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2008 AIChE Annual Meeting, AIChE 100

作者： Jaszczak, John A. Raber, Mary Bennett, Michael Alaraje, Nasser Bergstrom, Paul L. Department of Physics Michigan Technological University 1400 Townsend Dr. Houghton MI 49931 United States Enterprise Program Michigan Technological University 1400 Townsend Dr. Houghton MI 49931 United States Department of Social Sciences Michigan Technological University 1400 Townsend Dr. Houghton MI 49931 United States School of Technology Michigan Technological University 1400 Townsend Dr. Houghton MI 49931 United States Department of Electrical and Computer Engineering Michigan Technological University 1400 Townsend Dr. Houghton MI 49931 United States Science Technology and Society Vassar College Poughkeepsie NY 12604-0246 United States

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Magnetostatic dipolar domain-wall pinning in chains of permalloy triangular rings

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Physical Review B 2008年第17期78卷 174403-174403页

作者： P. Vavassori D. Bisero V. Bonanni A. Busato M. Grimsditch K. M. Lebecki V. Metlushko B. Ilic CIC nanoGUNE Consolider E-20009 San Sebastian Spain CNISM and Dipartimento di Fisica Università di Ferrara I-44100 Ferrara Italy CNR-INFM National Research Center S3 via Campi 213a I-41100 Modena Italy Materials Science Division Argonne National Laboratory Argonne Illinois 60439 USA Institute of Physics Polish Academy of Sciences 02-668 Warsaw Poland Department of Electrical and Computer Engineering University of Illinois at Chicago Chicago Illinois 60607 USA Cornell Nanofabrication Facility School of Applied and Engineering Physics Cornell University Ithaca New York 14853 USA

In a combined experimental and numerical study, we investigated the details of the motion and pinning of domain walls in isolated and interacting permalloy triangular rings (side 2 μm, width 250 nm, and thickness 25 nm). To induce interaction between the rings, they were arranged either in vertical chains with an apex of each triangle in proximity to the edge center of the triangle above it or in horizontal chains where the proximity is between the adjacent corners of the triangles. Using longitudinal and diffraction magneto-optic Kerr effects, magnetic force microscopy, and micromagnetic simulations, we determined the field dependence of the spin structure in the rings. In all cases the remnant state of each ring is an “onion” state characterized by two domain walls—one head to head the other tail to tail—pinned at the apexes. In isolated rings the magnetization reversal occurs between two onion states via the formation of an intermediate vortex state, which arises from the motion and annihilation of the two domain walls. In the case of the horizontal chains the reversal mechanism is unchanged except that the dipolar interaction affects the field range in which the rings are in the vortex state. In the case of vertical chains an additional intermediate state is observed during reversal. The new state involves a domain wall pinned at the center of the edge that is in close proximity to the apex of its neighbor. We show that the domain-wall motion in this last case can be modeled by a triple potential well. Because the new state requires that a domain wall be pinned at the neighboring apex, our observations can be viewed as a very elementary form of magnetic logic.

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Photolithography using an optical microscope

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Journal of Vacuum Science and Technology B: Microelectronics and Nanometer Structures 2007年第6期25卷 2451-2452页

作者： Gonski, Ron Melngailis, John Department of Electrical and Computer Engineering Institute for Research in Electronics and Applied Physics University of Maryland College Park MD 20742-3511

The authors propose and demonstrate how to use an ordinary optical microscope as a flexible optical lithography tool. Until the advent of digital cameras, most high power optical microscopes had a vertical cone shaped fixture with a Polaroid film holder to record optical micrographs on the film. For conversion to lithography, the Polaroid film holder is simply removed and a vu-graph transparency, which serves as a mask, is substituted in the plane of the film. The transparency has the desired pattern printed on it by a laser printer or a copier. Ideally, the transparency has to be backlighted by a converging light source such that (ignoring diffraction) a pinhole anywhere in the transparency illuminates the entire lens at the base of the cone shaped fixture. The authors used a 11.4 cm diameter, 12.7 cm focal length Fresnel lens and a fiber light to generate the appropriately converging mask illumination. With the highest magnification, 100× lens the image on the mask was demagnified approximately by 700× on the sample. With this lens, the authors could expose lines of slightly less than 1 μm width. © 2007 American Vacuum Society.

关键词： Photolithography

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Lithography, plasmonics, and subwavelength aperture exposure technology

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Journal of Vacuum Science and Technology B: Microelectronics and Nanometer Structures 2007年第6期25卷 2471-2475页

作者： Ngu, Yves Peckerar, Marty Dagenais, Mario Barry, John Dutt, Birendra Department of Electrical and Computer Engineering University of Maryland College Park MD 20742 Department of Electrical and Computer Engineering Institute of Research in Electronics and Applied Physics University of Maryland College Park MD 20742 Culver City CA 90230

This article presents the first experimental evidence that plasmonic excitation in metal films perforated with regular arrays of subwavelength apertures can produce high resolution far-field radiation patterns of sufficient intensity to expose photoresist when propagated through the optical system of a conventional stepper. The pattern fill factor (i.e., the total clear aperture area divided by the total mask area) is more than an order of magnitude smaller than the ratio of the mask clear area divided by the total mask area of a conventional mask. This could lead to a significant increase in mask making throughput. Contact window arrays were exposed with critical dimensions down to 260 nm using 248 nm incident radiation. While the exposure times are longer (somewhat less than three times more energy is required on the mask), the image pattern appears to be a cooperative effect of scattering from multiple apertures. If the array is defective, meaning that it contains a small number of unopened apertures, the pattern still prints as a coherent, cleared feature. © 2007 American Vacuum Society.

关键词： Metallic films

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Diophantine Frequency Synthesizer Design for Timekeeping Systems

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International Journal of Navigation and Observation 2008年第1期2008卷

作者： Paul P. Sotiriadis Gregory L. Weaver Electrical and Computer Engineering Johns Hopkins University Baltimore MD 21218 USA Space Department Johns Hopkins University Applied Physics Laboratory Laurel MD 20723 USA

Diophantine Frequency Synthesis (DFS), a number-theoretic approach to the design of very high resolution frequency synthesizers, was introduced in 2006. Further work concerning the impact of controlling mixing products for high-spectral purity was addressed and reported at the 2007 European Frequency and Time Forum. The focus of this paper is on the implementation of nested DFS architectures targeting microphase-type applications for precision timekeeping systems. We have shown that DFS does not impart any extraordinary design constraints on spectral purity in comparison to commonly used high resolution frequency synthesis techniques such as DDS or fractional N . Here we describe a design approach for 10 MHz synthesizers with 1E-13 fractional resolution in consecutive steps ranging ±10 Hz. The synthesizers generate their output from a 10 MHz reference standard. Such synthesizers are essential to accomplishing precision frequency correction in timekeeping systems.

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American Institute of Ultrasound in Medicine consensus report on potential bioeffects of diagnostic ultrasound: Executive summary

American Institute of Ultrasound in Medicine consensus repor...

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作者： Fowlkes, J. Brian Abramowicz, Jacques S. Church, Charles C. Holland, Christy K. Miller, Douglas L. O'Brien Jr., William D. Sanghvi, Narendra T. Stratmeyer, Melvin E. Zachary, James F. Deng, Cheri X. Harris, Gerald R. Herman, Bruce A. Hynynen, Kullervo H. Merritt, Christopher R. B. Thomenius, Kai E. Bailey, Michael R. Carson, Paul L. Carstensen, Edwin L. Frizzell, Leon A. Nyborg, Wesley L. Barnett, Stanley B. Duck, Francis A. Edmonds, Peter D. Ziskin, Marvin C. Abbott, John G. Dalecki, Diane Dunn, Floyd Greenleaf, James F. Salvesen, Kjell A. Siddiqi, Tariq A. Averkiou, Michalakis A. Brayman, Andrew A. Everbach, E. Carr Wible Jr., James H. Wu, Junru Simpson, Douglas G. Basic Radiological Sciences Division Department of Radiology University of Michigan Health System 200 Zina Pitcher Pl Ann Arbor MI 48109-0553 United States Department of Radiology University of Michigan Ann Arbor MI United States Department of Obstetrics and Gynecology Rush University Medical Center Chicago IL United States National Center for Physical Acoustics University of Mississippi University MS United States Departments of Biomedical Engineering and Radiology University of Cincinnati Cincinnati OH United States Bioacoustics Research Laboratory Department of Electrical and Computer Engineering University of Illinois Urbana IL United States Focus Surgery Inc. Indianapolis IN United States US Food and Drug Administration Center for Devices and Radiological Health Silver Spring MD United States Department of Veterinary Pathobiology University of Illinois Urbana IL United States Department of Biomedical Engineering Case Western Reserve University Cleveland OH United States Department of Radiology Brigham and Women's Hospital Harvard Medical School Boston MA United States Department of Radiology Thomas Jefferson University Hospital Philadelphia PA United States General Electric Global Research Niskayuna NY United States Applied Physics Laboratory University of Washington Seattle WA United States Rochester NY United States Burlington VT United States School of Biomedical Sciences University of Sydney Sydney NSW Australia Wessex Regional Medical Physics Service Royal United Hospital Combe Park Bath United Kingdom Menlo Park CA United States Department of Radiology Temple University Philadelphia PA United States Food and Drug Administration Center for Devices and Radiological Health Silver Spring MD United States Philips Medical Systems Bothell WA United States Department of Biomedical Engineering University of Rochester Rochester NY United States Urbana IL United States Department of Physiology and Biomedical Engineer

The continued examination of potential biological effects of ultrasound and their relationship to clinical practice is a key element in evaluating the safety of diagnostic ultrasound. Periodically, the American Institute of Ultrasound in Medicine (AIUM) sponsors conferences bringing experts together to examine the literature on ultrasound bioeffects and to develop conclusions and recommendations related to diagnostic ultrasound. The most recent effort included the examination of effects whose origins were thermal or nonthermal, with separate evaluations for potential effects related to fetal ultrasound. In addition, potential effects due to the introduction of ultrasound contrast agents were summarized. This information can be used to assess risks in comparison to the benefits of diagnostic ultrasound. The conclusions and recommendations are organized into 5 broad categories, with a comprehensive background and evaluation of each topic provided in the corresponding articles in this issue. The following summary is not meant as a substitute for the detailed examination of issues presented in each of the articles but rather as a means to facilitate further study of this consensus report and implementation of its recommendations. The conclusions and recommendations are the result of several rounds of deliberations at the consensus conference, subsequent review by the Bioeffects Committee of the AIUM, and approval by the AIUM Board of Governors. © 2008 by the American Institute of Ultrasound in Medicine.

关键词： Ultrasonics

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Anisotropic fluorocarbon plasma etching of Si/SiGe heterostruetures

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Journal of Vacuum Science and Technology B: Microelectronics and Nanometer Structures 2007年第2期25卷 404-409页

作者： Ding, R. Klein, L.J. Eriksson, M.A. Wendt, A.E. Materials Science Program University of Wisconsin-Madison Madison WI 53706 Department of Physics University of Wisconsin-Madison Madison WI 53706 Department of Electrical and Computer Engineering University of Wisconsin-Madison Madison WI 53706

Fluorocarbon plasma etching of Si/SiGe heterostructures is demonstrated as a method for fabrication of quantum devices with vertical sidewalls. The heterostructures consist of layers of Si and SiGe, and anisotropic etching of the heterostructures using plasmas to isolate device elements is an attractive approach to fabricating devices. A challenge that has limited the use of fluorocarbon etching is the difference in Si and SiGe etch rates under comparative conditions. Preferential etching of SiGe can lead to undercutting beneath the top Si layer, causing a reduction in critical device dimensions of unknown magnitude. By using fluorocarbon etch gases with high carbon content, fluorocarbon sidewall passivation improves the anisotropy of etched feature profiles by preventing lateral etching of SiGe. Etch results with a C 4F8/Ar/N2 gas mixture show a straight sidewall profile through the layers of the heterostructure. © 2007 American Vacuum Society.

关键词： Plasma etching

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Microfluidic interfaced for localized release of no into developing rat dorsal root ganglia 11

Microfluidic interfaced for localized release of no into dev...

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11th International Conference on Miniaturized Systems for Chemistry and Life Sciences, uTAS 2007

作者： Lavella, G. Padmanabhan, P. Wu, B. Meyerhoff, M.E. Maharbiz, M.M. Department of Electrical Engineering University of Michigan United States Applied Physics Program Department of Biomedical Engineering University of Michigan United States Department of Chemistry University of Michigan United States

ISBN: (纸本)9780979806407

We present a microfluidic device capable of generating micro-scale gradients of nitric oxide (NO) in cell cultures. NO release is achieved through the proton mediated reaction of a water-soluble low molecular weight poly(ethylenimine) (LMW PEI) NO donor and a pH buffer solution. Reactions, and subsequent NO release into the cell culture, occur at lithographically patterned laminar flow interfaces made of poly(dimethylsiloxane) (PDMS). The NO flux can be controlled during culture by regulating the flow rate. The device is capable of producing highly localized and physiologically relevant nitric oxide flux rates and is employed to study the role of nitric oxide on the development of neural morphology in the dorsal root ganglia (DRG). © 2007 CBMS.

关键词： Nitric oxide

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Many-body excitations in the tunneling current spectra of a few-electron quantum dot

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Physical Review B 2008年第16期77卷 165340-165340页

作者： D. V. Melnikov T. Fujisawa D. G. Austing S. Tarucha J.-P. Leburton Beckman Institute for Advanced Science and Technology and Department of Electrical and Computer Engineering University of Illinois at Urbana-Champaign 405 North Mathews Avenue Urbana Illinois 61801 USA NTT Basic Research Laboratories NTT Corporation Atsugi-shi Kanagawa 243-0198 Japan and Tokyo Institute of Technology 2-12-1 Okayama Meguro-ku Tokyo 152-8551 Japan Institute of Microstructural Sciences M50 National Research Council of Canada Montreal Road Ottawa Ontario Canada K1A 0R6 ICORP Spin Information Project JST Atsugi-shi Kanagawa 243-0198 Japan and Department of Applied Physics University of Tokyo Hongo Bunkyo-ku Tokyo 113-8656 Japan

Inherent asymmetry in the tunneling barriers of few-electron quantum dots induces intrinsically different tunneling currents for forward and reverse source-drain biases in the nonlinear transport regime. We demonstrate that in addition to spin selection rules, overlap matrix elements between many-body states are crucial for the correct description of tunneling transmission through quantum dots at large magnetic fields. Signatures of excited (N−1)-electron states in the transport process through the N-electron system are clearly identified in the measured transconductances. Overall, the computed current spectra are found to be in very good agreement with the experimental data.

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Femtosecond pump-probe studies of carrier transport and gain dynamics in quantum cascade lasers

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physica status solidi c 2008年第1期5卷

作者： Hyunyong Choi Laurent Diehl Marcella Giovannini Jérôme Faist Federico Capasso Theodore B. Norris Center for Ultrafast Optical Science and Department of Electrical Engineering and Computer Science University of Michigan Ann Arbor MI 48109-2099 USA Institute of Physics University of Neuchâtel 2000 Neuchâtel Switzerland School of Engineering and Applied Sciences Harvard University Cambridge Massachusetts 02138 USA

Time-resolved pump-probe differential transmission measurements have been performed on various sets of quantum cascade lasers below and above threshold. Bias-, temperature-, and polarization dependent studies enable a comprehensive understanding of the gain dynamics to be possible in terms of tunneling, transport, and coupling with the intra-cavity photon density. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

关键词： 42.55.Px 78.47.+p 78.6700000000000017.−n

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