The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Carolyn A. Larabell - One of the best experts on this subject based on the ideXlab platform.
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visualizing cell architecture and molecular location using soft x ray Tomography and correlated cryo light microscopy
Annual Review of Physical Chemistry, 2012Co-Authors: Gerry Mcdermott, Mark Le A Gros, Carolyn A. LarabellAbstract:Living cells are structured to create a range of microenvironments that support specific chemical reactions and processes. Understanding how cells function therefore requires detailed knowledge of both the subcellular architecture and the location of specific molecules within this framework. Here we review the development of two correlated cellular imaging techniques that fulfill this need. Cells are first imaged using cryogenic fluorescence microscopy to determine the location of molecules of interest that have been labeled with fluorescent tags. The same specimen is then imaged using soft X-Ray Tomography to generate a high-contrast, 3D reconstruction of the cells. Data from the two modalities are then combined to produce a composite, information-rich view of the cell. This correlated imaging approach can be applied across the spectrum of problems encountered in cell biology, from basic research to biotechnological and biomedical applications such as the optimization of biofuels and the development of new pharmaceuticals.
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quantitative analysis of yeast internal architecture using soft x ray Tomography
Yeast, 2011Co-Authors: Maho Uchida, Christian Knoechel, Mark Le A Gros, Dilworth Y Parkinson, Gerry Mcdermott, Carolyn A. Larabell, David G DrubinAbstract:We used soft X-Ray Tomography (SXT)--a high-resolution, quantitative imaging technique--to measure cell size and organelle volumes in yeasts. Cell size is a key factor in initiating cell division in yeasts, whereas the number and volume of the organelles have a profound impact on the function and viability of a cell. Consequently, determining these cell parameters is fundamentally important in understanding yeast biology. SXT is well suited to this type of analysis. Specimens are imaged in a near-native state, and relatively large numbers of cells can be readily analysed. In this study, we characterized haploid and diploid strains of Saccharomyces cerevisiae at each of the key stages in the cell cycle and determined the relationships that exist cellular and organelle volumes. We then compared these results with SXT data obtained from Schizosaccharomyces pombe, the three main phenotypes displayed by the opportunistic yeast pathogen Candida albicans and from a coff1-22 mutant strain of S. cerevisiae. This comparison revealed that volumetric ratios were invariant, irrespective of yeast strain, ploidy or morphology, leading to the conclusion these volumetric ratios are common in all yeasts.
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soft x ray Tomography of phenotypic switching and the cellular response to antifungal peptoids in candida albicans
Proceedings of the National Academy of Sciences of the United States of America, 2009Co-Authors: Maho Uchida, Christian Knoechel, Mark Le A Gros, Gerry Mcdermott, Carolyn A. Larabell, Annelise E. Barron, Modi Wetzler, Markko MyllysAbstract:The opportunistic pathogen Candida albicans can undergo phenotypic switching between a benign, unicellular phenotype and an invasive, multicellular form that causes candidiasis. Increasingly, strains of Candida are becoming resistant to antifungal drugs, making the treatment of candidiasis difficult, especially in immunocompromised or critically ill patients. Consequently, there is a pressing need to develop new drugs that circumvent fungal drug-resistance mechanisms. In this work we used soft X-Ray Tomography to image the subcellular changes that occur as a consequence of both phenotypic switching and of treating C. albicans with antifungal peptoids, a class of candidate therapeutics unaffected by drug resistance mechanisms. Peptoid treatment suppressed formation of the pathogenic hyphal phenotype and resulted in striking changes in cell and organelle morphology, most dramatically in the nucleus and nucleolus, and in the number, size, and location of lipidic bodies. In particular, peptoid treatment was seen to cause the inclusion of lipidic bodies into the nucleus.
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soft x ray Tomography and cryogenic light microscopy the cool combination in cellular imaging
Trends in Cell Biology, 2009Co-Authors: Gerry Mcdermott, Maho Uchida, Christian Knoechel, Mark Le A Gros, Carolyn A. LarabellAbstract:Soft X-Ray Tomography (SXT) is ideally suited to imaging sub-cellular architecture and organization, particularly in eukaryotic cells. SXT is similar in concept to the well-established medical diagnostic technique computed axial Tomography (CAT), except SXT is capable of imaging with a spatial resolution of 50nm, or better. In SXT, cells are imaged using photons from a region of the spectrum known as the ‘water window'. This results in quantitative, high-contrast images of intact, fully hydrated cells without the need to use contrast-enhancing agents. The cells that are visualized are in close-to-native, fully functional state. The utility of SXT has recently been enhanced by the development of high numerical aperture cryogenic light microscopy for correlated imaging. This multi-modal approach allows labelled molecules to be localized in the context of a high-resolution 3-D tomographic reconstruction of the cell.
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quantitative 3 d imaging of eukaryotic cells using soft x ray Tomography
Journal of Structural Biology, 2008Co-Authors: Dilworth Y Parkinson, Mark Le A Gros, Gerry Mcdermott, Carolyn A. Larabell, Laurence D EtkinAbstract:Imaging has long been one of the principal techniques used in biological and biomedical research. Indeed, the field of cell biology grew out of the first electron microscopy images of organelles in a cell. Since this landmark event, much work has been carried out to image and classify the organelles in eukaryotic cells using electron microscopy. Fluorescently labeled organelles can now be tracked in live cells, and recently, powerful light microscope techniques have pushed the limit of optical resolution to image single molecules. In this paper, we describe the use of soft X-Ray Tomography, a new tool for quantitative imaging of organelle structure and distribution in whole, fully hydrated eukaryotic Schizosaccharomyces pombe cells. In addition to imaging intact cells, soft X-Ray Tomography has the advantage of not requiring the use of any staining or fixation protocols—cells are simply transferred from their growth environment to a sample holder and immediately cryofixed. In this way the cells can be imaged in a near native state. Soft X-Ray Tomography is also capable of imaging relatively large numbers of cells in a short period of time, and is therefore a technique that has the potential to produce information on organelle morphology from statistically significant numbers of cells.
Eric Maire - One of the best experts on this subject based on the ideXlab platform.
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Effect of stress triaxiality on porosity evolution in notched bars: Quantitative agreement between a recent dilatational model and X-Ray Tomography data
Mechanics Research Communications, 2013Co-Authors: Benoit Revil-baudard, Oana Cazacu, Sandrine Thuillier, Eric MaireAbstract:Abstract In this paper, it is shown that a micromechanically motivated macroscopic model can predict with accuracy the role of the stress state on void evolution in engineering materials. Specifically, a recent criterion that accounts for the influence of all stress invariants on the dilatational response of porous metals is used to predict porosity evolution and strength reduction in aluminum alloy AA 6016-T4. A very good quantitative agreement between the simulation results and X-Ray Tomography damage measurements in specimens of different notch acuities is obtained. In contrast to existing models, the void volume fraction evolution correlates very well with the X-Ray data for all stress triaxialities.
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the damage process in a biomedical co 29cr 6mo 0 14n alloy analyzed by x ray Tomography and electron backscattered diffraction
Scripta Materialia, 2011Co-Authors: Shingo Kurosu, Hiroaki Matsumoto, Akihiko Chiba, Caroline Landron, Damien Fabregue, Eric MaireAbstract:The damage process leading to fracture during tensile testing of a biomedical grade Co–29Cr–6Mo–0.14N alloy was analyzed on the basis of three-dimensional damage observation using X-Ray Tomography and electron backscattered diffraction of the fractured specimen. Initial cracking occurred at grain and annealing twin boundaries, where strain concentrates due to impingement of e-hcp plates formed through strain-induced martensitic transformation (SIMT). Cracks propagated along the interface between the γ-fcc matrix and SIMTed e-hcp on {1 1 1}, resulting in the occurrence of a quasi-cleavage fracture.
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porosity analysis of long fiber reinforced ceramic matrix composites using x ray Tomography
Scripta Materialia, 2009Co-Authors: Anuar Moralesrodriguez, Pascal Reynaud, Jérôme Adrien, Gilbert Fantozzi, Eric MaireAbstract:This study has been devoted to a volumetric exploration of the meso-structure of a two-dimensional SiC f –SiC composite with cross-weave fibers using X-Ray Tomography. A series of projection images have been used to reconstruct the three-dimensional composite’s architecture and a quantitative analysis of the morphology of the porosity network has been carried out in order to characterize the fiber-tissue structure. The suitability of X-Ray Tomography for characterizing this structural material at a meso-scale level is critically assessed.
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observation of void nucleation growth and coalescence in a model metal matrix composite using x ray Tomography
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2008Co-Authors: Arnaud Weck, D S Wilkinson, Eric MaireAbstract:Abstract A model material with a core/shell design has been fabricated. The core consists of 50 μ m diameter ZrO 2 /SiO 2 particles in a pure aluminum matrix (99.9%) while the shell consists of particle-free aluminum. Such a design allows the sample to deform in a controlled manner. Void nucleation, growth and coalescence were precisely captured via in situ tensile tests coupled with X-Ray Tomography. Samples with various volume fraction of particles in their core and various notch sizes have been tested. We show that the higher the volume fraction of particles and stress triaxiality, the lower the nucleation and coalescence strains. Depending on the interactions between voids and neck geometry, void growth occurs either mainly in the tensile direction or through the formation of a diamond-like shape. Finite element simulations and slip line fields demonstrate that the shape of the voids is a result of plasticity and neck geometry. Finally, a modified version of the Brown and Embury model for coalescence is developed to take into account the lower coalescence strains at high stress triaxialities.
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x ray Tomography and three dimensional image analysis of epoxy glass syntactic foams
Philosophical Transactions of the Royal Society A, 2006Co-Authors: Eric Maire, Nelly Gimenez, Valerie Sauvantmoynot, H SautereauAbstract:Syntactic foams (glass hollow spheres embedded in an epoxy matrix) were produced on purpose to be used as test materials for the present study. Two kinds of spheres (MS1 and MS2) were adjoined to a same polymer matrix, MS1 with a volume fraction of 55 and MS2 with 30 and 55%. The samples were analysed by X-Ray Tomography using synchrotron radiation. The three-dimensional images were used to observe the qualitative differences between the three samples. Three-dimensional image processing was then carried out to quantify the differences. The images were used to retrieve the fraction of the different phases which was in fairly good agreement with the expected values. The external and internal diameter of the spheres and their thickness were also measured. The MS1 spheres are smaller, thicker and their size distribution is less homogeneous compared to the MS2. The size distribution of the spheres before blowing was retrieved and evidenced to be similar for the two kinds of spheres. The thickness depends only weakly on the diameter of the spheres.
Mark Le A Gros - One of the best experts on this subject based on the ideXlab platform.
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soft x ray Tomography reveals gradual chromatin compaction and reorganization during neurogenesis in vivo
Cell Reports, 2016Co-Authors: Mark Le A Gros, Markko Myllys, Josephine E Clowney, Angeliki Magklara, Angela Yen, Eirene Markenscoffpapadimitriou, Bradley M Colquitt, Manolis KellisAbstract:The realization that nuclear distribution of DNA, RNA, and proteins differs between cell types and developmental stages suggests that nuclear organization serves regulatory functions. Understanding the logic of nuclear architecture and how it contributes to differentiation and cell fate commitment remains challenging. Here, we use soft X-Ray Tomography (SXT) to image chromatin organization, distribution, and biophysical properties during neurogenesis in vivo. Our analyses reveal that chromatin with similar biophysical properties forms an elaborate connected network throughout the entire nucleus. Although this interconnectivity is present in every developmental stage, differentiation proceeds with concomitant increase in chromatin compaction and re-distribution of condensed chromatin toward the nuclear core. HP1β, but not nucleosome spacing or phasing, regulates chromatin rearrangements because it governs both the compaction of chromatin and its interactions with the nuclear envelope. Our experiments introduce SXT as a powerful imaging technology for nuclear architecture.
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visualizing cell architecture and molecular location using soft x ray Tomography and correlated cryo light microscopy
Annual Review of Physical Chemistry, 2012Co-Authors: Gerry Mcdermott, Mark Le A Gros, Carolyn A. LarabellAbstract:Living cells are structured to create a range of microenvironments that support specific chemical reactions and processes. Understanding how cells function therefore requires detailed knowledge of both the subcellular architecture and the location of specific molecules within this framework. Here we review the development of two correlated cellular imaging techniques that fulfill this need. Cells are first imaged using cryogenic fluorescence microscopy to determine the location of molecules of interest that have been labeled with fluorescent tags. The same specimen is then imaged using soft X-Ray Tomography to generate a high-contrast, 3D reconstruction of the cells. Data from the two modalities are then combined to produce a composite, information-rich view of the cell. This correlated imaging approach can be applied across the spectrum of problems encountered in cell biology, from basic research to biotechnological and biomedical applications such as the optimization of biofuels and the development of new pharmaceuticals.
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quantitative analysis of yeast internal architecture using soft x ray Tomography
Yeast, 2011Co-Authors: Maho Uchida, Christian Knoechel, Mark Le A Gros, Dilworth Y Parkinson, Gerry Mcdermott, Carolyn A. Larabell, David G DrubinAbstract:We used soft X-Ray Tomography (SXT)--a high-resolution, quantitative imaging technique--to measure cell size and organelle volumes in yeasts. Cell size is a key factor in initiating cell division in yeasts, whereas the number and volume of the organelles have a profound impact on the function and viability of a cell. Consequently, determining these cell parameters is fundamentally important in understanding yeast biology. SXT is well suited to this type of analysis. Specimens are imaged in a near-native state, and relatively large numbers of cells can be readily analysed. In this study, we characterized haploid and diploid strains of Saccharomyces cerevisiae at each of the key stages in the cell cycle and determined the relationships that exist cellular and organelle volumes. We then compared these results with SXT data obtained from Schizosaccharomyces pombe, the three main phenotypes displayed by the opportunistic yeast pathogen Candida albicans and from a coff1-22 mutant strain of S. cerevisiae. This comparison revealed that volumetric ratios were invariant, irrespective of yeast strain, ploidy or morphology, leading to the conclusion these volumetric ratios are common in all yeasts.
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soft x ray Tomography of phenotypic switching and the cellular response to antifungal peptoids in candida albicans
Proceedings of the National Academy of Sciences of the United States of America, 2009Co-Authors: Maho Uchida, Christian Knoechel, Mark Le A Gros, Gerry Mcdermott, Carolyn A. Larabell, Annelise E. Barron, Modi Wetzler, Markko MyllysAbstract:The opportunistic pathogen Candida albicans can undergo phenotypic switching between a benign, unicellular phenotype and an invasive, multicellular form that causes candidiasis. Increasingly, strains of Candida are becoming resistant to antifungal drugs, making the treatment of candidiasis difficult, especially in immunocompromised or critically ill patients. Consequently, there is a pressing need to develop new drugs that circumvent fungal drug-resistance mechanisms. In this work we used soft X-Ray Tomography to image the subcellular changes that occur as a consequence of both phenotypic switching and of treating C. albicans with antifungal peptoids, a class of candidate therapeutics unaffected by drug resistance mechanisms. Peptoid treatment suppressed formation of the pathogenic hyphal phenotype and resulted in striking changes in cell and organelle morphology, most dramatically in the nucleus and nucleolus, and in the number, size, and location of lipidic bodies. In particular, peptoid treatment was seen to cause the inclusion of lipidic bodies into the nucleus.
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soft x ray Tomography and cryogenic light microscopy the cool combination in cellular imaging
Trends in Cell Biology, 2009Co-Authors: Gerry Mcdermott, Maho Uchida, Christian Knoechel, Mark Le A Gros, Carolyn A. LarabellAbstract:Soft X-Ray Tomography (SXT) is ideally suited to imaging sub-cellular architecture and organization, particularly in eukaryotic cells. SXT is similar in concept to the well-established medical diagnostic technique computed axial Tomography (CAT), except SXT is capable of imaging with a spatial resolution of 50nm, or better. In SXT, cells are imaged using photons from a region of the spectrum known as the ‘water window'. This results in quantitative, high-contrast images of intact, fully hydrated cells without the need to use contrast-enhancing agents. The cells that are visualized are in close-to-native, fully functional state. The utility of SXT has recently been enhanced by the development of high numerical aperture cryogenic light microscopy for correlated imaging. This multi-modal approach allows labelled molecules to be localized in the context of a high-resolution 3-D tomographic reconstruction of the cell.
Gerry Mcdermott - One of the best experts on this subject based on the ideXlab platform.
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visualizing cell architecture and molecular location using soft x ray Tomography and correlated cryo light microscopy
Annual Review of Physical Chemistry, 2012Co-Authors: Gerry Mcdermott, Mark Le A Gros, Carolyn A. LarabellAbstract:Living cells are structured to create a range of microenvironments that support specific chemical reactions and processes. Understanding how cells function therefore requires detailed knowledge of both the subcellular architecture and the location of specific molecules within this framework. Here we review the development of two correlated cellular imaging techniques that fulfill this need. Cells are first imaged using cryogenic fluorescence microscopy to determine the location of molecules of interest that have been labeled with fluorescent tags. The same specimen is then imaged using soft X-Ray Tomography to generate a high-contrast, 3D reconstruction of the cells. Data from the two modalities are then combined to produce a composite, information-rich view of the cell. This correlated imaging approach can be applied across the spectrum of problems encountered in cell biology, from basic research to biotechnological and biomedical applications such as the optimization of biofuels and the development of new pharmaceuticals.
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quantitative analysis of yeast internal architecture using soft x ray Tomography
Yeast, 2011Co-Authors: Maho Uchida, Christian Knoechel, Mark Le A Gros, Dilworth Y Parkinson, Gerry Mcdermott, Carolyn A. Larabell, David G DrubinAbstract:We used soft X-Ray Tomography (SXT)--a high-resolution, quantitative imaging technique--to measure cell size and organelle volumes in yeasts. Cell size is a key factor in initiating cell division in yeasts, whereas the number and volume of the organelles have a profound impact on the function and viability of a cell. Consequently, determining these cell parameters is fundamentally important in understanding yeast biology. SXT is well suited to this type of analysis. Specimens are imaged in a near-native state, and relatively large numbers of cells can be readily analysed. In this study, we characterized haploid and diploid strains of Saccharomyces cerevisiae at each of the key stages in the cell cycle and determined the relationships that exist cellular and organelle volumes. We then compared these results with SXT data obtained from Schizosaccharomyces pombe, the three main phenotypes displayed by the opportunistic yeast pathogen Candida albicans and from a coff1-22 mutant strain of S. cerevisiae. This comparison revealed that volumetric ratios were invariant, irrespective of yeast strain, ploidy or morphology, leading to the conclusion these volumetric ratios are common in all yeasts.
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soft x ray Tomography of phenotypic switching and the cellular response to antifungal peptoids in candida albicans
Proceedings of the National Academy of Sciences of the United States of America, 2009Co-Authors: Maho Uchida, Christian Knoechel, Mark Le A Gros, Gerry Mcdermott, Carolyn A. Larabell, Annelise E. Barron, Modi Wetzler, Markko MyllysAbstract:The opportunistic pathogen Candida albicans can undergo phenotypic switching between a benign, unicellular phenotype and an invasive, multicellular form that causes candidiasis. Increasingly, strains of Candida are becoming resistant to antifungal drugs, making the treatment of candidiasis difficult, especially in immunocompromised or critically ill patients. Consequently, there is a pressing need to develop new drugs that circumvent fungal drug-resistance mechanisms. In this work we used soft X-Ray Tomography to image the subcellular changes that occur as a consequence of both phenotypic switching and of treating C. albicans with antifungal peptoids, a class of candidate therapeutics unaffected by drug resistance mechanisms. Peptoid treatment suppressed formation of the pathogenic hyphal phenotype and resulted in striking changes in cell and organelle morphology, most dramatically in the nucleus and nucleolus, and in the number, size, and location of lipidic bodies. In particular, peptoid treatment was seen to cause the inclusion of lipidic bodies into the nucleus.
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soft x ray Tomography and cryogenic light microscopy the cool combination in cellular imaging
Trends in Cell Biology, 2009Co-Authors: Gerry Mcdermott, Maho Uchida, Christian Knoechel, Mark Le A Gros, Carolyn A. LarabellAbstract:Soft X-Ray Tomography (SXT) is ideally suited to imaging sub-cellular architecture and organization, particularly in eukaryotic cells. SXT is similar in concept to the well-established medical diagnostic technique computed axial Tomography (CAT), except SXT is capable of imaging with a spatial resolution of 50nm, or better. In SXT, cells are imaged using photons from a region of the spectrum known as the ‘water window'. This results in quantitative, high-contrast images of intact, fully hydrated cells without the need to use contrast-enhancing agents. The cells that are visualized are in close-to-native, fully functional state. The utility of SXT has recently been enhanced by the development of high numerical aperture cryogenic light microscopy for correlated imaging. This multi-modal approach allows labelled molecules to be localized in the context of a high-resolution 3-D tomographic reconstruction of the cell.
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quantitative 3 d imaging of eukaryotic cells using soft x ray Tomography
Journal of Structural Biology, 2008Co-Authors: Dilworth Y Parkinson, Mark Le A Gros, Gerry Mcdermott, Carolyn A. Larabell, Laurence D EtkinAbstract:Imaging has long been one of the principal techniques used in biological and biomedical research. Indeed, the field of cell biology grew out of the first electron microscopy images of organelles in a cell. Since this landmark event, much work has been carried out to image and classify the organelles in eukaryotic cells using electron microscopy. Fluorescently labeled organelles can now be tracked in live cells, and recently, powerful light microscope techniques have pushed the limit of optical resolution to image single molecules. In this paper, we describe the use of soft X-Ray Tomography, a new tool for quantitative imaging of organelle structure and distribution in whole, fully hydrated eukaryotic Schizosaccharomyces pombe cells. In addition to imaging intact cells, soft X-Ray Tomography has the advantage of not requiring the use of any staining or fixation protocols—cells are simply transferred from their growth environment to a sample holder and immediately cryofixed. In this way the cells can be imaged in a near native state. Soft X-Ray Tomography is also capable of imaging relatively large numbers of cells in a short period of time, and is therefore a technique that has the potential to produce information on organelle morphology from statistically significant numbers of cells.
Mark L Rivers - One of the best experts on this subject based on the ideXlab platform.
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quantitative 3d petrography using x ray Tomography 3 documenting accessory phases with differential absorption Tomography
Geosphere, 2010Co-Authors: Guilherme A R Gualda, Ayla S Pamukcu, Lily L Claiborne, Mark L RiversAbstract:Accessory minerals preserve important records of the evolution of magmatic systems, but study of their textures and contact relations is hindered by the lack of suitable methods for characterization. We show here that differential absorption X-Ray Tomography can be used to yield three-dimensional maps of selected elements, particularly Zr and rare earth elements (REE), making it possible to qualitatively and quantitatively document the textures of zircon and REE minerals in situ and in three dimensions. We apply this method to pumice from the Peach Spring Tuff (Nevada, Arizona, California) and Mount St. Helens (Washington State) and present a few illustrative examples of the kinds of data that can be extracted using elemental and conventional tomographic data. Particularly when combined with compositional and age data, the ability to visualize and document accessory minerals in three dimensions and in textural context opens exciting new possibilities for the study of accessory minerals and the rocks that contain them.
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quantitative 3d petrography using x ray Tomography application to bishop tuff pumice clasts
Journal of Volcanology and Geothermal Research, 2006Co-Authors: Guilherme A R Gualda, Mark L RiversAbstract:Abstract Textures are traditionally studied using the petrographic microscope, which limits observations to 2D sections of 3D objects. Given the difficulty in retrieving information on shapes, sizes and spatial distribution of objects in 3D from random sections, a method that can yield observations in 3D is highly desirable. X-Ray Tomography yields a 3D map of the linear X-Ray attenuation coefficient, which is a function of the atomic number and density of the material, and the X-Ray energy used. Based on the compositional contrasts between different phases, various phases can be identified in a rock. Pumice clasts, characterized by isolated crystals surrounded by a low-density matrix, are ideal for the application of this technique. We present our first results obtained using X-Ray Tomography for pumice clasts from the Bishop Tuff. Samples studied are from units F7 and F8, and are representative of the variability in density and crystal contents observed in the early erupted Bishop Tuff. Data were collected on the GeoSoilEnvironCARS beamline at the Advanced Photon Source, Argonne National Laboratory, using a 22 keV monochromatic X-Ray beam. Image analysis was performed using the software Blob3D. Brightness contrasts in the resulting images allow the separation of magnetite, sanidine, quartz (including minor plagioclase), glass and vesicles. Crystals smaller than 5 voxels in diameter cannot be quantified properly, mostly due to noise in the images. This constrains the spatial resolution of the resulting images, such that there is a trade-off between sample size and spatial resolution. We employed two runs with samples of varying sizes (5 and 10 mm) to obtain adequate resolution (voxel sizes, ca. 8 and 17 μm). We have previously studied quartz size distributions in Bishop pumice clasts using a crushing, sieving, and winnowing procedure. The agreement between our new and previous results is excellent. Quartz size distributions obtained using the Tomography data are concave-upward on (population density vs. size plots) and resemble the size distributions for all quartz crystals (including both whole crystals and fragments). These size distributions were probably generated by fragmentation, through which large crystals were converted in a larger number of small crystals; petrographic observations suggest fragmentation occurred mostly under magmatic conditions. Sanidine size distributions are similar to those observed for quartz. Magnetite size distributions are typically linear, indicating a simple magmatic history, in contrast with the tektosilicates.
