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Gene Therapy: Suppression of VEGF by Reversible‐PEGylated Histidylated Polylysine in Cancer Therapy (Adv. Healthcare Mater. 11/2014)

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Advanced Healthcare Materials 2014年第11期3卷

作者： Xiaojun Cai Haiyan Zhu Haiqing Dong Yongyong Li Jiansheng Su Donglu Shi Shanghai East Hospital The Institute for Biomedical Engineering and Nano Science Tongji University School of Medicine Tongji University Shanghai 200120 China Laboratory of Oral Biomedical Science and Translational Medicine Department of Prosthodontics School of Stomatology Tongji University Shanghai 200072 China Materials Science and Engineering Program Department of Mechanical and Materials Engineering College of Engineering and Applied Science University of Cincinnati Cincinnati OH 10 45221 USA

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Parametric excitation of dc current in a single-dot shuttle system via spontaneous symmetry breaking

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Physical Review B 2013年第3期88卷 035412-035412页

作者： Milton E. Peña-Aza Alessandro Scorrano Leonid Y. Gorelik Department of Physics University of Gothenburg SE-412 96 Göteborg Sweden Department of Mechanical and Aerospace Engineering Sapienza University of Rome Via Eudossiana 18 00184 Rome Italy Department of Applied Physics Chalmers University of Technology SE-412 96 Göteborg Sweden

We investigate theoretically the dynamics of a spatially symmetric shuttle system subjected to an ac gate voltage. We demonstrate that in such a system parametric excitation gives rise to mechanical vibrations when the frequency of the ac signal is close to the eigenfrequency of the mechanical subsystem. These mechanical oscillations result in a dc shuttle current in a certain direction due to spontaneous symmetry breaking. The direction of the current is determined by the phase shift between the ac gate voltage and the parametrically excited mechanical oscillations. The dependence of the shuttle current on the dc gate voltage is also analyzed.

关键词： mechanical vibration research PARAMETRIC processes EXCITATION spectrum mechanical oscillations BROKEN symmetry (physics)

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Carbon fiber based custom orthoses for augmenting net ankle moment in gait

Carbon fiber based custom orthoses for augmenting net ankle ...

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SAMPE 2013 Conference and Exhibition: Education and Green Sky - Materials Technology for a Better World

作者： Khattra, Narinder S. Tierney, John J. Yarlagadda, Shridhar Shevchenko, Nicholas Gillespie Jr., John W. Schrank, Elisa S. Stanhope, Steven J. Center for Composite Materials University of Delaware Newark DE 19716 United States Department of Mechanical Engineering University of Delaware Newark DE 19716 United States Department of Civil and Environmental Engineering University of Delaware Newark DE 19716 United States Department of Materials Science and Engineering University of Delaware Newark DE 19716 United States Department of Kinesiology and Applied Physiology University of Delaware Newark DE 19716 United States Department of Biomedical Engineering University of Delaware Newark DE 19716 United States Biomechanics and Movement Science Interdisciplinary Program University of Delaware Newark DE 19716 United States

ISBN: (纸本)9781934551158

Passive-dynamic ankle-foot orthoses (PD-AFOs) are a common form of assistive braces prescribed to improve gait of patients having impaired ankle joint function. The PD-AFO structural bending response is used to compensate for a patient's reduced ankle moment. This work focuses on the design and analysis of a carbon fiber based composite PD-AFO that provides a thin, lighter weight alternative to the more commonly used plastic based PD-AFOs. The purpose of this study was to demonstrate feasibility of designing composite PD-AFOs having desired bending stiffness. A custom, 3D surface model of the brace is used to create the overall geometry. The composite lay-up and associated stiffness of the composite PD-AFO is determined numerically, as a function of ankle angle for the foot-flat phase of the gait cycle. It is shown that the brace can be designed to augment the lost natural ankle stiffness of a patient to match that of a healthy person. The results indicate that the geometry of a PD-AFO, composite lay-up and the material properties are key factors in achieving the desired stiffness characteristics. Copyright 2013 by Aurora Flight Sciences.

关键词： Carbon fibers

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Anisotropic transmission of light through a plasmonic bull's eye with an elliptical aperture

Anisotropic transmission of light through a plasmonic bull's...

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Pacific Rim Conference on Lasers and Electro-Optics (CLEO/Pacific Rim)

作者： M. Pournoury H. E. Joe T. Nazari J. H. Park Y. M. Sung B. K. Min S. Im D. Kim K. Oh Photonic Device Physics Laboratory Institute of Physics and Applied Physics Yonsei University Seoul South Korea School of mechanical engineering Yonsei University Seoul South Korea Electron Device Laboratory Institute of Physics and Applied Physics Yonsei University Seoul South Korea Department of Chemistry Yonsei University Seoul South Korea

ISBN: (纸本)9781467364751

Anisotropic transmission of light through a plasmonic bull's eye with an elliptical central aperture in a thin Au film is analyzed experimentally. The results show the light polarized along the minor axis of the elliptic aperture has significantly larger enhanced optical transmission (EOT) than the other orthogonal polarization, which can further utilized in polarized EOT devices.

关键词： Apertures Plasmons Polarization Photonics Optical polarization Educational institutions

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Angular-Momentum-Dependent Orbital-Free Density Functional Theory

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Physical Review Letters 2013年第6期111卷 066402-066402页

作者： Youqi Ke Florian Libisch Junchao Xia Lin-Wang Wang Emily A. Carter Department of Mechanical and Aerospace Engineering Program in Applied and Computational Mathematics and Andlinger Center for Energy and the Environment Princeton University Princeton New Jersey 08544 USA Material Science Division Lawrence Berkeley National Laboratory Berkeley California 94720 USA

Orbital-free (OF) density functional theory (DFT) directly solves for the electron density rather than the wave function of many electron systems, greatly simplifying and enabling large scale first principles simulations. However, the required approximate noninteracting kinetic energy density functionals and local electron-ion pseudopotentials severely restrict the general applicability of conventional OFDFT. Here, we present a new generation of OFDFT called angular-momentum-dependent (AMD)-OFDFT to harness the accuracy of Kohn-Sham DFT and the simplicity of OFDFT. The angular momenta of electrons are explicitly introduced within atom-centered spheres so that the important ionic core region can be accurately described. In addition to conventional OF total energy functionals, we introduce a crucial nonlocal energy term with a set of AMD energies to correct errors due to the kinetic energy density functional and the local pseudopotential. We find that our AMD-OFDFT formalism offers substantial improvements over conventional OFDFT, as we show for various properties of the transition metal titanium.

关键词： DENSITY functional theory ELECTRON density KINETIC energy PSEUDOPOTENTIAL method TRANSITION metal compounds ELECTRON-ion collisions

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Analysis of the operation of thin nanowire photoelectrodes for solar energy conversion (vol 5, pg 5203, 2012)

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ENERGY & ENVIRONMENTAL SCIENCE 2012年第12期5卷 9946-9946页

作者： Foley, Justin M. Price, Michelle J. Feldblyum, Jeremy I. Maldonado, Stephen Program in Applied Physics Macromolecular Engineering Department of Chemistry 930 N University Ann Arbor Michigan

The solar energy conversion properties of thin Si and GaP nanowire photoelectrodes in photoelectrochemical cells have been examined through sets of finite-element simulations. A discussion describing the motivation behind nanostructured, high aspect ratio semiconductor photoelectrode designs and a brief survey of current experimental results reported for nanostructured semiconductor photoelectrodes in photoelectrochemical cells are presented first. An analysis is then shown that outlines the primary recombination pathways governing the steady-state current-potential behaviors of thin, cylindrical nanowire photoelectrodes, with explicit expressions detailing the differences between planar and cylindrical photoelectrodes arising from the solution of carrier fluxes in planar and cylindrical geometries. Results from finite-element simulations used to model the key features of thin nanowire photoelectrodes under low-level injection conditions are shown that illustrate which recombination pathway(s) is operative under various experimental conditions. Specifically, the respective effects of non-uniform doping, tapering along the length, variation in charge carrier mobilities and lifetimes, changes in nanowire radius, and changes in the density of surface defects on the observable photocurrent-potential responses are reported. These cumulative results serve as guides for future experimental work aimed at improving the attainable solar energy conversion efficiencies of doped semiconductor nanowire photoelectrodes. Lastly, separate simulations that model lightly doped nanowire photoelectrodes under high-level injection conditions are discussed. These results suggest discrete, ohmic-selective contacts may afford a way to circumvent the stringent doping requirements discussed herein for thin nanowire photoelectrodes.

关键词： Nanowires

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Isostaticity at Frictional Jamming

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Physical Review Letters 2013年第19期110卷 198002-198002页

作者： Stefanos Papanikolaou Corey S. O’Hern Mark D. Shattuck Departments of Mechanical Engineering & Materials Science Yale University New Haven Connecticut 06520 USA Department of Physics Yale University New Haven Connecticut 06520 USA Department of Applied Physics Yale University New Haven Connecticut 06520 USA Benjamin Levich Institute and Physics Department The City College of the City University of New York New York New York 10031 USA

Amorphous packings of frictionless, spherical particles are isostatic at jamming onset, with the number of constraints (contacts) equal to the number of degrees of freedom. Their structural and mechanical properties are controlled by the interparticle contact network. In contrast, amorphous packings of frictional particles are typically hyperstatic at jamming onset. We perform extensive numerical simulations in two dimensions of the geometrical asperity (GA) model for static friction to further investigate the role of isostaticity. In the GA model, interparticle forces are obtained by summing up purely repulsive central forces between periodically spaced circular asperities on contacting grains. We compare the packing fraction, contact number, mobilization distribution, and vibrational density of states (in the harmonic approximation) using the GA model to those generated using the Cundall-Strack approach. We find that static packings of frictional disks obtained from the GA model are mechanically stable and isostatic when we consider interactions between asperities on contacting particles. The crossover in the structural and mechanical properties of static packings from frictionless to frictional behavior as a function of the static friction coefficient coincides with a change in the type of interparticle contacts and the disappearance of a peak in the density of vibrational modes for the GA model. These results emphasize that mesoscale features of the model for static friction play an important role in determining the properties of granular packings.

关键词： DEGREES of freedom COMPUTER simulation STATIC friction PACKING fractions DENSITY of states

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Optimization of a z-source DC circuit breaker

Optimization of a z-source DC circuit breaker

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IEEE Electric Ship Technologies Symposium, ESTS

作者： P. Prempraneerach M. G. Angle J. L. Kirtley G. E. Karniadakis C. Chryssostomidis Mechanical Engineering Department Rajamangala University of Technology Thunyaburi Pathumthani Thailand Electrical Engineering and Computer Science Department Research Laboratory for Electronics MIT Cambridge MA USA Division of Applied Mathematics Brown University Providence RI USA Department of Mechanical Engineering MIT MIT Sea Grant College Program Cambridge MA USA

DC faults may cause severe disruptions in continuity of service to vital loads in a shipboard integrated power system, hence detection, isolation, and protection against such faults must be incorporated in both medium-voltage DC (MVDC) and low-voltage DC (LVDC) systems. Here we consider the effectiveness of existing z-source breakers and propose several new designs more appropriate for fault detection in MVDC and LVDC systems. In particular, we perform an optimization study that aims to minimize dissipation and weight and we identify the key parameters for use in MVDC and LVDC systems. Preliminary verification and validation studies are also included.

关键词： Circuit faults Thyristors Switches Circuit breakers Capacitors Fault currents Optimization

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Delay-dependent conditions for finite time stability of continuous systems with latency

Delay-dependent conditions for finite time stability of cont...

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International Symposium on Intelligent Systems and Informatics (SISY)

作者： D. Lj. Debeljkovic I. M. Buzurovic A. M. Jovanovic N. J. Dimitrijevic Department of Control Engineering School of Mechanical Engineering Belgrade Serbia Medical Physics and Biophysics Division Harvard Medical School Boston MA USA School of High Applied Professional Education Vranje Serbia

In the present study, the practical and finite time stability of linear continuous system with latency has been investigated. The proposed result outlines the novel sufficient stability conditions for the systems represented by the following equation: x'(t)=A 0 x(t) - A 1 x(t - τ). The results can be applied to the analysis of both the practical and finite time stability of the continuous systems with time delay. For the derivation of the finite time stability conditions, the Lyapunov-Krassovski functionals were used. Unlike in the previously reported results, the functionals did not have to satisfy some strict mathematical conditions, such as positivity in the whole state space and possession of the negative derivatives along the system state trajectories. The numerical examples presented in this study additionally clarified the implementation of the methodology, and the calculations of the stability conditions. Generally, it was found that the proposed sufficient conditions were less restrictive compared to the ones previously reported.

关键词： Stability criteria Numerical stability Mathematical model Continuous time systems Equations Trajectory

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Nanoscale molecular dams and traps for low-abundance protein analysis

Nanoscale molecular dams and traps for low-abundance protein...

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第八届全国微全分析系统学术会议、第三届全国微纳尺度生物分离分析学术会议暨第五届国际微化学与微系统学术会议

作者： Chia-Fu Chou Kuo-Tang Liao Leonardo Lesser-Rojas K. K. Sriram Yii-Lih Lin Academia Sinica Taiwan Department of Chemistry National Taiwan UniversityTaiwan Nanoscience and Technology Program Taiwan International Graduate Program Academia Sinica Taiwan Research Center for Applied Sciences Institute of Physics Institute of Physics Department of Engineering and System Science National Tsing Hua UniversityTaiwan Institute of Physics Institute of Physics Genomics Research Center

Miniaturized biosensors and bioanalytical systems promise to revolutionize the field of health care and personalized medicine,in light of sample reduction,speed,and ***,mass transport has generally been recognized as a major limiting factor in the sensitivity and performance of miniaturized sensor platforms in that miniaturization poses penalties on passive transport of biomolecules to the sensor surface due to prolonged diffusion length from the bulk liquid or in the direction of the fluidic ***,for low-abundance protein analysis,sample enrichment is often regarded as the first prerequisite for high-resolution analysis,since chemical amplification methods are not readily available for *** factors pose major challenges for early or acute disease diagnostics and biomarker discovery using micro- or nanoscale sensor *** tackle these challenges,we developed nanofluidic and nanoelectronic platforms for the active transport of target analytes to the sensing *** example,nanoscale molecular dam,using nanoconstriction as field-focusing lens to enhance mass transport,may be used for ultrafast protein enrichment in nanofluidic channels by electrodeless dielectrophoresis [1] under physiological buffer conditions [2-4].On the other hand,sub-10 nm electrode nanogap may be used as an active molecular trap for SERS and tunneling current measurements for low-copy number protein analysis,potentially down to single-molecule *** platforms may open up a simple way for heterogeneous protein analysis.

关键词： Protein analysis nanogap electrode dielectrophoresis surface enhanced Raman spectroscopy (SERS) tunneling current

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