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81.
W. Swiech G.H. Fecher M. Huth O. Schmidt N.-F. Cheng C.-K. Lin C.-Y. Tung Y. Hwu 《Applied Physics A: Materials Science & Processing》1998,67(4):447-454
2 Al3 and YBa2Cu3O7/PrBa2Cu3O7. To investigate devices built from these complex materials we applied element-sensitive photoemission electron microscopy
(PEEM). Information about the chemical composition of the imaged sample can be obtained by PEEM via tuning the photon energy
to X-ray absorption edges. To apply spectromicroscopy we acquired microscopic images using photon energies near and at the
edges. Such images give the lateral distribution of a specific element. Microspectroscopy is performed by recording the intensity
of the true secondary electrons in selected spots during a sweep of the photon energy. The main aim of our work was to observe
oxygen-related defects and changes in the composition affecting the physical properties of the materials. Therefore, we applied
both methods to micro-patterned devices using soft-X-ray synchrotron radiation and found that small local defects and chemical
differences can be easily detected. Such defects and chemical differences are quite critical to the physical properties of
the devices, since they simulate spurious effects thus influencing the reliability of the devices.
Received: 13 March 1998/Accepted: 22 April 1998 相似文献
82.
83.
Noreen R Pineau R Chien CC Cestelli-Guidi M Hwu Y Marcelli A Moenner M Petibois C 《Analytical and bioanalytical chemistry》2011,401(3):795-801
Fourier-transform infrared (FTIR) imaging has been used to investigate brain tumor angiogenesis using a mice solid tumor model
and bare-gold (∅ 25 nm) or BaSO4 (∅ 500 nm) nanoparticles (NP) injected into blood vasculature. FTIR images of 20-μm-thick tissue sections were used for chemical
histology of healthy and tumor areas. Distribution of BaSO4-NP (using the 1,218–1,159 cm−1 spectral interval) revealed clearly all details of blood vasculature with morphological abnormalities of tumor capillaries,
while Au-NP (using the 1,046–1,002 cm−1 spectral interval) revealed also diffusion properties of leaky blood vessels. Diffusion of Au-NP out of vascular space reached
64 ± 29 μm, showing the fenestration of “leaky” tumor blood vessels, which should allow small NP (<100 nm, as for Au-NP) to
diffuse almost freely, while large NP should not (as for BaSO4-NP in this study). Therefore, we propose to develop FTIR imaging as a convenient tool for functional molecular histology
imaging of brain tumor vasculature, both for identifying blood capillaries and for determining the extravascular diffusion
space offered by vessel fenestration. 相似文献
84.
Noreen R Chien CC Delugin M Yao S Pineau R Hwu Y Moenner M Petibois C 《Analytical and bioanalytical chemistry》2011,401(3):845-852
Fourier transform infrared (FTIR) imaging has been used as a molecular histopathology tool on brain tissue sections after
intracranial implantation and development of glioma tumors. Healthy brain tissue (contralateral lobe) as well as solid and
diffuse tumor tissues were compared for their collagen contents. IR spectra were extracted from IR images for determining
the secondary structure of protein contents and compared to pure product spectra of collagens (types I, III, IV, V, and VI).
Multivariate statistical analyses of variance and correspondence factorial analysis were performed to differentiate healthy
and tumor brain tissues as well as their classification according to their secondary structure profiles. Secondary structure
profiles revealed that no collagen was present in healthy tissues; they are also significantly different from solid and diffuse
tumors (p < 0.05). Solid and diffuse tumors could be discriminated with respect to the secondary structure profile of fibrillar and
non-fibrillar collagens, respectively. We can thus propose to develop FTIR imaging for histopathology examination of tumors
on the basis of collagen contents. 相似文献
85.
Chen YT Chen TY Yi J Chu YS Lee WK Wang CL Kempson IM Hwu Y Gajdosik V Margaritondo G 《Optics letters》2011,36(7):1269-1271
Since its invention in 1930, Zernike phase contrast has been a pillar in optical microscopy and more recently in x-ray microscopy, in particular for low-absorption-contrast biological specimens. We experimentally demonstrate that hard-x-ray Zernike microscopy now reaches a lateral resolution below 30 nm while strongly enhancing the contrast, thus opening many new research opportunities in biomedicine and materials science. 相似文献
86.
Through the equivalence of potential energy and elastic strain energy, a molecular-continuum model combining the concepts of molecular dynamics and continuum mechanics is proposed. Unlike the usual test performed by applying forces, in this model a uniform strain field is employed in the representative volume element of specimens. Through this model, the Young’s moduli, Poisson’s ratios, and shear modulus of graphene sheets and carbon nanotubes (armchair, zigzag, or chiral) can all be written as a simple rational function in which the dependence of radius, chiral angle and thickness can be observed clearly from the explicit closed-form expression. Moreover, according to the proposed molecular-continuum model, an integrated symbolic and numerical computational scheme (ISNC) is established to deal with the general nanoscale elastic solids. Identical results of the closed-form solutions and ISNC verify the correctness of our derivation. Comparison with the results obtained by the other methods or by different potential energy function further justifies the simplicity, validity and efficiency of the proposed model. 相似文献
87.
88.
Chen KF Chang CS Shiue J Hwu Y Chang WH Kai JJ Chen FR 《Micron (Oxford, England : 1993)》2008,39(6):749-756
An electrostatic phase plate can provide better phase contrast, a fact that plays a promising role for the high-resolution observation of specimens containing light elements. However, in order to quantify the "phase" contrast from images recorded using the phase plate, the "absorption" (or scattering) contrast arising from electrons scattered elastically and inelastically outside of the phase-plate ring must be analyzed. Angular distributions of the elastic and inelastic scattering are predicted using the Lenz model. The mean absorptive potential, [Formula: see text] serving as an index for the contribution of "absorption" contrast, is calculated from the reciprocal mean free path of elastic and inelastic scattering, and is verified experimentally. The mean absorptive potential of a particular phase plate with inner and outer radii of 0.25mum (theta(1)=0.09mrad) and 1mum (theta(2)=0.4mrad), respectively, is approximately 0.11eV for carbon and is equivalent to that of an objective aperture of semiangle 17mrad (cutoff frequency 6.7nm(-1)). 相似文献
89.
90.
R. J. Hwu N. C. Luhmann D. B. Rutledge B. Hancock U. Lieneweg 《International Journal of Infrared and Millimeter Waves》1988,9(12):1011-1020
Thousands of solid-state diodes are monolithically integrated by a metal grid as a highly efficient frequency multiplier which promises watt-level CW output power throughout the millimeter and submillimeter wave region. Different devices such as GaAs Schottky diode, thin MOS diode, and GaAs Barrier-Intrinsic-N+ diode are employed in this study. The approach also results in low-cost fabication and small-size realization. 相似文献