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Individual Elements (individual + element)

Distribution by Scientific Domains

Engineering	50%
Life Sciences	33%

Selected Abstracts

Correcting mass isotopomer distributions for naturally occurring isotopes

BIOTECHNOLOGY & BIOENGINEERING, Issue 4 2002
Wouter A. Van Winden
In one method of metabolic flux analysis, simulated mass spectrometry data is fitted to measured mass distributions of metabolites that are isolated from cultures with defined feeding of 13C-labeled substrates. Doing so, simulated mass distributions must be corrected for the presence of naturally occurring isotopes. A method that was recently introduced for this purpose consists of consecutive correction steps for each isotope of each element in the considered compound. Here we show that all isotopes of each individual element must, however, be corrected in one single step. Furthermore, it is shown that the source of information with respect to isotopic compositions of the elements needs to be chosen with care. © 2002 Wiley Periodicals, Inc. Biotechnol Bioeng 80: 477,479, 2002. [source]

True carcinosarcoma of the esophagus

DISEASES OF THE ESOPHAGUS, Issue 1 2006
T. Iwaya
SUMMARY., Most esophageal carcinosarcomas are diagnosed as so-called carcinosarcoma, in which individual elements may be derived from a single common ancestor cell, and there have been a few reports describing true carcinosarcoma originating from two individual stem cells. We describe a case of esophageal carcinosarcoma exhibiting neoplastic osteoid formation. Immunoreactivity for vimentin and p53 was limited to only the sarcomatous component and was absent in the carcinomatous component. Furthermore, a point mutation in exon 7 of the p53 gene was observed only in the sarcomatous component. Both sarcoma and carcinoma cells distinctively metastasized to different lymph nodes. These observations led us to diagnose the esophageal tumor as a true carcinosarcoma. [source]

Beyond macronutrients: element variability and multielement stoichiometry in freshwater invertebrates

ECOLOGY LETTERS, Issue 12 2006
Roxanne Karimi
Abstract We contrasted concentrations of macronutrients (C, N and P), essential (As, Cu, Zn and Se) and non-essential metals (Pb, Hg and Cd) in invertebrates across five lakes and June to October in one lake. We predicted that somatic concentrations of tightly regulated elements would be less variable than weakly and unregulated elements. Within each taxon, variation was lowest in macronutrients, intermediate in essential micronutrients, and highest in non-essential metals, which corresponded in rank to homeostatic regulation strength for the same elements calculated from the literature. Hence, homeostatic regulation may strongly influence variation in element concentrations of biota in situ. Of the individual elements, only taxonomic differences in C and N were consistent across lakes and over a season. Nevertheless, canonical discriminant analyses successfully discriminated among taxa based on taxonomic multielement composition. Thus, relative taxonomic differences in multielement composition appear more informative than absolute stoichiometric formulae when considering the role of inherently variable trace elements in ecological investigations. [source]

Obtaining smooth mesh transitions using vertex optimization,

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 5 2008
M. Brewer
Abstract Mesh optimization has proven to be an effective way to improve mesh quality for arbitrary Lagrangian Eulerian (ALE) simulations. To date, however, most of the focus has been on improving the geometric shape of individual elements, and these methods often do not result in smooth transitions in element size or aspect ratio across groups of elements. We present an extension to the mean ratio optimization that addresses this problem and yields smooth transitions within regions and across regions in the ALE simulation. While this method is presented in the context of ALE simulations, it is applicable to a wider set of applications that require mesh improvement, including the mesh generation process. Published in 2007 by John Wiley & Sons, Ltd. [source]

A refined semi-analytic design sensitivity based on mode decomposition and Neumann series

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 1 2005
Maenghyo Cho
Abstract Among various sensitivity evaluation techniques, semi-analytical method (SAM) is quite popular since this method is more advantageous than analytical method (AM) and global finite difference method (GFD). However, SAM reveals severe inaccuracy problem when relatively large rigid body motions are identified for individual elements. Such errors result from the pseudo load vector calculated by differentiation using the finite difference scheme. In the present study, an iterative refined semi-analytical method (IRSAM) combined with mode decomposition technique is proposed to compute reliable semi-analytical design sensitivities. The improvement of design sensitivities corresponding to the rigid body mode is evaluated by exact differentiation of the rigid body modes and the error of SAM caused by numerical difference scheme is alleviated by using a Von Neumann series approximation considering the higher order terms for the sensitivity derivatives. In eigenvalue problems, the tendency of eigenvalue sensitivity is similar to that of displacement sensitivity in static problems. Eigenvector is decomposed into rigid body mode and pure deformation mode. The present iterative SAM guarantees that the eigenvalue and eigenvector sensitivities converge to the reliable values for the wide range of perturbed size of the design variables. Accuracy and reliability of the shape design sensitivities in static problems and eigenvalue problems by the proposed method are assessed through the various numerical examples. Copyright © 2004 John Wiley & Sons, Ltd. [source]

Chemical natures and distributions of metal impurities in multicrystalline silicon materials

PROGRESS IN PHOTOVOLTAICS: RESEARCH & APPLICATIONS, Issue 6 2006
T. Buonassisi
Abstract We present a comprehensive summary of our observations of metal-rich particles in multicrystalline silicon (mc-Si) solar cell materials from multiple vendors, including directionally-solidified ingot-grown, sheet, and ribbon, as well as multicrystalline float zone materials contaminated during growth. In each material, the elemental nature, chemical states, and distributions of metal-rich particles are assessed by synchrotron-based analytical x-ray microprobe techniques. Certain universal physical principles appear to govern the behavior of metals in nearly all materials: (a) Two types of metal-rich particles can be observed (metal silicide nanoprecipitates and metal-rich inclusions up to tens of microns in size, frequently oxidized), (b) spatial distributions of individual elements strongly depend on their solubility and diffusivity, and (c) strong interactions exist between metals and certain types of structural defects. Differences in the distribution and elemental nature of metal contamination between different mc-Si materials can largely be explained by variations in crystal growth parameters, structural defect types, and contamination sources. Copyright © 2006 John Wiley & Sons, Ltd. [source]