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1.
A. C. Gillet Jr. 《Fresenius' Journal of Analytical Chemistry》1969,247(3-4):163-165
Résumé On a mis au point une méthode de dosage de traces de Cr en solution aqueuse. Le méthode consiste à former l'oxinate de Cr(III), à l'extraire à l'aide d'oxine fondue, puis à le doser, par spectrophotométrie de sa solution chloroformique à 420 nm. La méthode est relativement spécifique et sa sensibilité peut atteindre quelques parties par milliard. On présente des exemples d'applications aux produits sodiques.
Spectrophotometric determination of traces of chromium, concentrated in molten oxine
A method is described for the determination of Cr in aqueous solutions. It is based on the formation of Cr(III) oxinate, its extraction by means of molten oxine and the spectrophotometric measurement of the chloroform solution at 420 nm. The method is relatively specific and the sensitivity is about 10–3 ppm. Several examples of application to sodium compounds are presented.相似文献
2.
B. Robrieux G. Desrousseaux A. Renou M. Gillet 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1989,12(1-4):27-29
In this paper, we show that it is possible to deduce the actual morphology of small particle condensed onto an insulator by combining the granularity analysis from electron micrographs and the electrical sheet conductance of the deposit on its substrate. Assuming the particles are truncated ellipsoids, we determine the excentricity and the contact angle with the substrate for Au on amorphous carbon and MgO substrates. 相似文献
3.
Paul Watson Peter Willett Valerie J. Gillet Marcel L. Verdonk 《Journal of computer-aided molecular design》2001,15(9):835-857
A knowledge-based method for calculating the similarity of functional groups is described and validated. The method is based on experimental information derived from small molecule crystal structures. These data are used in the form of scatterplots that show the likelihood of a non-bonded interaction being formed between functional group A (the `central group') and functional group B (the `contact group' or `probe'). The scatterplots are converted into three-dimensional maps that show the propensity of the probe at different positions around the central group. Here we describe how to calculate the similarity of a pair of central groups based on these maps. The similarity method is validated using bioisosteric functional group pairs identified in the Bioster database and Relibase. The Bioster database is a critical compilation of thousands of bioisosteric molecule pairs, including drugs, enzyme inhibitors and agrochemicals. Relibase is an object-oriented database containing structural data about protein-ligand interactions. The distributions of the similarities of the bioisosteric functional group pairs are compared with similarities for all the possible pairs in IsoStar, and are found to be significantly different. Enrichment factors are also calculated showing the similarity method is statistically significantly better than random in predicting bioisosteric functional group pairs. 相似文献
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Low pressure CO oxidation was studied over small supported Pd particles by means of static secondary ion mass spectrometry (SSIMS). The SSIMS spectra of adsorbed layers on Pd particles with diameters below ~7nm contained, besides other species, Pd n X+ ions (X=C, O, CO;n=1–3). In experiments with Pd films, Pd n C+ species were much less abundant or even absent from the mass spectra. We conclude that CO decomposed in appreciable amounts only on Pd particles. No significant influence of the support material (mica, MgO,α-Al2O3) was seen and posthumous TEM analysis revealed well defined particle morphologies with largely (111) and (100) facets. At total pressures below 10?4 Pa, the relative carbidic intensities Pd n C+/Pd n + , which were taken as proportional to the carbon surface concentrations, first increased with increasing temperatures and then decreased after they passed a maximum at T=400–440 K. The smaller the particle size, the more intense were the maxima. For T ?440 K, carbon was removed from the surface via reaction with oxygen. Strong hysteresis effects in the Cad and COad concentrations occurred during temperature variation measurements. The Pd n C+/Pd n + ratios displayed maxima during heating but not during cooling. While the Pd n CO+/Pd n + ratios were always high at 300 K and always low at T>550 K, they were more intense in the medium temperature range when subjecting the samples to heating. These hysteresis effects are discussed in terms of asymmetric adsorption and reaction behaviour of CO/O2 mixtures, involving inhibition of CO2 formation by adsorbed carbon and carbon monoxide. 相似文献
6.
Whittle M Gillet VJ Willett P Alex A Loesel J 《Journal of chemical information and computer sciences》2004,44(5):1840-1848
This paper evaluates the effectiveness of various similarity coefficients for 2D similarity searching when multiple bioactive target structures are available. Similarity searches using several different activity classes within the MDL Drug Data Report and the Dictionary of Natural Products databases are performed using BCI 2D fingerprints. Using data fusion techniques to combine the resulting nearest neighbor lists we obtain group recall results which, in many cases, are a considerable improvement on standard average recall values obtained for individual structures. It is shown that the degree of improvement can be related to the structural diversity of the activity class that is searched for, the best results being found for the most diverse groups. The group recall of active compounds using subsets of the class is also investigated: for highly self-similar activity classes, the group recall improvement saturates well before the full activity class size is reached. A rough correlation is found between the relative improvement using the group recall and the square of the number of unique compounds available in all of the merged lists. The Tanimoto coefficient is found unambiguously to be the best coefficient to use for the recovery of active compounds using multiple targets. Furthermore, when using the Tanimoto coefficient, the "MAX" fusion rule is found to be more effective than the "SUM" rule for the combination of similarity searches from multiple targets. The use of group recall can lead to improved enrichment in database searches and virtual screening. 相似文献
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The single-crystal elastic moduli of alpha-quartz were measured to above 20 GPa in a diamond-anvil cell by Brillouin spectroscopy. The behavior of the elastic moduli indicates that the high-pressure phase transition in quartz is ferroelastic in nature and is driven by softening of C44 through one of the Born stability criteria. The trends in elastic moduli confirm theoretical predictions, but there are important differences, particularly with respect to the magnitudes of the B(i). The quartz I-II transition occurs prior to complete softening of the mode and amorphization. 相似文献
9.
Acoustic Emission (AE) was investigated in order to monitor in real time the Mullins effect. Cyclic uniaxial tensile tests were carried out on two different natural rubbers. Different behaviour is revealed depending on whether or not the material undergoes the Mullins effect. The acoustic emission activity is very important during the first cycle, but decreases gradually with increasing number of cycles, when the Mullins effect is observed. On the contrary, when there is no Mullins effect no significant AE activity is recorded. 相似文献
10.