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Monolayer Pattern Evolution via Substrate Strain-Mediated Spinodal Decomposition

Physical Review Letters 2004年第16期93卷 166104-166104页

作者： Kevin S. Schneider Wei Lu Thomas M. Owens Daniel R. Fosnacht M. M. Banaszak Holl B. G. Orr Chemistry Department The University of Michigan Ann Arbor Michigan 48109-1055 USA Mechanical Engineering Department The University of Michigan Ann Arbor Michigan 48109-2125 USA Applied Physics Program The Harrison M. Randall Laboratory The University of Michigan Ann Arbor Michigan 48109-1120 USA Physics Department The Harrison M. Randall Laboratory The University of Michigan Ann Arbor Michigan 48109-1120 USA

Investigations of octylsilane (C8H17SiH3) monolayer pattern formation on Au(111) are reported. Scanning tunneling microscopy data display the evolution of a ∼6 nm scale pattern of interwoven features concomitant with ejection of surface Au atoms and relaxation of the Au(111) 23×3 surface reconstruction. Numerical simulations suggest the surface dynamics are governed by a substrate strain-mediated spinodal decomposition mechanism, novel to organic monolayer formation. Collectively, the experimental and theoretical data indicate strain-inducing Si-Au bond interactions drive the pattern formation and the alkyl chains play a negligible role.

关键词： Self assembly

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Resonant Oscillators with Carbon-Nanotube Torsion Springs

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Physical Review Letters 2004年第14期93卷 146101-146101页

作者： S. J. Papadakis A. R. Hall P. A. Williams L. Vicci M. R. Falvo R. Superfine S. Washburn Department of Physics and Astronomy University of North Carolina at Chapel Hill Chapel Hill North Carolina 27599 USA Curriculum in Applied and Materials Science University of North Carolina at Chapel Hill Chapel Hill North Carolina 27599 USA Department of Computer Science University of North Carolina at Chapel Hill Chapel Hill North Carolina 27599 USA Department of Biomedical Engineering University of North Carolina at Chapel Hill Chapel Hill North Carolina 27599 USA

We report on the characterization of nanometer-scale resonators. Each device incorporates one multiwalled carbon nanotube (MWNT) as a torsional spring. The devices are actuated electrostatically, and their deflections, both low frequency and on resonance, are detected optically. These are some of the smallest electromechanical devices ever created and are a demonstration of practical integrated MWNT-based oscillators. The results also show surprising intershell mechanical coupling behavior in the MWNTs.

关键词： Oscillators (electronic)

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Nanoscale study of conduction through carbon nanotube networks

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Physical Review B 2004年第20期69卷 201402(R)-201402(R)页

作者： M. Stadermann S. J. Papadakis M. R. Falvo J. Novak E. Snow Q. Fu J. Liu Y. Fridman J. J. Boland R. Superfine S. Washburn Department of Chemistry University of North Carolina at Chapel Hill Chapel Hill North Carolina 27599 USA Department of Physics and Astronomy University of North Carolina at Chapel Hill Chapel Hill North Carolina 27599 USA Curriculum in Applied and Materials Science University of North Carolina at Chapel Hill Chapel Hill North Carolina 27599 USA Naval Research Laboratory Nanostructures Section Code 6876 Washington DC 20375 USA Gross Chemistry Laboratory Duke University Box 90354 Durham North Carolina 27708 USA Department of Computer Science University of North Carolina at Chapel Hill Chapel Hill North Carolina 27599 USA Department of Chemistry Trinity College Dublin 2 Ireland Department of Biomedical Engineering University of North Carolina at Chapel Hill Chapel Hill North Carolina 27599 USA

We present local conductance measurements of carbon nanotube networks with nanometer scale resolution and show that there are discrete drops in conductance that correspond to junctions of metallic nanotubes and semiconducting nanotubes. The anomalies of these networks compared to thin films are shown, and a new method of discerning between semiconducting and metallic single-wall carbon nanotubes is demonstrated.

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Myogenesis contributes to functional electrical stimulation (fes)-induced recovery of myofiber excitability and mass of human long-term denervated muscles in spinal cord injury (SCI)

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Journal of the Peripheral Nervous System 2004年第2期9卷

作者： H Kern S Boncompagni K Rossigni W Mayr F Protasi U Carraro Ludwig Boltzmann Institute of Electrostimulation and Physical Rehabilitation Department of Physical Medicine Wilhelminenspital Vienna Austria CeSI University G. d’Annunzio Chieti Italy Laboratory of Applied Myology University of Padova Italy Biomedical Engineering and Physics University of Vienna Austria.

Many months after SCI, when an irreversible injury involves lower motoneurons, severe atrophy of human muscle is complicated by fibrosis and fat substitution (denervated, degenerated muscle, DDM). We will describe the effects of long-term lower motoneuron denervation on human muscle and present the structural results of muscle trained using FES. Antibody for embryonic myosin demonstrates that sustained myogenesis occurs in human DDM. By electron microscopy we studied: a) the overall structure of fibers and myofibrils in long-term DDM, including the effects of FES, and b) the structure and localization of calcium release units, or triads, the structure deputed to activate muscle contraction during excitation-contraction coupling (ECC). The poor excitability of human long-term DDM fibers during the first stages of FES training could be explained in terms of spatial disorder of both the ECC and contractile apparati. The structural studies are extremely encouraging since they demonstrate that FES training is effective in reverting long-term DDM atrophy and in maintaining the trophic state of the recovered myofibers.

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Visualization of acoustic streaming produced by lithotripsy field using a PIV method

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Journal of physics: Conference Series 2004年第1期1卷

作者： M J Choi D H Doh C H Cho K S Kang D G Paeng N H Ko K S Kim G H Rim A J Coleman Medical and Industrial Ultrasound Group NPL Teddington TW11 0LW UK Department of Medicine Cheju National University 690-756 Republic of Korea Interdisciplinary Postgraduate Program in Biomedical Eng. Cheju National University 690-756 Republic of Korea Mechanical & Information Eng Korea Maritime University Pusan Republic of Korea Applied Electrophysics Research Group KERI Chang-Wan Rep of Korea Department of Biomedical Eng Dong-Ah University Hospital Pusan Republic of Korea Medical Physics Department Guy's and St Thomas' Hospital London SE1 7EH UK

We visualized the acoustic streaming produced in water by an experimental lithotripter using a particle image velocimetry (PIV) method. Streaming generated around the beam focus has been optically visualized using light scattering particles and was easily noticeable even with naked eye for all electrical settings of the lithotripter. Spatial distributions of velocity vectors are complicated and several local peaks and vortices are observed. Measured streaming velocities are found to be in ranges of 1.5 - 3 cm/s. It should be noted that the measured velocity was averaged over 1/30 sec, the time resolution limited by video frame rate, and the true velocity is expected to be at least 10 times higher. Despite such an underestimation, it was shown that the streaming velocity increased with voltage settings and, as predicted by theory, is proportional to intensity and closely related to the shock-wave pressures generated. In particular, the velocity has almost a linear correlation with peak-negative pressures (r = 0.98683, p = 0.0018). This suggests that the streaming velocity measured using the PIV technique can be used to estimate the generated peak-pressures without disturbing the field.

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Corrigendum to “Experimental and theoretical investigation of directional permeability of human vertebral cancellous bone for cement infiltration”

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Journal of Biomechanics 2004年第11期37卷 1802-1802页

作者： G. Baroud R. Falk M. Crookshank S. Sponagel T. Steffen Orthopaedic Research Laboratory Division of Orthopaedic Surgery McGill University Royal Victoria Hospltal (Rm L4.65) 687 Pine Ave West Montreal QC Canada H3A 1A1 Co-operative Education Program Biological Sciences Simon Fraser University Vancouver BC Canada Co-operative Education Service Biological Engineering University of Guelph Guelph ON Canada Department of Biomedical Engineering University of Applied Science of Aachen (FH) Jülich Germany

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Investigation of possibilities of plasma treatment for dental caries

Investigation of possibilities of plasma treatment for denta...

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International Conference on Pulsed Power

作者： R.E.J. Sladek E. Stoffels R. Walraven P.J.A. Tielbeek R.A. Koolhoven Department of Biomedical Engineering Eindhovan University of Technology Eindhoven Netherlands Department of Biomedical Engineering Department of Applied Physics Eindhovan University of Technology Eindhoven Netherlands

Much effort is invested in development of tissue-saving methods in dentistry. Cleaning and sterilization of infected tissue in a dental cavity or in a root channel can be accomplished using laser techniques, but in addition to being too expensive, lasers cannot perform superficial treatment of an irregular surface. Recently, a non-thermal atmospheric plasma has been developed and its interactions with living objects have been studied [E. Stoffels, 2002]. Plasma is an efficient source of various radicals, capable of bacterial decontamination, while it operates at room temperature and does not cause bulk destruction of the tissue. Plasma treatment is potentially a novel tissue-saving technique, allowing to clean irregular structures and narrow channels within the diseased tooth.

关键词： Dentistry Plasma temperature Needles Plasma confinement Plasma materials processing Radiofrequency amplifiers Plasma sources Heating Radio frequency Plasma measurements

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Three-dimensional terahertz holography

Three-dimensional terahertz holography

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Conference on Lasers and Electro-Optics (CLEO)

作者： S. Wang B. Ferguson H. Zhong X.-C. Zhang Department of Physics Applied Physics and Astronomy Rensselaer Polytechnic Institute Troy NY USA Center for Biomedical Engineering and Department of Electrical and Electronic Engineering University of Adelaide SA Australia

We demonstrate three-dimensional terahertz (THz) holography with the use of the windowed Fourier transformation. The coherent nature of THz time domain spectroscopy allows measurement of the phase and amplitude of the... 详细信息

关键词： Holography Optical scattering Rayleigh scattering biomedical measurements Image reconstruction Holographic optical components Phase measurement Pulse measurements Spectroscopy Optical imaging

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Mechanical anisotropy of the human knee articular cartilage in compression

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Proceedings of the Institution of Mechanical Engineers, Part H: Journal of engineering in Medicine 2003年第3期217卷 215-219页

作者： Jurvelin, J.S. Buschmann, M.D. Hunziker, E.B. Department of Applied Physics University of Kuopio POB 1777 FIN-70211 Kuopio Finland Dept. Clin. Physiol. and Nucl. Med. Kuopio University Hospital University of Kuopio Kuopio Finland Biomedical Engineering Institute École Polytechnique Montreal Que. Canada M E Muller Inst. for Biomechanics University of Bern Bern Switzerland

Articular cartilage exhibits anisotropic mechanical properties when subjected to tension. However, mechanical anisotropy of mature cartilage in compression is poorly known. In this study, both confined and unconfined compression tests of cylindrical cartilage discs, taken from the adult human patello-femoral groove and cut either perpendicular (normal disc) or parallel (tangential disc) to the articular surface, were utilized to determine possible anisotropy in Young's modulus, E, aggregate modulus, Ha, Poisson's ratio, v and hydraulic permeability, k, of articular cartilage. The results indicated that Ha was significantly higher in the direction parallel to the articular surface as compared with the direction perpendicular to the surface (Ha = 1.237 ± 0.486 MPa versus Ha = 0.845 ± 0.383 MPa, p = 0.017, n = 10). The values of Poisson's ratio were similar, 0.158 ± 0.148 for normal discs compared with 0.180 ± 0.046 for tangential discs. Analysis using the linear biphasic model revealed that the decrease of permeability during the offset compression of 0-20 per cent was higher (p = 0.015, n = 10) in normal (from 25.5 × 10-15 to 1.8 × 10-15 m4/N s) than in tangential (from 12.3 × 10-15 to 1.3 × 10-15 m4/N s) discs. Based on the results, it is concluded that the mechanical characteristics of adult femoral groove articular cartilage are anisotropic also during compression. Anisotropy during compression may be essential for normal cartilage function. This property has to be considered when developing advanced theoretical models for cartilage biomechanics.

关键词： Biomechanics

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A course in micro- and nanoscale mechanics

A course in micro- and nanoscale mechanics

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2003 ASEE Annual Conference and Exposition: Staying in Tune with engineering Education

作者： Crone, Wendy C. Carpick, Robert W. Lux, Kenneth W. Johnson, Buck D. Department of Engineering Physics University of Wisconsin-Madison Madison WI 53706 United States Engineering Mechanics Program University of Wisconsin-Madison Madison WI 53706 United States Department of Biomedical Engineering University of Wisconsin-Madison Madison WI 53706 United States Mat. Res. Sci./Eng. Ctr. N.M./I. University of Wisconsin-Madison Madison WI 53706 United States

At small scales, mechanics enters a new regime where the role of surfaces, interfaces, defects, material property variations, and quantum effects play more dominant roles. A new course in nanoscale mechanics for engineering students was recently taught at the University of Wisconsin - Madison. This course provided an introduction to nanoscale engineering with a direct focus on the critical role that mechanics needs to play in this developing area. The limits of continuum mechanics were presented as well as newly developed mechanics theories and experiments tailored to study and describe micro- and nano-scale phenomena. Numerous demonstrations and experiments were used throughout the course, including synthesis and fabrication techniques for creating nanostructured materials, bubble raft models to demonstrate size scale effects in thin film structures, and a laboratory project to construct a nanofilter device. A primary focus of this paper is the laboratory content of this course, which includes an integrated series of laboratory modules utilizing atomic force microscopy, self-assembled monolayer deposition, and microfluidic technology.

关键词： Quantum theory

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