A gas sampler with lead shield has been designed for transferring the grab gas sample taken from the sampling station of Taiwan nuclear power reactor. The methods involving gas chromatography and gamma spectrometry have been developed for the determination of fission gases. A gas chromatograph equipped with TCD was used for measurement of gas composition. Column requirements are identified and optimum operating conditions are discussed. A single analysis is completed within 25 minutes for all of the gas constitutents and 12 minutes for only Xe and Kr. The detection limit is 0.005 mm partial pressure for Kr and Xe and a precision of ±1% relative is achieved for all the sample constituents. Combined error determinations for the method denote an attainable accuracy of less than ±2% for constituents at a sample pressure above 10 mm. Mixing and dispensing of the radioactive gases were carried out in a special gas mixing line. In experiment, calibration factors for measurement of133Xe and85Kr in ampules are determined in an isotope calibrator and by Ge(Li) gamma ray spectrometry. The relative precisions of 0.14% and 0.5% are readily achieved for85Kr and133Xe, respectively. The calibration uncertainty in85Kr measurement is 0.4%.
Organic peroxides (OPs) have caused many momentous explosions and runaway reactions, resulting from thermal instability, chemical
pollutants, and even mechanical shock. In Taiwan, dicumyl peroxide (DCPO), due to its unstable reactive nature, has caused
two thermal explosions and runaway reaction incidents in the manufacturing process. To evaluate thermal hazards of DCPO in
a batch reactor, we studied thermokinetic parameters, such as heat of decomposition (†Hd), exothermic onset temperature (T0), maximum temperature rise ((dT/dt)max), maximum pressure rise ((dP/dt)max), self-heating rate (dT/dt), etc., via differential scanning calorimetry (DSC) and vent sizing package 2 (VSP2).
A detail study of distribution, host range, and seasonal pattern of western flower thrips (WFT),
(Pergande), in Yunnan Province was conducted in 2004–2006. The pest is distributed throughout the province and was found in 22 out of 25 widely spaced locations surveyed. WFT was found feeding on 45 species of vegetables, ornamentals, and weeds in the province. Seasonal pattern of WFT on vegetables planted in open field and inside greenhouses was similar and, with exception of minor local differences, did not differ from information generated elsewhere. These findings may provide some useful data for the management of this and possibly other thrips pests in Yunnan.
Pentaerythritol diphosphonate melamine-urea-formaldehyde resin salt, a novel cheap macromolecular intumescent flame retardants
(IFR), was synthesized, and its structure was a caged bicyclic macromolecule containing phosphorus characterized by IR. Epoxy
resins (EP) were modified with IFR to get the flame retardant EP, whose flammability and burning behavior were characterized
by UL 94 and limiting oxygen index (LOI). 25 mass% of IFR were doped into EP to get 27.2 of LOI and UL 94 V-0.
The thermal properties of epoxy resins containing IFR were investigated with thermogravimetry (TG) and differential thermogravimetry
(DTG). Activation energy for the decomposition of samples was obtained using Kissinger equation. The resultant data show that
for EP containing IFR, compared with EP, IFR decreased mass loss, thermal stability and Rmax, increased the char yield. The activation energy for the decomposition of EP is 230.4 kJ mol−1 while it becomes 193.8 kJ mol−1 for EP containing IFR, decreased by 36.6 kJ mol−1, which shows that IFR can catalyze decomposition and carbonization of EP.
Authors:S. Song, Y. Tao, L. Zhao, P. Liu and Y. Wu
Barley yellow dwarf virus-GAV (BYDV-GAV) is one of the most serious viruses on wheat in China. In this study, five BYDV-GAV isolates collected from five regions in Northwestern China were sequenced. The complete genome sequences generated in this study along with nine genome sequences of BYDV-GAV isolates available in GeneBank were compared and analyzed. The comparative analysis indicated that the complete genomes of BYDV-GAV showed a low level of genetic diversity with nucleotide sequence identities ranging between 97.0% and 99.7%, and the RNA-dependent RNA polymerase gene (ORF1 + ORF2) was the most variable within the complete genome. Phylogenetic analysis indicated that the BYDV-GAV isolates in Northwestern China could be divided into two groups. In addition, two potential recombination events were detected among the 14 BYDV-GAV isolates. This study provided a detailed description of molecular characterization of BYDV-GAV in Northwestern China based on the complete genome sequences, which increased the understanding of genetic diversity of barley yellow dwarf viruses.
An Al2(WO4)3 target bombarded with a proton beam (28.5 MeV, 20 A) for 1 hour was completely dissolved in about 5 ml of hot 2N NaOH and the clear solution was neutralized with 2N HCl. The resulted white precipitate of Al2(WO4)3 can be separated from the solution by centrifugation and decantation. The supematant containing radioactive Re as ReO
was loaded onto a column (1 cm×10 cm) of activated alumina (100–200 mesh). Eluted with 10 ml of saline, the carrier-free ReO
was collected, while the small amount of Al2(WO4)3 in the supematant was adsorbed on the column. The total yield of ReO
was 94.7% and the breakthrough of WO
, only 1.0·10–6 M. The whole separation process can be accomplished within 30 minutes. This rapid and efficient Re/W separation protocol is applicable to the preparation of carrier-free186Re, when an enrichel Al2(186WO4)3 target is used.
A new method was proposed for determining the most probable mechanism function of a solid phase reaction. According to Coats-Redfern's
integral equation Eβ→0 was calculated by extrapolating β to zero using a series of TG curves with different heating rates. Similarly, Eα→0 was calculated according to Ozawa's equation. The most probable mechanism function of the solid phase dehydration of manganese(II)
oxalate dihydrate was confirmed to be G(α)=(1-α)1/2 by comparing Eα→0 with Eβ→0.