A pseudo-cyclic instrumental neutron activation analysis method in conjunction with anti-coincidence gamma-ray spectrometry
(PC-INAA-AC) has been developed for the determination of ppb levels of Se. The method consists of repetitions of the irradiation-decay-counting
cycles of a sample using the rapid transfer cyclic system at the Dalhousie University SLOWPOKE-2 reactor facility. The 162-keV
γ-ray of 77mSe (t1/2 = 17.4 s) has been found to be highly selective. The precision and detection limits are significantly improved and the total
experimental time drastically reduced by this method. Detection limits are between 2 and 9 ng. The accuracy of the method
has been evaluated by analyzing a number of nutritional reference materials. The PC-INAA-AC method has been applied for the
routine determination of Se to the composites of 135 food samples with values ranging from as low as 1 ng g−1 for tea to 1,045 ng g−1 for organ meats on fresh weight basis.
By applying the Skorohod martingale embedding method, a strong approximation theorem for partial sums of asymptotically negatively
dependent (AND) Gaussian sequences, under polynomial decay rates, is established. As applications, the law of the iterated
logarithm, the Chung-type law of the iterated logarithm and the almost sure central limit theorem for AND Gaussian sequences
To separate minor actinides from HLLW by extraction chromatography, a few novel silica-based di(2-ethylhexyl)phosphoric acid (HDEHP), 4,4¢,(5¢)-di(tert-butylcyclohexano)-18-crown-6 (DtBuCH18C6), octyl(phenyl)-N,N-diisobutylcarbamoylmethylphosphine oxide (CMPO), and N,N,N¢,N¢-tetraoctyl-3-oxapentane-1,5-diamide (TODGA) polymeric adsorption materials (HDEHP/SiO2-P, DtBuCH18C6/SiO2-P, CMPO/SiO2-P, and TODGA/SiO2-P) were synthesized by impregnating HDEHP, DtBuCH18C6, CMPO, and TODGA into the pores of porous SiO2-P particles, which were the new kind of inorganic/organic composites consisted of macroporous SiO2 and copolymer. The bleeding behavior of these composites was investigated by examining the effect of contact time and HNO3 concentration. It was found that in the tested HNO3 concentration range, a noticeable quantity of DtBuCH18C6, at least 600 ppm, leaked out from DtBuCH18C6/SiO2-P because of the protonation of DtBuCH18C6 with hydrogen ion, while the others were lower and basically equivalent to the solubility of HDEHP, CMPO, or TODGA in corresponding acidities solutions. Based on the batch experiment, the bleeding of CMPO/SiO2-P and TODGA/SiO2-P, the main adsorbents used in MAREC process for HLLW partitioning, was evaluated by column operation in 0.01M HNO3 and 3M HNO3. The quantity of CMPO leaked was ~48 ppm in 0.01M HNO3 and ~37 ppm in 3.0M HNO3. The bleeding of TODGA decreased from 23.2 ppm to 7.27 ppm at the initial stage and then basically kept constant. An actual bleeding of TODGA was evaluated by the separation of Sr(II) from a 2.0M HNO3 solution containing 5.0 . 10-3M of 6 typically simulated elements.
In order to investigate imaging properties of various magnetotelluric interpretation parameters over complicated models, we carried out numerical model calculations, where the models contained a 3D near-surface (``shallow") part and a 3D or 2D deep part. Various alternatively defined magnetotelluric responses, all of them based on rotational invariants of the magnetotelluric impedance tensor were considered. Then we calculated correlation coefficients between all these MT responses, and the characteristic geometrical parameters of the subsurface models, considered as a composition of “shallow+deep” elements.A systematic behaviour, similar to that had been observed in 1D situation was found: det(ReZ), Re det(Z) based apparent resistivity has the largest depth of investigation and the best lateral resolution. Furthermore, besides the phase, the Re det(Z) (a twin-parameter of the phase) seems to give the most direct response about deep structures. In presence of 3D near-surface inhomogeneities the most surprising result is that there are narrow period windows, where the deep model can be directly seen in the Re det(Z) and in the phase responses.
Authors:M. L. Zhang, M. L. Zhang, M. L. Zhang, A. Ren, A. Ren, A. Ren, D. Shao, D. Shao, D. Shao, X. Wang, X. Wang, and X. Wang
The sorption and desorption of radionuclide 90Sr2+were investigated on untreated calcareous soil and two treated soils to remove organic matter and calcium carbonate using
batch technique. The experiments were carried out at ambient condition, pH 7.8±0.1 and in the presence of 0.001M NaCl. Effects
of fulvic acid and ionic strength on the sorption of 90Sr2+on calcareous soil were also studied. It was found that the sorption isotherms are linear in the strontium concentration range
used herein, and the sorption of 90Sr2+on the calcareous soil can be described as a reversible sorption process and the sorption mechanism is mainly ion-exchange.
The sorption is dependent on ionic strength, and fulvic acid enhances the sorption of 90Sr2+on calcareous soil. Organic matter present in the calcareous soil is a significant trap of 90Sr2+and is responsible for the sorption.
Authors:J. Ji, J. Wang, Q. Zheng, J. Li, Z. Wang, X. Zhang, and A. Zhang
The introgressed alien chromosome in BC
progeny of the cross between common wheat (
Agropyron elongatum (Host) (2n=7X=70)
(Popd.) Barkworth & D.R. Dewey] was determined by genomic
hybridization (GISH), fluorescence
hybridization (FISH), using genomic DNA from
as a probe in GISH and repeat sequence pAs1, pSc119.2 as probes in FISH, and molecular marker techniques. The results revealed that the line was a chromosome additional line in which a pair of the chromosomes added was composed of chromosome segment from E-genome of
and short arm of 5B of common wheat cultivar Gao 38 identified by E-genome-specific primers. Powdery mildew test showed the line was highly resistant to powdery mildew as its
parent and this indicated that the gene of resistant to powdery mildew might come from
and localized on E-genome.
Authors:S. Landsberger, P. Zhang, D. Wu, and A. Chatt
During the past decade we have determined the concentrations of a variety of trace elements in the Arctic aerosol by using themal and epithemal neutron activation analysis (NAA). More recently we have employed Compton suppression NAA to lower the detection limits for radionuclides that are characteristic of single or mainly single gamma-ray emission. Using these various methods, we have been able to use elements such as indium and silicon. Furthermore we have achieved extremely low detection limits for iodine, arsenic and antimony. The usefulness of these NAA methods are discussed in a large sampling program that incorporates more than one thousand samples.
The Minor Actinides Recovery from HLW by Extraction Chromatography (MAREC) process was used mainly for the separation of minor
actinides (MAs) and some specific fission products (FPs) from highly active liquid waste (HLW) by the composite CMPO/SiO2-P of the macroporous silica based polymeric octyl(phenyl)-N,N-diisobutylcarbamoylmethylphoshine oxide (CMPO) and others.
In this study a cascade of chromatographic separation was performed on a 3.0M HNO3 solution containing 5.0 . 10-3M of 13 elements, at 323 K. The cascade consisted of three columns the first and second ones were packed with CMPO/SiO2-P and the third with SiO2-P particles. The first column was employed to prepare various eluents containing saturated CMPO. The second column was used
for separation into groups. The CMPO of CMPO/SiO2-P was recovered from the effluent by the third column and a CMPO-free effluent containing minor actinides was obtained. The
elements contained in the simulated HLW of 3.0M HNO3 were separated into (1) a non-adsorption group (Sr, Cs, and Ru etc.), (2) a MA-hRE (heavy rare earth)-Mo-Zr group, and (3) a lRE (light rare earth) group by eluting with 3.0M HNO3, 0.05M DTPA (diethylenetriaminepentaacetic acid) (pH 2.0) and HNO3 (pH 3.5), respectively. The resultant MA-hRE-Mo-Zr mixture containing minor actinides was then separated into the groups (1) Pd-Ru, (2) MA-hRE, and (3) Mo-Zr by utilizing 3.0M HNO3, distilled water, and 0.05M DTPA (pH 2.0) as eluents. More than 92% of CMPO in the MA-hRE containing effluent was adsorbed by SiO2-P particles. The effectivity and technical feasibility of MAREC process were demonstrated.