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1

Fluid dynamic issues in continuous wave short wavelength chemical lasers  

SciTech Connect

This paper addresses fluid dynamic issues of concern in the design and development of Continuous Wave (CW) Short Wavelength Chemical Lasers (SWCLs). Short Wavelength Chemical Laser technology is in its research stage and SWCL concepts are in their evolving mode. Researchers are presently addressing candidate chemical systems and activation concepts. Since these lasers will be flowing systems, it is necessary to discuss both the probable fluid dynamics issues, because of the inherent complexities fluid dynamicist can support this activity. In addition to addressing the SWCL fluid dynamic issues, this paper will review past fluid dynamic activities in high energy lasers and discuss additional research still required. This paper will also address the various levels of fluid dynamic modeling and how these models can be applied in studying the fluid dynamics of Short Wavelength Chemical Lasers. Where it is felt that specific fluid methodologies are not available, but are required in order to conduct specific analyses, they will be defined. 34 refs., 6 figs., 1 tab.

Mikatarian, R.R.; Jumper, E.J.; Woolhiser, C.

1988-01-01

2

Short wavelength FELS  

SciTech Connect

The generation of coherent ultraviolet and shorter wavelength light is presently limited to synchrotron sources. The recent progress in the development of brighter electron beams enables the use of much lower energy electron rf linacs to reach short-wavelengths than previously considered possible. This paper will summarize the present results obtained with synchrotron sources, review proposed short- wavelength FEL designs and then present a new design which is capable of over an order of magnitude higher power to the extreme ultraviolet. 17 refs., 10 figs.

Sheffield, R.L.

1991-01-01

3

Short wavelength laser  

DOEpatents

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

Hagelstein, P.L.

1984-06-25

4

Short wavelength laser  

DOEpatents

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

Hagelstein, Peter L. (Livermore, CA)

1986-01-01

5

Short wavelength chemical lasers  

SciTech Connect

Experimental results on the operation of HF chemical lasers on the v = 2 to v = 0 overtone transitions are presented. Two separate CW laser devices with gain lengths of 15 and 30 cm produced 21 and 56 W of overtone power. The comparable power on fundamental transitions of the same lasers was 97 and 180 W. Thus, these overtone HF lasers produce 22 and 31 percent of the available fundamental power, much higher percentages than previous overtone chemical lasers. The implications of this new short wavelength chemical laser for high power lasers are discussed briefly. 17 references.

Jeffers, W.Q.

1989-01-01

6

Short wave-length variation of seismic velocity anomalies associated with stagnant slab  

NASA Astrophysics Data System (ADS)

When mineral physicists discuss mantle properties associated with stagnant slab referring to seismological studies, they focus on long wave-length characteristics provided by seismic tomography studies. In this sense the gap between seismological studies and mineral physics is still large to explore mantle properties. On the other hand, triplicated regional body waves are highly sensitive to the transition zone structure and have ample information regarding seismic velocity anomaly and the discontinuity depth associated with stagnant cold slab. We present results of regional waveform modeling using data from deep focus earthquakes (Mw?5.5, depth?300 km) that occurred in the Kurile to Izu-Bonin subduction zones during the period of 1990 to 2005. Here the range of regional distance is considered up to 32 deg where triplication can be observed from a deep focus event due to the high velocity anomaly (HVA) and depression of the discontinuity depth. After examining the data quality, regional waveform data of about 50 events were selected for analysis. The body waves which sampled the region with apparent stagnant slab strongly, can be modeled by model M3.11 (HVA in the transition zone with depression of the discontinuity to 690 km, Tajima and Grand, 1998), model M2.0 (HVA similar to M3.11 but without broad depression of the discontinuity) or a model with their slight modifications if not by iasp91 (Kennett and Engdahl, 1991). Structural variation in the transition zone has been determined in terms of seismic model M3.11 for the Kuriles subduction zone, M2.0 for the region beneath the Japan sea and the northeastern rim of the Eurasian plate or others. The structural boundaries are sharp and distinct showing steep gradient of velocity anomaly between the regions of different structure. The variation of the discontinuity depths indicates lateral variation of temperature beneath the flattened slab. We also found anomalously broadened P waveforms that propagated through the vicinity of structural boundaries. We postulate that the broadened P waves are SV-to-P converted waves in a narrow zone of low velocity anomaly (or a high Poisson's ratio of ~ 0.32) associated with stagnant slab.

Nakagawa, T.; Tajima, F.

2006-12-01

7

Shock wave pressure enhancement using short wavelength (0. 35. mu. m) laser irradiation  

SciTech Connect

Shock velocities in planar aluminum targets irradiated at 0.35- and 1.06-..mu..m laser wavelengths have been measured. Absorbed intensities of approx.1.0 x 10/sup 14/ W/cm/sup 2/, produced by 700-ps full width at half-maximum Gaussian pulses, generated shock pressures of 1.0 +- 0.2 and 0.6 +- 0.2 TPa, respectively, demonstrating an enhancement of shock pressure at decreased laser wavelength.

Trainor, R.J.; Holmes, N.C.; Anderson, R.A.; Campbell, E.M.; Mead, W.C.; Olness, R.J.; Turner, R.E.; Ze, F.

1983-09-15

8

On the Crest Profile Histories of Short Wavelength Breaking Wind Waves  

NASA Astrophysics Data System (ADS)

Measurements of the profiles of wind-generated breaking waves were taken in a wind-wave tank that is 11.8 m long, 1.1 m wide and 1.8 m in height (1.0 m water depth, 10 m/s maximum wind speed). The profiles of the waves were measured with a photographic technique that employs a laser light sheet, fluorescent dye and a high-speed digital movie camera. The camera records the profiles of the wave crests along the center plane of the tank where the light sheet enters the water surface. The light-sheet-generating optics and the camera were mounted on a carriage that moved along the tank at the speed of the breaking wave crests. With this system, measurements of the temporal evolution of the wave-crest shape were obtained during the wave steepening and breaking process. In this talk, observations of the breaker behavior and measurements of the incipient breaking conditions are discussed and compared to similar waves breaking without wind.

Duncan, J. H.; Liu, X.; Tavakolinejad, M. R.

2004-11-01

9

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

NASA Astrophysics Data System (ADS)

The cosmic microwave background (CMB) is affected by the total radiation density around the time of decoupling. At that epoch, neutrinos comprised a significant fraction of the radiative energy, but there could also be a contribution from primordial gravitational waves with frequencies greater than ˜10-15Hz. If this cosmological gravitational wave background were produced under adiabatic initial conditions, its effects on the CMB and matter power spectrum would mimic massless noninteracting neutrinos. However, with homogenous initial conditions—as one might expect from certain models of inflation, prebig bang models, phase transitions, and other scenarios—the effect on the CMB would be distinct. We present updated observational bounds for both initial conditions using the latest CMB data at small scales from the South Pole Telescope in combination with Wilkinson Microwave Anisotropy Probe, current measurements of the baryon acoustic oscillations, and the Hubble parameter. With the inclusion of the data from the South Pole Telescope, the adiabatic bound on the cosmological gravitational wave background density is improved by a factor of 1.7 to 106?gwh2?8.7 at the 95% confidence level, with weak evidence in favor of an additional radiation component consistent with previous analyses. The constraint can be converted into an upper-limit on the tension of horizon-sized cosmic strings that could generate this gravitational wave component, with G??2×10-7 at 95% C. L., for string tension G?. The homogeneous bound improves by a factor of 3.5 to 106?gwh2?1.0 at 95% C. L., with no evidence for such a component from current data.

Sendra, Irene; Smith, Tristan L.

2012-06-01

10

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

11

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

NASA Astrophysics Data System (ADS)

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

Yuan, C. J.; Huang, S. J.; Wang, J. X.; Wang, P. X.

2012-05-01

12

Short Wavelength Laser/Materials Interactions.  

National Technical Information Service (NTIS)

This report summarizes work completed on Short Wavelength Laser/Materials Interactions. The following projects have been completed: 1)microscale lase/materials experiments using cw chemical and rp excimer laser irradiation sources, 2) studies of short wav...

M. J. Berry

1986-01-01

13

Short wavelength laser\\/materials interactions  

Microsoft Academic Search

This report summarizes work completed on Short Wavelength Laser\\/Materials Interactions. The following projects have been completed: (1) microscale laser\\/materials experiments using CW chemical and rp excimer laser irradiation sources; (2) studies of short wavelength interaction phenomenology and effects; (3) development and use of laser probe attenuation and absorption systems for measurements on laser ablated plumes; (4) quadrupole mass spectrometric studies

Michael J. Berry

1986-01-01

14

Short wavelength laser/materials interactions  

NASA Astrophysics Data System (ADS)

This report summarizes work completed on Short Wavelength Laser/Materials Interactions. The following projects have been completed: (1) microscale laser/materials experiments using CW chemical and rp excimer laser irradiation sources; (2) studies of short wavelength interaction phenomenology and effects; (3) development and use of laser probe attenuation and absorption systems for measurements on laser ablated plumes; (4) quadrupole mass spectrometric studies of laser pyrolysis products; and (5) laser hardened materials evaluations.

Berry, Michael J.

1986-11-01

15

Undulators for short wavelength FEL amplifiers  

SciTech Connect

Issues critical to the design of undulators for use in short wavelength FEL amplifiers, such as attainable on-axis field strength, device compactness, field quality, required magnetic gap, and strong focusing schemes, are discussed. The relative strength of various undulator technologies, including pure permanent magnet, hybrid, warm electromagnetic, pulsed, and superconducting electromagnetic devices in both helical and planar configurations are reviewed. Favored design options for proposed short wavelength FELs, such as the Linac Coherent Light Source at SLAC and the DUV Free-Electron Laser at BNL, are presented.

Schlueter, R.D.

1994-12-01

16

Undulators for short wavelength FEL amplifiers  

SciTech Connect

Issues critical to the design of undulators for use in short wavelength FEL amplifiers, such as attainable on-axis field strength, device compactness, field quality, required magnetic gap, and strong focusing schemes, are discussed. The relative strength of various undulator technologies, including pure permanent magnet, hybrid, warm electromagnetic, pulsed, and superconducting electromagnetic devices in both helical and planar configurations are reviewed. Favored design options for proposed short wavelength FELs, such as the Linac Coherent Light Source at SLAC and the DUV Free-Electron Laser at BNL, are presented.

Schlueter, R. [Lawrence Berkeley Lab., CA (United States). Accelerator and Fusion Research Div.

1994-08-01

17

Electricity and short wavelength radiation generator  

DOEpatents

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

George, E.V.

1985-08-26

18

Moiré interferometry of short wavelength Rayleigh-Taylor growth  

NASA Astrophysics Data System (ADS)

It is very important to observe ablative Rayleigh- Taylor(RT) instability at short wavelengths of 5-10 ?m. These wave lengths are below or close to the spatial resolution of most x-ray imagers u sed in the RT experiments. We have measured RT instability at these wavelengths with consi derably good spatial resolution using moiré interferometry we introduced before footnoteH. Azechi, M. Nakai, N. Izumi, K. Shigemori, T. Nagaya, and M. Mats uoka, Bull. Am. Phys. Soc., 42, 1893 (1997), M. Matsuoka, H. Azechi, M. Nakai, N. Izumi, K. Shigemori, T. Nagaya, and N. Miyanaga, Rev. Sci. Instrum., 70, 637 (1999). This is the first experiments about ablative RT instability near the cut-off wavelength. We have observed the time evolution of RT instability up to the wavelength of 4.7 ?m (The tested wavelengths were 3.2, 4.7, 5.7, 8.5 and 12 ?m.).

Matsuoka, M.; Azechi, H.; Nakai, M.; Izumi, N.; Nishikino, M.; Sakaiya, T.; Miyanaga, N.; Murai, K.

1999-11-01

19

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

20

Short wavelength ion temperature gradient turbulence  

NASA Astrophysics Data System (ADS)

The ion temperature gradient (ITG) mode in the high wavenumber regime (ky?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 (ky?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.; Brunner, S.; Ganesh, R.; Lapillonne, X.; Villard, L.; Jenko, F.

2012-10-01

21

Intraocular lens short wavelength light filtering.  

PubMed

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

Edwards, Keith H; Gibson, G Anthony

2010-11-01

22

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

23

Optical Detection in Ultrafast Short Wavelength Science  

SciTech Connect

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

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

2010-06-23

24

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

25

The solar coronal electron heating by short wavelength electromagnetic modes  

NASA Astrophysics Data System (ADS)

The electron heating of the solar coronal plasma has remained as one of the most important problems in solar physics. An explanation of the electron heating rests on the identification of the energy source and appropriate physical mechanisms via which the energy can be channelled to the electrons. Our objective here is to present an estimate for the electron heat in grate in the presence of finite amplitude short wavelength in comparison with the ion gyroradius dispersive electromagnetic (SWDEM) waves that propagate obliquely to the magnetic field in the solar corona, Specifically, it is demonstrated that the SWDEM waves can significantly contribute to the solar coronal electron heating via Joule heating involving electron-SWEDEM wave interactions. .

Shukla, Padma; Bingham, Robert; Stenflo, Lennart; Eliasson, B.

2010-11-01

26

The solar coronal electron heating by short wavelength electromagnetic modes  

NASA Astrophysics Data System (ADS)

The electron heating of the solar coronal plasma has remained as one of the most important problems in solar physics. An explanation of the electron heating rests on the identification of the energy source and appropriate physical mechanisms via which the energy can be channelled to the electrons. Our objective here is to present an estimate for the electron heating rate in the presence of finite amplitude short wavelength (in comparison with the ion gyroradius) dispersive electromagnetic (SWDEM) waves that propagate obliquely to the magnetic field in the solar corona. Specifically, it is demonstrated that the SWDEM waves can significantly contribute to the solar coronal electron heating via Joule heating involving electron-SWDEM wave interactions.

Shukla, P. K.; Bingham, R.

2006-10-01

27

Extended wavelength InGaAs on GaAs using InAlAs buffer for back-side-illuminated short-wave infrared detectors  

NASA Astrophysics Data System (ADS)

We conducted an experimental study of back-side-illuminated InGaAs photodiodes grown on GaAs and sensitive in the short-wave infrared up to 2.4 ?m. Standard metamorphic InGaAs or IR-transparent InAlAs buffers were grown by molecular-beam epitaxy. We studied dark current and photocurrent as a function of buffer thickness, buffer material, and temperature. A saturation of the dark current with buffer thickness was not observed. The maximum resistance area product was ~10 ? cm2 at 295 K. The dark current above 200 K was dominated by generation-recombination current. A pronounced dependence of the photocurrent on the buffer thickness was observed. The peak external quantum efficiency was 46% (at 1.6 ?m) without antireflective coating.

Zimmermann, Lars; John, Joachim; Degroote, Stefan; Borghs, Gustaaf; van Hoof, Chris; Nemeth, Stefan

2003-04-01

28

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

29

Short wavelength electron temperature gradient instability in toroidal plasmas  

SciTech Connect

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

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

2005-02-01

30

Ion heating and short wavelength fluctuations in a helicon plasma source  

NASA Astrophysics Data System (ADS)

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.; Galante, M.; Magee, R. M.; Hardin, R.

2013-03-01

31

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

32

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

33

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

34

Design formulas for short-wavelength FELs  

NASA Astrophysics Data System (ADS)

Simple formulas for optimization of vacuum ultraviolet (VUV) and X-ray self-amplified spontaneous emission (SASE) free electron lasers (FELs) are presented. The FEL gain length and the optimal ?-function are explicitly expressed in terms of the electron beam and undulator parameters. The FEL saturation length is estimated taking into account energy diffusion due to quantum fluctuations of the undulator radiation. Examples of the FEL optimization are given. Parameters of a SASE FEL, operating at the Compton wavelength, are suggested.

Saldin, E. L.; Schneidmiller, E. A.; Yurkov, M. V.

2004-05-01

35

Self-amplified spontaneous emission for short wavelength coherent radiation  

SciTech Connect

We review the recent progress in our understanding of the self-amplified spontaneous emission (SASE), emphasizing the application to short wavelength generation. Simple formulae are given for the start-up, exponential gain and the saturation of SASE. Accelerator technologies producing high brightness electron beams required for short wavelength SASE are discussed. An example utilizing electron beams from a photocathode-linac system to produce 4nm SASE in the multigigawatt range is presented.

Kim, K.J.; Xie, M.

1992-09-01

36

Estimates of SASE power in the short wavelength region  

SciTech Connect

Given a sufficiently bright electron beam, the self-amplified-spontaneous emission (SASE) can provide gigawatts of short wavelength coherent radiation. The advantages of SASE approach are that is requires neither optical cavity nor an imput seed laser. In this note, we estimate the peak power performance of SASE for wavelengths shorter than 1000 {Angstrom}. At each wavelength, we calculate the saturated power from a uniform parameter undulator and the enhanced power from a tapered undulator. The method described here is an adaptation of that discussed by L.H. Yu, who discussed the harmonic generation scheme with seeded laser, to the case of SASE.

Kim, Kwang-Je

1992-03-01

37

Doped photonic bandgap fibers for short-wavelength nonlinear devices  

NASA Astrophysics Data System (ADS)

Microstructured photonic bandgap fibers with a doped honeycomb cladding structure and the guiding defect defined by the absence of doping are proposed as nonlinear optical fibers for short wavelengths. It is shown that zero-dispersion wavelengths below 500 nm and corresponding effective areas of 1-2 ?m2 can be obtained if structures with interhole distances near 600 nm can be fabricated. The cutoff wavelength for guidance of second-order modes can be controlled by variation of the radius and index contrast of the doped regions.

Lægsgaard, Jesper; Bjarklev, Anders

2003-05-01

38

Wavelength conversion experiment using fiber four-wave mixing  

Microsoft Academic Search

Wavelength conversion using fiber four-wave mixing in an optical fiber is demonstrated. Utilizing the wavelength region around the zero-dispersion wavelength of a fiber, 622 Mbt\\/s FSK signal light is converted from 1555.2 to 1547.6 nm with a conversion efficiency of -24 dB

Kyo Inoue; Hiromu Toba

1992-01-01

39

Short cavity single-mode dual wavelength fiber laser array  

NASA Astrophysics Data System (ADS)

In this paper, a short polarization-maintaining Er:Yb co-doped fiber laser is experimented. A pair of FBGs are written in the Er:Yb co-doped sensitive fiber using UV beams. A 976nm pumping laser diode is used, and output wavelength is selected by two FBGs. The PM Er:Yb co-doped fiber is used to main the orthogonal polarizations SM lasing stability. The SM operation in each wavelength has been verified. On the basis of previous short cavity fiber, a simple DBR dual wavelength fiber laser array has been designed and experimented. Two sections of short Er:Yb co-doped fiber cavities are pumped by a 976nm LD simultaneously. The pump laser is splitted to pump each Er:Yb co-doped fiber. It used a WDM coupler at 1550nm to connect the output port of two DBR fiber laser, an isolator is spliced to the common arm of the WDM and used as the output port. The dual wavelength spacing is 0.31nm. The output power reaches 6mW with the optical signal to noise ratio of greater than 30dB. A 12.5Gb/s codes rate is used in the fiber laser transmission experiment. A nice optical eye diagram is recieved after long distance single-mode communications fiber transmission.

Wang, Tianshu; Qian, Sheng; Zhou, Xuefang; Qi, Yongmin; Li, Qiliang

2008-11-01

40

OMEGA: a short-wavelength laser for fusion experiments  

SciTech Connect

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

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

1983-01-01

41

Short wavelength temperature gradient driven modes in tokamak plasmas.  

PubMed

New unstable temperature gradient driven modes in an inhomogeneous tokamak plasma are identified. These modes represent temperature gradient (ion and electron) driven modes destabilized in the short wavelength regions with k( perpendicular )rho(i,e)>1, respectively. The instability occurs due to a specific plasma response that significantly deviates from Boltzmann distribution in the regions k( perpendicular )rho(i,e)>1. PMID:12225092

Smolyakov, A I; Yagi, M; Kishimoto, Y

2002-09-16

42

Method for fabricating photovoltaic device having improved short wavelength photoresponse  

DOEpatents

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

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

1989-07-04

43

Short cavity single-mode dual wavelength fiber laser array  

Microsoft Academic Search

In this paper, a short polarization-maintaining Er:Yb co-doped fiber laser is experimented. A pair of FBGs are written in the Er:Yb co-doped sensitive fiber using UV beams. A 976nm pumping laser diode is used, and output wavelength is selected by two FBGs. The PM Er:Yb co-doped fiber is used to main the orthogonal polarizations SM lasing stability. The SM operation

Tianshu Wang; Sheng Qian; Xuefang Zhou; Yongmin Qi; Qiliang Li

2008-01-01

44

Scattering of long-wavelength gravitational waves  

SciTech Connect

We consider the scattering of a low-frequency gravitational wave by a massive compact body in vacuum. We apply partial-wave methods to compute amplitudes for the helicity-conserving and helicity-reversing contributions to the cross section, accurate to first order in M{omega}. Contrary to previous claims, we find that the partial-wave cross section agrees with the cross section derived via perturbation-theory methods.

Dolan, Sam R. [School of Mathematical Sciences, University College Dublin, Belfield, Dublin 4 (Ireland)

2008-02-15

45

MIT (Massachusetts Institute of Technology) short-wavelength laser project  

NASA Astrophysics Data System (ADS)

We review the status of the short wavelength laser project at MIT. At this point we are on schedule relative to our initial proposal: the power amplifier is under construction at LLNL, the vacuum chamber has been designed, and development of the alignment system is underway. We report progress on the design of whisper gallery mirror EUV laser cavities, and have proposed a new scheme for frequency mixing in the EUV. We anticipate our first laser plasma experiment late spring or early summer of 1990.

Hagelstein, Peter; Basu, Santanu; Muendel, Martin; Kaushik, Sumanth; Braud, John Paul; Tauber, Dan; Wyss, Rolf A.

1990-06-01

46

An Experimental Investigation of Wind- and Mechanically Generated Short Wavelength Spilling Breakers  

NASA Astrophysics Data System (ADS)

Short wavelength spilling breakers are studied in a wind wave tank that is 12.8 m long and 1.15 m wide and 0.91 m deep. The crest profile histories during breaking are measured with a photographic technique that employs a high-speed digital movie camera, a laser light sheet, and fluorescent dye. The photographic system is mounted on an instrument carriage that is set to move along the tank in phase with the crests of the breaking waves. In the first step in the experiment, breakers generated by the wind are measured at three wind speeds and three fetches at each wind speed. In the second step in the experiment, a mechanical wave maker is used without wind to generate a wave train consisting of a dominant wave and two unstable sidebands. The amplitudes and frequencies of these wave components are adjusted to create breakers at the various fetches and dominant wave frequencies found in the wind wave experiments. The similarities and differences between the ripple patterns at the crest during breaking between the wind wave and mechanical wave cases are discussed.

Diorio, J. D.; Liu, X.; Duncan, J. H.

2006-11-01

47

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

48

Short-wavelength visible light emission from silicon nanocrystals  

NASA Astrophysics Data System (ADS)

Si is the material of choice for modern microelectronics but, as an indirect-bandgap semiconductor, it is not an efficient light emitter. An electrically pumped Si laser would present a breakthrough for optoelectronic integration that may enable optical interconnect to make computers faster. Si light emitting diodes may revolutionize solid-state lighting and displays because of the low cost and environmental friendliness of Si. One of the most challenging problems of Si-based lighting and displays is the lack of a reliable and efficient full visible spectrum emission. Si nanocrystals (Si-NCs) have so far been the most promising form of Si to emit light. Most of the synthesis approaches of Si-NCs, however, only lead to red light emission. Our recent work on Si-NCs synthesized by non-thermal plasmas has focused on extending their light emission into the short-wavelength range. Firstly, the process of oxidation-etching-oxidation of Si-NCs is investigated. This process causes the size of Si-NCs to decrease, leading to shorter wavelength light emission from Si-NCs. Yellow or green photoluminescence (PL) has been observed from initially oxidized red light emitting Si-NCs after HF vapour etching and atmospheric oxidation. The intensity of PL from Si-NCs, however, decreases by a factor up to 100. It is found that HF etching restructures the surface of Si-NCs. This leads to a decrease in the incorporation of O during subsequent oxidation, which finally results in silicon suboxide SiO1.9. Such an understoichiometry indicates a high density of defects such as Si dangling bonds at the Si-NC/oxide interface. Therefore, the PL efficiency is extremely low for short-wavelength light emitting Si-NCs obtained by the process of oxidation-etching-oxidation. Secondly, an integrated two-stage plasma system is employed to achieve the light emission from Si-NCs in the full visible spectrum range. Red-light-emitting Si-NCs are produced in the first stage by the plasma decomposition of SiH4. In the second stage a tetrafluoromethane (CF4)-based plasma etches Si-NCs and at the same time passivates them with carbon and fluorine. After the two-stage process Si-NCs emit light in the short-wavelength region from yellow to blue. We find that a self-limited oxidation process blueshifts the light emission until saturation is reached. Significantly, relatively high quantum yields of short-wavelength light emission from Si-NCs are obtained in spite of oxidation. It is interesting to note that Si-NCs treated by CF4-based plasma are hydrophilic while those without CF4-based plasma treatment are hydrophobic.

Pi, Xiaodong; Liptak, Rick; Campbell, Stephen; Kortshagen, Uwe

2007-03-01

49

Photoemission spectroscopy with high-intensity short-wavelength lasers  

NASA Astrophysics Data System (ADS)

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

Zhang, Song Bin; Rohringer, Nina

2014-01-01

50

Cloning and expression of a Xenopus short wavelength cone pigment.  

PubMed

The short wavelength visual pigment from Xenopus responsible for vision in the blue/violet portion of the spectrum was characterized by sequence spectroscopic analysis. The amino acid sequence was deduced by sequencing clones isolated by reverse transcription PCR, from retinal cDNA and genomic libraries. The gene contains 5 exons spanning 8.4 kb of genomic DNA and produces an mRNA of 2.4 kb in length. The deduced amino acid sequence predicts a protein of 347 amino acids with 76-78% identity to other short wavelength opsins. The mRNA encoding the Xenopus violet pigment was detected using in situ hybridization in cones, comprising a few percent of the total photoreceptors in the adult retina. The Xenopus violet opsin cDNA, modified to contain an epitope from the carboxyl terminus of bovine rhodopsin, was expressed in COS1 cells by transient transfection and analysed by UV-visible absorption spectroscopy. The protein expressed in COS1 cells migrated at 34 kD and was glycosylated at a single site in the amino terminus, exhibiting a diffuse pattern on SDS PAGE similar to bovine rhodopsin expressed in COS1 cells. Following incubation with 11-cis retinal, a light-sensitive pigment was formed with the lambdamax=425+/-2 nm. A Schiff base linkage between retinal and the violet opsin was demonstrated by acid denaturation. Xenopus violet opsin was sensitive to hydroxylamine in the dark, reacting with a half-time of 5 min at room temperature. This is the first group S pigment for amphibians. The pigment was expressed and purified from COS1 cells in a form that has permitted for the first time determination of the extinction coefficient, reactivity to hydroxylamine and presence of a Schiff base. PMID:9733587

Starace, D M; Knox, B E

1998-08-01

51

Characteristics of the ISO short wavelength spectrometer detectors  

NASA Astrophysics Data System (ADS)

The ISO (Infrared Space Observatory) Short Wavelength Spectrometer (SWS) employs four different types of detectors, which will all be operated at a low flux. Preliminary results of an extensive characterization of these detectors, both in the flight instrument and in a laboratory setup, are presented. In general, the performance of the instrument is as expected and quite low instrument noise equivalent powers are achieved (approximately 10 to the minus 17th power W/square root of Hz). However, the behavior of at least one of the detector types, Si:Sb, is troublesome. Characteristic features of this behavior are presented: long time transient response, memory effects, hook effects and excess noise. The Si:Sb transient responses can be described by two time constants. In contrast with the amplitude of the transient responses, these time constants depend only weakly on illumination power, temperature and bias voltage. This anomalous detector behavior implies specific designs of the observation strategies, which have to avoid 'flat-fielding' difficulties.

Wensink, J. W.; Luinge, W.; Beintema, D.; Valentijn, E. A.; de Graauw, T.; Katterloher, R.; Barl, L.; Young, E. T.

1992-12-01

52

Wavelength Tuning Characteristics of Idler Waves in Terahertz-Wave Parametric Oscillator Using Optical Double Resonance  

NASA Astrophysics Data System (ADS)

We experimentally investigated the wavelength tuning of oscillating idler (Stokes) waves by slightly translating the position of a mirror constituting an enhancement cavity in a terahertz (THz)-wave parametric oscillator (TPO) with optical double resonance. The wide tuning range of the idler wavelength was from 781.5 to 787.3 nm, corresponding to the frequency range of THz (signal) waves from 0.7 to 3.5 THz. The measured intersecting angle between pump and idler waves was in good agreement with the theoretical calculation of the noncollinear phase-matching condition in all the above tuning range.

Takida, Yuma; Ohira, Tatsuya; Tadokoro, Yuzuru; Kumagai, Hiroshi; Nashima, Shigeki

53

Europa Composition Using Visible to Short Wavelength Infrared Spectroscopy  

NASA Astrophysics Data System (ADS)

One of the major goals of the Jupiter Europa Orbiter (JEO) is to understand the chemistry of Europa's inorganic and organic materials. Europa's surface material composition is controlled by the original materials forming Europa and by their differentiation and chemical alterations. Material is probably still being transported to the surface by active processes in the interior. At the surface, the material is exposed to the effects of vacuum and temperature, irradiated by solar UV, and bombarded by material entrained in Jupiter's magnetic field. The materials on the surface and their distributions are evidence of the processes operating, both endogenic and exogenic. These processes include effects of a subsurface liquid ocean and its chemistry; the mechanisms of material emplacement from below; and photolysis and radiolysis. Visible to Short Wavelength Infrared (VSWIR) spectroscopy is a well-understood technique for mapping key inorganic, organic, and volatile compositions on remote surfaces such as Europa. Key spectral absorption features have been detected in both the icy and the non-icy Europa materials and many important constituents of the surface have been identified or proposed (e.g. hydrated salts, sulfuric acid hydrate, organics, CO2, H2O2, SO2). The determination of planetary surface composition from remote infrared spectroscopy depends upon adequate signal-to-noise, spectral resolution, and spatial scale to distinguish the diagnostic spectral features of the compounds of interest. For icy satellites, laboratory reference spectra obtained at the temperatures of the target bodies are also required. We have compared diagnostic spectral features in cryogenic laboratory spectra of hydrated salts relevant to Europa in order to optimize detection of these materials under realistic mission conditions. Effects of spectral resolution, signal to noise ratio, and areal mixtures are explored to determine the impacts on detection. This work was carried out at the Jet Propulsion Laboratory / California Institute of Technology under contract with NASA.

Blaney, Diana L.; Dalton, J. B.; Green, R. O.; Hibbits, K.; McCord, T.; Murchie, S.; Piccioni, G.; Tosi, F.

2010-10-01

54

Pupil Slicing Adaptive Optics:. Making Extremely Large Telescopes Diffraction Limited at Short Wavelengths  

Microsoft Academic Search

Extremely Large Telescopes (ELTs) will have aperture diameters up to 42 meters. Adaptive Optics (AO) at short wavelengths (< 1 micron) will be very hard to implement at these wavelengths because of the limited number of actuators on state-of-the-art deformable mirrors and because of the limited brightness of Laser Guide Stars (LGSs). For 1 arcsec seeing at 500 nm wavelength

Jacques M. Beckers

2009-01-01

55

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

Microsoft Academic Search

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

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

1992-01-01

56

Free-electron lasers - Prospects of extending classical electron oscillators into the short wave range  

Microsoft Academic Search

A topic of current interest is the feasibility of obtaining high-power narrow-band short-wave radiation by Doppler oscillation frequency conversion of ultrarelativistic electrons. In the present paper, theoretical and experimental data on the application of relativistic electron beams to the generation of electromagnetic waves at submillimetric and X-ray wavelengths are reviewed.

V. L. Bratman; N. S. Ginzburg; M. I. Petelin

1980-01-01

57

Short Wave Echoes and the Aurora Borealis  

Microsoft Academic Search

ON Feb. 29 of this year I received a letter from Engineer Jørgen Hals, Bygdø, Oslo, in which he says: ``I herewith have the honour to advise you that at the end of the summer 1927 I repeatedly heard signals from the Dutch short-wave transmitter station PCJJ (Eindhoven). At the same time as I heard the telegraph-signals I also heard

Carl Størmer

1928-01-01

58

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

59

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

60

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

61

Chalcogenide As S Suspended Core Fiber for Mid-IR Wavelength Conversion Based on Degenerate Four-Wave Mixing  

Microsoft Academic Search

A chalcogenide optical fiber of special design is proposed to convert a short-wavelength infrared radiation (around 2 mum) up to a second transparency window of atmospheric air (around 4.5 mu m) by degenerate four-wave mixing. The fiber supports a small core surrounded by three large air holes. The zero-dispersion wavelength is shifted down to 2 mum in this fiber by

Marcin Szpulak; Sébastien Fevrier

2009-01-01

62

The degradation of alzak by short wavelength ultraviolet radiation  

NASA Technical Reports Server (NTRS)

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

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

1972-01-01

63

Multi-Wavelength Study of Sgr A*: The Short Time Scale Variability  

Microsoft Academic Search

To understand the correlation and the radiation mechanism of flare emission in different wavelength bands, we have coordinated a number of telescopes to observe Sgr A* simultaneously. We focus only one aspect of the preliminary results of our multi-wavelength observing campaigns, namely, the short time scale variability of emission from Sgr A* in near-IR, X-ray and radio wavelengths. The structure

F. Yusef-Zadeh; J. Miller-Jones; D. Roberts; M. Wardle; M. Reid; K. Dodds-Eden; D. Porquet; N. Grosso

2011-01-01

64

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

Microsoft Academic Search

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

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

2002-01-01

65

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

66

Nine wave-length THz spectrum for identification using backward wave oscillator  

NASA Astrophysics Data System (ADS)

The sensing of the explosive is very important for homeland security and defense. We present a nine-wavelength continuous wave (CW) Terahertz (THz) spectroscopy for identification of explosive compounds (2,4-DNT, RDX and TNT) using three Backward Wave Oscillator (BWO) sources, which emit radiations from 0.2 THz to 0.38THz, 0.18THz to 0.26THz and 0.6THz to 0.7THz, respectively. To identify the target materials, only the transmitted THz power through the explosive pellets are measured at the nine discrete wavelengths. A hole, which is the same size as these pellets, is used as references to normalize the transmitted THz power. The measured discrete spectra was successfully identified and classified by using self-organizing map (SOM). These results prove that the backward wave oscillator is a convenient and powerful solution in future development of a standoff THz sensing and identification unit.

Lv, Mo; Zhong, Hua; Ge, Xin-Hao; He, Ting; Mu, Kaijun; Zhang, Cun-Lin

2009-11-01

67

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

NASA Astrophysics Data System (ADS)

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

Vural, Kadri

1987-03-01

68

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

NASA Technical Reports Server (NTRS)

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

Vural, Kadri

1987-01-01

69

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.

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

2012-01-01

70

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

71

Image measurements of short-period gravity waves at equatorial latitudes  

Microsoft Academic Search

A high-performance, all-sky imaging system has been used to obtain novel data on the morphology and dynamics of short-period (<1hour) gravity waves at equatorial latitudes. Gravity waves imaged in the upper mesosphere and lower thermosphere were recorded in three nightglow emissions, the near-infrared OH emission, and the visible wavelength OI (557.7 nm) and Na (589.2 nm) emissions spanning the altitude

M. J. Taylor; W. R. Pendleton; S. Clark; H. Takahashi; D. Gobbi

1997-01-01

72

A case of bilateral, acquired, and acute dysfunction of short-wavelength-sensitive cone systems.  

PubMed

To report a case of bilateral, acquired, and acute dysfunction of short-wavelength-sensitive (SWS) cone systems. The case was a healthy 39-year-old man. He noticed sudden onset of bilateral abnormal color vision. Ophthalmic examinations revealed normal fundi in both eyes. Farnsworth panel D-15 test and Farnsworth-Munsell 100-hue test showed tritanopia. White-on-white static perimetry showed no abnormality; however, blue-on-yellow static perimetry detected remarkably reduced sensitivity at the lower visual field in both eyes. ISCEV-standard full-field electroretinograms (ERGs) were normal; however, blue-on-yellow ERGs showed reduced amplitude of b-wave that was derived from SWS cone systems in both eyes. He was observed for 1 year, and no improvement in color vision was found during the observation. This is a unique case which showed bilateral, acquired, and acute dysfunction of SWS cone systems. The cause of the acquired tritanopia remains to be known. PMID:22610143

Kuniyoshi, Kazuki; Sakuramoto, Hiroyuki; Nakao, Akira; Takada, Sonoko; Shimomura, Yoshikazu

2012-08-01

73

Rogue Wave Modes for the Long Wave--Short Wave Resonance Model  

NASA Astrophysics Data System (ADS)

The long wave--short wave resonance model arises physically when the phase velocity of a long wave matches the group velocity of a short wave. It is a system of nonlinear evolution equations solvable by the Hirota bilinear method and also possesses a Lax pair formulation. ``Rogue wave'' modes, algebraically localized entities in both space and time, are constructed from the breathers by a singular limit involving a ``coalescence'' of wavenumbers in the long wave regime. In contrast with the extensively studied nonlinear Schrödinger case, the frequency of the breather cannot be real and must satisfy a cubic equation with complex coefficients. The same limiting procedure applied to the finite wavenumber regime will yield mixed exponential-algebraic solitary waves, similar to the classical ``double pole'' solutions of other evolution systems.

Chow, Kwok Wing; Chan, Hiu Ning; Kedziora, David Jacob; Grimshaw, Roger Hamilton James

2013-07-01

74

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

75

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

NASA Astrophysics Data System (ADS)

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

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

2012-10-01

76

On the mechanism of wavelength selection of self-organized shoreline sand waves  

NASA Astrophysics Data System (ADS)

Sandy shorelines exposed to very oblique wave incidence can be unstable and develop self-organized shoreline sand waves. Different types of models predict the formation of these sand waves with an initially dominant alongshore wavelength in the range 1-10 km, which is quite common in nature. Here we investigate the physical reasons for such wavelength selection with the use of a linear stability model. The existence of a minimum wavelength for sand wave growth is explained by an interplay of three physical effects: (a) largest relative (to the local shoreline) wave angle at the downdrift flank of the sand wave, (b) wave energy concentration at the updrift flank due to less refractive energy dispersion, and (c) wave energy concentration slightly downdrift of the crest due to refractive focusing. For small wavelengths, effects (a) and (c) dominate and cause decay, while for larger wavelengths, effect (b) becomes dominant and causes growth. However, the alongshore gradients in sediment transport decrease for increasing wavelength, making the growth rate diminish. There is therefore a growth rate maximum giving a dominant wavelength, LM. In contrast with previous studies, we show that LM scales with ?0/? (?0 is the wavelength of the offshore waves and ? is the mean shoreface slope, from shore to the wave base), an estimate of the order of magnitude of the distance waves travel to undergo appreciable transformation. Our model investigations show that the proportionality constant between LM and ?0/? is typically in the range 0.1-0.4, depending mainly on the wave incidence angle.

Berg, N.; Falqués, A.; Ribas, F.; Caballeria, M.

2014-03-01

77

CLASSICAL AREAS OF PHENOMENOLOGY: Investigation of pump-wavelength dependence of terahertz-wave parametric oscillator based on LiNbO3  

NASA Astrophysics Data System (ADS)

This paper investigates the performances of terahertz-wave parametric oscillators (TPOs) based on the LiNbO3 crystal at different pump wavelengths. The calculated results show that TPO characteristics, including the frequency tuning range, the THz-wave gain and the stability of THz-wave output direction based on the Si-prism coupler, can be significantly improved by using a short-wavelength pump. It also demonstrates that a long-wavelength-pump allows the employment of a short TPO cavity due to an enlarged phase-matching angle, that is, an increased angular separation between the pump and oscillated Stokes beams under the THz-wave generation at a specific frequency. The study provides an useful guide and a theoretical basis for the further improvement of TPO systems.

Sun, Bo; Liu, Jin-Song; Li, En-Bang; Yao, Jian-Quan

2009-07-01

78

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

79

Operational characteristics of the OMEGA short-wavelength laser fusion facility  

SciTech Connect

Twelve beams of the OMEGA, 24 beam direct-drive laser facility have been converted to 351-nm wavelength operation. The performance characteristics of this short-wavelength facility will be discussed. Beam-to-beam energy balance of +-2.3% and on-target energy, at 351-nm, in excess of 70 J per beam have been demonstrated. Long-term performance (>600 shots) of the system has been optimized by appropriate choice of index matching liquid, optical materials and coatings. The application of this system in direct-drive laser fusion experiments will be discussed.

Soures, J.M.; Hutchison, R.; Jacobs, S.; McCrory, R.L.; Peck, R.; Seka, W.

1984-01-01

80

Multi-Wavelength Study of Sgr A*: The Short Time Scale Variability  

Microsoft Academic Search

To understand the correlation and the radiation mechanism of flare emission\\u000ain different wavelength bands, we have coordinated a number of telescopes to\\u000aobserve SgrA* simultaneously. We focus only on one aspect of the preliminary\\u000aresults of our multi-wavelength observing campaigns, namely, the short time\\u000ascale variability of emission from SgrA* in near-IR, X-ray and radio\\u000awavelengths. The structure function

F. Yusef-Zadeh; J. Miller-Jones; D. Roberts; M. Wardle; M. Reid; K. Dodds-Eden; D. Porquet; N. Grosso

2010-01-01

81

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

NASA Technical Reports Server (NTRS)

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

Atakturk, Serhad S.; Katsaros, Kristina B.

1993-01-01

82

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

Microsoft Academic Search

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

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

1992-01-01

83

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

84

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

85

Phase-matched DAST DFG THz-wave generation using independently controllable dual wavelength light source  

Microsoft Academic Search

We report on the demonstration of an effective and widely tunable terahertz (THz)-wave generation using difference frequency generation (DFG) in an organic 4-dimethylamino-N-methyl-4-stilbazolium tosylate (DAST) by optimization of the pumping wavelength. We calculated the Type 0 phase-matching condition of DAST-DFG THz-wave generation over an ultrawide band (1.5-20 THz). A dual-wavelength optical parametric oscillator (OPO) with two KTP crystals mounted on

K. Miyamoto; A. Nawahara; T. Yamashita; H. Ito

2007-01-01

86

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

PubMed

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

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

2013-05-01

87

Experimental studies of X-ray emission physics and hydrodynamics using short wavelength lasers  

NASA Astrophysics Data System (ADS)

Several experimental efforts are currently under way at Low Alamos to study issues of importance for inertial confinement fusion with short wavelength lasers. These issues include the physics of X-ray conversion and the dynamics of short-wavelength laser interaction with high-Z plasmas; filamentation and self-focusing processes; and the growth of instabilities in laser-driven implosions. Most of these experiments are being pursued in collaboration with other laboratories, notably the University of Rochester and Lawrence Livermore National Laboratory. In addition, we are undertaking basic studies of the interaction of both atomic systems and solids with ultra-intense (approximately 10 to the minus 17th W/sq cm) subpicosecond lasers at Los Alamos. These experiments explore the response of atomic systems to strong fields, multiphoton excitation, and transient phenomena in dense plasmas.

Goldstone, P. D.; Casperson, D. E.; Cobble, J. A.; Coggeshall, S. V.; Gomez, C. C.; Hauer, A.; Kyrala, G. A.; Lee, P. H. Y.; Mead, W. C.; Schappert, G. T.

88

Long-term Fluctuation in Short-Wavelength Automated Perimetry in Glaucoma Suspects and Glaucoma Patients  

Microsoft Academic Search

PURPOSE. To determine the magnitude of the homogenous, LF(Ho), and the heterogeneous, LF(He), components of the long-term fluctuation (LF) in glaucoma suspects and in stable primary open angle glaucoma (POAG) patients undergoing short-wavelength automated perimetry (SWAP) and to com- pare the magnitude of the SWAP LF components with those elicited by standard white-on-white (W-W) perimetry. METHODS. The sample comprised 33

Natalie Hutchings; Sarah L. Hosking; John M. Wild; John G. Flanagan

2001-01-01

89

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

Microsoft Academic Search

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

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

1999-01-01

90

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

SciTech Connect

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

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

2011-03-16

91

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

SciTech Connect

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

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

2011-03-18

92

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

Microsoft Academic Search

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

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

93

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

PubMed Central

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

Figueiro, Mariana G.; Rea, Mark S.

2012-01-01

94

Finite-wavelength scattering of incident vorticity and acoustic waves at a shrouded-jet exit  

NASA Astrophysics Data System (ADS)

We consider a round jet shrouded for a finite downstream distance by a sharply-terminated concentric cylinder. As the vortical disturbances supported by a vortex-sheet model of the jet pass the sharp edge of the shroud exit some of the energy is scattered into acoustic waves. We quantify scattering into radiating acoustic modes by obtaining the far-field directivities. Of greater interest in the present study, however, is the scattering into upstream propagating acoustic modes, which is a potential mechanism for closing the resonance loop in the high-amplitude "howling" resonances that have been observed in various shrouded jet configurations over the years. We develop a model for this interaction at the shroud exit. The jet is represented as a uniform flow separated by a cylindrical vortex sheet from a concentric co-flow within the cylindrical shroud. A second vortex sheet separates the co-flow from an ambient flow outside the shroud, downstream of its exit. The Wiener-Hopf technique is used to solve the scattering problem and compute reflectivities at the shroud exit. Finite-wavelength (finite-frequency) analysis is essential for investigating this mechanism: the long-wavelength limit degenerates to a fully reflective fixed-pressure condition at the shroud exit, while the short-wavelength limit produces no reflection since the vortex sheet in this case does not interact with the shroud. The focus here is on wavelengths comparable to the shroud exit diameter for which resonances are observed. For some conditions it appears that the reflection of finite-wavelength hydrodynamic vorticity modes on the vortex sheet defining the jet could be sufficient to reinforce the shroud acoustic modes in a way that facilitate resonance. The analysis also gives the reflectivities for the shroud acoustic modes, which would also be important in establishing resonance conditions. Interestingly, it is also predicted that the shroud exit can be "transparent" for ranges of Mach numbers, with no reflection into any upstream propagating acoustic mode. This is phenomenologically consistent with observations in certain experiments that indicate a peculiar sensitivity of resonances of this kind to, say, jet Mach number.

Samanta, Arnab

95

Design for new structure InAs\\/In x Ga 1? x Sb superlattice two-color—short and long wavelength infrared photodetector  

Microsoft Academic Search

InAs\\/InxGa1?xSb superlattices have been used in short and long wavelength infrared photodetectors, respectively, as detective material with advanced molecular beam epitaxy (MBE) technology, but this two wave bands simultaneous detection at the same photodetector using the same detection material has rarely been realized. GaAs-based two-color infrared detection arrays using double detector structure that needs more complex photolithography and epitaxial processing

Wei-Feng Sun; Mei-Cheng Li; Lian-Cheng Zhao

2010-01-01

96

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

97

Pupil Slicing Adaptive Optics:. Making Extremely Large Telescopes Diffraction Limited at Short Wavelengths  

NASA Astrophysics Data System (ADS)

Extremely Large Telescopes (ELTs) will have aperture diameters up to 42 meters. Adaptive Optics (AO) at short wavelengths (< 1 micron) will be very hard to implement at these wavelengths because of the limited number of actuators on state-of-the-art deformable mirrors and because of the limited brightness of Laser Guide Stars (LGSs). For 1 arcsec seeing at 500 nm wavelength deformable mirrors (DMs) with about 150000 actuators will be needed and LGSs of a brightness of V = 8 to 9. That exceeds our present capabilities by a factor of about 100 and 2 magnitudes respectively. One might expect both to improve with time. We propose to combine the techniques of "pupil slicing" and AO to sharpen the telescope images at short wavelengths to the size of Airy disk of the pupil slices. I refer to this technique as "Pupil Slicing Adaptive Optics" or PSAO. At 500 nm wavelength that would correspond to the Airy disk of an approximately 5 meter diameter aperture, or a FWHM of 0.02 arcsec. As DMs increase in their number of actuators, the size of the pupil slices increases thus improving the angular resolution. Ultimately the full angular resolution of, for example, a 42 meter aperture would be reached (0.0024 arcsec at 500 nm). Of course, this does not resolve the issue of the limited brightness of LGSs. For it one has to wait for more powerful lasers and the development of perspective elongation correction techniques. Alternatively one would accept limited sky coverage (0.1%) when using natural guide stars (NGSs). Particularly interesting is the PSAO technique for high resolution spectroscopy where the smaller image sizes even for many slices results in a significant decrease in spectrograph dimensions. Note from Publisher: This article contains the abstract only.

Beckers, Jacques M.

2009-09-01

98

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

NASA Astrophysics Data System (ADS)

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

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

2013-06-01

99

[Comparative study on software demodulation for continuous wave and quasi-continuous wave wavelength modulation spectroscopy].  

PubMed

According to the modulation signal applied on laser diodes, wavelength modulation spectroscopy (WMS) can be divided into continuous wave (CW) WMS and quasi-continuous wave (QCW) WMS. In order to deeply compare CW-WMS and QCW-WMS, we used a specific software-realized lock-in amplifier for continuous and quasi-continuous modulation signal demodulation. The invalid signal in quasi-continuous modulation spectrum was filtered off, and then the effective detection signal was demodulated to obtain the second harmonic signal (WMS-2f). It was compared with the 2f signal demodulated continuous laser modulation spectrum with software. The results show that while the same system parameters are set, the signal-to-noise of the quasi-continuous modulation spectrum is 5% higher than the continuous modulation spectrum with software demodulation measurements, and the detection limit is 11.3% lower. And without the invalid signal in quasi-continuous modulation spectrum, the standard WMS-2f signal can be demodulated, which has potential to be used for the investigation of gas absorption profile. This work has provided accurate reference for selections of the laser modulation spectroscopy. PMID:24611415

Shao, Xin; Liu, Fu-Gui; Chen, Wen-Liang

2013-12-01

100

A numerical study of the long wave-short wave interaction equations  

Microsoft Academic Search

Abstract Two numerical methods,are presented for the periodic initial-value problem,of the long wave–short wave interaction equations describing the interaction between,one long longitudinal wave and two short transverse waves propagating in a generalized elastic medium. The first one is the relaxation method, which is implicit with second-order accuracy in both space and time. The second one is the split-step Fourier method,

H. Borluk; G. M. Muslu; H. A. Erbay

2007-01-01

101

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

102

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

103

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

104

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

105

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

NASA Astrophysics Data System (ADS)

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

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

1998-12-01

106

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

Microsoft Academic Search

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

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

2010-01-01

107

Wavelength conversion for WDM communication systems using four-wave mixing in semiconductor optical amplifiers  

Microsoft Academic Search

Four-wave mixing (FWM) in semiconductor optical amplifiers is an attractive mechanism for wavelength conversion in wavelength-division multiplexed (WDM) systems since it provides modulation format and bit rate transparency over wide tuning ranges. A series of systems experiments evaluating several aspects of the performance of these devices at bit rates of 2.5 and 10 Gb\\/s are presented. Included are single-channel conversion

David F. Geraghty; Robert B. Lee; Marc Verdiell; Mehrdad Ziari; Atul Mathur; Kerry J. Vahala

1997-01-01

108

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

109

Permittivity of water at millimeter wave-lengths  

NASA Technical Reports Server (NTRS)

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

Blue, M. D.

1976-01-01

110

Millimeter scale electrostatic mirror with sub-wavelength holes for terahertz wave scanning  

NASA Astrophysics Data System (ADS)

This work reports the design, microfabrication, and characterization of highly reflective electrostatic mirrors with sub-wavelength holes for scanning terahertz (THz) waves. The mirror consists of an aluminum coated silicon mirror plate precisely assembled on the top of two axis torsional microactuators. The mirror plate with sub-wavelength microholes not only provides high reflectivity over 98% at THz waves by decoupling the surface plasmon resonance but also reduces air damping by allowing air to flow through the mirror plate during the mirror scanning. The device can provide many opportunities for miniaturized THz time domain spectroscopic imaging systems.

Park, Hyeon-Cheol; Lee, Jung-Hwan; Park, Sang-Gil; Yee, Dae-Su; Jeong, Ki-Hun

2013-01-01

111

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

NASA Astrophysics Data System (ADS)

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

Yu, Huaqing; Li, Baojun

2013-04-01

112

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

PubMed Central

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

Yu, Huaqing; Li, Baojun

2013-01-01

113

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

PubMed

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

Yu, Huaqing; Li, Baojun

2013-01-01

114

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

Microsoft Academic Search

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

Andreas U Bayer; Carl Erb

2002-01-01

115

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

Microsoft Academic Search

A short-pulse laser beat wave scheme for advanced particle accelerator applications is examined. A short, intense (3-ps, >1018-W cm-2) two-frequency laser pulse is produced by use of a modified chirped-pulse amplification scheme and is shown to produce relativistic plasma waves during interactions with low-density plasmas. The generation of plasma waves was observed by measurement of forward Raman scattering. Resonance was

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

2002-01-01

116

Mesopause airglow modulation by ducted short-period gravity waves  

NASA Astrophysics Data System (ADS)

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 and O( 1S) 557.7 nm airglow emissions. Models include transport of relevant minor and major species, and time-dependent chemical kinetics of ozone and hydrogen, which exhibit chemical lifetimes on the order of gravity wave periods at airglow altitudes. The role of dynamics and chemical time dependence on airglow response to realistic short period gravity wave perturbations is then studied. The models allow direct calculation of integrated emission intensities, facilitating detailed comparisons with ground-based airglow imager data. We first validate our model while exploring three case studies for the excitation of thermally-ducted wave modes, by linear tunneling, and by breaking or nonlinear-propagation of other short period gravity waves. The modeled ducted wave modes are determined by Doppler shift and varying thermal structure. Consistent with past studies, numerically modeled ducted wave properties are found to agree with analytical models for fully-ducted modes in weak, constant and stable wind flow conditions. Two model case studies of short-period gravity wave events, clearly resembling events observed in experimental airglow data, are presented: First, we examine a front-like ducted wave event, observed during the ALOHA-93 campaign in Hawaii. The hypothetical nonlinear excitation of this ducted wave is modeled, and model airglow intensity modulation is calculated. Agreement, and potential disagreement, between model results and observed image data are found. When vertical transport of O3 is relatively weak, OH and OI emissions are found to emit in anti-phase for equal-phase wave temperature and vertical velocity perturbations. This effect results from the chemical time dynamics associated with the OH excitation reaction, which place dependence principally on H and O3. When steep gradients of O3 lead to strong density perturbations, the OH emission may exhibit opposite response above and below the peak of O3, consistent with the sign of the gradient. The region of the layer exhibiting stronger perturbation will dominate the integrated emission intensity, thereby determining the phase of the intensity measured by a ground-based imager. This reveals strong dependence on the shape of the minor species profiles of O and O3, and also on the local wave perturbation magnitude and packet spatial configuration. Caution is thus needed in the interpretation and modeling of short-period wave signatures in airglow, due to significant variability of minor species profiles and atmospheric structure. Second, we investigate a wave event observed at Bear Lake Observatory, UT, which also clearly exhibits antiphase perturbations of OH and OI intensity. Simultaneous radar wind data reveals the strong presence of a semidiurnal tidal motion; due to a tidal wind peak ˜50 m/s, the wave is fully-ducted by Doppler shift. Using idealized models of ducted wave forcing, several hypothetical waves are examined, which agree with the observed event. Modeled airglow intensities again suggest that the opposite-phase responses of OH and OI layers may be due to opposite photochemical responses, rather than to opposite wave dynamics at characteristic layer altitudes. Results are again highly sensitive to the actual profiles of minor species, and suggest that the phase of the integrated OH emission is determined by the structure of the wave perturbation with respect to the local O3 density gradients. Finally, we investigate the effects of dynamic background flow on the propagation of ducted waves. Under idealized static conditions, ducted gravity waves are dissipated principally by viscosity, however dynamic duct

Snively, Jonathan B.

117

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

Microsoft Academic Search

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

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

2000-01-01

118

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

PubMed

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

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

2013-10-01

119

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

PubMed Central

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

Figueiro, Mariana G.; Rea, Mark S.

2012-01-01

120

Mode coupling effects on alpha-particle-driven long wavelength Alfven wave instability  

SciTech Connect

It is demonstrated both analytically and numerically that mode couplings play an important role in the nonlinear evolution of alpha-particle-driven [ital long] [ital wavelength] Alfven wave instabilities. The mode coupling process is characterized by a beat between two linearly unstable Alfven waves having opposite frequencies, which generates a linearly stable, static (zero frequency) mode. The backreaction of the static mode tends to stabilize the Alfven instabilities by eliminating the phase shift between the alpha pressure and the Alfven fluctuations.

Gang, F.Y. (Plasma Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)); Leboeuf, J. (Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830 (United States))

1993-08-01

121

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

Microsoft Academic Search

Characteristics of the internal structure of the laser supported detonation (LSD) waves, such as the electron density ne and the electron temperature Te profiles behind the shock wave were measured using a two-wavelength Mach-Zehnder interferometer along with emission spectroscopy. A TEA CO2 laser with energy of 10 J\\/pulse produced explosive laser heating in atmospheric air. Results show that the peak

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

2011-01-01

122

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

123

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

124

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

Microsoft Academic Search

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

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

2000-01-01

125

A comparative study of three evolutionary algorithms for surface acoustic wave sensor wavelength selection  

Microsoft Academic Search

A surface acoustic wave sensor (the zNose™) was utilized to detect fruit defects by measuring and analyzing the volatile compounds emitted by apples. The zNose generates a spectrum with 512 wavelength values. This large number of variables not only increases the processing time, but reduces the classification accuracy due to irrelevant information and noise. In this study, three evolutionary techniques,

Changying Li; Paul H. Heinemann

2007-01-01

126

Improving Short Wave Breaking Behavior In Surfbeat Models  

NASA Astrophysics Data System (ADS)

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

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

2009-12-01

127

Ultraviolet- and short-wavelength cone contributions alter the early components of the ERG of young zebrafish.  

PubMed

The electroretinogram (ERG) is a commonly used measure to examine retinal processing in both basic and clinical research. The purpose of this study was to determine the retinal mechanisms responsible for the developmental differences found in the zebrafish ERG waveform. The ERG of young zebrafish possesses a voltage-negative response to ultraviolet- and short-wavelength stimuli, but not to middle- and long-wavelength stimuli; the ERG of adult zebrafish does not possess this response component. ERGs were obtained from young zebrafish before and after the introduction of either aspartate, or a combination of APB (DL-2-amino-4-phosphonobutyric acid) and PDA (cis-2,3-piperidinedicarboxylic acid) in order to suppress the responses of various types of retinal neurons. Log irradiance versus response amplitude functions of the ERG response to 200-ms stimuli of various wavelengths at various times following stimulus onset (70 and 120 ms) was derived as well as spectral sensitivity. Aspartate eliminated all voltage-positive responses regardless of stimulus wavelength; irradiance-response functions following aspartate were similar to the early responses of young control fish to ultraviolet- and short-wavelength stimuli. APB + PDA produced similar but not identical results as aspartate, suggesting that the combination of these agents does not completely eliminate all post-receptoral contributions to the ERG. Spectral sensitivity functions derived from aspartate-exposed subjects at various time measurements were dominated by contributions from ultraviolet- and short-wavelength-sensitive cone types. These wavelength-dependent ERG responses are similar to those found in humans with enhanced S-cone syndrome. Finally, ERG waveform differences across stimulus wavelength suggest that the circuitry of ultraviolet- and short-wavelength cone types is different to that of middle- and long-wavelength cone types in young zebrafish. PMID:15730883

Bilotta, Joseph; Trace, Sara E; Vukmanic, Eric V; Risner, Michael L

2005-02-01

128

Extraordinarily low evolutionary rates of short wavelength-sensitive opsin pseudogenes.  

PubMed

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

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

2014-01-15

129

Near-infrared wavelength intersubband transitions in GaN/AlN short period superlattices  

NASA Astrophysics Data System (ADS)

Intersubband transitions in GaN/AlN short period superlattices prepared by molecular beam epitaxy were investigated using the optical absorption technique. The peak position wavelengths of these transitions are found to span the spectral range of 1.35-2.90 ?m for samples cut into 45° waveguides with GaN quantum well thicknesses ranging between 1.70 and 2.41 nm. The Fermi energy levels are estimated from the carrier concentrations, which were measured using an electrochemical capacitance-voltage profiler. The well widths were inferred from comparing the measured peak position energy of the intersubband transitions and the bound state energy levels calculated using the transfer matrix method.

Decuir, E. A.; Fred, Emil; Passmore, B. S.; Muddasani, A.; Manasreh, M. O.; Xie, Jinqiao; Morkoç, Hadis; Ware, M. E.; Salamo, G. J.

2006-10-01

130

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

NASA Astrophysics Data System (ADS)

High-order harmonic generation efficiency is theoretically modeled and compared with experiments using 400 and 800 nm driver pulses. It is shown that, for a short drive wavelength and a Keldysh parameter larger than 1, the Ammosov-Delone-Krainov (ADK) ionization model does not give a good agreement between theory and experiment. Since the ADK ionization model only accounts for tunnel ionization, it underestimates the yield of low-order harmonics from the wings of the driver pulse. In contrast, the Yudin-Ivanov ionization model [Phys. Rev. APLRAAN1050-294710.1103/PhysRevA.64.013409 64, 013409 (2001)], which accounts for both tunnel and multiphoton ionization, gives much better agreement with the experimental results.

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

2011-07-01

131

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

USGS Publications Warehouse

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

Blakely, R. J.

1979-01-01

132

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

NASA Technical Reports Server (NTRS)

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

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

1988-01-01

133

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

134

Simultaneous recording of multifocal VEP responses to short-wavelength and achromatic stimuli  

PubMed Central

A paradigm is introduced that allows for simultaneous recording of the pattern-onset multifocal visual evoked potentials (mfVEP) to both short-wavelength (SW) and achromatic (A) stimuli. There were 5 sets of stimulus conditions, each of which is defined by two semi-concurrently presented stimuli, A64/SW (a 64% contrast achromatic stimulus and a short-wavelength stimulus), A64/A8 (64% achromatic/8% achromatic), A0/A8 (0% (gray) achromatic/8% achromatic), A64/A0 and A0/SW. When paired with A64 as part of A64/SW, the SW stimulus yielded mfVEP responses (SWmfVEP) with diminished amplitude in the fovea, consistent with the known sensitivity of the S-cone system. In addition, when A8, which is approximately equal to the L and M cone contribution of the SW stimulus, was recorded alone, the response to A8 was small, but significantly larger than noise. However, when A8 was paired with A64, the response to A8 was reduced to close to noise level, suggesting that the LM cone contribution of the SWmfVEP can be suppressed by A64. When A64 was recorded alone, the response to A64 was about 32% larger than the mfVEP for A64 when paired with the SW. Likewise, the presence of A64 stimulus also reduces the response of SWmfVEP by 35%. Finally, an intense narrow-band yellow background prolonged the latency of SW response for the A0/SW stimulus but not the latency of SW response for the A64/SW stimulus. These results indicate that it is possible to simultaneously record an SWmfVEP with little LM cone contribution along with an achromatic mfVEP.

Wang, Min; Hood, Donald C.

2010-01-01

135

Wavelength-stabilized tilted wave lasers with a narrow vertical beam divergence  

NASA Astrophysics Data System (ADS)

We studied laser diodes grown in the tilted wave geometry with cleaved facets. In this approach a cavity with the gain medium is coupled to the second cavity, while the phase matching of the modes of the two cavities results in the wavelength stabilization. The mode separation can be controlled by the tilt angle of the leaky wave emission and the thickness of the coupled cavity. In one case a ~100 µm thick transparent substrate with a polished and dielectric-coated back surface was used as a coupled waveguide. In the second case, a 10 µm thick GaAs layer followed by an InGaP evanescent reflector was applied. We observed an increase in the lasing mode wavelength spacing and the width of the vertical far-field lobes from ~0.7° to 5° (full width at half maximum, FWHM) with the reduction of the thickness of the coupled cavity, in agreement with expectations. The FWHM numbers correspond to the diffraction limit for 100 and 10 µm thick coupled waveguides, respectively. A high temperature stability of the lasing wavelengths (0.1 nm K-1) was revealed. The results indicate that a new generation of wavelength-stabilized lasers for applications requiring ultrahigh brightness and wavelength stabilization can be developed.

Novikov, I. I.; Shernyakov, Yu M.; Maximov, M. V.; Gordeev, N. Yu; Kaluzhniy, N. A.; Mintairov, S. A.; Lantratov, V. M.; Payusov, A. S.; Shchukin, V. A.; Ledentsov, N. N.

2008-07-01

136

Pulse width considerations for a short range millimeter wave radar  

Microsoft Academic Search

Simple means for optimizing the pulse width of a basic tracking short-range millimeter wave radar are shown. Ground-based or maritime use is assumed. The cases discussed include volume clutter due to rain or other particles within the antenna's main beam and surface clutter due to grass, soil, or snow. Depending on the available RF hardware and desired lowest detectable target

Jukka Ruoskanen; Arvi Serkola; Pekka Eskelinen; Heikki Heikkila

2004-01-01

137

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

NASA Technical Reports Server (NTRS)

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

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

1979-01-01

138

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

PubMed

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

Herrera, Rodrigo Acuna

2012-11-01

139

Terahertz wave generation and detection from a CdTe crystal characterized by different excitation wavelengths  

NASA Astrophysics Data System (ADS)

Terahertz (THz) wave generation and detection from a ‹110›-oriented CdTe crystal via optical rectification and electro-optic sampling has been performed with laser wavelengths ranging from 710 to 970 nm. Three optical rectification regimes are studied with various excitation wavelengths: a resonance-enhanced regime above the bandgap, a highly phase-mismatched regime near the band gap, and a semi-phase-matched regime. A CdTe crystal generates more THz power than a ZnTe crystal at 970 nm.

Xie, Xu; Xu, Jingzhou; Zhang, X.-C.

2006-04-01

140

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

141

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

PubMed

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

Kosec, Matjaž; Bürmen, Miran; Tomaževi?, Dejan; Pernuš, Franjo; Likar, Boštjan

2012-10-01

142

The Gravity-Capillary Wave Interaction Applied to Wind-Generated, Short-Gravity Waves.  

National Technical Information Service (NTIS)

The gravity-capillary wave interaction has been simplified for the special case where one component of the interacting triad is a short-gravity wave. Wind-speed effects have been included in an ad hoc manner by forcing the dispersion relation to conform t...

W. J. Plant

1979-01-01

143

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

PubMed Central

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

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

2011-01-01

144

Wave-length dependencies of light scattering in normal and cold swollen rabbit corneas and their structural implications*  

PubMed Central

1. The studies described herein involve the use of light scattering measurements to characterize the ultrastructural arrangement of the constituent collagen fibrils in rabbit corneal stromas. 2. Theoretical light scattering techniques for calculating the scattering to be expected from the structures revealed by electron micrographs are discussed, and comparison with the experimental light scattering tests the validity of these structures. 3. The wave-length dependence of light transmission and of angular light scattering from normal corneas is in agreement with the short range ordering of collagen fibrils depicted in electron micrographs. 4. The transmission measurements on oedematous rabbit corneas indicate that transmission decreases linearly with the ratio of thickness to normal thickness. 5. The wave-length dependence of transmission through cold swollen corneas indicates that the increased scattering is caused by large inhomogeneities in the ultrastructure. Electron micrographs do, indeed, reveal the presence of such inhomogeneities in the form of large regions completely devoid of fibrils. ImagesPlate 1Plate 2Plate 3

Farrell, R. A.; McCally, R. L.; Tatham, P. E. R.

1973-01-01

145

Full model analysis of the four-wave mixing anti-STOKES component growth in the wavelength-division multiplexing solitons systems near the zero-dispersion wavelength  

NASA Astrophysics Data System (ADS)

The growth of the anti-Stokes component (ASC) of the four-wave mixing (FWM) near the zero-dispersion wavelength (ZDWL) is analyzed in wavelength-division multiplexing (WDM) solitons systems. The study conducted under the full model analysis shows that the FWM decreases along the transmission line. For long distances, an analytical asymptotic solution of the FWM is used and confirms this feature beyond the tenth amplification node.

Mandeng Mandeng, L.; Fewo Ibraid, S.; Tchawoua, C.

2013-11-01

146

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

147

On stability of generalized short-crested water waves  

NASA Astrophysics Data System (ADS)

In this paper, we take up the question of dynamic stability of genuinely two-dimensional “generalized” hexagonal traveling wave patterns on the surface of a three-dimensional ideal fluid (i.e., stability of Generalized Short-Crested Wave (GSCW) solutions of the water wave problem). We restrict ourselves to a study of spectral stability which considers the linearization of the water wave operator about one of these traveling generalized hexagonal waves, and draws conclusions about stability from the spectral data of the resulting linear operator. Within the class of perturbations we are allowed to study, for a wide range of geometrical parameters, we find stable traveling waveforms which eventually destabilize with features that depend strongly on the problem configuration. In particular, we find “Zones of Instability” for patterns shaped as symmetric diamonds, while such zones are absent for asymmetric configurations. Furthermore, we note that within a geometrical configuration, as a “generalized SCW” ratio is varied (essentially the character of the linear solution), these waves become more unstable as the waves become more asymmetric.

McBride, Travis; Nicholls, David P.

2012-09-01

148

Polarization of Long-Wavelength Gravitational Waves by Rotating Black Holes  

Microsoft Academic Search

The scattering cross section for a long-wavelength planar gravitational wave impinging upon a rotating black hole is calculated, for the special case in which the direction of incidence is aligned with the rotation axis. We show that black hole rotation leads to a term in the cross section that is proportional to $a\\\\omega$. Hence, contrary to some claims, co-rotating and

Sam R. Dolan

2008-01-01

149

Polarization of Long-Wavelength Gravitational Waves by Rotating Black Holes  

Microsoft Academic Search

The scattering cross section for a long-wavelength planar gravitational wave\\u000aimpinging upon a rotating black hole is calculated, for the special case in\\u000awhich the direction of incidence is aligned with the rotation axis. We show\\u000athat black hole rotation leads to a term in the cross section that is\\u000aproportional to $a\\\\omega$. Hence, contrary to some claims, co-rotating and

Sam R. Dolan

2008-01-01

150

Dual-wavelength, two-crystal, continuous-wave optical parametric oscillator.  

PubMed

We report a cw optical parametric oscillator (OPO) in a novel architecture comprising two nonlinear crystals in a single cavity, providing two independently tunable pairs of signal and idler wavelengths. Based on a singly resonant oscillator design, the device permits access to arbitrary signal and idler wavelength combinations within the parametric gain bandwidth and reflectivity of the OPO cavity mirrors. Using two identical 30 mm long MgO:sPPLT crystals in a compact four-mirror ring resonator pumped at 532 nm, we generate two pairs of signal and idler wavelengths with arbitrary tuning across 850-1430 nm, and demonstrate a frequency separation in the resonant signal waves down to 0.55 THz. Moreover, near wavelength-matched condition, coherent energy coupling between the resonant signal waves, results in reduced operation threshold and increased output power. A total output power >2.8 W with peak-to-peak power stability of 16% over 2 h is obtained. PMID:21847150

Samanta, G K; Ebrahim-Zadeh, M

2011-08-15

151

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

NASA Astrophysics Data System (ADS)

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

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

1984-09-01

152

Room temperature continuous-wave operation of GaInNAs long wavelength VCSELs  

Microsoft Academic Search

Vertical cavity surface-emitting lasers (VCSELs) are becoming increasingly important for short-haul optical fiber transmission systems. Given the commercial success of GaAs-based 850 nm VCSELs, dramatic enhancements in transmission bandwidth and distance can be achieved in conventional single- and multi-mode fiber by extending the emission wavelength to the 1300 nm-1550 nm range. GaInNAs is a promising active layer material grown on

M. C. Larson; C. W. Coldren; S. G. Spruytte; H. E. Petersen; J. S. Harris

2000-01-01

153

Investigation of wavelength conversion by four-wave mixing in semiconductor optical amplifiers  

NASA Astrophysics Data System (ADS)

Four-wave mixing (FWM) in semiconductor optical amplifiers (SOAs) is investigated for wavelength conversion in high-speed, all-optical networks. The design of the wavelength converter is optimized and the system performance limitations imposed by the fundamental physical principles involved in the SOA FWM process are characterized. Single channel conversion performance is evaluated. The FWM efficiency ultimately determines many systems-level characteristics of the wavelength converter. The spectral range of our wavelength converter is characterized. Wide wavelength conversions of up to 18 nm and complete coverage of a 10 nm spectral range are demonstrated, while maintaining a BER performance of better than 10-9 at 10 Gb/s. The converter also demonstrates a large dynamic input range of over 10 dB at 2.5 Gb/s. And the first characterization of cascaded FWM SOA wavelength converters, cascading conversion of up to 10 nm at 10 Gb/s, is performed. With a simple modification of the converter design to a dual-pump configuration, the wavelength converter is able to provide nearly polarization insensitive performance. The converted signal's magnitude varies by less than 1.5 dB and its sensitivity varies by less than 2 dB for 2.5 Gb/s signals over the entire range of input polarizations. Time resolved spectral analysis is performed to evaluate the spectral properties of the wavelength converter. A pattern-dependent additional chirp is measured on the signal, primarily resulting from fluctuations in the gain saturation of the SOA. This degradation to the optical phase conjugation, intrinsic to the SOA FWM process, is minimal enough to allow dispersion compensation by mid- span spectral inversion. Error-free detection of a directly modulated 10 Gb/s signal is achieved over 120 km. Additional demonstrations are also presented. Multi- channel wavelength conversion and dynamic routing are successfully performed. Finally, some work on a microcavity erbium-doped fiber laser, initially designed and developed for use as a tunable source for wavelength- division multiplexed networks, is presented.

Geraghty, David Francis

1997-10-01

154

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

PubMed Central

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

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

2010-01-01

155

Observation of Short Wavelength Fluctuations in the DIII--D Tokamak  

NASA Astrophysics Data System (ADS)

Short wavelength fluctuations with k ~?_pe/c, k?_i ~6 were detected by a far-infared (FIR) scattering system on the DIII--D tokamak. They appeared in bursts synchronized with the switching time of two neutral beam sources which were turned on and off alternately with the same beam power but different injection angle. This was observed in ELMing H--mode plasmas with negative central magnetic shear. The plasma parameters were: B_t=2.0 T, I_p=1.6 MA, T_i(0)=7 keV, T_e(0)=4.5 keV, n_e(0)=3×10^13 cm-3, P_b=4.7 MW, P_ECH=1.3 MW, P_ICH<1 MW. These fluctuations were observed in the frequency band at 500 kHz ±20% propagating in the electron diamagnetic drift direction in the laboratory frame of reference. With the radial electric field Er determined by the motional Stark effect, the Doppler shift correction yielded a frequency comparable to the ion diamagnetic drift frequency in the plasma frame of reference with E_r=0.

Wong, K. L.; Rettig, C. L.; Petty, C. C.

1998-11-01

156

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

157

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

158

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

PubMed

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

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

2006-01-01

159

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

PubMed Central

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

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

2012-01-01

160

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

161

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 108 K with a high detectivity of DBLIP*=1.2×1011 Jones.

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

2008-03-01

162

The Rigorous Approximation of Long-Wavelength Capillary-Gravity Waves  

NASA Astrophysics Data System (ADS)

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

Schneider, Guido; Wayne, C. Eugene

163

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

164

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

Microsoft Academic Search

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

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

2012-01-01

165

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

166

Short wavelength automated perimetry can detect visual field changes in diabetic patients without retinopathy  

PubMed Central

Purpose: The purpose of the following study is to compare short wave automated perimetry (SWAP) versus standard automated perimetry (SAP) for early detection of diabetic retinopathy (DR). Materials and Methods: A total of 40 diabetic patients, divided into group I without DR (20 patients = 40 eyes) and group II with mild non-proliferative DR (20 patients = 40 eyes) were included. They were tested with central 24-2 threshold test with both shortwave and SAP to compare sensitivity values and local visual field indices in both of them. A total of 20 healthy age and gender matched subjects were assessed as a control group. Results: Control group showed no differences between SWAP and SAP regarding mean deviation (MD), corrected pattern standard deviation (CPSD) or short fluctuations (SF). In group I, MD showed significant more deflection in SWAP (?4.44 ± 2.02 dB) compared to SAP (?0.96 ± 1.81 dB) (P =0.000002). However, CPSD and SF were not different between SWAP and SAP. In group II, MD and SF showed significantly different values in SWAP (?5.75 ± 3.11 dB and 2.0 ± 0.95) compared to SAP (?3.91 ± 2.87 dB and 2.86 ± 1.23) (P =0.01 and 0.006 respectively). There are no differences regarding CPSD between SWAP and SAP. The SWAP technique was significantly more sensitive than SAP in patients without retinopathy (p), but no difference exists between the two techniques in patients with non-proliferative DR. Conclusion: The SWAP technique has a higher yield and efficacy to pick up abnormal findings in diabetic patients without overt retinopathy rather than patients with clinical retinopathy.

Zico, Othman Ali; El-Shazly, Amany Abdel-Fattah; Ahmed, Eslam Elsayed Abdel-Hamid

2014-01-01

167

Global Observations of Short Wavelength Topography on The Inner Core Boundary  

NASA Astrophysics Data System (ADS)

Using high quality earthquake doublets from the South Sandwich Islands observed at the Yellowknife array, Cao et al. (2007) found evidence for significant anomalies in the amplitude of the post-critical reflected phase PKiKP, particularly in the frequency band 1-2 Hz, which they interpreted as evidence for short wavelength topography on the Inner Core Boundary (ICB). While the observations reported were limited to a small region of the ICB, an interesting question is whether such topography is globally distributed or presents differences between the eastern and western hemispheres, for which clear differential travel times and attenuation have been reported for these phases. Constraining the nature and lateral variations of the ICB and top of the inner core may help shed light on core dynamics and in particular the generation of the geodynamo. We have now scanned the IRIS database from 1972 to 2005, and assembled a high quality global dataset of waveforms in the distance range 134-144o, for which PKIKP and PKiKP are sufficiently separated to warrant the quantification of amplitude ratios between these two phases. The measured PKIKP/PKiKP amplitude ratio R in the frequency band 1-2 Hz was used to divide the data set into "normal" or "anomalous", for which values of R are larger than the maximum that can be explained by any realistic reference earth model. We found no systematic pattern in the distribution of normal and anomalous observations, both observed throughout the areas sampled by the available distribution of sources and receivers. In particular, there is no hemispherical pattern, indicating that the latter must originate at some depth below the ICB, rather than on the ICB itself.

Lippman, J. D.; Cao, A.; Romanowicz, B.

2007-12-01

168

LOWTRAN 7: Status, review, and impact for short-to-long-wavelength infrared applications  

NASA Astrophysics Data System (ADS)

A summary of the recent improvements, modifications, and updates to the LOWTRAN 7 atmospheric transmittance and radiance computer program will be given. There were some significant changes to the LOWTRAN model in the latest version, LOWTRAN 7, that affect the manner in which the basic atmospheric transmittance and radiance calculations are performed as well as providing the user with greater flexibility and more capabilities. The LOWTRAN 7 code now calculates atmospheric transmittance, atmospheric background radiance, single-scattered and earth-reflected solar and lunar radiance, direct solar irradiance, and multiple-scattered solar and thermal radiance. The spectral range of the code was extended from 0 to 50,000 cm at a spectral resolution of 20 cm. The program can cope with an observer/target geometry and can include the effects of molecular, aerosol, fog, rain, and cloud absorption and scattering. Some of the basic changes to LOWTRAN 7, in particular the introduction of new molecular absorption transmission functions and separating the transmittances due to CO2, N2O, CO, CH4 and O2, will give rise to differences in the transmittance and radiance calculations (compared to those obtained with LOWTRAN 6) depending on the observer/target viewing geometry and spectral region. The dual purpose is to indicate how the new changes to LOWTRAN 7 affect atmospheric transmittance and background radiance calculations for specific applications. Both high-altitude, long-range and low-altitude, moderate-range scenarios are stressed and will show the impact that the recent changes to LOWTRAN 7 have made on the short, medium and long wavelength infrared atmospheric attenuation and background radiance, compared to calculations with LOWTRAN 6.

Kneizys, F. X.; Anderson, G. P.; Shettle, Eric P.; Abreu, L. W.; Chetwynd, J. H., Jr.; Selby, J. E. A.; Gallery, W. O.; Clough, S. A.

1990-03-01

169

Comparison of Near-Infrared and Short-Wavelength Autofluorescence in Retinitis Pigmentosa  

PubMed Central

Purpose. To compare near-infrared autofluorescence (NIR-AF) and short-wavelength (SW) AF in retinitis pigmentosa (RP) and assess their relationships to underlying retinal structure and visual function. Methods. SW-AF, NIR-AF, and spectral domain optical coherence tomography (SD-OCT) images were acquired from 31 patients (31 eyes) with RP and registered to each other. Microperimetry was performed on a subset of 12 patients. For both SW-AF and NIR-AF images, three independent observers measured the area enclosed by the outer border of the hyperautofluorescent ring and the distance from the fovea to the outer and inner border of the ring. For SD-OCT images, the distance from the fovea to the location where the inner segment ellipsoid (ISe) band became undetectable was measured. Results. All eyes had a hyperautofluorescent ring on both SW-AF and NIR-AF. The position of the outer border of the ring was similar for both modalities. On NIR-AF the signal outside the ring was lower than inside the ring, resulting in a high contrast between the two areas. Also, the inner border of the ring was closer to the fovea on NIR-AF than SW-AF, corresponding to a location on SD-OCT where the ISe band was at least partially intact. Visual sensitivity was relatively preserved within the ring, reduced across the ring, and markedly decreased or nonrecordable outside the ring. Conclusions. SW-AF and NIR-AF are both useful for monitoring disease progression in RP; however, NIR-AF may have advantages clinically and could unveil a process that precedes the formation of fluorophores that emit the SW-AF signal.

Duncker, Tobias; Tabacaru, Mirela R.; Lee, Winston; Tsang, Stephen H.; Sparrow, Janet R.; Greenstein, Vivienne C.

2013-01-01

170

Visualization of the Optic Fissure in Short-Wavelength Autofluorescence Images of the Fundus  

PubMed Central

Purpose. To document and explain the presence, inferior to the optic disc, of a distinct vertical boundary between two retinal areas of different short-wavelength autofluorescence (SW-AF) intensities. Methods. SW-AF images of the inferonasal region were acquired from 32 healthy subjects. Additionally, color, 488-nm reflectance (488-R), near-infrared reflectance (NIR-R), NIR autofluorescence (NIR-AF) images, and a spectral domain optical coherence tomography (SD-OCT) image were obtained in selected subjects. Gray levels (GL) on both sides of the demarcation line were measured in SW-AF and 488-R at fixed distances from the disc center. Results. A curved demarcation line inferior to the optic disc was observed on SW-AF images in 31/32 subjects. AF levels on the nasal side were 13% (±6%) lower than on the temporal side at 20° inferior to the disc center. The contrast between the nasal and the temporal areas was not significantly affected by age, sex, refractive error, race, or iris color. The demarcation line visible in SW-AF was also seen, though with reduced contrast, in approximately 80% of the 488-R images (lower reflectance on the nasal side) and 50% of color images. The boundary was not detected by NIR-R, NIR-AF, or by SD-OCT imaging. Conclusions. The location and the distinctness of the demarcation line may indicate a relationship to the closed embryonic optic fissure. The reduced SW-AF intensity and 488-R reflectance observed on the nasal side of this line may be attributable to lower lipofuscin and melanin content per unit area, possibly resulting from a difference in RPE cell shape.

Duncker, Tobias; Greenberg, Jonathan P.; Sparrow, Janet R.; Smith, R. Theodore; Quigley, Harry A.; Delori, Francois C.

2012-01-01

171

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

SciTech Connect

The theory of Walterscheid et al. (1987) to explain internal gravity wave induced oscillations in the emission intensity I and rotational temperature T of the OH nightglow was modified by Hickey (1988) to include the effects of eddy dissipation and Coriolis force. In the theory of Walterscheid et al. (1987) the ratio {eta} = ({delta}I/I{sub 0})/({delta}T/T{sub 0}) ({delta} refers to a perturbation quantity, and a zero subscript refers to an average) was found to be independent of horizontal wavelength at long periods, while in the extended theory of Hickey (1988) some such dependence was inferred. In the present paper the horizontal wavelength dependence of {eta} is examined. It is found that values of {eta} will be dependent on both wave period and horizontal wavelength, meaning that in order to compare measurement with theory, horizontal wavelengths will need to be measured in conjunction with the OH nightglow measurements. At long periods the modifications to {eta} by the inclusion of eddy dissipation are much larger for the shorter horizontal wavelength waves, although such modifications may be more observable for some of the longer horizontal wavelength waves. The Coriolis force is important only for waves of very large horizontal wavelength.

Hickey, M.P. (NASA Marshall Space Flight Center, Huntsville, AL (United States))

1988-05-01

172

Short Wavelength Tomography as a Constraint on the Mineralogical Heterogeneity of the Subcrustal Lithosphere beneath Stable Continents  

NASA Astrophysics Data System (ADS)

A recurrent question when interpreting lateral variations of velocity in the lithosphere is to know if their origin is thermal or mineralogical. On a large scale, the 10-15% velocity variations deduced from tomography is explained by changes in temperature and by partial melting. For Jordan (1978), Archean cratons are chemically distinct from the oceanic mantle but mineralogy only explains 1-2% velocity changes. For stable regions, one way P-vertical travel times are 1.5s faster (6%) through a craton than through a Paleozoic platform. We present several examples of tomographic studies - from teleseismics and from surface waves - which are difficult to reconcile with a thermal interpretation, as if short wavelength and long wavelength tomography results were contradictory. In many sites, velocity changes laterally within 20-50km on the entire thickness of the lithosphere. Some of these sutures have been inactive for a very long duration. In the Western Urals, a contrast in velocity has been preserved over more than 1.5 Ga. From a refraction survey recording 2 distant events, Masson et al. (1998) report abrupt local velocity variations beneath the moho of the Iapetus suture in Ireland. Any temperature effect should be smoothed and should not be preserved over several hundred million years. At a small scale, the subcrustal continental lithosphere appears as an assemblage of 50-200 km wide blocks with 2-3% different velocity and sharp subvertical or tilted limits. Subcrustal anisotropy is difficult to measure; but anisotropy is preserved with age and introduces local asymmetry (Babuska et al., 1993). The widespread observation of sharp and permanent lateral velocity gradients within stable continents implies chemical heterogeneity. At a larger scale, the seismic characteristics of subcontinental lithosphere can be related to the age of the overlying continents. The oldest > 3 Ga cratons have 200-250 km lithospheric roots with very high velocity. Peridotite xenoliths from this lithosphere have compositions different from those from younger lithosphere, being composed of unusually Fo-rich olivine and abundant orthopyroxene. The low density and high viscosity of this assemblage results in a buoyant, rigid lithosphere that has survived since the formation of continents. The origin of this lithosphere is related to high temperatures in the Archean mantle and efficient processes that extracted the low-density residual phases produced during high-degree mantle melting from denser normal mantle minerals. The secular variation in the seismic and chemical character of the continental lithosphere is thus related to the progressive cooling of the mantle.

Poupinet, G.; Arndt, N.; Pedersen, H.

2001-12-01

173

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.

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

174

Short-wavelength light sensitivity of circadian, pupillary, and visual awareness in humans lacking an outer retina.  

PubMed

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. These responses are driven primarily by stimulation of photosensitive retinal ganglion cells (pRGCs) that are most sensitive to short-wavelength ( approximately 480 nm) blue light and remain functional in the absence of rods and cones. 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 (lambda(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 ( approximately 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

2007-12-18

175

Retrieval of short ocean wave slope using polarimetric imaging  

NASA Astrophysics Data System (ADS)

We present a passive optical remote sensing technique for recovering shape information about a water surface, in the form of a two-dimensional slope map. The method, known as polarimetric slope sensing (PSS), uses the relationship between surface orientation and the change in polarization of reflected light to infer the instantaneous two-dimensional slope across the field-of-view of an imaging polarimeter. For unpolarized skylight, the polarization orientation and degree of linear polarization of the reflected skylight provide sufficient information to determine the local surface slope vectors. A controlled laboratory experiment was carried out in a wave tank with mechanically generated gravity waves. A second study was performed from a pier on the Hudson River, near Lamont-Doherty Earth Observatory. We demonstrated that the two-dimensional slope field of short gravity waves could be recovered accurately without interfering with the fluid dynamics of the air or water, and water surface features appear remarkably realistic. The combined field and laboratory results demonstrate that the polarimetric camera gives a robust characterization of the fine-scale surface wave features that are intrinsic to wind-driven air-sea interaction processes.

Zappa, Christopher J.; Banner, Michael L.; Schultz, Howard; Corrada-Emmanuel, Andres; Wolff, Lawrence B.; Yalcin, Jacob

2008-05-01

176

Dual-wavelength single-crystal double-pass KTP optical parametric oscillator and its application in terahertz wave generation.  

PubMed

A tunable dual-wavelength double-pass singly resonant optical parametric oscillator based on a single KTP crystal has been proposed and demonstrated. By setting the rear mirror tuning angle precisely, collinear and noncollinear dual phase matching can be established simultaneously and leads to a two-wavelength oscillation at steady state. With high-speed KTP angle tuning, two wavelengths and their frequency difference can be adjusted continuously and accurately. By using this newly developed dual-wavelength optical parametric oscillator to pump a DAST crystal, a monochromatic terahertz wave ranging from 0.5 to 3 THz has been successfully generated in a difference-frequency generation system. PMID:20479854

Tang, Ming; Minamide, Hiroaki; Wang, Yuye; Notake, Takashi; Ohno, Seigo; Ito, Hiromasa

2010-05-15

177

Wavelength conversion of 28 GBaud 16-QAM signals based on four-wave mixing in a silicon nanowire.  

PubMed

We demonstrate error-free wavelength conversion of 28 GBaud 16-QAM single polarization (112 Gb/s) signals based on four-wave mixing in a dispersion engineered silicon nanowire (SNW). Wavelength conversion covering the entire C-band is achieved using a single pump. We characterize the performance of the wavelength converter subsystem through the electrical signal to noise ratio penalty as well as the bit error rate of the converted signal as a function of input signal power. Moreover, we evaluate the degradation of the optical signal to noise ratio due to wavelength conversion in the SNW. PMID:24663730

Adams, Rhys; Spasojevic, Mina; Chagnon, Mathieu; Malekiha, Mahdi; Li, Jia; Plant, David V; Chen, Lawrence R

2014-02-24

178

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

179

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

NASA Astrophysics Data System (ADS)

Characteristics of the internal structure of the laser supported detonation (LSD) waves, such as the electron density ne and the electron temperature Te profiles behind the shock wave were measured using a two-wavelength Mach-Zehnder interferometer along with emission spectroscopy. A TEA CO2 laser with energy of 10 J/pulse produced explosive laser heating in atmospheric air. Results show that the peak values of ne and Te were, respectively, about 2 × 1024 m-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 ne 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; Hatai, Keigo; Kawamura, Koichi; Fukui, Akihiro; Fukuda, Akio; Wang, Bin; Yamaguchi, Toshikazu; Komurasaki, Kimiya; Arakawa, Yoshihiro

2011-04-01

180

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

PubMed

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

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

2014-06-20

181

Modelling single shot damage thresholds of multilayer optics for high-intensity short-wavelength radiation sources.  

PubMed

The single shot damage thresholds of multilayer optics for high-intensity short-wavelength radiation sources are theoretically investigated, using a model developed on the basis of experimental data obtained at the FLASH and LCLS free electron lasers. We compare the radiation hardness of commonly used multilayer optics and propose new material combinations selected for a high damage threshold. Our study demonstrates that the damage thresholds of multilayer optics can vary over a large range of incidence fluences and can be as high as several hundreds of mJ/cm(2). This strongly suggests that multilayer mirrors are serious candidates for damage resistant optics. Especially, multilayer optics based on Li(2)O spacers are very promising for use in current and future short-wavelength radiation sources. PMID:23263054

Loch, R A; Sobierajski, R; Louis, E; Bosgra, J; Bijkerk, F

2012-12-17

182

INTERACTION OF LASER RADIATION WITH MATTER. LASER PLASMA: Characteristics of plasma heating by short-wavelength excimer laser radiation  

NASA Astrophysics Data System (ADS)

Various x-ray spectroscopic methods were used to investigate a plasma generated by the interaction of short-wavelength excimer laser radiation pulses (12 ns, 0.308 ?m, 4×1012 W cm-2) with flat targets. A comparison of the profiles and intensities of a number of observed spectral lines of the H-like, He-like, and Li-like sodium, magnesium, and aluminium ions with the results of the reported calculations made it possible to determine the spatial distributions of the laser plasma parameters up to distances of ~0.4 mm from the target surface. These parameters were compared with the predictions of a simple theoretical model of the absorption of short-wavelength radiation in a plasma. This showed that the absorption of such radiation (with the intensities used in this investigation) involved inverse bremsstrahlung in regions with an electron density much lower than the critical value.

Faenov, A. Ya; Magunov, A. I.; Pikuz, T. A.; Skobelev, I. Yu; Pikuz, S. A.; Bollanti, S.; Di Lazzaro, P.; Lizi, N.; Flora, F.; Letardi, T.; Palladino, L.; Reale, A.; Scafati, A.; Grilli, A.; Batani, D.; Mauri, A.; Osterheld, A.; Goldstein, W. H.

1996-08-01

183

Monitoring of blending and polymerization processes by SW-NIR spectroscopy. [SW-NIR (short wavelength near infrared spectroscopy)  

Microsoft Academic Search

Two automated analytical systems incorporating short wavelength near infrared spectroscopy (SW-NIR) are presented. A computer-controlled mixing system is described. The system is particularly well suited for spectrophotometric titration and for the study of solvent-solute interaction. Then the mixing system is applied to the study of a model system of blending: methanol-water. Here, SW-NIR transmission measurements are combined with chemical regression

Caicai

1993-01-01

184

Study of short wavelength instabilities the confinement of a collision dominated plasma by a rotating magnetic field  

Microsoft Academic Search

A collision dominated plasma confined by a rotating magnetic field is stable if f>or approximately=0.02 vi where f is the frequency of rotation and vi the ion collision frequency. Short wavelength perturbations are the most difficult ones to stabilize. Growth rates of parametric instabilities are shown to be so large as to make impossible any attempt to use a frequency

F. Troyon

1971-01-01

185

Monitoring Quality Loss of Pasteurized Skim Milk Using Visible and Short Wavelength Near-Infrared Spectroscopy and Multivariate Analysis  

Microsoft Academic Search

Visible and short wavelength near-infrared diffuse reflectance spectroscopy (600 to 1,100 nm) was evalu- ated as a technique for detecting and monitoring spoil- age of pasteurized skim milk at 3 storage temperatures (6, 21, and 37°C) over 3 to 30 h (control, t = 0 h; n = 3). Spectra, total aerobic plate count, and pH were ob- tained, with

H. M. Al-Qadiri; M. Lin; M. A. Al-Holy; A. G. Cavinato; B. A. Rasco

2008-01-01

186

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

Microsoft Academic Search

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

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

2003-01-01

187

Solitary and E-Shock Waves in a Resonant System between Long and Short Waves  

NASA Astrophysics Data System (ADS)

In order to examine solitary and E-shock waves in a resonant system between long and short waves, a reduced set of ordinary differential equations (ODEs) are considered by a simple traveling-wave transformation. It is then shown that analytical solutions can be obtained systematically by means of the modified Hirota's method. A variety of numerical solutions including oscillatory solitary and E-shock waves are also found for various values of the parameters. In particular, characteristic properties of the solutions are examined for the case when the ODEs hold the Painlevé property. In this connection, integrability of the original partial differential equations (PDEs) in the nearly integrable region is discussed together with the Lyapunov exponent for the soliton-like solutions.

Yoshinaga, Takao; Kakutani, Tsunehiko

1994-02-01

188

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

Microsoft Academic Search

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

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

2011-01-01

189

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

190

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

NASA Technical Reports Server (NTRS)

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

Smith, Mark W.

1992-01-01

191

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

192

A Short-Wavelength Photoreceptor Class in a Deep-Sea Shrimp  

Microsoft Academic Search

In the world of midwater, mesopelagic animals, downwelling sunlight is filtered by the overlying water to a limited waveband centered near 475 nm. Consequently, the visual pigments of most of these species absorb maximally between 450 and 500 nm. The only exceptions occur in some fishes, which have additional visual pigments absorbing at long wavelengths (550-580 nm) matched to their

Thomas W. Cronin; Tamara M. Frank

1996-01-01

193

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

194

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.

Shinomori, Keizo; Werner, John S.

2012-01-01

195

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

NASA Technical Reports Server (NTRS)

Several scaled experiments of optical output couplers for submillimeter backward-wave oscillators (BWOs). Various designs of planar antennas (Vivaldi horns) lens-feed systems (hyperhemispherical lens) were constructed and tested between 20 and 100 GHz using a spectrum analyzer. The lens system was also tested at 337 GHz using a CO2 pumped FIR laser. It is found that Vivaldi horns have unsatisfactory resonances, perhaps because the horns studied were relatively short. Several techniques to maximize and flatten the frequency response of these horns are presented. The results suggest that alternate coupling schemes are superior to Vivaldi horns.

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

1989-01-01

196

Theoretical Study of Dual-wavelength PPKTP-OPO as a Source of DFG THz-wave  

Microsoft Academic Search

In this paper, we theoretically investigate the dual-wavelength periodically poled KTP optical parametric oscillator (PPKTP-OPO) operating near degeneracy. According to calculation, the dual-wavelength operation can be achieved by quasi-phase matching with a periodically poled structure. The tunable property of the grating period of the PPKTP crystal with temperature tuning determines that, quasi-CW or continuous tunable THz-wave generation can be achieved

Zhuo Wang; Bo Sun; Yuye Wang; Baigang Zhang; Yizhong Yu; Degang Xu; Huan Liu; Peng Wng; Jianquan Yao

2006-01-01

197

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

SciTech Connect

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

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

2011-01-15

198

Scaling of Ne-like x-ray laser schemes to short wavelength  

SciTech Connect

The driver and target parameters required to extend the successful results from an exploding foil Ne-like-Se soft x-ray laser at 206 A towards wavelengths of 40 A are investigated. The power requirements are found to scale as lambda/sup -4/, which is quite costly. The principal constraint is the refraction of the x-ray laser beam in these high density, single pass, exploding foil targets. Correcting mirrors or nonrefracting target designs could reduce this costly scaling.

Rosen, M.D.; London, R.A.; Hagelstein, P.L.

1988-03-01

199

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

Microsoft Academic Search

Experiments to examine the generation of relativistic plasma waves via a high-intensity short-pulse beat-wave scheme are described in detail. The pulse stretcher of the Vulcan chirped-pulse amplification (CPA) laser system was modified to produce two frequency, 3 ps pulses focusable to intensities up to 1018 W cm-2. Short high-intensity pulses were used to avoid limitations to the plasma-wave amplitude due

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

2006-01-01

200

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

NASA Astrophysics Data System (ADS)

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

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

2010-09-01

201

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

SciTech Connect

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

Xiang, D.; Colby, E.; Dunning, M.; Gilevich, S.; Hast, C.; Jobe, K.; McCormick, D.; Nelson, J.; Raubenheimer, T. O.; Soong, K.; Stupakov, G.; Szalata, Z.; Walz, D.; Weathersby, S.; Woodley, M.; Pernet, P.-L. [SLAC National Accelerator Laboratory, Menlo Park, California 94025 (United States); Ecole Polytechnique Federale de Lausanne, Lausanne (Switzerland)

2010-09-10

202

Improvement of quantum efficiency at short wavelengths in a high-low junction emitter silicon solar cells made by diffusion  

NASA Astrophysics Data System (ADS)

A new simple diffusion process was developed to form a high-low junction emitter silicon p(+)/p/n solar cell for improved quantum efficiency at short wavelengths. This solar cell offers a significantly improved UV and blue efficiency in comparison with conventional silicon solar cells. Experimental results show that the new cell offers an internal quantum efficiency of more than 80 percent at 400 nm, and around 90 percent throughout the visible spectrum. It is shown that the HLE structure has other advantages over conventional cells in suppressing emitter recombination current, surface recombination loss, and increasing minority carrier lifetime in the emitter.

Zhang, Feng Sheng; Hu, Shu Chun; Huang, Xuan; Zhu, Xian Gang; Zhang, Shen Jun

203

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

National Technical Information Service (NTIS)

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...

R. E. Abbink

1997-01-01

204

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

Microsoft Academic Search

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

Kazuo Ouchi

2000-01-01

205

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

206

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

Microsoft Academic Search

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

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

2009-01-01

207

Recent progress in short-wavelength VCSEL-based optical interconnections  

NASA Astrophysics Data System (ADS)

We report on recent progress in the design and application of vertical-cavity surface-emitting lasers (VCSELs) for optical interconnect applications in the 850 nm emission wavelength regime. Ongoing work toward parallel optical interconnect modules with channel data rates of 10 Gbit/s is reviewed and performance results of flip-chip integrated two-dimensional VCSEL arrays are presented. 10 Gbit/s speed as well as low thermal resistance of the lasers has been achieved. As a possible alternative to graded-index multimode fibers, we show 10 Gbit/s data transmission over 100 m length of a novel, entirely undoped multimode photonic crystal fiber. The use of VCSELs with output powers in the 10 mW range is demonstrated in a 16-channel free-space optical (FSO) module and VCSELs with even higher output power are shown to provide possible FSO connectivity up to data rates of 2.5 Gbit/s.

Michalzik, Rainer; Roscher, Hendrik; Stach, Martin; Wiedenmann, Dieter; Miller, Michael; Broeng, Jes; Petersson, Anders; Mortensen, Niels A.; Simonsen, Harald R.; Kube, Erhard

2003-12-01

208

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

209

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

USGS Publications Warehouse

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

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

2004-01-01

210

Interpretation of short-wavelength anomalies in aeromagnetic data from different epochs: a case study in Northern Germany  

NASA Astrophysics Data System (ADS)

Aeromagnetic data from reconnaissance surveys is routinely used for geological mapping and modelling of large-scale, deep-seated structures. In contrast to this, we have evaluated the content of the recently published map of the anomalies of the Earth's magnetic total field in Germany (LIAG, 2010) in the short-wavelength range, that is related to near-surface structures with an extent limited to a few kilometres. The main goal was to examine whether older regional surveys can be used to improve the geometric resolution of local geological units. We have used data acquired by Prakla GmbH (1965-1971) and compared it with a modern, high sensitivity aeromagnetic survey from Sander Geophysics (2005). Analysis and filtering of both data sets reveal short-wavelength anomalies in the North German Basin, and a notable spatial correlation with subcrops and outcrops of distinct Lower Cretaceous and Jurassic stages. Rock magnetic investigations of field and core samples indicate a weak remanent and induced magnetization (up to 0.15 A/m) in these layers. We have used these results to modify the structural models of two test sites with different stratigraphies by magnetized layers within the Lower Cretaceous and Jurassic. 3D forward modelling shows that the small-scale anomalies with amplitudes of 10 to 20 nT observed in both data sets can be explained by the introduced layers. In summary, the data from Prakla GmbH contain valuable information down to wavelengths of 2 km, and can be used to stabilize stratigraphic models

Gabriel, G.; Skiba, P.; Krawczyk, C. M.; König, M.; Bücker, C.

2012-04-01

211

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

NASA Astrophysics Data System (ADS)

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

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

2008-02-01

212

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

NASA Astrophysics Data System (ADS)

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

Brügmann, Michael H.; Feurer, Thomas

2014-01-01

213

Short-wavelength, direct-drive laser fusion experiments at the Laboratory for Laser Energetics  

SciTech Connect

Measurements are reported of absorption, hot electron generation, preheat, thermal transport and irradiation uniformity in direct-drive, spherical target experiments conducted with six 351-nm wavelength beams of the OMEGA symmetric irradiation facility. On-target energy in excess of 400 J, pulses of 650 ps duration and uniform irradiation at an intensity in the range of 10/sup 13/ to 10/sup 15/ W/cm/sup 2/ characterize the laser conditions for these experiments. Absorption varied from 100%, for Ti targets at an intensity of 10/sup 13/ W/cm/sup 2/, to 60% at an intensity of 2 x 10/sup 15/ W/cm/sup 2/. The suprathermal electron fraction was found to be less than 3 x 10/sup -3/ of the absorbed energy in these experiments. Higher ablation pressures were measured than in comparable 1054-nm experiments. At a laser intensity of 10/sup 15/ W/cm/sup 2/ an ablation pressure of 100 Mbar was deduced from plasma blowoff measurements. Measurement and calculation of the irradiation uniformity indicate that the 24 beam OMEGA, 351-nm laser should be capable of producing the required drive uniformity to compress targets to 200 times liquid DT density with less than 2000 joules of laser energy.

McCrory, R.L.; Barnouin, O.; Craxton, R.S.; Delettrez, J.; Epstein, R.; Forsley, L.; Goldman, L.M.; Hutchison, R.J.; Keck, R.L.; Kim, H.

1984-01-01

214

Three-dimensional blast-wave-driven Rayleigh-Taylor instability and the effects of long-wavelength modes  

SciTech Connect

This paper describes experiments exploring the three-dimensional (3D) Rayleigh-Taylor instability at a blast-wave-driven interface. This experiment is well scaled to the He/H interface during the explosion phase of SN1987A. In the experiments, {approx}5 kJ of energy from the Omega laser was used to create a planar blast wave in a plastic disk, which is accelerated into a lower-density foam. These circumstances induce the Richtmyer-Meshkov instability and, after the shock passes the interface, the system quickly becomes dominated by the Rayleigh-Taylor instability. The plastic disk has an intentional pattern machined at the plastic/foam interface. This perturbation is 3D with a basic structure of two orthogonal sine waves with a wavelength of 71 {mu}m and an amplitude of 2.5 {mu}m. Additional long-wavelength modes with a wavelength of either 212 or 424 {mu}m are added onto the single-mode pattern. The addition of the long-wavelength modes was motivated by the results of previous experiments where material penetrated unexpectedly to the shock front, perhaps due to an unintended structure. The current experiments and simulations were performed to explore the effects of this unintended structure; however, we were unable to reproduce the previous results.

Kuranz, C. C.; Drake, R. P.; Grosskopf, M. J.; Budde, A.; Krauland, C.; Marion, D. C.; Visco, A. J.; Ditmar, J. R. [University of Michigan, Ann Arbor, Michigan 48109 (United States); Robey, H. F.; Remington, B. A.; Miles, A. R.; Cooper, A. B. R.; Sorce, C. [Lawrence Livermore National Laboratory, Livermore, California 94550 (United States); Plewa, T. [Department of Scientific Computing, Florida State University, Tallahassee, Florida 32306 (United States); Hearn, N. C. [ASC Flash Center, University of Chicago, Chicago, Illinois 60637 (United States); Killebrew, K. L. [Sandia National Laboratory, Albuquerque, New Mexico 87185 (United States); Knauer, J. P. [Laboratory for Laser Energetics, University of Rochester, Rochester, New York (United States); Arnett, D. [Steward Observatory, University of Arizona, Tucson, Arizona 85721 (United States); Donajkowski, T. [Jet Propulsion Laboratory, Pasadena, California 91109 (United States)

2009-05-15

215

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

216

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

217

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

218

Spectra of multiply charged hollow ions in the plasma produced by a short-wavelength nanosecond laser  

SciTech Connect

Complex spectral structures located between the resonance lines of H- and He-like MgXII and MgXI ions were recorded in experiments on plasma heating by the radiation of a low-power short-wavelength excimer XeCl laser (12-ns pulses with an energy of 2 J). The above spectral structures were shown to arise from transitions in the so-called hollow multicharged ions, i.e., in ions with an empty 1s-shell, which were previously observed in laser produced plasmas only with ultrahigh-power femto- and picosecond laser facilities having extremely high-contrast laser pulses. (interaction of laser radiation with matter. laser plasma)

Abdallah, J [Los Alamos National Laboratory, Los Alamos (United States); Skobelev, I Yu; Faenov, A Ya [Multicharged Ion Spectra Data Center, All-Russia Research Institute of Psysicotechnical and Radio Enginering Measurments, Mendeleevo, Moscow Region (Russian Federation); Magunov, A I [A.M. Prokhorov General Physics Institute, Russian Academy of Sciences, Moscow (Russian Federation); Pikuz, T A [N.E. Bauman Moscow State Technical University, Moscow (Russian Federation); Flora, F; Bollanti, S; DiLazzaro, P; Letardi, T [ENEA, Frascati (Italy); Burattini, E; Grilli, A [Instituto Nazionale di Fisica Nucleare (Italy); Reale, A; Palladino, L; Tomassetti, G; Scafati, A; Reale, L [L'Aquila University (Italy)

2000-08-31

219

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

PubMed

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

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

2012-01-01

220

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

NASA Astrophysics Data System (ADS)

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

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

2014-04-01

221

Long-wavelength dispersion and soliton formation of longitudinal acoustic waves in crystalline solids  

NASA Astrophysics Data System (ADS)

In a general picosecond ultrasonic experiment, a sub-picosecond laser pulse (the pump) excites the sample and causes a change in optical reflectivity of the sample, and a time-delayed laser pulse (the probe) is directed to the excited region to measure the time-dependence of this change. The time delay is usually obtained by means of a conventional optical path and can be made as long as several nanoseconds. In this thesis we present a variation of the picosecond ultrasonic technique, in which an extra delay is achieved by using a later pulse from the laser as a probe. By doing so we can measure the effects that happen at a relatively long time scale compared with that in other picosecond ultrasonic experiments. The first application is the measurement of the dispersion of long-wavelength longitudinal acoustic phonons in Ge, Si, GaAs, z-cut quartz, and sapphire. In these experiments the pump light pulse generated a strain pulse at one surface of the sample. After propagation through the sample, the shape of this strain pulse was modified because of the phonon dispersion. From this change in shape, the magnitude of the dispersion could be determined. The results are compared with various lattice dynamical models. In the second application, by increasing the pulse energy of the pump pulse, we have studied the deformation of longitudinal acoustic pulses propagating in solid crystals due to dispersion and non-linearity. We found that the evolution of the one-dimensional wave can be described by Korteweg-de Vries equation. The experiments have been performed on Si, MgO, alpha-quartz, and sapphire. In each case we have observed the evidence of acoustic solitons and the results agree reasonably well with our computer simulations. In the end, we also report on measurements of the temperature dependence of the sound velocity and the acoustic attenuation.

Hao, Hsin-Yi

222

Patrol of the short wavelength activity and flares of Sun as star  

NASA Astrophysics Data System (ADS)

Monitoring of the spectral range which most affects solar-terrestrial relationship - soft X-ray and extreme UV-radiations allows to solve ? problem of solar activity influence on all aspects of the Sun - Earth ties and to select the most important precursors of solar flares and the solar events related with a flare (such as proton events, high-velocity plasma streams in the solar wind, shock waves, coronal mass ejection and, the most important, the beginning of principal magnetic storms). Solar activity is constantly monitored at present (in the USA) only in two sections of the spectrum of ionizing radiation: <0.8 nm and >115 (119) nm. However, so far there has been no monitoring of the flux in the most geoeffective region of the spectrum (0.8-115 nm) from the entire disk of the sun; this region completely monitors the main part of the ionosphere of the earth and the ionosphere of the other planets of the solar system, including the formation and status of the main ionospheric maxima. This occurs solely because of technical and methodological difficulties in performing the measurements and calibration in this spectral range on spacecraft, because it is necessity to use only windowless optics. At the present the solar the optical - electronic equipment (OEE) is testing and there are plans to launch OEE of Space Solar Patrol (SSP) consisting of solar radiometers and spectrometers at the Russian Module of the International Space Station. So the solving the problem of the permanent monitoring-patrol of ionizing radiation from the full disk of the Sun appears in the main tasks of fundamental scientific studies in space. The results of this monitoring can be contribution in development of simultaneous studies in several sciences, such as: - solar astrophysics (state of all solar atmospheric regions), - meteorology, physics of atmosphere (the influence of solar activity on global changes, climate and weather including the effects of atmo s pheric electricity), - aeronomy, astronautics (the influence of solar activity on density of upper atmo s phere and space craft slowing clown by it and characteristics of spacecraft outer atmo s phere), - radiophysics (determination and forecast ionospheric state of planets and radiowave transfer conditions), - heliobiology (the role of solar activity in biology and medical events), - seismology, possible sociology. There are the Resolutions with support of SSP Mission of the importance of this project from Commissions C, D and E of COSPAR, 1996, Commission G of URSI, 1996 and General Assembly of IAGA, 1999.

Afanasiev, I.; Avakyan, S.; Leonov, N.; Serova, A.; Voronin, N.

223

Widely tunable all-optical wavelength converter based on four-wave mixing using two orthogonally polarized pumps  

NASA Astrophysics Data System (ADS)

The principle of broad-band orthogonal-pump (BOP) four-wave mixing in semiconductor optical amplifiers is analyzed in theory. The conversion efficiency reduces rapidly as the detuning of wavelength between the signal and pump increase which can be solved by introducing a BOP method. The constant conversion efficiency and signal-to-noise ratio are obtained over a large wavelength detuning range. The wavelength conversion efficiency with variation smaller than 3.88 dB over 52-nm range has been experimentally demonstrated by using BOP, with the 10-GHz output of distributed feedback/electro-absorption modulator as signal. Conventional single-pump scheme is also performed for comparison and the experimental results fit well with the theory.

Wang, Zhaoying; Li, Zhiyong; Ge, Chunfeng; Hu, Zhiyong; Jia, Dongfang; Li, Shichen

2004-06-01

224

Higher-order statistical analysis of short wind wave fields  

NASA Astrophysics Data System (ADS)

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

Caulliez, Guillemette; GuéRin, Charles-Antoine

2012-06-01

225

Rapid and sensitive trace gas detection with continuous wave Optical Parametric Oscillator-based Wavelength Modulation Spectroscopy  

Microsoft Academic Search

A fiber-amplified Distributed Bragg Reflector diode laser is used to pump a continuous wave, singly resonant Optical Parametric\\u000a Oscillator (OPO). The output radiation covers the 3–4 ?m with ability of rapid (100 THz\\/s) and broad mode-hop-free tuning\\u000a (5 cm?1). Wavelength Modulation Spectroscopy is combined with the OPO to take optimal advantage of the spectral scan speed. The sensitivity\\u000a of the

D. D. Arslanov; M. Spunei; A. K. Y. Ngai; S. M. Cristescu; I. D. Lindsay; S. T. Persijn; K. J. Boller; F. J. M. Harren

2011-01-01

226

Rapid and sensitive trace gas detection with continuous wave Optical Parametric Oscillator-based Wavelength Modulation Spectroscopy  

Microsoft Academic Search

A fiber-amplified Distributed Bragg Reflector diode laser is used to pump a continuous wave, singly resonant Optical Parametric Oscillator (OPO). The output radiation covers the 3-4 mum with ability of rapid (100 THz\\/s) and broad mode-hop-free tuning (5 cm-1). Wavelength Modulation Spectroscopy is combined with the OPO to take optimal advantage of the spectral scan speed. The sensitivity of the

D. D. Arslanov; M. Spunei; A. K. Y. Ngai; S. M. Cristescu; I. D. Lindsay; S. T. Persijn; K. J. Boller; F. J. M. Harren

2011-01-01

227

Loop soliton solutions of a short wave model for a degasperis-procesi equation  

NASA Astrophysics Data System (ADS)

An analytic method, i.e. the homotopy analysis method, was applied for constructing the solutions of the short waves model equations associated with the Degasperis-Procesi (DP) shallow water waves equation. The explicit analytic solutions of loop soliton governing the propagation of short waves were obtained. By means of the transformation of independent variables, an analysis one-loop soliton solution expressed by a series of exponential functions was obtained, which agreed well with the exact solution. The results reveal the validity and great potential of the homotopy analysis method in solving complicated solitary water wave problems.

Zou, Li; Zong, Zhi; Wang, Zhen; Zhang, Shuo

2011-06-01

228

Short-Wave Near-Infrared Spectrometer for Alcohol Determination and Temperature Correction  

PubMed Central

A multichannel short-wave near-infrared (SW-NIR) spectrometer module based on charge-coupled device (CCD) detection was designed. The design relied on a tungsten lamp enhanced by light emitting diodes, a fixed grating monochromator and a linear CCD array. The main advantages were high optical resolution and an optimized signal-to-noise ratio (0.24?nm and 500, resp.) in the whole wavelength range of 650 to 1100?nm. An application to alcohol determination using partial least squares calibration and the temperature correction was presented. It was found that the direct transfer method had significant systematic prediction errors due to temperature effect. Generalized least squares weighting (GLSW) method was utilized for temperature correction. After recalibration, the RMSEP found for the 25°C model was 0.53% v/v and errors of the same order of magnitude were obtained at other temperatures (15, 35 and 40°C). And an r2 better than 0.99 was achieved for each validation set. The possibility and accuracy of using the miniature SW-NIR spectrometer and GLSW transfer calibration method for alcohol determination at different temperatures were proven. And the analysis procedure was simple and fast, allowing a strict control of alcohol content in the wine industry.

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

2012-01-01

229

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

PubMed

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

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

2012-01-01

230

Mutual pulse injection seeding by the use of two fabry-Perot laser diodes to produce wavelength-tunable optical short pulses  

Microsoft Academic Search

A mutual pulse injection-seeding scheme is developed to produce wavelength-tunable optical short pulses by the use of two Fabry-Perot laser diodes, of which one is gain-switched and the other is dc biased. Wavelength tuning of the optical pulses is achieved by simply adjusting a tunable optical filter while maintaining a constant repetition frequency of 3.0 GHz. The sidemode suppression ratio

Xiaohui Fang; D. N. Wang

2003-01-01

231

Generation of electrically wavelength-tunable optical short pulses using a Fabry-Perot laser diode in an external-injection seeding scheme with improved sidemode suppression ratio  

Microsoft Academic Search

Electrically wavelength-tunable optical short pulses are generated from a gain-switched Fabry-Perot (F-P) laser diode with another F-P laser diode used as the external-injection-seeding light source. The injection wavelength is selected by a tunable filter and intensified by the use of an erbium-doped fiber amplifier before being directed to the gain-switched F-P laser diode. The sidemode suppression ratio achieved is better

D. N. Wang; Xiaohui Fang

2003-01-01

232

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 45ñe, and field, accent="true">B˜?, which are guided by field lines, propagate in the electron diamagnetic drift direction, and exhibit a weakly damped (?/?0˜5% -10%) resonance near the natural QCM frequency. This result is significant, offering the possibility that externally driven modes may be used to enhance particle transport. In L-mode, the antenna drives only a non-resonant accent="true">B˜? response. The facts that the driven mode has the same wave 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

233

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

234

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

NASA Astrophysics Data System (ADS)

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

Shao, Hao; Li, Yan; Li, Li

2011-06-01

235

Quantifying the impact of shear wavelength and kernel size on shear wave speed estimation  

Microsoft Academic Search

Quantitative measurements of tissue stiffness can be obtained by measuring the speed of shear waves induced in tissue by acoustic radiation force. In homogeneous media, time-of-flight (TOF) measurements of shear wave speed (SWS) ideally are independent of the size of the region of interest (or reconstruction kernel). However, in heterogeneous media, shear wave morphology is altered by discontinuities in stiffness

Mark L Palmeri; Ned C Rouze; Michael H Wang; Xuan Ding; Kathryn R Nightingale

2010-01-01

236

Short surface waves in the Canadian Arctic in 2007 and 2008  

NASA Astrophysics Data System (ADS)

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

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

2013-07-01

237

Solitary Waves of the Regularized Short Pulse and Ostrovsky Equations  

Microsoft Academic Search

We derive a model for the propagation of short pulses in nonlinear media. The\\u000amodel is a higher order regularization of the short pulse equation (SPE). The\\u000aregularization term arises as the next term in the expansion of the\\u000asusceptibility in derivation of the SPE. Without the regularization term there\\u000ado not exist traveling pulses in the class of piecewise

Nicola Costanzino; Vahagn Manukian; Christopher K. R. T. Jones

2009-01-01

238

Breaking of Thunderstorm-Generated Gravity Waves as a Source of Short-Period Ducted Waves Observed at Mesopause Altitudes  

NASA Astrophysics Data System (ADS)

Atmospheric gravity waves with periods of 5 to 8 minutes have been observed at airglow altitudes [Taylor et al., GRL, 22, 2849, 1995; Walterscheid et al., JASTP, 61, 461, 1999; Hecht et al., JGR, 106, 5181, 2001; and references cited therein]. These waves are believed to propagate as thermally-ducted wave modes, trapped in the Brunt-Väisälä frequency minimum of the upper mesosphere and lower thermosphere [e.g., Walterscheid et al., 1999]. Many of these recently observed waves have been traced to thunderstorm activity located hundreds of kilometers from the point of observation. However, these gravity waves would be evanescent in most regions of atmosphere, where their frequency exceeds the local Brunt-Väisälä frequency. It is therefore improbable that the observed waves with short periods (? ˜=5 min) would be able to propagate freely from a tropospheric convective source to the lower thermosphere. Thunderstorms are known radiators of gravity waves, with typical forcing periods of 10 to 16 minutes (approximately equal to the Brunt-Väisälä period of the upper troposphere) [e.g., Pierce and Coroniti, Nature, 210(5042), 1209, 1966]. Recent numerical studies have demonstrated that the breaking of low frequency gravity waves can excite harmonic secondary waves, with frequencies and horizontal wavenumbers approximately twice that of the primary waves [e.g., Franke and Robinson, J. Atmos. Sci., 56, 3010, 1999, Zhou et al., JGR, 107(D7), doi:10.1029/2001JD001204, 2002]. It has also been proposed that these radiated secondary waves may be subject to ducting near the breaking region [Vadas et al., J. Atmos. Sci., 60, 194, 2003]. It can thus be predicted that if thunderstorm-generated gravity waves, with periods of 10 to 16 minutes, were to break near mesopause, they may excite secondary waves with short periods of 5 to 8 minutes. These waves would be trapped in the lower thermospheric duct. Using a high-resolution, two-dimensional, nonlinear numerical model, we examine this process in a thermally-realistic atmosphere for a tropospheric oscillatory source modeling the effects of convection. Simulated results demonstrate that breaking thunderstorm-generated gravity waves may be able to excite quasi-monochromatic, short-period, thermally ducted wave modes at airglow altitudes. These results will be compared with linear mechanisms (such as ``kissing" modes [e.g., Walterscheid et al. JGR, 106, 31825, 2001]); the applicability and limitations of the different mechanisms will be discussed.

Snively, J. B.; Pasko, V. P.

2003-12-01

239

Weakly nonlinear analysis of short-wave elliptical instability  

NASA Astrophysics Data System (ADS)

Two-dimensional inviscid flows with elliptical streamlines have linearly unstable three-dimensional modes close to the center of the ellipse. The linear instability equilibrates in the presence of enough viscosity, yielding a continuous set of neutrally stable plane waves known as Craik-Criminale waves (CCWs). For initial disturbance in a discrete superposition of plane waves our weakly nonlinear analysis yields a cubic ordinary differential equation for the slow-time evolution of the neutrally stable plane-wave amplitudes. In the subcritical region we find that all solutions eventually vanish, while in the supercritical region the amplitudes either saturate or have exponential growth; the existence of a finite-time blowup at cubic order being unlikely. The saturation to a steady state is possible only for special initial conditions, and for generic initial conditions the amplitudes saturate to a chaotic state. In contrast, a single CCW with exponential growth is still unstable, but it loses stability to cycles of growth and decay among the plane waves.

Rodrigues, Savio B.; de Luca, Jayme

2009-01-01

240

Design of Modified Short Backfire Antennas for Millimeter-Waves Wireless LAN Applications  

Microsoft Academic Search

A set of novel modified short backfire antennas are proposed and designed for the application of millimeter-wave wireless LAN systems, by using the FDTD method. By changing the geometrical parameters and feeding structure, the short backfire antennas can generate different kinds of radiation patterns, including narrow pattern, fan-like pattern and conical patterns. Antenna parameters such as reflection bandwidth, input impedance,

Shiwen Yang; SoonHie Tan; Jeffrey S. Fu

2002-01-01

241

Short backfire antennas for wireless LAN applications at millimeter-waves  

Microsoft Academic Search

A set of novel modified short backfire antennas are proposed and designed for the application of millimeter-wave wireless LAN systems, by using the FDTD method. By changing the geometrical parameters and feeding structure, the short backfire antennas can generate different kinds of radiation patterns, including a narrow pattern, a fan-like pattern and a conical patterns, for various wireless LAN applications

Shiwen Yang; Soon Hie Tan; JefTrey S. Fu

2000-01-01

242

An Analysis of Oxygen-Rich Dust Spectra from the Short Wavelength Spectrometer on the \\em{Infrared Space Observatory}  

NASA Astrophysics Data System (ADS)

We present initial results of an on-going analysis of the spectra from 160 oxygen-rich dust shells observed by the Short Wavelength Spectrometer (SWS) on the Infrared Space Observatory. The strength of the dust emission feature at 13 ? m correlates with the strength of another dust feature centered ~19.5 ? m. These features occasionally appear superimposed on the broader emission features from amorphous silicates at 10 and 18 ? m, but they appear more often in spectra showing lower-contrast dust emission from amorphous alumina or in some cases from spectra showing little or no other dust emission. Comparison of the spectra with laboratory data of crystalline alumina (? --Al2O3), which show emission features at 13 and 21 ? m, would strengthen the case for crystalline alumina as the carrier of the 13 ? m feature if the shift from 21 to 19.5 ? m could be explained. We also investigate several additional spectral features. These include the possible emission feature at 7 ? m, possible narrow dust features at 12 and 18 ? m which may be related to the 13 ? m feature, the CO2 emission bands (at 13.9, 14.9, and 16.2 ? m), and the atmospheric absorption bands from CO, SiO, and other molecules in the 2--10 ? m spectal region.

Sloan, G. C.; Goebel, J. H.; Kraemer, K. E.; Price, S. D.

2001-12-01

243

Short-wavelength near-infrared spectra of sucrose, glucose, and fructose with respect to sugar concentration and temperature.  

PubMed

Short-wavelength near-infrared (SW-NIR) (700-1100 nm) spectra of aqueous solutions of sucrose, D-glucose, and D-fructose were monitored with respect to change in temperature and sugar concentration. Sugar OH and CH related vibrations were identified by analysis of the spectra of sugar solutions in deuterium oxide (D2O), and of sucrose-d8 solutions in D2O. Absorption spectra were explained in terms of the second and third overtones of OH stretching vibrations and the third overtone of CH2 and CH stretchings. In deuterated solutions, CH and CH2 higher overtone vibration bands became apparent. The major spectral effect of decreased temperature or increased sugar concentration was a decrease in absorbance at 960 nm and an increase in absorbance at 984 nm, interpreted as an increase in the degree of H bonding. Partial least-squares (PLS) calibrations on sugar concentrations (with spectra collected at several sample temperatures) relied strongly on the 910 nm sugar CH related bands, whereas calibrations on temperature depended equally on all OH associated vibrations (750, 840, 960, and 985 nm). PMID:14610949

Golic, Mirta; Walsh, Kerry; Lawson, Peter

2003-02-01

244

[Boundary threshold value method used in crystalline material internal defect detection by short wavelength X-ray diffraction].  

PubMed

There are few references about crystalline material internal defect detected by X-ray diffraction tomography using common X-ray source. Short wavelength X-ray diffractometer (SWXRD), invented by Institute of Southwest Technology Engineering, is a relatively small and inexpensive instrument compared to synchrotron radiation or neutron reactor. Boundary determination of defect affects the imaging quality and the distinguishing of defect in X-ray diffraction tomography using SWXRD. In the present paper, threshold value method of diffracted intensity is put forward to process the test data, so the boundary of defect is legible. In order to study how the factors influence the threshold value, Gauss function is used in fitting the test data. The influence of varisized image quality indicator pressed in powdered aluminum on threshold value has been studied. The result shows that 91% of the diffraction intensity of substrate can be regarded as the threshold value. The experiment of slit in aluminum alloy sheet further verified the threshold value method. It's useful in detecting the defect boundary. PMID:21847964

Mu, Jian-Lei; Zhang, Jin; Gao, Zheng-Huan; Zheng, Lin; He, Chang-Guang

2011-06-01

245

Wavelength tuning and thermal dynamics of continuous-wave mid-infrared distributed feedback quantum cascade lasers  

NASA Astrophysics Data System (ADS)

We report on the wavelength tuning dynamics in continuous-wave distributed feedback quantum cascade lasers (QCLs). The wavelength tuning response for direct current modulation of two mid-IR QCLs from different suppliers was measured from 10 Hz up to several MHz using ro-vibrational molecular resonances as frequency-to-intensity converters. Unlike the output intensity, which can be modulated up to several gigahertz, the frequency-modulation bandwidth was found to be on the order of 200 kHz, limited by the laser thermal dynamics. A non-negligible roll-off and a significant phase shift are observed above a few hundred hertz already and explained by a thermal model.

Tombez, Lionel; Cappelli, Francesco; Schilt, Stéphane; Di Domenico, Gianni; Bartalini, Saverio; Hofstetter, Daniel

2013-07-01

246

Tunable optical delay line based on four-wave mixing wavelength conversion and dispersion in optical fibers  

NASA Astrophysics Data System (ADS)

In recent years,tunable optical delay line has attracted much research interest for its applications in optical communications,optical signal processing and optical control of phased array antennas in microwave communications. Compared with optical delay line based on slow light techniques, all-optical wavelength conversion followed by signal propagation in a dispersive medium presents an alternative approach to control the delay time because it is simpler and more controllable. In this paper, a tunable optical delay line with a large time delay up to 650ps based on four-wave mixing (FWM) wavelength conversion in 420m high nonlinearity fiber (HNLF) and dispersion in 8km standard single mode fiber (SMF) is experimentally demonstrated.Our experimental results are in good agreements with the principle.

Yang, Jingwen; Jia, Dongfang; Liu, Tonghui; Ge, Chunfeng; Jia, Weiwei; Wang, Zhaoying; Yang, Tianxin

2013-12-01

247

Collinear phase-matched terahertz-wave generation in GaP crystal using a dual-wavelength optical parametric oscillator  

Microsoft Academic Search

Tunable terahertz (THz)-wave generation in GaP crystal was theoretically and experimentally investigated using collinear difference frequency mixing. The wavelength range and length of GaP crystal for efficient difference frequency generation (DFG) were determined by calculating the phase-matching conditions. THz waves from 0.5 to 4.5 THz were generated by collinear phase-matched DFG using a dual-wavelength optical parametric oscillator with two KTiOPO4

T. Taniuchi; H. Nakanishi

2004-01-01

248

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

Microsoft Academic Search

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

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

2011-01-01

249

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

NASA Astrophysics Data System (ADS)

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

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

2014-04-01

250

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

Microsoft Academic Search

The machining of slow wave structures for high frequency backward-wave oscillators (BWO) is extremely difficult beyond 1 THz. Recently a microfabrication technique using photolithography and ion-beam assisted etching has been used to construct a prototype BWO operating at 200 to 265 GHz. The output coupler for such tubes remains a problem. Waveguides do not exist or are very lossy at

Jerry D. Cook; Norbert Stankiewicz; Mark Podany

1988-01-01

251

Properties and Applications of Ultra-Short Electromagnetic Mono- and Sub-Cycle Waves  

NASA Astrophysics Data System (ADS)

Properties and possible applications of ultra-short (femto- to pico-second) electromagnetic mono- and sub-cycle waves are studied. First, the structural characteristics of these waves are examined. Transient pulses of circularity polarized waves have more complicated structures than those of plane polarized ones. In addition, a pair of colliding pulses may locally and instantaneously generate purely electric or magnetic fields. A general method is presented to describe linear characteristics of these waves propagating through some homogeneous, dispersive media such as air, plasma and optical fibers. Although their spectra are ultra-wideband, should their time duration be short enough, these pulses can in some cases propagate through dispersive media for relatively long distances, approximately maintaining their original waveforms. In particular, such pulses traveling in a plasma shows a characteristic quite opposite to that of ordinary wave packets.

Akimoto, Kazuhiro

1996-07-01

252

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

253

Extended tunable optical delay using gain-transparent stimulated Brillouin scattering control in four-wave-mixing wavelength conversion.  

PubMed

We propose and experimentally demonstrate an extended range of tunable optical delay obtained from four-wave mixing wavelength conversion and dispersion. The conversion bandwidth and the maximum delay are enlarged through dynamic control of the optical phase by gain-transparent stimulated Brillouin scattering. The delay range is increased by 37%. Bit-error-rate measurements show a maximum power penalty of 2.0 dB with reference to back-to-back performance. The technique can be applied to different configurations of tunable delay lines constructed with a fiber parametric process and dispersion. PMID:24514130

Wang, Liang; Huang, Chaoran; Shu, Chester

2014-01-20

254

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

255

Human phase response curve to a single 6.5 h pulse of short-wavelength light  

PubMed Central

The photic resetting response of the human circadian pacemaker depends on the timing of exposure, and the direction and magnitude of the resulting shift is described by a phase response curve (PRC). Previous PRCs in humans have utilized high-intensity polychromatic white light. Given that the circadian photoreception system is maximally sensitive to short-wavelength visible light, the aim of the current study was to construct a PRC to blue (480 nm) light and compare it to a 10,000 lux white light PRC constructed previously using a similar protocol. Eighteen young healthy participants (18–30 years) were studied for 9–10 days in a time-free environment. The protocol included three baseline days followed by a constant routine (CR) to assess initial circadian phase. Following this CR, participants were exposed to a 6.5 h 480 nm light exposure (11.8 ?W cm?2, 11.2 lux) following mydriasis via a modified Ganzfeld dome. A second CR was conducted following the light exposure to re-assess circadian phase. Phase shifts were calculated from the difference in dim light melatonin onset (DLMO) between CRs. Exposure to 6.5 h of 480 nm light resets the circadian pacemaker according to a conventional type 1 PRC with fitted maximum delays and advances of ?2.6 h and 1.3 h, respectively. The 480 nm PRC induced ?75% of the response of the 10,000 lux white light PRC. These results may contribute to a re-evaluation of dosing guidelines for clinical light therapy and the use of light as a fatigue countermeasure.

Ruger, Melanie; St Hilaire, Melissa A; Brainard, George C; Khalsa, Sat-Bir S; Kronauer, Richard E; Czeisler, Charles A; Lockley, Steven W

2013-01-01

256

Multimode short-wavelength perturbation growth studies for the National Ignition Facility double-shell ignition target designs  

NASA Astrophysics Data System (ADS)

Detailed multimode two-dimensional simulations of short-wavelength perturbations imposed on the material interfaces of a recently proposed indirect-drive double-shell ignition target [Amendt et al., Phys. Plasmas 9, 2221 (2002)] are presented. In this work, the effect of roughness imposed only on the surfaces of the inner shell is studied. Realistic perturbations are adopted from a measured spectrum of a glass capsule (as a surrogate for the high-Z inner shell). It is found that perturbing the inner surface of the inner shell shows minimal degradation in capsule performance. On the other hand, when roughness is imposed on the outer surface of the inner shell, the growth of large Legendre mode number perturbations (l>200) leads to shell breakup. Further analysis reveals a new pathway for the Rayleigh-Taylor (RT) instability. L-shell radiation (>8 keV) from the high-Z hohlraum wall ablates the outer surface of the high-Z inner shell, promoting large outward expansion which is reversed by the converging outer shell. The classic conditions for RT instability are met: low density material pushing onto the higher density inner shell. It is shown that this effect can be controlled by tamping the outward expansion of the inner shell with a variety of materials. Simulations with separate CH and Ti tampers demonstrate that the redesigned capsule can withstand perturbations with high mode number content without exhibiting shell breakup. Furthermore, the outstanding question of determining the cutoff mode number (lc) is addressed by performing simulations with successively larger maximum l, reaching values beyond 1000, and calculating the mix width of the pusher/tamper interface for the CH-tamped case. These numerical studies suggest that the mix width approaches a constant value close to 40% of the shell width at peak compression. While not a proof that lc has been found, this result suggests that a mix-relevant mode number may be within reach of current simulation capabilities.

Milovich, J. L.; Amendt, P.; Marinak, M.; Robey, H.

2004-04-01

257

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

NASA Astrophysics Data System (ADS)

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

Smith, Mark William

258

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

259

Short-wave infrared colloidal quantum dot photodetectors on silicon  

NASA Astrophysics Data System (ADS)

In this paper, two kinds of colloidal quantum dots, PbS and HgTe, are explored for SWIR photodetectors application. The colloidal dots are prepared by hot injection chemical synthesis, with organic ligands around the dots keeping them stable in solution. For the purpose of achieving efficient carrier transport between the dots in a film, these long organic ligands are replaced by shorter, inorganic ligands. We report uniform, ultra-smooth colloidal QD films without cracks realized by dip-coating and corresponding ligand exchange on a silicon substrate. Metal-free inorganic ligands, such as OH- and S2-, are investigated to facilitate the charge carrier transport in the film. Both PbS and HgTe-based quantum dot photoconductors were fabricated on interdigitated gold electrodes. For PbS-based detectors a responsivity of 200A/W is measured at 1.5?m, due to the large internal photoconductive gain. A 2.2?m cut-off wavelength for PbS photodetectors and 2.8?m for HgTe quantum dot photodetectors are obtained.

Hu, Chen; Gassenq, Alban; Justo, Yolanda; Yakunin, Sergii; Heiss, Wolfgang; Hens, Zeger; Roelkens, Gunther

2013-01-01

260

Investigation of the sapphire window on short MM waves band  

NASA Astrophysics Data System (ADS)

A analytic method of the eguivalent network for RF sapphire window of 3mm diffraction radiation oscillator is given in the paper. Numerical simulate and experiment are carried out on 3mm wave band. The testing results show that the design method agrees with the practical windows, and it is the fast optimum method. We employ the universal method, the piece of the window can be equal to dielectric waveguide and one end of the window connects the coupling slit of the mirror of open cavity. The design window by means of this method is used satisfactorily on 3mm DRO. The tube operates in the 84 108GHZ band, the output power is about 250m W.

Chen, Jiayu; Zhang, Yongchuag; Duan, Yuxiang

1995-12-01

261

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

262

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

263

Tunable short-pulse beat-wave laser source operating at 1{ital } m  

Microsoft Academic Search

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

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

1997-01-01

264

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

NASA Astrophysics Data System (ADS)

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

Mimani, A.; Munjal, M. L.

2011-03-01

265

Passive millimeter-wave imaging at short and medium range  

NASA Astrophysics Data System (ADS)

During recent year's research on radiometric signatures, non-imaging, of the exhaust jet of missiles and imaging, on small vehicles in critical background scenarios were conducted by the mmW/submmW-group at FGAN-FHR. The equipment used for these investigations was of low technological status using simple single channel radiometers on a scanning pedestal. Meanwhile components of improved performance are available on a cooperative basis with the Institute for Applied Solid State Physics (Fraunhofer-IAF). Using such components a considerable progress concerning the temperature resolution and image generation time could be achieved. Emphasis has been put on the development of a demonstrator for CWD applications and on an imaging system for medium range applications, up to 200 m. The short range demonstrator is a scanning system operating alternatively at 35 GHz or 94 GHz to detect hidden materials as explosives, guns, knifes beneath the clothing. The demonstrator uses a focal plane array approach using 4 channels in azimuth, while mechanical scanning is used for the elevation. The medium range demonstrator currently employs a single channel radiometer on a pedestal for elevation over azimuth scanning. To improve the image quality, methods have been implemented using a Lorentzian algorithm with Wiener filtering.

Essen, H.; Fuchs, H.-H.; Nötel, D.; Klöppel, F.; Pergande, P.; Stanko, S.

2005-11-01

266

Investigation of short-period gravity waves with the Lindenberg 482 MHz tropospheric wind profiler  

NASA Astrophysics Data System (ADS)

During four consecutive days in May 2001, convectively forced short-period (6-45 min) gravity waves were observed with a 482 MHz wind profiler, which is continuously operated by the Deutscher Wetterdienst (German Weather Service) at the Lindenberg observatory, 60 km south-east of Berlin. The objective of this campaign was to investigate onset and development of convectively forced gravity waves in the lower and middle troposphere. The wave character could be unambiguously identified by simultaneous vertical wind and temperature measurements and their respective phase shift of /2. In accordance with previous findings, convection waves were found to be generated at the top of the convective boundary layer. They propagate predominantly horizontally with a slow but clearly recognizable vertical increase of wave activity. The layer with significant wave activity reached the upper detection range at 7.0 km within a couple of hours on each of the observational days. Gravity wave activity started to decay after 16 UTC with a slower rate than the simultaneously decaying forcing convection. Some wave activity remained during the night but at low amplitude levels. The vertical wind energy component of the free atmosphere was found to be about 30% of the corresponding convective boundary layer (CBL) energy, which is much more than previously reported values from numerical simulations. The wavelet analysis of highly resolved wind profiler vertical velocity data (t = 16 s, z = 250 m) in the boundary layer and free troposphere gives new insights into the temporal and vertical development of very-short-period convection waves through the troposphere. At the CBL top, a broad spectrum of wave scales with intrinsic periods between 6 and 45 min is generated. With increasing height, shorter scales (T 13 min) disappear and only longer ones remain. Wave trapping, which is confirmed by vertically orientated phase lines, is an important mechanism here.

Böhme, T.; Hauf, T.; Lehmann, V.

2004-10-01

267

Minimization of threshold current in short wavelength AlGaInP vertical-cavity surface-emitting lasers  

Microsoft Academic Search

This paper investigates the interdependence of wavelength and threshold current in an AlGaInP vertical-cavity surface-emitting laser with an emphasis on optimizing the performance of shorter wavelength lasers. We apply a model which includes bandstructure, band-filling and many body effects in a consistent manner, as well as leakage current effects, to evaluate the effect of strain and quantum confinement on threshold

Weng W. Chow; Mary Hagerott Crawford; Richard P. Schneider

1995-01-01

268

Critical wavelength for river meandering.  

PubMed

A fully nonlinear modal analysis identifies a critical centerline wave number q(c) for river meandering that separates long-wavelength bends, which grow to cutoff, from short-wavelength bends, which decay. Exact, numerical, and approximate analytical results for q(c) rely on the Ikeda, Parker, and Sawai [J. Fluid Mech. 112, 363 (1981)] model, supplemented by dynamical equations that govern the river migration and length. Predictions also include upvalley bend migration at long times and a peak in lateral migration rates at intermediate times. Experimental tests are suggested. PMID:11308902

Edwards, B F; Smith, D H

2001-04-01

269

Influence of temperature on the measurement of NaCl content of aqueous solution by short-wavelength near infrared spectroscopy (SW-NIR)  

Microsoft Academic Search

Short-wavelength near infrared (SW-NIR) spectroscopy can provide a rapid and nondestructive determination of salt content\\u000a in food products, and potentially monitor salt concentration of brines during processing. This is of significant importance\\u000a for ensuring the safety and quality of cured and smoked foods. One of the constraints is having reliable models to predict\\u000a salt concentration as temperature varies. The effect

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

2007-01-01

270

H1 horizontal cells of carp retina have different postsynaptic mechanisms to mediate short-versus long-wavelength visual signals  

Microsoft Academic Search

Vertebrate photoreceptors release neuro-transmitter substance(s) tonically in the dark and this release is curtailed by light. Recently, we have become increasingly aware of the possibility that short- and long-wavelength visual signals are mediated differently during the synaptic transmission to second-order retinal neurons. The experiment described here advances this notion further by demonstrating a postsynaptic difference. Treatment of the carp retina

S. Yasui; M. Yamada

1989-01-01

271

A singular perturbation analysis of the weakly nonlinear evolution of long and short water waves and waves in boundary layers  

Microsoft Academic Search

A singular-perturbation method is introduced for the solution of multiple-scale problems. The use of the method is first illustrated with some relatively simple ordinary and partial differential equations; it is then applied to two problems in fluid mechanics: the nonlinear interaction of long and short water waves and boundary-layer stability. The proposed method is referred to as the invariance-condition to

Stephen Laurence Woodruff

1987-01-01

272

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

Microsoft Academic Search

This dissertation describes the design, construction, and calibration of a portable short wave infrared (SWIR) spectroradiometer. The main use for the instrument is the collection of ground reflectance and radiance data for the radiometric calibration of operational and proposed high spectral resolution remote-sensing systems, such as the Airborne Visible and Infrared Imaging Spectrometer (AVIRIS), the Moderate Resolution Imaging Spectroradiometer (MODIS),

Mark William Smith

1992-01-01

273

Exposure limits for ultra-short wave radiation in work environments.  

PubMed

Exposure limit values for ultra-short wave radiation of humans were derived on the basis of epidemiological survey and experimental exposure of rabbits. Eighteen male rabbits were divided into 4 groups randomly. Three groups were irradiated with ultra-short waves (100 MHz) at 35, 1.5-3.5, and 0.07 mW/cm2 power density in an E-polarized TEM Cell at 24 +/- 4 degrees C ambient temperature. The last group in a sham chamber served as controls. Irradiation was performed 3 hours per day, 5 days per week for 24 weeks. Thermal effects occurred in the group irradiated at 35 mW/cm2. The thermal threshold limit value was set at 1.5 mW/cm2. An epidemiological survey was carried out on 136 factory workers and TV operators exposed over one year to ultra-short wave radiation at 0.2 mW/cm2. They were compared with 108 controls. The only complaint of the exposed group was neurosis. The exposure limit value (ELV) to short wave radiation was set at 0.2 mW/cm2 by using a 15- and 20-fold safety factor. PMID:7724881

Zhao, Z; Zhang, S; Wang, S; Yao, Z; Zho, H; Tao, S; Tao, L

1994-01-01

274

Inversion Method Study on Short Wave Infrared Remote Sensing Data High Temperature Surface Feature Temperature  

Microsoft Academic Search

The short wave infrared remote sensing data element DN value is synthesis reflectance of surface features reflex and the emission energy that the emission energy can be ignored generally in terms of the normal temperature surface features, but emission energy of the high temperature surface feature is close or higher than its reflex energy value, based on this, using the

Pan Jun; Xing Li-xin; Wen Jiu-cheng; Meng Tao; Jiang Li-jun

2009-01-01

275

Sub-wavelength quarter-wave plate based on plasmonic patch antennas  

NASA Astrophysics Data System (ADS)

A quarter-wave plate using plasmonic patch antennas has been investigated. The nanostructures can convert linear polarized light into circular polarized light in the visible range (633 nm). By further exploiting the dimer patch antenna structure composed of different metals, directional emission (with a directivity of 4.8) of circular polarized light (with a conversion efficiency of 27.8%) in an oblique direction with respect to the incident light is enabled. Compared with previous designs, the proposed structures are ultra-thin, and are more suitable for integration applications.

Zhao, Hang; Yang, Yuanqing; Li, Qiang; Qiu, Min

2013-12-01

276

A wide-band radiometer for the short-wavelength part of the millimeter range based on a superconducting point contact  

Microsoft Academic Search

A wideband radiometer for astronomical observations in the short end of the millimeter wave band with a superconducting point contact as the sensitive element is described. Radiation at the input of the quasi-optical channel is modulated with a frequency of 400 MHz, transmitted through a series of filters, and enters a detector section consisting of a superconducting point contact with

E. V. Antyukh; Yu. Ya. Divin; V. F. Zabolotnyi; F. Ya. Nad

1978-01-01

277

Rapid and sensitive trace gas detection with continuous wave Optical Parametric Oscillator-based Wavelength Modulation Spectroscopy  

NASA Astrophysics Data System (ADS)

A fiber-amplified Distributed Bragg Reflector diode laser is used to pump a continuous wave, singly resonant Optical Parametric Oscillator (OPO). The output radiation covers the 3-4 ?m with ability of rapid (100 THz/s) and broad mode-hop-free tuning (5 cm-1). Wavelength Modulation Spectroscopy is combined with the OPO to take optimal advantage of the spectral scan speed. The sensitivity of the system was determined as 0.8 ppbv (parts-per-billion by volume) for ethane (C2H6) for the absorption peak at 2996.9 cm-1 recorded in 1.3 seconds, corresponding to a noise equivalent absorption sensitivity (NEAS) of 1.2×10-9 cm-1/Hz1/2. A comparison between results using the 1st, 2nd and 4th harmonic derivative signal from wavelength modulation was performed. The broad continuous tunability was demonstrated by covering 35 cm-1 while recording absorption features of ethane, methane and water.

Arslanov, D. D.; Spunei, M.; Ngai, A. K. Y.; Cristescu, S. M.; Lindsay, I. D.; Persijn, S. T.; Boller, K. J.; Harren, F. J. M.

2011-04-01

278

Finite-wavelength scattering of incident vorticity and acoustic waves at a shrouded-jet exit  

NASA Astrophysics Data System (ADS)

As the vortical disturbances of a shrouded jet pass the sharp edge of the shroud exit some of the energy is scattered into acoustic waves. Scattering into upstream-propagating acoustic modes is a potential mechanism for closing the resonance loop in the resonances that have been observed in various shrouded jet configurations over the years. A model is developed for this interaction at the shroud exit. The jet is represented as a uniform flow separated by a cylindrical vortex sheet from a concentric co-flow within the cylindrical shroud. A second vortex sheet separates the co-flow from an ambient flow outside the shroud, downstream of its exit. The Wienertransparent’ for ranges of Mach numbers, with no reflection into any upstream-propagating acoustic mode. This is phenomenologically consistent with observations that indicate a peculiar sensitivity of resonances of this kind to, say, jet Mach number.

Samanta, Arnab; Freund, Jonathan B.

279

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

NASA Astrophysics Data System (ADS)

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

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

2014-03-01

280

Study of Tunable Terahertz-Wave Generation in Isotropic Semiconductor Crystals Based on Dual-Wavelength KTP-OPO Operating near Degenerate Point  

Microsoft Academic Search

Continuously tunable coherent terahertz-wave generation from 0.1 to 2.7 THz can be achieved in isotropic semiconductor nonlinear crystals by difference frequency mixing. We experimentally demonstrated a high-power, narrow-linewidth, angle-tuned pulsed dual-wavelength KTP-OPO operating near the degenerate point, which was used as the pump source for terahertz-wave generation. We theoretically studied the feasibility of the cross-Reststrahlen band dispersion compensation phase matching

B. Sun; J. Q. Yao; Z. Wang; P. Zhao; Y. Lu; H. Liu; D. G. Xu

2006-01-01

281

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

NASA Astrophysics Data System (ADS)

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

Keppel, Drew

2012-12-01

282

Modified Short Backfire Antenna.  

National Technical Information Service (NTIS)

Measurements have shown it possible to increase the gain of the short backfire antenna significantly in different ways: (1) By increasing the size of the reflectors. (2) By placing extra reflectors in multiples of a half wavelength from the surface wave r...

F. A. Hass

1971-01-01

283

Does one hour of bright or short-wavelength filtered tablet screenlight have a meaningful effect on adolescents' pre-bedtime alertness, sleep, and daytime functioning?  

PubMed

Electronic media use is prevalent among adolescent populations, as is the frequency of sleeplessness. One mechanism proposed for technology affecting adolescents' sleep is the alerting effects from bright screens. Two explanations are provided. First, screens emit significant amounts of short-wavelength light (i.e. blue), which produces acute alertness and alters sleep timing. Second, later chronotypes are hypothesised to be hypersensitive to evening light. This study analysed the pre-sleep alertness (GO/NOGO task speed, accuracy; subjective sleepiness), sleep (sleep diary, polysomnography), and morning functioning of 16 healthy adolescents (M?=?17.4?±?1.9?yrs, 56% f) who used a bright tablet screen (80?lux), dim screen (1?lux) and a filtered short-wavelength screen (f.lux; 50?lux) for 1?hr before their usual bedtime in a within-subjects protocol. Chronotype was analysed as a continuous between-subjects factor; however, no significant interactions occurred. Significant effects occurred between bright and dim screens for GO/NOGO speed and accuracy. However, the magnitude of these differences was small (e.g. GO/NOGO speed?=?23?ms, accuracy?=?13%), suggesting minimal clinical significance. No significant effects were found for sleep onset latency, slow-rolling eye movements, or the number of SWS and REM minutes in the first two sleep cycles. Future independent studies are needed to test short (1?hr) vs longer (>2?hrs) screen usage to provide evidence for safe-to-harmful levels of screenlight exposure before adolescents' usual bedtime. PMID:24397302

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

2014-05-01

284

Determination of Lead Associated with Airborne Particulate Matter by Flame Atomic Absorption and Wave-Length Dispersive X-Ray Fluorescence Spectrometry  

Microsoft Academic Search

The lead content of airborne particulate matter was determined by flame atomic absorption spectrometry (FAAS) following digestion with a mixture of nitric acid and hydrogen peroxide and also by wave-length dispersive x-ray fluorescence (WDXRF). The extraction procedure was checked by analyzing a standard reference material of airborne particulate matter (NIST, SRM — 1648). It was concluded that lead can quantitatively

S. M. Talebi

1998-01-01

285

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

PubMed

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

Jacobs, Gerald H

2013-03-01

286

Short-Term TEC Perturbations Associated With Planetary Waves Occurrence in the Ionosphere  

NASA Astrophysics Data System (ADS)

Analysis of TEC response to storm showed short-term perturbations which were observed after initial phase of geomagnetic storms. The perturbations demonstrated very well expressed latitudinal structure and were recognized on diurnal variations as surges of TEC enhancement of TEC. Ordinary such storm-time positive effect was associated with TAD. Duration of the perturbations was about 2-4 hours and their amplitude increased toward low latitudes. Such TEC perturbations have the longitudinal dependence. It is important that time location of surges have week dependence on latitude. The observed structure appeared to arrive from high latitudes, but at middle latitudes it was represented as a standing wave. It is assumed that such TEC perturbations can be produced due to superposition of the eastward and westward propagating planetary Poincare waves. The periods of these waves are usually several hours. Poincare waves can be excited at the atmosphere in storm time. At middle latitudes their superposition is as standing wave that forms observing TEC perturbations. In the report, the possibilities of application Poincare waves to the ionosphere dynamics studies are discussed and an explanation of the observed ionospheric effects is given.

Shagimuratov, I. I.; Karpov, I.; Krankowski, A.

2008-12-01

287

Continuous-Wave Magnetic Resonance Imaging of Short T 2 Materials  

Microsoft Academic Search

There is growing interest in the use of magnetic resonance imaging (MRI) to examine solid materials where the restricted motion of the probed spins leads to broad lines and short T2 values, rendering many interesting systems invisible to conventional 2DFT pulsed imaging methods. In EPR T2 seldom exceeds 0.1 ?s and continuous-wave methods are adopted for spectroscopy and imaging. In

G. R. Davies; D. J. Lurie; J. M. S. Hutchison; S. J. McCallum; I. Nicholson

2001-01-01

288

Continuous-Wave Magnetic Resonance Imaging of Short T2 Materials  

Microsoft Academic Search

There is growing interest in the use of magnetic resonance imaging (MRI) to examine solid materials where the restricted motion of the probed spins leads to broad lines and short T2 values, rendering many interesting systems invisible to conventional 2DFT pulsed imaging methods. In EPR T2 seldom exceeds 0.1 mus and continuous-wave methods are adopted for spectroscopy and imaging. In

G. R. Davies; D. J. Lurie; J. M. S. Hutchison; S. J. McCallum; I. Nicholson

2001-01-01

289

Compact FMCW design for short range millimeter-wave radar imaging applications  

Microsoft Academic Search

This paper presents the design of a new compact, low- cost, FMCW millimeter-wave radar for high-resolution, short- range imaging applications. In this design, problems that have limited the performance of classical FMCW radars were solved. A W-band FMCW radar with better than 0.3 m range resolution, 1 o beamwidth, 25 kHz chirp rate, 19 dBm output power, and operating in

Adib Y. Nashashibi; Juseop Lee; Kamal Sarabandi

2011-01-01

290

The short-wave model for the Camassa-Holm equation: a Riemann-Hilbert approach  

NASA Astrophysics Data System (ADS)

We present the inverse scattering transform approach to the Cauchy problem on the line for the short-wave model for the Camassa-Holm equation u_{txx}-2 u_x+2u_xu_{xx}+uu_{xxx}=0 in the form of an associated Riemann-Hilbert problem. This approach allows us to give a representation of the classical (smooth) solutions, describe their asymptotics as t ? ? and describe cuspons—non-smooth soliton solutions with a cusp.

Boutet de Monvel, Anne; Shepelsky, Dmitry; Zielinski, Lech

2011-10-01

291

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

Microsoft Academic Search

Multiwavelength airglow image data depicting a short-period (?4.9 min) atmospheric gravity wave characterized by a sharp leading front have been analyzed together with synoptic meteor radar wind data recorded simultaneously from Bear Lake Observatory, Utah (41.6°N, 111.6°W). The wind data suggest the presence of a semidiurnal tide with horizontal winds peaking at around 60 m\\/s along the SSE direction of

Jonathan B. Snively; Victor P. Pasko; Michael J. Taylor; Wayne K. Hocking

2007-01-01

292

Prediction of clear-air turbulence induced by short gravity waves  

NASA Astrophysics Data System (ADS)

A new auxiliary clear-air turbulence (CAT) predictor based on a triggering mechanism for clear-air turbulence, namely short (500m-20000m) gravity waves excited by shallow convection is considered. Case studies are presented in which the predictor is compared with other widely used CAT indices. One case is based on NWP (numerical weather prediction) model and other on on real sounding. Also comparison of real life sounding results with model generated ones is performed.

Kope?, Jacek M.; Haman, Krzysztof E.; Bajer, Konrad

2011-12-01

293

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

SciTech Connect

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

Setser, D.W.

1987-12-07

294

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

NASA Astrophysics Data System (ADS)

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

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

2013-10-01

295

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

296

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

Microsoft Academic Search

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

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

1995-01-01

297

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

NASA Technical Reports Server (NTRS)

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

Stobie, J.; Iwasa, S.

1981-01-01

298

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

299

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

300

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

301

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

PubMed

The GeSn direct gap material system, with Si complementary-metal-oxide semiconductor (CMOS) compatibility, presents a promising solution for direct incorporation of focal plane arrays with short wave infrared detection on Si. A temperature dependence study of GeSn photoconductors with 0.9, 3.2, and 7.0% Sn was conducted using both electrical and optical characterizations from 300 to 77 K. The GeSn layers were grown on Si substrates using a commercially available chemical vapor deposition reactor in a Si CMOS compatible process. Carrier activation energies due to ionization and trap states are extracted from the temperature dependent dark I-V characteristics. The temperature dependent spectral response of each photoconductor was measured, and a maximum long wavelength response to 2.1 ?m was observed for the 7.0% Sn sample. The DC responsivity measured at 1.55 ?m showed around two orders of magnitude improvement at reduced temperatures for all samples compared to room temperature measurements. The noise current and temperature dependent specific detectivity (D*) were also measured for each sample at 1.55 ?m, and a maximum D* value of 1 × 109 cm·?Hz/W was observed at 77 K. PMID:24977823

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

2014-06-30

302

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

NASA Astrophysics Data System (ADS)

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

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

2010-12-01

303

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

NASA Astrophysics Data System (ADS)

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

André, Matthieu A.; Bardet, Philippe M.

2014-04-01

304

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

NASA Astrophysics Data System (ADS)

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

Li, Maggie M.; Chen, Ray T.

1995-04-01

305

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

SciTech Connect

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

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

2013-09-28

306

Spatio-temporal development of the long and short-wave vortex-pair instabilities  

NASA Astrophysics Data System (ADS)

We consider the spatio-temporal development of the long-wave and short-wave instabilities in a pair of counter-rotating vortices in the presence of a uniform axial advection velocity. The stability properties depend upon the aspect ratio a/b of the vortex pair, where a is the core radius of the vortices and b their separation, and upon W0/U0 the ratio between the self-induced velocity of the pair and the axial advection velocity. For sufficiently small W0/U0, the instabilities are convective, but an increase of W0/U0 may lead to an absolute instability. Near the absolute instability threshold, spatial growth rates are larger than those predicted by temporal stability theory. Considering aeronautical applications, it is shown that instabilities of the type considered in this communication cannot become absolute in farfield wakes of high aspect ratio wings.

Fabre, David; Cossu, Carlo; Jacquin, Laurent

2000-05-01

307

Short-wave near-infrared spectroscopy of milk powder for brand identification and component analysis.  

PubMed

The aim of the present paper was to provide new insight into the short-wave near-infrared (NIR) spectroscopic analysis of milk powder. Near-infrared spectra in the 800- to 1,025-nm region of 350 samples were analyzed to determine the brands and quality of milk powders. Brand identification was done by a least squares support vector machine (LS-SVM) model coupled with fast fixed-point independent component analysis (ICA). The correct answer rate of the ICA-LS-SVM model reached as high as 98%, which was better than that of the LS-SVM (95%). Contents of fat, protein, and carbohydrate were determined by the LS-SVM and ICA-LS-SVM models. Both processes offered good determination performance for analyzing the main components in milk powder based on short-wave NIR spectra. The coefficients of determination for prediction and root mean square error of prediction of ICA-LS-SVM were 0.983, 0.231, and 0.982, and 0.161, 0.980, and 0.410, respectively, for the 3 components. However, there were less than 10 input variables in the ICA-LS-SVM model compared with 225 in the LS-SVM model. Thus, the processing time was much shorter and the model was simpler. The results presented in this paper demonstrate that the short-wave NIR region is promising for fast and reliable determination of the brand and main components in milk powder. PMID:18292249

Wu, D; Feng, S; He, Y

2008-03-01

308

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

NASA Astrophysics Data System (ADS)

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

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

2014-02-01

309

Hyperspectral imaging for thermal analysis and remote gas sensing in the short wave infrared  

NASA Astrophysics Data System (ADS)

A novel hyperspectral imaging device based on Fourier transform analysis applied to a low finesse scanning Fabry-Pérot (F-P) interferometer has been demonstrated in the short wave infrared (SWIR) region. The technique allows the realization of a lightweight and compact instrument yet allowing much faster and/or better quality hyperspectral images with respect to classical instruments based on a dispersive means or on a tunable band-pass filter. The potentialities in spectroscopic applications like remote gas sensing are presented as well as accurate thermal imaging capabilities.

Pisani, M.; Bianco, P.; Zucco, M.

2012-07-01

310

GeSn/Ge heterostructure short-wave infrared photodetectors on silicon.  

PubMed

A surface-illuminated photoconductive detector based on Ge0.91Sn0.09 quantum wells with Ge barriers grown on a silicon substrate is demonstrated. Photodetection up to 2.2µm is achieved with a responsivity of 0.1 A/W for 5V bias. The spectral absorption characteristics are analyzed as a function of the GeSn/Ge heterostructure parameters. This work demonstrates that GeSn/Ge heterostructures can be used to developed SOI waveguide integrated photodetectors for short-wave infrared applications. PMID:23262679

Gassenq, A; Gencarelli, F; Van Campenhout, J; Shimura, Y; Loo, R; Narcy, G; Vincent, B; Roelkens, G

2012-12-01

311

Electron acceleration in relativistic plasma waves generated by a single frequency short-pulse laser  

SciTech Connect

Experimental evidence for the acceleration of electrons in a relativistic plasma wave generated by Raman forward scattering (SRS-F) of a single-frequency short pulse laser are presented. A 1.053 {mu}m, 600 fsec, 5 TW laser was focused into a gas jet with a peak intensity of 8{times}10{sup 17} W/cm{sup 2}. At a plasma density of 2{times}10{sup 19} cm{sup {minus}3}, 2 MeV electrons were detected and their appearance was correlated with the anti-Stokes laser sideband generated by SRS-F. The results are in good agreement with 2-D PIC simulations. The use of short pulse lasers for making ultra-high gradient accelerators is explored.

Coverdale, C.A.; Darrow, C.B.; Decker, C.D. [Lawrence Livermore National Lab., CA (United States); Mori, W.B.; Tzeng, K.C., Clayton, C.E.; Marsh, K.A.; Joshi, C. [California Univ., Los Angeles, CA (United States)

1995-04-27

312

OH and OI airglow layer modulation by ducted short-period gravity waves: Effects of trapping altitude  

Microsoft Academic Search

Perturbations to the OH and OI [O(1S) 557.7 nm] airglow layers by ducted gravity waves near the Brunt-Väisälä period are investigated using a 2-D numerical model. Airglow signatures of these waves are strongly determined by perturbations of O, O3, and H, which exhibit peak densities near and above mesopause. Strong periodic vertical wind components of short-period gravity waves induce opposite

Jonathan B. Snively; Victor P. Pasko; Michael J. Taylor

2010-01-01

313

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

SciTech Connect

An integrable Yajima-Oikawa system is solved in the case of a finite density, which corresponds to a slowly varying (long-wavelength) wave with finite amplitude at infinity and a localized fast-oscillating (short-wavelength) wave. Application of the results to spinor Bose-Einstein condensates and other physical systems is discussed.

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

2009-11-15

314

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

315

Comparison of the three schemes to generate optical mm-wave signal and wavelength reuse for upstream connection in the radio-over-fiber systems  

NASA Astrophysics Data System (ADS)

Three different schemes to generate optical millimeter-wave and wavelength reuse for up-link connection in the radioover- fiber (ROF) systems have been theoretically and experimentally investigated. We have compared the performance of the three different schemes for the radio-over-fiber systems considering the cost and configuration of their architectures. A novel scheme to generate optical millimeter-wave and realize centralize lightwave operation in the radio-over-fiber (ROF) systems has been demonstrated. This scheme has shown high performance and low cost compared with the existing schemes.

Dong, Ze; Pi, Yazi; Lu, Jia; He, Jing; Chen, Lin

2008-11-01

316

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

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

317

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

NASA Astrophysics Data System (ADS)

A region of turbulence with large radial wavenumber (kr?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 Er well, the turbulence exhibits large amplitude n ˜/n˜40%, with large radial wavenumber |accent="true">k¯r/accent="true">k¯?|˜11 and short radial correlation length Lr/?i˜0.2. The turbulence inside the Er 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 kr/k?. 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 Er 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 kr turbulence there.

Rost, J. C.; Porkolab, M.; Dorris, J.; Burrell, K. H.

2014-06-01

318

Effect of laser pulse duration on short wavelength emission from femtosecond and picosecond laser-produced Ta plasmas  

NASA Astrophysics Data System (ADS)

To investigate the effect of laser-pulse duration on physical processes involved in short-pulse heating of solid targets, the conversion efficiency, the duration, and the spectral content of the emission from a laser-produced Ta plasma were measured for laser pulse durations ranging from 100 fs to 70 ps. A Nd:YAG laser system operating at 1.06 microns was used to produce subnanosecond duration heating, while subpicosecond duration heating was accomplished by pulses from a colliding-pulse mode-locked dye laser system operating at 620 nm. The emission from laser-produced Ta plasmas was characterized in a procedure described by Silfvast et al. (1983). Efficiencies ranged between 0.3 percent for 100-fs pulse duration to 2.65 percent for 70 ps pulses, and X-ray pulse durations ranged from less than 10-ps to 105 ps, for the respective laser-pulse durations. The emission spectra produced by 600 fs, 70 ps, and 25 ns duration laser pulses were similar, at least in broad outline.

Wood, O. R., II; Silfvast, W. T.; Tom, H. W. K.; Knox, W. H.; Fork, R. L.

1988-08-01

319

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

NASA Astrophysics Data System (ADS)

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

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

2008-12-01

320

Continuous-Wave Magnetic Resonance Imaging of Short T2 Materials  

NASA Astrophysics Data System (ADS)

There is growing interest in the use of magnetic resonance imaging (MRI) to examine solid materials where the restricted motion of the probed spins leads to broad lines and short T2 values, rendering many interesting systems invisible to conventional 2DFT pulsed imaging methods. In EPR T2 seldom exceeds 0.1 ?s and continuous-wave methods are adopted for spectroscopy and imaging. In this paper we demonstrate the use of continuous-wave MRI to obtain 2-dimensional images of short T2 samples. The prototype system can image samples up to 50 mm in diameter by 60 mm long and has been used to image polymers and water penetration in porous media. Typical acquisition times range between 10 and 40 min. Resolution of 1 to 2 mm has been achieved for samples with T2 values ranging from 38 to 750 ?s. There is the possibility of producing image contrast that is determined by the material properties of the sample.

Davies, G. R.; Lurie, D. J.; Hutchison, J. M. S.; McCallum, S. J.; Nicholson, I.

2001-02-01

321

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

322

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

323

Short-crested waves interaction with a concentric porous cylinder system with partially porous outer cylinder  

NASA Astrophysics Data System (ADS)

In this paper, based on the linear wave theory, the interaction of short-crested waves with a concentric dual cylindrical system with a partially porous outer cylinder is studied by using the scaled boundary finite element method (SBFEM), which is a novel semi-analytical method with the advantages of combining the finite element method (FEM) with the boundary element method (BEM). The whole solution domain is divided into one unbounded sub-domain and one bounded sub-domain by the exterior cylinder. By weakening the governing differential equation in the circumferential direction, the SBFEM equations for both domains can be solved analytically in the radial direction. Only the boundary on the circumference of the exterior porous cylinder is discretized with curved surface finite elements. Meanwhile, by introducing a variable porous-effect parameter G, non-homogeneous materials caused by the complex configuration of the exterior cylinder are modeled without additional efforts. Comparisons clearly demonstrate the excellent accuracy and computational efficiency associated with the present SBFEM. The effects of the wide range wave parameters and the structure configuration are examined. This parametric study will help determine the various hydrodynamic effects of the concentric porous cylindrical structure.

Liu, Jun; Lin, Gao; Li, Jian-bo

2012-06-01

324

Short wavelength electromagnetic perturbations excited near the Solar Probe Plus spacecraft in the inner heliosphere: 2.5D hybrid modeling  

NASA Astrophysics Data System (ADS)

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/Alfvén waves in the upstream connected with the bi-directional current closure that was observed in short-time 3D modeling SPPSC and near a tether in the ionosphere. The observed strong electromagnetic perturbations may be a crucial point in the electromagnetic measurements planned for the future Solar Probe Plus (SPP) mission. The results of modeling electromagnetic field perturbations in the SW due to "shot" noise in absence of SPPSC are also discussed.

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

2012-03-01

325

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

326

On-chip interconnect for mm-wave applications using an all-copper technology and wavelength reduction  

Microsoft Academic Search

Transmission lines are implemented using an all-copper backend developed for RF and microwave applications. Wavelength reduction is used to achieve a Q factor >20 from 20GHz to 40GHz, about three times higher than conventional transmission lines implemented with the same technology. It has 0.3dB\\/mm loss, and reduces the wavelength of a conventional transmission line by half thereby minimizing the space

T. S. D. Cheung; J. R. Long; K. Vaed; R. Volant; A. Chinthakindi; C. M. Schnabel; J. Florkey; K. Stein

2003-01-01

327

Heat Distribution in the Lower Leg from Pulsed Short-Wave Diathermy and Ultrasound Treatments  

PubMed Central

Objective: To compare tissue temperature rise and decay after 20-minute diathermy and ultrasound treatments. Design and Setting: We inserted 3 26-gauge thermistor microprobes into the medial aspect of the anesthetized triceps surae muscle at a depth of 3 cm and spaced 5 cm apart. Eight subjects received the diathermy treatment first, followed by the ultrasound treatment. This sequence was reversed for the remaining 8 subjects. The diathermy was applied at a frequency of 27.12 MHz at the following settings: 800 bursts per second, 400-microsecond burst duration, 850-microsecond interburst interval, peak root mean square amplitude of 150 W per burst, and an average root mean square output of 48 W per burst. The ultrasound was delivered at a frequency of 1 MHz and an intensity of 1.5 W/cm2 in the continuous mode for 20 minutes over an area of 40 times the effective radiating area. The study was performed in a ventilated research laboratory. Subjects: Sixteen (11 men, 5 women) healthy subjects (mean age = 23.56 ± 4.73 years) volunteered to participate in this study. Measurements: We recorded baseline, final, and decay temperatures for each of the 3 sites. Results: The average temperature increases over baseline temperature after pulsed short-wave diathermy were 3.02°C ± 1.02°C in site 1, 4.58°C ± 0.87°C in site 2, and 3.28°C ± 1.64°C in site 3. The average temperature increases over baseline temperature after ultrasound were only 0.17°C ± 0.40°C, 0.09°C ± 0.56°C, and -0.43°C ± 0.41°C in sites 1, 2, and 3, respectively. The temperature dropped only 1°C in 7.65 ± 4.96 minutes after pulsed short-wave diathermy. Conclusions: We conclude that pulsed short-wave diathermy was more effective than 1-MHz ultrasound in heating a large muscle mass and resulted in the muscles' retaining heat longer. ImagesFigure 1.Figure 2.Figure 3.Figure 4.Figure 5.

Garrett, Candi L.; Draper, David O.; Knight, Kenneth L.

2000-01-01

328

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

NASA Astrophysics Data System (ADS)

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

Lynnes, Christopher S.; Lay, Thorne

1990-03-01

329

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

330

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

Microsoft Academic Search

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

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

1981-01-01

331

Impacts of Thermal and Wind structures on Mesospheric Short-period Gravity Wave Propagation at High Latitudes  

NASA Astrophysics Data System (ADS)

Mesospheric short-period (<1-hr) gravity waves are of great importance for dynamics in the mesosphere-lower thermosphere (MLT) region, and are typically measured by instruments capable of high temporal and/or spatial resolutions, such as lidars and airglow imagers. These waves have been studied extensively at low- and mid-latitudes where known wave sources are well established. The results show strong dependence on the background wind and temperature fields, which can act as a barrier prohibiting vertical propagation of the waves, as well as providing a ducted environment in which the waves can travel large horizontal distances. In fact, results show that up to 75% of these waves may exhibit ducted wave motion. Recent efforts to quantify the existence and nature of these waves over the Antarctic continent have lead to a long-term (10 years) data set obtained with airglow imagers. Our results suggest that these southern polar waves are predominantly freely propagating in the airglow region, in stark contrast to results at other latitudes. A new study in the Arctic enables a comparison between the two data sets. In this work, we investigate the propagation nature of the observed wave field and attempt to identify dominant source regions and potential sources of polar gravity waves through ray tracing.

Nielsen, Kim; Taylor, Michael J.; Siskind, David; Collins, Richard; Harvey, V. Lynn; Russell, James; Irving, Brita; Negale, Michael

2012-07-01

332

Search for gravitational waves on short duration in TAMA300 data: stellar core collapse and black hole  

NASA Astrophysics Data System (ADS)

We present in the results of TAMA300 data analysis for short duration gravitational waves. The excess power filter, alternative linear filter (ALF) and TF(time-frequency) clustering methods have been employed for burst gravitational waves from stellar-core collapse, and matched filtering method used for the ringdown gravitational waves from black hole quasi-normal oscillations. The observational range of TAMA for the burst gravitational waves is roughly ~ 1 kpc, and the range for black hole ringdown covers most of our galaxy. We have been developed new method 'time-frequency (TF) clustering' to find the burst waves. This is a TF clustering method on spectrogram (sonogram). Using this method, we can efficiently identify some predicted gravitational wave forms[2] and can exclude typical unstable spike like noises.

Honda, R.; Kanda, N.; Akutsu, T.; Ando, M.; Tsunesada, Y.; TAMA Collaboration

2008-07-01

333

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.

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

2013-01-01

334

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

NASA Astrophysics Data System (ADS)

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

Rivière, P.; Iqbal, S.; Rost, J. M.

2014-06-01

335

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

336

Potential applications of millimeter wave radar to ballistic missile defense  

Microsoft Academic Search

Advantages of millimeter wave lengths for ballistic missile defense are discussed. Applications include target and interceptor tracking, homing, and fuzing in both natural and hostile environments. Millimeter wavelengths provide excellent resolution and measurement accuracy, and the short wavelength scattering is sensitive to small details in the target configuration providing enhanced discrimination possibilities. Applications of millimeter wave sensors for detection, tracking,

G. B. Jones

1977-01-01

337

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 (uc(Zhu) and uc(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.

2013-10-01

338

Heterogeneities in the field of short period seismic wave attenuation in the lithosphere of central Tien Shan  

Microsoft Academic Search

Records of deep-focus Hindu Kush earthquakes in the depth ranges 70–110 and 190–230 km made by 45 digital and analogue seismic\\u000a stations were analyzed to study the attenuation field of short period seismic waves in the lithosphere of central Tien Shan.\\u000a The dynamic characteristics studied include the ratio of peak amplitudes in S and P waves (S\\/P) and the ratio

Yu. F. Kopnichev; I. N. Sokolova

2007-01-01

339

Short-wave transverse instabilities of line solitons of the two-dimensional hyperbolic nonlinear Schrödinger equation  

NASA Astrophysics Data System (ADS)

We prove that line solitons of the two-dimensional hyperbolic nonlinear Schrödinger equation are unstable under transverse perturbations of arbitrarily small periods, i.e., short waves. The analysis is based on the construction of Jost functions for the continuous spectrum of Schrödinger operators, the Sommerfeld radiation conditions, and the Lyapunov-Schmidt decomposition. We derive precise asymptotic expressions for the instability growth rate in the limit of short periods.

Pelinovsky, D. E.; Rouvinskaya, E. A.; Kurkina, O. E.; Deconinck, B.

2014-04-01

340

Breaking of Thunderstorm-Generated Gravity Waves as a Source of Short-Period Ducted Waves Observed at Mesopause Altitudes  

Microsoft Academic Search

Atmospheric gravity waves with periods of 5 to 8 minutes have been observed at airglow altitudes [Taylor et al., GRL, 22, 2849, 1995; Walterscheid et al., JASTP, 61, 461, 1999; Hecht et al., JGR, 106, 5181, 2001; and references cited therein]. These waves are believed to propagate as thermally-ducted wave modes, trapped in the Brunt-Väisälä frequency minimum of the upper

J. B. Snively; V. P. Pasko

2003-01-01

341

Quantitative Millimetre Wavelength Spectrometry  

Microsoft Academic Search

This monograph presents an introduction to the current status and future potential in the application of millimetre wavelength spectrometry to the quantitative analysis of gaseous mixtures. It will therefore be of interest for chemists and other people working in this field or for those who want to start working there.Within the spectrum of electromagnetic waves, the millimetre wave range is

John F Alder; John G Baker

2002-01-01

342

Comparison of a short irradiation (50 sec) by different wavelengths on audiogenic seizures in magnesium-deficient mice: evidence for a preventive neuroprotective effect of yellow.  

PubMed

Audiogenic seizures triggered by an acoustic stimulus of determined frequency and amplitude have been described in many laboratory animals in many circumstances including magnesium deficiency. This model, recently validated, was used, in DBA/2 mice, to study the preventive neuroprotective effect of 6 wavelengths of the visible spectrum used in Chromatotherapia* (lambda(max) 440, 484, 528, 572, 616 and 660 nm) at low irradiance. Each short illumination lasted 50 seconds and was followed by 20 minutes of darkness. It appeared that yellow fully protected 16 out of 17 mice from seizure occurrence. Green allowed the survival of 69% of mice but did not protect them from seizure occurrence. On the contrary, the other four colors (orange, red, purple and blue) failed to protect the mice and showed a tendency to accelerate their death. White color was not protective but allowed the difficult survival of 30% of mice. Darkness had no protective effect. These results even though surprising open a great field of investigation. PMID:12735480

Pages, N; Bac, P; Maurois, P; Durlach, J; Agrapart, C

2003-03-01

343

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.

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

2011-01-01

344

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

NASA Astrophysics Data System (ADS)

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

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

2014-04-01

345

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

Microsoft Academic Search

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

E. Glass

1982-01-01

346

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

347

The temporal properties of the human short-wave photoreceptors and their associated pathways.  

PubMed

Flicker modulation sensitivity measurements made on high intensity orange steady backgrounds indicate that signals from short-wavelength sensitive cones (S-cones) have access to two pathways. At low S-cone adaptation levels the frequency response falls quickly with increasing frequency, but at higher adaptation levels it extends to much higher frequencies. At these higher S-cone adaptation levels, the following procedures can selectively expose either a process sensitive to low frequencies or one more sensitive to higher frequencies: (1) at high flicker frequencies, the S-cone signal can be nulled by a long-wavelength sensitive cone (L-cone) signal of suitable amplitude and phase, but at low frequencies a residual flicker persists; the modulation sensitivity for the residual flicker is lowpass in shape with a rapid decline in sensitivity with increasing flicker frequency; (2) sensitivity to flicker in the presence of a 17 Hz S- or L-cone mask is also lowpass with a similarly steep loss of high frequency sensitivity; yet (3) sensitivity to flicker during transient stimulation of the S-cones at 0.5 Hz is comparatively wideband (and slightly bandpass) in shape. The S-cone signal produced by the high frequency process is almost as well-maintained towards high frequencies as M- and L-cone signals. Furthermore, it is capable of participating in flicker photometric nulls with M- and L-cone signals. At low frequencies, however, when the low frequency S-cone signal is also present, satisfactory nulls can not be found. From these and phenomenological considerations, we identify the low and high frequency S-cone processes as S-cone inputs to the chromatic and luminance pathways, respectively. The phase adjustments needed to optimize flicker photometric nulls reveal that the S-cone input to the luminance pathway is actually inverted, but this is demonstrable only at relatively low frequencies: at medium or high frequencies the S-cone influence can be synergistic with that of the other cone types because of a delay in the transmission of S-cone signals. PMID:2017881

Stockman, A; MacLeod, D I; DePriest, D D

1991-01-01

348

Shear wave propagation in complex sub wavelength tissue geometries: Theoretical and experimental implications in the framework of cornea and skin shear wave imaging  

Microsoft Academic Search

Quantitative measurements of cornea and skin biomechanical properties have many applications in medicine. In ophthalmology, it could lead to a better diagnosis of pathologies or monitoring of treatments. In dermatology, it could help the skin lesions removal monitoring. In the framework of Supersonic Shear Imaging (SSI), these organs are characterized by their complex sub wavelength geometry (thin plate and thin

Thu-Mai Nguyen; Jean-Luc Gennisson; Mathieu Couade; David Touboul; Philippe Humbert; Jeremy Bercoff; Mathias Fink; Mickael Tanter

2010-01-01

349

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

SciTech Connect

High harmonic fast wave heating and current drive CD are being developed on the National Spherical Torus Experiment M. Ono et al., Nucl. Fusion 41, 1435 2001 for supporting startup and sustainment of the spherical torus plasma. Considerable enhancement of the core heating efficiency from 44% to 65% has been obtained for CD phasing of the antenna strap-to-strap = 90 , k= 8 m 1 by increasing the magnetic field from 4.5 to 5.5 kG. This increase in efficiency is strongly correlated to moving the location of the onset density for perpendicular fast wave propagation nonsetBk 2 / away from the antenna face and wall, and hence reducing the propagating surface wave fields. Radio frequency RF waves propagating close to the wall at lower B and k can enhance power losses from both the parametric decay instability PDI and wave dissipation in sheaths and structures around the machine. The improved efficiency found here is attributed to a reduction in the latter, as PDI losses are little changed at the higher magnetic field. Under these conditions of higher coupling efficiency, initial measurements of localized CD effects have been made and compared with advanced RF code simulations.

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

2008-01-01

350

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

351

Contribution of human short-wave cones to luminance and motion detection.  

PubMed

1. Human short-wave S cone signals are important for colour vision and here we examine whether the S cone signals also contribute to motion and luminance. 2. Detection was measured with moving patterns that selectively stimulated S cones-violet sine-wave gratings of 1 cycle deg-1 on an intense yellowish field. For rates up to 12 Hz, detection was governed by non-directional mechanisms, possibly of a chromatic nature, as shown by three findings: moving gratings had to be suprathreshold for their direction to be identified; the threshold ratio of counterphase flickering versus moving gratings was low; and direction-selective adaptation was essentially absent. 3. Evidence for less sensitive, directional mechanisms includes the following: at high velocity, the direction of movement of the violet gratings can be identified just slightly above the detection threshold; directional adaptation was strong with a suprathreshold test pattern; velocity was seen veridically for clearly suprathreshold patterns; and a counterphase flickering test, added in spatial-temporal quadrature phase to a similar suprathreshold mask, had identical detection and direction-identification thresholds. 4. Interactions of long-wave L cone and S cone signals in direction-selective mechanisms were measured with an orange counterphase grating and a violet counterphase test, both flickering at the same rate and presented in spatial quadrature phase on the yellowish adapting field. Direction identification thresholds, measured as a function of the temporal phase of two gratings, demonstrated both that the S cone signal lags considerably behind the L cone signal (an effect that strongly varies with S cone light adaptation), and more strikingly, the S cone signal summates with a negative sign and thus is effectively inverted in direction-selective mechanisms. 5. Quantitatively similar temporal phase functions were obtained with uniform violet and orange flicker when a luminance discrimination criterion was used: thus the S cone signal summates negatively with the L cone signal for both discrimination of luminance flicker and the direction of motion. 6. The temporal phase functions accurately predicted threshold summation for identifying the direction of motion of a pair of violet and orange gratings moving with the same velocity but with different spatial phase offsets. Once the relative temporal phase lag of the S cones was compensated for, there was linear threshold summation for the violet and orange patterns when presented in effective (physiological) spatial antiphase, and clear cancellation when presented in phase. This and related experiments show a linear summation of S, M and L cone signals for direction detection, with the S cones having a negative sign.(ABSTRACT TRUNCATED AT 400 WORDS) PMID:2600863

Lee, J; Stromeyer, C F

1989-06-01

352

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

NASA Astrophysics Data System (ADS)

We report Infrared Space Observatory (ISO) Short Wavelength Spectrometer infrared spectroscopy of the H II region Hubble V in NGC 6822 and the blue compact dwarf galaxy I Zw 36. Observations of Br?, [S III] at 18.7 and 33.5 ?m, and [S IV] at 10.5 ?m are used to determine ionic sulfur abundances in these H II regions. There is relatively good agreement between our observations and predictions of S+3 abundances based on photoionization calculations, although there is an offset in the sense that the models overpredict the S+3 abundances. We emphasize a need for more observations of this type in order to place nebular sulfur abundance determinations on firmer ground. The S/O ratios derived using the ISO observations in combination with optical data are consistent with values of S/O, derived from optical measurements of other metal-poor galaxies. We present a new formalism for the simultaneous determination of the temperature, temperature fluctuations, and abundances in a nebula, given a mix of optical and infrared observed line ratios. The uncertainties in our ISO measurements and the lack of observations of [S III] ?9532 or ?9069 do not allow an accurate determination of the amplitude of temperature fluctuations for Hubble V and I Zw 36. Finally, using synthetic data, we illustrate the diagnostic power and limitations of our new method. Based on observations with ISO, an ESA project with instruments funded by ESA member states (especially the PI countries: France, Germany, the Netherlands, and the United Kingdom) and with the participation of ISAS and NASA.

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

2002-12-01

353

Four-wave mixing and generation of short pulses in multimode class B laser amplifiers  

NASA Astrophysics Data System (ADS)

The linear and nonlinear amplification features of an optical signal by a multimode class B laser have been discussed. The four-wave mixing process between the cavity central mode and the amplified input signal produces a sequence of satellite lines. It is demonstrated that short pulses can be formed by phase beating the satellite lines. In the linear regime, the laser amplifier acts like a three-mode free-running laser where the oscillations of two right and left adjacent modes are substituted by those of the amplified input signal and its image satellite line. In the nonlinear regime, two more symmetrical adjacent satellite lines are first added to the cavity electric field components and then the frequency of the cavity central mode is shifted towards the image satellite lines. At the same time, the number of central-mode photons is gradually decreased by raising the input signal strength. The central-mode photons are ultimately reduced to zero, where an injection-locking phenomenon takes place. Finally, we derive a heuristic conservation relation between the input energies to the laser by sum of the pumping and injected signals, and those distributed between the signal and image satellite lines and spontaneous emission radiation.

Jahanpanah, J.; Moradi, H.

2013-04-01

354

Highlighting short-lived excited electronic states with pump-degenerate-four-wave-mixing.  

PubMed

Detection of short-lived transient species is a major challenge in femtosecond spectroscopy, especially when third-order techniques like transient absorption are used. Higher order methods employ additional interactions between light and matter to highlight such transient species. In this work we address numerically and experimentally the detection of ultrafast species with pump-Degenerate Four Wave Mixing (pump-DFWM). In this respect, conclusive identification of ultrafast species requires the proper determination of time-zero between all four laser pulses (pump pulse and the DFWM sequence). This is addressed here under the light of experimental parameters as well as molecular properties: The role of pulse durations, amount of pulse chirp as well as excited state life time is investigated by measuring a row of natural pigments differing mainly in the number of conjugated double bonds (N = 9 to 13). A comparison of the different signals reveals a strikingly unusual behavior of spheroidene (N = 10). Complete analysis of the pump-DFWM signal illustrates the power of the method and clearly assigns the uniqueness of spheroidene to a mixing of the initially excited state with a dark excited electronic state. PMID:23968082

Marek, Marie S; Buckup, Tiago; Southall, June; Cogdell, Richard J; Motzkus, Marcus

2013-08-21

355

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

356

Drift wave vortices in inhomogeneous plasmas  

Microsoft Academic Search

The effects of density and temperature gradients on drift wave vortex dynamics are studied using a fully nonlinear model with the Boltzmann density distribution. The equation based on the full Boltzmann relation, in the short wavelength region, possesses no localized monopole solution, while in the longer wavelength region the density profile governs the existence of monopolelike solutions. In the longer

X. N. Su; W. Horton; P. J. Morrison

1991-01-01

357

Numerical model for investigation of dynamics of short-cavity short-pulse standing-wave lasers  

NASA Astrophysics Data System (ADS)

Numerical model for calculations of spatio-temporal variations of amplitudes of counter-propagating pulses in a standing-wave laser cavity with gain/absorbing layers with reflecting boundaries is proposed. Proposed model is based on the transport-type equations for the envelopes of oppositely running pulses, spatial discretization along the cavity axis, and calculation of temporal variations both electric field amplitude and active media polarization/inversion at these points. Examples of stationary states and mode-locking regimes are presented.

Mazhirina, Yu. A.; Melnikov, L. A.

2012-09-01

358

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

SciTech Connect

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

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

2004-11-30

359

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

360

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

Microsoft Academic Search

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

Nikolaos A. Bakas; Brian F. Farrell

2008-01-01

361

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

362

Short-ranged and short-lived charge-density-wave order and pseudogap features in underdoped cuprate superconductors  

NASA Astrophysics Data System (ADS)

The pseudogap phase of high-Tc cuprates is controversially attributed to preformed pairs or to a phase which coexists and competes with superconductivity. One of the challenges is to develop theoretical and experimental studies in order to distinguish between both proposals. Very recently, researchers at Stanford have reported [M. Hashimoto , Nat. Phys.PRLTAO1745-247310.1038/nphys1632 6, 414 (2010); R.-H. He , ScienceSCIEAS0036-807510.1126/science.1198415 331, 1579 (2011)] angle-resolved photoemission spectroscopy experiments on Pb-Bi2201 supporting the point of view that the pseudogap is distinct from superconductivity and associated to a spacial symmetry breaking without long-range order. In this paper, we show that many features reported by these experiments can be described in the framework of the t-J model considering self-energy effects in the proximity to a d charge-density-wave instability.

Greco, Andrés; Bejas, Matías

2011-06-01

363

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

364

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

365

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

366

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

367

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

368

Brillouin study of long-wavelength spin waves in quasimonatomic Co films with uniaxial perpendicular magnetic anisotropy  

SciTech Connect

We have observed spin-wave Brillouin light scattering from ultrathin Co/Au/Cu(111) films with Co thicknesses t{sub Co} down to 1 monolayer (ML) and with a 1-ML Au interlayer. The detection of a well-defined spin-wave spectrum and the field dependence of its frequency show directly long-range collective and ferromagnetic ordering in these films at room temperature. From the field dependence of the spin-wave frequency, we derive uniaxial perpendicular magnetic anisotropy constants as a function of t{sub Co} with various overlayer materials, including Cu, Pd, and Au. With a Cu overlayer, we observe that the first-order perpendicular anisotropy K{sub u}{sup (1)} obeys well a linear relation between K{sub u}{sup (1)}t{sub Co} and t{sub Co} for t{sub Co}{>=}1.5 ML, which indicates a constant contribution of the interface anisotropy of 0.16 mJ/m2 in addition to the volume anisotropy of 0.73 MJ/m3. With an Au or a Pd overlayer, we find that both the interface and volume anisotropies are significantly larger than those with the Cu overlayer. We quantify magnetic inhomogeneities from the field dependence of the spectrum width. With the Au or Pd overlayer, K{sub u}{sup (1)} shows a steep decrease with decreasing t{sub Co} for t{sub Co}<3.0 ML, which agrees well with a significant increase in the structure-related magnetic inhomogeneity. We show directly that long-ranged ferromagnetic ordering exists, with the perpendicular anisotropy, in our quasimonatomic Co films thinner than 1.5 ML. K{sub u}{sup (1)} for each overlayer tends to be zero at 1 ML of Co, accompanied by heavy damping of the spin wave. In addition, we find the second-order perpendicular anisotropy is still maintained with a comparable value to K{sub u}{sup (1)} in such quasimonatomic Co films, indicating significant deformation of the uniaxial anisotropy. (c) 2000 The American Physical Society.

Murayama, Akihiro [Optical Sciences Center and Surface Science Division of Arizona Research Laboratories, University of Arizona, Tucson, Arizona 85721 (United States)] [Optical Sciences Center and Surface Science Division of Arizona Research Laboratories, University of Arizona, Tucson, Arizona 85721 (United States); Hyomi, Kyoko [Optical Sciences Center and Surface Science Division of Arizona Research Laboratories, University of Arizona, Tucson, Arizona 85721 (United States)] [Optical Sciences Center and Surface Science Division of Arizona Research Laboratories, University of Arizona, Tucson, Arizona 85721 (United States); Eickmann, James [Optical Sciences Center and Surface Science Division of Arizona Research Laboratories, University of Arizona, Tucson, Arizona 85721 (United States)] [Optical Sciences Center and Surface Science Division of Arizona Research Laboratories, University of Arizona, Tucson, Arizona 85721 (United States); Falco, Charles M. [Optical Sciences Center and Surface Science Division of Arizona Research Laboratories, University of Arizona, Tucson, Arizona 85721 (United States)] [Optical Sciences Center and Surface Science Division of Arizona Research Laboratories, University of Arizona, Tucson, Arizona 85721 (United States)

2000-04-01

369

Parametric study of short backfire antennas with different cavity profiles  

Microsoft Academic Search

A number of high aperture efficiency waveguide fed horn arrays have been investigated at millimetre wave frequencies for civil application. Short backfire antennas are a low profile alternative to horns, having a height of about 0.5?0, as opposed to several wavelengths. A large scale, dual polarised, waveguide fed array of short backfire antennas (SBA) has been proposed for DBS television

D. P. Gray; L. Shafai

2000-01-01

370

Production of ultra-short high-power microwave pulses in ?erenkov backward-wave systems (Review)  

Microsoft Academic Search

The article presents a review of works (mainly, of experimental ones) on production of subgigawatt and gigawatt microwave\\u000a pulses of extremely short duration (5–7 RF periods) using backward-wave systems fed with nanosecond and subnanosecond high-current\\u000a electron beams produced by compact accelerators. Theoretical approaches to the generation process (which is essentially non-steady-state)\\u000a are briefly summarized. Using the effect of spatial accumulation

N. S. Ginzburg; S. D. Korovin; I. V. Pegel; V. V. Rostov; M. I. Yalandin

2006-01-01

371

Novel method of parameter estimation for moving target in millimeter-wave short-range linear FMCW radar  

Microsoft Academic Search

Aiming at the Doppler spectrum aberration and range-velocity coupling phenomena in accelerated moving environment for millimeter-wave short-range linear FMCW radar, a novel method is presented which can estimate the target's acceleration, velocity and range effectively. The method can also compensate the Doppler signal with the estimated acceleration, solve Doppler aberration and range-velocity coupling, and improve the detection performance and parameter

Rongquan Zhang; Jianyu Yang; Jintao Xiong

2004-01-01

372

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

Microsoft Academic Search

A four-frequency moment characterization of backscatter from the near-vertical is applied to an analysis of the short pulse (SP) and dual frequency (DF) microwave techniques. It is found that (1)the range reflectivity modulation spectrum closely approximates the directional wave slope spectrum. Harmonic distortion is small and is a minimum near 10 ø incidence. (2) The SP measurement SNR (signal-to-noise ratio)

Frederick C. Jackson

1981-01-01

373

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

Microsoft Academic Search

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

Xin-Jiang Gao; Zun-Lie Tang; Xiu-Chuan Zhang; Yang Chen; Li-Qun Jiang; Hong-Bing Cheng

2009-01-01

374

The assessment of leaf water content using leaf reflectance ratios in the visible, near?, and short?wave?infrared  

Microsoft Academic Search

The common features of spectral reflectance from vegetation foliage upon leaf dehydration are decreasing water absorption troughs in the near?infrared (NIR) and short?wave?infrared (SWIR). We studied which leaf water index in the NIR and SWIR is most suitable for the assessment of leaf water content and the detection of leaf dehydration from the laboratory standpoint. We also examined the influence

A. Hoehn; L. S. Stodieck; D. M. Klaus; W. W. Adams III; W. J. Emery

2008-01-01

375

The Short Wave Aerostat-Mounted Imager (SWAMI): A novel platform for acquiring remotely sensed data from a tethered balloon  

Microsoft Academic Search

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 2km above ground level to

Lee A. Vierling; Mark Fersdahl; Xuexia Chen; Zhengpeng Li; Patrick Zimmerman

2006-01-01

376

A Soil Temperature\\/Short-Wave Radiation Growth Model for Butterhead Lettuce Under Protected Cultivation in Flanders  

Microsoft Academic Search

The objective of this study was to provide Flemish greenhouse farmers an accurate growth model for butterhead lettuce, based on two environmental parameters, i.e. soil temperature and short-wave radiation. During two consecutive years, a total of 27 growth experiments were followed up, whereby head fresh weight (at a 14 d interval), soil temperature at 10 cm depth (on a half-hour

Joost Salomez; Georges Hofman

2007-01-01

377

Exploring Binary-Neutron-Star-Merger Scenario of Short-Gamma-Ray Bursts by Gravitational-Wave Observation  

NASA Astrophysics Data System (ADS)

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-?-ray bursts, which are likely to be composed of a black hole and surrounding disk, therefore could be constrained by GW observation.

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

2010-04-01

378

On wave stability in relativistic cosmic-ray hydrodynamics  

NASA Technical Reports Server (NTRS)

Wave stability of a two-fluid hydrodynamical model describing the acceleration of cosmic rays by the first-order Fermi mechanism in relativistic, cosmic-ray-modified shocks is investigated. For a uniform background state, the short- and long-wavelength wave speeds are shown to interlace, thus assuring wave stability in this case. A JWKB analysis is performed to investigate the stability of short-wavelength thermal gas sound waves in the smooth, decelerating supersonic flow upstream of a relativistic, cosmic-ray-modified shock. The stability of the waves is assessed both in terms of the fluid velocity and density perturbations, as well as in terms of the wave action. The stability and interaction of the short-wavelength cosmic-ray coherent mode with the background flow is also studied.

Webb, G. M.

1989-01-01

379

A seismic Q-profile for the lower mantle from short-period P waves  

Microsoft Academic Search

A few studies of the quality factor Q (the ratio of peak-to-dissipated energies of seismic waves) in the Earth's mantle have used a limited data set of spectral ratios for body waves1-3. Most estimates of Q have come from the analysis of surface waves and free oscillations, but use of such data to estimate Q in the deep mantle suffers

Michael J. Shore

1984-01-01

380

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

PubMed

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

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

2013-07-20

381

Wavelength-doubling optical parametric oscillator  

DOEpatents

A wavelength-doubling optical parametric oscillator (OPO) comprising a type II nonlinear optical medium for generating a pair of degenerate waves at twice a pump wavelength and a plurality of mirrors for rotating the polarization of one wave by 90 degrees to produce a wavelength-doubled beam with an increased output energy by coupling both of the degenerate waves out of the OPO cavity through the same output coupler following polarization rotation of one of the degenerate waves.

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

2007-07-24

382

Short-period atmospheric gravity waves - A study of their statistical properties and source mechanisms  

NASA Technical Reports Server (NTRS)

Gravity waves for the one year period beginning 19 October 1976 around Palisades, New York, are investigated to determine their statistical properties and sources. The waves have typical periods of 10 min, pressure amplitudes of 3 Pa and velocities of 30 m/s. In general, the largest, amplitude waves occur during late fall and early winter when the upper tropospheric winds directly overhead are fastest and the static stability of the lower troposphere is greatest. Mean wave amplitudes correlate highly with the product of the mean maximum wind speed and the mean low level stratification directly aloft. A distinct diurnal variation of wave amplitudes with the largest waves occurring in the pre-dawn hours is also observed as a result of the increased static stability then. The majority of waves are generated by shear instability; however, a number of waves are generated by distant sources such as nuclear detonations or large thunderstorms. The waves with distant sources can be distinguished on the basis of their generally much higher coherency across the grid and velocities that depart markedly from the wind velocity at any point in the sounding.

Gedzelman, S. D.

1983-01-01

383

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

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

384

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

NASA Astrophysics Data System (ADS)

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

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

2011-10-01

385

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

386

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

387

New Parameterization of Surface Short Wave Radiation Based on Highly Accurate In-Situ Measurements in the Atlantic Ocean  

NASA Astrophysics Data System (ADS)

The major source of uncertainties in the existing parameterizations of solar radiation at sea surface is associated with the large scatter of the atmospheric transmission factor under different cloud types, even under the same total cloud cover. In order to resolve this problem and to discriminate between different cloud type conditions we performed 4-year (2004-2007) in-situ measurements of surface short wave radiation and associated meteorological characteristics on board research vessels traveling along meridional sections in the Atlantic Ocean from 60N to 60S under different cloud conditions. Surface short wave was measured by the Kipp&Zonen net radiometer CNR-1 with temporal resolution of 10 seconds. The compiled data base of in-situ measurements consisted of about 130 daily time series of short wave radiation measurements. For all measurements an accurate analysis of the impact of platform rolling on the accuracy of radiative measurements was provided. Collected data were used for the development of new parameterization of short wave radiation at sea surface. Contrasting to the traditional ones, our parameterization employs different approximations of the dependencies of the atmospheric transmission factor on the cloud cover for different cloud types. Furthermore, for the clear sky conditions we account for the non-linearity of the transmission factor dependency on the solar altitude. New parameterization also provides a special approximation for the eastern North Atlantic tropics and subtropics, influenced by the advection of Saharan aerosols. New parameterization demonstrates a clear improvement of the accuracy of computation of short wave radiation fluxes compared to the traditional schemes based exclusively on the total cloud cover. New approach is especially effective under high cloud cover and conditions close to the complete overcast, when its accuracy may be 20% than that for the traditional schemes. Comparison for the other cloud conditions demonstrates although smaller, but statistically significant improvement of the accuracy. Newly developed parameterization represents likely the upper limit of complexity that can be achieved with bulk parameterizations employing total/low cloud cover and cloud type information along with standard meteorological observations.

Sinitsyn, A.; Gulev, S. K.

2011-12-01

388

New parameterization of surface short wave radiation based on highly accurate in-situ measurements in the Atlantic Ocean  

NASA Astrophysics Data System (ADS)

The major source of uncertainties in the existing parameterizations of solar radiation at sea surface is associated with the large scatter of the atmospheric transmission factor under different cloud types, even under the same total cloud cover. In order to resolve this problem and to discriminate between different cloud type conditions we performed 4-year (2004-2007) in-situ measurements of surface short wave radiation and associated meteorological characteristics on board research vessels traveling along meridional sections in the Atlantic Ocean from 60N to 60S under different cloud conditions. Surface short wave was measured by the Kipp&Zonen net radiometer CNR-1 with temporal resolution of 10 seconds. The compiled data base of in-situ measurements consisted of about 130 daily time series of short wave radiation measurements. For all measurements an accurate analysis of the impact of platform rolling on the accuracy of radiative measurements was provided. Collected data were used for the development of new parameterization of short wave radiation at sea surface. Contrasting to the traditional ones, our parameterization employs different approximations of the dependencies of the atmospheric transmission factor on the cloud cover for different cloud types. Furthermore, for the clear sky conditions we account for the non-linearity of the transmission factor dependency on the solar altitude. New parameterization also provides a special approximation for the eastern North Atlantic tropics and subtropics, influenced by the advection of Saharan aerosols. New parameterization demonstrates a clear improvement of the accuracy of computation of short wave radiation fluxes compared to the traditional schemes based exclusively on the total cloud cover. New approach is especially effective under high cloud cover and conditions close to the complete overcast, when its accuracy may be 20% than that for the traditional schemes. Comparison for the other cloud conditions demonstrates although smaller, but statistically significant improvement of the accuracy. Newly developed parameterization represents likely the upper limit of complexity that can be achieved with bulk parameterizations employing total/low cloud cover and cloud type information along with standard meteorological observations.

Sinitsyn, A.; Gulev, S. K.

2010-09-01

389

Solid state power modulator for terrestrial and spaceborne short pulse millimeter wave radar transmitters  

Microsoft Academic Search

A new generation of power modulators has been developed especially for use in millimeter wave radar applications. The development was focused on a design suitable for a reliable long life operation in a rugged environment or in space. The design requirements for the power modulator are dedicated to a millimeter wave extended interaction klystron with an RF output power of

M. Gollor; W. Muller

2000-01-01

390

Short-Range Millimeter-Wave Radar Perception in a Polar Environment  

Microsoft Academic Search

Autonomous vehicle operations in Antarctica challenge robotic perception. Flying ice and snow, changing illumination due to low sun angles and lack of contrast degrade stereo and laser sensing. Millimeter-wave radar offers remarkable advan- tages as a robotic perception modality because it is not as sensi- tive to the aforementioned conditions. Experiments with millimeter-wave radar in an Antarctic environment show mini-

Alex Foessel; Sachin Chheda; Dimitrios Apostolopoulos

1999-01-01

391

A short comment on the effect of a shear layer on nonlinear water waves  

NASA Astrophysics Data System (ADS)

In this paper we study nonlinear periodic deep water waves propagating on a background shear current, which decays exponentially with depth. We extend the study of Cheng, Cang and Liao (2009) by introducing a second parameter which measures the depth of the shear current. A high-order convergent analytical series solution is obtained by the homotopy analysis method (HAM). A detailed analysis of the impact of the depth parameter is given. We find that increasing this parameter so that the shear current is thinner reduces the wave phase speed, smoothes the wave crest, sharpens the trough, and enlarges the maximum wave height for the case of propagating waves on an opposing current; while it produces the opposite effect on an aiding current.

Cang, Jie; Cheng, Jun; Grimshaw, Roger

2011-01-01

392

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

NASA Astrophysics Data System (ADS)

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

Khymchenko, Ielizaveta; Serebryany, Andrey

2013-04-01

393

Type III Radio Bursts at Long Wavelengths: STEREO/Waves Observations and Future Prospects for Inner Heliospheric Missions  

NASA Astrophysics Data System (ADS)

We investigate solar type III radio bursts observed by the S/Waves instruments on-board the STEREO spacecraft. These instruments provides us with goniopolarimetric (GP, also referred to as direction-finding) measurements between 125 kHz and 1975 kHz while amplitudes of electric field fluctuations are recorded up to 16 MHz. We have investigated large number of type III radio bursts from May 2007 till July 2010. Some of them have been associated with solar flares within the NOAA directory of active regions. That allows us to determine a source position of bursts when the electron density model of LeBlanc et al. (1998) has been considered. We have also located a region of type III radio bursts by triangulating the position using GP measurements. Observed type III radio bursts generally propagate in the solar equatorial plane. Our results indicate that the maximum flux density occurs at ~ 800 kHz. Future solar missions (e.g., Solar Orbiter and Solar Probe Plus) will provide new insights into properties of type III radio bursts as for instance sampling the region where this latter maximum occurs.

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

2011-12-01

394

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

395

Observation of strong oscillations of areal mass in an unsupported shock wave produced by a short laser pulse  

NASA Astrophysics Data System (ADS)

The first experimental study of hydrodynamic perturbation evolution in a strong unsupported shock wave, which is immediately followed by a rarefaction wave, is reported. Our planar solid polystyrene laser-machined targets, 50 to 100 ?m thick, rippled from the front side with a single-mode wavelength 30 or 45 ?m and peak-to-valley amplitude 4 to 6 ?m, were irradiated with a 350 ps long Nike KrF laser pulse at peak intensity of up to 330 TW/cm^2. The perturbation evolution in the target was observed using face-on monochromatic x-ray radiography while the pulse lasted and for 3 to 4 ns after it ended. While the driving pulse was on, the areal mass modulation amplitude in the target was observed to grow by a factor of up to ˜4 due to the ablative Richtmyer-Meshkov instability. After the end of the pulse, while the strong unsupported shock wave propagated through the unperturbed target, the theoretically predicted large oscillations of the areal mass [A. L. Velikovich et al., Phys. Plasmas 10, 3270 (2003)] were observed. Multiple phase reversals of the areal mass modulation have been detected.

Aglitskiy, Y.; Karasik, M.; Velikovich, A. L.; Serlin, V.; Weaver, J. L.; Kessler, T. J.; Schmitt, A. J.; Obenschain, S. P.; Metzler, N.; Oh, J.

2011-11-01

396

Yield Estimation of Novaya Zemlya Explosions from Short-Period Body Waves.  

National Technical Information Service (NTIS)

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 see...

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

1988-01-01

397

Effect of short-wave (6-22 MHz) magnetic fields on sleep quality and melatonin cycle in humans: the Schwarzenburg shut-down study  

Microsoft Academic Search

This paper describes the results of a unique ''natural experiment'' of the operation and cessation of a broadcast transmitter with its short-wave electromagnetic fields (6-22 MHz) on sleep quality and melatonin cycle in a general human population sample. In 1998, 54 volunteers (21 men, 33 women) were followed for 1 week each before and after shut-down of the short-wave radio

Ekkehardt-Siegfried Altpeter; Martin Röösli; Markus Battaglia; Dominik Pfluger; Christoph E. Minder; Theodor Abelin

2006-01-01

398

Design of mct1024×1 short wave infrared thermal camera  

Microsoft Academic Search

A thermal camera consists of 1024-element MCT line wavelength IRFPA with reading electrocircuit made in china. It is presented the composing of this infrared thermal camera and some key question of this thermal camera: 1) nonuniformity correction; 2) Correction of lines and rows. With same axial transmission optics and a 1-D equality angle scanner and 1024X1600 pixels per frame.the scan

Xian Zhong Jian; Su Ying Zhang

2005-01-01

399

Instabilities of a short-cavity standing-wave vibronic laser  

NASA Astrophysics Data System (ADS)

Self pulsing and chaotic dynamics of the short cavity vibronic alexandrite laser is reported. This phenomenon is explained by the process of energy pulling between the laser photons and the host crystal phonons.

Gadomski, W.; Ratajska-Gadomska, B.

1998-08-01

400

Wavelength Calibration  

NASA Astrophysics Data System (ADS)

This program contains observations that will define the wavelength calibration for the FUSE spectrograph. The intent is to use the wavelength calibration found from the spectrograph alignment measurements performed at CU for the high-order terms in the polynomial fit, and to determine the lowest-order terms from the flight measurements. If this proves impractical, we will use flight data to define all terms in the calibration. We will use absorption lines from interstellar gas to define the wavelength calibration, though in some cases emission lines may be used also. In most cases information from other instruments at longer wavelengths will be required to assign absolute velocities to individual IS gas clouds. Stars will be added to this program as observations determine that they are useful for this purpose. Stars with a fairly dense distribution of absorption lines will be required to define the complete wavelength solution, but spectra with only a few widely-spaced lines in each spectral channel are required for monitoring the wavelength stability.

Kruk, Jeffrey

401

Propagation of the spherical short duration shock wave in a straight tunnel  

NASA Astrophysics Data System (ADS)

Propagation processes of shock waves incident at the entrance of the straight shock tube have been photographed with a high-speed camera and pressure-time profiles have been recorded with piezoelectric gages. It is concluded that the shock front repeatedly changes a convex to a concave and vice versa with a series of damped oscillations and becomes a stable plane shock front determined by experimental conditions. Good agreement is found between the calculated and measured shock wave interaction angle and the velocity of the Mach stem for the region located up to 24 cm from the entrance. There is considerable difference between the calculated and measured pressure near the entrance of a shock tube but as the shock wave propagates farther, the difference becomes small and remains within the range of experimental error.

Ahn, Jae W.; Song, So Y.; Lee, Jun W.; Yang, Joon M.

1991-04-01

402

Advances in Submillimeter Wave Semiconductor-Based Device Designs and Processes at JPL  

NASA Technical Reports Server (NTRS)

Planar submillimeter wave circuits are slowly replacing whisker-contacted devices at frequencies above 100 GHz, but in many cases the size constraints dictated by the short wavelengths found at high frequencies have not been adequately addressed.

Siegel, P. H.; Smith, R. P.; Martin, S. C.; Kim, M.; Bruston, J.; Erickson, N.; Humphrey, D.

1997-01-01

403

Effect of short ray trajectories on the scattering statistics of wave chaotic systems.  

PubMed

In many situations, the statistical properties of wave systems with chaotic classical limits are well described by random matrix theory. However, applications of random matrix theory to scattering problems require introduction of system-specific information into the statistical model, such as the introduction of the average scattering matrix in the Poisson kernel. Here, it is shown that the average impedance matrix, which also characterizes the system-specific properties, can be expressed in terms of classical trajectories that travel between ports and thus can be calculated semiclassically. Theoretical results are compared with numerical solutions for a model wave chaotic system. PMID:19905275

Hart, J A; Antonsen, T M; Ott, E

2009-10-01

404

Excitation of a large amplitude plasma wave by a short laser pulse  

NASA Astrophysics Data System (ADS)

The laser wake-field accelerator (LWFA) originally proposed by Tajima and Dawson (1979) is a plasma-based accelerator which employs the large-amplitude wave excited by a laser pulse propagating through the plasma. A discussion is presented of recent results on the excitation of a large amplitude plasma wave by a single electromagnetic packet which are relevant to the LWFA scheme, giving attention to both the weak-pump, weakly-relativistic limit and the fully relativistic regime. An efficient wake-beat excitation mechanism is suggested for the case of ultrashort high intensity pulses.

de Angelis, U.

1990-01-01

405

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.

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

406

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

NASA Astrophysics Data System (ADS)

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

Du, Jianxin; Qian, Lihua; Chen, Qiuyue

2013-11-01

407

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

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

408

Propagation of the spherical short duration shock wave in a straight tunnel  

Microsoft Academic Search

Propagation processes of shock waves incident at the entrance of the straight shock tube have been photographed with a high-speed camera and pressure-time profiles have been recorded with piezoelectric gages. It is concluded that the shock front repeatedly changes a convex to a concave and vice versa with a series of damped oscillations and becomes a stable plane shock front

Jae W. Ahn; So Y. Song; Jun W. Lee; Joon M. Yang

1991-01-01

409

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

410

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.

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

2011-01-01

411

SEARCH FOR GRAVITATIONAL-WAVE INSPIRAL SIGNALS ASSOCIATED WITH SHORT GAMMA-RAY BURSTS DURING LIGO'S FIFTH AND VIRGO'S FIRST SCIENCE RUN  

SciTech Connect

Progenitor scenarios for short gamma-ray bursts (short GRBs) include coalescenses of two neutron stars or a neutron star and black hole, which would necessarily be accompanied by the emission of strong gravitational waves. We present a search for these known gravitational-wave signatures in temporal and directional coincidence with 22 GRBs that had sufficient gravitational-wave data available in multiple instruments during LIGO's fifth science run, S5, and Virgo's first science run, VSR1. We find no statistically significant gravitational-wave candidates within a [ - 5, + 1) s window around the trigger time of any GRB. Using the Wilcoxon-Mann-Whitney U-test, we find no evidence for an excess of weak gravitational-wave signals in our sample of GRBs. We exclude neutron star-black hole progenitors to a median 90% confidence exclusion distance of 6.7 Mpc.

Abadie, J.; Abbott, B. P.; Abbott, R.; Adhikari, R.; Ajith, P.; Anderson, S. B.; Araya, M.; Aso, Y. [LIGO-California Institute of Technology, Pasadena, CA 91125 (United States); Accadia, T. [Laboratoire d'Annecy-le-Vieux de Physique des Particules (LAPP), Universite de Savoie, CNRS/IN2P3, F-74941 Annecy-le-Vieux (France); Acernese, F. [INFN, Sezione di Napoli, Complesso Universitario di Monte Sant Angelo, I-80126 Napoli (Italy); Allen, B. [Albert-Einstein-Institut, Max-Planck-Institut fuer Gravitationsphysik, D-30167 Hannover (Germany); Allen, G. [Stanford University, Stanford, CA 94305 (United States); Ceron, E. Amador; Anderson, W. G. [University of Wisconsin-Milwaukee, Milwaukee, WI 53201 (United States); Amin, R. S. [Louisiana State University, Baton Rouge, LA 70803 (United States); Antonucci, F. [INFN, Sezione di Roma, I-00185 Roma (Italy); Aoudia, S. [Universite Nice-Sophia-Antipolis, CNRS, Observatoire de la Cote d'Azur, F-06304 Nice (France); Arain, M. A. [University of Florida, Gainesville, FL 32611 (United States); Arun, K. G. [LAL, Universite Paris-Sud, IN2P3/CNRS, F-91898 Orsay (France); Aston, S. [University of Birmingham, Birmingham, B15 2TT (United Kingdom)

2010-06-01

412

Short-scale Heterogeneity in the Lowermost Mantle Revealed Through Partition Modeling of Seismic Body Waves  

NASA Astrophysics Data System (ADS)

The existence of both chemical and thermal heterogeneities on a variety of scales in the lowermost mantle has been invoked to explain various types of seismological observations and the Earth's dynamics. Understanding the size and magnitude of these heterogeneities is important in the context of whole mantle dynamics. However, due to inaccurate approximation of data noise and the inadequate definition of the misfit function in the optimization framework, the size of heterogeneities has not been well constrained in present tomographic models of the lowermost mantle. Moreover, we need to be able to clearly see through the core-mantle boundary to properly understand the Earth's core. For example, in order to investigate anisotropy in the inner core, it is important to quantify the contribution to seismic travel times from the Earth's mantle. Furthermore, it is impossible to reconstruct the topography of the Earth's core without a full understanding of mantle heterogeneities. In addition, P-wave velocity maps of the lowermost mantle are rare in comparison to S-wave maps, yet both are needed to properly understand the physical and chemical state of the lowermost mantle. Here we use a Partition Modeling approach, in which trans-dimensional and hierarchical sampling methods are used to solve the above problems. The advantage of such an inversion method is that the number of model parameters, the size of the velocity cells, and the data noise are treated as unknowns in the problem. In this sense, the approach lets us consider the issue of model parameterization as part of the inversion process. A large ensemble of models is averaged to produce a final solution complete with uncertainty estimates. We map the P-wave velocity structure of the lowermost mantle from a dataset of hand-picked PKPab-df, PKPbc-df, and PcP-P differential travel times. We focus on covering gaps in spatial sampling of the lowermost mantle from PKPab-df and PcP-P of previous studies. Travel time residuals from these different datasets are individually and simultaneously inverted for a map of the P-wave velocity field parameterized in terms of Voronoi cells of variable shapes and number. Our results suggest that much smaller scale structure exists in the lowermost mantle than is predicted by previous seismic studies. The data justifies a scale-length of between 5 and 10 degrees (300 to 600 km) for the P-wave velocity perturbations in the 300 km of the lowermost mantle.

Young, M. K.; Tkalcic, H.; Bodin, T.

2012-04-01

413

Completion of spectral rotating shadowband radiometers and analysis of ARM spectral short-wave data  

NASA Astrophysics Data System (ADS)

Our ARM goal is to help improve both longwave and shortwave models used in GCM's by providing improved radiometric shortwave data. The inference of cloud cover and optical properties of clouds is another goal of this research effort. At the Atmospheric Sciences Research Center (ASRC) in Albany, New York, we are acquiring downwelling shortwave, including direct and diffuse irradiance, at six wavelengths, plus downwelling longwave, upwelling and downwelling broadband shortwave, and aerosol optical depth that we combine with National Weather Service surface and upper air data as a model test data set for ARM researchers. The major objective of our program has been to develop two spectral versions of the rotating shadowband radiometer (RSR). The multi-filter rotating shadowband radiometer (MFRSR) contains six filtered, narrow-passband detectors, and one unfiltered silicon detector that serves as a surrogate total shortwave sensor. The rotating shadowband spectroradiometer (RSS) contains a 256-channel diode array that spans the wavelengths 350-1050 nm with resolution varying between 0.6 nm and 8 nm. With some of the instrument development complete we are devoting more effort to analysis of the MFRSR data. Progress was made on several fronts this year, resulting in conference papers and submissions to refereed journals. Data from the ASRC roof has been used to develop corrections of the MFRSR shortwave sensor. SGP data has been used to develop and validate a retrieval technique for total column water vapor. Total column ozone has been estimated using MFRSR data, but validation at the SGP was not possible for lack of a suitable ozone column standard.