Lead-Uranyl Acetate staining following monotonic and fatigue loading of cortical bone beams.

<p>Staining of the tensile (A), neutral axis (C), and compressive (E) regions of monotonically loaded samples. Staining of the tensile (B), neutral axis (D), and compressive (F) regions of fatigue loaded samples. TXM images shown in transmission mode; white indicates high attenuating lead-uranyl acetate staining, grey indicates bone, and black indicates background. All scale bars are 25 microns.</p

Representative transmission x-ray microscopy images of cortical bone.

<p>Representative TXM absorption contrast image (acquired at 7.1 keV) illustrating lacunae and canaliculi present in rat cortical bone (slices 50 microns thick) with grey areas indicating bone, and black areas indicating background, lacunae and canaliculi. Left figure, 6×9 mosaic of low resolution images; right figure, single high resolution image of region. No staining is present in this image; grey-scale variation represents attenuation differences in the tissue.</p

Increased stain uptake in fatigue-loaded cortical bone samples.

<p>Summary of total staining in TXM images for cortical bone sections following fatigue and monotonic loading with both compressive and tensile regions pooled. Fatigue loading produced significantly more stain, indicating repeated loading creates greater damage formation allowing for increased uptake of the stain into bone tissue.</p

Classification of damage morphologies imaged in notched bone specimens.

<p>Summary of damage morphologies observed in the notched samples in each loading region (n = 23 samples total). The majority of samples had staining of bone structures in the compressive region, and damage occurred at the neutral axis in only one sample. The tensile microdamage was mainly staining of bone structures or cross hatching in the notched samples with a single sample having a propagated crack. Damage in the unnotched samples consisted only of bone structure staining.</p

Lead-Uranyl Acetate staining of damage morphologies in notched bone samples.

<p>(A, B) Staining of lacunae and canaliculi in the compressive region seen in 20 of the 23 samples; (C, D) Cross hatching damage around notch tip in the tensile region observed in 10 of 23 samples; (E, F) Crack propagating from notch tip in the tensile region in a single sample. Staining appears white due to high attenuation of lead-uranyl acetate, with bone tissue appearing grey and voids black. Scale bar: A,C,E = 50 µm; B,D,F = 5 µm. Sample created in the longitudinal plane of the bone.</p

Comparison of damage visualization with TXM compared to micro-CT scanning.

<p>Comparison of micro-CT with TXM images of similar region of interest in notched cortical beam samples. In all images white areas indicate high attenuating lead uranyl acetate, grey represents bone and black represents background. First image (A) shows micro-CT scan of staining, second (B) is TXM imaged binned to same pixel size as micro-CT scan, and third (C) is raw TXM image. These images illustrate differences in damage morphology and partial volume effect that occur between micro-CT and TXM. Staining of bone structures and nanoscale damage is not visible using micro-CT; scale bar = 25 microns.</p

Nanoscale Morphological and Chemical Changes of High Voltage Lithium–Manganese Rich NMC Composite Cathodes with Cycling

Understanding the evolution of chemical composition and morphology of battery materials during electrochemical cycling is fundamental to extending battery cycle life and ensuring safety. This is particularly true for the much debated high energy density (high voltage) lithium–manganese rich cathode material of composition Li_{1 + <i>x</i>}M_{1 – <i>x</i>}O₂ (M = Mn, Co, Ni). In this study we combine full-field transmission X-ray microscopy (TXM) with X-ray absorption near edge structure (XANES) to spatially resolve changes in chemical phase, oxidation state, and morphology within a high voltage cathode having nominal composition Li_1.2Mn_0.525Ni_0.175Co_0.1O₂. Nanoscale microscopy with chemical/elemental sensitivity provides direct quantitative visualization of the cathode, and insights into failure. Single-pixel (∼30 nm) TXM XANES revealed changes in Mn chemistry with cycling, possibly to a spinel conformation and likely including some Mn­(II), starting at the particle surface and proceeding inward. Morphological analysis of the particles revealed, with high resolution and statistical sampling, that the majority of particles adopted nonspherical shapes after 200 cycles. Multiple-energy tomography showed a more homogeneous association of transition metals in the pristine particle, which segregate significantly with cycling. Depletion of transition metals at the cathode surface occurs after just one cycle, likely driven by electrochemical reactions at the surface

mRNA Gene Expression Levels Altered Following Spaceflight.

<p>mRNA Gene Expression Levels Altered Following Spaceflight.</p

Spaceflight Causes Overexpression of the Cell Cycle Arrest Molecule, p21, Independently of p53 Activation.

<p>RT-PCR analysis revealed significant alterations in many cell cycle molecules including a 3.31 fold up-regulation of p21 and down-regulation of p53 (<b>G</b>). Immunohistochemical analysis localized this overexpression of p21 to osteoblasts along the periosteal surface of the proximal femur (<b>A</b>, ground control, <b>B</b>, flight). Interestingly, we also observed p21-positive nuclei in cross-sections and longitudinal sections of muscle fibers adjacent to the femur (<b>C–D</b>, ground control, <b>E–F</b>, flight). *indicates p<0.05, # indicates p<0.01.</p

Morphometric Parameters Investigated in µCT Analysis (n = 7).

*<p>Significantly less than ground control, p<0.05. Means are reported ± standard deviation.</p