We present design features and applications of a novel UV-visible-NIR FLIM system with optical sectioning, high resolution (50ps), and large temporal dynamic range (750ps-1μs) to probe cellular metabolism and detect ...
We developed a controlled-environment FLIM system towards intracellular oxygen sensing, with a resolution of approximately 8 μM, covering the entire physiologic range (0-300 μM). We measured oxygen levels in normal ...
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Numerical simulations of time-resolved light transport in inhomogeneous tissues reveal quantitative, 3D-distributions of excitation and fluorescent light. Visualizations generated can assist the optimization of endosc...
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Cancellous bone plays an important load-bearing role in the skeleton, yet relatively little is known about the microstructure-mechanical property relationships of the tissue at the sub-10 [.proportional]m level. Cance...
Cancellous bone plays an important load-bearing role in the skeleton, yet relatively little is known about the microstructure-mechanical property relationships of the tissue at the sub-10 [.proportional]m level. Cancellous tissue is characterized by a layered microstructure with variable proportions of collagen and mineral. The lamellar material is substantially stiffer than the interlamellar material at the nanomechanical level. However, the microstructural origin of the observed differences in mechanical properties of these structures has not been investigated. In this study, second harmonic generation microscopy was used to examine collagen in human vertebral cancellous bone. At the same location in the tissue, nanoindentation was used to assess the indentation modulus of lamellar and interlamellar bone. The stiff lamellae corresponded to areas of highly ordered, collagen-rich material, while the compliant interlamellar regions corresponded to areas of unoriented or collagen-poor material. The lamellar bone was approximately 30% stiffer and contained approximately 50% more oriented collagen than the interlamellar bone. These observed differences in the mechanical properties and collagen content and organization of lamellar and interlamellar tissue are consistent with previous scanning electron microscopy studies showing greater mineral and collagen content and organization in lamellar bone. Given the well-known coupling between collagen and mineral in bone tissue, the mineral distribution may mirror that of the aligned collagen. However, similar measurements of local variations in mineral content are needed to confirm this hypothesis and may provide additional insights into the tissue nanomechanical behavior.
One of the important issues in a nodal diffusion analysis of a PER core is the generation of accurate nodal constants. As compared to a light water reactor (LWR) lattice, in which the variation of the core properties ...
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One of the important issues in a nodal diffusion analysis of a PER core is the generation of accurate nodal constants. As compared to a light water reactor (LWR) lattice, in which the variation of the core properties in the axial direction is relatively weak and therefore a 2-D modeling appropriate, the calculation at the core sub-region level for a PER needs to account for the third spatial dimension because of the complex geometry (double heterogeneity) of packed arrangements of spherical pebbles. The purpose of the present work was to assess the capability of the MICROX-2 code to generate accurate nodal cross sections for PER lattices. This preliminary evaluation was based on comparison to a continuous-energy, doubly heterogeneous MCNP reference model. The terms of the comparison were the infinite medium multiplication factor, the few-group cell-homogenized total, capture and fission cross-sections, and the spectral indices. The principal phenomena covered by these choices pertain to resonance treatment and double heterogeneity. The models developed here do not attempt to evaluate the effect of packing randomness at either heterogeneity level. Such a study will be discussed elsewhere. The double heterogeneity of the lattice cell was fully modeled in the MCNP reference model. The cell-homogenized few-group cross sections and spectral parameters were calculated in MCNP by using the reaction rates and flux tallies. A spherical geometry model was used with MICROX-2. The analysis was completed at cold, room temperature (296 K) and at hot operating conditions (1073 K). For consistency, the same cross section data files were used for generating both the pointwise cross sections for MCNP and the fine-group cross sections for MICROX-2. Results showed significant differences between the MCNP and the MICROX-2 results, especially in the thermal and resonance energy range.
The atomic scale details of the pressure-induced polymorphism of Gd5Si2Ge2 have been established by in situ x-ray powder diffraction. At room temperature, the monoclinic Gd5Si2Ge2 phase (β) is transformed to the orth...
The atomic scale details of the pressure-induced polymorphism of Gd5Si2Ge2 have been established by in situ x-ray powder diffraction. At room temperature, the monoclinic Gd5Si2Ge2 phase (β) is transformed to the orthorhombic α−Gd5Si2Ge2, observed previously as the low temperature, high magnetic field, or high silicon content polymorph. The transition occurs between ∼10kbar and ∼20kbar. Diffraction data provide the missing link in order to achieve a more complete understanding of how a structural change in a material can be induced by a variety of thermodynamic variables.
Femtosecond laser ablation of Silicon (100) with thermal oxide thin films was studied in order to further understand the ablative properties of thin films and to evaluate their influence on the ablation of the substra...
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Structural phase diagrams of Gd5Ge4 have been constructed during heating of a zero magnetic-field-cooled sample and during cooling in various constant magnetic fields using temperature (5–50K) and magnetic field (0–...
Structural phase diagrams of Gd5Ge4 have been constructed during heating of a zero magnetic-field-cooled sample and during cooling in various constant magnetic fields using temperature (5–50K) and magnetic field (0–3.5T) dependent x-ray powder diffraction measurements. The structural results have been correlated with bulk magnetization measurements. Different experimental data are in excellent agreement with one another, thus indicating intimate relationships between the magnetic and crystal lattices in the material.
Femtosecond pulsed laser damage of Silicon (100) with thermal oxide thin films was studied in order to further understand the optical and electrical properties of thin films and to evaluate their influence on the dama...
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