排序方式: 共有31条查询结果,搜索用时 515 毫秒
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Akira Kitamura Kenso Fujiwara Morihiro Mihara Mark Cowper Gento Kamei 《Journal of Radioanalytical and Nuclear Chemistry》2013,298(1):485-493
The solubility of thorium and americium in pore water squeezed from a cement paste was investigated by a batch method from oversaturation. The cement paste was prepared by mixing ordinary Portland cement with deionised water; in some cases the deionised water contained a polycarboxylic acid–base type superplasticiser. Following solidification, pore water was squeezed from the cement paste and collected for use in the solubility experiments. The aim of these was to investigate whether there was any effect of superplasticiser on the solubility of thorium and americium in the squeezed cement pore waters. The obtained solubility values in the two squeezed pore waters (with and without superplasticiser present) were similar. Thermodynamic calculations were performed with the thermodynamic database developed by Japan Atomic Energy Agency and compared with the experimental data to verify their applicability. These results showed that the superplasticiser used in the present study after mixing with the cement paste did not have a significant effect on solubility of thorium and americium, and the thermodynamic calculations were applicable in the present system. Size distribution of colloidal species of thorium and americium was also investigated. 相似文献
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Thomas Boucher CJ Carey Melinda Darby Dyar Sridhar Mahadevan Samuel Clegg Roger Wiens 《Journal of Chemometrics》2015,29(9):484-491
Laser‐induced breakdown spectroscopy (LIBS) is currently being used onboard the Mars Science Laboratory rover Curiosity to predict elemental abundances in dust, rocks, and soils using a partial least squares regression model developed by the ChemCam team. Accuracy of that model is constrained by the number of samples needed in the calibration, which grows exponentially with the dimensionality of the data, a phenomenon known as the curse of dimensionality. LIBS data are very high dimensional, and the number of ground‐truth samples (i.e., standards) recorded with the ChemCam before departing for Mars was small compared with the dimensionality, so strategies to optimize prediction accuracy are needed. In this study, we first use an existing machine learning algorithm, locally linear embedding (LLE), to combat the curse of dimensionality by embedding the data into a low‐dimensional manifold subspace before regressing. LLE constructs its embedding by maintaining local neighborhood distances and discarding large global geodesic distances between samples, in an attempt to preserve the underlying geometric structure of the data. We also introduce a novel supervised version, LLE for regression (LLER), which takes into account the known chemical composition of the training data when embedding. LLER is shown to outperform traditional LLE when predicting most major elements. We show the effectiveness of both algorithms using three different LIBS datasets recorded under Mars‐like conditions. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
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Sunflower Trypsin Inhibitor (SFTI-1) analogues have been prepared from simple linear precursors produced either by chemical synthesis or following purification from Escherichia coli. We have shown, for the first time that these linear SFTI-1 derived peptide sequences can be converted to circular peptides via selective consecutive acyl transfer reactions, and that the products derived from synthetic and bacterial origin are identical. Preliminary analysis of the semi-synthetic SFTI-1 analogues confirmed SFTI-I10H as an inhibitor of Kallikrein-5 (KLK5) protease that could also mediate its action on human keratinocytes. The preliminary results obtained serve as a useful starting point for the biological production of SFTI-1 based, selective KLK5 inhibitors for the treatment of atopic dermatitis. 相似文献
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Indenbom MV van Der Beek CJ Konczykowski M Holtzberg F 《Physical review letters》2000,84(8):1792-1795
From magneto-optical imaging performed on heavy-ion-irradiated YBa(2)Cu(3)O(7-delta) single crystals, it is found that at fields and temperatures where strong single vortex pinning by individual irradiation-induced amorphous columnar defects is to be expected, vortex motion is limited by the nucleation of vortex kinks at the specimen surface. In the material bulk, vortex motion occurs through (easy) kink sliding. Depinning in the bulk determines the screening current only at fields comparable to or larger than the matching field, at which the majority of vortices is not trapped by an ion track. 相似文献
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Paul Cowper Adam Pockett Gabriele Kociok-Köhn Petra J. Cameron Simon E. Lewis 《Tetrahedron》2018,74(22):2775-2786
We report the synthesis of five new azulene containing dyes, having D-π-A type structures. These dyes are synthesised using a sulfonium salt cross-coupling reaction. The dyes have been evaluated spectroscopically, electrochemically, crystallographically, and as sensitizers in dye-sensitized solar cells. We propose a rationale for the dyes' spectroscopic properties and performance in cells, based on conformational data derived from their crystal structures. 相似文献
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Analysis of natural gas by gas chromatography reduction of correlated uncertainties by normalisation
Brown AS Milton MJ Cowper CJ Squire GD Bremser W Branch RW 《Journal of chromatography. A》2004,1040(2):215-225
The results of gas chromatographic analysis of natural gas mixtures reveal strong correlations (Pearson correlation coefficient of >0.96) between the uncertainty of each component and variations in the ambient pressure. Although correction for ambient pressure variations can reduce this variability, normalisation of the results of each analysis using the assumption that the sum of all component amount fractions is unity provides significantly greater reductions in the uncertainty of each measured component. We show that the uncertainty in normalised components can be estimated approximately using the correlation coefficient as a measure of the correlation present in the measurements, or exactly using a full calculation of the variance/covariance (V/C) structure of the data. 相似文献