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Structural Homogeneity (structural + homogeneity)

Distribution by Scientific Domains

Chemistry	40%

Selected Abstracts

ChemInform Abstract: Investigation of Optical and Structural Homogeneity of Ca4GdO(BO3)3 Single Crystals.

CHEMINFORM, Issue 1 2002
A. Klos
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]

Tailoring Titanium Hydride Decomposition Kinetics by Annealing in Various Atmospheres

ADVANCED ENGINEERING MATERIALS, Issue 5 2004
D. Lehmhus
With series production of aluminium foams according to the Fraunhofer process a reality, further improvement of structural homogeneity has gained interest. Since this characteristic is strongly influenced by blowing agent decomposition, means to adapt the latter have been investigated: The paper concentrates on thermal treatment of TiH2, comparing effects induced by treatment time, temperature and atmosphere variation. Structural characteristics of AlSi7 foams using TiH2 variants as foaming agent are evaluated. [source]

Further Characterisation of the 91500 Zircon Crystal

GEOSTANDARDS & GEOANALYTICAL RESEARCH, Issue 1 2004
Michael Wiedenbeck
zircon 91500; matériau de référence; intercomparaison entre techniques; valeurs de travail This paper reports the results from a second characterisation of the 91500 zircon, including data from electron probe microanalysis, laser ablation inductively coupled plasma-mass spectrometry (LA-ICP-MS), secondary ion mass spectrometry (SIMS) and laser fluorination analyses. The focus of this initiative was to establish the suitability of this large single zircon crystal for calibrating in situ analyses of the rare earth elements and oxygen isotopes, as well as to provide working values for key geochemical systems. In addition to extensive testing of the chemical and structural homogeneity of this sample, the occurrence of banding in 91500 in both backscattered electron and cathodoluminescence images is described in detail. Blind intercomparison data reported by both LA-ICP-MS and SIMS laboratories indicate that only small systematic differences exist between the data sets provided by these two techniques. Furthermore, the use of NIST SRM 610 glass as the calibrant for SIMS analyses was found to introduce little or no systematic error into the results for zircon. Based on both laser fluorination and SIMS data, zircon 91500 seems to be very well suited for calibrating in situ oxygen isotopic analyses. Cet article présente les résultats d'une nouvelle caractérisation du zircon 91500, dont des données de microanalyse par sonde électronique, d'analyse par ablation laser en couplage à un ICP-MS, d'analyse par sonde ionique (SIMS) et d'analyse par fluorination laser. Le but de cette étude etait de démontrer que ce large monocristal de zircon pouvait être utilisé pour la calibration d'analyses in situ de Terres Rares et des isotopes de I'Oxygène, et en même temps de fournir des valeurs "de travail" pour un certain nombre de systémes géochimiques cruciaux. En complément des tests systématiques d'homogénéité de I'échantillon, tant chimiquement que structurellement, /'ex/sfence, dans le zircon 91500, de zonages visibles en électrons retro diffusés et en cathodoluminescence, est décrite en détail, line comparaison en aveugle des résultats obtenus par LA-ICP-MS et par SIMS, dans des laboratoires différents, montre que les différences systématiques entre les ensembles de données obtenues par ces deux techniques sont très faibles. De plus, I'utilisation du verre NIST SRM 610 comme calibrant lors de I'analyse par SIMS n'introduit qu'une erreur systématique très faible si ce n'est inexistante sur les résultats du zircon. Sur la base des analyses par fluorination laser et par SIMS, le zircon 91500 semble être parfaitement adapte a son utilisation pour la calibration d'analyses isotopiques in situ d'oxygène. [source]

Semi-quantitative and structural metabolic phenotyping by direct infusion ion trap mass spectrometry and its application in genetical metabolomics

RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 15 2009
Albert Koulman
The identification of quantitative trait loci (QTL) for plant metabolites requires the quantitation of these metabolites across a large range of progeny. We developed a rapid metabolic profiling method using both untargeted and targeted direct infusion tandem mass spectrometry (DIMSMS) with a linear ion trap mass spectrometer yielding sufficient precision and accuracy for the quantification of a large number of metabolites in a high-throughput environment. The untargeted DIMSMS method uses top-down data-dependent fragmentation yielding MS2 and MS3 spectra. We have developed software tools to assess the structural homogeneity of the MS2 and MS3 spectra hence their utility for phenotyping and genetical metabolomics. In addition we used a targeted DIMS(MS) method for rapid quantitation of specific compounds. This method was compared with targeted LC/MS/MS methods for these compounds. The DIMSMS methods showed sufficient precision and accuracy for QTL discovery. We phenotyped 200 individual Loliumperenne genotypes from a mapping population harvested in two consecutive years. Computational and statistical analyses identified 246 nominal m/z bins with sufficient precision and homogeneity for QTL discovery. Comparison of the data for specific metabolites obtained by DIMSMS with the results from targeted LC/MS/MS analysis showed that quantitation by this metabolic profiling method is reasonably accurate. Of the top 100 MS1 bins, 22 ions gave one or more reproducible QTL across the 2 years. Copyright © 2009 John Wiley & Sons, Ltd. [source]

A comprehensive phylogeny of the bumble bees (Bombus)

BIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 1 2007
S. A. CAMERON
Bumble bees (Bombus Latreille) occupy a wide diversity of habitats, from alpine meadows to lowland tropical forest, yet they appear to be similar in morphology throughout their range, suggesting that behavioural adaptations play a more important role in colonizing diverse habitats. Notwithstanding their structural homogeneity, bumble bees exhibit striking inter- and intraspecific variation in colour pattern, purportedly the outcome of mimetic evolution. A robust phylogeny of Bombus would provide the framework for elucidating the history of their wide biogeographical distribution and the evolution of behavioural and morphological adaptations, including colour pattern. However, morphological studies of bumble bees have discovered too few phylogenetically informative characters to reconstruct a robust phylogeny. Using DNA sequence data, we report the first nearly complete species phylogeny of bumble bees, including most of the 250 known species from the 38 currently recognized subgenera. Bayesian analysis of nuclear (opsin, EF-1,, arginine kinase, PEPCK) and mitochondrial (16S) sequences results in a highly resolved and strongly supported phylogeny from base to tips, with clear-cut support for monophyly of most of the conventional morphology-based subgenera. Most subgenera fall into two distinct clades (short-faced and long-faced) associated broadly with differences in head morphology. Within the short-faced clade is a diverse New World clade, which includes nearly one-quarter of the currently recognized subgenera, many of which are restricted to higher elevations of Central and South America. The comprehensive phylogeny provides a firm foundation for reclassification and for evaluating character evolution in the bumble bees. © 2007 The Linnean Society of London, Biological Journal of the Linnean Society, 2007, 91, 161,188. [source]