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1

Short wavelength ion waves upstream of the earth's bow shock  

NASA Technical Reports Server (NTRS)

The identification and explanation of short wavelength antenna interference effects observed in spacecraft plasma wave data have provided an important new method of determining limits on the wavelength, direction of propagation, and Doppler shift of short wavelength electrostatic waves. Using the ISEE-1 wideband electric field data, antenna interference effects have been identified in the ion waves upstream of the earth's bow shock. This identification implies that wavelengths of the upstream ion waves are shorter than the antenna length. The interference effects also provide new measurements of the direction of propagation of the ion waves. The new measurements show that the wave vectors of the ion waves are not parallel to the interplanetary magnetic field (IMF) as previously reported. The direction of propagation does not appear to be controlled by the IMF. In addition, analysis of the Doppler shift of the short wavelength ion waves has provided a measurement of the dispersion relation. The upper limit of the rest frame frequency was found to be on the order of the ion plasma frequency. At this frequency, the wavelength is on the order of a few times the Debye length. The results of this study now provide strong evidence that the ion waves in the upstream region are Doppler-shifted ion acoustic waves. Previously announced in STAR as N83-36328

Fuselier, S. A.; Gurnett, D. A.

1984-01-01

2

Latitudinal Variations Observed in Gravity Waves with Short Vertical Wavelengths  

Microsoft Academic Search

Knowledge of the latitudinal variations in the occurrence of gravity waves is important for their parameter- ization in global models. Observations of gravity waves with short vertical scales have shown a pronounced peak in wave activity at tropical latitudes. In this paper, it is shown that such a peak may be a natural consequence of the latitudinal variation in the

M. Joan Alexander; Toshitaka Tsuda; Robert A. Vincent

2002-01-01

3

Short-wavelength electrostatic waves in the earth's magnetosheath  

NASA Technical Reports Server (NTRS)

Recent observations with the ISEE-1 spacecraft have found electric field emissions in the dayside magnetosheath whose frequency spectrum is modulated at twice the spacecraft spin period. The upper frequency cut-off in the frequency-time spectrum of the emissions has a characteristic parabola shape or festoon shape. The low frequency cutoff ranges from 100 Hz to 400 Hz, while the high frequency limit ranges from about 1 kHz to 4 kHz. The bandwidth is found to minimize for antenna orientations parallel to the wave vectors. The wave vector does not appear to be related to either the local magnetic field direction of the plasma flow velocity. The spacecraft observed frequency spectrum results from the spacecraft antenna response to the Doppler shifted wave vector spectrum which exists in the plasma. Imposed constraints on the plasma restframe wave vectors and frequencies indicate that the emissions occur within the frequency range from about 150 Hz to 1 kHz, with wavelengths between about 30 meters and 600 meters. These constraints strongly suggest that the festoon-shaped emissions are ion-acoustic waves. The small group velocity and k direction of the ion-acoustic mode are consistent with wave generation upstream at the bow shock and convection downstream to locations within the outer dayside magnetosheath.

Gallagher, D. L.

1985-01-01

4

Nanoscale dynamics by short-wavelength four wave mixing experiments  

NASA Astrophysics Data System (ADS)

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.

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

5

Short wavelength quantum electrodynamical correction to cold plasma-wave propagation  

SciTech Connect

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.

Lundin, J.; Brodin, G.; Marklund, M. [Department of Physics, Umeaa University, SE-90187 Umeaa (Sweden)

2006-10-15

6

Short wavelength quantum electrodynamical correction to cold plasma-wave propagation  

E-print Network

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 significant for plasma oscillations and for extraordinary modes. In particular, the QED correction allow plasma oscillations to propagate, and the extra-ordinary mode looses its stop band. The significance of our results is discussed.

J. Lundin; G. Brodin; M. Marklund

2006-06-12

7

Characteristics of Short-wavelength Oblique Alfven and Slow waves  

E-print Network

Linear properties of kinetic Alfv\\'en 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 {\\omega} and plasma-to-magnetic pressure ratio {\\beta}. The KAW frequency can reach and exceed the ion cyclotron frequency at ion kinetic scales, whereas the KSW frequency remains sub-cyclotron. At {\\beta}\\sim1, 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 exhibit several different properties. At high {\\beta}, the electric field polarization of KAW and KSW is opposite at the ion gyroradius scale, where KAWs are polarized in sense of electron gyration (right-hand polarized) and KSWs are left-hand polarized. The magnetic helicity {\\sigma}\\sim1 for KAWs and {\\sigma}\\sim-1 for KSWs, and the ion Alfv\\'en ratio R_{Ai}\\ll 1 for KAWs and R_{Ai}\\gg 1 for KSWs. We also found...

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

2014-01-01

8

Properties of Short-wavelength Oblique Alfvén and Slow Waves  

NASA Astrophysics Data System (ADS)

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 ? and plasma-to-magnetic pressure ratio ?. The KAW frequency can reach and exceed the ion-cyclotron frequency at ion kinetic scales, whereas the KSW frequency remains sub-cyclotron. At ? ~ 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 ?, 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 ? ~ 1 for KAWs and ? ~ -1 for KSWs, and the ion Alfvén ratio RAi Lt 1 for KAWs and RAi Gt 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.

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

2014-10-01

9

Short Wavelength Ion Waves Upstream of the Earth’s Bow Shock  

Microsoft Academic Search

ISEE-1 wide-band electric field data, antenna interference effects have been identified in the ion waves upstream of the earth's bow shock. This identification implies that wavelengths of the upstream ion waves are shorter than the antenna length. The interference effects also provide new measurements of the direction of propagation of the ion waves. The new measurements show that the wave

S. A. Fuselier; D. A. Gurnett

1984-01-01

10

Short wavelength laser  

DOEpatents

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.

Hagelstein, P.L.

1984-06-25

11

Short wavelength laser  

DOEpatents

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.

Hagelstein, Peter L. (Livermore, CA)

1986-01-01

12

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

USGS Publications Warehouse

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.

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

2005-01-01

13

Research on polarizing performance of Au-SiO2 sub-wavelength hybrid grating in short wave infrared (SWIR)  

NASA Astrophysics Data System (ADS)

Nanowire grating is designed within the wavelength range from 1?m to 3?m according to the sensitive wavelength of InGaAs short wave infrared (SWIR) detector. The polarization performance is analyzed on the basis of finite difference time domain (FDTD) method. In order to improve the polarization performance, we insert a SiO2 dielectric grating between metal grating and substrate to form Au-SiO2 hybrid grating. The numerical study shows transmittance of hybrid grating is almost 88× which is 18× higher than monolayer metal grating at 1.8?m. In addition, the hybrid grating with the grooved- SiO2 layer has higher transmittance efficiency than those with smooth SiO2 layer for special wave band. By optimizing the specific parameters of the hybrid grating such as period, thickness and the groove depth of SiO2, finally we obtain the optimal parameters of the designed hybrid grating: the grating period is 0.4 ?m, the thickness and groove depth of SiO2 are 0.4?m and 0.1?m respectively. Numerical study shows that the designed grating has advantages of wide band, high transmittance efficiency and high extinction ratio.

Rui, Wang; Li, Tao; Shao, Xiumei; Li, Xue; Gong, Haimei

2014-09-01

14

Improved limits on short-wavelength gravitational waves from the cosmic microwave background  

E-print Network

The cosmic microwave background (CMB) is affected by the total radiation density around the time of decoupling. At that epoch, neutrinos comprised a significant fraction of the radiative energy, but there could also be a contribution from primordial gravitational waves with frequencies greater than ~ 10^-15 Hz. If this cosmological gravitational wave background (CGWB) were produced under adiabatic initial conditions, its effects on the CMB and matter power spectrum would mimic massless non-interacting neutrinos. However, with homogenous initial conditions, as one might expect from certain models of inflation, pre big-bang models, phase transitions and other scenarios, the effect on the CMB would be distinct. We present updated observational bounds for both initial conditions using the latest CMB data at small scales from the South Pole Telescope (SPT) in combination with Wilkinson Microwave Anisotropy Probe (WMAP), current measurements of the baryon acoustic oscillations, and the Hubble parameter. With the in...

Sendra, Irene

2012-01-01

15

Improved limits on short-wavelength gravitational waves from the cosmic microwave background  

E-print Network

The cosmic microwave background (CMB) is affected by the total radiation density around the time of decoupling. At that epoch, neutrinos comprised a significant fraction of the radiative energy, but there could also be a contribution from primordial gravitational waves with frequencies greater than ~ 10^-15 Hz. If this cosmological gravitational wave background (CGWB) were produced under adiabatic initial conditions, its effects on the CMB and matter power spectrum would mimic massless non-interacting neutrinos. However, with homogenous initial conditions, as one might expect from certain models of inflation, pre big-bang models, phase transitions and other scenarios, the effect on the CMB would be distinct. We present updated observational bounds for both initial conditions using the latest CMB data at small scales from the South Pole Telescope (SPT) in combination with Wilkinson Microwave Anisotropy Probe (WMAP), current measurements of the baryon acoustic oscillations, and the Hubble parameter. With the inclusion of the data from SPT the adiabatic bound on the CGWB density is improved by a factor of 1.7 to 10^6 Omega_gw < 8.7 at the 95% confidence level (C.L.), with weak evidence in favor of an additional radiation component consistent with previous analyses. The constraint can be converted into an upper limit on the tension of horizon-sized cosmic strings that could generate this gravitational wave component, with Gmu < 2 10^-7 at 95% C.L., for string tension Gmu. The homogeneous bound improves by a factor of 3.5 to 10^6 Omega_gw < 1.0 at 95% C.L., with no evidence for such a component from current data.

Irene Sendra; Tristan L. Smith

2012-03-19

16

Towards short wavelengths FELs workshop  

SciTech Connect

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.

Ben-Zvi, I.; Winick, H.

1993-12-01

17

Modulating short wavelength fluorescence with long wavelength light.  

PubMed

Two molecules in which the intensity of shorter-wavelength fluorescence from a strong fluorophore is modulated by longer-wavelength irradiation of an attached merocyanine-spirooxazine reverse photochromic moiety have been synthesized and studied. This unusual fluorescence behavior is the result of quenching of fluorophore fluorescence by the thermally stable, open, zwitterionic form of the spirooxazine, whereas the photogenerated closed, spirocyclic form has no effect on the fluorophore excited state. The population ratio of the closed and open forms of the spirooxazine is controlled by the intensity of the longer-wavelength modulated light. Both square wave and sine wave modulation were investigated. Because the merocyanine-spirooxazine is an unusual reverse photochrome with a thermally stable long-wavelength absorbing form and a short-wavelength absorbing photogenerated isomer with a very short lifetime, this phenomenon does not require irradiation of the molecules with potentially damaging ultraviolet light, and rapid modulation of fluorescence is possible. Molecules demonstrating these properties may be useful in fluorescent probes, as their use can discriminate between probe fluorescence and various types of adventitious "autofluorescence" from other molecules in the system being studied. PMID:25072525

Copley, Graeme; Gillmore, Jason G; Crisman, Jeffrey; Kodis, Gerdenis; Gray, Christopher L; Cherry, Brian R; Sherman, Benjamin D; Liddell, Paul A; Paquette, Michelle M; Kelbauskas, Laimonas; Frank, Natia L; Moore, Ana L; Moore, Thomas A; Gust, Devens

2014-08-27

18

Review of short wavelength lasers  

SciTech Connect

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.

Hagelstein, P.L.

1985-03-18

19

Short wavelength magnetic buoyancy instability  

E-print Network

Magnetic buoyancy instability plays an important role in the evolution of astrophysical magnetic fields. Here we revisit the problem introduced by \\citet{Gilman_1970} 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-Schr\\"odinger 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,...

Mizerski, K A; Hughes, D W

2013-01-01

20

Comment on ''Electron acceleration by a short laser beam in the presence of a long-wavelength electromagnetic wave'' [J. Appl. Phys. 102, 056106 (2007)  

SciTech Connect

Gupta et al.[J. Appl. Phys. 102, 056106 (2007)] investigated vacuum electron acceleration by a short laser beam in the presence of a long-wavelength electromagnetic wave. However, we consider that their simulation results to be questionable. We have investigated their simulation in detail and present our own simulation results, which do not match the good acceleration as theirs given in the original paper.

Yuan, C. J.; Wang, P. X. [Applied Ion Beam Physics Laboratory, Key Laboratory of the Ministry of Education, China and Department of Nuclear Science and Technology, Institute of Modern Physics, Fudan University, Shanghai 200433 (China); Huang, S. J. [Department of Physics, Zhanjiang Normal University, Zhanjiang, Guangdong Province 524048 (China); Wang, J. X. [State Key Laboratory of Precision Spectroscopy, Department of Physics, East China Normal University, Shanghai 200062 (China)

2012-05-15

21

Short Wavelength Modes 5.1 Introduction  

E-print Network

Chapter 5 Short Wavelength Modes 5.1 Introduction In short wavelength regime (ki) 2 > 1 (cross field wavelength smaller than the ion Larmor radius), the toroidal ITG mode tends to be stabilized is the ion factor. In deuterium plasma with i = 1%, the ratio is approximately 4.3. As the wavelength

Saskatchewan, University of

22

Short wavelength electromagnetic propagation in magnetized quantum plasmas  

SciTech Connect

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.

Lundin, J.; Zamanian, J.; Marklund, M.; Brodin, G. [Department of Physics, Umeaa University, SE-90187 Umeaa (Sweden)

2007-06-15

23

Short wavelength electromagnetic propagation in magnetized quantum plasmas  

NASA Astrophysics Data System (ADS)

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.

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

2007-06-01

24

Physics of Very Short Wavelength Acceleration  

SciTech Connect

The motivation and physics issues for scaling particle accelerators to very short wavelengths is discussed. Issues of breakdown, dark current and stored energy argue for short wavelengths to increase accelerator gradients, and beam-beam physics at high energy colliders favor short bunches associated with short wavelength accelerators. However, the strong scaling of transverse wakefields at short wavelengths can lead to head-tail instability and difficult tolerances for the structure's fabrication. Several novel approaches such as photonic band gap structures and plasmas aim to overcome these issues with fundamentally new approaches.

Katsouleas, T. [University of Southern California, Los Angeles, CA 90089-0271 (United States)

2006-01-03

25

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)

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.

Hahne, G. E.

1991-01-01

26

A 50-MeV mm-wave electron linear accelerator system for production of tunable short wavelength synchrotron radiation  

SciTech Connect

The Advanced Photon Source (APS) at Argonne in collaboration with the University of Illinois at Chicago and the University of Wisconsin at Madison is developing a new millimeter wavelength, 50-MeV electron linear accelerator system for production of coherent tunable wavelength synchrotron radiation. Modern micromachining techniques based on deep etch x-ray lithography, LIGA (Lithografie, Galvanoformung, Abformung), capable of producing high-aspect ratio structures are being considered for the fabrication of the accelerating components.

Nassiri, A.; Kustom, R.L.; Mills, F.E.; Kang, Y.W.; Matthews, P.J.; Grudzien, D.; Song, J.; Horan, D. [Argonne National Lab., IL (United States). Advanced Photon Source Accelerator Systems Div.; Feinerman, A.D.; Willke, T.L. [Argonne National Lab., IL (United States). Advanced Photon Source Accelerator Systems Div.]|[Univ. of Illinois, Chicago, IL (United States). Dept. of Electrical Engineering and Computer Science; Henke, H. [Argonne National Lab., IL (United States). Advanced Photon Source Accelerator Systems Div.]|[Technische Univ., Berlin (Germany). Inst. fuer Theoretische Electrotechnik

1993-12-31

27

Fourier-Ray Modeling of Short-Wavelength Trapped Lee Waves Observed in Infrared Satellite Imagery near Jan Mayen  

Microsoft Academic Search

A time-dependent generalization of a Fourier-ray method is presented and tested for fast numerical computation of high-resolution nonhydrostatic mountain-wave fields. The method is used to model moun- tain waves from Jan Mayen on 25 January 2000, a period when wavelike cloud banding was observed long distances downstream of the island by the Advanced Very High Resolution Radiometer Version 3 (AVHRR-3).

Stephen D. Eckermann; Dave Broutman; Jun Ma; John Lindeman

2006-01-01

28

Short wavelength electromagnetic propagation in magnetized quantum plasmas  

E-print Network

The quantum electrodynamical (QED) short wavelength correction on plasma wave propagation for a non-relativistic quantum plasma is investigated. A general dispersion relation for a thermal multi-component 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 non-dispersive plasma modes. Applications to laboratory and astrophysical systems are discussed.

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

2007-03-14

29

Short wavelength electromagnetic propagation in magnetized quantum plasmas  

E-print Network

The quantum electrodynamical (QED) short wavelength correction on plasma wave propagation for a non-relativistic quantum plasma is investigated. A general dispersion relation for a thermal multi-component 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 non-dispersive plasma modes. Applications to laboratory and astrophysical systems are discussed.

Lundin, J; Marklund, M; Brodin, G

2007-01-01

30

Stable power multi-wavelength fibre laser based on four-wave mixing in a short length of highly non-linear fibre  

NASA Astrophysics Data System (ADS)

A multi-wavelength fibre laser utilizing the four-wave mixing (FWM) effect in a 100 m long highly non-linear fibre (HNLF) is proposed and demonstrated. The multi-wavelength fibre laser is configured in a ring cavity and only needs a low power erbium doped fibre amplifier (EDFA) as the gain medium to generate 11 lines in the range of 1582-1600 nm with a signal-to-noise ratio (SNR) of 43 dB. The proposed system is very stable, with only minor fluctuations of 0.1 dB in the output power of the generated multi-wavelengths observed for a test period of more than an hour. The multi-wavelength fibre laser has many potential applications in optical communications and optical sensing systems.

Awang, N. A.; Zulkifli, M. Z.; Latif, A. A.; Harun, S. W.; Ahmad, H.

2011-07-01

31

Electricity and short wavelength radiation generator  

DOEpatents

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.

George, E.V.

1985-08-26

32

Modulation compression for short wavelength harmonic generation  

SciTech Connect

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.

Qiang, J.

2010-01-11

33

Short wavelength ion temperature gradient turbulence  

SciTech Connect

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.

Chowdhury, J.; Ganesh, R. [Institute for Plasma Research, Bhat, Gandhinagar (India); Brunner, S.; Lapillonne, X.; Villard, L. [CRPP, Association EURATOM-Confederation Suisse, EPFL, 1015 Lausanne (Switzerland); Jenko, F. [Max-Planck-Institut fuer Plasmaphysik Boltzmannstr. 2, D-85748 Garching (Germany)

2012-10-15

34

On storage rings for short wavelength FELs  

SciTech Connect

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.

Chattopadhyay, S.

1990-01-01

35

Intraocular lens short wavelength light filtering.  

PubMed

There is increasing interest in the effects of reactive oxygen species ('free radicals') in ageing, both in the body overall and specifically in the eye. Cataract and age-related macular degeneration (AMD) are two major causes of blindness, with cataract accounting for 48 per cent of world blindness and AMD accounting for 8.7 per cent. Both cataract and AMD affect an older population (over 50?years of age) and while cataract is largely treatable provided resources are available, AMD is a common cause of untreatable, progressive visual loss. There is evidence that AMD is linked to exposure to short wavelength electromagnetic radiation, which includes ultraviolet, blue and violet wavelengths. The ageing crystalline lens provides some protection to the posterior pole because, as it yellows with age, its spectral absorption increasingly blocks the shorter wavelengths of light. Ultraviolet blocking intraocular lenses (IOLs) have been the standard of care for many years but a more recent trend is to include blue-blocking filters based on theoretical benefits. As these filters absorb part of the visible spectrum, they may affect visual function. This review looks at the risks and the benefits of filtering out short wavelength light in pseudophakic patients. PMID:20950366

Edwards, Keith H; Gibson, G Anthony

2010-11-01

36

Source of coherent short wavelength radiation  

DOEpatents

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.

Villa, Francesco (Alameda, CA)

1990-01-01

37

Optical Detection in Ultrafast Short Wavelength Science  

SciTech Connect

A new approach to coherent detection of ionising radiation is briefly motivated and recounted. The approach involves optical scattering of coherent light fields by colour centres in transparent solids. It has significant potential for diffractive imaging applications that require high detection dynamic range from pulsed high brilliance short wavelength sources. It also motivates new incarnations of Bragg's X-ray microscope for pump-probe studies of ultrafast molecular structure-dynamics.

Fullagar, Wilfred K.; Hall, Chris J. [School of Physics, Monash University, Victoria 3800 (Australia); Monash Centre for Synchrotron Science, Monash University, Victoria 3800 (Australia); Centre of Excellence for Coherent X-ray Science, School of Physics, University of Melbourne, Victoria, 3010 (Australia)

2010-06-23

38

Deformable mirror for short wavelength applications  

DOEpatents

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.

Chapman, Henry N. (2417 Kilkare Rd., Sunol, CA 94586); Sweeney, Donald W. (5020 Canyon Crest Dr., San Ramon, CA 94583)

1999-01-01

39

SHORT-WAVELENGTH MAGNETIC BUOYANCY INSTABILITY  

SciTech Connect

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.

Mizerski, K. A.; Davies, C. R.; Hughes, D. W., E-mail: kamiz@igf.edu.pl, E-mail: tina@maths.leeds.ac.uk, E-mail: d.w.hughes@leeds.ac.uk [Department of Applied Mathematics, University of Leeds, Leeds LS2 9JT (United Kingdom)

2013-04-01

40

Modulation of short waves by long waves. [ocean wave interactions  

NASA Technical Reports Server (NTRS)

Wave-tank experiments were performed to investigate the cyclic short-wave energy changes, related in phase to an underlying long wave, which occur during active generation of the short-wave field by wind. Measurements of time series of the short-wave slope were made by a laser-optical system, where the basic long-wave parameters were controlled and wind speeds were accurately reproducible. The short-wave slope variances were found to exhibit cyclic variations that are related to the phase of the long wave. The variations result from two combined effects: (1) the short wave frequency is varied by the long-wave orbital velocity; (2) the energy of the short waves is modulated by the actions of aerodynamic and hydrodynamic couplings that operate on the short waves in a manner related to the long-wave phase.

Reece, A. M., Jr.

1978-01-01

41

Short wavelength infrared hybrid focal plane arrays  

NASA Technical Reports Server (NTRS)

The employment of area focal plane arrays (FPA) has made it possible to obtain second generation infrared imaging systems with high resolution and sensitivity. The Short Wavelength Infrared (SWIR) region (1-2.5 microns) is of importance for imaging objects at high temperature and under conditions of reflected sunlight. The present investigation is concerned with electrooptical characterization results for 32 x 32 SWIR detector arrays and FPAs which are suitable for use in a prototype imaging spectrometer. The employed detector material is Hg(1-x)Cd(x)Te grown by liquid phase epitaxy on a CdTe transparent substrate. Attention is given to details of processing, the design of the detector array, the multiplexer, the fabrication of the hybrid FPA, and aspects of performance.

Vural, K.; Blackwell, J. D.; Marin, E. C.; Edwall, D. D.; Rode, J. P.

1983-01-01

42

Science Shorts: Making Waves  

NSDL National Science Digital Library

Children do not have to live near the coast to experience effects of water waves. They can throw stones into a pond and see the waves ripple outward, bob up and down while floating in a swimming pool, and splash water about while in a bathtub. As students discover how waves form and move, they can apply this understanding to other types of waves such as sound waves, light waves, and microwaves.

Adams, Barbara

2007-01-01

43

Nonlinear long-wavelength torsional Alfven waves  

NASA Astrophysics Data System (ADS)

Long-wavelength torsional (Alfven) waves in solar and stellar coronal structures experience geometrical amplification with height and hence are subject to nonlinear effects. We analyse this regime in frames the second order thin flux-tube approximation of Zhugzhda, which describes axisymmetric (sausage) magnetohydrodynamic perturbations of a straight untwisted and non-rotating magnetic flux-tube, representing e.g. a polar plume or a jet, or a coronal loop or a prominence filament. Attention is paid to the compressible motions nonlinearly induced by long-wavelength torsional waves of small, but finite amplitude. We obtained that propagating torsional waves induce compressible perturbations oscillating with double the frequency of the torsional waves. In contrast with plane shear Alfven waves, the amplitude of compressible perturbations is independent of the plasma-beta. Moreover, nonlinear evolution of torsional waves is not affected by the singularity appearing at the height when the local Alfven speed is equal to the sound speed. This result significantly reduces the efficiency of nonlinear cascade, and hence suggests that the present theories of the solar and stellar wind heating and acceleration by Alfven waves, based upon the plane wave theory, require modification.

Nakariakov, Valery

2012-07-01

44

Short wavelength electron temperature gradient instability in toroidal plasmas  

SciTech Connect

The electron temperature gradient (ETG) driven mode in the very short wavelength region k{sub perpendicular}{rho}{sub e}>1 is identified with a gyrokinetic integral equation code in toroidal plasmas. This 'double-humped' growth rate of the conventional ETG and short wavelength ETG modes is attributed to the toroidal drift resonance mechanism and the nonmonotonic behavior of normalized real frequency as the poloidal wavelength varies. This instability provides a possibility existence of a kind of turbulence source with very small size of cells. However, the wavelength of the short wavelength ETG mode is too short and induced transport may be small unless there are inverse cascade effects. In addition, the critical threshold of electron temperature gradient (R/L{sub Te}){sub c} for the short wavelength ETG mode is higher than that for the conventional ETG mode.

Gao Zhe; Sanuki, H.; Itoh, K.; Dong, J.Q. [Department of Engineering Physics, Tsinghua University, Beijing 100084 (China); National Institute for Fusion Science, Toki, Gifu 509-5292 (Japan); Southwestern Institute of Physics, Chengdu 610041 (China)

2005-02-01

45

SWCam: the short wavelength camera for the CCAT Observatory  

NASA Astrophysics Data System (ADS)

We describe the Short Wavelength Camera (SWCam) for the CCAT observatory including the primary science drivers, the coupling of the science drivers to the instrument requirements, the resulting implementation of the design, and its performance expectations at first light. CCAT is a 25 m submillimeter telescope planned to operate at 5600 meters, near the summit of Cerro Chajnantor in the Atacama Desert in northern Chile. CCAT is designed to give a total wave front error of 12.5 ?m rms, so that combined with its high and exceptionally dry site, the facility will provide unsurpassed point source sensitivity deep into the short submillimeter bands to wavelengths as short as the 200 ?m telluric window. The SWCam system consists of 7 sub-cameras that address 4 different telluric windows: 4 subcameras at 350 ?m, 1 at 450 ?m, 1 at 850 ?m, and 1 at 2 mm wavelength. Each sub-camera has a 6' diameter field of view, so that the total instantaneous field of view for SWCam is equivalent to a 16' diameter circle. Each focal plane is populated with near unit filling factor arrays of Lumped Element Kinetic Inductance Detectors (LEKIDs) with pixels scaled to subtend an solid angle of (?/D)2 on the sky. The total pixel count is 57,160. We expect background limited performance at each wavelength, and to be able to map < 35(°)2 of sky to 5 ? on the confusion noise at each wavelength per year with this first light instrument. Our primary science goal is to resolve the Cosmic Far-IR Background (CIRB) in our four colors so that we may explore the star and galaxy formation history of the Universe extending to within 500 million years of the Big Bang. CCAT's large and high-accuracy aperture, its fast slewing speed, use of instruments with large format arrays, and being located at a superb site enables mapping speeds of up to three orders of magnitude larger than contemporary or near future facilities and makes it uniquely sensitive, especially in the short submm bands.

Stacey, Gordon J.; Parshley, Stephen; Nikola, Thomas; Cortes-Medellin, German; Schoenwald, Justin; Rajagopalan, Ganesh; Niemack, Michael D.; Jenness, Tim; Gallardo, Patricio; Koopman, Brian; Dowell, Charles D.; Day, Peter K.; Hollister, Matthew I.; Kovacs, Attila; LeDuc, Henry G.; McKenney, Christopher M.; Monroe, Ryan M.; Yoshida, Hiroshige; Zmuidzinas, Jonas; Swenson, Loren J.; Radford, Simon J.; Nguyen, Hien Trong; Mroczkowski, Anthony K.; Glenn, Jason; Wheeler, Jordan; Maloney, Philip; Brugger, Spencer; Adams, Joseph D.; Bertoldi, Frank; Schaaf, Reinhold; Halpern, Mark; Scott, Douglas; Marsden, Galen; Sayers, Jack; Chapman, Scott; Vieira, Joaquin D.

2014-08-01

46

Ion heating and short wavelength fluctuations in a helicon plasma source  

SciTech Connect

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.

Scime, E. E.; Carr, J. Jr.; Galante, M.; Magee, R. M. [Department of Physics, West Virginia University, Morgantown, WV 26506 (United States); Hardin, R. [Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States)

2013-03-15

47

Laser damage thresholds at short wavelengths  

Microsoft Academic Search

A survey of single-pulse laser damage thresholds for a wide variety of commercially available film coatings and prepared surfaces is reported. Tests were conducted at 532, 355, and 248 nm. Pulses for the longer wavelengths, generated by harmonic conversion of 1064-nm light from a Nd:glass laser, had a duration of 0.7 nsec. The 248-nm pulses had a 20-nsec duration and

F. Rainer; T. F. Deaton

1982-01-01

48

Observing with the ISO Short-Wavelength Spectrometer  

Microsoft Academic Search

The Short-Wavelength Spectrometer (SWS) is one of the four instruments on-board ESA's Infrared Space Observatory (ISO), launched on November 17, 1995. The spectrometer covers the wavelength range of 2.38 to 45.2mum with a spectral resolution ranging from 1000 to 2000. By inserting Fabry-Perot filters the resolution can be enhanced by a factor 20 for the wavelength range from 11.4 to

Graauw de Th; L. N. Haser; D. A. Beintema; P. R. Roelfsema; H. van Agthoven; L. Barl; H. E. G. Bekenkamp; A.-J. Boonstra; D. R. Boxhoorn; J. Cote; P. de Groene; C. van Dijkhuizen; S. Drapatz; J. Evers; H. Feuchtgruber; M. Frericks; R. Genzel; G. Haerendel; A. M. Heras; K. A. van der Hucht; T. van der Hulst; R. Huygen; H. Jacobs; G. Jakob; T. Kamperman; R. O. Katterloher; D. J. M. Kester; D. Kunze; D. Kussendrager; F. Lahuis; K. Leech; S. van der Lei; R. van der Linden; W. Luinge; D. Lutz; F. Melzner; P. W. Morris; D. van Nguyen; G. Ploeger; S. Price; A. Salama; S. G. Schaeidt; N. Sijm; C. Smoorenburg; J. Spakman; H. Spoon; M. Steinmayer; J. Stoecker; E. A. Valentijn; B. Vandenbussche; H. Visser; C. Waelkens; L. B. F. M. Waters; J. Wensink; P. R. Wesselius; E. Wiezorrek; E. Wieprecht; J. J. Wijnbergen; K. J. Wildeman; E. Young

1996-01-01

49

InAs/AlSb short wavelength quantum cascade lasers.  

E-print Network

??Application of InAs/AlSb materials system for development of short-wavelength quantum cascade lasers is explored. Molecular beam epitaxy (MBE) technology allowing to grow multiperiodical unstrained InAs/AlSb… (more)

Devenson, Jan

2010-01-01

50

Four-wave mixing wavelength conversion efficiency in semiconductor traveling-wave amplifiers measured to 65 nm of wavelength shift  

Microsoft Academic Search

The efficiency of broadband optical wavelength conversion by four-wave mixing in semiconductor traveling-wave amplifiers is measured for wavelength shifts up to 65 nm using a tandem amplifier geometry. A quantity we call the relative conversion efficiency function, which determines the strength of the four-wave mixing nonlinearity, was extracted from the data. Using this quantity, gain requirements for lossless four-wave mixing

Jianhui Zhou; K. J. Vahala; M. A. Newkirk; B. I. Miller

1994-01-01

51

Phase advancing human circadian rhythms with short wavelength light  

Microsoft Academic Search

The photoreceptor(s) responsible for photoresetting of the human circadian system have not been identified. The aim of the present study was to assess the ability of short wavelength light to alter the timing of circadian rhythms. Eleven male subjects were studied in 15 4-day trials with a single 4 h light pulse administered on day 3, immediately after habitual wake

Victoria L. Warman; Derk-Jan Dijk; Guy R. Warman; Josephine Arendt; Debra J. Skene

2003-01-01

52

An opaque cloud cover model of sky short wavelength radiance  

Microsoft Academic Search

The average angular distribution of short wavelength sky radiance for clear, partly cloudy, and overcast sky conditions has been measured for the range of solar zenith angle 31° to 80°. Detailed analysis of the normalized sky radiance is presented by a semiempirical model.

A. W. Harrison; C. A. Coombes

1988-01-01

53

Special short wave finite elements for flow acoustics  

Microsoft Academic Search

Short wave problems of practical interest in acoustics include the modeling of sound attenuation in the ducted regions of turbofan aircraft engines where the convective and diffractive effects of the mean flow are significant. Also, in this case the acoustic wavelength is generally much smaller than the length scale of the scattering geometry and smaller than the characteristic length scale

Pablo Gamallo; Jeremy Astley

2003-01-01

54

Normal Values of Short-Wavelength Automated Perimetry  

Microsoft Academic Search

Background: The purpose of this study was to evaluate short-wavelength automated perimetry (SWAP, i.e., blue-yellow) in normal volunteers and to review the current normal values provided by the manufacturer. Methods: 28 eyes of 28 normal subjects (age range 21–48 years, mean age 36.5 years) had SWAP (Octopus 101, two phases of program G2, Interzeag AG, Schlieren, Switzerland). All subjects had

Daniel S. Mojon; Mario Zulauf

2003-01-01

55

A short-wavelength selective reach-through avalanche photodiode  

Microsoft Academic Search

A new reach-through avalanche photodiode, designed for use with sources of short-wavelength light such as scintillators, is described. The device has a double junction p+-p-n-p--n+ structure in which the central three layers, which comprise about 99% of the device thickness, are fully depleted. The p+ light-entry surface extends across the whole device and can be placed in contact with a

R. J. McIntyre; P. P. Webb; H. Dautet

1996-01-01

56

Method for fabricating photovoltaic device having improved short wavelength photoresponse  

DOEpatents

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.

Catalano, Anthony W. (P.O. Box 557, Rushland, PA 18956)

1989-07-04

57

Phosphide based Molecular Beam Epitaxy for High Power Short-Wavelength Diode Lasers  

NASA Astrophysics Data System (ADS)

The paper presents our recent results obtained in developing highpower GaInP/AlGaInP quantum well laser diodes for the short red-wavelength range. State-of-the-art performances have been obtained at 650nm (bright red) with high-power, in excess of 2W under continuous wave operation, emitted at 15°C. The emission wavelength was also brought down to 618nm, close to the shortest achievable wavelength with the AlGaInP material system. Our calculations and preliminary tests indicate that a significant increase of the emitted power and substantial reduction of the emission wavelength down to the amber 600nm range can be obtained by using advanced layer structures and more complex doping profiles.

Toikkanen, L.; Tukiainen, A.; Dumitrescu, M.; Viitala, S.; Rimpiläinen, V.; Hirvonen, I.; Pessa, M.

2004-01-01

58

Morphologic Comparisons Between Rhodopsin Mediated and Short-Wavelength Classes of Retinal Light Damage  

Microsoft Academic Search

I lie historic manifestations of rhodopsin-mediated versus short-wavelength classes of retinal photo- toxicity wore compared after spectral exposures of the albino rat retina. Animals were exposed to wave-hands ofli^lit centered at the peak of rhodopsin absorhance (green, 500 nm) or in the ultraviolet A (UVA; 360 nm). Intensity-damage curves generated for each wa\\\\c-hand indicated that UVA light was 50-80 times

Laurence M. Rapp; Stephanie C. Smith

59

Wavelength-scale stationary-wave integrated Fourier transform spectrometry  

E-print Network

1 Wavelength-scale stationary-wave integrated Fourier transform spectrometry Etienne le Coarer1 issued by either reflection (as the principle of colour photography by G. Lippmann) or counterpropagative an elegant way of reducing the volume of spectrometer to a few hundreds of cubic wavelengths

Boyer, Edmond

60

Nonlocal theory of long-wavelength plasma waves associated with sporadic E layers  

SciTech Connect

In this paper we calculate the nonlocal growth rate of gradient drift plasma waves under conditions where the electron density gradient scale length changes with altitude. The results are compared with the local growth rate and discussed in the context of the kilometer-scale waves which have been observed in the vicinity of mid-latitude sporadic E layers. These large-scale waves drastically violate the local approximation, kL/sub m/>>1, where k is the irregularity wave number and L/sub m/ is the minimum gradient scale length on the edge of a layer. The first step in the analysis is to derive a general eigenmode equation, starting with the same assumptions usually used in the derivation of the local dispersion relation for long wavelength waves. Modeling a sporadic E layer as a slab, the nonlocal growth rate spectrum is found by solving the eigenmode equation for this profile. The solution is an algebraic dispersion relation with a growth rate spectrum which is roughly proportional to k, rather than the k/sup 2/ dependence predicted by conventional local theory at long wavelengths. At short wavelengths the nonlocal growth rate determined with the slab is unbounded, in disagreement with local theory. The slab is an inadequate model for short wavelength waves and a bound on the growth rate is instead derived from a theory which can be applied to any realistic profile with nonzero L/sub m/. At short wavelengths this bound is identical to the local growth rate expression, while at long wavelengths the bound remains proportional to k and thus is consistent with the dispersion relation for a slab. Nonlocal effects alone do not explain the dominance of kilometer scales, but they do tend to favor the excitation of long wavelengths.

Riggin, D.; Kadish, A.

1989-02-01

61

Short wavelength limits of current shot noise suppression  

NASA Astrophysics Data System (ADS)

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.

Nause, Ariel; Dyunin, Egor; Gover, Avraham

2014-08-01

62

Sub-wavelength position measurements with running wave driving fields  

E-print Network

A scheme for sub-wavelength position measurements of quantum particles is discussed, which operates with running-wave laser fields as opposed to standing wave fields proposed in previous setups. The position is encoded in the phase of the applied fields rather than in the spatially modulated intensity of a standing wave. Therefore, disadvantages of standing wave schemes such as cases where the atom remains undetected since it is at a node of the standing wave field are avoided. Reversing the directions of parts of the driving laser fields allows to switch between different magnification levels, and thus to optimize the localization.

J. Evers; S. Qamar

2009-01-29

63

Volcano monitoring by short wavelength infrared satellite remote sensing  

NASA Technical Reports Server (NTRS)

The use of short wavelength IR Landsat TM data for volcano monitoring is examined. By determining the pixel-integrated from the TM data, it is possible to estimate the temperature and size of hot areas which occupy less than one complete pixel. Examples of volcano monitoring with remote sensing data are discussed. It is suggested that the entire volcanic temperature range (100-1200 C) could be accomplished by decreasing the band 6 gain by just one order of magnitude so that it was sensitive to radiance from 1 to 100 mW/sq cm/sr/micron.

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

1988-01-01

64

Ultraintense ion beams driven by a short-wavelength short-pulse laser  

SciTech Connect

The results of particle-in-cell simulations are reported which demonstrate that a short-wavelength (lambda<=0.5 mum) short-pulse laser driver can produce much more intense ion beams than the commonly used long-wavelength (lambdaapprox1 mum) ones. In particular, such a driver allows for efficient generation of ultrashort (<=100 fs), multi-MeV proton bunches of extremely high intensities (>10{sup 21} W/cm{sup 2}) and current densities (>10{sup 14} A/cm{sup 2}) even at moderate values of dimensionless laser amplitude a{sub 0}<=10.

Badziak, J.; Jablonski, S. [Institute of Plasma Physics and Laser Microfusion, Euratom Association, 01-497 Warsaw (Poland)

2010-07-15

65

Research with high-power short-wavelength lasers  

SciTech Connect

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.

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

1985-03-05

66

Low Noise, High Gain Short-Wave Infrared Nano-Injection Photon Detectors with Low Jitter  

E-print Network

Science, Northwestern University, Evanston, IL 60208 We present the near-infrared injection photodetectors in short wave infrared (SWIR) spectrum, particularly focusing at 1.55 m wavelength. Spanning a wide rangeLow Noise, High Gain Short-Wave Infrared Nano-Injection Photon Detectors with Low Jitter Omer

Mohseni, Hooman

67

Photoemission spectroscopy with high-intensity short-wavelength lasers  

E-print Network

We theoretically study the process of photoelectron emission of the Helium atom by a high-intensity short-wavelength laser at a resonance condition of the residual singly charged ion. Photoionization followed by strong resonance coupling in the ion leads to a change in the photoelectron spectrum due to Rabi oscillations in the residual ion. Similarly to resonance fluorescence at high laser intensity, the photoelectron spectrum at high intensities evolves into a multi-peaked structure. The number of peaks in the photoelectron spectrum is related to the number of Rabi cycles following the photoionization process. Moreover, the strong laser-induced coupling to nonresonant states of the residual ion have an imprint on the photoelectron spectrum, leading to additional, isolated peaks at the lower or higher energy sides. The effect should be observable at current seeded XUV free-electron lasers and persists after volume integration in a realistic experimental geometry.

Zhang, Song Bin

2014-01-01

68

In-flight calibration of large field of view sensors at short wavelengths using Rayleigh scattering  

Microsoft Academic Search

Two in-flight calibration methods for visible SPOT channels using Rayleigh scattering are proposed for large FOV sensors centered at short wavelengths. Two methods are evaluated. The first method directly relates the measured numerical signal in a short wavelength channel to the predicted reflectance. In the second method, a second channel centered at a longer wavelength is used to correct the

E. Vermote; R. Santer; P. Y. Deschamps; M. Herman

1992-01-01

69

Integrated waveguide gratings for wavelength-demultiplexing of free space waves from guided waves.  

PubMed

Optical waveguide demultiplexer was designed and fabricated by integration of two types of gratings, namely, guided-mode-selective focusing grating couplers (GMS-FGCs) and different-guided-mode-coupling distributed Bragg reflectors (DGM-DBRs) in a slab waveguide for constructing a wavelength-division-multiplexing chip-to-chip optical interconnecting board. In the waveguide demultiplexer, guided signal waves were separated wavelength-selectively by DGM-DBRs, and coupled out by GMS-FGCs to focused free space waves. Two-channel demultiplexing with 5-nm-wavelength spacing was demonstrated at around 850-nm wavelength. PMID:19483826

Kintaka, Kenji; Nishii, Junji; Ohmori, Junpei; Imaoka, Yoshitaka; Nishihara, Masaaki; Ura, Shogo; Satoh, Ryohei; Nishihara, Hiroshi

2004-07-12

70

Short wavelength limitation in high power AlGaInP laser diodes  

Microsoft Academic Search

In wavelength region of red color, luminous efficacy rapidly increases as wavelength shortens. In that sense, red laser diode (LD) with shorter wavelength is required for display applications. Experimental results for short wavelength limitation in AlGaInP LDs are shown and discussed in this paper. Broad area LDs with 625, 630, and 638 nm are successfully fabricated. Operation current versus output

Takehiro Nishida; Naoyuki Shimada; Tetsuya Ogawa; Motoharu Miyashita; Tetsuya Yagi

2011-01-01

71

Short wavelength topography on the inner-core boundary  

PubMed Central

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

Cao, Aimin; Masson, Yder; Romanowicz, Barbara

2007-01-01

72

Wavelength monitor based on two single-quantum-well absorbers sampling a standing wave pattern  

E-print Network

Wavelength monitor based on two single-quantum-well absorbers sampling a standing wave pattern H. L for publication 7 April 2000 We demonstrate a wavelength monitor and a two-wavelength detector based on two single-quantum-well absorbers that sample a standing wave created by a distributed Bragg reflector. As a wavelength monitor, our

Miller, David A. B.

73

COLOR PERCEPTION UNDER CHROMATIC ADAPTATION: RED\\/GREEN EQUILIBRIA WITH ADAPTED SHORT-WAVELENGTH-SENSITIVE CONES  

Microsoft Academic Search

Chromatic adaptation can dramatically alter the color appearance of a light. The specific effect of adapting short-wavelength-sensitive (SWS) cones is examined by using two adapting wavelengths that lie on a tritanopic confusion line. The change in color appearance caused by signals from adapted SWS cones is isolated by restricting the wavelengths of the test light to 550 nm or longer.

STEVEN K. SHEVELL; RICHARD A. HUMANSKI

74

Wavelength monitor based on two single quantum well absorbers in a standing wave  

E-print Network

Wavelength monitor based on two single quantum well absorbers in a standing wave H.L. Kung, D in wavelength division multiplexing has increased the need for integrated wavelength monitors and wavelength such device,[3] , a detector capable of rejecting a specific wavelength, was demonstrated. Chen et al.[4] also

Miller, David A. B.

75

The generation of Tollmien-Schlichting waves by long wavelength free stream disturbances  

NASA Technical Reports Server (NTRS)

The paper is primarily concerned with explaining how very long wavelength free stream disturbances are able to generate very short wavelength Tollmien-Schlichting waves in laminar boundary layers. Consideration is given to the case where the disturbances are of small amplitude and have harmonic time dependence and where the Mach number is effectively zero. It is shown that the free stream wavelength reduction occurs as a result of nonparallel flow effects which can arise from: (1) the slow viscous growth of the boundary layer, and (2) small but abrupt changes in surface geometry that produce only very weak static pressure variations. Analyses of these two mechanisms are carried out by linearizing the unsteady motion about an appropriate steady flow and asymptotically expanding the result in inverse powers of an appropriate Reynolds number. The analyses are compared with each other and with available experimental data, and they are used to explain the physics of the two mechanisms.

Goldstein, M. E.

1987-01-01

76

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

NASA Astrophysics Data System (ADS)

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 ?m. 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 ?m 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 ?m, which can be used as a seed signal in parametric amplifiers in designing petawatt laser systems.

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

2014-05-01

77

SS-MBE-grown short red wavelength range AlGaInP laser structures  

NASA Astrophysics Data System (ADS)

Short-wavelength GaInP/AlGaInP quantum-well (QW) laser diodes emitting in the 618-650 nm range at room temperature have been fabricated and characterized. Several variations in laser structures have been tested, including changes in QW composition, thickness, strain and number; changes in the barrier/waveguide composition and thickness; changes in cladding structure; use of multi-quantum-barriers and changes in the doping profile. The experiments showed that the threshold current characteristic temperature (T0) increases with the number of QWs and is higher for compressive strain. The use of graded-index (GRIN) waveguides and higher p-cladding doping induced both a reduction in threshold current density and an increase in T0, mostly at shorter wavelengths. Waveguide thickness optimization can be carried out, for both constant composition and GRIN waveguides, using the QW optical confinement as a first-approximation optimization criterion. Modified cladding structures reduced the vertical far-field full-width-at-half-maximum below 20o without significantly affecting the threshold current. Devices designed using some of the guidelines resulted from our study achieved, with different structures and under different operating conditions, performances like emitting more than 2W at 650 nm in continuous wave operation or lasing down to 618 nm at room temperature, which is among the shortest wavelengths from lasers grown by solid-source molecular-beam-epitaxy.

Toikkanen, Lauri; Dumitrescu, Mihail M.; Tukiainen, Antti; Viitala, Suvi; Suominen, Mikko; Eroj„rvi, Vesa; Rimpil„inen, Ville; R÷nkk÷, Risto; Pessa, Markus

2004-09-01

78

Short-wavelength InGaAlP visible laser diodes  

Microsoft Academic Search

Results achieved on the operation of short-wavelength InGaAlP visible-light laser diodes are described. It is found that there is a strong correlation between operation temperature and oscillation wavelength. The deterioration of favorable temperature characteristics in the short-wavelength region is attributed to an increase in the leakage current, which originates in a small conduction-band discontinuity inherent in the InGaAlP material system.

G. Hatakoshi; K. Itaya; M. Ishikawa; M. Okajima; Y. Uematsu

1991-01-01

79

Cameras Reveal Elements in the Short Wave Infrared  

NASA Technical Reports Server (NTRS)

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.

2010-01-01

80

The degradation of alzak by short wavelength ultraviolet radiation  

NASA Technical Reports Server (NTRS)

The changes in reflectance of thermal aluminum coating samples exposed to different irradiating utraviolet wavelengths are discussed. It is shown that the coating is damaged faster and further by 180 to 210 in radiation than by Lyman alpha radiation. On an equivalent incident energy basis, Lyman alpha does less damage than 180 to 210 nm radiation. Above 300 nm no degradation is observed for long exposures and below 300 nm increasing degradation with decreasing wavelength is found. It is concluded that Lyman alpha radiation need not be included in laboratory testing of this thermal coating for spacecraft structures.

Donohoe, M. J.; Mcintosh, R., Jr.; Henninger, J. H.

1972-01-01

81

Atomic diffraction by light gratings with very short wavelengths  

E-print Network

Lasers with wavelengths of the order of the atomic size are becoming available. We explore the behavior of light-matter interactions in this emergent field by considering the atomic Kapitza-Dirac effect. We derive the diffraction patterns, which are in principle experimentally testable. From a fundamental point of view, our proposal provides an example of system where the periodicity of the diffraction grating is comparable to the size of the diffracted object.

Pedro Sancho

2013-06-23

82

All-Optical Wavelength Conversion using Multi-Pump Raman-assisted Four-Wave Mixing  

E-print Network

All-Optical Wavelength Conversion using Multi-Pump Raman-assisted Four-Wave Mixing S. H. Wang,1, The Hong Kong Polytechnic University, Hung Hom, Hong Kong Abstract: We reported all-optical wavelength conversion using multi-pump Raman-assisted four-wave mixing. All-optical wavelength conversion with 10 nm

Wai, Ping-kong Alexander

83

Short-Wavelength Infrared Views of Messier 81  

NASA Technical Reports Server (NTRS)

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.

2003-01-01

84

Interpretation of long- and short-wavelength magnetic anomalies  

USGS Publications Warehouse

Magset was launched on October 30, 1979. More than a decade of examining existing data, devising appropriate models of the global magnetic field, and extending methods for interpreting long-wavelength magnetic anomalies preceded this launch Magnetic data collected by satellite can be interrupted by using a method of analysis that quantitively describes the magnetic field resulting from three-dimensional geologic structures that are bounded by an arbitrary number of polygonal faces, Each face my have any orientation and three or more sides. At each point of the external field, the component normal to each face is obtained by using an expression for the solid angle subtended by a generalized polygon. The "cross" of tangential components are relatively easy to obtain for the same polygons. No approximations have been made related to orbit height that restrict the dimensions of the polygons relative to the distance from the external field points. This permits the method to be used to model shorter wavelength anomalies obtained from aircraft or ground surveys. The magnetic fields for all the structures considered are determine in the same rectangular coordinate system. The coordinate system is in depended from the orientation of geologic trends and permits multiple structures or bodies to be included in the same magnetic field calculations. This single reference system also simplified adjustments in position and direction to account for earth curvature in regional interpretation.

DeNoyer, John M.

1980-01-01

85

Standard achromatic perimetry, short wavelength automated perimetry, and frequency doubling technology for detection of glaucoma damage  

Microsoft Academic Search

ObjectiveReevaluation of the relationship between short wavelength automated perimetry (SWAP), standard achromatic perimetry (SAP), and frequency doubling technology (FDT) in glaucoma and ocular hypertensive patients and in glaucoma suspects.

Mohamed A. E Soliman; Leo A. M. S de Jong; Al-Araby A Ismaeil; Thomas J. T. P van den Berg; Marc D de Smet

2002-01-01

86

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

E-print Network

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 ...

Kaertner, Franz X.

87

Dual-band ultraviolet-short-wavelength infrared imaging via luminescent downshifting with colloidal quantum dots  

E-print Network

The performance of short-wavelength infrared (SWIR) cameras in the visible and ultraviolet (UV) regions is limited by the absorption of high-energy photons in inactive regions of the imaging array. Dual-band UV-SWIR imaging ...

Geyer, Scott M.

88

SHORT-WAVELENGTH, SINGLE-PASS FREE-ELECTRON LASERS J. Rossbach, DESY, 22603 Hamburg, Germany  

E-print Network

SHORT-WAVELENGTH, SINGLE-PASS FREE-ELECTRON LASERS J. Rossbach, DESY, 22603 Hamburg, Germany in demonstration of high power gain at single- pass free-electron lasers operating in the wavelength range from in the undulator. Eq. (1) exhibits two main advantages of the free-electron laser: the free tunability

89

PHYSICAL REVIEW A 83, 013405 (2011) Precision calculation of above-threshold multiphoton ionization in intense short-wavelength laser  

E-print Network

in intense short-wavelength laser fields: The momentum-space approach and time-dependent generalized to the nonperturbative study of the multiphoton and ATI dynamics of a hydrogen atom exposed to intense short- wavelength

Chu, Shih-I

90

Short-Wavelength Automated Perimetry and Capillary Density in Early Diabetic Maculopathy  

Microsoft Academic Search

PURPOSE. To correlate short-wavelength cone-mediated sensitivity (SWS) assessed by blue-on-yellow perimetry with alterations of the perifoveal vascular bed in early diabetic maculopathy. METHODS. Thirty-one patients (21 M, 10 F; mean age, 35 6 12 years; no lens opacities) with no clinically significant macular edema were included in this study. All patients underwent short- wavelength automated perimetry (SWAP) and conventional white-on-white

Andreas Remky; Oliver Arend; Stefan Hendricks

2000-01-01

91

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

NASA Technical Reports Server (NTRS)

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.

Vural, Kadri

1987-01-01

92

Investigating short wavelength correlated errors on low resolution mode altimetry  

NASA Astrophysics Data System (ADS)

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.

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

2013-04-01

93

Increased signals from short-wavelength-excited fluorescent molecules using sub-Ti:Sapphire wavelengths  

PubMed Central

We report the use of an all-solid-state ultrashort pulsed source specifically for two-photon microscopy at wavelengths shorter than those of the conventional Ti:Sapphire laser. Our approach involves sum–frequency mixing of the output from an optical parametric oscillator (?= 1400–1640 nm) synchronously pumped by a Yb-doped fibre laser (?= 1064 nm), with the residual pump radiation. This generated an fs-pulsed output tunable in the red spectral region (?= 620–636 nm, ?150 mW, 405 fs, 80 MHz, M2? 1.3). We demonstrate the performance of our ultrashort pulsed system using fluorescently labelled and autofluorescent tissue, and compare with conventional Ti:Sapphire excitation. We observe a more than 3-fold increase in fluorescence signal intensity using our visible laser source in comparison with the Ti:Sapphire laser for two-photon excitation at equal illumination peak powers of 1.16 kW or less. PMID:23078118

NORRIS, G; AMOR, R; DEMPSTER, J; AMOS, W B; MCCONNELL, G

2012-01-01

94

Scattering of long-wavelength elastic waves from localized defects in solids  

E-print Network

Scattering of long-wavelength elastic waves from localized defects in solids W. Kahn Department November 1978) It is shown that long-wavelength elastic scattering data from an arbitrary localized defect to the long-wavelength limit, including the scattering from a homogeneous ellipsoid and a circular (penny

95

The Shoelace Antenna : a device to induce short-wavelength fluctuations in the edge plasma of the Alcator C-Mod Tokamak  

E-print Network

The "Shoelace" antenna is a unique device built to induce short-wavelength fluctuations in the edge plasma of the Alcator C-Mod tokamak, at a wave number and in the frequency range associated with the Quasi-Coherent Mode ...

Golfinopoulos, Theodore

2014-01-01

96

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

NASA Technical Reports Server (NTRS)

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.

Oya, H.

1971-01-01

97

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

NASA Technical Reports Server (NTRS)

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.

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

1974-01-01

98

Terahertz imaging of sub-wavelength particles with Zenneck surface waves  

SciTech Connect

Impact of sub-wavelength-size dielectric particles on Zenneck surface waves on planar metallic antennas is investigated at terahertz (THz) frequencies with THz near-field probe microscopy. Perturbations of the surface waves show the particle presence, despite its sub-wavelength size. The experimental configuration, which utilizes excitation of surface waves at metallic edges, is suitable for THz imaging of dielectric sub-wavelength size objects. As a proof of concept, the effects of a small strontium titanate rectangular particle and a titanium dioxide sphere on the surface field of a bow-tie antenna are experimentally detected and verified using full-wave simulations.

Navarro-Cía, M., E-mail: m.navarro@imperial.ac.uk [Optical and Semiconductor Devices Group, Department of Electrical and Electronic Engineering, Imperial College London, London SW7 2BT (United Kingdom); Centre for Plasmonics and Metamaterials, Imperial College London, London SW7 2AZ (United Kingdom); Centre for Terahertz Science and Engineering, Imperial College London, London SW7 2AZ (United Kingdom); Department of Electronic and Electrical Engineering, University College London, Torrington Place, London WC1E 7JE (United Kingdom); Natrella, M.; Graham, C.; Renaud, C. C.; Seeds, A. J.; Mitrofanov, O., E-mail: o.mitrofanov@ucl.ac.uk [Department of Electronic and Electrical Engineering, University College London, Torrington Place, London WC1E 7JE (United Kingdom); Dominec, F.; Kužel, P., E-mail: kuzelp@fzu.cz [Institute of Physics, Academy of Sciences of the Czech Republic, Na Slovance 2, 182 21 Prague 8 (Czech Republic); Delagnes, J. C.; Mounaix, P., E-mail: p.mounaix@loma.u-bordeaux1.fr [LOMA, Bordeaux 1 University, CNRS UMR 4798, 351 cours de la Libération, 33405 Talence (France)

2013-11-25

99

Fundamental mechanisms of optical damage in short-wavelength high-power lasers  

SciTech Connect

Evidence has been accumulating for many years that the physical mechanisms responsible for damage to optical materials in and from high-power, short-wave-length lasers (SWLs) differ in fundamental ways from the thermal processes identified in infrared and visible-wavelength laser damage problems. We propose that this difference stems primarily from the electronic nature of the absorption and excitation processes which occur when SWL photons strike an optical surface, and that electrons, ions and uv photons generated in the laser excitation cycle also contribute to optical damage. In this paper, we present recent experimental results which have pinpointed specific electronic excitation mechanisms which can operate in the high-power laser environment. In many optical materials of interest for SWLs, the deposition of electronic energy creates self-trapped excitons which decay through the energetic expulsion of atoms and molecules from the surface of the material. This erosion process is accompanied by the creation of permanent electronic defects which become nucleation sites for further damage. The relationship between these microscopic mechanisms and observed macroscopic damage phenomenology is discussed, along with evidence for the existence of a surface overlayer which may point the way to radically new techniques for protecting SWL optical elements from laser damage.

Haglund, R.F. Jr.; Tolk, N.H.; York, G.W.

1985-10-01

100

Short wavelength HgCdTe staring focal plane for low background astronomy applications  

NASA Technical Reports Server (NTRS)

The design of a 128x128 staring short wave infrared (SWIR) HgCdTe focal plane incorporating charge integrating transimpedance input preamplifiers is presented. The preamplifiers improve device linearity and uniformity, and provide signal gain ahead of the miltiplexer and readout circuitry. Detector's with cutoff wavelength of 2.5 microns and operated at 80 K have demonstrated impedances in excess of 10(exp 16) ohms with 60 percent quantum efficiency. Focal plane performance using a smaller format device is presented which demonstrates the potential of this approach. Although the design is capable of achieving less than 30 rms electrons with todays technology, initial small format devices demonstrated a read noise of 100 rms electrons and were limited by the atypical high noise performance of the silicon process run. Luminescence from the active silicon circuitry in the multiplexer limits the minimum detector current to a few hundred electrons per second. Approaches to eliminate this excessive source of current is presented which should allow the focal plane to achieve detector background limited performance.

Hall, D.; Stobie, J.; Hartle, N.; Lacroix, D.; Maschhoff, K.

1989-01-01

101

Four-wave mixing in an optical fiber in the zero-dispersion wavelength region  

Microsoft Academic Search

Fiber four-wave mixing (FWM) in the zero-dispersion wavelength region is described. The phase-matching characteristics are studied in the wavelength region where the first-order chromatic dispersion is zero. The results show that the phase-matching condition is satisfied and FWM light is efficiently generated at particular combinations of input light wavelengths. It is also shown that the deviation of the zero-dispersion wavelength

Kyo Inoue

1992-01-01

102

Short-wavelength electrostatic waves in the earth's magnetosheath  

Microsoft Academic Search

Recent observations with the ISEE 1 spacecraft have found electric field emissions in the dayside magnetosheath whose frequency spectrum is modulated at twice the spacecraft spin period. The upper frequency cutoff in the frequency-time spectrum of the emission has a characteristic parabola shape or ''festoon'' shape. The low-frequency cutoff ranges from 100 to 400 Hz, while the high-frequency limit ranges

D. L. Gallagher

1985-01-01

103

Enhancement of the short wavelength upconversion emission in inverse opal photonic crystals.  

PubMed

Upconversion luminescence properties of Yb-Tb codoped Bi4Ti3O12 inverse opals have been investigated. The results show that the upconversion emission can be modulated by the photonic band gap. More significantly, in the upconversion inverse opals, the excited-state absorption of Tb3+ is greatly enhanced by the suppression of upconversion spontaneous emissions of the intermediate excited state, and thus the short wavelength upconversion emission from Tb3+ is considerably improved. We believe that the present work will be valuable for not only the foundational study of upconversion emission modifications but also new optical devices in upconversion displays and short wavelength upconversion lasers. PMID:24734648

Wu, Hangjun; Zhu, Jialun; Yang, Zhengwen; Yan, Dong; Wang, Rongfei; Qiu, Jianbei; Song, Zhiguo; Yu, Xue; Yang, Yong; Zhou, Dacheng; Yin, Zhaoyi

2014-05-01

104

Effect of short-scale turbulence on kilometer wavelength irregularities in the equatorial electrojet  

Microsoft Academic Search

The kilometer scale irregularities in the daytime equatorial electrojet are studied within the framework of a two-fluid, nonlocal theory of the gradient drift instability. A separation of scales is introduced into the equations in order to model the effects of the subgrid, short-wavelength (λ < 100 m) modes. The presence of the short-scale turbulence is included in the large-scale equations

C. Ronchi; R. N. Sudan; P. L. Similon

1990-01-01

105

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

NASA Astrophysics Data System (ADS)

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.

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

1996-10-01

106

Sub-100 nm Focusing of Short Wavelength Plasmons in Homogeneous 2D Space.  

PubMed

We present a direct measurement of short-wavelength plasmons focused into a sub-100 nm spot in homogeneous (translation invariant) 2D space. The short-wavelength (SW) surface plasmon polaritons (SPP) are achieved in metal-insulator-insulator (MII) platform consisting of silver, silicon nitride, and air. This platform is homogeneous in two spatial directions and supports SPP at wavelength more than two times shorter than that in free space yet interacts with the outer world through the evanescent tail in air. We use an apertureless (scattering) near-field scanning optical microscope (NSOM) to map directly the amplitude and phase of these SW-SPP and show they can be focused to under 70 nm without structurally assisted confinement such as nanoantennas or nanofocusing. This, along with the use of visible light at 532 nm which is suitable for optical microscopy, can open new directions in direct biological and medical imaging at the sub-100 nm resolution regime. PMID:25180927

Gjonaj, B; David, A; Blau, Y; Spektor, G; Orenstein, M; Dolev, S; Bartal, G

2014-10-01

107

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

NASA Astrophysics Data System (ADS)

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.

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

2014-09-01

108

Is the Local Density Approximation Exact for Short Wavelength Fluctuations? Kieron Burke and John P. Perdew  

E-print Network

for the success of the local spin density (LSD) approximation is that it correctly accounts for short wavelength on a specific system (Hooke's atom). Nevertheless, we find that LSD is rather accurate for small interelectronic density (LSD) approximation [2]. Recently, systematic improvements on LSD have become possible

Langreth, David C.

109

Quantum key distribution system in standard telecommunications fiber using a short wavelength single photon source  

E-print Network

Quantum key distribution system in standard telecommunications fiber using a short wavelength of quantum key distribution QKD is performed using a single-photon source in a proof of concept test-bed over.1063/1.3327427 I. INTRODUCTION Quantum key distribution QKD provides a verifiably secure means for two authorized

Buller, Gerald S.

110

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

NASA Technical Reports Server (NTRS)

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.

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

1979-01-01

111

The Aharonov-Bohm effect in scattering of short-wavelength particles  

E-print Network

Quantum-mechanical scattering of nonrelativistic charged particles by a magnetic vortex of nonzero transverse size is considered. We show that the flux of the vortex serves as a gate for the strictly forward propagation of particles with short, as compared to the transverse size of the vortex, wavelengths. A possibility for the experimental detection of the scattering Aharonov-Bohm effect is discussed.

Sitenko, Yu A

2011-01-01

112

An analysis for the circular mode of magnetization in short wavelength recording  

Microsoft Academic Search

It has been deduced from the analysis of recording demagnetization mechanism in magnetic recording that in short wavelengths the remanent magnetization exhibits a closed-loop structure in the recording medium. In this paper a novel experimental method is presented to confirm the existence of such structure (a circular magnetization mode) and to investigate its mechanism for usual recording medium and heads.

S. Iwasaki; K. Takemura

1975-01-01

113

Distribution and Density of Medium and Short-wavelength Selective Cones in the Domestic Pig Retina  

Microsoft Academic Search

The topography of medium (M)- and short (S)-wavelength sensitive cone photoreceptors was studied in the domestic pig retina. Antisera specific for M or S opsin as well as cone photoreceptor proteins arrestin and alpha-transducin were used to label cone types. Retinal wholemounts and their blood vessel patterns were drawn and specific regions removed. The wholemounts were immunocytochemically labelled to detect

Anita Hendrickson; David Hicks

2002-01-01

114

Experimental study of the Rayleigh-Taylor instability initiated with a complex, short-wavelength initial perturbation.  

NASA Astrophysics Data System (ADS)

Experiments exploring the Rayleigh-Taylor (RT) instability initiated with a short-wavelength near single-mode initial perturbation have been performed. The experiments were conducted using a square Plexiglass tank mounted to a vertical rail system. The tank is filled with a stably stratified combination of two miscible liquids having an Atwood number of approximately 0.15. The instability is initiated with an imposed initial perturbation in the form of internal Faraday waves at the interface of the two fluids. RT instability is then generated by accelerating the tank down the rails through a pulley-weight system. Net accelerations ranging from 0.4 to 1.4 g's are achieved. The Faraday waves are created by oscillating the tank vertically. The current configuration is capable of creating Faraday waves with a three-dimensional nearly single-mode pattern with wavelengths ranging from 7 to 10 mm. PLIF images of the instability developing from these perturbations reveal what appears to be the beginnings of the development of a turbulent self-similar flow.

Olson, David

2005-11-01

115

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

NASA Technical Reports Server (NTRS)

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.

Atakturk, Serhad S.; Katsaros, Kristina B.

1993-01-01

116

A passive wavelength demodulation system for guided-wave Bragg grating sensors  

Microsoft Academic Search

A novel, passive, and self-referencing wavelength detection system (WDS) that measures the wavelength of the narrowband back-reflected spectrum of guided-wave Bragg gratings is described. This letter also reports on the use of such a detection system with fiber-optic Bragg gratings used as absolute strain sensors. The wavelength detection system demonstrated a 1% strain resolution of the total strain measurement range

Serge M. Melle; Kexing Liu; Raymond M. Measures

1992-01-01

117

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

SciTech Connect

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.

Fiuza, F.; Silva, L. O. [GoLP/Instituto de Plasmas e Fusao Nuclear, Instituto Superior Tecnico, 1049-001 Lisboa (Portugal)

2009-01-22

118

In-orbit performance of the ISO short-wavelength spectrometer  

NASA Astrophysics Data System (ADS)

The short wavelength spectrometer (SWS) is one of the four instruments on-board of ESA's IR SPace Observatory (ISO), launched on 15 November 1995. It covers the wavelength range of 2.38-45.2 microns with a spectral resolution ranging from 1000-2000. By inserting Fabry-Perot filters the resolution can be enhanced by a factor 20 for the wavelength range from 11.4-44.5 microns. After the successful launch the instrument was tested and calibrated during a period of spacecraft checkout and performance verification. The opto- mechanical construction of the instrument appears to behave extremely well. The instrument performance is on all aspects as expected, except for the detector sensitivity where the noise is dominated by effects of particle radiation. We given here an overview of the in-orbit performance, discuss the calibration and present some result from trend analysis of the most important instrument and detector parameters.

de Graauw, Thijs; Feuchtgruber, Helmut; Roelfsema, Peter R.; Salama, A.; Bauer, Otto H.; Beintema, Douwe A.; Boxhoorn, D.; Decin, L.; Haser, Leo N.; Heras, A.; Huygen, Rik; Katterloher, Reinhard O.; Kester, D.; Kunze, D.; Lahuis, F.

1998-08-01

119

Multiphoton Femtosecond Control of Resonance-Mediated Generation of Short-Wavelength Coherent Broadband Radiation  

E-print Network

We introduce a new scheme for generating short-wavelength coherent broadband radiation with well-controlled spectral characteristics. It is based on shaping long-wavelength femtosecond pulse to coherently control atomic resonance-mediated (2+1) three-photon excitation to a broad far-from-resonance continuum. Here, the spectrum (central frequency and bandwidth) of deep-ultraviolet coherent broadband radiation generated in Na vapor is experimentally controlled by tuning the linear chirp we apply to the driving phase-shaped near-infrared femtosecond pulse. This is a first step in implementing the full scheme for producing shaped femtosecond pulses at wavelengths down-to the vacuum-ultraviolet range.

Rybak, Leonid; Gandman, Andrey; Shakour, Naser; Amitay, Zohar

2009-01-01

120

Mode-selective wavelength conversion based on four-wave mixing in a multimode silicon waveguide.  

PubMed

We propose and demonstrate all-optical mode-selective wavelength conversion in a silicon waveguide. The mode-selective wavelength conversion relies on strong four-wave mixing when pump and signal light are on the same spatial mode, while weak four-wave mixing is obtained between different modes due to phase mismatch. A two-mode division multiplexing circuit with tapered directional coupler based (de)multiplexers and a multimode waveguide is designed and fabricated for this application. Experimental results show clear eye-diagrams and moderate power penalties for the wavelength conversion of both modes. PMID:24514974

Ding, Yunhong; Xu, Jing; Ou, Haiyan; Peucheret, Christophe

2014-01-13

121

Finite element modeling of short-wavelength folding on Venus: Implications for the plume hypothesis for crustal plateau formation  

E-print Network

Finite element modeling of short-wavelength folding on Venus: Implications for the plume hypothesis. We report here on finite element simulations designed to test the feasibility of the proposed thermal, the finite element meshes develop semibrittle zones in which short-wavelength folds can form, but development

Hansen, Vicki

122

Wavelength-scale stationary-wave integrated Fouriertransform spectrometry  

Microsoft Academic Search

Spectrometry is a general physical-analysis approach for investigating light-matter interactions. However, the complex designs of existing spectrometers render them resistant to simplification and miniaturization, both of which are vital for applications in micro- and nanotechnology and which are now undergoing intensive research. Stationary-wave integrated Fourier-transform spectrometry (SWIFTS)-an approach based on direct intensity detection of a standing wave resulting from either

Etienne Le Coarer; Sylvain Blaize; Pierre Benech; Ilan Stefanon; Alain Morand; Gilles Lérondel; Grégory Leblond; Pierre Kern; Jean Marc Fedeli; Pascal Royer

2007-01-01

123

Infrared Space Observatory Short Wavelength Spectrometer Observations of V1425 Aquilae (Nova Aquila 1995)  

NASA Astrophysics Data System (ADS)

We present observations of the classical nova V1425 Aquilae (Nova Aquila 1995) with the Infrared Space Observatory's (ISO) Short Wavelength Spectrometer, the Isaac Newton Telescope's Intermediate Dispersion Spectrograph, and the International Ultraviolet Explorer's Short-Wavelength Primary Spectrograph. Analysis of He II (1640 Å) development constrains the white dwarf turnoff to ~400 days after outburst. Photoionization modeling of the optical and ISO spectra obtained during the late nebular phase constrains the mass of the ejecta between 2.5-4.2×10-5 Msolar. This modeling also suggests C and O in the ejecta were enhanced by a factor of ~9, and N was enhanced by a factor of ~100 with respect to solar, while Ne was only slightly enhanced. Based upon these analyses, we determine that the white dwarf in the V1425 Aql system has a CO composition and is at a distance of 3.0+/-0.4 kpc.

Lyke, J. E.; Gehrz, R. D.; Woodward, C. E.; Barlow, M. J.; Péquignot, D.; Salama, A.; Schwarz, G. J.; Shore, S. N.; Starrfield, S.; Evans, A.; Gonzales-Riestra, R.; Greenhouse, M. A.; Hjellming, R. M.; Humphreys, R. M.; Jones, T. J.; Krautter, J.; Morisset, C.; Ögelman, H. B.; Orio, M.; Wagner, R. M.; Walton, N. A.; Williams, R. E.

2001-12-01

124

Short-wavelength infrared tuneable filters on HgCdTe photoconductors  

Microsoft Academic Search

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 °C has negligible effect on the electronic and optical performance of photoconductor test structures. Maximum responsivity, effective carrier lifetime and detectivity are 60×103 VW-1, 2×10-5 s and 8×1010 cmHz1\\/2W-1, respectively. The

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

2005-01-01

125

Study of Patients with Ocular Hypertension with Scanning Laser Polarimetry and Short-Wavelength Automatic Perimetry  

Microsoft Academic Search

Aims: To compare and correlate retinal nerve fiber layer (RNFL) measurements obtained by scanning laser polarimetry (SLP) with defects detected by short-wavelength automatic perimetry (SWAP) in eyes with ocular hypertension (OHT). Methods: SLP and SWAP were performed in 96 eyes of 48 consecutive patients with OHT. Results: Twenty-five eyes (26%) had SWAP visual field defects. Twenty-seven eyes (28.1%) had abnormal

Gerasimos T. Georgopoulos; Ioannis Halkiadakis; Eleni Patsea; Dimitrios Papakonstantinou; Michalis Alexiou; Ioannis Vergados; Dimitrios Andreanos; George Theodossiadis; Michalis Moschos

2006-01-01

126

Ionizing Radiation and Short Wavelength UV Activate NF-kappa B through Two Distinct Mechanisms  

Microsoft Academic Search

We examined the mechanisms by which two different types of photonic radiation, short wavelength UV (UV-C) and gamma radiation, activate transcription factor NF-kappa B. Exposure of mammalian cells to either form of radiation resulted in induction with similar kinetics of NF-kappa B DNA binding activity, nuclear translocation of its p65 (RelA) subunit, and degradation of the major NF-kappa B inhibitor

Nanxin Li; Michael Karin

1998-01-01

127

Observation of a short-wavelength laser pumped by Auger decay  

Microsoft Academic Search

We report the observation of gain in a new type of short-wavelength laser system at 108.9 nm. Soft x rays from a laser-produced plasma photoionize an inner-shell electron from xenon, and a population inversion is created by subsequent Auger decay to particular excited states. A model for this system is described, spectroscopic data are presented, and gain limitations due to

H. C. Kapteyn; R. W. Lee; R. W. Falcone

1986-01-01

128

Short-wavelength sensitive visual field loss in patients with clinically significant diabetic macular oedema  

Microsoft Academic Search

Summary   The aim of the study was to compare the sensitivity of short-wavelength and conventional automated static threshold perimetry\\u000a for the psychophysical detection of abnormality in patients with clinically significant diabetic macular oedema. The sample\\u000a comprised 24 patients with clinically significant diabetic macular oedema (mean age 59.75 years, range 45–75 years). One eye\\u000a of each patient was selected. Exclusion criteria

C. Hudson; J. G. Flanagan; G. S. Turner; H. C. Chen; L. B. Young; D. McLeod

1998-01-01

129

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

SciTech Connect

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.

Power, J. G.; Jiang, B.; Gai, W.; Liu, W.; Lindberg, R. (Advanced Photon Source); ( HEP); (Shanghai Inst. of Applied Physics)

2011-03-16

130

Emittance-Exchange-Based High Harmonic Generation Scheme for a Short-Wavelength Free Electron Laser  

SciTech Connect

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.

Jiang, B. [Argonne National Laboratory, 9700 South Cass Avenue, Argonne, Illinois 60439 (United States)] [Shanghai Institute of Applied Physics, CAS, Shanghai 201800 (China); Power, J. G.; Lindberg, R.; Liu, W.; Gai, W. [Argonne National Laboratory, 9700 South Cass Avenue, Argonne, Illinois 60439 (United States)

2011-03-18

131

Achromatic and Short-Wavelength Automated Perimetry in Patients With Glaucomatous Large Cups  

Microsoft Academic Search

Objective: To evaluate visual function and optic disc features in patients with large cup-disc ratios (C\\/Ds). Methods: One eye of 86 patients with vertical C\\/Ds by contour of at least 0.8, who had undergone both standard achromatic automated perimetry (SAP) and short- wavelength automated perimetry (SWAP) testing, was se- lected retrospectively. Two masked glaucoma specialists independently graded stereoscopic photographs for

Steven L. Mansberger; Pamela A. Sample; Linda Zangwill; Robert N. Weinreb

1999-01-01

132

Sub-optical wavelength acoustic wave modulation of integrated photonic resonators at microwave frequencies  

E-print Network

Light-sound interactions have long been exploited in various acousto-optic devices based on bulk crystalline materials. Conventionally these devices operate in megahertz frequency range where the acoustic wavelength is much longer than the optical wavelength and a long interaction length is required to attain significant coupling. With nanoscale transducers, acoustic waves with sub-optical wavelengths can now be excited to induce strong acousto-optic coupling in nanophotonic devices. Here we demonstrate microwave frequency surface acoustic wave transducers co-integrated with nanophotonic resonators on piezoelectric aluminum nitride substrates. Acousto-optic modulation of the resonance modes at above 10 GHz with the acoustic wavelength significantly below the optical wavelength is achieved. The phase and modal matching conditions in this scheme are investigated for efficient modulation. The new acousto-optic platform can lead to novel optical devices based on nonlinear Brillouin processes and provides a direct...

Tadesse, Semere Ayalew

2014-01-01

133

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

PubMed Central

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 (?max ? 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

Figueiro, Mariana G.; Rea, Mark S.

2012-01-01

134

Short wavelength limitation in high power AlGaInP laser diodes  

NASA Astrophysics Data System (ADS)

In wavelength region of red color, luminous efficacy rapidly increases as wavelength shortens. In that sense, red laser diode (LD) with shorter wavelength is required for display applications. Experimental results for short wavelength limitation in AlGaInP LDs are shown and discussed in this paper. Broad area LDs with 625, 630, and 638 nm are successfully fabricated. Operation current versus output power (P-I) characteristics and its temperature dependence of 625 nm LD are inferior to that of 630 and 638 nm ones. The main reason might be carrier leakage, and the results indicate that additional countermeasures to carrier leakage should be adopted to realize a 625 nm LD with the same temperature characteristics as 630 and 638 nm LDs. Conversion efficiencies from input electrical power to luminous flux output of the LDs are also studied. 625 nm LD has low efficiency, though brightness of 625 nm light is 1.7 times of 638nm one with the same output power. And 630 nm LD shows better conversion efficiency at high luminous flux region than 638 nm one, though the P-I characteristics of 630 nm is worse than that of 638 nm one. The tendency is inverted at low flux region, indicating that the lasing wavelength of red LD for laser display should be chosen carefully.

Nishida, Takehiro; Shimada, Naoyuki; Ogawa, Tetsuya; Miyashita, Motoharu; Yagi, Tetsuya

2011-03-01

135

The Rigorous Approximation of Long-Wavelength Capillary-Gravity Waves  

Microsoft Academic Search

In a previous paper we proved that long-wavelength solutions of the water-wave problem in the case of zero surface tension\\u000a split up into two wave packets, one moving to the right and one to the left, where each of these wave packets evolves independently\\u000a as a solution of a Korteweg-de Vries (KdV) equation. In this paper we examine the effect

Guido Schneider; C. Eugene Wayne

2002-01-01

136

Short-wavelength-sensitive perimetry can predict which glaucoma suspects will develop visual-field loss  

NASA Astrophysics Data System (ADS)

Previous investigations have demonstrated that when short wavelength light is detected exclusively by short wavelength sensitive mechanisms (SWS or S cone pathways), patients with ocular hypertension (elevated intraocular pressure) or early glaucomatous damage exhibit losses of sensitivity at the fovea and throughout the central 30 degrees of the visual field. We have recently developed a technique for measuring the sensitivity of short wavelength sensitive mechanisms throughout the central visual field by means of a modified automated perimeter. In order to determine the clinical significance and prognostic value of short wavelength sensitivity losses measured with this procedure, we conducted a prospective longitudinal five year investigation of 22 patients with early glaucomatous visual field loss (44 eyes), 38 ocular hypertensive patients (76 eyes) and 62 age-matched normal control subjects (124 eyes). All participants were evaluated annually with standard automated perimetry (AP) and short- wavelength-sensitive perimetry (SWSP). At the beginning of the study, 67 out of 76 eyes in the ocular hypertension patients had normal results for both AP and SWSP tests, while nine out of 76 had normal AP results but abnormal SWSP findings. Five years later, five out of nine ocular hypertensive eyes with initial SWSP abnormalities have developed evidence of glaucomatous visual field loss on standard AP testing. The abnormalities on AP testing occurred in the same general location as those found in earlier years for SWSP evaluations. None of the ocular hypertensive eyes with normal SWSP results in year one developed abnormal AP deficits after five years. Seven out of the 44 eyes of early glaucoma patients demonstrated reproducible evidence of progression of visual field loss on standard AP testing. In all seven instances, the SWSP deficits were larger than the AP abnormalities at the beginning of the study, and the progression of AP sensitivity losses over five years followed the pattern of SWSP deficits obtained in earlier years. These findings provide strong evidence that SWSP abnormalities are an early indicator of glaucomatous damage and are predictive of impending glaucomatous visual field loss for standard AP testing.

Johnson, Chris A.; Adams, Anthony J.; Casson, Evanne J.

1992-08-01

137

Short-Wave Infrared HgCdTe Avalanche Photodiodes  

NASA Astrophysics Data System (ADS)

Short-wave infrared (SWIR) HgCdTe avalanche photodiodes (APDs) have been developed to address low-flux applications at low operating temperature and for laser detection at higher temperatures. Stable multiplication gains in excess of 200 have been observed in homojunction APDs with cutoff wavelengths down to 2.8 ?m and operating temperatures up to 300 K, associated with low excess noise F < 1.3 and low 1/ f noise. The measured dark current density at 200 K of 6.2 ?A/cm2 is low enough to enable high-sensitivity single-element light detection and ranging (lidar) applications and time-of-flight imaging. Corresponding APD arrays have been hybridized on a readout integrated circuit (ROIC) designed for low-flux low-SNR imaging with low noise and frame rates higher than 1500 frames/s. Preliminary focal-plane array characterization has confirmed the nominal ROIC performance and showed pixel operability above 99.5% (pixels within ±50% of average gain). The bias dependence of the multiplication gain has been characterized as a function of temperature, cadmium composition, and junction geometry. A qualitative change in the bias dependence of the gain compared with mid-wave infrared (MWIR) HgCdTe has motivated the development of a modified local electric field model for the electron impaction ionization coefficient and multiplication gain. This model gives a close fit to the gain curves in both SWIR and MWIR APDs at temperatures between 80 K and 300 K, using two parameters that scale as a function of the energy gap and temperature. This property opens the path to quantitative predictive device simulations and to estimations of the junction geometry of APDs from the bias dependence of the gain.

Rothman, Johan; Mollard, Laurent; Bosson, Sylvie; Vojetta, Gautier; Foubert, Kevin; Gatti, Sylvain; Bonnouvrier, Gwladys; Salveti, Frederic; Kerlain, Alexandre; Pacaud, Olivier

2012-10-01

138

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

NASA Technical Reports Server (NTRS)

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.

Shuart, M. J.

1985-01-01

139

Stress field of Italy — Mean stress orientation at different depths and wave-length of the stress pattern  

NASA Astrophysics Data System (ADS)

We have studied the stress pattern of Italy using a dataset with 590 data records from the World Stress Map database release 2008 and 106 new data records to test the hypothesis the mean orientation of maximum horizontal stress SH is different at different depth sections. For this, we split the dataset into a shallow (0-6 km) and a deep (6-40 km) depth section. For the data analysis we used a new statistical tool that calculates the mean SH orientation on a 0.2° grid. The tool takes into account the distance to each grid point, number and quality of the data records within the search radius, and the radial distribution. The result is a smoothed Italian stress map that displays both; the mean SH orientation and the wave-length of the stress pattern. The stress pattern does not vary in depth except for two areas (Sardinia and southern Apulia). Therefore stress data from different depths can be used to estimate the mean SH orientation and the wave-length of the stress pattern in Italy. Furthermore, the smoothed Italian stress map reveals that most of Italy has short wave-length stress patterns (< 150 km). This indicates that the stress field is not controlled by first-order stress sources of plate tectonics, i.e. the convergence of Africa with respect to Eurasia, but that second-order stress sources such as topography, density, strength contrasts, and major faults systems are of great importance. In four regions (western part of the Alps, northern Tuscany, northern Adriatic Sea, Calabria and eastern part of Sicily) the wave-length is < 100 km. High values of the circular variance of the mean SH orientation observed here are driven by third-order local stress sources, such as basins or local neotectonic structures.

Pierdominici, Simona; Heidbach, Oliver

2012-04-01

140

Numerical Analysis of Effects of Incident Laser Wavelength on Thermal Nonequilibrium Laser-supported Detonation Wave  

NASA Astrophysics Data System (ADS)

Laser-supported detonation (LSD) waves are important because they can generate the high pressures and high temperatures necessary for laser propulsion systems. Although CO2 laser beams, which have a wavelength of 10.6 ?m, have been considered to be one of the most powerful sources of LSD waves, a glass laser beam (1.053?m), for example, also have high power. In this study, we numerically simulated LSD waves propagating through a diatomic gas, in order to evaluate the effects of incident laser wavelength on the construction of the LSD wave. We used the physical-fluid dynamics scheme, which has been developed for simulating unsteady and nonequilibrium LSD waves propagating through hydrogen gas.

Shiraishi, Hiroyuki; Koide, Takuya; Nakamori, Manabu

141

Output characteristics of SASE-driven short wavelength FEL`s  

SciTech Connect

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}.

Fawley, W.M.

1997-02-01

142

Assessment of radiography for diagnosing short wavelength instability growth and mix in NIF ignition capsules.  

SciTech Connect

Understanding and controlling hydrodynamic instabilities is critical to achieving ignition at National Ignition Facility (NIF). High resolution x-ray radiography of a NIF capsule may be able to measure key aspects of short wavelength instability growth including time dependent areal density variations, the dominant wavelength of growth, amount of growth from isolated capsule defects on the ablator and ice surfaces, and growth of perturbations as a result of the fill tube or dust contaminants. Radiography of the capsule limb may also place constraints on the width of the ice/ablator mix layer. Measurement of these various observables are important to determine what effect target design changes has on instability growth and to validate code predictions. We present an analysis of 2D and 3D HYDRA simulations and demonstrate how radiography can be used to diagnose signatures of mix in NIC capsules.

Peterson, Kyle J.; Haan, Steve (Lawrence Livermore National Laboratory); Hammel, Bruce (Lawrence Livermore National Laboratory); Suter, Laurence J. (Lawrence Livermore National Laboratory); Clark, Dan (Lawrence Livermore National Laboratory); Vesey, Roger Alan; Herrmann, Mark C.; Landen, Otto L. (Lawrence Livermore National Laboratory)

2008-11-01

143

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

PubMed

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

Colombi, Andrea; Roux, Philippe; Rupin, Matthieu

2014-08-01

144

Implications of controlled short-wavelength light exposure for sleep in older adults  

PubMed Central

Background Environmental and physiological conditions make older adults more likely to lose synchronization to their local time and experience sleep disturbances. A regular, 24-hour light/dark cycle promotes synchronization. It is now well established that the circadian system is maximally sensitive to short-wavelength (blue) light. The purpose of the present study was to measure dose effectiveness (amounts and durations) of short-wavelength (blue) light for stimulating the circadian systems of older adults. We investigated the impact of six corneal irradiances (0.7 to 72 ?W/cm2) of 470-nm light on nocturnal melatonin production. Nine participants, each over 50 years of age completed a within-subjects study. Each week, participants were exposed to one of the six irradiances of 470-nm light for 90 minutes. Findings A two-factor (6 corneal irradiances × 10 exposure durations), within-subjects analysis of variance (ANOVA) was conducted using the melatonin suppression levels. The ANOVA revealed a significant main effect of corneal irradiance (F5, 30 = 9.131, p < 0.0001), a significant main effect of exposure duration (F9, 54 = 5.731, p < 0.0001), and a significant interaction between these two variables (F45,270 = 1.927, p < 0.001). Post hoc t-tests revealed that corneal irradiances as low as 2 ?W/cm2 reliably suppressed melatonin after 90-minute exposure whereas 0.7 ?W/cm2 did not. Conclusions Sleep disorders are common and a serious problem for millions of older adults. The present results showed that comfortable, precise and effective doses of light can be prescribed to older adults to reliably stimulate the circadian system that presumably would promote entrainment and, thus, regular sleep. Field studies on the impact of short-wavelength-light doses on sleep efficiency in older adults should be performed. PMID:21902824

2011-01-01

145

High-power and wavelength-tunable traveling-wave semiconductor ring laser  

E-print Network

HIGH-POWER AND WAVELENGTH-TUNABLE TRAVELING-WAVE SEMICONDUCTOR RING LASER A Thesis EN TITUS PENG Submitted to the Office of Graduate Studies of Texas ARM University in partial fulfillment of the requirement for the degree of MASTER OF SCIENCE... May 1991 Major Subject: Electrical Engineering HIGH-POWER AND WAVELENGTH-TUNABLE TRAVELING-WAVE SEMICONDUCTOR RING LASER A Thesis by EN TITUS PENG Approved as to style and content by: Ch' B. Su (Chair of Committee) 0, 4 Ohannes E n yan...

Peng, En Titus

2012-06-07

146

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

SciTech Connect

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.

Gkortsas, Vasileios-Marios; Bhardwaj, Siddharth; Lai, Chien-Jen; Hong, Kyung-Han [Department of Electrical Engineering and Computer Science and Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); Falcao-Filho, Edilson L. [Departamento de Fisica, Universidade Federal de Pernambuco, 50670-901, Recife, Pernambuco (Brazil); Kaertner, Franz X. [Department of Electrical Engineering and Computer Science and Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); DESY-Center for Free-Electron Laser Science and Hamburg University, 22607 Hamburg (Germany)

2011-07-15

147

Electrostatic, short-wavelength, turbulence as the source of ion heating in the solar wind  

NASA Technical Reports Server (NTRS)

A mechanism is proposed for the nonthermal ion heating observed in the solar wind at 1 A.U. based on an electrostatic, short wavelength, instability between the ions in the observed colliding plasma streams. The modes lying on a plane perpendicular to the magnetic field thermalize most of the differential energy. The model suggests local electrostatic turbulence, that alpha-particles are heated more than protons, a maximum proton temperature T sub P 1 million k, and for the bulk speed U possibly a sq root of T sub P = aU + b relationship. These predictions are consistent with observations.

Papadoupoulis, K.

1971-01-01

148

Molecular dynamics simulation of short-wavelength collective dynamics of phospholipid membranes  

NASA Astrophysics Data System (ADS)

We investigated the short-wavelength longitudinal and transverse collective dynamics of the fluid and gel phases of phospholipid bilayers by means of molecular dynamics simulation. Similarly to a crystal, the spectrum of collective excitations in a bilayer consists of longitudinal and transverse acoustic modes, though modified by disorder. Beside acoustic modes, a series of broad dispersionless excitations are revealed. The dispersion curves of the observed excitations may be represented in a pseudo-Brillouin zone scheme centered around the spatial correlation peak of the acyl chains. The study provides evidence for a resonant interaction between the lowest frequency optical phonon and the longitudinal acoustic mode.

Conti Nibali, Valeria; D'Angelo, Giovanna; Tarek, Mounir

2014-05-01

149

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

PubMed Central

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

Yu, Huaqing; Li, Baojun

2013-01-01

150

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

NASA Astrophysics Data System (ADS)

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.

Yu, Huaqing; Li, Baojun

2013-04-01

151

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

PubMed

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

Yu, Huaqing; Li, Baojun

2013-01-01

152

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

SciTech Connect

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.

Nejdl, J. [Institute of Physics, Na Slovance 2, Prague 18221 (Czech Republic); FNSPE, Czech Technical University in Prague, Brehova 7, Prague 115 19 (Czech Republic); Kozlova, M.; Mocek, T.; Rus, B. [Institute of Physics, Na Slovance 2, Prague 18221 (Czech Republic)

2010-12-15

153

Short wavelength automated perimetry, frequency doubling technology perimetry, and pattern electroretinography for prediction of progressive glaucomatous standard visual field defects  

Microsoft Academic Search

PurposeTo evaluate the clinical use of a test battery of short wavelength automated perimetry (SWAP), frequency doubling technology perimetry (FDT), and pattern electroretinography (PERG) in predicting progressive glaucomatous visual field defects on standard automated perimetry (SAP).

Andreas U Bayer; Carl Erb

2002-01-01

154

Laboratory investigation of short wind wave breaking modulation in the long surface wave field  

NASA Astrophysics Data System (ADS)

Both the modulation of short wind wave breaking in the long surface wave field and the occurrence of breaking in the presence of a long wave were investigated in wind-wave tank. Short wind waves were generated by the air flow at various speeds, the long surface wave at various frequency and amplitude were generated by wave maker. Data of X- and Ka-band scatterometers, string wave recorder placed in the probing area, and web camera making video records of the probing area were synchronously recorded in the experiment. Also precision measurements using laser-optics system based on the high-speed video recording, laser illumination, and special algorithms of video processing allowed us to obtain a large ensemble of the wave profiles. It is shown that at relatively weak wind long surface wave causes short wind wave breaking, and at high wind speeds - breaking intensification. Wind wave breaking is mainly observed on the front slope of the long wave, the breaking observation area extends with increasing wind speed.

Bakhanov, V. V.; Bogatov, N. A.; Ermoshkin, A. V.; Kandaurov, A. A.; Kemarskaya, O. N.; Sergeev, D. A.; Troitskaya, Yu. I.

2013-10-01

155

Temporal dynamics of EEG activity during short- and long-wavelength light exposures in the early morning  

PubMed Central

Background It is well known that exposure to light, especially of short wavelength, enhances human alertness during the nighttime. However, more information is needed to elucidate the effects of light wavelength on alertness at other times of day. The present study investigated how two narrowband light spectra affected human alertness during the morning after awakening. We measured electroencephalography (EEG) during 48-minute exposure to narrowband short- and long-wavelength light and darkness in the early morning. Results Power densities of EEG during each light exposure were calculated. The time course of EEG power indicated that, compared with remaining in darkness, the power in the alpha frequency range (8–13 Hz) was significantly lower after approximately 30 minutes of exposures to both the short- and the long-wavelength light. Conclusions These results suggest that not only short-wavelength light but also long-wavelength light, which does not suppress melatonin levels at night, can affect alertness in the early morning. These results suggest that the alerting effects of light in the early morning hours may be mediated by mechanisms other than those that are exclusively sensitive to short-wavelength light. PMID:24568149

2014-01-01

156

Comparison of long-term variability for standard and short-wavelength automated perimetry in stable glaucoma patients  

Microsoft Academic Search

PURPOSE:To quantify and compare, on a point-by-point basis, the long-term variability of standard and short-wavelength automated perimetry in a group of stable glaucoma patients.METHODS:From a group of 53 glaucoma patients experienced in visual field testing, we identified one eye, randomly chosen, from each of 25 glaucoma patients whose condition was found to be stable, based on both standard and short-wavelength

Eytan Z Blumenthal; Pamela A Sample; Linda Zangwill; Alexander C Lee; Yoshiki Kono; Robert N Weinreb

2000-01-01

157

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

PubMed Central

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?short wavelengths may be an approach to reduce sleep disruption and improve performance in rotating-shift workers. (Author correspondence: casper@lunenfeld.ca) PMID:23834705

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

2013-01-01

158

Directional short wind wave spectra derived from the sea surface photography  

NASA Astrophysics Data System (ADS)

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.

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

2014-05-01

159

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

NASA Astrophysics Data System (ADS)

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 ?m. 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.

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

2014-07-01

160

Short wave spectrum modulation by a surface current field and long waves for SAR imaging process simulation  

Microsoft Academic Search

In the framework of the SAR imaging process simulator we are developing, the modification of the short wave spectrum by ocean surface is of great importance. Short waves at the sea surface produce the backscattering of the radar wave. So the modulation of the short wave distribution by ocean surface induces the modulation of the SAR image. In this paper

Morgan Lamy; Jean-Marc Le Caillec; R. Garello; A. Kenchaf

2004-01-01

161

Improving Short Wave Breaking Behavior In Surfbeat Models  

NASA Astrophysics Data System (ADS)

In present surfzone modeling three approaches are widely applied: short-wave resolving models, ‘surfbeat’ models, which resolve wave energy modulations on the time-scale of wave groups and their associated infragravity waves, and wave averaged models. In all three approaches, wave breaking is a process that is highly schematized and governed by several empirical coefficients. In this presentation we will focus on the breaking process in ‘surfbeat’ models, such as XBeach (Roelvink et al, 2009). These models need to describe the short wave dissipation by breaking as a function of the slowly-varying short wave energy or wave height. The model usually applied is that by Roelvink (1993), which combines a probability that waves are breaking as function of wave heigth over water depth ratio H/h with a bore-type dissipation formulation similar to that by Battjes and Janssen (1978). A drawback of such a formulation is that there is no ‘memory’ in the breaking process, and the amount of breaking instantly varies with the water depth (though the wave height itself does have a memory). For cases with bichromatic waves, or for long-period swell, this does not reflect reality enough: waves that start breaking do not instantly stop breaking once the water depth increases, but continue until some lower threshold is reached. This concept was captured in Dally’s (1992) wave-by-wave approach, where individual waves are tracked in a probabilistic setting. We have now implemented a similar formulation in XBeach, where the property that waves are breaking is tracked; it is switched on when H/h exceeds a first criterion; this property is propagated using an advection equation and when H/h gets below a second criterion breaking is switched off. This formulation can do two things the previous one can’t: maintain groupiness inside the surf zone and have a maximum of wave breaking in the trough after a steep bar, as was observed for instance in Arcilla et al’s (1994) test 1C. Obviously this has important consequences for the forcing of both long waves and mean currents. In our presentation we will show results of comparisons of both formulations. References. Arcilla, A.S., Roelvink, J.A., O'Connor, B.A. Reniers, A., and Jimenez. J.A. The Delta Flume '93 Experiment. Coastal Dynamics '94. Arcilla, Stive and Kraus (eds), ASCE, New York, pp. 488-502. Battjes, J.A. and J.P.F.M. Janssen, (1978), Energy loss and set-up due to breaking in random waves, Proc. 16th Int. Coastal Eng. Conf., Hamburg, vol. 1: 569-587. Dally, W.R. (1992) Random breaking waves: Field verification of a wave-by-wave algorithm for engineering application. Coastal Engineering, Volume 16, Issue 4, March 1992, Pages 369-397. Roelvink, Dano, Ad Reniers, Ap van Dongeren, Jaap van Thiel de Vries, Robert McCall, Jamie Lescinski. Modelling storm impacts on beaches, dunes and barrier islands, Coast. Eng. (2009), doi:10.1016/j.coastaleng.2009.08.006 Roelvink, J.A. Dissipation in random wave groups incident on a beach. Coastal Eng., 19 (1993) pp. 127-150.

Roelvink, J.; Daly, C.; Vandongeren, A. R.; van Thiel de Vries, J.; McCall, R.

2009-12-01

162

Diffraction of short pulses with boundary diffraction wave theory.  

PubMed

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

Horváth, Z L; Bor, Z

2001-02-01

163

Sub-optical wavelength acoustic wave modulation of integrated photonic resonators at microwave frequencies.  

PubMed

Light-sound interactions have long been exploited in various acousto-optic devices based on bulk crystalline materials. Conventionally, these devices operate in megahertz frequency range where the acoustic wavelength is much longer than the optical wavelength and a long interaction length is required to attain significant coupling. With nanoscale transducers, acoustic waves with sub-optical wavelengths can now be excited to induce strong acousto-optic coupling in nanophotonic devices. Here we demonstrate microwave frequency surface acoustic wave transducers co-integrated with nanophotonic resonators on piezoelectric aluminum nitride substrates. Acousto-optic modulation of the resonance modes at above 10?GHz with the acoustic wavelength significantly below the optical wavelength is achieved. The phase and modal matching conditions in this scheme are investigated for efficient modulation. The new acousto-optic platform can lead to novel optical devices based on nonlinear Brillouin processes and provides a direct, wideband link between optical and microwave photons for microwave photonics and quantum optomechanics. PMID:25400144

Tadesse, Semere Ayalew; Li, Mo

2014-01-01

164

Sub-optical wavelength acoustic wave modulation of integrated photonic resonators at microwave frequencies  

E-print Network

Light-sound interactions have long been exploited in various acousto-optic devices based on bulk crystalline materials. Conventionally these devices operate in megahertz frequency range where the acoustic wavelength is much longer than the optical wavelength and a long interaction length is required to attain significant coupling. With nanoscale transducers, acoustic waves with sub-optical wavelengths can now be excited to induce strong acousto-optic coupling in nanophotonic devices. Here we demonstrate microwave frequency surface acoustic wave transducers co-integrated with nanophotonic resonators on piezoelectric aluminum nitride substrates. Acousto-optic modulation of the resonance modes at above 10 GHz with the acoustic wavelength significantly below the optical wavelength is achieved. The phase and modal matching conditions in this scheme are investigated for efficient modulation. The new acousto-optic platform can lead to novel optical devices based on nonlinear Brillouin processes and provides a direct, wideband link between optical and microwave photons for microwave photonics and quantum optomechanics.

Semere Ayalew Tadesse; Mo Li

2014-10-04

165

Short wavelength Hg1-xCdxTe infrared detectors prepared by loophole technology  

NASA Astrophysics Data System (ADS)

Short wavelength Hg1-xCdxTe infrared detectors were novelly fabricated by loophole technique basing on Liquid Phase Epitaxial materials, rather than conventional ion implantation technology. The Hg1-xCdxTe material was p type doped by Hg vacancy. The formed sensitive area is an annulus centered on the circular junction. The dimension of the annulus depends on the diffusion lengths of minority carriers in both the p and n regions. Laser Beam Induced Current (LBIC) signals of Scan Laser Microscope measurement were used to determine the key parameters such as the minority diffusion length, the size of both n type and p type regions as well as uniformities of the arrays. Good uniformities were observed for the 4×4 HgCdTe photovoltaic arrays by LBIC signals analysis. Furthermore, exponential decays in LBIC signals revealed average minority carrier diffusion length in p type region was around 9 micron, and the average diameter of the n type annulus was 17 micron. The I-V characteristic measurement of the photodiodes determined average zero bias dynamic resistance R0 which was 1.2E9?, and zero bias dynamic resistance junction area product R0A was calculated to be average 7.02E3?cm2. Further investigations have been performed for the electro-optical performance examination. Infrared spectral response measurement results showed peak wavelength lay around 2.2 micron with cutoff wavelength about 3.5 micron under temperature 77K, average blackbody detectivity D* was 1.71E10cm Hz1/2W-1.

Shi, Yan-Li; Lei, Sheng-Qiong; Yang, Tie-Feng; Zhuang, Ju-Sheng; Cai, Yi

2005-10-01

166

Porous Structures and Short-Wavelength Photoluminescence of C+-Implanted SiO2 Films  

NASA Astrophysics Data System (ADS)

C ions of three different energies were sequentially implanted into SiO2 films grown by plasma enhanced chemical vapor deposition. Microstructures of the samples were studied with transmission electron microscopy (TEM) and secondary ion mass spectroscopy. As revealed by cross-sectional TEM, porous structures had been created in the implanted region during ion implantation. No photoluminescence (PL) was detected from the as-implanted samples. However, intense short-wavelength PL peaking at 360-370 nm and similar 450 nm was observed from the annealed samples. The blue light from samples excited by an Xe lamp can be observed by naked eyes at room temperature. The light emission mechanisms are briefly discussed.

Zhao, Jun; Mao, Dong-sheng; Ding, Xing-zhao; Lin, Zi-xin; Jiang, Bing-yao; Yu, Yue-hui; Yang, Gen-qing; Liu, Xiang-huai; S, Jin; H, Bender

1999-05-01

167

X-Band Microwave Undulators for Short Wavelength Free-Electron Lasers  

SciTech Connect

Microwave undulators have two features that make them attractive to use in free-electron lasers, when compared with conventional static magnetic undulators. One is that the beam aperture is larger than the period, and thus the undulator period is smaller than that achievable with static systems. The second is the possibility of easily producing both circular and planar polarization and dynamically controlling the polarization characteristic and the undulator field intensity. The recent development of high power klystrons and pulse compression techniques at X-band frequency, near 12 GHz, is making this type of undulators very attractive for use in short wavelength free-electron lasers operating in the few nanometers to the Angstrom spectral region. In this paper we discuss the choice of parameters for X-band microwave undulators, the effect of microwave energy losses in the waveguide walls and its possible compensation by tapering the waveguide geometry, and the characteristics of free-electron lasers based on these systems.

Pellegrini, C. [University of California at Los Angeles, Department of Physics and Astronomy, 405 (United States)

2006-01-03

168

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

NASA Technical Reports Server (NTRS)

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.

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

1988-01-01

169

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

NASA Technical Reports Server (NTRS)

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.

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

1988-01-01

170

Instabilities in magnetized rotational flows: A comprehensive short-wavelength approach  

E-print Network

We perform a local stability analysis of rotational flows in the presence of a constant vertical magnetic field and an azimuthal magnetic field with a general radial dependence characterized by an appropriate magnetic Rossby number. Employing the short-wavelength approximation we develop a unified framework for the investigation of the standard, the helical, and the azimuthal version of the magnetorotational instability, as well as of current-driven kink-type instabilities. Considering the viscous and resistive setup, our main focus is on the case of small magnetic Prandtl numbers which applies, e.g., to liquid metal experiments but also to the colder parts of accretion disks. We show in particular that the inductionless versions of MRI that were previously thought to be restricted to comparably steep rotation profiles extend well to the Keplerian case if only the azimuthal field slightly deviates from its field-free profile.

Kirillov, Oleg N; Fukumoto, Yasuhide

2014-01-01

171

Classification of 2.4-45.2 Micron Spectra from the ISO Short Wavelength Spectrometer  

E-print Network

The Infrared Space Observatory observed over 900 objects with the Short Wavelength Spectrometer in full-grating-scan mode (2.4-45.2 micron). We have developed a comprehensive system of spectral classification using these data. Sources are assigned to groups based on the overall shape of the spectral energy distribution (SED). The groups include naked stars, dusty stars, warm dust shells, cool dust shells, very red sources, and sources with emission lines but no detected continuum. These groups are further divided into subgroups based on spectral features that shape the SED such as silicate or carbon-rich dust emission, silicate absorption, ice absorption, and fine-structure or recombination lines. Caveats regarding the data and data reduction, and biases intrinsic to the database, are discussed. We also examine how the subgroups relate to the evolution of sources to and from the main sequence and how this classification scheme relates to previous systems.

Kathleen E. Kraemer; G. C. Sloan; Stephan D. Price; Helen J. Walker

2002-01-30

172

High detectivity short-wavelength II-VI quantum cascade detector  

NASA Astrophysics Data System (ADS)

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 ?m and 3.6 ?m. 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 × 1010 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 106 ? cm2 at 80 K to about 8000 ? cm2 at 300 K, indicative of the ultra-low Johnson noise in the detectors.

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

2014-08-01

173

Short-wavelength infrared tuneable filters on HgCdTe photoconductors.  

PubMed

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

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

2005-11-28

174

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

SciTech Connect

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.

Abbink, R.E.

1997-06-01

175

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

NASA Technical Reports Server (NTRS)

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.

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

1979-01-01

176

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

PubMed

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

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

177

Travelling-wave resonant four-wave mixing breaks the limits of cavity-enhanced all-optical wavelength conversion.  

PubMed

Wave mixing inside optical resonators, while experiencing a large enhancement of the nonlinear interaction efficiency, suffers from strong bandwidth constraints, preventing its practical exploitation for processing broad-band signals. Here we show that such limits are overcome by the new concept of travelling-wave resonant four-wave mixing (FWM). This approach combines the efficiency enhancement provided by resonant propagation with a wide-band conversion process. Compared with conventional FWM in bare waveguides, it exhibits higher robustness against chromatic dispersion and propagation loss, while preserving transparency to modulation formats. Travelling-wave resonant FWM has been demonstrated in silicon-coupled ring resonators and was exploited to realize a 630-?m-long wavelength converter operating over a wavelength range wider than 60 nm and with 28-dB gain with respect to a bare waveguide of the same physical length. Full compatibility of the travelling-wave resonant FWM with optical signal processing applications has been demonstrated through signal retiming and reshaping at 10 Gb s(-1). PMID:21540838

Morichetti, Francesco; Canciamilla, Antonio; Ferrari, Carlo; Samarelli, Antonio; Sorel, Marc; Melloni, Andrea

2011-01-01

178

GEOPHYSICS, ASTRONOMY AND ASTROPHYSICS: Numerical method of studying nonlinear interactions between long waves and multiple short waves  

NASA Astrophysics Data System (ADS)

Although the nonlinear interactions between a single short gravity wave and a long wave can be solved analytically, the solution is less tractable in more general cases involving multiple short waves. In this work we present a numerical method of studying nonlinear interactions between a long wave and multiple short harmonic waves in infinitely deep water. Specifically, this method is applied to the calculation of the temporal and spatial evolutions of the surface elevations in which a given long wave interacts with several short harmonic waves. Another important application of our method is to quantitatively analyse the nonlinear interactions between an arbitrary short wave train and another short wave train. From simulation results, we obtain that the mechanism for the nonlinear interactions between one short wave train and another short wave train (expressed as wave train 2) leads to the energy focusing of the other short wave train (expressed as wave train 3). This mechanism occurs on wave components with a narrow frequency bandwidth, whose frequencies are near that of wave train 3.

Xie, Tao; Kuang, Hai-Lan; William, Perrie; Zou, Guang-Hui; Nan, Cheng-Feng; He, Chao; Shen, Tao; Chen, Wei

2009-07-01

179

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

NASA Astrophysics Data System (ADS)

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.

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

2014-11-01

180

Backscattering of gyrotron radiation and short-wavelength turbulence during electron cyclotron resonance plasma heating in the L-2M stellarator  

SciTech Connect

Backscattering of gyrotron radiation ({theta} = {pi}) by short-wavelength density fluctuations (k{sub Up-Tack} = 30 cm{sup -1}) in the plasma of the L-2M stellarator was studied under conditions of electron cyclotron resonance (ECR) plasma heating at the second harmonic of the electron gyrofrequency (75 GHz). The scattering of the O-wave emerging due to the splitting of the linearly polarized gyrotron radiation into the X- and O-waves was analyzed. The signal obtained after homodyne detection of scattered radiation is a result of interference of the reference signal, the quasi-steady component, and the fast oscillating component. The coefficients of reflection of the quasi-steady component, R{sub =}{sup 2}(Y), and fast oscillating component, R{sub {approx}}{sup 2}(Y), of scattered radiation are estimated. The growth of the R{sub {approx}}{sup 2}(Y) coefficient from 3.7 Multiplication-Sign 10{sup -4} to 5.2 Multiplication-Sign 10{sup -4} with increasing ECR heating power from 190 to 430 kW is found to correlate with the decrease in the energy lifetime from 1.9 to 1.46 ms. The relative density of short-wavelength fluctuations is estimated to be Left-Pointing-Angle-Bracket n{sub {approx}}{sup 2} Right-Pointing-Angle-Bracket / Left-Pointing-Angle-Bracket n{sub e}{sup 2} Right-Pointing-Angle-Bracket = 3 Multiplication-Sign 10{sup -7}. It is shown that the frequencies of short-wavelength fluctuations are in the range 10-150 kHz. The recorded short-wavelength fluctuations can be interpreted as structural turbulence, the energy of which comprises {approx}10% of the total fluctuations energy. Simulations of transport processes show that neoclassical heat fluxes are much smaller than anomalous ones. It is suggested that short-wavelength turbulence plays a decisive role in the anomalous heat transport.

Batanov, G. M.; Borzosekov, V. D., E-mail: tinborz@gmail.com; Kovrizhnykh, L. M.; Kolik, L. V.; Konchekov, E. M.; Malakhov, D. V.; Petrov, A. E.; Sarksyan, K. A.; Skvortsova, N. N.; Stepakhin, V. D.; Kharchev, N. K. [Russian Academy of Sciences, Prokhorov General Physics Institute (Russian Federation)

2013-06-15

181

Observation of a Solar Flare at 4.3-mm. Wave-length  

Microsoft Academic Search

DURING a programme of solar observations at a wave-length of 4.3 mm., scans were made across the Sun on September 25, 26 and 27, 1957. The radio telescope used for these observations has a half-power beam-width of 6.7 minutes of arc. The antenna reflector is an aluminium paraboloid, 10 feet in diameter with a focal length of 35.8 inches. The

R. J. Coates

1958-01-01

182

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

NASA Astrophysics Data System (ADS)

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.

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

2007-04-01

183

The Design of the Short Wavelength Camera for the CCAT Telescope  

NASA Astrophysics Data System (ADS)

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.

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

184

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

PubMed Central

The peak sensitivities (?max) 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 ?max 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

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

2012-01-01

185

Dual-wavelength single-frequency fiber laser based on FP-LD injection locking for millimeter-wave generation  

NASA Astrophysics Data System (ADS)

We propose and successfully demonstrate a dual-wavelength single-frequency fiber laser based on two cascaded Fabry Pérot laser diodes (FP-LDs) and a WaveShaper. Both the cascaded FP-LDs and the WaveShaper perform the dual-wavelength selection. Injection locking of the FP-LDs in laser cavity and narrow bandwidth filtering effect of the WaveShaper guarantee single-frequency operation of the laser. By adjustment of the drive currents of the two FP-LDs and the filtering characteristic of the WaveShaper, dual-wavelength single-frequency output with switchable wavelength spacing can be obtained, which can be used for switchable millimeter-wave generation.

Zhou, Jingjuan; Feng, Xinhuan; Wang, Yuzhuo; Li, Zhaohui; Guan, Bai-ou

2014-12-01

186

Array rotation aperture synthesis for short-range imaging at millimeter wavelengths  

NASA Astrophysics Data System (ADS)

Millimeter-wave interferometric synthetic aperture imagers are currently being developed for short-range applications such as concealed weapons detection. In contrast to the traditional snapshot imaging approach, we investigate the potential of mechanical scanning between the scene and the array in order to reduce the number of antennas and correlators. We assess the trade-off between this hardware reduction, the radiometric sensitivity and the imaging frame rate of the system. We show that rotational scanning achieves a more uniform coverage of the (u, v) plane than the more conventional linear scanning. We use a genetic algorithm to optimize two-dimensional arrays for maximum uniform (u, v) coverage after a rotational mechanical scan and demonstrates improvements in the array point spread function. Imaging performance is assessed with simulated millimeter-wave scenes. Results show an increased image quality is achieved with the optimized array compared with a conventional power law Y-shaped array. Finally we discuss the increased demands on system stability and calibration that the increased acquisition time of the proposed technique places.

Lucotte, B. M.; Grafulla-GonzáLez, B.; Harvey, A. R.

2009-02-01

187

The spectral sensitivity of the human short-wavelength sensitive cones derived from thresholds and color matches  

Microsoft Academic Search

We used two methods to estimate short-wave (S) cone spectral sensitivity. Firstly, we measured S-cone thresholds centrally and peripherally in five trichromats, and in three blue-cone monochromats, who lack functioning middle-wave (M) and long-wave (L) cones. Secondly, we analyzed standard color-matching data. Both methods yielded equivalent results, on the basis of which we propose new S-cone spectral sensitivity functions. At

Andrew Stockman; Lindsay T. Sharpe; Clemens Fach

1999-01-01

188

Wavelength-scale stationary-wave integrated Fourier-transform spectrometry  

E-print Network

Spectrometry is a general physical-analysis approach for investigating light-matter interactions. However, the complex designs of existing spectrometers render them resistant to simplification and miniaturization, both of which are vital for applications in micro- and nanotechnology and which are now undergoing intensive research. Stationary-wave integrated Fourier-transform spectrometry (SWIFTS)-an approach based on direct intensity detection of a standing wave resulting from either reflection (as in the principle of colour photography by Gabriel Lippmann) or counterpropagative interference phenomenon-is expected to be able to overcome this drawback. Here, we present a SWIFTS-based spectrometer relying on an original optical near-field detection method in which optical nanoprobes are used to sample directly the evanescent standing wave in the waveguide. Combined with integrated optics, we report a way of reducing the volume of the spectrometer to a few hundreds of cubic wavelengths. This is the first attempt...

Coarer, Etienne Le; Benech, Pierre; Stefanon, Ilan; Morand, Alain; Lérondel, Gilles; Leblond, Grégory; Kern, Pierre; Fedeli, Jean Marc; Royer, Pascal

2007-01-01

189

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

PubMed Central

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

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

2006-01-01

190

Short-wavelength ablation of polymers in the high-fluence regime  

NASA Astrophysics Data System (ADS)

Short-wavelength ablation of poly(1,4-phenylene ether-ether-sulfone) (PPEES) and poly(methyl methacrylate) (PMMA) was investigated using extreme ultraviolet (XUV) and soft x-ray (SXR) radiation from plasma-based sources. The initial experiment was performed with a 10 Hz desktop capillary-discharge XUV laser lasing at 46.9 nm. The XUV laser beam was focused onto the sample by a spherical mirror coated with a Si/Sc multilayer. The same materials were irradiated with 13.5 nm radiation emitted by plasmas produced by focusing an optical laser beam onto a xenon gas-puff target. A Schwarzschild focusing optics coated with a Mo/Si multilayer was installed at the source to achieve energy densities exceeding 0.1 J cm-2 in the tight focus. The existing experimental system at the Laser Laboratorium Göttingen was upgraded by implementing a 1.2 J driving laser. An increase of the SXR fluence was secured by improving the alignment technique.

Liberatore, Chiara; Mann, Klaus; Müller, Matthias; Pina, Ladislav; Juha, Libor; Vyšín, Ludek; Rocca, Jorge J.; Endo, Akira; Mocek, Tomas

2014-05-01

191

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

PubMed

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 (?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 ?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 ?max from sequence data alone. J. Exp. Zool. (Mol. Dev. Evol.) 322B: 529-539, 2014. © 2014 Wiley Periodicals, Inc. PMID:24890094

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

2014-11-01

192

Massive Star Formation and Evolution in Starburst Galaxies: Mid?infrared Spectroscopy with the ISO Short Wavelength Spectrometer  

Microsoft Academic Search

We present new Infrared Space Observatory Short Wavelength Spectrometer data for a sample of 27 starburst galaxies, and with these data we examine the issues of formation and evolution of the most massive stars in starburst galaxies. Using starburst models which incorporate time evolution, new stellar atmosphere models for massive stars, and a starburst model geometry derived from observations of

Michele D. Thornley; Natascha M. Forster Schreiber; Dieter Lutz; Reinhard Genzel; Henrik W. W. Spoon; Dietmar Kunze; Amiel Sternberg

2000-01-01

193

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

PubMed

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

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

2014-10-23

194

Short-wavelength automated perimetry: it’s role in the clinic and for understanding ganglion cell function  

Microsoft Academic Search

Short-wavelength automated perimetry (SWAP) is a more sensitive test than standard achromatic perimetry for early loss of vision due to glaucoma and other ocular and neurological diseases. SWAP is also more successful for detecting changes in vision as glaucoma progresses. Results from various visual function-specific tests, including SWAP, suggest that there are individual differences in ocular hypertensive and glaucoma eyes

Pamela A Sample

2000-01-01

195

Adaptive two-wave mixing wavelength demodulation of fiber Bragg grating sensor for monitoring dynamic strains  

NASA Astrophysics Data System (ADS)

A two-wave mixing (TWM) wavelength demodulator using InP:Fe photorefractive crystal (PRC) in the C-band (1530-1570nm) is demonstrated. The system can be used as a wavelength demodulator for use with Fiber Bragg Grating (FBG) sensors to monitor dynamic strains. In this configuration, the FBG is illuminated with a broadband source, and any strain in the FBG is encoded as a wavelength shift of the light reflected by the FBG. The reflected light from the FBG is spilt into two unbalanced paths and both beams (pump and signal) mix in the PRC. Any wavelength shift of the reflected light results in an equivalent phase shift between the pump and signal beams as they travel unbalanced path lengths. Since TWM is an adaptive process, the two interfering beams are naturally in quadrature and remain in quadrature even in the presence of large quasi-static strains. We demonstrate that FBG demodulation using TWM has the ability to selectively monitor dynamic strains without the need for active compensation of large quasi-static strains that otherwise would cause the FBG sensor to drift. As TWM interferometers can be readily multiplexed at relatively low cost; the proposed technique can be used to demodulate signals from a network of FBG sensors for use in structural health monitoring.

Qiao, Yi; Zhou, Yi; Krishnaswamy, Sridhar

2005-05-01

196

Wavelength switchable semiconductor laser using half-wave V-coupled cavities.  

PubMed

A new semiconductor laser structure with digitally switchable wavelength is proposed. The device comprises two coupled cavities with different optical path lengths, which form V-shaped branches with a reflective 2x2 half-wave optical coupler at the closed end. The reflective 2x2 coupler is designed to have a pi-phase difference between cross-coupling and self-coupling so as to produce synchronous power transfer functions. High single-mode selectivity is achieved by optimizing the coupling coefficient. The switchable wavelength range is greatly increased by using Vernier effect. Using deep-etched trenches as partial reflectors, additional waveguide branch structures are used outside the laser cavities to form a complete Mach-Zehnder interferometer, allowing space switching, variable attenuation, or high speed modulation to be realized simultaneously. Detailed design principle and numerical results are presented. PMID:18542486

He, Jian-Jun; Liu, Dekun

2008-03-17

197

Dispersive wave emission and supercontinuum generation in a silicon wire waveguide pumped around the 1550 nm telecommunication wavelength  

E-print Network

We demonstrate dispersive wave generation, soliton fission and supercontinuum generation in a silicon wire at telecom wavelengths. Despite the strong nonlinear absorption inherent to silicon at telecom wavelengths, we experimentally demonstrate that the compression and subsequent splitting of higher order solitons remains possible. Moreover we observe the emission of resonant radiation from the solitons, leading to the generation a broad supercontinuum.

Leo, François; Safioui, Jassem; Kockaert, Pascal; Coen, Stéphane; Dave, Utsav; Kuyken, Bart; Roelkens, Gunther

2014-01-01

198

Dual-channel all-optical wavelength conversion switching by four-wave mixing.  

PubMed

We report an experimental demonstration of dual-channel all-optical wavelength conversion switching in hot Rb vapor. In a four-level atomic system, a coupling field and a pump field interact with both (87)Rb and (85)Rb isotopes simultaneously and facilitate the generation of two nonlinear signals when the probe field is applied to the corresponding transition. Each nonlinear signal is switched on and off separately by the pump field at different frequencies based on four-wave mixing and isotope shifts. PMID:20052260

Wang, Gang; Xue, Yan; Wu, Jin-Hui; Liu, Si-Sheng; Jiang, Yun; Kang, Zhi-Hui; Gao, Jin-Yue

2009-12-01

199

Modelling Transient Effects in the IR Array of the Short Wavelength Channel of ISOCAM  

NASA Astrophysics Data System (ADS)

The short-wave channel (SW) of ISOCAM, the IR camera on board the ISO satellite, is equipped with a 32 × 32 CID InSb array. This array shares with other detectors of ISO instruments the characteristic of being subject to some time lag when responding to a flux variation. Known as transient effect, this default which is not quite understood (in particular, it does not correspond to a simple time constant), must be corrected for in data processing. Starting from the remark that the lower the signal, the longer the equivalent time constant, we have developed a mathematical model that reproduces quite well the observed behaviour, using only a small set of parameters. In practice, the model consists of solving a functional equation. The model provides the asymptotic value of the stabilized signal, which is in general the information one looks for. An a posteriori analysis of the form of the functional equation suggests that the effect relates to surface traps in the semi-conductor, as a rough estimation would confirm.

Tiphène, D.; Rouan, D.; Epstein, G.; Le Coupanec, P.

2000-08-01

200

Wavelength conversion, time demultiplexing and multicasting based on cross-phase modulation and four-wave mixing in dispersion-flattened highly nonlinear photonic crystal fiber  

NASA Astrophysics Data System (ADS)

We propose the use of cross-phase modulation (XPM) and four-wave mixing (FWM) in dispersion-flattened highly nonlinear photonic crystal fibers (HNL-PCFs) to implement the functionalities of wavelength conversion, simultaneous time demultiplexing and wavelength multicasting in optical time-division multiplexing (OTDM) systems. The experiments on wavelength conversion at 80 Gbit s-1and OTDM demultiplexing from 80 to 10 Gbit s-1 with wavelength multicasting of two channels are successfully demonstrated to validate the proposed scheme, which are carried out by using two segments of dispersion-flattened HNL-PCFs with lengths of 100 and 50 m, respectively. Moreover, the bit error rate (BER) performance is also measured. The results show that our designed system can achieve a power penalty of less than 4.6 dB for two multicasting channels with a 24 nm wavelength span at the BER of 10-9 when compared with the 10 Gbit/s back-to-back measurement. The proposed system is transparent to bit rate since only an ultrafast third-order nonlinear effect is used. The resulting configuration is compact, robust and reliable, benefiting from the use of dispersion-flattened HNL-PCFs with short lengths. This also makes the proposed system more flexible in the operational wavelengths than those based on dispersion-shifted fibers and traditional highly nonlinear fibers. The work was supported in part by the CAS/SAFEA International Partnership Program for Creative Research Teams.

Hui, Zhan-Qiang; Zhang, Jian-Guo

2012-05-01

201

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

NASA Technical Reports Server (NTRS)

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.

Blessinger, M. A.; Herring, M.

1984-01-01

202

Cone signals for spectacle-lens compensation: Differential responses to short and long wavelengths  

PubMed Central

Chick eyes compensate for defocus imposed by spectacle lenses by making compensatory changes in eye length and choroidal thickness, a laboratory model of emmetropization. To investigate the roles of longitudinal chromatic aberration and of chromatic mechanisms in emmetropization, we examined the participation of different cone classes, and we compared the efficacy of lens compensation under monochromatic illumination with that under white light of the same illuminance to the chick eye. Chicks wore positive or negative 6 D or 8 D lenses on one eye for three days, under either blue (460nm) or red (620nm) light at 0.67 lux or under white light at 0.67 or 0.2 lux (all measures are corrected for chick photopic sensitivity). The illumination conditions were chosen to differentially stimulate either the short-wavelength and ultraviolet cones or the long-wavelength and double cones. Measurements are expressed as the relative change: the inter-ocular difference in the amount of change over the three days of lens wear. We find that under this low illumination the two components of lens compensation were differentially affected by the monochromatic illumination: in blue light lens compensation was mainly due to changes in eye length, whereas in red light lens compensation was mainly due to changes in choroidal thickness. In general, white light produced better lens compensation than monochromatic illumination. Negative lenses Under white light negative lenses caused an increase in eye length (60 ?m) together with a decrease in choroidal thickness (-51 ?m) relative to the fellow eye. Under blue light, although there was an increase in eye length (32 ?m), there was no change in choroidal thickness (5 ?m). In contrast, under red light there was a decrease in choroidal thickness (-62 ?m) but no increase in eye length (8 ?m). Relative ocular elongation was the same in white and monochromatic light. Positive lenses Under white light positive lenses caused a decrease in eye length (-142 ?m) together with an increase in choroidal thickness (68 ?m) relative to the fellow eye. Under blue light, there was a decrease in eye length (-64 ?m), but no change in choroidal thickness (2 ?m). In contrast, under red light there was an increase (90 ?m) in choroidal thickness but less of a decrease (-36 ?m) in eye length. Lens compensation by inhibition of ocular elongation was less effective under monochromatic illumination than under white light (white v red: p=0.003; white v blue p=0.014). The differential effects of red and blue light on the choroidal and ocular length compensatory responses suggest that they are driven by different proportions of the cone-types, implying that, although chromatic contrast is not essential for lens compensation and presumably for emmetropization as well, the retinal substrates exist for utilizing chromatic contrast in these compensatory responses. The generally better lens compensation in white than monochromatic illumination suggests that longitudinal chromatic aberration may be used in lens compensation. PMID:18585403

Rucker, Frances J.; Wallman, Josh

2009-01-01

203

Modulation of short wind waves by a long surface wave: a mechanism for feedback with an air flow  

Microsoft Academic Search

The paper concentrates on the evolution of a spectrum of short wind waves (SW) along the profile of a long surface wave (LW).\\u000a Short wave spectral variations are considered in the relaxation approximation. The SW spectrum is modulated by the orbital\\u000a velocities of long waves and by the variations of wind stress along the LW profile. The latter effect occurs

V. N. Kudryavtsev; K. Mastenbroek; V. K. Makin

1997-01-01

204

Short-wavelength oscillatory modes in a magnetized neutral plasma, and theoretical derivation of a density limit  

E-print Network

By applying the fundamental equations of microscopic electrodynamics to an idealized model of magnetized neutral plasma at zero temperature, we obtain dispersion relations for all wavelengths ranging from zero up to the mean separation between particles. These relations reduce for long wavelengths to the well-known ones of magnetohydrodynamics. At short wavelengths they reveal instead the existence of modes of oscillation which become unstable when the plasma density exceeds a critical value proportional to the square of the magnetic field. The order of magnitude of this critical value appears to be fairly consistent with most of the available experimental data on the operational density limit of conventional tokamak devices, which represents a crucial issue for the achievement of controlled nuclear fusion with magnetic confinement.

Marino, M; Carati, A; Martines, E; Galgani, L

2010-01-01

205

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

PubMed

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 1 cm 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 38 pm wavelength spacing and a total emitted power of 2.8 mW is obtained from this DBR fiber laser. A microwave signal at 4.58 GHz is generated by the heterodyne detection of the dual-wavelength laser. PMID:24979414

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

2014-06-20

206

Imaging and Analysis of THz Surface Plasmon Polariton Waves with the Integrated Sub-wavelength Aperture Probe  

Microsoft Academic Search

We demonstrate that the integrated sub-wavelength aperture probe designed for THz near-field scanning probe microscopy can\\u000a be used to map surface plasmon waves at THz frequencies. Observed near-field images of metallic patterns reveal surface plasmon\\u000a waves superimposed over THz transmission images. We discuss the coupling mechanism for the surface waves and arrive to an\\u000a important conclusion that the detected surface

Raimund Mueckstein; Chris Graham; Cyril C. Renaud; Alwyn J. Seeds; James A. Harrington; Oleg Mitrofanov

2011-01-01

207

The long-wave instability of short-crested waves, via embedding in the oblique two-wave interaction  

NASA Astrophysics Data System (ADS)

The motivation for this work is the stability problem for short-crested Stokes waves. A new point of view is proposed, based on the observation that an understanding of the linear stability of short-crested waves (SCWs) is closely associated with an understanding of the stability of the oblique non-resonant interaction between two waves. The proposed approach is to embed the SCWs in a six-parameter family of oblique non-resonant interactions. A variational framework is developed for the existence and stability of this general two-wave interaction. It is argued that the resonant SCW limit makes sense a posteriori, and leads to a new stability theory for both weakly nonlinear and finite-amplitude SCWs. Even in the weakly nonlinear case the results are new: transverse weakly nonlinear long-wave instability is independent of the nonlinear frequency correction for SCWs whereas longitudinal instability is influenced by the SCW frequency correction, and, in parameter regions of physical interest there may be more than one unstable mode. With explicit results, a critique of existing results in the literature can be given, and several errors and misconceptions in previous work are pointed out. The theory is developed in some generality for Hamiltonian PDEs. Water waves and a nonlinear wave equation in two space dimensions are used for illustration of the theory.

Bridges, Thomas J.; Laine-Pearson, Fiona E.

2005-10-01

208

Latent Period and Antigenicity of Murine Tumors Induced in C3H Mice by Short-Wavelength Ultraviolet Radiation  

Microsoft Academic Search

Skin tumors were induced in C3H\\/HeNCr1BR mice with chronic short-wavelength ultraviolet (UVC) irradiation using a germicidal lamp (254 nm). Fifty percent of mice had developed tumors by 9 1\\/2 months (range 8–12 months). With progressive irradiation, mice developed multiple tumors on the back reaching a mean of 2.9 tumors\\/mouse at 11 1\\/2 months. No tumors developed on the ears. Of

Patsy H. Lill

1983-01-01

209

Measurements for enhanced bandwidth performance over 62.5-?m multimode fiber in short-wavelength local area networks  

Microsoft Academic Search

The Telecommunications Industry Association (TIA) FO-2.2.1 Working Group on the modal dependence of bandwidth has conducted industrywide interlaboratory comparisons on measurements aimed at improving the bandwidth performance of short-wavelength, laser-based, multimode-fiber local area networks (LANs). Measurements of both transceiver encircled flux and fiber restricted-mode-launch bandwidth can together successfully predict an enhanced system performance, provided that the proper limiting criteria are

J. B. Schlager; Michael J. Hackert; Petar Pepeljugoski; J. Gwinn

2003-01-01

210

Regulation of Photoactivation in Vertebrate Short Wavelength Visual Pigments:  Protonation of the Retinylidene Schiff Base and a Counterion Switch  

Microsoft Academic Search

Xenopus violet cone opsin (VCOP) and its counterion variant (VCOP-D108A) are expressed in mammalian COS1 cells and regenerated with 11-cis-retinal. The phototransduction process in VCOP- D108A is investigated via cryogenic electronic spectroscopy, homology modeling, molecular dynamics, and molecular orbital theory. The VCOP-D108A variant is a UV-like pigment that displays less efficient photoactivation than the mouse short wavelength sensitive visual pigment

Lavoisier S. Ramos; Min-Hsuan Chen; Barry E. Knox; Robert R. Birge

2007-01-01

211

Wavelength-scale stationary-wave integrated Fourier-transform spectrometry  

NASA Astrophysics Data System (ADS)

Spectrometry is a general physical-analysis approach for investigating light-matter interactions. However, the complex designs of existing spectrometers render them resistant to simplification and miniaturization, both of which are vital for applications in micro- and nanotechnology and which are now undergoing intensive research. Stationary-wave integrated Fourier-transform spectrometry (SWIFTS)-an approach based on direct intensity detection of a standing wave resulting from either reflection (as in the principle of colour photography by Gabriel Lippmann) or counterpropagative interference phenomenon-is expected to be able to overcome this drawback. Here, we present a SWIFTS-based spectrometer relying on an original optical near-field detection method in which optical nanoprobes are used to sample directly the evanescent standing wave in the waveguide. Combined with integrated optics, we report a way of reducing the volume of the spectrometer to a few hundreds of cubic wavelengths. This is the first attempt, using SWIFTS, to produce a very small integrated one-dimensional spectrometer suitable for applications where microspectrometers are essential.

Le Coarer, Etienne; Blaize, Sylvain; Benech, Pierre; Stefanon, Ilan; Morand, Alain; Lérondel, Gilles; Leblond, Grégory; Kern, Pierre; Fedeli, Jean Marc; Royer, Pascal

2007-08-01

212

Suppression of short sea waves in ship wakes: Measurements and observations  

Microsoft Academic Search

Measurements of short wave energy, surface tension distributions, and radar imagery of centerline ship wakes are presented. A direct association between reduced radar return and reduced scattering wave energy is demonstrated. The dominant influences of ship-generated turbulence and surface film distributions upon reduced short wave energy in ship wakes are shown. The effect of turbulence is emphasized by the very

J. H. Milgram; R. D. Peltzer; O. M. Griffin

1993-01-01

213

Wavelength and Intensity Dependence of Short Pulse Laser Xenon Double Ionization between 500 and 2300 nm  

SciTech Connect

The wavelength and intensity dependence of xenon ionization with 50 fs laser pulses has been studied using time-of-flight mass spectrometry. We compare the ion yield distribution of singly and doubly charged xenon with the Perelomov-Popov-Terent'ev (PPT) theory, Perelomov, Popov, and Terent'ev, Zh. Eksp. Teor. Fiz. 50, 1393 (1966) [Sov. Phys. JETP 23, 924 (1966)], in the regime between 500 and 2300 nm. The intensity dependence for each wavelength is measured in a range between 1x10{sup 13} and 1x10{sup 15} W/cm{sup 2}. The Xe{sup +}-ion signal is in good agreement with the PPT theory at all used wavelengths. In addition we demonstrate that ionic 5s5p{sup 6} {sup 2}S state is excited by an electron impact excitation process and contributes to the nonsequential double ionization process.

Gingras, G.; Tripathi, A.; Witzel, B. [Centre d'Optique, Photonique et Laser, Universite Laval, Pavillon d'optique-photonique Quebec (Quebec), G1V 0A6 (Canada)

2009-10-23

214

Short-time-evolved wave functions for solving quantum many-body problems  

E-print Network

converges essentially to the exact ground state in a relatively short time. Thus a short-time evolved wave function can be an excellent approximation to the exact ground state. Such a short-time-evolved wave function can be obtained by factorizing...

Ciftja, O.; Chin, Siu A.

2003-01-01

215

Detection of ocean waves by microwave radar; The modulation of short gravity-capillary waves  

Microsoft Academic Search

Short gravity-capillary waves, the predominant radar scatterers under many oceanic and radar-viewing conditions, are modulated in amplitude, velocity and orientation by the larger-scale motions of the ocean surface. These modulations render the larger scales observable to microwave radar. The high data rate and advanced technology of modern radar systems make it possible to measure these modulations and, in some cases,

J. W. Wright

1978-01-01

216

High Sensitivity of Human Melatonin, Alertness, Thermoregulation, and Heart Rate to Short Wavelength Light  

Microsoft Academic Search

Light can elicit acute physiological and alerting responses in humans, the magnitude of which depends on the timing, in- tensity, and duration of light exposure. Here, we report that the alerting response of light as well as its effects on thermo- regulation and heart rate are also wavelength dependent. Ex- posure t o2ho fmonochromatic light at 460 nm in the

Christian Cajochen; Mirjam Munch; Szymon Kobialka; Kurt Krauchi; Roland Steiner; Peter Oelhafen; Selim Orgul; Anna Wirz-Justice

217

Short-wavelength geoid, bathymetry and the convective pattern beneath the Pacific Ocean  

Microsoft Academic Search

Geoid and topography over the Pacific Ocean are filtered to enhance small and intermediate wavelength. The filtered maps and rotations characterizing the absolute motion of the Pacific Plate are used to discuss the origin of lineaments coinciding with tracks issued from spots of known recent volcanism. It is concluded that the convective pattern beneath the plates consists of numerous rising

L. Fleitout; C. Moriceau

1992-01-01

218

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

NASA Astrophysics Data System (ADS)

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.

Kanna, T.; Vijayajayanthi, M.; Lakshmanan, M.

2014-10-01

219

Group III nitride semiconductors for short wavelength light-emitting devices  

NASA Astrophysics Data System (ADS)

The group III nitrides (AlN, GaN and InN) represent an important trio of semiconductors because of their direct band gaps which span the range 1.95-6.2 eV, including the whole of the visible region and extending well out into the ultraviolet (UV) range. They form a complete series of ternary alloys which, in principle, makes available any band gap within this range and the fact that they also generate efficient luminescence has been the main driving force for their recent technological development. High brightness visible light-emitting diodes (LEDs) are now commercially available, a development which has transformed the market for LED-based full colour displays and which has opened the way to many other applications, such as in traffic lights and efficient low voltage, flat panel white light sources. Continuously operating UV laser diodes have also been demonstrated in the laboratory, exciting tremendous interest for high-density optical storage systems, UV lithography and projection displays. In a remarkably short space of time, the nitrides have therefore caught up with and, in some ways, surpassed the wide band gap II-VI compounds (ZnCdSSe) as materials for short wavelength optoelectronic devices. The purpose of this paper is to review these developments and to provide essential background material in the form of the structural, electronic and optical properties of the nitrides, relevant to these applications. We have been guided by the fact that the devices so far available are based on the binary compound GaN (which is relatively well developed at the present time), together with the ternary alloys AlGaN and InGaN, containing modest amounts of Al or In. We therefore concentrate, to a considerable extent, on the properties of GaN, then introduce those of the alloys as appropriate, emphasizing their use in the formation of the heterostructures employed in devices. The nitrides crystallize preferentially in the hexagonal wurtzite structure and devices have so far been based on this material so the majority of our paper is concerned with it, however, the cubic, zinc blende form is known for all three compounds, and cubic GaN has been the subject of sufficient work to merit a brief account in its own right. There is significant interest based on possible technological advantages, such as easier doping, easier cleaving (for laser facets) and easier contacting. It also appears, at present, that the cubic form gives higher electron and hole mobilities than the hexagonal form. The dominant hexagonal structure is similar to that found in a number of II-VI compounds such as CdS and they can therefore be taken as role models. In particular, the lower symmetry gives rise to three separate valence bands at the zone centre and exciton spectra associated with each of these have been reported by many workers for GaN. Interpretation is complicated by the presence of strain in many samples due to the fact that most material consists of epitaxial thin films grown on non-lattice-matched substrates (bulk GaN crystals not being widely available). However, much progress has been made in understanding the physics of these films and we discuss the current position with regard to band gaps, effective masses, exciton binding energies, phonon energies, dielectric constants, etc. Apart from a lack of knowledge of the anticipated valence band anisotropy, it can be said that GaN is now rather well documented. Less detail is available for AlN or InN and we make no attempt to provide similar data for them. The structure of the paper is based on a historical introduction, followed by a brief account of the various crystal growth methods used to produce bulk GaN and epitaxial films of GaN and the ternary alloys. This is then followed by an account of the structural properties of hexagonal GaN as measured by x-ray diffraction and electron microscopy, phonon properties from infrared and Raman spectroscopy, electrical properties, with emphasis on n- and p-type doping, and optical properties, measured mainly by photoluminescence. A brief comparative acco

Orton, J. W.; Foxon, C. T.

1998-01-01

220

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

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.

Zhou Zhongyuan [Department of Chemistry, University of Kansas, Lawrence, Kansas 66045 (United States); Chu, Shih-I [Department of Chemistry, University of Kansas, Lawrence, Kansas 66045 (United States); Center for Quantum Science and Engineering, Department of Physics, National Taiwan University, Taipei 10617, Taiwan (China)

2011-01-15

221

Measurements of Short Ocean Waves during the MBL ARI West Coast Experiment  

E-print Network

. In order to gain deeper insight into the dynamics and the energy balance of ocean wind waves, i.e., the energy input by the wind, nonlinear wave-wave interaction, and energy dissipation, it is necessary165 Measurements of Short Ocean Waves during the MBL ARI West Coast Experiment Jochen Klinke 1

Jaehne, Bernd

222

Quantum key distribution system in standard telecommunications fiber using a short wavelength single photon source  

Microsoft Academic Search

A demonstration of the principles of quantum key distribution (QKD) is performed using a single-photon source in a proof of concept test-bed over a distance of 2 km in standard telecommunications optical fiber. The single-photon source was an optically-pumped quantum dot in a microcavity emitting at a wavelength of 895 nm. Characterization of the QKD parameters was performed at a

R. J. Collins; P. J. Clarke; V. Fernández; K. J. Gordon; M. N. Makhonin; J. A. Timpson; A. Tahraoui; M. Hopkinson; A. M. Fox; M. S. Skolnick; G. S. Buller

2010-01-01

223

A Short Wavelength GigaHertz Clocked Fiber-Optic Quantum Key Distribution System  

Microsoft Academic Search

A quantum key distribution system has been developed, using standard telecommunications optical fiber, which is capable of operating at clock rates of greater than 1 GHz. The quantum key distribution system implements a polarization encoded version of the B92 protocol. The system employs vertical-cavity surface-emitting lasers with emission wavelengths of 850 nm as weak coherent light sources, and silicon single

K. J. Gordon; V. Fernandez; P. D. Townsend; G. S. Buller

2004-01-01

224

A short wavelength GigaHertz clocked fiber-optic quantum key distribution system  

Microsoft Academic Search

A quantum key distribution system has been developed, using standard\\u000atelecommunications optical fiber, which is capable of operating at clock rates\\u000aof greater than 1 GHz. The quantum key distribution system implements a\\u000apolarization encoded version of the B92 protocol. The system employs\\u000avertical-cavity surface-emitting lasers with emission wavelengths of 850 nm as\\u000aweak coherent light sources, and silicon single

Karen J. Gordon; Veronica Fernandez; Paul D. Townsend; Gerald S. Buller

2004-01-01

225

Short-red-wavelength, high-power, AlGaInP laser diodes  

Microsoft Academic Search

AlGaInP-based, high power laser diodes operating at wavelengths of 630 to 645 nm have been designed, fabricated, and characterized. Cw output powers approaching 1 Watt and thresholds below 400 A\\/cm2 have been achieved. Measurement of internal laser parameters indicates low internal loss and transparency current, high gain, and moderate internal quantum efficiency. Characteristic temperature data suggest that the lowest practical

Harvey B. Serreze; Ying-Chih Chen

1993-01-01

226

Short wavelength AlGaInP laser diode research at SONY  

Microsoft Academic Search

Recent research and development work on AlGaInP visible laser diodes by SONY are reviewed. Performance and reliability of a gain-guided 670 nm laser with a tapered geometry are described. Efforts for achieving shorter wavelengths around 650 nm using (III)B substrates, lower threshold current, as well as higher power versions around 10 - 100 nW are also discussed.

T. Mamine; K. Honda; H. Satoh; I. Umezawa; C. Kojima

1989-01-01

227

Relativistic single-cycled short-wavelength laser pulse compressed from a chirped pulse induced by laser-foil interaction.  

PubMed

By particle-in-cell simulation and analysis, we propose a plasma approach to generate a relativistic chirped pulse based on a laser-foil interaction. When two counterpropagating circularly polarized pulses interact with an overdense foil, the driving pulse (with a larger laser field amplitude) will accelerate the whole foil to form a double-layer structure, and the scattered pulse (with a smaller laser field amplitude) is reflected by this flying layer. Because of the Doppler effect and the varying velocity of the layer, the reflected pulse is up-shifted for frequency and chirped; thus, it could be compressed to a nearly single-cycled relativistic laser pulse with a short wavelength. Simulations show that a nearly single-cycled subfemtosecond relativistic pulse can be generated with a wavelength of 0.2 ?m after dispersion compensation. PMID:20867711

Ji, L L; Shen, B F; Li, D X; Wang, D; Leng, Y X; Zhang, X M; Wen, M; Wang, W P; Xu, J C; Yu, Y H

2010-07-01

228

Relativistic Single-Cycled Short-Wavelength Laser Pulse Compressed from a Chirped Pulse Induced by Laser-Foil Interaction  

SciTech Connect

By particle-in-cell simulation and analysis, we propose a plasma approach to generate a relativistic chirped pulse based on a laser-foil interaction. When two counterpropagating circularly polarized pulses interact with an overdense foil, the driving pulse (with a larger laser field amplitude) will accelerate the whole foil to form a double-layer structure, and the scattered pulse (with a smaller laser field amplitude) is reflected by this flying layer. Because of the Doppler effect and the varying velocity of the layer, the reflected pulse is up-shifted for frequency and chirped; thus, it could be compressed to a nearly single-cycled relativistic laser pulse with a short wavelength. Simulations show that a nearly single-cycled subfemtosecond relativistic pulse can be generated with a wavelength of 0.2 {mu}m after dispersion compensation.

Ji, L. L.; Shen, B. F.; Li, D. X.; Wang, D.; Leng, Y. X.; Zhang, X. M.; Wen, M.; Wang, W. P.; Xu, J. C.; Yu, Y. H. [State Key Laboratory of High Field Laser Physics, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, P.O. Box 800-211, Shanghai 201800 (China)

2010-07-09

229

Suppression of short sea waves in ship wakes: Measurements and observations  

NASA Astrophysics Data System (ADS)

Measurements of short wave energy, surface tension distributions, and radar imagery of centerline ship wakes are presented. A direct association between reduced radar return and reduced scattering wave energy is demonstrated. The dominant influences of ship-generated turbulence and surface film distributions upon reduced short wave energy in ship wakes are shown. The effect of turbulence is emphasized by the very slow regrowth of attenuated wave energy in the especially turbulent wake of a towed barge. The effect of surface film distributions is emphasized by the suppression of short wave growth during a wind puff in a wake that is about 1 hour old.

Milgram, J. H.; Peltzer, R. D.; Griffin, O. M.

1993-01-01

230

The traveling wave MRI in cylindrical Taylor-Couette flow: comparing wavelengths and speeds in theory and experiment  

E-print Network

We study experimentally the flow of a liquid metal confined between differentially rotating cylinders, in the presence of externally imposed axial and azimuthal magnetic fields. For increasingly large azimuthal fields a wave-like disturbance arises, traveling along the axis of the cylinders. The wavelengths and speeds of these structures, as well as the field strengths and rotation rates at which they arise, are broadly consistent with theoretical predictions of such a traveling wave magnetorotational instability.

Guenther Ruediger; Rainer Hollerbach; Frank Stefani; Thomas Gundrum; Gunter Gerbeth; Robert Rosner

2006-07-04

231

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

SciTech Connect

We report the first experimental demonstration of the echo-enabled harmonic generation 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 harmonics 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 echo-enabled harmonic generation technique for seeded x-ray free electron lasers.

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. [SLAC National Accelerator Laboratory, Menlo Park, California 94025 (United States); Ecole Polytechnique Federale de Lausanne, Lausanne (Switzerland)

2010-09-10

232

Mather-type dense plasma focus as a new optical pump for short-wavelength high-power lasers  

SciTech Connect

For the first time, a Mather-type dense plasma focus (MDPF) is successfully operated as an optical pump for lasers. Rhodamine-6G dye is optically pumped using the MDPF fluorescence, producing a laser pulse 1 ..mu..s in duration and more than 50 kW in output power. No optimization is attempted either of the laser cavity or of the lasing medium concentration and volume. A brief description of the experimental setup is presented, along with a summary and discussion of the results. The advantages of the present optical pump source and, in particular, their implications for the pumping of short-wavelength lasers are discussed.

Fanning, J.J.; Kim, K.

1984-04-01

233

Tracking Waves and Spiral Drift in Reaction-Diffusion Systems with Finite Bandwidth Dispersion Relations  

E-print Network

are unstable, pacemakers can generate short-wavelength patterns in which fast waves periodically annihilate, for large wavelengths following a hyperbolic-tangent depen- dence8 and have a short-wavelength limit below for short wavelengths and anoma- lous slopes for long wavelengths. In such systems, solitary pulses

Steinbock, Oliver

234

Measurements of short wavelength VLF bursts in the auroral ionosphere: A case for electromagnetic mode conversion?  

E-print Network

are produced by the scat- tering of incident electromagnetic whistlers from electron density irregularities since these examples are not well correlated with electron density depletions. In addition, these waves in the vicinity of many of these electro- static bursts, along with continual electron density turbulence of 1

California at Berkeley, University of

235

Quantum key distribution system in standard telecommunications fiber using a short wavelength single-photon source  

E-print Network

A demonstration of the principles of quantum key distribution is performed using a single-photon source in a proof of concept test-bed over a distance of 2 km in standard telecommunications optical fiber. The single-photon source was an optically-pumped quantum dot in a microcavity emitting at a wavelength of 895 nm. Characterization of the quantum key distribution parameters was performed at a range of different optical excitation powers. An investigation of the effect of varying the optical excitation power of the quantum dot microcavity on the quantum bit error rate and cryptographic key exchange rate of the system are presented.

R. J. Collins; P. J. Clarke; V. Fernandez; K. J. Gordon; M. N. Makhonin; J. A. Timpson; A. Tahraoui; M. Hopkinson; A. M. Fox; M. S. Skolnick; G. S. Buller

2010-04-27

236

A Short Wavelength GigaHertz Clocked Fiber-Optic Quantum Key Distribution System  

E-print Network

A quantum key distribution system has been developed, using standard telecommunications optical fiber, which is capable of operating at clock rates of greater than 1 GHz. The quantum key distribution system implements a polarization encoded version of the B92 protocol. The system employs vertical-cavity surface-emitting lasers with emission wavelengths of 850 nm as weak coherent light sources, and silicon single photon avalanche diodes as the single photon detectors. A distributed feedback laser of emission wavelength 1.3 micro-metres, and a linear gain germanium avalanche photodiode was used to optically synchronize individual photons over the standard telecommunications fiber. The quantum key distribution system exhibited a quantum bit error rate of 1.4%, and an estimated net bit rate greater than 100,000 bits-per-second for a 4.2 km transmission range. For a 10 km fiber range a quantum bit error rate of 2.1%, and estimated net bit rate of greater than 7,000 bits-per-second was achieved.

Karen J. Gordon; Veronica Fernandez; Paul D. Townsend; Gerald S. Buller

2006-05-26

237

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

NASA Astrophysics Data System (ADS)

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.

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

238

A theory on the distribution function of backscatter radar cross section from ocean waves of individual wavelength  

Microsoft Academic Search

A new and simple method of interpreting the “distribution” of the backscatter radar cross section (RCS) from ocean waves of individual wavelength is presented. Using the Kirchhoff scattering (Physical Optics) theory, the “cumulative” RCS from the ambient waveheight spectrum is first computed as a function of the wavenumber. Differentiating this cumulative RCS yields the distribution function of the RCS from

Kazuo Ouchi

2000-01-01

239

Short Wave Amplification and Extreme Runup by the 2011 Tohoku Tsunami  

NASA Astrophysics Data System (ADS)

Watermarks found during the post-event surveys of the 2011 Tohoku tsunami confirmed extreme runup heights at several locations along the central to northern part of the Sanriku coast, Japan. We measured the maximum height of nearly 40 m above mean sea level at a narrow coastal valley of the Aneyoshi district. Wave records by offshore GPS-buoys suggest that the remarkably high runup was associated with a leading, impulsive crest of the tsunami amplified by local bathymetry and topography. In order to elucidate the underlying amplification mechanism, we apply a numerical model to reproduce the measured distribution of tsunami heights along the target coastline. A series of numerical tests under different boundary conditions suggests that a spectral component with a dominant period of 4-5 min in the leading wave play a key role in generating the extreme runup. Further analyses focusing on the Aneyoshi district confirm that the short wavelength component undergoes critical amplification in a narrow inlet. Our findings highlight the importance of resolving offshore waveforms as well as local bathymetry and topography when simulating extreme runup events.

Shimozono, Takenori; Cui, Haiyang; Pietrzak, Julie D.; Fritz, Hermann M.; Okayasu, Akio; Hooper, Andrew J.

2014-03-01

240

Using short-wave infrared imaging for fruit quality evaluation  

NASA Astrophysics Data System (ADS)

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.

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

2013-12-01

241

Short-Pulse Dual-Wavelength System Based on Mode-Locked Diode Lasers With a Single Polarization-Maintaining Yb:Fiber Amplifier  

Microsoft Academic Search

In this paper, we report on the development of a short-pulse dual-wavelength source consisting of mode-locked diode lasers and a single Yb-doped double-clad fiber amplifier. Two mode-locked external-cavity semiconductor oscillators operating at a repetition rate of 577 MHz with center wavelengths of 1040 nm and 1079 nm are synchronized, producing short pulses that are injected into a Yb-doped polarization-maintaining fiber

A. J. Budz; J. Waisman; H. F. Tiedje; H. K. Haugen

2009-01-01

242

STUDY OF OPTICAL PROPERTIES OF SKIN TISSUES FROM ULTRA-VIOLET TO SHORT-WAVE INFRARED  

E-print Network

STUDY OF OPTICAL PROPERTIES OF SKIN TISSUES FROM ULTRA-VIOLET TO SHORT-WAVE INFRARED A Dissertation Xiaoyan Ma STUDY OF OPTICAL PROPERTIES OF SKIN TISSUES FROM ULTRA-VIOLET TO SHORT-WAVE INFRARED. (Under methods and theoretical models for the inverse determination of optical parameters of mammalian tissues

243

Widely tunable dual-wavelength Er3+-doped fiber laser for tunable continuous-wave terahertz radiation.  

PubMed

We propose a widely tunable dual-wavelength Erbium-doped fiber laser that uses two micro-heater-integrated Fabry-Perot laser diodes (FP-LDs) and two fiber Bragg gratings (FBGs) for tunable continuous-wave (CW) terahertz (THz) radiation. Each wavelength can be independently tuned by using an FP-LD and an FBG. The wavelength fine tuning is achieved by simultaneously applying current to the micro-heater on the FP-LD and strain to the FBG. The side-mode suppression ratio is more than 35 dB for both wavelengths. The wavelength spacing of the dual wavelength can be continuously tuned from 3.2 nm to 9.6 nm. Continuous frequency tuning of the CW THz radiation is also successfully achieved using an InGaAs-based photomixer with our dual-wavelength fiber laser as the optical beat source. The emitted CW THz radiation is continuously tuned from 0.3 to 0.8 THz. PMID:20588354

Jeon, Min Yong; Kim, Namje; Shin, Jaeheon; Jeong, Jong Sool; Han, Sang-Pil; Lee, Chul Wook; Leem, Young Ahn; Yee, Dae-Su; Chun, Hyang Sook; Park, Kyung Hyun

2010-06-01

244

Comparative theoretical analysis of continuous wave laser cutting of metals at 1 and 10 ?m wavelength  

NASA Astrophysics Data System (ADS)

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 ?m 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-?m 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-?m beams.

Brügmann, Michael H.; Feurer, Thomas

2014-09-01

245

Continuous-wave single-frequency laser with dual wavelength at 1064 and 532??nm.  

PubMed

A continuous-wave high-power single-frequency laser with dual-wavelength output at 1064 and 532 nm is presented. The dependencies of the output power on the transmission of the output coupler and the phase-matching temperature of the LiB3O5 (LBO) crystal are studied. An output coupler with transmission of 19% is used, and the temperature of LBO is controlled to the optimal phase-matching temperature of 422 K; measured maximal output powers of 33.7 W at 1064 nm and of 1.13 W at 532 nm are obtained with optical-optical conversion efficiency of 45.6%. The laser can be single-frequency operated stably and mode-hop-free, and the measured frequency drift is less than 15 MHz in 1 min. The measured Mx2 and My2 for the 1064 nm laser are 1.06 and 1.09, respectively. The measured Mx2 and My2 for the 532 nm laser are 1.12 and 1.11, respectively. PMID:25322220

Zhang, Chenwei; Lu, Huadong; Yin, Qiwei; Su, Jing

2014-10-01

246

Analysis, modeling, and design of short-wavelength laser-plasma experiments  

SciTech Connect

We present analysis and LASNEX modeling of two experiments designed to explore the mechanisms and scaling of laser-plasma coupling in high-Z plasmas. The first used layered Au-on-CH spheres irradiated symmetrically using the Omega (Laboratory for Laser Energetics) 0.35 ..mu..m laser to observe the x-ray emission and energy penetration in gold plasmas. Measurements of the subkilovolt and kilovolt emission from targets with varying Au-coating thicknesses were made using diagnostics of varying spectral, temporal, and spatial resolution. The results indicate that the x-ray conversion efficiency is a function of target size, with larger targets yielding x-ray emission in excellent agreement with calculations. The x-ray emission fall-off with decreasing gold thickness agrees well with predictions. The second experiment used the Novette (Lawrence Livermore National Laboratory) laser to irradiate solid gold disk targets, examining wavelength scaling to 0.26 ..mu..m. The measured subkilovolt x-ray emission is in good agreement with calculations using mildly inhibited thermal electron transport, indicating enhanced target coupling, compared with previous experiments using smaller spot sizes. The experiment also indicates very low suprathermal electron populations, on the order of 0.1% at about 30 keV effective temperature. Finally, we present preliminary plans and designs for experiments which will use the Aurora 5 kJ, 5 ns, 0.25 ..mu..m KrF laser now being constructed at Los Alamos.

Mead, W.C.; Coggeshall, S.V.; Goldman, S.R.; Stover, E.K.; Goldstone, P.D.; Hauer, A.; Kindel, J.M.; Montierth, L.

1985-01-01

247

Short Wavelength Analysis of the Evolution of Perturbations in a Two-component Cosmological Fluid  

E-print Network

The equations describing a two-component cosmological fluid with linearized density perturbations are investigated in the small wavelength or large $k$ limit. The equations are formulated to include a baryonic component, as well as either a hot dark matter (HDM) or cold dark matter (CDM) component. Previous work done on such a system in static spacetime is extended to reveal some interesting physical properties, such as the Jeans wavenumber of the mixture, and resonant mode amplitudes. A WKB technique is then developed to study the expanding universe equations in detail, and to see whether such physical properties are also of relevance in this more realistic scenario. The Jeans wavenumber of the mixture is re-interpreted for the case of an expanding background spacetime. The various modes are obtained to leading order, and the amplitudes of the modes are examined in detail to compare to the resonances observed in the static spacetime results. It is found that some conclusions made in the literature about static spacetime results cannot be carried over to an expanding cosmology.

R. M. Gailis; N. E. Frankel

2006-07-24

248

IUE short-wavelength high-dispersion line list for the symbiotic nova RR Telescopii  

NASA Technical Reports Server (NTRS)

An 820 minute and other long-exposure archival SWP IUE high-dispersion spectra of symbiotic star RR Tel have been combined to form a composite spectrum. In most of these spectra many lines are saturated, but weaker features appear above the continuum. Their wavelengths were measured from the composite spectrum and compared with the line list from a thorough study of RR Tel by Penston et al. (1983). Among the revised line list are 22 new line identifications from ions C III, O I, N I, Mg VI, Si I, S I, S IV, Fe II, and Ni II. N I exists inside RR Tel's H II region and is pumped by the hot component's continuum. The fluxes for all the lines in each of the spectra are presented. All of the observed ions show a secular flux decrease between 1978 and 1988. A list of SWP high-dispersion camera artifacts is also presented. The list was generated by comparing RR Tel spectra to a long-exposure sky flat.

Aufdenberg, Jason P.

1993-01-01

249

Cryogenic optical mounting for short-wave infrared spectrometers  

NASA Astrophysics Data System (ADS)

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.

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

250

Kilowatt-peak Terahertz-wave Generation and Sub-femtojoule Terahertz-wave Pulse Detection Based on Nonlinear Optical Wavelength-conversion at Room Temperature  

NASA Astrophysics Data System (ADS)

Intense Terahertz (THz)-wave generation and highly sensitive THz-wave detection were obtained by wavelength conversion with nonlinear optical susceptibility ?(2) of LiNbO3 crystals. Maximum peak output of about 50 kW (5 ?J/pulse) was demonstrated in an injection-seeded THz-wave parametric generator pumped by post-amplified emission from a microchip Nd:YAG laser. Using the sub-nanosecond pulse duration of the laser proposed herein provides effective mitigation of stimulated Brillouin scattering in LiNbO3, producing higher gain for wavelength conversion between near-infrared (near-IR) pump light and THz waves. Monochromatic THz radiation was obtained in the continuous tuning range of 0.7-2.9 THz. Additionally, highly sensitive THz-wave detection was demonstrated based on up-conversion from THz waves to near-IR light as well as efficient THz-wave generation. The signal generated with non-collinear phase-matching condition showed spectroscopic detection on the screen apart from the LiNbO3 crystal. Highly sensitive detection with minimum energy of about 80 aJ/pulse (0.8 ?W at peak) and a large dynamic range of more than 100 dB were achieved in this experiment.

Minamide, Hiroaki; Hayashi, Shin'ichiro; Nawata, Koji; Taira, Takunori; Shikata, Jun-ichi; Kawase, Kodo

2013-12-01

251

Search for gravitational waves associated with the InterPlanetary Network short gamma ray bursts  

E-print Network

Search for gravitational waves associated with the InterPlanetary Network short gamma ray bursts V with short gamma ray bursts detected by the InterPlanetary Network (IPN) during LIGO's fifth science run and Virgo's first science run. The IPN localisation of short gamma ray bursts is limited to extended error

California at Berkeley, University of

252

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

NASA Astrophysics Data System (ADS)

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.

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

2014-05-01

253

Short-wavelength turbulence in the solar wind: Linear theory of whistler and kinetic Alfvén fluctuations  

NASA Astrophysics Data System (ADS)

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 ?e $\\ll$ 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 ?e $\\ll$ 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.

Gary, S. Peter; Smith, Charles W.

2009-12-01

254

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

NASA Technical Reports Server (NTRS)

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.

Piazzolla, Sabino

2007-01-01

255

Short-wavelength light beam in situ monitoring growth of InGaN/GaN green LEDs by MOCVD.  

PubMed

In this paper, five-period InGaN/GaN multiple quantum well green light-emitting diodes (LEDs) were grown by metal organic chemical vapor deposition with 405-nm light beam in situ monitoring system. Based on the signal of 405-nm in situ monitoring system, the related information of growth rate, indium composition and interfacial quality of each InGaN/GaN QW were obtained, and thus, the growth conditions and structural parameters were optimized to grow high-quality InGaN/GaN green LED structure. Finally, a green LED with a wavelength of 509?nm was fabricated under the optimal parameters, which was also proved by ex situ characterization such as high-resolution X-ray diffraction, photoluminescence, and electroluminescence. The results demonstrated that short-wavelength in situ monitoring system was a quick and non-destroyed tool to provide the growth information on InGaN/GaN, which would accelerate the research and development of GaN-based green LEDs. PMID:22650991

Sun, Xiaojuan; Li, Dabing; Song, Hang; Chen, Yiren; Jiang, Hong; Miao, Guoqing; Li, Zhiming

2012-01-01

256

Short-wavelength light beam in situ monitoring growth of InGaN/GaN green LEDs by MOCVD  

NASA Astrophysics Data System (ADS)

In this paper, five-period InGaN/GaN multiple quantum well green light-emitting diodes (LEDs) were grown by metal organic chemical vapor deposition with 405-nm light beam in situ monitoring system. Based on the signal of 405-nm in situ monitoring system, the related information of growth rate, indium composition and interfacial quality of each InGaN/GaN QW were obtained, and thus, the growth conditions and structural parameters were optimized to grow high-quality InGaN/GaN green LED structure. Finally, a green LED with a wavelength of 509 nm was fabricated under the optimal parameters, which was also proved by ex situ characterization such as high-resolution X-ray diffraction, photoluminescence, and electroluminescence. The results demonstrated that short-wavelength in situ monitoring system was a quick and non-destroyed tool to provide the growth information on InGaN/GaN, which would accelerate the research and development of GaN-based green LEDs.

Sun, Xiaojuan; Li, Dabing; Song, Hang; Chen, Yiren; Jiang, Hong; Miao, Guoqing; Li, Zhiming

2012-05-01

257

Short-wavelength light beam in situ monitoring growth of InGaN/GaN green LEDs by MOCVD  

PubMed Central

In this paper, five-period InGaN/GaN multiple quantum well green light-emitting diodes (LEDs) were grown by metal organic chemical vapor deposition with 405-nm light beam in situ monitoring system. Based on the signal of 405-nm in situ monitoring system, the related information of growth rate, indium composition and interfacial quality of each InGaN/GaN QW were obtained, and thus, the growth conditions and structural parameters were optimized to grow high-quality InGaN/GaN green LED structure. Finally, a green LED with a wavelength of 509?nm was fabricated under the optimal parameters, which was also proved by ex situ characterization such as high-resolution X-ray diffraction, photoluminescence, and electroluminescence. The results demonstrated that short-wavelength in situ monitoring system was a quick and non-destroyed tool to provide the growth information on InGaN/GaN, which would accelerate the research and development of GaN-based green LEDs. PMID:22650991

2012-01-01

258

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

NASA Astrophysics Data System (ADS)

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 ?m at 300 K.

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

2014-09-01

259

Glacial impact on short-wavelength topography and long-lasting effects on the denudation of a deglaciated mountain range  

NASA Astrophysics Data System (ADS)

Distinct alpine landforms in most high to mid-latitude mountain chains highlight the importance of glacial erosion in shaping mountain topography. The modifications to the initially, fluvially shaped landscape are associated with a massive and sustainable change in the distribution and magnitude of denudation following deglaciation. In this paper we focus on the glacially induced modifications to the short-wavelength topography of the deglaciated European Central Alps in an attempt to characterize the degree of glacial erosion on mountain topography and to explore the potential impact on millennial scale catchment denudation. We propose that short-wavelength topography is characteristically obliterated by glacial action and a measure of this process is provided by drainage density, which can be obtained by measuring the topographic curvature extracted from a DEM. Drainage density is well correlated with catchment-wide denudation rates from cosmogenic nuclides (10Be), but in two separate domains, identified by the degree of glacial conditioning. At lower elevations, where fluvial erosion processes dominate at present, drainage density tends to increase with denudation rate and mean slope. At higher elevations drainage density tends to decrease with increasing denudation rate but is not sensitive to mean slope. The transition between these domains is approximately coincident with the equilibrium line altitude of the last glacial maximum. Our results indicate that the decreasing drainage density in the higher domain reflects the cumulative impact of glacial erosion. We speculate that the commensurate lengthening of hillslopes increases slope instability and mass flux, thereby resulting in higher denudation rates. Rock mass strength seems to have a further significant effect on these relationships.

Salcher, Bernhard C.; Kober, Florian; Kissling, Eduard; Willett, Sean D.

2014-04-01

260

PARAMETRIC INSTABILITY OF WHISTLER WAVES IN THE ELECTRON MAGNETOHYDRODYNAMICS  

SciTech Connect

Using an electron magnetohydrodynamic model, we investigate the parametric decay among three whistler waves. A nonlinear equation to describe both linear and nonlinear properties of whistler waves is derived. Then we discuss the growth rate of the parametric decay of whistler waves in the long-wavelength region and show that the growth rate for two reverse decay waves is larger than that for two decay waves in the same direction. The nonlinear interaction among the long-wavelength and short-wavelength waves is also studied in this paper. This wave-wave interaction implies that long-wavelength waves can be decayed to short-wavelength waves and then dissipate their energy in the short-wavelength region. The possibility of applying our results to account for the generation of sunward propagating whistler waves is also discussed.

Zhao, J. S.; Wu, D. J. [Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing 210008 (China); Lu, J. Y., E-mail: js_zhao@pmo.ac.c, E-mail: djwu@pmo.ac.c, E-mail: lujy@cma.gov.c [National Center for Space Weather, China Meteorology Administration, Beijing 100081 (China)

2010-05-01

261

Short Wavelength Laser Gain Studies in Plasmas Produced by a Small NEODYMIUM:GLASS Slab Laser  

NASA Astrophysics Data System (ADS)

A high-power, high-repetition-rate Nd:glass laser system was developed and used to study a collisionally pumped x-ray laser scheme near 200 A. The laser system used a commercial oscillator injecting 60-psec modelocked pulses at 1053 nm into a Nd:glass zig-zag slab amplifier which was developed for this project. The amplifier was capable of producing 2-J, near-diffraction-limited pulses at repetition rates of up to 0.3 Hz. Single-pass gains of up to 7.5 were measured with storage efficiencies of 3-4%, and the gain profile was flat to within 10%. Use of air cooling and subhertz repetition rates alleviated thermal distortion, stringent coolant channel sealing requirements, and optical surface degradation. An optical system was designed which incorporated flattop rectangular beams and relay imaging to generate 15-?m -wide, uniform line foci on the target. The focused laser radiation was used to generate linear plasma columns suitable for amplified-spontaneous -emission laser output near 200 A. An electron collisionally pumped scheme in Ni-like Nb, analogous to previously demonstrated Ni-like schemes at higher Z, was investigated experimentally. A solid Nb target was irradiated with modelocked trains of pump pulses; a gain at 204 A of about 5 cm^ {-1} in a length of 3 mm at pump energies of 1.1 J/pulse was inferred from experiments in which the line focus length was varied. Comparable amounts of gain were seen following the second and third pump pulses, suggesting that an x-ray cavity might be feasible using this pumping scheme. Supporting evidence for gain was observed in the angular and temporal dependence of the emission. The measured gain was low compared to predictions, and the pump laser power appeared therefore to have been insufficient to achieve a high gain-length product. Theoretical work supporting the experimental efforts included calculation of ionization and recombination rate coefficients, development of a hydrodynamics model for the plasma cooling phase between pulses, and study of the extension of nonlinear four-wave-mixing and tripling processes to the soft x-ray regime. (Copies available exclusively from MIT Libraries, Rm. 14-0551, Cambridge, MA 02139-4307. Ph. 617 -253-5668; Fax 617-253-1690.).

Muendel, Martin Heinrich

262

Scattered P'P' waves observed at short distances  

USGS Publications Warehouse

We detect previously unreported 1 Hz scattered waves at epicentral distances between 30° and 50° and at times between 2300 and 2450 s after the earthquake origin. These waves likely result from off-azimuth scattering of PKPbc to PKPbc in the upper mantle and crust and provide a new tool for mapping variations in fine-scale (10 km) mantle heterogeneity. Array beams from the Large Aperture Seismic Array (LASA) clearly image the scattered energy gradually emerging from the noise and reaching its peak amplitude about 80 s later, and returning to the noise level after 150 s. Stacks of transverse versus radial slowness (?t, ?r) show two peaks at about (2, -2) and (-2,-2) s/°, indicating the waves arrive along the major arc path (180° to 360°) and significantly off azimuth. We propose a mantle and surface PKPbc to PKPbc scattering mechanism for these observations because (1) it agrees with the initiation time and distinctive slowness signature of the scattered waves and (2) it follows a scattering path analogous to previously observed deep-mantle PK•KP scattering (Chang and Cleary, 1981). The observed upper-mantle scattered waves and PK•KP waves fit into a broader set of scattered waves that we call P?•d•P?, which can scatter from any depth, d, in the mantle.

Earle, Paul S.; Rost, Sebastian; Shearer, Peter M.; Thomas, Christine

2011-01-01

263

Short-wave near-infrared spectrometer for alcohol determination and temperature correction.  

PubMed

A multichannel short-wave near-infrared (SW-NIR) spectrometer module based on charge-coupled device (CCD) detection was designed. The design relied on a tungsten lamp enhanced by light emitting diodes, a fixed grating monochromator and a linear CCD array. The main advantages were high optical resolution and an optimized signal-to-noise ratio (0.24?nm and 500, resp.) in the whole wavelength range of 650 to 1100?nm. An application to alcohol determination using partial least squares calibration and the temperature correction was presented. It was found that the direct transfer method had significant systematic prediction errors due to temperature effect. Generalized least squares weighting (GLSW) method was utilized for temperature correction. After recalibration, the RMSEP found for the 25°C model was 0.53% v/v and errors of the same order of magnitude were obtained at other temperatures (15, 35 and 40°C). And an r(2) better than 0.99 was achieved for each validation set. The possibility and accuracy of using the miniature SW-NIR spectrometer and GLSW transfer calibration method for alcohol determination at different temperatures were proven. And the analysis procedure was simple and fast, allowing a strict control of alcohol content in the wine industry. PMID:22649750

Fu, Qingbo; Wang, Jinming; Lin, Guannan; Suo, Hui; Zhao, Chun

2012-01-01

264

Dynamics of PDE, Vol.6, No.4, 291-310, 2009 Wave breaking in the short-pulse equation  

E-print Network

transformation for the short- pulse equationDynamics of PDE, Vol.6, No.4, 291-310, 2009 Wave breaking in the short-pulse equation Yue Liu. Sufficient conditions for wave breaking are found for the short- pulse equation describing wave packets

Pelinovsky, Dmitry

265

Sun glitter imaging of submarine sand waves on the Taiwan Banks: Determination of the relaxation rate of short waves  

NASA Astrophysics Data System (ADS)

Above sand waves on the seafloor, surface short waves, which are responsible for the radiance distribution in remote sensing imagery, are modulated gradually by the submarine topography. The relaxation rate ?r characterizes the rate at which the short waves reach their saturation range after being disturbed. It is a key parameter in the weak hydrodynamic interaction theory and is also a most important parameter in the imaging mechanism used for mapping submarine bottom topography. In this study, a robust expression containing intensity and phase (advection effect) modulations of the perturbed action spectrum of short waves was deduced, by using the first-order weak hydrodynamic interaction theory. On the basis of the phase modulation, a method was developed to determine the relaxation rate in the Sun glitter imaging mechanism. The relaxation rates were estimated using in situ data measured on a cruise over the sand waves of the Taiwan Banks, a sea area between the East China Sea and the South China Sea, on 28-29 August 2006. Results showed that, under a wind speed of 5.0 m s-1, the relaxation rate of short waves was about 0.055 s-1 in response to current variations and about 0.025 s-1 equivalently in response to sea bottom topographic variations. The former value could be applied to interpret the amplitude of submarine topography by using satellite imagery, while the latter one (equivalent relaxation rate ?'r) could help to more accurately calibrate the spatial position of the retrieved sea bottom topography.

Shao, Hao; Li, Yan; Li, Li

2011-06-01

266

ARM: Short Wave Flux Analysis: 15-min resolution on SIRS data, Long algorithm  

DOE Data Explorer

Short Wave Flux Analysis: 15-min resolution on SIRS data, Long algorithm. Measurements began in January, 1994, and have continued to the present time. Data collected are from the Southern Great Plains (SGP) location.

Stoffel, Tom; Kay, Bev; Habte, Aron; Anderberg, Mary; Kutchenreiter, Mark

267

Extraction of ocean wave height and dominant wavelength from Geos 3 altimeter data  

Microsoft Academic Search

The Geos 3 satellite radar altimeter has the capability to provide accurate, low-noise measurements of the significant wave height of ocean waves through their effect on the shape of the return pulse. When the amplitude and timing biases are removed from the Geos 3 sample and hold (SH) gates, the mean return wave forms can be excellently fitted with a

Edward J. Walsh

1979-01-01

268

Extraction of Ocean Wave Height and Dominant Wavelength From Geos 3 Altimeter Data  

Microsoft Academic Search

The Geos 3 satellite radar altimeter has the capability to provide accurate, low-noise measurements of the significant wave height of ocean waves through their effect on the shape of the return pulse. When the amplitude and timing biases are removed from the Geos 3 sample and hold (SH) gates, the mean return wave forms can be excellently fitted with a

Edward J. Walsh

1979-01-01

269

Bismuth-oxide-based nonlinear fiber with a high SBS threshold and its application to four-wave-mixing wavelength conversion using a pure continuous-wave pump  

Microsoft Academic Search

The unique and practical benefits of the use of bismuth-oxide-based nonlinear fiber (Bi-NLF) in implementing a four-wave-mixing (FWM)-based wavelength converter for fiber-optic-communication-system applications are experimentally demonstrated. First, the Kerr-nonlinearity and stimulated-Brillouin-scattering (SBS) characteristics of our fabricated Bi-NLF are experimentally investigated. The Bi-NLF is found to have the superior advantage of a significantly high SBS threshold in addition to its ultrahigh

Ju Han Lee; Tatsuo Nagashima; Tomoharu Hasegawa; Seiki Ohara; Naoki Sugimoto; Kazuro Kikuchi

2006-01-01

270

Short surface waves in the Canadian Arctic in 2007 and 2008  

NASA Astrophysics Data System (ADS)

We have collected time series data of short oceanic waves as a part of the International Polar Year (IPY) 2007-2008. Using a shipboard laser wave slope (LAWAS) system operating at 900 nm, we have obtained wave slopes measurements up to 60 rad m-1 wave number. We have compared our in situ wave slopes with collocated and concurrent high-resolution upwind Normalized Radar Cross Sections (NRCS) collected by QuikSCAT. The LAWAS measured wave slope spectra were consistent with local wind speeds and QuikSCAT measured NRCS. Our measured short wave mean slopes indicate their enhancement by long waves (0-1 rad m-1) at small values of long-wave slope. Concurrent with wave slope measurements, the strength of the reflected LAWAS light beam was analyzed in terms of the light attenuation coefficient at 900 nm. We have observed a correlation between surface elevation and light attenuation. The mechanism of wave modulated beam attenuation was found to be related to the instantaneous long wave skewness.

Bogucki, D. J.; Drennan, W. M.; Woods, S.; Gremes-Cordero, S.; Long, D. G.; Mitchell, C.

2013-07-01

271

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

NASA Astrophysics Data System (ADS)

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?=1.5±0.1 cm-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)].

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.

2014-05-01

272

Long- and short-wave instabilities in helical vortices  

NASA Astrophysics Data System (ADS)

We review two instability mechanisms that may be active in wind turbine wakes and contribute to their downstream evolution, by considering simplified configurations of one or several spatially uniform helical vortices. One category of instabilities involves displacement perturbations of the vortices, with wavelengths that are large compared to the size of their cores; they can be analysed using a filament approach. Previous theoretical results, confirmed by our recent experiments, show that the predicted instability modes are related to the pairing phenomenon found in periodic arrays of vortices. A second group of instabilities involves internal perturbations of the vortex cores, with wavelengths scaling on the core size. They result from deformations of the cores due to curvature, torsion or the strain induced by neighbouring helix loops. Our experiments show that the non-linear evolution of the shortwave instabilities, combined with the pairing mechanism, leads to a rapid destruction of the helical wake vortices.

Leweke, T.; Quaranta, H. U.; Bolnot, H.; Blanco-Rodríguez, F. J.; Le Dizès, S.

2014-06-01

273

Extra-broadband wavelength-tunable actively mode-locked short-cavity fiber ring laser using a bismuth-based highly nonlinear erbium-doped fiber  

NASA Astrophysics Data System (ADS)

We demonstrate an ultra-wideband wavelength-tunable actively mode-locked short-cavity laser employing a 151-cm-long bismuth-based highly nonlinear erbium-doped fiber (Bi-HNL-EDF). A wavelength tuning range of 87 nm from 1533 nm to 1620 nm can be achieved because the Bi-HNL-EDF has an ultra-wide gain bandwidth. High nonlinearity of the Bi-HNL-EDF also collaborates with spectral filtering by an optical bandpass filter to suppress the supermode noise quite effectively. Total length of the fiber ring cavity is as short as 16 m. Thus, stable and clean 5.6-6.1 ps pulses with a repetition rate of 10 GHz are successfully obtained over the wavelength tuning range almost completely covering both the conventional wavelength band (1530-1565 nm) and the longer wavelength band (1565-1625 nm). The bismuth-based short-cavity fiber laser also shows good performance in the back-to-back bit-error-rate measurements, and maintains bit-error-free mode-locking operation throughout the entire wavelength tuning range.

Fukuchi, Yutaka; Hirata, Kouji; Ikeoka, Hiroshi

274

The Contribution of Ultraviolet and Short-Wavelength Sensitive Cone Mechanisms to Color Vision in Rainbow Trout  

Microsoft Academic Search

Color vision in rainbow trout was studied by characterizing the spectral sensitivity of single units in three areas of visual processing: optic nerve; optic tectum; and torus semicircularis. Sensitivity to medium wavelength stimuli was a common feature of all single units examined. Additionally, long wavelength sensitivity was found in all units that were not medium wavelength-only or monophasic. Ultraviolet and

David J. Coughlin; Craig W. Hawryshyn

1994-01-01

275

A Two-Wave Mixing Interferometer for Phase and Wavelength Demodulation of Fiber-Optic Ultrasound Sensors  

NASA Astrophysics Data System (ADS)

A two-wave mixing (TWM) interferometer using InP:Fe in the C-band wavelength at 1550nm is demonstrated. The system can be used as a conventional phase-demodulator for laser ultrasonic applications. In addition, a wavelength demodulation configuration of the TWM interferometer is proposed for use with Fiber Bragg-Grating (FBG) ultrasound sensors. In this configuration, the FBG is illuminated with a broadband source, and any strain in the FBG is encoded as a wavelength change of the light reflected by the FBG. The reflected light from the FBG is spilt into two unbalanced paths and both beams (pump and signal) are mixed in the TWM system. A small wavelength change in the FBG reflected light can be thought of as an equivalent phase change between the pump and signal beams as they travel unbalanced path lengths. FBG demodulation using TWM enables selective monitoring of dynamic strains induced by ultrasound and acoustic emissions, even in the presence of large quasi-static strains that otherwise would cause the FBG sensor to drift. Since TWM interferometers can be readily multiplexed, the proposed technique can be used to demodulate signals from a network of FBG ultrasound (acoustic emission) sensors for use in structural health monitoring.

Zhou, Yi; Qiao, Yi; Krishnaswamy, Sridhar

2005-04-01

276

Continuous-wave vertical-cavity surface-emitting lasers with emission wavelengths near 650 nm  

NASA Astrophysics Data System (ADS)

Red VCSELs for emission wavelengths near 650nm find applications in emerging technologies such as plastic-fiber-based data communication. However, these devices are challenging due to low band offsets and high electrical and thermal resistivity of especially the p-DBR. The paper presents the optimization of p-DBR and QW design for the reduction of the series resistance and the threshold current density. VCSEL structures were grown using MOVPE and processed to air-post mesas. The resistance of the p:DBR mirrors was optimized using different dopants and interfaces. By changing from Zn doping and abrupt interfaces to the dopant C and introducing graded interfaces the differential resistance decreased. Due to a relative shift across the wafer between the DBR stop-band and gain peak wavelength defined by the MQW active region, devices are available with lasing wavelengths between 638nm and 662nm in pulsed-mode operation. Threshold current densities of 3.6kA/cm2 at 650nm are measured. For improving device parameters a current aperture was processed by selective wet oxidation of AlxGa1-xAs with varying x. Cw laser operation is achieved for wavelengths between 644nm and 657nm at 10°C ambient temperature. With threshold currents under 4mA maximum cw output powers of 160´W are obtained at wavelengths of 657nm and 650 nm.

Oster, Andrea; Zorn, M.; Vogel, Klaus; Fricke, Jorg; Sebastian, Juergen; John, W.; Weyers, Marcus; Traenkle, Guenther

2001-05-01

277

High brightness electron beams from density transition laser wakefield acceleration for short-wavelength free-electron lasers  

NASA Astrophysics Data System (ADS)

We use three-dimensional simulations to study injection and electron beam quality in laser wakefield acceleration (LWFA) using the density transition technique. We vary the density transition length scale, covering both the sharp and gradual density transition regimes. We find that the injected charge decreases monotonically as the density transition scale length increases, and as a consequence the energy-spread and emittance improve monotonically. Therefore, there is no optimal transition length that gives the best quality beam, contrary to earlier suggestions. However, the density transition technique does give high brightness electron beams with kA current, energy-spread of around 1% and normalized rms emittance of around 1? mm-mrad. We study the application of these LWFA beams as drivers for a short-wavelength free-electron laser (FEL), using analytic formulae as well as three-dimensional simulations. Because higher current favours a shorter transition length, while smaller energy-spread and emittance favour a longer transition length, there is now an optimal density transition scale length (for our parameters, 50 µm) that gives the best FEL performance: lasing at 270 nm, with a saturated power of around 360 MW, over an undulator length of only 6 m. Further improvements, like lower plasma density and laser guiding, could result in GeV-class beams of sufficient brightness to drive a soft x-ray FEL.

Samant, Sushil Arun; Upadhyay, Ajay Kumar; Krishnagopal, Srinivas

2014-09-01

278

Latent period and antigenicity of murine tumors induced in C3H mice by short-wavelength ultraviolet radiation  

SciTech Connect

Skin tumors were induced in C3H/HeNCr1BR mice with chronic short-wavelength ultraviolet (UVC) irradiation using a germicidal lamp (254 nm). Fifty percent of mice had developed tumors by 9 1/2 months (range 8-12 months). With progressive irradiation, mice developed multiple tumors on the back reaching a mean of 2.9 tumors/mouse at 11 1/2 months. No tumors developed on the ears. Of 83 lesions examined histologically 66 (80%) were squamous cell carcinomas, 6 (7%) were fibrosarcomas, and 10 (12%) were proliferative squamous lesions without evident invasion. Twenty-two squamous cell carcinomas were transplanted s.c. into normal syngeneic mice and into mice immunosuppressed by adult thymectomy, lethal x-irradiation, and bone marrow or neonatal liver reconstitution. Transplantation of squamous cell carcinomas was successful in a total of 17/22 (77%) cases. Only 11/22 (50%) tumors grew progressively in normal mice. Six of 22 (27%) tumors grew progressively in immunosuppressed mice but not normal syngeneic recipients. Three fibrosarcomas were also transplanted. All 3 grew progressively in immunosuppressed hosts but failed to grow in normal syngeneic recipients. Two fibrosarcomas that were induced by a germicidal lamp were found to grow significantly better in UVB-irradiated (280-320 nm) mice than in normal mice. Conversely, a UVB-induced fibrosarcoma showed enhanced growth in UVC-irradiated mice compared to growth in normal, age-matched controls.

Lill, P.H.

1983-10-01

279

Laboratory research on effective test area of short-crested waves generated by two-sided segmented wavemakers  

NASA Astrophysics Data System (ADS)

The size and shape of the effective test area are crucial to consider when short-crested waves are created by segmented wavemakers. The range of the effective test area of short-crested waves simulated by two-sided segmented wavemakers is analyzed in this paper. The experimental investigation on the wave field distribution of short-crested waves generated by two-sided segmented wavemakers is conducted by using an array of wave gauges. Wave spectra and directional spreading function are analyzed and the results show that when the main direction is at a certain angle with the normal line of wave generators, the wave field of 3D short-crested waves generated by two-sided segmented wavemakers has good spatial uniformity within the model test area. The effective test area can provide good wave environments for seakeeping model tests of various ocean engineering structures in the deep ocean engineering basin.

Li, Jun; Chen, Gang; Yang, Jian-min; Peng, Tao

2014-04-01

280

Stimulated Brillouin scattering from surface acoustic waves in sub-wavelength photonic microwires  

E-print Network

Brillouin scattering in optical fibres is a fundamental interaction between light and sound with important implications ranging from optical sensors to slow and fast light. In usual optical fibres, light both excites and feels shear and longitudinal bulk elastic waves, giving rise to forward guided acoustic wave Brillouin scattering and backward stimulated Brillouin scattering. In a subwavelength-diameter optical fibre, the situation changes dramatically, as we here report with the first experimental observation of stimulated Brillouin scattering from surface acoustic waves. These Rayleigh-type hypersound waves travel the wire surface at a specific velocity of 3400 m.s$^{\\mathrm{-1}}$ and backscatter the light with a Doppler shift of about 6 GHz. As these acoustic resonances are highly sensitive to surface defects or features, surface acoustic wave Brillouin scattering opens new opportunities for various sensing applications, but also in other domains such as microwave photonics and nonlinear plasmonics.

Beugnot, Jean-Charles; Pauliat, Gilles; Maillotte, Hervé; Laude, Vincent; Sylvestre, Thibaut

2014-01-01

281

Detection of optic neuropathy in glaucomatous eyes with normal standard visual fields using a test battery of short-wavelength automated perimetry and pattern electroretinography  

Microsoft Academic Search

PurposeTo evaluate the clinical use of a test battery of short-wavelength automated perimetry (SWAP), frequency-doubling technology (FDT) perimetry, and pattern-electroretinography (PERG) in patients with definite primary open-angle glaucoma (POAG) but normal results on standard automated perimetry (SAP).

Andreas U Bayer; Klaus-Peter Maag; Carl Erb

2002-01-01

282

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

E-print Network

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[subscript ?] = 1.5 ± 0.1 cm[superscript ...

Parker, R. R.

283

The Effect of Wavelength-Dependent Emissivity on the Melting Temperatures of Iron From Shock Wave Measurements  

NASA Astrophysics Data System (ADS)

The high-pressure melting curve of iron at the conditions of the outer core is anchored by the shock wave measurements of Bass et. al. 1987. They used spectral radiometric techniques, looking at shocked iron films or foils through a transparent anvil. They assumed that the emissivity of the iron was independent of wavelength. The wavelength dependence of the emissivity of fcc and bcc iron was measured by Taylor, 1952. Both structures have a change in emissivity of 20% over 200nm in the visible, although the absolute magnitude of the emissivity is different. In the measurement of temperature using spectral radiometry, the absolute value of the emissivity does not effect the temperature measurement. In iron the 3d-bands straddle the Fermi Energy in any close packed structure (Boness and Brown, 1990). The electrons at the Fermi Energy can easily be promoted into the empty states of the conduction band, and thus are the basis of the electronic contribution to the heat capacity. It is these same electrons in the 3d-bands that also control the emissivity. With increasing wavelength, more electrons are promoted into the conduction band, which means the emissivity is higher at shorter wavelengths than at longer wavelengths. We reanalyzed the shock wave data of Bass et. al. using the wavelength dependent emissivity. The corrected melting temperature of iron at 243 GPa is 5900 +/-500 K compared to Bass et. al.'s determination of 6700 +/- 400 K. This is just slightly higher then the estimate (based upon the assumption of the heat capacity being equal to 5R) of Brown and McQueen, 1986 of 5000-5700 K, and in good agreement with theoretical calculations of Alfe, 2010. Alfe, D., 2010, Rev. Min. and Geochem., 71, 337-354. Bass, J. D., B. Svendsen, and T. J. Ahrens, 1987, M. H. Manghnani and Y. Syono, Terra Scientific Publishing Co. / American Geophysical Union, Washington, D. C., 393-402. Boness, D. A., and J. M. Brown, 1990, JGR, 95, 21,721-30. Brown, J. M. and R. G. McQueen, 1986, JGR, 91, 7485-94. Taylor, J. E., 1952, Jour. Optical Soc. America, 42, 33-36.

Heinz, D. L.; Mark, H.

2012-12-01

284

Polypropylene Embedded Metal-Mesh Broadband Achromatic Half Wave Plate for Millimeter Wavelengths  

E-print Network

We describe a novel multi-layered metal mesh achromatic half wave plate for use in astronomical polarimetric instruments. The half wave plate is designed to operate across the frequency range from 125-250 GHz. The wave plate is manufactured from 12-layers of thin film metallic inductive and capacitive grids patterned onto polypropylene sheets, which are then bonded together using a hot pressing technique. Transmission line modelling and 3-D electromagnetic simulations are used to optimize the parameters of the metal-mesh patterns and to evaluate their optical properties. A prototype half wave plate has been fabricated and its performance characterized in a polarizing Fourier transform spectrometer. The device performance is consistent with the modelling although the measured differential phase shift for two orthogonal polarizations is lower than expected. This difference is likely to result from imperfect patterning of individual layers and misalignment of the grids during manufacture.

Zhang, Jin; Mauskopf, Philip; Savini, Giorgio; Moncelsi, Lorenzo; Whitehouse, Nicola; 10.1364/AO.50.003750

2011-01-01

285

Design, Construction, and Calibration of a Portable Short Wave Infrared Spectroradiometer  

NASA Astrophysics Data System (ADS)

This dissertation describes the design, construction, and calibration of a portable short wave infrared (SWIR) spectroradiometer. The main use for the instrument is the collection of ground reflectance and radiance data for the radiometric calibration of operational and proposed high spectral resolution remote-sensing systems, such as the Airborne Visible and Infrared Imaging Spectrometer (AVIRIS), the Moderate Resolution Imaging Spectroradiometer (MODIS), the High Resolution Imaging Spectrometer (HIRIS), and the Advanced Spaceborne Thermal Emission and Reflectance Radiometer (ASTER). The instrument will also be used for cross calibrating Earth Observing System (EOS) calibration facilities and for a variety of high spectral resolution studies in earth science. The instrument is designed to be carried as a backpack unit, on a vehicle, or in a helicopter or airplane. The spectroradiometer covers the range from 1.05 to 2.45 mum. The spectral sampling interval is 1.37 nm and the spectral resolution is variable from about 5 nm to more than 100 nm. A single spectrum can be acquired in as little as 1 s. The signal-to-noise ratio (SNR) for a single 1-s scan is about 90 at a wavelength of 2.2 ?m for a lambertian surface of 100% reflectance illuminated by the sun at normal incidence with 14-nm spectral resolution, a 25^circ background temperature, and no atmospheric attenuation. The SNR can be improved by averaging multiple scans. Field -of-view defining optics are coupled by a flexible fiber optics bundle to the spectroradiometer, which consists of a non-scanning concave holographic diffraction grating with flat focal field imaged onto a 1024-element liquid -nitrogen-cooled PtSi linear-array detector. The combination of concave grating and linear-array detector was chosen in preference to Fourier transform, Hadamard transform, and scanned grating monochromator systems on the basis of simplicity, high SNR, and greatest radiometric accuracy.

Smith, Mark William

286

Ultra-short pulsed millimeter-wave laser  

NASA Astrophysics Data System (ADS)

High peak power pulses of 1.22-mm wavelength radiation have recently been obtained from a novel cavity-dumped far-infrared optically-pumped laser^1. Smooth reproducible pulses with the following characteristics have been routinely obtained: peak power=25-kW, pulsewidth (FWHM)=5-ns, repetition rate=10 pps. (This compares favorably to typical far-infrared, cavity-dumped output - 11-kW, 30-ns, 1 pps - available from the University of California - Santa Barbara Free Electron Laser). The pumping laser is a grating-tuned, hybrid TEA CO2 laser providing 1J / pulse at the 9P32 transition. The far-infrared gain medium is isotopic (C^13) methyl flouride. Experiments are underway for using the novel source to resonantly excite coherent pulses of 250-GHz longitudinal acoustic phonons in silicon doping superlattices. ^1 Thomas E. Wilson, "Modeling the high-speed switching of far-infrared radiation by photoionization in a semiconductor", Phys. Rev. B 59 (20), 12996 (1999).

Wilson, Thomas

2000-10-01

287

An analysis of short pulse and dual frequency radar techniques for measuring ocean wave spectra from satellites  

Microsoft Academic Search

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

F. C. Jackson

1980-01-01

288

Effects of a chronic reduction of short-wavelength light input on melatonin and sleep patterns in humans: evidence for adaptation.  

PubMed

Light is an important environmental stimulus for the entrainment of the circadian clock and for increasing alertness. The intrinsically photosensitive ganglion cells in the retina play an important role in transferring this light information to the circadian system and they are elicited in particular by short-wavelength light. Exposure to short wavelengths is reduced, for instance, in elderly people due to yellowing of the ocular lenses. This reduction may be involved in the disrupted circadian rhythms observed in aged subjects. Here, we tested the effects of reduced blue light exposure in young healthy subjects (n?=?15) by using soft orange contact lenses (SOCL). We showed (as expected) that a reduction in the melatonin suppressing effect of light is observed when subjects wear the SOCL. However, after chronic exposure to reduced (short wavelength) light for two consecutive weeks we observed an increase in sensitivity of the melatonin suppression response. The response normalized as if it took place under a polychromatic light pulse. No differences were found in the dim light melatonin onset or in the amplitude of the melatonin rhythms after chronic reduced blue light exposure. The effects on sleep parameters were limited. Our results demonstrate that the non-visual light system of healthy young subjects is capable of adapting to changes in the spectral composition of environmental light exposure. The present results emphasize the importance of considering not only the short-term effects of changes in environmental light characteristics. PMID:24597610

Giménez, Marina C; Beersma, Domien G M; Bollen, Pauline; van der Linden, Matthijs L; Gordijn, Marijke C M

2014-06-01

289

Numerical simulation of lowest-order short-crested wave instabilities  

NASA Astrophysics Data System (ADS)

A numerical study of doubly periodic deep-water short-crested wave instabilities, arising from various quartet resonant interactions, is conducted using a high-order Boussinesq-type model. The model is first verified through a series of simulations involving classical class I plane wave instabilities. These correctly lead to well-known (nearly symmetric) recurrence cycles below a previously established breaking threshold steepness, and to an asymmetric evolution (characterized by a permanent transfer of energy to the lower side-band) above this threshold, with dissipation from a smoothing filter promoting this behaviour in these cases. A series of class Ia short-crested wave instabilities, near the plane wave limit, are then considered, covering a wide range of incident wave steepness. A close match with theoretical growth rates is demonstrated near the inception. It is shown that the unstable evolution of these initially three-dimensional waves leads to an asymmetric evolution, even for weakly nonlinear cases presumably well below breaking. This is characterized by an energy transfer to the lower side-band, which is also accompanied by a similar transfer to more distant upper side-bands. At larger steepness, the evolution leads to a permanent downshift of both the mean and peak frequencies, driven in part by dissipation, effectively breaking the quasi-recurrence cycle. A single case involving a class Ib short-crested wave instability at relatively large steepness is also considered, which demonstrates a reasonably similar evolution. These simulations consider the simplest physical situations involving three-dimensional instabilities of genuinely three-dimensional progressive waves, revealing qualitative differences from classical two-dimensional descriptions. This study is therefore of fundamental importance in understanding the development of three-dimensional wave spectra.

Fuhrman, David R.; Madsen, Per A.; Bingham, Harry B.

2006-09-01

290

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)

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.

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

2010-09-01

291

Powerful short-pulse lasers pumped by the light of a shock wave front  

Microsoft Academic Search

Radiation of a shock wave front proved to be very powerful light source for pumping of high power lasers. Particularly, explosively pumped iodine photodissociation lasers (EPIL) are nowadays well developed type of device of multikilojoule level, rather convenient for many applications. Usually such lasers work in free running mode and generate pulses of microsecond duration. Generating short pulses of nanosecond

Gennadi A. Kirillov; V. A. Eroshenko; Gennady G. Kochemasov; Stanislav M. Kulikov; S. N. Pevny; Stanislav A. Sukharev

2000-01-01

292

A Short-Wave Infrared Nanoinjection Imager With 2500 A/W Responsivity and Low  

E-print Network

. 1. Introduction Improving sensitivity in the infrared spectrum is a challenging task due to the minute energy of each photon at less than 1 aJ. An important part of the infrared spectrum is the short-wave infrared (SWIR), which is used in many applications including telecommunications, biophotonics [1], optical

Mohseni, Hooman

293

Short wave length approximation of a boundary integral operator for homogeneous and isotropic elastic bodies  

E-print Network

We derive a short wave length approximation of a boundary integral operator for two-dimensional isotropic and homogeneous elastic bodies of arbitrary shape. Trace formulae for elastodynamics can be deduced in this way from first principles starting directly from Navier-Cauchy's equation.

Gregor Tanner; Niels Sondergaard

2006-08-17

294

Infrared Space Observatory Short Wavelength Spectrometer Observations of H II Regions in NGC 6822 and I Zwicky 36: Sulfur Abundances and Temperature Fluctuations  

Microsoft Academic Search

We report Infrared Space Observatory (ISO) Short Wavelength Spectrometer infrared spectroscopy of the H II region Hubble V in NGC 6822 and the blue compact dwarf galaxy I Zw 36. Observations of Bralpha, [S III] at 18.7 and 33.5 mum, and [S IV] at 10.5 mum are used to determine ionic sulfur abundances in these H II regions. There is

Joshua G. Nollenberg; Evan D. Skillman; Donald R. Garnett; Harriet L. Dinerstein

2002-01-01

295

Modulation and kinematics of mechanically-generated short gravity waves riding on long waves  

E-print Network

system. 25 3. 7 Laser slope gauge components (alter Spell et ak 1992) . . . . . . . . . . 28 3. 3 Schematic of the beam geometry used to derive the relationship be- tween the wave slope dii/ck and the displacement z of the light spot on the diffusion... system. 25 3. 7 Laser slope gauge components (alter Spell et ak 1992) . . . . . . . . . . 28 3. 3 Schematic of the beam geometry used to derive the relationship be- tween the wave slope dii/ck and the displacement z of the light spot on the diffusion...

Spell, Charles Anthony

2012-06-07

296

Compact spectrometer modelling based on wavelength-scale stationary wave Fourier transform in integrated optic  

NASA Astrophysics Data System (ADS)

Recently, a new generation of high-resolution ultra-compact spectrometers (SWIFTS) has been investigated in integrated optics. Its principle consists of sampling an interferogram obtained by a stationary waves in an optical waveguide without moving parts. Then a Fourier transform of the interference pattern gives the spectral response of the optical source under test. The sampling is obtained thanks to metallic nanowires set upon the surface of the waveguide. Only a small part of the light, proportional to the light under the metallic element is scattered outside. Then this radiated part is detected on a camera through an optical lens. In this paper, this device is modelized using an Aperiodic Fourier Modal Method allowing simulation of a long SOI waveguide composed of very small metallic elements described by a complex refractive index. We demonstrate the possibility of obtaining the spectral response with this method. Instead of using a classical lens associated to a camera, we also modelize an entire compact device composed of a linear photo-detector array above the waveguide separated by a peculiar gap. This gap is chosen in order to image the interferogram without damaging the initial interferogram. Spectral resolution close to 4 nm is obtained with 1 mm waveguide length.

Morand, Alain; Custillon, Guillaume; Benech, Pierre; Le Coarer, Etienne; Leblond, Gregory; Blaize, Sylvain

2008-04-01

297

High-Speed Imaging of Short Wind Waves by Shape from Refraction  

NASA Astrophysics Data System (ADS)

This paper introduces the first high-speed system for slope imaging of wind-induced short water waves. The imaging slope gauge method is used, which is based on the shape from refraction principle. The downward looking camera with a telecentric lens observes the refraction of light rays coming from a high power custom telecentric LED light source that is placed underneath the wind wave facility. The light source can be programmed to arbitrary intensity gradients in the x- and y-direction, so that the origin of a light ray is coded in intensity. Four gradient images (acquired at 6000 fps) are combined for one 2D slope image. By only using intensity ratios, the measurements become independent of lens effects from the curved water surface and inhomogeneities in the light source. Independence of wave height is guaranteed by using telecentric illumination and telecentric imaging. The system is capable to measure the slopes of a wind-driven water surface in the Heidelberg Aeolotron wind-wave facility on a footprint of 200 x 160 mm with a spatial resolution of 0.22 mm and a temporal resolution of more than 1500 fps. For the first time, it is now possible to investigate the structure of short wind-induced waves with sufficient spatial and temporal resolution to study their dynamic characteristics without aliasing effects. Example images and a video of a 3D reconstructed water surface are shown to illustrate the principle.

Kiefhaber, D.; Reith, S.; Rocholz, R.; Jähne, B.

2014-03-01

298

Possibility of rarefaction shock wave under short pulse laser ablation of solids.  

PubMed

Attention is drawn to a phenomenon that may give a radically different explanation for the recent observations of the system of dark rings above a solid surface vaporized by a short laser pulse. If a substance is heated to near-critical temperature, the existence of the compression shock wave becomes impossible, whereas the rarefaction wave takes a form of shock. The rarefaction shock can be considered as an interface in the expanding near-critical substance to form Newton rings in time-resolved optical microscopy experiments. The qualitative picture of the laser-ablated material expansion in vacuum with the generation of the rarefaction shock is discussed. PMID:11970267

Bulgakova, N M

1999-10-01

299

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

PubMed

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

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

1997-11-15

300

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

NASA Technical Reports Server (NTRS)

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.

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

1997-01-01

301

Search for gravitational waves associated with the InterPlanetary Network short gamma ray bursts  

E-print Network

We outline the scientific motivation behind a search for gravitational waves associated with short gamma ray bursts detected by the InterPlanetary Network (IPN) during LIGO's fifth science run and Virgo's first science run. The IPN localisation of short gamma ray bursts is limited to extended error boxes of different shapes and sizes and a search on these error boxes poses a series of challenges for data analysis. We will discuss these challenges and outline the methods to optimise the search over these error boxes.

V. Predoi; for the LIGO Scientific Collaboration; for the Virgo Collaboration; K. Hurley; for IPN

2011-12-07

302

Powerful short-pulse lasers pumped by the light of a shock wave front  

NASA Astrophysics Data System (ADS)

Radiation of a shock wave front proved to be very powerful light source for pumping of high power lasers. Particularly, explosively pumped iodine photodissociation lasers (EPIL) are nowadays well developed type of device of multikilojoule level, rather convenient for many applications. Usually such lasers work in free running mode and generate pulses of microsecond duration. Generating short pulses of nanosecond range require employing amplification scheme where amplifiers must work in waiting mode. It implies substantially other composition of active medium and entails rather important consequences for kinetics of the processes which follow photodissociation. Present report considers these problems as well as some experimental results obtained with short pulse EPIL.

Kirillov, Gennadi A.; Eroshenko, V. A.; Kochemasov, Gennady G.; Kulikov, Stanislav M.; Pevny, S. N.; Sukharev, Stanislav A.

2000-04-01

303

Multidetector F-statistic metric for short-duration nonprecessing inspiral gravitational-wave signals  

NASA Astrophysics Data System (ADS)

We derive explicit expressions for the multidetector F-statistic metric applied to short-duration nonprecessing inspiral signals. This is required for template bank production associated with coherent searches for short-duration nonprecessing inspiral signals in gravitational-wave data from a network of detectors. We compare the metric’s performance with explicit overlap calculations for all relevant dimensions of parameter space and find the metric accurately predicts the loss of detection statistic above overlaps of 95%. We also show the effect that neglecting the variations of the detector response functions has on the metric.

Keppel, Drew

2012-12-01

304

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

PubMed

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

Zhang, Tao; Fu, Yingbin

2013-08-01

305

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)

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.

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

2014-09-01

306

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

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

Heath, Melanie; Sutherland, Cate; Bartel, Kate; Gradisar, Michael; Williamson, Paul; Lovato, Nicole; Micic, Gorica

2014-05-01

307

Underestimation of GCM-Calculated Short-Wave Atmospheric Absorption in Areas Affected by Biomass burning  

Microsoft Academic Search

Many current General Circulation Models (GCMs) exhibit a common problem, namely that their atmosphere is too transparent to\\u000a solar radiation. The underestimation of atmospheric short-wave absorption by these models is particularly large in areas and\\u000a seasons where extensive biomass burning takes place. This is shown using surface radiation measurements combined with co-located\\u000a satellite observations at sites affected by biomass burning

Martin Wild

308

Improvement of Short-Wave InfraRed Hyperspectral Imaging by Direct Polarization Measurements  

Microsoft Academic Search

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

G. E. Leblanc; S. Allux

2010-01-01

309

Investigation of the spectrum of short-wave Görtler vortices in a gas  

Microsoft Academic Search

The linear stage of short-wave Görtler vortices in the boundary layer near a concave surface is studied for the regime of\\u000a weak hypersonic viscid-inviscid interaction at high Reynolds and Görtler numbers. It is assumed that the gas is perfect and\\u000a the viscosity is a linear function of the enthalpy. It is found that neutral vortices are located near the surface

V. V. Bogolepov

1998-01-01

310

The assessment of a towed laser slopemeter for measuring short scale sea surface wave slopes  

NASA Astrophysics Data System (ADS)

The advent of satellite-borne Synthetic Aperture Radar (SAR) has generated much interest in sea surface waves of less than a metre in wavelength. Many oceanographic processes can be identified within SAR images of the world's oceans. The limited understanding of the interactions between these phenomena and the wind-wave field and the scatter mechanisms leading to the returned radar signal has restricted the full quantitative application of this important remote sensing tool. In an effort to address this gap in our understanding there is a need for in-situ measurements. A Towed Laser Slopemeter has been designed and developed at the University of Southampton. This is capable of measuring two orthogonal components of surface slope of between +/-35° over a wavelength range of 1m to 0.007m at a rate of 250 Hz. Values of slope are determined using a laser beam and an optical detection system without the need to measure surface wave height. The instrument is towed parallel to a larger vessel to ensure that an undisturbed surface profile is sampled. It has been established that the effect of towing the slopemeter leads to a hybrid wavenumber-frequency spectrum Studies conducted in this thesis are concerned with the characterisation of the TLS and the verification of its ability to measure sea surface wave slope. To investigate the effect of vehicle velocity on the observed spectrum a new numerical model was developed. The model was capable of providing true wavenumber, true wave frequency and wavenumber-frequency spectra. The direction between the true and observed wavenumbers was found to be a minimum at small angles to the direction of travel of the wave and at high tow speeds. Using the numerical model methods for providing a true wavenumber spectrum from the wavenumber-frequency spectrum were investigated. Data from the first deployment of the slopemeter was thoroughly investigated to assess its oceanographic content. Wave profiles, spectra and slope distributions were found to agree with accepted forms. The wave profile was noisier than expected. From an analysis of this noise, sources were identified and this led directly to a refit of the TLS. Slicks evident on the sea surface were sampled by the slopemeter during the trial. The time at which these features were intercepted by the TLS was logged. The logged time agreed with a decrease in the recorded wave slopes. The ability of the TLS to provide a sensitive and precise measurement of sea surface roughness was reinforced with an extensive comparison of the TLS and video records from the second deployment. Waves seen within the video could be seen within the TLS record. The TLS proved to be more sensitive to changes in wave slope for a larger range of sea states than the video record. A variety of signal processing tools were found to be useful in the analysis of the TLS data sets. Confidence was gained in the ability of the TLS as a device capable of providing sensitive in-situ measurements of the interaction of ocean processes with the sea surface wave profile. (Abstract shortened by UMI.)

Willoughby, Barrie John

311

Storm time, short-lived bursts of relativistic electron precipitation detected by subionospheric radio wave propagation  

NASA Astrophysics Data System (ADS)

In this study we report on ground-based observations of short bursts of relativistic electron precipitation (REP), detected by a subionospheric propagation sensor in Sodankylä, Finland during 2005. In two ˜4 hour case study periods from L = 5.2, around local midnight, several hundred short-lived radio wave perturbations were observed, covering a wide range of arrival azimuths. The vast majority (˜99%) of these perturbations were not simultaneous with perturbations on other paths, consistent with a precipitation "rainstorm" producing ionospheric changes of small spatial sizes around the Sodankylä receiver. The recovery time of these radio wave perturbations are ˜1.2 s, which is consistent with the modeled effects of a burst of >2 MeV precipitating electrons. This agrees with satellite observations of the microburst energy spectrum. The energetic nature of the precipitation which produces the FAST perturbations suggests that they should be observable in both day and night conditions. While it is widely assumed that satellite-detected REP microbursts are due to wave-particle interactions with very low-frequency chorus waves, the energy spectra predicted by our current models of chorus propagation and wave-particle interaction are not consistent with the experimentally observed radio wave perturbations presented here or previously reported satellite observations of REP microbursts. The results inferred from both the satellite and subionospheric observations, namely the absence of a large, dominant component of <100 keV precipitating electrons, fundamentally disagrees with a mechanism of chorus-driven precipitation. Nonetheless, further work on the modeling of chorus-driven precipitation is required.

Rodger, Craig J.; Clilverd, Mark A.; Nunn, David; Verronen, Pekka T.; Bortnik, Jacob; Turunen, Esa

2007-07-01

312

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

SciTech Connect

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.

Ikeno, Masaaki; Kajima, Ryoichi; Matsuyama, Masafumi; Sakakiyama, Tsutomu [Central Research Inst. of Electric Power Industry, Abiko (Japan)

1995-12-31

313

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

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.

Setser, D.W.

1987-12-07

314

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

NASA Astrophysics Data System (ADS)

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 (?max = 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.

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

2014-09-01

315

All-sky measurements of short period waves imaged in the OI(557.7 nm), Na(589.2 nm) and near infrared OH and O2(0,1) nightglow emissions during the ALOHA93 campaign  

Microsoft Academic Search

As part of the ALOHA-93 campaign a high performance all-sky CCD imaging system was operated at Haleakala Crater, Maui, to obtain novel information on the properties and sources of short period gravity waves over an extended height range ~80-100 km. Sequential observations of the near infrared OH and O2(0,1) bands and the visible wavelength OI(557.7 nm) and Na(589.2 nm) line

M. J. Taylor; M. B. Bishop; V. Taylor

1995-01-01

316

Prospects for joint gravitational wave and short gamma-ray burst observations  

E-print Network

We present a detailed evaluation of the expected rate of joint gravitational-wave and short gamma-ray burst (GRB) observations over the coming years. We begin by evaluating the improvement in distance sensitivity of the gravitational wave 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 doubling the number of detectable gravitational wave 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 gravitational wave detector network. We show that in the early advanced gravitational wave detector observing runs, from 2015-2017, 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 Interplanetary 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.

J. Clark; H. Evans; S. Fairhurst; I. W. Harry; E. Macdonald; D. Macleod; P. J. Sutton; A. R. Williamson

2014-09-29

317

Prospects for joint gravitational wave and short gamma-ray burst observations  

E-print Network

We present a detailed evaluation of the expected rate of joint gravitational-wave and short gamma-ray burst (GRB) observations over the coming years. We begin by evaluating the improvement in distance sensitivity of the gravitational wave 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 doubling the number of detectable gravitational wave 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 gravitational wave detector network. We show that in the early advanced gravitational wave detector observing runs, from 2015-2017, 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...

Clark, J; Fairhurst, S; Harry, I W; Macdonald, E; Macleod, D; Sutton, P J; Williamson, A R

2014-01-01

318

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

NASA Astrophysics Data System (ADS)

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.

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

2014-05-01

319

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

NASA Astrophysics Data System (ADS)

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.

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

2010-12-01

320

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

NASA Astrophysics Data System (ADS)

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.

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

2014-06-01

321

Formation of two-section cross-shore profile under joint influence of random short waves and groups of long waves  

Microsoft Academic Search

We show that beach profiles may develop a two-section almost-equilibrium structure under joint impact of short wind waves and groups of long waves with duration of a few minutes and properties that are independent of wind waves. The upper section of the profile is convex and follows the power law h~x4\\/3 at small depths and in the swash zone. Wind

Ira Didenkulova; Tarmo Soomere

2011-01-01

322

Five-channel surface-normal wavelength-division demultiplexer using substrate-guided waves in conjunction with a polymer-based Littrow hologram  

NASA Astrophysics Data System (ADS)

We report on a five-channel wavelength-division demultiplexer using substrate-guided waves in conjunction with a polymer-based Littrow hologram operating at 700, 710, 720, 730, and 740 nm. An average cross talk of -40 dB between adjacent channels is measured. Diffraction efficiencies of 69%, 78%, 83%, 77%, and 69% are both experimentally and theoretically confirmed for the five-channel device. We also present further study aimed at reducing the wavelength channel separation to 1 nm and find that achieving such a goal requires a device length of 6.4 cm corresponding to a propagation distance of 9.05 cm.

Li, Maggie M.; Chen, Ray T.

1995-04-01

323

Multi-physics investigation on the failure mechanism and short-time scale wave motion in flip-chip configuration  

E-print Network

employed to characterize the waves and the various failure modes associated with the moving of these short-lived dynamical disturbances in bulk materials and along interfaces. A qualitative measure for failure was also developed which enables the extent...

Oh, Yoonchan

2005-11-01

324

Jumping solitary waves in an autonomous reactiondiffusion system with subcritical wave instability  

E-print Network

Jumping solitary waves in an autonomous reaction­diffusion system with subcritical wave instability as solutions to a reaction­diffusion system with a subcritical short-wavelength instability. We demonstrate and standing waves. Traveling waves in reaction­diffusion systems, particularly the Belousov­Zhabotinsky (BZ

Epstein, Irving R.

325

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

PubMed

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

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

2013-04-20

326

Investigation of the effect of bilayer membrane structures and fluctuation amplitudes on SANS/SAXS profile for short membrane wavelength  

NASA Astrophysics Data System (ADS)

The effect of bilayer membrane structures and fluctuation amplitudes on small angle neutron scattering (SANS) and small angle X-ray scattering (SAXS) profile is investigated based on harmonic motions of the surfactant bilayers with bending as well as thickness fluctuation motions. In this study we consider the case in which the wavelength of the bilayer membrane is shorter than the thickness of the membrane. We find that the thickness of the surfactant bilayer membrane, dm, affects both qdip and qpeak of I(q,0) profile, and that the fluctuation amplitude, a, of the membrane changes the peak of I(q,0). A simple formula is derived to estimate the thickness of the bilayer based on the qdip of the profile obtained from the simulation. The resulting estimates of the thickness of the bilayer with harmonic motion showed accuracy within 1%. Moreover, the bilayer thicknesses estimated from the proposed formula show an excellent agreement with the SANS and SAXS experimental results available in the literatures. We also propose a curve fit model, which describes the relationship between the fluctuation amplitude and the normalized qpeak ratio. The present results show the feasibility of the simple formula to estimate the fluctuation amplitude based on the SANS and SAXS profiles.

Lee, Victor; Hawa, Takumi

2013-09-01

327

Investigation of the effect of bilayer membrane structures and fluctuation amplitudes on SANS/SAXS profile for short membrane wavelength  

SciTech Connect

The effect of bilayer membrane structures and fluctuation amplitudes on small angle neutron scattering (SANS) and small angle X-ray scattering (SAXS) profile is investigated based on harmonic motions of the surfactant bilayers with bending as well as thickness fluctuation motions. In this study we consider the case in which the wavelength of the bilayer membrane is shorter than the thickness of the membrane. We find that the thickness of the surfactant bilayer membrane, d{sub m}, affects both q{sub dip} and q{sub peak} of I(q,0) profile, and that the fluctuation amplitude, a, of the membrane changes the peak of I(q,0). A simple formula is derived to estimate the thickness of the bilayer based on the q{sub dip} of the profile obtained from the simulation. The resulting estimates of the thickness of the bilayer with harmonic motion showed accuracy within 1%. Moreover, the bilayer thicknesses estimated from the proposed formula show an excellent agreement with the SANS and SAXS experimental results available in the literatures. We also propose a curve fit model, which describes the relationship between the fluctuation amplitude and the normalized q{sub peak} ratio. The present results show the feasibility of the simple formula to estimate the fluctuation amplitude based on the SANS and SAXS profiles.

Lee, Victor; Hawa, Takumi [School of Aerospace and Mechanical Engineering, The University of Oklahoma, Norman, Oklahoma 73019 (United States)] [School of Aerospace and Mechanical Engineering, The University of Oklahoma, Norman, Oklahoma 73019 (United States)

2013-09-28

328

Physical enviroment of 2-D animal cell aggregates formed in a short pathlength ultrasound standing wave trap  

Microsoft Academic Search

2-D mammalian cell aggregates can be formed and levitated in a 1.5 MHz single half wavelength ultrasound standing wave trap. The physical environment of cells in such a trap has been examined. Attention was paid to parameters such as temperature, acoustic streaming, cavitation and intercellular forces. The extent to which these factors might be intrusive to a neural cell aggregate

Despina Bazou; Larisa A. Kuznetsova; W. Terence Coakley

2005-01-01

329

The gravitational wave signal of the short rise fling of galactic run away pulsars  

E-print Network

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 run away pulsars (RAPs) that were flung at very high speed and undergo large displacements, some gravitational-wave (GW) signals produced by such large accelerations appear to be detectable, after calibration against the Advanced LIGO (LII). Motivated by this insight, we address the pulsar kick at birth or {\\sl short rise fling} with the theory for phenomena of emission of GW with memory. We show that during the short rise fling each run away pulsar (RAP) should have generated a GW signal with characteristic amplitude and frequency potentially detectable by current GW interferometers. An efficiency parameter quantifies the use of the rise time kinetic energy, which is estimated from the linear momentum conservation law applied to the supernova explosion that flings th...

Cuesta, Herman J Mosquera

2007-01-01

330

Resonant interaction between a localized fast wave and a slow wave with constant asymptotic amplitude  

SciTech Connect

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.

Zabolotskii, A. A., E-mail: zabolotskii@iae.nsk.s [Russian Academy of Sciences, Institute of Automation and Electrometry, Siberian Branch (Russian Federation)

2009-11-15

331

Short period wave generation in Moss Landing Harbor caused by offshore landslides induced by the Loma Prieta earthquake  

SciTech Connect

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.

Gardner-Taggart, J.M.; Barminski, R.F. Jr. (Moss Landing Marine Lab., CA (United States))

1991-07-01

332

Miniature Fourier transform spectrometer based on wavelength dependence of half-wave voltage of a LiNbO? waveguide interferometer.  

PubMed

A simple and reliable spectrum-retrieval method was proposed for the development of miniature stationary Fourier transform (FT) spectrometers based on a LiNbO? (LN) waveguide Mach-Zehnder interferometer (MZI) modulator. The method takes into account the wavelength dependence of the optical pathlength difference (OPD) and allows us to use a nonlinear voltage ramp to modulate the OPD. The method is based on the dispersion of the half-wave voltage, which was measured to be a monotonous polynomial function of the wavelength for the LN waveguide MZI used. With the measured dispersion of the half-wave voltage, the OPD, as a linear function of the modulating voltage, can be accurately determined at each wavelength in the near-infrared region in which the MZI used is a single-mode device. A prototype FT spectrometer was prepared using a LN waveguide MZI modulator based on the above method. The experimental results demonstrated that the spectrometer can be used for accurate determination of the laser wavelength and for liquid absorptiometry. PMID:24978772

Li, Jinyang; Lu, Dan-feng; Qi, Zhi-mei

2014-07-01

333

Variety identification of brown sugar using short-wave near infrared spectroscopy and multivariate calibration  

NASA Astrophysics Data System (ADS)

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.

Yang, Haiqing; Wu, Di; He, Yong

2007-11-01

334

High color rendering index of remote-type white LEDs with multi-layered quantum dot-phosphor films and short-wavelength pass dichroic filters  

NASA Astrophysics Data System (ADS)

This paper introduces high color rendering index (CRI) white light-emitting diodes (W-LEDs) coated with red emitting (Sr,Ca)AlSiN3:Eu phosphors and yellowish-green emitting AgIn5S8/ZnS (AIS/ZS) quantum dots (QDs) on glass or a short-wavelength pass dichroic filter (SPDF), which transmit blue wavelength regions and reflect yellow wavelength regions. The red emitting (Sr,Ca)AlSiN3:Eu phosphor film is coated on glass and a SPDF using a screen printing method, and then the yellowish-green emitting AIS/ZS QDs are coated on the red phosphor (Sr,Ca)AlSiN3:Eu film-coated glass and SPDF using the electrospray (e-spray) method.To fabricate the red phosphor film, the optimum amount of phosphor is dispersed in a silicon binder to form a red phosphor paste. The AIS/ZS QDs are mixed with dimethylformamide (DMF), toluene, and poly(methyl methacrylate) (PMMA) for the e-spray coating. The substrates are spin-coated with poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) to fabricate a conductive surface. The CRI of the white LEDs is improved through inserting the red phosphor film between the QD layer and the glass substrate. Furthermore, the light intensities of the multi-layered phosphor films are enhanced through changing the glass substrate to the SPDF. The correlated color temperatures (CCTs) vary as a function of the phosphor concentration in the phosphor paste. The optical properties of the yellowish-green AIS/ZS QDs and red (Sr,Ca)AlSiN3:Eu phosphors are characterized using photoluminescence (PL), and the multi-layered QD-phosphor films are measured using electroluminescence (EL) with an InGaN blue LED (?max = 450 nm) at 60 mA.

Yoon, Hee Chang; Oh, Ji Hye; Do, Young Rag

2014-09-01

335

Geometrical measurement of cardiac wavelength in reaction-diffusion models.  

PubMed

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. PMID:25273213

Dupraz, Marie; Jacquemet, Vincent

2014-09-01

336

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)

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.

Blaney, D. L.

2002-01-01

337

Multiplexed adaptive two-wave mixing wavelength demodulation of fiber Bragg grating sensor for monitoring both dynamic and quasi-static drifts  

NASA Astrophysics Data System (ADS)

A multiplexed 4-channel version of two-wave mixing (TWM) wavelength demodulator using InP:Fe photorefractive crystal (PRC) in the C-band (1530-1570nm) is demonstrated. The system can be used as a wavelength demodulator for use with Fiber Bragg Grating (FBG) sensors to monitor both dynamic strains and quasi-static strains. In this configuration, the FBG is illuminated with a broadband source, and any strain in the FBG is encoded as a wavelength shift of the light reflected by the FBG. The reflected light from the FBG is spilt into two unbalanced paths and both beams (pump and signal) mix in the PRC. Any wavelength shift of the reflected light results in an equivalent phase shift between the pump and signal beams as they travel unbalanced path lengths. Since TWM is an adaptive process, the two interfering beams are naturally in quadrature and remain in quadrature even in the presence of large quasi-static strains. In this paper, the demonstrated 4-channel TWM wavelength demodulator is able to demodulate dynamic strains from four FBG sensors simultaneously in the presence of quasi-static drifts. And with the aid of a spectrum analyzer, the quasi-static shifts caused by static strains or temperature changes are obtained by monitoring the spectral shift of the transmitted light through the FBG sensors.

Qiao, Yi; Krishnaswamy, Sridhar

2006-03-01

338

Assessment of viscous and elastic properties of sub-wavelength layered soft tissues using shear wave spectroscopy: theoretical framework and in vitro experimental validation.  

PubMed

In elastography, quantitative imaging of soft tissue elastic properties is provided by local shear wave speed estimation. Shear wave imaging in a homogeneous medium thicker than the shear wavelength is eased by a simple relationship between shear wave speed and local shear modulus. In thin layered organs, the shear wave is guided and thus undergoes dispersive effects. This case is encountered in medical applications such as elastography of skin layers, corneas, or arterial walls. In this work, we proposed and validated shear wave spectroscopy as a method for elastic modulus quantification in such layered tissues. Shear wave dispersion curves in thin layers were obtained by finite-difference simulations and numerical solving of the boundary conditions. In addition, an analytical approximation of the dispersion equation was derived from the leaky Lamb wave theory. In vitro dispersion curves obtained from phantoms were consistent with numerical studies (deviation <1.4%). The least-mean-squares fitting of the dispersion curves enables a quantitative and accurate (error < 5% of the transverse speed) assessment of the elasticity. Dispersion curves were also found to be poorly influenced by shear viscosity. This phenomenon allows independent recovery of the shear modulus and the viscosity, using, respectively, the dispersion curve and the attenuation estimation along the propagation axis. PMID:22083764

Nguyen, Thu-Mai; Couade, Mathieu; Bercoff, Jeremy; Tanter, Mickael

2011-11-01

339

Comparative proteome analysis of Penicillium verrucosum grown under light of short wavelength shows an induction of stress-related proteins associated with modified mycotoxin biosynthesis.  

PubMed

In this study the differentially expressed protein population of Penicillium verrucosum grown either in the dark or under light with a wavelength of 450nm has been analyzed. Light of short wavelength led to oxidative stress in the fungal cell; under this condition the mycotoxin biosynthesis revealed a mutual shift from ochratoxin A to citrinin. Using a proteomic approach combining an optimized protein extraction method with 2-dimensional SDS-PAGE followed by HPLC-ESI-TOF-MS/MS mass spectrometric analysis, initially 56 significantly differential proteins (light vs. dark) were detected comprising proteins of a broad range of isoelectric points and molecular masses. In total, 46 proteins could be identified further by database query, most of these proteins are assumed to be involved in response to stress (e.g. antioxidative proteins, heat shock proteins) and general metabolic processes (e.g. glycolysis, ATP supply). Proteome analyses are necessary to unravel the regulation of secondary metabolite biosynthesis at a translational level. This may enable identification of proteins which are involved in mycotoxin biosynthesis, adaption processes or even stress compensation mechanisms. This study depicts the first proteome analysis of P. verrucosum. PMID:24508532

Stoll, Dominic A; Link, Sebastian; Kulling, Sabine; Geisen, Rolf; Schmidt-Heydt, Markus

2014-04-01

340

Short Wavelength Electromagnetic Perturbations Excited Near the Solar Probe Plus Spacecraft in the Inner Heliosphere: 2.5D Hybrid Modeling  

NASA Technical Reports Server (NTRS)

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.

Lipatov, Alexander S.; Sittler, Edward C.; Hartle, Richard E.; Cooper, John F.

2011-01-01

341

The effect of a UV preionization pulse on short-wave radiation output from a laser-produced-plasma source with a Xe gas-jet target  

NASA Astrophysics Data System (ADS)

Experiments aimed to raise the emissivity of a laser-produced plasma source with a Xe gas target in the far-UV spectral range are described. In these experiments, the main pulse of the IR Nd:YAG laser was preceded by a pre-ionization pulse of a UV KrF excimer laser. The consequences of applying the prepulse and its influence on the short-wavelength emission intensity were traced up to main-pulse delays of about 5 ?s with respect to the prepulse. It is supposed that the main mechanism by which the prepulse affects the evolution of the plasma and its emission intensity is related to the density waves excited in the gas target by this pulse.

Zabrodskii, V. V.; Zadiranov, Yu. M.; Kalmykov, S. G.; Mozharov, A. M.; Petrenko, M. V.; Sasin, M. E.; Seisyan, R. P.

2014-08-01

342

Exoplanet atmospheres Characterization Observatory payload short-wave infrared channel: EChO SWiR  

NASA Astrophysics Data System (ADS)

EChO (Exoplanet atmospheres Characterization Observatory), a proposal for exoplanets exploration space mission, is considered the next step for planetary atmospheres characterization. It would be a dedicated observatory to uncover a large selected sample of planets spanning a wide range of masses (from gas giants to super-Earths) and orbital temperatures (from hot to habitable). All targets move around stars of spectral types F, G, K, and M. EChO would provide an unprecedented view of the atmospheres of planets in the solar neighbourhood. The consortium formed by various institutions of different countries proposed as ESA M3 an integrated spectrometer payload for EChO covering the wavelength interval 0.4 to 16 µm. This instrument is subdivided into 4 channels: a visible channel, which includes a fine guidance system (FGS) and a VIS spectrometer, a near infrared channel (SWiR), a middle infrared channel (MWiR), and a long wave infrared module (LWiR). In addition, it contains a common set of optics spectrally dividing the wavelength coverage and injecting the combined light of parent stars and their exoplanets into the different channels. The proposed payload meets all of the key performance requirements detailed in the ESA call for proposals as well as all scientific goals. EChO payload is based on different spectrometers covering the spectral range mentioned above. Among them, SWiR spectrometer would work from 2.45 microns to 5.45 microns. In this paper, the optical and mechanical designs of the SWiR channel instrument are reported on.

Ramos Zapata, Gonzalo; Belenguer, Tomás.; Balado, Ana; Encinas, José M.; Armendáriz, Iñaki; Carretero, Ángel; Arza, César; Alcacera, María. Á.; Fernández, José A.; Muñoz, Elisa; Tinetti, Giovanna; Eccleston, Paul; Swinyard, Bruce; Middleton, Kevin; Bryson, Ian; Zapatero, María. Rosa

2014-08-01

343

Short-term wave forecasting with AR models in real-time optimal control of wave energy converters  

Microsoft Academic Search

Time domain control of wave energy converters requires knowledge of future incident wave elevation in order to approach conditions for optimal energy extraction. Autoregressive models revealed to be a promising approach to the prediction of future values of the wave elevation only from its past history. Results on real wave observations from different ocean locations show that AR models allow

Francesco Fusco; John V. Ringwood

2010-01-01

344

Parametric interaction and spatial collapse of beam-driven Langmuir waves in the solar wind  

Microsoft Academic Search

This paper presents observations of the parametric decay and spatial collapse of Langmuir waves driven by an electron beam streaming into the solar wind from the Jovian bow shock. High-resolution frequency-time spectrograms from Voyager 1 and 2 show that long wavelength Langmuir waves upstream of the bow shock are very effectively converted into short wavelength Langmuir waves which are no

D. A. Gurnett; J. E. Maggs; D. L. Gallagher; W. S. Kurth; F. L. Scarf

1981-01-01

345

Parametric interaction and spatial collapse of beam-driven Langmuir waves in the solar wind  

Microsoft Academic Search

Observations are presented of the parametric decay and spatial collapse of Langmuir waves driven by an electron beam streaming into the solar wind from the Jovian bow shock. Long wavelength Langmuir waves upstream of the bow shock are effectively converted into short wavelength waves no longer in resonance with the beam. The conversion is shown to be the result of

D. A. Gurnett; J. E. Maggs; D. L. Gallagher; W. S. Kurth; F. L. Scarf

1981-01-01

346

Effects of lateral velocity heterogeneity under the Nevada Test Site on short-period P wave amplitudes and travel times  

NASA Astrophysics Data System (ADS)

Short-period teleseismic P waves from the Nevada Test Site (NTS) show systematic variations in amplitudes and travel times, with low amplitudes corresponding to fast travel times, suggesting elastic focussing-defocussing effects. Also, the azimuthal amplitude and travel time patterns for events at the Pahute Mesa subsite are systematically different from those at the Yucca Flat subsite, indicating the presence of a near-source component in both the amplitude and travel-time variations. This component is isolated by removing the mean station pattern for all of NTS from the observations. A very-near-source component in the Pahute Mesa observations is also isolated by removing subsite station means from the measurements, whereas the Yucca Flat observations exhibited no coherent very-near-source component. These anomalies are back-projected through laterally homogeneous structure to form thin lens models at various depths. Travel-time delays are predicted from the amplitude variations using the equation for wavefront curvature. The long-wavelength components of the predicted and observed time delays correlate well, at depths of 25 km for the very-near-source component under Pahute Mesa and 160 km for the regional component under NTS. The time delay surfaces predicted by the amplitudes at these depths are mapped into warped velocity discontinuities suitable for the calculation of synthetic seismograms using the Kirchhoff-Helmholtz integral formulation. Both the intersite (near-source) and intrasite (very-near-source) differences in amplitudes are qualitatively predicted very well, although the range of variation is somewhat underpredicted. This deficiency is likely due to the destructive interference of anomalies inherent in back-projection to a single layer.

Lynnes, Christopher S.; Lay, Thorne

1990-03-01

347

Collective atomic recoil motion in short-pulse matter-wave superradiance  

SciTech Connect

We show that a Bragg resonance is substantially incapacitated in short-pulse, matter-wave superradiant scatterings and both positive- and negative-order scatterings contribute equally. We further show that propagation gain is small and scattering events primarily occur at the ends of the condensate where the generated field has maximum strength. This explains the apparent 'asymmetry' in the scattered components with respect to the condensate center. In contrast to long-pulse excitation, we prove that the generated field travels near the speed of light in vacuum and show that this has a significant impact on scattering. Finally, we show that when the excitation rate increases, the front-edge steepening and forward shifting of the peak of the generated field are due to depletion of the condensate.

Deng, L. [Physics Laboratory, National Institute of Standards and Technology, Gaithersburg, Maryland 20899 (United States); Center for Cold Atom Physics, Wuhan Institute of Physics and Mathematics, Chinese Academy of Science, Wuhan 430071 (China); Hagley, E. W. [Physics Laboratory, National Institute of Standards and Technology, Gaithersburg, Maryland 20899 (United States)

2010-11-15

348

Resonant excitation of coupled Rayleigh waves in a short and narrow fluid channel clad between two identical metal plates  

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.

García-Chocano, Victor M. [Universitat Polit#18;ecnica de Val#18;encia (Spain); López-Rios, Tomás [CNRS and University Joseph Fourier, Grenoble (France); Krokhin, Arkadii [Universitat Polit#18;ecnica de Val#18;encia (Spain) and University of North Texas, Denton, TX (United States); Sanchez-Dehesa, Jose [Universitat Polit#18;ecnica de Val#18;encia (Spain)

2011-12-23

349

QPSK-to-2×BPSK wavelength and modulation format conversion through phase-sensitive four-wave mixing in a highly nonlinear optical fiber.  

PubMed

A phase-sensitive four-wave mixing (FWM) scheme enabling the simultaneous conversion of the two orthogonal quadratures of an optical signal to different wavelengths is demonstrated for the first time under dynamic operation using a highly nonlinear optical fiber (HNLF) as the nonlinear medium. The scheme is first optimized with respect to the power levels and phases of the four phase-coherent pumps. The successful modulation and wavelength conversion of the two complex quadratures of a quadrature phase-shift keying (QPSK) signal to two binary phase-shift keying (BPSK) signals is then demonstrated experimentally with no power penalty at a bit-error-ratio (BER) of 10(-9) compared to direct interferometric demodulation of the QPSK signal. PMID:24514386

Da Ros, Francesco; Dalgaard, Kjeld; Lei, Lei; Xu, Jing; Peucheret, Christophe

2013-11-18

350

A New Charge Transporting Host Material for Short Wavelength Organic Electrophosphorescence: 2,7–Bis(diphenylphosphine oxide)–9,9–dimethylfluorene  

SciTech Connect

We report the synthesis, crystal structure, photophysical and electroluminescent properties of a new charge transporting host material for short wavelength phosphor-doped organic light emitting devices (OLEDs) based on 2,7-bis(diphenylphosphine oxide)-9,9-dimethylfluorene (PO6). The P=O moiety is used as a point of saturation between the fluorene bridge and outer phenyl groups so that the triplet exciton energy of PO6 is 2.72 eV, similar to that of a dibromo substituted fluorene, but it is more amenable to vacuum sublimation and has good film forming properties. Computational analysis (B3LYP/6-31G*) predicts the HOMO and LUMO energies of PO6 to be lower by 1.5 eV and 0.59 eV, respectively, compared to a similar diphenylamino substituted derivative. In a simple bilayer OLED device, PO6 exhibits structured UV electroluminescence (EL) at a peak wavelength of 335 nm and structured lower energy emission with peaks at 380 nm and 397 nm, similar to the solid film and crystalline solid photoluminescence spectra. The longer wavelength peaks are attributed to aggregate formation via strong intermolecular interactions (P-O---H-C and edge-to-face C-H---??contacts?) and longer range electrostatic interactions between P=O moieties leading to ordered regions in the film. Devices incorporating PO6 as the host material doped with iridium(III)bis(4,6-(di-fluorophenyl)-pyridinato-N,C2.)picolinate (FIrpic) exhibited sky blue emission with peak external quantum efficiency (?ext,max) of 8.1 % and luminous power efficiency (?p,max) of 25.3 lm/W. At a brightness of 800 cd/m2, generally considered to be sufficient for lighting applications, the ?ext and ?p are 6.7 % and 11.8 lm/W and the operating voltage is 5.6 V, which is significantly lower than has been demonstrated previously using this dopant.

Padmaperuma, Asanga B.; Sapochak, Linda S.; Burrows, Paul E.

2006-05-01

351

Coincidence searches of gravitational waves and short gamma-ray bursts  

E-print Network

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.

Andrea Maselli; Valeria Ferrari

2014-05-28

352

Inversion of Source Parameters for Moderate Earthquakes Using Short-Period Teleseismic P Waves  

NASA Astrophysics Data System (ADS)

In this paper, we introduce a new method for estimating the source parameters of moderate earthquakes ( M w ~5.0) by modeling short-period teleseismic waveforms. This method uses a grid-search algorithm to minimize misfits between observed data and synthetic seismograms in depth, magnitude, and mechanism domain in a relative high-frequency range of 0.8-2.0 Hz, similar to the traditional cut-and-paste method used in regional modeling ( Zhu and Helmberger, Bull Sesimol Soc Am 86:1634-1641, 1996). In this frequency range, a significant challenge is determining the initial P-wave polarity because of a low signal-to-noise ratio (SNR). Therefore we first determine source properties for a master earthquake with a relative strong SNR. Both the travel time and amplitude corrections are developed relative to the reference 1D model along each path used in inverting the master event. We then applied these corrections to other earthquakes clustered in the same area to constrain the initial P polarities. Thus the focal mechanisms can be determined reasonably well. We inverted focal mechanisms for a small set of events beneath Qeshm Island in southern Iran and demonstrate the importance of radiation pattern at short periods.

Chu, Risheng; Ni, Sidao; Pitarka, Arben; Helmberger, Don V.

2014-07-01

353

The gravitational wave signal of the short rise fling of galactic run away pulsars  

E-print Network

Determination of pulsar parallaxes and proper motions addresses fundamental astrophysical open issues. Here, the ATNF Catalog is scrutinized searching for pulsar distances and proper motions. For a sample of 212 run away 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. We show that during the short rise fling each run away 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 to spin. Thus, a comparison with the spin of ATNF pulsars having velocity in the interval 400-500 km s$^{-1}$ is performed. The resulting difference suggests that other mechanisms 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. Thus pulsar astrometry from micro- to nano-arsec scales might be of much help. In case of a supernova, the RAP GW signal could be a benchmark for the GW signal from the core collapse.

Herman J. Mosquera Cuesta; Carlos A. Bonilla Quintero

2007-11-20

354

Wave properties of light Light is energy whose wavelength is the distance traveled in order to complete one cycle.  

E-print Network

to complete one cycle. The frequency of light refers to the number of cycles in one second. Low-energy light a small portion of the light encountered in every day life. Low energy radio, TV, and microwave signals The light emitted by a lightbulb or a star is formed from a continuum of different wavelengths. But how

Zworski, Maciej

355

Search for Gravitational-wave Inspiral Signals Associated with Short Gamma-ray Bursts During Ligo’s Fifth and Virgo’s First Science Run  

E-print Network

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. ...

Barsotti, Lisa

356

Effect of electron-cyclotron resonance heating conditions on the local parameters of short-wavelength plasma turbulence in the L-2M stellarator  

NASA Astrophysics Data System (ADS)

Changes in the energy spectra of short-wavelength ( k s ? 35 cm-1) plasma density fluctuations in the local region of the plasma column ( r/ a = 0.5-0.6) of the L-2M stellarator were studied by the method of collective scattering of 150-GHz radiation. The plasma was heated at the second harmonic of the electron gyrofrequency, the microwave heating power being in the range of 90-170 kW. A sector limiter was introduced in the peripheral plasma ( r/a ? 0.8), and the Shafranov shift of the magnetic axis was varied by varying the vertical magnetic field. The results of measurements were averaged over 9-16 discharges. It is found that an increase in the heating power and/or the introduction of the sector limiter in the plasma lead to an increase in the energy of density fluctuations, which correlates with a decrease in the plasma energy lifetime. In the spectra of fluctuations, a broad spectral band in the range of 3-50 kHz was observed in which the spectral density was one order of magnitude higher than in the rest of the spectrum. Analysis of the Fourier spectra showed that the introduction of the sector limiter in the plasma resulted in an increase in both the spectral density of fluctuations in the range of 3-50 kHz and the fraction of quasi-coherent structures in turbulent density fluctuations.

Batanov, G. M.; Borzosekov, V. D.; Kolik, L. V.; Malakhov, D. V.; Petrov, A. E.; Pshenichnikov, A. A.; Sarksyan, K. A.; Skvortsova, N. N.; Kharchev, N. K.

2014-04-01

357

Gravitational wave signal of the short rise fling of galactic runaway pulsars  

SciTech Connect

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.

Mosquera Cuesta, Herman J; Bonilla Quintero, Carlos A, E-mail: hermanjc@cbpf.br, E-mail: gravitaxion@gmail.com [Instituto de Cosmologia, Relatividade e Astrofisica (ICRA-BR), Centro Brasileiro de Pesquisas Fisicas, Rua Dr Xavier Sigaud 150, CEP 22290-180, Urca, Rio de Janeiro, RJ (Brazil)

2008-11-15

358

Gravitational wave signal of the short rise fling of galactic runaway pulsars  

NASA Astrophysics Data System (ADS)

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 ?~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.

Mosquera Cuesta, Herman J.; Bonilla Quintero, Carlos A.

2008-11-01

359

Feasibility Study of Using Short Wave Infrared Cavity Ringdown Spectroscopy (SWIR-CRDS) for Biological Agent Detection  

Microsoft Academic Search

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

Pam M. Aker; Timothy J. Johnson; Richard M. Williams; Nancy B. Valentine

2007-01-01

360

A novel radio over fiber system with DWDM mm-wave generation and wavelength reuse for upstream data connection.  

PubMed

We proposed and experimentally demonstrated a novel radio-over-fiber architecture using an electrical mixer and an optical intensity modulator based on double side-band modulation scheme to generate dense wavelength-division multiplexing (DWDM) optical millimeter for carrying downstream data and centralized lightwave for carrying upstream data. Since the remaining optical carriers with high power have been reused, the optical power is effectively utilized; therefore the system cost can be reduced. PMID:19532849

Chen, Lin; Lei, Xiaoyan; Wen, Shuangchun; Yu, Jianguo

2007-04-30

361

Black Hole Spin Evolution: Implications for Short-hard Gamma Ray Bursts and Gravitational Wave Detection  

E-print Network

The evolution of the spin and tilt of black holes in compact black hole - neutron star and black hole - black hole binary systems is investigated within the framework of the coalescing compact star binary model for short gamma ray bursts via the population synthesis method. Based on recent results on accretion at super critical rates in slim disk models, estimates of natal kicks, and the results regarding fallback in supernova models, we obtain the black hole spin and misalignment. It is found that the spin parameter, a_spin}, is less than 0.5 for initially non rotating black holes and the tilt angle, i_tilt, is less than 45 deg for 50% of the systems in black hole - neutron star binaries. Upon comparison with the results of black hole - neutron star merger calculations we estimate that only a small fraction (~ 0.01) of these systems can lead to the formation of a torus surrounding the coalesced binary potentially producing a short-hard gamma ray burst. On the other hand, for high initial black hole spin parameters (a_spin>0.6) this fraction can be significant (~ 0.4). It is found that the predicted gravitational radiation signal for our simulated population does not significantly differ from that for non rotating black holes. Due to the (i) insensitivity of signal detection techniques to the black hole spin and the (ii) predicted overall low contribution of black hole binaries to the signal we find that the detection of gravitational waves are not greatly inhibited by current searches with non spinning templates. It is pointed out that the detection of a black hole - black hole binary inspiral system with LIGO or VIRGO may provide a direct measurement of the initial spin of a black hole.

Krzysztof Belczynski; Ronald E. Taam; Emmanouela Rantsiou; Marc van der Sluys

2007-03-06

362

Traveling wave pumping of ultra-short pulse x-ray lasers  

SciTech Connect

Pumping of proposed inner-shell photo-ionized (ISPI) x-ray lasers places stringent requirements on the optical pump source. We investigate these requirements for an example x-ray laser (XRL) in Carbon lasing on the 2p-1s transition at 45 A. Competing with this lasing transition is the very fast Auger decay rate out of the upper lasing state, such that the x-ray laser would self-terminate on a femto- second time scale. XRL gain may be demonstrated if pump energy is delivered in a time short when compared to the Auger rate. The fast self-termination also demands that we sequentially pump the length of the x-ray laser at the group velocity of the x-ray laser. This is the classical traveling wave requirement. It imposes a condition on the pumping source that the phase angle of the pump laser be precisely de- coupled from the pulse front angle. At high light intensities, this must be performed with a vacuum grating delay line. We will also include a discussion of issues related to pump energy delivery, i.e. pulse-front curvature, temporal blurring and puke fidelity. An all- reflective optical system with low aberration is investigated to see if it fulfills the requirements. It is expected that these designs together with new high energy (>1J) ultra-short pulse (< 40 fs) pump lasers now under construction may fulfill our pump energy conditions and produce a tabletop x-ray laser.

Snavely, R.A.; Da Silva, L.B.; Eder, D.C.; Matthews, D.L.; Moon, S.J.

1997-11-10

363

High Harmonic Fast Wave Heating Efficiency Enhancemen and Current Drive at Longer Wavelength on the National Spherical Torus Experiment  

SciTech Connect

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 (?) from 44% to 65% has been obtained for CD phasing of the antenna (strap-to-strap ? = -90o, k? = -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 ? ??× 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 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

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

364

High Harmonic Fast Wave Heating Efficiency Enhancement and Current Drive at Longer Wavelength on the National Spherical Torus Experiment  

SciTech Connect

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.

Hosea, J. [Princeton Plasma Physics Laboratory (PPPL); Bell, R. E. [Princeton Plasma Physics Laboratory (PPPL); LeBlanc, B [Princeton Plasma Physics Laboratory (PPPL); Phillips, Cynthia [Princeton Plasma Physics Laboratory (PPPL); Taylor, G. [Princeton Plasma Physics Laboratory (PPPL); Valeo, Dr Ernest [Princeton Plasma Physics Laboratory (PPPL); Wilson, J. R. [Princeton Plasma Physics Laboratory (PPPL); Jaeger, Erwin Frederick [ORNL; Ryan, Philip Michael [ORNL; Wilgen, John B [ORNL; Yuh, H. [Nova Photonics; Levinton, F. [Fusion Physics and Technology; Sabbagh, S. A. [Columbia University; Tritz, K. [Johns Hopkins University; Parker, J. [Cornell University; Bonoli, P. [Massachusetts Institute of Technology (MIT); Harvey, R. W. [CompX, Del Mar, CA

2008-01-01

365

Characterization results of the TROPOMI Short Wave InfraRed detector  

NASA Astrophysics Data System (ADS)

The TROPOMI Earth-observing instrument is the single payload on board ESA's Sentinel-5 Precursor mission. It is the successor of the Sciamachy instrument (ESA ENVISAT) and the OMI instrument (NASA EOS/Aura), and combines and improves the best of both instruments. TROPOMI copies the push broom observation geometry of OMI allowing for daily global coverage due to its instantaneous field of view of 108 degrees, or 2600 km swath on ground. From Sciamachy the 2305 - 2385 nm Short-Wave Infra-Red (SWIR) observational band is copied with which methane and carbon monoxide are observed. This paper reports on the development of the SWIR detector module and the detailed characterization of the 1000x256 SWIR Saturn detector array produced by Sofradir (F) as measured with the SRON-developed Front-End Electronics. The detailed characterization comprises not only the regular properties such as dark current, noise and photo-response, but also more complex characteristics including non-linearity and memory. Characterization of the detection module was performed for all operational parameters: detector temperature (135 - 145 K), bias voltage and integration time. Thanks to the detector-characterization program, the operational clocking of the detector could be optimized, resulting in significantly improved performance.

Hoogeveen, R. W. M.; Voors, R.; Robbins, M. S.; Tol, P. J. J.; Ivanov, T. I.

2013-10-01

366

Coincidence searches of gravitational waves and short gamma-ray bursts  

E-print Network

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 shor...

Maselli, Andrea

2014-01-01

367

Exploring short gamma-ray bursts as gravitational-wave standard sirens  

E-print Network

Recent observations support the hypothesis that a large fraction of "short-hard" gamma-ray bursts (SHBs) are associated with compact binary inspiral. 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 independently determine both its luminosity distance and redshift. Such a "standard siren" (the GW analog of a standard candle) would provide an excellent probe of the relatively nearby universe's expansion, complementing other standard candles. In this paper, we examine binary measurement using a Markov Chain Monte Carlo technique to build the probability distributions describing measured parameters. We assume that each SHB observation gives both sky position and the time of coalescence, and we take both binary neutron stars 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. (Abridged)

Samaya Nissanke; Daniel E. Holz; Scott A. Hughes; Neal Dalal; Jonathan L. Sievers

2009-04-07

368

Integrating visible, near infrared and short wave infrared hyperspectral and multispectral thermal imagery for geological mapping at Cuprite, Nevada  

NASA Astrophysics Data System (ADS)

Visible, near infrared (VNIR), and short wave infrared (SWIR) hyperspectral and thermal infrared (TIR) multispectral remote sensing have become potential tool for geological mapping. In this dissertation, a series of studies were carried out to investigate the potential impact of combining VNIR/SWIR hyperspectral and TIR multispectral data for surface geological mapping. First, a series of simulated data sets based on the characteristics of hyperspectral AVIRIS and multispectral TIR MASTER sensors was created from surface reflectance and emissivity library spectra. Five common used classification methods including minimum distance, maximum likelihood, spectral angle mapper (SAM), spectral feature fitting (SFF), and binary encoding were applied to these simulated data sets to test the hypothesis. It was found that most methods applied to the combined data actually obtained improvement in overall accuracy of classification by comparison of the results to the simulated AVIRIS data or TIR MASTER alone. And some minerals and rocks with strong spectral features got a marked increase in classification accuracy. Second, two real data sets such as AVIRIS and MASTER of Cuprite, Nevada were used. Four classification methods were each applied to AVIRIS, MASTER, and a combined set. The results of these classifications confirmed most findings from the simulated data analyses. Most silicate bearing rocks achieved great improvement in classification accuracy with the combined data. SFF applied to the combination of AVIRIS with MASTER TIR data are especially valuable for identification of silicified alteration and quartzite sandstone which exhibit strong distinctive absorption features in the TIR region. SAM showed some advantages over SFF in dealing with multiple broad band TIR data, obtaining higher accuracy in discriminating low albedo volcanic rocks and limestone which do not have strong characteristic absorption features in the TIR region. One of the main objectives of these studies is to develop an automated classification algorithm which is effective for the analysis of VNIR/SWIR hyperspectral and TIR multispectral data. A rule based system was constructed to draw the strengths of disparate wavelength regions and different algorithms for geological mapping.

Chen, Xianfeng

369

Momentum and Energy Transport by Gravity Waves in Stochastically Driven Stratified Flows. Part II: Radiation of Gravity Waves from a Gaussian Jet  

Microsoft Academic Search

Interaction between the midlatitude jet and gravity waves is examined, focusing on the nonnormality of the underlying linear dynamics, which plays an essential role in processing the wave activity and selecting structures that dominate wave momentum and energy transport. When the interior of a typical midlatitude jet is stochastically forced, waves with short horizontal wavelength are trapped inside the jet

Nikolaos A. Bakas; Brian F. Farrell

2008-01-01

370

Generation of shock waves and formation of craters in a solid material irradiated by a short laser pulse  

SciTech Connect

The results of investigations are presented which are concerned with laser radiation absorption in a target, the plasma state of its ablated material, the energy transfer to the solid target material, the characteristics of the shock wave and craters on the target surface. The investigation involved irradiation of a planar target by a subnanosecond plasma-producing laser pulse. The experiments were carried out with massive aluminium targets using the PALS iodine laser, whose pulse duration (0.4 ns) was much shorter than the shock wave attenuation and on-target crater formation times (50-200 ns). The investigations were conducted for a laser radiation energy of 100 J at two wavelengths of 0.438 and 1.315 {mu}m. For a given pulse energy, the irradiation intensity was varied in a broad range (10{sup 13}-10{sup 16} W cm{sup -2}) by varying the radius of the laser beam. The efficiency of laser radiation-to-shock energy transfer was determined as a function of the intensity and wavelength of laser radiation; also determined were the characteristics of the plasma plume and the shock wave propagating in the solid target, including the experimental conditions under which two-dimensional effects are highly significant. (invited paper)

Gus'kov, Sergei Yu [P.N. Lebedev Physics Institute, Russian Academy of Sciences, Moscow (Russian Federation); Borodziuk, S; Kasperczuk, A; Pisarczyk, T [Institute of Plasma Physics and Laser Microfusion, Warsaw (Poland); Kalal, M; Limpouch, J [Czech Technical University, Prague (Czech Republic); Kralikova, B; Krousky, E; Masek, K; Pfeifer, M; Rohlena, K; Skala, J; Ullschmied, J [PALS Research Center, Acad. Sci. CR, Prague (Czech Republic); Pisarczyk, P [Warsaw University of Technology, Warsaw (Poland)

2004-11-30

371

Modulation of centimetric waves by long gravity waves - Progress report on field and laboratory results  

NASA Technical Reports Server (NTRS)

Results are presented from laboratory and field experiments on the modulation of short waves by long waves. The field study employed a wave follower capable of tracking ocean waves with frequencies less than 1.0 Hz and heights less than 2.0 m. A high-response laser-optical system was used to detect upwind-downwind and cross-wind slopes of short waves. The laboratory study was conducted with wind over periodic long waves. The laboratory findings are discussed and compared with laboratory radar measurements and also short wave measurements obtained in the field. It is found that long waves significantly modulate the short wave dispersion by their orbital velocity, and that demodulation is necessary if the data collected by remote sensors are to be compared to surface penetrating devices. The modulation level is weak for wavelengths in the range 2.76-3.30 cm. Other relevant results are also presented.

Shemdin, O. H.

1978-01-01

372

Short time scale thermal mechanical shock wave propagation in high performance microelectronic packaging configuration  

E-print Network

predict vastly different results in the vicinity of the heat source but that the differences diminish within a larger time window. Results from both theories indicate that the rapid thermal-mechanical waves cause high frequency, broadband stress waves...

Nagaraj, Mahavir

2004-11-15

373

Wavelength and Energy  

NSDL National Science Digital Library

This is an activity about wavelength and frequency. Using a 30 to 50 foot rope and two volunteers, learners will observe as one end of the rope is shaken and wavelength patterns are created. They will estimate the wavelength, the distance between two similar points of a wave, such as peak-to-peak, and the frequency of the waves, the number of waves reaching the far end of the rope per second. Through group discussion afterwards, this information is then related electromagnetic spectrum. This activity requires a long length of rope and a large enough space for the entire group to see the whole rope at once. This activity is from the Stanford Solar Center's All About the Sun: Sun and Stars activity guide for Grades 5-8 and can also accompany the Stanford Solar Center's Build Your Own Spectroscope activity.

374

Mid-frequency sound propagation through internal waves at short range with  

E-print Network

wave passes above the acoustic source. © 2008 Acoustical Society of America PACS numbers: 43.30.Ft, 43 In shallow water, there is extensive ongoing research into the impact of nonlinear internal waves on low- and strong-scattering theories for random media would apply.5 Nonlinear internal waves are often modeled

375

EXPLORING SHORT GAMMA-RAY BURSTS AS GRAVITATIONAL-WAVE STANDARD SIRENS  

SciTech Connect

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.

Nissanke, Samaya; Dalal, Neal; Sievers, Jonathan L. [CITA, University of Toronto, 60 St. George St., Toronto, ON M5S 3H8 (Canada); Holz, Daniel E. [Theoretical Division, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Hughes, Scott A. [Department of Physics and MIT Kavli Institute, 77 Massachusetts Avenue, Cambridge, MA 02139 (United States)

2010-12-10

376

OPERATIONAL NEAR REAL-TIME DERIVATION OF LAND SURFACE ALBEDO AND DOWNWELLING SHORT-WAVE RADIATION FROM MSG OBSERVATIONS  

Microsoft Academic Search

In the framework of the EUMETSAT Satellite Applica- tion Facility for Land Surface Analysis (Land-SAF) we develop surface albedo and short-wave radiation products which will be generated in near real-time from observa- tions provided by the MSG\\/SEVIRI instrument. The albedo algorithm exploits the diurnal variation of the illumination angle, which provides information on the angular variation of reflectance, in order

Bernhard Geiger; Laurent Franchist; Dulce Lajas; Jean-Louis Roujean

2004-01-01

377

Exploring binary-neutron-star-merger scenario of short-gamma-ray bursts by gravitational-wave observation  

E-print Network

We elucidate the feature of gravitational waves (GWs) from 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.

Kenta Kiuchi; Yuichiro Sekiguchi; Masaru Shibata; Keisuke Taniguchi

2010-02-13

378

Nonlinear excitation of short scale turbulence in solar corona by kinetic Alfven waves  

SciTech Connect

The model equations for the nonlinear interaction between kinetic Alfven waves and ion acoustic waves in the intermediate-{beta} (thermal to background magnetic pressure ratio) plasmas are presented. The nonlinear dynamical equations satisfy the modified Zakharov system of equations by taking the nonadiabatic response of the background density. Numerical solution has been obtained to study this nonlinear process. The localized magnetic filamentary structures are found in solar corona along with the density dips and humps associated with the kinetic Alfven waves. The power spectra of magnetic field fluctuations indicate that the nonlinear interactions may be redistributing energy among higher wave numbers. The heating of the solar corona observed by Yohkoh and Solar and Heliospheric Observatory may be produced by the coupling of kinetic Alfven waves and ion acoustic waves via filamentation process.

Kumar, Sachin; Sharma, R. P.; Singh, H. D. [Plasma Simulation Laboratory, Centre for Energy Studies, Indian Institute of Technology Delhi, New Delhi 110016 (India)

2009-07-15

379

Portable dynamic positioning control system on a barge in short-crested waves using the neural network algorithm  

NASA Astrophysics Data System (ADS)

This paper develops a nonlinear mathematical model to simulate the dynamic motion behavior of the barge equipped with the portable outboard Dynamic Positioning (DP) system in short-crested waves. The self-tuning Proportional-Derivative (PD) controller based on the neural network algorithm is applied to control the thrusters for optimal adjustment of the barge position in waves. In addition to the wave, the current, the wind and the nonlinear drift force are also considered in the calculations. The time domain simulations for the six-degree-of-freedom motions of the barge with the DP system are solved by the 4th order Runge-Kutta method which can compromise the efficiency and the accuracy of the simulations. The technique of the portable alternative DP system developed here can serve as a practical tool to assist those ships without being equipped with the DP facility while the dynamic positioning missions are needed.

Fang, Ming-chung; Lee, Zi-yi

2013-08-01

380

Waves and Wave Properties  

NSDL National Science Digital Library

Students learn about the types of waves and how they change direction, as well as basic wave properties such as wavelength, frequency, amplitude and speed. During the presentation of lecture information on wave characteristics and properties, students take notes using a handout. Then they label wave parts on a worksheet diagram and draw their own waves with specified properties (crest, trough and wavelength). They also make observations about the waves they drew to determine which has the highest and the lowest frequency. With this knowledge, students better understand waves and are a step closer to understanding how humans see color.

Research Experience for Teachers (RET) Program, Center of Advancement of Engineering Fibers and Films,

381

Wavelength-doubling optical parametric oscillator  

DOEpatents

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.

Armstrong, Darrell J. (Albuquerque, NM); Smith, Arlee V. (Albuquerque, NM)

2007-07-24

382

The color appearance of stimuli detected via short-wavelength-sensitive cones: Comparisons with visual adaptation and visual field data for peri- or post-menopausal women under 70 years of age  

Microsoft Academic Search

Dynamics of foveal light adaptation for vision mediated via short-wavelength-sensitive (SWS) cones were compared for two groups of healthy amenorrheic (peri- or post-menopausal) women not using hormonal medication. Each subject was assigned to a group based on the color name—“lavender” (?2\\/3 of all subjects) or “white” (?1\\/3 of all subjects)—chosen in a forced-response paradigm to best describe a threshold-level 440-nm

Alvin Eisner; Maureen D. Toomey

2008-01-01

383

Predicting sodium chloride content in commercial king ( Oncorhynchus tshawytscha) and chum ( O. keta) hot smoked salmon fillet portions by short-wavelength near-infrared (SW-NIR) spectroscopy  

Microsoft Academic Search

Partial least square (PLS) based short-wavelength near-infrared (SW-NIR) prediction models for salt content in commercial hot smoked fillet portions of king or Chinook (Oncorhynchus tshawytscha) (N=140; 212–468 g) and chum (O. keta) salmon (N=120; 137–356 g) were developed. Spectra were collected in the diffuse reflectance mode (600–1100 nm). The total salt content ranged from 1.66 to 5.95% w\\/w for king

Mengshi Lin; Anna G. Cavinato; Yiqun Huang; Barbara A. Rasco

2003-01-01

384

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)

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.

Zhu, Zihang; Zhao, Shanghong; Yao, Zhoushi; Tan, Qinggui; Li, Yongjun; Chu, Xingchun; Shi, Lei; Hou, Rui

2012-11-01

385

p-on-n HgCdTe Infrared Focal-Plane Arrays: From Short-Wave to Very-Long-Wave Infrared  

NASA Astrophysics Data System (ADS)

This paper reports on recent developments made at the DEFIR joint laboratory on fabrication of planar p-on-n arsenic (As)-ion-implanted HgCdTe photodiodes. Our infrared focal-plane arrays (IRFPAs) cover a wide spectral range, from the short-wave infrared (SWIR) to the very-long-wave infrared (VLWIR). Our planar p-on-n technology is a classical one based on ion implantation followed by diffusion and activation. The p-type doping is obtained by As implantation, and n-type indium (In) doping is achieved during the epilayer growth. Our p-on-n IRFPAs show state-of-the-art performance from the SWIR to VLWIR spectral range. Mid-wave infrared (MWIR) and long-wave infrared (LWIR) FPAs have been designed with a television (TV) format and 15 ?m pixel pitch. Preliminary results of high-operating-temperature detectors obtained in the MWIR (? c = 5.3 ?m at 80 K) have shown highly promising electrooptical performance above 130 K. For space applications, imagers dedicated to low-flux detection have first been produced as TV/4 focal-plane arrays, with 15 ?m pitch in the SWIR range (2 ?m). Finally, TV/4 arrays with 30 ?m pixel pitch have been manufactured for the VLWIR range. The measured dark current fits the "Rule 07," with homogeneous imagers.

Mollard, L.; Bourgeois, G.; Lobre, C.; Gout, S.; Viollet-Bosson, S.; Baier, N.; Destefanis, G.; Gravrand, O.; Barnes, J. P.; Milesi, F.; Kerlain, A.; Rubaldo, L.; Manissadjian, A.

2013-10-01

386

VARIABLE GAMMA-RAY EMISSION FROM THE CRAB NEBULA: SHORT FLARES AND LONG 'WAVES'  

SciTech Connect

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.

Striani, E.; Tavani, M.; Vittorini, V.; Donnarumma, I.; Argan, A.; Cardillo, M.; Costa, E.; Del Monte, E.; Pacciani, L.; Piano, G.; Sabatini, S. [INAF/IASF-Roma, I-00133 Roma (Italy)] [INAF/IASF-Roma, I-00133 Roma (Italy); Giuliani, A.; Mereghetti, S. [INAF/IASF-Milano, I-20133 Milano (Italy)] [INAF/IASF-Milano, I-20133 Milano (Italy); Pucella, G.; Rapisarda, M. [ENEA Frascati, I-00044 Frascati (Roma) (Italy)] [ENEA Frascati, I-00044 Frascati (Roma) (Italy); Bulgarelli, A. [INAF/IASF-Bologna, I-40129 Bologna (Italy)] [INAF/IASF-Bologna, I-40129 Bologna (Italy); Colafrancesco, S. [INAF - Osservatorio Astronomico di Roma via Frascati 33, I-00040 Monteporzio (Italy)] [INAF - Osservatorio Astronomico di Roma via Frascati 33, I-00040 Monteporzio (Italy); Ferrari, A. [CIFS-Torino, I-10133 Torino (Italy)] [CIFS-Torino, I-10133 Torino (Italy); Pellizzoni, A. [INAF-Osservatorio Astronomico di Cagliari, localita' Poggio dei Pini, strada 54, I-09012 Capoterra (Italy)] [INAF-Osservatorio Astronomico di Cagliari, localita' Poggio dei Pini, strada 54, I-09012 Capoterra (Italy); Pittori, C. [ASI Science Data Center, I-00044 Frascati (Roma) (Italy)] [ASI Science Data Center, I-00044 Frascati (Roma) (Italy); and others

2013-03-01

387

X-ray conversion of ultra-short laser pulses on a solid sample: Role of electron waves excited in the pre-plasma  

NASA Astrophysics Data System (ADS)

Flat silicon samples were irradiated with 40 fs, 800 nm laser pulses at an intensity at the best focus of 2.1018 Wcm-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 2? and 3?/2 emission allowed the contributions to the X-ray yield to be identified as originating from laser interaction with either the near-critical density (nc) region or with the nc/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.

Baffigi, F.; Cristoforetti, G.; Fulgentini, L.; Giulietti, A.; Koester, P.; Labate, L.; Gizzi, L. A.

2014-07-01

388

Low latency search for Gravitational waves from BH-NS binaries in coincidence with Short Gamma Ray Bursts  

E-print Network

We propose a procedure to be used in the search for gravitational waves from black hole-neutron star coalescing binaries, in coincidence with short gamma-ray bursts. It is based on two recently proposed semi-analytic fits, one reproducing the mass of the remnant disk surrounding the black hole which forms after the merging as a function of some binary parameters, the second relating the neutron star compactness, i.e. the ratio of mass and radius, with its tidal deformability. Using a Fisher matrix analysis and the two fits, we assign a probability that the emitted gravitational signal is associated to the formation of an accreting disk massive enough to supply the energy needed to power a short gamma ray burst. This information can be used in low-latency data analysis to restrict the parameter space searching for gravitational wave signals in coincidence with short gamma-ray bursts, and to gain information on the dynamics of the coalescing system and on the internal structure of the components. In addition, when the binary parameters will be measured with high accuracy, it will be possible to use this information to trigger the search for off-axis gamma-ray bursts afterglows.

Andrea Maselli; Valeria Ferrari

2013-12-18

389

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  

NASA Astrophysics Data System (ADS)

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 ~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.

Boss, Alan P.; Keiser, Sandra A.

2013-06-01

390

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

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.

Boss, Alan P.; Keiser, Sandra A., E-mail: boss@dtm.ciw.edu, E-mail: keiser@dtm.ciw.edu [Department of Terrestrial Magnetism, Carnegie Institution, 5241 Broad Branch Road, NW, Washington, DC 20015-1305 (United States)

2013-06-10

391

Experimental examination of the effect of short ray trajectories in two-port wave-chaotic scattering systems  

NASA Astrophysics Data System (ADS)

Predicting the statistics of realistic wave-chaotic scattering systems requires, in addition to random matrix theory, introduction of system-specific information. This paper investigates experimentally one aspect of system-specific behavior, namely, the effects of short ray trajectories in wave-chaotic systems open to outside scattering channels. In particular, we consider ray trajectories of limited length that enter a scattering region through a channel (port) and subsequently exit through a channel (port). We show that a suitably averaged value of the impedance can be computed from these trajectories and that this can improve the ability to describe the statistical properties of the scattering systems. We illustrate and test these points through experiments on a realistic two-port microwave scattering billiard.

Yeh, Jen-Hao; Hart, James A.; Bradshaw, Elliott; Antonsen, Thomas M.; Ott, Edward; Anlage, Steven M.

2010-10-01

392

A Short-Wave Infrared Nanoinjection Imager With 2500 A\\/W Responsivity and Low Excess Noise  

Microsoft Academic Search

We report on a novel nanoinjection-based short-wave infrared imager, which consists of InGaAs\\/GaAsSb\\/InAlAs\\/InP-based nanoinjection detectors with internal gain. The imager is 320×256 pixels with a 30-m pixel pitch. The test pixels show responsivity values in excess of 2500 A\\/W, indicating generation of more than 2000 electrons\\/photon with high quantum efficiency. This amplification is achieved at complementary metal-oxide semiconductor (CMOS) compatible,

Omer Gokalp Memis; John Kohoutek; Wei Wu; Ryan M. Gelfand; Hooman Mohseni

2010-01-01

393

Wavelength conversion in optical transport networks  

Microsoft Academic Search

The introduction of optical technology in the path layer of a transport network is analyzed; in particular, the impact of all-optical wavelength conversion is examined. Two basic optical cross-connect schemes based on space switching and on wave-length switching, respectively, and two types of wavelength converters are considered. The wavelength converters are, respectively, based on four-wave miring (FWM) in semiconductor optical

R. Sabella; E. Iannone

1996-01-01

394

Spin wave excitation patterns generated by spin torque oscillators  

NASA Astrophysics Data System (ADS)

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.

Macià, F.; Hoppensteadt, F. C.; Kent, A. D.

2014-01-01

395

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

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

Kim, Hyoung-Jun; Song, Jong-In

2012-03-26

396

Impact of four-wave mixing on dispersion-managed frequency-shift-keying dense-wavelength-division-multiplexing system including various light-propagating effects  

NASA Astrophysics Data System (ADS)

We describe a semi-analytic model used to deterministically and exactly calculate the variance of degenerate and nondegenerate four-wave mixing (FWM) noises for 128×10 Gb/s return-to-zero frequency-shift-keying dispersion-managed dense-wavelength-division-multiplexing system. The analytic model includes various important light-propagating effects such as walk-off between channels, oscillation of pulse width with transmission distance, and stochastic variation of birefringence strength and orientation along fiber. The achievable maximum Q-factor and allowed maximum input powers for different dispersion management schemes and transmission distances are shown including overall FWM noises from different channel combinations, signal-amplified spontaneous emission (ASE) beat noise, and others. Achievable maximum transmission distances for such systems are studied. The upper limit of local dispersion of the dispersion map is discussed. In the case of allowed maximum input powers for the system, the variances of overall FWM noise are observed to be about half of those of signal-ASE beat noise when averaged for different transmission distances. It is found that for high-local dispersion, when transmission distance is long enough, effect of nondegenerate FWM noise, compared with degenerate FWM noise, can be ignored.

Du, Jianxin; Qian, Lihua; Chen, Qiuyue

2013-11-01

397

All-optical four-wavelength 2R regeneration based on data-pump four-wave-mixing with offset filtering  

NASA Astrophysics Data System (ADS)

A simultaneous all-optical 2R regeneration of 4 × 12.5 Gb/s return-to-zero (RZ) signals is demonstrated based on the data-pump four-wave-mixing in a single highly nonlinear fiber, in which the channel spacing and duty cycle are 200 GHz and 50%. Both the bidirectional configuration and time-interleaved technology are used to reduce the crosstalk from other channels. For further improving the performance of the multichannel regenerator, an offset filtering (OF) method is employed to minimize the influence from the opposite input signal. Our experiments show that the extinction ratio (ER) of regenerated signals is about two times larger than that of the degraded signals and the maximum ER improvement is about 6.5 dB. By using the offset filtering method, the sensitivity improvements of four-wavelength regenerated signals are 2.05 dB, 2.53 dB, 3.57 dB and 2.8 dB, respectively.

Wen, Feng; Wu, Bao-Jian; Zhou, Xing-Yu; Yuan, Hao; Qiu, Kun

2014-06-01

398

Dual-wavelength multifrequency photothermal wave imaging combined with optical coherence tomography for macrophage and lipid detection in atherosclerotic plaques using gold nanoparticles  

PubMed Central

Abstract. 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. PMID:22502567

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.

2012-01-01

399

Low speed target detection with short CIT in HF surface wave radar  

Microsoft Academic Search

High frequency surface wave radar can detect targets beyond the horizon. It needs long coherent integration time (CIT) to detect low speed targets, such as ships, in the environment with sea clutter. In order to improve the efficiency of the radar system, and avoid the Doppler broadening caused by long CIT, it is necessary to shorten coherent integration time. Modern

Shang Shang; Zhang Ning

2010-01-01

400

A unified directional spectrum for long and short wind-driven waves  

Microsoft Academic Search

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 Jähne and Riemer [1990] and Hara

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

1997-01-01

401

Wave Properties  

NSDL National Science Digital Library

In this lesson plan students will learn the components of a wave, then discuss the effects of wave height, wavelength, and wave period in determining the overall size of a wave. They will use the National Geographic Wave Simulator to experiment with creating different kinds of waves. Discussion will then focus on the effects of geography on wave size as well as additional forces on boats trying to navigate waves.

402

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)

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 ?PL 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.

Verma, Daisy; Kharkwal, Aneeta; Singh, S. N.; Singh, P. K.; Sharma, S. N.; Mehdi, S. S.; Husain, M.

2014-11-01

403

Nonlocal wave turbulence in the Charney-Hasegawa-Mima equation: a short review  

E-print Network

Rossby wave turbulence, as modelled by the Charney-Hasegawa-Mima (CHM) equation, is nonlocal in scale. As a result, the formal stationary Kolmogorov-Zakharov solutions of the Rossby wave kinetic equation, which describe local cascades, are not valid. Rather the solution of the kinetic equation is dominated by interactions between the large and small scales. This suggests an alternative analytic approach based on an expansion of the collision integral in a small parameter obtained from scale separation. This expansion approximates the integral collision operator in the kinetic equation by anisotropic diffusion operators in wavenumber space as first shown in a series of papers by Balk, Nazarenko and Zakharov in the early 1990's. In this note we summarize the foundations of this theory and provide the technical details which were absent from the original papers.

Colm Connaughton; Sergey Nazarenko; Brenda Quinn

2010-12-13

404

Parametric Excitations of Fast Plasma Waves by Counter-propagating Laser Beams  

SciTech Connect

Short- and long-wavelength plasma waves can become strongly coupled in the presence of two counter-propagating laser pump pulses detuned by twice the cold plasma frequency. What makes this four-wave interaction important is that the growth rate of the plasma waves occurs much faster than in the more obvious co-propagating geometry.

G. Shvets; N.J. Fisch

2001-03-19

405

SEARCH FOR GRAVITATIONAL-WAVE INSPIRAL SIGNALS ASSOCIATED WITH SHORT GAMMA-RAY BURSTS DURING LIGO'S FIFTH AND VIRGO'S FIRST SCIENCE RUN  

SciTech Connect

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.

Abadie, J.; Abbott, B. P.; Abbott, R.; Adhikari, R.; Ajith, P.; Anderson, S. B.; Araya, M.; Aso, Y. [LIGO-California Institute of Technology, Pasadena, CA 91125 (United States); Accadia, T. [Laboratoire d'Annecy-le-Vieux de Physique des Particules (LAPP), Universite de Savoie, CNRS/IN2P3, F-74941 Annecy-le-Vieux (France); Acernese, F. [INFN, Sezione di Napoli, Complesso Universitario di Monte Sant Angelo, I-80126 Napoli (Italy); Allen, B. [Albert-Einstein-Institut, Max-Planck-Institut fuer Gravitationsphysik, D-30167 Hannover (Germany); Allen, G. [Stanford University, Stanford, CA 94305 (United States); Ceron, E. Amador; Anderson, W. G. [University of Wisconsin-Milwaukee, Milwaukee, WI 53201 (United States); Amin, R. S. [Louisiana State University, Baton Rouge, LA 70803 (United States); Antonucci, F. [INFN, Sezione di Roma, I-00185 Roma (Italy); Aoudia, S. [Universite Nice-Sophia-Antipolis, CNRS, Observatoire de la Cote d'Azur, F-06304 Nice (France); Arain, M. A. [University of Florida, Gainesville, FL 32611 (United States); Arun, K. G. [LAL, Universite Paris-Sud, IN2P3/CNRS, F-91898 Orsay (France); Aston, S. [University of Birmingham, Birmingham, B15 2TT (United Kingdom)

2010-06-01

406

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)

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.

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.; Budzy?ski, 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.; Lubi?ski, 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.

2010-06-01

407

NASA Wavelength  

NSDL National Science Digital Library

NASA Wavelength is your pathway into a digital collection of Earth and space science resources for educators of all levels - from elementary to college, to out-of-school programs. These resources, developed through funding of the NASA Science Mission Directorate (SMD), have undergone a peer-review process through which educators and scientists ensure the content is accurate and useful in an educational setting. Use NASA Wavelength to quickly and easily locate resources, connect them to other websites using atom feeds, and even share the resources you discover with others through social media and email.

2014-04-07

408

Ocean Waves  

NSDL National Science Digital Library

This webpage, from Hyperphysics, provides a detailed explanation of how waves form in the ocean. A series of diagrams show how the water moves as a wave passes by. The site shows how a water wave's speed depends on wavelength, and how the shape of a wave depends on its amplitude. A description of why waves break on a beach is included.

Nave, Carl R.

2010-07-13

409

Wave Function and Strange Correlator of Short-Range Entangled States  

NASA Astrophysics Data System (ADS)

We demonstrate the following conclusion: If |?? is a one-dimensional (1D) or two-dimensional (2D) nontrivial short-range entangled state and |?? is a trivial disordered state defined on the same Hilbert space, then the following quantity (so-called "strange correlator") C(r,r')=??|?(r)?(r')|??/??|?? either saturates to a constant or decays as a power law in the limit |r-r'|?+?, even though both |?? and |?? are quantum disordered states with short-range correlation; ?(r) is some local operator in the Hilbert space. This result is obtained based on both field theory analysis and an explicit computation of C(r,r') for four different examples: 1D Haldane phase of spin-1 chain, 2D quantum spin Hall insulator with a strong Rashba spin-orbit coupling, 2D spin-2 Affleck-Kennedy-Lieb-Tasaki state on the square lattice, and the 2D bosonic symmetry-protected topological phase with Z2 symmetry. This result can be used as a diagnosis for short-range entangled states in 1D and 2D.

You, Yi-Zhuang; Bi, Zhen; Rasmussen, Alex; Slagle, Kevin; Xu, Cenke

2014-06-01

410

Real-time simulation of combined short-wave and long-wave infrared vision on a head-up display  

NASA Astrophysics Data System (ADS)

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.

Peinecke, Niklas; Schmerwitz, Sven

2014-05-01

411

Dual-wavelength generation by vertical external cavity surface-emitting laser.  

PubMed

A high-power dual-wavelength AlGaInAs / GaAs laser operating in a vertical external-cavity surface emitting geometry, grown by molecular beam epitaxy, is reported. The active regions of the laser are separated by an optical long-wave-pass filter to prevent absorption of short-wavelength radiation in the long-wavelength gain area. The maximum output power achieved at 15 degrees C was 0.75 W at lambda approximately 966 nm and 1.38 W at lambda approximately 1047 nm for the pump power of 21.2 W. PMID:19550614

Leinonen, Tomi; Ranta, Sanna; Laakso, Antti; Morozov, Yuri; Saarinen, Mika; Pessa, Markus

2007-10-01

412

What Processes can Damp Waves in Quiescent Prominences ?  

NASA Astrophysics Data System (ADS)

We discuss the possible non-ideal mechanisms acting in quiescent prominences within the context of linear compressional wave damping. The results show that the predominant damping mechanism is thermal radition provided prominences are optically thin. Waves can damp due to thermal conduction provided they have short wavelengths.

Ballai, I.; Walker, S. N.

2005-12-01

413

Miniature indium gallium arsenide short-wave infrared camera for unattended imaging applications  

NASA Astrophysics Data System (ADS)

Indium gallium arsenide (InGaAs) focal plane arrays and cameras have demonstrated significant potential in battlefield applications. Room temperature detectivities, D*, in excess of 1014 cm-(root)Hz/W have enabled night vision imaging under low light level conditions. The 0.9 micrometers to 1.7 micrometers wavelength band allows the use of eye- safe lasers for target designation and covert active illumination. We report here a miniature InGaAs camera designed for unattended ground sensor and robot-mounted applications. The camera is approximately the size of a D- cell battery, weighs less than 200 g. has a 320 X 240 pixel spatial resolution and maintains D* > 1014 cm- (root)Hz/W. The miniature camera is fully self contained. The only input is DC power (3.6 V). The camera has both analog (RS170) and 12-bit digital (LVDS) video outputs. It is intended as a demonstration vehicle for battlefield distributed robotic vision but will find use in other applications as an unattended sensor or rifle site.

Cohen, Marshall J.; O'Grady, Matthew T.; Vermaak, Jacobus S.; Groppe, Joseph V.; Olsen, Gregory H.

2000-07-01

414

Physical enviroment of 2-D animal cell aggregates formed in a short pathlength ultrasound standing wave trap.  

PubMed

2-D mammalian cell aggregates can be formed and levitated in a 1.5 MHz single half wavelength ultrasound standing wave trap. The physical environment of cells in such a trap has been examined. Attention was paid to parameters such as temperature, acoustic streaming, cavitation and intercellular forces. The extent to which these factors might be intrusive to a neural cell aggregate levitated in the trap was evaluated. Neural cells were exposed to ultrasound at a pressure amplitude of 0.54 MPa for 30 s; a small aggregate had been formed at the center of the trap. The pressure amplitude was then decreased to 0.27 MPa for 2 min, at which level the aggregation process continued at a slower rate. The pressure amplitude was then decreased to 0.06 MPa for 1 h. Temperature measurements that were conducted in situ with a 200 microm thermocouple over a 30 min period showed that the maximum temperature rise was less than 0.5 K. Acoustic streaming was measured by the particle image velocimetry method (PIV). It was shown that the hydrodynamic stress imposed on cells by acoustic streaming is less than that imposed by gentle preparative centrifugation procedures. Acoustic spectrum analysis showed that cavitation activity does not occur in the cell suspensions sonicated at the above pressures. White noise was detected only at a pressure amplitude of 1.96 MPa. Finally, it was shown that the attractive acoustic force between ultrasonically agglomerated cells is small compared with the normal attractive van der Waals force that operates at close cell surface separations. It is concluded that the standing wave trap operates only to concentrate cells locally, as in tissue, and does not modify the in vitro expression of surface receptor interactions. PMID:15749566

Bazou, Despina; Kuznetsova, Larisa A; Coakley, W Terence

2005-03-01

415

Short-Period Waves That Heat the Corona Detected at the 1999 Eclipse  

E-print Network

As a part of a study of the cause of solar coronal heating, we searched for high-frequency (~1 Hz) intensity oscillations in coronal loops in the [Fe XIV] coronal green line. We summarize results from observations made at the 11 August 1999 total solar eclipse from Ramnicu-Valcea, Romania, through clear skies. We discuss the image reduction and analysis through two simultaneous series of coronal CCD images digitized at 10 Hz for a total time of about 140 s. One series of images was taken through a 3.6 A filter isolating the 5303 A [Fe XIV] coronal green line and the other through a 100 A filter in the nearby K-corona continuum. Previous observations, described in Pasachoff et al. (2000), showed no evidence for oscillations in the [Fe XIV] green line at a level great than 2% of coronal intensity. We describe several improvements made over the 1998 eclipse that led to increased image clarity and sensitivity. The corona was brighter in 1999 with the solar maximum, further improving the data. We use Fourier analysis to search in the [Fe XIV] channel for intensity oscillations in loops at the base of the corona. Such oscillations in the 1-Hz range are predicted as a result of density fluctuations from the resonant absorption of MHD waves. The dissipation of a significant amount of mechanical energy from the photosphere into the corona through this mechanism could provide sufficient energy to hear the corona. A Monte-Carlo model of the data suggests the presence of enhanced power, particularly in the 0.75-1.0 Hz range, and we conclude that MHD waves remain a viable method for coronal heating.

Jay M. Pasachoff; Bryce A. Babcock; Kevin D. Russell; Daniel B. Seaton

2002-02-12

416

Revisiting coincidence rate between Gravitational Wave detection and short Gamma-Ray Burst for the Advanced and third generation  

E-print Network

We use realistic Monte-Carlo simulations including both gravitational-wave and short gamma-ray burst 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 $~3$ 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.

Regimbau, T; Meacher, D; Gendre, B; er, M Bo\\"

2014-01-01

417

The Short Wave Aerostat-Mounted Imager (SWAMI): A novel platform for acquiring remotely sensed data from a tethered balloon  

USGS Publications Warehouse

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.

Vierling, L. A.; Fersdahl, M.; Chen, X.; Li, Z.; Zimmerman, P.

2006-01-01

418

Spectral transmission and short-wave absorbing pigments in the fish lens--I. Phylogenetic distribution and identity.  

PubMed

Fish lens transmission was found to vary depending on the type and concentration of short-wave absorbing compounds present within the lens. Pigments extracted from lenses of ten species were identified as mycosporine-like amino acids (mainly palythine, palythene and asterina-330, lambda maxs around 320-360 nm) which are also thought to be present in the majority of the 120 species examined here. A novel mycosporine-like pigment with lambda max 385 nm was isolated from the lens of the flying fish, Exocoetus obtusirostris, while lenses of several closely related tropical freshwater species were found to have high concentrations of the tryptophan catabolite 3-hydroxykynurenine (lambda max 370 nm). The type of lens pigment a species possesses and its concentration depends upon both the animal's phylogenetic group and its "optical niche". PMID:8447101

Thorpe, A; Douglas, R H; Truscott, R J

1993-02-01

419

Short-wave solar radiation level willingly tolerated by lactating Holstein cows in an equatorial semi-arid environment.  

PubMed

The amount of short-wave solar radiation willingly tolerated by lactating Holstein cows on pasture was determined in an equatorial semi-arid environment. The study was carried out on a dairy farm located in Limoeiro do Norte, CE, northeastern Brazil. The observed behaviours were as follows: grazing, under the sun, under the shade, standing, lying, ruminating, idling and wallowing in the water. The behaviours were recorded using instantaneous scan sampling at regular intervals of 15 min from 0600 to 1800 hours over 5 days. On all sampling days, the meteorological variables, including local short-wave solar radiation (R S-W, W m(-2)), were recorded. The R S-W data were divided into five levels. The sun exposure was more frequent under low (100 %) and moderately low (97 %) levels, when R S-W remained below 500 W m(-2). The grazing was more intense under low (100 %) and moderately low (93 %) levels. Above 500 W m(-2), the grazing time significantly decreased (11 %). The cows avoided grazing under high (0 %) and very high (0 %) levels, when R S-W exceeded 700 W m(-2). The ruminating behaviour was more frequent under high (33 %) and very high (37 %) levels, in which the highest averages of R S-W were recorded (815 and 958 W m(-2), respectively). The standing posture was more frequent under low (100 %) and moderately low (97 %) levels. Therefore, the critical R S-W level that motivates cows to stop grazing and seek shade was in the interval between 500 and 700 W m(-2). PMID:25134806

Oliveira, Steffan Edward Octávio; Costa, Cíntia Carol de Melo; de Souza, João Batista Freire; de Queiroz, João Paulo Araújo Fernandes; Maia, Alex Sandro Campos; Costa, Leonardo Lelis de Macedo

2014-12-01

420

Millimeter-wave Ground-based Synthetic Aperture Radar Imaging for Foreign Object Debris Detection: Experimental Studies at Short Ranges  

NASA Astrophysics Data System (ADS)

In this paper, millimeter-wave imaging of foreign object debris (FOD)-type objects on the ground is studied with the help of ground-based synthetic aperture radar (GB-SAR) technique. To test the feasibility of detecting runway FODs with this technique, some preliminary experiments are conducted within short antenna-to-target ranges of small imaging patches. An automated stripmap GB-SAR system with stepped-frequency transmission is constructed together with a quasi-monostatic data collection operation. The imaging experiments for various braces and screws are then carried out by using 32- 36 GHz and 90- 95 GHz frequency bands of the millimeter-wave. Images reconstructed by a matched-filter based algorithm are analyzed to determine the proper system parameters for an efficient imaging and to comprehend the factors against a successful detection. Results demonstrate the capability of GB-SAR imaging in accurately locating these FOD-like targets under near-range operating conditions.

Yigit, Enes; Demirci, Sevket; Unal, Atilla; Ozdemir, Caner; Vertiy, Alexey

2012-12-01

421

Excitation of ion-wave wakefield by the resonant absorption of a short pulsed microwave with plasma.  

PubMed

Unmagnetized, inhomogeneous laboratory plasma irradiated by a high power (eta=E(2)(0)/4pin(e)kT(e) approximately 5.0x10(-2)) short pulsed microwave with pulse length of the order of ion-plasma period (tau(pi) less, similar 2pi/omega(pi)) is studied. Large density perturbation traveling through the underdense plasma with a velocity much greater than the ion sound speed produced by the resonant absorption of the microwave pulse has been observed. In the beginning the density perturbation has large amplitude (deltan/n(0) approximately 40%) and propagates with a velocity of the order of 10(6) cm/s. But later its amplitude as well as the velocity decrease rapidly, and finally the velocity arrives with twice the ion sound speed. The oscillating incident electromagnetic waves enhance highly localized electric field by the resonant absorption process and develop time-averaged force field which pushes plasma electrons from the resonant layer. As the electrons are accelerated to be ejected, they pull plasma ions as a bunch with them by means of self-consistent Coulomb force. This suprathermal ion bunch can excite an ion-wave wakefield. PMID:14524900

Kamal-Al-Hassan, Md; Starodubtsev, Mikhail; Ito, Hiroaki; Yugami, Noboru; Nishida, Yasushi

2003-09-01

422

Black carbon fractal morphology and short-wave radiative impact: a modelling study  

NASA Astrophysics Data System (ADS)

We investigate the impact of the morphological properties of freshly emitted black carbon aerosols on optical properties and on radiative forcing. To this end, we model the optical properties of fractal black carbon aggregates by use of numerically exact solutions to Maxwell's equations within a spectral range from the UVC to the mid-IR. The results are coupled to radiative transfer computations, in which we consider six realistic case studies representing different atmospheric pollution conditions and surface albedos. The spectrally integrated radiative impacts of black carbon are compared for two different fractal morphologies, which brace the range of recently reported experimental observations of black carbon fractal structures. We also gauge our results by performing corresponding calculations based on the homogeneous sphere approximation, which is commonly employed in climate models. We find that at top of atmosphere the aggregate models yield radiative impacts that can be as much as 2 times higher than those based on the homogeneous sphere approximation. An aggregate model with a low fractal dimension can predict a radiative impact that is higher than that obtained with a high fractal dimension by a factor ranging between 1.1-1.6. Although the lower end of this scale seems like a rather small effect, a closer analysis reveals that the single scattering optical properties of more compact and more lacy aggregates differ considerably. In radiative flux computations there can be a partial cancellation due to the opposing effects of different error sources. However, this cancellation effect can strongly depend on atmospheric conditions and is therefore quite unpredictable. We conclude that the fractal morphology of black carbon aerosols and their fractal parameters can have a profound impact on their radiative forcing effect, and that the use of the homogeneous sphere model introduces unacceptably high biases in radiative impact studies. We emphasise that there are other potentially important morphological features that have not been addressed in the present study, such as sintering and coating of freshly emitted black carbon by films of organic material. Finally, we found that the spectral variation of the absorption cross section of black carbon significantly deviates from a simple 1/? scaling law. We therefore discourage the use of single-wavelength absorption measurements in conjunction with a 1/? scaling relation in broadband radiative forcing simulations of black carbon.

Kahnert, M.; Devasthale, A.

2011-11-01

423

Electrostatic lower hybrid waves excited by electromagnetic whistler mode waves scattering from planar magnetic-field-aligned plasma density irregularities  

SciTech Connect

Recent satellite observations demonstrate that high amplitude, short wavelength (5 m {le} {lambda} {le} 100 m) electrostatic waves are commonly excited by electromagnetic whistler mode waves propagating in regions of the magnetosphere and topside ionosphere where small-scale magnetic-field-aligned plasma density irregularities are thought to exist. A new theoretical model of this phenomenon is presented, based upon passive linear scattering in a cold magnetoplasma. In this model the electrostatic waves are excited by linear mode coupling as the incident electromagnetic whistler mode waves scatter from the magnetic-field-aligned plasma density irregularities. The excited short wavelength waves are quasi-electrostatic whistler mode waves, a type of lower hybrid wave, whose wave normal lies near the whistler mode resonance cone where the wave refractive index becomes very large. The amplitude of the exci