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1

Spin pumping by parametrically excited short-wavelength spin waves  

Microsoft Academic Search

We use both parallel and perpendicular parametric pumping techniques to excite short-wavelength spin waves in an yttrium iron garnet film and study the spin current generation from spin waves excited by these pumping methods with the help of the inverse spin-Hall effect in the adjacent Pt layer. We observed clear spin current generations for these pumping techniques and find that

H. Kurebayashi; O. Dzyapko; V. E. Demidov; D. Fang; A. J. Ferguson; S. O. Demokritov

2011-01-01

2

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

3

Excitation of short-wavelength spin waves in magnonic waveguides  

Microsoft Academic Search

By using phase-resolved micro-focus Brillouin light scattering spectroscopy, we demonstrate experimentally a phenomenon of wavelength conversion of spin waves propagating in tapered Permalloy waveguides. We show that this phenomenon enables efficient excitation of spin waves with sub-micrometer wavelengths being much smaller than the width of the microstrip antenna used for the excitation. The proposed excitation mechanism removes restrictions on the

V. E. Demidov; M. P. Kostylev; K. Rott; G. Reiss; S. O. Demokritov

2011-01-01

4

Latitudinal Variations Observed in Gravity Waves with Short Vertical Wavelengths  

Microsoft Academic Search

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

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

2002-01-01

5

Electron pressure gradient-driven short-wavelength drift-wave instability and its nonlinear evolution  

Microsoft Academic Search

Electron Del p-driven short-wavelength drift-wave oscillations in a magnetized plasma are investigated. Using a kinetic model for the ions and the fluid-guiding center model for the electrons, the authors derive a set of nonlinear mode coupling equations. In the linear limit, dispersion relations are derived under the local approximation, as well as the nonlocal approximation for a sheared magnetic field.

R. Bharuthram; P. K. Shukla

1987-01-01

6

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

NASA Astrophysics Data System (ADS)

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

Mori, N.

2009-10-01

7

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

Microsoft Academic Search

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

S. A. Fuselier; D. A. Gurnett

1984-01-01

8

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

9

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

10

Pulse-front tilt for short-wavelength lasing by means of traveling-wave plasma-excitation.  

PubMed

Generation of coherent short-wavelength radiation across a plasma column is dramatically improved under traveling-wave excitation (TWE). The latter is optimized when its propagation is close to the speed of light, which implies small-angle target-irradiation. Yet, short-wavelength lasing needs large irradiation angles in order to increase the optical penetration of the pump into the plasma core. Pulse-front back-tilt is considered to overcome such trade-off. In fact, the TWE speed depends on the pulse-front slope (envelope of amplitude), whereas the optical penetration depth depends on the wave-front slope (envelope of phase). Pulse-front tilt by means of compressor misalignment was found effective only if coupled with a high-magnification front-end imaging/focusing component. It is concluded that speed matching should be accomplished with minimal compressor misalignment and maximal imaging magnification. PMID:23262624

Bleiner, Davide; Feurer, Thomas

2012-12-20

11

A Determination of he from the Short Wave-Length Limit of the Continuous X-Ray Spectrum  

Microsoft Academic Search

Two precision determinations of the short wave-length limits of the continuous x-ray spectrum have been made, one in the region of 10,000 volts, the other in the region of 20,000 volts by the method of isochromats under very steady applied voltage. The two crystal spectrometer was used as a monochromator. The Kbeta2 line of molybdenum and the Lbeta1 line of

Jesse Dumond; Vernon Bollman

1937-01-01

12

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

13

A High Resolving Power, Curved-Crystal Focusing Spectrometer for Short Wave-Length X-Rays and Gamma-Rays  

Microsoft Academic Search

Description is given of a transmission-type, curved-crystal focusing spectrometer for short wave-length x-rays, and gamma-rays having a dispersion of 1.186 x.u. per mm at short wave-lengths. The spectrometer utilizes the (310) planes of quartz in a crystalline plate of dimensions 80×70×1.0 mm curved cylindrically to a radius of two meters. High luminosity is obtained since the useful aperture in the

Jesse W. M. DuMond

1947-01-01

14

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

15

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

USGS Publications Warehouse

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

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

2005-01-01

16

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

17

Equatorial Atmosphere Radar observations of short vertical wavelength gravity waves in the upper troposphere and lower stratosphere region induced by localized convection  

NASA Astrophysics Data System (ADS)

Equatorial Atmosphere Radar (EAR) observations made at Koto Tabang (0.2°S, 100.32°E) revealed that gravity waves with a short vertical wavelength (~2-4 km) were evident in the upper troposphere and lower stratosphere (UTLS). Results are based on two convective events observed on 11 April and 26 April 2004. Above the convective region (~12-13 km heights) the decrease in the vertical wavelength (?z) found in vertical wind profiles was noticeable. Large portions of the induced gravity waves with short ?z dissipated in the lower stratosphere and hence their role is considered to be of importance for the dynamics of UTLS region. Gradual decrease in ?z of gravity waves between 12 km and 20 km heights is partly made by a steady increase in Brunt Väisälla frequency from ~12 km to 20 km heights. The decrease in amplitude in UTLS may be due to damping mechanism.

Dhaka, S. K.; Yamamoto, M. K.; Shibagaki, Y.; Hashiguchi, H.; Fukao, S.; Chun, H.-Y.

2006-10-01

18

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

SciTech Connect

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

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

2012-05-15

19

Rossby wave equation for long wavelength  

NASA Astrophysics Data System (ADS)

It is well known that the nonlinear Rossby wave equation has a dipole vortex solution, the so-called modon, in the short-wavelength regime. For a steady state in the long-wavelength regime, we find an appropriate variable transformation to express the potential vorticity in conservatin form, and obtain a nonlinear Schroedinger equation for the stream function. It is found by numerical analysis that the equation has a monopole vortex solution for small separatrix radius.

Orito, Kohtaro; Sato, Masatomo; Irie, Haruyuki

1995-06-01

20

Short wavelength interferometer for ITER  

SciTech Connect

There is a need for a real time, reliable density measurement compatible with the restricted access and radiation environment on ITER. Due to the large plasma path length, high density and field, refraction and Faraday rotation effects makes the use of contemporary long wavelength (>50{mu}m) interferometers impractical. In this paper we consider the design of a short wavelength vibration compensated interferometer which allows operation without a prohibitively large vibration isolated structure and permits the optics to be conveniently mounted directly in or on the tokamak. A density interferometer design for ITER incorporating a 10.6 {mu}m CO{sub 2} interferometer with vibration compensation provided by a 3. 39 {mu}m HeNe laser is discussed. The proposed interferometer design requires only a small intrusion into the ITER tokamak without a large support structure, refraction and Faraday rotation problems are avoided, and it provides a density resolution of at least 0.5%. Results are presented from an interferometer installed on the DIII-D tokamak incorporating essential elements of the proposed ITER design including 10.6 and 3.39 {mu}m lasers, a retro-reflector mounted on the vacuum wall of the DIII-D tokamak and real-time density feedback control. In this paper we consider a short wavelength interferometer design that incorporates vibration compensation for use on ITER. Our primary concern is to develop a interferometer design that will produce a reliable real time density monitor. We use the ITER conceptual design activity report as the basis of the design.

Snider, R.T.; Carlstrom, T.N.

1992-04-01

21

Short wavelength electromagnetic propagation in magnetized quantum plasmas  

SciTech Connect

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

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

2007-06-15

22

Physics of Very Short Wavelength Acceleration  

NASA Astrophysics Data System (ADS)

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

Katsouleas, T.

2006-01-01

23

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

SciTech Connect

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

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

1993-12-31

24

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

NASA Astrophysics Data System (ADS)

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

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

2013-09-01

25

Undulators for short wavelength FEL amplifiers.  

National Technical Information Service (NTIS)

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 ...

R. D. Schlueter

1994-01-01

26

Short Wavelength Fluctuations and Electron Transport in TFTR  

SciTech Connect

Correlation between electron heat diffusivity and short wavelength (kri {approximately} 5) fluctuation amplitude was observed in the Tokamak Fusion Test Reactor (TFTR) tokamak in the core of enhanced reversed shear (ERS) plasmas [1]. These fluctuations propagate in the ion diamagnetic drift direction with wave number comparable to wpe/c. Further analysis of these data yields the ratios ce/ci and ce/De, and their values are consistent with the picture that the electron transport is mainly induced by the short wavelength fluctuations in the plasma core where the long wavelength (kri {approximately} 1) fluctuations are absent. Although there is not enough information to identify these short wavelength modes, the values of ce is found to be comparable to theoretical predictions based on the current diffusive ballooning mode theory [2].

K.L. Wong; K. Itoh; S.-I. Itoh; A. Fukuyama; M. Yagi

2000-09-08

27

On the Formation of Short-Wavelength Nonlinear Alfvenic Disturbances in the Solar Wind  

NASA Astrophysics Data System (ADS)

Short-wavelength Alfvenic disturbances are commonly observed in the leading edge and the trailing edge of the high-speed solar wind (e.g., Belcher and Davis, 1971; Mavromichalaki et al., 1988; Neugebauer and Buti, 1990). Due to the incompressible nature of the shear-Alfven mode in the MHD plasma, the short-wavelength shear-Alfven wave cannot be developed directly from the long-wavelength shear-Alfven wave via nonlinear steepening. Thus, the formation of the short-wavelength nonlinear Alfven waves in the solar wind must rely on either kinetic processes or a more complicated nonlinear process in the fluid plasma. In this study, we use simulation to show that the short-wavelength nonlinear Alfven waves can be developed from the fast- mode Mach-cone-like nonlinear waves. It has been shown that the fast-mode Mach-cone-like nonlinear waves can be generated by velocity shear instability when the propagation speed of the surface wave is greater than the fast-mode speed in the ambient plasma (e.g., Lai and Lyu, 2006; 2008). The constructive interference and the nonlinear steepening of the fast-mode waves make the Mach-cone-like nonlinear wave a short-wavelength solitary wave. Wave-mode conversion can take place when the fast-mode Mach-cone-like nonlinear waves propagate into a medium in which the magnetic field slowly changes its direction. The Alfven waves that were converted from the short-wavelength fast-mode solitary waves are also of short wavelength. Our results not only solve the non-evolutionary problem of the short-wavelength nonlinear Alfven waves, but also provide a good explanation on why the short-wavelength Alfvenic disturbances commonly occur near the velocity shear regions in the solar wind.

Lyu, L.; Lai, S.

2008-12-01

28

Source of coherent short wavelength radiation  

DOEpatents

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

Villa, Francesco (Alameda, CA)

1990-01-01

29

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

30

Probable X-Ray Mass Absorption Coefficients for Wave-Lengths Shorter Than the K Critical Absorption Wave-Length  

Microsoft Academic Search

Absorption coefficients of all elements may be calculated, from short wave-lengths up to the K critical absorption wave-length by the expression: ??&rgr;=??3Z2(2Z?A)???4Z5(2Z?A)+?eN0(Z?A). This formula holds for all elements when suitable values for ? and ? are chosen. Factors ? and ? are related to the atomic number, Z, by the expressions ?=(aZ2+bZ?c), and ?=(dZ2?eZ+f). Different values of the constants a,

John A. Victoreen

1943-01-01

31

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

32

Dissipation regimes for short wind waves  

NASA Astrophysics Data System (ADS)

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

Caulliez, Guillemette

2013-02-01

33

Determination of the Yard in Terms of the Wave-length of Light  

Microsoft Academic Search

IN the issue of NATURE for May 9, p. 726, a short account is given of an investigation by Dr. A. E. H. Tutton of the length of the yard in terms of the wave-length of light. This being the first occasion on which the value of the yard in wave-lengths has been directly determined, considerable interest naturally attaches to

J. E. Sears

1931-01-01

34

Short-wavelength automated perimetry in patients with migraine  

Microsoft Academic Search

Background  The aim was to investigate short-wavelength sensitivity deficits in patients with migraine.Methods  Fifteen migraine and 18 age-matched healthy volunteers with normal ophthalmologic examination participated in this study. Migraine characteristics were graded by the Migraine Disability Assessment Questionnaire (MIDAS). All participants underwent SWAP (short wavelength amplitude perimetry) testing using a Humphrey field analyzer; there was a 30-2 presentation pattern.Results  Short wavelength amplitude perimetry

Özlem Yenice; Ahmet Temel; Burçin Incili; Ne?e Tuncer

2006-01-01

35

Science Shorts: Making Waves  

NSDL National Science Digital Library

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

Adams, Barbara

2007-01-01

36

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

37

Short wavelength regenerative amplifier free electron lasers  

NASA Astrophysics Data System (ADS)

In this paper we discuss extending the operating wavelength range of tunable Regenerative Amplifier FELs to shorter wavelengths than current design proposals, notably into the XUV regions of the spectrum and beyond where the reflectivity of broadband optics is very low. Simulation studies are presented which demonstrate the development of good temporal coherence in generic systems with a broadband radiation feedback of less than one part in ten thousand.

Dunning, D. J.; McNeil, B. W. J.; Thompson, N. R.

2008-08-01

38

Garnets for short wavelength magneto-optic recording  

Microsoft Academic Search

The bismuth substituted iron garnets have attracted considerable attention as alternative blue wavelength magneto-optic recording media due to their large magneto-optic effects in the short wavelength region of the visible spectrum. However, these materials currently require a high temperature processing step and have not been deposited on inexpensive substrates with adequate carrier to noise ratios. The low CNR is a

Walter R. Eppler; Mark H. Kryder

1995-01-01

39

Research on Short-Wavelength Visible Laser Diodes.  

National Technical Information Service (NTIS)

This research project aims to develop new materials for short-wavelength LD's, Quantum-well LD's for shortening the lasing wavelength, and a surface-emitting LD. A technique for molecular beam epitaxy (MBE) growth of high quality and high purity ZnSe and ...

T. Yao M. Ogura

1984-01-01

40

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

41

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

42

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

Microsoft Academic Search

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

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

1994-01-01

43

On the wavelength of self-organized shoreline sand waves  

NASA Astrophysics Data System (ADS)

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

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

2012-04-01

44

Tunable quarter-wave plate for determining light wavelength  

NASA Astrophysics Data System (ADS)

In order to assess the possibility of using a tunable quarter-wave plate for determining light wavelength, we have studied the propagation of coherent and incoherent light through a system consisting of two identical birefringent (mica) crystals with various parameters and determined the adjustable mutual rotation angle as a function of the light wavelength. The principal possibility of determining a change in the wavelength of coherent light to within 0.03 nm in a 3 nm range is demonstrated.

Kundikova, N. D.; Suvorova, A. M.

2009-01-01

45

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

Microsoft Academic Search

Recent improvements in the fabrication of short-wave infrared (SW-IR) quantum detectors have opened a new era in radiation\\u000a thermometry. Ambient and higher temperatures can be measured with low uncertainties using thermoelectrically (TE) cooled extended-InGaAs\\u000a (E-IGA) and short-wave photovoltaic-HgCdTe (SW-MCT) detectors. Since these detectors have low cut-off wavelengths (2.5 ?m\\u000a and 2.8 ?m, respectively), they do not respond past cut-off and are less

G. P. Eppeldauer; H. W. Yoon

2008-01-01

46

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

Microsoft Academic Search

Recent improvements in the fabrication of short-wave infrared (SW-IR) quantum detectors have opened a new era in radiation thermometry. Ambient and higher temperatures can be measured with low uncertainties using thermoelectrically (TE) cooled extended-InGaAs (E-IGA) and short-wave photovoltaic-HgCdTe (SW-MCT) detectors. Since these detectors have low cut-off wavelengths (2.5 mum and 2.8 mum, respectively), they do not respond past cut-off and

G. P. Eppeldauer; H. W. Yoon

2008-01-01

47

Traveling-wave polymer devices as wavelength converters for wavelength-division multiplexing applications  

NASA Astrophysics Data System (ADS)

Wavelength conversion of optical signals as a result of refraction through a moving interface in traveling-wave electro-optic phase modulators has been analyzed. The connection between wavelength conversion and phase modulation with velocity mismatch has been investigated both analytically and by use of computer simulation. The configuration of a device performing the conversion is proposed, and the operating requirements are determined. Devices based on the described technique are especially promising for wavelength conversion in wavelength-division multiplexing applications and possess several advantages over competing all-optical methods.

Poberezhskiy, Ilya Y.; Fetterman, Harold R.

2002-03-01

48

Traveling-wave polymer devices as wavelength converters for wavelength-division multiplexing applications.  

PubMed

Wavelength conversion of optical signals as a result of refraction through a moving interface in traveling-wave electro-optic phase modulators has been analyzed. The connection between wavelength conversion and phase modulation with velocity mismatch has been investigated both analytically and by use of computer simulation. The configuration of a device performing the conversion is proposed, and the operating requirements are determined. Devices based on the described technique are especially promising for wavelength conversion in wavelength-division multiplexing applications and possess several advantages over competing all-optical methods. PMID:18007823

Poberezhskiy, Ilya Y; Fetterman, Harold R

2002-03-15

49

Multi-wavelength Q-switched erbium doped fiber laser with a short carbon nanotube based saturable absorber  

NASA Astrophysics Data System (ADS)

We demonstrate an all-fiber passively multi-wavelength Q-switched Erbium doped fiber laser (EDFL) based on a short Carbon Nanotube based saturable absorber. With the saturable absorber connected in a longer standing wave based fiber laser cavity, stable single, dual, and multiple wavelength Q-switched low threshold EDFL are achieved. Experimental results show that the output pulse of the filtered single wavelength has the same repetition rate as that of the multi-wavelength output while its average output power is lower than that of the multi-wavelength output.

Dong, Bo; Hu, Junhao; Yu, Changyuan; Hao, Jianzhong

2012-08-01

50

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

NASA Astrophysics Data System (ADS)

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

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

2004-11-01

51

Short wavelength ion temperature gradient instability in toroidal plasmas  

NASA Astrophysics Data System (ADS)

Series of ion temperature gradient (ITG or ?i) driven modes in the short wavelength region, |k??i|>1, are investigated with a gyrokinetic integral equation code in toroidal plasmas. These instabilities exist even if electrons are assumed adiabatic. However, nonadiabatic electron response can influence these short wavelength ITG (SWITG) modes, especially the fundamental l=0 mode. At typical parameters, excitation of the l=0 mode requires that both ?i and ?e exceed thresholds, while the l=1 and l=2 modes with higher harmonic eigenfunctions persist unstable even at ?e=0. Dependence of the SWITG modes on other parameters is also investigated. The l=1 mode with an odd potential eigenfunction grows faster than the l=0 mode and may be dominant in low ?e, high ?, weak positive magnetic shear, and/or weak toroidicity regions.

Gao, Zhe; Sanuki, H.; Itoh, K.; Dong, J. Q.

2005-02-01

52

Some Experiences with Short-Wave Wireless Telegraphy  

Microsoft Academic Search

An analysis is given of the factors that may be expected to determine the transmission phenomena peculiar to any given short-wave channel. It is considered that the wavelength that will give the greatest probability of satisfactory communication is determined by (a) the great circle distance between sender and receiver, (b) the geographical positions of the stations, (c) the time of

N. H. Edes

1930-01-01

53

Cloning and expression of a Xenopus Short Wavelength Cone Pigment  

Microsoft Academic Search

The short wavelength visual pigment fromXenopusresponsible 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

D. M. STARACE; B. E. KNOX

1998-01-01

54

LETTER: Ablative stabilization of short wavelength Rayleigh-Taylor instability  

Microsoft Academic Search

The linear evolution of the Rayleigh-Taylor instability (RTI) at the ablation front of a laser irradiated foil is studied by high resolution two dimensional Lagrangian hydrodynamic simulations, with simple initialization of the perturbation. Laser and target parameters relevant to reactor-size direct-drive laser fusion targets are considered. Growth rates smaller than the classical value and full stabilization at short wavelength are

S. Atzeni

1996-01-01

55

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

Microsoft Academic Search

Evidence has been accumulating for many years that the physical mechanisms responsible for damage to optical materials in and from high-power, short-wave-length lasers (SWLs) differ in fundamental ways from the thermal processes identified in infrared and visible-wavelength laser damage problems. We propose that this difference stems primarily from the electronic nature of the absorption and excitation processes which occur when

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

1985-01-01

56

Ion Heating Arising from the Damping of Short Wavelength Fluctuations at the Edge of a Helicon Plasma Source  

NASA Astrophysics Data System (ADS)

In previous studies, the appearance of substantial ion heating at the specific combinations of driving antenna frequency and magnetic field strength that result in the equivalence of the driving antenna frequency with the lower hybrid frequency provided strong, but indirect, evidence of the damping of short wavelength, ``slow'' wave fluctuations in the edge of helicon sources. For typical helicon source parameters, the driving antenna can couple to two plasma modes; the weakly damped ``helicon'' wave, and the strongly damped, slow wave. Internal magnetic field measurements routinely demonstrate the existence of wave fields consistent with fast waves in helicon sources. However, measurement of the slow wave is considerably more difficult given its extremely short wavelength and evanescent nature. Here we present two direct measurements of spatially localized, few hundred kHz, short wavelength fluctuations that are parametrically driven by the primary antenna. 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 time evolution of the ion temperature and fluctuation profiles provide additional confirmation of the ion heating through wave damping hypothesis.

Scime, Earl; Magee, Richard; Galante, Matthew; Hardin, Robert

2012-10-01

57

Local Analysis Approach for Short Wavelength Geopotential Variations  

NASA Astrophysics Data System (ADS)

The value of global spherical harmonic analyses for determining 15 day to 30 day changes in the Earth's gravity field has been demonstrated extensively using data from the GRACE mission and previous missions. However, additional useful information appears to be obtainable from local analyses of the data. A number of such analyses have been carried out by various groups. In the energy approximation, the changes in the height of the satellite altitude geopotential can be determined from the post-fit changes in the satellite separation during individual one-revolution arcs of data from a GRACE-type pair of satellites in a given orbit. For a particular region, it is assumed that short wavelength spatial variations for the arcs crossing that region during a time T of interest would be used to determine corrections to the spherical harmonic results. The main issue in considering higher measurement accuracy in future missions is how much improvement in spatial resolution can be achieved. For this, the shortest wavelengths that can be determined are the most important. And, while the longer wavelength variations are affected by mass distribution changes over much of the globe, the shorter wavelength ones hopefully will be determined mainly by more local changes in the mass distribution. Future missions are expected to have much higher accuracy for measuring changes in the satellite separation than GRACE. However, how large an improvement in the derived results in hydrology will be achieved is still very much a matter of study, particularly because of the effects of uncertainty in the time variations in the atmospheric and oceanic mass distributions. To be specific, it will be assumed that improving the spatial resolution in continental regions away from the coastlines is the objective, and that the satellite altitude is in the range of roughly 290 to 360 km made possible for long missions by drag-free operation. The advantages of putting together the short wavelength results from different arcs crossing the region can be seen most easily for an orbit with moderate inclination, such as 50 to 65 deg., so that the crossing angle between south-to-north (S-N) and N-S passes is fairly large over most regions well away from the poles. In that case, after filtering to pass the shorter wavelengths, the results for a given time interval can be combined to give the short wavelength W-E variations in the geopotential efficiently. For continents with extensive meteorological measurements available, like Europe and North America, a very rough guess at the surface mass density variation uncertainties is about 3 kg/m^2. This is based on the apparent accuracy of carefully calibrated surface pressure measurements. If a substantial part of the resulting uncertainties in the geopotential height at satellite altitude are at wavelengths less than about 1,500 km, they will dominate the measurement uncertainty at short spatial wavelengths for a GRACE-type mission with laser interferometry. This would be the case, even if the uncertainty in the atmospheric and oceanic mass distribution at large distances has a fairly small effect. However, the geopotential accuracy would still be substantially better than for the results achievable with a microwave ranging system.

Bender, P. L.

2009-12-01

58

Output characteristics of SASE-driven short-wavelength FELs  

NASA Astrophysics Data System (ADS)

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

Fawley, William M.

1997-05-01

59

Short wave infrared imager cockpit interface issues  

NASA Astrophysics Data System (ADS)

With the introduction of the night-vision goggle (NVG) into vehicle cockpits, the transfer of visual information to the observer became more complex. This problem stems primarily from the fact that the image intensifier tube photocathode was sensitive to much of the visible spectrum. NVGs were capable of sensing and amplifying visible cockpit light, making the observation of the scene outside of the cockpit, the primary use for NVGs, difficult if not impossible. One solution was to establish mutually exclusive spectral bands; a band of shorter wavelengths reserved for transmission of visible information from the cockpit instrumentation to the observer and a longer wavelength region left to the night vision goggle for imaging the night environment. Several documents have been published outlining the night vision imaging system (NVIS) compatible lighting performance enabling this approach, seen as necessary for military and civilian aviation. Recent advances in short wave infrared (SWIR) sensor technology make it a possible alternative to the image intensifiers for night imaging application. However, application-specific integration issues surrounding the new sensor type must still be thoroughly investigated. This paper examines the impact of the SWIR spectral sensitivity on several categories of lighting found in vehicle cockpits and explores cockpit integration issues that may arise from the SWIR spectral sensitivity.

Marasco, Peter L.

2007-05-01

60

Research with high-power short-wavelength lasers  

SciTech Connect

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

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

1985-03-05

61

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

62

Solar Irradiance Short Wave Radiation Users Guide.  

National Technical Information Service (NTIS)

Solar irradiance for short wave radiation (400-700 nm) at the sea surface can be calculated using inputs obtained from satellite systems and model estimates. The short wave solar irradiance is important for estimating the surface heating that occurs in th...

P. Martinolich R. A. Arnone

1995-01-01

63

Optical determination of the phase velocity of short gravity waves  

NASA Astrophysics Data System (ADS)

Images of short wind-driven gravity waves were taken from an offshore platform, using a charge coupled device television camera recording diffuse sky radiance reflected from the ocean surface. A two-dimensional power spectrum was calculated from nine statistically independent images. The resultant ensemble-averaged spectrum exhibited good statistical stability and provided information on the angular spread and direction of the wave components present. One-dimensional sampling of each image in a sequence allowed a space-time image to be constructed which clearly shows the effects of wave dispersion as well as the modulation of the phase velocities of the short wavelength waves by the long wavelength components. An ensemble-averaged space-time spectrum, when combined with the directional parameters, is compared with the predictions of linear gravity wave dispersion theory. Two distinct wave systems were present: the local wind driven system showed a space-time spectrum in agreement with linear theory out to ˜1 cyc/m, but with excess phase velocity at higher spatial frequencies. The second wave system, which was presumably generated by a distant wind field, showed a deficiency in phase velocity when compared to linear theory.

Gotwols, B. L.; Irani, G. B.

1980-07-01

64

Put a Short-Wave Radio in Your Foreign Language Classroom  

ERIC Educational Resources Information Center

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

Oksenholt, Svein

1977-01-01

65

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

66

E region coherent backscatter at short wavelength and large aspect angle  

SciTech Connect

During a special experiment carried out in June 1987, the European incoherent scatter UHF radar system was operated at an unusually low elevation angle, and detected coherent echoes from the auroral E region at times when the ion drift velocity in the F region was large. This appears to be the first time that coherent echoes have been detected at such a short radar wave-length (0.32 m; frequency 933 MHz) and at such a large angle away from perpendicular to the Earth's magnetic field (up to 6{degrees}).

Moorcroft, D.R.; Schlegel, K. (Max-Planck-Inst. fuer Aeronomie, Katlenburg-Lindau (West Germany))

1988-03-01

67

Wavelength engineering of surface-emitting lasers for high-capacity short-reach systems  

Microsoft Academic Search

In this paper, we present the wavelength engineering of surface emitting lasers for use in high speed short reach systems, which may include the wavelength expansion, the wavelength integration and the wavelength stabilization based on fully monolithic VCSEL technologies. We have developed highly strained GaInAs\\/GaAs QW VCSELs emitting at 1.1-1.2 µm band and GaInNAs\\/GaAs VCSELs at 1.3 µm wavelength. Excellent

Fumio Koyama

2003-01-01

68

Short wavelength topography on the inner-core boundary  

PubMed Central

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

Cao, Aimin; Masson, Yder; Romanowicz, Barbara

2007-01-01

69

Short wavelength topography on the inner-core boundary.  

PubMed

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

Cao, Aimin; Masson, Yder; Romanowicz, Barbara

2006-12-26

70

Short Wavelength Topography on the Inner Core Boundary  

NASA Astrophysics Data System (ADS)

Constraining the topography of the inner core boundary (ICB) is important for studies of core-mantle coupling and the generation of the geodynamo. We present evidence for significant temporal variability in the amplitude of the inner core reflected phase PKiKP for an exceptionally high quality earthquake doublet, which occurred in the South Sandwich Islands within a ten year interval (1993/2003). This doublet was observed post-critically at the short period Yellowknife seismic array (YK). The analysis of PKIKP/PKiKP amplitude ratios indicates that the PKiKP phases for the 1993 event - but not the 2003 event - are significantly defocused by structure near the inner core boundary (ICB). This observation cannot be explained by small differences in the eearthquake source, interference with another local, regional or teleseismic event, or different scattering from local heterogeneities near the stations or the sources. Combined with data from several other doublets, we infer the presence of topography at the inner- core boundary, with a horizontal wavelength of about 10 km. Such topography could be sustained by small scale convection at the top of the inner core, and is compatible with a rate of super-rotation of the inner core of ~0.1-0.15 deg/year. In the absence of inner core rotation, decadal scale temporal changes in the ICB topography would provide an upper bound on the viscosity at the top of the inner core.

Romanowicz, B.; Cao, A.; Masson, Y.

2006-12-01

71

Understanding airglow signatures of short-period gravity waves  

NASA Astrophysics Data System (ADS)

Airglow imaging is a primary tool in the study of gravity waves at mesospheric and lower-thermospheric (MLT) altitudes, clearly revealing signatures of small-scale (<100 km) and short-period (<30 min) waves. Short-period waves are in particular able to carry significant momentum into the MLT [e.g., Fritts and Alexander, 2003, Rev. Geophys., 41(1)]. However, quantification of short-period wave fluxes and propagation characteristics is complicated by their susceptibility to refraction by ambient wind and thermal structure at airglow altitudes. These effects lead to vertical wavelengths that vary dramatically with altitude throughout the airglow layers, and reflection and ducting, which can prevent the accurate assessment of ampli-tude and vertical direction of propagation [e.g., Fritts, 2000, JGR, 105(D17), 22,355-22,360]. To investigate airglow signatures of short-period gravity waves, we utilize a two-dimensional nonlinear dynamics model coupled with OH Meinel band and OI 557.7 nm airglow photochem-istry models. Case studies where the ambient atmospheric structure significantly influences wave propagation are presented, for both ducted and reflected waves, and also for waves ap-proaching critical levels. Arising from Doppler shifts to higher and lower intrinsic frequencies, respectively, these effects contribute to significant variation of vertical wavelength throughout the airglow region, and may limit the altitude of propagation. Cancellation effects of vertically-integrated airglow volume emission rate perturbations are discussed, along with observable nonlinear features due to large amplitude [e.g., Huang et al., 2003, JGR, 108(A5), 1173], and effects of partial perturbations to airglow layers by vertically-confined waves [e.g., Snively et al., JGR, In Review, 2010]. In particular, it is demonstrated that high temporal and spatial resolution measurements of airglow intensity and brightness-weighted temperature, combined with detailed descriptions of ambient wind and temperature, are needed to accurately charac-terize the interactions of short-period gravity waves with MLT structure. Implications for the interpretation of observed data are discussed.

Snively, Jonathan; Taylor, Michael J.; Pendleton, William R., Jr.; Pautet, Pierre-Dominique

72

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

73

Wavelength Conversion and Dispersion Compensation Using Cavity-Enhanced Four-Wave Mixing in Semiconductor Lasers.  

NASA Astrophysics Data System (ADS)

In this dissertation, I have investigated several elements which can be used to construct a high-speed, multiple wavelength optical communication network. I have reported the first demonstration of an electrically-tunable mode-locked laser source consisting of an anti-reflection coated InGaAsP distributed-Bragg -reflector laser chip and a single-mode fiber extended cavity. Measured output pulses were as short as 14 ps. The maximum wavelength tuning range exceeded 8 nm. This laser was used to measure the temporal response of a wavelength converter which used cavity-enhanced four -wave mixing in an injection-locked semiconductor laser. The information bandwidth of the device was found to increase with decreasing bias current or increasing injected pump power. These measurements were in agreement with a two -mode rate equation analysis, and suggest that these wavelength converters could be used to switch multi-gigabit optical channels. I report satisfactory bit-error-rate performance of the wavelength converter for data rates of 2.5 and 10 Gb/s. Operation at 10 Gb/s exceeds the previous best result for this type of device by an order of magnitude. The 7.5-nm wavelength-conversion range corresponds to a frequency -conversion range of 0.94 THz. Using the mid-span spectral inversion technique, which exploits the phase-conjugate property of four-wave mixing, the wavelength converter was used to perform dispersion compensation in a 10-Gb/s 333-km long-haul optical transmission system over conventional single-mode fiber. The bit-rate times distance product of 3330 (Gb -km)/s surpasses the previous best result for a semiconductor device by more than a factor of 13.

Iannone, Patrick Paul

74

Experimental investigation of identical wavelength short light pulses crossing in underdense plasma  

NASA Astrophysics Data System (ADS)

Energy Energy transfer between a long (3-10 ps) "pump" pulse and a short (400 fs) "seed" one, both at a wavelength of 1.057?m quasi counterpropagating in an underdense preformed plasma and produced from the ionization of a gas jet, was observed. Numerical simulations reveal that the energy transfer is due to the coupling involving ion acoustic waves excited in the Stimulated Brillouin Backscattering in the strong coupling regime. The plasma characteristics were tailored using a high-energy ionization laser beam and the plasma density was controlled using a Thomson scattering diagnostic. The energy exchange was observed for different gas (ion) types, pressures (plasma densities), polarization and intensities of the interacting beams.

Lancia, L.; Marquès, J.-R.; Fuchs, J.; Nakatsutsumi, M.; Mancic, A.; Antici, P.; Riconda, C.; Weber, S.; Tikhonchuck, V. T.; Héron, A.; Hüller, S.; Adam, J.-C.; Audebert, P.

2009-05-01

75

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

76

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

77

SASE free electron lasers as short wavelength coherent sources  

Microsoft Academic Search

During the last few years free electron lasers (FELs) based on self-amplified spontaneous emission (SASE) have been demonstrated at wavelengths of 12 µm [1], 830 nm [2], 530 nm [3] and 385 nm [3], and around 100 nm [4]. Recently, saturation has been observed in the vacuum ultraviolet (VUV) spectral region between 82 nm and 125 nm at the TESLA

R. Treusch; J. Feldhaus

2003-01-01

78

Short wavelength nickel-like x-ray laser development  

SciTech Connect

Ni-like x-ray lasers have been produced at wavelengths near to, and below the carbon K edge (43.76-{Angstrom}). Recent work has concentrated on the development of the Ni-like Ta amplifier at 44.83-{Angstrom}. Amplification occurs in a laser produced plasma created by irradiating a thin foil of Ta with two beams of the Nova laser. Up to 8 gainlengths have been demonstrated so far, with a gain coefficient of 3.2 cm{sup {minus}1} and a gain duration of 250 psec. The wavelength of 44.83-{Angstrom} is close to optimal for holographic imaging of live cells. It remains to optimize the coherent output power of the amplifier to use it as a source for future x-ray holography experiments. 19 refs., 10 figs., 2 tabs.

MacGowan, B.J.; Da Silva, L.B.; Fields, D.J.; Fry, A.R.; Keane, C.J.; Koch, J.A.; Matthews, D.L.; Maxon, M.S.; Mrowka, S.; Osterheld, A.L.; Scofield, J.H.; Shimkaveg, G.

1991-01-07

79

Bistatic-Radar Techniques for Observing Long-Wavelength Directional Ocean-Wave Spectra  

Microsoft Academic Search

Bistatic-radar Bragg scattering of medium-to long-wavelength radio waves by ocean waves can be used as a means for observing directional ocean-wave spectra. Only moderate antenna directivity is required; areal and directional resolution are provided by high-resolution delay-Doppler processing of the radar echoes. Directional characteristics of long-wavelength (80-200 m) ocean waves have been observed using LORAN A transmission (1.85 MHz) and

Calvin Teague

1971-01-01

80

Novel method for fabrication of high-efficiency optics for short wavelength radiation  

Microsoft Academic Search

Extreme ultraviolet lithography (EUVL) is the most likely next generation lithography technique which uses radiation near 13.4 nm wavelength. At this short wavelength, most materials readily absorb the radiation, making refractive lens optical systems unusable. We demonstrate a novel method for fabrication of highly efficient optics for extreme ultraviolet (EUV) radiation using focused ion beam (FIB). These optics are based

Rashi Garg; James Evertsen; Gregory Denbeaux

2006-01-01

81

Broad-band wavelength conversion based on cross-gain modulation and four-wave mixing in InAs-InP quantum-dash semiconductor optical amplifiers operating at 1550 nm  

Microsoft Academic Search

Wavelength conversion based on four-wave mixing (FWM) and cross-gain modulation (XGM) is experimentally demonstrated for the first time in a 1550-nm InAs-InP quantum-dash semiconductor optical amplifier. Continuous-wave FWM with a symmetric conversion efficiency dependence on detuning direction and FWM mediated short-pulse wavelength conversion are demonstrated. Using XGM, we have successfully implemented short-pulse wavelength conversion over 10 THz and error-free data

A. Bilenca; R. Alizon; V. Mikhelashhvili; D. Dahan; G. Eisenstein; R. Schwertberger; D. Gold; J. P. Reithmaier; A. Forchel

2003-01-01

82

Ablative Rayleigh-Taylor Instability at Short Wavelengths Observed with Moiré Interferometry  

Microsoft Academic Search

One of the most important quantities to be measured for better understanding of the ablative Rayleigh-Taylor (RT) instability is the growth rate in the short wavelength region at which the RT instability is significantly reduced. The short wavelength ( 4.7-12 mum) RT growth rates for direct-drive targets were measured for the first time by utilizing the innovated moiré interferometry [M.

T. Sakaiya; H. Azechi; M. Matsuoka; N. Izumi; M. Nakai; K. Shigemori; H. Shiraga; A. Sunahara; H. Takabe; T. Yamanaka

2002-01-01

83

Techniques for Short Wavelength Photoionization Lasers: a 2-HZ 109-NM Laser.  

NASA Astrophysics Data System (ADS)

This dissertation presents two new techniques for the production of short-wavelength photoionization lasers. In a photoionization laser, soft-x-rays are emitted from a laser-produced plasma and photoionize an ambient gaseous medium. Because certain end products of the photoionization are more probable than others, a population inversion can be created on a radiating transition in the resultant ions. The stipulation that this transition be "short-wavelength" combined with a variety of possible inversion-quenching mechanisms places rather severe requirements on the soft -x-ray source. The pumping fluence delivered to the gain medium must be high, although not so high that quenching mechanisms dominate, and the pumping time must be very short. The methods developed in this thesis represent different, yet complimentary, approaches to improving the pump source. Both have been applied to the Xe III 109 -nm Auger laser. We have invented an oblique-incidence laser-produced plasma geometry, which produces a long traveling-wave excitation source without sacrificing soft-x-ray conversion efficiency. Using the traveling-wave geometry, we demonstrated the first single-pass saturation of a photoionization laser. With 3.5 J of 1064-nm energy in a 300 psec pump pulse, we produced a total small-signal gain of exp(40) and a 109-nm output energy of 20 muJ. Further refinement of the technique lead to saturation of the laser with only 500 mJ of pump energy, at a repetition rate of 2 Hz. We have characterized the effect of prepulsing on laser-produced plasma conversion efficiency, and we have applied this technique to pumping photoionization lasers. Prepulsing can improve the conversion efficiency, into the photon energy bandwidth which pumps the Xe laser, of plasmas formed by 20 psec, 1064-nm pulses at 10 ^{12}W cm^{ -2} by about a factor of 6. We have prepulsed a Xe laser, which was pumped by an 80 psec pulse, and observed a greater than 10-fold improvement in output energy.

Sher, Mark Henry

1990-01-01

84

Optical guiding simulations for high gain-short wavelength FELs  

NASA Astrophysics Data System (ADS)

Optical guiding in the linear growth regime of an FEL amplifier has been reported in simulations by Scharlemann et al., using the LLNL 2D code FRED. We present the results of a parameter space investigation of optical guiding in an FEL using the FRED code with a realistic range of input parameters: optical wavelength, mode size and focus, current density, emittance, and wiggler period. We find that optical guiding has a profound impact on gain, and that within existing mirror technology and for the operating characteristics expected of the Stanford storage ring FEL now in construction, oscillation is achievable from the visible through 300 Å. We also describe the relative importance of guiding in different regimes. In support of these predictions we present ``FRED'' benchmarking results. Lawrence Livermore National Laboratory, University of California, Livermore, CA 94550, USA.

Lasala, J. E.; Deacon, D. A. G.; Scharlemann, E. T.

1986-09-01

85

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

86

GHz low noise short wavelength infrared (SWIR) photoreceivers  

NASA Astrophysics Data System (ADS)

Next generation LIDAR mapping systems require multiple channels of sensitive photoreceivers that operate in the wavelength region of 1.06 to 1.55 microns, with GHz bandwidth and sensitivity less than 300 fW/?Hz. Spectrolab has been developing high sensitivity photoreceivers using InAlAs impact ionization engineering (I2E) avalanche photodiodes (APDs) structures for this application. APD structures were grown using metal organic vapor epitaxy (MOVPE) and mesa devices were fabricated using these structures. We have achieved low excess noise at high gain in these APD devices; an impact ionization parameter, k, of about 0.15 has been achieved at gains >20 using InAlAs/InGaAlAs as a multiplier layer. Electrical characterization data of these devices show dark current less than 2 nA at a gain of 20 at room temperature; and capacitance of 0.4 pF for a typical 75 micron diameter APD. Photoreceivers were built by integrating I2E APDs with a low noise GHz transimpedance amplifier (TIA). The photoreceivers showed a bandwidth of 1 GHz and a noise equivalent power (NEP) of 150 fW/rt(Hz) at room temperature.

Bai, Xiaogang; Yuan, Ping; McDonald, Paul; Boisvert, Joseph; Chang, James; Woo, Robyn; Labios, Eduardo; Sudharsanan, Rengarajan; Krainak, Michael; Yang, Guangning; Sun, Xiaoli; Lu, Wei; McIntosh, Dion; Zhou, Qiugui; Campbell, Joe

2011-05-01

87

LSWAVE 2000: Lasers and short-wavelength applications  

NASA Astrophysics Data System (ADS)

LSWAVE 2000 was organized as a Satellite Workshop to the Seventh International Conference on Synchrotron Radiation Instrumentation SRI 2000. It was held on Saturday, August 26, 2000, at the Technische Universität Berlin, and was jointly organized by the Max Born Institute for Nonlinear Optics and Short Pulse Spectroscopy (MBI) and the Technical University Berlin (TUB). The organizing committee consisted of Wilhelm Raith (chairman), Wolfgang Sandner, Ingolf Hertel, Manfred Wick, Bernd Winter, Tatjana Gießel, Holger Stiel, Ingo Will, Ursula Bayr (secretary) and Silvia Szlapka (secretary). Continuing information on the Workshop and its proceedings may be found under http://www.mbi-berlin.de/lswave2000/.

Sandner, W.

2001-07-01

88

Short-wavelength plasmons in low-dimensional systems  

SciTech Connect

The dispersion of plasma waves in systems of various dimensions is investigated up to the end point of the spectrum. In 2D and 3D systems, the plasmon spectrum still ends (due to Landau damping) within the applicability range of the quasi-classical approximation, i.e., for {Dirac_h}k << p{sub F} ({Dirac_h}k is the plasmon momentum and p{sub F} is the electron Fermi momentum). In 1D systems, the results are qualitatively different, since the Landau damping is concentrated in a region where the quantum effects cannot be ignored. This peculiarity of 1D systems gives rise to undamped branches of acoustic plasmons with a phase velocity lower than the electron Fermi velocity in multicomponent 1D plasmas.

Vitlina, R. Z.; Magarill, L. I., E-mail: levm@isp.nsc.ru; Chaplik, A. V. [Russian Academy of Sciences, Siberian Branch, Institute of Semiconductor Physics (Russian Federation)

2008-04-15

89

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

PubMed

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, M(2) ~ 1.3). We demonstrate the performance of our ultrashort pulsed system using fluorescently labelled and autofluorescent tissue, and compare with conventional Ti:Sapphire excitation. We observe a more than 3-fold increase in fluorescence signal intensity using our visible laser source in comparison with the Ti:Sapphire laser for two-photon excitation at equal illumination peak powers of 1.16 kW or less. PMID:23078118

Norris, G; Amor, R; Dempster, J; Amos, W B; McConnell, G

2012-11-01

90

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

91

Analysis of wavelength deviation of guided waves with electromagnetic acoustic transducers  

NASA Astrophysics Data System (ADS)

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

Zhai, Guofu; Jiang, Tao; Kang, Lei

2012-10-01

92

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

93

Duality-invariant Einstein-Planck relation and the speed of light at very short wavelengths  

NASA Astrophysics Data System (ADS)

We propose a generalized Einstein-Planck relation for photons which is invariant under the change ?/alP to alP/?, ? being the photon wavelength, lP Planck’s length, and a a numerical constant. This yields a wavelength-dependent speed of light v(?)=c/(1+a2(lP/?)2), with c the usual speed of light in vacuo, indicating that the speed of light should decrease for sufficiently short wavelengths. We discuss the conceptual differences with the previous proposals related to a possible decrease of the speed of light for very short wavelengths based on quantum fluctuations of the space-time, as well as its consequences on Heisenberg’s uncertainty principle up to second order in lP.

Jou, D.; Mongiovi, M. S.

2011-11-01

94

Wavelength-tunable optical short pulse generation with constant repetition frequency and pulsewidth  

NASA Astrophysics Data System (ADS)

A system to generate wavelength-tunable optical short pulses with a constant repetition frequency and pulse width by a gain-switched Fabry-Pérot laser diode (FPLD) in a self-injection scheme is demonstrated. A variable optical delay line is used to control the self-injection scheme to maintain a constant repetition frequency and pulse width at different wavelengths. The optical sidemode suppression ratio (SMSR) of this system is better than 33 dB over the wavelength-tunable range of 33 nm.

Peng, Peng-Chun; Chi, Sien

2005-06-01

95

160 GHz wavelength conversion using four-wave mixing in quantum dots  

Microsoft Academic Search

We experimentally investigate wavelength conversion in quantum-dot semiconductor optical amplifiers via four-wave mixing. Using four 40-GHz probes we demonstrate greater than 100% conversion over 160 GHz with a large signal-to-noise ratio.

David Nielsen; Shun-Lien Chuang; N. J. Kim; Donghan Lee; S. H. Pyun; W. G. Jeong

2009-01-01

96

Ablative Rayleigh-Taylor instability at short wavelengths observed with moiré interferometry.  

PubMed

One of the most important quantities to be measured for better understanding of the ablative Rayleigh-Taylor (RT) instability is the growth rate in the short wavelength region at which the RT instability is significantly reduced. The short wavelength ( 4.7-12 microm) RT growth rates for direct-drive targets were measured for the first time by utilizing the innovated moiré interferometry [M. Matsuoka et al., Rev. Sci. Instrum. 70, 637 (1999)]. These growth rates were reasonably well reproduced by the simulation that solves the Fokker-Planck equation for nonlocal heat transport. PMID:11955155

Sakaiya, T; Azechi, H; Matsuoka, M; Izumi, N; Nakai, M; Shigemori, K; Shiraga, H; Sunahara, A; Takabe, H; Yamanaka, T

2002-03-25

97

Sexual dimorphism of short-wavelength photoreceptors in the small white butterfly, Pieris rapae crucivora.  

PubMed

The eyes of the female small white butterfly, Pieris rapae crucivora, are furnished with three classes of short-wavelength photoreceptors, with sensitivity peaks in the ultraviolet (UV) (lambda(max) = 360 nm), violet (V) (lambda(max) = 425 nm), and blue (B) (lambda(max) = 453 nm) wavelength range. Analyzing the spectral origin of the photoreceptors, we isolated three novel mRNAs encoding opsins corresponding to short-wavelength-absorbing visual pigments. We localized the opsin mRNAs in the retinal tissue and found that each of the short-wavelength-sensitive photoreceptor classes exclusively expresses one of the opsin mRNAs. We, accordingly, termed the visual pigments PrUV, PrV, and PrB, respectively. The eyes of the male small white butterfly also use three classes of short-wavelength photoreceptors that equally uniquely express PrUV, PrV, and PrB. However, whereas the spectral sensitivities of the male photoreceptors with PrUV and PrB closely correspond to those of the female, the male photoreceptor expressing PrV has a double-peaked blue (dB) spectral sensitivity, strongly deviating from the spectral sensitivity of the female V photoreceptor. The male eyes contain a pigment that distinctly fluoresces under blue-violet as well as UV excitation light. It coexists with the dB photoreceptors and presumably acts as a spectral filter with an absorbance spectrum peaking at 416 nm. The narrow-band spectral sensitivity of the male dB photoreceptors probably evolved to improve the discrimination of the different wing colors of male and female P. rapae crucivora in the short-wavelength region of the spectrum. PMID:15976082

Arikawa, Kentaro; Wakakuwa, Motohiro; Qiu, Xudong; Kurasawa, Masumi; Stavenga, Doekele G

2005-06-22

98

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

99

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

NASA Astrophysics Data System (ADS)

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

Olson, David

2005-11-01

100

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

Microsoft Academic Search

BACKGROUND: Vertebrate SWS1 visual pigments mediate visual transduction in response to light at short wavelengths. Due to their importance in vision, SWS1 genes have been isolated from a surprisingly wide range of vertebrates, including lampreys, teleosts, amphibians, reptiles, birds, and mammals. The SWS1 genes exhibit many of the characteristics of genes typically targeted for phylogenetic analyses. This study investigates both

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

2006-01-01

101

Saturation gain-length product during short-wavelength plasma lasing  

NASA Astrophysics Data System (ADS)

A scaling-law, function of the longitudinal and the transverse aspect ratios of a laser-produced plasma gain-medium, is derived to predict the saturation gain-length product for short-wavelength lasing. Benchmarking with experimental data from the literature shows how critical is the plasma geometry and, henceforth, the focusing of the pump laser pulse.

Bleiner, Davide

2012-08-01

102

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

PubMed

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

Tanner, Gregor; Søndergaard, Niels

2007-03-15

103

Wavelength conversion via four-wave mixing in a triple-coupled multilayer cavity  

NASA Astrophysics Data System (ADS)

Four-wave mixing in a triple-coupled multilayer cavity has been investigated for planar-type wavelength conversion devices. Three half-wavelength cavity layers are connected in series using GaAs/AlAs distributed Bragg reflector multilayers to yield three cavity modes with equal frequency separation. The enhanced internal electric fields of the three cavity modes indicate that efficient ultrafast wavelength conversion via four-wave mixing can be achieved even in the normal incidence configuration. Wavelength conversion was experimentally demonstrated using spectrally shaped laser pulses. A clear converted wavelength signal was observed in the measured spectrum. The temporal response was almost limited by the photon lifetime of each cavity mode.

Kitada, Takahiro; Yasunaga, Yukinori; Nakagawa, Yoshinori; Morita, Ken; Isu, Toshiro

2013-09-01

104

Wavelength-scale stationary-wave integrated Fouriertransform spectrometry  

Microsoft Academic Search

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

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

2007-01-01

105

Short-wavelength instability and decay of a vortex pair in a stratified fluid  

NASA Astrophysics Data System (ADS)

The evolution of a counter-rotating vortex pair in a stably stratified fluid is investigated using direct numerical simulations. The study focuses on the short-wavelength elliptic instability occurring in this flow and the subsequent decay of the vortices. Depending on the level of stratification, as characterized by the Froude number which indicates the time scale of buoyancy to that of the instability, and the stage of evolution, stratification effects may significantly alter the behaviour of the flow. In the case of weak to moderate stratification, the elliptic instability develops qualitatively in the same manner as in unstratified fluid. The primary effect of stratification is to reduce the vortex separation distance which enhances the mutually induced strain. Consequently, the instability has an earlier onset and higher growth rate with increasing stratification. The behaviour is essentially described by linear stability theory for unstratified flow if the varying separation distance is taken into account. On the other hand, the final breakdown and decay of the flow may be greatly modified by stratification since buoyancy effects eventually emerge after sufficient time has elapsed. The decay is enhanced owing to additional mechanisms not present in unstratified flow. Secondary vertical vortex structures form between the primary vortices promoting fluid exchange in the transverse direction. Detrainment of fluid from the primary vortices by the generated baroclinic torque also contributes to the more rapid breakdown of the flow. In the case of strong stratification, in which the time scale of buoyancy is comparable to that of the instability, the flow is significantly altered. As a result of strong baroclinic torque, the primary vortices are brought together and detrainment occurs earlier. The associated reduction in radii of the vortices results in a higher axial wave mode and a more complex radial structure of the instability. Detrainment and mixing accelerate their decay. Late time evolution is dominated by the successive generation of alternate signed baroclinic torque which results in an oscillation of the total flow circulation at the buoyancy frequency.

Nomura, Keiko K.; Tsutsui, Hideaki; Mahoney, Daniel; Rottman, James W.

2006-04-01

106

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

SciTech Connect

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

107

Observation of Rayleigh{endash}Taylor growth to short wavelengths on Nike  

SciTech Connect

The uniform and smooth focal profile of the Nike KrF laser [S. Obenschain {ital et al.}, Phys. Plasmas {bold 3}, 2098 (1996)] was used to ablatively accelerate 40 {mu}m thick polystyrene planar targets with pulse shaping to minimize shock heating of the compressed material. The foils had imposed small-amplitude sinusoidal wave perturbations of 60, 30, 20, and 12.5 {mu}m wavelength. The shortest wavelength is near the ablative stabilization cutoff for Rayleigh{endash}Taylor growth. Modification of the saturated wave structure due to random laser imprint was observed. Excellent agreement was found between the two-dimensional simulations and experimental data for most cases where the laser imprint was not dominant. {copyright} {ital 1999 American Institute of Physics.}

Pawley, C.J.; Bodner, S.E.; Dahlburg, J.P.; Obenschain, S.P.; Schmitt, A.J.; Sethian, J.D.; Sullivan, C.A. [Plasma Physics Division, Naval Research Laboratory, Washington DC 20375 (United States); Gardner, J.H. [Laboratory for Computational Physics and Fluid Dynamics, Naval Research Laboratory, Washington DC 20375 (United States); Aglitskiy, Y.; Chan, Y.; Lehecka, T. [Science Applications International Corp., McLean, Virginia 22310 (United States)

1999-02-01

108

Observation of Rayleigh-Taylor growth to short wavelengths on Nike  

Microsoft Academic Search

The uniform and smooth focal profile of the Nike KrF laser [S. Obenschain et al., Phys. Plasmas 3, 2098 (1996)] was used to ablatively accelerate 40 mum thick polystyrene planar targets with pulse shaping to minimize shock heating of the compressed material. The foils had imposed small-amplitude sinusoidal wave perturbations of 60, 30, 20, and 12.5 mum wavelength. The shortest

C. J. Pawley; S. E. Bodner; J. P. Dahlburg; S. P. Obenschain; A. J. Schmitt; J. D. Sethian; C. A. Sullivan; J. H. Gardner; Y. Aglitskiy; Y. Chan; T. Lehecka

1999-01-01

109

Long Wave Short Wave Resonance in Nonlinear Negative Refractive Index Media  

Microsoft Academic Search

We show that long wave short wave resonance can be achieved in a second-order nonlinear negative refractive index medium when the short wave lies on the negative index branch. With the medium exhibiting a second-order nonlinear susceptibility, a number of nonlinear phenomena such as solitary waves, paired solitons, and periodic wave trains are possible or enhanced through the cascaded second-order

Aref Chowdhury; John A. Tataronis

2008-01-01

110

Carbon nanotube/polymer composite coated tapered fiber for four wave mixing based wavelength conversion.  

PubMed

In this paper, we demonstrate a nonlinear optical device based on a fiber taper coated with a carbon nanotube (CNT)/polymer composite. Using this device, four wave mixing (FWM) based wavelength conversion of 10 Gb/s Non-return-to-zero signal is achieved. In addition, we investigate wavelength tuning, two photon absorption and estimate the effective nonlinear coefficient of the CNTs embedded in the tapered fiber to be 1816.8 W(-1)km(-1). PMID:23481821

Xu, Bo; Omura, Mika; Takiguchi, Masato; Martinez, Amos; Ishigure, Takaaki; Yamashita, Shinji; Kuga, Takahiro

2013-02-11

111

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

112

A Short Wavelength IUE Atlas of Pre-Main-Sequence Stars  

Microsoft Academic Search

We present an atlas of IUE low-dispersion short-wavelength spectra of pre-main-sequence (PMS) stars. These spectra are coadditions from all useful images which have been reprocessed with NEWSIPS and placed in the IUE final archive. Compared to the earlier processing of the spectra with IUESIPS, each spectrum has significantly higher signal\\/noise and most blemishes and cosmic ray hits are now removed.

Christopher M. Johns-Krull; Jeff A. Valenti; Jeffrey L. Linsky

1998-01-01

113

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

SciTech Connect

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

Braud, J.P.

1991-12-31

114

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

NASA Astrophysics Data System (ADS)

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

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

2000-03-01

115

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

116

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

117

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

PubMed

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

Neupane, Bhanu; Zhao, Luyang; Wang, Gufeng

2013-08-08

118

Conditional second-order short-crested water waves applied to extreme wave episodes  

NASA Astrophysics Data System (ADS)

A derivation of the mean second-order short-crested wave pattern and associated wave kinematics, conditional on a given magnitude of the wave crest, is presented. The analysis is based on the second-order Sharma and Dean finite-water wave theory. A comparison with a measured extreme wave profile, the Draupner New Year Wave, shows a good agreement in the mean, indicating that this second-order wave can be a good identifier of the shape and occurrence of extreme wave events. A discussion on its use as an initial condition for a fully nonlinear three-dimensional surface wave analysis is given.

Juncher Jensen, Jørgen

2005-12-01

119

Theory of long-wavelength spin waves in exchange biased bilayers  

SciTech Connect

Long-wavelength spin waves are examined in an exchange biased ferromagnet/antiferromagnet bilayer. The frequencies of the excitations are calculated as a function of external field strength and orientation. It is suggested that the angular dependence of the frequencies can lead to linewidth enhancements, in agreement with recent experimental results. It is also shown that the study of the spin wave frequencies can yield the strengths of the antiferromagnet anisotropy and interlayer coupling. {copyright} 2001 American Institute of Physics.

Kim, Joo-Von; Stamps, R. L.

2001-06-01

120

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

121

Output characteristics of SASE-driven short wavelength FEL`s  

SciTech Connect

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

Fawley, W.M.

1997-02-01

122

Comparison of long- and short-wavelength optical transmitters for optical PCB applications  

NASA Astrophysics Data System (ADS)

Two kinds of optical transmitter (Tx) modules using an 1310 nm long-wavelength and an 850 nm short-wavelength 4-channel VCSELs have been fabricated and characterized for comparison. 4-channel VCSEL driver has been fabricated by a CMOS 0.18 ?m process and used in common for the fabrication of both modules. Both of the modules showed less than 1 x 10-12 of bit error rates (BERs) and clear eye openings at the speed of 2.5 Gbps and 3. 5 Gbps. 3dB bandwidths of the two different Tx modules of 850 nm and 1310 nm VCSELs are 3.76 GHz for 850 nm VCSEL and 3.80 GHz for 1310 nm VCSEL. The optical crosstalks of the both transmitter modules are less than -50 dB in common. Crosstalk evaluation of the two optical interconnection systems using these two Tx modules shows that the application of the 1310 nm wavelength VCSEL as well as 850 nm wavelength VCSEL for the optical interconnections is expected to be possible.

Kim, Do-Won; Shirazy, Md. Shorab Muslim; Ukaegbu, Augustine Ikechi; Lee, Tae-Woo; Cho, Mu Hee; Kim, Sung Jun; Yoo, Byueng-Su; Park, Hyo-Hoon

2009-02-01

123

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

124

On the Wavelength of the Rossby Waves Radiated by Tropical Cyclones  

Microsoft Academic Search

The authors present a theory for the zonal wavelength of tropical depression-type disturbances, which occur as a result of Rossby wave radiation from a preexisting tropical cyclone (TC). In some cases, such disturbances undergo tropical cyclogenesis, resulting in a pair of tropical cyclones; the theory then predicts the zonal separation distance of such tropical cyclone pairs. Numerical experiments are presented

Kyle D. Krouse; Adam H. Sobel; Lorenzo M. Polvani

2008-01-01

125

Long-Wavelength Analysis of Plane Wave Irradiation of an Ellipsoidal Model of Man  

Microsoft Academic Search

Expressions are derived for the induced eletric fields in an ellipsoidal model of man, and experimental animals irradiated by an electromagnetic (EM) plane wave when the wavelength is long compared to the dimensions of the ellipsoid. Calculations of the power absorbed by an ellipsoidal model of man are given for six different orientations of the ellipsoid with respect to the

H. Massoudi; C. H. Durney; C. C. Johnson

1977-01-01

126

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

127

High-extinction-ratio micro polarizing beam splitter for short wavelength optical storage applications.  

PubMed

A surface-micromachined high-extinction-ratio polarizing beam splitter (PBS) using low absorptive silicon nitride layers for blue wavelength applications are demonstrated. The micro polarizing beam splitter consists of novel stack of two silicon nitride layers separated by an air gap. A PBS optimization model is established to achieve both high extinction-ratio and adequate process margin. The polarization extinction ratios of 25 dB for the reflected light and 15 dB for the transmitted light were experimentally achieved at lambda=405 nm. The fabrication of the PBS is compatible with other micro diffractive elements to build a micro optical bench, thus, feasible for short wavelength optical storage applications. PMID:19503244

Lee, Chi-Hung; Chiu, Yi; Shieh, Han-Ping D

2005-12-12

128

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

SciTech Connect

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

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

2008-11-01

129

On the nature of short-period mesospheric gravity wave propagation over Halley, Antarctica  

NASA Astrophysics Data System (ADS)

As part of a collaborative program between British Antarctic Survey and Utah State University, measurements were made using an all-sky airglow imager located at the U.K. Halley Station (76°S, 27°W) during the 2000 and 2001 austral winter seasons from April through to early September. A co-located imaging Doppler interferometer was utilized to obtain coincident wind measurements for a total of 171 wave events. This study comprises the first detailed climatological investigation of the propagation nature (freely propagating, Doppler ducted, or evanescent) of individual quasi-monochromatic, short-period wave events at a high southern latitude. Distributions of the derived vertical wavelength exhibit an interquartile range from ˜16-48 km with a median vertical wavelength of 21 km. The majority of the wave events were found to be freely propagating waves, with only ˜5% exhibiting a clear Doppler ducted signature, while 15% of the waves were found to be evanescent in nature. Although no coincident temperature measurements were available, subsequent SABER temperature measurements suggest that up to ˜28% of the measured temperature profiles are capable of providing a ducted environment for the observed wave field. This is in sharp contrast to findings at mid- and low latitudes where these waves have been shown to be prone to Doppler ducted motion. It is suggested that the relatively weak wind field and associated tidal wind amplitudes over Halley are not capable of forming a significant Doppler ducted region to sustain a substantial amount of ducted waves belonging to the detectable spectrum of the airglow imager. As these wind fields are comparable to wind fields found at other polar latitudes, we hypothesize that the majority of short-period gravity waves observed in the polar mesosphere are freely propagating and thus an important source of energy transfer into the MLT region.

Nielsen, K.; Taylor, M. J.; Hibbins, R. E.; Jarvis, M. J.; Russell, J. M., III

2012-03-01

130

Sub-surface Models of Long- and Short-wavelength Gravity Anomalies in Pennsylvania  

NASA Astrophysics Data System (ADS)

Over the past several years we have been collecting and compiling gravity data in various areas in Pennsylvania to complement existing data previously compiled by the National Image and Mapping Agency and GeoNet. Supported by the Pennsylvania Geological Survey, the aim of this project is to generate a gravity map for the state. This has involved the collection of approximately 4000 new observations and identification of previously acquired data from other sources that had not been included in the above listed data bases. While we are still in the process of cleaning up the data set, it is now possible to use the data to model subsurface density changes for both short and long-wavelength anomalies. An intriguing feature of the gravity map of Pennsylvania is the long-wavelength NE-SW-trending positive and negative anomalies that have little direct correlation with the observed surface geology. The negative anomalies range in amplitude from -12 to - 40 mgals, with wavelengths from 80 to 150 km, while the positive anomalies have amplitudes from 11 to 54 mgals and wavelengths between 100 and 135 km. We have modeled several of these using both wavelength analysis and simple two-dimensional modeling. The results suggest that, unlike previous interpretations that suggested shallow basins or intrusions, part of the cause of these anomalies may be as deep as topographic variations at the crust-mantle boundary. With well-constrained regional trends we have also been able to use these data to isolate and model short- wavelength anomalies. Within the Newark Basin in southeastern Pennsylvania one focus has been on the diabase intrusions. The gravity data demonstrate a remarkable special coincidence of 5 to 10 mgal positive anomalies with the known outcrop pattern of the sills, however there are also some areas where the sill is observed to outcrop, but where the gravity signature is minimal or does not exist. The density models of the sills range in thickness from .3 km to almost 1 km and generally increase in structural thickness from east to west, suggesting a possible source towards the west-central portion of the basin, or conversely greater removal of material (and uplift) towards the east.

Malinconico, L. L.; Morabito, J.; Hudacek, W.; Harhen, M.; McAtee, B.

2008-12-01

131

Kolmogorov spectra of long wavelength ion-drift waves in dusty plasmas  

NASA Astrophysics Data System (ADS)

Weakly turbulent Kolmogorov spectra of ion-drift waves in dusty plasmas with an arbitrary ratio between the ion-drift and the Shukla-Varma frequencies are investigated. It is shown that in the long wavelength limit, when the contribution to the wave dispersion associated with the inhomogeneity of the dust component is larger than that related to the plasma inhomogeneity, the wave dispersion and the matrix interaction element coincide with those for the Rossby or the electron-drift waves described by the Charney or Hasegawa-Mima equations with an accuracy of unessential numerical coefficients. It is found that the weakly turbulent spectra related to the conservation of the wave energy are local and thus the energy flux is directed towards smaller spatial scales.

Onishchenko, O. G.; Pokhotelov, O. A.; Sagdeev, R. Z.; Pavlenko, V. P.; Stenflo, L.; Shukla, P. K.; Zolotukhin, V. V.

2002-05-01

132

Short-wavelength intersubband staircase lasers, with and without AlAs-blocking barriers  

Microsoft Academic Search

We present short-wavelength Ga0.322In0.678As\\/Al0.635In0.365As quantum-cascade lasers without injector regions (staircase lasers), with and without AlAs-blocking barriers, emitting at ~4.55 µm and ~4.2 µm, respectively. By introducing AlAs-barriers into the active region, a thermally activated escape of electrons from the upper laser state into the quasicontinuum is avoided. The sample without AlAs-barriers shows a maximum operating temperature of 220 K with

A. Friedrich; G. Boehm; M. C. Amann

2007-01-01

133

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

134

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

NASA Astrophysics Data System (ADS)

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

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

2013-06-01

135

Characteristics of ion emission from plasma produced by high-energy short-wavelength (438 nm) laser radiation  

Microsoft Academic Search

Efficient production of highly charged (z>45) high-energy (up to ~20 MeV) Ta ions by the interaction of a short-wavelength subnanosecond laser pulse with a solid target has been demonstrated by experimental studies of ion emission from plasma generated by the PALS high-energy short-wavelength (3omega0) iodine laser system (<=0.25 kJ, 0.4 ns, 0.438 mum, <=1016 W cm-2) in Prague. The plasma

J. Wolowski; J. Badziak; F. P. Boody; S. Gammino; H. Hora; K. Jungwirth; J. Krása; L. Láska; P. Parys; M. Pfeifer; K. Rohlena; A. Szydlowski; L. Torrisi; J. Ullschmied; E. Woryna

2003-01-01

136

Generation of Wavelength-Matched Guided Wave in Tube by Arrayed Laser Beam Method  

NASA Astrophysics Data System (ADS)

The laser ultrasonic technique has been considered as a useful non-contact method to generate the ultrasonic guided wave in tube. In practical applications of the guided wave technique, however, it is very important, though often difficult, to identify propagating modes. In this paper, we propose a wavelength-matched method using the ring-arrayed laser illumination that enables to generate only the specific longitudinal mode of which wavelength is determined by the array spacing. The effect of ring-arrayed illumination is uniformly launching the wavelength-matched guided wave along the circumferential direction. In order to test the performance, the experimental system including optics to produce the ring-arrayed beam pattern is constructed, and tube specimens are tested. The laser source is Nd:YAG and the detector is the air-coupled transducer that is able to detect only a single mode by tuning its detection angle. Experimental results show that the predicted mode is clearly generated and detected. The proposed technique is fully non-contact, and it also has the advantage of greatly enhanced mode selectivity. This advantage makes it possible to avoid complication in the detected wave signal.

Lim, B. O.; Lee, T. H.; Jhang, K. Y.; Park, I. K.

2007-03-01

137

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

PubMed Central

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

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

2013-01-01

138

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

139

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

PubMed

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

Wood, E R; Ghané, F; Grogan, D W

1997-09-01

140

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

PubMed Central

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

Wood, E R; Ghane, F; Grogan, D W

1997-01-01

141

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

142

Continuous-wave laser oscillation of Yb:FAP crystals at a wavelength of 1043 nm  

NASA Astrophysics Data System (ADS)

A continuous-wave laser oscillation was demonstrated with a Yb-doped fluorapatite (FAP) crystal pumped with a 905 nm Ti:sapphire laser. The output characteristics for different output couplers were investigated. A maximum power of 67mW at a 1043nm wavelength was obtained with 10% output coupler, pumped by a Ti:sapphire laser with 910mW power. This corresponds to a slope efficiency of 26.5%.

Yang, Hui; Zhao, Zhi-wei; Zhang, Jun; Deng, Pei-zhen; Xu, Jun; Wei, Zhi-yi; Zhang, Jie

2001-12-01

143

The Absorption of X-Rays of Wave-Length down to.08A  

Microsoft Academic Search

Mass absorption coffiecients of C, paraffine, S and 16 metal elements from Al to U for wave-lengths.56 to.08A have been measured in continuation of previous work1 which covered most of these elements in the range.71 to.10A. The general radiation from a tungsten target (operated at voltages up to 200 kv) was dispersed by a crystal into an ionization chamber. By

S. J. Allen

1926-01-01

144

Short-wavelength Contractional Structures in Venusian Fold Belts: Additional Constraints From New Models  

NASA Astrophysics Data System (ADS)

We have previously reported on the development of very short-wavelength (<1 km) contractional topography (VST) in Venusian crustal plateau fold belts, which show structures with wavelengths from ~100 m to >30 km [1, 2]. We simulated the initiation and growth of VST using finite-element models with uniform composition and elasto-visco-plastic rheology undergoing simultaneous cooling and shortening. The models were constrained by Magellan SAR imagery and motivated by the current plume hypothesis for crustal plateau origin [3, 4]. We determined that VST developed only in models with surface temperatures near 1000 K and elevated thermal gradients derived from a halfspace cooling model with initial uniform temperatures of 1200-1400 K. Model rheological profiles indicated a truly viscoplastic character, in which both creep and plastic mechanisms were significant at shallow depths. The resulting topography showed both very short-wavelength components and slightly longer-wavelength, low amplitude folds, as is common in Venusian crustal plateau fold belts. New simulations with greater spatial extent and higher mesh resolution allow further exploration of the interplay between viscous and plastic processes during VST development. Wider models allow more detailed investigation of viscous folding on the 1-4 km scale. We also employ temperature-dependent thermal conductivity [5] to better represent the thermal behavior of the model crust. The additional insight and expanded parameter space provided by these new models allow us to place improved constraints on the early thermal and mechanical evolution of crustal plateaus. [1] Ghent, R.R., R.J. Phillips, V.L. Hansen, and D.C. Nunes, Eos Trans. AGU, 83(19), Spring Meet. Suppl., Abstract P21A-05, 2002. [2] Ghent, R.R., R.J. Phillips, and V.L. Hansen, 2001, Eos Trans. AGU, 82(47), Spring Meet. Suppl., Abstract T41B-0865, 2001. [3] Hansen, V.L. and J.J. Willis, Icarus, 132, 321-343, 1998. [4] Phillips, R.J. and V.L. Hansen, Science, 279, p1492, 1998. [5] Hofmeister, A, Science, 283, p1699, 1999.

Ghent, R.; Phillips, R.; Hansen, V.; Nunes, D.

2002-12-01

145

Sensitivity of the short-to-intermediate wavelength geoid to rheologic structure in subduction zones  

NASA Astrophysics Data System (ADS)

It is well established that the long wavelength geoid and dynamic topography are responsive to the radial viscosity structure of the mantle, but recent studies indicate that lateral viscosity variations affect the geoid at shorter wavelengths. These studies, however, only consider Newtonian viscosity structures, although experimental deformation studies of mantle minerals and seismic observations of lattice preferred orientation in the upper mantle provide evidence that dislocation creep is an active deformation mechanism at mantle conditions. In addition, the lithosphere is expected to yield plastically at high stresses based on laboratory measurements of yield strength. To quantify the effects of lateral viscosity variations and realistic flow laws on the short-to-intermediate wavelength dynamic topography and geoid near subduction zones, we consider a composite viscosity that accounts both for Newtonian and stress-dependent deformation mechanisms, including plastic yielding. Regional models of instantaneous stokes flow models are computed on a variable resolution mesh using CitcomS, where the resolution ranges from 25 km away from the subduction zone to 5 km in the vicinity of the subducting slab. The slab is defined as an 80 million year old lithosphere temperature anomaly smoothed above and below by half-space cooling models, and extends 100 km into the lower mantle. The buoyancy and stress fields are expanded to spherical harmonic degree 360, corresponding to a spatial resolution of about 110 km. These fields include the effects of self-gravitation and are used to solve for the surface geoid, as well as for dynamic topography at the surface and core-mantle boundary. Results of preliminary, layered mantle viscosity models are consistent with previous geoid studies, the main conclusion being that a more positive geoid at subduction zones is the product of relative viscosity increases with depth. In layered models, increased viscous support of the down-going slab with depth decreases its velocity, resulting in lower pressure gradients above the slab, decreased dynamic topography at the surface and a more positive geoid relative to the case of a uniform viscosity mantle. In contrast, relatively stronger layers above the slab increase coupling to the surface, thereby increasing dynamic topography and leading to a more negative geoid. Future models with temperature-dependent viscosities will include lateral variations in viscosity due to the temperature anomaly of the slab. These model results will be compared with those from models that include both linear and non-linear viscosities to determine the sensitivity of the short-to-intermediate wavelength geoid to increasingly realistic subduction zone rheologies.

Hines, J. M.; Billen, M. I.

2010-12-01

146

Construction of exact periodic wave and solitary wave solutions for the long-short wave resonance equations by VIM  

NASA Astrophysics Data System (ADS)

In this paper, He’s variational iteration method is employed to construct periodic wave and solitary wave solutions for the long-short wave resonance equations. The chosen initial solution can be in soliton form with some unknown parameters, which can be determined in the solution procedure. Some examples are given. The results reveal that the method is very effective and convenient.

Deng, Chaofa; Shang, Yadong

2009-04-01

147

On the bandwidth of a short traveling wave tube  

NASA Astrophysics Data System (ADS)

The bandwidth of a short traveling wave tube is analyzed. When no beam is present the bandwidth is proportional to the group velocity and inversely proportional to the total length of the system. The bandwidth of the gain factor, the imaginary part of the wave vector, is mainly determined by the beam current. However, regardless of the current intensity, the gain factor is identically zero for frequencies which, in the empty structure, correspond to phase velocities larger than the speed of light. The bandwidth of a short amplifier, is narrowed relative to the 'cold' bandwidth by the same amount the amplitude of the growing wave increases, provided that the frequency and the current allow the growing wave to be dominant. This relation is verified with experimental data and good agreeement is found.

Schachter, Levi; Nation, John A.; Kerslick, Graham

1990-12-01

148

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

149

Towards shorter wavelength x-ray lasers using a high power, short pulse pump laser  

SciTech Connect

A near-terawatt, KrF* laser system, focussable to power densities >10{sup 18} W/cm{sup 2} has been constructed for use as a pump laser in various schemes aimed at the development of x-ray lasing below 5nm. The laser system along with output characteristics such as the pulse duration, the focal spot size, and the percentage of amplified spontaneous emission (ASE) emitted along with the laser pulse will be presented. Schemes intended to lead to shorter wavelength x-ray emission will be described. The resultant requirements on the pump laser characteristics and the target design will be outlined. Results from recent solid target experiments and two-laser experiments, showing the interaction of a high-power, short pulse laser with a preformed plasma, will be presented. 13 refs., 5 figs.

Tighe, W.; Krushelnick, K.; Valeo, E.; Suckewer, S.

1991-05-01

150

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

151

Short period gravity waves in the Arctic atmosphere over Alaska  

NASA Astrophysics Data System (ADS)

The propagation nature and sources of short-period gravity waves have been studied extensively at low and mid-latitudes, while their extent and nature at the polar regions are less known. During the last decade, observations from select sites on the Antarctic continent have revealed a significant presence of these waves over the southern Polar Region as well as shown unexpected dynamical behavior. In contrast, observations over the Arctic region are few and the dynamical behavior is unknown. A recent project was initiated in January 2011 to investigate the presence and dynamics of these waves over interior Alaska. This site provides an exceptional opportunity to establish a long-term climatology of short-period gravity waves in the Arctic, including their dominant source regions, influences of large-scale tidal and planetary wave motion, as well as impact of dominant weather systems such as the polar vortex and Aleutian low. Here we present initial measurements of short-period gravity waves in the Arctic atmosphere over Alaska.

Negale, Michael; Nielsen, Kim; Taylor, Mike; Irving, Brita; Collins, Richard

2012-10-01

152

Layered convection in Io: Implications for short-wavelength surface topography and heat flow  

NASA Astrophysics Data System (ADS)

Io, one of the four Galilean moons of Jupiter is remarkable for its extensive volcanism and extreme interior tidal heating. The tidal heating likely yields a very low viscosity asthenosphere and consequently a very high Rayleigh number of O(1012) for convection in the interior. In a state of quasi-steady balance the internally generated heat must be transported from the interior to the base of the Io lithosphere and exhausted to space. The mechanisms whereby the convective radial heat transfer is evacuated involve both conduction and volcanism. Despite Io's ubiquitous volcanism, only 4% of its mountains (montes) appear to have a volcanic origin and most of the mountainous regions seem to be related to tectonic processes. By employing an original control volume based numerical model we investigate the style of convection in the interior of Io and the correlation of the scale of convection with the Ionian surface heat flux and topography. Our control volume results support the existence of significant asthenospheric heating and demonstrate that short wavelength features of the surface heat flux are well correlated in scale to an expected layered intra-lithospheric style small-scale convection. These numerical analyses suggest that the amplitude of the short wavelength topography of Io is expected to be on the order of a few hundreds of meters. The model results also demonstrate that the Ionian highs cannot be produced by a lithospheric flexure process above the hot upwellings and therefore other tectonic events, such as have previously been suggested; must be responsible for the formation of the high Ionian mountains that reach in excess of 17 km in elevation.

Shahnas, M. H.; Pysklywec, R. N.; Peltier, W. R.

2013-07-01

153

Optical measurements of the modulation of short wind waves by long waves and their effects on observed C-band radar reflectivity  

NASA Astrophysics Data System (ADS)

Laboratory measurements to quantify the effect of long waves on the modulation of short waves and the effect that this modulation has on radar have been conducted at the Air-Sea Interaction Saltwater Tank (ASIST) facility of the University of Miami. The critical parameters for the modulation of radar reflectivity were directly observed using non-intrusive techniques. The directional wave spectrum was remotely sampled using a triad of laser elevation sensors. Two-dimensional surface slopes were imaged at a rate of 120 Hz using a video technique. Experiments were run with various wind velocities modulated by a 1 Hz mechanical long-wave. Co-incident with these measurements, the radar backscatter was sampled over the same region of the surface using a dual-polarized C-band Doppler radar. The 2-D slope gauge directly observed the modulation by longer waves of the short waves responsible for radar reflectivity. When there were no long waves, the short wave structure as observed by the 2-D slope gauge was well developed with peaks in surface slopes corresponding to the wavelength of the peak wind waves and having a clear group structure. This organization was in sharp contrast to the variability of the slopes observed when a 1 Hz mechanical long-wave was generated in the same direction as the wind waves. The slopes linked to the wind wave were suppressed, while there was modulation at the 1 Hz long-wave frequency. The surface slopes corresponding to the radar Bragg-scattering scale have increased energy by a factor of two linked to the modulation by the long wave. Significant modulation of the C-band HH polarized radar return was evident at the long wave frequency. The modulation transfer functions were derived from these measurements.

Haus, B. K.; Donelan, M. A.; Plant, W. J.

2003-04-01

154

Intense interactions of molecules with a short-wavelength electromagnetic radiation field: I. The fundamentals of the nonadiabatic theory  

Microsoft Academic Search

The intense interactions between short-wavelength (SW) electromagnetic radiation with a wavelength ? ? 1 ? and intensity up\\u000a to 1014 W\\/cm2 and simple and polyatomic molecules are studied with the coherent excitations of high-lying Rydberg and autoionizing states\\u000a taken into account. The Hamiltonian of a system “molecule + SW radiation” is obtained by using the methods of quantum electrodynamics.\\u000a Conditions

A. I. Pegarkov

2001-01-01

155

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

156

Into French and the World via Short Wave.  

ERIC Educational Resources Information Center

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

Rorke, Robert Cornelius

1978-01-01

157

Short-Wave Radio: An Aid to Language Learning.  

ERIC Educational Resources Information Center

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

Lutcavage, Charles P.

1982-01-01

158

The Optical Constants of Certain Liquids for Short Electric Waves  

Microsoft Academic Search

Optical constants of liquids for short electric waves of length 4 to 27 mm were measured by use of special Hertzian oscillators and radiometer receivers developed by Nichols and Tear, for water, glycerin, and methyl and ethyl alcohol. For the extinction coefficient, glass and ebonite cells were used; for the coefficient of reflection, the liquid was held in a tilted

J. D. Tear

1923-01-01

159

Multimode broadening of short-wave signals on extended paths  

NASA Astrophysics Data System (ADS)

The paper examines experimental results on the multimode broadening of pulsed short-wave signals under equinox conditions on the Nikolaev-Havana and Moscow-Molodezhnaia paths. Theoretical calculations of the multimode broadening of such signals on the Nikolaev-Havana path are also presented. Data obtained from ionogram processing are found to agree better with calculations than experimental data for fixed frequencies.

Lobachevskii, L. A.; Nekrasov, B. Iu.; Smirnov, V. B.; Suares, Kh. B.; Tushentsova, I. A.; Fishchuk, D. I.; Tsedilina, E. E.; Shumilov, I. A.; Izraitel, A. G.

1981-08-01

160

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

Microsoft Academic Search

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

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

1977-01-01

161

Symmetric highly efficient (?0 dB) wavelength conversion based on four-wave mixing in quantum dot optical amplifiers  

Microsoft Academic Search

Conversion efficiency to longer wavelengths in four-wave-mixing-based wavelength conversion in optical semiconductor amplifiers is generally much lower than that in the opposite direction. This study demonstrates experimentally that this feature is drastically improved, and the asymmetry between conversion directions is eliminated by using quantum dots in the active layer. We attribute this to a reduction in linewidth enhancement factor due

Tomoyuki Akiyama; Haruhiko Kuwatsuka; Nobuaki Hatori; Yoshiaki Nakata; Hiroji Ebe; Mitsuru Sugawara

2002-01-01

162

THE EFFECTS OF ULTRA-VIOLET RADIATIONS OF VARIOUS WAVE-LENGTHS UPON CLEAVAGE OF SEA URCHIN EGGS  

Microsoft Academic Search

In a preceding paper retarding effects of radiations of X2537A upon cleavage of eggs of the sea urchin, Strongylocentrotus purpuratus, were reported (Giese, 1938). The following account, extending the above study to wave-lengths of 2654, 2804, 3025, 3130 and 3660A, attempts to determine (1) the amount of retardation, if any, produced by known dosages of the above wave-lengths; (2) the

ARTHUR C. GIESE

163

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

PubMed Central

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

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

2012-01-01

164

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

NASA Astrophysics Data System (ADS)

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

Trepmann, C. A.; Stöckhert, B.

2013-04-01

165

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

NASA Astrophysics Data System (ADS)

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 found to occur at an electron density many times that expected, owing to ponderomotive displacement of plasma within the focal region.

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

2002-12-01

166

Microwave backscatter from the sea surface: Bragg scattering by short gravity waves  

NASA Astrophysics Data System (ADS)

Resonant Bragg scattering forms the basis for the composite or dual-scale model for microwave backscatter from the sea surface. The scatterers are short surface waves that are spatially resonant with the incident electromagnetic waves. Bragg scattering is most easily identified when the intrinsic velocity of the scattering agents can be deduced and compared with theoretical surface wave phase velocities. In this paper we present S band (wavelength 10 cm) microwave backscatter data taken at low grazing angles for three situations where the scatterer velocity could be separated from the surface currents. These include a situation where pack ice acts as an additional tracer on the water surface, a wind direction reversal, and an azimuthal scan during low wind speed conditions where two Bragg peaks are visible in the Doppler spectra. These data show that under these conditions the scattering is dominated by propagating 5-cm resonant waves. Doppler spectra recorded at low grazing angles are interpreted in terms of the angular distribution of the scattering waves, the contributions of wave orbital velocities, and the effects of geometric shadowing.

Poulter, E. M.; Smith, M. J.; McGregor, J. A.

1994-04-01

167

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

NASA Astrophysics Data System (ADS)

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

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

2009-02-01

168

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

169

Beam dynamics in a high brightness linac for short wavelength SASE-FEL experiments  

NASA Astrophysics Data System (ADS)

Short wavelength SASE-FEL requires generation and transport up to the undulator entrance of low emittance (~1 2 mm mrad) high peak current (~1 3 kA) electron beams with energy higher than 1 GeV. The propagation of such a high brightness beam takes place in a transition regime from space charge to emittance dominated dynamics, as the beam energy increases. In addition, in downstream magnetic compressor devices where the peak current increases up to kA range, the transition may occur again. Under these conditions, the electron beam has to be properly matched to the linac accelerating sections in order to keep under control emittance oscillations driven by residual space charge effects. Generalized invariant envelope matching conditions are discussed in this paper, showing that an equilibrium between RF focusing forces and space charge/emittance defocusing forces can be attained without any additional external focusing along the linac (no quadrupoles), thus reducing alignment problems and mitigating emittance dilutions due to misalignments and beam parameter jitters.

Ferrario, M.; Fusco, V.; Ronsivalle, C.; Serafini, L.; Vaccarezza, C.

2006-11-01

170

Short wavelength-automated perimetry compared with standard achromatic perimetry in autosomal dominant optic atrophy  

PubMed Central

Background Autosomal dominant optic atrophy (ADOA, Kjer?type) is a heterogeneous, non?inflammatory degeneration of retinal ganglion cells. The diagnosis of ADOA can be challenging owing to its insidious onset and large variability in phenotypic expression, both within and between individual pedigrees. The earliest literature reports relatively mild centrocaecal scatomas to white targets in ADOA, but extensive and dense peripheral field loss to coloured targets, especially blue, with Bjerrum perimetry. The phrase “inverted peripheral visual fields to coloured targets” has been used to describe this phenomenon. Methods Humphrey standard achromatic perimetry (SAP) and short wavelength?automated perimetry (SWAP) were carried out on five patients with ADOA. Results Regardless of wide variations in patient age, visual acuity, disc appearance and colour vision, the SWAP mean deviation (MD) was between 10 and 20?times more depressed than the SAP MD. The actual differences ranged from 9.38 to 13.78?dB. Conclusions These data are consistent with the original reports suggesting that, early in this disease process, the blue?target deficits are typically peripheral and that this difference between SAP and SWAP perimetry may be a robust indicator of ADOA in both early and late stages of this disease.

Walters, J W; Gaume, A; Pate, L

2006-01-01

171

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

172

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

SciTech Connect

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

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

1992-04-01

173

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

SciTech Connect

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

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

1992-04-01

174

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

PubMed Central

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

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

2006-01-01

175

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

SciTech Connect

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

Yoakum, S.; Moorman, L.

1993-05-01

176

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

177

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

178

Short-wave scattering near the boundary inflection point  

SciTech Connect

The authors investigate the problem of tangential incidence of short waves onto a surface with an inflection point. Formal solutions of the corresponding equation are constructed near the inflection point in the form of a quasihomogeneous function series. The formal solution is joined with the geometrical optics solution far from the inflection point of the boundary. The problem is restated as a scattering problem for the Schrodinger equation; existence, uniqueness, and smoothness theorems are proved. The formal asymptotic expansion are proved.

Smyshlyaev, V.P.

1987-07-10

179

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

180

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

NASA Astrophysics Data System (ADS)

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

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

2010-02-01

181

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

NASA Astrophysics Data System (ADS)

Targets meant to achieve ignition on the National Ignition Facility (NIF) [J. A. Paisner, J. D. Boyes, S. A. Kumpan, W. H. Lowdermilk, and M. S. Sorem, Laser Focus World 30, 75 (1994)] have been redesigned and their performance simulated. Simulations indicate dramatically reduced growth of short wavelength hydrodynamic instabilities, resulting from two changes in the designs. First, better optimization results from systematic mapping of the ignition target performance over the parameter space of ablator and fuel thickness combinations, using techniques developed by one of us (Herrmann). After the space is mapped with one-dimensional simulations, exploration of it with two-dimensional simulations quantifies the dependence of instability growth on target dimensions. Low modes and high modes grow differently for different designs, allowing a trade-off of the two regimes of growth. Significant improvement in high-mode stability can be achieved, relative to previous designs, with only insignificant increase in low-mode growth. This procedure produces capsule designs that, in simulations, tolerate several times the surface roughness that could be tolerated by capsules optimized by older more heuristic techniques. Another significant reduction in instability growth, by another factor of several, is achieved with ablators with radially varying dopant. In this type of capsule the mid-Z dopant, which is needed in the ablator to minimize x-ray preheat at the ablator-ice interface, is optimally positioned within the ablator. A fabrication scenario for graded dopants already exists, using sputter coating to fabricate the ablator shell. We describe the systematics of these advances in capsule design, discuss the basis behind their improved performance, and summarize how this is affecting our plans for NIF ignition.

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

2005-05-01

182

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

183

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

SciTech Connect

Targets meant to achieve ignition on the National Ignition Facility (NIF) [J. A. Paisner, J. D. Boyes, S. A. Kumpan, W. H. Lowdermilk, and M. S. Sorem, Laser Focus World 30, 75 (1994)] have been redesigned and their performance simulated. Simulations indicate dramatically reduced growth of short wavelength hydrodynamic instabilities, resulting from two changes in the designs. First, better optimization results from systematic mapping of the ignition target performance over the parameter space of ablator and fuel thickness combinations, using techniques developed by one of us (Herrmann). After the space is mapped with one-dimensional simulations, exploration of it with two-dimensional simulations quantifies the dependence of instability growth on target dimensions. Low modes and high modes grow differently for different designs, allowing a trade-off of the two regimes of growth. Significant improvement in high-mode stability can be achieved, relative to previous designs, with only insignificant increase in low-mode growth. This procedure produces capsule designs that, in simulations, tolerate several times the surface roughness that could be tolerated by capsules optimized by older more heuristic techniques. Another significant reduction in instability growth, by another factor of several, is achieved with ablators with radially varying dopant. In this type of capsule the mid-Z dopant, which is needed in the ablator to minimize x-ray preheat at the ablator-ice interface, is optimally positioned within the ablator. A fabrication scenario for graded dopants already exists, using sputter coating to fabricate the ablator shell. We describe the systematics of these advances in capsule design, discuss the basis behind their improved performance, and summarize how this is affecting our plans for NIF ignition.

Haan, S.W.; Herrmann, M.C.; Dittrich, T.R.; Fetterman, A.J.; Marinak, M.M.; Munro, D.H.; Pollaine, S.M.; Salmonson, J.D.; Strobel, G.L.; Suter, L.J. [Lawrence Livermore National Laboratory, Livermore, California 94550 (United States)

2005-05-15

184

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

185

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

NASA Astrophysics Data System (ADS)

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

Morozov, M. Yu; Morozov, Yu A.; Krasnikova, I. V.

2013-09-01

186

The laboratory performance of the short wavelength instrument for the Along Track Scanning Radiometer ATSR-2 (initial results)  

NASA Astrophysics Data System (ADS)

ATSR-2 is a follow up instrument to ATSR due to be launched in 1994 as part of the ERS-2 payload, and the unit level testing is proceeding as the instrument nears completion. In addition to the identical four channel sea surface temperature measuring radiometer, used on ATSR, there is an additional three channel short wavelength (visible) radiometer, for land and vegetation sensing using selected wavelengths of 555, 659 and 865 nm. The arrangement of the instrument is shown and some performance data from the visible radiometer currently under test is given.

Read, P. D.; Field, D.; Hardie, A. L.; Lidiard, K. A.; Magraw, J. E.; Taylor, H. S.; Tosh, I. A. J.; Trower, M. A.; White, D. J.

1992-12-01

187

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

SciTech Connect

In this work, the efficiency of laser generation of surface acoustic waves (SAWs) in ceramic materials is reported to be wavelength dependent. A pulsed Nd:YAG laser operating at wavelengths of 1064 or 532 nm was used to generate SAWs on ceramic (silicon nitride and silicon carbide) and metal substrates. It was observed that 1064 nm radiation is more efficient than 532 nm radiation for SAW generation on ceramics, whereas the opposite is the case for metals. While the wavelength dependence of SAW generation efficiency in metals is due to stronger optical absorption at the shorter wavelength, the dependence for the ceramics is attributed to a longer absorption length at the longer wavelength. {copyright} {ital 1997 American Institute of Physics.}

Flannery, C.M.; Kelly, P.V.; Beechinor, J.T.; Crean, G.M. [National Microelectronics Research Centre, University College, Lee Maltings, Prospect Row, Cork (Ireland)

1997-12-01

188

Array Observations of Short Period Pdiff Coda Waves  

NASA Astrophysics Data System (ADS)

There have been several reports of short-period, coherent coda waves following Pdiff at distances of approximately 95° -120°. Early interpretations favored topographical scattering at the core-mantle boundary or strong volumetric scattering in the lowermost mantle (D"). However, a recent study suggested these observations can be explained by relatively mild, uniform scattering throughout the lower mantle. In this study, we present a new data set that can be used to test the competing hypotheses for the generation of short-period Pdiff coda waves. We downloaded data for 824 earthquakes with magnitudes of 5.7 mb - 7.9 mb, depths shallower than 100~km, and at distances of 50° - 120° from the Yellowknife array (YKA) in Western Canada. YKA is a medium-aperture (20~km) array, with 19 short-period, vertical-component seismometers arranged in a cross. By using an array we can increase signal-to-noise ratio and infer the directions from which the coda waves are arriving. We included earthquakes at distances smaller than 90° so that we can test the vertical change in heterogeneity strength as waves approach D". The earthquakes are clustered in three regions: Asia, South America, and Tonga-Fiji. For each event, we used a sliding window slowness analysis technique to estimate the beam power as a function of time. Then we normalized each beam envelope by PP amplitude and corrected the amplitudes for radiation pattern effects, eliminating those data in which P, Pdiff, or PP was close to a nodal plane. We then stacked the data in 2° bins, and fit a log-linear relationship between energy and time to determine the coda decay rate (CDR). The CDRs show a clear distance dependence. Asia and South America have the same pattern above D": high CDR from 50° to 70°, low CDR in the range 72°-80°, followed by a CDR increase. At distances after 90° the coda decay rates in the three clusters show significant variations, with events from Asia having the highest CDR. We are currently experimenting with various methods for simulating Pdiff coda waves including a frequency-wavenumber integration technique for 1D stochastic models and a single-scattering ray theory based technique, modified to account for diffraction induced amplitude decay.

Xu, Y.; Koper, K. D.

2007-12-01

189

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

190

Non-destructive prediction of translucent flesh disorder in intact mangosteen by short wavelength near infrared spectroscopy  

Microsoft Academic Search

A non-destructive measurement and data evaluation technique to predict an internal translucent flesh disorder in intact mangosteen fruit is proposed by using short wavelength near infrared (SW-NIR) transmittance spectroscopy. The optimum conditions of measurement were investigated for spectra acquisition at an integration time of 78ms with a 200W light source. The NIR absorption spectra of 193 mangosteen samples were obtained

Sontisuk Teerachaichayut; Kwon Young Kil; Anupun Terdwongworakul; Warunee Thanapase; Yutaka Nakanishi

2007-01-01

191

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

192

Stimulated Brillouin scattering gains and decay times of hypersonic waves in optical crystals at the 10.6 ? wavelength  

Microsoft Academic Search

The known constants of crystals transparent in the 10.6 ? wavelength range are used to calculate the stimulated Brillouin scattering gains and decay times of hypersonic waves. The most promising materials for stimulated Brillouin scattering at 10.6 ? are identified and the requirements in respect of CO2 lasers needed to ensure efficient excitation of such scattering are formulated.

Valerii I Kovalev; M A Musaev; F S Fa?zullov; A K Shmelev

1984-01-01

193

Absorption of radio waves by water vapor in the earth atmosphere at wavelengths of 0.8-20 mm  

Microsoft Academic Search

The paper calculates the water-vapor absorption of millimeter and submillimeter waves propagating vertically in the atmosphere at geographical latitudes of 75, 60, 45, and 30 deg N for winter and summer and at a geographical latitude of 15 deg N for the average yearly model. Water-vapor absorption is studied as a function of wavelength, season, latitude, and height at which

A. Iu. Zrazhevskii; I. A. Iskhakov

1978-01-01

194

Wavelength interleaving towards DWDM and spectral efficiency in dual-toned millimeter-wave radio-over-fiber systems [invited  

Microsoft Academic Search

Wavelength interleaving scheme that has the potential to implement DWDM channel spacing smaller than the millimeter-wave radio frequencies in high-speed radio-over-fiber systems are addressed. Optical subsystems potentially enabling the scheme practically are also briefly discussed.

Masuduzzaman Bakaul; Ampalavanapillai Nirmalthas; Christina Lim; Dalma Novak; R. Waterhouse

2009-01-01

195

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

196

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

NASA Astrophysics Data System (ADS)

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

Zimmer, D.; Ros, D.; Guilbaud, O.; Habib, J.; Kazamias, S.; Zielbauer, B.; Bagnoud, V.; Ecker, B.; Hochhaus, D. C.; Aurand, B.; Neumayer, P.; Kuehl, T.

2010-07-01

197

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

PubMed

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

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

2013-01-01

198

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

NASA Astrophysics Data System (ADS)

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

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

2013-05-01

199

Sub-wavelength patterning of organic monolayers via nonlinear processing with continuous-wave lasers  

NASA Astrophysics Data System (ADS)

In recent years, nonlinear processing with continuous-wave lasers has been demonstrated to be a facile means of rapid nanopatterning of organic monolayers down to the sub-100 nm range. In this study, we report on laser patterning of thiol-based organic monolayers with sub-wavelength resolution. Au-coated silicon substrates are functionalized with 1-hexadecanethiol. Irradiation with a focused beam of an Ar+ laser operating at ?=514 nm allows one to locally remove the monolayer. Subsequently, the patterns are transferred into the Au film via selective etching in a ferri-/ferrocyanide solution. Despite a 1/e2 spot diameter of about 2.8 ?m, structures with lateral dimensions down to 250 nm are fabricated. The underlying nonlinear dependence of the patterning process on laser intensity is traced back to the interplay between the laser-induced transient local temperature rise and the thermally activated desorption of the thiol molecules. A simple thermokinetic analysis of the data allows us to determine the effective kinetic parameters. These results complement our previous work on photothermal laser patterning of ultrathin organic coatings, such as silane-based organic monolayers, organo/silicon interfaces and supported membranes. A general introduction to nonlinear laser processing of organic monolayers is presented.

Mathieu, Mareike; Hartmann, Nils

2010-12-01

200

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

PubMed

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

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

2010-07-08

201

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

SciTech Connect

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

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

2010-07-09

202

Short wavelength-sensitive opsins from the Saharan silver and carpenter Ants  

Microsoft Academic Search

We have previously cloned the opsins coding for the long-wavelength visual pigments from the Saharan silver ant and carpenter\\u000a ant. Here we report two new cDNA clones isolated from cDNA libraries which also code for opsin proteins. These cDNAs code\\u000a for deduced proteins with 369 amino acids which are 91% identical to each other, but only 38% identical to the

W. Clay Smith; Donald M. Ayers; Michael P. Popp; Paul A. Hargrave

1997-01-01

203

A distinct contribution of short-wavelength-sensitive cones to light-evoked activity in the mouse pretectal olivary nucleus.  

PubMed

Melanopsin-expressing intrinsically photosensitive retinal ganglion cells (ipRGCs) combine inputs from outer-retinal rod/cone photoreceptors with their intrinsic phototransduction machinery to drive a wide range of so-called non-image-forming (NIF) responses to light. Defining the contribution of each photoreceptor class to evoked responses is vital for determining the degree to which our sensory capabilities depend on melanopsin and for optimizing NIF responses to benefit human health. We addressed this problem by recording electrophysiological responses in the mouse pretectal olivary nucleus (PON) (a target of ipRGCs and origin of the pupil light reflex) to a range of gradual and abrupt changes in light intensity. Dim stimuli drove minimal changes in PON activity, suggesting that rods contribute little under these conditions. To separate cone from melanopsin influences, we compared responses to short (460 nm) and longer (600/655 nm) wavelengths in mice carrying a red shifted cone population (Opn1mw®) or lacking melanopsin (Opn4?/?). Our data reveal a surprising difference in the quality of information available from medium- and short-wavelength-sensitive cones. The majority cone population (responsive to 600/655 nm) supported only transient changes in firing and responses to relatively sudden changes in light intensity. In contrast, cones uniquely sensitive to the shorter wavelength (S-cones) were better able to drive responses to gradual changes in illuminance, contributed a distinct off inhibition, and at least partially recapitulated the ability of melanopsin to sustain responses under continuous illumination. These data reveal a new role for S-cones unrelated to color vision and suggest renewed consideration of cone contributions to NIF vision at shorter wavelengths. PMID:22090509

Allen, Annette E; Brown, Timothy M; Lucas, Robert J

2011-11-16

204

A distinct contribution of short wavelength sensitive cones to light evoked activity in the mouse pretectal olivary nucleus (PON)  

PubMed Central

Melanopsin-expressing intrinsically photosensitive retinal ganglion cells (ipRGCs) combine inputs from outer-retinal rod/cone photoreceptors with their intrinsic phototransduction machinery to drive a wide range of so-called non-image forming (NIF) responses to light. Defining the contribution of each photoreceptor class to evoked responses is vital for determining the degree to which our sensory capabilities depend on melanopsin, and for optimising NIF responses to benefit human health. We addressed this problem by recording electrophysiological responses in the mouse PON (a target of ipRGCs and origin of the pupil light reflex) to a range of gradual and abrupt changes in light intensity. Dim stimuli drove minimal changes in PON activity, suggesting that rods contribute little under these conditions. To separate cone from melanopsin influences we compared responses to short (460nm) and longer (600/655nm) wavelengths in mice carrying a red shifted cone population (Opn1mwR) or lacking melanopsin (Opn4-/-). Our data reveal a surprising difference in the quality of information available from medium- and short-wavelength sensitive cones. The majority cone population (responsive to 600/655nm) supported only transient changes in firing and responses to relatively sudden changes in light intensity. By contrast, cones uniquely sensitive to the shorter wavelength (S-cones) were better able to drive responses to gradual changes in illuminance; contributed a distinct off inhibition; and at least partially recapitulated melanopsin’s ability to sustain responses under continuous illumination. These data reveal a new role for S-cones unrelated to colour vision, and suggest renewed consideration of cone contributions to NIF vision at shorter wavelengths.

Allen, Annette E; Brown, Timothy M; Lucas, Robert J

2011-01-01

205

Expanding the dynamic range of short wave infrared (SWIR) imagery  

NASA Astrophysics Data System (ADS)

Advances have been made in short wave infrared (SWIR) imaging technology to address the most demanding imaging and surveillance applications. Multiple techniques have been developed and deployed in Goodrich's SWIR indium gallium arsenide (InGaAs) cameras to optimize the dynamic range performance of standard, commercial off-the-shelf (COTS) products. New developments have been implemented on multiple levels to give these cameras the unique ability to automatically compensate for changes in light levels over more than 5 orders of magnitude, while improving intra-scenic dynamic range. Features recently developed and implemented include a new Automatic Gain Control (AGC) algorithm, image flash suppression, and a proprietary image-enhancement algorithm with a simplified but powerful user command structure.

Hansen, Marc; Stern, Mark C.

2010-04-01

206

Aging of human short-wave cone pathways.  

PubMed

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

Shinomori, Keizo; Werner, John S

2012-07-30

207

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

NASA Astrophysics Data System (ADS)

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

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

2007-04-01

208

Short-wavelength contractional structures in crustal plateau fold belts on Venus: constraints on early thermal state  

NASA Astrophysics Data System (ADS)

Marginal fold belts within Venusian crustal plateaus are characterized by contractional tectonic features showing a range of spatial wavelengths from <100 m to >30 km. Previous studies have proposed that these features are folds formed by layer-normal compression during crustal plateau formation [e.g., 1] and that the characteristic deformation wavelength(s) expressed by these features reflect the thickness of a competent surface layer during deformation [1, 2]. We investigate the conditions under which the shortest wavelength features represented in these fold belts may have formed. Specifically, we report on finite element simulations of concurrent shortening and cooling in models with uniform composition and elasto-visco-plastic (EVP) rheology. The models are constrained by observations of crustal plateau marginal fold belts using Magellan SAR imagery and are motivated by the current plume tectonic hypothesis for crustal plateau formation [2, 3]. The models are unique because a) the EVP rheology more accurately represents the actual crust than viscous or viscoelastic models; and b) our models incorporate spatially uniform material properties but temperature-dependent rheology [4], so that the strength profile through the crust evolves with cooling. This allows local thermal and stress conditions to determine the instantaneous effective surface layer thickness and strength, which in turn determines surface topographic wavelengths. We find that short-wavelength contractional features can form under hot conditions consistent with the plume scenario but do not form under cooler conditions. The final model topography results from simultaneous brittle faulting and viscous folding. We conclude that the shortest-wavelength features preserved in marginal fold belts record an early stage of crustal plateau evolution and require an elevated thermal gradient and surface temperature. [1] Ghent, R.R., and V.L. Hansen 1999. Structural and kinematic analysis of eastern Ovda Regio,Venus: Implications for crustal plateau formation, Icarus, 139, 116-136. [2] Hansen, V.L. and J.J. Willis 1998. Ribbon terrain formation, southwestern Fortuna Tessera, Venus: implications for lithosphere evolution. Icarus, 321-343. [3] Phillips, R.J. and V.L. Hansen 1998. Geological evolution of Venus: A geodynamical and magmatic framework. Science, 279,1492-1497. [4] Mackwell, S.J., M.E. Zimmerman and D.L. Kohlstedt 1998. High-temperature deformation of dry diabase with application to tectonics on Venus. JGR 103, 975-984.

Ghent, R. R.; Phillips, R. J.; Hansen, V. L.; Nunes, D. C.

2002-05-01

209

Simulation and design of optical gain in In(Al)GaN/GaN short wavelength lasers  

NASA Astrophysics Data System (ADS)

In this contribution, microscopic simulation of optical gain in GaN-based short-wavelength lasers is presented. The model is used to perform a design study of different active regions, and to discuss the impact of inhomogeneous broadening, carrier-induced screening of the piezo charges, and well thickness on material gain and laser threshold current. As a reference, the model parameters are calibrated with temperature dependent Hakki-Paoli measurements of spectral gain. Excellent agreement between measurement and simulation is achieved, which gives the design studies a quantitative character.

Witzigmann, Bernd; Laino, Valerio; Luisier, Mathieu; Roemer, Friedhard; Feicht, Georg; Schwarz, Ulrich T.

2006-04-01

210

A short-wavelength measurement of the cosmic background radiation anisotropy  

SciTech Connect

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

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

1990-09-01

211

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

NASA Astrophysics Data System (ADS)

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

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

2007-02-01

212

Short wavelength-sensitive opsins from the Saharan silver and carpenter ants.  

PubMed

We have previously cloned the opsins coding for the long-wavelength visual pigments from the Saharan silver ant and carpenter ant. Here we report two new cDNA clones isolated from cDNA libraries which also code for opsin proteins. These cDNAs code for deduced proteins with 369 amino acids which are 91% identical to each other, but only 38% identical to the previously cloned opsins. Phyletic comparisons suggest that these opsins are likely the ultraviolet sensitive visual pigments, a conclusion that is supported by the presence of a phenylalanine at the counterion position in the third transmembrane segment. PMID:9706701

Smith, W C; Ayers, D M; Popp, M P; Hargrave, P A

1997-06-01

213

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

SciTech Connect

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

Krzywinski, J.; Sobierajski, R; Jurek, M.; Nietubyc, R.; Pelka, J. B.; Juha, L.; Bittner, M.; Letal, V.; Vorlicek, V.; Andrejczuk, A.; Feldhaus, J.; Keitel, B.; Saldin, E. L.; Schneidmiller, E. A.; Treusch, R.; Yurkov, M. V. [Institute of Physics, Polish Academy of Sciences, Al. Lotnikow 32/46, PL-02-668 Warsaw (Poland); Soltan Institute for Nuclear Studies, PL-05-400 Swierk (Poland); Institute of Physics, Polish Academy of Sciences, Al. Lotnikow 32/46, PL-02-668 Warsaw (Poland); Institute of Physics, Czech Academy of Sciences, Na Slovance 2, 182 21 Prague 8 (Czech Republic); Institute of Experimental Physics, University of Bialystok, Lipowa 41, PL-15-424 Bialystok (Poland); Deutsches Elektronen-Synchrotron DESY, Notkestrasse 85, D-22603 Hamburg (Germany)

2007-02-15

214

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

PubMed

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

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

2004-12-07

215

A Fourier-Boussinesq method for short wave coastal problems  

NASA Astrophysics Data System (ADS)

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

Bingham, H. B.

2002-12-01

216

PARAMETRIC INSTABILITY OF WHISTLER WAVES IN THE ELECTRON MAGNETOHYDRODYNAMICS  

SciTech Connect

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

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

2010-05-01

217

Monitoring quality loss of pasteurized skim milk using visible and short wavelength near-infrared spectroscopy and multivariate analysis.  

PubMed

Visible and short wavelength near-infrared diffuse reflectance spectroscopy (600 to 1,100 nm) was evaluated as a technique for detecting and monitoring spoilage of pasteurized skim milk at 3 storage temperatures (6, 21, and 37 degrees C) over 3 to 30 h (control, t = 0 h; n = 3). Spectra, total aerobic plate count, and pH were obtained, with a total of 60 spectra acquired per sample. Multivariate statistical procedures, including principal component analysis, soft independent modeling of class analogy, and partial least squares calibration models were developed for predicting the degree of milk spoilage. Principal component analysis showed apparent clustering and segregation of milk samples that were stored at different time intervals. Milk samples that were stored for 30 h or less at different temperatures were noticeably separated from control and distinctly clustered. Soft independent modeling of class analogy analysis could correctly classify 88 to 93% of spectra of incubated samples from control at 30 h. A partial least squares model with 5 latent variables correlating spectral features with bacterial counts and pH yielded a correlation coefficient (R = 0.99 and 0.99) and a standard error of prediction (0.34 log(10) cfu/mL and 0.031 pH unit), respectively. It may be feasible to use short wavelength near-infrared spectroscopy to detect and monitor milk spoilage rapidly and noninvasively by correlating changes in spectral features with the level of bacterial proliferation and milk spoilage. PMID:18292250

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

2008-03-01

218

Scaling of laser produced plasma UTA emission down to 3 nm for next generation lithography and short wavelength imaging  

NASA Astrophysics Data System (ADS)

An engineering prototype high average power 13.5-nm source has been shipped to semiconductor facilities to permit the commencement of high volume production at a 100 W power level in 2011. In this source, UTA (unresolved transition array) emission of highly ionized Sn is optimized for high conversion efficiency and full recovery of the injected fuel is realized through ion deflection in a magnetic field. By use of a low-density target, satellite emission is suppressed and full ionization attained with short pulse CO2 laser irradiation. The UTA is scalable to shorter wavelengths, and Gd is shown to have similar conversion efficiency to Sn (13.5 nm) at a higher plasma temperature, with a narrow spectrum centered at 6.7 nm, where a 70% reflectivity mirror is anticipated. Optimization of short pulse CO2 laser irradiation is studied, and further extension of the same method is discussed, to realize 100 W average power down to a wavelength of 3 nm.

Li, Bowen; Endo, Akira; Otsuka, Takamitsu; O'Gorman, Colm; Cummins, Thomas; Donnelly, Tony; Kilbane, Deirdre; Jiang, Weihua; Higashiguchi, Takeshi; Yugami, Noboru; Dunne, Padraig; O'Sullivan, Gerry

2011-09-01

219

Tunable millimeter-wave frequency synthesis up to 100 GHz by dual-wavelength Brillouin fiber laser.  

PubMed

We demonstrate the generation of microwave and millimeter-wave frequencies from 26 to 100 GHz by heterodyning the output modes of a dual-wavelength fiber laser based on stimulated Brillouin scattering. The output frequency is tunable in steps of 10.3 MHz, equal to the free spectral range of the resonator. The noise properties of the beat frequency indicate a microwave linewidth of <2 Hz. We discuss potential for operation into the terahertz regime. PMID:20588461

Gross, Michael C; Callahan, Patrick T; Clark, Thomas R; Novak, Dalma; Waterhouse, Rodney B; Dennis, Michael L

2010-06-21

220

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

SciTech Connect

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

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

1985-01-01

221

Atom “meta-optics”: Negative-index media for matter waves in the nm wavelength range  

Microsoft Academic Search

Meta-optics is extended to matter waves. ldquoCo-movingrdquo magnetic fields in Stern-Gerlach interferometers allows producing negative group velocity of atomic wave packets, resulting into a negative refraction of the matter wave and atom ldquometa-lensesrdquo.

M. Hamamda; G. Dutier; M. Boustimi; V. Bocvarski; J. Grucker; F. Perales; J. Baudon; M. Ducloy

2009-01-01

222

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

Microsoft Academic Search

We present the definition, design, and construction of a 3.3X continuous-zoom short-wave infrared (SWIR) telephoto lens. Compared to visible and mid-wave infrared lenses, defining the appropriate lens requirements of short-wave lenses have some different trade-offs in terms of balancing radiometry and optimum focal plane sampling. In addition, the design process of optimizing a visible zoom design form of given first-order

Craig Olson; Tim Goodman; Chris Addiego; Steve Mifsud

2010-01-01

223

Nucleon-nucleon short-range wave function and hard bremsstrahlung pp-->ppgamma  

Microsoft Academic Search

Various opportunities to investigate the short-range NN wave function are discussed, having in mind, in particular, the quark degrees of freedom. It is shown that hard bremsstrahlung in the process pp-->ppgamma at proton beam energies of 350-500 MeV discriminates efficiently pp-wave functions with the short-range nodes in S and P waves that correspond to the Moscow potential of the NN

N. A. Khokhlov; V. A. Knyr; V. G. Neudatchin; A. M. Shirokov

2000-01-01

224

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

SciTech Connect

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

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

2005-04-21

225

Influence of temperature treatment on radiation stability of plastic scintillator and wave-length shifter  

Microsoft Academic Search

The influence of temperature treatment before or after irradiation on the radiation damage of plastic scintillators and wavelength shifters was measured. The influence of temperature treatment on the radiation stability before or after irradiation was investigated. The polymethyl-methacrylate (PMMA)-based wavelength shifters showed strong recovery in argon with heating after irradiation, whereas the polystyrene-based scintillator SCSN-38 in air suffered with heating

B. Bicken; A. Dannemann; U. Holm; T. Neumann; K. Wick

1992-01-01

226

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

NASA Astrophysics Data System (ADS)

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

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

2013-09-01

227

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

SciTech Connect

A radiometer is described for the short-wavelength part of the millimeter range for which the sensitive element is a superconducting point contact. The best value of the measured fluctuation sensitivity of the radiometer to ''blackbody'' radiation is 0.01 /sup 0/K at a time constant of 1 sec. In this case the limiting sensitivity (NEP) is approx.8x10/sup -14/ W/Hz/sup 1/2/ at an effective wavelength of 1 mm and approx.2arrow-right-left10/sup -14/ W/Hz/sup 1/2/ at 1.87 mm (at the maximum of the spectral response). Test observations of the sun and of the self-emission of the earth's atmosphere are made in the 0.9--2.8 mm range. The spectral distribution of the transmission of the earth's atmosphere is measured in the 1.0--2.1 mm region for a zenith distance of 40/sup 0/ and an absolute humidity of 4.3 g/m/sup 3/.

Antyukh, E.V.; Divin, Y.Y.; Zabolotnyi, V.F.; Nad', F.Y.

1978-07-01

228

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

2012-05-31

229

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

PubMed Central

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

2012-01-01

230

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

231

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

SciTech Connect

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

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

2009-06-15

232

Partially-degenerated four-wave-mixing assisted three-wavelength Raman fiber lasers using a Ge-doped silica fiber  

NASA Astrophysics Data System (ADS)

We report a three-wavelength Raman fiber laser (RFL) with the equal spaced wavelengths based on partially-degenerated four-wave mixing (PD-FWM) in a highly Ge-doped fiber. The FWM processes in cascaded RFLs reduce the threshold power and improve the slope efficiency for two configurations of three-wavelength RFLs. We show a comparison between two configurations of RFLs characterized by their slope efficiency and their threshold.

Im, Young-Eun; Park, Chang-Soo; Hann, Swook; Kim, Dong-Hwan

2006-10-01

233

Short wavelength heterogeneity in the Galápagos plume: Evidence from compositionally diverse basalts on Isla Santiago  

NASA Astrophysics Data System (ADS)

Analyses of basalts from the Galápagos archipelago and adjacent spreading center have shown that the underlying mantle plume is isotopically heterogeneous over length scales of 10s to 100s of km. We show that the convecting mantle is also compositionally heterogeneous on smaller length scales (kms). Our evidence comes from recent small-volume mildly alkaline and tholeiitic basalts on Isla Santiago, central Galápagos. Flows from volcanic vents <5 km apart are homogeneous in terms of incompatible-trace element and isotopic ratios but inter-vent variations in these ratios are large, such that Santiago basalts display some of the most extensive ranges known for any Galápagos island. Geochemical indexes of depth of melting correlate with an eastward decrease in geophysical estimates of lithospheric thickness-from 55 to 43 km over a ˜10 km horizontal distance beneath Isla Santiago-suggesting that melts have not undergone significant lateral transport in the underlying crust. This lithospheric `step' below the center of the island generally results in a greater proportion of enriched mantle melts contributing to basalts from west Santiago, than to those in the east, due to less melting of more depleted mantle as the plume upwells beneath thicker lithosphere. Nevertheless, the sporadic occurrence of isotopically enriched flows with low [Sm/Yb]n, and more isotopically depleted compositions with elevated [Sm/Yb]n, across Santiago suggests that portions of the underlying Galápagos plume are compositionally heterogeneous in terms of enriched and depleted reservoirs over short length scales (kilometers). In this respect the Galápagos mantle plume is similar to plumes beneath Hawaii and Canary Islands.

Gibson, S. A.; Geist, D. G.; Day, J. A.; Dale, C. W.

2012-09-01

234

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

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

235

Thermal and optical characterization of push–pull azo dye-doped poly(methylmethacrylate) thin film as short wavelength optical recording media  

Microsoft Academic Search

A new push–pull azo dye-doped polymer material has been developed for short wavelength write-once optical recording by means of a spin-coating process. The absorption spectrum of the spin-coated thin film shows a strong and broad absorption region at 400–550 nm, which matches well with the wavelength of the Ar+ laser. Thermal properties indicate that the rapid decomposition of the azo

Guangbin Wang; Lisong Hou; Fuxi Gan

1999-01-01

236

Power MOSFET's for medium-wave and short-wave transmitters  

NASA Astrophysics Data System (ADS)

This paper describes design and performance of a high-frequency power MOST used for switching-mode power amplifiers in the medium-wave (500 kHz to 1.5 MHz) or short-wave (1.5 MHz to 30 MHz) transmitters whose output power is in the vicinity of 1 kW. To obtain the drain-source voltages greater than 200 V with on-resistance remaining approximately 1 Ohm, the offset gate length and field plate length of the high-frequency power MOST are optimized as well as offset gate layer concentration. Employing the molybdenum gate fabricated by RF diode sputter, the MOST operates at high speed with turn-on and turn-off times of 22 and 25 ns, respectively. A high-temperature operation test was performed to assure the stability and reliability of the device. The test results indicate that phosphosilicate glass polarization affects the device reliability only when offset gate layer concentration is much lower than the optimized value.

Ikeda, H.; Ashikawa, K.; Urita, K.

1980-02-01

237

Numerical modeling of long-wavelength vertical-cavity surface-emitting semiconductor lasers. I. Continuous-wave modeling  

NASA Astrophysics Data System (ADS)

Long-wavelength vertical-cavity surface-emitting semiconductor lasers are investigated and heating effects on the light vs. current characteristics of VCSELs are analyzed by thermal-electric, optical, and electronic modeling. The model includes nonuniform current injection, carrier diffusion, stimulated emission, distributed heat sources, and active material band structure calculations. Device parameters such as threshold current, and external quantum efficiency are evaluated. Simulated power vs. current characteristics exhibit the typical thermal roll-over in continuous wave operation. The model is applied to two specific optimized underetched structure designs in order to provide an understanding of the current-funneling mechanism and the thermal limitations of such devices.

Tsigopoulos, A.; Paschos, V.; Salet, Paul; Jacquet, Joel

1998-07-01

238

Ultra-short-wave propagation in the jungle  

Microsoft Academic Search

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

C. Burrows

1966-01-01

239

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

240

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

241

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

242

Scattered P'P' waves observed at short distances  

USGS Publications Warehouse

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

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

2011-01-01

243

Vein structures, like ripple marks, are formed by short-wavelength shear waves  

Microsoft Academic Search

Vein structure, a distinctive structure in deep-sea hemipelagic clayey and siliceous mudstones at convergent plate boundaries, consists of closely spaced mud-filled veins forming an array usually parallel to the bedding plane. This structure has been regarded as a seismite that formed during earthquake shaking by resonance of fractures. Our detailed field observations and shaking model experiments verified that both basic

Tsuneo Ohsumi; Yujiro Ogawa

2008-01-01

244

Scattering from an elliptical cylindrical plasma for electromagnetic waves with wavelength much greater than the dimensions of the plasma cross-section  

Microsoft Academic Search

The distribution of the electric potential inside and outside a cold plasma column with elliptical cross-section when electromagnetic waves scatter from it are obtained. It is assumed that the wavelength of incident wave is much greater than the dimensions of the cross section of the plasma column. The electrical potential inside and outside a magnetized elliptical plasma column for an

A. Abdoli-Arani; R. Ramezani-Arani; B. Jazi; S. Golharani

2012-01-01

245

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

246

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

247

Skin damage thresholds with continuous-wave laser exposures at the infrared wavelength of 1319 nm  

NASA Astrophysics Data System (ADS)

ABSTRACT Damage thresholds (ED50) for skin using Yucatan mini-pig (Sus scrofa domestica) have been determined at the operational wavelength of 1319 nm with beam diameters of 0.61 cm and 0.96 cm. Exposure durations of 0.25, 1.0, 2.5 and 10 seconds were used to determine trends in damage threshold with respect to exposure time and beam diameter at this moderately-high penetrating wavelength. A relatively narrow range of total radiant exposure from 37.4 J/cm2 to 62.3 J/cm2 average was observed for threshold damage with laser parameters encompassing a factor of two in beam area and a factor of forty in exposure duration.

Oliver, Jeffrey W.; Harbert, Corey A.; Noojin, Gary D.; Noojin, Isaac D.; Schuster, Kurt J.; Shingledecker, Aurora D.; Stolarski, David J.; Kumru, Semih S.

2011-02-01

248

Interferometric Observation at Mid-Infrared Wave-lengths with MIDI  

Microsoft Academic Search

MIDI, the MID-Infrared Interferometricnterferometric Instrument for ESO's Very Large Telescope Interferometer (VLTI), will be the first instrument for combining\\u000a mid-infrared light directly in order to obtain angular resolution up to 10 mas (assuming a 200 m baseline) in a wavelength\\u000a range from 8 to 13 ?m. Currently in the phase of commissioning at Paranal, the start of its scientific operation

Frank Przygodda; O. Chesneau; U. Graser; Ch. Leinert; S. Morel

2003-01-01

249

Continuous-Wave Dual-Wavelength Nd:YAG Ceramic Laser at 1112 and 1116 nm  

NASA Astrophysics Data System (ADS)

An efficient dual-wavelength laser-diode-pumped Nd:YAG ceramic laser operating at 1112 and 1116nm is demonstrated. We obtain a maximum total output power of 3.43 W including a 1.77W 1112nm component and a 1.66W 1116nm component under a pump power of 16.1 W, corresponding to a slope efficiency of 23.7% and a total optical-to-optical efficiency of 21.3%.

Zhang, Hua-Nian; Chen, Xiao-Han; Wang, Qing-Pu; Li, Ping

2013-10-01

250

Short-wave limit of the gravitational focusing effect imposed by asphericity of the gravity field of the lens star  

SciTech Connect

At short wavelengths (visible light, x rays, ..gamma.. rays), the gravitational focusing effect will be significantly influenced by deviations of the gravitational field of the lens star from sphericity. The dependence of the lens amplification on the wavelength lambda of the electromagnetic wave and on the asphericity of the gravitational field is analyzed qualitatively. There is a limiting wavelength lambda/sub min/ below which asphericity effects become important. For a homogeneous model ellipsoid of revolution with a relative oblateness of 5 x 10/sup -5/, a gravitational radius r/sub g/=3 km, and a mean radius R=7 x 10/sup 5/ km, the limit will be lambda/sub min/approx. =5(R/l)/sup 2/ cm, where l=2r/sub g//(D/sub s//sup -1/ +D/sub p//sup -1/))/sup 1/2/ (D/sub s/, D/sub p/ are the distances from the lens to the source and the observer, respectively).

Minakov, A.A.

1978-09-01

251

Particle precipitation induced by short-duration VLF waves in the magnetosphere  

Microsoft Academic Search

An extension of a previous test particle simulation model (Inan et al.,1978) of the gyroresonance wave-particle interaction in the magnetosphere is used to compute the detailed time variation of the precipitated energy flux induced by monochromatic short-duration VLF waves. The resulting precipitation pulse is found to have a characteristic shape dependent on the L value, a cold plasma density wave

T. F. Bell; H. C. Chang

1982-01-01

252

[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

253

Spectroscopy and wavelength conversion by four-wave mixing in semiconductor optical amplifiers  

Microsoft Academic Search

The first part of this thesis is dedicated to the study of the physics of the four-wave mixing (FWM) optical non- linearity in semiconductor optical amplifiers (SOAS). We focus our attention on the polarization properties of FWM and spectroscopic measurements of ultrafast carrier dynamics in these amplifiers. The second part presents investigations of FWM applications in the context of high-speed

Guido H. Hunziker

1998-01-01

254

High Frequency Drift Waves with Wavelengths Below the Ion Gyroradius in Equatorial Spread F.  

National Technical Information Service (NTIS)

Evidence is given for intense VHF and UHF radar backscatter during equatorial Spread F resulting from irregularities of 1 meter and 36 cm, respectively. The linear theory for high frequency drift waves, generated by the drift-cyclotron and lower-hybrid-dr...

D. M. Towle J. D. Huba P. K. Chaturvedi S. L. Ossakow

1978-01-01

255

High performance guided-wave heralded single photon source at telecom wavelength  

NASA Astrophysics Data System (ADS)

We report on a guided wave asynchronous heralded photon source based on the creation of non-degenerate photon pairs by spontaneous parametric down conversion in a Periodically Poled Lithium Niobate waveguide. We show that using the signal photon at 1310\

Alibart, O.; Tanzilli, S.; Ostrowsky, D. B.; De Micheli, M. P.; Baldi, Pascal

2005-07-01

256

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

Microsoft Academic Search

Atherosclerosis and specifically rupture of vulnerable plaques account for 23% of all deaths worldwide, far surpassing both infectious diseases and cancer. In atherosclerosis, macrophages can infiltrate plaques which are often associated with lipid deposits. Photothermal wave imaging is based on the periodic thermal modulation of a sample using intensity modulated light. Intensity modulated light enters the sample and is absorbed

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

2010-01-01

257

STUDY OF EFFECT OF RAIN AND DUST ON PROPAGATION OF RADIO WAVES AT MILLIMETER WAVELENGTH  

Microsoft Academic Search

The propagation of Electromagnetic waves in millimeter band is severely affected by rain rate, drop size and dust particle size in terms of attenuation, de-polarization and noise. The vertical looking radiometers will give vertical path attenuation due to rain as well as dust and line of sight link will give horizontal path attenuation whereas the satellite link gives slant path

O. P. N. Calla; J. S. Purohit

258

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

NASA Astrophysics Data System (ADS)

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

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

2010-12-01

259

Wavelength-dependence of momentum-space images of low-energy electrons generated by short, intense laser pulses at high intensities  

Microsoft Academic Search

We have measured highly resolved momentum-space images of low energy electrons generated by the interaction of short intense laser pulses with argon atoms at high intensities (tunneling regime). We have done this over a wavelength range from 400 to 800 nm. The spectra show considerable structure in both the energy and angular distributions of the electrons. Some, but not all,

Chakra Maharjan; Ali Alnaser; Predrag Ranitovic; Igor Litvinyuk; Charles Cocke

2006-01-01

260

Long-wave explicit and Short-wave implicit (LESI) treatment of the barotropic mode to accurately calculate slow modes in ocean models  

NASA Astrophysics Data System (ADS)

Many ocean models are primarily concerned with calculating currents of slowly propagating modes that are dynamically associated with buoyancy, Coriolis, field accelerations, and slowly-varying forcing. Calculating such slow modes involves adjustments by the very much faster barotropic mode. In order to minimize the computational cost, two approaches are commonly used. The split-explicit method solves for both fast and slow modes explicitly but with different time steps. The semi-implicit method uses the same time step for fast and slow modes but treats the fast barotropic waves implicitly and the slow modes explicitly. The present work demonstrates a refinement to the semi-implicit method. Weighted Jacobi iterations are used to low-pass filter the fast barotropic mode so that long wavelengths can be treated explicitly. The short-wave part of the fast barotopic mode is still treated implicitly. Damping of the fast barotropic modes is less severe than for the corresponding implicit calculation. Importantly, tests show that a slow internal wave is accurately modelled and the solution is stable, even with the addition of barotropic noise. The method is demonstrated using a three-dimensional model of a lagoon system.

Sanderson, Brian G.

261

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

NASA Astrophysics Data System (ADS)

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

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

2010-07-01

262

Inter-hemispheric Comparison of Mesospheric Short-period Gravity Wave Propagation  

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 airglow imaging measurements over Antarctica have revealed a large number of short-period gravity waves in absence of the prominent wave sources present at lower latitudes. In contrast to results at lower latitudes, very few waves (˜5%) observed over Halley (76°S) exhibited Doppler ducted motion. In this work, we utilize airglow imagery, SABER temperature measurements, together with the Navy's high-altitude numerical weather prediction system, NOGAPS-ALPHA, to investigate propagation conditions (particularly, the role of thermal ducting) over Rothera (68°S). Data acquired from a newly installed airglow imager operating at Poker Flat, Alaska (65°N) and the co-located lidar provide an opportunity to perform an inter-hemispheric comparison of propagation conditions over two polar sites at similar latitudes.

Nielsen, K.; Taylor, M. J.; Collins, R. L.; Irving, B. K.; Negale, M.; Siskind, D. E.; Eckermann, S. D.; Hoppel, K.; Harvey, V.; Russell, J. M.

2011-12-01

263

The Half-Width Microstrip Leaky Wave Antenna With the Periodic Short Circuits  

Microsoft Academic Search

A half-width microstrip leaky wave antenna (LWA) with peri- odic short circuits is presented. The backward-to-forward beam-scanning capability is achieved by periodic construction. The proposed antenna con- sists of a long rectangular patch with the short circuits that are placed with a series of shorting pins between the antenna patch and the ground plane periodically. The measurement results show that

Yuanxin Li; Quan Xue; Hong-Zhou Tan; Yunliang Long

2011-01-01

264

Widely-tunable parametric short-wave infrared transmitter for CO2 trace detection.  

PubMed

An all-fiber, tunable, short-wave infrared transmitter is demonstrated using efficient four-wave mixing in conventional L and O bands. To realize this source a highly-nonlinear fiber, exhibiting low bend loss over the short-wave infrared spectral band, is employed because of its advantageous properties as a nonlinear mixing medium. The transmitter was subsequently exploited to probe and detect trace levels of carbon dioxide in the 2051-nm spectral region where its beam properties, tunability, narrow linewidth, and stability all coalesce to permit this application. This work indicates this transmitter can serve as a robust source for sensing carbon dioxide and other trace gasses in the short-wave infrared spectral region and should therefore play an important role in future applications. PMID:21643067

Moro, Slaven; Danicic, Aleksandar; Alic, Nikola; Usechak, Nicholas G; Radic, Stojan

2011-04-25

265

Harmonic Non-Axisymmetric Waves with Short Wave Lengths Propagating in Composite Rods.  

National Technical Information Service (NTIS)

The asymptotic phase velocities at very large wave numbers of non-axisymmetric waves, traveling in composite rods are established analytically. Frequency spectra and mode shapes of composite rods are presented and compared with those of simple (made of on...

A. E. Armenakas H. E. Keck

1969-01-01

266

High frequency drift waves with wavelengths below the iron gyroradius in equatorial spread F  

Microsoft Academic Search

Evidence is given for intense VHF and UHF radar backscatter during equatorial Spread F resulting from irregularities of 1 meter and 36 cm, respectively. The linear theory for high frequency drift waves, generated by the drift-cyclotron and lower-hybrid-drift instabilities, is presented. This linear theory is set forth as a possible explanation for the occurrence of these irregularities below the ion

J. D. Huba; P. K. Chaturvedi; S. L. Ossakow; D. M. Towle

1978-01-01

267

High frequency drift waves with wavelengths below the ion gyroradius in equatorial spread F. Interim report  

Microsoft Academic Search

Evidence is given for intense VHF and UHF radar backscatter during equatorial Spread F resulting from irregularities of 1 meter and 36 cm, respectively. The linear theory for high frequency drift waves, generated by the drift-cyclotron and lower-hybrid-drift instabilities, is presented. This linear theory is set forth as a possible explanation for the occurrence of these irregularities below the ion

J. D. Huba; P. K. Chaturvedi; S. L. Ossakow; D. M. Towle

1978-01-01

268

Investigation of wavelength-specific characteristics of quasi- and millimeter-waves  

Microsoft Academic Search

The validity of the safety guidelines of quasi- and millimeter-waves was evaluated by measuring ocular temperature during exposure. The cornea, lens, and vitreous temperatures of rabbits were recorded during 26.5, 35, and 40 GHz quasi- and millimeter-exposures under four conditions: 1) in vivo, 2) after sacrifice, 3) air substitution of the aqueous humor, and 4) after removal of both the

M. Kojima; T. Sakai; Y. Yamashiro; Y. Suzuki; A. Hirata; Y. Sakamoto; Y. Kawakami; S. Watanabe; K. Wake; M. Taki; Y. Kamimura; H. Sasaki; K. Sasaki

269

Fully guided gravity waves at short periods and gravity wave-critical layer interaction  

Microsoft Academic Search

Gravity waves play a dominant role in establishing the thermal, wind, and constituent structure throughout the middle atmosphere and are especially important in the mesopause region where wave amplitudes are very large. Studies of gravity waves are now receiving increasing attention because of their effects on the global change problems. The Airborne Lidar and Observations of Hawaiian Airglow (ALOHA-93) Campaign

Hyunmin Hur

1998-01-01

270

Terahertz Surface Waves Propagating on Metals with Sub-wavelength Structure and Grating Reliefs  

NASA Astrophysics Data System (ADS)

Due to their long propagation length at a metal surface in the far infrared, surface plasmons make potentially feasible the design and realization of 2D integrated terahertz systems over a metallic substrate. In this article, we present a review of recent works dedicated to surface plasmon properties on structured metallic surfaces. We study excitation, propagation, diffraction and reflection of terahertz surface plasmon on shallow gratings and of spoof plasmons on deep sub-wavelength structures. The analysis of the experimental data supplied by terahertz time-domain spectroscopy allows us to point out the main parameters that govern this diffraction process and the propagation of a surface plasmon over a flat or corrugated metal surface.

Nazarov, M.; Coutaz, J.-L.

2011-10-01

271

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

PubMed Central

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

Eisner, Alvin; Demirel, Shaban

2009-01-01

272

Short-wavelength chemical lasers driven by intense light source. Final report, 15 August 1985--15 August 1987  

SciTech Connect

The goal of this research effort has been to assess the possibility of producing a short-wavelength chemical laser system pumped by an intense light source. The lasing systems that we have concentrated on are XeCl, which emits at 308 mn, and Xe{sub 2}Cl, with a peak emission at 480 nm. The latter is favored in systems with high Xe concentrations. Both systems have been demonstrated to be efficient lasers when discharge or electron-beam pumping is utilized. We have considered pumping by an intense, blackbody (Planckian) light source. Thus, we have studied the excimer fluorescence yield over a wide range of excitation energies accessible with a 40,000 K blackbody (6.4 to > 12.8 eV) source. Several photochemical reaction channels have been identified in Xe/Cl{sub 2} mixtures that produce the desired excimers. The scaling of the fluorescence yield with reactant pressure has been studied for each reaction mechanism. The reaction channels scale differently with reactant pressure, causing the scaling behavior of the total fluorescence output to be interrelated and complex. Quenching processes in the excimer systems have been studied and a rate constant for quenching of Xe{sub 2}Cl by CCl{sub 4}, an alternative chlorine source, has been measured. The efficiency of coupling radiant energy into the excimer system via absorption by Cl{sub 2} or collision-induced absorption by Xe-Cl{sub 2} collision pairs in the vacuum-UV (VUV) region of the spectrum remain two major unknown factors in assessing the system performance.

Berman, M.R.; Bragg, S.L. [McDonnell Douglas Research Labs., St. Louis, MO (United States)

1987-12-31

273

New optical probe using ZnO whiskers: analyses . of sub-wavelength dithering and evanescent wave propagation  

NASA Astrophysics Data System (ADS)

Elaborating nanoprobes with a very sharp tip is a great challenge in near-field microscopies. Attainable resolutions are closely dependent on the tip apex curvature radius. In this paper, we present a new method for obtaining nanoprobes by placing a ZnO whisker at the extremity of an electrochemically etched tungsten tip. We have fabricated thus a nanoprobe whose final dimension varies from 100 to 20 nm. As a proof, we immersed the tip extremity into an evanescent wave created using a conventional STOM-architecture microscope. We also show that the diffracted light collects laterally at the glass/air interface. Finally, we demonstrate that it is possible to detect optically the dithering of a sub-wavelength probe.

Pieralli, C.; Hoummady, M.

274

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

275

Metal-mesh achromatic half-wave plate for use at submillimeter wavelengths.  

PubMed

A metal-mesh achromatic half-wave plate (HWP) has been designed, manufactured, and tested for potential use in millimeter and submillimeter astronomical instruments. The prototype device presented here is based on a 12-grid Shatrow [IEEE Trans. Antennas Propag. 43, 109 (1995)] recipe to operate over the frequency range of 120-180 GHz. Transmission line modeling and finite-element analysis [Ansoft HFSS website: http://www.ansoft.com/hfss/] were used to optimize the design geometrical parameters in terms of the device transmission, reflection, absorption, phase-shift, and cross-polarization as a function of frequency. The resulting prototype device was constructed and characterized using incoherent radiation from a polarizing Fourier transform spectrometer to explore its frequency and polarization behavior. These measurements are shown to be in excellent agreement with the models. Lists of the achieved HWP performance characteristics are reported. PMID:19023391

Pisano, Giampaolo; Savini, Giorgio; Ade, Peter A R; Haynes, Vic

2008-11-20

276

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

277

Ponderomotive effect on electron acceleration by plasma wave and betatron resonance in short pulse laser  

SciTech Connect

The ponderomotive force at the front of an intense short pulse laser, propagating through a plasma, strongly influences the acceleration of electrons by a plasma wave or by the laser itself via betatron resonance in self-generated azimuthal magnetic field. It can enhance the electron energy gain several fold through the sustainment of the electron in the accelerating phase of the plasma wave and the laser beam.

Liu, C.S.; Tripathi, V.K. [National Central University, Chung Li 320, Taiwan (China)

2005-04-15

278

Dynamics of bright soliton bound states in ( 2+1)-dimensional multicomponent long wave-short wave system  

NASA Astrophysics Data System (ADS)

In this paper, we construct the bright-soliton bound states of an integrable (2 + 1)-dimensional multicomponent long wave-short wave resonance interaction (LSRI) system by using the exact bright-soliton solutions obtained in Ref. [24] and analyze their interesting collision dynamics. We show that the beating and breathing oscillations of the bound solitons can be controlled by tuning the polarization parameters. Also, we explore the interaction between the bound-soliton and a standard soliton. We also point out that the two bound-soliton state seems to be robust against collision with a standard soliton and remain to be bounded even after collision.

Sakkaravarthi, K.; Kanna, T.

2013-07-01

279

Low-frequency spectra in a harbour excited by short and random incident waves  

NASA Astrophysics Data System (ADS)

We present a spectral theory of the low-frequency response of a harbour to short and random incident waves. Assuming the incident sea to be stationary and Gaussian, nonlinear extensions are made for the response spectrum. Advantage is taken of the typical wind-wave spectrum which is dominated by high-frequency components. After showing that nonlinearity is needed only up to the second order in wave steepness, we extend the mild-slope approximation for constructing the transfer functions. Numerical examples are presented for a square harbour and constant depth. Discounting friction losses, the effects of different entrances are compared.

Chen, Meng-Yi; Mei, Chiang C.; Chang, Chien-Kee

2006-09-01

280

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

Microsoft Academic Search

In this study we report on ground-based observations of short bursts of relativistic electron precipitation (REP), detected by a subionospheric propagation sensor in Sodankylä, Finland during 2005. In two ~4 hour case study periods from L = 5.2, around local midnight, several hundred short-lived radio wave perturbations were observed, covering a wide range of arrival azimuths. The vast majority (~99%)

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

2007-01-01

281

Currents and Charges Induced in an Arbitrarily Oriented Electrically Thin Conductor with Length up to One and One-Half Wavelengths in a Plane-Wave Field  

Microsoft Academic Search

Distributions of induced current and charge per unit length are displayed for electrically thin antennas not longer than one and one-half wavelengths that are illuminated by an incident plane wave. It is shown that the distributions of current and charge have significant even and odd parts which vary with the angle of incidence.

R. W. P. King; A. W. Glisson; S. Govind; R. D. Nevels; J. O. Prewitt

1977-01-01

282

Reconnection of magnetic field lines through an electrostatic wave  

Microsoft Academic Search

The effect of a short-wavelength electrostatic wave on the rate of reconnection of magnetic field lines by a growing long-wavelength tearing mode is investigated. The influence of the electrostatic wave depends strongly on the parity of the wave potential about the resonant surface of the tearing mode and on the relative magnitude of the plasma resistivity &eegr; and viscosity ?,

Robert G. Kleva

1991-01-01

283

A numerical study of capillary-gravity waves  

Microsoft Academic Search

Surface tension provides a restoring force which cannot be ignored for water waves of short wavelengths. Even for large wavelengths its presence precludes any sharp corner developing on the free surface. Here, the effects of surface tension on steep water waves are investigated numerically; the periodic progressive capillary-gravity waves under resonant conditions and their time-marching results are discussed as well

Jin Huh

1991-01-01

284

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

NASA Astrophysics Data System (ADS)

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

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

2012-02-01

285

Upper Meter Processes: Short Wind Waves, Surface Flow, and Micro- Turbulence.  

National Technical Information Service (NTIS)

The primary goal of this project is to advance the knowledge of small-scale air-sea interaction processes at the ocean surface, focussing on the dynamics of short waves, the surface flow field and the microturbulence. Since ground truth on the small-scale...

B. Jaehne J. Klinke X. Zhang

1998-01-01

286

Rapidly swept, continuous-wave cavity ringdown spectroscopy with optical heterodyne detection: single- and multi-wavelength sensing of gases  

NASA Astrophysics Data System (ADS)

Spectroscopic sensing of gases can be performed with high sensitivity and photometric precision by cavity ringdown (CRD) absorption spectroscopy. Our cavity ringdown spectrometer incorporates continuous-wave (cw) tunable diode lasers, fibre-optic coupling and standard photonics and optical telecommunications components. It comprises a rapidly swept optical cavity in a single-ended optical heterodyne transmitter-receiver configuration, enabling optical absorption of gases to be recorded either as single-frequency scanned spectra or as simultaneous, multi-wavelength tailored spectra. By measuring weak near-infrared rovibrational spectra of carbon dioxide gas (CO2), with high resolution in the vicinity of 1.53 ?m, we have realised a noise-limited absorption sensitivity of 2.5×10-9 cm-1 Hz-1/2. Analytical sensitivity limits (both actual and projected) and prospective gas-diagnostic applications are discussed. Our approach to cw-CRD spectroscopy offers high performance in a relatively simple, low-cost, compact instrument that is amenable to chemical analysis of trace gases in medical, agricultural, industrial and environmental situations.

He, Y.; Orr, B. J.

287

Wavelength-resonant enhanced gain/absorption structure for standing-wave optoelectronic devices and its application to surface-emitting semiconductor lasers  

SciTech Connect

A novel design for optoelectronic devices which utilize interaction between electromagnetic standing wave and carrier population is described. The structure consists of quantum well layers spaced at one half the wavelength of a particular optical transition in quantum wells. In such periodic medium, the gain (or absorption) for a selected wavelength determined by the periodicity is enhanced by a factor of two compared to uniform medium. The design has been implemented experimentally by growing a surface-emitting semiconductor laser structure in GaAs/AlGaAs system and have demonstrated lasing with the shortest gain medium length (320 nm) ever reported for a semiconductor laser. 7 refs., 4 figs.

Raja, M.Y.A.; Brueck, S.R.J.; Osinski, M.; Schaus, C.F.; McInerney, J.G.; Brennan, T.M.; Hammons, B.E.

1988-01-01

288

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

NASA Astrophysics Data System (ADS)

The exact ground state of a strongly interacting quantum many-body system can be obtained by evolving a trial state with finite overlap with the ground state to infinite imaginary time. In many cases, since the convergence is exponential, the system converges essentially to the exact ground state in a relatively short time. Thus a short-time evolved wave function can be an excellent approximation to the exact ground state. Such a short-time-evolved wave function can be obtained by factorizing, or splitting, the evolution operator to high order. However, for the imaginary time Schrödinger equation, which contains an irreversible diffusion kernel, all coefficients, or time steps, must be positive. (Negative time steps would require evolving the diffusion process backward in time, which is impossible.) Heretofore, only second-order factorization schemes can have all positive coefficients, but without further iterations, these cannot be used to evolve the system long enough to be close to the exact ground state. In this work, we use a newly discovered fourth-order positive factorization scheme which requires knowing both the potential and its gradient. We show that the resulting fourth-order wave function alone, without further iterations, gives an excellent description of strongly interacting quantum systems such as liquid 4He, comparable to the best variational results in the literature. This suggests that such a fourth-order wave function can be used to study the ground state of diverse quantum many-body systems, including Bose-Einstein condensates and Fermi systems.

Ciftja, Orion; Chin, Siu A.

2003-10-01

289

A mechanism of the effect of non-uniform current on the spectrum of short wind waves  

Microsoft Academic Search

A mechanism is suggested in this paper concerning the effect of non-uniform current on the spectrum of short wind waves. According\\u000a to this mechanism, a non-uniform current brings changes to the breaking criteria of short wind waves through modulating the\\u000a surface drift, and hence enhances or weakens wave breaking. Some modification is proposed to the source term, which represents\\u000a the

Guizhen Zheng; Lifang Sheng; Peixiu Cong

2004-01-01

290

Wakefield effects and solitary waves of an intense short laser pulse propagation in a plasma channel  

SciTech Connect

In the presence of relativistic and channel-coupling nonlinearity and wakefield effects, the propagation characteristics and solitary waves of an intense short laser pulse in a preformed plasma channel are investigated. The evolution equation of the laser spot size is derived by using variational technique, the initial laser and plasma parameters for propagation with constant spot size, periodic defocusing and focusing oscillations, and solitary waves are identified. For illustration, some numerical results are also presented. It is found that the laser focusing is enhanced by the wakefield effects that result in a significant reduced focusing power.

Hong Xueren [College of Nuclear Science and Technology, Beijing Normal University, Beijing 100875 (China); College of Physics and Electronic Engineering, Northwest Normal University, Lanzhou 730070 (China); Xie Baisong; Zhao Xueyan [College of Nuclear Science and Technology, Beijing Normal University, Beijing 100875 (China); Zhang Shan [College of Nuclear Science and Technology, Beijing Normal University, Beijing 100875 (China); Department of Mathematics and Physics, Shijiazhuang Tiedao University, Shijiazhuang 050043 (China); Wu Haicheng [Center for Applied Physics and Technology, Peking University, Beijing 100084 (China)

2011-10-15

291

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

292

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

293

Polarization measurement of SR from a helical undulator using a quarter-wave plate for a wavelength of 12.8 nm  

Microsoft Academic Search

At a wavelength of 12.8 nm, polarization states of nominally circularly polarized light emitted from a helical undulator and monochromatized by a grating monochromator were measured (KEK-PF BL-28A). With a transmission-type multilayer quarter-wave plate and a multilayer mirror polarization analyzer mounted on a beamline ellipsometer, all polarization parameters of the circularly polarized SR at various conditions were determined. The best

H. Kimura; T. Miyahara; Y. Goto; K. Mayama; M. Yanagihara; M. Yamamoto

1995-01-01

294

Short-period AM CVn systems as optical, X-ray and gravitational wave sources  

Microsoft Academic Search

We model the population of AM CVn systems in the Galaxy and discuss the\\u000adetectability of these systems with optical, X-ray and gravitational wave\\u000adetectors. We concentrate on the short period (P < 1500 s) systems, some of\\u000awhich are expected to be in a phase of direct impact accretion. Using a\\u000aself-consistent model for the star formation history and

G. Nelemans; L. R. Yungelson; S. F. Portegies Zwart

2003-01-01

295

Magnetic Effects on Short-Wave Convective Cells in Finite-Pressure Plasma  

Microsoft Academic Search

Within the context of the general theory of low-frequency electromagnetic plasma fluctuations, the stationary spectra of short-wave convective and magnetostatic perturbations and the heat conductivity coefficient in finite-pressure plasma with betae ˜ betaI ˜ 1, are obtained. It is shown that the nonlinear broadening of the potential spectrum can be determined by the magnetic field fluctuations when betae ˜ 1.

Maxim O. Vakulenko; Petro P. Sosenko

2000-01-01

296

MODELING SHORT-PERIOD SURFACE WAVES FROM SMALL EXPLOSIONS AT THE SHAGAN TEST SITE  

Microsoft Academic Search

The objective of our research is to study the generation and propagation of short-period (0.2 to 12 secs) surface waves from a variety of different classifications of explosions. Thus, we have assembled a dataset of local and regional recordings of single-fired chemical explosions (Non-Proliferation Experiment and Balapan Depth of Burial shots), coal-mining explosions (including cast and coal shots from northern

Jessie L. Bonner; Jeffrey L. Orrey

297

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

298

Prediction of clear-air turbulence induced by short gravity waves  

Microsoft Academic Search

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

Jacek M Kope?; Krzysztof E Haman; Konrad Bajer

2011-01-01

299

Millimeter-wave backscatter diagnostic for the study of short scale length plasma fluctuations (invited)  

Microsoft Academic Search

The development, laboratory tests, and experimental results relating to a new high-k diagnostic technique for the study of short scale length turbulence are reported. The system is based on backscattering of a millimeter-wave (94 GHz) probe beam by density fluctuations within the plasma. This diagnostic has been fully integrated with an upgraded far-infrared forward scattering system on the DIII-D tokamak.

T. L. Rhodes; W. A. Peebles; X. Nguyen; M. A. VanZeeland; J. S. deGrassie; E. J. Doyle; G. Wang; L. Zeng

2006-01-01

300

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

Microsoft Academic Search

Near-infrared spectroscopy (NIRS) with the characteristics of high speed, non-destructiveness, high precision and reliable detection data, etc. is a pollution-free, rapid, quantitative and qualitative analysis method. A new approach for variety discrimination of brown sugars using short-wave NIR spectroscopy (800-1050nm) was developed in this work. The relationship between the absorbance spectra and brown sugar varieties was established. The spectral data

Haiqing Yang; Di Wu; Yong He

2007-01-01

301

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

302

Development and application of a quality control procedure for short-wave diathermy units  

Microsoft Academic Search

Short-wave diathermy (SWD) is a form of radiofrequency (RF) radiation, operating at 27.12 MHz, that is used therapeutically\\u000a by physiotherapists. Although this form of therapy is widely available, the management of the equipment is not often addressed\\u000a by either physiotherapists or by medical physics\\/clinical engineering. A quality control protocol for SWD units, examining\\u000a power output and electrical and mechanical condition,

N. Shields; N. O'Hare; G. Boyle; J. Gormley

2003-01-01

303

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

Microsoft Academic Search

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

Martin Wild

304

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

305

Depth-varying Eddy Viscosity and Short-wave Forcing in SHORECIRC  

NASA Astrophysics Data System (ADS)

The quasi-3D nearshore circulation model SHORECIRC developed at the University of Delaware (Svendsen et al 2002) is based on the mathematical frame work of Putrevu and Svendsen (1999). In that work, they determine the horizontal variation of the depth-averaged velocities from the short-wave-averaged depth-integrated horizontal momentum equations. These equations include depth integrals of the depth varying velocities which act as a momentum dispersive mixing mechanism. The depth-dependent velocities are solved from the local non-integrated momentum equations and use to evaluate the integrals in the depth averaged momentum equations. The only assumption invoked in Putrevu and Svendsen (1999) is the hydrostatic pressure. However, when applying Putrevu and Svendsen (1999)'s work to the numerical model SHORECIRC, further simplifications, such as using depth-uniform eddy viscosity and shallow water theory for the short wave forcing are introduced, enabling the 3D dispersive terms to be integrated analytically. In the present work, we will extend the SHORECIRC to relaxing these simplifications to include the depth-varying forcing and eddy viscosity. To achieve this, the Chebyshev polynomials are utilized to approximate the short-wave-forcing and eddy viscosity. The 3D dispersive terms are therefore solved numerically. As the first step, we will investigate the effect of depth-varying forcing and eddy viscosity on longshore and cross-shore currents in different situations including rip currents.

Zhao, Q.; Svendsen, I. A.; Haas, K. A.

2002-12-01

306

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

NASA Astrophysics Data System (ADS)

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

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

2013-05-01

307

FAST TRACK COMMUNICATION: The collision of multimode dromions and a firewall in the two-component long-wave-short-wave resonance interaction equation  

NASA Astrophysics Data System (ADS)

In this communication, we investigate the two-component long-wave-short-wave resonance interaction equation and show that it admits the Painlevé property. We then suitably exploit the recently developed truncated Painlevé approach to generate exponentially localized solutions for the short-wave components S(1) and S(2) while the long wave L admits a line soliton only. The exponentially localized solutions driving the short waves S(1) and S(2) in the y-direction are endowed with different energies (intensities) and are called 'multimode dromions'. We also observe that the multimode dromions suffer from intramodal inelastic collision while the existence of a firewall across the modes prevents the switching of energy between the modes.

Radha, R.; Senthil Kumar, C.; Lakshmanan, M.; Gilson, C. R.

2009-03-01

308

Harmonic generation beyond the Strong-Field Approximation: the physics behind the short-wave-infrared scaling laws.  

PubMed

The physics of laser-mater interactions beyond the perturbative limit configures the field of extreme non-linear optics. Although most experiments have been done in the near infrared ( lambda wavelengths (<5 microm), opening new perspectives in the synthesis of shorter XUV attosecond pulses and higher frequencies. The theory of intense-field interactions is based either on the exact numerical integration of the time-dependent Schrödinger equation or in the development of models, mostly based on the strong-field approximation. Recent studies in the short-wave infrared show a divergence between the predictions of these models and the exact results. In this paper we will show that this discrepancy reveals the incompleteness of our present understanding of high-order harmonic generation. We discuss the physical grounds, provide a theoretical framework beyond the standard approximations and develop a compact approach that accounts for the correct scaling of the harmonic yield. PMID:19506639

Pérez-Hernández, J A; Roso, L; Plaja, L

2009-06-01

309

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

PubMed

Field trial results of a 5 W all-fiber broadband supercontinuum (SC) laser covering the short-wave infrared (SWIR) wavelength bands from ?1.55 to 2.35 ?m are presented. The SC laser is kept on a 12 story tower at the Wright Patterson Air Force Base and propagated through the atmosphere to a target 1.6 km away. Beam quality of the SC laser after propagating through 1.6 km is studied using a SWIR camera and show a near diffraction limited beam with an M2 value of <1.3. The SC laser is used as the illumination source to perform spectral reflectance measurements of various samples at 1.6 km, and the results are seen to be in good agreement with in-lab measurements using a conventional lamp source. Spectral stability measurements are performed after atmospheric propagation through 1.6 km and show a relative variability of ?4%-8% across the spectrum depending on the atmospheric turbulence effects. Spectral stability measurements are also performed in-lab and show a relative variability of <0.6% across the spectrum. PMID:24085183

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

2013-09-20

310

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

311

Linear Waves and Stability in Ideal Magnetohydrodynamics.  

National Technical Information Service (NTIS)

Linear waves superimposed on an arbitrary basic state in ideal magnetohydrodynamics are studied by an asymptotic expansion valid for short wavelengths. The theory allows for a gravitational potential, and it may therefore be applied both in astrophysics a...

K. S. Eckhoff

1987-01-01

312

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

PubMed

The effect of bilayer membrane structures and fluctuation amplitudes on small angle neutron scattering (SANS) and small angle X-ray scattering (SAXS) profile is investigated based on harmonic motions of the surfactant bilayers with bending as well as thickness fluctuation motions. In this study we consider the case in which the wavelength of the bilayer membrane is shorter than the thickness of the membrane. We find that the thickness of the surfactant bilayer membrane, dm, affects both qdip and qpeak of I(q,0) profile, and that the fluctuation amplitude, a, of the membrane changes the peak of I(q,0). A simple formula is derived to estimate the thickness of the bilayer based on the qdip of the profile obtained from the simulation. The resulting estimates of the thickness of the bilayer with harmonic motion showed accuracy within 1%. Moreover, the bilayer thicknesses estimated from the proposed formula show an excellent agreement with the SANS and SAXS experimental results available in the literatures. We also propose a curve fit model, which describes the relationship between the fluctuation amplitude and the normalized qpeak ratio. The present results show the feasibility of the simple formula to estimate the fluctuation amplitude based on the SANS and SAXS profiles. PMID:24089802

Lee, Victor; Hawa, Takumi

2013-09-28

313

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

NASA Astrophysics Data System (ADS)

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

Lee, Victor; Hawa, Takumi

2013-09-01

314

Brillouin-light-scattering study of long-wavelength spin waves in a single-crystal 300-Å gadolinium film  

Microsoft Academic Search

The temperature dependence of the energy of ferromagnetic spin waves in an epitaxially grown 300-Å [0001] Gd film is shown to depend on the bulk values of the c-axis magnetic-stiffness constant Dc, defined by omega(q)=tsumiDiq2i, where ||qa||<<1, and the axial-anisotropy constant P2, defined by scrHaniso =P2 (Sz)2+.... Two bulk spin waves and one Damon-Eshbach surface magnetostatic wave were probed with

S. H. Kong; M. V. Klein; F. Tsui; C. P. Flynn

1992-01-01

315

Room-temperature continuous-wave operation of lateral current injection wavelength-scale embedded active-region photonic-crystal laser.  

PubMed

We have developed a wavelength-scale embedded active-region photonic-crystal laser using lateral p-i-n structure. Zn diffusion and Si ion implantation are used for p- and n-type doping. Room-temperature continuous-wave lasing behavior is clearly observed from the injection current dependence of the output power, 3dB-bandwidth of the peak, and lasing wavelength. The threshold current is 390 ?A and the estimated effective threshold current is 9.4 ?A. The output power in output waveguide is 1.82 ?W for a 2.0-mA current injection. These results indicate that the embedded active-region structure effectively reduce the thermal resistance. Ultrasmall electrically driven lasers are an important step towards on-chip photonic network applications. PMID:22418134

Matsuo, Shinji; Takeda, Koji; Sato, Tomonari; Notomi, Masaya; Shinya, Akihiko; Nozaki, Kengo; Taniyama, Hideaki; Hasebe, Koichi; Kakitsuka, Takaaki

2012-02-13

316

Hybrid metal-dielectric ring resonators for homogenizable optical metamaterials with strong magnetic response at short wavelengths down to the ultraviolet range.  

PubMed

We derive an analytical LC model from Maxwell's equations for the magnetic resonance of subwavelength ring resonators. Using the LC model, we revisit the scaling of split-ring resonators. Inspired by the LC model, we propose a hybrid metal-dielectric ring resonator mainly composed of high index dielectric material (e.g., TiO2) with some gaps filled with metal (e.g., Ag). The saturation frequency of magnetic response for the hybrid metal-dielectric ring resonator is much higher (up to the ultraviolet range) than that for split-ring resonators, and can be controlled by the metal fraction in the ring. The hybrid metal-dielectric ring resonator can also overcome the homogenization problem of all-dielectric magnetic resonators, and therefore can form homogenizable magnetic metamaterials at short wavelengths down to the ultraviolet range. PMID:24104264

Tang, Jianwei; He, Sailing

2013-10-01

317

Masked deposition techniques for achieving multilayer period variations required for short-wavelength (68-A) soft-x-ray imaging optics.  

PubMed

Practical issues in the development of multilayer coatings for reflective imaging systems operating at ? ? 68 Å are discussed. The 1% bandpass of Ru/B(4) C multilayers at this short wavelength imposes stringent tolerances with which the actual multilayer period variation across the curved surfaces must match the ideal period variation for a 20× demagnifying Schwarzschild objective. New deposition techniques that use masks to correct the period variation across the curved surfaces of each optic have been developed to ensure reflectance over the entire clear aperture. The narrow bandpass together with steep lateralperiod gradients and steeply curved surfaces requires improved metrology for an acceptable period variation to be obtained and the overlap of the reflectance peaks on the two mirrors to be verified. PMID:20856552

Kortright, J B; Gullikson, E M; Denham, P E

1993-12-01

318

Bruise detection in Pacific pink salmon (Oncorhynchus gorbuscha) by visible and short-wavelength near-infrared (SW-NIR) spectroscopy (600-1100 nm).  

PubMed

Visible and short-wavelength near-infrared (SW-NIR) spectroscopy (600-1100 nm) was used to detect bruises in intact, whole Pacific pink salmon (Oncorhynchus gorbuscha). The measurements were performed noninvasively through the skin and scales in the diffuse reflectance mode. Digital images of bruised and nonbruised regions of fish were captured after the fish samples were filleted. Image analysis was conducted using Adobe Photoshop 7.0 with relative gray values used as reference values in a partial least-squares (PLS) model. A PLS cross-validation model using six latent variables yielded a standard error of prediction (SEP = 0.05%, R = 0.83). Approximately 84% of all nonbruised spectra were correctly classified, whereas approximately 81% of all bruised spectra were correctly classified. These results suggest that visible and SW-NIR could be used to control the bruise defect of fish products during processing, thereby improving product consistency and quality. PMID:14558754

Lin, Mengshi; Cavinato, Anna G; Mayes, David M; Smiley, Scott; Huang, Yiqun; Al-Holy, Murad; Rasco, Barbara A

2003-10-22

319

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

320

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

321

Scattering of spin waves by pores in ferrimagnetic materials  

Microsoft Academic Search

The differential cross section of the spherical pores in ferrimagnetic materials is calculated by using the Born approximation in scattering theory. Using this scattering cross section, the theory is developed for evaluating the wave-vector dependence of the spin-wave linewidth. The wave-vector dependence of the spin-wave linewidth is 1k in the long-wavelength region and is proportional to k for the short-wavelength

E. Sawado

1976-01-01

322

Scattering of spin waves by pores in ferrimagnetic materials  

Microsoft Academic Search

The differential cross section of spherical pores in ferrimagnetic materials is calculated by using the Born approximation in scattering theory. Using this scattering cross section, the theory is developed for evaluating the wave-vector dependence of the spin-wave linewidth. The wave-vector dependence of the spin-wave linewidth is 1\\/k in the long-wavelength region and is proportional to k for the short-wavelength region,

E. Sawado

1976-01-01

323

What's a Wavelength?  

NSDL National Science Digital Library

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

University Of Houston

324

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

325

Light Reflection and Wavelength-downshifting from Relativistic Flying Mirrors Formed in Plasma  

Microsoft Academic Search

The relativistic flying mirror concept uses nonlinear plasma waves formed by an ultra-short intense laser pulse in tenuous plasma to reflect incoming laser light. Because the nonlinear plasma wave is moving approximately at the speed of light, the reflected light is downshifted in wavelength and shortened in pulse length. This concept has been originally invented to intensify focused laser intensity

Masaki Kando

2009-01-01

326

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

NASA Astrophysics Data System (ADS)

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

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

2013-06-01

327

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

NASA Astrophysics Data System (ADS)

Near-infrared spectroscopy (NIRS) with the characteristics of high speed, non-destructiveness, high precision and reliable detection data, etc. is a pollution-free, rapid, quantitative and qualitative analysis method. A new approach for variety discrimination of brown sugars using short-wave NIR spectroscopy (800-1050nm) was developed in this work. The relationship between the absorbance spectra and brown sugar varieties was established. The spectral data were compressed by the principal component analysis (PCA). The resulting features can be visualized in principal component (PC) space, which can lead to discovery of structures correlative with the different class of spectral samples. It appears to provide a reasonable variety clustering of brown sugars. The 2-D PCs plot obtained using the first two PCs can be used for the pattern recognition. Least-squares support vector machines (LS-SVM) was applied to solve the multivariate calibration problems in a relatively fast way. The work has shown that short-wave NIR spectroscopy technique is available for the brand identification of brown sugar, and LS-SVM has the better identification ability than PLS when the calibration set is small.

Yang, Haiqing; Wu, Di; He, Yong

2007-11-01

328

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

329

Near-field scanning millimeter-wave microscope using a standard resonant waveguide probe at millimeter wavelengths  

Microsoft Academic Search

We demonstrate a millimeter-wave surface imaging technique using a near-field scanning millimeter-wave microscope with a resonant standard waveguide probe. The operating frequency is 30-39 GHz. The probe tip is mounted in a standard resonant waveguide. By tuning the insertion length of the probe tip, we could modulate the coupling power between the probe tip and the resonant waveguide. Measuring the

Kiejin Lee; Jooyoung Kim; Myungsick Kim; Hyun Kim; B. Friedman

2003-01-01

330

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

331

Signature of gravitational wave radiation in afterglows of short gamma-ray bursts?  

NASA Astrophysics Data System (ADS)

Short gamma-ray bursts (GRBs), brief intense emission of ? rays characterized by a duration shorter than 2 s that are plausibly powered by the coalescence of binary neutron stars, are believed to be strong gravitational wave radiation (GWR) sources. The test of such a speculation has been thought to be impossible until the performance of the detectors like advanced LIGO. Recently there has been growing evidence for the formation of a highly magnetized neutron star (i.e., magnetar) in the double neutron star mergers. In this work we reexamine the interpretation of the x-ray plateau followed by an abrupt decline detected in some short GRB afterglows within the supramassive magnetar model and find that the maximum gravitational mass of the nonrotating neutron stars is ˜2.3M? and the observed duration of some x-ray plateaus are significantly shorter than that expected in the magnetic dipole radiation scenario, suggesting that the collapse of the supramassive magnetars has been considerably enhanced by the energy loss via GWR. Such a result demonstrates that the signature of GWR may have already existed in current electromagnetic data of short GRBs.

Fan, Yi-Zhong; Wu, Xue-Feng; Wei, Da-Ming

2013-09-01

332

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

333

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

334

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

SciTech Connect

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

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

2006-05-01

335

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

336

Short Time Interval Solar Spectroscopy: A Possible Method for Detecting Gravitational Waves  

NASA Astrophysics Data System (ADS)

Detection of short time interval variations of visible light in solar spectra may be a possible method for detecting gravitational waves. Aim: Design and build a spectrometry system capable of detecting 0.15 mÅ shifts in the central frequency of solar absorption lines captured at 1-200 fps. Design: A coelostat was built using a 12" diameter flat primary mirror on a computer controlled tracking mount and a static 12" flat secondary cold mirror. Reflected light enters a horizontally mounted 10" diameter Schmidt-Cassegrain telescope. Emerging light passes through an Iodine vapor cell providing a local spectral reference and then into a 25-micron air slit of a 4 meter focal length spectrometer with 3,600 l/mm grating. Spectra are recorded with a 640x480x16 bit monochrome video camera and analyzed using the MIDAS astronomical software. Construction completion date: May 2008.

Benn, Douglas K.

2008-05-01

337

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

338

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

NASA Astrophysics Data System (ADS)

The linear stage of short-wave Görtler vortices in the boundary layer near a concave surface is studied for the regime of weak hypersonic viscid-inviscid interaction at high Reynolds and Görtler numbers. It is assumed that the gas is perfect and the viscosity is a linear function of the enthalpy. It is found that neutral vortices are located near the surface if it has zero temperature. When the surface is heated, the vortices move away from it, whereas all newly incipient vortices are located near the surface. It is shown that the growth rate of the vortices has a maximum and the heating of the surface has a stabilizing effect on the vortices.

Bogolepov, V. V.

1998-09-01

339

Long wavelength free electron lasers in 1994  

Microsoft Academic Search

A short summary of the current status and most important future directions for long wavelength free-electron lasers is presented. For the purposes of the discussion, long wavelength refers to wavelengths longer than 0.5 mm. The distinction between long and short wavelengths is not entirely arbitrary since different physical processes may be important. For example, higher current beams are typically employed

H. P. Freund; V. L. Granatstein

1995-01-01

340

Generation of electron nanobunches and short-wavelength radiation upon reflection of a relativistic-intensity laser pulse from a finite-size target  

NASA Astrophysics Data System (ADS)

We have proposed an efficient scheme of generation of short dense electron bunches during the interaction at large angles of incidence of a laser pulse with a thin transversally semibounded laser target. Streams of bunches can be used to simultaneously and independently generate pulsed X-ray radiation as fast electrons hit secondary targets. Dependences of bunch parameters (the number of particles in the bunch and the bunch energy and thickness) on the angle of incidence and laser intensity have been obtained. It has been shown that, upon reflection from the target, the relativistic-intensity laser wave is efficiently converted (the energy-conversion factor reaches ˜20%) into a sequence of electromagnetic tens-of-nanometer-long atto pulses, which follow one after another in the period of the initial laser wave. We have investigated how the parameters of the atto pulse depend on the angle of incidence and the laser intensity. We have shown that atto pulses are generated most efficiently at large angles of incidence (?50°) of the laser pulse on the target.

Andreev, A. A.; Platonov, K. Yu.

2013-05-01

341

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

342

SHORT-PERIOD P- AND S-WAVE RADIATION FROM LARGE EARTHQUAKES: IMPLICATIONS FOR SPECTRAL SCALING RELATIONS  

Microsoft Academic Search

Recent measurements of peak P-wave amplitudes on World Wide Standardized Seismographic Network short-period instruments by Houston and Kanamori (1986) provided the opportunity to investigate source radiation from great earth- quakes at higher frequencies than have previously been available. The depend- ence on moment magnitude (M) of the amplitude measurements (A) and the dominant period (T) in the P-wave seismograms are

DAVID M. BOORE

1986-01-01

343

Recent developments in high-power short-wave mid-infrared semiconductor disk lasers  

NASA Astrophysics Data System (ADS)

Many applications exist for high performance lasers in the short-wave, mid-infrared spectral regime between 1.9 and 2.5?m - from long-range communications systems through to remote atmospheric gas sensing and pollution monitoring. However, a simple, efficient laser source offering the desired performance characteristics and flexibility has not been available. In the last few years considerable progress has been made in the development of optically-pumped (AlGaIn)(AsSb) quantum well semiconductor disk lasers emitting in the 2.X?m mid-infrared spectral region - continuous-wave and pulsed-pumped output power levels now exceed 6W and 16W respectively. Furthermore, singlefrequency operation with linewidths <4MHz and broad tunability of up to 170nm have also been demonstrated, all at near-diffraction-limited beam quality. Such performance metrics are only possible through the very best materials growth, a sound understanding of the design principles of these highly multi-layered devices and, importantly, the application of effective thermal management.

Burns, D.; Hopkins, J.-M.; Kemp, A. J.; Rösener, B.; Schulz, N.; Manz, C.; Köhler, K.; Rattunde, M.; Wagner, J.

2009-02-01

344

Application of laser resonance saturation to the development of efficient short wavelength lasers. Annual report for period ending 30 Sep 82  

SciTech Connect

Laser resonance saturation represents an extremely rapid and efficient new method of coupling laser energy into either a gas or plasma. We have continued to study this process both theoretically and experimentally and have shown that this interaction can lead to a very high degree of ground level burnout for the laser pumped species. During the past year we have undertaken the first time resolved Stark width measurements of the free electron density within a sodium plasma created by laser resonance saturation. Currently we are exploring the feasibility of using this ground level burnout feature as the basis of a new approach towards the development of an efficient short wavelength laser. In a preliminary experiment we have been able to show that sudden joule heating of a thin foil looks promising as a technique for creating the steep gradient of neutral atoms necessary for charge exchange formation of a ground level population inversion within the species having suffered a ground level burnout through laser resonance saturation.

Measures, R.M.

1982-09-01

345

Building advanced climatology of short-wave solar radiation over the global oceans using a new parameterization of short wave radiation  

NASA Astrophysics Data System (ADS)

Short-wave (SW) radiation is one of the key air-sea flux components playing an important role in on the ocean heat balance. Global climatologies of SW radiation are now available from different satellite missions and reanalyses. However, satellite based products cover only the last few decades and in reanalyses SW radiation appears to be one of the most inaccurate diagnostic variables. An alternative way to produce long-term time series of SW radiation is to use Voluntary Observing Ship (VOS) data and bulk parameterizations of SW radiation. Nevertheless, during the last years there was a little of effort to improve existing parameterizations of SW radiation which are typically based on the radiative flux dependencies on the total cloud cover and solar altitude. We make use a full collection of VOS data from the International Comprehensive Data Set (ICOADS) and a new parameterization of SW radiation developed at the Sea Atmosphere Interaction And Climate Laboratory of P.P.Shirshov Institute of Oceanology (SAIL) to produce a new generation global gridded data set for SW radiation for the period 1900-2008. The major feature of the SAIL parameterization is the use of the information about cloud types along with the routine information about total cloud cover. This approach allows for derivation of different dependencies of the atmospheric transmission functions onto cloud amount for different types of clouds. Relationships parameterizing these dependencies were developed using 4 years of highly accurate in-situ measurements in the Atlantic. This approach results in a critical improvement of the results for the situations close to complete overcast (6-8 oktas)..Using new parameterization and special approaches to avoid inhomogeneous sampling effect we developed a global monthly climatology of SW radiative fluxes over the global ocean at a 2-degree resolution. Special attention has been paid to the homogenization of fields in the Southern Ocean characterized by extremely poor sampling density. Although qualitatively consistent, new climatology exhibits significant quantitative differences from those derived from the traditional parameterizations. The nature of these differences is discussed in terms of the regional mechanisms driving SW radiation fluxes over the ocean.

Aleksandrova, M.; Sinitsyn, A.; Gulev, S. K.

2011-12-01

346

Gain saturation characteristics of traveling-wave semiconductor laser amplifiers in short optical pulse amplification  

NASA Astrophysics Data System (ADS)

The gain saturation characteristics of traveling-wave semiconductor laser amplifiers (TWAs) are theoretically and experimentally investigated. In the amplification of an isolated pulse whose repetition period is short compared to the carrier lifetime, the gain saturation is related through the carrier lifetime to the gain saturation in CW amplification. The saturation energy is given as the output pulse energy at which the pulse energy gain is reduced by 2.35 dB from the unsaturated value, while the signal gain in CW amplification is decreased by 4.34 dB from the unsaturated value when the output signal intensity is equal to the saturation intensity. When the output pulse energy is smaller than the saturation energy, short optical pulses can be amplified without pulse shape distortion, whereas high-energy pulses suffer from pulse shape distortion due to the temporal gain variation during the pulse radiation. FWHM pulse duration variation in amplification by TWAs depends on the input pulse shape. The pulse energy gain saturation was experimentally confirmed to be independent of pulse durations and to be determined only by the pulse energy. When the pulse repetition period becomes comparable to or smaller than the carrier lifetime, the initial gain becomes smaller than the unsaturated gain value. In extremely-high-repetition-rate pulse amplification, the saturation of the pulse energy gain is determined by the average signal power. TWAs can amplify ultra-high-speed signals because they have a wide gain bandwidth.

Saitoh, Tadashi; Mukai, Takaaki

1990-12-01

347

Gain saturation characteristics of traveling-wave semiconductor laser amplifiers in short optical pulse amplification  

SciTech Connect

The gain saturation characteristics of traveling-wave semiconductor laser amplifiers (TWA's) are theoretically and experimentally investigated. In the amplification of an isolated pulse whose repetition period is short compared to the carrier lifetime, the gain saturation is related through the carrier lifetime to the gain saturation in CW amplification. The saturation energy is given as the output pulse energy at which the pulse energy gain is reduced by 2.35 dB from the unsaturated value, while the signal gain in CW amplification is decreased by 4.34 dB from the unsaturated value when the output signal intensity is equal to the saturation intensity. When the output pulse energy is smaller than the saturation energy, short optical pulses can be amplified without pulse shape distortion, whereas high-energy pulses suffer from pulse shape distortion due to the temporal gain variation during the pulse duration. FWHM pulse duration variation in amplification by TWA's depends on the input pulse shape. The pulse energy gain saturation is experimentally confirmed to be independent of pulse durations and to be determined only by the pulse energy.

Saitoh, T.; Mukai, T. (NTT Basic Research Lab., Musashino-shi, Tokyo 180 (JP))

1990-12-01

348

Optimal design of high frequency readout IC for short-wave IRFPA  

NASA Astrophysics Data System (ADS)

High frequency readout-integrated circuit(ROIC) of 512×256 staring short wavelength(SW) infrared focal plane arrays(IRFPAs), focusing on high-frame rate output and noise suppression is implemented in this paper. The design of ROIC mentioned in it takes the previous version into account. The complete analog signal chain contains a novel input stage of capacitor feedback transimpedance amplifier(CTIA) preamplifier, a CDS (correlated double sampling) module, an amplifier of charge and complementary output stage. This ROIC is a full-custom flow integrated circuit design. The parasitic parameters are extracted once the layout is finished. Then the design is improved according to the result of post-layout simulation, which leads to the great improvements of the majority of parameters. The test and simulation results show that the output voltage range is 2.8V, the frame rate is 250Hz and the linearity within useful voltage range is above 99.1 percent, even when the temperature is 77K.

Wang, Pan; Chen, Guo-qiang; Gao, Lei; Zhou, Jie; Ding, Rui-jun

2012-12-01

349

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

NASA Astrophysics Data System (ADS)

Determination of pulsar parallaxes and proper motions addresses fundamental astrophysical open issues. Here, after scrutinizing the ATNF Catalog searching for pulsar distances and proper motions, we verify that for an ATNF sample of 212 galactic runaway pulsars (RAPs), which currently run across the Galaxy at very high speed and undergo large displacements, some gravitational wave (GW) signals produced by such present accelerations appear to be detectable after calibration against the Advanced LIGO (LIGO II). Motivated by this insight, we address the issue of the pulsar kick at birth, or the short rise fling from a supernova explosion, by adapting the theory for emission of GW by ultrarelativistic sources in this case in which the Lorentz factor is ?~1. We show that during the short rise fling each runaway pulsar (RAP) generates a GW signal with characteristic amplitude and frequency that makes it detectable by current GW interferometers. For a realistic analysis, an efficiency parameter is introduced to quantify the expenditure of the rise fling kinetic energy, which is estimated from the linear momentum conservation law applied to the supernova explosion that kicks out the pulsar. The remaining energy is supposed to be used to make the star spin. Thus, a comparison with the spin of ATNF pulsars having velocities in the range 400-500 km s-1 is performed. The resulting difference suggests that other mechanisms (like differential rotation, magnetic breaking or magneto-rotational instability) should dissipate part of that energy to produce the observed pulsar spin periods. Meanwhile, the kick phenomenon may also occur in globular and open star clusters at the formation or disruption of very short period compact binary systems wherein abrupt velocity and acceleration similar to those given to RAPs during the short rise fling can be imparted to each orbital partner. To better analyze these cases, pulsar astrometry from micro-to nano-arcsec scales might be of great help. In the case of a supernova, the RAP GW signal could be a benchmark for the GW signal from the core collapse.

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

2008-11-01

350

Therapeutic effect of spa therapy and short wave therapy in knee osteoarthritis: a randomized, single blind, controlled trial.  

PubMed

Spa therapy and short wave therapy are two of the most commonly used non-pharmacological approaches for osteoarthritis. The aim of this study was to assess their efficacy in comparison to conventional therapy in patients with osteoarthritis of the knee in a single blind, randomized, controlled trial. Seventy-four outpatients were enrolled; 30 patients were treated with a combination of daily local mud packs and arsenical ferruginous mineral bath water from the thermal resort of Levico Terme (Trento, Italy) for 3 weeks; 24 patients were treated with short wave therapy for the same period and 20 patients continued regular, routine ambulatory care. Patients were assessed at baseline, upon completion of the 3-week treatment period, and 12 weeks later. Spa therapy and short wave therapy both demonstrated effective symptomatic treatment in osteoarthritis of the knee at the end of the treatment, but only the spa therapy was shown to have efficacy persistent over time. Our study demonstrated the superiority of arsenical ferruginous spa therapy compared to short wave therapy in the treatment of osteoarthritis of the knee, probably in relationship to the specific effects of the minerals in this water. PMID:17106661

Cantarini, Luca; Leo, Graziana; Giannitti, Chiara; Cevenini, Gabriele; Barberini, Pietro; Fioravanti, Antonella

2006-11-15

351

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

Microsoft Academic Search

Short-wave diathermy (SWD), a form of radiofrequency radiation used therapeutically by physiotherapists, may be applied in continuous (CSWD) or pulsed (PSWD) mode using either capacitive or inductive methods. Stray radiation emitted by these units may exceed exposure guidelines close to the equipment. Discrepant guidelines exist on a safe distance from an operating unit for operators and other personnel. Stray electric

Nora Shields; Neil O'Hare; John Gormley

2004-01-01

352

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

Technology Transfer Automated Retrieval System (TEKTRAN)

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

353

Hindcast modeling of short waves at the mouth of the Columbia River estuary  

Microsoft Academic Search

The region around the mouth of the Columbia River estuary is subject to high waves, which augmented by the presence of offshore shoals and tidal currents, lead to strong wave focusing near the mouth of the estuary. The large waves are a navigational hazard and a possible mechanism for sediment transport in this region. Hindcast modeling of wave propagation has

A. Chawla; A. M. Baptista

2004-01-01

354

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

355

Directional spreading function of the sea wave spectrum at short scale, inferred from multifrequency radar observations  

NASA Astrophysics Data System (ADS)

Several models of the directional spreading function of the sea wave spectrum have been proposed in the literature for low wavenumbers. In this paper we propose a high-wavenumber extrapolation of those models, obtained by fitting a correcting term which vanishes at large scales (low wavenumbers). At short scales (high wavenumbers) the correcting term is constrained by multifrequency microwave observations of the normalized radar cross section ?° from P band (frequency = 0.43 GHz) up to Ka band (frequency = 34.43 GHz), together with optical observations of the sea surface slope variance. Two formulations are given, one providing a high-wavenumber extrapolation to Apel's [1994] formulation and the other providing a high-wavenumber extrapolation to Donelan et al.'s [1985] and Banner's [1990] formulation. The correcting term ?, expressed as a function of wavenumber k and wind speed U by means of six least squares fitted parameters, is found to vary strongly with k and slightly with U. Another simpler expression for ?, involving only the dependence with k by means of three fitted parameters, is therefore also proposed. According to our fitted model of the spreading function, there is a spectral region in the short gravity range where the sea spectrum shows only a weak dependence on the direction, in accordance with the previous models. However, unlike them, our model gives an increase of the anisotropy of the spreading function at higher wavenumbers, in such a way that the ratio between the cross-wind and along-wind spectral densities of the folded spectrum is reduced to no more than 35% at high wavenumbers (k ? 1000 rad/m). This increase of anisotropy at high frequency is in accordance with conclusions drawn by previous authors from radar backscatter data, which were, however, limited to narrow spectral bands since their analyses involved only single-frequency radar data.

Caudal, G.; Hauser, D.

1996-07-01

356

A novel OCS millimeter-wave generation scheme with data carried only by one sideband and wavelength reuse for uplink connection  

NASA Astrophysics Data System (ADS)

We propose a novel optical carrier suppression (OCS) millimeter-wave generation scheme with data carried only by one sideband using a dual-drive Mach–Zehnder modulator (MZM) in radio-over-fiber system, and the transmission performance is also investigated. As the signal is transmitted along the fiber, there is no time shifting of the codes caused by chromatic dispersion. Simulation results show that the eye diagram keeps open and clear even when the optical millimeter-waves are transmitted over 110km and the power penalty is about 1.9dB after fiber transmission distance of 60km. Furthermore, due to the +1 order sideband carrying no data, a full duplex radio-over-fiber link based on wavelength reuse is also built to simplify the base station. The bidirectional 2.5Gbit/s data is successfully transmitted over a 40km standard single mode fiber with less than 0.8dB power penalty in the simulation. Both theoretical analysis and simulation results show that our scheme is feasible and we can obtain a simple cost-efficient configuration and good performance over long-distance transmission.

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

2012-11-01

357

Standing Electric Waves on Parallel Wires  

Microsoft Academic Search

Measurement of short electric wave-length with a parallel wire receiving system.-Electromagnetic waves of from one to ten meters in length and highly constant in nature were obtained by means of a valve oscillator. Two types of generating circuits are described. Analysis of the possible free modes of electric vibration of the parallel wire receiving system indicates that for normal coupling

W. S. Huxford

1925-01-01

358

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

NASA Astrophysics Data System (ADS)

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

Chen, Xianfeng

359

Ultraviolet Wavelength Smoke Detector.  

National Technical Information Service (NTIS)

In the patent application collimated ultraviolet light radiation at wavelengths of 2537A and 3129A is alternately directed across the space to be monitored for smoke indicative of a fire. Particulate matter in the beam paths will effect the different wave...

T. M. Trumble

1975-01-01

360

Short-wave infrared reflectance investigation of sites of paleobiological interest: applications for Mars exploration.  

PubMed

Rover missions to the rocky bodies of the Solar System and especially to Mars require lightweight, portable instruments that use minimal power, require no sample preparation, and provide suitably diagnostic mineralogical information to an Earth-based exploration team. Short-wave infrared (SWIR) spectroscopic instruments such as the Portable Infrared Mineral Analyser (PIMA, Integrated Spectronics Pty Ltd., Baulkham Hills, NSW, Australia) fulfill all these requirements. We describe an investigation of a possible Mars analogue site using a PIMA instrument. A survey was carried out on the Strelley Pool Chert, an outcrop of stromatolitic, silicified Archean carbonate and clastic succession in the Pilbara Craton, interpreted as being modified by hydrothermal processes. The results of this study demonstrate the capability of SWIR techniques to add significantly to the geological interpretation of such hydrothermally altered outcrops. Minerals identified include dolomite, white micas such as illite-muscovite, and chlorite. In addition, the detection of pyrophyllite in a bleached and altered unit directly beneath the succession suggests acidic, sulfur-rich hydrothermal activity may have interacted with the silicified sediments of the Strelley Pool Chert. PMID:15383240

Brown, Adrian; Walter, Malcolm; Cudahy, Thomas

2004-01-01

361

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

USGS Publications Warehouse

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

Micijevic, E.; Helder, D. L.

2005-01-01

362

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

NASA Astrophysics Data System (ADS)

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.

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

2013-08-01

363

Short-baseline neutrino oscillation waves in ultra-large liquid scintillator detectors  

NASA Astrophysics Data System (ADS)

Powerful new multi-kiloton liquid scintillator neutrino detectors, including NO?A and, possibly, LENA, will come on-line within the next decade. When coupled with a modest-power decay-at-rest (DAR) neutrino source at short-baseline, these detectors can decisively address signals for neutrino oscillations at high ?m2. Along the greater than 50 m length of the detector, the characteristic oscillation wave will be apparent, providing powerful verification of the oscillation phenomenon. LENA can simultaneously perform ?? ? ?e appearance and ?e ? ?e disappearance searches while NO?A is likely limited to ?e disappearance. For the appearance channel, a LENA-like detector could test the LSND and MiniBooNE signal regions at >5 ? with a fiducial volume of 5 kt and a 10 kW neutrino source. The LENA and NO?A ?e disappearance sensitivities are complementary to the recent reactor anomaly indicating possible ?e disappearance and would cover this possible oscillation signal at ~3 ?.

Agarwalla, Sanjib Kumar; Conrad, J. M.; Shaevitz, M. H.

2011-12-01

364

Effects of confinement on short-period surface waves: Observations from a new dataset  

SciTech Connect

The Source Phenomenology Experiment (SPE) was conducted during the summer of 2003 in Arizona. Single-fired chemical shots were detonated and recorded at two locations, including a coal mine in the Black Mesa district of northern Arizona. This article reports on research into the effects of confinement on the generation of short-period, fundamental-mode Rayleigh waves (Rg), using a subset of the SPE data. Results show important differences between the Rg amplitudes of confined and unconfined explosions which must be understood to develop discriminants for mining explosions, which are an important aspect of nuclear test monitoring. Rg energy and frequency content depend on explosive weight and confinement, and unconfined explosions generate up to eight times less energy than equivalent confined explosions. For this reason, unconfined mining explosions cannot be simulated using a Mueller and Murphy (1971) source without including an empirical chemical decoupling factor. Rg chemical decoupling factors for unconfined shots vary from 0.5 to 8.2 at frequencies between 0.5 and 11 Hz. The effects of the bench free face are evident in radiation patterns. Explosions on the topographic bench show increased spectral energies for Rg (by a factor of 1.5) at azimuths behind the bench. This suggests that a discriminant based on the relative azimuthal spectral energies of Rg may be a possibility.

Hooper, H.; Bonner, J.; Leidig, M. [Weston Geophysics Corp., Lexington, MA (United States)

2006-04-15

365

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

NASA Astrophysics Data System (ADS)

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

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

2003-12-01

366

Small craft ID criteria (N50/V50) for short wave infrared sensors in maritime security  

NASA Astrophysics Data System (ADS)

The need for Anti-Terrorism and Force Protection (AT/FP), for both shore and sea platform protection, has resulted in a need for imager design and evaluation tools which can predict field performance against maritime asymmetric threats. In the design of tactical imaging systems for target acquisition, a discrimination criterion is required for successful sensor realization. It characterizes the difficulty of the task being performed by the observer and varies for different target sets. This criterion is used in both assessment of existing infrared sensor and in the design of new conceptual sensors. In this experiment, we collected 8 small craft signatures (military and civilian) in the short wave infrared (SWIR) band during the day. These signatures were processed to determine the targets' characteristic dimension and contrast. They were also processed to bandlimit the signature's spatial information content (simulating longer range) and a perception experiment was performed to determine the task difficulty (N50 and V50). The results are presented in this paper and can be used for maritime security imaging sensor design and evaluation.

Krapels, Keith; Driggers, Ronald G.; Larson, Paul; Garcia, Jose; Walden, Barry; Agheera, Sameer; Deaver, Dawne; Hixson, Jonathan; Boettcher, Evelyn

2008-05-01

367

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

368

Study on dispersion in 60GHz short millimeter-wave broadband wireless access systems over POF link  

NASA Astrophysics Data System (ADS)

Our researches are based on such a system architecture that is intended to utilize the good characteristic of the interaction between millimeter-wave and lightwave to implement the 60GHz short millimeter-wave broadband wireless access system over fiber links. The networks include fiber optic links between the center stations (CS) and the base stations (BSs) and millimeter-wave air channel between the BSs and the networks terminals. The polymer optical fiber (POF) is deployed as optical fiber link medium due to its marked competitiveness in short haul, large capability communication systems. In this paper, we focus on suppressing dispersion of the radio-over-fiber transmission system. The POF is a dominant fiber chromatic dispersion source, which behaves multi-mode properties and produces inter-mode dispersion to heavily cause the POF bandwidth degradation. We present analysis on modal dispersion characteristics of 60 GHz short millimeter-wave broadband wireless access system over polymer optical fiber (POF) transmission link and present our scheme, which chooses proper launch condition to control the number of low-order modes and high-order modes excited in the POF link to improve system dispersion characteristic.

Xiu, Minglei; Qin, Hailin; Lin, Rujian; Chen, Xinqiao; Guo, Shuqin

2005-12-01

369

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

Microsoft Academic Search

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

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

2008-01-01

370

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

NASA Astrophysics Data System (ADS)

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

van Prooijen, Bram Christiaan; Wang, Zheng Bing

2013-09-01

371

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

Microsoft Academic Search

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

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

1996-01-01

372

Short communication Background current affects the internal wave structure of the northern South China Sea  

Microsoft Academic Search

The internal wave modal equations are solved with the consideration of background currents. Analytical and numerical solutions of some specific examples, including observations in the northern South China Sea (SCS), are obtained to investigate the effect of back- ground current on internal wave vertical structure. The effects of current shear and curvature on internal wave vertical structure are eval- uated

Shuqun Cai; Xiaomin Long; Danpeng Dong; Shengan Wang

373

Efficient generation of record-short and record-long wavelengths based on backward and forward parametric interaction in lithium niobate  

NASA Astrophysics Data System (ADS)

In our recent work, we have generated the shortest wavelengths from periodically-poled lithium niobate (PPLN) in the vicinity of 62.5 microns at the poling period of 7.1 microns. We have demonstrated large enhancements in the output powers from three gratings. For the long-poling periods, we have generated THz radiation with output wavelengths in the range of 126-1382 ?m and output powers as high as 432 ?W, corresponding to the photon conversion efficiency of 29%. We have also efficiently generated far-infrared radiation at the wavelengths centered at 20.8 microns in the vicinity of one of the polariton resonances of lithium niobate. Such an efficient nonlinear conversion is made possible by exploiting phase-matching for difference-frequency generation in lithium niobate. The highest peak power reached 233 W. These wavelengths correspond to the shortest wavelength in the terahertz region and longest wavelength in the mid-infrared/far-infrared regions from lithium niobate, respectively.

Chen, Ruolin; Sun, Guan; Lin, Xiaomu; Ding, Yujie J.

2013-03-01

374

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

PubMed

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

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

2013-07-06

375

Toward an Understanding of Short Distance Repulsions among Baryons in QCD--- NBS Wave Functions and Operator Product Expansion ---  

NASA Astrophysics Data System (ADS)

We report on our recent attempts to determine the short distance behaviors of general 2-baryon and 3-baryon forces, which are defined from the Nambu-Bethe-Salpeter (NBS) wave function, by using the operator product expansion and a renormalization group analysis in QCD. We have found that the repulsion at short distance increases as the number of valence quarks increases or when the number of different flavors involved decreases. This global tendency suggests a Pauli suppression principle among quark fields at work.

Aoki, S.; Balog, J.; Weisz, P.

2012-12-01

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

On the Earth's surface energy exchange determination from ERS satellite ATSR data: Part 2. Short-wave radiation  

Microsoft Academic Search

This is the second in a series of papers which discusses determination of the Earth's surface energy exchange from ERS satellite Along-Track Scanning Radiometer (ATSR) data. The paper concentrates on short-wave radiation on sea and land surfaces. In this paper, three methods were used to determine solar irradiance by using ERS ATSR-2 data. We referred to them as 'D scheme',

Yong Xue; D. T. Llewellyn-Jones; S. P. Lawrence; C. T. Mutlow

2000-01-01

378

Short-term variability of the underwater light field in the oligotrophic ocean in response to surface waves and clouds  

Microsoft Academic Search

Examples of short-term variations of the underwater light field associated with surface-wave focusing and cloud cover, and occurring at intermediate depths of the euphotic zone in the oligotrophic ocean are discussed. Time series of water pressure, spectral downwelling irradiance (Ed), and spectral upwelling radiance (Lu) at 412, 443, 490, 510, 555, 665, and 683nm were acquired with moored instruments. The

Malgorzata Stramska; Tommy D. Dickey

1998-01-01

379

Theory of wave-front reversal of short pulses in dynamically tuned zero-gap periodic systems  

SciTech Connect

Recently [Sivan and Pendry, Phys. Rev. Lett. 106, 193902 (2011)], we have shown that the wave front of short pulses can be accurately and efficiently reversed by use of simple one-dimensional zero-gap photonic crystals. In this paper, we describe the analytical approach in detail, and discuss specific structures and modulation techniques as well as the required steps for achieving complete time reversal. We also show that our scheme is only very weakly sensitive to material losses and dispersion.

Sivan, Yonatan; Pendry, John B. [Blackett Laboratory, Department of Physics, Imperial College London, London SW72AZ (United Kingdom)

2011-09-15

380

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

NASA Astrophysics Data System (ADS)

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

Fang, Ming-chung; Lee, Zi-yi

2013-08-01

381

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

SciTech Connect

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

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

2009-07-15

382

All-optical frequency downconversion technique utilizing a four-wave mixing effect in a single semiconductor optical amplifier for wavelength division multiplexing radio-over-fiber applications.  

PubMed

An all-optical frequency downconversion utilizing a four-wave mixing effect in a single semiconductor optical amplifier (SOA) was experimentally demonstrated for wavelength division multiplexing (WDM) radio-over-fiber (RoF) applications. Two WDM optical radio frequency (RF) signals having 155 Mbps differential phase shift keying (DPSK) data at 28.5 GHz were simultaneously down-converted to two WDM optical intermediate frequency (IF) signals having an IF frequency of 4.5 GHz by mixing with an optical local oscillator (LO) signal having a LO frequency of 24 GHz in the SOA. The bit-error-rate (BER) performance of the RoF up-links with different optical fiber lengths employing all-optical frequency downconversion was investigated. The receiver sensitivity of the RoF up-link with a 6 km single mode fiber and an optical IF signal in an optical double-sideband format was approximately -8.5 dBm and the power penalty for simultaneous frequency downconversion was approximately 0.63 dB. The BER performance showed a strong dependence on the fiber length due to the fiber dispersion. The receiver sensitivity of the RoF up-link with the optical IF signal in the optical single-sideband format was reduced to approximately -17.4 dBm and showed negligible dependence on the fiber length. PMID:22453476

Kim, Hyoung-Jun; Song, Jong-In

2012-03-26

383

[partial differential]n/[partial differential]T Measurements performed with guided waves and their application to the temperature sensitivity of wavelength-division multiplexing filters  

NASA Astrophysics Data System (ADS)

Measurements of [partial differential]n/[partial differential]T of thin films by the m-lines technique are presented. The importance of the substrate material is shown. An example of the wavelength shift of an optical thin-film filter with temperature is studied both theoretically and experimentally. The theoretical wavelength shift of a dense wavelength-division multiplexing filter is discussed.

Drouard, Emmanuel; Huguet-Chantome, Pascal; Escoubas, Ludovic; Flory, Francois

2002-06-01

384

High Resolution Full Wave Modeling of Fast Waves in NSTX  

NASA Astrophysics Data System (ADS)

High Harmonic Fast Waves (HHFW) are being used in NSTX for plasma heating and noninductive current profile control. Numerical solutions for the wave fields obtained with the full wave TORIC and AORSA codes with ultrafine spatial resolution reveal the presence of a short wavelength feature that is predominantly polarized in the direction parallel to the equilibrium magnetic field and which is predicted by the codes to damp on electrons. A similar short wavelength mode also appears in simulations of the rf fields in C-Mod in the ICRF regime. Preliminary analysis indicates that the mode may be related to a slow mode that can propagate above the fundamental ion cyclotron frequency. The predicted power deposition profiles will be compared to those inferred from experimental measurements to see if the mode has a significant effect on the wave propagation and absorption. Possibilities for detecting the mode in NSTX and C-Mod will be discussed.

Phillips, C. K.; Berk, L.; Hosea, J. C.; Leblanc, B. P.; Taylor, G.; Valeo, E. J.; Wilson, J. R.; Berry, L. A.; Jaeger, E. F.; Ryan, P. M.; Bonoli, P. T.; Wright, J. C.

2010-11-01

385

Wave Properties  

NSDL National Science Digital Library

In this lesson plan students will learn the components of a wave, then discuss the effects of wave height, wavelength, and wave period in determining the overall size of a wave. They will use the National Geographic Wave Simulator to experiment with creating different kinds of waves. Discussion will then focus on the effects of geography on wave size as well as additional forces on boats trying to navigate waves.

386

A Boussinesq-type wave driver for a morphodynamical model to predict short-term morphology  

Microsoft Academic Search

The prediction of near-shore morphology on the time scale of a storm event and the length scale of a few surf zone widths is an active area of research. Intense wave breaking drives offshore-directed currents (undertow) carrying sediment seawards, resulting in offshore bar migration. In contrast, higher order nonlinear properties, such as wave asymmetry (velocity skewness) and velocity asymmetry, are

Ivo Wenneker; Ap van Dongeren; Jamie Lescinski; Dano Roelvink; Mart Borsboom

2011-01-01

387

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

388

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

389

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

390

Hindcast modeling of short waves at the mouth of the Columbia River estuary  

NASA Astrophysics Data System (ADS)

The region around the mouth of the Columbia River estuary is subject to high waves, which augmented by the presence of offshore shoals and tidal currents, lead to strong wave focusing near the mouth of the estuary. The large waves are a navigational hazard and a possible mechanism for sediment transport in this region. Hindcast modeling of wave propagation has been done to assess the ability of two numerical models (SWAN and REF/DIF S) to simulate waves in this region. Both models account for wave refraction and strong wave-current interactions, but while SWAN accounts for locally generated wind waves, REF/DIF S accounts for diffraction effects. Nearshore currents have been obtained from a regional circulation model (ELCIRC) that incorporates tidal, fluvial and atmospheric forcings. Measured field data from an offshore NOAA buoy (located approximately 20 km west of the mouth of the estuary) are used as input conditions for the models. Initial results comparing the two models for a test case were presented at the Ocean Sciences 2004 meeting, where significant differences between the two model results were observed. In this study the models have been compared against data from an extensive field exercise carried out by the Coastal Hydraulics Laboratory of USACE (Special thanks to Hans R. Moritz of USACE for discussions on this data set). The field gauges were placed at four locations around the mouth of the estuary for prolonged periods between 1997 and 1999. This study is limited to local wave propagation processes within a 40x40 km grid around the mouth of the estuary.

Chawla, A.; Baptista, A. M.

2004-12-01

391

Parametric Excitations of Fast Plasma Waves by Counter-propagating Laser Beams  

SciTech Connect

Short- and long-wavelength plasma waves can become strongly coupled in the presence of two counter-propagating laser pump pulses detuned by twice the cold plasma frequency. What makes this four-wave interaction important is that the growth rate of the plasma waves occurs much faster than in the more obvious co-propagating geometry.

G. Shvets; N.J. Fisch

2001-03-19

392

The Vertical Propagation of Tropospheric Rossby Waves and its Variation with Climate  

Microsoft Academic Search

Rossby wave propagation is theoretically affected by zonal wind gradients, in particular the second derivative of the zonal wind shear in the vertical and meridional directions. Vertical propagation is hindered by the strong winds in the upper troposphere, particularly for short wavelength waves, or by critical levels where the background wind velocity equals the wave phase velocity. In practice, tropospheric

D. H. Rind; J. Perlwitz

2002-01-01

393

Multiple Wavelength Surface Emitting Semiconductor Laser Array  

Microsoft Academic Search

We present the wavelength engineering of vertical cavity surface emitting lasers (VCSELs) for use in high speed short reach sys- tems, which may include the wavelength expansion, the wavelength integration and the wavelength stabilization based on fully monolithic technologies. We have developed highly strained GaInAs\\/GaAs quantum well (QW) VCSELs emitting at 1.1-1.2 µm wavelength band. Excellent temperature characteristics have been

Fumio KOYAMA

394

CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES: Novel Bilayer Structures for Short Wavelength High Density Magneto-Optical Data Storage  

NASA Astrophysics Data System (ADS)

We report a novel bi-layer thin film structure for high density magneto-optical (MO) data storage, which combines the advantages of blue wavelength and magnetically induced superresolution (MSR) recording. A double-layer system of exchange-coupled light rare-earth (LRE) element doped NdGdFeCo and traditional TbFeCo is used as the recording medium. The experimental results demonstrate that this NdGdFeCo/TbFeCo double layer has large Kerr rotation under blue wavelength. Centre aperture detection (CAD) MSR effect with temperature rising is also observed. Theoretical calculation is also carried out to verify the experimental results. These results collectively suggest that the new bilayer structure is very promising in next generation high density MO data storage.

Wang, Xian-Ying; Wang, Jing; Wang, Zhan-Yong; Yang, Jun-He

2008-06-01

395

SASE free electron lasers as short wavelength coherent sources. From first results at 100 nm to a 1 Å X-ray laser  

NASA Astrophysics Data System (ADS)

During the last few years free electron lasers (FELs) based on self-amplified spontaneous emission (SASE) have been demonstrated at wavelengths of 12 ?m [CITE], 830 nm [CITE], 530 nm [CITE] and 385 nm [CITE], and around 100 nm [CITE]. Recently, saturation has been observed in the vacuum ultraviolet (VUV) spectral region between 82 nm and 125 nm at the TESLA Test Facility (TTF) at DESY. The radiation pulses have been characterized with respect to pulse energy, statistical fluctuations, angular divergence and spectral distribution, both in the linear gain and in the saturation regime of the FEL [CITE]. The results are in good agreement with theoretical simulations, providing a solid basis for other projects aiming at still shorter wavelengths down to the 0.1 nm range [CITE].

Treusch, R.; Feldhaus, J.

2003-10-01

396

Enhanced short wavelength response in laser-scanned-photodiode image sensor using an aSiC:H\\/aSi:H tandem structure  

Microsoft Academic Search

We report in this paper the recent advances we obtained in optimizing a color image sensor based on the laser-scanned-photodiode (LSP) technique. A novel device structure based on a a-SiC:H\\/a-Si:H pin\\/pin tandem structure has been tested for a proper color separation process that takes advantage on the different filtering properties due to the different light penetration depth at different wavelengths

A. Fantoni; P. Louro; M. Fernandes; M. Vieira; G. Lavareda; C. Nunes De Carvalho

2005-01-01

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

THE COLOR APPEARANCE OF STIMULI DETECTED VIA SHORT-WAVELENGTH-SENSITIVE CONES: COMPARISONS WITH VISUAL ADAPTATION AND VISUAL FIELD DATA FOR PERI- OR POST-MENOPAUSAL WOMEN UNDER 70 YEARS OF AGE  

PubMed Central

Dynamics of foveal light adaptation for vision mediated via short-wavelength-sensitive (SWS) cones were compared for two groups of healthy amenorrheic (peri- or post-menopausal) women not using hormonal medication. Each subject was assigned to a group based on the color name – “lavender” (~2/3 of all subjects) or “white” (~1/3 of all subjects) – chosen in a forced-response paradigm to best describe a threshold-level 440-nm test presented on a larger 3.6 log td 580-nm background that had been viewed for ~5 minutes. During the first 20–30 seconds after this 3.6 log td background abruptly replaced a much dimmer background, the threshold elevations (relative to the steady-state levels measured at ~5 minutes) were significantly greater for the lavender-naming subjects than for the white-naming subjects. However, exponential rates of recovery were indistinguishable for the two groups. A viable interpretation is that the gain of the visual response at background onset is greater for lavender-naming subjects than for white-naming subjects at or distal to a site where responses from middle-wavelength-sensitive and long-wavelength-sensitive (MWS and LWS) cones oppose responses from SWS cones. In addition, the color names derived from foveal testing were related systematically to extrafoveal sensitivities measured with Short Wavelength Automated Perimetry (SWAP), in a manner suggesting that response gain and/or response speed may be greater for lavender-naming subjects in the direction of increased SWS response also. Evidence from other subject populations suggests that the choice of color name and the dynamics of visual response each can be affected by alterations (particularly reductions) of estrogen synthesis and response.

Eisner, Alvin; Toomey, Maureen D.

2008-01-01

399

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

PubMed

Dynamics of foveal light adaptation for vision mediated via short-wavelength-sensitive (SWS) cones were compared for two groups of healthy amenorrheic (peri- or post-menopausal) women not using hormonal medication. Each subject was assigned to a group based on the color name-"lavender" ( approximately 2/3 of all subjects) or "white" (approximately 1/3 of all subjects)-chosen in a forced-response paradigm to best describe a threshold-level 440-nm test presented on a larger 3.6 log td 580-nm background that had been viewed for approximately 5 min. During the first 20-30s after this 3.6 log td background abruptly replaced a much dimmer background, the threshold elevations (relative to the steady-state levels measured at approximately 5 min) were significantly greater for the lavender-naming subjects than for the white-naming subjects. However, exponential rates of recovery were indistinguishable for the two groups. A viable interpretation is that the gain of the visual response at background onset is greater for lavender-naming subjects than for white-naming subjects at or distal to a site where responses from middle-wavelength-sensitive and long-wavelength-sensitive (MWS and LWS) cones oppose responses from SWS cones. In addition, the color names derived from foveal testing were related systematically to extrafoveal sensitivities measured with Short Wavelength Automated Perimetry (SWAP), in a manner suggesting that response gain and/or response speed may be greater for lavender-naming subjects in the direction of increased SWS response also. Evidence from other subject populations suggests that the choice of color name and the dynamics of visual response each can be affected by alterations (particularly reductions) of estrogen synthesis and response. PMID:18343478

Eisner, Alvin; Toomey, Maureen D

2008-03-17

400

Shallow Seismic Attenuation and Shear Waves Splitting In The Short Period Range of Deception Island Volcano (antarctica)  

NASA Astrophysics Data System (ADS)

The occurrence of a seismic series in Deception Island volcano (Antarctica), com- posed by hundreds of local volcano-tectonic earthquakes, has permitted us to study the seismic attenuation of such a volcanic environment in the short-distance and high- frequency range. This study has been performed using P, S and coda waves and ap- plying different, frequency dependent and independent, techniques. The methods used for this analysis have been: Spectral and Broadening of the Pulse, for direct P and S waves, Coda Normalization for S-waves and Single Back-Scattering model for coda waves. The results show that, in general, Q values are significantly smaller, for all the frequency range used (6-30 Hz), than those found in other volcanic and tectonic areas. The attenuation for P-waves is greater than for S-waves in the frequency in- dependent methods, with a Qb/QP ratio that ranges between 1.9 and 3.2. Comparing the Q factor obtained for S-waves we have observed clear differences as a function of the method used; the Coda Normalization Method has supplied significantly higher Q values (Qd) than the other two methods (Qb). These Qd values are similar to the Q factor for coda waves (Qc). We have interpreted this discrepancy as an effect of the methods: Coda Normalization and Single Back-Scattering methods eliminate the con- tribution of the near surface attenuation in their Q values. Comparing both Qb and Qd we have estimated the near surface attenuation under the recording site, named Qk. On the other hand, we have observed that Qd has an anomalous frequency dependence, with a minimum value at 21 Hz. This pattern is interpreted as an effect of strong scat- tering of the seismic waves in the source area of the earthquakes. Qc values depend clearly with frequency and lapse time, and the lapse time dependence is interpreted as a depth dependence of the seismic attenuation in Deception Island volcano. The de- rived Q values have allowed us to separate the contribution of intrinsic and scattering attenuation, deriving that the scattering attenuation is predominant over the intrinsic effects. Finally, in order to investigate how the heterogeneous medium of the volcanic island could produce other effects, we have measured the splitting of the shear waves of the same data set. The observations reveal that the arrival delay of the shear waves horizontal components varies between 0.02 and 0.14 seconds, a big amount if we take into account the short hypocentral distances (less than 5 km). The study of the polar- 1 ization direction indicates a main E-W direction. All these evidences reveal the strong heterogeneous structure of Deception Island volcano. 2

Martínez-Arévalo, C.; Bianco, F.; Ibáñez, J. M.; del Pezzo, E.

401

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

NASA Astrophysics Data System (ADS)

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

Hu, Yaogai; Zhao, Zhengyu; Zhang, Yuannong

2011-07-01

402

Influence of winds on temporally varying short and long period gravity waves in the near shore regions of Eastern Arabian Sea  

NASA Astrophysics Data System (ADS)

Wave data collected off Ratnagiri, west coast of India during 1 May 2010 to 30 April 2012 is used in the study. Seasonal and annual variation in wave data controlled by the local wind system such as sea breeze and land breeze, and remote wind generated long period waves observed along the west coast of India, is studied. Sea breeze plays an important role in determining the sea state during pre and post monsoon seasons and the maximum wave height is observed during peak hours of sea breeze at 15:00 UTC. Long period waves (peak period over 13 s) are observed mainly during the pre and the post monsoon season. Maximum peak period observed during the study is 22 s and is in the month of October. Long period waves observed during the south west monsoon period of 2011 are identified as swell propagated from the Southern Ocean with an estimated travelling time of 5-6 days. The swells reaching the Arabian Sea from the South Indian Ocean and Southern Ocean, due to storms during the pre and post monsoon periods will modify the near surface winds, due to the dominant wave induced wind regime. Energy spectrum of observed waves indicates onset and decline of strong south west monsoon winds. Convergence of energy-containing frequency bands corresponding to short period waves (Tp < 8 s) and long period waves (Tp > 13 s) to intermediate period waves (8 < Tp < 13 s) are observed at the end of the pre monsoon season; divergence is observed during the start of the post monsoon period from intermediate period waves to short period waves and long period waves. South west monsoon period is characterized by the energy corresponding to the frequency band of intermediate period waves along the west coast of India.

Glejin, J.; Sanil Kumar, V.; Balakrishnan Nair, T. N.; Singh, J.

2012-09-01

403

Elastic waves in a short cylinder, impacted by a thin bar  

Microsoft Academic Search

The wave motion resulting from the elastic impact of a semi-infinite steel bar on an aluminium cylinder, of much larger diameter but of finite length, were studied experimentally and numerically. First the strains were measured at different points on the cylinder surface by using semiconductor strain gauges. Subsequently the experimental situation was simulated numerically with a dynamic finite element program

L. Guex; W. Janach

1980-01-01

404

A unified directional spectrum for long and short wind-driven waves  

Microsoft Academic Search

Review of several recent ocean surface wave models finds that while comprehensive in many regards, these spectral models do not satisfy certain additional, but fundamental, criteria. We propose that these criteria include the ability to properly describe diverse fetch conditions and to provide agreement with in situ observations of Cox and Munk [1954] and Jähne and Riemer [1990] and Hara

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

1997-01-01

405

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

SciTech Connect

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

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

2010-06-01

406

Imaging short-period seismic radiation from the 27 February 2010 Chile (MW 8.8) earthquake by back-projection of P, PP, and PKIKP waves  

NASA Astrophysics Data System (ADS)

Teleseismic short-period (0.5-5 s) P waves from the 27 February 2010 Chile earthquake (Mw 8.8) are back projected to the source region to image locations of coherent short-period seismic wave radiation. Several receiver array configurations are analyzed using different P wave arrivals, including networks of stations in North America (P), Japan (PKIKP), and Europe (PP), as well as a global configuration of stations with a broad azimuthal distribution and longer-period P waves (5-20 s). Coherent bursts of short-period radiation from the source are concentrated below the Chilean coastline, along the downdip portion of the megathrust. The short-period source region expands bilaterally, with significant irregularity in the radiation. Comparison with finite fault slip models inverted from longer-period seismic waves indicates that the regions of large slip on the megathrust are located updip of the regions of short-period radiation, a manifestation of frequency-dependent seismic radiation, similar to observations for the great 2011 Tohoku earthquake (Mw 9.0). Back projection of synthetic P waves generated from the finite fault models demonstrates that if the short-period energy had radiated with the same space-time distribution as the long-period energy, back-projection analysis would image it in the correct location, updip. We conclude that back-projection imaging of short-period signals provides a distinct view of the seismic source that is missed by studies based only on long-period seismic waves, geodetic data, and/or tsunami observations.

Koper, Keith D.; Hutko, Alexander R.; Lay, Thorne; Sufri, Oner

2012-02-01

407

Effective short-range interaction for spin-singlet P-wave nucleon-nucleon scattering  

SciTech Connect

Distorted-wave methods are used to remove the effects of one- and two-pion exchange up to order Q{sup 3} from the empirical {sup 1}P{sub 1} phase shift. The one divergence that arises can be renormalized using an order-Q{sup 2} counterterm which is provided by the (Weinberg) power counting appropriate to the effective field theory for this channel. The residual interaction is used to estimate the scale of the underlying physics.

Ipson, Katie L.; Birse, Michael C. [Theoretical Physics Group, School of Physics and Astronomy, University of Manchester, Manchester M13 9PL (United Kingdom); Helmke, Katharina [Fakultaet fuer Physik und Astronomie, Ruhr-Universitaet Bochum, D-44780 Bochum (Germany)

2011-01-15

408

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

NASA Astrophysics Data System (ADS)

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

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

2009-10-01

409

Millimetre wave and terahertz technology for detection of concealed threats - a review  

Microsoft Academic Search

There has been intense interest in the use of millimetre wave and terahertz technology for the detection of concealed weapons, explosives and other threats. Radiation at these frequencies is safe, penetrates barriers and has short enough wavelengths to allow discrimination between objects. In addition, many solids including explosives have characteristic spectroscopic signatures at terahertz wavelengths which can be used to

Michael C Kemp

2007-01-01

410

Detecting hidden objects: Security imaging using millimetre-waves and terahertz  

Microsoft Academic Search

There has been intense interest in the use of millimetre wave and terahertz technology for the detection of concealed weapons, explosives and other threats. Radiation at these frequencies is safe, penetrates barriers and has short enough wavelengths to allow discrimination between objects. In addition, many solids including explosives have characteristic spectroscopic signatures at terahertz wavelengths which can be used to

Mike C. Kemp

2007-01-01

411

The effects of wet radome on a short millimetre-wave link in Singapore  

Microsoft Academic Search

A short line-of-sight link has been set up at the Nanyang Technological University (NTU) in Singapore to monitor the effect of rain on microwave link performance at 38 GHz. The results suggest that the rain attenuations derived from the measured received levels are much greater than those computed using the ITU-R models. Other studies at the School of EEE, using

Gang Liu; J. T. Ong; Emily Choo; C. G. Teo

2000-01-01

412

Comparative study of travelling-wave and numerical solutions for the coupled short pulse (CSP) equation  

NASA Astrophysics Data System (ADS)

The Lie symmetry analysis is performed for the coupled short plus (CSP) equation. We derive the infinitesimals that admit the classical symmetry group. Five types arise depending on the nature of the Lie symmetry generator. In all types, we find reductions in terms of system of ordinary differential equations, and exact solutions of the CSP equation are derived, which are compared with numerical solutions using the classical fourth-order Runge—Kutta scheme.

Vikas, Kumar; K. Gupta, R.; Ram, Jiwari

2013-05-01

413

Non-Gaussianity analysis of a gravitational wave background made by short-duration burst signals  

NASA Astrophysics Data System (ADS)

We study an observational method to analyze non-Gaussianity of a gravitational wave (GW) background made by superposition of weak burst signals. The proposed method is based on fourth-order correlations of data from four detectors, and might be useful to discriminate the origin of a GW background. With a formulation newly developed to discuss geometrical aspects of the correlations, it is found that the method provides us with linear combinations of two interesting parameters, I2 and V2 defined by the Stokes parameters of individual GW burst signals. We also evaluate sensitivities of specific detector networks to these parameters.

Seto, Naoki

2009-08-01

414

Non-Gaussianity analysis of a gravitational wave background made by short-duration burst signals  

SciTech Connect

We study an observational method to analyze non-Gaussianity of a gravitational wave (GW) background made by superposition of weak burst signals. The proposed method is based on fourth-order correlations of data from four detectors, and might be useful to discriminate the origin of a GW background. With a formulation newly developed to discuss geometrical aspects of the correlations, it is found that the method provides us with linear combinations of two interesting parameters, I{sub 2} and V{sub 2} defined by the Stokes parameters of individual GW burst signals. We also evaluate sensitivities of specific detector networks to these parameters.

Seto, Naoki [Department of Physics, Kyoto University, Kyoto 606-8502 (Japan)

2009-08-15

415

Light Reflection and Wavelength-downshifting from Relativistic Flying Mirrors Formed in Plasma  

NASA Astrophysics Data System (ADS)

The relativistic flying mirror concept uses nonlinear plasma waves formed by an ultra-short intense laser pulse in tenuous plasma to reflect incoming laser light. Because the nonlinear plasma wave is moving approximately at the speed of light, the reflected light is downshifted in wavelength and shortened in pulse length. This concept has been originally invented to intensify focused laser intensity towards extremely high electric field, in which a vacuum starts to break. This scheme is also useful to generate ultra-short, soft-X-ray to XUV light.

Kando, Masaki

416

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

NASA Astrophysics Data System (ADS)

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

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

2000-07-01

417

Stimulated short-wave emission of charged particles in natural hollow crystalline channels  

NASA Astrophysics Data System (ADS)

A quantum theory of the spontaneous and stimulated emission of relativistic and nonrelativistic charged particles moving in natural hollow cylindrical crystalline channels is elaborated with reference to the development of X-ray and gamma lasers. The example of channels in zeolite and chrysolite-asbestos is used to illustrate the features of the quantized motion of particles in such structures, as well as the angular and frequency characteristics of the stimulated and spontaneous emission, slowdown and dechanneling mechanisms, and methods for the excitation of population inversion. It is shown that relativistic positrons with an energy of 50 MeV can be used to achieve the threshold amplification condition in the 1-10 A wavelength range at a beam current density of 10 to the 6th to 10 to the 8th A/sq cm. A beam of nonrelativistic protons with an energy of 0.3 MeV can be used to achieve amplification in the 2-200 micron range at a current density of 100 A/sq cm.

Vysotskii, V. I.; Kuzmin, P. N.

418

Surface Waves in alpha -Nuclei Elastic Scattering.  

National Technical Information Service (NTIS)

We develop in detail a theory of surface waves, excited by the grazing rays in the elastic scattering of alpha particles on nuclei, working within the framework of the short wavelength approximation. The nuclear interaction region is schematized as an abs...

E. Di Salvo G. A. Viano

1982-01-01

419

Does direct impact of SST on short wind waves matter for scatterometry?  

NASA Astrophysics Data System (ADS)

Scatterometer radar backscatter depends on the relationship linking surface stress and surface roughness. SST can alter the growth rate of centimeter-scale waves through its impact on air and water density and water viscosity. This SST-dependency has not been included in the standard Geophysical Model Functions. This study uses a radar imaging model to evaluate this SST-dependence and compares the results to observations from QuikScat Ku-band and ASCAT C-band scatterometers. A SST correction could raise wind speeds by up to 0.2 ms-1 in the storm track region of the Southern Ocean for C-band scatterometers. For the higher frequency Ku-band scatterometers, a SST-induced reduction up to 0.4 ms-1 is predicted south of 60°S, where SST is cold and winds are moderate.

Grodsky, Semyon A.; Kudryavtsev, Vladimir N.; Bentamy, Abderrahim; Carton, James A.; Chapron, Bertrand

2012-06-01

420

Short Range Correlations and Wave Function Factorization in Light and Finite Nuclei  

NASA Astrophysics Data System (ADS)

Recent BNL and Jlab data provided new evidence on two nucleon correlations (2NC) in nuclei. The data confirm the validity of the convolution model, describing the spectral function (SF) of a correlated pair moving in the mean field with high and low relative and center-of-mass (cm) momenta, respectively. The model is built assuming that the wave function (WF) of a nucleus A, describing a configuration where the cm momentum of a correlated pair is low and its relative momentum is high, factorizes into the product of the two-body WF and that of the A-2 system. Such a factorization has been shown to occur in nuclear matter (NM). Here it is shown that few-body systems exhibit factorization, which seems to be therefore a general property, to be reproduced also in studies of the WF of finite nuclei.

Atti, C. Ciofi degli; Kaptari, L. P.; Morita, H.; Scopetta, S.

2011-05-01

421

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

PubMed

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

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

2013-07-10

422

Optimized Weighted Essentially Nonoscillatory Schemes for Linear Waves with Discontinuity  

Microsoft Academic Search

ENO (essentially nonoscillatory) and weighted ENO (WENO) schemes were designed for high resolution of discontinuities, such as shock waves, while optimized schemes such as the DRP (dispersion–relation–preserving) schemes were optimized for short waves (with respect to the grid spacing ?x, e.g., waves that are 6–8?x in wavelength) in the wavenumber space. In this paper, we seek to unite the advantages

Z. J. Wang; R. F. Cheny

2001-01-01

423

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

NASA Astrophysics Data System (ADS)

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

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

2005-04-01

424

Polarization-insensitive wavelength conversion for polarization multiplexing non-return-to-zero quadrature phase shift keying signals based on four-wave mixing in a semiconductor optical amplifier using digital coherent detection  

NASA Astrophysics Data System (ADS)

We have theoretically and numerically investigated polarization-insensitive all-optical wavelength conversion for polarization multiplexing quadrature phase shift keying (QPSK) signals based on four-wave mixing (FWM) in a semiconductor optical amplifier (SOA) with a polarization diversity and digital coherent detection. The simulation results show that the different frequency spacing between pumps and the signal have serious effects on the conversion efficiency, that there is an optimal SOA injection current by considering a high conversion efficiency and a small pattern effect, and that the pattern effect on polarization multiplexing QPSK signals is much lower than non-return-to-zero signals.

Zhou, Hui; Yu, Jianjun; Tang, Jin; Chen, Lin

2013-02-01

425

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

SciTech Connect

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

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

2010-11-12

426

Astronomical Images in Different Wavelengths  

NSDL National Science Digital Library

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

Foundation, Wgbh E.

2004-02-20

427

Integrated platform of millimeter-wave radio-over-fiber and baseband services in a reconfigurable ring\\/bus access network using wavelength interleaving and polarization multiplexing  

Microsoft Academic Search

A novel polarization demultiplexing for wavelength-interleaved 1.25-Gb\\/s baseband signals and 155-Mb\\/s 60-GHz radio-over-fiber signals, combined with tunable filtering for access to consecutive remote access nodes in a ring\\/bus network are experimentally demonstrated.

C. P. Tsekrekos; K.-I. Kitayama; T. Kuri

2009-01-01

428

Temperature dependence of radio wave absorption by atmospheric water vapors at wavelengths ranging from 10 cm to 0.27 mm  

Microsoft Academic Search

The absorption coefficients are calculated for a constant air pressure and a constant relative water-vapor volume concentration for temperatures between 173 and 373 K. The computed data are used to calculate the temperature dependence of absorption on the wavelength in the centimeter, millimeter, and submillimeter range. The temperature coefficient is found to range from 3.2 to 4 in the atmospheric

K. A. Aganbekian; A. Iu. Zrazhevskii; V. G. Malinkin

1975-01-01

429

Plasma waves associated with energetic particles streaming into the solar wind from the earth's bow shock  

Microsoft Academic Search

In the upstream solar wind, three dominant types of plasma waves are observed associated with energetic particle streams coming from the earth's bow shock: ion acoustic waves, electron plasma oscillations, and whistler mode waves. The ion acoustic waves occur simultaneously with either ion beams or a dispersed ion population in the energy range from approx.0.5 to >45 keV. These short-wavelength

R. R. Anderson; G. K. Parks; T. E. Eastman; D. A. Gurnett; L. A. Frank

1981-01-01

430

A search at two eclipses for short-period waves that heat the corona  

NASA Astrophysics Data System (ADS)

As part of a study of the cause of solar coronal heating, we searched for high-frequency (~1 Hz) intensity oscillations in coronal loops in the [Fexiv] coronal green line. We summarize results from observations made at the 3 November 1994, total solar eclipse from the International Astronomical Union site in Putre, Chile, through partly cloudy skies, and at the 26 February 1998 total solar eclipse from Nord, Aruba, through clear skies. We discuss the image reduction and analysis of two simultaneous series of coronal CCD images digitized at 10 Hz for a total time of 160 s in Chile. One series of images was taken through a filter isolating the 5303 Å[Fexiv] coronal green line and the other through a 100 Å filter in the nearby K-corona continuum. We then discuss the modifications made for the 1998 eclipse, and the image reduction and analysis for those image sequences. After standard calibrations and image alignment of both data sets, we use Fourier analysis to search in the [Fexiv] channel for intensity oscillations in loops at the base of the corona. Such oscillations in the 1-Hz range are predicted as a result of density fluctuations from the resonant absorption of MHD waves. The dissipation of a significant amount of mechanical energy from the photosphere into the corona through this mechanism could provide sufficient energy to heat the corona. At neither eclipse do we find evidence for oscillations in the [Fexiv] green line at a level greater than 2% of coronal intensity.

Pasachoff, Jay M.; Babcock, Bryce A.; Russell, Kevin D.; McConnochie, Timothy H.; Diaz, J. Sebastian

2000-08-01

431

Highly strained InxGa(1-x)As-InyAl(1-y)As(x>0.8,y<0.3) layers for short wavelength QWIP and QCL structures grown by MBE  

NASA Astrophysics Data System (ADS)

Highly strained quantum cascade laser (QCL) and quantum well infrared photodetector (QWIPs) structures based on InxGa(1-x)As-InyAl(1-y)As(x>0.8,y<0.3) layers have been grown by molecular beam epitaxy. Conditions of exact stoichiometric growth were used at a temperature of ~420°C to produce structures that are suitable for both emission and detection in the 2-5?m mid-infrared regime. High structural integrity, as assessed by double crystal X-ray diffraction, room temperature photoluminescence and electrical characteristics were observed. Strong room temperature intersubband absorption in highly tensile strained and strain-compensated In0.84Ga0.16As/AlAs/In0.52Al0.48As double barrier quantum wells grown on InP substrates is demonstrated. ?-? intersubband transitions have been observed across a wide range of the mid-infrared spectrum (2-7?m) in three structures of differing In0.84Ga0.16As well width (30, 45, and 80Å). We demonstrate short-wavelength IR, intersubband operation in both detection and emission for application in QC and QWIP structures. By pushing the InGaAs-InAlAs system to its ultimate limit, we have obtained the highest band offsets that are theoretically possible in this system both for the ?-? bands and the ?-X bands, thereby opening up the way for both high power and high efficiency coupled with short-wavelength operation at room temperature. The versatility of this material system and technique in covering a wide range of the infrared spectrum is thus demonstrated.

Missous, M.; Mitchell, C.; Sly, J.; Lai, K. T.; Gupta, R.; Haywood, S. K.

2004-01-01

432

Influence of winds on temporally varying short and long period gravity waves in the near shore regions of the eastern Arabian Sea  

NASA Astrophysics Data System (ADS)

Wave data collected off Ratnagiri, west coast of India, during 1 May 2010 to 30 April 2012 are used in this study. Seasonal and annual variations in wave data controlled by the local wind system such as sea breeze and land breeze, and remote wind generated long period waves are also studied. The role of sea breeze on the sea state during pre- and postmonsoon seasons is studied and it is found that the maximum wave height is observed at 15:00 UTC during the premonsoon season, with an estimated difference in time lag of 1-2 h in maximum wave height between premonsoon and postmonsoon seasons. Observed waves are classified in to (i) short waves (Tp < 8 s), (ii) intermediate waves (8 < Tp < 13 s), and (iii) long waves (Tp> 13 s) based on peak period (Tp) and the percentages of occurrence of each category are estimated. Long period waves are observed mainly during the pre- and the postmonsoon seasons. During the southwest monsoon period, the waves with period > 13 s are a minimum. An event during 2011 is identified as swells propagated from the Southern Ocean with an estimated travelling time of 5-6 days. The swells reaching the Arabian Sea from the south Indian Ocean and Southern Ocean, due to storms during the pre- and postmonsoon periods, modify the near surface winds due to higher phase wave celerity than the wind speed. Estimation of inverse wave age using large-scale winds such as NCEP (National Centers for Environmental Prediction) reflects the presence of cyclonic activity during pre- and postmonsoon seasons but not the effect of the local sea breeze/land breeze wind system.

Glejin, J.; Sanil Kumar, V.; Balakrishnan Nair, T. M.; Singh, J.

2013-03-01

433

Continuous wave terahertz generation up to 2 THz by photomixing on ion-irradiated In{sub 0.53}Ga{sub 0.47}As at 1.55 {mu}m wavelengths  

SciTech Connect

We report the generation of continuous terahertz waves from microwave frequencies of up to 2 THz obtained by photomixing two optical waves at 1.55 {mu}m wavelengths in ion-irradiated In{sub 0.53}Ga{sub 0.47}As interdigitated photomixers. A 200 nm thick silicon nitride coating is used for antireflection and passivation layer, improving the reliability and the heat tolerance of the photomixer. In such devices, output powers greater than 40 nW at 0.5 THz and 10 nW at 1 THz have been achieved. Considering the observed saturation of the outpu