Search Results - (Author, Cooperation:J. S. Smith)

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  1. 1
    Staff View
    Publication Date:
    2018-04-12
    Publisher:
    BMJ Publishing
    Electronic ISSN:
    2044-6055
    Topics:
    Medicine
    Keywords:
    Open access, Ear, nose and throat/otolaryngology
    Published by:
    http://group.bmj.com/

    Latest Papers from Table of Contents or Articles in Press
  2. 2
    Staff View
    Publication Date:
    2018-05-10
    Publisher:
    American Physical Society (APS)
    Print ISSN:
    1098-0121
    Electronic ISSN:
    1095-3795
    Topics:
    Physics
    Keywords:
    Superfluidity and superconductivity
    Published by:
    http://www.aps.org/

    Latest Papers from Table of Contents or Articles in Press
  3. 3
    J. C. Lemos ; M. J. Wanat ; J. S. Smith ; B. A. Reyes ; N. G. Hollon ; E. J. Van Bockstaele ; C. Chavkin ; P. E. Phillips
    Nature Publishing Group (NPG)
    Published 2012
    Staff View
    Publication Date:
    2012-09-21
    Publisher:
    Nature Publishing Group (NPG)
    Print ISSN:
    0028-0836
    Electronic ISSN:
    1476-4687
    Topics:
    Biology
    Chemistry and Pharmacology
    Medicine
    Natural Sciences in General
    Physics
    Keywords:
    Animals ; Appetitive Behavior/drug effects/*physiology ; Avoidance Learning/drug effects/*physiology ; Corticotropin-Releasing Hormone/*metabolism/pharmacology ; Dopamine/metabolism/secretion ; Male ; Mice ; Mice, Inbred C57BL ; Nucleus Accumbens/*metabolism/physiopathology ; Receptors, Corticotropin-Releasing Hormone/agonists/antagonists & ; inhibitors/deficiency/metabolism ; Signal Transduction/drug effects ; Stress, Psychological/*metabolism/physiopathology
    Published by:
    http://www.nature.com/

    Latest Papers from Table of Contents or Articles in Press
  4. 4
    Staff View
    Publication Date:
    2011-02-26
    Publisher:
    Nature Publishing Group (NPG)
    Print ISSN:
    0028-0836
    Electronic ISSN:
    1476-4687
    Topics:
    Biology
    Chemistry and Pharmacology
    Medicine
    Natural Sciences in General
    Physics
    Keywords:
    Calcium/analysis ; Carbon/analysis ; Carbon Dioxide/analysis ; *Climate ; Droughts/*history/statistics & numerical data ; Fossils ; Fresh Water ; Geologic Sediments/analysis/chemistry ; Global Warming/statistics & numerical data ; History, Ancient ; Human Activities ; New Mexico ; Plant Development ; Plants/metabolism ; Pollen/chemistry ; Rain ; Seasons ; Soil Microbiology ; Temperature ; Time Factors
    Published by:
    http://www.nature.com/

    Latest Papers from Table of Contents or Articles in Press
  5. 5
    N. J. Allen ; M. L. Bennett ; L. C. Foo ; G. X. Wang ; C. Chakraborty ; S. J. Smith ; B. A. Barres
    Nature Publishing Group (NPG)
    Published 2012
    Staff View
    Publication Date:
    2012-06-23
    Publisher:
    Nature Publishing Group (NPG)
    Print ISSN:
    0028-0836
    Electronic ISSN:
    1476-4687
    Topics:
    Biology
    Chemistry and Pharmacology
    Medicine
    Natural Sciences in General
    Physics
    Keywords:
    Animals ; Astrocytes/cytology/*metabolism/secretion ; Cerebellum/cytology/metabolism ; Culture Media, Conditioned/metabolism/pharmacology ; Excitatory Postsynaptic Potentials/*physiology ; Female ; Glypicans/deficiency/*metabolism/pharmacology ; Hippocampus/cytology/metabolism ; Humans ; Male ; Mice ; Mice, Inbred C57BL ; Rats ; Rats, Sprague-Dawley ; Receptors, AMPA/*metabolism ; Retinal Ganglion Cells/cytology/drug effects/metabolism ; Synapses/drug effects/*metabolism/pathology
    Published by:
    http://www.nature.com/

    Latest Papers from Table of Contents or Articles in Press
  6. 6
    Staff View
    Publication Date:
    2013-11-26
    Publisher:
    Nature Publishing Group (NPG)
    Print ISSN:
    0028-0836
    Electronic ISSN:
    1476-4687
    Topics:
    Biology
    Chemistry and Pharmacology
    Medicine
    Natural Sciences in General
    Physics
    Keywords:
    Animals ; Astrocytes/cytology/*metabolism ; Brain/cytology ; In Vitro Techniques ; Lateral Thalamic Nuclei/cytology/metabolism ; Learning/physiology ; Membrane Proteins/deficiency/genetics/*metabolism ; Mice ; Mice, Transgenic ; Neural Pathways/cytology/*metabolism ; *Phagocytosis ; Proto-Oncogene Proteins/deficiency/genetics/*metabolism ; Receptor Protein-Tyrosine Kinases/deficiency/genetics/*metabolism ; Retina/physiology ; Synapses/*metabolism
    Published by:
    http://www.nature.com/

    Latest Papers from Table of Contents or Articles in Press
  7. 7
    Maruyama, T. ; Garwin, E. L. ; Mair, R. A. ; Prepost, R. ; Smith, J. S. ; Walker, J. D.

    [S.l.] : American Institute of Physics (AIP)
    Published 1993
    Staff View
    ISSN:
    1089-7550
    Source:
    AIP Digital Archive
    Topics:
    Physics
    Notes:
    The polarization of photoemitted electrons from thin AlxGa1−xAs layers grown by molecular-beam epitaxy has been studied as a function of Al concentration by varying x in steps of 0.05 from 0.0 to 0.15. As the fraction x is increased, the wavelength dependence of the polarization shifts toward shorter wavelengths, permitting wavelength tuning of the region of maximum polarization. A maximum electron polarization of 42%–43% is obtained for AlxGa1−xAs samples with x≥0.05 while the maximum polarization of GaAs (x=0) samples reaches 49%. To investigate the lower polarization of AlxGa1−xAs, additional samples have been studied, including a short-period superlattice (GaAs)7 - (AlAs)1 .
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1063/1.353744

    Articles: DFG German National Licenses
  8. 8
    Chen, G. ; Hadley, M. A. ; Smith, J. S.

    [S.l.] : American Institute of Physics (AIP)
    Published 1994
    Staff View
    ISSN:
    1089-7550
    Source:
    AIP Digital Archive
    Topics:
    Physics
    Notes:
    The thermal characteristics of p-type substrate external-cavity surface-emitting laser diodes (SELDs) under pulsed and continuous-wave operation are studied both theoretically and experimentally. The theoretical work establishes models for the current flow, spontaneous emission transfer, heat generation, and temperature rise in the laser. The models incorporate the reduced and anisotropic electrical and thermophysical properties of the Bragg reflectors. The temperature rise at the active region of an external-cavity SELD is determined by measuring the output wavelength as a function of the injection current, modulation frequency, and substrate temperature. Simulation results agree reasonably well with experimental data on the external-cavity SELD. It is shown that the thermal resistance of the studied laser is smaller than previously reported values for the n-type substrate SELDs because of the current spreading in the p-type mirror and its close proximity to the substrate.
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1063/1.357447

    Articles: DFG German National Licenses
  9. 9
    Verma, A. K. ; Smith, J. S. ; Fujioka, H. ; Weber, E. R.

    [S.l.] : American Institute of Physics (AIP)
    Published 1995
    Staff View
    ISSN:
    1089-7550
    Source:
    AIP Digital Archive
    Topics:
    Physics
    Notes:
    Using high resolution x-ray diffraction techniques, we have studied the lattice parameter behavior of low-temperature (LT) AlxGa1−xAs as a function of annealing temperature and aluminum content. Similar to LT GaAs, the as-grown LT AlxGa1−xAs layers exhibit a dilated lattice constant which, upon annealing, contracts to that of "normal'' material. The onset of this contraction in LT Al0.3Ga0.7As, however, is found to occur at an annealing temperature nearly 100 °C higher than that required for LT GaAs. In addition, the relative lattice expansion in the as-grown LT layer is found to be a decreasing function of Al content, ranging from 0.099% for LT GaAs to 0.059% for LT Al0.3Ga0.7As. This is attributed to lower than expected As incorporation in the LT AlxGa1−xAs during growth. © 1995 American Institute of Physics.
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1063/1.359473

    Articles: DFG German National Licenses
  10. 10
    Dijaili, S. P. ; Smith, J. S. ; Dienes, A.

    Woodbury, NY : American Institute of Physics (AIP)
    Published 1989
    Staff View
    ISSN:
    1077-3118
    Source:
    AIP Digital Archive
    Topics:
    Physics
    Notes:
    Timing sychronization between a colliding-pulse mode-locked dye laser and a gain-switched Fabry–Perot-type AlGaAs laser diode has been achieved with less than 40 fs of relative timing jitter by using a pulsed optical phase lock loop. The relative timing jitter was measured using the error voltage of the feedback loop which has a 5 kHz bandwidth. This technique of measuring the relative timing jitter is accurate since the frequencies of all the timing fluctuations fall within the loop bandwidth. The novel element in the implementation of the pulsed optical phase lock loop is the time delay discriminator which is based on a cross correlation between the two pulse trains. Under locked conditions, the output of the cross correlator operates quiescently about a point of nonzero temporal slope.
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1063/1.101883

    Articles: DFG German National Licenses
  11. 11
    Kuchta, D. ; Whinnery, J. R. ; Smith, J. S. ; Woodall, J. M. ; Pettit, D.

    Woodbury, NY : American Institute of Physics (AIP)
    Published 1990
    Staff View
    ISSN:
    1077-3118
    Source:
    AIP Digital Archive
    Topics:
    Physics
    Notes:
    High performance photoconductive switches are demonstrated using a molecular beam epitaxy grown graded layer of InxGa1−xAs to make an ohmic contact to semi-insultating GaAs. It is found that the graded layer results in a peak signal amplitude that is more than a factor of 2 larger than what is obtained using conventional alloyed AuGeNi contacts.
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1063/1.103344

    Articles: DFG German National Licenses
  12. 12
    Walker, J. D. ; Malloy, K. ; Wang, S. ; Smith, J. S.

    Woodbury, NY : American Institute of Physics (AIP)
    Published 1990
    Staff View
    ISSN:
    1077-3118
    Source:
    AIP Digital Archive
    Topics:
    Physics
    Notes:
    Extremely high quality AlGaAs Bragg reflectors have been fabricated by molecular beam epitaxy using advanced growth techniques including phase-locked epitaxy, short-period superlattices, and growth interruptions. These techniques are used to control the layer periodicity, interface flatness, and producibility of the structures. The experimental reflectance spectrum shows an extremely square stop band and very regular side lobes closely matching the theoretical spectrum. A comparison of experimental to theoretical reflectance spectra is used to show that the layer periodicity is maintained within 1% and the interface flatness controls the optical loss per interface to less than 0.1%. Experimental results show a maximum reflectance of 98.5% for a (AlAs)6(GaAs)3/(AlAs)1(GaAs)4 35.5-period Bragg reflector.
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1063/1.102890

    Articles: DFG German National Licenses
  13. 13
    Vakhshoori, D. ; Walker, J. ; Wang, S. ; Smith, J. S. ; Soccolich, C. E. ; Islam, M. N.

    Woodbury, NY : American Institute of Physics (AIP)
    Published 1989
    Staff View
    ISSN:
    1077-3118
    Source:
    AIP Digital Archive
    Topics:
    Physics
    Notes:
    A new class of optical correlator which is integrable and potentially compatible with semiconductor lasers is experimentally tested. The correlator proposed earlier (a special GaAs/AlGaAs waveguide) is shown to be broad band capable of correlating pulse trains with average power in the correlator in sub-mW range with wavelengths at least ranging from 1.06 to 1.7 μm. To show compatibility with semiconductor laser diodes the correlator device was also used to generate sum frequency signal from mixing a 400 μW cw beam of a 1.06 μm Nd:YAG laser with a 400 μW cw beam of a 1.3 μm semiconductor laser diode. The latest result shows the potential of direct measurement of optical pulses from semiconductor laser diodes at different wavelengths with a single integrable compact correlator without any mechanical translation.
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1063/1.101374

    Articles: DFG German National Licenses
  14. 14
    Vakhshoori, D. ; Walker, J. ; Dijaili, S. ; Wang, S. ; Smith, J. S.

    Woodbury, NY : American Institute of Physics (AIP)
    Published 1989
    Staff View
    ISSN:
    1077-3118
    Source:
    AIP Digital Archive
    Topics:
    Physics
    Notes:
    In this letter we demonstrate a new kind of spectrometer capable of resolving the modes of a 1.3 μm quaternary laser diode. The device uses the nonlinear sum frequency generation of light in the semiconductor waveguide to map out the frequency spectrum of the input beam. This device was used to obtain the spectrum of a multimode Fabry–Perot 1.3 μm laser diode. Furthermore, the same device was used to observe the shift in the individual Fabry–Perot mode as well as the shift in the overall spectrum of the laser diode as a function of current. These observations indicate that the waveguide spectrometer can be useful for applications like implementing frequency division multiplexing communication systems by allowing the determination of absolute and relative frequencies of different channels in a compact fashion.
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1063/1.101685

    Articles: DFG German National Licenses
  15. 15
    Wilson, G. C. ; Kuchta, D. M. ; Walker, J. D. ; Smith, J. S.

    Woodbury, NY : American Institute of Physics (AIP)
    Published 1994
    Staff View
    ISSN:
    1077-3118
    Source:
    AIP Digital Archive
    Topics:
    Physics
    Notes:
    We measure spatial hole burning in weakly index guided vertical-cavity surface-emitting laser diodes (VCSELs) by spatially and spectrally resolving the spontaneous emission near field above threshold and show that spatial holes produce a significant lensing effect. We demonstrate experimentally, and with a simple model, that in weakly index guided VCSELs, self-focusing causes the fundamental mode width to decrease with increasing output power, exacerbating the spatial hole burning problem and inducing a transition to multimode operation at relatively low powers.
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1063/1.111097

    Articles: DFG German National Licenses
  16. 16
    Hadley, M. A. ; Wilson, G. C. ; Lau, K. Y. ; Smith, J. S.

    Woodbury, NY : American Institute of Physics (AIP)
    Published 1993
    Staff View
    ISSN:
    1077-3118
    Source:
    AIP Digital Archive
    Topics:
    Physics
    Notes:
    Room-temperature cw electrically pumped external-cavity surface-emitting laser diodes are reported. The external cavity provides a way to control the transverse modes of the surface-emitting laser diodes. Powers greater than 100 mW pulsed and 2.4 mW cw in the lowest order (TEM00) transverse mode are reported. The surface-emitting laser diode was grown on a p-doped substrate, resulting in uniform current injection in devices as large as 100 μm in diameter. To our knowledge, this is also the first report of a working surface-emitting laser diode grown on a p-type substrate.
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1063/1.110710

    Articles: DFG German National Licenses
  17. 17
    Linder, N. ; Gabler, T. ; Gulden, K. H. ; Kiesel, P. ; Kneissl, M. ; Riel, P. ; Döhler, G. H. ; Wu, X. ; Walker, J. ; Smith, J. S.

    Woodbury, NY : American Institute of Physics (AIP)
    Published 1993
    Staff View
    ISSN:
    1077-3118
    Source:
    AIP Digital Archive
    Topics:
    Physics
    Notes:
    Transmission changes in a n-i-p-i doping superlattice have been measured. The structures were grown by a newly developed epitaxial shadow mask technique allowing to apply selective contacts to the n and p layers. For a voltage swing between only Upn=−4 and 0.8 V relative transmission changes of 65% below the band gap have been measured in a 2.66-μm-thick structure. The changes are larger than 50% in a wavelength range of more than 13 nm. The pure absorption changes are enhanced by a carrier- and field-induced-Bragg effect within the n-i-p-i crystal. The experimental results are in very good quantitative agreement with calculations.
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1063/1.109543

    Articles: DFG German National Licenses
  18. 18
    Gulden, K. H. ; Kneissl, M. ; Kiesel, P. ; Malzer, S. ; Döhler, G. H. ; Wu, X. ; Smith, J. S.

    Woodbury, NY : American Institute of Physics (AIP)
    Published 1994
    Staff View
    ISSN:
    1077-3118
    Source:
    AIP Digital Archive
    Topics:
    Physics
    Notes:
    We report on large changes of the absorption coefficient due to a constructive superposition of the band-filling effect and Franz–Keldysh absorption in a selectively contacted In0.07Ga0.93As/GaAs hetero n-i-p-i structure. By changing the applied bias Upn from −2.5 to +0.8 V the internal fields in the GaAs layers can be tuned from 6.3×105 V/cm to 1.3×105 V/cm. Simultaneously the carrier concentration in the In0.07Ga0.93As quantum wells changes from 0 to 7.4×1012 cm−2. The maximum changes of the absorption coefficient observed at photon energies of 1.39 eV exceed 2000 cm−1 referred to the total sample thickness. This large absorption change is consistent with the theoretically expected constructive superposition of the sub-band-gap Franz–Keldysh absorption in the GaAs layers and the (red shifted) band-filling effect in the InGaAs quantum wells.
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1063/1.111128

    Articles: DFG German National Licenses
  19. 19
    Walker, J. D. ; Kuchta, D. M. ; Smith, J. S.

    Woodbury, NY : American Institute of Physics (AIP)
    Published 1991
    Staff View
    ISSN:
    1077-3118
    Source:
    AIP Digital Archive
    Topics:
    Physics
    Notes:
    We report 10 mW cw room-temperature operation of an electrically pumped vertical-cavity surface-emitting laser diode without a heat sink. This same laser produces 19 mW cw when cooled slightly below room temperature. In addition, we present a 9 mW cw laser with a threshold voltage of 1.6 V, and series resistance of 18 Ω. These are the first surface-emitting lasers fabricated by phase-locked epitaxy. They are also believed to be the highest power and lowest threshold voltage electrically pumped vertical-cavity structures reported to date. These results establish that phase-locked epitaxy has important applications in the fabrication of surface-emitting lasers and many other structures with similar materials requirements.
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1063/1.106414

    Articles: DFG German National Licenses
  20. 20
    Wilson, G. C. ; Kuchta, D. M. ; Walker, J. D. ; Smith, J. S.

    Woodbury, NY : American Institute of Physics (AIP)
    Published 1994
    Staff View
    ISSN:
    1077-3118
    Source:
    AIP Digital Archive
    Topics:
    Physics
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1063/1.112002

    Articles: DFG German National Licenses