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81.
82.
Steven J. Granger Roland Bol Wolfram Meier‐Augenstein Melanie J. Leng Helen F. Kemp Tim H. E. Heaton Sue M. White 《Rapid communications in mass spectrometry : RCM》2010,24(5):475-482
Stable isotopes of water have been previously used in catchment studies to separate rain‐event water from pre‐event groundwater. However, there are a lack of studies at the smaller scale looking at the separation of event water from pre‐event water. This is particularly relevant for heavy clay soil systems through which the movement of water is uncertain but is thought to be rainwater‐dominated. The data presented here were collected at a rural site in the south‐west of England. The historic rainfall at the site was isotopically varied but similar to the global meteoric water line, with annual weighted means of ?37‰ for δ2H and ?5.7‰ for δ18O and with no seasonal variation. Drainage was sampled from the inter‐flow (surface runoff + lateral through‐flow) and drain‐flow (55 cm deep mole drains) pathways of two 1 ha lysimeters during two rainfall events, which had δ2H values of ?68‰ and ?92‰, respectively. The δ2H values of the lysimeter drainage water suggest that there was no contribution of event water during the first, small discharge (Q) event; however, the second larger event did show isotopic variation in δ2H values negatively related to Q indicating that rainwater was contributing to Q. A hydrograph separation indicated that only 49–58% of the inter‐flow and 18–25% of the drain‐flow consisted of event water. This was surprising given that these soil types are considered retentive of soil water. More work is needed on heavy clay soils to understand better the nature of water movement from these systems. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
83.
84.
85.
Leroy H. Klemm Timothy J. R. Weakley Myungok Yoon Robert S. Clegg 《Journal of heterocyclic chemistry》2000,37(4):763-766
X‐ray crystallographic studies of thieno[2,3‐b:4,5‐b′]dipyridine ( 1 ) and its monohydroperchlorate salt ( 1a ) show that 1 is protonated at N1 in ring A and not at N6 in ring C. In each compound individual rings are planar, but there is a small dihedral angle‐of‐twist between the A and C rings. On going from 1 to 1a the largest changes in bond angles and bond lengths occur in ring A. 1H and l3C nmr spectra of 1 plus the 13C nmr spectrum of 1a are reported. 相似文献
86.
Synthesis of Modular “Inorganic–Organic–Inorganic” Polyoxometalates and Their Assembly into Vesicles
87.
E. R. Dixon M. S. A. Blackwell M. S. Dhanoa Z. Berryman N. de la Fuente Martinez D. Junquera A. Martinez P. J. Murray H. F. Kemp W. Meier‐Augenstein A. Duffy R. Bol 《Rapid communications in mass spectrometry : RCM》2010,24(5):511-518
Variations in natural abundance of carbon (C) and nitrogen (N) stable isotopes are widely used as tools for many aspects of scientific research. By examining variations in the ratios of heavy to light stable isotopes, information can be obtained as to what physical, chemical and biological processes may be occurring. The spatial heterogeneity of soil δ15N‐ and δ13C‐values across a range of scales and under different land use have been described by a number of researchers and the natural abundances of the C and N stable isotopes in soils have been found to be correlated with many factors including hydrology, topography, land use, vegetation cover and climate. In this study the Latin square sampling +1 (LSS+1) sampling method was compared with a simple grid sampling approach for δ13C and δ15N measurement at the field scale. A set of 144 samples was collected and analysed for δ15N and δ13C from a 12 × 12 grid (in a 1 ha improved grassland field in south‐west England). The dimension of each cell of the grid was approximately 11 × 6 m. The 12 × 12 grid was divided into four 6 × 6 grids and the LSS+1 sampling technique was applied to these and the main 12 × 12 grid for a comparison of sample means and variation. The LSS+1 means from the 12 × 12 grid and the four 6 × 6 grids compared well with the overall grid mean because of the low variation within the field. The LSS+1 strategy (13 samples) generated representative samples from the 12 × 12 grid, and hence would be an acceptable method for sampling similar plots for the measurement of mean isotopic composition. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
88.
C. Leroy V. Boujut F. Michelot H.-R. Jauslin 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1999,5(2):257-265
We analyze the implementation of the time-reversal (TR) transformation in the algebraic approach to tetrahedral local molecules through the chain of groups U(5) é U(4) é K(4)=A(4)ùS(4) é S(4) ? TdU(5)\supset U(4)\supset K(4)=A(4)\wedge S(4)\supset S(4)\approx T_d. We determine the general form of the TR operation using a purely algebraic realization, based exclusively on the requirement that the irreducible representations must not be changed under the time inversion symmetry. As a result we can determine the TR behavior of purely algebraic operators. 相似文献
89.
P Cardon J P Parente Y Leroy J Montreuil B Fournet 《Journal of chromatography. A》1986,356(1):135-146
High-performance liquid chromatography has been applied to the separation of isomers of mono-, di-, tri- and tetrasialylated oligosaccharides derived from alpha 1-acid glycoprotein by hydrazinolysis. The separation of the sialyl-oligosaccharides on the basis of their negative charges was carried out with quaternary amine-bonded silica. Within each class, the anionic oligosaccharides were fractionated on the basis of their net carbohydrate content on alkylamine-modified silica using a mobile phase consisting of a mixture of acetonitrile and potassium dihydrogen phosphate with 0.01% of 1,4-diaminobutane or 0.01% of tetraethylpentamine. 相似文献
90.
The five lowest doubly excited deformational vibrational bands ν4 + ν6, 2ν6, ν3 + ν4, ν3 + ν6, and 2ν3 of PH2D have been recorded for the first time using a Bruker 120 HR interferometer with a resolution 0.0033 cm−1 and analysed. Some transitions belonging to a very weak band 2ν4 have been also assigned. From the fit 24 and 86, respectively, diagonal and resonance interaction parameters were obtained which reproduce 1089 upper energy levels obtained from more than 4600 assigned transitions with the rms deviation of 0.00059 cm−1. 相似文献