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Fast atom bombardment, combined with high-energy collision-induced tandem mass spectrometry, has been used to investigate gas-phase metal-ion interactions with captopril, enalaprilat and lisinopril, all angiotensin-converting enzyme inhibitors.Suggestions for the location of metal-binding sites are presented. For captopril, metal binding occurs most likely at both the sulphur and the nitrogen atom. For enalaprilat and lisinopril, binding preferably occurs at the amine nitrogen. Copyright 1999 John Wiley & Sons, Ltd.  相似文献   
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This study outlines the use of mid-infrared (MIR) spectroscopy combined with principal component analysis (PCA) and linear discriminant analysis (LDA) for the varietal classification of commercial red and white table wines. Three red varieties (Cabernet Sauvignon, Shiraz and Merlot) and four white varieties (Chardonnay, Riesling, Sauvignon Blanc and Viognier) were sourced from different wine regions in Australia. Wine samples were scanned in transmission on a FOSS WineScan FT 120 from wave numbers 926 to 5012 cm−1. All samples were sourced from the 2006 vintage and had not been blended with any other variety or wine from other regions. Spectral data were reduced to a small number of principal components (PCs) and LDA was then performed to successfully separate the wines into the different varieties. To test the robustness of the LDA models developed for the red wines, a set of red wines scanned in 2005 were used. Correct classification of over 95% was achieved for the validation set.  相似文献   
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Following with the discovery of the electron by J. J. Thomson at the end of the nineteenth century a steady elucidation of the structure of the atom occurred over the next 40 years culminating in the discovery of nuclear fission in 1938–1939. The significant steps after the electron discovery were: discovery of the nuclear atom by Rutherford (Philos Mag 6th Ser 21:669–688, 1911), the transformation of elements by Rutherford (Philos Mag 37:578–587, 1919), discovery of artificial radioactivity by Joliot-Curie and Joliot-Curie (Comptes Rendus Acad Sci Paris 198:254–256, 1934), and the discovery of the neutron by Chadwick (Nature 129:312, 1932a, Proc R Soc Ser A 136:692–708, 1932b; Proc R Soc Lond Ser A 136:744–748, 1932c). The neutron furnished scientists with a particle able to penetrate atomic nuclei without expenditure of large amounts of energy. From 1934 until 1938–1939 investigations of the reaction between a neutron and uranium were carried out by E. Fermi in Rome, O. Hahn, L. Meitner and F. Strassmann in Berlin and I. Curie and P. Savitch in Paris. Results were interpreted as the formation of transuranic elements. After sorting out complex radio-chemistry and radio-physics O. Hahn and F. Strassmann came to the conclusion, beyond their belief, that the uranium nucleus split into smaller fragments, that is nuclear fission. This was soon followed in 1939 by its theoretical interpretation by L. Mietner and O. Frisch.  相似文献   
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The potential of femtosecond laser time-of-flight mass spectrometry (FLMS) for uniform quantitative analysis of molecules has been investigated. Various samples of molecular gases and vapours have been studied, using ultra-fast ( approximately 50 fs) laser pulses with very high intensity (up to 1.6 x 10(16) Wcm(-2)) for non-resonant multiphoton ionisation/tunnel ionisation. Some of these molecules have high ionisation potentials, requiring up to ten photons for non-resonant ionisation. The relative sensitivity factors (RSF) have been determined as a function of the laser intensity and it has been demonstrated that for molecules with very different masses and ionisation potentials, uniform ionisation has been achieved at the highest laser intensities. Quantitative laser mass spectrometry of molecules is therefore a distinct possibility. Copyright 1999 John Wiley & Sons, Ltd.  相似文献   
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With the development of high intensity femtosecond lasers, the ionisation and dissociation dynamics of molecules has become an area of considerable interest. Using the technique of femtosecond laser mass spectrometry (FLMS), the molecules carbon disulphide, pyrimidine, toluene, cyclohexanone and benzaldehyde are studied with pulse widths of 50 fs in the near infrared (IR) wavelength region (790 nm). Results are presented and contrasted for laser beam intensities around 10(15) and 10(16) W cm(-2). For the lower intensities, the mass spectra yield dominant singly charged parent ions. Additionally, the appearance of doubly charged parent ions is evident for carbon disulphide, toluene and benzaldehyde with envelopes of doubly charged satellite species existing in these local regions. Carbon disulphide also reveals a small triply charged component. Such atomic-like features are thought to be a strong fingerprint of FLMS at these intensities. However, upon increasing the laser intensity to approximately 10(16) W cm(-2), parent ion dominance decreases and the appearance of multiply charged atomic species occurs, particularly carbon. This phenomenon has been attributed to Coulomb explosions in which the fast absorption of many photons may produce transient highly ionised parent species which can subsequently blow apart. Copyright 1999 John Wiley & Sons, Ltd.  相似文献   
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