Search

Carbon fibers have been widely used for their lightweight and high mechanical properties. In order to extensively use carbon fibers, it is important to accurately understand and account for their highly anisotropic characteristics. The anisotropy of carbon fibers can be expressed as elastic constants, however evaluation of these constants is very difficult. This study reviews literatures that have analyzed the elastic constants of carbon fibers to clarify the elastic constants of various carbon fibers. This knowledge will lead to more accurate deformation and stress state calculations for structural materials, aiding future development of even higher performance composite materials. The accurate determination of the elastic constants of carbon fibers is also expected to lead to advances in the manufacturing process of carbon fibers and further improve their mechanical properties. [ABSTRACT FROM AUTHOR]

The self-diffusivity of oxygen in amorphous Al2O3 (a-Al2O3), a-Ta2O5, and a-Nb2O5 was investigated along with structural analysis in terms of pair distribution function (PDF). The low activation energy, ~1.2 eV, for diffusion in the oxides suggests a single atomic jump of oxygen ions mediated via vacancy-like defects. However, the pre-exponential factor for a-Ta2O5 and a-Nb2O5 with lower bond energy was two orders of magnitude larger than that for a-Al2O3 with higher bond energy. PDF analyses revealed that the short-range configuration in a-Ta2O5 and a-Nb2O5 was more broadly distributed than that in a-Al2O3. Due to the larger variety of atomic configurations of a-Ta2O5 and a-Nb2O5, these oxides have a higher activation entropy for diffusion than a-Al2O3. The entropy term for diffusion associated with short-range structures was shown to be a dominant factor for diffusion in amorphous oxides. [ABSTRACT FROM AUTHOR]

The effect of W on the nanovoid formation in annealed amorphous Al2O3 was studied by transmission electron microscopy and molecular dynamics simulations. A comparison of the void formation behavior in electron-beam deposited Al2O3 (without W) and resistance-heating deposited Al2O3 (with 10 at. % W) revealed that W enhances the formation and growth of nanovoids. An analysis of the pair distribution function (PDF) in both types of amorphous Al2O3 showed that the introduction of W into amorphous Al2O3 brings about a significant change in the amorphous structure. Furthermore, it was found by high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) that sub-nm sized W clusters exist in as-deposited Al2O3 prepared by resistance-heating and then dissolve in the amorphous matrix with annealing. The combination of PDF analysis and HAADF-STEM observation provides evidence that the enhancement of void formation originates in the heterogeneous short-range atomic configurations induced by the addition of W. [ABSTRACT FROM AUTHOR]

We studied the anisotropic electrical conductivity of lotus-type porous nickel, with cylindrical pores aligned unidirectionally. We measured the electrical conductivities in the directions parallel and perpendicular to the longitudinal axis of the pore with four-probe method. The electrical conductivity of lotus nickel shows the anisotropy that reflects the anisotropic porous structure and can be summarized with a well-known power-law formula sArchie's lawd; the conductivity in the direction parallel to the pore decreases linearly with increase in porosity, and that in the perpendicular direction decreases steeply with porosity increase, in agreement with Archie's power-law formula. Furthermore, we constructed the effective-mean-field sEMFd theory to predict the effective electrical conductivity of composites. The electrical conductivity of lotus nickel, evaluated by this theory, is consistent with measurement data, and this EMF theory can fully simulate Archie's power-law formula. [ABSTRACT FROM AUTHOR]

Abstract: The formation mechanism of a high density of nanovoids by annealing amorphous Al2O3 thin films prepared by an electron beam deposition method was investigated. Transmission electron microscopy observations revealed that nanovoids ∼1–2nm in size were formed by annealing amorphous Al2O3 thin films at 973K for 1–12h, where the amorphous state was retained. The elastic stiffness, measured by a picosecond laser ultrasound method, and the density, measured by X-ray reflectivity, increased drastically after the annealing process, despite nanovoid formation. These increases indicate a change in the amorphous structure during the annealing process. Molecular dynamics simulations indicated that an increase in stable AlO6 basic units and the change in the ring distribution lead to a drastic increase in both the elastic stiffness and the density. It is probable that a pre-annealed Al2O3 amorphous film consists of unstable low-density regions containing a low fraction of stable AlO6 units and stable high-density regions containing a high fraction of stable AlO6 units. Thus, local density growth in the unstable low-density regions during annealing leads to nanovoid formation (i.e., local volume shrinkage). [Copyright &y& Elsevier]

Abstract: The composition and temperature dependence of the elastic properties and phase stability of quaternary Ti–Nb–Ta–Zr β-phase alloys with a body-centered cubic structure, developed for biomedical applications, were investigated using their single crystals, in order to clarify the origin of the low Young’s modulus in polycrystals. Transmission electron microscopy observations clarified that α″ martensitic transformation occurred in a temperature range that depended on the β-phase stability below room temperature. Electromagnetic acoustic resonance measurements clarified that the shear moduli c′ and c 44 of single crystals softened upon cooling from room temperature and became rather low near the martensitic transformation start temperature, i.e. the lower limit of β-phase stability. An analysis by the Hill approximation indicates that low c′ and c 44 caused the low Young’s modulus, and thus it is probable that the softening in c′ and c 44 is the origin of the low Young’s modulus. [ABSTRACT FROM AUTHOR]

Objectives: A novel approach to the PET image reconstruction is presented, based on the inclusion of image deconvolution during conventional OSEM reconstruction. Deconvolution is here used to provide a recovered PET image to be included as "a priori" information to guide OSEM toward an improved solution.Methods: Deconvolution was implemented using the Lucy-Richardson (LR) algorithm: Two different deconvolution schemes were tested, modifying the conventional OSEM iterative formulation: 1) We built a regularizing penalty function on the recovered PET image obtained by deconvolution and included it in the OSEM iteration. 2) After each conventional global OSEM iteration, we deconvolved the resulting PET image and used this "recovered" version as the initialization image for the next OSEM iteration. Tests were performed on both simulated and acquired data.Results: Compared to the conventional OSEM, both these strategies, applied to simulated and acquired data, showed an improvement in image spatial resolution with better behavior in the second case. In this way, small lesions, present on data, could be better discriminated in terms of contrast.Conclusions: Application of this approach to both simulated and acquired data suggests its efficacy in obtaining PET images of enhanced quality. [ABSTRACT FROM AUTHOR]

Un enfoque cualitativo descriptivo, exploratorio. Tuvo como objetivo investigar la experiencia del personal de enfermería con la muerte de niños indígenas hospitalizados y los sentimientos que surgieron de esta experiencia. Participaron en la encuesta 11 profesionales. La recolección de datos se llevó a cabo en la Unidad Pediátrica de un hospital público municipal en el estado de Mato Grosso, Brasil. Tras el análisis, las entrevistas fueron agrupados en los siguientes temas: los sentimientos expresados por el cuidador; estrategias de afrontamiento; el apoyo a la muerte de la familia antes de la muerte; la experiencia de la muerte indígenas versus no indígenas; experiencias de abandono y perjuicio; el impacto de la muerte, de la vida y de la salud profesional; impacto en la vida de los profesionales; y el apoyo psicológico profesional. El personal de enfermería sufre antes de la muerte del niño indígena que influye en sus vidas y actitudes tanto dentro como fuera del entorno hospitalario.

The self-diffusivity of oxygen in amorphous Al2O3 (a-Al2O3), a-Ta2O5, and a-Nb2O5 was investigated along with structural analysis in terms of pair distribution function (PDF). The low activation energy, ~1.2 eV, for diffusion in the oxides suggests a single atomic jump of oxygen ions mediated via vacancy-like defects. However, the pre-exponential factor for a-Ta2O5 and a-Nb2O5 with lower bond energy was two orders of magnitude larger than that for a-Al2O3 with higher bond energy. PDF analyses revealed that the short-range configuration in a-Ta2O5 and a-Nb2O5 was more broadly distributed than that in a-Al2O3. Due to the larger variety of atomic configurations of a-Ta2O5 and a-Nb2O5, these oxides have a higher activation entropy for diffusion than a-Al2O3. The entropy term for diffusion associated with short-range structures was shown to be a dominant factor for diffusion in amorphous oxides. [ABSTRACT FROM AUTHOR]

Background: Flower-shaped nuclei in plasma cells are rare in multiple myeloma., Case Presentation: We report on an 88-year-old male who presented with a mass lesion in the clavicular region. A biopsy of the mass revealed an increase in mature plasma cells with round nuclei. In contrast, a bone marrow examination showed increased plasma cells with flower-shaped nuclei. The patient tested negative for human T-lymphotropic virus type-1 and was diagnosed with multiple myeloma., Conclusions: While multiple myeloma is known for intra-tumor heterogeneity, reports of morphological heterogeneity based on the site of tumor sampling are limited. In this case, the presence of plasma cells with flower-shaped nuclei enabled the identification of site-dependent morphological tumor heterogeneity.