Note: This page contains sample records for the topic vims wavelength scale from Science.gov.
While these samples are representative of the content of Science.gov,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of Science.gov
to obtain the most current and comprehensive results.
Last update: August 15, 2014.
1

Carbon dioxide on the satellites of Saturn: Results from the Cassini VIMS investigation and revisions to the VIMS wavelength scale  

USGS Publications Warehouse

Several of the icy satellites of Saturn show the spectroscopic signature of the asymmetric stretching mode of C-O in carbon dioxide (CO2) at or near the nominal solid-phase laboratory wavelength of 4.2675 ??m (2343.3 cm-1), discovered with the Visible-Infrared Mapping Spectrometer (VIMS) on the Cassini spacecraft. We report here on an analysis of the variation in wavelength and width of the CO2 absorption band in the spectra of Phoebe, Iapetus, Hyperion, and Dione. Comparisons are made to laboratory spectra of pure CO2, CO2 clathrates, ternary mixtures of CO2 with other volatiles, implanted and adsorbed CO2 in non-volatile materials, and ab initio theoretical calculations of CO2 * nH2O. At the wavelength resolution of VIMS, the CO2 on Phoebe is indistinguishable from pure CO2 ice (each molecule's nearby neighbors are also CO2) or type II clathrate of CO2 in H2O. In contrast, the CO2 band on Iapetus, Hyperion, and Dione is shifted to shorter wavelengths (typically ???4.255 ??m (???2350.2 cm-1)) and broadened. These wavelengths are characteristic of complexes of CO2 with different near-neighbor molecules that are encountered in other volatile mixtures such as with H2O and CH3OH, and non-volatile host materials like silicates, some clays, and zeolites. We suggest that Phoebe's CO2 is native to the body as part of the initial inventory of condensates and now exposed on the surface, while CO2 on the other three satellites results at least in part from particle or UV irradiation of native H2O plus a source of C, implantation or accretion from external sources, or redistribution of native CO2 from the interior. The analysis presented here depends on an accurate VIMS wavelength scale. In preparation for this work, the baseline wavelength calibration for the Cassini VIMS was found to be distorted around 4.3 ??m, apparently as a consequence of telluric CO2 gas absorption in the pre-launch calibration. The effect can be reproduced by convolving a sequence of model detector response profiles with a deep atmospheric CO2 absorption profile, producing distorted detector profile shapes and shifted central positions. In a laboratory blackbody spectrum used for radiance calibration, close examination of the CO2 absorption profile shows a similar deviation from that expected from a model. These modeled effects appear to be sufficient to explain the distortion in the existing wavelength calibration now in use. A modification to the wavelength calibration for 13 adjacent bands is provided. The affected channels span about 0.2 ??m centered on 4.28 ??m. The maximum wavelength change is about 10 nm toward longer wavelength. This adjustment has implications for interpretation of some of the spectral features observed in the affected wavelength interval, such as from CO2, as discussed in this paper.

Cruikshank, D. P.; Meyer, A. W.; Brown, R. H.; Clark, R. N.; Jaumann, R.; Stephan, K.; Hibbitts, C. A.; Sandford, S. A.; Mastrapa, R. M. E.; Filacchione, G.; Ore, C. M. D.; Nicholson, P. D.; Buratti, B. J.; McCord, T. B.; Nelson, R. M.; Dalton, J. B.; Baines, K. H.; Matson, D. L.

2010-01-01

2

Wavelength Scaling of High Harmonic Generation Efficiency  

SciTech Connect

Using longer wavelength laser drivers for high harmonic generation is desirable because the highest extreme ultraviolet frequency scales as the square of the wavelength. Recent numerical studies predict that high harmonic efficiency falls dramatically with increasing wavelength, with a very unfavorable lambda{sup -(5-6)} scaling. We performed an experimental study of the high harmonic yield over a wavelength range of 800-1850 nm. A thin gas jet was employed to minimize phase matching effects, and the laser intensity and focal spot size were kept constant as the wavelength was changed. Ion yield was simultaneously measured so that the total number of emitting atoms was known. We found that the scaling at constant laser intensity is lambda{sup -6.3+}-{sup 1.1} in Xe and lambda{sup -6.5+}-{sup 1.1} in Kr over the wavelength range of 800-1850 nm, somewhat worse than the theoretical predictions.

Shiner, A. D.; Trallero-Herrero, C.; Kajumba, N.; Corkum, P. B.; Villeneuve, D. M. [National Research Council of Canada, 100 Sussex Drive, Ottawa, Ontario K1A 0R6 (Canada); Bandulet, H.-C.; Comtois, D.; Legare, F.; Giguere, M.; Kieffer, J-C. [INRS-Energie et Materiaux, 1650 boulevard Lionel-Boulet, C.P. 1020, Varennes (Quebec) J3X 1S2 (Canada)

2009-08-14

3

Wavelength-scale deformed microdisk lasers  

SciTech Connect

We investigate lasing and output directionality of limacon-shaped microdisk lasers of dimensions comparable to the emission wavelength. The far-field patterns are shown to differ between lasing modes, unlike in large cavities where lasing modes exhibit universal emission directionality determined by chaotic ray dynamics. Unidirectional emission is obtained for certain modes in the wavelength-scale cavities. It results from weak coupling of nearly isotropic high-quality resonances to anisotropic low-quality resonances, combined with chiral symmetry breaking of clockwise and counterclockwise propagating waves. The latter is described by an extended ray dynamics which includes the Goos-Haenchen shift and the Fresnel filtering. Mode hybridization and wave effects in open cavities make it possible to control the output properties of individual lasing modes in wavelength-scale lasers.

Song, Q. H.; Cao Hui [Department of Applied Physics, Yale University, New Haven, Connecticut 06520-8482 (United States); Ge Li [Department of Electrical Engineering, Princeton University, Princeton, New Jersey 08544 (United States); Wiersig, J.; Shim, J.-B.; Unterhinninghofen, J.; Eberspaecher, A. [Institut fuer Theoretische Physik, Universitaet Magdeburg, Postfach 4120, D-39016 Magdeburg (Germany); Fang, W.; Solomon, G. S. [Joint Quantum Institute, NIST and University of Maryland, Gaithersburg, Maryland 20899 (United States)

2011-12-15

4

Zero-Points of FOS Wavelength Scales  

NASA Astrophysics Data System (ADS)

We have investigated the internal zero-points of the HST's Faint object spectrograph (FOS) on-orbit wavelength calibration between 1990 (launch) and 1997 (de-commissioning). The analysis is based on cross-correlating about 1200 WAVECAL exposures for the high-resolution dispersers, using as templates those exposures which define the dispersion solutions currently in use by the FOS pipeline. FOS has two channels BLUE/RED using two independent Digicon detectors. For BLUE systematic shifts of the zero-points are present, which amount to a maximum offset of 7 pixels (1.75 diodes) over the entire period. The zero-points for RED modes present an apparently random distribution with a peak-to-peak range of 7 pixels. We discu ss the effect of the geomagnetic environment as a possible cause for the observed behaviour and describe the ongoing work to reduce the uncertainty in the wavelength scale.

Rosa, Michael R.; Kerber, Florian

5

Scaled Strong Field Interactions at Long Wavelengths  

NASA Astrophysics Data System (ADS)

The strong field regime describes interactions between light and matter where the electric field of the laser is a significant fraction of the binding field of the atom. Short pulsed lasers are capable of producing local fields on the order of the atomic unit of electric field. Under the influence of such strong fields, the ionization regime and electron dynamics are highly dependent on the wavelength used to drive the interaction. Few studies have been performed in the mid-infrared (MIR) spectral range. Using MIR wavelengths, the ponderomotive energy, Up, imposed on the electrons can be a factor of 20 greater than in the visible and near-infrared. Experiments on above threshold ionization (ATI) of cesium, nonsequential ionization (NSI) of noble gases, and high harmonic generation (HHG) in condensed phase media highlight the benefits of performing strong field investigations in the MIR. The photoelectron energy spectrum from above threshold ionization (ATI) of atoms provides details about the strong field interaction. Cesium atoms driven by a 3.6 mum laser indicate that excited states can play a large role in ionization from the ground state. Previous experiments on argon in the near-infrared can be compared to cesium at 3.6 im due to their similar Keldysh-scaling. Unlike argon, the measured ionization yield in cesium saturates at a higher intensity than predicted due to the Stark shift of the ground state. Such shifts have not been detected in argon. The low-lying 6P excited states of cesium produce a strong effect on the photoelectron energy spectrum, resulting in a splitting of each ATI peak. Enhancements in the photoelectron energy spectrum similar to those found in argon are observed in cesium. These enhancements are relatively insensitive to ellipticity of the drive laser. To take advantage of the large ponderomotive energy associated with Mid-IR lasers, ionization of argon, krypton and xenon is studied at 3.6 im. The factor of 20 increase in Up between the near-infrared and MIR experiments allows electrons to return with up to ~300eV in energy. Inelastic scattering of returning electrons impinging on their parent ion results in impact ionization, producing up to the 6th charge state in xenon. The large increase in the ionization yield produced by impact ionization is understood by scaling the impact ionization cross section by the electron return energy distribution and the calculated wavepacket spread. Elastic scattering of the returning electrons provides information about the structure of the parent ion, as the differential cross section can be extracted from the experimental photoelectron angular distribution. High harmonic generation (HHG) in atomic gases occurs with notoriously low conversion efficiency. The advantages of a MIR laser system are used to study HHG in liquid and solid samples. The long wavelength makes possible the first demonstration of high order harmonics from the bulk of a crystalline solid. Harmonics generated in liquids appear perturbative in nature, while those generated in a crystal are highly nonperturbative. The high order harmonics yield information about the strong field response of the crystal's band structure. The use of MIR wavelengths allows the observation of new strong field phenomena. As all of the above methods are applicable to molecules as well as atoms, MIR studies have a strong impact on understanding the interaction between light and matter.

Sistrunk, Emily Frances

6

Principal components analysis of Jupiter VIMS spectra  

USGS Publications Warehouse

During Cassini - Jupiter flyby occurred in December 2000, Visual-Infrared mapping spectrometer (VIMS) instrument took several image cubes of Jupiter at different phase angles and distances. We have analysed the spectral images acquired by the VIMS visual channel by means of a principal component analysis technique (PCA). The original data set consists of 96 spectral images in the 0.35-1.05 ??m wavelength range. The product of the analysis are new PC bands, which contain all the spectral variance of the original data. These new components have been used to produce a map of Jupiter made of seven coherent spectral classes. The map confirms previously published work done on the Great Red Spot by using NIMS data. Some other new findings, presently under investigation, are presented. ?? 2004 Published by Elsevier Ltd on behalf of COSPAR.

Bellucci, G.; Formisano, V.; D'Aversa, E.; Brown, R. H.; Baines, K. H.; Bibring, J. P.; Buratti, B. J.; Capaccioni, F.; Cerroni, P.; Clark, R. N.; Coradini, A.; Cruikshank, D. P.; Drossart, P.; Jaumann, R.; Langevin, Y.; Matson, D. L.; McCord, T. B.; Mennella, V.; Nelson, R. M.; Nicholson, P. D.; Sicardy, B.; Sotin, C.; Chamberlain, M. C.; Hansen, G.; Hibbits, K.; Showalter, M.; Filacchione, G.

2004-01-01

7

Spectral properties and temperature radial profiles of Saturn's main rings by Cassini-VIMS: variability with solar phase and elevation  

NASA Astrophysics Data System (ADS)

We report about Saturn's rings average spectral properties and temperature as retrieved from ten Cassini VIMS radial mosaics acquired between october 2004 and january 2010. The dataset includes observations taken with solar phase running between 12° to 136° and elevation angle between -21° to +5°. These observations, after being reduced in spectrograms, e.g. 2D arrays containing the VIS-IR spectral (0.35-5.0 ?m) and spatial (from 73.500 to 141.375 km) information, allow us a direct comparison of the derived spectral properties on a common spatial scale. Significant changes in VIS reddening, water ice abundance and grain sizes are observed across different rings radial regions. When observed at high solar phases, a remarkable increase of VIS reddening and water ice band depths is found, as a consequence of the presence of a red contaminant intimately mixed within water ice grains. Ring's particles temperature is retrieved by using the wavelength of the 3.6 ?m continuum peak on reflectance spectra as a marker. For pure water ice the position of the peak, as measured in laboratory, shifts towards shorter wavelengths when temperature decreases, from about 3.65 ?m at 123 K to about 3.55 ?m at 88 K. When applied to VIMS rings observations, this method allow us to infer the average temperature across ring regions sampled with 400 km-wide radial bins. VIMS temperature radial profiles are compared with similar CIRS measurements acquired at the same time. We have found a substantial agreement between VIMS and CIRS results for the A and B ring while VIMS measures higher temperatures than CIRS across C ring and CD as a consequence of the lower optical depth and deviation from pure water ice composition. In summary, VIMS results show that 1) across C ring and CD the 3.6 ?m peak wavelength is always higher than across B and A rings: C and CD are warmer than A and B rings; 2) when the solar elevation angle decreases to 0° (equinox) the peak's position shifts at shorter wavelengths: rings become colder; 3) when both afternoon and morning ansae observations are available, we have measured higher temperature across the afternoon ansa

Filacchione, Gianrico; Capaccioni, F.; Ciarniello, M.; Clark, R. N.; Nicholson, P. D.; Cruikshank, D. P.; Brown, R. H.; Cuzzi, J. N.; Altobelli, N.; Spilker, L. J.; Hedman, M. M.; Dalle Ore, C. M.; Cerroni, P.

2013-10-01

8

Mapping and interpretation of Sinlap crater on Titan using Cassini VIMS and RADAR data  

NASA Astrophysics Data System (ADS)

Only a few impact craters have been unambiguously detected on Titan by the Cassini-Huygens mission. Among these, Sinlap is the only one that has been observed both by the RADAR and VIMS instruments. This paper describes observations at centimeter and infrared wavelengths which provide complementary information about the composition, topography, and surface roughness. Several units appear in VIMS false color composites of band ratios in the Sinlap area, suggesting compositional heterogeneities. A bright pixel possibly related to a central peak does not show significant spectral variations, indicating either that the impact site was vertically homogeneous, or that this area has been recovered by homogeneous deposits. Both VIMS ratio images and dielectric constant measurements suggest the presence of an area enriched in water ice around the main ejecta blanket. Since the Ku-band SAR may see subsurface structures at the meter scale, the difference between infrared and SAR observations can be explained by the presence of a thin layer transparent to the radar. An analogy with terrestrial craters in Libya supports this interpretation. Finally, a tentative model describes the geological history of this area prior, during, and after the impact. It involves mainly the creation of ballistic ejecta and an expanding plume of vapor triggered by the impact, followed by the redeposition of icy spherules recondensed from this vapor plume blown downwind. Subsequent evolution is then driven by erosional processes and aeolian deposition.

Le Mouélic, Stéphane; Paillou, Philippe; Janssen, Michael A.; Barnes, Jason W.; Rodriguez, Sébastien; Sotin, Christophe; Brown, Robert H.; Baines, Kevin H.; Buratti, Bonnie J.; Clark, Roger N.; Crapeau, Marc; Encrenaz, Pierre J.; Jaumann, Ralf; Geudtner, Dirk; Paganelli, Flora; Soderblom, Laurence; Tobie, Gabriel; Wall, Steve

2008-04-01

9

Mapping and interpretation of Sinlap crater on Titan using Cassini VIMS and RADAR data  

USGS Publications Warehouse

Only a few impact craters have been unambiguously detected on Titan by the Cassini-Huygens mission. Among these, Sinlap is the only one that has been observed both by the RADAR and VIMS instruments. This paper describes observations at centimeter and infrared wavelengths which provide complementary information about the composition, topography, and surface roughness. Several units appear in VIMS false color composites of band ratios in the Sinlap area, suggesting compositional heterogeneities. A bright pixel possibly related to a central peak does not show significant spectral variations, indicating either that the impact site was vertically homogeneous, or that this area has been recovered by homogeneous deposits. Both VIMS ratio images and dielectric constant measurements suggest the presence of an area enriched in water ice around the main ejecta blanket. Since the Ku-band SAR may see subsurface structures at the meter scale, the difference between infrared and SAR observations can be explained by the presence of a thin layer transparent to the radar. An analogy with terrestrial craters in Libya supports this interpretation. Finally, a tentative model describes the geological history of this area prior, during, and after the impact. It involves mainly the creation of ballistic ejecta and an expanding plume of vapor triggered by the impact, followed by the redeposition of icy spherules recondensed from this vapor plume blown downwind. Subsequent evolution is then driven by erosional processes and aeolian deposition. Copyright 2008 by the American Geophysical Union.

Le, Mouelic, S.; Paillou, P.; Janssen, M. A.; Barnes, J. W.; Rodriguez, S.; Sotin, C.; Brown, R. H.; Baines, K. H.; Buratti, B. J.; Clark, R. N.; Crapeau, M.; Encrenaz, P. J.; Jaumann, R.; Geudtner, D.; Paganelli, F.; Soderblom, L.; Tobie, G.; Wall, S.

2008-01-01

10

A close look at Saturn's rings with Cassini VIMS  

USGS Publications Warehouse

Soon after the Cassini-Huygens spacecraft entered orbit about Saturn on 1 July 2004, its Visual and Infrared Mapping Spectrometer obtained two continuous spectral scans across the rings, covering the wavelength range 0.35-5.1 ??m, at a spatial resolution of 15-25 km. The first scan covers the outer C and inner B rings, while the second covers the Cassini Division and the entire A ring. Comparisons of the VIMS radial reflectance profile at 1.08 ??m with similar profiles at a wavelength of 0.45 ??m assembled from Voyager images show very little change in ring structure over the intervening 24 years, with the exception of a few features already known to be noncircular. A model for single-scattering by a classical, many-particle-thick slab of material with normal optical depths derived from the Voyager photopolarimeter stellar occultation is found to provide an excellent fit to the observed VIMS reflectance profiles for the C ring and Cassini Division, and an acceptable fit for the inner B ring. The A ring deviates significantly from such a model, consistent with previous suggestions that this region may be closer to a monolayer. An additional complication here is the azimuthally-variable average optical depth associated with "self-gravity wakes" in this region and the fact that much of the A ring may be a mixture of almost opaque wakes and relatively transparent interwake zones. Consistently with previous studies, we find that the near-infrared spectra of all main ring regions are dominated by water ice, with a typical regolith grain radius of 5-20 ??m, while the steep decrease in visual reflectance shortward of 0.6 ??m is suggestive of an organic contaminant, perhaps tholin-like. Although no materials other than H2O ice have been identified with any certainty in the VIMS spectra of the rings, significant radial variations are seen in the strength of the water-ice absorption bands. Across the boundary between the C and B rings, over a radial range of ???7000 km, the near-IR band depths strengthen considerably. A very similar pattern is seen across the outer half of the Cassini Division and into the inner A ring, accompanied by a steepening of the red slope in the visible spectrum shortward of 0.55 ??m. We attribute these trends-as well as smaller-scale variations associated with strong density waves in the A ring-to differing grain sizes in the tholin-contaminated icy regolith that covers the surfaces of the decimeter-to-meter sized ring particles. On the largest scale, the spectral variations seen by VIMS suggest that the rings may be divided into two larger 'ring complexes,' with similar internal variations in structure, optical depth, particle size, regolith texture and composition. The inner complex comprises the C and B rings, while the outer comprises the Cassini Division and A ring. ?? 2007 Elsevier Inc. All rights reserved.

Nicholson, P. D.; Hedman, M. M.; Clark, R. N.; Showalter, M. R.; Cruikshank, D. P.; Cuzzi, J. N.; Filacchione, G.; Capaccioni, F.; Cerroni, P.; Hansen, G. B.; Sicardy, B.; Drossart, P.; Brown, R. H.; Buratti, B. J.; Baines, K. H.; Coradini, A.

2008-01-01

11

Scaling laws for photoelectron holography in the midinfrared wavelength regime.  

PubMed

Midinfrared strong-field laser ionization offers the promise of measuring holograms of atoms and molecules, which contain both spatial and temporal information of the ion and the photoelectron with subfemtosecond temporal and angstrom spatial resolution. We report on the scaling of photoelectron holographic interference patterns with the laser pulse duration, wavelength, and intensity. High-resolution holograms for the ionization of metastable xenon atoms by 7-16???m light from the FELICE free electron laser are presented and compared to semiclassical calculations that provide analytical insight. PMID:23031101

Huismans, Y; Gijsbertsen, A; Smolkowska, A S; Jungmann, J H; Rouzée, A; Logman, P S W M; Lépine, F; Cauchy, C; Zamith, S; Marchenko, T; Bakker, J M; Berden, G; Redlich, B; van der Meer, A F G; Ivanov, M Yu; Yan, T-M; Bauer, D; Smirnova, O; Vrakking, M J J

2012-07-01

12

Laboratory Imaging Spectroscopy (0.4-5.1 MU m) of Rocks and Minerals with the Cassini VIMS Instrument  

Microsoft Academic Search

The Cassini Visual and Infrared Mapping Spectrometer (VIMS) instrument is an imaging spectrometer covering the 0.4 to 5.1 mu m wavelength region with 352 spectral channels, and with a spacing of approximately 16 nm, and a Full Width at Half Maximum (FWHM) of approximately 13 nm. The VIMS is also a spatial imager with a field of view of 64

R. N. Clark; R. H. Brown; K. H. Baines; G. Bellucci; J. P. Bibring; B. J. Buratti; E. Bussoletti; F. Capaccioni; P. Cerroni; M. Combes; A. Coradini; D. P. Cruikshank; P. Drossart; V. Formisano; K. Herkenhoff; R. Jaumann; Y. Langevin; D. L. Matson; T. B. McCord; R. Nelson; P. Nicholson; B. Sicardy; C. Sotin; D. Juergens; G. Klein; E. Miller

1996-01-01

13

Photonic crystal lasers using wavelength-scale embedded active region  

NASA Astrophysics Data System (ADS)

Lasers with ultra-low operating energy are desired for use in chip-to-chip and on-chip optical interconnects. If we are to reduce the operating energy, we must reduce the active volume. Therefore, a photonic crystal (PhC) laser with a wavelength-scale cavity has attracted a lot of attention because a PhC provides a large Q-factor with a small volume. To improve this device's performance, we employ an embedded active region structure in which the wavelength-scale active region is buried with an InP PhC slab. This structure enables us to achieve effective confinement of both carriers and photons, and to improve the thermal resistance of the device. Thus, we have obtained a large external differential quantum efficiency of 55% and an output power of -10 dBm by optical pumping. For electrical pumping, we use a lateral p-i-n structure that employs Zn diffusion and Si ion implantation for p-type and n-type doping, respectively. We have achieved room-temperature continuous-wave operation with a threshold current of 7.8 µA and a maximum 3 dB bandwidth of 16.2 GHz. The results of an experimental bit error rate measurement with a 10 Gbit s-1 NRZ signal reveal the minimum operating energy for transferring a single bit of 5.5 fJ. These results show the potential of this laser to be used for very short reach interconnects. We also describe the optimal design of cavity quality (Q) factor in terms of achieving a large output power with a low operating energy using a calculation based on rate equations. When we assume an internal absorption loss of 20 cm-1, the optimized coupling Q-factor is 2000.

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

2014-01-01

14

Wavelength scaling of terahertz generation by gas ionization.  

PubMed

Low-frequency currents induced by ultrashort laser-driven ionization can emit extremely broadband, single-cycle terahertz pulses. We present a model that predicts a strong wavelength dependence of the THz emission in good agreement with our experimental study. This reveals that the combined effects of plasma currents rising proportionally to the square of the pump wavelength and wavelength-dependent focusing conditions lead to 30 times higher THz emission at 1800 nm compared to an 800 nm wavelength. Unrivaled single-cycle electric field strengths of 4.4??MV/cm are achieved with this compact table-top setup. PMID:23829737

Clerici, Matteo; Peccianti, Marco; Schmidt, Bruno E; Caspani, Lucia; Shalaby, Mostafa; Giguère, Mathieu; Lotti, Antonio; Couairon, Arnaud; Légaré, François; Ozaki, Tsuneyuki; Faccio, Daniele; Morandotti, Roberto

2013-06-21

15

Wavelength scaling of implosion symmetry, ablation pressure, and hydrodynamic efficiency in laser fusion  

SciTech Connect

We examine the scaling of implosion symmetry, ablation pressure, and hydrodynamic efficiency with the wavelength of the laser, using a recent theoretical analysis of ablative laser driven implosions as a tool. Symmetrization by a hot atmosphere is most effective for long wavelength lasers, whereas ablation pressure and hydrodynamic efficiency are best for shorter laser wavelengths.

Max, C.E.; Lindl, J.D.; Mead, W.C.

1981-07-31

16

Cassini-VIMS Observations of Stellar Occultations by Saturn's Rings  

NASA Astrophysics Data System (ADS)

Between May 24 and August 9, 2005 the Cassini Visual and Infrared Mapping Spectrometer (VIMS) observed four grazing occultations of the long-period variable star, o Ceti (spectral type M7 III, m_K = -2.60). The first occultation track penetrated the rings to a minimum radius of 115,000~km in the B ring, while the second and third tracks penetrated to 126,000~km and 132,000~km in the A Ring, and the last track reached 139,500~km, just interior to the F Ring. The sampling interval was 80~ms,but the radial resolution is limited by the projected stellar diameter which ranges from 0.4 -- 4~km, depending on ring longitude. Due to the very small ring inclination to the line of sight of 3.45°, the B ring and much of the A ring appear almost opaque, while extremely high S/N ratio lightcurves were obtained of low optical depth regions such as the F ring and Cassini Division. All cuts across the eccentric F ring reveal a dense central strand of FWHM 10 -- 50~km flanked by inner and outer strands which are variable both in normal optical depth and radial separation. All three strands are embedded in a broad `skirt' which is at least 1200~km wide. Within the 325-km wide Encke Gap in the outer A ring are three quasi-circular narrow ringlets, as seen in Cassini images (Porco et al., 2005), with variable normal optical depths in the range 0.001VIMS observed a single occultation of the star ? Scorpii (spectral type M1 Iab, m_K = -3.78). The occultation track penetrated to a radius of 101,200~km in the B-Ring. The sample interval was 40~ms, which determined the radial resolution of about 0.4~km. Since the inclination angle for this observation was much higher, 32.1°, 25 -- 50% of the light was transmitted through the A ring. For all parts of the ring with significant optical depth, the signal varies erratically from sample to sample. These fluctuations are larger than the noise observed with the unocculted star and they are strongly correlated across all wavelength channels, indicating that they are due to fine scale structure in the rings as described in Showalter and Nicholson (1990). This work was supported by NASA under a contract with the Cassini-Huygens Project.

Hedman, M. M.; Nicholson, P. D.; Wallis, B. D.

2005-12-01

17

Crystalline and Amorphous Ice on Enceladus: Observations from the Cassini Visual Infrared Mapping Spectrometer (VIMS)  

NASA Astrophysics Data System (ADS)

Photometric and spectral analysis of data from the Cassini Visual and Infrared Mapping Spectrometer (VIMS) has yielded intriguing findings regarding the properties and composition of the surface of Saturn's satellite Enceladus. Spectral cubes, which contain both spatial and spectral information, were obtained of this satellite with a wavelength distribution in the infrared far more extensive than from any previous observations. Using these cubes, we have discovered a distribution of amorphous and crystalline ices on the southern pole of Enceladus, indicating intense ion bombardment in those latitudes and recent geological activity at the "tiger stripe" linea. Using a composite mosaic of the satellite, we map this distribution of ices according to a "crystallinity factor" and consider investigation of the time scale of the geologic activity on the surface of Enceladus based on amorphization rates in the outer Solar System. Work funded by NASA.

Newman, Sarah; Buratti, B. J.; Brown, R. H.; Jaumann, R.; Bauer, J.; Momary, T.

2006-09-01

18

VIM: The Communication Link for Professionals  

ERIC Educational Resources Information Center

Describes the organization and operating policies of the Vocational Instructional Materials Section (VIM) in the New and Related Services Division of the American Vocational Association (AVA). VIM was established in 1969 to give organization and visibility to instructional materials development personnel within AVA. (MF)

Jensen, Arthur

1978-01-01

19

Saturn's satellites temperatures inferred from Cassini-VIMS reflectance spectra  

NASA Astrophysics Data System (ADS)

The spectral position of the 3.6 ?m continuum peak measured on Cassini-VIMS reflectance spectra is used as a marker to infer the temperature of the regolith particles covering the surfaces of Saturn's icy satellites. Laboratory measurements indicate that for pure water ice the position of the 3.6 ?m peak is temperature-dependent: it shifts towards shorter wavelengths when the ice is cooled, moving from about 3.65 ?m at T=123 K to about 3.55 ?m at T=88 K. Starting from this experimental evidence we have used a 4th-degree polynomial fit between 3.2 and 3.8 µm to measure the wavelength at which the peak occurs with the view toward using it as a marker to retrieve the temperatures of the satellites. This method is applied to about 240 disk-integrated observations of Saturn's regular satellites collected by VIMS between 2004 and 2011 (Filacchione et al. Icarus 220, 2012) with solar phase in the 20-40 deg range, corresponding to late morning-early afternoon local times. From these observations we have retrieved average temperatures for Mimas (~88 K), Enceladus (<<88 K), Tethys (<88 K), Dione (~100 K), Rhea (~108 K), Hyperion (~113 K), Iapetus trailing (~138K) and Iapetus leading hemisphere (>170K). For some satellites, like Tethys and Dione, for which observations on both leading and trailing hemispheres are available, we have measured average temperatures higher by about 10 K on the trailing than on the leading hemisphere. Temperatures measured by VIMS with this method are in general much higher than corresponding ones reported by CIRS: this is a consequence of the shallow skindepth (few microns) to which VIMS is sensitive while CIRS measures temperature at greater depth (few millimeters). Grain size and contaminants embedded in water ice may also play a role in the 3.6 ?m peak properties and these effects have yet to be investigated. Combining VIMS and CIRS measurements will allow us to better characterize the regolith physical proper ties and heat transport mechanisms

Filacchione, G.; Capaccioni, F.; Clark, R. N.; Ciarniello, M.; Brown, R. H.; Cruikshank, D. P.; Buratti, B. J.; Cuzzi, J. N.; Spilker, L. J.; Nicholson, P. D.; Dalle Ore, C.; Cerroni, P.; Tosi, F.; Scipioni, F.

2013-12-01

20

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

Microsoft Academic Search

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

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

2011-01-01

21

Global spectral properties of Rhea measured by VIMS  

NASA Astrophysics Data System (ADS)

The icy Saturnian satellite Rhea is often regarded as twin to its neighboring satellite Dione especially with respect to its geological history [1,2] and its spectral surface properties [3]. Cassini VIMS detected the satellites surfaces in the wavelength range from 0.35 to 5.1?m and offers the first spatially resolved hyperspectral data of the Saturnian satellites [4], which allow a detailed comparison of the spatial distribution of the spectral properties of Rhea in comparison the results achieved for Dione [5,6]. Images acquired by Cassini ISS camera offer the opportunity to study any relationships between the spectral variations to geological and morphological surface features.

Stephan, K.; Jaumann, R.; Wagner, R.; Clark, R. N.; Cruikshank, D. P.; Hibbitts, C. A.; Roatsch, T.; Giese, B.; Brown, R. H.; Filacchione, G.; Cappacione, F.; Buratti, B. J.; Hansen, G. B.; Nicholson, P. D.; Baines, K. H.; Nelson, R. M.; Matson, D. L.; Matz, K.-D.

2011-10-01

22

Empirical correction of Titan surface photometry and atmospheric scattering from Cassini/VIMS data  

NASA Astrophysics Data System (ADS)

The Visual and Infrared Mapping Spectrometer (VIMS) onboard the Cassini spacecraft is able to image Titan's surface in 7 atmospheric windows in the infrared domain. However, surface photometry, atmospheric scattering and atmospheric absorption effects produce seams and a general blurring effect at short wavelengths in VIMS global mosaics of individual cubes. The aim of this study is therefore to correct empirically the VIMS cubes for atmospheric scattering, absorption and surface photometry, in order to produce seamless albedo maps. We refined the surface photometric correction using a new global mosaic integrating all Titan flybys from Ta to T90. This photometric function corresponds to a Lunar-Lambert law, which in turns allows the estimation of the atmospheric opacity at 5 ?m. This value is consistent with recent values retrieved from solar occultations and specular reflections on North polar lakes. Two approaches to remove the atmospheric scattering are compared in this study. The first one is based on the removal of the atmospheric windows bands wings. The second one is based on band ratios computed on a series of VIMS cubes of the Huygens Landing Site. Albedo values corrected with these methods are consistent with albedo values calculated thanks to complete radiative transfer models established for the Huygens landing site. This confirms the possibility to implement a global first order correction of VIMS cubes in a simple and fast way to obtain the spectral information of the surface.

Cornet, T.; Philippe, S.; Le Mouélic, S.; Rodriguez, S.; Sotin, C.; Brown, R. H.; Barnes, J. W.; Baines, K. H.; Buratti, B. J.; Clark, R. N.; Nicholson, P. D.

2013-12-01

23

IR-dust observations of Comet Tempel 2 with CRAF VIMS  

NASA Technical Reports Server (NTRS)

Measurement strategies are now being planned for using the Visual and Infrared Mapping Spectrometer (VIMS) to observe the asteroid Hestia, and the nucleus, and the gas and dust in the coma of comet P/Tempel 2 as part of the Comet Rendezvous Asteroid Flyby (CRAF) mission. The spectral range of VIMS will cover wavelengths from 0.35 to 5.2 micrometers, with a spectral resolution of 11 nm from 0.35 to 2.4 micrometers and of 22 nm from 2.4 to 5.2 micrometers. The instantaneous field of view (IFOV) provided by the foreoptics is 0.5 milliradians, and the current design of the instrument provides for a scanning secondary mirror which will scan a swath of length 72 IFOVs. The CRAF high resolution scan platform motion will permit slewing VIMS in a direction perpendicular to the swath. This enables the building of a two dimensional image in any or all wavelength channels. Important measurements of the dust coma will include the onset of early coma activity, the mapping of gas and dust jets and correlations with active nucleus areas, observations of the dust coma from various scattering phase angles, coverage of the low wavelength portion of the thermal radiation, and the 3.4 micrometer hydrocarbon emission. A description of the VIMS instrument is presented.

Combi, Michael R.; Mccord, T. B.; Bell, J. F.; Brown, R. H.; Clark, R. N.; Cruikshank, D. P.; Johnson, T. V.; Lebofsky, L. A.; Matson, D. L.

1988-01-01

24

Phase-dependent interference fringes in the wavelength scaling of harmonic efficiency  

NASA Astrophysics Data System (ADS)

We describe phase-dependent wavelength scaling of high-order-harmonic generation efficiency driven by ultrashort laser fields in the midinfrared. We employ both numerical solution of the time-dependent Schrödinger equation and the strong field approximation to analyze the fine-scale oscillations in the harmonic yield in the context of channel-closing effects. We show, by varying the carrier-envelope phase, that the amplitude of these oscillations depends strongly on the number of returning electron trajectories. Furthermore, the peak positions of the oscillations vary significantly as a function of the carrier-envelope phase. Owing to its practical applications, we also study the wavelength dependence of harmonic yield in the "single-cycle" limit, and observe a smooth variation in the wavelength scaling originating from the vanishing fine-scale oscillations.

Yavuz, I.; Bleda, E. A.; Altun, Z.; Topcu, T.

2014-05-01

25

Monitoring Enceladus' activity with Cassini-VIMS  

NASA Astrophysics Data System (ADS)

The plumes of water vapor and ice grains spewing out from cracks near Enceladus' south pole are one of Cassini's most remarkable discoveries. However, it is not yet clear what processes control or power this geological activity. One way to constrain what is going on below Enceladus' surface is to look for temporal variability in the plume. In certain tidal models, the activity level of individual plume sources may rise or fall on orbital timescales due to flexing, but variations on longer time scales are also conceivable. The Visual and Infrared Mapping Spectrometer (VIMS) onboard the Cassini Spacecraft has observed Enceladus' plumes roughly 20 times between 2005 and 2012. These observations cover a wide range of viewing conditions, with phase angles ranging from 150 to 170 degrees. In general, comparing such observations to one another is challenging due to the relatively weak signals, high background levels and significant phase effects involved. However, the currently-available data sets include multiple observations made at almost the same phase angles, but a range of different times and orbital phases relative to pericenter. Hence we can now make controlled comparisons of the plume's brightness at a given viewing geometry. Preliminary investigations of these data hint that the total brightness of the plume might vary with orbital phase relative to pericenter and/or with longer seasonal timescales. Thus when this analysis is complete, we should be able to constrain and quantify temporal variations in the plume's activity.

Hedman, M. M.; Gosmeyer, C.; Nicholson, P. D.

2012-12-01

26

Hapke modeling of Rhea surface properties through Cassini-VIMS spectra  

USGS Publications Warehouse

The surface properties of the icy bodies in the saturnian system have been investigated by means of the Cassini-VIMS (Visual Infrared Mapping Spectrometer) hyperspectral imager which operates in the 0.35-5.1. ??m wavelength range. In particular, we have analyzed 111 full disk hyperspectral images of Rhea ranging in solar phase between 0.08?? and 109.8??. These data have been previously analyzed by Filacchione et al. (Filacchione, G. et al. [2007]. Icarus 186, 259-290; Filacchione, G. et al. [2010]. Icarus 206, 507-523) to study, adopting various "spectral indicators" (such as spectral slopes, band depth, and continuum level), the relations among various saturnian satellites. As a further step we proceed in this paper to a quantitative evaluation of the physical parameters determining the spectrophotometric properties of Rhea's surface. To do this we have applied Hapke (Hapke, B. [1993]. Theory of Reflectance and Emittance Spectroscopy, Topics in Remote Sensing: 3 Springer, Berlin) IMSA model (Isotropic Multiple Scattering Approximation) which allow us to model the phase function at VIS-IR (visible-infrared) wavelengths as well as the spectra taking into account various types of mixtures of surface materials. Thanks to this method we have been able to constrain the size of water ice particles covering the surface, the amount of organic contaminants, the large scale surface roughness and the opposition effect surge. From our analysis it appears that wavelength dependent parameters, e.g. opposition surge width (h) and single-particle phase function parameters (b,. v), are strongly correlated to the estimated single-scattering albedo of particles. For Rhea the best fit solution is obtained by assuming: (1) an intraparticle mixture of crystalline water ice and a small amount (0.4%) of Triton tholin; (2) a monodisperse grain size distribution having a particle diameter am= 38. ??m; and (3) a surface roughness parameter value of 33??. The study of phase function shows that both shadow hiding and coherent backscattering contribute to the opposition surge. This study represents the first attempt, in the case of Rhea, to join the spectral and the photometric analysis. The surface model we derived gives a good quantitative description of both spectrum and phase curve of the satellite. The same approach and model, with appropriate modifications, shall be applied to VIMS data of the other icy satellites of Saturn, in order to reveal similarities and differences in the surface characteristics to understand how these bodies interact with their environment. ?? 2011 Elsevier Inc.

Ciarniello, M.; Capaccioni, F.; Filacchione, G.; Clark, R. N.; Cruikshank, D. P.; Cerroni, P.; Coradini, A.; Brown, R. H.; Buratti, B. J.; Tosi, F.; Stephan, K.

2011-01-01

27

Acoustic focusing of sub-wavelength scale achieved by multiple Fabry-Perot resonance effect  

NASA Astrophysics Data System (ADS)

It is demonstrated that a novel design of a multi-branch structure can converge plane acoustic waves to a focal region of sub-wavelength scale. The structure consists of multiple sub-wavelength apertures; each has length equal to the integer times that of the shortest aperture. The periodicity length of the inlet array is selected equal to the length of the structure, inducing a cooperation between the surface resonances and the Fabry-Perot (FP) resonances in apertures. The design allows FP resonances to exhibit in all apertures simultaneously, hence a multiple FP resonance is achieved. The generated evanescent waves are amplified effectively, and the acoustic focusing of sub-wavelength scale is realized within a wide frequency range, with an approximate maximum transmission gain of 7 dB.

Lin, Zhou; Guo, Xiasheng; Tu, Juan; Cheng, Jianchun; Wu, Junru; Zhang, Dong

2014-03-01

28

Scaling of laser-plasma interactions with laser wavelength and plasma size  

Microsoft Academic Search

Plasma size is an important parameter in wavelength scaling experiments because it determines both the threshold and potential gain for a variety of laser plasma instabilities. Most experiments to date have of necessity produced relatively small plasmas, due to laser energy and pulse length limitations. Three experiments which had large enough plasmas that some instability thresholds were exceeded or approached

C. E. Max; E. M. Campbell; W. C. Mead; W. L. Kruer; D. W. Phillion; R. E. Turner; B. F. Lasinski; K. G. Estabrook

1983-01-01

29

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

SciTech Connect

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

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

1988-03-01

30

Cassini Vims Observations Of Thermal Emission From The Warmest 'Tiger Stripes' Near The South Pole On Enceladus  

NASA Astrophysics Data System (ADS)

The discovery and continuing investigation of the long linear fissures near Enceladus’ south pole is a major highlight of the Cassini mission to Saturn. Known as the ‘tiger stripes’, these fissures are the source of water dominated plumes and extensive thermal emission (Spencer et al, 2006; Porco et al, 2006). This paper presents new observational constraints on the highest temperature component of the tiger stripes thermal emission using VIMS (Visible and Infrared Mapping Spectrometer) spectra. Because VIMS detects the thermal emission at 4 to 5 micrometer wavelengths, VIMS is sensitive to the rising edge of Planck function for temperatures near 200 K, making the new VIMS spectra complementary to the CIRS observations acquired at longer wavelengths. Although the thermal emission spectra of the hottest areas is only a small piece of the Enceladus and tiger stripe puzzle, it is an important missing piece that we will use to model how and where the detected heat is generated and the physical processes that transport the heat to the observable surface. Our first definitive detection of thermal emission from Baghdad Sulcus was reported in Blackburn et al (LPSC 2012) from VIMS data acquired during E11 (August 2010). Due to seasonal change during the mission, the Enceladus S. pole region has entered the perpetual winter night and reflected sunlight does not interfere with VIMS measurements of the faint thermal emission as it did early in the mission. During the 75 km altitude targeted encounter E18 (April 2012), VIMS acquired a 2 minute long sequence of 25 ms integration time spectra through a single high resolution pixel as Cassini passed over the South pole. The resulting data has the best spatial resolution of the thermal emission acquired to date. This work was supported in part by a grant from NASA’s Outer Planets Research Program.

Goguen, Jay D.; Buratti, B. J.; Brown, R. H.; Clark, R. N.; Nicholson, P. D.; Hedman, M. M.; Sotin, C.; Cruikshank, D. P.; Baines, K. H.; Lawrence, K. J.; Spencer, J. R.; Blackburn, D.

2012-10-01

31

VIM: Initial ENDF/B-VI experience  

SciTech Connect

The VIM Monte Carlo particle transport code uses detailed continuous-energy cross sections produced from ENDF/B data by a set of specialized codes developed or adapted for use at Argonne National Laboratory. ENDF/B-IV data were used until about 1979, and Version V data since then. These VIM libraries were extensively benchmarked against the MC{sup 2}-2 code and against ZPR and ZPPR criticals for fast spectrum calculations, as well as other fast and thermal experiments and calculations. Recently, the cross section processing codes have been upgraded to accommodate ENDF/B-VI files, and a small library has been tested. Several fundamental tasks comprise the construction of a faithful representation of ENDF data for VIM calculations: (1) The resolved resonance parameters are converted to Doppler-broadened continuous-energy cross sections with energy grids suitable for linear-linear interpolation. (2) The unresolved resonance parameter distributions are sampled to produce many (40-400) resonance ladders in each energy band. These are converted to Doppler-broadened continuous energy resonance cross sections that are then binned by cross section, accumulating ladders until statistical convergence, the result being probability tables of total cross sections and conditional mean scattering and fission cross sections. VIM samples these tables at run time, and File 3 back ground cross sections are added. (3) Anisotropic angular distribution data are converted to angular probability tables. All other ENDF data are unmodified, except for format.

Blomquist, R.N.

1997-08-01

32

Cassini VIMS observations of the Galilean satellites including the VIMS calibration procedure  

USGS Publications Warehouse

The Visual and Infrared Mapping Spectrometer (VIMS) observed the Galilean satellites during the Cassini spacecraft's 2000/2001 flyby of Jupiter, providing compositional and thermal information about their surfaces. The Cassini spacecraft approached the jovian system no closer than about 126 Jupiter radii, about 9 million kilometers, at a phase angle of < 90 ??, resulting in only sub-pixel observations by VIMS of the Galilean satellites. Nevertheless, most of the spectral features discovered by the Near Infrared Mapping Spectrometer (NIMS) aboard the Galileo spacecraft during more than four years of observations have been identified in the VIMS data analyzed so far, including a possible 13C absorption. In addition, VIMS made observations in the visible part of the spectrum and at several new phase angles for all the Galilean satellites and the calculated phase functions are presented. In the process of analyzing these data, the VIMS radiometric and spectral calibrations were better determined in preparation for entry into the Saturn system. Treatment of these data is presented as an example of the VIMS data reduction, calibration and analysis process and a detailed explanation is given of the calibration process applied to the Jupiter data. ?? 2004 Elsevier Inc. All rights reserved.

McCord, T. B.; Coradini, A.; Hibbitts, C. A.; Capaccioni, F.; Hansen, G. B.; Filacchione, G.; Clark, R. N.; Cerroni, P.; Brown, R. H.; Baines, K. H.; Bellucci, G.; Bibring, J. -P.; Buratti, B. J.; Bussoletti, E.; Combes, M.; Cruikshank, D. P.; Drossart, P.; Formisano, V.; Jaumann, R.; Langevin, Y.; Matson, D. L.; Nelson, R. M.; Nicholson, P. D.; Sicardy, B.; Sotin, C.

2004-01-01

33

Comparison between VIMS and radar data on Sinlap crater on Titan  

NASA Astrophysics Data System (ADS)

Only few impact craters have been observed so far on Titan by the CASSINI imaging instruments. A 80 km diameter crater named Sinlap has been observed by the ISS, radar and VIMS instruments, with a resolution up to 14 km/pixel for VIMS. Observations at infrared and radar wavelengths provide complementary information on the composition, topography and surface roughness of the surface materials. Despite scattering by haze particles and strong absorption of light by methane contained in the atmosphere, there are several infrared windows that allow the observations of the surface of Titan with VIMS, enabling first order analysis of surface heterogeneities thanks to the use of band ratios. Several distinct units appear in these band ratios, with a possible enrichment in water ice around the main bright ejecta blanket. We report here on the cross comparison between VIMS band ratios and the radar T3 observations, in order to investigate the compositional and physical characteristics of the materials excavated by the impact.

Le Mouelic, S.; Paillou, P.; Rodriguez, S.; Crapeau, M.; Sotin, C.; Hirtzig, M.; Brown, R. H.; Soderblom, L.; Clark, R.; Buratti, B.

34

Metal slit array Fresnel lens for wavelength-scale optical coupling to nanophotonic waveguides.  

PubMed

We propose a novel metal slit array Fresnel lens for wavelength-scale optical coupling into a nanophotonic waveguide. Using the plasmonic waveguide structure in Fresnel lens form, a much wider beam acceptance angle and wavelength-scale working distance of the lens was realized compared to a conventional dielectric Fresnel lens. By applying the plasmon waveguide dispersion relation to a phased antenna array model, we also develop and analyze design rules and parameters for the suggested metal slit Fresnel lens. Numerical assessment of the suggested structure shows excellent coupling efficiency (up to 59%) of the 10 mum free-space Gaussian beam to the 0.36 mum Si waveguide within a working distance of a few mum. PMID:20372619

Jung, Young Jin; Park, Dongwon; Koo, Sukmo; Yu, Sunkyu; Park, Namkyoo

2009-10-12

35

VIMS Molluscan Ecology Oyster Reef Community Research  

NSDL National Science Digital Library

This site describes the Molluscan Ecology research program at the Virginia Institute of Marine Science (VIMS). Research projects investigate cephalopods, coastal habitats, hard clams, oysters, and rapa whelks. Background information is given regarding the history of the research, including management efforts and associated publications. Maps of restoration areas are available in addition to information about molluscan educational materials (including instructional publications and cds). Fees apply for cds.

2011-10-04

36

Directional waveguide coupling from a wavelength-scale deformed microdisk laser  

NASA Astrophysics Data System (ADS)

We demonstrate uni-directional evanescent coupling of lasing emission from a wavelength-scale deformed microdisk to a waveguide. This is attributed to the Goos-Hänchen shift and Fresnel filtering effect that result in a spatial separation of the clockwise (CW) and counter-clockwise (CCW) propagating ray orbits. By placing the waveguide tangentially at different locations to the cavity boundary, we may selectively couple the CW (CCW) wave out, leaving the CCW (CW) wave inside the cavity, which also reduces the spatial hole burning effect. The device geometry is optimized with a full-wave simulation tool, and the lasing behavior and directional coupling are confirmed experimentally.

Redding, Brandon; Ge, Li; Solomon, Glenn S.; Cao, Hui

2012-02-01

37

Light in materials with periodic gain-loss modulation on a wavelength scale  

SciTech Connect

We analyze light-wave dynamics in artificial materials characterized by periodically modulated gain or loss on the wavelength scale. The study of the temporal dispersion in one-dimensionally modulated materials predicts mode-locked states and superluminal light propagation regimes in the parameter regions close to the locking regions. The study of spatial dispersion for a two-dimensional gain-loss modulation predicts nontrivial beam propagation effects such as self-collimation, angle-sensitive gain, and negative diffraction in such gain-loss-modulated materials.

Botey, Muriel [Departament de Fisica i Enginyeria Nuclear, Urgell 187, ES-08036 Barcelona (Spain); Herrero, Ramon [Departament de Fisica i Enginyeria Nuclear, Universitat Politecnica de Catalunya, Colom 11, ES-08222 Terrassa (Spain); Staliunas, Kestutis [Departament de Fisica i Enginyeria Nuclear, Universitat Politecnica de Catalunya, Colom 11, ES-08222 Terrassa (Spain); Institucio Catalana de Recerca i Estudis Avancats, Pg. Ernest Lluch/Rambla Sant Nebridi, ES-08222 Terrassa (Spain)

2010-07-15

38

Wavelength-scale imaging of trapped ions using a phase Fresnel lens.  

PubMed

A microfabricated phase Fresnel lens was used to image ytterbium ions trapped in a radio frequency Paul trap. The ions were laser cooled close to the Doppler limit on the 369.5 nm transition, reducing the ion motion so that each ion formed a near point source. By detecting the ion fluorescence on the same transition, near-diffraction-limited imaging with spot sizes of below 440 nm (FWHM) was achieved. To our knowledge, this is the first demonstration of wavelength-scale imaging of trapped ions and the highest imaging resolution ever achieved with atoms in free space. PMID:21499360

Jechow, A; Streed, E W; Norton, B G; Petrasiunas, M J; Kielpinski, D

2011-04-15

39

Wavelength Scaling of High-Harmonic Yield: Threshold Phenomena and Bound State Symmetry Dependence  

SciTech Connect

Describing harmonic generation (HG) in terms of a system's complex quasienergy, the harmonic power P{sub {delta}}{sub E}({lambda}) (over a fixed interval, {delta}E, of harmonic energies) is shown to reproduce the wavelength scaling predicted recently by two groups of authors based on solutions of the time-dependent Schroedinger equation: P{sub {delta}}{sub E}({lambda}){approx}{lambda}{sup -x}, where x{approx_equal}5-6. Oscillations of P{sub {delta}}{sub E}({lambda}) on a fine {lambda} scale are then shown to have a quantum origin, involving threshold phenomena within a system of interacting ionization and HG channels, and to be sensitive to the bound state wave function's symmetry.

Frolov, M. V.; Manakov, N. L. [Department of Physics, Voronezh State University, Voronezh 394006 (Russian Federation); Starace, Anthony F. [Department of Physics and Astronomy, The University of Nebraska, Lincoln, Nebraska 68588-0111 (United States)

2008-05-02

40

Cassini/VIMS observations of the moon  

USGS Publications Warehouse

In this paper, we present preliminary scientific results obtained from the analysis of VIMS (Visible and Infrared Mapping Spectrometer) lunar images and spectra. These data were obtained during the Cassini Earth flyby in August 1999. Spectral ratios have been produced in order to derive lunar mineralogical maps. Some spectra observed at the north-east lunar limb, show few unusual absorption features located at 0.357, 0.430 and 0.452 ??m, the origin of which is presently unknown. ?? 2002 COSPAR. Published by Elsevier Science Ltd. All rights reserved.

Belluci, G.; Brown, R. H.; Formisano, V.; Baines, K. H.; Bibring, J. -P.; Buratti, B. J.; Capaccioni, F.; Cerroni, P.; Clark, R. N.; Coradini, A.; Cruikshank, D. P.; Drossart, P.; Jaumann, R.; Langevin, Y.; Matson, D. L.; McCord, T. B.; Mennella, V.; Miller, E.; Nelson, R. M.; Nicholson, P. D.; Sicardy, B.; Sotin, C.

2002-01-01

41

Draft Whole-Genome Sequence of VIM-1-Producing Multidrug-Resistant Enterobacter cloacae EC_38VIM1.  

PubMed

The VIM-1-producing multidrug-resistant strain Enterobacter cloacae was isolated from blood culture. The strain showed multiple resistances to clinically used antibiotics, including all ?-lactams, fluoroquinolones, aminoglycosides, and sulfonamides. Sequence analysis showed the presence of 14 genes associated with resistance to antibiotics, including the metallo-?-lactamase VIM-1 gene, which was located in a class 1 integron. PMID:24009122

Villa, Jennifer; Viedma, Esther; Otero, Joaquín R; Chaves, Fernando

2013-01-01

42

Development of vehicle intelligent monitoring system (VIMS)  

NASA Astrophysics Data System (ADS)

In an urban highway network system such as Tokyo Metropolitan Expressway, to detect conditions of road pavement and expansion joints is a very important issue. Although accurate surface condition can be captured by using a road profiler system, the operating cost is expensive and development of a simpler and more inexpensive system is really needed to reduce monitoring cost. "Vehicle Intelligent Monitoring System (VIMS)" developed for this purpose is described in this paper. An accelerometer and GPS are installed to an ordinary road patrol car. GPS together with a PC computer are used to measure the road surface condition and to identify the location of the vehicle, respectively. Dynamic response of the vehicle is used as a measure of the road pavements surface condition as well as the expansion joints. A prototype of VIMS is installed to a motor car and measurement is made at the actual roads. Accuracy of measuring result and effectiveness of this system are demonstrated; the outline of the system and some of the measurement results are reported herein.

Fujino, Yozo; Kitagawa, Keisuke; Furukawa, Takashi; Ishii, Hironori

2005-05-01

43

Study of wavelength-shifting chemicals for use in large-scale water Cherenkov detectors  

SciTech Connect

Cherenkov detectors employ various methods to maximize light collection at the photomultiplier tubes (PMTs). These generally involve the use of highly reflective materials lining the interior of the detector, reflective materials around the PMTs, or wavelength-shifting sheets around the PMTs. Recently, the use of water-soluble wavelength-shifters has been explored to increase the measurable light yield of Cherenkov radiation in water. These wave-shifting chemicals are capable of absorbing light in the ultravoilet and re-emitting the light in a range detectable by PMTs. Using a 250 L water Cherenkov detector, we have characterized the increase in light yield from three compounds in water: 4-Methylumbelliferone, Carbostyril-124, and Amino-G Salt. We report the gain in PMT response at a concentration of 1 ppm as: 1.88 {+-} 0.02 for 4-Methylumbelliferone, stable to within 0.5% over 50 days, 1.37 {+-} 0.03 for Carbostyril-124, and 1.20 {+-} 0.02 for Amino-G Salt. The response of 4-Methylumbelliferone was modeled, resulting in a simulated gain within 9% of the experimental gain at 1 ppm concentration. Finally, we report an increase in neutron detection performance of a large-scale (3.5 kL) gadolinium-doped water Cherenkov detector at a 4-Methylumbelliferone concentration of 1 ppm.

Sweany, M; Bernstein, A; Dazeley, S; Dunmore, J; Felde, J; Svoboda, R; Tripathi, S M

2011-09-21

44

Multigroup calculations using VIM: A user's guide to ISOVIM  

SciTech Connect

Monte Carlo calculations have long been used to benchmark more a mate approximate solution methods for reactor physics problems. The power of VIM (ref 1) lies partly in the detailed geometrical representations incorporating the (generally) curved surfaces of combinatorial geometry, and partly in the fine energy detail of pointwise cross sections which are independent of the neutron spectrum. When differences arise between Monte Carlo and deterministic calculations, the question arises, is the error in the multigroup cross sections, in the treatment of transport effects, or in the mesh-based treatment of space in the deterministic calculation The answers may not be obvious, but may be identified by combining the exact geometry capability of VIM with the multigroup formalism. We can now run VIM in a multigroup mode by producing special VIM Material files which contain point-wise data describing multigroup data with histograms. This forces VIM to solve the multigroup problem with only three small code modifications. P[sub N] scattering is simulated with the usual tabulated angular distributions with 20 equally-sized scattering angle cosine meshes. This document describes the VIM multigroup capability, the procedures for generating multigroup cross sections for VIM, and their use. The multigroup cross section generating code, ISOVIM, is described, and benchmark testing is documented.

Blomquist, R.N.

1992-09-01

45

Modeling Scale and Orientation-Dependent Effects in Snow Particles at Microwave Wavelengths  

NASA Astrophysics Data System (ADS)

With the advent of satellite-borne radar and radiometers, it is now possible to observe cloud processes throughout the globe with unprecedented levels of precision. However, interpreting the large amount of data generated by such instruments requires detailed understanding of how light is scattered in-cloud by ice. Unlike liquid water, ice exhibits complex shapes and orientation-dependent effects. This is of particularly great importance at microwave wavelengths, where ice aggregates are easily detected by radar and radiometers. When modeling such irregular particles, it is desirable to have a large collection of particle that resemble those found in nature. There is a tradeoff, however, in modeling fine features of particles and system resources (processing time and memory requirements). This becomes increasingly significant at particle sizes that are significantly larger than the considered wavelengths. Both pristine flakes and aspect-ratio correct bullet rosette aggregates were first considered using the Discrete Dipole Approximation. These initial flakes were subjected to a variety of decimation conditions, where adjacent dipoles were combined, thus producing equivalent particles with slightly lower fractal complexity. Calculations using such decimated particles were an order of magnitude faster, and exhibited scattering cross-sections to within twenty percent of initial values. Similar methods of approximating particles with dielectric-scaled ellipsoids and clusters of spherical particles were also examined using the T-matrix method. Many microwave radiative transfer models currently make the implicit assumption that all scattering sources are randomly oriented. This is generally true of the bulk atmosphere, but dynamical simulations suggest that this does not hold for asymmetric ice crystals in nonturbulent conditions. Ensembles of such particles were constructed according to established size, density and aspect ratio relationships. Relative orientation profiles within the ensemble were determined by restricting the free kinetic and potential energy of the system. Orientation-dependent effects on brightness temperatures were then determined using the Doubling-Adding and Monte-Carlo methods.

Honeyager, R. E.; Liu, G.; Nowell, H.

2013-12-01

46

Large-scale integration of wavelength-addressable all-optical memories on a photonic crystal chip  

NASA Astrophysics Data System (ADS)

Photonic integration has long been pursued, but remains immature compared with electronics. Nanophotonics is expected to change this situation. However, despite the recent success of nanophotonic devices, there has been no demonstration of large-scale integration. Here, we describe the large-scale and dense integration of optical memories in a photonic crystal chip. To achieve this, we introduce a wavelength-addressable serial integration scheme using a simple cavity-optimization rule. We fully exploit the wavelength-division-multiplexing capability, which is the most important advantage of photonics over electronics, and achieve an extremely large wavelength-channel density. This is the first demonstration of the large-scale photonic integration of nanophotonic devices coupled to waveguides in a single chip, and also the first dense wavelength-division-multiplexing nanophotonic devices other than filters. This work paves the way for optical random-access memories and for a large-scale wavelength-division-multiplexing photonic network-on-chip.

Kuramochi, Eiichi; Nozaki, Kengo; Shinya, Akihiko; Takeda, Koji; Sato, Tomonari; Matsuo, Shinji; Taniyama, Hideaki; Sumikura, Hisashi; Notomi, Masaya

2014-06-01

47

Application of wavelength-scanned wavelength-modulation spectroscopy H2O absorption measurements in an engineering-scale high-pressure coal gasifier  

NASA Astrophysics Data System (ADS)

A real-time, in situ water vapor (H2O) sensor using a tunable diode laser near 1,352 nm was developed to continuously monitor water vapor in the synthesis gas of an engineering-scale high-pressure coal gasifier. Wavelength-scanned wavelength-modulation spectroscopy with second harmonic detection (WMS-2f) was used to determine the absorption magnitude. The 1f-normalized, WMS-2f signal (WMS-2f/1f) was insensitive to non-absorption transmission losses including beam steering and light scattering by the particulate in the synthesis gas. A fitting strategy was used to simultaneously determine the water vapor mole fraction and the collisional-broadening width of the transition from the scanned 1f-normalized WMS-2f waveform at pressures up to 15 atm, which can be used for large absorbance values. This strategy is analogous to the fitting strategy for wavelength-scanned direct absorption measurements. In a test campaign at the US National Carbon Capture Center, the sensor demonstrated a water vapor detection limit of ~800 ppm (25 Hz bandwidth) at conditions with more than 99.99 % non-absorption transmission losses. Successful unattended monitoring was demonstrated over a 435 h period. Strong correlations between the sensor measurements and transient gasifier operation conditions were observed, demonstrating the capability of laser absorption to monitor the gasification process.

Sun, Kai; Sur, Ritobrata; Jeffries, Jay B.; Hanson, Ronald K.; Clark, Tommy; Anthony, Justin; Machovec, Scott; Northington, John

2014-05-01

48

Understand and replay cloud platform SDK with vimShark  

Microsoft Academic Search

In this paper, we present vimShark, an automated monitoring\\/analyzing\\/replaying tool which identifies and extracts VMware vSphere Web Services API to effectively understand the communications between various vSphere components and Virtual Infrastructure Management (VIM) solutions. This has proven useful in the performance analysis of various VMware management solution products with VMware vCenter Server and VMware ESX (hypervisor) hosts. The contribution of

John Liang; Aalap Desai; Jin Heo; Xuwen Yu; Joanna Guan; Rajit Kambo

2011-01-01

49

Cassini/VIMS observation of an Io post-eclipse brightening event  

USGS Publications Warehouse

During the Cassini-Jupiter flyby, VIMS observed Io at different phase angles, both in full sunlight and in eclipse. By using the sunlight measurements, we were able to produce phase curves in the visual through all the near infrared wavelengths covered by the VIMS instrument (0.85-5.1 ??m). The phase angle spanned from ???2?? to ???120??. The measurements, done just after Io emerged from Jupiter's shadow, show an increase of about 15% in Io's reflectance with respect to what would be predicted by the phase curve. This behavior is observed at wavelengths >1.2 ??m. Moreover, just after emergence from eclipse an increase of about 25% is observed in the depth of SO2 frost bands at 4.07 and 4.35 ??m. At 0.879

Bellucci, G.; D'Aversa, E.; Formisano, V.; Cruikshank, D.; Nelson, R. M.; Clark, R. N.; Baines, K. H.; Matson, D.; Brown, R. H.; McCord, T. B.; Buratti, B. J.; Nicholson, P. D.

2004-01-01

50

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

Microsoft Academic Search

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

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

2010-01-01

51

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

52

Biochemical Characterization of Metallo-?-Lactamase VIM-11 from a Pseudomonas aeruginosa Clinical Strain? †  

PubMed Central

A detailed biochemical characterization of the Pseudomonas aeruginosa VIM-11 metallo-?-lactamase (M?L) is reported. The only substitution differentiating VIM-11 from VIM-2 (N165S) promoted a slightly improved catalytic efficiency of the former on 3 out of 12 substrates, notably the bulky cephalosporins. Thus, M?L-mediated resistance also may be modulated by remote mutations.

Marchiaro, Patricia; Tomatis, Pablo E.; Mussi, Maria A.; Pasteran, Fernando; Viale, Alejandro M.; Limansky, Adriana S.; Vila, Alejandro J.

2008-01-01

53

Isoelectronic scaling of recombination lasers to higher ion stages and shorter wavelengths  

SciTech Connect

Laser action in the visible and ultraviolet (at wavelengths as short as 298 nm) in the higher ionization stages of a number of metal vapors has been produced by a population inversion mechanism based on segmented plasma excitation and recombination. Many of the transitions have never been observed in laser action before by any excitation means and a number of the oscillating transitions in silver, cadmium, and indium form isoelectronic sequences.

Silfvast, W.T.; Szeto, L.H.; Wood, O.R. II

1981-08-01

54

Tracking and Reporting Data Using VIMS and VAMS. Module.  

ERIC Educational Resources Information Center

This module on tracking and reporting data is 1 in a series of 10 modules written for vocational education teacher education programs. It is designed to provide a basic understanding of Missouri's Vocational Instructional Management System (VIMS) and Vocational Administrative Management System (VAMS). Introductory materials include the following:…

Downs, W. A.

55

Analysis Of Selected VIMS And RADAR Data Over The Surface Of Titan Through Multivariate Statistical Methods  

NASA Astrophysics Data System (ADS)

In this work we have searched through Cassini/VIMS hyperspectral cubes, selecting those data which have convenient viewing geometry and which overlap with Cassini/RADAR footprints having comparable ground resolution, in order to properly look for correlations between the infrared and microwave ranges explored by the two instruments. In RADAR data we have considered two geophysical quantities: the normalized backscatter cross-section obtained from the scatterometer measurement, corrected for the incidence angle, and the brightness temperature determined from the radiometer measurement, as found in publicly available data products. In VIMS data, combining spatial and spectral information, we have selected some atmospheric windows in the spectral range between 2 and 5 ?m, providing the best optical depth to measure surface reflectance. The two RADAR parameters are combined with the VIMS data, with estimated errors, to produce an aggregate data set, that we process using multivariate classification methods to identify homogeneous taxonomic units in the multivariate space of the samples. The use of data sets from different instruments onboard the Cassini spacecraft is a necessary step towards understanding the nature and history of Titan, since correlations between different physical processes can be highlighted. A first analysis has been done with the G-mode method, which has been successfully used in the past for the classification of such diverse data sets as lunar rock samples, asteroids and planetary surfaces. Due to the large number of Titan data, the classification work is still ongoing; nevertheless the obtained results are generally in agreement with previous works aimed both to the analysis of the scatterometry data through physical models and to the correlation between SAR and radiometry data at a high resolution scale. These evidences, evaluated for the first time through a multivariate statistical method, can provide constraints on the geophysical models under development for the surface of Titan.

Tosi, F.; Orosei, R.; Seu, R.; Filacchione, G.; Coradini, A.; Lunine, J. I.; Capaccioni, F.; Cerroni, P.; Adriani, A.; Moriconi, M. L.; Cassini Team

2008-12-01

56

Empirical Approaches To Reduce The Atmospheric Component In VIMS Surface Images Of Titan  

NASA Astrophysics Data System (ADS)

The Visual and Infrared Mapping Spectrometer (VIMS) onboard Cassini can see the surface of Titan in seven narrow atmospheric windows in the infrared at 0.93, 1.08, 1.27, 1.59, 2.01, 2.68-2.78, and 4.9-5.1 microns. In addition to the strong absorption by atmospheric gases (mainly methane and nitrogen), the presence of aerosols in the atmosphere blurs the images at short wavelengths due to a very strong scattering effect, which acts as an additive component to the signal coming from the surface. We have produced a global hyperspectral mosaic of the complete VIMS archive between T0 (July 2004) and T66 flyby (January 2010), by merging all the data cubes sorted by increasing spatial resolution in order to put the high resolution images on top and to use the low resolution images as background. We filtered out the observing geometry in order to remove the pixels acquired in too extreme illuminating and viewing conditions, which systematically amplify the atmospheric artifacts. We used thresholds of 80° both on the incidence and emission angles, and 100° on the phase angle. We first focused our study on the 5 microns window, where the additive component from the haze scattering is negligible, in order to investigate the multiplicative factor which should be used to normalize the viewing geometry between all flybys, and thus to reconcile observations acquired in very different viewing conditions. Indeed, if we exclude transient phenomena (mainly clouds and possible surface changes), the seams between all individual images should disappear after correction. We then investigated other windows at shorter wavelengths, where the additive scattering component cannot be neglected. We found that the wings of the atmospheric windows can be used as a proxy for the amount of additive scattering present in the center of these windows, where the surface is best seen by VIMS. In the band wings, the solar flux never reaches the ground. The corresponding signal therefore gives the contribution of the upper layers of the atmosphere, which is also present in the center of the atmospheric window (which probes the full atmospheric path up to the surface). The ultimate goal would be to produce homogeneous mosaics in each surface window corrected from the additive scattering component, in order to use the band ratio technique. Band ratios emphasize very subtle compositional heterogeneities provided that no additive component is present in the numerator and denominator. Examples will be given at the meeting.

Le Mouélic, S.; Cornet, T.; Rodriguez, S.; Sotin, C.; Barnes, J. W.; Brown, R. H.; Baines, K. H.; Buratti, B. J.; Clark, R. N.; Nicholson, P. D.

2010-12-01

57

Correlations between VIMS and RADAR data over the surface of Titan: Implications for Titan's surface properties.  

NASA Astrophysics Data System (ADS)

We present new results combining the VIMS and RADAR data on Titan's surface. In RADAR data we consider two geophysical quantities: the normalized backscatter cross-section obtained from the scatterometer measurement, corrected for the incidence angle, and the calibrated antenna temperature determined from the radiometer measurement, as found in publicly available data products. In VIMS data, combining spatial and spectral information, we have selected some atmospheric windows in the spectral range between 2 and 5 ?m, providing the best optical depth to measure surface reflectance. The two RADAR parameters are combined with VIMS data, with estimated errors, to produce an aggregate data set, that we process using multivariate classification methods to identify homogeneous taxonomic units in the multivariate space of the samples. The use of data sets from different instruments onboard the Cassini spacecraft has the potential to deepen our understanding of the nature of the surface. Our analysis relies on the G-mode method, which has been successfully used in the past for the classification of such diverse data sets as lunar rock samples, asteroids and planetary surfaces. Due to the large number of data of Titan, the classification work proceeds in several steps. In a previous work (Tosi et al., 2010), we analyzed the data acquired in Titan flybys: T3, T4, T8, T13 and T16, covering mostly the major bright and dark features seen around the equator, combined with VIMS infrared data, in order to validate the classification method. Now we focus on flybys: T23, T25, T28, T30, and T43, covering also regions of Titan located at higher latitudes, and partly including the polar regions. The obtained results are generally in agreement with previous work devoted both to the analysis of the scatterometry data through physical models and to the correlation between SAR and radiometry data at a high resolution scale. This evidence, evaluated for the first time through a multivariate statistical method, constrains the geophysical models under development for the Titan surface. This work is supported by an Italian Space Agency (ASI) grant.

Tosi, Federico; Orosei, Roberto; Seu, Roberto; Coradini, Angioletta; Lunine, Jonathan; Filacchione, Gianrico; Capaccioni, Fabrizio; Cerroni, Priscilla; Brown, Robert

2010-05-01

58

Helium Abundance of Saturn from Cassini VIMS and CIRS Combined Analysis  

NASA Astrophysics Data System (ADS)

The Cassini VIMS instrument has obtained about 11 stellar occultations of sufficient quality that they can be used to infer the atmospheric structure where the stellar light cuts through Saturn's atmosphere on its way to thespacecraft. For 5 of these stellar occultations, the Cassini CIRS instrument obtained spectra of Saturn's limb at nearly the same time and place. By combining these observations, we have previously demonstrated that we can produce an estimate of the Helium abundance on Saturn (e.g., Banfield et al., DPS BAAS, 2011). The Helium abundance of Saturn is of great interest due to its leverage on our understanding of the formation and internal evolution processes of the giant planets in our Solar System, as well as giant exoplanets in other solar systems. The Helium abundance is also of significant interest due to a long-standing discrepancy between estimates obtained using a combined IR Spectra/Radio Science Occultation technique (He/H2~0.03, Conrath et al., '84) and those obtained using IR spectra alone (He/H2~0.13, Conrath & Gautier, '00). We will present our results from the Cassini VIMS/CIRS analysis of this problem. The technique uses the Cassini CIRS limb spectra to produce an estimate of the temperature profile between about 0.01 mbar and 5 mbar. The VIMS stellar occultations are used to produce a scale height profile over a similar vertical region, but with much better information content (and thus tighter constraints) between about 1 mbar and 5 mbar. By comparing these two results and demanding consistency we can infer the mean molecular mass of the atmosphere (and thus the Helium abundance) in the region of overlap (~1mbar to 5 mbar). Realistically, both sets of observations are quite challenging to perform. The signal levels are relatively low for the CIRS limb spectra (compared to nadir spectra), making calibration especially challenging. Not all VIMS occultations are successful with variable stellar baselines or stray light corrupting the signal after ingress. Cassini observed many stellar occultations to yield the 5 cases that we could analyze to completion. Our preliminary results are more consistent with the IR spectra alone results (Conrath and Gautier, '00), but we are still in the process of evaluating all of the potential sources of error in our results. This work was supported by a grant from NASA's Cassini Data Analysis Program.

Banfield, D. J.; Gierasch, P. J.; Conrath, B. J.; Nicholson, P. D.; Hedman, M. M.

2013-12-01

59

High-Resolution Enceladus Atlas and Compositional Maps derived from Cassini ISS and VIMS  

NASA Astrophysics Data System (ADS)

The first version of the high-resolution Enceladus atlas was released in 2006 [1]. The Cassini Imaging Science Sub-system (ISS) acquired more high-resolution images (< 1 km/pixel) during five close flybys of Enceladus in 2008 and 2009. We combined these images with lower-resolution coverage taken between 2007 and 2009 to improve the high-resolution global mosaic of Enceladus. The whole mosaic was shifted by 3.5° to the West to be consistent with the IAU definition of the prime meridian location. This new global mosaic is the baseline for the second release of the high-resolution Enceladus atlas that consists again of 15 tiles mapped at a scale of 1:500,000. We proposed 29 additional names for features which will be used as nomenclature in the atlas. We are awaiting validation of the new nomenclature by the IAU. The new release of the atlas will be made available to the public through CICLOPS (http://ciclops.org) and PDS (http://pds.jpl.nasa.gov). The Cassini Visual and Infrared Imaging Spectrometer (VIMS) observed Enceladus during a couple of flybys between 2005 and 2009. This gave us the possibility to combine these data into a global VIMS mosaic. Based on this mosaic maps of Enceladus' spectral properties could be derived. Thus, global maps illustrating the spatial variations of the absorption band depth of water ice were calculated, which are indicative of varying sizes of the water ice particles [2]. The authors gratefully acknowledge the planning and operation work of their colleagues from the Cassini-ISS team lead by Carolyn Porco and from the Cassini-VIMS team lead by Robert Brown. [1] Roatsch, Th. et al., High-resolution Enceladus atlas derived from Cassini-ISS images. Planetary Space Sciences 56, 109-116, 2008. [2] Jaumann, R., Stephan, K., Hansen, G.B., Clark, R.N., Buratti, B.J., Brown, R.H., Baines, K.H., Newman, S.F., Bellucci, G., Filacchione, G., Coradini, A., Cruikshank, D.P., Griffith, C.A., Hibbitts, C.A., McCord, T.B., Nelson, R.M., Nicholson, P.D., Sotin, C., and Wagner, R., 2008: Distribution of icy particles across Enceladus' surface as derived from Cassini-VIMS measurements. Icarus 193.

Roatsch, Thomas; Kersten, Elke; Wählisch, Marita; Hoffmeister, Angelika; Stephan, Katrin; Jaumann, Ralf

2010-05-01

60

1.3 mm WAVELENGTH VLBI OF SAGITTARIUS A*: DETECTION OF TIME-VARIABLE EMISSION ON EVENT HORIZON SCALES  

SciTech Connect

Sagittarius A*, the {approx}4 x 10{sup 6} M{sub sun} black hole candidate at the Galactic center, can be studied on Schwarzschild radius scales with (sub)millimeter wavelength very long baseline interferometry (VLBI). We report on 1.3 mm wavelength observations of Sgr A* using a VLBI array consisting of the JCMT on Mauna Kea, the Arizona Radio Observatory's Submillimeter Telescope on Mt. Graham in Arizona, and two telescopes of the CARMA array at Cedar Flat in California. Both Sgr A* and the quasar calibrator 1924-292 were observed over three consecutive nights, and both sources were clearly detected on all baselines. For the first time, we are able to extract 1.3 mm VLBI interferometer phase information on Sgr A* through measurement of closure phase on the triangle of baselines. On the third night of observing, the correlated flux density of Sgr A* on all VLBI baselines increased relative to the first two nights, providing strong evidence for time-variable change on scales of a few Schwarzschild radii. These results suggest that future VLBI observations with greater sensitivity and additional baselines will play a valuable role in determining the structure of emission near the event horizon of Sgr A*.

Fish, Vincent L.; Doeleman, Sheperd S.; Beaudoin, Christopher; Bolin, David E.; Rogers, Alan E. E. [Massachusetts Institute of Technology, Haystack Observatory, Route 40, Westford, MA 01886 (United States); Blundell, Ray; Gurwell, Mark A.; Moran, James M.; Primiani, Rurik [Harvard-Smitshonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Bower, Geoffrey C.; Plambeck, Richard [Department of Astronomy, Radio Astronomy Laboratory, University of California Berkeley, 601 Campbell, Berkeley, CA 94720-3411 (United States); Chamberlin, Richard [Caltech Submillimeter Observatory, 111 Nowelo Street, Hilo, HI 96720 (United States); Freund, Robert [Arizona Radio Observatory, Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721-0065 (United States); Friberg, Per [James Clerk Maxwell Telescope, Joint Astronomy Centre, 660 North A'ohoku Place, University Park, Hilo, HI 96720 (United States); Honma, Mareki; Oyama, Tomoaki [National Astronomical Observatory of Japan, Osawa 2-21-1, Mitaka, Tokyo 181-8588 (Japan); Inoue, Makoto [Institute of Astronomy and Astrophysics, Academia Sinica, P.O. Box 23-141, Taipei 10617, Taiwan (China); Krichbaum, Thomas P. [Max-Planck-Institut fuer Radioastronomie, Auf dem Huegel 69, D-53121 Bonn (Germany); Lamb, James [OVRO, California Institute of Technology, 100 Leighton Lane, Big Pine, CA 93513-0968 (United States); Marrone, Daniel P., E-mail: vfish@haystack.mit.edu [Kavli Institute for Cosmological Physics, University of Chicago, 5640 South Ellis Avenue, Chicago, IL 60637 (United States)

2011-02-01

61

Radiative Transfer on Titan: Towards a Massive Inversion of Atmospheric and Surface Properties From VIMS/Cassini Observations of Titan  

NASA Astrophysics Data System (ADS)

Titan, the largest moon of Saturn, is the only one to possess a dense, extended and hazy atmosphere, primarily composed of N2 and a few percents of CH4. Nitrogen and methane are photo-chemically dissociated to produce a plethora of complex nitrogenous and organic compounds, leading to the formation of an extensive haze of organic aerosols. CH4 absorptions and scattering from haze particles contribute to the almost complete hiding of Titan's surface at UV-visible-NIR wavelengths, letting Titan's surface until recently largely unknown. Since 2004, the Visual and Infrared Mapping Spectrometer (VIMS) aboard the Cassini spacecraft has provided a wealth of hyperspectral observations of Titan (more than 30,000 data cubes). VIMS can image Titan's surface in seven narrow near-IR spectral windows, where atmospheric methane absorptions are the weakest. In order to retrieve the absolute surface albedo, high-fidelity radiative transfer models are used, taking as inputs physical properties of gases and aerosols as a function of the altitude. These calculations are extremely time consuming and thus used to analyze only a few number of isolated Titan's spectra, although with a very high level of accuracy. Our goal is to massively invert the VIMS dataset. A smart inversion scheme is thus required, providing a good compromise between accuracy and computation time. We will proceed in four steps. First, we will choose the best-suited radiative transfer model for the geometry of the observation. Indeed, plane-parallel radiative transfer models are very accurate for low to moderate incidence and emergence angles but provide wrong results for high air mass (usually for incidence or emergence angles higher than 70°). On the other hand, spherical 3D Monte Carlo models are slower than plane-parallel model but give accurate results for extreme geometries. A sensitivity analysis is underway to define the geometry conditions in which 3D Monte Carlo computations are needed. The second step consists in inverting the absolute surface albedo of several homogeneous Titan's regions imaged for very different geometries of observation in order to check the consistency of the inversion scheme. Then we will build look-up tables (LUT) for a range of discrete values of incidence, emergence and azimuth angles, opacity of the aerosols and surface albedo, using the best-suited radiative transfer model as a function of the geometry. The computation time could be strongly reduced by the use of surface-atmosphere coupling analytical set of equations. The final step will consist in inverting the atmospheric and surface properties for several VIMS cubes, then for the whole VIMS dataset and thus draw maps of Titan's surface absolute infrared albedos.

Appéré, T.; Rodriguez, S.; Vincendon, M.; Douté, S.; Rannou, P.; Le Mouélic, S.; Coustenis, A.; Barnes, J. W.; Sotin, C.; Brown, R. H.

2013-12-01

62

Spectral challenges of individual wavelength-scale particles: strong phonons and their distorted lineshapes.  

PubMed

Beyond our own interest in airborne particulate matter, the prediction of extinction and absorption spectra of single particles of mixed composition has wide use in astronomy, geology, atmospheric sciences, and nanotechnology. Single particle spectra present different challenges than traditional spectroscopic approaches. To quantify the amount of a material in a bulk sample (molecules in solution or the gas phase), one might employ the Beer-Lambert law assuming a simple slab-type assay geometry and averaging over orientation, whereas with single particles one might have a specific orientation and require a nonlinear, Mie-like particle theory. The complicating single particle issues include: strong and broad scattering at wavelengths similar to the particle size, phonon lineshape phase shifting, particle shape effects, distortion of transition lineshapes by strong vibrational bands, bi- and trirefringence, crystal orientation effects including dispersion, and composition mixtures. This work uses a combination of three-dimensional finite difference time domain (3D-FDTD) calculations and experimental infrared spectra on single, crystalline quartz particles to illustrate some of the challenges--in particular the distortion of lineshapes by strong phonons that lie within a range of strong scattering. It turns out that many mineral dust components in the inhalable size range have strong phonons. A Mie-Bruggeman model for single particle spectra is presented to isolate the effects of strong phonons on lineshapes which has utility for analysing the spectra of single, mixed-composition particles. This model will ultimately enable the determination of volume fractions of components in single particles that are mixtures of many materials with strong phonons, as are the dust particles breathed into people's lungs. PMID:23703537

Ravi, Aruna; Malone, Marvin A; Luthra, Antriksh; Lioi, David; Coe, James V

2013-07-01

63

Rotated grating coupled surface plasmon resonance on wavelength-scaled shallow rectangular gratings  

NASA Astrophysics Data System (ADS)

Theoretical investigation of rotated grating coupling phenomenon was performed on a multilayer comprising 416-nmperiodic shallow rectangular polymer grating on bimetal film made of gold and silver layers. During the multilayer illumination by 532 nm wavelength p-polarized light the polar and azimuthal angles were varied. In presence of 0-35 nm, 0-50 nm and 15-50 nm thick polymer-layers at the valleys and hills splitting was observed on the dual-angle dependent reflectance in two regions: (i) close to 0° azimuthal angle corresponding to incidence plane parallel to the periodic pattern (P-orientation); and (ii) around ~33.5°/29°/30° azimuthal angle (C-orientation), in agreement with our previous experimental studies. The near-field study revealed that in P-orientation the E-field is enhanced at the glass side with p/2 periodicity at the first minimum appearing at 49°/50°/52° polar angles, and comprises maxima below both the valleys and hills; while E-field enhancement is observable both at the glass and polymer side with p-periodicity at the second minimum developing at 55°/63/64° tilting, comprising maxima intermittently below the valleys or above the hills. In Corientation coupled plasmonic modes are observable, involving modes propagating along the valleys at the secondary maxima appearing at ~35°/32°/32° azimuthal and ~49°/51°/56° polar angles, while modes confined along the polymer hills are observable at the primary minima, which are coupled most strongly at the ~31.5°/25°/28° azimuthal and ~55°/63°/66° polar angles. The secondary peak observable in C-orientation is proposed for biosensing applications, since the supported modes are confined along the valleys, where biomolecules prefer to attach.

Szalai, A.; Szekeres, G.; Balázs, J.; Somogyi, A.; Csete, Maria

2013-09-01

64

Cassini VIMS Preliminary Exploration of Titan's Surface Hemispheric Albedo Dichotomy  

NASA Technical Reports Server (NTRS)

We present preliminary evidence that suggests a hemispheric albedo dichotomy on Titan, the largest planetary satellite in the Solar System. We have also studied the photometric properties of several dark circular features on Titan's surface to test if they might be of impact origin. The evidence is derived from photometric analysis of selected surface regions taken at different Titanian longitudes and solar phase angles using images from the Cassini Saturn Orbiter Visual and Infrared Mapping Spectrometer (VIMS). The VIMS instrument is able to image Titan's surface at spectral windows (e.g. 2.02 microns) in its atmosphere where methane, the principal atmospheric absorber is transparent. Additional information is included in the original extended abstract.

Nelson, R. M.; Brown, R. H.; Hapke, B. W.; Smythe, W. D.; Kamp, L.; Boryta, M.; Baines, K. H.; Bellucci, G.; Bibring, J.-P.; Buratti, B. J.

2005-01-01

65

Outflows in protostellar clusters: a multi-wavelength, multi-scale view  

NASA Astrophysics Data System (ADS)

While protostellar outflows are generally understood as necessary components of isolated star formation, further observations are needed to constrain parameters of outflows particularly within protostellar clusters. In protostellar clusters where most stars form, outflows impact the cluster environment by injecting momentum and energy into the cloud, dispersing the surrounding gas and feeding turbulent motions. Here we present several studies of very dense, active regions within low- to intermediate-mass protostellar clusters. Our observations include interferometer (i.e. CARMA) and single dish (e.g. FCRAO, IRAM 30m, APEX) observations, probing scales over several orders of magnitude. Based on these observations, we calculate the masses and kinematics of outflows in these regions, and provide constraints for models of clustered star formation. These results are presented for NGC 1333 by Plunkett et al. (2013), and comparisons among star-forming regions at different evolutionary stages are forthcoming.

Plunkett, Adele; Arce, Hector; Corder, Stuartt; Dunham, Mike; Mardones, Diego

2013-07-01

66

High-resolution CASSINI-VIMS mosaics of Titan and the icy Saturnian satellites  

Microsoft Academic Search

The Visual Infrared Mapping Spectrometer (VIMS) onboard the CASSINI spacecraft obtained new spectral data of the icy satellites of Saturn after its arrival at Saturn in June 2004. VIMS operates in a spectral range from 0.35 to 5.2?m, generating image cubes in which each pixel represents a spectrum consisting of 352 contiguous wavebands.As an imaging spectrometer VIMS combines the characteristics

R. Jaumann; K. Stephan; R. H. Brown; B. J. Buratti; R. N. Clark; T. B. McCord; A. Coradini; F. Capaccioni; G. Filacchione; P. Cerroni; K. H. Baines; G. Bellucci; J.-P. Bibring; M. Combes; D. P. Cruikshank; P. Drossart; V. Formisano; Y. Langevin; D. L. Matson; R. M. Nelson; P. D. Nicholson; B. Sicardy; C. Sotin; L. A. Soderbloom; C. Griffith; K.-D. Matz; Th. Roatsch; F. Scholten; C. C. Porco

2006-01-01

67

Biochemical characterization of metallo-beta-lactamase VIM-11 from a Pseudomonas aeruginosa clinical strain.  

PubMed

A detailed biochemical characterization of the Pseudomonas aeruginosa VIM-11 metallo-beta-lactamase (MbetaL) is reported. The only substitution differentiating VIM-11 from VIM-2 (N165S) promoted a slightly improved catalytic efficiency of the former on 3 out of 12 substrates, notably the bulky cephalosporins. Thus, MbetaL-mediated resistance also may be modulated by remote mutations. PMID:18362187

Marchiaro, Patricia; Tomatis, Pablo E; Mussi, María A; Pasteran, Fernando; Viale, Alejandro M; Limansky, Adriana S; Vila, Alejandro J

2008-06-01

68

Cassini VIMS observations of Saturn's infrared H3+ aurora during the 2013 multi-instrument campaign  

NASA Astrophysics Data System (ADS)

During the recent Saturn auroral observing campaign in April-May 2013 the Hubble Space Telescope (HST) and ground-based infrared telescopes observed Saturn's northern aurora while Cassini instruments observed either the northern or southern aurorae. This provided opportunity for unprecedented simultaneous observations of the auroral morphology and intensity in both hemispheres, as well as complementary sampling of the northern emissions at different spatial, spectral, and temporal scales. Here we present first results from the Cassini Visual and Infrared Mapping Spectrometer (VIMS) observations of the infrared emissions from the H+3 ionized molecule. We discuss the presence of rotating and poleward-moving blobs, planetary period modulation of auroral intensity, correspondence with in situ detection of field-aligned currents in the magnetic field data, and interhemispheric conjugate and non-conjugate features.

Badman, S. V.; Melin, H.; Stallard, T.; Blake, J. S. D.; O'Donoghue, J.; Bunce, E. J.; Nichols, J. D.; Baines, K. H.; Brown, R. H.; Dougherty, M. K.

2013-09-01

69

The Saturnian satellite Rhea as seen by Cassini VIMS  

USGS Publications Warehouse

Since the arrival of the Cassini spacecraft at Saturn in June 2004, the Visual and Infrared Mapping Spectrometer has obtained new spectral data of the icy satellites of Saturn in the spectral range from 0.35 to 5.2 ??m. Numerous flybys were performed at Saturn's second largest satellite Rhea, providing a nearly complete coverage with pixel-ground resolutions sufficient to analyze variations of spectral properties across Rhea's surface in detail. We present an overview of the VIMS observations obtained so far, as well as the analysis of the spectral properties identified in the VIMS spectra and their variations across its surface compared with spatially highly resolved Cassini ISS images and digital elevation models. Spectral variations measured across Rhea's surface are similar to the variations observed in the VIMS observations of its neighbor Dione, implying similar processes causing or at least inducing their occurrence. Thus, magnetospheric particles and dust impacting onto the trailing hemisphere appear to be responsible for the concentration of dark rocky/organic material and minor amounts of CO 2 in the cratered terrain on the trailing hemisphere. Despite the prominent spectral signatures of Rhea's fresh impact crater Inktomi, radiation effects were identified that also affect the H 2O ice-rich cratered terrain of the leading hemisphere. The concentration of H 2O ice in the vicinity of steep tectonic scarps near 270??W and geologically fresh impact craters implies that Rhea exhibits an icy crust at least in the upper few kilometers. Despite the evidence for past tectonic events, no indications of recent endogenically powered processes could be identified in the Cassini data. ?? 2011 Elsevier Ltd. All rights reserved.

Stephan, K.; Jaumann, R.; Wagner, R.; Clark, R. N.; Cruikshank, D. P.; Giese, B.; Hibbitts, C. A.; Roatsch, T.; Matz, K. -D.; Brown, R. H.; Filacchione, G.; Cappacioni, F.; Scholten, F.; Buratti, B. J.; Hansen, G. B.; Nicholson, P. D.; Baines, K. H.; Nelson, R. M.; Matson, D. L.

2012-01-01

70

Remote sensing applications in marine science programs at VIMS  

NASA Technical Reports Server (NTRS)

Scientists at the Virginia Institute of Marine Science (VIMS) utilized remote sensing in three programs: (1) tonal variations in imagery of wetlands; (2) use of the thermal infrared to delineate the discharge cooling water at the Virginia Electric and Power Company (VEPCO) nuclear power station on the James River; and (3) the use of aerial photography to determine the volume storage function for water in the marsh-bay complex fed by Wachapreague Inlet on the Eastern Shore of Virginia. Details of the investigations are given, along with significant results.

Gordon, H. H.; Penney, M. E.; Byrne, R. J.

1974-01-01

71

Laboratory Investigations Relevant to Cassini VIMS Reports of Coherent Constructive Interference in Saturn's Rings  

NASA Astrophysics Data System (ADS)

The Cassini spacecraft has flown between the sun and Saturn on several occasions during its orbital tour creating circumstances in which the zero phase point passed through the rings. The Visual and Infrared Mapping Spectrometer (VIMS) recorded spectral image cubes (0.4 to 5.2 microns that showed the opposition effect (OE) at zero phase. The OE is a spike in the intensity of reflected light observed near zero phase when it is displayed as a function of phase angle. This is the first time the OE has been resolved for small areas on the rings. Laboratory investigations of angular scattering properties of particulate materials show that the OE arises from two distinct processes, shadow hiding (SHOE) and coherent backscattering (CBOE). The SHOE process causes an OE by the elimination of shadows cast by regolith grains upon one another as phase angle decreases. The CBOE process causes an OE by constructive interference between photons traveling in opposite directions along the same path within the medium. SHOE is expected to dominate the contribution to the OE in absorbing media where multiple scattering of photons is not significant. CBOE is expected to dominate the contribution to the OE in highly reflective media with much multiple scattering. We have made spectral dimension scans of the VIMS images that traverse the zero phase point. We selected narrow spectral bands that represent a variety of wavelengths and reflectance levels. In this way, phase curves of the ringlet were obtained for each band. We have compared these data to data we acquired in the laboratory using the JPL long arm goniometer where we measured the phase curve of particulate materials that simulate the surface of Saturn's ring particles. We argue here that the OE is due to coherent backscattering because: 1) The theoretical CBOE function fit to the data is excellent. 2) The OE width is extremely narrow 3) The angular width of the peak increases with wavelength. CBOE theory also predicts that the width depends on the transport mean free path (TMFP) in the medium. We find that the OE is caused by coherent interactions between sub-particles in the outer layers of the ring particles, and that these sub-particles are of the order of 40 microns in size.

Nelson, Robert

72

Metallo -Lactamases in Clinical Pseudomonas Isolates in Taiwan and Identification of VIM3, a Novel Variant of the VIM2 Enzyme  

Microsoft Academic Search

A total of 209 clinical isolates of Pseudomonas (193 Pseudomonas aeruginosa ,1 0P. putida ,4 P. stutzeri, and 2 P. fluorescens isolates) with reduced susceptibilities to imipenem and\\/or ceftazidime were subjected to PCR assays with primers specific for blaIMP-1, blaIMP-2, blaVIM-1, and blaVIM-2 and sequence analysis to identify the metallo-b-lactamases (MBLs) prevalent among these organisms in Taiwan; and 21 isolates

JING-JOU YAN; PO-REN HSUEH; WEN-CHIEN KO; KWEN-TAY LUH; SHU-HUEI TSAI; HSIU-MEI WU; JIUNN-JONG WU

2001-01-01

73

Saturn's north polar cyclone and hexagon at depth revealed by Cassini/VIMS  

USGS Publications Warehouse

A high-speed cyclonic vortex centered on the north pole of Saturn has been revealed by the visual-infrared mapping spectrometer (VIMS) onboard the Cassini-Huygens Orbiter, thus showing that the tropospheres of both poles of Saturn are occupied by cyclonic vortices with winds exceeding 135 m/s. High-spatial-resolution (~200 km per pixel) images acquired predominantly under night-time conditions during Saturn's polar winter-using a thermal wavelength of 5.1 ??m to obtain time-lapsed imagery of discrete, deep-seated (>2.1-bar) cloud features viewed in silhouette against Saturn's internally generated thermal glow-show a classic cyclonic structure, with prograde winds exceeding 135 m/s at its maximum near 88.3?? (planetocentric) latitude, and decreasing to <30 m/s at 89.7?? near the vortex center and<20 m/s at 80.5??. High-speed winds, exceeding 125 m/s, were also measured for cloud features at depth near 76?? (planetocentric) latitude within the polar hexagon consistent with the idea that the hexagon itself, which remains nearly stationary, is a westward (retrograde) propagating Rossby wave - as proposed by Allison (1990, Science 247, 1061-1063) - with a maximum wave speed near 2-bars pressure of ~125 m/s. Winds are ~25 m/s stronger than observed by Voyager, suggesting temporal variability. Images acquired of one side of the hexagon in dawn conditions as the polar winter wanes shows the hexagon is still visible in reflected sunlight nearly 28 years since its discovery, that a similar 3-lane structure is observed in reflected and thermal light, and that the cloudtops may be typically lower in the hexagon than in nearby discrete cloud features outside of it. Clouds are well-correlated in visible and 5.1 ??m images, indicating little windshear above the ~2-bar level. The polar cyclone is similar in size and shape to its counterpart at the south pole; a primary difference is the presence of a small (<600 km in diameter) nearly pole-centered cloud, perhaps indicative of localized upwelling. Many dozens of discrete, circular cloud features dot the polar region, with typical diameters of 300-700 km. Equatorward of 87.8??N, their compact nature in the high-wind polar environment suggests that vertical shear in horizontal winds may be modest on 1000 km scales. These circular clouds may be anticyclonic vortices produced by baroclinic instabilities, barotropic instabilities, moist convection or other processes. The existence of cyclones at both poles of Saturn indicates that cyclonic circulation may be an important dynamical style in planets with significant atmospheres. ?? 2009 Elsevier Ltd. All rights reserved.

Baines, K. H.; Momary, T. W.; Fletcher, L. N.; Showman, A. P.; Roos-Serote, M.; Brown, R. H.; Buratti, B. J.; Clark, R. N.; Nicholson, P. D.

2009-01-01

74

Large-scale wavelength and polarization insensitive optical switch on SOI from 1260 nm to 1360 nm  

NASA Astrophysics Data System (ADS)

The 2x2 optical switch is a crucial component to the future of optical communications and integrated optics. Optical switches on the silicon-on-insulator (SOI) platform have shown advantages in terms of device footprint and switching speed. However, due to the intrinsic properties of SOI rib waveguides, these devices suffer from a strong wavelength and polarization dependent response. Our work presents an SOI based Mach-Zehnder interferometer (MZI) switch which is both polarization and wavelength insensitive over a large bandwidth of 1260-1360 nm. We have completed detailed analyses on the polarization and wavelength performance of the MZI, and obtained optimized parameters in a novel design to reduce the crosstalk f or transverse electric (TE) and transverse magnetic (TM) modes over the wavelength range 1260-1360 nm. Our simulations suggest that we successfully obtained a polarization and wavelength insensitive MZI. A crosstalk level below -18 dB is achieved for both the TE and TM modes in the on-state and the off-state, across the 100 nm bandwidth. Such a polarization and wavelength insensitive switch has a variety of applications in wavelength division multiplexing and other communication systems.

Dorin, Bryce A.; Goodwill, Dominic; Bernier, Eric; Ye, Winnie N.

2013-10-01

75

Multigroup calculations using VIM: A user`s guide to ISOVIM  

SciTech Connect

Monte Carlo calculations have long been used to benchmark more a mate approximate solution methods for reactor physics problems. The power of VIM (ref 1) lies partly in the detailed geometrical representations incorporating the (generally) curved surfaces of combinatorial geometry, and partly in the fine energy detail of pointwise cross sections which are independent of the neutron spectrum. When differences arise between Monte Carlo and deterministic calculations, the question arises, is the error in the multigroup cross sections, in the treatment of transport effects, or in the mesh-based treatment of space in the deterministic calculation? The answers may not be obvious, but may be identified by combining the exact geometry capability of VIM with the multigroup formalism. We can now run VIM in a multigroup mode by producing special VIM Material files which contain point-wise data describing multigroup data with histograms. This forces VIM to solve the multigroup problem with only three small code modifications. P{sub N} scattering is simulated with the usual tabulated angular distributions with 20 equally-sized scattering angle cosine meshes. This document describes the VIM multigroup capability, the procedures for generating multigroup cross sections for VIM, and their use. The multigroup cross section generating code, ISOVIM, is described, and benchmark testing is documented.

Blomquist, R.N.

1992-09-01

76

MULTI-WAVELENGTH VIEW OF KILOPARSEC-SCALE CLUMPS IN STAR-FORMING GALAXIES AT z {approx} 2  

SciTech Connect

This paper studies the properties of kiloparsec-scale clumps in star-forming galaxies at z {approx} 2 through multi-wavelength broadband photometry. A sample of 40 clumps is identified from Hubble Space Telescope (HST)/Advanced Camera for Surveys (ACS) z-band images through auto-detection and visual inspection from 10 galaxies with 1.5 < z < 2.5 in the Hubble Ultra Deep Field, where deep and high-resolution HST/WFC3 and ACS images enable us to resolve structures of z {approx} 2 galaxies down to the kiloparsec scale in the rest-frame UV and optical bands and to detect clumps toward the faint end. The physical properties of clumps are measured through fitting spatially resolved seven-band (BVizYJH) spectral energy distribution to models. On average, the clumps are blue and have similar median rest-frame UV-optical color as the diffuse components of their host galaxies, but the clumps have large scatter in their colors. Although the star formation rate (SFR)-stellar mass relation of galaxies is dominated by the diffuse components, clumps emerge as regions with enhanced specific star formation rates, contributing individually {approx}10% and together {approx}50% of the SFR of the host galaxies. However, the contributions of clumps to the rest-frame UV/optical luminosity and stellar mass are smaller, typically a few percent individually and {approx}20% together. On average, clumps are younger by 0.2 dex and denser by a factor of eight than diffuse components. Clump properties have obvious radial variations in the sense that central clumps are redder, older, more extincted, denser, and less active on forming stars than outskirt clumps. Our results are broadly consistent with a widely held view that clumps are formed through gravitational instability in gas-rich turbulent disks and would eventually migrate toward galactic centers and coalesce into bulges. Roughly 40% of the galaxies in our sample contain a massive clump that could be identified as a proto-bulge, which seems qualitatively consistent with such a bulge-formation scenario.

Guo Yicheng; Giavalisco, Mauro; Cassata, Paolo [Astronomy Department, University of Massachusetts, 710 N. Pleasant St., Amherst, MA 01003 (United States); Ferguson, Henry C.; Koekemoer, Anton M., E-mail: yicheng@astro.umass.edu [Space Telescope Science Institute, 3700 San Martin Dr., Baltimore, MD 21218 (United States)

2012-10-01

77

VIMS spectral mapping observations of Titan during the Cassini prime mission  

USGS Publications Warehouse

This is a data paper designed to facilitate the use of and comparisons to Cassini/visual and infrared mapping spectrometer (VIMS) spectral mapping data of Saturn's moon Titan. We present thumbnail orthographic projections of flyby mosaics from each Titan encounter during the Cassini prime mission, 2004 July 1 through 2008 June 30. For each flyby we also describe the encounter geometry, and we discuss the studies that have previously been published using the VIMS dataset. The resulting compliation of metadata provides a complementary big-picture overview of the VIMS data in the public archive, and should be a useful reference for future Titan studies. ?? 2009 Elsevier Ltd.

Barnes, J. W.; Soderblom, J. M.; Brown, R. H.; Buratti, B. J.; Sotin, C.; Baines, K. H.; Clark, R. N.; Jaumann, R.; McCord, T. B.; Nelson, R.; Le, Mouelic, S.; Rodriguez, S.; Griffith, C.; Penteado, P.; Tosi, F.; Pitman, K. M.; Soderblom, L.; Stephan, K.; Hayne, P.; Vixie, G.; Bibring, J. -P.; Bellucci, G.; Capaccioni, F.; Cerroni, P.; Coradini, A.; Cruikshank, D. P.; Drossart, P.; Formisano, V.; Langevin, Y.; Matson, D. L.; Nicholson, P. D.; Sicardy, B.

2009-01-01

78

Iapetus as Seen Through the Multispectral Eyes of Cassini VIMS  

NASA Astrophysics Data System (ADS)

The Cassini targeted flyby of Saturn's moon Iapetus on Sept. 10, 2007 will enable the first detailed study of the composition of this satellite within the context of geologic features and evolution. Detailed maps of the volatiles and components constructed by data from the Visual Infrared Mapping Spectrometer (VIMS) will follow on earlier detections. These materials include carbon dioxide (Buratti et al. Ap. J., 2005), polycyclic aromatic hydrocarbons (PAHS; Cruikshank, Icarus, 2007) and trace ammonia (Clark et al. Icarus, 2007). The flyby offers good coverage of the bright-dark interface, and it should enable observations of compositional markers in low-albedo features (e.g., dark floor craters) on the moon's high-albedo hemisphere. Funded by NASA.

Buratti, B. J.; Clark, R. N.; Cruikshank, D. P.; Brown, R. H.; Baines, K. H.; Nicholson, P. D.; Bauer, J. M.; Momary, T.; Newman, S. F.; Lee, J. S.

2007-12-01

79

Titan's surface: Search for spectral diversity and composition using the Cassini VIMS investigation  

NASA Astrophysics Data System (ADS)

The surface composition of Titan is of great importance for understanding both the internal evolution of Titan and its atmosphere. The Visual and Infrared Mapping Spectrometer (VIMS) investigation on Cassini is observing Titan from 0.35 to 5.11 ?m with spatial resolution down to a few kilometers during each flyby of the spacecraft as it orbits Saturn. Our search for spectral diversity using seven methane transmission windows in the near infrared suggests that spectrally distinct units exist on the surface of Titan and that most of the surface can be modeled using only a few distinct spectral units: water frost, CO 2 frost, atmospheric scattering, and an unknown material bright at 2 ?m. A dark, spectrally neutral material is also implied. Use of an atmospheric scattering component with spectral mixing analysis may provide a method for partially removing atmospheric effects. In some locations, atmospheric scattering accounts for the majority of the signal. There are also small regions with unusual spectra that may be due to low signal and high noise and/or may be exotic materials of interest. Further, we searched within the methane windows for spectral features associated with Titan's surface. Only the 5-?m and, to a lesser extent, the 2-?m window provide a reasonable opportunity for this, as the shorter-wavelength windows are too narrow and the 2.8-?m window is cluttered with an unknown atmospheric constituent. We find evidence for only one spectral feature: near 4.92 ?m for the 5-?m bright Tui Regio region. CO 2 frost with grains smaller than about 10 ?m is the best candidate we have found so far to explain this absorption as well as the feature's spectral contrast between the 2.7- and the 2.8-?m atmosphere subwindows. This suggested CO 2 identification is supported by the presence of an endmember in the spectral mixture analysis that is consistent with CO 2 frost with large grain sizes. We find no other absorption features that are statistically significant, including those reported earlier by others. These results are consistent with but greatly extend our early analysis that treated only the T data set [McCord, T.B., et al., 2006a. Planet. Space Sci. 54, 1524-1539]. In the spectral feature search process, we explored in detail the noise characteristics of the VIMS data within the 5-?m window, which has generally very low signal (4-20 DN), due to the measurement conditions and low illumination levels. We find noise of nearly Gaussian statistics except for some erratic darks and noise spikes, and the data set seems generally well behaved. We present examples of our attempt to improve on the standard VIMS pipeline data calibration.

McCord, Thomas B.; Hayne, Paul; Combe, Jean-Philippe; Hansen, Gary B.; Barnes, Jason W.; Rodriguez, Sébastien; Le Mouélic, Stéphane; Baines, E. Kevin H.; Buratti, Bonnie J.; Sotin, Christophe; Nicholson, Philip; Jaumann, Ralf; Nelson, Robert; the Cassini VIMS Team

2008-03-01

80

Detection of Thermal Emission from Enceladus' Tiger Stripes with Cassini VIMS  

NASA Astrophysics Data System (ADS)

We announce the detection of thermal emission from Damascus and Cairo with the Cassini VIMS in the 4-5 µm region of the spectrum. These new spectra put strong constraints on the emitting area at the hottest temperatures.

Blackburn, D. G.; Goguen, J. D.; Buratti, B. J.; Clark, R. N.; Howell, R. R.; Spencer, J. R.

2012-03-01

81

Distinguishing between primary endocervical and endometrial adenocarcinomas: is a 2-marker (Vim/CEA) panel enough?  

PubMed

Gynecological pathologists are used to operating many panels of various markers in combination for the diagnostic distinction between primary endocervical and endometrial adenocarcinomas. The conventional 3-marker (ER/Vim/CEA) panel is the most promising tool. In this study, our aim is to investigate whether a 2-marker panel is enough to distinguish between these two gynecologic malignancies. Additionally, we wish to determine which one is the most favorable among eight panels tested, including six 2-marker (ER/CEA, PR/CEA, Vim/CEA, ER/p16(INK4a), PR/p16(INK4a), Vim/p16(INK4a)) and two 3-marker (ER/Vim/CEA, ER/Vim/p16(INK)) panels. A tissue microarray was constructed using paraffin-embedded, formalin-fixed tissues from 35 hysterectomy specimens, including 14 primary endocervical adenocarcinomas and 21 primary endometrial adenocarcinomas. Utilizing the avidin-biotin complex (ABC) method, tissue array sections were immunostained with five commercially available antibodies (ER, Vim, CEA, PR, and p16(INK4a)) to evaluate their individual frequencies of expression. We found that all eight aforementioned panels showed an encouraging range of overall accuracy (69.2% to 78.3%). However, one panel of 2-markers (Vim, CEA) exhibited the most efficiency (78.3%) in the diagnostic distinction between primary endocervical and endometrial adenocarcinomas. Based on the analyzed data, we conclude that the 2-marker (Vim/CEA) panel seems adequate to be an appropriate, convenient, and efficient means to distinguish between primary endocervical and endometrial adenocarcinomas. Even though there were a limited number of cases, this study still provides valuable references to help avoid wasting resources and unnecessary marker testing. PMID:20221633

Liao, Chiung-Ling; Hsu, Jeng-Dong; Lee, Ming-Yung; Kok, Lai-Fong; Li, Yi-Ju; Wang, Po-Hui; Yao, Chung-Chin; Han, Chih-Ping

2010-04-01

82

Outbreak of vim-1-carbapenemase-producing Enterobacter cloacae in a pediatric intensive care unit.  

PubMed

Pediatric patients are rarely infected with metallo-?-lactamase-producing Enterobacteriaceae. We describe 3 cases of children infected with VIM-1-producing clonal Enterobacter cloacae. Patients were treated with amikacin and cotrimoxazole. The blaVIM-1 gene was carried into a class 1 integron and an IncHI2 incompatibility group plasmid. Emergence of pediatric infections caused by carbapenemases-producing Enterobacteriaceae is a critical issue as they are resistant to most ?-lactam antibiotics. PMID:20686438

Oteo, Jesús; Hernández-Almaraz, José Luis; Gil-Antón, Javier; Vindel, Ana; Fernández, Sara; Bautista, Verónica; Campos, José

2010-12-01

83

Internal FUV Wavelength Verification  

NASA Astrophysics Data System (ADS)

This program will be executed after the uplink of the OSM1 position updates derived from the determination of the wavelength-scale zero points and desired spectral ranges for each grating in activity COS29 {program 11487 - COS FUV Internal/External Wavelength Scales}. This program will verify that the operational spectral ranges for each grating, central wavelength, and FP-POS are those desired. Subsequent to a successful verification, COS FUV ERO observations and FUV science can be enabled. An internal wavelength calibration spectrum using the default PtNe lamp {lamp 1} with each FUV grating at each central wavelength setting and each FP-POS position will be obtained for the verification. Additional exposures and waits between certain exposures will be required to avoid - and to evaluate - mechanism drifts.;

Keyes, Charles

2008-07-01

84

Spectrophotometric Modeling of Enceladus Surface Properties and Composition from Vims Data  

NASA Astrophysics Data System (ADS)

The Visual and Infrared Mapping Spectrometer (VIMS) instrument onboard the Cassini spacecraft, is an imaging spectrometer that produces monochromatic images in the 0.35 - 5.12 µm range. During the five years of Cassini mission in the system of Saturn the instrument produced more than 1400 full-disk images of the moons in a wide range of solar phase angles. This huge amount of data allows the study of the spectral and photometric surface properties of the Saturnian satellites. Our work started with the analysis of Rhea’s surface properties (Ciarniello et al., submitted) and we now focus on Enceladus. We applied the Hapke’s radiative transfer model (Hapke,1993) to study the satellite’s spectrum at each available phase angle and the phase curve at each wavelength in the VIMS range. This approach allows to constrain physical properties of the medium composing the surface such as grain size, amount of contaminants, opposition effect mechanisms and surface roughness. The 1.5, 2.0 and 3.0 µm absorption bands in the spectrum indicate that the surface of the moon is mainly composed of water ice. However the spectrum shows a small UV downturn which can be explained by the presence of organic contaminants. In order to reproduce this behavior we modeled the surface using a monodisperse grain size distribution of water ice with small inclusions of contaminants. Three mixing modes have been investigated: areal, intimate and intraparticle. Four different organic contaminants have been used: Triton tholin, Titan tholin, Hydrogenated amorphous carbon and tholin from Khare et al. 1993. The best fit is obtained with an intraparticle mixture of water ice and a tiny amount of Triton tholin (0.001%) with particle radius between 60-70 µm. The spectral fit allows to decouple spectral effects by photometric ones and represents the starting point for the phase curve fit allowing to compute the single scattering albedo of the medium. The fit of phase curve for each wavelength shows a correlation between the parameters affecting its shape (opposition effect amplitude and width, single particle phase function parameters and surface roughness slope) with the single scattering albedo. We compared the result of this work with our previous study performed on Rhea in order to point out compositional similarities between the two moons. The approach we developed in this work is applicable to all the Saturn’s icy moons and represents a powerful tool to characterize their surface properties and to understand the processes that model them. Additionally, this method will allow to determine the distribution of organic compounds in the Saturnian system and to study the surface evolution of the moons. This work is supported by an Italian Space Agency grant.

Ciarniello, M.; Capaccioni, F.; Filacchione, G.; Clark, R. N.; Cruikshank, D. P.; Cerroni, P.; Coradini, A.; Brown, R. H.; Buratti, B. J.; Tosi, F.; Stephan, K.

2010-12-01

85

Multi-wavelength Observations of the Spatio-temporal Evolution of Solar Flares with AIA/SDO. I. Universal Scaling Laws of Space and Time Parameters  

NASA Astrophysics Data System (ADS)

We extend a previous statistical solar flare study of 155 GOES M- and X-class flares observed with AIA/SDO to all seven coronal wavelengths (94, 131, 171, 193, 211, 304, and 335 Å) to test the wavelength dependence of scaling laws and statistical distributions. Except for the 171 and 193 Å wavelengths, which are affected by EUV dimming caused by coronal mass ejections (CMEs), we find near-identical size distributions of geometric (lengths L, flare areas A, volumes V, and fractal dimension D 2), temporal (flare durations T), and spatio-temporal parameters (diffusion coefficient ?, spreading exponent ?, and maximum expansion velocities v max) in different wavelengths, which are consistent with the universal predictions of the fractal-diffusive avalanche model of a slowly driven, self-organized criticality (FD-SOC) system, i.e., N(L)vpropL -3, N(A)vpropA -2, N(V)vpropV -5/3, N(T)vpropT -2, and D 2 = 3/2, for a Euclidean dimension d = 3. Empirically, we find also a new strong correlation ?vpropL 0.94 ± 0.01 and the three-parameter scaling law Lvprop? T 0.1, which is more consistent with the logistic-growth model than with classical diffusion. The findings suggest long-range correlation lengths in the FD-SOC system that operate in the vicinity of a critical state, which could be used for predictions of individual extreme events. We find also that eruptive flares (with accompanying CMEs) have larger volumes V, longer flare durations T, higher EUV and soft X-ray fluxes, and somewhat larger diffusion coefficients ? than confined flares (without CMEs).

Aschwanden, Markus J.; Zhang, Jie; Liu, Kai

2013-09-01

86

Purification and Biochemical Characterization of the VIM-1 Metallo-?-Lactamase  

PubMed Central

VIM-1 is a new group 3 metallo-?-lactamase recently detected in carbapenem-resistant nosocomial isolates of Pseudomonas aeruginosa from the Mediterranean area. In this work, VIM-1 was purified from an Escherichia coli strain carrying the cloned blaVIM-1 gene by means of an anion-exchange chromatography step followed by a gel permeation chromatography step. The purified enzyme exhibited a molecular mass of 26 kDa in sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and an acidic pI of 5.1 in analytical isoelectric focusing. Amino-terminal sequencing showed that mature VIM-1 results from the removal of a 26-amino-acid signal peptide from the precursor. VIM-1 hydrolyzes a broad array of ?-lactam compounds, including penicillins, narrow- to expanded-spectrum cephalosporins, carbapenems, and mechanism-based serine-?-lactamase inactivators. Only monobactams escape hydrolysis. The highest catalytic constant/Km ratios (>106 M?1 · s?1) were observed with carbenicillin, azlocillin, some cephalosporins (cephaloridine, cephalothin, cefuroxime, cefepime, and cefpirome), imipenem, and biapenem. Kinetic parameters showed remarkable variability with different ?-lactams and also within the various penam, cephem, and carbapenem compounds, resulting in no clear preference of the enzyme for any of these ?-lactam subfamilies. Significant differences were observed with some substrates between the kinetic parameters of VIM-1 and those of other metallo-?-lactamases. Inactivation assays carried out with various chelating agents (EDTA, 1,10-o-phenanthroline, and pyridine-2,6-dicarboxylic acid) indicated that formation of a ternary enzyme-metal-chelator complex precedes metal removal from the zinc center of the protein and revealed notable differences in the inactivation parameters of VIM-1 with different agents.

Franceschini, Nicola; Caravelli, Berardo; Docquier, Jean-Denis; Galleni, Moreno; Frere, Jean-Marie; Amicosante, Gianfranco; Rossolini, Gian Maria

2000-01-01

87

Molecular epidemiology of Enterobacteriaceae that produce VIMs and IMPs from the SMART surveillance program.  

PubMed

A study was designed to characterize 35 non-repeat isolates of VIM- and IMP-producing Enterobacteriaceae obtained from the SMART surveillance program. Characterization was done by polymerase chain reaction, sequencing, and multi-locus sequencing. The VIM-1, -2, -5, -26, -27, -33, and IMP-1 and -26-producing Enterobacteriaceae were obtained from Greece, Italy, Spain, Philippines, Turkey, Australia, Mexico, USA, and India. Plasmids varied in size from 60 to 300 kb and belonged to IncA/C, IncF, IncHI1, IncL/M, IncN, and IncK incompatibility groups. The most common gene cassettes consisted of blaIMP-26, qacG, aacA4 and blaVIM, aacA7, dhfrI, and aadA1. Intercountry, interhospital, intrahospital, interspecies, and intraclonal spread of blaVIM and blaIMP containing plasmids and sequence types (STs) occurred in Greece, Italy, Spain, and Philippines. ST147 with IncA/C and IncF plasmids is an important drug-resistant ST among Klebsiella pneumoniae with VIMs. Our study highlights the importance of surveillance programs using molecular techniques as powerful tools to identify the transmission of STs with their respective plasmids. PMID:24387958

Peirano, Gisele; Lascols, Christine; Hackel, Meredith; Hoban, Daryl J; Pitout, Johann D D

2014-03-01

88

Infections with VIM-1 Metallo-?-Lactamase-Producing Enterobacter cloacae and Their Correlation with Clinical Outcome?  

PubMed Central

The aim of this study was to ascertain the incidence and clinical significance of metallo-?-lactamases among Enterobacter strains isolated from patients with nosocomial infections. We prospectively collected data on patients with Enterobacter infection during a 13-month period. All of the strains were investigated for antibiotic susceptibility, the presence and expression of metallo-?-lactamases, and clonality. Of 29 infections (11 involving the urinary tract, 7 pneumonias, 3 skin/soft tissue infections, 3 intra-abdominal infections, 3 bacteremias, and 2 other infections), 7 (24%) were caused by Enterobacter cloacae strains harboring a blaVIM-1 gene associated or not with a blaSHV12 gene. Infections caused by VIM-1-producing strains were more frequently associated with a recent prior hospitalization (P = 0.006), cirrhosis (P = 0.03), relapse of infection (P < 0.001), and more prolonged duration of antibiotic therapy (P = 0.01) than were other infections. All of the isolates were susceptible to imipenem and meropenem and had blaVIM-1 preceded by a weak P1 promoter and inactivated P2 promoters. Most VIM-1-producing Enterobacter isolates belonged to a main clone, but four different clones were found. Multiclonal VIM-1-producing E. cloacae infections are difficult to diagnose due to an apparent susceptibility to various beta-lactams, including carbapenems, and are associated with a high relapse rate and a more prolonged duration of antibiotic therapy.

Falcone, Marco; Mezzatesta, Maria Lina; Perilli, Mariagrazia; Forcella, Chiara; Giordano, Alessandra; Cafiso, Viviana; Amicosante, Gianfranco; Stefani, Stefania; Venditti, Mario

2009-01-01

89

The Saturnian Satellite Tethys Observed By Cassini-VIMS  

NASA Astrophysics Data System (ADS)

We present a detailed analysis of the variations in spectral properties across the surface of Saturn's satellite Tethys using Cassini/VIMS data and their relationships to geological and/or morphological characteristics as seen in the Cassini/ISS images. Despite the spectral dominance of water ice on Tethys’ surface distinct spectral variations could be detected, which are surprisingly very different from what was expected from the visible albedo derived from Voyager and Cassini camera data. The abundance of water ice usually follows the visible surface albedo as seen on many other satellites. Although on Tethys, the weakest water ice signature could be also measured on the trailing hemisphere as known from Dione and Rhea [1-3], the detailed mapping, however, shows a more complex pattern. Two relatively narrow N/S-trending bands characterized by larger ice particle sizes rather than the higher abundance of water ice separate the Saturn-facing and the anti-Saturnian hemisphere of Tethys. So far, larger ice particles could only be found in geologically young, less weathered portions of the surfaces of the icy Saturnian satellites [2,3]. On Tethys, however, the observed variations might be more complex due to the influence of fine particles from the E-ring coating the surface. In contrast to the prominent graben systems on Dione and Rhea, which show fresh ice exposed on steep walls, no spectral properties could be exclusively associated to Tethys’ extended graben system Ithaca Chasma supporting its geologically old age and that its formation was not caused by the impact event that created Odysseus [4]. References: [1] Clark, R. N., et al. (2008), Icarus, 193(2), 372-386. [2] Stephan, K., et al. (2010) Icarus, 206(2), 631-652. [3] Stephan, K. et al. (2012) PSS, 61(1), 142-160. [4] Giese et al., (2007) GRL, 34(21), L21203.

Stephan, Katrin; Jaumann, R.; Wagner, R.; Clark, R. N.; Cruikshank, D. P.; Dalle Ore, C.; Hansen, G. B.; Brown, R. H.; Giese, B.; Roatsch, T.; Matson, D.; Baines, K.; Filiacchione, G.; Cappacione, F.; Rodriguez, S.; Buratti, B. J.; Nicholson, P. D.; Sotin, C.

2012-10-01

90

North vs South on Saturn: Discovery of a Pronounced Hemispherical Asymmetry in Saturn's 5-Micron Emission and Associated Deep Cloud Structure by Cassini/VIMS  

NASA Astrophysics Data System (ADS)

We report the discovery of a pronounced North/South hemispherical asymmetry in the 5-micron radiation emitted from Saturn's interior observed by Cassini/VIMS in global-scale spectral images of the planet's nightside. These nightside images, uncontaminated by sunlight which otherwise adds significant reflected light to the southern summer hemisphere, shows that northern latitudes poleward of 8 degrees latitude emit about twice the 5-micron flux as their southern latitude counterparts. Such asymmetry has now been seen consistently in 2005 and 2006, whenever VIMS has been able to image both the north and south nightside hemispheres. The 2:1 difference in hemispherical emission is nearly uniform over the entire 5-micron emission spectrum from 4.8 to 5.1 microns, spanning 21 VIMS channels. As noted previously (Baines et al., Earth, Moon, and Planets 96, 119-147), such 2:1 5-micron flux variations are regularly seen in high-spatial resolution imagery on Saturn, indicating significant small-scale variability in cloud cover near the 2-bar level (Baines et al., BAAS 37, 658). Similarly, the 2:1 hemispherical variability likely indicates a global-scale variation in the opacity of Saturn's deep clouds, with northern clouds having an average 5-micron optical depth about 0.7 less than the average southern cloud. This hemispherical difference may be a manifestation of seasonal changes at depth on Saturn, with distinct thinning of deep-seated (likely ammonium hydrosulfide and/or water) clouds in the winter northern hemisphere and/or thickening of these deep clouds in the summer southern hemisphere. Such possible seasonal variability in Saturn's deep-cloud structure will be monitored over the next few years as Saturn encounters equinox conditions in 2010.

Baines, Kevin H.; Momary, T. W.; Roos-Serote, M.; Cassini/VIMS Science Team

2006-09-01

91

Simultaneous multi-wavelength observations of Saturn's aurorae : energy budget and magnetospheric dynamics  

NASA Astrophysics Data System (ADS)

Similarly to other magnetized planets, accelerated electrons entering Saturn's auroral regions generate powerful emissions. They divide into Ultraviolet (UV) and Infrared (IR) aurorae, originating from collisions with the upper atmosphere, and Saturn's Kilometric Radiation (SKR), radiated by an electron cyclotron resonance above the atmosphere up a few Saturn's radii (Rs). Previous studies have identified a large scale conjugacy between radio and UV, as well as IR and UV auroral emissions. Here, we investigate two days of observations of Saturn's aurorae at radio, UV and IR wavelengths, by the Cassini RPWS, UVIS and VIMS instruments, and their relationship with a reservoir of equatorial energetic particles mapped by energetic neutral atoms (ENA), as measured by MIMI-INCA (see Figure ??). This interval of time reveals a series of regular SKR modulations at the southern SKR phase, and interestingly includes an unusual (while also regular) enhancement of the auroral activity observed simultaneously at all wavelengths. This event is likely to illustrate a (regular) nightside injection of energetic particles, possibly induced by a plasmoid ejection, then co-rotating with the planet at the southern SKR period, while feeding an extended longitudinal sector of intense auroral emissions. We analyze quantitatively complementary informations brought by these different datasets in terms of energy budget transferred to the southern auroral region, as well as magnetospheric dynamics, in order to address the nature and the scheme of the Saturn's southern rotational modulation.

Lamy, L.

2011-10-01

92

Not So Titanic Winds: Cassini\\/VIMS Observations of Cloud Features in the Southern Hemisphere of Titan  

Microsoft Academic Search

One atmospheric science objective of VIMS is to measure windspeeds of cloud features in the Saturnian system at known altitudes, as determined from the 352 spectral bands that VIMS provides. The Titan encounter of 2 July 2004 provided the first opportunity to measure cloud-tracked winds on Titan. Spectral imagery revealed that cloud coverage of Titan was sparse, covering less than

T. W. Momary; K. H. Baines; B. J. Buratti; C. Griffith; R. H. Brown; R. Jaumann; P. Drossart; Cassini VIMS

2004-01-01

93

A compact RCS-range based on a phase hologram for scale model measurements at sub-mm-wavelengths  

Microsoft Academic Search

The HUT Radio Laboratory develops a novel compact radar cross section (RCS) test range for scale model measurements. The test range is based on a phase hologram that converts the feed horn radiation to a plane wave. The measurements are performed using CW at 310 GHz in a quasi-monostatic radar configuration where the identical receiving and transmitting corrugated horn antennas

A. V. Raisanen; A. Lonnqvist; J. Mallat; E. Noponen; J. Ala-Laurinaho; J. Saily; T. Koskinen; J. Hakli

2003-01-01

94

Multi-wavelength studies of Saturn's rings to constrain ring particle properties and ring structure  

NASA Astrophysics Data System (ADS)

A great deal can be learned about the nature of Saturn's ring particles and their regoliths by modeling the changes in brightness, color and temperature with changing viewing geometry over a wide range of wavelengths, from ultraviolet through the thermal infrared. Data from Cassini's Composite Infrared Spectrometer (CIRS), Visual and Infrared Mapping Spectrometer (VIMS), Imaging Science Subsystem (ISS) and Ultraviolet Imaging Spectrograph (UVIS) are jointly being studied using scans of the lit and unlit main rings (A, B, C and Cassini Division) at multiple geometries and solar elevations. Using multi-wavelength data sets allow us to test different thermal models by combining the effects of particle albedo, regolith grain size and surface roughness with thermal emissivity and inertia, particle spin rate and spin axis orientation. With the high spatial resolution of the Cassini data it is now possible to analyze these effects at smaller spatial scales and characterize regions such as the C ring plateaus and ringlets, where albedo differences may be present. In the CIRS data, over a range of solar elevations from -23 degrees to -8 degrees, the bulk of the temperature variations are confined primarily to phase angle. Only small temperature differences are observed with changing spacecraft elevation. Similar behavior is seen in the ISS color data. Color and temperature dependence with changing solar elevation angle are also observed. VIMS observations show that the IR ice absorption band depths are (almost) independent of phase angle, out to ~140 deg phase, suggesting that interparticle light scattering is relatively unimportant except at very high phase angles. These results imply that the individual properties of the ring particles may play a larger role than the collective properties of the rings, in particular at visible wavelengths. The temperature and color variation with phase angle may be a result of scattering within the regolith and on possibly rough surfaces of the clumps, as well as a contribution from scattering between individual particles in a many-particle-thick layer. Preliminary results from our joint studies will be presented. This research was carried out in part at the Jet Propulsion Laboratory, California Institute of Technology, under contract with NASA. Copyright 2012 California Institute of Technology. Government sponsorship is acknowledged.

Spilker, L.; Deau, E.; Morishima, R.; Filacchione, G.; Hedman, M.; Nicholson, P.; Colwell, J.; Bradley, T.

2012-04-01

95

Hot Electron and X-ray Production from Intense Laser Irradiation of Wavelength-scale Polystyrene Spheres  

NASA Astrophysics Data System (ADS)

In an attempt to control the electric fields at the surface of a high intensity solid target we have studied hot electron generation and x-ray production from targets coated with microspheres. This work is motivated by the possibility that spheres with size comparable to the wavelength of the incident laser radiation can result in electric field enhancements through well know Mie resonances. This local field enhancement can then lead to more efficient electron generation. We investigated hard x-ray (above 100 keV) generation from copper and fused silica targets coated with a monolayer covering of polystyrene microspheres. We performed the experiment using the 20 TW THOR laser system at the University of Texas. We frequency doubled the laser to improve temporal contrast and irradiated the spheres with 400 nm pulses at an intensity of 2 x 1017 W/cm2. Hard X-ray emission from the plasma was observed using filtered NaI scintillation detectors and K-alpha emission was measured with a Von Hamos spectrometer. We illuminated polystyrene spheres of diameters 0.1 -2.9 microns on a glass substrate, with the 400 nm 100fs pulse, and find that there is a clear Mie enhancement in the field and hot electron generation for a specific range of sphere sizes.

Ditmire, T.; Sumeruk, H. A.; Kneip, S.; Symes, D. R.; Churina, I. V.; Belolipetski, A. V.; Dyer, G.; Bernstein, A.; Donnelly, T. D.

2008-04-01

96

Simultaneous Cassini VIMS/UVIS and ground-based observations during the 2013 auroral campaign  

NASA Astrophysics Data System (ADS)

During April and May 2013 there was a large and unprecedented co-ordinated campaign of observations using observatoins of Saturn's aurora, using Cassini instruments, the Cassini spacecraft, the Hubble Space Telescope, Keck telescope, NASA IRTF and the Very Large Telescope. Here, we present the analysis of the Cassini VIMS and UVIS observations obtained during this period that were simultenous in space and time, enabling the study of the energy balance of the upper atmosphere of Saturn. We cross-correlate the properties of H3+ derived from Cassini VIMS observations to those derived using Keck NIRSPEC observations.

Melin, H.; Stallard, T. S.; Badman, S. V.; O'Donoghue, J.; Baines, K. H.; Pryor, W. R.; Blake, J. S. D.

2013-09-01

97

VIMS/Cassini mission at Titan: Scientific objectives and observational scenarios  

NASA Technical Reports Server (NTRS)

The scientific objectives and observational scenarios of the Cassini/Visual Infrared Mapping Spectrometer (VIMS) Mission at Titan are addressed. The VIMS represents a powerful and effective means to both investigate, in four dimensions (latitude, longitude, altitude, and time), Titan's atmospheric structure and to map the near infrared spectral character of Titan's surface. Its broad spectral coverage from 0.35 to 5.1 micrometers together with its significant spectral resolution allows it to determine minor constituent distributions and cloud optical/microphysical properties from the surface to several hundred km. A promising means of obtaining high vertical resolution stratospheric profiles of hydrocarbons, oxides, and hazes via stellar occultation observations is discussed.

Baines, Kevin H.; Brown, R. H.; Matson, Dennis L.; Nelson, R. M.; Buratti, B. J.; Bibring, J. P.; Langevin, Y.; Sotin, C.; Carusi, A.; Coradini, Angioletta

1992-01-01

98

Wavelength Calibration  

NASA Astrophysics Data System (ADS)

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

Kruk, Jeffrey

99

Cassini-VIMS Observations of Stellar Occultations by Saturn's Rings.  

NASA Astrophysics Data System (ADS)

On May 24 and June 11, 2005 the Cassini Visual and Infrared Mapping Spectrometer (VIMS) observed grazing occultations of the long-period variable star, o Ceti (spectral type M7 III, mK = -2.60). The first occultation track penetrated the rings to a minimum radius of 115,000 km, providing 2 complete profiles of the F and A rings as well as the Cassini Division, while the second track penetrated to a radius of 126,000 km, in the inner A ring. The sampling interval was 80 ms, but the radial resolution is limited by the projected stellar diameter which ranges from 0.25 -- 2.7 km, depending on ring longitude. Due to the very small ring inclination to the line of sight of 3.45o, the B ring and much of the A ring appear almost opaque, while extremely high S/N ratio lightcurves were obtained of low optical depth regions such as the F ring and Cassini Division. All four cuts across the eccentric F ring reveal a dense central strand of FWHM 25 -- 45 km flanked by inner and outer strands which are variable both in normal optical depth (0.005

Nicholson, P. D.; Hedman, M. M.; Wallis, B.; Cassini VIMS Team

2005-08-01

100

Audiovisual Aids and Publications Available from the VIMS/Sea Grant Marine Education Center.  

ERIC Educational Resources Information Center

This catalog contains an inventory of 16mm films, filmstrips, film loops, slide programs, records, and publications about the marine sciences and sea life that are available from VIMS/Sea Grant Marine Education Center; information on the borrowing of the AV materials is included, as well as prices for books and leaflets. The entries are listed…

Gammisch, Sue, Comp.

101

VIMS spectral mapping observations of Titan during the Cassini prime mission  

Microsoft Academic Search

This is a data paper designed to facilitate the use of and comparisons to Cassini\\/visual and infrared mapping spectrometer (VIMS) spectral mapping data of Saturn's moon Titan. We present thumbnail orthographic projections of flyby mosaics from each Titan encounter during the Cassini prime mission, 2004 July 1 through 2008 June 30. For each flyby we also describe the encounter geometry,

Jason W. Barnes; Jason M. Soderblom; Robert H. Brown; Bonnie J. Buratti; Christophe Sotin; Kevin H. Baines; Roger N. Clark; Ralf Jaumann; Thomas B. McCord; Robert Nelson; Stéphane Le Mouélic; Sebastien Rodriguez; Caitlin Griffith; Paulo Penteado; Federico Tosi; Karly M. Pitman; Laurence Soderblom; Katrin Stephan; Paul Hayne; Graham Vixie; Jean-Pierre Bibring; Giancarlo Bellucci; Fabrizio Capaccioni; Priscilla Cerroni; Angioletta Coradini; Dale P. Cruikshank; Pierre Drossart; Vittorio Formisano; Yves Langevin; Dennis L. Matson; Phillip D. Nicholson; Bruno Sicardy

2009-01-01

102

Audiovisual Aids and Publications Available from the VIMS/Sea Grant Marine Education Center.  

National Technical Information Service (NTIS)

This catalog contains an inventory of 16mm films, filmstrips, film loops, slide programs, records, and publications about the marine sciences and sea life that are available from VIMS/Sea Grant Marine Education Center; information on the borrowing of the ...

S. Gammisch

1977-01-01

103

High prevalence of VIM-4 and NDM-1 metallo-?-lactamase among carbapenem-resistant Enterobacteriaceae.  

PubMed

The purpose of this study was to identify the mechanisms leading to carbapenem resistance among multidrug-resistant Enterobacteriaceae isolates recovered from hospitalized patients with nosocomial infections in Mubarak Al Kabeer Hospital, Kuwait. Fourteen carbapenem-resistant Enterobacteriaceae isolates were obtained from inpatients in different wards and intensive care units between April 2009 and February 2011. Antibiotic susceptibilities were determined using the E-test method. Genes encoding ?-lactamases were characterized by specific PCR amplification, sequencing and conjugation assays. All isolates were identified as metallo-?-lactamase (MBL) producers using phenotypic and molecular methods. Eleven of the 14 isolates produced VIM-4 (six Klebsiella pneumoniae, three Escherichia coli, one Enterobacter cloacae and one Klebsiella oxytoca). Three K. pneumoniae isolates produced the MBL NDM-1 and co-produced the plasmid-encoded AmpC CMY-4. The VIM-4-producing isolates co-produced extended-spectrum ?-lactamases including CTX-M-15 and some SHV derivatives. The VIM-4 gene was not transferable by conjugation studies of six selected strains. We demonstrated here the emergence of VIM-4- and NDM-1-producing isolates in the largest teaching hospital in Kuwait. PMID:23639985

Jamal, Wafaa; Rotimi, Vincent O; Albert, M John; Khodakhast, Fatima; Nordmann, Patrice; Poirel, Laurent

2013-08-01

104

Role of vimA in cell surface biogenesis in Porphyromonas gingivalis  

PubMed Central

The Porphyromonas gingivalis vimA gene has been previously shown to play a significant role in the biogenesis of gingipains. Further, in P. gingivalis FLL92, a vimA-defective mutant, there was increased auto-aggregation, suggesting alteration in membrane surface proteins. In order to determine the role of the VimA protein in cell surface biogenesis, the surface morphology of P. gingivalis FLL92 was further characterized. Transmission electron microscopy demonstrated abundant fimbrial appendages and a less well defined and irregular capsule in FLL92 compared with the wild-type. In addition, atomic force microscopy showed that the wild-type had a smoother surface compared with FLL92. Western blot analysis using anti-FimA antibodies showed a 41?kDa immunoreactive protein band in P. gingivalis FLL92 which was missing in the wild-type P. gingivalis W83 strain. There was increased sensitivity to globomycin and vancomycin in FLL92 compared with the wild-type. Outer membrane fractions from FLL92 had a modified lectin-binding profile. Furthermore, in contrast with the wild-type strain, nine proteins were missing from the outer membrane fraction of FLL92, while 20 proteins present in that fraction from FLL92 were missing in the wild-type strain. Taken together, these results suggest that the VimA protein affects capsular synthesis and fimbrial phenotypic expression, and plays a role in the glycosylation and anchorage of several surface proteins.

Osbourne, Devon O.; Aruni, Wilson; Roy, Francis; Perry, Christopher; Sandberg, Lawrence; Muthiah, Arun; Fletcher, Hansel M.

2010-01-01

105

Emergence of VIM-2 metallo-beta-lactamase producing Ralstonia pickettii clinical isolate in India.  

PubMed

A multidrug-resistant clinical isolate of Ralstonia pickettii from a woman was analysed. Modified Hodge test was positive for carbapenemase production. Conjugation experiment revealed the presence of conjugative plasmid of >140 Kb size typed as IncN type. This is the first report of emergence blaVIM-2 in R. pickettii in India. PMID:24713914

Khajuria, A; Praharaj, A K; Grover, N; Kumar, M

2014-01-01

106

NASA Wavelength  

NSDL National Science Digital Library

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

2014-04-07

107

Aromatic and aliphatic organic materials on Iapetus: Analysis of Cassini VIMS data  

NASA Astrophysics Data System (ADS)

We present a quantitative analysis of the hydrocarbon and other organic molecular inventory as a component of the low-albedo material of Saturn’s satellite Iapetus, based on a revision of the calibration of the Cassini VIMS instrument. Our study uses hyperspectral data from a mosaic of Iapetus’ surface (Pinilla-Alonso, N., Roush, T.L., Marzo, G.A., Cruikshank, D.P., Dalle Ore, C.M. [2011]. Icarus 215, 75-82) constructed from VIMS data on a close fly-by of the satellite. We extracted 2235 individual spectra of the low-albedo regions, and with a clustering analysis tool (Dalle Ore, C.M., Cruikshank, D.P., Clark, R.N. [2012]. Icarus 221, 735-743), separated them into two spectrally distinct groups, one concentrated on the leading hemisphere of Iapetus, and the other group on the trailing. This distribution is broadly consistent with that found from Cassini ISS data analyzed by Denk et al. (Denk, T. et al. [2010]. Science 327, 435-439). We modeled the average spectra of the two geographic regions using the materials and techniques described by Clark et al. (Clark, R.N., Cruikshank, D.P., Jaumann, R., Brown, R.H., Stephan, K., Dalle Ore, C.M., Livio, K.E., Pearson, N., Curchin, J.M., Hoefen, T.M., Buratti, B.J., Filacchione, G., Baines, K.H., Nicholson, P.D. [2012]. Icarus 218, 831-860), and after dividing the Iapetus spectrum by the model for each case, we extracted the resulting spectra in the interval 2.7-4.0 ?m for analysis of the organic molecular bands. The spectra reveal the Csbnd H stretching modes of aromatic hydrocarbons at ?3.28 ?m (?3050 cm-1), plus four blended bands of aliphatic sbnd CH2sbnd and sbnd CH3 in the range ?3.36-3.52 ?m (?2980-2840 cm-1). In these data, the aromatic band, probably indicating the presence of polycyclic aromatic hydrocarbons (PAH), is unusually strong in comparison to the aliphatic bands, as was found for Hyperion (Dalton, J.B., Cruikshank, D.P., Clark, R.N. [2012]. Icarus 220, 752-776; Dalle Ore, C.M., Cruikshank, D.P., Clark, R.N. [2012], op. cit.) and Phoebe (Dalle Ore, C.M., Cruikshank, D.P., Clark, R.N. [2012], op. cit.). Our Gaussian decomposition of the organic band region suggests the presence of molecular bands in addition to those noted above, specifically bands attributable to cycloalkanes, olefinic compounds, CH3OH, and N-substituted PAHs, as well as possible Hn-PAHs (PAHs with excess peripheral H atoms). In a minimalist interpretation of the Gaussian band fitting, we find the ratio of aromatic CH to aliphatic CH2 + CH3 functional groups for both the leading and trailing hemispheres of Iapetus is ?10, with no clear difference between them. In the aliphatic component of the surface material, the ratio CH2/CH3 is 4.0 on the leading hemisphere and 3.0 on the trailing; both values are higher than those found in interstellar dust and other Solar System materials and the difference between the two hemispheres may be statistically significant. The superficial layer of low-albedo material on Iapetus originated in the interior of Phoebe and is being transported to and deposited on Iapetus (and Hyperion) in the current epoch via the Phoebe dust ring (Tosi, F., Turrini, D., Coradini, A., Filacchione, G., and the VIMS Team [2010]. Mon. Not. R. Astron. Soc. 403, 1113-1130; Tamayo, D., Burns, J.A., Hamilton, D.P., Hedman, M.M. [2011]. Icarus 215, 260-278). The PAHs on Iapetus exist in a H2O-rich environment, and consequently are subject to UV destruction by hydrogenation on short time-scales. The occurrence of this material is therefore consistent with the assertion that the deposition of the PAH-bearing dust is occurring at the present time. If the organic inventory we observe represents the interior composition of Phoebe, we may be sampling the original material from a region of the solar nebula beyond Neptune where Phoebe formed prior to its capture by Saturn (Johnson, T.V., Lunine, J.I. [2005]. Nature 435, 69-71).

Cruikshank, Dale P.; Dalle Ore, Cristina M.; Clark, Roger N.; Pendleton, Yvonne J.

2014-05-01

108

VIM-Based Dynamic Sparse Grid Approach to Partial Differential Equations.  

PubMed

Combining the variational iteration method (VIM) with the sparse grid theory, a dynamic sparse grid approach for nonlinear PDEs is proposed in this paper. In this method, a multilevel interpolation operator is constructed based on the sparse grids theory firstly. The operator is based on the linear combination of the basic functions and independent of them. Second, by means of the precise integration method (PIM), the VIM is developed to solve the nonlinear system of ODEs which is obtained from the discretization of the PDEs. In addition, a dynamic choice scheme on both of the inner and external grid points is proposed. It is different from the traditional interval wavelet collocation method in which the choice of both of the inner and external grid points is dynamic. The numerical experiments show that our method is better than the traditional wavelet collocation method, especially in solving the PDEs with the Nuemann boundary conditions. PMID:24723805

Mei, Shu-Li

2014-01-01

109

Looking at some equatorial regions on Titan using Cassini/VIMS and RADAR data: a case for changes in surface properties  

NASA Astrophysics Data System (ADS)

Titan, Saturn's largest moon, has a complex, dynamic and -in some aspects- Earth-like atmosphere and surface. Data from the remote sensing instruments on board Cassini, particularly VIMS and the RADAR, have shown the presence of diverse terrains on the surface, suggesting exogenic and endogenic processes [1;2;3]. In this research we focus on some equatorial regions that have been identified as possibly subject to changes, having particular spectral properties and possibly being the strongest cryovolcanic candidate regions, that is: Sotra Patera, Hotei Regio and Tui Regio [1,4,5]. We use VIMS data, to which we apply a state-of-the-art Principal Component Analysis (PCA) and radiative transfer methods [4;7] with updated parameterization for the spectroscopic data and infer the surface albedos of all of these regions, that we interpret in terms of possible surface composition and morphology combining with information from RADAR data. Indeed, by including despeckled SAR images we identify geomorphological units and investigate spatial and temporal geological relationships [6]. This combination provides us with implications on the surface composition of different units. By looking at evolution with time, we find that two of these regions show albedo changes with time, for Tui Regio from 2005-2009 (darkening) and Sotra Patera from 2005-2006 (brightening) at all wavelengths, indicating that dynamical processes control the regions, compatible with their complex morphology. In conclusion, we also associate radiometry and topographic data with the compositional information from VIMS to derive constraints on the chemical composition and the geology of the surface and finally the nature of these regions. References: [1] Lopes, R.M.C., et al.: JGR, 118, 416-435; [2] Solomonidou, A., et al.: PSS, 70, 77-104; [3] Moore, J.M., and Howard, A.D.: GRL, 37, L22205, 2010; [4] Solomonidou, A., et al.: submitted(a); [5] Solomonidou, A., et al.: submitted(b); [6] Bratsolis, E., et al.: PSS, 61, 108-113; [7] Hirtzig, M., et al.: Icarus, 226, 470-486.

Solomonidou, Anezina; Coustenis, Athena; Lopes, Rosaly; Hirtzig, Mathieu; Bratsolis, Emmanuel; Drossart, Pierre; Le Mouélic, Stephane; Rodriguez, Sebastien; Jaumann, Ralf; Stephan, Katrin; Bampasidis, Georgios; Sotin, Christophe; Brown, Robert

2014-05-01

110

Correlations between Cassini VIMS spectra and RADAR SAR images: Implications for Titan's surface composition and the character of the Huygens Probe Landing Site  

NASA Astrophysics Data System (ADS)

Titan's vast equatorial fields of RADAR-dark longitudinal dunes seen in Cassini RADAR synthetic aperture images correlate with one of two dark surface units discriminated as "brown" and "blue" in Visible and Infrared Mapping Spectrometer (VIMS) color composites of short-wavelength infrared spectral cubes (RGB as 2.0, 1.6, 1.3 ?m). In such composites bluer materials exhibit higher reflectance at 1.3 ?m and lower at 1.6 and 2.0 ?m. The dark brown unit is highly correlated with the RADAR-dark dunes. The dark brown unit shows less evidence of water ice suggesting that the saltating grains of the dunes are largely composed of hydrocarbons and/or nitriles. In general, the bright units also show less evidence of absorption due to water ice and are inferred to consist of deposits of bright fine precipitating tholin aerosol dust. Some set of chemical/mechanical processes may be converting the bright fine-grained aerosol deposits into the dark saltating hydrocarbon and/or nitrile grains. Alternatively the dark dune materials may be derived from a different type of air aerosol photochemical product than are the bright materials. In our model, both the bright aerosol and dark hydrocarbon dune deposits mantle the VIMS dark blue water ice-rich substrate. We postulate that the bright mantles are effectively invisible (transparent) in RADAR synthetic aperture radar (SAR) images leading to lack of correlation in the RADAR images with optically bright mantling units. RADAR images mostly show only dark dunes and the water ice substrate that varies in roughness, fracturing, and porosity. If the rate of deposition of bright aerosol is 0.001-0.01 ?m/yr, the surface would be coated (to optical instruments) in hundreds-to-thousands of years unless cleansing processes are active. The dark dunes must be mobile on this very short timescale to prevent the accumulation of bright coatings. Huygens landed in a region of the VIMS bright and dark blue materials and about 30 km south of the nearest occurrence of dunes visible in the RADAR SAR images. Fluvial/pluvial processes, every few centuries or millennia, must be cleansing the dark floors of the incised channels and scouring the dark plains at the Huygens landing site both imaged by Descent Imager/Spectral Radiometer (DISR).

Soderblom, Laurence A.; Kirk, Randolph L.; Lunine, Jonathan I.; Anderson, Jeffrey A.; Baines, Kevin H.; Barnes, Jason W.; Barrett, Janet M.; Brown, Robert H.; Buratti, Bonnie J.; Clark, Roger N.; Cruikshank, Dale P.; Elachi, Charles; Janssen, Michael A.; Jaumann, Ralf; Karkoschka, Erich; Mouélic, Stéphane Le; Lopes, Rosaly M.; Lorenz, Ralph D.; McCord, Thomas B.; Nicholson, Philip D.; Radebaugh, Jani; Rizk, Bashar; Sotin, Christophe; Stofan, Ellen R.; Sucharski, Tracie L.; Tomasko, Martin G.; Wall, Stephen D.

2007-11-01

111

Saturn's icy satellites investigated by Cassini-VIMS. I. Full-disk properties: 350-5100 nm reflectance spectra and phase curves  

USGS Publications Warehouse

Saturn's icy satellites are among the main scientific objectives of the Cassini-VIMS (Visual and Infrared Mapping Spectrometer) experiment. This paper contains a first systematic and comparative analysis of the full-disk spectral properties of Dione, Enceladus, Epimetheus, Hyperion, Iapetus, Mimas, Phoebe, Rhea and Tethys as observed by VIMS from July 2004 to June 2005. The disk integrated properties (350-5100 nm reflectance spectra and phase curves at 550-2232 nm) and images of satellites are reported and discussed in detail together with the observed geometry. In general, the spectra in the visible spectral range are almost featureless and can be classified according to the spectral slopes: from the bluish Enceladus and Phoebe to the redder Iapetus, Hyperion and Epimetheus. In the 1000-1300 nm range the spectra of Enceladus, Tethys, Mimas and Rhea are characterized by a negative slope, consistent with a surface largely dominated by water ice, while the spectra of Iapetus, Hyperion and Phoebe show a considerable reddening pointing out the relevant role played by darkening materials present on the surface. In between these two classes are Dione and Epimetheus, which have a flat spectrum in this range. The main absorption bands identified in the infrared are the 1520, 2020, 3000 nm H2O/OH bands (for all satellites), although Iapetus dark terrains show mostly a deep 3000 nm band while the 1520 and 2020 nm bands are very faint. In this spectral range, the Iapetus spectrum is characterized by a strong reddening. The CO2 band at 4260 nm and the Fresnel ice peak around 3100 nm are evident only on Hyperion, Phoebe and Iapetus. The phase curves at 550 and at 2232 nm are reported for all the available observations in the 0??-144?? range; Rhea shows an opposition surge at visible wavelengths in the 0.5??-1.17?? interval. The improvement on the retrieval of the full-disk reflectance spectra can be appreciated by a direct comparison with ground-based telescopic data available from literature. Finally, data processing strategies and recent upgrades introduced in the VIMS-V calibration pipeline (flat-field and destriping-despiking algorithm) are discussed in appendices. ?? 2006 Elsevier Inc. All rights reserved.

Filacchione, G.; Capaccioni, F.; McCord, T. B.; Coradini, A.; Cerroni, P.; Bellucci, G.; Tosi, F.; D'Aversa, E.; Formisano, V.; Brown, R. H.; Baines, K. H.; Bibring, J. P.; Buratti, B. J.; Clark, R. N.; Combes, M.; Cruikshank, D. P.; Drossart, P.; Jaumann, R.; Langevin, Y.; Matson, D. L.; Mennella, V.; Nelson, R. M.; Nicholson, P. D.; Sicardy, B.; Sotin, C.; Hansen, G.; Hibbitts, K.; Showalter, M.; Newman, S.

2007-01-01

112

Correlations between Cassini VIMS spectra and RADAR SAR images: Implications for Titan's surface composition and the character of the Huygens Probe Landing Site  

USGS Publications Warehouse

Titan's vast equatorial fields of RADAR-dark longitudinal dunes seen in Cassini RADAR synthetic aperture images correlate with one of two dark surface units discriminated as "brown" and "blue" in Visible and Infrared Mapping Spectrometer (VIMS) color composites of short-wavelength infrared spectral cubes (RGB as 2.0, 1.6, 1.3 ??m). In such composites bluer materials exhibit higher reflectance at 1.3 ??m and lower at 1.6 and 2.0 ??m. The dark brown unit is highly correlated with the RADAR-dark dunes. The dark brown unit shows less evidence of water ice suggesting that the saltating grains of the dunes are largely composed of hydrocarbons and/or nitriles. In general, the bright units also show less evidence of absorption due to water ice and are inferred to consist of deposits of bright fine precipitating tholin aerosol dust. Some set of chemical/mechanical processes may be converting the bright fine-grained aerosol deposits into the dark saltating hydrocarbon and/or nitrile grains. Alternatively the dark dune materials may be derived from a different type of air aerosol photochemical product than are the bright materials. In our model, both the bright aerosol and dark hydrocarbon dune deposits mantle the VIMS dark blue water ice-rich substrate. We postulate that the bright mantles are effectively invisible (transparent) in RADAR synthetic aperture radar (SAR) images leading to lack of correlation in the RADAR images with optically bright mantling units. RADAR images mostly show only dark dunes and the water ice substrate that varies in roughness, fracturing, and porosity. If the rate of deposition of bright aerosol is 0.001-0.01 ??m/yr, the surface would be coated (to optical instruments) in hundreds-to-thousands of years unless cleansing processes are active. The dark dunes must be mobile on this very short timescale to prevent the accumulation of bright coatings. Huygens landed in a region of the VIMS bright and dark blue materials and about 30 km south of the nearest occurrence of dunes visible in the RADAR SAR images. Fluvial/pluvial processes, every few centuries or millennia, must be cleansing the dark floors of the incised channels and scouring the dark plains at the Huygens landing site both imaged by Descent Imager/Spectral Radiometer (DISR). ?? 2007 Elsevier Ltd. All rights reserved.

Soderblom, L. A.; Kirk, R. L.; Lunine, J. I.; Anderson, J. A.; Baines, K. H.; Barnes, J. W.; Barrett, J. M.; Brown, R. H.; Buratti, B. J.; Clark, R. N.; Cruikshank, D. P.; Elachi, C.; Janssen, M. A.; Jaumann, R.; Karkoschka, E.; Mouelic, S. L.; Lopes, R. M.; Lorenz, R. D.; McCord, T. B.; Nicholson, P. D.; Radebaugh, J.; Rizk, B.; Sotin, C.; Stofan, E. R.; Sucharski, T. L.; Tomasko, M. G.; Wall, S. D.

2007-01-01

113

Control of single-master multi-slave manipulator system using VIM  

Microsoft Academic Search

A single-master, multiple-slave manipulator system and its task-oriented control using VIM (virtual internal model) are proposed. By using this system, the operator no longer has to consider how to control the slave arms in coordination, so the operator can concentrate on his\\/her task during the operation. An experimental single-master, multislave manipulator system with two slave arms, each of which has

K. Kosuge; J. Ishikawa; K. Furuta; M. Sakai

1990-01-01

114

First nosocomial outbreak of VIM-16-producing Serratia marcescens in Argentina.  

PubMed

Seven metallo-?-lactamase-positive isolates of Serratia marcescens were recovered from three patients hospitalized in a neonatal ward in an Argentinean hospital during the period July-September 2011. All the isolates were multidrug-resistant, they belonged to a single clone, and carried a blaVIM-16 -containing class I integron structure. This represents the first nosocomial outbreak of metallo-?-lactamase in Enterobacteriaceae in Argentina. PMID:22862810

Nastro, M; Monge, R; Zintgraff, J; Vaulet, L G; Boutureira, M; Famiglietti, A; Rodriguez, C H

2013-07-01

115

Sources of diversity of carbapenem resistance levels in Klebsiella pneumoniae carrying blaVIM-1  

Microsoft Academic Search

Objectives: To elucidate the mechanisms responsible for the diversity of b-lactam resistance phenotypes among isolates of a VIM-1-producing Klebsiella pneumoniae (VPKP) strain that is endemic in Greek hospitals. Methods: Five VPKP clinical isolates were studied. MICs of b-lactams were determined by agar dilution. PFGE of XbaI-digested genomic DNA was used for typing. Profiles of outer membrane proteins (OMPs) were determined

A. Loli; L. S. Tzouvelekis; E. Tzelepi; A. Carattoli; A. C. Vatopoulos; P. T. Tassios; V. Miriagou

2006-01-01

116

Titan solar occultation observed by Cassini/VIMS: Gas absorption and constraints on aerosol composition  

NASA Astrophysics Data System (ADS)

A solar occultation by Titan's atmosphere has been observed through the solar port of the Cassini/VIMS instrument on January 15th, 2006. Transmission spectra acquired during solar egress probe the atmosphere in the altitude range 70 to 900 km at the latitude of 71° S. Several molecular absorption bands of CH 4 and CO are visible in these data. A line-by-line radiative transfer calculation in spherical geometry is used to model three methane bands (1.7, 2.3, 3.3 ?m) and the CO 4.7 ?m band. Above 200 km, the methane 2.3 ?m band is well fit with constant mixing ratio between 1.4 and 1.7%, in agreement with in situ and other Cassini measurements. Under 200 km, there are discrepancies between models and observations that are yet fully understood. Under 480 km, the 3.3 ?m CH 4 band is mixed with a large and deep additional absorption. It corresponds to the C-H stretching mode of aliphatic hydrocarbon chains attached to large organic molecules. The CO 4.7 ?m band is observed in the lower stratosphere (altitudes below 150 km) and is well fit with a model with constant mixing ratio of 33±10 ppm. The continuum level of the observed transmission spectra provides new constraints on the aerosol content of the atmosphere. A model using fractal aggregates and optical properties of tholins produced by Khare et al. [Khare, B.N., Sagan, C., Arakawa, E.T., Suits, F., Callcott, T.A., Williams, M.W., 1984. Icarus 60, 127-137] is developed. Fractal aggregates with more than 1000 spheres of radius 0.05 ?m are needed to fit the data. Clear differences in the chemical composition are revealed between tholins and actual haze particles. Extinction and density profiles are also retrieved using an inversion of the continuum values. An exponential increase of the haze number density is observed under 420 km with a typical scale height of 60 km.

Bellucci, A.; Sicardy, B.; Drossart, P.; Rannou, P.; Nicholson, P. D.; Hedman, M.; Baines, K. H.; Burrati, B.

2009-05-01

117

COS Internal NUV Wavelength Verification  

NASA Astrophysics Data System (ADS)

This program will be executed after the uplink of the OSM1 position updates derived from the determination of the wavelength-scale zero points and desired spectral ranges for each grating in activity COS14 {program 11474 - COS NUV Internal/External Wavelength Scales}. This program will verify that the operational spectral ranges for each grating, central wavelength, and FP-POS are those desired. Subsequent to a successful verification, COS NUV ERO observations and NUV science can be enabled. An internal wavelength calibration spectrum using the default PtNe lamp {lamp 1} with each NUV grating at each central wavelength setting and each FP-POS position will be obtained for the verification. Additional exposures and waits between certain exposures will be required to avoid - and to evaluate - mechanism drifts.;

Keyes, Charles

2008-07-01

118

High resolution VIMS images of Titan's surface: implications for its composition, internal structure and dynamics  

NASA Astrophysics Data System (ADS)

With a field of view of 0.5 mrad per pixel, the VIMS (Visual and Infrared Mapping Spectrometer) onboard the Cassini spacecraft can acquire images with a resolution of 500 m per pixel at closest approach during a typical Titan flyby. This resolution is comparable to the resolution of the radar instrument and allows comparisons between the radar images and optical images in the six infrared windows where the surface can be observed. Such opportunities were not set up for the nominal tour before Saturn insertion. The opportunity was offered during the TA flyby [Sotin et al., Nature, 2005] and the results lead the Cassini program to give VIMS the prime observations during closest approach at the T24 and T38 flybys. Two different implementations were experienced. During the T24 flyby (01/29/2007), we used a push-broom mode allowing VIMS to image a long path before pointing to a specific site at the limit between the light and dark terrains. This observation allowed us to see the dunes and to infer some information on their composition [Barnes et al., Icarus, 2008], to image channels and to infer information of erosion processes of the bright equatorial regions [Jaumann et al., Icarus, in press] and to observe the strong correlation between radar images and the VIMS images over a bright area interpreted as a flow feature [Lopes et al., Icarus, 2007]. During the T38 flyby over Ontario Lacus (12/05/2007), it was decided to point to the lake and get different images which provide us with a set of observations obtained with different emergence angles. This observation allowed us to infer the liquid nature of the lake and the composition of the lake [Brown et al., Nature, 2008]. In addition, this mode gives good information on the atmospheric component and will help us remove that component to get better spectra of Titan's surface. During the extended mission, two observations are forecasted at the beginning and at the end of the Cassini Equinox Mission. The first one will happen on November 19, 2008. The VIMS has been programmed to observe the Huygens landing site area at a resolution of 1 km/pixel. Before and after this observation, the push-broom mode will be used in order to cross-cut some of the radar paths. Because Titan's spin rate may be different from synchronous [Stiles et al., 2007; Lorenz et al., 2008], there is some uncertainty on the pointing. This study will report on the results of this flyby. This work has been carried out at the JPL, Caltech, under contract with NASA.

Sotin, C.; Le Mouelic, S.; Le Corre, L.; Barnes, J.; Brown, R. H.; Jaumann, R.; Buratti, B.; Baines, K.; Clark, R.; Nicholson, P.; Soderblom, L.

2008-12-01

119

Opposition Surges on Icy Moons: Observations by Cassini VIMS and ISS between 0.2 and five microns  

NASA Astrophysics Data System (ADS)

The opposition effect is the surge in brightness that most airless bodies exhibit as they become fully illuminated to an observer. Important information about the physical nature of the surface, including the constituent particle sizes and their size distribution, the compaction state of the upper regolith, and composition are embedded in the effect. Models that describe the surge in terms of physical parameters have been developed during recent decades. The acquisition of "true opposition" is rare and fleeting (and for objects in inclined orbits, nearly unattainable), so testing and application of the models has been hampered. During the 9 years of the Cassini-Huygens mission, a wealth of data at and near opposition has been collected for the 6 main icy satellites of Saturn: Mimas, Enceladus, Tethys, Dione, Rhea, and Iapetus, including some recently obtained key data for Enceladus and Mimas. Furthermore, the combined spectral range of the Imaging Science Subsystem (ISS) and Visible Infrared Mapping Spectrometer (VIMS) cameras spans 0.20-5.1 microns, which includes many spectral regions not observable from the ground. This extraordinary coverage in solar phase angle and in spectral range provides in essence a laboratory in which to test models of the opposition effect. Although these moons are bright in the visible region, where multiple scattering complicates the modeling, they are dark in many regions of the infrared, enabling a more robust analysis. Some satellites have data for both leading and trailing sides, allowing an investigation of alteration effects such as meteoritic and magnetospheric bombardment and accretion of E-ring particles. Small particles accreted onto their surfaces from the E-ring appear to become "invisible" at the longer wavelengths. All of the moons exhibit a very steep curve at solar phase angles less than one degree, suggesting that coherent backscatter is present. However, this "supersurge" is present even at wavelengths where there is little multiple scattering: since coherent backscatter is a phenomenon that depends on multiple scattering, it does not fully explain the small-angle surge. One of our most significant findings is that the wavelength dependence of the width and amplitude of the opposition surge does not follow a trend that clearly applies to every moon. Funded by NASA.

Buratti, Bonnie; Dalba, Paul; Brown, Robert; Clark, Roger; Hillier, John; Mosher, Joel; Baines, Kevin; Nicholson, Phillip

2013-04-01

120

The Structure of Saturn's Poles Determined by Cassini VIMS: Constraints on Winds and Horizontal and Vertical Cloud Distributions.  

NASA Astrophysics Data System (ADS)

We present new imagery and quantitative results for wind and cloud structures in both polar regions of Saturn, obtained by Cassini/VIMS. For the north pole, currently experiencing winter darkness, only 5-?m thermal images of Saturn's depths near the 3-bar level are useful. Saturn's northern Polar Hexagon, discovered in Voyager imagery by Godfrey (Icarus 76, 335-356, 1988), is a prominent feature, extending downward at least several bars of pressure. The re-acquisition of this feature indicates that the hexagon is a multi-decade, long-lived feature which survives the Saturn seasons. Observed three times over a 12-day period in late 2006, both hexagonal features stay fixed in a rotational system defined by the Voyager-era radio rotation rate (Desch and Kaiser, Geophys. Res. Lett, 8, 253-256, 1981) to within an accuracy of 11 seconds per rotational period. This agrees with the stationary nature of the wave in this rotation system found by Godfrey (1988), but is inconsistent with rotation rates found during the current Cassini era. Individual clouds, observed as dark silhouettes, are seen racing around the edges of the 5-?m-bright hexagon at speeds of 100 m/s. At the south pole, a hurricane-like vortex feature is observed with a deep "eye” of cloud-free skies extending about 1 bar deeper than the surrounding ring of clouds. Discrete clouds at 88 degrees S. planetographic latitude whip around the pole at speeds approaching 200 m/s. In contrast, clouds near 77 degrees S. latitude are nearly stationary. Two distinct types of reflective, discrete clouds are observed interspersed throughout the region: bright clouds at continuum wavelengths from 0.6 to 2.7 ?m characterized in our preliminary modeling as having imaginary indices of refraction near 0.002 at 0.7 ?m, and spectrally dark clouds with twice that value, indicating different chemical compositions for the two types of cloud particles.

Baines, Kevin H.; Momary, T. W.; Temma, T.; Buratti, B. J.; Roos-Serote, M.; Showman, A.; Brown, R. H.; Clark, R. N.; Nicholson, P. D.; Atreya, S. K.; Graham, J.; Marquez, E.; Cassini/VIMS Science Team

2007-10-01

121

Polar views of Saturn's deep atmosphere from Cassini/VIMS: New insights into waves, storms, and global circulation  

NASA Astrophysics Data System (ADS)

We present recently-acquired imagery of cloud and wave systems spanning the depths of Saturn down to the 3-bar level in the polar regions of Saturn, obtained by the Visual Infrared Mapping Spectrometer (VIMS) onboard the Cassini/Huygens orbiter. Images taken in both reflected sunlight and in Saturn's thermal glow at 5 microns wavelengths, will be presented. The 5-micron images reveal thick clouds at depth, seen silhouetted against the upwelling radiation. In the south polar region, a significant fraction of these deep discrete clouds appear surprisingly dark in reflected sunlight, indicating a nearly wavelength-independent dark absorber spanning the 0.5-3 micron region exists in or above these clouds. These compositionally-different cloud regions then may indicate that unusually strong vertical upwelling occurs at discrete locations near the south pole. In the north polar region, Saturn's Polar Hexagon, discovered in Voyager imagery by Godfrey (Icarus 76, 335-356, 1988), is a prominent feature at 5 microns, indicating that the feature is comprised of relatively large particles (> 1 micron) and extends at least several bars of pressure down into the atmosphere. The re-acquisition of this feature near 77.5 degrees planetocentric latitude indicates that the hexagon is a multi-decade, long-lived feature which survives the Saturn seasons. A second hexagon, significantly darker at 5 micron than the brighter historical feature, is located near 74.2 degrees planetocentric latitude. The clouds in the 5-micron-bright hexagon are relatively deep: 3.5 bars compared to the 2.5-3.0-bar level of clouds in the dark hexagon. Observed three times over a 12-day period between October 29 and November 10, 2006, both hexagonal features stay fixed in a rotational system defined by the Voyager-era radio rotation rate (Desch and Kaiser, Geophys. Res. Lett, 8, 253- 256, 1981) to within an accuracy of 11 seconds per rotational period. This agrees with the stationary nature of the wave in this rotation system found by Godfrey (1988), but is inconsistent with more recent Saturn rotation rates found during the current Cassini era. Together with our new constraints on the depth of the feature, this result indicates that the feature is not linked to Saturn's radio emissions nor to auroral activity as speculated by Godfrey. (1988). New dynamical modeling indicates that the feature can be adequately explained as a stationary planetary Rossby wave, as proposed by Allison (Science 247, 1061-1063,1990). Images and movies of these and other discrete features - including the north polar aurarae - will be shown and discussed.

Baines, K.; Momary, T.; Temma, T.; Roos-Serote, M.; Showman, A.; Morales-Juberias, R.; Dowling, T.; Atreya, S.; Brown, R. H.; Buratti, B. J.; Clark, R. N.; Nicholson, P. D.

2007-08-01

122

Cassini/VIMS Discovery of Organic Evaporite Deposits in Titan's Dry Lakebeds  

NASA Astrophysics Data System (ADS)

Near-infrared spectral mapping of Titan's north polar lake district from the Cassini Visual and Infrared Mapping Spectrometer (VIMS) during the T69 flyby (2010 June 5) shows numerous, isolated ice-free spectral units. Comparison of the spectral map to RADAR data reveals that many of these units sit at the bottom of empty lakes as identified by the RADAR team. Because not all lakes show the spectral signature, and because nearby terrains and channel beds do not show it either, we interpret these deposits to be evaporites. On Titan, these would form by dissolution of haze or surface material by liquid methane, which then flows into seas and precipitates the solutes out as the methane evaporates. Most of the available soluble chemicals in Titan's environment are organic, thus we expect that the composition of the evaporites is organic as well, though we are as yet unable to make a positive chemical identification. The presence of evaporitic deposits on Titan signifies a critical role for the methanological cycle in transporting and concentrating organic compounds, constrains the formation of Titan's lakes, and suggests that other areas with similar spectral character (Tui and Hotei Regios) could plausibly represent lakebeds as well. This is a combined RADAR and VIMS view of the area south of Ligeia Mare on Titan that is to be the subject of the talk. Here in HSV color space VIMS has been assigned hue and saturation, and RADAR is the value. The evaporitic areas appear orange in this view, and many (but not all ) correspond to steep-walled empty lakes as seen by RADAR.

Barnes, J. W.; Bow, J.; Schwartz, J.; Brown, R. H.; Soderblom, J. M.; Hayes, A. G.; Le Mouélic, S.; Rodriguez, S.; Sotin, C.; Jaumann, R.; Stephan, K.; Soderblom, L. A.; Clark, R. N.; Buratti, B. J.; Baines, K. H.; Nicholson, P. D.

2010-12-01

123

Activity of imipenem against VIM-1 metallo-beta-lactamase-producing Klebsiella pneumoniae in the murine thigh infection model.  

PubMed

The in-vivo activity of imipenem against VIM-1-producing Klebsiella pneumoniae (VPKP) was assessed in a thigh infection model in neutropenic mice. Animals were infected with three VPKP isolates (imipenem MICs 2, 4 and 32 mg/L, respectively) and a susceptible clinical isolate (MIC 0.125 mg/L) that did not produce any beta-lactamase with broad-spectrum activity. Bacterial density at the site of infection was determined after imipenem treatment (30 and 60 mg/kg every 2 h for 24 h). The log(10) reduction in CFU/thigh was greatest for the wild-type isolate, intermediate for the two imipenem-susceptible VPKP isolates, and lowest for the imipenem-resistant VPKP isolate. Whilst in-vivo imipenem activity appeared reduced against in-vitro susceptible VIM-1 producers compared with a VIM-1-negative control, an increased drug dosage could moderate this reduction. PMID:17328735

Daikos, G L; Panagiotakopoulou, A; Tzelepi, E; Loli, A; Tzouvelekis, L S; Miriagou, V

2007-02-01

124

Evaluation of Etest MBL for Detection of blaIMP-1 and blaVIM-2 Allele-Positive Clinical Isolates of Pseudomonas spp. and Acinetobacter spp.  

PubMed Central

The Etest MBL (AB BIODISK, Solna, Sweden) correctly differentiated all 57 isolates of Acinetobacter spp. and Pseudomonas aeruginosa with the blaIMP-1 allele and 135 of 137 (98.5%) Acinetobacter spp. and Pseudomonas spp. isolates with the blaVIM-2 allele. The Etest MBL was reliable for detecting the IMP-1- and VIM-2-producing Pseudomonas and Acinetobacter isolates.

Lee, Kyungwon; Yong, Dongeun; Yum, Jong Hwa; Lim, Yong Sik; Bolmstrom, Anne; Qwarnstrom, Anette; Karlsson, Asa; Chong, Yunsop

2005-01-01

125

Spectroscopic identification and comparison of Dione's and Rhea's terrain based on Cassini VIMS data  

NASA Astrophysics Data System (ADS)

Saturn's icy satellites were observed several times by the Cassini spacecraft in its nominal and extended mission from 2004 to 2010. We selected 133 Cassini/VIMS (Visual and Infrared Mapping Spectrometer) hyperspectral cubes of Dione and 68 of Rhea in the IR range between 0.85 and 5.1 ?m and we applied Spectral Angle Mapper (SAM) clustering technique to classify different surface units on the basis of their spectral properties. We were able to identify nine and twelve different terrain types for Dione and Rhea respectively, correlated to specific surface morphologies.

Scipioni, F.; Tosi, F.; Capaccioni, F.; Cerroni, P.; Stephan, K.; Filacchione, G.

2012-09-01

126

Multiemission wavelength picosecond time-resolved fluorescence decay data obtained on the millisecond time scale: application to protein--DNA interactions and protein-folding reactions  

Microsoft Academic Search

One of the major aspects of fluorescence spectroscopy which differentiates this technique from many other spectroscopic approaches is the inherent multidimensional nature of the data. For instance, the basic pulsed-laser fluorescence data set is characterized by fluorescence versus: emission wavelength, polarization state (parallel and perpendicular intensities), time of emission (picoseconds to nanoseconds), and time of biological reaction (milliseconds to minutes).

Joseph M. Beechem

1992-01-01

127

Pterin pigment granules are responsible for both broadband light scattering and wavelength selective absorption in the wing scales of pierid butterflies  

Microsoft Academic Search

A small but growing literature indicates that many animal colours are produced by combinations of structural and pigmentary mechanisms. We investigated one such complex colour phenotype: the highly chromatic wing colours of pierid butterflies including oranges, yellows and patterns which appear white to the human eye, but strongly absorb the ultraviolet (UV) wavelengths visible to butterflies. Pierids produce thesebrightcoloursusingwingscalesthatcontaincollectionsofminutegranules.However,todate,nowork has

Nathan I. Morehouse; Peter Vukusic; Ron Rutowski

2007-01-01

128

Aerosol optical depth assimilation for a size-resolved sectional model: impacts of observationally constrained, multi-wavelength and fine mode retrievals on regional scale forecasts  

NASA Astrophysics Data System (ADS)

An aerosol optical depth (AOD) three-dimensional variational data assimilation technique is developed for the Gridpoint Statistical Interpolation (GSI) system when WRF-Chem forecasts are performed with a detailed sectional model (MOSAIC). Within GSI, forward AOD and adjoint sensitivities are performed using Mie computations from the WRF-Chem optical properties module providing consistency with the forecast. GSI tools such as recursive filters and weak constraints are used to provide correlation within aerosol size bins and upper and lower bounds for the optimization. The system is used to perform assimilation experiments with fine vertical structure and no data thinning or re-gridding on a 12 km horizontal grid over the region of California, USA. A first set of simulations is performed comparing the assimilation impacts of operational MODIS dark target retrievals to observationally constrained ones (i.e. calibrated with AERONET data), the latter ones showing higher error reductions and increased fraction of improved PM2.5 and AOD ground-based monitors. A second set of experiments reveals that the use of fine mode fraction AOD and ocean multi-wavelength retrievals can improve the representation of the aerosol size distribution, while assimilating only 550 nm AOD retrievals produces no or at times degraded impact. While assimilation of multi-wavelength AOD shows positive impacts on all analyses performed, future work is needed to generate observationally constrained multi-wavelength retrievals, which when assimilated will generate size distributions more consistent with AERONET data and will provide better aerosol estimates.

Saide, P. E.; Carmichael, G. R.; Liu, Z.; Schwartz, C. S.; Lin, H. C.; da Silva, A. M.; Hyer, E.

2013-05-01

129

First report of an extensively drug-resistant VIM-2 metallo-?-lactamase-producing Brevundimonas diminuta clinical isolate.  

PubMed

In the literature, only three Brevundimonas diminuta environmental isolates carrying metallo-?-lactamase genes were recently published. However, so far, no B. diminuta clinical isolates carrying these carbapenem resistance genes have been described. Here we report the first VIM-2 metallo-?-lactamase-producing B. diminuta clinical isolate obtained from an immunocompromised patient. PMID:22692741

Almuzara, Marisa N; Barberis, Claudia M; Rodríguez, Carlos H; Famiglietti, Angela M R; Ramirez, Maria S; Vay, Carlos A

2012-08-01

130

Geology of Titan from Cassini/VIMS images at T20 and T24  

NASA Astrophysics Data System (ADS)

The Visual and Infrared Mapping Spectrometer (VIMS) allows us to construct maps of Titan revealing the morphology of surface features and their spectral characteristics within 7 infrared windows. It acquires 64*64 pixels images in 352 spectral channels from 0.3 to 5 ?m. The best spatial resolution was obtained during the T20 flyby (25 October 2006), reaching up to 500m/pixel during the closest approach phase. This resolution is similar to the one we have for the images acquired in SAR mode by the RADAR instrument. Several units have been recognized in T20 and T24 flybys using false color composite images of band ratios, namely, dark terrains with longitudinal dunes, bright regions cut by dark channels, very bright terrains at 5 microns, and "blue" terrains likely to be enriched in water ice content. We look in particular at the correlation between VIMS images and radar SAR passes. The former is mainly sensitive to the first tens of micrometers of Titan's surface. The latter provides complementary information about topography and roughness of surface and subsurface, with a penetration depth of several centimeters. A possible cryovolcanic flow-like feature located near Menrva crater can be identified in T3 radar swath: bright materials seem to flow out from a circular feature with bright rims. Moreover, it is striking to see that in infrared sharp boundaries of a bright flow are found at the same location than the rough material (bright in radar). This kind of correlation between VIMS and radar images can be also noted for T24 images on a large bright area, but it is not systematic. Thereby, both correlations and lack of correlations between bright and dark areas can be found in the T20 data set. One of the best example found so far is the match between the dunes observed by both data sets. Bright regions in infrared appear to be covered by sinuous dark channels related to methane rainfalls and may be filled with organic material, reminding those observed by DISR. Finally, we will also present the T34 flyby which will be achieved by the end of July 2007, unveiling new terrains from Senkio, Belet, to Adiri, ending at Huygens landing site.

Le Corre, L.; Le Mouélic, S.; Sotin, C.; Brown, R. H.; Barnes, J.; Buratti, B.; Soderblom, L. A.; Jaumann, R.; Baines, K. H.; Clark, R.

2007-08-01

131

Saturn's icy satellites investigated by Cassini-VIMS. II. Results at the end of nominal mission  

USGS Publications Warehouse

We report the detailed analysis of the spectrophotometric properties of Saturn's icy satellites as derived by full-disk observations obtained by visual and infrared mapping spectrometer (VIMS) experiment aboard Cassini. In this paper, we have extended the coverage until the end of the Cassini's nominal mission (June 1st 2008), while a previous paper (Filacchione, G., and 28 colleagues [2007]. Icarus 186, 259-290, hereby referred to as Paper I) reported the preliminary results of this study. During the four years of nominal mission, VIMS has observed the entire population of Saturn's icy satellites allowing us to make a comparative analysis of the VIS-NIR spectral properties of the major satellites (Mimas, Enceladus, Tethys, Dione, Rhea, Hyperion, Iapetus) and irregular moons (Atlas, Prometheus, Pandora, Janus, Epimetheus, Telesto, Calypso, Phoebe). The results we discuss here are derived from the entire dataset available at June 2008 which consists of 1417 full-disk observations acquired from a variety of distances and inclinations from the equatorial plane, with different phase angles and hemispheric coverage. The most important spectrophotometric indicators (as defined in Paper I: I/F continua at 0.55 ??m, 1.822 ??m and 3.547 ??m, visible spectral slopes, water and carbon dioxide bands depths and positions) are calculated for each observation in order to investigate the disk-integrated composition of the satellites, the distribution of water ice respect to "contaminants" abundances and typical regolith grain properties. These quantities vary from the almost pure water ice surfaces of Enceladus and Calypso to the organic and carbon dioxide rich Hyperion, Iapetus and Phoebe. Janus visible colors are intermediate between these two classes having a slightly positive spectral slope. These results could help to decipher the origins and evolutionary history of the minor moons of the Saturn's system. We introduce a polar representation of the spectrophotometric parameters as function of the solar phase angle (along radial distance) and of the effective longitude interval illuminated by the Sun and covered by VIMS during the observation (in azimuth) to better investigate the spatial distribution of the spectrophotometric quantities across the regular satellites hemispheres. Finally, we report the observed spectral positions of the 4.26 ??m band of the carbon dioxide present in the surface material of three outermost moons Hyperion, Iapetus and Phoebe. ?? 2009 Elsevier Inc.

Filacchione, G.; Capaccioni, F.; Clark, R. N.; Cuzzi, J. N.; Cruikshank, D. P.; Coradini, A.; Cerroni, P.; Nicholson, P. D.; McCord, T. B.; Brown, R. H.; Buratti, B. J.; Tosi, F.; Nelson, R. M.; Jaumann, R.; Stephan, K.

2010-01-01

132

Aerosol optical depth assimilation for a size-resolved sectional model: impacts of observationally constrained, multi-wavelength and fine mode retrievals on regional scale analyses and forecasts  

NASA Astrophysics Data System (ADS)

An aerosol optical depth (AOD) three-dimensional variational data assimilation technique is developed for the Gridpoint Statistical Interpolation (GSI) system for which WRF-Chem forecasts are performed with a detailed sectional model, the Model for Simulating Aerosol Interactions and Chemistry (MOSAIC). Within GSI, forward AOD and adjoint sensitivities are performed using Mie computations from the WRF-Chem optical properties module, providing consistency with the forecast. GSI tools such as recursive filters and weak constraints are used to provide correlation within aerosol size bins and upper and lower bounds for the optimization. The system is used to perform assimilation experiments with fine vertical structure and no data thinning or re-gridding on a 12 km horizontal grid over the region of California, USA, where improvements on analyses and forecasts is demonstrated. A first set of simulations was performed, comparing the assimilation impacts of using the operational MODIS (Moderate Resolution Imaging Spectroradiometer) dark target retrievals to those using observationally constrained ones, i.e., calibrated with AERONET (Aerosol RObotic NETwork) data. It was found that using the observationally constrained retrievals produced the best results when evaluated against ground based monitors, with the error in PM2.5 predictions reduced at over 90% of the stations and AOD errors reduced at 100% of the monitors, along with larger overall error reductions when grouping all sites. A second set of experiments reveals that the use of fine mode fraction AOD and ocean multi-wavelength retrievals can improve the representation of the aerosol size distribution, while assimilating only 550 nm AOD retrievals produces no or at times degraded impact. While assimilation of multi-wavelength AOD shows positive impacts on all analyses performed, future work is needed to generate observationally constrained multi-wavelength retrievals, which when assimilated will generate size distributions more consistent with AERONET data and will provide better aerosol estimates.

Saide, P. E.; Carmichael, G. R.; Liu, Z.; Schwartz, C. S.; Lin, H. C.; da Silva, A. M.; Hyer, E.

2013-10-01

133

Method of Controlling Lasing Wavelength(s)  

NASA Technical Reports Server (NTRS)

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

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

2000-01-01

134

Precipitation-induced surface brightenings seen on Titan by Cassini VIMS and ISS  

NASA Astrophysics Data System (ADS)

Observations from Cassini VIMS and ISS show localized but extensive surface brightenings in the wake of the 2010 September cloudburst. Four separate areas, all at similar latitude, show similar changes: Yalaing Terra, Hetpet Regio, Concordia Regio, and Adiri. Our analysis shows a general pattern to the time-sequence of surface changes: after the cloudburst the areas darken for months, then brighten for a year before reverting to their original spectrum. From the rapid reversion timescale we infer that the process driving the brightening owes to a fine-grained solidified surface layer. The specific chemical composition of such solid layer remains unknown. Evaporative cooling of wetted terrain may play a role in the generation of the layer, or it may result from a physical grain-sorting process.

Barnes, Jason W.; Buratti, Bonnie J.; Turtle, Elizabeth P.; Bow, Jacob; Dalba, Paul A.; Perry, Jason; Brown, Robert H.; Rodriguez, Sebastien; Mouélic, Stéphane Le; Baines, Kevin H.; Sotin, Christophe; Lorenz, Ralph D.; Malaska, Michael J.; McCord, Thomas B.; Clark, Roger N.; Jaumann, Ralf; Hayne, Paul O.; Nicholson, Philip D.; Soderblom, Jason M.; Soderblom, Laurence A.

2013-12-01

135

The Vertical Structure and Phosphine Distribution on Saturn as Determined by Cassini/VIMS  

NASA Astrophysics Data System (ADS)

We present the preliminary results of our study on the variations of (1) the vertical aerosol layer structure and (2) the phosphine (PH3) distribution on Saturn, utilizing Cassini/VIMS spectral imagery. From the Cassini/VIMS infrared channel spectral data of Saturn acquired in 2004, we sample a dozen pixels at each of the following four latitudes (-10, -27, -47, and -73 degree) to create a set of multi-spectral center-limb profiles for our radiative transfer analysis. We first fit the NIR methane band spectra to determine the altitude of the upper tropospheric haze at the four latitudes, using the newest CH4 near-infrared correlated-k coefficients (Irwin et al. 2006, Icarus, 181, 309-319) and a multi-layer model. This latitudinal variation in the haze altitude is an important clue to unveil Saturn's global climate system. On that basis, we fit the phosphine band spectrum near 3 micron to constrain the phosphine column abundance, using recently published PH3 absorption data sets (Temma et al. 2006, JGR, accepted). Since phosphine is a disequilibrium species in Saturn's upper atmosphere, its increase suggests enhanced convective activity from the deep interior. We thus map the latitudinal phosphine distribution on Saturn, including the analysis of the south polar region where an anomalously strong phosphine absorption was reported (Baines et al. 2005, Earth, Moon, and Planets, 96, 119--147). This work was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under contract with NASA. The first author of this presentation is supported by the NASA Postdoctoral Fellowship at the Jet Propulsion Laboratory.

Temma, Takafumi; Baines, K. H.; Momary, T. W.; Cassini/VIMS Team

2006-09-01

136

The Vertical Structure and Phosphine Distribution on Saturn as Determined by Cassini/VIMS  

NASA Astrophysics Data System (ADS)

We present the preliminary results of our study on the variations of (1) the vertical aerosol layer structure and (2) the phosphine (PH3) distribution on Saturn, utilizing Cassini/VIMS spectral imagery. From the Cassini/VIMS infrared channel spectral data of Saturn acquired in 2004, we sample a dozen pixels at each of the following four latitudes (-10, -27, -47, and -73 degree) to create a set of multi-spectral center-limb profiles for our radiative transfer analysis. We first fit the NIR methane band spectra to determine the altitude of the upper tropospheric haze at the four latitudes, using the newest CH4 near-infrared correlated-k coefficients (Irwin et al. 2006, Icarus, 181, 309-319) and a multi-layer model. This latitudinal variation in the haze altitude is an important clue to unveil Saturn's global climate system. On that basis, we fit the phosphine band spectrum near 3 micron to constrain the phosphine column abundance, using recently published PH3 absorption data sets (Temma et al. 2006, JGR, accepted). Since phosphine is a disequilibrium species in Saturn's upper atmosphere, its increase suggests enhanced convective activity from the deep interior. We thus map the latitudinal phosphine distribution on Saturn, including the analysis of the south polar region where an anomalously strong phosphine absorption was reported (Baines et al. 2005, Earth, Moon, and Planets, 96, 119--147). This work was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under contract with NASA. The first author of this presentation is supported by the NASA Postdoctoral Fellowship at the Jet Propulsion Laboratory.

Temma, T.; Baines, K. H.; Momary, T. W.

2006-12-01

137

Potentially active regions on Titan with Cassini/VIMS and Radar data: Terrestrial analogues.  

NASA Astrophysics Data System (ADS)

We present our study on Titan's geology in order to develop our current understanding of the satellite's active zones [1],[2]. The key aim is to study Titan's geology holistically, by means of internal activity and surface properties, in addition to terrestrial comparisons. We have applied the Principal Components Analysis (PCA) method in order to collect combined information of the seven infrared spectral windows, using the Cassini Mission Visual and Infrared Mapping Spectrometer (VIMS) data. The study areas for the moment are Tui Regio (located at 20°S, 130°W) and Hotei Regio (located at 26°S, 78°W). The main goal is to identify the composition as well as the alterations of the components that compose the possible calderas and lava flows [3], by using the principal components of the PCA method. Principal component analysis (PCA) is recommended, as our primary concern is to determine the minimum number of factors that will account for the maximum variance in the data in use in this particular multivariate analysis. Moreover, Cassini/Radar images have been processed [4] in order to study morphologically the active zones within the areas of Tui and Hotei Regio and to identify any analogues with terrestrial features. Both VIMS and Radar data [5] have provided significant information regarding the geology of the two areas, which should enable us to determine a possible internal activity as well as to identify superficial geologic structures. References [1] Nelson, R. M. (2009) Icarus 199, 429-441. [2] Solomonidou, A. (2009) European Planetary Science Congress Vol. 4, EPSC2009-710. [3] Sotin, C. (2005) Nature, Vol 435. [4] Bratsolis, E. & Sigelle, M. (2003) IEEE Transactions on Geoscience and Remote Sensing, 41, pp. 2890-2899. [5] Le Mouélic, S. (2008) Journal of Geophysical Research, Volume 113, Issue E4.

Solomonidou, Anezina; Coustenis, Athena; Le Mouélic, Stephane; Sotin, Christophe; Bratsolis, Emmanuel; Bampasidis, Georgios; Kyriakopoulos, Konstantinos; Moussas, Xenophon

2010-05-01

138

Saturn's B Ring and Cassini Division from Cassini RSS, VIMS, and UVIS Occultations  

NASA Astrophysics Data System (ADS)

Saturn's B ring demarcates the inner edge of the dynamically fascinating Cassini Division, replete with eccentric and circular ringlets and gaps. We present kinematical models for ringlets and gaps in the Cassini Division, and the outer edge of the B ring, from more than 100 individual Cassini occultations using RSS, VIMS, and UVIS instruments. Recent investigations of the B ring outer edge and Cassini Division features, using two decades of Earth-based and spacecraft occultation measurements, show hints of regularity amidst the complexity of the region. Hedman et al. (2010), using Cassini VIMS stellar occultation data and Cassini RSS and historical data from French et al. (2010), found a quasi-regular spacing of ringlets and gaps, with inner edges of gaps measurably non-circular and outer edges nearly circular. They proposed a dynamical mechanism whereby the non-circular B ring edge resonantly controls the structure of the Cassini Division gaps. The shape of the B ring edge is dominated by an m=2 mode, controlled by Mimas, although the dynamical interaction is still poorly understood. Cassini ISS images show the presence of multiple modes, possibly transient (Spitale et al. 2010). The long time series of the present data set, densely sampling the Cassini orbital tour from 2005-2009, coupled with the Voyager 1 and 2 data from 1980 and 1981, the widely-observed 28 Sgr stellar occultation of 1989, and Hubble Space Telescope stellar occultations in 1991 and 1995, provide the opportunity to determine the orbital elements and precession rates of the non-circular Cassini Division features, and to compare multi-mode libration and circulation models for the B ring edge. These are essential ingredients for detailed tests of dynamical models for the structure of the Cassini Division and its possible connection to the B ring.

French, Richard; Colwell, Joshua; Nicholson, Phillip; Hedman, Matthew; Marouf, Essam; Rappaport, Nicole J.; McGhee, Colleen; Batista, A.; de Silva, A.; Flores, S.; Geiling, N.; Graves, K.; Guo, L.; Kee, L. Huang. Y.; Larson, K.; Moreno, J.; Mowla, L.; Nelson, E.; Pang, Z.; Sanchez, T.; Stephens, K.; Strother, C.; Judd, K.; Snyderman, R.; Stroud, D.; Youngblood, A.

139

Dual Wavelength Lasers  

NASA Technical Reports Server (NTRS)

Dual wavelength lasers are discussed, covering fundamental aspects on the spectroscopy and laser dynamics of these systems. Results on Tm:Ho:Er:YAG dual wavelength laser action (Ho at 2.1 m and Er at 2.9 m) as well as Nd:YAG (1.06 and 1.3 m) are presented as examples of such dual wavelength systems. Dual wavelength lasers are not common, but there are criteria that govern their behavior. Based on experimental studies demonstrating simultaneous dual wavelength lasing, some general conclusions regarding the successful operation of multi-wavelength lasers can be made.

Walsh, Brian M.

2010-01-01

140

blaVIM-2 Cassette-Containing Novel Integrons in Metallo-?-Lactamase-Producing Pseudomonas aeruginosa and Pseudomonas putida Isolates Disseminated in a Korean Hospital  

PubMed Central

We investigated the phenotypic and genetic properties of metallo-?-lactamase-producing Pseudomonas isolates collected at a tertiary-care hospital in Korea since 1995. The prevalence of imipenem resistance among Pseudomonas aeruginosa isolates reached 16% in 1997, when 9% of the resistant organisms were found to produce VIM-2 ?-lactamase, a class B enzyme previously found only in P. aeruginosa isolates from Europe. VIM-2-producing isolates of Pseudomonas putida were also detected. Resistance was transferable from both these species to P. aeruginosa PAO4089Rp by filter mating, although the resistance determinant could not be found on any detectable plasmid. Serotyping showed that many of the VIM-2-producing P. aeruginosa isolates belonged to serotypes O:11 and O:12, and pulsed-field gel electrophoresis of XbaI-digested genomic DNA revealed that many had identical profiles, whereas the P. putida isolates were diverse. Sequencing showed that the blaVIM-2 genes resided as cassettes in class 1 integrons. In contrast to previous VIM-encoding integrons, the integron sequenced from a P. aeruginosa isolate had blaVIM located downstream of a variant of aacA4. blaVIM also lay in a class 1 integron in a representative P. putida strain, but the organization of this integron was different from that sequenced from the P. aeruginosa strain. In conclusion, the metallo-?-lactamase produced by these imipenem-resistant Pseudomonas isolates was VIM-2, and the accumulation of producers reflected clonal dissemination as well as horizontal spread. Strict measures are required in order to control a further spread of resistance.

Lee, Kyungwon; Lim, Jong Back; Yum, Jong Hwa; Yong, Dongeun; Chong, Yunsop; Kim, June Myung; Livermore, David M.

2002-01-01

141

Evaluation of Etest MBL for detection of blaIMP-1 and blaVIM-2 allele-positive clinical isolates of Pseudomonas spp. and Acinetobacter spp.  

PubMed

The Etest MBL (AB BIODISK, Solna, Sweden) correctly differentiated all 57 isolates of Acinetobacter spp. and Pseudomonas aeruginosa with the bla(IMP-1) allele and 135 of 137 (98.5%) Acinetobacter spp. and Pseudomonas spp. isolates with the bla(VIM-2) allele. The Etest MBL was reliable for detecting the IMP-1- and VIM-2-producing Pseudomonas and Acinetobacter isolates. PMID:15695713

Lee, Kyungwon; Yong, Dongeun; Yum, Jong Hwa; Lim, Yong Sik; Bolmström, Anne; Qwärnström, Anette; Karlsson, Asa; Chong, Yunsop

2005-02-01

142

Characterization of Class 1 Integrons from Pseudomonas aeruginosa That Contain the blaVIM-2 Carbapenem-Hydrolyzing  Lactamase Gene and of Two Novel Aminoglycoside Resistance Gene Cassettes  

Microsoft Academic Search

Two clonally unrelated Pseudomonas aeruginosa clinical strains, RON-1 and RON-2, were isolated in 1997 and 1998 from patients hospitalized in a suburb of Paris, France. Both isolates expressed the class B carbapenem-hydrolyzing b-lactamase VIM-2 previously identified in Marseilles in the French Riviera. In both isolates, the blaVIM-2 cassette was part of a class 1 integron that also encoded aminoglycoside-modifying enzymes.

LAURENT POIREL; THIERRY LAMBERT; SALIH TURKOGLU; ESTHEL RONCO; JEAN-LOUIS GAILLARD; PATRICE NORDMANN

2001-01-01

143

NH-1,2,3-Triazole-based Inhibitors of the VIM-2 Metallo-?-Lactamase: Synthesis and Structure-Activity Studies  

PubMed Central

Metallo-ß-lactamases (MBL) are an emerging cause of bacterial resistance to antibiotic treatment. The VIM-2 ß-lactamase is the most commonly encountered MBL in clinical isolates worldwide. Described here are potent and selective small molecule inhibitors of VIM-2 containing the arylsulfonyl-NH-1,2,3-triazole chemotype that potentiate the efficacy of the ß-lactam, imipenem, in E. coli.

Weide, Timo; Saldanha, S. Adrian; Minond, Dmitriy; Spicer, Timothy P.; Fotsing, Joseph R.; Spaargaren, Michael; Frere, Jean-Marie; Bebrone, Carine; Sharpless, K. Barry; Hodder, Peter S.; Fokin, Valery V.

2010-01-01

144

Aerosol Optical Depth Assimilation for a Size-Resolved Sectional Model: Impacts of Observationally Constrained, Multi-Wavelength and Fine Mode Retrievals on Regional Scale Analyses and Forecasts  

NASA Astrophysics Data System (ADS)

An aerosol optical depth (AOD) three-dimensional variational data assimilation technique is developed for the Gridpoint Statistical Interpolation (GSI) system when WRF-Chem forecasts are performed with a detailed sectional model (MOSAIC). Within GSI, forward AOD and adjoint sensitivities are performed using Mie computations from the WRF-Chem optical properties module providing consistency with the forecast. GSI tools such as recursive filters and weak constraints are used to provide correlation within aerosol size bins and upper and lower bounds for the optimization. The system is used to perform assimilation experiments with fine vertical structure and no data thinning or re-gridding on a 12-km horizontal grid over the region of California, USA. A first set of simulations is performed comparing the assimilation impacts of operational MODIS dark target retrievals to observationally constrained ones (i.e. calibrated with AERONET data), the latter ones showing higher error reductions and increased fraction of improved PM2.5 and AOD ground-based monitors. A second set of experiments reveals that the use of fine mode fraction AOD and ocean multi-wavelength retrievals can improve the representation of the aerosol size distribution, while assimilating only 550nm AOD retrievals produces no or at times degraded impact. A demonstration of these tools will also be presented for operational forecast for flight planning of the SEAC4RS campaign. Left panels: May 2010 average maps of operational MODIS Terra (top-left), NASA-NNR (top-middle) product for the same MODIS Terra data, non-assimilated model (bottom-left) and assimilated using NASA NNR (bottom-middle). Monthly averages of the raw and observationally constrained retrievals can be quite different, and assimilation brings model estimates closer to the observation. Right panels: 550-870nm Angstrom exponent fractional error reductions from non-assimilated to assimilated model computed with respect to Aqua retrievals. Figure on top assimilates only MODIS 550nm AOD while the one on the bottom assimilates MODIS 550, 660, 870, and 1240nm over ocean and only 550nm over land. Higher error reductions on angstrom exponent when using multi-wavelength data point towards improvements in aerosol size distributions.

Carmichael, G. R.; Saide, P. E.; Liu, Z.; Lin, H.; Schwartz, C.; da Silva, A.; Hyer, E. J.

2013-12-01

145

Design of the focal plane array assembly for the Mars Observer/Visual and Infrared Mapping Spectrometer (MO/VIMS)  

NASA Astrophysics Data System (ADS)

A unique focal plane array (FPA) assembly combining both electronic and optical components in a single hermetically sealed hybrid package has been designed to meet the performance requirements imposed on the focal plane assembly in the Visual and Infrared Mapping Spectrometer (VIMS) for the Mars Observer (MO) mission. Inside the FPA package is a configuration of three multiplexed linear arrays containing 320 detector elements, a combination of Si and InSb, allowing continuous spectral coverage from 0.35 to 5.14 microns. An optical subassembly consisting of two spectral order-sorting filters with intrinsic field-of-view apertures requiring critical optical alignment is also internal to the hybrid. Several engineering issues arose during the MO/VIMS FPA development phase which had challenging design ramifications. FPA performance requirements, design approach, and critical issues are discussed.

Niblack, Curtiss A.; Evans, Thomas G.; Toft, J. Brian

146

Tn6001, a Transposon-Like Element Containing the blaVIM-3-Harboring Integron In450?  

PubMed Central

We describe the structure of a transposon-like element named Tn6001, which contains a blaVIM-3-harboring integron In450, which was derived from a multidrug-resistant Pseudomonas aeruginosa clinical isolate in Taiwan. The transposon backbone structure is most closely related to those of Tn1404* and Tn1403. Tn6001 was inserted into the chromosome of the clinical isolate.

Tseng, Sung-Pin; Hsueh, Po-Ren; Tsai, Jui-Chang; Teng, Lee-Jene

2007-01-01

147

Wavelength selectable photonic transport system applicable to unequal channel spacing  

Microsoft Academic Search

A photonic transport system with optoelectronic wavelength converter applicable to unequal channel spacing is demonstrated. A compact 8×8 wavelength selective switch and a polarization independent electroabsorption modulator are developed for designing the large-scale system

T. Kawai; M. Teshima; H. Yasaka; M. Kobayashi; M. Koga

1998-01-01

148

Titan's cloud seasonal activity from winter to spring with Cassini/VIMS  

USGS Publications Warehouse

Since Saturn orbital insertion in July 2004, the Cassini orbiter has been observing Titan throughout most of the northern winter season (October 2002-August 2009) and the beginning of spring, allowing a detailed monitoring of Titan's cloud coverage at high spatial resolution with close flybys on a monthly basis. This study reports on the analysis of all the near-infrared images of Titan's clouds acquired by the Visual and Infrared Mapping Spectrometer (VIMS) during 67 targeted flybys of Titan between July 2004 and April 2010.The VIMS observations show numerous sporadic clouds at southern high and mid-latitudes, rare clouds in the equatorial region, and reveal a long-lived cloud cap above the north pole, ubiquitous poleward of 60??N. These observations allow us to follow the evolution of the cloud coverage during almost a 6-year period including the equinox, and greatly help to further constrain global circulation models (GCMs). After 4. years of regular outbursts observed by Cassini between 2004 and 2008, southern polar cloud activity started declining, and completely ceased 1. year before spring equinox. The extensive cloud system over the north pole, stable between 2004 and 2008, progressively fractionated and vanished as Titan entered into northern spring. At southern mid-latitudes, clouds were continuously observed throughout the VIMS observing period, even after equinox, in a latitude band between 30??S and 60??S. During the whole period of observation, only a dozen clouds were observed closer to the equator, though they were slightly more frequent as equinox approached. We also investigated the distribution of clouds with longitude. We found that southern polar clouds, before disappearing in mid-2008, were systematically concentrated in the leading hemisphere of Titan, in particular above and to the east of Ontario Lacus, the largest reservoir of hydrocarbons in the area. Clouds are also non-homogeneously distributed with longitude at southern mid-latitudes. The n= 2-mode wave pattern of the distribution, observed since 2003 by Earth-based telescopes and confirmed by our Cassini observations, may be attributed to Saturn's tides. Although the latitudinal distribution of clouds is now relatively well reproduced and understood by the GCMs, the non-homogeneous longitudinal distributions and the evolution of the cloud coverage with seasons still need investigation. If the observation of a few single clouds at the tropics and at northern mid-latitudes late in winter and at the start of spring cannot be further interpreted for the moment, the obvious shutdown of the cloud activity at Titan's poles provides clear signs of the onset of the general circulation turnover that is expected to accompany the beginning of Titan's northern spring. According to our GCM, the persistence of clouds at certain latitudes rather suggests a 'sudden' shift in near future of the meteorology into the more illuminated hemisphere. Finally, the observed seasonal change in cloud activity occurred with a significant time lag that is not predicted by our model. This may be due to an overall methane humidity at Titan's surface higher than previously expected. ?? 2011 Elsevier Inc.

Rodriguez, S.; Le, Mouelic, S.; Rannou, P.; Sotin, C.; Brown, R. H.; Barnes, J. W.; Griffith, C. A.; Burgalat, J.; Baines, K. H.; Buratti, B. J.; Clark, R. N.; Nicholson, P. D.

2011-01-01

149

Virtual interactive musculoskeletal system (VIMS) in orthopaedic research, education and clinical patient care  

PubMed Central

The ability to combine physiology and engineering analyses with computer sciences has opened the door to the possibility of creating the "Virtual Human" reality. This paper presents a broad foundation for a full-featured biomechanical simulator for the human musculoskeletal system physiology. This simulation technology unites the expertise in biomechanical analysis and graphic modeling to investigate joint and connective tissue mechanics at the structural level and to visualize the results in both static and animated forms together with the model. Adaptable anatomical models including prosthetic implants and fracture fixation devices and a robust computational infrastructure for static, kinematic, kinetic, and stress analyses under varying boundary and loading conditions are incorporated on a common platform, the VIMS (Virtual Interactive Musculoskeletal System). Within this software system, a manageable database containing long bone dimensions, connective tissue material properties and a library of skeletal joint system functional activities and loading conditions are also available and they can easily be modified, updated and expanded. Application software is also available to allow end-users to perform biomechanical analyses interactively. Examples using these models and the computational algorithms in a virtual laboratory environment are used to demonstrate the utility of these unique database and simulation technology. This integrated system, model library and database will impact on orthopaedic education, basic research, device development and application, and clinical patient care related to musculoskeletal joint system reconstruction, trauma management, and rehabilitation.

Chao, Edmund YS; Armiger, Robert S; Yoshida, Hiroaki; Lim, Jonathan; Haraguchi, Naoki

2007-01-01

150

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

151

Cloning and Characterization of blaVIM, a New Integron-Borne Metallo-?-Lactamase Gene from a Pseudomonas aeruginosa Clinical Isolate  

PubMed Central

Production of a metallo-?-lactamase activity was detected in a carbapenem-resistant Pseudomonas aeruginosa clinical isolate (isolate VR-143/97) from an Italian inpatient at the Verona University Hospital (northern Italy). The metallo-?-lactamase determinant was isolated from a genomic library of VR-143/97, constructed in an Escherichia coli plasmid vector, by screening for clones with reduced susceptibility to imipenem. Sequencing of the cloned gene revealed that it encoded a new class B ?-lactamase that was named VIM-1. At the sequence level VIM-1 was rather divergent from the other class B enzymes (16.4 to 38.7% identity), overall being more similar to members of subclass B1 including the ?-lactamase II of Bacillus cereus (Bc-II), the Bacteroides fragilis CcrA, the Chryseobacterium meningosepticum BlaB, and the cassette-encoded IMP-1 enzymes. Among these, VIM-1 showed the highest degree of similarity to Bc-II. Similarly to blaIMP, blaVIM was also found to be carried on a gene cassette inserted into a class 1 integron. The blaVIM-containing integron was located on the chromosome of P. aeruginosa VR-143/97, and the metallo-?-lactamase-encoding determinant was not transferable to E. coli by conjugation. Expression of the integron-borne blaVIM gene in E. coli resulted in a significant decrease in susceptibility to a broad array of ?-lactams (ampicillin, carbenicillin, piperacillin, mezlocillin, cefotaxime, cefoxitin, ceftazidime, cefoperazone, cefepime, and carbapenems), revealing a very broad substrate specificity of the VIM-1 enzyme.

Lauretti, Laura; Riccio, Maria Letizia; Mazzariol, Annarita; Cornaglia, Giuseppe; Amicosante, Gianfranco; Fontana, Roberta; Rossolini, Gian Maria

1999-01-01

152

Cloning and characterization of blaVIM, a new integron-borne metallo-beta-lactamase gene from a Pseudomonas aeruginosa clinical isolate.  

PubMed

Production of a metallo-beta-lactamase activity was detected in a carbapenem-resistant Pseudomonas aeruginosa clinical isolate (isolate VR-143/97) from an Italian inpatient at the Verona University Hospital (northern Italy). The metallo-beta-lactamase determinant was isolated from a genomic library of VR-143/97, constructed in an Escherichia coli plasmid vector, by screening for clones with reduced susceptibility to imipenem. Sequencing of the cloned gene revealed that it encoded a new class B beta-lactamase that was named VIM-1. At the sequence level VIM-1 was rather divergent from the other class B enzymes (16.4 to 38.7% identity), overall being more similar to members of subclass B1 including the beta-lactamase II of Bacillus cereus (Bc-II), the Bacteroides fragilis CcrA, the Chryseobacterium meningosepticum BlaB, and the cassette-encoded IMP-1 enzymes. Among these, VIM-1 showed the highest degree of similarity to Bc-II. Similarly to blaIMP, blaVIM was also found to be carried on a gene cassette inserted into a class 1 integron. The blaVIM-containing integron was located on the chromosome of P. aeruginosa VR-143/97, and the metallo-beta-lactamase-encoding determinant was not transferable to E. coli by conjugation. Expression of the integron-borne blaVIM gene in E. coli resulted in a significant decrease in susceptibility to a broad array of beta-lactams (ampicillin, carbenicillin, piperacillin, mezlocillin, cefotaxime, cefoxitin, ceftazidime, cefoperazone, cefepime, and carbapenems), revealing a very broad substrate specificity of the VIM-1 enzyme. PMID:10390207

Lauretti, L; Riccio, M L; Mazzariol, A; Cornaglia, G; Amicosante, G; Fontana, R; Rossolini, G M

1999-07-01

153

Wavelength independent interferometer  

NASA Technical Reports Server (NTRS)

A polychromatic interferometer utilizing a plurality of parabolic reflective surfaces to properly preserve the fidelity of light wavefronts irrespective of their wavelengths as they pass through the instrument is disclosed. A preferred embodiment of the invention utilizes an optical train which comprises three off-axis parabolas arranged in conjunction with a beam-splitter and a reference mirror to form a Twyman-Green interferometer. An illumination subsystem is provided and comprises a pair of lasers at different preselected wavelengths in the visible spectrum. The output light of the two lasers is coaxially combined by means of a plurality of reflectors and a grating beam combiner to form a single light source at the focal point of the first parabolic reflection surface which acts as a beam collimator for the rest of the optical train. By using visible light having two distinct wavelengths, the present invention provides a long equivalent wavelength interferogram which operates at visible light wherein the effective wavelength is equal to the product of the wavelengths of the two laser sources divided by their difference in wavelength. As a result, the invention provides the advantages of what amounts to long wavelength interferometry but without incurring the disadvantage of the negligible reflection coefficient of the human eye to long wavelength frequencies which would otherwise defeat any attempt to form an interferogram at that low frequency using only one light source.

Hochberg, Eric B. (Inventor); Page, Norman A. (Inventor)

1991-01-01

154

An Absolute Radius Scale for Saturn's Rings from Cassini Occultations  

NASA Astrophysics Data System (ADS)

Abstract (2,250 Maximum Characters): The Cassini mission has provided a remarkable opportunity to investigate the structure and dynamics of the Saturn ring system at the sub-km radial scale, using hundreds of individual stellar and radio occultations from the UVIS, VIMS, and RSS instruments. From precise measurements of ring and gap edges, we have been able to determine the orbital characteristics of over one hundred features in the rings. A crucial step in the orbital determination is the establishment of a highly accurate radius scale for the rings. This is compounded by uncertainties in the positions of the occulted stars, km-scale trajectory errors in the spacecraft location, and inexact knowledge of the direction and precession rate of Saturn’s pole. We have taken an iterative approach in which we identify a set of 30 or so putative circular, equatorial features, solve for along-track trajectory errors for each occultation, and use this best-fitting orbital solution to establish the reference system for determination of the orbits of non-circular ring features. Using thousands of individual measurements of rings in the Cassini data, we have determined an absolute radius scale for each contributing occultation with an accuracy of about 200 m for the C and B rings and the Cassini Division. This enables us to detect and measure very small dynamical effects such as weak normal modes in ring edges, and to determine the phases of density waves, including very short wavelength outer Lindblad resonances in the C ring, as reported at this meeting. We calculate the sensitivity of the radius scale to the assumed pole direction and precession rate. Ultimately, we will combine these results with Voyager, HST, and pre-Cassini Earth-based occultation measurements to refine our knowledge of Saturn’s pole direction and precession.

McGhee, Colleen; French, R. G.; Jacobson, R. A.; Nicholson, P. D.; Colwell, J. E.; Marouf, E. A.; Lonergan, K.; Sepersky, T.

2013-05-01

155

The Saturnian satellite Tethys observed by the Cassini-VIMS instrument  

NASA Astrophysics Data System (ADS)

In order to further our understanding of the Saturnian system we studied the variations in spectral properties across the surface of Saturn's satellite Tethys using Cassini/VIMS data and their relationships to geological and/or morphological characteristics as seen in the Cassini/ISS images. Despite the spectral dominance of water ice on Tethys' surface distinct spectral variations could be detected, which are surprisingly very different from what was expected from the visible albedo derived from Voyager and Cassini data. The abundance of water ice usually follows the visible surface albedo as seen on many other satellites. Thus, the weakest water ice signature could be also measured on the trailing hemisphere of Tethys, as known from Dione and Rhea [1-3]. The detailed mapping, however, shows a more complex pattern. Two relatively narrow N/S-trending bands, interpreted to be composed of larger ice particle sizes rather than the higher abundance of water ice, separate the Saturn-facing and the anti-Saturnian hemisphere of Tethys. So far, larger ice particles could only be found in geologically young, less weathered portions of the surfaces of the icy Saturnian satellites [2,3]. On Tethys, however, the observed variations might be more complex due to the influence of fine particles from the E-ring coating the surface. In contrast to the prominent graben systems on Dione and Rhea, which show fresh ice exposed on steep walls, no spectral properties could be exclusively associated to Tethys' extended graben system Ithaca Chasma supporting its geologically old age and that its formation was not caused by the impact event that created Odysseus [4]. References: [1] Clark, R. N., et al. (2008), Icarus, 193(2), 372-386. [2] Stephan, K., et al. (2010) Icarus, 206(2), 631-652. [3] Stephan, K. et al. (2012) PSS, 61(1), 142-160. [4] Giese et al., (2007) GRL, 34(21), L21203.

Stephan, Katrin; Jaumann, Ralf; Wagner, Roland; Clark, Roger N.; Cruikshank, Dale P.; Dalle Ore, Christina; Hansen, Gary B.; Brown, Robert H.; Giese, Bernd; Roatsch, Thomas; Matson, Dennis; Baines, Kevin; Filiacchione, Gianrico; Rodriguez, Sebastian; Buratti, Bonnie J.; Nicholson, Phil D.; Sotin, Christophe

2013-04-01

156

Implications for Titan's potentially active regions: A study on Cassini/VIMS data.  

NASA Astrophysics Data System (ADS)

Continuing investigations of Titan's surface have shown that this Earth-like Saturnian satellite presents an extremely complex geology [1, 2, 3]. The Cassini Mission Visual and Infrared Mapping Spectrometer (VIMS) acquires data operating as a multi-spectral camera that allow for a complete analysis of the composition, geology and morphology of Titan's surface [4]. Two of the most geologically interesting areas on Titan are Xanadu's Tui Regio (20S, 130W) and Hotei Regio (26S, 78W) as they present higher 5m reflectivities than the surrounding areas [5] and have been interpreted as cryovolcanic in origin [6]. We present our study on both possibly active regions with the aim to identify the composition as well as the alterations of the components that compose the possible calderas and lava flows [7], by using radiative transfer modeling [8] and a classical staitistical method, the Principal Component Analysis [9]. [1] Jaumann, R. et al., (2009) Springer Netherlands pp. 75-140. [2] Nelson, R. M. et al., (2009) Icarus 199, 429-441. [3] Solomonidou, A. et al., (2009) European Planetary Science Congress Vol. 4, EPSC2009-710. [4] Jaumann, R. et al., (2006) Planet Space Science 54:1146-1155. [5] Barnes, J. W. et al., (2006) Geophysical Research Letters Vol. 33, L16204. [6] Lopes, R. M. C. et al., (2010) Icarus Vol. 205 pp:540-558. [7] Sotin, C. (2005) Nature, Vol 435. [8] Rodriguez, S. et al., (2009) Workshop on Hyperspectral Image and Signal Processing: Evolution on Remore Sensing pp. 1-4. [9] Bellucci, G. et al., (2004) Advances in Space Research 34 pp. 1640-1646.

Solomonidou, Anezina; Coustenis, Athena; Rodriguez, Sebastien; Bratsolis, Emmanuel; Le Mouelic, Stephane; Sotin, Christophe; Bampasidis, Georgios; Kyriakopoulos, Konstantinos; Moussas, Xenophon

157

New processing of Cassini/VIMS data on potentially geologically varying regions  

NASA Astrophysics Data System (ADS)

We present a study of Titan's geology with a view to enhance our current understanding of the satellite's potentially geologically varying regions. We apply here a statistical method, the Principal Component Analysis (PCA) [1, 2] and a radiative transfer method [3, 1] on three potentially "active" regions on Titan, i.e. regions possibly subject to change over time (in brightness and/or in color etc) [4] namely Tui Regio, Hotei Regio, and Sotra Facula. With our method of PCA we have managed to isolate specific regions of distinct and diverse chemical composition. Then, with our follow-up RT method, we retrieved the surface albedo of the three isolated regions and of the surrounding terrains with different spectral response. These methods enabled us to evaluate the atmospheric contribution and allowed us to better constrain the real surface alterations, by comparing the spectra of these regions. Finally, the temporal surface variation of Hotei Regio as suggested by Nelson et al. 2009 [5], has been tested through the use of the RT method while we have superimposed this area's Cassini Visual and Infrared Mapping Spectrometer (VIMS) and RADAR data in order to 'view' the morphological potential. Even though we have used exactly the same dataset as Nelson and coauthors in 2009, we did not detect any significant surface albedo variations over time; this led us to revise the definition of "active" regions: even if these regions have not visually changed over the course of the Cassini mission, the determination of the chemical composition and the correlation with the morphological structures [6] observed in these areas do not rule out that past and/or ongoing cryovolcanic processes are still a possible interpretation.

Solomonidou, A.; Hirtzig, M.; Bratsolis, E.; Bampasidis, G.; Coustenis, A.; Kyriakopoulos, K.; Le Mouélic, S.; Rodriguez, S.; Jaumann, R.; Stephan, K.; Drossart, P.; Sotin, C.; Brown, R. H.; Seymour, K.; Moussas, X.

2012-09-01

158

Cassini/VIMS Data Analysis of Potentially Geologically Varying Regions on Titan  

NASA Astrophysics Data System (ADS)

We present a study of Titan's geology with a view to enhance our current understanding of some particular regions on the satellite's surface, which may be varying in brightness and/or in color etc. We apply here a statistical method, the Principal Component Analysis (PCA) [1] and a radiative transfer code (RT) [1,2] on three such potentially "active" regions: Tui Regio, Hotei Regio, and Sotra Facula, within which we isolate specific regions of distinct and diverse chemical composition with PCA. Then, with our follow-up RT method, we retrieve the surface albedo of these specific isolated regions and of the surrounding terrains exhibiting different spectral responses. We thus evaluate the atmospheric contribution and can constrain the real surface alterations, by comparing the spectra of these regions. We search for the temporal surface variations of Hotei Regio (as reported by Nelson et al. 2009 [3]), with our RT code and the same data from 2004-2006, and do not find any significant surface albedo variations over time. We then superimposed this area's Cassini Visual and Infrared Mapping Spectrometer (VIMS) and RADAR data in order to 'view' the morphological potential. We find that even if these regions have not visually changed over the course of the Cassini mission, the determination of the chemical composition and the correlation with the morphological structures [4] observed in these areas do not rule out past and/or ongoing cryovolcanic processes as a possible interpretation. [1] Solomonidou, A., et al.: In preparation. [2] Hirtzig, M. et al.: In preparation. [3] Nelson, R. et al.: Icarus 199, 429-441, 2009. [4] Solomonidou, A et al.: PSS, accepted, 2012.

Solomonidou, Anezina; Hirtzig, M.; Bratsolis, E.; Bampasidis, G.; Coustenis, A.; Kyriakopoulos, K.; Le Mouélic, S.; Rodriguez, S.; Jaumann, R.; Stephan, K.; Lopes, R. M. C.; Drossart, P.; Sotin, C.; Brown, R. H.; Seymour, K. S.; Moussas, X.

2012-10-01

159

Geological mapping and temporal survey of Ontario Lacus on Titan from 2005 to 2009, using VIMS, ISS and Radar data  

NASA Astrophysics Data System (ADS)

In June 2004 and July 2005, the ISS multispectral camera onboard the Cassini spacecraft imaged a 235 km-long and 75 km-wide dark feature near the south pole of Titan (McEwen et al., 2005). By comparison with other landforms observed near Titan’s north pole with the Radar instrument (Stofan et al., 2007), this feature has been interpreted as an hydrocarbon lake and named Ontario Lacus. Other observations of the lake, by the VIMS hyperspectral camera in December 2007 and the Radar altimeter in December 2008 are consistent with a liquid filled lake (Brown et al., 2008, Barnes et al., 2009), which lies in an extremely flat depression (Lorenz et al., 2009). In March 2009, VIMS acquired new hyperspectral cubes with a spatial resolution similar to the first ones. Finally, the new Radar observations in SAR mode in June and July 2009, 3 months after the VIMS observation, provided the first spatially resolved images of the lake. By merging all these data sets, we performed an integrated geomorphological and compositional study of Ontario Lacus and its surroundings. Comparisons with optical and radar satellite images of analogous landforms in the Etosha Basin, a semi-arid region of Namibia, allowed us to produce an interpretative geological map of Ontario Lacus in 2009. We also checked for potential surface changes of the lake between 2005 and 2009, i.e. during the austral summer and autumn. To achieve this work, we developed a new empirical processing method to remove atmospheric effects in VIMS images and to improve the surface mapping. This correction pipeline is also applied to ISS images. Our interpretative geological map shows that the lake is surrounded mostly by flat plains, except in the North where mountains are present (rough areas with dendritic valleys and triangular facets in the SAR images). The typical radar-dark signature of liquids is present over half the surface area of the lake only. Channels draining the plains SW of Ontario Lacus can be followed on the lake floor on the Radar images. This suggests that the lake floor, most probably composed of (perhaps soggy) sediment, is not covered by significant amounts of liquids over its whole surface. A set of lines curving along the eastern shoreline of the lake can be interpreted, by analogy with similar landforms observed in Namibia and other semi-arid areas on Earth, as “lunette-dunes”, which form by accumulation at downwind lake shorelines, of fine sediments provided by wind deflation of exposed and desiccated lake floors. This unit can be reconciled with 5µm-bright areas in the VIMS images. Alternatively, this set of lines may be interpreted as a series of ancient shorelines, which would indicate past episodes of lake high-stands. If this interpretation is correct, it means that Ontario Lacus has been subject to drying episodes in the past. Finally, at the spatial resolution of ISS and VIMS, we observe no significant change of the lake contour between 2005 and 2009 in the common part of the lake.

Cornet, T.; Bourgeois, O.; Le Mouélic, S.; Rodriguez, S.; Tobie, G.; Sotin, C.; Barnes, J. W.; Brown, R. H.; Baines, K. H.; Buratti, B. J.; Clark, R. N.; Nicholson, P. D.

2010-12-01

160

Imaging of a Newly Forming Polar Hood Over The South Pole of Titan By VIMS/Cassini  

NASA Astrophysics Data System (ADS)

Since August 2009 equinox, the southern hemisphere of Titan entered in fall. A polar hood corresponding to an area of denser haze appears to be progressively forming right above the south pole of Titan, according to the latest observations made by the optical imaging instruments onboard Cassini spacecraft. This behavior is predicted to occur by the GCMs, when the south pole is progressively entering into darkness with the coming southern winter. We focus here on the observations made by the Visual and Infrared Mapping Spectrometer (VIMS). The newly observed phenomenon clearly appears in hyperspectral images acquired by VIMS during the T83 (22 May 2012), T84 (6 June 2012) and T85 (24 July 2012) targeted flybys. No equivalent feature had been observed before in the entire VIMS data set since the insertion of the Cassini spacecraft in Saturn orbit in July 2004. The altitude of this newly observed polar hood during the T83 observation is higher than 250 km, indicating that it does not correspond to any usual cloud observed so far. The inclined orbit of Cassini has allowed observations of this polar hood on the limb of Titan (T83, T84, T85) with a phase angle less than 36°, and directly from above with a phase angle of 96° during an untargeted flyby on 27 June 2012. A vast polar cloud was observed above the north pole at the beginning of the Cassini mission, but considering that a season on Titan lasts seven years, the feature that is currently forming over the south pole might corresponds to the very first stages of what was observed in the north. The Cassini solstice mission will allow the continuous monitoring of this phenomenon up to 2017.

Le Mouelic, S.; Rodriguez, S.; Sotin, C.; West, R. A.; Rannou, P.; Barnes, J. W.; Brown, R. H.; Cornet, T.; Baines, K. H.; Buratti, B. J.; Clark, R. N.; Nicholson, P. D.

2012-12-01

161

Combined disc methods for the detection of KPC- and/or VIM-positive Klebsiella pneumoniae: improving reliability for the double carbapenemase producers.  

PubMed

Klebsiella pneumoniae strains co-producing klebsiella pneumoniae carbapenemase (KPC) and verona integron-encoded metallo-beta-lactamase (VIM) are frequently isolated in Greece and have also occurred in other European countries. Conventional combined disc tests exhibit low sensitivity against these emerging pathogens. We have evaluated modifications of the KPC/Metallo-?-Lactamase Confirmation kit (ROSCO) exhibiting high diagnostic value against KPC, VIM and KPC + VIM producers. The key changes were the inclusion of additional combined tablets containing meropenem plus two inhibitors (dipicolinic acid (1000 ?g per tablet) for metallo-?-lactamases and a boronic acid derivative for KPCs) and the replacement of aminophenylboronic acid by phenylboronic acid (400 ?g per tablet). PMID:23627340

Miriagou, V; Tzelepi, E; Kotsakis, S D; Daikos, G L; Bou Casals, J; Tzouvelekis, L S

2013-09-01

162

Emergence of VIM-4 metallo-?-lactamase-producing Klebsiella pneumoniae ST15 clone in the Clinical Centre University of Pécs, Hungary.  

PubMed

Since November 2009 carbapenemase-producing Klebsiella pneumoniae isolates have been detected in increasing numbers at the Clinical Centre University of Pécs. Molecular typing was performed for 102 clinical isolates originating from different time periods and various departments of the Clinical Centre. Pulsed-field gel electrophoresis revealed the predominance of a single clone (101/102), identified as sequence type ST15. PCR and sequencing showed the presence of blaCTX-M-15 and blaVIM-4 genes. The blaVIM-4 was located on a class 1 integron designated In238b. To our knowledge, this is the first description of a blaVIM-4 gene in the predominant CTX-M-15 extended spectrum ?-lactamase-producing Hungarian Epidemic Clone/ST15. PMID:23809141

Melegh, S; Kovács, K; Gám, T; Nyul, A; Patkó, B; Tóth, A; Damjanova, I; Mestyán, G

2014-01-01

163

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

164

Precise absolute gamma-ray wavelength measurements  

NASA Astrophysics Data System (ADS)

Gamma-ray wavelengths measured with the joint NIST/ILL GAMS4 facility at the High Flux Reactor, Grenoble, France, are discussed. This primary goal of these measurements is gamma-ray wavelengths which are consistent with the optical wavelength scale and the Rydberg constant with an uncertainty no larger than 0.1 ppm for energies up to 5 MeV. The current status of the Bragg angle and crystal lattice spacing measurements on reference energy values, the neutron mass, and the determination of fundamental constants is reviewed. Measurement of structure factors at high energies is also considered.

Kessler, E. G.; Dewey, M. S.; Greene, G. L.; Deslattes, R. D.; Börner, H.

1991-10-01

165

Prospective Observational Study of the Impact of VIM-1 Metallo-?-Lactamase on the Outcome of Patients with Klebsiella pneumoniae Bloodstream Infections?  

PubMed Central

VIM-1-producing Klebsiella pneumoniae (VPKP) is an emerging pathogen. A prospective observational study was conducted to evaluate the importance of VIM production on outcome of patients with K. pneumoniae bloodstream infections (BSIs). Consecutive patients with K. pneumoniae BSIs were identified and followed up until patient discharge or death. A total of 162 patients were included in the analysis; 67 (41.4%) were infected with VPKP, and 95 were infected with non-VPKP. Fourteen of the patients infected with VPKP were carbapenem resistant (Carbr) (MIC > 4 ?g/ml), whereas none of the non-VPKP exhibited carbapenem resistance. The patients infected with a Carbr organism were more likely (odds ratio, 4.08; 95% confidence interval [CI], 1.29 to 12.85; P = 0.02) to receive inappropriate empirical therapy. The all-cause 14-day mortality rates were 15.8% (15 of 95) for patients infected with VIM-negative organisms, 18.9% (10 of 53) for those infected with VIM-positive carbapenem-susceptible organisms, and 42.9% (6 of 14) for those infected with VIM-positive Carbr organisms (P = 0.044). In Cox regression analysis, age (hazard ratio [HR], 1.03; 95% CI, 1.01 to 1.06; P = 0.021), rapidly fatal underlying disease (HR, 2.84; 95% CI, 1.26 to 6.39; P = 0.012), and carbapenem resistance (HR, 2.83; 95% CI, 1.08 to 7.41; P = 0.035) were independent predictors of death. After adjustment for inappropriate empirical or definitive therapy, the effect of carbapenem resistance on outcome was reduced to a level of nonsignificance. In patients with K. pneumoniae BSIs, carbapenem resistance, advanced, age, and severity of underlying disease were independent predictors of outcome, whereas VIM production had no effect on mortality. The higher mortality associated with carbapenem resistance was probably mediated by the failure to provide effective therapy.

Daikos, George L.; Petrikkos, Panayiotis; Psichogiou, Mina; Kosmidis, Chris; Vryonis, Evangelos; Skoutelis, Athanasios; Georgousi, Kleoniki; Tzouvelekis, Leonidas S.; Tassios, Panayotis T.; Bamia, Christina; Petrikkos, George

2009-01-01

166

Sequence of pNL194, a 79.3-Kilobase IncN Plasmid Carrying the blaVIM-1 Metallo-?-Lactamase Gene in Klebsiella pneumoniae?  

PubMed Central

The nucleotide sequence of pNL194, a VIM-1-encoding plasmid, is described in this study. pNL194 (79,307 bp) comprised an IncN-characteristic segment (38,940 bp) and a mosaic structure (40,367 bp) including blaVIM-1, aacA7, aadA1, aadA2, dfrA1, dfrA12, aphA1, strA, strB, and sul1. Tn1000 or Tn5501 insertion within fipA probably facilitated recruitment of additional mobile elements carrying resistance genes.

Miriagou, V.; Papagiannitsis, C. C.; Kotsakis, S. D.; Loli, A.; Tzelepi, E.; Legakis, N. J.; Tzouvelekis, L. S.

2010-01-01

167

Throughput of Wavelength Routing Networks.  

National Technical Information Service (NTIS)

We consider the problem of interconnecting N local area networks (LANs) through a wavelength routing all optical network (wavelength-routing AON) supporting F wavelengths at R b/s per wavelength. A wavelength-routing AON is one in which the path of a sign...

P. A. Humblet R. A. Barry

1994-01-01

168

Target localization based on wavelength multiplexing  

NASA Astrophysics Data System (ADS)

We present a method to localize a target in the three-dimensional space. The use of a white light optical correlator that gives us a different response depending on the scale of the input image permits to know the depth position of the particular target, since each different depth position of the target produces an image of different size when captured with a CCD camera. The setup is based on wavelength multiplexing since each different depth position, or analogously, each different scale in the captured image is detected with a different wavelength in the correlation plane.

Ferreira, Carlos; Refregier, Philippe; Esteve-Taboada, Jose J.; Garcia, Javier

2003-11-01

169

Early Detection of Colonization by VIM-1-Producing Klebsiella pneumoniae and NDM-1-Producing Escherichia coli in Two Children Returning to France ?  

PubMed Central

Rapid identification of metallo-?-lactamase-producing Gram-negative species is crucial for the timely implementation of infection control measures. We describe two pediatric cases in which colonization by VIM-1- and New Delhi metallo-beta-lactamase 1-producing Enterobacteriaceae was rapidly detected by phenotypic and genotypic methods. Phenotypic methods can be useful for routine detection of carbapenemase production.

Birgy, Andre; Doit, Catherine; Mariani-Kurkdjian, Patricia; Genel, Nathalie; Faye, Albert; Arlet, Guillaume; Bingen, Edouard

2011-01-01

170

Long wavelength infrared detector  

NASA Astrophysics Data System (ADS)

Long wavelength infrared detection is achieved by a detector made with layers of quantum well material bounded on each side by barrier material to form paired quantum wells, each quantum well having a single energy level. The width and depth of the paired quantum wells, and the spacing therebetween, are selected to split the single energy level with an upper energy level near the top of the energy wells. The spacing is selected for splitting the single energy level into two energy levels with a difference between levels sufficiently small for detection of infrared radiation of a desired wavelength.

Vasquez, Richard P.

1993-02-01

171

Multi-wavelength Sun  

NASA Technical Reports Server (NTRS)

This is a composite Sun in which four images, taken almost at the same time by the STEREO Behind spacecraft on May 1, 2007, were merged together. All of the images were taken in extreme ultraviolet wavelengths by the SECCHI instrument. Images in each wavelength capture solar features at different temperatures (from 60, 000 degrees C. to two million degrees C.) and at different levels above the Sun. Bright areas indicate active regions of intense magnetic activity. The spurt heading off to the right at the two o'clock position is an erupting prominence.

2007-01-01

172

Long wavelength infrared detector  

NASA Technical Reports Server (NTRS)

Long wavelength infrared detection is achieved by a detector made with layers of quantum well material bounded on each side by barrier material to form paired quantum wells, each quantum well having a single energy level. The width and depth of the paired quantum wells, and the spacing therebetween, are selected to split the single energy level with an upper energy level near the top of the energy wells. The spacing is selected for splitting the single energy level into two energy levels with a difference between levels sufficiently small for detection of infrared radiation of a desired wavelength.

Vasquez, Richard P. (inventor)

1993-01-01

173

Characterization of VIM-2, a Carbapenem-Hydrolyzing Metallo-?-Lactamase and Its Plasmid- and Integron-Borne Gene from a Pseudomonas aeruginosa Clinical Isolate in France  

PubMed Central

Pseudomonas aeruginosa COL-1 was identified in a blood culture of a 39-year-old-woman treated with imipenem in Marseilles, France, in 1996. This strain was resistant to ?-lactams, including ureidopenicillins, ticarcillin-clavulanic acid, cefepime, ceftazidime, imipenem, and meropenem, but remained susceptible to the monobactam aztreonam. The carbapenem-hydrolyzing ?-lactamase gene of P. aeruginosa COL-1 was cloned, sequenced, and expressed in Escherichia coli DH10B. The deduced 266-amino-acid protein was an Ambler class B ?-lactamase, with amino acid identities of 32% with B-II from Bacillus cereus; 31% with IMP-1 from several gram-negative rods in Japan, including P. aeruginosa; 27% with CcrA from Bacteroides fragilis; 24% with BlaB from Chryseobacterium meningosepticum; 24% with IND-1 from Chryseobacterium indologenes; 21% with CphA-1 from Aeromonas hydrophila; and 11% with L-1 from Stenotrophomonas maltophilia. It was most closely related to VIM-1 ?-lactamase recently reported from Italian P. aeruginosa clinical isolates (90% amino acid identity). Purified VIM-2 ?-lactamase had a pI of 5.6, a relative molecular mass of 29.7 kDa, and a broad substrate hydrolysis range, including penicillins, cephalosporins, cephamycins, oxacephamycins, and carbapenems, but not monobactams. As a metallo-?-lactamase, its activity was zinc dependent and inhibited by EDTA (50% inhibitory concentration, 50 ?M). VIM-2 conferred a resistance pattern to ?-lactams in E. coli DH10B that paralleled its in vitro hydrolytic properties, except for susceptibility to ureidopenicillins, carbapenems, and cefepime. blaVIM-2 was located on a ca. 45-kb plasmid that in addition conferred resistance to sulfamides and that was not self-transmissible either from P. aeruginosa to E. coli or from E. coli to E. coli. blaVIM-2 was the only gene cassette located within the variable region of a novel class 1 integron, In56, that was weakly related to the blaVIM-1-containing integron. VIM-2 is the second carbapenem-hydrolyzing metalloenzyme characterized from a P. aeruginosa isolate outside Japan.

Poirel, Laurent; Naas, Thierry; Nicolas, Delphine; Collet, Louis; Bellais, Samuel; Cavallo, Jean-Didier; Nordmann, Patrice

2000-01-01

174

Estimating the dunes coverage on Titan using VIMS/Cassini hyperspectral camera and RADAR/Cassini SAR swaths  

NASA Astrophysics Data System (ADS)

In order to study Titan's surface, we use the VIMS (Visual and Infrared Mapping Spectrometer) instrument which is able to see through Titan's methane atmosphere in seven spectral windows. VIMS is mainly sensitive to composition and grain size, and has a spatial resolution ranging from 500 m/pixel to several tens of km/pixel. RADAR images give complementary information on the surface: roughness, topography and morphology with a spatial resolution up to 300 m/pixel. In infrared, spectral criteria were used after empirical correction of aerosols in order to map the distribution of heterogeneous units (Le Mouélic et al., 2008) using false color composite images (red as 1.59/1.27-µm, green as 2.03/1.27-µm and blue as 1.27/1.08-µm). We have integrated these data with RADAR data in SAR mode from Ta (October 26th, 2004) to T41 (February 22th, 2008) into a Geographical Information System. The objective is to assess whether infrared units correlate with specific units in RADAR. Several distinct units can be identified in the infrared global maps: dark blue units, very bright features at 5 µm, white unit, and brown units. We observed in particular that brown units cover 18% of the whole Titan's surface and are found in equatorial regions. Dark blue units cover roughly 2% of Titan's surface. They are systematically associated with bright terrains. The dune fields (located in sand seas) in SAR images generally match the brown infrared terrains: 82% of SAR dunes are located in brown units. Dunes can also be found on dark blue terrains: 4.5% of SAR dunes are in dark blue units, as for example in the regions mapped by Barnes et al. (2007) and Soderblom et al. (2007). From this global mapping, we infer that dunes in the RADAR data are highly correlated with brown infrared terrains, and can overlap dark blue areas. Only 40% of the surface will be mapped by the RADAR at the end of the extended mission in 2010. The global coverage of the surface at medium resolution by VIMS can therefore be used to derive the distribution of dune materials, providing constrains on the total inventory of hydrocarbons on Titan.

Le Corre, L.; Le Mouélic, S.; Sotin, C.; Barnes, J.; Brown, R. H.; Buratti, B.; Jaumann, R.; Soderblom, J.; Soderblom, L. A.; Baines, K.

2009-04-01

175

Quantitative Millimetre Wavelength Spectrometry  

Microsoft Academic Search

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

John F Alder; John G Baker

2002-01-01

176

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

177

Long wavelength semiconductor lasers  

Microsoft Academic Search

During the last decade there has been immense activity in the field of semiconductor lasers. Long wavelength lasers have now reached the developmental stage and are being used in high speed optical fiber communications throughout the world. Research at AT and T Bell Labs has resulted in major developments in the area of semiconductor lasers. This book is the end

G. P. Agrawal; N. K. Dutta

1986-01-01

178

Scales  

ScienceCinema

Musical scales involve notes that, sounded simultaneously (chords), sound good together. The result is the left brain meeting the right brain — a Pythagorean interval of overlapping notes. This synergy would suggest less difference between the working of the right brain and the left brain than common wisdom would dictate. The pleasing sound of harmony comes when two notes share a common harmonic, meaning that their frequencies are in simple integer ratios, such as 3/2 (G/C) or 5/4 (E/C).

179

Scales  

SciTech Connect

Musical scales involve notes that, sounded simultaneously (chords), sound good together. The result is the left brain meeting the right brain — a Pythagorean interval of overlapping notes. This synergy would suggest less difference between the working of the right brain and the left brain than common wisdom would dictate. The pleasing sound of harmony comes when two notes share a common harmonic, meaning that their frequencies are in simple integer ratios, such as 3/2 (G/C) or 5/4 (E/C).

Murray Gibson

2007-04-27

180

Scales  

ScienceCinema

Musical scales involve notes that, sounded simultaneously (chords), sound good together. The result is the left brain meeting the right brain ? a Pythagorean interval of overlapping notes. This synergy would suggest less difference between the working of the right brain and the left brain than common wisdom would dictate. The pleasing sound of harmony comes when two notes share a common harmonic, meaning that their frequencies are in simple integer ratios, such as 3/2 (G/C) or 5/4 (E/C).

Murray Gibson

2010-01-08

181

Long wavelength irregularities in the equatorial electrojet  

Microsoft Academic Search

We have used the radar interferometer technique at Jicamarca to study in detail irregularities with wavelengths of a few kilometers generated in the unstable equatorial electrojet plasma during strong type 1 conditions. In-situ rocket observations of the same instability process are discussed in a companion paper. These large scale primary waves travel essentially horizontally and have large amplitudes. The vertical

Erhan Kudeki; Donald T. Farley; Bela G. Fejer

1982-01-01

182

Simultaneous infrared and ultraviolet observations of Saturn's aurora using Cassini VIMS and UVIS during the 2013 auroral campaign (Invited)  

NASA Astrophysics Data System (ADS)

The co-ordinated observing campaign of Saturn's aurora in April and May 2013 offered an unprecedented view of the auroral process, utilizing Cassini's remote sensing and in-situ instruments, ground-based infrared telescopes and the Hubble Space Telescope. Here, we focus on simultaneous infrared and ultraviolet emissions that were captured by the Cassini Visual and Infrared Mapping Spectrometer (VIMS) and the Ultraviolet Imaging Spectrograph (UVIS) instruments. These observations provides a view of a) the auroral precipitation inputs: electron energy flux, primary electron energy, and energy of secondaries that excite molecular hydrogen, and b) the response of the thermosphere and ionosphere to these inputs, via the analysis of the H3+ infrared spectrum. We explore the relation between energy input atmospheric response, and evaluate what role auroral energy deposition plays on the global energy balance.

Melin, H.; Stallard, T.; Badman, S. V.; Gustin, J.; Tao, C.; O'Donoghue, J.; Pryor, W. R.; Baines, K. H.; Blake, J. S.

2013-12-01

183

Detection of bla(IMP) and bla(VIM) metallo-?-lactamases genes among Pseudomonas aeruginosa strains.  

PubMed

Acquired Metallo-?-Lactamases (MBLs) are emerging resistance determinants in Pseudomonas aeruginosa and other gram-negative bacteria.Using Combination Disk Diffusion test, it was found that among 83 imipenem non-susceptible P. aeruginosa strains, 48 (57.9%) were MBL producers. PCR and Sequencing methods proved that these isolates were positive for blaIMP-1 genes, whereas none were positive for bla(VIM) genes. The mortality rate due to MBL-producing Pseudomonas infection was 4 (8.3%) among the hospitalized patients. Therefore, identification of drug resistance patterns in P. aeruginosa and detection of MBLs producing isolates are of great importance in the prevention and control of infections. PMID:23638331

Fallah, Fatemeh; Borhan, Rebwar Shams; Hashemi, Ali

2013-01-01

184

Detection of bla(IMP) and bla(VIM) metallo-?-lactamases genes among Pseudomonas aeruginosa strains  

PubMed Central

Acquired Metallo-?-Lactamases (MBLs) are emerging resistance determinants in Pseudomonas aeruginosa and other gram-negative bacteria.Using Combination Disk Diffusion test, it was found that among 83 imipenem non-susceptible P. aeruginosa strains, 48 (57.9%) were MBL producers. PCR and Sequencing methods proved that these isolates were positive for blaIMP-1 genes, whereas none were positive for bla(VIM) genes. The mortality rate due to MBL-producing Pseudomonas infection was 4 (8.3%) among the hospitalized patients. Therefore, identification of drug resistance patterns in P. aeruginosa and detection of MBLs producing isolates are of great importance in the prevention and control of infections.

Fallah, Fatemeh; Borhan, Rebwar Shams; Hashemi, Ali

2013-01-01

185

The atmospheres of Saturn and Titan in the near-infrared: First results of Cassini/Vims  

USGS Publications Warehouse

The wide spectral coverage and extensive spatial, temporal, and phase-angle mapping capabilities of the Visual Infrared Mapping Spectrometer (VIMS) onboard the Cassini-Huygens Orbiter are producing fundamental new insights into the nature of the atmospheres of Saturn and Titan. For both bodies, VIMS maps over time and solar phase angles provide information for a multitude of atmospheric constituents and aerosol layers, providing new insights into atmospheric structure and dynamical and chemical processes. For Saturn, salient early results include evidence for phosphine depletion in relatively dark and less cloudy belts at temperate and mid-latitudes compared to the relatively bright and cloudier Equatorial Region, consistent with traditional theories of belts being regions of relative downwelling. Additional Saturn results include (1) the mapping of enhanced trace gas absorptions at the south pole, and (2) the first high phase-angle, high-spatial-resolution imagery of CH4 fluorescence. An additional fundamental new result is the first nighttime near-infrared mapping of Saturn, clearly showing discrete meteorological features relatively deep in the atmosphere beneath the planet's sunlit haze and cloud layers, thus revealing a new dynamical regime at depth where vertical dynamics is relatively more important than zonal dynamics in determining cloud morphology. Zonal wind measurements at deeper levels than previously available are achieved by tracking these features over multiple days, thereby providing measurements of zonal wind shears within Saturn's troposphere when compared to cloudtop movements measured in reflected sunlight. For Titan, initial results include (1) the first detection and mapping of thermal emission spectra of CO, CO2, and CH3D on Titan's nightside limb, (2) the mapping of CH4 fluorescence over the dayside bright limb, extending to ??? 750 km altitude, (3) wind measurements of ???0.5 ms-1, favoring prograde, from the movement of a persistent (multiple months) south polar cloud near 88??S latitude, and (4) the imaging of two transient mid-southern-latitude cloud features. ?? Springer Science+Business Media, Inc. 2006.

Baines, K. H.; Momary, T. W.; Buratti, B. J.; Matson, D. L.; Nelson, R. M.; Drossart, P.; Sicardy, B.; Formisano, V.; Bellucci, G.; Coradini, A.; Griffith, C.; Brown, R. H.; Bibring, J. P.; Langevin, Y.; Capaccioni, F.; Cerroni, P.; Clark, R. N.; Combes, M.; Cruikshank, D. P.; Jaumann, R.; McCordt, T. B.; Mennella, V.; Nicholson, P. D.; Sotin, C.

2006-01-01

186

Saturn's North Polar Vortex Revealed by Cassini/VIMS: Zonal Wind Structure and Constraints on Cloud Distributions  

NASA Astrophysics Data System (ADS)

We present the first high-spatial resolution, near-nadir imagery and movies of Saturn's north polar region that reveal the wind structure of a north polar vortex. Obtained by Cassini/VIMS on June 15, 2008 from high over Saturn's polar region (sub-spacecraft latitude of 65 degrees N. lat) at an altitude of 0.42 million km during the long polar night, these 210-per-pixel images of the polar region north of 73 degrees N. latitude show several concentric cloud rings and hundreds of individual cloud features in silhouette against the 5-micron background thermal glow of Saturn's deep atmosphere. In contrast to the clear eye of the south polar vortex, the north polar vortex sports a central cloud feature about 650-km in diameter. Zonal winds reach a maximum of 150 m/s near 88 degrees N. latitude (planetocentric) - comparable to the south polar vortex maximum of 190 m/s near 88 degrees S. latitude - and fall off nearly monotonically to 10 m/s near 80 degrees N. latitude. At slightly greater distance from the pole, inside the north polar hexagon in the 75-77 degree N. latitude region, zonal winds increase dramatically to 130 m/s, as silhouetted clouds are seen speeding aroud the "race track” of the hexagonal feature. VIMS 5-micron thermal observations over a 1.6-year period from October 29, 2006 to June 15, 2008 are consistent with the polar hexagon structure itself remaining fixed in the Voyager-era radio rotation rate (Desch and Kaiser, Geophys. Res. Lett, 8, 253-256, 1981) to within an accuracy of 3 seconds per rotational period. This agrees with the stationary nature of the wave in this rotation system found by Godfrey (Icarus 76, 335-356, 1988), but is inconsistent with rotation rates found during the current Cassini era.

Baines, Kevin H.; Momary, T. W.; Fletcher, L. N.; Buratti, B. J.; Roos-Serote, M.; Showman, A. P.; Brown, R. H.; Clark, R. N.; Nicholson, P. D.

2008-09-01

187

Sub-wavelength diffractive optics  

SciTech Connect

This report represents the completion of a three-year Laboratory-Directed Research and Development (LDRD) program to investigate sub-wavelength surface relief structures fabricated by direct-write e-beam technology as unique and very high-efficiency optical elements. A semiconductor layer with sub-wavelength sized etched openings or features can be considered as a layer with an effective index of refraction determined by the fraction of the surface filled with semiconductor relative to the fraction filled with air or other material. Such as a layer can be used to implement planar gradient-index lenses on a surface. Additionally, the nanometer-scale surface structures have diffractive properties that allow the direct manipulation of polarization and altering of the reflective properties of surfaces. With this technology a single direct-write mask and etch can be used to integrate a wide variety of optical functions into a device surface with high efficiencies; allowing for example, direct integration of polarizing optics into the surface with high efficiencies; allowing for example, direct integration of polarizing optics into the surfaces of devices, forming anti-reflection surfaces or fabricating high-efficiency, high-numerical aperture lenses, including integration inside vertical semiconductor laser cavities.

Warren, M.E.; Wendt, J.R.; Vawter, G.A.

1998-03-01

188

Astronomical Studies at Infrared Wavelengths  

NASA Technical Reports Server (NTRS)

Astronomical studies at infrared wavelengths have dramatically improved our understanding of the universe, and observations with Spitzer, Herschel, and SOFIA will continue to provide exciting new discoveries. The relatively low angular resolution of these missions, however, is insufficient to resolve the physical scale on which mid-to far-infrared emission arises, resulting in source and structure ambiguities that limit our ability to answer key science questions. Interferometry enables high angular resolution at these wavelengths - a powerful tool for scientific discovery. We will build the Balloon Experimental Twin Telescope for Infrared Interferometry (BETTII), an eight-meter baseline Michelson stellar interferometer to fly on a high-altitude balloon. BETTII's spectral-spatial capability, provided by an instrument using double-Fourier techniques, will address key questions about the nature of disks in young star clusters and active galactic nuclei and the envelopes of evolved stars. BETTII will also lay the technological groundwork for future balloon programs, paving the way for interferometric observations of exoplanets.

Rinehart, Stephen A.

2009-01-01

189

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

190

Mechanical Property and Stress Corrosion Evaluation of VIM-ESR-VAR (Vaccum Induction Melted, Electro-Slag Remelted, Vaccum Are Remelted) Work Strengthened and Direct Double Aged Inconel 718 Bar Material.  

National Technical Information Service (NTIS)

Presented are the mechanical properties and the stress corrosion resistance of triple melted vacuum induction melted (VIM), electro-slag remelted (ESR), and vacuum arc remelted (VAR), solution treated, work strengthened and direct double aged Inconel 718 ...

J. W. Montano

1986-01-01

191

Connectivity and Sparse Wavelength Conversion in Wavelength-Routing Networks  

Microsoft Academic Search

Wavelength-routing networks offer the advantages of wavelength re-use and scalability over broadcast-and-select networks and are therefore suitable for wide area networks (WANs). We study the effects of topological connectivity and wavelength conversion in circuit-switched all-optical wavelength-routing networks. An approximate blocking analysis of such network is performed. We first propose an improved framework for the analysis of networks with arbitrary topology.

Suresh Subramaniam; Murat Azizoglu; Arun K. Somani

1996-01-01

192

Short wavelength chemical lasers  

SciTech Connect

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

Jeffers, W.Q.

1989-01-01

193

Wavelength conversion in optical networks  

Microsoft Academic Search

In many models of optical routing, we are given a set of communication paths in a network, and we must assign a wavelength to each path so that paths sharing an edge receive dieren t wavelengths. The goal is to assign as few wavelengths as possible, in order to make as ecien t use as possible of the optical bandwidth.

Jon M. Kleinberg; Amit Kumar

1999-01-01

194

Dynamic digital holographic wavelength filtering  

Microsoft Academic Search

This paper describes the theory and results of a new generic technology for use in optical telecommunications and wavelength division multiplexing (WDM): dynamic digital holographic wavelength filtering. The enabling component is a polarization-insensitive ferroelectric liquid crystal (FLC) spatial light modulator (SLM) in conjunction with a highly wavelength-dispersive fixed diffractive element. The technology has been used to perform demultiplexing of single

Michael C. Parker; Adam D. Cohen; Robert J. Mears

1998-01-01

195

Wavelength meter having elliptical wedge  

DOEpatents

A wavelength meter is disclosed which can determine the wavelength of a laser beam from a laser source within an accuracy range of two parts in 10[sup 8]. The wavelength meter has wedge having an elliptically shaped face to the optical path of the laser source and includes interferometer plates which form a vacuum housing. 7 figs.

Hackel, R.P.; Feldman, M.

1992-12-01

196

Wavelength sensitivity in polymer photodegradation  

Microsoft Academic Search

This review examines the terminology and experimental approaches used to describe wavelength sensitivity in polymer photodegradation and summarizes the data published on the subject. Wavelength sensitivity or the efficacy of different regions or individual wavelengths in the ultra violet-visible region of the spectrum is usually expressed in terms of action and activation spectra. An action spectrum shows the effectiveness of

Anthony L. Andrady

197

Wavelength meter having elliptical wedge  

DOEpatents

A wavelength meter is disclosed which can determine the wavelength of a laser beam from a laser source within an accuracy range of two parts in 10.sup.8. The wavelength meter has wedge having an elliptically shaped face to the optical path of the laser source and includes interferometer plates which form a vacuum housing.

Hackel, Richard P. (Livermore, CA) [Livermore, CA; Feldman, Mark (Livermore, CA) [Livermore, CA

1992-01-01

198

Metallo-?-lactamase-producing Enterobacteriaceae isolates in a university hospital in Taiwan: prevalence of IMP8 in Enterobacter cloacae and first identification of VIM2 in Citrobacter freundii  

Microsoft Academic Search

A total of 9082 clinical isolates of Enterobacteriaceae other than Klebsiella spp. collected in 1999 and 2000 at a university hospital in Taiwan were investigated for the production of metallo- ?-lactamases (MBLs). Thirty-six (2.9%) of the 1261 Enterobacter cloacae isolates and one (0.3%) of the 340 Citrobacter freundii isolates were found to carry blaIMP-8 and blaVIM-2, respectively, by colony hybridization,

Jing-Jou Yan; Wen-Chien Ko; Chin-Luan Chuang; Jiunn-Jong Wu

199

Nosocomial Outbreak of VIM-1-Producing Klebsiella pneumoniae Isolates of Multilocus Sequence Type 15: Molecular Basis, Clinical Risk Factors, and Outcome  

PubMed Central

We study the epidemiology, molecular basis, clinical risk factors, and outcome involved in the clonal dissemination of VIM-1-producing Klebsiella pneumoniae isolates in the hospital setting. All patients infected/colonized by carbapenem-nonsusceptible K. pneumoniae (CNSKP) in 2009 were included. Molecular epidemiology was studied by pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST). Antibiotic resistance genes were analyzed by PCR and sequencing. Plasmids were studied by PFGE with S1 nuclease digestion and for incompatibility group by a PCR-based replicon typing scheme. Risk factors associated with CNSKP colonization/infection were assessed by an observational case-control study. All 55 patients studied were infected (n = 28) or colonized (n = 27) by VIM-1-producing K. pneumoniae. All but one acquired isolates of a single clone (PFGE cluster 1 [C1], sequence type 15 [ST15]), while another clone (PFGE C2, ST340) was detected in four patients. C1 isolates also produced the new extended-spectrum ?-lactamase SHV-134. blaVIM-1 was carried in a class 1 integron and an untypeable plasmid of ?50 bp. The number of days that the patient received mechanical ventilation, the use of parenteral nutrition, previous treatment with linezolid, and treatment with extended-spectrum cephalosporins for more than 7 days were detected to be independent risk factors for CNSKP acquisition. The VIM-1-producing K. pneumoniae ST15 clone has a high capacity to spread among intensive care unit patients with severe underlying conditions. A high rate of associated mortality and great difficulty in controlling the spread of this clone, without permanent behavioral changes in the personnel, were observed.

Sanchez-Romero, Isabel; Asensio, Angel; Munoz-Algarra, Maria; Isidoro, Beatriz; Vindel, Ana; Alvarez-Avello, Jose; Balandin-Moreno, Barbara; Cuevas, Oscar; Fernandez-Romero, Sara; Azanedo, Luisa; Saez, David; Campos, Jose

2012-01-01

200

Linkage of acquired quinolone resistance (qnrS1) and metallo-b-lactamase (blaVIM-1) genes in multiple species of Enterobacteriaceae from Bolzano, Italy  

Microsoft Academic Search

Results: The 24 isolates with positive EDTA\\/imipenem synergy tests had blaVIM-1 carried on 40-150 kb plasmids. Imipenem MICs ranged from 2 to >32 mg\\/L, while those of meropenem and ertapenem were lower. The isolates included a clonal cluster of 10 Klebsiella pneumoniae, two other K. pneumoniae isolates, and diverse isolates of Escherichia coli (seven), Klebsiella oxytoca (three) and Citrobacter freundii

Richard Aschbacher; Michel Doumith; David M. Livermore; Clara Larcher; Neil Woodford

2008-01-01

201

Nosocomial outbreak of VIM-1-producing Klebsiella pneumoniae isolates of multilocus sequence type 15: molecular basis, clinical risk factors, and outcome.  

PubMed

We study the epidemiology, molecular basis, clinical risk factors, and outcome involved in the clonal dissemination of VIM-1-producing Klebsiella pneumoniae isolates in the hospital setting. All patients infected/colonized by carbapenem-nonsusceptible K. pneumoniae (CNSKP) in 2009 were included. Molecular epidemiology was studied by pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST). Antibiotic resistance genes were analyzed by PCR and sequencing. Plasmids were studied by PFGE with S1 nuclease digestion and for incompatibility group by a PCR-based replicon typing scheme. Risk factors associated with CNSKP colonization/infection were assessed by an observational case-control study. All 55 patients studied were infected (n = 28) or colonized (n = 27) by VIM-1-producing K. pneumoniae. All but one acquired isolates of a single clone (PFGE cluster 1 [C1], sequence type 15 [ST15]), while another clone (PFGE C2, ST340) was detected in four patients. C1 isolates also produced the new extended-spectrum ?-lactamase SHV-134. bla(VIM-1) was carried in a class 1 integron and an untypeable plasmid of ?50 bp. The number of days that the patient received mechanical ventilation, the use of parenteral nutrition, previous treatment with linezolid, and treatment with extended-spectrum cephalosporins for more than 7 days were detected to be independent risk factors for CNSKP acquisition. The VIM-1-producing K. pneumoniae ST15 clone has a high capacity to spread among intensive care unit patients with severe underlying conditions. A high rate of associated mortality and great difficulty in controlling the spread of this clone, without permanent behavioral changes in the personnel, were observed. PMID:22005997

Sánchez-Romero, Isabel; Asensio, Angel; Oteo, Jesús; Muñoz-Algarra, María; Isidoro, Beatriz; Vindel, Ana; Alvarez-Avello, José; Balandín-Moreno, Bárbara; Cuevas, Oscar; Fernández-Romero, Sara; Azañedo, Luisa; Sáez, David; Campos, José

2012-01-01

202

Photometric properties of Titan's surface from Cassini VIMS: Relevance to titan's hemispherical albedo dichotomy and surface stability  

USGS Publications Warehouse

The Visual and Infrared Mapping Spectrometer (VIMS) instrument on the Cassini Saturn Orbiter returned spectral imaging data as the spacecraft undertook six close encounters with Titan beginning 7 July, 2004. Three of these flybys each produced overlapping coverage of two distinct regions of Titan's surface. Twenty-four points were selected on approximately opposite hemispheres to serve as photometric controls. Six points were selected in each of four reflectance classes. On one hemisphere each control point was observed at three distinct phase angles. From the derived phase coefficients, preliminary normal reflectances were derived for each reflectance class. The normal reflectance of Titan's surface units at 2.0178 ??m ranged from 0.079 to 0.185 for the most absorbing to the most reflective units assuming no contribution from absorbing haze. When a modest haze contribution of ??=0.1 is considered these numbers increase to 0.089-0.215. We find that the lowest three reflectance classes have comparable normal reflectance on either hemisphere. However, for the highest brightness class the normal reflectance is higher on the hemisphere encompassing longitude 14-65?? compared to the same high brightness class for the hemisphere encompassing 122-156?? longitude. We conclude that an albedo dichotomy observed in continental sized units on Titan is due not only to one unit having more areal coverage of reflective material than the other but the material on the brighter unit is intrinsically more reflective than the most reflective material on the other unit. This suggests that surface renewal processes are more widespread on Titan's more reflective units than on its less reflective units. We note that one of our photometric control points has increased in reflectance by 12% relative to the surrounding terrain from July of 2004 to April and May of 2005. Possible causes of this effect include atmospheric processes such as ground fog or orographic clouds; the suggestion of active volcanism cannot be ruled out. Several interesting circular features which resembled impact craters were identified on Titan's surface at the time of the initial Titan flyby in July of 2004. We traced photometric profiles through two of these candidate craters and attempted to fit these profiles to the photometric properties expected from model depressions. We find that the best-fit attempt to model these features as craters requires that they be unrealistically deep, approximately 70 km deep. We conclude that despite their appearance, these circular features are not craters, however, the possibility that they are palimpsests cannot be ruled out. We used two methods to test for the presence of vast expanses of liquids on Titan's surface that had been suggested to resemble oceans. Specular reflection of sunlight would be indicative of widespread liquids on the surface; we found no evidence of this. A large liquid body should also show uniformity in photometric profile; we found the profiles to be highly variable. The lack of specular reflection and the high photometric variability in the profiles across candidate oceans is inconsistent with the presence of vast expanses of flat-lying liquids on Titan's surface. While liquid accumulation may be present as small, sub-pixel-sized bodies, or in areas of the surface which still remain to be observed by VIMS, the presence of large ocean-sized accumulations of liquids can be ruled out. The Cassini orbital tour offers the opportunity for VIMS to image the same parts of Titan's surface repeatedly at many different illumination and observation geometries. This creates the possibility of understanding the properties of Titan's atmosphere and haze by iteratively adapting models to create a best fit to the surface reflectance properties. ?? 2006 Elsevier Ltd. All rights reserved.

Nelson, R. M.; Brown, R. H.; Hapke, B. W.; Smythe, W. D.; Kamp, L.; Boryta, M. D.; Leader, F.; Baines, K. H.; Bellucci, G.; Bibring, J. -P.; Buratti, B. J.; Capaccioni, F.; Cerroni, P.; Clark, R. N.; Combes, M.; Coradini, A.; Cruikshank, D. P.; Drossart, P.; Formisano, V.; Jaumann, R.; Langevin, Y.; Matson, D. L.; McCord, T. B.; Mennella, V.; Nicholson, P. D.; Sicardy, B.; Sotin, C.

2006-01-01

203

Antibiotic Resistance Pattern and Evaluation of Metallo-Beta Lactamase Genes Including bla- IMP and bla- VIM Types in Pseudomonas aeruginosa Isolated from Patients in Tehran Hospitals.  

PubMed

Beta-lactamase producing strains of Pseudomonas aeruginosa are important etiological agents of hospital infections. Carbapenems are among the most effective antibiotics used against Pseudomonas infections, but they can be rendered infective by group B ? -lactamase, commonly called metallo-beta lactamase. In this study, the antimicrobial sensitivity patterns of P. aeruginosa strains isolated from 9 different hospitals in Tehran, Iran, as well as the prevalence of MBLs genes (bla- VIM and bla- IMP ) were determined. A total of 212 strains of P. aeruginosa recovered from patients in hospitals in Tehran were confirmed by both biochemical methods and PCR. Their antimicrobial sensitivity patterns were determined by Kirby-Bauer disk diffusion method. Following MIC determination, imipenem resistant strains were selected by DDST method which was followed by PCR tests for determination of MBLs genes: bla- IMP and bla- VIM . The results indicated that, in the DDST phenotypic method, among the 100 imipenem resistant isolates, 75 strains were MBLs positive. The PCR test indicated that 70 strains (33%) carried bla- VIM gene and 20 strains (9%) harbored bla- IMP . The results indicated that the extent of antibiotic resistance among Pseudomonas aeruginosa is on the rise. This may be due to production of MBLs enzymes. Therefore, determination of antibiotic sensitivity patterns and MBLs production by these bacteria, can be important in control of clinical Pseudomonas infection. PMID:24944839

Aghamiri, Samira; Amirmozafari, Nour; Fallah Mehrabadi, Jalil; Fouladtan, Babak; Samadi Kafil, Hossein

2014-01-01

204

A newly discovered impact crater in Titan's Senkyo: Cassini VIMS observations and comparison with other impact features  

USGS Publications Warehouse

Senkyo is an equatorial plain on Titan filled with dunes and surrounded by hummocky plateaus. During the Titan targeted flyby T61 on August 25, 2009, the Cassini Visual and Infrared Mapping Spectrometer (VIMS) onboard the Cassini spacecraft observed a circular feature, centered at 5.4?? N and 341??W, that superimposes the dune fields and a bright plateau. This circular feature, which has been named Paxsi by the International Astronomical Union, is 120??10 km in diameter (measured from the outer edge of the crater rim) and exhibits a central bright area that can be interpreted as the central peak or pit of an impact crater. Although there are only a handful of certain impact craters on Titan, there are two other craters that are of similar size to this newly discovered feature and that have been studied by VIMS: Sinlap (Le Mou??lic et al, 2008) and Selk (Soderblom et al, 2010). Sinlap is associated with a large downwind, fan-like feature that may have been formed from an impact plume that rapidly expanded and deposited icy particles onto the surface. Although much of the surrounding region is covered with dunes, the plume region is devoid of dunes. The formation process of Selk also appears to have removed (or covered up) dunes from parts of the adjacent dune-filled terrain. The circular feature on Senkyo is quite different: there is no evidence of an ejecta blanket and the crater itself appears to be infilled with dune material. The rim of the crater appears to be eroded by fluvial processes; at one point the rim is breached. The rim is unusually narrow, which may be due to mass wasting on its inside and subsequent infill by dunes. Based on these observations, we interpret this newly discovered feature to be a more eroded crater than both Sinlap and Selk. Paxsi may have formed during a period when Titan was warmer and more ductile than it is currently. ?? 2011 Elsevier Ltd. All rights reserved.

Buratti, B. J.; Sotin, C.; Lawrence, K.; Brown, R. H.; Le, Mouelic, S.; Soderblom, J. M.; Barnes, J.; Clark, R. N.; Baines, K. H.; Nicholson, P. D.

2012-01-01

205

Compositional mapping of Saturn's satellite Dione with Cassini VIMS and implications of dark material in the Saturn system  

USGS Publications Warehouse

Cassini VIMS has obtained spatially resolved imaging spectroscopy data on numerous satellites of Saturn. A very close fly-by of Dione provided key information for solving the riddle of the origin of the dark material in the Saturn system. The Dione VIMS data show a pattern of bombardment of fine, sub-0.5-??m diameter particles impacting the satellite from the trailing side direction. Multiple lines of evidence point to an external origin for the dark material on Dione, including the global spatial pattern of dark material, local patterns including crater and cliff walls shielding implantation on slopes facing away from the trailing side, exposing clean ice, and slopes facing the trailing direction which show higher abundances of dark material. Multiple spectral features of the dark material match those seen on Phoebe, Iapetus, Hyperion, Epimetheus and the F-ring, implying the material has a common composition throughout the Saturn system. However, the exact composition of the dark material remains a mystery, except that bound water and, tentatively, ammonia are detected, and there is evidence both for and against cyanide compounds. Exact identification of composition requires additional laboratory work. A blue scattering peak with a strong UV-visible absorption is observed in spectra of all satellites which contain dark material, and the cause is Rayleigh scattering, again pointing to a common origin. The Rayleigh scattering effect is confirmed with laboratory experiments using ice and 0.2-??m diameter carbon grains when the carbon abundance is less than about 2% by weight. Rayleigh scattering in solids is also confirmed in naturally occurring terrestrial rocks, and in previously published reflectance studies. The spatial pattern, Rayleigh scattering effect, and spectral properties argue that the dark material is only a thin coating on Dione's surface, and by extension is only a thin coating on Phoebe, Hyperion, and Iapetus, although the dark material abundance appears higher on Iapetus, and may be locally thick. As previously concluded for Phoebe, the dark material appears to be external to the Saturn system and may be cometary in origin. We also report a possible detection of material around Dione which may indicate Dione is active and contributes material to the E-ring, but this observation must be confirmed.

Clark, R. N.; Curchin, J. M.; Jaumann, R.; Cruikshank, D. P.; Brown, R. H.; Hoefen, T. M.; Stephan, K.; Moore, J. M.; Buratti, B. J.; Baines, K. H.; Nicholson, P. D.; Nelson, R. M.

2008-01-01

206

ECM at millimeter wavelengths  

NASA Astrophysics Data System (ADS)

ECM techniques appropriate to the millimeter wave band are examined with particular reference to the physics of the atmosphere and component performance capability. Model calculations show that even for state-of-the-art threat radars, the required ECM receiver sensitivity is well within the state-of-the-art for broadband superheterodyne systems. For ECM jammers, the most fundamental limitation arises from deficiencies in broadband/high power amplifiers. The solution to this problem will require different ECM system architectures than used at the lower frequencies. At millimeter wavelengths, atmospheric effects permit new jamming techniques requiring lower jamming power. For example, scattering by hydrometeors significantly raises the apparent sidelobe level of even low sidelobe antennas of threat radars, which reduces the power required to infringe through the sidelobes.

Copper, H. W.; Littlepage, R. S.

1982-09-01

207

Semiconductor Wavelength Tunable Optical Filters  

NASA Astrophysics Data System (ADS)

Wavelength-division multiplexing (WDM) lightwave transmission systems and wavelength-division (WD) photonic switching systems are attractive for improvement in line capacity for lightwave telecommunication services, because they utilize a huge wavelength (frequency) domain as signal channels. Wavelength tunable optical filters are key devices for these WDM and WD systems in direct detection scheme. In particular, semiconductor wavelength tunable optical filters are suitable for monolithic integration with photonic devices such as semiconductor lasers, switches and detectors. Also, the switching speed of wavelength is faster than that of other optical filters. This paper briefly summarizes the state-of-the-art semiconductor wavelength tunable optical filters and their applications to WD photonic switching systems.

Numai, T.

208

Storm clouds on Saturn: Lightning-induced chemistry and associated materials consistent with Cassini/VIMS spectra  

USGS Publications Warehouse

Thunderstorm activity on Saturn is associated with optically detectable clouds that are atypically dark throughout the near-infrared. As observed by Cassini/VIMS, these clouds are ~20% less reflective than typical neighboring clouds throughout the spectral range from 0.8 ??m to at least 4.1 ??m. We propose that active thunderstorms originating in the 10-20 bar water-condensation region vertically transport dark materials at depth to the ~1 bar level where they can be observed. These materials in part may be produced by chemical processes associated with lightning, likely within the water clouds near the ~10 bar freezing level of water, as detected by the electrostatic discharge of lightning flashes observed by Cassini/RPWS (e.g., Fischer et al. 2008, Space Sci. Rev., 137, 271-285). We review lightning-induced pyrolytic chemistry involving a variety of Saturnian constituents, including hydrogen, methane, ammonia, hydrogen sulfide, phosphine, and water. We find that the lack of absorption in the 1-2 ??m spectral region by lightning-generated sulfuric and phosphorous condensates renders these constituents as minor players in determining the color of the dark storm clouds. Relatively small particulates of elemental carbon, formed by lightning-induced dissociation of methane and subsequently upwelled from depth - perhaps embedded within and on the surface of spectrally bright condensates such as ammonium hydrosulfide or ammonia - may be a dominant optical material within the dark thunderstorm-related clouds of Saturn. ?? 2009 Elsevier Ltd. All rights reserved.

Baines, K. H.; Delitsky, M. L.; Momary, T. W.; Brown, R. H.; Buratti, B. J.; Clark, R. N.; Nicholson, P. D.

2009-01-01

209

Saturn's Great Storm of 2010-2011: Evidence for ammonia and water ices from analysis of VIMS spectra  

NASA Astrophysics Data System (ADS)

Our analysis of Cassini/VIMS near-infrared spectra of Saturn's Great Storm of 2010-2011 reveals a multi-component aerosol composition comprised primarily of ammonia ice, with a significant component of water ice. The most likely third component is ammonium hydrosulfide or some weakly absorbing material similar to what dominates visible clouds outside the storm region. Horizontally heterogeneous models favor ammonium hydrosulfide as the third component, while horizontally uniform models favor the weak absorber. Both models rely on water ice absorption to compensate for residual spectral gradients produced by ammonia ice from 3.0 ?m to 3.1 ?m and need the third component to fill in the sharp ammonia ice absorption peak near 2.96 ?m. The best heterogeneous model has spatial coverage fractions of 55% ammonia ice, 22% water ice, and 23% ammonium hydrosulfide. The best homogeneous model has an optically thin layer of weakly absorbing particles above an optically thick layer of water ice particles coated by ammonia ice. This is the first spectroscopic evidence of water ice in Saturn's atmosphere, found near the level of Saturn's visible cloud deck where it could only be delivered by powerful convection originating from ˜200 km deeper in the atmosphere.

Sromovsky, L. A.; Baines, K. H.; Fry, P. M.

2013-09-01

210

Self-gravity wake structures in Saturn's a ring revealed by Cassini vims  

USGS Publications Warehouse

During the summer of 2005, the Visual and Infrared Mapping Spectrometer onboard the Cassini spacecraft observed a series of occultations of the star o Ceti (Mira) by Saturn's rings. These observations revealed pronounced variations in the optical depth of the A ring with longitude, which can be attributed to oriented structures in the rings known as self-gravity wakes. While the wakes themselves are only tens of meters across and below the resolution of the measurements, we are able to obtain information about the orientation and shapes of these structures by comparing the observed transmission at different longitudes with predictions from a simple model. Our findings include the following: (1) The orientation of the wakes varies systematically with radius, trailing by between 64?? and 72?? relative to the local radial direction. (2) The maximum transmission peaks at roughly 8% for B = 3.45?? in the middle A ring (???129,000 km). (3) Both the wake orientation and maximum transmission vary anomalously in the vicinity of two strong density waves (Janus 5:4 and Mimas 5:3). (4) The ratio of the wake vertical thickness H to the wake pattern wavelength ?? (assuming infinite, straight, regularly-spaced wake structures) varies from 0.12 to 0.09 across the A ring. Gravitational instability theory predicts ?? ??? 60 m, which suggests that the wake structures in the A ring are only ???6 m thick. ?? 2007. The American Astronomical Society. All rights reserved.

Hedman, M. M.; Nicholson, P. D.; Salo, H.; Wallis, B. D.; Buratti, B. J.; Baines, K. H.; Brown, R. H.; Clark, R. N.

2007-01-01

211

Digital holography at millimetre wavelengths  

Microsoft Academic Search

In this paper, we describe a method for wavefront reconstruction at millimetre wavelengths using off-axis holography, a frequently used image recording technique at visible wavelengths first demonstrated in the 1960’s. Millimetre radiation has been highlighted recently in the imaging of non-conducting materials and objects, which often show significant transparency at these long wavelengths, even though opaque at visible and infrared

Ronan J. Mahon; J. Anthony Murphy; William Lanigan

2006-01-01

212

Titan: Preliminary results on surface properties and photometry from VIMS observations of the early flybys  

USGS Publications Warehouse

Cassini observations of the surface of Titan offer unprecedented views of its surface through atmospheric windows in the 1-5 ??m region. Images obtained in windows for which the haze opacity is low can be used to derive quantitative photometric parameters such as albedo and albedo distribution, and physical properties such as roughness and particle characteristics. Images from the early Titan flybys, particularly T0, Ta, and T5 have been analyzed to create albedo maps in the 2.01 and 2.73 ??m windows. We find the average normal reflectance at these two wavelengths to be 0.15??0.02 and 0.035??0.003, respectively. Titan's surface is bifurcated into two albedo regimes, particularly at 2.01 ??m. Analysis of these two regimes to understand the physical character of the surface was accomplished with a macroscopic roughness model. We find that the two types of surface have substantially different roughness, with the low-albedo surface exhibiting mean slope angles of ???18??, and the high-albedo terrain having a much more substantial roughness with a mean slope angle of ???34??. A single-scattering phase function approximated by a one-term Henyey-Greenstein equation was also fit to each unit. Titan's surface is back-scattering (g???0.3-0.4), and does not exhibit substantially different backscattering behavior between the two terrains. Our results suggest that two distinct geophysical domains exist on Titan: a bright region cut by deep drainage channels and a relatively smooth surface. The two terrains are covered by a film or a coating of particles perhaps precipitated from the satellite's haze layer and transported by eolian processes. Our results are preliminary: more accurate values for the surface albedo and physical parameters will be derived as more data is gathered by the Cassini spacecraft and as a more complete radiative transfer model is developed from both Cassini orbiter and Huygens Lander measurements. ?? 2006 Elsevier Ltd. All rights reserved.

Buratti, B. J.; Sotin, C.; Brown, R. H.; Hicks, M. D.; Clark, R. N.; Mosher, J. A.; McCord, T. B.; Jaumann, R.; Baines, K. H.; Nicholson, P. D.; Momary, T.; Simonelli, D. P.; Sicardy, B.

2006-01-01

213

Metallo-beta-lactamase-producing Gram-negative bacilli in Korean Nationwide Surveillance of Antimicrobial Resistance group hospitals in 2003: continued prevalence of VIM-producing Pseudomonas spp. and increase of IMP-producing Acinetobacter spp.  

PubMed

Metallo-beta-lactamase (MBL)-producing Pseudomonas spp. and Acinetobacter spp. were prevalent in Korean hospitals. In this study, the prevalence and presence of MBL-producing isolates among imipenem-nonsusceptible and imipenem-susceptible isolates, respectively, were screened. The genetic and phenotypic characteristics of MBL-producing isolates were determined. Among imipenem-nonsusceptible isolates, 52 (11.1%) of 467 Pseudomonas spp. were blaVIM-like allele-positive, and 33 (15.1%) of 218 Acinetobacter spp. were either blaVIM- or blaIMP-like allele-positive. One blaVIM-like allele-positive isolate of Acinetobacter spp. was detected among 84 imipenem-susceptible Acinetobacter isolates. The minimum inhibitory concentration for 90% of isolates of imipenem was higher (>128 microg/mL) for Pseudomonas spp. than Acinetobacter spp. (16 microg/mL), although both had blaVIM-like allele. The source of MBL-producing isolates was mostly the sputum and urine of patients in the intensive care unit. Pulsed-field gel electrophoresis analysis suggested the intra- and inter-hospital spread of MBL-producing strains at some hospitals. In conclusion, blaVIM-like allele-positive P. aeruginosa remained highly prevalent, and the proportion of blaIMP-like allele-positive Acinetobacter spp. has increased significantly in most Korean hospitals. PMID:15380278

Lee, Kyungwon; Ha, Gyoung Yim; Shin, Bo-Moon; Kim, Jin Ju; Kang, Jung Oak; Jang, Sook Jin; Yong, Dongeun; Chong, Yunsop

2004-09-01

214

Wavelength conversion devices and techniques  

Microsoft Academic Search

Wavelength division multiplexed (WDM) networks are currently subject to an immense interest because of the extra capacity and flexibility they provide together with the possibilities for graceful system upgrades. For full network flexibility it is very attractive to be able to translate the channel wavelengths in an easy way and preferably without opto-electronic conversion. Here, we will first briefly look

K. E. Stubkjaer; C. Joergensen; S. L. Danielsen; B. Mikkelsen; M. Vaa; R. J. Pedersen; H. Povlsen; M. Schilling; K. Daub; K. Dutting; W. Idler; M. Klenk; E. Lach; G. Laube; K. Wunstel; P. Doussiere; A. Jourdan; F. Pommerau; G. Soulange; L. Goldstein; J. Y. Emery; N. Vodjdani; F. Ratovelomanana; A. Enard; G. Glastre; D. Rondi; R. Blondeau

1996-01-01

215

Blackbody Radiation: Frequency and Wavelength  

NSDL National Science Digital Library

The Blackbody Radiation: Frequency and Wavelength model simulates the blackbody radiation curves of Planck both as a function of frequency and as a function of wavelength to allow for comparison of the two functions. The Planck radiation law can be derived both as a function of frequency and as a function of wavelength. In doing so, one gets two slightly different expressions for the energy density per frequency (wavelength) as a function of frequency (wavelength. Shown in the main window is a schematic of a blackbody cavity showing (on the right) the color of the radiation emitted. The graph plots the energy density per frequency (wavelength) as a function of frequency (wavelength and shows the visible spectrum. One can switch between the two functions by using the radio buttons provided. A slider alows the twmperature to be set or changed. The Blackbody Radiation: Frequency and Wavelength model was created using the Easy Java Simulations (EJS) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the ejs_qm_blackbody_fw.jar file will run the program if Java is installed.

Palop, Jose I.

2010-12-12

216

On the discovery of CO nighttime emissions on Titan by Cassini/VIMS: Derived stratospheric abundances and geological implications  

USGS Publications Warehouse

We present a quantitative analysis of CO thermal emissions discovered on the nightside of Titan by Baines et al. [2005. The atmospheres of Saturn and Titan in the near-infrared: First results of Cassini/VIMS. Earth, Moon, and Planets, 96, 119-147]. in Cassini/VIMS spectral imagery. We identify these emission features as the P and R branches of the 1-0 vibrational band of carbon monoxide (CO) near 4.65 ??m. For CH3D, the prominent Q branch of the ??2 fundamental band of CH3D near 4.55 ??m is apparent. CO2 emissions from the strong v3 vibrational band are virtually absent, indicating a CO2 abundance several orders of magnitude less than CO, in agreement with previous investigations. Analysis of CO emission spectra obtained over a variety of altitudes on Titan's nightside limb indicates that the stratospheric abundance of CO is 32??15 ppm, and together with other recent determinations, suggests a vertical distribution of CO nearly constant at this value from the surface throughout the troposphere to at least the stratopause near 300 km altitude. The corresponding total atmospheric content of CO in Titan is ???2.9??1.5??1014 kg. Given the long lifetime of CO in the oxygen-poor Titan atmosphere (???0.5-1.0 Gyr), we find a mean CO atmospheric production rate of 6??3??105 kg yr-1. Given the lack of primordial heavy noble gases observed by Huygens [Niemann et al., 2005. The abundances of constituents of Titan's atmosphere from the GCMS on the Huygens probe. Nature, 438, 779-784], the primary source of atmospheric CO is likely surface emissions. The implied CO/CH4 mixing ratio of near-surface material is 1.8??0.9??10-4, based on an average methane surface emission rate over the past 0.5 Gyr of 1.3??10-13 gm cm-2 s-1 as required to balance hydrocarbon haze production via methane photolysis [Wilson and Atreya, 2004. Current state of modeling the photochemistry of Titan's mutually dependent atmosphere and ionosphere. J. Geophys. Res. 109, E06002 Doi:10.1029/2003JE002181]. This low CO/CH4 ratio is much lower than expected for the sub-nebular formation region of Titan and supports the hypothesis [e.g., Atreya et al., 2005. Methane on Titan: photochemical-meteorological-hydrogeochemical cycle. Bull. Am. Astron. Soc. 37, 735] that the conversion of primordial CO and other carbon-bearing materials into CH4-enriched clathrate-hydrates occurs within the deep interior of Titan via the release of hydrogen through the serpentinization process followed by Fischer-Tropsch catalysis. The time-averaged predicted emission rate of methane-rich surface materials is ???0.02 km3 yr-1, a value significantly lower than the rate of silicate lava production for the Earth and Venus, but nonetheless indicative of significant active geological processes reshaping the surface of Titan. ?? 2006 Elsevier Ltd. All rights reserved.

Baines, K. H.; Drossart, P.; Lopez-Valverde, M. A.; Atreya, S. K.; Sotin, C.; Momary, T. W.; Brown, R. H.; Buratti, B. J.; Clark, R. N.; Nicholson, P. D.

2006-01-01

217

On the Discovery of CO Nighttime Emissions on Titan by Cassini/VIMS: Derived Stratospheric Abundances and Geological Implications  

NASA Technical Reports Server (NTRS)

We present a quantitative analysis of CO thermal emissions discovered on the nightside of Titan by Baines et al. [2005. The atmospheres of Saturn and Titan in the near-infrared: First results of Cassini/VIMS. Earth, Moon, and Planets, 96, 119-147] in Cassini/VIMS spectral imagery. We identify these emission features as the P and R branches of the 1-0 vibrational band of carbon monoxide (CO) near 4.65 microns. For CH3D, the prominent Q branch of the nu(2) fundamental band of CH3D near 4.55 microns is apparent. CO2 emissions from the strong nu(3) vibrational band are virtually absent, indicating a CO2 abundance several orders of magnitude less than CO, in agreement with previous investigations. Analysis of CO emission spectra obtained over a variety of altitudes on Titan's nightside limb indicates that the stratospheric abundance of CO is 32 +/- 15 ppm, and together with other recent determinations, suggests a vertical distribution of CO nearly constant at this value from the surface throughout the troposphere to at least the stratopause near 300 km altitude. The corresponding total atmospheric content of CO in Titan is similar to 2.9 +/- 1.5 x 10(exp 14) kg. Given the long lifetime of CO in the oxygen-poor Titan atmosphere (similar to 0.5-1.0 Gyr), we find a mean CO atmospheric production rate of 6 +/- 3 x 10(exp 5) kg yr(exp -1). Given the lack of primordial heavy noble gases observed by Huygens [Niemann et al., 2005. The abundances of constituents of Titan's atmosphere from the GCMS on the Huygens probe. Nature, 438, 779-784], the primary source of atmospheric CO is likely surface emissions. The implied CO/CH4 mixing ratio of near-surface material is 1.8 +/- 0.9 x 10(exp -4), based on an average methane surface emission rate over the past 0.5 Gyr of 1.3 x 10(exp -13) gm cm(exp -2) s(exp -1) as required to balance hydrocarbon haze production via methane photolysis [Wilson and Atreya, 2004. Current state of modeling the photochemistry of Titan's mutually dependent atmosphere and ionosphere. J. Geophys. Res. 109, E06002 Doi: 10.1029/2003JE002181]. This low CO/CH4 ratio is much lower than expected for the sub-nebular formation region of Titan and supports the hypothesis [e.g., Atreya et al., 2005. Methane on Titan: photochemical-meteorological-hydrogeochemical cycle. Bull. Am. Astron. Soc. 37, 735] that the conversion of primordial CO and other carbon-bearing materials into CH4-enriched clathrate-hydrates occurs within the deep interior of Titan via the release of hydrogen through the serpentinization process followed by Fischer-Tropsch catalysis. The time-averaged predicted emission rate of methane-rich surface materials is approximately 0.02 km(exp 3) yr (exp -1), a value significantly lower than the rate of silicate lava production for the Earth and Venus, but nonetheless indicative of significant geological processes reshaping the surface of Titan.

Bainesa, Kevin H.; Drossart, Pierre; Lopez-Valverde, Miguel A.; Atreya, Sushil K.; Sotin, Christophe; Momary, Thomas W.; Brown, Robert H.; Buratti, Bonnie J.; Clark, Roger N.; Nicholson, Philip D.

2006-01-01

218

A comprehensive catalog of features in Saturn's rings from Cassini RSS, VIMS, and UVIS occultations  

NASA Astrophysics Data System (ADS)

The most detailed pre-Cassini investigation of the geometry of Saturn's rings was published two decades ago as part of an effort to determine Saturn's pole direction and the radius scale for the ring system [1] (henceforth F93). This study was based on the Voyager 1 egress RSS ring occultation from 1980, the 1981 Voyager 2 egress PPS stellar occultation of ? Sco, and high-SNR earth-based 28 Sgr occultation measurements that were limited in radial resolution by the 20 km projected diameter of the occulted star; Bosh [2] expanded on these "historical" results by incorporating occultation results from the Hubble Space Telescope (HST). The wealth of Cassini occultation observations has provided detailed views of the structure of Saturn's rings at much higher spatial resolution and better SNR than ever before [3], especially in the optically thick B ring, and our Cassini-based orbit fits to the rings have provided important corrections to the F93 radius scale of the rings. The F93 results were based on orbit fits to 38 putatively circular features from an atlas of 66 numbered features visible in the Voyager and 28 Sgr data, with a grand total of 452 data points from three occultations fitted to obtain Saturn's pole direction and the ring radius scale. Compared to these solutions, we have increased the number of occultations from three to over 150 and the catalog of consistently identifiable, persistent sharp-edged features from 66 to over 300, mostly in the C and B rings, and the Cassini Division (the A ring is etched by almost innumerable density waves produced by Saturn's plethora of satellites). Figure 1 shows a portion of our updated atlas of features. We have determined the orbital elements of all of these features, with an estimated accuracy of ~250 m in orbital radius. Much of the newly-explored structure in the B ring is poorly understood, and may represent viscous overstabilities in the denser parts of the rings [3]; these accurate orbit solutions, coupled with the decade timescale of the Cassini observations, will enable us to set limits on possible changes in the locations of these abrupt features. The comprehensive catalog, accurately registered in absolute radius, will also provide a guide to other investigators who wish to determine the absolute radius of nearby features in imaging and occultation observations.

McGhee, C.; French, R. G.; Lonergan, K.; Sepersky, T.; Nicholson, P.; Hedman, M.; Marouf, E.; Colwell, .

2013-09-01

219

vimA Gene Downstream of recA Is Involved in Virulence Modulation in Porphyromonas gingivalis W83  

PubMed Central

A 0.9-kb open reading frame encoding a unique 32-kDa protein was identified downstream of the recA gene of Porphyromonas gingivalis. Reverse transcription-PCR and Northern blot analysis showed that both the recA gene and this open reading frame are part of the same transcriptional unit. This cloned fragment was insertionally inactivated using the ermF-ermAM antibiotic resistance cassette to create a defective mutant by allelic exchange. When plated on Brucella blood agar, the mutant strain, designated P. gingivalis FLL92, was non-black pigmented and showed significant reduction in beta-hemolysis compared with the parent strain, P. gingivalis W83. Arginine- and lysine-specific cysteine protease activities, which were mostly soluble, were approximately 90% lower than that of the parent strain. Expression of the rgpA, rgpB, and kgp protease genes was the same in P. gingivalis FLL92 as in the wild-type strain. In contrast to the parent strain, P. gingivalis FLL92 showed increased autoaggregration in addition to a significant reduction in hemagglutinating and hemolysin activities. In in vivo experiments using a mouse model, P. gingivalis FLL92 was dramatically less virulent than the parent strain. A molecular survey of this mutant and the parent strain using all known P. gingivalis insertion sequence elements as probes suggested that no intragenomic changes due to the movement of these elements have occurred in P. gingivalis FLL92. Taken together, these results suggest that the recA downstream gene, designated vimA (virulence-modulating gene), plays an important role in virulence modulation in P. gingivalis W83, possibly representing a novel posttranscriptional or translational regulation of virulence factors in P. gingivalis.

Abaibou, Hafid; Chen, Zhuo; Olango, G. Jon; Liu, Yi; Edwards, Jessica; Fletcher, Hansel M.

2001-01-01

220

Comparison of Optical and SEM-BEI Inclusion Analyses of VIM-VAR Nickel-Titanium Alloy  

NASA Astrophysics Data System (ADS)

The ASTM Standard for NiTi alloys does not specify the method to be used for the analysis of inclusions. Quantitative analysis is generally done by optical metallography with a computer program to measure size and area fraction. This study gives a comparison of quantitative analyses of inclusions by scanning electron microscopy using backscattered electron imaging (SEM-BEI) and quantitative analyses by optical metallography. Seven samples of 6.3-mm hot-rolled NiTi were evaluated. The coil samples were selected to exhibit a wide range of inclusion content. Each sample had a different Ni to Ti ratio corresponding to a different transformation temperature range (TTR) from A s = -25 °C (Ni = 50.79 a/o) to A s = +95 °C (Ni = 49.63 a/o). Quantitative analyses by optical and by SEM-BEI are in reasonable good agreement for maximum particle size and maximum area fraction. Both methods of analysis show that carbide and intermetallic oxide inclusion populations in VIM-VAR hot-rolled coil vary significantly in the amount and size of inclusions with the alloy transformation temperature. Therefore, an analysis of a larger number of samples at each TTR is needed to develop statistically precise data. All carbide inclusions were less than 12.5 ?m and less than 1.0% area fraction in all the samples. Maximum size and area fraction of carbides decreased as TTR increased. Intermetallic oxide size and area fraction increased with increasing TTR Intermetallic oxides are fractured and separated from the matrix during hot working. However, stringering is very limited. The fracturing appears to happen in high TTR alloys but not in low TTR alloys. This dependence on TTR suggests that chemistry in or around the oxides affects their fracture behavior.

Sczerzenie, Frank; Paul, Graeme W.; Belden, Clarence; Fasching, Audrey

2011-07-01

221

Comparison of Inclusions in Cold Drawn Wire and Precursor Hot-Rolled Rod Coil in VIM-VAR Nickel-Titanium Alloy  

NASA Astrophysics Data System (ADS)

Inclusion content is important for the mechanical behavior and performance of Nitinol wires, particularly in fatigue-rated devices. The purpose of this work was to make a quantitative comparison between inclusion populations in cold drawn wires and the precursor populations in hot-rolled rod coil. Inclusion content was examined in a series of VIM-VAR alloys with different transformation temperatures (TTR) controlled by the Ni to Ti ratio. This range of chemistry was chosen to assess the effect of Ni to Ti ratio on inclusion formation. In order to understand the differences in behavior between carbides and intermetallic oxides in wire drawing, carbides, and intermetallic oxide inclusions were measured separately using optical metallography pursuant to ASTM F2063. In VIM-VAR alloys at higher Ni to Ti ratios about 50.79 a/o Ni the formation of intermetallic oxides appears to be suppressed in the as-cast material through the presence of carbon and the precipitation of eutectic TiC in place of eutectic Ti4Ni2O x . The structure of VIM-VAR alloy also varies after hot working depending on the TTR of the alloy. Higher TTR binary alloys with lower Ni to Ti ratios tend to have more and larger intermetallic oxides and fewer and smaller carbides after hot working. Microsegregation plays a role in inclusion formation. That is, during solidification, C, O, N diffuse to the interdendritic regions. This increases the potential for the precipitation of nonmetallic species. Carbides and intermetallic oxides behave differently in hot working and cold drawing. The change in maximum carbide size from coil to wire is very near zero for all Ni to Ti ratios. The change in maximum inclusion size from coil to wire is driven mainly by the fracture of intermetallic oxides and the formation of intermetallic oxide stringers.

Sczerzenie, Frank; Paul, Graeme; Belden, Clarence

2011-07-01

222

Wavelength-encoded OCDMA system using opto-VLSI processors  

Microsoft Academic Search

We propose and experimentally demonstrate a 2.5 Gbits\\/sper user wavelength-encoded optical code-division multiple-access encoder-decoder structure based on opto-VLSI processing. Each encoder and decoder is constructed using a single 1D opto-very-large-scale-integrated (VLSI) processor in conjunction with a fiber Bragg grating (FBG) array of different Bragg wavelengths. The FBG array spectrally and temporally slices the broadband input pulse into several components and

Muhsen Aljada; Kamal Alameh

2007-01-01

223

Multiple-wavelength tunable laser  

NASA Technical Reports Server (NTRS)

A tunable laser includes dispersion optics for separating generated laser pulses into first and second wavelength pulses directed along first and second optical paths. First and second reflective mirrors are disposed in the first and second optical paths, respectively. The laser's output mirror is partially reflective and partially transmissive with respect to the first wavelength and the second wavelength in accordance with provided criteria. A first resonator length is defined between the output mirror and the first mirror, while a second resonator length is defined between the output mirror and the second mirror. The second resonator length is a function of the first resonator length.

Barnes, Norman P. (Inventor); Walsh, Brian M. (Inventor); Reichle, Donald J. (Inventor)

2010-01-01

224

Multiple-wavelength Raman lidar measurements of atmospheric water vapor  

SciTech Connect

Height profiles of atmospheric water vapor obtained using a multiple-wavelength Raman lidar are examined. The water vapor profiles exhibit vertical structure with scales on the order of the resolution of the lidar (75 m). To determine whether such structure is atmospheric in origin, measurements obtained simultaneously in a common volume at two independent wavelengths were compared. Correlation of the gradients of the water vapor profiles obtained from these two wavelengths yielded an average correlation factor of 0.88. It was also observed that for the given meteorological conditions, the vertical structure decorrelated with a time constant of approximately three hours. 7 refs., 4 figs., 1 tab.

Rajan, S.; Kane, T.J.; Philbrick, C.R. [Pennsylvania State Univ., University Park, PA (United States)] [Pennsylvania State Univ., University Park, PA (United States)

1994-11-15

225

Sequence of pNL194, a 79.3-kilobase IncN plasmid carrying the blaVIM-1 metallo-beta-lactamase gene in Klebsiella pneumoniae.  

PubMed

The nucleotide sequence of pNL194, a VIM-1-encoding plasmid, is described in this study. pNL194 (79,307 bp) comprised an IncN-characteristic segment (38,940 bp) and a mosaic structure (40,367 bp) including bla(VIM-1), aacA7, aadA1, aadA2, dfrA1, dfrA12, aphA1, strA, strB, and sul1. Tn1000 or Tn5501 insertion within fipA probably facilitated recruitment of additional mobile elements carrying resistance genes. PMID:20660690

Miriagou, V; Papagiannitsis, C C; Kotsakis, S D; Loli, A; Tzelepi, E; Legakis, N J; Tzouvelekis, L S

2010-10-01

226

Dual Wavelength Surgical Laser System.  

National Technical Information Service (NTIS)

The present invention relates to lasers and particularly to a dual wavelength surgical laser system that would inflict significantly less collateral tissue damage during surgery than currently available scalpels or medical lasers.

L. Esterowitz C. Marquardt

1995-01-01

227

Solid colloidal optical wavelength filter  

NASA Astrophysics Data System (ADS)

A method for constructing a solid colloidal optical wavelength filter is discussed. The device was developed to filter optical wavelengths for spectroscopy, protection from intense radiation, monochromatizing, and analyzing optical radiation. The filter is formed by suspending spherical particles in a coagulable medium (such as setting plastic); agitating the particles and coagulable medium to produce an emulsion of particles suspended in the coagulable medium; and allowing the coagulable medium and suspended emulsion of particles to cool.

Alvarez, J. L.

1990-05-01

228

Wavelength selector for tunable laser  

SciTech Connect

A wavelength selector is described for use in a laser cavity comprising a diffraction grating mounted at an angle near grazing incidence with respect to the beam travelling away from the excited medium and a reflector which reflects the beam diffracted by the grating back along its incidence path. Wavelength tuning is accomplished by rotating this reflector, while the grating remains fixed. Rotation of the grating provides linewidth variation.

Shoshan, I.

1980-10-21

229

Carbapenemase-producing Enterobacteriaceae in a tertiary hospital in Madrid, Spain: high percentage of colistin resistance among VIM-1-producing Klebsiella pneumoniae ST11 isolates.  

PubMed

Here we describe the carbapenemase genes, genetic relatedness and antimicrobial susceptibility data of 123 carbapenemase-producing Enterobacteriaceae (CPE) clinical isolates recovered from 2010 to 2012, comprising Klebsiella pneumoniae (n = 79), Klebsiella oxytoca (n = 13), Serratia marcescens (n = 14), Enterobacter cloacae (n = 12), Enterobacter asburiae (n = 4) and Enterobacter aerogenes (n = 1). VIM-1 was the most common carbapenemase (n = 101) followed by KPC-2 (n = 19), OXA-48 (n = 2) and IMP-22 (n = 1). Among the K. pneumoniae isolates, nine sequence types (STs) were identified but two clones were dominant: ST11 (54/79) containing mainly VIM-1-producing isolates; and ST101 (13/79) constituted by KPC-2-producing strains. Pulsed-field gel electrophoresis (PFGE) showed a higher genetic diversity among the remaining Enterobacteriaceae. Amikacin and fosfomycin were the most active agents with 82.9% and 80.5% susceptibility, respectively. Non-susceptibility to tigecycline was detected in 36.5% of strains. Overall, colistin resistance was 24.7% and was as high as 47% in Enterobacter spp. An increase in colistin resistance from 13.5% to 31.7% was observed among K. pneumoniae isolates during the study period. Resistance was focused on ST11 since 83.3% of colistin-resistant strains belonged to this clone. The high level of colistin resistance observed in this study is worrying with respect to the already limited therapeutic options for infections caused by multidrug-resistant Gram-negative bacteria. PMID:24657043

Pena, Irene; Picazo, Juan J; Rodríguez-Avial, Carmen; Rodríguez-Avial, Iciar

2014-05-01

230

Multi-centre evaluation of real-time multiplex PCR for detection of carbapenemase genes OXA-48, VIM, IMP, NDM and KPC  

PubMed Central

Background Resistance to carbapenem antibiotics is emerging worldwide among Enterobacteriaceae. To prevent hospital transmission due to unnoticed carriage of carbapenemase producing micro-organisms in newly admitted patients, or follow-up of patients in an outbreak setting, a molecular screening method was developed for detection of the most prevalent carbapenemase genes; blaOXA-48, blaVIM, blaIMP, blaNDM and blaKPC. Methods A real-time multiplex PCR assay was evaluated using a collection of 86 Gram negative isolates, including 62 carbapenemase producers. Seven different laboratories carried out this method and used the assay for detection of the carbapenemase genes on a selection of 20 isolates. Results Both sensitivity and specificity of the multiplex PCR assay was 100%, as established by results on the strain collection and the inter-laboratory comparisons. Conclusions In this study, we present a multiplex real-time PCR that is a robust, reliable and rapid method for the detection of the most prevalent carbapenemases blaOXA-48, blaVIM, blaIMP, blaNDM and blaKPC, and is suitable for screening of broth cultured rectal swabs and for identification of carbapenemase genes in cultures.

2014-01-01

231

A case of tremor reduction and almost complete ageusia under bilateral thalamic (VIM) deep brain stimulation in essential tremor--a therapeutic dilemma.  

PubMed

Essential tremor (ET) is a neurological disorder that can be treated effectively by means of bilateral thalamic ventral intermediate nucleus (VIM) deep brain stimulation (DBS). We present a rare case of stimulation-dependent reversible ageusia that poses a therapeutic dilemma on the one hand and serves as an instructive example to elucidate the as yet incompletely defined gustatory pathways on the other. A 69-year-old patient with successful reduction of his disabling upper extremity ET experienced an almost complete but during stimulation cessation reversible ageusia under bilateral VIM DBS. An evaluation of diffusion tensor (DTI) neuroimaging studies was performed in order to detect effective electrode positions and volumes of activated tissue (VTA) in relation to the medial lemniscus (ML) and dentato-rubro-thalamic tract (DRT). Repeated subjective gustometry was conducted with differential manipulation of stimulation settings. This case report stresses the importance of fiber tracts for DBS surgery. Reconciled with previous findings in lesion cases, we assume the coexistence of decussating and non-decussating fibers in the gustatory tract combined with hemispheric dominance in the processing of gustatory information. A therapeutic option for this dilemma may be a patient-selectable stimulation program or bipolar stimulation establishing a smaller ovoid VTA. PMID:21984073

Sajonz, Bastian; Mädler, Burkhard; Herberhold, Stephan; Paus, Sebastian; Coenen, Volker A

2011-12-01

232

What Wavelength Goes With a Color?  

NSDL National Science Digital Library

This web page provides a brief introduction to the wavelengths of visible light. It discusses the wavelengths of the standard visual colors, mentions wavelengths outside of the visible spectrum, and provides links to other information.

2009-09-30

233

Critical wavelength for river meandering.  

PubMed

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

Edwards, B F; Smith, D H

2001-04-01

234

Multi-wavelength interferometric testing  

Microsoft Academic Search

We have built a modified Twyman-Green interferometer illuminated with a krypton laser. The configuration allows for center of curvature or autocollimation testing at various selected wavelengths. Software data reduction uses a Zernike polynomial fit to the wavefront. The interferograms are all made without moving the source, so the effects of axial color, lateral color, and chromatic variation of aberrations will

W. Swantner; C. R. Hayslett

1977-01-01

235

Laser-plasma instabilities in large plasmas irradiated at 1. 06. mu. m and the wavelength scaling of the absorption, hot-electron production, ablation pressure for 1. 06-, 0. 53-, and 0. 35-. mu. m light  

SciTech Connect

Plasmas were created by exploding 7000 A thick CH foils at the irradiation conditions: 1.064 ..mu..m, 3 kJ, 2.5 x 10/sup 15/ W/cm/sup 2/, 900 ps FWHM, 400 ..mu..m spot diameter. Ten percent of the laser energy appeared as Raman light and 0.04% as 3..omega../sub 0//2 light. The 3..omega../sub 0//2 light and the 30-70 keV X rays occurred simultaneouly at t=-120/sup +50//sub -//sub 200/ psec and lasted only 300 psec FWHM. The foil was calculated to explode to n/sub c/4 at t=-300 psec. The spectrum and angular distribution of the Raman light were also measured. Time-resolved spectral measurements have been made in experiments with 5320 A laser light in a 600-900 psec FWHM pulse. The scaling of the 3..omega../sub 0//2 light with both the laser spot size and pulse length has been studied.

Phillion, D.W.; Campbell, E.M.; Turner, R.E.

1982-01-01

236

A preliminary mechanical property and stress corrosion evaluation of VIM-VAR work strengthened and direct aged Inconel 718 bar material  

NASA Technical Reports Server (NTRS)

This report presents a preliminary mechanical property and stress corrosion evaluation of double melted (vacuum induction melted (VIM), and vacuum arc remelted (VAR)), solution treated, work strengthened and direct aged Inconel 718 alloy bar (5.50 in. (13.97 cm) diameter). Two sets of tensile specimens, one direct single aged and the other direct double aged, were tested at ambient temperature in both the longitudinal and transverse directions. Longitudinal tensile and yield strengths in excess of 200 ksi (1378.96 MPa) and 168 ksi (1158.33 MPa), respectively, were realized at ambient temperature, for the direct double aged specimen. No failures occurred in the single or double edged longitudinal and transverse tensile specimens stressed to 75 and 100 percent of their respective yield strengths and exposed to a salt fog environment for 180 days. Tensile tests performed after the stress corrosion test showed no mechanical property degradation.

Montano, J. W.

1987-01-01

237

Wavelength-multiplexed entanglement distribution  

NASA Astrophysics Data System (ADS)

The realization of an entanglement distribution optical fiber network connecting multiple parties would permit implementation of many information security applications such as entanglement-based quantum key distribution and quantum secret sharing. However, due to material absorption and scattering in optical fiber, photons that are the carriers of quantum entanglement experience loss during propagation and the overall photon arrival rate can be very low in such a network. One way to increase photon arrival rate is to make full use of the available transmission bandwidth of optical fiber and this is achievable via wavelength-multiplexing. We review our recent work on wavelength-multiplexed entanglement distribution and discuss system design considerations from a telecommunication engineering perspective.

Lim, Han Chuen; Yoshizawa, Akio; Tsuchida, Hidemi; Kikuchi, Kazuro

2010-08-01

238

Quantum detection at millimeter wavelengths  

Microsoft Academic Search

Photon-assisted tunneling of electrons through an insulating barrier may be used to detect long-wavelength radiation with a sensitivity approaching the limit imposed by the Heisenberg uncertainty principle. A new generation of ultra-low-noise millimeter-wave receivers, currently being developed for astronomical observation, utilizes the extremely sharp nonlinearity produced by single-electron quasiparticle tunneling between two superconductors in a superconductor-insulator-superconductor (SIS) tunnel junction. At

John Tucker; Marc Feldman

1985-01-01

239

Astronomical Images in Different Wavelengths  

NSDL National Science Digital Library

This interactive feature allows viewers to see what various astronomical objects look like in visible light and in the radio, infrared, and X-ray portions of the electromagnetic spectrum. Each image is accompanied by a brief description of the object and what can be seen in the different wavelengths. There is also a page that shows the electromagnetic spectrum and some of the instruments designed to sense different portions of it.

240

Multi-wavelength study of the opposition effect on Saturn's Rings  

NASA Astrophysics Data System (ADS)

The opposition effect manifests itself as an important surge of the radiance factor when the phase angle approaches 0°. Since its discovery on Saturn's rings (1), several effects have been proposed to explain it, such as the Ring-Shadow Hiding Opposition Effect (R-SHOE), the Coherent Backscattering Opposition Effect (CBOE) or the SHOE within the regolith that may cover ring particles. The relative importance of all these effects is still badly constraint (2). It is usually assumed that the R-SHOE cannot provide such a narrow peak as observed and is therefore considered as negligible. We will show that if the full viewing and lighting geometry are considered, this effect has to be taken into account, therefore providing a very good probe to measure the thickness and the filling factor of Saturn's Rings. Furthermore, the regolith contributions to the effect, i.e. CBOE and SHOE, depend on its absorption coefficient and its mean free path (3) and therefore should then depend on the wavelength. This is not the case for the R-SHOE because it mostly depends on the filling factor, the thickness and the particle size. We will present a multi-wavelength study of Saturn's rings opposition effect supported by the data of the VIMS-CASSINI instrument (Visual and Infrared Mapping Spectrometer) and show if our understanding of those effects is incomplete as proposed by (4) or not. (1) H,Abhandl.Bayer.Akad.Wiss.K1.II18,172,188 (2) Salo and French, Icarus, 2010 (3) Hapke, Icarus, 2002, (4) Hapke et al., Journal of Geophysical Reasearch, Vol 117, 2012

Degiorgio, K.; Ferrari, C. C.; Rodriguez, S.

2012-12-01

241

Alternative wavelengths for optically pumped alkali lasers  

NASA Astrophysics Data System (ADS)

As pump intensity in Diode Pumped Alkali Lasers (DPAL) is scaled to more than 100 times threshold, several nonlinear optical processes are encountered including two photon absorption and stimulated Raman scattering. A pulsed, optically pumped potassium laser with pump intensities exceeding 1 MW/cm2 has been demonstrated with output intensities exceeding 100 kW/cm2, requiring helium buffer gas pressures above 3 atm. At low pressure Stimulated Electronic Raman Scattering (SERS) has been observed in the same system. Indeed, second and third order SERS has been observed from the DPAL upper laser level. Two-photon absorption at wavelengths near then DPAL pump transition has also been observed and used to demonstrate lasing in the blue and mid infrared. Lasing in the blue has also been achieved by direct excitation of the second excited 2P3/2 level in Cs.

Perram, Glen P.

2012-05-01

242

Radiative Smoothing in Clouds at Transparent and Absorbing Wavelengths  

NASA Technical Reports Server (NTRS)

For absorbing and transparent wavelengths, we discuss the effect of horizontal solar radiative fluxes in clouds on the accuracy of a conventional plane-parallel radiative transfer calculations for a single pixel, known as the Independent Pixel Approximation (IPA). We address the question of correlations between horizontal fluxes, IPA accuracies and radiative smoothing. By smoothing we understand a radiative transfer process whereby radiation does not follow the small-scale fluctuations of cloud structure, producing much smoother radiation fields. The scale eta that characterizes this process is called "radiative smoothing scale." We relate radiative smoothing to the photon's horizontal displacement that characterizes a "spot" of reflected light associated with a point source. We generalize the "spot-size" estimate derived for conservative scattering using the diffusion theory to the case of non-conservative scattering. For reflected light, theoretical results are confirmed with numerical simulations. The radiative smoothing scale eta is a critical value where IPA effectively breaks down; for scales smaller than TI, real radiation field are much smoother than their IPA counterparts for the same cloud structure. In addition to the estimate of il for absorbing wavelengths, we show that: (1) with more absorption, the scale break determined by eta in a log-log plot of wavenumber spectra moves towards smaller scales and (2) the smaller eta the flatter the small-scale slope which means less radiative smoothing, thus more accuracy in the IPA reflection.

Marshak, A.; Davis, A.; Oreopoulos, L.; Wiscombe, W.; Cahalan, R.

1999-01-01

243

Dual wavelength holographic interferometry system  

NASA Technical Reports Server (NTRS)

A two-wave holographic interferometry system and method is described. In such systems, a reference beam holographic is superimposed on an object beam, the object beam being an image obtained by passing a beam through an object regarding which some parameter (e.g., temperature gradient) is to be measured. A photograph of the superimposed beams is taken. This invention employs two object and two reference beams and the invention is particularly concerned with the use of a prism assembly which causes the two different wavelengths of the object beams to emerge from the prism at slightly different angles, thereby providing two holographic images which are slightly displaced from each other.

Witherow, William K. (inventor); Ecker, Andreas (inventor)

1988-01-01

244

Measurement of thin films using very long acoustic wavelengths  

NASA Astrophysics Data System (ADS)

A procedure for measuring material thickness by means of necessarily long acoustic wavelengths is examined. The approach utilizes a temporal phase lag caused by the impulse time of wave momentum transferred through a thin layer that is much denser than its surrounding medium. In air, it is predicted that solid or liquid layers below approximately 1/2000 of the acoustic wavelength will exhibit a phase shift with an arctangent functional dependence on thickness and layer density. The effect is verified for thin films on the scale of 10 ?m using audible frequency sound (7 kHz). Soap films as thin as 100 nm are then measured using 40 kHz air ultrasound. The method's potential for imaging applications is demonstrated by combining the approach with near-field holography, resulting in reconstructions with sub-wavelength resolution in both the depth and lateral directions. Potential implications at very high and very low acoustic frequencies are discussed.

Clement, G. T.; Nomura, H.; Adachi, H.; Kamakura, T.

2013-12-01

245

Wavelength dependence of the apparent diameter of retinal blood vessels  

NASA Astrophysics Data System (ADS)

Imaging of retinal blood vessels may assist in the diagnosis and monitoring of diseases such as glaucoma, diabetic retinopathy, and hypertension. However, close examination reveals that the contrast and apparent diameter of vessels are dependent on the wavelength of the illuminating light. In this study multispectral images of large arteries and veins within enucleated swine eyes are obtained with a modified fundus camera by use of intravitreal illumination. The diameters of selected vessels are measured as a function of wavelength by cross-sectional analysis. A fixed scale with spectrally independent dimension is placed above the retina to isolate the chromatic effects of the imaging system and eye. Significant apparent differences between arterial and venous diameters are found, with larger diameters observed at shorter wavelengths. These differences are due primarily to spectral absorption in the cylindrical blood column.

Park, Robert; Twietmeyer, Karen; Chipman, Russell; Beaudry, Neil; Salyer, David

2005-04-01

246

Making Displaced Holograms At Two Wavelengths  

NASA Technical Reports Server (NTRS)

Two-wavelength holographic system augmented with pair of prisms to introduce small separation between holograms formed simultaneously at two wavelengths on holographic plate. Principal use in study of flows. Gradients in index of refraction of fluid caused by variations in temperature, concentration, or both. Holography at one wavelength cannot be used to distinguish between two types of variations. Difference between spacings of fringes in photographs reconstructed from holograms taken simultaneously at two different wavelengths manipulated mathematically to determine type of variation.

Witherow, William K.; Ecker, Andreas

1989-01-01

247

Flare stars at radio wavelengths  

NASA Technical Reports Server (NTRS)

The radio emission from dMe flare stars is discussed using Very Large Array and Arecibo observations as examples. Active flare stars emit weak, unpolarized, quiescent radio radiation that may be always present. Although thermal bremsstrahlung and/or thermal gyroresonance radiation account for the slowly-varying, quiescent radio radiation of solar active regions, these processes cannot account for the long-wavelength quiescent radiation observed from nearby dMe flare stars. It has been attributed to nonthermal gyrosynchrotron radiation, but some as yet unexplained mechanism must be continually producing the energetic electrons. Long duration, narrow-band radiation is also emitted from some nearby dMe stars at 20 cm wavelength. Such radiation may be attributed to coherent plasma radiation or to coherent electron-cyclotron masers. Impulsive stellar flares exhibit rapid variations that require radio sources that are smaller than the star in size, and high brightness temperatures greater than 10(exp 15) K that are also explained by coherent radiation processes. Quasi-periodic temporal fluctuations suggest pulsations during some radio flares. Evidence for frequency structure and positive or negative frequency drifts during radio flares from dMe stars is also presented.

Lang, Kenneth R.

1990-01-01

248

Flare stars at radio wavelengths  

NASA Technical Reports Server (NTRS)

The radio emission from dMe flare stars is discussed using Very Large Array and Arecibo observations as examples. Active flare stars emit weak, unpolarized, quiescent radio radiation that may be always present. Although thermal bremsstrahlung and/or thermal gyroresonance radiation account for the slowly-varying, quiescent radio radiation of solar active regions, these processes cannot account for the long-wavelength quiescent radiation observed from nearby dMe flare stars. It has been attributed to nonthermal gyrosynchrotron radiation, but some as yet unexplained mechanism must be continually producing the energetic electrons. Long duration, narrow-band radiation is also emitted from some nearby dMe stars at 20 cm wavelength. Such radiation may be attributed to coherent plasma radiation or to coherent electron-cyclotron masers. Impulsive stellar flares exhibit rapid variations that require radio sources that are smaller than the star in size, and high brightness temperatures greater than 10(exp 15) K that are also explained by coherent radiation processes. Quasi-periodic temporal fluctuations suggest pulsations during some radio flares. Evidence for frequency structure and positive or negative frequency drifts during radio flares from dMe stars is also presented.

Lang, Kenneth R.

1989-01-01

249

Optical wavelength converters: techniques and system aspects  

NASA Astrophysics Data System (ADS)

Optical wavelength conversion will be a key function in photonic networks. Therefore the development of effective and practical all-optical wavelength converters is subject to considerable attention. Here, the application is outlined and the performance of wavelength conversion by semiconductor optical amplifiers reviewed.

Joergensen, Carsten; Danielsen, Soren L.; Mikkelsen, Benny; Stubkjaer, Kristian E.; Vodjdani, Nakita; Ratovelomanana, F.; Enard, Alain; Glastre, Genevieve; Rondi, D.; Blondeau, Robert R.; Doussiere, P.; Garabedian, G.; Graver, C.; Jourdan, Amaury; Schilling, Michael; Idler, Wilfried; Wunstel, K.

1996-03-01

250

Optimum wavelengths for two color ranging  

Microsoft Academic Search

The range uncertainties associated with the refractive atmosphere can be mitigated by the technique of two color, or dual wavelength, ranging. The precision of the differential time of flight (DTOF) measurement depends on the atmospheric dispersion between the two wavelengths, the received pulsewidths and photoelectron counts, and on the amount of temporal averaging. In general, the transmitted wavelengths are not

John J. Degnan

1993-01-01

251

Wavelength-tunable optical parametric regenerator.  

PubMed

We designed a wavelength-tunable optical parametric regenerator, where functions of reamplification, reshaping, and wavelength conversion are incorporated into a highly nonlinear fiber component. The uniform power transfer functions and negative penalties over a 20nm input wavelength range are experimentally demonstrated. PMID:20967102

Gao, Mingyi; Kurumida, Junya; Namiki, Shu

2010-10-15

252

Multiple wavelength light collimator and monitor  

NASA Technical Reports Server (NTRS)

An optical system for receiving and collimating light and for transporting and processing light received in each of N wavelength ranges, including near-ultraviolet, visible, near-infrared and mid-infrared wavelengths, to determine a fraction of light received, and associated dark current, in each wavelength range in each of a sequence of time intervals.

Gore, Warren J. (Inventor)

2011-01-01

253

Evaluation of a DNA Microarray (Check-MDR CT102) for Rapid Detection of TEM, SHV, and CTX-M Extended-Spectrum ?-Lactamases and of KPC, OXA-48, VIM, IMP, and NDM-1 Carbapenemases?  

PubMed Central

The Check-MDR CT102 microarray, aimed at identifying bacteria producing extended-spectrum ?-lactamase (ESBL) (SHV, TEM, and CTX-M) and carbapenemase (KPC, OXA-48, VIM, IMP, and NDM-1), was evaluated on a total of 144 Gram-negative strains expressing various ?-lactamases. The sensitivity and specificity were 100% for most tested genes, suggesting that this assay allows accurate identification of common ESBL and carbapenemase producers from bacterial cultures.

Naas, Thierry; Cuzon, Gaelle; Bogaerts, Pierre; Glupczynski, Youri; Nordmann, Patrice

2011-01-01

254

The 2007 International Vocabulary of Metrology (VIM), JCGM 200:2008 [ISO/IEC Guide 99]: Meeting the need for intercontinentally understood concepts and their associated intercontinentally agreed terms.  

PubMed

Unambiguous and consistent concepts and terms such as measurand, metrological traceability, measurement uncertainty, comparability of measurement results, target measurement uncertainty, etc., must govern the description of measurements in order to enable a valid comparison of measurement results. That is not yet the case as numerous workshops over the last decade have shown worldwide and as chemical literature continuously displays. For international trade in food and feed to be fair, for border-crossing implementation of environmental regulations to be the same for all parties concerned, for interchangeability of results of clinical measurements to become a reality, for any border-crossing interpretation of measurement results in chemistry to become possible, well understood and mutually accepted, common and well defined concepts and terms are essential. Similarly, their translations from one language--English--to 30-40 other languages, must be realized and fixed unequivocally. Countries using English as common language have not yet fully realized that they are at a considerable advantage over countries where such translated terms describing concepts may not yet be available, let alone understood and accepted. A number of ambiguities in the definitions and terms are described which illustrate the importance of the revision (1997-2007) of the International Vocabulary of Metrology (VIM), henceforth conveniently called "VIM3", especially since chemical measurement is covered in this VIM for the first time in history: 'measurand' 'metrological comparability of measurement results' 'metrology' 'metrological compatibility of measurement results' 'measurement result' 'metrological traceability' (incl 'to the SI') 'measurement uncertainty' 'target measurement uncertainty' 'calibration hierarchy' 'quantity' and many others. It is concluded that the revised VIM is of primordial importance for good understanding within and between the measurement communities worldwide. PMID:19863914

De Bièvre, Paul

2009-03-01

255

Evaluation of a DNA microarray (Check-MDR CT102) for rapid detection of TEM, SHV, and CTX-M extended-spectrum ?-lactamases and of KPC, OXA-48, VIM, IMP, and NDM-1 carbapenemases.  

PubMed

The Check-MDR CT102 microarray, aimed at identifying bacteria producing extended-spectrum ?-lactamase (ESBL) (SHV, TEM, and CTX-M) and carbapenemase (KPC, OXA-48, VIM, IMP, and NDM-1), was evaluated on a total of 144 Gram-negative strains expressing various ?-lactamases. The sensitivity and specificity were 100% for most tested genes, suggesting that this assay allows accurate identification of common ESBL and carbapenemase producers from bacterial cultures. PMID:21325547

Naas, Thierry; Cuzon, Gaelle; Bogaerts, Pierre; Glupczynski, Youri; Nordmann, Patrice

2011-04-01

256

Geomorphological significance of Ontario Lacus on Titan: Integrated interpretation of Cassini VIMS, ISS and RADAR data and comparison with the Etosha Pan (Namibia)  

NASA Astrophysics Data System (ADS)

Ontario Lacus is the largest lake of the whole southern hemisphere of Titan, Saturn's major moon. It has been imaged twice by each of the Cassini imaging systems (Imaging Science Subsystem (ISS) in 2004 and 2005, Visual and Infrared Mapping Spectrometer (VIMS) in 2007 and 2009 and RADAR in 2009 and 2010). We compile a geomorphological map and derive a "hydrogeological" interpretation of Ontario Lacus, based on a joint analysis of ISS, VIMS and RADAR SAR datasets, along with the T49 altimetric profile acquired in December 2008. The morphologies observed on Ontario Lacus are compared to landforms of a semi-arid terrestrial analog, which resembles Titan's lakes: the Etosha Pan, located in the Owambo Basin (Namibia). The Etosha Pan is a flat-floored depression formed by dissolution, under semi-arid conditions, of a surface evaporitic layer (calcretes) controlled by groundwater vertical motions. We infer that Ontario Lacus is an extremely flat and shallow depression lying in an alluvial plain surrounded by small mountain ranges under climatic conditions similar to those of terrestrial semi-arid regions. Channels are seen in the southern part of Ontario Lacus in VIMS and RADAR data, acquired at a 2-years time interval. Their constancy in location with time implies that the southern portion of the depression is probably not fully covered by a liquid layer at the time of the observations, and that they most probably run on the floor of the depression. A shallow layer of surface liquids, corresponding to the darkest portions of the RADAR images, would thus cover about 53% of the surface area of the depression, of which almost 70% is located in its northern part. These liquid-covered parts of the depression, where liquid ethane was previously identified, are interpreted as topographic lows where the "alkanofer" raises above the depression floor. The rest of the depression, and mostly its southern part, is interpreted as a flat and smooth exposed floor, likely composed of a thick and liquid-saturated coating of photon-absorbing materials in the infrared. This hypothesis could explain its dark appearance both in the infrared and radar data and the persistence of channels seen on the depression floor over the time. Shorelines are observed on the border of Ontario Lacus suggesting past high-stand levels of the alkanofer table. The analogy with the Etosha Pan suggests that Ontario Lacus' depression developed at the expense of a soluble layer covering the region. Dissolution of this layer would be controlled by vertical motions of the alkanofer table over the time. During flooding events, liquid hydrocarbons covering the depression floor would dissolve the surface layer, increasing progressively the diameter of the depression on geological timescales. During drought episodes, liquid hydrocarbons of the underground alkanofer would evaporate, leading to crystallization of "evaporites" in the pores and at the surface of the substratum, and to the formation of the regional soluble layer. The presence of specific landforms (lunette dunes or evaporites) is compatible with such evaporitic regional settings. Alternatively, but not exclusively, the surface soluble layer might have formed by accumulation on the ground of soluble compounds formed in the atmosphere.

Cornet, T.; Bourgeois, O.; Le Mouélic, S.; Rodriguez, S.; Lopez Gonzalez, T.; Sotin, C.; Tobie, G.; Fleurant, C.; Barnes, J. W.; Brown, R. H.; Baines, K. H.; Buratti, B. J.; Clark, R. N.; Nicholson, P. D.

2012-04-01

257

Antibiotic Resistance Pattern and Evaluation of Metallo-Beta Lactamase Genes Including bla-IMP and bla-VIM Types in Pseudomonas aeruginosa Isolated from Patients in Tehran Hospitals  

PubMed Central

Beta-lactamase producing strains of Pseudomonas aeruginosa are important etiological agents of hospital infections. Carbapenems are among the most effective antibiotics used against Pseudomonas infections, but they can be rendered infective by group B ?-lactamase, commonly called metallo-beta lactamase. In this study, the antimicrobial sensitivity patterns of P. aeruginosa strains isolated from 9 different hospitals in Tehran, Iran, as well as the prevalence of MBLs genes (bla-VIM and bla-IMP) were determined. A total of 212 strains of P. aeruginosa recovered from patients in hospitals in Tehran were confirmed by both biochemical methods and PCR. Their antimicrobial sensitivity patterns were determined by Kirby-Bauer disk diffusion method. Following MIC determination, imipenem resistant strains were selected by DDST method which was followed by PCR tests for determination of MBLs genes: bla-IMP and bla-VIM. The results indicated that, in the DDST phenotypic method, among the 100 imipenem resistant isolates, 75 strains were MBLs positive. The PCR test indicated that 70 strains (33%) carried bla-VIM gene and 20 strains (9%) harbored bla-IMP. The results indicated that the extent of antibiotic resistance among Pseudomonas aeruginosa is on the rise. This may be due to production of MBLs enzymes. Therefore, determination of antibiotic sensitivity patterns and MBLs production by these bacteria, can be important in control of clinical Pseudomonas infection.

Aghamiri, Samira; Amirmozafari, Nour; Fallah Mehrabadi, Jalil; Fouladtan, Babak; Samadi Kafil, Hossein

2014-01-01

258

Retinal spot size with wavelength  

NASA Astrophysics Data System (ADS)

We have made an indirect in-vivo determination of spot size focusing in the rhesus monkey model. Measurement of the laser induced breakdown threshold both in-vitro and in-vivo allow correlation and assignment of a spot size after focusing through the living eye. We discuss and analyze the results and show how trends in minimum visible lesion data should be assessed in light of chromatic aberration. National laser safety standards are based on minimal visual lesion (MVL) threshold studies in different animal models. The energy required for a retinal lesion depends upon may parameters including wavelength and retinal spot size. We attempt to explain trends in reported MVL threshold studies using a model of the eye which allows calculation of changes in retinal spot size due to chromatic aberration.

Rockwell, Benjamin A.; Hammer, Daniel X.; Kennedy, Paul K.; Amnotte, Rodney E.; Eilert, Brent; Druessel, Jeffrey J.; Payne, Dale J.; Phillips, Shana L.; Stolarski, David J.; Noojin, Gary D.; Thomas, Robert J.; Cain, Clarence P.

1997-06-01

259

Michelson interferometer for laser wavelength  

NASA Astrophysics Data System (ADS)

A wavemeter based on Michelson interferometer accurately measure static wavelength of a tunable laser. Its operation principle is formulated in details. Double longitudinal-mode He-Ne laser with frequency stabilization is used as the reference optical source of the wavemeter. Voice-coil motor using PID means can realize to move in uniform motion. Phase-locked loop circuit including NE564 and 74LS193 is used to enhance resolution of the wavemeter. Data processing is carried out by the counter unit including two 8254 programmable timer, a MCU, a LCD. The test shows that its measurement accuracy is 1×10 -6 and is higher than those of other wavemeters such as Fizeau interference and Fabry-Perot wavemeter.

Wang, Liqiang; Ren, Wenjie

2005-12-01

260

Bolometric Arrays for Millimeter Wavelengths  

NASA Astrophysics Data System (ADS)

During last years, semiconductor bolometers using thin films have been developed at INAOE, specifically boron-doped hydrogenated amorphous silicon films. The characteristics shown by these devices made them attractive to be used in astronomical instrumentation, mainly in two-dimentional arrays. These detector arrays used at the Large Millimeter Telescope will make possible to obtain astronomical images in millimeter and sub-millimeter wavelengths. With this in mind, we are developing a method to produce, with enough reliability, bolometer arrays at INAOE. Until now, silicon nitride diaphragm arrays, useful as radiation absorbers, have succesfully been obtained. Sizes going from one to four millimeter by element in a consistent way; however we have not tested thermometers and metallic contact deposition yet. At the same time, we are working on two possible configurations for the readout electronics; one of them using commercial components while the other will be an integrated circuit specifically designed for this application. Both versions will work below 77K.

Castillo, E.; Serrano, A.; Torres-Jácome, A.

2009-11-01

261

Introducing sub-wavelength pixel THz camera for the understanding of close pixel-to-wavelength imaging challenges  

NASA Astrophysics Data System (ADS)

Conventional guidelines and approximations useful in macro-scale system design can become invalidated when applied to the smaller scales. An illustration of this is when camera pixel size becomes smaller than the diffraction-limited resolution of the incident light. It is sometimes believed that there is no benefit in having a pixel width smaller than the resolving limit defined by the Raleigh criterion, 1.22 ? F/#. Though this rarely occurs in today's imaging technology, terahertz (THz) imaging is one emerging area where the pixel dimensions can be made smaller than the imaging wavelength. With terahertz camera technology, we are able to achieve sub-wavelength pixel sampling pitch, and therefore capable of directly measuring if there are image quality benefits to be derived from sub-wavelength sampling. Interest in terahertz imaging is high due to potential uses in security applications because of the greater penetration depth of terahertz radiation compared to the infrared and the visible. This paper discusses the modification by INO of its infrared MEMS microbolometer detector technology toward a THz imaging platform yielding a sub-wavelength pixel THz camera. Images obtained with this camera are reviewed in this paper. Measurements were also obtained using microscanning to increase sampling resolution. Parameters such as imaging resolution and sampling are addressed. A comparison is also made with results obtained with an 8-12 ?m band camera having a pixel pitch close to the diffractionlimit.

Bergeron, A.; Marchese, L.; Bolduc, M.; Terroux, M.; Dufour, D.; Savard, E.; Tremblay, B.; Oulachgar, H.; Doucet, M.; Le Noc, L.; Alain, C.; Jerominek, H.

2012-05-01

262

Radar scattering laws and wavelength dependence of the lunar surface  

NASA Technical Reports Server (NTRS)

Data from Apollo lunar bistatic radar experiments have been processed to give probability density functions for surface slopes. These show best agreement with a Hagfors scattering law, though data having both gaussian and exponential characteristics also exist. Surface roughness estimates range from 4 deg in maria to at least 8 deg in highlands, values which are appropriate to 25 m horizontal scales and which are areal averages over tens of square kilometers. Roughness varies with wavelength, most strongly in maria.

Simpson, R. A.

1978-01-01

263

A Novel Portable Multi-Wavelength Laser System  

Microsoft Academic Search

There is an established need for a portable and affordable Q-switched laser system for use in studio conservation and small\\u000a scale field use. The ideal system would be capable of producing a variety of wavelengths ranging from the ultraviolet to the\\u000a infrared with sufficient energy per pulse to treat a wide range of materials including stone, marble, terracotta, wood, organic

Andy Charlton; B. Dickinson

264

Wavelength division multiplexing and demultiplexing with photonic crystal waveguide couplers  

Microsoft Academic Search

A multiplexer-demultiplexer (MUX-DEMUX) based on PC waveguide couplers is proposed, and its wavelength demultiplexing properties are theoretically investigated. First, a two-channel MUX-DEMUX is designed and characterized, and then, by cascading, two stages of photonic crystal (PC) waveguide couplers with different coupling coefficients are constructed. The device sizes are expected to be drastically reduced from a scale of a few tens

Masanori Koshiba

2001-01-01

265

Sub-Wavelength Focusing at the Multi-Wavelength Range Using Superoscillations: An Experimental Demonstration  

Microsoft Academic Search

We experimentally demonstrate the formation of a superoscillatory sub-wavelength focus at a multi-wavelength working distance. We first discuss and distinguish superlensing, superdirectivity and superoscillation as different methods which, in their respective ways, achieve sub-diffraction resolution. After establishing superoscillation as a potential way towards sub-wavelength focusing at the multi-wavelength range, we pro- ceed to design, synthesize and demonstrate a superoscillatory sub-wavelength

Alex M. H. Wong; George V. Eleftheriades

2011-01-01

266

Multiple-Wavelength Phase Shifting Interferometry  

NASA Astrophysics Data System (ADS)

The problems of combining ideas of phase shifting interferometry (PSI) and synthetic-wavelength techniques to extend the phase measurement range of conventional single -wavelength PSI are investigated. This combination of PSI and synthetic-wavelengths gives multiple-wavelength phase -shifting interferometry the advantages of: (1) larger phase measurement range and (2) higher accuracy of phase measurement. Advantages, error sources, and limitations of single-wavelength PSI are discussed. Some practical methods to calibrate the piezoelectric transducer (PZT), used to phase shift the reference beam, are presented with experimental results. Two methods of two-wavelength PSI are used to solve the 2(pi) ambiguity problem of single-wavelength PSI. For the first method, two sets of phase data (with 2(pi) ambiguities) for shorter wavelengths are calculated and stored in the computer which calculates the new phase data for the equivalent-wavelength (lamda)(,eq). The "error magnification effect," which reduces the measurement precision of the first method, is then investigated. The second, more accurate method, uses the results of the first method as a reference to correct the 2(pi) ambiguities in the single-wavelength phase data. Experimental results are included to confirm theoretical predictions. The enhancement of two-wavelength PSI is investigated, and requires the phase data of a third wavelength. Experiments are performed to verify the capability of multiple-wavelength PSI. For the wavefront being measured, the difference of the optical-path-difference (OPD) between adjacent pixels is as large as 3.3 waves. After temporal averaging of five sets of data, the repeatability of the measurement is better than 2.5 nm (0.0025%) rms ((lamda) = 632.8 nm). This work concludes with recommendations for future work that should make the MWLPSI a more practical technique for the testing of steep aspheric surfaces.

Cheng, Yeou-Yen

267

Use of Imipenem To Detect KPC, NDM, OXA, IMP, and VIM Carbapenemase Activity from Gram-Negative Rods in 75 Minutes Using Liquid Chromatography-Tandem Mass Spectrometry.  

PubMed

Resistance to extended-spectrum ?-lactam antibiotics has led to a greater reliance upon carbapenems, but the expression of carbapenemases threatens to limit the utility of these drugs. Current methods to detect carbapenemase activity are suboptimal, requiring prolonged incubations during which ineffective therapy may be prescribed. We previously described a sensitive and specific assay for the detection of carbapenemase activity using ertapenem and liquid chromatography-tandem mass spectrometry (LC-MS/MS). In this study, we assessed 402 Gram-negative rods, including both Enterobacteriaceae and non-Enterobacteriaceae expressing IMP, VIM, KPC, NDM, and/or OXA carbapenemases, by using imipenem, meropenem, and ertapenem with LC-MS/MS assays. LC-MS/MS methods for the detection of intact and hydrolyzed carbapenems from an enrichment broth were developed. No ion suppression was observed, and the limits of detection for all three drugs were below 0.04 ?g/ml. The sensitivity and specificity of meropenem and ertapenem for carbapenemase activity among non-Enterobacteriaceae were low, but imipenem demonstrated a sensitivity and specificity of 96% and 95%, respectively, among all Gram-negative rods (GNR) tested, including both Enterobacteriaceae and non-Enterobacteriaceae. LC-MS/MS allows for the analysis of more complex matrices, and this LC-MS/MS assay could easily be adapted for use with primary specimens requiring growth enrichment. PMID:24789180

Kulkarni, M V; Zurita, A N; Pyka, J S; Murray, T S; Hodsdon, M E; Peaper, D R

2014-07-01

268

A mechanical property and stress corrosion evaluation of VIM-ESR-VAR work strengthened and direct double aged Inconel 718 bar material  

NASA Technical Reports Server (NTRS)

Presented are the mechanical properties and the stress corrosion resistance of triple melted vacuum induction melted (VIM), electro-slag remelted (ESR), and vacuum arc remelted (VAR), solution treated, work strengthened and direct double aged Inconel 718 alloy bars 4.00 in. (10.16) and 5.75 in. (14.60 cm) diameter. Tensile, charpy v-notched impact, and compact tension specimens were tested at ambient temperature in both the longitudinal and transverse directions. Longitudinal tensile and yield strengths in excess of 220 ksi (1516.85 MPa) and 200 ksi (1378.00 MPa) respectively, were realized at ambient temperature. Additional charpy impact and compact tension tests were performed at -100 F (-73 C). Longitudinal charpy impact strength equalled or exceeded 12.0 ft-lbs (16.3 Joules) at ambient and at -100 F(-73 C) while longitudinal compact (LC) tension fracture toughness strength remained above 79 ksi (86.80 MPa) at ambient and at -100 F(-73 C) temperatures. No failures occurred in the longitudinal or transverse tensile specimens stressed to 75 and 100 percent of their respective yield strengths and exposed to a salt fog environment for 180 days. Tensile tests performed after the stress corrosion test indicated no mechanical property degradation.

Montano, J. W.

1986-01-01

269

A mechanical property and stress corrosion evaluation of VIM-ESR-VAR work strengthened and direct double aged Inconel 718 bar material  

NASA Astrophysics Data System (ADS)

Presented are the mechanical properties and the stress corrosion resistance of triple melted vacuum induction melted (VIM), electro-slag remelted (ESR), and vacuum arc remelted (VAR), solution treated, work strengthened and direct double aged Inconel 718 alloy bars 4.00 in. (10.16) and 5.75 in. (14.60 cm) diameter. Tensile, charpy v-notched impact, and compact tension specimens were tested at ambient temperature in both the longitudinal and transverse directions. Longitudinal tensile and yield strengths in excess of 220 ksi (1516.85 MPa) and 200 ksi (1378.00 MPa) respectively, were realized at ambient temperature. Additional charpy impact and compact tension tests were performed at -100 F (-73 C). Longitudinal charpy impact strength equalled or exceeded 12.0 ft-lbs (16.3 Joules) at ambient and at -100 F(-73 C) while longitudinal compact (LC) tension fracture toughness strength remained above 79 ksi (86.80 MPa) at ambient and at -100 F(-73 C) temperatures. No failures occurred in the longitudinal or transverse tensile specimens stressed to 75 and 100 percent of their respective yield strengths and exposed to a salt fog environment for 180 days. Tensile tests performed after the stress corrosion test indicated no mechanical property degradation.

Montano, J. W.

1986-09-01

270

Dissemination of Clinical Isolates of Klebsiella oxytoca Harboring CMY-31, VIM-1, and a New OXY-2-Type Variant in the Community ?  

PubMed Central

The aim of the present study was to investigate the epidemiological link of multidrug-resistant Klebsiella oxytoca isolates causing community-onset infections among patients attending our outpatient department and to investigate the underlying resistance mechanisms. The isolates were tested by agar dilution MICs, phenotypic carbapenemase testing, enterobacterial repetitive intergenic consensus-PCR, and pulsed-field gel electrophoresis (PFGE). PCR assays and nucleotide sequencing were employed for the identification of bla gene types and the mapping of the integron-containing metallo-?-lactamase (MBL) gene. During the study period (January 2005 to April 2007), nine broad-spectrum cephalosporin-resistant K. oxytoca clinical isolates were prospectively collected from separate outpatients with urinary tract infections. In all cases, the patients had been hospitalized or exposed to health care facilities during the preceding year. Molecular typing revealed that all isolates belonged to the same K. oxytoca clonal type, which contained five PFGE subtypes. A novel chromosomal OXY-2 ?-lactamase type variant (OXY-2-9) was detected in all isolates, but no mutations in the promoter region justifying blaOXY gene overproduction were detected. In addition, all isolates harbored the plasmidic CMY-31 (LAT-4) AmpC cephalosporinase, while three of them harbored VIM-1 MBL in a class 1 integron structure. This is the first study to present the dissemination in the community of multidrug-resistant K. oxytoca isolates causing extrahospital infections.

Tsakris, Athanassios; Poulou, Aggeliki; Markou, Fani; Pitiriga, Vassiliki; Piperaki, Evangelia-Theophano; Kristo, Ioulia; Pournaras, Spyros

2011-01-01

271

Optical wavelength converters for photonic band gap microcircuits  

NASA Astrophysics Data System (ADS)

We demonstrate compact optical wavelength conversion architecture for picosecond laser pulses and data streams within photonic band gap waveguides. These multimode waveguides are seeded with resonantly driven, inhomogeneously broadened, distributions of quantum dots whose optical transition center frequency is placed near a sharp discontinuity in the local (electromagnetic) density of states (LDOS). This discontinuity is provided by a cutoff in one of the waveguide modes. Wavelength conversion of an optical pulse propagating in the single-mode spectral range of the waveguide, near the LDOS jump, is provided by a steady-state holding field with frequency matched to the center frequency of the quantum dot distribution. In the absence of an incident laser pulse, the holding field is absorbed by the quantum dots. When the incident pulse intensity is sufficient to cause population inversion of a suitable fraction of the quantum dots, the holding field is amplified and the incident pulse profile is imprinted on to the holding field, leading to wavelength conversion in the range of 3-20 nm at wavelengths near 1.5?m . Larger wavelength shifts typically require higher power levels for operation (milliwatt scale) but enable conversion of shorter (picosecond) pulses. Small wavelength shifts typically require narrower distribution of quantum dot resonance frequencies. Using finite-difference time-domain simulations, we show that an optical pulse (Gaussian in time) can create another equivalent optical pulse with either higher or lower center frequency inside the photonic band gap of the structure. Optical pulses of a given center frequency can also be selectively amplified or absorbed depending on the coincident arrival of another laser pulse with different center frequency, enabling all-optical logic operations within a multiwavelength-channel optical circuit.

Vujic, Dragan; John, Sajeev

2009-05-01

272

The Fine-Structure Constant and Wavelength Calibration  

NASA Astrophysics Data System (ADS)

The fine-structure constant is a fundamental constant of the universe--and widely thought to have an unchanging value. However, the past decade has witnessed a controversy unfold over the claimed detection that the fine-structure constant had a different value in the distant past. These astrophysical measurements were made with spectrographs at the world's largest optical telescopes. The spectrographs make precise measurements of the wavelength spacing of absorption lines in the metals in the gas between the quasar background source and our telescopes on Earth. The wavelength spacing gives a snapshot of the atomic physics at the time of the interaction. Whether the fine-structure constant has changed is determined by comparing the atomic physics in the distant past with the atomic physics of today. We present our contribution to the discussion by analyzing three nights data taken with the HIRES instrument (High Resolution Echelle Spectrograph) on the Keck telescope. We provide an independent measurement on the fine-structure constant from the Damped Lyman alpha system at a redshift of z =2.309 (10.8 billion years ago) quasar PHL957. We developed a new method for calibrating the wavelength scale of a quasar exposure to a much higher precision than previously achieved. In our subsequent analysis, we discovered unexpected wavelength calibration errors that has not been taken into account in the previously reported measurements. After characterizing the wavelength miscalibrations on the Keck-HIRES instrument, we obtained several nights of data from the main competing instrument, the VLT (Very Large Telescope) with UVES (Ultraviolet and Visual Echelle Spectrograph). We applied our new wavelength calibration method and uncovered similar in nature systematic errors as found on Keck-HIRES. Finally, we make a detailed Monte Carlo exploration of the effects that these miscalibrations have on making precision fine-structure constant measurements.

Whitmore, Jonathan

273

Optical wavelength converters for photonic band gap microcircuits  

SciTech Connect

We demonstrate compact optical wavelength conversion architecture for picosecond laser pulses and data streams within photonic band gap waveguides. These multimode waveguides are seeded with resonantly driven, inhomogeneously broadened, distributions of quantum dots whose optical transition center frequency is placed near a sharp discontinuity in the local (electromagnetic) density of states (LDOS). This discontinuity is provided by a cutoff in one of the waveguide modes. Wavelength conversion of an optical pulse propagating in the single-mode spectral range of the waveguide, near the LDOS jump, is provided by a steady-state holding field with frequency matched to the center frequency of the quantum dot distribution. In the absence of an incident laser pulse, the holding field is absorbed by the quantum dots. When the incident pulse intensity is sufficient to cause population inversion of a suitable fraction of the quantum dots, the holding field is amplified and the incident pulse profile is imprinted on to the holding field, leading to wavelength conversion in the range of 3-20 nm at wavelengths near 1.5 {mu}m. Larger wavelength shifts typically require higher power levels for operation (milliwatt scale) but enable conversion of shorter (picosecond) pulses. Small wavelength shifts typically require narrower distribution of quantum dot resonance frequencies. Using finite-difference time-domain simulations, we show that an optical pulse (Gaussian in time) can create another equivalent optical pulse with either higher or lower center frequency inside the photonic band gap of the structure. Optical pulses of a given center frequency can also be selectively amplified or absorbed depending on the coincident arrival of another laser pulse with different center frequency, enabling all-optical logic operations within a multiwavelength-channel optical circuit.

Vujic, Dragan; John, Sajeev [Department of Physics, University of Toronto, 60 St. George Street, Toronto, Ontario, M5S-1A7 (Canada)

2009-05-15

274

Maps based on 53 GHz (5.7 mm wavelength)  

NASA Technical Reports Server (NTRS)

Maps based on 53 GHz (5.7 mm wavelength) observations made with the DMR over the entire 4-year mission (top) on a scale from 0 - 4 K, showing the near-uniformity of the CMB brightness, (middle) on a scale intended to enhance the contrast due to the dipole described in the slide 19 caption, and (bottom) following subtraction of the dipole component. Emission from the Milky Way Galaxy is evident in the bottom image. See slide 19 caption for information about map smoothing and projection.

2002-01-01

275

Single-wavelength STED microscope  

NASA Astrophysics Data System (ADS)

The zero-point STED microscope (US Pat. 5,866,911)1 was the first far-field microscope to overcome the diffraction limit, but optimally it requires two expensive synchronized short-pulsed lasers. Replacing the synchronized pulsed lasers with CW lasers had been proposed to reduce costs1, but this seriously reduced resolution compared to a similarly powered pulsed STED microscope. A recent theoretical and experimental study (Nat. Methods 4, 915 (2007))3 argued that CW STED has better resolution than previously believed, but there appear to be flaws in the theory sufficient to raise questions about its reported experimental confirmation. We describe an alternative approach to reducing cost of the STED microscope while preserving resolution. A portion of the beam from a femtosecond pulsed laser of a wavelength able to excite fluorescence by multiphoton absorption, is passed through a long optical fiber to stretch the pulses to reduce their peak power so they can no longer excite but can quench by stimulated emission. The stretched pulses are shaped into a doughnut profile and then recombined with the first beam for interaction with the specimen. With suitable fluorophores, this instrument should be able to match the resolution performance of the pulsed laser STED microscope using separate lasers. Particularly when added to an existing multiphoton microscope, such performance should be achievable at extremely low added cost.

Baer, Stephen C.

2011-02-01

276

Dual-wavelength ultrashort Yb: fiber amplifier  

Microsoft Academic Search

Pump-probe spectroscopy of molecular systems requires high average power, short pulse, mid-infrared sources. Today, OPOs can deliver wavelengths of up to 4 µm and THz systems can supply wavelengths beyond 20 µm. To achieve tunable wavelengths in between these two regions, the signal and idler beams of the OPO can be difference frequency mixed again. This two-step nonlinear process necessarily

Dongfeng Liu; Jie Song; Donna Strickland

2004-01-01

277

Wavelength-doubling optical parametric oscillator  

DOEpatents

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

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

2007-07-24

278

Wavelength Compensation in Fused Fiber Couplers.  

NASA Astrophysics Data System (ADS)

The performance of fused fiber couplers is wavelength dependent. Wavelength spectral compensation is a technique to decrease the effect of the wavelength dependence, which is an essential task for many applications in fiber optic communication systems. Fiber devices such as wavelength -flattened couplers (WFCs) can be fabricated using wavelength spectral compensation methods. In this dissertation, wavelength spectral compensation techniques in fused biconical taper (FBT) couplers including both multimode and single-mode fiber couplers are studied in detail. In multimode fiber coupler operation, a novel theoretical model based on frustrated total internal reflection (FTIR) has been developed to effectively describe the power coupling and loss mechanism. Experimental results support the theoretical predictions. In single -mode fiber couplers, the conventional technique of fabricating WFCs is discussed. An alternative analytical model has been developed based upon coupled mode theory, which provides a relatively simple and mathematically sound explanation to the wavelength spectral compensation. Aiming to simplify WFC fabrication, a new way of constructing WFCs is proposed and demonstrated by connecting regular single-mode fiber couplers, some of which serve as wavelength spectral compensators. WFCs of various structures including 2 x 2, 1 x 3, 1 x 2 ^{N}, and 4 x 4 have been developed, and the experimental data agree with theoretical predictions of performance. Potential applications and future research directions in wavelength spectral compensation are also presented.

Wang, Zhi G.

279

Effective wavelength for multicolor/pyrometry.  

PubMed

The concept of a temperature varying effective wavelength has recently been applied in multiwavelength pyrometry. The effective wavelength is shown to be discontinuous at a particular temperature, and the properties of the effective wavelength over a wide temperature range are explained. It is shown that a simple relationship is sufficient to calculate the effective wavelength and hence radiance at a given temperature without resorting to a convolution integration, in particular where broad filters are used to improve signal levels in a pyrometer. PMID:20234565

Gardner, J L

1980-09-15

280

Wavelength-extended photovoltaic infrared photodetectors  

NASA Astrophysics Data System (ADS)

We report the incorporation of a long-wavelength photovoltaic response (up to 8 ?m) in a short-wavelength p-type GaAs heterojunction detector (with the activation energy of EA˜0.40 eV), operating at 80 K. This wavelength-extended photovoltaic response is enabled by employing a non-symmetrical band alignment. The specific detectivity at 5 ?m is obtained to be 3.5 × 1012 cm Hz1/2/W, an improvement by a factor of 105 over the detector without the wavelength extension.

Lao, Yan-Feng; Pitigala, P. K. D. D. P.; Unil Perera, A. G.; Li, L. H.; Khanna, S. P.; Linfield, E. H.

2014-03-01

281

Inter-network regions of the Sun at millimetre wavelengths  

NASA Astrophysics Data System (ADS)

Aims:The continuum intensity at wavelengths around 1 mm provides an excellent way to probe the solar chromosphere and thus valuable input for the ongoing controversy on the thermal structure and the dynamics of this layer. The synthetic continuum intensity maps for near-millimetre wavelengths presented here demonstrate the potential of future observations of the small-scale structure and dynamics of internetwork regions on the Sun. Methods: The synthetic intensity/brightness temperature maps are calculated on basis of three-dimensional radiation (magneto-)hydrodynamic (MHD) simulations. The assumption of local thermodynamic equilibrium (LTE) is valid for the source function. The electron densities are also treated in LTE for most maps but also in non-LTE for a representative model snapshot. Quantities like intensity contrast, intensity contribution functions, spatial and temporal scales are analysed in dependence on wavelength and heliocentric angle. Results: While the millimetre continuum at 0.3 mm originates mainly from the upper photosphere, the longer wavelengths considered here map the low and middle chromosphere. The effective formation height increases generally with wavelength and also from disk-centre towards the solar limb. The average intensity contribution functions are usually rather broad and in some cases they are even double-peaked as there are contributions from hot shock waves and cool post-shock regions in the model chromosphere. The resulting shock-induced thermal structure translates to filamentary brightenings and fainter regions in between. Taking into account the deviations from ionisation equilibrium for hydrogen gives a less strong variation of the electron density and with it of the optical depth. The result is a narrower formation height range although the intensity maps still are characterised by a highly complex pattern. The average brightness temperature increases with wavelength and towards the limb although the wavelength-dependence is reversed for the MHD model and the NLTE brightness temperature maps. The relative contrast depends on wavelength in the same way as the average intensity but decreases towards the limb. The dependence of the brightness temperature distribution on wavelength and disk-position can be explained with the differences in formation height and the variation of temperature fluctuations with height in the model atmospheres. The related spatial and temporal scales of the chromospheric pattern should be accessible by future instruments. Conclusions: Future high-resolution millimetre arrays, such as the Atacama Large Millimeter Array (ALMA), will be capable of directly mapping the thermal structure of the solar chromosphere. Simultaneous observations at different wavelengths could be exploited for a tomography of the chromosphere, mapping its three-dimensional structure, and also for tracking shock waves. The new generation of millimetre arrays will be thus of great value for understanding the dynamics and structure of the solar atmosphere.

Wedemeyer-Böhm, S.; Ludwig, H. G.; Steffen, M.; Leenaarts, J.; Freytag, B.

2007-09-01

282

Practical wavelength calibration considerations for UV-visible Fourier-transform spectroscopy  

NASA Astrophysics Data System (ADS)

The intrinsic wavelength scale in a modern reference laser-controlled Michelson interferometer-sometimes referred to as the Connes advantage-offers excellent wavelength accuracy with relative ease. Truly superb wavelength accuracy, with total relative uncertainty in line position of the order of several parts in 108, should be within reach with single-point, multiplicative calibration. The need for correction of the wavelength scale arises from two practical off-axis rays propagate through the interferometer, and imperfect geometric alignment of the sample beam with the reference beam and the optical axis of the moving mirror. Although an analytical correction can be made for the finite-aperture effect, calibration with a trusted wavelength standard is typically used to accomplish both corrections. Practical aspects of accurate calibration of an interferometer in the UV-visible region are discussed. Critical issues regarding accurate use of a standard external to the sample source and the evaluation and selection of an appropriate standard are addressed. Anomalous results for two different potential wavelength standards measured by Fabry-Perot interferometry (Ar II and 198 Hg I) are observed. Fourier-transform spectroscopy, wavelength accuracy, wavelength standards, inductively coupled-plasma spectroscopy, spectral interferences, spectral atlas.

Salit, Marc L.; Travis, John C.; Winchester, Michael R.

1996-06-01

283

A dual-wavelength erbium-doped fiber laser with widely tunable wavelength spacing  

NASA Astrophysics Data System (ADS)

A stable dual-wavelength erbium-doped fiber laser (EDFL) with tunable wavelength spacing and equalized output power is proposed and experimentally demonstrated. The fiber laser uses two fiber Fabry-Perot tunable filters (FFPTFs) as the wavelength filter. The main cavity is divided into two sub-cavities with imbalance cavity losses through a 30/70 optical coupler. The tunable wavelength spacing can be achieved by changing the center wavelength of the filters and the equalized dual-wavelength output power can be achieved by properly controlling the variable optical attenuator (VOA) inserted in the lower-loss cavity.

Zhang, Wei-hua; Tong, Zheng-rong; Cao, Ye

2014-03-01

284

[Theoretical analysis of wavelength choice in tri-wavelength method of temperature measurement].  

PubMed

In this paper, a non-dimensional emissivity model with universality is established. For the tri-wavelength method of temperature measurement, based on the non-dimensional emissivity, the applicable measurement condition and theoretical analysis of wavelength choice are mainly introduced. In the discussion of theoretical analysis of wavelength choice, by optimizing the analysis of measurement method and the concept of isothermal line induced by the measurement coordinates, two kinds of ideal choice rules of measurement wavelength are put forward, which will be necessary to the technology application of this tri-wavelength method. Meanwhile the optimizing idea is also applicable to multi-wavelength method of temperature measurement. PMID:15852846

Fu, Tai-ran; Cheng, Xiao-fang; Fan, Xue-liang; Ding, Jin-lei

2005-02-01

285

Wavelength specific excitation of gold nanoparticle thin-films  

NASA Astrophysics Data System (ADS)

Advances in microelectromechanical systems (MEMS) continue to empower researchers with the ability to sense and actuate at the micro scale. Thermally driven MEMS components are often used for their rapid response and ability to apply relatively high forces. However, thermally driven MEMS often have high power consumption and require physical wiring to the device. This work demonstrates a basis for designing light-powered MEMS with a wavelength specific response. This is accomplished by patterning surface regions with a thin film containing gold nanoparticles that are tuned to have an absorption peak at a particular wavelength. The heating behavior of these patterned surfaces is selected by the wavelength of laser directed at the sample. This method also eliminates the need for wires to power a device. The results demonstrate that gold nanoparticle films are effective wavelength-selective absorbers. This "hybrid" of infrared absorbent gold nanoparticles and MEMS fabrication technology has potential applications in light-actuated switches and other mechanical structures that must bend at specific regions. Deposition methods and surface chemistry will be integrated with three-dimensional MEMS structures in the next phase of this work. The long-term goal of this project is a system of light-powered microactuators for exploring cellular responses to mechanical stimuli, increasing our fundamental understanding of tissue response to everyday mechanical stresses at the molecular level.

Lucas, Thomas M.; James, Kurtis T.; Beharic, Jasmin; Moiseeva, Evgeniya V.; Keynton, Robert S.; O'Toole, Martin G.; Harnett, Cindy K.

2014-01-01

286

Wavelength-domain RF photonic signal processing  

NASA Astrophysics Data System (ADS)

This thesis presents a novel approach to RF-photonic signal processing applications based on wavelength-domain optical signal processing techniques using broadband light sources as the information carriers, such as femtosecond lasers and white light sources. The wavelength dimension of the broadband light sources adds an additional degree of freedom to conventional optical signal processing systems. Two novel wavelength-domain optical signal processing systems are presented and demonstrated in this thesis. The first wavelength-domain RF photonic signal processing system is a wavelength-compensated squint-free photonic multiple beam-forming system for wideband RF phased-array antennas. Such a photonic beam-forming system employs a new modulation scheme developed in this thesis, which uses traveling-wave tunable filters to modulate wideband RF signals onto broadband optical light sources in a frequency-mapped manner. The wavelength dimension of the broadband light sources provides an additional dimension in the wavelength-compensated Fourier beam-forming system for mapping the received RF frequencies to the linearly proportional optical frequencies, enabling true-time-delay beam forming, as well as other novel RF-photonic signal processing functions such as tunable filtering and frequency down conversion. A new slow-light mechanism, the SLUGGISH light, has also been discovered with an effective slow-light velocity of 86 m/s and a record time-bandwidth product of 20. Experimental demonstration of true-time-delay beam forming based on the SLUGGISH light effect has also been presented in this thesis. In the second wavelength-domain RF photonic signal processing system, the wavelength dimension increases the information carrying capacity by spectrally multiplexing multiple wavelength channels in a wavelength-division-multiplexing fiber-optic communication system. A novel ultrafast all-optical 3R (Re-amplification, Retiming, Re-shaping) wavelength converter based on interactions between (3+1)-D optical solitons has been developed and demonstrated numerically in this thesis, which can exchange information between different wavelength channels and enhance the network maneuverability. Dispersion management for the generation of (3+1)-D optical solitons using a pair of negative dispersive mirrors is proposed and demonstrated. An ultrafast all-optical wavelength converter based on the dragging interaction between light bullets with different colors is presented, which features a compact size of 100mumx 100mumx 1mm, an ultra-high conversion speed of over 1 TB/s, and a wavelength conversion range of more than 50 nm.

Gao, Lu

287

Optimum wavelengths for two color ranging  

NASA Astrophysics Data System (ADS)

The range uncertainties associated with the refractive atmosphere can be mitigated by the technique of two color, or dual wavelength, ranging. The precision of the differential time of flight (DTOF) measurement depends on the atmospheric dispersion between the two wavelengths, the received pulsewidths and photoelectron counts, and on the amount of temporal averaging. In general, the transmitted wavelengths are not independently chosen but instead are generated via nonlinear optics techniques (harmonic crystals, Raman scattering, etc.) which also determine their relative pulsewidths. The mean received photoelectrons at each wavelength are calculated via the familiar radar link equation which contains several wavelength dependent parameters. By collecting the various wavelength dependent terms, one can define a wavelength figure of merit for a two color laser ranging system. In this paper, we apply the wavelength figure of merit to the case of an extremely clear atmosphere and draw several conclusions regarding the relative merits of fundamental-second harmonic, fundamental-third harmonic, second-third harmonic, and Raman two color systems. We find that, in spite of the larger dispersion between wavelengths, fundamental-third harmonic systems have the lowest figure of merit due to a combination of poor detector performance at the fundamental and poor atmospheric transmission at the third harmonic. The fundamental-second harmonic systems (approximately 700 nm and 350 nm) have the highest figure of merit, but second-third harmonic systems, using fundamental transmitters near 1000 nm, are a close second. Raman-shifted transmitters appear to offer no advantage over harmonic systems because of the relatively small wavelength separation that can be achieved in light gases such as hydrogen and the lack of good ultrashort pulse transmitters with an optimum fundamental wavelength near 400 nm.

Degnan, John J.

1993-06-01

288

The Theory of Scale Relativity  

Microsoft Academic Search

Basing our discussion on the relative character of all scales in nature and on the explicit dependence of physical laws on scale in quantum physics, we apply the principle of relativity to scale transformations. This principle, in combination with its breaking above the Einstein-de Broglie wavelength and time, leads to the demonstration of the existence of a universal, absolute and

Laurent Nottale

1992-01-01

289

Short wavelength laser\\/materials interactions  

Microsoft Academic Search

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

Michael J. Berry

1986-01-01

290

Wavelength Selection in Systems Far from Equilibrium  

Microsoft Academic Search

It is shown that for systems developing stationary periodic patterns there exists at most one stable wavelength state if a supercritical region is connected to a subcritical one by the imposition of a slow spatial variation of the external parameters. In nonpotential systems the selected wavelength depends on the particular combination of parameters that vary but not on the (slow)

Lorenz Kramer; Eshel Ben-Jacob; Helmut Brand; M. C. Cross

1982-01-01

291

Multi-wavelength Astronomy using VOSpec  

Microsoft Academic Search

VOSpec is a multi-wavelength spectral analysis tool developed by the ESA Virtual Observatory Team. The tool is able to handle spectra in the VO context as well as providing analysis capabilities and easy integration of spectra coming from different data providers, wavelengths and different metadata. Since its first development from a very simple interface, VOSpec has gone through a series

D. Baines; P. Osuna; J. Gonzalez; A. Laruelo; J. Salgado; I. Barbarisi

2009-01-01

292

Wavelength measurements with a concave grating spectrograph  

Microsoft Academic Search

Certain disadvantages and limitations in conventional methods of ; measuring wavelengths from grating spectrograms are discussed, and some ; alternative procedures described. It is shown that by fitting thorium standards ; to the dispersion of the Argonne 9.15-m spectrograph, using a polynomial least-; squares program with a digital computer, wavelengths accurate to 1 in 10⁸ ; can be obtained at

Frank S. Tomkins; Mark Fred

1963-01-01

293

Wavelength Modulation in Free Electron Lasers.  

National Technical Information Service (NTIS)

The optical wavelength of a Free Electron Laser (FEL) is dependent on the input electron beam energy. So, as the energy of this beam varies, the optical wavelength from the laser will vary as well. In many applications, this effect may be unwanted and in ...

W. R. Pinkley

1995-01-01

294

Multiple wavelength x-ray monochromators.  

National Technical Information Service (NTIS)

An apparatus and method is provided for separating input x-ray radiation containing first and second x-ray wavelengths into spatially separate first and second output radiation which contain the first and second x-ray wavelengths, respectively. The appara...

P. A. Steinmeyer

1991-01-01

295

Multi-wavelength time domain optical mammography.  

PubMed

A time-resolved optical mammograph operating at 7 wavelengths (637, 683, 785, 832, 905, 916, and 975 nm) in compressed breast geometry was developed. Its clinical application was started on patients bearing malignant and benign lesions. Late gated intensity images are used to obtain information on the spatial distribution of the absorption properties of breast. Scattering images derived from the diffusion theory are also applied for lesion detection and characterization. Cancers are identified in intensity images at short wavelengths, due to the high blood content, while cysts are typically characterized by low scattering at all wavelengths. The increase (from 4 to 7) in the number of wavelengths as compared to the previous versions of the instrument aims at improving the robustness of the fitting procedures for a better estimate of tissue composition and structure and of physiological parameters. Moreover, the new wavelengths contribute to the qualitatively identify tissue composition from intensity images, and could assist lesion detection. PMID:16173823

Taroni, P; Spinelli, L; Torricelli, A; Pifferi, A; Danesini, G M; Cubeddu, R

2005-10-01

296

Multiple wavelength and wavelength switchable actively mode-locked laser based on semiconductor optical amplifier  

Microsoft Academic Search

In this paper, a novel multi-wavelength and wavelength switchable actively mode-locked ring laser based on a semiconductor optical amplifier and cascaded fiber Bragg gratings has been proposed and discussed. Stable wavelength switchable mode-locked pulses have been obtained. Simultaneous multi-wavelength operation is also demonstrated using this scheme through properly designing the length of the ring cavity and the spacing between adjacent

J. He; K. T. Chan

2003-01-01

297

An architecture for a wavelength-interchanging cross-connect utilizing parametric wavelength converters  

Microsoft Academic Search

This paper proposes an architecture for a wavelength-interchanging cross-connect (WIXC) that can be used as a switching node of strictly transparent and scalable networks with all-optical routing and all-optical wavelength conversion capabilities. This architecture utilizes all-optical parametric wavelength converters based on difference-frequency-generation (DFG) or four-wave mixing (FWM), although this work focuses only on the implementation using difference-frequency-generation wavelength converters. The

N. Antoniades; S. J. B. Yoo; Krishna Bala; Georgios Ellinas; Thomas E. Stern; Life Fellow

1999-01-01

298

Evaluation of double- and triple-antibiotic combinations for VIM- and NDM-producing Klebsiella pneumoniae by in vitro time-kill experiments.  

PubMed

Combination therapy is recommended for infections with carbapenemase-producing Klebsiella pneumoniae. However, limited data exist on which antibiotic combinations are the most effective. The aim of this study was to find effective antibiotic combinations against metallo-beta-lactamase-producing K. pneumoniae (MBL-KP). Two VIM- and two NDM-producing K. pneumoniae strains, all susceptible to colistin, were exposed to antibiotics at clinically relevant static concentrations during 24-h time-kill experiments. Double- and triple-antibiotic combinations of aztreonam, ciprofloxacin, colistin, daptomycin, fosfomycin, meropenem, rifampin, telavancin, tigecycline, and vancomycin were used. Synergy was defined as a ?2 log10 decrease in CFU/ml between the combination and its most active drug after 24 h, and bactericidal effect was defined as a ?3 log10 decrease in CFU/ml after 24 h compared with the starting inoculum. Synergistic or bactericidal activity was demonstrated for aztreonam, fosfomycin, meropenem, and rifampin in double-antibiotic combinations with colistin and also for aztreonam, fosfomycin, and rifampin in triple-antibiotic combinations with meropenem and colistin. Overall, the combination of rifampin-meropenem-colistin was the most effective regimen, demonstrating synergistic and bactericidal effects against all four strains. Meropenem-colistin, meropenem-fosfomycin, and tigecycline-colistin combinations were not bactericidal against the strains used. The findings of this and other studies indicate that there is great potential of antibiotic combinations against carbapenemase-producing K. pneumoniae. However, our results deviate to some extent from those of previous studies, which might be because most studies to date have included KPC-producing rather than MBL-producing strains. More studies addressing MBL-KP are needed. PMID:24395223

Tängdén, T; Hickman, R A; Forsberg, P; Lagerbäck, P; Giske, C G; Cars, O

2014-03-01

299

Interferometric observations of the quiet sun at 8 millimeter wavelength  

NASA Technical Reports Server (NTRS)

Results are reported for observations of a quiet region at the center of the sun with an interferometer operating at a wavelength of 8.33 mm and with an east-west baseline giving a maximum angular resolution of 28 arcsec. It is found that strong fluctuations occur over time scales of approximately 10 to 30 min and dominate the data at large hour angles, that smaller and more rapid fluctuations in both amplitude and phase are detected at all hour angles, and that the strong fluctuations are consistent with those that may be produced by the natural time variation of the fringe pattern during observation of a fixed source distribution. The weaker and more rapid fluctuations are tentatively attributed to antenna-tracking variations and the observation of features in a greatly extended source. The results are compared directly with those of two other interferometric studies of the quiet sun at millimeter wavelengths.

Janssen, M. A.; Olsen, E. T.; Lang, K. R.

1979-01-01

300

Wavelength-tunable light shaping with cholesteric liquid crystal microlenses.  

PubMed

The ability to guide light on the mesoscopic scale is important both scientifically and technologically. Especially relevant is the development of wavelength-tunable light-shaping microdevices. Here we demonstrate the use of cholesteric liquid crystal polygonal textures organized as an array of microlenses for this purpose. The beam shaping is controlled by tuning the wavelength of the incident light in the visible spectrum. By taking advantage of the self-organization property of liquid crystals, the structure of the lens and its optical response are tailored by changing the annealing time of the single layer material during a completely integrated one-step process. The intrinsic helical organization of the layer is the cause of the light shaping and not the shape of the surface as for conventional lenses. A new concept of light manipulation using the structure chirality of liquid crystals is demonstrated, which concerns soft matter photonic circuits to mould the light. PMID:24789329

Bayon, Chloé; Agez, Gonzague; Mitov, Michel

2014-06-21

301

A novel wavelength availability advertisement based ASON routing protocol implementation  

NASA Astrophysics Data System (ADS)

A novel wavelength availability advertisement based ASON routing protocol implementation is proposed in this paper which is derived from Open Shortest Path First protocol (OSPF) version 2. It can be applied to ASON network with a single control domain and can be easily extended to support routing in the multi-domain scenarios. Two new types of link state advertisement (LSA) are suggested for disseminating wavelength availability and network topology information. The OSPF mechanisms are inherited to ensure that the routing messages are delivered more reliably and converged more quickly while with fewer overheads. The topology auto discovery is realized through LSA flooding interacting with auto neighbor discovery using Link Management Protocol. The new LSA formats are given and how the link state database (LSD) is comprised is described. The new data structures proposed include topology resource list, adjacency list and route table. Then we analyze the differences of ASON in link state exchange, routing information flooding procedure, flushing procedure and new resources participating, i.e. new links or nodes join in an existing ASON. The link or node failure and recovery effect and how to deal with them are settled as well. In order to adopt different Routing and Wavelength Assignment (RWA) algorithms, a standard and efficient interface is designed. After extensive simulation we give the numerical analysis and come to the following conclusions: wavelength availability information flooding Convergence Time is about 30 milliseconds and it is not affected by RWA algorithms and the call traffic load; routing Protocol Average Overhead rises linearly with the increase of traffic load; Average Connection Setup Time decreases with the increase of traffic load because of the decrease of Average Routing Distance of the successfully lightpaths; Wavelength availability advertisement can greatly promote the blocking performance of ASON in relatively low traffic load; ASON operator can make a good trade off between the wavelength availability advertisement Protocol Average Overhead and Blocking Probability by adopting and adjusting the routing update triggers; and the last is that wavelength availability advertisement throughout the optical network is applicable and our ASON routing protocol implementation could be applied in ASON when its scale is not too large and if the calls do not arrive and leave the network in a too frequent pace.

Li, Jian; Liu, Juan; Zhang, Jie; Gu, Wanyi

2005-12-01

302

Wavelengths effective in induction of malignant melanoma  

SciTech Connect

It is generally agreed that sunlight exposure is one of the etiologic agents in malignant melanoma of fair-skinned individuals. However, the wavelengths responsible for tumorigenesis are not known, although DNA is assumed to be the target because individuals defective in the repair of UV damage to DNA are several thousandfold more prone to the disease than the average population. Heavily pigmented back-cross hybrids of the genus Xiphophorus (platyfish and swordtails) are very sensitive to melanoma induction by single exposures to UV. The authors irradiated groups of five 6-day-old fish with narrow wavelength bands at 302, 313, 365, 405, and 436 nm and score the irradiated animals for melanomas 4 months later. They used several exposures at each wavelength to obtain estimates of the sensitivity for melanoma induction as a function of exposure and wavelength. The action spectrum (sensitivity per incident photon as a function of wavelength) for melanoma induction shows appreciable sensitivity at 365, 405, and probably 436 nm, suggesting that wavelengths not absorbed directly in DNA are effective in induction. They interpret the results as indicating that light energy absorbed in melanin is effective in inducing melanomas in this animal model and that, in natural sunlight, 90-95% of melanoma induction may be attributed to wavelengths >320 nm-the UV-A and visible spectral regions. 25 refs., 4 figs., 1 tab.

Setlow, R.B.; Grist, E.; Thompson, K.; Woodhead, A.D. (Brookhaven National Laboratory, Upton, NY (United States))

1993-07-15

303

Evolution of wavelength shrinkage in lithography  

NASA Astrophysics Data System (ADS)

Optical lithography has driven on-going miniaturization in the microelectronics industry, thereby enabling continuation of 'Moore's Law'. To achieve this, lithographers have steadily reduced the wavelength of the illumination light used in the optical systems. However, as we transition from the visible spectrum, through ultra-violet, and now towards the soft x-ray wavelength regime, a host of new challenges are introduced. The majority of these challenges are related to material properties, as wavelength reduction significantly narrows the field of available materials that are both sufficiently transparent, as well as radiation resistant to the illumination light. We also are limited by the actual wavelengths that can be produced which deliver sufficient power to provide a production-worthy light source. In this paper, we will examine the history of wavelength transition in optical lithography, explaining the key material developments that enabled wavelengths such as 248nm to be highly successful, as well as explain the reasons wavelengths such as 157nm and 126nm were not adopted.

Kameyama, Masaomi; McCallum, Martin; Owa, Soichi

2009-05-01

304

Sub-wavelength focusing meta-lens.  

PubMed

We show that a planar plasmonic metamaterial with spatially variable meta-atom parameters can focus transmitted light into sub-wavelength hot-spots located beyond the near-field of the metamaterial. By nano-structuring a gold film we created an array of meta-lenses generating foci of 160 nm (0.2?) in diameter when illuminated by a wavelength of 800 nm. We attribute the occurrence of sub-wavelength hotspots beyond the near field to the phenomenon of superoscillation. PMID:23546140

Roy, Tapashree; Rogers, Edward T F; Zheludev, Nikolay I

2013-03-25

305

Wavelength modulation in free electron lasers  

NASA Astrophysics Data System (ADS)

The optical wavelength of a Free Electron Laser (FEL) is dependent on the input electron beam energy. So, as the energy of this beam varies, the optical wavelength from the laser will vary as well. In many applications, this effect may be unwanted and in others it may be desirable. At the Stanford University Superconducting Free Electron Laser Facility, a feedback mechanism has been implemented to study the effects of electron beam energy fluctuation. Here, numerical techniques are used to study optical wavelength modulation caused by electron beam energy modulation where the amplitude modulation is within the gain spectrum bandwidth of the FEL.

Pinkley, W. R.

1995-03-01

306

Wavelength references for interferometry in air.  

PubMed

Cavity-mode wavelengths in air are determined by measuring a laser's frequency while it is locked to the mode in vacuum during a calibration step and subsequently correcting the mode wavelength for atmospheric pressure compression, temperature difference, and material aging. Using a Zerodur ring cavity, we demonstrate a repeatability of +/- 2 x 10(-8) (3sigma), with the wavelength accuracy limited to +/- 4 x 10(-8) by knowledge of the absolute helium gas temperature during the pressure calibration. Mirror cleaning perturbed the mode frequency by less than deltav/v approximately 3 x 10(-9), limited by temperature correction residuals. PMID:16381529

Fox, Richard W; Washburn, Brian R; Newbury, Nathan R; Hollberg, Leo

2005-12-20

307

Dual wavelength laser thermal processing of semiconductors  

NASA Astrophysics Data System (ADS)

The annealing of ion implantation damage in semiconductors by laser irradiation is optimized by employing a dual wavelength laser source and tailoring the time delay between pulses at the two wavelengths. The strong temperature dependence of the absorption coefficient for the initially less strongly absorbed wavelength is neutralized. A solid state laser emitting high intensity was used in conjunction with an optical fiber delay line to study the annealing characteristics of an arsenic implanted silicon solar cell wafer. The results are in agreement with a theoretical model based on melting and liquid phase epitaxial regrowth.

Cohen, M. G.; Liu, K. C.; Kaplan, R. A.

1980-06-01

308

Wavelength references for interferometry in air  

SciTech Connect

Cavity-mode wavelengths in air are determined by measuring a laser's frequency while it is locked to the mode in vacuum during a calibration step and subsequently correcting the mode wavelength for atmospheric pressure compression, temperature difference, and material aging. Using a Zerodur ring cavity, we demonstrate a repeatability of {+-}2x10-8(3{sigma}), with the wavelength accuracy limited to {+-}4x10-8by knowledge of the absolute helium gas temperature during the pressure calibration. Mirror cleaning perturbed the mode frequency by less than {delta} {nu}/{nu}{approx}3x10-9, limited by temperature correction residuals.

Fox, Richard W.; Washburn, Brian R.; Newbury, Nathan R.; Hollberg, Leo

2005-12-20

309

Three-wavelength scheme to optimize hohlraum coupling on the National Ignition Facility  

SciTech Connect

By using three tunable wavelengths on different cones of laser beams on the National Ignition Facility, numerical simulations show that the energy transfer between beams can be tuned to redistribute the energy within the cones of beams most prone to backscatter instabilities. These radiative hydrodynamics and laser-plasma interaction simulations have been tested against large-scale hohlraum experiments with two tunable wavelengths and reproduce the hohlraum energetics and symmetry. Using a third wavelength provides a greater level of control of the laser energy distribution and coupling in the hohlraum, and could significantly reduce stimulated Raman scattering losses and increase the hohlraum radiation drive while maintaining a good implosion symmetry.

Michel, P.; Divol, L.; Town, R. P. J.; Rosen, M. D.; Callahan, D. A.; Meezan, N. B.; Schneider, M. B.; Moody, J. D.; Dewald, E. L.; Widmann, K.; Bond, E.; Thomas, C. A.; Dixit, S.; Williams, E. A.; Hinkel, D. E.; Berger, R. L.; Landen, O. L.; Edwards, M. J.; MacGowan, B. J.; Lindl, J. D. [Lawrence Livermore National Laboratory, Livermore, California 94551 (United States)

2011-04-15

310

Semiconductor devices for optical communications in 1 micron band of wavelength. [gallium indium arsenide phosphide lasers and diodes  

NASA Technical Reports Server (NTRS)

Crystal growth and the characteristics of semiconductor lasers and diodes for the long wavelength band used in optical communications are examined. It is concluded that to utilize the advantages of this band, it is necessary to have a large scale multiple wavelength communication, along with optical cumulative circuits and optical exchangers.

Suematsu, Y.; Iga, K.

1980-01-01

311

SHORT-WAVELENGTH ELECTROSTATIC FLUCTUATIONS IN THE SOLAR WIND  

SciTech Connect

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

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

2011-09-20

312

WAVELENGTH CALIBRATION OF THE VLT-UVES SPECTROGRAPH  

SciTech Connect

We attempt to measure possible miscalibration of the wavelength scale of the VLT-UVES spectrograph. We take spectra of QSO HE0515-4414 through the UVES iodine cell which contains thousands of well-calibrated iodine lines and compare these lines to the wavelength scale from the standard thorium-argon pipeline calibration. Analyzing three exposures of this z = 1.71 QSO, we find two distinct types of calibration shifts needed to correct the Th/Ar wavelength scale. First, there is an overall average velocity shift of between 100 m s{sup -1} and 500 m s{sup -1} depending upon the exposure. Second, within a given exposure, we find intra-order velocity distortions of 100 m s{sup -1} up to more than 200 m s{sup -1}. These calibration errors are similar to, but smaller than, those found earlier in the Keck HIRES spectrometer. We discuss the possible origins of these two types of miscalibration. We also explore the implications of these calibration errors on the systematic error in measurements of {Delta}{alpha}/{alpha}, the change in the fine-structure constant derived from measurement of the relative redshifts of absorption lines in QSO absorption systems. The overall average, exposure-dependent shifts should be less relevant for fine-structure work, but the intra-order shifts have the potential to affect these results. Using either our measured calibration offsets or a Gaussian model with sigma of around 90 m s{sup -1}, Monte Carlo mock experiments find errors in {Delta}{alpha}/{alpha} of between 1 x 10{sup -6} N {sup -1/2}{sub sys} and 3 x 10{sup -6} N {sup -1/2}{sub sys}, where N{sub sys} is the number of systems used and the range is due to dependence on how many metallic absorption lines in each system are compared.

Whitmore, Jonathan B.; Griest, Kim [Department of Physics, University of California, San Diego, CA 92093 (United States); Murphy, Michael T., E-mail: jonathan.b.whitmore@gmail.co, E-mail: mmurphy@swin.edu.a, E-mail: kgriest@ucsd.ed [Centre for Astrophysics and Supercomputing, Swinburne University of Technology, Melbourne, Victoria 3122 (Australia)

2010-11-01

313

Short Wavelength Laser/Materials Interactions.  

National Technical Information Service (NTIS)

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

M. J. Berry

1986-01-01

314

Multiple-Wavelength Pyrometry Independent Of Emissivity  

NASA Technical Reports Server (NTRS)

Multiple-wavelength pyrometric method provides for determination of two sequential temperatures of same surface or temperatures of two surfaces made of same material. Temperatures measured, without knowing emissivity, by uncalibrated spectral radiometer.

Ng, Daniel

1996-01-01

315

Wavelength-selective infrared Salisbury screen absorber.  

PubMed

Experimental long wavelength infrared spectral response characterization of a narrowband Salisbury screen absorber suitable for use in microbolometer focal plane arrays is presented. We have demonstrated a microfabricated germanium dielectric support structure layer that replaces the usual silicon nitride structural layer in microbolometers. The fabricated Salisbury screen absorber consists of a chromium resistive sheet as an absorber layer above a germanium dielectric/air-gap/interference structure. In order to produce wavelength-selective narrowband absorption, the general design rules for the germanium dielectric supported Salisbury screen show that the thickness of the air gap should be a half wavelength thick and the optical thickness of the germanium layer a quarter dielectric wavelength thick. PMID:24787414

Jung, Joo-Yun; Park, Jong Yeon; Han, Sangwook; Weling, Aniruddha S; Neikirk, Dean P

2014-04-10

316

Multiple wavelength photolithography for preparing multilayer microstructures  

DOEpatents

The invention relates to a multilayer microstructure and a method for preparing thereof. The method involves first applying a first photodefinable composition having a first exposure wavelength on a substrate to form a first polymeric layer. A portion of the first photodefinable composition is then exposed to electromagnetic radiation of the first exposure wavelength to form a first pattern in the first polymeric layer. After exposing the first polymeric layer, a second photodefinable composition having a second exposure wavelength is applied on the first polymeric layer to form a second polymeric layer. A portion of the second photodefinable composition is then exposed to electromagnetic radiation of the second exposure wavelength to form a second pattern in the second polymeric layer. In addition, a portion of each layer is removed according to the patterns to form a multilayer microstructure having a cavity having a shape that corresponds to the portions removed.

Dentinger, Paul Michael (Livermore, CA); Krafcik, Karen Lee (Livermore, CA)

2003-06-24

317

Wavelength-agile optical access networking system  

NASA Astrophysics Data System (ADS)

In this paper, we introduce our Home2015 project - wavelength-agile optical access networking system. We propose a multi-wavelength access network to offer higher system capacities for next-generation optical access. Our proposed concept of virtual PON (VPON) is introduced to realize dynamic ONU re-grouping functionality. Optical network units (ONUs) in the PON system can dynamically form different TDM-PON by using a different downlink and uplink wavelength channel. Novel photonic silicon chip integration techniques are introduced to reduce size and cost of the ONUs. We also introduce our works on live 3D hologram video transmission platform design and live 3D hologram video transmission via the 10-Gb/s wavelength-agile optical access network. Our demostration shows that our system has good transmission performances.

Cheng, Xiaofei; Yeo, Yong-Kee; Li, Chao; Xu, Xuewu

2011-11-01

318

Short wavelength laser/materials interactions  

NASA Astrophysics Data System (ADS)

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

Berry, Michael J.

1986-11-01

319

SALSA - A lunar submillimeter-wavelength array  

NASA Technical Reports Server (NTRS)

A conceptual design for a Synthesis Array for Lunar Submillimeter Astronomy (SALSA) is described with emphasis on information relevant to its implementation. SALSA is optimized to synthesize images of astronomical sources at wavelengths between 60 and 300 microns with an angular resolution of 10 milliarcseconds at the shortest wavelength. The discussion covers engineering considerations and descriptions of subsystems, including the environmental shield, antenna, and beam transport.

Mahoney, M. J.; Marsh, K. A.

1992-01-01

320

Focal plane imaging systems for millimeter wavelengths  

Microsoft Academic Search

The authors discuss critical aspects of imaging system design and describe several different imaging systems employing focal plane array receivers operating in the 3-mm-2-mm wavelength range. Recent progress in millimeter-wavelength optics, antennas, receivers and other components permits greatly enhanced system performance in a wide range of applications. A radiometric camera for all-weather autonomous aircraft landing capability and a high sensitivity

P. F. Goldsmith; C.-T. Hsieh; G. R. Huguenin; J. Kapitzky; E. L. Moore

1993-01-01

321

Wavelength-Division Multiplexing With Integrated Optics  

NASA Technical Reports Server (NTRS)

High-density wavelength-division-multiplexed optoelectronic integrated circuits developed for use as transceivers in fiber-optic communications between computers, according to proposal. One of proposed multiplexer/demultiplexer units provides simultaneous communication on 32 wavelength channels at overall data rate greater than 40 Gb/s, increasing channel capacity, simplifying transmitting and receiving electronics and reducing delay by eliminating serial-to-parallel and parallel-to-serial "bottlenecks."

Lang, Robert J.; Forouhar, Siamak

1995-01-01

322

Single sub-wavelength aperture with greatly enhanced transmission  

NASA Astrophysics Data System (ADS)

High transmission efficiency at terahertz (THz) frequency is reported for a single aperture with sub-wavelength dimensions having a Siemens-star shape, microfabricated in the metal film and surrounded by periodic surface corrugations. Compared to theoretical predictions for a simple circular hole of equivalent area, up to ˜106 transmission enhancements were observed experimentally. Such a pointed-shape aperture was also used to obtain the detailed profile of the electric field distribution in the focal plane of a linearly polarized focused THz beam. Applications could be extended to other regions of the electromagnetic spectrum by appropriate scaling of aperture microstructure.

Bulgarevich, D. S.; Watanabe, M.; Shiwa, M.

2012-05-01

323

Damping of long-wavelength kinetic alfven fluctuations: linear theory  

SciTech Connect

The full electromagnetic linear dispersion equation for kinetic Alfven fluctuations in a homogeneous, isotropic, Maxwellian electron-proton plasma is solved numerically in the long wavelength limit. The solutions are summarized by an analytic expression for the damping rate of such modes at propagation sufficiently oblique to the background magnetic field B{sub o} which scales as k{sub {perpendicular}}{sup 2} k{sub {parallel}} where the subscripts denote directions relative to B{sub o}. This damping progressively (although not monotonically) increases with increasing electron {beta}, corresponding to four distinct damping regimes: nonresonant, electron Landau, proton Landau, and proton transit-time damping.

Gary, S Peter [Los Alamos National Laboratory; Borovsky, Joseph E [Los Alamos National Laboratory

2008-01-01

324

Wavelength-tunable duplex integrated light source  

NASA Astrophysics Data System (ADS)

A monolithically integrated opto-electronic device is proposed as a fast wavelength-switching light source. This tunable duplex integrated light source comprises two wavelength-tunable distributed Bragg reflector (DBR) laser diodes (LDs), two MQW-electro-absorption optical switches, a Y-shaped waveguide coupler, a MQW-electro-absorption modulator, and two thermal drift compensators (TDCs). The wavelength-switching time of the optical switches was estimated to be 60 ps including a 50-ps rise time for the electrical-pulse generator. The wavelength of a 10-Gbit/s NRZ-modulated optical signal can be switched without bit loss. The function of the TDCs is to keep the device-chip temperature constant. Thermal-transient- induced wavelength drift with a millisecond-order time constant, which has been reported for DBR-LDs, and thermal crosstalk between the tuning regions of the integrated LDs, which causes wavelength fluctuation, are effectively suppressed by thermal-drift-compensation operation using the TDCs.

Okamoto, Hiroshi; Yasaka, H.; Oe, K.

1996-04-01

325

Smoke optical depths: magnitude, variability, wavelength dependence  

SciTech Connect

The Ames airborne, autotracking sunphotometer has been operated aboard a Sandia Laboratories research aircraft to measure magnitudes, temporal/spatial variabilities, and wavelength dependence of optical depths in the near-ultraviolet to near-infrared spectrum of smoke from two forest fires and one jet fuel fire and of background air. The results were corrected for Rayleigh scattering and for estimated absorption by ozone and nitrogen dioxide. Characteristic differences in the aerosol optical depths of background atmospheres and of different types of smokes are the following (1) the magnitude and wavelength dependence of ''background'' optical depths vary with the geographic location at which the measurements are performed; (2) the wavelength dependence of smoke optical depths depends on the fuels that feed the fires and on the residence time of the smoke cloud in the atmosphere. In general, the jet fuel smoke optical depths tended to be less wavelength dependent (near-ultraviolet to near-infrared) than background aerosol optical depths. Forest fire smoke optical depths showed a wide range of wave-length dependences, including incidents of wavelength-independent extinction. copyright American Geophysical Union 1988

Pueschel, R.F.; Livingston, J.M.; Russell, P.B.; Colburn, D.A.; Ackerman, T.P.; Allen, D.A.; Zak, B.D.; Einfeld, W.

1988-07-20

326

A Comparison of Allocation Policies in Wavelength Routing Networks  

Microsoft Academic Search

We consider wavelength routing networks with and without wavelength converters, and several wavelength allocation policies. Through numerical and simulation results we obtain upper and lower bounds on the blocking probabilities for two wavelength allocation policies that are most likely to be used in practice, namely, most-used and first-fit allocation. These bounds are the blocking probabilities obtained by the random wavelength

Yuhong Zhu; George N. Rouskas; Harry G. Perros

2000-01-01

327

The dynamics of interacting nonlinearities governing long wavelength driftwave turbulence  

SciTech Connect

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

Newman, D.E.

1993-09-01

328

Ant colony optimisation for virtual-wavelength-path routing and wavelength allocation  

Microsoft Academic Search

Ant Colony Optimisation (ACO) is applied to the problem of routing and wavelength allocation in a multi-wavelength all-optical virtual-wavelength-path routed transport network. Three variants of our ACO algorithm are proposed: local update (LU), global update\\/distance (GU\\/D) and global update\\/occupancy (GU\\/O). All three extend the usual practice that ants are attracted by the pheromone trail of ants from their own colony:

Griselda Navarro Varela; Mark C. Sinclair

1999-01-01

329

Use of Dual-wavelength Radar for Snow Parameter Estimates.  

National Technical Information Service (NTIS)

Use of dual-wavelength radar, with properly chosen wavelengths, will significantly lessen the ambiguities in the retrieval of microphysical properties of hydrometeors. In this paper, a dual-wavelength algorithm is described to estimate the characteristic ...

L. Liao R. Meneghini T. Iguchi A. Detwiler

2005-01-01

330

Two wavelength satellite laser ranging using SPAD  

NASA Technical Reports Server (NTRS)

When ranging to satellites with lasers, there are several principal contributions to the error budget: from the laser ranging system on the ground, from the satellite retroarray geometry, and from the atmosphere. Using a single wavelength, we have routinely achieved a ranging precision of 8 millimeters when ranging to the ERS-1 and Starlette satellites. The systematic error of the atmosphere, assuming the existing dispersion models, is expected to be of the order of 1 cm. Multiple wavelengths ranging might contribute to the refinement of the existing models. Taking into account the energy balance, the existing picosecond lasers and the existing receiver and detection technology, several pairs or multiple wavelengths may be considered. To be able to improve the atmospheric models to the subcentimeter accuracy level, the differential time interval (DTI) has to be determined within a few picoseconds depending on the selected wavelength pair. There exist several projects based on picosecond lasers as transmitters and on two types of detection techniques: one is based on photodetectors, like photomultipliers or photodiodes connected to the time interval meters. Another technique is based on the use of a streak camera as an echo signal detector, temporal analyzer, and time interval vernier. The temporal analysis at a single wavelength using the streak camera showed the complexity of the problem.

Prochazka, Ivan; Hamal, Karel; Jelinkova, Helena; Kirchner, Georg; Koidl, F.

1993-01-01

331

Dual-wavelength ultrashort Yb: fiber amplifier  

NASA Astrophysics Data System (ADS)

Pump-probe spectroscopy of molecular systems requires high average power, short pulse, mid-infrared sources. Today, OPOs can deliver wavelengths of up to 4 µm and THz systems can supply wavelengths beyond 20 µm. To achieve tunable wavelengths in between these two regions, the signal and idler beams of the OPO can be difference frequency mixed again. This two-step nonlinear process necessarily leads to average powers much less than the OPO pump, typically a 1 W Ti:Sapphire laser. The goal of this work is to generate high average power (>1W) pump and signal beams for difference frequency generation at around 15 µm. In this paper, we report initial experimental results of two-wavelength amplification in Yb-doped double cladding fiber (DCF). A novel dual wavelength (1042nm and 1100nm) ultrashort optical pulse Yb fiber amplifier is described. The single stage Yb:fibre amplifier which is pumped by a 965nm diode laser achieved 500 gain yielding 150 mW total power including ASE. The ASE is eliminated with a notch filter. The power in the two colours was increased to 450 mW, with the ASE suppressed in a second Yb fiber amplifier also pumped by a 965nm laser diode.

Liu, Dongfeng; Song, Jie; Strickland, Donna

2004-11-01

332

Millimeter wavelength spectroscopy and continuum studies of the planets  

NASA Technical Reports Server (NTRS)

Careful observations were made at 86.1 GHz to derive the absolute brightness temperatures of the Sun (7914 + or - 192 K), Venus (357.5 + or - 13.1 K), Jupiter (179.4 + or - 4.7K), and Saturn (153.4 + or - 4.8 K) with a standard error of about 3%. This is a significant improvement in accuracy over previous results. A stable transmitter and novel superheterodyne receiver were constructed and used to determine the effective collecting area of the MWO 4.9 m antenna relative to a previously calibrated standard gain horn. The thermal scale was set by calibrating the radiometer with carefully constructed and tested hot and cold loads. The brightness temperatures may be used to establish an absolute calibration scale and to determine the antenna aperture and beam efficiencies of other radio telescopes at 3.5 mm wavelength.

Vandenbout, P. A.; Davis, J. H.

1979-01-01

333

Blocking in Wavelength Routing Networks, Part II: Mesh Topologies  

Microsoft Academic Search

this paper we consider the problem of computing call blocking probabilities in mesh wavelength routingnetworks with fixed and alternate routing and random wavelength allocation. We develop an iterative

Yuhong Zhu; George N. Rouskas; Harry G. Perros

1999-01-01

334

Polymer nanowrinkles with continuously tunable wavelengths.  

PubMed

This paper describes a parallel method to generate polymer nanowrinkles over large areas with wavelengths that were continuously tuned down to 30 nm. Reactive ion etching using fluorinated gases was used to chemically treat thermoplastic polystyrene films, which resulted in a stiff skin layer. Upon heating, the treated thermoplastic, microscale, and nanoscale wrinkles were formed. We used variable-angle spectroscopic ellipsometry to characterize the thickness of the skin layer; this thickness could then be used to predict and control the nanowrinkle wavelength. Because the properties of these nanotextured polymer surfaces can be tuned over a large range of wrinkle wavelengths, they are promising for a broad range of applications, especially those that require large-area and uniform surface patterning. PMID:23758140

Huntington, Mark D; Engel, Clifford J; Hryn, Alexander J; Odom, Teri W

2013-07-10

335

Multi-wavelength laser active coherent combination  

NASA Astrophysics Data System (ADS)

A seed laser oscillating at different frequencies is proved to have the potential to mitigate the stimulated Brillouin scattering (SBS) effect in a fiber amplifier, which may increase the emission power of a coherent beam combination (CBC) system greatly. In this study, a basic mathematical model describing the multi-wavelength CBC is proposed on the fundamentals of CBC. A useful method for estimating the combination effect and analysing the feasibility and the validity of the multi-wavelength coherent combination is provided. In the numerical analysis, accordant results with four-wavelength four-channel CBC experiments are obtained. Through calculations of some examples with certain spectra, the unanticipated excellent combination effect with a few frequencies involved is explained, and the dependence of the combination effect on the variance of the amplifier chain length and the channel number is clarified.

Han, Kai; Xu, Xiao-Jun; Liu, Ze-Jin

2012-05-01

336

Silicon CCD optimized for NIR wavelengths.  

NASA Astrophysics Data System (ADS)

CCDs processed on typical substrates exhibit low NIR QE. Because the relatively thin epitaxial layer allows a high percentage of long wavelength photons to pass through and the reflection loss of back surface is high. A thick epitaxial layer allows the longer wavelength photons to be absorbed into the epitaxial layer where the resultant electrons generated will be collected in the potential wells. The drawback of processing with this method is a resultant degradation of carrier diffusion MTF. Increasing the depleted region under each gate, which can be realized by using high resistivity substrates, can enhance MTF. A new kind of CCD fabricated on high resisitivity silicon at Lick Observatory has superior red performance beyond 800 nm wavelength. The application of thin film AR coating directly on to the CCD back surface can significantly reduce reflection loss from UV to NIR and greatly decrease interference fringing on back illuminated CCDs.

Song, Qian; Ji, Kaifan; Cao, Wenda

337

Mechanisms and Methods for Selective Wavelength Filtering  

NASA Technical Reports Server (NTRS)

An optical filter includes a dielectric waveguide layer, supporting waveguide modes at specific wavelengths and receiving incident light, a corrugated film layer, composed of one of a metal and a semiconductor and positioned adjacent to a second surface of the waveguide layer and a sensor layer, wherein the sensor layer is capable of absorbing optical energy and generating a corresponding electrical signal. The metal film layer supports a plurality of plasmons, the plurality of plasmons producing a first field and is excited by a transverse mode of the waveguide modes at a wavelength interval. The first field penetrates the sensor layer and the sensor layer generates an electrical signal corresponding to an intensity of received incident light within the wavelength interval.

Tuma, Margaret (Inventor); Brown, Thomas G. (Inventor); Gruhlke, Russell (Inventor)

2007-01-01

338

Wavelength sharing in WDM passive optical networks  

NASA Astrophysics Data System (ADS)

Progress towards the definition of next-generation passive optical networks (PONs) based on wavelength-division multiplexing (WDM) is reviewed and compared to emerging requirements. A key challenge is providing ultra-high (e.g. 10 Gbps) bandwidth for demanding users while cost-effectively supporting less-demanding users. A new approach is presented in which diverse bandwidth requirements are supported on a conventional WDM PON outside plant through the use of flexible wavelength sharing in the local office. An example is demonstrated experimentally showing that with 16 users per passive node, each wavelength can be shared by up to 16 users distributed across up to 16 PONs served by the same local office. Factors limiting sharing and throughput are discussed.

Darcie, Thomas E.; Barakat, Neil; Iannone, Patrick P.; Reichmann, Kenneth C.

2008-11-01

339

Device for wavelength-selective imaging  

DOEpatents

An imaging device captures both a visible light image and a diagnostic image, the diagnostic image corresponding to emissions from an imaging medium within the object. The visible light image (which may be color or grayscale) and the diagnostic image may be superimposed to display regions of diagnostic significance within a visible light image. A number of imaging media may be used according to an intended application for the imaging device, and an imaging medium may have wavelengths above, below, or within the visible light spectrum. The devices described herein may be advantageously packaged within a single integrated device or other solid state device, and/or employed in an integrated, single-camera medical imaging system, as well as many non-medical imaging systems that would benefit from simultaneous capture of visible-light wavelength images along with images at other wavelengths.

Frangioni, John V. (Wayland, MA)

2010-09-14

340

Cryogenic Amplifier Based Receivers at Submillimeter Wavelengths  

NASA Technical Reports Server (NTRS)

The operating frequency of InP high electron mobility transistor (HEMT) based amplifiers has moved well in the submillimeter-wave frequencies over the last couple of years. Working amplifiers with usable gain in waveguide packages has been reported beyond 700 GHz. When cooled cryogenically, they have shown substantial improvement in their noise temperature. This has opened up the real possibility of cryogenic amplifier based heterodyne receivers at submillimeter wavelengths for ground-based, air-borne, and space-based instruments for astrophysics, planetary, and Earth science applications. This paper provides an overview of the science applications at submillimeter wavelengths that will benefit from this technology. It also describes the current state of the InP HEMT based cryogenic amplifier receivers at submillimeter wavelengths.

Chattopadhyay, Goutam; Reck, Theodore and; Schlecht, Erich; Lin, Robert; Deal, William

2012-01-01

341

Tailoring the wavelength of semiconductor disk lasers  

NASA Astrophysics Data System (ADS)

Optically-pumped semiconductor disk lasers (SDLs) represent a proven approach for generation of multi-watt output powers with excellent beam quality [1-6]. They combine many advantages of solid-state lasers with the added benefit of wavelength tailoring provided by the semiconductor gain material. During the past few years a wafer fusion technique has been used extensively in the producing of vertical-cavity surface-emitting lasers operating at the telecom wavelengths of 1.3 - 1.55 ?m. This technique allows the integration of non-lattice-matched semiconductor materials, e.g. GaAs and InP, which cannot be grown monolithically. Here we describe the first wafer fused SDLs operating at the wavelength of 1.3 and 1.57 ?m in both continuous-wave and mode-locked regimes. The quantum dot semiconductors provide an interesting alternative to quantum-well (QW) structures since these materials alleviate the requirement for lattice matching. Recently, we have demonstrated first quantum dot based gain medium in SDL architecture. Since then, different wavelengths have been demonstrated both in continuous-wave and mode-locked regimes with a performance comparable to quantum-well-based lasers. The (AlGaIn)(AsSb) material system establishes a steady platform for optoelectronic devices operating in the mid-infrared spectral range. Latticematched or strain-compensated structures employing InGaAsSb as an active material and AlGaAsSb for barrier and cladding layers grown on GaSb substrates are demonstrated to be compounds of choice for long-wavelength lasers and photodetectors. In this study we report an optically-pumped semiconductor disk laser emitting radiation around 2.5 ?m tunable over 130 nm. To our knowledge, this is the widest spectral range reported to date at this wavelength.

Okhotnikov, Oleg G.

2011-02-01

342

Millimeter wavelength observations of solar active regions  

NASA Technical Reports Server (NTRS)

Polarization properties of active regions at 9 mm are discussed, and the observed degree of polarization is used to obtain an estimate of chromospheric magnetic fields. Also discussed is the polarization structure at 9 mm of an active region that produced a minor flare around 1900 UT on September 28, 1971. Total power observations indicate that new regions develop, or weak regions intensify at millimeter wavelengths as a result of bursts at distant sites. The spectra of the peak flux density of moderately strong bursts observed at 9 mm show a sharp drop toward the shorter millimeter wavelengths. The weak bursts at 3.5 mm are manifest mainly as heating phenomena.

Kundu, M. R.

1973-01-01

343

Short wavelength ion temperature gradient turbulence  

SciTech Connect

The ion temperature gradient (ITG) mode in the high wavenumber regime (k{sub y}{rho}{sub s}>1), referred to as short wavelength ion temperature gradient mode (SWITG) is studied using the nonlinear gyrokinetic electromagnetic code GENE. It is shown that, although the SWITG mode may be linearly more unstable than the standard long wavelength (k{sub y}{rho}{sub s}<1) ITG mode, nonlinearly its contribution to the total thermal ion heat transport is found to be low. We interpret this as resulting from an increased zonal flow shearing effect on the SWITG mode suppression.

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

2012-10-15

344

New strategy for optimizing wavelength converter placement.  

PubMed

This paper proposes a new strategic alternate-path routing to be combined with the particle swarm optimization (PSO) algorithm to better solve the wavelength converters placement problem. The strategic search heuristic is designed to provide network connectivity topologies for the converters to be placed more effectively. The new strategy is applied to the 14-node NSFNET to examine its efficiency in reducing the blocking probability in sparse wavelength conversion network. Computed results show that, when applied to the identical optimization framework, our search method outperforms both the equal-cost multipath routing and traffic-engineering-aware shortest-path routing. PMID:19488383

Foo, Y; Chien, S; Low, Andy; Teo, C; Lee, Youngseok

2005-01-24

345

Undulators for short wavelength FEL amplifiers  

SciTech Connect

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

Schlueter, R.D.

1994-12-01

346

Undulators for short wavelength FEL amplifiers  

SciTech Connect

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

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

1994-08-01

347

Short wavelength ion temperature gradient turbulence  

NASA Astrophysics Data System (ADS)

The ion temperature gradient (ITG) mode in the high wavenumber regime (ky?s>1), referred to as short wavelength ion temperature gradient mode (SWITG) is studied using the nonlinear gyrokinetic electromagnetic code GENE. It is shown that, although the SWITG mode may be linearly more unstable than the standard long wavelength (ky?s<1) ITG mode, nonlinearly its contribution to the total thermal ion heat transport is found to be low. We interpret this as resulting from an increased zonal flow shearing effect on the SWITG mode suppression.

Chowdhury, J.; Brunner, S.; Ganesh, R.; Lapillonne, X.; Villard, L.; Jenko, F.

2012-10-01

348

VIMS Marine Education Students Page  

NSDL National Science Digital Library

Resources for student independent research and extracurricular activities. Provides links to: science fair project help; science laboratory supply companies; ocean science topic content websites; online data; ask a scientist services; summer programs; and field trips. Virginia resources are emphasized.

349

Dual-wavelength erbium-doped fiber laser with tunable wavelength spacing using a twin core fiber-based filter  

NASA Astrophysics Data System (ADS)

A dual-wavelength erbium-doped fiber laser with tunable wavelength spacing was proposed and experimentally demonstrated by using a twin core fiber (TCF)–based filter. Benefiting from the polarization dependence of the TCF-based filter, the laser operated in dual-wavelength oscillation with two orthogonal polarization states. By adjusting the polarization controller, the wavelength spacing was tuned from 0.1 nm to 1.2 nm without shifting the centre position of the two wavelengths. By stretching the TCF, the two wavelengths were simultaneously tuned with fixed wavelength spacing. Such a dual-wavelength fiber laser could find applications in optical fiber sensors and microwave photonics generation.

Yin, Guolu; Lou, Shuqin; Wang, Xin; Han, Bolin

2014-05-01

350

Using Long Wavelength Gravity to Understand Continental Structure and Processes  

NASA Astrophysics Data System (ADS)

In most interpretations of gravity data, the long wavelength signal is removed as an unimportant regional contribution. This convention is largely historical; in the past it was difficult to model data at a variety of scales, and regional/residual separation became standard practice. This is especially true in exploration studies where near surface ore deposits are the target (e.g. LaFehr and Nabighian, 2012). With the development of a large variety of rapid 2D and 3D gravity modelling packages that are widely available, a more regional context for ore deposits and other crustal features can be considered. The inclusion of the regional long wavelength signal in the interpretation can dramatically alter the result, especially when the scale of consideration is on the order of the scale of crustal flexure. Large basins, such as the South African Karoo basin (Mesozoic) and even the smaller Witwatersrand basin (Archean), are likely to have deformed the Moho during their formation, although not all of these features appear to be preserved in present-day Moho geometry. Gravity modelling to Moho depths may dramatically alter the detailed interpretation of the deeper sections of these basins, with implications for resources such as gold, coal, gas and even carbon capture and storage (CCS). A clear cut example of this is seen in the interpretation of the gravity data of the Bushveld Complex (BC). When the crust is allowed to flex, the mafic lithologies of the BC can be allowed to connect laterally, resulting in an enormous layered intrusion 400 x 400 km across. This interpretation has been confirmed by the presence of BC xenoliths in a kimberlite near the centre of the Complex (Webb, Ashwal and Cawthorn, 2011, Contrib. Mineral. Petrol., 162: 101-107). The implication is that the BC mineral resources are also likely to be laterally connected, easily quadrupling the amount of mineralization, although the depth of the deposits remains uncertain. Due to the inherent ambiguity of gravity interpretations, inversion results tend to concentrate density variations towards the surface, making it difficult to accurately invert for Moho depth from gravity measurements. An added complication is the density variations in the uppermost mantle associated with Archaean cratonic keels. These lateral variations have similar gravity wavelengths to the gravity signal due to Moho variations; these two signals are unlikely to be resolved independently through inversion. As more crustal thickness data become available, large scale features, and even smaller mineral deposits can be more accurately evaluated.

Webb, Susan

2013-04-01

351

Multi-Wavelength Dye Laser System.  

National Technical Information Service (NTIS)

A four-wavelength dye laser system consisted of four dye lasers is developed. Its laser parameters and time characteristic after mixing four beams have been measured. The factors which have an effect on efficient dye laser power are discussed briefly. The...

T. Xingli S. G. Cheng

1995-01-01

352

RESOLVING THE MOTH AT MILLIMETER WAVELENGTHS  

SciTech Connect

HD 61005, also known as ''The Moth'', is one of only a handful of debris disks that exhibit swept-back ''wings'' thought to be caused by interaction with the ambient interstellar medium (ISM). We present 1.3 mm Submillimeter Array observations of the debris disk around HD 61005 at a spatial resolution of 1.''9 that resolve the emission from large grains for the first time. The disk exhibits a double-peaked morphology at millimeter wavelengths, consistent with an optically thin ring viewed close to edge-on. To investigate the disk structure and the properties of the dust grains we simultaneously model the spatially resolved 1.3 mm visibilities and the unresolved spectral energy distribution (SED). The temperatures indicated by the SED are consistent with expected temperatures for grains close to the blowout size located at radii commensurate with the millimeter and scattered light data. We also perform a visibility-domain analysis of the spatial distribution of millimeter-wavelength flux, incorporating constraints on the disk geometry from scattered light imaging, and find suggestive evidence of wavelength-dependent structure. The millimeter-wavelength emission apparently originates predominantly from the thin ring component rather than tracing the ''wings'' observed in scattered light. The implied segregation of large dust grains in the ring is consistent with an ISM-driven origin for the scattered light wings.

Ricarte, Angelo; Moldvai, Noel; Hughes, A. Meredith; Duchene, Gaspard [Department of Astronomy, University of California Berkeley, 601 Campbell Hall, Berkeley, CA 94720 (United States); Williams, Jonathan P. [Institute for Astronomy, University of Hawaii, Honolulu, HI 96822 (United States); Andrews, Sean M.; Wilner, David J. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)

2013-09-01

353

Fresnel zone plate antennas at millimeter wavelengths  

Microsoft Academic Search

The performance characteristics of Fresnel zone plates are described with emphasis on applications at millimeter wavelengths. Recent results are included along with a summary from numerous earlier investigations. Parameters described include design information, efficiency, bandwidth, focal characteristics, off-axis performance, axial intensity dependence, aberrations, and far-field pattern. Both transmission and reflection configurations are discussed, mostly for cases where the focal length

James E. Garrett; James C. Wiltse

1991-01-01

354

Wavelengths effective in induction of malignant melanoma  

Microsoft Academic Search

It is generally agreed that sunlight exposure is one of the etiologic agents in malignant melanoma of fair-skinned individuals. However, the wavelengths responsible for tumorigenesis are not known, although DNA is assumed to be the target because individuals defective in the repair of UV damage to DNA are several thousandfold more prone to the disease than the average population. Heavily

R. B. Setlow; E. Grist; K. Thompson; A. D. Woodhead

1993-01-01

355

Local wavelength estimation for magnetic resonance elastography  

Microsoft Academic Search

A newly developed magnetic resonance imaging technique can directly visualize propagating acoustic strain waves in tissue-like materials. By estimating the local wavelength of the acoustic wave pattern, quantitative values of shear modulus can be calculated and images generated that depict tissue elasticity or stiffness. Since tumors are significantly stiffer than normal tissue (the basis of their detection by palpation), this

A. Manduca; R. Muthupillai; P. J. Rossman; J. F. Greenleaf; R. L. Ehman

1996-01-01

356

Long wavelength magnetic fluctuations in toroidal plasmas  

SciTech Connect

Fluctuating bootstrap currents provide a mechanism for long wavelength electromagnetic fluctuations in tokamak plasmas. The existence of micro-magnetic islands may be responsible for the experimental observations of core density fluctuations. A fluctuation model is introduced for the tokamak that describes the magnetic topology as a time-varying mix of magnetic islands, stochastic zones and good'' magnetic surfaces.

Hegna, C.C.; Callen, J.D.

1992-10-01

357

Long wavelength magnetic fluctuations in toroidal plasmas  

SciTech Connect

Fluctuating bootstrap currents provide a mechanism for long wavelength electromagnetic fluctuations in tokamak plasmas. The existence of micro-magnetic islands may be responsible for the experimental observations of core density fluctuations. A fluctuation model is introduced for the tokamak that describes the magnetic topology as a time-varying mix of magnetic islands, stochastic zones and ``good`` magnetic surfaces.

Hegna, C.C.; Callen, J.D.

1992-10-01

358

Null ellipsometer with multi-wavelength  

NASA Astrophysics Data System (ADS)

A multi-wavelength null ellipsometer with variable incident angle has been developed recently. The ellipsometer consists of five parts, mainly including a source set with three semiconductor lasers, a rotating component with step motor, sample stage of variable incident angle, detector, and the system of computer control procedure and data processing procedure. The light source set is composed of three semiconductor lasers at a wavelength of 635nm, 532nm, and 780nm respectively and prisms used for dividing a beam of laser into two beams. An improved formula of ellipsometric parameters (named psi and delta) has been adopted to obtain more accuracy data, as a quarter-wave plate at the wavelength of 635nm is used as the compensator for the multi-wavelength null ellipsometer. In order to make the instrument meet the need of ellipsometric parameters measurement of different types of substrate samples, a novel iterative algorithm is presented. Experimental results show that the accuracy of the ellipsometric parameters can reach to 0.01°, and the precision of film thickness is 0.1nm.

Xiao, Guohui; Lin, Tianxia; Yang, Ting; Huang, Zuohua

2010-05-01

359

Discrete wavelength-locked external cavity laser  

NASA Technical Reports Server (NTRS)

An external cavity laser (and method of generating laser light) comprising: a laser light source; means for collimating light output by the laser light source; a diffraction grating receiving collimated light; a cavity feedback mirror reflecting light received from the diffraction grating back to the diffraction grating; and means for reliably tuning the external cavity laser to discrete wavelengths.

Pilgrim, Jeffrey S. (Inventor); Silver, Joel A. (Inventor)

2005-01-01

360

PROPAGATION OF LONG WAVELENGTH DISTURBANCES IN PLASMA  

Microsoft Academic Search

The long wavelength modes of excitation of a two component plasma in a ; steady magnetic field are examined. Two linearized Boltzmann equations are given ; with collision terms which are coupled through the difference in temperatures and ; difference in velocities of the two gases. A formal means of classification of ; phenomena is described in terms of the

Liboff

1962-01-01

361

Long-Wavelength Phenomena in a Plasma  

Microsoft Academic Search

The long-wavelength modes of excitation of a twocomponent plasma in a ; steady magnetic field are examined. Two linearized Boltzmann equations are given ; with collision terms that are coupled through the difference in temperatures and ; difference in velocities of the two gases. A formal means of classification of ; phenomena is described in terms of the nature of

Richard L. Liboff

1962-01-01

362

Long-Wavelength Phenomena in a Plasma  

Microsoft Academic Search

The long-wavelength modes of excitation of a two-component plasma in a steady magnetic field are examined. Two linearized Boltzmann equations are given with collision terms which are coupled through the difference in temperatures and difference in velocities of the two gases. A formal means of classification of phenomena is described in terms of the nature of the roots about k

Richard L. Liboff

1962-01-01

363

Self Calibration of a 2-wavelength Pyrometer  

NASA Technical Reports Server (NTRS)

Pyrometers require calibrations to determine their instrument constants before they can be used in remote temperature measurements. These constants reflect the combined effects of detector response, the transmissivities of intervening optical media (windows and gases) and the emissivity of the measured surface. We describe here the principal and the demonstration of self calibrating 2-wavelength pyrometer.

Ng, Daniel

1998-01-01

364

Polymeric slot waveguide at visible wavelength.  

PubMed

Polymeric slot waveguide structure, which pushes the mode field toward the surrounding media, was designed and characterized. The slot waveguide was fabricated by using nanoimprint lithography, and the operation of the slot was demonstrated at 633 nm wavelength with an integrated Young interferometer. The experimental result shows that the nanolithography method provides possibilities to fabricate disposable slot waveguide sensors. PMID:23114325

Hiltunen, Marianne; Hiltunen, Jussi; Stenberg, Petri; Petäjä, Jarno; Heinonen, Esa; Vahimaa, Pasi; Karioja, Pentti

2012-11-01

365

Optimization of laser wavelength in oceanographic lidars  

Microsoft Academic Search

The recent developments in manufacturing of various types of lasers, including new modifications of Nd:YAG, Cu+ vapor, and dye lasers, are considered from the point of view of application in airborne systems designed for remote sensing of natural water bodies. The general expressions are given to analyze the effect of laser source wavelength on expressions and general optical detection theory

Victor I. Feigels; Yurij I. Kopilevich

1996-01-01

366

Dual-wavelength cascaded Raman fiber laser  

Microsoft Academic Search

We have investigated the characteristics of a dual-wavelength cascaded Raman laser based on a composite resonator configuration using a fiber WDM coupler and two pairs of fiber Bragg gratings. The WDM coupler, which served to form a ring cavity and acted as an output coupler simultaneously, made the laser system simple and effective. Since the WDM coupler is made by

Do Il Chang; Dong Sung Lim; Min Yong Jeon; Hak Kyu Lee; Kyong Hon Kim

2000-01-01

367

Two-wavelength spatial-heterodyne holography  

DOEpatents

Systems and methods are described for obtaining two-wavelength differential-phase holograms. A method includes determining a difference between a filtered analyzed recorded first spatially heterodyne hologram phase and a filtered analyzed recorded second spatially-heterodyned hologram phase.

Hanson, Gregory R. (Clinton, TN); Bingham, Philip R. (Knoxville, TN); Simpson, John T. (Knoxville, TN); Karnowski, Thomas P. (Knoxville, TN); Voelkl, Edgar (Austin, TX)

2007-12-25

368

Resolving the Moth at Millimeter Wavelengths  

NASA Astrophysics Data System (ADS)

HD 61005, also known as "The Moth," is one of only a handful of debris disks that exhibit swept-back "wings" thought to be caused by interaction with the ambient interstellar medium (ISM). We present 1.3 mm Submillimeter Array observations of the debris disk around HD 61005 at a spatial resolution of 1.''9 that resolve the emission from large grains for the first time. The disk exhibits a double-peaked morphology at millimeter wavelengths, consistent with an optically thin ring viewed close to edge-on. To investigate the disk structure and the properties of the dust grains we simultaneously model the spatially resolved 1.3 mm visibilities and the unresolved spectral energy distribution (SED). The temperatures indicated by the SED are consistent with expected temperatures for grains close to the blowout size located at radii commensurate with the millimeter and scattered light data. We also perform a visibility-domain analysis of the spatial distribution of millimeter-wavelength flux, incorporating constraints on the disk geometry from scattered light imaging, and find suggestive evidence of wavelength-dependent structure. The millimeter-wavelength emission apparently originates predominantly from the thin ring component rather than tracing the "wings" observed in scattered light. The implied segregation of large dust grains in the ring is consistent with an ISM-driven origin for the scattered light wings.

Ricarte, Angelo; Moldvai, Noel; Hughes, A. Meredith; Duchêne, Gaspard; Williams, Jonathan P.; Andrews, Sean M.; Wilner, David J.

2013-09-01

369

Wavelength switching components for future photonic networks  

Microsoft Academic Search

This article provides a review of integrated laser and semiconductor optical amplifier components that have been configured to provide a variety of all-optical functions such as wavelength conversion, routing, signal regeneration, and add-drop multiplexing. The components have been devised so that they can be reliably and simply used within a multiwavelength network. The article introduces the components by outlining the

Ian White; Richard Penty; Matthew Webster; Yew Jun Chai; Adrian Wonfor; Sadegh Shahkooh

2002-01-01

370

Electricity and short wavelength radiation generator  

DOEpatents

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

George, E.V.

1985-08-26

371

Long wavelength gravity and topography anomalies  

NASA Technical Reports Server (NTRS)

It is shown that gravity and topography anomalies on the earth's surface may provide new information about deep processes occurring in the earth, such as those associated with mantle convection. Two main reasons are cited for this. The first is the steady improvement that has occurred in the resolution of the long wavelength gravity field, particularly in the wavelength range of a few hundred to a few thousand km, mainly due to increased coverage of terrestrial gravity measurements and the development of radar altimeters in orbiting satellites. The second reason is the large number of numerical and laboratory experiments of convection in the earth, including some with deformable upper and lower boundaries and temperature-dependent viscosity. The oceans are thought to hold the most promise for determining long wavelength gravity and topography anomalies, since their evolution has been relatively simple in comparison with that of the continents. It is also shown that good correlation between long wavelength gravity and topography anomalies exists over some portions of the ocean floor

Watts, A. B.; Daly, S. F.

1981-01-01

372

Intraocular lens short wavelength light filtering.  

PubMed

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

Edwards, Keith H; Gibson, G Anthony

2010-11-01

373

Wavelength beam combining of ytterbium fiber lasers.  

PubMed

Wavelength beam combining of five ytterbium fiber lasers is demonstrated in a master-oscillator power-amplifier configuration at combined powers up to 6 W. The combined beam profile has an M2 value of 1.14, which is equal to that of an individual fiber. Beam steering in one dimension over 140 resolvable spots is also demonstrated. PMID:12659434

Augst, S J; Goyal, A K; Aggarwal, R L; Fan, T Y; Sanchez, A

2003-03-01

374

Long-wavelength equation for vertically falling films  

NASA Astrophysics Data System (ADS)

An equation is derived for describing wave evolution on the surface of a vertically falling viscous film. The traditional long-wavelength scaling is replaced by a new scaling to reduce the two dimensional Navier-Stokes equations to a single evolution equation for the scaled film thickness h(x,t) . The scaling suggests that the Weber number ( We ) must be used instead of the Reynolds number (Re) to distinguish between viscous and inertia dominated regimes for vertically falling films. This equation includes viscous dissipation and pressure correction terms that are missing in the existing single evolution equations at the same order. Comparison of the neutral stability curves and growth rates predicted by different models to that of the Orr-Sommerfeld (OS) equation shows that our equation matches with the OS results better than the existing single evolution equations. However, our equation is not free from finite time blowup. Selective regularization leads to a two mode model in flow rate and film thickness. The regularized equation is free from finite time blowup and predicts two families of solitary waves. Numerical simulations of the derived equation and its regularized version in the traveling wave coordinate show the transition of wave structure from regular (periodic) to chaotic profiles. Model predictions on maximum wave amplitude on the low celerity branch show good agreement with experimental data.

Panga, Mohan K. R.; Mudunuri, Ramesh R.; Balakotaiah, Vemuri

2005-03-01

375

Widely tunable wavelength spacing dual-wavelength single longitudinal mode erbium doped fiber laser  

NASA Astrophysics Data System (ADS)

A simple widely tunable wavelength spacing dual-wavelength single longitudinal mode (SLM) erbium doped fiber laser (EDFL) based on cascaded fiber Bragg gratings (FBGs) and birefringent fiber filter is proposed and demonstrated. Experimental results show that the lasing wavelength spacing is widely tunable in a range from 2 nm to 18 nm, which has potential to generate frequency tunable terahertz (THz) waves by beating the lasing dual-wavelength in a high speed photodetector. The birefringent fiber filter acts as an ultra-narrow bandpass filter and benefits the simultaneous oscillation of dual-wavelength in a single laser cavity. The output peak power of the lasing dual-wavelength is approximately equalized at room temperature, and a high optical signal-to-noise ratio (OSNR) is realized in the whole tuning range. The SLM operation of dual-wavelength fiber laser is verified by Fabry–Perot (F–P) scanning interferometer, and the clear eye diagram proves that the proposed fiber laser is effective in the application of fiber optic communication system.

Sun, Tiegang; Guo, Yubin; Wang, Tianshu; Huo, Jiayu; Zhang, Le

2014-06-01

376

Limiting Wavelength Converter Usage in Resilient WDM Networks  

Microsoft Academic Search

A careful wavelength assignment (WA) to lambda services must be performed to reduce the total number of wavelength converters (WCs) that are required when the wavelength continuity constraint cannot be met in wavelength division multiplexing (WDM) networks. With the successful introduction of reconfigurable optical add-drop multiplexers (ROADMs), WDM networks are now growing in size, both in the number of optical

Miguel Razo; S. Billenahalli; W. Huang; A. Sivasankaran; L. Tang; H. Vardhan; P. Monti; M. Tacca; A. Fumagalli

2010-01-01

377

Long-wavelength infrared (LWIR) quantum-dot infrared photodetector (QDIP) focal plane array  

Microsoft Academic Search

We have exploited the artificial atomlike properties of epitaxially grown self-assembled quantum dots for the development of high operating temperature long wavelength infrared (LWIR) focal plane arrays. Quantum dots are nanometer-scale islands that form spontaneously on a semiconductor substrate due to lattice mismatch. QDIPs are expected to outperform quantum well infrared detectors (QWIPs) and are expected to offer significant advantages

S. D. Gunapala; S. V. Bandara; C. J. Hill; D. Z. Ting; J. K. Liu; S. B. Rafol; E. R. Blazejewski; J. M. Mumolo; S. A. Keo; S. Krishna; Y. C. Chang; C. A. Shott

2006-01-01

378

Interactions of dispersion-managed solitons in wavelength-division-multiplexed optical transmission lines.  

PubMed

We investigate interactions between pulses in dispersion-managed multichannel wavelength-division-multiplexed soliton systems, using an improved variational approximation. The frequency shifts are found to be smallest for moderate, i.e., relatively short-scale, dispersion management. The position shifts increase monotonically with map strength. PMID:18040502

Wald, M; Malomed, B A; Lederer, F

2001-07-01

379

Reference wavelength method for a two-color pyrometer  

Microsoft Academic Search

The reference wavelength method is used for a two-color pyrometer and, with the reference wavelength method, an analytical formula of the ratio temperature for the two-color pyrometer is derived. For one channel of the two-color pyrometer, with a triangular spectral response of 100-nm FWHM and 2.0-micron peak wavelength, the effective wavelength and the correction factors with several reference wavelengths are

Jae Won Hahn; Chunghi Rhee

1987-01-01

380

Subpicometer accuracy laser wavelength sensor using multiplexed Bragg gratings  

Microsoft Academic Search

Wavelength- and angle-multiplexed holographic Bragg gratings are used as a highly sensitive wavelength sensor. An absolute wavelength accuracy as high as 0.3 pm has been demonstrated with gratings recorded in an Fe-doped LiNbO 3 photorefractive crystals of dimension of 5×5×4 (mm 3). This technique provides a simple and accurate solution to laser wavelength measurement in applications such as wavelength division

Feng Zhao; Koichi Sayano; Harold E. Miller; Neven Karlovac

1997-01-01

381

Relevance of resistance levels to carbapenems and integron-borne blaIMP-1, blaIMP-7, blaIMP-10 and blaVIM-2 in clinical isolates of Pseudomonas aeruginosa.  

PubMed

Molecular detection and surveillance of the resistance genes harboured by Pseudomonas aeruginosa are becoming increasingly important in assessing and controlling spread and colonization in hospitals, and in guiding the treatment of infections. This study analysed the resistance mechanisms of carbapenem-resistant clinical isolates of P. aeruginosa and identified the associated integron-borne metallo-beta-lactamase (MBL)-encoding genes. Twenty-seven imipenem (IPM)-resistant clinical isolates of P. aeruginosa were divided into three groups according to their resistance levels to carbapenems. Strains bearing bla(IMP-10) showed extremely high-level resistance to IPM, with MICs of 512-2048 microg ml(-1). By comparison, strains bearing bla(IMP-1), bla(IMP-7) and bla(VIM-2) showed an intermediate level of resistance, with MICs of 32-256 microg ml(-1). The non-MBL-producing strains showed a low level of resistance, with MICs of 8-32 microg ml(-1). The same trend in resistance levels was also observed when resistance to other carbapenems, such as meropenem and panipenem, was determined. DNA sequencing showed that the MBL-encoding gene cassettes were carried by class 1 integrons. The bla(IMP-1), bla(IMP-7) and bla(IMP-10) gene cassettes were preceded by a hybrid P(ant) promoter, TGGACA-N(17)-TAAACT, and the bla(VIM-2) gene cassette was preceded by a weak promoter, TGGACA-N(17)-TAAGCT. Most of the MBL-encoding genes were linked to one or two resistance genes encoding aminoglycoside-modifying enzymes, such as aac(6')Iae, aac(6')II, aacA7, aacC4, aadA1, aadA2 and aadA6, highlighting the multidrug-resistant properties of these clinical isolates. PMID:19528141

Zhao, Wei-Hua; Chen, Gelin; Ito, Ribu; Hu, Zhi-Qing

2009-08-01

382

Wavelength-dependent scattering of light during Nd:YAG laser heating of porcine septal cartilage  

NASA Astrophysics Data System (ADS)

Heat alters the bulk physical properties of cartilage tissue, including the optical scattering and absorption coefficients. The purpose of this investigation was to measure wavelength dependent scattering of light using three different probe lasers ((lambda) = 488 nm, 670 nm, 808 nm) during Nd:YAG laser ((lambda) = 1.32 micrometers , 50 Hz pulse repetition rate) heating of porcine septal cartilage. An integrating sphere was used to collect diffusely backscattered light from these probe lasers and three lock- in amplifiers were used to discriminate between the different signals. Peak signal intensity of the backscattered light was observed at different temperature depending on the probe laser wavelength and specimen thickness. The observed changes are unlikely due to axial thermal gradients created during Nd:YAG laser heating and do not correlate with the fluence distribution of the three probe laser wavelengths evaluated. The observed wavelength dependent differences suggest that tissue matrix alterations during heating are due to macromolecular conformation changes that occur on the scale of the wavelength of the probe laser light. As changes in the bulk properties of cartilage can be inferred by using simple non-contact techniques such as light scattering, the characterization of the wavelength dependence of these phenomena will become increasingly important.

Basu, Reshmi; Wong, Brian J.; Madsen, Steen J.

2001-07-01

383

Multi-wavelength injection seeded mid-infrared optical parametric oscillator for DIAL  

SciTech Connect

We have constructed and fielded a multi-wavelength injection seeded mid-IR OPO source for DIAL. This OPO system was built for ground based remote sensing measurements of species with both broad (300 cm{sup -1}) and narrow absorption bandwidths (0.07 cm{sup -1} FWHM). The OPO utilizes a single frequency tunable diode laser for the injection seeded signal wavelength in the region from 6400 to 6700 cm{sup -1} and an angle phase-matched 5 cm LiNbO3 crystal to provide large tuning excursions on a slow time scale. The pump was a diode pumped Nd:YAG MOPA (9398 cm{sup -1}) running at 180 Hz. This pump source was repeatedly injection seeded with a different wavelength on each of film sequential shots forming a set of three pulses having wavelength separations on the order of 0.4 cm{sup -1} at a three color set repetition rate of 60 Hz. This combination of OPO signal and pump source produced a set of three time staggered idler wavelengths separated by 0.4 cm{sup -1} with the center wavelength tunable from 2700 to 3000 cm{sup -1}. This OPO system was used in field test experiments to detect the release of chemicals from a standoff distance of 3.3 Km. We present key OPO design criteria, performance data, and numerical simulations that agree with our observations of pump induced spectral impurities in the OPO output.

Webb, M.S.; Stanion, K.B.; Deane, D.J. [and others

1996-01-27

384

A superradiant clock laser on a magic wavelength optical lattice  

NASA Astrophysics Data System (ADS)

An ideal superradiant laser on an optical clock transition of noninteracting cold atoms is predicted to exhibit an extreme frequency stability and accuracy far below mHz-linewidth. In any concrete setup sufficiently many atoms have to be confined and pumped within a finite cavity mode volume. Using a magic wavelength lattice minimizes light shifts and allows for almost uniform coupling to the cavity mode. Never- theless, the atoms are subject to dipole-dipole interaction and collective spontaneous decay which compromises the ultimate frequency stability. In the high density limit the Dicke superradiant linewidth enhancement will broaden the laser line and nearest neighbor couplings will induce shifts and fluctuations of the laser frequency. We estimate the magnitude and scaling of these effects by direct numerical simulations of few atom systems for different geometries and densities. For Strontium in a regularly filled magic wavelength configuration atomic interactions induce small laser frequency shifts only and collective spontaneous emission weakly broadens the laser. These interactions generally enhance the laser sensitivity to cavity length fluctuations but for optimally chosen operating conditions can lead to an improved synchronization of the atomic dipoles.

Maier, Thomas; Kraemer, Sebastian; Ostermann, Laurin; Ritsch, Helmut

2014-06-01

385

A superradiant clock laser on a magic wavelength optical lattice.  

PubMed

An ideal superradiant laser on an optical clock transition of noninteracting cold atoms is predicted to exhibit an extreme frequency stability and accuracy far below mHz-linewidth. In any concrete setup sufficiently many atoms have to be confined and pumped within a finite cavity mode volume. Using a magic wavelength lattice minimizes light shifts and allows for almost uniform coupling to the cavity mode. Nevertheless, the atoms are subject to dipole-dipole interaction and collective spontaneous decay which compromises the ultimate frequency stability. In the high density limit the Dicke superradiant linewidth enhancement will broaden the laser line and nearest neighbor couplings will induce shifts and fluctuations of the laser frequency. We estimate the magnitude and scaling of these effects by direct numerical simulations of few atom systems for different geometries and densities. For Strontium in a regularly filled magic wavelength configuration atomic interactions induce small laser frequency shifts only and collective spontaneous emission weakly broadens the laser. These interactions generally enhance the laser sensitivity to cavity length fluctuations but for optimally chosen operating conditions can lead to an improved synchronization of the atomic dipoles. PMID:24921521

Maier, Thomas; Kraemer, Sebastian; Ostermann, Laurin; Ritsch, Helmut

2014-06-01

386

ps-laser scribing of CIGS films at different wavelengths  

NASA Astrophysics Data System (ADS)

Continuous growth of the thin-film electronics market stimulates the development of versatile technologies for large-scale patterning of thin-film materials on rigid and flexible substrates, and laser technologies are a promising method to accomplish the scribing processes. Lasers with picosecond pulse duration were applied in scribing of complex multilayered CuIn x Ga(1- x)Se2 (CIGS) solar cells deposited on a polyimide substrate. The ablative properties of the films were examined as a function of the wavelength of laser radiation, pulse energy, and the irradiation dose. The selective removal of ITO and CIGS layers was achieved with 355 nm irradiation without any significant damage to the underlying layers in the ITO/CIGS/Mo/PI solar cell system. The 355 nm wavelength was also found to be favorable for scribing of absorber layer in a ZnO/CIGS/Mo/PI solar cell system. 266 nm radiation significantly modified the film structure due to high absorption. Extensive melt formation in the CIGS layer was found when 532 nm radiation was applied, though the trenches were smooth and crack-free.

Ge?ys, P.; Ra?iukaitis, G.; Ehrhardt, M.; Zimmer, K.; Gedvilas, M.

2010-11-01

387

Polarizabilities, Atomic Clocks, and Magic Wavelengths  

NASA Astrophysics Data System (ADS)

I will describe the high-precision calculations of the static and frequency-dependent polarizabilities in alkali-metal atoms and Ca^+. The resulting polarizability values are used for a variety of applications from reducing the decoherence in quantum logic gates to the evaluation of the black-body radiation (BBR) shifts for optical frequency standards. Our alkali-metal atom polarizability calculations can be used to predict the oscillation frequencies of optically-trapped atoms, and particularly the ratios of frequencies of different species held in the same trap. We identify wavelengths at which two different alkali atoms have the same oscillation frequency. We also evaluate ``magic'' wavelengths in alkali-metal atoms for which np and ns levels have the same ac-Stark shift enabling state-insensitive optical cooling and trapping. The calculation of the BBR shift for the optical frequency standard with Ca^+ ion is also described.

Safronova, Marianna

2008-05-01

388

Wavelength Calibration of the Hamilton Echelle Spectrograph  

NASA Astrophysics Data System (ADS)

We present the wavelength calibration of the Hamilton Echelle Spectrograph at Lick Observatory. The main problem with the calibration of this spectrograph arises from the fact that thorium lines are absent in the spectrum of the presumed ThAr hollow-cathode lamp now under operation; numerous unknown strong lines, which have been identified as titanium lines, are present in the spectrum. We estimate the temperature of the lamp's gas which permits us to calculate the intensities of the lines and to select a large number of relevant Ti I and Ti II lines. The resulting titanium line list for the Lick hollow-cathode lamp is presented. The wavelength calibration using this line list was made with an accuracy of about 0.006 Å.

Pakhomov, Yu. V.; Zhao, G.

2013-10-01

389

Discrete Wavelength-Locked External Cavity Laser  

NASA Technical Reports Server (NTRS)

A prototype improved external cavity laser (ECL) was demonstrated in the second phase of a continuing effort to develop wavelength-agile lasers for fiber-optic communications and trace-gas-sensing applications. This laser is designed to offer next-generation performance for incorporation into fiber-optic networks. By eliminating several optical components and simplifying others used in prior designs, the design of this laser reduces costs, making lasers of this type very competitive in a price-sensitive market. Diode lasers have become enabling devices for fiber optic networks because of their cost, compactness, and spectral properties. ECLs built around diode laser gain elements further enhance capabilities by virtue of their excellent spectral properties with significantly increased (relative to prior lasers) wavelength tuning ranges. It is essential to exploit the increased spectral coverage of ECLs while simultaneously insuring that they operate only at precisely defined communication channels (wavelengths). Heretofore, this requirement has typically been satisfied through incorporation of add-in optical components that lock the ECL output wavelengths to these specific channels. Such add-in components contribute substantially to the costs of ECL lasers to be used as sources for optical communication networks. Furthermore, the optical alignment of these components, needed to attain the required wavelength precision, is a non-trivial task and can contribute substantially to production costs. The design of the present improved ECL differs significantly from the designs of prior ECLs. The present design relies on inherent features of components already included within an ECL, with slight modifications so that these components perform their normal functions while simultaneously effecting locking to the required discrete wavelengths. Hence, add-in optical components and the associated cost of alignment can be eliminated. The figure shows the locking feedback signal, and the frequency locking achieved by use of this signal, as a mirror is tilted through a range of angles to tune the ECL through 48 channels. The data for the frequency plot were obtained, simultaneously with the data for the locking-signal plot, by using a scanning Michelson interferometer to precisely determine the ECL wavelength (and, hence, frequency). Given the ability of the Michelson interferometer to obtain highly precise readings, the frequency plot can be taken to be a reliable indication of single-mode operation. The discontinuities in the frequency plot signify the switching of the ECL between channels; in other words, they indicate tuning with locking to discrete frequencies. The peaks of the feedbacklocking signal correspond to the centers, or near centers, of the mirror angle scan through the corresponding channels. Thus, it is clear that when the feedback-locking signal is at a local maximum, the ECL is operating at single frequency at or near the middle frequency of the selected channel. This is all that is required for precisely locking the ECL output wavelength. The locking is achieved without additional external optical components.

Pilgrim, Jeffrey S.; Silver, Joel A.

2004-01-01

390

Coordinated observations of PHEMU at radio wavelengths.  

NASA Astrophysics Data System (ADS)

We present preliminary results for our study of mutual phenomena of the Galilean satellites performed at radio wavelengths with the Medicina and Noto antennas of the Istituto di Radioastronomia \\textendash{} INAF, and with the Effelsberg 100-m radio telescope of the Max-Planck-Institute for Radioastronomy. Measurements of the radio flux density variation occurred during the mutual occultations of Io by Europa and Ganymede were carried out during the PHEMU09 campaign at K- and Q-band. Flux density variations observed for the first time at radio wavelengths are consistent with the typical optical patterns measured when partial occultations occurred. The flux density drops indicate a non-linear dependence with the percentage of overlapped area.

Pluchino, S.; Schillirò, F.; Salerno, E.; Pupillo, G.; Kraus, A.; Mack, K.-H.

391

Electrooptic tunable filters for infrared wavelengths  

NASA Astrophysics Data System (ADS)

This paper describes the performance characteristics of an electronically tunable infrared filter based on the electrooptic effect. Like the acoustooptic tunable filter, this device operates by selectively coupling principal polarizations in a birefringent crystal at a phase-matched wavelength by means of a spatially periodic refractive index perturbation. Instead of a traveling acoustic wave, however, the electrooptic tunable filter employs a temporally static electric field. The main advantages of this filter are its very low power consumption and it versatility of passband programming by virtue of separately addressable voltages under microprocessor control. Two experimental embodiments of the filter are described, one using longitudinal fields, collinear with the light beam, the other using transverse fields in a 'thick waveguide' configuration. Experimental results of filter characteristics in the wavelength range 2-10 microns are presented. Examples of passband synthesis that are achieved by apodizing the amplitude of the applied electric field perturbations are also presented.

Lotspeich, J. F.; Stephens, R. R.; Henderson, D. M.

1982-08-01

392

Optimization of laser wavelength in oceanographic lidars  

NASA Astrophysics Data System (ADS)

The recent developments in manufacturing of various types of lasers, including new modifications of Nd:YAG, Cu+ vapor, and dye lasers, are considered from the point of view of application in airborne systems designed for remote sensing of natural water bodies. The general expressions are given to analyze the effect of laser source wavelength on expressions and general optical detection theory based on Sakett's D-index of discriminability, a criterion is formulated for optical choice of sounding radiation wavelength for airborne lidar systems which takes into account the sun light composition as well as spectral dependencies of PMT photocathod sensitivity, hydro-optical characteristics of sea water and bottom reflectivity. Several results are presented to compare the effectiveness of different laser sources for lidar bathymetry applications for various types of ocean waters and meteorological conditions.

Feigels, Victor I.; Kopilevich, Yurij I.

1996-11-01

393

Wavelength-selective uncaging of oligonucleotides.  

PubMed

Caged compounds are light-sensitive molecules with temporarily inactivated biological function. The active compound is released upon irradiation, in which exact spatial and temporal control is accomplished. Beyond this inherently irreversible concept of triggering, the idea of multi-wavelength uncaging provides experiments with more complexity. This unit describes the syntheses of protected nucleoside phosphoramidites of caged dT(NpHP) [pHP = (p-hydroxyphenacyl)], dT(DEACM) {DEACM = [(7-diethylaminocoumarin-4-yl)methyl]} or a dC(NDBF) {NDBF = [1-(3-nitrodibenzofuran-1-yl)ethyl]} modification on the nucleobase, their incorporation in oligonucleotides, characterization, and their wavelength-selective uncaging up to four levels. Curr. Protoc. Nucleic Acid Chem. 57:6.11.1-6.11.32. © 2014 by John Wiley & Sons, Inc. PMID:24961722

Rodrigues-Correia, Alexandre; Seyfried, Patrick; Heckel, Alexander

2014-01-01

394

Multi-Wavelength Observations of Supernova Remnants  

NASA Technical Reports Server (NTRS)

Supernova remnants (SNRs) provide a laboratory for studying various astrophysical processes, including particle acceleration, thermal and non thermal emission processes across the spectrum, distribution of heavy elements, the physics of strong shock waves, and the progenitor systems and environments of supernovae. Long studied in radio and X-rays, the past decade has seen a dramatic increase in the detection and subsequent study of SNRs in the infrared and gamma-ray regimes. Understanding the evolution of SNRs and their interaction with the interstellar medium requires a multi-wavelength approach. I will review the various physical processes observed in SNRs and how these processes are intertwined. In particular, I will focus on X-ray and infrared observations, which probe two very different but intrinsically connected phases of the ISM: gas and dust. I will discuss results from multi-wavelength studies of several SNRs at various stages of evolution, including Kepler, RCW 86, and the Cygnus Loop.

Williams, B.

2012-01-01

395

Long Wavelength Fluorescence Ratiometric Zinc Biosensor  

PubMed Central

A protein-based emission ratiometric fluorescence biosensor is described that exhibits sensitivity to free zinc ion solutions down to picomolar concentrations. Ratiometric measurements are widely used to assure accurate quantitation, and emission ratios are preferred for laser scanning microscopes such as confocal fluorescence microscopes. The relatively long emission wavelengths used are well suited to studies in tissues and other matrices which exhibit significant fluorescence background, and the apo-carbonic anhydrase moiety recognizes zinc ion with high and controllable specificity.

Zeng, Hui Hui; Matveeva, Evgenia; Stoddard, Andrea K.; Fierke, Carol A.; Thompson, Richard B.

2013-01-01

396

Deformable mirror for short wavelength applications  

DOEpatents

A deformable mirror compatible with short wavelength (extreme ultraviolet) radiation that can be precisely controlled to nanometer and subnanometer accuracy is described. Actuators are coupled between a reaction plate and a face plate which has a reflective coating. A control system adjusts the voltage supplied to the actuators; by coordinating the voltages supplied to the actuators, the reflective surface of the mirror can be deformed to correct for dimensional errors in the mirror or to produce a desired contour.

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

1999-01-01

397

Design formulas for short-wavelength FELs  

NASA Astrophysics Data System (ADS)

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

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

2004-05-01

398

Varactor diodes for millimeter and submillimeter wavelengths  

NASA Technical Reports Server (NTRS)

Whisker-contacted GaAs Schottky barrier varactor diodes are the most common high-frequency multiplier element in use today. They are inherently simple devices that have very high frequency response and have been used to supply local oscillator power for Schottky heterodyne receivers to frequencies approaching 700 GHz. This paper discusses the development of improved varactor diode technology for space based applications at millimeter and submillimeter wavelengths.

Rizzi, Brian J.; Hesler, Jeffrey L.; Dossal, Hasan; Crowe, Thomas W.

1992-01-01

399

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

400

Multiple wavelength X-ray monochromators  

DOEpatents

An improved apparatus and method is provided for separating input x-ray radiation containing first and second x-ray wavelengths into spatially separate first and second output radiation which contain the first and second x-ray wavelengths, respectively. The apparatus includes a crystalline diffractor which includes a first set of parallel crystal planes, where each of the planes is spaced a predetermined first distance from one another. The crystalline diffractor also includes a second set of parallel crystal planes inclined at an angle with respect to the first set of crystal planes where each of the planes of the second set of parallel crystal planes is spaced a predetermined second distance from one another. In one embodiment, the crystalline diffractor is comprised of a single crystal. In a second embodiment, the crystalline diffractor is comprised of a stack of two crystals. In a third embodiment, the crystalline diffractor includes a single crystal that is bent for focussing the separate first and second output x-ray radiation wavelengths into separate focal points.

Steinmeyer, Peter A. (Arvada, CO)

1992-11-17

401

Multiple wavelength X-ray monochromators  

DOEpatents

An improved apparatus and method is provided for se