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Abstract  

Rare-Earth Element (REE) concentrations in briny groundwaters are very low, and range from ppb to ppt levels. REE can be measured at these low levels using prechemistry to concentrate the REE, postchemistry as an REE group separation following neutron activation, and reactivation for chemical yields. The brine solutions appear to be stable with respect to trace elements (such as the REE) over the four years of sample storage. The brine REE patterns are highly fractionated from light REE to heavy REE, including a negative Eu anomaly. The REE patterns appear to be characteristic of each formation and its source region.

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Abstract  

Current techniques for determining low levels of dissolved thorium involve chemical separations, generally by coprecipitation with a carrier cation, purification by ion exchange procedures, electroplating and, finally, alpha counting by alpha spectrometry. Similarly, measurements of low228Ra and224Ra activities requires concentration, by coprecipitation with barium sulfate, followed by gamma counting. An improved method for determining radium and thorium from the232Th decay series has been developed which measures the activity of220Rn as an assay of its parents. Although some ingrowth corrections and minor separation procedures for Th are required, the results to date show that the dynamic counting of220Rn via de-emanation and alpha counting by the alpha-scintillation method is a preferable approach for determining these radium and thorium isotopes accurately and efficiently. The method for lower limit detection depends on the emanation rate, which depends on purge-gas flow rate and sample volume analyzed. Using 50-cc and 1000-cc bubblers, and maximum effective purge gas flow rate, a lower limit of detection of 0.4 and 0.06 pCi/L220Rn can be obtained, respectively.

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Testing the ecological communities of different areas for convergence, in the sense of remarkable similarity in the characteristics of the species present, has a long history in biology. Recently, numerical methods have been developed for comparing community-level convergence to an explicit null model. No valid method has been known for testing the significance of texture convergence when the species are weighted by their abundance. Six combinations of method variants are tested on random datasets. A valid P value (i. e., with P . 0. 05 in no more than 5% of the cases) is obtained so long as for each species the distribution of abundances across sites is retained, and only the assignment of character values is randomised. Further restriction is not necessary for obtaining a valid P value, and can lead to a test with considerably lower power to detect convergence. The power of the test with free matching of character values to species is only moderate with 10 sites, though improved with larger numbers of sites. Previous methods for detecting texture convergence have examined convergence only in the mean value for any character. It is possible that the external environment might be reflected in the community mean of a character, leaving the imprint of convergence on the shape of the distribution, rather than the mean. A method for comparing the shape is described, and it is shown that the null model is valid also for this test statistic.  

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We investigated the neighbourhood-scale effect of weeding on native plants in Lance McCaskill Nature Reserve, Canterbury, New Zealand. The reserve is an unproductive basin of limestone debris. Originally set up to protect the Castle Hill buttercup, Ranunculus crithmifolius var. paucifolius , the reserve also offers protection for nationally endangered species: Myosotis colensoi and Lepidium sisymbrioides . Our aim was to investigate whether removal of introduced plants increased the cover of remaining native species. We removed introduced plants, by hand, every year for 6 years from half of the plots. We used nonparametric multivariate analysis to compare overall species cover.The results suggest that weeding does benefit the native plants in this area. There was a significant difference in the mean of the overall native species cover between the weeded and the non-weeded plots. For the ten species measured, the mean area covered per square metre was higher in the weeded plots than in the non-weeded plots in most years of the study. There was considerable variation in the data and we discuss possible reasons for this.

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Abstract

Experiments to determine the effect of surface area, head space, and containment on liquid gun propellant degradation at temperatures of 100 and 148°C were conducted. The conclusions from these tests are that an increased surface area in LP containment can significantly increase the rate of LP decomposition. The head space is not a significant factor in altering the rate of degradation, but if the gaseous products are allowed to escape, the degradation rate is significantly lowered.

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Abstract  

The normal levels of arsenic in human tissue are reported together with the arsenic concentrations found in the investigation of a large number of industrial exposure incidents. These results are useful for establishing that industrial exposure has taken place and for confirming arsenic poisoning but they cannot be used realistically to predict that any person or group will suffer a visible deterioration in health because no correlation between arsenic contamination and symptoms can be made. Industrial workers who are affected by arsenic exposure are often no more exposed than their co-workers.

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Abstract  

Separation and analysis of235U fission produced rare earth elements (REE) is described. Rare earth elements were separated using a high presure ion chromatographic separation where by each rare earth is isolated and individually detected. Detection is performed by inductively coupled plasma mass spectrometry (ICP/MS) and solid scintillation beta counting. The resulting detection methods allow complete evaluation of all stable (non-radioactive) and many radioactive REE fission products. The two detection methods (ICP/MS and Beta) illustrate how mass selective and radiometric data can be used to provide complimentary information regarding the isotopic characterization of radioactive samples.

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Over recent years a number of attempts have been made to assess the carbon mitigation potential of European agricultural land. Here we review the progress made by comparing pre- and post-Kyoto estimates of C mitigation potential, and review recent advances, such as the inclusion of trace gases in C mitigation calculations. We then briefly discuss ways in which our regional estimates of agricultural carbon mitigation potential might be improved. Finally, we set the findings for Europe in the context of the global terrestrial carbon cycle, and the historical global loss of carbon from soils due to agriculture.

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A new tin dithiocarbamate containing sulphur bridges, di-μ-sulphidobis [bis(N,N-diethyldithiocarbamato)tin(IV)], has been isolated from the thermal decomposition of tetrakis(N,N-diethyldithiocarbamato)tin(IV). A dimeric structure is proposed on the basis of results from mass spectrometry, infrared spectroscopy, thermal analysis and vapour pressure osmometry.

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