The disintegration of four radionuclides undergoing electron-capture decay was followed for one to ten half-lives. Least-squares analyses of the gamma-ray counting data using non-linear Taylor differential correction yielded the following half-lives: 7Be, 53.42±0.01 days; 54Mn, 312.6±0.5 days; 83Rb, 86.2±0.1 days and 84Rb, 33.1±0.1 days. These values are consistent with literature data, with comparable or much better precision than most previous determinations.
Sixteen minor and trace element contents of diet samples collected from the Pratas islanders were determined using instrumental neutron activation analysis. Samples were prepared by the duplicate portion technique, collecting during a 3-day period in winter. Dry weight elemental concentrations and daily dietary intake by islanders are compared with those taken by urban population living in Taiwan, resulting in higher intake of most elements. In addition, concentration of natural radionuclides and artificial fallout in daily diet were determined by means of -spectroscopy; the annual intake of radioactivity was evaluated and compared with those in population of neighboring Taiwan and South China. Features of the elemental concentration and radioactive concentration in the diet are discussed.
By means of nuclear analyses the concentrations of Au, Ag, Cu, Ir, Os, Pt, Co and Hg were measured in the 12 artifacts of
the gold hoard discovered in 1837 at Pietroasa, Buzäu county in Romania. The concentrations of the first four elements were
used to compare different stylistic groups assumed by historians. Comparisons with gold nuggets from the old Dacian territory
and gold Roman imperial coins were also made. A good agreement was found with the oldest hypothesis which considers that the
hoard is represented by three styles appropriated mainly by the Goths.
The radionuclide concentration in environmental samples and radiation level on Pratas Island are measured prior to the commercial operation of Da-Ya Bay Nuclear Power Plant nearby. Except for some minute amount of60Co and157Cs, radiation background is mainly from naturally occurring radionuclides. Automatic radiation surveillance and a routine sampling program on Pratas Island are essential to provide early warning for Taiwan in case of nuclear emergency.
The molar heat capacities
of the pure samples of acetone and methanol, and the azeotropic mixture composed
of acetone and methanol were measured with an adiabatic calorimeter in the
temperature range 78–320 K. The solid–solid and solid–liquid
phase transitions of the pure samples and the mixture were determined based
on the curve of the heat capacity with respect to temperature. The phase transitions
took place at 126.160.68 and 178.961.47 K for the sample of
acetone, 157.790.95 and 175.930.95 K for methanol, which were
corresponding to the solid–solid and the solid–liquid phase transitions
of the acetone and the methanol, respectively. And the phase transitions occurred
at 126.580.24, 157.160.42, 175.500.46 and 179.740.89
K corresponding to the solid–solid and the solid–liquid phase
transitions of the acetone and the methanol in the mixture, respectively.
The thermodynamic functions and the excess thermodynamic functions of the
mixture relative to standard temperature 298.15 K were derived based on the
relationships of the thermodynamic functions and the function of the measured
heat capacity with respect to temperature.
2CaO·3B2O3·H2O which has non-linear optical (NLO) property was synthesized under hydrothermal condition and identified by XRD, FTIR and
TG as well as by chemical analysis. The molar enthalpy of solution of 2CaO·3B2O3·H2O in HCl·54.572H2O was determined. From a combination of this result with measured enthalpies of solution of H3BO3 in HCl·54.501H2O and of CaO in (HCl+H3BO3) solution, together with the standard molar enthalpies of formation of CaO(s), H3BO3(s), and H2O(l), the standard molar enthalpy of formation of −(5733.7±5.2) kJ mol−1 of 2CaO·3B2O3·H2O was obtained. Thermodynamic properties of this compound were also calculated by a group contribution method.
The concentrations of hydrogen peroxide formed in the coolant due to radiolysis were studied during THOR operation at 1 MW. The relation between doses and hydrogen peroxide formation in a neutron-gamma mixed field was investigated. The initial concentration was 2.3×10–5 g/ml at the beginning of reactor operation, and then it was increased rather rapidly at the first 9 h. The increasing rate was slowed down till the end of 30 h operation. The maximum concentration of hydrogen peroxide was found to be 4.7×10–5 g/ml, and its decrease followed the exponential curve.