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1

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

2

Flat short-circuited strip of one wavelength width and acting at quarter-wave resonance  

Microsoft Academic Search

Properties of a large, flat short-circuited half-radiating strip acting at a quarterwave resonance are presented. It is excited by means of several feed points. The obtained bandwidth is large. When the width is about one wavelength, it appears as an antenna with excellent efficiency and high directivity. Correct agreement is obtained between theoretical and experimental results.

G. Dubost

1981-01-01

3

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

4

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

5

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

6

Characteristics of gravity waves with short vertical wavelengths observed with radiosonde and GPS occultation during DAWEX  

E-print Network

occultation during DAWEX (Darwin Area Wave Experiment) Toshitaka Tsuda,1 M. Venkat Ratnam,1 Peter T. May,2 M. We also analyzed a latitude-height section of Ep in October to December 2001 using GPS occultation; KEYWORDS: gravity wave, radiosonde, GPS occultation Citation: Tsuda, T., M. V. Ratnam, P. T. May, M. J

Alexander, M. Joan

7

Irreversible transport in the stratosphere by internal waves of short vertical wavelength  

NASA Technical Reports Server (NTRS)

Measurements performed during stratospheric flights of the U-2 aircraft confirm that cross-jet transport is dominated by waves, not by large-scale circulations. Monotonic gradients of trace constituents normal to the jet axis, with upper stratospheric tracers increasing poleward and tropospheric tracers increasing equatorward, are augmented by large-scale confluence as the jet intensifies during cyclogenesis. These gradients are rotated, intensified, and significantly increased in areas as their mixing ratio surfaces are folded by the differential transport of a very low frequency transverse wave. The quasi-horizontal transport produces a laminar structure with stable layers rich in upper stratospheric tracers alternating vertically with less stable layers rich in tropospheric tracers. The transport proceeds toward irreversibility at higher frequency, shear-gravity waves extend the folding to smaller horizontal scales.

Danielsen, Edwin F.; Hipskind, R. S.; Starr, Walter L.; Vedder, James F.; Gaines, Steven E.; Kley, Dieter; Kelley, Ken K.

1991-01-01

8

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

9

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

10

Short wavelength chemical laser development  

NASA Astrophysics Data System (ADS)

Short wavelength chemical lasers (SWCL) operating in the near infrared are becoming candidates for strategic missions. Chemical lasers which operate at short wavelengths at or near the visible are discussed. These lasers offer potential brightness enhancements which will be required for future high energy laser systems. Recent progress in basic research and efforts to demonstrate lasing are reviewed. Several systems are described and a critique of recent reports of chemically generated gain in the BiF(A-x) and Na2(B-x) systems is presented. New chemistries for providing singlet electronic states of NF and NCl from halogen azides provide new opportunities for energy extraction schemes based on energy pooling. A new concept for utilizing vibrational excitation in the lasant species to enhance the excitation rate for iodine monofluoride and the development of new facilities for laser demonstration efforts are discussed.

Patterson, S. P.; Duncan, W. A.; Graves, B. R.; Perram, Glen; Jones, C. R.

1992-07-01

11

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

12

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

13

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

14

Bibliography of short wavelength chemical laser research  

Microsoft Academic Search

High power short wavelength chemical laser (SWCL) systems offer great advantages for strategic and tactical military applications, including both weapons and imaging missions. The promise of very high brightness, high mass efficiency, and wavelength agility has justified a modest basic research program for more than a decade. Significant progress towards the demonstration of a visible chemical laser has been made

Glen P. Perram

1993-01-01

15

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

16

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

17

Far-field measurements of short-wavelength surface plasmons  

NASA Astrophysics Data System (ADS)

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

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

2015-03-01

18

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

19

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

20

Short wavelength striations on expanding plasma clouds  

SciTech Connect

The growth and evolution of short wavelength (

Winske, D.; Gary, S.P.

1989-01-01

21

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

22

Bibliography of short wavelength chemical laser research  

NASA Astrophysics Data System (ADS)

High power short wavelength chemical laser (SWCL) systems offer great advantages for strategic and tactical military applications, including both weapons and imaging missions. The promise of very high brightness, high mass efficiency, and wavelength agility has justified a modest basic research program for more than a decade. Significant progress towards the demonstration of a visible chemical laser has been made during the past few years. Highly efficient methods of chemically producing metastable electronic states at concentrations exceeding 3 x 10(exp 16) molecules/cu cm have been developed. Energy transfer from these metastables to suitable lasant species has been used to demonstrate gain in the visible. Chemically generated gain of 0.029 %/cm on the (A-X) electronic transition in bismuth fluoride has been demonstrated using pulsed thermolysis of fluorine azide and trimethyl bismuth mixtures. Recently, a table-top shock facility has been used to achieve unsaturated lasing in the same system. During the past ten years, over 400 articles and reports have resulted from this research program. This bibliography summarizes this Department of Defense sponsored research on short wavelength chemical lasers since 1980.

Perram, Glen P.

1993-05-01

23

Short wavelength chemical laser status update  

NASA Astrophysics Data System (ADS)

Future high energy laser weapon systems will require very high brightness levels. Two short wavelength chemical lasers (SWCLs), the chemical oxygen iodine laser and hydrogen fluoride overtone, are already becoming candidates for strategic missions. This paper will discuss chemical lasers operating at still shorter wavelengths in and near the visible. These lasers offer potential for even further brightness enhancements. Since, for constant output energy, the brightness of a laser scales inversely with the square of its wavelength, SWCLs offer potential system benefits. Gain measurements have been made on several SWCL candidates, but these devices are still in the developmental stage and require further demonstration and scaling before they can become viable candidates to perform strategic missions. The Strategic Defense Initiative Organization (SDIO) sponsors research in a number of the more promising SWCL technology areas through its agents at the Air Force Office of Scientific Research (AFOSR) and the U.S. Army Missile Command (MICOM). This paper provides an overview of the status of research and experiments aimed at developing visible SWCLs.

Patterson, S. P.; Duncan, W. A.; Graves, B. R.; Perram, Glen; Jones, C. R.

24

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

25

Short and long waves in the cochlea.  

PubMed

Mathematically, it is attractive to model cochlear dynamics as a one-dimensional problem. This implies the hypothesis that the (smallest) wavelength is large compared to the cross-section of the cochlear channels. It is suspected that this hypothesis is not justified at and near the place where the wavelength is smallest. For several types of model the response is computed with due allowance for short waves. The results show that in the pertinent region short waves completely dominate the response. Several consequences of this finding are discussed. PMID:7410251

de Boer, E

1980-06-01

26

Laser-to-electricity energy converter for short wavelengths  

NASA Technical Reports Server (NTRS)

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

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

1975-01-01

27

Short-wave Diathermy  

PubMed Central

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

1935-01-01

28

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

29

Lithographic spiral antennas at short wavelengths  

NASA Technical Reports Server (NTRS)

We have extended the high efficiency of lithographic antennas to mid-infrared wavelengths. Pattern measurements made at 9.5/zm wavelength on a 65 deg, self-complementary, spiral antenna exhibit a ratio of response to orthogonal linear polarizations of 1.35 dB, a beamwidth of 85 deg (3 dB full width), a directivity of 8.2 dB, and surprisingly, a close resemblance to the theoretical pattern for a 65 deg spiral in free space. Direct detection measurements made with an ambient temperature blackbody source yield an antenna efficiency of 52 +/- 7 percent, when corrected for incomplete filling of the antenna beam by the source, at a mean effective wavelength of 19 micron.

Grossman, E. N.; Sauvageau, J. E.; Mcdonald, D. G.

1991-01-01

30

Lethal effects of short-wavelength visible light on insects  

PubMed Central

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

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

2014-01-01

31

Lethal effects of short-wavelength visible light on insects  

NASA Astrophysics Data System (ADS)

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

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

2014-12-01

32

OMEGA: a short-wavelength laser for fusion experiments  

SciTech Connect

The OMEGA, Nd:glass laser facility was constructed for the purpose of investigating the feasibility of direct-drive laser fusion. With 24 beams producing a total energy of 4 kJ or a peak power of 12 TW, OMEGA is capable of nearly uniform illumination of spherical targets. Six of the OMEGA beams have recently been converted to short-wavelength operation (351 nm). In this paper, we discuss details of the system design and performance, with particular emphasis on the frequency-conversion system and multi-wavelength diagnostic system.

Soures, J.M.; Hutchison, R.J.; Jacobs, S.D.; Lund, L.D.; McCrory, R.L.; Richardson, M.C.

1983-01-01

33

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

E-print Network

Wave properties of light Light is energy whose wavelength is the distance traveled in order to complete one cycle. The frequency of light refers to the number of cycles in one second. Low-energy light has a long wavelength and a low frequency. High-energy light has a short wavelength and a high

Zworski, Maciej

34

Short Wavelength Seeding through Compression for Fee Electron Lasers  

SciTech Connect

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

Qiang, Ji

2010-03-29

35

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

36

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

37

Output characteristics of SASE-driven short-wavelength FELs  

NASA Astrophysics Data System (ADS)

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

Fawley, William M.

1997-05-01

38

Short wavelength limits of current shot noise suppression  

SciTech Connect

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, E-mail: arielnau@post.tau.ac.il [Faculty of Exact Sciences, Department of Physics, Tel Aviv University, Tel Aviv (Israel); Dyunin, Egor; Gover, Avraham [Faculty of Engineering, Department of Physical Electronics, Tel Aviv University, Tel Aviv (Israel)

2014-08-15

39

Short wavelength far infrared laser polarimeter with silicon photoelastic modulatorsa)  

NASA Astrophysics Data System (ADS)

A short wavelength far infrared laser whose wavelength ? is about 50?m is preferable for a polarimeter and an interferometer for high density operations in the Large Helical Device (LHD) and on future large fusion devices such as ITER. This is because the beam bending effect (??2) in a plasma, which causes fringe jump errors, is small and the Faraday and the Cotton-Mouton effects are moderate. We have developed a polarimeter with highly resistive silicon photoelastic modulators (PEMs) for the CH3OD laser (? =57.2 and 47.7?m). We performed bench tests of the polarimeter with a dual PEM and demonstrated the feasibility for the polarimeter. Good linearity between actual and evaluated polarization angles is achieved with an angular resolution of 0.05° and a temporal resolution of 1ms. The baseline drift of the polarization angle is about 0.1° for 1000s.

Akiyama, T.; Kawahata, K.; Tanaka, K.; Okajima, S.; Nakayama, K.

2008-10-01

40

Modulated Standing Waves in a Short Reaction-Diffusion System Milos Dolnik, Anatol M. Zhabotinsky,* and Irving R. Epstein  

E-print Network

Modulated Standing Waves in a Short Reaction-Diffusion System Milos Dolnik, Anatol M. Zhabotinsky. As the system length is varied, modulated standing waves, characterized by short-lived alternating nodes, are found between the domains of the half-wavelength and the one-wavelength standing waves. The space- time

Epstein, Irving R.

41

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

42

Determination of vertical and horizontal wavelengths of gravity waves  

NASA Technical Reports Server (NTRS)

The determination of horizontal and vertical wavelengths of gravity waves obviously relies on measurement of wave parameters in horizontal and vertical directions. A very suitable parameter, measured fairly easily with MST radars, is the fluid velocity. Average velocities and superimposed turbulent fluctuations are much larger in the horizontal than in the vertical direction. Vertical and horizontal fluid velocities due to wave-like events are mostly about equal in magnitude. Vertical fluid velocities due to waves therefore can be more reliably detected than horizontal velocities. Estimates of gravity wave events using MST radar data are calculated and results are indicated.

Rottger, J.

1983-01-01

43

Stability of short wavelength tearing and twisting modes  

SciTech Connect

The stability and mutual interaction of tearing and twisting modes in a torus is governed by matrices that generalize the well-known {Delta}{prime} stability index. The diagonal elements of these matrices determine the intrinsic stability of modes that reconnect the magnetic field at a single resonant surface. The off-diagonal elements indicate the strength of the coupling between the different modes. The author shows how the elements of these matrices can be evaluated, in the limit of short wavelength, from the free energy driving radially extended ballooning modes. The author applies the results by calculating the tearing and twisting {Delta}{prime} for a model high-beta equilibrium with circular flux surfaces.

Waelbroeck, F.L.

1998-09-22

44

A Novel Short Extended Cavity Diode Laser for Red Wavelengths  

NASA Astrophysics Data System (ADS)

We present the design and characterization of a short extended cavity diode laser with immediate applications in ultracold atomic physics. To reach wavelengths unavailable in commercial laser diodes, a laser was constructed such that it could be cooled without loss in performance. We demonstrate that this laser design has a mode-hop-free tuning range of 20 GHz or greater when modulating laser current, and that it can also be adjusted using temperature controls and a piezo-electric output coupler mount. We also show that this laser achieves stable single-mode operaction with both 90% and 50% reflective output couplers without degrading its performance. Finally, we present an application of this laser as a repumper in cooling and trapping experiments of ^88Sr, including increasing the yield of trapped atoms and studying the lifetimes of metastable atomic states.

Dunn, Aaron

2008-05-01

45

Dual-wavelength ultra-short pulse laser damage testing  

NASA Astrophysics Data System (ADS)

In the femtosecond regime laser damage thresholds are often determined by the electric field distribution within the optical component. Commercially available ultra-short pulse laser systems provide ever increasing output powers in fundamental and harmonic wavelengths. Therefore, an increasing demand for frequency conversion or multiwavelengths optics with high damage thresholds for both, fundamental and second harmonic wavelengths is given. These optics are under increased strain and face even more design difficulties. Also, the electric field distribution is of higher complexity and favors multi-photon excitation of high efficiencies. We investigate the LIDT of dichroic high reflecting mirrors under simultaneous exposure to fundamental and second harmonic radiation. As laser source we use a Ti:Sa system delivering sub 200 fs pulses at 780nm/390nm. A delay-line was incorporated to ensure temporal overlap of the 2 pulses in the test plane. Further, the LIDT of a single layer of Ta2O5 under irradiation with fundamental and second harmonic radiation is calculated and results are compared with our experiment.

Gyamfi, Mark; Jürgens, Peter; Mende, Mathias; Jensen, Lars; Ristau, Detlev

2014-11-01

46

Independent measurements of the frequency and wavelength of electromagnetic waves  

NASA Astrophysics Data System (ADS)

Very few measurements that directly investigate the frequency of electromagnetic waves are accessible to undergraduate or high school laboratories because of the expense of most spectrum analyzers as well as the extremely high frequencies of many electromagnetic waves. However, an affordable setup for measuring electromagnetic wave properties, including frequency and wavelength, can be made using a wireless network spectrum analyzer. Capabilities of an inexpensive spectrum analyzer are examined and illustrative samples of wave property measurements are presented. These allow determination of the speed of propagation so that comparison with the speed of visible light can help integrate student understanding of the electromagnetic spectrum.

Howald, Craig

2009-10-01

47

Put a Short-Wave Radio in Your Foreign Language Classroom  

ERIC Educational Resources Information Center

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

Oksenholt, Svein

1977-01-01

48

Detection of direction and wavelength of ocean wave by power spectrum of ocean wave image  

Microsoft Academic Search

The detection of ocean waves can be used to monitor ocean and to forecast wind-storms upon the ocean surface. The paper presents a method for extracting wave direction and wavelength of ocean waves from a sea image. Based on the assumption that the power spectrum of an ocean wave can be thought of as a thin plane consisting of discrete

Tang Huiming; Xu Shengrong

1992-01-01

49

Partial scaling of finite element models for the analysis of the coupling between short and long structural wavelengths  

NASA Astrophysics Data System (ADS)

This work deals with the analysis of the coupling between long and short structural wavelengths on simple test configurations. The aim is pursued using standard and scaled finite element models. The first is the classical one based on the sampling of the given wavelength; the second is built by scaling only the finite element model of the component carrying the shortest waves. The physical domain carrying the shortest waves is thus reduced and its original damping is increased to recover the correct energy response. The results highlight the limits and the advantages of such scaling procedure in analysing the specific coupling schemes.

De Rosa, S.; Franco, F.; Polito, T.

2015-02-01

50

Massively sub-wavelength guiding of electromagnetic waves.  

PubMed

Recently a new form of ultra-thin flexible waveguide consisting of a conducting comb-like structure with a thickness of the order of 1/600(th) of the operating wavelength was presented. However, whilst the thickness of the guide was massively sub-wavelength, the remaining dimensions (the height and period of the comb) were much longer. In this paper we propose, and experimentally verify, that a modified guiding geometry consisting of a chain of ultra-thin conducting spirals allows guiding of electromagnetic waves with wavelengths that are many times (40+) longer than any characteristic dimension of the guide, enabling super-sub-wavelength guiding and localisation of electromagnetic energy. PMID:25510662

Hooper, I R; Tremain, B; Dockrey, J A; Hibbins, A P

2014-01-01

51

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-quantum-well absorbers that sample a standing wave created by a distributed Bragg reflector. As a wavelength monitor, our for wavelength demultiplexing.3 A class of devices based on thin absorbers in standing waves was proposed4

Miller, David A. B.

52

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

53

Wavelength division multiplexed optical interconnects using short pulses  

Microsoft Academic Search

Optical interconnects for silicon electronics have been shown to have many advantages over traditional electrical interconnects, particularly in dense, high-capacity systems. One approach used to achieve the very high data rates used in telecommunications today is wavelength division multiplexing (WDM). As bandwidth needs increase, WDM becomes an attractive solution for shorter distance links as well, such as chip-to-chip or board-to-board

Bianca Elizabeth Nelson Keeler

2003-01-01

54

Wavelength Halving in a Transition between Standing Waves and Traveling Waves Akiko Kaminaga, Vladimir K. Vanag, and Irving R. Epstein  

E-print Network

Wavelength Halving in a Transition between Standing Waves and Traveling Waves Akiko Kaminaga-in-oil aerosol OT/Span-20 microemulsion, the transition between standing waves and traveling waves is accompanied, 82.33.Nq The transition between standing waves (SW) and trav- eling waves (TW) is a well

Epstein, Irving R.

55

Dark current generating mechanisms in short wavelength infrared photovoltaic detectors  

Microsoft Academic Search

The current-voltage characteristics and quantum efficiencies of double layer planar heterostructure photodiodes were investigated.\\u000a Results are reported on devices with cutoff wavelengths of 1.8, 2.4, and 3.3 m. For these respective devices, the dominant\\u000a currents for temperatures >250,>200,>150K are diffusion currents limited by shallow Shockley-Hall-Read (SHR) processes. The\\u000a remarkable result is that the electrical and optoelectronic properties of these devices

R. E. Dewames; D. D. Edwall; M. Zandian; L. O. Bubulac; J. G. Pasko; W. E. Tennant; J. M. Arias; A. D’Souza

1998-01-01

56

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

SciTech Connect

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

Downer, M.C. [Univ. of Texas, Austin, TX (United States). Dept. of Physics; Siders, C.W. [Los Alamos National Lab., NM (United States)

1996-12-31

57

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

NASA Astrophysics Data System (ADS)

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

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

2014-09-01

58

The applications of a short-wavelength FEL (invited, abstract)  

NASA Astrophysics Data System (ADS)

The third-generation synchrotron light sources today offer exciting new scientific capabilities due to the high brightness of their hard x-ray beams. Yet further dramatic increases in source brightness are becoming technically feasible, with the advent of free-electron lasers (FELs) operating in the hard x-ray region. The peak brightness of machines under consideration exceeds that of today's third-generation sources by more than ten orders of magnitude. In addition, an FEL would produce an x-ray beam with very high transverse coherence and subpicosecond pulse length. These characteristics should open up completely new areas of x-ray science, such as nonlinear x-ray optics and femtosecond time-domain spectroscopy. Some areas of current research, such as imaging and interferometry, could be extended to much shorter wavelengths and faster measurements. The intense beam could also be used to modify materials on a nanometer scale. Formidable technical problems in the areas of optics, sample preparation, and data collection will need to be solved before an FEL beam could be effectively utilized. Research in these areas is now beginning to be pursued in the U.S., Germany, and Japan.

Arthur, John

1996-09-01

59

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

60

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

61

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

PubMed

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

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

2014-01-01

62

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

63

Substrate-Removed HgCdTe-Based Focal-Plane Arrays for Short-Wavelength Infrared Astronomy  

Microsoft Academic Search

Removal of the CdZnTe substrate offers several performance benefits for near-infrared (NIR, 1.7 ?m) and short-wave infrared (SWIR, 2.5 ?m) focal-plane arrays (FPAs). Among these are visible wavelength detection, improved infrared sensitivity and uniformity,\\u000a and greatly reduced susceptibility to the effects of ionizing radiation. Data for substrate-removed NIR FPAs fabricated for\\u000a the Wide Field Camera 3 (WFC3) upgrade to the Hubble Space

E. C. Piquette; D. D. Edwall; H. Arnold; A. Chen; J. Auyeung

2008-01-01

64

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

65

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

66

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

67

Widely Wavelength-Tunable Blue-Shifted Dispersive Waves for Broadband Visible Wavelength Generation in a Photonic Crystal Fiber Cladding  

NASA Astrophysics Data System (ADS)

Blue-shifted dispersive waves (DWs) are efficiently generated from the red-shifted solitons by coupling the 120 fs pulses into the fundamental mode of the multi-knots of a photonic crystal fiber cladding. When the femtosecond pulses at the wavelength of 825 nm and the average power of 300 mW are coupled into knots 1-3, the conversion efficiency ?DW of 32% and bandwidth BDW of 50 nm are obtained. The ultrashort pulses generated by the DWs can be tunable over the whole visible wavelength by adjusting the wavelengths of the pump pulses coupled into different knots. It can be believed that this widely wavelength-tunable ultrashort visible pulse source has important applications in ultrafast photonics and resonant Raman scattering.

Yuan, Jin-Hui; Sang, Xin-Zhu; Yu, Chong-Xiu; Shen, Xiang-Wei; Wang, Kui-Ru; Yan, Bin-Bin; Han, Ying; Zhou, Gui-Yao; Hou, Lan-Tian

2012-10-01

68

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

69

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

70

Short Wavelength Temperature Gradient Driven Modes in Tokamak Plasmas A. I. Smolyakov,1,2  

E-print Network

Short Wavelength Temperature Gradient Driven Modes in Tokamak Plasmas A. I. Smolyakov,1,2 M. Yagi,3 August 2002) New unstable temperature gradient driven modes in an inhomogeneous tokamak plasma are identified. These modes represent temperature gradient (ion and electron) driven modes destabilized

Smolyakov, Andrei

71

Applications of High-Field and Short-Wavelength Sources INTRODUCTION  

E-print Network

biology. This special issue of JOSA B is devoted to the latest de- velopments in this field. The symbiosisApplications of High-Field and Short-Wavelength Sources INTRODUCTION High-field interactions breakthroughs is well represented by the breadth of papers showcased in this issue. In a series of contributions

Ditmire, Todd

72

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

Microsoft Academic Search

Color class of wheat is an important attribute for the identification of cultivars and the marketing of wheat, but is not always easy to measure in the visible spectral range because of variation in vitreosity and surface structure of the kernels. This work examines whether short-wavelength near IR imaging in the range 632-1098 nm can be used to distinguish different

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

1999-01-01

73

Short-wavelength upconversion emissions in codoped glass ceramic and the optical  

E-print Network

-theranostic Technologies, Harbin Institute of Technology, Harbin 150001, China 4 Materials Research InstituteShort-wavelength upconversion emissions in Ho3+ /Yb3+ codoped glass ceramic and the optical of electrical engineering, Yanshan University, Qinhuangdao, 066004, China 3 Laboratory of Sono- and photo

Cao, Wenwu

74

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.

75

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

NASA Astrophysics Data System (ADS)

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

Zhang, Xiaorong; Li, Bincheng

2015-02-01

76

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

PubMed

Surface thermal lens is a highly sensitive photothermal technique to measure low absorption losses of various solid materials. In such applications, the sensitivity of surface thermal lens is a key parameter for measuring extremely low absorption. In this paper, we experimentally investigated the influence of probe beam wavelength on the sensitivity of surface thermal lens for measuring the low absorptance of optical laser components. Three probe lasers with wavelength 375 nm, 633 nm, and 1570 nm were used, respectively, to detect the surface thermal lens amplitude of a highly reflective coating sample excited by a cw modulated Gaussian beam at 1064 nm. The experimental results showed that the maximum amplitude of surface thermal lens signal obtained at corresponding optimized detection distance was inversely proportional to the wavelength of the probe beam, as predicted by previous theoretical model. The sensitivity of surface thermal lens could, therefore, be improved by detecting surface thermal lens signal with a short-wavelength probe beam. PMID:25725872

Zhang, Xiaorong; Li, Bincheng

2015-02-01

77

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

PubMed

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

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

2015-04-01

78

The winter anomaly (WA) of short waves  

NASA Astrophysics Data System (ADS)

Mechanisms responsible for the enhanced wintertime absorption of short waves in the altitude interval 75-90 km are investigated. Absorption augmentation of 1.5-2 times the normal daily winter levels have been observed. The heights at which the anomalous absorption occurs are regions where strong ionic species variations are present on a seasonal basis. It is shown that the absorption intensity is dependent on the species concentration, which is higher during the winter. A formulation is defined for the electronic production profiles and evaluated for January and July. Account is taken of the speed of ion production and the radiative input. Data is presented from absorption measurements at 1 MHz and comparisons are made with predictions. It is found that the winter augmentation is influenced by the temperature, species, and the atmospheric density.

Velinov, P. I.; Vlaskov, V. A.; Smirnova, N. A.

79

Analysis of wavelength deviation of guided waves with electromagnetic acoustic transducers  

NASA Astrophysics Data System (ADS)

It is usually considered that the wavelength of guided waves propagating in plates is equal to the double spacing interval of the meander-line coil of electromagnetic acoustic transducers (EMATs). However, the actual value of the wavelength might deviate from the double spacing. This paper takes Shear Horizontal (SH) waves for instance to study the relationship between the wavelength deviation and the parameters of EMATs. It is shown that the wavelength deviation occurs when the operating point of EMATs does not locate on the dispersion curves of a certain SH mode. A wavelength measurement method is proposed to evaluate the deviation by the time-frequency analysis of detected wave signals. Experiments are set up to study the phenomenon of wavelength deviation and verify the validity of the proposed method.

Zhai, Guofu; Jiang, Tao; Kang, Lei

2012-10-01

80

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

DOEpatents

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

Balooch, Mehdi (Berkeley, CA); Dinh, Long N. (Concord, CA); Siekhaus, Wigbert J. (Berkeley, CA)

2000-01-01

81

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

82

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 element modeling of short-wavelength folding on Venus: Implications for the plume hypothesis for crustal plateaus preserve some of Venus' oldest observed and most extensive structural deformation. If crustal

Hansen, Vicki

83

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

NASA Technical Reports Server (NTRS)

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

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

2012-01-01

84

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

SciTech Connect

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

Sahraoui, F.; Belmont, G. [Laboratoire de Physique des Plasmas, CNRS-Ecole Polytechnique-UPMC, Observatoire de Saint-Maur, 4 avenue de Neptune, 94107 Saint-Maur-des-Fosses (France); Goldstein, M. L., E-mail: fouad.sahraoui@lpp.polytechnique.fr [NASA Goddard Space Flight Center, Code 673, Greenbelt, MD 20771 (United States)

2012-04-01

85

Laser induced short plane acoustic wave focusing in water  

Microsoft Academic Search

Laser induced high frequency acoustic wave generation, propagation, and focusing in water are studied. A large area, flat, and short duration acoustic wave was generated by the thermoelastic interaction of a homogenized short pulsed laser beam with the liquid-solid interface and propagated at the speed of sound. Laser flash Schlieren photography was used to visualize the transient interaction of the

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

2007-01-01

86

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

87

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

88

Short-wavelength automated perimetry in patients with diabetes mellitus without macular edema  

Microsoft Academic Search

Background The short-wavelength-sensitive (SWS) cone-mediated sensitivity is a sensitive indicator of functional changes of the macula in diabetic maculopathy. This study was performed to investigate whether functional losses of the macula are detectable in patients without a significant macular edema. Methods In 45 patients with diabetes mellitus with clear optical media and no macular edema, conventional white-on-white perimetry (WWP) and

Andreas Remky; Anke Weber; Stefan Hendricks; Kristina Lichtenberg; Oliver Arend

2003-01-01

89

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

PubMed

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. PMID:21469866

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

2011-03-18

90

Influence of blue light spectrum filter on short-wavelength and standard automated perimetries  

Microsoft Academic Search

Purpose: To evaluate the influence of a blue light spectrum filter (BLSF), similar in light spectrum transmittance to the intraocular lens Acrysof NaturalTM, on standard automated perimetry (SAP) and short-wavelength automated perimetry (SWAP). Methods: Twenty young individuals (?30 y.o.), without any systemic or ocular alterations (twenty eyes) underwent a random sequence of four Humphrey visual field tests: standard automated perimetry

Eduardo Sone Soriano; Luiz Alberto; Soares Melo; Augusto Paranhos Jr

91

Calibration of GOES5 and GOES6 VISSR\\/VAS short-wavelength channels  

Microsoft Academic Search

The GOES-5 and GOES-6 VISSR\\/VAS short wavelength channels are calibrated for the periods from October 1983 through July 1984 (GOES-5) and from October 1983 through January 1985 (GOES-6). The White Sands Monument area in New Mexico and space are used as calibration targets. The radiance directed to the satellite from the surface target is computed using a radiative transfer model.

R. Frouin; C. Gautier

1985-01-01

92

Four-Wave Mixing in Photonic Crystal Fibres for Wavelength Conversion in Optical Networks  

E-print Network

Four-Wave Mixing in Photonic Crystal Fibres for Wavelength Conversion in Optical Networks D. J wavelength conversion capability in a pre-determined transmission band. 2. Theory The optical fibre cannot is launched into a fibre, the linearity of the optical response is lost giving rise to diverse non

Haddadi, Hamed

93

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

94

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

95

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

96

Soliton trapping of dispersive waves in photonic crystal fiber with two zero dispersive wavelengths.  

PubMed

Based on the generalized nonlinear Schrödinger equation, we present a numerical study of trapping of dispersive waves by solitons during supercontinuum generation in photonic crystal fibers pumped with femtosecond pulses in the anomalous dispersion region. Numerical simulation results show that the generated supercontinuum is bounded by two branches of dispersive waves, namely blue-shifted dispersive waves (B-DWs) and red-shifted dispersive waves (R-DWs). We find a novel phenomenon that not only B-DWs but also R-DWs can be trapped by solitons across the zero-dispersion wavelength when the group-velocity matching between the soliton and the dispersive wave is satisfied, which may led to the generation of new spectral components via mixing of solitons and dispersive waves. Mixing of solitons with dispersive waves has been shown to play an important role in shaping not only the edge of the supercontinuum, but also its central part around the higher zero-dispersion wavelength. Further, we show that the phenomenon of soliton trapping of dispersive waves in photonic crystal fibers with two zero-dispersion wavelengths has a very close relationship with pumping power and the interval between two zero-dispersion wavelengths. In order to clearly display the evolution of soliton trapping of dispersive waves, the spectrogram of output pulses is observed using cross-correlation frequency-resolved optical gating technique (XFROG). PMID:23669979

Wang, Weibin; Yang, Hua; Tang, Pinghua; Zhao, Chujun; Gao, Jing

2013-05-01

97

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

98

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

NASA Technical Reports Server (NTRS)

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

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

2003-01-01

99

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

100

Multi-wavelength generation by self-seeded four-wave mixing.  

PubMed

A cost effective method of generating multi-wavelength based on the cascaded four wave mixing effect is experimentally demonstrated. The proposed scheme is free from external tunable laser sources and pump modulators, resulting from the use of a broadened linewidth tunable dual wavelength erbium-doped fiber laser as intracavity pump. In this configuration, the number of four wave mixing cascades becomes larger in tandem with the increment of erbium-doped fiber amplifier output power. When its output power is set at 20.57 dBm, six waves having optical signal to noise ratio larger than 10 dB are generated. The six waves are stable with peak power fluctuations less than 1 dB within 30 minutes period and tunable with wavelength spacing ranging from 1.03 nm to 11.31 nm. PMID:23482181

Cholan, N A; Al-Mansoori, M H; Noor, A S M; Ismail, A; Mahdi, M A

2013-03-11

101

FUNGAL DAMAGE DETECTION IN WHEAT USING SHORT-WAVE NEAR-INFRARED HYPERSPECTRAL AND DIGITAL COLOUR IMAGING  

Microsoft Academic Search

Healthy and fungal-damaged wheat kernels infected by the species of storage fungi namely Penicillium spp., Aspergillus glaucus, and A. niger were scanned using short-wave near-infrared hyperspectral imaging system in the 700–1100 nm wavelength range and an area scan colour camera. Multivariate image (MVI) analysis was used to reduce the dimensionality of the hyperspectral data and to select the significant wavelength

C. B. Singh; D. S. Jayas; J. Paliwal; N. D. G. White

2010-01-01

102

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

103

Standing spin waves excited optically across an indirect gap in short graphene nanoribbons  

SciTech Connect

We report theoretical investigations that unveil unique electronic excitations in graphene nanoribbons of \\textit{nanoscale length}. The main point is that electronic states in short nanowires are standing particle-in-a-box-like waves, amenable to excitation by electromagnetic radiation; the unusual electronic and magnetic properties of graphene nanoribbons add another feature: terahertz (THz) radiation induces \\textit{edge standing spin waves} with different wavelengths at the two edges and a resonant frequency that can be controlled by an external gate voltage, opening the possibility of THz-spintronic applications.

Lu, Jun-Qiang [ORNL; Zhang, Xiaoguang [ORNL; Pantelides, Sokrates T. [Vanderbilt University

2009-01-01

104

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

Microsoft Academic Search

The key geological observations and structural interpretations associated with the current plume hypothesis for Venusian crustal plateau formation are that (1) short-wavelength, spatially periodic tectonic structures originated as mechanical instabilities in a regionally extensive surface brittle layer whose basal boundary was thermally generated and controlled; (2) characteristic wavelengths of spatially periodic structures record the brittle layer thickness at the time

Rebecca R. Ghent; Roger J. Phillips; Vicki L. Hansen; Daniel C. Nunes

2005-01-01

105

Impedance match of long-wavelength electromagnetic waves incident into magnetic photonic crystals  

Microsoft Academic Search

By utilizing an effective-medium method, the effective dielectric constant and effective magnetic permeability of magnetic photonic crystals at long-wavelength limits were calculated. We also examined the impedance ratio when a long-wavelength electromagnetic wave is incident to a magnetic photonic crystal. In this work, we focus on investigating the impact of the magnetic permeability of rods forming magnetic photonic crystals on

S. Y. Yang

2007-01-01

106

Short wavelength (visible) quantum well lasers grown by molecular beam epitaxy  

NASA Astrophysics Data System (ADS)

We have fabricated AlGaAs multiple quantum well lasers from a variety of structures grown by molecular beam epitaxy with the objective of achieving operation at a short wavelength with GaAs wells. A series of structures with well widths from 55Å down to 13Å gave pulsed room temperature laser operation at wavelengths from 837nm to 707nm. All the devices operated at longer wavelengths than that calculated for the n=1(e-hh) transition, though from measurements of their electroluminescence spectra at currents as low as 7% of threshold we find no evidence for changes in the sub-band separation at high injection. The threshold current density of a simple broad area MQW device with 160Å wide GaAs wells operating at ?880nm was 1.2kA cm -2 and an analysis of the threshold current density and losses in these device suggests that interface optical scattering is small.

Blood, P.; Fletcher, E. D.; Woodbridge, K.; Hulyer, P. J.

1985-03-01

107

Effects of filtering visual short wavelengths during nocturnal shiftwork on sleep and performance.  

PubMed

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

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

2013-10-01

108

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

109

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

110

Why are very short times so long and very long times so short in elastic waves?  

E-print Network

In a first study of thermoelastic waves, such as on the textbook of Landau and Lifshitz, one might at first glance understand that when the given period is very short, waves are isentropic because heat conduction does not set in, while if the given period is very long waves are isothermal because there is enough time for thermalization to be thoroughly accomplished. When one pursues the study of these waves further, by the mathematical inspection of the complete thermoelastic wave equation he finds that if the period is very short, much shorter than a characteristic time of the material, the wave is isothermal, while if it is very long, much longer than the characteristic time, the wave is isentropic. One also learns that this fact is supported by experiments: at low frequencies the elastic waves are isentropic, while they are isothermal when the frequencies are so high that can be attained in few cases. The authors show that there is no contradiction between the first glance understanding and the mathematical treatment of the elastic wave equation: for thermal effects very long periods are so short and very short periods are so long.

Guido Parravicini; Serena Rigamonti

2010-09-23

111

Why are very short times so long and very long times so short in elastic waves?  

NASA Astrophysics Data System (ADS)

In a first study of thermoelastic waves, such as in the textbook of Landau and Lifshitz, one might at first glance understand that when the given period is very short, waves are isentropic because heat conduction does not set in, while if the given period is very long, waves are isothermal because there is enough time for thermalization to be thoroughly accomplished. When one pursues the study of these waves further, by the mathematical inspection of the complete thermoelastic wave equation one finds that if the period is very short, much shorter than a characteristic time of the material, the wave is isothermal, while if it is very long, much longer than the characteristic time, the wave is isentropic. One also learns that this fact is supported by experiments: at low frequencies the elastic waves are isentropic, while they are isothermal when the frequencies are so high that can be attained in few cases. The authors show that there is no contradiction between first-glance understanding and the mathematical treatment of the elastic wave equation: for thermal effects very long periods are so short and very short periods are so long.

Parravicini, Guido; Rigamonti, Serena

2011-01-01

112

Short wave phase shifts by large free surface solitary waves: Experiments and models  

NASA Astrophysics Data System (ADS)

In this paper, we compare experiments on short gravity wave phase shifting by surface solitary waves to a Wentzel-Kramers-Brillouin-Jeffreys (WKBJ) refraction theory. Both weak interactions (head-on interaction) and strong interactions (overtaking interaction) are examined. We derive a dispersion relation and wave action conservation relation which are similar to the ones obtained for short waves refraction on slowly varying media. The model requires an exact solitary wave solution. To this end, a steady wave solution is numerically computed using the algorithm devised by Byatt-Smith [Proc. R. Soc. London, Ser. A 315, 405 (1970)]. However, two other solitary wave solutions are incorporated in the model, namely the classical Korteweg and De Vries (KdV) [Phil. Mag. 39, 422 (1895)] solution (weakly nonlinear/small amplitude solitary wave) and the Rayleigh [Phil. Mag. 1, 257 (1876)] solution (strongly nonlinear/large amplitude solitary wave). Measurements of the short wave phase shift show better agreement with the theoretical predictions based on the Byatt-Smith numerical solution and the Rayleigh solution rather than the Korteweg and De Vries one for large amplitude solitary waves. Theoretical phase shifts predictions based on Rayleigh and Byatt-Smith numerical solutions agree with the experiments for A/h0?0.5. A new heuristic formula for the phase shift allowing for large amplitude solitary waves is proposed as a limiting case when the short wave wave number increases.

Guizien, Katell; Barthélemy, Eric

2001-12-01

113

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

1991-01-01

114

A 4-way wavelength demultiplexer based on the plasmonic broadband slow wave system.  

PubMed

We propose a broadband slow wave system based on the thin metal-insulator-metal (MIM) graded grating structure composed of two corrugated metal strips with periodic array of grooves on a thin dielectric substrate. The guided spoof surface plasmon polaritons (SSPPs) at different frequencies can be localized at different positions along the ultrathin MIM grating. By introducing specially designed non-corrugated MIM branches with specific lengths at the locations where the EM waves are trapped, the trapped EM waves can be released and propagate along these branches. A 4-way wavelength demultiplexer based on such plasmonic broadband slow wave system is then demonstrated and fabricated. To improve the isolations between different branches at lower frequencies, band-reject filters are inserted at the front of some MIM branches. The measurements and the simulation results have shown very good agreements, which validate the feasibility of the 4-way wavelength demultiplexer. PMID:25321538

Zhou, Yong Jin; Yang, Bao Jia

2014-09-01

115

On the design of coaxial coupler having multi-section short transformer for compact sized power helix travelling wave tubes  

Microsoft Academic Search

Summary form only given. A coaxial coupler, used for the extraction of microwave power from broadband compact power helix traveling wave tubes (TWTs) consists of a multi-section short transformer and a rf window assembly. For such tubes multi-section ?\\/4 (?: wavelength) transformers are not feasible and in place multi-section short transformers (section length less than ?\\/4) have to be used,

A. K. Sinha; V. V. P. Singh; V. Srivastava; S. N. Joshi

2000-01-01

116

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

117

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

PubMed Central

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

Kessel, Line; Larsen, Michael

2015-01-01

118

Present status of short-wavelength group-III nitride-based laser diodes  

NASA Astrophysics Data System (ADS)

The continuous-wave (CW) operation of InGaN multi-quantum- well-structure laser diodes (LDs) was demonstrated at room temperature (RT) with a lifetime of 35 hours. The threshold current and the voltage of the LDs were 80 mA and 5.5 V, respectively. The threshold current density was 3.6 kA/cm2. Longitudinal modes with a mode separation of 0.042 nm were observed under CW operation at RT. When the temperature of the LDs was varied, large mode hopping of the emission wavelength was observed. The peak wavelength also showed mode hopping toward higher energy with increasing operating current. Each single-mode laser emission was located at a peak of each periodic subband emission. These periodic subband emissions probably result from the transitions between the subband energy levels of the InGaN quantum dots formed from In-rich regions in the InGaN well layers. The carrier lifetime and the threshold carrier density were estimated to be 10 ns and 2 X 1020/cm3, respectively. The beam full width at half- power values for the parallel and the perpendicular near- field patterns were 1.6 micrometers and 0.8 micrometers , respectively. Those of the far-field patterns were 6.8 degrees and 33.6 degrees, respectively.

Nakamura, Shuji

1997-06-01

119

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

USGS Publications Warehouse

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

Blakely, R.J.

1979-01-01

120

High detectivity short-wavelength II-VI quantum cascade detector  

SciTech Connect

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?×?10{sup 10?}cm ?Hz/W. Comparison of background illuminated and dark current-voltage measurements demonstrates a BLIP temperature of 200?K. The device differential resistance-area product, decreases from about 10{sup 6} ? cm{sup 2} at 80?K to about 8000 ? cm{sup 2} at 300?K, indicative of the ultra-low Johnson noise in the detectors.

Ravikumar, Arvind P., E-mail: aravikum@princeton.edu; Gmachl, Claire F. [Department of Electrical Engineering, Princeton University, Princeton, New Jersey 08544 (United States); Garcia, Thor A.; Tamargo, Maria C. [Department of Chemistry, The Graduate Center and The City College of New York, CUNY, New York, New York 10031 (United States); Jesus, Joel De [Department of Physics, The Graduate Center and The City College of New York, CUNY, New York, New York 10031 (United States)

2014-08-11

121

Extraordinarily low evolutionary rates of short wavelength-sensitive opsin pseudogenes  

PubMed Central

Aquatic organisms such as cichlids, coelacanths, seals, and cetaceans are active in UV-blue color environments, but many of them mysteriously lost their abilities to detect these colors. The loss of these functions is a consequence of the pseudogenization of their short wavelength-sensitive (SWS1) opsin genes without gene duplication. We show that the SWS1 gene (BdenS1?) of the deep-sea fish, pearleye (Benthalbella dentata), became a pseudogene in a similar fashion about 130 million years ago (Mya) yet it is still transcribed. The rates of nucleotide substitution (~1.4 × 10?9 /site/year) of the pseudogenes of these aquatic species as well as some prosimian and bat species are much smaller than the previous estimates for the globin and immunoglobulin pseudogenes. PMID:24125953

Yokoyama, Shozo; Starmer, William T.; Liu, Yang; Tada, Takashi; Britt, Lyle

2013-01-01

122

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

NASA Astrophysics Data System (ADS)

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. APLRAAN1050-294710.1103/PhysRevA.64.013409 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; Falcão-Filho, Edilson L.; Kärtner, Franz X.

2011-07-01

123

Plasma treatment for restoration of dielectric multilayer mirrors in short-wavelength free-electron lasers.  

PubMed

Dielectric multilayer mirrors, degraded through irradiation by high-energy undulator radiation, were successfully restored by surface treatment with RF-induced O(2) plasma. The mirror loss, which had been increased up to ~1000 parts in 10(6) (ppm) through the mirror degradation, was drastically reduced to ~100 ppm during the treatment. Such a mirror-restoration technique has been desired especially in short-wavelength free-electron lasers (FEL's), because the laser gain is so small that even a mirror loss as small as ~1000 ppm interferes with the FEL oscillation. The mirror degradation is most likely caused by the deposition and doping of carbon atoms onto the dielectric surface. The surface analysis by the x-ray photoelectron spectroscopy revealed that the plasma treatment effectively removed the carbon contamination covering the mirror surfaces without serious surface damage by high-energy particles from the plasma. PMID:21052254

Yamada, K; Yamazaki, T; Shimizu, T; Sei, N; Mikado, T

1995-07-20

124

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

125

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

NASA Astrophysics Data System (ADS)

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

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

2015-02-01

126

Short-wavelength cone-opponent retinal ganglion cells in mammals  

PubMed Central

In all of the mammalian species studied to date, the short-wavelength-sensitive (S) cones and the S-cone bipolar cells that receive their input are very similar, but the retinal ganglion cells that receive synapses from the S-cone bipolar cells appear to be quite different. Here, we review the literature on mammalian retinal ganglion cells that respond selectively to stimulation of S-cones and respond with opposite polarity to longer wavelength stimuli. There are at least three basic mechanisms to generate these color-opponent responses, including: (1) opponency is generated in the outer plexiform layer by horizontal cells and is conveyed to the ganglion cells via S-cone bipolar cells, (2) inputs from bipolar cells with different cone inputs and opposite response polarity converge directly on the ganglion cells, and (3) inputs from S-cone bipolar cells are inverted by S-cone amacrine cells. These are not mutually exclusive; some mammalian ganglion cells that respond selectively to S-cone stimulation seem to utilize at least two of them. Based on these findings, we suggest that the small bistratified ganglion cells described in primates are not the ancestral type, as proposed previously. Instead, the known types of ganglion cells in this pathway evolved from monostratified ancestral types and became bistratified in some mammalian lineages. PMID:24759445

MARSHAK, DAVID W.; MILLS, STEPHEN L.

2014-01-01

127

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

128

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

PubMed

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

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

2015-03-01

129

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

130

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

NASA Astrophysics Data System (ADS)

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.

Tadesse, Semere Ayalew; Li, Mo

2014-11-01

131

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

132

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

133

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

134

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

135

Long-Wavelength Elastic Wave Propagation Across Naturally Fractured Rock Masses  

NASA Astrophysics Data System (ADS)

Geophysical site investigation techniques based on elastic waves have been widely used to characterize rock masses. However, characterizing jointed rock masses by using such techniques remains challenging because of a lack of knowledge about elastic wave propagation in multi-jointed rock masses. In this paper, the roughness of naturally fractured rock joint surfaces is estimated by using a three-dimensional (3D) image-processing technique. The classification of the joint roughness coefficient (JRC) is enhanced by introducing the scan line technique. The peak-to-valley height is selected as a key indicator for JRC classification. Long-wavelength P-wave and torsional S-wave propagation across rock masses containing naturally fractured joints are simulated through the quasi-static resonant column (QSRC) test. In general, as the JRC increases, the S-wave velocity increases within the range of stress levels considered in this paper, whereas the P-wave velocity and the damping ratio of the shear wave decrease. In particular, the two-dimensional joint specimen underestimates the S-wave velocity while overestimating the P-wave velocity. This suggests that 3D joint surfaces should be implicated to obtain the reliable elastic wave velocity in jointed rock masses. The contact characteristic and degree of roughness and waviness of the joint surface are identified as a factor influencing P-wave and S-wave propagation in multi-jointed rock masses. The results indicate a need for a better understanding of the sensitivity of contact area alterations to the elastic wave velocity induced by changes in normal stress. This paper's framework can be a reference for future research on elastic wave propagation in naturally multi-jointed rock masses.

Mohd-Nordin, Mohd Mustaqim; Song, Ki-Il; Cho, Gye-Chun; Mohamed, Zainab

2014-03-01

136

Impedance match of long-wavelength electromagnetic waves incident into magnetic photonic crystals.  

PubMed

By utilizing an effective-medium method, the effective dielectric constant and effective magnetic permeability of magnetic photonic crystals at long-wavelength limits were calculated. We also examined the impedance ratio when a long-wavelength electromagnetic wave is incident to a magnetic photonic crystal. In this work, we focus on investigating the impact of the magnetic permeability of rods forming magnetic photonic crystals on the impedance ratio. Furthermore, we analyze the dependencies of the incident angle at impedance match on the magnetic permeability and filling factor of rods. PMID:19547092

Yang, S Y

2007-06-11

137

Impedance match of long-wavelength electromagnetic waves incident into magnetic photonic crystals  

NASA Astrophysics Data System (ADS)

By utilizing an effective-medium method, the effective dielectric constant and effective magnetic permeability of magnetic photonic crystals at long-wavelength limits were calculated. We also examined the impedance ratio when a long-wavelength electromagnetic wave is incident to a magnetic photonic crystal. In this work, we focus on investigating the impact of the magnetic permeability of rods forming magnetic photonic crystals on the impedance ratio. Furthermore, we analyze the dependencies of the incident angle at impedance match on the magnetic permeability and filling factor of rods.

Yang, S. Y.

2007-06-01

138

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

139

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

NASA Astrophysics Data System (ADS)

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

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

2013-11-01

140

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

NASA Astrophysics Data System (ADS)

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

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

2012-09-01

141

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

142

Diffractive Short Pulse Asymptotics for Nonlinear Wave Equations  

E-print Network

Diffractive Short Pulse Asymptotics for Nonlinear Wave Equations Deborah ALTERMAN \\Lambda pulses. In a separate paper the equations used to construct the approximate solutions are derived using the slowly varying amplitude assumption. These lasers typically pass a point in times measured

Rauch, Jeffrey

143

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

PubMed Central

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

144

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

145

The Whistler Anisotropy Instability and the Inverse Cascade of Short-Wavelength Turbulence  

NASA Astrophysics Data System (ADS)

Three-dimensional electromagnetic (EM) particle-in-cell (PIC) simulations are carried out within a domain of scale 102.4 times the electron inertial length (c/?e) in each dimension, and with Debye length resolution. Electrons as well as ions are represented as macro-particles, and a steady state magnetic field (B0) is imposed along a single principal axis in order to emulate a collisionless, homogeneous, magnetized plasma. Initial conditions are placed on the electrons such that Te?>Te?, where the subscripts ? and ? denote directions relative to B0. The intention for applying such initial conditions is to induce the whistler anisotropy plasma instability and to observe the evolution of the whistler turbulence that ensues. The results reveal that at onset of the instability fluctuations grow rapidly at wavenumbers (k) such that kc/?e?1 and have a strong preference to propagate along the magnetic field lines (k??0). As the simulation proceeds, magnetic fluctuation energy is transferred from these wavevectors toward much smaller k, indicating an inverse cascade process. In this long wavelength regime, the waves propagate primarily across the magnetic field lines (k?>>k?). Finally, at late times, the bulk of the fluctuation energy splits into two regimes. Magnetic fluctuation spectra are both elongated and contracted as the fluctuation energy at k? c/?e?1 gradually shifts to both k? c/?e>1 and k? c/?e<1.

Hughes, R. S.; Gary, S. P.; Wang, J.; Chang, O.

2013-12-01

146

Demonstration of guided-wave phenomena at extreme-ultraviolet and soft-x-ray wavelengths  

Microsoft Academic Search

We report an explicit demonstration of classical guided-wave propagation at XUV and soft-x-ray wavelengths. Experiments were performed using narrow-band synchrotron radiation at 5, 20.8, 21, and 30 nm. Free-standing gold transmission gratings served as waveguide structures. These structures had a 300-nm grating period with waveguide channel widths as small as 100 nm and were as thick as 700 nm in

Natale M. Ceglio; A. M. Hawryluk; D. G. Stearns; M. Kuehne; P. Muller

1988-01-01

147

Demonstration of guided-wave phenomena at extreme-ultraviolet and soft-X-ray wavelengths  

Microsoft Academic Search

An explicit demonstration of classical guided-wave propagation at XUV and soft-X-ray wavelengths is presented. Experiments were performed using narrow-band synchrotron radiation at 5, 20.8, 21, and 30 nm. Free-standing gold transmission gratings served as waveguide structures. These structures had a 300-nm grating period with waveguide channel widths as small as 100 nm, and were as thick as 700 nm in

N. M. Ceglio; A. M. Hawryluk; D. G. Stearns; M. Kuehne; P. Mueller

1988-01-01

148

Morphological changes of short-wavelength cones in the developing S334ter-3 Transgenic rat  

PubMed Central

The S334ter-3 rat is a transgenic model of retinal degeneration (RD) developed to express a rhodopsin mutation similar to that found in human retinitis pigmentosa. Due to this advantage over other models of RD, a few retina transplant studies have been reported on this animal model. Currently, no information is available on cone photoreceptor changes that occur in the S334ter RD model. In this study, we investigated the effect of RD on the morphology, distribution, and synaptic connectivity of short-wavelength cones (S-cones) during development of S334ter-3 rat retinas. At P21 RD retinas, the outer-nuclear layer was significantly narrower, while S-cones showed shortening of their segments and axons compared to control retinas. From P90 onward, S-opsin-immunoreactive cells appeared at the outer margin of the inner-nuclear layer of RD retinas. Double-labelling experiments showed these cells contained recoverin and cone arrestin. Furthermore, ultra-structure study showed that synaptic ribbons are conserved in the S-cone at P180 RD retinas. Although cell density of S-cones significantly dropped after P90, survival rates depended on the retinal region. Overall, the S334ter-3 RD model shows hallmarks of cone remodelling due to photoreceptor degeneration. PMID:20114037

Hombrebueno, Jose R.; Tsai, Melody M.; Kim, Hong-Lim; De Juan, Joaquin; Grzywacz, Norberto M.; Lee, Eun-Jin

2010-01-01

149

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; Müller, Johannes; Chang, Belinda SW

2006-01-01

150

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

151

A microsphere-based short-wavelength recombination x-ray laser  

SciTech Connect

We describe a scheme for obtaining very short wavelengths ({lambda} {similar to} 10{Angstrom}) in recombination lasers. The rapid cooling rates necessary to achieve population inversion during recombination are attained by adiabatic expansion of sub micron spheres. The lasing region is made up of many such spheres. The spheres are heated impulsively by a powerful picosecond laser. First, they ionize, then as they expand, they cool and recombine. We have calculated the optimum sphere size and initial temperature for maximum gain in the n = 3 to n = 2 transition of hydrogen-like ions of elements with atomic numbers, Z, between 10 and 30. Gain of about 10{sup 3}cm{sup {minus}1} is calculated in aluminum at 38.8{Angstrom}. Gain rapidly decreases with Z so that gain in titanium at 13.6{Angstrom} is about 40 cm{minus}1. We have calculated the required pump laser intensity and found it to be attainable with current lasers. The propagation of the pump through the gas'' of spheres is considered and the problems arising from pump scattering by the spheres are discussed.

Valeo, E.J.; Cowley, S.C.

1992-04-01

152

A microsphere-based short-wavelength recombination x-ray laser  

SciTech Connect

We describe a scheme for obtaining very short wavelengths ({lambda} {similar_to} 10{Angstrom}) in recombination lasers. The rapid cooling rates necessary to achieve population inversion during recombination are attained by adiabatic expansion of sub micron spheres. The lasing region is made up of many such spheres. The spheres are heated impulsively by a powerful picosecond laser. First, they ionize, then as they expand, they cool and recombine. We have calculated the optimum sphere size and initial temperature for maximum gain in the n = 3 to n = 2 transition of hydrogen-like ions of elements with atomic numbers, Z, between 10 and 30. Gain of about 10{sup 3}cm{sup {minus}1} is calculated in aluminum at 38.8{Angstrom}. Gain rapidly decreases with Z so that gain in titanium at 13.6{Angstrom} is about 40 cm{minus}1. We have calculated the required pump laser intensity and found it to be attainable with current lasers. The propagation of the pump through the ``gas`` of spheres is considered and the problems arising from pump scattering by the spheres are discussed.

Valeo, E.J.; Cowley, S.C.

1992-04-01

153

VANISHING VISCOSITY WITH SHORT WAVE LONG WAVE INTERACTIONS FOR SYSTEMS OF CONSERVATION LAWS  

E-print Network

VANISHING VISCOSITY WITH SHORT WAVE LONG WAVE INTERACTIONS FOR SYSTEMS OF CONSERVATION LAWS JO systems of conservation laws. We prove the strong convergence of the solutions of the vanishing viscosity laws. For all these models we study the convergence of the vanishing viscosity method. In general

154

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

PubMed

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

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

2005-07-01

155

Increasing robustness of indirect drive capsule designs against short wavelength hydrodynamic instabilities  

SciTech Connect

Target designs are described that are meant to achieve ignition on the National Ignition Facility. Simulations of recent indirect drive cryogenic capsule designs indicate dramatically reduced growth of short wavelength hydrodynamic instabilities, resulting from two changes in the designs. First, better optimization results from systematic mapping of the ignition target performance over the parameter space of ablator and DT-ice thickness combinations, using techniques developed by one of us (Herrmann). After the space is mapped with one-dimensional simulations, exploration of it with two-dimensional simulations quantifies the dependence of instability growth on target dimensions. Low modes and high modes grow differently in different regions of the space, allowing a trade-off of the two regimes of growth. Significant improvement in high-mode stability can be achieved, relative to previous designs, with only insignificant increase in low-mode growth. This procedure produces capsule designs that, in simulations, tolerate several times the surface roughness that could be tolerated by capsules optimized by older more heuristic techniques. Another significant reduction in instability growth, by another factor of several, is achieved with ablators with 'graded dopants.' In this type of capsule the mid-Z dopant, which is needed in the ablator to minimize x-ray preheat at the ablator-ice interface, is optimally positioned within the ablator. A fabrication scenario for graded dopants already exists, using sputter coating to fabricate the ablator shell. We describe the systematics of these advances in capsule design, discuss the basis behind their improved performance, and summarize how this is affecting our plans for NIF ignition.

Haan, S W; Herrmann, M C; Dittrich, T R; Fetterman, A J; Marinak, M M; Munro, D; Pollaine, S M; Salmonson, J D; Strobel, G L; Suter, L J

2004-11-12

156

Fungal Damage Detection in Wheat Using Short-Wave Near-Infrared Hyperspectral and Digital Colour Imaging  

Microsoft Academic Search

Healthy and fungal-damaged wheat kernels infected by the species of storage fungi, namely Penicillium spp., Aspergillus glaucus, and A. niger, were scanned using a short-wave near-infrared hyperspectral imaging system in the 700–1100 nm wavelength range and an area scan colour camera. A multivariate image analysis was used to reduce the dimensionality of the hyperspectral data and to select the significant

C. B. Singh; D. S. Jayas; J. Paliwal; N. D. G. White

2012-01-01

157

A study of short wave instability on vortex filaments  

SciTech Connect

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

Wang, Hong Yun

1996-12-01

158

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

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

159

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

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

160

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

161

Dual-wavelength operation of continuous-wave and mode-locked erbium-doped fiber lasers  

NASA Astrophysics Data System (ADS)

We study numerically and experimentally multiple-wavelength operation of an erbium-doped figure-eight fiber laser including a multiple-bandpass optical filter formed by two concatenated fiber tapers. Both continuous-wave and pulsed operations are considered. In the continuous-wave regime, stable long-term operation at multiple closely spaced wavelengths is only obtained if fine adjustments of the cavity losses are performed. Under these conditions, simultaneous lasing at up to four wavelengths separated by 1.5 nm was observed experimentally. Tunable single-wavelength operation over more than 20 nm is also observed in the continuous-wave regime. In the passive mode locking regime, numerical simulations indicate that mechanisms involving the filter losses and the nonlinear transmission characteristic of the NOLM contribute in principle to stabilize dual-wavelength operation, allowing less demanding cavity loss adjustments. In this regime, the problem of synchronization between the pulse trains generated at each wavelength adds an additional dimension to the problem. In presence of cavity dispersion, the pulses at each wavelength tend to be asynchronous if the wavelength separation is large, however they can be synchronous in the case of closely spaced wavelengths, if cross-phase modulation is able to compensate for the dispersion-induced walkoff. Experimentally, fundamental and 2nd-order harmonic mode locking was observed, characterized by the generation of noise-like pulses. Finally, a regime of multi-wavelength passive Q-switching was also observed. We believe that this work will be helpful to guide the design of multiple-wavelength fiber laser sources, which are attractive for a wide range of applications including Wavelength Division Multiplexing transmissions, signal processing and sensing.

Pottiez, O.; Martinez-Rios, A.; Monzon-Hernandez, D.; Ibarra-Escamilla, B.; Kuzin, E. A.; Hernandez-Garcia, J. C.

2012-06-01

162

Influence of laser photocoagulation for clinically significant diabetic macular oedema (DMO) on short-wavelength and conventional automated perimetry  

Microsoft Academic Search

Summary   The aim of the study was to determine the effect of laser photocoagulation for clinically significant diabetic macular oedema\\u000a (DMO) on macular visual function as assessed by conventional and short-wavelength automated static threshold perimetry. The\\u000a sample comprised 24 patients who required laser photocoagulation for clinically significant DMO (mean age 59.75 years, range\\u000a 45–75 years). One eye of each patient

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

1998-01-01

163

Photonic crystal fibre enables short-wavelength two-photon laser scanning fluorescence microscopy with fura-2  

NASA Astrophysics Data System (ADS)

We report on a novel and compact reliable laser source capable of short-wavelength two-photon laser scanning fluorescence microscopy based on soliton self-frequency shift effects in photonic crystal fibre. We demonstrate the function of the system by performing two-photon microscopy of smooth muscle cells and cardiac myocytes from the rat pulmonary vein and Chinese hamster ovary cells loaded with the fluorescent calcium indicator fura-2/AM.

McConnell, Gail; Riis, Erling

2004-10-01

164

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

SciTech Connect

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

Shimamura, Kohei; Kawamura, Koichi; Fukuda, Akio; Wang Bin; Yamaguchi, Toshikazu; Komurasaki, Kimiya [Department of Advanced Energy, University of Tokyo, 5-1-5 Kashiwa-no-ha, Kashiwa, Chiba 277-8561 (Japan); Hatai, Keigo; Fukui, Akihiro; Arakawa, Yoshihiro [Department of Aeronautics and Astronautics, University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-8656 (Japan)

2011-04-15

165

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

166

SHORT-WAVELENGTH TECHNOLOGY AND THE POTENTIAL FOR DISTRIBUTED NETWORKS OF SMALL RADAR SYSTEMS  

E-print Network

, Kelvin Droegemeierc , Sandra Cruz-Pold , Francesc Junyentb , Jerald Brotzgec , David Westbrooka , Nitin to significant improvement in the short-range forecasting and warning of severe thunderstorms, tornadoes

Droegemeier, Kelvin K.

167

Effect of nonlinear optical three-wave interaction on the lasing parameters of a dual-wavelength vertical-external-cavity surface-emitting laser  

SciTech Connect

The influence of nonlinear optical interaction in a semiconductor dual-wavelength vertical-external-cavity surface-emitting laser on the main parameters of dual-wavelength radiation and lasing in the long-wavelength part of the mid-IR range, obtained in this laser as a result of nonlinear wave mixing, is investigated. An increase in the pump power leads to saturation of the short-wavelength lasing intensity and to a more rapid rise in the long-wavelength lasing intensity in comparison with the linear increase in lasing intensity in these regions in the absence of nonlinear interaction. Under the conditions of nonlinear interaction, the carrier concentration in the active layers is not stabilised near the lasing threshold but changes with an increase in the pump intensity and provides the corresponding gain in the laser active region, thus maintaining steadystate lasing. Some ways for modifying the laser active region in order to obtain the most efficient lasing in the mid-IR range are proposed. (nonlinear optical phenomena)

Morozov, M Yu; Morozov, Yu A [Kotel'nikov Institute of Radio Engineering and Electronics, Russian Academy of Sciences, Saratov Branch, Saratov (Russian Federation); Krasnikova, I V [Yu A Gagarin Saratov State Technical University, Saratov (Russian Federation)

2013-09-30

168

Standing Waves in a Two-Dimensional Reaction-Diffusion Model with the Short-Wave Instability  

E-print Network

Standing Waves in a Two-Dimensional Reaction-Diffusion Model with the Short-Wave Instability Milos 25, 1998; In Final Form: October 19, 1998 Various patterns of standing waves are found beyond with rotational symmetry in systems with circular geometry. We also find standing waves consisting of periodic

Epstein, Irving R.

169

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

E-print Network

the infrared down to 80 nanometers. Several devices have even achieved laser saturation at gain levels and medical diagnostics. Rapid progress was driven by improvements in the technology of electron storage rings with the periodicity of the radiation wavelength ph by a resonant process taking place in the combined presence

170

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

PubMed

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

Yoon, H W; Eppeldauer, G P

2008-01-21

171

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

172

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

173

Simulations of the OSNR and laser linewidth limits for reliable wavelength conversion of DQPSK signals using four-wave mixing  

NASA Astrophysics Data System (ADS)

We calculate the pump laser linewidths required to achieve specific system performance when undertaking wavelength conversion of DQPSK data signals at 10 and 25 Gbaud using four-wave mixing in a semiconductor optical amplifier. The results highlight the class of laser that can be used to implement this scheme. We show that the limits are consistent with expected theories and indicate guidelines for implementing multiple wavelength conversions using this scheme in an optical network.

Naimi, Sepideh T.; Dúill, Seán Ó.; Barry, Liam P.

2014-01-01

174

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

175

Demonstration of the echo-enabled harmonic generation technique for short-wavelength seeded free electron lasers.  

PubMed

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. PMID:20867575

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

2010-09-10

176

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

177

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

NASA Astrophysics Data System (ADS)

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

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

2007-02-01

178

A short-wavelength measurement of the cosmic background radiation anisotropy  

SciTech Connect

The results of a measurement of the cosmic microwave background (CMB) anisotropy at wavelengths between 0.4 and 2 mm, carried out using a balloon-borne 1.2 m telescope, are reported. A high Galactic latitude region about 15 deg wide with a 25 arcmin FWHM beam, switching in the sky with an amplitude of 108 arcmin, was observed. A sky signal correlated with the 100-micron diffuse emission mapped by the IRAS satellite was detected and used for calibration. After removal of this contribution, the residual intensity fluctuations give an upper limit to the anisotropy of the CMB at an equivalent frequency of 9.0/cm. 17 refs.

De Bernardis, P.; Amicone, L.; De Luca, A.; De Petris, M.; Epifani, M. (Roma I Universita, Rome (Italy))

1990-09-01

179

Aging of human short-wave cone pathways  

PubMed Central

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

Shinomori, Keizo; Werner, John S.

2012-01-01

180

Continuous wave-pumped wavelength conversion in low-loss silicon nitride waveguides.  

PubMed

In this Letter we introduce a complementary metal-oxide semiconductor (CMOS)-compatible low-loss Si3N4 waveguide platform for nonlinear integrated optics. The waveguide has a moderate nonlinear coefficient of 285??W/km, but the achieved propagation loss of only 0.06??dB/cm and the ability to handle high optical power facilitate an optimal waveguide length for wavelength conversion. We observe a constant quadratic dependence of the four-wave mixing (FWM) process on the continuous-wave (CW) pump when operating in the C-band, which indicates that the waveguide has negligible high-power constraints owing to nonlinear losses. We achieve a conversion efficiency of -26.1??dB and idler power generation of -19.6??dBm. With these characteristics, we present for the first time, to the best of our knowledge, CW-pumped data conversion in a non-resonant Si3N4 waveguide. PMID:25768135

Krückel, Clemens J; Torres-Company, Víctor; Andrekson, Peter A; Spencer, Daryl T; Bauters, Jared F; Heck, Martijn J R; Bowers, John E

2015-03-15

181

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

PubMed

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

Kanna, T; Vijayajayanthi, M; Lakshmanan, M

2014-10-01

182

Experimental realization of multi, zero, dual order and achromatic gypsum wave plate in a wavelength range 400-1000 nm  

NASA Astrophysics Data System (ADS)

In a wide wavelength range (400-1000 nm), the birefringence channeled spectra produced from interference of polarized white light is used to extract the birefringence ?n of gypsum crystal. In the same spectral range, the dispersion of gypsum birefringence is extracted and fitted to Cauchy dispersion function with relative error in finding ?n of an order 2×10-4. The calculated retardation introduced by gypsum crystal confirms that gypsum plate of thickness ?2 mm can act as a multiple order half and quarter wave plate for most of Ar+, Kr and He-Ne laser lines. Zero order full, half and quarter wave plate are experimentally realized at 675 nm, 633 nm and 633 nm, respectively. In addition, a dual wavelength quarter wave plate working at 550 nm and 930 nm is also experimentally obtained. Finally, in the same spectral range quarter and half achromatic wave plate are practically realized by combining gypsum with MgF2 crystal.

Emam-Ismail, M.

2013-04-01

183

Short-wavelength infrared (1.3-2.6 ??m) observations of the nucleus of Comet 19P/Borrelly  

USGS Publications Warehouse

During the last two minutes before closest approach of Deep Space 1 to Comet 19P/Borrelly, a long exposure was made with the short-wavelength infrared (SWIR) imaging spectrometer. The observation yielded 46 spectra covering 1.3-2.6 ??m; the footprint of each spectrum was ???160 m ?? width of the nucleus. Borrelly's highly variegated and extremely dark 8-km-long nucleus exhibits a strong red slope in its short-wavelength infrared reflection spectrum. This slope is equivalent to J-K and H-K colors of ???0.82 and ???0.43, respectively. Between 2.3-2.6 ??m thermal emission is clearly detectable in most of the spectra. These data show the nucleus surface to be hot and dry; no trace of H2O ice was detected. The surface temperature ranged continuously across the nucleus from ???300 K near the terminator to a maximum of ???340 K, the expected sub-solar equilibrium temperature for a slowly rotating body. A single absorption band at ???2.39 ??m is quite evident in all of the spectra and resembles features seen in nitrogen-bearing organic molecules that are reasonable candidates for compositional components of cometary nuclei. However as of yet the source of this band is unknown. ?? 2003 Elsevier Inc. All rights reserved.

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

2004-01-01

184

Efficient large-frequency-shifted three-wave mixing in low dispersion wavelength region in single-mode optical fibre  

Microsoft Academic Search

Three-wave mixing in a single-mode fibre, capable of generating intense emission at multiple wavelengths with large equidistant frequency separation, is reported. The experimental setup is described, and the relevant experimental results are presented. Certain modifications are proposed for expanding tunability and spectral range.

K. Washio; K. Inoue; S. Kishida

1980-01-01

185

Highly coherent red-shifted dispersive wave generation around 1.3 ?m for efficient wavelength conversion  

NASA Astrophysics Data System (ADS)

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

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

2015-03-01

186

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

187

Chemical composition of high proper-motion stars based on short-wavelength optical spectra  

NASA Astrophysics Data System (ADS)

The results of spectroscopic observations made with the NES echelle spectrograph of the 6-m BTA telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences in the wavelength interval of 3550-5100 Å with a spectral resolution of R?50000 are used to determine the fundamental parameters and atmospheric abundances of more than 20 chemical elements including heavy s- and r-process elements from Sr to Dy for a total of 14 metal-poor G-K-type stars. The abundances of Mg, Al, Sr, and Ba were calculated with non-LTE line-formation effects accounted for. The inferred overabundance of europium with respect to iron agrees with the results obtained for the stars of similar metallicity. The chemical composition of the star BD+80°245 located far from the Galactic plane is typical of stars of the accreted halo: this star exhibits, in addition to the over-deficiency of ?-process elements, also the over-deficiency of the ?-process element Ba: [Ba/Fe]= -1.46. The kinematical parameters and chemical composition imply that the stars studied belong to different Galactic populations. The abundance of the long-living element Th relative to that of the r-process element Eu is determined for six stars using the synthetic-spectrum method.

Klochkova, V. G.; Mishenina, T. V.; Panchuk, V. E.; Korotin, S. A.; Marsakov, V. A.; Usenko, I. A.; Tsymbal, V. V.

2011-01-01

188

Wave Characteristics of Large-Diameter, High-Density Helicon Plasma with Short Axial Length  

NASA Astrophysics Data System (ADS)

We have developed a large-diameter (73.8 cm) helicon device with an axial length of 486 cm that utilizes a flat spiral antenna at ISAS/JAXA [1]. It has been realized that a shorter axial length is desirable in certain applications. Therefore, the axial length has been shortened in a range of 12 to 123 cm by installing a movable termination plate. Even with very short axial length, the plasma density can exceed 10^12 cm-3 (pAr = 0.75 mTorr) with the input rf power of less than 4 kW, showing a rather high plasma production efficiency. When the axial length is relatively longer, the excitation of the higher order radial eigenmodes is found to be correlated with the magnetic field configuration and the radial density profile. When the axial length is further shortened, the axial wave structure tends to become standing wave like, where its wavelength depends on the plasma density and axial length as is expected. The details of the experimental results will be discussed in the presentation. [1] S. Shinohara and T. Tanikawa, Rev. Sci. Instrum. 75, 1941 (2004) & Phys. Plasmas 12, 044502 (2005).

Motomura, Taisei; Tanaka, Kenji; Murakami, Katsuhiko; Shinohara, Shunjiro; Tanikawa, Takao; Konstantin, Shamrai

2008-11-01

189

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.

2014-12-01

190

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

191

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 LiB(3)O(5) (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

192

Doppler ducting of short-period gravity waves by midlatitude tidal wind structure  

E-print Network

. Snively,1 Victor P. Pasko,1 Michael J. Taylor,2 and Wayne K. Hocking3 Received 2 June 2006; revised 30, and W. K. Hocking (2007), Doppler ducting of short-period gravity waves by midlatitude tidal wind examples of short period gravity waves have been reported [e.g., Taylor et al., 1995; Smith et al., 2003

Pasko, Victor

193

Enhanced intermodal four-wave mixing for visible and near-infrared wavelength generation in a photonic crystal fiber.  

PubMed

We demonstrate experimentally an enhanced intermodal four-wave mixing (FWM) process through coupling positively chirped femtosecond pulses into the deeply normal dispersion region of the fundamental mode of an in-house fabricated photonic crystal fiber (PCF). In the intermodal phase-matching scheme, the energy of the pump waves at 800 nm in the fundamental mode is efficiently converted into the anti-Stokes waves around 553 nm and the Stokes waves within the wavelength range of 1445-1586 nm in the second-order mode. The maximum conversion efficiency of ?as and ?s of anti-Stokes and Stokes waves can be up to 21% and 16%, respectively. The Stokes frequency shift ? is 5580??cm-1. The fiber bending and intermodal walk-off effect of pulses do not have significant influence on the nonlinear optical process. PMID:25831327

Yuan, Jinhui; Sang, Xinzhu; Wu, Qiang; Zhou, Guiyao; Li, Feng; Zhou, Xian; Yu, Chongxiu; Wang, Kuiru; Yan, Binbin; Han, Ying; Tam, Hwa Yaw; Wai, P K A

2015-04-01

194

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

195

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

196

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

2015-02-01

197

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

198

Ways and peculiarities of submillimeter wavelength detection with short-channel field-effect transistors  

SciTech Connect

The detection properties of some short-channel field-effect transistors (FETs) have been analyzed using the steady-state output characteristics of these devices. The calculated dependences of voltage-power sensitivity on applied voltage are compared with the corresponding curves obtained from high-frequency measurements. It is shown that the nonmonotonic dependence of the FET photosensitivity on gate voltage that is observed in the frequency range of 400-750 GHz is not related to resonant excitation of 2D plasmons in the subgate plasma but is due to the change in the distribution of stationary fields in the structure and, as a result, to the change in the efficiency of nonresonant nonlinearity procedures in the transistor's electron subsystem with an increase in the gate-channel voltage. This conclusion is confirmed by analysis of the frequency dependences of photoresponse in the range under consideration, which do not exhibit resonant behavior at the frequencies corresponding to the peaks in the curves measured at a fixed frequency and different gate voltages.

Orlov, M. L., E-mail: orlovm@ipm.sci-nnov.ru; Panin, A. N.; Orlov, L. K. [Russian Academy of Sciences, Institute for Physics of Microstructures (Russian Federation)

2009-06-15

199

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

E-print Network

165 Measurements of Short Ocean Waves during the MBL ARI West Coast Experiment Jochen Klinke 1 of the oceanic capillary waves. Estimates of the equilibrium spectra oceanic capillary-gravity and capillary. In order to gain deeper insight into the dynamics and the energy balance of ocean wind waves, i

Jaehne, Bernd

200

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

201

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

202

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

203

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

SciTech Connect

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

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. [Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)] [Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)

2014-05-15

204

An Open-Source Implementation for Full-Wave 20 Scattering by Million-Wavelength-Size Objects  

Microsoft Academic Search

In this contribution, we demonstrate that recent improvements in “fast methods” allow for fully error-controlled full-wave simulations of two-dimensional objects with sizes over a million wavelengths using relatively simple computing environments. We review how a fully scalable parallel version of the Multilevel Fast Multipole Algorithm (MLFMA) is obtained to accelerate a two-dimensional boundary integral equation for the scattering by multiple

Jan Fostier; Femke Olyslager

2010-01-01

205

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

NASA Astrophysics Data System (ADS)

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

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

2014-10-01

206

Simultaneous Multiplexing and Demultiplexing of Wavelength-Interleaved Channels in DWDM Millimeter-Wave Fiber-Radio Networks  

NASA Astrophysics Data System (ADS)

A simultaneous multiplexing and demultiplexing (MUX/DEMUX) scheme for wavelength-interleaved millimeter-wave 37.5-GHz-band fiber-radio channels spaced at 25 GHz has been proposed. The proposed MUX/DEMUX technique potentially realizes simple, compact, and low-cost central office and remote nodes by avoiding the use of wavelength-selective pre-and postprocessing hardware. The novel scheme incorporates an arrayed-waveguide grating with multiple loop-backs between the input and the output ports, in addition to multiple optical circulators and optical isolators. The multiplexing functionality of the proposed technology enables a carrier subtraction technique and consequently reduces the carrier-to-sideband ratios of the multiplexed channels. Multiplexing of the uplink channels generated via several methods is demonstrated experimentally. These techniques include generation of the channels by using the optical carriers that correspond to wavelengths spaced at the free spectral range (FSR) or multiples of the FSR from the downlink (DL) optical carriers and reuse of the DL optical carriers that are recovered by applying a wavelength reuse technique (?UL = ?DL pm n × FSR, where n = 0, 1, 2, 3, ldots). The demultiplexing functionality of the proposed scheme that separates the 37.5-GHz-band wavelength-interleaved DL channels spaced at 25 GHz is also demonstrated. In addition, the effect of optical crosstalk on the transmission performance of the demultiplexed channels is also characterized experimentally.

Bakaul, Masuduzzaman; Nirmalathas, Ampalavanapillai Thas; Lim, Christina; Novak, Dalma; Waterhouse, Rod B.

2006-09-01

207

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

NASA Astrophysics Data System (ADS)

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

Zhukov, Valery A.

2014-12-01

208

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

E-print Network

waves, and wave-current interaction. Conversely, the weak or slow interactions, such as the Benjamin-Feir instability, resonant wave-wave interactions, and enve- lope solitons formation, are limited to the dominant waves in the wave field and may...

Spell, Charles Anthony

1992-01-01

209

Characterization of Low Noise TES Detectors Fabricated by D-RIE Process for SAFARI Short-Wavelength Band  

NASA Astrophysics Data System (ADS)

SRON is developing TES detectors based on a superconducting Ti/Au bilayer on a suspended SiN membrane for the short-wavelength band of the SAFARI instrument on SPICA mission. We have recently replaced the wet KOH etching of the Si substrate by deep reactive ion etching. The new process enables us to fabricate the detectors on the substrate and release the membrane at the very last step. Therefore the production of SAFARI large arrays (4343) on thin SiN membrane (250 nm) is feasible. It also makes it possible to realize narrow supporting SiN legs of 1 m, which are needed to meet SAFARI NEP requirements. Here we report the current-voltage characteristics, noise performance and impedance measurement of these devices. The measured results are then compared with the distributed leg model that takes into account the thermal fluctuation noise due to the SiN legs. We measured a dark NEP of 0.7 aW/, which is 1.6 times higher than the theoretically expected phonon noise.

Khosropanah, P.; Suzuki, T.; Hijmering, R. A.; Ridder, M. L.; Lindeman, M. A.; Gao, J.-R.; Hoevers, H.

2014-08-01

210

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

211

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

PubMed

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

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

2011-10-01

212

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

213

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.

214

Effects of an advanced sleep schedule and morning short wavelength light exposure on circadian phase in young adults with late sleep schedules  

Microsoft Academic Search

ObjectiveWe examined the effects of an advanced sleep\\/wake schedule and morning short wavelength (blue) light in 25 adults (mean age±SD=21.8±3years; 13 women) with late sleep schedules and subclinical features of delayed sleep phase disorder (DSPD).

Katherine M. Sharkey; Mary A. Carskadon; Mariana G. Figueiro; Yong Zhu; Mark S. Rea

2011-01-01

215

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

216

Virucidal short wavelength ultraviolet light treatment of plasma and factor VIII concentrate: protection of proteins by antioxidants.  

PubMed

The use of solvent/detergent mixtures and various forms of heat treatment to inactivate viruses has become widespread in the preparation of blood derivatives. Because viruses that lack lipid envelopes and/or are heat resistant, eg, hepatitis A virus (HAV) or parvovirus B19 may be present, the use of two methods of virus elimination that operate by different mechanisms has been advocated. We now report on short wavelength ultraviolet light (UVC) irradiation for virus inactivation and enhancement of its compatibility with proteins by quenchers of reactive oxygen species (ROS). Treatment of an antihemophilic factor (AHF) concentrate or whole plasma with 0.1 J/cm2 inactivated 10(5) to > or = 10(6) infectious doses (ID) of encephalomyocarditis virus (EMCV), HAV, bacteriophage M13, vesicular stomatitis virus (VSV), and porcine parvovirus. However, the recovery of factor VIII was 30% or lower on treatment of an AHF concentrate and 60% on treatment of plasma. Factor VIII recovery could be increased with little or no effect on virus kill by addition of rutin, a flavonoid known to quench both type I and type II ROS. On treatment of plasma in the presence of rutin, the recovery of several other coagulation factors was also enhanced by rutin addition and typically exceeded 75%. Electrophoretic analysis of treated AHF concentrate confirmed the advantage of rutin presence; UVC irradiation of plasma did not cause discernible changes in electrophoretic banding patterns, even in the absence of rutin. We conclude that addition of UVC treatment to existing processes used in the manufacture of blood derivatives will provide an added margin of safety, especially for nonenveloped or heat-stable viruses. PMID:7492794

Chin, S; Williams, B; Gottlieb, P; Margolis-Nunno, H; Ben-Hur, E; Hamman, J; Jin, R; Dubovi, E; Horowitz, B

1995-12-01

217

Ultra-Wideband Bandpass Filters Using Quarter-Wave Short-Circuited Shunt Stubs and Quarter-Wave Series Transformers  

Microsoft Academic Search

This letter introduces a topology of a very wideband filter intended for the use in ultra-wideband 3.1-10.6 GHz applications. Basic filter configuration consists of quarter-wave short-circuited stubs and quarter-wave series transformers. To improve the out-of-band rejection, a low-pass filter is added across the symmetry plane. The proposed component is fabricated in a planar microstrip configuration; however, the topology can be

Manseok Uhm; Kichul Kim; Dejan S. Filipovic

2008-01-01

218

A monolithically integrated HgCdTe short-wavelength infrared photodetector and micro-electro-mechanical systems-based optical filter  

Microsoft Academic Search

A monolithically integrated low-temperature micro-electro-mechanical systems (MEMS) and HgCdTe infrared (IR) detector technology\\u000a is introduced, implemented, and characterized. The ultimate aim of this project is to develop a MEMS-based optical filter,\\u000a integrated with an IR detector, that selects narrow wavelength bands within the short-wavelength IR (SWIR) region of the spectrum.\\u000a The entire fabrication process is compatible with two-dimensional IR focal

J. Antoszewski; K. J. Winchester; A. J. Keating; T. Nguyen; C. A. Musca; J. M. Dell; L. Faraone; P. Mitra; J. D. Beck; M. R. Skokan; J. E. Robinson

2005-01-01

219

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

220

Analysis of sub-wavelength cavity leaky-wave antennas with high-impedance surfaces  

Microsoft Academic Search

We present simple and accurate analysis techniques to simulate and design high-gain Fabry-Perot resonant leaky-wave antennas (LWA). To control the radiation properties of these antennas, two metallodielectric periodic structures are used, one acting as a partially reflective surface (PRS) and a second acting as a high impedance surface (HIS). Full-wave method of moments (MoM) is employed for the estimation of

C. Mateo-Segura; M. Garcia-Vigueras; G. Goussetis; J. L. Gomez-Tornero; A. Feresidis

2009-01-01

221

Characterization of efficient wavelength conversion by four-wave mixing in sub-micron silicon waveguides.  

PubMed

We characterize silicon waveguide based wavelength converters using a commercial semiconductor optical amplifier (SOA) based wavelength converter as a benchmark. Conversion efficiency as high as -5.5 dB can be achieved using a 2.5 cm long sub-micron silicon-on-insulator rib waveguide. Comparison with the SOA reveals that silicon offers broader conversion bandwidth, higher OSNR, and negligible channel crosstalk. The impact of two-photon absorption and free carrier absorption on the conversion efficiency and the dependence of the efficiency on the rib waveguide dimensions are investigated theoretically. Using a nonlinear index coefficient of 4x10(-14) cm(2)/W for silicon, we obtain good agreement between simulations and measurements. PMID:18852783

Mathlouthi, Walid; Rong, Haisheng; Paniccia, Mario

2008-10-13

222

Improved methods for detecting gravitational waves associated with short gamma-ray bursts  

NASA Astrophysics Data System (ADS)

In the era of second generation ground-based gravitational wave detectors, short gamma-ray bursts (GRBs) will be among the most promising astrophysical events for joint electromagnetic and gravitational wave observation. A targeted, coherent search for gravitational wave compact binary merger signals in coincidence with short GRBs was developed and used to analyze data from the first generation LIGO and Virgo instruments. In this paper, we present improvements to this search that enhance our ability to detect gravitational wave counterparts to short GRBs. Specifically, we introduce an improved method for estimating the gravitational wave background to obtain the event significance required to make detections; implement a method of tiling extended sky regions, as required when searching for signals associated to poorly localized GRBs from the Fermi Gamma-ray Burst Monitor or the InterPlanetary Network; and incorporate astrophysical knowledge about the beaming of GRB emission to restrict the search parameter space. We describe the implementation of these enhancements and demonstrate how they improve the ability to observe binary merger gravitational wave signals associated with short GRBs. A targeted, coherent GRB search provides a 25% increase in distance sensitivity, or a doubling of the event rate, for well-localized GRBs when compared with a nontargeted, coincident analysis.

Williamson, A. R.; Biwer, C.; Fairhurst, S.; Harry, I. W.; Macdonald, E.; Macleod, D.; Predoi, V.

2014-12-01

223

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

SciTech Connect

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

Van Eester, D.; Lerche, E. [LPP-ERM/KMS, Association Euratom-Belgian State, TEC Partner, Brussels (Belgium)

2014-02-12

224

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

NASA Astrophysics Data System (ADS)

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

Van Eester, D.; Lerche, E.

2014-02-01

225

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

E-print Network

) to infrared radiations (1�105 nm). With the recent development of intense and ultrashort-wavelength free-electron lasers [32­34], the study of multiphoton * zyzhou@ku.edu sichu@ku.edu processes in the high

Chu, Shih-I

226

Enhancing the photo-currents of CdTe thin-film solar cells in both short and long wavelength regions  

NASA Astrophysics Data System (ADS)

The recent increases in the record efficiency of CdTe thin-film solar cell technology largely benefited from enhancements in short circuit current densities (JSC) in the short-wavelength regions by reducing the thicknesses of CdS window layers. Here, we report that the JSC can be enhanced in both short and long wavelength regions by using CdSe as the window layer. Comparing to CdS, CdSe has a higher solubility in CdTe, resulting in stronger interdiffusion at the CdSe/CdTe interface and the formation of CdTe1-xSex alloys with high x values. Due to bowing effects, the CdTe1-xSex alloys exhibit narrower band gaps than CdTe, enhancing the JSC in the CdTe-based solar cells for long-wavelengths. We further report that the use of combined CdS/CdSe window layers can realize high open circuit voltages and maintain the JSC enhancements. Our results suggest a viable approach to improve the performance of CdTe thin-film solar cells.

Paudel, Naba R.; Yan, Yanfa

2014-11-01

227

Statistical characterization of short wind waves from stereo images of the sea surface  

NASA Astrophysics Data System (ADS)

We propose a methodology to extract short-scale statistical characteristics of the sea surface topography by means of stereo image reconstruction. The possibilities and limitations of the technique are discussed and tested on a data set acquired from an oceanographic platform at the Black Sea. The analysis shows that reconstruction of the topography based on stereo method is an efficient way to derive non-trivial statistical properties of surface short- and intermediate-waves (say from 1 centimer to 1 meter). Most technical issues pertaining to this type of datasets (limited range of scales, lacunarity of data or irregular sampling) can be partially overcome by appropriate processing of the available points. The proposed technique also allows one to avoid linear interpolation which dramatically corrupts properties of retrieved surfaces. The processing technique imposes that the field of elevation be polynomially detrended, which has the effect of filtering out the large scales. Hence the statistical analysis can only address the small-scale components of the sea surface. The precise cut-off wavelength, which is approximatively half the patch size, can be obtained by applying a high-pass frequency filter on the reference gauge time records. The results obtained for the one- and two-points statistics of small-scale elevations are shown consistent, at least in order of magnitude, with the corresponding gauge measurements as well as other experimental measurements available in the literature. The calculation of the structure functions provides a powerful tool to investigate spectral and statistical properties of the field of elevations. Experimental parametrization of the third-order structure function, the so-called skewness function, is one of the most important and original outcomes of this study. This function is of primary importance in analytical scattering models from the sea surface and was up to now unavailable in field conditions. Due to the lack of precise reference measurements for the small-scale wave field, we could not quantify exactly the accuracy of the retrieval technique. However, it appeared clearly that the obtained accuracy is good enough for the estimation of second-order statistical quantities (such as the correlation function), acceptable for third-order quantities (such as the skwewness function) and insufficient for fourth-order quantities (such as kurtosis). Therefore, the stereo technique in the present stage should not be thought as a self-contained universal tool to characterize the surface statistics. Instead, it should be used in conjunction with other well calibrated but sparse reference measurement (such as wave gauges) for cross-validation and calibration. It then completes the statistical analysis in as much as it provides a snapshot of the three-dimensional field and allows for the evaluation of higher-order spatial statistics.

Mironov, Alexey; Yurovskaya, Maria; Dulov, Vladimir; Hauser, Danièle; Guérin, Charles-Antoine

2013-04-01

228

Type III Radio Bursts at Long Wavelengths: Statistics from STEREO/Waves 2007-2010  

NASA Astrophysics Data System (ADS)

During increased solar activity type III radio bursts are frequently observed by the S/Waves instrument on-board both STEREO spacecraft. These radio bursts are generated by a non-linear conversion of the Langmuir waves which have been excited by beams of fast electrons connected with solar flares and/or CME driven shocks. The High Frequency Receiver (HFR; a part of S/Waves) records fluctuations of the electric field from 125 kHz up to 1975 kHz with goniopolarimetric (GP) capabilities that allows us to perform propagation analysis of an incident wave. We present extensive statistics of more than 100 intense events observed between March 2007 and July 2010. We have found that type III radio bursts generally propagate in the solar equatorial plane. For larger frequencies dispersion of the central directions toward the sources distribution decreases suggesting that scattering of the primary beam pattern plays a key role in propagation comparing to refraction. Our results indicate that type III radio bursts have the apparent source 23 size half-width of 25 - 30 degrees.

Krupar, V.; Santolik, O.; Maksimovic, M.; Cecconi, B.

2010-12-01

229

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

E-print Network

is deliberately not a Fabry-Perot resonator;[2] the top surface is antireflection coated.) The thin absorbers-sensitive detectors. Various devices have been proposed (see, e.g., references in [1]), including Fabry-Perot resonator devices.[2] A class of devices based on thin absorbers in standing waves was proposed[1] and one

Miller, David A. B.

230

Four-wave mixing with short pulses and optimized atomic coherence  

NASA Astrophysics Data System (ADS)

We present a time-dependent calculation for four-wave mixing using a combination of long, short, and time delayed laser pulses in the context of electromagnetically induced transparency. Two transform limited nanosecond lasers are used to create a highly coherent mixture of the ground state and an excited state via a two-photon process. Once the induced transparency is established, a laser with short pulse length is injected after a suitable delay to generate four-wave mixing. We show that the wave mixing process is phase matched for all detunings, and with appropriately selected atomic coherence and populations, near 100% photon flux conversion efficiency can be obtained, independent of the intensity of the short pulse laser. In addition, we show that for small detunings for the short pulse laser, the four-wave mixing field travels with the speed of light in vacuum and suffers no pulse distortion even though the medium is highly dispersive at the frequency of the generated wave. These advantages open a door for future applications of the scheme for highly efficient, very stable UV generation.

Deng, L.; Payne, M. G.; Garrett, W. R.

2001-04-01

231

Transverse plane wave analysis of short elliptical chamber mufflers: An analytical approach  

NASA Astrophysics Data System (ADS)

Short elliptical chamber mufflers are used often in the modern day automotive exhaust systems. The acoustic analysis of such short chamber mufflers is facilitated by considering a transverse plane wave propagation model along the major axis up to the low frequency limit. The one dimensional differential equation governing the transverse plane wave propagation in such short chambers is solved using the segmentation approaches which are inherently numerical schemes, wherein the transfer matrix relating the upstream state variables to the downstream variables is obtained. Analytical solution of the transverse plane wave model used to analyze such short chambers has not been reported in the literature so far. This present work is thus an attempt to fill up this lacuna, whereby Frobenius solution of the differential equation governing the transverse plane wave propagation is obtained. By taking a sufficient number of terms of the infinite series, an approximate analytical solution so obtained shows good convergence up to about 1300 Hz and also covers most of the range of muffler dimensions used in practice. The transmission loss (TL) performance of the muffler configurations computed by this analytical approach agrees excellently with that computed by the Matrizant approach used earlier by the authors, thereby offering a faster and more elegant alternate method to analyze short elliptical muffler configurations.

Mimani, A.; Munjal, M. L.

2011-03-01

232

Electron-deuteron tensor polarization and the short range behavior of the deuteron wave function  

Microsoft Academic Search

We investigate to what extent measurements of the polarization of recoil deuterons in electron-deuteron scattering would allow us to determine the short-range behavior of the deuteron wave function. We find that even if such measurements were performed out to q=10 fm-1 with an error of +\\/-10% and in some cases even within +\\/-1%, a considerable variation in the deuteron wave

L. J. Allen; H. Fiedeldey

1979-01-01

233

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

PubMed

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

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

2014-11-01

234

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

NASA Astrophysics Data System (ADS)

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

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

2014-11-01

235

Direct measurement of the wavelength of sound waves in the human skull.  

PubMed

The results of a study of the three-dimensional vibration of two dry human skulls in response to harmonic excitation are presented. The vibratory response exhibits three distinct types of motion across the range of audible frequencies. At low frequencies below 1000 Hz, whole-head quasi-rigid motion is seen. At the middle frequencies between 1000 and 6000 Hz, the motion exhibits a series of increasingly complex modal patterns. Above 6000 Hz, the response is wavelike and clear wavefronts can be distinguished in the vibration data. In this regime the relationship between wavelength and frequency is calculated and compared to a number of theories of skull vibration that have been proposed. PMID:23297890

McKnight, Carmen L; Doman, Darrel A; Brown, Jeremy A; Bance, Manohar; Adamson, Robert B A

2013-01-01

236

Spectral form and source term balance of short gravity wind waves  

NASA Astrophysics Data System (ADS)

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

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

2014-11-01

237

Investigating Gait Recognition in the Short-Wave Infrared (SWIR) Spectrum: Dataset and Challenges  

E-print Network

that can confound recognition accuracy. In the context of automated human gait recognition, evaluation has piqued interest in performing gait recognition in other spectral bands such as short-wave infrared (SWIR environments. Further, in many operational scenarios, the environmental variables are not controlled, thereby

Ross, Arun Abraham

238

Land cover classification in SE Asia using near and short wave infrared bands  

Microsoft Academic Search

A land cover classification map is necessary for modelling interac- tions between the land surface and the atmosphere, monitoring the environment and estimating food production. In order to classify land cover in SE Asia in 2000, Normalized Difference Vegetation Index (NDVI), reflectance of near- infrared (NIR) band, and reflectance of short wave infrared (SWIR) band of Systeme pour l'Observation de

H. P. Sato; R. Tateishi

2004-01-01

239

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

240

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

241

Improving the detectability of gravitational wave counterparts of short-hard gamma ray bursts  

NASA Astrophysics Data System (ADS)

With multiple observatories and missions being planned for detecting orphaned afterglows associated with gamma-ray bursts (GRBs) we emphasize the importance of developing data analysis strategies for searching their possible counterpart signals in the data of gravitational wave detectors in the advanced detector era. This is especially attractive since short hard gamma-ray bursts (SGRBs) may have compact binary coalescences involving neutron stars (CBCNS) as their progenitors, which emit gravitational waves. Joint electromagnetic and gravitational wave observations of these objects will enrich our understanding of their beaming, energetics, galactic environment, and shed light on a host of other outstanding questions related to them. We recognize some of the astrophysical factors that determine what fraction of these sources can generate orphaned afterglows. We developed a search pipeline by modifying the existing blind hierarchical coherent search pipeline, targeting their sky-position and time of occurrence known from EM observations to enable it to search for counterparts of SGRB and SGRB afterglows in gravitational wave detector data. The modifications allows it to analyze extended periods of time in the gravitational wave data in the past of the afterglow detection epoch, while targeting its known sky-position, to search for gravitational waves from the common progenitor. We assess the improvement in gravitational wave detectability to be had from utilizing the sky-position information. We also propose a method for mitigating the effects on the detection efficiency of targeted searches of gravitational wave signals from the putative CBCNS sources of afterglows and short gamma-ray bursts arising from the presence of errors in detector calibration or CBCNS waveform models used in the search.

Ghosh, Shaon

242

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

243

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

244

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

245

Signal-to-noise performance of a short-wave infrared nanoinjection imager.  

PubMed

We report on the signal-to-noise performance of a nanoinjection imager, which is based on a short-wave IR InGaAs/GaAsSb/InP detector with an internal avalanche-free amplification mechanism. Test pixels in the imager show responsivity values reaching 250 A/W at 1550 nm, -75 degrees C, and 1.5V due to an internal charge amplification mechanism in the detector. In the imager, the measured imager noise was 28 electrons (e(-)) rms at a frame rate of 1950 frames/s. Additionally, compared to a high-end short-wave IR imager, the nanoinjection camera shows 2 orders of magnitude improved signal-to-noise ratio at thermoelectric cooling temperatures primarily due to the small excess noise at high amplification. PMID:20717428

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

2010-08-15

246

Four-wave mixing with short pulses and optimized atomic coherence  

Microsoft Academic Search

We present a time-dependent calculation for four-wave mixing using a combination of long, short, and time delayed laser pulses in the context of electromagnetically induced transparency. Two transform limited nanosecond lasers are used to create a highly coherent mixture of the ground state and an excited state via a two-photon process. Once the induced transparency is established, a laser with

L. Deng; M. G. Payne; W. R. Garrett

2001-01-01

247

Relationship between statistical parameters of short-wave signals in vertical and oblique ionospheric sounding  

Microsoft Academic Search

UDC 621.371.25 Some results of comprehensive experiments involving vertical sounding (VS) and oblique sounding (OS) of the ionosphere are given. The statistical parameters were found to be equivalent only in a small number of observation sessions; this was associated with the temporal and spatial nonstationarity of the process of short-wave scattering in the ionosphere. It is shown that no definite

V. A. Alimov; L. M. Erukhimov; L. F. Mironenko; L. A. Skrebkova; A. V. Rakhlin; V. P. Uryadov; K. I. Yurin

1975-01-01

248

Single Step Generation of Micro and Radio Wave Signals in a Short Cavity Fiber Laser  

Microsoft Academic Search

Generation of stable micro or radio waves by fre- quency down-conversion has always been a challenging but rewarding task in radio over fiber systems. In this letter, a novel method for such a generation using a short-cavity fiber laser is demonstrated. For this purpose, an all-fiber laser is designed to have two stable longitudinal laser modes, each of them having

Udari Basnayaka; Xavier Fernando; Xijia Gu

2011-01-01

249

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

Microsoft Academic Search

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

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

2010-01-01

250

An algorithm of an adaptive equalizer for short-wave communication  

Microsoft Academic Search

An algorithm for a decision feedback equalizer is proposed. Its feedforward section uses a square root Kalman (SRK) algorithm, while its feedback section uses a gradient algorithm. Comparison of this algorithm with a conventionally used SRK algorithm is given. The implementation of the two algorithms with TMS32020 is discussed. It shows the new algorithm is ideal for high-speed short-wave communication.

ZHANG TIE JUN

1994-01-01

251

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

252

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

NASA Astrophysics Data System (ADS)

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

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

2013-10-01

253

Short-Term Repeatability of Electrocardiographic P Wave Indices and PR Interval  

PubMed Central

Background P wave indices and PR interval from 12-lead electrocardiograms (ECGs) are predictors of cardiovascular morbidity and mortality, but their repeatability has not been examined. Objectives Determine the short-term repeatability of P wave indices (P axis, maximum P area and duration, P dispersion and P terminal force in V1) and PR interval. Methods Participants (n=63) underwent two standard ECGs at each of two visits, two weeks apart. We calculated the intra-class correlation coefficient (ICC), weighted Kappa, and minimal detectable change and difference. Results ICCs were 0.93 for PR interval, 0.78 for P axis, 0.77 for maximum P area, and 0.58 for maximum P duration. Within- and between-visit Kappa were 0.30 and 0.11 for P dispersion, and 0.68 and 0.46 for P terminal force. Conclusion Repeatability of PR duration was excellent, that of P wave axis and maximum area was fair, and maximum P wave duration and terminal force was poor. Repeatability of P wave dispersion was fair within visit, yet poor between visits. These results illustrate potential biases when measurement error of some P wave indices is ignored in clinical and epidemiologic studies. PMID:24360345

Snyder, Michelle L; Soliman, Elsayed Z; Whitsel, Eric A; Gellert, Kapuaola S; Heiss, Gerardo

2014-01-01

254

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

255

Optimum electron temperature and density for short-wavelength plasma-lasing from nickel-like ions  

NASA Astrophysics Data System (ADS)

Soft X-ray lasing across a Ni-like plasma gain-medium requires optimum electron temperature and density for attaining to the Ni-like ion stage and for population inversion in the 3d94d1(J=0)?3d94p1(J=1) laser transition. Various scaling laws, function of operating parameters, were compared with respect to their predictions for optimum temperatures and densities. It is shown that the widely adopted local thermodynamic equilibrium (LTE) model underestimates the optimum plasma-lasing conditions. On the other hand, non-LTE models, especially when complemented with dielectronic recombination, provided accurate prediction of the optimum plasma-lasing conditions. It is further shown that, for targets with Z equal or greater than the rare-earth elements (e.g. Sm), the optimum electron density for plasma-lasing is not accessible for pump-pulses at ?=1?=1?m. This observation explains a fundamental difficulty in saturating the wavelength of plasma-based X-ray lasers below 6.8 nm, unless using 2? pumping.

Masoudnia, Leili; Bleiner, Davide

2014-03-01

256

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

257

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

NASA Astrophysics Data System (ADS)

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

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

2014-11-01

258

Manufacturing and characterizing of all-dielectric band-pass filters for the short-wave infrared region  

NASA Astrophysics Data System (ADS)

Besides the typical channels in the visible and near infrared spectrum, optical remote sensing of the earth from air and space utilizes also several channels in the short-wave infrared spectrum from 1000 nm to 3000 nm. Thin-film optical filters are applied to select these channels, but the application of classical multiple-cavity band-pass filters is impossible. Because of their additional blocking elements they are disallowed due to geometrical or other non-optical reasons. Within the sensitivity region of an MCT detector as typical detector device, the selection and blocking of radiation by the filter has to be provided by a single multilayer system. The spectral region of the SWIR as well as blocking width and depth require necessarily designs with overall thicknesses of more than 20 ?m, with layer numbers up to 100. SiO2 and TiO2 were used as thin-film materials deposited with reactive e-beam evaporation under ion assistance in a Leybold SyrusPro box coater. A special challenge was the thickness measurement of the thin films by an optical broadband monitoring device in the visible range. The results of manufacturing and characterizing of such filters are presented by three examples for the center wavelengths of 1375 nm, 1610 nm, and 2190 nm.

Bauer, T.; Lappschies, M.; Schallenberg, U.; Jakobs, S.

2011-09-01

259

Spectral discrimination of hydrothermally altered materials using ASTER short-wave infrared bands: Evaluation in a tropical savannah environment  

NASA Astrophysics Data System (ADS)

ASTER short-wave infrared bands were used to investigate the spectral discrimination of hydrothermally altered materials, based on the presence of minerals with diagnostic spectral features in wavelengths around 2200 nm (e.g. kaolinite and K-micas). Due to the presence of widespread albitized-greisenized materials, the Serra do Mendes granitoid, located in area of tropical savannah environment in Central Brazil, was selected for this study. The Spectral Angle Mapper (SAM) technique was used as an attempt to detect the presence of hydroxyl-bearing minerals in the domain of the hydrothermally altered materials. Results indicated that areas of altered materials were discriminated from the surrounding mainly due to the high overall reflectance of the whitish lithosols in these areas. The detection of hydroxyl-bearing minerals was blurred by the presence of a sparse grass cover in the alteration zone, which caused a slight increase in the SAM classification angles. As a consequence, the remote detection of hydroxyl-bearing minerals was restricted to a small number of pixels from barren areas. Results indicate that, for the environmental conditions of the study area, ASTER data are more efficacious for spectral characterization of rock-soil-vegetation associations than for the detection of alteration-derived minerals.

Galvão, Lênio Soares; Almeida-Filho, Raimundo; Vitorello, Ícaro

2005-08-01

260

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

261

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

SciTech Connect

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

Yunes, Nicolas [Department of Physics, Princeton University, Princeton, New Jersey 08544 (United States); Department of Physics, Institute for Gravitation and the Cosmos, Pennsylvania State University, University Park, Pennsylvania 16802 (United States); O'Shaughnessy, Richard [Department of Physics, Institute for Gravitation and the Cosmos, Pennsylvania State University, University Park, Pennsylvania 16802 (United States); Owen, Benjamin J. [Department of Physics, Institute for Gravitation and the Cosmos, Pennsylvania State University, University Park, Pennsylvania 16802 (United States); Max Planck Institut fuer Gravitationsphysik (Albert Einstein Institut), Callinstr. 38, 30167 Hannover (Germany); Alexander, Stephon [Department of Physics, Institute for Gravitation and the Cosmos, Pennsylvania State University, University Park, Pennsylvania 16802 (United States); Department of Physics and Astronomy, Haverford College, Haverford, Pennsylvania 19041 (United States)

2010-09-15

262

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

263

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

264

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

265

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

NASA Technical Reports Server (NTRS)

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

Freilich, Michael H.; Dunbar, R. Scott

1993-01-01

266

Velocity field, surface profile and curvature resolution of steep and short free-surface waves  

NASA Astrophysics Data System (ADS)

On steep, millimeter-scale, 2D water waves, surface profile, and subsurface velocity field are measured with high-spatio-temporal resolution. This allows resolving surface vorticity, which is captured in the surface boundary layer and compared with its direct computation from interface curvature and velocity. Data are obtained with a combination of high-magnification time-resolved particle image velocimetry (PIV) and planar laser-induced fluorescence. The latter is used to resolve the surface profile and serves as a processing mask for the former. PIV processing schemes are compared to optimize accuracy locally, and profilometry data are treated to obtain surface curvature. This diagnostic enables new insights into free-surface dynamic, in particular, wave growth and surface vorticity generation, for flow regimes not studied previously. The technique is demonstrated on a high-speed water jet discharging in quiescent air at a Reynolds number of 4.8 × 104. Shear-layer instability below the surface leads to streamwise traveling waves with wavelength ? ~ 2 mm and steepness , where a is the crest to trough amplitude. Flow structures are resolved at these scales by recording at 16 kHz with a magnification of 4.

André, Matthieu A.; Bardet, Philippe M.

2014-04-01

267

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

268

Short wavelength turbulence generated by shear in the quiescent H-mode edge on DIII–D  

SciTech Connect

A region of turbulence with large radial wavenumber (k{sub r}?{sub s}>1) is found in the high-shear portion of the plasma edge in Quiescent H-mode (QH-mode) on DIII–D using the Phase Contrast Imaging (PCI) diagnostic. At its peak outside the minimum of the E{sub r} well, the turbulence exhibits large amplitude n{sup ~}/n?40%, with large radial wavenumber |k{sup ¯}{sub r}/k{sup ¯}{sub ?}|?11 and short radial correlation length L{sub r}/?{sub i}?0.2. The turbulence inside the E{sub r} well minimum is characterized by the opposite sign in radial wavenumber from that of turbulence outside the minimum, consistent with the expected effects of velocity shear. The PCI diagnostic provides a line-integrated measurement of density fluctuations, so data are taken during a scan of plasma position at constant parameters to allow the PCI to sample a range in k{sub r}/k{sub ?}. Analysis of the Doppler shift and plasma geometry allows the turbulence to be localized to a narrow region 3?mm inside the last closed flux surface, outside the minimum of the E{sub r} well. The turbulence amplitude and radial wavenumber and correlation length are determined by fitting the PCI results with a simple non-isotropic turbulence model with two regions of turbulence. These PCI observations, made in QH-mode, are qualitatively similar to those made in standard edge localized modes (ELM)-free H-mode and between ELMs, suggesting a similar role for large k{sub r} turbulence there.

Rost, J. C.; Porkolab, M.; Dorris, J. [Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); Burrell, K. H. [General Atomics, P.O. Box 85608, San Diego, California 92186-5608 (United States)

2014-06-15

269

Broad-band continuous-wave-pumped fiber optical parametric amplifier with 49dB gain and wavelength-conversion efficiency  

Microsoft Academic Search

A broad-band continuous-wave (CW) pumped fiber-based parametric amplifier with 39 dB of internal gain and wavelength conversion efficiency, corresponding to a black box gain\\/efficiency of 38 dB, is demonstrated. Bit-error-rate (BER) measurements indicate performance comparable to erbium-doped fiber amplifiers (EDFAs). These amplifiers may thus find new applications in future lightwave systems

Jonas Hansryd; Peter A. Andrekson

2001-01-01

270

X, Gamma-Rays, and Gravitational Waves Emission in a Short Gamma-Ray Burst  

NASA Astrophysics Data System (ADS)

The recent progress in the understanding the physical nature of neutron stars (NSs) and the first observational evidence of a genuinely short gamma-ray burst (GRB), GRB 090227B, allow to give an estimate of the gravitational waves versus the X and gamma-rays emission in a short GRB. NS binaries represent good candidates for the detection of gravitational waves emitted during the spiraling-in and final merging phase of the system that leads to the short GRB emission. The data analysis of the GRB 090227B by Muccino et al. (2013) have been shown to be consistent with a NS binary progenitor with masses M1 = M2 = 1.34 M_{?}, radii R1 = R2 = 12.2 km, and a crust thickness ? r ? 0. 47 km, obtained from the new mass-radius relation by Belvedere et al. (2012) of NSs fulfilling global charge neutrality. Muccino et al. (2013) estimated that GRB 090227B is located at redshift z ? 1. 6, corresponding to a luminosity distance d L ? 12. 2 Gpc. We assess the detectability of this source by the Advanced LIGO interferometer computing the signal-to-noise ratio (SNR) averaged over all polarizations and possible positions of the source with respect to the interferometer. We simulate the dynamics of the binary up to the contact point using the effective one-body formalism (EOB) in the fourth post-Newtonian approximation. We find that the gravitational waves signal would have been produced an SNR = 0.32 for a redshift z = 1. 61. We find that, instead, this GRB would have been detected with an SNR = 8 if it would have been located at a redshift z ? 0. 05, or d L ? 200 Mpc.

Oliveira, F. G.; Rueda, Jorge A.; Ruffini, R.

271

In-depth Plasma-Wave Heating of Dense Plasma Irradiated by Short Laser Pulses  

NASA Astrophysics Data System (ADS)

We investigate the mechanism by which relativistic electron bunches created at the surface of a target irradiated by a very short and intense laser pulse transfer energy to the deeper parts of the target. In existing theories, the dominant heating mechanism is that of resistive heating by the neutralizing return current. In addition to this, we find that large amplitude plasma waves are induced in the plasma in the wake of relativistic electron bunches. The subsequent collisional damping of these waves represents a source of heating that can exceed the resistive heating rate. As a result, solid targets heat significantly faster than has been previously considered. A new hybrid model, capable of reproducing these results, is described.

Sherlock, M.; Hill, E. G.; Evans, R. G.; Rose, S. J.; Rozmus, W.

2014-12-01

272

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

PubMed

We investigate the mechanism by which relativistic electron bunches created at the surface of a target irradiated by a very short and intense laser pulse transfer energy to the deeper parts of the target. In existing theories, the dominant heating mechanism is that of resistive heating by the neutralizing return current. In addition to this, we find that large amplitude plasma waves are induced in the plasma in the wake of relativistic electron bunches. The subsequent collisional damping of these waves represents a source of heating that can exceed the resistive heating rate. As a result, solid targets heat significantly faster than has been previously considered. A new hybrid model, capable of reproducing these results, is described. PMID:25554889

Sherlock, M; Hill, E G; Evans, R G; Rose, S J; Rozmus, W

2014-12-19

273

Vector acoustic solitons from the coupling of long and short waves in a paramagnetic crystal  

NASA Astrophysics Data System (ADS)

We investigate the propagation of a longitudinal-transverse elastic pulse in a statically deformed crystal containing paramagnetic impurities and placed in an external magnetic field. We derive a system of three nonlinear wave equations describing the interaction of the pulse with the paramagnetic impurities in the quasiresonance approximation in the Faraday geometry. We assume that the transverse components of the pulse, which cause quantum transitions, have carrier frequencies and are short-wave (acoustic), while the longitudinal component has no carrier frequency and is long-wave. We show that in the case of an equilibrium initial distribution of populations of quantum levels of paramagnetic impurities, the coupling between the longitudinal and transverse components is weak, the pulse is therefore strictly transverse, and its dynamics are described by the Manakov system. With a nonequilibrium initial distribution of populations, conditions of effective interaction between all components of the elastic pulse can be reached, and their nonlinear dynamics are described by a vector generalization of the Zakharov equations. In the case of a unidirectional propagation of the pulse, these equations reduce to the Yajima-Oikawa vector system. We show that the obtained system of equations and its version with an arbitrary number of short-wave components can be integrated using the inverse scattering transform. We construct infinite hierarchies of solutions of the Yajima-Oikawa vector system (including a solution on a nontrivial background). We consider stationary (complex-valued Garnier system) and self-similar reductions of that system, also admitting a representation in the form of compatibility conditions.

Sazonov, S. V.; Ustinov, N. V.

2014-02-01

274

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

275

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

276

A photonic crystal is a periodic dielectric structure with a lattice constant of the order of the wavelength of the electromagnetic wave that one wants to control. In photonic crystals, the  

E-print Network

of the order of the wavelength of the electromagnetic wave that one wants to control. In photonic crystals and is positive. Typical for a photonic crystal is that electromagnetic waves in a certain frequency range and range is called a stopgap. If the propagation of the electromagnetic wave is forbidden for any

277

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

278

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

279

Developing a Short-Period, Fundamental-Mode Rayleigh-Wave Attenuation Model for Asia  

NASA Astrophysics Data System (ADS)

We are developing a 2D, short-period (12 - 22 s), fundamental-mode Rayleigh-wave attenuation model for Asia. This model can be used to invert for a 3D attenuation model of the Earth's crust and upper mantle as well as to implement more accurate path corrections in regional surface-wave magnitude calculations. The prerequisite for developing a reliable Rayleigh-wave attenuation model is the availability of accurate fundamental-mode Rayleigh-wave amplitude measurements. Fundamental-mode Rayleigh-wave amplitudes could be contaminated by a variety of sources such as multipathing, focusing and defocusing, body wave, higher-mode surface wave, and other noise sources. These contaminations must be reduced to the largest extent possible. To achieve this, we designed a procedure by taking advantage of certain Rayleigh-wave characteristics, such as dispersion and elliptical particle motion, for accurate amplitude measurements. We first analyze the dispersion of the surface-wave data using a spectrogram. Based on the characteristics of the data dispersion, we design a phase-matched filter by using either a manually picked dispersion curve, or a group-velocity-model predicted dispersion curve, or the dispersion of the data, and apply the filter to the seismogram. Intelligent filtering of the seismogram and windowing of the resulting cross-correlation based on the spectrogram analysis and the comparison between the phase-match filtered data spectrum, the raw-data spectrum and the theoretical source spectrum effectively reduces amplitude contaminations and results in reliable amplitude measurements in many cases. We implemented these measuring techniques in a graphic-user-interface tool called Surface Wave Amplitude Measurement Tool (SWAMTOOL). Using the tool, we collected and processed waveform data for 200 earthquakes occurring throughout 2003-2006 inside and around Eurasia. The records from 135 broadband stations were used. After obtaining the Rayleigh-wave amplitude measurements, we analyzed the attenuation behavior of the amplitudes using source- and receiver-specific terms calculated from a 3D velocity model of the region. Based on the results, we removed amplitudes that yielded negative average attenuation coefficients, and included an additional parameter in the inversion to account for the possible bias of the CMT moments. Using the high-quality amplitude measurements in a tomographic inversion, we obtained a fundamental-mode Rayleigh-wave attenuation- coefficient model for periods between 12 and 22 s for Asia and surrounding regions. The inverted attenuation model is consistent with the geological features of Asia. We observe low attenuation in stable regions such as eastern Europe, the Siberian platforms, the Indian shield, the Arabian platform, the Yangtze craton, and others. High attenuation is observed in tectonically active regions such as the Himalayas, the Tian Shan, Pamir and Zagros mountains.

Yang, X.; Levshin, A. L.; Barmin, M. P.; Ritzwoller, M. H.

2008-12-01

280

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

281

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

NASA Technical Reports Server (NTRS)

Scanning beam microwave radars were used to measure ocean wave directional spectra from satellites. In principle, surface wave spectral resolution in wave number can be obtained using either short pulse (SP) or dual frequency (DF) techniques; in either case, directional resolution obtains naturally as a consequence of a Bragg-like wave front matching. A four frequency moment characterization of backscatter from the near vertical using physical optics in the high frequency limit was applied to an analysis of the SP and DF measurement techniques. The intrinsic electromagnetic modulation spectrum was to the first order in wave steepness proportional to the large wave directional slope spectrum. Harmonic distortion was small and was a minimum near 10 deg incidence. NonGaussian wave statistics can have an effect comparable to that in the second order of scattering from a normally distributed sea surface. The SP technique is superior to the DF technique in terms of measurement signal to noise ratio and contrast ratio.

Jackson, F. C.

1980-01-01

282

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

283

The Dual Nature of Light Wave and Particle  

E-print Network

1 The Dual Nature of Light Wave and Particle Light as a particle Particles or packets of light = slow Light as a wave The distance moved by a photon during one of it vibrations is referred to as its-9 meter = nu = my shorthand for light Long wavelength Low energy Short wavelength High energy Effective

Cochran-Stafira, D. Liane

284

IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING, VOL. 52, NO. 1, JANUARY 2014 679 Revisiting the Short-Wave Spectrum of the  

E-print Network

the Short-Wave Spectrum of the Sea Surface in the Light of the Weighted Curvature Approximation Alexandra for the short-wave spectrum of the sea surface are not consistent with microwave satellite data when multi-wave omnidirec- tional spectrum of the sea surface on the basis of a three-band (C, Ku, and Ka) and multi

285

Analysis of temporal contrast degradation due to wave front deviation in large aperture ultra-short pulse focusing system  

NASA Astrophysics Data System (ADS)

In extremely intense laser system used for plasma physics experiments, temporal contrast is an important property of the ultra-short pulse. In this paper, we theoretically study the temporal contrast degradation due to wave front deviation in large aperture ultra-short pulse focusing system. Two-step focusing fast Fourier transform (FFT) algorithm with the coordinate transform based on Fresnel approximation in space domain and Fourier integral transform method in time domain were used to simulate the focusing process spatially and temporally, in which the spatial distribution of ultra-short pulse temporal contrast characteristics at the focal spot is related to the wave front in large aperture off-axis parabolic mirror focusing optical system. Firstly, temporal contrast degradation due to wave front noise with higher spatial frequency is analyzed and appropriate evaluation parameter for large aperture ultra-short pulse focusing system is put forward from the perspective of temporal contrast. Secondly, the influence of wave front distortion with lower spatial frequency on temporal contrast is revealed comparing different degradation characteristics of various aberrations. At last, a method by controlling and optimizing the wave front to prevent temporal contrast degradation in large aperture ultra-short laser system is proposed, which is of great significance for high temporal contrast petawatt laser facilities.

Zhu, Ping; Xie, Xinglong; Zhu, Jianqiang; Zhu, Haidong; Yang, Qingwei; Kang, Jun; Guo, Ailin; Gao, Qi

2014-11-01

286

What's a Wavelength?  

NSDL National Science Digital Library

Students measure the wavelength of sounds and learn basic vocabulary associated with waves. As a class, they brainstorm the difference between two tuning forks and the sounds they produce. Then they come up with a way to measure that difference. Using a pipe in a graduated cylinder filled with water, students measure the wavelength of various tuning forks by finding the height the pipe must be held at to produce the loudest note. After calculating the wavelength and comparing it to the pitch of each tuning fork, students discover the relationship between wavelength and pitch.

National Science Foundation GK-12 and Research Experience for Teachers (RET) Programs,

287

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

288

Short wavelength rocketborne infrared spectrometer  

Microsoft Academic Search

An IR spectrometer, used to obtain measurements of faint atmospheric emission spectra from a rocket carrier, is described. The sensor scans the 2.07 to 5.47 micron spectral region at the rate of 2 scan\\/s. The spectral resolution of the sensor, which employs a circular variable filter (CVF), ranges from 1.0 to 3.0%. The entire optical subsection, indium antimonide detector, CVF,

C. L. Wyatt; D. G. Frodsham

1977-01-01

289

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

290

Monte Carlo simulation of wave sensing with a short pulse radar  

NASA Technical Reports Server (NTRS)

A Monte Carlo simulation is used to study the ocean wave sensing potential of a radar which scatters short pulses at small off-nadir angles. In the simulation, realizations of a random surface are created commensurate with an assigned probability density and power spectrum. Then the signal scattered back to the radar is computed for each realization using a physical optics analysis which takes wavefront curvature and finite radar-to-surface distance into account. In the case of a Pierson-Moskowitz spectrum and a normally distributed surface, reasonable assumptions for a fully developed sea, it has been found that the cumulative distribution of time intervals between peaks in the scattered power provides a measure of surface roughness. This observation is supported by experiments.

Levine, D. M.; Davisson, L. D.; Kutz, R. L.

1977-01-01

291

Tumor Selective Hyperthermia Induced by Short-Wave Capacitively-Coupled RF Electric-Fields  

PubMed Central

There is a renewed interest in developing high-intensity short wave capacitively-coupled radiofrequency (RF) electric-fields for nanoparticle-mediated tumor-targeted hyperthermia. However, the direct thermal effects of such high-intensity electric-fields (13.56 MHZ, 600 W) on normal and tumor tissues are not completely understood. In this study, we investigate the heating behavior and dielectric properties of normal mouse tissues and orthotopically-implanted human hepatocellular and pancreatic carcinoma xenografts. We note tumor-selective hyperthermia (relative to normal mouse tissues) in implanted xenografts that can be explained on the basis of differential dielectric properties. Furthermore, we demonstrate that repeated RF exposure of tumor-bearing mice can result in significant anti-tumor effects compared to control groups without detectable harm to normal mouse tissues. PMID:23861912

Raoof, Mustafa; Cisneros, Brandon T.; Corr, Stuart J.; Palalon, Flavio; Curley, Steven A.; Koshkina, Nadezhda V.

2013-01-01

292

Electronic excitation by short x-ray pulses: from quantum beats to wave packet revivals  

NASA Astrophysics Data System (ADS)

We propose a simple way to determine the periodicities of wave packets (WPs) in quantum systems directly from the energy differences of the states involved. The resulting classical periods and revival times are more accurate than those obtained with the traditional expansion of the energies about the central quantum number \\overline{n}, especially when \\overline{n} is low. The latter type of WP motion occurs upon excitation of highly charged ions with short XUV or x-ray pulses. Moreover, we formulate the WP dynamics in such a form that it directly reveals the origin of phase shifts in the maxima of the autocorrelation function, a phenomenon most prominent in the low \\overline{n} WP dynamics.

Rivière, P.; Iqbal, S.; Rost, J. M.

2014-06-01

293

O the Relative Importance of Nonlinearity and Mean Flow Variability in the Generation of Nonstationary Trapped Mountain Lee Waves  

Microsoft Academic Search

A number of observational studies over the past three decades have noted that trapped mountain lee waves can undergo substantial structural changes on time scales as short as an hour. These structural changes range from smooth wavelength transitions to more complex transitions with wave patterns of highly variable wavelength and amplitude. Nonstationary trapped-lee waves are often viewed as a linear

Louisa Bogar Nance

1995-01-01

294

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

DOE PAGESBeta

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

295

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

296

Coincidence Searches of Gravitational Waves and Short Gamma-Ray Bursts  

NASA Astrophysics Data System (ADS)

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.

Maselli, Andrea; Ferrari, Valeria

297

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

298

Short-pulse Calorimetric Load for High Power Millimeter-wave Beams  

NASA Astrophysics Data System (ADS)

A spherical compact matched load, for high vacuum operation suited for short pulses (2 MW, 0.1 s) precise measurement has been designed to test high power gyrotrons Bruschi, Gandini, Muzzini, Spinicchia, Cirant, Gittini, Granucci, Mellera, Nardone, Simonetto, and Sozzi (Fusion Eng. Des. 56 57:649 654, 2001); Bruschi, Cirant, Gandini, Granucci, Mellera, Muzzini, Nardone, Simonetto, Sozzi, and Spinicchia (Nucl. Fusion 43:1513 1519, 2003); Bruschi, Cirant, Gandini, Gittini, Granucci, Mellera, Muzzini, Nardone, Simonetto, Sozzi, Spinicchia, Angella, and Signorelli (Development of CW and short-pulse calorimetric loads for high power millimeter-wave Beams, 23rd Symposium on Fusion Technology, September 20 24, 2004, Venice, Italy). In order to enhance the power handling capability of the load and to reduce the operation problems that may arise from an excessive reflection from the load, a ray tracing code has been written to model the power distribution on the inner surface and the pattern of the reflected radiation. The outcome of this code has been used to select a more convenient profile for the spreading mirror of the load and to optimize a pre-load specially conceived to minimize the power reflected fraction.

Gandini, F.; Bruschi, A.; Cirant, S.; Gittini, G.; Granucci, G.; Muzzini, V.; Sozzi, C.; Spinicchia, N.

2007-02-01

299

Wavelength-Filter Based Spectral Calibrated Wave number - Linearization in 1.3 mm Spectral Domain Optical Coherence  

PubMed Central

In this study, we demonstrate the enhanced spectral calibration method for 1.3 ?m spectral-domain optical coherence tomography (SD-OCT). The calibration method using wavelength-filter simplifies the SD-OCT system, and also the axial resolution and the entire speed of the OCT system can be dramatically improved as well. An externally connected wavelength-filter is utilized to obtain the information of the wavenumber and the pixel position. During the calibration process the wavelength-filter is placed after a broadband source by connecting through an optical circulator. The filtered spectrum with a narrow line width of 0.5 nm is detected by using a line-scan camera. The method does not require a filter or a software recalibration algorithm for imaging as it simply resamples the OCT signal from the detector array without employing rescaling or interpolation methods. One of the main drawbacks of SD-OCT is the broadened point spread functions (PSFs) with increasing imaging depth can be compensated by increasing the wavenumber-linearization order. The sensitivity of our system was measured at 99.8 dB at an imaging depth of 2.1 mm compared with the uncompensated case. PMID:25688338

Wijeisnghe, Ruchire Eranga Henry; Cho, Nam Hyun; Park, Kibeom; Shin, Yongseung; Kim, Jeehyun

2014-01-01

300

VEGETATION WATER CONTENT ESTIMATION FOR CORN AND SOYBEANS USING SPECTRAL INDICES DERIVED FROM MODIS NEAR- AND SHORT- WAVE INFRARED BANDS  

Technology Transfer Automated Retrieval System (TEKTRAN)

Vegetation water content (VWC) information can be valuable in hydrology, forestry, agriculture and meteorology. The estimation of VWC over a full crop-growing period was performed here using the near infrared (NIR) and short-wave infrared (SWIR) bands of the Terra - MODerate Resolution Imaging Spect...

301

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

E-print Network

with wavelengths from visible lights (4×102 nm) to infrared radiations (1×105 nm). With the recent development of intense and ultrashort-wavelength free-electron lasers [32–34], the study of multiphoton *zyzhou@ku.edu †sichu@ku.edu processes in the high...

Chu, Shih-I; Zhou, Zhongyuan

2011-01-19

302

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

303

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.

304

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

2008-04-16

305

Vertical propagation of lakewide internal waves  

NASA Astrophysics Data System (ADS)

Internal waves with diurnal period dominated velocities measured by an Acoustic Doppler Profiler (ADP) in a small lake (main basin 3000 m by 400 m by 18 m). ADP profiles and an along-lake temperature section indicate that the observed waves, like seiches, had horizontal wavelengths exceeding the metalimnion length. However, unlike non-dissipative seiches, the observed waves propagated vertically, carrying energy to the lakebed where waves were absorbed, rather than being strongly reflected. This absorption is predicted by a standard parameterization of boundary layer dissipation. The absence of upward-propagating energy precludes seiche resonance, limits focusing of waves toward attractors, and suggests that hypolimnion dissipation was limited by the supply of downward-propagating energy. Vertical wavelengths were less than the lake depth. Simplified calculations suggest that vertically-propagating waves, as opposed to vertically standing seiches, are most likely where vertical wavelengths are short, near-bed stratification is strong, and lakes are short and deep.

Henderson, Stephen M.; Deemer, Bridget R.

2012-03-01

306

Short wavelength and high amplitude (~ 1 km) surface uplift in the western Colorado Plateau driven by recent and ongoing mantle flow  

NASA Astrophysics Data System (ADS)

On the southwestern edge of the Colorado Plateau, two tributaries to the Virgin River record differing amounts of epeirogenic uplift in their longitudinal profiles and thus provide a geologic test for models of mantle-driven dynamic topography. The North and East Forks of the Virgin River have similar bedrock lithologies and drainage basin areas such that they should have similar longitudinal profiles and incision histories. Instead, the North Fork is steeper with an average channel slope of 0.023 compared to the East Fork which has a slope of 0.014. The headwaters of the North Fork are also ca. 500 m higher than that of the East Fork. These differences in the longitudinal profiles of the rivers are best explained by the fact that they straddle one of the largest mantle velocity gradients (4.5% at 80 km depth over 200 km) in the western U.S. The East Fork drains a region that has ca. 1% higher upper mantle velocity than the North Fork. Throughout this area of high mantle velocity gradient, between the Colorado Plateau rim and the Escalante, UT area, channel slope at a given drainage basin area is strongly linked to the upper mantle velocity structure. At drainage basin areas less than 0.5 km2, only streams underlain by upper mantle with negative velocities have channel slope values greater than 0.015. This relationship is seen despite bedrock strength variations along the streams and the presence of transient kickpoints due to old base level falls and strongly indicates that uplift of the area is recent if not ongoing. Recent and ongoing uplift of the area under the North Fork can explain the high relief and dramatic slot canyons of Zion National Park, which it flows through. Published Virgin River incision rates also show differential block uplift of ca. 1000 m across the Hurricane and Washington faults. Similar differential block uplift of ca. 700 m has been documented across the Hurricane fault in Grand Canyon. This indicates that buoyancy differences in the upper mantle are driving differential uplift of the lithosphere along the western flank of the Colorado Plateau. The differential uplift across the faults and the length scale of the high mantle velocity gradient area indicate that the zone of uplift has an amplitude of ca. 1000 m and a wavelength of ca. 200 m. High amplitude and short wavelength dynamic topography reflect mantle flow forcings, suggested by the extremely sharp mantle velocity gradients, filtered through a thinned lithosphere with high heat flow and thin effective elastic thickness that suggest upper mantle melt-filled shear zone conduits. This new geologic evidence for recent and ongoing surface uplift offers an important constraint for geodynamic models which are beginning to elucidate the mantle processes that are producing dynamic topography on the western edge of the Colorado Plateau.

Crow, R.; Karlstrom, K. E.

2011-12-01

307

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

308

Integrated Analysis of Carbonatite using Short Wave Infra-Red and Visible/Near Infra-Red Reflectance Characteristics  

NASA Astrophysics Data System (ADS)

Carbonatites are among the most important hosts for economically important rare-earth element (REE) deposits. An ongoing challenge has been the identification of carbonatites, which may outcrop as small bodies with indistinct field characteristics. Remote sensing techniques may provide a routine and reliable method to identify such deposits. We have used short wave infra-red (SWIR) and visible/near infra-red (VNIR) reflectance characteristics of a well exposed carbonatite located in the north east of the United Arab Emirates to develop techniques to facilitate the distinction of carbonatites from other rock types. This project has focused on the wavelength region from 0.45 to 2.43 ?m of SWIR and VNIR subsystems on the imaging instrument onboard ASTER. We hypothesize that based on spectral and spatial data derived from computer segmentation algorithms of the SWIR (7) and VNIR (4, 1) bands we will be able to identify carbonatite rocks. In order to build a technique that can capture the intrinsic associations between carbonatite anomalies, rock class types, and attributes, we assembled the spectral and spatial information derived from computer segmentation algorithms into a single segment image. During our investigation of the spatial data two principal questions arose: 1) How should spatial structures, or "neighborhoods" for each pixel within the image be automatically defined? 2) How should spatial and spectral information be combined in the classification? We addressed these questions by using unsupervised and supervised segmentation algorithm strategies based on pixel values and locations. Pixels that are spatially connected and have similar values were grouped in a single segment (fixed neighborhood pixels) on the basis of the integration of the maximum-likelihood supervised classification technique within a Markov Random Fields framework. We then developed guidelines for combining the spatial information extracted through segmentation with spectral information within a classifier. These techniques allowed us to devise classification techniques using region-growing segmentation based upon automatically derived markers for identifying spatial structures of carbonatite. We were able to develop methods that are able to handle high-dimensional data and use adaptive spatial neighborhoods derived from segmentation results. The final strategy concentrated on techniques to reduce over-segmentation of the resulting images. An important component of this strategy consisted of analyzing potential classification results for the most reliably classified pixels to be used as markers of spatial zones. We present our results as a thematic image in which pixel values represent a specific spectra signature of class types of contiguous raster objects of carbonatites materials.

Assiri, A.; Rooney, T. O.; Velbel, M. A.

2012-12-01

309

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

E-print Network

, during, and after the passage of a nonlinear internal wave on 18 August, 2006. Using oceanographic data collected at a nearby location, a plane-wave model for the nonlinear internal wave's posi- tion In shallow water, there is extensive ongoing research into the impact of nonlinear internal waves on low

310

The Short-Wave Aerostat Mounted Imager (SWAMI): a Novel Hyperspectral Remote Sensing Instrument Platform  

NASA Astrophysics Data System (ADS)

The Short-Wave Aerostat Mounted Imager (SWAMI) is a newly designed remote sensing platform attached to the tether line of a 3500 m3 research balloon. We are using the SWAMI to study terrestrial ecosystems by bridging the spatial gap between radiometric measurements collected near the surface and those collected by other aircraft or satellite. Primary instruments of the SWAMI include an Analytical Spectral Devices Dual VNIR spectrometer, video camera, and thermal infrared sensor, which are mounted upon a pointable view hatch with active stabilization. Secondary instruments include a GPS receiver and numerous meteorological sensors. Downloads of sensor data and remote control of the spectrometer occurs via wireless transmission to a ground control station. The balloon can be flown at altitudes up to 2km AGL. Data collected during Summer 2003 over a ponderosa pine forest, a conifer forest/grassland ecotone, and grassland areas are being used to investigate spectral mixture algorithms commonly used in sub-pixel analysis. Portions of the SWAMI platform are planned for use at an Ameriflux tower site in the Black Hills of South Dakota to collect data relevant to SpecNet. Applications of SWAMI technology to the proposed SpecNet network, including wireless spectrometer control and active pointing control mechanisms, will be discussed.

Vierling, L.; Chen, X.; Fersdahl, M.; Zimmerman, P.

2003-12-01

311

Short-wave aerosol radiative efficiency over the global oceans derived from satellite data  

NASA Astrophysics Data System (ADS)

Using 5 yr (December 2000-November 2005) of satellite data from the clouds and the earths radiant energy system (CERES) and moderate resolution imaging spectroradiometer (MODIS), we examine the instantaneous short-wave radiative efficiency (E?) of aerosols during the morning Terra satellite overpass time over the global oceans (60°N-60°S). We calculate E? using two commonly used methods. The first method uses the MODIS aerosol optical thickness (AOT) at 0.55 ?m with radiative transfer calculations, whereas the second method utilizes the same AOT values along with a new generation of aerosol angular distribution models to convert the CERES-measured broad-band radiances to fluxes. Over the 5 yr, the global mean instantaneous E? between the methods is remarkably consistent and within 5 W m-2 ?-1 with a mean value of -70 W m-2 ?-1. The largest differences between the methods occur in high-latitude regions, primarily in the Southern Hemisphere, where AOT is low. In dust dominated regions, there is an excellent agreement between the methods with differences of <3 W m-2?-1. These differences are largely due to assumptions in aerosol models and definition of clear sky backgrounds. Independent assessments of aerosol radiative effects from different satellite sensors and methods are extremely valuable and should be used to verify numerical modelling simulations.

Christopher, Sundar A.; Jones, Thomas A.

2008-09-01

312

Outgassing models for Landsat-4 thematic mapper short wave infrared bands  

USGS Publications Warehouse

Detector responses to the Internal Calibrator (IC) pulses in the Landsat-4 Thematic Mapper (TM) have been observed to follow an oscillatory behavior. This phenomenon is present only in the Short Wave Infrared (SWIR) bands and has been observed throughout the lifetime of the instrument, which was launched in July 1982 and imaged the Earth's surface until late 1993. These periodic changes in amplitude, which can be as large as 7.5 percent, are known as outgassing effects and are believed to be due to optical interference caused by a gradual buildup of an ice-like material on the window of the cryogenically cooled dewar containing the SWIR detectors. Similar outgassing effects in the Landsat-5 TM have been characterized using an optical thin-film model that relates detector behavior to the ice film growth rate, which was found to gradually decrease with time. A similar approach, which takes into consideration the different operational history of the instrument, has been applied in this study to three closely sampled data sets acquired throughout the lifetime of the Landsat-4 TM. Although Landsat-4 and Landsat-5 Thematic Mappers are essentially identical instruments, data generated from analyses of outgassing effects indicate subtle, but important, differences between the two. The estimated lifetime model could improve radiometric accuracy by as much as five percent.

Micijevic, E.; Helder, D.L.

2005-01-01

313

Interactive Simulation and Visualization of Lamb Wave Propagation in Isotropic and Anisotropic  

E-print Network

-destructive testing (NDT) methods based on ultrasonic waves have been used on a more local level. In parallel to the concept of SHM. The associated short wavelengths of the ultrasonic waves lead to measurable wave of ultrasonic waves that remain guided between two parallel free surfaces, such as the upper and lower surfaces

Blanz, Volker

314

Analysis of performance of three- and five-stack achromatic half-wave plates at millimeter wavelengths  

E-print Network

We study the performance of achromatic half-wave plates (AHWP) as a function of their construction parameters, the detection bandwidth of a power detector operating in the millimeter wave band, and the spectral shape of the incident radiation. We focus particular attention on the extraction of the degree of incident polarization and its orientation angle from the intensity measured as a function of AHWP rotation angle, which we call the IVA (intensity versus angle). We quantify the phase offset of the IVA and point to potential systematic errors in the extraction of this offset in cases where the incident spectrum is not sufficiently well known. We show how the phase offset and modulation efficiency of the AHWP depend on the relative angles between the plates in the stack and find that high modulation efficiency can be achieved with alignment accuracy of few degrees.

Tomotake Matsumura; Shaul Hanany; Bradley R. Johnson; Terry J. Jones; Prashanth Jonnalagadda

2008-06-09

315

Dependence of the Normalized Radar Cross Section of Water Waves on Bragg Wavelength-Wind Speed Sensitivity  

NASA Technical Reports Server (NTRS)

Measurements of the normalized radar cross section (sigma(sup o)) made by the YSCAT ultrawideband scatterometer during an extended deployment on the Canada Centre for Inland Waters(CCIW) Research Tower located at Lake Ontario are analyzed and compared with anemometer wind measurements to study the sensitivity of (sigma(sup o)) to the wind speed as a function of the Bragg wavelength. This paper concentrates on upwind and downwind azimuth angles in the wind speed range of 4.5-12 m/s. While YSCAT collected measurements of sigma(sup o) at a variety of frequencies and incidence angles, this paper focuses on frequencies of 2.0, 3.05, 5.30, 10.02, and 14.0 GHz and incidence angles within the Bragg regime, 30-50 deg. Adopting a power law model to describe the relationship between sigma(sup o) and wind speed, both wind speed exponents and upwind/downwind (u/d) ratios of sigma(sup o) are found using least squares linear regression. The analysis of the wind speed exponents and u/d ratios show that shorter Bragg wavelengths (Lambda less than 4 cm) are the most sensitive to wind speed and direction. Additionally, vertical polarization (V-pol) sigma(sup o) is shown to be more sensitive to wind speed than horizontal polarization (H-pol) sigma(sup o), while the H-pol u/d ratio is larger than the V-pol u/d ratio.

Long, David G.; Collyer, R. Scott; Reed, Ryan; Arnold, David V.

1996-01-01

316

60GHz Photonic Millimeter-Wave Link for Short to Medium-Range Wireless Transmission Up to 12.5 Gb\\/s  

Microsoft Academic Search

In this paper, a 60-GHz photonic millimeter-wave link system for short- to medium-range broadband wireless data transmission is investigated. The system employs advanced mm-wave photonic components and radio-over-fiber (RoF) techniques for the generation of a DSB-SC optical mm-wave carrier and its subsequent on-off-keying modulation and transmission. For short-range applications, we have constructed a compact wireless RoF transmitter consisting of a

M. Weiss; Mathieu Huchard; Andreas Stohr; Benoît Charbonnier; Sascha Fedderwitz; Dieter Stefan Jager

2008-01-01

317

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

318

Application of Artificial Neural Network to Search for Gravitational-Wave Signals Associated with Short Gamma-Ray Bursts  

E-print Network

We apply a machine learning algorithm, the artificial neural network, to the search for gravitational-wave signals associated with short gamma-ray bursts. The multi-dimensional samples consisting of data corresponding to the statistical and physical quantities from the coherent search pipeline are fed into the artificial neural network to distinguish simulated gravitational-wave signals from background noise artifacts. Our result shows that the data classification efficiency at a fixed false alarm probability is improved by the artificial neural network in comparison to the conventional detection statistic. Therefore, this algorithm increases the distance at which a gravitational-wave signal could be observed in coincidence with a gamma-ray burst. In order to demonstrate the performance, we also evaluate a few seconds of gravitational-wave data segment using the trained networks and obtain the false alarm probability. We suggest that the artificial neural network can be a complementary method to the conventional detection statistic for identifying gravitational-wave signals related to the short gamma-ray bursts.

Kyungmin Kim; Ian W. Harry; Kari A. Hodge; Young-Min Kim; Chang-Hwan Lee; Hyun Kyu Lee; John J. Oh; Sang Hoon Oh; Edwin J. Son

2015-03-03

319

Enhancement of the evanescent wave coupling effect in a sub-wavelength-sized GaAs/AlGaAs ridge structure by low-refractive-index surface layers.  

PubMed

We have investigated the three-dimensional emission patterns of GaAs/AlGaAs ridge structures with a sub-wavelength-sized top-flat facet by angle-resolved photoluminescence (PL). We found that the integrated PL intensity, and hence the light-extraction efficiency, can be enhanced by about 34% just by covering the ridge surface with a thin SiO2 layer. A double-coupling effect of evanescent waves that occurs at both the semiconductor-SiO2 and SiO2-air interfaces is suggested to be responsible for the improvement, based on a finite-difference time-domain simulation of the electromagnetic field around the ridge top. PMID:25607313

Wang, Xue-Lun; Hao, Guo-Dong; Takahashi, Tokio

2014-10-20

320

Investigating gait recognition in the short-wave infrared (SWIR) spectrum: dataset and challenges  

NASA Astrophysics Data System (ADS)

In the biometrics community, challenge datasets are often released to determine the robustness of state-of-the- art algorithms to conditions that can confound recognition accuracy. In the context of automated human gait recognition, evaluation has predominantly been conducted on video data acquired in the active visible spectral band, although recent literature has explored recognition in the passive thermal band. The advent of sophisticated sensors has piqued interest in performing gait recognition in other spectral bands such as short-wave infrared (SWIR), due to their use in military-based tactical applications and the possibility of operating in nighttime environments. Further, in many operational scenarios, the environmental variables are not controlled, thereby posing several challenges to traditional recognition schemes. In this work, we discuss the possibility of performing gait recognition in the SWIR spectrum by first assembling a dataset, referred to as the WVU Outdoor SWIR Gait (WOSG) Dataset, and then evaluate the performance of three gait recognition algorithms on the dataset. The dataset consists of 155 subjects and represents gait information acquired under multiple walking paths in an uncontrolled, outdoor environment. Detailed experimental analysis suggests the benefits of distributing this new challenging dataset to the broader research community. In particular, the following observations were made: (a) the importance of SWIR imagery in acquiring data covertly for surveillance applications; (b) the difficulty in extracting human silhouettes in low-contrast SWIR imagery; (c) the impact of silhouette quality on overall recognition accuracy; (d) the possibility of matching gait sequences pertaining to different walking trajectories; and (e) the need for developing sophisticated gait recognition algorithms to handle data acquired in unconstrained environments.

DeCann, Brian; Ross, Arun; Dawson, Jeremy

2013-05-01

321

Stabilized platform for tethered balloon soundings of broadband long- and short-wave radiation  

SciTech Connect

Changes in the composition of trace gases in the earth's atmosphere have been reported by many observers, and a general concern has been expressed regarding possible changes to the earth's climate that may be caused by radiatively active gases introduced into the earth's atmosphere by man's activities. Radiatively active trace gases produce temperature changes in the earth's atmosphere through changes in radiative flux divergence. Our knowledge of and means of measuring radiative flux divergence is very limited. A few observations of vertical radiative flux divergences have been reported from aircraft from radiometersondes from towers and from large tethered balloons. These measurement techniques suffers from one or more drawbacks, including shallow sounding depths (towers), high cost (aircraft), complicated logistics (large tethered balloons), and limitation to nighttime hours (radiometersondes). Changes in radiative flux divergence caused by anthropogenic trace gases are expected to be quite small, and will be difficult to measure with existing broadband radiative flux instruments. The emphasis of present research in global climate change is thus being focused on improving radiative transfer algorithms in global climate models. The radiative parameterizations in these models are at an early stage of development and information is needed regarding their performance, especially in cloudy conditions. The impetus for the research reported in this paper is the need for a device that can supplement existing means of measuring vertical profiles of long- and short-wave irradiance and radiative flux divergence. We have designed a small tethered-balloon-based system that can make radiometric soundings through the atmospheric boundary layer. This paper discusses the concept, the design considerations, and the design and construction of this sounding system. The performance of the system will be tested in a series of balloon flights scheduled for the fall and winter of 1992.

Alzheimer, J.M.; Anderson, G.A.; Whiteman, C.D.

1993-01-01

322

Stabilized platform for tethered balloon soundings of broadband long- and short-wave radiation  

SciTech Connect

Changes in the composition of trace gases in the earth`s atmosphere have been reported by many observers, and a general concern has been expressed regarding possible changes to the earth`s climate that may be caused by radiatively active gases introduced into the earth`s atmosphere by man`s activities. Radiatively active trace gases produce temperature changes in the earth`s atmosphere through changes in radiative flux divergence. Our knowledge of and means of measuring radiative flux divergence is very limited. A few observations of vertical radiative flux divergences have been reported from aircraft from radiometersondes from towers and from large tethered balloons. These measurement techniques suffers from one or more drawbacks, including shallow sounding depths (towers), high cost (aircraft), complicated logistics (large tethered balloons), and limitation to nighttime hours (radiometersondes). Changes in radiative flux divergence caused by anthropogenic trace gases are expected to be quite small, and will be difficult to measure with existing broadband radiative flux instruments. The emphasis of present research in global climate change is thus being focused on improving radiative transfer algorithms in global climate models. The radiative parameterizations in these models are at an early stage of development and information is needed regarding their performance, especially in cloudy conditions. The impetus for the research reported in this paper is the need for a device that can supplement existing means of measuring vertical profiles of long- and short-wave irradiance and radiative flux divergence. We have designed a small tethered-balloon-based system that can make radiometric soundings through the atmospheric boundary layer. This paper discusses the concept, the design considerations, and the design and construction of this sounding system. The performance of the system will be tested in a series of balloon flights scheduled for the fall and winter of 1992.

Alzheimer, J.M.; Anderson, G.A.; Whiteman, C.D.

1993-01-01

323

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

324

Exploring Short Gamma-ray Bursts as Gravitational-wave Standard Sirens  

NASA Astrophysics Data System (ADS)

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 <~ 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; Holz, Daniel E.; Hughes, Scott A.; Dalal, Neal; Sievers, Jonathan L.

2010-12-01

325

Response Time Measurements in Short-Wave Infrared HgCdTe e-APDs  

NASA Astrophysics Data System (ADS)

The impulse response time has been measured as a function of reverse bias, gain, and temperature in backside-illuminated short-wave infrared HgCdTe avalanche photodiodes (APDs) with variable junction geometry. The APD geometry was altered using HgCdTe substrates of variable thickness and by variation of device fabrication parameters. This approach allowed study of the drift-diffusion dynamics of the electrons before entering the junction and the electron and hole dynamics during the junction transition in APDs with different carrier collection distances and junction widths. The response time was typically limited by a double exponential decay, which is attributed to contributions from the impedance mismatch between the interconnection circuit and the 50-? radiofrequency probe, and a delayed diffusion response from carriers generated far from the junction. These contributions limited the maximum bandwidth of the diodes to about 600 MHz, independently of gain and temperature. The hot carrier velocities are estimated by fitting the measured response with numerical calculations, taking into account contributions from a direct drift-multiplication response and a delayed diffusion response. This analysis shows that the hot carrier dynamics is close to independent of temperature and that the electron drift velocity saturates at the gain onset to a value of 1 × 107 cm/s, decreasing upon a further increase of the electric field E to a value of about 3 × 106 cm/s at E = 100 kV/cm. The hole velocity shows a slow variation from 3 × 106 cm/s at low electric fields to 1.5 × 106 cm/s at high electric fields.

Rothman, Johan; Foubert, Kevin; Lasfargues, Gilles; Largeron, Christophe

2014-08-01

326

Comparison of the efficacy of ketoprofen phonophoresis, ultrasound, and short-wave diathermy in knee osteoarthritis.  

PubMed

The present study aimed to compare the efficacy of three different deep heating modalities: phonophoresis (PH), short-wave diathermy (SWD), and ultrasound (US), in knee osteoarthritis. Patients who consented to participate in the study were randomly divided into the following three groups. Group 1 (n = 33) received PH, Group 2 (n = 33) received US, and Group 3 (n = 35) received SWD. These deep heating therapies were applied by the same therapist. Each therapy began with 20-min hot pack application. Each of the three physical therapy modalities was applied 5 days a week for 2 weeks (a total of 10 sessions). The patients were evaluated using visual analogue scale (VAS) at rest, 15-m walking time, and the Western Ontario and McMaster Universities Arthritis Index (WOMAC) both before and after the treatment. Moreover, at the end of the treatment, both the physician and the patient made an overall evaluation, by rating the treatment efficacy. The results of the study showed that VAS, 15-m walking time, and WOMAC parameters were improved with all three deep heating modalities, and all the three modalities were effective. However, there was no significant difference between the three modalities in terms of efficacy. There was also no significant difference between the three groups in terms of post-treatment general evaluation of the physician and the patient. The present study is the first to suggest that choosing one of PH/US/SWD therapy options would provide effective results and none of them are superior to the others, and we believe that these findings will be a basis for further studies. PMID:23832291

Boyaci, Ahmet; Tutoglu, Ahmet; Boyaci, Nurefsan; Aridici, Rifat; Koca, Irfan

2013-11-01

327

Chaos Experiments Wave Chaos and Electromagnetic  

E-print Network

Dimensional Quarter Bow Tie Wave Chaotic cavity · Classical ray trajectories are chaotic - short wavelengthChaos Experiments ­ Wave Chaos and Electromagnetic Interference in Enclosures ·Faculty: Steven M · Coupling of external radiation to computer circuits is a complex processes: apertures resonant cavities

Anlage, Steven

328

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

PubMed

We elucidate the feature of gravitational waves (GWs) from a binary-neutron-star merger collapsing to a black hole by general relativistic simulation. We show that GW spectrum imprints the coalescence dynamics, formation process of disk, equation of state for neutron stars, total masses, and mass ratio. A formation mechanism of the central engine of short-gamma-ray bursts, which are likely to be composed of a black hole and surrounding disk, therefore could be constrained by GW observation. PMID:20481927

Kiuchi, Kenta; Sekiguchi, Yuichiro; Shibata, Masaru; Taniguchi, Keisuke

2010-04-01

329

Dual-wavelength, continuous-wave Yb:YAG laser for high-resolution photothermal common-path interferometry.  

PubMed

We present a continuous-wave (CW) intracavity frequency-doubled Yb:YAG laser providing 1030 and 515 nm output simultaneously. This laser system was designed for photothermal common-path interferometry to measure spatially resolved profiles of the linear absorption in dielectric media and coatings for visible or infrared light as well as of the nonlinear absorption for the combination of both. A Z-shape laser cavity was designed, providing a beam waist in which an LBO crystal was located for effective second-harmonic generation (SHG). Suitable frequency conversion parameters and cavity configurations were discussed to achieve the optimal performance of a diode-pumped CW SHG laser. A 12.4 W 1030 nm laser and 5.4 W 515 nm laser were developed simultaneously in our experiment. PMID:23872763

Zhuang, Fengjiang; Jungbluth, Bernd; Gronloh, Bastian; Hoffmann, Hans-Dieter; Zhang, Ge

2013-07-20

330

A full-duplex radio-over-fiber link with 12-tupling mm-wave generation and wavelength reuse for upstream signal  

NASA Astrophysics Data System (ADS)

A full-duplex radio-over-fiber (RoF) link with a novel scheme to generate 60 GHz mm-waves from a 5 GHz RF signal source is investigated. In the RoF downlink, the required frequency of the RF oscillator is reduced greatly. Since the optical carrier is not modulated by downstream data, part of it is reused to carry upstream data and the upstream data is transmitted to the central station using optical single-sideband modulation. In this way, a single wavelength is used for both downstream and upstream transmissions. Based on this scheme, a full-duplex RoF link is built and its transmission performance is analyzed. Theoretical analysis and numerical simulation show that the downstream signal cannot only eliminate code form distortion caused by time shift of the code edges, but also reduce the influence of the fading effect as the 60 GHz DSB optical mm-wave signal is transmitted along the fiber, and the upstream signal is immune to both fading effect and time shift of the code edges.

Chen, Yang; Wen, Aijun; Shang, Lei; Wang, Yong

2011-10-01

331

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

NASA Technical Reports Server (NTRS)

A four frequency moment characterization of backscatter from the near-vertical is applied to an analysis of the short pulse and dual frequency microwave techniques. The range reflectivity modulation spectrum closely approximates the directional wave slope spectrum, while harmonic distortion is small and is a minimum near 10 deg incidence. The short pulse measurement signal-to-noise ratio (SNR) is typically greater than the narrowband dual frequency SNR, with the difference being the ratio of the range beam extent to pulse length, minus the ratio of beam-limited to pulse-limited Doppler spreads. It is concluded that dual frequency measurements are basically impractical, although short pulse measurements are useful and can employ existing space-qualified microwave hardware.

Jackson, F. C.

1981-01-01

332

Short-Period Rayleigh Wave Dispersion Measurements as an evaluation tool to estimate Madeira heat source depths  

NASA Astrophysics Data System (ADS)

Madeira is an intraplate volcanic island, located at the eastern North Atlantic Ocean, in front of the Moroccan cost, with an emerged area of 737 km2 and maximum altitude of 1861 m. The existence of recent volcanism (6 my) with well preserved volcanic cones and thermal evidences suggest the presence of a heat source at shallow levels. An attempt to define the depths of these heat sources depths in Madeira is being conducted by the integration of petrological, geochemical and geophysical methods, including seismic tomography. Constrains like source-receiver geometry, irregular seismicity distribution or, for some methods, low seismicity occurrence did not allow to obtain high-resolution models of the Madeira shallow structure using traditional passive seismology. Seismic interferometry/ambient noise surface-waves tomography allows imaging regions with a resolution that mainly depends on the seismic network coverage. From May 2011 to September 2012, a temporary pool of 23 seismometers (Fig.1) has been continuously recording at Madeira Island. This deployment, complemented with other local permanent stations, provided a dense coverage of the island. Cross-correlation of the ambient seismic noise recorded at the 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 obtain lateral variations of the Rayleigh-wave group-velocities as function of the period. As a result we were able to address some of the unknowns regarding the crustal structure beneath Madeira. The dispersion curves, extracted from the Rayleigh-wave group-velocity maps, have been inverted to obtain a quasi-3-D model of the crustal shear wave velocities.

Matos, Catarina; Silveira, Graça; Matias, Luis; Caldeira, Rita; Rosa, Carlos; Ribeiro, Luisa; Dias, Nuno; Krueger, Frank; Nunes, Joana; Rosa, Diogo

2013-04-01

333

Interference of birefractive waves in CdGa2S4 crystals  

NASA Astrophysics Data System (ADS)

In ?dG?2S4 crystals the Fabry-Perot and birefringence interference spectra were investigated. Spectral dependences of refraction indexes for ordinary (no) and extraordinary (ne) light waves are defined. The spectral dependence ?n=ne-no from the short and long-wavelength parts of isotropic wavelength ?0=485.7 nm (300 K) is determined. It is established that at ?>?0 ?n is positive and at ?Wavelength ?0=485.7 nm shifts with decreasing temperature to short-wavelengths. The phase difference of ordinary and extraordinary light waves for ?>?0 and ?wavelength has a small halfwidth (?3-5 Å). Another isotropic wavelength was found in the short-wavelength region (433 nm) for crystals obtained by iodine transport method.

Syrbu, N. N.; Tiron, A. V.; Parvan, V. I.; Zalamai, V. V.; Tiginyanu, I. M.

2015-04-01

334

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

SciTech Connect

Flat silicon samples were irradiated with 40 fs, 800?nm laser pulses at an intensity at the best focus of 2·10{sup 18} Wcm{sup ?2}, in the presence of a pre-plasma on the sample surface. X-ray emission in the spectral range from 2 to 30?keV was detected inside and outside the plane of incidence, while varying pre-plasma scale length, laser intensity, and polarization. The simultaneous detection of 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 (n{sub c}) region or with the n{sub c}/4 region. In the presence of a moderate pre-plasma, our measurements reveal that, provided the pre-plasma reaches a scale-length of a few laser wavelengths, X-ray emission is dominated by the contribution from the interaction with the under dense plasma, where electron plasma waves can grow, via laser stimulated instabilities, and, in turn, accelerate free electrons to high energies. This mechanism leads also to a clear anisotropy in the angular distribution of the X-ray emission. Our findings can lead to an enhancement of the conversion efficiency of ultra short laser pulses into X-rays.

Baffigi, F., E-mail: federica.baffigi@ino.it; Cristoforetti, G.; Fulgentini, L.; Giulietti, A.; Koester, P.; Labate, L.; Gizzi, L. A. [Intense Laser Irradiation Laboratory, Istituto Nazionale di Ottica, CNR Campus, Via G. Moruzzi 1, 56124, Pisa (Italy)

2014-07-15

335

Observations of quasi-inertial and short-period internal waves from stationary platform in the Black Sea  

NASA Astrophysics Data System (ADS)

It is well known that the major factor of the generation of the intensive internal waves on the shelves of the oceans and open seas is barotropic tide. Despite of the Black sea is closed and free-tidal sea nevertheless there are exist quite intense internal wave field in here. The results of long-term observations of long- and short-period internal waves measured in the Black Sea are analyzed. These studies were carried out from the stationary platform of the Marine Hydrophysical Institute of the National Academy of Sciences of Ukraine in the summer 2010 and 2011. The platform is situated on the Southern coast of Crimea in 600 m from the shore, where sea depth is about 30 m. The measurements were taken by acoustic Doppler current profilometer (ADCP) "Rio Grande 600 kHz", thermistor chain of ten sensors "Star-Oddi" and oceanographic mini profiler «MiniSVP» with measuring parameters of sound velocity and temperature. We observed the well-defined temporal thermocline oscillations with period close to local inertial (17.2 hours) period. At the same time the clockwise rotation of the vector of currents with the inertial period was detected. During the expedition in 2011 the whole water column synchronous oscillations of the first-mode were observed for the first 5 days, which than changed into the second-mode oscillations. Observations of 2011 were for conditions when thermocline was in the middle of water column. Observed oscillations of inertial waves in 2010 were for conditions of bottom thermocline. The amplitudes of thermocline oscillations were up to 10 -12 m. Also intense short-period waves with period from 2 to 20 minutes and heights from 1 to 6 m were registered. Several cases of second mode short-period internal waves were observed. Also several passages of solitary internal waves were noticed. The peaks of inertial and high-frequency oscillations were revealed by the spectral analysis of current data and temperature records. This work was partly supported by the Russian Foundation for Basic Research.

Khymchenko, Ielizaveta; Serebryany, Andrey

2013-04-01

336

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,

337

900 1000 1100 1200 Wavelength ()  

E-print Network

water, the short wavelength cutoff moves to longer wavelengths . Maintaining9 high sensitivity at OVI in the instrument. An additional precaution taken in order to keep the reflectivities high was limiting pointing, a target is occulted by the earth every orbit. Since the satellite remains pointed at the object (using its

338

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

2014-02-24

339

Seasonal variation of short-period (<2 h) gravity wave activity over Gadanki, India (13.5°N, 79.2°E)  

Microsoft Academic Search

We have analyzed the seasonal variation of short-period (<2 h) gravity wave activity in the troposphere and lower stratosphere using the wind observations made with VHF radar at Gadanki (13.5°N, 79.2°E), India. Four years of high resolution (?3 min) wind data (2003–2006) have been used to study variance and momentum flux of short-period gravity waves. Both horizontal and vertical variances

Gopa Dutta; Toshitaka Tsuda; P. Vinay Kumar; M. C. Ajay Kumar; Simon P. Alexander; Toshiaki Kozu

2008-01-01

340

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

341

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

E-print Network

The generalized theory of thermoelasticity was employed to characterize the coupled thermal and mechanical wave propagation in high performance microelectronic packages. Application of a Gaussian heat source of spectral profile similar to high...

Nagaraj, Mahavir

2004-11-15

342

Large-Scale Flow Response to Short Gravity Waves Breaking in a Rotating Shear Flow  

Microsoft Academic Search

A two-dimensional rotating anelastic model is used to analyze the large-scale flow (LSF) response to the breaking of gravity waves (GWs) at critical levels. In the response the balanced part is separated from the inertial oscillations (IOs) and the inertia-gravity waves (IGWs). Interest also focuses on the relative importance of the two, when the regime of the critical levels interaction

FRANCO ISLOTT

2003-01-01

343

The interaction of short surface waves with stratified flow in Raccoon Strait  

NASA Astrophysics Data System (ADS)

Strong tidal currents and complex wave-current interaction characterize the west side of Raccoon Strait, the narrow waterway between Angel Island and the Tiburon Peninsula in San Francisco Bay. The surface and internal hydrodynamics in this area are strongly affected by the presence of a shallow sill (depth ~10m) that extends partially across the strait near the western tip of Angel Island. In this work we present observations collected during several field experiments in 2011 and 2012 in Raccoon Strait, San Francisco Bay, using shipboard ADCP, bottom mounted ADCPs, CTDs, and Wave Resolving Drifters (WRDs). By combining observations from bottom-mounted, fixed (Eulerian) instruments and newly developed Lagrangian drifters that can resolve wind wave dynamics and surface drifts, we relate the spatial structure of the stratified flow dynamics with the observed wave evolution in the area. We analyze the interaction and characteristics of the wave blocking dynamics observed near the sill, the development of a subduction zone of surface waters during flood tide, and the occurrence of an internal lee wave downstream of the sill.

Janssen, T. T.; Pearman, D. W.; Herbers, T. H.; Largier, J. L.; McIntyre, S.; Jessen, P.

2012-12-01

344

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

345

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

346

Dynamic characteristics of a multi-wavelength Brillouin-Raman fiber laser assisted by multiple four-wave mixing processes in a ring cavity  

NASA Astrophysics Data System (ADS)

Dynamic characteristics of a multi-wavelength Brillouin-Raman fiber laser (MBRFL) assisted by four-wave mixing have been investigated through the development of Stokes and anti-Stokes lines under different combinations of Brillouin and Raman pump power levels and different Raman pumping schemes in a ring cavity. For a Stokes line of order higher than three, the threshold power was less than the saturation power of its last-order Stokes line. By increasing the Brillouin pump power, the nth order anti-Stokes and the (n+4)th order Stokes power levels were unexpectedly increased almost the same before the Stokes line threshold power. It was also found out that the SBS threshold reduction (SBSTR) depended linearly on the gain factor for the 1st and 2nd Stokes lines, as the first set. This relation for the 3rd and 4th Stokes lines as the second set, however, was almost linear with the same slope before SBSTR -6 dB, then, it approached to the linear relation in the first set when the gain factor was increased to 50 dB. Therefore, the threshold power levels of Stokes lines for a given Raman gain can be readily estimated only by knowing the threshold power levels in which there is no Raman amplification.

Shirazi, M. R.; Mohamed Taib, J.; De La Rue, R. M.; Harun, S. W.; Ahmad, H.

2015-03-01

347

Dual-wavelength multifrequency photothermal wave imaging combined with optical coherence tomography for macrophage and lipid detection in atherosclerotic plaques using gold nanoparticles  

NASA Astrophysics Data System (ADS)

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.

Wang, Tianyi; Jacob Mancuso, J.; Sapozhnikova, Veronika; Dwelle, Jordan; Ma, Li L.; Willsey, Brian; Shams Kazmi, S. M.; Qiu, Jinze; Li, Xiankai; Asmis, Reto; Johnston, Keith P.; Feldman, Marc D.; Milner, Thomas E.

2012-03-01

348

Toward finding gravitational-wave signals from progenitors of short hard gamma-ray bursts and orphaned afterglows  

E-print Network

With multiple observatories and missions being planned for detecting orphaned afterglows associated with gamma-ray bursts (GRBs) we emphasize the importance of developing data analysis strategies for searching their possible counterpart signals in the data of gravitational wave (GW) detectors in the advanced detector era. This is especially attractive since short hard gamma-ray bursts (SGRBs) may have compact binary coalescences involving neutron stars (CBCNSs) as their progenitors, which emit gravitational waves. Joint electromagnetic (EM) and GW observations of these objects will enrich our understanding of their beaming, energetics, galactic environment, and shed light on a host of other outstanding questions related to them. Here we recognize some of the astrophysical factors that determine what fraction of CBCNS sources can generate orphaned afterglows. Pipelines already exist that target the sky-position and time of occurrence of SGRBs, known from EM observations, to search for their counterparts in GW ...

Ghosh, Shaon

2013-01-01

349

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

350

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

351

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

352

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

353

Waves  

NSDL National Science Digital Library

We will review some basic properties of waves and then further explore sound and light. For a quick overview of some properties of all waves, click on this first site. Make sure you fill out your hand out as you work! Waves and Wave Motion : Describing Waves Practice what you've already learned about waves with this site: Waves This site will let you play around some more with transverse waves: Wave on a String Sound waves are mechanical waves, ...

Mrs. Petersen

2014-05-27

354

Prediction and measurement of the electromagnetic environment of high-power medium-wave and short-wave broadcast antennas in far field.  

PubMed

With the increasing city size, high-power electromagnetic radiation devices such as high-power medium-wave (MW) and short-wave (SW) antennas have been inevitably getting closer and closer to buildings, which resulted in the pollution of indoor electromagnetic radiation becoming worsened. To avoid such radiation exceeding the exposure limits by national standards, it is necessary to predict and survey the electromagnetic radiation by MW and SW antennas before constructing the buildings. In this paper, a modified prediction method for the far-field electromagnetic radiation is proposed and successfully applied to predict the electromagnetic environment of an area close to a group of typical high-power MW and SW wave antennas. Different from currently used simplified prediction method defined in the Radiation Protection Management Guidelines (H J/T 10. 3-1996), the new method in this article makes use of more information such as antennas' patterns to predict the electromagnetic environment. Therefore, it improves the prediction accuracy significantly by the new feature of resolution at different directions. At the end of this article, a comparison between the prediction data and the measured results is given to demonstrate the effectiveness of the proposed new method. PMID:24553048

Tang, Zhanghong; Wang, Qun; Ji, Zhijiang; Shi, Meiwu; Hou, Guoyan; Tan, Danjun; Wang, Pengqi; Qiu, Xianbo

2014-12-01

355

An airborne short wave infrared /SWIR/ pushbroom imaging system using a 64-element PbS detector array  

NASA Technical Reports Server (NTRS)

Research evidence indicates that data in the short wave infrared (SWIR) spectral region will greatly improve the information content of remotely sensed data. Bands are required in the 1.55-1.75 micron and 2.08-2.35 micron spectral regions for a variety of agricultural and geological investigations. It is anticipated that future Landsat sensors will use pushbroom linear array technology to obtain high resolution, improved sensitivity and increased system reliability. To obtain early laboratory and field data, an airborne pushbroom image system has been designed for operation in the short wave infrared spectral region. The system uses a 64-element staggered PbS array and is operated at 195 K; the instrument has been designed to operate in an aircraft and will view a 19 degree swath width with a 5.8 mrad IFOV. The spectral bandwidth of each channel is .05 micron and the noise equivalent reflectivity in the order of .2% is provided. The requirements for more advanced detector arrays for use in future NASA spacecraft remote sensing instruments are also discussed.

Husain-Abidi, A. S.; Tom, D.; Blaine, L. R.; Ostrow, G.

1980-01-01

356

Wave Characteristics of Large-Diameter, High-Density Helicon Plasma with Short Axial Length II  

NASA Astrophysics Data System (ADS)

We have demonstrated that a large-diameter, high-density (>= 10^12 cm-3) helicon plasma can be produced in a low aspect ratio (the ratio of the axial length L to the diameter R; in our case, R =73.8 cm and 5.5 cm <= L <= 35 cm) device using a flat spiral antenna (4-turn, 43 cm in diameter) installed just outside the quartz-glass window at one end of the device [1]. As a first step to understand the role of helicon waves in the discharge process, helicon wave characteristics in plasma has been investigated in detail [2]. It has been found that discrete axial eigenmodes, whose characteristics depend on the plasma density profile and the axial boundary conditions, exist in the excited helicon wave. The effects of the background magnetic field profile and the rf input power on the excited wave have also been examined in detail. [1] T. Motomura et al., J. Plasma Fusion Res. Ser., in press. [2] T. Motomura et al., Bull. Ameri. Phys. Soc. 53 (14), 175 (2008).

Motomura, Taisei; Shinohara, Shunjiro; Tanikawa, Takao; Shamrai, Konstantin P.

2009-11-01

357

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

358

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

E-print Network

-wave infrared (SWIR), which is used in many applications including telecommunications, biophotonics [1], optical tomography [2], explosives detection [3], and nondestructive material evaluation [4]. It includes the fiber optical tomography rely on SWIR since it has great penetration depth through the skin [8] and, therefore

Mohseni, Hooman

359

Short surface waves in the Canadian Arctic in 2007 and 2008 D. J. Bogucki,1  

E-print Network

al., 2012] or inferred based on the strength of the microwave backscatter off the oceanic surface scatterometers such as QuikS- CAT (or future Ocean Vector Winds missions) are capable of obtaining a wide overpasses to verify the accuracy of microwave wave measurements. Our research aims to bridge that gap

Long, David G.

360

Nonlocal heat wave propagation due to skin layer plasma heating by short laser pulses  

Microsoft Academic Search

A model, which accounts for the heat flux delocalization has been applied to study nonlocal heat wave propagation from laser-heated skin layer of an overdense plasma into a cold target. The skin layer absorption model includes collisional, frequency dependent and nonlocal effects. The practical formula for the nonlocal nonlinear heat flux has been tested in Fokker–Planck simulation of the hot

A. V. Brantov; V. Yu. Bychenkov; O. V. Batishchev; W. Rozmus

2004-01-01

361

Localization of Short Duration Gravitational-wave Transients with the Early Advanced LIGO and Virgo Detectors  

NASA Astrophysics Data System (ADS)

The Laser Interferometer Gravitational wave Observatory (LIGO) and Virgo advanced ground-based gravitational-wave detectors will begin collecting science data in 2015. With first detections expected to follow, it is important to quantify how well generic gravitational-wave transients can be localized on the sky. This is crucial for correctly identifying electromagnetic counterparts as well as understanding gravitational-wave physics and source populations. We present a study of sky localization capabilities for two search and parameter estimation algorithms: coherent WaveBurst, a constrained likelihood algorithm operating in close to real-time, and LALInferenceBurst, a Markov chain Monte Carlo parameter estimation algorithm developed to recover generic transient signals with latency of a few hours. Furthermore, we focus on the first few years of the advanced detector era, when we expect to only have two (2015) and later three (2016) operational detectors, all below design sensitivity. These detector configurations can produce significantly different sky localizations, which we quantify in detail. We observe a clear improvement in localization of the average detected signal when progressing from two-detector to three-detector networks, as expected. Although localization depends on the waveform morphology, approximately 50% of detected signals would be imaged after observing 100-200 deg2 in 2015 and 60-110 deg2 in 2016, although knowledge of the waveform can reduce this to as little as 22 deg2. This is the first comprehensive study on sky localization capabilities for generic transients of the early network of advanced LIGO and Virgo detectors, including the early LIGO-only two-detector configuration.

Essick, Reed; Vitale, Salvatore; Katsavounidis, Erik; Vedovato, Gabriele; Klimenko, Sergey

2015-02-01

362

Analysis of a spinning polygon wavelength swept laser  

E-print Network

It has been known for quite some time that spinning polygon, and similar, swept lasers used in OCT favor the short to long wavelength sweep direction because of four wave mixing in the gain medium. Here we have reformulated the problem in the time domain and show experimentally and through numerical simulation that these lasers are pulsed. The emitted pulses modulate the gain medium refractive index to red shift the light. Instead of new wavelengths being built up slowly from spontaneous emission, each pulse hops to a longer wavelength by nonlinear means, tracking the tunable filter. This allows high speed, low noise tuning in the blue to red direction. Based on this model, we make the first coherence length calculations for a swept source.

Johnson, Bart; Kuznetsov, Mark; Goldberg, Brian D; Whitney, Peter; Flanders, Dale C

2015-01-01

363

Large amplitude stationary Rossby waves in the Southern Hemisphere  

NASA Technical Reports Server (NTRS)

Observational evidence of the characteristics of the large amplitude, short wavelength stationary waves found in the lee of South America and Australia during the complete first special observing period of the first GARP global experiment is presented. The structure and evolution of the waves are described and their possible origin discussed.

Kalnay, E.; Halem, M.

1981-01-01

364

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.

365

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

366

Horizontal coherence of low-frequency fixed-path sound in a continental shelf region with internal-wave activity  

E-print Network

Horizontal coherence of low-frequency fixed-path sound in a continental shelf region with internal-wave) populated with tidally generated long- and short-wavelength internal waves. Sound paths are 19 km and explain sound field spatial and temporal variability under these conditions. The intermittent internal-wave

367

Stretching and compressing of short laser pulses by chirped volume Bragg gratings: analytic and numerical modeling  

NASA Astrophysics Data System (ADS)

The theory of stretching and compression of short light pulses by chirped volume Bragg gratings (CBGs) is reviewed based on spectral decomposition of short pulses and on wavelength-dependent coupled wave equations. Analytic theory of diffraction efficiency of CBG with constant chirp and approximate theory time-delay dispersion is presented. Comparison of approximate analytic results with exact numeric coupled-wave modeling shows excellent agreement for smooth heterogeneities of CBGs.

Kaim, Sergiy; Mokhov, Sergiy; Zeldovich, Boris Y.; Glebov, Leonid B.

2014-05-01

368

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

369

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

370

320x240 pixel InGaAs/InP focal plane array for short-wave infrared and visible light imaging  

NASA Astrophysics Data System (ADS)

We report on the recent production release of our 320x240 pixel InGaAs/InP focal plane array and camera for visible and short-wavelength infrared light imaging. For this camera, we have fabricated a substrate-removed backside-illuminated InGaAs/InP photodiode array hybridized to a silicon read out integrated circuit (ROIC). Removing the InP substrate from the focal plane array allows visible wavelengths, which would otherwise be absorbed by the InP substrate due to its 920 nm wavelength cut-off, to reach the pixels" active region. Quantum efficiency is approximately 15% at 500 nm, 70% at 850 nm, 85% at 1310 nm and 80% at 1550 nm. This focal plane array is useable for visible imaging as well as imaging eye-safe lasers and is of particular interest for day and low light level imaging as well as hyperspectral imaging.

Martin, Tara; Dixon, Peter; Gagliardi, Mari-Anne; Masaun, Navneet

2005-04-01

371

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

372

Toward finding gravitational-wave signals from progenitors of short hard gamma-ray bursts and orphaned afterglows  

E-print Network

With multiple observatories and missions being planned for detecting orphaned afterglows associated with gamma-ray bursts (GRBs) we emphasize the importance of developing data analysis strategies for searching their possible counterpart signals in the data of gravitational wave (GW) detectors in the advanced detector era. This is especially attractive since short hard gamma-ray bursts (SGRBs) may have compact binary coalescences involving neutron stars (CBCNSs) as their progenitors, which emit gravitational waves. Joint electromagnetic (EM) and GW observations of these objects will enrich our understanding of their beaming, energetics, galactic environment, and shed light on a host of other outstanding questions related to them. Here we recognize some of the astrophysical factors that determine what fraction of CBCNS sources can generate orphaned afterglows. Pipelines already exist that target the sky-position and time of occurrence of SGRBs, known from EM observations, to search for their counterparts in GW detector data. Modifying them to analyze extended periods of time in the GW data in the past of the afterglow detection, while targeting a single sky-position, can search for GWs from the common progenitor. We assess the improvement in GW detectability to be had from utilizing the sky-position information. We also propose a method for improving the detection efficiency of targeted searches of GW signals from the putative CBCNS sources of afterglows and short gamma ray bursts in the presence of errors in detector calibration or CBCNS waveform models used in the search. The improvement arises from searching in a wider patch of the sky even when the sky-position is known accurately from EM observations and utilizes the covariance of the errors in waveform parameters with those in the sky position.

Shaon Ghosh; Sukanta Bose

2013-08-28

373

On the role of non-uniform stratification and short-wave instabilities in three-layer quasi-geostrophic turbulence  

NASA Astrophysics Data System (ADS)

The role of short-wave instabilities on geostrophic turbulence is studied in a simplified model consisting of three layers in the quasi-geostrophic approximation. The linear stability analysis shows that short-wave instabilities are created by the interplay between the shear in the upper and lower layers. If the stratification is non-uniform, in particular surface intensified, the linear growth rate is larger for short-wave instabilities than for long-wave instabilities and the layers are essentially decoupled, with the small scales growing independently. The fully developed homogeneous turbulence is studied in a number of numerical experiments. Results show that in both the case of equal layer depths and surface intensified stratification an inverse cascade in kinetic energy is observed. The modal kinetic energy spectra for the case with surface intensified stratification show higher energy for higher baroclinic numbers at small scales, due to the decoupling of the layers. As a result, while the case with equal layer depths shows large barotropic instabilities with large scale gradients of potential temperature, the surface intensified stratification is characterized by a transition from surface dynamics, characterized by a patchy distribution of vorticity, to interior dynamics, characterized by vorticity filamentation. The effect of the short-wave instabilities can be seen in the probability distribution functions of the potential vorticity anomaly, which reduces to a Gaussian distribution when the growth rate of the short-wave instabilities is larger than the growth rate for the long-wave instabilities. The surface intensified stratification also alters the vertical structure of the potential vorticity fluxes and shows deviations of the fluxes from a scaling obtained assuming that the turbulence acts as a downgradient diffusion. Experiments with a passive tracer shows a dominance of the coherent structures at large scales, and of filamentation at smaller scales, in the tracer dispersion.

Badin, Gualtiero

2014-09-01

374

Explanation of the Normal Winter Anomaly from the Seasonal Variation of Short Wave Absorption  

NASA Technical Reports Server (NTRS)

The frequency dependence of the winter anomaly (WA) of radio wave absorption indicates the altitude range where the considered seasonal variation of absorption, L, takes place: 75-95 km. In this height region considerable seasonal variations of ionic composition and effective recombination coefficient, alpha sub e, exist, which can cause seasonal variations of electron concentration, N, and absorption, L. An attempt to render a qualitative estimation of the normal WA, i.e., the increased ratio of winter over summer absorption, L sub w/L sub s, at medium latitudes 40 deg and 50 deg, for solar zenith angles CHi = 60 deg and 75 deg is made. This is compared with existing experimental data.

Velinov, P. J.; Smirnova, N. V.; Vlaskov, V. A.

1984-01-01

375

Creating and Manipulating Vortices in Atomic Wave Functions with Short Electric Field Pulses  

SciTech Connect

We demonstrate the creation of vortices in the electronic probability density of an atom subject to short electric field pulses, how these vortices evolve and can be manipulated by varying the applied pulses, and that they persist to macroscopic distances in the spectrum of ejected electrons. This opens the possibility to use practical femtosecond or shorter laser pulses to create and manipulate these vortex quasiparticles at the atomic scale and observe them in the laboratory. Within a hydrodynamic interpretation we also show, since the Schroedinger equation is a particular instance of the Navier-Stokes equations, that for compressible fluids vortices can appear spontaneously and with a certain time delay, which is not expected to occur from the conventional point of view, illustrating applicability of the present study to vortex formation more broadly.

Ovchinnikov, S. Yu; Sternberg, J. B. [Department of Physics and Astronomy, University of Tennessee, Knoxville, Tennessee 37496 (United States); Macek, J. H. [Department of Physics and Astronomy, University of Tennessee, Knoxville, Tennessee 37496 (United States); Physics Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, 37831 (United States); Lee, Teck-Ghee [Department of Physics, Auburn University, Auburn, Alabama, 36849 (United States); Schultz, D. R. [Physics Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, 37831 (United States)

2010-11-12

376

Short-Range Wireless Communications for Next-Generation Networks: UWB, 60 GHz Millimeter-Wave WPAN, And ZigBee  

Microsoft Academic Search

This article presents standardization, regulation, and development issues associated with short-range wireless technologies for next-generation personal area networks (PAN). Ultra-wideband (UWB) and 60 GHz millimeter-wave communication technologies promise unprecedented short-range broadband wireless communication and are the harbingers of multigigabit wireless networks. Despite the huge potential for PAN, standardization and global spectrum regulations challenge the success of UWB. On the other

Theordore Rappaport

2007-01-01

377

Contribution of external parameter orthogonalisation for calibration transfer in short waves--near infrared spectroscopy application to gasoline quality.  

PubMed

The octane number rating of a gasoline gives an indication of the gasoline performances, under various engine conditions. Two different ratings are included: Research Octane Number (RON) and Motor Octane Number (MON). The standard laboratory method for octane number determination is the knock engine method in which a gasoline is burned and its combustion characteristics compared to known standards. This method is time consuming and labor intensive, and provides no ability for real time control of production. NIR can be applied in real time directly in process monitoring or as a laboratory procedure. Near infrared spectra of gasoline samples were collected thanks to four different short wavelengths near infrared analysers, built with strictly the same technology. The aim of this study was to transfer the calibration built on one spectrometer to the other ones. We applied the external parameter orthogonalisation (EPO) correction to get rid of the apparatus influence on information contained in spectra. By this method, we managed to improve prediction values of two major gasolines' properties, i.e. Research and Motor Octane Number. PMID:19427453

Amat-Tosello, S; Dupuy, N; Kister, J

2009-05-29

378

Attenuating Photostress and Glare Disability in Pseudophakic Patients through the Addition of a Short-Wave Absorbing Filter  

PubMed Central

To evaluate the effects of filtering short wavelength light on visual performance under intense light conditions among pseudophakic patients previously implanted with a clear intraocular lens (IOL). This was a patient-masked, randomized crossover study conducted at 6 clinical sites in the United States between September 2013 and January 2014. One hundred fifty-four bilaterally pseudophakic patients were recruited. Photostress recovery time and glare disability thresholds were measured with clip-on blue-light-filtering and placebo (clear; no blue-light filtration) glasses worn over patients' habitual correction. Photostress recovery time was quantified as the time necessary to regain sight of a grating target after intense light exposure. Glare disability threshold was assessed as the intensity of a white-light annulus necessary to obscure a central target. The order of filter used and test eye were randomized across patients. Photostress recovery time and glare disability thresholds were significantly improved (both P < 0.0001) when patients used blue-light-filtering glasses compared with clear, nonfiltering glasses. Compared with a nonfiltering placebo, adding a clip-on blue-absorbing filter to the glasses of pseudophakic patients implanted with clear IOLs significantly increased their ability to cope with glare and to recover normal viewing after an intensive photostress. This result implies that IOL designs with blue-light-filtering characteristics may be beneficial under intense light conditions.

Hammond, Billy R.

2015-01-01

379

Dynamics of shock waves and cavitation bubbles in bilinear elastic-plastic media, and the implications to short-pulsed laser surgery  

NASA Astrophysics Data System (ADS)

The dynamics of shock waves and cavitation bubbles generated by short laser pulses in water and elastic-plastic media were investigated theoretically in order to get a better understanding of their role in short-pulsed laser surgery. Numerical simulations were performed using a spherical model of bubble dynamics which include the elastic-plastic behaviour of the medium surrounding the bubble, compressibility, viscosity, density and surface tension. Breakdown in water produces a monopolar acoustic signal characterized by a compressive wave. Breakdown in an elastic-plastic medium produces a bipolar acoustic signal, with a leading positive compression wave and a trailing negative tensile wave. The calculations revealed that consideration of the tissue elasticity is essential to describe the bipolar shape of the shock wave emitted during optical breakdown. The elastic-plastic response of the medium surrounding the bubble leads to a significant decrease of the maximum size of the cavitation bubble and pressure amplitude of the shock wave emitted during bubble collapse, and shortening of the oscillation period of the bubble. The results are discussed with respect to collateral damage in short-pulsed laser surgery.

Brujan, E.-A.

2005-01-01

380

[Study on phase-matching of four-wave mixing spectrum in photonic crystal fiber].  

PubMed

In the present paper, the four-wave mixing principle of fiber was analyzed, and the high-gain phase-matching conditions were shown. The nonlinear coefficient and dispersion characteristics of photonic crystal fibers were calculated by multipole method. The phase mismatch characteristics of fibers with multiple zero-dispersion wavelengths were analyzed for the first time. The changing rules of phase matching wavelength with the pump wavelength and the pump power were obtained, and the phase matching curves were shown. The characteristics of phase matching wavelengths for different dispersion curves were analyzed. There are four new excitation wavelengths of four-wave mixing spectrum in two zero-dispersion wavelength photonic crystal fiers. Four-wave mixing spectroscopy of photonic crystal fibers with two zero-dispersion wavelengths was obtained in the experi-ent, which is consistent with the theoretical analysis, and verified the reliability of the phase matching theory. The fiber with multiple zero-dispersion wavelengths can create a ricbhphase-matching topology, excite more four-wave mixing wavelengths, ena-ling enhanced control over the spectral locations of the four-wave mixing and resonant-radiation bands emitted by solitons and short pulses. These provide theoretical guidance for photonic crystal fiber wavelength conversion and supercontinoum generation based on four-wave mixing. PMID:25358145

Liu, Xiao-xu; Wang, Shu-tao; Zhao, Xing-tao; Chen, Shuang; Zhou, Gui-yao; Wu, Xi-jun; Li, Shu-guang; Hou, Lan-Tian

2014-06-01

381

Short period gravity wave momentum fluxes observed in the tropical troposphere, stratosphere and mesosphere  

NASA Astrophysics Data System (ADS)

Using long-term data (1998-2008) collected from mesosphere-stratosphere-troposphere (MST) radar and Rayleigh Lidar located at a tropical station, Gadanki (13.5°N, 79.2°E), India, vertical flux of the momentum from troposphere to mesosphere associated with the gravity waves of periods in the range 20 min to 2 h is investigated for the first time. The emphasis is on seasonal variability of mean zonal and meridional momentum fluxes in mesosphere and troposphere and vertical flux of horizontal momentum in the stratosphere. At tropospheric altitudes of 11-16 km large enhancement in flux is noticed during equinoxes. In the lower mesosphere in the altitude region 58-62 km the maximum values of flux (?2.8 m2/s2) observed are pragmatic in winter and spring. Interestingly, the vertical flux of horizontal momentum estimated from lidar is in the range of those estimated from radar data in the overlap altitude region, though the estimates are from two different techniques. In the mesosphere, large variations with altitude in zonal momentum flux are noticed with a magnitude ?0-4 m2/s2 in summer. In winter and summer the zonal wind direction is opposite to the momentum flux direction between 73 and 80 km and in equinoxes zonal wind follows the momentum flux. The meridional fluxes in the mesosphere are higher in equinoxes (?10-12 m2/s2).

Eswaraiah, S.; Ratnam, M. Venkat; Murthy, B. V. Krishna; Guharay, A.; Rao, S. Vijaya Bhaskara

2013-12-01

382

Modeling short wave solar radiation using the JGrass-NewAge System  

NASA Astrophysics Data System (ADS)

This paper presents two new modelling components based on the Object Modelling System v3 for the calculation of the shortwave incident radiation (Rsw\\downarrow) on complex topography settings, and the implementation of several ancillary tools. The first component, NewAGE-SwRB, accounts for slope, aspect, shadow and the topographical information of the sites, and use suitable parametrisation for obtaining the cloudless irradiance. A second component, NewAGE-DEC-MOD's is implemented to estimate the irradiance reduction due to the presence of clouds, according to three parameterisations. To obtain a working modelling composition, suitable to be compared with ground data at measurement stations, the two components are connected to a Kriging component, and, with the use of a further component NewAGE-V (verification package), the performance of modeled (Rsw\\downarrow) is quantitatively evaluated. The two components (and the various parametrisations they contain) are tested using the data from three basins catchments, and some simple verification test is made to assess the goodness of the methods used. The components are part of a larger system, JGrass-NewAGE, their input and outputs are given as geometrical objects immediately visualisable in a GIS (for instance the companion uDig), and can be used seamlessly with the various modelling solutions available in JGrass-NewAGE for the estimation of long wave radiation, evapotranspiration, and snow melting, as well as stand-alone components to just estimate shortwave radiation for various uses. The modularity of the approach is shown to be extensible to more accurate physical-statistical studies aimed to assess in deep the components performances and extends spatially their results, without the necessity of recoding any part of the component but just making using of connective scripts.

Formetta, G.; Rigon, R.; Chávez, J. L.; David, O.

2012-12-01

383

Linear Wave Propagation in Mildly Relativistic Thermal Pair Plasmas  

Microsoft Academic Search

We present dispersion relations and eigenmodes for linear waves propagating in fluid-like mildly relativistic thermal pair plasmas For any given wavevector, four modes are possible: two with sound wave-like properties, and two that are isobaric and essentially non-propagating. One of the isobaric modes strongly perturbs the pair balance, while the other does so much more weakly. Short-wavelength sound waves propagate

Paola Pietrini; Julian H. Krolik

1994-01-01

384

Astronomical Images in Different Wavelengths  

NSDL National Science Digital Library

Visible light is just one portion of the electromagnetic spectrum that a telescope may detect. This collection of images produced for Teachers' Domain features radio wave, infrared, visible light, and X-ray images of distant stars and galaxies as well as images of the telescopes designed to detect the various wavelengths of radiation.

2004-02-20

385

Search for gravitational-wave inspiral signals associated with short gamma-ray bursts during LIGO'S fifth and VIRGO'S first science run  

Microsoft Academic Search

Progenitor scenarios for short gamma-ray bursts (short\\u000a\\u0009\\u0009 GRBs) include coalescenses of two neutron stars or a\\u000a\\u0009\\u0009 neutron star and black hole, which would necessarily be\\u000a\\u0009\\u0009 accompanied by the emission of strong gravitational waves.\\u000a\\u0009\\u0009 We present a search for these known gravitational-wave\\u000a\\u0009\\u0009 signatures in temporal and directional coincidence with 22\\u000a\\u0009\\u0009 GRBs that had sufficient gravitational-wave data available\\u000a\\u0009\\u0009 in multiple instruments during

J. Abadie; B. P. Abbott; R. Abbott; T. Accadia; F. Acernese; R. Adhikari; P. Ajith; B. Allen; G. Allen; E. Amador Ceron; R. S. Amin; S. B. Anderson; W. G. Anderson; F. Antonucci; S. Aoudia; M. A. Arain; M. Araya; K. G. Arun; Y. Aso; S. Aston; P. Astone; P. Aufmuth; C. Aulbert; S. Babak; P. Baker; G. Ballardin; S. Ballmer; D. Barker; F. Barone; B. Barr; P. Barriga; L. Barsotti; M. Barsuglia; M. A. Barton; I. Bartos; R. Bassiri; M. Bastarrika; Th. S. Bauer; B. Behnke; M. G. Beker; A. Belletoile; M. Benacquista; J. Betzwieser; P. T. Beyersdorf; S. Bigotta; I. A. Bilenko; G. Billingsley; S. Birindelli; R. Biswas; M. A. Bizouard; E. Black; J. K. Blackburn; L. Blackburn; D. A. BROWN; B. Bland; M. Blom; C. Boccara; O. Bock; T. P. Bodiya; R. Bondarescu; F. Bondu; L. Bonelli; R. Bonnand; R. Bork; M. Born; S. Bose; L. Bosi; S. Braccini; C. Bradaschia; P. R. Brady; V. B. Braginsky; J. E. Brau; J. Breyer; D. O. Bridges; A. Brillet; M. Brinkmann; V. Brisson; M. Britzger; A. F. Brooks; R. Budzynski; T. Bulik; A. Bullington; H. J. Bulten; A. Buonanno; J. Burguet-Castell; O. Burmeister; D. Buskulic; C. Buy; R. L. Byer; L. Cadonati; G. Cagnoli; J. Cain; E. Calloni; J. B. Camp; E. Campagna; J. Cannizzo; K. C. Cannon; B. Canuel; J. Cao; C. D. Capano; F. Carbognani; L. Cardenas; S. Caudill; M. Cavaglià; F. Cavalier; R. Cavalieri; G. Cella; C. Cepeda; E. Cesarini; T. Chalermsongsak; E. Chalkley; P. Charlton; E. Chassande-Mottin; S. Chatterji; S. Chelkowski; Y. Chen; A. Chincarini; N. Christensen; S. S. Y. Chua; C. T. Y. Chung; D. Clark; J. Clark; J. H. Clayton; F. Cleva; E. Coccia; C. N. Colacino; J. Colas; A. Colla; M. Colombini; R. Conte; D. Cook; T. R. C. Corbitt; N. Cornish; A. Corsi; J.-P. Coulon; D. Coward; D. C. Coyne; J. D. E. Creighton; T. D. Creighton; A. M. Cruise; R. M. Culter; A. Cumming; L. Cunningham; E. Cuoco; K. Dahl; S. L. Danilishin; S. D’Antonio; K. Danzmann; V. Dattilo; B. Daudert; M. Davier; G. Davies; E. J. Daw; R. Day; T. Dayanga; R. De Rosa; D. DeBra; J. Degallaix; M. del Prete; V. Dergachev; R. DeSalvo; S. Dhurandhar; L. Di Fiore; A. Di Lieto; M. Di Paolo Emilio; A. Di Virgilio; M. Díaz; A. Dietz; F. Donovan; K. L. Dooley; E. E. Doomes; M. Drago; R. W. P. Drever; J. Driggers; I. Duke; J.-C. Dumas; M. Edgar; M. Edwards; A. Effler; P. Ehrens; T. Etzel; M. Evans; T. Evans; V. Fafone; S. Fairhurst; Y. Faltas; D. Fazi; H. Fehrmann; I. Ferrante; F. Fidecaro; Lee Samuel Finn; I. Fiori; R. Flaminio; K. Flasch; S. Foley; C. Forrest; N. Fotopoulos; J.-D. Fournier; S. Frasca; F. Frasconi; M. Frede; M. Frei; Z. Frei; A. Freise; R. Frey; T. T. Fricke; D. Friedrich; P. Fritschel; V. V. Frolov; P. Fulda; M. Fyffe; M. Galimberti; L. Gammaitoni; J. A. Garofoli; F. Garufi; G. Gemme; E. Genin; A. Gennai; S. Ghosh; J. A. Giaime; S. Giampanis; K. D. Giardina; A. Giazotto; E. Goetz; L. M. Goggin; G. González; S. Goßler; R. Gouaty; M. Granata; A. Grant; S. Gras; C. Gray; R. J. S. Greenhalgh; A. M. Gretarsson; C. Greverie; R. Grosso; H. Grote; S. Grunewald; G. M. Guidi; E. K. Gustafson; R. Gustafson; B. Hage; J. M. Hallam; D. Hammer; G. D. Hammond; C. Hanna; J. Hanson; J. Harms; G. M. Harry; I. W. Harry; E. D. Harstad; K. Haughian; T. Hayler; J. Heefner; H. Heitmann; P. Hello; I. S. Heng; A. Heptonstall; M. Hewitson; S. Hild; E. Hirose; D. Hoak; K. A. Hodge; D. J. Hosken; J. Hough; E. Howell; D. Hoyland; B. Hughey; S. Husa; S. H. Huttner; D. R. Ingram; T. Isogai; A. Ivanov; P. Jaranowski; W. W. Johnson; D. I. Jones; G. Jones; R. Jones; L. Ju; P. Kalmus; V. Kalogera; S. Kandhasamy; J. Kanner; E. Katsavounidis; K. Kawabe; S. Kawamura; F. Kawazoe; W. Kells; D. G. Keppel; A. Khalaidovski; F. Y. Khalili; R. Khan; E. Khazanov; H. Kim; P. J. King; J. S. Kissel; S. Klimenko; K. Kokeyama; V. Kondrashov; R. Kopparapu; S. Koranda; I. Kowalska; D. Kozak; V. Kringel; B. Krishnan; A. Królak; G. Kuehn; J. Kullman; R. Kumar; P. Kwee; P. K. Lam; M. Landry; B. Lantz; N. Lastzka; A. Lazzarini; P. Leaci; M. Lei; N. Leindecker; I. Leonor; N. Leroy; N. Letendre; T. G. F. Li; H. Lin; P. E. Lindquist; T. B. Littenberg; N. A. Lockerbie; D. Lodhia; M. Lorenzini; V. Loriette; M. Lormand; G. Losurdo; P. Lu; M. Lubinski; A. Lucianetti; H. Lück; A. Lundgren; B. Machenschalk; M. MacInnis; M. Mageswaran; K. Mailand; E. Majorana; C. Mak; I. Maksimovic; N. Man; I. Mandel; V. Mandic; M. Mantovani; F. Marchesoni; S. Márka; Z. Márka; A. Markosyan; J. Markowitz; E. Maros; J. Marque; F. Martelli; I. W. Martin; R. M. Martin; J. N. Marx; K. Mason; A. Masserot; F. Matichard; L. Matone; R. A. Matzner; N. Mavalvala; R. McCarthy; D. E. McClelland; S. C. McGuire; G. McIntyre; D. J. A. McKechan; M. Mehmet; A. Melatos; A. C. Melissinos; G. Mendell; D. F. Menendez; R. A. Mercer; L. Merill; S. Meshkov; C. Messenger; M. S. Meyer; H. Miao; C. Michel; L. Milano; J. Miller; Y. Minenkov; S. Mitra; V. P. Mitrofanov; G. Mitselmakher

2010-01-01

386

Effect of laser-pulse structure and wavelength on wound healing  

NASA Astrophysics Data System (ADS)

We have investigated wound healing of incisions in the buccal mucosa of a canine model created with the Vanderbilt Free Electron Laser tuned to 6.1, 6.45 and 6.8 microns. We have also used a carbon dioxide laser, continuous wave and with a short-pulse structure (100 microseconds) to access wavelength and pulse structure components to wound healing from laser incisions. The tissue was evaluated histologically and with tensiometry acutely and at post operative days 3, 7, and 14. The data indicate that shorter laser pulse durations create less lateral thermal injury and wounds with greater tensile strength, resulting in earlier wound healing. Wound healing was only slightly dependent upon the wavelength of the laser. These results demonstrate that surgical carbon dioxide lasers with a short-pulse structure of approximately 100 microseconds or less could offer more prompt wound healing while maintaining the advantages of a 10.6 micron wavelength laser.

Fortune, D. S.; Huang, Shan; Bryant, G. L.; Garrett, C. Gaelyn; Reinisch, Lou

1998-07-01

387

Nonlinear wavelength conversion in photonic crystal fibers with three zero-dispersion points  

SciTech Connect

In this theoretical study, we show that a simple endlessly single-mode photonic crystal fiber can be designed to yield, not just two, but three zero-dispersion wavelengths. The presence of a third dispersion zero creates a rich phase-matching topology, enabling enhanced control over the spectral locations of the four-wave-mixing and resonant-radiation bands emitted by solitons and short pulses. The greatly enhanced flexibility in the positioning of these bands has applications in wavelength conversion, supercontinuum generation, and pair-photon sources for quantum optics.

Stark, S. P.; Biancalana, F.; Podlipensky, A.; St. J. Russell, P. [Max Planck Institute for the Science of Light Guenther-Scharowsky Str. 1/Bau 24, D-91058 Erlangen (Germany)

2011-02-15

388

Characteristics of Short Wavelength Compressional Alfven Eigenmodes  

SciTech Connect

Most Alfvenic activity in the frequency range between Toroidal Alfven Eigenmodes and roughly one half of the ion cyclotron frequency on NSTX [M. Ono, et al., Nucl. Fusion 40 (2000) 557], that is, approximately 0.3 MHz up to ? 1.2 MHz, are modes propagating counter to the neutral beam ions. These have been modeled as Compressional and Global Alfven Eigenmodes (CAE and GAE) and are excited through a Doppler-shifted cyclotron resonance with the beam ions. There is also a class of co-propagating modes at higher frequency than the counter-propagating CAE and GAE. These modes have been identified as CAE, and are seen mostly in the company of a low frequency, n=1 kink-like mode. In this paper we present measurements of the spectrum of these high frequency CAE (hfCAE), and their mode structure. We compare those measurements to a simple model of CAE and present evidence of a curious non-linear coupling of the hfCAE and the low frequency kink-like mode.

Fredrickson, E D; Podesta, M; Bortolon, A; Crocker, N A; Gerhardt, S P; Bell, R E; Diallo, A; LeBlanc, B; Levinton, F M

2012-12-19

389

Genomic organization of duplicated short wave-sensitive and long wave-sensitive opsin genes in the green swordtail, Xiphophorus helleri  

PubMed Central

Background Long wave-sensitive (LWS) opsin genes have undergone multiple lineage-specific duplication events throughout the evolution of teleost fishes. LWS repertoire expansions in live-bearing fishes (family Poeciliidae) have equipped multiple species in this family with up to four LWS genes. Given that color vision, especially attraction to orange male coloration, is important to mate choice within poeciliids, LWS opsins have been proposed as candidate genes driving sexual selection in this family. To date the genomic organization of these genes has not been described in the family Poeciliidae, and little is known about the mechanisms regulating the expression of LWS opsins in any teleost. Results Two BAC clones containing the complete genomic repertoire of LWS opsin genes in the green swordtail fish, Xiphophorus helleri, were identified and sequenced. Three of the four LWS loci identified here were linked in a tandem array downstream of two tightly linked short wave-sensitive 2 (SWS2) opsin genes. The fourth LWS opsin gene, containing only a single intron, was not linked to the other three and is the product of a retrotransposition event. Genomic and phylogenetic results demonstrate that the LWS genes described here share a common evolutionary origin with those previously characterized in other poeciliids. Using qualitative RT-PCR and MSP we showed that each of the LWS and SWS2 opsins, as well as three other cone opsin genes and a single rod opsin gene, were expressed in the eyes of adult female and male X. helleri, contributing to six separate classes of adult retinal cone and rod cells with average ?max values of 365 nm, 405 nm, 459 nm, 499 nm, 534 nm and 568 nm. Comparative genomic analysis identified two candidate teleost opsin regulatory regions containing putative CRX binding sites and hormone response elements in upstream sequences of LWS gene regions of seven teleost species, including X. helleri. Conclusions We report the first complete genomic description of LWS and SWS2 genes in poeciliids. These data will serve as a reference for future work seeking to understand the relationship between LWS opsin genomic organization, gene expression, gene family evolution, sexual selection and speciation in this fish family. PMID:20353595

2010-01-01

390

Wave Interference  

NSDL National Science Digital Library

Students interact with an applet to experiment with waveform interference. The activity should be performed in a computer laboratory, with each student at a workstation. They should each be provided with a copy of the following handout, available in Word and pdf format, which they should fill in as they proceed through the exercise. At the completion of the exercise, they should hand it in for grading. Wave Interference Student Activity Sheet (Word) (Acrobat (PDF) 26kB Feb24 10) Wave Interference Student Activity Sheet (pdf) (Acrobat (PDF) 16kB Feb24 10) Wave Interference Applet Original applet page: Wave Interference Applet If the applet below fails to appear properly on the page, with sliders for setting the amplitude, wavelength, phase, and speed of the waves, browse to the above link to the original applet page. Java Applet created by Konstantin Lukin with supervision by Glenn A. Richard, Project Java Webmaster The two green curves are parallel sinusoidal waveforms that have identical wavelengths, amplitudes, and phases when the applet initializes. The blue sinusoidal waveform at the bottom is the sum of the two green parallel waveforms. You can change the phase of the green sinusoidal waveforms by dragging the circles at the left end of the waveform. You can change the wavelength and the amplitude by dragging the other two circles. The sliders to the right of the waveforms offer alternative means of making similar changes. To animate the waveforms, click on the start button, and to stop the animation, click again. In order to change the speed of the animation of the two green waveforms, you can use the sliders on the lower right, but you must halt the animation in order to adjust the speed. Once your speeds are selected, start the animation again. The speeds are actually phase velocity. In other words, when the two green waveforms animate at equal speeds, each one will advance by an equal number of wavelengths during a given amount of time. Therefore, if they are set to the same speed, but different wavelengths, the waveform with the longer wavelength will advance faster than the other one. Wave Interference Applet with Initial Settings Wave Interference Applet with Constructive Interference We have constructive interference when the wavelength, amplitude, and phase of the two component (blue) waves are identical. Wave Interference Applet with Destructive Interference We have destructive interference when the wavelength and amplitude of the two component (blue) waves are identical and the phases differ by 180 degrees. Wave Interference Applet with component wave phase difference of 90 degrees With the wavelengths and the amplitudes of the component waves identical and their phases different by 90 degrees, there is partial constructive interference. Wave Interference Applet with a complex sum With the amplitudes of the two component waves identical and the wavelength of one component wave twice the wavelength of the other, the phase can be adjusted to produce a sum with a more complex form. Wave Interference Applet with wave beat With the amplitudes of the two component waves identical and the wavelengths slightly different, the sum exhibits wave beat. Wave Interference Applet with settings that will result in retrograde wave beat. The start button can be used the initiate an animation that exhibits the retrograde wave beat. On the live applet, click the stop button to halt the animation. Screen capture of Wave Interference Applet for three waves. For the actual applet, see Wave Interaction Applet - Three Waves Original applet location: Wave Interference Applet Java Source code and class files are in this archive: Wave Interference Applet jar File (Jar Archive 22kB Feb23 10) Java Source code and class files for a three-wave sum are in this archive:Wave Interaction Applet: Three Wave Sum (Jar Archive 9kB Feb23 10)

Glenn Richard

391

The dynamics of interacting nonlinearities governing long wavelength driftwave turbulence  

SciTech Connect

Because of the ubiquitous nature of turbulence and the vast array of different systems which have turbulent solutions, the study of turbulence is an area of active research. Much present day understanding of turbulence is rooted in the well established properties of homogeneous Navier-Stokes turbulence, which, due to its relative simplicity, allows for approximate analytic solutions. This work examines a group of turbulent systems with marked differences from Navier-Stokes turbulence, and attempts to quantify some of their properties. This group of systems represents a variety of drift wave fluctuations believed to be of fundamental importance in laboratory fusion devices. From extensive simulation of simple local fluid models of long wavelength drift wave turbulence in tokamaks, a reasonably complete picture of the basic properties of spectral transfer and saturation has emerged. These studies indicate that many conventional notions concerning directions of cascades, locality and isotropy of transfer, frequencies of fluctuations, and stationarity of saturation are not valid for moderate to long wavelengths. In particular, spectral energy transfer at long wavelengths is dominated by the E {times} B nonlinearity, which carries energy to short scale in a manner that is highly nonlocal and anisotropic. In marked contrast to the canonical self-similar cascade dynamics of Kolmogorov, energy is efficiently passed between modes separated by the entire spectrum range in a correlation time. At short wavelengths, transfer is dominated by the polarization drift nonlinearity. While the standard dual cascade applies in this subrange, it is found that finite spectrum size can produce cascades that are reverse directed and are nonconservative in enstrophy and energy similarity ranges. In regions where both nonlinearities are important, cross-coupling between the nolinearities gives rise to large no frequency shifts as well as changes in the spectral dynamics.

Newman, D.E.

1993-09-01

392

Short-term variability in the migrating diurnal tide caused by interactions with the quasi 2 day wave  

Microsoft Academic Search

Quasi 2 day wave events known to result in migrating diurnal tide variabilityWave-tide interaction simulated using TIME-GCM to understand driving mechanismsQTDW induced mean wind changes drive resolved tidal variability

Loren C. Chang; Scott E. Palo; Han-Li Liu

2011-01-01

393

Propagation of acoustic waves in the partly ionized interstellar medium  

NASA Astrophysics Data System (ADS)

The properties of linear acoustic waves propagating in the interstellar medium, which is a mixture of electron-proton plasma and hydrogen atoms, are studied analytically. The plasma component interacts with hydrogen atoms through resonant charge exchange between the atoms and protons. To make the problem tractable, only short-wavelength disturbances are considered. Namely, the wavelength is assumed to be small as compared with the mean free path of atoms with respect to charge exchange. It is shown that short waves are damped out due to the charge exchange process, and the magnitude of decrement increases with the cross-section for charge exchange, number density of atoms and sound speed. In the first approximation, decrement does not depend on the wavelength, and acoustic waves are dispersionless. The advantage of our model is fully kinetic treatment of the interstellar atom motion.

Chalov, S. V.

2014-07-01

394

Spin Pumping Driven by Bistable Exchange Spin Waves  

NASA Astrophysics Data System (ADS)

Spin pumping driven by bistable exchange spin waves is demonstrated in a Pt/Y3Fe5O12 film under parametric excitation. In the Pt/Y3Fe5O12 film, the spin pumping driven by parametric excitation selectively enhances the relaxation of short-wavelength exchange spin waves, indicating strong coupling between the exchange spin waves and spin currents at the interface through efficient spin transfer. The parametric spin pumping, furthermore, allows direct access to nonlinear spin wave dynamics in combination with the inverse spin Hall effect, revealing unconventional bistability of the exchange spin waves.

Ando, K.; Saitoh, E.

2012-07-01

395

Effect of variations of the electric field and charged-particle precipitation on the characteristics of short-wave radio signals on an auroral radio path  

Microsoft Academic Search

Data concerning the inclined sounding of the auroral ionosphere by short waves on the Linakhamari-Umba path (400 km long) during November-December 1982 are analyzed along with measurements of variations of the electric field and hard-electron fluxes. It is shown that the effects of variations of the electric field and electron fluxes on the amplitude of scattered radio signals at different

B. V. Tkachenko; A. O. Melnikov; V. K. Ridler; L. L. Lazutin; A. K. Dudakov

1985-01-01

396

Laser Wavelength Dependency of Laser Supported Detonation  

NASA Astrophysics Data System (ADS)

The development of high power Neodymium glass (Nd:glass) laser allows for application in laser propulsion. The Nd:glass laser is one of a candidate of the driver for the propulsion. However, there is a lack of study with using the solid state laser. Previous studies found that plasma induced using the glass laser absorbs the laser energy during a short laser supported detonation (LSD) regime compared with CO2 lasers. To investigate a laser wavelengths dependency of LSD in comparison with the CO2 laser, we used plasma emission spectroscopy and measured the electron temperature and electron density. As a result, these parameters of the glass laser appear to be higher value than those for the CO2 laser plasma. Besides, the absorption depth behind the shock wave is longer than that one of the CO2 laser. The results reveal that the long depth absorbs the energy conversion efficiency at almost same order despite a short LSD duration, as compared with the CO2 laser.

Shimamura, Kohei; Michigami, Keisuke; Wang, Bin; Yamaguchi, Toshikazu; Komurasaki, Kimiya; Arakawa, Yoshihiro

2011-11-01

397

D-wave bipolaronic condensate with short range repulsive electronic correlations in an extended hubbard model of high Tc cuprate superconductors  

NASA Astrophysics Data System (ADS)

The question as to whether Fermion pairs interacting with a short range Coulomb repulsion and longer range attractive tail can form a Condensate is a key question for High Temperature Superconductivity [1-30]. If such a form of interaction can support a bound state it is commonly suggested that Bose-Einstein condensation of such pairs may occur, as in widely discussed Bipolaron models of High Temperature Cuprate superconductivity where the paired Fermions are holes. On the other hand it is frequently stated that strongly overlapping real-space pairing with a strong short range Coulomb repulsion is a priori implausible [4]. In this paper a review is made of our work on D-wave pairing [7-19] in real-space between electrons on a Cuprate lattice due to any effective interaction with a short range repulsive part and a longer range attractive tail such as might arise from Bipolaronic coupling.

Dunne, L. J.; Brändas, E. J.

398

Gravitational Wave Propulsion  

NASA Astrophysics Data System (ADS)

There is only one experimental proof that gravitational waves exist. With such a limitation, it may seem premature to suggest the possibility that gravitational waves can became a preferred space propulsion technique. The present understanding of the problem indicates that this is not the case. The emission of gravitational waves from astrophysical sources has been confirmed by observation, the respective detection at large distance from the source is difficult and actually we have no confirmation of a successful detection. Therefore the required preliminary discovery has been already made. This opinion is enforced by many different proposals for building the required powerful gravitational wave generators that have recently appeared in the literature and discussed at conferences. It is no longer reasonable to wait for additional confirmation of the existence of gravitational waves to start a program for building generators and testing their possible application to space travel. A vast literature shows that gravitational waves can be employed for space propulsion. Gravitational wave rockets have been proposed, non-linearity of Einstein equations allows the conversion of gravitational waves to a static gravitational field and ``artificial gravity assist'' may become a new way of travelling in space-time. Different approaches to gravitational wave propulsion are reviewed and compared. Gravitational wave propulsion is also compared to traditional rocket propulsion and an undeniable advantage can be demonstrated in terms of efficiency and performance. Testing the predictions will require gravitational wave generators with high power and wavelength short enough for producing high energy densities. Detectors designed for the specific application must be developed, taking into account that non-linearity effects are expected. The study and development of Gravitational wave propulsion is a very challenging endeavor, involving the most complex theories, sophisticated materials and testing techniques ever conceived by science. The development of Gravitational wave propulsion appears to be within the reach of a large national or a worldwide research program.

Fontana, Giorgio

2005-02-01

399

Chemical Sensing Using Infrared Cavity Enhanced Spectroscopy: Short Wave Infrared Cavity Ring Down Spectroscopy (SWIR CRDS) Sensor  

SciTech Connect

The principal goal of Pacific Northwest National Laboratory's (PNNL's) Remote Spectroscopy Project is to explore and develop the science and technology behind point and stand off infrared (IR) spectroscopic chemical sensors that are needed for detecting weapons proliferation activity and countering terrorism. Missions addressed include detecting chemical, biological, and nuclear weapons and their production; counter terrorism measures that involve screening luggage, personnel, and shipping containers for explosives, firearms, narcotics, chemical weapons and/or their residues; and mapping of contaminated areas. The science and technology developed in this program is dual use in that it additionally supports progress in a diverse set of agendas that include chemical weapons defense programs, air operations activities, emissions monitoring, law enforcement, and medical diagnostics. Sensors for these missions require extremely low limits of detection because many of the targeted signature species are either present in low concentrations or have extremely low vapor pressures. The sensors also need to be highly selective as the environments that they will be operated in will contain a variety of interferent species and false positive detection is not an option. PNNL has been working on developing a class of sensors that draw vapor into optical cavities and use laser-based spectroscopy to identify and quantify the vapor chemical content. The cavity enhanced spectroscopies (CES) afford extreme sensitivity, excellent selectivity, noise immunity, and rapid, real-time, in-situ chemical characterization. PNNL's CES program is currently focused on developing two types of sensors. The first one, which is based on cavity ring down spectroscopy (CRDS), uses short wave infrared (SWIR) lasers to interrogate species. The second sensor, which is based on noise immune cavity-enhanced optical heterodyne molecular spectroscopy (NICE OHMS), uses long wave infrared (LWIR) quantum cascade lasers as the light source. This report details the research and discoveries made on the SWIR CRDS project. While chemical detection limits in the SWIR is not expected to be as low as that in the LWIR, there are a number of reasons for designing sensors that operate in this region. First and foremost is that high quality SWIR lasers, detectors and optics are commercially available. Technological advances made in the telecommunications sector have yielded photonic components that are robust, low power, compact and operate at room temperature. These components can be quickly combined and assembled to produce a sensor prototype. This is exactly what we have done with our cavity ring down sensor. We assembled our first prototype instrument in FY02, tested it in the laboratory, developed the chemometrics, and defined several improvements that needed to be implemented before trialing this sensor in the field. In FY03 we completed the refinements, retested the sensor in the laboratory, and then conducted our first field campaign. Our success was demonstrated by the ability of our SWIR CRDS to run autonomously and continuously for 7 days when located in PNNL's Shipping and Receiving Building. No false positive alarms were detected even though the environment was contaminated with vehicle exhaust fumes, dirt, dust, and volatile organic chemicals associated with packaging materials. The instrument maintained its detection threshold and calibration throughout the test. Small fluctuations that we observed in the background concentration levels have led us to develop a more robust method for calibrating the instrument, and separate tests we conducted in the laboratory have afforded a means to account interference from species that have very broad, but weak absorption in this spectral region. We outline all of these accomplishments in detail in the body of this report.

Williams, Richard M.; Harper, Warren W.; Aker, Pam M.; Thompson, Jason S.; Stewart, Timothy L.

2003-10-01

400

A full-duplex multiband access radio-over-fiber link with frequency multiplying millimeter-wave generation and wavelength reuse for upstream signal  

NASA Astrophysics Data System (ADS)

A full-duplex radio-over-fiber (RoF) link providing multiband wireless accesses including 20 GHz, 40 GHz and 60 GHz millimeter (mm)-wave signal using a 10 GHz RF signal source is proposed. According to our theoretical analysis and simulation of the transmission performance of the signal along the single mode fiber, the code form distortion caused by the sideband walk-off effect due to the fiber chromatic dispersion can be eliminated, and the degradation caused by the fading effect on the down-stream signal is removed by adjusting the relative phase shift between the two sidebands. The upstream signal carried by the optical carrier abstracted from the downlink signal is also immune to the code outline distortion. The numerical simulation results show that the 20 km full-duplex RoF link with our generated optical mm-wave signal maintains good performance.

Ma, Jianxin; Li, Yanjie

2015-01-01

401

A global study of the lowermost mantle using short and long period scattered PKKP waves (PK?KP)  

NASA Astrophysics Data System (ADS)

The short-period (1 Hz) seismic wavefield shows strong evidence for scattered energy from the interior of the Earth. This energy mainly arrives in the coda following major seismic phases; however, several ray configurations exist in which seismic energy from the lowermost mantle arrives as precursors to main phases, allowing analysis of heterogeneities in the deep Earth, undisturbed by crustal interference. Here we use the phase PKKP to infer small-scale structure at the Core-Mantle Boundary (CMB) and in the D? layer. PKKP back-scattered at, or above, the CMB (PK?KP where the ? represents the location of scattering) is observed in a time window starting about 1720 s after origin (for a surface focus) and can be observed from 0° to greater than 60° epicentral distance. This time and distance window is free from other seismic arrivals thus allowing identification of the scattered PKKP energy, despite its relatively low amplitude. The ray path of PK?KP is complicated with scattering occurring off great-circle path, thus avoiding the attenuating inner core. Due to its raypath, PK?KP waves sample regions of the Core-Mantle Boundary inaccessible to most other scattering probes. Back-scattering in this frequency range is controlled by the acoustic impedance of the scattering heterogeneity. This method, therefore, could resolve density contrasts in the deep Earth. When combined with forward scattering probes, such as PKP, which are sensitive to elastic moduli, all the material properties of the scattering heterogeneity could be resolved. Here we use the dense, small to medium aperture arrays of the International Monitoring System of the CTBTO to extract the small amplitude PK?KP from seismic noise. Directivity information from the arrays and ray tracing allows us to infer the location of heterogeneity in the deep Earth. We use the frequency-wavenumber (fk) analysis in conjunction with the F-statistic coherency measure, commonly used in forensic seismology, to greatly increase the slowness vector resolution of the small aperture arrays of the International Monitoring System. The dataset comprises 653 earthquakes, with magnitudes larger than 6.0, resulting in 2094 source-receiver pairs. This allows unprecedented coverage of the CMB, particularly of the area beneath the Atlantic ocean and surrounding continents. We find strong lateral variation in scattering height and amplitude, indicating varying distribution of heterogeneities in the lowermost mantle. The location of these anomalies, both in terms of lateral distribution and height, is related to larger scale mantle structure and flow as shown by comparisons with tomographic and dynamical models. Short period observations of PK?KP energy at 1-2 Hz indicate that the scatterers are discrete heterogeneities with a scale length of ˜10 km. Using single broadband stations from the Global Seismic Network we probe the nature of the PK?KP wavefield. By analysing PK?KP at a range of frequencies we resolve the dominant size of the heterogeneity in the lowermost mantle. We aim to test the hypothesis that small-scale heterogeneities are derived from larger scale debris from the convection process.

Frost, D. A.; Rost, S.; Selby, N.

2013-12-01

402

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

SciTech Connect

This project focused on determining the feasibility of using short wave infrared (SWIR) cavity ring down spectroscopy (CRDS) as a means for real-time detection of biological aerosols. The first part of the project involved identifying biological agent signatures that could be detected with SWIR CRDS. After an exhaustive search of the open literature it was determined that whole biological spores and/or cells would not be good candidates for direct SWIR CRDS probing because they have no unique SWIR signatures. It was postulated that while whole cells or spores are not good candidates for SWIR CRDS detection, their pyrolysis break-down products might be. A literature search was then conducted to find biological pyrolysis products with low molecular weights and high symmetry since these species most likely would have overtone and combination vibrational bands that can be detected in the SWIR. It was determined that pyrrole, pyridine and picolinamide were good candidates for evaluation. These molecules are formed when proteins and porphyrins, proteins and dipicolinic acid, and dipicolinic acid are pyrolyzed, respectively. The second part of the project involved measuring quantitative SWIR spectra of pyrrole, pyridine and picolinamide in PNNL’s FTIR Spectroscopy Laboratory. Spectral information about these molecules, in the vapor phase is sparse – there were only a few prior studies that measured line positions and no information on absorption cross sections. Absorption cross sections are needed in order to estimate the SWIR CRDS detection sensitivity, and line position determines what type of laser will be needed for the sensor. The results of the spectroscopy studies allowed us to estimate the SWIR CRDS detection sensitivity for pyrrole to be 3 x 1012 molec cm-3 or 0.1 ppmv, and for pyridine it was 1.5 x 1015 molec cm-3 or 0.6 ppmv. These detection sensitivity limits are close what we have measured for ammonia. Given these detection limits we then estimated the amount of biological material that would have to be collected for analysis in a sensor that combined pyrolysis with SWIR CRDS. Using conservative estimates of pyrolysis yields and precursor species concentration we determined that it would be necessary to collect and pyrolyze biological aerosol samples in the 10’s of mg. This is a large amount and is far larger than required for current sensors. It is therefore concluded that while possible, the large amounts of material required preclude using SWIR CRDS for detecting biological agents at this time.

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

2007-10-01

403

Combined short and long-delay tandem shock waves to improve shock wave lithotripsy according to the Gilmore-Akulichev theory.  

PubMed

Extracorporeal shock wave lithotripsy is a common non-invasive treatment for urinary stones whose fragmentation is achieved mainly by acoustic cavitation and mechanical stress. A few years ago, in vitro and in vivo experimentation demonstrated that such fragmentation can be improved, without increasing tissue damage, by sending a second shock wave hundreds of microseconds after the previous wave. Later, numerical simulations revealed that if the second pulse had a longer full width at half maximum than a standard shock wave, cavitation could be enhanced significantly. On the other side, a theoretical study showed that stress inside the stone can be increased if two lithotripter shock waves hit the stone with a delay of only 20?s. We used the Gilmore-Akulichev formulation to show that, in principle, both effects can be combined, that is, stress and cavitation could be increased using a pressure pulse with long full width at half maximum, which reaches the stone within hundreds of microseconds after two 20?s-delayed initial shock waves. Implementing the suggested pressure profile into clinical devices could be feasible, especially with piezoelectric shock wave sources. PMID:25553714

de Icaza-Herrera, Miguel; Fernández, Francisco; Loske, Achim M

2015-04-01

404

A comprehensive observational filter for satellite infrared limb sounding of gravity waves  

NASA Astrophysics Data System (ADS)

This paper describes a comprehensive observational filter for satellite infrared limb sounding of gravity waves. The filter considers instrument visibility and observation geometry with a high level of accuracy. It contains four main processes: visibility filter, projection of the wavelength on the tangent-point track, aliasing effect, and calculation of the observed vertical wavelength. The observation geometries of the SABER (Sounding of the Atmosphere using Broadband Emission Radiometry) and HIRDLS (High Resolution Dynamics Limb Sounder) are mimicked. Gravity waves (GWs) simulated by coupling a convective GW source (CGWS) scheme and the gravity wave regional or global ray tracer (GROGRAT) are used as an example for applying the observational filter. Simulated spectra in terms of horizontal and vertical wave numbers (wavelengths) of gravity wave momentum flux (GWMF) are analyzed under the influence of the filter. We find that the most important processes, which have significant influence on the spectrum are the visibility filter (for both SABER and HIRDLS observation geometries) and aliasing for SABER and projection on tangent-point track for HIRDLS. The vertical wavelength distribution is mainly affected by the retrieval as part of the "visibility filter" process. In addition, the short-horizontal-scale spectrum may be projected for some cases into a longer horizontal wavelength interval which originally was not populated. The filter largely reduces GWMF values of very short horizontal wavelength waves. The implications for interpreting observed data are discussed.

Trinh, Q. T.; Kalisch, S.; Preusse, P.; Chun, H.-Y.; Eckermann, S. D.; Ern, M.; Riese, M.

2015-03-01

405

A comprehensive observational filter for satellite infrared limb sounding of gravity waves  

NASA Astrophysics Data System (ADS)

This paper describes a comprehensive observational filter for satellite infrared limb sounding of gravity waves. The filter considers instrument visibility and observation geometry with a high level of accuracy. It contains four main processes: visibility filter, projection of the wavelength on the tangent-point track, aliasing effect, and calculation of the observed vertical wavelength. The observation geometries of the SABER (Sounding of the Atmosphere using Broadband Emission Radiometry) and HIRDLS (High Resolution Dynamics Limb Sounder) are mimicked. Gravity waves (GWs) simulated by coupling a convective GW source (CGWS) scheme and the gravity wave regional or global ray tracer (GROGRAT) are used as an example for applying the observational filter. Simulated spectra in terms of horizontal and vertical wave numbers (wavelengths) of gravity wave momentum flux (GWMF) are analyzed under the influence of the filter. We find that the most important processes, which have significant influence on the spectrum are: visibility filter (for both SABER and HIRDLS observation geometries), aliasing for SABER and projection on tangent-point track for HIRDLS. The vertical wavelength distribution is mainly affected by the retrieval as part of the "visibility filter" process. In addition, the short-horizontal-scale spectrum may be projected for some cases into a longer horizontal wavelength interval which originally was not populated. The filter largely reduces GWMF values of very short horizontal wavelength waves. The implications for interpreting observed data are discussed.

Trinh, Q. T.; Kalisch, S.; Preusse, P.; Chun, H.-Y.; Eckermann, S. D.; Ern, M.; Riese, M.

2014-10-01

406

Studies of classical radiation emission from plasma wave undulators  

NASA Technical Reports Server (NTRS)

We examine the characteristics of the classical radiation emitted by a relativistic electron beam that propagates perpendicularly through a large amplitude relativistic plasma wave. Such a study is useful for evaluating the feasibility of using relativistic plasma waves as extremely short wavelength undulators for generating short wavelength radiation. The electron trajectories in a plasma wave undulator are obtained using perturbation techniques and are then compared to numerical simulation results. The frequency spectrum and angular distribution of the spontaneous radiation emitted by a single electron and the stimulated radiation gain are obtained analytically, and are then compared to 3-D numerical simulations. The characteristics of the plasma wave undulator are compared to the ac FEL undulator and the conventional FEL.

Williams, Ronald L.; Clayton, C. E.; Joshi, C.; Katsouleas, Thomas C.

1993-01-01

407

Finding Monster Waves  

NSDL National Science Digital Library

In this lesson, students learn about the varying sizes of ocean waves, what causes such variation, and where to find giant waves. Students will learn the parts of a wave, and discuss wave height, wavelength, and wave period. They will explore variables that influence wave size through scientific visualizations. They will then experiment with creating waves on the National Geographic Wave Simulator and discuss how geography affects waves.

408

Introduction to Waves  

NSDL National Science Digital Library

In this National Geographic Xpedition lesson, students learn about ocean waves. They begin by learning the components of a wave, and then discuss the meaning of wave height and wavelength. A demonstration sparks discussion about how to make waves, and an activity with the National Geographic Wave Simulator allows students to experiment with creating waves of varying sizes.

409

Compensated anisotropic metamaterials: Manipulating sub-wavelength images  

Microsoft Academic Search

In this presentation, I will analyze the image focusing, rotation, lateral shift, as well as the image magnification with sub-wavelength resolutions through differently designed structures of compensated anisotropic metamaterials. The verifications of all the proposed structures by full wave electromagnetic simulations will also be demonstrated. Utilizing the proposed structures, planar optical image of sub-wavelength objects can be magnified to wavelength

Yijun Feng

2008-01-01

410

Functional characterization of spectral tuning mechanisms in the great bowerbird short-wavelength sensitive visual pigment (SWS1), and the origins of UV/violet vision in passerines and parrots  

PubMed Central

Background One of the most striking features of avian vision is the variation in spectral sensitivity of the short wavelength sensitive (SWS1) opsins, which can be divided into two sub-types: violet- and UV- sensitive (VS & UVS). In birds, UVS has been found in both passerines and parrots, groups that were recently shown to be sister orders. While all parrots are thought to be UVS, recent evidence suggests some passerine lineages may also be VS. The great bowerbird (Chlamydera nuchalis) is a passerine notable for its courtship behaviours in which males build and decorate elaborate bower structures. Results The great bowerbird SWS1 sequence possesses an unusual residue combination at known spectral tuning sites that has not been previously investigated in mutagenesis experiments. In this study, the SWS1 opsin of C. nuchalis was expressed along with a series of spectral tuning mutants and ancestral passerine SWS1 pigments, allowing us to investigate spectral tuning mechanisms and explore the evolution of UV/violet sensitivity in early passerines and parrots. The expressed C. nuchalis SWS1 opsin was found to be a VS pigment, with a ?max of 403 nm. Bowerbird SWS1 mutants C86F, S90C, and C86S/S90C all shifted ?max into the UV, whereas C86S had no effect. Experimentally recreated ancestral passerine and parrot/passerine SWS1 pigments were both found to be VS, indicating that UV sensitivity evolved independently in passerines and parrots from a VS ancestor. Conclusions Our mutagenesis studies indicate that spectral tuning in C. nuchalis is mediated by mechanisms similar to those of other birds. Interestingly, our ancestral sequence reconstructions of SWS1 in landbird evolution suggest multiple transitions from VS to UVS, but no instances of the reverse. Our results not only provide a more precise prediction of where these spectral sensitivity shifts occurred, but also confirm the hypothesis that birds are an unusual exception among vertebrates where some descendants re-evolved UVS from a violet type ancestor. The re-evolution of UVS from a VS type pigment has not previously been predicted elsewhere in the vertebrate phylogeny. PMID:24499383

2013-01-01

411

Light as Waves  

NSDL National Science Digital Library

Overview: This Science Object is the second of four Science Objects in the Nature of Light SciPack. It provides conceptual and real world understanding of the idea that waves (including sound and seismic waves, waves on water, and light waves) have energy and can transfer energy when they interact with matter. Wave behavior can be described in terms of how fast the disturbance propagates, and of the distance between successive crests or troughs of the wave (the wavelength). Accelerating electric charges produce electromagnetic waves which can be organized into a spectrum of varying wavelengths (and frequencies): radio waves, microwaves, radiant heat or infrared radiation, visible light, ultraviolet radiation, x-rays, and gamma rays. These wavelengths vary from radio waves (the longest) to gamma rays (the shortest). Human eyes only respond to a narrow range of wavelengths of electromagnetic radiation--what we call visible light. In empty space, electromagnetic waves of all wavelengths move at the same speed--the "speed of light." Learning Outcomes: Provide examples of energy transfer by light (such as tanning, light warming a surface, solar cells, etc.) Describe the characteristics of transverse waves and explain how waves transfer energy from place to place. Describe the relationship between the wavelength and frequency of light waves. Explain how electromagnetic waves are produced either in nature or by humans. Identify the various parts of the electromagnetic spectrum, and place them in order of increasing or decreasing wavelength. Determine the behavior of two light waves that interfere with one another.

National Science Teachers Association (NSTA)

1900-01-01

412

Electrostatic lower hybrid waves excited by electromagnetic whistler mode waves scattering from planar magnetic-field-aligned plasma density irregularities  

Microsoft Academic Search

Recent satellite observations demonstrate that high amplitude, short wavelength (5 m ⤠λ ⤠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

T. F. Bell; H. D. Ngo

1990-01-01

413

Ripple Waves  

NSDL National Science Digital Library

The applet demonstrates a ripple tank with two point sources that are generating waves. The two sources produce an interference pattern. We can use this pattern to calculate the wavelength of the sources.

Wolfgang Christian

414

Making Waves  

NSDL National Science Digital Library

Provided by Living Graphs, Making Waves is a freely downloaded interactive physics package that helps students visualize and understand the motion and interference of transverse and longitudinal waves. Designed for senior high school and college physics students, the interactive program allows users to manipulate wave properties such as their amplitude, wavelength, phase shift, speed, frequency and damping; standing waves; and mks units. The site even provides online help and tutorials for teachers to help them integrate the software into curricula.

1969-12-31

415

Transport equations for lower hybrid waves in a turbulent plasma  

NASA Astrophysics Data System (ADS)

We consider the limits of validity of ray tracing and ray diffusion equations, for short wavelength waves propagating in a turbulent plasma background. We derive an improved transport equation for the electric field autocorrelation function, where first order diffraction effects associated with these waves are included. We apply this description to the case of lower hybrid (LH) waves propagating in non-stationary plasma where density perturbations can occur due to drift wave turbulence, as well as magnetic field perturbations due to MHD turbulence. This is relevant to the problem of LH current drive.

Mendonça, J. T.; Horton, W.; Galvão, R. M. O.; Elskens, Yves; Elskens

2015-04-01

416

Numerical simulation of propagation of short waves with consideration for the models of the global distribution of the electron density and local irregularities  

NASA Astrophysics Data System (ADS)

Based on the IRI-2012 global model and assimilative model of the electron density distribution in the Earth ionosphere and the bicharacteristic system of ordinary differential equations a numerical algorithm for calculation of the ray and caustic structure, the group delay, and the intensity of the short-wave field is implemented. To determine the intensity of the ray tubes, it is necessary to calculate divergence Jacobian and wave absorption. The numerical algorithm takes into account the terrestrial magnetic field specified by the World Magnetic Model (WMM), International Geomagnetic Reference Field (IGRF) and dipole approximation. Also, it can take into account local irregularities, which are created, for example, by ionospheric heating facility. The obtained numerical results are compared with the experimental data on remote sensing.

Cherniak, Yakov; Lukin, Dmitry

417

Improved dipole moments by combining short-range gradient-corrected density-functional theory with long-range wave-function methods  

SciTech Connect

Previously proposed schemes of coupling short-range density-functional-based with long-range wave-function-based methods are tested for the notoriously difficult case of correctly describing the charge distribution in compounds containing late transition elements. We show that for the dipole moments of the group-11 transition metal hydrides and halides the recently developed Coulomb-attenuated Becke three-parameter Lee-Yang-Parr hybrid functional already leads to a substantial improvement compared to other density functionals. Further improvement is achieved by combining a gradient-corrected short-range functional of the Perdew-Burke-Ernzerhof type with coupled-cluster theory. The results clearly demonstrate that mixing of long-range ab initio Hartree-Fock and post-Hartree-Fock methods helps to remove deficiencies of current density functionals.

Goll, Erich; Stoll, Hermann; Thierfelder, Christian; Schwerdtfeger, Peter [Institut fuer Theoretische Chemie, Universitaet Stuttgart, D-70550 Stuttgart (Germany); Centre of Theoretical Chemistry and Physics, Institute of Advanced Studies and the Institute of Fundamental Sciences, Massey University (Albany Campus), Private Bag 102904, North Shore MSC, Auckland (New Zealand)

2007-09-15

418

Short-term effects of thermotherapy for spasticity on tibial nerve F-waves in post-stroke patients  

NASA Astrophysics Data System (ADS)

Thermotherapy is generally considered appropriate for post-stroke patients with spasticity, yet its acute antispastic effects have not been comprehensively investigated. F-wave parameters have been used to demonstrate changes in motor neuron excitability in spasticity and pharmacological antispastic therapy. The present study aimed to confirm the efficacy of thermotherapy for spasticity by evaluating alterations in F-wave parameters in ten male post-stroke patients with spastic hemiparesis (mean age: 49.0±15.0 years) and ten healthy male controls (mean age: 48.7±4.4 years). The subjects were immersed in water at 41°C for 10 min. Recordings were made over the abductor hallucis muscle, and antidromic stimulation was performed on the tibial nerve at the ankle. Twenty F-waves were recorded before, immediately after, and 30 min following thermotherapy for each subject. F-wave amplitude and F-wave/M-response ratio were determined. Changes in body temperature and surface-skin temperature were monitored simultaneously. The mean and maximum values of both F-wave parameters were higher on the affected side before thermotherapy. In the post-stroke patients, the mean and maximum values of both parameters were significantly reduced after thermotherapy ( P<0.01). Hence, the antispastic effects of thermotherapy were indicated by decreased F-wave parameters. Body temperature was significantly increased both immediately after and 30 min after thermotherapy in all subjects. This appeared to play an important role in decreased spasticity. Surface-skin temperature increased immediately after thermotherapy in both groups and returned to baseline 30 min later. These findings demonstrate that thermotherapy is an effective nonpharmacological antispastic treatment that might facilitate stroke rehabilitation.

Matsumoto, Shuji; Kawahira, Kazumi; Etoh, Seiji; Ikeda, Satoshi; Tanaka, Nobuyuki

2006-03-01

419

A discontinuous Galerkin method with plane waves and Lagrange multipliers for the solution of short wave exterior Helmholtz problems on unstructured meshes  

Microsoft Academic Search

Recently, a discontinuous Galerkin method with plane wave basis functions and Lagrange multiplier degrees of freedom was proposed for the efficient solution of the Helmholtz equation in the mid-frequency regime. This method was fully developed however only for regular meshes, and demonstrated only for interior Helmholtz problems. In this paper, we extend it to irregular meshes and exterior Helmholtz problems

Charbel Farhat; Paul Wiedemann-Goiran; Radek Tezaur

2004-01-01

420

Excitation of ion rarefaction waves in a low pressure plasma by applying a short high negative voltage pulse  

SciTech Connect

The ion rarefaction response to a high negative voltage pulse (U{sub 0} >> kT{sub e}/e) applied to a metal plate immersed in a low pressure argon plasma, for time duration lower than ion plasma period, is experimentally examined. In the present experiment the pulse duration is kept intermediate between the ion and electron plasma response times. Such a pulse duration is chosen so that ions are collectively undisturbed and, according to general understanding, no force is given to ions. Hence no ion rarefaction wave should be excited. But contrary to the general understanding, excitation of a rarefaction wave is observed. The results indicate that the speed of the rarefaction waves for various conditions (like plasma density, applied pulse magnitude, and pulse duration) is supersonic. After a distance from the exciter (biased plate), typically three-fourth of the exciter diameter, the rarefaction waves are turned into ion acoustic waves. The experimental results indicate that even though the bias durations are shorter than the ion plasma period, if the bias magnitude is large enough, some collective plasma behavior can still be excited.

Kar, S.; Mukherjee, S.; Saxena, Y. C. [Institute for Plasma Research, Bhat, Gandhinagar 382 428 (India)

2011-05-15

421

Short-period Rayleigh wave group and phase velocities of the Reno-Truckee Meadows basin from ambient seismic noise  

NASA Astrophysics Data System (ADS)

The Reno-Truckee Meadows basin in western Nevada experiences high seismicity rates, exposing the population to significant seismic hazards. We expect that earthquake ground-motions are amplified in this basin, however current-generation ground motion prediction equations were developed with few measurements from sensors sited within deep sedimentary basins. Improved estimates of ground motion require detailed knowledge of 3D basin structure and the use of 3D numerical ground motion simulations. The main goal of this work is to develop a 3D shear wave velocity model of the near surface (depths less than 2 km) of the Reno basin using ambient seismic noise analyses. In order to investigate shallow structures in the Reno basin, we deployed 12 broadband seismic stations, with average station spacings ranging 2-3 km, and recorded continuous ground velocities between late February and March 2011. We calculate interstation Green's functions from ambient seismic noise and report on the progress of our analyses here. We cross-correlate vertical component time series to recover 91 empirical Green's functions (EGFs). EGFs contain surface wave energy in 0.5-5 s period band, with inter-station distances ranging from 2-18 km. From the frequency content of the cross-correlations, we expect to resolve shear wave velocity structures above 2 km. Based on the asymmetry of the EGFs, ambient seismic noise sources 2-3 s period appear to locate west of the array, and perhaps originate near the coastlines; shorter period signals show greater symmetry in the EGFs and may result from local, possibility cultural, sources. However, further work will be required to definitively identify the locations of the noise sources. We measure surface wave group and phase velocities by frequency-time analyses and find clear agreements between the lateral distributions of surface wave speeds and the inferred basin depths. Future work will focus on inversion of the inter-station surface wave dispersion measurements for lateral distribution of surface wave speeds, and inversion for 3D shear wave velocity structure. Most previous ambient noise tomography studies obtain group and phase surface velocity dispersion measurements at periods T > 5-10 s (i.e. Shapiro and Campillo (2004); Yao et al., (2006); Yang et al. (2008)), which are longer that those used in this study. As a result, a secondary goal of this study is to investigate the ability of a small, temporary, broadband seismic array to characterize the shallow subsurface at depths beyond those retrieved by standard geotechnical methods.

Noriega Salmon, R.; Moschetti, M. P.; Stephenson, W. J.; Meremonte, M. E.

2013-12-01

422

Excitation of parasitic waves near cutoff in forward-wave amplifiers  

SciTech Connect

In this paper, excitation of parasitic waves near cutoff in forward-wave amplifiers is studied in a rather general form. This problem is important for developing high-power sources of coherent, phase controlled short-wavelength electromagnetic radiation because just the waves which can be excited near cutoff have low group velocities. Since the wave coupling to an electron beam is inversely proportional to the group velocity, these waves are the most dangerous parasitic waves preventing stable amplification of desired signal waves. Two effects are analyzed in the paper. The first one is the effect of signal wave parameters on the self-excitation conditions of such parasitic waves. The second effect is the role of the beam geometry on excitation of these parasitic waves in forward-wave amplifiers with spatially extended interaction space, such as sheet-beam devices. It is shown that a large-amplitude signal wave can greatly influence the self-excitation conditions of the parasitic waves which define stability of operation. Therefore the effect described is important for accurate designing of high-power amplifiers of electromagnetic waves.

Nusinovich, Gregory S.; Sinitsyn, Oleksandr V.; Antonsen, Thomas M. Jr. [Institute for Research in Electronics and Applied Physics, University of Maryland, College Park, Maryland 20742-3511 (United States)

2010-10-15

423

Theoretical study of the optical gain characteristics of a Ge1?xSnx alloy for a short-wave infrared laser  

NASA Astrophysics Data System (ADS)

Optical gain characteristics of Ge1?xSnx are simulated systematically. With an injection carrier concentration of 5 × 1018/cm3 at room temperature, the maximal optical gain of Ge0.922Sn0.078 alloy (with n-type doping concentration being 5 × 1018/cm3) reaches 500 cm?1. Moreover, considering the free-carrier absorption effect, we find that there is an optimal injection carrier density to achieve a maximal net optical gain. A double heterostructure Ge0.554Si0.289Sn0.157/Ge0.922Sn0.078/Ge0.554Si0.289Sn0.157 short-wave infrared laser diode is designed to achieve a high injection efficiency and low threshold current density. The simulation values of the device threshold current density Jth are 6.47 kA/cm2 (temperature: 200 K, and ? = 2050 nm), 10.75 kA/cm2 (temperature: 200 K, and ? = 2000 nm), and 23.12 kA/cm2 (temperature: 300 K, and ? = 2100 nm), respectively. The results indicate the possibility to obtain a Si-based short-wave infrared Ge1?xSnx laser. Project supported by the Major State Basic Research Development Program of China (Grant No. 2013CB632103), the National High-Technology Research and Development Program of China (Grant No. 2012AA012202), and the National Natural Science Foundation of China (Grant Nos. 61177038 and 61176013).

Dong-Liang, Zhang; Bu-Wen, Cheng; Chun-Lai, Xue; Xu, Zhang; Hui, Cong; Zhi, Liu; Guang-Ze, Zhang; Qi-Ming, Wang

2015-02-01

424

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

E-print Network

that within the first few hundred nanoseconds upon power-on, there were fast attenuating, dispersive shock waves of extremely high frequency propagating in the package. The notions of high cycle fatigue, power density and joint time-frequency analysis were...

Oh, Yoonchan

2005-11-01

425

Waves and Tsunami Project  

ERIC Educational Resources Information Center

Demonstrating wave processes quantitatively in the classroom using standard classroom tools (such as Slinkys and wave tanks) can be difficult. For example, waves often travel too fast for students to actually measure amplitude or wavelength. Also, when teaching propagating waves, reflections from the ends set up standing waves, which can confuse…

Frashure, K. M.; Chen, R. F.; Stephen, R. A.; Bolmer, T.; Lavin, M.; Strohschneider, D.; Maichle, R.; Micozzi, N.; Cramer, C.

2007-01-01