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Physical Review Letters 2005年第11期94卷 114801-114801页

作者： A. L. Cavalieri D. M. Fritz S. H. Lee P. H. Bucksbaum D. A. Reis J. Rudati D. M. Mills P. H. Fuoss G. B. Stephenson C. C. Kao D. P. Siddons D. P. Lowney A. G. MacPhee D. Weinstein R. W. Falcone R. Pahl J. Als-Nielsen C. Blome S. Düsterer R. Ischebeck H. Schlarb H. Schulte-Schrepping Th. Tschentscher J. Schneider O. Hignette F. Sette K. Sokolowski-Tinten H. N. Chapman R. W. Lee T. N. Hansen O. Synnergren J. Larsson S. Techert J. Sheppard J. S. Wark M. Bergh C. Caleman G. Huldt D. van der Spoel N. Timneanu J. Hajdu R. A. Akre E. Bong P. Emma P. Krejcik J. Arthur S. Brennan K. J. Gaffney A. M. Lindenberg K. Luening J. B. Hastings FOCUS Center Departments of Physics and Applied Physics Program University of Michigan Ann Arbor MI 48109 USA Advanced Photon Source Argonne National Laboratory Argonne IL 60439 USA Materials Science Division Argonne National Laboratory Argonne IL 60439 USA National Synchrotron Light Source Brookhaven National Laboratory Upton NY 11973 USA Department of Physics University of California Berkeley CA 94720 USA Consortium for Advanced Radiation Sources The University of Chicago Chicago IL 60637 USA Niels Bohr Institute Copenhagen University 2100 Copenhagen Ø Denmark Deutsches Elektronen-Synchrotron DESY Notkestrasse 85 22607 Hamburg Germany European Synchrotron Radiation Facility 38043 Grenoble Cedex 9 France Institut für Optik und Quantenelektronik Friedrich-Schiller-Universität Jena Max-Wien-Platz 1 07743 Jena Germany Physics Department Lawrence Livermore National Laboratory Livermore CA 94550 USA Department of Physics Lund Institute of Technology P.O. Box 118 S-22100 Lund Sweden Max Plank Institute for Biophysical Chemistry Am Faßberg 11 37077 Göttingen Germany Department of Physics Clarendon Laboratory Parks Road University of Oxford Oxford OX1 3PU United Kingdom Department of Cell and Molecular Biology Biomedical Centre Uppsala University SE-75124 Uppsala Sweden Stanford Linear Accelerator Center Menlo Park CA 94025 USA Stanford Synchrotron Radiation Laboratory/SLAC Menlo Park CA 94025 USA

Linear-accelerator-based sources will revolutionize ultrafast x-ray science due to their unprecedented brightness and short pulse duration. However, time-resolved studies at the resolution of the x-ray pulse duration are hampered by the inability to precisely synchronize an external laser to the accelerator. At the Sub-Picosecond Pulse Source at the Stanford Linear-Accelerator Center we solved this problem by measuring the arrival time of each high energy electron bunch with electro-optic sampling. This measurement indirectly determined the arrival time of each x-ray pulse relative to an external pump laser pulse with a time resolution of better than 60 fs rms.

关键词： X rays

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Observation of Structural Anisotropy and the Onset of Liquidlike Motion During the Nonthermal Melting of InSb

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Physical Review Letters 2005年第12期95卷 125701-125701页

作者： K. J. Gaffney A. M. Lindenberg J. Larsson K. Sokolowski-Tinten C. Blome O. Synnergren J. Sheppard C. Caleman A. G. MacPhee D. Weinstein D. P. Lowney T. Allison T. Matthews R. W. Falcone A. L. Cavalieri D. M. Fritz S. H. Lee P. H. Bucksbaum D. A. Reis J. Rudati A. T. Macrander P. H. Fuoss C. C. Kao D. P. Siddons R. Pahl K. Moffat J. Als-Nielsen S. Duesterer R. Ischebeck H. Schlarb H. Schulte-Schrepping J. Schneider D. von der Linde O. Hignette F. Sette H. N. Chapman R. W. Lee T. N. Hansen J. S. Wark M. Bergh G. Huldt D. van der Spoel N. Timneanu J. Hajdu R. A. Akre E. Bong P. Krejcik J. Arthur S. Brennan K. Luening J. B. Hastings Stanford Synchrotron Radiation Laboratory/SLAC Menlo Park California 94025 USA Department of Physics Lund Institute of Technology P.O. Box 118 S-22100 Lund Sweden Institut für Optik und Quantenelektronik Friedrich-Schiller Jena Max-Wien-Platz 1 07743 Jena Germany Institut für Experimentelle Physik Universität Duisburg-Essen D-45117 Essen Germany Deutsches Elektronen-Synchrotron DESY Notkestrasse 85 22607 Hamburg Germany Department of Physics Clarendon Laboratory Parks Road University of Oxford Oxford OX1 3PU United Kingdom Department of Cell and Molecular Biology Biomedical Centre Uppsala University SE-75124 Uppsala Sweden Department of Physics University of California Berkeley California 94720 USA FOCUS Center Departments of Physics and Applied Physics Program University of Michigan Ann Arbor Michigan 48109 USA Max-Planck-Institute of Quantum Optics Hans-Kopfermann-Str. 1 D-85748 Garching Germany Advanced Photon Source Argonne National Laboratory Argonne Illinois 60439 USA Materials Science Division Argonne National Laboratory Argonne Illinois 60439 USA National Synchrotron Light Source Brookhaven National Laboratory Upton New York 11973 USA Consortium for Advanced Radiation Sources The University of Chicago Chicago Illinois 60637 USA Niels Bohr Institute Copenhagen University 2100 Copenhagen Ø Denmark European Synchrotron Radiation Facility 38043 Grenoble Cedex 9 France Physics Department Lawrence Livermore National Laboratory Livermore California 94550 USA Stanford Linear Accelerator Center Menlo Park California 94025 USA

The melting dynamics of laser excited InSb have been studied with femtosecond x-ray diffraction. These measurements observe the delayed onset of diffusive atomic motion, signaling the appearance of liquidlike dynamics. They also demonstrate that the root-mean-squared displacement in the [111] direction increases faster than in the [110] direction after the first 500 fs. This structural anisotropy indicates that the initially generated fluid differs significantly from the equilibrium liquid.

关键词： Semiconducting indium compounds

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A nanoscale approach to stamp fabrication in hard materials using high intensity ultrafast lasers

A nanoscale approach to stamp fabrication in hard materials ...

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2003 MRS Fall Meeting

作者： McDonald, Joel P. Picard, Yoosuf N. Yalisove, Steven M. Liu, Hsiao-Hua Blaszczak, Joseph Guo, Lingji J. Dept. of Materials Science and Engineering University of Michigan Ann Arbor MI 48109-2176 United States Center for Ultrafast Optical Science University of Michigan Ann Arbor MI 48109-2099 United States Applied Physics Program University of Michigan Ann Arbor MI 48109-1120 United States Dept. of Electrical Engineering and Computer Science University of Michigan Ann Arbor MI 48109-2122

Nanomorphing with ultrafast lasers may have a significant role in direct write stamp production. Surface conditions play a critical role in the ablative properties of materials. We have conducted femtosecond laser (pulse duration;120 fs, wavelength;780 nm) threshold studies of silicon with the native oxide and silicon with atomically clean surfaces in an ultra-high vacuum environment. We have discovered that a -1.5 nm thick oxide layer can alter the ablation threshold of Si (100) by 25 ± 5%. Additionally, our work has shown that collateral damage can be controlled on the nanoscale. Transmission electron microscopy (TEM) images of femtosecond laser machined holes in Si (100) show that collateral damage extends only 10 nm from the edge. © 2004 Materials Research Society.

关键词： Ultrafast phenomena

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The role of the native oxide on silicon in femtosecond laser damage threshold studies at grazing incidence

The role of the native oxide on silicon in femtosecond laser...

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Conference on Lasers and Electro-Optics, CLEO

作者： Picard, Yoosuf N. Yalisove, Steven M. McDonald, Joel P. Department of Materials Science and Engineering University of Michigan 2300 Hayward Street Ann Arbor MI 48109-2136 United States Applied Physics Program University of Michigan 500 E. University Avenue Ann Arbor MI 48109-1120 United States

Femtosecond laser ablation studies of silicon with and without the native oxide on the surface were conducted in an ultrahigh vacuum environment. SEM results show a clear difference in the laser intensity threshold fo... 详细信息

关键词： Oxides

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Micro-bathymetric mapping using acoustic range images

Micro-bathymetric mapping using acoustic range images

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OCEANS

作者： C. Roman H. Singh MIT/WHOI Joint Program in Applied Ocean Science and Engineering Massachusetts Institute of Technology Cambridge MA USA Department of Applied Ocean Physics and Engineering Woods Hole Oceanographic Institution Woods Hole MA USA

This work focuses on the creation of high resolution micro-bathymetric maps using a high frequency pencil beam sonar. These maps typically cover areas of 10's to 100's of square meters. Data is collected using a sonar mounted to an underwater vehicle that can be positioned at discrete locations on the sea floor or flown in a survey pattern above the bottom. Specifically, we are focused on improving the accuracy of these terrain maps by merging sonar pings taken from multiple vantage points over the same location. This requires the adaption of data registration techniques to handle errors related to the sonar sensor. The registration can also be modified to incorporate the navigation data available from an instrumented underwater vehicle. A two axis scanning sonar was used to gather data in the form of densely sampled range images. The data registration works on the 3D projection of these range images in a scan-matching manner. Through this process regions occluded in a single scan are filled with data available from other scans and individual pings which show a poor return are removed. Refined estimates of the scan vantage points are also generated during the registration. The initial estimates of these locations are provided by navigation data. The practical application of this work complements photographic mapping when visibility is limited. It also provides additional measurements which can be used to improve vehicle navigation.

关键词： Sonar navigation Sonar measurements Remotely operated vehicles Underwater vehicles Sea floor Underwater acoustics Layout Oceans Acoustical engineering Acoustic beams

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Visually augmented navigation in an unstructured environment using a delayed state history

Visually augmented navigation in an unstructured environment...

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IEEE International Conference on Robotics and Automation (ICRA)

作者： R. Eustice O. Pizarro H. Singh MIT/WHOI Joint Program in Applied Ocean Science and Engineering Massachusetts Institute of Technology Cambridge MA USA Department of Applied Ocean Physics and Engineering Woods Hole Oceanographic Institution Woods Hole MA USA

This work describes a framework for sensor fusion of navigation data with camera-based 5 DOF relative pose measurements for 6 DOF vehicle motion in an unstructured 3D underwater environment. The fundamental goal of this work is to concurrently estimate online current vehicle position and its past trajectory. This goal is framed within the context of improving mobile robot navigation to support sub-sea science and exploration. Vehicle trajectory is represented by a history of poses in an augmented state Kalman filter. Camera spatial constraints from overlapping imagery provide partial observation of these poses and are used to enforce consistency and provide a mechanism for loop-closure. The multi-sensor camera + navigation framework is shown to have compelling advantages over a camera-only based approach by: 1) improving the robustness of pairwise image registration, 2) setting the free gauge scale, and 3) allowing for a unconnected camera graph topology. Results are shown for a real world data set collected by an autonomous underwater vehicle in an unstructured undersea environment.

关键词： Navigation Delay History Cameras Underwater vehicles Robot vision systems Sensor fusion Motion measurement Mobile robots Robustness

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Possibilities to use the practice of telemedicine in actual technological conditions to remote areas

Possibilities to use the practice of telemedicine in actual ...

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25th Annual International Conference of the IEEE-Engineering-in-Medicine-and-Biology-Society

作者： Kmeteuk, O de Amorim, MF Graduate Program in Applied Computer Science Exact Sciences and Technology Center Pontifical Catholic University of Paraná Brazil

ISBN: (纸本)0780377893

One of the main factors that impede the practice of the telemedicine is not the lack of new technologies for the communication, but the lack of studies on the use of the technology already installed in the distant areas, in way to be used of a rational way. The objective of the telemedicine is to provide help to the cares with the health with quality the distant areas of the great attendance centers. Therefore, it cannot ignore the fact that these areas do not make use of point technologies for communication. Then, it is justified the need to accomplish studies that facilitate the practice of the independent telemedicine of the installed technology. Then, the objective of this work is to use as pilot an unit of remote health, contributing with a support system that allows the practice of the telemedicine using the technology of available transmission in the respective place, avoiding that the factor cost is a barrier for the telemedicine projects and can begin an improvement process in the quality of the attendance in units of distant health of the great centers of medical attendance.

关键词： telemedicine support system

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Possibilities to use the practice of telemedicine in actual technological conditions to remote areas

Possibilities to use the practice of telemedicine in actual ...

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Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC)

作者： O.K. Filho M.F. de Amorim Graduate Program in Applied Computer Science Exact Sciences and Technology Center Pontifical Catholic University of Paraná Brazil

关键词： Telemedicine Communications technology Modems Databases computer science Impedance Costs Urban areas Planets Operating systems

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Grazing-angle scattering of electromagnetic waves in slanted holographic gratings in a guiding slab with gain

Grazing-angle scattering of electromagnetic waves in slanted...

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Frontiers in Optics, FiO 2003

作者： Mason, D.R. Nieminen, T.A. Gramotnev, D.K. Applied Optics Program School of Physical and Chemical Sciences Queensland University of Technology GPO Box 2434 BrisbaneQLD4001 Australia Centre for Biophotonics and Laser Science Department of Physics The University of Queensland St. LuciaQLD4072 Australia

ISBN: (纸本)1557527598

Theoretical analysis and physical interpretation of a new type of weakly leaking modes guided by a slanted periodic grating is carried out in the presence of small gain/dissipation. Infinitely strong resonances are predicted in gratings with optimal gain, where the energy losses due to leakage are compensated by the gain. © 2000 Optical Society of America

关键词： Energy dissipation

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A new type of mode of a slab with a periodic grating

A new type of mode of a slab with a periodic grating

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Frontiers in Optics, FiO 2003

作者： Goodman, S.J. Gramotnev, D.K. Nieminen, T.A. Applied Optics Program School of Physical and Chemical Sciences Queensland University of Technology GPO Box 2434 BrisbaneQLD4001 Australia Centre for Biophotonics and Laser Science Department of Physics The University of Queensland St. LuciaQLD4072 Australia

ISBN: (纸本)1557527598

A new type of grating eigenmode has been predicted and analyzed numerically for holographic gratings in a slab with mean permittivity larger than the surrounding media. These eigenmodes were shown to exist in the geometry of grazing angle scattering, i.e., when the +1 diffracted order propagates almost parallel to the grating boundaries. © 1999 Optical Society of America

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