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Novel Optical Instrumentation for Biomedical Applications II

作者： Zhong, Wei Sud, Dhruv Wu, Mei Merrick, Karl A. Merajver, Sofia D. Beer, David G. Mycek, Mary-Ann Dept. of Biomedical Engineering University of Michigan Ann Arbor MI 48109 Department of Internal Medicine Medical School University of Michigan Ann Arbor MI 48109 Comprehensive Cancer Center University of Michigan Medical School Ann Arbor MI 48109 Department of Surgery Medical School University of Michigan Ann Arbor MI 48109 Applied Physics Program University of Michigan Ann Arbor MI 48109

In contrast to intensity-based fluorescence microscopy, fluorescence lifetime imaging microscopy (FLIM) bases image contrast on fluorophore excited-state lifetime. This technique is sensitive to the fluorophore's local environment (temperature, ion concentration, dissolved gas concentration, and molecular associations), while being independent of factors impacting fluorescence intensity (fluorophore concentration, photobleaching, scattering, and absorption). We present design features of a novel UV-visible-NIR wide-field time-domain FLIM system with optical sectioning (10 μm), high temporal discrimination (50 ps), and large temporal dynamic range (750 ps - 1 μs), and apply the system to probe cellular metabolic function and detect molecular activity in vivo. © 2005 SPIE and OSA.

关键词： Image processing

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Editorial

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Surface and Coatings Technology 2005年第1-3 SPEC. ISS.期198卷 1-1页

作者： Zhang, Sam Teixeira, Vasco Thin Film Technology Strategic Research Program School of Mechanical and Aerospace Engineering Nanyang Technological University 50 Nanyang Avenue Singapore 639798 Singapore GRF-Functional Coatings Group Physics Department University of Minho Campus de Azurém P-4800-058 Guimarães Portugal

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Hydrostatic pressure control of the magnetostructural phase transition in Gd5Si2Ge2 single crystals

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Physical Review B 2005年第2期72卷 024416-024416页

作者： C. Magen L. Morellon P. A. Algarabel M. R. Ibarra Z. Arnold J. Kamarad T. A. Lograsso D. L. Schlagel V. K. Pecharsky A. O. Tsokol K. A. Gschneidner, Jr. Departamento de Física de la Materia Condensada and Instituto de Ciencia de Materiales de Aragón Universidad de Zaragoza and Consejo Superior de Investigaciones Científicas 50009 Zaragoza Spain Institute of Physics AS CR Na Slovance 2 182 21 Prague 8 Czech Republic Materials and Engineering Physics Program Ames Laboratory Iowa State University Ames Iowa 50011-3020 USA Department of Materials Science and Engineering Iowa State University Ames Iowa 50011-2300 USA

Magnetic and structural properties of single crystalline Gd5Si2Ge2 under hydrostatic pressure have been characterized by using magnetization, linear thermal expansion, and compressibility measurements. A strong dependence of Curie temperature on pressure, dTC∕dP=+4.8K∕kbar, is observed in contrast with the smaller values of about 3K∕kbar found in polycrystalline specimens. This difference reflects the role the microstructure may play in pressure-induced magnetic-crystallographic phase changes, likely related to stress relaxation at the grain boundaries, domain pinning and/or nucleation of defects. The pressure dependence of the critical magnetic field, d(dHC∕dT)∕dP, drops at the rate −0.122(5)kOe∕Kkbar, which points to an enhancement of the magnetoelastic coupling with pressure. The latter affects the magnetocaloric behavior of the material at the rate d(ΔSM)∕dP≅1.8J∕kgKkbar. The linear thermal expansion confirms the strongly anisotropic change of the lattice parameters through the orthorhombic to monoclinic crystallographic transformation with Δa∕a=+0.94%, Δb∕b=−0.13%, and Δc∕c=−0.22%. The structural transition temperature varies with pressure synchronously with the Curie temperature, and the size and shape of the strain anomalies remain nearly unaffected by the hydrostatic pressure, indicating, respectively, that the structural and magnetic transformations remain coupled, and the anisotropic behavior of the lattice is preserved as pressure increases. The room temperature linear compressibility data show that the magnetostructural transformation can be triggered isothermally at ∼6kbar and that the compressibility is anisotropic.

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Molecular dynamics simulations of the mechanical strength of Si∕Si3N4 interfaces

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Physical Review B 2005年第9期72卷 094115-094115页

作者： Martina E. Bachlechner Jennifer Zhang Ye Wang Jarrod Schiffbauer Steven R. Knudsen Dimitris Korakakis Physics Department West Virginia University Morgantown West Virginia 26506 USA NASA Independent Verification and Validation Facility Science and Engineering Apprenticeship Program—Morgantown High School Morgantown West Virginia 26501 USA Institute for Scientific Research Inc. Fairmont West Virginia 26555 USA Lane Department for Computer Science and Electrical Engineering West Virginia University Morgantown West Virginia 26506 USA

Molecular dynamics simulations are performed on parallel computers to investigate the crystalline Si(111)∕Si3N4(0001) interface that is modeled as an eight-component system. The average total energy per particle and the average kinetic energy per particle of the subsystems are monitored during the preparation of the system. The Young’s modulus of the interface is compared with that of the silicon part alone and that of the silicon-nitride film, respectively. The results for one extended simulation feature a crack in the silicon-nitride film and dislocated atoms in silicon below the crack. Simulations at rates of strain ranging from 0.00125to0.05ps−1 show that for lower strain rates, the systems stretched faster reach their ultimate strength at a higher strain value than those that were stretched more slowly. At the highest strain rates, however, the failure mechanisms change qualitatively indicative of a more ductile behavior.

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Carbon nanotubes: Anomalous photo-galvanic effect, electromechanical instability, and IR detection

Carbon nanotubes: Anomalous photo-galvanic effect, electrome...

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Frontiers in Optics, FiO 2005

作者： Rakitin, A. Meĺnikov, I.V. Haus, J.W. Aitchison, J.S. Department of Physics and Astronomy York University 4700 Keele Street North York Ontario M3P 1P3 Canada Comtex Consulting Inc 162 Princess Margaret Boulevard Etobicoke Ontario M9B 2Z5 Canada Electro-Optics Program School of Engineering University of Dayton 300 College Park Dayton Ohio 45469-0245 United States The E. S. Rogers Sr. Department of Electrical and Computer Engineering University of Toronto 10 King's College Road Toronto. Ontario M5S 3G4 Canada

ISBN: (纸本)1557527970

Carbon nanotubes (CNTs) are hollow cylinders composed of one or more concentric layers of carbon atoms arranged in a honeycomb lattice. CNTs are widely considered as an elemental material for a future nanoelectronic technology. This is not simply due to their small size but rather to their overall properties: CNTs are known to exhibit either metallic or semiconducting behaviour, with the band gap being dependent on the nanotube diameter. Both active devices (transistors) and interconnects can be made out of semiconducting and metallic nanotubes, respectively. The key nanotube dimension, their diameter, is controlled by chemistry, not conventional fabrication. The strong covalent bonding gives the CNTs high mechanical and thermal stability and ability to sustain current densities as high as 10 A/cm2.

关键词： Atoms Carbon nanotubes Chemistry Curvature Infrared detection Scattering

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Stalactite Growth as a Free-Boundary Problem: A Geometric Law and Its Platonic Ideal

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Physical Review Letters 2005年第1期94卷 018501-018501页

作者： Martin B. Short James C. Baygents J. Warren Beck David A. Stone Rickard S. Toomey, III Raymond E. Goldstein Department of Physics University of Arizona Tucson Arizona 85721 USA Department of Chemical and Environmental Engineering University of Arizona Tucson Arizona 85721 USA Program in Applied Mathematics University of Arizona Tucson Arizona 85721 USA Accelerator Mass Spectrometry Facility University of Arizona Tucson Arizona 85721 USA Department of Soil Water and Environmental Science University of Arizona Tucson Arizona 85721 USA Kartchner Caverns State Park P.O. Box 1849 Benson Arizona 85602 USA

The chemical mechanisms underlying the growth of cave formations such as stalactites are well known, yet no theory has yet been proposed which successfully accounts for the dynamic evolution of their shapes. Here we consider the interplay of thin-film fluid dynamics, calcium carbonate chemistry, and CO2 transport in the cave to show that stalactites evolve according to a novel local geometric growth law which exhibits extreme amplification at the tip as a consequence of the locally-varying fluid layer thickness. Studies of this model show that a broad class of initial conditions is attracted to an ideal shape which is strikingly close to a statistical average of natural stalactites.

关键词： Limestone

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Residual stress measurements in welded and plastically deformed target structural materials

Journal of ASTM International

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Journal of ASTM International 2005年第6期2卷 67-79页

作者： Roy, Ajit K. Venkatesh, Anand Dronavalli, Satish Marthandam, Vikram Wells, Douglas Selim, Farida Rogge, Ronald Department of Mechanical Engineering University of Nevada Las Vegas Box 454027 4505 Maryland Parkway Las Vegas NV 89154 Department of Physics Idaho State University Campus Box 8106 785 S. 8th Ave. Pocatello ID 83209 Department of Physics Idaho State University Campus Box 8263 785 S. 8th Ave. Pocatello ID 83209 National Research Council Neutron Program for Materials Research Chalk River Laboratories Chalk River Ont. KOJ 1JO Canada

Transmutation of spent nuclear fuels (SNF) is currently being considered to transform long-lived isotopes to species with relatively short half-lives and reduced radioactivity through capture and decay of minor actinides and fission products. This process is intended for geologic disposal of SNF for shorter durations in the proposed repository at the Yucca Mountain site. The structural material (Type 304L stainless steel/Alloy EP-823) surrounding the transmutation target will be subjected to welding operation and plastic deformation during fabrication, which could induce residual stresses in it. Destructive ring-core, and nondestructive x-ray diffraction, neutron diffraction, and positron annihilation spectroscopic techniques were used to evaluate residual stresses in welded and cold-worked specimens of both materials. The results indicate that, in general, for a welded specimen consisting of Alloy EP-823 and Type 304L stainless steel on opposite sides, compressive and tensile residual stresses were observed in the former and latter materials, respectively. However, a welded specimen consisting of only Alloy EP-823 on both sides showed tensile residual stresses. The extent of residual stresses in cold-worked specimens was enhanced with increased level of cold-reduction. In case of a bent specimen, compressive and tensile residual stresses were noticed in the convex and concave sides, respectively. Copyright © 2005 by ASTM International.

关键词： Residual stresses

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Experiments on Random Packings of Ellipsoids

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Physical Review Letters 2005年第19期94卷 198001-198001页

作者： Weining Man Aleksandar Donev Frank H. Stillinger Matthew T. Sullivan William B. Russel David Heeger Souheil Inati Salvatore Torquato P. M. Chaikin Department of Physics and Princeton Institute for the Science and Technology of Materials Princeton University Princeton New Jersey 08544 USA Program in Applied and Computational Mathematics and Princeton Institute for the Science and Technology of Materials Princeton University Princeton New Jersey 08544 USA Department of Chemistry and Princeton Institute for the Science and Technology of Materials Princeton University Princeton New Jersey 08544 USA Department of Chemical Engineering and Princeton Institute for the Science and Technology of Materials Princeton University Princeton New Jersey 08544 USA Department of Psychology and Center for Neural Science New York University New York New York 10003 USA

Recent simulations indicate that ellipsoids can pack randomly more densely than spheres and, remarkably, for axes ratios near 1.25∶1∶0.8 can approach the densest crystal packing (fcc) of spheres, with a packing fraction of 74%. We demonstrate that such dense packings are realizable. We introduce a novel way of determining packing density for a finite sample that minimizes surface effects. We have fabricated ellipsoids and show that, in a sphere, the radial packing fraction ϕ(r) can be obtained from V(h), the volume of added fluid to fill the sphere to height h. We also obtain ϕ(r) from a magnetic resonance imaging scan. The measurements of the overall density ϕavr, ϕ(r) and the core density ϕ0=0.74±0.005 agree with simulations.

关键词： .ellipsoids Princeton New Jersey

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Confinement Effects in Nanoscale Anodic Alumina Structures on Silicon

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MRS Online Proceedings Library 2005年第1期854卷 U11.5.1-U11.5.6页

作者： Griffin, Patrick J. Carpick, Robert W. Stone, Donald S. Materials Science Program University of Wisconsin-Madison Madison U.S.A. Engineering Physics Department University of Wisconsin-Madison Madison U.S.A. Materials Science and Engineering Department University of Wisconsin-Madison Madison U.S.A.

Anodic aluminum oxide (AAO) has long been considered a viable material for templated growth of nanomaterials for electronic, magnetic and optical applications due to the ability to form self-organized, high aspect-ratio nanochannels. More recently these porous materials have been incorporated with silicon to create a template for nanostructured materials on a semiconducting substrate. However, there has been no investigation into how pore growth is affected by confining the pre-anodized aluminum dimensions to the nanometer scale. We have used electron beam lithography to pattern 200 nm thick aluminum structures on Si with lateral features ranging from 100 nm to several microns in size. Structures consisting of 1–10 individual pores 10–15 nm in diameter are routinely fabricated. Confinement effects in the narrowest features assist in pore ordering in the porous structures without the use of pre-patterning or a two step anodization.

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Influence of power on the structure and mechanical properties of TiN coatings deposited by rf magnetron

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physica status solidi c 2005年第10期2卷

作者： J. E. Alfonso Fernando Pacheco Álvaro Castro P. J. Torres Physics of Condensed Matter Group Physics Department Universidad Nacional de Colombia Bogotá Centro Internacional de Física (CIF) Bogotá Colombia M. Sc. Program of Materials and Processes Mechanics and Mechatronics Engineering Department Universidad Nacional de Colombia Bogotá

Nitrides of transition metals, such as Ti, attract significant interest since they find a wide field of applications ranging from cutting tools to electronic device applications. Titanium nitride is broadly used as a hard protective coating for tribologic applications and for high temperature structural materials. In this work we present the results obtained in the growth of the titanium nitride (TiN) thin films in reactive phase by rf magnetron technique on AISI 420 steels. The depositions of TiN were carried out at a pressure of 7 × 10 –3 mbar in an atmosphere of N 2 and Ar; we took as study parameter the incident power on the target of Ti (99.9). The films were characterized by X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM). The study of XRD showed that films grown with power at 200 W are polycrystalline, while films grown between 350 W and 750 W built the (111) plane of the TiN phase in predominant form and at 800 W there is a change of the growth direction to the (200) plane. The analysis of the Energy Dispersive X-ray Spectroscopy (EDXS) indicated that the films grew stoichiometrically. On the other hand, the hardness tests determined that the films have micro-hardness with values that increased with the power applied to the target; the highest value was 2300 Knoops for the films grown at 500 W. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

关键词： 68.55.Jk 68.55.Nq 68.60.Bs 81.15.Cd

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