34 research outputs found

    STEM annular dark field image and matching EDXS maps of longitudinal sections of human bone.

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    <p>a) STEM image; Box outlines area shown in EDXS map, b) EDXS map of Ca distribution of area bounded by box in A. Lowest levels of Ca are over overlap zones, highest levels are over the NW-SE trending mineral structures. c) Boxes 1, 2, and 3 are areas of analysis described later in the text.</p

    Series of bright-field TEM images of a single section at varying orientation (tilt).

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    <p>The section was initially cut at 45° to the axis of the femur, and tilted while being viewed in the electron microscope: a) tilted to −45°, showing bands of mineral structures aligned parallel to fibrils; b) tilted to +45°, showing open, lacy structure of mineral structures.</p

    Measurements of Mineral Sections in Cross-section Image (Figure 3).

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    <p>Measurements of Mineral Sections in Cross-section Image (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0029258#pone-0029258-g003" target="_blank">Figure 3</a>).</p

    Simplified isometric model of unit volume of bone.

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    <p>The model shows the composite fibril/mineral structural makeup of cortical bone for the purpose of using EDXS data to estimate spatial distribution of mineral. The subvolumes H, G, V and O are identified in the text. EDXS X-rays are recorded emerging from top of this structure.</p

    In Liquid Observation and Quantification of Nucleation and Growth of Gold Nanostructures Using in Situ Transmission Electron Microscopy

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    In situ liquid transmission electron microscopy (TEM) is a powerful technique for observing nanoscale processes in their native liquid environment and in real time. However, the imaging electron beam can have major interferences with the processes under study, altering the experimental outcome. Here, we use in situ liquid TEM to understand the differences between beam-induced and electrodeposition processes that result in nucleation and growth of gold crystallites. Through this study, we find that beam-induced and electrodeposition processes result in crystallites that deposit at different locations within the liquid cell and differ significantly in morphology. Furthermore, we develop a strategy based on increasing the liquid layer thickness for reducing the amount of beam-induced crystallites to negligible levels. Through this optimized system, we study the electrodeposition of gold on carbon electrodes by correlating current time transients and their corresponding time-resolved scanning TEM images. This analysis demonstrates that even when the electron-beam plays a negligible role in gold deposition under optimal conditions, there is a large discrepancy between the amount of deposits observed and the amount measured using the current time transients. This finding sheds light on the heterogeneity of the deposition process and provides insights into designing a new class of in situ liquid TEM systems

    Human femur sectioned parallel to long axis of femur.

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    <p>a) bright field (BF) image: faint bands oriented NW-SE, repeated every 68 nm, denote concentration of HA in gap zones in collagen fibrils which run perpendicular to the bands. Perpendicular to the bands are ∼23 nm wide bundles spaced ∼50 nm apart comprised of clusters of linear features (arrow) 5±1 nm wide, and up to 200 nm in length; b) selected area diffraction pattern indexed to HA; note that 00l reflections form arcs indicating preferred orientation of the c axes of the HA parallel to the to the fibrils, while other reflections form complete circles, lack of alignment of the a and b axes.</p

    Sharply defined borders between gap zone and overlap zone.

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    <p>Bright field TEM image of longitudinal section of human bone. Image shows sharp border between high-contrast gap zones and low-contrast overlap zones. There is no evidence that the higher-contrast material (presumably HA) penetrates into the overlap zone. Arrows point to possible boundaries of constituent crystals (see <i>Conclusions</i>).</p

    Measurements of Mineral Sections in Longitudinal Section Image (Figure 1).

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    <p>*Note – ends of mineral structures are obstructed by other structures or extend out of the focal plane of the image.</p

    Longitudinal TEM bright field images of other bone samples.

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    <p>a) femoral cortex of 19 y-old healthy male (allograft specimen) Scale = 100 nm; b) allograft remainder of 60 y-old male; scale = 100 nm; c) bovine femur; scale = 50 nm; d) elephant (mammoth [<i>Mammuthus sp.</i>]), c. 10,000 y old, Siberia; scale = 100 nm; e) Salmon (<i>Oncorhynchus</i> sp.)vertebra; scale = 300 nm; f) femur of a 6-month-old mouse (<i>Mus musculus</i>); scale = 100 nm.</p

    TEM image of cross-section of femur.

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    <p>a) Bright-field image; scale bar = 100 nm. Low-contrast (light) areas surrounded by dark linear features are believed to be sections through collagen fibrils, many of which have been punctured by ion beam during ion milling; b) selected area diffraction pattern; note spotty 00l rings confirming that c-axes of HA are oriented normal to plane of section.</p
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