This study reports the development of a sensitive LC-MS/MS assay for the determination of capsaicin in mouse plasma. The sample pretreatment involved a one-step extraction of 20 μL plasma with t-butyl methyl ether. Separations were achieved on a C18 column and the detection was performed on an LC-ESI-MS/MS by multiple reaction monitoring. The assay was linear over a wide concentration range from 0.325 to 650 ng mL−1 (r > 0.999), with a LLOQ of 0.325 ng mL−1. The developed method was applied to i.v. (dose 0.325 and 0.65 mg kg) and oral absorption (dose 40 mg kg) studies in mice. After i.v. injection, the t 1/2,λz, V z and CL s ranged from 0.13–0.16 h, 127.6–141.8 mL, and 547.3–775.4 mL/h, respectively. After oral administration, a secondary peak was observed and the terminal half-life was prolonged (1.51 h). Capsaicin was poorly absorbed, with the absolute oral bioavailability (F) ranging from 1.02% to 1.56%. The developed assay may be useful in studies where sample volumes are limited.
This study was aimed at evaluating the efficacy of different mineral separation procedures to validate the EN1788 (2001) European Union standard protocol for better identification of irradiated fish and shellfish. The silicate minerals were isolated with physical density separation method from two types of non-irradiated freeze-dried fish and shellfish that included Pacific saury (Cololabis saira), mackerel (Scomber japonicus), shrimp (Penaeidae metapenaeus), and mussel (Mytilus coruscus). Radiation-specific thermoluminescence (TL) peaks (glow curve 1) were observed between 150–250 °C. The peaks are typical for the irradiated food; despite the samples being not irradiated. Apparently it showed that the isolated minerals were contaminated with organic materials such as bone, etc. Acid-hydrolysis digestion was employed to remove the possible contaminants. The minerals obtained through alternative pre-treatment showed no TL curves in radiation specific temperature range. Moreover, acid hydrolysis extraction resulted in producing higher mineral yields and lower background luminescence. Results were also confirmed by calculating TL ratios (glow curve 1/glow curve 2) to confirm the irradiation history of samples. Furthermore, different time and temperature treatments on TL intensity of irradiated standard quartz (SiO2) minerals showed that the acid-hydrolysis can be adjusted to 50 °C and 3 h for better luminescence determinations.
Abstract
Zinc isotope separation was studied by column chromatographies using resorcinol-formaldehyde-resin grafted with benzo-15-crown-5 in the porous silica beads. Chromatography was performed in a break-through manner by feeding the acetone solution of zinc chloride into the columns. Zinc isotopic abundance ratios of 66Zn/64Zn and 68Zn/64Zn were measured by ICP-MS. It has been found that the heavier isotopes are preferentially enriched at the front boundary region. This result proves 64Zn depleted zinc can be obtained by collecting the effluents of front boundary region. The separation coefficient (ɛ) observed by five meters migration treatment is 0.81 · 10−3 for the isotopic pair of 68Zn/64Zn at 25 °C and higher separation coefficient was obtained from more concentrated zinc chloride solution.
To solve a geophysical inverse problem means applying measurements to determine the parameters of the selected model. The inverse problem is formulated as the Bayesian inference. The Gaussian probability density functions are applied in the Bayes's equation. The CHAMP satellite gravity data are determined at the altitude of 400 km altitude over the South part of the Pannonian Basin. The model of interpretation is the right vertical cylinder. The parameters of the model are obtained from the minimum problem solved by the Simplex method.
Abstract
A macroporous silica-based supramolecular recognition absorbent (Calix[4] + Dodecanol)/SiO2–P, was prepared by successive impregnation and fixing the 1,3-[(2,4-diethylheptylethoxy)oxy]-2,4-crown-6-Calix[4]arene (Calix[4]arene-R14) and its molecule modifier 1-Dodecanol onto SiO2 silica-based polymer support. The characterization of (Calix[4] + Dodecanol)/SiO2–P was examined by thermal gravimetry and differential thermal analysis and electron probe microanalysis. Relatively large separation factors of Cs and other metal ions (α Cs/M n+ ) above 60 were obtained in the presence of 3 M HNO3. The adsorption data of Cs(I) fitted well with Langmuir isotherm and the maximum adsorption capacity was estimated to be 0.19 mmol g−1. The Cs(I) in 3 M HNO3 were also effectively adsorption on (Calix[4] + Dodecanol)/SiO2–P in the column operation, and the loaded Cs(I) was successfully eluted with an eluent of H2O. The column packed with (Calix[4] + Dodecanol)/SiO2–P had excellent reusability after three cycles.
