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1

Short wavelength quantum electrodynamical correction to cold plasma-wave propagation  

E-print Network

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

J. Lundin; G. Brodin; M. Marklund

2006-08-16

2

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

NASA Astrophysics Data System (ADS)

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

Mori, N.

2009-10-01

3

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

PubMed

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

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

2012-07-30

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

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

6

Short wavelength (??4.3 ?m) high-performance continuous-wave quantum-cascade lasers  

Microsoft Academic Search

We report continuous-wave (CW) operation of a 4.3-?m quantum-cascade laser from 80 K to 313 K. For a high-reflectivity-coated 11-?m-wide and 4-mm-long laser, CW output powers of 1.34 W at 80 K and 26 mW at 313 K are achieved. At 298 K, the CW threshold current density of 1.5 kA\\/cm2 is observed with a CW output power of 166

J. S. Yu; A. Evans; S. Slivken; S. R. Darvish; M. Razeghi

2005-01-01

7

Short wavelength electromagnetic propagation in magnetized quantum plasmas  

Microsoft Academic Search

The quantum electrodynamical (QED) short wavelength correction on plasma wave propagation for a nonrelativistic quantum plasma is investigated. A general dispersion relation for a thermal multicomponent quantum plasma is derived. It is found that the classical dispersion relation for any wave mode can be modified to include quantum and short wavelength QED effects by simple substitutions of the thermal velocity

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

2007-01-01

8

Short vertical-wavelength inertia-gravity waves generated by a jet-front system at Arctic latitudes - VHF radar, radiosondes and numerical modelling  

NASA Astrophysics Data System (ADS)

Inertia-gravity waves with very short vertical wavelength (?z?1000 m) are a very common feature of the lowermost stratosphere as observed by the 52 MHz radar ESRAD (Esrange MST radar) in northern Scandinavia (67.88° N, 21.10° E). The waves are seen most clearly in radar-derived profiles of buoyancy frequency (N). Here, we present a case study of typical waves from 21 February to 22 February 2007. Good agreement between N2 derived from radiosondes and by radar shows the validity of the radar determination of N2. Large-amplitude wave signatures in N2 are clearly observed by the radar and the radiosondes in the lowermost stratosphere, from 9 km to 14-16 km height. Vertical profiles of horizontal wind components and potential temperature from the radiosondes show the same waves. Mesoscale simulations with the Weather Research and Forecasting (WRF) model are carried out to complement the analysis of the waves. Good agreement between the radar and radiosonde measurements and the model (except for the wave amplitude) shows that the model gives realistic results and that the waves are closely associated to the upper-level front in an upper-troposphere jet-front system. Hodographs of the wind fluctuations from the radiosondes and model data show that the waves propagate upward in the lower stratosphere confirming that the origin of the waves is in the troposphere. The observations and modelling all indicate vertical wavelengths of 700 ± 200 m. The radiosonde hodograms indicate horizontal wavelengths between 40 and 110 km and intrinsic periods between 6 and 9 h. The wave amplitudes indicated by the model are however an order of magnitude less than in the observations. Finally, we show that the profiles of N2 measured by the radar can be used to estimate wave amplitudes, horizontal wavelengths, intrinsic periods and momentum fluxes which are consistent with the estimates from the radiosondes.

Réchou, A.; Kirkwood, S.; Arnault, J.; Dalin, P.

2014-07-01

9

Characteristics of gravity waves with short vertical wavelengths observed with radiosonde and GPS occultation during DAWEX (Darwin Area Wave Experiment)  

Microsoft Academic Search

We conducted radiosonde soundings during three intensive observation periods (IOP) of the Darwin Area Wave Experiment (DAWEX) campaign in October to December 2001 and measured humidity, temperature, and wind velocity up to ?30–35 km every 3 hours for 40 times at three sites in each IOP. We analyzed height profiles of kinetic (Ek) and potential (Ep) energy per unit mass

Toshitaka Tsuda; M. Venkat Ratnam; Peter T. May; M. Joan Alexander; Robert A. Vincent; Andrew MacKinnon

2004-01-01

10

Review of short wavelength lasers  

SciTech Connect

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

Hagelstein, P.L.

1985-03-18

11

Short wavelength electromagnetic propagation in magnetized quantum plasmas  

E-print Network

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

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

2007-03-14

12

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

13

Modulation compression for short wavelength harmonic generation  

SciTech Connect

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

Qiang, J.

2010-01-11

14

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

15

Short Wavelength Chemical Laser (SWCL) Workshop  

NASA Astrophysics Data System (ADS)

The workshop was held for the purpose of identifying the government's interest in SWCL technology, reviewing past and present efforts in this area and presenting the government's plans for a new thrust in SWCL source development. In addition, the workshop was to provide a forum for interaction between members of the Strategic Defense Initiation Organization (SDIO) and the 6.1 agencies with the technical community in order to create an enthusiastic response to the SWCL thrust and to generate new concepts as well as to involve new participants in this technically challenging area. This document contains abstracts of papers presented at the workshops. Some of the topics discussed in the sessions include: HF Lasers - What have we learned?; Chemical Oxygen Iodine Laser Review; Why So FEw Chemical Lasers?; Approach to Efficient Short-Wavelength Chemical Lasers; Metal/Oxidizer Systems; Pyrotechnic Systems; Metastable State Production; Metastable Transfer Systems; Energy Exchange Mechanisms.

Watt, W.

1984-12-01

16

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

17

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

18

Science Shorts: Making Waves  

NSDL National Science Digital Library

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

Adams, Barbara

2007-01-01

19

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

20

Long Wave Short Wave Interaction Induced by Stimulated Polariton Scattering  

Microsoft Academic Search

The parametric down conversion of the light wave induced by stimulated polariton scattering in polar crystals is investigated from the aspect of long wave short wave interaction. Assuming that the light wave is the superposition of short wave (near-infrared light) and long wave (terahertz wave), time-evolution equations for the long wave and the envelope of the short wave are derived

Takeya Tsurumi

2005-01-01

21

SHORT-WAVELENGTH ELECTROSTATIC FLUCTUATIONS IN THE SOLAR WIND  

SciTech Connect

Hybrid Vlasov-Maxwell simulations have been used recently to investigate the dynamics of the solar-wind plasma in the tail at short wavelengths of the energy cascade. These simulations have shown that a significant level of electrostatic activity is detected at wavelengths smaller than the proton inertial scale in the longitudinal direction with respect to the ambient magnetic field. In this paper, we describe the results of a new series of hybrid Vlasov-Maxwell simulations that allow us to investigate in more detail the generation process of these electrostatic fluctuations in terms of the electron-to-proton temperature ratio T{sub e} /T{sub p} . This analysis gives evidence for the first time that even in the case of cold electrons, T{sub e} {approx_equal} T{sub p} (the appropriate condition for solar-wind plasmas), the resonant interaction of protons with large-scale left-hand polarized ion-cyclotron waves is responsible for the excitation of short-scale electrostatic fluctuations with an acoustic dispersion relation. Moreover, through our numerical results we propose a physical mechanism to explain the generation of longitudinal proton-beam distributions in typical conditions of the solar-wind environment.

Valentini, F.; Perrone, D.; Veltri, P. [Dipartimento di Fisica and CNISM, Universita della Calabria, 87036 Rende (Italy)

2011-09-20

22

Electric Field and Plasma Density Observations of Long Wavelength Structures and Localized Packets of Short Scale Waves Associated with Sporadic-E Layers in the Presence of QP Radar Echoes  

NASA Astrophysics Data System (ADS)

Electric field and plasma density data gathered on sounding rockets launched in the presence of sporadic-E layers and QP radar echoes reveal a complex electrodynamics including both DC parameters and plasma waves detected over a large range of scales. We present results from two different sounding rocket experiments equipped with similar instrumentation which were conducted in the presence of intense QP radar echoes: a NASA sporadic-E investigation launched from Wallops Island, Va., in 1999 and the Japanese "SEEK-2" rocket launched from Uchinoura, Japan in 2002. Electric field data from both experiments reveal the presence of km-scale waves as well as well-defined packets of broadband (10's of meters to meters) irregularities. What is surprising is that in both experiments, neither the large scale nor short scale waves appear to be distinctly organized by the sporadic-E density layer. Data from the NASA rocket revealed large scale structures with wavelengths of 2-4 km and amplitudes of 1-2 mV/m that were most intense in the region of 90-110 km during the downleg trajectory of this flight. The waves were oriented in the NE-SW quadrants. On the other hand, during the SEEK-2 experiment, the electric field data above the sporadic-E layer on the upleg, from 110 km to the rocket apogee of 151 km, revealed a continuous train of distinct, large scale, quasi-periodic structures with wavelengths of 10-15 km that also propagated between the NE-SW quadrants. The electric field structures had typical amplitudes of 3-5 mV/m with some excursions to 8-9 mV/m, and had associated perturbations in the plasma density. The electric field waveforms showed evidence for steepening and/or convergence effects and may have mapped upwards along the magnetic field from the sporadic-E region below. Candidate mechanisms to explain the origin of these structures include the Kelvin-Helmholtz instability and the Es Layer instability. In both cases, the same shear that formed the sporadic-E layer would presumably provide the energy to generate the km-scale structures. Other possibilities include a gravity wave explanation or a combination of these processes. The data suggest that these structures were associated with the lower altitude density striations that were the seat of the QP radar echoes observed simultaneously. The SEEK-2 structures may also have been associated with the mechanism responsible for a well-defined pattern of "whorls" in the neutral wind data that were revealed in a chemical trail released by a second sounding rocket launched 15 minutes later. Well-defined packets of higher frequency (shorter scales < 100 m) broadband waves were also observed in-situ on both rockets, consistent with the observations of intense radar backscatter during the times of each launch. The linear gradient drift instability involving the DC electric field and the vertical plasma gradient is shown to be incapable of driving most, although not all, of the short scale waves observed during each flight. The data suggest that other sources of free energy may have been important factors for wave growth, and we conclude that drift waves associated with winds and horizontal plasma density gradients, as well as thermal or other instabilities, are necessary to explain the short-scale wave generation observed during these sporadic-E encounters.

Pfaff, R. F.; Freudenreich, H.; Kudeki, E.; Larsen, M.

2006-05-01

23

InAs/AlSb short wavelength quantum cascade lasers.  

E-print Network

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

Devenson, Jan

2010-01-01

24

Very-short-wavelength collective modes in fluids  

Microsoft Academic Search

The existence of very-short-wavelength collective modes in fluids is discussed. These collective modes are the extensions of the five hydrodynamic (heat, sound, viscous) modes to wavelengths of the order of the mean free path in a gas or to a fraction of the molecular size in a liquid. They are computed here explicitly on the basis of a model kinetic

I. M. de Schepper; E. G. D. Cohen

1982-01-01

25

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

26

Lethal effects of short-wavelength visible light on insects.  

PubMed

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

27

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

28

Short-wavelength Yb:fiber laser analysis  

NASA Astrophysics Data System (ADS)

Yb:fiber lasers have shown excellent performance in the 980–1100 nm wavelength range. To extend the range below 980 nm, it becomes difficult to reach the transparent condition due to the smaller ratio between emission and absorption cross sections. As a result, a high demand of population inversion is needed, and the selection of pump wavelength as well as other intra-cavity parameters are crucial for lasing in the 920–960 nm wavelength range. To find a feasible solution, the pump wavelength, fiber length, and laser cavity transmittance were systematically studied. Based on the experimental result of a 960 nm Yb:fiber laser, the re-absorption loss and temperature dependent gain can be reliably modeled. The result shows promise in the development of a Yb:fiber laser at a wavelength as short as 920 nm.

Yi, J. Y.; Chang, S. F.; Hsu, C. N.

2013-12-01

29

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

30

The MIT Short-Wavelength Laser Project: A Status Report  

SciTech Connect

The goal of the MIT Short-Wavelength Laser Project is to develop a small-scale, high repetition rate, EUV laser suitable for practical applications. The present report summarizes recent progress in this effort, both experimental and theoretical. Our experimental work has dealt with development of the pump laser, design of the target chamber and the associated target alignment system, investigation of short-wavelength laser cavities, and design of appropriate EUV diagnostics. Our theoretical work has included a study of the kinetics of transiently pumped laser plasmas, the development of efficient numerical algorithms applicable to laser-plasma rate equations, an investigation of frequency mixing in the EUV, and an analysis of x-ray detection using GaAs quantum-well structures.

Hagelstein, P.L.; Basu, S.; Muendel, M.H.; Braud, J.P.; Tauber, D.; Kaushik, S.; Goodberlet, J. (Massachusetts Inst. of Tech., Cambridge, MA (United States)); Hung, T.Y. (Princeton Univ., NJ (United States). Plasma Physics Lab.); Maxon, S. (Lawrence Livermore National Lab., CA (United States))

1990-01-01

31

Short Wavelength Technology and the Potential for Distributed Networks of Short-Range Radar Systems  

E-print Network

Short Wavelength Technology and the Potential for Distributed Networks of Short-Range Radar Systems's curvature and terrain-induced blockage. For example, the WSR-88D (NEXRAD) system is unable to view ~ 80 due to the Earth's curvature and improve resolution degradation caused by beam spreading. In addition

Cruz-Pol, Sandra L.

32

Long Wave Short Wave Interaction Induced by Stimulated Polariton Scattering  

NASA Astrophysics Data System (ADS)

The parametric down conversion of the light wave induced by stimulated polariton scattering in polar crystals is investigated from the aspect of long wave short wave interaction. Assuming that the light wave is the superposition of short wave (near-infrared light) and long wave (terahertz wave), time-evolution equations for the long wave and the envelope of the short wave are derived by means of a reductive perturbation method. Further, depending on the crystal properties, these equations describe two different situations. In one situation, the nonlinear effect of the short wave is dominant. In the other situation, the dispersion effect of the long wave is significant. For both cases, linear stability analysis is applied to the equations, and traveling wave solutions are obtained.

Tsurumi, Takeya

2005-03-01

33

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

34

Alerting effects of short-wavelength (blue) and long-wavelength (red) lights in the afternoon.  

PubMed

Light has an acute effect on neuroendocrine responses, performance, and alertness. Most studies to date have linked the alerting effects of light to its ability to suppress melatonin, which is maximally sensitive to short-wavelength light. Recent studies, however, have shown alerting effects of white or narrowband short-wavelength lights during daytime, when melatonin levels are low. While the use of light at night to promote alertness is well understood, it is important to develop an understanding of how light impacts alertness during the daytime, especially during the post-lunch hours. The aim of the current study was to investigate how 48-minute exposures to short-wavelength (blue) light (40 lux, 18.9 microWatts/cm(2) ?(max) = 470 nanometers [nm]) or long-wavelength (red) light (40 lux, 18.9 microWatts/cm(2) ?(max) = 630 nm) close to the post-lunch dip hours affect electroencephalogram measures in participants with regular sleep schedules. Power in the alpha, alpha theta, and theta ranges was significantly lower (p<0.05) after participants were exposed to red light than after they remained in darkness. Exposure to blue light reduced alpha and alpha theta power compared to darkness, but these differences did not reach statistical significance (p>0.05). The present results extend those performed during the nighttime, and demonstrate that light can be used to increase alertness in the afternoon, close to the post-lunch dip hours. These results also suggest that acute melatonin suppression is not needed to elicit an alerting effect in humans. PMID:23535242

Sahin, Levent; Figueiro, Mariana G

2013-05-27

35

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

36

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

37

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

38

Predicting Ripple Wavelength in Wave-Current Flows  

NASA Astrophysics Data System (ADS)

Empirical predictors of the wavelength of sand ripples created by waves typically express ripple wavelength normalized by the wave semi-orbital excursion ?/A as a function of a nondimensional term representing the ratio of the mobilizing force of waves to the stabilizing force of gravity: either wave orbital diameter normalized by median grain size d_o/D50, or the wave mobility number ?. For ripples formed by combinations of waves and currents, a logical extension is to substitute a length scale dwc or velocity scale uwc, representing the combined mobilizing force of the waves and currents, for do or wave orbital velocity ub in calculating the force ratios, as suggested by Khelifa and Ouellet (J. Waterway, Port, Coastal and Ocean Engr., 2000)(KO). With a formulation slightly different from KO, we calculate dwc as the maximum excursion distance during a wave period, and uwc as the maximum wave-current velocity, so that uwc reduces to ub when the current speed is zero. We test this scaling with data from two laboratory experiments investigating ripples formed by combinations of waves and currents. In one experiment, we simulated waves and curents at varying angles using an oscillating plate of sand in a 4-m wide flume. The ratio do/D ranged from 1400 to 4000, conditions corresponding to orbital and suborbital ripples in the absence of currents. In the other set of experiments (conducted by KO) a steady current crossed a wave flume, and do/D ranged from 50 to 400, corresponding to orbital ripples. For both data sets, substitution of dwc for do and uwc for ub improved agreement with published predictors of ?/A. These results suggest that, to first order, predictive relationships developed for dimensions of wave ripples apply to combined wave-current flows when scaled appropriately. For the KO orbital ripples, wavelength ? and height ? increased with current velocity, whereas in our experiments ? and ? decreased with increasing current. In both cases the effect is analogous to that of an increase in wave energy: orbital ripples grow while suborbital ripples decay with increasing wave energy, for a constant grain size.

Lacy, J. R.; Rubin, D. M.; Hanes, D. M.

2006-12-01

39

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

40

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

41

Short wavelength topography on the inner-core boundary  

PubMed Central

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

Cao, Aimin; Masson, Yder; Romanowicz, Barbara

2007-01-01

42

Zero-dispersion wavelength mapping in short single-mode optical fibers using parametric amplification  

E-print Network

-dispersion wavelength map along a short optical fiber span with a high spatial resolution. The improved resolution to long fiber spans with a good accuracy but give a spatial resolution limited to about a hundred metersZero-dispersion wavelength mapping in short single-mode optical fibers using parametric

Paris-Sud XI, Université de

43

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

44

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

45

AC-Mode Short-Wavelength IR Radiation Thermometers for Measurement of Ambient Temperatures  

NASA Astrophysics Data System (ADS)

Recent improvements in the fabrication of short-wave infrared (SW-IR) quantum detectors have opened a new era in radiation thermometry. Ambient and higher temperatures can be measured with low uncertainties using thermoelectrically (TE) cooled extended-InGaAs (E-IGA) and short-wave photovoltaic-HgCdTe (SW-MCT) detectors. Since these detectors have low cut-off wavelengths (2.5 ?m and 2.8 ?m, respectively), they do not respond past cut-off and are less sensitive to the background infrared radiation, resulting in orders of magnitude lower background noise than traditional broad-band infrared detectors such as cryogenically cooled quantum detectors or thermal detectors. At the same time, the cut-off is far enough in the infrared to obtain a large enough signal from the source of interest. Because of the low detector cut-off wavelength, traditional glass-based optics can be used in the radiation thermometers. A chopper-produced alternating-current (AC) signal was used to measure low temperatures by separating the AC signal from the background-radiation-produced direct-current (DC) signal and its fluctuations. Design considerations and characteristics of a newly developed SW-IR radiation thermometer are discussed. A noise-equivalent temperature difference (NETD) of < 3mK for a 50°C blackbody was measured. At the human body temperature of 36°C, the obtained NETD of ~10mK indicates that these detectors can be used in non-contact temperature measurements to replace thermopile- or pyroelectric-based radiation thermometers.

Eppeldauer, G. P.; Yoon, H. W.

2008-06-01

46

Special short wave finite elements for flow acoustics  

NASA Astrophysics Data System (ADS)

Short wave problems of practical interest in acoustics include the modeling of sound attenuation in the ducted regions of turbofan aircraft engines where the convective and diffractive effects of the mean flow are significant. Also, in this case the acoustic wavelength is generally much smaller than the length scale of the scattering geometry and smaller than the characteristic length scale for variations in the mean flow. The Partition of Unity Method (PUM) [J. M. Melenk and I. Babuška, Comput. Methods Appl. Mech. Eng. 139, 289-314 (1996)] is a proved efficient numerical method for solving short wave problems in the absence of flow (Helmholtz equation) [Lagrouche et al., Int. J. Numer. Methods Eng. 54, 1501-1533 (2002)]. The PUM approach is based on the use of a discrete set plane of wave as a local basis for the spatial discretization. When flow is present the wave number of each locally defined plane wave becomes dependent upon the magnitude and direction of the mean flow. The implementation of such scheme for the harmonic acoustic propagation within an irrotational mean flow is proposed in this work. One- and two-dimensional model problems are presented to demonstrate the effectiveness of the approach. [Work supported by EPSRC.

Gamallo, Pablo; Astley, Jeremy

2003-10-01

47

Resonant Properties of Short Expansion Chambers in a Circular Duct: Including Extremely Short Cases and Asymmetric Mode Wave Incidence Cases  

NASA Astrophysics Data System (ADS)

Resonant properties of short expansion chambers are studied comprehensively using a traditional analytical approach with simply refined equations. Containing enough number of radial modes in calculation, properties of chambers including the cases of extremely short ones and/or asymmetric mode waves incidence are investigated, and confirmed experimentally with the well-designed apparatus. For various dimensions of chambers and for any mode wave incidence, resonant properties are simply summarized using the resonant frequency, which is almost decisively normalized by the chamber depth and the wavelength of the plane wave for an extremely short one; and by the chamber diameter for a relatively long one with the transition length from acoustically short (resonant-type) to long (common-type): the length is also decided by the chamber diameter. As the case may be, the extremely short chamber might be applicable as a compact resonator muffler.

SADAMOTO, A.; MURAKAMI, Y.

2002-01-01

48

Extreme nonlinear optics: attosecond photonics at short wavelengths  

Microsoft Academic Search

We discuss coherent up-conversion of near-infrared femtosecond laser light into the extreme ultraviolet and soft-X-ray regions of the spectrum using the process of high-harmonic generation. We show that by using concepts from visible wavelength photonics, it is now possible to extend nonlinear optics well into the X-ray region of the spectrum. By manipulating the dynamics of the high harmonic process

Emily A. Gibson; Xiaoshi Zhang; Tenio Popmintchev; Ariel Paul; Nick Wagner; Amy Lytle; Ivan P. Christov; Margaret M. Murnane; Henry C. Kapteyn

2004-01-01

49

Short-wavelength static optical recording properties of nickel phthalocynine thin film  

Microsoft Academic Search

Nickel phthalocyanine thin film was prepared by vacuum deposition, the absorption and transmission spectra, the thermal stability of the film were reported. And the static optical recording properties of the thin film were investigated with a self-developed short-wavelength optical tester with high NA objective lens. The results show that this film occupied suitable absorption and transmission properties for short-wavelength (514.5

Yiqun Wu; Yang Wang; Donghong Gu; Fuxi Gan

2003-01-01

50

Short-Wavelength Infrared Views of Messier 81  

NASA Technical Reports Server (NTRS)

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

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

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

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

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

2003-01-01

51

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

52

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

53

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

54

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

55

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

56

High-power parametric conversion from near-infrared to short-wave infrared  

E-print Network

dispersion measurement of optical fibers with a tunable fiber laser," IEEE Photon. Technol. Lett. 18, 1825High-power parametric conversion from near-infrared to short-wave infrared Adrien Billat,1,* Steevy up to 700 mW of power at 1940 nm. The source is tunable over wavelength intervals comprised between

Dalang, Robert C.

57

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

58

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

59

Short wavelength HgCdTe staring focal plane for low background astronomy applications  

NASA Technical Reports Server (NTRS)

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

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

1989-01-01

60

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

PubMed

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

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

2014-05-01

61

Excellent optical thermometry based on short-wavelength upconversion emissions in Er3  

E-print Network

of electrical trans- former temperature in power stations, oil refineries, coal mines, and building fire under a compact and cost-effective continuous wave near infra- red diode laser excitation [2­6]. However into the high temperature range, shorter wavelength emissions should be utilized because they can effectively

Cao, Wenwu

62

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

Microsoft Academic Search

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

Kyo Inoue

1992-01-01

63

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

64

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

Microsoft Academic Search

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

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

2006-01-01

65

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.

66

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

PubMed

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

Zhai, Guofu; Jiang, Tao; Kang, Lei

2014-02-01

67

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

68

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

69

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

70

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

71

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

SciTech Connect

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

Braud, J.P.

1991-01-01

72

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

SciTech Connect

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

Braud, J.P.

1991-12-31

73

10 Gb\\/s multiple wavelength, coherent short pulse source based on spectral carving of supercontinuum generated in fibers  

Microsoft Academic Search

We demonstrate a high-power, multi-wavelength, short pulse source at 10 Gb\\/s based on spectral slicing of supercontinuum (SC) generated in short fibers. We show that short fiber SC can be used for dense wavelength division multiplexing applications because of its >7.9 dBm\\/nm power spectral density, 140 nm spectral bandwidth, and ±0.5 dB spectral uniformity over 40 mn. Pulse carving up

O. Boyraz; J. Kim; M. N. Islam; E. Coppinger; B. Jalali

2000-01-01

74

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

75

Mesopause airglow modulation by ducted short-period gravity waves  

Microsoft Academic Search

In this thesis, we examine the excitation and propagation of ducted short-period gravity waves at mesopause altitudes, and the associated wave-induced modulation of nighttime airglow emissions. A new, fully-nonlinear, two-dimensional, numerical model is developed for the simulation of atmospheric gravity waves in a realistic atmosphere, and coupled with photochemical models to allow calculations of wave-induced modulation of mesopause OH NIR

Jonathan B. Snively

2007-01-01

76

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

77

High performance bias-selectable dual-band short-/mid-wavelength infrared photodetectors based on type-II InAs/GaSb/AlSb superlattices  

NASA Astrophysics Data System (ADS)

Active and passive imaging in a single camera based on the combination of short-wavelength and mid-wavelength infrared detection is highly needed in a number of tracking and reconnaissance missions. Due to its versatility in band-gap engineering, Type-II InAs/GaSb/AlSb superlattice has emerged as a candidate highly suitable for this multi-spectral detection. In this paper, we report the demonstration of high performance bias-selectable dual-band short-/mid-wavelength infrared photodetectors based on InAs/GaSb/AlSb type-II superlattice with designed cut-off wavelengths of 2 ?m and 4 ?m. Taking advantages of the high performance short-wavelength and mid-wavelength single color photodetectors, back-to-back p-i-n-n-i-p photodiode structures were grown on GaSb substrate by molecular beam epitaxy. At 150 K, the short-wave channel exhibited a quantum efficiency of 55%, a dark current density of 1.0x10-9 A/cm2 at -50 mV bias voltage, providing an associated shot noise detectivity of 3.0x1013 Jones. The mid-wavelength channel exhibited a quantum efficiency of 33% and a dark current density of 2.6x10-5 A/cm2 at 300 mV bias voltage, resulting in a detectivity of 4.0x1011 Jones. The operations of the two absorber channels are selectable by changing the polarity of applied bias voltage.

Hoang, A. M.; Chen, G.; Haddadi, A.; Razeghi, M.

2013-01-01

78

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

79

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

E-print Network

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

Tadesse, Semere Ayalew

2014-01-01

80

MST radar observations of short-period gravity wave during overhead tropical cyclone  

NASA Astrophysics Data System (ADS)

Short-period gravity waves associated with the passage of tropical cyclone using mesosphere-stratosphere-troposphere (MST) radar located at Gadanki (13.5°N, 79.2°E) has been discussed. The observed stratospheric gravity wave is found to have a periodicity of ˜42 min, vertical and horizontal wavelength of ˜3.5 km and 14 km, respectively. Maximum amplitude of gravity wave is observed in the upper troposphere and lower stratosphere (UTLS) region due to which periodic updrafts and downdrafts are observed. This weakens the stability of tropopause, which is observed in radar signal-to-noise ratio (SNR). The enhancement of vertical momentum flux of order ˜-0.6 m2/s2 observed in the lower stratosphere is attributed to the cyclone generated gravity waves. The obstacle effect is found to be the generative mechanism for the observed gravity waves associated with the tropical cyclone.

Das, Siddarth Shankar; Uma, K. N.; Das, Subrata Kumar

2012-04-01

81

Short-Wave Infrared HgCdTe Avalanche Photodiodes  

NASA Astrophysics Data System (ADS)

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

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

2012-10-01

82

Highly efficient white-light-emitting diodes fabricated with short-wavelength yellow oxynitride phosphors  

NASA Astrophysics Data System (ADS)

We have already reported orangish yellow Ca -?-SiAlON:Eu2+ phosphors, and applied them to fabricate warm white light-emitting diodes (LEDs). In this letter, we report on greenish yellow Li-?-SiAlON:Eu2+ phosphors, and use them to create daylight when coupled to an InGaN blue LED chip (460nm ). The newly discovered Li -?-SiAlON:Eu2+ phosphors emit at shorter wavelengths of 573-577nm under the 460nm excitation, and exhibit a smaller Stokes shift than Ca -?-SiAlON:Eu2+ does. By using this short-wavelength yellow oxynitride phosphor, bright daylight emissions from white LEDs can be generated. Thus, highly efficient white LEDs with tunable white light can be fabricated with ?-SiAlON :Eu2+ phosphors, enabling them for a wider range of applications.

Xie, Rong-Jun; Hirosaki, Naoto; Mitomo, Mamoru; Takahashi, Kosei; Sakuma, Ken

2006-03-01

83

Development of an Electromagnetic Acoustic Transducer with Multi-Wavelength for Lamb Wave  

NASA Astrophysics Data System (ADS)

Lamb waves are normally utilized for inspecting thin metal sheets, and a wheel type probe with piezoelectric oscillators is used as the sensor, although it has a few serious disadvantages such as a dramatic change in sensitivity. We then studied a useful electromagnetic acoustic transducer (EMAT) without a couplant. The trial EMAT consists of a meandering coil with a narrow distance between the intervals which can generate Lamb waves of variable wavelengths corresponding to the frequency range from approximately 150 kHz to 4.0 MHz. This transducer, for example, can select Lamb waves with optimum wavelengths on the factory line that produces thin sheets with variable thicknesses. The described EMAT can be used to inspect steel sheets of different thicknesses. It is also shown that the S0-mode Lamb wave with the longer wavelength is the most effective for a thick sheet (up to 6 mm).

Murayama, Riichi; Mizutani, Koichi

2002-05-01

84

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

85

Short-wavelength Fluctuations of the Specific Heat in a Superconducting Thick Film  

NASA Astrophysics Data System (ADS)

A theoretical study of short-wavelength fluctuation effects on the specific heat above is reported for superconducting thick films with the arbitrary conduction dimensionality between two and three dimensions (2D and 3D). In the present calculations, momentum cutoff effects in the fluctuation spectrum are taken into consideration in the context of the Aslamazov-Larkin theory. Our result covers the 2D or 3D formula presented previously in each limit, and shows a temperature dependent dimensionality between 2D and 3D. Effects of a total-energy cutoff and experimental situations are briefly discussed.

Yamaki, T.; Mori, N.; Kasahara, M.; Cotón, N.; Ramallo, M. V.

86

Comparatively Large Second-Order Hyperpolarizability of Aromatic Sulfonate Anion with Short Cutoff Wavelength  

NASA Astrophysics Data System (ADS)

The second-order hyperpolarizabilities (?) of ionic species of sodium p-toluenesulfonate ( pTSNa) and its corresponding neutral derivative methyl p-toluenesulfonate ( p TSMe) in methanol were evaluated to be 2.2×10-29 and 1.2×10-29 esu, respectively, using the hyper Rayleigh scattering method at 1064 nm. Since ionic p TSNa has short cutoff wavelength of 280 nm as well as comparatively large |?| value, i.e., about twice that of neutral p TSMe and about two-thirds that of p-nitroaniline, aromatic sulfonate ions are concluded to be worth investigating as potential chromophores for second-order nonlinear optics.

Duan, Xuan-Ming; Okada, Shuji; Oikawa, Hidetoshi; Matsuda, Hiro; Nakanishi, Hachiro

1994-11-01

87

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

PubMed Central

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

2014-01-01

88

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

PubMed Central

Circadian phase resetting is sensitive to visual short wavelengths (450–480?nm). Selectively filtering this range of wavelengths may reduce circadian misalignment and sleep impairment during irregular light-dark schedules associated with shiftwork. We examined the effects of filtering short wavelengths (<480?nm) during night shifts on sleep and performance in nine nurses (five females and four males; mean age?±?SD: 31.3?±?4.6 yrs). Participants were randomized to receive filtered light (intervention) or standard indoor light (baseline) on night shifts. Nighttime sleep after two night shifts and daytime sleep in between two night shifts was assessed by polysomnography (PSG). In addition, salivary melatonin levels and alertness were assessed every 2?h on the first night shift of each study period and on the middle night of a run of three night shifts in each study period. Sleep and performance under baseline and intervention conditions were compared with daytime performance on the seventh day shift, and nighttime sleep following the seventh daytime shift (comparator). On the baseline night PSG, total sleep time (TST) (p?short wavelengths may be an approach to reduce sleep disruption and improve performance in rotating-shift workers. (Author correspondence: casper@lunenfeld.ca) PMID:23834705

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

2013-01-01

89

Point defects and short-wavelength luminescence of LiB3O5 single crystals  

NASA Astrophysics Data System (ADS)

The results of the study both on short-wavelength luminescence and point defects in the large LiB3O5 crystals grown by the advanced technique are reported. It was revealed that corpuscular or photon radiation with energy exceeding Eg efficiently excites the complex broad luminescence band at 290 nm. Decay kinetics involves a principal fast component with lifetime of 4 ns and several components of millisecond range. On irradiation at 77 K, LiB3O5 crystals yield the new ESR-signals, resulted from the B2+ electron and O- hole trapped centers which are stable at temperatures below RT. The obtained data suggest that these centers are responsible for the radiation-induced optical absorption band at 306 nm. We also investigated accumulation and thermal annealing of the point defects. The most acceptable models of defects, recombination processes with defects participation and the origin of the LiB3O5 short-wavelength luminescence are discussed.

Ogorodnikov, I. N.; Kuznetsov, A. Yu; Kruzhalov, A. V.; Maslov, V. A.

90

Genetic responses of the thermophilic archaeon Sulfolobus acidocaldarius to short-wavelength UV light.  

PubMed Central

The archaea which populate geothermal environments are adapted to conditions that should greatly destabilize the primary structure of DNA, yet the basic biological aspects of DNA damage and repair remain unexplored for this group of prokaryotes. We used auxotrophic mutants of the extremely thermoacidophilic archaeon Sulfolobus acidocaldarius to assess genetic and physiological effects of a well-characterized DNA-damaging agent, short-wavelength UV light. Simple genetic assays enabled quantitative dose-response relationships to be determined and correlated for survival, phenotypic reversion, and the formation of genetic recombinants. Dose-response relationships were also determined for survival and phenotypic reversion of the corresponding Escherichia coli auxotrophs with the same equipment and procedures. The results showed S. acidocaldarius to be about twice as UV sensitive as E. coli and to be equally UV mutable on a surviving-cell basis. Furthermore, UV irradiation significantly increased the frequency of recombinants recovered from genetic-exchange assays of S. acidocaldarius. The observed UV effects were due to the short-wavelength (i.e., UV-C) portion of the spectrum and were effectively reversed by subsequent illumination of S. acidocaldarius cells with visible light (photoreactivation). Thus, the observed responses are probably initiated by the formation of pyrimidine dimers in the S. acidocaldarius chromosome. To our knowledge, these results provide the first evidence of error-prone DNA repair and genetic recombination induced by DNA damage in an archaeon from geothermal habitats. PMID:9294423

Wood, E R; Ghané, F; Grogan, D W

1997-01-01

91

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

92

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

NASA Astrophysics Data System (ADS)

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

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

1999-01-01

93

Simulations and experiments of short intense envelope solitons of surface water waves  

NASA Astrophysics Data System (ADS)

The problem of existence of stable nonlinear groups of gravity waves in deep water is considered by means of laboratory and numerical simulations with the focus on strongly nonlinear waves. Wave groups with steepness up to Acr?m2/g ? 0.30 are reproduced in laboratory experiments (Acr is the wave crest amplitude, ?m is the mean angular frequency, and g is the gravity acceleration). We show that the groups remain stable and exhibit neither noticeable radiation nor structural transformation for more than 60 wavelengths or about 15-30 group lengths. These solitary wave patterns differ from the conventional envelope solitons, as only a few individual waves are contained in the group. Very good agreement is obtained between the laboratory results and numerical simulations of the potential Euler equations. The envelope soliton solution of the nonlinear Schrödinger equation is shown to be a reasonable first approximation for specifying the wave-maker driving signal. The short intense envelope solitons possess vertical asymmetry similar to regular Stokes waves with the same frequency and crest amplitude. Nonlinearity is found to have remarkably stronger effect on the speed of envelope solitons in comparison to the nonlinear correction to the Stokes wave velocity.

Slunyaev, A.; Clauss, G. F.; Klein, M.; Onorato, M.

2013-06-01

94

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

95

Destabilization of long-wavelength Love and Stoneley waves in slow sliding  

E-print Network

Love waves are dispersive interfacial waves that are a mode of response for anti-plane motions of an elastic layer bonded to an elastic half-space. Similarly, Stoneley waves are interfacial waves in bonded contact of dissimilar elastic half-spaces, when the displacements are in the plane of the solids. It is shown that in slow sliding, long wavelength Love and Stoneley waves are destabilized by friction. Friction is assumed to have a positive instantaneous logarithmic dependence on slip rate and a logarithmic rate weakening behavior at steady-state. Long wavelength instabilities occur generically in sliding with rate- and state-dependent friction, even when an interfacial wave does not exist. For slip at low rates, such instabilities are quasi-static in nature, i.e., the phase velocity is negligibly small in comparison to a shear wave speed. The existence of an interfacial wave in bonded contact permits an instability to propagate with a speed of the order of a shear wave speed even in slow sliding, indicating that the quasi-static approximation is not a valid one in such problems.

K. Ranjith

2009-03-04

96

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

97

Depletion of short-wavelength radiation under intracavity nonlinear frequency conversion in a dual-wavelength vertical external cavity surface-emitting laser  

NASA Astrophysics Data System (ADS)

Steady-state operational characteristics of a dual-wavelength vertical external cavity surface-emitting laser (VECSEL) with a nonlinear quasi-phase-matched crystal placed in the laser cavity have been simulated. We have demonstrated the dramatic effect of three-wave nonlinear optical interaction on the intensity of both fundamental optical fields of the laser. Potential capability of the dual-wavelength VECSEL for efficient generation of midor far-infrared radiation by means of the intracavity nonlinear frequency down-conversion has been shown.

Morozov, Yuri A.; Morozov, Mikhail Y.

2013-02-01

98

Continuous-wave multi-wavelength diode-pumped Yb:GYSO laser  

NASA Astrophysics Data System (ADS)

We report on tunable simultaneous continuous-wave multi-wavelength Yb:GYSO lasers in a stable three-folded resonator with an intra-cavity prism for the first time to our knowledge. A fused silica dispersive prism used in a three-mirror cavity at an angle intentionally deviating from the Brewster angle has been shown to be effective in controlling the losses of different transitions in the cavity, providing multi-wavelength emissions, leading to a stable multi-wavelength oscillation over a long timescale. The multi-wavelength oscillation can be easily controlled by adjusting the output coupler, allowing flexible selectivity of the different wavelengths and full controllability of the multi-wavelength lasing. Under different cavity alignments, dual-, three-and four-wavelength lasers were successfully realized around 1041-1043, 1048-1052, 1056-1063 and 1080-1089 nm, indicating that all the multi-wavelength laser emissions originated from the resonance transitions from a shared excited level to different terminal sub-levels.

Li, Wenxue; Hao, Qiang; Ding, Jingxin; Zeng, Heping

2008-09-01

99

Theoretical characterization of c-axis paraconductivity in short-wavelength fluctuation region  

NASA Astrophysics Data System (ADS)

Effects of short-wavelength cutoffs on the c-axis (out-of-plane) fluctuation conductivity ?c? in a layered superconductor are studied for Aslamazov-Larkin (AL), Maki-Thompson (MT) and density of states (DOS) terms. A theoretical equation for ?c? in each term is derived under two types of the cutoff conditions: a momentum cutoff (MC) and a total-energy cutoff (EC) in the fluctuation spectrum. The MC effect provides appreciable contributions to ?c? of the MT and DOS terms as in the case of the AL term. On the other hand, the EC effect plays no explicit role in ?c? as far as anomalous and regular MT terms are concerned. Difference between MC and EC effects is numerically presented and our results are compared to experiments on ?c?.

Yonezawa, T.; Imanari, K.; Mori, N.

2008-09-01

100

Superconducting fluctuations of the specific heat in the short wavelength fluctuation regime  

NASA Astrophysics Data System (ADS)

Effects of the short wavelength fluctuations on the specific heat ?C in a superconductor are studied within the scheme of the Aslamazov-Larkin (AL) theory. By imposing the momentum cutoff in the fluctuation spectrum, formulae for ?C are derived in a layered system as well as in n-dimensional (nD) systems (n=1, 2 and 3). Formulae under a total-energy cutoff condition are also presented. It is found that ?C is significantly suppressed at high-reduced temperatures in a similar manner as in the paraconductivity. Our formulae in 3D and layered systems may be better fitted to experiments on YBa2Cu3O7-? crystals in a wider temperature region than the standard AL formulae without any cutoff effect.

Mori, N.; Enomoto, H.; Takano, Y.; Cotón, N.; Ramallo, M. V.

101

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

102

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

E-print Network

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

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

2002-01-30

103

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

104

Wavelength reuse in the WDM optical interface of a millimeter-wave fiber-wireless antenna base station  

Microsoft Academic Search

A novel technique for wavelength reuse has been proposed to simplify the upstream optical interface of an antenna base station in a millimeter-wave fiber-wireless system incorporating wavelength division multiplexing. This technique is based on recovering the optical carrier used in downstream signal transmission and reusing the same wavelength for upstream signal transmission. Two novel configurations for optical carrier recovery and

Ampalavanapillai Nirmalathas; Dalma Novak; Christina Lim; Rodney B. Waterhouse

2001-01-01

105

Traveling waves of the regularized short pulse equation  

NASA Astrophysics Data System (ADS)

The properties of the so-called regularized short pulse equation (RSPE) are explored with a particular focus on the traveling wave solutions of this model. We theoretically analyze and numerically evolve two sets of such solutions. First, using a fixed point iteration scheme, we numerically integrate the equation to find solitary waves. It is found that these solutions are well approximated by a finite sum of hyperbolic secants powers. The dependence of the soliton's parameters (height, width, etc) to the parameters of the equation is also investigated. Second, by developing a multiple scale reduction of the RSPE to the nonlinear Schrödinger equation, we are able to construct (both standing and traveling) envelope wave breather type solutions of the former, based on the solitary wave structures of the latter. Both the regular and the breathing traveling wave solutions identified are found to be robust and should thus be amenable to observations in the form of few optical cycle pulses.

Shen, Y.; Horikis, T. P.; Kevrekidis, P. G.; Frantzeskakis, D. J.

2014-08-01

106

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

107

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

NASA Astrophysics Data System (ADS)

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

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

2007-04-01

108

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

109

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

110

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

111

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

112

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

113

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

114

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

115

Broadband tuning of continuous wave quantum cascade lasers in long wavelength (> 10 ?m) range.  

PubMed

Broadband spectral tuning in the long wavelength range (greater than 10 ?m) was demonstrated with an external-cavity quantum cascade laser. The tunable wavelength of the laser ranged from 9.5 to 11.4 ?m (176 cm(-1); corresponding to 18% of the center wavelength) in continuous wave (cw) operation at room temperature, without any anti-reflection coating. The gain chip based on the anti-crossed dual-upper-state (DAU) design provided a cw lasing up to 300 K, with a low threshold current density of 2.1 kA/cm2. The highly stable broadband spectral tuning and high laser performance were enabled by the spectrally homogeneous gain profile of the anti-crossed DAU active region. PMID:25321203

Dougakiuchi, Tatsuo; Fujita, Kazuue; Sugiyama, Atsushi; Ito, Akio; Akikusa, Naota; Edamura, Tadataka

2014-08-25

116

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

117

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

NASA Astrophysics Data System (ADS)

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

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

2011-06-01

118

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

119

A Two-Wavelength Interferometric Measurement of the Reflection Process in an Ionizing Shock Wave  

Microsoft Academic Search

Electron and atom number densities of partially ionized krypton behind the reflected shock waves were measured by using a two-wavelength Mach-Zehnder interferometer. Measurements were carried out for flows with an initial pressure p1{=}1.5 Torr and incident shock Mach numbers Ms˜12. Electron and atom number densities in equilibrium were measured to be (2.00± 0.09)× 1017 cm-3 and (9.5± 0.7)× 1017 cm-3

Masahiko Kawamura; Hiromichi Ezumi; Noriaki Gohda

1981-01-01

120

Short wavelength (4 ?m) quantum cascade detector based on strain compensated InGaAs/InAlAs  

NASA Astrophysics Data System (ADS)

We report on a quantum cascade detector based on nearly strain compensated InGaAs /InAlAs pseudomorphically grown on InP substrate and detecting light at short wavelengths around 4?m. The background limited infrared performance (BLIP) condition is met at a temperature of 108K with a high detectivity of DBLIP*=1.2×1011Jones.

Giorgetta, F. R.; Baumann, E.; Théron, R.; Pellaton, M. L.; Hofstetter, D.; Fischer, M.; Faist, J.

2008-03-01

121

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

PubMed

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

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

2014-11-01

122

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

NASA Astrophysics Data System (ADS)

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

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

2009-02-01

123

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

124

Short-Wavelength Light Sensitivity of Circadian, Pupillary, and Visual Awareness in Humans Lacking an Outer Retina  

PubMed Central

Summary As the ear has dual functions for audition and balance, the eye has a dual role in detecting light for a wide range of behavioral and physiological functions separate from sight [1–11]. These responses are driven primarily by stimulation of photosensitive retinal ganglion cells (pRGCs) that are most sensitive to short-wavelength (?480 nm) blue light and remain functional in the absence of rods and cones [8–10]. We examined the spectral sensitivity of non-image-forming responses in two profoundly blind subjects lacking functional rods and cones (one male, 56 yr old; one female, 87 yr old). In the male subject, we found that short-wavelength light preferentially suppressed melatonin, reset the circadian pacemaker, and directly enhanced alertness compared to 555 nm exposure, which is the peak sensitivity of the photopic visual system. In an action spectrum for pupillary constriction, the female subject exhibited a peak spectral sensitivity (?max) of 480 nm, matching that of the pRGCs but not that of the rods and cones. This subject was also able to correctly report a threshold short-wavelength stimulus (?480 nm) but not other wavelengths. Collectively these data show that pRGCs contribute to both circadian physiology and rudimentary visual awareness in humans and challenge the assumption that rod- and cone-based photoreception mediate all “visual” responses to light. PMID:18082405

Zaidi, Farhan H.; Hull, Joseph T.; Peirson, Stuart N.; Wulff, Katharina; Aeschbach, Daniel; Gooley, Joshua J.; Brainard, George C.; Gregory-Evans, Kevin; Rizzo, Joseph F.; Czeisler, Charles A.; Foster, Russell G.; Moseley, Merrick J.; Lockley, Steven W.

2007-01-01

125

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

126

SPITFIRE multi-band short-wave and mid-wave polarimetric camera  

Microsoft Academic Search

Polarimetric sensors are valued for their capability to distinguish man-made objects from surrounding clutter. The SPITFIRE (Spectral Polarimetric Imaging Test Field InstRumEnt) polarimetric camera is designed to function in multiple bands in the Short Wave Infrared (SWIR) and Mid-Wave Infrared (MWIR) regions. SPITFIRE is a Stokes micro-grid polarimetric system with a 4 band spectral filter wheel. The focal plane array

Hiren J. Patel; Robert T. Mack; Daniel A. Lemaster; James S. Harris; David Forrai; Jan M. Servaites

2010-01-01

127

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

E-print Network

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

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

2014-01-01

128

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

Microsoft Academic Search

In this work, the efficiency of laser generation of surface acoustic waves (SAWs) in ceramic materials is reported to be wavelength dependent. A pulsed Nd:YAG laser operating at wavelengths of 1064 or 532 nm was used to generate SAWs on ceramic (silicon nitride and silicon carbide) and metal substrates. It was observed that 1064 nm radiation is more efficient than

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

1997-01-01

129

Wavelength of ionization waves and the electron energy losses in the d. c. discharge in rare gases  

Microsoft Academic Search

Changes in the wavelength expressed by the wave potential (the product of wavelength and the longitudinal electric field intensity) are investigated in the dependence on (similarity) parameters of the neon and argon d.c. discharge. The measured dependences show the influence of different state of the electron gas, which behaves hydrodynamically or kinetically (with spatial resonances) in dependence on the type

J. Krasa; V. Pe?ina; L. Pekarek

1977-01-01

130

MODIS correction algorithm for out-of-band response in the short-wave IR bands  

NASA Astrophysics Data System (ADS)

The MODerate Resolution Imaging Spectroradiometer (MODIS) has 36 spectral bands with wavelengths from 0.41 to 14.5 micrometers. The 36 spectral bands, with a total of 490 detectors, are distributed on four focal plane assemblies (FPAs): visible (VIS), near infrared (NIR), short- mid-wave infrared (SMIR), and long wave infrared (LWIR). Nearly identical copies of the MODIS are currently operating onboard the NASA EOS Terra (launched on December 18,1999) and Aqua spacecraft (launched on May 4, 2002). Prelaunch and on-orbit characterizations of both Terra and Aqua MODIS have shown small but non-negligible out-of-band (OOB) response in the sensor's short-wave infrared bands (SWIR): bands 5-7, and band 26. To minimize the impact due to OOB response on the MODIS SWIR bands calibration and the Earth scene product retrieval, an algorithm has been developed and implemented in the Level 1B (L1B) software for both Terra and Aqua MODIS. In this paper, we describe the algorithm and its applications to the MODIS L1B calibration algorithms. We illustrate how the correction coefficients are derived from on-orbit observations and discuss the test procedures involved before the final implementation in the L1B code. Performance is evaluated for both Terra and Aqua MODIS and the two results are compared.

Xiong, Xiaoxiong; Chiang, Kwo-Fu; Adimi, Farida; Li, Weiwei; Yatagai, Hiroshi; Barnes, William L.

2004-02-01

131

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

132

Short Wavelength 128 By 128 Focal Plane Arrays For Remote Sensing Applications  

NASA Astrophysics Data System (ADS)

Short wavelength (1-2.5 ?m) 128 by 128 focal plane arrays have been fabricated and demonstrated with high pixel yields and dark current limited performance. Smaller arrays (32 by 32 and 64 by 64) have already been used successfully in the Airborne Imaging Spectrometer (AIS) instrument in the United States, Australia, and Western Europe. Ground-track swath width is enhanced by the development of 128 by 128 arrays. The long-term goal is to develop a 150 by 1000 mosaicked focal plane for use in the High Resolution Imaging Spectrometer (HIRIS) instrument, a facility instrument on the Earth Observing System (Eos). This instrument will map the earth with from 5 to 10 nm spectral resolution and 30 m spatial resolution for flux levels of 1010 to 1012 ph/cm2-s with An f/3.8 optical system. The detector material is HgCdTe grown by liquid phase epitaxy on a sapphire substrate which yields high-performance uniform detectors. The detectors are ion implanted photodiodes with ZnS passivation. They are mated to a silicon multiplexer through indium columns to fabricate the hybrid. Operational pixel yields of greater than 99 percent have been obtained. Reliability tests on 128 by 128 hybrids show that the device is mechanically durable to more than 50 thermal cycles. The detector arrays have been characterized at temperatures of 80-150 K. Mean RoA values of 4 x 106 ohms-cm2 and leakage currents below 5 x 10-13 A have been measured at 150 K. The peak quantum efficiency at 2.4 ?m is 80 percent. These results indicate that the detectors have sufficient performance for dark current limited operation at low scene albedos. The multiplexer is an EG&G Reticon FET switch imager with two output amplifiers. It is a standard visible imager that has been modified for indium column growth and detector substrate bias control. The internal circuitry has not been changed. The charge is integrated in the detector capacitance under reverse bias and then transferred through common video lines into odd and even bucket brigades and clocked out through the output amplifiers. The read noise of the multiplexer is 950 electrons, and the maximum readout rate is 10 MHz. The maximum charge storage capacity is 5 x 106 electrons.

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

1989-01-01

133

Demonstration of high performance bias-selectable dual-band short-/mid-wavelength infrared photodetectors based on type-II InAs/GaSb/AlSb superlattices  

NASA Astrophysics Data System (ADS)

High performance bias-selectable dual-band short-/mid-wavelength infrared photodetector based on InAs/GaSb/AlSb type-II superlattice with designed cut-off wavelengths of 2 ?m and 4 ?m was demonstrated. At 150 K, the short-wave channel exhibited a quantum efficiency of 55%, a dark current density of 1.0 × 10-9 A/cm2 at -50 mV bias voltage, providing an associated shot noise detectivity of 3.0 × 1013 Jones. The mid-wavelength channel exhibited a quantum efficiency of 33% and a dark current density of 2.6 × 10-5 A/cm2 at 300 mV bias voltage, resulting in a detectivity of 4.0 × 1011 Jones. The spectral cross-talk between the two channels was also discussed for further optimization.

Hoang, A. M.; Chen, G.; Haddadi, A.; Razeghi, M.

2013-01-01

134

A Two-Wavelength Interferometric Measurement of the Reflection Process in an Ionizing Shock Wave  

NASA Astrophysics Data System (ADS)

Electron and atom number densities of partially ionized krypton behind the reflected shock waves were measured by using a two-wavelength Mach-Zehnder interferometer. Measurements were carried out for flows with an initial pressure p1{=}1.5 Torr and incident shock Mach numbers Ms˜12. Electron and atom number densities in equilibrium were measured to be (2.00± 0.09)× 1017 cm-3 and (9.5± 0.7)× 1017 cm-3 respectively. These values are in good agreement with those given by theory.

Kawamura, Masahiko; Ezumi, Hiromichi; Gohda, Noriaki

1981-05-01

135

K+ waves in brain cortex visualized using a long-wavelength K+-sensing fluorescent indicator.  

PubMed

We synthesized a water-soluble, long-wavelength K(+) sensor, TAC-Red, consisting of triazacryptand coupled to 3,6-bis(dimethylamino)xanthylium, whose fluorescence increased 14-fold at 0-50 mM K(+) with K(+)-to-Na(+) selectivity >30. We visualized K(+) waves in TAC-Red-stained brain cortex in mice during spreading depression, with velocity 4.4 +/- 0.5 mm/min, and K(+) release and reuptake half-times (t(1/2)) of 12 +/- 2 and 32 +/- 4 s, respectively. Aquaporin-4 (AQP4) deletion slowed K(+) reuptake about twofold, suggesting AQP4-dependent K(+) uptake by astroglia. PMID:16278651

Padmawar, Prashant; Yao, Xiaoming; Bloch, Orin; Manley, Geoffrey T; Verkman, A S

2005-11-01

136

Classification of 2.4-45.2 Micron Spectra from the Infrared Space Observatory Short Wavelength Spectrometer  

Microsoft Academic Search

The Infrared Space Observatory observed over 900 objects with the Short Wavelength Spectrometer in full-grating scan mode (2.4-45.2 mum). We have developed a comprehensive system of spectral classification using these data. Sources are assigned to groups based on the overall shape of the spectral energy distribution (SED). The groups include naked stars, dusty stars, warm dust shells, cool dust shells,

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

2002-01-01

137

A novel scheme for DWDM optical millimeter-wave generation and wavelength reuse for uplink connection  

NASA Astrophysics Data System (ADS)

We proposed and demonstrated a novel full-duplex radio-over-fiber system using an optical phase modulator and optical interleaver to generate DWDM optical millimetre wave for carrying downstream data and wavelength reuse for uplink connection. Since the optical phase modulator we used has not a dc-bias controller, and the optical interleaver is not as sensitive to temperature as a fiber Bragg grating, the stability of the generated DWDM optical millimeter wave is largely improved, and the optical power is effectively utilized because the remaining optical carriers with high power have been reused. Moreover, the limitation of chromatic dispersion is greatly reduced due to avoiding the generation of higher order sidebands via driving the phase modulator with optimized RF signal. So this system shows cost-efficient configuration and good performance over long-distance delivery.

Hu, Liliang; Huang, Cheng; Chen, Lin; Wen, Shuangchun

2007-11-01

138

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

139

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

140

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

PubMed

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

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

2014-05-01

141

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

142

Group III nitride semiconductors for short wavelength light-emitting devices  

NASA Astrophysics Data System (ADS)

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

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

1998-01-01

143

Nanorose and lipid detection in atherosclerotic plaque using dual-wavelength photothermal wave imaging  

NASA Astrophysics Data System (ADS)

Atherosclerosis and specifically rupture of vulnerable plaques account for 23% of all deaths worldwide, far surpassing both infectious diseases and cancer. In atherosclerosis, macrophages can infiltrate plaques which are often associated with lipid deposits. Photothermal wave imaging is based on the periodic thermal modulation of a sample using intensity modulated light. Intensity modulated light enters the sample and is absorbed by targeted chromophores and generates a periodic thermal modulation. We report use of photothermal wave imaging to visualize nanoroses (taken up by macrophages via endocytosis) and lipids in atherosclerotic plaques. Two excitation wavelengths were selected to image nanoroses (800 nm) and lipids (1210 nm). Atherosclerotic plaque in a rabbit abdominal artery was irradiated (800 nm and 1210 nm separately) at a frequency of 4 Hz to generate photothermal waves. The radiometric temperature at the tissue surface was recorded by an infrared (IR) camera over a 10 second time period at the frame rate of 25.6 Hz. Extraction of images (256 × 256 pixels) at various frequencies was performed by Fourier transform at each pixel. Frequency amplitude images were obtained corresponding to 800 nm and 1210 nm laser irradiation. Computed images suggest that the distributions of both nanorose and lipid can be identified in amplitude images at a frequency of 4 Hz. Nanoroses taken up by macrophages are distributed at the edges of lipid deposits. Observation of high concentration of nanoroses in atherosclerotic plaque confirms that nanoroses are present at locations associated with lipid deposits.

Wang, Tianyi; Qiu, Jinze; Ma, Li Leo; Li, Xiankai; Sun, Jingjing; Ryoo, Seungyup; Johnston, Keith P.; Feldman, Marc D.; Milner, Thomas E.

2010-02-01

144

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

145

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

146

Short-wavelength soft-x-ray laser pumped in double-pulse single-beam non-normal incidence  

SciTech Connect

We demonstrated a 7.36 nm Ni-like samarium soft-x-ray laser, pumped by 36 J of a neodymium:glass chirped-pulse amplification laser. Double-pulse single-beam non-normal-incidence pumping was applied for efficient soft-x-ray laser generation. In this case, the applied technique included a single-optic focusing geometry for large beam diameters, a single-pass grating compressor, traveling-wave tuning capability, and an optimized high-energy laser double pulse. This scheme has the potential for even shorter-wavelength soft-x-ray laser pumping.

Zimmer, D. [LASERIX-CLUPS, LPGP UMR 8578, Universite Paris-Sud 11, F-91405 Orsay (France); GSI Helmholtzzentrum fuer Schwerionenforschung GmbH, D-64291 Darmstadt (Germany); Institut fuer Physik, Johannes Gutenberg-Universitaet Mainz, D-55099 Mainz (Germany); Ros, D.; Guilbaud, O.; Habib, J.; Kazamias, S. [LASERIX-CLUPS, LPGP UMR 8578, Universite Paris-Sud 11, F-91405 Orsay (France); Zielbauer, B. [LASERIX-CLUPS, LPGP UMR 8578, Universite Paris-Sud 11, F-91405 Orsay (France); GSI Helmholtzzentrum fuer Schwerionenforschung GmbH, D-64291 Darmstadt (Germany); Helmholtz Institut Jena, Friedrich-Schiller Universitaet, D-07743 Jena (Germany); Bagnoud, V. [GSI Helmholtzzentrum fuer Schwerionenforschung GmbH, D-64291 Darmstadt (Germany); Helmholtz Institut Jena, Friedrich-Schiller Universitaet, D-07743 Jena (Germany); Ecker, B.; Aurand, B.; Kuehl, T. [GSI Helmholtzzentrum fuer Schwerionenforschung GmbH, D-64291 Darmstadt (Germany); Institut fuer Physik, Johannes Gutenberg-Universitaet Mainz, D-55099 Mainz (Germany); Helmholtz Institut Jena, Friedrich-Schiller Universitaet, D-07743 Jena (Germany); Hochhaus, D. C.; Neumayer, P. [GSI Helmholtzzentrum fuer Schwerionenforschung GmbH, D-64291 Darmstadt (Germany); ExtreMe Matter Institute EMMI, GSI Helmholtzzentrum fuer Schwerionenforschung, D-64291 Darmstadt (Germany); Institut fuer Angewandte Physik, Goethe-Universitaet Frankfurt am Main, D-60438 Frankfurt am Main (Germany)

2010-07-15

147

Field-trial evaluation of the Q-factor penalty introduced by fiber four-wave mixing wavelength converters  

Microsoft Academic Search

The performance of tunable all-optical wavelength converters based on four-wave mixing in optical fibers is experimentally tested in a field-trial network. Two converters were built with two different fibers. The first one was made with a small variation in the zero-dispersion wavelength (ZDW) dispersion shifted fiber and the second one with a highly nonlinear fiber that presents great ZDW variations.

J. D. Marconi; F. A. Callegari; M. L. F. Abbade; H. L. Fragnito

2009-01-01

148

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

149

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

150

Cosmic-Ray Acceleration at Ultrarelativistic Shock Waves: Effects of Downstream Short-Wave Turbulence  

E-print Network

The present paper is the last of a series studying the first-order Fermi acceleration processes at relativistic shock waves with the method of Monte Carlo simulations applied to shocks propagating in realistically modeled turbulent magnetic fields. The model of the background magnetic field structure of Niemiec & Ostrowski (2004, 2006) has been augmented here by a large-amplitude short-wave downstream component, imitating that generated by plasma instabilities at the shock front. Following Niemiec & Ostrowski (2006), we have considered ultrarelativistic shocks with the mean magnetic field oriented both oblique and parallel to the shock normal. For both cases simulations have been performed for different choices of magnetic field perturbations, represented by various wave power spectra within a wide wavevector range. The results show that the introduction of the short-wave component downstream of the shock is not sufficient to produce power-law particle spectra with the "universal" spectral index 4.2. On the contrary, concave spectra with cutoffs are preferentially formed, the curvature and cutoff energy being dependent on the properties of turbulence. Our results suggest that the electromagnetic emission observed from astrophysical sites with relativistic jets, e.g. AGN and GRBs, is likely generated by particles accelerated in processes other than the widely invoked first-order Fermi mechanism.

Jacek Niemiec; Michal Ostrowski; Martin Pohl

2006-03-14

151

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

NASA Astrophysics Data System (ADS)

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

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

1997-12-01

152

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

E-print Network

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

153

Model Tests With a Single-Point Mooring System In ShortCrested Waves  

Microsoft Academic Search

Laboratory experiments with a deep-water singlepoint moored tanker model in irregular waves are reported. A rigid mooring arm is used. Wave induced forces and motions in both long-crested and short-crested sea are investigated. Short-crested waves are usually believed to decrease the wave loadings. In many cases this is not necessarily the case. The aim of the present paper is to

Morten Hulie; C. T. Stansberg; Per Werenskiold

1983-01-01

154

High speed short wave infrared (SWIR) imaging and range gating cameras  

NASA Astrophysics Data System (ADS)

Imaging in the Short Wave Infrared (SWIR) provides unique surveillance capabilities, both with passive illumination from the night glow in the atmosphere or with active illumination from covert LED or eye-safe lasers. Spectral effects specific to the 0.9 to 1.7 um wavelength range reveal camouflage and chemical signatures of ordinance. The longer wavelength range also improves image resolution over visible cameras in foggy or dusty environments. Increased military interest in cameras that image all laser range finders and target designators on the battlefield has driven development of a new class of uncooled InGaAs cameras with higher resolution and larger field of view than previously available. Current and upcoming needs include: imaging in all lighting conditions, from direct sunlight to partial starlight while using minimal power; range gating the camera to image through obscurants or beyond unimportant objects; and high speed capture of muzzle flare, projectile tracking, guide star and communications laser-beam tracking and wavefront correction. This paper will present images from new COTS cameras now available to address these needs and discuss the technology roadmap for further improvements.

Malchow, Douglas; Battaglia, Jesse; Brubaker, Robert; Ettenberg, Martin

2007-04-01

155

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

156

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

NASA Astrophysics Data System (ADS)

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

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

2014-10-01

157

Plasmon-mediated synthesis of silver cubes with unusual twinning structures using short wavelength excitation.  

PubMed

The plasmon-mediated synthesis of silver nanoparticles is a versatile synthetic method which leverages the localized surface plasmon resonance (LSPR) of nanoscale silver to generate particles with non-spherical shapes and control over dimensions. Herein, a method is reported for controlling the twinning structure of silver nanoparticles, and consequently their shape, via the plasmon-mediated synthesis, solely by varying the excitation wavelength between 400, 450, and 500 nm, which modulates the rate of Ag? reduction. Shorter, higher energy excitation wavelengths lead to faster rates of reaction, which in turn yield structures containing a greater number of twin boundaries. With this method, silver cubes can be synthesized using 450 nm excitation, which represents the first time this shape has been realized by a plasmon-mediated synthetic approach. In addition, these cubes contain an unusual twinning structure composed of two intersecting twin boundaries or multiple parallel twin boundaries. With respect to their twinning structure, these cubes fall between planar-twinned and multiply twinned nanoparticles, which are synthesized using 500 and 400 nm excitation, respectively. PMID:23292747

Personick, Michelle L; Langille, Mark R; Zhang, Jian; Wu, Jinsong; Li, Shuyou; Mirkin, Chad A

2013-06-10

158

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

NASA Technical Reports Server (NTRS)

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

Walsh, E. J.

1979-01-01

159

AlGaN-based laser diodes for the short-wavelength ultraviolet region  

NASA Astrophysics Data System (ADS)

We have demonstrated the room-temperature operation of GaN/AlGaN and indium-free AlGaN multiple-quantum-well (MQW) laser diodes under the pulsed-current mode. We have successfully grown low-dislocation-density AlGaN films with AlN mole fractions of 20 and 30% on sapphire substrates using the hetero-facet-controlled epitaxial lateral overgrowth (hetero-FACELO) method. GaN/AlGaN and AlGaN MQW laser diodes have been fabricated on the low-dislocation-density Al0.2Ga0.8N and Al0.3Ga0.7N films, respectively. The GaN/AlGaN MQW laser diodes lased at a peak wavelength ranging between 359.6 and 354.4 nm. A threshold current density of 8 kA cm-2, an output power as high as 80 mW and a differential external quantum efficiency (DEQE) of 17.4% have been achieved. The AlGaN MQW laser diodes lased at a peak wavelength down to 336.0 nm far beyond the GaN band gap. For the GaN/AlGaN MQW laser diodes, the modal gain coefficient and the optical internal loss are estimated to be 4.7±0.6 cm kA-1 and 10.6±2.7 cm-1, respectively. We have observed that the characteristic temperature T0 ranges from 132 to 89 K and DEQE shows an almost stable tendency with increase of temperature. A temperature coefficient of 0.049 nm K-1 is also found for the GaN/AlGaN MQW laser diode. The results for the AlGaN-based laser diodes grown on high-quality AlGaN films presented here will be essential for the future development of laser diodes emitting much shorter wavelengths.

Yoshida, Harumasa; Kuwabara, Masakazu; Yamashita, Yoji; Takagi, Yasufumi; Uchiyama, Kazuya; Kan, Hirofumi

2009-12-01

160

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

E-print Network

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

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

2006-07-04

161

Development of Short-Wavelength Far-Infrared Lasers and Optical Elements for Plasma Diagnostics  

NASA Astrophysics Data System (ADS)

Powerful 48- and 57-?m CH3OD lasers pumped by a 9R(8) CO2 laser have been developed to establish a new two-color FIR laser interferometer system for high density and large volume plasma diagnostics. To design the collimated beams for the interferometer, the beam profiles and the divergence angles have been measured for the 48- and 57-?m CH3OD lasers oscillated simultaneously. Water vapor absorptions for the laser wavelengths have been measured at 22 °C C to realize an efficient transmission line. Optical constants and transmittance and reflectance of crystal quartz, silicon, CVD-diamond, polyethylene sheet, Mylar film, TPX plate, metal mesh and wire grid have been measured to design the optical components (observation windows and beam splitters) in the 48- and 57-?m laser interferometer system.

Nakayama, Kazuya; Tomimoto, Masahiro; Okajima, Shigeki; Kawahata, Kazuo; Tanaka, Kenji; Tokuzawa, Tokihiko; Akiyama, Tsuyoshi; Ito, Yasuhiko

162

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

163

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

PubMed

We experimentally and numerically study dispersive wave emission, soliton fission, and supercontinuum generation in a silicon wire at telecommunication wavelengths. Through dispersion engineering, we experimentally confirm a previously reported numerical study and show that the emission of resonant radiation from the solitons can lead to the generation of a supercontinuum spanning over 500 nm. An excellent agreement with numerical simulations is observed. PMID:24978552

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

2014-06-15

164

SPITFIRE multi-band short-wave and mid-wave polarimetric camera  

NASA Astrophysics Data System (ADS)

Polarimetric sensors are valued for their capability to distinguish man-made objects from surrounding clutter. The SPITFIRE (Spectral Polarimetric Imaging Test Field InstRumEnt) polarimetric camera is designed to function in multiple bands in the Short Wave Infrared (SWIR) and Mid-Wave Infrared (MWIR) regions. SPITFIRE is a Stokes micro-grid polarimetric system with a 4 band spectral filter wheel. The focal plane array (FPA) as well as the filter wheel are located in a Dewar which is cooled via liquid nitrogen. By cooling the band-pass filter to the same temperature as the FPA, self-emission noise is decreased. In this paper we discuss the design and fabrication of the polarimetric camera (optics, Dewar, filter wheel and FPA), the data capture and processing system, initial characterization of the camera's performance, and future plans for the camera.

Patel, Hiren J.; Mack, Robert T.; LeMaster, Daniel A.; Harris, James S.; Forrai, David; Servaites, Jan M.

2010-04-01

165

Using short-wave infrared imaging for fruit quality evaluation  

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

166

Laser-Induced Damage In The Limits Of Ultrashort Pulses And Short Wavelengths  

SciTech Connect

The interaction of electromagnetic radiation with condensed matter bears two important aspects: A physical one, as the most significant source of information about solids; and a technological aspect -- the possibility to structure materials with the help of laser light.In this paper, investigations of several materials (dielectrics, metals, semiconductors) with laser pulses as short as 5 fs will be shown, the behavior of the solid close to the threshold of optical breakdown is explored. The results lead to important implications for the feasibility and efficiency of femtosecond machining. Due to nonlinear processes at high intensities machining precision beyond the diffraction limit can be achieved.On the other hand, the application of UV radiation leads to new levels of precision in micromachining, as well. This will be shown for the example of corneal ablation for Laser Vision Correction.

Lenzner, Matthias [Physics Deparment, City College, 138th Street at Convent Ave, New York, NY 10033 (United States)

2005-04-21

167

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

168

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

PubMed

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

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

2013-01-01

169

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

170

Expression and Evolution of Short Wavelength Sensitive Opsins in Colugos: A Nocturnal Lineage That Informs Debate on Primate Origins.  

PubMed

A nocturnal activity pattern is central to almost all hypotheses on the adaptive origins of primates. This enduring view has been challenged in recent years on the basis of variation in the opsin genes of nocturnal primates. A correspondence between the opsin genes and activity patterns of species in Euarchonta-the superordinal group that includes the orders Primates, Dermoptera (colugos), and Scandentia (treeshrews)-could prove instructive, yet the basic biology of the dermopteran visual system is practically unknown. Here we show that the eye of the Sunda colugo (Galeopterus variegatus) lacks a tapetum lucidum and has an avascular retina, and we report on the expression and spectral sensitivity of cone photopigments. We found that Sunda colugos have intact short wavelength sensitive (S-) and long wavelength sensitive (L-) opsin genes, and that both opsins are expressed in cone photoreceptors of the retina. The inferred peak spectral sensitivities are 451 and 562 nm, respectively. In line with adaptation to nocturnal vision, cone densities are low. Surprisingly, a majority of S-cones coexpress some L-opsin. We also show that the ratio of rates of nonsynonymous to synonymous substitutions of exon 1 of the S-opsin gene is indicative of purifying selection. Taken together, our results suggest that natural selection has favored a functional S-opsin in a nocturnal lineage for at least 45 million years. Accordingly, a nocturnal activity pattern remains the most likely ancestral character state of euprimates. PMID:24293738

Moritz, Gillian L; Lim, Norman T-L; Neitz, Maureen; Peichl, Leo; Dominy, Nathaniel J

2013-01-01

171

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

NASA Technical Reports Server (NTRS)

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

Piazzolla, Sabino

2007-01-01

172

Localized measurement of short wavelength plasma fluctuations with the DIII-D phase contrast imaging diagnostic  

SciTech Connect

A novel rotating mask system has been designed and implemented on the DIII-D phase contrast imaging (PCI) diagnostic to produce the first spatially localized PCI measurements of a tokamak plasma. The localization technique makes use of the variation in the magnetic field component perpendicular to the viewing chord as a function of chord height. This new capability provides measurements in the range of 2wave numbers up to 40 cm{sup -1} to probe electron scale turbulence in the plasma core.

Dorris, J. R.; Rost, J. C.; Porkolab, M. [Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)

2009-02-15

173

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

174

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

175

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

176

Dynamic Characteristics Analysis of Wavelength-Division-Multiplexing Guided-Wave Separation Switch Using Acoustooptic Effect  

Microsoft Academic Search

Dynamic switching characteristics in waveguide-type collinear acoustooptic (AO) devices are investigated for applications to wavelength-selective matrix switches and routers in wavelength-division-multiplexing (WDM) photonic networks. The device has the feature of simultaneous controllability for multiple wavelengths over a range of more than 100 nm. Experimental studies on optical filtering have been investigated. In order to find the optimum high-effciency design of

Nobuo Goto; Yasumitsu Miyazaki; Koichi Takahashi

2003-01-01

177

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

178

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

179

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

180

Continuous-wave simultaneous dual-wavelength operation at 912 nm and 1063 nm in Nd:GdVO4  

NASA Astrophysics Data System (ADS)

A continuous-wave, diode-pumped Nd:GdVO4 thin disk laser with simultaneous dual-wavelength emission at the 912 nm 4 F 3/2?4 I 9/2 quasi-three-level transition and the 1063 nm 4 F 3/2?4 I 11/2 four-level transition is demonstrated and analyzed. Output powers of 1.7 W at 912 nm and of 1.6 W at 1063 nm were achieved simultaneously from a 0.3-at.%, 300-?m thick Nd:GdVO4 crystal that was multi-pass excited with 26.8 W of available diode pump power. Second harmonic generation to 456 nm with LiB3O5 yielded 0.96 W in 912 nm single-wavelength operation and 0.73 W in 912 nm/1063 nm dual-wavelength operation.

Lünstedt, K.; Pavel, N.; Petermann, K.; Huber, G.

2007-01-01

181

Ultra-short-wave propagation in the jungle  

Microsoft Academic Search

The predominant characteristic of propagation in the VHF frequency range is the presence of a reflected wave which tends to cancel the direct wave and results in the received field being proportional to the product of the antenna heights, and inversely proportional to the square of the distance; and the radio gain being independent of frequency. For propagation in the

C. Burrows

1966-01-01

182

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

183

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

E-print Network

Recent observations support the hypothesis that a large fraction of "short-hard" gamma-ray bursts (SHBs) are associated with the inspiral and merger of compact binaries. Since gravitational-wave (GW) measurements of ...

Hughes, Scott A

184

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

185

Study on Wavelength-Tunable Photodetector with Surface Plasma Wave Excitation Filter  

Microsoft Academic Search

Surface plasma wave excitation filters is used in the new photodetector in this paper. The detectivity is enhanced by excitation of surface plasma waves (SPWs) using a Metal Aperture Arrays grating. A bias-tunable broadband response is achieved.

Yufeng Shang; Yongqing Huang; Xiaofeng Duan; Xian Ye; Hui Huang; Shiwei Cai; Qi Wang; Xiaomin Ren

2010-01-01

186

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

E-print Network

The recent progress in the understanding the physical nature of neutron star equilibrium configurations and the first observational evidence of a genuinely short gamma-ray burst, GRB 090227B, allows to give an estimate of the gravitational waves versus the X and Gamma-ray emission in a short gamma-ray burst.

F. G. Oliveira; Jorge A. Rueda; Remo Ruffini

2012-05-31

187

The effect of laser wavelength in the simulation of laser generated surface waves in human skin model.  

PubMed

A finite element (FE) simulation of the thermoelastic laser generated surface waves in a 3-layered model of human skin is presented. Commercial finite element code ANSYS is used to study the effects of changing laser wavelength and hence the optical absorption has on the generated surface waves. The FE model consists of a thermal analysis with a volumetric heat generation boundary condition to simulate the thermal effect of the laser source penetrating into the skin. The results from the thermal analysis are then subsequently applied as a load in a mechanical analysis where the out-of plane displacement histories and temperature fields are analysed using two different laser sources to generate the ultrasonic waves. PMID:17946226

L'Etang, Adéle; Huang, Zhihong

2006-01-01

188

The Velocity of Radio Waves over Short Paths  

Microsoft Academic Search

The velocity of radio waves was measured directly in the following manner. Two radio stations were set up on frequencies of 3492.5 and 2398 kilocycles, respectively. One station was fixed while the other was portable. The fixed station sent out pulses which were received at the portable station. A thyratron control set off return pulses which came back to the

R. C. Colwell; H. Atwood; J. E. Bailey; C. O. Marsh

1942-01-01

189

Digital Audio Broadcasting in the Short Wave Bands  

NASA Technical Reports Server (NTRS)

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

Vaisnys, Arvydas

1998-01-01

190

VARIABILITY IN SHORT WAVELENGTH AUTOMATED PERIMETRY AMONG PERI- OR POST-MENOPAUSAL WOMEN: A DEPENDENCE ON PHYTOESTROGEN CONSUMPTION?  

PubMed Central

Purpose To determine whether the hill of vision for Short-Wavelength Automated Perimetry (SWAP) is shallower for women who consume phytoestrogen-rich foods than for women who do not. Methods Visual field data were compared for two groups of healthy amenorrheic women 48-69 years-old with normal vision and not using hormone replacement: (1) 24 subjects who reported consuming soy and/or flax products and (2) 20 subjects who reported not consuming these products. Two types of 24-2 visual fields were measured: (1) Full Threshold SWAP, and (2) a white-on-white (W/W) field obtained using a Swedish Interactive Threshold Algorithm (SITA Standard). Results The reduction of SWAP sensitivity from the center of the field [4 loci, mean eccentricity = 4.2°] to the periphery [20 loci, mean eccentricity = 21.9°] was less for soy/flax consumers than for non-consumers, both with age-referencing (mean difference = 1.7 dB, p = .018) and without (p = .012). Corresponding distinctions existed for the SWAP – W/W difference, and there was minimal effect for W/W fields alone. The peripheral age-referenced SWAP sensitivities averaged 2.5 dB higher for consumers than non-consumers (p = .022). Conclusion The between-group distinctions are consistent with the possibility (derived from the women’s health literature) that phytoestrogens may counteract a decline of SWS-cone-mediated response among post-menopausal women. These results suggest another potential application for SWAP outside its original intended purpose as a glaucoma test. Future studies should assess whether phytoestrogen consumption is most beneficial for women who are sufficiently young and/or not too far beyond menopause. PMID:19958290

Eisner, Alvin; Demirel, Shaban

2009-01-01

191

Effect of Yellow-Tinted Intraocular Lens on Standard Automated Perimetry and Short Wavelength Automated Perimetry in Patients with Glaucoma  

PubMed Central

Purpose: To investigate the effect of cataract surgery and yellow-tinted intraocular lens (IOLs) implantation on perimetry indices of short-wavelength automated perimetry (SWAP) and standard automated perimetry (SAP) testing in patients with coexisting cataract and glaucoma. Materials and Methods: In this prospective comparative case series, phacoemulsification with implantation of yellow-tinted Acrysof Natural IOL was performed in 16 eyes of 16 patients with visually significant cataract (best-corrected visual acuity (VA) better than 20/120) and mild to moderate glaucoma. Pre- and postoperative values for VA and for perimetry indices including mean deviation (MD), pattern standard deviation (PSD), and foveal threshold (FT) from both SAP and SWAP testing were compared. Results: Postoperative VA improved significantly after cataract surgery and yellow-tinted IOL implantation (P < 0.001). After cataract extraction and IOL implantation, MD and FT on SWAP testing improved significantly (P = 0.001); however, there was no statistically significant change with SAP testing between the pre- and postoperative perimetry indices. There was no statistically significant change in PSD with either SAP or SWAP testing postoperatively. The differences between pre- and postoperative values for all perimetry indices under study were not significant when comparing SAP with SWAP tests, except for MD which had improved statistically significantly in SWAP testing (P = 0.03). Conclusions: In mild to moderate glaucoma patients with cataracts, the perimetry indices of SWAP testing improved after phacoemulsification and yellow-tinted IOL implantation. This suggests that the yellow-tinted IOLs have less effect on SWAP testing than visually significant cataracts. PMID:25100904

Nilforushan, Naveed; Parsamanesh, Mohammad; Yu, Fei; Nassiri, Nariman; Miraftabi, Arezoo; Coleman, Anne L.

2014-01-01

192

Wavelength reuse for uplink on dense wave-division multiplexing single-fiber ring for radio over fiber broadband systems with downlink signal generation in optical domain  

NASA Astrophysics Data System (ADS)

We have presented a single-fiber dense wave-division multiplexing (DWDM) ring scheme with wavelength reuse for uplink and optical signal generation for downlink. Instead of using a new laser for uplink, the wavelength already used for wavelength beating to generate the downlink signal in optical domain is reused for uplink. Algorithms for power optimization using Erbium-doped fiber amplifier, wavelength routing, and wavelength assignment are developed and simulated. The DWDM-radio over fiber scheme reusing the wavelength can support the data rate in the range of 1 Gbps. Fifteen remote antenna units (RAUs) are simulated in this scheme; however, these can be increased by adding more wavelengths. The proposed scheme simplifies the architecture or RAUs, decreases the overall cost while enhancing the bandwidth and operational flexibility of radio over fiber systems.

Mumtaz, Ateeq; Khawar Islam, Muhammad; Zafrullah, Muhammad

2011-10-01

193

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

NASA Astrophysics Data System (ADS)

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

Heinz, D. L.; Mark, H.

2012-12-01

194

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

195

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

196

Ultra-short pulsed millimeter-wave laser  

NASA Astrophysics Data System (ADS)

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

Wilson, Thomas

2000-10-01

197

Modified model for four-wave mixing-based wavelength conversion in silicon micro-ring resonators  

NASA Astrophysics Data System (ADS)

A modified model for wavelength conversion based on the four-wave mixing (FWM) in a silicon micro-ring resonator is presented. Unlike previous contributions, the nonlinear phase shifts caused by self-phase modulation and cross-phase modulation are also taken into account in the present theoretical analysis besides the linear propagation loss and the nonlinear losses caused by two-photon absorption and free-carrier absorption. Analysis shows that the nonlinear phase shifts will cause different red shifts for the pump and signal (or converted) resonant wavelengths, and consequently an additional wavelength difference between the signal transmission dip and the efficiency peak, which will increase/decrease the conversion efficiency of the signal channel far from/near the pump. The conversion efficiency and the conversion peak width of each signal channel are both affected by the micro-ring radius and coupling coefficient. A broader conversion peak width can be obtained by using a micro-ring resonator with a smaller Q factor.

Li, Zhiqiang; Gao, Shiming; Liu, Qiang; He, Sailing

2011-04-01

198

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

199

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

200

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

201

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

NASA Astrophysics Data System (ADS)

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

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

2010-09-01

202

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

203

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

204

Development of an Electromagnetic Acoustic Transducer with Multi-Wavelength for Lamb Wave  

Microsoft Academic Search

Lamb waves are normally utilized for inspecting thin metal sheets, and a wheel type probe with piezoelectric oscillators is used as the sensor, although it has a few serious disadvantages such as a dramatic change in sensitivity. We then studied a useful electromagnetic acoustic transducer (EMAT) without a couplant. The trial EMAT consists of a meandering coil with a narrow

Riichi Murayama; Koichi Mizutani

2002-01-01

205

Spectral form and source term balance of short gravity wind waves  

NASA Astrophysics Data System (ADS)

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

206

Polarization investigation of a tunable high-speed short-wavelength bulk-micromachined MEMS-VCSEL  

NASA Astrophysics Data System (ADS)

We report the investigation of the state of polarization (SOP) of a tunable vertical-cavity surface-emitting laser (VCSEL) operating near 850 nm with a mode-hop free single-mode tuning range of about 12 nm and an amplitude modulation bandwidth of about 5 GHz. In addition, the effect of a sub-wavelength grating on the device and its influence on the polarization stability and polarization switching has been investigated. The VCSEL with an integrated sub-wavelength grating shows a stable SOP with a polarization mode suppression ratio (PMSR) more than 35 dB during the tuning.

Davani, H. A.; Kögel, B.; Debernardi, P.; Grasse, C.; Gierl, C.; Zogal, K.; Haglund, Å.; Gustavsson, J.; Westbergh, P.; Gründl, T.; Komissinskiy, P.; Bitsch, T.; Alff, L.; Küppers, F.; Larsson, A.; Amann, M.-C.; Meissner, P.

2012-03-01

207

Short-wave infrared, medium-wave infrared, and long-wave infrared imaging study for optical readout microcantilever array infrared sensing system  

NASA Astrophysics Data System (ADS)

We aim to study the short-wave infrared (SWIR), medium-wave infrared (MWIR), and long-wave infrared (LWIR) imaging ability based on optical readout bimaterial microcantilever focal plane array (FPA) uncooled infrared imaging system. First, the principle of the bimaterial microcantilever sensing and the fabrication of the microcantilever array are introduced. Second, the optical-thermal-mechanical sensing theories based on the FPA are given. Finally, an optical readout microcantilever FPA infrared imaging system is developed for SWIR, MWIR, and LWIR imaging experiments. The experimental results show that the system can acquire the clear images of the SWIR, MWIR, and LWIR targets.

Gong, Cheng; Zhao, Yuejin; Dong, Liquan; Hui, Mei; Yu, Xiaomei; Liu, Xiaohua

2013-02-01

208

Pseudo-phase-matched four-wave mixing in soliton wavelength-division multiplexing transmission.  

PubMed

In a soliton transmission system using lumped amplifiers, pseudo phase matching allows four-wave mixing fields from soliton-soliton collisions to grow uncontrollably and inf lict severe penalties. Through numerical simulation, we show that this growth can be eliminated, or at least greatly reduced, through the use of fiber whose dispersion is tapered, either continuously or in steps, in conformity with the fiber loss curve. PMID:19865417

Mamyshev, P V; Mollenauer, L F

1996-03-15

209

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

210

Broad-band tunable wavelength conversion using Raman-assisted parametric four-wave mixing in highly nonlinear fibers with double-pass geometry  

Microsoft Academic Search

Efficient wavelength conversion using distributed Raman gain and the Raman-assisted parametric four-wave mixing in 1 km of highly nonlinear fibers (HNLFs) is demonstrated in this letter. We present the theoretical analysis of the Raman-assisted parametric process and investigate the mechanism of wavelength conversion between parametric Stokes and anti-Stokes light. The system is implemented in a double-pass Raman amplifier where a

Ming Tang; Yandong Gong; Ping Shum

2005-01-01

211

arXiv:0709.2711v1[astro-ph]17Sep2007 Population synthesis at short wavelengths and  

E-print Network

, the pioneer- ing 70's marked the beginning of ultraviolet astronomy; satellites like ANS, OAO, and IUE opened-passing, for the first time, the blocking effect of Earth atmosphere. Since then, ultraviolet astronomy has received-wavelengths, and their implementation for population synthesis models, we briefly review here some special properties of ultraviolet

Buzzoni, Alberto

212

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

PubMed

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

Dang, Ngoc T; Pham, Anh T

2010-05-10

213

Generation of tunable coherent extreme-ultraviolet radiation at wavelengths as low as 66 nm by resonant four-wave mixing.  

PubMed

Tunable coherent extreme-ultraviolet (XUV) radiation at wavelengths as low as 66.86 nm was generated by two-photon resonant four-wave mixing in a hydrogen molecular gas jet. In this investigation, an ArF excimer laser was tuned to the E,F(1)Sigma(+)(g)(upsilon' = 6)-X(1)Sigma(+)(g)(upsilon' = 0) Q(1) transition of H(2), and the second-harmonic radiation of a dye laser was mixed to obtain the resultant XUV radiation. To our knowledge, this tunable XUV radiation is the shortest wavelength obtained so far by two-photon resonant four-wave mixing. PMID:19802256

Hirakawa, Y; Nagai, A; Muraoka, K; Okada, T; Maeda, M

1993-05-01

214

Sensitivity of directional spreading for low-frequency motions in short-crested waves  

SciTech Connect

To accept lower environmental safety factors in the design of mooring systems, the use of short-crested waves in the analysis has been investigated. This is motivated from several experiments and analysis which show that long-created waves induce significantly overpredicted mooring loads on column supported floating platforms. However, on other floating concepts like turret moored ships or single point moored ships, long-created waves have been shown to induce underpredicted mooring loads and motions. Sensitivity to directional spread and influence of second-order directional interaction is in particular investigated in this paper. Further, sensitivity of frequency dependent directional spreading in the wave field is investigated. The analysis is illustrated by numerical computations applied on an exemplified TLP (tension leg platform).

Krokstad, J.R. [Marintek A/S, Trondheim (Norway)

1994-12-31

215

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

216

Fluctuation-induced conductivity in quenched and furnace-cooled Bi2Sr2CaCu2O8+?: Aslamazov-Larkin or short-wavelength fluctuations  

NASA Astrophysics Data System (ADS)

The fluctuation-induced conductivity of quenched and furnace-cooled Bi2Sr2CaCu2O8+? (Bi-2212) is investigated to compare the dimensionality of fluctuations above the mean-field critical temperature. The processing conditions of a superconductor affect its conductivity in different ways. The fluctuation-induced conductivity of the quenched sample can be explained in the framework of Aslamazov-Larkin theory whereas that of the furnace-cooled Bi-2212 sample shows short-wavelength fluctuations. Possible explanations are included in this paper.

Ghosh, Ajay Kumar; Basu, A. N.

1999-05-01

217

Termination of spiral wave breakup in a Fitzhugh-Nagumo model via short and long duration stimuli  

NASA Astrophysics Data System (ADS)

Rotating spiral waves have been observed in a variety of nonlinear biological and physical systems. Spiral waves are found in excitable and oscillatory systems and can be stationary, meander, or even degenerate into multiple unstable rotating waves (a process called "spiral wave breakup"). In the heart, spiral wave breakup is thought to be the underlying mechanism of cardiac fibrillation. The spatiotemporal complexity of multiple unstable spiral waves is difficult to control or terminate. Here, the mechanisms of the termination of spiral wave breakup in response to global stimulation are investigated. A modified Fitzhugh-Nagumo model was used to represent cellular kinetics to study the role of the fast (activation) and slow (recovery) variables. This simplified model allows a theoretical analysis of the termination of spiral wave breakup via both short and long duration pulses. Simulations were carried out in both two-dimensional sheets and in a three-dimensional geometry of the heart ventricles. The short duration pulses affected only the fast variable and acted to reset wave propagation. Monophasic pulses excited tissue ahead of the wave front thus reducing the amount of excitable tissue. Biphasic shocks did the same, but they also acted to generate new wave fronts from the pre-existing wave tails by making some active regions excitable. Thus, if the short duration stimuli were strong enough, they acted to fill in excitable tissue via propagating wave fronts and terminated all activity. The long duration wave forms were selected such that they had a frequency spectrum similar to that of the pseudoelectrocardiograms recorded during fibrillation. These long duration wave forms affected both the recovery and activation variables, and the mechanism of unstable multiple spiral wave termination was different compared to the short duration wave forms. If the long duration stimuli were strong enough, they acted to alter the "state" (i.e., combination of fast and slow variables) of the tissue throughout 1.5 cycles, thus "conditioning" the tissue such that by the end of the stimuli almost no excitable tissue remained. The peak current, total energy, and average power of stimuli required to terminate spiral wave breakup were less for the long duration wave forms compared to the short duration wave forms. In addition, closed loop feedback via stimulation with a wave form that was the difference of the pseudoelectrocardiogram and a strongly periodic chaotic signal was successful at terminating spiral wave breakup. These results suggest that it may be possible to improve cardiac defibrillation efficacy by using long duration wave forms to affect recovery variables in the heart as opposed to the traditional brief duration wave forms that act only on the fast variables.

Gray, Richard A.

2002-09-01

218

Fabrication of gas-sensing semiconductor oxide thin films by using a short-wavelength excimer laser  

NASA Astrophysics Data System (ADS)

Semiconducting metal oxides are widely used in chemical, electronic devices and in gas sensing applications. Among the many different deposition techniques, ablating the target materials with a high power laser is one of the most effective techniques in fabricating high quality gassensitive thin films. In this work, we used a 193-nm-wavelength ArF excimer laser, the shortest wavelength used in the fabrication of semiconductor oxides, to deposit high quality transition-metaloxide thin films. We used X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman spectroscopy, optical transmission spectroscopy, and conductivity measurements to characterize the films. The fabricated MoO3 thin films were observed to show a good nanoplate structure in the orthorhombic ?-MoO3 phase. Depending on the deposition temperatures, MoO3 showed significantly different surface structures. Good gas sensitivity of a MoO3 thin-film-based sensor exposed to low concentrations ethanol vapor was found by using resistance measurements.

Kang, J. H.; Park, J. H.; Ahmad, Muhammad Z.; Wlodarski, W.

2012-11-01

219

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

220

Effective generation of fast particles and short wavelength radiation from nano-structure targets irradiated by relativistic intensity laser pulse  

NASA Astrophysics Data System (ADS)

In the present paper it is offered to significantly increase target absorption and to optimize parameters of a relief and basic part of a target so that an absorbed energy is transferred to an accelerated particles and reflected (transmitted) energy is radiated as attosecond pulses. The choice of optimum characteristics of a target is made by means of analytical and multi-dimensional numerical modeling of a target set with characteristics near to optimum values. It is shown, that at reflection from a target the laser wave of relativistic intensity is effectively converted in sequence of electromagnetic pulses of tens nanometer length, the following one after another through the period of an initial laser wave. Dependence of its parameters on angle of incidence and laser intensity is investigated.

Andreev, A. A.; Priebe, G.; Platonov, K. Y.

2013-05-01

221

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

222

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

PubMed

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

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

2013-09-20

223

Detection of aqueous glucose based on a cavity size- and optical-wavelength-independent continuous-wave photoacoustic technique.  

PubMed

Toward the achievement of noninvasive and continuous monitoring of blood glucose level, we developed a new measurement method based on the continuous-wave photoacoustic (CW-PA) technique and performed the first validation in vitro with calibrated aqueous glucose solutions. The PA technique has been studied in the past but exclusively based on the pulse setup since the CW one exhibits dependence on the cavity dimensions, which is not compatible with the final application requirements. This paper describes a new strategy relying on the monitoring of the resonant-frequency relative shift induced by the change of glucose concentrations rather than amplitude signal levels at a fixed frequency. From in vitro results, we demonstrate a stable and reproducible response to glucose at various cavity dimensions and optical wavelengths, with a slope of 0.19 ±0.01%/g/dL. From theoretical considerations, this method is consistent with a relative acoustic velocity measurement, which also explains the aforementioned stability. The proposed method then resolves most of the issues usually associated with the CW-PA technique and makes it a potential alternative for the noninvasive and continuous monitoring of glycemia levels. However, experimental determination of sensor responses to albumin and temperature as two potential interferents shows similar levels, which points to the selectivity to glucose as a major issue we should deal with in future development. PMID:22548281

Camou, S; Haga, T; Tajima, T; Tamechika, E

2012-06-01

224

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

225

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

226

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

227

Short submillimeter operation of the Planar Orotron  

Microsoft Academic Search

Recent experimental results demonstrating Planar Orotron operation in the short submillimeter wavelength regime of 1 mm to 400 mum are presented. This device belongs to the class of Smith-Purcell free electron lasers that utilize periodic metal grating structures to support electromagnetic waves with phase velocities lower than the speed of light. The J.E interaction between this slow wave and a

E. J. Price; J. E. Walsh; M. F. Kimmitt

1991-01-01

228

Characterization of Au-YBa 2Cu 3O 7- y composites by paraconductivity analysis with a short-wavelength cutoff  

NASA Astrophysics Data System (ADS)

Bulk composites of Au-YBa 2Cu 3O 7- y are characterized by means of paraconductivity analyses by taking account of a short-wavelength cutoff in the fluctuation spectrum. General expressions for the Aslamazov-Larkin, Maki-Thompson and density of state terms are derived in the momentum-cutoff regime, which are found to describe fairly well observed paraconductivity at overall temperatures investigated. From the theoretical fittings, we estimate several parameters, including the anisotropy parameter, fluctuation amplitude, scattering lifetime, and phase-breaking time. A normalized absorption of AC susceptibility is also investigated. It is found that many of these parameters exhibit rapid variations with a small amount of gold, which may be attributed to enhanced disorder upon doping, while behavior in those parameters at higher doping levels is related to a percolative nature of the composites. We could observe evidence of a pronounced two-dimensional character due perhaps to better crystallinity upon Au doping.

Mori, Natsuki; Satoh, Hirokazu

2003-10-01

229

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.

230

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

PubMed

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

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

2014-04-01

231

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

232

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

233

Optical system design for a short-wave infrared imaging spectrometer  

NASA Astrophysics Data System (ADS)

A short-wave infrared (SWIR) imaging spectrometer with all reflective elements was designed, covering the spectral range 1000-2500nm with a spectral resolution of 10nm. The imaging spectrometer is composed of an off-axis three-mirror anastigmatic (TMA) telescope and an Offner spectral imaging system with convex grating. The design result shows that the system has compact structure, light weight, wide field of view, small smile and keystone, excellent image quality and practical feasibility. The design method is simple and easy-operating.

Huang, Han; Li, Xiaotong; Cen, Zhaofeng

2012-11-01

234

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

235

Single-arm three-wave interferometer for measuring dispersion of short lengths of fiber.  

PubMed

We present a simple fiber-based single-arm spectral interferometer to measure directly the second-order dispersion parameter of short lengths of fiber (< 50 cm). The standard deviation of the measured dispersion on a 39.5-cm-long SMF28(TM) fiber is 1x10(-4) ps/nm, corresponding to 1% relative error, without employing any curve fitting. Our technique measures the second-order dispersion by examining the envelope of the interference pattern produced by three reflections: two from the facets of the test fiber and one from a mirror placed away from the fiber facet at a distance that introduces the same group delay as the test fiber at the measured wavelength. The operational constraints on system parameters, such as required bandwidth, wavelength resolution, and fiber length, are discussed in detail. Experimental verification of this technique is carried out via comparison of measurements of single mode fiber (SMF28(TM)) with published data and via comparison of measurements of a dispersion compensating fiber with those taken using conventional techniques. Moreover, we used this new technique to measure the dispersion coefficient of a 45-cm-long twin-hole fiber over a 70 nm bandwidth. It is the first time dispersion measurement on this specialty fiber is reported. PMID:19550980

Galle, Michael A; Mohammed, Waleed S; Qian, Li; Smith, Peter W

2007-12-10

236

Multi-wavelength Erbium-doped fiber laser based on four-wave-mixing effect in single mode fiber and high nonlinear fiber.  

PubMed

A multi-wavelength Erbium-doped fiber (EDF) laser based on four-wave-mixing is proposed and experimentally demonstrated. The 5 km single mode fiber in the cavity enhances the four-wave-mixing to suppress the homogenous broadening of the erbium-doped fiber and get the stable multi-wavelength comb. The lasing stability is investigated. When the pump power is 300 mW, the fiber laser has 5-lasing lines and the maximum fluctuation of the output power is about 3.18 dB. At the same time, a laser with 110 m high nonlinear fiber (HNFL) is demonstrated. When the pump power is 300 mW, it has 7-lasing lines (above -30 dBm) and the maximum fluctuation is 0.18dB. PMID:23736476

Wang, Pinghe; Weng, Danmei; Li, Kun; Liu, Yong; Yu, Xuecai; Zhou, Xiaojun

2013-05-20

237

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

238

Sub-part-per-billion monitoring of nitric oxide by use of wavelength modulation spectroscopy in combination with a thermoelectrically cooled, continuous-wave quantum cascade laser  

Microsoft Academic Search

We used a thermoelectrically cooled, continuous-wave, quantum cascade laser operating between 1847 and 1854 cm(-1) in combination with wavelength modulation spectroscopy for the detection of nitric oxide (NO) at the sub-part-per-billion by volume (ppbv) level. The laser emission overlaps the P-7.5 doublet of NO centered around 1850.18 cm(-1). Using an astigmatic multiple-pass absorption cell with an optical path length of

B. W. M. Moeskops; S. M. Cristescu; F. J. M. Harren

2006-01-01

239

Growth of InAs/GaSb short-period superlattices for high-resolution mid-wavelength infrared focal plane array detectors  

NASA Astrophysics Data System (ADS)

InAs/GaSb short-period superlattices (SLs) with a broken gap type-II band alignment are investigated for the fabrication of photovoltaic pin-photodetectors on GaSb substrates. The structures were grown by molecular beam epitaxy using valved cracker cells for arsenic and antimony. Effective bandgap and strain in the SL were adjusted by varying the thickness of the InAs and GaSb layers in the SL and the controlled formation of InSb-like or GaAs-like bonds at the interfaces. MBE growth conditions were investigated and optimized in order to achieve good morphological, electrical and optical properties. IR-photodiodes with a cut-off wavelength of 5.4 ?m reveal quantum efficiencies around 30% and detectivity values exceeding 10 13 Jones at 77 K. A focal plane array camera with 256×256 detector elements and 40 ?m pitch based on InAs/GaSb short-period SLs was fabricated for the first time. The camera system reveals an excellent thermal resolution with a noise equivalent temperature difference below 12 mK for an integration time of 5 ms using f/2 optics. The detector performance, comparable with state of the art mercury-cadmium-telluride IR detectors, makes this material system very interesting for the fabrication of advanced thermal imaging systems.

Walther, M.; Schmitz, J.; Rehm, R.; Kopta, S.; Fuchs, F.; Fleißner, J.; Cabanski, W.; Ziegler, J.

2005-05-01

240

Design and development of wafer-level short wave infrared micro-camera  

NASA Astrophysics Data System (ADS)

Low cost IR Sensors are needed for a variety of Defense and Commercial Applications as low cost imagers for various Army and Marine missions. SiGe based IR Focal Planes offers a low cost alternative for developing wafer-level shortwave infrared micro-camera that will not require any cooling and can operate in the Visible-NIR band. The attractive features of SiGe based IRFPA's will take advantage of Silicon based technology, that promises small feature size and compatibility with the low power silicon CMOS circuits for signal processing. SiGe technology offers a low cost alternative for developing Visible-NIR sensors that will not require any cooling and can operate from 0.4- 1.7 microns. The attractive features of SiGe based IRFPA's will take advantage of Silicon based technology that can be processed on 12-inch silicon substrates, that can promise small feature size and compatibility with the Silicon CMOS circuit for signal processing. In this paper, we will discuss the design and development of Wafer-Level Short Wave Infrared (SWIR) Micro-Camera. We will discuss manufacturing approaches and sensor configurations for short wave infrared (SWIR) focal plane arrays (FPAs) that significantly reduce the cost of SWIR FPA packaging, optics and integration into micro-systems.

Sood, Ashok K.; Richwine, Robert A.; Pethuraja, Gopal; Puri, Yash R.; Lee, Je-Ung; Haldar, Pradeep; Dhar, Nibir K.

2013-06-01

241

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

242

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

243

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

PubMed

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

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

2011-11-01

244

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

245

Con_A-carbone nanotube conjugate with short wave near-infrared laser ablation for tumor therapy  

NASA Astrophysics Data System (ADS)

Using the characteristics of T cell mitogen called lectin protein from the jack-beam Canavalia ensiformis Concanavalin A (Con_A) with dual activities, cytotoxicity and immunomodulation, we have shown it has a therapeutic effect on hepatoma. Injection of Con_A can eradicate the established malign tumor, because Con_A can induce tumor cell autophagic, cell-programmed death, as well as activate the effector T cells. Combined, in this paper, with the absorption exceeding the Carbon NanoTube (CNT) band-gap (?bg=~1/CNT diameter) with an active short wave near-infrared (SWIR) (1.2~1.5 micron wavelengths), which happened to be translucent to the irradiation upon animal skin, similar to that used in hospital fingertip-clamped Pulse Oxymetry. Once the Con_ACNT is guided to hepatoma cells, it is bonded and internalized into the mitochondria (MC) compartment, the cellular energy factory. Con_A has the higher specificity for tumor cells useful for targeting because of the abnormal glycosylation on tumor cells. When CNT hitch hike with Con_A, they can t together like a laser-denotable chemical missile surgically targeting at the tumor cells precisely by Con_A-guidance. We switch on SWIR laser, when the Con_A-CNT conjugated complex has been bonded and internalized to MC of malign cells and already commenced cellular programmed death. Thus, it might appear to casual readers that we have initiated an overkill, chemical drugged autophage followed with physical laser ablation, but what if we can eradicate hepatoma totally if no blue print is left behind inadvertently in case of a partial failure. We conclude that using Con_A-CNT conjugated complex targeting specifically at malign tumor cells is a novel targeted-laser-radiation therapy for tumors in mice.

Lei, Huan-Yao; Peng, Ching-An; Tang, Ming-Jer; Reindhart, Kit; Szu, Harold H.

2009-04-01

246

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

247

Time-domain ultrasonic NDE of the wave velocity of a sub-half-wavelength elastic layer  

SciTech Connect

The purpose of this paper is to report a new technique for ultrasonic NDE of the wavespeed of a sub-half-wavelength layer (given its thickness) using only the time-domain information. The new technique was applied to aluminum plates with h/[lambda] ranging from 0.082 to 2.0 where h and [lambda] are the plate thickness and the nominal wavelength, respectively. A satisfactory comparison between the measured values and the nominal value was observed.

Kinra, V.K.; Zhu, Changyi (Texas A and M Univ., College Station, TX (United States))

1993-01-01

248

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

SciTech Connect

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

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

2010-11-15

249

Short pulse radar used to measure sea surface wind speed and SWH. [Significant Wave Height  

NASA Technical Reports Server (NTRS)

A joint airborne measurement program is being pursued by NRL and NASA Wallops Flight Center to determine the extent to which wind speed and sea surface significant wave height (SWH) can be measured quantitatively and remotely with a short pulse (2 ns), wide-beam (60 deg), nadir-looking 3-cm radar. The concept involves relative power measurements only and does not need a scanning antenna, Doppler filters, or absolute power calibration. The slopes of the leading and trailing edges of the averaged received power for the pulse limited altimeter are used to infer SWH and surface wind speed. The interpretation is based on theoretical models of the effects of SWH on the leading edge shape and rms sea-surface slope on the trailing-edge shape. The models include the radar system parameters of antenna beam width and pulsewidth.

Hammond, D. L.; Mennella, R. A.; Walsh, E. J.

1977-01-01

250

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

251

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

252

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

253

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

Transmission of ultrasonic waves through a slit between two water immersed brass plates is studied for sub-wavelength plate thicknesses and slit apertures. Extraordinary high absorption is observed at discrete frequencies corresponding to resonant excitation of Rayleigh waves on the both sides of the channel. The coupling of the Rayleigh waves occurs through the fluid and the corresponding contribution to the dispersion has been theoretically derived and also experimentally confirmed. Symmetric and anti-symmetric modes are predicted but only the symmetric mode resonances have been observed. It follows from the dispersion equation that the coupled Rayleigh waves cannot be excited in a channel with apertures less than the critical one. The calculated critical aperture is in a good agreement with the measured acoustic spectra. These findings could be applied to design a broadband absorptive metamaterial.

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

2011-12-23

254

Effects of an Advanced Sleep Schedule and Morning Short Wavelength Light Exposure on Circadian Phase in Young Adults with Late Sleep Schedules  

PubMed Central

Objective We examined the effects of an advanced sleep/wake schedule and morning short wavelength (blue) light in 25 adults (mean age±SD = 21.8±3 years; 13 women) with late sleep schedules and subclinical features of delayed sleep phase syndrome (DSPD). Methods After a baseline week, participants kept individualized, fixed, advanced 7.5-hour sleep schedules for 6 days. Participants were randomly assigned to groups to receive “blue” (470 nm, ~225 lux, n=12) or “dim” (< 1 lux, n=13) light for one hour after waking each day. Head-worn “Daysimeters” measured light exposure; actigraphs and sleep diaries confirmed schedule compliance. Salivary dim light melatonin onset (DLMO), self-reported sleep, and mood were examined with 2×2 ANOVA. Results After 6 days, both groups showed significant circadian phase advances, but morning blue-light was not associated with larger phase shifts than dim-light exposure. The average DLMO advances (mean±SD) were 1.5±1.1 hours in the dim light group and 1.4±0.7 hours in the blue light group. Conclusions Adherence to a fixed advanced sleep/wake schedule resulted in significant circadian phase shifts in young adults with subclinical DSPD with or without morning blue light exposure. Light/dark exposures associated with fixed early sleep schedules are sufficient to advance circadian phase in young adults. PMID:21704557

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

2011-01-01

255

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

256

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

257

Ultra-short electron bunches by Velocity Bunching as required for plasma wave accelerations  

NASA Astrophysics Data System (ADS)

The generation of ultra-short bunches is nowadays a critical requirement for plasma wave accelerators, on which many laboratories world-wide are investigating or are close to starting with experimental activities. This requirement is true for both: external injection into “laser wake field accelerators”, where injected beams need lengths around or shorter than 10 fs; and the “plasma wake field accelerators”, where the wake field intensity scales like the driver bunch charge over the square of the rms bunch length (Qb/?z2). This work presents beam dynamic simulations, which show how to use the Velocity Bunching (VB) technique to obtain ultra-short bunches. The VB technique is applied to small bunch charges (0.5-15 pc) and it is driven with a proper control of the bunch density versus the bunch energy gain, which permits one to control the transverse beam emittance, the bunch length and the correlated longitudinal energy spread, in a peculiar manner. The compression optimizations by VB, shown in this work, are obtained using a layout very similar to SPARC's Linac one, which is a Linac designed to maximize VB performances.

Bacci, A.; Rossi, A. R.

2014-03-01

258

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

259

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

E-print Network

Progenitor scenarios for short gamma-ray bursts (short GRBs) include coalescenses of two neutron stars or a neutron star and black hole, which would necessarily be accompanied by the emission of strong gravitational waves. ...

Barsotti, Lisa

260

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

261

Determination of Particle Size and Number Density of Opaque Colloidal Mixtures Using Diffuse Photon Density Waves and Two-Wavelength Light Sources  

NASA Astrophysics Data System (ADS)

A diffuse photon density wave (DPDW) propagates as a spherical energy wave in highly scattering media, such as opaque colloidal mixtures. The advantage of using DPDW is that the absorption and reduced scattering coefficients of the opaque colloidal mixtures can be measured without dilution and calibration. We propose a method for the estimation of the mean particle size and number density of the opaque colloidal mixtures using the relationship between estimated values and optical properties. In this study, we first determined the mean particle size and number density of colloidal silica, a single-particle dispersive medium, to confirm the validity of the method and evaluated the accuracy of the measurement. Then, we determined the mean particle size and number density of casein micelles and fat globules in milk, which is regarded as a typical opaque colloidal mixture, using two light sources with different wavelengths.

Taniguchi, Jun; Murata, Hiroshi; Okamura, Yasuyuki

2007-05-01

262

FUNDAMENTAL AREAS OF PHENOMENOLOGY (INCLUDING APPLICATIONS): Amplitude Regenerative Characteristics of RZ-DPSK Wavelength Converter Based on Four-Wave Mixing in SOA  

NASA Astrophysics Data System (ADS)

We investigate the phase-preserving amplitude regenerative characteristics of the return-to-zero (RZ) differential-phase-shift-keying (DPSK) wavelength conversion based on four-wave mixing (FWM) in a semiconductor optical amplifier (SOA). The Q-factor and the optical signal-to-noise ratio (OSNR) before and after conversion are experimentally obtained and analysed in different input noise power levels. In both the continuous-wave and synchronous clock pumping cases, we find that there is amplitude clamping in the FWM conversion due to the gain saturation of SOA, which can suppress the amplitude fluctuation of the converted DPSK signal before and after demodulation. We have achieved 2-dB Q penalty improvement in our experiment demonstration of 10Gbit/s RZ-DPSK signal with OSNR lower than 19dB.

Jiang, Huan; Wen, He; Han, Liu-Yan; Guo, Yi-Li; Zhang, Han-Yi

2008-05-01

263

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...

264

Short term analgesic effect of extracorporeal shock wave therapy in horses with proximal palmar metacarpal\\/plantar metatarsal pain  

Microsoft Academic Search

Extracorporeal shock wave therapy (ESWT) is an accepted form of treatment for chronic cases of proximal suspensory desmitis (PSD). Subjective evaluation of horses shortly after being treated with ESWT has led clinicians to comment on an immediate reduction in lameness. This study aimed to evaluate the analgesic effect of ESWT on 16 horses with PSD or PSD-like pain in a

Isabel Imboden; Nina M. Waldern; Thomas Wiestner; Christoph J. Lischer; Gottlieb Ueltschi; Michael A. Weishaupt

2009-01-01

265

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

266

Pulsed and continuous-wave operation of long wavelength infrared (?=9.3 ?m) quantum cascade lasers  

Microsoft Academic Search

The operation of quantum cascade lasers at a wavelength (?≃9.3 ?m) well within the 8-13-?m atmospheric window is reported. A detailed study of intersubband luminescence in a vertical transition structure shows linewidths as narrow as ~10 meV at cryogenic temperatures, increasing to 20 meV at room temperature. Pulsed operation is demonstrated up to 220 K with a peak power ≈10

C. Sirtori; J. Faist; F. Capasso; D. L. Sivco; A. L. Hutchinson; A. Y. Cho

1997-01-01

267

Modeling Wavelength Switching of Widely Tunable Sampled-Grating DBR Lasers Using Traveling-Wave Model With Digital Filter Approach  

Microsoft Academic Search

A dynamic theoretical model has been proposed for simulating the wavelength switching performance of widely tunable sampled-grating distributed Bragg reflector lasers. The active region of the device is still operated in time domain while the passive parts are first modeled by transfer-matrix method and then transformed into the time domain via digital filter approach. The switching performance and corresponding mode-competition

Lei Dong; Ruikang Zhang; Dingli Wang; Shan Jiang; Yonglin Yu; Shengzhi Zhao; Shuihua Liu

2008-01-01

268

New developments regarding traveling-wave tubes and backward-wave oscillators in the millimeter-wavelength region. I - Electronic engineering  

NASA Astrophysics Data System (ADS)

The steadily increasing importance of the millimetric waves in physical and chemical research applications, and in communication technology has led to the development of a number of backward-wave oscillators and high-power traveling-wave tubes. A description is provided of the procedures employed in connection with these developments for the dimensioning of the individual assemblies, taking into account arising problems and measured data. Basic design features and principles of operation for traveling-wave tubes and backward-wave oscillators are discussed, and the dimensioning of a delay line is considered. Attention is also given to the vacuum window, the transition between hollow waveguide and delay line, and the attenuation between input and output for decoupling.

Glass, E.

269

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

270

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

271

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

272

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

273

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

274

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

275

On the onset of surface wind drift at short fetches as observed in a wind wave flume  

NASA Astrophysics Data System (ADS)

Ocean surface drift is of great relevance to properly model wind waves and specially the early stages of surface waves development and ocean-atmosphere fluxes during incipient wind events and storms. In particular, wave models are not so accurate predicting wave behaviour at short fetches, where wind drift onset might be very important. The onset of surface drift induced by wind and waves is being studied through detailed laboratory measurements in a large wind-wave flume. Wind stress over the water surface, waves and surface drift are measured in the 40m long wind-wave tank at IRPHE, Marseille. While momentum fluxes are estimated directly through the eddy correlation method in a station about the middle of the tank, they provide reference information to the corresponding surface drift onset recorded at rather short non-dimensional fetches. At each experimental run very low wind was on (about 1m/s) for a certain period and suddenly it was constantly accelerated to reach about 13 m/s (as well as 8 and 5 m/s during different runs) in about 15 sec to as long as 600 sec. The wind was kept constant at that high speed for 2 to 10 min, and then suddenly and constantly decelerate to 0. Surface drift values were up to 0.5 cm/s for the highest wind while very distinctive shear was detected in the upper 1.5 cm. Rather linear variation of surface drift was observed with depth. Evolution of the surface drift velocity is analysed and onset behaviour is addressed with particular emphasis in accelerated winds. This work represents a RugDiSMar Project (CONACYT 155793) contribution. The support from ANUIES-ECOS M09-U01 project, CONACYT-187112 Estancia Sabática, and Institute Carnot, is greatly acknowledged.

Ocampo-Torres, Francisco J.; Branger, Hubert; Osuna, Pedro; Robles, Lucia

2014-05-01

276

Short-wavelength multiline erbium-doped fiber ring laser by a broadband long-period fiber grating inscribed in a taper transition  

NASA Astrophysics Data System (ADS)

A stable multiwavelength all-fiber erbium-doped fiber ring laser (EDFRL) based on a broadband long-period fiber grating (LPFG) inscribed in a fiber taper transition is presented. The LPFG’s characteristics were engineered to provide a higher loss at the natural lasing wavelength of the laser cavity. The LPFG inscribed on a taper transition provided a depth greater than 25 dB, and posterior chemical etching provided a broad notch band to inhibit laser generation on the long-wavelength side of the EDF gain. Up to four simultaneous laser wavelengths are generated in the range of 1530–1535 nm.

Anzueto-Sánchez, G.; Martínez-Rios, A.

2014-01-01

277

A 1D model for tides waves and fine sediment in short tidal basins—Application to the Wadden Sea  

NASA Astrophysics Data System (ADS)

In order to simulate the dynamics of fine sediments in short tidal basins, like the Wadden Sea basins, a 1D cross-sectional averaged model is constructed to simulate tidal flow, depth-limited waves, and fine sediment transport. The key for this 1D model lies in the definition of the geometry (width and depth as function of the streamwise coordinate). The geometry is computed by implementing the water level and flow data, from a 2D flow simulation, and the hypsometric curve in the continuity equation. By means of a finite volume method, the shallow-water equations and sediment transport equations are solved. The bed shear stress consists of the sum of shear stresses by waves and flow, in which the waves are computed with a depth-limited growth equation for wave height and wave frequency. A new formulation for erosion of fines from a sandy bed is proposed in the transport equation for fine sediment. It is shown by comparison with 2D simulations and field measurements that a 1D schematization gives a proper representation of the dynamics in short tidal basins.

van Prooijen, Bram Christiaan; Wang, Zheng Bing

2013-12-01

278

A new numerical method for the problem of nonlinear long-short wave interactions  

E-print Network

The scope of this thesis is the development of a new numerical method to address the problem of nonlinear interactions of free-surface gravity waves. More specifically, this study addresses the case of wave interactions ...

Kofiani, Kirki N. (Kirki Nikolaos)

2009-01-01

279

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

280

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

281

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

282

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

283

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

284

Supersonic Ionization Wave Driven by Radiation Transport in a Short-Pulse Laser-Produced Plasma  

Microsoft Academic Search

Through the use of an ultrashort (2ps) optical probe, we have time resolved the propagation of an ionization wave into solid fused silica. This ionization wave results when a plasma is created by the intense irradiation of a solid target with a 2ps laser pulse. We find that the velocity of the ionization wave is consistent with radiation driven thermal

T. Ditmire; E. T. Gumbrell; R. A. Smith; L. Mountford; M. H. Hutchinson

1996-01-01

285

Impact of chirp on soliton trapping of dispersive waves in photonic crystal fiber with two zero dispersive wavelengths  

NASA Astrophysics Data System (ADS)

We present a numerical study of soliton trapping of dispersive waves with the effect of chirp during supercontinuum generation in photonic crystal fibers (PCF) pumped with femtosecond pulses in the anomalous dispersion region. For different propagation length along the PCF, we can see that the evolution of pulse can be divided into three stages: initial broadening stage, dramatic broadening stage and saturation broadening stage. We find a fascinating phenomenon that the intensity of blue-shifted dispersive waves (B-DWs) and red-shifted dispersive waves (R-DWs) will be enhanced with positive chirped. It reveals that the coupling between the Raman soliton and the DW under suitable chirp conditions may be a key mechanism in controlling the spectral broadening and soliton trapping of DW. Numerical study shows that initial chirp dramatically influences both the DW generation, spectral recoil and soliton trapping of DW. In order to clearly display the evolution of soliton trapping of DW by chirped pulses, we observed the spectrogram of output pulses using cross-correlation frequency-resolved optical gating technique (XFROG).

Yang, Hua; Zeng, Qilin; Hu, Hui; Wang, Boyan; Wang, Weibin

2014-08-01

286

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

287

ON THE OPTICAL CONSTANTS OF METALS AT WAVELENGTHS SHORTER THAT THEIR CRITICAL WAVELENGTHS (1)  

E-print Network

154. ON THE OPTICAL CONSTANTS OF METALS AT WAVELENGTHS SHORTER THAT THEIR CRITICAL WAVELENGTHS (1 investigated in the extreme ultraviolet at wavelengths shorter than their critical wavelengths. It was found of electro- magnetic waves in a medium containing free charges is the existence of a critical wavelength Ã?c

Paris-Sud XI, Université de

288

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

289

Effect of the atmosphere on the short-wave boundary of solar UV radiation at the earth surface  

NASA Astrophysics Data System (ADS)

Fluxes of direct solar radiation in the 200-350 nm range at different levels in the atmosphere and at the earth surface were calculated. Rayleigh scattering, absorption by ozone and oxygen molecules, and aerosol attenuation were taken into account. An analysis was made of the relative contribution of these three factors to the attenuation of the solar flux and of their effect on the position of the short-wave boundary of the solar UV radiation.

Banakh, G. F.; Ippolitov, I. I.; Lopasova, T. A.

1986-11-01

290

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

291

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

292

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

Microsoft Academic Search

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

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

2005-01-01

293

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

NASA Astrophysics Data System (ADS)

Hyperspectral imaging is susceptible to a myriad of atmospheric effects that cause undesirable effects when applying advanced processing techniques. Principally, scattering of incoming solar energy and the resulting “haze” produced has a considerable influence on the resulting quality of the data acquired in the ShortWave InfraRed (SWIR) region (850nm to 2500nm) of the electromagnetic spectrum. To alleviate this condition we have devised a polarization system for the Flight Research Laboratory’s (FRL) airborne SWIR hyperspectral imaging system and have collected data from various sources via ground-based and airborne environments. The Polarized SWIR (PSWIR) system we have devised incorporates a linear 90° polarization filter, within a framework that has been attached to FRL’s SWIR system. The polarizer lens is aligned to the 0° axis of the optical slit and can be rotated a full 360°. For the ground-based data collection, the PSWIR was mounted on a z-axis 360° rotation mount which allowed for scanning within the vertical plane as the imager is a push-broom imager that requires motion of the system in order to obtain spatial information. Data was acquired at various polarization orientations in steps of 45° from 0° through to 180°. The data was then analysed using Principle Component Analysis (PCA) and results show that substantial improvement signal-to-noise in higher-order PC’s are obtained in the PSWIR system compared to the SWIR system without polarization. Further, the higher order PC’s derived from the PSWIR system once compared to the SWIR system alone, lead us to conclude that many “artefacts” often ascribed to sensor problems can, in fact, be attributed to unresolved scatter issues in the data. The entire system was then installed aboard FRL’s Twin Otter aircraft and flown over various target materials of interest (man-made, vegetation, soils...) several times over the course of 3-weeks in July/August 2010. As a result of analysing these data, we show that the issue with scattered incoming solar energy is significantly reduced, for the SWIR region, within the airborne environment compared to ground-based acquisition. Furthermore, we also show that the use of the PSWIR system as a method to detect man-made objects does so with a much lower number of false alarms as compared to using the SWIR system alone.

Leblanc, G. E.; Allux, S.

2010-12-01

294

Satellite Estimates of Surface Short-wave Fluxes: Issues of Implementation  

NASA Technical Reports Server (NTRS)

Surface solar radiation reaching the Earth's surface is the primary forcing function of the land surface energy and water cycle. Therefore, there is a need for information on this parameter, preferably, at global scale. Satellite based estimates are now available at accuracies that meet the demands of many scientific objectives. Selection of an approach to estimate such fluxes requires consideration of trade-offs between the use of multi-spectral observations of cloud optical properties that are more difficult to implement at large scales, and methods that are simplified but easier to implement. In this study, an evaluation of such trade-offs will be performed. The University of Maryland Surface Radiation Model (UMD/SRB) has been used to reprocess five years of GOES-8 satellite observations over the United States to ensure updated calibration and improved cloud detection over snow. The UMD/SRB model was subsequently modified to allow input of information on aerosol and cloud optical depth with information from independent satellite sources. Specifically, the cloud properties from the Atmospheric Radiation Measurement (ARM) Satellite Data Analysis Program (Minnis et al., 1995) are used to drive the modified version of the model to estimate surface short-wave fluxes over the Southern Great Plain ARM sites for a twelve month period. The auxiliary data needed as model inputs such as aerosol optical depth, spectral surface albedo, water vapor and total column ozone amount were kept the same for both versions of the model. The estimated shortwave fluxes are evaluated against ground observations at the ARM Central Facility and four satellite ARM sites. During summer, the estimated fluxes based on cloud properties derived from the multi-spectral approach were in better agreement with ground measurements than those derived from the UMD/SRB model. However, in winter, the fluxes derived with the UMD/SRB model were in better agreement with ground observations than those estimated from cloud properties provided by the ARM Satellite Data Analysis Program. During the transition periods, the results were comparable.

Wang, H.; Pinker, Rachel; Minnis, Patrick

2006-01-01

295

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

296

WAVES AT THE NEMATIC-ISOTROPIC V. Popa-Nita  

E-print Network

in the short wavelength limit, while in the long wavelength limit viscous damping becomes im- portant early stage process (nucleation or spinodal decomposition), domain walls (interfaces) soon form. In this paper, we analyze the problem of damping of capillary waves at these interfaces. In the case of a "pure

Sluckin, Tim

297

Single-arm three-wave interferometer for measuring dispersion of short lengths of fiber  

E-print Network

on system parameters, such as required bandwidth, wavelength resolution, and fiber length, are discussed fiber and picosecond pulses from semiconductor film lasers," IEEE J. Lightwave Technol. 2, 464-468 (1984 phase-shift method for the measure of the chromatic dispersion in a single-mode fiber coiled on a cover

Qian, Li

298

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

299

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

300

Short-wavelength (≲6400 A?) room-temperature continuous operation of p-n In0.5(AlxGa1?x)0.5P quantum well lasers  

Microsoft Academic Search

Data are presented demonstrating short-wavelength (≲6400 A?) continuous (cw) laser operation of p-n diode In0.5(AlxGa1?x)0.5P multiple quantum well heterostructure (QWH) lasers grown lattice matched on GaAs substrates using metalorganic chemical vapor deposition. In the range from ?30 °C to room temperature (RT≊300 K, ?≊6395 A?) the threshold current density changes from 2.3×103 A\\/cm2 (?30 °C) to 3.7×103 A\\/cm2 (RT, 300

J. M. Dallesasse; D. W. Nam; D. G. Deppe; N. Holonyak; R. M. Fletcher; C. P. Kuo; T. D. Osentowski; M. G. Craford

1988-01-01

301

Short-wavelength (approx. <6400 A) room-temperature continuous operation of p-n In\\/sub 0. 5\\/(Al\\/sub x\\/Gaââ\\/sub x\\/)\\/sub 0. 5\\/P quantum well lasers  

Microsoft Academic Search

Data are presented demonstrating short-wavelength (approx. <6400 A) continuous (cw) laser operation of p-n diode In\\/sub 0.5\\/(Al\\/sub x\\/Gaââ\\/sub x\\/)\\/sub 0.5\\/P multiple quantum well heterostructure (QWH) lasers grown lattice matched on GaAs substrates using metalorganic chemical vapor deposition. In the range from -30 °C to room temperature (RTapprox. =300 K, lambdaapprox. =6395 A) the threshold current density changes from 2.3 x

J. M. Dallesasse; D. W. Nam; D. G. Deppe; Holonyak N. Jr; R. M. Fletcher; C. P. Kuo; T. D. Osentowski; M. G. Craford

1988-01-01

302

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

303

Computational optimization analysis of a gas-jet target in a laser-plasma short-wave radiation source  

NASA Astrophysics Data System (ADS)

A computational method is developed for optimizing the xenon gas jet used as the target in a laserplasma short-wave radiation source. The method is based on numerical hydrodynamic simulation of the jet flowing from the nozzle into vacuum, followed by computation of the optimization criterion describing the observed intensity of plasma glow. The application of this method permits an unambiguous and objective choice of optical experimental geometries and flow conditions; as a result, the radiation yield can be increased by several times. The calculated results are compared with available experimental data.

Garbaruk, A. V.; Demidov, D. A.; Kalmykov, S. G.; Sasin, M. E.

2011-06-01

304

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

305

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

306

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

PubMed

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

2012-03-01

307

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

308

Ionospheric disturbances produced by chemical releases and the resultant effects on short-wave ionospheric propagation  

NASA Astrophysics Data System (ADS)

As an effective means to actively modify the ionosphere, chemical releases can produce artificial ionospheric holes as a consequence of ionization reduction, which can have a great impact on radio wave propagation. To investigate the morphology control of ionospheric holes by various chemical releases and the resultant effects on radio wave propagation, a quantitative numerical model is developed on the basis of the approximate solutions of the diffusion equation of single-point release in uniform atmosphere. While single-point release produces ellipsoidal ionospheric holes, multipoint release can produce other types of ionospheric holes (such as parabola-like tubular ones), which is strongly dependent on changes in the release species, release altitude, and mass of released neutral gas. Releases of both H2O and SF6 can produce ionospheric holes with a similar spatial extent, but the latter tends to result in clearer boundaries and more pronounced electron density reductions. In addition, either an increase in released amount or releases at higher altitudes can lead to a broader hole. To evaluate the effects of an ionospheric hole on radio wave propagation, three-dimensional ray tracing simulations are performed. The ellipsoidal ionospheric holes can act as a lens focusing and bending radio waves, leading to multiple wave reflections inside the holes. In contrast, in the paraboloid tubular ionospheric holes, the rays can penetrate the disturbed region or reflect back, showing a strong dependence on radio frequency. It is well demonstrated that chemical releases can efficiently give rise to artificial ionospheric disturbances and thus modify ionospheric propagation of radio waves.

Hu, Yaogai; Zhao, Zhengyu; Zhang, Yuannong

2011-07-01

309

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

310

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, ...

Petersen, Mrs.

2014-05-27

311

Short-wave contributions in the storm surge associated with Xynthia, February 2010, western France  

NASA Astrophysics Data System (ADS)

This study aims to hindcast and analyze the storm surge caused by Xynthia, a mid-latitude storm that severely hit the central part of the Bay of Biscay on the 27-28th of February 2010. This storm surge locally exceeded 1.5 m and peaked at the same time as a high spring tide (Bertin et al., 2012). A new storm surge modeling system was applied, based on the unstructured-grid circulation model SELFE (Zhang and Batista, 2008) and the spectral wave model WWM II (Roland et al., 2008). These two models are fully coupled and parallelized and share the same grid and domain decomposition. The modelling system was implemented over the North-East Atlantic Ocean and the space was discretized using an unstructured grid with a resolution ranging from 30 km in Deep Ocean to 25 m in near shore zones. Such a fine resolution was required to properly represent the surf zone. The modelling system resulted in tidal and wave predictions with errors of the order of 2 and 15%, respectively. The storm surge associated with Xynthia was also well predicted along the Bay of Biscay, with root mean square errors of the order of 0.10 m. Numerical experiments were then performed to analyze the physical processes controlling the development of the storm surge and revealed firstly that the wind caused most of the water level anomaly through an Ekman setup process. The comparison between a wave-dependant and a quadratic parameterization to compute wind stress showed that the storm surge was strongly amplified by the presence of steep and young wind-waves, related to their rapid development in the restricted fetch of the Bay of Biscay. The gradient of wave radiation stress contributed to the whole storm surge by about 0.05 to 0.10 m at the available tide gages. Nevertheless, these gages were located in sheltered harbors and modeling results showed that wave-induced setup locally exceeded 0.5 m in areas more exposed to ocean waves. The unstructured grid is currently being extended inland to simulate the flooding associated with Xynthia. Keywords: Xynthia, storm surge, coastal flooding, unstructured grid model, wave setup, friction velocity.

Bertin, X.; Li, K.; Roland, A.; Breilf, J. F.; Chaumillon, E.

2012-04-01

312

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

E-print Network

solvable parts, and further iterates this short-time propagator to longer time. This is essentially the approach of the diffusion Monte Carlo ~DMC! method.1?3 The need for iterations introduces the complication of branching, which is the hallmark... of diffu- sion and Green?s-function Monte Carlo methods.4 Our idea is to develop a short-time propagator via higher-order decom- position that can be applied for a sufficiently long time to project out an excellent approximation to the ground state...

Ciftja, O.; Chin, Siu A.

2003-01-01

313

NASA Wavelength  

NSDL National Science Digital Library

NASA Wavelength is your pathway into a digital collection of Earth and space science resources for educators of all levels - from elementary to college, to out-of-school programs. These resources, developed through funding of the NASA Science Mission Directorate (SMD), have undergone a peer-review process through which educators and scientists ensure the content is accurate and useful in an educational setting. Use NASA Wavelength to quickly and easily locate resources, connect them to other websites using atom feeds, and even share the resources you discover with others through social media and email.

2014-04-07

314

Short-wavelength (approx. <6400 A) room-temperature continuous operation of p-n In/sub 0. 5/(Al/sub x/Ga/sub 1//sub -//sub x/)/sub 0. 5/P quantum well lasers  

SciTech Connect

Data are presented demonstrating short-wavelength (approx. <6400 A) continuous (cw) laser operation of p-n diode In/sub 0.5/(Al/sub x/Ga/sub 1-//sub x/)/sub 0.5/P multiple quantum well heterostructure (QWH) lasers grown lattice matched on GaAs substrates using metalorganic chemical vapor deposition. In the range from -30 /sup 0/C to room temperature (RTapprox. =300 K, lambdaapprox. =6395 A) the threshold current density changes from 2.3 x 10/sup 3/ A/cm/sup 2/ (-30 /sup 0/C) to 3.7 x 10/sup 3/ A/cm/sup 2/ (RT, 300 K). The cw 300 K photopumped laser operation of the same quaternary QWH crystal is an order of magnitude lower in threshold (7 x 10/sup 3/ W/cm/sup 2/, J/sub eq/approx.2.9 x 10/sup 3/ A/cm/sup 2/) than previously reported for this crystal system, and agrees with the successful demonstration of cw 300 K laser diodes at this short wavelength.

Dallesasse, J.M.; Nam, D.W.; Deppe, D.G.; Holonyak N. Jr.; Fletcher, R.M.; Kuo, C.P.; Osentowski, T.D.; Craford, M.G.

1988-11-07

315

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

316

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

317

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

318

Millimeter wavelength thermographic scanner.  

PubMed

Two new types of thermographic instruments sensitive to millimeter-wave electromagnetic radiation have been designed, constructed, and tested. These instruments utilize wavelengths that are three orders of magnitude longer and much more penetrating than those used in conventional infrared thermography. The instruments are capable of detecting apparent thermal variations as small as a fraction of a degree existing at tissue depths of several millimeters below the skin. By comparison, conventional IR thermographic units are limited to sampling radiation emitted only from the surface. The millimeter wave thermographic units are designed to contribute to the clinical detection of breast abnormalities with the specific aim of accurately and noninvasively detecting breast cancer. PMID:7322066

Cacak, R K; Winans, D E; Edrich, J; Hendee, W R

1981-01-01

319

Short-term effectiveness of bi-phase oscillatory waves versus hyperthermia for isolated long head biceps tendinopathy  

PubMed Central

Summary Introduction: Long head biceps (LHB) tendinopathy is a common cause of anterior shoulder pain. Isolated LHB pathology is most common among younger people who practise overhead sports. The authors conducted a short-term prospective randomised study to test the effectiveness of two different methods for the treatment of isolated LHB tendinopathy: biphasic oscillatory waves and hyperthermia. Study design: The study is a prospective randomised study (Level II). Material and methods: The authors identified 20 patients who had clinical and ultrasound (US) evidence of LHB tendinopathy. No patient was a high-level athlete. The patients were randomly assigned to two groups. Group A (10 patients) was treated with bi-phasic oscillatory waves, while Group B received hyperthermia. During the treatment period, no other electromedical therapy, injections with corticosteroids, oral analgesics or nonsteroidal anti-inflammatory drugs were allowed. All the patients were assessed at baseline (T0), immediately after the end of the treatment period (T1) and 6 months after the end of treatment (T2) using a visual analogic scale (VAS) and Constant-Murley Score (CMS). Furthermore, all patients underwent US examinations at T0 and at T1. All the US examinations were performed by the same radiologist. Results: The VAS scores showed a highly statistically significant reduction of pain at T1 both in Group A (65%; p=0,004) and in Group B (50%; p=0,0002). The CMS also showed a statistically significant improvement between the pre-intervention, the post-treatment and the short-term follow-up in both groups. In addition, the peritendinous fluid evident on US examination at T0 was no longer present in all cases at T1. Conclusion: These findings suggest that both bi-phasic oscillatory waves and hyperthermia are able to relieve pain in patients with isolated LHB tendinopathy. This is a Class II level of evidence. PMID:23738257

Oliva, Francesco; Via, Alessio Giai; Rossi, Silvio

2011-01-01

320

Short large-amplitude magnetic structures and whistler wave precursors in a full-particle quasi-parallel shock simulation  

NASA Astrophysics Data System (ADS)

A one-dimensional (1-D) full-particle electromagnetic simulation code (PIC) is used to investigate the role of upstream whistler and low-frequency upstream waves during cyclic reformation of a medium Alfvén Mach number quasi-parallel collisionless shock (magnetic field - shock normal angle = 30°). The ion to electron mass ratio is assumed to be 100. Compared with previous PIC simulations, the upstream region is large enough to allow for the emergence of low-frequency upstream waves by the interaction of backstreaming ions with the solar wind via an ion/ion beam instability in the far upstream region. It is shown that the low-frequency upstream waves steepen up into pulsations (or short large-amplitude magnetic structures (SLAMS)), as has been shown earlier by hybrid simulations. As these pulsations are added to the shock and thus comprise the shock, the upstream edge radiates a phase standing whistler train. This whistler train propagates partway into the newly arriving pulsation. The nonlinear interaction of reflected ions and incoming solar wind ions in the electrostatic potential of the whistler leads to ion trapping and rapid whistler damping. This results in SLAMS consisting of two regions with different ion temperatures. The cyclic reformation is essentially due to the SLAMS being added to the shock and is of larger scale (˜10 ion inertial lengths) as compared with the whistler scale.

Scholer, Manfred; Kucharek, Harald; Shinohara, Iku

2003-07-01

321

Nonlocal wave turbulence in the Charney-Hasegawa-Mima equation: a short review  

E-print Network

Rossby wave turbulence, as modelled by the Charney-Hasegawa-Mima (CHM) equation, is nonlocal in scale. As a result, the formal stationary Kolmogorov-Zakharov solutions of the Rossby wave kinetic equation, which describe local cascades, are not valid. Rather the solution of the kinetic equation is dominated by interactions between the large and small scales. This suggests an alternative analytic approach based on an expansion of the collision integral in a small parameter obtained from scale separation. This expansion approximates the integral collision operator in the kinetic equation by anisotropic diffusion operators in wavenumber space as first shown in a series of papers by Balk, Nazarenko and Zakharov in the early 1990's. In this note we summarize the foundations of this theory and provide the technical details which were absent from the original papers.

Colm Connaughton; Sergey Nazarenko; Brenda Quinn

2010-12-13

322

A tunable continuous wave (CW) and short-pulse optical source for THz brain imaging applications  

NASA Astrophysics Data System (ADS)

We demonstrate recent advances toward the development of a novel 2D THz imaging system for brain imaging applications both at the macroscopic and at the bimolecular level. A frequency-synthesized THz source based on difference frequency generation between optical wavelengths is presented, utilizing supercontinuum generation in a highly nonlinear optical fiber with subsequent spectral carving by means of a fiber Fabry-Perot filter. Experimental results confirm the successful generation of THz radiation in the range of 0.2-2 THz, verifying the enhanced frequency tunability properties of the proposed system. Finally, the roadmap toward capturing functional brain information by exploiting THz imaging technologies is discussed, outlining the unique advantages offered by THz frequencies and their complementarity with existing brain imaging techniques.

Bakopoulos, P.; Karanasiou, I.; Pleros, N.; Zakynthinos, P.; Uzunoglu, N.; Avramopoulos, H.

2009-10-01

323

Combined slope-height measurements of short wind waves: first results from field and laboratory measurements  

Microsoft Academic Search

A new optical instrument has been designed for combined slope\\/height measurements of the small-scale structure of the ocean surface. The compact and rugged sensor head contains two light sources and a short-base CCD stereo camera setup mounted 4 - 6 m above the water surface and looking straight down onto the water surface. It takes stereo images of the specular

Stefan Waas; Bernd Jaehne

1992-01-01

324

Wave function and strange correlator of short-range entangled states.  

PubMed

We demonstrate the following conclusion: If |?? is a one-dimensional (1D) or two-dimensional (2D) nontrivial short-range entangled state and |?? is a trivial disordered state defined on the same Hilbert space, then the following quantity (so-called "strange correlator") C(r,r('))=??|?(r)?(r('))|??/??|?? either saturates to a constant or decays as a power law in the limit |r-r(')|?+?, even though both |?? and |?? are quantum disordered states with short-range correlation; ?(r) is some local operator in the Hilbert space. This result is obtained based on both field theory analysis and an explicit computation of C(r,r(')) for four different examples: 1D Haldane phase of spin-1 chain, 2D quantum spin Hall insulator with a strong Rashba spin-orbit coupling, 2D spin-2 Affleck-Kennedy-Lieb-Tasaki state on the square lattice, and the 2D bosonic symmetry-protected topological phase with Z(2) symmetry. This result can be used as a diagnosis for short-range entangled states in 1D and 2D. PMID:24996105

You, Yi-Zhuang; Bi, Zhen; Rasmussen, Alex; Slagle, Kevin; Xu, Cenke

2014-06-20

325

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

326

Ocean Waves  

NSDL National Science Digital Library

This webpage, from Hyperphysics, provides a detailed explanation of how waves form in the ocean. A series of diagrams show how the water moves as a wave passes by. The site shows how a water wave's speed depends on wavelength, and how the shape of a wave depends on its amplitude. A description of why waves break on a beach is included.

Nave, Carl R.

2010-07-13

327

Miniature indium gallium arsenide short-wave infrared camera for unattended imaging applications  

NASA Astrophysics Data System (ADS)

Indium gallium arsenide (InGaAs) focal plane arrays and cameras have demonstrated significant potential in battlefield applications. Room temperature detectivities, D*, in excess of 1014 cm-(root)Hz/W have enabled night vision imaging under low light level conditions. The 0.9 micrometers to 1.7 micrometers wavelength band allows the use of eye- safe lasers for target designation and covert active illumination. We report here a miniature InGaAs camera designed for unattended ground sensor and robot-mounted applications. The camera is approximately the size of a D- cell battery, weighs less than 200 g. has a 320 X 240 pixel spatial resolution and maintains D* > 1014 cm- (root)Hz/W. The miniature camera is fully self contained. The only input is DC power (3.6 V). The camera has both analog (RS170) and 12-bit digital (LVDS) video outputs. It is intended as a demonstration vehicle for battlefield distributed robotic vision but will find use in other applications as an unattended sensor or rifle site.

Cohen, Marshall J.; O'Grady, Matthew T.; Vermaak, Jacobus S.; Groppe, Joseph V.; Olsen, Gregory H.

2000-07-01

328

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 in the along-shore (along internal-wave crest) direction and 30 km in the cross-shore direction. Spatial

329

Active and passive short-wave infrared and near-infrared imaging for horizontal and slant paths close to ground.  

PubMed

This paper investigates active and passive short-wave infrared (SWIR) imaging for slant paths close to ground. The main sensor, a gated SWIR camera, was collecting both passive and active images along a 2 km long path over an airfield and also from our rooftop laboratory looking over open fields. For some investigations we also used a gated system working in the near-infrared region and thermal as well as color CCD cameras. The sensor was elevated by a lift in steps from 1.6-13.5 m or placed in a rooftop laboratory 13 m above ground. Targets were resolution charts and man targets. The turbulence was measured along the path with anemometers and scintillometers. The image performance was evaluated by measurement of the image blur and also by performing observer perception tests. The results reveal a strong dependence on the sensor height especially during daytime. PMID:23852188

Steinvall, Ove; Elmqvist, Magnus; Chevalier, Tomas; Gustafsson, Ove

2013-07-10

330

Revisiting Coincidence Rate between Gravitational Wave Detection and Short Gamma-Ray Burst for the Advanced and Third Generation  

NASA Astrophysics Data System (ADS)

We use realistic Monte Carlo simulations including both gravitational-wave (GW) and short gamma-ray burst (sGRB) selection effects to revisit the coincident rate of binary systems composed of two neutron stars or a neutron star and a black hole. We show that the fraction of GW triggers that can be observed in coincidence with sGRBs is proportional to the beaming factor at z = 0, but increases with the distance until it reaches 100% at the GW detector horizon distance. When this is taken into account the rate is improved by a factor of three compared to the simple beaming factor correction. We provide an estimate of the performance future GRB detectors should achieve in order to fully exploit the potentiality of the planned third-generation GW antenna Einstein Telescope, and we propose a simple method to constrain the beaming angle of sGRBs.

Regimbau, T.; Siellez, K.; Meacher, D.; Gendre, B.; Boër, M.

2015-01-01

331

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

332

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

333

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

334

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

335

Finite-frequency structural sensitivities of short-period compressional body waves  

NASA Astrophysics Data System (ADS)

We present an extension of the method recently introduced by Zhao & Chevrot for calculating Fréchet kernels from a precomputed database of strain Green's tensors by normal mode summation. The extension involves two aspects: (1) we compute the strain Green's tensors using the Direct Solution Method, which allows us to go up to frequencies as high as 1 Hz; and (2) we develop a spatial interpolation scheme so that the Green's tensors can be computed with a relatively coarse grid, thus improving the efficiency in the computation of the sensitivity kernels. The only requirement is that the Green's tensors be computed with a fine enough spatial sampling rate to avoid spatial aliasing. The Green's tensors can then be interpolated to any location inside the Earth, avoiding the need to store and retrieve strain Green's tensors for a fine sampling grid. The interpolation scheme not only significantly reduces the CPU time required to calculate the Green's tensor database and the disk space to store it, but also enhances the efficiency in computing the kernels by reducing the number of I/O operations needed to retrieve the Green's tensors. Our new implementation allows us to calculate sensitivity kernels for high-frequency teleseismic body waves with very modest computational resources such as a laptop. We illustrate the potential of our approach for seismic tomography by computing traveltime and amplitude sensitivity kernels for high frequency P, PKP and Pdiff phases. A comparison of our PKP kernels with those computed by asymptotic ray theory clearly shows the limits of the latter. With ray theory, it is not possible to model waves diffracted by internal discontinuities such as the core-mantle boundary, and it is also difficult to compute amplitudes for paths close to the B-caustic of the PKP phase. We also compute waveform partial derivatives for different parts of the seismic wavefield, a key ingredient for high resolution imaging by waveform inversion. Our computations of partial derivatives in the time window where PcP precursors are commonly observed show that the distribution of sensitivity is complex and counter-intuitive, with a large contribution from the mid-mantle region. This clearly emphasizes the need to use accurate and complete partial derivatives in waveform inversion.

Fuji, Nobuaki; Chevrot, Sébastien; Zhao, Li; Geller, Robert J.; Kawai, Kenji

2012-07-01

336

Black carbon fractal morphology and short-wave radiative impact: a modelling study  

NASA Astrophysics Data System (ADS)

We investigate the impact of the morphological properties of freshly emitted black carbon aerosols on optical properties and on radiative forcing. To this end, we model the optical properties of fractal black carbon aggregates by use of numerically exact solutions to Maxwell's equations within a spectral range from the UVC to the mid-IR. The results are coupled to radiative transfer computations, in which we consider six realistic case studies representing different atmospheric pollution conditions and surface albedos. The spectrally integrated radiative impacts of black carbon are compared for two different fractal morphologies, which brace the range of recently reported experimental observations of black carbon fractal structures. We also gauge our results by performing corresponding calculations based on the homogeneous sphere approximation, which is commonly employed in climate models. We find that at top of atmosphere the aggregate models yield radiative impacts that can be as much as 2 times higher than those based on the homogeneous sphere approximation. An aggregate model with a low fractal dimension can predict a radiative impact that is higher than that obtained with a high fractal dimension by a factor ranging between 1.1-1.6. Although the lower end of this scale seems like a rather small effect, a closer analysis reveals that the single scattering optical properties of more compact and more lacy aggregates differ considerably. In radiative flux computations there can be a partial cancellation due to the opposing effects of different error sources. However, this cancellation effect can strongly depend on atmospheric conditions and is therefore quite unpredictable. We conclude that the fractal morphology of black carbon aerosols and their fractal parameters can have a profound impact on their radiative forcing effect, and that the use of the homogeneous sphere model introduces unacceptably high biases in radiative impact studies. We emphasise that there are other potentially important morphological features that have not been addressed in the present study, such as sintering and coating of freshly emitted black carbon by films of organic material. Finally, we found that the spectral variation of the absorption cross section of black carbon significantly deviates from a simple 1/? scaling law. We therefore discourage the use of single-wavelength absorption measurements in conjunction with a 1/? scaling relation in broadband radiative forcing simulations of black carbon.

Kahnert, M.; Devasthale, A.

2011-11-01

337

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

338

[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

339

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

340

Gravity waves generated by convection during TWP-ICE: I. Inertia-gravity waves  

NASA Astrophysics Data System (ADS)

Gravity waves are analyzed in radiosonde soundings taken during the Tropical Warm Pool-International Cloud Experiment (TWP-ICE) campaign. The properties of the inertia-gravity waves are analyzed in Part I, whereas Part II focuses on high-frequency gravity waves. Two groups of inertia-gravity waves are detected: group L (Long vertical wavelength) in the middle stratosphere during the suppressed monsoon period and group S (Short vertical wavelength) in the lower stratosphere during the monsoon break period. Waves belonging to group L propagate to the southeast with a mean intrinsic period of 35 h and have vertical and horizontal wavelengths of about 5-6 km and 3000-6000 km, respectively. Ray-tracing calculations indicate that these waves originate from a deep convective region near Indonesia. Waves belonging to group S propagate to the south-southeast with an intrinsic period, vertical wavelength, and horizontal wavelength of about 45 h, 2 km, and 2000-4000 km, respectively. These waves appear to originate from convection in the vicinity of New Guinea.

Hankinson, Mai C. N.; Reeder, M. J.; Lane, T. P.

2014-05-01

341

Hydromagnetic wave heating of low density interstellar gas  

NASA Technical Reports Server (NTRS)

The origin of the observed wave spectrum for hot gas in the ISM is considered theoretically. The governing equations for the generation, propagation, and dissipation of compressive waves are reviewed, and particular attention is given to the heating of warm neutral gas and the implications for radio-wave scattering. It is shown that little power from interactions between SN shocks and hot coronal gas reaches short wavelengths, and that scintillation probably does not originate in a warm weakly ionized gas.

Zweibel, Ellen G.; Ferriere, Katia M.; Shull, J. Michael

1988-01-01

342

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

343

The parallel-antiparallel signal difference in double-wave-vector diffusion-weighted MR at short mixing times: A phase evolution perspective  

NASA Astrophysics Data System (ADS)

Experiments with two diffusion weightings applied in direct succession in a single acquisition, so-called double- or two-wave-vector diffusion-weighting (DWV) experiments at short mixing times, have been shown to be a promising tool to estimate cell or compartment sizes, e.g. in living tissue. The basic theory for such experiments predicts that the signal decays for parallel and antiparallel wave vector orientations differ by a factor of three for small wave vectors. This seems to be surprising because in standard, single-wave-vector experiments the polarity of the diffusion weighting has no influence on the signal attenuation. Thus, the question how this difference can be understood more pictorially is often raised. In this rather educational manuscript, the phase evolution during a DWV experiment for simple geometries, e.g. diffusion between parallel, impermeable planes oriented perpendicular to the wave vectors, is considered step-by-step and demonstrates how the signal difference develops. Considering the populations of the phase distributions obtained, the factor of three between the signal decays which is predicted by the theory can be reproduced. Furthermore, the intermediate signal decay for orthogonal wave vector orientations can be derived when investigating diffusion in a box. Thus, the presented “phase gymnastics” approach may help to understand the signal modulation observed in DWV experiments at short mixing times.

Finsterbusch, Jürgen

2011-01-01

344

Short submillimeter operation of the Planar Orotron  

NASA Astrophysics Data System (ADS)

Recent experimental results demonstrating Planar Orotron operation in the short submillimeter wavelength regime of 1 mm to 400 ?m are presented. This device belongs to the class of Smith-Purcell free electron lasers that utilize periodic metal grating structures to support electromagnetic waves with phase velocities lower than the speed of light. The J· E interaction between this slow wave and a mildly relativistic electron beam (25-150 keV) produces coherent radiation. Supporting theory involving dispersive and tuning characteristics of specific grating geometries is discussed. Single-particle gain calculations for fundamental and higher order mode operation are presented.

Price, E. J.; Walsh, J. E.; Kimmitt, M. F.

1991-07-01

345

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

346

Power measurements at submillimetre wavelengths  

Microsoft Academic Search

Techniques for power measurements in the submillimeter wavelength region for lasers and similar sources are considered. Applications of submillimeter waves in plasma diagnostics, stratospheric monitoring, spectroscopy, radar and communications, component and system specification and design and spectroradiometry are indicated, and a distinction is made between continuum and narrow-band radiation sources. Examples of power measurement problems encountered for lasers and other

T. G. Blaney

1980-01-01

347

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.

Foundation, Wgbh E.

2004-02-20

348

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

349

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

350

Short Wavelength Modes 5.1 Introduction  

E-print Network

and the electron skin depth c/pe are related through ipe c = r mi me 4nTi B2 = r mi 2me i, where i = 8nTi/B2 because ion dynamics tends to be adiabatic, ni - e Ti n0, (ki)2 Ã? 1. However, the slab ITG mode persists

Saskatchewan, University of

351

Physics of short-wavelength-laser design  

SciTech Connect

The physics and design of vuv and soft x-ray lasers pumped by ICF class high intensity infrared laser drivers are described (for example, the SHIVA laser facility at LLNL). Laser design and physics issues are discussed in the case of a photoionization pumping scheme involving Ne II and line pumping schemes involving H-like and He-like neon.

Hagelstein, P.L.

1981-01-01

352

Two-wavelength pulsed-laser ranging system with an accuracy of centimeters  

Microsoft Academic Search

Theoretical analysis and experimental results of a two-wavelength pulsed laser ranging system are presented. In the system, a short Q-switched pulsewidth Nd:YAG laser and its second harmonic wave are used, MCP\\/PMT and APD are used to detect 0.53 micrometers and 1.06 micrometers , respectively, and a multichannel analyzer with CFD is used to measure the time interval of the two

Shengyuan Zhong; Pin Cheng

1993-01-01

353

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

354

Spin pumping by parametrically excited short-wavelength spin waves H. Kurebayashi, O. Dzyapko, V. E. Demidov, D. Fang, A. J. Ferguson et al.  

E-print Network

of tris(8-hydroxyquinoline)iron: Experimental and theoretical investigation Appl. Phys. Lett. 99, 153306 (2011) Magnetic properties of tris(8-hydroxyquinoline)iron: Experimental and theoretical investigation

Demokritov, S.O.

355

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

356

An evaluation of safety guidelines to restrict exposure to stray radiofrequency radiation from short-wave diathermy units  

NASA Astrophysics Data System (ADS)

Short-wave diathermy (SWD), a form of radiofrequency radiation used therapeutically by physiotherapists, may be applied in continuous (CSWD) or pulsed (PSWD) mode using either capacitive or inductive methods. Stray radiation emitted by these units may exceed exposure guidelines close to the equipment. Discrepant guidelines exist on a safe distance from an operating unit for operators and other personnel. Stray electric (E-field) and magnetic (H-field) field strengths from 10 SWD units in six departments were examined using a PMM 8053 meter and two isotropic probes (EP-330, HP-032). A 5 l saline phantom completed the patient circuit. Measurements were recorded in eight directions between 0.5 m and 2 m at hip and eye levels while the units operated at maximum output and data compared to current guidelines. Results found stray fields from capacitive CSWD fell below operator limits at 2 m (E-field 4.8-39.8 V/m; H-field 0.015-0.072 A/m) and at 1 m for inductive CSWD (E-field 0-36 V/m; H-field 0.01-0.065 A/m). Capacitive PSWD fields fell below the limits at 1.5 m (E-field 1.2-19.9 V/m; H-field 0.002-0.045 A/m) and at 1m for inductive PSWD (E-field 0.7-4.0 V/m; H-field 0.009-0.03 A/m). An extra 0.5 m was required before fields fell below the guidelines for other personnel. These results demonstrate, under a worst case scenario, emissions from SWD exceed the guidelines for operators at distances currently recommended as safe. Future guidelines should include recommendations for personnel other than physiotherapists.

Shields, Nora; O'Hare, Neil; Gormley, John

2004-07-01

357

Soft x-ray laser holography with wavelength P. W. Wachulak, M. C. Marconi,* R. A. Bartels, C. S. Menoni, and J. J. Rocca  

E-print Network

Soft x-ray laser holography with wavelength resolution P. W. Wachulak, M. C. Marconi,* R. A and nanotechnology. Shortly after the intro- duction of in-line holography by Gabor [1], the feasibility demonstration of soft x-ray holography with wave- length resolution. 2. EXPERIMENT The hologram's lateral

Rocca, Jorge J.

358

Night illumination in the near- and short-wave infrared spectral bands and the potential for silicon and indium-gallium-arsenide imagers to perform night targeting  

NASA Astrophysics Data System (ADS)

On a moonless night, the primary source of natural illumination in the near infrared and short-wave infrared spectral bands is airglow. We use data gathered by astronomers and atmospheric scientists to estimate the magnitude and variability of airglow ground illumination. Based on that foundation, we analyze the target acquisition performance of imagers that use silicon and indium-gallium-arsenide focal plane arrays.

Vollmerhausen, Richard H.; Driggers, Ronald G.; Hodgkin, Van A.

2013-04-01

359

Directional spectra of ocean waves from microwave backscatter: A physical optics solution with application to the short-pulse and two-frequency measurement techniques  

NASA Technical Reports Server (NTRS)

Two simple microwave radar techniques that are potentially capable of providing routine satellite measurements of the directional spectrum of ocean waves were developed. One technique, the short pulse technique, makes use of very short pulses to resolve ocean surface wave contrast features in the range direction; the other technique, the two frequency correlation technique makes use of coherency in the transmitted waveform to detect the large ocean wave contrast modulation as a beat or mixing frequency in the power backscattered at two closely separated microwave frequencies. A frequency domain analysis of the short pulse and two frequency systems shows that the two measurement systems are essentially duals; they each operate on the generalized (three frequency) fourth-order statistical moment of the surface transfer function in different, but symmetrical ways, and they both measure the same directional contrast modulation spectrum. A three dimensional physical optics solution for the fourth-order moment was obtained for backscatter in the near vertical, specular regime, assuming Gaussian surface statistics.

Jackson, F. C.

1979-01-01

360

Langmuir waves in magnetic holes: source mechanism and consequences  

SciTech Connect

Plasma wave observations from the Ulysses spacecraft indicate that electrostatic waves at frequencies approximately equal to the electron plasma frequency f{sub pe} are commonly found in magnetic holes. Magnetic holes are short-duration reductions in the amplitude of the interplanetary magnetic field. A model of the electron dynamics in a magnetic hole suggests that the waves are generated by electron beams of thermal energies, formed by adiabatic focusing of the electrons. These waves, presumed to be Langmuir mode, will have extremely short wavelengths, of the order of 100-1000 m. Such waves, observed in the solar wind, would be significantly Doppler shifted, which can be measured by the plasma wave receiver. The prevalence of waves in magnetic holes suggests that the magnetic structures are not stable and can provide constraints on their formation and evolution.

MacDowall, R. J.; Lin, N.; Kellogg, P. J.; Balogh, A.; Forsyth, R. J.; Neugebauer, M. [Laboratory for Extraterrestrial Physics, NASA Goddard Space Flight Center, Greenbelt, Maryland 20771 (United States); University of Minnesota, Minneapolis, Minnesota 55455 (United States); Blackett Laboratory, Imperial College, London SW7 2BZ (United Kingdom); Jet Propulsion Laboratory, Pasadena, California 91109 (United States)

1996-07-20

361

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

362

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

363

Short wave infrared InGaAs focal plane arrays detector: the performance optimization of photosensitive element  

NASA Astrophysics Data System (ADS)

Significant progress has been achieved in technology of the InGaAs focal plane arrays (FPA) detector operating in short wave infrared (SWIR) last two decades. The no cryogenic cooling, low manufacturing cost, low power, high sensitivity and maneuverability features inherent of InGaAs FPA make it as a mainstream SWIR FPA in a variety of critical military, national security, aerospace, telecommunications and industrial applications. These various types of passive image sensing or active illumination image detecting systems included range-gated imaging, 3-Dimensional Ladar, covert surveillance, pulsed laser beam profiling, machine vision, semiconductor inspection, free space optical communications beam tracker, hyperspectroscopy imaging and many others. In this paper the status and perspectives of hybrid InGaAs FPA which is composed of detector array (PDA) and CMOS readout integrate circuit (ROIC) are reviewed briefly. For various low light levels applications such as starlight or night sky illumination, we have made use of the interface circuit of capacitive feedback transimpedance amplifier (CTIA) in which the integration capacitor was adjustable, therefore implements of the physical and electrical characteristics matches between detector arrays and readout intergrate circuit was achieved excellently. Taking into account the influences of InGaAs detector arrays' optoelectronic characteristics on performance of the FPA, we discussed the key parameters of the photodiode in detailed, and the tradeoff between the responsivity, dark current, impedance at zero bias and junction capacitance of photosensitive element has been made to root out the impact factors. As a result of the educed approach of the photodiode's characteristics optimizing which involve with InGaAs PDA design and process, a high performance InGaAs FPA of 30um pixel pitch and 320×256 format has been developed of which the response spectrum range over 0.9um to 1.7um, the mean peak detectivity (?=1.55?m) was 6×1012 cmHz1/2W-1 and dynamics range reached 68 dB at room temperature. Making use of the fabricated 320×256 InGaAs FPA, the concerning objects can be imaged in the low light level or nightglow background.

Gao, Xin-jiang; Tang, Zun-lie; Zhang, Xiu-chuan; Chen, Yang; Jiang, Li-qun; Cheng, Hong-bing

2009-07-01

364

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

365

Stability of traveling wave solutions to the Whitham equation  

NASA Astrophysics Data System (ADS)

The Whitham equation was proposed as an alternate model equation for the simplified description of unidirectional wave motion at the surface of an inviscid fluid. An advantage of the Whitham equation over the KdV equation is that it provides a more faithful description of short waves of small amplitude. Recently, Ehrnström and Kalisch [19] established that the Whitham equation admits periodic traveling-wave solutions. The focus of this work is the stability of these solutions. The numerical results presented here suggest that all large-amplitude solutions are unstable, while small-amplitude solutions with large enough wavelength L are stable. Additionally, periodic solutions with wavelength smaller than a certain cut-off period always exhibit modulational instability. The cut-off wavelength is characterized by kh0=1.145, where k=2?/L is the wave number and h0 is the mean fluid depth.

Sanford, Nathan; Kodama, Keri; Carter, John D.; Kalisch, Henrik

2014-06-01

366

Waves and Scales in Heterogeneous Rocks  

NASA Astrophysics Data System (ADS)

In heterogeneous, fluid saturated rocks, scattering effects, and viscoelastic fluid effects cause seismic waves to be dispersive. An important issue for seismic imaging and interpretation is that the inferred velocities depend not only on the rock and fluid properties, but also on the scale and frequency of measurement. This dissertation aims at understanding the frequency-dependent fluid effects, and the scale-dependent scattering effects on seismic velocities, and gives practical methods for estimating the velocity dispersion. A simple technique is presented to relate high -frequency to low-frequency seismic velocity in saturated, anisotropic rocks. At very low frequencies fluid flow equilibrates the wave induced pore pressure gradients. At very high frequencies, regions of unequilibrated pore pressures make the rock stiffer, increasing the wave velocity. The formulation avoids assumptions of idealized crack geometries, and limitations of low crack densities, by utilizing measured pressure dependence of dry rock compliances. The velocity is found to depend on the frequency, distribution of crack -like porosity, intrinsic anistropy, fluid modulus, and effective pressure. Scale-dependence of velocities in heterogeneous rocks is investigated by studying wave propagation in 1 -dimensional stratified media, and in 2- and 3-dimensional random heterogeneous media. Velocities are faster in the short wavelength, ray theory limit than in the long wavelength, effective medium limit. A simple practical upscaling recipe that successively uses a local effective medium average, and then applies ray theory appears to accurately estimate arrival times in layered media when neither ray nor effective medium theories can be used. In 2- and 3-dimensional heterogeneous media, in addition to the 1-dimensional scale effects, there is a further velocity shift at short wavelengths due to fast path effect. Short wavelengths tend to diffract around slower heterogeneities, biasing the traveltimes to lower values. Statistics of the traveltime fluctuations contain information about the spatial variability of the medium. The short and long wavelength limits are modeled using ray and effective medium theories, and numerical simulations are used to study the transition.

Mukerji, Tapan

1995-01-01

367

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.

368

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.

369

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

370

Method of Controlling Lasing Wavelength(s)  

NASA Technical Reports Server (NTRS)

A method is provided to control the lasing wavelength of a laser material without changing or adjusting the mechanical components of a laser device, The rate at which the laser material is pumped with the pumping energy is controlled so that lasing occurs at one or more lasing wavelengths based on the rate. The lasing wavelengths are determined by transition lifetimes and/or energy transfer rates.

Barnes, Norman P. (Inventor); Murray, Keith E. (Inventor); Hutcheson, Ralph L. (Inventor)

2000-01-01

371

Three-field photometer observations of short-period gravity wave intrinsic parameters in the 80 to 100 km height region  

NASA Astrophysics Data System (ADS)

A three-field photometer (3FP) for making observations of airglow in the Mesosphere Lower Thermosphere (MLT) region has been operated at the center of the large MF aerial array located near Adelaide (138°E, 35°S) since 1993. Observations of the 557.7 nm airglow intensity emitted by atomic oxygen (OI) at heights near 97 km and the 730.0 nm airglow intensity emitted by hydroxyl (OH) near 87 km have been made simultaneously with MF spaced antenna observations of wind velocities in the 80-100 km height region. The 3FP measures the intensity of the 557.7 nm airglow in three fields separated by about 13 km at heights near 97 km, and then the intensity of the 730 nm airglow in three fields separated by about 12 km at heights near 87 km, on a 60 s cycle. These data have been analyzed to yield gravity wave observed phase speeds and horizontal wavelengths. Simultaneous MF radar data have been analyzed to yield measurements of the neutral wind velocity in 2 km height steps in the 80-100 km height interval every 2 min, and these have been used together with the observed wave parameters to calculate intrinsic gravity wave parameters. This paper presents a very brief overview of the system, the motivation for the work, and preliminary analysis of the data from 1995 until 2000.

Reid, I. M.; Woithe, J. M.

2005-11-01

372

Observationally constrained modeling of sound in curved ocean internal waves: examination of deep ducting and surface ducting at short range.  

PubMed

A study of 400 Hz sound focusing and ducting effects in a packet of curved nonlinear internal waves in shallow water is presented. Sound propagation roughly along the crests of the waves is simulated with a three-dimensional parabolic equation computational code, and the results are compared to measured propagation along fixed 3 and 6 km source/receiver paths. The measurements were made on the shelf of the South China Sea northeast of Tung-Sha Island. Construction of the time-varying three-dimensional sound-speed fields used in the modeling simulations was guided by environmental data collected concurrently with the acoustic data. Computed three-dimensional propagation results compare well with field observations. The simulations allow identification of time-dependent sound forward scattering and ducting processes within the curved internal gravity waves. Strong acoustic intensity enhancement was observed during passage of high-amplitude nonlinear waves over the source/receiver paths, and is replicated in the model. The waves were typical of the region (35 m vertical displacement). Two types of ducting are found in the model, which occur asynchronously. One type is three-dimensional modal trapping in deep ducts within the wave crests (shallow thermocline zones). The second type is surface ducting within the wave troughs (deep thermocline zones). PMID:21895060

Duda, Timothy F; Lin, Ying-Tsong; Reeder, D Benjamin

2011-09-01

373

Pulsed wideband orotrons of millimeter and submillimeter waves  

NASA Astrophysics Data System (ADS)

We have developed a series of low-voltage orotrons operated in the short-wave part of the millimeter and long-wave section of the submillimeter wavelength range. The use of an open resonator as the electrodynamic system of the orotron ensures high stability of the radiation frequency and a wide band of frequency tuning. The output orotron power achieved experimentally amounts to hundreds of milliwatts, which is sufficient for many promising spectroscopy methods.

Bratman, V. L.; Gintsburg, V. A.; Grishin, Yu. A.; Dumesh, B. S.; Rusin, F. S.; Fedotov, A. É.

2006-11-01

374

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

375

Note: A large aperture four-mirror reflective wave-plate for high-intensity short-pulse laser experiments  

NASA Astrophysics Data System (ADS)

We report on a four-mirror reflective wave-plate system based on a phase-shifting mirror (PSM) for a continuous variation of elliptical polarization without changing the beam position and direction. The system presented and characterized here can replace a conventional retardation plate providing all advantages of a PSM, such as high damage-threshold, large scalability, and low dispersion. This makes reflective wave-plates an ideal tool for ultra-high power laser applications.

Aurand, B.; Rödel, C.; Zhao, H.; Kuschel, S.; Wünsche, M.; Jäckel, O.; Heyer, M.; Wunderlich, F.; Kaluza, M. C.; Paulus, G. G.; Kuehl, T.

2012-03-01

376

Note: A large aperture four-mirror reflective wave-plate for high-intensity short-pulse laser experiments.  

PubMed

We report on a four-mirror reflective wave-plate system based on a phase-shifting mirror (PSM) for a continuous variation of elliptical polarization without changing the beam position and direction. The system presented and characterized here can replace a conventional retardation plate providing all advantages of a PSM, such as high damage-threshold, large scalability, and low dispersion. This makes reflective wave-plates an ideal tool for ultra-high power laser applications. PMID:22462970

Aurand, B; Rödel, C; Zhao, H; Kuschel, S; Wünsche, M; Jäckel, O; Heyer, M; Wunderlich, F; Kaluza, M C; Paulus, G G; Kuehl, T

2012-03-01

377

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

378

Identification of insect-damaged wheat kernels using short-wave near-infrared hyperspectral and digital colour imaging  

Microsoft Academic Search

Healthy wheat kernels and wheat kernels damaged by the feeding of the insects: rice weevil (Sitophilus oryzae), lesser grain borer (Rhyzopertha dominica), rusty grain beetle (Cryptolestes ferrugineus), and red flour beetle (Tribolium castaneum) were scanned using a near-infrared (NIR) hyperspecrtal imaging system (700–1100nm wavelength range) and a colour imaging system. Dimensionality of hyperspectral data was reduced and statistical and histogram

Chandra B. Singh; Digvir S. Jayas; Jitendra Paliwal; Noel D. G. White

2010-01-01

379

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

380

Wave Packet  

Microsoft Academic Search

A wave packet is a concentrated train of (quantum) waves of various wavelengths or momenta with the property that the packet\\u000a is confined within a small region of space. Such a packet can be constructed by adding a very large number of waves so chosen\\u000a that their sum interferes destructively everywhere except in a small region. If harmonic waves of

Helge Kragh

381

Simultaneous Triggered Collapse of the Presolar Dense Cloud Core and Injection of Short-Lived Radioisotopes by a Supernova Shock Wave  

E-print Network

Cosmochemical evidence for the existence of short-lived radioisotopes (SLRI) such as $^{26}$Al and $^{60}$Fe at the time of the formation of primitive meteorites requires that these isotopes were synthesized in a massive star and then incorporated into chondrites within $\\sim 10^6$ yr. A supernova shock wave has long been hypothesized to have transported the SLRI to the presolar dense cloud core, triggered cloud collapse, and injected the isotopes. Previous numerical calculations have shown that this scenario is plausible when the shock wave and dense cloud core are assumed to be isothermal at $\\sim 10$ K, but not when compressional heating to $\\sim 1000$ K is assumed. We show here for the first time that when calculated with the FLASH2.5 adaptive mesh refinement (AMR) hydrodynamics code, a 20 km/sec shock wave can indeed trigger the collapse of a 1 $M_\\odot$ cloud while simultaneously injecting shock wave isotopes into the collapsing cloud, provided that cooling by molecular species such as H$_2$O, CO$_2$, and H$_2$ is included. These calculations imply that the supernova trigger hypothesis is the most likely mechanism for delivering the SLRI present during the formation of the solar system.

Alan P. Boss; Sergei I. Ipatov; Sandra A. Keiser; Elizabeth A. Myhill; Harri A. T. Vanhala

2008-09-18

382

Finite difference simulations of seismic scattering Implications for the propagation of short-period seismic waves in the crust and models of crustal heterogeneity  

NASA Technical Reports Server (NTRS)

Synthetic seismographs that were obtained by the finite difference method are presently applied to the study of elastic and acoustic wave scattering in two-dimensional media with random spatial variations in seismic velocity. The seismograms are analyzed to determine the variation in travel times and waveforms across arrays of receivers. The random media with Gaussian and exponential correlation functions considered differ in the spectral falloff of their velocity fluctuations at wavelengths smaller than 2pi times the correlation distance. It is found that alternative models of crustal heterogeneity can be tested by improved measurements of the frequency dependence of the crustal Q at frequencies greater than about 1 Hz, assuming that scattering is responsible for most of the attenuation at such frequencies.

Frankel, A.; Clayton, R. W.

1986-01-01

383

Dense core compression and fragmentation induced by the scattering of hydromagnetic waves  

E-print Network

We have performed 2D hydromagnetic simulations with an adaptive mesh refinement code to examine the response of a pre-existing initially spherical dense core to a non-linear fast-mode wave. One key parameter is the ratio of the wavelength to the initial core radius. If that ratio is large and the wave amplitude is sufficient, significant compression of the core occurs, as envisaged by Myers & Lazarian (1998) in their "turbulent cooling flow" picture. For smaller values of that ratio, an initial value of the ratio of the thermal pressure to magnetic pressure of 0.2, and sufficiently large wave amplitude, the scattering induces the production of dense substructure in the core. This substructure may be related to that detected in the dense core associated with the cyanopolyyne peak in TMC-1. Our simulations also show that short-wavelength waves, contrary to large-wavelength waves, do not confine dense cores.

S. Van Loo; S. A. E. G. Falle; T. W. Hartquist

2007-01-05

384

Broadband wavelength conversion of incoherent light in silicon nanowaveguides  

Microsoft Academic Search

We demonstrate broadband wavelength conversion of an incoherent light source via four-wave mixing in a silicon rib nanowaveguide. We observe a conversion efficiency of -24 dB over the entire wavelength range of the incoherent source. OCIS codes: (190.4380) Nonlinear optics, four-wave mixing; (130.7405) Wavelength conversion devices While the telecom band has benefited greatly from readily available sources and detectors, the

Ryan K. W. Lau; Yoshitomo Okawachi; Michael Menard; Michal Lipson; Alexander L. Gaeta

2011-01-01

385

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

386

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

387

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

Microsoft Academic Search

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

Corey T Watson; Krzysztof P Lubieniecki; Ellis Loew; William S Davidson; Felix Breden

2010-01-01

388

TRIGGERING COLLAPSE OF THE PRESOLAR DENSE CLOUD CORE AND INJECTING SHORT-LIVED RADIOISOTOPES WITH A SHOCK WAVE. I. VARIED SHOCK SPEEDS  

SciTech Connect

The discovery of decay products of a short-lived radioisotope (SLRI) in the Allende meteorite led to the hypothesis that a supernova shock wave transported freshly synthesized SLRI to the presolar dense cloud core, triggered its self-gravitational collapse, and injected the SLRI into the core. Previous multidimensional numerical calculations of the shock-cloud collision process showed that this hypothesis is plausible when the shock wave and dense cloud core are assumed to remain isothermal at approx10 K, but not when compressional heating to approx1000 K is assumed. Our two-dimensional models with the FLASH2.5 adaptive mesh refinement hydrodynamics code have shown that a 20 km s{sup -1} shock front can simultaneously trigger collapse of a 1 M{sub sun} core and inject shock wave material, provided that cooling by molecular species such as H{sub 2}O, CO, and H{sub 2} is included. Here, we present the results for similar calculations with shock speeds ranging from 1 km s{sup -1} to 100 km s{sup -1}. We find that shock speeds in the range from 5 km s{sup -1} to 70 km s{sup -1} are able to trigger the collapse of a 2.2 M{sub sun} cloud while simultaneously injecting shock wave material: lower speed shocks do not achieve injection, while higher speed shocks do not trigger sustained collapse. The calculations continue to support the shock-wave trigger hypothesis for the formation of the solar system, though the injection efficiencies in the present models are lower than desired.

Boss, Alan P.; Keiser, Sandra A.; Ipatov, Sergei I.; Myhill, Elizabeth A.; Vanhala, Harri A. T., E-mail: boss@dtm.ciw.ed, E-mail: keiser@dtm.ciw.ed, E-mail: siipatov@hotmail.co, E-mail: elizabeth.myhill@marymount.ed, E-mail: HarriVanhala@ncesse.or [Department of Terrestrial Magnetism, Carnegie Institution of Washington, 5241 Broad Branch Road, NW, Washington, DC 20015-1305 (United States)

2010-01-10

389

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

390

Study of All-Optical Wavelength Conversion and Regeneration Subsystems for use in Wavelength Division  

E-print Network

the signal to noise ratio (SNR). Chromatic dispersion affects the pulse shape, while different types, the noise properties of the converted signal generated by the four-wave mixing based wavelength conversion are based on the non-linear four-wave mixing process which occurs when fields with proper spectral and power

Kouroupetroglou, Georgios

391

The short envelope soliton dynamics in inhomogeneous dispersive media with allowance for stimulated scattering by damped low-frequency waves  

NASA Astrophysics Data System (ADS)

We consider the soliton dynamics in terms of the extended nonlinear Schrödinger equation taking into account the inhomogeneous linear second-order dispersion (SOD) and stimulated scattering by damped low-frequency waves (SSDW). It is shown that the wave number downshift due to SSDW is compensated by an upshift due to the SOD decrease on the spatial coordinate. A new class of stationary nonlinear localized solutions (solitons) arising as an equilibrium of SSDW and decreasing spatial SOD is found analytically within the framework of the extended inhomogeneous nonlinear Schrödinger equation. A regime of the dynamic equilibrium of SSDW and inhomogeneous dispersive medium with the soliton parameters periodically varied in time is found. Analytical and numerical results are in good agreement for this regime.

Aseeva, N. V.; Gromov, E. M.; Tyutin, V. V.

2013-08-01

392

A short-term admission improved brachial–ankle pulse wave velocity in type 2 diabetic patients  

Microsoft Academic Search

Brachial–ankle pulse wave velocity (baPWV) is a non-invasive method for assessing arterial stiffness associated with atherosclerosis. We examined whether baPWV could improve during a 2-week hospital-based education program in patients with type 2 diabetes and whether improvement associates with changes in known atherogenic risk factors. Body mass index (BMI), blood pressure (BP), fasting plasma glucose (FPG), insulin, lipid profiles and

Akemi Yamamoto; Yasuyuki Katayama; Koji Tomiyama; Hiroshi Hosoai; Fumihiko Hirata; Hiroko Yasuda

2005-01-01

393

Yield estimation of Novaya Zemlya explosions from short-period body waves. Final technical report, June 1987-June 1988  

SciTech Connect

This study investigates the characteristics of Novaya Zemlya explosions using various body wave phases. This information will be used to calibrate the yields of these explosions. The azimuthal variation of amplitude for the Novaya Zemlya explosions as seen from WWSSN recordings indicates that there is a strong component of near-source heterogeneity due to multiple-source excitation, near-source structural heterogeneity, or source anisotropy. The systematic azimuthal variation in amplitude may be modeled with a sin (2 Theta) curve, which allows an estimate of the magnitude bias due to certain network-station distributions. Several events that have an azimuthal variation in amplitude which departs from a sin (2 Theta) curve may be possible multiple explosions. Clear pP and pPcP depth phases can be observed in deconvolved teleseismic P-wave and PcP-wave source time functions from Novaya Zemlya events. With few exceptions, pP and pPcP delay times show a systematic increase with increasing size. Relative explosion-source size estimates are presented based on spectral measures of P, PcP, and P diff at EKA and WRA arrays. These spectral energy measurements may be correlated with the mb estimates to provide an independent calibration of magnitudes. The time-domain measurements of P'P' for Novaya Zemlya recorded on WWSSN stations are used to provide a calibration of the mb estimates from P waves which are quite often clipped for large events. Using a distance-amplitude correction obtained from the data set, the mb estimates for P'P' are computed using a generalized linear model.

Chan, W.W.; McLaughlin, K.L.; Cessaro, R.K.; Marshall, M.E.; Lees, A.C.

1988-08-01

394

Operation of a Smith-Purcell free-electron laser at submillimeter wavelengths  

NASA Astrophysics Data System (ADS)

Experimental results demonstrating Planar Orotron operation in the submillimeter wavelength regime of 1 cm to 400 microns are presented. This device belongs to the class of Smith-Purcell free-electron lasers that utilize periodic metal grating structures to support electromagnetic waves with phase velocities slower than the speed of light. The J(vector) * E(vector) interaction between this slow wave and a mildly relativistic electron beam (15-130 keV) produces coherent radiation. Dispersion, electronic tuning, single particle gain, and start oscillation current expressions are developed for unique grating geometries that are seen to possess superior high frequency and tuning capabilities. Experimental data taken over a wide spectral range is extensively compared to the theoretical developments and excellent agreement is seen. Comparing the experimentally measured power of the device to a generic power model has resulted in valuable insights into designing device parameters that will optimize short wavelength operation. The experimental observation of multiple modes of laser operation has led to the development of several new models of how the device works, including one that links the TM dispersion formalism with the viewpoint of Smith and Purcell. This viewpoint is significant in that it allows for a statement on the ultimate short wavelength limits of the device to be made.

Price, Edwin James

395

Operation of a Smith-Purcell Free-Electron Laser at Submillimeter Wavelengths  

NASA Astrophysics Data System (ADS)

Experimental results demonstrating Planar Orotron operation in the submillimeter wavelength regime of 1 cm to 400 ?m are presented. This device belongs to the class of Smith-Purcell free-electron lasers that utilize periodic metal grating structures to support electromagnetic waves with phase velocities slower than the speed of light. The vec {rm J}cdotvec {rm E} interaction between this slow wave and a mildly relativistic electron beam (15-130 keV) produces coherent radiation. Dispersion, electronic tuning, single particle gain and start oscillation current expressions are developed for unique grating geometries that are seen to possess superior high frequency and tuning capabilities. Experimental data taken over a wide spectral range is extensively compared to the theoretical developments and excellent agreement is seen. Comparing the experimentally measured power of the device to a generic power model has resulted in valuable insights into designing device parameters that will optimize short wavelength operation. The experimental observation of multiple modes of laser operation has led to the development of several new models of how the device works, including one that links the TM dispersion formalism with the viewpoint of Smith and Purcell. This viewpoint is significant in that it allows for a statement on the ultimate short wavelength limits of the device to be made.

Price, Edwin James

1991-02-01

396

Short Term Changes in Shear Wave Splitting at Sierra Negra Volcano, 2010: Possible Indicator of a Magmatic Intrusion  

NASA Astrophysics Data System (ADS)

The Sierra Negra volcano, Galapagos, is a basaltic shield volcano with the largest caldera (7x10 km) in the islands. Frequent eruptions have been dated, with a time interval between them typically in the order of decades (7 were confirmed in the last century), the last one occurred in 2005. We present new results from a shear wave splitting study performed at Sierra Negra volcano using nearly two years (Aug 2009-Jun 2011) of data obtained from SIGNET (Sierra Negra Integrated Geophysical Network) project. Changes in fast shear wave polarity are detected during the period of 4-10 June 2010, which are interpreted as the result of a crustal (6-10 km) magmatic intrusion event. The goal of this study was to determine the state of crustal stress at and around Sierra Negra in order to establish how different possible stress sources (i.e. the Galapagos spreading center, the Nazca plate movement along the insular platform, the loads of Sierra Negra and its interaction with nearby active volcanoes) are controlling volcanism within the region, as well as to test the method as a potential tool for detecting and forecasting changes in eruptive activity. Shear wave splitting (SWS) is an indicator of seismic anisotropy and is expected in volcanic regions as explained by extensive-dilatancy anisotropy (EDA) theory. Thus, we selected the SWS method to identify the local and regional state of stress. In stations far from the caldera two regional main stress directions are determined, oriented N-S or E-W, which may be associated with either the influence of the Galapagos spreading center or to the Nazca plate movement respectively. SWS results around the caldera were stable and agreed with radial or circumferential fissure strikes. During the 4-10 June 2010 however, daily seismic event rates increased reaching average monthly event numbers in just a few days. The majority of these events were located in the southeastern part of Sierra Negra's edifice. In this period the polarization direction of fast shear waves changed noticeably in some stations close to the caldera whereas remained almost unchanged in other stations. We propose these changes are related to a sill or dike intrusion. After the proposed intrusion period was over, the SWS measurements rapidly returned to the pre-intrusion directions, thus confirming the sensitivity SWS to changes in the stress state related to volcanic activity within Sierra Negra.

Anzieta, J. C.; Ruiz, M. C.; Ebinger, C. J.; Geist, D.

2012-12-01

397

Parametric interaction and spatial collapse of beam-driven Langmuir waves in the solar wind. [upstream of Jupiter bow shock  

NASA Technical Reports Server (NTRS)

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 a nonlinear interaction involving the beam-driven pump, a sideband emission, and a low level of ion-acoustic turbulence. The beam-driven Langmuir wave emission breaks up into a complex sideband structure with both positive and negative Doppler shifts. In some cases, the sideband emission consists of isolated wave packets with very short duration bursts, which are very intense and are thought to consist of envelope solitons which have collapsed to spatial scales of only a few Debye lengths.

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

1981-01-01

398

Suppression of infrared instability in transsonic flows by condensation of zero-frequency short wave length phonons  

NASA Astrophysics Data System (ADS)

We analyze the peculiar infrared instability that characterizes stationary inhomogeneous flows when their velocity crosses the sound speed by decreasing values. For definiteness, we work in the context of one-dimensional atomic Bose condensates. These flows are unstable under ultra-low real frequency perturbations because of the unbounded mode amplification near the sonic horizon. This results in a condensation of low-frequency phonons which produces a spatially structured flow in the supersonic domain. Numerical simulations reveal that this zero-frequency undulation suppresses the instability when its spatial extension is infinite, and when its phase is near that of a "shadow soliton" solution attached to the sonic horizon. These phenomena are akin to the condensation of rotons in flowing superfluid He 4 when exceeding the Landau velocity. They also pertain to shallow water waves propagating on transcritical flows.

Busch, Xavier; Michel, Florent; Parentani, Renaud

2014-11-01

399

Suppression of infrared instability in trans-sonic flows by condensation of zero-frequency short wave length phonons  

E-print Network

We analyze the peculiar infrared instability that characterizes stationary inhomogeneous flows when their velocity crosses the sound speed by decreasing values. For definiteness, we work in the context of one dimensional atomic Bose condensates. These flows are unstable under ultra low real frequency perturbations because of the unbounded mode amplification near the sonic horizon. This results in a condensation of low frequency phonons which produces a spatially structured flow in the supersonic domain. Numerical simulations reveal that this zero-frequency undulation suppresses the instability when its spatial extension is infinite, and when its phase is near that of a "shadow soliton" solution attached to the sonic horizon. These phenomena are akin to the condensation of rotons in flowing superfluid helium-4 when exceeding the Landau velocity. They also pertain to shallow water waves propagating on transcritical flows.

Xavier Busch; Florent Michel; Renaud Parentani

2014-08-11

400

Suppression of infrared instability in trans-sonic flows by condensation of zero-frequency short wave length phonons  

E-print Network

We analyze the peculiar infrared instability that characterizes stationary inhomogeneous flows when their velocity crosses the sound speed by decreasing values. For definiteness, we work in the context of one dimensional atomic Bose condensates. These flows are unstable under ultra low real frequency perturbations because of the unbounded mode amplification near the sonic horizon. This results in a condensation of low frequency phonons which produces a spatially structured flow in the supersonic domain. Numerical simulations reveal that this zero-frequency undulation suppresses the instability when its spatial extension is infinite, and when its phase is near that of a "shadow soliton" solution attached to the sonic horizon. These phenomena are akin to the condensation of rotons in flowing superfluid helium-4 when exceeding the Landau velocity. They also pertain to shallow water waves propagating on transcritical flows.

Busch, Xavier; Parentani, Renaud

2014-01-01

401

Synergy of short gamma ray burst and gravitational wave observations: Constraining the inclination angle of the binary and possible implications for off-axis gamma ray bursts  

E-print Network

Compact binary mergers are the strongest candidates for the progenitors of Short Gamma Ray Bursts (SGRBs). If a gravitational wave (GW) signal from the compact binary merger is observed in association with a SGRB, such a synergy can help us understand many interesting aspects of these bursts. We examine the accuracies with which a world wide network of gravitational wave interferometers would measure the inclination angle (the angle between the angular momentum axis of the binary and the observer's line of sight) of the binary. We compare the projected accuracies of GW detectors to measure the inclination angle of double neutron star (DNS) and neutron star-black hole (NS-BH) binaries for different astrophysical scenarios. We find that a 5 detector network can measure the inclination angle to an accuracy of $\\sim 5.1 (2.2)$ degrees for a DNS(NS-BH) system at 200 Mpc if the direction of the source as well as the redshift is known electromagnetically. We argue as to how an accurate estimation of the inclination angle of the binary can prove to be crucial in understanding off-axis GRBs, the dynamics and the energetics of their jets, and help the searches for (possible) orphan afterglows of the SGRBs.

K. G. Arun; Hideyuki Tagoshi; Chandra Kant Mishra; Archana Pai

2014-12-15

402

Color from invisible flicker: a failure of the Talbot-Plateau law caused by an early 'hard' saturating nonlinearity used to partition the human short-wave cone pathway  

Microsoft Academic Search

The Talbot-Plateau law fails for flicker detected by the short-wavelength-sensitive (S) cones: a 30-40 Hz target, flickering too fast for the flicker to be resolved, looks more yellow than a steady target of the same average intensity. The color change, which is produced by distortion at an early compressive nonlinearity, was used to reveal a slightly bandpass S-cone temporal response

Andrew Stockman; Daniel J. Plummer

1998-01-01

403

The harmonic structure of solar microbursts at meter wavelengths  

NASA Astrophysics Data System (ADS)

We analyze in detail the dynamic characteristics (frequency drift rate df/dt = f(f) and duration tau(f)) of meter-wave solar microbursts observed at two radio observatories in the USA and India at f ~ 50 MHz. The average measured characteristics of harmonically related type III bursts over a wide wavelength range from 1 to 50 m were used as a reference in our study. Our results support the hypothesis that meter-wave microbursts are related to weak type III emission. The drift rates of microbursts fall into two groups, in the same way as normal, intense type III bursts; these groups are associated with the first (F) and second (H) harmonics of the local plasma frequency f_p in the solar corona. The majority (about 80%) of the observed microbursts are characterized by essentially the same parameters f(f) and tau(f) as type IIIH bursts. Like comparatively short type IIIF bursts, the other group of microbursts has higher (by approximately a factor of 1.6) drift rates. The dynamic characteristics of the microbursts provide evidence that weak meter-wave type III bursts are generated at both the fundamental (f ~ f_p) and second-harmonic (f ~ 2f_p) frequencies. Observations indicate that the probability of detecting a weak burst at the fundamental frequency (IIIF) is relatively small, and, on the whole, microbursts at the second-harmonic frequency (IIIH) dominate.

Tsybko, Ya. G.

1998-11-01

404

SDIO long wavelength infrared detector requirements  

NASA Technical Reports Server (NTRS)

The Strategic Defense Initiative Organization (SDIO) has a significant requirement for infrared sensors for surveillance, tracking and discrimination of objects in space. Projected SDIO needs cover the range from short wavelengths out to 30 microns. Large arrays are required, and producibility and cost are major factors. The SDIO is pursuing several approaches including innovative concepts based on semiconductors and superconductors.

Duston, Dwight

1990-01-01

405

A Systematic Evaluation of Short Tandem Repeats in Lipid Candidate Genes: Riding on the SNP-Wave  

PubMed Central

Structural genetic variants as short tandem repeats (STRs) are not targeted in SNP-based association studies and thus, their possible association signals are missed. We systematically searched for STRs in gene regions known to contribute to total cholesterol, HDL cholesterol, LDL cholesterol and triglyceride levels in two independent studies (KORA F4, n?=?2553 and SAPHIR, n?=?1648), resulting in 16 STRs that were finally evaluated. In a combined dataset of both studies, the sum of STR alleles was regressed on each phenotype, adjusted for age and sex. The association analyses were repeated for SNPs in a 200 kb region surrounding the respective STRs in the KORA F4 Study. Three STRs were significantly associated with total cholesterol (within LDLR, the APOA1/C3/A4/A5/BUD13 gene region and ABCG5/8), five with HDL cholesterol (3 within CETP, one in LPL and one inAPOA1/C3/A4/A5/BUD13), three with LDL cholesterol (LDLR, ABCG5/8 and CETP) and two with triglycerides (APOA1/C3/A4/A5/BUD13 and LPL). None of the investigated STRs, however, showed a significant association after adjusting for the lead or adjacent SNPs within that gene region. The evaluated STRs were found to be well tagged by the lead SNP within the respective gene regions. Therefore, the STRs reflect the association signals based on surrounding SNPs. In conclusion, none of the STRs contributed additionally to the SNP-based association signals identified in GWAS on lipid traits. PMID:25050552

Lamina, Claudia; Haun, Margot; Coassin, Stefan; Kloss-Brandstätter, Anita; Gieger, Christian; Peters, Annette; Grallert, Harald; Strauch, Konstantin; Meitinger, Thomas; Kedenko, Lyudmyla; Paulweber, Bernhard; Kronenberg, Florian

2014-01-01

406

The Long Wavelength Array (LWA) and Interplanetary Scintillation (IPS)  

E-print Network

The Long Wavelength Array (LWA) and Interplanetary Scintillation (IPS) Patrick C. Crane 12 January scintillation (IPS) is the random fluctuation in the intensity and phase of electromagnetic waves passing

Ellingson, Steven W.

407

Fast wave evanescence in filamentary boundary plasmas  

SciTech Connect

Radio frequency waves for heating and current drive of plasmas in tokamaks and other magnetic confinement devices must first traverse the scrape-off-layer (SOL) before they can be put to their intended use. The SOL plasma is strongly turbulent and intermittent in space and time. These turbulent properties of the SOL, which are not routinely taken into account in wave propagation codes, can have an important effect on the coupling of waves through an evanescent SOL or edge plasma region. The effective scale length for fast wave (FW) evanescence in the presence of short-scale field-aligned filamentary plasma turbulence is addressed in this paper. It is shown that although the FW wavelength or evanescent scale length is long compared with the dimensions of the turbulence, the FW does not simply average over the turbulent density; rather, the average is over the exponentiation rate. Implications for practical situations are discussed.

Myra, J. R. [Lodestar Research Corporation, Boulder, Colorado 80027 (United States)] [Lodestar Research Corporation, Boulder, Colorado 80027 (United States)

2014-02-15

408

Prototype for Long Wavelength Array Sees First Light  

NASA Astrophysics Data System (ADS)

Astronomers at the Naval Research Laboratory have produced the first images of the sky from a prototype of the Long Wavelength Array (LWA), a revolutionary new radio telescope to be constructed in southwestern New Mexico. The images show emissions from the center of our Galaxy, a supermassive black hole, and the remnant of a star that exploded in a supernova over 300 years ago. Not only a milestone in the development of the LWA, the images are also a first glimpse through a new window on the cosmos. "First light" is an astronomical term for the first image produced with a telescope. It is a key milestone for any telescope because it indicates that all of the individual components are working in unison as planned. Once completed, the LWA will provide an entirely novel view of the sky, in the radio frequency range of 20-80 MHz, currently one of the most poorly explored regions of the electromagnetic spectrum in astronomy. The LWA will be able to make sensitive high-resolution images, and scan the sky rapidly for new and transient sources of radio waves, which might represent the explosion of distant, massive stars, the emissions from planets outside of our own solar system or even previously unknown objects or phenomena. "The LWA will allow us to make the sharpest images ever possible using very long wavelength radio waves. This newly opened window on the universe will help us understand the acceleration of relativistic particles in a variety of extreme astrophysical environments including from the most distant supermassive black holes. But perhaps most exciting is the promise of new source classes waiting to be discovered," says Dr. Namir Kassim, an NRL astronomer in the Remote Sensing Division and LWA Project Scientist. Dr. Tracy Clarke, of Interferometrics, Inc. in Herndon, Virginia, another astronomer on the NRL team adds, "By detecting distant clusters of galaxies the LWA may also provide new insights on the cosmological evolution of the mysterious dark matter and dark energy." Although radio astronomy was discovered at low frequencies (near 20 MHz, corresponding to wavelengths of 15 meters), well below the current FM band, astronomers quickly moved up to higher frequencies (centimeter wavelengths) in search of higher resolution and to escape the corrupting effects of the Earth's ionosphere, a region of charged particles between about 50 and 600 miles above the surface. The ionosphere, which can "bend" radio waves to produce long-distance reception of AM and short-wave radio signals, also causes distortions in radio telescope images in much the same way that atmospheric irregularities cause twinkling of stars. Ionospheric effects become much worse at low frequencies, but new imaging techniques developed at NRL and elsewhere have allowed the "ionospheric barrier" to be broken and enabled high-resolution astronomical imaging at these low frequencies for the first time. These new imaging techniques provide an improved view of not only the astronomical sky, but the Earth's ionosphere as well. The full LWA will generate richly detailed measurements of the ionosphere that will complement other ionospheric data sources. Understanding the ionosphere is critically important to the Department of Defense because of its effects on communications and navigation systems. The current prototype, referred to as the Long Wavelength Demonstrator Array (LWDA) to differentiate it from the larger LWA project, completed installation on the Plains of San Agustin in southwestern New Mexico in the fall of 2006. Funded by NRL and built by the Applied Research Laboratories of the University of Texas, Austin (ARL:UT), the telescope consists of 16 antennas connected to a suite of electronics that combine the signals from each antenna. Each antenna is only 4 feet tall and acts much like an old style television antenna, receiving radio waves from many different directions simultaneously. When combined, the data from the individual antennas is comparable to that from a more traditional dish style tele

2007-03-01

409

X-ray standing-wave study of (AlAs){sub m}(GaAs){sub n} short-period superlattices  

SciTech Connect

X-ray standing-waves (XSW) are used for an investigation of the structure of (AlAs){sub m}(GaAs){sub n} short-period superlattices (SL{close_quote}s). The XSW induced modulation of x-ray fluorescence from the Al, As, and Ga atoms and the total photoelectron yield are monitored around the 0th order SL satellite (AlAs)(GaAs)(004,0) and the GaAs(004) substrate Bragg reflection. From the specific shape of these modulations and the sample reflectivity, an atomic model about the interfaces is derived. This is accomplished by comparing the experimental data with dynamical calculations of x-ray wavefield distribution and reflectivity, which are based on the Takagi-Taupin equation. The fluorescence measurements at the 0th order SL satellite reveal a high crystalline order in the AlAs layers of the short-period SL, whereas in the GaAs layers, a fraction of the Ga and As atoms is not on the ideal lattice positions. From the analysis, a model of the atomic distribution along the [001] direction can be determined. This reveals that at each internal interface in the GaAs layers, two Ga atom planes are shifted by up to 0.035 nm and one As atom plane by 0.023 nm. At each interface, the shifts are directed towards the substrate. In addition, the XSW field at the GaAs(004) substrate reflection results in a moir{acute e} or beating effect in the SL structure, which can be used to determine the information depth {Lambda}{sub e} of total electron-yield measurements in a more detailed approach. {copyright} {ital 1999} {ital The American Physical Society}

Lessmann, A.; Brennan, S.; Munkholm, A. [Stanford Synchrotron Radiation Laboratory SSRL/SLAC, 2575 Sand Hill Road, Menlo Park, California 94025 (United States)] [Stanford Synchrotron Radiation Laboratory SSRL/SLAC, 2575 Sand Hill Road, Menlo Park, California 94025 (United States); Schuster, M.; Riechert, H. [Siemens AG, Corporate Technology, Otto-Hahn-Ring 6, D-81739 Munich (Germany)] [Siemens AG, Corporate Technology, Otto-Hahn-Ring 6, D-81739 Munich (Germany); Materlik, G. [Hamburger Synchrotronstrahlungslabor HASYLAB am Deutschen Elektronen-Synchrotron DESY, Notkestrasse 85, D-22603 Hamburg (Germany)] [Hamburger Synchrotronstrahlungslabor HASYLAB am Deutschen Elektronen-Synchrotron DESY, Notkestrasse 85, D-22603 Hamburg (Germany)

1999-04-01

410

The Long Wavelength Array  

Microsoft Academic Search

Application of self-calibration techniques to low-frequency (< 150 MHz) radio interferometric data has enabled high-resolution, high sensitivity imaging at long wavelengths for the first time. We illustrate these advances using NRAO Very Large Array (VLA) 74 MHz images having sub-arcminute resolution and sub-Jansky sensitivity. The VLA 74 MHz breakthrough has inspired the Long Wavelength Array (LWA), a completely electronic array

N. E. Kassim; E. J. Polisensky; T. E. Clarke; B. C. Hicks; P. C. Crane; K. P. Stewart; P. S. Ray; K. W. Weiler; L. J. Rickard; T. J. W. Lazio; A. S. Cohen; M. E. Nord; W. C. Erickson; R. A. Perley

2005-01-01

411

ATMOSPHERIC PHASE NOISE AND APERTURE SYNTHESIS IMAGING AT MILLIMETER WAVELENGTHS  

E-print Network

wavelength aperture synthesis images is limited by atmospheric turbulence. Observing techniques and dataATMOSPHERIC PHASE NOISE AND APERTURE SYNTHESIS IMAGING AT MILLIMETER WAVELENGTHS M. C. H. Wright on short baselines and in turbulent weather. The rms phase at a 1 km baseline is 1 mm, with a variation

Militzer, Burkhard

412

Radio-echo studies of meteors at 68-centimeter wavelength  

Microsoft Academic Search

Radio-echo observations of sporadic meteors at 68 cm are described. Sufficient information was gathered to permit the computation of the velocity, height, duration, and intensity for most of the meteors. The principal conclusions reached are that (a) the meteors recorded at this short wavelength are seen ov. era height range not sensibly different from that at long wavelengths; (b) the

J. V. Evans

1965-01-01

413

Increased Range of Motion and Function in an Individual with Breast Cancer and Necrotizing Fasciitis—Manual Therapy and Pulsed Short-Wave Diathermy Treatment  

E-print Network

Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Necrotizing fasciitis is a severe soft tissue infection of the subcutaneous tissue and fascia affecting those predisposed to immune system compromise. It is a life threatening condition; mortality can be reduced by rapid diagnosis, adequate early surgical debridement and antibiotic ointment. In this case report we present the use of manual therapy (MT) techniques, joint and soft tissue mobilization, following a regimen of pulsed short wave diathermy (PSWD) in the treatment of a woman 3 years post necrotizing fasciitis developed during chemotherapy treatment for breast cancer. During her course of chemotherapy, she developed necrotizing fasciitis which was treated with extensive surgical debridement (8 linear feet of incisions) followed by debridement to both hips and the pelvis area. When we started working with her, we put her on a course of PSWD/MT. After six weeks of following this regimen, she gained 25 ? of external rotation in both her left and right hips, 15 ? of left hip flexion and 17 ? of right hip flexion. The patient gained 10 ? of right hip extension, yet there was no improvement in left hip extension. The treatments led to a dramatic reduction in pain and scarring from previous surgeries. The patient also returned to running. 1. Background and Significance Physical therapy intervention for individuals after breast cancer is an important area of practice, especially as the

Article Id; Wayne Johnson; David O. Draper

414

Increased Range of Motion and Function in an Individual with Breast Cancer and Necrotizing Fasciitis—Manual Therapy and Pulsed Short-Wave Diathermy Treatment  

PubMed Central

Necrotizing fasciitis is a severe soft tissue infection of the subcutaneous tissue and fascia affecting those predisposed to immune system compromise. It is a life threatening condition; mortality can be reduced by rapid diagnosis, adequate early surgical debridement and antibiotic ointment. In this case report we present the use of manual therapy (MT) techniques, joint and soft tissue mobilization, following a regimen of pulsed short wave diathermy (PSWD) in the treatment of a woman 3 years post necrotizing fasciitis developed during chemotherapy treatment for breast cancer. During her course of chemotherapy, she developed necrotizing fasciitis which was treated with extensive surgical debridement (8 linear feet of incisions) followed by debridement to both hips and the pelvis area. When we started working with her, we put her on a course of PSWD/MT. After six weeks of following this regimen, she gained 25° of external rotation in both her left and right hips, 15° of left hip flexion and 17° of right hip flexion. The patient gained 10° of right hip extension, yet there was no improvement in left hip extension. The treatments led to a dramatic reduction in pain and scarring from previous surgeries. The patient also returned to running. PMID:20706546

Johnson, Wayne; Draper, David O.

2010-01-01

415

Nonlinear continuum growth model of multiscale reliefs as applied to rigorous analysis of multilayer short-wave scattering intensity. I. Gratings  

PubMed Central

It is shown that taking into proper account certain terms in the nonlinear continuum equation of thin-film growth makes it applicable to the simulation of the surface of multilayer gratings with large boundary profile heights and/or gradient jumps. The proposed model describes smoothing and displacement of Mo/Si and Al/Zr boundaries of gratings grown on Si substrates with a blazed groove profile by magnetron sputtering and ion-beam deposition. Computer simulation of the growth of multilayer Mo/Si and Al/Zr gratings has been conducted. Absolute diffraction efficiencies of Mo/Si and Al/Zr gratings in the extreme UV range have been found within the framework of boundary integral equations applied to the calculated boundary profiles. It has been demonstrated that the integrated approach to the calculation of boundary profiles and of the intensity of short-wave scattering by multilayer gratings developed here opens up a way to perform studies comparable in accuracy to measurements with synchrotron radiation, at least for known materials and growth techniques. PMID:24046500

Goray, Leonid; Lubov, Maxim

2013-01-01

416

Nonlinear continuum growth model of multiscale reliefs as applied to rigorous analysis of multilayer short-wave scattering intensity. I. Gratings.  

PubMed

It is shown that taking into proper account certain terms in the nonlinear continuum equation of thin-film growth makes it applicable to the simulation of the surface of multilayer gratings with large boundary profile heights and/or gradient jumps. The proposed model describes smoothing and displacement of Mo/Si and Al/Zr boundaries of gratings grown on Si substrates with a blazed groove profile by magnetron sputtering and ion-beam deposition. Computer simulation of the growth of multilayer Mo/Si and Al/Zr gratings has been conducted. Absolute diffraction efficiencies of Mo/Si and Al/Zr gratings in the extreme UV range have been found within the framework of boundary integral equations applied to the calculated boundary profiles. It has been demonstrated that the integrated approach to the calculation of boundary profiles and of the intensity of short-wave scattering by multilayer gratings developed here opens up a way to perform studies comparable in accuracy to measurements with synchrotron radiation, at least for known materials and growth techniques. PMID:24046500

Goray, Leonid; Lubov, Maxim

2013-08-01

417

Omnidirectional spin-wave nanograting coupler  

PubMed Central

Magnonics as an emerging nanotechnology offers functionalities beyond current semiconductor technology. Spin waves used in cellular nonlinear networks are expected to speed up technologically, demanding tasks such as image processing and speech recognition at low power consumption. However, efficient coupling to microelectronics poses a vital challenge. Previously developed techniques for spin-wave excitation (for example, by using parametric pumping in a cavity) may not allow for the relevant downscaling or provide only individual point-like sources. Here we demonstrate that a grating coupler of periodically nanostructured magnets provokes multidirectional emission of short-wavelength spin waves with giantly enhanced amplitude compared with a bare microwave antenna. Exploring the dependence on ferromagnetic materials, lattice constants and the applied magnetic field, we find the magnonic grating coupler to be more versatile compared with gratings in photonics and plasmonics. Our results allow one to convert, in particular, straight microwave antennas into omnidirectional emitters for short-wavelength spin waves, which are key to cellular nonlinear networks and integrated magnonics. PMID:24189978

Yu, Haiming; Duerr, G.; Huber, R.; Bahr, M.; Schwarze, T.; Brandl, F.; Grundler, D.

2013-01-01

418

Traveling Waves and Superposition Demonstration  

NSDL National Science Digital Library

The applet shows two waves and their superposition. While keeping the parameters for one wave the same, change the parameters for the other wave to create a standing wave. Note that you can't change the speed directly. Change the wavelength and frequency in order that both waves have the same speed.

Christian, Wolfgang; Belloni, Mario

2008-02-19

419

Diffraction optics for terahertz waves  

NASA Astrophysics Data System (ADS)

Conventional lenses are important components for many terahertz applications, but ordinary lenses are very difficult to fabricate for short-focal lengths. Multi-level phase-corrected zoned lens antennas have been investigated with particular application at terahertz wavelengths. These zoned lenses (or diffractive optics) give better performance than ordinary lenses, and because of their planar construction are easier and cheaper to fabricate. The depths of cut needed for a grooved zone plate are quite small, even when materials with low dielectric constants are used. Zoned lenses have been built and tested at various frequencies from 100 GHz to 1.5 THz, with phase correction levels of half-wave, quarter-wave, or eighth-wavelength. The inherent losses in transparent materials increase monotonically over this frequency range. Typical low-loss materials include polystyrene, polyethylene, Teflon, polycarbonate, polystyrene foam, foamed polyethylene, low density polytetrafluoroethylene (PTFE), TPX, quartz, sapphire, and silicon. Low dielectric-constant materials are normally preferred to reduce reflection and attenuation losses. Techniques for cutting or milling the materials to small dimensions are important, because at 1.0 THz an eighth-wavelength correction for silicon is only 15 ?m. Another characteristic of zoned diffraction optics is their frequency behavior. Previous investigations have considered their bandwidth dependence and quasi-periodic extended frequency response for a specified focal length. As frequency changes, the focal point moves along the axis of the zoned lens. An analysis is given to explain this effect.

Wiltse, James C.

2004-09-01

420

Continuous-wave operation of distributed feedback AlAs\\/GaAs superlattice quantum-cascade lasers  

Microsoft Academic Search

We report on continuous-wave operation of first-order distributed feedback quantum-cascade lasers at lambda=11.8 mum, based on interminiband transitions in a chirped AlAs\\/GaAs superlattice. Short devices operate in continuous-wave up to ~30 K. The single-mode emission wavelength is continuously tunable with the temperature. A metallized surface-relief grating is used for feedback to achieve single-mode emission.

W. Schrenk; N. Finger; S. Gianordoli; E. Gornik; G. Strasser

2000-01-01