573 research outputs found
Retirement and Social Security Reform Expectations: A Solution to the New Early Retirement Puzzle
Robust Output-Feedback Stabilization for Incompressible Flows using Low-Dimensional H<sub>∞</sub>-Controllers
SPUTTER DEPTH PROFILING OF OPTICAL WAVEGUIDES USING SECONDARY ION MASS SPECTROMETRY
The technique of sputter depth profiling by means of secondary ion mass spectrometry
of samples with high resistivity is reviewed. As examples we discuss optical waveguides made
in lithium niobate by titanium indiffusion and implantation and also yttrium iron garnet
waveguides grown by liquid phase epitaxy on gadolinium gallium garnet. Depth profiling of
these waveguide structures has been performed and the necessary precautions to prevent
charging by the primary ion beam are discussed. In some cases, coating with a metallic layer
is adequate, but a more universal method is charge neutralization by an additional electron
beam
Body Image of Dancers in Los Angeles: The Cult of Slenderness and Media Influence Among Dance Students
Body image and self-esteem are examined through personal stories among Los Angeles college dancers who grew up in the Hollywood culture of the cult of slenderness. The study incorporates a body image survey, eating disorder screen, and an interview process capturing dancers’ lived experiences with daily pressures. Dancers reveal their experiences with body image struggles and empowerment. Quantitative and qualitative results point to a need for future social activist intervention with dancers in their formative years when body image concepts are formed. At this time of need and rebellion, the dance community could support change by increasing focus on wellness to better support girls and women so mediated pressures will not continue to squelch the self-esteem of girls and women
Changes in the electrical transport of ZnO under visible light
Complex impedance spectroscopy data in the frequency range 16Hz < f < 3 MHz
at room temperature were acquired on pure ZnO single crystal and thin film. The
measured impedance of the ZnO samples shows large changes with time after
exposure to or covering them from visible light. At fixed times
Cole-Cole-diagrams indicate the presence of a single relaxation process. A
simple analysis of the impedance data allows us to obtain two main relaxation
times. The behavior for both, ZnO crystal and thin film, is similar but the
thin film shows shorter relaxation times. The analysis indicates the existence
of two different photo-active defects with activation energies between ~0.8 eV
and ~1.1 eV.Comment: 11 pages, 9 figures. Solid state communications, in pres
Adsorption of oxygen on Pt3Sn studied by scanning tunneling microscopy and x-ray photoelectron diffraction
Robust Controller versus Numerical Model Uncertainties for Stabilization of Navier-Stokes Equations
Hierarchical super-structure identified by polarized light microscopy, electron microscopy and nanoindentation: Implications for the limits of biological control over the growth mode of abalone sea shells
Mollusc shells are commonly investigated using high-resolution imaging techniques based on cryo-fixation. Less detailed information is available regarding the light-optical properties. Sea shells of Haliotis pulcherina were embedded for polishing in defined orientations in order to investigate the interface between prismatic calcite and nacreous aragonite by standard materialographic methods. A polished thin section of the interface was prepared with a defined thickness of 60 μm for quantitative birefringence analysis using polarized light and LC-PolScope microscopy. Scanning electron microscopy images were obtained for comparison. In order to study structural-mechanical relationships, nanoindentation experiments were performed.Incident light microscopy revealed a super-structure in semi-transparent regions of the polished cross-section under a defined angle. This super-structure is not visible in transmitted birefringence analysis due to the blurred polarization of small nacre platelets and numerous organic interfaces. The relative orientation and homogeneity of calcite prisms was directly identified, some of them with their optical axes exactly normal to the imaging plane. Co-oriented "prism colonies" were identified by polarized light analyses. The nacreous super-structure was also visualized by secondary electron imaging under defined angles. The domains of the super-structure were interpreted to consist of crystallographically aligned platelet stacks. Nanoindentation experiments showed that mechanical properties changed with the same periodicity as the domain size.In this study, we have demonstrated that insights into the growth mechanisms of nacre can be obtained by conventional light-optical methods. For example, we observed super-structures formed by co-oriented nacre platelets as previously identified using X-ray Photo-electron Emission Microscopy (X-PEEM) [Gilbert et al., Journal of the American Chemical Society 2008, 130:17519–17527]. Polarized optical microscopy revealed unprecedented super-structures in the calcitic shell part. This bears, in principle, the potential for in vivo studies, which might be useful for investigating the growth modes of nacre and other shell types
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Hierarchical super-structure identified by polarized light microscopy, electron microscopy and nanoindentation: implications for the limits of biological control over the growth mode of abalone sea shells
Background: Mollusc shells are commonly investigated using high-resolution imaging techniques based on cryo-fixation. Less detailed information is available regarding the light-optical properties. Sea shells of Haliotis pulcherina were embedded for polishing in defined orientations in order to investigate the interface between prismatic calcite and nacreous aragonite by standard materialographic methods. A polished thin section of the interface was prepared with a defined thickness of 60 μm for quantitative birefringence analysis using polarized light and LC-PolScope microscopy. Scanning electron microscopy images were obtained for comparison. In order to study structural-mechanical relationships, nanoindentation experiments were performed. Results: Incident light microscopy revealed a super-structure in semi-transparent regions of the polished cross-section under a defined angle. This super-structure is not visible in transmitted birefringence analysis due to the blurred polarization of small nacre platelets and numerous organic interfaces. The relative orientation and homogeneity of calcite prisms was directly identified, some of them with their optical axes exactly normal to the imaging plane. Co-oriented "prism colonies" were identified by polarized light analyses. The nacreous super-structure was also visualized by secondary electron imaging under defined angles. The domains of the super-structure were interpreted to consist of crystallographically aligned platelet stacks. Nanoindentation experiments showed that mechanical properties changed with the same periodicity as the domain size. Conclusions:
In this study, we have demonstrated that insights into the growth mechanisms of nacre can be obtained by conventional light-optical methods. For example, we observed super-structures formed by co-oriented nacre platelets as previously identified using X-ray Photo-electron Emission Microscopy (X-PEEM) [Gilbert et al., Journal of the American Chemical Society 2008, 130:17519–17527]. Polarized optical microscopy revealed unprecedented super-structures in the calcitic shell part. This bears, in principle, the potential for in vivo studies, which might be useful for investigating the growth modes of nacre and other shell types
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