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Sample records for wave short wavelength

  1. Nanoscale dynamics by short-wavelength four wave mixing experiments

    NASA Astrophysics Data System (ADS)

    Bencivenga, F.; Baroni, S.; Carbone, C.; Chergui, M.; Danailov, M. B.; De Ninno, G.; Kiskinova, M.; Raimondi, L.; Svetina, C.; Masciovecchio, C.

    2013-12-01

    Multi-dimensional spectroscopies with vacuum ultraviolet (VUV)/x-ray free-electron laser (FEL) sources would open up unique capabilities for dynamic studies of matter at the femtosecond-nanometer time-length scales. Using sequences of ultrafast VUV/x-ray pulses tuned to electron transitions enables element-specific studies of charge and energy flow between constituent atoms, which embody the very essence of chemistry and condensed matter physics. A remarkable step forward towards this goal would be achieved by extending the four wave mixing (FWM) approach at VUV/soft x-ray wavelengths, thanks to the use of fully coherent sources, such as seeded FELs. Here, we demonstrate the feasibility of VUV/soft x-ray FWM at Fermi@Elettra and we discuss its applicability to probe ultrafast intramolecular dynamics, charge injection processes involving metal oxides and electron correlation and magnetism in solid materials. The main advantage in using VUV/soft x-ray wavelengths is in adding element-sensitivity to FWM methods by exploiting the core resonances of selected atoms in the sample.

  2. Short wavelength quantum electrodynamical correction to cold plasma-wave propagation

    SciTech Connect

    Lundin, J.; Brodin, G.; Marklund, M.

    2006-10-15

    The effect of short wavelength quantum electrodynamic (QED) correction on plasma-wave propagation is investigated. The effect on plasma oscillations and on electromagnetic waves in an unmagnetized as well as a magnetized plasma is investigated. The effects of the short wavelength QED corrections are most evident for plasma oscillations and for extraordinary modes. In particular, the QED correction allow plasma oscillations to propagate, and the extraordinary mode loses its stop band. The significance of our results is discussed.

  3. Tunable short-wavelength spin wave excitation from pinned magnetic domain walls

    PubMed Central

    Van de Wiele, Ben; Hämäläinen, Sampo J.; Baláž, Pavel; Montoncello, Federico; van Dijken, Sebastiaan

    2016-01-01

    Miniaturization of magnonic devices for wave-like computing requires emission of short-wavelength spin waves, a key feature that cannot be achieved with microwave antennas. In this paper, we propose a tunable source of short-wavelength spin waves based on highly localized and strongly pinned magnetic domain walls in ferroelectric-ferromagnetic bilayers. When driven into oscillation by a microwave spin-polarized current, the magnetic domain walls emit spin waves with the same frequency as the excitation current. The amplitude of the emitted spin waves and the range of attainable excitation frequencies depend on the availability of domain wall resonance modes. In this respect, pinned domain walls in magnetic nanowires are particularly attractive. In this geometry, spin wave confinement perpendicular to the nanowire axis produces a multitude of domain wall resonances enabling efficient spin wave emission at frequencies up to 100 GHz and wavelengths down to 20 nm. At high frequency, the emission of spin waves in magnetic nanowires becomes monochromatic. Moreover, pinning of magnetic domain wall oscillators onto the same ferroelectric domain boundary in parallel nanowires guarantees good coherency between spin wave sources, which opens perspectives towards the realization of Mach-Zehnder type logic devices and sensors. PMID:26883893

  4. Tunable short-wavelength spin wave excitation from pinned magnetic domain walls

    NASA Astrophysics Data System (ADS)

    van de Wiele, Ben; Hämäläinen, Sampo J.; Baláž, Pavel; Montoncello, Federico; van Dijken, Sebastiaan

    2016-02-01

    Miniaturization of magnonic devices for wave-like computing requires emission of short-wavelength spin waves, a key feature that cannot be achieved with microwave antennas. In this paper, we propose a tunable source of short-wavelength spin waves based on highly localized and strongly pinned magnetic domain walls in ferroelectric-ferromagnetic bilayers. When driven into oscillation by a microwave spin-polarized current, the magnetic domain walls emit spin waves with the same frequency as the excitation current. The amplitude of the emitted spin waves and the range of attainable excitation frequencies depend on the availability of domain wall resonance modes. In this respect, pinned domain walls in magnetic nanowires are particularly attractive. In this geometry, spin wave confinement perpendicular to the nanowire axis produces a multitude of domain wall resonances enabling efficient spin wave emission at frequencies up to 100 GHz and wavelengths down to 20 nm. At high frequency, the emission of spin waves in magnetic nanowires becomes monochromatic. Moreover, pinning of magnetic domain wall oscillators onto the same ferroelectric domain boundary in parallel nanowires guarantees good coherency between spin wave sources, which opens perspectives towards the realization of Mach-Zehnder type logic devices and sensors.

  5. Tunable short-wavelength spin wave excitation from pinned magnetic domain walls.

    PubMed

    Van de Wiele, Ben; Hämäläinen, Sampo J; Baláž, Pavel; Montoncello, Federico; van Dijken, Sebastiaan

    2016-01-01

    Miniaturization of magnonic devices for wave-like computing requires emission of short-wavelength spin waves, a key feature that cannot be achieved with microwave antennas. In this paper, we propose a tunable source of short-wavelength spin waves based on highly localized and strongly pinned magnetic domain walls in ferroelectric-ferromagnetic bilayers. When driven into oscillation by a microwave spin-polarized current, the magnetic domain walls emit spin waves with the same frequency as the excitation current. The amplitude of the emitted spin waves and the range of attainable excitation frequencies depend on the availability of domain wall resonance modes. In this respect, pinned domain walls in magnetic nanowires are particularly attractive. In this geometry, spin wave confinement perpendicular to the nanowire axis produces a multitude of domain wall resonances enabling efficient spin wave emission at frequencies up to 100 GHz and wavelengths down to 20 nm. At high frequency, the emission of spin waves in magnetic nanowires becomes monochromatic. Moreover, pinning of magnetic domain wall oscillators onto the same ferroelectric domain boundary in parallel nanowires guarantees good coherency between spin wave sources, which opens perspectives towards the realization of Mach-Zehnder type logic devices and sensors. PMID:26883893

  6. Paraconductivity for a d-wave superconductor in short-wavelength fluctuation regime

    NASA Astrophysics Data System (ADS)

    Mori, N.

    2009-10-01

    A theoretical study of the fluctuation conductivity above Tc (paraconductivity) is reported for a d-wave superconductor with resonant scattering impurities. A d-wave system is modeled by tight-binding electrons in the two-dimensional squared lattice, and the impurity scattering is treated in the T-matrix approximation in a unitary limit. In calculating the Aslamazov-Larkin (AL) and the Maki-Thompson (MT) terms, we also consider effects of a short-wavelength cutoff in the fluctuation spectrum. The d-wave character in the AL and MT terms manifests itself to renormalization effects on the fluctuation amplitude and reduced temperature, whereas an anomalous-MT term is absent. The present calculations can describe fairly well experiments on the paraconductivity in zinc-doped cuprate superconductors provided that effects of a total-energy cutoff are taken into account.

  7. Continuous-wave, short-wavelength infrared mixer using dispersion-stabilized highly-nonlinear fiber.

    PubMed

    Kuo, Bill P-P; Hirano, Masaaki; Radic, Stojan

    2012-07-30

    A new type of highly nonlinear fiber (HNLF) was designed and fabricated. The new HNLF was engineered to reduce dispersion shift due to transverse fluctuations while maintaining the modal confinement superior to that of the conventional fibers. The new design strategy was validated by the measurements of the global and local dispersive characteristics under considerable core and index profile deformation induced by tensile stress, which indicated that the dispersive and phase matching characteristics of the fiber did not change even under the highest tensile stress. The characteristics effectively decoupled tension-based Brillouin suppression from phase-matching impairments in parametric mixers for the first time. The new HNLF was used to demonstrate the first coherence-preserving mixer operating in the short-wavelength infrared (SWIR) band. The SWIR mixer was driven by continuous-wave near-infrared (NIR) pump and did not require pump phase dithering to suppress Brillouin scattering. PMID:23038393

  8. Short wavelength laser

    DOEpatents

    Hagelstein, P.L.

    1984-06-25

    A short wavelength laser is provided that is driven by conventional-laser pulses. A multiplicity of panels, mounted on substrates, are supported in two separated and alternately staggered facing and parallel arrays disposed along an approximately linear path. When the panels are illuminated by the conventional-laser pulses, single pass EUV or soft x-ray laser pulses are produced.

  9. Short wavelength laser

    DOEpatents

    Hagelstein, Peter L.

    1986-01-01

    A short wavelength laser (28) is provided that is driven by conventional-laser pulses (30, 31). A multiplicity of panels (32), mounted on substrates (34), are supported in two separated and alternately staggered facing and parallel arrays disposed along an approximately linear path (42). When the panels (32) are illuminated by the conventional-laser pulses (30, 31), single pass EUV or soft x-ray laser pulses (44, 46) are produced.

  10. A modified beam-to-earth transformation to measure short-wavelength internal waves with an acoustic Doppler current profiler

    USGS Publications Warehouse

    Scotti, A.; Butman, B.; Beardsley, R.C.; Alexander, P.S.; Anderson, S.

    2005-01-01

    The algorithm used to transform velocity signals from beam coordinates to earth coordinates in an acoustic Doppler current profiler (ADCP) relies on the assumption that the currents are uniform over the horizontal distance separating the beams. This condition may be violated by (nonlinear) internal waves, which can have wavelengths as small as 100-200 m. In this case, the standard algorithm combines velocities measured at different phases of a wave and produces horizontal velocities that increasingly differ from true velocities with distance from the ADCP. Observations made in Massachusetts Bay show that currents measured with a bottom-mounted upward-looking ADCP during periods when short-wavelength internal waves are present differ significantly from currents measured by point current meters, except very close to the instrument. These periods are flagged with high error velocities by the standard ADCP algorithm. In this paper measurements from the four spatially diverging beams and the backscatter intensity signal are used to calculate the propagation direction and celerity of the internal waves. Once this information is known, a modified beam-to-earth transformation that combines appropriately lagged beam measurements can be used to obtain current estimates in earth coordinates that compare well with pointwise measurements. ?? 2005 American Meteorological Society.

  11. Properties of short-wavelength oblique Alfvén and slow waves

    SciTech Connect

    Zhao, J. S.; Wu, D. J.; Voitenko, Y.; Yu, M. Y.; Lu, J. Y.

    2014-10-01

    Linear properties of kinetic Alfvén waves (KAWs) and kinetic slow waves (KSWs) are studied in the framework of two-fluid magnetohydrodynamics. We obtain the wave dispersion relations that are valid in a wide range of the wave frequency ω and plasma-to-magnetic pressure ratio β. The KAW frequency can reach and exceed the ion-cyclotron frequency at ion kinetic scales, whereas the KSW frequency remains sub-cyclotron. At β ∼ 1, the plasma and magnetic pressure perturbations of both modes are in anti-phase, so that there is nearly no total pressure perturbations. However, these modes also exhibit several opposite properties. At high β, the electric polarization ratios of KAWs and KSWs are opposite at the ion gyroradius scale, where KAWs are polarized in the sense of electron gyration (right-hand polarized) and KSWs are left-hand polarized. The magnetic helicity σ ∼ 1 for KAWs and σ ∼ –1 for KSWs, and the ion Alfvén ratio R{sub Ai} << 1 for KAWs and R{sub Ai} >> 1 for KSWs. We also found transition wavenumbers where KAWs change their polarization from left-handed to right-handed. These new properties can be used to discriminate KAWs and KSWs when interpreting kinetic-scale electromagnetic fluctuations observed in various solar-terrestrial plasmas. This concerns, in particular, identification of modes responsible for kinetic-scale pressure-balanced fluctuations and turbulence in the solar wind.

  12. Towards short wavelengths FELs workshop

    SciTech Connect

    Ben-Zvi, I.; Winick, H.

    1993-12-01

    This workshop was caged because of the growing perception in the FEL source community that recent advances have made it possible to extend FEL operation to wavelengths about two orders of magnitude shorter than the 240 nm that has been achieved to date. In addition short wavelength FELs offer the possibilities of extremely high peak power (several gigawatts) and very short pulses (of the order of 100 fs). Several groups in the USA are developing plans for such short wavelength FEL facilities. However, reviewers of these plans have pointed out that it would be highly desirable to first carry out proof-of-principle experiments at longer wavelengths to increase confidence that the shorter wavelength devices will indeed perform as calculated. The need for such experiments has now been broadly accepted by the FEL community. Such experiments were the main focus of this workshop as described in the following objectives distributed to attendees: (1) Define measurements needed to gain confidence that short wavelength FELs will perform as calculated. (2) List possible hardware that could be used to carry out these measurements in the near term. (3) Define a prioritized FEL physics experimental program and suggested timetable. (4) Form collaborative teams to carry out this program.

  13. Review of short wavelength lasers

    SciTech Connect

    Hagelstein, P.L.

    1985-03-18

    There has recently been a substantial amount of research devoted to the development of short wavelength amplifiers and lasers. A number of experimental results have been published wherein the observation of significant gain has been claimed on transitions in the EUV and soft x-ray regimes. The present review is intended to discuss the main approaches to the creation of population inversions and laser media in the short wavelength regime, and hopefully aid workers in the field by helping to provide access to a growing literature. The approaches to pumping EUV and soft x-ray lasers are discussed according to inversion mechanism. The approaches may be divided into roughly seven categories, including collisional excitation pumping, recombination pumping, direct photoionization and photoexcitation pumping, metastable state storage plus optical pumping, charge exchange pumping, and finally, the extension of free electron laser techniques into the EUV and soft x-ray regimes. 250 references.

  14. Influence of four-wave mixing in short- and medium-range 1310  nm dense wavelength division multiplexing systems.

    PubMed

    Markowski, Konrad; Chorchos, Łukasz; Turkiewicz, Jarosław Piotr

    2016-04-10

    In this paper, we demonstrate a comprehensive analysis of the impact of four-wave mixing (FWM) on the quality of transmission in short- and medium-range dense wavelength division multiplexing (DWDM) systems in the 1310 nm wavelength domain. The presented analysis proves that, for the system with uniform power per channel assignment, setting proper input channel power can substantially reduce the influence of the FWM effect on bit error rate in low channel spaced short-range systems, despite the position of the DWDM grid around the zero-dispersion wavelength. Simulations and experimental analysis of the possibility of FWM suppression have been provided. The power penalty measurements show that the influence of FWM on system performance may be as low as 0.3 dB with reasonable input power (i.e., -11  dBm per channel), making possible the transmission of data by fiber over distances of 25 km. Finally, we demonstrate that, for channel spacing as low as 120 GHz, error-free transmission in the 1310 nm wavelength domain is possible, despite high efficiency of FWM generation. The results prove that utilization of the 1310 nm wavelength domain in a system with low channel spacing, i.e., with better bandwidth allocation, is an interesting solution for data storage and processing center applications. PMID:27139874

  15. Short wavelength electromagnetic propagation in magnetized quantum plasmas

    SciTech Connect

    Lundin, J.; Zamanian, J.; Marklund, M.; Brodin, G.

    2007-06-15

    The quantum electrodynamical (QED) short wavelength correction on plasma wave propagation for a nonrelativistic quantum plasma is investigated. A general dispersion relation for a thermal multicomponent quantum plasma is derived. It is found that the classical dispersion relation for any wave mode can be modified to include quantum and short wavelength QED effects by simple substitutions of the thermal velocity and the plasma frequency. Furthermore, the dispersion relation has been modified to include QED effects of strong magnetic fields. It is found that strong magnetic fields together with the short wavelength QED correction will induce dispersion both in vacuum and in otherwise nondispersive plasma modes. Applications to laboratory and astrophysical systems are discussed.

  16. Transition operators in acoustic-wave diffraction theory. I - General theory. II - Short-wavelength behavior, dominant singularities of Zk0 and Zk0 exp -1

    NASA Technical Reports Server (NTRS)

    Hahne, G. E.

    1991-01-01

    A formal theory of the scattering of time-harmonic acoustic scalar waves from impenetrable, immobile obstacles is established. The time-independent formal scattering theory of nonrelativistic quantum mechanics, in particular the theory of the complete Green's function and the transition (T) operator, provides the model. The quantum-mechanical approach is modified to allow the treatment of acoustic-wave scattering with imposed boundary conditions of impedance type on the surface (delta-Omega) of an impenetrable obstacle. With k0 as the free-space wavenumber of the signal, a simplified expression is obtained for the k0-dependent T operator for a general case of homogeneous impedance boundary conditions for the acoustic wave on delta-Omega. All the nonelementary operators entering the expression for the T operator are formally simple rational algebraic functions of a certain invertible linear radiation impedance operator which maps any sufficiently well-behaved complex-valued function on delta-Omega into another such function on delta-Omega. In the subsequent study, the short-wavelength and the long-wavelength behavior of the radiation impedance operator and its inverse (the 'radiation admittance' operator) as two-point kernels on a smooth delta-Omega are studied for pairs of points that are close together.

  17. Design and preparation of frequency-doubled laser optical coatings for double wavelength with low waviness in short-wave

    NASA Astrophysics Data System (ADS)

    Liu, Huasong; Wang, Lishuan; Jiang, Yugang; Jiang, Chenghui; Ji, Yiqin

    2013-09-01

    Coating for double wavelength is one of the important elements in frequency-doubled solid state laser. In this paper, the normal design and whole numerical optimal design were compared. With the same total number of layers, the waviness of coating for double wavelength is more than 0.4139% based on normal design method, while it will be reduced to 0.0109% by whole numerical design, and also the bandwidth can reach 50nm. In experiments, the HfO2/SiO2 multilayer films were prepared by IBS. The test results of film designed by the second method show that the transmissivity is above 99% at 532nm, waviness is 0.4%, and the reflectivity is above 99.9% at 1064nm.

  18. Short wavelength FELs using the SLAC linac

    SciTech Connect

    Winick, H.; Bane, K.; Boyce, R.

    1993-08-01

    Recent technological developments have opened the possibility to construct a device which we call a Linac Coherent Light Source (LCLS); a fourth generation light source, with brightness, coherence, and peak power far exceeding other sources. Operating on the principle of the free electron laser (FEL), the LCLS would extend the range of FEL operation to much aborter wavelength than the 240 mn that has so far been reached. We report the results of studies of the use of the SLAC linac to drive an LCLS at wavelengths from about 3-100 nm initially and possibly even shorter wavelengths in the future. Lasing would be achieved in a single pass of a low emittance, high peak current, high energy electron beam through a long undulator. Most present FELs use an optical cavity to build up the intensity of the light to achieve lasing action in a low gain oscillator configuration. By eliminating the optical cavity, which is difficult to make at short wavelengths, laser action can be extended to shorter wavelengths by Self-Amplified-Spontaneous-Emission (SASE), or by harmonic generation from a longer wavelength seed laser. Short wavelength, single pass lasers have been extensively studied at several laboratories and at recent workshops.

  19. Electricity and short wavelength radiation generator

    DOEpatents

    George, E.V.

    1985-08-26

    Methods and associated apparati for use of collisions of high energy atoms and ions of He, Ne, or Ar with themselves or with high energy neutrons to produce short wavelength radiation (lambda approx. = 840-1300 A) that may be utilized to produce cathode-anode currents or photovoltaic currents.

  20. Short wavelength ion temperature gradient turbulence

    SciTech Connect

    Chowdhury, J.; Ganesh, R.; Brunner, S.; Lapillonne, X.; Villard, L.; Jenko, F.

    2012-10-15

    The ion temperature gradient (ITG) mode in the high wavenumber regime (k{sub y}{rho}{sub s}>1), referred to as short wavelength ion temperature gradient mode (SWITG) is studied using the nonlinear gyrokinetic electromagnetic code GENE. It is shown that, although the SWITG mode may be linearly more unstable than the standard long wavelength (k{sub y}{rho}{sub s}<1) ITG mode, nonlinearly its contribution to the total thermal ion heat transport is found to be low. We interpret this as resulting from an increased zonal flow shearing effect on the SWITG mode suppression.

  1. Modulation compression for short wavelength harmonic generation

    SciTech Connect

    Qiang, J.

    2010-01-11

    Laser modulator is used to seed free electron lasers. In this paper, we propose a scheme to compress the initial laser modulation in the longitudinal phase space by using two opposite sign bunch compressors and two opposite sign energy chirpers. This scheme could potentially reduce the initial modulation wavelength by a factor of C and increase the energy modulation amplitude by a factor of C, where C is the compression factor of the first bunch compressor. Such a compressed energy modulation can be directly used to generate short wavelength current modulation with a large bunching factor.

  2. Far-field measurements of short-wavelength surface plasmons

    SciTech Connect

    Blau, Yochai; Gjonaj, Bergin; David, Asaf; Dolev, Shimon; Shterman, Doron; Bartal, Guy

    2015-03-23

    We present direct far-field measurements of short-wavelength surface plasmon polaritons (SPP) by conventional optics means. Plasmonic wavelength as short as 231 nm was observed for 532 nm illumination on a Ag−Si{sub 3}N{sub 4} platform, demonstrating the capability to characterize SPPs well below the optical diffraction limit. This is done by scaling a sub-wavelength interferometric pattern to a far-field resolvable periodicity. These subwavelength patterns are obtained by coupling light into counter-propagating SPP waves to create a standing-wave pattern of half the SPP wavelength periodicity. Such patterns are mapped by a scattering slit, tilted at an angle so as to increase the periodicity of the intensity pattern along it to more than the free-space wavelength, making it resolvable by diffraction limited optics. The simplicity of the method as well as its large dynamic range of measurable wavelengths make it an optimal technique to characterize the properties of plasmonic devices and high-index dielectric waveguides, to improve their design accuracy and enhance their functionality.

  3. On storage rings for short wavelength FELs

    SciTech Connect

    Chattopadhyay, S.

    1990-01-01

    Significant advances have been made recently in the understanding of FEL physics and the technology of associated systems. We have witnessed experimental successes in the operation of FELs from the far infrared to the visible and near UV. All of the basic physics of FELs, as advanced up to date, in the small and high gain regimes (including exponential growth from noise, optical guiding, etc.) have been proved experimentally in the near or far infrared. These successes motivate us to explore the design of FEL systems at even shorter wavelengths, in the UV, XUV and soft x-ray regions, assuming that the same physics remain valid at these wavelengths. This paper is concerned with issues in the physics and design of storage rings as drivers of short wavelength FELs. 10 refs., 4 figs., 1 tab.

  4. Short wavelength striations on expanding plasma clouds

    SciTech Connect

    Winske, D.; Gary, S.P.

    1989-01-01

    The growth and evolution of short wavelength (

  5. Deformable mirror for short wavelength applications

    DOEpatents

    Chapman, Henry N.; Sweeney, Donald W.

    1999-01-01

    A deformable mirror compatible with short wavelength (extreme ultraviolet) radiation that can be precisely controlled to nanometer and subnanometer accuracy is described. Actuators are coupled between a reaction plate and a face plate which has a reflective coating. A control system adjusts the voltage supplied to the actuators; by coordinating the voltages supplied to the actuators, the reflective surface of the mirror can be deformed to correct for dimensional errors in the mirror or to produce a desired contour.

  6. Source of coherent short wavelength radiation

    DOEpatents

    Villa, Francesco (Alameda, CA)

    1990-01-01

    An apparatus for producing coherent radiation ranging from X-rays to the far ultraviolet (i.e., 1 Kev to 10 eV) utilizing the Compton scattering effect. A photon beam from a laser is scattered on a high energy electron bunch from a pulse power linac. The short wavelength radiation produced by such scattering has sufficient intensity and spatial coherence for use in high resolution applications such as microscopy.

  7. SHORT-WAVELENGTH MAGNETIC BUOYANCY INSTABILITY

    SciTech Connect

    Mizerski, K. A.; Davies, C. R.; Hughes, D. W. E-mail: tina@maths.leeds.ac.uk

    2013-04-01

    Magnetic buoyancy instability plays an important role in the evolution of astrophysical magnetic fields. Here we revisit the problem introduced by Gilman of the short-wavelength linear stability of a plane layer of compressible isothermal fluid permeated by a horizontal magnetic field of strength decreasing with height. Dissipation of momentum and magnetic field is neglected. By the use of a Rayleigh-Schroedinger perturbation analysis, we explain in detail the limit in which the transverse horizontal wavenumber of the perturbation, denoted by k, is large (i.e., short horizontal wavelength) and show that the fastest growing perturbations become localized in the vertical direction as k is increased. The growth rates are determined by a function of the vertical coordinate z since, in the large k limit, the eigenmodes are strongly localized in the vertical direction. We consider in detail the case of two-dimensional perturbations varying in the directions perpendicular to the magnetic field, which, for sufficiently strong field gradients, are the most unstable. The results of our analysis are backed up by comparison with a series of initial value problems. Finally, we extend the analysis to three-dimensional perturbations.

  8. Short-wave Diathermy

    PubMed Central

    1935-01-01

    It is submitted that the thermal action of short-wave therapy does not account for the therapeutic results obtained. The theory is put forward that many of the results obtained can be better explained by the disruptive and dispersive action of the impact of the electromagnetic vibrations. An analogy, indicating such disruptive effects at high frequency, is drawn from the molecular vibrationstransmitted through transformer oil, and excited by the application of high frequency currents to the layers of quartz in the piezo-electric oscillator of quartz. It is submitted that these disruptive and dispersive effects will be greatest where the conductivity of the tissues is low, such as in bones and fat, and it is shown that it is in these regions that the therapeutic action of these currents is most obvious. It is also pointed out that, if effects, comparable to those obtained in the subcutaneous area, are obtained in the deeper tissues and organs, the application of deep-wave therapy would be attended by serious risk. PMID:19990107

  9. Dissipation regimes for short wind waves

    NASA Astrophysics Data System (ADS)

    Caulliez, Guillemette

    2013-02-01

    The dissipation processes affecting short wind waves of centimeter and decimeter scales are investigated experimentally in laboratory. The processes include damping due to molecular viscosity, generation of capillary waves, microbreaking, and breaking. The observations were made in a large wind wave tank for a wide range of fetches and winds, using a laser sheet and a high-resolution video camera. The work aims at constructing a comprehensive picture of dissipative processes in the short wind wave field, to find for which scales particular dissipative mechanism may become important. Four distinct regimes have been identified. For capillary-gravity wave fields, i.e., for dominant waves with scales below 4 cm, viscous damping is found to be the main dissipation mechanism. The gravity-capillary wave fields with dominant wavelength less than 10 cm usually exhibit a train of capillary ripples at the crest wavefront, but no wave breaking. For such waves, the main dissipation process is molecular viscosity occurring through nonlinear energy cascade toward high-frequency motions. Microscale breaking takes place for waves longer than 10 cm and manifests itself in a very localized surface disruption on the forward face of the crest. Such events generate turbulent motions in water and thus enhance wave dissipation. Plunging breaking, characterized by formation of a crest bulge, a microjet hitting the water surface and a splash-up, occurs for short gravity waves of wavelength exceeding 20 cm. Macroscale spilling breaking is also observed for longer waves at high winds. In both cases, the direct momentum transfer from breaking waves to the water flow contributes significantly to wave damping.

  10. Wave Tank Studies of Phase Velocities of Short Wind Waves

    NASA Astrophysics Data System (ADS)

    Ermakov, S.; Sergievskaya, I.; Shchegolkov, Yu.

    Wave tank studies of phase velocities of short wind waves have been carried out using Ka-band radar and an Optical Spectrum Analyser. The phase velocities were retrieved from measured radar and optical Doppler shifts, taking into account measurements of surface drift velocities. The dispersion relationship was studied in centimetre (cm)- and millimetre(mm)-scale wavelength ranges at different fetches and wind speeds, both for a clean water surface and for water covered with surfactant films. It is ob- tained that the phase velocities do not follow the dispersion relation of linear capillary- gravity waves, increasing with fetch and, therefore, depending on phase velocities of dominant decimetre (dm)-centimetre-scale wind waves. One thus can conclude that nonlinear cm-mm-scale harmonics bound to the dominant wind waves and propagat- ing with the phase velocities of the decimetric waves are present in the wind wave spectrum. The resulting phase velocities of short wind waves are determined by re- lation between free and bound waves. The relative intensity of the bound waves in the spectrum of short wind waves is estimated. It is shown that this relation depends strongly on the surfactant concentration, because the damping effect due to films is different for free and bound waves; this results to changes of phase velocities of wind waves in the presence of surfactant films. This work was supported by MOD, UK via DERA Winfrith (Project ISTC 1774P) and by RFBR (Project 02-05-65102).

  11. Silicon-integrated short-wavelength hybrid-cavity VCSEL.

    PubMed

    Haglund, Emanuel P; Kumari, Sulakshna; Westbergh, Petter; Gustavsson, Johan S; Roelkens, Gunther; Baets, Roel; Larsson, Anders

    2015-12-28

    We demonstrate a short-wavelength hybrid-cavity vertical-cavity surface-emitting laser (VCSEL) heterogeneously integrated on silicon. A GaAs-based "half-VCSEL" has been attached to a dielectric distributed Bragg reflector (DBR) on a silicon wafer using ultra-thin divinylsiloxane-bis-benzocyclobutene (DVS-BCB) adhesive bonding, thereby creating a cavity with the standing-wave optical field extending over the silicon- and GaAs-based parts of the cavity. A 9 µm oxide aperture diameter VCSEL with a threshold current of 1.2 mA produces 1.6 mW optical output power at 6.0 mA bias current with a wavelength of ~845 nm. PMID:26832027

  12. Laser-to-electricity energy converter for short wavelengths

    NASA Technical Reports Server (NTRS)

    Stirn, R. J.; Yeh, Y. C. M.

    1975-01-01

    Short-wavelength energy converter can be made using Schottky barrier structure. It has wider band gap than p-n junction silicon semiconductors, and thus it has improved response at wavelengths down to and including ultraviolet region.

  13. Ion heating and short wavelength fluctuations in a helicon plasma source

    SciTech Connect

    Scime, E. E.; Carr, J. Jr.; Galante, M.; Magee, R. M.; Hardin, R.

    2013-03-15

    For typical helicon source parameters, the driving antenna can couple to two plasma modes; the weakly damped 'helicon' wave, and the strongly damped, short wavelength, slow wave. Here, we present direct measurements, obtained with two different techniques, of few hundred kHz, short wavelength fluctuations that are parametrically driven by the primary antenna and localized to the edge of the plasma. The short wavelength fluctuations appear for plasma source parameters such that the driving frequency is approximately equal to the lower hybrid frequency. Measurements of the steady-state ion temperature and fluctuation amplitude radial profiles suggest that the anomalously high ion temperatures observed at the edge of helicon sources result from damping of the short wavelength fluctuations. Additional measurements of the time evolution of the ion temperature and fluctuation profiles in pulsed helicon source plasmas support the same conclusion.

  14. Short Wavelength SASE Experiments at BNL

    NASA Astrophysics Data System (ADS)

    Wang, X. J.

    1998-04-01

    It is now widely recognized in both free electron laser (FEL) and synchrotron light source community that, next generation light source most likely will be FEL based X-ray and UV coherent source. Self Amplified Spontaneous Emission (SASE) and High Gain Harmonic Generation (HGHG) are two most promising candidates for UV to X-ray FELs. National synchrotron light source of Brookhaven National Laboratory has been actively pursuit research in both SASE and HGHG FELs in the past decade. As part of US national experimental effort of proof-of-principle for SASE and HGHG fels, several demonstrational experiments are now underway at the Brookhaven Accelerator Test Facility (ATF) and NSLS Source Development Laboratory (SDL) for SASE and HGHG FELs for wavelength range from near IR to UV. SASE at wavelength 1064 nm and 633 nm were observed using MIT microwiggler at ATF for electron beam energies of 34 MeV and 48 MeV. For 1064 nm radiation, enhancement of emission from 2 to 6 times of the spontaneous emission were measured. In collaboration with ANL APS, a SASE FEL for 5 to 10 micrometer using a two meter long wiggler is now installed at the ATF. For a 40 MeV electron beam produced by the ATF photocathode RF gun (Normalized rms emittance 2.5 mm-mrad, peak current more than 200 A), several orders of magnitude gain in SASE is expected. We intend to carry out detailed studies of SASE FELs, such as gain length as function of electron beam parameters, start-up noise and angular divergence of the SASE radiation

  15. Anisotropic Short-Wavelength Friedel Oscillation with Adjustable Envelope in Graphene

    NASA Astrophysics Data System (ADS)

    Chen, Jian; Xu, Huai-Zhe

    2015-07-01

    We investigate theoretically the intervalley charge density oscillation and the screened ionic potential in graphene caused by the intervalley scattering. We demonstrate that the contribution from the intervalley scattering is comparable with that from the intravalley scattering, and oscillation rather than decaying dominates at a large distance away from the external impurity. We show that the intervalley oscillation is strongly anisotropic because of the inequivalency between neighboring valleys. The anisotropic oscillation consists of an anisotropic short-wavelength oscillation with an anisotropic fixed wavelength and an isotropic long-wavelength envelop with an isotropic wavelength modulated by doping, making an adjustable-widthed wave-packet propagation. One weakens the screening and gets anisotropic short-wavelength oscillation by introducing short-range mechanism in graphene and graphene-like materials. Supported by the National Basic Research Program of China (973 Program) under Grant No. 2013CB934001, the State Key Laboratory of Software Development Environment under Grant No. SKLSDE-2013ZX-28

  16. Short-wavelength plasma turbulence and temperature anisotropy instabilities: recent computational progress

    PubMed Central

    Gary, S. Peter

    2015-01-01

    Plasma turbulence consists of an ensemble of enhanced, broadband electromagnetic fluctuations, typically driven by multi-wave interactions which transfer energy in wavevector space via non- linear cascade processes. Temperature anisotropy instabilities in collisionless plasmas are driven by quasi-linear wave–particle interactions which transfer particle kinetic energy to field fluctuation energy; the resulting enhanced fluctuations are typically narrowband in wavevector magnitude and direction. Whatever their sources, short-wavelength fluctuations are those at which charged particle kinetic, that is, velocity-space, properties are important; these are generally wavelengths of the order of or shorter than the ion inertial length or the thermal ion gyroradius. The purpose of this review is to summarize and interpret recent computational results concerning short-wavelength plasma turbulence, short-wavelength temperature anisotropy instabilities and relationships between the two phenomena. PMID:25848081

  17. Short-wavelength plasma turbulence and temperature anisotropy instabilities: Recent computational progress

    DOE PAGESBeta

    Gary, S. Peter

    2015-04-06

    Plasma turbulence consists of an ensemble of enhanced, broadband electromagnetic fluctuations, typically driven by multi-wave interactions which transfer energy in wavevector space via non- linear cascade processes. In addition, temperature anisotropy instabilities in collisionless plasmas are driven by quasi-linear wave–particle interactions which transfer particle kinetic energy to field fluctuation energy; the resulting enhanced fluctuations are typically narrowband in wavevector magnitude and direction. Whatever their sources, short-wavelength fluctuations are those at which charged particle kinetic, that is, velocity-space, properties are important; these are generally wavelengths of the order of or shorter than the ion inertial length or the thermal ion gyroradius.more » The purpose of this review is to summarize and interpret recent computational results concerning short-wavelength plasma turbulence, short-wavelength temperature anisotropy instabilities and relationships between the two phenomena.« less

  18. Short-wavelength plasma turbulence and temperature anisotropy instabilities: Recent computational progress

    SciTech Connect

    Gary, S. Peter

    2015-04-06

    Plasma turbulence consists of an ensemble of enhanced, broadband electromagnetic fluctuations, typically driven by multi-wave interactions which transfer energy in wavevector space via non- linear cascade processes. In addition, temperature anisotropy instabilities in collisionless plasmas are driven by quasi-linear wave–particle interactions which transfer particle kinetic energy to field fluctuation energy; the resulting enhanced fluctuations are typically narrowband in wavevector magnitude and direction. Whatever their sources, short-wavelength fluctuations are those at which charged particle kinetic, that is, velocity-space, properties are important; these are generally wavelengths of the order of or shorter than the ion inertial length or the thermal ion gyroradius. The purpose of this review is to summarize and interpret recent computational results concerning short-wavelength plasma turbulence, short-wavelength temperature anisotropy instabilities and relationships between the two phenomena.

  19. Lethal effects of short-wavelength visible light on insects

    NASA Astrophysics Data System (ADS)

    Hori, Masatoshi; Shibuya, Kazuki; Sato, Mitsunari; Saito, Yoshino

    2014-12-01

    We investigated the lethal effects of visible light on insects by using light-emitting diodes (LEDs). The toxic effects of ultraviolet (UV) light, particularly shortwave (i.e., UVB and UVC) light, on organisms are well known. However, the effects of irradiation with visible light remain unclear, although shorter wavelengths are known to be more lethal. Irradiation with visible light is not thought to cause mortality in complex animals including insects. Here, however, we found that irradiation with short-wavelength visible (blue) light killed eggs, larvae, pupae, and adults of Drosophila melanogaster. Blue light was also lethal to mosquitoes and flour beetles, but the effective wavelength at which mortality occurred differed among the insect species. Our findings suggest that highly toxic wavelengths of visible light are species-specific in insects, and that shorter wavelengths are not always more toxic. For some animals, such as insects, blue light is more harmful than UV light.

  20. Lethal effects of short-wavelength visible light on insects

    PubMed Central

    Hori, Masatoshi; Shibuya, Kazuki; Sato, Mitsunari; Saito, Yoshino

    2014-01-01

    We investigated the lethal effects of visible light on insects by using light-emitting diodes (LEDs). The toxic effects of ultraviolet (UV) light, particularly shortwave (i.e., UVB and UVC) light, on organisms are well known. However, the effects of irradiation with visible light remain unclear, although shorter wavelengths are known to be more lethal. Irradiation with visible light is not thought to cause mortality in complex animals including insects. Here, however, we found that irradiation with short-wavelength visible (blue) light killed eggs, larvae, pupae, and adults of Drosophila melanogaster. Blue light was also lethal to mosquitoes and flour beetles, but the effective wavelength at which mortality occurred differed among the insect species. Our findings suggest that highly toxic wavelengths of visible light are species-specific in insects, and that shorter wavelengths are not always more toxic. For some animals, such as insects, blue light is more harmful than UV light. PMID:25488603

  1. Short-wavelength III-V LEDs and their applications

    NASA Astrophysics Data System (ADS)

    Uemura, Toshiya; Shibata, Naoki; Yamaguchi, Hisao; Yasukawa, Takemasa

    2003-07-01

    III-V nitride semiconductors are suitable for LEDs having color range from blue to green. Luminous intensity and color purity of these LEDs are so high that they have been used for many applications for full color display and LCD backlight and so on. In addition to natural colored LEDs, we have developed short wavelength LED, named TG Purple, which wavelength is typically around 380nm. TG Purple has been realized by controlling Indium composition in GaInN well layers. It can activate photo-catalysts such as TiOx, and therefore, the air purifier for automotive has been developed by combining TG Purple and TiOx photo-catalyst. The short wavelength LED is now the best light source for automotive air purifier using photo-catalyst, because LEDs fulfill the mercury-less requirement for an environmental issue and don't need special circuit like conventional UV lamps such as black light lamps and cold cathode lamps. Furthermore this short wavelength LED is used for phosphor excitation that generates many colors like blue, green, red, etc. It is likely that, with this technology, LEDs will take some part in illumination market as one of primary light sources like incandescent lamps and fluorescent lamps.

  2. Short Wavelength Seeding through Compression for Fee Electron Lasers

    SciTech Connect

    Qiang, Ji

    2010-03-29

    In this paper, we propose a seeding scheme that compresses an initial laser modulation in the longitudinal phase space of an electron beam by using two opposite sign bunch compressors and two opposite sign energy chirpers. This scheme could potentially reduce the initial modulation wavelength by a factor of C and increase the energy modulation amplitude by a factor of C , where Cis the compression factor of the first bunch compressor. Using two lasers as energy chirpers, such a modulation compression scheme can generate kilo-Ampershort wavelength current modulation with significant bunching factor from an initial a few tens Amper current. This compression scheme can also be used togenerate a prebunched single atto-second short wavelength current modulation and prebunched two color, two atto-second modulations.

  3. Short-wavelength ablation of solids: pulse duration and wavelength effects

    NASA Astrophysics Data System (ADS)

    Juha, Libor; Bittner, Michal; Chvostova, Dagmar; Letal, Vit; Krasa, Josef; Otcenasek, Zdenek; Kozlova, Michaela; Polan, Jiri; Prag, Ansgar R.; Rus, Bedrich; Stupka, Michal; Krzywinski, Jacek; Andrejczuk, Andrzej; Pelka, Jerzy B.; Sobierajski, Ryszard H.; Ryc, Leszek; Feldhaus, Josef; Boody, Frederick P.; Fiedorowicz, Henryk; Bartnik, Andrzej; Mikolajczyk, Janusz; Rakowski, Rafal; Kubat, P.; Pina, Ladislav; Grisham, Michael E.; Vaschenko, Georgiy O.; Menoni, Carmen S.; Rocca, Jorge J. G.

    2004-11-01

    For conventional wavelength (UV-Vis-IR) lasers delivering radiation energy to the surface of materials, ablation thresholds, ablation (etch) rates, and the quality of ablated structures often differ dramatically between short (typically nanosecond) and ultrashort (typically femtosecond) pulses. Various short-wavelength (l < 100 nm) lasers emitting pulses with durations ranging from ~ 10 fs to ~ 1 ns have recently been put into a routine operation. This makes it possible to investigate how the ablation characteristics depend on the pulse duration in the XUV spectral region. 1.2-ns pulses of 46.9-nm radiation delivered from a capillary-discharge Ne-like Ar laser (Colorado State University, Fort Collins), focused by a spherical Sc/Si multilayer-coated mirror were used for an ablation of organic polymers and silicon. Various materials were irradiated with ellipsoidal-mirror-focused XUV radiation (λ = 86 nm, τ = 30-100 fs) generated by the free-electron laser (FEL) operated at the TESLA Test Facility (TTF1 FEL) in Hamburg. The beam of the Ne-like Zn XUV laser (λ = 21.2 nm, τ < 100 ps) driven by the Prague Asterix Laser System (PALS) was also successfully focused by a spherical Si/Mo multilayer-coated mirror to ablate various materials. Based on the results of the experiments, the etch rates for three different pulse durations are compared using the XUV-ABLATOR code to compensate for the wavelength difference. Comparing the values of etch rates calculated for short pulses with those measured for ultrashort pulses, we can study the influence of pulse duration on XUV ablation efficiency. Ablation efficiencies measured with short pulses at various wavelengths (i.e. 86/46.9/21.2 nm from the above-mentioned lasers and ~ 1 nm from the double stream gas-puff Xe plasma source driven by PALS) show that the wavelength influences the etch rate mainly through the different attenuation lengths.

  4. Method for fabricating photovoltaic device having improved short wavelength photoresponse

    DOEpatents

    Catalano, Anthony W.

    1989-07-04

    Amorphous p-i-n silicon photovoltaic cells with improved short wavelength photoresponse are fabricated with reduced p-dopant contamination at the p/i interface. Residual p-dopants are removed by flushing the deposition chamber with a gaseous mixture capable of reacting with excess doping contaminants prior to the deposition of the i-layer and subsequent to the deposition of the p-layer.

  5. Output characteristics of SASE-driven short-wavelength FELs

    NASA Astrophysics Data System (ADS)

    Fawley, William M.

    1997-05-01

    This paper investigates various properties of the 'microspikes' associated with self-amplified spontaneous emission (SASE) in a short wavelength free-electron laser (FEL). Using results from the 2-D numerical simulation code GINGER, we confirm theoretical predictions such as the convective group velocity in the exponential gain regime. In the saturated gain regime beyond the initial saturation, we find that the average radiation power continues to grow with an approximately linearly dependence upon undulator length. Moreover, the spectrum significantly broadens and shifts in wavelength to the redward direction, with P(omega) approaching a constant, asymptotic value. This is in marked contrast to the exponential gain regime where the spectrum steadily narrows, P(omega) grows, and the central wavelength remains constant with z. Via use of a spectrogram diagnostic S(omega, t), it appears that the radiation pattern in the saturated gain regime is composed of an ensemble of distinct 'sinews' whose widths (Delta) (lambda) remain approximately constant but whose central wavelengths can 'chirp' by varying a small extent with t.

  6. Finite-Wavelength Stabilityof Capillary-Gravity Solitary Waves

    NASA Astrophysics Data System (ADS)

    Haragus, Mariana; Scheel, Arnd

    We consider the Euler equations describing nonlinear waves on the free surface of a two-dimensional inviscid, irrotational fluid layer of finite depth. For large surface tension, Bond number larger than 1/3, and Froude number close to 1, the system possesses a one-parameter family of small-amplitude, traveling solitary wave solutions. We show that these solitary waves are spectrally stable with respect to perturbations of finite wave-number. In particular, we exclude possible unstable eigenvalues of the linearization at the soliton in the long-wavelength regime, corresponding to small frequency, and unstable eigenvalues with finite but bounded frequency, arising from non-adiabatic interaction of the infinite-wavelength soliton with finite-wavelength perturbations.

  7. Short wavelength limits of current shot noise suppression

    SciTech Connect

    Nause, Ariel; Dyunin, Egor; Gover, Avraham

    2014-08-15

    Shot noise in electron beam was assumed to be one of the features beyond control of accelerator physics. Current results attained in experiments at Accelerator Test Facility in Brookhaven and Linac Coherent Light Source in Stanford suggest that the control of the shot noise in electron beam (and therefore of spontaneous radiation and Self Amplified Spontaneous Emission of Free Electron Lasers) is feasible at least in the visible range of the spectrum. Here, we present a general linear formulation for collective micro-dynamics of e-beam noise and its control. Specifically, we compare two schemes for current noise suppression: a quarter plasma wavelength drift section and a combined drift/dispersive (transverse magnetic field) section. We examine and compare their limits of applicability at short wavelengths via considerations of electron phase-spread and the related Landau damping effect.

  8. Research with high-power short-wavelength lasers

    NASA Astrophysics Data System (ADS)

    Holzrichter, J. F.; Campbell, E. M.; Lindl, J. D.; Storm, E.

    1985-03-01

    Three high-temperature, high-density experiments were conducted using the 10-TW, short-wavelength Novette laser system. Successful solutions to problems that arose during previous experiments with long wavelength lasers in which inertial confinement fusion (ICF), X-ray laser, and other high-temperature physics concepts were tested are demonstrated. The demonstrations are: (1) large-scale plasmas were produced in which potentially deleterious laser-plasma instabilities were collisionally damped; (2) deuterium-tritium fuel was imploded to a density of 20 g/sub cm and a pressure of 10(1) atm; (3) a 700-fold amplification of soft X rays by stimulated emission at 206 and 209 A from Se(+24) ions is observed in a laser-generated plasma. Isoelectronic scaling to 155 A in Y(+29) is also demonstrated.

  9. Research with high-power short-wavelength lasers

    SciTech Connect

    Holzrichter, J.F.; Campbell, E.M.; Lindl, J.D.; Storm, E.

    1985-03-05

    Three important high-temperature, high-density experiments were conducted recently using the 10-TW, short-wavelength Novette laser system at the Lawrence Livermore National Laboratory. These experiments demonstrated successful solutions to problems that arose during previous experiments with long wavelength lasers (lambda greater than or equal to 1..mu..m) in which inertial confinement fusion (ICF), x-ray laser, and other high-temperature physics concepts were being tested. The demonstrations were: (1) large-scale plasmas (typical dimensions of up to 1000 laser wavelengths) were produced in which potentially deleterious laser-plasma instabilities were collisionally damped. (2) Deuterium-tritium fuel was imploded to a density of 20 g/cm/sup 3/ and a pressure of 10/sup 10/ atm. (3) A 700-fold amplification of soft x rays by stimulated emission at 206 and 209 A (62 eV) from Se/sup +24/ ions was observed in a laser-generated plasma. Isoelectronic scaling to 155 A (87 eV) in Y/sup +29/ was also demonstrated.

  10. On the wavelength of self-organized shoreline sand waves

    NASA Astrophysics Data System (ADS)

    Falqués, A.; van den Berg, N.; Ribas, F.; Caballeria, M.; Calvete, D.

    2012-04-01

    Shoreline sand waves are undulations of the shoreline that extend into the bathymetry up to a certain depth. Here we will focus on self-organized sand waves that form due to shoreline instability in case of very oblique wave incidence (Ashton et al., 2001). The model of Ashton and co-authors did not predict any wavelength selection for the emerging sand waves whereas Falqués and Calvete (2005) predicted a wavelength selection in the range 4-15 km. This difference is attributable to that Falqués and Calvete (2005) computed wave refraction and shoaling over the actual curvilinear depth contours while Ashton et al. (2001) assumed locally rectilinear and parallel contours. Although there exist shoreline features at a larger scale (Ashton et al. 2001; Falqués et al. 2011) sand waves at a few km scale are more common (Ruessink and Jeuken, 2002; Davidson-Arnott and van Heyningen, 2003; Falqués et al., 2011; Medellin et al., 2008) . While their characteristic wavelength is a robust model output (Falqués and Calvete, 2005; Uguccioni et al., 2006; van den Berg et al., 2011) the physical reasons for the existence of a wavelength selection are still unknown. Furthermore, the parameter dependence of the dominant wavelength, Lm, is largely unexplored. In particular, the disparity between the large length scale of sand waves and the relevant length scales of the problem: width of the surf zone, water wave wavelength, etc. is intriguing. The aim of the present contribution is to gain insight into those physical reasons and the dependence of Lm on beach profile and water wave properties. The essence of sandwave behaviour can be captured with the simple one-line shoreline modelling concept by looking at the alongshore position of the maximum in total transport rate Q, which is here investigated with both the linearized model of Falqués and Calvete (2005) and the nonlinear model of van den Berg et al. (2011) . It is found that the position of that maximum is largely controlled by the alongshore distribution of wave energy associated to the sand wave, mainly affected in turn by : A) refractive wave energy spreading and B) refractive energy focusing by the crest. Furthermore, for large L the growthrate decreases to 0 since the gradients in wave energy and hence the gradients in Q decrease. As a result, there is a minimum wavelength, Lc, for growth and an optimum wavelength Lm > Lcof maximum growth. Experiments with different bathymetric profiles and different wave conditions are made to investigate the sensitivity of Lm . It is found that Lm scales with λ0/β where λ0 is the water wave wavelength in deep water and β the beach slope.

  11. Wavelength division multiplexed optical interconnects using short pulses

    NASA Astrophysics Data System (ADS)

    Keeler, Bianca Elizabeth Nelson

    Optical interconnects for silicon electronics have been shown to have many advantages over traditional electrical interconnects, particularly in dense, high-capacity systems. One approach used to achieve the very high data rates used in telecommunications today is wavelength division multiplexing (WDM). As bandwidth needs increase, WDM becomes an attractive solution for shorter distance links as well, such as chip-to-chip or board-to-board interconnects. While telecommunications WDM systems traditionally use a separate laser for each wavelength channel, a simpler, less expensive alternative is needed for interconnects on scales of a few meters or less. One such solution is to use a single, broadband laser source. In this work, operation of a 10-channel chip-to-chip WDM optical interconnect using a modelocked Ti:Sapphire laser and surface-normal electroabsorption modulators is demonstrated. The short pulses from a modelocked laser have a broad spectral bandwidth, which allows the wavelength channels to be defined by spectral slicing of a single source. However, the short pulse duration, high peak power, and low jitter of these pulses provide additional advantages in optical interconnects, several of which will also be discussed. The possible performance limitations of such a WDM interconnect are explored, and several future improvements are proposed. Many of the wavelength-separating devices used for WDM, such as arrayed waveguide gratings (AWGs), are complex to fabricate and relatively costly. Other de-multiplexers include traditional dispersive devices, such as diffraction gratings and prisms. While being much simpler and less expensive than AWGs, these devices typically have an angular dispersion less than one degree/mm, which prevents them from being sufficiently compact. Recent work suggests that the "superprism effect" of periodic structures may provide a compact alternative, with angular dispersion many times higher than that of a conventional grating or prism. This work experimentally demonstrates that the same beam-steering effect, previously shown for 3D photonic crystals, exists in a simple 1D dielectric stack structure, and discusses its possible application within WDM systems.

  12. Carbon Monoxide Retrievals From Short Wave Infrared Observations Of Sciamachy

    NASA Astrophysics Data System (ADS)

    Schreier, Franz; Gimeno-Garcia, Sebastian; Lihtenberg, Gunter; Hess, Michael

    2013-12-01

    For the estimation of vertical column densities from short-wave near infrared nadir observations from SCIA- MACHY (and similar instruments like GOSAT) the “Beer InfraRed Retrieval Algorithm” BIRRA has been developed that performs a nonlinear or separable least squares fit of concentration profile scaling factors along with some auxiliary parameters. Our recent work focuses on improvements with respect to wavelength calibration, a more flexible multiwindow fitting scheme, and a better modeling of SCIAMACHY's channel 8 spectral response function. Here we present results from carbon monoxide retrevials from SCIAMACHY's channel 8 indicating the significant impact of fitting the wavelength shift.

  13. Put a Short-Wave Radio in Your Foreign Language Classroom

    ERIC Educational Resources Information Center

    Oksenholt, Svein

    1977-01-01

    Advantages of the short-wave radio as a supplement to foreign language instruction as well as practical hints on wavelength, antenna, and techniques for use are provided. Selective annotated bibliography. (STS)

  14. Coherent control with a short-wavelength free-electron laser

    NASA Astrophysics Data System (ADS)

    Prince, K. C.; Allaria, E.; Callegari, C.; Cucini, R.; de Ninno, G.; di Mitri, S.; Diviacco, B.; Ferrari, E.; Finetti, P.; Gauthier, D.; Giannessi, L.; Mahne, N.; Penco, G.; Plekan, O.; Raimondi, L.; Rebernik, P.; Roussel, E.; Svetina, C.; Trovò, M.; Zangrando, M.; Negro, M.; Carpeggiani, P.; Reduzzi, M.; Sansone, G.; Grum-Grzhimailo, A. N.; Gryzlova, E. V.; Strakhova, S. I.; Bartschat, K.; Douguet, N.; Venzke, J.; Iablonskyi, D.; Kumagai, Y.; Takanashi, T.; Ueda, K.; Fischer, A.; Coreno, M.; Stienkemeier, F.; Ovcharenko, Y.; Mazza, T.; Meyer, M.

    2016-03-01

    Extreme ultraviolet and X-ray free-electron lasers (FELs) produce short-wavelength pulses with high intensity, ultrashort duration, well-defined polarization and transverse coherence, and have been utilized for many experiments previously possible only at long wavelengths: multiphoton ionization, pumping an atomic laser and four-wave mixing spectroscopy. However one important optical technique, coherent control, has not yet been demonstrated, because self-amplified spontaneous emission FELs have limited longitudinal coherence. Single-colour pulses from the FERMI seeded FEL are longitudinally coherent, and two-colour emission is predicted to be coherent. Here, we demonstrate the phase correlation of two colours, and manipulate it to control an experiment. Light of wavelengths 63.0 and 31.5 nm ionized neon, and we controlled the asymmetry of the photoelectron angular distribution by adjusting the phase, with a temporal resolution of 3 as. This opens the door to new short-wavelength coherent control experiments with ultrahigh time resolution and chemical sensitivity.

  15. Semianalytical approach to short-wavelength dispersion and modal properties of photonic crystal fibers.

    PubMed

    Mortensen, Niels Asger

    2005-06-15

    Photonic crystal fibers made from arbitrary base materials are considered, and a unified semianalytical approach for the dispersion and modal properties is derived that applies to the short-wavelength regime. In particular, the dispersion and the effective index are calculated and compared with fully vectorial plane-wave simulations, and excellent agreement is found. Asymptotic results for the mode-field diameter and the V parameter are also calculated, and from the latter it is predicted that the fibers are endlessly single mode for a normalized airhole diameter smaller than 0.42, independently of the base material. PMID:16007772

  16. Short wavelength topography on the inner-core boundary

    PubMed Central

    Cao, Aimin; Masson, Yder; Romanowicz, Barbara

    2007-01-01

    Constraining the topography of the inner-core boundary is important for studies of core–mantle coupling and the generation of the geodynamo. We present evidence for significant temporal variability in the amplitude of the inner core reflected phase PKiKP for an exceptionally high-quality earthquake doublet, observed postcritically at the short-period Yellowknife seismic array (YK), which occurred in the South Sandwich Islands within a 10-year interval (1993/2003). This observation, complemented by data from several other doublets, indicates the presence of topography at the inner-core boundary, with a horizontal wavelength on the order of 10 km. Such topography could be sustained by small-scale convection at the top of the inner core and is compatible with a rate of super rotation of the inner core of ≈0.1–0.15° per year. In the absence of inner-core rotation, decadal scale temporal changes in the inner-core boundary topography would provide an upper bound on the viscosity at the top of the inner core. PMID:17190798

  17. Ultra-short wavelength operation of a thulium fibre laser in the 1660-1750 nm wavelength band.

    PubMed

    Daniel, J M O; Simakov, N; Tokurakawa, M; Ibsen, M; Clarkson, W A

    2015-07-13

    Ultra-short wavelength operation of a thulium fibre laser is investigated. Through use of core pumping and high feedback efficiency wavelength selection, a continuously-tunable fibre laser source operating from 1660 nm to 1720 nm is demonstrated in a silica host. We discuss the range of applications within this important wavelength band such as polymer materials processing and medical applications targeting characteristic C-H bond resonance peaks. As a demonstration of the power scalability of thulium fibre lasers in this band, fixed wavelength operation at 1726 nm with output power up 12.6 W and with slope efficiency > 60% is also shown. PMID:26191883

  18. Laboratory study of the fine structure of short surface waves due to breaking: Two-directional wave propagation

    NASA Astrophysics Data System (ADS)

    Rozenberg, A.; Ritter, M.

    2005-02-01

    This study was stimulated by the need to identify the influence of breaking on the evolution of the short surface wave field responsible for microwave scattering. Laboratory measurements of the fine space-time structure of short gravity-capillary waves and Ku band scattering at grazing and moderate incidence from spilling and plunging breaking waves in a laboratory wave channel are presented. Unsteady breaking waves are generated by focusing wave groups in space-time domains. A scanning laser slope gauge was used for measuring capillary-gravity waves with wavelengths of 2 mm to 10 cm and frequency ranges of up to 150 Hz. A dual polarized (VV, HH) coherent pulsed Ku band scatterometer with a 3 ns temporal resolution was used to simultaneously obtain Doppler spectra of the scattered signals from the breaking area for grazing angles from 6 to 25. Two-dimensional filtering in the wave number-frequency plane as well as plus/minus Doppler spectra were used to separate the direction of propagation of the surface waves within the breaking region. It was found that the breaking splash is the main source of the surface wave generation. The short surface wave slope field produced by breaking could be separated into short (4-8 mm wavelength), fast waves and free gravity-capillary waves. Both types of waves were found to be co- and counterpropagate relative to the dominant wave propagation direction. The Doppler spectrograms reveal the presence of high-frequency waves at the moment of breaking that can be associated with short, fast waves. The low-frequency part of the Doppler spectrogram is consistent with the appearance of free waves.

  19. Submicrojoule femtosecond erbium-doped fibre laser for the generation of dispersive waves at submicron wavelengths

    SciTech Connect

    Kotov, L V; Koptev, M Yu; Anashkina, E A; Muravyev, S V; Andrianov, A V; Kim, A V; Bubnov, M M; Likhachev, M E; Ignat'ev, A D; Lipatov, D S; Gur'yanov, A N

    2014-05-30

    We have demonstrated a femtosecond erbium-doped fibre laser system built in the master oscillator/power amplifier (MOPA) approach. The final amplifier stage utilises a specially designed large mode area active fibre cladding-pumped by multimode laser diodes. The system is capable of generating submicrojoule pulses at a wavelength near 1.6 μm. We have obtained 530-fs pulses with an energy of 400 nJ. The output of the system can be converted to wavelengths shorter than 1 μm through the generation of dispersive waves in passive nonlinear fibre. We have obtained ultra-short 7-nJ pulses with a spectral width of ∼100 nm and a centre wavelength of 0.9 μm, which can be used as a seed signal in parametric amplifiers in designing petawatt laser systems. (lasers)

  20. Cameras Reveal Elements in the Short Wave Infrared

    NASA Technical Reports Server (NTRS)

    2010-01-01

    Goodrich ISR Systems Inc. (formerly Sensors Unlimited Inc.), based out of Princeton, New Jersey, received Small Business Innovation Research (SBIR) contracts from the Jet Propulsion Laboratory, Marshall Space Flight Center, Kennedy Space Center, Goddard Space Flight Center, Ames Research Center, Stennis Space Center, and Langley Research Center to assist in advancing and refining indium gallium arsenide imaging technology. Used on the Lunar Crater Observation and Sensing Satellite (LCROSS) mission in 2009 for imaging the short wave infrared wavelengths, the technology has dozens of applications in military, security and surveillance, machine vision, medical, spectroscopy, semiconductor inspection, instrumentation, thermography, and telecommunications.

  1. Wavelength selection and symmetry breaking in orbital wave ripples

    NASA Astrophysics Data System (ADS)

    Nienhuis, Jaap H.; Perron, J. Taylor; Kao, Justin C. T.; Myrow, Paul M.

    2014-10-01

    Sand ripples formed by waves have a uniform wavelength while at equilibrium and develop defects while adjusting to changes in the flow. These patterns arise from the interaction of the flow with the bed topography, but the specific mechanisms have not been fully explained. We use numerical flow models and laboratory wave tank experiments to explore the origins of these patterns. The wavelength of "orbital" wave ripples (λ) is directly proportional to the oscillating flow's orbital diameter (d), with many experimental and field studies finding λ/d ≈ 0.65. We demonstrate a coupling that selects this ratio: the maximum length of the flow separation zone downstream of a ripple crest equals λ when λ/d ≈ 0.65. We show that this condition maximizes the growth rate of ripples. Ripples adjusting to changed flow conditions develop defects that break the bed's symmetry. When d is shortened sufficiently, two new incipient crests appear in every trough, but only one grows into a full-sized crest. Experiments have shown that the same side (right or left) wins in every trough. We find that this occurs because incipient secondary crests slow the flow and encourage the growth of crests on the next flank. Experiments have also shown that when d is lengthened, ripple crests become increasingly sinuous and eventually break up. We find that this occurs because crests migrate preferentially toward the nearest adjacent crest, amplifying any initial sinuosity. Our results reveal the mechanisms that form common wave ripple patterns and highlight interactions among unsteady flows, sediment transport, and bed topography.

  2. Non-linear plasma wave decay to longer wavelength

    NASA Astrophysics Data System (ADS)

    Anderegg, F.; Affolter, M.; Ashourvan, A.; Dubin, D. H. E.; Valentini, F.; Driscoll, C. F.

    2015-06-01

    We measure the decay of plasma waves to longer wavelengths, for both "standard" Trivelpiece-Gould waves with vϕ≫v¯ , and for the lower phase velocity "EAW" modes with vϕ˜v¯ . These are θ-symmetric standing modes on pure ion or pure electron plasma columns with discrete wavenumbers kz = mz π/Lp. A large amplitude mz = 2 Trivelpiece-Gould wave causes phase-locked exponential growth of the mz = 1 wave when they are near resonant, at growth rates Γe ∝ δn2/n consistent with cold fluid theory. For larger detuning Δ ≡ 2f1-f2, mode amplitude A1 is observed to "bounce" at rate Δf, with amplitude excursions ΔA1 ∝ δn2/n also consistent with cold fluid theory; but A1 often exhibits a slower overall growth, as yet unexplained by theory. In contrast, a large amplitude mz = 2 EAW mode generally causes either strong phase-locked mz = 1 growth or no growth at all, apparently because the EAW "frequency fungibility" enables Δf = 0, and EAW mode damping is strong until the velocity distribution F(vphase) is "flattened."

  3. Dark- and bright-rogue-wave solutions for media with long-wave-short-wave resonance.

    PubMed

    Chen, Shihua; Grelu, Philippe; Soto-Crespo, J M

    2014-01-01

    Exact explicit rogue-wave solutions of intricate structures are presented for the long-wave-short-wave resonance equation. These vector parametric solutions feature coupled dark- and bright-field counterparts of the Peregrine soliton. Numerical simulations show the robustness of dark and bright rogue waves in spite of the onset of modulational instability. Dark fields originate from the complex interplay between anomalous dispersion and the nonlinearity driven by the coupled long wave. This unusual mechanism, not available in scalar nonlinear wave equation models, can provide a route to the experimental realization of dark rogue waves in, for instance, negative index media or with capillary-gravity waves. PMID:24580164

  4. Short-Wavelength Infrared Views of Messier 81

    NASA Technical Reports Server (NTRS)

    2003-01-01

    The magnificent spiral arms of the nearby galaxy Messier 81 are highlighted in this NASA Spitzer Space Telescope image. Located in the northern constellation of Ursa Major (which also includes the Big Dipper), this galaxy is easily visible through binoculars or a small telescope. M81 is located at a distance of 12 million light-years from Earth.

    Because of its proximity, M81 provides astronomers with an enticing opportunity to study the anatomy of a spiral galaxy in detail. The unprecedented spatial resolution and sensitivity of Spitzer at infrared wavelengths show a clear separation between the several key constituents of the galaxy: the old stars, the interstellar dust heated by star formation activity, and the embedded sites of massive star formation. The infrared images also permit quantitative measurements of the galaxy's overall dust content, as well as the rate at which new stars are being formed.

    The infrared image was obtained by Spitzer's infrared array camera. It is a four-color composite of invisible light, showing emissions from wavelengths of 3.6 microns (blue), 4.5 microns (green), 5.8 microns (yellow) and 8.0 microns (red). Winding outward from the bluish-white central bulge of the galaxy, where old stars predominate and there is little dust, the grand spiral arms are dominated by infrared emission from dust. Dust in the galaxy is bathed by ultraviolet and visible light from the surrounding stars. Upon absorbing an ultraviolet or visible-light photon, a dust grain is heated and re-emits the energy at longer infrared wavelengths. The dust particles, composed of silicates (which are chemically similar to beach sand) and polycyclic aromatic hydrocarbons, trace the gas distribution in the galaxy. The well-mixed gas (which is best detected at radio wavelengths) and dust provide a reservoir of raw materials for future star formation.

    The infrared-bright clumpy knots within the spiral arms denote where massive stars are being born in giant H II (ionized hydrogen) regions. The 8-micron emission traces the regions of active star formation in the galaxy. Studying the locations of these regions with respect to the overall mass distribution and other constituents of the galaxy (e.g., gas) will help identify the conditions and processes needed for star formation. With the Spitzer observations, this information comes to us without complications from absorption by cold dust in the galaxy, which makes interpretation of visible-light features uncertain.

    The white stars scattered throughout the field of view are foreground stars within our own Milky Way galaxy.

  5. Gyrokinetic simulation of short wavelength residual zonal flows

    NASA Astrophysics Data System (ADS)

    Yoon, E. S.; Hahm, T. S.; Ku, S.

    2010-11-01

    It is widely recognized that zonal flow plays a crucial role in saturating the level of turbulence. Therefore, estimation of residual (i.e., undamped) zonal flow level is important in predicting turbulence transport. There has been considerable theoretical progress on this topic [1,2,3]. In particular, Wang and Hahm [3] formulated an analytic expression for residual zonal flows which is valid for arbitrary wavelength, taking into account of both neoclassical and classical polarization shielding of both species. This is in broad agreement with the previous gyrokinetic simulation results by Jenko et al. [4]. In this work, we examine various parametric dependences of residual zonal flow level in wide wavelength range using gyrokinetic simulation, and compare with the analytic predictions [3]. [1] M.N. Rosenbluth and F.L. Hinton, Phys. Rev. Lett. 80, 724 (1998) [2] Y. Xiao and P.J. Catto, Phys. Plasmas 13, 102311 (2006) [3] L. Wang and T.S. Hahm, Phys. Plamsas 16, 062309 (2009) [4] F. Jenko, W. Dorland, M. Kotschenreuther, and B.N. Rogers, Phys. Plasmas 7, 1904 (2000)

  6. All-incoherent wavelength conversion in highly nonlinear fiber using four-wave mixing

    NASA Astrophysics Data System (ADS)

    Kharraz, Osayd M.; Ahmad, Harith; Forsyth, David I.; Dernaika, Mohamad; Zulkifli, Mohd Zamani B.; Ismail, Mohd Faizal B.; Mohammad, Abu Bakar B.

    2014-09-01

    This work describes efficient and polarization insensitive, all-incoherent four-wave mixing wavelength conversion achieved within a short length of highly nonlinear fiber medium, created by using both spectrally sliced pump and probe channels from a single-amplified spontaneous emission source coupled to two narrowband Fiber Bragg grating (FBG) filters. This simple and cost-effective scheme is capable of generating a down-converted probe channel across a 17.2-nm wavelength span, while still maintaining a high conversion efficiency of around -22 dB and an optical-signal-to-noise ratio of ˜21 dB. The effects of pump power, FBG detuning, and polarization are also reported.

  7. Comparative study of the frequency-doubling performance on ring and linear cavity at short wavelength region.

    PubMed

    Yang, Wenhai; Wang, Yajun; Zheng, Yaohui; Lu, Huadong

    2015-07-27

    We theoretically and experimentally perform a comparative study on performance of the linear standing-wave cavity and ring cavity for external cavity frequency doubling at the wavelength from 795 nm to 397.5 nm. The two cavities show obvious differences of the thermal effect of nonlinear crystal, cavity sensitivity, and maximum output power. The results show that ring cavity as the external enhancement cavity is a better choice than standing-wave cavity at short wavelength region. At last, a 397.5 nm violet laser with 408 mW corresponding to an input power of 992 mW is obtained by using the ring cavity, considering the original mode-matching efficiency of 98% between the 795 nm laser and frequency doubling cavity, the conversion efficiency is 41.9%. PMID:26367620

  8. Ultrafast terawatt laser sources for high-field particle acceleration and short wavelength generation

    SciTech Connect

    Downer, M.C.; Siders, C.W.

    1996-12-31

    The Laser Sources working group concerned itself with recent advances in and future requirements for the development of laser sources relevant to high-energy physics (HEP) colliders, small scale accelerators, and the generation of short wave-length radiation. We heavily emphasized pulsed terawatt peak power laser sources for several reasons. First, their development over the past five years has been rapid and multi-faceted, and has made relativistic light intensity available to the advanced accelerator community, as well as the wider physics community, for the first time. Secondly, they have strongly impacted plasma-based accelerator research over the past two years, producing the first experimental demonstrations of the laser wakefield accelerator (LWFA) in both its resonantly-driven and self-modulated forms. Thirdly, their average power and wall-plug efficiency currently fall well short of projected requirements for future accelerators and other high average power applications, but show considerable promise for improving substantially over the next few years. A review of this rapidly emerging laser technology in the context of advanced accelerator research is therefore timely.

  9. Investigating short wavelength correlated errors on low resolution mode altimetry

    NASA Astrophysics Data System (ADS)

    Poisson, Jean-Christophe; Thibaut, Pierre; Dibarboure, Gérald; Labroue, Sylvie; Lasne, Yannick; Boy, François; Picot, Nicolas

    2013-04-01

    Although conventional radar altimetry products (Jason1, Jason2, LRM CRYOSAT2, etc) have a spatial resolution as high as 300 m, the observation of ocean scales smaller than 100 km is limited by the existence of a "spectral hump", i.e. a geographically coherent error. In the frame of the future altimetry missions (SAR for Cryosat -2 and Sentinel-3 missions and interferometry for the SWOT mission) it becomes crucial to investigate again and to better understand the signals obtained at small scales by conventional altimeter missions. Through an analysis of simulations, we show that heterogeneous backscattering scenes can result in the corruption of the altimeter waveforms and retracked parameters. The retrackers used in current ground processors cannot well fit the Brown model during backscattering events because this model has been designed for a homogeneous scene. The error is also propagated along-track because of the size and shape of the low resolution mode (LRM) disc-shaped footprint. The hump phenomenon is shown to be almost ubiquitous in the ocean, yet more intense at low latitudes and in the Indian Ocean and Western Pacific Ocean, where backscattering events are more frequent. Its overall signature could be a Gaussian-like random signal smooth for wavelengths smaller than 15 km, i.e. white noise on 1 Hz products. The analysis of current data from 5 altimetry missions highlights the influence of the instrument design and altitude, and the influence of the retracker used. The spectral hump is a systematic response to random events and it is possible to mitigate it with new processing. Simulations and geographically limited datasets from the synthetic aperture radar mode (SARM) of Cryosat-2 show that the thin stripe-shaped synthetic footprint of SARM might be less sensitive to the artifact.

  10. Gravitational waves and short gamma ray bursts

    NASA Astrophysics Data System (ADS)

    Predoi, Valeriu

    2012-07-01

    Short hard gamma-ray bursts (GRB) are believed to be produced by compact binary coalescences (CBC) { either double neutron stars or neutron star{black hole binaries. The same source is expected to emit strong gravitational radiation, detectable with existing and planned gravitational wave observatories. The focus of this work is to describe a series of searches for gravitational waves (GW) from compact binary coalescence (CBC) events triggered by short gamma-ray burst detections. Specifically, we will present the motivation, frameworks, implementations and results of searches for GW associated with short gamma-ray bursts detected by Swift, Fermi{GBM and the InterPlanetary Network (IPN) gamma-ray detectors. We will begin by presenting the main concepts that lay the foundation of gravitational waves emission, as they are formulated in the theory of General Relativity; we will also brie y describe the operational principles of GW detectors, together with explaining the main challenges that the GW detection process is faced with. Further, we will motivate the use of observations in the electromagnetic (EM) band as triggers for GW searches, with an emphasis on possible EM signals from CBC events. We will briefly present the data analysis techniques including concepts as matched{filtering through a collection of theoretical GW waveforms, signal{to{ noise ratio, coincident and coherent analysis approaches, signal{based veto tests and detection candidates' ranking. We will use two different GW{GRB search examples to illustrate the use of the existing coincident and coherent analysis methods. We will also present a series of techniques meant to improve the sensitivity of existing GW triggered searches. These include shifting background data in time in order to obtain extended coincident data and setting a prior on the GRB inclination angle, in accordance with astrophysical observations, in order to restrict the searched parameter space. We will describe the GW data analysis and present results from a GW search around 12 short gamma-ray bursts detected by the InterPlanetary Network (IPN) between 2006 and 2007. The IPN{detected bursts usually have extended localization error boxes and a search for GW was performed at different sky locations across these error regions. Since no GW detection was made, we set upper limits on the distances to the GRB progenitors; we briefly discuss the implications that two IPN GRBs error regions overlap two nearby galaxies.

  11. Gravitational waves and short gamma ray bursts

    NASA Astrophysics Data System (ADS)

    Predoi, Valeriu

    Short hard gamma-ray bursts (GRB) are believed to be produced by compact binary coalescences (CBC), either double neutron stars or neutron star black hole binaries. The same source is expected to emit strong gravitational radiation, detectable with existing and planned gravitational wave observatories. The focus of this work is to describe a series of searches for gravitational waves (GW) from compact binary coalescence (CBC) events triggered by short gamma-ray burst detections. Specifically, we will present the motivation, frameworks, implementations and results of searches for GW associated with short gamma-ray bursts detected by Swift, Fermi{GBM and the InterPlanetary Network (IPN) gamma-ray detectors. We will begin by presenting the main concepts that lay the foundation of gravitational waves emission, as they are formulated in the theory of General Relativity; we will also brie y describe the operational principles of GW detectors, together with explaining the main challenges that the GW detection process is faced with. Further, we will motivate the use of observations in the electromagnetic (EM) band as triggers for GW searches, with an emphasis on possible EM signals from CBC events. We will briefly present the data analysis techniques including concepts as matched filtering through a collection of theoretical GW waveforms, signal{to{ noise ratio, coincident and coherent analysis approaches, signal{based veto tests and detection candidates' ranking. We will use two different GW GRB search examples to illustrate the use of the existing coincident and coherent analysis methods. We will also present a series of techniques meant to improve the sensitivity of existing GW triggered searches. These include shifting background data in time in order to obtain extended coincident data and setting a prior on the GRB inclination angle, in accordance with astrophysical observations, in order to restrict the searched parameter space. We will describe the GW data analysis and present results from a GW search around 12 short gamma-ray bursts detected by the InterPlanetary Network (IPN) between 2006 and 2007. The IPN detected bursts usually have extended localization error boxes and a search for GW was performed at different sky locations across these error regions. Since no GW detection was made, we set upper limits on the distances to the GRB progenitors; we briefly discuss the implications that two IPN GRBs error regions overlap two nearby galaxies.

  12. Mercury cadmium telluride short- and medium-wavelength infrared staring focal plane arrays

    NASA Technical Reports Server (NTRS)

    Vural, Kadri

    1987-01-01

    Short and medium IR wavelength 64 x 64 hybrid focal plane arrays (FPAs) have been developed using sapphire-grown HgCdTe. The short wavelength arrays were developed for a prototype airborne imaging spectrometer, while those of medium wavelength are suitable for tactical missile seekers and strategic surveillance systems. Attention is presently given to results obtained for these FPAs' current-voltage characteristics, as well as for their characterization at different temperatures. The detector arrays were also mated to a multiplexer and characterized under different operating conditions. The unit cell size used is 52 x 52 microns.

  13. Short-wave cooperative instabilities in representative aircraft vortices

    NASA Astrophysics Data System (ADS)

    Fabre, David; Jacquin, Laurent

    2004-05-01

    This paper considers the short-wave cooperative instabilities in a family of vortices representative of aircraft wakes. These vortices are characterized by two core scales, an internal core scale a1 and an external core scale a2, and their azimuthal velocity follows a power law V(r)˜r-α in the intermediate zone (a1wavelengths and the structure of the unstable modes are characterized as functions of the base flow parameters α and a2/a1. For 0.5⩽α⩽1, the wavelength of the instability is of the order of the internal scale a1 and the unstable modes only affect the internal core. In this case the growth rate of the instability is in accordance with the predictions of the elliptical instability theory and is a growing function of the parameter a2/a1. For 0⩽α<0.4, the wavelength of the instability is of the order of the external scale a2 and the unstable modes extend into the intermediate zone. In this case the growth rate of the instability differs from the predictions of the elliptical instability theory and is independent upon the parameter a2/a1. Interestingly, a sharp transition between these two regimes occurs for 0.4<α<0.5, in a range of parameters corresponding to experimentally measured trailing wakes. In this range, the bands of wave numbers affected by the instability are particularly large and may coalesce into a broadband spectrum.

  14. Conversion of electrostatic plasma waves into electromagnetic waves - Numerical calculation of the dispersion relation for all wavelengths.

    NASA Technical Reports Server (NTRS)

    Oya, H.

    1971-01-01

    The dispersion curves have been computed for a wide range of wavelengths from electromagnetic waves to electrostatic waves in a magnetoactive warm plasma with a Maxwellian velocity distribution function. The computation was carried out mainly for the perpendicular propagation mode. The upper hybrid resonance is the connection point of the electrostatic waves and the electromagnetic waves. The electrostatic waves not associated with the upper hybrid resonance are subjected to electron cyclotron damping when the wavelength becomes long. Oblique propagation is allowed for the electrostatic waves in a frequency range from the plasma frequency to the upper hybrid resonance frequency in the long-wavelength region where Landau damping can be neglected and where the electrostatic mode smoothly connects to the electromagnetic X-mode. In a slightly inhomogeneous plasma, the Bernstein-mode electrostatic wave can escape by being converted into the O-mode electromagnetic wave; two reflections take place during this escape process.

  15. Absence of functional short-wavelength sensitive cone pigments in hamsters (Mesocricetus).

    PubMed

    Williams, Gary A; Jacobs, Gerald H

    2008-05-01

    Studies of Syrian golden hamsters (Mesocricetus auratus) have yielded contradictory evidence as to whether the retina of this species supports a population of cones containing short-wavelength sensitive pigments. We undertook a re-examination of this issue by (a) measuring lens transmission, (b) determining complete spectral sensitivity functions using electroretinogram (ERG) flicker photometry, (c) employing a sensitive chromatic-adaptation paradigm in conjunction with ERG measurements to conduct a specific search for the presence of a short-wavelength sensitive mechanism, and (d) assaying for the presence of retinal mRNA using real-time, reverse transcription polymerase chain reactions (RT-PCR). Parallel measurements were made on Turkish hamster (Mesocricetus brandtii) and control measurements were derived from recordings made on a rodent whose retina is known to contain a population of short-wavelength sensitive cones (the rat, Rattus norvegicus). Although UV opsin transcripts can be detected in the retina of the Syrian hamster, the electrophysiological measurements imply that these are not translated. Syrian hamsters thus lack a functional short-wavelength sensitive pigment, and that seems also true for the Turkish hamster. Members of this genus belong to a disparate group of mammals that have lost function of their short-wavelength sensitive cone pigments through ancestral opsin gene mutations. PMID:18259758

  16. On seeing yellow: the case for, and against, short-wavelength light-absorbing intraocular lenses.

    PubMed

    Simunovic, Matthew P

    2012-07-01

    The normal human crystalline lens absorbs UV and short-wavelength visible electromagnetic radiation. Early intraocular lenses (IOLs) permitted the transmission of such radiation to the retina following cataract extraction. Experimental studies of the absorption profile of the crystalline lens and animal studies demonstrating the deleterious effects of short-wavelength radiation on the retina led to the development of UV-absorbing, and later, short-wavelength light-absorbing (SLA) IOLs. Short-wavelength light-absorbing IOLs were designed to mimic the absorption properties of the normal crystalline lens by absorbing some short-wavelength light in addition to UV radiation; however, debate continues regarding the relative merits of such lenses over UV-absorbing IOLs. Advocates of SLA IOLs suggest that they may theoretically offer increased photoprotection and decreased glare sensitivity and draw on in vitro, animal, and limited clinical studies that infer possible benefits. Detractors suggest that there is no direct evidence supporting a role for SLA IOLs in preventing retinal dysfunction in humans and suggest that they may have negative effects on color perception, scotopic vision, and circadian rhythms. This article examines the theoretical and empirical evidence for, and against, such lenses. PMID:22776932

  17. Nonlinear coupling of Alfvén waves with widely different cross-field wavelengths in space plasmas

    NASA Astrophysics Data System (ADS)

    Voitenko, Yuriy M.; Goossens, Marcel

    2005-10-01

    Multiscale activity and dissipation of Alfvén waves play an important role in a number of space and astrophysical plasmas. A popular approach to study the evolution and damping of MHD Alfvén waves assumes a gradual evolution of the wave energy to small dissipative length scales. This can be done by local nonlinear interactions among MHD waves with comparable wavelengths resulting in turbulent cascades or by phase mixing and resonant absorption. We investigate an alternative nonlocal transport of wave energy from large MHD length scales directly into the dissipation range formed by the kinetic Alfvén waves (KAWs). KAWs have very short wavelengths across the magnetic field irrespectively of their frequency. We focus on the nonlinear mechanism for the excitation of KAWs by MHD Alfvén waves via resonant decay AW → KAW1 + KAW2. The resonant decay conditions can be satisfied in a rarified plasmas, where the gas/magnetic pressure ratio is less than the electron/ion mass ratio. The decay is efficient at low amplitudes of the magnetic field in the MHD waves, B/B0 ˜ 10-2. In turn, the nonlinearly driven KAWs have sufficiently short wavelengths for the dissipative effects to become significant. Therefore the cross-scale nonlinear coupling of Alfvén waves can provide a mechanism for the replenishment of the dissipation range and the consequent energization in space plasmas. Two relevant examples of this scenario in the solar corona and auroral zones are discussed.

  18. Skylab radar altimeter: short-wavelength perturbations detected in ocean surface profiles.

    PubMed

    Leitao, C D; McGoogan, J T

    1974-12-27

    Short-wavelength anomalies in sea surface topography, caused by the gravitational effects of major ocean bottom topographic features, have been detected by the radar altimeter aboard Skylab. Some features, such as deep ocean trenches, seamounts, and escarpments, displace the ocean surface by as much as 15 meters over 100-kilometer wavelengths. This experiment demonstrates the potential of satellite altimetry for determining the ocean geoid and for mapping major features of the ocean bottom. PMID:17833933

  19. Skylab radar altimeter - Short-wavelength perturbations detected in ocean surface profiles

    NASA Technical Reports Server (NTRS)

    Leitao, C. D.; Mcgoogan, J. T.

    1974-01-01

    Short-wavelength anomalies in sea surface topography, caused by the gravitational effects of major ocean bottom topographic features, have been detected by the radar altimeter aboard Skylab. Some features, such as deep ocean trenches, seamounts, and escarpments, displace the ocean surface by as much as 15 meters over 100-kilometer wavelengths. This experiment demonstrates the potential of satellite altimetry for determining the ocean geoid and for mapping major features of the ocean bottom.

  20. Variations in the short wavelength cut-off of the solar UV spectra.

    PubMed

    Parisi, A V; Turner, J

    2006-03-01

    Cloud and solar zenith angle (SZA) are two major factors that influence the magnitude of the biologically damaging UV (UVBD) irradiances for humans. However, the effect on the short wavelength cut-off due to SZA and due to clouds has not been investigated for biologically damaging UV for cataracts. This research aims to investigate the influence of cloud and SZA on the short wavelength cut-off of the spectral UVBD for cataracts. The spectral biologically damaging UV for cataracts on a horizontal plane was calculated by weighting the spectral UV measured with a spectroradiometer with the action spectrum for the induction of cataracts in a porcine lens. The UV spectra were obtained on an unshaded plane at a latitude of 29.5 degrees S. The cut-off wavelength (lambdac) was defined as the wavelength at which the biologically damaging spectral irradiance was 0.1% of the maximum biologically damaging irradiance for that scan. For the all sky conditions, the short wavelength cut-off ranged by 12 nm for the SZA range of 5 to 80 degrees and the maximum in the spectral UVBD ranged by 15 nm. Similarly, for the cloud free cases, the short wavelength cut-off ranged by 9 nm for the same SZA range. Although, cloud has a large influence on the magnitude of the biologically damaging UV for cataracts, the influence of cloud on the short wavelength cut-off for the biologically damaging UV for cataracts is less than the influence of the solar zenith angle. PMID:16520869

  1. Short Wavelength Cone Opsin Is Not Expressed in the Retina of Arboreal African Pangolin (Manis tricuspis)

    PubMed Central

    Adekanmbi, Adejoke J.; Adekanmbi, Adefisayo A.; Akinola, Oluwole B.

    2016-01-01

    This paper reports a study of cone photoreceptors present in the retina of Manis tricuspis. Specifically, the LWS (L-) opsin expressed in longwave-sensitive cones and SWS1 (S-) opsin shortwave-sensitive cones were targeted. Vertical sections revealed reactivity to a cone marker, peanut agglutinin (PNA), and to an LWS antibody, but not to an SWS1 antibody. This suggests that the Manis tricuspis visual system is not able to discriminate shorter wavelengths from longer wavelengths because the short wavelength cones are not expressed in their retina.

  2. Fluorescence lifetimes of protochlorophyllide in plants with different proportions of short-wavelength and long-wavelength protochlorophyllide spectral forms.

    PubMed

    Myśliwa-Kurdziel, Beata; Amirjani, Mohammad R; Strzałka, Kazimierz; Sundqvist, Christer

    2003-08-01

    Dark-grown leaves of maize (Zea mays), wheat (Triticum aestivum), wild-type pea (Pisum sativum) and its light-independent photomorphogenesis mutant (lip1) have different proportions of protochlorophyllide (Pchlide) forms as revealed by low-temperature fluorescence emission spectra. Four discrete spectral forms of Pchlide, with emission peaks around 633, 640, 656 and 670 nm, could be distinguished after Gaussian deconvolution. In maize and wheat the 656 nm component was the most prominent, whereas for wild-type pea and its lip1 mutant, the 633 and 640 nm components contributed mostly to the fluorescence emission spectra. For the fluorescence lifetimes measured at 77 K a double exponential model was the most adequate to describe the Pchlide fluorescence decay not only for the Pchlide(650-656) form but also for the short-wavelength Pchlide forms. A fast component in the range 0.3-0.8 ns and a slow component in the range 5.1-7.1 ns were present in all samples, but the values varied, depending on species. The long-wavelength Pchlide(650-656) form had a slow component with a lifetime between 5.1 and 6.7 ns, probably reflecting the fluorescence from aggregated Pchlide. The short-wavelength Pchlide(628-633) form had values of the slow component varying between 6.2 and 7.1 ns. This represents a monomeric but probably protein-bound Pchlide form because the free Pchlide in solution has a much longer lifetime around 10 ns at 77 K. The contribution of different Pchlide forms to the measured lifetime values is discussed. PMID:12945590

  3. Analysis of multiple wavelengths of Lamb waves generated by meander-line coil EMATs.

    PubMed

    Zhai, Guofu; Jiang, Tao; Kang, Lei

    2014-02-01

    The electromagnetic acoustic transducers (EMATs) with a meander-line coil possess the capability of generating Lamb waves carrying multiple wavelengths, and the characteristics of multiple wavelengths is analyzed by developing a spatial transversal filter model for the EMAT. It is shown that the characteristics is due to the wavelength spectrum of the EMATs, which is a wavelength-domain representation of information about the wavelength components, and the magnitude of each components is modulated by an envelope which depends on the geometric pattern of the meander-line coil. The characteristics of multiple wavelengths might cause the multi-modes phenomenon, therefore a method for removing the effect of multiple wavelengths is proposed. It is shown that the effect can be removed by designing an EMAT which can produce a special envelop to suppress the harmonic wavelengths. Experiments are set up to study the characteristics of multiple wavelengths and verify the validity of the proposed method. PMID:24074750

  4. Coexisting rogue waves within the (2+1)-component long-wave-short-wave resonance.

    PubMed

    Chen, Shihua; Soto-Crespo, Jose M; Grelu, Philippe

    2014-09-01

    The coexistence of two different types of fundamental rogue waves is unveiled, based on the coupled equations describing the (2+1)-component long-wave-short-wave resonance. For a wide range of asymptotic background fields, each family of three rogue wave components can be triggered by using a slight deterministic alteration to the otherwise identical background field. The ability to trigger markedly different rogue wave profiles from similar initial conditions is confirmed by numerical simulations. This remarkable feature, which is absent in the scalar nonlinear Schrödinger equation, is attributed to the specific three-wave interaction process and may be universal for a variety of multicomponent wave dynamics spanning from oceanography to nonlinear optics. PMID:25314555

  5. Four-wave mixing in wavelength-division-multiplexed soliton systems: damping and amplification

    NASA Astrophysics Data System (ADS)

    Ablowitz, M. J.; Biondini, G.; Chakravarty, S.; Jenkins, R. B.; Sauer, J. R.

    1996-10-01

    Four-wave mixing in wavelength-division-multiplexed soliton systems with damping and amplification is studied. An analytical model is introduced that explains the dramatic growth of the four-wave terms. The model yields a resonance condition relating the soliton frequency and the amplifier distance. It correctly predicts all essential features regarding the resonant growth of the four-wave contributions.

  6. Exploiting the short wavelength gain of silica-based thulium-doped fiber amplifiers.

    PubMed

    Li, Z; Jung, Y; Daniel, J M O; Simakov, N; Tokurakawa, M; Shardlow, P C; Jain, D; Sahu, J K; Heidt, A M; Clarkson, W A; Alam, S U; Richardson, D J

    2016-05-15

    Short wavelength operation (1650-1800 nm) of silica-based thulium-doped fiber amplifiers (TDFAs) is investigated. We report the first demonstration of in-band diode-pumped silica-based TDFAs working in the 1700-1800 nm waveband. Up to 29 dB of small-signal gain is achieved in this spectral region, with an operation wavelength accessible by diode pumping as short as 1710 nm. Further gain extension toward shorter wavelengths is realized in a fiber laser pumped configuration. A silica-based TDFA working in the 1650-1700 nm range with up to 29 dB small-signal gain and noise figure as low as 6.5 dB is presented. PMID:27176961

  7. Short wavelength approximation of a boundary integral operator for homogeneous and isotropic elastic bodies.

    PubMed

    Tanner, Gregor; Søndergaard, Niels

    2007-03-01

    A short wavelength approximation of a boundary integral operator for two-dimensional isotropic and homogeneous elastic bodies is derived from first principles starting from the Navier-Cauchy equation. Trace formulas for elastodynamics are deduced connecting the eigenfrequency spectrum of an elastic body to the set of periodic rays where mode conversion enters as a dynamical feature. PMID:17500809

  8. Internal stress and degradation in short-wavelength AlGaAs double-heterojunction devices

    NASA Technical Reports Server (NTRS)

    Ladany, I.; Furman, T. R.; Marinelli, D. P.

    1979-01-01

    Aging tests of incoherently operated zinc-doped double-heterojunction (DH) lasers designed for short-wavelength (0.71-0.72 micron) operation show that the introduction of buffer layers between the substrate and the DH structure leads to a drastic reduction in gradual degradation. This is attributed to a decrease in lattice mismatch stress.

  9. Sensitivity enhancement of surface thermal lens technique with a short-wavelength probe beam: Experiment

    SciTech Connect

    Zhang, Xiaorong; Li, Bincheng

    2015-02-15

    Surface thermal lens is a highly sensitive photothermal technique to measure low absorption losses of various solid materials. In such applications, the sensitivity of surface thermal lens is a key parameter for measuring extremely low absorption. In this paper, we experimentally investigated the influence of probe beam wavelength on the sensitivity of surface thermal lens for measuring the low absorptance of optical laser components. Three probe lasers with wavelength 375 nm, 633 nm, and 1570 nm were used, respectively, to detect the surface thermal lens amplitude of a highly reflective coating sample excited by a cw modulated Gaussian beam at 1064 nm. The experimental results showed that the maximum amplitude of surface thermal lens signal obtained at corresponding optimized detection distance was inversely proportional to the wavelength of the probe beam, as predicted by previous theoretical model. The sensitivity of surface thermal lens could, therefore, be improved by detecting surface thermal lens signal with a short-wavelength probe beam.

  10. Short-wavelength enrichment of polychromatic light enhances human melatonin suppression potency.

    PubMed

    Brainard, George C; Hanifin, John P; Warfield, Benjamin; Stone, Marielle K; James, Mary E; Ayers, Melissa; Kubey, Alan; Byrne, Brenda; Rollag, Mark

    2015-04-01

    The basic goal of this research is to determine the best combination of light wavelengths for use as a lighting countermeasure for circadian and sleep disruption during space exploration, as well as for individuals living on Earth. Action spectra employing monochromatic light and selected monochromatic wavelength comparisons have shown that short-wavelength visible light in the blue-appearing portion of the spectrum is most potent for neuroendocrine, circadian, and neurobehavioral regulation. The studies presented here tested the hypothesis that broad spectrum, polychromatic fluorescent light enriched in the short-wavelength portion of the visible spectrum is more potent for pineal melatonin suppression in healthy men and women. A total of 24 subjects were tested across three separate experiments. Each experiment used a within-subjects study design that tested eight volunteers to establish the full-range fluence-response relationship between corneal light irradiance and nocturnal plasma melatonin suppression. Each experiment tested one of the three types of fluorescent lamps that differed in their relative emission of light in the short-wavelength end of the visible spectrum between 400 and 500 nm. A hazard analysis, based on national and international eye safety criteria, determined that all light exposures used in this study were safe. Each fluence-response curve demonstrated that increasing corneal irradiances of light evoked progressively increasing suppression of nocturnal melatonin. Comparison of these fluence-response curves supports the hypothesis that polychromatic fluorescent light is more potent for melatonin regulation when enriched in the short-wavelength spectrum. PMID:25726691

  11. Laser induced short plane acoustic wave focusing in water

    NASA Astrophysics Data System (ADS)

    Ko, Seung H.; Ryu, Sang G.; Misra, Nipun; Pan, Heng; Grigoropoulos, Costas P.; Kladias, Nick; Panides, Elias; Domoto, Gerald A.

    2007-07-01

    Laser induced high frequency acoustic wave generation, propagation, and focusing in water are studied. A large area, flat, and short duration acoustic wave was generated by the thermoelastic interaction of a homogenized short pulsed laser beam with the liquid-solid interface and propagated at the speed of sound. Laser flash Schlieren photography was used to visualize the transient interaction of the flat acoustic wave with a cylindrical concave lens and the subsequent acoustic wave focusing. Numerical simulations showed the acoustic wave could be focused to several tens of microns in size and 7bars in pressure.

  12. Water Surface Currents, Short Gravity-Capillary Waves and Radar Backscatter

    NASA Technical Reports Server (NTRS)

    Atakturk, Serhad S.; Katsaros, Kristina B.

    1993-01-01

    Despite their importance for air-sea interaction and microwave remote sensing of the ocean surface, intrinsic properties of short gravity-capillary waves are not well established. This is largely due to water surface currents and their effects on the direct measurements of wave parameters conducted at a fixed point. Frequencies of small scale waves propagating on a surface which itself is in motion, are subject to Doppler shifts. Hence, the high frequency tail of the wave spectra obtained from such temporal observations is smeared. Conversion of this smeared measured-frequency spectra to intrinsic-frequency (or wavenumber) spectra requires corrections for the Doppler shifts. Such attempts in the past have not been very successful in particular when field data were used. This becomes evident if the amplitude modulation of short waves by underlying long waves is considered. Microwave radar studies show that the amplitude of a short wave component attains its maximum value near the crests and its minimum in the troughs of the long waves. Doppler-shifted wave data yield similar results but much larger in modulation magnitude, as expected. In general, Doppler shift corrections reduce the modulation magnitude. Overcorrection may result in a negligible modulation or even in a strong modulation with the maximum amplitude in the wave troughs. The latter situation is clearly contradictory to our visual observations as well as the radar results and imply that the advection by currents is overestimated. In this study, a differential-advection approach is used in which small scale waves are advected by the currents evaluated not at the free surface, but at a depth proportional to their wavelengths. Applicability of this approach is verified by the excellent agreement in phase and magnitude of short-wave modulation between results based on radar and on wave-gauge measurements conducted on a lake.

  13. Low work function surface layers produced by laser ablation using short-wavelength photons

    DOEpatents

    Balooch, Mehdi; Dinh, Long N.; Siekhaus, Wigbert J.

    2000-01-01

    Short-wavelength photons are used to ablate material from a low work function target onto a suitable substrate. The short-wavelength photons are at or below visible wavelength. The elemental composition of the deposit is controlled by the composition of the target and the gaseous environment in which the ablation process is performed. The process is carried out in a deposition chamber to which a short-wavelength laser is mounted and which includes a substrate holder which can be rotated, tilted, heated, or cooled. The target material is mounted onto a holder that spins the target during laser ablation. In addition, the deposition chamber is provided with a vacuum pump, an external gas supply with atomizer and radical generator, a gas generator for producing a flow of molecules on the substrate, and a substrate cleaning device, such as an ion gun. The substrate can be rotated and tilted, for example, whereby only the tip of an emitter can be coated with a low work function material.

  14. Controlled generation of short-wavelength periodic megagauss magnetic fields in plasmas

    SciTech Connect

    Fiuza, F.; Silva, L. O.

    2009-01-22

    We examine the possibility of producing short-wavelength MG magnetic fields by exciting a magnetic mode from the collision of electromagnetic light pulses with relativistic ionization fronts. PIC simulation results demonstrate the validity of the scheme to generate compact coherent long lived magnetic structures that can be used to produce ultrashort-wavelength radiation with existing state-of-the-art laser systems. In particular, we analyze the possibility of making a compact Gamma-ray synchrotron source based on this magnetic mode.

  15. New Insight into Short-Wavelength Solar Wind Fluctuations from Vlasov Theory

    NASA Technical Reports Server (NTRS)

    Sahraoui, Fouad; Belmont, G.; Goldstein, M. L.

    2012-01-01

    The nature of solar wind (SW) turbulence below the proton gyroscale is a topic that is being investigated extensively nowadays, both theoretically and observationally. Although recent observations gave evidence of the dominance of kinetic Alfven waves (KAWs) at sub-ion scales with omega < omega(sub ci), other studies suggest that the KAW mode cannot carry the turbulence cascade down to electron scales and that the whistler mode (i.e., omega > omega (sub ci)) is more relevant. Here, we study key properties of the short-wavelength plasma modes under limited, but realistic, SW conditions, Typically Beta(sub i) approx. > Beta (sub e) 1 and for high oblique angles of propagation 80 deg <= Theta (sub kB) < 90 deg as observed from the Cluster spacecraft data. The linear properties of the plasma modes under these conditions are poorly known, which contrasts with the well-documented cold plasma limit and/or moderate oblique angles of propagation (Theta (sub kB) < 80 deg). Based on linear solutions of the Vlasov kinetic theory, we discuss the relevance of each plasma mode (fast, Bernstein, KAW, whistler) in carrying the energy cascade down to electron scales. We show, in particular, that the shear Alfven mode (known in the magnetohydrodynamic limit) extends at scales kappa rho (sub i) approx. > 1 to frequencies either larger or smaller than omega (sub ci), depending on the anisotropy kappa (parallel )/ kappa(perpendicular). This extension into small scales is more readily called whistler (omega > omega (sub ci)) or KAW (omega < omega (sub ci)) although the mode is essentially the same. This contrasts with the well-accepted idea that the whistler branch always develops as a continuation at high frequencies of the fast magnetosonic mode. We show, furthermore, that the whistler branch is more damped than the KAW one, which makes the latter the more relevant candidate to carry the energy cascade down to electron scales. We discuss how these new findings may facilitate resolution of the controversy concerning the nature of the small-scale turbulence, and we discuss the implications for present and future spacecraft wave measurements in the SW.

  16. NEW INSIGHT INTO SHORT-WAVELENGTH SOLAR WIND FLUCTUATIONS FROM VLASOV THEORY

    SciTech Connect

    Sahraoui, F.; Belmont, G.; Goldstein, M. L.

    2012-04-01

    The nature of solar wind (SW) turbulence below the proton gyroscale is a topic that is being investigated extensively nowadays, both theoretically and observationally. Although recent observations gave evidence of the dominance of kinetic Alfven waves (KAWs) at sub-ion scales with {omega} < {omega}{sub ci}, other studies suggest that the KAW mode cannot carry the turbulence cascade down to electron scales and that the whistler mode (i.e., {omega} > {omega}{sub ci}) is more relevant. Here, we study key properties of the short-wavelength plasma modes under limited, but realistic, SW conditions, typically {beta}{sub i} {approx}> {beta}{sub e} {approx} 1 and for high oblique angles of propagation 80 Degree-Sign {<=} {Theta}{sub kB} < 90 Degree-Sign as observed from the Cluster spacecraft data. The linear properties of the plasma modes under these conditions are poorly known, which contrasts with the well-documented cold plasma limit and/or moderate oblique angles of propagation ({Theta}{sub kB} < 80 Degree-Sign ). Based on linear solutions of the Vlasov kinetic theory, we discuss the relevance of each plasma mode (fast, Bernstein, KAW, whistler) in carrying the energy cascade down to electron scales. We show, in particular, that the shear Alfven mode (known in the magnetohydrodynamic limit) extends at scales k{rho}{sub i} {approx}> 1 to frequencies either larger or smaller than {omega}{sub ci}, depending on the anisotropy k{sub ||}/k . This extension into small scales is more readily called whistler ({omega} > {omega}{sub ci}) or KAW ({omega} < {omega}{sub ci}), although the mode is essentially the same. This contrasts with the well-accepted idea that the whistler branch always develops as a continuation at high frequencies of the fast magnetosonic mode. We show, furthermore, that the whistler branch is more damped than the KAW one, which makes the latter the more relevant candidate to carry the energy cascade down to electron scales. We discuss how these new findings may facilitate resolution of the controversy concerning the nature of the small-scale turbulence, and we discuss the implications for present and future spacecraft wave measurements in the SW.

  17. Analysis of Laser Ablation of CFRP by Ultra-Short Laser Pulses with Short Wavelength

    NASA Astrophysics Data System (ADS)

    Emmelmanna, C.; Petersen, M.; Goeke, A.; Canisius, M.

    Material processing of carbon fiber-reinforced polymers (CFRP) by means of shape-cutting technologies is state-of-the-art today. These processes still perform in some applications with lack of part quality such as delamination and low processes productivity. Therefore, laser processing by ultra-short laser pulses has a great potential in material ablation of CFRP. Nevertheless laser process parameters have to be adjusted carefully to reduce extension of heat affected zone (HAZ) and its influence on part quality [1].

  18. New methods for calculating short-wave radio paths

    NASA Astrophysics Data System (ADS)

    Popov, A. V.; Tsedilina, E. E.; Cherkashin, Iu. N.

    Recent research on the calculation of short-wave paths at IZMIRAN (the Soviet Institute for the Study of Terrestrial Magnetism, the Ionosphere, and the Propagation of Radio Waves) is reviewed. Particular attention is given to: (1) the development of approximate analytical methods for ray-tracing calculations and for determining the geometrical-optics characteristics of a radio signal in a horizontally irregular ionosphere; (2) investigations of the long-range and short-wave propagation of decametric waves; and (3) the development of a parabolic-equation method for considering diffraction and scattering in a medium with regular and random irregularities.

  19. Nonlinear-optical generation of short-wavelength radiation controlled by laser-induced interference structures

    SciTech Connect

    Popov, A K; Kimberg, V V

    1998-03-31

    A study is reported of the combined influence of laser-induced resonances in the energy continuum, of splitting of discrete resonances in the field of several strong radiations, and of absorption of the initial and generated radiations on totally resonant parametric conversion to the short-wavelength range. It is shown that the radiation power can be increased considerably by interference processes involving quantum transitions. (nonlinear optical phenomena and devices)

  20. Whispering-gallery mirrors for short-wavelength laser cavities: Shapes and tolerances

    SciTech Connect

    Braud, J.P.

    1991-12-31

    The whispering-gallery mirrors desired for use in short-wavelength laser cavities are seen to be highly aspheric and very different from the shapes encountered in conventional optics. Fabrication tolerance are established by examining the effects of various surface imperfections. The mirrors are found to be relatively insensitive to figures errors. The requirements on surface finish are shown to be fairly strict, though less severe than with normal-incidence optics.

  1. Whispering-gallery mirrors for short-wavelength laser cavities: Shapes and tolerances

    SciTech Connect

    Braud, J.P.

    1991-01-01

    The whispering-gallery mirrors desired for use in short-wavelength laser cavities are seen to be highly aspheric and very different from the shapes encountered in conventional optics. Fabrication tolerance are established by examining the effects of various surface imperfections. The mirrors are found to be relatively insensitive to figures errors. The requirements on surface finish are shown to be fairly strict, though less severe than with normal-incidence optics.

  2. Emittance-exchange-based high harmonic generation scheme for short-wavelength free electron laser.

    SciTech Connect

    Power, J. G.; Jiang, B.; Gai, W.; Liu, W.; Lindberg, R.

    2011-03-16

    Generation of short-wavelength radiation by a free-electron laser using up-frequency conversion of an electron bunch density modulation is currently an area of active research. We propose a new scheme for producing the longitudinal electron bunch density modulation similar to the recently proposed echo-enabled harmonic generation but based on an emittance exchange beam line and a multislit mask. Beam line analysis and start-to-end simulation are presented.

  3. Near infrared spectroscopy for mastitis diagnosis: Two-dimensional correlation study in short wavelength region

    NASA Astrophysics Data System (ADS)

    Tsenkova, Roumiana; Murayama, Koichi; Kawano, Sumio; Wu, Yuqing; Toyoda, Kiyohiko; Ozaki, Yukihiro

    2000-03-01

    We describe the application of two-dimensional correlation spectroscopic (2DCOS) technique for mastitic diagnosis. Seven average spectra in the short wavelength region (700-1100 nm) of mastitic levels separated from healthy to disease were subjected to 2DCOS analysis. Synchronous correlation map clearly showed water and fat bands. Asynchronous correlation map indicated the dynamical variations of milk constituents in milk occurred when a cow gets mastitis.

  4. Short-Wavelength Light Enhances Cortisol Awakening Response in Sleep-Restricted Adolescents

    PubMed Central

    Figueiro, Mariana G.; Rea, Mark S.

    2012-01-01

    Levels of cortisol, a hormone produced by the adrenal gland, follow a daily, 24-hour rhythm with concentrations reaching a minimum in the evening and a peak near rising time. In addition, cortisol levels exhibit a sharp peak in concentration within the first hour after waking; this is known as the cortisol awakening response (CAR). The present study is a secondary analysis of a larger study investigating the impact of short-wavelength (λmax ≈ 470 nm) light on CAR in adolescents who were sleep restricted. The study ran over the course of three overnight sessions, at least one week apart. The experimental sessions differed in terms of the light exposure scenarios experienced during the evening prior to sleeping in the laboratory and during the morning after waking from a 4.5-hour sleep opportunity. Eighteen adolescents aged 12–17 years were exposed to dim light or to 40 lux (0.401 W/m2) of 470-nm peaking light for 80 minutes after awakening. Saliva samples were collected every 20 minutes to assess CAR. Exposure to short-wavelength light in the morning significantly enhanced CAR compared to dim light. Morning exposure to short-wavelength light may be a simple, yet practical way to better prepare adolescents for an active day. PMID:22899916

  5. Short-wavelength buckling and shear failures for compression-loaded composite laminates. Ph.D. Thesis

    NASA Technical Reports Server (NTRS)

    Shuart, M. J.

    1985-01-01

    The short-wavelength buckling (or the microbuckling) and the interlaminar and inplane shear failures of multi-directional composite laminates loaded in uniaxial compression are investigated. A laminate model is presented that idealizes each lamina. The fibers in the lamina are modeled as a plate, and the matrix in the lamina is modeled as an elastic foundation. The out-of-plane w displacement for each plate is expressed as a trigonometric series in the half-wavelength of the mode shape for laminate short-wavelength buckling. Nonlinear strain-displacement relations are used. The model is applied to symmetric laminates having linear material behavior. The laminates are loaded in uniform end shortening and are simply supported. A linear analysis is used to determine the laminate stress, strain, and mode shape when short-wavelength buckling occurs. The equations for the laminate compressive stress at short-wavelength buckling are dominated by matrix contributions.

  6. Permittivity of water at millimeter wave-lengths

    NASA Technical Reports Server (NTRS)

    Blue, M. D.

    1976-01-01

    Work performed on the permittivity of seawater and ice at 100 GHz was described. Measurements on water covered the temperature range from 0 to 50 C, while the measurements on ice were taken near - 10 C. In addition, a small number of measurements were made on the reflectivity of absorber materials used in a previous program on research in millimeter wave techniques. Normal incidence reflectivity was measured, and the result was used to obtain the index of refraction. For the case of normal incidence, reflectivity at a fixed temperature was reproducible to 1% for values near 40%. For reflectivity measurements on ice, the lack of attenuation leads to reflection from the back surface of the sample; this complication was circumvented by using a wedge shaped sample and freezing the water in a container lined with absorber material.

  7. Output characteristics of SASE-driven short wavelength FEL`s

    SciTech Connect

    Fawley, W.M.

    1997-02-01

    This paper investigates various properties of the ``microspikes`` associated with self-amplified spontaneous emission (SASE) in a short wavelength free-electron laser (FEL). Using results from the 2-D numerical simulation code GINGER, we confirm theoretical predictions such as the convective group velocity in the exponential gain regime. In the saturated gain regime beyond the initial saturation, we find that the average radiation power continues to grow with an approximately linearly dependence upon undulator length. Moreover, the spectrum significantly broadens and shifts in wavelength to the redward direction, with{ital P(w)} approaching a constant, asymptotic value. This is in marked contrast to the exponential gain regime where the spectrum steadily narrows, {ital P(w)} grows, and the central wavelength remains constant with {ital z}. Via use of a spectrogram diagnostic {ital S(w,t)}, it appears that the radiation pattern in the saturated gain regime is composed of an ensemble of distinct ``sinews`` whose widths AA remain approximately constant but whose central wavelengths can ``chirp`` by varying a small extent with {ital t}.

  8. Phase engineered wavelength conversion of ultra-short optical pulses in TI:PPLN waveguides

    NASA Astrophysics Data System (ADS)

    Babazadeh, Amin; Nouroozi, Rahman; Sohler, Wolfgang

    2016-02-01

    A phase engineered all-optical wavelength converter for ultra-short pulses (down to 140 fs) in a Ti-diffused, periodically poled lithium niobate (Ti:PPLN) waveguide is proposed. The phase engineering, due to the phase conjugation between signal and idler (converted signal) pulses which takes place in the cascaded second harmonic generation and difference frequency generation (cSHG/DFG) based wavelength conversion, already leads to shorter idler pulses. The proposed device consists of an unpoled (passive) waveguide section beside of the PPLN waveguide section in order to compensate pulse broadening and phase distortion of the idler pulses induced by the wavelength conversion (in the PPLN section). For example numerical analysis shows that a 140 fs input signal pulse is only broadened by 1.6% in a device with a combination of 20 mm and 6 mm long periodically poled and unpoled waveguide sections. Thus, cSHG/DFG based wavelength converters of a bandwidth of several Tbits/s can be designed.

  9. Sub-wavelength energy trapping of elastic waves in a metamaterial.

    PubMed

    Colombi, Andrea; Roux, Philippe; Rupin, Matthieu

    2014-08-01

    Deep sub-wavelength focusing has been demonstrated for locally resonant metamaterials using electromagnetic and acoustic waves. The elastic equivalents of such objects are made of sub-wavelength resonating beams fixed to a two-dimensional plate, as presented here. Independent of a random or regular arrangement of the resonators, the metamaterial shows large bandgaps that are independent of the incident wave direction. Numerical simulations demonstrate that the insertion of a defect in the layout, as a shorter resonator, creates strong amplification of the wave-field on the defect. This energy trapping, which is localized on a spatial scale that is much smaller than the wavelength in the two-dimensional plate, leads to a >1 factor in terms of the local density of energy. PMID:25096146

  10. Task I: A Computational Model for Short Wavelength Stall Inception and Development In Multi-Stage Compressors

    NASA Technical Reports Server (NTRS)

    Suder, Kenneth (Technical Monitor); Tan, Choon-Sooi

    2003-01-01

    A computational model is presented for simulating axial compressor stall inception and development via disturbances with length scales on the order of several (typically about three) blade pitches. The model was designed for multi-stage compressors in which stall is initiated by these short wavelength disturbances, also referred to as spikes. The inception process described is fundamentally nonlinear, in contrast to the essentially linear behavior seen in so-called modal stall inception . The model was able to capture the following experimentally observed phenomena: (1) development of rotating stall via short wavelength disturbances, (2) formation and evolution of localized short wavelength stall cells in the first stage of a mismatched compressor, (3) the switch from long to short wavelength stall inception resulting from the re-staggering of the inlet guide vane, (4) the occurrence of rotating stall inception on the negatively sloped portion of the compressor characteristic. Parametric investigations indicated that (1) short wavelength disturbances were supported by the rotor blade row, (2) the disturbance strength was attenuated within the stators, and (3) the reduction of inter-blade row gaps can suppress the growth of short wavelength disturbances. It is argued that each local component group (rotor plus neighboring stators) has its own instability point (i.e. conditions at which disturbances are sustained) for short wavelength disturbances, with the instability point for the compressor set by the most unstable component group.

  11. A fast-response and short-wavelength nonlinear optical chromophore for a photorefractive composite

    NASA Astrophysics Data System (ADS)

    Chen, Zhijian; Wang, Feng; Yao, Cong; Huang, Zhiwen; Gong, Qihuang; Chen, Yiwang; Chen, Huiying

    1998-12-01

    A nonlinear optical molecule, β,β-diacetyl-4-methoxylstyrene (DAMST), was synthesized and used as the electro-optic chromophore in a photorefractive polymeric composite. Its absorption peak lies at 320 nm and shows no absorption at wavelengths longer than 400 nm. In a 100 μm thickness film of DAMST:poly(N-vinylcarbazole):2,4,7-trinitro-9-fluorenone with a weight ratio of 59:40:1, two-beam coupling gain was measured as high as 32 cm-1 at a wavelength of 543 nm. A response time as short as 17 ms was estimated at an applied electric field of 84 V/μm with a writing beam intensity of 1 W/cm2.

  12. Coherent reflection in a two-dimensional cochlea: Short-wave versus long-wave scattering in the generation of reflection-source otoacoustic emissions

    NASA Astrophysics Data System (ADS)

    Shera, Christopher A.; Tubis, Arnold; Talmadge, Carrick L.

    2005-07-01

    The theory of coherent reflection filtering explains the empirical form of the cochlear reflectance by showing how it emerges from the coherent ``backscattering'' of forward-traveling waves by impedance perturbations in the mechanics of the cochlear partition. Since the theory was developed using the one-dimensional (1-D) transmission-line model of the cochlea, an obvious logical shortcoming is the failure of the long-wavelength approximation near the peak of the traveling wave, where coherent backscattering is purported to occur. Indeed, existing theory suggests that wave reflection may be strongly suppressed in the short-wave regime. To understand how short-wave behavior near the peak modifies the predictions of the long-wave theory, this paper solves the scattering problem in the 2-D cochlear model. The 2-D problem is reduced to a 1-D wave equation and the solution expressed as an infinite series in which successive terms arise via multiple scattering within the cochlea. The cochlear reflectance is computed in response-matched models constructed by solving the inverse problem to control for variations in mechanical tuning among models of different heights and dimensionality. Reflection from the peak region is significantly enhanced by the short-wave hydrodynamics, but other conclusions of the 1-D analysis-such as the predicted relation between emission group delay and the wavelength of the traveling wave-carry over with only minor modifications. The results illustrate the important role of passive hydromechanical effects in shaping otoacoustic emissions and cochlear tuning. .

  13. Wavelength-converted wave-guiding in dye-doped polymer nanofibers

    PubMed Central

    Yu, Huaqing; Li, Baojun

    2013-01-01

    Nanoscale wavelength-converted optical components are promising components for communication and optical information processing in integrated photonic system. In this work, we report a facile strategy for realizing continuously tunable wavelength-converted wave-guiding in dye-doped nanofibers. The nanofibers with diameters of 200–800 nm have an absorption coefficient of about 80 cm−1 and a self-absorption coefficient of about 30 cm−1, and exhibit relatively high PL efficiency and high photobleaching resistance under an optical pump. By launching the pump light into the nanofibers, the excited light in the nanofibers got self-absorption and reemitted at a longer wavelength, resulting in a gradual wavelength conversion during propagation. On the basis of this wavelength-converted wave-guiding, nanoscale wavelength-converted splitters were demonstrated by assembling the nanofibers into crossed structures. We believe that the dye-doped nanofibers would bring new exciting opportunities in developing new wavelength-converted optical components for nanophotonic device integration. PMID:23591750

  14. Effect of thermal stress and short-wavelength visible radiation on phosphor-embedded LED encapsulant degradation

    NASA Astrophysics Data System (ADS)

    Appaiah, Prathika; Narendran, Nadarajah; Perera, Indika U.; Zhu, Yiting; Liu, Yi-wei

    2015-08-01

    This study evaluated the effects of short-wavelength radiation and thermal stress leading to thermal degradation of an LED encapsulant, which contributes to reduced light output. The effect of light transmission was measured in encapsulant samples with different YAG:Ce phosphor concentrations mixed in epoxy, which were subjected to short-wavelength optical radiation and thermal stress. Encapsulant samples with increasing phosphor concentrations showed lower degradation rates of the encapsulant under thermal stress, while under short-wavelength optical radiation the samples with phosphor showed higher degradation rates.

  15. Up-conversion luminescence of gold nanospheres when excited at nonsurface plasmon resonance wavelength by a continuous wave laser.

    PubMed

    Neupane, Bhanu; Zhao, Luyang; Wang, Gufeng

    2013-09-11

    We show that, when gold nanospheres are excited at the red side of the surface plasmon resonance (SPR) wavelength at 592 nm by a continuous wave (CW) laser, they give substantial up-converted luminescence in the SPR wavelength range. The luminescence intensity scales as a second-order function of the excitation power, with a quantum yield ~1/50 of down-conversion luminescence when illuminated at a power of 30 MW/cm(2). The luminescence spectrum is completely different than the SPR profile, indicating a new emission mechanism possibly involving interband transitions coupled with phonons or localized vibration of neighboring gold atoms. Such luminescence is also observed to be substantial for short gold nanorods with an aspect ratio of ~2 but weak for bulk gold. This study provides new insight to the understanding of gold nanoparticle luminescence and opens a new detection scheme for gold nanoparticle-based biological imaging. PMID:23914976

  16. Interplay of mulitphoton and tunneling ionization in short-wavelength-driven high-order harmonic generation

    SciTech Connect

    Gkortsas, Vasileios-Marios; Bhardwaj, Siddharth; Lai, Chien-Jen; Hong, Kyung-Han; Falcao-Filho, Edilson L.; Kaertner, Franz X.

    2011-07-15

    High-order harmonic generation efficiency is theoretically modeled and compared with experiments using 400 and 800 nm driver pulses. It is shown that, for a short drive wavelength and a Keldysh parameter larger than 1, the Ammosov-Delone-Krainov (ADK) ionization model does not give a good agreement between theory and experiment. Since the ADK ionization model only accounts for tunnel ionization, it underestimates the yield of low-order harmonics from the wings of the driver pulse. In contrast, the Yudin-Ivanov ionization model [Phys. Rev. A 64, 013409 (2001)], which accounts for both tunnel and multiphoton ionization, gives much better agreement with the experimental results.

  17. Measuring the electron density gradients of dense plasmas by deflectometry using short-wavelength probe

    SciTech Connect

    Nejdl, J.; Kozlova, M.; Mocek, T.; Rus, B.

    2010-12-15

    A new and simple experimental technique for the measurement of electron density gradients in dense laser-produced plasmas using an electromagnetic wave probe is presented. The main advantage of this method is the low requirements on coherence of the probing beam. The method is based on measuring the deformation of the Talbot pattern of a two-dimensional grating that stems from the distortion of the probe beam wave-front caused by the gradients of the index of refraction. The compromise between spatial resolution and sensitivity for the given wavelength of the probe beam is set by the experimental design. The proposed technique was experimentally verified on plasmas that were created by either a point focus or a line focus of a laser interacting with various solid targets. In the experiments reported here, all plasmas were probed by a Ne-like Zn x-ray laser beam at 21.2 nm, but the technique is applicable for any wavelength of the probe.

  18. A short wave infrared hyperspectral imager for landmine detection

    NASA Astrophysics Data System (ADS)

    McFee, John E.; Achal, Steve; Ivanco, Tyler; Anger, Cliff

    2005-06-01

    DRDC Suffield and Itres Research have jointly investigated the use of visible and infrared hyperspectral imaging for landmine detection since 1988. There has been considerable success detecting surface-laid landmines by classification of their visible/near infrared (VNIR - 400 to 1000 nm wavelength) spectral signatures, but it has not been possible to find VNIR spectral characteristics that would generically distinguish anthropogenic objects from natural features such as rocks, vegetation, soil, etc. Preliminary studies in 1998 suggested that it might be possible to develop such a generic classifier in the short wave infrared (SWIR) and that detection performance might improve. Because of a lack of available SWIR hyperspectral imagers with adequate performance for mine detection, a prototype pushbroom SWIR hyperspectral imager was developed and completed in summer 2002. The now commercially available instrument, sasi, has 160 bands over a spectral range of 850 to 2450 nm, signal to noise ratio of 400:1 with f/1.8 fore-optics, and 600 pixels over a 37.7° field of view. A number of mission flights have been carried out and excellent imagery obtained. In October 2003, Itres and DRDC Suffield personnel obtained field SWIR hyperspectral imagery in the DRDC Suffield Mine Pen of numerous surface-laid mines, one buried mine, other surface-laid human-made items, background materials and people from a horizontally scanning personnel-lift at an altitude of roughly 5 m. Preliminary indications are that a simple generic classification decision boundary should be able to distinguish surface-laid landmines from many human-made artifacts and natural materials. The buried mine was not detected, but the mine had been buried for several years and hence there would be no residual surface disturbance. Furthermore, the small sample size and limited observation time make it difficult to generalize about SWIR performance for buried mines. The instrument is described and the preliminary results of the trial, planned improvements and future research are discussed.

  19. Photonic band gaps of wurtzite GaN and AlN photonic crystals at short wavelengths

    NASA Astrophysics Data System (ADS)

    Melo, E. G.; Alayo, M. I.

    2015-04-01

    Group III-nitride materials such as GaN and AlN have attracted a great attention in researches on photonic devices that operate at short light wavelengths. The large band gaps of these materials turn them suitable for nanophotonic devices that operate in light ranges from visible to deep ultraviolet. The physical properties of wurtzite GaN and AlN such as their second and third order nonlinear susceptibilities, and their thermal and piezoelectric coefficients, also make them excellent candidates for integrate photonic devices with electronics, microelectromechanics, microfluidics and general sensing applications. Using a plane wave expansion method (PWE) the photonic band gap maps of 36 different two-dimensional photonic crystal lattices in wurtzite GaN and AlN were obtained and analyzed. The wavelength dependence and the effects of the material anisotropy on the position of the photonic band gaps are also discussed. The results show regions with slow group velocity at the edges of a complete photonic band gap in the M-K direction of the triangular lattices with circular, hexagonal, and rhombic air holes. Was also found a very interesting disposition of the photonic band gaps in the lattices composed of rhombic air holes.

  20. Effects of Filtering Visual Short Wavelengths During Nocturnal Shiftwork on Sleep and Performance

    PubMed Central

    Rahman, Shadab A.; Shapiro, Colin M.; Wang, Flora; Ainlay, Hailey; Kazmi, Syeda; Brown, Theodore J.

    2013-01-01

    Circadian phase resetting is sensitive to visual short wavelengths (450–480 nm). Selectively filtering this range of wavelengths may reduce circadian misalignment and sleep impairment during irregular light-dark schedules associated with shiftwork. We examined the effects of filtering short wavelengths (<480 nm) during night shifts on sleep and performance in nine nurses (five females and four males; mean age ± SD: 31.3 ± 4.6 yrs). Participants were randomized to receive filtered light (intervention) or standard indoor light (baseline) on night shifts. Nighttime sleep after two night shifts and daytime sleep in between two night shifts was assessed by polysomnography (PSG). In addition, salivary melatonin levels and alertness were assessed every 2 h on the first night shift of each study period and on the middle night of a run of three night shifts in each study period. Sleep and performance under baseline and intervention conditions were compared with daytime performance on the seventh day shift, and nighttime sleep following the seventh daytime shift (comparator). On the baseline night PSG, total sleep time (TST) (p < 0.01) and sleep efficiency (p = 0.01) were significantly decreased and intervening wake times (wake after sleep onset [WASO]) (p = 0.04) were significantly increased in relation to the comparator night sleep. In contrast, under intervention, TST was increased by a mean of 40 min compared with baseline, WASO was reduced and sleep efficiency was increased to levels similar to the comparator night. Daytime sleep was significantly impaired under both baseline and intervention conditions. Salivary melatonin levels were significantly higher on the first (p < 0.05) and middle (p < 0.01) night shifts under intervention compared with baseline. Subjective sleepiness increased throughout the night under both conditions (p < 0.01). However, reaction time and throughput on vigilance tests were similar to daytime performance under intervention but impaired under baseline on the first night shift. By the middle night shift, the difference in performance was no longer significant between day shift and either of the two night shift conditions, suggesting some adaptation to the night shift had occurred under baseline conditions. These results suggest that both daytime and nighttime sleep are adversely affected in rotating-shift workers and that filtering short wavelengths may be an approach to reduce sleep disruption and improve performance in rotating-shift workers. (Author correspondence: casper@lunenfeld.ca) PMID:23834705

  1. Calculation of resonant short-crested waves in deep water

    NASA Astrophysics Data System (ADS)

    Debiane, Mohammed; Kharif, Christian

    2009-06-01

    Solving the problem of resonant short-crested waves is very challenging because the appearance of small divisors causes the classical perturbation methods to fail. From a numerical point of view, the case of resonant gravity short-crested waves has been studied, but as far as we know, there are very few results in the case of resonant capillary-gravity short-crested waves. In fact, to the best of our knowledge, the most related study which has been made is the one of Craig and Nicholls [SIAM J. Math. Anal. 32, 323 (2000)] who gave existence theorems for the case where the surface tension is supposed not to be too small. There is a need for such an investigation, and the work considered herein therefore provides a calculation technique and presents new results on resonant short-crested gravity-capillary waves. We overcome the technical problems associated with small divisors by using a method derived from Whitham's variational formulation of the classical problem of short-crested waves. Whitham's method is not modified in essence, but computations are carried out and organized to obtain a method that has been applied to series of cases demonstrating the robustness and flexibility of the approach. In particular, numerical solutions corresponding to three-dimensional Wilton ripples have been obtained. Moreover, these waves are also obtained for long wave configurations. This method is able to handle the case of small or zero surface tension, including the resonant cases, and works well very near the limiting two-dimensional cases.

  2. Directional short wind wave spectra derived from the sea surface photography

    NASA Astrophysics Data System (ADS)

    Dulov, Vladimir; Yurovskaya, Maria; Chapron, Bertrand; Kudryavtsev, Vladimir

    2014-05-01

    New field measurements of 2-D wave number short wind wave spectra in the wavelength range from few millimeters to few decimeters are reported and discussed. The measurement method proposed by [Kosnik and Dulov, 2011] is based on stereophotography and image brightness contrast processing. The method strongly builds on the brightness cross-spectral analysis to reduce the noise within this short wave gravity and capillary range. Field measurements of wind wave spectra are still rare, and the reported data thus provide valuable information to bring new evidences on the 2-D spectral distribution of short wind waves in the wavelength range from decimeters to millimeters. As found, the folded spectra of decimeter waves are very weakly dependent on the wind speed and its direction. Wind speed and direction sensitivity only starts to appear in the short wavelength range, more precisely in the vicinity of the wave number 100 rad/m, where the wind exponent grows from 0.5 to 1.5-2.5 at 800 rad/m, and angular anisotropy parameter introduced by [Elfouhaily et al., 1997] amounts the value of 0.5. These aspects are consistent with other previously reported optical and radar data. For the latter, we solely extracted the polarization sensitivity to best isolate the contribution associated to the wave saturation spectrum around the Bragg resonant wave number. For the former, mean-squared slope statistics were used to assess the integrated shortscale directional spectral properties. As revealed, observed direction spectral distributions are significantly different from those previously suggested [Elfouhaily et al., 1997; Kudryavtsev et al., 2003, 2005]. On the basis of these new in situ measurements, we then propose to revise the semiempirical analytical model of short wind wave spectra developed by [Kudryavtsev et al., 2003, 2005]. In this model the key parameter is exponent n governing the nonlinear dissipation rate as D ~ Bn+1, where B is saturation spectrum. Accordingly, new additional constraints are used to refine the dependence of the n on dimensionless wave number to match the inferred wind exponent data. As appeared, such a constraint is a key to refine the directional spectrum. The mean saturation spectrum is further adjusted to be consistent with the robust Cox and Munk [1954] dependence of mean-square slope on wind speed. As developed, the proposed two-dimensional wave number spectrum is valid over the ultragravity and capillary large wave numbers, and is analytically amenable to different usage. This revised model can readily be implemented in other studies (radar scattering, air-sea interaction issues, etc.), where detailed knowledge of short wind wave spectra is crucial. The core support of this work was provided by the mega grant of the Russian Federation Government under grant 11.G34.31.0078, and IFREMER-DVS contracts 2011 2 20712376 and 2012 2 20712805. The research leading to these results has also received funding from the European Community's Seventh Framework Programme (FP7/2007-2013) under grant Agreement 287844 for the project COCONET, the Russian Federal Programme under contracts N14.B37.21.0619 and N2012-1.2.1-12-000-2007-078 and Ukrainian State Agency of Science, Innovations and Information under contracts F53/117-2013 and M/281-2013. Authors gratefully acknowledge continuing support of these foundations.

  3. The opto-cryo-mechanical design of the short wavelength camera for the CCAT Observatory

    NASA Astrophysics Data System (ADS)

    Parshley, Stephen C.; Adams, Joseph; Nikola, Thomas; Stacey, Gordon J.

    2014-07-01

    The CCAT observatory is a 25-m class Gregorian telescope designed for submillimeter observations that will be deployed at Cerro Chajnantor (~5600 m) in the high Atacama Desert region of Chile. The Short Wavelength Camera (SWCam) for CCAT is an integral part of the observatory, enabling the study of star formation at high and low redshifts. SWCam will be a facility instrument, available at first light and operating in the telluric windows at wavelengths of 350, 450, and 850 μm. In order to trace the large curvature of the CCAT focal plane, and to suit the available instrument space, SWCam is divided into seven sub-cameras, each configured to a particular telluric window. A fully refractive optical design in each sub-camera will produce diffraction-limited images. The material of choice for the optical elements is silicon, due to its excellent transmission in the submillimeter and its high index of refraction, enabling thin lenses of a given power. The cryostat's vacuum windows double as the sub-cameras' field lenses and are ~30 cm in diameter. The other lenses are mounted at 4 K. The sub-cameras will share a single cryostat providing thermal intercepts at 80, 15, 4, 1 and 0.1 K, with cooling provided by pulse tube cryocoolers and a dilution refrigerator. The use of the intermediate temperature stage at 15 K minimizes the load at 4 K and reduces operating costs. We discuss our design requirements, specifications, key elements and expected performance of the optical, thermal and mechanical design for the short wavelength camera for CCAT.

  4. Chromatic aberration short-wave infrared spectroscopy: nanoparticle spectra without a spectrometer.

    PubMed

    Streit, Jason K; Bachilo, Sergei M; Weisman, R Bruce

    2013-02-01

    A new method is described for measuring the short-wave infrared (SWIR) emission wavelengths of numerous individual nanoparticles without using a dedicated spectrometer. Microscope objectives designed for use at visible wavelengths often show severe axial chromatic aberration in the SWIR. This makes coplanar objects emitting at different SWIR wavelengths appear to focus at different depths. After this aberration has been calibrated for a particular objective lens, the depth at which an emissive nanoparticle appears brightest and best focused can be used to deduce its peak emission wavelength. The method is demonstrated using a dilute, structurally polydisperse sample of single-walled carbon nanotubes deposited onto a microscope slide. Discrete emission centers in this sample have different peak wavelengths corresponding to specific nanotube structural species. A set of images was recorded at stepped focus settings and analyzed to find the sharpest focus depth of each nanotube. The chromatic aberration calibration curve converted these depths into peak emission wavelengths with a spectral resolution better than 3 nm, allowing identification of each nanotube's structure. Chromatic aberration spectroscopy is a practical tool for using existing microscopic equipment to extract significant spectral information on coplanar nanoparticle samples that emit or scatter light. PMID:23286305

  5. Development of short-wavelength near-infrared spectral imaging for grain color classification

    NASA Astrophysics Data System (ADS)

    Archibald, Douglas D.; Thai, Chi N.; Dowell, Floyd E.

    1999-01-01

    Color class of wheat is an important attribute for the identification of cultivars and the marketing of wheat, but is not always easy to measure in the visible spectral range because of variation in vitreosity and surface structure of the kernels. This work examines whether short-wavelength near IR imaging in the range 632-1098 nm can be used to distinguish different cultivars. The spectral characteristics of six hard white winter and hard red spring wheats were first studied by bulk-sample SW-NIR reflectance spectroscopy using regression analysis to select appropriate wavelengths and sets of wavelengths. Prediction of percent red wheat was better if C-H or O-H vibrational overtones were included in the models in addition to the tail from the visible chromophore absorbance, apparently because the vibrational bands make it possible to normalize the color measurement to the dry matter content of the samples. Next, a reflectance spectral image of 640 X 480 spatial pixels and 11 wavelengths was acquired for a mixture of the two contrasting wheat samples using a CCD camera and a liquid crystal tunable filter. The cultivars were distinguished in the image of principal component (PC) score number two that was calculated from the spectral image. The discrimination is due to the tail from the absorbance band that peaks in the visible. PC images 3 and 6 seem to arise mainly from O-H and C-H bands, respectively, and it is speculated that these spectral features will be important for generating multivariate models to predict the color class of grain. It is shown that the contrast between the red-wheat, white- wheat and background can be increased by applying histogram equalization and segmentation of the kernels in the images.

  6. Short wavelengths active bichromatic pulsed pyrometer for solids and liquids designed for measurements in harsh environments

    NASA Astrophysics Data System (ADS)

    Navello, L.; Lebedinsky, J.; Offret, J. P.; Serio, B.; Davin, T.; Bailly, Y.; Hervé, P.

    2015-05-01

    Optical passive methods for temperature measurements such as thermography or optical pyrometry are very interesting because they allow a non-intrusive measurement when the emissivity is known. The knowledge of this coefficient is critical for determining the actual temperature of a surface from the thermal radiation emitted in a wavelength band. The bichromatic pulsed pyrometer allows to overcome the knowledge of this parameter provided that precautions are taken in the choice of the values of wavelengths. When the object to be measured is placed in harsh environments, such passive optical methods are greatly disturbed by the presence of an optically absorbing medium. They are also distorted when the measured objects are located in very hot environments emitting intense disturbing radiation. In this study, we present an active bichromatic radiometric method for measuring the temperature of a surface in harsh environments. The method is based on a localized excitation by a modulated laser source in the infrared range. Detecting the temperature modulation, which is correlated with the excitation, is performed using a lock-in amplifier able to extract the signal embedded in a noise up to a million times superior. Working at short wavelengths (visible range and near infrared range) offers a large dynamic range and minimizes the error due to variations in emissivity with the wavelength. This system collects the radiation emitted by the object at a distance from a few meters up to dozens of meters depending on the configuration of the optical system. Both the principle and the design of the active bichromatic optical surface thermometer are presented and discussed. To demonstrate the method, results obtained on a molten ceramic stream are presented.

  7. A model for forecasting solr short-wave UV emission

    NASA Astrophysics Data System (ADS)

    Kazachevskaya, T. V.; Nusinov, A. A.

    Variations of short-wave (10 - 105 nm) solar ultraviolet emission are generally caused by changes in two components - background emisson of undisturbed solar surface and emission from active regions. These components vary nonlinearly with the corresponding components of radioemission at 10.7 cm. Model computations were compared to direct measurements of short-wave emission. Mean diurnal data on the integral flux obtained from Prognoz-7 in 1978 - 1979 were used, relative precision being 1.5%. Model calculatons are in good agreement (within 10%) with the observed day-to-day variations of UV radiation.

  8. Higher-order statistical analysis of short wind wave fields

    NASA Astrophysics Data System (ADS)

    Guérin, C.-A.; Caulliez, G.

    2012-04-01

    Today, satellite remote sensing opens the possibility of characterizing the ocean surface both at global scale and at fine resolution. Following the recent improvements in techniques and theories, links have been established between the backscattered radar cross-section of the sea surface and a large number of oceanic parameters, such as wind speed and direction, wave heights and slopes, wave spectrum, surface current, temperature and salinity, etc. However, the success of the inversion procedure relies crucially on an accurate phase resolving statistical description of the sea surface topography. In this respect, non-Gaussian characteristics of short wind waves are of primary importance, as they have a strong influence on the microwave radar return. Observations of alongwind surface wave profiles were made in the large Luminy wind wave tank for a broad range of wind (3-10 m/s) and fetch (2-26 m) conditions. The processing of high resolution camera snapshots enables us to carry on a thorough statistical analysis of short wind wave geometrical properties. We consider distinctively four different wind wave fields characterized by a comprehensive image analysis in the range of capillary-gravity to gravity scales. This set of data makes it possible to describe and discuss the behavior of the distribution of wave heights, longitudinal wave slopes and curvatures in terms of their second- and higher-order moments as well as a function of the dominant wave scale. We calculate the autocorrelation and related functions and evidence the self-similar nature of wind wave fields. We also derive a simple and universal expression for the structure functions of third (skewness) and fourth (kurtosis) order which are needed for the simulation of sea radar return in the microwave regime.

  9. High power, high efficiency millimeter wavelength traveling wave tubes for high rate communications from deep space

    NASA Technical Reports Server (NTRS)

    Dayton, James A., Jr.

    1991-01-01

    The high-power transmitters needed for high data rate communications from deep space will require a new class of compact, high efficiency traveling wave tubes (TWT's). Many of the recent TWT developments in the microwave frequency range are generically applicable to mm wave devices, in particular much of the technology of computer aided design, cathodes, and multistage depressed collectors. However, because TWT dimensions scale approximately with wavelength, mm wave devices will be physically much smaller with inherently more stringent fabrication tolerances and sensitivity to thermal dissipation.

  10. Wavelength dependence in radio-wave scattering and specular-point theory

    NASA Technical Reports Server (NTRS)

    Tyler, G. L.

    1976-01-01

    Radio-wave scattering from natural surfaces contains a strong quasispecular component that at fixed wavelengths is consistent with specular-point theory, but often has a strong wavelength dependence that is not predicted by physical optics calculations under the usual limitations of specular-point models. Wavelength dependence can be introduced by a physical approximation that preserves the specular-point assumptions with respect to the radii of curvature of a fictitious, effective scattering surface obtained by smoothing the actual surface. A uniform low-pass filter model of the scattering process yields explicit results for the effective surface roughness versus wavelength. Interpretation of experimental results from planetary surfaces indicates that the asymptotic surface height spectral densities fall at least as fast as an inverse cube of spatial frequency. Asymptotic spectral densities for Mars and portions of the lunar surface evidently decrease more rapidly.

  11. Lack of short-wavelength light during the school day delays dim light melatonin onset (DLMO) in middle school students

    PubMed Central

    Figueiro, Mariana G.; Rea, Mark S.

    2012-01-01

    OBJECTIVE Circadian timing affects sleep onset. Delayed sleep onset can reduce sleep duration in adolescents required to awake early for a fixed school schedule. The absence of short-wavelength (“blue”) morning light, which helps entrain the circadian system, can hypothetically delay sleep onset and decrease sleep duration in adolescents. The goal of this study was to investigate whether removal of short-wavelength light during the morning hours delayed the onset of melatonin in young adults. METHODS Dim light melatonin onset (DLMO) was measured in eleven 8th-grade students before and after wearing orange glasses, which removed short-wavelength light, for a five-day school week. RESULTS DLMO was significantly delayed (30 minutes) after the five-day intervention, demonstrating that short-wavelength light exposure during the day can be important for advancing circadian rhythms in students. CONCLUSIONS Lack of short-wavelength light in the morning has been shown to delay the circadian clock in controlled laboratory conditions. The results presented here are the first to show, outside laboratory conditions, that removal of short-wavelength light in the morning hours can delay DLMO in 8th-grade students. These field data, consistent with results from controlled laboratory studies, are directly relevant to lighting practice in schools. PMID:20150866

  12. Strong localization of an acoustic wave in a sub-wavelength slot between two plates.

    PubMed

    Cai, Feiyan; Li, Fei; Meng, Long; Wu, Junru; Zheng, Hairong

    2015-03-01

    The dispersion relation of the acoustic field in a sub-wavelength slot (its width is smaller than the acoustic wavelength) between two identical plates immersed in an inviscid liquid is theoretically analyzed. Each plate has a phononic crystal structure consisting of periodical grooves drilled in one of outer sides of each plate. It is found that highly localization of acoustic energy can be achieved in the sub-wavelength slot when a traveling acoustic wave is incident upon the slots. The associate physical principle is as follows: The lowest anti-symmetric non-leaky A0 mode of the Lamb wave of each individual thin plate propagating as an evanescent wave extends to the liquid from opposite direction; when the width of the slot is much smaller than the characteristic decay length of the evanescent wave in the liquid, the constructive interference of evanescent waves of the both plates takes place, leading to a strong acoustic field in the slot. This system has potential to serve as an excellent candidate for the ultrasensitive microscopic chemical/biological stimulators and sensors. PMID:25786938

  13. Diffraction of short pulses with boundary diffraction wave theory.

    PubMed

    Horváth, Z L; Bor, Z

    2001-02-01

    The diffraction of short pulses is studied on the basis of the Miyamoto-Wolf theory of the boundary diffraction wave, which is a mathematical formulation of Young's idea about the nature of diffraction. It is pointed out that the diffracted field is given by the superposition of the boundary wave pulse (formed by interference of the elementary boundary diffraction waves) and the geometric (direct) pulse (governed by the laws of geometrical optics). The case of a circular aperture is treated in details. The diffracted field on the optical axis is calculated analytically (without any approximation) for an arbitrary temporal pulse shape. Because of the short pulse duration and the path difference the geometric and the boundary wave pulses appear separately, i.e., the boundary waves are manifested in themselves in the illuminated region (in the sense of geometrical optics). The properties of the boundary wave pulse is discussed. Its radial intensity distribution can be approximated by the Bessel function of zero order if the observation points are in the illuminated region and far from the plane of the aperture and close to the optical axis. Although the boundary wave pulse propagates on the optical axis at a speed exceeding c, it does not contradict the theory of relativity. PMID:11308595

  14. Action Spectrum for Photobleaching of Human Lenses by Short Wavelength Visible Irradiation

    PubMed Central

    Kessel, Line; Larsen, Michael

    2015-01-01

    Purpose Cataract is the world-leading cause of blindness. In search for a new treatment of cataract we have found that the yellow discolouration of aged human lenses can be photobleached using a non-invasive, infra-red, femtosecond laser treatment. These results were presented in an earlier PlosOne publication. The objective of the study was to characterize the single-photon photobleaching action spectrum of the aged human lens in vitro. Methods Ninety-one human donor lenses were irradiated with continuous wave laser light at 375, 405, 420, 445, 457 or 473 nm. Photobleaching was monitored by photography and transmission measurements. Results The action spectrum peaked at 420 nm followed by, in order of decreasing effect, 445, 457, 473, 405 and 375 nm. Younger and less absorbent lenses showed smaller changes than older and more absorbent lenses. There was a dose-dependent increase in lens transmission with increasing laser irradiation. Conclusions For a 75 year old lens an effect corresponding to elimination of 15 years or more of optical ageing was obtained. This study of the spectral characteristics and intensity needed to bleach the human lens with single-photon laser effects found an action-spectrum peak at 420 nm tailing gradually off toward longer wavelengths and more steeply toward shorter wavelengths. The results may be used to guide experiments with two-photon bleaching. PMID:25884924

  15. Short-Wave Radio: An Aid to Language Learning.

    ERIC Educational Resources Information Center

    Lutcavage, Charles P.

    1982-01-01

    Discusses use of short-wave radio broadcasts as method for expanding students' appreciation of practical advantages of language learning. Suggests use of news broadcasts and gives guidelines for using broadcasts such as level of aural comprehension in class. (Author/BK)

  16. Into French and the World via Short Wave.

    ERIC Educational Resources Information Center

    Rorke, Robert Cornelius

    1978-01-01

    A report on the introduction and use of short wave broadcasts in an intensive spoken French class. The kinds of materials used, class structure, the nature of assignments, student motivation, testing, cultural advantages, student reactions, and suggestions for further application are discussed. A list of useful references is included. (AMH)

  17. Radio wave propagation at frequencies exceeding MUF-F2 in the short wave band

    NASA Technical Reports Server (NTRS)

    Ashkaliyev, Y. F.; Bocharov, V. I.

    1972-01-01

    The results of measurements of field strength and signal/noise ratio on experimental ionospheric-scattering short wave radio links are presented. It is shown that the seasonal and diurnal variations of field strength are determined by features of solar and meteoric activity. The role of the sporadic E-layer in propagation of short radio waves at frequencies exceeding MUF-F2 is noted.

  18. Wavelength-assignable 1310/1550 nm wavelength conversion using completely phase-matched two-pump four-wave mixing in a silicon waveguide

    NASA Astrophysics Data System (ADS)

    Chen, Jian; Gao, Shiming

    2015-12-01

    A wavelength converter between 1310 and 1550 nm bands is presented based on two-pump four-wave mixing (FWM) in a silicon waveguide. The principle of the inter-band wavelength conversion is analyzed. For an arbitrary incident signal, the converted idler wavelength can be freely assigned by suitably setting the two pump wavelengths to completely satisfy the phase-matching condition. Simulation results show that the signal can be flexibly converted between 1310 and 1550 bands. The conversion efficiencies for the signals with different wavelengths are very stable because the FWM phase-matching condition is completely met. Using this two-pump FWM configuration, channel-selective function can also be realized for wavelength division multiplexing (WDM) signals by engineering the dispersion profile of the silicon waveguide according to the WDM channel spacing.

  19. Rough surface wavelength measurement through self mixing of Doppler microwave backscatter. [from ocean waves

    NASA Technical Reports Server (NTRS)

    Weissman, D. E.; Johnson, J. W.

    1979-01-01

    A microwave backscatter technique is presented that has the ability to sense the dominant surface wavelength of a random rough surface. The purpose of this technique is to perform this measurement from an aircraft or spacecraft, wherein the horizontal velocity of the radar is an important parameter of the measurement system. Attention will be directed at water surface conditions for which a dominant wavelength can be defined, then the spatial variations of reflectivity will have a two dimensional spectrum that is sufficiently close to that of waves to be useful. The measurement concept is based on the relative motion between the water waves and a nadir looking radar, and the fact that while the instantaneous Doppler frequency at the receiver returned by any elementary group of scatterers on a water wave is monotonically changing, the difference in the Doppler frequency between any two scattering 'patches' stays approximately constant as these waves travel parallel to the major axis of an elliptical antenna footprint. The results of a theoretical analysis and a laboratory experiment with a continuous wave (CW) radar that encompasses several of the largest waves in the illuminated area show how the structure in the Doppler spectrum of the backscattered signal is related to the surface spectrum and its parameters in an especially direct and simple way when an incoherent envelope detector is the receiver.

  20. Influence of wavelength-dependent-loss on dispersive wave in nonlinear optical fibers.

    PubMed

    Herrera, Rodrigo Acuna

    2012-11-01

    In this work, we study numerically the influence of wavelength-dependent loss on the generation of dispersive waves (DWs) in nonlinear fiber. This kind of loss can be obtained, for instance, by the acousto-optic effect in fiber optics. We show that this loss lowers DW frequency in an opposite way that the Raman effect does. Also, we see that the Raman effect does not change the DW frequency too much when wavelength-dependent loss is included. Finally, we show that the DW frequency is not practically affected by fiber length. PMID:23128688

  1. Random crustal magnetization and its effect on coherence of short-wavelength marine magnetic anomalies

    USGS Publications Warehouse

    Blakely, R.J.

    1979-01-01

    Recent studies of DSDP samples from layer 2A of oceanic basement have found complex magnetic stratigraphies that seem incompatible with the frequent existence of linear short-wavelength anomalies caused by palaeomagnetic field behavior. Statistical models are developed for the lateral variation of the average magnetization of layer 2A: a Poisson series for reversals of the earth's field and a stairstep random series for discrete magnetic units. It is shown with the power-density spectra of these statistical models that lateral inhomogeneities must average out over distances of less than a few hundred meters. Specifically, individual magnetic units of the type seen at DSDP Site 332 cannot extend uniformly for distances greater than a few hundred meters. ?? 1979.

  2. Emitted short wavelength infrared radiation for detection and monitoring of volcanic activity

    NASA Technical Reports Server (NTRS)

    Rothery, D. A.; Francis, P. W.; Wood, C. A.

    1988-01-01

    Thematic Mapper images from LANDSAT were used to monitor volcanoes. Achievements include: (1) the discovery of a magmatic precursor to the 16 Sept. 1986 eruption of Lascar, northern Chile, on images from Mar. and July 1985 and of continuing fumarolic activity after the eruption; (2) the detection of unreported major changes in the distribution of lava lakes on Erta'Ale, Ethiopia; and (3) the mapping of a halo of still-hot spatter surrounding a vent on Mount Erebus, Antarctica, on an image acquired 5 min after a minor eruption otherwise known only from seismic records. A spaceborne short wavelength infrared sensor for observing hot phenomena of volcanoes is proposed. A polar orbit is suggested.

  3. SWAT system performance predictions. Project report. [SWAT (Short-Wavelength Adaptive Techniques)

    SciTech Connect

    Parenti, R.R.; Sasiela, R.J.

    1993-03-10

    In the next phase of Lincoln Laboratory's SWAT (Short-Wavelength Adaptive Techniques) program, the performance of a 241-actuator adaptive-optics system will be measured using a variety of synthetic-beacon geometries. As an aid in this experimental investigation, a detailed set of theoretical predictions has also been assembled. The computational tools that have been applied in this study include a numerical approach in which Monte-Carlo ray-trace simulations of accumulated phase error are developed, and an analytical analysis of the expected system behavior. This report describes the basis of these two computational techniques and compares their estimates of overall system performance. Although their regions of applicability tend to be complementary rather than redundant, good agreement is usually obtained when both sets of results can be derived for the same engagement scenario.... Adaptive optics, Phase conjugation, Atmospheric turbulence Synthetic beacon, Laser guide star.

  4. Short wavelength 128 by 128 focal plane arrays for remote sensing applications

    NASA Technical Reports Server (NTRS)

    Bothwell, Mary; Bailey, Gary C.; Wright, Valerie G.; Vural, Kadri; Blessinger, Michael A.

    1988-01-01

    Short-wavelength (1-2.5-micron) 128x128 focal plane arrays have been fabricated and demonstrated with high pixel yields and dark-current-limited performance. The detector material is HgCdTe grown by LPE on a sapphire substrate which yields high-performance uniform detectors. The detector arrays were characterized at temperatures of 80-150 K; the peak quantum efficiency at 2.4 microns is 80 percent. The multiplexer is a Reticon FET switch with output amplifiers. It is noted that the long-term goal of this project is to develop a 150x1000 mosaicked focal plane for use in the HIRIS instrument on the Earth Observing System.

  5. Impurity effects on short wavelength ion temperature gradient mode in elongated tokamak plasmas

    SciTech Connect

    Du, Huarong; Wang, Zheng-Xiong; Dong, J. Q.

    2015-02-15

    The effects of impurity ions on the short wavelength ion temperature gradient (SWITG) driven instability in elongated tokamak plasmas are numerically investigated with the gyrokinetic integral eigenmode equation. It is found that for a moderate electron density gradient, the SWITG mode is first destabilized and then stabilized with increasing elongation κ, which is different from the conventional long wavelength ITG mode. For a large electron density gradient, the elongation can effectively stabilize the SWITG mode. Moreover, the low Z impurity ions with inwardly (outwardly) peaked density profiles have stabilizing (destabilizing) effects on the SWITG modes in elongated plasmas. Interestingly, the high Z tungsten impurity ions with inwardly peaked density profiles play a stronger stabilizing role in the SWITG modes than the low Z impurity ions (such as carbon and oxygen) do. In particular, the high Z tungsten impurity ions with a weakly outwardly peaked density profile still have a stabilizing effect. Finally, the critical threshold of impurity density gradient scale length for exciting impurity mode is also numerically obtained, indicating that the impurity mode is harder to be excited in elongated plasmas than in circular ones.

  6. Short-wavelength infrared tuneable filters on HgCdTe photoconductors.

    PubMed

    Soh, Martin; Nguyen, T; Silva, K K; Westerhout, R; Antoszewski, J; Keating, A; Savvides, N; Musca, C; Dell, J; Faraone, L

    2005-11-28

    The design, micro-fabrication, and electronic and optical performance of a tuneable short-wavelength infrared Fabry-Pérot microresonator on a mercury cadmium telluride photoconductor is presented. The maximum processing temperature of 125 degrees C has negligible effect on the electronic and optical performance of photoconductor test structures. Maximum responsivity, effective carrier lifetime and detectivity are 60x103 VW-1, 2x10-5 s and 8x1010 cmHz1/2W-1, respectively. The maximum effective carrier lifetime and specific detectivity are in good agreement with the theoretical maxima. Uncooled device operation is possible since responsivity is observed not to improve with thermo-electric cooling. Spectral tuning of the micro-filters is demonstrated over the wavelength range 1.7 to 2.2 mum using drive voltages up to 8 V, with the full-width-half-maximum of the resonance approximately 100 nm. Membrane deflection can be up to 40% of the cavity width. PMID:19503174

  7. Short-wavelength interband cascade infrared photodetectors operating above room temperature

    NASA Astrophysics Data System (ADS)

    Lotfi, Hossein; Li, Lu; Lei, Lin; Jiang, Yuchao; Yang, Rui Q.; Klem, John F.; Johnson, Matthew B.

    2016-01-01

    High temperature operation (250-340 K) of short-wavelength interband cascade infrared photodetectors (ICIPs) with InAs/GaSb/Al0.2In0.8Sb/GaSb superlattice absorbers has been demonstrated with a 50% cutoff wavelength of 2.9 μm at 300 K. Two ICIP structures, one with two and the other with three stages, were designed and grown to explore this multiple-stage architecture. At λ = 2.1 μm, the two- and three-stage ICIPs had Johnson-noise-limited detectivities of 5.1 × 109 and 5.8 × 109 cm Hz1/2/W, respectively, at 300 K. The better device performance of the three-stage ICIP over the two-stage ICIP confirmed the advantage of more stages for this cascade architecture. An Arrhenius activation energy of 450 meV is extracted for the bulk resistance-area product, which indicates the dominance of the diffusion current at these high temperatures.

  8. Short-wavelength interband cascade infrared photodetectors operating above room temperature

    DOE PAGESBeta

    Lotfi, Hossein; Li, Lu; Lei, Lin; Jiang, Yuchao; Yang, Rui Q.; Klem, John F.; Johnson, Matthew B.

    2016-01-13

    High temperature operation (250–340 K) of short-wavelength interband cascade infrared photodetectors (ICIPs) with InAs/GaSb/Al0.2In0.8Sb/GaSb superlattice absorbers has been demonstrated with a 50% cutoff wavelength of 2.9 μm at 300 K. Two ICIP structures, one with two and the other with three stages, were designed and grown to explore this multiple-stage architecture. At λ = 2.1 μm, the two- and three-stage ICIPs had Johnson-noise-limited detectivities of 5.1 × 109 and 5.8 ×109 cm Hz1/2/W, respectively, at 300 K. The better device performance of the three-stage ICIP over the two-stage ICIP confirmed the advantage of more stages for this cascade architecture. Furthermore,more » an Arrhenius activation energy of 450 meV is extracted for the bulk resistance-area product, which indicates the dominance of the diffusion current at these high temperatures.« less

  9. Substantial Improvement of Short Wavelength Response in n-SiNW/PEDOT:PSS Solar Cell.

    PubMed

    Ge, Zhaoyun; Xu, Ling; Cao, Yunqing; Wu, Tao; Song, Hucheng; Ma, Zhongyuan; Xu, Jun; Chen, Kunji

    2015-12-01

    We report herein on the effects of silicon nanowire with different morphology on the device performance of n-SiNW/PEDOT:PSS hybrid solar cells. The power conversion efficiency (PCE) and external quantum efficiency (EQE) of the SiNW/PEDOT:PSS hybrid solar cells can be optimized by varying the length of the silicon nanowires. The optimal length of silicon nanowires is 0.23?m, and the hybrid solar cell with the optimal length has the V oc of 569mV, J sc of 30.1mA/cm(2), and PCE of 9.3%. We fabricated more isolated silicon nanowires with the diluted etching solution. And the J sc of the hybrid solar cell with more isolated nanowires has a significant enhancement, from 30.1 to 33.2mA/cm(2). The remarkable EQE in the wavelength region of 300 and 600nm was also obtained, which are in excess of 80%. Our work provides a simple method to substantially improve the EQE of hybrid solar cell in the short wavelength region. PMID:26283449

  10. Design considerations for the development of a space qualification Short Wavelength Imaging Fourier Transform Spectrometer (SWIFTS)

    SciTech Connect

    Abbink, R.E.

    1997-06-01

    This document is the final report on work performed at Sandia National Laboratories during FY 1992 and 1993 for a Laboratory Directed Research and Development (LDRD) program to look at problems associated with the design and long term operation of a short wavelength imaging Fourier Transform (FT) spectrometer for use in space. In attempts to answer two fundamental questions: is a FT spectrometer with a resolution of 1 cm{sup {minus}1} covering the silicon detector wavelength range of 0.4 to 1.1 microns feasible in a long life space instrument and, if so, is it the best method of obtaining the desired information? Emphasis has been on identifying methods which minimize reliance on precision mechanical alignment and precise velocity control. An important consideration has also been to develop methods which will be compatible with a variety of self-scanning solid state imaging devices. A breadboard instrument was constructed using cube corner retroreflectors and a laser diode position reference. Some preliminary results are reported. This work is primarily intended to act as an aid to engineers at Sandia who wish to pursue the fabrication of a flight qualified instrument. The theoretical parts are intended to be somewhat tutorial in nature to aid the engineer who is not familiar with FT spectroscopy.

  11. Low-power continuous-wave four-wave mixing wavelength conversion in AlGaAs-nanowaveguide microresonators.

    PubMed

    Kultavewuti, Pisek; Pusino, Vincenzo; Sorel, Marc; Stewart Aitchison, J

    2015-07-01

    We experimentally demonstrate enhanced wavelength conversion in a Q?7500 deeply etched AlGaAs-nanowaveguide microresonator via degenerate continuous-wave four-wave mixing with a pump power of 24mW. The maximum conversion efficiency is -43??dB and accounts for 12dB enhancement compared to that of a straight nanowaveguide. The experimental results and theoretical predictions agree very well and show optimized conversion efficiency of -15??dB. This work represents a step toward realizing a fully integrated optical devices for generating new optical frequencies. PMID:26125359

  12. Review of short-wave infrared spectroscopy and imaging methods for biological tissue characterization

    NASA Astrophysics Data System (ADS)

    Wilson, Robert H.; Nadeau, Kyle P.; Jaworski, Frank B.; Tromberg, Bruce J.; Durkin, Anthony J.

    2015-03-01

    We present a review of short-wave infrared (SWIR, defined here as ˜1000 to 2000 nm) spectroscopy and imaging techniques for biological tissue optical property characterization. Studies indicate notable SWIR absorption features of tissue constituents including water (near 1150, 1450, and 1900 nm), lipids (near 1040, 1200, 1400, and 1700 nm), and collagen (near 1200 and 1500 nm) that are much more prominent than corresponding features observed in the visible and near-infrared (VIS-NIR, defined here as ˜400 to 1000 nm). Furthermore, the wavelength dependence of the scattering coefficient has been observed to follow a power-law decay from the VIS-NIR to the SWIR region. Thus, the magnitude of tissue scattering is lower at SWIR wavelengths than that observed at VIS or NIR wavelengths, potentially enabling increased penetration depth of incident light at SWIR wavelengths that are not highly absorbed by the aforementioned chromophores. These aspects of SWIR suggest that the tissue spectroscopy and imaging in this range of wavelengths have the potential to provide enhanced sensitivity (relative to VIS-NIR measurements) to chromophores such as water and lipids, thereby helping to characterize changes in the concentrations of these chromophores due to conditions such as atherosclerotic plaque, breast cancer, and burns.

  13. Quantitative short-wave infrared multispectral imaging of in vivo tissue optical properties

    PubMed Central

    Wilson, Robert H.; Nadeau, Kyle P.; Jaworski, Frank B.; Rowland, Rebecca; Nguyen, John Q.; Crouzet, Christian; Saager, Rolf B.; Choi, Bernard; Tromberg, Bruce J.; Durkin, Anthony J.

    2014-01-01

    Abstract. Extending the wavelength range of spatial frequency domain imaging (SFDI) into the short-wave infrared (SWIR) has the potential to provide enhanced sensitivity to chromophores such as water and lipids that have prominent absorption features in the SWIR region. Here, we present, for the first time, a method combining SFDI with unstructured (zero spatial frequency) illumination to extract tissue absorption and scattering properties over a wavelength range (850 to 1800 nm) largely unexplored by previous tissue optics techniques. To obtain images over this wavelength range, we employ a SWIR camera in conjunction with an SFDI system. We use SFDI to obtain in vivo tissue reduced scattering coefficients at the wavelengths from 850 to 1050 nm, and then use unstructured wide-field illumination and an extrapolated power-law fit to this scattering spectrum to extract the absorption spectrum from 850 to 1800 nm. Our proof-of-principle experiment in a rat burn model illustrates that the combination of multispectral SWIR imaging, SFDI, and unstructured illumination can characterize in vivo changes in skin optical properties over a greatly expanded wavelength range. In the rat burn experiment, these changes (relative to normal, unburned skin) included increased absorption and increased scattering amplitude and slope, consistent with changes that we previously reported in the near-infrared using SFDI. PMID:25120175

  14. Quantitative short-wave infrared multispectral imaging of in vivo tissue optical properties.

    PubMed

    Wilson, Robert H; Nadeau, Kyle P; Jaworski, Frank B; Rowland, Rebecca; Nguyen, John Q; Crouzet, Christian; Saager, Rolf B; Choi, Bernard; Tromberg, Bruce J; Durkin, Anthony J

    2014-08-01

    Extending the wavelength range of spatial frequency domain imaging (SFDI) into the short-wave infrared (SWIR) has the potential to provide enhanced sensitivity to chromophores such as water and lipids that have prominent absorption features in the SWIR region. Here, we present, for the first time, a method combining SFDI with unstructured (zero spatial frequency) illumination to extract tissue absorption and scattering properties over a wavelength range (850 to 1800 nm) largely unexplored by previous tissue optics techniques. To obtain images over this wavelength range, we employ a SWIR camera in conjunction with an SFDI system. We use SFDI to obtain in vivo tissue reduced scattering coefficients at the wavelengths from 850 to 1050 nm, and then use unstructured wide-field illumination and an extrapolated power-law fit to this scattering spectrum to extract the absorption spectrum from 850 to 1800 nm. Our proof-of-principle experiment in a rat burn model illustrates that the combination of multispectral SWIR imaging, SFDI, and unstructured illumination can characterize in vivo changes in skin optical properties over a greatly expanded wavelength range. In the rat burn experiment, these changes (relative to normal, unburned skin) included increased absorption and increased scattering amplitude and slope, consistent with changes that we previously reported in the near-infrared using SFDI. PMID:25120175

  15. Review of short-wave infrared spectroscopy and imaging methods for biological tissue characterization

    PubMed Central

    Wilson, Robert H.; Nadeau, Kyle P.; Jaworski, Frank B.; Tromberg, Bruce J.; Durkin, Anthony J.

    2015-01-01

    Abstract. We present a review of short-wave infrared (SWIR, defined here as ∼1000 to 2000 nm) spectroscopy and imaging techniques for biological tissue optical property characterization. Studies indicate notable SWIR absorption features of tissue constituents including water (near 1150, 1450, and 1900 nm), lipids (near 1040, 1200, 1400, and 1700 nm), and collagen (near 1200 and 1500 nm) that are much more prominent than corresponding features observed in the visible and near-infrared (VIS-NIR, defined here as ∼400 to 1000 nm). Furthermore, the wavelength dependence of the scattering coefficient has been observed to follow a power-law decay from the VIS-NIR to the SWIR region. Thus, the magnitude of tissue scattering is lower at SWIR wavelengths than that observed at VIS or NIR wavelengths, potentially enabling increased penetration depth of incident light at SWIR wavelengths that are not highly absorbed by the aforementioned chromophores. These aspects of SWIR suggest that the tissue spectroscopy and imaging in this range of wavelengths have the potential to provide enhanced sensitivity (relative to VIS-NIR measurements) to chromophores such as water and lipids, thereby helping to characterize changes in the concentrations of these chromophores due to conditions such as atherosclerotic plaque, breast cancer, and burns. PMID:25803186

  16. Review of short-wave infrared spectroscopy and imaging methods for biological tissue characterization.

    PubMed

    Wilson, Robert H; Nadeau, Kyle P; Jaworski, Frank B; Tromberg, Bruce J; Durkin, Anthony J

    2015-03-01

    We present a review of short-wave infrared (SWIR, defined here as ∼1000 to 2000 nm) spectroscopy and imaging techniques for biological tissue optical property characterization. Studies indicate notable SWIR absorption features of tissue constituents including water (near 1150, 1450, and 1900 nm), lipids (near 1040, 1200, 1400, and 1700 nm), and collagen (near 1200 and 1500 nm) that are much more prominent than corresponding features observed in the visible and near-infrared (VIS-NIR, defined here as ∼400 to 1000 nm). Furthermore, the wavelength dependence of the scattering coefficient has been observed to follow a power-law decay from the VIS-NIR to the SWIR region. Thus, the magnitude of tissue scattering is lower at SWIR wavelengths than that observed at VIS or NIR wavelengths, potentially enabling increased penetration depth of incident light at SWIR wavelengths that are not highly absorbed by the aforementioned chromophores. These aspects of SWIR suggest that the tissue spectroscopy and imaging in this range of wavelengths have the potential to provide enhanced sensitivity (relative to VIS-NIR measurements) to chromophores such as water and lipids, thereby helping to characterize changes in the concentrations of these chromophores due to conditions such as atherosclerotic plaque, breast cancer, and burns. PMID:25803186

  17. Concentric waves and short-period oscillations observed in the ionosphere after the 2013 Moore EF5 tornado

    NASA Astrophysics Data System (ADS)

    Nishioka, Michi; Tsugawa, Takuya; Kubota, Minoru; Ishii, Mamoru

    2013-11-01

    We detected clear concentric waves and short-period oscillations in the ionosphere after an Enhanced Fujita scale (EF)5 tornado hit Moore, Oklahoma, U.S., on 20 May 2013 using dense wide-coverage ionospheric total electron content (TEC) observations in North America. These concentric waves were nondispersive, with a horizontal wavelength of ~120 km and a period of ~13 min. They were observed for more than 7 h throughout North America. TEC oscillations with a period of ~4 min were also observed to the south of Moore for more than 8 h. A comparison between the TEC observations and infrared cloud image from the GOES satellite indicates that the concentric waves and short-period oscillations are caused by supercell-induced atmospheric gravity waves and acoustic resonances, respectively. This observational result provides the first clear evidence of a severe meteorological event causing atmospheric waves propagating upward in the upper atmosphere and reaching the ionosphere.

  18. Large-amplitude plasma wave generation with a high-intensity short-pulse beat wave.

    PubMed

    Walton, B; Najmudin, Z; Wei, M S; Marle, C; Kingham, R J; Krushelnick, K; Dangor, A E; Clarke, R J; Poulter, M J; Hernandez-Gomez, C; Hawkes, S; Neely, D; Collier, J L; Danson, C N; Fritzler, S; Malka, V

    2002-12-15

    A short-pulse laser beat wave scheme for advanced particle accelerator applications is examined. A short, intense (3-ps, >10(18)-W cm(-2)) two-frequency laser pulse is produced by use of a modified chirped-pulse amplification scheme and is shown to produce relativistic plasma waves during interactions with low-density plasmas. The generation of plasma waves was observed by measurement of forward Raman scattering. Resonance was found to occur at an electron density many times that expected, owing to ponderomotive displacement of plasma within the focal region. PMID:18033483

  19. Adaptive optics at short wavelengths. Expected performance and sky coverage of the FLAO system going toward visible wavelengths

    NASA Astrophysics Data System (ADS)

    Agapito, Guido; Arcidiacono, Carmelo; Quirs-Pacheco, F.; Esposito, Simone

    2014-11-01

    The First Light Adaptive Optics (FLAO) system has been successfully commissioned at the Large Binocular Telescope. It delivers extreme adaptive optics performance using bright natural guide stars reaching 90 % Strehl Ratios in H-band. Observations with current adaptive optics systems are limited to the near infrared wavelengths, in these bands the diffraction limited resolution of the largest ground-based telescopes (8-10 meter class) is comparable to the one of the much smaller Hubble Space Telescope that observes in the visible bands. This study aims to demonstrate the feasibility of an adaptive optics system designed to achieve very high order correction at visible wavelengths (0.5 to 0.8 ? m) with significant sky coverage. Upgrading the FLAO design with a low noise CCD relaxes the reference magnitude limit needed to achieve greater performance. In particular, we demonstrate that a gain of 1-2 magnitudes is possible by upgrading the wavefront sensor with a very low read out noise CCD. For future AO systems, in addition to low noise CCDs, deformable (secondary) mirrors with a higher actuator density will be able to move the high order correction capability from the near infrared to the visible wavelengths (Strehl Ratio of 80 % in R (0.7 ? m), 60 % in V (0.5 ? m)). We investigate, by means of numerical simulation, the gain in imaging performance obtained at Near Infrared, Visible, and UV wavelengths. The results of these simulations have been used to derive the empirical relation between Strehl Ratio and magnitude of the reference star and we then use this relationship to perform a detailed sky coverage analysis based on astronomical catalog data. The detailed simulations of the Point Spread Functions allow us to compute Ensquared Energy and Strehl Ratio for the magnitude working range of such an Adaptive Optics system. We present the results of the instrumental isoplanatic angle determination. We then used these values to compute the relationship between correction level and the off-axis angle from the reference star. The Strehl Ratio relationship with the reference magnitude and the angular distance provides the information needed to perform the sky-coverage analysis, which demonstrates that the designed system is able to provide V and R bands correction on a not negligible few percent of the sky.

  20. Automated model-based calibration of short-wavelength infrared (SWIR) imaging spectrographs.

    PubMed

    Kosec, Matjaž; Bürmen, Miran; Tomaževič, Dejan; Pernuš, Franjo; Likar, Boštjan

    2012-10-01

    Among the variety of available hyperspectral imaging systems, the line-scan technique stands out for its short acquisition time and good signal-to-noise ratio. However, due to imperfections in the camera lens and, in particular, optical components of the imaging spectrograph, the acquired images are spatially and spectrally distorted, which can significantly degrade the accuracy of the subsequent hyperspectral image analysis. In this work, we propose and evaluate an automated method for correction of spatial and spectral distortions introduced by a line-scan hyperspectral imaging system operating in the short wavelength infrared (SWIR) spectral range from 1000 nm to 2500 nm. The proposed method is based on non-rigid registration of the distorted and reference images corresponding to two passive calibration objects. The results of the validation show that the proposed method is accurate, efficient, and applicable for calibration of line-scan hyperspectral imaging systems. Moreover, the design of the method and of the calibration objects allows integration with systems operating in diffuse reflectance or transmittance modes. PMID:23031695

  1. MHz gravitational waves from short-term anisotropic inflation

    NASA Astrophysics Data System (ADS)

    Ito, Asuka; Soda, Jiro

    2016-04-01

    We reveal the universality of short-term anisotropic inflation. As a demonstration, we study inflation with an exponential type gauge kinetic function which is ubiquitous in models obtained by dimensional reduction from higher dimensional fundamental theory. It turns out that an anisotropic inflation universally takes place in the later stage of conventional inflation. Remarkably, we find that primordial gravitational waves with a peak amplitude around 10-26~ 10-27 are copiously produced in high-frequency bands 10 MHz~100 MHz. If we could detect such gravitational waves in future, we would be able to probe higher dimensional fundamental theory.

  2. Spectral tuning and evolution of primate short-wavelength-sensitive visual pigments

    PubMed Central

    Carvalho, Livia S.; Davies, Wayne L.; Robinson, Phyllis R.; Hunt, David M.

    2012-01-01

    The peak sensitivities (λmax) of the short-wavelength-sensitive-1 (SWS1) pigments in mammals range from the ultraviolet (UV) (360–400 nm) to the violet (400–450 nm) regions of the spectrum. In most cases, a UV or violet peak is determined by the residue present at site 86, with Phe conferring UV sensitivity (UVS) and either Ser, Tyr or Val causing a shift to violet wavelengths. In primates, however, the tuning mechanism of violet-sensitive (VS) pigments would appear to differ. In this study, we examine the tuning mechanisms of prosimian SWS1 pigments. One species, the aye-aye, possesses a pigment with Phe86 but in vitro spectral analysis reveals a VS rather than a UVS pigment. Other residues (Cys, Ser and Val) at site 86 in prosimians also gave VS pigments. Substitution at site 86 is not, therefore, the primary mechanism for the tuning of VS pigments in primates, and phylogenetic analysis indicates that substitutions at site 86 have occurred at least five times in primate evolution. The sole potential tuning site that is conserved in all primate VS pigments is Pro93, which when substituted by Thr (as found in mammalian UVS pigments) in the aye-aye pigment shifted the peak absorbance into the UV region with a λmax value at 371 nm. We, therefore, conclude that the tuning of VS pigments in primates depends on Pro93, not Tyr86 as in other mammals. However, it remains uncertain whether the initial event that gave rise to the VS pigment in the ancestral primate was achieved by a Thr93Pro or a Phe86Tyr substitution. PMID:21697177

  3. Short wavelength undulatory extinction in quartz recording coseismic deformation in the middle crust - an experimental study

    NASA Astrophysics Data System (ADS)

    Trepmann, C. A.; Stckhert, B.

    2013-04-01

    Deformation experiments are carried out on natural vein quartz in a modified Griggs-type solid medium apparatus to explore the preservation potential of microfabrics created by crystal-plastic deformation at high stress, overprinted during subsequent creep at lower stress. a corresponding stress history is expected for the upper plastosphere, where fault slip during an earthquake causes quasi-instantaneous loading to high stress, followed by stress relaxation. The question is whether evidence of crystal-plastic deformation at high stress, hence an indicator of past seismic activity, can still be identified in the microstructure after overprint by creep at lower stresses. Firstly, quartz samples are deformed at a temperature of 400 C and constant strain rate of 10-4 s-1 ("kick"), and then held at 900 to 1000 C at residual stress ("creep"). In quartz exclusively subject to high-stress deformation, lamellar domains of slightly differing crystallographic orientation (misorientation angle <2) and a few tens of micrometers wide occur. In transmission electron microscope (TEM), these areas show a high density of tangled dislocations and cellular structures. After "kick and creep" experiments, pronounced short-wavelength undulatory extinction (SWUE) is observed in the optical microscope. The wavelength of SWUE is up to 10 ?m, with oscillatory misorientation of up to a few degrees. TEM inspection reveals domains with high density of dislocations and differing diffraction contrast bound by poorly-ordered dislocation walls. Only zones with exceptional damage generated during high-stress deformation are replaced by small new grains with a diameter of about 10 to 20 ?m, forming strings of recrystallized grains. For large original grains showing SWUE, the Schmid factor for basal ?a? glide is found to be high. SWUE is taken to reflect high-stress crystal-plastic deformation, the modified microstructure being sufficiently stable to be recognized after subsequent creep as an indicator of past seismic activity.

  4. The Design of the Short Wavelength Camera for the CCAT Telescope

    NASA Astrophysics Data System (ADS)

    Stacey, Gordon J.; Parshley, S.; Nikola, T.; Dowell, C. D.; Adams, J. D.; Bertoldi, F.; Chapman, S.; Cortes, G.; Day, P.; Glenn, J.; Halpern, M.; Hollister, M.; Kovacs, A.; LeDuc, H.; McKenney, C.; Monroe, R.; Mroczkowski, T.; Nguyen, H. T.; Niemack, M.; Rajagopalan, G.; Radford, S. J.; Schaaf, R.; Scott, D.; Schoenwald, J.; Swenson, L.; Yoshida, H.; Zmuidzinas, J.

    2013-01-01

    We present the design for the Short Wavelength Camera (SWCam) that we are proposing for use on the 25 meter CCAT submillimeter telescope. SWCam utilizes the absorber-coupled MKID based detector arrays that are being developed at JPL, and will soon be tested in the MAKO camera on the CSO. The primary SWCam band is centered on the 350 um telluric window but we plan capabilities in the 450 and 200 um telluric windows as well. Due to the curvature of the CCAT focal plane, the camera is split into 7 sub-cameras - a central camera and six cameras in a closed-packed outer ring. Each silicon lens-based camera illuminates an array consisting of ~7750 pixels with a plate scale of 3”/pixel which corresponds to an image plane sampling of lambda/D per pixel at 350 um. The combined pixel count is ~ 54,000 and the effective instantaneous field of view is ~ 13’ in diameter. All the cameras are contained in a single closed-cycle cryostat simplifying the optical/cryo/mechanical systems. The system is expected to achieve a back-ground limited sensitivity ~20 to 30 mJy/sqrt(Hz) under good weather conditions 0.43 mm precipitatable water vapor burden), so that the SWCam on CCAT approaches (5 sigma) the expected confusion noise for distant infrared bright galaxies on CCAT (<1 mJy) in about 4 hours integration time, and can map a degree of sky to this limit in about 100 hours of integration time. The primary science for SWCam is to investigate star, galaxy and structure formation over cosmic time through large scale (10s of square degrees) surveys in the submm continuum bands. SWCam is a key part of a triad of instruments that enable this science, including a long wavelength camera (LWCam), and a broad-band direct detection spectrometer (X-Spec) - instruments also described within this session.

  5. TES arrays for the short wavelength band of the SAFARI instrument on SPICA

    NASA Astrophysics Data System (ADS)

    Khosropanah, P.; Hijmering, R.; Ridder, M.; Gao, J. R.; Morozov, D.; Mauskopf, P. D.; Trappe, N.; O'Sullivan, C.; Murphy, A.; Griffin, D.; Goldie, D.; Glowacka, D.; Withington, S.; Jackson, B. D.; Audley, M. D.; de Lange, G.

    2012-09-01

    SPICA is an infra-red (IR) telescope with a cryogenically cooled mirror (~5K) with three instruments on board, one of which is SAFARI that is an imaging Fourier Transform Spectrometer (FTS) with three bands covering the wavelength of 34-210 μm. We develop transition edge sensors (TES) array for short wavelength band (34-60 μm) of SAFARI. These are based on superconducting Ti/Au bilayer as TES bolometers with a Tc of about 105 mK and thin Ta film as IR absorbers on suspended silicon nitride (SiN) membranes. These membranes are supported by long and narrow SiN legs that act as weak thermal links between the TES and the bath. Previously an electrical noise equivalent power (NEP) of 4×10-19 W/√Hz was achieved for a single pixel of such detectors. As an intermediate step toward a full-size SAFARI array (43×43), we fabricated several 8×9 detector arrays. Here we describe the design and the outcome of the dark and optical tests of several of these devices. We achieved high yield (<93%) and high uniformity in terms of critical temperature (<5%) and normal resistance (7%) across the arrays. The measured dark NEPs are as low as 5×10-19 W/√Hz with a response time of about 1.4 ms at preferred operating bias point. The optical coupling is implemented using pyramidal horns array on the top and hemispherical cavity behind the chip that gives a measured total optical coupling efficiency of 30±7%.

  6. Non-destructive determination of metronidazole powder by using artificial neural networks on short-wavelength NIR spectroscopy

    NASA Astrophysics Data System (ADS)

    Zhao, Lingzhi; Dou, Ying; Mi, Hong; Ren, Meiyan; Ren, Yulin

    2007-04-01

    The present study aimed at providing a new method in sight into short-wavelength near-infrared (NIR) spectroscopy of in pharmaceutical quantitative analysis. To do that, 124 experimental samples of metronidazole powder were analyzed using artificial neural networks (ANNs) in the 780-1100 nm region of short-wavelength NIR spectra. In this paper, metronidazole was as active component and other two components (magnesium stearate and starch) were as excipients. Different preprocessing spectral data (first-derivative, second-derivative, standard normal variate (SNV) and multiplicative scatter correction (MSC)) were applied to establish the ANNs models of metronidazole powder. The degree of approximation, a new evaluation criterion of the networks was employed to prove the accuracy of the predicted results. The results presented here demonstrate that the short-wavelength NIR region is promising for the fast and reliable determination of major component in pharmaceutical analysis.

  7. The 248 nm - new short wavelength for pumping lasers employing vapors of complex molecules

    SciTech Connect

    Gruzinskiy, V.V.; Degtyarenko, K.M.; Kopylova, T.N.; Pavlova, V.T.

    1984-09-01

    Lasing at lambda-248 nm is achieved in an excimer laser by increasing the stability of the excited molecules by using an outside gas and a compound in which the quantum yield changes little as the stored vibrational energy increases. Pentane was used in the first case, and perylene in the second. The fluorescence spectra of pure vapors of POPOP and perylene are presented. Different classes of organic compounds with which lasing at lambda 248 nm is achieved are presented. The lasing with vapors of organic compounds excited by high energy light quanta indicates the possibility of lasing with complex molecules in the short wave ultraviolet region of the spectrum, as well as the efficiency of transforming the powerful radiation from excimer lasers to the near ultraviolet and visible portion of the spectrum.

  8. A study of short wave instability on vortex filaments

    SciTech Connect

    Wang, Hong Yun

    1996-12-01

    The numerical stability and accuracy of the vortex method are studied. The effect of the ordinary differential equations (ODE) solver and of the time step on the numerical stability is analyzed. Various ODE solvers are compared and a best performer is chosen. A new constraint on the time step based on numerical stability is proposed and verified in numerical simulations. It is shown through numerical examples that empirical rules for selecting the spatial discretization obtained in simple test problems may not be extended to more general problems. The thin tube vortex filament method is applied to the problem of Widnall`s instability on vortex rings. Numerical results different from previous calculations are presented and the source of the discrepancies is explained. The long time behavior of the unstable mode on thin vortex rings is simulated and analyzed. The short wave instability on vortex filaments is investigated both theoretically and numerically. It is shown that the short wave instability always occurs on co-rotating vortex filaments of fixed core structure. Furthermore when they are close to each other, vortex filaments produce short wave unstable modes which lead to wild stretching and folding. However, when the inter-filament distance is large in comparison with the core size of the filaments, unstable modes are bounded by a small fraction of the core size and the vortex filaments do not create hairpins nor wild stretching. These findings may explain the smooth behavior of the superfluid vortices. The formation of hairpin structures on numerical vortex filaments is investigated. It is shown that the formation of hairpin structures is independent of the ODE solver, of the time step and of other numerical parameters. The hairpin structures are primarily caused by short wave instability on co-rotating vortex filaments.

  9. Coherence of sonic waves at short near-surface paths

    NASA Astrophysics Data System (ADS)

    Mamyshev, V. P.; Odintsov, S. L.

    2015-11-01

    The coherence of sonic waves at short paths in the atmospheric surface layer is analyzed. The violation of coherence is considered from the viewpoint of variations of phase difference in spatially separated observation sites. The statistics of phase difference at the multichannel reception of signals and its correlation with the statistics of the wind field are studied. Meteorological conditions at the sound propagation path were monitored by ultrasonic anemometersthermometers.

  10. Wavelength dependence of eddy dissipation and Coriolis force in the dynamics of gravity wave driven fluctuations in the OH nightglow

    NASA Technical Reports Server (NTRS)

    Hickey, M. P.

    1988-01-01

    This paper examines the effect of inclusion of Coriolis force and eddy dissipation in the gravity wave dynamics theory of Walterscheid et al. (1987). It was found that the values of the ratio 'eta' (where eta is a complex quantity describing the ralationship between the intensity oscillation about the time-averaged intensity, and the temperature oscillation about the time-averaged temperature) strongly depend on the wave period and the horizontal wavelength; thus, if comparisons are to be made between observations and theory, horizontal wavelengths will need to be measured in conjunction with the OH nightglow measurements. For the waves with horizontal wavelengths up to 1000 km, the eddy dissipation was found to dominate over the Coriolis force in the gravity wave dynamics and also in the associated values of eta. However, for waves with horizontal wavelengths of 10,000 km or more, the Coriolis force cannot be neglected; it has to be taken into account along with the eddy dissipation.

  11. Short wind waves on the ocean: Long-wave and wind-speed dependences

    NASA Astrophysics Data System (ADS)

    Plant, William J.

    2015-09-01

    This second paper of our set on short wind waves on the ocean utilizes the wavenumber-frequency spectrum of short wave heights, F(k,f), derived in our previous paper to investigate kinematic effects on the dependence of the frequency spectrum, F(f), and the wavenumber spectrum, F(k), on long-wave height. We show that the model predicts that neither F(f) nor F(k) are exactly power law functions of their independent variables and that F(f) varies with significant wave height much more than F(k) does. After calibrating the model against wave gauges, we also investigate the dependence of mean-square-slopes (mss), mean-square heights (msh) and root-mean-square orbital velocities (rmsv) of short ocean waves on wind speed and maximum frequency or wavenumber. We use data from the wire wave gauges on University of Miami's Air-Sea Interaction Spar (ASIS) buoy for calibration purposes. Frequency spectra from the wave gauges begin to be affected by noise at about 2.5 Hz. Therefore, above 1 Hz, we utilize F(f) from the modeled F(k,f) to extend the frequency dependence up to 180 Hz. We set modeled spectral densities by matching measured spectra at 1 Hz. Using the calibrated F(f,k), we are able to estimate the average value of the total mss, for long and short waves, and its upwind and crosswind components up to 180 Hz for a variety of wind speeds. The average mss values are in good agreement with the measurements of Cox and Munk [1954], although the upwind and crosswind components agree less well.

  12. The Rigorous Approximation of Long-Wavelength Capillary-Gravity Waves

    NASA Astrophysics Data System (ADS)

    Schneider, Guido; Wayne, C. Eugene

    In a previous paper we proved that long-wavelength solutions of the water-wave problem in the case of zero surface tension split up into two wave packets, one moving to the right and one to the left, where each of these wave packets evolves independently as a solution of a Korteweg-de Vries (KdV) equation. In this paper we examine the effect of surface tension on this scenario. We find that we obtain three different physical regimes depending on the strength of the surface tension. For weak surface tension, the propagation of the wave packets is very similar to that in the zero surface tension case. For strong surface tension, the evolution is again governed by a pair of KdV equations, but the coefficients in these equations have changed in such a way that the KdV soliton now represents a wave of depression on the fluid surface. Finally, at a special, intermediate value of the surface tension (where the Bond number equals 1/3 ) the KdV description breaks down and it is necessary to introduce a new approximating equation, the Kawahara equation, which is a fifth order, nonlinear partial differential equation. In each of these regimes we give rigorous estimates of the difference between the solution of the appropriate modulation equation and the solution of the true water-wave problem.

  13. Coherent reflection in a two-dimensional cochlea: Short-wave versus long-wave scattering in the generation of reflection-source otoacoustic emissions.

    PubMed

    Shera, Christopher A; Tubis, Arnold; Talmadge, Carrick L

    2005-07-01

    The theory of coherent reflection filtering explains the empirical form of the cochlear reflectance by showing how it emerges from the coherent "backscattering" of forward-traveling waves by impedance perturbations in the mechanics of the cochlear partition. Since the theory was developed using the one-dimensional (1-D) transmission-line model of the cochlea, an obvious logical shortcoming is the failure of the long-wavelength approximation near the peak of the traveling wave, where coherent backscattering is purported to occur. Indeed, existing theory suggests that wave reflection may be strongly suppressed in the short-wave regime. To understand how short-wave behavior near the peak modifies the predictions of the long-wave theory, this paper solves the scattering problem in the 2-D cochlear model. The 2-D problem is reduced to a 1-D wave equation and the solution expressed as an infinite series in which successive terms arise via multiple scattering within the cochlea. The cochlear reflectance is computed in response-matched models constructed by solving the inverse problem to control for variations in mechanical tuning among models of different heights and dimensionality. Reflection from the peak region is significantly enhanced by the short-wave hydrodynamics, but other conclusions of the 1-D analysis--such as the predicted relation between emission group delay and the wavelength of the traveling wave--carry over with only minor modifications. The results illustrate the important role of passive hydromechanical effects in shaping otoacoustic emissions and cochlear tuning. PMID:16119350

  14. Characteristics of short-period internal waves in the Kara Sea inferred from satellite SAR data

    NASA Astrophysics Data System (ADS)

    Kozlov, I. E.; Kudryavtsev, V. N.; Zubkova, E. V.; Zimin, A. V.; Chapron, B.

    2015-12-01

    In this paper we present the results of short-period internal wave (SIW) observations in the Kara Sea on the basis of satellite ENVISAT ASAR data between July and October 2007. Altogether, 248 internal wave (IW) packets and solitons are identified in 89 SAR images. Detailed spatial statistics of IW signatures and their properties in the Kara Sea is presented. The primary regions of IW activity are the areas near the Kara Gates Strait, the southeastern part of the Novaya Zemlya Trough, and in the vicinity of Cape Zhelaniya. We identify the regions where large IW packets are observed with wavelengths up to 2-3 km and the front length exceeding 200 km. The mean interpacket distance for observed IWs is about 20 km, but it may reach 50-60 km. Consequent IW packets are observed to travel up to 500 km from the presumed generation points. The results of satellite observations are compared with results of previous studies.

  15. A conserved aromatic residue regulating photosensitivity in short-wavelength sensitive cone visual pigments.

    PubMed

    Kuemmel, Colleen M; Sandberg, Megan N; Birge, Robert R; Knox, Barry E

    2013-07-30

    Visual pigments have a conserved phenylalanine in transmembrane helix 5 located near the β-ionone ring of the retinal chromophore. Site-directed mutants of this residue (F207) in a short-wavelength sensitive visual pigment (VCOP) were studied using UV-visible spectroscopy to investigate its role in photosensitivity and formation of the light-activated state. The side chain is important for pigment formation: VCOP(F207A), VCOP(F207L), VCOP(F207M), and VCOP(F207W) substitutions all bound 11-cis-retinal and formed a stable visual pigment, while VCOP(F207V), VCOP(F207S), VCOP(F207T), and VCOP(F207Y) substitutions do not. The extinction coefficients of all pigments are close, ranging between 35800 and 45600 M⁻¹ cm⁻¹. Remarkably, the mutants exhibit an up to 5-fold reduction in photosensitivity and also abnormal photobleaching behavior. One mutant, VCOP(F207A), forms an isomeric composition of the retinal chromophore after illumination comparable to that of wild-type VCOP yet does not release the all-trans-retinal chromophore. These findings suggest that the conserved F207 residue is important for a normal photoactivation pathway, formation of the active conformation and the exit of all-trans-retinal from the chromophore-binding pocket. PMID:23808485

  16. Conserved residues in the extracellular loops of short-wavelength cone visual pigments.

    PubMed

    Chen, Min-Hsuan; Sandberg, Daniel J; Babu, Kunnel R; Bubis, Jose; Surya, Arjun; Ramos, Lavoisier S; Zapata, Heidi J; Galan, Jhenny F; Sandberg, Megan N; Birge, Robert R; Knox, Barry E

    2011-08-16

    The role of the extracellular loop region of a short-wavelength sensitive pigment, Xenopus violet cone opsin, is investigated via computational modeling, mutagenesis, and spectroscopy. The computational models predict a complex H-bonding network that stabilizes and connects the EC2-EC3 loop and the N-terminus. Mutations that are predicted to disrupt the H-bonding network are shown to produce visual pigments that do not stably bind chromophore and exhibit properties of a misfolded protein. The potential role of a disulfide bond between two conserved Cys residues, Cys(105) in TM3 and Cys(182) in EC2, is necessary for proper folding and trafficking in VCOP. Lastly, certain residues in the EC2 loop are predicted to stabilize the formation of two antiparallel β-strands joined by a hairpin turn, which interact with the chromophore via H-bonding or van der Waals interactions. Mutations of conserved residues result in a decrease in the level of chromophore binding. These results demonstrate that the extracellular loops are crucial for the formation of this cone visual pigment. Moreover, there are significant differences in the structure and function of this region in VCOP compared to that in rhodopsin. PMID:21688771

  17. Ultraviolet and short wavelength visible light exposure: why ultraviolet protection alone is not adequate.

    PubMed

    Reichow, Alan W; Citek, Karl; Edlich, Richard F

    2006-01-01

    The danger of exposure to ultraviolet (UV) radiation in both the natural environment and artificial occupational settings has long been recognized by national and international standards committees and worker safety agencies. There is an increasing body of literature that suggests that protection from UV exposure is not enough. Unprotected exposure to the short wavelengths of the visible spectrum, termed the "blue light hazard", is gaining acceptance as a true risk to long-term visual health. Global standards and experts in the field are now warning that those individuals who spend considerable time outdoors should seek sun filter eyewear with high impact resistant lenses that provide 100% UV filtration, high levels of blue light filtration, and full visual field lens/frame coverage as provided by high wrap eyewear. The Skin Cancer Foundation has endorsed certain sunglasses as "product[s]...effective [as] UV filter[s] for the eyes and surrounding skin". However, such endorsement does not necessarily mean that the eyewear meets all the protective needs for outdoor use. There are several brands that offer products with such protective characteristics. Performance sun eyewear by Nike Vision, available in both corrective and plano (nonprescription) forms, is one such brand incorporating these protective features. PMID:17073573

  18. Short-wavelength sensitive opsin (SWS1) as a new marker for vertebrate phylogenetics

    PubMed Central

    van Hazel, Ilke; Santini, Francesco; Müller, Johannes; Chang, Belinda SW

    2006-01-01

    Background Vertebrate SWS1 visual pigments mediate visual transduction in response to light at short wavelengths. Due to their importance in vision, SWS1 genes have been isolated from a surprisingly wide range of vertebrates, including lampreys, teleosts, amphibians, reptiles, birds, and mammals. The SWS1 genes exhibit many of the characteristics of genes typically targeted for phylogenetic analyses. This study investigates both the utility of SWS1 as a marker for inferring vertebrate phylogenetic relationships, and the characteristics of the gene that contribute to its phylogenetic utility. Results Phylogenetic analyses of vertebrate SWS1 genes produced topologies that were remarkably congruent with generally accepted hypotheses of vertebrate evolution at both higher and lower taxonomic levels. The few exceptions were generally associated with areas of poor taxonomic sampling, or relationships that have been difficult to resolve using other molecular markers. The SWS1 data set was characterized by a substantial amount of among-site rate variation, and a relatively unskewed substitution rate matrix, even when the data were partitioned into different codon sites and individual taxonomic groups. Although there were nucleotide biases in some groups at third positions, these biases were not convergent across different taxonomic groups. Conclusion Our results suggest that SWS1 may be a good marker for vertebrate phylogenetics due to the variable yet consistent patterns of sequence evolution exhibited across fairly wide taxonomic groups. This may result from constraints imposed by the functional role of SWS1 pigments in visual transduction. PMID:17107620

  19. High detectivity short-wavelength II-VI quantum cascade detector

    SciTech Connect

    Ravikumar, Arvind P. Gmachl, Claire F.; Garcia, Thor A.; Tamargo, Maria C.; Jesus, Joel De

    2014-08-11

    We report on the experimental demonstration of a ZnCdSe/ZnCdMgSe-based short-wavelength photovoltaic Quantum Cascade Detector (QCD). The QCD operates in two spectral bands centered around 2.6 μm and 3.6 μm. Calibrated blackbody measurements yield a peak responsivity of 0.1 mA/W or 2400 V/W at 80 K, and a corresponding 300 K background radiation limited infrared performance detectivity (BLIP) of ∼2.5 × 10{sup 10 }cm √Hz/W. Comparison of background illuminated and dark current-voltage measurements demonstrates a BLIP temperature of 200 K. The device differential resistance-area product, decreases from about 10{sup 6} Ω cm{sup 2} at 80 K to about 8000 Ω cm{sup 2} at 300 K, indicative of the ultra-low Johnson noise in the detectors.

  20. High dynamic solutions for short-wavelength infrared imaging based on InGaAs

    NASA Astrophysics Data System (ADS)

    Reverchon, Jean-Luc; Decobert, Jean; Djedidi, Anis; Gentner, Jean-Louis; Huet, Odile; Lagay, Nadine; Rouvié, Anne; Robo, Jean-Alexandre; Truffer, Jean-Patrick; Costard, Eric; Ni, Yang; Arion, Bogdan; Zhu, Yiming; Potet, Pierre

    2011-06-01

    Short-wavelength infrared image sensors based on p-i-n photodiode arrays present a tremendous interest in applications such as passive and active imagery for laser detection/warning, hot spot or detection for lasers sensors, enhanced vision systems or low light level sensors. The capability to work at room temperature with dark current equivalent to silicon-based devices is another motivation for the fast development of this technology. This paper presents several modules and camera based on InGaAs photodiode arrays from the III-VLab. First, we describe the electro-optics performance in terms of dark signal, sensitivity, and particularly the visible extension capability. We also present a nucless logarithmic sensor based on a 1/2 video graphics array (VGA) format at a pitch of 25 μm initially designed for visible CMOS camera chip. We will also present the next generation of focal plane arrays based on a VGA format of 640×512 pixels with a pitch of 15 μm. This array will be associated to a CTIA readout circuit and also to an innovative CMOS logarithmic wide dynamic range ROIC, developed by New Imaging Technologies. This VGA logarithmic device developed for automotive safety will involve visible extension capability in a European project named 2Wide_sense.

  1. Conserved Residues in the Extracellular Loops of Short-Wavelength Cone Visual Pigments

    PubMed Central

    Chen, Min-Hsuan; Sandberg, Daniel J.; Babu, Kunnel R.; Bubis, Jose; Surya, Arjun; Ramos, Lavoisier S.; Zapata, Heidi J.; Galan, Jhenny F.; Sandberg, Megan N.; Birge, Robert R.; Knox, Barry E.

    2012-01-01

    The role of the extracellular loop region of a short-wavelength sensitive pigment, Xenopus violet cone opsin, is investigated via computational modeling, mutagenesis, and spectroscopy. The computational models predict a complex H-bonding network which stabilizes and connects the EC2-EC3 loop and the N-terminus. Mutations which are predicted to disrupt the H-bonding network are shown to produce visual pigments that do not stably bind chromophore and exhibit properties of misfolded protein. The potential role of a disulfide bond between two conserved Cys residues, Cys105 in TM3 and Cys182 in EC2, is necessary for proper folding and trafficking in VCOP. Lastly, certain residues in the EC2 loop are predicted to stabilize the formation of two anti-parallel β strands joined by a hairpin turn, which interact with the chromophore via H-bonding or Van der Waals interactions. Mutations to conserved residues result in a decrease in chromophore binding. These results demonstrate that the extracellular loops are crucial for the formation of this cone visual pigment. Moreover, there are significant differences in structure and function of this region in VCOP compared to rhodopsin. PMID:21688771

  2. Wavelength and temperature dependence of continuous-wave laser absorptance in Kapton thin films

    NASA Astrophysics Data System (ADS)

    Palm, William J.; Marciniak, Michael A.; Perram, Glen P.; Gross, Kevin C.; Bailey, William F.; Walters, Craig T.

    2012-12-01

    Optical properties and laser damage characteristics of thin-film aluminized Kapton were investigated. Spectral absorptance of virgin and irradiated samples was measured from the Kapton side of multilayered insulation over 0.2 to 15 μm wavelengths at both room temperature and 150°C. The laser-damage parameters of penetration time and maximum temperature were then measured in a vacuum environment at laser wavelengths of 1.07 and 10.6 μm. Differences in damage behavior at these two wavelengths were observed due to differences in starting absorption properties at these wavelengths. During laser irradiation, the Kapton thin film was observed with a calibrated FLIR thermal imager in the 8 to 9.2 μm band to determine its temperature evolution. Spectral radiance throughout the mid- and long-wave infrared was also observed with a Fourier transform spectrometer, allowing temperature-dependent spectral emittance to be determined. Kapton emittance increased after the material heated past approximately 500°C, and continued to increase as it cooled posttest. This evolving temperature-dependent spectral emittance successfully predicts the increasing absorptance that led to shortened penetration times and increased heating rates for the 1.07 μm laser. For tests with constant absorptance and no material breakdown, a simplified one-dimensional thermal conduction and radiation model successfully predicts the temporally evolving temperature.

  3. Spectral tuning in vertebrate short wavelength-sensitive 1 (SWS1) visual pigments: can wavelength sensitivity be inferred from sequence data?

    PubMed

    Hauser, Frances E; van Hazel, Ilke; Chang, Belinda S W

    2014-11-01

    The molecular mechanisms underlying the enormous diversity of visual pigment wavelength sensitivities found in nature have been the focus of many molecular evolutionary studies, with particular attention to the short wavelength-sensitive 1 (SWS1) visual pigments that mediate vision in the ultraviolet to violet range of the electromagnetic spectrum. Over a decade of study has revealed that the remarkable extension of SWS1 absorption maxima (λ max ) into the ultraviolet occurs through a deprotonation of the Schiff base linkage of the retinal chromophore, a mechanism unique to this visual pigment type. In studies of visual ecology, there has been mounting interest in inferring visual sensitivity at short wavelengths, given the importance of UV signaling in courtship displays and other behaviors. Since experimentally determining spectral sensitivities can be both challenging and time-consuming, alternative strategies such as estimating λ max based on amino acids at sites known to affect spectral tuning are becoming increasingly common. However, these estimates should be made with knowledge of the limitations inherent in these approaches. Here, we provide an overview of the current literature on SWS1 site-directed mutagenesis spectral tuning studies, and discuss methodological caveats specific to the SWS1-type pigments. We focus particular attention on contrasting avian and mammalian SWS1 spectral tuning mechanisms, which are the best studied among vertebrates. We find that avian SWS1 visual pigment spectral tuning mechanisms are fairly consistent, and therefore more predictable in terms of wavelength absorption maxima, whereas mammalian pigments are not well suited to predictions of λ max from sequence data alone. PMID:24890094

  4. Multi-photon ionization of atoms in intense short-wavelength radiation fields

    NASA Astrophysics Data System (ADS)

    Meyer, Michael

    2015-05-01

    The unprecedented characteristics of XUV and X-ray Free Electron Lasers (FELs) have stimulated numerous investigations focusing on the detailed understanding of fundamental photon-matter interactions in atoms and molecules. In particular, the high intensities (up to 106 W/cm2) giving rise to non-linear phenomena in the short wavelength regime. The basic phenomenology involves the production of highly charged ions via electron emission to which both sequential and direct multi-photon absorption processes contribute. The detailed investigation of the role and relative weight of these processes under different conditions (wavelength, pulse duration, intensity) is the key element for a comprehensive understanding of the ionization dynamics. Here the results of recent investigations are presented, performed at the FELs in Hamburg (FLASH) and Trieste (FERMI) on atomic systems with electronic structures of increasing complexity (Ar, Ne and Xe). Mainly, electron spectroscopy is used to obtain quantitative information about the relevance of various multi-photon ionization processes. For the case of Ar, a variety of processes including above threshold ionization (ATI) from 3p and 3s valence shells, direct 2p two-photon ionization and resonant 2p-4p two-photon excitations were observed and their role was quantitatively determined comparing the experimental ionization yields to ab-initio calculations of the cross sections for the multi-photon processes. Using Ar as a benchmark to prove the reliability of the combined experimental and theoretical approach, the more complex and intriguing case of Xe was studied. Especially, the analysis of the two-photon ATI from the Xe 4d shell reveals new insight into the character of the 4d giant resonance, which was unresolved in the linear one-photon regime. Finally, the influence of intense XUV radiation to the relaxation dynamics of the Ne 2s-3p resonance was investigated by angle-resolved electron spectroscopy, especially be observing the intensity dependent variation of the angular distribution patterns for the sequential ionization process.

  5. Continuous-wave dual-wavelength Nd:YAG laser operation at 1319 and 1338 nm

    NASA Astrophysics Data System (ADS)

    Sun, G. C.; Lee, Y. D.; Zao, Y. D.; Xu, L. J.; Wang, J. B.; Chen, G. B.; Lu, J.

    2013-04-01

    We report an efficient continuous-wave (CW) dual-wavelength operation of an Nd:YAG (YAG: yttrium aluminum garnet) laser at 1319 and 1338 nm. An output power of 2.47 W for the dual-wavelength operation was achieved at the incident pump power of 16.7 W. Intracavity sum-frequency mixing at 1319 and 1338 nm was then realized in an LBO (lithium triborate) crystal to reach the red range. A maximum output power of 879 mW in the red spectral range at 664 nm has been achieved. The red output stability is better than 3.4%. The red beam quality M2 values are about 1.21 and 1.35 in the horizontal and vertical directions respectively.

  6. A short-wavelength infrared emitting multimodal probe for non-invasive visualization of phagocyte cell migration in living mice.

    PubMed

    Tsukasaki, Y; Komatsuzaki, A; Mori, Y; Ma, Q; Yoshioka, Y; Jin, T

    2014-11-28

    For the non-invasive visualization of cell migration in deep tissues, we synthesized a short-wavelength infrared (SWIR) emitting multimodal probe that contains PbS/CdS quantum dots, rhodamine 6G and iron oxide nanoparticles. This probe enables multimodal (SWIR fluorescence/magnetic resonance) imaging of phagocyte cell migration in living mice. PMID:25296382

  7. A comparative analysis of short- and long-wavelength multi-chip optical transmitter modules for optical PCBs applications

    NASA Astrophysics Data System (ADS)

    Shirazy, Md. S. M.; Ukaegbu, Augustune I.; Kim, Do-won; Lee, Tae-Woo; Cho, Mu Hee; Kim, Sung Jun; Yoo, Byueng-Su; Park, Hyo-Hoon

    2009-02-01

    Optical interface multichip modules promise to alleviate the bottlenecks of electrical interconnection. Two kinds of optical transmitter multichip module were fabricated for optical printed circuit board (OPCB) based interconnections for performance analysis. Each of the modules consist of 1 x 4 bottom-emitting VCSELs flip-chip bonded on a CMOS driver array IC for optical interconnection; among them one is an 850nm short-wavelength and the other is a 1310nm long-wavelength VCSEL. The short- and long-wavelength VCSELs have -3dB bandwidth of about 3.6 GHz and 2.6 GHz, respectively. Four-channel driver array which has been fabricated in a 0.18?m Si-CMOS technology requires 1.8V of power supply, is used for the both multichip transmitter modules. Short- and long-wavelength multichip modules are bumped with Au/Sn solder and gold stud bump wire respectively using the flip-chip bonding technology. The multichip modules have a dimension of 1.1mm x 1.2mm x 0.5mm for the four channels. The multichip module employing flip-chip bonding technology reduces unwanted crosstalk due to bond wires. The two modules showed BER less than 10-12 and clear eye openings at 2.5 Gbps. We measured the frequency response and crosstalk of long-wavelength multichip module and will compare them with the short-wavelength multichip module to evaluate which module is preferable for the optical interconnection applications on optical PCBs.

  8. Four-wave mixing stability in hybrid photonic crystal fibers with two zero-dispersion wavelengths.

    PubMed

    Sévigny, Benoit; Vanvincq, Olivier; Valentin, Constance; Chen, Na; Quiquempois, Yves; Bouwmans, Géraud

    2013-12-16

    The four-wave mixing process in optical fibers is generally sensitive to dispersion uniformity along the fiber length. However, some specific phase matching conditions show increased robustness to longitudinal fluctuations in fiber dimensions, which affect the dispersion, even for signal and idler wavelengths far from the pump. In this paper, we present the method by which this point is found, how the fiber design characteristics impact on the stable point and demonstrate the stability through propagation simulations using the non-linear Schrödinger equation. PMID:24514659

  9. Spoof four-wave mixing for all-optical wavelength conversion.

    PubMed

    Gong, Yongkang; Huang, Jungang; Li, Kang; Copner, Nigel; Martinez, J J; Wang, Leirang; Duan, Tao; Zhang, Wenfu; Loh, W H

    2012-10-01

    We present for the first time an all-optical wavelength conversion (AOWC) scheme supporting modulation format independency without requiring phase matching. The new scheme is named "spoof" four wave mixing (SFWM) and in contrast to the well-known FWM theory, where the induced dynamic refractive index grating modulates photons to create a wave at a new frequency, the SFWM is different in that the dynamic refractive index grating is generated in a nonlinear Bragg Grating (BG) to excite additional reflective peaks at either side of the original BG bandgap in reflection spectrum. This fundamental difference enable the SFWM to avoid the intrinsic shortcoming of stringent phase matching required in the conventional FWM, and allows AOWC with modulation format transparency and ultrabroad conversion range, which may have great potential applications for next generation of all-optical networks. PMID:23188370

  10. Wavelength dependence near a degeneracy point of lasing and 4-wave mixing processes in Na vapor

    SciTech Connect

    Yoakum, S.; Moorman, L.

    1993-05-01

    Accurate measurements were made of lasing and 4-wave mixing processes in Na-vapor inside a double heatpipe oven. Scanning Nd:YAG pumped pulsed dye laser through the two-photon resonance 3s{sup 2}S{sub 1/2} {yields} 5s{sup 2}S{sub 1/2}, and a high resolution double-monochromator near the 5s - 4p{sup 2}P{sub 1/2,3/2} single photon resonance, we easily distinguished the two lasing multiplets due to J = {1/2} and 3/2 populations emitting blue 330 nm light. We also observed two other components. By varying the laser polarization, intensity and Na density these were determined to be parametric 4-wave mixing lines with maximum intensity for slight phase mismatch. As the dye laser was scanned, the wavelengths of the lasing and 4-wave mixing peaks shifted, each pair with its own slope, and crossed - a process providing a spectroscopic pump mechanism to populate the {vert_bar}M{sub J} {>=}{vert_bar} + {1/2} > magnetic substate of the ground state. Similar experiments are underway for other 4 wave mixing processes.

  11. Internal structure of laser supported detonation waves by two-wavelength Mach-Zehnder interferometer

    SciTech Connect

    Shimamura, Kohei; Kawamura, Koichi; Fukuda, Akio; Wang Bin; Yamaguchi, Toshikazu; Komurasaki, Kimiya; Hatai, Keigo; Fukui, Akihiro; Arakawa, Yoshihiro

    2011-04-15

    Characteristics of the internal structure of the laser supported detonation (LSD) waves, such as the electron density n{sub e} and the electron temperature T{sub e} profiles behind the shock wave were measured using a two-wavelength Mach-Zehnder interferometer along with emission spectroscopy. A TEA CO{sub 2} laser with energy of 10 J/pulse produced explosive laser heating in atmospheric air. Results show that the peak values of n{sub e} and T{sub e} were, respectively, about 2 x 10{sup 24} m{sup -3} and 30 000 K, during the LSD regime. The temporal variation of the laser absorption coefficient profile estimated from the measured properties reveals that the laser energy was absorbed perfectly in a thin layer behind the shock wave during the LSD regime, as predicted by Raizer's LSD model. However, the absorption layer was much thinner than a plasma layer, the situation of which was not considered in Raizer's model. The measured n{sub e} at the shock front was not zero while the LSD was supported, which implies that the precursor electrons exist ahead of the shock wave.

  12. Results of testing short wavelength HgCdTe hybrid focal plane arrays for earth remote sensing applications

    NASA Technical Reports Server (NTRS)

    Blessinger, M. A.; Herring, M.

    1984-01-01

    The NASA Imaging Spectrometer program has the objective to develop the next generation of earth remote sensing systems. One part of the program is concerned with the production of advanced short-wavelength mercury cadmium telluride (HgCdTe) hybrid focal plane arrays (FPAs). These arrays are needed for several instruments, including the Shuttle Imaging Spectrometer (SIS), which requires a mosaic of six 64 x 64-element arrays with a cutoff wavelength of 2.5 microns. A device description is provided and the test results are considered. The Airborne Imaging Spectrometer (AIS) is discussed, taking into account an instrument description, focal plane requirements, and AIS results.

  13. From individual spiking neurons to population behavior: Systematic elimination of short-wavelength spatial modes

    NASA Astrophysics Data System (ADS)

    Steyn-Ross, Moira L.; Steyn-Ross, D. A.

    2016-02-01

    Mean-field models of the brain approximate spiking dynamics by assuming that each neuron responds to its neighbors via a naive spatial average that neglects local fluctuations and correlations in firing activity. In this paper we address this issue by introducing a rigorous formalism to enable spatial coarse-graining of spiking dynamics, scaling from the microscopic level of a single type 1 (integrator) neuron to a macroscopic assembly of spiking neurons that are interconnected by chemical synapses and nearest-neighbor gap junctions. Spiking behavior at the single-neuron scale ℓ ≈10 μ m is described by Wilson's two-variable conductance-based equations [H. R. Wilson, J. Theor. Biol. 200, 375 (1999), 10.1006/jtbi.1999.1002], driven by fields of incoming neural activity from neighboring neurons. We map these equations to a coarser spatial resolution of grid length B ℓ , with B ≫1 being the blocking ratio linking micro and macro scales. Our method systematically eliminates high-frequency (short-wavelength) spatial modes q ⃗ in favor of low-frequency spatial modes Q ⃗ using an adiabatic elimination procedure that has been shown to be equivalent to the path-integral coarse graining applied to renormalization group theory of critical phenomena. This bottom-up neural regridding allows us to track the percolation of synaptic and ion-channel noise from the single neuron up to the scale of macroscopic population-average variables. Anticipated applications of neural regridding include extraction of the current-to-firing-rate transfer function, investigation of fluctuation criticality near phase-transition tipping points, determination of spatial scaling laws for avalanche events, and prediction of the spatial extent of self-organized macrocolumnar structures. As a first-order exemplar of the method, we recover nonlinear corrections for a coarse-grained Wilson spiking neuron embedded in a network of identical diffusively coupled neurons whose chemical synapses have been disabled. Intriguingly, we find that reblocking transforms the original type 1 Wilson integrator into a type 2 resonator whose spike-rate transfer function exhibits abrupt spiking onset with near-vertical takeoff and chaotic dynamics just above threshold.

  14. Short monolithic dual-wavelength single-longitudinal-mode DBR phosphate fiber laser.

    PubMed

    Xiong, Lingyun; Hofmann, Peter; Schlzgen, Axel; Peyghambarian, N; Albert, Jacques

    2014-06-20

    We propose and demonstrate a 5-cm-long monolithic dual-wavelength single-longitudinal mode distributed Bragg reflector (DBR) all-phosphate fiber laser. Strong UV-induced fiber Bragg gratings are directly written in highly Er/Yb codoped phosphate fiber. The separation between gratings is selected as 1cm to only excite two longitudinal modes in the DBR cavity. By exploiting the spatial hole burning effect and the polarization hole burning effect, stable narrow-linewidth dual-wavelength lasing emission with 38pm wavelength spacing and a total emitted power of 2.8mW is obtained from this DBR fiber laser. A microwave signal at 4.58GHz is generated by the heterodyne detection of the dual-wavelength laser. PMID:24979414

  15. First Demonstration of the Echo-Enabled Harmonic Generation Technique for Short-Wavelength Seeded Free Electron Lasers

    SciTech Connect

    Xiang, D.; Colby, E.; Dunning, M.; Gilevich, S.; Hast, C.; Jobe, K.; McCormick, D.; Nelson, J.; Raubenheimer, T.O.; Soong, K.; Stupakov, G.; Szalata, Z.; Walz, D.; Weathersby, S.; Woodley, M.; Pernet, P.-L.; /Ecole Polytechnique, Lausanne

    2010-08-25

    We report the first experimental demonstration of the echo-enabled harmonic generation (EEHG) technique which holds great promise for generation of high power, fully coherent short-wavelength radiation. In this experiment, coherent radiation at the 3rd and 4th harmonic of the second seed laser is generated from the so-called beam echo effect. The experiment confirms the physics behind this technique and paves the way for applying the EEHG technique for seeded x-ray free electron lasers.

  16. Video rate nine-band multispectral short-wave infrared sensor.

    PubMed

    Kutteruf, Mary R; Yetzbacher, Michael K; DePrenger, Michael J; Novak, Kyle M; Miller, Corey A; Downes, Trijntje Valerie; Kanaev, Andrey V

    2014-05-01

    Short-wave infrared (SWIR) imaging sensors are increasingly being used in surveillance and reconnaissance systems due to the reduced scatter in haze and the spectral response of materials over this wavelength range. Typically SWIR images have been provided either as full motion video from framing panchromatic systems or as spectral data cubes from line-scanning hyperspectral or multispectral systems. Here, we describe and characterize a system that bridges this divide, providing nine-band spectral images at 30 Hz. The system integrates a custom array of filters onto a commercial SWIR InGaAs array. We measure the filter placement and spectral response. We demonstrate a simple simulation technique to facilitate optimization of band selection for future sensors. PMID:24921889

  17. Design and initial performance evaluation of a portable short wave infrared spectroradiometer

    NASA Technical Reports Server (NTRS)

    Smith, Mark W.

    1992-01-01

    The design, initial calibration, and performance evaluations of a portable short wave infrared (SWIR) spectroradiometer are described. The spectroradiometer covers the range from 1.1 to 2.5 microns with a spectral resolution that may be varied from less than 10 nm to more than 100 nm. A single spectrum is acquired in about 2 sec. The SNR is about 230 at a wavelength of 2.2 microns for a Lambertian surface of 90-percent reflectance illuminated by the sun at normal incidence with 14.8-nm resolution, a 25 C background temperature, and no atmospheric attenuation. FOV-defining optics are coupled by a flexible fiber-optics bundle to the spectroradiometer, which consists of a concave holographic diffraction grating with a flat focal field imaged onto a 1024-element platinum silicide linear-array detector.

  18. Measurement of thermal radiation using regular glass optics and short-wave infrared detectors.

    PubMed

    Yoon, H W; Eppeldauer, G P

    2008-01-21

    The measurement of thermal radiation from ambient-temperature objects using short-wave infrared detectors and regular glass optics is described. The detectors are chosen to operate in the 2.0 microm to 2.5 microm atmospheric window. Selection of detectors with high shunt resistance along with the 4-stage thermo-electric cooling of the detectors to -85 degrees C results in detectivity, D*, of 4 x 10(13) cm Hz(1/2)/W which is near the background limited performance at 295 K. Furthermore, the use of regular-glass commercial optics to collect the thermal radiation results in diffraction-limited imaging. The use of a radiation thermometer constructed with these elements for the measurement of a blackbody from 20 degrees C to 50 degrees C results in noise-equivalent temperature difference (NETD) of < 3 mK at 50 degrees C. The operation at shorter wavelengths than traditional thermal sensors also leads to lower sensitivity to the emissivity of the object in determining the temperature of the object. These elements are used to construct a calibrator for an infrared collimator, and such a system demonstrates noise-equivalent irradiances of < 5 fW/cm(2). These results indicate that radiometers using short-wave infrared sensors could be constructed utilizing commercial glass optics with possible better performance and lower NETD than existing radiometers using cryogenically-cooled mid-infrared or thermal infrared detectors. PMID:18542168

  19. Aging of human short-wave cone pathways

    PubMed Central

    Shinomori, Keizo; Werner, John S.

    2012-01-01

    The retinal image is sampled concurrently, and largely independently, by three physiologically and anatomically distinct pathways, each with separate ON and OFF subdivisions. The retinal circuitry giving rise to an ON pathway receiving input from the short-wave-sensitive (S) cones is well understood, but the S-cone OFF circuitry is more controversial. Here, we characterize the temporal properties of putative S-cone ON and OFF pathways in younger and older observers by measuring thresholds for stimuli that produce increases or decreases in S-cone stimulation, while the middle- and long-wave-sensitive cones are unmodulated. We characterize the data in terms of an impulse response function, the theoretical response to a flash of infinitely short duration, from which the response to any temporally varying stimulus may be predicted. Results show that the S-cone response to increments is faster than to decrements, but this difference is significantly greater for older individuals. The impulse response function amplitudes for increment and decrement responses are highly correlated across individuals, whereas the timing is not. This strongly suggests that the amplitude is controlled by neural circuitry that is common to S-cone ON and OFF responses (photoreceptors), whereas the timing is controlled by separate postreceptoral pathways. The slower response of the putative OFF pathway is ascribed to different retinal circuitry, possibly attributable to a sign-inverting amacrine cell not present in the ON pathway. It is significant that this pathway is affected selectively in the elderly by becoming slower, whereas the temporal properties of the S-cone ON response are stable across the life span of an individual. PMID:22847416

  20. Mixed solitons in a (2+1)-dimensional multicomponent long-wave-short-wave system.

    PubMed

    Kanna, T; Vijayajayanthi, M; Lakshmanan, M

    2014-10-01

    We derive a (2+1)-dimensional multicomponent long-wave-short-wave resonance interaction (LSRI) system as the evolution equation for propagation of N-dispersive waves in weak Kerr-type nonlinear medium in the small-amplitude limit. The mixed- (bright-dark) type soliton solutions of a particular (2+1)-dimensional multicomponent LSRI system, deduced from the general multicomponent higher-dimensional LSRI system, are obtained by applying the Hirota's bilinearization method. Particularly, we show that the solitons in the LSRI system with two short-wave components behave like scalar solitons. We point out that for an N-component LSRI system with N>3, if the bright solitons appear in at least two components, interesting collision behavior takes place, resulting in energy exchange among the bright solitons. However, the dark solitons undergo standard elastic collision accompanied by a position shift and a phase shift. Our analysis on the mixed bound solitons shows that the additional degree of freedom which arises due to the higher-dimensional nature of the system results in a wide range of parameters for which the soliton collision can take place. PMID:25375561

  1. Sensitivity of toad rods: Dependence on wave-length and background illumination.

    PubMed Central

    Fain, G L

    1976-01-01

    1. There are five morphological types of photoreceptors in the retina of the toad, Bufo marinus: red and green rods, single cones, and the principal and accessory members of double cones. The largest and most abundant of these is the red rod. 2. Intracellular recordings were used to investigate the dependence of the sensitivity of red rod responses on wave-length and background light. 3. The spectral sensitivity of dark-adapted and moderately light-adapted red rods can be satisfactorily fitted with the absorbance spectrum of the red rod photopigment. There are no significant contributions to red rod responses from cones or green rods. 4. In contrast, L-type horizontal cells, whose responses are dominated by input from the red rods near threshold, can be shown also to receive input from cones. 5. Steady background light produces a response in the red rods consisting of an initial hyperpolarization, followed by a decay of potential to a steady-state plateau level. The slow decay of response amplitude is accompanied by an increase in sensitivity to increment test flashes. 6. The increment sensitivity at steady-state decreases with increasing background intensity according to a modified Weber-Fechner relation. The dependence of increment sensitivity on the wave-length of the background light can be predicted by the red rod spectral sensitivity, showing that cones do not influence the light adaptation of rods. 7. At a backgound intensity of 11-5 log equivalent quanta cm-2sec-1, sensitivity begins to deviate from the Weber-Fechner relation. In background light one log unit brighter, the rods are completely saturated. 8. Small responses having the spectral sensitivity of cones can be recorded from saturated rods. These potentials have a prominent off response whose wave form resembles the d-wave of the e.r.g. 9. A comparison of the increment--sensitivity curves of single receptors shows that rods are light-adapted by backgrounds one thousand times dimmer than those which affect cones. The increment--sensitivity curves of rods and cones cross, so that single cones become more sensitive than single rods even before the rods begin to saturate. Images Fig. 1 Fig. 2 PMID:825637

  2. A biological quarter-wave retarder with excellent achromaticity in the visible wavelength region

    NASA Astrophysics Data System (ADS)

    Roberts, N. W.; Chiou, T.-H.; Marshall, N. J.; Cronin, T. W.

    2009-11-01

    Animals make use of a wealth of optical physics to control and manipulate light, for example, in creating reflective animal colouration and polarized light signals. Their precise optics often surpass equivalent man-made optical devices in both sophistication and efficiency. Here, we report a biophysical mechanism that creates a natural full-visible-range achromatic quarter-wave retarder in the eye of a stomatopod crustacean. Analogous, man-made retardation devices are important optical components, used in both scientific research and commercial applications for controlling polarized light. Typical synthetic retarders are not achromatic, and more elaborate designs, such as, multilayer subwavelength gratings or bicrystalline constructions, only achieve partial wavelength independence. In this work, we use both experimental measurements and theoretical modelling of the photoreceptor structure to illustrate how a novel interplay of intrinsic and form birefringence results in a natural achromatic optic that significantly outperforms current man-made optical devices.

  3. Whole-wavelength description of a wave boundary layer over permeable wall

    NASA Astrophysics Data System (ADS)

    Miozzi, Massimo; Postacchini, Matteo; Corvaro, Sara; Brocchini, Maurizio

    2015-06-01

    This paper describes the whole-wavelength, highly resolved velocity field statistics in an oscillatory boundary layer driven by gravity waves, evolving on both impermeable and permeable beds. Velocity data from PTV measurements are acquired in a small window and then extended to the whole wavelength by means of a new phase-locked slotting technique. This technique increases the robustness of statistics and resolution by improving the number of the data samples available for each spatial cell in the Eulerian representation of the oscillatory boundary layer. The into- and out-of-bed volume flux is evaluated and its effects on the velocity field are reported, together with its influence on vorticity evolution. The presence of coherent structures embedded in a shear-dominated scenario is emphasized. The Lagrangian flow features extracted by PTV are presented in the context of the generalized Lagrangian-mean theory. The Stokes drift vertical profile is estimated by comparing the Eulerian and Lagrangian velocities. A critical height-separating region where the volume flux due to ventilation has different effects on both orbital amplitudes and Stokes drift is found. This distance corresponds to the maximum height of the still-attached vorticity layer.

  4. Visualization of short surface acoustic waves by stroboscopic x-ray topography: analysis of contrast

    NASA Astrophysics Data System (ADS)

    Shilo, D.; Zolotoyabko, E.

    2003-05-01

    In this paper the capabilities of stroboscopic x-ray topography to visualize the propagation of short (<10 μm) surface acoustic waves (SAW) in single crystals are analysed. Experiments with LiNbO3 crystals under SAW excitation were carried out at the ID19 beam line of the European synchrotron radiation facility. The developed theoretical analysis of the SAW-induced contrast in Bragg scattering geometry helped to optimize experimental conditions and receive high quality images with well-resolved individual acoustic wave fronts. The basic contrast mechanism is related to the SAW-induced corrugation of atomic planes that causes the focusing of x-rays. The focal distance is directly proportional to the SAW wavelength and inversely proportional to the deformation amplitude at the crystal surface. Simulations of diffraction contrast allowed us to conclude that the best contrast is achieved when the acoustic wave vector is perpendicular to the x-ray scattering plane and the sample/film distance equals 2-4 focal distances.

  5. Multi-spacecraft observations of magnetopause surface waves - ISEE 1 and 2 determinations of amplitude, wavelength and period

    NASA Technical Reports Server (NTRS)

    Song, PU; Elphic, R. C.; Russell, C. T.

    1988-01-01

    The multispacecraft ISEE mission made it possible to study propagation of surface waves on the magnetopause. One case studied in detail was near local noon at a latitude of 24.4 deg. The inferred instantaneous magnetopause normal vectors oscillated about the model magnetopause normal vector in a manner expected for a wave propagating along the magnetopause from the subsolar region. By assuming a model monochromatic wave and a constant magnetopause thickness, the best-fit that yields the three wave parameters( amplitude, wavelength, and period) is determined.

  6. Analysis of GEOS-3 altimeter data and extraction of ocean wave height and dominant wavelength

    NASA Technical Reports Server (NTRS)

    Walsh, E. J.

    1979-01-01

    When the amplitude and timing biases are removed from the GEOS-3 Sample and Hold (S&H) gates, the mean return waveforms can be excellently fitted with a theoretical template which represents the convolution of: (1) the radar point target response; (2) the range noise (jitter) in the altimeter tracking loop; (3) the sea surface height distribution; and (4) the antenna pattern as a function of the range to mean sea level. Several techniques of varying complexity to remove the effect of the tracking loop jitter in computing the wave height are considered. They include: (1) realigning the S&H gates to their actual positions with respect to mean sea level before averaging; (2) using the observed standard deviation on the altitude measurement to remove the integrated effect of the tracking loop jitter, and (3) using a look-up table to correct for the expected value of range noise. Analysis of skewness in the GEOS return waveform demonstrates the potential of a satellite radar altimeter to determine the dominant wavelength of ocean waves.

  7. Observation of wavelength-dependent generation efficiency of laser-induced ultrasonic surface acoustic waves on ceramic materials

    NASA Astrophysics Data System (ADS)

    Flannery, C. M.; Kelly, P. V.; Beechinor, J. T.; Crean, G. M.

    1997-12-01

    In this work, the efficiency of laser generation of surface acoustic waves (SAWs) in ceramic materials is reported to be wavelength dependent. A pulsed Nd:YAG laser operating at wavelengths of 1064 or 532 nm was used to generate SAWs on ceramic (silicon nitride and silicon carbide) and metal substrates. It was observed that 1064 nm radiation is more efficient than 532 nm radiation for SAW generation on ceramics, whereas the opposite is the case for metals. While the wavelength dependence of SAW generation efficiency in metals is due to stronger optical absorption at the shorter wavelength, the dependence for the ceramics is attributed to a longer absorption length at the longer wavelength.

  8. Continuous-wave dual-wavelength operation of a diode-end-pumped Nd:GGG laser

    NASA Astrophysics Data System (ADS)

    Sun, G. C.; Li, Y. D.; Zhao, M.; Jin, G. Y.; Wang, J. B.

    2011-08-01

    A diode-end-pumped continuous-wave (CW) simultaneous dual-wavelength laser operation at 1062 and 1331 nm in a single Nd:GGG was demonstrated. A total output power of 1.08 W at the two fundamental wavelengths was achieved at the incident pump power of 18.2 W. The optical-to-optical conversion is up to 5.9% with respect to the incident pump power. To the best of our knowledge, this is first work on CW simultaneous dual-wavelength operation of a diode pumped Nd:GGG laser. The article is published in the original.)

  9. Precision calculation of above-threshold multiphoton ionization in intense short-wavelength laser fields: The momentum-space approach and time-dependent generalized pseudospectral method

    SciTech Connect

    Zhou Zhongyuan; Chu, Shih-I

    2011-01-15

    We present an approach in momentum (P) space for the accurate study of multiphoton and above-threshold ionization (ATI) dynamics of atomic systems driven by intense laser fields. In this approach, the electron wave function is calculated by solving the P-space time-dependent Schroedinger equation (TDSE) in a finite P-space volume under a simple zero asymptotic boundary condition. The P-space TDSE is propagated accurately and efficiently by means of the time-dependent generalized pseudospectral method with optimal momentum grid discretization and a split-operator time propagator in the energy representation. The differential ionization probabilities are calculated directly from the continuum-state wave function obtained by projecting the total electron wave function onto the continuum-state subspace using the projection operator constructed by the continuum eigenfunctions of the unperturbed Hamiltonian. As a case study, we apply this approach to the nonperturbative study of the multiphoton and ATI dynamics of a hydrogen atom exposed to intense short-wavelength laser fields. High-resolution photoelectron energy-angular distribution and ATI spectra have been obtained. We find that with the increase of the laser intensity, the photoelectron energy-angular distribution changes from circular to dumbbell shaped and is squeezed along the laser field direction. We also explore the change of the maximum photoelectron energy with laser intensity and strong-field atomic stabilization phenomenon in detail.

  10. Nearly lattice-matched short-wave infrared InGaAsBi detectors on InP

    NASA Astrophysics Data System (ADS)

    Gu, Y.; Zhang, Y. G.; Chen, X. Y.; Ma, Y. J.; Xi, S. P.; Du, B.; Li, Hsby.

    2016-01-01

    This work reports on the demonstration of a short-wave infrared detector nearly lattice matched to InP substrate using quaternary InGaAsBi as the absorption layer. The bismuth content of about 3.2% has red-shifted the 50% cut-off wavelength from about 1.6 μm to 2.1 μm at room temperature, indicating a bandgap reduction of about 180 meV due to bismuth incorporation. The detector shows an encouraging dark current density of 2.4 × 10-4 A/cm2 at bias voltage of -10 mV at 300 K. This work shows the promising potential of InP-based lattice-matched InGaAsBi detectors for short-wave infrared detection.

  11. A Fourier-Boussinesq method for short wave coastal problems

    NASA Astrophysics Data System (ADS)

    Bingham, H. B.

    2002-12-01

    Predicting the nonlinear propagation of dispersive waves over a bathymetry is desirable in many coastal and offshore applications. Realistic problems require analysis over a complicated geometry on the order of a hundred by a hundred significant wavelengths, and in relative water depths all the way from practically infinite to zero. Such problems pose a formidable challenge and are generally treated using potential flow methods. Typically the velocity potential is expanded in a set of basis functions which individually satisfy the Laplace equation; and the expansion coefficients are determined to satisfy the remaining conditions on the fluid boundary. The number of degrees of freedom (usually a set of values of the potential or its derivatives on the boundary) is hence significantly smaller than would result from discretizing the entire fluid volume. The most commonly used basis functions are polynomials, singular Green's functions, and Fourier functions; each of which has advantages and disadvantages depending on the phenomena of primary interest. Polynomial based methods, such as the Boussinesq method, are perhaps the most widely used for coastal applications. This abstract describes a new Boussinesq method which is fully dispersive in the sense that the errors of the approximation are small for all kh (k=| vec k}| the magnitude of the wavenumber and h the water depth). We call the new method a Fourier-Boussinesq method as it includes a Fourier transform. In contrast to other polynomial based methods, the Fourier-Boussinesq method approximates the dispersion operator tanh (kh)/(kh) by a rational function of kh rather than k2h2, and can thus be made asymptotically correct in both limits of kh. The odd powers of kh are evaluated in physical-space by introducing the generalized Hilbert operator, which is efficiently implemented using the Fast Fourier Transform (FFT). This leads to approximations with small errors in dispersion over the entire domain 0<= kh < ∞ . Variable bottom terms are derived both in mild-slope form, and in augmented mild-slope form including all terms that are linear in derivatives of h. Calculations will be presented which demonstrate the performance of the method using a number of nonlinear wave propagation problems on both flat and variable bottoms.

  12. Conductors, semiconductors, and insulators irradiated with short-wavelength free-electron laser

    NASA Astrophysics Data System (ADS)

    Krzywinski, J.; Sobierajski, R.; Jurek, M.; Nietubyc, R.; Pelka, J. B.; Juha, L.; Bittner, M.; Létal, V.; Vorlíček, V.; Andrejczuk, A.; Feldhaus, J.; Keitel, B.; Saldin, E. L.; Schneidmiller, E. A.; Treusch, R.; Yurkov, M. V.

    2007-02-01

    The results of a study of irreversible changes induced at surfaces of metals, semiconductors, and insulators by extreme ultraviolet (λ<100nm) ultrashort pulses provided by TESLA Test Facility Free-Electron Laser, Phase 1 (TTF1 FEL) are reported and discussed. The laser was tuned at 86, 89, and 98nm during the experiments reported here. Energy spectra of ions ejected from the irradiated surfaces are also reported. Special attention is paid to the difference in the ablation behavior of (semi)conductors and insulators that we have observed. The difference is dramatic, while the absorption coefficients are similar for all materials at the TTF1 FEL wavelength.

  13. Using short-wave infrared imaging for fruit quality evaluation

    NASA Astrophysics Data System (ADS)

    Zhang, Dong; Lee, Dah-Jye; Desai, Alok

    2013-12-01

    Quality evaluation of agricultural and food products is important for processing, inventory control, and marketing. Fruit size and surface quality are two important quality factors for high-quality fruit such as Medjool dates. Fruit size is usually measured by length that can be done easily by simple image processing techniques. Surface quality evaluation on the other hand requires more complicated design, both in image acquisition and image processing. Skin delamination is considered a major factor that affects fruit quality and its value. This paper presents an efficient histogram analysis and image processing technique that is designed specifically for real-time surface quality evaluation of Medjool dates. This approach, based on short-wave infrared imaging, provides excellent image contrast between the fruit surface and delaminated skin, which allows significant simplification of image processing algorithm and reduction of computational power requirements. The proposed quality grading method requires very simple training procedure to obtain a gray scale image histogram for each quality level. Using histogram comparison, each date is assigned to one of the four quality levels and an optimal threshold is calculated for segmenting skin delamination areas from the fruit surface. The percentage of the fruit surface that has skin delamination can then be calculated for quality evaluation. This method has been implemented and used for commercial production and proven to be efficient and accurate.

  14. High sensitivity of human melatonin, alertness, thermoregulation, and heart rate to short wavelength light.

    PubMed

    Cajochen, Christian; Münch, Mirjam; Kobialka, Szymon; Kräuchi, Kurt; Steiner, Roland; Oelhafen, Peter; Orgül, Selim; Wirz-Justice, Anna

    2005-03-01

    Light can elicit acute physiological and alerting responses in humans, the magnitude of which depends on the timing, intensity, and duration of light exposure. Here, we report that the alerting response of light as well as its effects on thermoregulation and heart rate are also wavelength dependent. Exposure to 2 h of monochromatic light at 460 nm in the late evening induced a significantly greater melatonin suppression than occurred with 550-nm monochromatic light, concomitant with a significantly greater alerting response and increased core body temperature and heart rate ( approximately 2.8 x 10(13) photons/cm(2)/sec for each light treatment). Light diminished the distal-proximal skin temperature gradient, a measure of the degree of vasoconstriction, independent of wavelength. Nonclassical ocular photoreceptors with peak sensitivity around 460 nm have been found to regulate circadian rhythm function as measured by melatonin suppression and phase shifting. Our findings-that the sensitivity of the human alerting response to light and its thermoregulatory sequelae are blue-shifted relative to the three-cone visual photopic system-indicate an additional role for these novel photoreceptors in modifying human alertness, thermophysiology, and heart rate. PMID:15585546

  15. Optical property of Ce3+-doped lutetium lithium fluoride for the short-wavelength device application

    NASA Astrophysics Data System (ADS)

    Shimizu, Toshihiko; Yamanoi, Kohei; Arita, Ren; Hori, Tatsuhiro; Fukuda, Kazuhito; Minami, Yuki; Cadatal-Raduban, Marilou; Sarukura, Nobuhiko; Fukuda, Tsuguo; Nagasono, Mitsuru; Ishikawa, Tetsuya

    2014-10-01

    We report on the optical properties of Ce:LLF excited by the 61-nm wavelength emission of the SPring-8 compact self amplification of spontaneous emission source (SCSS) test accelerator, which is a prototype self-amplified stimulated emission (SASE)-type free electron laser (FEL) that emits extreme ultraviolet (EUV) radiation. Ce:LLF fluorescence at 308 nm and 322 nm wavelength was observed using a streak camera. The temporal profile exhibited a 62.1-ns fast decay component and 8.63-ns slow decay component. This double exponential behavior is observed with EUV-FEL excitation and is due to the de-excitation process involving several relaxation steps because of the energetically long distance and intricate band structure between the excitation and emission states. The double exponential nature of fluorescence decay is not observable with low-energy excitation sources; hence, our results show the importance of novel light sources, such as the FEL, for the development and characterization of new materials.

  16. Highly coherent red-shifted dispersive wave generation around 1.3 μm for efficient wavelength conversion

    NASA Astrophysics Data System (ADS)

    Li, Xia; Chen, Wei; Xue, Tianfeng; Bi, Wanjun; Gao, Weiqing; Hu, Lili; Liao, Meisong

    2015-03-01

    This research investigates the mechanism of the optical dispersive wave (DW) and proposes a scheme that can realize an efficient wavelength conversion. In an elaborately designed photonic crystal fiber, a readily available ytterbium laser operating at ˜1 μm can be transferred to the valuable 1.3 μm wavelength range. A low-order soliton is produced to concentrate the energy of the DW into the target wavelength range and improve the degree of coherence. The input chirp is demonstrated to be a factor that enhances the wavelength conversion efficiency. With a positive initial chirp, 76.6% of the pump energy in the fiber can be transferred into a spectral range between 1.24 and 1.4 μm. With the use of a grating compressor, it is possible to compress the generated coherent DW of several picoseconds into less than 90 fs.

  17. Highly coherent red-shifted dispersive wave generation around 1.3 μm for efficient wavelength conversion

    SciTech Connect

    Li, Xia; Bi, Wanjun; Chen, Wei; Xue, Tianfeng; Hu, Lili; Liao, Meisong; Gao, Weiqing

    2015-03-14

    This research investigates the mechanism of the optical dispersive wave (DW) and proposes a scheme that can realize an efficient wavelength conversion. In an elaborately designed photonic crystal fiber, a readily available ytterbium laser operating at ∼1 μm can be transferred to the valuable 1.3 μm wavelength range. A low-order soliton is produced to concentrate the energy of the DW into the target wavelength range and improve the degree of coherence. The input chirp is demonstrated to be a factor that enhances the wavelength conversion efficiency. With a positive initial chirp, 76.6% of the pump energy in the fiber can be transferred into a spectral range between 1.24 and 1.4 μm. With the use of a grating compressor, it is possible to compress the generated coherent DW of several picoseconds into less than 90 fs.

  18. Atomic layer deposition of absorbing thin films on nanostructured electrodes for short-wavelength infrared photosensing

    NASA Astrophysics Data System (ADS)

    Xu, Jixian; Sutherland, Brandon R.; Hoogland, Sjoerd; Fan, Fengjia; Kinge, Sachin; Sargent, Edward H.

    2015-10-01

    Atomic layer deposition (ALD), prized for its high-quality thin-film formation in the absence of high temperature or high vacuum, has become an industry standard for the large-area deposition of a wide array of oxide materials. Recently, it has shown promise in the formation of nanocrystalline sulfide films. Here, we demonstrate the viability of ALD lead sulfide for photodetection. Leveraging the conformal capabilities of ALD, we enhance the absorption without compromising the extraction efficiency in the absorbing layer by utilizing a ZnO nanowire electrode. The nanowires are first coated with a thin shunt-preventing TiO2 layer, followed by an infrared-active ALD PbS layer for photosensing. The ALD PbS photodetector exhibits a peak responsivity of 10-2 A W-1 and a shot-derived specific detectivity of 3 × 109 Jones at 1530 nm wavelength.

  19. Material processing with ultra-short pulse lasers working in 2μm wavelength range

    NASA Astrophysics Data System (ADS)

    Voisiat, B.; Gaponov, D.; Gečys, P.; Lavoute, L.; Silva, M.; Hideur, A.; Ducros, N.; Račiukaitis, G.

    2015-03-01

    New wavelengths of laser radiation are of interest for material processing. Results of application of the all-fiber ultrashort pulsed laser emitting in 2 µm range, manufactured by Novae, are presented. Average output power was 4.35 W in a single-spatial-mode beam centered at the 1950 nm wavelength. Pulses duration was 40 ps, and laser operated at 4.2 MHz pulse repetition rate. This performance corresponded to 25 kW of pulse peak power and almost 1 µJ in pulse energy. Material processing was performed using three different focusing lenses (100, 30 and 18 mm) and mechanical stages for the workpiece translation. 2 µm laser radiation is strongly absorbed by some polymers. Swelling of PMMA surface was observed for scanning speed above 5 mm/s using the average power of 3.45 W focused with the 30 mm lens. When scanning speed was reduced below 4 mm/s, ablation of PMMA took place. The swelling of PMMA is a consequence of its melting due to absorbed laser power. Therefore, experiments on butt welding of PMMA and overlapping welding of PMMA with other polymers were performed. Stable joint was achieved for the butt welding of two PMMA blocks with thickness of 5 mm. The laser was used to cut a Kapton film on a paper carrier with the same set-up as previous. The cut width depended on the cutting speed and focusing optics. A perfect cut with a width of 11 µm was achieved at the translation speed of 60 mm/s.

  20. Picosecond pulses from wavelength-swept continuous-wave Fourier domain mode-locked lasers.

    PubMed

    Eigenwillig, Christoph M; Wieser, Wolfgang; Todor, Sebastian; Biedermann, Benjamin R; Klein, Thomas; Jirauschek, Christian; Huber, Robert

    2013-01-01

    Ultrafast lasers have a crucial function in many fields of science; however, up to now, high-energy pulses directly from compact, efficient and low-power semiconductor lasers are not available. Therefore, we introduce a new approach based on temporal compression of the continuous-wave, wavelength-swept output of Fourier domain mode-locked lasers, where a narrowband optical filter is tuned synchronously to the round-trip time of light in a kilometre-long laser cavity. So far, these rapidly swept lasers enabled orders-of-magnitude speed increase in optical coherence tomography. Here we report on the generation of ~60-70 ps pulses at 390 kHz repetition rate. As energy is stored optically in the long-fibre delay line and not as population inversion in the laser-gain medium, high-energy pulses can now be generated directly from a low-power, compact semiconductor-based oscillator. Our theory predicts subpicosecond pulses with this new technique in the future. PMID:23673633

  1. Feasibility study on a short-pulsed IR wavelength for effective calculus fragmentation

    NASA Astrophysics Data System (ADS)

    Kang, Hyun Wook

    2015-05-01

    Laser-induced lithotripsy has been used for a minimally-invasive surgery to treat kidney-stone disease associated with urinary obstruction. A short-pulsed Tm:YAG laser (λ = 2.01 µm) was developed to improve fragmentation efficiency and was evaluated with a Ho:YAG laser (λ = 2.12 μm) as to its ablation feature and mass removal rate. Application of a train of sub-microsecond pulses with a lower energy at a frequency of 500 Hz created multiple events of cavitation that accompanied strong acoustic transients. During Tm:YAG irradiation, both high light absorption and secondary photomechanical impacts readily fragmented the calculus into small pieces (< 3 mm) and removed them 130 times faster than photothermal Ho:YAG lithotripsy. The proposed short-pulsed Tm:YAG approach may be an effective lithotripter for treating calculus disease.

  2. Transition between short and long wavelength limits in quantum mechanical reflection from a linear potential

    NASA Astrophysics Data System (ADS)

    Kennedy, S. M.; Paganin, D. M.; Jesson, D. E.

    2008-02-01

    The phase changes experienced by a wave reflected from an interface are a familiar fixture in introductory physics courses. Examples include the ±π phase shift acquired upon reflection from a hard mirror (for example, in thin film interference patterns and Newton's rings) and the -π/2 phase shift studied in soft mirror reflections (for example, in mirage ray paths and the WKB connection formulas). We focus on the transition between these two limits, where the phase change upon reflection evolves continuously between the limiting cases of -π and -π/2. We study a simple quantum system that exhibits this transition: a one-dimensional free electron reflected from a linear potential.

  3. Cryogenic optical mounting for short-wave infrared spectrometers

    NASA Astrophysics Data System (ADS)

    Grant, J.; Wood, T.; Bhatti, I.; Cañas, A.; Reddick, P.; van Wyk, P.; Bharadia, S.; Storey, T.; Potterton, T.; Rits, W.; Meijer, H.

    2014-07-01

    In order to measure atmospheric concentrations of carbon monoxide, methane, water and carbon dioxide from spaceborne platforms, Short-Wave Infrared (SWIR) immersed grating spectrometers are employed. Due to the need to minimise detector dark current and internal black body radiation from the spectrometer's own structure, these instruments are operated at cryogenic temperatures. ESA's Sentinel 5-Precursor is a small satellite science mission; the platform comprises the Tropospheric Monitoring Instrument (TROPOMI), which includes a SWIR module. Optical mounts have been developed for the SWIR module which meet the requirements to cope with the differences in thermal expansion between the optical elements and their structural mounts over cryogenic temperature ranges, be robust against the mechanical environment during launch, and maintain optical alignment stability with a tight volume constraint. Throughout the design of the SWIR spectrometer, flexures were deployed to control deformations due to thermal expansion, the design of interfaces between materials of differing coefficient of thermal expansion was carefully managed, and the geometry of adhesive pads was tightly controlled. Optical mounting concepts were evaluated using finite element analysis (FEA). A breadboard programme was undertaken to verify these concepts. FEA and breadboard results were correlated to provide confidence in the design. The breadboard programme consisted of thermal cycling and pull-testing of adhesive joints, as well as environmental and optical testing of representative subsystems. Analysis and breadboarding demonstrated that the optical mounting design will survive the mechanical and thermal environments, and verified the stability of the optical alignment requirements. Novel optical mounting structures have been designed, analysed, assembled, tested and integrated into the optical assemblies of the TROPOMI SWIR spectrometer, creating a compact and robust state of the art instrument. These concepts are applicable to instruments for astronomical missions aiming to characterise exoplanets, as well as Earth observation missions.

  4. Atomic layer deposition of absorbing thin films on nanostructured electrodes for short-wavelength infrared photosensing

    SciTech Connect

    Xu, Jixian; Sutherland, Brandon R.; Hoogland, Sjoerd; Fan, Fengjia; Sargent, Edward H.; Kinge, Sachin

    2015-10-12

    Atomic layer deposition (ALD), prized for its high-quality thin-film formation in the absence of high temperature or high vacuum, has become an industry standard for the large-area deposition of a wide array of oxide materials. Recently, it has shown promise in the formation of nanocrystalline sulfide films. Here, we demonstrate the viability of ALD lead sulfide for photodetection. Leveraging the conformal capabilities of ALD, we enhance the absorption without compromising the extraction efficiency in the absorbing layer by utilizing a ZnO nanowire electrode. The nanowires are first coated with a thin shunt-preventing TiO{sub 2} layer, followed by an infrared-active ALD PbS layer for photosensing. The ALD PbS photodetector exhibits a peak responsivity of 10{sup −2} A W{sup −1} and a shot-derived specific detectivity of 3 × 10{sup 9} Jones at 1530 nm wavelength.

  5. The two spectroscopically different short wavelength protochlorophyllide forms in pea epicotyls are both monomeric.

    PubMed

    Böddi; Kis-Petik; Kaposi; Fidy; Sundqvist

    1998-07-20

    The spectral properties of the protochlorophyllide forms in the epicotyls of dark-grown pea seedlings have been studied in a temperature range, from 10 to 293 K with conventional fluorescence emission and excitation spectroscopy as well as by fluorescence line narrowing (FLN) at cryogenic temperatures. The conventional fluorescence techniques at lower temperatures revealed separate bands at 628, 634-636, 644 and 655 nm. At room temperature (293 K) the 628 and 634-636 nm emission bands strongly overlapped and the band shape was almost independent of the excitation wavelength. Under FLN conditions, vibronically resolved fluorescence spectra could be measured for the 628 and 634-636 nm bands. The high resolution of this technique excluded the excitonic nature of respective excited states and made it possible to determine the pure electronic (0,0) range of the spectra of the two components. Thus it was concluded that the 628 and 634-636 nm (0,0) emission bands originate from two monomeric forms of protochlorophyllide and the spectral difference is interpreted as a consequence of environmental effects of the surrounding matrix. On the basis of earlier results and the data presented here, a model is discussed in which the 636 nm form is considered as an enzyme-bound protochlorophyllide and the 628 nm form as a protochlorophyllide pool from which the substrate is replaced when the epicotyl is illuminated with continuous light. PMID:9757084

  6. Assessment of the Atmospheric Channel for Short (Ka-Band and Optical) Wavelengths

    NASA Technical Reports Server (NTRS)

    Piazzolla, Sabino

    2007-01-01

    Atmospheric turbulence under clear sky conditions is an impairment of the atmospheric channel that greatly affects propagation of optical signal in the troposphere. The turbulence manifests itself in a number of forms within the optical domain, from the twinkling of a star in a clear night, to resolution degradation in a large aperture telescope. Therefore, a body of analytical, numerical, and experimental tools has been developed in optics to study, simulate, and control effects of atmospheric turbulence on an optical signal. Incidentally, there has been an increasing demand for high data rate returns from NASA missions which has led to envision utilizing a carrier signal in the Ka-Band range. The impact of atmospheric turbulence effects must be evaluated and considered for this frequency domain. The purpose of this work is to show that when the turbulence strength from the optical case to the KaBand ease is properly scaled, one can apply the same mathematical simulation developed for optical to predict turbulence effects within the Ka-Band domain. As a demonstration of this principle, we present how the scintillations of a Ka-Band downlink return of a deep space signal was successfully reproduced through wave-optics simulation.

  7. Glacial modifications of short-wavelength topography and potential feedbacks on the denudation of a deglaciated mountain range

    NASA Astrophysics Data System (ADS)

    Salcher, Bernhard; Kober, Florian; Kissling, Eduard; Willett, Sean

    2014-05-01

    Distinct erosional landforms in the European Alps and other mid- to high-latitude mountain belts highlight the importance of glacial erosion in shaping mountain topography. Here we focus on the glacially induced modifications to the short-wavelength topography of the European Central Alps in an attempt to characterize the impact of glacial erosion on topography and to highlight potential feedback mechanisms on the denudation of the deglaciated mountain range. Glacial induced changes to the short-wavelength topography were analyzed by measuring the variations of drainage density and hillslope relief across the range. Variations of denudation rates were analyzed by compiling catchment-averaged concentrations of cosmogenic 10Be from existing studies covering Alpine and Foreland basins. Our results underline the importance of the LGM ELA elevation (i.e. the Equilibrium Line Altitude at the Late Glacial Maximum) as an important limit for the destruction of short-wavelength topography: The cumulative impact of glacial erosion above the LGM ELA has progressively decreased (i) drainage density, (ii) channel integration and (iii) commensurately increased hillslopes length (or hillslope relief). Exceptions from this trend are the highest and steepest peaks and ridges, nunataks even during the LGM. Alpine catchments in the orogen parts below this limit (i.e. Alpine foothills) lack strong modifications by glaciers. Here, glacial erosion is largely restricted to glacial troughs. There is also a statistically significant correlation between drainage density (or hillslope length) and catchment-wide denudation rates. The correlation does not define a single-valued function; rather there are two populations above and below the LGM ELA, one with a positive correlation for low-elevation, fluvially-dominated landscapes and a second for high-elevation, glacially-eroded basins in which this correlation is negative. We speculate that the commensurate lengthening of hillslopes increase slope instability and mass flux, thereby resulting in higher denudation rates. Rock mass strength seems to have a further significant effect on these relationships. Our results might indicate an important driving mechanism behind surface denudation of glacially conditioned mountain ranges operating over glacial-interglacial time scales.

  8. Higher-order statistical analysis of short wind wave fields

    NASA Astrophysics Data System (ADS)

    Caulliez, Guillemette; GuRin, Charles-Antoine

    2012-06-01

    Observations of along-wind surface wave profiles were made in the large Marseille-Luminy wind wave tank for a broad range of wind and fetch conditions. The processing of high resolution camera snapshots enables us to carry on a thorough statistical analysis of wind wave geometrical properties. We consider distinctively the four different wind wave fields characterized by a comprehensive image analysis in the range of capillary-gravity to gravity scales. This set of data makes it possible to describe and discuss the behavior of the distribution of wave heights, longitudinal wave slopes and curvatures in terms of their second- and higher-order moments as well as a function of the dominant wave scale. We calculate the autocorrelation and related functions and evidence the self-similar nature of wind wave fields. We also derive a simple and universal expression for the structure functions of third (skewness) and fourth (kurtosis) order which are needed for the simulation of sea radar return in the microwave regime.

  9. Time-resolved measurements of short-wavelength fluorescence from x-ray-excited ions.

    PubMed

    Kapteyn, H C; Murnane, M M; Falcone, R W

    1987-09-01

    We demonstrate a novel technique for time-resolved spectroscopic studies of highly excited ions. The technique uses a laser-produced plasma as a short-pulse, soft-x-ray light source with a high repetition rate. A Nd:YAG laser with a pulse duration of 90 psec, a pulse energy of 70 microJ, and repetition rate of 10(4) pulses per second is focused onto a rotating metal target. Soft x rays from the resulting plasma photoionize a gas surrounding the target, and fluorescence from the gas is detected by using a spectrometer and a high-speed photodetector. Using the technique of time-correlated photon counting, we determined the radiative lifetime and collisional quenching rate of the Xe III 5s(0)5p(6)(1)S(0) state by observing its fluorescence at 108.9 nm. A time resolution of better than 400 psec was obtained. We also measured relative Auger decay yields of a core hole state in xenon using a higher-energy laser-produced plasma light source at a lower repetition rate. PMID:19741832

  10. A tunable dual-wavelength pump source based on simulated polariton scattering for terahertz-wave generation

    NASA Astrophysics Data System (ADS)

    Sun, Bo; Liu, Jinsong; Yao, Jianquan; Li, Enbang

    2013-11-01

    We propose a dual-wavelength pump source by utilizing stimulated polariton scattering in a LiNbO3 crystal. The residual pump and the generated tunable Stokes waves can be combined to generate THz-wave generation via difference frequency generation (DFG). With a pump energy of 49 mJ, Stokes waves with a tuning range from 1067.8 to 1074 nm have been generated, and an output energy of up to 14.9 mJ at 1070 nm has been achieved with a conversion efficiency of 21.7%. A sum frequency generation experiment was carried out to demonstrate the feasibility of the proposed scheme for THz-wave DFG.

  11. Short to long-wave IR detectors based on InAs/GaSb superlattices in multi-color application

    NASA Astrophysics Data System (ADS)

    Guo, Jie; Wang, Guowei; Lin, Xu; Hao, Ruiting

    2013-09-01

    Recently excellent infrared detectors have been demonstrated using InAs/GaSb superlattice materials sensitive at wavelength from 3um to greater than 32um. Using empirical tight binding method (ETBM), different structures as InAs(xML)/GaSb(8ML), (x=2, 4, 6, 8) and InAs(14ML)/GaSb(7ML) were designed for various cut-off wavelengths from short to long IR wavelength. These materials were grown by MBE with valved cracker cells for arsenic and antimony on p-type GaSb(001) substrates. The microstructure and the bandgap Eg were verified by high resolution X-ray diffraction and photoresponse spectra. The temperature dependence of Eg and photoresponse responsivity Rv were studied. The differential resistance under zero bias R0 in MWIR photodiode was measured up to 106 ohms. The ideality factor in the range of 1.5 to 2.1 indicates the generation-recombination current and surface leakage current are the dominant leakage in the depletion region. These results will promote InAs/GaSb superlattices infrared detectors research in multi-color from short to long wave IR application.

  12. Short wavelength vertical fluctuations of the melting regime in the suboceanic melting region

    NASA Astrophysics Data System (ADS)

    Brunelli, D.; Seyler, M.; Paganelli, E.; Barbieri, E.

    2011-12-01

    Modelling of mantle residua cpx REE patterns allow recognizing short wavelenght vertical variability of the porosity regime of a melting region differing from that deriving after melt focusing processes ultimately leading to dunitic channelling of the mantle section. A trace element detailed study of residual clinopyroxenes from the ultraslow eastern SWIR section shows compositional trends crosscutting the expected partial melting trends at the typical kilometre lenghtscale. In the REE compositional space these trends appear as pattern rotations around a mid-point. Open-system melting modelling reveals the intensity of the rotation and the position of the pivot element depending mainly on the ratio between input/output melt flux and on the enrichment of the percolating melt with respect to the depleted screen. We derived two important indications on the process: first some regions experience near-batch melting, i.e. melt accumulation with very low output melt flux, in regions soon after the grt/sp transition. This observations suggest permeability barriers to occur in the main melting region possibly due to porosity consumption by melt/rock reaction enhanced by grt breakdown energy competition. Consequently melt stagnation processes similar to those described for the plagioclase facies may act in the spinel field portion of the melting region. Second: we attest the presence of enriched melts delivered to the spinel field region. These melts may derive from very low degrees of melting in the garnet field of a DMM source or by consumption of an enriched heterogeneity with a lower melting point than the surrounding mantle.

  13. A novel millimetre-wave band radio-over-fiber system with dense wavelength division multiplexing star architecture

    NASA Astrophysics Data System (ADS)

    Zhang, Xiupu; Liu, Baozhu; Yao, Jianping; Wu, Ke; Kashyap, Raman

    2005-09-01

    In this paper, we propose a novel millimeter-wave (mm-wave) band radio over fiber (RoF) system with dense wavelength division multiplexing (DWDM) star architecture. Two lasers with a small wavelength difference, phase locked and polarization-aligned, are allocated at a central station (CS) for connecting the CS and each base station (BS); one laser is used for transmitting light and the other for the remote local oscillator. For the conceptual illustration, we consider a DWDM RoF system with a channel spacing of 12.5 GHz and radio frequency (RF) of ~30-GHz mm-wave band. In the downlink system, a single-side band (SSB) subcarrier is used with low RF imposed onto an optical carrier at the CS, and an mm-wave band RF signal is obtained at each BS using direct photo-detection by the SSB subcarrier beat with the remote oscillator. In the uplink system, the received mm-wave band RF signal at each BS is imposed onto the two optical carriers simultaneously, one optical carrier with the closest SSB subcarrier is optically filtered out and fed into in the uplink transmission fiber without frequency interleaving; the electrical signal with a low intermediate frequency can be photo-detected directly at the CS. Such a RoF system has simple, cost-effective and maintenance reduced BS's, and is immune to laser phase noise in principle.

  14. Short wavelength emission of AlGaInP quantum dots grown on GaP substrate.

    PubMed

    Gerhard, S; Kremling, S; Höfling, S; Worschech, L; Forchel, A

    2011-10-14

    We report on the growth of AlGaInP quantum dots (QDs) with Al contents between 0% and 10% on GaP substrate by gas-source molecular beam epitaxy and the investigation of their morphological and low temperature photoluminescence properties. These high areal density QDs show short wavelength emission between 575 and 612 nm depending on their composition. The authors interpret the QD emission as originating from indirect type-II transitions. This interpretation is supported by a single-band effective-mass model, which allows us to describe the role of differing barrier composition in the QD emission. Time-resolved photoluminescence measurements are performed and discussed with respect to the calculations. PMID:21918297

  15. Non-relativistic particle higher-order harmonic radiation based short-wavelength laser and the operation stability

    NASA Astrophysics Data System (ADS)

    Luo, Xiao-Hua; Wu, Mu-Ying; He, Wei; Shao, Ming-Zhu; Luo, Shiyu

    2011-07-01

    Under classical mechanics, the general equation of particle motion in the periodic field is derived. In the dampless case, the existence possibility of the higher-order harmonic radiation is explored by using Bessel function expansion of a generalized trigonometrical function and the multi-scale method. In the damping case, the critical properties and a chaotic behavior are discussed by the Melnikov method. The results show that the use of a higher-order harmonic radiation of non-relativistic particles as a short-wavelength laser source is perfectly possible, and the system's critical condition is related to its parameters. Only by adjusting parameters suitablely, the stable higher-order harmonic radiation with bigger intensity can be obtained.

  16. Short-wavelength infrared photodetector on Si employing strain-induced growth of very tall InAs nanowire arrays.

    PubMed

    Shin, Hyun Wook; Lee, Sang Jun; Kim, Doo Gun; Bae, Myung-Ho; Heo, Jaeyeong; Choi, Kyoung Jin; Choi, Won Jun; Choe, Jeong-woo; Shin, Jae Cheol

    2015-01-01

    One-dimensional crystal growth enables the epitaxial integration of III-V compound semiconductors onto a silicon (Si) substrate despite significant lattice mismatch. Here, we report a short-wavelength infrared (SWIR, 1.4-3 μm) photodetector that employs InAs nanowires (NWs) grown on Si. The wafer-scale epitaxial InAs NWs form on the Si substrate without a metal catalyst or pattern assistance; thus, the growth is free of metal-atom-induced contaminations, and is also cost-effective. InAs NW arrays with an average height of 50 μm provide excellent anti-reflective and light trapping properties over a wide wavelength range. The photodetector exhibits a peak detectivity of 1.9 × 10(8) cm · Hz(1/2)/W for the SWIR band at 77 K and operates at temperatures as high as 220 K. The SWIR photodetector on the Si platform demonstrated in this study is promising for future low-cost optical sensors and Si photonics. PMID:26035286

  17. Anodic fluoride passivation of type II InAs/GaSb superlattice for short-wavelength infrared detector

    NASA Astrophysics Data System (ADS)

    Zhang, Li Xue; Sun, Wei Guo; Lv, Yan Qiu; Li, Mo; Ding, Jia Xin; Si, Jun Jie

    2015-02-01

    One of the major challenges of antimonide-based devices arises owing to the large number of surface states generated during fabrication processes. Surface passivation and subsequent capping of the surfaces are absolutely essential for any practical applicability of this material system. In this paper, we proposed a new passivation method (zinc sulfide coating after anodic fluoride) for InAs/GaSb superlattice infrared detectors. InAs/GaSb superlattice short-wavelength infrared materials were grown by molecular beam epitaxy on GaSb (100) substrates. A GaSb buffer layer, which can decrease the occurrence of defects with similar pyramidal structure, was grown for optimized superlattice growth condition. High resolution X-ray diffraction indicated that the period of the superlattice corresponding to fourth satellite peak was 39.77 Å. The atomic force microscopy images show the roughness was below 1.7 nm. The result of photoresponse spectra shows that the cutoff wavelength was 3.05 μm at 300 K.

  18. Anodic fluoride passivation of type II InAs/GaSb superlattice for short-wavelength infrared detector

    NASA Astrophysics Data System (ADS)

    Zhang, Li Xue; Sun, Wei Guo; Lv, Yan Qiu; Li, Mo; Ding, Jia Xin; Si, Jun Jie

    2014-09-01

    One of the major challenges of antimonide-based devices arises owing to the large number of surface states generated during fabrication processes. Surface passivation and subsequent capping of the surfaces are absolutely essential for any practical applicability of this material system. In this paper, we proposed a new passivation method (zinc sulfide coating after anodic fluoride) for InAs/GaSb superlattice infrared detectors. InAs/GaSb superlattice short-wavelength infrared materials were grown by molecular beam epitaxy on GaSb (100) substrates. A GaSb buffer layer, which can decrease the occurrence of defects with similar pyramidal structure, was grown for optimized superlattice growth condition. High resolution X-ray diffraction indicated that the period of the superlattice corresponding to fourth satellite peak was 39.77 Å. The atomic force microscopy images show the roughness was below 1.7 nm. The result of photoresponse spectra shows that the cutoff wavelength was 3.05 μm at 300 K.

  19. Short-wavelength, mid- and far-infrared intersubband absorption in nonpolar GaN/Al(Ga)N heterostructures

    NASA Astrophysics Data System (ADS)

    Lim, Caroline B.; Beeler, Mark; Ajay, Akhil; Lähnemann, Jonas; Bellet-Amalric, Edith; Bougerol, Catherine; Schörmann, Jörg; Eickhoff, Martin; Monroy, Eva

    2016-05-01

    This paper assesses nonpolar m-oriented GaN:Si/Al(Ga)N heterostructures grown on free-standing GaN for intersubband optoelectronics in the short-wavelength, mid- and far-infrared ranges. Characterization results are compared with reference c-plane samples and interpreted by correlation with self-consistent Schrödinger–Poisson calculations. In the near- and mid-infrared regions, we demonstrate m-GaN/Al(Ga)N multi-quantum-wells exhibiting room-temperature intersubband absorption tunable in the range of 1.5–5.8 µm (827–214 meV), the long wavelength limit being set by the second order of the Reststrahlen band in the GaN substrates. Extending the study to the far-infrared region, low-temperature intersubband transitions in the 1.5–9 THz range (6.3–37.4 meV) are observed in larger m-plane GaN/AlGaN multi-quantum-wells, covering most of the 7–10 THz band forbidden to GaAs-based technologies.

  20. Short-wavelength infrared photodetector on Si employing strain-induced growth of very tall InAs nanowire arrays

    PubMed Central

    Wook Shin, Hyun; Jun Lee, Sang; Gun Kim, Doo; Bae, Myung-Ho; Heo, Jaeyeong; Jin Choi, Kyoung; Jun Choi, Won; Choe, Jeong-woo; Cheol Shin, Jae

    2015-01-01

    One-dimensional crystal growth enables the epitaxial integration of III-V compound semiconductors onto a silicon (Si) substrate despite significant lattice mismatch. Here, we report a short-wavelength infrared (SWIR, 1.4–3 μm) photodetector that employs InAs nanowires (NWs) grown on Si. The wafer-scale epitaxial InAs NWs form on the Si substrate without a metal catalyst or pattern assistance; thus, the growth is free of metal-atom-induced contaminations, and is also cost-effective. InAs NW arrays with an average height of 50 μm provide excellent anti-reflective and light trapping properties over a wide wavelength range. The photodetector exhibits a peak detectivity of 1.9 × 108  cm·Hz1/2/W for the SWIR band at 77 K and operates at temperatures as high as 220 K. The SWIR photodetector on the Si platform demonstrated in this study is promising for future low-cost optical sensors and Si photonics. PMID:26035286

  1. Short-Wavelength Infrared (SWIR) spectroscopy of low-grade metamorphic volcanic rocks of the Pilbara Craton

    NASA Astrophysics Data System (ADS)

    Abweny, Mohammad S.; van Ruitenbeek, Frank J. A.; de Smeth, Boudewijn; Woldai, Tsehaie; van der Meer, Freek D.; Cudahy, Thomas; Zegers, Tanja; Blom, Jan-Kees; Thuss, Barbara

    2016-05-01

    This paper shows the results of Short-Wavelength Infrared (SWIR) spectroscopy investigations of volcanic rocks sampled from low-grade metamorphic greenstone belts of the Archean Pilbara Craton in Western Australia. From the reflectance spectra a range of spectrally active minerals were identified, including chlorites, hornblende, actinolite, epidote and white micas. The rock samples were grouped into mineral assemblages based on their spectrally identified minerals and stratigraphic positions. The metamorphic amphibolite and greenschist facies could be identified from the SWIR spectroscopic data as well as three sub zones of the greenschist facies: 1) a zone containing Fe-chlorite; 2) a zone containing intermediate chlorite and epidote; and 3) a zone containing intermediate chlorite, actinolite and hornblende. Spectral parameters were calculated from the reflectance spectra to assess the metamorphic grade and zones. Plots of the depth parameters of the Fe-OH feature near 2250 nm versus the Mg-OH feature near 2390 nm differentiate the metamorphic amphibolite and greenschist facies and a transition zone between the two. The wavelength position parameter of the Mg-OH absorption feature near 2340 nm also serves to discriminate between the various metamorphic sub zones. The identification of the metamorphic grades of the volcanic sequences in greenstone belts with SWIR spectroscopy is useful for regional geological field studies, exploration for metamorphic mineral deposits hosted in the greenstone belts and the interpretation of hyperspectral remote sensing data sets covering similar types of terranes.

  2. Short-wave infrared (SWIR) spectral imager based on Fabry-Perot interferometer for remote sensing

    NASA Astrophysics Data System (ADS)

    Mannila, Rami; Holmlund, Christer; Ojanen, Harri J.; Näsilä, Antti; Saari, Heikki

    2014-10-01

    VTT Technical Research Centre of Finland has developed a spectral imager for short-wave infrared (SWIR) wavelength range. The spectral imager is based on a tunable Fabry-Perot interferometer (FPI) accompanied by a commercial InGaAs Camera. The FPI consists of two dielectric coated mirrors separated by a tunable air gap. Tuning of the air gap tunes also transmitted wavelength and therefore FPI acts as a tunable band bass filter. The FPI is piezo-actuated and it uses three piezo-actuators in a closed capacitive feedback loop for air gap tuning. The FPI has multiple order transmission bands, which limit free spectral range. Therefore spectral imager contains two FPI in a stack, to make possible to cover spectral range of 1000 - 1700 nm. However, in the first tests imager was used with one FPI and spectral range was limited to 1100-1600 nm. The spectral resolution of the imager is approximately 15 nm (FWHM). Field of view (FOV) across the flight direction is 30 deg. Imaging resolution of the spectral imager is 256 x 320 pixels. The focal length of the optics is 12 mm and F-number is 3.2. This imager was tested in summer 2014 in an unmanned aerial vehicle (UAV) and therefore a size and a mass of the imager were critical. Total mass of the imager is approximately 1200 grams. In test campaign the spectral imager will be used for forest and agricultural imaging. In future, because results of the UAV test flights are promising, this technology can be applied to satellite applications also.

  3. Continuous-wave wavelength conversion for high-power applications using an external cavity diamond Raman laser.

    PubMed

    Kitzler, Ondrej; McKay, Aaron; Mildren, Richard P

    2012-07-15

    We demonstrate continuous-wave (cw) operation of a diamond Raman laser at 1240 nm in an external cavity configuration. The output power increased linearly with pump power with a 49.7% slope efficiency and reached 10.1 W at the maximum available pump power of 31 W. The combination of resonator design with diamond provides a novel approach to power-scalable cw wavelength and beam conversion. PMID:22825135

  4. Extraordinary transmission of electromagnetic waves through sub-wavelength slot arrays mediated by spoof surface plasmon polaritons

    NASA Astrophysics Data System (ADS)

    Pang, Yongqiang; Wang, Jiafu; Ma, Hua; Feng, Mingde; Xia, Song; Xu, Zhuo; Qu, Shaobo

    2016-05-01

    One-dimensional gratings consisting of sub-wavelength metallic slot arrays have been widely applied in the design of novel devices due to their polarization-selective characteristics. When the incident electric field is polarized along the slot direction, the slot arrays are opaque, behaving like a metal surface. Here we propose a scheme of making slot arrays transparent for electromagnetic (EM) waves, which is achieved by the incorporation of corrugated metal strip arrays. Incident waves are first converted into spoof surface plasmon polaritons (SSPPs) propagating along the strips. Since SSPPs confine EM fields in sub-wavelength scales, EM waves can penetrate through the sub-wavelength slots. High transmission was thus obtained, with an efficiency as high as 95%. Moreover, position and bandwidth of the transmission band can be tailored by adjusting the groove depth and the slot width, respectively. It is expected that the design may find potential applications in the multifunctional devices with frequency- and polarization-selective features.

  5. Large Scale (~25 m2) metal diffraction grating of submicron period as possible optoelectronic detector for short scalar gravitational waves

    NASA Astrophysics Data System (ADS)

    Zhukov, Valery A.

    2014-12-01

    A method of detecting of short scalar gravitational waves with a wavelength of λ ~ 0.5 μm is proposed, in contrast to LIGO Project, aimed at detecting of long quadrupole gravitational waves (λ ~ 43 ÷ 10000 km). The conduction electrons in a metal are proposed to use as gravitational receiving antennas instead of massive pendulums. It is shown that using a Large Scale metal diffraction grating you can convert the mechanical vibrations of the conduction electrons of metal into a plane electromagnetic wave propagating along the normal to the grating. It is shown that when the amplitude of the scalar gravitational wave in a source (in quasar at the center of our galaxy) is greater than Ago ≍ 5 1020cm/s2, you can register it with the help of a large optical telescope equipped with the proposed diffraction grating. It is shown that the special theory of relativity allows the amplitude of the scalar gravitational waves in this source by 5 orders of magnitude greater than the above-mentioned minimum value.

  6. Short gravity-capillary waves modulation due to long surface and internal wave: laboratory and field experiment

    NASA Astrophysics Data System (ADS)

    Sergievskaya, I. A.; Ermakov, S. A.

    2011-11-01

    Modulation of short wind gravity-capillary waves (SGCW) due to long surface and internal waves in the presence of surface films of different surfactant concentrations has been studied in wave tank and field experiments using Ka-band radar. Wave tank experiments were carried out in the oval wind wave tank of the Institute of Applied Physics RAS at different wind velocities (2 m/s to 5 m/s) and at two fetches. It was obtained that the Modulation Transfer Function (MTF) magnitude in film slicks was several times larger than in non-slick areas, the phase of MTF was also changed in the presence of films. Similar conclusions were made from field observations of radar backscatter modulation due to long surface and internal waves, here the effect of enhanced surface waves modulation in slick zones was revealed, too. Different physical mechanisms were taken into account to explain experiment, namely, geometrical effects, modulation of surfactant concentration, transformation of the wind velocity over the long wave profile. Theoretical analysis has demonstrated that the effect of enhanced modulation could not be explained using only the mechanisms mentioned above. MTF is assumed to be determined by the effect of bound components of short wind-wave spectrum.

  7. Sinusoidal Wave Estimation Using Photogrammetry and Short Video Sequences

    PubMed Central

    Rupnik, Ewelina; Jansa, Josef; Pfeifer, Norbert

    2015-01-01

    The objective of the work is to model the shape of the sinusoidal shape of regular water waves generated in a laboratory flume. The waves are traveling in time and render a smooth surface, with no white caps or foam. Two methods are proposed, treating the water as a diffuse and specular surface, respectively. In either case, the water is presumed to take the shape of a traveling sine wave, reducing the task of the 3D reconstruction to resolve the wave parameters. The first conceived method performs the modeling part purely in 3D space. Having triangulated the points in a separate phase via bundle adjustment, a sine wave is fitted into the data in a least squares manner. The second method presents a more complete approach for the entire calculation workflow beginning in the image space. The water is perceived as a specular surface, and the traveling specularities are the only observations visible to the cameras, observations that are notably single image. The depth ambiguity is removed given additional constraints encoded within the law of reflection and the modeled parametric surface. The observation and constraint equations compose a single system of equations that is solved with the method of least squares adjustment. The devised approaches are validated against the data coming from a capacitive level sensor and on physical targets floating on the surface. The outcomes agree to a high degree. PMID:26690171

  8. Sinusoidal Wave Estimation Using Photogrammetry and Short Video Sequences.

    PubMed

    Rupnik, Ewelina; Jansa, Josef; Pfeifer, Norbert

    2015-01-01

    The objective of the work is to model the shape of the sinusoidal shape of regular water waves generated in a laboratory flume. The waves are traveling in time and render a smooth surface, with no white caps or foam. Two methods are proposed, treating the water as a diffuse and specular surface, respectively. In either case, the water is presumed to take the shape of a traveling sine wave, reducing the task of the 3D reconstruction to resolve the wave parameters. The first conceived method performs the modeling part purely in 3D space. Having triangulated the points in a separate phase via bundle adjustment, a sine wave is fitted into the data in a least squares manner. The second method presents a more complete approach for the entire calculation workflow beginning in the image space. The water is perceived as a specular surface, and the traveling specularities are the only observations visible to the  cameras, observations that are notably single image. The depth ambiguity is removed given additional constraints encoded within the law of reflection and the modeled parametric surface. The observation and constraint equations compose a single system of equations that is solved with the method of least squares adjustment. The devised approaches are validated against the data coming from a capacitive level sensor and on physical targets floating on the surface. The outcomes agree to a high degree. PMID:26690171

  9. Short-wavelength undulatory extinction in quartz recording coseismic deformation in the middle crust - an experimental study

    NASA Astrophysics Data System (ADS)

    Trepmann, C. A.; Stckhert, B.

    2013-09-01

    Deformation experiments are carried out on natural vein quartz in a modified Griggs-type solid medium apparatus to explore the preservation potential of microfabrics created by crystal-plastic deformation at high stress, overprinted during subsequent creep at lower stress. A corresponding stress history is expected for the upper plastosphere, where fault slip during an earthquake causes quasi-instantaneous loading to high stress, followed by stress relaxation. The question is whether evidence of crystal-plastic deformation at high stress, hence an indicator of past seismic activity, can still be identified in the microstructure after overprint by creep at lower stresses. First, quartz samples are deformed at a temperature of 400 C and constant strain rate of 10-4 s-1 ("kick"), and then held at 900 to 1000 C at residual stress ("creep"). In quartz exclusively subject to high-stress deformation, lamellar domains of slightly differing crystallographic orientation (misorientation angle < 2) and a few tens of micrometres wide occur. In the transmission electron microscope (TEM), these areas show a high density of tangled dislocations and cellular structures. After "kick and creep" experiments, pronounced short-wavelength undulatory extinction (SWUE) is observed in the polarization microscope. The wavelength of SWUE is up to 10 ?m, with oscillatory misorientation of up to a few degrees. TEM inspection reveals domains with high density of dislocations and differing diffraction contrast bound by poorly ordered dislocation walls. Only zones with exceptional damage generated during high-stress deformation are replaced by small new grains with a diameter of about 10 to 20 ?m, forming strings of recrystallized grains. For large original grains showing SWUE, the Schmid factor for basal ? a ? glide is found to be high. SWUE is taken to reflect high-stress crystal-plastic deformation, the modified microstructure being sufficiently stable to be recognized after subsequent creep as an indicator of past seismic activity.

  10. Evidence for nonuniversal behavior of paraconductivity caused by predominant short-wavelength Gaussian fluctuations in YBa2Cu3O6.9

    NASA Astrophysics Data System (ADS)

    Gauzzi, Andrea; Pavuna, Davor

    1995-06-01

    We report on in-plane paraconductivity measurements in thin YBa2Cu3O6.9 films. Our analysis of the data shows that the temperature dependence of paraconductivity is affected by lattice disorder and deviates at all temperatures from the universal power laws predicted by both scaling and mean-field theories. This gives evidence for the absence of critical fluctuations and for the failure of the Aslamazov-Larkin universal relation between critical exponent and dimensionality of the spectrum of Gaussian fluctuations. We account quantitatively for the data within the experimental error by introducing a short-wavelength cutoff into this spectrum. This implies that three-dimensional short-wavelength Gaussian fluctuations dominate in YBa2Cu3O6.9 and suggests a rapid attenuation of these fluctuations with decreasing wavelength in short-coherence-length systems as compared to the case of the conventional Ginzburg-Landau theory.

  11. Spiral Arm Pitch Angle Measurements of Galaxies in Different Wavelengths of Light to Investigate a Prediction of Density Wave Theory

    NASA Astrophysics Data System (ADS)

    Pour Imani, Hamed; Davis, Benjamin L.; Shields, Douglas W.; Kennefick, Julia; Kennefick, Daniel

    2015-08-01

    Spiral structure in disk galaxies has been an important study of astronomy for decades. In understanding this structure one of the major parameters is the pitch angle of spiral arms. The density wave theory was proposed by C.Lin and F.Shu in the mid-1960s to explain the spiral arm structure of spiral galaxies [1]. A prediction of this theory is that the pitch angle of spiral arms for galaxies with blue-light wavelength images should be smaller than for infrared-light, so we have tighter spiral arms in blue band images. Young (blue) stars in arms of the galaxies move head of the old (red) stellar populations, clouds and dust. This implies that blue stars should exhibit tighter arms. In ref [2], E.M Garcia et al (2014) investigate the behavior of the pitch angle of spiral arms depending on optical wavelength. They worked on five galaxies and their images band-pass wavelength are in the optical range and their results show that just three of those five galaxies are consistent with density wave theory.In this research, we worked with a bigger samples and for each galaxy we used an optical wavelength image (B-Band: 445 nm) and another image from the Spitzer Space Telescope in a deep infrared range (Infrared: 8.0 μm) and we measured the pitch angle with the 2DFFT code [3]. Our results show that for optical range images we have smaller pitch angle compared to the infrared range and all of our measurements support with the density wave theory. Our results for 42 NGC galaxies show that spiral arms for images with optical range wavelength are clearly tighter typically by a few degrees than spiral arms in infrared range wavelength.Reference:[1]. Bertin, G. and Lin, C. (1996), MIT Press[2]. E.M Garcia et al, 2014 ApJ 793 L19[3]. Benjamin L. Davis et al. 2012 ApJS 199 33

  12. Digital Audio Broadcasting in the Short Wave Bands

    NASA Technical Reports Server (NTRS)

    Vaisnys, Arvydas

    1998-01-01

    For many decades the Short Wae broadcasting service has used high power, double-sideband AM signals to reach audiences far and wide. While audio quality was usually not very high, inexpensive receivers could be used to tune into broadcasts fro distant countries.

  13. Design and construction of a short-wave infrared 3.3X continuous zoom lens

    NASA Astrophysics Data System (ADS)

    Olson, Craig; Goodman, Tim; Addiego, Chris; Mifsud, Steve

    2010-08-01

    We present the definition, design, and construction of a 3.3X continuous-zoom short-wave infrared (SWIR) telephoto lens. Compared to visible and mid-wave infrared lenses, defining the appropriate lens requirements of short-wave lenses have some different trade-offs in terms of balancing radiometry and optimum focal plane sampling. In addition, the design process of optimizing a visible zoom design form of given first-order properties to work in the SWIR band reveals some challenges in glass selection and subsequent aberration balancing. A comparison of the actual measured MTF performance of a prototype lens shows reasonable performance compared to the design.

  14. High sensitivity to short wavelengths in a lizard and implications for understanding the evolution of visual systems in lizards

    PubMed Central

    Fleishman, Leo J.; Loew, Ellis R.; Whiting, Martin J.

    2011-01-01

    Progress in developing animal communication theory is frequently constrained by a poor understanding of sensory systems. For example, while lizards have been the focus of numerous studies in visual signalling, we only have data on the spectral sensitivities of a few species clustered in two major clades (Iguania and Gekkota). Using electroretinography and microspectrophotometry, we studied the visual system of the cordylid lizard Platysaurus broadleyi because it represents an unstudied clade (Scinciformata) with respect to visual systems and because UV signals feature prominently in its social behaviour. The retina possessed four classes of single and one class of double cones. Sensitivity in the ultraviolet region (UV) was approximately three times higher than previously reported for other lizards. We found more colourless oil droplets (associated with UV-sensitive (UVS) and short wavelength-sensitive (SWS) photoreceptors), suggesting that the increased sensitivity was owing to the presence of more UVS photoreceptors. Using the Vorobyev–Osorio colour discrimination model, we demonstrated that an increase in the number of UVS photoreceptors significantly enhances a lizard's ability to discriminate conspecific male throat colours. Visual systems in diurnal lizards appear to be broadly conserved, but data from additional clades are needed to confirm this. PMID:21389031

  15. Relationship between short-wavelength automatic perimetry and Heidelberg retina tomograph parameters in eyes with ocular hypertension

    PubMed Central

    Pitsas, Christos; Papaconstantinou, Dimitrios; Georgalas, Ilias; Halkiadakis, Ioannis

    2015-01-01

    AIM To compare and correlate optic nerve head parameters obtained by Heidelberg retina tomograph (HRT) with short-wavelength automatic perimetry (SWAP) indices in eyes with ocular hypertension (OHT). METHODS One hundred and forty-six patients with OHT included in the present study. All subjects had reliable SWAP and HRT measurements performed within a 2wk period. The eyes were classified as normal/abnormal according to visual field criteria and Moorfields regression analysis (MRA). Correlations between visual field indices and HRT parameters were analyzed using Pearson correlation coefficient (r). RESULTS Twenty-nine eyes (19.9%) had SWAP defects. Twenty-nine eyes (19.9%) were classified as abnormal according to global MRA. Six eyes (4.1%) had abnormal global MRA and SWAP defects. The k statistic is 0.116 (P=0.12) indicating a very poor agreement between the methods. No statistical significant correlation between HRT and SWAP parameters was detected. CONCLUSION SWAP defects may coexist with abnormalities of optic disc detected by HRT in eyes with OHT. In most eyes, however, the two methods detect different glaucoma properties. PMID:26558219

  16. Infragravity-wave modulation of short-wave celerity in the surf zone

    NASA Astrophysics Data System (ADS)

    Tissier, M.; Bonneton, P.; Michallet, H.; Ruessink, B. G.

    2015-10-01

    The cross-shore evolution of individual wave celerity is investigated using two high-resolution laboratory experiments on bichromatic waves. Individual waves are tracked during their onshore propagation and their characteristics, including celerity, are estimated. The intrawave variability in celerity is low in the shoaling zone but increases strongly after breaking. It is maximum when the infragravity-wave height to water depth ratio is the largest, that is to say close to the shoreline. There the observed range of individual wave celerity can be as large as the mean celerity value. This variability can be largely explained by the variations in water depth and velocity induced by the infragravity waves. The differences in celerity are such that they lead to the merging of the waves in the inner surf zone for most of the wave conditions considered. Again, the location at which the first waves start merging strongly correlates with the infragravity-wave height to water depth ratio. The consequences of these findings for celerity-based depth-inversion techniques are finally discussed. Surprisingly, accounting for the infragravity-wave modulation of the velocity field in the celerity estimate does not significantly improve depth estimation in the surf zone. However, it is shown that the occurrence of bore merging decreases significantly the coherence of the wavefield in the surf zone. This loss of coherence could hamper celerity estimation from pixel intensity time series and explain, at least partly, the relatively poor performance of depth-inversion techniques in the inner surf zone.

  17. [Comparative experimental morphological study of efficacy and safety of near-infrared and visible wave-length laser iridoplasty].

    PubMed

    Gamidov, A A; Fedorov, A A; Siplivyĭ, V I

    2011-01-01

    The features of interaction of laser radiation with iris tissue were determined in experimental morphological study. The potential of laser irradiation with different spectral characteristics for pupil ectopia correction is estimated. The results of morphometry showed effectiveness of near-infrared diode laser radiation, that presents as an iris contraction in coagulation region with minimal tissue trauma. This fact allows us to propose a near-infrared diode laser radiation as a treatment option for correction of pupil form and location. Alternatively visible wave-length laser showed to be less effective and more traumatic. PMID:21882642

  18. Multi-Wavelength Observations of Prominence and Filament Oscillations Induced by Shock Waves

    NASA Astrophysics Data System (ADS)

    Shen, Yuandeng

    2015-08-01

    Large amplitude prominence (filament) oscillations could be classified into two categories: the transverse and the longitudinal oscillations. Previous observations indicated that the former type is often trigger by chromosphere Moreton waves in association with remote flares, while the latter is usually associated with nearby micro flare, filament, and jet activities . Using the high temporal and spatial resolution data taken by the SDO, STEREO, and SMART, we present two cases of prominence/filament oscillations induced by large-scale coronal shock waves. For the first case, a chain of oscillating filaments are observed in a proper order after the shock wave associated with a remote X2.1 flare on September 06, 2011, and the filament oscillations were triggered by the surface component of the EUV wave associated with the flare. For the second case, simultaneous transverse oscillation of a limb prominence and longitudinal oscillation in an on-disk filament are launched by the shock wave in association with the X6.9 flare on August 09, 2011. In these observations, the parameters of the oscillating filaments are determined, and they are used to estimate the filament magnetic field. These observations provide new evidence for diagnosing the properties of the oscillating filaments and the associated coronal shock waves.

  19. Application of short-wave infrared (SWIR) spectroscopy in quantitative estimation of clay mineral contents

    NASA Astrophysics Data System (ADS)

    You, Jinfeng; Xing, Lixin; Liang, Liheng; Pan, Jun; Meng, Tao

    2014-03-01

    Clay minerals are significant constituents of soil which are necessary for life. This paper studied three types of clay minerals, kaolinite, illite, and montmorillonite, for they are not only the most common soil forming materials, but also important indicators of soil expansion and shrinkage potential. These clay minerals showed diagnostic absorption bands resulting from vibrations of hydroxyl groups and structural water molecules in the SWIR wavelength region. The short-wave infrared reflectance spectra of the soil was obtained from a Portable Near Infrared Spectrometer (PNIS, spectrum range: 1300~2500 nm, interval: 2 nm). Due to the simplicity, quickness, and the non-destructiveness analysis, SWIR spectroscopy has been widely used in geological prospecting, chemical engineering and many other fields. The aim of this study was to use multiple linear regression (MLR) and partial least squares (PLS) regression to establish the optimizing quantitative estimation models of the kaolinite, illite and montmorillonite contents from soil reflectance spectra. Here, the soil reflectance spectra mainly refers to the spectral reflectivity of soil (SRS) corresponding to the absorption-band position (AP) of kaolinite, illite, and montmorillonite representative spectra from USGS spectral library, the SRS corresponding to the AP of soil spectral and soil overall spectrum reflectance values. The optimal estimation models of three kinds of clay mineral contents showed that the retrieval accuracy was satisfactory (Kaolinite content: a Root Mean Square Error of Calibration (RMSEC) of 1.671 with a coefficient of determination (R2) of 0.791; Illite content: a RMSEC of 1.126 with a R2 of 0.616; Montmorillonite content: a RMSEC of 1.814 with a R2 of 0.707). Thus, the reflectance spectra of soil obtained form PNIS could be used for quantitative estimation of kaolinite, illite and montmorillonite contents in soil.

  20. Short-wave infrared barriode detectors using InGaAsSb absorption material lattice matched to GaSb

    SciTech Connect

    Craig, A. P.; Percy, B.; Marshall, A. R. J.; Jain, M.; Wicks, G.; Hossain, K.; Golding, T.; McEwan, K.; Howle, C.

    2015-05-18

    Short-wave infrared barriode detectors were grown by molecular beam epitaxy. An absorption layer composition of In{sub 0.28}Ga{sub 0.72}As{sub 0.25}Sb{sub 0.75} allowed for lattice matching to GaSb and cut-off wavelengths of 2.9 μm at 250 K and 3.0 μm at room temperature. Arrhenius plots of the dark current density showed diffusion limited dark currents approaching those expected for optimized HgCdTe-based detectors. Specific detectivity figures of around 7×10{sup 10} Jones and 1×10{sup 10} Jones were calculated, for 240 K and room temperature, respectively. Significantly, these devices could support focal plane arrays working at higher operating temperatures.

  1. Integro-differential modeling of ICRH wave propagation and damping at arbitrary cyclotron harmonics and wavelengths in tokamaks

    NASA Astrophysics Data System (ADS)

    Van Eester, D.; Lerche, E.

    2014-02-01

    Both at low and higher cyclotron harmonics, properly accounting for finite Larmor radius effects is crucial in many ion cyclotron resonance frequency heating scenarios creating high energy tails. The present paper discusses ongoing work to extend the 1D TOMCAT wave equation solver [D. Van Eester & R. Koch, Plasma Phys. Contr. Fusion 40 (1998) 1949] to arbitrary harmonics and arbitrary wavelengths. Rather than adopting the particle position, the guiding center position is used as the independent variable when writing down an expression for the dielectric response. Adopting a philosophy originally due to Kaufman [A.N. Kaufman, Phys. Fluids 15 (1972) 1063], the relevant dielectric response in the Galerkin formalism is written in a form where the electric field and the test function vector appear symmetrically, which yields a power balance equation that guarantees non-negative absorption for any wave type for Maxwellian plasmas. Moreover, this choice of independent variable yields intuitive expressions that can directly be linked to the corresponding expressions in the RF diffusion operator. It also guarantees that a positive definite power transfer from waves to particles is ensured for any of the wave modes in a plasma in which all populations have a Maxwellian distribution, as is expected from first principles. Rather than relying on a truncated Taylor series expansion of the dielectric response, an integro-differential approach that retains all finite Larmor radius effects [D. Van Eester & E. Lerche, Plasma Phys. Control. Fusion 55 (2013) 055008] is proposed.

  2. Integro-differential modeling of ICRH wave propagation and damping at arbitrary cyclotron harmonics and wavelengths in tokamaks

    SciTech Connect

    Van Eester, D.; Lerche, E.

    2014-02-12

    Both at low and higher cyclotron harmonics, properly accounting for finite Larmor radius effects is crucial in many ion cyclotron resonance frequency heating scenarios creating high energy tails. The present paper discusses ongoing work to extend the 1D TOMCAT wave equation solver [D. Van Eester and R. Koch, Plasma Phys. Contr. Fusion 40 (1998) 1949] to arbitrary harmonics and arbitrary wavelengths. Rather than adopting the particle position, the guiding center position is used as the independent variable when writing down an expression for the dielectric response. Adopting a philosophy originally due to Kaufman [A.N. Kaufman, Phys. Fluids 15 (1972) 1063], the relevant dielectric response in the Galerkin formalism is written in a form where the electric field and the test function vector appear symmetrically, which yields a power balance equation that guarantees non-negative absorption for any wave type for Maxwellian plasmas. Moreover, this choice of independent variable yields intuitive expressions that can directly be linked to the corresponding expressions in the RF diffusion operator. It also guarantees that a positive definite power transfer from waves to particles is ensured for any of the wave modes in a plasma in which all populations have a Maxwellian distribution, as is expected from first principles. Rather than relying on a truncated Taylor series expansion of the dielectric response, an integro-differential approach that retains all finite Larmor radius effects [D. Van Eester and E. Lerche, Plasma Phys. Control. Fusion 55 (2013) 055008] is proposed.

  3. The model and output characteristics of intra-cavity pumped continuous-wave self-Raman three-wavelength lasers

    NASA Astrophysics Data System (ADS)

    Wang, Hai-Liang; Zhu, Leng-Xi; Dong, Yuan; Li, Ye; Zhang, Fengdong; Li, Shutao; Jin, Guangyong

    2015-08-01

    In this paper, the scheme of intra-cavity pumped self-Raman continuous-wave lasers used to simultaneously output the quasi-three-level, four-level fundamental and first Stokes three-wavelength lasers is given, and a theoretical model based on this scheme is proposed. In this model, the plane wave approximation is employed, and the analytical expressions of the output power of three-wavelength lasers are derived. The impact of crystal length on the output characteristics of the Nd:YAG-Nd:YVO4 pair and Nd:YVO4-Nd:YVO4 pair are investigated by numerical simulation, and the focal length of the thermal lens is calculated. The comparison results show that the output characteristics of them are nearly identical, however, the thermal effect of the Nd:YAG-Nd:YVO4 pair is lower than that of the Nd:YVO4-Nd:YVO4 pair, so we can draw the conclusion that the Nd:YAG-Nd:YVO4 pair is slightly better than the Nd:YVO4-Nd:YVO4 pair.

  4. A Simple Technique for Controlling the Görtler Vortex Wavelength in Hypersonic Shock-Wave/Boundary-Layer Interaction

    NASA Astrophysics Data System (ADS)

    Itoh, Hajime; Honda, Hirokazu

    This paper describes results of an exploratory study to investigate the capability of a passive approach for controlling the characteristic spanwise length of Görtler vortices generated in hypersonic flows: a serrated leading edge. Heat transfer, pressure measurements, encapsulated thermochromic liquid crystal, schlieren and glow spark visualizations were conducted with a flat plate/ramp model whose leading edge had a triangular wave shape in a gun tunnel at Mach number 10. Effect of wavelength ? of the triangular waves on downstream flows was studied. Aerodynamic heating patterns observed with the liquid crystal confirmed that the vortex wavelength was equal to ?. This was also supported by the spark results that filamentary bright lines perpendicular to an installed line-anode parallel to the spanwise direction at the ramp surface emerged at intervals of ?. Phase lag was observed only between heat transfer data measured in the spanwise direction, which suggests that the vortex structure existed in the reattaching boundary layers. Pressure distribution in the streamwise direction was similar among all of the ? tested. In contrast, the heat transfer data points exhibited a large scatter and the peak heating value for the finite ? was somewhat larger than that for the infinite ?. Schlieren results indicated that the appropriate ? can mitigate flow separation.

  5. Short wave infrared imaging spectrometer with simultaneous thermal imaging

    NASA Astrophysics Data System (ADS)

    Johnson, William R.; Wilson, Daniel W.; Diaz, Alejandro

    2010-08-01

    A computed tomographic imaging spectrometer (CTIS) has been developed to allow simultaneous shortwave infrared (SWIR: 1-1.4 μm) spectral imaging and mid-wave infrared (MWIR: 3-5 μm) thermal imaging. The instrument utilizes a mechanically cooled indium antimonide focal plane array which is optically coupled using an Offner relay to a state-of the-art two-dimensional grating. The grating is a computer-generated hologram design fabricated by electron-beam lithography on a convex substrate. The system performs shapshot capture of the spatial and spectral information in a scene, enabling transient events to be characterized. The shortwave spectral information in the higher diffraction orders was reconstructed using existing expectation maximization methodologies while a co-registered thermal image from the zerothorder was analyzed. A co-registered contour map of the shortwave information was displayed superimposed on the thermal image and processed for accurate retrieval of scene knowledge. Spectral accuracy and radiometric test and evaluation results such as noise equivalence temperature difference (NEDT) and minimum resolvable temperature difference (MRTD) are presented for this new spectral imager and a general explanation is given for the theory of its tomographic operation.

  6. Short wavelength lateral variability of lithospheric mantle beneath the Middle Atlas (Morocco) as recorded by mantle xenoliths

    NASA Astrophysics Data System (ADS)

    El Messbahi, Hicham; Bodinier, Jean-Louis; Vauchez, Alain; Dautria, Jean-Marie; Ouali, Houssa; Garrido, Carlos J.

    2015-05-01

    The Middle Atlas is a region where xenolith-bearing volcanism roughly coincides with the maximum of lithospheric thinning beneath continental Morocco. It is therefore a key area to study the mechanisms of lithospheric thinning and constrain the component of mantle buoyancy that is required to explain the Moroccan topography. Samples from the two main xenolith localities, the Bou Ibalghatene and Tafraoute maars, have been investigated for their mineralogy, microstructures, crystallographic preferred orientation, and whole-rock and mineral compositions. While Bou Ibalghatene belongs to the main Middle Atlas volcanic field, in the 'tabular' Middle Atlas, Tafraoute is situated about 45 km away, on the North Middle Atlas Fault that separates the 'folded' Middle Atlas, to the South-East, from the 'tabular' Middle Atlas, to the North-West. Both xenolith suites record infiltration of sub-lithospheric melts that are akin to the Middle Atlas volcanism but were differentiated to variable degrees as a result of interactions with lithospheric mantle. However, while the Bou Ibalghatene mantle was densely traversed by high melt fractions, mostly focused in melt conduits, the Tafraoute suite records heterogeneous infiltration of smaller melt fractions that migrated diffusively, by intergranular porous flow. As a consequence the lithospheric mantle beneath Bou Ibalghaten was strongly modified by melt-rock interactions in the Cenozoic whereas the Tafraoute mantle preserves the record of extensional lithospheric thinning, most likely related to Mesozoic rifting. The two xenolith suites illustrate distinct mechanisms of lithospheric thinning: extensional thinning in Tafraoute, where hydrous incongruent melting triggered by decompression probably played a key role in favouring strain localisation, vs. thermal erosion in Bou Ibalghatene, favoured and guided by a dense network of melt conduits. Our results lend support to the suggestion that lithospheric thinning beneath the Atlas mountains results from the combination of different mechanisms and occurred in a piecewise fashion at a short wavelength scale.

  7. Multi-wavelength quasi-continuous wave all-solid-state system based on Raman lasers

    NASA Astrophysics Data System (ADS)

    Vodchits, Alexander I.; Busko, Dmitry N.; Orlovich, Valentin A.; Lisinetskii, Viktor A.; Grabtchikov, Alexander S.; Apanasevich, Pavel A.; Eichler, Hans J.

    2007-06-01

    High-repetition-pulse-rate nanosecond laser system is developed. It is based on Raman lasers with barium nitrate and KGW crystals. The minimum Raman threshold of laser generation corresponds to only 0.2-0.4 kW of peak pumping power. The laser system generates the radiation at 22 wavelengths in the 280-1600 nm spectral range with average powers from several mW to 1.4 W. The maximum Raman conversion efficiency reaches 40 %. The minimum spectral width of the generated radiation is equal to 0.1 cm -1. This laser system can be used for spectroscopy studies, medicine, and for other applications.

  8. Guided lamb waves and L-SAFT processing technique for enhanced detection and imaging of corrosion defects in plates with small depth-to-wavelength ratio.

    PubMed

    Sicard, René; Chahbaz, Ahmad; Goyette, Jacques

    2004-10-01

    The Lamb synthetic aperture focusing technique (L-SAFT) imaging algorithm in the Fourier domain is used to produce Lamb wave imaging in plates while considering the wave dispersive properties. This artificial focusing technique produces easy-to-interpret, modified B-scan type images of Lamb wave inspection results. The high level of sensitivity of Lamb waves combined with the L-SAFT algorithm allows one to detect and to produce images of corrosion defects with small depth-to-wavelength ratio. This paper briefly presents the formulated L-SAFT algorithm used for Lamb waves and, in more details, some experimental results obtained on simulated and real corrosion pits, demonstrating the benefit of combining L-SAFT with pulse-echo Lamb wave inspection. The obtained images of the real corrosion defects showed detection of pits with a depth-to-wavelength ratio of approximately 2/11. PMID:15553513

  9. Multicomponent long-wave-short-wave resonance interaction system: Bright solitons, energy-sharing collisions, and resonant solitons.

    PubMed

    Sakkaravarthi, K; Kanna, T; Vijayajayanthi, M; Lakshmanan, M

    2014-11-01

    We consider a general multicomponent (2+1)-dimensional long-wave-short-wave resonance interaction (LSRI) system with arbitrary nonlinearity coefficients, which describes the nonlinear resonance interaction of multiple short waves with a long wave in two spatial dimensions. The general multicomponent LSRI system is shown to be integrable by performing the Painlevé analysis. Then we construct the exact bright multisoliton solutions by applying the Hirota's bilinearization method and study the propagation and collision dynamics of bright solitons in detail. Particularly, we investigate the head-on and overtaking collisions of bright solitons and explore two types of energy-sharing collisions as well as standard elastic collision. We have also corroborated the obtained analytical one-soliton solution by direct numerical simulation. Also, we discuss the formation and dynamics of resonant solitons. Interestingly, we demonstrate the formation of resonant solitons admitting breather-like (localized periodic pulse train) structure and also large amplitude localized structures akin to rogue waves coexisting with solitons. For completeness, we have also obtained dark one- and two-soliton solutions and studied their dynamics briefly. PMID:25493863

  10. External excitation of a short-wavelength fluctuation in the Alcator C-Mod edge plasma and its relationship to the quasi-coherent mode

    SciTech Connect

    Golfinopoulos, T.; LaBombard, B.; Parker, R. R.; Burke, W.; Davis, E.; Granetz, R.; Greenwald, M.; Irby, J.; Leccacorvi, R.; Marmar, E.; Parkin, W.; Porkolab, M.; Terry, J.; Vieira, R.; Wolfe, S.

    2014-05-15

    A novel “Shoelace” antenna has been used to inductively excite a short-wavelength edge fluctuation in a tokamak boundary layer for the first time. The principal design parameters, k{sub ⊥}=1.5±0.1 cm{sup −1} and 45wave number and propagation direction as the QCM, and is resonant at the QCM frequency, suggest the antenna may couple to this mode, which we have shown elsewhere to be predominantly drift-mode-like [B. LaBombard et al., Phys. Plasmas 21, 056108 (2014)].

  11. Study of optical output couplers for submillimeter wavelength backward-wave oscillators (BWO's)

    NASA Technical Reports Server (NTRS)

    Cook, Jerry D.; Stankiewicz, Norbert; Podany, Mark

    1988-01-01

    The machining of slow wave structures for high frequency backward-wave oscillators (BWO) is extremely difficult beyond 1 THz. Recently a microfabrication technique using photolithography and ion-beam assisted etching has been used to construct a prototype BWO operating at 200 to 265 GHz. The output coupler for such tubes remains a problem. Waveguides do not exist or are very lossy at the frequencies of interest (300 to 2000 GHz). This paper discusses several scaled experiments of optical output couplers for submillimeter BWOs. Various designs of planar antennas (Vivaldi horns) and lens-feed systems (Hyperhemispherical lens) were constructed and tested between 20 and 100 GHz using a spectrum analyzer. The lens system was also tested at 337 GHz using a CO2 pumped FIR laser.

  12. On the radiation phase stability of a relativistic coaxial backward-wave oscillator at decimeter wavelengths

    NASA Astrophysics Data System (ADS)

    Totmeninov, E. M.; Klimov, A. I.; Konev, V. Yu.; Rostov, V. V.; Stepchenko, A. S.; Tsygankov, R. V.

    2015-01-01

    The stability of the microwave radiation phase of A relativistic coaxial backward-wave oscillator with a modulating reflector relative to a fixed voltage at a rising edge of the feeding high-voltage pulse is shown. At a carrying frequency of 1.3 Ghz, the standard phase deviation in a series of 50 consecutive pulses was not more than 20 ps for the microwave pulse duration of 80 ns.

  13. Spectral form and source term balance of short gravity wind waves

    NASA Astrophysics Data System (ADS)

    Tamura, Hitoshi; Drennan, William M.; Sahlée, Erik; Graber, Hans C.

    2014-11-01

    We investigated the spectral structure and source term balance of short gravity waves, based on in situ observations of wave number spectra retrieved by air-sea interaction spar (ASIS) buoys. The behaviors of wave number spectra up to 10 rad/m (the gravity wave regime) were analyzed for a wide range of wind and wave conditions. The observed wave number spectra showed the spectral power laws described by Toba (1973) and Phillips (1958) in addition to the characteristic nodal point at ˜10 rad/m where spectral energy becomes constant over the entire wind speed range. We also improved the third-generation wave model using the nonlinear dissipation term. The wave model reproduced the spectral form in the higher wave number domain. In the equilibrium range, nonlinear transfer played a major role in maintaining equilibrium conditions. On the other hand, in the saturation range, which starts at the upper limit of the equilibrium range, the nonlinear transfer tended to be out of balance with other source terms, and the dissipation term was in balance with wind input.

  14. Surface Acoustic Wave Scattering from an Array of Irregularities Comparable with a Wavelength

    NASA Astrophysics Data System (ADS)

    Yankin, Sergey S.; Suchkov, Sergey G.; Shatrova, Iuliia A.; Suchkov, Dmitry S.; Komkov, Sergey V.; Pilovets, Aleksey A.; Nikitov, Sergey A.

    The properly defined reflection, transmission and scattering coefficients were numerically evaluated as functions of the reflector's thickness, from infinitively small to comparable with wavelength. It was shown that these dependencies for projections are quasi-periodic and related to excitation of Eigen resonance modes in array of reflectors. In contrast to projections scattering from deep grooves does not have periodic behavior and with the depth's growth SAW scattering into volume increases while reflection coefficient doesn't reach more than 40%. The calculation of the 2D pattern of the scattered fields makes it possible to estimate the reflecting structures efficiency and clearly shows the range of the parameters for which an intensive SAW-energy radiation into the bulk occurs.

  15. A temperature inversion in WASP-33b? Large Binocular Telescope occultation data confirm significant thermal flux at short wavelengths

    NASA Astrophysics Data System (ADS)

    von Essen, C.; Mallonn, M.; Albrecht, S.; Antoci, V.; Smith, A. M. S.; Dreizler, S.; Strassmeier, K. G.

    2015-12-01

    We observed a secondary eclipse of WASP-33 b quasi-simultaneously in the optical (~0.55 μm) and the near-infrared (~1.05 μm) using the 2×8.4 m Large Binocular Telescope. WASP-33 is a δ Scuti star pulsating with periods comparable to the eclipse duration, making the determination of the eclipse depth challenging. We use previously determined oscillation frequencies to model and remove the pulsation signal from the light curves, isolating the secondary eclipse. The determined eclipse depth is ΔF = 1.03 ± 0.34 parts per thousand, corresponding to a brightness temperature of TB = 3398 ± 302 K. Combining previously published data with our new measurement we find the equilibrium temperature of WASP-33 b to be TB = 3358 ± 165 K. We compare all existing eclipse data to a blackbody spectrum, to a carbon-rich non-inverted model and to a solar composition model with an inverted temperature structure. We find that current available data on WASP-33 b's atmosphere can be best represented by a simple blackbody emission, without the need for more sophisticated atmospheric models with temperature inversions. Although our data cannot rule out models with or without a temperature inversion, they do confirm a high brightness temperature for the planet at short wavelengths. WASP-33 b is one of the hottest exoplanets known till date, and its equilibrium temperature is consistent with rapid reradiation of the absorbed stellar light and a low albedo. The LBT is an international collaboration among institutions in the United States, Italy and Germany. LBT Corporation partners are: The University of Arizona on behalf of the Arizona university system; Instituto Nazionale di Astrofisica, Italy; LBT Beteiligungsgesellschaft, Germany, representing the Max-Planck Society, the Leibniz-Institute for Astrophysics Potsdam, and Heidelberg University; The Ohio State University, and The Research Corporation, on behalf of The University of Notre Dame, University of Minnesota and University of Virginia.Appendix A is available in electronic form at http://www.aanda.org

  16. Approximating SIR-B response characteristics and estimating wave height and wavelength for ocean imagery

    NASA Technical Reports Server (NTRS)

    Tilley, David G.

    1987-01-01

    NASA Space Shuttle Challenger SIR-B ocean scenes are used to derive directional wave spectra for which speckle noise is modeled as a function of Rayleigh random phase coherence downrange and Poisson random amplitude errors inherent in the Doppler measurement of along-track position. A Fourier filter that preserves SIR-B image phase relations is used to correct the stationary and dynamic response characteristics of the remote sensor and scene correlator, as well as to subtract an estimate of the speckle noise component. A two-dimensional map of sea surface elevation is obtained after the filtered image is corrected for both random and deterministic motions.

  17. Measurements of plasma-wave generation using a short-pulse high-intensity laser beat wave

    SciTech Connect

    Walton, B.; Najmudin, Z.; Wei, M.S.; Marle, C.; Kingham, R.J.; Krushelnick, K.; Dangor, A.E.; Clarke, R.J.; Poulter, M. J.; Hernandez-Gomez, C.; Hawkes, S.; Neely, D.; Collier, J.L.; Danson, C.N.; Fritzler, S.; Malka, V.

    2006-01-15

    Experiments to examine the generation of relativistic plasma waves via a high-intensity short-pulse beat-wave scheme are described in detail. The pulse stretcher of the Vulcan chirped-pulse amplification (CPA) laser system was modified to produce two frequency, 3 ps pulses focusable to intensities up to 10{sup 18} W cm{sup -2}. Short high-intensity pulses were used to avoid limitations to the plasma-wave amplitude due to the modulational instability. Two experiments were undertaken, at 3 and 10 TW, with the generation of plasma waves diagnosed by measuring the sidebands produced in the spectrum of the forward scattered beam. A resonance in the sideband signal was observed for an initial plasma density higher than expected for the given beat frequency. This resonance shift can be attributed to transverse ponderomotive expulsion of plasma electrons from the laser focal region. A monotonically increasing background was also observed, which was due to nonresonant cross-phase modulation.

  18. The Patterns of Surface Capillary-gravity Short-crested Waves with Uniform Current Fields in Coastal Waters

    NASA Astrophysics Data System (ADS)

    Huang, Hu; Fu, Jia

    2006-10-01

    A fully three-dimensional surface gravity-capillary short-crested wave system is studied as two progressive wave-trains of equal amplitude and frequency, which are collinear with uniform currents and doubly-periodic in the horizontal plane, are propagating at an angle to each other. The first- and second-order asymptotic analytical solutions of the short-crested wave system are obtained via a perturbation expansion in a small parameter associated with the wave steepness, therefore depicting a series of typical three-dimensional wave patterns involving currents, shallow and deep water, and surface capillary waves, and comparing them with each other.

  19. Performance analysis of incoherent multi-wavelength OCDMA systems under the impact of four-wave mixing.

    PubMed

    Dang, Ngoc T; Pham, Anh T

    2010-05-10

    In this paper, we comprehensively analyze the impact of four wave mixing (FWM) on the performance of incoherent multi-wavelength optical code-division multiple-access (MW-OCDMA) systems. We also consider many other interferences and noises, including multiple access interference, optical beating interference, and receiver noise, in the analysis. From the numerical results, we can find the power ranges of different MW-OCDMA systems, in which the impact of FWM is dominant and consequently results in an increase in the bit-error rate of the systems. We also find that the impact of FWM becomes more severe when the frequency spacing is small and/or dispersion-shifted fiber is used. In addition, we quantitatively discuss the impact of FWM on the number of supportable users and power penalty in the MW-OCDMA systems. PMID:20588844

  20. Radio-over-fiber system with tunable millimeter-wave generation and wavelength reuse for uplink connection

    NASA Astrophysics Data System (ADS)

    Zhang, Chan; Ning, Tigang; Li, Jing; Lin, Heng; Liu, Zhiming

    2016-03-01

    We propose and demonstrate a radio-over-fiber system to generate an optical millimeter wave (MMW) and realize wavelength reuse for an uplink connection. A tunable optical comb generated by a single Fabry-Perot laser serves as the optical source. The central carrier is separated by an optical circulator cascaded with a fiber Bragg grating. For the downlink, the unmodulated central carrier is coupled with one subcarrier, which has been modulated with 2.5-Gb/s data. Then, different MMWs can be generated by choosing different subcarriers. While for the uplink, the same central carrier is reused for an uplink connection with 1.25-Gb/s data. In the scheme, a 60-GHz MMW is obtained and the bidirectional data are simultaneously transmitted over 60-km transmission with <0.5-dB power penalty. This system shows a simple cost-efficient configuration and good performance over long-distance delivery.

  1. Influence of the absorption behavior of sunscreens in the short-wavelength UV range (UVB) and the long-wavelength UV range (UVA) on the relation of the UVB absorption to sun protection factor

    NASA Astrophysics Data System (ADS)

    Weigmann, Hans-Juergen; Schanzer, Sabine; Antoniou, Christina; Sterry, Wolfram; Lademann, Juergen

    2010-09-01

    The absorption of filter substances in sunscreens, reducing the incident ultraviolet (UV) radiation, is the basis for the protecting ability of such formulations. The erythema-correlated sun protection factor (SPF), depending mainly on the intensity of the UVB radiation, is the common value to quantify the efficacy of the formulations avoiding sunburn. An ex vivo method combining tape stripping and optical spectroscopy is applied to measure the absorption of sunscreens in the entire UV spectral range. The obtained relations between the short-wavelength UV (UVB) absorption and the SPF confirm a clear influence of the long-wavelength UV (UVA) absorption on the SPF values. The data reflect the historical development of the relation of the concentration of UVB and UVA filters in sunscreens and points to the influence of additional ingredients, e.g., antioxidants and cell-protecting agents on the efficacy of the products.

  2. Global observations of gravity waves from High Resolution Dynamics Limb Sounder temperature measurements: A yearlong record of temperature amplitude and vertical wavelength

    NASA Astrophysics Data System (ADS)

    Yan, Xiuping; Arnold, Neil; Remedios, John

    2010-05-01

    Global observations of gravity waves have been performed using the High Resolution Dynamics Limb Sounder (HIRDLS) temperature data. A background field that was derived by dynamically calculating 31 day (15 day) means to block the stationary component and the slowly varying planetary-scale waves, was first subtracted from the HIRDLS temperature measurements. An additional step was then taken to remove rapidly moving planetary-scale waves by developing an along-track temperature filter, which was created by averaging the profiles within a 1000 km along-track window. Finally, each individual temperature perturbation vertical profile was analyzed using a fast Fourier transform to estimate gravity wave temperature amplitudes and vertical wavelengths. The investigation of the monthly mean gravity wave temperature amplitudes for the year 2006 found that gravity wave activity in the stratosphere is highly variable with season and can be very orographically dependent, especially in the winter extratropics. The monthly zonal means show that the peak vertical wavelengths correspond closely to the peak amplitudes. The increasing amplitudes and vertical wavelengths are faster and generated at lower altitudes in the winter extratropical and high-latitude stratosphere than those in the summer tropical stratosphere. This is consistent with the lower source altitudes of orographic gravity waves in the extratropics and high latitudes and the higher source altitudes of convectively generated gravity waves in the tropics. Three cases were studied for the observed gravity waves over large mountain ranges using the European Centre for Medium-Range Weather Forecasts wind data. Investigations of episodes of enhanced gravity wave activity over the southern Andes, the Cascade Range, and the Rockies in winter months of 2006 indicate that orographic gravity waves refract downwind from the mountains and propagate along the direction of the intense winds. By way of contrast, observations of gravity waves around the Himalayas show a strong relationship with the cyclones in that region.

  3. Short- and long-wavelength-sensitive opsins are involved in photoreception both in the retina and throughout the central nervous system of crayfish.

    PubMed

    Kingston, Alexandra C N; Cronin, Thomas W

    2015-12-01

    Crayfish have two classes of photoreceptors in the retinas of their reflecting superposition eyes. Long-wavelength-sensitive photoreceptors, comprised of microvilli from R1-7 cells, make up the main rhabdoms. Eighth retinular cells, located distal to the main rhabdoms, house short-wavelength-sensitive photoreceptors. While the opsin involved in long-wavelength sensitivity has long been known, we present the first description of the short-wavelength-sensitive opsin in the retina of the red swamp crayfish, Procambarus clarkii. The expression patterns of these SWS and LWS opsin proteins in the retina are consistent with the previously described locations of SWS and LWS receptors. Crayfish also have a well-characterized extraocular photoreceptor, called the caudal photoreceptor, located in the sixth abdominal ganglion. To search for retinal opsins in the caudal photoreceptor (and elsewhere in the CNS), we used RT-PCR and immunohistochemical labeling. We found both SWS and LWS opsin transcripts not only in the sixth abdominal ganglion, but also in all ganglia of the nerve cord. Immunolabeling shows that both opsins are expressed in nerve fibers that extend from the brain through the entire length of the CNS. Thus, the same two photopigments are used both for vision in the retina and for extraocular functions throughout the CNS of crayfish. PMID:26445969

  4. Climatic variations of the ionospheric absorption of radio waves in the short-wave range

    NASA Astrophysics Data System (ADS)

    Nestorov, G.; Pancheva, D.; Danilov, A. D.

    1991-12-01

    Variations of radio-wave absorption were measured with the A3 method on a France-Bulgaria path during 1959-1986, and a systematic increase of this absorption was found. It is shown that the most probable cause of this increase is a decrease of atmospheric temperature in the mesopause region by 5 K over the time period considered.

  5. Deep-Tow magnetics near 20°S on the East Pacific Rise: A study of short wavelength anomalies at a very fast spreading center

    NASA Astrophysics Data System (ADS)

    Perram, Laura Jean; MacDonald, Ken C.; Miller, Stephen P.

    1990-08-01

    Six Deep-Tow magnetic profiles across the axis of the East Pacific Rise [EPR] in two small areas between 19°25' and 20°10'S were collected during the 1983 Protea 1 cruise of the R/V Melville. These near-bottom profiles are of extremely high resolution allowing the interpretation of very short wavelength features. We have inverted the magnetic field data to determine the rock magnetization distribution near the axis of this ultrafast speading center (162 mm yr-1). The solutions reveal large amplitude (up to 35 A m-1) short wavelength (1 3 km) variations in magnetization. Specifically all crossings show a narrow (0.5 to 1.5 km) low in magnetization superimposed on a broader (2.5 to 4 km) high directly over the ridge axis. Four profiles in the northern area (19°25' to 19°33'S) also show symmetrical near-axis (within 4 km) lows which are remarkably continuous along strike. Explanations for the short-wavelength variations are discussed which fall into the following categories: (1) variations in the thickness of the magnetized layer, (2) variations in rock chemistry (e.g. alteration due to hydrothermal activity), and (3) paleofield intensity variations. None of the mechanisms discussed alone adequately explain the observed phenomena in the study area or on a world-wide scale. Further sampling and high resolution surveying will be required in order to accurately determine the relative importance of the mechanisms discussed.

  6. Effect of electron plasma waves with relativistic phase velocity on large-angle stimulated Raman scattering of modulated short laser pulse in plasmas

    NASA Astrophysics Data System (ADS)

    Andreev, Nikolai E.; Kalmykov, S. Y.

    2001-03-01

    Suppression of a large-angle stimulated Raman scattering (LA-SRS) of a short modulated (two-frequency) laser pulse in a transparent plasma in the presence of a linear long- wavelength electron plasma wave (LW EPW) having relativistic phase velocity is considered under the conditions of weak and strong coupling. The laser spectrum includes two components with a frequency shift equal to the frequency of the LW EPW. The mutual influence of different spectral components of a laser on the SRS under a given angle in the presence of the LW EPW is examined.

  7. Observationally constraining gravitational wave emission from short gamma-ray burst remnants

    NASA Astrophysics Data System (ADS)

    Lasky, Paul D.; Glampedakis, Kostas

    2016-02-01

    Observations of short gamma-ray bursts indicate ongoing energy injection following the prompt emission, with the most likely candidate being the birth of a rapidly rotating, highly magnetised neutron star. We utilise X-ray observations of the burst remnant to constrain properties of the nascent neutron star, including its magnetic field-induced ellipticity and the saturation amplitude of various oscillation modes. Moreover, we derive strict upper limits on the gravitational wave emission from these objects by looking only at the X-ray light curve, showing the burst remnants are unlikely to be detected in the near future using ground-based gravitational wave interferometers such as Advanced LIGO.

  8. Signatures of tunneling and multiphoton ionization by short-laser pulses: The partial-wave distribution

    NASA Astrophysics Data System (ADS)

    Arbó, Diego G.; Lemell, Christoph; Burgdörfer, Joachim

    2015-09-01

    We analyze the two-dimensional angular momentum-energy distribution of electrons emitted from argon by short laser pulses. We identify characteristic features of both multiphoton and tunneling ionization in the partial-wave distribution for Keldysh parameters close to unity. We observe a remarkable degree of quantum-classical correspondence in the photoinization process which becomes even more pronounced after intensity averaging over the focal volume. We derive an energy-dependent cut-off for the highest angular momentum accessible within the framework of the strong-field approximation, which accurately reproduces the partial wave distributions found from solutions of the time-dependent Schrödinger equation.

  9. Observationally constraining gravitational wave emission from short gamma-ray burst remnants

    NASA Astrophysics Data System (ADS)

    Lasky, Paul D.; Glampedakis, Kostas

    2016-05-01

    Observations of short gamma-ray bursts indicate ongoing energy injection following the prompt emission, with the most likely candidate being the birth of a rapidly rotating, highly magnetized neutron star. We utilize X-ray observations of the burst remnant to constrain properties of the nascent neutron star, including its magnetic field-induced ellipticity and the saturation amplitude of various oscillation modes. Moreover, we derive strict upper limits on the gravitational wave emission from these objects by looking only at the X-ray light curve, showing the burst remnants are unlikely to be detected in the near future using ground-based gravitational wave interferometers, such as Advanced LIGO.

  10. Sensing short range forces with a nanosphere matter-wave interferometer

    NASA Astrophysics Data System (ADS)

    Geraci, Andrew; Goldman, Hart

    2015-09-01

    We describe a method for sensing short range forces using matter-wave interference in dielectric nanospheres. When compared with atom interferometers, the larger mass of the nanosphere results in reduced wave-packet expansion, enabling investigations of forces nearer to surfaces in a free-fall interferometer. By laser cooling a nanosphere to the ground state of an optical potential and releasing it by turning off the optical trap, acceleration sensing at the 10-8 m /s2 level is possible. The approach can yield improved sensitivity to Yukawa-type deviations from Newtonian gravity at the 5 μ m length scale by a factor of 104 over current limits.

  11. Tunable short-pulse beat-wave laser source operating at 1 microm.

    PubMed

    Hankla, A K; Bullock, A B; White, W E; Squier, J A; Barty, C P

    1997-11-15

    We have demonstrated a chirped-pulse-amplification system utilizing an air-spaced etalon inside a regenerative amplifier to produce two simultaneous 2.0-ps pulses, one centered at the gain peak of Nd:phosphate glass (1052 nm) and the other centered at the gain peak of Nd:silicate (1061 nm). Autocorrelations of the resulting beat wave demonstrate a beat frequency of 2.3 THz. We achieved wavelength tunability over a 10-nm range by electronically adjusting the etalon spacing and variable pulse width by changing the etalon rotation. PMID:18188344

  12. A Unified Directional Spectrum for Long and Short Wind-Driven Waves

    NASA Technical Reports Server (NTRS)

    Elfouhaily, T.; Chapron, B.; Katsaros, K.; Vandemark, D.

    1997-01-01

    Review of several recent ocean surface wave models finds that while comprehensive in many regards, these spectral models do not satisfy certain additional, but fundamental, criteria. We propose that these criteria include the ability to properly describe diverse fetch conditions and to provide agreement with in situ observations of Cox and Munk [1954] and Jiihne and Riemer [1990] and Hara et al. [1994] data in the high-wavenumber regime. Moreover, we find numerous analytically undesirable aspects such as discontinuities across wavenumber limits, nonphysical tuning or adjustment parameters, and noncentrosymmetric directional spreading functions. This paper describes a two-dimensional wavenumber spectrum valid over all wavenumbers and analytically amenable to usage in electromagnetic models. The two regime model is formulated based on the Joint North Sea Wave Project (JONSWAP) in the long-wave regime and on the work of Phillips [1985] and Kitaigorodskii [1973] at the high wavenumbers. The omnidirectional and wind-dependent spectrum is constructed to agree with past and recent observations including the criteria mentioned above. The key feature of this model is the similarity of description for the high- and low-wavenumber regimes; both forms are posed to stress that the air-sea interaction process of friction between wind and waves (i.e., generalized wave age, u/c) is occurring at all wavelengths simultaneously. This wave age parameterization is the unifying feature of the spectrum. The spectrum's directional spreading function is symmetric about the wind direction and has both wavenumber and wind speed dependence. A ratio method is described that enables comparison of this spreading function with previous noncentrosymmetric forms. Radar data are purposefully excluded from this spectral development. Finally, a test of the spectrum is made by deriving roughness length using the boundary layer model of Kitaigorodskii. Our inference of drag coefficient versus wind speed and wave age shows encouraging agreement with Humidity Exchange Over the Sea (HEXOS) campaign results.

  13. A non-polarization short-wave-pass thin film edge filter

    NASA Astrophysics Data System (ADS)

    Yu, Kan; Zhou, Xiao-yang; Wang, Jia-qi; Xu, Jing-jing; Yin, Juan-juan

    2014-07-01

    Multilayer dielectric thin film edge filter has serious polarization sensitivity under oblique incidence. The cutoff-bands of the s-polarization and p-polarization light in conventional edge filter will separate obviously under 45° oblique incidence, which limits its application. Based on the two chosen materials TiO2 and SiO2, a novel stack structure is proposed to design the non-polarization short-wave-pass thin film edge filter. By using the (4 H 4 L 4 H) as the matching layers, the polarization separation at 3 dB transmittance for the thin film edge filter cutoff-band is less than 1 nm at the incident angle of 45°. In this way, the non-polarization short-wave-pass edge filter is easily designed and fabricated.

  14. Multi-instrument gravity-wave measurements over Tierra del Fuego and the Drake Passage - Part 1: Potential energies and vertical wavelengths from AIRS, COSMIC, HIRDLS, MLS-Aura, SAAMER, SABER and radiosondes

    NASA Astrophysics Data System (ADS)

    Wright, C. J.; Hindley, N. P.; Moss, A. C.; Mitchell, N. J.

    2015-07-01

    Gravity waves in the terrestrial atmosphere are a vital geophysical process, acting to transport energy and momentum on a wide range of scales and to couple the various atmospheric layers. Despite the importance of these waves, the many studies to date have often exhibited very dissimilar results, and it remains unclear whether these differences are primarily instrumental or methodological. Here, we address this problem by comparing observations made by a diverse range of the most widely-used gravity wave resolving instruments in a common geographic region around the southern Andes and Drake Passage, an area known to exhibit strong wave activity. Specifically, we use data from three limb-sounding radiometers (MLS-Aura, HIRDLS and SABER), the COSMIC GPS-RO constellation, a ground-based meteor radar, the AIRS infrared nadir sounder and radiosondes to examine the gravity wave potential energy (GWPE) and vertical wavelengths (?z) of individual gravity wave packets from the lower troposphere to the edge of the lower thermosphere. Our results show important similarities and differences. Limb sounder measurements show high intercorrelation, typically > 0.80 between any instrument pair. Meteor-radar observations agree in form with the limb sounders, despite vast technical differences. AIRS and radiosonde observations tend to be uncorrelated or anticorrelated with the other datasets, suggesting very different behaviour of the wave field in the different spectral regimes accessed by each instrument. Except in spring, we see little dissipation of GWPE throughout the stratosphere and lower mesosphere. Observed GWPE for individual wave packets exhibits a log-normal distribution, with short-timescale intermittency dominating over a well-repeated monthly-median seasonal cycle. GWPE and ?z exhibit strong correlations with the stratospheric winds, but not with local surface winds. Our results provide guidance for interpretation and intercomparison of such datasets in their full context, and reinforce the vital point that no one dataset can represent the whole spectrum of gravity waves in the terrestrial atmosphere.

  15. Identification of extreme precipitation threat across midlatitude regions based on short-wave circulations

    NASA Astrophysics Data System (ADS)

    Wang, Shih-Yu; Davies, Robert E.; Gillies, Robert R.

    2013-10-01

    most severe thunderstorms, producing extreme precipitation, occur over subtropical and midlatitude regions. Atmospheric conditions conducive to organized, intense thunderstorms commonly involve the coupling of a low-level jet (LLJ) with a synoptic short wave. The midlatitude synoptic activity is frequently modulated by the circumglobal teleconnection (CGT), in which meridional gradients of the jet stream act as a guide for short Rossby waves. Previous research has linked extreme precipitation events with either the CGT or the LLJ but has not linked the two circulation features together. In this study, a circulation-based index was developed by combining (a) the degree of the CGT and LLJ coupling, (b) the extent to which this CGT-LLJ coupling connects to regional precipitation and (c) the spatial correspondence with the CGT (short wave) trending pattern over the recent 32 years (1979-2010). Four modern-era global reanalyses, in conjunction with four gridded precipitation data sets, were utilized to minimize spurious trends. The results are suggestive of a link between the CGT/LLJ trends and several recent extreme precipitation events, including those leading to the 2008 Midwest flood in U.S., the 2011 tornado outbreaks in southeastern U.S., the 2010 Queensland flood in northeastern Australia, and to the opposite side the 2012 central U.S. drought. Moreover, an analysis of three Coupled Model Intercomparison Project Phase 5 models from the historical experiments points to the role of greenhouse gases in forming the CGT trends during the warm season.

  16. A Phe-rich region in short-wavelength sensitive opsins is responsible for their aggregation in the absence of 11-cis-retinal.

    PubMed

    Zhang, Tao; Fu, Yingbin

    2013-08-01

    Human blue and mouse S-opsin are prone to aggregation in the absence of 11-cis-retinal, which underlie the rapid cone degeneration in human patients and animal models of Leber congenital amaurosis (LCA). By in silico analysis and domain swapping experiments, we show that a Phe-rich region in short-wavelength sensitive (SWS) opsins, but not in medium/long-wavelength sensitive opsins, is responsible for SWS opsin aggregation. Mutagenesis studies suggest that Phe residues in this region are critical in mediating protein aggregation. Fusing the Phe-rich region of SWS opsins to GFP causes the latter to aggregate. Our findings suggest that new therapeutics can be designed to disrupt the Phe-rich region in preventing cone degeneration due to S-opsin aggregation in LCA. PMID:23792161

  17. A Phe-rich region in short-wavelength sensitive opsins is responsible for their aggregation in the absence of 11-cis-retinal

    PubMed Central

    Zhang, Tao; Fu, Yingbin

    2013-01-01

    Human blue and mouse S-opsin are prone to aggregation in the absence of 11-cis-retinal, which underlie the rapid cone degeneration in human patients and animal models of Leber congenital amaurosis (LCA). By in silico analysis and domain swapping experiments, we show that a Phe-rich region in short-wavelength sensitive (SWS) opsins, but not in medium/long-wavelength sensitive opsins, is responsible for SWS opsin aggregation. Mutagenesis studies suggest that Phe residues in this region are critical in mediating protein aggregation. Fusing the Phe-rich region of SWS opsins to GFP causes the latter to aggregate. Our findings suggest that new therapeutics can be designed to disrupt the Phe-rich region in preventing cone degeneration due to S-opsin aggregation in LCA. PMID:23792161

  18. Improved performance of P3HT:PCBM solar cells by both anode modification and short-wavelength energy utilization using Tb(aca)3phen

    NASA Astrophysics Data System (ADS)

    Zhuo, Zu-Liang; Wang, Yong-Sheng; He, Da-Wei; Fu, Ming

    2014-09-01

    The performance of P3HT:PCBM solar cells was improved by anode modification using spin-coated Tb(aca)3phen ultrathin films. The modification of the Tb(aca)3phen ultrathin film between the indium tin oxide (ITO) anode and the PE-DOT:PSS layer resulted in a maximum power conversion efficiency (PCE) of 2.99% compared to 2.66% for the reference device, which was due to the increase in the short-circuit current density (Jsc). The PCE improvement could be attributed to the short-wavelength energy utilization and the optimized morphology of the active layers. Tb(aca)3phen with its strong down-conversion luminescence properties is suitable for the P3HT:PCBM blend active layer, and the absorption region of the ternary blend films is extended into the near ultraviolet region. Furthermore, the crystallization and the surface morphology of P3HT:PCBM films were improved with the Tb(aca)3phen ultrathin film. The ultraviolent—visible absorption spectra, atomic force microscope (AFM), and X-ray diffraction (XRD) of the films were investigated. Both anode modification and short-wavelength energy utilization using Tb(aca)3phen in P3HT:PCBM solar cells led to about a 12% PCE increase.

  19. Characteristics of short-crested waves and currents behind offshore man-made island type power plant

    SciTech Connect

    Ikeno, Masaaki; Kajima, Ryoichi; Matsuyama, Masafumi; Sakakiyama, Tsutomu

    1995-12-31

    This paper describes the diffracted waves with breaking and the nearshore currents caused by short-crested waves, behind a man-made island, on which nuclear power plants are constructed. Firstly, hydraulic model tests with a multi-directional wave maker were performed. Effects of the irregularity and directional spreading of waves, and the effects of cooling water intake flow on diffracted waves and nearshore currents behind a man-made island, were investigated experimentally. Secondly, a numerical model was developed to simulate deformation of multi-directional irregular waves and nearshore currents. The validity of the numerical model was verified through comparison with the experimental results.

  20. Comparative theoretical analysis of continuous wave laser cutting of metals at 1 and 10 μm wavelength

    NASA Astrophysics Data System (ADS)

    Brügmann, Michael H.; Feurer, Thomas

    2014-09-01

    We present a derivation and, based on it, an extension of a model originally proposed by V.G. Niziev to describe continuous wave laser cutting of metals. Starting from a local energy balance and by incorporating heat removal through heat conduction to the bulk material, we find a differential equation for the cutting profile. This equation is solved numerically and yields, besides the cutting profiles, the maximum cutting speed, the absorptivity profiles, and other relevant quantities. Our main goal is to demonstrate the model's capability to explain some of the experimentally observed differences between laser cutting at around 1 and 10 μm wavelengths. To compare our numerical results to experimental observations, we perform simulations for exactly the same material and laser beam parameters as those used in a recent comparative experimental study. Generally, we find good agreement between theoretical and experimental results and show that the main differences between laser cutting with 1- and 10-μm beams arise from the different absorptivity profiles and absorbed intensities. Especially the latter suggests that the energy transfer, and thus the laser cutting process, is more efficient in the case of laser cutting with 1-μm beams.

  1. Losses of functional opsin genes, short-wavelength cone photopigments, and color vision--a significant trend in the evolution of mammalian vision.

    PubMed

    Jacobs, Gerald H

    2013-03-01

    All mammalian cone photopigments are derived from the operation of representatives from two opsin gene families (SWS1 and LWS in marsupial and eutherian mammals; SWS2 and LWS in monotremes), a process that produces cone pigments with respective peak sensitivities in the short and middle-to-long wavelengths. With the exception of a number of primate taxa, the modal pattern for mammals is to have two types of cone photopigment, one drawn from each of the gene families. In recent years, it has been discovered that the SWS1 opsin genes of a widely divergent collection of eutherian mammals have accumulated mutational changes that render them nonfunctional. This alteration reduces the retinal complements of these species to a single cone type, thus rendering ordinary color vision impossible. At present, several dozen species from five mammalian orders have been identified as falling into this category, but the total number of mammalian species that have lost short-wavelength cones in this way is certain to be much larger, perhaps reaching as high as 10% of all species. A number of circumstances that might be used to explain this widespread cone loss can be identified. Among these, the single consistent fact is that the species so affected are nocturnal or, if they are not technically nocturnal, they at least feature retinal organizations that are typically associated with that lifestyle. At the same time, however, there are many nocturnal mammals that retain functional short-wavelength cones. Nocturnality thus appears to set the stage for loss of functional SWS1 opsin genes in mammals, but it cannot be the sole circumstance. PMID:23286388

  2. Near Bed Turbulent Coherent Structures and Sea Bed Evolution Due to Long and Short Waves

    NASA Astrophysics Data System (ADS)

    Carlson, E.; Foster, D. L.

    2014-12-01

    The influence of long and short waves on the generation and evolution of near bed turbulent coherent structures and the sea floor geometry has remained an important but often poorly resolved parameterization within tsunami and wave propagation models. A laboratory study to examine the near bed turbulent evolution and sediment bed response was conducted at near field scale. Two-dimensional observations of the flow field were obtained with a submerged Particle Imaging Velocimetry system looking at a 9 cm by 17 cm region just above a movable ripple sand bed subjected to forcing caused by free-surface gravity waves with 30 cm wave height and a 4 second period. Robust particle tracking techniques and high resolution cameras allowed for millimeter scale resolution of the velocity field and sea floor evolution. Periods of high suspension were concomitant with high near-bed velocities as observed with a high resolution acoustic Doppler profiler. The growth of the boundary layer was particularly observable during the longer duration offshore directed flow. The vortex is created during flow reversal in the ripple trough, growing to roughly the height of the ripple. The coherent structure is ejected during the subsequent half wave cycle and sheared apart at the peak of the onshore directed flow. The high shear associated with the vortices are correlated to sediment suspension and subsequent sediment transport resulting in an onshore migration rate of 1.5 mm/min.

  3. Multi-Year Analysis of Short-Period Gravity Waves Over Alaska

    NASA Astrophysics Data System (ADS)

    Johnson, Kasey; Nielsen, Kim; Negale, Michael; Pautet, Pierre-Dominique; Taylor, Michael; Chandran, Amal; Harvey, Lynn

    2014-05-01

    We present a four-year analysis of short period gravity waves measured by an airglow imager situated in Poker Flat, Alaska (65 N, 147 W). The imager is the cornerstone of the mesospheric airglow imaging and dynamics (MAID) project. This project is a collaborative effort between Utah Valley University, University of Alaska, Fairbanks and Utah State University, and employs the NICT Rayleigh Lidar System together with support observations from the co-located MF Radar and the NSF sponsored Poker Flat ISR. The overarching goal of the project is to characterize the waves, their variability, and how stratospheric weather impacts the observed wave field. A recent study utilizing two years of data (2011-2012) showed a preponderance for eastward propagating waves, which is in stark contrast to other polar sites that have shown dominant westward motions. Furthermore, the study revealed a significant year to year variability in the observed phase speeds. In the study presented here, two years of additional data have been analyzed to further investigate the year to year variability and correlate the observed wave parameters to stratospheric weather phenomena including the Aleutian low, the polar vortex, and sudden stratospheric warming events.

  4. Testing gravitational parity violation with coincident gravitational waves and short gamma-ray bursts

    SciTech Connect

    Yunes, Nicolas; O'Shaughnessy, Richard; Owen, Benjamin J.; Alexander, Stephon

    2010-09-15

    Gravitational parity violation is a possibility motivated by particle physics, string theory, and loop quantum gravity. One effect of it is amplitude birefringence of gravitational waves, whereby left and right circularly polarized waves propagate at the same speed but with different amplitude evolution. Here we propose a test of this effect through coincident observations of gravitational waves and short gamma-ray bursts from binary mergers involving neutron stars. Such gravitational waves are highly left or right circularly polarized due to the geometry of the merger. Using localization information from the gamma-ray burst, ground-based gravitational wave detectors can measure the distance to the source with reasonable accuracy. An electromagnetic determination of the redshift from an afterglow or host galaxy yields an independent measure of this distance. Gravitational parity violation would manifest itself as a discrepancy between these two distance measurements. We exemplify such a test by considering one specific effective theory that leads to such gravitational parity violation, Chern-Simons gravity. We show that the advanced LIGO-Virgo network and all-sky gamma-ray telescopes can be sensitive to the propagating sector of Chern-Simons gravitational parity violation to a level roughly 2 orders of magnitude better than current stationary constraints from the LAGEOS satellites.

  5. Realization of quantum dot-based polarized white LEDs using short-wavelength pass dichroic filters and reflective polarizer films

    NASA Astrophysics Data System (ADS)

    Yang, Su Ji; Oh, Ji Hye; Lee, Keyong Nam; Do, Young Rag

    2014-09-01

    This study introduces quantum dot (QD)-based polarized white light-emitting diodes (W-LEDs) combined with a shortwavelength pass dichroic filter (SPDF), which transmit blue wavelength regions and reflect yellow wavelength regions, and a reflective polarizer film (RPF)-sandwiched AgIn5S8-ZnS QD layer using an electrospray (e-spray) method. The AgIn5S8-ZnS QDs are good candidates for W-LEDs because of their broad emission band (~100 nm) from the donoracceptor emission. The yellow emitting AgIn5S8-ZnS QDs are synthesized using a colloidal hot injection method and mixed with dimethylformamide (DMF), toluene, and poly(methyl methacrylate) (PMMA) for e-spray coating on glass. Furthermore, SPDFs are used instead of glass substrates to enhance the yellow emission from the QD layer. To create the polarized light, the RPF is fabricated on QD-coated glass and SPDFs. To create white light, a blue LED chip (λmax = 450 nm) is used as the blue light source and an excitation source for the yellow QD film with an applied current of 60 mA. The electroluminescence (EL) intensity with an angular orientation of the polarizer is measured as a function of the polarizer-rotating angle from -90° to 90° at 10° intervals.

  6. Photon-matter interaction at short wavelengths and ultra-high intensity - Gas-phase experiments at FLASH

    NASA Astrophysics Data System (ADS)

    Richter, M.; Bobashev, S. V.; Sorokin, A. A.; Tiedtke, K.

    2008-11-01

    In different focused beams at the new soft X-ray Free-electron LASer in Hamburg FLASH, ion time-of-flight spectroscopy on gas targets was performed. Irradiation levels above 1013 up to 1016 W cm-2 were achieved in the vacuum and extreme ultra-violet. The first group of experiments was performed on nitrogen molecules and neon and helium atoms at wavelengths around 30 nm, i.e. at photon energies around 40 eV. Absolute cross sections for one- and two-photon ionization could be derived. The second group of experiments was performed on different rare gases at the wavelength of 13.3 nm, i.e. at the photon energy of 93 eV. As an example, the generation of Xe21+ was observed which requires a total energy of at least 5 keV absorbed per atom, starting from neutral Xe, within the FLASH pulse duration of about 10 fs. Here, the situation might be beyond the multiphoton scheme and perturbation theory.

  7. Reactions of N/sub 2/(A/sup 3/SIGMA/sub u//sup +/) and candidates for short wavelength lasers, March 1, 1984-February 28, 1985

    SciTech Connect

    Setser, D.W.

    1987-12-07

    There are several potential schemes for efficiently generating high concentrations of the first electronically excited state of nitrogen, N/sub 2/(A/sup 3/..sigma../sub u//sup +/, 6.2 eV) by either chemical or electrical pumping. The goal of this proposal is to study ways of utilizing the energy of the N/sub 2/(A) molecules for developing efficient, short wavelength gas lasers. Such lasers are of potential interest for laser fusion. The authors report both excitation-transfer and dissociative excitation-transfer reactions of N/sub 2/(A) that yield electronically-excited diatomic molecules as products. 25 refs.

  8. Short-Period Rayleigh Wave Dispersion Measurements across the Cape Verde Archipelago using Ambient Noise

    NASA Astrophysics Data System (ADS)

    Silveira, M. M.; Matias, L. M.; Nunes, J.; Teves-Costa, P.

    2010-12-01

    The Cape Verde archipelago consists of 10 islands and several islets located on the southwest flank of the Cape Verde Rise, 500 to 800 km west of Senegal, off the African coast. This is an elevated region of ocean floor approximately 1200 km wide and encompassing an area greater than 3 x 105 km2. The islands form a horseshoe-shaped chain with a general age progression from east to west. Under the umbrella of the CV-PLUME and COBO projects, a temporary pool of 39 BB seismometers has been continuously recording between November 2007 and September 2008. This deployment provided a dense coverage of the archipelago with an unprecedented resolution. Ambient noise tomography has proved to be an efficient tool to construct high resolution maps of lithospheric shallower structures. Firstly, they allow measurements at periods shorter than 20 sec, which are hard to obtain from earthquake surface waves. Secondly, being independent of the epicentre-station geometry, they are suitable on regions of low seismicity. Cross-correlation of about 10 months of ambient seismic noise recorded at the CV-PLUME temporary network allowed us to measure short-period Rayleigh waves on all interstation paths. These cross-correlograms enabled us to compute short-period surface-wave group-velocity measurements on interstation paths. We used these measurements to construct maps of Rayleigh-wave group-velocity lateral variations at different periods. The most striking feature on the obtained record-sections is the presence of a secondary Rayleigh wave train in both causal and anti-causal parts of the cross-correlograms obtained for the paths crossing the western edge of the “horseshoe”. This study was supported by projects “CV-PLUME: An investigation on the geometry and deep signature of the Cape Verde mantle plume” (PTDC/CTE-GIN/64330/2006) and “COBO: Cape Verdes Origin from Broadband Observations”, GDSS, GFZ-Potsdam.

  9. 1.0 to 2.5 micrometer short wavelength infrared /SWIR/ linear array technology for low background applications

    NASA Technical Reports Server (NTRS)

    Stobie, J.; Iwasa, S.

    1981-01-01

    A design concept is presented for a hybrid linear focal plane array operating in the 1.0 to 2.5 micron band under low background conditions such as encountered in spaceborne missions. The concept is based on direct gate coupling of the input from a photovoltaic mercury-cadmium telluride detector into a CCD multiplexer. Theoretical analysis indicates a specific detectivity at peak wavelength on the order of 10 to the 12th cm sq rt Hz/W when the system is operating at 200 K. Values of the voltage responsivity, specific detectivity and the relative voltage noise levels of the coupled system obtained in experimental studies with direct-gate-coupled 4.0-micron detectors support the theoretical analysis performed for the case of system detectivity limited by the CCD 1/f noise.

  10. Short-wavelength stimulated raman scattering in a silica fiber pumped by an XeBr excimer laser

    SciTech Connect

    Mizunami, T.; Takagi, K.

    1989-08-01

    A UV-grade silica optical fiber was pumped by a 281.8 nm XeBr excimer laser. The first Stokes spectrum was observed at 285 nm. The spectral width was one half of that of the spontaneous Raman spectrum. A numerical analysis of stimulated Raman scattering which includes two-photon absorption loss is presented. The Raman-gain coefficient was determined by the analysis of observed nonlinearity in Stokes output and was found to be 1.8 x 10/sup -5/ cm/MW. It was also shown that two-photon absorption is a more important loss factor than linear attenuation. The shortest limit of wavelength for amplification by stimulated Raman scattering is also discussed.

  11. Circularly polarized few-optical-cycle solitons in the short-wave-approximation regime

    SciTech Connect

    Leblond, Herve; Triki, Houria; Mihalache, Dumitru

    2011-08-15

    We consider the propagation of few-cycle pulses (FCPs) beyond the slowly varying envelope approximation in media in which the dynamics of constituent atoms is described by a two-level Hamiltonian by taking into account the wave polarization. We consider the short-wave approximation, assuming that the resonance frequency of the two-level atoms is well below the inverse of the characteristic duration of the optical pulse. By using the reductive perturbation method (multiscale analysis), we derive from the Maxwell-Bloch-Heisenberg equations the governing evolution equations for the two polarization components of the electric field in the first order of the perturbation approach. We show that propagation of circularly polarized (CP) few-optical-cycle solitons is described by a system of coupled nonlinear equations, which reduces in the scalar case to the standard sine Gordon equation describing the dynamics of linearly polarized FCPs in the short-wave-approximation regime. By direct numerical simulations, we calculate the lifetime of CP FCPs, and we study the transition to two orthogonally polarized single-humped pulses as a generic route of their instability.

  12. White-Light Observations of Major Flares Compared to Total Solar Irradiance and Short-Wavelength Observations

    NASA Astrophysics Data System (ADS)

    Petrie, Gordon; Kopp, Greg; Harvey, J. W.

    2014-06-01

    The NSO’s GONG network produces “white light” (WL) continuum intensity images from one-minute integrations averaged across a 0. Å wide band pass centered at 676 Å at one minute cadence using six sites worldwide. Clear WL signatures of solar flares are present in GONG intensity data for only the largest flares because of low spatial resolution (2.5 arcsec pixel size). For six major flares (GOES class X6.5 - X28) observed by GONG, we compare integrated GONG full-disk WL intensity curves with SORCE/TIM total solar irradiance (TSI) measurements. Distinctive p-mode signatures are evident in both GONG and SORCE time series, though the correlation between GONG and SORCE data varies from flare to flare. In some cases a clear TSI peak and an interruption of the GONG p-mode pattern accompany the flare. The flare signature is generally weaker in the GONG data, suggesting that most of the TIM flare signal arises from wavelengths shorter than the GONG band pass. The flare kernels nevertheless are clear and last many minutes in the spatially resolved GONG image time series. We also compare the GONG active region intensity observations with shorter-wavelength data. In one case observed by TRACE, the GONG and TRACE WL curves are very similar and the TRACE 160 Å curve shows a significant precursor and a long tail. In most cases the GONG WL and RHESSI 25-100 keV counts appear well correlated in time. This work utilizes GONG data obtained by the NSO Integrated Synoptic Program (NISP), managed by the National Solar Observatory, which is operated by AURA, Inc. under a cooperative agreement with the National Science Foundation.

  13. Temperature dependent spectral response and detectivity of GeSn photoconductors on silicon for short wave infrared detection.

    PubMed

    Conley, Benjamin R; Mosleh, Aboozar; Ghetmiri, Seyed Amir; Du, Wei; Soref, Richard A; Sun, Greg; Margetis, Joe; Tolle, John; Naseem, Hameed A; Yu, Shui-Qing

    2014-06-30

    The GeSn direct gap material system, with Si complementary-metal-oxide semiconductor (CMOS) compatibility, presents a promising solution for direct incorporation of focal plane arrays with short wave infrared detection on Si. A temperature dependence study of GeSn photoconductors with 0.9, 3.2, and 7.0% Sn was conducted using both electrical and optical characterizations from 300 to 77 K. The GeSn layers were grown on Si substrates using a commercially available chemical vapor deposition reactor in a Si CMOS compatible process. Carrier activation energies due to ionization and trap states are extracted from the temperature dependent dark I-V characteristics. The temperature dependent spectral response of each photoconductor was measured, and a maximum long wavelength response to 2.1 μm was observed for the 7.0% Sn sample. The DC responsivity measured at 1.55 μm showed around two orders of magnitude improvement at reduced temperatures for all samples compared to room temperature measurements. The noise current and temperature dependent specific detectivity (D*) were also measured for each sample at 1.55 μm, and a maximum D* value of 1 × 10(9) cm·√Hz/W was observed at 77 K. PMID:24977823

  14. Field trial of active remote sensing using a high-power short-wave infrared supercontinuum laser.

    PubMed

    Alexander, Vinay V; Shi, Zhennan; Islam, Mohammed N; Ke, Kevin; Kalinchenko, Galina; Freeman, Michael J; Ifarraguerri, Agustin; Meola, Joseph; Absi, Anthony; Leonard, James; Zadnik, Jerome A; Szalkowski, Anthony S; Boer, Gregory J

    2013-09-20

    Field trial results of a 5 W all-fiber broadband supercontinuum (SC) laser covering the short-wave infrared (SWIR) wavelength bands from ~1.55 to 2.35 μm are presented. The SC laser is kept on a 12 story tower at the Wright Patterson Air Force Base and propagated through the atmosphere to a target 1.6 km away. Beam quality of the SC laser after propagating through 1.6 km is studied using a SWIR camera and show a near diffraction limited beam with an M(2) value of <1.3. The SC laser is used as the illumination source to perform spectral reflectance measurements of various samples at 1.6 km, and the results are seen to be in good agreement with in-lab measurements using a conventional lamp source. Spectral stability measurements are performed after atmospheric propagation through 1.6 km and show a relative variability of ~4%-8% across the spectrum depending on the atmospheric turbulence effects. Spectral stability measurements are also performed in-lab and show a relative variability of <0.6% across the spectrum. PMID:24085183

  15. Design, simulation and test of silicon immersed gratings: key to compact spectrometers in the short-wave infrared

    NASA Astrophysics Data System (ADS)

    van Amerongen, Aaldert H.; Tol, Paul J. J.; Coppens, Tonny H. M.; Schuurhof, Ruud; Laubert, Phillip P.; Ruijter, Jos; Hoogeveen, Ruud W. M.

    2014-10-01

    We present results of our integrated approach to the development of novel diffraction gratings. At SRON we manufacture prism-shaped silicon immersed gratings. Diffraction takes place inside the high-refractive index medium, boosting the resolving power and the angular dispersion. This enables highly compact spectrometer designs. We are continuously improving the cycle of design, simulation and test to create custom gratings for space and ground-based spectroscopic applications in the short-wave infrared wavelength range. Applications are space-based monitoring of greenhouse and pollution gases in the Earth atmosphere and ground-based SWIR spectroscopy for, a.o., characterization of exo-planet atmospheres [1]. We make gratings by etching V-shaped grooves in mono-crystalline silicon. The groove facets are aligned with the crystal lattice yielding a smooth and highly deterministic groove shape. This enables us to predict the polarized efficiency performance accurately by simulation. Feeding back manufacturing tolerances from our production process, we can also determine reliable error bars for the predicted performance. Combining the simulated values for polarized efficiency with ray-tracing, we can optimize the shape of the grating prism to eliminate unwanted internal reflections. In this contribution we present the architecture of our design and simulation platform as well as a description of test setups and typical results.

  16. Four-wave mixing analyses for future ultrafast wavelength conversion at 0.64 Tb/s in a semiconductor optical amplifier

    NASA Astrophysics Data System (ADS)

    Kharraz, Osayd M.; Ahmad, Harith; Forsyth, David I.; Dernaika, Mohamad; Mohammad, Abu Bakar B.; Zulkifli, Mohd Zamani B.; Ismail, Mohd Faizal B.; Supa'at, Abu Sahmah B. Mohd

    2014-11-01

    This paper describes numerical and analytical analyses relating to the use of nonlinear four-wave mixing in a semiconductor optical amplifier medium for anticipated wavelength conversion at ultrahigh data rates of 320 and 640 Gb/s. The proposed system guidelines and design show that a maximum wavelength shift of 30 nm can be achieved at 640 Gb/s, while still maintaining an acceptable bit error rate. In addition, the impact of the pump-probe ratio and semiconductor optical amplifier bias current are investigated and the results are reported.

  17. Short-wavelength infrared (1.3-2.6 μm) observations of the nucleus of Comet 19P/Borrelly

    USGS Publications Warehouse

    Soderblom, L.A.; Britt, D.T.; Brown, R.H.; Buratti, B.J.; Kirk, R.L.; Owen, T.C.; Yelle, R.V.

    2004-01-01

    During the last two minutes before closest approach of Deep Space 1 to Comet 19P/Borrelly, a long exposure was made with the short-wavelength infrared (SWIR) imaging spectrometer. The observation yielded 46 spectra covering 1.3–2.6 μm; the footprint of each spectrum was ∼160 m × width of the nucleus. Borrelly's highly variegated and extremely dark 8-km-long nucleus exhibits a strong red slope in its short-wavelength infrared reflection spectrum. This slope is equivalent to J–K and H–K colors of ∼0.82 and ∼0.43, respectively. Between 2.3–2.6 μm thermal emission is clearly detectable in most of the spectra. These data show the nucleus surface to be hot and dry; no trace of H2O ice was detected. The surface temperature ranged continuously across the nucleus from ⩽300 K near the terminator to a maximum of ∼340 K, the expected sub-solar equilibrium temperature for a slowly rotating body. A single absorption band at ∼2.39 μm is quite evident in all of the spectra and resembles features seen in nitrogen-bearing organic molecules that are reasonable candidates for compositional components of cometary nuclei. However as of yet the source of this band is unknown.

  18. ERS-1 and Seasat scatterometer measurements of ocean winds: Model functions and the directional distribution of short waves

    NASA Technical Reports Server (NTRS)

    Freilich, Michael H.; Dunbar, R. Scott

    1993-01-01

    Calculation of accurate vector winds from scatterometers requires knowledge of the relationship between backscatter cross-section and the geophysical variable of interest. As the detailed dynamics of wind generation of centimetric waves and radar-sea surface scattering at moderate incidence angles are not well known, empirical scatterometer model functions relating backscatter to winds must be developed. Less well appreciated is the fact that, given an accurate model function and some knowledge of the dominant scattering mechanisms, significant information on the amplitudes and directional distributions of centimetric roughness elements on the sea surface can be inferred. accurate scatterometer model functions can thus be used to investigate wind generation of short waves under realistic conditions. The present investigation involves developing an empirical model function for the C-band (5.3 GHz) ERS-1 scatterometer and comparing Ku-band model functions with the C-band model to infer information on the two-dimensional spectrum of centimetric roughness elements in the ocean. The C-band model function development is based on collocations of global backscatter measurements with operational surface analyses produced by meteorological agencies. Strengths and limitations of the method are discussed, and the resulting model function is validated in part through comparison with the actual distributions of backscatter cross-section triplets. Details of the directional modulation as well as the wind speed sensitivity at C-band are investigated. Analysis of persistent outliers in the data is used to infer the magnitudes of non-wind effects (such as atmospheric stratification, swell, etc.). The ERS-1 C-band instrument and the Seasat Ku-band (14.6 GHz) scatterometer both imaged waves of approximately 3.4 cm wavelength assuming that Bragg scattering is the dominant mechanism. Comparisons of the C-band and Ku-band model functions are used both to test the validity of the postulated Bragg mechanism and to investigate the directional distribution of the imaged waves under a variety of conditions where Bragg scatter is dominant.

  19. Reducing Short-Wavelength Blue Light in Dry Eye Patients with Unstable Tear Film Improves Performance on Tests of Visual Acuity

    PubMed Central

    Kaido, Minako

    2016-01-01

    Purpose To investigate whether suppression of blue light can improve visual function in patients with short tear break up time (BUT) dry eye (DE). Methods Twenty-two patients with short BUT DE (10 men, 12 women; mean age, 32.4 ± 6.4 years; age range, 23–43 years) and 18 healthy controls (10 men, 8 women; mean age, 30.1 ± 7.4 years; age range, 20–49 years) underwent functional visual acuity (VA) examinations with and without wearing eyeglasses with 50% blue light blocked lenses. The functional VA parameters were starting VA, functional VA, and visual maintenance ratio. Results The baseline mean values (logarithm of the minimum angle of resolution, logMAR) of functional VA and the visual maintenance ratio were significantly worse in the DE patients than in the controls (P < 0.05), while no significant difference was observed in the baseline starting VA (P > 0.05). The DE patients had significant improvement in mean functional VA and visual maintenance ratio while wearing the glasses (P < 0.05), while there were no significant changes with and without the glasses in the control group (P > 0.05), Conclusions Protecting the eyes from short-wavelength blue light may help to ameliorate visual impairment associated with tear instability in patients with DE. This finding represents a new concept, which is that the blue light exposure might be harmful to visual function in patients with short BUT DE. PMID:27045760

  20. The Verriest Lecture: Short-wave-sensitive cone pathways across the life span.

    PubMed

    Werner, John S

    2016-03-01

    Structurally and functionally, the short-wave-sensitive (S) cone pathways are thought to decline more rapidly with normal aging than the middle- and long-wave-sensitive cone pathways. This would explain the celebrated results by Verriest and others demonstrating that the largest age-related color discrimination losses occur for stimuli on a tritan axis. Here, we challenge convention, arguing from psychophysical data that selective S-cone pathway losses do not cause declines in color discrimination. We show substantial declines in chromatic detection and discrimination, as well as in temporal and spatial vision tasks, that are mediated by S-cone pathways. These functional losses are not, however, unique to S-cone pathways. Finally, despite reduced photon capture by S cones, their postreceptoral pathways provide robust signals for the visual system to renormalize itself to maintain nearly stable color perception across the life span. PMID:26974914

  1. System design process for refractive simultaneous short and long wave infrared imaging.

    PubMed

    Herman, Eric; Czajkowski, Amber; Stroschine, Daniel; Sparrold, Scott

    2013-04-20

    The future of optical design is multispectral imaging. Advancements in detector technology have led to the challenge of imaging over both short wave infrared and long wave infrared spectrums. This paper discusses the technical hurdles associated with designing a refractor to image over both of these spectrums, such as minimizing chromatic focal shift while maximizing contrast. The design process is outlined on an eight element F/1, 23° full field of view solution. Optomechanical design forms are evaluated by analyzing possible stresses and tolerance errors. Antireflection coating designs are discussed to complete the full system. This entire design process is highlighted as a feasibility study for the future of multispectral imaging devices. PMID:23669687

  2. In-depth plasma-wave heating of dense plasma irradiated by short laser pulses.

    PubMed

    Sherlock, M; Hill, E G; Evans, R G; Rose, S J; Rozmus, W

    2014-12-19

    We investigate the mechanism by which relativistic electron bunches created at the surface of a target irradiated by a very short and intense laser pulse transfer energy to the deeper parts of the target. In existing theories, the dominant heating mechanism is that of resistive heating by the neutralizing return current. In addition to this, we find that large amplitude plasma waves are induced in the plasma in the wake of relativistic electron bunches. The subsequent collisional damping of these waves represents a source of heating that can exceed the resistive heating rate. As a result, solid targets heat significantly faster than has been previously considered. A new hybrid model, capable of reproducing these results, is described. PMID:25554889

  3. X, Gamma-Rays, and Gravitational Waves Emission in a Short Gamma-Ray Burst

    NASA Astrophysics Data System (ADS)

    Oliveira, F. G.; Rueda, Jorge A.; Ruffini, R.

    The recent progress in the understanding the physical nature of neutron stars (NSs) and the first observational evidence of a genuinely short gamma-ray burst (GRB), GRB 090227B, allow to give an estimate of the gravitational waves versus the X and gamma-rays emission in a short GRB. NS binaries represent good candidates for the detection of gravitational waves emitted during the spiraling-in and final merging phase of the system that leads to the short GRB emission. The data analysis of the GRB 090227B by Muccino et al. (2013) have been shown to be consistent with a NS binary progenitor with masses M1 = M2 = 1.34 M_{?}, radii R1 = R2 = 12.2 km, and a crust thickness ? r ? 0. 47 km, obtained from the new mass-radius relation by Belvedere et al. (2012) of NSs fulfilling global charge neutrality. Muccino et al. (2013) estimated that GRB 090227B is located at redshift z ? 1. 6, corresponding to a luminosity distance d L ? 12. 2 Gpc. We assess the detectability of this source by the Advanced LIGO interferometer computing the signal-to-noise ratio (SNR) averaged over all polarizations and possible positions of the source with respect to the interferometer. We simulate the dynamics of the binary up to the contact point using the effective one-body formalism (EOB) in the fourth post-Newtonian approximation. We find that the gravitational waves signal would have been produced an SNR = 0.32 for a redshift z = 1. 61. We find that, instead, this GRB would have been detected with an SNR = 8 if it would have been located at a redshift z ? 0. 05, or d L ? 200 Mpc.

  4. GeSn/Ge heterostructure short-wave infrared photodetectors on silicon.

    PubMed

    Gassenq, A; Gencarelli, F; Van Campenhout, J; Shimura, Y; Loo, R; Narcy, G; Vincent, B; Roelkens, G

    2012-12-01

    A surface-illuminated photoconductive detector based on Ge0.91Sn0.09 quantum wells with Ge barriers grown on a silicon substrate is demonstrated. Photodetection up to 2.2µm is achieved with a responsivity of 0.1 A/W for 5V bias. The spectral absorption characteristics are analyzed as a function of the GeSn/Ge heterostructure parameters. This work demonstrates that GeSn/Ge heterostructures can be used to developed SOI waveguide integrated photodetectors for short-wave infrared applications. PMID:23262679

  5. Equatorial electrojet as a nonlinear ULF antenna for the short-wave heating facility

    NASA Astrophysics Data System (ADS)

    Bespalov, Peter A.; Savina, Olga N.

    2015-11-01

    In this paper, we discuss some questions related to the nature and manifestation of the equatorial electrojet. We study theoretically the equatorial electrojet as a nonlinear antenna for generating ultra-low-frequency electromagnetic signals during periodic heating of the ionosphere by the short-wave heater radiation. It is shown that for periodic heating at the frequency corresponding to the ULF band the generation of electromagnetic signals can be significantly intensified. This effect is especially important for the daytime magnetosphere where there are eigenfrequencies of the plasma magnetospheric maser in the electron radiation belts in the same frequency band. This can lead to a modification of VLF emissions in the subauroral magnetosphere.

  6. Spectroscopic and thermal properties of short wavelength metal (II) complexes containing α-isoxazolylazo-β-diketones as co-ligands

    NASA Astrophysics Data System (ADS)

    Huang, Fuxin; Wu, Yiqun; Gu, Donghong; Gan, Fuxi

    2005-10-01

    Two new azo dyes of α-isoxazolylazo-β-diketones and their Ni(II) and Cu(II) complexes with blue-violet light wavelength were synthesized using a coupling component, different diazo components and metal (II) ions (Ni 2+ and Cu 2+). Based on the elemental analysis, MS spectra and FT-IR spectral analyses, azo dyes were unequivocally shown to exist as hydrazoketo and azoenol forms which were respectively obtained from the solution forms and from the solid forms. The action of sodium methoxide (NaOMe) on azo dyes in solutions converts hydrazoketo form into azoenol form, so azo dyes are coordinated with metal (II) ions as co-ligands in the azoenol forms. The solubility of all the compounds in common organic solvents such as 2,2,3,3-tetrafluoro-1-propanol (TFP) or chloroform (CHCl 3) and absorption properties of spin-coating thin films were measured. The difference of absorption maxima from the complexes to their ligands was discussed. In addition, the TG analysis of the complexes was also determined, and their thermal stability was evaluated. It is found that these new metal (II) complexes had potential application for high-density digital versatile disc-recordable (HD-DVD-R) system due to their good solubility in organic solvents, reasonable and controllable absorption spectra in blue-violet light region and high thermal stability.

  7. Advanced short-wavelength infrared range-gated imaging for ground applications in monostatic and bistatic configurations.

    PubMed

    Repasi, Endre; Lutzmann, Peter; Steinvall, Ove; Elmqvist, Magnus; Göhler, Benjamin; Anstett, Gregor

    2009-11-01

    Some advanced concepts for gated viewing are presented, including spectral diversity illumination techniques, non-line-of-sight imaging, indirect scene illumination, and in particular setups in bistatic configurations. By using a multiple-wavelength illumination source target speckles could be substantially reduced, leading to an improved image quality and enhanced range accuracy. In non-line-of-sight imaging experiments we observed the scenery through the reflections in a window plane. The scene was illuminated indirectly as well by a diffuse reflection of the laser beam at different nearby objects. In this setup several targets could be spotted, which, e.g., offers the capability to look around the corner in urban situations. In the presented measuring campaigns the advantages of bistatic setups in comparison with common monostatic configurations are discussed. The appearance of shadows or local contrast enhancements as well as the mitigation of retroreflections supports the human observer in interpreting the scene. Furthermore a bistatic configuration contributes to a reduced dazzling risk and to observer convertness. PMID:19881663

  8. Short period wave generation in Moss Landing Harbor caused by offshore landslides induced by the Loma Prieta earthquake

    SciTech Connect

    Gardner-Taggart, J.M.; Barminski, R.F. Jr. )

    1991-07-01

    Short period waves were observed in the Moss Landing Harbor approximately 2 minutes after the October 17, 1989 Loma Prieta earthquake. Offshore submarine landslides in the region of wave generation was noted by scuba divers and recorded by side scanning sonographs, fathometer records and ROV video footage taken in the area after the quake. These waves are believed to have been generated by offshore submarine landslides along the canyon walls of the Monterey Canyon directly offshore of the Moss Landing Marine Laboratories.

  9. Does one hour of bright or short-wavelength filtered tablet screenlight have a meaningful effect on adolescents' pre-bedtime alertness, sleep, and daytime functioning?

    PubMed

    Heath, Melanie; Sutherland, Cate; Bartel, Kate; Gradisar, Michael; Williamson, Paul; Lovato, Nicole; Micic, Gorica

    2014-05-01

    Electronic media use is prevalent among adolescent populations, as is the frequency of sleeplessness. One mechanism proposed for technology affecting adolescents' sleep is the alerting effects from bright screens. Two explanations are provided. First, screens emit significant amounts of short-wavelength light (i.e. blue), which produces acute alertness and alters sleep timing. Second, later chronotypes are hypothesised to be hypersensitive to evening light. This study analysed the pre-sleep alertness (GO/NOGO task speed, accuracy; subjective sleepiness), sleep (sleep diary, polysomnography), and morning functioning of 16 healthy adolescents (M = 17.4 ± 1.9 yrs, 56% f) who used a bright tablet screen (80 lux), dim screen (1 lux) and a filtered short-wavelength screen (f.lux; 50 lux) for 1 hr before their usual bedtime in a within-subjects protocol. Chronotype was analysed as a continuous between-subjects factor; however, no significant interactions occurred. Significant effects occurred between bright and dim screens for GO/NOGO speed and accuracy. However, the magnitude of these differences was small (e.g. GO/NOGO speed = 23 ms, accuracy = 13%), suggesting minimal clinical significance. No significant effects were found for sleep onset latency, slow-rolling eye movements, or the number of SWS and REM minutes in the first two sleep cycles. Future independent studies are needed to test short (1 hr) vs longer (>2 hrs) screen usage to provide evidence for safe-to-harmful levels of screenlight exposure before adolescents' usual bedtime. PMID:24397302

  10. Nd:(Gd0.3Y0.7)2SiO5 crystal: A novel efficient dual-wavelength continuous-wave medium

    NASA Astrophysics Data System (ADS)

    Xu, Xiaodong; Di, Juqing; Zhang, Jian; Tang, Dingyuan; Xu, Jun

    2016-05-01

    Efficient dual-wavelength continuous-wave (CW) and passively Q-switched laser operation of Nd:(Gd0.3Y0.7)2SiO5 crystal were investigated for the first time to our knowledge. Maximum CW output power of 2.3 W was obtained under the absorbed pump power of 4.6 W, corresponding to the slope efficiency of 55%. Dual-wavelength CW laser with respective wavelengths around 1074 nm and 1078 nm were achieved. With Cr4+:YAG as the saturable absorber, passive Q-switched performance was obtained. The slope efficiency of passively Q-switched operation was 45%. The shortest pulse width, the corresponding pulse energy and peak power were calculated to be 13.1 ns, 50.2 μJ and 3.8 kW, respectively.

  11. Simultaneous multichannel wavelength multicasting and XOR logic gate multicasting for three DPSK signals based on four-wave mixing in quantum-dot semiconductor optical amplifier.

    PubMed

    Qin, Jun; Lu, Guo-Wei; Sakamoto, Takahide; Akahane, Kouichi; Yamamoto, Naokatsu; Wang, Danshi; Wang, Cheng; Wang, Hongxiang; Zhang, Min; Kawanishi, Tetsuya; Ji, Yuefeng

    2014-12-01

    In this paper, we experimentally demonstrate simultaneous multichannel wavelength multicasting (MWM) and exclusive-OR logic gate multicasting (XOR-LGM) for three 10Gbps non-return-to-zero differential phase-shift-keying (NRZ-DPSK) signals in quantum-dot semiconductor optical amplifier (QD-SOA) by exploiting the four-wave mixing (FWM) process. No additional pump is needed in the scheme. Through the interaction of the input three 10Gbps DPSK signal lights in QD-SOA, each channel is successfully multicasted to three wavelengths (1-to-3 for each), totally 3-to-9 MWM, and at the same time, three-output XOR-LGM is obtained at three different wavelengths. All the new generated channels are with a power penalty less than 1.2dB at a BER of 10(-9). Degenerate and non-degenerate FWM components are fully used in the experiment for data and logic multicasting. PMID:25606876

  12. Gravitational Waves versus X-Ray and Gamma-Ray Emission in a Short Gamma-Ray Burst

    NASA Astrophysics Data System (ADS)

    Oliveira, F. G.; Rueda, Jorge A.; Ruffini, R.

    2014-06-01

    Recent progress in the understanding of the physical nature of neutron star equilibrium configurations and the first observational evidence of a genuinely short gamma-ray burst (GRB), GRB 090227B, allows us to give an estimate of the gravitational waves versus the X-ray and gamma-ray emission in a short GRB.

  13. Gravitational waves versus X-ray and gamma-ray emission in a short gamma-ray burst

    SciTech Connect

    Oliveira, F. G.; Rueda, Jorge A.; Ruffini, R. E-mail: jorge.rueda@icra.it

    2014-06-01

    Recent progress in the understanding of the physical nature of neutron star equilibrium configurations and the first observational evidence of a genuinely short gamma-ray burst (GRB), GRB 090227B, allows us to give an estimate of the gravitational waves versus the X-ray and gamma-ray emission in a short GRB.

  14. Short-wavelength turbulence in the solar wind: Linear theory of whistler and kinetic Alfvén fluctuations

    NASA Astrophysics Data System (ADS)

    Gary, S. Peter; Smith, Charles W.

    2009-12-01

    There is a debate as to the identity of the fluctuations which constitute the relatively high-frequency plasma turbulence observed in the solar wind. One school holds that these modes are kinetic Alfvén waves, whereas another opinion is that they are whistler modes. Here linear kinetic theory for electromagnetic fluctuations in homogeneous, collisionless, magnetized plasmas is used to compute two dimensionless transport ratios, the electron compressibility Ce and the magnetic compressibility C$\\parallel$ for these two modes. The former is a measure of the amplitude of density fluctuations, and the latter indicates the relative energy in magnetic fluctuations in the component parallel to the background magnetic field Bo. For βe $\\ll$ 1, [C$\\parallel$]Alfven $\\ll$ [C$\\parallel$]whistler, and the latter quantity is of order 0.5 at whistler propagation strongly oblique to Bo. Such values of C$\\parallel$ are sometimes measured at relatively high frequencies and βe $\\ll$ 1 in the solar wind; thus, it is concluded that such observations correspond to whistler mode turbulence. But other solar wind observations indicate that kinetic Alfvén fluctuations also contribute to relatively high-frequency solar wind turbulence.

  15. Variety identification of brown sugar using short-wave near infrared spectroscopy and multivariate calibration

    NASA Astrophysics Data System (ADS)

    Yang, Haiqing; Wu, Di; He, Yong

    2007-11-01

    Near-infrared spectroscopy (NIRS) with the characteristics of high speed, non-destructiveness, high precision and reliable detection data, etc. is a pollution-free, rapid, quantitative and qualitative analysis method. A new approach for variety discrimination of brown sugars using short-wave NIR spectroscopy (800-1050nm) was developed in this work. The relationship between the absorbance spectra and brown sugar varieties was established. The spectral data were compressed by the principal component analysis (PCA). The resulting features can be visualized in principal component (PC) space, which can lead to discovery of structures correlative with the different class of spectral samples. It appears to provide a reasonable variety clustering of brown sugars. The 2-D PCs plot obtained using the first two PCs can be used for the pattern recognition. Least-squares support vector machines (LS-SVM) was applied to solve the multivariate calibration problems in a relatively fast way. The work has shown that short-wave NIR spectroscopy technique is available for the brand identification of brown sugar, and LS-SVM has the better identification ability than PLS when the calibration set is small.

  16. Short-Period Surface-Wave Tomography Beneath the Central and Eastern Tibetan Plateau

    NASA Astrophysics Data System (ADS)

    Arias, E. Y.; Ammon, C. J.

    2002-12-01

    Despite significant effort, the mechanism driving the Tibetan Plateau uplift remains controversial because most results are from geophysical studies concentrated on the southern part of Tibet or used data that traverse the Plateau boundary. Data from two PASSCAL experiments, the Tibetan Plateau Passive Source Seismic Experiment in 1991-1992 and the INDEPTH III experiment in 1997-1999, provide an opportunity to map the subsurface geology and advance our understanding of the Plateau's dynamics and tectonic evolution. We present the results of our efforts to construct least-squares tomographic maps of short-period Love and Rayleigh wave group velocities across the central and eastern Plateau. We only utilize measurements made using stations and events within the Plateau to localize our sensitivity to Plateau structures. Although the short-period dispersion observations cannot not reliably resolve features below the upper crust, they can be combined with other data such as global surface-wave dispersion models and receiver functions to improve resolution throughout the lithosphere. Our inversion is based on observations using a set of 49 shallow events recorded on the 11 stations of the 1991-1992 experiment. We plan to include additional data from INDEPTH III to extend the study area into the central and southern Plateau. For the data for which we have completed the dispersion analysis, event location and origin time appear to cause noticeable scatter in the dispersion curves. This variation is consistent with inconsistency in small-to-moderate size event locations in global earthquake catalogs and in more refined regional locations. We will investigate the potential of an iterative tomographic and epicenter re-location procedure using surface-wave dispersion values to improve the event epicenters. We have made measurements in the period range from 4 to 50 seconds on about 50 events with magnitudes in the 4-to-5 range. As expected, the shortest and longest periods produce a path coverage too sparse for an informative tomographic reconstruction. In the period range from 10 to 40 seconds, the number of measurements for both Rayleigh and Love waves range between 80 and 250, with a spatial distribution sufficient for the tomographic analysis. We plan to experiment with different approaches to improve epicentral locations and to map subsurface geologic variations. Our ultimate goal is localize short-period dispersion measurements that complement other measurements sensitive to Plateau structure such as receiver functions.

  17. Experimental study on the effects of surface gravity waves of different wavelengths on the phase averaged performance characteristics of marine current turbine

    NASA Astrophysics Data System (ADS)

    Luznik, L.; Lust, E.; Flack, K. A.

    2014-12-01

    There are few studies describing the interaction between marine current turbines and an overlying surface gravity wave field. In this work we present an experimental study on the effects of surface gravity waves of different wavelengths on the wave phase averaged performance characteristics of a marine current turbine model. Measurements are performed with a 1/25 scale (diameter D=0.8m) two bladed horizontal axis turbine towed in the large (116m long) towing tank at the U.S. Naval Academy equipped with a dual-flap, servo-controlled wave maker. Three regular waves with wavelengths of 15.8, 8.8 and 3.9m with wave heights adjusted such that all waveforms have the same energy input per unit width are produced by the wave maker and model turbine is towed into the waves at constant carriage speed of 1.68 m/s. This representing the case of waves travelling in the same direction as the mean current. Thrust and torque developed by the model turbine are measured using a dynamometer mounted in line with the turbine shaft. Shaft rotation speed and blade position are measured using in in-house designed shaft position indexing system. The tip speed ratio (TSR) is adjusted using a hysteresis brake which is attached to the output shaft. Free surface elevation and wave parameters are measured with two optical wave height sensors, one located in the turbine rotor plane and other one diameter upstream of the rotor. All instruments are synchronized in time and data is sampled at a rate of 700 Hz. All measured quantities are conditionally sampled as a function of the measured surface elevation and transformed to wave phase space using the Hilbert Transform. Phenomena observed in earlier experiments with the same turbine such as phase lag in the torque signal and an increase in thrust due to Stokes drift are examined and presented with the present data as well as spectral analysis of the torque and thrust data.

  18. An analysis of short pulse and dual frequency radar techniques for measuring ocean wave spectra from satellites

    NASA Technical Reports Server (NTRS)

    Jackson, F. C.

    1980-01-01

    Scanning beam microwave radars were used to measure ocean wave directional spectra from satellites. In principle, surface wave spectral resolution in wave number can be obtained using either short pulse (SP) or dual frequency (DF) techniques; in either case, directional resolution obtains naturally as a consequence of a Bragg-like wave front matching. A four frequency moment characterization of backscatter from the near vertical using physical optics in the high frequency limit was applied to an analysis of the SP and DF measurement techniques. The intrinsic electromagnetic modulation spectrum was to the first order in wave steepness proportional to the large wave directional slope spectrum. Harmonic distortion was small and was a minimum near 10 deg incidence. NonGaussian wave statistics can have an effect comparable to that in the second order of scattering from a normally distributed sea surface. The SP technique is superior to the DF technique in terms of measurement signal to noise ratio and contrast ratio.

  19. Short wavelength turbulence generated by shear in the quiescent H-mode edge on DIII–D

    SciTech Connect

    Rost, J. C.; Porkolab, M.; Dorris, J.; Burrell, K. H.

    2014-06-15

    A region of turbulence with large radial wavenumber (k{sub r}ρ{sub s}>1) is found in the high-shear portion of the plasma edge in Quiescent H-mode (QH-mode) on DIII–D using the Phase Contrast Imaging (PCI) diagnostic. At its peak outside the minimum of the E{sub r} well, the turbulence exhibits large amplitude n{sup ~}/n∼40%, with large radial wavenumber |k{sup ¯}{sub r}/k{sup ¯}{sub θ}|∼11 and short radial correlation length L{sub r}/ρ{sub i}∼0.2. The turbulence inside the E{sub r} well minimum is characterized by the opposite sign in radial wavenumber from that of turbulence outside the minimum, consistent with the expected effects of velocity shear. The PCI diagnostic provides a line-integrated measurement of density fluctuations, so data are taken during a scan of plasma position at constant parameters to allow the PCI to sample a range in k{sub r}/k{sub θ}. Analysis of the Doppler shift and plasma geometry allows the turbulence to be localized to a narrow region 3 mm inside the last closed flux surface, outside the minimum of the E{sub r} well. The turbulence amplitude and radial wavenumber and correlation length are determined by fitting the PCI results with a simple non-isotropic turbulence model with two regions of turbulence. These PCI observations, made in QH-mode, are qualitatively similar to those made in standard edge localized modes (ELM)-free H-mode and between ELMs, suggesting a similar role for large k{sub r} turbulence there.

  20. Resonant interaction between a localized fast wave and a slow wave with constant asymptotic amplitude

    SciTech Connect

    Zabolotskii, A. A.

    2009-11-15

    An integrable Yajima-Oikawa system is solved in the case of a finite density, which corresponds to a slowly varying (long-wavelength) wave with finite amplitude at infinity and a localized fast-oscillating (short-wavelength) wave. Application of the results to spinor Bose-Einstein condensates and other physical systems is discussed.

  1. Propagation of short period (10-40 min) atmospheric gravity waves from troposphere to mesosphere over Gadanki, India

    NASA Astrophysics Data System (ADS)

    Chakravarty, S. C.; Nagaraja, Kamsali

    2015-09-01

    The Indian MST radar at Gadanki (13.5°N, 79.2°E) has been utilised to conduct a detailed study of the close coupling between the troposphere and the mesosphere through the vertically propagating atmospheric gravity waves. For this purpose two cases from a special campaign dedicated to the simultaneous measurement of the fluctuations in the UTLS (Upper Troposphere and Lower Stratosphere) and in the mesosphere during 2001 and one case from a follow up observation in 2002 have been investigated. By using both the FFT and wavelet techniques, the near simultaneous tropospheric and mesospheric data of radar return signal strengths and tropospheric wind fields are analysed. The signatures of relatively high frequency gravity waves with periods between ~10 and 40 min have been clearly traced as propagating waves from the tropospheric turbulent layer heights (~8-18 km) to the lower mesospheric heights (65-80 km). Significant peak correlation coefficients of 0.56 and 0.45 have been found between the SNR time series of pairs of troposphere and mesosphere levels indicating the propagation of high speed gravity waves. The time series of wavelet spectra determined for the tropospheric SNR/zonal winds and the mesospheric SNR show that the detectability of the gravity waves increases at mesospheric heights. It is shown that the continuous SNR values received from the mesosphere can be used as an effective parameter for studies featuring mesospheric wave dynamics. Based on the observed values of vertical wavelengths and wave amplitudes, the horizontal wavelengths, wave phase and group velocities have been estimated for different wave periods. These results have implications on monitoring of the ubiquitous atmospheric gravity waves generated mainly by the tropospheric weather system of the tropical region from their imprint on the mesospheric turbulence structures.

  2. Detailed gravimetric geoid confirmation of short wavelength features of sea surface topography detected by the Skylab S-193 altimeter in the Atlantic Ocean

    NASA Technical Reports Server (NTRS)

    Marsh, J. G.; Vincent, S.; Mcclinton, A. T.; Chang, E. S.

    1975-01-01

    A detailed gravimetric geoid was computed for the Northwest Atlantic Ocean and Caribbean Sea area in support of the calibration and evaluation of the GEOS-C altimeter. This geoid, computed on a 15 ft. x 15 ft. grid was based upon a combination of surface gravity data with the GSFC GEM-6 satellite derived gravity data. A comparison of this gravimetric geoid with 10 passes of SKYLAB altimeter data is presented. The agreement of the two data types is quite good with the differences generally less than 2 meters. Sea surface manifestations of numerous short wavelength (approximately 100 km) oceanographic features are now indicated in the gravimetric geoid and are also confirmed by the altimetry data.

  3. Visible to Short Wavelength Infrared Spectroscopy on Rovers: Why We Need it on Mars and What We Need to do on Earth

    NASA Technical Reports Server (NTRS)

    Blaney, D. L.

    2002-01-01

    The next stage of Mars exploration will include the use of rovers to seek out specific mineralogies. Understanding the mineralogical diversity of the locale will be used to determining which targets should be investigated with the full suite of in situ capability on the rover. Visible to Short Wavelength Infrared (VSWIR) spectroscopy is critical in evaluating the mineralogical diversity and to validate the global remote sensing data sets to be collected by Mars Express and the Mars Reconnaissance Orbiter. However, spectroscopy on mobile platforms present challenges in both the design of instruments and in the efficient operation of the instrument and mission. Field-testing and validation on Earth can be used to develop instrument requirements analysis tools needed for used on Mars.

  4. Modeling the influence of short wavelength defects in a railway track on the dynamic behavior of the Non-Suspended Masses

    NASA Astrophysics Data System (ADS)

    Giannakos, Konstantinos

    2016-02-01

    The motion of a railway vehicle on the rail running table, that is the area of the rail-head where the wheel is rolling, is a forced oscillation with a forcing excitation (track defects), and damping expressed by a random function. In the case of the Non-Suspended Masses the forces resulting from the excitation of short wavelength are large and have great effect on the rolling of the wheel. The track, is simulated as an elastic means with damping. In this paper the second order differential equation is presented for the case of a railway vehicle rolling on a railway track and its solution is presented for the Non-Suspended Masses of the vehicle. Furthermore the influence of the depth of the defect is examined and a sensitivity analysis of the influence of the Non-Suspended Masses and the track defects on the Acting loads is performed.

  5. Signature of gravitational wave radiation in afterglows of short gamma-ray bursts?

    NASA Astrophysics Data System (ADS)

    Fan, Yi-Zhong; Wu, Xue-Feng; Wei, Da-Ming

    2013-09-01

    Short gamma-ray bursts (GRBs), brief intense emission of ? rays characterized by a duration shorter than 2 s that are plausibly powered by the coalescence of binary neutron stars, are believed to be strong gravitational wave radiation (GWR) sources. The test of such a speculation has been thought to be impossible until the performance of the detectors like advanced LIGO. Recently there has been growing evidence for the formation of a highly magnetized neutron star (i.e., magnetar) in the double neutron star mergers. In this work we reexamine the interpretation of the x-ray plateau followed by an abrupt decline detected in some short GRB afterglows within the supramassive magnetar model and find that the maximum gravitational mass of the nonrotating neutron stars is 2.3M? and the observed duration of some x-ray plateaus are significantly shorter than that expected in the magnetic dipole radiation scenario, suggesting that the collapse of the supramassive magnetars has been considerably enhanced by the energy loss via GWR. Such a result demonstrates that the signature of GWR may have already existed in current electromagnetic data of short GRBs.

  6. A feasibility study on the use of visible and short wavelengths in the near-infrared region for the non-destructive measurement of wine composition.

    PubMed

    Cozzolino, D; Kwiatkowski, M J; Waters, E J; Gishen, M

    2007-03-01

    The aim of this study was to explore the capability of spectroscopy in the visible (Vis) and short wavelength near-infrared (NIR) regions for the non-destructive measurement of wine composition in intact bottles. In this study we analysed a wide range of commercial wines obtained in Australia in different types of bottles (e.g. colours, diameters and heights), including different wine styles and varieties. Wine bottles were scanned in the Vis-NIR region (600-1,100 nm) in a monochromator instrument in transflectance mode. Principal component analysis (PCA) and partial least-squares (PLS) regression were used to interpret the spectra and develop calibrations for wine composition. Due to the relatively small number of samples available full cross-validation (leave-one-out) was used as validation. The coefficient of correlation in calibration [Formula: see text] and the standard error of cross-validation (SECV) were 0.67 (SECV: 0.48%), 0.83 (SECV: 4.01 mg L-1), 0.70 (SECV: 28.6 mg L-1) and 0.50 (SECV: 0.15) for alcohol content, total SO2, free SO2 and pH, respectively, in the set of wine samples analysed. These preliminary results showed that the assessment of wine composition by Vis and short wavelengths in the NIR is possible for either qualitative analysis (e.g. low-, medium- and high-quality grading), or for screening of composition during bottling and storage. Although low accuracy and precision were obtained for the chemical parameters routinely analysed in wine, calibration models for the chemical parameters were considered acceptable for screening purposes in terms of the standard errors obtained. PMID:17203262

  7. Short range structure of hadron and nuclear wave functions at high x

    SciTech Connect

    Hoyer, P.; Brodsky, S.J.

    1990-11-01

    We discuss the short-range structure of hadronic and nuclear wave functions expected in QCD. In addition to the extrinsic'' contributions associated with radiation from single partons, there is an intrinsic'' hardness of the high-mass fluctuations of the wave function due to the spatial overlap of two or more partons. We argue that intrinsically-hard partons, having large mass and/or large transverse momentum, will dominate in the region of large Feynman x{sub F}. Their rescattering in nuclear targets is expected to be larger than for extrinsically-hard partons, leading to a suppressed production cross section for hadrons scattering on heavy nuclei. Experimental evidence for this exists for open chars. J/{psi}, and {gamma} production at large x{sub F}. The effects of intrinsic hardness may be particularly striking in nuclear wave functions, where the overlap of partons belonging to different nucleons can give rise to cumulative (x > 1) phenomena. The data on backward cumulative particle production from nuclei supports the existence of an intrinsically-hard component in nuclear wave functions. Partons at large x{sub F} may also be associated with the enhanced subthreshold production of particles observed in hadron-nucleus and nucleus-nucleus collisions. We discuss the evidence for anomalies in the large angle pp {yields} pp cross section near the charm threshold. Arguments are presented that chromium states may bind to nuclei through the QCD Van der Waals force. This would lead to a striking signal in charm production near threshold. 49 refs., 7 figs.

  8. Short Period Surface-wave Tomography Beneath the Central Tibetan Plateau

    NASA Astrophysics Data System (ADS)

    Arias, E.

    2003-12-01

    Data from the PASSCAL experiments, the Tibetan Plateau Passive Source Seismic Experiment in 1991-1992 (TIPLT), INDEPTHIII experiment in 1997-1999 and BUTHAN and stations LSA and LZH, provide an opportunity to map the subsurface geology and advance our understanding of the Plateau's dynamics and tectonic evolution. I present the results of the effort to construct least-squares tomographic maps of short-period Love and Rayleigh wave group velocities across the central and eastern Plateau. I utilize measurements made using stations and events within the Plateau to localize sensitivity to Plateau structures. The inversion is based on observations using a set of 190 shallow events recorded on the 29 broadband stations. I performed a least-square inversion using the conjugate gradient method by Paige and Saunders (1982) at the 6-to 45 s period range. The ray path coverage and checkerboard tests obtained in this study show evidence of reliable tomographic images from Rayleigh and Love wave group velocities across central and east of the Tibetan Plateau. The resolved region of the Qiangtang terrane is one of the slowest features in the model for all periods for both Love and Rayleigh waves. The Lhasa terrane is relatively fast until perhaps 40-seconds, where slow regions emerge in Rayleigh wave group velocities, particularly close to the terrane's southern boundary. An interesting feature is the low-velocity region along the southern terrane boundary. The resolution of such a small feature could be questioned, but it may indicate a region of abnormally low velocities along the suture, caused perhaps by melt or structural anisotropy. Qualitatively, these observations suggest that the upper crust of the Qiangtang terrane is slower than the Lhasa terrane to the south, and that the difference may decrease below a few tens of kilometers, in the middle crust. There is a suggestion of a low-velocity zone at a depth of 20-30 km beneath the Lhasa terrane, but the conclusion is not strongly supported by the present study. The recent characterizations of the upper-middle crust of the Lhasa terrane as containing broad regions of partial melt is neither consistent with the regional and global tomography results nor those of the local-regional tomography of this study. In constrast, the images produced here show the upper crust beneath the Lhasa terrane to be faster on average than that to the north beneath the Qiantang terrane. Deeper structures are beyond the reach of the short-period surface waves employed here, but the existence of wide-spread low-velocity regions as shallow as 12 km is not consistent with the observed group velocities. The use of short-path observations in this tomographic analysis has illuminated several problems. Foremost is the sensitivity of the observed group velocities to source location and origin time. By comparing the Eurasian model mean dispersion values for Central Tibet of Ritzwoller and Levshin (1998) and the mean values from this study the agreement is superb in the range where both data sets are most reliable and the results deviate slightly at the shortest and longest periods. The use of a large number of data has allowed us to overcome this limitation in this study as indicated by the consistent mean results after comparing with the Ritzwoller and Levshin (1998) model, and the correlation of the tomographic images with the terrane geology. Future wok involves an iterative tomographic and epicenter re-location procedure using surface-wave dispersion values to improve the event epicenters, and therefore to precisely define the geological structures in the upper crust of the Plateau.

  9. A free surface interpolation approach for rapid simulation of short waves in meshless numerical wave tank based on the radial basis function

    NASA Astrophysics Data System (ADS)

    Xiao, Longfei; Yang, Jianmin; Peng, Tao; Tao, Longbin

    2016-02-01

    The meshless Numerical Wave Tank (NWT) has been developed based on the collocation method and the radial basis function. For simulating short waves, a free surface interpolation approach is proposed in this study in order to mitigate numerical dissipation and accelerate the simulation. A number of fundamental free surface nodes are employed in the procedure of solving algebraic equations with a full coefficient matrix, while many more free surface nodes are utilized in the time-stepping and smoothing procedure by applying the interpolation technique between each adjacent fundamental nodes. The NWT with the free surface interpolation approach is applied to simulate regular waves and irregular waves, and is then validated by both analytical solutions and experimental results. The numerical results are significantly improved by using the approach to increase the number of free surface boundary nodes, whilst the time consumption increases proportionally. For shorter waves, more interpolation nodes need be used. The good agreement between the present numerical results and the analytical and experimental results indicates that the free surface interpolation approach succeeds in rapidly and accurately simulating the propagation of short waves and irregular waves, covering a wide range of wave frequencies.

  10. The effect of a short wavelength mode on the evolution of a long wavelength perturbation driven by a strong blast wave

    SciTech Connect

    Miles, A R; Edwards, M; Blue, B; Hansen, J F; Robey, H F; Drake, R P; Kuranz, C; Leibrandt, D R

    2004-03-16

    Shock-accelerated material interfaces are potentially unstable to both the Richtmyer-Meshkov and Rayleigh-Taylor instabilities. Shear that develops along with these instabilities in turn drives the Kelvin-Helmholtz instability. When driven by strong shocks, the evolution and interaction of these instabilities is further complicated by compressibility effects. In this paper, we present a computational study of the formation of jets at strongly driven hydrodynamically unstable interfaces, and the interaction of these jets with one another and with developing spikes and bubbles. This provides a nonlinear spike-spike and spike-bubble interaction mechanism that can have a significant impact on the large-scale characteristics of the mixing layer. These interactions result in sensitivity to the initial perturbation spectrum, including the relative phases of the various modes, that persists long into the nonlinear phase of instability evolution. We describe implications for instability growth rates, the bubble merger process, and the degree of mix in the layer. Finally, we consider results from relevant deceleration RT experiments, performed on OMEGA, to demonstrate some of these effects.

  11. The effect of a short-wavelength mode on the evolution of a long-wavelength perturbation driven by a strong blast wave

    SciTech Connect

    Miles, A.R.; Edwards, M.J.; Blue, B.; Hansen, J.F.; Robey, H.F.; Drake, R.P.; Kuranz, C.; Leibrandt, D.R.

    2004-12-01

    Shock-accelerated material interfaces are potentially unstable to both the Richtmyer-Meshkov and Rayleigh-Taylor (RT) instabilities. Shear that develops along with these instabilities in turn drives the Kelvin-Helmholtz instability. When driven by strong shocks, the evolution and interaction of these instabilities is further complicated by compressibility effects. This paper details a computational study of the formation of jets at strongly driven hydrodynamically unstable interfaces, and the interaction of these jets with one another and with developing spikes and bubbles. This provides a nonlinear spike-spike and spike-bubble interaction mechanism that can have a significant impact on the large-scale characteristics of the mixing layer. These interactions result in sensitivity to the initial perturbation spectrum, including the relative phases of the various modes, that persists long into the nonlinear phase of instability evolution. Implications for instability growth rates, the bubble merger process, and the degree of mix in the layer are described. Results from relevant deceleration RT experiments, performed on OMEGA [J. M. Soures et al., Phys. Plasmas 5, 2108 (1996)], are shown to demonstrate some of these effects.

  12. Short and Long Wave Radiative Forcing from Desert Dust and Impacts on Weather and Climate

    NASA Astrophysics Data System (ADS)

    Kallos, G.; Spyrou, C.; Mitsakou, C.

    2009-04-01

    The presence of desert dust in the atmosphere has considerable impacts on radiative transfer, clouds and precipitation. Desert dust is a considerable climate modifier. The impacts of desert dust to land and marine ecosystems are considerable as well in humans. Modeling tools have been developed for studying the dust cycle in both global and regional scales. The uncertainties associated with the dust production, transport and deposition processes are still high for various reasons. Most of them are associated with the surface properties and dust production as well as with the radiative forcing parameterization. Modeling the impacts on radiation and cloud is a complicated task that is either oversimplified or absent in most of the dust models. Radiative transfer corrections due to the presence of dust particles for the incoming solar radiation can be applied (shading effects) by utilizing look up tables in the calculation of Aerosol Optical Depth (AOD). The impacts of dust on long wave radiation transfer are more complicated. A new version of the SKIRON/Dust modeling system incorporates the Rapid Radiative Transfer Model - RRTM for both short and long wave radiation. The new radiative transfer scheme has many properties that allow the partitioning of both short and long wave radiation according to the dust concentration and size distribution. In this presentation we discuss the new model characteristics and especially the dust radiative properties as described by both: lookup tables and empirical formulation as well as the new approach by utilizing RRTM. Several cases with dust outbreaks in the Mediterranean and Europe have been analyzed. Heating rates of 2-10 degrees K/day (or even higher in cases of a strong episode) have been calulated within the dust layer. The model results are compared with soundings, lidar and AERONET observations. As it was found, the dust cloud has as a result the surface cooling of 50-80 Wm-2 in remote locations. Near the source areas is double or even triple to these amounts. The long wave radiation forcing below and above the dust cloud is considerable and results in mid and low tropospheric warming that has as impact the stabilization of the atmosphere and reduction of precipitation.

  13. Short Wavelength Electromagnetic Perturbations Excited Near the Solar Probe Plus Spacecraft in the Inner Heliosphere: 2.5D Hybrid Modeling

    NASA Technical Reports Server (NTRS)

    Lipatov, Alexander S.; Sittler, Edward C.; Hartle, Richard E.; Cooper, John F.

    2011-01-01

    A 2.5D numerical plasma model of the interaction of the solar wind (SW) with the Solar Probe Plus spacecraft (SPPSC) is presented. These results should be interpreted as a basic plasma model derived from the SW-interaction with the spacecraft (SC), which could have consequences for both plasma wave and electron plasma measurements on board the SC in the inner heliosphere. Compression waves and electric field jumps with amplitudes of about 1.5 V/m and (12-18) V/m were also observed. A strong polarization electric field was also observed in the wing of the plasma wake. However, 2.5D hybrid modeling did not show excitation of whistler/Alfven waves in the upstream connected with the bidirectional current closure that was observed in short-time 3D modeling SPPSC and near a tether in the ionosphere. The observed strong electromagnetic perturbations may be a crucial point in the electromagnetic measurements planned for the future Solar Probe Plus (SPP) mission. The results of modeling electromagnetic field perturbations in the SW due to shot noise in absence of SPPSC are also discussed.

  14. Short wavelength electromagnetic perturbations excited near the Solar Probe Plus spacecraft in the inner heliosphere: 2.5D hybrid modeling

    NASA Astrophysics Data System (ADS)

    Lipatov, Alexander S.; Sittler, Edward C., Jr.; Hartle, Richard E.; Cooper, John F.

    2012-03-01

    A 2.5D numerical plasma model of the interaction of the solar wind (SW) with the Solar Probe Plus spacecraft (SPPSC) is presented. These results should be interpreted as a basic plasma model derived from the SW interaction with the spacecraft (SC), which could have consequences for both plasma wave and electron plasma measurements on board the SC in the inner heliosphere. Compression waves and electric field jumps with amplitudes of about 1.5 V/m and (12-18) V/m were also observed. A strong polarization electric field was also observed in the wing of the plasma wake. However, 2.5D hybrid modeling did not show excitation of whistler/Alfvn waves in the upstream connected with the bi-directional current closure that was observed in short-time 3D modeling SPPSC and near a tether in the ionosphere. The observed strong electromagnetic perturbations may be a crucial point in the electromagnetic measurements planned for the future Solar Probe Plus (SPP) mission. The results of modeling electromagnetic field perturbations in the SW due to "shot" noise in absence of SPPSC are also discussed.

  15. Long and short wavelengths of Indian Ocean geoid and gravity lows: Mid-to-upper mantle sources, rapid drift and seismicity of Kachchh and Shillong plateau, India

    NASA Astrophysics Data System (ADS)

    Mishra, D. C.; Ravi Kumar, M.

    2012-10-01

    Spectral analysis of the Indian Ocean geoid low provides depth to the large wavelength sources as ˜1300, ˜700 and 340 km that are supported from the spectral analysis and the modeling of the corresponding large wavelength regional gravity anomaly with negative density contrasts at these levels. The three levels coincide with the sharp changes in the gradient of the seismic velocities related to the olivine-spinel transformation of successively increasing Fe/Mg ratio as depth increases, known as transition zones. The first two segments are supported from continuous wavelet transform analysis of the large wavelength component of the corresponding gravity field. The low density rocks in this section appear to be related to the subducted Indian/Tethyan lithosphere that roll back and drifted southwards after subduction as inferred from tomography experiments. The relatively short wavelength sources of the spectrum of the geoid data at depths of 162 and 85 km suggest sources along the lithosphere - asthenosphere boundary (LAB) under the Indian continent and surrounding oceans, respectively. A low viscosity zone has been envisaged below 660 km discontinuity that may correspond to the low density rocks in this section which is popularly referred to as graveyards of the subducted rocks under geoid lows. The subducted slab is hydrated due to dehydration from metamorphism that causes upwelling in the mid-to-upper mantle which is likely to set in baby plumes. Presence of fluid may transform part of olivine to serpentine further reducing the bulk density of rocks in this section. They would make this region buoyant that appears to be responsible for the Central Indian Ocean Deformation Zone with large scale folding, faulting, seismicity, and high heat flow. The same also appear to be responsible for the rapid drift of the Indian plate. Short wavelength component of the Indian Ocean geoid low reflects most of the surface/shallow tectonics of the region similar to the gravity anomaly providing an additional data set for this purpose. Kachchh and the Shillong plateau inspite of being in the intra plate region are highly seismogenic that compare almost to the activity along the plate boundaries. Tectonics and residual geoid anomalies of the Indian continent and adjoining regions suggest that the geoid highs of Kachchh and the Shillong plateau along the NW and the NE corners of India are connected to the geoid highs of the plate boundaries through several lineaments and faults that also show geoid highs and trends of seismic activity leading to plate boundaries. Geoid highs indicating high density mafic rocks suggest their connections/extensions to plate boundaries indicating them to be plausibly part of diffused plate boundaries. Besides, both these regions are affected by (i) prominent lithospheric flexure of the Indian plate (ii) large scale mafic intrusions and (iii) interaction of proterozoic mobile belts with effects of present day Himalayan orogeny that make them more vulnerable for seismic activity.

  16. Geometrical measurement of cardiac wavelength in reaction-diffusion models

    NASA Astrophysics Data System (ADS)

    Dupraz, Marie; Jacquemet, Vincent

    2014-09-01

    The dynamics of reentrant arrhythmias often consists in multiple wavelets propagating throughout an excitable medium. An arrhythmia can be sustained only if these reentrant waves have a sufficiently short wavelength defined as the distance traveled by the excitation wave during its refractory period. In a uniform medium, wavelength may be estimated as the product of propagation velocity and refractory period (electrophysiological wavelength). In order to accurately measure wavelength in more general substrates relevant to atrial arrhythmias (heterogeneous and anisotropic), we developed a mathematical framework to define geometrical wavelength at each time instant based on the length of streamlines following the propagation velocity field within refractory regions. Two computational methods were implemented: a Lagrangian approach in which a set of streamlines were integrated, and an Eulerian approach in which wavelength was the solution of a partial differential equation. These methods were compared in 1D/2D tissues and in a model of the left atrium. An advantage of geometrical definition of wavelength is that the wavelength of a wavelet can be tracked over time with high temporal resolution and smaller temporal variability in an anisotropic and heterogeneous medium. The results showed that the average electrophysiological wavelength was consistent with geometrical measurements of wavelength. Wavelets were however often shorter than the electrophysiological wavelength due to interactions with boundaries and other wavelets. These tools may help to assess more accurately the relation between substrate properties and wavelet dynamics in computer models.

  17. Con_A-carbone nanotube conjugate with short wave near-infrared laser ablation for tumor therapy

    NASA Astrophysics Data System (ADS)

    Lei, Huan-Yao; Peng, Ching-An; Tang, Ming-Jer; Reindhart, Kit; Szu, Harold H.

    2009-04-01

    Using the characteristics of T cell mitogen called lectin protein from the jack-beam Canavalia ensiformis Concanavalin A (Con_A) with dual activities, cytotoxicity and immunomodulation, we have shown it has a therapeutic effect on hepatoma. Injection of Con_A can eradicate the established malign tumor, because Con_A can induce tumor cell autophagic, cell-programmed death, as well as activate the effector T cells. Combined, in this paper, with the absorption exceeding the Carbon NanoTube (CNT) band-gap (?bg=~1/CNT diameter) with an active short wave near-infrared (SWIR) (1.2~1.5 micron wavelengths), which happened to be translucent to the irradiation upon animal skin, similar to that used in hospital fingertip-clamped Pulse Oxymetry. Once the Con_ACNT is guided to hepatoma cells, it is bonded and internalized into the mitochondria (MC) compartment, the cellular energy factory. Con_A has the higher specificity for tumor cells useful for targeting because of the abnormal glycosylation on tumor cells. When CNT hitch hike with Con_A, they can t together like a laser-denotable chemical missile surgically targeting at the tumor cells precisely by Con_A-guidance. We switch on SWIR laser, when the Con_A-CNT conjugated complex has been bonded and internalized to MC of malign cells and already commenced cellular programmed death. Thus, it might appear to casual readers that we have initiated an overkill, chemical drugged autophage followed with physical laser ablation, but what if we can eradicate hepatoma totally if no blue print is left behind inadvertently in case of a partial failure. We conclude that using Con_A-CNT conjugated complex targeting specifically at malign tumor cells is a novel targeted-laser-radiation therapy for tumors in mice.

  18. Growth of InAs/GaSb short-period superlattices for high-resolution mid-wavelength infrared focal plane array detectors

    NASA Astrophysics Data System (ADS)

    Walther, M.; Schmitz, J.; Rehm, R.; Kopta, S.; Fuchs, F.; Fleißner, J.; Cabanski, W.; Ziegler, J.

    2005-05-01

    InAs/GaSb short-period superlattices (SLs) with a broken gap type-II band alignment are investigated for the fabrication of photovoltaic pin-photodetectors on GaSb substrates. The structures were grown by molecular beam epitaxy using valved cracker cells for arsenic and antimony. Effective bandgap and strain in the SL were adjusted by varying the thickness of the InAs and GaSb layers in the SL and the controlled formation of InSb-like or GaAs-like bonds at the interfaces. MBE growth conditions were investigated and optimized in order to achieve good morphological, electrical and optical properties. IR-photodiodes with a cut-off wavelength of 5.4 μm reveal quantum efficiencies around 30% and detectivity values exceeding 10 13 Jones at 77 K. A focal plane array camera with 256×256 detector elements and 40 μm pitch based on InAs/GaSb short-period SLs was fabricated for the first time. The camera system reveals an excellent thermal resolution with a noise equivalent temperature difference below 12 mK for an integration time of 5 ms using f/2 optics. The detector performance, comparable with state of the art mercury-cadmium-telluride IR detectors, makes this material system very interesting for the fabrication of advanced thermal imaging systems.

  19. Tumor selective hyperthermia induced by short-wave capacitively-coupled RF electric-fields.

    PubMed

    Raoof, Mustafa; Cisneros, Brandon T; Corr, Stuart J; Palalon, Flavio; Curley, Steven A; Koshkina, Nadezhda V

    2013-01-01

    There is a renewed interest in developing high-intensity short wave capacitively-coupled radiofrequency (RF) electric-fields for nanoparticle-mediated tumor-targeted hyperthermia. However, the direct thermal effects of such high-intensity electric-fields (13.56 MHZ, 600 W) on normal and tumor tissues are not completely understood. In this study, we investigate the heating behavior and dielectric properties of normal mouse tissues and orthotopically-implanted human hepatocellular and pancreatic carcinoma xenografts. We note tumor-selective hyperthermia (relative to normal mouse tissues) in implanted xenografts that can be explained on the basis of differential dielectric properties. Furthermore, we demonstrate that repeated RF exposure of tumor-bearing mice can result in significant anti-tumor effects compared to control groups without detectable harm to normal mouse tissues. PMID:23861912

  20. Tumor Selective Hyperthermia Induced by Short-Wave Capacitively-Coupled RF Electric-Fields

    PubMed Central

    Raoof, Mustafa; Cisneros, Brandon T.; Corr, Stuart J.; Palalon, Flavio; Curley, Steven A.; Koshkina, Nadezhda V.

    2013-01-01

    There is a renewed interest in developing high-intensity short wave capacitively-coupled radiofrequency (RF) electric-fields for nanoparticle-mediated tumor-targeted hyperthermia. However, the direct thermal effects of such high-intensity electric-fields (13.56 MHZ, 600 W) on normal and tumor tissues are not completely understood. In this study, we investigate the heating behavior and dielectric properties of normal mouse tissues and orthotopically-implanted human hepatocellular and pancreatic carcinoma xenografts. We note tumor-selective hyperthermia (relative to normal mouse tissues) in implanted xenografts that can be explained on the basis of differential dielectric properties. Furthermore, we demonstrate that repeated RF exposure of tumor-bearing mice can result in significant anti-tumor effects compared to control groups without detectable harm to normal mouse tissues. PMID:23861912

  1. Monte Carlo simulation of wave sensing with a short pulse radar

    NASA Technical Reports Server (NTRS)

    Levine, D. M.; Davisson, L. D.; Kutz, R. L.

    1977-01-01

    A Monte Carlo simulation is used to study the ocean wave sensing potential of a radar which scatters short pulses at small off-nadir angles. In the simulation, realizations of a random surface are created commensurate with an assigned probability density and power spectrum. Then the signal scattered back to the radar is computed for each realization using a physical optics analysis which takes wavefront curvature and finite radar-to-surface distance into account. In the case of a Pierson-Moskowitz spectrum and a normally distributed surface, reasonable assumptions for a fully developed sea, it has been found that the cumulative distribution of time intervals between peaks in the scattered power provides a measure of surface roughness. This observation is supported by experiments.

  2. Short pulse radar used to measure sea surface wind speed and SWH. [Significant Wave Height

    NASA Technical Reports Server (NTRS)

    Hammond, D. L.; Mennella, R. A.; Walsh, E. J.

    1977-01-01

    A joint airborne measurement program is being pursued by NRL and NASA Wallops Flight Center to determine the extent to which wind speed and sea surface significant wave height (SWH) can be measured quantitatively and remotely with a short pulse (2 ns), wide-beam (60 deg), nadir-looking 3-cm radar. The concept involves relative power measurements only and does not need a scanning antenna, Doppler filters, or absolute power calibration. The slopes of the leading and trailing edges of the averaged received power for the pulse limited altimeter are used to infer SWH and surface wind speed. The interpretation is based on theoretical models of the effects of SWH on the leading edge shape and rms sea-surface slope on the trailing-edge shape. The models include the radar system parameters of antenna beam width and pulsewidth.

  3. Multi-instrument gravity-wave measurements over Tierra del Fuego and the Drake Passage - Part 1: Potential energies and vertical wavelengths from AIRS, COSMIC, HIRDLS, MLS-Aura, SAAMER, SABER and radiosondes

    NASA Astrophysics Data System (ADS)

    Wright, Corwin J.; Hindley, Neil P.; Moss, Andrew C.; Mitchell, Nicholas J.

    2016-03-01

    Gravity waves in the terrestrial atmosphere are a vital geophysical process, acting to transport energy and momentum on a wide range of scales and to couple the various atmospheric layers. Despite the importance of these waves, the many studies to date have often exhibited very dissimilar results, and it remains unclear whether these differences are primarily instrumental or methodological. Here, we address this problem by comparing observations made by a diverse range of the most widely used gravity-wave-resolving instruments in a common geographic region around the southern Andes and Drake Passage, an area known to exhibit strong wave activity. Specifically, we use data from three limb-sounding radiometers (Microwave Limb Sounder, MLS-Aura; HIgh Resolution Dynamics Limb Sounder, HIRDLS; Sounding of the Atmosphere using Broadband Emission Radiometry, SABER), the Constellation Observing System for Meteorology, Ionosphere and Climate (COSMIC) GPS-RO constellation, a ground-based meteor radar, the Advanced Infrared Sounder (AIRS) infrared nadir sounder and radiosondes to examine the gravity wave potential energy (GWPE) and vertical wavelengths (λz) of individual gravity-wave packets from the lower troposphere to the edge of the lower thermosphere ( ˜ 100 km). Our results show important similarities and differences. Limb sounder measurements show high intercorrelation, typically > 0.80 between any instrument pair. Meteor radar observations agree in form with the limb sounders, despite vast technical differences. AIRS and radiosonde observations tend to be uncorrelated or anticorrelated with the other data sets, suggesting very different behaviour of the wave field in the different spectral regimes accessed by each instrument. Evidence of wave dissipation is seen, and varies strongly with season. Observed GWPE for individual wave packets exhibits a log-normal distribution, with short-timescale intermittency dominating over a well-repeated monthly-median seasonal cycle. GWPE and λz exhibit strong correlations with the stratospheric winds, but not with local surface winds. Our results provide guidance for interpretation and intercomparison of such data sets in their full context.

  4. Resonant excitation of coupled Rayleigh waves in a short and narrow fluid channel clad between two identical metal plates

    DOE PAGESBeta

    García-Chocano, Victor M.; López-Rios, Tomás; Krokhin, Arkadii; Sanchez-Dehesa, Jose

    2011-12-23

    Transmission of ultrasonic waves through a slit between two water immersed brass plates is studied for sub-wavelength plate thicknesses and slit apertures. Extraordinary high absorption is observed at discrete frequencies corresponding to resonant excitation of Rayleigh waves on the both sides of the channel. The coupling of the Rayleigh waves occurs through the fluid and the corresponding contribution to the dispersion has been theoretically derived and also experimentally confirmed. Symmetric and anti-symmetric modes are predicted but only the symmetric mode resonances have been observed. It follows from the dispersion equation that the coupled Rayleigh waves cannot be excited in amore » channel with apertures less than the critical one. The calculated critical aperture is in a good agreement with the measured acoustic spectra. These findings could be applied to design a broadband absorptive metamaterial.« less

  5. Resonant excitation of coupled Rayleigh waves in a short and narrow fluid channel clad between two identical metal plates

    SciTech Connect

    García-Chocano, Victor M.; López-Rios, Tomás; Krokhin, Arkadii; Sanchez-Dehesa, Jose

    2011-12-23

    Transmission of ultrasonic waves through a slit between two water immersed brass plates is studied for sub-wavelength plate thicknesses and slit apertures. Extraordinary high absorption is observed at discrete frequencies corresponding to resonant excitation of Rayleigh waves on the both sides of the channel. The coupling of the Rayleigh waves occurs through the fluid and the corresponding contribution to the dispersion has been theoretically derived and also experimentally confirmed. Symmetric and anti-symmetric modes are predicted but only the symmetric mode resonances have been observed. It follows from the dispersion equation that the coupled Rayleigh waves cannot be excited in a channel with apertures less than the critical one. The calculated critical aperture is in a good agreement with the measured acoustic spectra. These findings could be applied to design a broadband absorptive metamaterial.

  6. Statistical characterization of short wind-waves from stereo images of the sea surface

    NASA Astrophysics Data System (ADS)

    Mironov, A.; Hauser, D.; Kosnik, M.; Dulov, V.; Guerin, C. A.

    2012-04-01

    Today, direct in situ measurement of the topography of the sea surface is still a challenging issue. Spatial properties of the sea surface are routinely characterized by indirect measurements such as radar or optical remote sensing, time series at a fixed location (gauge, buoys, laser) or controlled tank experiments. These techniques, however, suffer from known shortcomings and limitations. With the ever increasing accuracy of satellite microwave radar sensors for geophysical purpose and the progress of the electromagnetic wave interaction models, there is a need for direct measurements of short waves in natural conditions. In this respect, the technique of stereo image reconstruction is very promising. It has been recently employed in the context of ocean waves for the reconstruction of the topography and estimation of the elevation spectrum. However, the processing of these data raises technical issues when it comes to the estimation of their key statistical parameters. In this work we propose a methodology to extract spatial statistical characteristics of the sea surface topography by means of stereo image reconstruction. We discuss the possibilities and limitations of this technique and validate the results of data set acquired from an oceanographic platform at the Black Sea with simultaneous in situ measurements as well as results from the literature. In spite of the limited resolution and restricted field of view of the images, we show that the following quantities can be well estimated: the probability distribution and spectrum of small-scale elevations, the variance and kurtosis of total and filtered slopes and the so-called skewness function of small-scale elevations. This last quantity is less conventional but is of primary importance in analytical scattering models from the sea surface.

  7. Coincidence Searches of Gravitational Waves and Short Gamma-Ray Bursts

    NASA Astrophysics Data System (ADS)

    Maselli, Andrea; Ferrari, Valeria

    Black-hole neutron-star coalescing binaries have been invoked as one of the most suitable scenario to explain the emission of short gamma-ray bursts. Indeed, if the black-hole which forms after the merger, is surrounded by a massive disk, neutrino annihilation processes may produce high-energy and collimated electromagnetic radiation. In this paper, we devise a new procedure, to be used in the search for gravitational waves from black-hole-neutron-star binaries, to assign a probability that a detected gravitational signal is associated to the formation of an accreting disk, massive enough to power gamma-ray bursts. This method is based on two recently proposed semi-analytic fits, one reproducing the mass of the remnant disk surrounding the black hole as a function of some binary parameters, the second relating the neutron star compactness, with its tidal deformability. Our approach can be used in low-latency data analysis to restrict the parameter space searching for gravitational signals associated with short gamma-ray bursts, and to gain information on the dynamics of the coalescing system and on the neutron star equation of state.

  8. Geoacoustic inversion of short range source data using a plane wave reflection coefficient approach.

    PubMed

    Stotts, S A; Knobles, D P; Keller, J A; Piper, J N; Thompson, L A

    2006-12-01

    Acoustic time series data were collected in a shallow, hard bottom lake environment located in central Texas using both short range (2 m) implosive data, obtained with the source and a single hydrophone located near mid-depth in the waveguide, along with longer range implosive and explosive data from a near surface source to a bottom mounted hydrophone. Matched field inversions using simulated annealing were performed with a ray trace plus complex plane wave reflection coefficient forward propagation model that was validated in previous work. Isolating bottom interacting paths to perform the inversions is shown to be essential to reduce parameter uncertainties in the hard bottom environment and enables a systematic approach to the inversions which establishes the number of layers needed to represent the lake environment. Measured transmission loss data from a towed source were compared through a RMS error analysis to modeled transmission loss, constructed with the parameters from inversions of data from several source types, to further establish the validity of the inversion approach for this environment. Geoacoustic parameters obtained by inversions of short range, low frequency impulsive data are used to predict transmission loss at longer ranges and higher frequencies. The range dependence of the global minimum is discussed. PMID:17225390

  9. Improved multiple-wavelength Brillouin-Raman fiber laser assisted by four-wave mixing with a micro-air cavity.

    PubMed

    Li, Xuejiao; Ren, Liyong; Lin, Xiao; Ju, Haijuan; Chen, Nana; Liang, Jian; Ren, Kaili; Xu, Yiping

    2015-11-20

    In this paper, a multiple-wavelength Brillouin-Raman fiber laser (MBRFL) with enhanced performance is presented. This is attributed to the improved Fresnel reflection, thus strengthening four-wave mixing in the fiber laser cavity due to the insertion of a micro-air cavity. As a result, compared with the conventional MBRFL without a micro-air cavity, the thresholds of Brillouin Stokes (BS) lines are observed to be reduced, and more BS lines can be generated. In the experiment, a MBRFL having 40 BS lines is achieved with good stability on laser wavelengths and output power. In view of the fact that more BS lines can be established with a simple scheme and low pump power, our MBRFL promises to be employed as a multiwavelength source for optical communication. PMID:26836558

  10. Determination of Seed Soundness in Conifers Cryptomeria japonica and Chamaecyparis obtusa Using Narrow-Multiband Spectral Imaging in the Short-Wavelength Infrared Range.

    PubMed

    Matsuda, Osamu; Hara, Masashi; Tobita, Hiroyuki; Yazaki, Kenichi; Nakagawa, Toshinori; Shimizu, Kuniyoshi; Uemura, Akira; Utsugi, Hajime

    2015-01-01

    Regeneration of planted forests of Cryptomeria japonica (sugi) and Chamaecyparis obtuse (hinoki) is the pressing importance to the forest administration in Japan. Low seed germination rate of these species, however, has hampered low-cost production of their seedlings for reforestation. The primary cause of the low germinability has been attributed to highly frequent formation of anatomically unsound seeds, which are indistinguishable from sound germinable seeds by visible observation and other common criteria such as size and weight. To establish a method for sound seed selection in these species, hyperspectral imaging technique was used to identify a wavelength range where reflectance spectra differ clearly between sound and unsound seeds. In sound seeds of both species, reflectance in a narrow waveband centered at 1,730 nm, corresponding to a lipid absorption band in the short-wavelength infrared (SWIR) range, was greatly depressed relative to that in adjacent wavebands on either side. Such depression was absent or less prominent in unsound seeds. Based on these observations, a reflectance index SQI, abbreviated for seed quality index, was formulated using reflectance at three narrow SWIR wavebands so that it represents the extent of the depression. SQI calculated from seed area-averaged reflectance spectra and spatial distribution patterns of pixelwise SQI within each seed area were both proven as reliable criteria for sound seed selection. Enrichment of sound seeds was accompanied by an increase in germination rate of the seed lot. Thus, the methods described are readily applicable toward low-cost seedling production in combination with single seed sowing technology. PMID:26083366

  11. Determination of Seed Soundness in Conifers Cryptomeria japonica and Chamaecyparis obtusa Using Narrow-Multiband Spectral Imaging in the Short-Wavelength Infrared Range

    PubMed Central

    Matsuda, Osamu; Hara, Masashi; Tobita, Hiroyuki; Yazaki, Kenichi; Nakagawa, Toshinori; Shimizu, Kuniyoshi; Uemura, Akira; Utsugi, Hajime

    2015-01-01

    Regeneration of planted forests of Cryptomeria japonica (sugi) and Chamaecyparis obtuse (hinoki) is the pressing importance to the forest administration in Japan. Low seed germination rate of these species, however, has hampered low-cost production of their seedlings for reforestation. The primary cause of the low germinability has been attributed to highly frequent formation of anatomically unsound seeds, which are indistinguishable from sound germinable seeds by visible observation and other common criteria such as size and weight. To establish a method for sound seed selection in these species, hyperspectral imaging technique was used to identify a wavelength range where reflectance spectra differ clearly between sound and unsound seeds. In sound seeds of both species, reflectance in a narrow waveband centered at 1,730 nm, corresponding to a lipid absorption band in the short-wavelength infrared (SWIR) range, was greatly depressed relative to that in adjacent wavebands on either side. Such depression was absent or less prominent in unsound seeds. Based on these observations, a reflectance index SQI, abbreviated for seed quality index, was formulated using reflectance at three narrow SWIR wavebands so that it represents the extent of the depression. SQI calculated from seed area-averaged reflectance spectra and spatial distribution patterns of pixelwise SQI within each seed area were both proven as reliable criteria for sound seed selection. Enrichment of sound seeds was accompanied by an increase in germination rate of the seed lot. Thus, the methods described are readily applicable toward low-cost seedling production in combination with single seed sowing technology. PMID:26083366

  12. Gravitational wave signal of the short rise fling of galactic runaway pulsars

    SciTech Connect

    Mosquera Cuesta, Herman J; Bonilla Quintero, Carlos A E-mail: gravitaxion@gmail.com

    2008-11-15

    Determination of pulsar parallaxes and proper motions addresses fundamental astrophysical open issues. Here, after scrutinizing the ATNF Catalog searching for pulsar distances and proper motions, we verify that for an ATNF sample of 212 galactic runaway pulsars (RAPs), which currently run across the Galaxy at very high speed and undergo large displacements, some gravitational wave (GW) signals produced by such present accelerations appear to be detectable after calibration against the Advanced LIGO (LIGO II). Motivated by this insight, we address the issue of the pulsar kick at birth, or the short rise fling from a supernova explosion, by adapting the theory for emission of GW by ultrarelativistic sources in this case in which the Lorentz factor is {gamma}{approx}1. We show that during the short rise fling each runaway pulsar (RAP) generates a GW signal with characteristic amplitude and frequency that makes it detectable by current GW interferometers. For a realistic analysis, an efficiency parameter is introduced to quantify the expenditure of the rise fling kinetic energy, which is estimated from the linear momentum conservation law applied to the supernova explosion that kicks out the pulsar. The remaining energy is supposed to be used to make the star spin. Thus, a comparison with the spin of ATNF pulsars having velocities in the range 400-500 km s{sup -1} is performed. The resulting difference suggests that other mechanisms (like differential rotation, magnetic breaking or magneto-rotational instability) should dissipate part of that energy to produce the observed pulsar spin periods. Meanwhile, the kick phenomenon may also occur in globular and open star clusters at the formation or disruption of very short period compact binary systems wherein abrupt velocity and acceleration similar to those given to RAPs during the short rise fling can be imparted to each orbital partner. To better analyze these cases, pulsar astrometry from micro-to nano-arcsec scales might be of great help. In the case of a supernova, the RAP GW signal could be a benchmark for the GW signal from the core collapse.

  13. Gravitational wave signal of the short rise fling of galactic runaway pulsars

    NASA Astrophysics Data System (ADS)

    Mosquera Cuesta, Herman J.; Bonilla Quintero, Carlos A.

    2008-11-01

    Determination of pulsar parallaxes and proper motions addresses fundamental astrophysical open issues. Here, after scrutinizing the ATNF Catalog searching for pulsar distances and proper motions, we verify that for an ATNF sample of 212 galactic runaway pulsars (RAPs), which currently run across the Galaxy at very high speed and undergo large displacements, some gravitational wave (GW) signals produced by such present accelerations appear to be detectable after calibration against the Advanced LIGO (LIGO II). Motivated by this insight, we address the issue of the pulsar kick at birth, or the short rise fling from a supernova explosion, by adapting the theory for emission of GW by ultrarelativistic sources in this case in which the Lorentz factor is γ~1. We show that during the short rise fling each runaway pulsar (RAP) generates a GW signal with characteristic amplitude and frequency that makes it detectable by current GW interferometers. For a realistic analysis, an efficiency parameter is introduced to quantify the expenditure of the rise fling kinetic energy, which is estimated from the linear momentum conservation law applied to the supernova explosion that kicks out the pulsar. The remaining energy is supposed to be used to make the star spin. Thus, a comparison with the spin of ATNF pulsars having velocities in the range 400-500 km s-1 is performed. The resulting difference suggests that other mechanisms (like differential rotation, magnetic breaking or magneto-rotational instability) should dissipate part of that energy to produce the observed pulsar spin periods. Meanwhile, the kick phenomenon may also occur in globular and open star clusters at the formation or disruption of very short period compact binary systems wherein abrupt velocity and acceleration similar to those given to RAPs during the short rise fling can be imparted to each orbital partner. To better analyze these cases, pulsar astrometry from micro-to nano-arcsec scales might be of great help. In the case of a supernova, the RAP GW signal could be a benchmark for the GW signal from the core collapse.

  14. Comparison of photonic integrated circuits for millimeter-wave signal generation between dual-wavelength sources for optical heterodyning and pulsed mode-locked lasers

    NASA Astrophysics Data System (ADS)

    Carpintero, Guillermo; Gordon, Carlos; Guzman, Robinson; Leijtens, Xaveer; Van Dijk, Frédéric; Kervella, Gaël.; Fice, Martyn J.; Balakier, Katarzyna; Renaud, Cyril C.

    2015-03-01

    A comparative study of two different Photonic Integrated Circuits (PICs) structures for continuous-wave generation of millimeter-wave (MMW) signals is presented, each using a different approach. One approach is optical heterodyning, using an integrated dual-wavelength laser source based on Arrayed Waveguide Grating. The other is based on ModeLocked Laser Diodes (MLLDs). A novel building block -Multimode Interference Reflectors (MIRs) - is used to integrate on-chip both structures, without need of cleaved facets to define the laser cavity. This fact enables us to locate any of these structures at any location within the photonic chip. As will be shown, the MLLD structure provides a simple source for low frequencies. Higher frequencies are easier to achieve by optical heterodyne. Both types of structures have been fabricated on a generic foundry in a commercial MPW PIC technology.

  15. High-power diode-pumped continuous-wave Nd(3+) lasers at wavelengths near 1.44 microm.

    PubMed

    Kretschmann, H M; Heine, F; Ostroumov, V G; Huber, G

    1997-04-01

    We demonstrate longitudinally diode-pumped operation of Nd:YAG and Nd:YAP lasers at the long-wavelength end of the (4)F(3/2) ? (4)I(13/2) transition in the eye-safe spectral region at 1444 and 1430 nm, respectively. Special crystal coatings were required for achievement of lasing at these wavelengths. Output powers of up to 4.9 and 2.2 W, with slope efficiencies of up to 22% and 8%, respectively, were achieved. Polarized operation of the Nd:YAG laser yielded output powers of 76% as compared with unpolarized operation. Because of thermal stress, both YAG and YAP crystals were fractured at roughly 25 W of absorbed longitudinal pump power. PMID:18183236

  16. Shallow structure of part of northwestern Iberia from short-period Rayleigh-wave observations

    NASA Astrophysics Data System (ADS)

    Sarrate, J.; Canas, J. A.; Pujades, L.; Badal, J.; Corchete, V.; Payo, G.

    1993-04-01

    Propagation of 0.2-2.5 s short-period Rayleigh-waves across a part of northwestern Iberia is investigated. Analysis of a seismic profile line with recorded seismograms up to distances of 70 km from the shot-point, provides group-velocities and attenuation coefficients of the fundamental mode. First higher-mode group-velocity has been obtained for only one of the studied cases. The studied region has been divided into two subrogions, the northwestern and the southeastern side from the shot-point. Inversion procedures applied to the velocity and attenuation data yield the shear velocity and the Q-1β models up to a depth of about 1.5 km for the NW, and 2.4 for the SE side. From the shear-wave obtained models corresponding to the NW and to the SE sides, it is possible to infer the existence of some degree of lateral variation of S velocity. The NW side presents velocities varying between 1.8 km · s -1 (at the surface) and 3.3 km · s -1 (at 1.2 km depth). The velocities in the SE model, for the same depths, are 2.2 and 3.4 km · s -1, respectively. Using only the fist six traces of the SE side, it is possible to infer a low-velocity region located between 0.4 km and 0.7 km depth. It seems that the velocities are higher in the complex geological region of the SE side than in the NW one, which is in agreement with P velocity models found by others. From the tentative anelastic attenuation coefficients, Q-1β models have been inferred for both sides of the seismic refraction profile. Although the obtained Q-1β models are somehow different in shape, the maximum Q-1β value is about 0.05 in both cases.

  17. FUNDAMENTAL AREAS OF PHENOMENOLOGY (INCLUDING APPLICATIONS): Thermal Analysis of InAs/AlSb Short Wavelength Mid-IR Quantum Cascade Lasers

    NASA Astrophysics Data System (ADS)

    Wei, Lin; Li, Ai-Zhen; Xu, Gang-Yi

    2009-06-01

    We present the effects of hetero-interfaces and major key parameters on the thermal behaviors and performance of short wavelength mid-IR InAs/AlSb quantum cascade lasers (QCLs). We use a finite element method (FEM) with commercial software, ANSYS, to simulate the heat dissipation in QCLs in cw operation mode with an epilayer-down mounting package. The thermal performance is characterized by the temperature increase ΔT (self-heating effect) between the active region of QCLs and the heatsink. Results show that (1) the self-heating effects of InAs/AlSb QCLs are much less than those in AlInAs/GaInAs QCLs, (2) narrower ridges lead to significantly cooler active regions of InAs/AlSb QCLs due to poor heat transport in the cross-plane direction (across interfaces) and that most of the heat flows out of the active region in the lateral direction, and (3) the cavity length of the laser has little influence on the self-heating effect of the device, but the long cavity reduces mirror loss and threshold current density.

  18. High Harmonic Fast Wave Heating Efficiency Enhancemen and Current Drive at Longer Wavelength on the National Spherical Torus Experiment

    SciTech Connect

    J. Hosea, R. E. Bell, B.P. LeBlanc, C.K. Phillips, G. Taylor, E. Valeo, J.R. Wilson, E.F. Jaeger, P.M. Ryan, J. Wilgen, H. Yuh, F. Levinton, S. Sabbagh, K. Tritz, J. Parker, P.T. Bonoli, R. Harvey, and the NSTX Team

    2008-01-14

    High harmonic fast wave heating and current drive (CD) are being developed on the National Spherical Torus Experiment (NSTX) [M. Ono et al., Nucl. Fusion 41, 1435 (2001)] for supporting startup and sustainment of the ST plasma. Considerable enhancement of the core heating efficiency (η) from 44% to 65% has been obtained for CD phasing of the antenna (strap-to-strap φ = -90o, kφ = -8 m-1) by increasing the magnetic field from 4.5 kG to 5.5 kG. This increase in efficiency is strongly correlated to moving the location of the onset density for perpendicular fast wave propagation (nonset ∝ ΒΦ× k|| 2/w) away from the antenna face and wall, and hence reducing the propagating surface wave fields. RF waves propagating close to the wall at lower BΦ and k|| can enhance power losses from both the parametric decay instability (PDI) and wave dissipation in sheaths and structures around the machine. The improved efficiency found here is attributed to a reduction in the latter, as PDI losses are little changed at the higher magnetic field. Under these conditions of higher coupling efficiency, initial measurements of localized CD effects have been made and compared with advanced RF code simulations

  19. High Harmonic Fast Wave Heating Efficiency Enhancement and Current Drive at Longer Wavelength on the National Spherical Torus Experiment

    SciTech Connect

    Hosea, J.; Bell, R. E.; LeBlanc, B; Phillips, Cynthia; Taylor, G.; Valeo, Dr Ernest; Wilson, J. R.; Jaeger, Erwin Frederick; Ryan, Philip Michael; Wilgen, John B; Yuh, H.; Levinton, F.; Sabbagh, S. A.; Tritz, K.; Parker, J.; Bonoli, P.; Harvey, R. W.

    2008-01-01

    High harmonic fast wave heating and current drive CD are being developed on the National Spherical Torus Experiment M. Ono et al., Nucl. Fusion 41, 1435 2001 for supporting startup and sustainment of the spherical torus plasma. Considerable enhancement of the core heating efficiency from 44% to 65% has been obtained for CD phasing of the antenna strap-to-strap = 90 , k= 8 m 1 by increasing the magnetic field from 4.5 to 5.5 kG. This increase in efficiency is strongly correlated to moving the location of the onset density for perpendicular fast wave propagation nonsetBk 2 / away from the antenna face and wall, and hence reducing the propagating surface wave fields. Radio frequency RF waves propagating close to the wall at lower B and k can enhance power losses from both the parametric decay instability PDI and wave dissipation in sheaths and structures around the machine. The improved efficiency found here is attributed to a reduction in the latter, as PDI losses are little changed at the higher magnetic field. Under these conditions of higher coupling efficiency, initial measurements of localized CD effects have been made and compared with advanced RF code simulations.

  20. High harmonic fast wave heating efficiency enhancement and current drive at longer wavelength on the National Spherical Torus Experiment

    SciTech Connect

    Hosea, J.; Bell, R. E.; LeBlanc, B. P.; Phillips, C. K.; Taylor, G.; Valeo, E.; Wilson, J. R.; Jaeger, E. F.; Ryan, P. M.; Wilgen, J.; Yuh, H.; Levinton, F.; Sabbagh, S.; Tritz, K.; Parker, J.; Bonoli, P. T.; Harvey, R.

    2008-05-15

    High harmonic fast wave heating and current drive (CD) are being developed on the National Spherical Torus Experiment [M. Ono et al., Nucl. Fusion 41, 1435 (2001)] for supporting startup and sustainment of the spherical torus plasma. Considerable enhancement of the core heating efficiency ({eta}) from 44% to 65% has been obtained for CD phasing of the antenna (strap-to-strap {phi}=-90 deg., k{sub {phi}}=-8 m{sup -1}) by increasing the magnetic field from 4.5 to 5.5 kG. This increase in efficiency is strongly correlated to moving the location of the onset density for perpendicular fast wave propagation (n{sub onset}{proportional_to}Bxk{sub parallel}{sup 2}/{omega}) away from the antenna face and wall, and hence reducing the propagating surface wave fields. Radio frequency (RF) waves propagating close to the wall at lower B and k{sub parallel} can enhance power losses from both the parametric decay instability (PDI) and wave dissipation in sheaths and structures around the machine. The improved efficiency found here is attributed to a reduction in the latter, as PDI losses are little changed at the higher magnetic field. Under these conditions of higher coupling efficiency, initial measurements of localized CD effects have been made and compared with advanced RF code simulations.

  1. Emerging liquid crystal waveguide technology for low SWaP active short-wave infrared imagers

    NASA Astrophysics Data System (ADS)

    Keller, Sean D.; Uyeno, Gerald P.; Lynch, Ted; Davis, Scott R.; Rommel, Scott D.; Pino, Juan

    2015-03-01

    Raytheon's innovative active short wave infrared (SWIR) imager uses Vescent Photonic's emerging liquid crystal waveguide (LCWG) technology to continuously steer the illumination laser beam over the imager field of view (FOV). This approach instantly illuminates a very small fraction of the FOV, which significantly reduces the laser power compared to flash illumination. This reduced laser power directly leads to a reduction in the size, weight and power (SWaP) of the laser. The reduction in laser power reduces the input power and thermal rejection, which leads to additional reduction in the SWaP of the power supplies and thermal control. The high-speed steering capability of the LCWG enables the imager's SWaP reduction. The SWaP reduction is possible using either global or rolling shutter detectors. In both cases, the LCWG steers the laser beam over the entire FOV while the detector is integrating. For a rolling shutter detector, the LCWG synchronizes the steering with the rolling shutter to illuminate only regions currently integrating. Raytheon's approach enables low SWaP active SWIR imagers without compromising image quality. This paper presents the results of Raytheon's active SWIR imager demonstration including steering control and synchronization with the detector integration.

  2. Short-wave infrared reflectance investigation of sites of paleobiological interest: applications for Mars exploration.

    PubMed

    Brown, Adrian; Walter, Malcolm; Cudahy, Thomas

    2004-01-01

    Rover missions to the rocky bodies of the Solar System and especially to Mars require lightweight, portable instruments that use minimal power, require no sample preparation, and provide suitably diagnostic mineralogical information to an Earth-based exploration team. Short-wave infrared (SWIR) spectroscopic instruments such as the Portable Infrared Mineral Analyser (PIMA, Integrated Spectronics Pty Ltd., Baulkham Hills, NSW, Australia) fulfill all these requirements. We describe an investigation of a possible Mars analogue site using a PIMA instrument. A survey was carried out on the Strelley Pool Chert, an outcrop of stromatolitic, silicified Archean carbonate and clastic succession in the Pilbara Craton, interpreted as being modified by hydrothermal processes. The results of this study demonstrate the capability of SWIR techniques to add significantly to the geological interpretation of such hydrothermally altered outcrops. Minerals identified include dolomite, white micas such as illite-muscovite, and chlorite. In addition, the detection of pyrophyllite in a bleached and altered unit directly beneath the succession suggests acidic, sulfur-rich hydrothermal activity may have interacted with the silicified sediments of the Strelley Pool Chert. PMID:15383240

  3. Prospects for Joint Gravitational Wave and Short Gamma-Ray Burst Observations

    NASA Astrophysics Data System (ADS)

    Clark, J.; Evans, H.; Fairhurst, S.; Harry, I. W.; Macdonald, E.; Macleod, D.; Sutton, P. J.; Williamson, A. R.

    2015-08-01

    We present a detailed evaluation of the expected rate of joint gravitational-wave (GW) and short gamma-ray burst (GRB) observations over the coming years. We begin by evaluating the improvement in distance sensitivity of the GW search that arises from using the GRB observation to restrict the time and sky location of the source. We argue that this gives a 25% increase in sensitivity when compared to an all-sky, all-time search, corresponding to more than double the number of detectable GW signals associated with GRBs. Using this, we present the expected rate of joint observations with the advanced LIGO and Virgo instruments, taking into account the expected evolution of the GW detector network. We show that in the early advanced GW detector observing runs, from 2015 to 2017, there is only a small chance of a joint observation. However, as the detectors approach their design sensitivities, there is a good chance of joint observations, provided wide field GRB satellites, such as Fermi and the Inter planetary Network, continue operation. The rate will also depend critically upon the nature of the progenitor, with neutron star-black hole systems observable to greater distances than double neutron star systems. The relative rate of binary mergers and GRBs will depend upon the jet opening angle of GRBs. Consequently, joint observations, as well as accurate measurement of both the GRB rate and binary merger rates, will allow for an improved estimation of the opening angle of GRBs.

  4. Short-Wave Infrared Reflectance Investigation of Sites of Paleobiological Interest: Applications for Mars Exploration

    NASA Astrophysics Data System (ADS)

    Brown, Adrian; Walter, Malcolm; Cudahy, Thomas

    2004-09-01

    Rover missions to the rocky bodies of the Solar System and especially to Mars require lightweight, portable instruments that use minimal power, require no sample preparation, and provide suitably diagnostic mineralogical information to an Earth-based exploration team. Short-wave infrared (SWIR) spectroscopic instruments such as the Portable Infrared Mineral Analyser (PIMA, Integrated Spectronics Pty Ltd., Baulkham Hills, NSW, Australia) fulfill all these requirements. We describe an investigation of a possible Mars analogue site using a PIMA instrument. A survey was carried out on the Strelley Pool Chert, an outcrop of stromatolitic, silicified Archean carbonate and clastic succession in the Pilbara Craton, interpreted as being modified by hydrothermal processes. The results of this study demonstrate the capability of SWIR techniques to add significantly to the geological interpretation of such hydrothermally altered outcrops. Minerals identified include dolomite, white micas such as illite- muscovite, and chlorite. In addition, the detection of pyrophyllite in a bleached and altered unit directly beneath the succession suggests acidic, sulfur-rich hydrothermal activity may have interacted with the silicified sediments of the Strelley Pool Chert.

  5. Outgassing models for Landsat-4 thematic mapper short wave infrared bands

    USGS Publications Warehouse

    Micijevic, E.; Helder, D.L.

    2005-01-01

    Detector responses to the Internal Calibrator (IC) pulses in the Landsat-4 Thematic Mapper (TM) have been observed to follow an oscillatory behavior. This phenomenon is present only in the Short Wave Infrared (SWIR) bands and has been observed throughout the lifetime of the instrument, which was launched in July 1982 and imaged the Earth's surface until late 1993. These periodic changes in amplitude, which can be as large as 7.5 percent, are known as outgassing effects and are believed to be due to optical interference caused by a gradual buildup of an ice-like material on the window of the cryogenically cooled dewar containing the SWIR detectors. Similar outgassing effects in the Landsat-5 TM have been characterized using an optical thin-film model that relates detector behavior to the ice film growth rate, which was found to gradually decrease with time. A similar approach, which takes into consideration the different operational history of the instrument, has been applied in this study to three closely sampled data sets acquired throughout the lifetime of the Landsat-4 TM. Although Landsat-4 and Landsat-5 Thematic Mappers are essentially identical instruments, data generated from analyses of outgassing effects indicate subtle, but important, differences between the two. The estimated lifetime model could improve radiometric accuracy by as much as five percent.

  6. Small craft ID criteria (N50/V50) for short wave infrared sensors in maritime security

    NASA Astrophysics Data System (ADS)

    Krapels, Keith; Driggers, Ronald G.; Larson, Paul; Garcia, Jose; Walden, Barry; Agheera, Sameer; Deaver, Dawne; Hixson, Jonathan; Boettcher, Evelyn

    2008-04-01

    The need for Anti-Terrorism and Force Protection (AT/FP), for both shore and sea platform protection, has resulted in a need for imager design and evaluation tools which can predict field performance against maritime asymmetric threats. In the design of tactical imaging systems for target acquisition, a discrimination criterion is required for successful sensor realization. It characterizes the difficulty of the task being performed by the observer and varies for different target sets. This criterion is used in both assessment of existing infrared sensor and in the design of new conceptual sensors. In this experiment, we collected 8 small craft signatures (military and civilian) in the short wave infrared (SWIR) band during the day. These signatures were processed to determine the targets' characteristic dimension and contrast. They were also processed to bandlimit the signature's spatial information content (simulating longer range) and a perception experiment was performed to determine the task difficulty (N50 and V50). The results are presented in this paper and can be used for maritime security imaging sensor design and evaluation.

  7. Determining the composition of ammonia/water mixtures using short-wave near-infrared spectroscopy.

    PubMed

    Barba, M Isabel; Salavera, Daniel; Larrechi, M Soledad; Coronas, Alberto

    2016-01-15

    This paper proposes a methodology based on short-wave near-infrared spectroscopy to determine the ammonia content of ammonia/water mixtures with ammonia mass fraction in the range 0.35-0.65. Establishing this methodology meant modeling the relationship between the pressure bar (15-25)bar, temperature (20-50)°C and composition of the ammonia-water in the mixture (0.35-0.65 in ammonia mass fraction) with absorbance at 1033nm. The experiments were designed to optimize experimental work. A 2(3) factorial design+3 center points was used to establish and analyze the significance of the variables in the absorbance using analysis of variance (ANOVA). A linear model for absorbance was obtained using the least squares method. The trueness of the results versus the values obtained was assessed using a reference method; density measurement was chosen for this study. The accuracy of the results in terms of root-mean-square deviation (RMSD) was 3.7%. The methodology proposed represents a fast alternative for the "in-situ" measurement of the ammonia composition of ammonia-water mixtures in absorption refrigeration systems. PMID:26592584

  8. Analytical modeling and numerical simulation of the short-wave infrared electron-injection detectors

    NASA Astrophysics Data System (ADS)

    Movassaghi, Yashar; Fathipour, Vala; Fathipour, Morteza; Mohseni, Hooman

    2016-03-01

    This paper describes comprehensive analytical and simulation models for the design and optimization of the electron-injection based detectors. The electron-injection detectors evaluated here operate in the short-wave infrared range and utilize a type-II band alignment in InP/GaAsSb/InGaAs material system. The unique geometry of detectors along with an inherent negative-feedback mechanism in the device allows for achieving high internal avalanche-free amplifications without any excess noise. Physics-based closed-form analytical models are derived for the detector rise time and dark current. Our optical gain model takes into account the drop in the optical gain at high optical power levels. Furthermore, numerical simulation studies of the electrical characteristics of the device show good agreement with our analytical models as well experimental data. Performance comparison between devices with different injector sizes shows that enhancement in the gain and speed is anticipated by reducing the injector size. Sensitivity analysis for the key detector parameters shows the relative importance of each parameter. The results of this study may provide useful information and guidelines for development of future electron-injection based detectors as well as other heterojunction photodetectors.

  9. Study of degenerate four-wave mixing in germanium and rhenate-doped potassium chloride at carbon dioxide laser wavelengths

    SciTech Connect

    Watkins, D.E.

    1982-02-01

    Theoretical and experimental studies of degenerate four-wave mixing (DFWM) by three different mechanisms are presented. These are the nonlinear index of refraction of a lossless, Kerr-like medium, the saturable absorption of a resonant optical transition, and the formation of a free-carrier grating.

  10. Impact of chirp on soliton trapping of dispersive waves in photonic crystal fiber with two zero dispersive wavelengths

    NASA Astrophysics Data System (ADS)

    Yang, Hua; Zeng, Qilin; Hu, Hui; Wang, Boyan; Wang, Weibin

    2014-08-01

    We present a numerical study of soliton trapping of dispersive waves with the effect of chirp during supercontinuum generation in photonic crystal fibers (PCF) pumped with femtosecond pulses in the anomalous dispersion region. For different propagation length along the PCF, we can see that the evolution of pulse can be divided into three stages: initial broadening stage, dramatic broadening stage and saturation broadening stage. We find a fascinating phenomenon that the intensity of blue-shifted dispersive waves (B-DWs) and red-shifted dispersive waves (R-DWs) will be enhanced with positive chirped. It reveals that the coupling between the Raman soliton and the DW under suitable chirp conditions may be a key mechanism in controlling the spectral broadening and soliton trapping of DW. Numerical study shows that initial chirp dramatically influences both the DW generation, spectral recoil and soliton trapping of DW. In order to clearly display the evolution of soliton trapping of DW by chirped pulses, we observed the spectrogram of output pulses using cross-correlation frequency-resolved optical gating technique (XFROG).

  11. Short-ranged and short-lived charge-density-wave order and pseudogap features in underdoped cuprate superconductors

    NASA Astrophysics Data System (ADS)

    Greco, Andrés; Bejas, Matías

    2011-06-01

    The pseudogap phase of high-Tc cuprates is controversially attributed to preformed pairs or to a phase which coexists and competes with superconductivity. One of the challenges is to develop theoretical and experimental studies in order to distinguish between both proposals. Very recently, researchers at Stanford have reported [M. Hashimoto , Nat. Phys.PRLTAO1745-247310.1038/nphys1632 6, 414 (2010); R.-H. He , ScienceSCIEAS0036-807510.1126/science.1198415 331, 1579 (2011)] angle-resolved photoemission spectroscopy experiments on Pb-Bi2201 supporting the point of view that the pseudogap is distinct from superconductivity and associated to a spacial symmetry breaking without long-range order. In this paper, we show that many features reported by these experiments can be described in the framework of the t-J model considering self-energy effects in the proximity to a d charge-density-wave instability.

  12. A 1D model for tides waves and fine sediment in short tidal basins—Application to the Wadden Sea

    NASA Astrophysics Data System (ADS)

    van Prooijen, Bram Christiaan; Wang, Zheng Bing

    2013-12-01

    In order to simulate the dynamics of fine sediments in short tidal basins, like the Wadden Sea basins, a 1D cross-sectional averaged model is constructed to simulate tidal flow, depth-limited waves, and fine sediment transport. The key for this 1D model lies in the definition of the geometry (width and depth as function of the streamwise coordinate). The geometry is computed by implementing the water level and flow data, from a 2D flow simulation, and the hypsometric curve in the continuity equation. By means of a finite volume method, the shallow-water equations and sediment transport equations are solved. The bed shear stress consists of the sum of shear stresses by waves and flow, in which the waves are computed with a depth-limited growth equation for wave height and wave frequency. A new formulation for erosion of fines from a sandy bed is proposed in the transport equation for fine sediment. It is shown by comparison with 2D simulations and field measurements that a 1D schematization gives a proper representation of the dynamics in short tidal basins.

  13. Dependence of the Normalized Radar Cross Section of Water Waves on Bragg Wavelength-Wind Speed Sensitivity

    NASA Technical Reports Server (NTRS)

    Long, David G.; Collyer, R. Scott; Reed, Ryan; Arnold, David V.

    1996-01-01

    Measurements of the normalized radar cross section (sigma(sup o)) made by the YSCAT ultrawideband scatterometer during an extended deployment on the Canada Centre for Inland Waters(CCIW) Research Tower located at Lake Ontario are analyzed and compared with anemometer wind measurements to study the sensitivity of (sigma(sup o)) to the wind speed as a function of the Bragg wavelength. This paper concentrates on upwind and downwind azimuth angles in the wind speed range of 4.5-12 m/s. While YSCAT collected measurements of sigma(sup o) at a variety of frequencies and incidence angles, this paper focuses on frequencies of 2.0, 3.05, 5.30, 10.02, and 14.0 GHz and incidence angles within the Bragg regime, 30-50 deg. Adopting a power law model to describe the relationship between sigma(sup o) and wind speed, both wind speed exponents and upwind/downwind (u/d) ratios of sigma(sup o) are found using least squares linear regression. The analysis of the wind speed exponents and u/d ratios show that shorter Bragg wavelengths (Lambda less than 4 cm) are the most sensitive to wind speed and direction. Additionally, vertical polarization (V-pol) sigma(sup o) is shown to be more sensitive to wind speed than horizontal polarization (H-pol) sigma(sup o), while the H-pol u/d ratio is larger than the V-pol u/d ratio.

  14. Modeling short wave radiation and ground surface temperature: a validation experiment in the Western Alps

    NASA Astrophysics Data System (ADS)

    Pogliotti, P.; Cremonese, E.; Dallamico, M.; Gruber, S.; Migliavacca, M.; Morra di Cella, U.

    2009-12-01

    Permafrost distribution in high-mountain areas is influenced by topography (micro-climate) and high variability of ground covers conditions. Its monitoring is very difficult due to logistical problems like accessibility, costs, weather conditions and reliability of instrumentation. For these reasons physically-based modeling of surface rock/ground temperatures (GST) is fundamental for the study of mountain permafrost dynamics. With this awareness a 1D version of GEOtop model (www.geotop.org) is tested in several high-mountain sites and its accuracy to reproduce GST and incoming short wave radiation (SWin) is evaluated using independent field measurements. In order to describe the influence of topography, both flat and near-vertical sites with different aspects are considered. Since the validation of SWin is difficult on steep rock faces (due to the lack of direct measures) and validation of GST is difficult on flat sites (due to the presence of snow) the two parameters are validated as independent experiments: SWin only on flat morphologies, GST only on the steep ones. The main purpose is to investigate the effect of: (i) distance between driving meteo station location and simulation point location, (ii) cloudiness, (iii) simulation point aspect, (iv) winter/summer period. The temporal duration of model runs is variable from 3 years for the SWin experiment to 8 years for the validation of GST. The model parameterization is constant and tuned for a common massive bedrock of crystalline rock like granite. Ground temperature profile is not initialized because rock temperature is measured at only 10cm depth. A set of 9 performance measures is used for comparing model predictions and observations (including: fractional mean bias (FB), coefficient of residual mass (CMR), mean absolute error (MAE), modelling efficiency (ME), coefficient of determination (R2)). Results are very encouraging. For both experiments the distance (Km) between location of the driving meteo station and location of simulation doesn't play a significant effect (below 230 Km) on ME and R2 values. The incoming short wave radiation on flat sites is very well modeled and only the cloudiness can be a significant source of error in therms of underestimation. Also the GST on steep sites is very well modeled and very good values of both ME and R2 are obtained. MAE values are always quite big (1÷5°C) but the role of fixed parameterization is probably strong is such sense. Over and under-estimations occur during winter and summer respectively and can be an effect of not well modeling of SWin on near-vertical morphologies. In the future the direct validation of SWin on steep sites is needed together with a validation of snow accumulation/melting on flat sites and relative analysis of the effect on ground thermal regime. This require very good precipitation datasets in middle-high-mountain areas.

  15. EXPLORING SHORT GAMMA-RAY BURSTS AS GRAVITATIONAL-WAVE STANDARD SIRENS

    SciTech Connect

    Nissanke, Samaya; Dalal, Neal; Sievers, Jonathan L.; Holz, Daniel E.; Hughes, Scott A.

    2010-12-10

    Recent observations support the hypothesis that a large fraction of 'short-hard' gamma-ray bursts (SHBs) are associated with the inspiral and merger of compact binaries. Since gravitational-wave (GW) measurements of well-localized inspiraling binaries can measure absolute source distances, simultaneous observation of a binary's GWs and SHB would allow us to directly and independently determine both the binary's luminosity distance and its redshift. Such a 'standard siren' (the GW analog of a standard candle) would provide an excellent probe of the nearby (z {approx}< 0.3) universe's expansion, independent of the cosmological distance ladder, thereby complementing other standard candles. Previous work explored this idea using a simplified formalism to study measurement by advanced GW detector networks, incorporating a high signal-to-noise ratio limit to describe the probability distribution for measured parameters. In this paper, we eliminate this simplification, constructing distributions with a Markov Chain Monte Carlo technique. We assume that each SHB observation gives source sky position and time of coalescence, and we take non-spinning binary neutron star and black hole-neutron star coalescences as plausible SHB progenitors. We examine how well parameters (particularly distance) can be measured from GW observations of SHBs by a range of ground-based detector networks. We find that earlier estimates overstate how well distances can be measured, even at fairly large signal-to-noise ratio. The fundamental limitation to determining distance proves to be a degeneracy between distance and source inclination. Overcoming this limitation requires that we either break this degeneracy, or measure enough sources to broadly sample the inclination distribution.

  16. Stabilized platform for tethered balloon soundings of broadband long- and short-wave radiation

    SciTech Connect

    Alzheimer, J.M.; Anderson, G.A.; Whiteman, C.D.

    1993-01-01

    Changes in the composition of trace gases in the earth`s atmosphere have been reported by many observers, and a general concern has been expressed regarding possible changes to the earth`s climate that may be caused by radiatively active gases introduced into the earth`s atmosphere by man`s activities. Radiatively active trace gases produce temperature changes in the earth`s atmosphere through changes in radiative flux divergence. Our knowledge of and means of measuring radiative flux divergence is very limited. A few observations of vertical radiative flux divergences have been reported from aircraft from radiometersondes from towers and from large tethered balloons. These measurement techniques suffers from one or more drawbacks, including shallow sounding depths (towers), high cost (aircraft), complicated logistics (large tethered balloons), and limitation to nighttime hours (radiometersondes). Changes in radiative flux divergence caused by anthropogenic trace gases are expected to be quite small, and will be difficult to measure with existing broadband radiative flux instruments. The emphasis of present research in global climate change is thus being focused on improving radiative transfer algorithms in global climate models. The radiative parameterizations in these models are at an early stage of development and information is needed regarding their performance, especially in cloudy conditions. The impetus for the research reported in this paper is the need for a device that can supplement existing means of measuring vertical profiles of long- and short-wave irradiance and radiative flux divergence. We have designed a small tethered-balloon-based system that can make radiometric soundings through the atmospheric boundary layer. This paper discusses the concept, the design considerations, and the design and construction of this sounding system. The performance of the system will be tested in a series of balloon flights scheduled for the fall and winter of 1992.

  17. Stabilized platform for tethered balloon soundings of broadband long- and short-wave radiation

    SciTech Connect

    Alzheimer, J.M.; Anderson, G.A.; Whiteman, C.D.

    1993-01-01

    Changes in the composition of trace gases in the earth's atmosphere have been reported by many observers, and a general concern has been expressed regarding possible changes to the earth's climate that may be caused by radiatively active gases introduced into the earth's atmosphere by man's activities. Radiatively active trace gases produce temperature changes in the earth's atmosphere through changes in radiative flux divergence. Our knowledge of and means of measuring radiative flux divergence is very limited. A few observations of vertical radiative flux divergences have been reported from aircraft from radiometersondes from towers and from large tethered balloons. These measurement techniques suffers from one or more drawbacks, including shallow sounding depths (towers), high cost (aircraft), complicated logistics (large tethered balloons), and limitation to nighttime hours (radiometersondes). Changes in radiative flux divergence caused by anthropogenic trace gases are expected to be quite small, and will be difficult to measure with existing broadband radiative flux instruments. The emphasis of present research in global climate change is thus being focused on improving radiative transfer algorithms in global climate models. The radiative parameterizations in these models are at an early stage of development and information is needed regarding their performance, especially in cloudy conditions. The impetus for the research reported in this paper is the need for a device that can supplement existing means of measuring vertical profiles of long- and short-wave irradiance and radiative flux divergence. We have designed a small tethered-balloon-based system that can make radiometric soundings through the atmospheric boundary layer. This paper discusses the concept, the design considerations, and the design and construction of this sounding system. The performance of the system will be tested in a series of balloon flights scheduled for the fall and winter of 1992.

  18. Investigating gait recognition in the short-wave infrared (SWIR) spectrum: dataset and challenges

    NASA Astrophysics Data System (ADS)

    DeCann, Brian; Ross, Arun; Dawson, Jeremy

    2013-05-01

    In the biometrics community, challenge datasets are often released to determine the robustness of state-of-the- art algorithms to conditions that can confound recognition accuracy. In the context of automated human gait recognition, evaluation has predominantly been conducted on video data acquired in the active visible spectral band, although recent literature has explored recognition in the passive thermal band. The advent of sophisticated sensors has piqued interest in performing gait recognition in other spectral bands such as short-wave infrared (SWIR), due to their use in military-based tactical applications and the possibility of operating in nighttime environments. Further, in many operational scenarios, the environmental variables are not controlled, thereby posing several challenges to traditional recognition schemes. In this work, we discuss the possibility of performing gait recognition in the SWIR spectrum by first assembling a dataset, referred to as the WVU Outdoor SWIR Gait (WOSG) Dataset, and then evaluate the performance of three gait recognition algorithms on the dataset. The dataset consists of 155 subjects and represents gait information acquired under multiple walking paths in an uncontrolled, outdoor environment. Detailed experimental analysis suggests the benefits of distributing this new challenging dataset to the broader research community. In particular, the following observations were made: (a) the importance of SWIR imagery in acquiring data covertly for surveillance applications; (b) the difficulty in extracting human silhouettes in low-contrast SWIR imagery; (c) the impact of silhouette quality on overall recognition accuracy; (d) the possibility of matching gait sequences pertaining to different walking trajectories; and (e) the need for developing sophisticated gait recognition algorithms to handle data acquired in unconstrained environments.

  19. Total-Field Technique for 3-D Modeling of Short Period Teleseismic Waves

    NASA Astrophysics Data System (ADS)

    Monteiller, V.; Beller, S.; Operto, S.; Nissen-Meyer, T.; Tago Pacheco, J.; Virieux, J.

    2014-12-01

    The massive development of dense seismic arrays and the rapid increase in computing capacity allow today to consider application of full waveform inversion of teleseismic data for high-resolution lithospheric imaging. We present an hybrid numerical method that allows for the modellingof short period teleseismic waves in 3D lithospheric target with both the discontinuous Galerkin finite elements method and finite difference method, opening the possibility to perform waveform inversion of seismograms recorded by dense regional broadband arrays. However, despite the supercomputer ability, the forward-problem remains expensive at global scale for teleseismic configuration especially when 3D numerical methods are considered. In order to perform the forward problem in a reasonable amount of time, we reduce the computational domain in which full waveform modelling is performed. We define a 3D regional domain located below the seismological network that is embedded in a homogeneous background or axisymmetric model, in which the seismic wavefield can be computed efficiently. The background wavefield is used to compute the full wavefield in the 3D regional domain using the so-called total-field/scattered-field technique. This method relies on the decomposition of the wavefield into a background and a scattered wavefields. The computational domain is subdivided into three sub-domains: an outer domain formed by the perfectly-matched absorbing layers, an intermediate domain in which only the outgoing wavefield scattered by the lithospheric heterogeneities is computed, and the inner domain formed by the lithospheric target in which the full wavefield is computed. In this study, we shall present simulations in realistic lithospheric target when the axisymetric background wavefield is computed with the AxiSEM softwave and the 3D simulation in lithospheric target model is performed with the discontinuous Galerkin or finite difference method.

  20. Structural and theoretical investigations of short hydrogen bonds: neutron diffraction and plane-wave DFT calculations of urea phosphoric acid

    NASA Astrophysics Data System (ADS)

    Wilson, Chick C.; Morrison, Carole A.

    2002-08-01

    Low temperature neutron diffraction and high level computational methods have been applied to investigate the short hydrogen bond in urea-phosphoric acid. It is found that isolated molecule calculations predict a `normal' O-H⋯O hydrogen bond, in strong disagreement with the very short, 3 c-4 e hydrogen bond found from the neutron diffraction. Extending these calculations into a periodic environment using plane-wave DFT methods give much improved agreement with experiment, with a much shorter, stronger hydrogen bond, and significant elongation of the O-H `covalent' bond.

  1. Vertical variability of aerosol backscatter from an airborne-focused continuous-wave CO2 lidar at 9.1-microm wavelength.

    PubMed

    Jarzembski, M A; Srivastava, V; Rothermel, J

    1999-02-20

    Atmospheric aerosol backscatter measurements taken with a continuous-wave focused Doppler lidar at 9.1-microm wavelength were obtained over western North America and the Pacific Ocean from 13 to 26 September 1995 as part of a NASA airborne mission. Backscatter variability was measured for approximately 52 flight hours, covering an equivalent horizontal distance of approximately 30,000 km in the troposphere. Some quasi-vertical backscatter profiles were also obtained during various ascents and descents at altitudes that ranged from approximately 0.1 to 12 km. Similarities and differences for aerosol loading over land and ocean were observed. A midtropospheric aerosol backscatter background mode near 3 x 10(-11) to 1 x 10(-10) m(-1) sr(-1) was obtained, which is consistent with those of previous airborne and ground-based data sets. PMID:18305690

  2. All-optical ultrafast wavelength and mode converter based on inter-modal four-wave mixing in few-mode fibers

    NASA Astrophysics Data System (ADS)

    Weng, Yi; He, Xuan; Wang, Junyi; Pan, Zhongqi

    2015-08-01

    An ultrafast all-optical simultaneous wavelength and mode conversion scheme is purposed based on intermodal four-wave mixing (IM-FWM), with the capability of switching state of polarization (SOP) and mode degeneracy orientation (MDO) in few-mode fibers (FMF). The relation among the conversion efficiency, pump power and phase matching conditions is investigated in theory analysis and simulation. Using this scheme, cross-polarization modulation (XPolM) and cross-mode modulation (XMM) can be achieved, by in the best case up to 50% conversion efficiency. Furthermore, numerical results further indicate that the proposed configuration has the potential application for generating doughnut modes by the mixing of three characteristic spatial frequencies.

  3. Widely tunable dispersive wave generation and soliton self-frequency shift in a tellurite microstructured optical fiber pumped near the zero dispersion wavelength

    NASA Astrophysics Data System (ADS)

    Zhang, Lei; Tuan, Tong-Hoang; Liu, Lai; Gao, Wei-Qing; Kawamura, Harutaka; Suzuki, Takenobu; Ohishi, Yasutake

    2015-12-01

    Widely tunable dispersive waves (DW) and Raman solitons are generated in a tellurite microstructured optical fiber (TMOF) by pumping in the anomalous dispersion regime, close to the zero dispersion wavelength (ZDW). The DW can be generated from 1518.3 nm to 1315.5 nm, and the soliton can be shifted from the pump wavelength of 1570 nm to 1828.7 nm, by tuning the average pump power from 3 dBm to 17.5 dBm. After the average pump power is increased to 18.8 dBm, two DW peaks (centered at 1323 nm and 1260 nm) and three soliton peaks (centered at 1762 nm, 1825 nm, and 1896 nm) can be observed simultaneously. When the average pump power is greater than 23.4 dBm, a flat and broadband supercontinuum (SC) can be formed by the combined nonlinear effects of soliton self-frequency shift (SSFS), DW generation, and cross phase modulation (XPM).

  4. Excitation of surface waves by a short laser pulse in a conductor

    SciTech Connect

    Uryupin, S A; Frolov, A A

    2013-12-31

    We have studied the possibility of exciting surface waves in a conductor, which is irradiated by a focused femtosecond laser pulse incident along the normal to the surface. The time-dependent ponderomotive force is shown to lead to the excitation of surface waves in the terahertz frequency range. It is also shown that the total energy and the pulse amplitude of the surface waves increases with increasing effective electron collision frequency. (terahertz radiation)

  5. Exploring binary-neutron-star-merger scenario of short-gamma-ray bursts by gravitational-wave observation.

    PubMed

    Kiuchi, Kenta; Sekiguchi, Yuichiro; Shibata, Masaru; Taniguchi, Keisuke

    2010-04-01

    We elucidate the feature of gravitational waves (GWs) from a binary-neutron-star merger collapsing to a black hole by general relativistic simulation. We show that GW spectrum imprints the coalescence dynamics, formation process of disk, equation of state for neutron stars, total masses, and mass ratio. A formation mechanism of the central engine of short-gamma-ray bursts, which are likely to be composed of a black hole and surrounding disk, therefore could be constrained by GW observation. PMID:20481927

  6. Dual-wavelength, continuous-wave Yb:YAG laser for high-resolution photothermal common-path interferometry.

    PubMed

    Zhuang, Fengjiang; Jungbluth, Bernd; Gronloh, Bastian; Hoffmann, Hans-Dieter; Zhang, Ge

    2013-07-20

    We present a continuous-wave (CW) intracavity frequency-doubled Yb:YAG laser providing 1030 and 515 nm output simultaneously. This laser system was designed for photothermal common-path interferometry to measure spatially resolved profiles of the linear absorption in dielectric media and coatings for visible or infrared light as well as of the nonlinear absorption for the combination of both. A Z-shape laser cavity was designed, providing a beam waist in which an LBO crystal was located for effective second-harmonic generation (SHG). Suitable frequency conversion parameters and cavity configurations were discussed to achieve the optimal performance of a diode-pumped CW SHG laser. A 12.4 W 1030 nm laser and 5.4 W 515 nm laser were developed simultaneously in our experiment. PMID:23872763

  7. Dual-wavelength, continuous-wave Yb:YAG laser for high-resolution photothermal common-path interferometry.

    TOXLINE Toxicology Bibliographic Information

    Zhuang F; Jungbluth B; Gronloh B; Hoffmann HD; Zhang G

    2013-07-20

    We present a continuous-wave (CW) intracavity frequency-doubled Yb:YAG laser providing 1030 and 515 nm output simultaneously. This laser system was designed for photothermal common-path interferometry to measure spatially resolved profiles of the linear absorption in dielectric media and coatings for visible or infrared light as well as of the nonlinear absorption for the combination of both. A Z-shape laser cavity was designed, providing a beam waist in which an LBO crystal was located for effective second-harmonic generation (SHG). Suitable frequency conversion parameters and cavity configurations were discussed to achieve the optimal performance of a diode-pumped CW SHG laser. A 12.4 W 1030 nm laser and 5.4 W 515 nm laser were developed simultaneously in our experiment.

  8. Predicting short-period, wind-wave-generated seismic noise in coastal regions

    NASA Astrophysics Data System (ADS)

    Gimbert, Florent; Tsai, Victor C.

    2015-09-01

    Substantial effort has recently been made to predict seismic energy caused by ocean waves in the 4-10 s period range. However, little work has been devoted to predict shorter period seismic waves recorded in coastal regions. Here we present an analytical framework that relates the signature of seismic noise recorded at 0.6-2 s periods (0.5-1.5 Hz frequencies) in coastal regions with deep-ocean wave properties. Constraints on key model parameters such as seismic attenuation and ocean wave directionality are provided by jointly analyzing ocean-floor acoustic noise and seismic noise measurements. We show that 0.6-2 s seismic noise can be consistently predicted over the entire year. The seismic noise recorded in this period range is mostly caused by local wind-waves, i.e. by wind-waves occurring within about 2000 km of the seismic station. Our analysis also shows that the fraction of ocean waves traveling in nearly opposite directions is orders of magnitude smaller than previously suggested for wind-waves, does not depend strongly on wind speed as previously proposed, and instead may depend weakly on the heterogeneity of the wind field. This study suggests that wind-wave conditions can be studied in detail from seismic observations, including under specific conditions such as in the presence of sea ice.

  9. Application of artificial neural network to search for gravitational-wave signals associated with short gamma-ray bursts

    NASA Astrophysics Data System (ADS)

    Kim, Kyungmin; Harry, Ian W.; Hodge, Kari A.; Kim, Young-Min; Lee, Chang-Hwan; Lee, Hyun Kyu; Oh, John J.; Oh, Sang Hoon; Son, Edwin J.

    2015-12-01

    We apply a machine learning algorithm, the artificial neural network, to the search for gravitational-wave signals associated with short gamma-ray bursts (GRBs). The multi-dimensional samples consisting of data corresponding to the statistical and physical quantities from the coherent search pipeline are fed into the artificial neural network to distinguish simulated gravitational-wave signals from background noise artifacts. Our result shows that the data classification efficiency at a fixed false alarm probability (FAP) is improved by the artificial neural network in comparison to the conventional detection statistic. Specifically, the distance at 50% detection probability at a fixed false positive rate is increased about 8%-14% for the considered waveform models. We also evaluate a few seconds of the gravitational-wave data segment using the trained networks and obtain the FAP. We suggest that the artificial neural network can be a complementary method to the conventional detection statistic for identifying gravitational-wave signals related to the short GRBs.

  10. Improvement of Short-Wave InfraRed Hyperspectral Imaging by Direct Polarization Measurements

    NASA Astrophysics Data System (ADS)

    Leblanc, G. E.; Allux, S.

    2010-12-01

    Hyperspectral imaging is susceptible to a myriad of atmospheric effects that cause undesirable effects when applying advanced processing techniques. Principally, scattering of incoming solar energy and the resulting “haze” produced has a considerable influence on the resulting quality of the data acquired in the ShortWave InfraRed (SWIR) region (850nm to 2500nm) of the electromagnetic spectrum. To alleviate this condition we have devised a polarization system for the Flight Research Laboratory’s (FRL) airborne SWIR hyperspectral imaging system and have collected data from various sources via ground-based and airborne environments. The Polarized SWIR (PSWIR) system we have devised incorporates a linear 90° polarization filter, within a framework that has been attached to FRL’s SWIR system. The polarizer lens is aligned to the 0° axis of the optical slit and can be rotated a full 360°. For the ground-based data collection, the PSWIR was mounted on a z-axis 360° rotation mount which allowed for scanning within the vertical plane as the imager is a push-broom imager that requires motion of the system in order to obtain spatial information. Data was acquired at various polarization orientations in steps of 45° from 0° through to 180°. The data was then analysed using Principle Component Analysis (PCA) and results show that substantial improvement signal-to-noise in higher-order PC’s are obtained in the PSWIR system compared to the SWIR system without polarization. Further, the higher order PC’s derived from the PSWIR system once compared to the SWIR system alone, lead us to conclude that many “artefacts” often ascribed to sensor problems can, in fact, be attributed to unresolved scatter issues in the data. The entire system was then installed aboard FRL’s Twin Otter aircraft and flown over various target materials of interest (man-made, vegetation, soils...) several times over the course of 3-weeks in July/August 2010. As a result of analysing these data, we show that the issue with scattered incoming solar energy is significantly reduced, for the SWIR region, within the airborne environment compared to ground-based acquisition. Furthermore, we also show that the use of the PSWIR system as a method to detect man-made objects does so with a much lower number of false alarms as compared to using the SWIR system alone.

  11. A novel OCS millimeter-wave generation scheme with data carried only by one sideband and wavelength reuse for uplink connection

    NASA Astrophysics Data System (ADS)

    Zhu, Zihang; Zhao, Shanghong; Yao, Zhoushi; Tan, Qinggui; Li, Yongjun; Chu, Xingchun; Shi, Lei; Hou, Rui

    2012-11-01

    We propose a novel optical carrier suppression (OCS) millimeter-wave generation scheme with data carried only by one sideband using a dual-drive Mach-Zehnder modulator (MZM) in radio-over-fiber system, and the transmission performance is also investigated. As the signal is transmitted along the fiber, there is no time shifting of the codes caused by chromatic dispersion. Simulation results show that the eye diagram keeps open and clear even when the optical millimeter-waves are transmitted over 110 km and the power penalty is about 1.9 dB after fiber transmission distance of 60 km. Furthermore, due to the +1 order sideband carrying no data, a full duplex radio-over-fiber link based on wavelength reuse is also built to simplify the base station. The bidirectional 2.5 Gbit/s data is successfully transmitted over a 40 km standard single mode fiber with less than 0.8 dB power penalty in the simulation. Both theoretical analysis and simulation results show that our scheme is feasible and we can obtain a simple cost-efficient configuration and good performance over long-distance transmission.

  12. An analysis of short pulse and dual frequency radar techniques for measuring ocean wave spectra from satellites

    NASA Technical Reports Server (NTRS)

    Jackson, F. C.

    1981-01-01

    A four frequency moment characterization of backscatter from the near-vertical is applied to an analysis of the short pulse and dual frequency microwave techniques. The range reflectivity modulation spectrum closely approximates the directional wave slope spectrum, while harmonic distortion is small and is a minimum near 10 deg incidence. The short pulse measurement signal-to-noise ratio (SNR) is typically greater than the narrowband dual frequency SNR, with the difference being the ratio of the range beam extent to pulse length, minus the ratio of beam-limited to pulse-limited Doppler spreads. It is concluded that dual frequency measurements are basically impractical, although short pulse measurements are useful and can employ existing space-qualified microwave hardware.

  13. VARIABLE GAMMA-RAY EMISSION FROM THE CRAB NEBULA: SHORT FLARES AND LONG 'WAVES'

    SciTech Connect

    Striani, E.; Tavani, M.; Vittorini, V.; Donnarumma, I.; Argan, A.; Cardillo, M.; Costa, E.; Del Monte, E.; Pacciani, L.; Piano, G.; Sabatini, S.; Bulgarelli, A.; Ferrari, A.; Pellizzoni, A.; Pittori, C.; and others

    2013-03-01

    Gamma-ray emission from the Crab Nebula has been recently shown to be unsteady. In this paper, we study the flux and spectral variability of the Crab above 100 MeV on different timescales ranging from days to weeks. In addition to the four main intense and day-long flares detected by AGILE and Fermi-LAT between 2007 September and 2012 September, we find evidence for week-long and less intense episodes of enhanced gamma-ray emission that we call 'waves'. Statistically significant 'waves' show timescales of 1-2 weeks, and can occur by themselves or in association with shorter flares. We present a refined flux and spectral analysis of the 2007 September-October gamma-ray enhancement episode detected by AGILE that shows both 'wave' and flaring behavior. We extend our analysis to the publicly available Fermi-LAT data set and show that several additional 'wave' episodes can be identified. We discuss the spectral properties of the 2007 September 'wave'/flare event and show that the physical properties of the 'waves' are intermediate between steady and flaring states. Plasma instabilities inducing 'waves' appear to involve spatial distances l {approx} 10{sup 16} cm and enhanced magnetic fields B {approx} (0.5-1) mG. Day-long flares are characterized by smaller distances and larger local magnetic fields. Typically, the deduced total energy associated with the 'wave' phenomenon (E{sub w} {approx} 10{sup 42} erg, where E{sub w} is the kinetic energy of the emitting particles) is comparable with that associated to the flares, and can reach a few percent of the total available pulsar spin-down energy. Most likely, flares and waves are the product of the same class of plasma instabilities that we show acting on different timescales and radiation intensities.

  14. Variable Gamma-Ray Emission from the Crab Nebula: Short Flares and Long "Waves"

    NASA Astrophysics Data System (ADS)

    Striani, E.; Tavani, M.; Vittorini, V.; Donnarumma, I.; Giuliani, A.; Pucella, G.; Argan, A.; Bulgarelli, A.; Colafrancesco, S.; Cardillo, M.; Costa, E.; Del Monte, E.; Ferrari, A.; Mereghetti, S.; Pacciani, L.; Pellizzoni, A.; Piano, G.; Pittori, C.; Rapisarda, M.; Sabatini, S.; Soffitta, P.; Trifoglio, M.; Trois, A.; Vercellone, S.; Verrecchia, F.

    2013-03-01

    Gamma-ray emission from the Crab Nebula has been recently shown to be unsteady. In this paper, we study the flux and spectral variability of the Crab above 100 MeV on different timescales ranging from days to weeks. In addition to the four main intense and day-long flares detected by AGILE and Fermi-LAT between 2007 September and 2012 September, we find evidence for week-long and less intense episodes of enhanced gamma-ray emission that we call "waves." Statistically significant "waves" show timescales of 1-2 weeks, and can occur by themselves or in association with shorter flares. We present a refined flux and spectral analysis of the 2007 September-October gamma-ray enhancement episode detected by AGILE that shows both "wave" and flaring behavior. We extend our analysis to the publicly available Fermi-LAT data set and show that several additional "wave" episodes can be identified. We discuss the spectral properties of the 2007 September "wave"/flare event and show that the physical properties of the "waves" are intermediate between steady and flaring states. Plasma instabilities inducing "waves" appear to involve spatial distances l ~ 1016 cm and enhanced magnetic fields B ~ (0.5-1) mG. Day-long flares are characterized by smaller distances and larger local magnetic fields. Typically, the deduced total energy associated with the "wave" phenomenon (Ew ~ 1042 erg, where Ew is the kinetic energy of the emitting particles) is comparable with that associated to the flares, and can reach a few percent of the total available pulsar spin-down energy. Most likely, flares and waves are the product of the same class of plasma instabilities that we show acting on different timescales and radiation intensities.

  15. Spectral characterization of Fabry-Perot etalon operating in Short Wave Infra-Red (SWIR) region

    NASA Astrophysics Data System (ADS)

    Dutta, Moumita; Ankush, K.; Kumar, K. Ajay; Ghag, Prathmesh; Sarkar, S. S.

    2015-06-01

    A promising technique for precise spectral characterization of solid Etalon operating in SWIR wavelength is demonstrated using tunable laser with a minimum wavelength scan step interval of 1 picometer. Measurement is carried out for 1640nm - 1660nm, an important region containing greenhouse gas absorption spectra. The etalon considered for characterization is made of fused silica. The thickness is nearly 346 micron with physical diameter of 25.4 mm and clear aperture of 23 mm. The etalon has a finesse of 7.25 and extremely narrow bandwidth like 0.4 nm or 400 picometer. The measurement was as well carried out with an Optical Spectrum Analyzer (OSA). The conventional OSA instrument had a resolution of 80 picometer limiting the measurement capability to detect a spectral shift as fine as 50 picometer. Also the measured bandwidth had an error of ± 40 picometer over a spectral bandwidth of 400 picometer which is nearly ±10 %. This leads to the use of a tunable laser exhibiting a provision to vary the wavelength at a step of 1 picometer. This method provides measurement accuracy at least 4 times better than the earlier method. Accuracy may be further improved by making the wavelength scan step interval even finer. The absorption due to presence of greenhouse gas like methane is higher for the etalons with narrower bandwidth. This method can provide very good accuracy for characterization of etalons with spectral bandwidth as narrow as 50 picometer.

  16. Radiative electron capture to the continuum and the short-wavelength limit of electron-nucleus bremsstrahlung in 90A MeV U88 + ((1s2)(2s2))+N2 Collisions.

    PubMed

    Nofal, M; Hagmann, S; Stöhlker, Th; Jakubassa-Amundsen, D H; Kozhuharov, Ch; Wang, X; Gumberidze, A; Spillmann, U; Reuschl, R; Hess, S; Trotsenko, S; Banas, D; Bosch, F; Liesen, D; Moshammer, R; Ullrich, J; Dörner, R; Steck, M; Nolden, F; Beller, P; Rothard, H; Beckert, K; Franczak, B

    2007-10-19

    We have measured the continuum momentum distribution for radiative electron capture to the continuum (RECC) cusp electrons in 90A MeV U88+ + N2-->U88+ + N2 +* + ecusp(0 degrees ) + hnu (RECC) collisions. We demonstrate that x rays coincident with RECC cusp electrons originate from the short-wavelength limit of the electron-nucleus bremsstrahlung and explain the asymmetric cusp shape by comparison with theory within the relativistic impulse approximation. PMID:17995248

  17. The Modified Simple Equation Method, the Exp-Function Method, and the Method of Soliton Ansatz for Solving the Long-Short Wave Resonance Equations

    NASA Astrophysics Data System (ADS)

    Zayed, E. M. E.; Al-Nowehy, Abdul-Ghani

    2016-02-01

    The modified simple equation method, the exp-function method, and the method of soliton ansatz for solving nonlinear partial differential equations are presented. Based on these three different methods, we obtain the exact solutions and the bright-dark soliton solutions with parameters of the long-short wave resonance equations which describe the resonance interaction between the long wave and the short wave. When these parameters take special values, the solitary wave solutions are derived from the exact solutions. We compare the results obtained using the three methods. Also, a comparison between our results and the well-known results is given.

  18. Wavelength-doubling optical parametric oscillator

    DOEpatents

    Armstrong, Darrell J.; Smith, Arlee V.

    2007-07-24

    A wavelength-doubling optical parametric oscillator (OPO) comprising a type II nonlinear optical medium for generating a pair of degenerate waves at twice a pump wavelength and a plurality of mirrors for rotating the polarization of one wave by 90 degrees to produce a wavelength-doubled beam with an increased output energy by coupling both of the degenerate waves out of the OPO cavity through the same output coupler following polarization rotation of one of the degenerate waves.

  19. Evidence for nonuniversal behavior of paraconductivity caused by predominant short-wavelength Gaussian fluctuations in YBa{sub 2}Cu{sub 3}O{sub 6.9}

    SciTech Connect

    Gauzzi, A.; Pavuna, D.

    1995-06-01

    We report on in-plane paraconductivity measurements in thin YBa{sub 2}Cu{sub 3}O{sub 6.9} films. Our analysis of the data shows that the temperature dependence of paraconductivity is affected by lattice disorder and deviates at all temperatures from the universal power laws predicted by both scaling and mean-field theories. This gives evidence for the absence of critical fluctuations and for the failure of the Aslamazov-Larkin universal relation between critical exponent and dimensionality of the spectrum of Gaussian fluctuations. We account quantitatively for the data within the experimental error by introducing a short-wavelength cutoff into this spectrum. This implies that three-dimensional short-wavelength Gaussian fluctuations dominate in YBa{sub 2}Cu{sub 3}O{sub 6.9} and suggests a rapid attenuation of these fluctuations with decreasing wavelength in short-coherence-length systems as compared to the case of the conventional Ginzburg-Landau theory.

  20. Observation of strong oscillations of areal mass in an unsupported shock wave produced by a short laser pulse

    NASA Astrophysics Data System (ADS)

    Aglitskiy, Y.; Karasik, M.; Velikovich, A. L.; Serlin, V.; Weaver, J. L.; Kessler, T. J.; Schmitt, A. J.; Obenschain, S. P.; Metzler, N.; Oh, J.

    2011-10-01

    The first experimental study of hydrodynamic perturbation evolution in a strong unsupported shock wave, which is immediately followed by a rarefaction wave, is reported. Our planar solid polystyrene laser-machined targets, 50 to 100 μm thick, rippled from the front side with a single-mode wavelength 30 or 45 μm and peak-to-valley amplitude 4 to 6 μm, were irradiated with a 350 ps long Nike KrF laser pulse at peak intensity of up to 330 TW/cm2. The perturbation evolution in the target was observed using face-on monochromatic x-ray radiography while the pulse lasted and for 3 to 4 ns after it ended. While the driving pulse was on, the areal mass modulation amplitude in the target was observed to grow by a factor of up to ~4 due to the ablative Richtmyer-Meshkov instability. After the end of the pulse, while the strong unsupported shock wave propagated through the unperturbed target, the theoretically predicted large oscillations of the areal mass [A. L. Velikovich et al., Phys. Plasmas 10, 3270 (2003)] were observed. Multiple phase reversals of the areal mass modulation have been detected. Work supported by DOE/NNSA and Office of Naval Research.

  1. The interaction of short surface waves with stratified flow in Raccoon Strait

    NASA Astrophysics Data System (ADS)

    Janssen, T. T.; Pearman, D. W.; Herbers, T. H.; Largier, J. L.; McIntyre, S.; Jessen, P.

    2012-12-01

    Strong tidal currents and complex wave-current interaction characterize the west side of Raccoon Strait, the narrow waterway between Angel Island and the Tiburon Peninsula in San Francisco Bay. The surface and internal hydrodynamics in this area are strongly affected by the presence of a shallow sill (depth ~10m) that extends partially across the strait near the western tip of Angel Island. In this work we present observations collected during several field experiments in 2011 and 2012 in Raccoon Strait, San Francisco Bay, using shipboard ADCP, bottom mounted ADCPs, CTDs, and Wave Resolving Drifters (WRDs). By combining observations from bottom-mounted, fixed (Eulerian) instruments and newly developed Lagrangian drifters that can resolve wind wave dynamics and surface drifts, we relate the spatial structure of the stratified flow dynamics with the observed wave evolution in the area. We analyze the interaction and characteristics of the wave blocking dynamics observed near the sill, the development of a subduction zone of surface waters during flood tide, and the occurrence of an internal lee wave downstream of the sill.

  2. X-ray conversion of ultra-short laser pulses on a solid sample: Role of electron waves excited in the pre-plasma

    SciTech Connect

    Baffigi, F. Cristoforetti, G.; Fulgentini, L.; Giulietti, A.; Koester, P.; Labate, L.; Gizzi, L. A.

    2014-07-15

    Flat silicon samples were irradiated with 40 fs, 800 nm laser pulses at an intensity at the best focus of 2·10{sup 18} Wcm{sup −2}, in the presence of a pre-plasma on the sample surface. X-ray emission in the spectral range from 2 to 30 keV was detected inside and outside the plane of incidence, while varying pre-plasma scale length, laser intensity, and polarization. The simultaneous detection of 2ω and 3ω/2 emission allowed the contributions to the X-ray yield to be identified as originating from laser interaction with either the near-critical density (n{sub c}) region or with the n{sub c}/4 region. In the presence of a moderate pre-plasma, our measurements reveal that, provided the pre-plasma reaches a scale-length of a few laser wavelengths, X-ray emission is dominated by the contribution from the interaction with the under dense plasma, where electron plasma waves can grow, via laser stimulated instabilities, and, in turn, accelerate free electrons to high energies. This mechanism leads also to a clear anisotropy in the angular distribution of the X-ray emission. Our findings can lead to an enhancement of the conversion efficiency of ultra short laser pulses into X-rays.

  3. Improving atmospheric correction for highly productive coastal waters using the short wave infrared retrieval algorithm with water-leaving reflectance constraints at 412 nm.

    PubMed

    Oo, Min; Vargas, Marco; Gilerson, Alex; Gross, Barry; Moshary, Fred; Ahmed, Sam

    2008-07-20

    The recently developed short wave infrared (SWIR) atmospheric correction algorithm for ocean color retrieval uses long wavelength channels to retrieve atmospheric parameters to avoid bright pixel contamination. However, this retrieval is highly sensitive to errors in the aerosol model, which is magnified by the higher variability of aerosols observed over urban coastal areas. While adding extra regional aerosol models into the retrieval lookup tables would tend to increase retrieval error since these models are hard to distinguish in the IR, we explore the possibility that for highly productive waters with high colored dissolved organic matter, an estimate of the 412 nm channel water-leaving reflectance can be used to constrain the aerosol model retrieval and improve the water-leaving reflectance retrieval. Simulations show that this constraint is particularly useful where aerosol diversity is significant. To assess this algorithm we compare our retrievals with the operational SeaWiFS Data Analysis System (SeaDAS) SWIR and near infrared retrievals using in situ validation data in the Chesapeake Bay and show that, especially for absorbing aerosols, significant improvement is obtained. Further insight is also obtained by the intercomparison of retrieved remote sensing reflectance images at 443 and 551 nm, which demonstrates the removal of anomalous artifacts in the operational SeaDAS retrieval. PMID:18641754

  4. TRIGGERING COLLAPSE OF THE PRESOLAR DENSE CLOUD CORE AND INJECTING SHORT-LIVED RADIOISOTOPES WITH A SHOCK WAVE. II. VARIED SHOCK WAVE AND CLOUD CORE PARAMETERS

    SciTech Connect

    Boss, Alan P.; Keiser, Sandra A. E-mail: keiser@dtm.ciw.edu

    2013-06-10

    A variety of stellar sources have been proposed for the origin of the short-lived radioisotopes that existed at the time of the formation of the earliest solar system solids, including Type II supernovae (SNe), asymptotic giant branch (AGB) and super-AGB stars, and Wolf-Rayet star winds. Our previous adaptive mesh hydrodynamics models with the FLASH2.5 code have shown which combinations of shock wave parameters are able to simultaneously trigger the gravitational collapse of a target dense cloud core and inject significant amounts of shock wave gas and dust, showing that thin SN shocks may be uniquely suited for the task. However, recent meteoritical studies have weakened the case for a direct SN injection to the presolar cloud, motivating us to re-examine a wider range of shock wave and cloud core parameters, including rotation, in order to better estimate the injection efficiencies for a variety of stellar sources. We find that SN shocks remain as the most promising stellar source, though planetary nebulae resulting from AGB star evolution cannot be conclusively ruled out. Wolf-Rayet (WR) star winds, however, are likely to lead to cloud core shredding, rather than to collapse. Injection efficiencies can be increased when the cloud is rotating about an axis aligned with the direction of the shock wave, by as much as a factor of {approx}10. The amount of gas and dust accreted from the post-shock wind can exceed that injected from the shock wave, with implications for the isotopic abundances expected for a SN source.

  5. Thermally induced transparency for short spin wave pulses in yttrium iron garnet (YIG) films

    NASA Astrophysics Data System (ADS)

    Ordonez Romero, Cesar Leonardo; Kolokoltsev, Oleg; Gomez Arista, Ivan; Qureshi, Naser; Monsiváis Galindo, Guillermo; Vargas Hernández, Hesiquio

    2014-03-01

    The compensation of spin wave propagation losses plays a very important role in the development of novel magnonic devices. Up to now, however, most of the known amplification methods present relative narrow frequency bandwidths due to their resonant nature. In this work, we present compensation of the propagation losses or pseudo-amplification of travelling spin waves by tailoring the bias magnetic field profile. The thermally-induced non-uniform profile of the magnetization introduced on an Yttrium Iron Garnet (YIG) thin film by a localized spot of a cw argon-ion laser creates the conditions to observe the complete compensation of the spin wave propagation losses. The spin wave evolution was mapped with a time and spaced resolved inductive magneto-dynamic prove system. The experiment was carried out using a uniform sample of single-crystal YIG film grown on a gallium-gadolinium garnet (GGG) substrate. The 2mm-wide, 20mm-long and 6microns-thick YIG strip was saturated with an external magnetic field enabling the set up for the propagation of magneto-static surface waves. This work was supported by the UNAM-DGAPA-PAPIIT IA100413.

  6. Exactly solvable model of resonance tunneling of an electromagnetic wave in plasma containing short-scale inhomogeneities

    SciTech Connect

    Erokhin, N. S. Zakharov, V. E.; Zol’nikova, N. N.; Mikhailovskaya, L. A.

    2015-02-15

    Different variants of resonance tunneling of a transverse electromagnetic wave through a plasma layer containing short-scale (subwavelength) inhomogeneities, including evanescence regions to which approximate methods are inapplicable, are analyzed in the framework of an exactly solvable one-dimensional model. Complex plasma density profiles described by a number of free parameters determining the permittivity modulation depth, the characteristic scale lengths of plasma structures, their number, and the thickness of the inhomogeneous plasma layer are considered. It is demonstrated that reflection-free propagation of the wave incident on the layer from vacuum (the effect of wave-barrier transillumination) can be achieved for various sets of such structures, including plasma density profiles containing a stochastic component. Taking into account cubic nonlinearity, it is also possible to obtain an exact solution to the one-dimensional problem on the nonlinear transillumination of nonuniform plasma. In this case, the thicknesses of the evanescence regions decrease appreciably. The problem of resonance tunneling of electromagnetic waves through such barriers is of interest for a number of practical applications.

  7. Rapid calculation of the compression wave generated by a train entering a tunnel with a vented hood: Short hoods

    NASA Astrophysics Data System (ADS)

    Howe, M. S.; Winslow, A.; Iida, M.; Fukuda, T.

    2008-03-01

    A numerical procedure for the rapid prediction of the compression wave generated by a high-speed train entering a tunnel was presented and validated by Howe et al. [Rapid calculation of the compression wave generated by a train entering a tunnel with a vented hood, Journal of Sound and Vibration 297 (2006) 267-292]. The method was devised to deal principally with compression wave generation in long hoods typically of length 10 times the tunnel height and 'vented' by means of a series of windows distributed along the hood walls. Hoods of this kind will be needed to control wave generation by newer trains operating at speeds U exceeding about 350 km/h. In this paper experimental results are presented and compared with predictions in order to extend the range of applicability of the numerical method of Howe et al. (2006) to include short hoods with lengths as small as just twice the tunnel height (the situation for most hoods currently deployed on the Japanese Shinkansen) and for U as large as 400 km/h.

  8. Short-term and long-term evolution of modulational wave train under influence of current

    NASA Astrophysics Data System (ADS)

    Houtani, H.; Waseda, T.; Toffoli, A.

    2012-04-01

    The modulational instability or the quasi-resonance is considered to play a pivotal role in the generation of freak waves in the ocean. The steepness and the frequency bandwidth, which are known to govern the initial stability of both regular and irregular wave train, are now used to predict the long-term evolution. In this study we extend the pioneering works of Toffoli et al. (2011) and Onorato et al. (2011) demonstrating the influence of current on the wave train evolution via modification of these basic parameters. We have conducted a laboratory experiment at the Ocean Engineering Tank of the Univ. of Tokyo (Kinoshita Lab) investigating the evolution of the marginally stable modulational wave train under influence of opposing current. The experimental results were compared against the numerical solution of the NLSC (Current modified NonLinear Schrodinger) derived by Hjelmervik and Trulsen (2009). For the cases that transitioned into unstable condition, the spatial scale of the evolution was well reproduced by the NLSC. The maximum wave amplitudes reached the level of experimental observation at a realistic spatial scale. On the other hand, there was a case that evolved much faster in the wave tank than the NLSC solution. However, even in this case, the maximum amplitudes observed in the experiment well agreed with the maximum amplitude estimated by Onorato et al. (2011); this was reported earlier by Toffoli et al. (2011) at WISE. Finally, the evolution of the cases that remained stable largely varied between the experiment and NLSC solution. The straightforward interpretation of the successful comparison of the NLSC solution and the tank experiment is that the evolution after encounter with the opposing current is governed by the enhanced nonlinearity. We have compared the amplification of the wave amplitude estimated by action balance and by the NLSC. It turns out that the two estimates do not match. This is because the first term of the r.h.s. of the NLSC is inconsistent with the action conservation principle. If this term alone should account for the action balance, the term should be increased by two-fold. We have also taken into consideration the wave number change corresponding to the second term of the r.h.s., but that did not correct the action conservation based on NLSC. Nevertheless, the work by Onorato et al. (2011) and our experimental result reported by Toffoli et al. (2011, WISE) indicate that the key to understand the impact of the evolution of the wave train encountering an opposing current, is the enhancement of the nonlinearity. In the comparisons above, we assumed that the current speed changes from one value to the other and remains the same afterwards.Now how does the structure of f(x) influence the wave train evolution? If all can be explained by enhanced nonlinearity after the current speed reached the value Uo, the structure of f(x) is irrelevant. We have numerically compared the difference of f(x)=Uo*sinx2 and f(x)=0.5Uo(1+tanh(x)). The result is that the estimated maximum modulation amplitude compares well between the two cases. What was most significantly influenced was the recurrence period. The recurrence period did not change with current speed for the sinusoidal cases, but for the hyperbolic tangent cases, the recurrence period largely varied with current speed. Stiassini and Kroszynski (1982) theoretically derived that the recurrence period depends on three parameters, ratio of steepness to frequency bandwidth (i.e. inverse of BFI), side-band wave amplitude and phase. Inspired by this theory, we have numerically experimented the long-term evolution of unstable wave train with various opposing current speeds. With the hyperbolic tangent case, the recurrence period changed with current speed and seemed to depend on the modified inverse BFI under current influence, in qualitative agreement with the S&K theory.

  9. Short-wave contributions in the storm surge associated with Xynthia, February 2010, western France

    NASA Astrophysics Data System (ADS)

    Bertin, X.; Li, K.; Roland, A.; Breilf, J. F.; Chaumillon, E.

    2012-04-01

    This study aims to hindcast and analyze the storm surge caused by Xynthia, a mid-latitude storm that severely hit the central part of the Bay of Biscay on the 27-28th of February 2010. This storm surge locally exceeded 1.5 m and peaked at the same time as a high spring tide (Bertin et al., 2012). A new storm surge modeling system was applied, based on the unstructured-grid circulation model SELFE (Zhang and Batista, 2008) and the spectral wave model WWM II (Roland et al., 2008). These two models are fully coupled and parallelized and share the same grid and domain decomposition. The modelling system was implemented over the North-East Atlantic Ocean and the space was discretized using an unstructured grid with a resolution ranging from 30 km in Deep Ocean to 25 m in near shore zones. Such a fine resolution was required to properly represent the surf zone. The modelling system resulted in tidal and wave predictions with errors of the order of 2 and 15%, respectively. The storm surge associated with Xynthia was also well predicted along the Bay of Biscay, with root mean square errors of the order of 0.10 m. Numerical experiments were then performed to analyze the physical processes controlling the development of the storm surge and revealed firstly that the wind caused most of the water level anomaly through an Ekman setup process. The comparison between a wave-dependant and a quadratic parameterization to compute wind stress showed that the storm surge was strongly amplified by the presence of steep and young wind-waves, related to their rapid development in the restricted fetch of the Bay of Biscay. The gradient of wave radiation stress contributed to the whole storm surge by about 0.05 to 0.10 m at the available tide gages. Nevertheless, these gages were located in sheltered harbors and modeling results showed that wave-induced setup locally exceeded 0.5 m in areas more exposed to ocean waves. The unstructured grid is currently being extended inland to simulate the flooding associated with Xynthia. Keywords: Xynthia, storm surge, coastal flooding, unstructured grid model, wave setup, friction velocity.

  10. Prediction and measurement of the electromagnetic environment of high-power medium-wave and short-wave broadcast antennas in far field.

    PubMed

    Tang, Zhanghong; Wang, Qun; Ji, Zhijiang; Shi, Meiwu; Hou, Guoyan; Tan, Danjun; Wang, Pengqi; Qiu, Xianbo

    2014-12-01

    With the increasing city size, high-power electromagnetic radiation devices such as high-power medium-wave (MW) and short-wave (SW) antennas have been inevitably getting closer and closer to buildings, which resulted in the pollution of indoor electromagnetic radiation becoming worsened. To avoid such radiation exceeding the exposure limits by national standards, it is necessary to predict and survey the electromagnetic radiation by MW and SW antennas before constructing the buildings. In this paper, a modified prediction method for the far-field electromagnetic radiation is proposed and successfully applied to predict the electromagnetic environment of an area close to a group of typical high-power MW and SW wave antennas. Different from currently used simplified prediction method defined in the Radiation Protection Management Guidelines (H J/T 10. 3-1996), the new method in this article makes use of more information such as antennas' patterns to predict the electromagnetic environment. Therefore, it improves the prediction accuracy significantly by the new feature of resolution at different directions. At the end of this article, a comparison between the prediction data and the measured results is given to demonstrate the effectiveness of the proposed new method. PMID:24553048

  11. Miniaturized optical wavelength sensors

    NASA Astrophysics Data System (ADS)

    Kung, Helen Ling-Ning

    Recently semiconductor processing technology has been applied to the miniaturization of optical wavelength sensors. Compact sensors enable new applications such as integrated diode-laser wavelength monitors and frequency lockers, portable chemical and biological detection, and portable and adaptive hyperspectral imaging arrays. Small sensing systems have trade-offs between resolution, operating range, throughput, multiplexing and complexity. We have developed a new wavelength sensing architecture that balances these parameters for applications involving hyperspectral imaging spectrometer arrays. In this thesis we discuss and demonstrate two new wavelength-sensing architectures whose single-pixel designs can easily be extended into spectrometer arrays. The first class of devices is based on sampling a standing wave. These devices are based on measuring the wavelength-dependent period of optical standing waves formed by the interference of forward and reflected waves at a mirror. We fabricated two different devices based on this principle. The first device is a wavelength monitor, which measures the wavelength and power of a monochromatic source. The second device is a spectrometer that can also act as a selective spectral coherence sensor. The spectrometer contains a large displacement piston-motion MEMS mirror and a thin GaAs photodiode flip-chip bonded to a quartz substrate. The performance of this spectrometer is similar to that of a Michelson in resolution, operating range, throughput and multiplexing but with the added advantages of fewer components and one-dimensional architecture. The second class of devices is based on the Talbot self-imaging effect. The Talbot effect occurs when a periodic object is illuminated with a spatially coherent wave. Periodically spaced self-images are formed behind the object. The spacing of the self-images is proportional to wavelength of the incident light. We discuss and demonstrate how this effect can be used for spectroscopy. In the conclusion we compare these two new miniaturized spectrometer architectures to existing miniaturized spectrometers. We believe that the combination of miniaturized wavelength sensors and smart processing should facilitate the development real-time, adaptive and portable sensing systems.

  12. Influence of natural surfactants on short wind waves in the coastal Peruvian waters

    NASA Astrophysics Data System (ADS)

    Kiefhaber, D.; Zappa, C. J.; Jähne, B.

    2015-07-01

    Results from measurements of wave slope statistics during the R/V Meteor M91 cruise in the coastal upwelling regions off the coast of Peru are reported. Wave slope probability distributions were measured with an instrument based on the reflection of light at the water surface and a method very similar to the Cox and Munk (1954b) sun glitter technique. During the cruise, the mean square slope (mss) of the waves was found to be very variable, despite the limited range of encountered wind speeds. The Cox and Munk (1954b) parameterization for clean water is found to overestimate mss, but most measurements fall in the range spanned by their clean water and slick parameterizations. The observed variability of mss is attributed to the wave damping effect of surface films, generated by increased biological production in the upwelling zones. The small footprint and high temporal resolution of the measurement allows for tracking abrupt changes in conditions caused by the often patchy structure of the surface films.

  13. Dual-wavelength multifrequency photothermal wave imaging combined with optical coherence tomography for macrophage and lipid detection in atherosclerotic plaques using gold nanoparticles

    NASA Astrophysics Data System (ADS)

    Wang, Tianyi; Jacob Mancuso, J.; Sapozhnikova, Veronika; Dwelle, Jordan; Ma, Li L.; Willsey, Brian; Shams Kazmi, S. M.; Qiu, Jinze; Li, Xiankai; Asmis, Reto; Johnston, Keith P.; Feldman, Marc D.; Milner, Thomas E.

    2012-03-01

    The objective of this study was to assess the ability of combined photothermal wave (PTW) imaging and optical coherence tomography (OCT) to detect, and further characterize the distribution of macrophages (having taken up plasmonic gold nanorose as a contrast agent) and lipid deposits in atherosclerotic plaques. Aortas with atherosclerotic plaques were harvested from nine male New Zealand white rabbits divided into nanorose- and saline-injected groups and were imaged by dual-wavelength (800 and 1210 nm) multifrequency (0.1, 1 and 4 Hz) PTW imaging in combination with OCT. Amplitude PTW images suggest that lateral and depth distribution of nanorose-loaded macrophages (confirmed by two-photon luminescence microscopy and RAM-11 macrophage stain) and lipid deposits can be identified at selected modulation frequencies. Radiometric temperature increase and modulation amplitude of superficial nanoroses in response to 4 Hz laser irradiation (800 nm) were significantly higher than native plaque (P<0.001). Amplitude PTW images (4 Hz) were merged into a coregistered OCT image, suggesting that superficial nanorose-loaded macrophages are distributed at shoulders on the upstream side of atherosclerotic plaques (P<0.001) at edges of lipid deposits. Results suggest that combined PTW-OCT imaging can simultaneously reveal plaque structure and composition, permitting characterization of nanorose-loaded macrophages and lipid deposits in atherosclerotic plaques.

  14. Dynamic characteristics of a multi-wavelength Brillouin-Raman fiber laser assisted by multiple four-wave mixing processes in a ring cavity

    NASA Astrophysics Data System (ADS)

    Shirazi, M. R.; Mohamed Taib, J.; De La Rue, R. M.; Harun, S. W.; Ahmad, H.

    2015-03-01

    Dynamic characteristics of a multi-wavelength Brillouin-Raman fiber laser (MBRFL) assisted by four-wave mixing have been investigated through the development of Stokes and anti-Stokes lines under different combinations of Brillouin and Raman pump power levels and different Raman pumping schemes in a ring cavity. For a Stokes line of order higher than three, the threshold power was less than the saturation power of its last-order Stokes line. By increasing the Brillouin pump power, the nth order anti-Stokes and the (n+4)th order Stokes power levels were unexpectedly increased almost the same before the Stokes line threshold power. It was also found out that the SBS threshold reduction (SBSTR) depended linearly on the gain factor for the 1st and 2nd Stokes lines, as the first set. This relation for the 3rd and 4th Stokes lines as the second set, however, was almost linear with the same slope before SBSTR -6 dB, then, it approached to the linear relation in the first set when the gain factor was increased to 50 dB. Therefore, the threshold power levels of Stokes lines for a given Raman gain can be readily estimated only by knowing the threshold power levels in which there is no Raman amplification.

  15. All-optical frequency downconversion technique utilizing a four-wave mixing effect in a single semiconductor optical amplifier for wavelength division multiplexing radio-over-fiber applications.

    PubMed

    Kim, Hyoung-Jun; Song, Jong-In

    2012-03-26

    An all-optical frequency downconversion utilizing a four-wave mixing effect in a single semiconductor optical amplifier (SOA) was experimentally demonstrated for wavelength division multiplexing (WDM) radio-over-fiber (RoF) applications. Two WDM optical radio frequency (RF) signals having 155 Mbps differential phase shift keying (DPSK) data at 28.5 GHz were simultaneously down-converted to two WDM optical intermediate frequency (IF) signals having an IF frequency of 4.5 GHz by mixing with an optical local oscillator (LO) signal having a LO frequency of 24 GHz in the SOA. The bit-error-rate (BER) performance of the RoF up-links with different optical fiber lengths employing all-optical frequency downconversion was investigated. The receiver sensitivity of the RoF up-link with a 6 km single mode fiber and an optical IF signal in an optical double-sideband format was approximately -8.5 dBm and the power penalty for simultaneous frequency downconversion was approximately 0.63 dB. The BER performance showed a strong dependence on the fiber length due to the fiber dispersion. The receiver sensitivity of the RoF up-link with the optical IF signal in the optical single-sideband format was reduced to approximately -17.4 dBm and showed negligible dependence on the fiber length. PMID:22453476

  16. LOCALIZATION OF SHORT DURATION GRAVITATIONAL-WAVE TRANSIENTS WITH THE EARLY ADVANCED LIGO AND VIRGO DETECTORS

    SciTech Connect

    Essick, Reed; Vitale, Salvatore; Katsavounidis, Erik; Vedovato, Gabriele; Klimenko, Sergey

    2015-02-20

    The Laser Interferometer Gravitational wave Observatory (LIGO) and Virgo advanced ground-based gravitational-wave detectors will begin collecting science data in 2015. With first detections expected to follow, it is important to quantify how well generic gravitational-wave transients can be localized on the sky. This is crucial for correctly identifying electromagnetic counterparts as well as understanding gravitational-wave physics and source populations. We present a study of sky localization capabilities for two search and parameter estimation algorithms: coherent WaveBurst, a constrained likelihood algorithm operating in close to real-time, and LALInferenceBurst, a Markov chain Monte Carlo parameter estimation algorithm developed to recover generic transient signals with latency of a few hours. Furthermore, we focus on the first few years of the advanced detector era, when we expect to only have two (2015) and later three (2016) operational detectors, all below design sensitivity. These detector configurations can produce significantly different sky localizations, which we quantify in detail. We observe a clear improvement in localization of the average detected signal when progressing from two-detector to three-detector networks, as expected. Although localization depends on the waveform morphology, approximately 50% of detected signals would be imaged after observing 100-200 deg{sup 2} in 2015 and 60-110 deg{sup 2} in 2016, although knowledge of the waveform can reduce this to as little as 22 deg{sup 2}. This is the first comprehensive study on sky localization capabilities for generic transients of the early network of advanced LIGO and Virgo detectors, including the early LIGO-only two-detector configuration.

  17. SASE free electron lasers as short wavelength coherent sources. From first results at 100 nm to a 1 Å X-ray laser

    NASA Astrophysics Data System (ADS)

    Treusch, R.; Feldhaus, J.

    2003-10-01

    During the last few years free electron lasers (FELs) based on self-amplified spontaneous emission (SASE) have been demonstrated at wavelengths of 12 μm [CITE], 830 nm [CITE], 530 nm [CITE] and 385 nm [CITE], and around 100 nm [CITE]. Recently, saturation has been observed in the vacuum ultraviolet (VUV) spectral region between 82 nm and 125 nm at the TESLA Test Facility (TTF) at DESY. The radiation pulses have been characterized with respect to pulse energy, statistical fluctuations, angular divergence and spectral distribution, both in the linear gain and in the saturation regime of the FEL [CITE]. The results are in good agreement with theoretical simulations, providing a solid basis for other projects aiming at still shorter wavelengths down to the 0.1 nm range [CITE].

  18. Detection range enhancement using circularly polarized light in scattering environments for infrared wavelengths

    DOE PAGESBeta

    van der Laan, J. D.; Sandia National Lab.; Scrymgeour, D. A.; Kemme, S. A.; Dereniak, E. L.

    2015-03-13

    We find for infrared wavelengths there are broad ranges of particle sizes and refractive indices that represent fog and rain where the use of circular polarization can persist to longer ranges than linear polarization. Using polarization tracking Monte Carlo simulations for varying particle size, wavelength, and refractive index, we show that for specific scene parameters circular polarization outperforms linear polarization in maintaining the intended polarization state for large optical depths. This enhancement with circular polarization can be exploited to improve range and target detection in obscurant environments that are important in many critical sensing applications. Specifically, circular polarization persists bettermore » than linear for radiation fog in the short-wave infrared, for advection fog in the short-wave infrared and the long-wave infrared, and large particle sizes of Sahara dust around the 4 micron wavelength.« less

  19. Detection range enhancement using circularly polarized light in scattering environments for infrared wavelengths

    SciTech Connect

    van der Laan, J. D.; Scrymgeour, D. A.; Kemme, S. A.; Dereniak, E. L.

    2015-03-13

    We find for infrared wavelengths there are broad ranges of particle sizes and refractive indices that represent fog and rain where the use of circular polarization can persist to longer ranges than linear polarization. Using polarization tracking Monte Carlo simulations for varying particle size, wavelength, and refractive index, we show that for specific scene parameters circular polarization outperforms linear polarization in maintaining the intended polarization state for large optical depths. This enhancement with circular polarization can be exploited to improve range and target detection in obscurant environments that are important in many critical sensing applications. Specifically, circular polarization persists better than linear for radiation fog in the short-wave infrared, for advection fog in the short-wave infrared and the long-wave infrared, and large particle sizes of Sahara dust around the 4 micron wavelength.

  20. An airborne short wave infrared /SWIR/ pushbroom imaging system using a 64-element PbS detector array

    NASA Technical Reports Server (NTRS)

    Husain-Abidi, A. S.; Tom, D.; Blaine, L. R.; Ostrow, G.

    1980-01-01

    Research evidence indicates that data in the short wave infrared (SWIR) spectral region will greatly improve the information content of remotely sensed data. Bands are required in the 1.55-1.75 micron and 2.08-2.35 micron spectral regions for a variety of agricultural and geological investigations. It is anticipated that future Landsat sensors will use pushbroom linear array technology to obtain high resolution, improved sensitivity and increased system reliability. To obtain early laboratory and field data, an airborne pushbroom image system has been designed for operation in the short wave infrared spectral region. The system uses a 64-element staggered PbS array and is operated at 195 K; the instrument has been designed to operate in an aircraft and will view a 19 degree swath width with a 5.8 mrad IFOV. The spectral bandwidth of each channel is .05 micron and the noise equivalent reflectivity in the order of .2% is provided. The requirements for more advanced detector arrays for use in future NASA spacecraft remote sensing instruments are also discussed.

  1. Over 100 W ultra-flat broadband short-wave infrared supercontinuum generation in a thulium-doped fiber amplifier.

    PubMed

    Yin, Ke; Li, Lei; Yao, Jinmei; Zhang, Bin; Hou, Jing

    2015-10-15

    An ultra-flat high-power short-wave infrared super-continuum (SC) source generated in an all-fiber thulium-doped fiber amplifier (TDFA) is reported. The SC had a high-spectral flatness with a 10 dB spectral bandwidth spanning from 1970 to 2431 nm and a power spectral density >23??dBm/nm. The output SC beam had Gaussian-shape profiles with a maximum average power of 101.6 W, a SC pulse repetition rate of 2 MHz, and a temporal duration of ?5??ns. Benefiting from the high duty cycle of the 2 ?m seed pulses, the power conversion efficiency from the 793 nm pump light to the maximal SC output power in the TDFA was as high as 35.4%, and the slope efficiency of the TDFA was linearly fitted to be 36.5%. Long-term high-power operation of the SC source showed its outstanding temporal stability. To the best of the authors' knowledge, the results obtained in this Letter represent a new power record for ultra-flat SC in the short-wave infrared region. PMID:26469620

  2. Dual-wavelength phase-shifting digital holography selectively extracting wavelength information from wavelength-multiplexed holograms.

    PubMed

    Tahara, Tatsuki; Mori, Ryota; Kikunaga, Shuhei; Arai, Yasuhiko; Takaki, Yasuhiro

    2015-06-15

    Dual-wavelength phase-shifting digital holography that selectively extracts wavelength information from five wavelength-multiplexed holograms is presented. Specific phase shifts for respective wavelengths are introduced to remove the crosstalk components and extract only the object wave at the desired wavelength from the holograms. Object waves in multiple wavelengths are selectively extracted by utilizing 2π ambiguity and the subtraction procedures based on phase-shifting interferometry. Numerical results show the validity of the proposed technique. The proposed technique is also experimentally demonstrated. PMID:26076268

  3. Development and Short-Range Testing of a 100 kW Side-Illuminated Millimeter-Wave Thermal Rocket

    NASA Technical Reports Server (NTRS)

    Bruccoleri, Alexander; Eilers, James A.; Lambot, Thomas; Parkin, Kevin

    2015-01-01

    The objective of the phase described here of the Millimeter-Wave Thermal Launch System (MTLS) Project was to launch a small thermal rocket into the air using millimeter waves. The preliminary results of the first MTLS flight vehicle launches are presented in this work. The design and construction of a small thermal rocket with a planar ceramic heat exchanger mounted along the axis of the rocket is described. The heat exchanger was illuminated from the side by a millimeter-wave beam and fed propellant from above via a small tank containing high pressure argon or nitrogen. Short-range tests where the rocket was launched, tracked, and heated with the beam are described. The rockets were approximately 1.5 meters in length and 65 millimeters in diameter, with a liftoff mass of 1.8 kilograms. The rocket airframes were coated in aluminum and had a parachute recovery system activated via a timer and Pyrodex. At the rocket heat exchanger, the beam distance was 40 meters with a peak power intensity of 77 watts per square centimeter. and a total power of 32 kilowatts in a 30 centimeter diameter circle. An altitude of approximately 10 meters was achieved. Recommendations for improvements are discussed.

  4. Interference of birefractive waves in CdGa2S4 crystals

    NASA Astrophysics Data System (ADS)

    Syrbu, N. N.; Tiron, A. V.; Parvan, V. I.; Zalamai, V. V.; Tiginyanu, I. M.

    2015-04-01

    In СdGа2S4 crystals the Fabry-Perot and birefringence interference spectra were investigated. Spectral dependences of refraction indexes for ordinary (no) and extraordinary (ne) light waves are defined. The spectral dependence Δn=ne-no from the short and long-wavelength parts of isotropic wavelength λ0=485.7 nm (300 K) is determined. It is established that at λ>λ0 Δn is positive and at λ<λ0 Δn is negative. Wavelength λ0=485.7 nm shifts with decreasing temperature to short-wavelengths. The phase difference of ordinary and extraordinary light waves for λ>λ0 and λ<λ0 was determined. The band in reflection spectra observed at the isotropic wavelength has a small halfwidth (∽3-5 Å). Another isotropic wavelength was found in the short-wavelength region (433 nm) for crystals obtained by iodine transport method.

  5. Statistical characterization of short wind waves from stereo images of the sea surface

    NASA Astrophysics Data System (ADS)

    Mironov, A. S.; Yurovskaya, M. V.; Dulov, V. A.; Hauser, D.; GuéRin, C. A.

    2012-12-01

    We propose a methodology to extract short-scale statistical characteristics of the sea surface topography by means of stereo image reconstruction. The possibilities and limitations of the technique are discussed and tested on a data set acquired from an oceanographic platform at the Black Sea. A validation is made with simultaneous in situ measurements as well as results from the literature. We show that one- and two-point properties of the short-scale roughness can be well estimated without resorting to an interpolation procedure or an underlying surface model. We obtain the first cumulants of the probability distribution of small-scale elevations and slopes as well as related structure functions. We derive an empirical parametrization for the skewness function that is of primary importance in analytical scattering models from the sea surface.

  6. Application of ZnO nanoparticles to enhance photoluminescence in porous silicon and its possible utilization for improving the short wavelength quantum efficiency of silicon solar cell

    NASA Astrophysics Data System (ADS)

    Verma, Daisy; Kharkwal, Aneeta; Singh, S. N.; Singh, P. K.; Sharma, S. N.; Mehdi, S. S.; Husain, M.

    2014-11-01

    We have formed photoluminescent porous silicon (PS) layers and over which a ZnO layer (hereafter called ZnOPS layers) is deposited. We studied the photoluminescent properties of individual layers as well as the composite layer under excitation with 405 nm wavelength. Using the data of PL a theoretical analysis of a solar cell having such a composite layer of a given photoluminescent conversion efficiency ηPL on the front surface has been done. The condition of a photoluminescent composite layer (ZnOPS) useful for enhancing the spectral response of n+-p-p+ structured silicon solar cell has been identified.

  7. Spin wave excitation patterns generated by spin torque oscillators.

    PubMed

    Macià, F; Hoppensteadt, F C; Kent, A D

    2014-01-31

    Spin torque nano-oscillators (STNO) are nanoscale devices that can convert a direct current into short wavelength spin wave excitations in a ferromagnetic layer. We show that arrays of STNO can be used to create directional spin wave radiation similarly to electromagnetic antennas. Combining STNO excitations with planar spin waves also creates interference patterns. We show that these interference patterns are static and have information on the wavelength and phase of the spin waves emitted from the STNO. We describe a means of actively controlling spin wave radiation patterns with the direct current flowing through STNO, which is useful in on-chip communication and information processing and could be a promising technique for studying short wavelength spin waves in different materials. PMID:24398756

  8. Advances in Submillimeter Wave Semiconductor-Based Device Designs and Processes at JPL

    NASA Technical Reports Server (NTRS)

    Siegel, P. H.; Smith, R. P.; Martin, S. C.; Kim, M.; Bruston, J.; Erickson, N.; Humphrey, D.

    1997-01-01

    Planar submillimeter wave circuits are slowly replacing whisker-contacted devices at frequencies above 100 GHz, but in many cases the size constraints dictated by the short wavelengths found at high frequencies have not been adequately addressed.

  9. Search for Gravitational-wave Inspiral Signals Associated with Short Gamma-ray Bursts During LIGO's Fifth and Virgo's First Science Run

    NASA Astrophysics Data System (ADS)

    Abadie, J.; Abbott, B. P.; Abbott, R.; Accadia, T.; Acernese, F.; Adhikari, R.; Ajith, P.; Allen, B.; Allen, G.; Amador Ceron, E.; Amin, R. S.; Anderson, S. B.; Anderson, W. G.; Antonucci, F.; Aoudia, S.; Arain, M. A.; Araya, M.; Arun, K. G.; Aso, Y.; Aston, S.; Astone, P.; Aufmuth, P.; Aulbert, C.; Babak, S.; Baker, P.; Ballardin, G.; Ballmer, S.; Barker, D.; Barone, F.; Barr, B.; Barriga, P.; Barsotti, L.; Barsuglia, M.; Barton, M. A.; Bartos, I.; Bassiri, R.; Bastarrika, M.; Bauer, Th. S.; Behnke, B.; Beker, M. G.; Belletoile, A.; Benacquista, M.; Betzwieser, J.; Beyersdorf, P. T.; Bigotta, S.; Bilenko, I. A.; Billingsley, G.; Birindelli, S.; Biswas, R.; Bizouard, M. A.; Black, E.; Blackburn, J. K.; Blackburn, L.; Blair, D.; Bland, B.; Blom, M.; Boccara, C.; Bock, O.; Bodiya, T. P.; Bondarescu, R.; Bondu, F.; Bonelli, L.; Bonnand, R.; Bork, R.; Born, M.; Bose, S.; Bosi, L.; Braccini, S.; Bradaschia, C.; Brady, P. R.; Braginsky, V. B.; Brau, J. E.; Breyer, J.; Bridges, D. O.; Brillet, A.; Brinkmann, M.; Brisson, V.; Britzger, M.; Brooks, A. F.; Brown, D. A.; Budzyński, R.; Bulik, T.; Bullington, A.; Bulten, H. J.; Buonanno, A.; Burguet-Castell, J.; Burmeister, O.; Buskulic, D.; Buy, C.; Byer, R. L.; Cadonati, L.; Cagnoli, G.; Cain, J.; Calloni, E.; Camp, J. B.; Campagna, E.; Cannizzo, J.; Cannon, K. C.; Canuel, B.; Cao, J.; Capano, C. D.; Carbognani, F.; Cardenas, L.; Caudill, S.; Cavaglià, M.; Cavalier, F.; Cavalieri, R.; Cella, G.; Cepeda, C.; Cesarini, E.; Chalermsongsak, T.; Chalkley, E.; Charlton, P.; Chassande-Mottin, E.; Chatterji, S.; Chelkowski, S.; Chen, Y.; Chincarini, A.; Christensen, N.; Chua, S. S. Y.; Chung, C. T. Y.; Clark, D.; Clark, J.; Clayton, J. H.; Cleva, F.; Coccia, E.; Colacino, C. N.; Colas, J.; Colla, A.; Colombini, M.; Conte, R.; Cook, D.; Corbitt, T. R. C.; Cornish, N.; Corsi, A.; Coulon, J.-P.; Coward, D.; Coyne, D. C.; Creighton, J. D. E.; Creighton, T. D.; Cruise, A. M.; Culter, R. M.; Cumming, A.; Cunningham, L.; Cuoco, E.; Dahl, K.; Danilishin, S. L.; D'Antonio, S.; Danzmann, K.; Dattilo, V.; Daudert, B.; Davier, M.; Davies, G.; Daw, E. J.; Day, R.; Dayanga, T.; De Rosa, R.; DeBra, D.; Degallaix, J.; del Prete, M.; Dergachev, V.; DeSalvo, R.; Dhurandhar, S.; Di Fiore, L.; Di Lieto, A.; Emilio, M. Di Paolo; Di Virgilio, A.; Díaz, M.; Dietz, A.; Donovan, F.; Dooley, K. L.; Doomes, E. E.; Drago, M.; Drever, R. W. P.; Driggers, J.; Dueck, J.; Duke, I.; Dumas, J.-C.; Edgar, M.; Edwards, M.; Effler, A.; Ehrens, P.; Etzel, T.; Evans, M.; Evans, T.; Fafone, V.; Fairhurst, S.; Faltas, Y.; Fan, Y.; Fazi, D.; Fehrmann, H.; Ferrante, I.; Fidecaro, F.; Finn, L. S.; Fiori, I.; Flaminio, R.; Flasch, K.; Foley, S.; Forrest, C.; Fotopoulos, N.; Fournier, J.-D.; Franc, J.; Frasca, S.; Frasconi, F.; Frede, M.; Frei, M.; Frei, Z.; Freise, A.; Frey, R.; Fricke, T. T.; Friedrich, D.; Fritschel, P.; Frolov, V. V.; Fulda, P.; Fyffe, M.; Galimberti, M.; Gammaitoni, L.; Garofoli, J. A.; Garufi, F.; Gemme, G.; Genin, E.; Gennai, A.; Ghosh, S.; Giaime, J. A.; Giampanis, S.; Giardina, K. D.; Giazotto, A.; Goetz, E.; Goggin, L. M.; González, G.; Goßler, S.; Gouaty, R.; Granata, M.; Grant, A.; Gras, S.; Gray, C.; Greenhalgh, R. J. S.; Gretarsson, A. M.; Greverie, C.; Grosso, R.; Grote, H.; Grunewald, S.; Guidi, G. M.; Gustafson, E. K.; Gustafson, R.; Hage, B.; Hallam, J. M.; Hammer, D.; Hammond, G. D.; Hanna, C.; Hanson, J.; Harms, J.; Harry, G. M.; Harry, I. W.; Harstad, E. D.; Haughian, K.; Hayama, K.; Hayler, T.; Heefner, J.; Heitmann, H.; Hello, P.; Heng, I. S.; Heptonstall, A.; Hewitson, M.; Hild, S.; Hirose, E.; Hoak, D.; Hodge, K. A.; Holt, K.; Hosken, D. J.; Hough, J.; Howell, E.; Hoyland, D.; Huet, D.; Hughey, B.; Husa, S.; Huttner, S. H.; Ingram, D. R.; Isogai, T.; Ivanov, A.; Jaranowski, P.; Johnson, W. W.; Jones, D. I.; Jones, G.; Jones, R.; Ju, L.; Kalmus, P.; Kalogera, V.; Kandhasamy, S.; Kanner, J.; Katsavounidis, E.; Kawabe, K.; Kawamura, S.; Kawazoe, F.; Kells, W.; Keppel, D. G.; Khalaidovski, A.; Khalili, F. Y.; Khan, R.; Khazanov, E.; Kim, H.; King, P. J.; Kissel, J. S.; Klimenko, S.; Kokeyama, K.; Kondrashov, V.; Kopparapu, R.; Koranda, S.; Kowalska, I.; Kozak, D.; Kringel, V.; Krishnan, B.; Królak, A.; Kuehn, G.; Kullman, J.; Kumar, R.; Kwee, P.; Lam, P. K.; Landry, M.; Lang, M.; Lantz, B.; Lastzka, N.; Lazzarini, A.; Leaci, P.; Lei, M.; Leindecker, N.; Leonor, I.; Leroy, N.; Letendre, N.; Li, T. G. F.; Lin, H.; Lindquist, P. E.; Littenberg, T. B.; Lockerbie, N. A.; Lodhia, D.; Lorenzini, M.; Loriette, V.; Lormand, M.; Losurdo, G.; Lu, P.; Lubiński, M.; Lucianetti, A.; Lück, H.; Lundgren, A.; Machenschalk, B.; MacInnis, M.; Mageswaran, M.; Mailand, K.; Majorana, E.; Mak, C.; Maksimovic, I.; Man, N.; Mandel, I.; Mandic, V.; Mantovani, M.; Marchesoni, F.; Marion, F.; Márka, S.; Márka, Z.; Markosyan, A.; Markowitz, J.; Maros, E.; Marque, J.; Martelli, F.; Martin, I. W.; Martin, R. M.; Marx, J. N.; Mason, K.; Masserot, A.; Matichard, F.; Matone, L.; Matzner, R. A.; Mavalvala, N.; McCarthy, R.; McClelland, D. E.; McGuire, S. C.; McIntyre, G.; McKechan, D. J. A.; Mehmet, M.; Melatos, A.; Melissinos, A. C.; Mendell, G.; Menéndez, D. F.; Mercer, R. A.; Merill, L.; Meshkov, S.; Messenger, C.; Meyer, M. S.; Miao, H.; Michel, C.; Milano, L.; Miller, J.; Minenkov, Y.; Mino, Y.; Mitra, S.; Mitrofanov, V. P.; Mitselmakher, G.; Mittleman, R.; Miyakawa, O.; Moe, B.; Mohan, M.; Mohanty, S. D.; Mohapatra, S. R. P.; Moreau, J.; Moreno, G.; Morgado, N.; Morgia, A.; Mors, K.; Mosca, S.; Moscatelli, V.; Mossavi, K.; Mours, B.; MowLowry, C.; Mueller, G.; Mukherjee, S.; Mullavey, A.; Müller-Ebhardt, H.; Munch, J.; Murray, P. G.; Nash, T.; Nawrodt, R.; Nelson, J.; Neri, I.; Newton, G.; Nishida, E.; Nishizawa, A.; Nocera, F.; Ochsner, E.; O'Dell, J.; Ogin, G. H.; Oldenburg, R.; O'Reilly, B.; O'Shaughnessy, R.; Ottaway, D. J.; Ottens, R. S.; Overmier, H.; Owen, B. J.; Page, A.; Pagliaroli, G.; Palomba, C.; Pan, Y.; Pankow, C.; Paoletti, F.; Papa, M. A.; Pardi, S.; Parisi, M.; Pasqualetti, A.; Passaquieti, R.; Passuello, D.; Patel, P.; Pathak, D.; Pedraza, M.; Pekowsky, L.; Penn, S.; Peralta, C.; Perreca, A.; Persichetti, G.; Pichot, M.; Pickenpack, M.; Piergiovanni, F.; Pietka, M.; Pinard, L.; Pinto, I. M.; Pitkin, M.; Pletsch, H. J.; Plissi, M. V.; Poggiani, R.; Postiglione, F.; Prato, M.; Predoi, V.; Principe, M.; Prix, R.; Prodi, G. A.; Prokhorov, L.; Puncken, O.; Punturo, M.; Puppo, P.; Quetschke, V.; Raab, F. J.; Rabeling, D. S.; Radkins, H.; Raffai, P.; Raics, Z.; Rakhmanov, M.; Rapagnani, P.; Raymond, V.; Re, V.; Reed, C. M.; Reed, T.; Regimbau, T.; Rehbein, H.; Reid, S.; Reitze, D. H.; Ricci, F.; Riesen, R.; Riles, K.; Roberts, P.; Robertson, N. A.; Robinet, F.; Robinson, C.; Robinson, E. L.; Rocchi, A.; Roddy, S.; Röver, C.; Rolland, L.; Rollins, J.; Romano, J. D.; Romano, R.; Romie, J. H.; Rosińska, D.; Rowan, S.; Rüdiger, A.; Ruggi, P.; Ryan, K.; Sakata, S.; Salemi, F.; Sammut, L.; Sancho de la Jordana, L.; Sandberg, V.; Sannibale, V.; Santamaría, L.; Santostasi, G.; Saraf, S.; Sarin, P.; Sassolas, B.; Sathyaprakash, B. S.; Sato, S.; Satterthwaite, M.; Saulson, P. R.; Savage, R.; Schilling, R.; Schnabel, R.; Schofield, R.; Schulz, B.; Schutz, B. F.; Schwinberg, P.; Scott, J.; Scott, S. M.; Searle, A. C.; Seifert, F.; Sellers, D.; Sengupta, A. S.; Sentenac, D.; Sergeev, A.; Shapiro, B.; Shawhan, P.; Shoemaker, D. H.; Sibley, A.; Siemens, X.; Sigg, D.; Sintes, A. M.; Skelton, G.; Slagmolen, B. J. J.; Slutsky, J.; Smith, J. R.; Smith, M. R.; Smith, N. D.; Somiya, K.; Sorazu, B.; Stein, A. J.; Stein, L. C.; Steplewski, S.; Stochino, A.; Stone, R.; Strain, K. A.; Strigin, S.; Stroeer, A.; Sturani, R.; Stuver, A. L.; Summerscales, T. Z.; Sung, M.; Susmithan, S.; Sutton, P. J.; Swinkels, B.; Szokoly, G. P.; Talukder, D.; Tanner, D. B.; Tarabrin, S. P.; Taylor, J. R.; Taylor, R.; Thorne, K. A.; Thorne, K. S.; Thüring, A.; Titsler, C.; Tokmakov, K. V.; Toncelli, A.; Tonelli, M.; Torres, C.; Torrie, C. I.; Tournefier, E.; Travasso, F.; Traylor, G.; Trias, M.; Trummer, J.; Turner, L.; Ugolini, D.; Urbanek, K.; Vahlbruch, H.; Vajente, G.; Vallisneri, M.; van den Brand, J. F. J.; Van Den Broeck, C.; van der Putten, S.; van der Sluys, M. V.; Vass, S.; Vaulin, R.; Vavoulidis, M.; Vecchio, A.; Vedovato, G.; van Veggel, A. A.; Veitch, J.; Veitch, P. J.; Veltkamp, C.; Verkindt, D.; Vetrano, F.; Viceré, A.; Villar, A.; Vinet, J.-Y.; Vocca, H.; Vorvick, C.; Vyachanin, S. P.; Waldman, S. J.; Wallace, L.; Wanner, A.; Ward, R. L.; Was, M.; Wei, P.; Weinert, M.; Weinstein, A. J.; Weiss, R.; Wen, L.; Wen, S.; Wessels, P.; West, M.; Westphal, T.; Wette, K.; Whelan, J. T.; Whitcomb, S. E.; Whiting, B. F.; Wilkinson, C.; Willems, P. A.; Williams, H. R.; Williams, L.; Willke, B.; Wilmut, I.; Winkelmann, L.; Winkler, W.; Wipf, C. C.; Wiseman, A. G.; Woan, G.; Wooley, R.; Worden, J.; Yakushin, I.; Yamamoto, H.; Yamamoto, K.; Yeaton-Massey, D.; Yoshida, S.; Yu, P. P.; Yvert, M.; Zanolin, M.; Zhang, L.; Zhang, Z.; Zhao, C.; Zotov, N.; Zucker, M. E.; Zweizig, J.; LIGO Scientific Collaboration; Virgo Collaboration

    2010-06-01

    Progenitor scenarios for short gamma-ray bursts (short GRBs) include coalescenses of two neutron stars or a neutron star and black hole, which would necessarily be accompanied by the emission of strong gravitational waves. We present a search for these known gravitational-wave signatures in temporal and directional coincidence with 22 GRBs that had sufficient gravitational-wave data available in multiple instruments during LIGO's fifth science run, S5, and Virgo's first science run, VSR1. We find no statistically significant gravitational-wave candidates within a [ - 5, + 1) s window around the trigger time of any GRB. Using the Wilcoxon-Mann-Whitney U-test, we find no evidence for an excess of weak gravitational-wave signals in our sample of GRBs. We exclude neutron star-black hole progenitors to a median 90% confidence exclusion distance of 6.7 Mpc.

  10. Wavelength-selective planar holograms.

    PubMed

    Ford, J E; Xu, F; Fainman, Y

    1996-01-01

    Planar gratings and holograms are normally readout-wavelength insensitive. We show, however, that a binary phase surface-relief hologram can be transparent at one wavelength (lambda) yet diffract efficiently at another (lambda'), provided that the phase delay is an integer number of waves (e.g., 3) at lambda and a half-integer number of waves (e.g., 2.5) at lambda'. We fabricated a 7.9-microm-deep binary phase grating in BK7 glass that separates the standard telecommunications wavelengths, 1.3 and 1.55 microm, with 80% efficiency (neglecting Fresnel losses) and greater than 30:1 contrast. PMID:19865311

  11. Real-time simulation of combined short-wave and long-wave infrared vision on a head-up display

    NASA Astrophysics Data System (ADS)

    Peinecke, Niklas; Schmerwitz, Sven

    2014-05-01

    Landing under adverse weather conditions can be challenging, even if the airfields are well known to the pilots. This is true for civil as well as military aviation. Within the scope of this paper we concentrate especially on fog conditions. The work has been conducted within the project ALICIA. ALICIA is a research and development project co-funded by European Commission under the Seventh Framework Programme. ALICIA aims at developing new and scalable cockpit applications which can extend operations of aircraft in degraded conditions: All Conditions Operations. One of the systems developed is a head-up display that can display a generated symbology together with a raster-mode infrared image. We will detail how we implemented a real-time enabled simulation of a combined short-wave and long-wave infrared image for landing. A major challenge was to integrate several already existing simulation solutions, e.g., for visual simulation and sensors with the required data-bases. For the simulations DLRs in-house sensor simulation framework F3S was used, together with a commercially available airport model that had to be heavily modified in order to provide realistic infrared data. Special effort was invested for a realistic impression of runway lighting under foggy conditions. We will present results and sketch further improvements for future simulations.

  12. Active and passive infrared imager based on short-wave and mid-wave type-II superlattice dual-band detectors.

    PubMed

    Huang, Edward Kwei-wei; Haddadi, Abbas; Chen, Guanxi; Hoang, Anh-Minh; Razeghi, Manijeh

    2013-01-01

    A versatile dual-band detector capable of active and passive use is demonstrated using short-wave (SW) and mid-wave (MW) IR type-II superlattice photodiodes. A bilayer etch-stop scheme is introduced for back-side-illuminated detectors, which enhanced the external quantum efficiency both in the SWIR and MWIR spectral regions. Temperature-dependent dark current measurements of pixel-sized 27 μm detectors found the dark current density to be ~1 × 10(-5) A/cm(2) for the ~4.2 μm cutoff MWIR channel at 140 K. This corresponded to a reasonable imager noise equivalent difference in temperature of ~49 mK using F/2.3 optics and a 10 ms integration time (t(int)), which lowered to ~13 mK at 110 K using t(int)=30 ms, illustrating the potential for high-temperature operation. The SWIR channel was found to be limited by readout noise below 150 K. Excellent imagery from the dual-band imager exemplifying pixel coincidence is shown. PMID:23282825

  13. Measuring noise equivalent irradiance of a digital short-wave infrared imaging system using a broadband source to simulate the night spectrum

    NASA Astrophysics Data System (ADS)

    Green, John R.; Robinson, Timothy

    2015-05-01

    There is a growing interest in developing helmet-mounted digital imaging systems (HMDIS) for integration into military aircraft cockpits. This interest stems from the multiple advantages of digital vs. analog imaging such as image fusion from multiple sensors, data processing to enhance the image contrast, superposition of non-imaging data over the image, and sending images to remote location for analysis. There are several properties an HMDIS must have in order to aid the pilot during night operations. In addition to the resolution, image refresh rate, dynamic range, and sensor uniformity over the entire Focal Plane Array (FPA); the imaging system must have the sensitivity to detect the limited night light available filtered through cockpit transparencies. Digital sensor sensitivity is generally measured monochromatically using a laser with a wavelength near the peak detector quantum efficiency, and is generally reported as either the Noise Equivalent Power (NEP) or Noise Equivalent Irradiance (NEI). This paper proposes a test system that measures NEI of Short-Wave Infrared (SWIR) digital imaging systems using a broadband source that simulates the night spectrum. This method has a few advantages over a monochromatic method. Namely, the test conditions provide spectrum closer to what is experienced by the end-user, and the resulting NEI may be compared directly to modeled night glow irradiance calculation. This comparison may be used to assess the Technology Readiness Level of the imaging system for the application. The test system is being developed under a Cooperative Research and Development Agreement (CRADA) with the Air Force Research Laboratory.

  14. Intervalley scattering of electrons by short-wave phonons in (GaAs)8(AlAs)8(001) superlattice

    NASA Astrophysics Data System (ADS)

    Grinyaev, S. N.; Nikitina, L. N.; Tyuterev, V. G.

    2016-05-01

    Intervalley transitions induced by short-wavelength phonons in the conduction band of a superlattice (GaAs)8(AlAs)8(001) are investigated on the basis of the pseudopotential method and in the phenomenological model of interatomic forces. The main attention in the study centers around the transitions associated with the vibrations confined inside the layers. It is shown that the deformation potentials for the majority of intervalley transitions in a superlattice exceed the potentials of corresponding transitions in the binary crystals because of the localization of atomic displacements and wavefunctions of electrons inside the same layer of the superlattice. The bottom of the conduction band in (GaAs)8(AlAs)8(001) superlattice corresponds to the states Γ1(1), Z3, M1, M4 originating from sphalerite's X bar valleys localized in AlAs layers. Transitions between them are the most intense ones and they are caused by optical vibrations of Al atoms. "Semi-interface" vibrations being mainly localized in the one side of the GaAs layer are involved in the Γ1(2) -X1 , Γ1(2) -R1 and X1-Z1 transitions which are analogs of Γ bar - L bar transitions in binaries. The transitions Γ1(2) -M1 and Γ1(2) -M4 are governed by smooth parts of wave-functions and pseudopotentials. As a consequence their intensities are comparable with those of Γ bar - X bar sphalerite transitions in spite that these states are localized in the different layers of the superlattice.

  15. Improving Atmospheric Correction for Visible/Short Wave Infrared (VSWIR) Imaging Spectrometers with Iterative Fitting of Absorption By Three Phases of Water

    NASA Astrophysics Data System (ADS)

    Pennington, E. A.; Thompson, D. R.; Green, R. O.; Gao, B. C.

    2014-12-01

    Airborne imaging spectrometers like the Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) offer valuable insight into the Earth's terrestrial and ocean ecosystems, mineralogy, and land use. Estimating surface reflectance requires accounting for atmospheric absorption, which is sensitive to the local abundance of water vapor. Analysts typically estimate water vapor concentrations using the depths of absorption features, which can be inaccurate by up to 50% over surface features containing liquid water or ice. This can bias the retrieved water vapor maps and create atmospheric artifacts in reflectance spectra. A new retrieval method offers significant accuracy improvements over plant canopies or ice by estimating the path lengths of all three phases of water simultaneously, adjusting absorptions to best fit the measurement over a broader spectral interval. This paper assesses the remaining sources of error for the three-phase retrieval technique. We analyze retrievals for synthetic data when the 940 and 1140 nm wavelength features are fitted, for initial vapor path estimates ranging from 0 to ±50% accuracy. These tests indicate that most error comes from inaccuracy in the initial path estimate used to obtain vapor absorption coefficients. We evaluate a modified algorithm that uses multiple iterations to refine this estimate. Error is found to approach a constant value, demonstrating improved robustness to initialization conditions. We also assess the new iterative method using corrected AVIRIS data over various environments. The iterative method yields significantly better water vapor maps, reducing spurious correlations between vegetation canopy water and vapor estimates. The new iterative method offers accuracy improvements over traditional Visible/Short Wave Infrared (VSWIR) atmospheric correction methods, at modest computational cost.

  16. Impacts of aerosol scattering on the short-wave infrared satellite observations of CO2

    NASA Astrophysics Data System (ADS)

    Fan, M.; Chen, L.; Li, S.; Tao, J.; Su, L.; Zou, M.

    2014-12-01

    Atmospheric aerosols and carbon dioxide (CO2), as two key factors driving the global climate change, have earned enormous attention from scientist around the world. One challenge for the satellite measurements of CO2 using this SWIR wavelength range (~1.6μm) is the impact of multiple scattering by aerosols and cirrus. Since the rapid economic growth and associated increase in fossil fuel consumption have caused serious particulate pollution in many regions of China, remote sensing of CO2 using SWIR band in China needs to pay more attention to the scattering properties of aerosol particles and the multiple scattering. Considering the complexity of morphological and chemical properties, aerosol particles are grouped based on a large number of TEM/SEM images, and then their scattering properties at 1.6μm band are calculated by the T-matrix method and GMM method. In this study, the Monte Carlo method is used to solve the multiple scattering problem by simulating photons transport in the scattering media. We combined this multiple scattering model with the LBLRTM as a forward radiative transfer model for studying the impact of aerosol scattering on the satellite observations of CO2 using SWIR band. Finally, based on the GOCART aerosol component products, AERONET aerosol size distribution products, CALIPSO aerosol profile products, and MODIS aerosol optical depth and surface albedo products, the monthly variability of errors in CO2 concentrations over China were calculated and analyzed. The results indicate that CO2 concentrations are overestimated in western regions of China, especially in desert areas (a maximum of ~7.08%), and those are underestimated in eastern regions (a minimum of ~-6.9%).

  17. Spin-wave logic devices based on isotropic forward volume magnetostatic waves

    SciTech Connect

    Klingler, S. Pirro, P.; Brächer, T.; Leven, B.; Hillebrands, B.; Chumak, A. V.

    2015-05-25

    We propose the utilization of isotropic forward volume magnetostatic spin waves in modern wave-based logic devices and suggest a concrete design for a spin-wave majority gate operating with these waves. We demonstrate by numerical simulations that the proposed out-of-plane magnetized majority gate overcomes the limitations of anisotropic in-plane magnetized majority gates due to the high spin-wave transmission through the gate, which enables a reduced energy consumption of these devices. Moreover, the functionality of the out-of-plane majority gate is increased due to the lack of parasitic generation of short-wavelength exchange spin waves.

  18. Creating and Manipulating Vortices in Atomic Wave Functions with Short Electric Field Pulses

    NASA Astrophysics Data System (ADS)

    Ovchinnikov, S. Yu; Sternberg, J. B.; Macek, J. H.; Lee, Teck-Ghee; Schultz, D. R.

    2010-11-01

    We demonstrate the creation of vortices in the electronic probability density of an atom subject to short electric field pulses, how these vortices evolve and can be manipulated by varying the applied pulses, and that they persist to macroscopic distances in the spectrum of ejected electrons. This opens the possibility to use practical femtosecond or shorter laser pulses to create and manipulate these vortex quasiparticles at the atomic scale and observe them in the laboratory. Within a hydrodynamic interpretation we also show, since the Schrödinger equation is a particular instance of the Navier-Stokes equations, that for compressible fluids vortices can appear spontaneously and with a certain time delay, which is not expected to occur from the conventional point of view, illustrating applicability of the present study to vortex formation more broadly.

  19. Active and passive short-wave infrared and near-infrared imaging for horizontal and slant paths close to ground.

    PubMed

    Steinvall, Ove; Elmqvist, Magnus; Chevalier, Tomas; Gustafsson, Ove

    2013-07-10

    This paper investigates active and passive short-wave infrared (SWIR) imaging for slant paths close to ground. The main sensor, a gated SWIR camera, was collecting both passive and active images along a 2 km long path over an airfield and also from our rooftop laboratory looking over open fields. For some investigations we also used a gated system working in the near-infrared region and thermal as well as color CCD cameras. The sensor was elevated by a lift in steps from 1.6-13.5 m or placed in a rooftop laboratory 13 m above ground. Targets were resolution charts and man targets. The turbulence was measured along the path with anemometers and scintillometers. The image performance was evaluated by measurement of the image blur and also by performing observer perception tests. The results reveal a strong dependence on the sensor height especially during daytime. PMID:23852188

  20. The Short Wave Aerostat-Mounted Imager (SWAMI): A novel platform for acquiring remotely sensed data from a tethered balloon

    USGS Publications Warehouse

    Vierling, L.A.; Fersdahl, M.; Chen, X.; Li, Z.; Zimmerman, P.

    2006-01-01

    We describe a new remote sensing system called the Short Wave Aerostat-Mounted Imager (SWAMI). The SWAMI is designed to acquire co-located video imagery and hyperspectral data to study basic remote sensing questions and to link landscape level trace gas fluxes with spatially and temporally appropriate spectral observations. The SWAMI can fly at altitudes up to 2 km above ground level to bridge the spatial gap between radiometric measurements collected near the surface and those acquired by other aircraft or satellites. The SWAMI platform consists of a dual channel hyperspectral spectroradiometer, video camera, GPS, thermal infrared sensor, and several meteorological and control sensors. All SWAMI functions (e.g. data acquisition and sensor pointing) can be controlled from the ground via wireless transmission. Sample data from the sampling platform are presented, along with several potential scientific applications of SWAMI data. ?? 2006 Elsevier Inc. All rights reserved.

  1. REVISITING COINCIDENCE RATE BETWEEN GRAVITATIONAL WAVE DETECTION AND SHORT GAMMA-RAY BURST FOR THE ADVANCED AND THIRD GENERATION

    SciTech Connect

    Regimbau, T.; Siellez, K.; Meacher, D.; Gendre, B.; Boër, M.

    2015-01-20

    We use realistic Monte Carlo simulations including both gravitational-wave (GW) and short gamma-ray burst (sGRB) selection effects to revisit the coincident rate of binary systems composed of two neutron stars or a neutron star and a black hole. We show that the fraction of GW triggers that can be observed in coincidence with sGRBs is proportional to the beaming factor at z = 0, but increases with the distance until it reaches 100% at the GW detector horizon distance. When this is taken into account the rate is improved by a factor of three compared to the simple beaming factor correction. We provide an estimate of the performance future GRB detectors should achieve in order to fully exploit the potentiality of the planned third-generation GW antenna Einstein Telescope, and we propose a simple method to constrain the beaming angle of sGRBs.

  2. Measurements of snow and ice surface reflectance and penetration to short laser pulses at zero phase angles and 532 and 1064-nm wavelengths

    NASA Astrophysics Data System (ADS)

    Sun, X. X.; Cooper, J. W.; Hom, M. G.; Shuman, C. A.; Harding, D. J.

    2006-12-01

    Laser ranging has become a powerful tool in geological and geophysical studies of Earth, moon, and other celestial bodies. However, there have been uncertainties in difference between the surface reflectance measured passively using sunlight and those seen by the laser rangers with the laser beam and the receiver line of sight exactly co-aligned (i.e., at zero phase angle, or opposition). The surface reflectance at opposition can be several times higher than those measured at other phase angles, as we have observed from ICESat data. There have also been uncertainties in laser pulse broadening and the resulted range bias due to laser penetration and diffusions in translucent materials, such as snow and ice. Understanding of the optical properties of various Earth surface types at opposition will help to interpret the data and to improve the design of future airborne and space borne laser ranging instruments. We have performed a series of measurements of surface reflectance and penetration in the laboratory with the laser beam and the receiver at opposition in a laser ranger measurement configuration. The laser used in the measurement was a Microchip laser with 0.5-ns pulse width and single polarization at 532 or 1064-nm wavelength. The receiver consisted of a high-speed photodiode and a digital oscilloscope with a 13.5-ps equivalent sample interval and 8-bit pulse amplitude resolution. Measurements included surface reflectance, transmitted and echo laser pulse waveforms, and time-of-flight, in two polarizations and at both laser wavelengths. The samples tested included fresh and old snow blocks collected from New Hampshire, USA, and Greenland, fragile river edge ice, see ice press ridge, sand, natural salt, soil, and water. The reflectance measurements were calibrated against a set of spectral reflectance standards traceable to the US National Institute of Standards and Technology (NIST). The estimated measurement accuracy using our test setup was about 20-ps in pulse width and time-of-flight, 2% in reflectance measurement, and 4% in depolarization ratio measurement, which were more than adequate for the laser ranger design and data calibration purposes. The test results show no pulse broadening or trail within the 20-ps measurement accuracy in the received laser pulse waveform due to laser penetration effects at either 532 or 1064-nm laser wavelength and either polarization. The time-of-flight of the reflected pulse, defined by either centroid or Gaussian fit of the laser pulses, matched well to the distance from the sample surface to the reference plane measured with a yardstick. It appeared that the contribution from the laser light penetrated into the surface and back to the receiver through multiple scattering was negligible compared to the signal directly reflected from the surface. The detailed test setup, calibration, and test results will be described in this presentation.

  3. Volt-time characteristics of short air gaps under nonstandard lightning voltage waves

    SciTech Connect

    Chowdhuri, P.; Mishra, A.K.; McConnell, B.W.

    1996-02-01

    The breakdown voltage level of a dielectric system under a transient voltage of a given waveshape is not a constant parameter. When transient voltages of the same waveshape but of increasing amplitude are applied to a dielectric system, the dielectric breaks down at higher voltage levels at shorter time delays for the higher applied voltages. This characteristic, known as the volt-time or time-lag characteristic, significantly influences the insulation coordination of an electric power system. The volt-time characteristics of 5-cm long rod-plane and rod-rod air gaps were experimentally determined with five different waveshapes of the applied impulse voltage. The front time of the waves was varied from 25 ns to 10 {micro}s, and the time to half value was varied from 0.5 {micro}s to 100 {micro}s. The volt-time characteristics were also checked analytically using the concept of disruptive effect. The parameters for the disruptive effect were experimentally determined.

  4. Modeling short wave solar radiation using the JGrass-NewAge System

    NASA Astrophysics Data System (ADS)

    Formetta, G.; Rigon, R.; Chávez, J. L.; David, O.

    2012-12-01

    This paper presents two new modelling components based on the Object Modelling System v3 for the calculation of the shortwave incident radiation (Rsw\\downarrow) on complex topography settings, and the implementation of several ancillary tools. The first component, NewAGE-SwRB, accounts for slope, aspect, shadow and the topographical information of the sites, and use suitable parametrisation for obtaining the cloudless irradiance. A second component, NewAGE-DEC-MOD's is implemented to estimate the irradiance reduction due to the presence of clouds, according to three parameterisations. To obtain a working modelling composition, suitable to be compared with ground data at measurement stations, the two components are connected to a Kriging component, and, with the use of a further component NewAGE-V (verification package), the performance of modeled (Rsw\\downarrow) is quantitatively evaluated. The two components (and the various parametrisations they contain) are tested using the data from three basins catchments, and some simple verification test is made to assess the goodness of the methods used. The components are part of a larger system, JGrass-NewAGE, their input and outputs are given as geometrical objects immediately visualisable in a GIS (for instance the companion uDig), and can be used seamlessly with the various modelling solutions available in JGrass-NewAGE for the estimation of long wave radiation, evapotranspiration, and snow melting, as well as stand-alone components to just estimate shortwave radiation for various uses. The modularity of the approach is shown to be extensible to more accurate physical-statistical studies aimed to assess in deep the components performances and extends spatially their results, without the necessity of recoding any part of the component but just making using of connective scripts.

  5. Contribution of external parameter orthogonalisation for calibration transfer in short waves--near infrared spectroscopy application to gasoline quality.

    PubMed

    Amat-Tosello, S; Dupuy, N; Kister, J

    2009-05-29

    The octane number rating of a gasoline gives an indication of the gasoline performances, under various engine conditions. Two different ratings are included: Research Octane Number (RON) and Motor Octane Number (MON). The standard laboratory method for octane number determination is the knock engine method in which a gasoline is burned and its combustion characteristics compared to known standards. This method is time consuming and labor intensive, and provides no ability for real time control of production. NIR can be applied in real time directly in process monitoring or as a laboratory procedure. Near infrared spectra of gasoline samples were collected thanks to four different short wavelengths near infrared analysers, built with strictly the same technology. The aim of this study was to transfer the calibration built on one spectrometer to the other ones. We applied the external parameter orthogonalisation (EPO) correction to get rid of the apparatus influence on information contained in spectra. By this method, we managed to improve prediction values of two major gasolines' properties, i.e. Research and Motor Octane Number. PMID:19427453

  6. Attenuating Photostress and Glare Disability in Pseudophakic Patients through the Addition of a Short-Wave Absorbing Filter

    PubMed Central

    Hammond, Billy R.

    2015-01-01

    To evaluate the effects of filtering short wavelength light on visual performance under intense light conditions among pseudophakic patients previously implanted with a clear intraocular lens (IOL). This was a patient-masked, randomized crossover study conducted at 6 clinical sites in the United States between September 2013 and January 2014. One hundred fifty-four bilaterally pseudophakic patients were recruited. Photostress recovery time and glare disability thresholds were measured with clip-on blue-light-filtering and placebo (clear; no blue-light filtration) glasses worn over patients' habitual correction. Photostress recovery time was quantified as the time necessary to regain sight of a grating target after intense light exposure. Glare disability threshold was assessed as the intensity of a white-light annulus necessary to obscure a central target. The order of filter used and test eye were randomized across patients. Photostress recovery time and glare disability thresholds were significantly improved (both P < 0.0001) when patients used blue-light-filtering glasses compared with clear, nonfiltering glasses. Compared with a nonfiltering placebo, adding a clip-on blue-absorbing filter to the glasses of pseudophakic patients implanted with clear IOLs significantly increased their ability to cope with glare and to recover normal viewing after an intensive photostress. This result implies that IOL designs with blue-light-filtering characteristics may be beneficial under intense light conditions. PMID:25838942

  7. Dynamics of shock waves and cavitation bubbles in bilinear elastic-plastic media, and the implications to short-pulsed laser surgery

    NASA Astrophysics Data System (ADS)

    Brujan, E.-A.

    2005-01-01

    The dynamics of shock waves and cavitation bubbles generated by short laser pulses in water and elastic-plastic media were investigated theoretically in order to get a better understanding of their role in short-pulsed laser surgery. Numerical simulations were performed using a spherical model of bubble dynamics which include the elastic-plastic behaviour of the medium surrounding the bubble, compressibility, viscosity, density and surface tension. Breakdown in water produces a monopolar acoustic signal characterized by a compressive wave. Breakdown in an elastic-plastic medium produces a bipolar acoustic signal, with a leading positive compression wave and a trailing negative tensile wave. The calculations revealed that consideration of the tissue elasticity is essential to describe the bipolar shape of the shock wave emitted during optical breakdown. The elastic-plastic response of the medium surrounding the bubble leads to a significant decrease of the maximum size of the cavitation bubble and pressure amplitude of the shock wave emitted during bubble collapse, and shortening of the oscillation period of the bubble. The results are discussed with respect to collateral damage in short-pulsed laser surgery.

  8. Nonlinear saturation spectra of electric fields and density fluctuations in drift wave turbulence

    NASA Technical Reports Server (NTRS)

    Kelley, M. C.

    1982-01-01

    The detection of drift waves in the nonlinear evolution of a space plasma process driven at long wavelengths is considered, adducing measurements of the electric field and density fluctuation power spectra as evidence. Since the driving mechanism is clearly at long wavelengths, the detection of drift waves suggests that they may play an important role in the transfer of wave energy from long to short wavelengths in a low beta plasma. The saturated spectral density is compared with theoretical results in order to estimate the anomalous diffusion rate. The observed spectral form and amplitude is in excellent agreement with drift wave predictions.

  9. Epitaxial seeded growth of rare-earth nanocrystals with efficient 800 nm near-infrared to 1525 nm short-wavelength infrared downconversion photoluminescence for in vivo bioimaging.

    PubMed

    Wang, Rui; Li, Xiaomin; Zhou, Lei; Zhang, Fan

    2014-11-01

    Novel β-NaGdF4/Na(Gd,Yb)F4:Er/NaYF4:Yb/NaNdF4:Yb core/shell 1/shell 2/shell 3 (C/S1/S2/S3) multi-shell nanocrystals (NCs) have been synthesized and used as probes for in vivo imaging. They can be excited by near-infrared (800 nm) radiation and emit short-wavelength infrared (SWIR, 1525 nm) radiation. Excitation at 800 nm falls into the "biological transparency window", which features low absorption by water and low heat generation and is considered to be the ideal excitation wavelength with the least impact on biological tissues. After coating with phospholipids, the water-soluble NCs showed good biocompatibility and low toxicity. With efficient SWIR emission at 1525 nm, the probe is detectable in tissues at depths of up to 18 mm with a low detection threshold concentration (5 nM for the stomach of nude mice and 100 nM for the stomach of SD rats). These results highlight the potential of the probe for the in vivo monitoring of areas that are otherwise difficult to analyze. PMID:25196421

  10. Genomic organization of duplicated short wave-sensitive and long wave-sensitive opsin genes in the green swordtail, Xiphophorus helleri

    PubMed Central

    2010-01-01

    Background Long wave-sensitive (LWS) opsin genes have undergone multiple lineage-specific duplication events throughout the evolution of teleost fishes. LWS repertoire expansions in live-bearing fishes (family Poeciliidae) have equipped multiple species in this family with up to four LWS genes. Given that color vision, especially attraction to orange male coloration, is important to mate choice within poeciliids, LWS opsins have been proposed as candidate genes driving sexual selection in this family. To date the genomic organization of these genes has not been described in the family Poeciliidae, and little is known about the mechanisms regulating the expression of LWS opsins in any teleost. Results Two BAC clones containing the complete genomic repertoire of LWS opsin genes in the green swordtail fish, Xiphophorus helleri, were identified and sequenced. Three of the four LWS loci identified here were linked in a tandem array downstream of two tightly linked short wave-sensitive 2 (SWS2) opsin genes. The fourth LWS opsin gene, containing only a single intron, was not linked to the other three and is the product of a retrotransposition event. Genomic and phylogenetic results demonstrate that the LWS genes described here share a common evolutionary origin with those previously characterized in other poeciliids. Using qualitative RT-PCR and MSP we showed that each of the LWS and SWS2 opsins, as well as three other cone opsin genes and a single rod opsin gene, were expressed in the eyes of adult female and male X. helleri, contributing to six separate classes of adult retinal cone and rod cells with average λmax values of 365 nm, 405 nm, 459 nm, 499 nm, 534 nm and 568 nm. Comparative genomic analysis identified two candidate teleost opsin regulatory regions containing putative CRX binding sites and hormone response elements in upstream sequences of LWS gene regions of seven teleost species, including X. helleri. Conclusions We report the first complete genomic description of LWS and SWS2 genes in poeciliids. These data will serve as a reference for future work seeking to understand the relationship between LWS opsin genomic organization, gene expression, gene family evolution, sexual selection and speciation in this fish family. PMID:20353595

  11. The parallel-antiparallel signal difference in double-wave-vector diffusion-weighted MR at short mixing times: A phase evolution perspective

    NASA Astrophysics Data System (ADS)

    Finsterbusch, Jürgen

    2011-01-01

    Experiments with two diffusion weightings applied in direct succession in a single acquisition, so-called double- or two-wave-vector diffusion-weighting (DWV) experiments at short mixing times, have been shown to be a promising tool to estimate cell or compartment sizes, e.g. in living tissue. The basic theory for such experiments predicts that the signal decays for parallel and antiparallel wave vector orientations differ by a factor of three for small wave vectors. This seems to be surprising because in standard, single-wave-vector experiments the polarity of the diffusion weighting has no influence on the signal attenuation. Thus, the question how this difference can be understood more pictorially is often raised. In this rather educational manuscript, the phase evolution during a DWV experiment for simple geometries, e.g. diffusion between parallel, impermeable planes oriented perpendicular to the wave vectors, is considered step-by-step and demonstrates how the signal difference develops. Considering the populations of the phase distributions obtained, the factor of three between the signal decays which is predicted by the theory can be reproduced. Furthermore, the intermediate signal decay for orthogonal wave vector orientations can be derived when investigating diffusion in a box. Thus, the presented “phase gymnastics” approach may help to understand the signal modulation observed in DWV experiments at short mixing times.

  12. Towards Removing the Southern Ocean Short Wave Bias in HadGEM3: Mixed-phase Cloud Improvements.

    NASA Astrophysics Data System (ADS)

    Field, P.; Furtado, K.

    2014-12-01

    Many IPCC models suffer from significant Sea Surface Temperature (SST) biases in the Southern Ocean that adversely affects the representation of the cryosphere and global circulation in these models. Evidence suggests that much of this error is linked to Short Wave (SW) radiation, sensible and latent heat biases. Flaws in the representation of clouds and a deficit of supercooled liquid water in mixed-phase clouds are suspected as a likely source of the SW error. A physically based method that uses subgrid turbulence to control a new liquid production term has been developed. Comparisons between theory, based on a stochastic differential equation used to represent supersaturation fluctuations, and decametre resolution Large Eddy Simulations will be presented. An implementation of this approach in a GCM shows an increased prevalance of supercooled liquid water and a reduction in the magnitude of the Southern Ocean SW bias. To conclude, we will summarize the complete package of changes that have been made to tackle the Southern Ocean SST bias in a physically meaningful way.

  13. Satellite-based forest monitoring: spatial and temporal forecast of growing index and short-wave infrared band.

    PubMed

    Bayr, Caroline; Gallaun, Heinz; Kleb, Ulrike; Kornberger, Birgit; Steinegger, Martin; Winter, Martin

    2016-01-01

    For detecting anomalies or interventions in the field of forest monitoring we propose an approach based on the spatial and temporal forecast of satellite time series data. For each pixel of the satellite image three different types of forecasts are provided, namely spatial, temporal and combined spatio-temporal forecast. Spatial forecast means that a clustering algorithm is used to group the time series data based on the features normalised difference vegetation index (NDVI) and the short-wave infrared band (SWIR). For estimation of the typical temporal trajectory of the NDVI and SWIR during the vegetation period of each spatial cluster, we apply several methods of functional data analysis including functional principal component analysis, and a novel form of random regression forests with online learning (streaming) capability. The temporal forecast is carried out by means of functional time series analysis and an autoregressive integrated moving average model. The combination of the temporal forecasts, which is based on the past of the considered pixel, and spatial forecasts, which is based on highly correlated pixels within one cluster and their past, is performed by functional data analysis, and a variant of random regression forests adapted to online learning capabilities. For evaluation of the methods, the approaches are applied to a study area in Germany for monitoring forest damages caused by wind-storm, and to a study area in Spain for monitoring forest fires. PMID:27087034

  14. Short term analgesic effect of extracorporeal shock wave therapy in horses with proximal palmar metacarpal/plantar metatarsal pain.

    PubMed

    Imboden, Isabel; Waldern, Nina M; Wiestner, Thomas; Lischer, Christoph J; Ueltschi, Gottlieb; Weishaupt, Michael A

    2009-01-01

    Extracorporeal shock wave therapy (ESWT) is an accepted form of treatment for chronic cases of proximal suspensory desmitis (PSD). Subjective evaluation of horses shortly after being treated with ESWT has led clinicians to comment on an immediate reduction in lameness. This study aimed to evaluate the analgesic effect of ESWT on 16 horses with PSD or PSD-like pain in a fore- or hindlimb. To objectively assess lameness, gait analysis was performed on an instrumented treadmill before and 6, 24, 48 and 72h after ESWT of the origin of the suspensory ligament and the results compared to the effects of local anaesthesia. Stride frequency, stance duration, vertical impulse and peak vertical force were determined. Thermographic imaging and evaluation of skin sensitivity of the treated area were carried out before and after ESWT in the same interval as gait analysis. The results showed that there were no significant improvements in the investigated parameters at any time after ESWT; however, in horses with affected forelimbs the contralateral weightbearing asymmetry decreased significantly 72h after ESWT. Neither skin sensitivity nor thermographic imaging revealed changes that could be attributed to ESWT. PMID:18069025

  15. CXCR-4 Targeted, Short Wave Infrared (SWIR) Emitting Nanoprobes for Enhanced Deep Tissue Imaging and Micrometastatic Cancer Lesion Detection.

    PubMed

    Zevon, Margot; Ganapathy, Vidya; Kantamneni, Harini; Mingozzi, Marco; Kim, Paul; Adler, Derek; Sheng, Yang; Tan, Mei Chee; Pierce, Mark; Riman, Richard E; Roth, Charles M; Moghe, Prabhas V

    2015-12-01

    Realizing the promise of precision medicine in cancer therapy depends on identifying and tracking cancerous growths to maximize treatment options and improve patient outcomes. This goal of early detection remains unfulfilled by current clinical imaging techniques that fail to detect lesions due to their small size and suborgan localization. With proper probes, optical imaging techniques can overcome this by identifying the molecular phenotype of tumors at both macroscopic and microscopic scales. In this study, the first use of nanophotonic short wave infrared technology is proposed to molecularly phenotype small lesions for more sensitive detection. Here, human serum albumin encapsulated rare-earth nanoparticles (ReANCs) with ligands for targeted lesion imaging are designed. AMD3100, an antagonist to CXCR4 (a classic marker of cancer metastasis) is adsorbed onto ReANCs to form functionalized ReANCs (fReANCs). fReANCs are able to preferentially accumulate in receptor positive lesions when injected intraperitoneally in a subcutaneous tumor model. fReANCs can also target subtissue microlesions at a maximum depth of 10.5 mm in a lung metastatic model of breast cancer. Internal lesions identified with fReANCs are 2.25 times smaller than those detected with ReANCs. Thus, an integrated nanoprobe detection platform is presented, which allows target-specific identification of subtissue cancerous lesions. PMID:26514367

  16. Diode-pumped continuous-wave dual-wavelength c-cut Pr3+:LiYF4 laser at 696 and 719  nm.

    PubMed

    Luo, Saiyu; Xu, Bin; Cui, Shengwei; Chen, Han; Cai, Zhiping; Xu, Huiying

    2015-12-01

    A continuous-wave, InGaN-LD-pumped dual-wavelength laser is demonstrated with simultaneous emission at 696 (P30→F33) and 719 nm (P30→F34) using a c-cut Pr3+:LiYF4, for the first time to our knowledge. Maximum output power of 102 mW at these two wavelengths is achieved with slope efficiency of about 15.6% with respect to the absorbed pump power. The beam propagation factors in x and y directions are measured to be 1.50 and 1.32, respectively. PMID:26836659

  17. Fabrication of all-solid AsSe2-As2S5 microstructured optical fiber with two zero-dispersion wavelengths for generation of mid-infrared dispersive waves

    NASA Astrophysics Data System (ADS)

    Cheng, Tonglei; Hoang Tuan, Tong; Liu, Lai; Xue, Xiaojie; Matsumoto, Morio; Tezuka, Hiroshige; Suzuki, Takenobu; Ohishi, Yasutake

    2016-02-01

    We design and fabricate an all-solid chalcogenide microstructured optical fiber (MOF) with four rods in the cladding, in order to generate mid-infrared (MIR) dispersive waves (DWs). The high-index background is made of AsSe2 glass, and the four low-index rods are made of As2S5 glass. This MOF has two zero-dispersive wavelengths: ˜3,720 and 4,230 nm. The propagation loss is ˜1.9 dB/m at 2,000 nm, and the nonlinear coefficient is ˜4 × 103 km-1 W-1 at 3,000 nm. Using a pulse of ˜80 MHz and ˜200 fs emitted from an optical parametric oscillator as the pump source, the resulting MIR DWs are investigated at different pump wavelengths.

  18. [Study on phase-matching of four-wave mixing spectrum in photonic crystal fiber].

    PubMed

    Liu, Xiao-xu; Wang, Shu-tao; Zhao, Xing-tao; Chen, Shuang; Zhou, Gui-yao; Wu, Xi-jun; Li, Shu-guang; Hou, Lan-Tian

    2014-06-01

    In the present paper, the four-wave mixing principle of fiber was analyzed, and the high-gain phase-matching conditions were shown. The nonlinear coefficient and dispersion characteristics of photonic crystal fibers were calculated by multipole method. The phase mismatch characteristics of fibers with multiple zero-dispersion wavelengths were analyzed for the first time. The changing rules of phase matching wavelength with the pump wavelength and the pump power were obtained, and the phase matching curves were shown. The characteristics of phase matching wavelengths for different dispersion curves were analyzed. There are four new excitation wavelengths of four-wave mixing spectrum in two zero-dispersion wavelength photonic crystal fiers. Four-wave mixing spectroscopy of photonic crystal fibers with two zero-dispersion wavelengths was obtained in the experi-ent, which is consistent with the theoretical analysis, and verified the reliability of the phase matching theory. The fiber with multiple zero-dispersion wavelengths can create a ricbhphase-matching topology, excite more four-wave mixing wavelengths, ena-ling enhanced control over the spectral locations of the four-wave mixing and resonant-radiation bands emitted by solitons and short pulses. These provide theoretical guidance for photonic crystal fiber wavelength conversion and supercontinoum generation based on four-wave mixing. PMID:25358145

  19. Experimental determination of short- and long-wave dust radiative effects in the Central Mediterranean and comparison with model results

    NASA Astrophysics Data System (ADS)

    Romano, S.; Burlizzi, P.; Perrone, M. R.

    2016-05-01

    Downward and upward irradiance measurements, in the short-wave (SW) and long-wave (LW) spectral range, have been used in combination with simultaneous aerosol optical depths (AODs) to experimentally determine the instantaneous and clear-sky aerosol Direct Radiative Forcing (DRF) at the surface, during a desert dust outbreak which affected the Central Mediterranean from 9 to 13 July 2012. AODs were retrieved from AERONET (AErosol RObotic NETwork) sun/sky photometer measurements collocated in space and time. The importance of downward and upward radiative flux measurements to properly account for both the surface albedo dependence on the solar zenith angle, and the land surface temperature (TLS) has been highlighted. Measured radiative fluxes were in reasonable agreement with the CERES (Clouds and the Earth's Radiant Energy System) and AERONET corresponding ones collocated in space and time. SW and LW downward fluxes at the surface decreased up to 9% and increased up to 13%, respectively, as a consequence of a factor 5 increase of the AOD at 675 nm (AOD675). This is due to the cooling and warming effect of desert dust in the SW and LW spectral range, respectively. In fact, we have also found that the TLS increased at a rate of about 250 K per unit increase of the AOD675. The aerosol DRF at the surface varied from - 8 to - 74 W m- 2 and from + 1.2 to + 9.6 W m- 2 in the SW and LW spectral domains, respectively. In particular, we have found that the LW-DRF on average offsets 14% of the related SW component. It is shown that a two-stream radiative transfer model can reproduce the experimental findings at the surface by replacing the refractive indices typical of dust particles with the ones obtained for a mixture made of dust and soot particles. The dust contamination by anthropogenic particles during its transport to the monitoring site located several hundred kilometers away from the source region was responsible for this last result. We have also found by model simulations that the LW-DRF increased linearly with TLS both at the surface and at the top of the atmosphere.

  20. Hydromagnetic wave heating of low density interstellar gas

    NASA Technical Reports Server (NTRS)

    Zweibel, Ellen G.; Ferriere, Katia M.; Shull, J. Michael

    1988-01-01

    The origin of the observed wave spectrum for hot gas in the ISM is considered theoretically. The governing equations for the generation, propagation, and dissipation of compressive waves are reviewed, and particular attention is given to the heating of warm neutral gas and the implications for radio-wave scattering. It is shown that little power from interactions between SN shocks and hot coronal gas reaches short wavelengths, and that scintillation probably does not originate in a warm weakly ionized gas.

  1. Sparse short-distance connections enhance calcium wave propagation in a 3D model of astrocyte networks

    PubMed Central

    Lallouette, Jules; De Pittà, Maurizio; Ben-Jacob, Eshel; Berry, Hugues

    2014-01-01

    Traditionally, astrocytes have been considered to couple via gap-junctions into a syncytium with only rudimentary spatial organization. However, this view is challenged by growing experimental evidence that astrocytes organize as a proper gap-junction mediated network with more complex region-dependent properties. On the other hand, the propagation range of intercellular calcium waves (ICW) within astrocyte populations is as well highly variable, depending on the brain region considered. This suggests that the variability of the topology of gap-junction couplings could play a role in the variability of the ICW propagation range. Since this hypothesis is very difficult to investigate with current experimental approaches, we explore it here using a biophysically realistic model of three-dimensional astrocyte networks in which we varied the topology of the astrocyte network, while keeping intracellular properties and spatial cell distribution and density constant. Computer simulations of the model suggest that changing the topology of the network is indeed sufficient to reproduce the distinct ranges of ICW propagation reported experimentally. Unexpectedly, our simulations also predict that sparse connectivity and restriction of gap-junction couplings to short distances should favor propagation while long–distance or dense connectivity should impair it. Altogether, our results provide support to recent experimental findings that point toward a significant functional role of the organization of gap-junction couplings into proper astroglial networks. Dynamic control of this topology by neurons and signaling molecules could thus constitute a new type of regulation of neuron-glia and glia-glia interactions. PMID:24795613

  2. CXCR-4 Targeted, Short Wave Infrared (SWIR) Emitting Nanoprobes for Enhanced Deep Tissue Imaging and Micrometastatic Lesion Detection

    PubMed Central

    Zevon, Margot; Ganapathy, Vidya; Kantamneni, Harini; Mingozzi, Marco; Kim, Paul; Adler, Derek; Sheng, Yang; Tan, Mei Chee; Pierce, Mark; Riman, Richard E.; Roth, Charles M.; Moghe, Prabhas V.

    2016-01-01

    Realizing the promise of precision medicine in cancer therapy depends on identifying and tracking of cancerous growths in order to maximize treatment options and improve patient outcomes. However, this goal of early detection remains unfulfilled by current clinical imaging techniques that fail to detect diseased lesions, due to their small size and sub-organ localization. With proper probes, optical imaging techniques can overcome this limitation by identifying the molecular phenotype of tumors at both macroscopic and microscopic scales. In this study, we propose the first use of nanophotonic short wave infrared technology to molecularly phenotype small sub-surface lesions for more sensitive detection and improved patient outcomes. To this end, we designed human serum albumin encapsulated rare-earth (RE) nanoparticles (ReANCs)[1, 2] with ligands for targeted lesion imaging. AMD3100, an antagonist to CXCR4 (a chemokine receptor involved in cell motility and a classic marker of cancer metastasis) was adsorbed onto ReANCs to form functionalized ReANCs (fReANCs). Functionalized nanoparticles were able to discriminate and preferentially accumulate in receptor positive lesions when injected intraperitoneally in a subcutaneous tumor model. Additionally, fReANCs, administered intravenously, were able to target sub-tissue tumor micro-lesions, at a maximum depth of 10.5 mm, in a lung metastatic model of breast cancer. Internal lesions identified with fReANCs were 2.25 times smaller than those detected with unfunctionalized ReANCs (p < .01) with the smallest tumor being 18.9 mm3. Thus, we present an integrated nanoprobe detection platform that allows target-specific identification of sub-tissue cancerous lesions. PMID:26514367

  3. A simple 2 W continuous-wave laser system for trapping ultracold metastable helium atoms at the 319.8 nm magic wavelength

    NASA Astrophysics Data System (ADS)

    Rengelink, R. J.; Notermans, R. P. M. J. W.; Vassen, W.

    2016-05-01

    High-precision spectroscopy on the 2 ^3 S → 2 ^1 S transition is possible in ultracold optically trapped helium, but the accuracy is limited by the ac-Stark shift induced by the optical dipole trap. To overcome this problem, we have built a trapping laser system at the predicted magic wavelength of 319.8 nm. Our system is based on frequency conversion using commercially available components and produces over 2 W of power at this wavelength. With this system, we show trapping of ultracold atoms, both thermal (~0.2 μk) and in a Bose-Einstein condensate, with a trap lifetime of several seconds, mainly limited by off-resonant scattering.

  4. A study of doping influences on transmission of large-diameter gallium antimonide substrates for long-wave (LWIR) to very long wavelength (VLWIR) infra-red applications

    NASA Astrophysics Data System (ADS)

    Martinez, Rebecca; Tybjerg, Marius; Smith, Brian; Mowbray, Andrew; Furlong, Mark J.

    2015-06-01

    Gallium antimonide (GaSb) is an important Group III-V compound semiconductor for infra-red (IR) photodetectors used in sensing and imaging applications. Operating in the mid (3-5 μm) to long wavelength region (8-12 μm) of the IR spectrum, the application of GaSb detectors is extensive, encompassing military, industrial, medical and environmental uses. A significant developing technology for GaSb based detectors are those effective in the very long wavelength (VLWIR) infra-red region (13 μm and beyond) which are advantageous in space and stealth based applications which necessitate high operating temperatures. In this study different doping levels of GaSb are considered and the IR transmission spectra examined by Fourier Transform IR analysis. GaSb n-type doped material consistent in delivering long to very long wavelength transmission is demonstrated which is preferable to p-type material which requires backside thinning for IR transmission. Czochralski (Cz) grown GaSb wafers are assessed for electrical quality and uniformity results, on Hall mobility, resistivity and carrier level reported. Results of this work will establish the carrier concentration that ultimately results in high transparency substrates. In summary enhancements in IR transmission will be shown to be achieved in GaSb bulk crystals by tellurium (Te) compensation.

  5. Physics of short-wavelength-laser design

    SciTech Connect

    Hagelstein, P.L.

    1981-01-01

    The physics and design of vuv and soft x-ray lasers pumped by ICF class high intensity infrared laser drivers are described (for example, the SHIVA laser facility at LLNL). Laser design and physics issues are discussed in the case of a photoionization pumping scheme involving Ne II and line pumping schemes involving H-like and He-like neon.

  6. Short wavelength striations on expanding plasma clouds

    NASA Technical Reports Server (NTRS)

    Winske, D.; Gary, S. P.

    1990-01-01

    The present evaluation of current understanding of the growth and evolution of less-than-1 ion gyroradius 'flute modes' on a plasma as it expands across and ambient magnetic field notes that the mechanism by which the instability is generated, and its approximate linear theory (encompassing nonlocal, finite-beta, and collisional effects), have reached a satisfactory degree of development. AMPTE Ba releases have been the bases of most of the observational studies. Substantial progress is also noted in the development of a nonlinear mode-coupling theory which can resolve remaining differences between theory and observation.

  7. Plants and the Solar System Organized by Unique Longitudinal Waves.

    NASA Astrophysics Data System (ADS)

    Wagner, Orvin E.

    2001-03-01

    From my experimental work and measurements, covering more than 20 years, I hypothesize that the larger systems of our universe like stars and galaxies emit unique long wavelength waves which drive other oscillating systems. Operating frequencies depend on the dimensions of the oscillator so long wavelength waves convert to short wavelengths of the order of the dimensions of the driven system. For example, the sun emits large amplitude wavelengths of the order of dimensions of the sun. The waves automatically become standing waves in a receiving system because of the reaction of the vacuum. These waves tend to organize the system that contains them. For example plants, which seem to be organized by these waves, operate with more than 100 different wavelengths having to do with a plants interaction with gravity, macroscopic and microscopic plant growth, and most other features of plant growth and development. The waves discussed here appear to penetrate everything but still can be reflected and guided. Plants appear to be unique wave guides for these waves. See the Wagner web site.

  8. Theoretical estimation and experimental design of high-intensity far-infrared to MM-wave coherent synchrotron radiation generated by short electron bunches at BFEL

    NASA Astrophysics Data System (ADS)

    Junbiao, Zhu; Yonggui, Li; Jialin, Xie

    2000-06-01

    Broadband continuous and high-intensity coherent synchrotron radiation (CSR) emitted from 4 ps electron bunches provided by the 30 MeV RF linac of Beijing FEL is analyzed and numerically calculated using an exact series expansion for the infinite integral of fractional modified Bessel function. CSR in the mm-wave and far-IR to mm-wave regions can be respectively generated by directly using these bunches and by applying those ones compressed to ≤=1 ps. The CSR powers, approximately as 10 8-10 9 times as the SR ones, in the range from several hundred microwatts to milliwatts are dependent on chosen electron density distribution, wavelength range, and gathering angle. The power produced by rectangular bunches is greater than that generated by Gaussian ones. The shorter the bunch, the stronger the produced CSR, the greater the energy concentrated to the far-IR end. Experiments to generate CSR and measure the bunch length are designed.

  9. Theory of waves incoherently scattered

    NASA Technical Reports Server (NTRS)

    Bauer, P.

    1974-01-01

    Electromagnetic waves impinging upon a plasma at frequencies larger than the plasma frequency, suffer weak scattering. The scattering arises from the existence of electron density fluctuations. The received signal corresponds to a particular spatial Fourier component of the fluctuations, the wave vector of which is a function of the wavelength of the radiowave. Wavelengths short with respect to the Debye length of the medium relate to fluctuations due to non-interacting Maxwellian electrons, while larger wavelengths relate to fluctuations due to collective Coulomb interactions. In the latter case, the scattered signal exhibits a spectral distribution which is characteristic of the main properties of the electron and ion gases and, therefore, provides a powerful diagnosis of the state of the ionosphere.

  10. Dispersion equation of gravito-MHD waves

    NASA Astrophysics Data System (ADS)

    Jovanović, Gordana

    2016-03-01

    We derive the dispersion equation for gravito-MHD waves in an isothermal, gravitationally stratified plasma with a horizontal inhomogeneous magnetic field. In the present model the sound and the Alfvén speeds are constant. It is known that in this model analytical solutions can be obtained for linearized perturbations. There are three modes propagating in the considered plasma: the fast, the slow and the Alfvén mode, all modified by gravity. In the extreme short wavelength limit, these waves propagate in a locally uniform plasma. The waves with larger wavelengths will be affected by the nonuniformity of the medium resulting from the action of gravitational force ρg. In the case without magnetic field these waves become gravito-acoustic waves.

  11. Triggering collapse of the presolar dense cloud core and injecting short-lived radioisotopes with a shock wave. III. Rotating three-dimensional cloud cores

    SciTech Connect

    Boss, Alan P.; Keiser, Sandra A.

    2014-06-10

    A key test of the supernova triggering and injection hypothesis for the origin of the solar system's short-lived radioisotopes is to reproduce the inferred initial abundances of these isotopes. We present here the most detailed models to date of the shock wave triggering and injection process, where shock waves with varied properties strike fully three-dimensional, rotating, dense cloud cores. The models are calculated with the FLASH adaptive mesh hydrodynamics code. Three different outcomes can result: triggered collapse leading to fragmentation into a multiple protostar system; triggered collapse leading to a single protostar embedded in a protostellar disk; or failure to undergo dynamic collapse. Shock wave material is injected into the collapsing clouds through Rayleigh-Taylor fingers, resulting in initially inhomogeneous distributions in the protostars and protostellar disks. Cloud rotation about an axis aligned with the shock propagation direction does not increase the injection efficiency appreciably, as the shock parameters were chosen to be optimal for injection even in the absence of rotation. For a shock wave from a core-collapse supernova, the dilution factors for supernova material are in the range of ∼10{sup –4} to ∼3 × 10{sup –4}, in agreement with recent laboratory estimates of the required amount of dilution for {sup 60}Fe and {sup 26}Al. We conclude that a type II supernova remains as a promising candidate for synthesizing the solar system's short-lived radioisotopes shortly before their injection into the presolar cloud core by the supernova's remnant shock wave.

  12. Directional spectra of ocean waves from microwave backscatter: A physical optics solution with application to the short-pulse and two-frequency measurement techniques

    NASA Technical Reports Server (NTRS)

    Jackson, F. C.

    1979-01-01

    Two simple microwave radar techniques that are potentially capable of providing routine satellite measurements of the directional spectrum of ocean waves were developed. One technique, the short pulse technique, makes use of very short pulses to resolve ocean surface wave contrast features in the range direction; the other technique, the two frequency correlation technique makes use of coherency in the transmitted waveform to detect the large ocean wave contrast modulation as a beat or mixing frequency in the power backscattered at two closely separated microwave frequencies. A frequency domain analysis of the short pulse and two frequency systems shows that the two measurement systems are essentially duals; they each operate on the generalized (three frequency) fourth-order statistical moment of the surface transfer function in different, but symmetrical ways, and they both measure the same directional contrast modulation spectrum. A three dimensional physical optics solution for the fourth-order moment was obtained for backscatter in the near vertical, specular regime, assuming Gaussian surface statistics.

  13. Linear plane waves in dissipative relativistic fluids

    NASA Astrophysics Data System (ADS)

    Hiscock, William A.; Lindblom, Lee

    1987-06-01

    This paper analyzes the dispersion relations for linear plane waves in the Eckart and the Israel-Stewart theories of dissipative relativistic hydrodynamics. We show that in the long-wavelength (compared to a typical mean-free-path-length) limit the complicated dynamical structure of the Israel-Stewart theory reduces to the familiar dynamics of classical fluids: 9 of the 14 modes of an Israel-Stewart fluid are strongly damped in this limit, two propagate at the adiabatic sound speed (with appropriate viscous and thermal damping), two transverse shear modes decay at the classical viscous damping rate, and the final longitudinal mode is damped at the classical thermal diffusion rate. The short-wavelength limit of these dispersion relations is also examined. We demonstrate that the phase and group velocities of these waves must approach the characteristic velocities in the short-wavelength limit. Finally, we show how some of the perturbations of an Eckart fluid violate causality.

  14. Chemical Sensing Using Infrared Cavity Enhanced Spectroscopy: Short Wave Infrared Cavity Ring Down Spectroscopy (SWIR CRDS) Sensor

    SciTech Connect

    Williams, Richard M.; Harper, Warren W.; Aker, Pam M.; Thompson, Jason S.; Stewart, Timothy L.

    2003-10-01

    The principal goal of Pacific Northwest National Laboratory's (PNNL's) Remote Spectroscopy Project is to explore and develop the science and technology behind point and stand off infrared (IR) spectroscopic chemical sensors that are needed for detecting weapons proliferation activity and countering terrorism. Missions addressed include detecting chemical, biological, and nuclear weapons and their production; counter terrorism measures that involve screening luggage, personnel, and shipping containers for explosives, firearms, narcotics, chemical weapons and/or their residues; and mapping of contaminated areas. The science and technology developed in this program is dual use in that it additionally supports progress in a diverse set of agendas that include chemical weapons defense programs, air operations activities, emissions monitoring, law enforcement, and medical diagnostics. Sensors for these missions require extremely low limits of detection because many of the targeted signature species are either present in low concentrations or have extremely low vapor pressures. The sensors also need to be highly selective as the environments that they will be operated in will contain a variety of interferent species and false positive detection is not an option. PNNL has been working on developing a class of sensors that draw vapor into optical cavities and use laser-based spectroscopy to identify and quantify the vapor chemical content. The cavity enhanced spectroscopies (CES) afford extreme sensitivity, excellent selectivity, noise immunity, and rapid, real-time, in-situ chemical characterization. PNNL's CES program is currently focused on developing two types of sensors. The first one, which is based on cavity ring down spectroscopy (CRDS), uses short wave infrared (SWIR) lasers to interrogate species. The second sensor, which is based on noise immune cavity-enhanced optical heterodyne molecular spectroscopy (NICE OHMS), uses long wave infrared (LWIR) quantum cascade lasers as the light source. This report details the research and discoveries made on the SWIR CRDS project. While chemical detection limits in the SWIR is not expected to be as low as that in the LWIR, there are a number of reasons for designing sensors that operate in this region. First and foremost is that high quality SWIR lasers, detectors and optics are commercially available. Technological advances made in the telecommunications sector have yielded photonic components that are robust, low power, compact and operate at room temperature. These components can be quickly combined and assembled to produce a sensor prototype. This is exactly what we have done with our cavity ring down sensor. We assembled our first prototype instrument in FY02, tested it in the laboratory, developed the chemometrics, and defined several improvements that needed to be implemented before trialing this sensor in the field. In FY03 we completed the refinements, retested the sensor in the laboratory, and then conducted our first field campaign. Our success was demonstrated by the ability of our SWIR CRDS to run autonomously and continuously for 7 days when located in PNNL's Shipping and Receiving Building. No false positive alarms were detected even though the environment was contaminated with vehicle exhaust fumes, dirt, dust, and volatile organic chemicals associated with packaging materials. The instrument maintained its detection threshold and calibration throughout the test. Small fluctuations that we observed in the background concentration levels have led us to develop a more robust method for calibrating the instrument, and separate tests we conducted in the laboratory have afforded a means to account interference from species that have very broad, but weak absorption in this spectral region. We outline all of these accomplishments in detail in the body of this report.

  15. Feasibility Study of Using Short Wave Infrared Cavity Ringdown Spectroscopy (SWIR-CRDS) for Biological Agent Detection

    SciTech Connect

    Aker, Pam M.; Johnson, Timothy J.; Williams, Richard M.; Valentine, Nancy B.

    2007-10-01

    This project focused on determining the feasibility of using short wave infrared (SWIR) cavity ring down spectroscopy (CRDS) as a means for real-time detection of biological aerosols. The first part of the project involved identifying biological agent signatures that could be detected with SWIR CRDS. After an exhaustive search of the open literature it was determined that whole biological spores and/or cells would not be good candidates for direct SWIR CRDS probing because they have no unique SWIR signatures. It was postulated that while whole cells or spores are not good candidates for SWIR CRDS detection, their pyrolysis break-down products might be. A literature search was then conducted to find biological pyrolysis products with low molecular weights and high symmetry since these species most likely would have overtone and combination vibrational bands that can be detected in the SWIR. It was determined that pyrrole, pyridine and picolinamide were good candidates for evaluation. These molecules are formed when proteins and porphyrins, proteins and dipicolinic acid, and dipicolinic acid are pyrolyzed, respectively. The second part of the project involved measuring quantitative SWIR spectra of pyrrole, pyridine and picolinamide in PNNL’s FTIR Spectroscopy Laboratory. Spectral information about these molecules, in the vapor phase is sparse – there were only a few prior studies that measured line positions and no information on absorption cross sections. Absorption cross sections are needed in order to estimate the SWIR CRDS detection sensitivity, and line position determines what type of laser will be needed for the sensor. The results of the spectroscopy studies allowed us to estimate the SWIR CRDS detection sensitivity for pyrrole to be 3 x 1012 molec cm-3 or 0.1 ppmv, and for pyridine it was 1.5 x 1015 molec cm-3 or 0.6 ppmv. These detection sensitivity limits are close what we have measured for ammonia. Given these detection limits we then estimated the amount of biological material that would have to be collected for analysis in a sensor that combined pyrolysis with SWIR CRDS. Using conservative estimates of pyrolysis yields and precursor species concentration we determined that it would be necessary to collect and pyrolyze biological aerosol samples in the 10’s of mg. This is a large amount and is far larger than required for current sensors. It is therefore concluded that while possible, the large amounts of material required preclude using SWIR CRDS for detecting biological agents at this time.

  16. Short wave infrared InGaAs focal plane arrays detector: the performance optimization of photosensitive element

    NASA Astrophysics Data System (ADS)

    Gao, Xin-jiang; Tang, Zun-lie; Zhang, Xiu-chuan; Chen, Yang; Jiang, Li-qun; Cheng, Hong-bing

    2009-07-01

    Significant progress has been achieved in technology of the InGaAs focal plane arrays (FPA) detector operating in short wave infrared (SWIR) last two decades. The no cryogenic cooling, low manufacturing cost, low power, high sensitivity and maneuverability features inherent of InGaAs FPA make it as a mainstream SWIR FPA in a variety of critical military, national security, aerospace, telecommunications and industrial applications. These various types of passive image sensing or active illumination image detecting systems included range-gated imaging, 3-Dimensional Ladar, covert surveillance, pulsed laser beam profiling, machine vision, semiconductor inspection, free space optical communications beam tracker, hyperspectroscopy imaging and many others. In this paper the status and perspectives of hybrid InGaAs FPA which is composed of detector array (PDA) and CMOS readout integrate circuit (ROIC) are reviewed briefly. For various low light levels applications such as starlight or night sky illumination, we have made use of the interface circuit of capacitive feedback transimpedance amplifier (CTIA) in which the integration capacitor was adjustable, therefore implements of the physical and electrical characteristics matches between detector arrays and readout intergrate circuit was achieved excellently. Taking into account the influences of InGaAs detector arrays' optoelectronic characteristics on performance of the FPA, we discussed the key parameters of the photodiode in detailed, and the tradeoff between the responsivity, dark current, impedance at zero bias and junction capacitance of photosensitive element has been made to root out the impact factors. As a result of the educed approach of the photodiode's characteristics optimizing which involve with InGaAs PDA design and process, a high performance InGaAs FPA of 30um pixel pitch and 320×256 format has been developed of which the response spectrum range over 0.9um to 1.7um, the mean peak detectivity (λ=1.55μm) was 6×1012 cmHz1/2W-1 and dynamics range reached 68 dB at room temperature. Making use of the fabricated 320×256 InGaAs FPA, the concerning objects can be imaged in the low light level or nightglow background.

  17. Multi-wavelength emission through self-induced second-order wave-mixing processes from a Nd3+ doped crystalline powder random laser.

    PubMed

    Moura, André L; Jerez, Vladimir; Maia, Lauro J Q; Gomes, Anderson S L; de Araújo, Cid B

    2015-01-01

    Random lasers (RLs) based on neodymium ions (Nd(3+)) doped crystalline powders rely on multiple light scattering to sustain laser oscillation. Although Stokes and anti-Stokes Nd(3+) RLs have been demonstrated, the optical gain obtained up to now was possibly not large enough to produce self-frequency conversion. Here we demonstrate self-frequency upconversion from Nd(3+) doped YAl3(BO3)4 monocrystals excited at 806 nm, in resonance with the Nd(3+) transition (4)I9/2 → (4)F5/2. Besides the observation of the RL emission at 1062 nm, self-converted second-harmonic at 531 nm, and self-sum-frequency generated emission at 459 nm due to the RL and the excitation laser at 806 nm, are reported. Additionally, second-harmonic of the excitation laser at 403 nm was generated. These results exemplify the first multi-wavelength source of radiation owing to nonlinear optical effect in a Nd(3+) doped crystalline powder RL. Contrary to the RLs based on dyes, this multi-wavelength light source can be used in photonic devices due to the large durability of the gain medium. PMID:26334517

  18. Multi-wavelength emission through self-induced second-order wave-mixing processes from a Nd3+ doped crystalline powder random laser

    NASA Astrophysics Data System (ADS)

    Moura, André L.; Jerez, Vladimir; Maia, Lauro J. Q.; Gomes, Anderson S. L.; de Araújo, Cid B.

    2015-09-01

    Random lasers (RLs) based on neodymium ions (Nd3+) doped crystalline powders rely on multiple light scattering to sustain laser oscillation. Although Stokes and anti-Stokes Nd3+ RLs have been demonstrated, the optical gain obtained up to now was possibly not large enough to produce self-frequency conversion. Here we demonstrate self-frequency upconversion from Nd3+ doped YAl3(BO3)4 monocrystals excited at 806 nm, in resonance with the Nd3+ transition 4I9/2 → 4F5/2. Besides the observation of the RL emission at 1062 nm, self-converted second-harmonic at 531 nm, and self-sum-frequency generated emission at 459 nm due to the RL and the excitation laser at 806 nm, are reported. Additionally, second-harmonic of the excitation laser at 403 nm was generated. These results exemplify the first multi-wavelength source of radiation owing to nonlinear optical effect in a Nd3+ doped crystalline powder RL. Contrary to the RLs based on dyes, this multi-wavelength light source can be used in photonic devices due to the large durability of the gain medium.

  19. Multi-wavelength emission through self-induced second-order wave-mixing processes from a Nd3+ doped crystalline powder random laser

    PubMed Central

    Moura, André L.; Jerez, Vladimir; Maia, Lauro J. Q.; Gomes, Anderson S. L.; de Araújo, Cid B.

    2015-01-01

    Random lasers (RLs) based on neodymium ions (Nd3+) doped crystalline powders rely on multiple light scattering to sustain laser oscillation. Although Stokes and anti-Stokes Nd3+ RLs have been demonstrated, the optical gain obtained up to now was possibly not large enough to produce self-frequency conversion. Here we demonstrate self-frequency upconversion from Nd3+ doped YAl3(BO3)4 monocrystals excited at 806 nm, in resonance with the Nd3+ transition 4I9/2 → 4F5/2. Besides the observation of the RL emission at 1062 nm, self-converted second-harmonic at 531 nm, and self-sum-frequency generated emission at 459 nm due to the RL and the excitation laser at 806 nm, are reported. Additionally, second-harmonic of the excitation laser at 403 nm was generated. These results exemplify the first multi-wavelength source of radiation owing to nonlinear optical effect in a Nd3+ doped crystalline powder RL. Contrary to the RLs based on dyes, this multi-wavelength light source can be used in photonic devices due to the large durability of the gain medium. PMID:26334517

  20. Direct multi-wavelength observation and analysis of wave-like propagating intensity disturbances along pseudo-open field lines above a sunspot

    NASA Astrophysics Data System (ADS)

    Stekel, T. R. C.; Stenborg, G.; Dal Lago, A.

    2014-12-01

    The observation of both fast and slow magnetoacoustic waves were only possible through high-resolution images, such as those provided by the extreme ultraviolet (EUV) imagers onboard the SOHO, TRACE, STEREO, and SDO missions. These observations created the observational foundation for new methodologies for coronal plasma diagnostics, i.e., coronal seismology. We have developed a technique to create height-time intensity maps along arbitrary paths on EUV images from different instruments (e.g., STEREO/EUVI and SDO/AIA) in all available channels simultaneously. In this work, we report the first direct observation (along with a comprehensive kinematical characterization) of an arc-shaped wave-like front recorded in several SDO/AIA channels on 2011 July 6. The front is observed to propagate coherently along several pseudo-open field lines with origin on a sunspot of active region AR 1243. Wavelet-processed SDO/AIA images make the wave-like disturbances clearly discernible with the naked eye. The intensity disturbances propagate with an average plane-of-sky phase velocity of about 50 km/sec in the 131 Å, 171 Å, 193 Å, 211 Å, 304 Å and 335 Å channels, exhibiting a ~3 min periodicity in all cases. Its origin could be tracked down to a higher-than-average intensity point inside the umbra of the corresponding spot (i.e., an umbral dot) as observed in the 1600 Å and 1700 Å SDO/AIA channels. The intensity of the source oscillates in phase with the wave-like phenomenon observed in the other channels.