Sample records for vims wavelength scale

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

    NASA Astrophysics Data System (ADS)

    Cruikshank, Dale P.; Meyer, Allan W.; Brown, Robert H.; Clark, Roger N.; Jaumann, Ralf; Stephan, Katrin; Hibbitts, Charles A.; Sandford, Scott A.; Mastrapa, Rachel M. E.; Filacchione, Gianrico; Dalle Ore, Cristina M.; Nicholson, Philip D.; Buratti, Bonnie J.; McCord, Thomas B.; Nelson, Robert M.; Dalton, J. Brad; Baines, Kevin H.; Matson, Dennis L.

    2010-04-01

    Several of the icy satellites of Saturn show the spectroscopic signature of the asymmetric stretching mode of C-O in carbon dioxide (CO 2) 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 CO 2 absorption band in the spectra of Phoebe, Iapetus, Hyperion, and Dione. Comparisons are made to laboratory spectra of pure CO 2, CO 2 clathrates, ternary mixtures of CO 2 with other volatiles, implanted and adsorbed CO 2 in non-volatile materials, and ab initio theoretical calculations of CO 2 * nH 2O. At the wavelength resolution of VIMS, the CO 2 on Phoebe is indistinguishable from pure CO 2 ice (each molecule's nearby neighbors are also CO 2) or type II clathrate of CO 2 in H 2O. In contrast, the CO 2 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 CO 2 with different near-neighbor molecules that are encountered in other volatile mixtures such as with H 2O and CH 3OH, and non-volatile host materials like silicates, some clays, and zeolites. We suggest that Phoebe's CO 2 is native to the body as part of the initial inventory of condensates and now exposed on the surface, while CO 2 on the other three satellites results at least in part from particle or UV irradiation of native H 2O plus a source of C, implantation or accretion from external sources, or redistribution of native CO 2 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 CO 2 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 CO 2 absorption profile, producing distorted detector profile shapes and shifted central positions. In a laboratory blackbody spectrum used for radiance calibration, close examination of the CO 2 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 CO 2, as discussed in this paper.

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

    USGS Publications Warehouse

    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

    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.

  3. An absolute radius scale for Saturn's rings from Cassini RSS, VIMS, and UVIS occultations

    NASA Astrophysics Data System (ADS)

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

    2013-09-01

    The Cassini mission continues to transform our understanding of the dynamics and structure of Saturn's rings, thanks to a rich set of complementary observations from multiple instruments at a variety of wavelengths and over a wide range of viewing geometries [1], [2]. Many of the discoveries have come from the highest resolution Cassini observations of the rings, provided by over a hundred stellar occultation profiles obtained at ultraviolet (UVIS) and near-IR (VIMS) wavelengths and dozens of earth occultations at radio wavelengths by the RSS instrument. By studying these ring features in quantitative detail, we can learn a great deal about their surface mass density and detect a wide variety of weak dynamical effects that shape the rings and their detailed internal structure. Ultimately, we will be able to characterize the internal mass distribution of Saturn itself, since this governs the precession rate of Saturn's rotational axis as well as the apsidal and nodal precession rates of the narrow ringlets, both of which can be determined from precise occultation measurements of the rings. All such investigations require the precise measurement of the locations of ring edges and gaps, their registration onto an accurate absolute radius scale for the rings, and a robust orbitfitting code to determine the orbital properties of the rings, using individual measurements of ring features in hundreds of occultation profiles. To these ends, we have developed a least-squares fitting code to solve simultaneously for the orbital elements of ring features, corrections to the Cassini spacecraft trajectory, and Saturn's pole direction. We have also determined by least squares profile fitting the precise radial locations of ~100 ring features in each of ~150 Cassini RSS, VIMS, and UVIS occultation profiles, for a total of over 10,000 measurements in all. (For sharpedged features, the typical measurement uncertainty is less than 100 meters in ring plane radius.) With these results in hand, we have determined an absolute radius scale for the rings, with an estimated accuracy of ~250 m, using an iterative approach in which we identify a set of over 50 or so putative circular, equatorial features, solve for along-track spacecraft trajectory errors for each occultation, and use this best-fitting orbital solution to establish the reference system to register each occultation on an absolute radius scale. We compare these results to the ring radius scale [3] derived from Voyager 1 and 2 occultations and observations of the 28 Sgr stellar occultation in 1989. We also calculate the sensitivity of the radius scale to the assumed pole direction and precession rate.

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

    E-print Network

    of Arizona, Tucson, AZ 85721, USA d U.S. Geological Survey, Mail Stop 964, Box 25046, Denver Federal Center , Dennis L. Matson j a NASA Ames Research Center, Mail Stop 245-6, Moffett Field, CA 94035-1000, USA b USRA, NASA Ames Research Center, Moffett Field, CA 94035-1000, USA c Lunar and Planetary Lab., University

  5. The “VIM” users group

    Microsoft Academic Search

    F. William Rambo

    1975-01-01

    The “VIM” Users organization was established in 1965 and subsequently incorporated in 1970. The letters “VIM”, as suggested by Professor Max Goldstein of NYU, were originally meant to represent 6000 in Pseudo-Roman numerals. To qualify for membership, an organization must have installed or on order a CDC 6000, 7000, CYBER 70 or CYBER 170 series computer. VIM INC presently consists

  6. Effective Wavelength Scaling for Optical Antennas Lukas Novotny*

    E-print Network

    Novotny, Lukas

    Effective Wavelength Scaling for Optical Antennas Lukas Novotny* Institute of Optics, University of Rochester, Rochester, New York, USA (Received 27 March 2007; published 27 June 2007) In antenna theory, antenna parameters are directly related to the wavelength of incident radiation, but this scaling fails

  7. Blue and Green Light? Wavelength Scaling for NIF

    SciTech Connect

    Suter, L; Miller, M; Moody, J; Kruer, W

    2003-08-21

    Use of the National Ignition Facility to also output frequency-doubled (.53{micro}m) laser light would allow significantly more energy to be delivered to targets as well as significantly greater bandwidth for beam smoothing. This green light option could provide access to new ICF target designs and a wider range of plasma conditions for other applications. The wavelength scaling of the interaction physics is a key issue in assessing this green light option. Wavelength scaling theory based on the collisionless plasma approximation is explored, and some limitations associated with plasma collisionality are examined. Important features of the wavelength scaling are tested using the current data base, which is growing. It appears that, with modest restrictions, .53{micro}m light couples with targets as well as .35{micro}m light does. A more quantitative understanding of the beneficial effects of SSD on the interaction physics is needed for both .53{micro}m and .35{micro}m light.

  8. Principal components analysis of Jupiter VIMS spectra

    USGS Publications Warehouse

    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

    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.

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

    NASA Astrophysics Data System (ADS)

    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

    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.

  10. Development of Titan Atmospheric Removal Models for Cassini VIMS Data

    Microsoft Academic Search

    Karly M. Pitman; B. J. Buratti; K. H. Baines; R. A. West; M. J. Wolff; R. H. Brown; C. Sotin; R. Jaumann; P. D. Nicholson; R. N. Clark

    2007-01-01

    I\\/F spectra of Titan's surface acquired by Cassini's Visual & Infrared Mapping Spectrometer (VIMS) include signal contributions from both Titan's surface and atmosphere; the strength and wavelength coverage of the atmospheric absorptions leaves on the order of 10 data points with which spectral identification of surface ices and hydrocarbons can be reasonably attempted. Plane parallel radiative transfer (RT) correction methods

  11. A close look at Saturn's rings with Cassini VIMS

    USGS Publications Warehouse

    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

    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.

  12. Surface-Atmospheric Separation Models for Titan: Plane Parallel vs. Spherical Shell Radiative Transfer Solutions for Cassini VIMS Data

    Microsoft Academic Search

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

    2007-01-01

    The Cassini orbiter's Visual & Infrared Mapping Spectrometer (VIMS) observes Titan's surface intensity at wavelengths where its methane-rich atmosphere is heavily absorbing and light is strongly scattering. Therefore, most analyses of Titan's surface that require use of the VIMS dataset (e.g., photoclinometry, geologic interpretation, spectral identification of surface materials, photometry) are impeded until a method to separate the atmospheric from

  13. Photonic crystal lasers using wavelength-scale embedded active region

    NASA Astrophysics Data System (ADS)

    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

    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.

  14. Wavelength Scaling of High Harmonic Generation Close to the Multiphoton Ionization Regime

    E-print Network

    Lai, Chien-Jen

    We study the wavelength scaling of high harmonic generation efficiency with visible driver wavelengths in the transition between the tunneling and the multiphoton ionization regimes where the Keldysh parameter is around ...

  15. Observations with the Visual and Infrared Mapping Spectrometer (VIMS) during Cassini's flyby of Jupiter

    Microsoft Academic Search

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

    2003-01-01

    The Cassini Visual and Infrared Mapping Spectrometer (VIMS) is an imaging spectrometer covering the wavelength range 0.3–5.2 ?m in 352 spectral channels, with a nominal instantaneous field of view of 0.5 mrad. The Cassini flyby of Jupiter represented a unique opportunity to accomplish two important goals: scientific observations of the jovian system and functional tests of the VIMS instrument under

  16. Saturn's Rings Observed with Cassini-VIMS

    NASA Astrophysics Data System (ADS)

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

    2007-12-01

    Since Saturn Orbit Insertion (SOI) in July 2004, the Cassini spacecraft has completed over 50 orbits around Saturn. During this time, the Visual and Infrared Mapping Spectrometer (VIMS) has made numerous observations of the rings, including high-resolution multi-spectral scans covering the wavelength range from 0.35 to 5.1~?m, at various phase angles and illumination geometries; spectral imaging at both very low (<1°) and very high (>175°) phase angles; imaging the edge-on rings; and occultations by the sun and several bright stars. In this review we will concentrate on radial variations in the rings' reflectance spectrum, with implications for ice grain size and purity, and on structural features revealed by the VIMS stellar occultation data. Included in the latter are self-gravity wakes in the A and B rings, evident in azimuthal variations in the average transmission as well as in ring microstructure; several unidentified wave trains in the C ring; evidence for a bimodal optical depth distribution in the inner B ring; and anomalous dispersive effects seen in dusty regions such as the F ring and Encke Gap. This work was supported by NASA under a contract with the Cassini-Huygens Project.

  17. S im ulation And Analysis Of VIM Measurements: Feedback On Design Parameters

    NASA Astrophysics Data System (ADS)

    Orozco Suárez, D.; Bellot Rubio, L. R.; Vargas, S.; Bonet, J. A.; Martíez Pillet, V.; del Toro Iniesta, J. C.

    2007-01-01

    The Visible-light Imager and Magnetograph (VIM) proposed for the ESA Solar Orbiter mission will observe a photo spheric spectral line at high spatial resolution. Here we simulate and interpret VIM measurements. Realistic MHD models are used to synthesize "observed" Stokes profiles of the photospheric Fe I 617.3 nm line. The profiles are degraded by telescope diffraction and detector pixel size to a spatial resolution of 162 km on the solar surface. We stufy the influence of spectral resolving power, noise, and limited wavelength sampling on the vector magnetic fields and line-of-sight velocities derived from Milne-Eddington inversions of the simulated measurements. VIM will provide reasonably accurate values of the atmospheric parametes even with the filter widths of 120 Å and 3 wavelength positions plus continuum, as long as the noise level is kept below 10-3 Ic.

  18. Universal Instability for Wavelengths below the Ion Larmor Scale

    NASA Astrophysics Data System (ADS)

    Landreman, Matt; Antonsen, Thomas M.; Dorland, William

    2015-03-01

    We demonstrate that the universal mode driven by the density gradient in a plasma slab can be absolutely unstable even in the presence of reasonable magnetic shear. Previous studies from the 1970s that reached the opposite conclusion used an eigenmode equation limited to Lx??i , where Lx is the scale length of the mode in the radial direction, and ?i is the ion Larmor radius. Here we instead use a gyrokinetic approach which does not have this same limitation. Instability is found for perpendicular wave numbers ky in the range 0.7 ?ky?i?100 , and for sufficiently weak magnetic shear: Ls/Ln?17 , where Ls and Ln are the scale lengths of magnetic shear and density. Thus, the plasma drift wave in a sheared magnetic field may be unstable even with no temperature gradients, no trapped particles, and no magnetic curvature.

  19. Universal Instability for Wavelengths below the Ion Larmor Scale.

    PubMed

    Landreman, Matt; Antonsen, Thomas M; Dorland, William

    2015-03-01

    We demonstrate that the universal mode driven by the density gradient in a plasma slab can be absolutely unstable even in the presence of reasonable magnetic shear. Previous studies from the 1970s that reached the opposite conclusion used an eigenmode equation limited to L_{x}??_{i}, where L_{x} is the scale length of the mode in the radial direction, and ?_{i} is the ion Larmor radius. Here we instead use a gyrokinetic approach which does not have this same limitation. Instability is found for perpendicular wave numbers k_{y} in the range 0.7?k_{y}?_{i}?100, and for sufficiently weak magnetic shear: L_{s}/L_{n}?17, where L_{s} and L_{n} are the scale lengths of magnetic shear and density. Thus, the plasma drift wave in a sheared magnetic field may be unstable even with no temperature gradients, no trapped particles, and no magnetic curvature. PMID:25793821

  20. Wavelength-selective and anisotropic light-diffusing scale on the wing of the Morpho butterfly.

    PubMed Central

    Yoshioka, Shinya; Kinoshita, Shuichi

    2004-01-01

    We have found that cover scales on the wing of the butterfly Morpho didius possess specially designed microscopic structures for wavelength-selective reflection and contribute considerably to the brilliant blue colour of the wing. In addition, the cover scale functions as an anisotropic optical diffuser which diffuses light only in one plane, while it makes the range of reflection narrower in the orthogonal plane. The quantitative analyses for the wavelength-selection mechanism and the peculiar optical diffuser are given and the role of such a special optical effect is discussed from physical and biological viewpoints. PMID:15156915

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

    NASA Astrophysics Data System (ADS)

    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

    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.

  2. Wavelength scaling of optimal hollow-core fiber compressors in the single-cycle limit.

    PubMed

    Granados, Eduardo; Chen, Li-Jin; Lai, Chien-Jen; Hong, Kyung-Han; Kärtner, Franz X

    2012-04-01

    We systematically investigate supercontinuum generation using three-dimensional numerical simulations of nonlinear femtosecond pulse propagation in hollow-core fibers (HCF) at different pump wavelengths ranging from 400 nm to 2 ?m. A general design strategy for HCF compressors is presented, maximizing the spectral broadening while preserving high beam quality for given pump pulse energy, duration and wavelength. We show close fitting of the modeled results with simple analytical formulas, enabling the construction of high-energy pulse compressors at the wavelength range of interest. Based on the presented wavelength scaling study, we propose an orthogonally polarized two-color pumping scheme in a single HCF compressor for the coherent synthesis of the electric fields in the sub-cycle regime with mJ level energies. PMID:22513621

  3. Global characterization of Titan's dune fields by RADAR and VIMS observations

    NASA Astrophysics Data System (ADS)

    garcia, A.; Rodriguez, S.; Lucas, A.; Appéré, T.; Le Gall, A.; Reffet, E.; Le Corre, L.; Le Mouélic, S.; Cornet, T.; Courrech Du Pont, S.; Narteau, C.; Bourgeois, O.; Radebaugh, J.; Arnold, K.; Barnes, J. W.; Sotin, C.; Brown, R. H.; Lorenz, R. D.; Turtle, E. P.

    2013-12-01

    Cassini/RADAR high-resolution images of Titan's surface revealed linear features, geomorphologically similar to longitudinal dunes. Those dunes cover a large portion of the whole surface of Titan, i.e 7.8%, and 13.4% are present on the 58.4% of the surface imaged by the RADAR/SAR from July 2004 to July 2013 (fig.1). 99.6% of the dunes are confined at the equatorial regions (30°N-30°S). Formed and sculpted by the wind, those features represent clues for the understanding of the climatic history on the satellite. By using the joint analysis between RADAR/SAR observations and the infrared VIMS mosaic corrected for atmospheric contributions acquired through July 2013 and June 2010 respectively, we found a very high degree of correlation at global scale (more than 70%) between the RADAR dunes and a specific infrared VIMS spectral unit, the 'dark brown unit'. Some RADAR dunes, less than 2%, also belong in a commonly referenced unit, the 'dark blue unit'. These two units have been delimited by defining for each a specific set of spectral criteria. We have shown that those two units present a spectral behavior different, especially at short wavelengths (below 2 ?m) allowing to say that the 'dark brown unit' is dominated by organic sediment, similar to atmospheric aerosols, namely tholins, and the 'dark blue' is most likely enriched in water ice compared to the rest of Titan's surface. Given the strong correlation between RADAR dunes and the infrared 'dark brown unit' we are now able to extrapolate the total surface area of the dunes material to the total surface area of the 'dark brown unit' which correspond to 17% of the Titan's surface. This permits to estimate the volume of sediment of 360,000 km3 (total mass ? 290,000 GT). Thus, these estimates based on the RADAR dunes/VIMS units correlation make the dune fields the largest organic reservoir on Titan's surface and characterize more precisely the composition of the dune material over the total extend of the dune regions.

  4. Titan's surface composition and atmospheric transmission with solar occultation measurements by Cassini VIMS

    NASA Astrophysics Data System (ADS)

    Hayne, Paul O.; McCord, Thomas B.; Sotin, Christophe

    2014-11-01

    Solar occultation measurements by the Cassini Visual and Infrared Mapping Spectrometer (VIMS) reveal the near-infrared transmission of Titan's atmosphere down to an altitude of ?40 km. By combining these observations with VIMS reflectance measurements of Titan's surface and knowledge of haze and gas opacity profiles from the Huygens probe, we constrain a simple model for the transfer of radiation in Titan's atmosphere in order to derive surface reflectance in the methane windows used for compositional analysis. The advantages of this model are twofold: (1) it is accurate enough to yield useful results, yet simple enough to be implemented in just a few lines of code, and (2) the model parameters are directly constrained by the VIMS occultation and on-planet measurements. We focus on the 2.0, 2.7, 2.8 and 5.0 ?m windows, where haze opacity is minimized, and diagnostic vibrational bands exist for water ice and other candidate surface species. A particularly important result is the strong atmospheric attenuation at 2.7 ?m compared to 2.8 ?m, resulting in a reversal of apparent spectral slope in a compositionally diagnostic wavelength range. These results show that Titan's surface reflectance is much "bluer" and more closely matched by water ice than the uncorrected spectra would indicate, although the majority of Titan's surface has a spectrum consistent with mixtures (either intimate or areal) of water ice and haze particles precipitated from the atmosphere. Compositions of geologic units can be accurately modeled as mixtures ranging from predominantly water ice (Sinlap crater ejecta and margins of dark equatorial terrain) to predominantly organic-rich (Tui Regio and Hotei Regio), with particles in the size range ?10-20 ?m. In distinguishing between hypothesized formation mechanisms for Tui and Hotei Regio, their organic-rich composition favors a process that concentrates precipitated haze particles, such as playa lake evaporite deposition (Barnes, J.W., Bow, J., Schwartz, J., Brown, R.H., Soderblom, J.M., Hayes, A.G., Vixie, 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. [2011]. Icarus, 216, 136-140). In other places, kilometer-scale exposures of nearly pure water ice bedrock on Titan's surface indicate relatively locally rapid erosion compared to rates of accumulation of solid hydrocarbons precipitated from the atmosphere. Somewhat surprisingly, Titan's vast equatorial dune fields appear slightly enriched in water ice compared to the surrounding bright regions, but the spectrum of the dune material itself may nonetheless be consistent with a predominantly organic haze-derived composition.

  5. About the Portuguese VIM3 version

    NASA Astrophysics Data System (ADS)

    Pellegrino, O.; Cruz, A.; Oliveira, J. C.; Filipe, E.

    2015-02-01

    For the first time, a unique Portuguese version of the International Vocabulary of Metrology (VIM) was organized and published by the National Metrology Institutes (NMIs) of Portugal and Brazil. This challenge could be met thanks to the experiences of the respective translations of the previous editions of the VIM and to the new Orthographic Agreement (AO) of the Portuguese speaking countries. After a brief historical review of the VIMs and their Portuguese versions, this communication aims to display the main steps that led to the final joint translation. Advantage was taken of this 3rd edition and of the AO to update the Portuguese multiplicative prefix writing "kilo" in coherence with the respective symbol "k". By way of answer to the questions raised by the recent edition of the VIM (VIM3) that stresses on the concepts associated to the terms, some suggestions are proposed and inconsistencies are identified, in order to facilitate the understanding and the dissemination of the document. These few suggestions for the next edition of the VIM also intended to standardize the terminology found in normative texts of different scientific fields which unfortunately does not necessarily tend to be consistent between them.

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

    Microsoft Academic Search

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

    2004-01-01

    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

  7. Hapke modeling of Rhea surface properties through Cassini-VIMS spectra

    USGS Publications Warehouse

    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

    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.

  8. Hapke modeling of Rhea surface properties through Cassini-VIMS spectra

    NASA Astrophysics Data System (ADS)

    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.

    2011-08-01

    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 a m = 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.

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

    NASA Astrophysics Data System (ADS)

    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

    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.

  10. Mapping Titan's surface features within the visible spectrum via Cassini VIMS

    NASA Astrophysics Data System (ADS)

    Vixie, Graham; Barnes, Jason W.; Bow, Jacob; Le Mouélic, Stéphane; Rodriguez, Sébastien; Brown, Robert H.; Cerroni, Priscilla; Tosi, Federico; Buratti, Bonnie; Sotin, Christophe; Filacchione, Gianrico; Capaccioni, Fabrizio; Coradini, Angioletta

    2012-01-01

    Titan shows its surface through many methane windows in the 1-5 ?m region. Windows at shorter wavelengths also exist, polluted by scattering off of atmospheric haze that reduces the surface contrast. At visible wavelengths, the surface of Titan has been observed by Voyager I, the Hubble Space Telescope, and ground-based telescopes. We present here global surface mapping of Titan using the visible wavelength channels from Cassini's Visual and Infrared Mapping Spectrometer (VIMS). We show global maps in each of the VIMS-V channels extending from 0.35 to 1.05 ?m. We find methane windows at 0.637, 0.681, 0.754, 0.827, 0.937, and 1.046 ?m and apply an RGB color scheme to the 0.754, 0.827 and 0.937 ?m windows to search for surface albedo variations. Our results show that Titan appears gray at visible wavelengths; hence scattering albedo is a good approximation of the Bond albedo. Maps of this genre have already been made and published using the infrared channels of VIMS. Ours are the first global maps of Titan shortward of 0.938 ?m. We compare the older IR maps to the new VIMS-V maps to constrain surface composition. For instance Tui Regio and Hotei Regio, referred to as 5-?m bright spots in previous papers, do not distinguish themselves at all visible wavelengths. The distinction between the dune areas and the bright albedo spots, however, such as the difference between Xanadu and Senkyo, is easily discernible. We employ an empirically derived algorithm to remove haze layers from Titan, revealing a better look at the surface contrast.

  11. Fiber-Optic Near-Field Chemical Sensors Based on Wavelength Scale Tin Dioxide Particle Layers

    Microsoft Academic Search

    Antonietta Buosciolo; Marco Consales; Marco Pisco; Andrea Cusano; Michele Giordano

    2008-01-01

    In this paper, the surprising sensing performance of fiber-optic near-field chemical sensors, based on wavelength scale tin dioxide particle layers, against chemical pollutants in air environment at room temperature are reported. The layers were deposited upon the distal end of standard single-mode optical fibers by means of the very simple, versatile, and low-cost electrostatic spray pyrolysis technique. The morphologic and

  12. Cassini VIMS Measurements of Thermal Emission from the Tiger Stripes on Enceladus

    NASA Astrophysics Data System (ADS)

    Goguen, Jay D.; Buratti, Bonnie J.

    2014-11-01

    The 3 to 5?m sensitivity of the Cassini VIMS instrument detects the rising, short-wavelength edge Planck thermal radiation from the highest temperature ( 200 K) component of the active fissures at the south pole of Enceladus. The tiger stripe fissures are heated by the escaping warm water vapor that forms the plumes. During an extremely low 7 km altitude pass through the plumes in 2012, Goguen et al. (2013) used VIMS in the high-speed occultation mode to measure the temperature and width of an active site along the Baghdad fissure. In this presentation, we will give an overview of the some of the other VIMS measurements of thermal emission from the tiger stripes and compare the emission from different active locations at different times for data that is already archived in the Planetary Data System.Goguen, J.D., et al. (2013). The Temperature and Width of an Active Fissure on Enceladus Measured with Cassini VIMS during the 14 April 2012 South Pole Flyover. Icarus 226,1128-1137.

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

    Microsoft Academic Search

    Kevin H. Baines; Thomas W. Momary; Leigh N. Fletcher; Adam P. Showman; Maarten Roos-Serote; Robert H. Brown; Bonnie J. Buratti; Roger N. Clark; Philip D. Nicholson

    2009-01-01

    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 135m\\/s. High-spatial-resolution (~200km per pixel) images acquired predominantly under night-time conditions during Saturn's polar winter—using a thermal wavelength

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

    USGS Publications Warehouse

    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

    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.

  15. VIMS Sea Grant Seafood Education Program

    NSDL National Science Digital Library

    Information on education programs at VIMS and on-line informational resources in seafood, fisheries, and related topics including links, news, publications, workshops and seminars. Also cooking demonstrations, professional development, and programs for chefs. Includes information on seafood safety, quality, and availability.

  16. 1.3 mm WAVELENGTH VLBI OF SAGITTARIUS A*: DETECTION OF TIME-VARIABLE EMISSION ON EVENT HORIZON SCALES

    E-print Network

    Fish, Vincent L.

    Sagittarius A*, the ~4 × 10[superscript 6] M ? 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 ...

  17. Power scaling long-wavelength ytterbium-doped silica fiber lasers for frequency doubling to yellow

    NASA Astrophysics Data System (ADS)

    Sinha, Supriyo

    Ytterbium-doped silica fiber lasers and amplifiers operating at very long wavelengths were designed and demonstrated for frequency doubling to the yellow. Obtaining efficient oscillation and amplification at these long wavelengths in Yb3+-doped silica is difficult due to the low available gain and gain competition from shorter wavelengths with higher emission cross-sections. These challenges led us to develop techniques to mitigate photodarkening and maximize the suppression of amplified spontaneous emission (ASE) in silica fiber with high levels of ytterbium doping. These advances resulted in the development of an integrated fiber oscillator operating at 1150 nm with 213 mW of CW output power with a full-width half-maximum linewidth of 8 pm and a polarization extinction ratio of 21 dB. Using additional ASE management techniques, we developed a fiber amplifier that scaled the oscillator power to 3.35 W CW and 2.25 W of average power in microsecond pulses. The CW amplifier output power was frequency doubled in a periodically poled lithium niobate (PPLN) waveguide to produce 255 mW of power at 575 nm. The output of the microsecond-pulse amplifier was frequency doubled in a bulk periodically poled near-stoichiometric lithium tantalate (PPSLT) chip to nearly 1 W of average power. In addition to generating yellow radiation, issues in scaling to higher average and peak powers in fiber amplifiers were studied. In particular, the noise characteristics of large-mode area (LMA) fiber amplifiers were investigated and the use of silicate bonding to mitigate damage to fiber ends and minimize feedback was explored.

  18. Mimas: Preliminary Evidence For Amorphous Water Ice from VIMS

    NASA Technical Reports Server (NTRS)

    Cruikshank, Dale P.; Marzo, G. A.; Pinilla-Alonso, N.; Roush, T. L.; Mastrapa, R. M.; DalleOre, C. M.; Buratti, B. J.; Stephan, K.

    2010-01-01

    We have conducted a statistical clustering analysis (1,2) on a mosaic of VIMS data cubes obtained on February 13, 2010, for Saturn s satellite Mimas. Seven VIMS cubes were geometrically projected and re-sampled to a common spatial resolution. The clustering technique consists of a partitioning algorithm coupled to a criterion that prevents sub-optimal solutions and tests for the influence of random noise in the measurements. The clustering technique is agnostic about the meaning of the clusters, and scientific interpretation requires their a posteriori evaluation. The preliminary results yielded five clusters, demonstrating that spectral variability across Mimas surface is statistically significant. The ratios of the means calculated for each of the clusters show structure within the 1.6- micron water ice band, as well as the shape and the central wavelength of the strong ice band at 2 micron, that map spatially in patterns apparently related to the topography of Mimas, in particular certain regions in and around Herschel crater. The mean spectra of the five clusters, show similarities with laboratory spectra of amorphous and crystalline H2O ice (3) that are suggestive of the presence of an amorphous ice component in certain regions of Mimas, notably on the central peak of Herschel, on the crater floor, and in faults surrounding the crater. This may represent a mixture of both ice phases, or perhaps a layer of amorphous ice on a base of crystalline ice. Another possible occurrence of amorphous ice appears southwest of Herschel, close to the south pole.

  19. 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.

  20. The visible channel of OMEGA-VIMS

    Microsoft Academic Search

    V. Formisano; G. Bellucci; G. Chionchio; A. Carusi; F. Capaccioni; A. Coradini; A. Adriani; M. Viterbini; R. Bathia; F. Angrilli

    1989-01-01

    OMEGA-VIMS (Observatoire pour la Mineralogie, l'Eau, les Glaces et l'Activite - Visual and Infrared Mapping Spectrometer) is an infrared spectrometer selected for the Soviet mission Mars 94. The instrumentation is designed to support remote sensing of planetary surfaces by an infrared multispectral imager. It provides recognition of planetary bodies in the spectral range 0.30 to 1.05 microns. The main purpose

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

    E-print Network

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

    2011-10-14

    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 $\\pm$ 0.02 for 4-Methylumbelliferone, stable to within 0.5% over 50 days, 1.37 $\\pm$ 0.03 for Carbostyril-124, and 1.20 $\\pm$ 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.

  2. Organized Chromophoric Assemblies for Nonlinear Optical Materials: Towards (Sub)wavelength Scale Architectures.

    PubMed

    Xu, Jialiang; Semin, Sergey; Rasing, Theo; Rowan, Alan E

    2015-03-01

    Photonic circuits are expected to greatly contribute to the next generation of integrated chips, as electronic integrated circuits become confronted with bottlenecks such as heat generation and bandwidth limitations. One of the main challenges for the state-of-the-art photonic circuits lies in the development of optical materials with high nonlinear optical (NLO) susceptibilities, in particular in the wavelength and subwavelength dimensions which are compatible with on-chip technologies. In this review, the varied approaches to micro-/nanosized NLO materials based on building blocks of bio- and biomimetic molecules, as well as synthetic D-?-A chromophores, have been categorized as supramolecular self-assemblies, molecular scaffolds, and external force directed assemblies. Such molecular and supramolecular NLO materials have intrinsic advantages, such as structural diversities, high NLO susceptibilities, and clear structure-property relationships. These "bottom-up" fabrication approaches are proposed to be combined with the "top-down" techniques such as lithography, etc., to generate multifunctionality by coupling light and matter on the (sub)wavelength scale. PMID:25358754

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

    SciTech Connect

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

    2011-09-21

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2015-02-01

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

  5. Probing the Parsec-scale Accretion Flow of 3C 84 with Millimeter Wavelength Polarimetry

    NASA Astrophysics Data System (ADS)

    Plambeck, R. L.; Bower, G. C.; Rao, Ramprasad; Marrone, D. P.; Jorstad, S. G.; Marscher, A. P.; Doeleman, S. S.; Fish, V. L.; Johnson, M. D.

    2014-12-01

    We report the discovery of Faraday rotation toward radio source 3C 84, the active galactic nucleus in NGC 1275 at the core of the Perseus Cluster. The rotation measure (RM), determined from polarization observations at wavelengths of 1.3 and 0.9 mm, is (8.7 ± 2.3)× 105 rad m-2, among the largest ever measured. The RM remained relatively constant over a 2 yr period even as the intrinsic polarization position angle wrapped through a span of 300°. The Faraday rotation is likely to originate either in the boundary layer of the radio jet from the nucleus or in the accretion flow onto the central black hole. The accretion flow probably is disk-like rather than spherical on scales of less than a parsec, otherwise the RM would be even larger.

  6. Switchable multi-wavelength and dual-scale soliton fiber laser incorporating cascaded chirped fiber Bragg gratings

    NASA Astrophysics Data System (ADS)

    Zeng, C.; Cui, Y. D.

    2015-04-01

    A simple scheme of a switchable multi-wavelength and dual-scale soliton fiber laser is proposed by cascading three chirped fiber Bragg gratings (CFBGs). By managing the cavity dispersion and controlling the losses of attenuators, quadruple-wavelength switchable pulses are generated, including one dissipative soliton (DS) and three conventional solitons (CSs). The central wavelength of the DS is 1565?nm with a pulse duration of 12.5?ps which can be compressed to ~571?fs after a 70?m single mode fiber external to cavity. Three CSs are achieved at 1539.5, 1544.5, and 1549.5?nm with pulse durations of 9.6, 8.7, and 8.8?ps, corresponding to the CFBG-based comb spectral filtering. These results demonstrate that the proposed method offers potential opportunities to exploit the flexibly switchable multi-wavelength CS/DS-pulse sources at picosecond and femtosecond scales.

  7. Single-ionization of helium at Ti:Sapphire wavelengths: rates and scaling laws

    NASA Astrophysics Data System (ADS)

    Parker, J. S.; Meharg, K. J.; McKenna, G. A.; Taylor, K. T.

    2007-05-01

    We present a numerical and theoretical study of intense-field single-electron ionization of helium at 390 nm and 780 nm. Accurate ionization rates (over an intensity range of (0.175-34) × 1014 W cm-2, at 390 nm, and (0.275-14.4) × 1014 W cm-2 at 780 nm) are obtained from full-dimensionality integrations of the time-dependent helium-laser Schrödinger equation. We show that the power law of lowest order perturbation theory, modified with a ponderomotive-shifted ionization potential, is capable of modelling the ionization rates over an intensity range that extends up to two orders of magnitude higher than that applicable to perturbation theory alone. Writing the modified perturbation theory in terms of scaled wavelength and intensity variables, we obtain to first approximation a single ionization law for both the 390 nm and 780 nm cases. To model the data in the high intensity limit as well as in the low, a new function is introduced for the rate. This function has, in part, a resemblance to that derived from tunnelling theory but, importantly, retains the correct frequency-dependence and scaling behaviour derived from the perturbative-like models at lower intensities. Comparison with the predictions of classical ADK tunnelling theory confirms that ADK performs poorly in the frequency and intensity domain treated here.

  8. Visible And Infrared Mapping Spectrometer (VIMS): A Facility Instrument For Planetary Missions

    NASA Astrophysics Data System (ADS)

    Wellman, John B.; Duval, James; Juergens, David; Voss, Jeffrey

    1987-01-01

    Infrared mapping spectrometry, a new remote sensing tool in which a scene is imaged simultaneously in hun-dreds of wavelengths, will be used on several approved planetary missions. A second-generation visible and infrared mapping spectrometer (VIMS) has been selected for both the Mars Observer and Comet Rendezvous Asteroid Flyby (CRAF) missions. The modular VIMS design can be adapted easily to the differing characteristics of several planetary missions planned through the end of the century. VIMS is a scanning spectrometer with a focal plane consisting of linear arrays of visible and infrared detectors, cooled by a radiative cooler. The foreoptics may be tailored to different missions, according to their field-of-view and resolution requirements. A wide-angle scan is implemented for Mars Observer, using a full-aperture scan mirror. A narrow-angle scan is achieved for the CRAF mission, using a scanning secondary mirror within a Cassegrain foreoptic. A significant on-board data processing capability has been designed to provide software flexibility, thus allowing for varying mission objectives and highly variable telecommunication data rates.

  9. Connections between spectra and structure in Saturn’s main rings based on Cassini VIMS data

    NASA Astrophysics Data System (ADS)

    Hedman, M. M.; Nicholson, P. D.; Cuzzi, J. N.; Clark, R. N.; Filacchione, G.; Capaccioni, F.; Ciarniello, M.

    2013-03-01

    Saturn’s main rings exhibit variations in both their opacity and their spectral properties on a broad range of spatial scales, and the correlations between these parameters can provide insights into the processes that shape the composition and dynamics of the rings. The Visual and Infrared Mapping Spectrometer (VIMS) instrument onboard the Cassini Spacecraft has obtained spectra of the rings between 0.35 and 5.2 ?m with sufficient spatial resolution to discern variations on scales below 200 km. These relatively high-resolution spectral data reveal that both the depths of the near-infrared water-ice absorption bands and the visible spectral slopes are often correlated with structural parameters such as the rings’ optical depth. Using a simplified model for the ring-particles’ regolith properties, we have begun to disentangle the trends due to changes in the gross composition of the ring particles from those that may be due to shifts in the texture of the ring particles’ regolith. Consistent with previous studies, this analysis finds that the C ring and the Cassini Division possess enhanced concentrations of a contaminant that absorbs light over a broad range of wavelengths. On the other hand, a second contaminant that preferentially absorbs at short visible and near-ultraviolet wavelengths is found to be more evenly distributed throughout the rings. The optical activity of this short-wavelength absorber increases inwards of 100,000 km from Saturn center, which may provide clues to the origin of this contaminant. The spectral variations identified as shifts in the regolith texture are in some places clearly correlated with the ring’s optical depth, and in other locations they appear to be associated with the disturbances generated by strong mean-motion resonances with Saturn’s various moons. These variations therefore seem to be controlled by the ring particles’ dynamical environment, and may even provide a new avenue for constraining the structure and mass density of Saturn’s most opaque ring regions.

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

    PubMed Central

    Villa, Jennifer; Viedma, Esther; Otero, Joaquín R.

    2013-01-01

    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

  11. Development of vehicle intelligent monitoring system (VIMS)

    NASA Astrophysics Data System (ADS)

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

    2005-05-01

    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.

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

    SciTech Connect

    Blomquist, R.N.

    1992-09-01

    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.

  13. Wavelength scaling of optimal hollow-core fiber compressors in the single-cycle limit

    E-print Network

    Granados, Eduardo

    We systematically investigate supercontinuum generation using three-dimensional numerical simulations of nonlinear femtosecond pulse propagation in hollow-core fibers (HCF) at different pump wavelengths ranging from 400 ...

  14. VIMS Observations of Titan During the First Two Close Flybys by the Cassini-Huygens Mission

    NASA Technical Reports Server (NTRS)

    Rodriquez, S.; LeMouelic, S.; Sotin, C.; Buratti, B. J.; Brown, R. H.

    2005-01-01

    The joint NASA-ESA-ASI Cassini-Huygens mission reached the saturnian system on July 1st 2004. It started the observations of Saturn s environment including its atmosphere, rings, and satellites (Phoebe, Iapetus and Titan). Titan, one of the primary scientific interests of the mission, is veiled by an ubiquitous thick haze. Its surface cannot be seen in the visible but as the haze effects decrease with increasing wavelength, there is signal in the infrared atmospheric windows if no clouds are present. Onboard the Cassini spacecraft, the VIMS instrument (Visual and Infrared Mapping Spectrometer) is expected to pierce the veil of the hazy moon and successfully image its surface in the infrared wavelengths, taking hyperspectral images in the range 0.4 to 5.2 micron. On 26 October (TA) and 13 December 2004 (TB), the Cassini-Huygens mission flew over Titan at an altitude lower than 1200 km at closest approach. VIMS acquired several tens of image cubes with spatial resolution ranging from a few tens of kilometers down to 1.5 kilometer per pixel, demonstrating its capability for studying Titan s geology.

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

    USGS Publications Warehouse

    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

    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

  16. CASSINI VIMS-V Jupiter fly-by results

    Microsoft Academic Search

    A. Coradini

    2002-01-01

    During Cassini-Huygens probe Jupiter fly-by in December 2000, VIMS-V acquired multispectral data cubes of Jupiter atmosphere and of Galileian satellites surfaces. VIMS-V (Visual and Infrared Imaging Spectrometer) is one of the principal contributions of ASI (Italian Space Agency) to the Cassini-Huygens mission to Saturn; this imaging spectrometer is able to collect data-cubes in the range from 0.3 to 1.05 micron,

  17. Guiding, focusing, and sensing on the sub-wavelength scale using metallic wire arrays

    E-print Network

    Shvets, G; Sarychev, A; Trendafilov, S

    2007-01-01

    We show that two-dimensional arrays of thin metallic wires can guide transverse electromagnetic (TEM) waves and focus them to the spatial dimensions much smaller that the vacuum wavelength. This guiding property is retained for the tapered wire bundles which can be used as multi-channel TEM endoscopes: they capture a detailed electromagnetic field profile created by deeply sub-wavelength features of the studied sample and magnify it for observation. The resulting imaging method is superior to the conventional scanning microscopy because of the parallel nature of the image acquisition by multiple metal wires. Possible applications include terahertz and mid-infrared endoscopy with nanoscale resolution.

  18. Beam displacement as a function of temperature and turbulence length scale at two different laser radiation wavelengths.

    PubMed

    Isterling, William M; Dally, Bassam B; Alwahabi, Zeyad T; Dubovinsky, Miro; Wright, Daniel

    2012-01-01

    Narrow laser beams directed from aircraft may at times pass through the exhaust plume of the engines and potentially degrade some of the laser beam characteristics. This paper reports on controlled studies of laser beam deviation arising from propagation through turbulent hot gases, in a well-characterized laboratory burner, with conditions of relevance to aircraft engine exhaust plumes. The impact of the temperature, laser wavelength, and turbulence length scale on the beam deviation has been investigated. It was found that the laser beam displacement increases with the turbulent integral length scale. The effect of temperature on the laser beam angular deviation, ?, using two different laser wavelengths, namely 4.67 ?m and 632.8 nm, was recorded. It was found that the beam deviation for both wavelengths may be semiempirically modeled using a single function of the form, ?=a(b+(1/T)(2))(-1), with two parameters only, a and b, where ? is in microradians and T is the temperature in °C. PMID:22270413

  19. 1.3 mm WAVELENGTH VLBI OF SAGITTARIUS A*: DETECTION OF TIME-VARIABLE EMISSION ON EVENT HORIZON SCALES

    SciTech Connect

    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

    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*.

  20. Titan’s surface and atmosphere from Cassini/VIMS data with updated methane opacity

    NASA Astrophysics Data System (ADS)

    Hirtzig, M.; Bézard, B.; Lellouch, E.; Coustenis, A.; de Bergh, C.; Drossart, P.; Campargue, A.; Boudon, V.; Tyuterev, V.; Rannou, P.; Cours, T.; Kassi, S.; Nikitin, A.; Mondelain, D.; Rodriguez, S.; Le Mouélic, S.

    2013-09-01

    We present an analysis of Titan data acquired by the Cassini Visual and Infrared Mapping Spectrometer (VIMS), making use of recent improvements in methane spectroscopic parameters in the region 1.3-5.2 ?m. We first analyzed VIMS spectra covering a 8 × 10-km2 area near the Huygens landing site in order to constrain the single scattering albedo (?0) of the aerosols over all of the VIMS spectral range. Our aerosol model agrees with that derived from Huygens Probe Descent Imager/Spectral Radiometer (DISR) in situ measurements below 1.6 ?m. At longer wavelengths, ?0 steadily decreases from 0.92 at 1.6 ?m to about 0.70 at 2.5 ?m and abruptly drops to about 0.50 near 2.6 ?m, a spectral variation that differs from that of Khare et al.’s (Khare, B.N., Sagan, C., Arakawa, E.T., Suits, F., Callcott, T.A., Williams, M.W. [1984]. Icarus 60, 127-137) laboratory tholins. Our analysis shows that the far wings of the strong methane bands on both sides of the transparency windows provide a significant source of opacity in these windows, and that their unknown sub-Lorentzian behavior limits our ability to determine precisely the surface albedos. Below 1.6 ?m, the retrieved surface albedos agree with those derived from Huygens/DISR. The VIMS spectrum at 2.0 ?m indicates a surface albedo of 0.11 ± 0.01, larger than derived in previous studies, and inconsistent with the signature of water ice. A series of VIMS data taken from 2004 to 2010 between 40°S and 40°N were then analyzed to monitor the latitudinal and temporal evolution of the atmospheric aerosol content. In the 2004-2008 period, the haze extinction is larger at Northern mid-latitudes by ?20% with respect to the Huygens site, whereas Southern mid-latitudes are depleted by ?15-20%. In 2009-2010, a progressive decline of the haze content in the Northern hemisphere is observed but no reversal of the North-to-South asymmetry is seen till mid-2010. Finally, data from five regions in Tui Regio and Fensal that show markedly different spectral behaviors and morphologies were analyzed to investigate the wavelength dependence of their surface albedo. The difference between bright and dark regions can be explained by different contents of small-sized tholins at the surface, brighter regions being more tholin-rich than dark regions, including the Huygens landing site. On the other hand, the albedo spectrum of the so-called blue regions, either dark or bright, can be explained by an excess of water ice particles, compared with the Huygens landing site. The spectrum of a 5-?m bright region in Tui Regio indicates a large excess of small-sized tholins relative to the Huygens site, but does not point to any particular surface composition.

  1. A large-scale cosmic microwave background anisotropy measurement at millimeter and submillimeter wavelengths

    SciTech Connect

    Page, L.A.; Cheng, E.S.; Meyer, S.S. (MIT, Cambridge, MA (USA))

    1990-05-01

    A balloon-borne experiment to measure the anisotropy of the cosmic microwave background radiation at angular scales of 4 deg or greater is reported. The instrument simultaneously measures in four spectral bands centered on 5.6, 8.7, 15.8, and 22.5/cm. Three results are presented: (1) the 95-percent confidence limit for monochromatic anisotropies is 0.0001 or less on angular scales of 10 deg; (2) the Galactic plane dust emission at l = 42 deg is consistent with a nu-squared emissivity law at frequencies above 15/cm, with excess emission below 15/cm; and (3) atmospheric ozone at an altitude of 35 km may form clumps as large as Delta emissivity/emissivity = 0.002. 21 refs.

  2. A large-scale cosmic microwave background anisotropy measurement at millimeter and submillimeter wavelengths

    NASA Technical Reports Server (NTRS)

    Page, Lyman A.; Cheng, Edward S.; Meyer, Stephan S.

    1990-01-01

    A balloon-borne experiment to measure the anisotropy of the cosmic microwave background radiation at angular scales of 4 deg or greater is reported. The instrument simultaneously measures in four spectral bands centered on 5.6, 8.7, 15.8, and 22.5/cm. Three results are presented: (1) the 95-percent confidence limit for monochromatic anisotropies is 0.0001 or less on angular scales of 10 deg; (2) the Galactic plane dust emission at l = 42 deg is consistent with a nu-squared emissivity law at frequencies above 15/cm, with excess emission below 15/cm; and (3) atmospheric ozone at an altitude of 35 km may form clumps as large as Delta emissivity/emissivity = 0.002.

  3. Novel VIM metallo-beta-lactamase variant from clinical isolates of Enterobacteriaceae from Algeria.

    PubMed

    Robin, Frédéric; Aggoune-Khinache, Nadjet; Delmas, Julien; Naim, Malek; Bonnet, Richard

    2010-01-01

    Five different strains of bacteria belonging to the family Enterobacteriaceae were isolated from two patients hospitalized in the intensive care unit of the Central Military Hospital of Algiers, Algeria. All five strains, one Providencia stuartii strain, two Escherichia coli strains, and two Klebsiella pneumoniae strains, were intermediate or resistant to all beta-lactams, including carbapenems. Synergy between imipenem and EDTA was observed for all five strains. The results of the PCR experiment confirmed the presence of a bla(VIM) gene in all five strains. The bla(VIM) genes were located as part of a class 1 integron on a 180-kb conjugative plasmid. They encoded a novel metallo-beta-lactamase designated VIM-19, which differed from the parental enzyme VIM-1 by only two substitutions: Ser228Arg, previously observed in the closely related enzyme VIM-4, and Asn215Lys, not previously observed in other VIM-type carbapenemases. VIM-19 was further characterized after purification through determination of its kinetic constants. This enzyme was inhibited by EDTA and hydrolyzed penicillins, cephalosporins, and carbapenems, as observed for other VIM-type carbapenemases but with greater catalytic efficiency against penicillins than VIM-1. VIM-19 is the first carbapenemase enzyme identified from an isolate from Algeria. These results confirm the emergence of VIM-4-like enzymes in members of the family Enterobacteriaceae from Mediterranean countries. PMID:19901092

  4. Novel VIM Metallo-?-Lactamase Variant from Clinical Isolates of Enterobacteriaceae from Algeria ?

    PubMed Central

    Robin, Frédéric; Aggoune-Khinache, Nadjet; Delmas, Julien; Naim, Malek; Bonnet, Richard

    2010-01-01

    Five different strains of bacteria belonging to the family Enterobacteriaceae were isolated from two patients hospitalized in the intensive care unit of the Central Military Hospital of Algiers, Algeria. All five strains, one Providencia stuartii strain, two Escherichia coli strains, and two Klebsiella pneumoniae strains, were intermediate or resistant to all ?-lactams, including carbapenems. Synergy between imipenem and EDTA was observed for all five strains. The results of the PCR experiment confirmed the presence of a blaVIM gene in all five strains. The blaVIM genes were located as part of a class 1 integron on a 180-kb conjugative plasmid. They encoded a novel metallo-?-lactamase designated VIM-19, which differed from the parental enzyme VIM-1 by only two substitutions: Ser228Arg, previously observed in the closely related enzyme VIM-4, and Asn215Lys, not previously observed in other VIM-type carbapenemases. VIM-19 was further characterized after purification through determination of its kinetic constants. This enzyme was inhibited by EDTA and hydrolyzed penicillins, cephalosporins, and carbapenems, as observed for other VIM-type carbapenemases but with greater catalytic efficiency against penicillins than VIM-1. VIM-19 is the first carbapenemase enzyme identified from an isolate from Algeria. These results confirm the emergence of VIM-4-like enzymes in members of the family Enterobacteriaceae from Mediterranean countries. PMID:19901092

  5. Temperature maps of Saturn’s satellites retrieved from Cassini-VIMS observations

    NASA Astrophysics Data System (ADS)

    Filacchione, Gianrico; Capaccioni, Fabrizio; Ciarniello, Mauro; Tosi, Federico; D'Aversa, Emiliano; Clark, Roger N.; Brown, Robert N.; Buratti, Bonnie J.; Cruikshank, Dale P.; Dalle Ore, Cristina M.; Scipioni, Francesca; Cerroni, Priscilla

    2014-11-01

    The spectral position of the 3.6 µm continuum peak measured on Cassini-VIMS reflectance spectra is used to infer the temperature of the regolith particles covering the surfaces of Saturn’s icy satellites. Laboratory measurements by Clark et al. (2012) have shown that 3.6 µm peak for pure crystalline water ice particles shifts towards shorter wavelengths when the sample is cooled, moving from about 3.65 µm at T=123 K to about 3.55 µm at T=88 K. A similar trend is observed also in the imaginary part (k) of the refractive index of water ice when the sample is cooled from T=140 K to 20 K (Mastrapa et al., 2009). Since water ice is the dominant endmember on Saturn’s satellites surfaces (Clark and Owensby, 1981; Clark et al., 1984; Filacchione et al., 2012), the measurement of the wavelength at which the 3.6 µm reflectance peak occurs can be considered as a temperature indicator. We report on our temperature maps of Mimas, Enceladus, Tethys, Dione and Rhea derived by applying this method to Cassini-VIMS data taken at spatial resolution of 20-40 km/pixel. These maps allow us to correlate the temperature distribution with solar illumination conditions and with geological features. On average Enceladus’ mid-latitudes regions appear at T<100 K while the south pole tiger-stripes active area shows a thermal emission at T>115 K. Tethys’ and Mimas’ equatorial lenses show significant thermal anomalies: despite the fact that these features have low visible albedo they appear colder than the surrounding mid-latitude regions as a consequence of a much higher thermal inertia. On Mimas, the floor of Herschel crater appears warmer (T>115 K) than the adjacent equatorial lens area (T<110 K). Finally, the analysis of Dione shows that the temperature across the bright wispy terrains is lower than the nearby low albedo areas.

  6. The Cassini Visual And Infrared Mapping Spectrometer (Vims) Investigation

    Microsoft Academic Search

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

    2004-01-01

    The Cassini visual and infrared mapping spectrometer (VIMS) investigation is a multidisciplinary study of the Saturnian system. Visual and near-infrared imaging spectroscopy and high-speed spectrophotometry are the observational techniques. The scope of the investigation includes the rings, the surfaces of the icy satellites and Titan, and the atmospheres of Saturn and Titan. In this paper, we will elucidate the major

  7. The VIMS CBOS Observing System Buoy, an Initial Scientific Analysis

    Microsoft Academic Search

    L. H. Brasseur; J. M. Brubaker; C. T. Friedrichs; L. D. Wright

    2004-01-01

    The Virginia Institute of Marine Science (VIMS) has recently deployed a data buoy at Gloucester Point, York River, Virginia as part of the Chesapeake Bay Observing System (CBOS). The data streams collected by the buoy and its associated sensors are wind speed and direction, incoming solar radiation, air temperature, water temperature, salinity, turbidity, fluorescence, and dissolved oxygen. In addition, water

  8. A measurement of the large-scale cosmic microwave background anisotropy at 1.8 millimeter wavelength

    NASA Technical Reports Server (NTRS)

    Meyer, Stephan S.; Cheng, Edward S.; Page, Lyman A.

    1991-01-01

    This measurement of the large-scale cosmic microwave background radiation (CMBR) anisotropy places the most stringent constraints to date on fluctuations in the CMBR on angular scales greater than about 4 deg. Using a four-channel bolometric radiometer operating at 1.8, 1.1, 0.63, and 0.44 mm, the diffuse sky brightness over half of the northern hemisphere has been mapped with an angular resolution of 3.8 deg. Analysis of the sky map at the longest wavelength for Galactic latitudes of 15 deg or more yields a 95-percent confidence level upper limit on fluctuations of the CMBR at Delta T/T of 1.6 x 10 to the -5th with a statistical power of 92 percent for Gaussian fluctuations at a correlation angle of 13 deg. Between 3 deg and 22 deg, the upper limit of fluctuations is 4.0 x 10 to the -5th . An anisotropy is detected in the map, but it cannot yet be attributed to primordial sources. The ultimate sensitivity for this experiment is 7 x 10 to the -6th over this angular range for Gaussian fluctuations.

  9. Characterization of novel VIM carbapenemase, VIM-38, and first detection of GES-5 carbapenem-hydrolyzing ?-lactamases in Pseudomonas aeruginosa in Turkey.

    PubMed

    Iraz, Meryem; Duzgun, Azer Ozad; Cicek, Aysegul Copur; Bonnin, Rémy A; Ceylan, Aysenur; Saral, Aysegul; Nordmann, Patrice; Sandalli, Cemal

    2014-03-01

    Pseudomonas aeruginosa isolates were collected form a Turkish hospital. Antimicrobial susceptibility was performed using the Vitek 2 Compact system, and 24 isolates were categorized as multidrug resistant (n = 18), extensively-drug resistant (n = 5), or pan-drug resistant (n = 1). PCR and DNA sequence analysis revealed that 1 strain possessed the blaGES-5 and another carried a novel blaVIM variant, named VIM-38. This new gene exhibited 1 amino acid substitution (Ala265Val) in comparison to its closest variant, VIM-5. Both VIM encoding genes were clones and demonstrated similar susceptibility profile when expressed in identical background. The presence of VIM-38 increases the diversity of carbapenemases in Turkey. PMID:24428980

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

    NASA Technical Reports Server (NTRS)

    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

    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.

  11. Spectroscopic investigation of Dione' surface using Cassini VIMS images

    NASA Astrophysics Data System (ADS)

    Scipioni, F.; Coradini, A.; Tosi, F.; Capaccioni, F.; Cerroni, P.; Filacchine, G.; Federico, C.

    2011-10-01

    Dione was observed several times by the Cassini spacecraft in its nominal and extended mission from 2004 to 2010. We have selected 76 Cassini/VIMS hyperspectral cubes of Dione in the IR range between 0.85 and 5.1 ?m and we have applied the Spectral Angle Mapper (SAM) clustering technique to classify different surface units on the basis of their spectral properties. We identify nine different terrain types correlated to specific Dione' surface morphologies.

  12. VIMS Molluscan Ecology Program: Ongoing Rapana Venosa Research

    NSDL National Science Digital Library

    This marine snail (Rapana venosa) from Asia was discovered in the Chesapeake Bay in 1998. VIMS scientists report their research on this exotic species, how its biology and life cycle allowed it to invade US waters via ballast water, and what impacts it may have on local ecology and shellfish populations. Describes reporting and bounty system for monitoring the species. Site provides the opportunity to order a CD and teacher booklet on this case study in invasive marine species.

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

    Microsoft Academic Search

    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

    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

  14. Evolution of 30 years of the International Vocabulary of Metrology (VIM)

    NASA Astrophysics Data System (ADS)

    Mari, Luca

    2015-02-01

    Since its first edition, published in 1984, the International Vocabulary of Metrology (VIM) has become a landmark for the language of measurement, and in its three editions it has evolved together with the evolution of measurement science and its applications. This paper discusses the fundamental features of the VIM as a concept system and proposes some highlights about the way in the VIM some basic and general concepts of measurement have changed their definitions in the last thirty years.

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

    NASA Astrophysics Data System (ADS)

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

    2013-10-01

    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.

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

    SciTech Connect

    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

    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.

  17. The source of widespread 3-$\\mu$m absorption in Jupiter's clouds: Constraints from 2000 Cassini VIMS observations

    E-print Network

    Sromovsky, Lawrence

    2015-01-01

    The Cassini flyby of Jupiter in 2000 provided spatially resolved spectra of Jupiter's atmosphere using the Visual and Infrared Mapping Spectrometer (VIMS). These spectra contain a strong absorption at wavelengths from about 2.9 $\\mu$m to 3.1 $\\mu$m, previously noticed in a 3-$\\mu$m spectrum obtained by the Infrared Space Observatory (ISO) in 1996. While Brooke et al. (1998, Icarus 136, 1-13) were able to fit the ISO spectrum very well using ammonia ice as the sole source of particulate absorption, Sromovsky and Fry (2010, Icarus 210, 211-229), using significantly revised NH$_3$ gas absorption models, showed that ammonium hydrosulfide (NH$_4$SH) provided a better fit to the ISO spectrum than NH$_3$ , but that the best fit was obtained when both NH$_3$ and NH$_4$SH were present. Although the large FOV of the ISO instrument precluded identification of the spatial distribution of these two components, the VIMS spectra at low and intermediate phase angles show that 3-$\\mu$m absorption is present in zones and belts...

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

    USGS Publications Warehouse

    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

    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.

  19. The Saturnian satellite Rhea as seen by Cassini VIMS

    USGS Publications Warehouse

    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

    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.

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

    Microsoft Academic Search

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

    2001-01-01

    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

  1. Cassini VIMS at Saturn: The First 6 Months

    NASA Technical Reports Server (NTRS)

    Brown, R. H.; Baines, K.; Bellucci, G.; Buratti, B.; Capaccioni, F.; Cerroni, P.; Clark, R. N.; Coradini, A.; Cruikshank, D.; Drossart, P.

    2005-01-01

    The Cassini Visual and Infrared Mapping Spectrometer (VIMS) is an imaging spectrometer on the Cassini spacecraft that covers the spectral range of 0.35 - 5.2 m in 352 spectral channels, a nominal instantaneous field of view of 0.5 mrad and an image format of 64 x 64 pixels. It has completed it s first 6 months in orbit around Saturn. During that time it has made extensive observations of Saturn s rings, it s icy satellites, in particular Phoeba and Iapetus, and had 1 distant and 2 close flybys of Titan.

  2. Spectroscopic investigation of Dione' surface using Cassini VIMS images

    NASA Astrophysics Data System (ADS)

    Scipioni, F.; Coradini, A.; Tosi, F.; Capaccioni, F.; Cerroni, P.; Filacchione, G.; Federico, C.; Cassini VIMS Team

    Dione is the second largest inner moon of Saturn. It is composed primarily of water ice (rho = 1.475 ± 0.003 g/cm3), and is the third densest of Saturn's moons (after Enceladus and Titan). This satellite was observed several times by the Cassini spacecraft in its nominal and extended mission from 2004 to 2008. The VIMS (Visual and Infrared Mapping Spectrometer) instrument onboard the Cassini Orbiter is able to acquire hyperspectral image cubes in the overall spectral range from 0.35 to 5.1 mu m. We select 76 VIMS cubes of Dione in the IR range between 0.85 and 5.1 mu m, choosing those data which show at the same time: a spatial resolution better than 100 km, a phase angle smaller than 40o and a good S/N ratio. We apply Spectral Angle Mapper (SAM) clustering technique to the spectra of the surface in order to emphasize the presence of different terrain units; then we investigate the compositional and photometric characteristics of these terrain types. In this work we choose the two cubes with the highest spatial resolution among the whole data set to show classification results.

  3. VIS-IR spectrograms of Saturn's rings retrieved from Cassini-VIMS radial mosaics

    NASA Astrophysics Data System (ADS)

    Filacchione, G.; Capaccioni, F.; Ciarniello, M.; Nicholson, P.; Hedmann, M. M.; Clark, R. N.; Brown, R. H.; Cerroni, P.

    2011-10-01

    Context: Cassini-VIMS has harvested a large number of Saturn's rings radial mosaics at very different observation geometries. Aims: This work is focused on the retrieval of rings average composition (water ice and red cromophores), regolith grain sizes and photometric parameters. Method: We have implemented a procedure to build ring spectrograms, e.g., 2D arrays that contain the full spectral (0.35 - 5.0 ?m) and spatial (from 73.500 to 141.375 km) information sampled at 400 km/bin spatial resolution. This processing is applied to several mosaics acquired at different illumination phases (12° to 136°) and opening angles (-21° to +5°). Results: Ring spectra show reddening at VIS wavelengths while maintaining a strong similarity to water ice in the IR. Differences both in VIS reddening, water ice abundance and grain sizes are retrieved across different rings regions. Conclusions: Two important findings are that 1) both VIS reddening and water ice band depths increase at high phases, thus indicating that the red contaminant is intimately mixed in water ice grains; 2) typical regolith grain sizes are between 10-40 ?m in the C ring, 40-60 ?m in the Cassini Division (CD) and >100 ?m in the A and B rings.

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

    SciTech Connect

    Blomquist, R.N.

    1992-09-01

    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.

  5. VimA mediates multiple functions that control virulence in Porphyromonas gingivalis

    PubMed Central

    Aruni, A. Wilson; Robles, A.; Fletcher, H.M.

    2013-01-01

    SUMMARY Porphyromonas gingivalis, a black-pigmented, gram-negative anaerobe, is an important etiological agent of periodontal disease. Its ability to survive in the periodontal pocket and orchestrate the microbial/host activities that can lead to disease suggest that P. gingivalis possesses a complex regulatory network involving transcriptional and post-transcriptional mechanisms. The vimA (virulence modulating) gene is part of the 6.15-kb bcp-recA-vimA-vimE-vimF-aroG locus and plays a role in oxidative stress resistance. In addition to the glycosylation and anchorage of several surface proteins including the gingipains, VimA can also modulate sialylation, acetyl coenzyme A transfer, lipid A and its associated proteins and may be involved in protein sorting and transport. In this review, we examine the multifunctional role of VimA and discuss its possible involvement in a major regulatory network important for survival and virulence regulation in P. gingivalis. It is postulated that the multifunction of VimA is modulated via a post-translational mechanism involving acetylation. PMID:23279905

  6. Latitudinal variations in Titan’s methane and haze from Cassini VIMS observations

    NASA Astrophysics Data System (ADS)

    Penteado, Paulo F.; Griffith, Caitlin A.; Tomasko, Martin G.; Engel, Steffi; See, Charles; Doose, Lyn; Baines, Kevin H.; Brown, Robert H.; Buratti, Bonnie J.; Clark, Roger; Nicholson, Phillip; Sotin, Christophe

    2010-03-01

    We analyze observations taken with Cassini's Visual and Infrared Mapping Spectrometer (VIMS), to determine the current methane and haze latitudinal distribution between 60°S and 40°N. The methane variation was measured primarily from its absorption band at 0.61 ?m, which is optically thin enough to be sensitive to the methane abundance at 20-50 km altitude. Haze characteristics were determined from Titan's 0.4-1.6 ?m spectra, which sample Titan's atmosphere from the surface to 200 km altitude. Radiative transfer models based on the haze properties and methane absorption profiles at the Huygens site reproduced the observed VIMS spectra and allowed us to retrieve latitude variations in the methane abundance and haze. We find the haze variations can be reproduced by varying only the density and single scattering albedo above 80 km altitude. There is an ambiguity between methane abundance and haze optical depth, because higher haze optical depth causes shallower methane bands; thus a family of solutions is allowed by the data. We find that haze variations alone, with a constant methane abundance, can reproduce the spatial variation in the methane bands if the haze density increases by 60% between 20°S and 10°S (roughly the sub-solar latitude) and single scattering absorption increases by 20% between 60°S and 40°N. On the other hand, a higher abundance of methane between 20 and 50 km in the summer hemisphere, as much as two times that of the winter hemisphere, is also possible, if the haze variations are minimized. The range of possible methane variations between 27°S and 19°N is consistent with condensation as a result of temperature variations of 0-1.5 K at 20-30 km. Our analysis indicates that the latitudinal variations in Titan's visible to near-IR albedo, the north/south asymmetry (NSA), result primarily from variations in the thickness of the darker haze layer, detected by Huygens DISR, above 80 km altitude. If we assume little to no latitudinal methane variations we can reproduce the NSA wavelength signatures with the derived haze characteristics. We calculate the solar heating rate as a function of latitude and derive variations of ˜10-15% near the sub-solar latitude resulting from the NSA. Most of the latitudinal variations in the heating rate stem from changes in solar zenith angle rather than compositional variations.

  7. Latitudinal variations in Titan's methane and haze from Cassini VIMS observations

    USGS Publications Warehouse

    Penteado, P.F.; Griffith, C.A.; Tomasko, M.G.; Engel, S.; See, C.; Doose, L.; Baines, K.H.; Brown, R.H.; Buratti, B.J.; Clark, R.; Nicholson, P.; Sotin, C.

    2010-01-01

    We analyze observations taken with Cassini's Visual and Infrared Mapping Spectrometer (VIMS), to determine the current methane and haze latitudinal distribution between 60??S and 40??N. The methane variation was measured primarily from its absorption band at 0.61 ??m, which is optically thin enough to be sensitive to the methane abundance at 20-50 km altitude. Haze characteristics were determined from Titan's 0.4-1.6 ??m spectra, which sample Titan's atmosphere from the surface to 200 km altitude. Radiative transfer models based on the haze properties and methane absorption profiles at the Huygens site reproduced the observed VIMS spectra and allowed us to retrieve latitude variations in the methane abundance and haze. We find the haze variations can be reproduced by varying only the density and single scattering albedo above 80 km altitude. There is an ambiguity between methane abundance and haze optical depth, because higher haze optical depth causes shallower methane bands; thus a family of solutions is allowed by the data. We find that haze variations alone, with a constant methane abundance, can reproduce the spatial variation in the methane bands if the haze density increases by 60% between 20??S and 10??S (roughly the sub-solar latitude) and single scattering absorption increases by 20% between 60??S and 40??N. On the other hand, a higher abundance of methane between 20 and 50 km in the summer hemisphere, as much as two times that of the winter hemisphere, is also possible, if the haze variations are minimized. The range of possible methane variations between 27??S and 19??N is consistent with condensation as a result of temperature variations of 0-1.5 K at 20-30 km. Our analysis indicates that the latitudinal variations in Titan's visible to near-IR albedo, the north/south asymmetry (NSA), result primarily from variations in the thickness of the darker haze layer, detected by Huygens DISR, above 80 km altitude. If we assume little to no latitudinal methane variations we can reproduce the NSA wavelength signatures with the derived haze characteristics. We calculate the solar heating rate as a function of latitude and derive variations of ???10-15% near the sub-solar latitude resulting from the NSA. Most of the latitudinal variations in the heating rate stem from changes in solar zenith angle rather than compositional variations. ?? 2009 Elsevier Inc. All rights reserved.

  8. Saturn's tropospheric composition and clouds from Cassini/VIMS 4.6-5.1 ?m nightside spectroscopy

    NASA Astrophysics Data System (ADS)

    Fletcher, Leigh N.; Baines, Kevin H.; Momary, Thomas W.; Showman, Adam P.; Irwin, Patrick G. J.; Orton, Glenn S.; Roos-Serote, Maarten; Merlet, C.

    2011-08-01

    The latitudinal variation of Saturn's tropospheric composition (NH 3, PH 3 and AsH 3) and aerosol properties (cloud altitudes and opacities) are derived from Cassini/VIMS 4.6-5.1 ?m thermal emission spectroscopy on the planet's nightside (April 22, 2006). The gaseous and aerosol distributions are used to trace atmospheric circulation and chemistry within and below Saturn's cloud decks (in the 1- to 4-bar region). Extensive testing of VIMS spectral models is used to assess and minimise the effects of degeneracies between retrieved variables and sensitivity to the choice of aerosol properties. Best fits indicate cloud opacity in two regimes: (a) a compact cloud deck centred in the 2.5-2.8 bar region, symmetric between the northern and southern hemispheres, with small-scale opacity variations responsible for numerous narrow light/dark axisymmetric lanes; and (b) a hemispherically asymmetric population of aerosols at pressures less than 1.4 bar (whose exact altitude and vertical structure is not constrained by nightside spectra) which is 1.5-2.0× more opaque in the summer hemisphere than in the north and shows an equatorial maximum between ±10° (planetocentric). Saturn's NH 3 spatial variability shows significant enhancement by vertical advection within ±5° of the equator and in axisymmetric bands at 23-25°S and 42-47°N. The latter is consistent with extratropical upwelling in a dark band on the poleward side of the prograde jet at 41°N (planetocentric). PH 3 dominates the morphology of the VIMS spectrum, and high-altitude PH 3 at p < 1.3 bar has an equatorial maximum and a mid-latitude asymmetry (elevated in the summer hemisphere), whereas deep PH 3 is latitudinally-uniform with off-equatorial maxima near ±10°. The spatial distribution of AsH 3 shows similar off-equatorial maxima at ±7° with a global abundance of 2-3 ppb. VIMS appears to be sensitive to both (i) an upper tropospheric circulation (sensed by NH 3 and upper-tropospheric PH 3 and hazes) and (ii) a lower tropospheric circulation (sensed by deep PH 3, AsH 3 and the lower cloud deck).

  9. VIMS spectral mapping observations of Titan during the Cassini prime mission

    USGS Publications Warehouse

    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

    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.

  10. Hidden VIM-1 metallo-beta-lactamase phenotypes among Acinetobacter baumannii clinical isolates.

    PubMed

    Ikonomidis, Alexandros; Ntokou, Eleni; Maniatis, Antonios N; Tsakris, Athanassios; Pournaras, Spyros

    2008-01-01

    A total of 87 Acinetobacter baumannii nonrepetitive consecutive clinical isolates were tested for the presence of metallo-beta-lactamases (MBLs). Results of phenotypic assays (MBL Etest, imipenem/imipenem-EDTA combined-disk test, and imipenem/EDTA double-disk synergy test) were negative in all cases, but molecular testing revealed the presence of two bla(VIM-1)-carrying isolates. One isolate had bla(VIM-1) preceded by a weak P1 promoter, and both had inactivated P2 promoters and reduced bla(VIM-1) expression, partially justifying the results revealing hidden MBL phenotypes. PMID:18032624

  11. Are scaling laws of sub-optical wavelength electric field confinement in arrays of metal nanoparticles related to plasmonics or to geometry?

    PubMed

    Mezeme, M Essone; Brosseau, C

    2012-07-30

    In this work, we describe finite element simulations of the plasmonic resonance (PLR) properties of a self-similar chain of plasmonic nanostructures. Using a broad range of conditions, we find strong numerical evidence that the electric field confinement behaves as (?/?)(PLR)[proporationality] EFE(-?), where EFE is the electric field enhancement, ?is the linear size of the focusing length, and ? is the wavelength of the resonant excitation. We find that the exponent ? is close to 1, i.e. significantly lower than the 1.5 found for two-dimensional nanodisks. This scaling law provides support for the hypothesis of a universal regime in which the sub-optical wavelength electric field confinement is controlled by the Euclidean dimensionality and is independent of nanoparticle size, metal nature, or embedding medium permittivity. PMID:23038312

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

    NASA Astrophysics Data System (ADS)

    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

    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.

  13. Cassini-VIMS Observations Of Self-gravity Wakes In Saturn's Rings

    NASA Astrophysics Data System (ADS)

    Nicholson, Philip D.; Hedman, M. M.; Cassini-VIMS Team

    2006-06-01

    Between May 24 and August 9, 2005 Cassini's Visual and Infrared Mapping Spectrometer (VIMS) observed four occultations of the long-period variable star, o Ceti (Mira) by Saturn's rings. Large, systematic variations in the transmission of the A ring with longitude are evident in the data, with a maximum in transmission occurring at a longitude of 250° relative to the observer. This is consistent both with the well-known azimuthal asymmetry in reflected light from the A ring, and with numerical models of spontaneous gravitational wakes (e.g., Salo et al. 2004). The physics underlying such wakes is essentially the same as the "swing amplifier" which was studied in the context of galactic disks by Julian & Toomre (1966) and Toomre & Kalnajs (1991). We have developed a simple model of transmission through a set of parallel wakes, modelled as opaque cylinders with elliptical cross-sections. By fitting the predictions of this model to the observed variations of transmission with longitude, we find the following. (1) The orientation of the wakes varies slightly but systematically across the A ring, from 18° to 26? relative to the azimuthal direction. (2) The peak transmission reaches a maximum in the middle A ring at a radius of 129,000 km, in good agreement with the radius of minimum reflected brightness seen in the Voyager images by Dones et al. (1993). (3) Both the orientation and peak transmission vary anomalously in the vicinity of strong density waves. (4) The width of the transmission peak implies an average vertical thickness for the wakes, H, which varies from 9-12% of the wake wavelength, ?. On the assumption that ? is given by Toomre's critical wavelength for axisymmetric instability in a self-gravitating disk, ?2/4?2G?, we estimate an effective ring thickness of 5 m. Supported by NASA and the Cassini-Huygens Project.

  14. MULTI-WAVELENGTH OBSERVATIONS OF THE SPATIO-TEMPORAL EVOLUTION OF SOLAR FLARES WITH AIA/SDO. I. UNIVERSAL SCALING LAWS OF SPACE AND TIME PARAMETERS

    SciTech Connect

    Aschwanden, Markus J. [Lockheed Martin Advanced Technology Center, Org. ADBS, Bldg. 252, 3251 Hanover St., Palo Alto, CA 94304 (United States); Zhang, Jie; Liu, Kai, E-mail: aschwanden@lmsal.com, E-mail: jzhang7@gmu.edu [School of Physics, Astronomy and Computational Sciences, George Mason University, 4400 University Dr., MSN 6A2, Fairfax, VA 22030 (United States)

    2013-09-20

    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{sub 2}), temporal (flare durations T), and spatio-temporal parameters (diffusion coefficient ?, spreading exponent ?, and maximum expansion velocities v{sub 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)?L {sup –3}, N(A)?A {sup –2}, N(V)?V {sup –5/3}, N(T)?T {sup –2}, and D{sub 2} = 3/2, for a Euclidean dimension d = 3. Empirically, we find also a new strong correlation ??L {sup 0.94±0.01} and the three-parameter scaling law L?? T {sup 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)

  15. The VIMS CBOS Observing System Buoy, an Initial Scientific Analysis

    NASA Astrophysics Data System (ADS)

    Brasseur, L. H.; Brubaker, J. M.; Friedrichs, C. T.; Wright, L. D.

    2004-12-01

    The Virginia Institute of Marine Science (VIMS) has recently deployed a data buoy at Gloucester Point, York River, Virginia as part of the Chesapeake Bay Observing System (CBOS). The data streams collected by the buoy and its associated sensors are wind speed and direction, incoming solar radiation, air temperature, water temperature, salinity, turbidity, fluorescence, and dissolved oxygen. In addition, water velocities throughout the water column are recorded every 5 minutes and wave statistics including directional wave spectra are calculated every hour from an upward looking RD Instruments Acoustic Doppler Current Profiler (ADCP) in 8 meters of water in conjunction with the data buoy. All data are collected in real time and are available to scientists with a 15 minute to 1 hour time lag. These data are used in conjunction with other long tem data sets in the York River and lower Chesapeake Bay such as the Chesapeake Bay National Estuarine Research Reserve (CBNERR) sites' water quality data in the York River and USGS stream flow data to investigate several questions of scientific interest. One of these questions is the observed reverse salinity gradient in the York River during spring flood tides. It was previously thought that this was caused by a temporal mismatch in the phase of flood tide between the lower Chesapeake Bay and the mouth of the York River subestuary only during spring tides when the currents are strongest and the tidal range is large. In 2004, however, this effect can be seen during both spring and neap tides on several occasions in the spring and summer. This phenomenon and others are evaluated in the context of the VIMS observing system buoy and the initial data collected from the buoy are also evaluated in terms of instrument accuracy, ease of data retrieval, and possible uses for this information.

  16. Single-cycle megawatt terahertz pulse generation from a wavelength-scale plasma oscillator driven by ultrashort laser pulses

    E-print Network

    Wu, H C; Zhang, J; Sheng, Zheng-Ming; Wu, Hui-Chun; Zhang, Jie

    2007-01-01

    The tremendous applications of terahertz (THz) spectroscopy and imaging require THz sources in different parameters. We propose a novel scheme to generate single-cycle powerful THz pulses by ultrashort intense laser pulses incident obliquely on a tenuous plasma slab of few THz wavelengths in thickness. This is made possible by driving a large amplitude electron plasma wave in the plasma slab, thus producing a net transient current at the plasma surfaces. Theory and simulations show that such a THz source is capable of providing megawatt power and field strength of MV/cm, which may open up new horizons for nonlinear THz science and applications.

  17. Measurements in the raw gas of a full scale municipal waste incinerator using a wavelength resolved REMPI mass spectrometer.

    PubMed

    Nomayo, M; Thanner, R; Pokorny, H; Grotheer, H H; Stützle, R

    2001-01-01

    A resonance enhanced multiphoton ionization (REMPI) mass spectrometer consisting of a tunable laser unit (Nd:YAG pump laser and OPO) and a reflectron mass spectrometer have been upgraded to cope with the difficult conditions such as vibrations, temperature fluctuations and dust, prevailing in an incinerator. On-line measurements of the raw gas have been carried out at the municipal waste incinerator in Stuttgart. Although this test series could not be completed the results are encouraging. They show that wavelength resolution can provide valuable information beyond the one obtainable by fixed frequency REMPI. Examples discussed include separation of interferants to the aniline signal and identification of phenantrene. PMID:11372827

  18. Connections between Spectra and Structure in Saturn's Main Rings Based on Cassini VIMS Data

    E-print Network

    Hedman, M M; Cuzzi, J N; Clark, R N; Filacchione, G; Capaccioni, F; Ciarniello, M

    2012-01-01

    Saturn's main rings exhibit variations in both their opacity and spectral properties on a broad range of spatial scales, and the correlations between these parameters can provide insights into the processes that shape the composition and dynamics of the rings. The Visual and Infrared Mapping Spectrometer (VIMS) instrument onboard the Cassini Spacecraft has obtained spectra of the rings between 0.35 and 5.2 microns with sufficient spatial resolution to discern variations on scales below 200 km. These relatively high-resolution spectral data reveal that both the depths of the near-infrared water-ice absorption bands and the visible spectral slopes are often correlated with structural parameters such as the rings' optical depth. Using a simplified model for the ring-particles' regolith properties, we have begun to disentangle the trends due to changes in the gross composition of the ring particles from those that may be due to shifts in the texture of the ring particles' regolith. Consistent with previous studie...

  19. Emitted Power Of Jupiter Based On Cassini CIRS And VIMS Observations

    NASA Technical Reports Server (NTRS)

    Li, Liming; Baines, Kevin H.; Smith, Mark A.; West, Robert A.; Perez-Hoyos, Santiago; Trammel, Harold J.; Simon-Miller, Amy A.; Conrath, Barney J.; Gierasch, Peter J.; Orton, Glenn S.; Nixon, Conor A.; Filacchione, Gianrico; Fry, Patrick M.; Momary, Thomas W.

    2012-01-01

    The emitted power of Jupiter and its meridional distribution are determined from observations by the Composite Infrared Spectrometer (CIRS) and Visual and Infrared Spectrometer (VIMS) onboard Cassini during its flyby en route to Saturn in late 2000 and early 2001. Jupiter's global- average emitted power and effective temperature are measured to be 14.10+/-0.03 W/sq m and 125.57+/-0.07 K, respectively. On a global scale, Jupiter's 5-micron thermal emission contributes approx. 0.7+/-0.1 % to the total emitted power at the global scale, but it can reach approx. 1.9+/-0.6% at 15degN. The meridional distribution of emitted power shows a significant asymmetry between the two hemispheres with the emitted power in the northern hemisphere 3.0+/-0.3% larger than that in the southern hemisphere. Such an asymmetry shown in the Cassini epoch (2000-01) is not present during the Voyager epoch (1979). In addition, the global-average emitted power increased approx. 3.8+/-1.0% between the two epochs. The temporal variation of Jupiter's total emitted power is mainly due to the warming of atmospheric layers around the pressure level of 200 mbar. The temporal variation of emitted power was also discovered on Saturn (Li et al., 2010). Therefore, we suggest that the varying emitted power is a common phenomenon on the giant planets.

  20. Global mapping and characterization of Titan's dune fields with Cassini: Correlation between RADAR and VIMS observations

    NASA Astrophysics Data System (ADS)

    Rodriguez, S.; Garcia, A.; Lucas, A.; Appéré, T.; Le Gall, A.; Reffet, E.; Le Corre, L.; Le Mouélic, S.; Cornet, T.; Courrech du Pont, S.; Narteau, C.; Bourgeois, O.; Radebaugh, J.; Arnold, K.; Barnes, J. W.; Stephan, K.; Jaumann, R.; Sotin, C.; Brown, R. H.; Lorenz, R. D.; Turtle, E. P.

    2014-02-01

    Vast fields of linear dunes have been observed in the equatorial regions of Titan, Saturn's largest moon. As the Cassini mission, in orbit around Saturn since July 2004 and extended until May 2017, carries on, the high-resolution coverage of Titan's surface increases, revealing new dune fields and allowing refinements in the examination of their properties. In this paper, we present the joint analysis of Cassini's microwave and infrared global scale observations of Titan. Integrating within an up-to-date global map of Titan all the Cassini RADAR and VIMS (Visual and Infrared Mapping Spectrometer) images - the latter being empirically corrected for atmospheric scattering and surface photometry, from July 2004 through July 2013 and June 2010 respectively, we found very good qualitative and quantitative spatial matching between the geographic distribution of the dune fields and a specific infrared spectral unit (namely the “dark brown” unit). The high degree of spatial correlation between dunes and the “dark brown” unit has important implications for Titan's geology and climate. We found that RADAR-mapped dunes and the “dark brown” unit are similarly confined within the equatorial belt (±30° in latitudes) with an equivalent distribution with latitude, suggesting an increasing sediment availability and mobility at Titan's tropics relative to higher latitudes, compatible with the lower ground humidity predicted in equatorial regions by General Circulation Models. Furthermore, the strong correlation between RADAR-mapped dunes and the VIMS “dark brown” unit (72%) allows us to better constrain the total surface area covered by dune material, previously estimated from the extrapolation of the RADAR observations alone. According to our calculations, dune material cover 17.5 ± 1.5% of Titan's surface area, equivalent to a total surface area of 14.6 ± 1.2 million km2 (˜1.5 times the surface area of Earth's Sahara desert). The VIMS “dark brown” coloration of the dune material is here confirmed at large spatial scale. If the sand particle composition is dominated by solid organics produced in and settling from the atmosphere, as supported by our spectral modeling and by previous spectral analysis, microwave radiometric data and atmospheric modeling, dune fields are one of the major surface hydrocarbon reservoirs on Titan. Assuming two possible scenarios for the sand distribution (either the sand is (1) entirely trapped in dune landforms, or (2) trapped in dunes at places where dune landforms are firmly observed and in sand sheets elsewhere), we estimate the volume of hydrocarbons trapped in the dune sediment to be comprised between 1.7 and 4.4 × 105 km3, corresponding to an average total mass of 230,000 GT, in comparison with ˜4000-30,000 GT of hydrocarbons in the polar lakes and seas. This indicates a maximum age for the dune sediments of ˜730-Myr, consistent with estimations of the ages of the current Titan's atmospheric methane and surface.

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

    PubMed Central

    Morehouse, Nathan I; Vukusic, Peter; Rutowski, Ron

    2006-01-01

    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 these bright colours using wing scales that contain collections of minute granules. However, to date, no work has directly characterized the molecular composition or optical properties of these granules. We present results that indicate these granules contain pterin pigments. We also find that pterin granules increase light reflection from single wing scales, such that wing scales containing denser granule arrays reflect more light than those with less dense granule collections. As male wing scales contain more pterin granules than those of females, the sexual dichromatism found in many pierid species can be explained by differences in wing scale pterin deposition. Additionally, the colour pattern elements produced by these pterins are known to be important during mating interactions in a number of pierid species. Therefore, we discuss the potential relevance of our results within the framework of sexual selection and colour signal evolution. PMID:17164199

  2. Uplift of the South African Plateau: mantle-scale deformation, long wavelength relief growth and offshore sediment budget

    NASA Astrophysics Data System (ADS)

    Guillocheau, François; Dauteuil, Olivier; Baby, Guillaume; Robin, Cécile

    2013-04-01

    The South African Plateau is one of the largest very long wavelength relief (x1000 km) of the world that could be related to mantle dynamics and the effect of the African superplume. Unfortunately, the timing of the uplift and the different steps of the relief growth are still debated with a Late Cretaceous uplift scenario and an Oligocene one. Whatever model, few attentions were paid to the evolution of the overall geomorphic system, from the upstream erosional system to the downstream depositional system. This study is based, onshore, on the mapping and chronology of all the macroforms (weathering surfaces and associated alterites, pediments and pediplains, incised rivers, wave-cut platforms) dated by intersection with the few preserved sediments and the volcanics (mainly kimberlites pipes) and, offshore, on a more classical dataset of seismic lines and petroleum wells (characterization and dating of forced regression, sediment volume measurement, etc..). The main result of this study is that the South African Plateau is an old Late Cretaceous Plateau reactivated during Paleogene times and fossilized since the Middle Miocene. • During Late Cretaceous, in a semiarid climatic setting, the main uplift occurred from the east (around 95 Ma) to the west (around 75 Ma) and could result from the migration of the African plate over the African superplume: This is the paroxysm of the erosion with the growth of a large delta offshore present-day Orange River mouth (sedimentation rate around 100 000 km3/Ma). • During Paleocene - Mid Eocene times, in more humid conditions and in response to a more subtle long wavelength deformation, pedimentation occurred mainly localised along Cape Fold Belt feeding a large delta offshore western Cape Peninsula. During Mid Eocene times, all those landscapes are fossilized and weathered by laterites. • Late Eocene and Oligocene is the second period of uplift of the Plateau, localised along its Indian Ocean side (Drackensberg Moutains), feeding a smaller delta offshore Tugela River (Durban area - sedimentation rate around 15 000 km3/Ma). The mechanism of uplift, located along the Agulhas - Falklands Fracture Zone, is unknown. • Since at least Middle Miocene times, all those relief have been fossilized, with very low erosion rates (x1m/Ma), in response to the major aridification of southern Africa. Keywords: South Africa, Plateau uplift, Mantle dynamics, Climate, Siliciclastic sediment fluxes

  3. A new season of Saturn auroral observations by Cassini/VIMS

    NASA Astrophysics Data System (ADS)

    Badman, S. V.; Baines, K. H.; Brown, R. H.; Melin, H.; Stallard, T.

    2012-09-01

    Cassini Visual and Infrared Mapping Spectrometer (VIMS) observations of Saturn's infrared H+3 auroral emissions have revealed insights into solar windmagnetosphere- ionosphere-thermosphere coupling at Saturn. These observations include: • Large-scale polar morphology unique to the H+3 emissions [1] - e.g. Fig. 1 • Inter-hemispheric differences in emission intensity [2] - e.g. Fig. 2 • Multiple arcs at different latitudes, without consistent UV H and H2 emission counterparts [3] • Significant local time asymmetry [4] • Intensity modulation by rotating field-aligned current systems [4] These analyses were performed using data acquired in Cassini's early sequences of inclined orbits (during 2006-2009), while Saturn experienced southern summer. The intensity of the H3+ aurora is strongly dependent on the thermospheric temperature, while the strength of auroral field-aligned current systems depends on the ionospheric conductivity. Thesse parameters can therefore be influenced by solar illumination, i.e. by changing season. Over summer 2012, Cassini will agai increase the inclination of its orbit affording a new view of the aurora under post-equinox conditions. We will present some highlights of the post-equinox observations acquired so far, with preliminary analysis in comparison to the trends described above.

  4. Constraints On Titan's Surface Composition From 5-µm Cassini/VIMS Observations

    NASA Astrophysics Data System (ADS)

    Hayne, Paul; McCord, T. B.; Combe, J.; Hansen, G.

    2007-10-01

    Observing Titan's surface is complicated by the strong absorbing and scattering properties of the atmosphere. Fortunately, there exist several "windows” between methane absorptions, where the surface is viewable. The 5-µm window is least affected by haze scattering, although the signal is low in this spectral region. We present the results of an extensive search for absorption features in the VIMS hyperspectral data using a statistically unbiased band-fitting algorithm. The approach is optimized for finding narrow absorption lines in the 5-µm window. If a candidate absorption meets any of the following criteria, it is deemed significant: i) The feature is apparent above the noise in the average of all pixels in a dataset. ii) Contiguous subset(s) of an image contain a higher concentration of pixels showing the feature than predicted by the data noise statistics. This excess should be observed consistently in different images containing the region. iii) The feature is spatially correlated with a morphologically and/or spectrally distinct unit, again consistent through time. Using these criteria, one statistically significant absorption is found: near 4.9 µm, it is strongly correlated with the Tui Regio bright anomaly (described by Barnes et al., GRL, 2005). The wavelength location and strength of this absorption are consistent with CO2 ice, likely complexed with other materials such as H2O ice (McCord et al., this meeting). Other localized regions of Titan also show the feature, notably Omacatl Macula (Hayne et al., AGU abstract, 2006). Not finding any other absorptions, for example due to organics predicted to precipitate on Titan's surface (Wilson et al., JGR, 2003), we can place tentative upper limits on the spatial coverage by these hypothetical constituents. The methods described are also being applied to other icy Saturnian satellites.

  5. Wave constraints for Titan's Jingpo Lacus and Kraken Mare from VIMS specular reflection lightcurves

    USGS Publications Warehouse

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

    2011-01-01

    Stephan et al. (Stephan, K. et al. [2010]. Geophys. Res. Lett. 37, 7104-+.) first saw the glint of sunlight specularly reflected off of Titan's lakes. We develop a quantitative model for analyzing the photometric lightcurve generated during a flyby in which the specularly reflected light flux depends on the fraction of the solar specular footprint that is covered by liquid. We allow for surface waves that spread out the geographic specular intensity distribution. Applying the model to the VIMS T58 observations shows that the waves on Jingpo Lacus must have slopes of no greater than 0.15??, two orders of magnitude flatter than waves on Earth's oceans. Combining the model with theoretical estimates of the intensity of the specular reflection allows a tighter constraint on the waves: <0.05?? Residual specular signal while the specular point lies on land implies that either the land is wetted, the wave slope distribution is non-Gaussian, or that 5% of the land off the southwest edge of Jingpo Lacus is covered in puddles. Another specular sequence off of Kraken Mare acquired during Cassini's T59 flyby shows rapid flux changes that the static model cannot reproduce. Points just 1. min apart vary in flux by more than a factor of two. The present dataset does not uniquely determine the mechanism causing these rapid changes. We suggest that changing wind conditions, kilometer-wavelength waves, or moving clouds could account for the variability. Future specular observations should be designed with a fast cadence, at least 6 points per minute, in order to differentiate between these hypotheses. Such new data will further constrain the nature of Titan's lakes and their interactions with Titan's atmosphere. ?? 2010 Elsevier Inc.

  6. Rapid detection of blaVIM-1-37 and blaKPC1/2-12 alleles from clinical samples by multiplex PCR-based assays.

    PubMed

    Frasson, Ilaria; Biasolo, Maria Angela; Bartolini, Andrea; Cavallaro, Antonietta; Richter, Sara N; Palù, Giorgio

    2013-07-01

    VIM and KPC are two major families of carbapenemases involved in nosocomial outbreaks of multidrug-resistant Gram-negative bacilli. To rapidly detect bla(VIM)- and bla(KPC)-encoding strains, three multiplex PCR-based methods were designed and validated: (i) a real-time PCR to detect all reported VIM alleles, namely bla(VIM-1-19, 23-37); (ii) a real-time PCR to identify bla(VIM)-type and bla(KPC) carbapenemases in an ultrarapid single reaction; and (iii) a standard PCR to amplify and sequence all VIM alleles. All three methods detected 33 VIM-positive samples among 107 Gram-negative isolates with imipenem and meropenem minimum inhibitory concentrations ?1 mg/L. The three methods displayed 100% sensitivity, specificity and concordance. Sequencing of the bla(VIM) amplicons revealed that 30 samples encoded bla(VIM-1) and 3 samples encoded bla(VIM-2). The real-time assay, optimised for the simultaneous detection of bla(VIM) and bla(KPC), identified 3 and 12 isolates positive for both bla(VIM)/bla(KPC) and for bla(KPC), respectively. The analytical sensitivity of the real-time assays was linear over 6 log dilutions, with a reproducible detection limit of 1 CFU. No cross-reactivity was detected. The developed assays provide powerful tools for rapid identification of VIM and KPC carbapenemase producers, therefore contributing to the prevention and containment of resistance dissemination. PMID:23642765

  7. Characterization of long-wavelength errors in large scale deformation studies: Application to the Central Nevada Seismic Belt

    NASA Astrophysics Data System (ADS)

    Greene, F.; Amelung, F.; Wdowinski, S.

    2011-12-01

    We present the contemporary velocity field in the western Basin and Range province observed by ~ 20 years of satellite radar imagery. A recent study in the Central Nevada Seismic Belt (CNSB) reported a broad area of uplift (~ 2-3 mm/yr) explained by postseismic mantle relaxation after a sequence of four earthquakes (M ~ 7) that occurred in the first half of the 20th century. This previous study is limited in temporal coverage, since only ~ 9 years of SAR data was used. In this study we use two different approaches to investigate the contemporary crustal deformation at the CNSB. In the first approach we produce line of sight (LOS) velocity fields for different time periods (1992 - 2000, 1999 - 2009 and 1992 - 2009) by averaging independent interferograms with small perpendicular baselines (< 150 m). In the second approach we produce time-series using the European Remote Sensing Satellites ERS 1/2 and Envisat from two decades of data. Both approaches suggest that the uplift velocity decreased for the last ten years, which is consistent with models of postseismic relaxation. Unfortunately, long-wavelength noise can be introduced to InSAR data from uncertainties in the satellite orbits and the signal can easily be confused. To understand how these errors affect our results, we analyze InSAR data of non-deforming areas from 20 years of ERS and Envisat data. Since deformation is not present, we can directly parameterize orbital phase contributions in terms of vertical and horizontal baseline errors and analyze the statistical distributions of these errors in different regions of the world. Finally, we apply to our area of study (a swath nearly 600 km long in CNSB) a recently proposed method to remove orbital phase errors from the InSAR deformation time series by using continuous GPS observations and a physical orbital model. The error distribution in non-deforming areas is valuable for the assessment of the apparent deformation signal observed at CNSB.

  8. Cassini-VIMS at Jupiter: Solar occultation measurements using Io

    USGS Publications Warehouse

    Formisano, V.; D'Aversa, E.; Bellucci, G.; Baines, K.H.; Bibring, J.-P.; Brown, R.H.; 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.

    2003-01-01

    We report unusual and somewhat unexpected observations of the jovian satellite Io, showing strong methane absorption bands. These observations were made by the Cassini VIMS experiment during the Jupiter flyby of December/January 2000/2001. The explanation is straightforward: Entering or exiting from Jupiter's shadow during an eclipse, Io is illuminated by solar light which has transited the atmosphere of Jupiter. This light, therefore becomes imprinted with the spectral signature of Jupiter's upper atmosphere, which includes strong atmospheric methane absorption bands. Intercepting solar light refracted by the jovian atmosphere, Io essentially becomes a "miffor" for solar occultation events of Jupiter. The thickness of the layer where refracted solar light is observed is so large (more than 3000 km at Io's orbit), that we can foresee a nearly continuous multi-year period of similar events at Saturn, utilizing the large and bright ring system. During Cassini's 4-year nominal mission, this probing tecnique should reveal information of Saturn's atmosphere over a large range of southern latitudes and times. ?? 2003 Elsevier Inc. All rights reserved.

  9. Cassini-VIMS observations of Saturn's main rings: I. Spectral properties and temperature radial profiles variability with phase angle and elevation

    NASA Astrophysics Data System (ADS)

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

    2014-10-01

    The spectral properties and thermal behavior of Saturn's rings are determined from a dataset of ten radial mosaics acquired by Cassini-VIMS (Visual and Infrared Mapping Spectrometer) between October 29th 2004 and January 27th 2010 with phase angle ranging between 5.7° and 132.4° and elevation angles between -23.5° and 2.6°. These observations, after reduction to spectrograms, e.g. 2D arrays containing the VIS-IR (0.35-5.1 ?m) spectral information versus radial distance from Saturn (from 73.500 to 141.375 km, 400 km/bin), allow us to compare the derived spectral and thermal properties of the ring particles on a common reference. Spectral properties: rings spectra are characterized by an intense reddening at visible wavelengths while they maintain a strong similarity with water ice in the infrared domain. Significant changes in VIS reddening, water ice abundance and grain sizes are observed across different radial regions resulting in correlation with optical depth and local structures. The availability of observations taken at very different phase angles allows us to examine spectrophotometric properties of the ring's particles. When observed at high phase angles, a remarkable increase of visible reddening and water ice band depths is found, probably as a consequence of the presence of a red-colored contaminant intimately mixed within water ice grains and of multiple scattering. At low phases the analysis of the 3.2-3.6 ?m range shows faint spectral signatures at 3.42-3.52 ?m which are compatible with the CH2 aliphatic stretch. The 3.29 ?m PAH aromatic stretch absorption is not clearly detectable on this dataset. VIMS results indicate that ring particles contain about 90-95% water ice while the remaining 5-10% is consistent with different contaminants like amorphous carbon or tholins. However, we cannot exclude the presence of nanophase iron or hematite produced by iron oxidation in the rings tenuous oxygen atmosphere, intimately mixed with the ice grains. Greater pollution caused by meteoritic material is seen in the C ring and Cassini division while the low levels of aliphatic material observed by VIMS in the A and B rings particles are an evidence that they are pristine. Thermal properties: the ring-particles' temperature is retrieved by fitting the spectral position of the 3.6 ?m continuum peak observed on reflectance spectra: in case of pure water ice the position of the peak, as measured in laboratory, shifts towards shorter wavelengths when temperature decreases, moving from about 3.65 ?m at 123 K to about 3.55 ?m at 88 K. When applied to VIMS rings observations, this method allows us to infer the average temperature across ring regions sampled through 400 km-wide radial bins. Comparing VIMS temperature radial profiles with similar CIRS measurements acquired at the same time we have found a substantial agreement between the two instruments' results across the A and B rings. In general VIMS measures higher temperatures than CIRS across C ring and Cassini division as a consequence of the lower optical depth and the resulting pollution that creates a deviation from pure water ice composition of these regions. VIMS results point out that across C ring and CD the 3.6 ?m peak wavelength is always higher than across B and A rings and therefore C ring and CD are warmer than A and B rings. VIMS observations allow us to investigate also diurnal and seasonal effects: comparing antisolar and subsolar ansae observations we have measured higher temperature on the latter. As the solar elevation angle decreases to 0° (equinox), the peak's position shifts at shorter wavelengths because ring's particles becomes colder. Merging multi-wavelength data sets allow us to test different thermal models, combining the effects of particle albedo, regolith composition, grain size and thermal properties with the ring structures.

  10. THE ATMOSPHERES OF SATURN AND TITAN IN THE NEAR-INFRARED: FIRST RESULTS OF CASSINI\\/VIMS

    Microsoft Academic Search

    K. H. BAINES; P. Drossart; T. W. MOMARY; V. Formisano; C. Griffith; G. Bellucci; J. P. BIBRING; R. H. BROWN; B. J. BURATTI; F. Capaccioni; P. Cerroni; R. N. CLARK; A. Coradini; M. Combes; D. P. CRUIKSHANK; R. Jaumann; Y. Langevin; D. L. MATSON; T. B. MCCORD; V. Mennella; R. M. NELSON; P. D. NICHOLSON; B. Sicardy; C. Sotin

    2005-01-01

    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,

  11. Multi-wavelength high-resolution observations of a small-scale emerging magnetic flux event and the chromospheric and coronal response

    E-print Network

    Dominguez, Santiago Vargas; Yurchyshyn, Vasyl

    2014-01-01

    State-of-the-art solar instrumentation is revealing magnetic activity of the Sun with unprecedented resolution. Observations with the 1.6m New Solar Telescope of the Big Bear Solar Observatory are making next steps in our understanding of the solar surface structure. Granular-scale magnetic flux emergence and the response of the solar atmosphere are among the key research. As part of a joint observing program with NASA's IRIS mission, the NST observed active region NOAA 11810 in photospheric and chromospheric wavelengths. Complimentary data are provided by SDO and Hinode space-based telescopes. The region displayed a group of solar pores, in the vicinity of which we detect a small-scale buoyant horizontal magnetic flux tube causing abnormal granulation and interacting with the pre-existing ambient field in upper atmospheric layers. Following the expansion of distorted granules at the emergence site, we observed a sudden appearance of an extended surge in the HeI data. IRIS catched ejection of a hot plasma jet...

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

    NASA Technical Reports Server (NTRS)

    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

    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.

  13. The geology of Hotei Regio, Titan: Correlation of Cassini VIMS and RADAR

    NASA Astrophysics Data System (ADS)

    Soderblom, Laurence A.; Brown, Robert H.; Soderblom, Jason M.; Barnes, Jason W.; Kirk, Randolph L.; Sotin, Christophe; Jaumann, Ralf; Mackinnon, David J.; Mackowski, Daniel W.; Baines, Kevin H.; Buratti, Bonnie J.; Clark, Roger N.; Nicholson, Philip D.

    2009-12-01

    Joint Cassini VIMS and RADAR SAR data of ˜700-km-wide Hotei Regio reveal a rich collection of geological features that correlate between the two sets of images. The degree of correlation is greater than anywhere else seen on Titan. Central to Hotei Regio is a basin filled with cryovolcanic flows that are anomalously bright in VIMS data (in particular at 5 ?m) and quite variable in roughness in SAR. The edges of the flows are dark in SAR data and appear to overrun a VIMS-bright substrate. SAR-stereo topography shows the flows to be viscous, 100-200 m thick. On its southern edge the basin is ringed by higher (˜1 km) mountainous terrain. The mountains show mixed texture in SAR data: some regions are extremely rough, exhibit low and spectrally neutral albedo in VIMS data and may be partly coated with darker hydrocarbons. Around the southern margin of Hotei Regio, the SAR image shows several large, dendritic, radar-bright channels that flow down from the mountainous terrain and terminate in dark blue patches, seen in VIMS images, whose infrared color is consistent with enrichment in water ice. The patches are in depressions that we interpret to be filled with fluvial deposits eroded and transported by liquid methane in the channels. In the VIMS images the dark blue patches are encased in a latticework of lighter bands that we suggest to demark a set of circumferential and radial fault systems bounding structural depressions. Conceivably the circular features are tectonic structures that are remnant from an ancient impact structure. We suggest that impact-generated structures may have simply served as zones of weakness; no direct causal connection, such as impact-induced volcanism, is implied. We also speculate that two large dark features lying on the northern margin of Hotei Regio could be calderas. In summary the preservation of such a broad suite of VIMS infrared color variations and the detailed correlation with features in the SAR image and SAR topography evidence a complex set of geological processes (pluvial, fluvial, tectonic, cryovolcanic, impact) that have likely remained active up to very recent geological time (<10 4 year). That the cryovolcanic flows are excessively bright in the infrared, particularly at 5 ?m, might signal ongoing geological activity. One study [Nelson, R.M., and 28 colleagues, 2009. Icarus 199, 429-441] reported significant 2-?m albedo changes in VIMS data for Hotei Arcus acquired between 2004 and 2006, that were interpreted as evidence for such activity. However in our review of that work, we do not agree that such evidence has yet been found.

  14. Virginia Wetlands Report Center for Coastal Resources Management www.ccrm.vims.edu

    E-print Network

    Virginia Wetlands Report Center for Coastal Resources Management www.ccrm.vims.edu Volume 23, Issue 1 A Biannual Publication Focused on Virginia Wetland Issues and Training Spring 2008 This year, tidal wetland delineation, pre-application strategies, and permit processing and evaluation. The half

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

    USGS Publications Warehouse

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

    2006-01-01

    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 of both a spectrometer and an imaging instrument. This makes it possible to analyze the spectrum of each pixel separately and to map the spectral characteristics spatially, which is important to study the relationships between spectral information and geological and geomorphologic surface features. The spatial analysis of the spectral data requires the determination of the exact geographic position of each pixel on the specific surface and that all 352 spectral elements of each pixel show the same region of the target. We developed a method to reproject each pixel geometrically and to convert the spectral data into map projected image cubes. This method can also be applied to mosaic different VIMS observations. Based on these mosaics, maps of the spectral properties for each Saturnian satellite can be derived and attributed to geographic positions as well as to geological and geomorphologic surface features. These map-projected mosaics are the basis for all further investigations. ?? 2006 Elsevier Ltd. All rights reserved.

  16. T hermal Feasibility Study Of The Solar Orbiter Visible Light Imager And Magnetograph (VIM)

    NASA Astrophysics Data System (ADS)

    Pérez-Grande, I.; Martínez-Pillet, V.; Woch, J.; Hartwig, H.

    2007-01-01

    In order to determine the feasibility of the Solar Orbiter instrument Visible Light Imager and Magnetograph (VIM), a thermal analysis focused on the critical elements of the instrument has been carried out. The thermal solution has been sought for the hot case and the performance in the cold operational and survival modes has been analysed.

  17. Clouds on Titan during the Cassini prime mission: A complete analysis of the VIMS data

    Microsoft Academic Search

    Michael E. Brown; Jessica E. Roberts; Emily L. Schaller

    2010-01-01

    We use data from the VIMS instrument on board the Cassini spacecraft to construct high sensitivity and high spatial-resolution maps of the locations of tropospheric clouds on Titan in the late northern winter season during which the Cassini prime mission took place. These observations show that, in this season, clouds on Titan are strongly hemispherically asymmetric. Mid-latitude clouds, in particular,

  18. Distribution of icy particles across Enceladus' surface as derived from Cassini-VIMS measurements

    Microsoft Academic Search

    R. Jaumann; K. Stephan; G. B. Hansen; R. N. Clark; B. J. Buratti; R. H. Brown; K. H. Baines; S. F. Newman; G. Bellucci; G. Filacchione; A. Coradini; D. P. Cruikshank; C. A. Griffith; C. A. Hibbitts; T. B. McCord; R. M. Nelson; P. D. Nicholson; C. Sotin; R. Wagner

    2008-01-01

    The surface of Enceladus consists almost completely of water ice. As the band depths of water ice absorptions are sensitive to the size of particles, absorptions can be used to map variations of icy particles across the surface. The Visual and Infrared Mapping Spectrometer (VIMS) observed Enceladus with a high spatial resolution during three Cassini flybys in 2005 (orbits EN

  19. Efficiency of differential transformation method for nonlinear oscillation: Comparison with HPM and VIM

    Microsoft Academic Search

    S. Ghafoori; M. Motevalli; M. G. Nejad; F. Shakeri; D. D. Ganji; M. Jalaal

    2011-01-01

    In this study, a nonlinear oscillation equation is solved using a series-based analytical method called differential transformation method (DTM). The concept of differential transformation is briefly introduced, and its application for a nonlinear oscillator is studied. The results obtained employing DTM are compared with those achieved by using two other series-based analytical techniques named variation iteration method (VIM) and homotopy

  20. Characterization of Titan’s Ontario Lacus region from Cassini/VIMS observations

    NASA Astrophysics Data System (ADS)

    Moriconi, M. L.; Lunine, J. I.; Adriani, A.; D'Aversa, E.; Negrão, A.; Filacchione, G.; Coradini, A.

    2010-12-01

    Liquid hydrocarbons were long predicted on Titan's surface before the RADAR instrument onboard Cassini detected lakes poleward of 70°N in July 2006. Before that the Cassini Imaging Science Subsystem (ISS) observed a lake-like feature in the South Pole, named Ontario Lacus, in July 2004. Here we analyze one observation of Ontario Lacus taken by the Visual and Infrared Mapping Spectrometer (VIMS) on 2007 December 5, during the T 38 flyby. This is the best spatially resolved image of a Titan lake to date by an imaging spectrometer, and has been previously reported in Brown et al. (Brown, R.H., Soderblom, L.A., Soderblom, J.M., Clark, R.N., Jaumann, R., Barnes, J.W., Sotin, C., Buratti, B., Baines, K.H., Nicholson, P.D. [2008]. Nature 454, 607-610) and in Barnes et al. (Barnes, J.W. et al. [2009]. Icarus 201, 217-225). The observing geometry and our data processing will be explained, followed by a discussion of the main characteristics of the image. The analyzed image covers a small portion of Ontario Lacus and shows what appears from RADAR data to be a region of modest slope ("ramp") adjacent to the dark lake itself. Our analysis of 5.0 ?m spectral data suggests that the previously reported absorption feature of ethane seen at shorter wavelengths may be produced by damp sediments adjacent to the main liquid basin. The latter appears to be absorbing all of the photons incident upon it in the 5 ?m spectral region and shows no discernible absorption features. A characterization of the basin composition and morphology is developed with the help of ISS and RADAR observations. The simplest model consistent with the data is an optically deep lake surrounded by a region in which ethane, propane, possibly methane, and other, less volatile hydrocarbons and nitriles are present mixed into spectroscopically neutral sediments. The dominance of relatively low vapor pressure organics outside the lake itself suggests a retreat of Ontario Lacus associated with evaporation on seasonal or longer timescales, consistent with analysis of RADAR and ISS images.

  1. Surface Albedo retrieval from Cassini/VIMS data of Titan's geologically interesting areas

    NASA Astrophysics Data System (ADS)

    Solomonidou, Anezina; Coustenis, Athena; Hirtzig, Mathieu; Bratsolis, Emmanuel; Drossart, Pierre; Bampasidis, Georgios; Kyriakopoulos, Konstantinos; Le Mouélic, Stephane; Rodriguez, Sebastien; Jaumann, Ralf; Stephan, Katrin; Lopes, Rosaly M. C.; Sotin, Christophe; Brown, Robert H.; Stamatelopoulou-Seymour, Karen; Moussas, Xenophon

    2013-04-01

    The Cassini Visual and Infrared Mapping Spectrometer (VIMS) obtained data of Titan's surface from flybys performed during the last eight years. In the 0.8-5.2 µm range, these spectro-imaging data showed that the surface consists of a multivariable geological terrain hosting complex geological processes. The data from the seven narrow methane spectral "windows" centered at 0.93, 1.08, 1.27, 1.59, 2.03, 2.79, and 5.00 µm provide some information on the lower atmospheric context and the surface parameters that we want to determine. Atmospheric scattering and absorption need to be clearly evaluated before we can extract the surface properties. We apply here a statistical method and a radiative transfer method on three geologically interested areas on Titan: Tui Regio (20°S, 130°W), Hotei Regio (26°S, 78°W), and Sotra Facula (15°S, 42°W), where all of them have been suggested as volcanic-like sites presenting terrestrial analogues [e.g. 1;2]. With our method of Principal Component Analysis (PCA) we have managed to isolate heterogenic regions of interest (RoI) of distinct and diverse chemical composition. We have tested this method on the previously studied Sinlap crater, delimitating compositional heterogeneous regions compatible with the conclusions published by [3]. Our follow-up method focuses on retrieving the spectral differences among the regions of interest with different spectral response by applying a radiative transfer (RT) code [4]. We have used as inputs most of the Huygens Atmospheric Structure Instrument (HASI) and the Descent Imager/Spectral Radiometer (DISR) measurements, as well as new methane absorption coefficients, which are important to evaluate the atmospheric contribution and to allow us to better constrain the real surface alterations, by comparing the spectra of these regions. The dynamical range in surface albedo within the three regions indicates that the bright RoIs are always brighter than the dark by significant amounts. For Tui Regio and Hotei Regio the largest differences in surface albedo are in the longer wavelengths while for Sotra Facula the offsets are rather homogenously distributed throughout the spectrum ending with the largest ones at 5?m. Additionally, we were able to compare the albedos within the three areas concluding that Sotra Facula is never as bright as Tui Regio [5]. [1] Lopes, R.M.C., et al.: JGR, in press, 2012. [2] Solomonidou, A., et al.: PSS, in press, 2012. [3] Le Mouélic, S., et al.: JGR 113, E04003, 2008. [4] Hirtzig, M., et al.: submitted to Icarus. [5] Solomonidou, A., et al.: in prep.

  2. Temporal Variations of Titan’s Surface Regions with Cassini/VIMS

    NASA Astrophysics Data System (ADS)

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

    2013-10-01

    We investigate three potentially “active” areas on Titan [e.g. 1;2;7]., i.e. locations subject to change over time (in brightness and/or in color etc.), namely Tui Regio, Hotei Regio and Sotra Patera. We apply two methods on Cassini/VIMS data in order to retrieve their surface properties and monitor temporal variations. First, we apply the Principal Component Analysis (PCA) statistical method [3;4], isolating regions of distinct and diverse chemical composition (Region of interest -RoI). Then, we focus on retrieving the spectral differences (with respect to the Huygens landing site albedo) among the RoIs by applying a radiative transfer code (RT) [5;3]. We are thus able to evaluate the dynamical range and the differences in surface albedo among the RoIs of the three areas. In addition, using this double procedure, we study the temporal surface variations of the same areas. Hotei Regio has been previously suggested to present brightness variations over a two-year period (2004-2005) [3]. However, we find that to-date available observations of that area have issues (e.g. geometry conditions), which prevent an accurate application of our plane-parallel RT code. The surface information we infer for Hotei Regio does not show variations from 2004-2009 but the uncertainties here are high [8]. On the other hand, our findings indicate a significant darkening for Tui Regio from 2005-2009 (at all wavelengths). For Sotra Patera a brightening is observed from 2005-2006 [8], while test cases from two distinct dunes fields for the same period of time show that their surface albedo does not change with time. We will discuss the relation of these surface variations with the presence of volcanic-like features [7] within these areas and interior processes (tidal forces) [6] and the implications for the satellite’s astrobiological potential. [1] Soderblom, L.A. et al.: Icarus 204, 610-618, 2009. [2] Nelson, R. et al.: Icarus 199, 429-441, 2009. [3] Solomonidou, A., et al.: submitted. [4] Stephan, K. et al.: PSS 56, 406-419, 2008. [5] Hirtzig, M. et al.: Icarus 226, 470-486, 2013. [6] Sohl, F. et al.: submitted. [7] Lopes, R.M.C., et al.: JGR 118, 1-20, 2013. [8] Solomonidou, A., et al.: in prep.

  3. Epidemiology of VIM-1-imipenem resistant Pseudomonas aeruginosa in Iran: A systematic review and meta-analysis

    PubMed Central

    Sedighi, Mansour; Salehi-Abargouei, Amin; Oryan, Golfam; Faghri, Jamshid

    2014-01-01

    Background: Pseudomonas aeruginosa is an opportunistic human pathogen which causes serious problems, especially in people who have immunodeficiency. Metallo beta-lactamase (MBL) resistance in this bacterium has led some difficulties in treating bacterial infections. MBLs are being reported with increasing frequency worldwide. The aim of the present systematic review and meta-analysis was to collect data about the relative frequency (RF) of VIM-1-imipenem resistant P. aeruginosa (VIM-1-IRPA) in different regions of Iran and report an overall prevalence if possible. Materials and Methods: PubMed, ISI web of science, Scopus and Google Scholar were searched using following key terms: “P. aeruginosa,” “imipenem,” “VIM-1” and “Iran” were. Articles/abstracts, which used clinical specimens and had done polymerase chain reaction to detect the VIM-1 gene of MBL genes, were included in this review. STATA SE version 11.2 (StataCorp, College Station, TX, USA) was used for statistical analysis. Results: Out of 5457 results found, 10 articles were eligible to be included in our systematic review and meta-analysis. These studies were carried out in Tehran, Isfahan, Kurdistan, Ahvaz, Markazi and Northwest of Iran (Orumieh and Tabriz). Pooled estimation of 1972 P. aeruginosa samples showed that 13% (95% confidence interval = 10.5-16.5%]) of strains were VIM-1 positive. VIM-1-IRPA RF in different studies varied from 0% to 19.5% in Isfahan and Markazi provinces, respectively. We found a moderate heterogeneity (Chochran Q-test, P = 0.032, I-squared = 50.7%) of VIM-1-IRPA RF among studies. Conclusion: According to the results of this study VIM-1-IRPA RF in Iran is in low-level Prevention strategies to reduce the prevalence rates of VIM-1 positive strains in Iran are needed. PMID:25535506

  4. Saturn’s Helium Abundance from Cassini VIMS Stellar Occultations and CIRS Limb Temperature Profiles

    NASA Astrophysics Data System (ADS)

    Banfield, Don; Gierasch, Peter J.; Conrath, Barney J.; Achterberg, Richard K.; Nicholson, Phillip D.; Hedman, Matthew M.

    2014-11-01

    We have used Saturn stellar occultations as observed by Cassini VIMS, in concert with Saturn limb temperature profiles derived from Cassini CIRS data to determine the Helium abundance in Saturn’s atmosphere near a few mbars. This quantity is long sought, as indication of the internal evolution that Saturn has undergone. Additionally, previous attempts to determine this quantity have produced inconsistent results ranging from He/H2=0.03±0.02 using Voyager IRIS and RSS (Conrath et al., 1984) to He/H2=0.13±0.02 using only Voyager IRIS (Conrath & Gautier, 2000) with a similar result being found by Orton and Ingersoll (1980) using Pioneer IRR and RSS (He/H2=0.11±0.04). These discordant results motivate us to try yet another approach to yield this quantity, in this case using the Cassini VIMS stellar occultations to yield a profile of atmospheric density, and nearly co-located Cassini CIRS limb profiles to yield atmospheric temperature. Combining the two results then yields the mean molecular weight and thus the He/H2 mixing ratio. We reported preliminary values from an occultation from the 151st Cassini orbit at DPS in 2011 (He/H2=0.14±0.05), but have since identified errors in that analysis that have caused us to revisit the problem. Additionally, that occultation occurred near the large Saturn northern hemisphere storm, with significant longitudinal temperature gradients present. The longitudinal separation between the CIRS and VIMS footprints could have skewed the results. In this report, we will discuss our latest results with the algorithm errors corrected, and using data from an occultation of Betelgeuse on the 161st Cassini orbit. These data have the best S/N of all stellar occultations caught by Cassini VIMS to date, and the combination of the VIMS/CIRS data doesn’t suffer from problems due to proximity to the storm and its associated spatial gradients in temperature.

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

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

    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).

  6. A close look at Saturn's rings with Cassini VIMS

    Microsoft Academic Search

    Philip D. Nicholson; Matthew M. Hedman; Roger N. Clark; Mark R. Showalter; Dale P. Cruikshank; Jeffrey N. Cuzzi; Gianrico Filacchione; Fabrizio Capaccioni; Priscilla Cerroni; Gary B. Hansen; Bruno Sicardy; Pierre Drossart; Robert H. Brown; Bonnie J. Buratti; Kevin H. Baines; Angioletta Coradini

    2008-01-01

    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

  7. Multi-wavelength High-resolution Observations of a Small-scale Emerging Magnetic Flux Event and the Chromospheric and Coronal Response

    NASA Astrophysics Data System (ADS)

    Vargas Domínguez, Santiago; Kosovichev, Alexander; Yurchyshyn, Vasyl

    2014-10-01

    State-of-the-art solar instrumentation is now revealing magnetic activity of the Sun with unprecedented temporal and spatial resolutions. Observations with the 1.6 m aperture New Solar Telescope (NST) of the Big Bear Solar Observatory are making next steps in our understanding of the solar surface structure. Granular-scale magnetic flux emergence and the response of the solar atmosphere are among the key research topics of high-resolution solar physics. As part of a joint observing program with NASA's Interface Region Imaging Spectrograph (IRIS) mission on 2013 August 7, the NST observed active region NOAA 11,810 in the photospheric TiO 7057 Å band with a resolution of pixel size of 0.''034 and chromospheric He I 10830 Å and H? 6563 Å wavelengths. Complementary data are provided by the Solar Dynamics Observatory (SDO) and Hinode space-based telescopes. The region displayed a group of solar pores, in the vicinity of which we detect a small-scale buoyant horizontal magnetic flux tube causing granular alignments and interacting with the preexisting ambient field in the upper atmospheric layers. Following the expansion of distorted granules at the emergence site, we observed a sudden appearance of an extended surge in the He I 10830 Å data (bandpass of 0.05 Å). The IRIS transition region imaging caught ejection of a hot plasma jet associated with the He I surge. The SDO/HMI data used to study the evolution of the magnetic and Doppler velocity fields reveal emerging magnetic loop-like structures. Hinode/Ca II H and IRIS filtergrams detail the connectivities of the newly emerged magnetic field in the lower solar chromosphere. From these data, we find that the orientation of the emerging magnetic field lines from a twisted flux tube formed an angle of ~45° with the overlying ambient field. Nevertheless, the interaction of emerging magnetic field lines with the pre-existing overlying field generates high-temperature emission regions and boosts the surge/jet production. The localized heating is detected before and after the first signs of the surge/jet ejection. We compare the results with previous observations and theoretical models and propose a scenario for the activation of plasma jet/surges and confined heating triggered by buoyant magnetic flux tubes rising up into a magnetized upper environment. Such process may play a significant role in the mass and energy flow from the interior to the corona.

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

    USGS Publications Warehouse

    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

    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.

  9. 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)

    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

    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.

  10. Retrieval of HCN Concentrations from Cassini/VIMS Limb Observations of the Titan's Upper Atmosphere

    NASA Astrophysics Data System (ADS)

    Adriani, A.; Dinelli, B. M.; Lopez-Puertas, M.; Garcia-Comas, M.; Moriconi, M. L.; D'Aversa, E.; Funke, B.; Coradini, A.

    2011-10-01

    Vertical profiles of hydrogen cyanide (HCN) have been retrieved from Cassini/VIMS limb observations in the region from 600 to 1100 km of the Titan's atmosphere by analyzing the 3 ?m emission. HCN concentrations show a very good correlation with solar zenith angles, for different latitudes and local times. This would indicate that HCN is in (or close to) photochemical equilibrium in the sounded region.

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

    Microsoft Academic Search

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

    2010-01-01

    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

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

    Microsoft Academic Search

    Kevin H. Baines; Thomas W. Momary; Leigh N. Fletcher; Adam P. Showman; Maarten Roos-Serote; Robert H. Brown; Bonnie J. Buratti; Roger N. Clark; Philip D. Nicholson

    2009-01-01

    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

  13. Titan's surface and atmosphere from Cassini/VIMS data with updated methane opacity

    NASA Astrophysics Data System (ADS)

    Hirtzig, M.; Bézard, B.; Coustenis, A.; Lellouch, E.; Drossart, P.; deBergh, C.; Campargue, A.; Boudon, V.; Tyuterev, V.; Rannou, P.; Cours, T.; Kassi, S.; Nikitin, A.; Wang, L.; Solomonidou, A.; Schmitt, B.; Rodriguez, S.

    2012-04-01

    In this paper we present an updated analysis of VIMS data in view of recent developments on the methane opacity in the 1.3-5.2 µm region, a very important parameter in simulating Titan's spectrum. We use a multi-stream radiative transfer model, benefitting from the latest methane absorption coefficients available [1], which allows us to determine more accurately the haze and surface contributions. This code is applied to Cassini/VIMS spectro-imaging data of various regions with very different spectral responses to extract information on the content of the lower atmosphere (0-200 km) as well as on the surface properties. In particular, we update the DISR aerosol model [2] for the Huygens landing site that we then adjust to fit the data for other locations on Titan's disk. Fitting VIMS data taken from 2004 to 2010 (TA to T70), around Titan's mid-latitudes (40°S-40°N), we determine the latitudinal and temporal evolution of the aerosol population, monitoring the North-South Asymmetry. While around the equinox [3] witnessed the collapse of the detached haze layer, we measure a continuous depletion of the aerosols throughout the atmosphere, although the NSA remains with a brighter northern hemisphere. Using this improved atmospheric model, we also retrieve surface albedos simultaneously for all the seven windows in the whole VIMS range for these regions, also recovering the shape of the surface albedo within each window. Eventually, we look for Titan's surface probable chemical composition, using mixtures of dark and complex hydrocarbons like bitumens and tholins, as well as bright CH4, CO2, NH3 and H2O ices of various grain sizes. [4] [1] Campargue, A. et al., (2012) Icarus, submitted. [2] Tomasko, M. et al., (2008) Planetary and Space Science, 56, 669. [3] West, R.A. et al., (2011) Geophysical Research Letters, 38, L06204. [4] Hirtzig, M. et al., (2012) Planetary and Space Science, submitted.

  14. Spread of Integron-Associated VIM-Type Metallo Lactamase Genes among Imipenem-Nonsusceptible Pseudomonas aeruginosa Strains in Greek Hospitals

    Microsoft Academic Search

    P. Giakkoupi; G. Petrikkos; L. S. Tzouvelekis; S. Tsonas; N. J. Legakis; A. C. Vatopoulos

    2003-01-01

    Fifty-eight imipenem-nonsusceptible (MIC > 8 g\\/ml) Pseudomonas aeruginosa strains isolated during May 2001 in 15 Greek hospitals were studied. Thirty-six isolates derived from nine hospitals carried VIM-type metallo--lactamase genes, as found by PCR. In 34 isolates, blaVIM was associated with class 1 integrons of various sizes. DNA sequencing indicated the presence of blaVIM-2 gene cassettes in a variety of integron

  15. The temperature and width of an active fissure on Enceladus measured with Cassini VIMS during the 14 April 2012 South Pole flyover

    NASA Astrophysics Data System (ADS)

    Goguen, Jay D.; Buratti, Bonnie J.; Brown, Robert H.; Clark, Roger N.; Nicholson, Phillip D.; Hedman, Matthew M.; Howell, Robert R.; Sotin, Christophe; Cruikshank, Dale P.; Baines, Kevin H.; Lawrence, Kenneth J.; Spencer, John R.; Blackburn, David G.

    2013-09-01

    The width and temperature of the active fissures on Saturn’s satellite Enceladus provide key observable constraints on physical models of these geyser-like eruptions. We analyze a sequence of high spatial resolution near-infrared spectra acquired with VIMS at 0.025 s intervals during a 74 km altitude flyover of the South Pole of Enceladus by the Cassini spacecraft on 14 April 2012 UTC. A thermal-emission spectrum covering 3- to 5-?m wavelengths was detected as the field of view crossed one of the four major fissures, Baghdad Sulcus, within 1 km of 82.36S latitude and 28.24W longitude. We interpret this spectrum as thermal emission from a linear fissure with temperature 197 ± 20 K and width 9 m. At the above wavelengths, the spectrum is dominated by the warmest temperature component. Looking downward into the fissure at only 13° from the vertical, we conclude that our results measure the temperature of the interior fissure walls (and the H2O vapor) at depths within 40 m of the surface.

  16. Fecal colonization of VIM-1-producing Klebsiella pneumoniae and in vivo transfer of multidrug-resistant IncN plasmid in a renal transplant patient.

    PubMed

    Naseer, Umaer; Eriksen, Bjørn Odvar; Sundsfjord, Arnfinn; Samuelsen, Ørjan

    2012-04-01

    We report a case of long-term colonization of a carbapenemase (VIM)-producing Klebsiella pneumoniae clone in a renal transplant patient and demonstrate the in vivo transmission of a broad-host-range multidrug-resistant IncN plasmid containing bla(VIM), bla(SHV-12), and qnrS to Escherichia coli. PMID:22300955

  17. The de-striping of the VIMS-V images and the observations of HCN limb emission in the Titan atmosphere at 3 mu m

    Microsoft Academic Search

    A. Adriani; M. L. Moriconi; G. Filacchione; F. Tosi; A. Coradini; R. H. Brown; K. H. Baines; B. J. Buratti; D. L. Matson; R. M. Nelson; T. W. Momary; G. Bellucci; V. Formisano; F. Capaccioni; P. Cerroni; R. N. Clark; D. P. Cruikshank; M. R. Showalter; P. Drossart; B. Sicardy; R. Jaumannr; N. Baugh; C. A. Griffith; Y. Langevin; T. B. McCord; G. B. Hansen; C. A. Hibbitts; V. Mennella; P. D. Nicholson; C. Sotin

    2007-01-01

    In this paper two different tools for the analysis of VIMS hyperspectral images will be presented. A statistical methodology has been realized to correct the striped appearance of the VIMS-V images. This destriping procedure applies to each pixel of the images in the visible range and can be used both for the raw and calibrated data. Respect to their original

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

    E-print Network

    Brest, Université de

    Geomorphological significance of Ontario Lacus on Titan: Integrated interpretation of Cassini VIMS 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

  19. Vertical structure mapping of Saturn's 2011 giant vortex by means of Cassini VIMS-V data analysis.

    NASA Astrophysics Data System (ADS)

    Oliva, Fabrizio; Adriani, Alberto; Moriconi, Maria Luisa; D'Aversa, Emiliano; Liberti, Gian Luigi

    On December 2010 a giant storm erupted in Saturn's North springtime hemisphere. A giant vortex formed in the storm wake and persisted after the principal outburst exhausted on July 2011. The vortex had been imaged several times by the Visual and Infrared Mapping Spectrometer (VIMS) on board the Cassini probe, starting from May 2011, and it was still present in the December 2012 observations In this work we have analyzed the data recorded by the visual channel of the spectrometer (VIMS-V). VIMS-V operates in the spectral range 350 - 1050 nm with a nominal spectral resolution of 7.3 nm and a nominal angular resolution of 500 ?rad. Spectral data have been first analyzed by a forward radiative transfer model based on the LibRadtran code, then an inverse model has used to retrieve microphysical and geometrical properties of the clouds overlying the vortex. The forward model relies on the assumptions of a plane parallel atmosphere, multiple scattering, the Mie theory to compute single scattering properties and the molecular scattering adapted to Saturn’s atmosphere. The inverse code is based on the optimal estimation technique, it is robust and capable to handle several free parameters at a time. The best fits to the observed radiance spectra are obtained by means of a least square analysis, in which the cost function is minimized taking advantage of the Gauss-Newton method. Applying this procedure, we produced spatial maps for each of the free parameters, including: effective radii for the particles size distributions of each cloud or aerosol deck; total number densities of the particles; and top pressures of each deck. In this work we focused on the data retrieved by VIMS on August 2011. We plan to extend the analysis on data retrieved months later, to map the evolution the parameters undergo in time. The analysis extension to the range 1.0-5.0 micron, covered by the infrared channel of VIMS (VIMS-IR) is also planned.

  20. Saturn's Dynamic Atmosphere at Depth: Physical Characteristics and Zonal Winds Derived from Clouds Near the 2-bar Level and Their Dynamical Implications from Cassini-Huygens/VIMS

    NASA Astrophysics Data System (ADS)

    Momary, Thomas W.; Baines, K. H.; Fletcher, L. N.; Kim, J. H.; Buratti, B. J.; Roos-Serote, M.; Showman, A. P.; Brown, R. H.; Clark, R. N.; Nicholson, P. D.; Cassini/VIMS Science Team

    2008-09-01

    A wide variety of cloud structures - comprised, putatively, of ammonia and ammonia hydrosulfide , but perhaps with an admixture of water - has been characterized by Cassini/VIMS, including dozens of axisymmetric zonal features, planetary waves, classic vortex structures at both the north and south poles, and a hexagonal slow-speed wave feature centered on the north pole. At depth, the axisymmetric zonal features average just 1.7 degrees in latitudinal width, less than half of that at the 0.05- and 0.5-bar levels observed in reflected sunlight, suggesting that either (1) the patterns of ascending/descending motion have smaller latitudinal length scales at > 1.3 bar than at shallower levels, and/or (2) horizontal mixing is better able to "smooth out" the cloud structure at shallow levels than at depth. Numerous long-lived (> 1.5-years) discrete cloud structures have been observed in the northern hemisphere, including annular ("donut") clouds near 49 and 57 degrees north latitude (planetocentric) and a "string of pearls” of some two-dozen similarly sized ( 1500 km diameter) cloud-clearings nearly uniformly spaced across 100 degrees of longitude near 33.5 degrees latitude. The "string of pearls” and the mid-latitude annular cloud exhibit the fastest retrograde speeds on Saturn (in the Voyager rotational frame). In the south, the fastest retrograde jet correlates with the only thunderstorm-associated clouds observed on Saturn. VIMS daytime spectra indicate that two kinds of clouds predominate there: spectrally bright and spectrally dark. The bright clouds are the first spectrally-identified ammonia clouds on Saturn, presumably formed by ammonia-laden air propelled upward by thunderstorm-related convection originating > 75 km below. Thus both vertically-extensive (thunderstorms) and long-lived, coherent cloud features ("pearls” and "donuts") correlate well with retrograde motions, perhaps indicating unusually low vertical shears there which preserve coherency and allow convective flows to rise relatively unimpeded over large vertical distances.

  1. His224 Alters the R2 Drug Binding Site and Phe218 Influences the Catalytic Efficiency of the Metallo-?-Lactamase VIM-7

    PubMed Central

    Skagseth, Susann; Edvardsen, Kine Susann Waade; Lorentzen, Marit Sjo; Bjerga, Gro Elin Kjæreng; Leiros, Ingar; Samuelsen, Ørjan

    2014-01-01

    Metallo-?-lactamases (MBLs) are the causative mechanism for resistance to ?-lactams, including carbapenems, in many Gram-negative pathogenic bacteria. One important family of MBLs is the Verona integron-encoded MBLs (VIM). In this study, the importance of residues Asp120, Phe218, and His224 in the most divergent VIM variant, VIM-7, was investigated to better understand the roles of these residues in VIM enzymes through mutations, enzyme kinetics, crystal structures, thermostability, and docking experiments. The tVIM-7-D120A mutant with a tobacco etch virus (TEV) cleavage site was enzymatically inactive, and its structure showed the presence of only the Zn1 ion. The mutant was less thermostable, with a melting temperature (Tm) of 48.5°C, compared to 55.3°C for the wild-type tVIM-7. In the F218Y mutant, a hydrogen bonding cluster was established involving residues Asn70, Asp84, and Arg121. The tVIM-7-F218Y mutant had enhanced activity compared to wild-type tVIM-7, and a slightly higher Tm (57.1°C) was observed, most likely due to the hydrogen bonding cluster. Furthermore, the introduction of two additional hydrogen bonds adjacent to the active site in the tVIM-7-H224Y mutant gave a higher thermostability (Tm, 62.9°C) and increased enzymatic activity compared to those of the wild-type tVIM-7. Docking of ceftazidime in to the active site of tVIM-7, tVIM-7-H224Y, and VIM-7-F218Y revealed that the side-chain conformations of residue 224 and Arg228 in the L3 loop and Tyr67 in the L1 loop all influence possible substrate binding conformations. In conclusion, the residue composition of the L3 loop, as shown with the single H224Y mutation, is important for activity particularly toward the positively charged cephalosporins like cefepime and ceftazidime. PMID:24913158

  2. Cassini/VIMS methane 3.3 ?m emission in Titan's upper atmosphere

    NASA Astrophysics Data System (ADS)

    García-Comas, M.; López-Puertas, M.; Funke, B.; Dinelli, B. M.; Moriconi, M. L.; Adriani, A.; Molina, A.; Coradini, A.

    2011-10-01

    This paper summarizes the work presented in [1]. In that work, we fulfilled a thorough analysis of Titan's methane limb emission at 3.3 ?m measured by VIMS in Titan. Methane is, after nitrogen, the most abundant species in Titan's atmosphere. It plays an important role in its chemistry and energy budget and strongly emits during daytime around 3.3 ?m. In Titan's upper atmosphere, where pressure is low, that emission is affected by non-local thermodynamic equilibrium. Therefore, its analysis needs from a modeling of the population of the emitting levels considering specifically the mechanisms able to excite and de-excite them. We developed a sophisticated non-LTE model that includes all known excitation mechanisms and calculates the population of 22 CH4 vibrational levels from two isotopes. We simulated VIMS radiance and identified the bands that significantly contribute to the total measured signal. We also retrieved daytime methane abundance from 500 to 1100 km and compared our results with other measurements and results from models.

  3. Distribution of icy particles across Enceladus' surface as derived from Cassini-VIMS measurements

    USGS Publications Warehouse

    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.; Wagner, R.

    2008-01-01

    The surface of Enceladus consists almost completely of water ice. As the band depths of water ice absorptions are sensitive to the size of particles, absorptions can be used to map variations of icy particles across the surface. The Visual and Infrared Mapping Spectrometer (VIMS) observed Enceladus with a high spatial resolution during three Cassini flybys in 2005 (orbits EN 003, EN 004 and EN 011). Based on these data we measured the band depths of water ice absorptions at 1.04, 1.25, 1.5, and 2 ??m. These band depths were compared to water ice models that represent theoretically calculated reflectance spectra for a range of particle diameters between 2 ??m and 1 mm. The agreement between the experimental (VIMS) and model values supports the assumption that pure water ice characterizes the surface of Enceladus and therefore that variations in band depth correspond to variations in water ice particle diameters. Our measurements show that the particle diameter of water ice increases toward younger tectonically altered surface units with the largest particles exposed in relatively "fresh" surface material. The smallest particles were generally found in old densely cratered terrains. The largest particles (???0.2 mm) are concentrated in the so called "tiger stripes" at the south pole. In general, the particle diameters are strongly correlated with geologic features and surface ages, indicating a stratigraphic evolution of the surface that is caused by cryovolcanic resurfacing and impact gardening. ?? 2007 Elsevier Inc. All rights reserved.

  4. Experimental scaling laws for mass-ablation rate, ablation pressure in planar laser-produced plasmas with laser intensity, laser wavelength, and target atomic number

    Microsoft Academic Search

    Faiz Dahmani; Boulevard Frantz Fanon

    1993-01-01

    Layered-target experiments at 1.06 ?m for carbon and silicon materials have been carried out to measure mass-ablation rate m˙ and ablation pressure Pa as a function of absorbed laser intensity Ia, laser wavelength ?L, and target atomic number Z at irradiances of 1013–1015 W\\/cm2. The results can be put in the forms m˙(kg\\/s cm2)&bartil;55 [Ia(W\\/cm2)\\/1014]1\\/3?L?4\\/3(?m) Z3\\/8 and Pa(Mbar)&bartil;7.4 [Ia(W\\/cm2)\\/1014]2\\/3?L?2\\/3(?m) Z3\\/16.

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

    Microsoft Academic Search

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

    2006-01-01

    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

  6. Multiplex real-time PCR probe-based for identification of strains producing: OXA48, VIM, KPC and NDM.

    PubMed

    Favaro, Marco; Sarti, Mario; Fontana, Carla

    2014-11-01

    The spread of multi-resistant enterobacteria, particularly carbapenem-resistant Enterobacteriaceae (CRE), in both community and hospital settings is a global problem. The phenotypic identification of CRE is complex, occasionally inconclusive and time consuming. However, commercially available molecular assays are very expensive, and many do not allow the simultaneous identification of all genetic markers of resistance that have been recognised in CRE (bla KPC, bla OXA-48, bla VIM and bla NDM). The aim of the present study is to describe a new test: a multiplex real time PCR probe-based assay designed for the simultaneous detection of KPC, OXA-48, VIM and NDM in a short time (no longer than 90 min from the extraction of DNA to detection). Our assay correctly identified 63 CRE isolates and all standard reference strains tested, in agreement with and extending the results of phenotypic identification tests; additionally, a KPC-VIM co-expressing Enterobacter aerogenes isolate was identified using the new assay, whereas traditional methods failed to detect it. The assay was also able to correctly detect 28 CRE-producers from 50 positive blood cultures, again detecting, in four specimens, the presence of CRE co-expressing KPC and VIM, which were only partially identified by traditional methods. Finally, when used directly on rectal swabs, the assay enabled the identification of CRE-carrier patients, for whom isolation is mandatory in a hospital setting. PMID:25154795

  7. First Report of an Extensively Drug-Resistant VIM-2 Metallo-?-Lactamase-Producing Brevundimonas diminuta Clinical Isolate

    PubMed Central

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

    2012-01-01

    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

  8. Titan's atmosphere as observed by Cassini/VIMS solar occultations: CH4, CO and evidence for C2H6 absorption

    NASA Astrophysics Data System (ADS)

    Maltagliati, Luca; Bézard, Bruno; Vinatier, Sandrine; Hedman, Matthew M.; Lellouch, Emmanuel; Nicholson, Philip D.; Sotin, Christophe; de Kok, Remco J.; Sicardy, Bruno

    2015-03-01

    We present an analysis of the VIMS solar occultations dataset, which allows us to extract vertically resolved information on the characteristics of Titan's atmosphere between ?100 and 700 km with a vertical resolution of ?10 km. After a series of data treatment procedures to correct problems in pointing stability and parasitic light, 4 occultations out of 10 are retained. This sample covers different seasons and latitudes of Titan. The transmittances show clearly the evolution of the haze, with the detection of the detached layer at ?310 km in September 2011 at mid-northern latitudes. Through the inversion of the transmission spectra with a line-by-line radiative transfer code we retrieve the vertical distribution of CH4 and CO mixing ratio. For methane inversion we use its 1.4, 1.7 and 2.3 ?m bands. The first two bands are always in good agreement and yield an average stratospheric abundance of 1.28 ± 0.08%, after correcting for forward-scattering effects, with no significant differences between the occultations. This is significantly less than the value of 1.48% obtained by the GCMS/Huygens instrument. We find that the 2.3 ?m band cannot be used for the extraction of methane abundance because it is blended with other absorptions, not included in our atmospheric model. The analysis of the residual spectra after the inversion shows that such additional absorptions are present through a great part of the VIMS wavelength range. We attribute many of these bands, including the one at 2.3 ?m, to gaseous ethane, whose near-infrared spectrum is not well modeled yet. Ethane also contributes significantly to the strong absorption at 3.2-3.5 ?m that was previously attributed only to C-H stretching bands from aerosols. Ethane bands may affect the surface windows too, especially at 2.7 ?m. Other residual bands are generated by stretching modes of C-H, C-C and C-N bonds. In addition to the C-H stretch from aliphatic hydrocarbons at 3.4 ?m, we detect a strong and narrow absorption at 3.28 ?m which we tentatively attribute to the presence of PAHs in the stratosphere. C-C and C-N stretching bands are possibly present between 4.3 and 4.5 ?m. Finally, we obtain the CO mixing ratio between 70 and 170 km, through the inversion of its 4.7 ?m band. The average result of 46 ± 16 ppm is in good agreement with previous studies.

  9. Resistome Analysis of Enterobacter cloacae CY01, an Extensively Drug-Resistant Strain Producing VIM-1 Metallo-?-Lactamase from China

    PubMed Central

    Yang, Ling; Wu, Ai-Wu; Su, Dan-Hong; Lin, Yong-Ping

    2014-01-01

    Resistome analysis of clinical VIM-1-producing Enterobacter cloacae strain CY01 from China revealed the presence of multiple resistance determinants. Two resistance plasmids were identified in CY01. The pCY-VIM plasmid was 14 kb in size and possessed a replicase gene (repA), a gene cluster encoding the partitioning function (parABC), and a carbapenemase gene (blaVIM-1). Another 5.9-kb plasmid, pCY-MdT, with an aac(6?)-Ib gene, was very closely related (13 nucleotide differences) to pMdT1, a ColE1 plasmid carrying aac(6?)-Ib-cr4. PMID:25114139

  10. Six years of continuous observation of Titan cloud activity with Cassini/VIMS

    NASA Astrophysics Data System (ADS)

    Rodriguez, S.; Le Mouélic, S.; Rannou, P.; Sotin, C.; Brown, R. H.

    2013-11-01

    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^{o}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^{o}S and 60^{o}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.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.

  11. Distribution of HCN in Titan's upper atmosphere from Cassini/VIMS observations at 3 ?m

    NASA Astrophysics Data System (ADS)

    Adriani, A.; Dinelli, B. M.; López-Puertas, M.; García-Comas, M.; Moriconi, M. L.; D'Aversa, E.; Funke, B.; Coradini, A.

    2011-08-01

    Cassini/VIMS limb observations have been used to retrieve vertical profiles of hydrogen cyanide (HCN) from its 3 ?m emission in the region from 600 to 1100 km altitude at daytime. While the daytime emission is large up to about 1100 km, it vanishes at nighttime at very low altitudes, suggesting that the daytime emission originates under non-LTE conditions. The spectrally integrated radiances around 3.0 ?m shows a monotonically decrease with tangent altitude, and a slight increase with solar zenith angle in the 40-80° interval around 800 km. A sophisticated non-LTE model of HCN energy levels has been developed in order to retrieve the HCN abundance. The population of the HCN 0 0 0 1 energy level, that contributes mostly to the 3.0 ?m limb radiance, has been shown to change significantly with the solar zenith angle (SZA) and HCN abundance. Also its population varies with the collisional rate coefficients, whose uncertainties induced errors in the retrieved HCN of about 10% at 600-800 km and about 5% above. HCN concentrations have been retrieved from a set of spectra profiles, covering a wide range of latitudes and solar zenith angles, by applying a line-by-line inversion code. The results show a significant atmospheric variability above ˜800 km with larger values for weaker solar illumination. The HCN shows a very good correlation with solar zenith angles, irrespective of latitude and local time, suggesting that HCN at these high altitudes is in or close to photochemical equilibrium. A comparison with UVS and UVIS measurements show that these are close to the lower limit (smaller SZAs) of the VIMS observations above 750 km. However, they are in reasonable agreement when combining the rather large UV measurement errors and the atmospheric variability observed in VIMS. A comparison of the mean profile derived here with the widely used profile reported by Yelle and Griffith (Yelle R.V., Griffith, C.A. [2003]. Icarus 166, 107-115) shows a good agreement for altitudes ranging from 850 to 1050 km, while below these altitudes our result exhibits higher concentrations.

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

    USGS Publications Warehouse

    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

    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.

  13. MULTI-WAVELENGTH OBSERVATIONS OF THE SPATIO-TEMPORAL EVOLUTION OF SOLAR FLARES WITH AIA/SDO. II. HYDRODYNAMIC SCALING LAWS AND THERMAL ENERGIES

    SciTech Connect

    Aschwanden, Markus J. [Lockheed Martin Advanced Technology Center, Org. ADBS, Bldg. 252, 3251 Hanover St., Palo Alto, CA 94304 (United States); Shimizu, Toshifumi, E-mail: aschwanden@lmsal.com, E-mail: shimizu.toshifumi@isas.jaxa.jp [Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 3-1-1 Yoshinodai, Chuo, Sagamihara, Kanagawa 252-5210 (Japan)

    2013-10-20

    In this study we measure physical parameters of the same set of 155 M- and X-class solar flares observed with AIA/SDO as analyzed in Paper I, by performing a differential emission measure analysis to determine the flare peak emission measure EM{sub p} , peak temperature T{sub p} , electron density n{sub p} , and thermal energy E{sub th}, in addition to the spatial scales L, areas A, and volumes V measured in Paper I. The parameter ranges for M- and X-class flares are log (EM{sub p}) = 47.0-50.5, T{sub p} = 5.0-17.8 MK, n{sub p} = 4 × 10{sup 9}-9 × 10{sup 11} cm{sup –3}, and thermal energies of E{sub th} = 1.6 × 10{sup 28}-1.1 × 10{sup 32} erg. We find that these parameters obey the Rosner-Tucker-Vaiana (RTV) scaling law T{sub p}{sup 2}?n{sub p} L and H?T {sup 7/2} L {sup –2} during the peak time t{sub p} of the flare density n{sub p} , when energy balance between the heating rate H and the conductive and radiative loss rates is achieved for a short instant and thus enables the applicability of the RTV scaling law. The application of the RTV scaling law predicts power-law distributions for all physical parameters, which we demonstrate with numerical Monte Carlo simulations as well as with analytical calculations. A consequence of the RTV law is also that we can retrieve the size distribution of heating rates, for which we find N(H)?H {sup –1.8}, which is consistent with the magnetic flux distribution N(?)??{sup –1.85} observed by Parnell et al. and the heating flux scaling law F{sub H} ?HL?B/L of Schrijver et al.. The fractal-diffusive self-organized criticality model in conjunction with the RTV scaling law reproduces the observed power-law distributions and their slopes for all geometrical and physical parameters and can be used to predict the size distributions for other flare data sets, instruments, and detection algorithms.

  14. Multi-Wavelength Observations of the Spatio-Temporal Evolution of Solar Flares with AIA/SDO: II. Hydrodynamic Scaling Laws and Thermal Energies

    E-print Network

    Aschwanden, Markus J

    2013-01-01

    In this study we measure physical parameters of the same set of 155 M and X-class solar flares observed with AIA/SDO as analyzed in Paper I, by performing a {\\sl differential emission measure (DEM)} analysis to determine the flare peak emission measure $EM_p$, peak temperature $T_p$, electron density $n_p$, and thermal energy $E_{th}$, in addition to the spatial scales $L$, areas $A$, and volumes $V$ measured in Paper I. The parameter ranges for M and X-class flares are: $\\log(EM_p)=47.0-50.5$, $T_p=5.0-17.8$ MK, $n_p=4 \\times 10^9-9 \\times 10^{11}$ cm$^{-3}$, and thermal energies of $E_{th}=1.6 \\times 10^{28}-1.1 \\times 10^{32}$ erg. We find that these parameters obey the Rosner-Tucker-Vaiana (RTV) scaling law $T_p^2 \\propto n_p L$ and $H \\propto T^{7/2} L^{-2}$ during the peak time $t_p$ of the flare density $n_p$, when energy balance between the heating rate $H$ and the conductive and radiative loss rates is achieved for a short instant, and thus enables the applicability of the RTV scaling law. The applic...

  15. Fast forward modeling of Titan's infrared spectra to invert VIMS/Cassini hyperspectral images

    USGS Publications Warehouse

    Rodriguez, S.; Mouelic, S.L.; Rannou, P.; Combe, J.-P.; Corre, L.L.; Tobie, G.; Barnes, J.W.; Sotin, C.; Brown, R.H.; Baines, K.H.; Buratti, B.J.; Clark, R.N.; Nicholson, P.D.

    2009-01-01

    The surface of Titan, the largest icy moon of Saturn, is veiled by a very thick and hazy atmosphere. The Visual and Infrared Mapping Spectrometer onboard the Cassini spacecraft, in orbit around Saturn since July 2004, conduct an intensive survey of Titan with the objective to understand the complex nature of the atmosphere and surface of the mysterious moon and the way they interact. Accurate radiative transfer modeling is necessary to analyze Titan's infrared spectra, but are often very computer resources demanding. As Cassini has gathered hitherto millions of spectra of Titan and will still observe it until at least 2010, we report here on the development of a new rapid, simple and versatile radiative transfer model specially designed to invert VIMS datacubes. ?? 2009 IEEE.

  16. Characterization of Inclusions in VIM/VAR NiTi Alloys

    NASA Astrophysics Data System (ADS)

    Coda, A.; Zilio, S.; Norwich, D.; Sczerzenie, F.

    2012-12-01

    Inclusions content is important for the mechanical behavior and performances of NiTi-based products particularly in fatigue-rated devices. Higher inclusions content has been correlated to reductions in transformation temperatures and strain recovery under mechanical or thermo-mechanical cycling. Moreover, most fatigue fractures show inclusions at the initiation site. However, there is a general lack of information on the nature and characteristics of such inclusions, especially those typically recognized as intermetallics oxides. In this study, the common scanning electron microscopy technique has been used to investigate the chemistry and morphology of inclusions in commercial standard VIM/VAR binary NiTi alloys. The defined experimental procedure, results, and their significance will be presented and discussed.

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

    NASA Astrophysics Data System (ADS)

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

    2010-05-01

    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.

  18. What's a Wavelength?

    NSDL National Science Digital Library

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

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

  19. Multiclonal spread of VIM-1-producing Enterobacter cloacae isolates associated with In624 and In488 integrons located in an IncHI2 plasmid.

    PubMed

    Villa, Jennifer; Viedma, Esther; Brañas, Patricia; Orellana, M Angeles; Otero, Joaquín R; Chaves, Fernando

    2014-05-01

    Over a 6-year period (2007-2012), the emergence of Enterobacter cloacae isolates resistant to ?-lactams and with reduced susceptibility to carbapenems was observed in Hospital Universitario 12 de Octubre (Madrid, Spain). To determine the possible role of metallo-?-lactamases (MBLs) in the resistance profile of these isolates, a molecular and clinical epidemiological study was performed, including determination of patients' clinical characteristics, genetic diversity of strains, resistance mechanisms to carbapenems, and the genetic environment of VIM-1. A total of 73 E. cloacae isolates showed resistance to extended-spectrum cephalosporins and reduced susceptibility to at least one carbapenem during 2007-2012. PCR amplification revealed the presence of bla(VIM-1) gene in 37 isolates, bla(VIM-2) in 1 isolate and bla(KPC) in 5 isolates. Molecular typing showed high clonal diversity of E. cloacae isolates carrying bla(VIM-1). The genetic environment of bla(VIM-1) was investigated and two integron structures were found: intI-bla(VIM-1)-aacA4-dfrB1-aadA1-catB2-qacE?1/sul1 (In624); and intI-bla(VIM-1)-aacA4-aadA1-qacE?1/sul1 (In488). Isolates belonging to three clones (A, F and G) harboured different types of integron (In624 or In488) despite belonging to the same clone. Conjugal experiments showed an association with a conjugative plasmid of ca. 300 kb belonging to IncHI2 group, which is common in Spanish hospitals, suggesting that the widespread dissemination of bla(VIM-1) may be due to horizontal transfer of mobile genetic determinants rather than the result of spreading of a few clones. These results have implications for infection control programmes in the hospital. PMID:24702943

  20. Emergence of VIM-2 and IMP-15 Carbapenemases and Inactivation of oprD Gene in Carbapenem-Resistant Pseudomonas aeruginosa Clinical Isolates from Lebanon

    PubMed Central

    Al Bayssari, Charbel; Diene, Seydina M.; Loucif, Lotfi; Gupta, Sushim Kumar; Dabboussi, Fouad; Mallat, Hassan; Hamze, Monzer

    2014-01-01

    We report here the emergence of VIM-2 and IMP-15 carbapenemases in a series of clinical isolates of carbapenem-resistant Pseudomonas aeruginosa in Lebanon. We also describe the disruption of the oprD gene by either mutations or insertion sequence (IS) elements ISPa1328 and ISPre2 isoform. Our study reemphasizes a rapid dissemination of the VIM-2 carbapenemase-encoding gene in clinical isolates of P. aeruginosa in the Mediterranean basin. PMID:24913164

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

    NASA Technical Reports Server (NTRS)

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

    1989-01-01

    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.

  2. Coherent Backscattering Effect in Icy Satellites: Model, Cassini VIMS, and Ground-Based Near-Infrared Spectra

    NASA Astrophysics Data System (ADS)

    Pitman, Karly M.; Kolokolova, L.; Verbiscer, A. J.

    2013-10-01

    Compositional mapping of icy satellite surfaces is usually based on correlating spectral absorption band depths with the abundance of ice/non-ice species and/or particle size alone. However, absorption band depths and shapes also depend on observation geometry, specifically the solar phase angle ?. The constructive interference of light that is responsible for the coherent backscattering effect (CBE) should significantly alter the interpretation of spacecraft spectra obtained at ? < 2 degrees in particular (Helfenstein et al. 1997 Icarus 128, 2-14), but the magnitude of the CBE on band depth has not yet been quantified or studied in detail. In this work, we explore the relationship between ?, spectral band depth and shape caused by CBE for both Cassini Visual & Infrared Mapping Spectrometer (VIMS) and ground-based near-infrared observations of bright and dark satellites. We report numerical CBE modeling performed using the publicly available multisphere T-matrix (MSTM) computer code to simulate the change in absorption bands with the solar phase angle seen in the spectra of icy bodies. We compare these models to Cassini VIMS extracted I/F spectra for selected icy satellites (e.g., Rhea, Iapetus, Enceladus) as well as ground-based ? = 0.9 - 2.4 ?m spectra of Tethys, Dione, Iapetus, Rhea, and Enceladus acquired using Triplespec (R=3000) at Apache Point Observatory, New Mexico. Such results ultimately place limits on the size and packing fraction of icy satellite regolith particles and aid in interpretations of the structure, composition, and evolution of icy satellites. This work is supported by NASA’s Outer Planets Research program (NNX12AM76G; PI Pitman), Planetary Astronomy program (NNX09AD06G; PI Verbiscer), and NASA’s Advanced Supercomputing Division. Calibrated Cassini VIMS data cubes appear courtesy of B. J. Buratti and the Cassini VIMS team.

  3. Plasmid Profile Analysis and bla VIM Gene Detection of Metalo ?-lactamase (MBL) Producing Pseudomonas aeruginosa Isolates from Clinical Samples

    PubMed Central

    M, Jeya

    2014-01-01

    Introduction:Pseudomonas aeruginosa is a frequent colonizer of hospitalized patients. They are responsible for serious infections such as meningitis, urological infections, septicemia and pneumonia. Carbapenem resistance of Pseudomonas aeruginosa is currently increasingly reported which is often mediated by production of metallo-?-lactamase (MBL). Multidrug resistant Pseudomonas aeruginosa isolates may involve reduced cell wall permeability, production of chromosomal and plasmid mediated ? lactamases, aminoglycosides modifying enzymes and an active multidrug efflux mechanism. Objective: This study is aimed to detect the presence and the nature of plasmids among metallo-?-lactamase producing Pseudomonas aeruginosa isolates. Also to detect the presence of bla VIM gene from these isolates. Materials and Methods: Clinical isolates of Pseudomonas aeruginosa showing the metalo-?-lactamase enzyme (MBL) production were isolated. The MBL production was confirmed by three different methods. From the MBL producing isolates plasmid extraction was done by alkaline lysis method. Plasmid positive isolates were subjected for blaVIM gene detection by PCR method. Results: Two thousand seventy six clinical samples yielded 316 (15.22%) Pseudomonas aeruginosa isolates, out of which 141 (44.62%) were multidrug resistant. Among them 25 (17.73%) were metallo-?-lactamase enzyme producers. Plasmids were extracted from 18 out of 25 isolates tested. Five out of 18 isolates were positive for the blaVIM gene detection by the PCR amplification. Conclusion: The MBL producers were susceptible to polymyxin /colistin with MIC ranging from 0.5 – 2?g/ml. Molecular detection of specific genes bla VIM were positive among the carbapenem resistant isolates. PMID:25120980

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

    NASA Astrophysics Data System (ADS)

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

    2013-05-01

    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.

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

    USGS Publications Warehouse

    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

    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.

  6. The Polar Winds of Saturn as Determined by Cassini/VIMS: Seasonally Variable or Not?

    NASA Astrophysics Data System (ADS)

    Momary, Thomas W.; Baines, K. H.; Brown, R. H.; Buratti, B. J.; Clark, R. N.; Nicholson, P. D.; Sotin, C.; Cassini/VIMS Science Team

    2013-10-01

    The high inclination of Cassini's current orbit allows VIMS to once again obtain spectacular views of Saturn’s poles, not seen since 2008. We present new imagery and investigate the effect of seasonal variability on Saturn’s polar winds. The north pole now basks in spring daylight and we again observe the long-enduring northern Polar Hexagon, discovered in Voyager imagery by Godfrey (Icarus 76, 335-356, 1988). This feature seemed to stay fixed in a rotational system defined by the Voyager-era radio rotation rate (Desch & Kaiser, Geophys. Res. Lett, 8, 253-256, 1981) in both original Voyager and 2008 VIMS observations. Yet new images indicate a shift, with the hexagon rotating ~10° of longitude from Nov. 2012 to May 2013. Discrete clouds still race around the edges of the 5-?m-bright hexagon at speeds of ~100 m/s, as we observed in 2008 (Baines, Momary, et al., Plan. Space. Sci 57, 1671-1681, 2009). We also recover a massive storm system residing just inside the hexagon edge at ~80° N. lat. Since 2008, this storm has shifted poleward by 1.5° and turned 5 ?m dark (cloudy), where it was 5 ?m bright when last observed (i.e. cloud free). It now moves zonally faster at ~25 m/s vs. ~14 m/s in 2008. This enduring "shepherd" storm may force and maintain the hexagon shape. We also recover twin 5-?m-dark storms (Snake Eyes) moving slowly at ~15 m/s near 67° N lat. However, while the two features appear to maintain a relatively constant zonal separation on average (14° ), with the trailing feature remaining near 67° N lat., the leading storm appears to oscillate ~1° in latitude and drift in longitude. At the south pole, discrete clouds whirl, now in darkness, around a hurricane-like vortex consisting of a cloudless "eye" extending at least 1 bar deeper than surrounding rings of clouds. These clouds still appear to be moving as a classical vortex with winds reaching a maximum of ~200 m/s near 87° S lat. and then falling off to zero at the pole. In contrast, clouds near 75° S. lat. are nearly stationary, consistent with 2008 observations. Our preliminary results suggest limited seasonal variability of Saturn’s polar winds.

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

    PubMed Central

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

    2007-01-01

    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. PMID:17343764

  8. Wavelength and Energy

    NSDL National Science Digital Library

    This is an activity about wavelength and frequency. Using a 30 to 50 foot rope and two volunteers, learners will observe as one end of the rope is shaken and wavelength patterns are created. They will estimate the wavelength, the distance between two similar points of a wave, such as peak-to-peak, and the frequency of the waves, the number of waves reaching the far end of the rope per second. Through group discussion afterwards, this information is then related electromagnetic spectrum. This activity requires a long length of rope and a large enough space for the entire group to see the whole rope at once. This activity is from the Stanford Solar Center's All About the Sun: Sun and Stars activity guide for Grades 5-8 and can also accompany the Stanford Solar Center's Build Your Own Spectroscope activity.

  9. Long wavelength infrared detector

    NASA Technical Reports Server (NTRS)

    Vasquez, Richard P. (inventor)

    1993-01-01

    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.

  10. Short wavelength laser

    DOEpatents

    Hagelstein, P.L.

    1984-06-25

    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.

  11. Long wavelength semiconductor lasers

    Microsoft Academic Search

    G. P. Agrawal; N. K. Dutta

    1986-01-01

    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

  12. 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)

    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

    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.

  13. First identification of an Escherichia coli clinical isolate producing both metallo-beta-lactamase VIM-2 and extended-spectrum beta-lactamase IBC-1.

    PubMed

    Galani, I; Souli, M; Chryssouli, Z; Katsala, D; Giamarellou, H

    2004-08-01

    An Escherichia coli strain with decreased susceptibility to carbapenems was isolated from a hospitalised patient in Athens, Greece. The strain was resistant to all beta-lactams, including aztreonam, whereas the MIC of imipenem and meropenem was 0.5 mg/L. A positive EDTA-disk synergy test suggested the production of a metallo-beta-lactamase. PCR experiments revealed the presence of the bla(VIM-2), bla(IBC-1), and bla(TEM-1) genes. Resistance to beta-lactams was not transferable by conjugation. This is the first report of a clinical isolate of E. coli producing VIM-2, and the first report of the coexistence of bla(VIM-2) and bla(IBC-1) in a single clinical isolate. PMID:15301681

  14. Search for and limits on plume activity on Mimas, Tethys, and Dione with the Cassini Visual Infrared Mapping Spectrometer (VIMS)

    USGS Publications Warehouse

    Buratti, B.J.; Faulk, S.P.; Mosher, J.; Baines, K.H.; Brown, R.H.; Clark, R.N.; Nicholson, P.D.

    2011-01-01

    Cassini Visual Infrared Mapping Spectrometer (VIMS) observations of Mimas, Tethys, and Dione obtained during the nominal and extended missions at large solar phase angles were analyzed to search for plume activity. No forward scattered peaks in the solar phase curves of these satellites were detected. The upper limit on water vapor production for Mimas and Tethys is one order of magnitude less than the production for Enceladus. For Dione, the upper limit is two orders of magnitude less, suggesting this world is as inert as Rhea (Pitman, K.M., Buratti, B.J., Mosher, J.A., Bauer, J.M., Momary, T., Brown, R.H., Nicholson, P.D., Hedman, M.M. [2008]. Astrophys. J. Lett. 680, L65-L68). Although the plumes are best seen at ???2.0. ??m, Imaging Science Subsystem (ISS) Narrow Angle Camera images obtained at the same time as the VIMS data were also inspected for these features. None of the Cassini ISS images shows evidence for plumes. The absence of evidence for any Enceladus-like plumes on the medium-sized saturnian satellites cannot absolutely rule out current geologic activity. The activity may below our threshold of detection, or it may be occurring but not captured on the handful of observations at large solar phase angles obtained for each moon. Many VIMS and ISS images of Enceladus at large solar phase angles, for example, do not contain plumes, as the active "tiger stripes" in the south pole region are pointed away from the spacecraft at these times. The 7-year Cassini Solstice Mission is scheduled to gather additional measurements at large solar phase angles that are capable of revealing activity on the saturnian moons. ?? 2011 Elsevier Inc.

  15. Probe ligation and real-time detection of KPC, OXA-48, VIM, IMP, and NDM carbapenemase genes.

    PubMed

    Cuzon, G; Naas, T; Bogaerts, P; Glupczynski, Y; Nordmann, P

    2013-08-01

    The Check-MDR Carba test (Check-Points, Wageningen, Netherlands), which is based on specific molecular recognition of blaNDM, blaKPC, blaOXA-48, blaVIM, and blaIMP genes by DNA probe ligation and real-time PCR detection, was evaluated on 183 well-characterized Gram-negative rods. Representatives of the 5 gene families were accurately identified (specificities and sensitivities of 100%) within 4.5 hours. This test may be helpful to differentiate carbapenem resistance mediated by carbapenemases from those involving other mechanisms. PMID:23791387

  16. Sub-wavelength diffractive optics

    SciTech Connect

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

    1998-03-01

    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.

  17. Short wavelength laser

    DOEpatents

    Hagelstein, Peter L. (Livermore, CA)

    1986-01-01

    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.

  18. Scale

    ERIC Educational Resources Information Center

    Schaffhauser, Dian

    2009-01-01

    The common approach to scaling, according to Christopher Dede, a professor of learning technologies at the Harvard Graduate School of Education, is to jump in and say, "Let's go out and find more money, recruit more participants, hire more people. Let's just keep doing the same thing, bigger and bigger." That, he observes, "tends to fail, and fail…

  19. Metabolome variations in the Porphyromonas gingivalis vimA mutant during hydrogen peroxide-induced oxidative stress.

    PubMed

    McKenzie, R M E; Aruni, W; Johnson, N A; Robles, A; Dou, Y; Henry, L; Boskovic, D S; Fletcher, H M

    2015-04-01

    The adaptability and survival of Porphyromonas gingivalis in the oxidative microenvironment of the periodontal pocket are indispensable for survival and virulence, and are modulated by multiple systems. Among the various genes involved in P. gingivalis oxidative stress resistance, vimA gene is a part of the 6.15-kb locus. To elucidate the role of a P. gingivalis vimA-defective mutant in oxidative stress resistance, we used a global approach to assess the transcriptional profile, to study the unique metabolome variations affecting survival and virulence in an environment typical of the periodontal pocket. A multilayered protection strategy against oxidative stress was noted in P. gingivalis FLL92 with upregulation of detoxifying genes. The duration of oxidative stress was shown to differentially modulate transcription with 94 (87%) genes upregulated twofold during 10 min and 55 (83.3%) in 15 min. Most of the upregulated genes (55%), fell in the hypothetical/unknown/unassigned functional class. Metabolome variation showed reduction in fumarate and formaldehyde, hence resorting to alternative energy generation and maintenance of a reduced metabolic state. There was upregulation of transposases, genes encoding for the metal ion binding protein transport and secretion system. PMID:25055986

  20. Wavelength meter having elliptical wedge

    DOEpatents

    Hackel, R.P.; Feldman, M.

    1992-12-01

    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.

  1. Wavelength meter having elliptical wedge

    DOEpatents

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

    1992-01-01

    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.

  2. Protocol for Work place adjusted Intelligent physical exercise reducing Musculoskeletal pain in Shoulder and neck (VIMS): a cluster randomized controlled trial

    Microsoft Academic Search

    Lars L Andersen; Mette K Zebis; Mogens T Pedersen; Kirsten K Roessler; Christoffer H Andersen; Mette M Pedersen; Helene Feveile; Ole S Mortensen; Gisela Sjøgaard

    2010-01-01

    BACKGROUND: Neck and shoulder complaints are common among employees in sedentary occupations characterized by intensive computer use. Specific strength training is a promising type of physical exercise for relieving neck and shoulder pain in office workers. However, the optimal combination of frequency and exercise duration, as well as the importance of exercise supervision, is unknown. The VIMS study investigates in

  3. Galilean Satellite Surface Non-Ice Constituents: New Results from the Cassini/Huygens VIMS Jupiter Flyby in the Context of the Galileo NIMS Results

    NASA Technical Reports Server (NTRS)

    McCord, T. B.; Brown, R.; Baines, K.; Bellucci, G.; Bibring, J.-P.; Buratti, B.; Capaccioni, F.; Cerroni, P.; Clark, R.; Coradini, A.

    2001-01-01

    The Cassini mission Visible and Infrared Mapping Spectrometer (VIMS) is currently returning data for the Galilean satellites. Examples of the new satellite data and the initial interpretations will be presented in the context of the Galileo NIMS data and results. Additional information is contained in the original extended abstract.

  4. Multibeam Observations of Mine Scour and Burial near Clearwater, Florida, Including a Test of the VIMS 2D Mine Burial Model

    E-print Network

    New Hampshire, University of

    Multibeam Observations of Mine Scour and Burial near Clearwater, Florida, Including a Test of the VIMS 2D Mine Burial Model by Monica L. Wolfson A thesis submitted in partial fulfillment #12;Acknowledgements Funding for this research was provided by the Office of Naval Research Mine

  5. Hpm and Vim Methods for Finding the Exact Solutions of the Nonlinear Dispersive Equations and Seventh-Order Sawada-Kotera Equation

    Microsoft Academic Search

    D. D. Ganji; N. Jamshidi; Z. Z. Ganji

    2009-01-01

    In this paper, nonlinear dispersive equations and seventh-order Sawada-Kotera equation are solved using homotopy perturbation method (HPM) and variational iteration method (VIM). The results obtained by the proposed methods are then compared with that of Adomian decomposition method (ADM). The comparisons demonstrate that the two obtained solutions are in excellent agreement. The numerical results calculated show that the methods can

  6. Scales

    ScienceCinema

    Murray Gibson

    2010-01-08

    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).

  7. JLT-16042-2014: K.-P. Ho et al, "Wavelength-Selective Switches for Mode-Division Multiplexing" 1 Abstract--Wavelength-selective switches for mode-

    E-print Network

    Kahn, Joseph M.

    JLT-16042-2014: K.-P. Ho et al, "Wavelength-Selective Switches for Mode-Division Multiplexing" 1 Abstract--Wavelength-selective switches for mode- division-multiplexing systems are designed by scaling switches from single-mode systems. All modes at a given wavelength are switched as a unit, which

  8. Molecular detection of metallo-?-lactamase gene blaVIM-1 in imipenem-resistant Pseudomonas aeruginosa strains isolated from hospitalized patients in the hospitals of Isfahan

    PubMed Central

    Sedighi, Mansour; Vaez, Hamid; Moghoofeie, Mohsen; Hadifar, Shima; Oryan, Golfam; Faghri, Jamshid

    2015-01-01

    Background: Pseudomonas aeruginosa is an opportunistic human pathogen that causes serious problems, especially in people, who have immunodeficiency. In recent times, metallo-?-lactamase (MBLs) resistance in this bacterium has led to some difficulties in treating bacterial infections. The metallo-beta-lactamase family of genes, including blaVIM-1, is being reported with increasing frequency worldwide. The aim of this study is the detection of the metallo-?-lactamase gene blaVIM-1 in imipenem-resistant P. aeruginosa (IRPA) strains isolated from hospitalized patients. Materials and Methods: In this study, 106 P. aeruginosa samples were isolated from various nosocomial infections. The isolates were identified, tested for susceptibility to various antimicrobial agents by the Kirby-Bauer disk diffusion method, and all the imipenem-resistant isolates were screened for the presence of MBLs by using the combined disk (IMP-EDTA). The minimal inhibitory concentration (MIC) of imipenem was determined by E-test on the Mueller-Hinton agar. To detect the blaVIM-1 gene, the isolates were subjected to a polymerase chain reaction (PCR). Results: Of all the P. aeruginosa isolates, 62 (58.5%) were found to be imipenem-resistant P. aeruginosa (MIC ?32 ?g/ml). Twenty-six (42%) of the imipenem-resistant isolates were MBL positive. None of these isolates carried the blaVIM-1 gene using the PCR assay. Conclusion: The results demonstrated the serious therapeutic threat of the MBL-producing P. aeruginosa populations. The rate of imipenem resistance due to MBL was increased dramatically. Early detection and infection-control practices are the best antimicrobial strategies for this organism. None of MBL-producing isolates in this study carry the blaVIM-1 gene; therefore, another gene in the MBL family should be investigated.

  9. Atmospheric Seeing at Infrared Wavelengths

    NASA Astrophysics Data System (ADS)

    Bester, M.; Danchi, W. C.; Townes, C. H.; Treuhaft, R. N.

    1993-05-01

    Data taken with the Infrared Spatial Interferometer (ISI) at Mt. Wilson have been analyzed to characterize atmospheric pathlength fluctuations, in preparation for astrometric work. In this paper we will discuss two features observed in recent astrometric phase time series data: 1) The presence of non-random fluctuations, and 2) the correlation of pathlength variations near the ground with those along the path to the stars. The data analysis indicates that fluctuations in pathlength through the entire atmosphere at 11 microns as well as fluctuations near the ground show substantial deviations from the Kolmogorov-Taylor model with the commonly assumed large (>>1 km) outer scale. Under excellent seeing conditions, the ISI astrometric phase structure functions are consistent with an outer scale in the range of 5 -- 20 m. Generally the results indicate that large-aperture telescopes and long baseline interferometers, particularly at IR wavelengths, will likely perform better than is expected on the basis of the Kolmogorov-Taylor model. Under certain conditions, spikes are observed in the phase time series which are consistent with brief excursions of the index of refraction of air toward smaller values. The presence of such spikes could partially account for discrepancies in slopes between structure functions and power spectra of phase fluctuations as observed with the ISI. A high correlation (~0.6) between the atmospheric fluctuations within the telescope optics and those along the path to the star has been observed for some of the ISI data. A statistical model of the fluctuations has been developed to optimally utilize this correlation in the application of ground-based calibrations to the stellar data. A byproduct of this model is a calculation of the height of the dominant atmospheric turbulence above Mt. Wilson, based on the observed ground-based/stellar correlation. This height is in the range of 10 -- 20 meters, consistent with the small outer scales inferred from structure-function analyses.

  10. Internal to external wavelength calibration

    NASA Astrophysics Data System (ADS)

    Sahu, Kailash C.

    1999-01-01

    The spectra of Hen 1357 (the Stingray nebula) were used to check the internal to external wavelength calibration of the STIS first order CCD modes. The radial velocity of the Stingray nebula is known to high accuracy (< 1 km/sec) and the line with of the nebular line is very narrow (< 8 km/sec for the integrated nebula). Thus the observations of the Stingray nebula are ideal to check the internal to external wavelength calibration of the first order modes. The observations were taken in G430L and G750M modes using a 52 x 0.05 arcsec slit covering the wavelength range 2900 to 5700 A and 6295 to 6867 A, respectively. The observed wavelength range includes many nebular emission lines. The wavelengths of the nebular lines derived using the pipeline internal wavelength calibration were compared with the wavelengths derived from other ground based observations. In all cases, the wavelength match between the two is of the same order as the accuracy to which the line center can be measured. These results imply that there is no significant offset between the internal and external wavelength calibrations for these modes. The HDF-S QSO observations were also used for this test both for the first order and the Echelle modes. The results of the HDF-S QSO observations further confirm the above finding for the first order modes, and imply that there is no significant offset between the internal and external wavelength calibration for the Echelle modes.

  11. Wavelength-conserving grating router for intermediate wavelength density

    DOEpatents

    Deri, Robert J.; Patel, Rajesh R.; Bond, Steven W.; Bennett, Cory V.

    2007-03-20

    A wavelength router to be used for fiber optical networking router is based on a diffraction grating which utilizes only N wavelengths to interconnect N inputs to N outputs. The basic approach is to augment the grating with additional couplers or wavelength selective elements so than N-1 of the 2N-1 outputs are combined with other N outputs (leaving only N outputs). One embodiment uses directional couplers as combiners. Another embodiment uses wavelength-selective couplers. Another embodiment uses a pair of diffraction gratings to maintain parallel propagation of all optical beams. Also, beam combining can be implemented either by using retroflection back through the grating pair or by using couplers.

  12. S pace Qualification Of A Thin Wafer Lithium Niobate Etalon For The Visible Light Imager And Magnetograph (Vim)

    NASA Astrophysics Data System (ADS)

    Schühle, U.; Mathew, S. K.; Wedemeier, M.; Hartwig, H.; Ballesteros, E.; Martinez Pillet, V.; Solanki, S. K.

    2007-01-01

    For the Visible Light Imager and Magnetograph (VIM) a high-resolution filtergraph is under design. The system takes advantage of a lithium niobate (LiNbO3) crystal which can be used as a scanning filter using high voltage for tuning. We have undertaken first studies to qualify a lithium niobate wafer of 70 mm aperture size for deployment and use in space. We show the results of the mechanical mounting and vibration and thermal cycling tests as well as stability tests under fast voltage tuning in vacuum. Although these tests have all been very successful, further environmental testing is necessary to fully space-qualify the filter for the Solar Orbiter mission.

  13. Hospital outbreak of carbapenem-resistant Pseudomonas aeruginosa producing VIM-1, a novel transferable metallo-beta-lactamase.

    PubMed

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

    2000-11-01

    A total of 8 Pseudomonas aeruginosa isolates was collected from 7 different patients in different wards of the University Hospital of Verona, Italy, from February 1997 to February 1998. The high level of resistance to carbapenems (imipenem minimum inhibitory concentration was always >128 microg/mL) and other broad-spectrum beta-lactams and the rate of imipenem hydrolysis and its inhibition by ethylenediamine-tetra-acetic acid were all suggestive of production of a carbapenem-hydrolyzing metallo-beta-lactamase. A specific DNA probe derived from the recently cloned bla(VIM-1) gene hybridized to all the isolates. A genomic DNA fingerprinting profile revealed clonal relatedness for 7 of 8 isolates. A description of this hospital outbreak is reported, the occurrence of which confirms that proliferation of metallo-beta-lactamase-producing strains multiply resistant to beta-lactams is already a reality outside Japan. These findings emphasize the need for early recognition of similar isolates. PMID:11073738

  14. Full-disk observations of the saturnian moons in the VIS-NIR spectral range by Cassini- VIMS

    NASA Astrophysics Data System (ADS)

    Filacchione, G.; Capaccioni, F.; Coradini, A.; Cerroni, P.; Tosi, F.; Adriani, A.; McCord, T. B.; Baines, K. H.; Bellucci, G.; Brown, R. H.; Bibring, J.; Buratti, B. J.; Clark, R. N.; Combes, M.; Cruikshank, D. P.; Drossart, P.; Formisano, V.; Jaumann, R.; Langevin, Y.; Matson, D. L.; Mennella, V.; Robert, N. M.; Nicholson, P. D.; Sicardy, B.; Sotin, C.; Moriconi, M.

    2006-12-01

    During the first two years of the Cassini's nominal mission, VIMS (Visual and Infrared Mapping Spectrometer) has explored the whole system of Saturnian icy satellites. Here we report a comparative analysis of more than 600 full-disk observations obtained from July 2004 to nowadays for 15 regular and minor satellites: Atlas, Prometheus, Pandora, Janus, Epimetheus, Mimas, Enceladus, Tethys, Telesto, Calypso, Dione, Rhea, Hyperion, Iapetus and Phoebe. These observations, done from the equatorial plane, are particularly suitable to highlight the spectral differences between the leading and trailing sides of the regular satellites as function of the illumination angle (Filacchione et al., 2006a, 2006b); a byproduct of this activity is the measurement of the phase curves. The combined use of several VIS and IR spectral quantities (e.g. spectral slopes, water ice bands strengths, continuum levels, etc.) allows to find correlations between classes of satellites orbiting at different distances from Saturn: in this way it is possible to discriminate the almost pure ice surfaces of Enceladus and Calypso from the organic rich Hyperion, Iapetus and Phoebe (Tosi et al., 2006). This research was completed thanks to the support of the Italian Space Agency (ASI), Grant ASI/Cassini I/031/05/0. Filacchione et al., 2006a. Saturn's icy satellites investigated by Cassini-VIMS. I. Full-disk properties: 350-5100 nm reflectance spectra and phase curves, Icarus, in press. Filacchione et al., 2006b. VIS-NIR Spectral Properties of Saturn's Minor Icy Moons. 37th LPSC, abstract no.1271 Tosi et al., 2006. Iapetus, Phoebe and Hyperion: Are They Related? 37th LPSC, abstract no.1582

  15. The Atmospheres of Saturn and Titan in the Near-Infrared: First Results of Cassini/VIMS

    NASA Technical Reports Server (NTRS)

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

    2005-01-01

    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 approximately 750 km altitude, (3) wind measurements of approximately 0.5 ms(exp -1), favoring prograde, from the movement of a persistent (multiple months) south polar cloud near 88 deg S latitude, and (4) the imaging of two transient mid-southern-latitude cloud features.

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

    USGS Publications Warehouse

    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

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2004-11-01

    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 1.5% of the observed sunlit surface. Nevertheless several clouds were followed during the encounter. The most prominent cloud, comprising the bulk of the cloud coverage, was located near the South Pole ( 87 degrees south, 0 degrees lon) and was roughly circular with a diameter of 600 ± 110 km. We tracked this feature over 11 images spanning a 13 hour period. In an attempt to quantify movement of the clouds in a Titanian windstream, we navigated the clouds using three distinct methods: 1) by tracking the brightest pixel in each cloud feature and employing SPICE kernel derived geometry, 2) similarly, by tracking the centroid of the main cloud feature, and 3) for the first time for an outer solar system body, by tracking relative to surface features seen in atmospheric spectral windows, most notably at 2.02 microns. The variable brightness of the most prominent cloud feature and its proximity to the South Pole of Titan make it rather difficult to track accurately. However, preliminary results obtained by tracking the centroid of the main cloud feature, as well as by tracking relative to surface features, indicate that there is little movement over a period of 13 hours. Specifically, we measure a mean windspeed of 0.5 ± 3.3 m/s in the prograde direction.

  18. Virginia Institute of Marine Science Faculty and Staff Check In Form 11/20/2012 This sheet must be signed by each person listed below and returned to the VIMS Mail Room to properly complete the

    E-print Network

    Swaddle, John

    Middle Suffix Spouses Name Home Phone Office Phone Cell Phone Home Mailing Address e-mail VIMS Mail for Surplus and unwanted equipment. Facilities Management Briefing on Pool Vehicle Usage, maintenance contact

  19. NASA Wavelength Digital Library

    NSDL National Science Digital Library

    The NASA Wavelength website serves as a "pathway into a digital collection of Earth and space science resources for educators of all levels." These resources have been developed through funding from the NASA Science Mission Directorate and aim to answer some important questions like, "How do planets and life originate?" and "Are we alone?" From the homepage, visitors can use the Browse our Collections feature to find worksheets, classroom activities, and more. The site also includes an Image of the Day, which brings together a wonderful trove of images collected by NASA over the years. Moving on to Data & Images, visitors will find a fine annotated list of resources, ranging from AstroPix to the Solar Dynamics Observatory Gallery, that contains high-quality images and data sets for classroom use. The Strandmaps area should not be missed; the tools here provide a way to find resources from online collections that relate to specific science and math concepts. It's a great resource and one that warrants close attention.

  20. Smithsonian Submillimeter Wavelength Array

    NASA Astrophysics Data System (ADS)

    Moran, James M.; Ho, Paul T.

    1994-06-01

    The SAO Submillimeter Wavelength Array is under construction and is expected to be ready for observations in late 1997. It will consist of six telescopes with baselines from 9 to 470 m and resolutions as fine as 0.'1. Eight receivers will cover all bands from 180 to 900 GHz in linear polarization; two orthogonal polarizations will be available at 350 GHz. Multiyear site testing on Mauna Kea shows that the precipitable water vapor is less than 1 mm for 17% of the total time, and the rms phase fluctuations on a baseline of 100 m are less than 55micrometers for 25% of the total time. The configuration of the array will be optimized to provide nearly uniform coverage in the uv plane within a circular boundary for an instantaneous observation of a source at the zenith. To achieve this distribution, the antennas will be placed along the sides of Reuleaux triangles. The basic electronic architecture follows conventional practice in radio interferometry and involves heterodyne frequency conversion. The correlator-spectrometer will have 92000 spectral channels (6144 lags per baseline) and will be able to provide 1.6-MHz resolution for a total bandwidth of 4 GHz. There were several significant design changes in the past year: a sixth mirror was added to the optical path in each antenna; the antenna configuration was changed to four tangential rings rather than four concentric rings; the correlator rings; the correlator clock rate was increased from 40 to 52 MHz and the IF conversion scheme was changed from a single-sideband conversion to two conventional mixer conversions, in order to improve the image rejection.

  1. Short wavelength chemical laser status update

    NASA Astrophysics Data System (ADS)

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

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

  2. 900 1000 1100 1200 Wavelength ()

    E-print Network

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

  3. Power-independent wavelength determination by hot carrier collection in metal-insulator-metal devices

    NASA Astrophysics Data System (ADS)

    Wang, Fuming; Melosh, Nicholas A.

    2013-04-01

    Wavelength separation and detection is generally performed by spatial dispersal of incident light onto separate detectors, or by appropriate wavelength-selective filters. Here we demonstrate direct wavelength determination of monochromatic light in a power-independent fashion with a single metal-insulator-metal device. This simple platform allows facile fabrication and scaling, and may be useful for on-chip optical communications. Although a single wavelength is power-independent, with two or more concurrent input signals, the output obeys a simple current sum rule, allowing the output to be tuned by choosing the input wavelengths and power. Finally, we demonstrate real-time deconvolution of three different wavelength asynchronous signals.

  4. Predominance of carbapenem-resistant Pseudomonas aeruginosa isolates carrying blaIMP and blaVIM metallo-?-lactamases in a major hospital in Costa Rica.

    PubMed

    Toval, Francisco; Guzmán-Marte, Anel; Madriz, Vivian; Somogyi, Teresita; Rodríguez, César; García, Fernando

    2015-01-01

    This study aimed to assess the molecular basis of the resistance to carbapenems in clinical isolates of Pseudomonas aeruginosa recovered from a tertiary-level health facility in San José, Costa Rica. A total of 198 non-duplicated isolates were evaluated for their susceptibility to ?-lactams, aminoglycosides and fluoroquinolones. The production of metallo-?-lactamases (MBLs), the presence of MBL encoding genes (blaIMP, blaVIM and blaGIM-1) and the occurrence of these genes within class 1 integrons were investigated. In addition, an ERIC2 PCR fingerprinting method was used to elucidate the distribution of the detected MBL genes within the strain collection. Of the 198 isolates tested, 125 (63.1?%) were categorized as carbapenem-resistant. The majority (88.8?%) of the carbapemen-resistant isolates also showed resistance to ceftazidime, cefepime, aztreonam, ticarcillin/clavulanic acid, amikacin, gentamicin, tobramycin, ciprofloxacin and gatifloxacin. Among the carbapenem-resistant isolates, 102 (81.6?%) showed MBL activity. Strikingly, both blaIMP and blaVIM genes were simultaneously detected in most (94.1?%) of the 102 MBL producers. Five carbapenem-resistant MBL producers were positive only for blaIMP genes. Almost 70?% of the isolates examined harboured the intI1 gene, accompanied by the sul1 and qacE?1 genes in 136 (99?%) and 122 (89?%) isolates, respectively. The majority (94.4?%) of the carbapenem-resistant isolates carried the intI1 gene, in contrast to 26?% of the carbapenem-susceptible isolates. Ninety-three out of 96 (96.9?%) isolates carrying both blaIMP and blaVIM genes also harboured the intI1, sul1 and qacE?1 genes. Gene cassettes from carbapenem-susceptible and MBL-negative carbapenem-resistant isolates encoded aminoglycoside-resistance enzymes (aadA2, aadA4 and aadA6) as well as orfD and qacF genes. RAPD analysis distributed 126 of the isolates in 29 clusters. Eighty of the 90 blaIMP (+) blaVIM (+) isolates were sorted into 16 different clusters, suggesting that the blaIMP and blaVIM genes detected were located within a genetic element capable of lateral transfer. Carbapenem-resistant MBL-positive isolates were recovered from almost all hospital wards and were over-represented in samples obtained from the surgical emergency and intensive care therapy units. Remarkably, three carbapenem-resistant isolates, exhibiting MBL activity and carrying both blaIMP and blaVIM genes, were recovered from outpatients. Sequence analysis of both bla genes in various isolates revealed that they correspond to the alleles blaIMP-18 and blaVIM-2. To our knowledge, this is the first report of the combination of two metallo-?-lactamases encoded by the blaIMP-18 and blaVIM-2 genes in P. aeruginosa. PMID:25355933

  5. DNA methylation analysis of SFRP2, GATA4/5, NDRG4 and VIM for the detection of colorectal cancer in fecal DNA.

    PubMed

    Lu, Hongna; Huang, Shiliang; Zhang, Xie; Wang, Danping; Zhang, Xuesong; Yuan, Xiaogang; Zhang, Qiubo; Huang, Zhigang

    2014-10-01

    Aberrantly methylated genes are increasingly being established as biomarkers for the detection of colorectal cancer (CRC). In the present study, the methylation levels of the secreted frizzled-related protein gene 2 (SFRP2), GATA binding protein 4/5 (GATA4/5), N-Myc downstream-regulated gene 4 (NDRG4) and vimentin (VIM) promoters were evaluated for their use as markers in the noninvasive detection of CRC. Methylation-specific polymerase chain reaction was performed to analyze promoter CpG methylation of SFRP2, GATA4/5, NDRG4 and VIM in the fecal DNA of 56 patients with CRC and 40 individuals exhibiting normal colonoscopy results. Promoter methylation levels of SFRP2, GATA4/5, NDRG4 and VIM in CRC patients were 57.1% (32/56), 42.9% (24/56), 83.9% (47/56), 28.6% (16/56) and 41.1% (23/56), respectively. Furthermore, the specificity of the genes were 90.0% (4/40), 95.0% (2/40), 82.5% (7/40), 97.5% (4/40) and 85.0% (6/40), respectively. The overall sensitivity of detection for fecal DNA with at least one methylated gene was 96.4% (54/56) in CRC patients. By contrast, only 14 of the 40 normal individuals exhibited methylated DNA in the aforementioned promoter regions. Methylation of the SFRP2, GATA4/5, NDRG4 and VIM promoters in fecal DNA is associated with the presence of colorectal tumors. Therefore, the detection of aberrantly methylated DNA in fecal samples may present a promising, noninvasive screening method for CRC. PMID:25202404

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

    Microsoft Academic Search

    Frank Sczerzenie; Graeme Paul; Clarence Belden

    2011-01-01

    Inclusion content is important for the mechanical behavior and performance of Nitinol wires, particularly in fatigue-rated\\u000a devices. The purpose of this work was to make a quantitative comparison between inclusion populations in cold drawn wires\\u000a and the precursor populations in hot-rolled rod coil. Inclusion content was examined in a series of VIM-VAR alloys with different\\u000a transformation temperatures (TTR) controlled by

  7. Similar frequencies of Pseudomonas aeruginosa isolates producing KPC and VIM carbapenemases in diverse genetic clones at tertiary-care hospitals in Medellín, Colombia.

    PubMed

    Vanegas, Johanna M; Cienfuegos, Astrid V; Ocampo, Ana M; López, Lucelly; del Corral, Helena; Roncancio, Gustavo; Sierra, Patricia; Echeverri-Toro, Lina; Ospina, Sigifredo; Maldonado, Natalia; Robledo, Carlos; Restrepo, Andrea; Jiménez, J Natalia

    2014-11-01

    Carbapenem-resistant Pseudomonas aeruginosa has become a serious health threat worldwide due to the limited options available for its treatment. Understanding its epidemiology contributes to the control of antibiotic resistance. The aim of this study was to describe the clinical and molecular characteristics of infections caused by carbapenem-resistant P. aeruginosa isolates in five tertiary-care hospitals in Medellín, Colombia. A cross-sectional study was conducted in five tertiary-care hospitals from June 2012 to March 2014. All hospitalized patients infected by carbapenem-resistant P. aeruginosa were included. Clinical information was obtained from medical records. Molecular analyses included PCR for detection of bla(VIM), bla(IMP), bla(NDM), bla(OXA-48), and bla(KPC) genes plus pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST) for molecular typing. A total of 235 patients were enrolled: 91.1% of them were adults (n = 214), 88.1% (n = 207) had prior antibiotic use, and 14.9% (n = 35) had urinary tract infections. The bla(VIM-2) and bla(KPC-2) genes were detected in 13.6% (n = 32) and 11.5% (n = 27), respectively, of all isolates. Two isolates harbored both genes simultaneously. For KPC-producing isolates, PFGE revealed closely related strains within each hospital, and sequence types (STs) ST362 and ST235 and two new STs were found by MLST. With PFGE, VIM-producing isolates appeared highly diverse, and MLST revealed ST111 in four hospitals and five new STs. These results show that KPC-producing P. aeruginosa is currently disseminating rapidly and occurring at a frequency similar to that of VIM-producing P. aeruginosa isolates (approximately 1:1 ratio) in Medellín, Colombia. Diverse genetic backgrounds among resistant strains suggest an excessive antibiotic pressure resulting in the selection of resistant strains. PMID:25210071

  8. Molecular characterisation and diversity in Enterobacter cloacae from Edinburgh and Egypt carrying bla(CTX-M-14) and bla(VIM-4) ?-lactamase genes.

    PubMed

    Dimude, J U; Amyes, S G B

    2013-06-01

    The purpose of this study was to compare the carbapenemases and extended-spectrum ?-lactamases (ESBLs) associated with resistance, the genetic environment of these genes, and their location on plasmids among Enterobacter cloacae isolates from Edinburgh (UK) and Egypt. Nine E. cloacae isolates were obtained from Egypt (n=3) and Edinburgh (n=6). Antimicrobial susceptibility testing was performed by agar dilution. Molecular detection of carbapenemase genes, blaCTX-M-14 and the presence of integron structures was done by PCR and sequencing. Genotyping of the strains was performed by pulsed-field gel electrophoresis (PFGE) with XbaI restriction. Plasmids were extracted to determine the location of the resistance genes. PCR sequencing revealed that all of the isolates carried the blaCTX-M-14 ESBL gene, whilst two isolates also carried the blaVIM-4 metallo-?-lactamase gene. The blaCTX-M-14 genes in two isolates were associated with the ISEcp1 transposase. Analysis of the integrons found an intI1 integron associated with the complex ISCR1. The blaVIM-4 gene was identified in the form of a gene cassette within the class 1 integron, followed downstream by the resistance genes aacA7, dfrA1 and aadA2. PFGE revealed genetic relatedness among six isolates, whereas the others were diverse although related. Plasmid analysis revealed a single plasmid carrying both blaVIM-4 and blaCTX-M-14. In conclusion, the presence of insertion sequence ISEcp1 upstream of blaCTX-M-14 suggests its involvement in the expression and mobilisation of this gene. Linked carriage of blaVIM-4 and blaCTX-M-14 on the same plasmid in E. cloacae results in resistance to all ?-lactams and limits antibiotic treatment options. PMID:23622881

  9. DNA methylation analysis of SFRP2, GATA4/5, NDRG4 and VIM for the detection of colorectal cancer in fecal DNA

    PubMed Central

    LU, HONGNA; HUANG, SHILIANG; ZHANG, XIE; WANG, DANPING; ZHANG, XUESONG; YUAN, XIAOGANG; ZHANG, QIUBO; HUANG, ZHIGANG

    2014-01-01

    Aberrantly methylated genes are increasingly being established as biomarkers for the detection of colorectal cancer (CRC). In the present study, the methylation levels of the secreted frizzled-related protein gene 2 (SFRP2), GATA binding protein 4/5 (GATA4/5), N-Myc downstream-regulated gene 4 (NDRG4) and vimentin (VIM) promoters were evaluated for their use as markers in the noninvasive detection of CRC. Methylation-specific polymerase chain reaction was performed to analyze promoter CpG methylation of SFRP2, GATA4/5, NDRG4 and VIM in the fecal DNA of 56 patients with CRC and 40 individuals exhibiting normal colonoscopy results. Promoter methylation levels of SFRP2, GATA4/5, NDRG4 and VIM in CRC patients were 57.1% (32/56), 42.9% (24/56), 83.9% (47/56), 28.6% (16/56) and 41.1% (23/56), respectively. Furthermore, the specificity of the genes were 90.0% (4/40), 95.0% (2/40), 82.5% (7/40), 97.5% (4/40) and 85.0% (6/40), respectively. The overall sensitivity of detection for fecal DNA with at least one methylated gene was 96.4% (54/56) in CRC patients. By contrast, only 14 of the 40 normal individuals exhibited methylated DNA in the aforementioned promoter regions. Methylation of the SFRP2, GATA4/5, NDRG4 and VIM promoters in fecal DNA is associated with the presence of colorectal tumors. Therefore, the detection of aberrantly methylated DNA in fecal samples may present a promising, noninvasive screening method for CRC. PMID:25202404

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

    USGS Publications Warehouse

    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

    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.

  11. AWG Filter for Wavelength Interrogator

    NASA Technical Reports Server (NTRS)

    Black, Richard J. (Inventor); Costa, Joannes M. (Inventor); Faridian, Fereydoun (Inventor); Moslehi, Behzad (Inventor); Sotoudeh, Vahid (Inventor)

    2015-01-01

    A wavelength interrogator is coupled to a circulator which couples optical energy from a broadband source to an optical fiber having a plurality of sensors, each sensor reflecting optical energy at a unique wavelength and directing the reflected optical energy to an AWG. The AWG has a detector coupled to each output, and the reflected optical energy from each grating is coupled to the skirt edge response of the AWG such that the adjacent channel responses form a complementary pair response. The complementary pair response is used to convert an AWG skirt response to a wavelength.

  12. Multiple-wavelength tunable laser

    NASA Technical Reports Server (NTRS)

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

    2010-01-01

    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.

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

    USGS Publications Warehouse

    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

    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.

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

    USGS Publications Warehouse

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

    2008-01-01

    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.

  15. The structural and functional basis of the p97/valosin-containing protein (VCP)-interacting motif (VIM): mutually exclusive binding of cofactors to the N-terminal domain of p97.

    PubMed

    Hänzelmann, Petra; Schindelin, Hermann

    2011-11-01

    The AAA (ATPase associated with various cellular activities) ATPase p97, also referred to as valosin-containing protein (VCP), mediates essential cellular processes, including ubiquitin-dependent protein degradation, and has been linked to several human proteinopathies. p97 interacts with multiple cofactors via its N-terminal (p97N) domain, a subset of which contain the VCP-interacting motif (VIM). We have determined the crystal structure of the p97N domain in complex with the VIM of the ubiquitin E3 ligase gp78 at 1.8 ? resolution. The ?-helical VIM peptide binds into a groove located in between the two subdomains of the p97N domain. Interaction studies of several VIM proteins reveal that these cofactors display dramatically different affinities, ranging from high affinity interactions characterized by dissociation constants of ?20 nm for gp78 and ANKZF1 to only weak binding in our assays. The contribution of individual p97 residues to VIM binding was analyzed, revealing that identical substitutions do not affect all cofactors in the same way. Taken together, the biochemical and structural studies define the framework for recognition of VIM-containing cofactors by p97. Of particular interest to the regulation of p97 by its cofactors, our structure reveals that the bound ?-helical peptides of VIM-containing cofactors overlap with the binding site for cofactors containing the ubiquitin regulatory X (UBX) domain present in the UBX protein family or the ubiquitin-like domain of NPL4 as further corroborated by biochemical data. These results extend the concept that competitive binding is a crucial determinant in p97-cofactor interactions. PMID:21914798

  16. Towards short wavelengths FELs workshop

    SciTech Connect

    Ben-Zvi, I.; Winick, H.

    1993-12-01

    This workshop was caged because of the growing perception in the FEL source community that recent advances have made it possible to extend FEL operation to wavelengths about two orders of magnitude shorter than the 240 nm that has been achieved to date. In addition short wavelength FELs offer the possibilities of extremely high peak power (several gigawatts) and very short pulses (of the order of 100 fs). Several groups in the USA are developing plans for such short wavelength FEL facilities. However, reviewers of these plans have pointed out that it would be highly desirable to first carry out proof-of-principle experiments at longer wavelengths to increase confidence that the shorter wavelength devices will indeed perform as calculated. The need for such experiments has now been broadly accepted by the FEL community. Such experiments were the main focus of this workshop as described in the following objectives distributed to attendees: (1) Define measurements needed to gain confidence that short wavelength FELs will perform as calculated. (2) List possible hardware that could be used to carry out these measurements in the near term. (3) Define a prioritized FEL physics experimental program and suggested timetable. (4) Form collaborative teams to carry out this program.

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

    E-print Network

    Sromovsky, Lawrence; Fry, Patrick

    2015-01-01

    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 microns to 3.1 microns and need the third component to fill in the sharp ammonia ice absorption peak near 2.96 microns. 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 coa...

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

    USGS Publications Warehouse

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

    2009-01-01

    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.

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

    USGS Publications Warehouse

    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

    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.

  20. An integrated wavelength locker for waveguide DEMUXes

    Microsoft Academic Search

    E. S. Koteles; J. J. He; B. Lamontagne; L. Erickson; A. Delage

    1999-01-01

    A simple technique for precisely monitoring a reference wavelength in order to lock the wavelength channels of a waveguide demultiplexer is proposed and experimentally verified. It incorporates a differential wavelength monolithically integrated on the DEMUX

  1. A wavelength-convertible optical network

    Microsoft Academic Search

    Kuo-Chun Lee; V. O. K. Li

    1993-01-01

    Wavelength-division multiplexing (WDM) is emerging as the dominant technology in future all-optical networks. To efficiently use the wavelengths, wavelength converters are employed for a circuit-switched optical network in which a circuit can change its wavelength to resolve wavelength conflicts and to reuse the wavelengths. To improve the efficiency, a few converters are provided and shared by the incoming circuits in

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

    USGS Publications Warehouse

    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

    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.

  3. Six Years of Fermi-LAT and Multi-Wavelength Monitoring of the Broad-Line Radio Galaxy 3c 120: Jet Dissipation At Sub-Parsec Scales from the Central Engine

    NASA Astrophysics Data System (ADS)

    Tanaka, Y. T.; Doi, A.; Inoue, Y.; Cheung, C. C.; Stawarz, L.; Fukazawa, Y.; Gurwell, M. A.; Tahara, M.; Kataoka, J.; Itoh, R.

    2015-02-01

    We present multi-wavelength monitoring results for the broad-line radio galaxy 3C 120 in the MeV/GeV, sub-millimeter, and 43 GHz bands over 6 yr. Over the past 2 yr, the Fermi-Large Area Telescope sporadically detected 3C 120 with high significance and the 230 GHz data also suggest an enhanced activity of the source. After the MeV/GeV detection from 3C 120 in MJD 56240–56300, 43 GHz Very Long Baseline Array (VLBA) monitoring revealed a brightening of the radio core, followed by the ejection of a superluminal knot. Since we observed the ?-ray and VLBA phenomena in temporal proximity to each other, it is naturally assumed that they are physically connected. This assumption was further supported by the subsequent observation that the 43 GHz core brightened again after a ?-ray flare occurred around MJD 56560. We can then infer that the MeV/GeV emission took place inside an unresolved 43 GHz core of 3C 120 and that the jet dissipation occurred at sub-parsec distances from the central black hole (BH), if we take the distance of the 43 GHz core from the central BH as ˜0.5 pc, as previously estimated from the time lag between X-ray dips and knot ejections. Based on our constraints on the relative locations of the emission regions and energetic arguments, we conclude that the ? rays are more favorably produced via the synchrotron self-Compton process, rather than inverse Compton scattering of external photons coming from the broad line region or hot dusty torus. We also derived the electron distribution and magnetic field by modeling the simultaneous broadband spectrum.

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

    NASA Technical Reports Server (NTRS)

    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

    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.

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

    USGS Publications Warehouse

    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

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2011-07-01

    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.

  7. Analysis of Titan CH 4 3.3 ?m upper atmospheric emission as measured by Cassini/VIMS

    NASA Astrophysics Data System (ADS)

    García-Comas, Maya; López-Puertas, Manuel; Funke, Bernd; Dinelli, Bianca M.; Luisa Moriconi, Maria; Adriani, Alberto; Molina, Antonio; Coradini, Angioletta

    2011-08-01

    After molecular nitrogen, methane is the most abundant species in Titan's atmosphere and plays a major role in its energy budget and its chemistry. Methane has strong bands at 3.3 ?m emitting mainly at daytime after absorption of solar radiation. This emission is strongly affected by non-local thermodynamic equilibrium (non-LTE) in Titan's upper atmosphere and, hence, an accurate modeling of the non-LTE populations of the emitting vibrational levels is necessary for its analysis. We present a sophisticated and extensive non-LTE model which considers 22 CH 4 levels and takes into account all known excitation mechanisms in which they take part. Solar absorption is the major excitation process controlling the population of the v3-quanta levels above 1000 km whereas the distribution of the vibrational energy within levels of similar energy through collisions with N 2 is also of importance below that altitude. CH 4-CH 4 vibrational exchange of v4-quanta affects their population below 500 km. We found that the ?3 ? ground band dominates Titan's 3.3 ?m daytime limb radiance above 750 km whereas the ?3 + ?4 ? ?4 band does below that altitude and down to 300 km. The ?3 + ?2 ? ?2, the 2 ?3 ? ?3, and the 13CH 4?3 ? ground bands each contribute from 5% to 8% at regions below 800 km. The ?3 + 2 ?4 ? 2 ?4and ?2 + ?3 + ?4 ? ?2 + ?4 bands each contribute from 2% to 5% below 650 km. Contributions from other CH 4 bands are negligible. We have used the non-LTE model to retrieve the CH 4 abundance from 500 to 1100 km in the southern hemisphere from Cassini-VIMS daytime measurements near 3.3 ?m. Our retrievals show good agreement with previous measurements and model results, supporting a weak deviation from well mixed values from the lower atmosphere up to 1000 km.

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

    NASA Astrophysics Data System (ADS)

    Sczerzenie, Frank; Paul, Graeme; Belden, Clarence

    2011-07-01

    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.

  9. Evolution of a Dark Anti-Cyclone on Saturn Associated with the Great Lightning Storm of 2010/2011 Through the Eyes of Cassini/VIMS

    NASA Astrophysics Data System (ADS)

    Momary, Thomas W.; Baines, K. H.; Brown, R. H.; Buratti, B. J.; Clark, R. N.; Nicholson, P. D.; Sotin, C.

    2012-10-01

    A massive dark anti-cyclonic storm system on Saturn spanning some 7? of longitude and 2? of latitude was observed by Cassini/VIMS at a planetocentric latitude of 37? on 4 January 2012 and 26 January 2012. During this time, it drifted some 54? of longitude at a speed of 23.1 ± 0.2 m/s prograde, a drift speed which correlates well with the canonical Voyager (and VIMS) wind profiles for Saturn at this latitude. The spot also drifted northward during this time by 1? and became noticeably "squished" in morphology. Using this drift rate and extrapolating backward, we find that the position corresponds to the large (> 5,000 km) anti-cyclone observed by VIMS on 11 May 2011 at 35.4? latitude (pc) and 49.4? W. longitude. This would represent 8 months of observation of this titanic feature, which was associated with the major lightning storm of 2010-2011, following the spot as it changed in size and morphology and drifted northward. The spot underwent a dramatic shift in shape in the 3 weeks of January, changing from roughly oval to a highly elongated pancake shape as it apparently bumped up against the dark band at 40? latitude and experienced a powerful shear. The evolution suggests that we are watching the death throes of this feature in our most recent observations. Finally, the dark spot was darker than surrounding regions in May 2011 and maintained its dark color across all pseudo-continua from 1.0 to 4.0 ?m between May 2011 and early January 2012.

  10. Astronomical Images in Different Wavelengths

    NSDL National Science Digital Library

    2004-02-20

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

  11. Solid colloidal optical wavelength filter

    DOEpatents

    Alvarez, Joseph L. (Boulder, CO)

    1992-01-01

    A solid colloidal optical wavelength filter includes a suspension of spheal particles dispersed in a coagulable medium such as a setting plastic. The filter is formed by suspending spherical particles in a coagulable medium; 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.

  12. The Submillimeter Wavelength Array (SMA)

    Microsoft Academic Search

    J. M. Moran

    1996-01-01

    The Submillimeter Wavelength Array (SMA), is under construction and is expected to begin operations in 1998 on Mauna Kea, near the CSO and JCMT facilities. The array will consist initially of six 6--meter diameter antennas arranged on the sides of Reuleaux triangles. Four configurations will be available with diameters of approximately 24, 64, 171 and 470 m. Each antenna will

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

    NASA Astrophysics Data System (ADS)

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

    2013-09-01

    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.

  14. Evolution of possibly active regions on Titan using Cassini/VIMS data analysis

    NASA Astrophysics Data System (ADS)

    Solomonidou, Anezina; Coustenis, Athena; Hirtzig, Mathieu; Bratsolis, Emmanuel; Drossart, Pierre; Bampasidis, Georgios; Kyriakopoulos, Konstantinos; Le Mouélic, Stephane; Rodriguez, Sebastien; Jaumann, Ralf; Stephan, Katrin; Lopes, Rosaly M. C.; Sotin, Christophe; Brown, Robert H.; Stamatelopoulou-Seymour, Karen; Moussas, Xenophon

    2013-04-01

    We present a study of Titan's complex geology with a focus on the satellite's surface regions that are showing spectral variations with time possibly linked to geological activity. We apply a statistical method, the Principal Component Analysis (PCA) [1] and a radiative transfer method (RT) [1,2] on three potentially 'active' regions on Titan, i.e. surface areas possibly subject to change over time (in brightness and/or in color etc.), namely Tui Regio (20°S, 130°W), a 1,500-km long flow-like figure, Hotei Regio (26°S, 78°W), a 700-km wide volcanic-like terrain, and Sotra Facula (15°S, 42°W), a 235-km in diameter area. With our PCA method we manage to isolate regions of distinct spectral response in all data available for our three study areas. Then, with our follow-up radiative transfer code we retrieve the surface albedo of the isolated regions with respect to the Huygens landing site albedo, which we use as a reference region and we compare them. Using this double procedure, we study the temporal surface variations of the three regions witnessing albedo changes with time for Tui Regio from 2005-2009 (darkening) and Sotra Facula from 2005-2006 (brightening) at all wavelengths. Hotei Regio has been suggested to present brightness variations over a two-year period (2004-2005) by Nelson et al. 2009 [3]. However, we find that the to-date available observations of that region present issues (geometry, resolution) that prevent an accurate application of our radiative transfer model to infer surface information with the desired accuracy. Therefore, we do not detect any significant surface albedo variations over time from 2004 and until 2009 given the uncertainties involved. The surface albedo variations, which we currently investigate in terms of chemical composition, and the volcanic-like features such as calderas, domes and lobate flows, which are present within the regions as shown by RADAR data analysis [e.g. 4], suggest that these features are compatible with internal phenomena such as cryovolcanism. Another study focusing on these areas suggests that Tui Regio and Hotei Regio could be paleolake clusters [5]. In the future, considering that the extracted surface albedos contain information on the chemical composition of the regions and their nature, we plan to better evaluate the temporal changes and to associate chemical composition inferences with morphological information to determine the nature of these regions. References: [1] Solomonidou, A., et al.: in prep. [2] Hirtzig, M., et al.: submitted to Icarus. [3] Nelson, R., et al.: Icarus 199, 429-441, 2009. [4] Lopes, R.M.C., et al.: JGR, in press. [5] Moore, J.M., and Howard, A.D.: GRL 37, L22205, 2010.

  15. Far-field measurements of short-wavelength surface plasmons

    NASA Astrophysics Data System (ADS)

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

    2015-03-01

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

  16. Short wavelength chemical laser development

    NASA Astrophysics Data System (ADS)

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

    1992-07-01

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

  17. Wavelength-multiplexed entanglement distribution

    NASA Astrophysics Data System (ADS)

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

    2010-08-01

    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.

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

    PubMed

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

    2014-05-01

    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

  19. Dry friction between laser-patterned surfaces: Role of alignment, structural wavelength and

    E-print Network

    Mueser, Martin

    1 Dry friction between laser-patterned surfaces: Role of alignment, structural wavelength.gachot@mx.uni-saarland.de Abstract The ability to tune friction by tailoring surface topographies at micron length scales friction between laser-textured surfaces. Line-like laser patterns with varying structural wavelengths

  20. Multi-wavelength study of MGRO J2019+37

    NASA Astrophysics Data System (ADS)

    Hou, Chao; Chen, Song-Zhan; Yuan, Qiang; Cao, Zhen; He, Hui-Hai; Sheng, Xiang-Dong

    2014-08-01

    MGRO J2019+37, within the Cygnus region, is a bright extended source revealed by Milagro at 12-35 TeV. This source is almost as bright as the Crab Nebula in the northern sky, but is not confirmed by ARGO-YBJ around the TeV scale. Up to now, no obvious counterpart at low energy wavelengths has been found. Hence, MGRO J2019+37 is a rather mysterious object and its VHE ?-ray emission mechanism is worth investigating. In this paper, a brief summary of the multi-wavelength observations from radio to ?-rays is presented. All the available data from XMM-Newton and INTEGRAL at X-ray, and Fermi-LAT at ?-ray bands, are used to get constraints on its emission flux at low energy wavelengths. Then, its possible counterparts and the VHE emission mechanism are discussed.

  1. Wavelength dependence of the apparent diameter of retinal blood vessels

    NASA Astrophysics Data System (ADS)

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

    2005-04-01

    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.

  2. Continuously wavelength tunable high pressure CO2 lasers

    NASA Astrophysics Data System (ADS)

    von Bergmann, Hubertus; Morkel, Francois

    2015-02-01

    Results obtained from a small discharge cross section (10×10 mm), high pressure (10 bar) TE CO2 laser are presented demonstrating continuous wavelength tunability of the laser. Two arbitrary wavelength regions in the 9P and 10P branches are chosen to demonstrate the continuous tunability of the laser wavelength. Furthermore stability of the laser output is demonstrated over extended periods of operation. Other output parameters of the high pressure laser such as temporal pulse profile and peak pulse power were also measured. Preliminary results will be presented of a discharge system scaled to larger discharge cross sections intended for high pressure amplifiers in ultra short pulse terawatt laser systems. Electrode separations of up to 50 mm have been investigated with measured discharge widths of 80 mm. The system has been operated at gas pressures of up to 3.5 bar with various CO2 laser gas mixtures. Discharge stability studies and gain measurements are reported.

  3. Measurement of thin films using very long acoustic wavelengths

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

    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.

  4. Compact silicon photonic wavelength-tunable laser diode with ultra-wide wavelength tuning range

    NASA Astrophysics Data System (ADS)

    Kita, Tomohiro; Tang, Rui; Yamada, Hirohito

    2015-03-01

    We present a wavelength-tunable laser diode with a 99-nm-wide wavelength tuning range. It has a compact wavelength-tunable filter with high wavelength selectivity fabricated using silicon photonics technology. The silicon photonic wavelength-tunable filter with wide wavelength tuning range was realized using two ring resonators and an asymmetric Mach-Zehnder interferometer. The wavelength-tunable laser diode fabricated by butt-joining a silicon photonic filter and semiconductor optical amplifier shows stable single-mode operation over a wide wavelength range.

  5. Limits of long wavelength High Harmonic Generation

    E-print Network

    Bhardwaj, Siddharth

    2010-01-01

    Many researchers are pushing for long wavelength driver pulses for High Harmonic Generation (HHG). The advantage of longer wavelengths is that the cut-off of the harmonic spectrum can be increased without the need for large ...

  6. Wavelength tunable alexandrite regenerative amplifier

    SciTech Connect

    Harter, D.J.; Bado, P.

    1988-11-01

    We describe a wavelength tunable alexandrite regenerative amplifier which is used to amplify nanosecond slices from a single-frequency cw dye laser or 50-ps pulses emitted by a diode laser to energies in the 10-mJ range. The amplified 5-ns slices generated by the cw-pumped line narrowed dye laser are Fourier transform limited. The 50-ps pulses emitted by a gain-switched diode laser are amplified by more than 10 orders of magnitude in a single stage.

  7. Wavelength-Tunable Laser-Diode Interferometer

    Microsoft Academic Search

    Yukihiro Ishii

    1999-01-01

    Laser diodes (LDs) have been applied to a phase-measuring interferometer through the wavelength tunability of LDs by controlling their currents. Laser-diode interferometers based on a heterodyne technique are reviewed. A two-wavelength laser-diode interferometer is demonstrated with current control of dual LDs in opposite directions. A synthetic wavelength makes it possible to extend the range of interferometric measurements. The wavelength is

  8. Real-time Streaming Correlation for Long Wavelength Array (LWA) Radio Astronomy Applications

    E-print Network

    -scale interferometric radio telescope arrays. The Solution: PASI correlates 256, dual-polarized 50-100 KHz antennaReal-time Streaming Correlation for Long Wavelength Array (LWA) Radio Astronomy Applications

  9. LONG WAVELENGTH OBSERVATIONS OF HIGH GALACTIC LATITUDE DUST

    E-print Network

    George F. Smoot

    1995-05-03

    The properties of high latitude dust are of great interest to extragalactic astronomers and cosmologists. It is proposed here that essentially all high Galactic latitude interstellar dust is at a typical temperature of about 20~K (i.e. it is warm dust) and that if any cold high latitude interstellar dust exists, its emission at mm-wavelengths is less than 5\\%\\ of that from the primary component of warm dust observed by IRAS. Thus the IRAS maps reveal the high latitude dust of import. The crucial issue is how the emissivity of the dust scales with wavelength. The mm-wavelength emission in this warm dust only model is consistent with roughly a wavelength%, $\\lambda$, dependent emissivity $\\epsilon(\\lambda) \\propto \\lambda^{-1.5}$. Such a dependence has been observed in the infrared previously. What is new here is the proposal that this extends to the mm-wavelength region. Proceedings of Workshop on Molecules, Dust, & Backgrounds to be published in Planetary & Space Sciences

  10. Multiple wavelength light collimator and monitor

    NASA Technical Reports Server (NTRS)

    Gore, Warren J. (Inventor)

    2011-01-01

    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.

  11. Radar scattering laws and wavelength dependence of the lunar surface

    NASA Technical Reports Server (NTRS)

    Simpson, R. A.

    1978-01-01

    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.

  12. Emergence of a pandrug-resistant VIM-1-producing Providencia stuartii clonal strain causing an outbreak in a Greek intensive care unit.

    PubMed

    Douka, Evangelia; Perivolioti, Efstathia; Kraniotaki, Elena; Fountoulis, Kimon; Economidou, Foteini; Tsakris, Athanassios; Skoutelis, Athanassios; Routsi, Christina

    2015-05-01

    Here we describe an outbreak caused by a pandrug-resistant Providencia stuartii strain involving 15 critically ill patients in a Greek intensive care unit (ICU) during September-November 2011. All isolates harboured the blaVIM-1 gene and a class 1 integron structure of 1913 bp as well as blaSHV-5 and blaTEM-1. Pulsed-field gel electrophoresis (PFGE) demonstrated that isolates from all 15 patients belonged to a single P. stuartii clonal type. As all of the infected patients were hospitalised during overlapping time periods, horizontal intra-ICU transmission was considered as the main route for the dissemination of the outbreak strain. The outbreak ended following reinforcement of infection control measures, including implementation of additional barrier precautions for infected patients. PMID:25749199

  13. First description of NDM-1-, KPC-2-, VIM-2- and IMP-4-producing Klebsiella pneumoniae strains in a single Chinese teaching hospital.

    PubMed

    Liu, Y; Wan, L-G; Deng, Q; Cao, X-W; Yu, Y; Xu, Q-F

    2015-01-01

    A total of 180 non-duplicate carbapenem-resistant Klebsiella pneumoniae isolates were recovered from patients hospitalized between December 2010 and January 2012 at a Chinese hospital. Eight KPC-2, four NDM-1, one VIM-2, and five KPC-2 plus IMP-4 producers were identified and all were multidrug resistant due to the presence of other resistance determinants, including extended-spectrum ?-lactamases (CTX-M-15, SHV-12), 16S rRNA methylases (armA, rmtB) and plasmid-mediated quinolone-resistance determinants (qnrA, B, S, aac(6')-Ib-cr). Nine K. pneumoniae clones (Kpn-A1/ST395, Kpn-A3/ST11, Kpn-A2/ST134, Kpn-B/ST263, Kpn-C/ST37, Kpn-D/ST39, Kpn-E/ST1151, Kpn-F/ST890, Kpn-G/ST1153) were identified. bla KPC-2 was located on transferable ~65 kb IncL/M (ST395, ST11, ST134, ST39) and ~100 kb IncA/C (ST37, ST1153, ST890) plasmids, respectively. On the other hand, bla NDM-1 was associated with a ~70 kb IncA/C plasmid (ST263). However, non-typable plasmids of ~40 kb containing bla VIM-2 were detected in the ST1151 clone. This work reports the first co-occurrence of four diverse types of carbapenemase of K. pneumoniae clones from a single hospital in China. IncA/C, IncL/M, and other successful plasmids may be important for the dissemination of carbapenemases, producing a complex epidemiological picture. PMID:24762211

  14. Extensively Drug-Resistant Pseudomonas aeruginosa Isolates Containing blaVIM-2 and Elements of Salmonella Genomic Island 2: a New Genetic Resistance Determinant in Northeast Ohio

    PubMed Central

    Perez, Federico; Hujer, Andrea M.; Marshall, Steven H.; Ray, Amy J.; Rather, Philip N.; Suwantarat, Nuntra; Dumford, Donald; O'Shea, Patrick; Domitrovic, T. Nicholas J.; Salata, Robert A.; Chavda, Kalyan D.; Chen, Liang; Kreiswirth, Barry N.; Vila, Alejandro J.; Haussler, Susanne; Jacobs, Michael R.

    2014-01-01

    Carbapenems are a mainstay of treatment for infections caused by Pseudomonas aeruginosa. Carbapenem resistance mediated by metallo-?-lactamases (MBLs) remains uncommon in the United States, despite the worldwide emergence of this group of enzymes. Between March 2012 and May 2013, we detected MBL-producing P. aeruginosa in a university-affiliated health care system in northeast Ohio. We examined the clinical characteristics and outcomes of patients, defined the resistance determinants and structure of the genetic element harboring the blaMBL gene through genome sequencing, and typed MBL-producing P. aeruginosa isolates using pulsed-field gel electrophoresis (PFGE), repetitive sequence-based PCR (rep-PCR), and multilocus sequence typing (MLST). Seven patients were affected that were hospitalized at three community hospitals, a long-term-care facility, and a tertiary care center; one of the patients died as a result of infection. Isolates belonged to sequence type 233 (ST233) and were extensively drug resistant (XDR), including resistance to all fluoroquinolones, aminoglycosides, and ?-lactams; two isolates were nonsusceptible to colistin. The blaMBL gene was identified as blaVIM-2 contained within a class 1 integron (In559), similar to the cassette array previously detected in isolates from Norway, Russia, Taiwan, and Chicago, IL. Genomic sequencing and assembly revealed that In559 was part of a novel 35-kb region that also included a Tn501-like transposon and Salmonella genomic island 2 (SGI2)-homologous sequences. This analysis of XDR strains producing VIM-2 from northeast Ohio revealed a novel recombination event between Salmonella and P. aeruginosa, heralding a new antibiotic resistance threat in this region's health care system. PMID:25070102

  15. Wavelength comparison study for bioaerosol detection

    NASA Astrophysics Data System (ADS)

    Campbell, Steven D.; Tremblay, David P.; Daver, Freddie; Cousins, Daniel

    2005-05-01

    This paper reports on an investigation into optimal excitation and emission wavelengths for bioaerosol detection. Excitation/Emission Matrix (EEM) fluorescence data were gathered for a variety of materials, including biowarfare (BW) simulants, cell constituents, growth media and known interferents. These data were used to investigate multi-wavelength discrimination algorithms using pattern classification techniques. The results suggest that using two excitation wavelengths and narrower emission bands can improve discrimination between BW agents and interferents.

  16. Wavelength-doubling optical parametric oscillator

    DOEpatents

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

    2007-07-24

    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.

  17. Ronchi test with equivalent wavelength

    NASA Astrophysics Data System (ADS)

    García-A., Anmi; Granados-A., Fermín Solomon; Cornejo-R., Alejandro

    2010-02-01

    The Ronchi test has been consolidated as one of the most successful and powerful techniques applied to determine the quality of optical surfaces.5 In recent years, the development and availability of LCD's (Liquid Crystal Displays) have allowed the incorporation of LCD's instead of the traditional static ruling. The easy change of the characteristics of the fringes in the ruling, such as frequency, position, and geometrical form, transformed this technique into a dynamic test.1, 8 Its physical interpretation fully connected with a lateral sheared interferometer 5, 6 and some concepts and results associated with the interferometric concept of equivalent wavelenght have been applied in this proposal for the evaluation of optical surfaces. The procedure described here to evaluate an optical surface uses the Ronchi test with the equivalent wavelenght.6, 10 This is achieved by registering and computing Ronchigrams obtained by employing, separately, two distinct wavelengths. For a particular mirror, some results are shown in order to demonstrate the enhancement of the test with this proposal.

  18. Meter-wavelength VLBI. III - Pulsars

    NASA Technical Reports Server (NTRS)

    Vandenberg, N. R.; Clark, T. A.; Erickson, W. C.; Resch, G. M.; Broderick, J. J.

    1976-01-01

    Observations of pulsars, especially the Crab Nebula pulsar, made in very long baseline interferometry (VLBI) experiments are discussed. Based on a crude 144 MHz visibility curve which is consistent with a Gaussian brightness distribution, the measured visibilities at 196, 111, and 74 MHz were interpreted to yield apparent angular diameters (at half-power) of about 0.03 sec, 0.07 sec, and 0.18 sec, respectively. These sizes scale approximately as wavelength-squared, and the 74 MHz size agrees with recent observations using interplanetary scintillation techniques. The total flux densities lie on the extrapolation from higher frequencies of the pulsing flux densities. Variations in the total flux density up to 25 per cent were observed. A lack of fine structure other than the pulsar in the nebula is indicated by the simple visibility curves. The pulse shapes are similar to single-dish measurements at 196 MHz but reveal a steady, nonpulsing component at 111 MHz. The ratio of pulsing to total power was approximately equal to one-half but varied with time. It was found that four strong, low-dispersion pulsars were only slightly resolved.

  19. Athermal waveguides for optical communication wavelengths.

    PubMed

    Miloševi?, Milan M; Emerson, Neil G; Gardes, Frederic Y; Chen, Xia; Adikaari, A A D T; Mashanovich, Goran Z

    2011-12-01

    We report on the design, fabrication, and characterization of temperature insensitive strip silicon-on-insulator racetrack resonators. The influence of various parameters, such as waveguide width, waveguide height, ring radius, coupling length, ring gap, and operating wavelength, on temperature-dependent wavelength shift is examined. A resonant wavelength shift of 0.2 pm/K at a 1550 nm wavelength is measured for 335 nm × 220 nm waveguides. A significant reduction of waveguide propagation losses, improved ring Q value, and higher extinction ratio are obtained after overlaying the silicon waveguides with a polymer cladding. PMID:22139275

  20. Research with high-power short-wavelength lasers

    SciTech Connect

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

    1985-03-05

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

  1. Wavelength Calibration of Near-Infrared Spectra

    Microsoft Academic Search

    Kenneth H. Hinkle; Richard R. Joyce; Abigail Hedden; Lloyd Wallace; Rolf Engleman Jr.

    2001-01-01

    An atlas of a thorium-argon hollow cathode lamp in selected intervals of the 1-2.5 mum region is presented. Accurate wavelengths of the ~500 lines recorded are given in a table. This material is intended for wavelength calibration of near-infrared spectra and is especially critical for high-resolution work.

  2. Semiconductor laser with multiple lasing wavelengths

    DOEpatents

    Fischer, Arthur J.; Choquette, Kent D.; Chow, Weng W.

    2003-07-29

    A new class of multi-terminal vertical-cavity semiconductor laser components has been developed. These multi-terminal laser components can be switched, either electrically or optically, between distinct lasing wavelengths, or can be made to lase simultaneously at multiple wavelengths.

  3. Imaging Jupiter's Aurora at Visible Wavelengths

    Microsoft Academic Search

    Andrew P. Ingersoll; Ashwin R. Vasavada; Blane Little; Clifford D. Anger; Scott J. Bolton; Claudia Alexander; Kenneth P. Klaasen; W. Kent Tobiska

    1998-01-01

    On November 9, 1996 and again on April 2, 1997, the Galileo spacecraft's Solid State Imaging (SSI) camera targeted the northern auroral region of Jupiter. These observations represent (i) the first spatially resolved images of the jovian auroral oval either at visible wavelengths or on the nightside of the planet, (ii) the first image at visible wavelengths of an auroral

  4. External wavelength contention resolution for optical crossconnects

    E-print Network

    Wai, Ping-kong Alexander

    External wavelength contention resolution for optical crossconnects C.Y. Li and P.K.A. Wai outside the crossconnects (OXCs) in an external device to simplify the implemen- tation and deployment hardware and complicated engineering work. In many occasions, we observe that external wavelength

  5. Bibliography of short wavelength chemical laser research

    Microsoft Academic Search

    Glen P. Perram

    1993-01-01

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

  6. IUE data reduction: Wavelength determinations and line identifications using a VAX/750 computer

    NASA Technical Reports Server (NTRS)

    Davidson, J. P.; Bord, D. J.

    1982-01-01

    A fully automated, interactive system for determining the wavelengths of features in extracted IUE spectra is described. Wavelengths are recorded from video displays of expanded plots of individual orders using a movable cursor, and then corrected for IUE wavelength scale errors. The estimated accuracy of an individual wavelength in the final tabulation is 0.050 A. Such lists are ideally suited for line identification work using the method of wavelength coincidence statistics (WCS). The results of WCS studies of the ultraviolet spectra of the chemically peculiar (CP) stars iota Coronae Borealis and kappa Camcri. Aside from confirming a number of previously reported aspects of the abundance patterns in these stars, the searches produced some interesting, new discoveries, notably the presence of Hf in the spectrum of kappa Camcri. The implications of this work for theories designed to account for anomalous abundances in chemically peculiar stars are discussed.

  7. Use of two wavelengths in microscopic TV holography for nondestructive testing

    NASA Astrophysics Data System (ADS)

    Upputuri, Paul Kumar; Umapathy, Somasundaram; Pramanik, Manojit; Kothiyal, Mahendra Prasad; Nandigana, Krishna Mohan

    2014-11-01

    Single wavelength TV holography is a widely used whole-field noncontacting optical method for nondestructive testing (NDT) of engineering structures. However, with a single wavelength configuration, it is difficult to quantify the large amplitude defects due to the overcrowding of fringes in the defect location. In this work, we propose a two wavelength microscopic TV holography using a single-chip color charge-coupled device (CCD) camera for NDT of microspecimens. The use of a color CCD allows simultaneous acquisition of speckle patterns at two different wavelengths and makes the data acquisition as simple as that of the single wavelength case. For the quantitative measurement of the defect, an error compensating eight-step phase-shifted algorithm is used. The design of the system and a few experimental results on small-scale rough specimens are presented.

  8. A plasmonic metal grating wavelength splitter

    NASA Astrophysics Data System (ADS)

    Yu, Yue; Sun, Chen; Li, Junhao; Deng, Xiaoxu

    2015-01-01

    A plasmonic metal grating wavelength splitter is theoretically investigated and experimentally demonstrated. Based on the periodical waveguide theories, the negative real part of the propagation constant of surface plasmon polaritons (SPPs) (\\text{Re}?ft[? \\right]<0 ) in metal grating is derived in a wavelength range which is determined by the grating parameters. The transmission prohibition at the negative \\text{Re}?ft[? \\right] is utilized to realize the wavelength splitting by the metal grating with different grating periods and fill factors on the left and right half. The metal grating plasmonic splitter is simulated by the finite difference time domain simulation method, the characteristics of which are consistent well with theoretical predictions. The plasmonic wavelength splitter is fabricated by electron beam lithography and the ion beam etching process. The SPPs excited by an incident wavelength of 532 and 650?nm are experimentally split and observed under an optical microscope using a charge-coupled device camera.

  9. GHRS Cycle 5 Echelle Wavelength Monitor

    NASA Astrophysics Data System (ADS)

    Soderblom, David

    1995-07-01

    This proposal defines the spectral lamp test for Echelle A. It is an internal test which makes measurements of the wavelength lamp SC2. It calibrates the carrousel function, Y deflections, resolving power, sensitivity, and scattered light. The wavelength calibration dispersion constants will be updated in the PODPS calibration data base. This proposal defines the spectral lamp test for Echelle B. It is an internal test which makes measurements of the wavelength lamp SC2. It calibrates the carrousel function, Y deflections, resolving power, sensitivity, and scattered light. The wavelength calibration dispersion constants will be updated in the PODPS calibration data base. It will be run every 4 months. The wavelengths may be out of range according to PEPSI or TRANS. Please ignore the errors.

  10. The Circular Polarization of Sagittarius A* at Submillimeter Wavelengths

    NASA Astrophysics Data System (ADS)

    Muñoz, D. J.; Marrone, D. P.; Moran, J. M.; Rao, R.

    2012-02-01

    We report the first detections of circularly polarized emission at submillimeter wavelengths from the compact radio source and supermassive black hole candidate Sgr A* at a level of 1.2% ± 0.3% at 1.3 mm wavelength (230 GHz) and 1.6% ± 0.3% at 860 ?m (345 GHz) with the same handedness, left circular polarization (LCP), as observed at all lower frequencies (1.4-15 GHz). The observations, taken with the Submillimeter Array in multiple epochs, also show simultaneous linear polarization (LP) at both wavelengths of about 6%. These properties differ sharply from those at wavelengths longer than 1 cm (frequencies below 30 GHz), where weak circular polarization (CP) (~0.5%) dominates over LP, which is not detected at similar fractional limits. We describe an extensive set of tests to ensure the accuracy of our measurements. We find no CP in any other source, including the bright quasar 1924-292, which traces the same path on the sky as Sgr A* and therefore should be subject to identical systematic errors originating in the instrument frame. Since a relativistic synchrotron plasma is expected to produce little CP, the observed CP is probably generated close to the event horizon by the Faraday conversion process. We use a simple approximation to show that the phase shift associated with Faraday conversion can be nearly independent of frequency, a sufficient condition to make the handedness of CP independent of frequency. Because the size of the ? = 1 surface changes by more than an order of magnitude between 1.4 and 345 GHz, the magnetic field must be coherent over such scales to consistently produce LCP. To improve our understanding of the environment of SgrA* critical future measurements includes determining whether the Faraday rotation deviates from a ?2 dependence in wavelength and whether the circular and linear components of the flux density are correlated.

  11. THE CIRCULAR POLARIZATION OF SAGITTARIUS A* AT SUBMILLIMETER WAVELENGTHS

    SciTech Connect

    Munoz, D. J.; Moran, J. M. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Marrone, D. P. [Kavli Institute for Cosmological Physics, University of Chicago, 5640 South Ellis Avenue, Chicago, IL 60637 (United States); Rao, R., E-mail: dmunoz@cfa.harvard.edu [Submillimeter Array, Academia Sinica Institute of Astronomy and Astrophysics, 645 N. Aohoku Place, Hilo, HI 96720 (United States)

    2012-02-01

    We report the first detections of circularly polarized emission at submillimeter wavelengths from the compact radio source and supermassive black hole candidate Sgr A* at a level of 1.2% {+-} 0.3% at 1.3 mm wavelength (230 GHz) and 1.6% {+-} 0.3% at 860 {mu}m (345 GHz) with the same handedness, left circular polarization (LCP), as observed at all lower frequencies (1.4-15 GHz). The observations, taken with the Submillimeter Array in multiple epochs, also show simultaneous linear polarization (LP) at both wavelengths of about 6%. These properties differ sharply from those at wavelengths longer than 1 cm (frequencies below 30 GHz), where weak circular polarization (CP) ({approx}0.5%) dominates over LP, which is not detected at similar fractional limits. We describe an extensive set of tests to ensure the accuracy of our measurements. We find no CP in any other source, including the bright quasar 1924-292, which traces the same path on the sky as Sgr A* and therefore should be subject to identical systematic errors originating in the instrument frame. Since a relativistic synchrotron plasma is expected to produce little CP, the observed CP is probably generated close to the event horizon by the Faraday conversion process. We use a simple approximation to show that the phase shift associated with Faraday conversion can be nearly independent of frequency, a sufficient condition to make the handedness of CP independent of frequency. Because the size of the {tau} = 1 surface changes by more than an order of magnitude between 1.4 and 345 GHz, the magnetic field must be coherent over such scales to consistently produce LCP. To improve our understanding of the environment of SgrA* critical future measurements includes determining whether the Faraday rotation deviates from a {lambda}{sup 2} dependence in wavelength and whether the circular and linear components of the flux density are correlated.

  12. The Submillimeter Wavelength Array (SMA)

    NASA Astrophysics Data System (ADS)

    Moran, J. M.

    1996-05-01

    The Submillimeter Wavelength Array (SMA), is under construction and is expected to begin operations in 1998 on Mauna Kea, near the CSO and JCMT facilities. The array will consist initially of six 6--meter diameter antennas arranged on the sides of Reuleaux triangles. Four configurations will be available with diameters of approximately 24, 64, 171 and 470 m. Each antenna will be equipped with a cryostat at its Nasmyth focus and will accept eight receivers covering all useable bands from 230 to 850 GHz. The maximum angular resolution will vary from 0.4 to 0.1 '' over the frequency range. Signal processing will be performed on a special purpose XF correlator, which is based on a chip developed at the Haystack Observatory and the NASA/SERC for VLSI Design. The correlator will accept two channels (for either dual polarization or dual frequency operation) from each antenna of 2 GHz bandwidth each. The subchannel bandwidth is 104 MHz. Spectral resolutions as fine as 0.6 km/s will be available with full processing capacity. The Smithsonian Astrophysical Observatory is the general contractor for the project. The first antenna is expected to be assembled and ready for receiver installation in July 1996. The antennas have reflector backup structures constructed of carbon fiber tubes and steel nodes. Each primary reflector consists of 72 machined aluminum panels, which have rms accuracies of about 5 microns. The overall reflector surface is expected to have an rms accuracy of 12 microns. In the laboratory, receiver temperatures of 25, 30 and 65 K(DSB) have been achieved at 230, 345 and 460 GHz, respectively, for SIS mixer receivers with junctions fabricated at JPL. Initial interferometric tests on celestial sources are planned for early 1997 at the assembly site at Haystack Observatory in Westford, MA. An agreement for collaboration has been reached between SAO and the Institute of Astronomy and Astrophysics of the Academy of Science (Taiwan). ASIAA will initially provide two additional antennas to the array. Preparations are also being made to include the 15-m JCMT and 10-m CSO telescope in the array on a part time basis.

  13. A review of routing and wavelength assignment approaches for wavelength-routed optical wdm networks

    Microsoft Academic Search

    H. Zang; J. P. Jue; B. Mukherjee

    2000-01-01

    Abstract: This study focuses on the routing and wavelength assignment (RWA) problem in wavelength-routedoptical WDM networks. Most of the attention is devoted to such networks operating under the wavelengthcontinuity constraint, in which lightpaths are set up for connection requests between node pairs, and asingle lightpath must occupy the same wavelength on all of the links that it spans. In setting

  14. Wavelength Determination for Solar Features Observed by the EUV Imaging Spectrometer on Hinode

    SciTech Connect

    Brown,C.; Hara, H.; Kamio, S.; Feldman, U.; Seely, J.; Doschek, G.; Mariska, J.; Korendyke, C.; Lang, J.; Dere, K.

    2007-01-01

    A wavelength calibration of solar lines observed by the high resolution EUV Imaging Spectrometer (EIS) on the Hinode satellite is reported. Spectral features of the quiet sun and of two mildly active areas were measured and calibrated. A listing of the stronger observed lines with identification of the leading contributor ions is presented. 41 lines are reported, with 90% identified. Wavelength precisions (2{sigma}) of {+-}0.0031 Angstroms for the EIS short band and {+-}0.0029 Angstroms for the EIS long band are obtained. These lines, typical of 1-2x10{sup 6} K plasmas, are recommended as standards for the establishment of EIS wavelength scales. The temperature of EIS varies by about 1.5 C around the orbit and also with spacecraft pointing. The correlation of these temperature changes with wavelength versus pixel number scale changes is reported.

  15. 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

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

    2014-01-01

    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

  16. The Anticyclonic Eye of the Storm: Evolution of Saturn’s Great Storm Region and Associated Anticyclone as seen by Cassini/VIMS

    NASA Astrophysics Data System (ADS)

    Momary, Thomas W.; Baines, Kevin H.

    2014-11-01

    A massive storm system erupted in Saturn’s northern hemisphere in late 2010, ultimately sweeping clean the cloudy region previously occupied by the long-lived (> 5 years) String of Pearls feature. This latitude band has remained relatively cloud free (5 ?m bright) ever since, but for a massive anticyclonic oval storm system. We have observed this persistent feature with Cassini/VIMS over several years and find that it has oscillated latitudinally north and south in this stormy region. It was centered at 35.9° planetocentric latitude in May 2011, drifting northward to 37.8° in 2012, hovering around 37° through much of 2013, then settling southward to ~35.9° in 2014. It periodically bumps up against the dark band above it, even interacting with it in Aug. 2013. We measure a prograde drift speed of ~22 m/s in 2012, increasing as much as 60% as it drifted northward in 2013, then finally relaxing back to a more moderate ~15 m/s in July 2014 as the oval sagged southward, all consistent with the Voyager wind profile for these latitudes. The feature has evolved in morphology as well. It spanned 4.9° x 3.18° in 2011. By 2012-2013 it had elongated zonally and contracted latitudinally to span on average ~7.3° x ~2.9°, contracting further to an average ~5.5° x 2.9°. The oval has varied in terms of cloudiness, being ~90% 5-?m dark (obscured) in 2011, whereas by 2013 it was mostly bright (clear) with a thin dark edge, resembling a smoke ring. It is currently about half obscured and half bright. Since 2012, the storm latitude of ~33 - 38° N itself has remained remarkably clear, being much more 5-?m intense than anything on the planet. Preliminary results indicate however that it has begun to dim. Between early 2012 and 2014 it has steadily diminished in brightness relative to the nearby clouds above it by ~46%. We are continuing to monitor the evolution of this storm region and the related anticyclone over time with Cassini/VIMS.

  17. Wavelengths effective in induction of malignant melanoma

    SciTech Connect

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

    1993-07-15

    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.

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

    NASA Technical Reports Server (NTRS)

    Suematsu, Y.; Iga, K.

    1980-01-01

    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.

  19. Magic wavelengths for terahertz clock transitions

    NASA Astrophysics Data System (ADS)

    Zhou, Xiaoji; Xu, Xia; Chen, Xuzong; Chen, Jingbiao

    2010-01-01

    Magic wavelengths for laser trapping of boson isotopes of alkaline-earth metal atoms Sr, Ca, and Mg are investigated while considering terahertz clock transitions between the 3P0, 3P1, and 3P2 metastable triplet states. Our calculation shows that magic wavelengths for laser trapping do exist. This result is important because those metastable states have already been used to make accurate clocks in the terahertz frequency domain. Detailed discussions for magic wavelengths for terahertz clock transitions are given in this article.

  20. Multimode fiber optic wavelength division multiplexing

    NASA Technical Reports Server (NTRS)

    Spencer, J. L.

    1982-01-01

    Optical wavelength division multiplexing (WDM) systems, with signals transmitted on different wavelengths through a single optical fiber, can have increased bandwidth and fault isolation properties over single wavelength optical systems. Two WDM system designs that might be used with multimode fibers are considered and a general description of the components which could be used to implement the system are given. The components described are sources, multiplexers, demultiplexers, and detectors. Emphasis is given to the demultiplexer technique which is the major developmental component in the WDM system.

  1. Sub-wavelength focusing meta-lens.

    PubMed

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

    2013-03-25

    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

  2. Magic wavelengths for terahertz clock transitions

    SciTech Connect

    Zhou Xiaoji; Xu Xia; Chen Xuzong; Chen Jingbiao [School of Electronics Engineering and Computer Science, Peking University, Beijing 100871 (China)

    2010-01-15

    Magic wavelengths for laser trapping of boson isotopes of alkaline-earth metal atoms Sr, Ca, and Mg are investigated while considering terahertz clock transitions between the {sup 3}P{sub 0}, {sup 3}P{sub 1}, and {sup 3}P{sub 2} metastable triplet states. Our calculation shows that magic wavelengths for laser trapping do exist. This result is important because those metastable states have already been used to make accurate clocks in the terahertz frequency domain. Detailed discussions for magic wavelengths for terahertz clock transitions are given in this article.

  3. Optical amplification at the 1. 31 wavelength

    DOEpatents

    Cockroft, N.J.

    1994-02-15

    An optical amplifier operating at the 1.31 [mu]m wavelength for use in such applications as telecommunications, cable television, and computer systems is described. An optical fiber or other waveguide device is doped with both Tm[sup 3+] and Pr[sup 3+] ions. When pumped by a diode laser operating at a wavelength of 785 nm, energy is transferred from the Tm[sup 3+] ions to the Pr[sup 3+] ions, causing the Pr[sup 3+] ions to amplify at a wavelength of 1.31. 1 figure.

  4. Apparatus for shifting the wavelength of light

    DOEpatents

    McCulla, William H. (Oak Ridge, TN); Allen, Jr., John D. (Knoxville, TN)

    1983-01-01

    A light beam is reflected back and forth between a rotating body having a retroreflection corner at opposite ends thereof and a fixed mirror to change the wavelength of the light beam by the Doppler effect.

  5. Damping of long-wavelength kinetic alfven fluctuations: linear theory

    SciTech Connect

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

    2008-01-01

    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.

  6. The fabrication of millimeter-wavelength accelerating structures

    SciTech Connect

    Chou, P.J.; Bowden, G.B.; Copeland, M.R. [and others

    1996-11-01

    There is a growing interest in the development of high gradient ({ge} 1 GeV/m) accelerating structures. The need for high gradient acceleration based on current microwave technology requires the structures to be operated in the millimeter wavelength. Fabrication of accelerating structures at millimeter scale with sub-micron tolerances poses great challenges. The accelerating structures impose strict requirements on surface smoothness and finish to suppress field emission and multipactor effects. Various fabrication techniques based on conventional machining and micromachining have been evaluated and tested. These will be discussed and measurement results presented.

  7. 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

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

    2014-07-01

    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

  8. Titan's atmosphere as observed by Cassini/VIMS solar occultations: CH$_4$, CO and evidence for C$_2$H$_6$ absorption

    E-print Network

    Maltagliati, L; Vinatier, S; Hedman, M M; Lellouch, E; Nicholson, P D; Sotin, C; de Kok, R J; Sicardy, B

    2014-01-01

    We present an analysis of the VIMS solar occultations dataset, which allows us to extract vertically resolved information on the characteristics of Titan's atmosphere between 100-700 km with a characteristic vertical resolution of 10 km. After a series of data treatment procedures, 4 occultations out of 10 are retained. This sample covers different seasons and latitudes of Titan. The transmittances show clearly the evolution of the haze and detect the detached layer at 310 km in Sept. 2011 at mid-northern latitudes. Through the inversion of the transmission spectra with a line-by-line radiative transfer code we retrieve the vertical distribution of CH$_4$ and CO mixing ratio. The two methane bands at 1.4 and 1.7 {\\mu}m are always in good agreement and yield an average stratospheric abundance of $1.28\\pm0.08$%. This is significantly less than the value of 1.48% obtained by the GCMS/Huygens instrument. The analysis of the residual spectra after the inversion shows that there are additional absorptions which aff...

  9. Tune-out wavelengths for metastable helium

    NASA Astrophysics Data System (ADS)

    Mitroy, J.; Tang, Li-Yan

    2013-11-01

    The six longest tune-out wavelengths for the He(1s2s3S1e) metastable state are determined by explicit calculation. The tune-out wavelength at 413.02 nm is expected to be sensitive to finite mass, relativistic, and quantum electrodynamic effects upon the transition matrix elements and its measurement would provide a nonenergy test of fundamental atomic structure theory.

  10. Wavelength mapping of mixed semiconductors using an automatic IR spectrophotometer

    NASA Astrophysics Data System (ADS)

    Capper, P.; Jones, C. L.; Kenworthy, I.; Bennett, M. R.; Davidson, D.; McIntosh, J.

    1984-09-01

    IR transmission measurements are now widely used as a non-destructive technique in compositional assessment and growth-mechanism studies of bulk-grown mixed-semiconductor crystals, where problems of segregation result in composition variations in both axial and radial directions, necessitating detailed measurements on a small scale. The design principles and constructional details of a computer-controlled, double-beam IR spectrophotometer covering the range 1.5-14 ?m and capable of producing transmission profiles and room-temperature cut-on wavelength maps of slices of material on a millimetre-sized grid are described. The associated computer software is also detailed. Results are presented for the mixed semiconductor Cd xHg 1- xTe prepared by the Bridgman growth technique. Measurement times are approx. 10 min for a short-wavelength, 13mm dia slice and 30 min for a long-wavelength slice. These results can be related back to the growth mechanisms and help to predict the suitability of material for device manufacture.

  11. Multi-wavelength fiber optical parametric oscillator with ultra-narrow wavelength spacing.

    PubMed

    Chen, Daru; Sun, Bing

    2010-08-16

    We propose a novel multi-wavelength fiber optical parametric oscillator (MW-FOPO) based on a ring cavity. A highly nonlinear fiber and a Mach-Zehnder interferometer formed by two 3-dB optical couplers are used as the gain medium and the comb filter, respectively. Multi-wavelength lasing of the MW-FOPO with an ultra-narrow wavelength spacing of about 0.08 nm is achieved. The output spectrum of the MW-FOPO covers a wavelength regime from 1510 nm to 1615 nm (for lasing wavelengths with the power that exceeds -60 dBm). The stability of the MW-FOPO is discussed and experimentally demonstrated. A comparison of the output spectra between the MW-FOPO and the multi-wavelength Erbium-doped fiber laser is also presented. PMID:20721237

  12. The dynamics of interacting nonlinearities governing long wavelength driftwave turbulence

    SciTech Connect

    Newman, D.E.

    1993-09-01

    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.

  13. A Practical Approach for Routing and Wavelength Assignment in Large Wavelength-Routed Optical Networks

    Microsoft Academic Search

    Dhritiman Banerjee; Biswanath Mukherjee

    1996-01-01

    We consider large optical networks in which nodes employ wavelength-routing switches whichenable the establishment of wavelength-division-multiplexed (WDM) channels, called lightpaths,between node pairs. We propose a practical approach to solve routing and wavelength assignment(RWA) of lightpaths in such networks. A large RWA problem is partitioned into severalsmaller subproblems, each of which may be solved independently and efficiently using wellknownapproximation techniques. A...

  14. Millimeter wavelength spectroscopy and continuum studies of the planets

    NASA Technical Reports Server (NTRS)

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

    1979-01-01

    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.

  15. A new type of wavelength dependence in strong-field ionization

    NASA Astrophysics Data System (ADS)

    Romanov, Dmitri; Moore, Katharine; Compton, Ryan; Levis, Robert J.

    2006-03-01

    It is commonly assumed that in mid-IR region the strong-field ionization approaches quasistatic limit (tunneling, or ADK regime) and ceases to depend on the laser wavelength. Contrary to this notion, ionization yields for the noble gas Xe at intensities from 10^13-10^15 W cm-2 for wavelengths spanning from 800 to 1500nm reveal strong and counterintuitive wavelength dependence. There is an increasing ionization probability in the strong field regime as the excitation wavelength increases from 800nm to 1500 nm at fixed field intensity. The measured thresholds for the ionization event scale approximately as ?-2. We developed a simple quantitative model that extends through-the-barrier tunneling with single photon ionization from a Rydberg intermediate state and captures the observed wavelength dependence. This wavelength dependence will be reduced to some degree if the ionization occurs in a strong DC electric field that is capable to independently ionize the Rydberg states. The wavelength dependence of ionization rate in the quasitstatic regime is of considerable importance for ascertaining the correct physics for various strong field processes.

  16. High-power all-fiber wavelength-tunable thulium doped fiber laser at 2 ?m.

    PubMed

    Yin, Ke; Zhang, Bin; Xue, Guanghui; Li, Lei; Hou, Jing

    2014-08-25

    Power scaling of an all-fiber wavelength-tunable thulium doped fiber laser (TDFL) based on a monolithic master oscillator power amplifier (MOPA) system is presented. The whole configuration is comprised of a low-power seed oscillator and two stages of double-cladding thulium doped fiber amplifiers (TDFAs). The tuning of the operating wavelength is realized by inserting a spectral tunable filter into the seed oscillator. Maximum average output power of 115 W is obtained at 1950 nm with a linearly fitted slope efficiency of 51.7%. This laser has superior spectral characteristics with wavelength tunable from 1940 nm to 2070 nm. To the best of our knowledge, this is the first demonstration of an all-fiber wavelength-tunable TDFL at 2 ?m with output power exceeding 100 W. The results are of great interest for many application areas. PMID:25321205

  17. Lithographic spiral antennas at short wavelengths

    NASA Technical Reports Server (NTRS)

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

    1991-01-01

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

  18. Device for wavelength-selective imaging

    DOEpatents

    Frangioni, John V. (Wayland, MA)

    2010-09-14

    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.

  19. Radio Wavelength Observatories within the Exploration Architecture

    E-print Network

    J. Lazio; R. J. Macdowall; J. Burns; L. Demaio; D. L. Jones; K. W. Weiler

    2007-01-26

    Observations at radio wavelengths address key problems in astrophysics, astrobiology, and lunar structure including the first light in the Universe (the Epoch of Reionization), the presence of magnetic fields around extrasolar planets, particle acceleration mechanisms, and the structure of the lunar ionosphere. Moreover, achieving the performance needed to address these scientific questions demands observations at wavelengths longer than those that penetrate the Earth's ionosphere, observations in extremely "radio quiet" locations such as the Moon's far side, or both. We describe a series of lunar-based radio wavelength interferometers of increasing capability. The Radio Observatory for Lunar Sortie Science (ROLSS) is an array designed to be deployed during the first lunar sorties (or even before via robotic rovers) and addressing particle acceleration and the lunar ionosphere. Future arrays would be larger, more capable, and deployed as experience is gained in working on the lunar surface.

  20. Driving-laser wavelength dependence of high-order harmonic generation in H{sub 2}{sup +} molecules

    SciTech Connect

    Liu Candong; Zeng Zhinan; Wei Pengfei; Liu Peng; Li Ruxin; Xu Zhizhan [State Key Laboratory of High Field Laser Physics, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800 (China)

    2010-03-15

    The electron-nuclear dynamics of one-dimensional H{sub 2}{sup +} molecular high harmonic generation is investigated by numerical integration of the non-Born-Oppenheimer time-dependent Schroedinger equation. It is found that the nuclear motion and electron ionization are more significant for the longer wavelength and the stronger intensity of the driving laser pulse. When the ground-state H{sub 2}{sup +} molecule is driven by a short laser pulse (ten optical cycles in the calculations), a strong signature of nuclear motion is seen in the wavelength scaling (800-2000 nm) of harmonic yield, following a {lambda}{sup -(7-8)} scaling law at a constant laser intensity. It is attributed to the fast ground-state depletion induced by the strong nuclear motion, when using the long wavelength. Consequently, the wavelength scaling gives an insight into the nuclear dynamics.

  1. Wide-range all-optical wavelength conversion using dual-wavelength-pumped fiber Raman converter

    Microsoft Academic Search

    Atsushi Uchida; Masahiro Takeoka; Tsuneo Nakata; Fumihiko Kannari

    1998-01-01

    A wavelength conversion scheme based on a fiber Raman converter is proposed, in which an externally injected high power pump laser and the associated Stokes laser are used to assist the Raman conversion process of signal light coded with optical information. Because the Raman gain spectrum in fibers is extremely broad, a wavelength conversion device with wide-range tunability is feasible.

  2. Short wavelength ion temperature gradient turbulence

    SciTech Connect

    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

    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.

  3. Multi-wavelength Luminosity Functions of Galaxies

    NASA Technical Reports Server (NTRS)

    Gardner, J. P.; Miller, N. A.

    2002-01-01

    Multivariate or multi-wavelength luminosity functions will reveal the interplay between star formation, chemical evolution, and absorption and re-emission of dust within evolving galaxy populations. By using principal component analysis to reduce the dimensionality of the problem, we optimally extract the relevant photometric information from large galaxy catalogs. As a demonstration of the technique, we derive the multi-wavelength luminosity function for the galaxies in the released SDSS catalog, and compare the results with those obtained by traditional methods. This technique will be applicable to catalogs of galaxies from datasets obtained by 2MASS, and the SIRTF and GALEX missions.

  4. Multi-Wavelength Luminosity Functions of Galaxies

    NASA Technical Reports Server (NTRS)

    Gardner, Jonathan P.

    2002-01-01

    Multivariate or multi-wavelength luminosity functions will reveal the interplay between star formation, chemical evolution, and ab- sorption and re-emission of dust within evolving galaxy populations. By using principal component analysis to reduce the dimensionality of the problem, I optimally extract the relevant photometric information from large galaxy catalogs. As a demonstration of the technique, I derive the multi-wavelength luminosity function for the galaxies in the released SDSS catalog, and compare the results with those obtained by traditional methods. This technique will be applicable to catalogs of galaxies from datasets obtained by 2MASS, and the SIRTF and GALEX missions.

  5. Peak wavelength shifts and opponent color theory

    NASA Astrophysics Data System (ADS)

    Ashdown, Ian; Salsbury, Marc

    2007-09-01

    We adapt the tenets of Hering's opponent color theory to the processing of data obtained from a tristimulus colorimeter to independently determine the intensity and possible peak wavelength shift of a narrowband LED. This information may then be used for example in an optical feedback loop to maintain constant intensity and chromaticity for a light source consisting of two LEDs with different peak wavelengths. This approach is particularly useful for LED backlighting of LCD display panels using red, green, and blue LEDs, wherein a tristimulus colorimeter can be used to maintain primary chromaticities to within broadcast standard limits in real time.

  6. Effects of wavelength change in holographic reconstructions

    NASA Astrophysics Data System (ADS)

    Menzel, R. W.

    1981-08-01

    Holographic imaging is necessary in some particulate measurements in test facilities at AEDC. Additionally, projection of holographic images of infrared (IR) test objects is being considered to enhance the IR sensor test capability at AEDC. Lasers of different wavelengths often are necessary in the recording and reconstruction of the required holograms. As a result, a study of the effects of a wavelength change between the recording and reconstruction illumination on the aberration, resolution, and location of holographically reconstructed images was experimentally undertaken. Control of aberration and resolution degradation, to the extent possible, is described.

  7. Effects of Laser Wavelength on Ablator Testing

    NASA Technical Reports Server (NTRS)

    White, Susan M.

    2014-01-01

    Wavelength-dependent or spectral radiation effects are potentially significant for thermal protection materials. NASA atmospheric entry simulations include trajectories with significant levels of shock layer radiation which is concentrated in narrow spectral lines. Tests using two different high powered lasers, the 10.6 micron LHMEL I CO2 laser and the near-infrared 1.07 micron fiber laser, on low density ablative thermal protection materials offer a unique opportunity to evaluate spectral effects. Test results indicated that the laser wavelength can impact the thermal response of an ablative material, in terms of bond-line temperatures, penetration times, mass losses, and char layer thicknesses.

  8. OXA-46, a New Class D ?-Lactamase of Narrow Substrate Specificity Encoded by a blaVIM-1-Containing Integron from a Pseudomonas aeruginosa Clinical Isolate

    PubMed Central

    Giuliani, Francesco; Docquier, Jean-Denis; Riccio, Maria Letizia; Pagani, Laura; Rossolini, Gian Maria

    2005-01-01

    A novel OXA-type enzyme, named OXA-46, was found to be encoded by a gene cassette inserted into a class 1 integron from a multidrug-resistant Pseudomonas aeruginosa clinical isolate. The variable region of the integron also contained a blaVIM-1 metallo-?-lactamase cassette and a duplicated aacA4 aminoglycoside acetyltransferase cassette. OXA-46 belongs to the OXA-2 lineage of class D ?-lactamases. It exhibits 78% sequence identity with OXA-2 and the highest similarity (around 92% identity) with another OXA-type enzyme detected in clinical isolates of Burkholderia cepacia and in unidentified bacteria from a wastewater plant. Expression of blaOXA-46 in Escherichia coli decreased susceptibility to penicillins and narrow-spectrum cephalosporins but not to extended-spectrum cephalosporins, cefsulodin, aztreonam, or carbapenems. The enzyme was overproduced in E. coli and purified by two anion-exchange chromatography steps (approximate yield, 6 mg/liter). OXA-46 was made of a 28.5-kDa polypeptide and exhibited an alkaline pI (7.8). In its native form OXA-46 appeared to be dimeric, and the oligomerization state was not affected by EDTA. Kinetic analysis of OXA-46 revealed a specificity for narrow-spectrum substrates, including oxacillin, other penicillins (but not temocillin), and narrow-spectrum cephalosporins. The enzyme apparently did not interact with temocillin, oxyimino-cephalosporins, or aztreonam. OXA-46 was inactivated by tazobactam and carbapenems and, although less efficiently, also by clavulanic acid. Enzyme activity was not affected either by EDTA or by divalent cations and exhibited low susceptibility to NaCl. These findings underscore the functional and structural diversity that can be encountered among class D ?-lactamases. PMID:15855521

  9. Using Long Wavelength Gravity to Understand Continental Structure and Processes

    NASA Astrophysics Data System (ADS)

    Webb, Susan

    2013-04-01

    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.

  10. An international evaluation of holmium oxide solution reference materials for wavelength calibration in molecular absorption spectrophotometry.

    PubMed

    Travis, John C; Zwinkels, Joanne C; Mercader, Flora; Ruíz, Arquímedes; Early, Edward A; Smith, Melody V; Noël, Mario; Maley, Marissa; Kramer, Gary W; Eckerle, Kenneth L; Duewer, David L

    2002-07-15

    Commercial spectrophotometers typically use absorption-based wavelength calibration reference materials to provide wavelength accuracy for their applications. Low-mass fractions of holmium oxide (Ho2O3) in dilute acidic aqueous solution and in glass matrixes have been favored for use as wavelength calibration materials on the basis of spectral coverage and absorption band shape. Both aqueous and glass Ho2O3 reference materials are available commercially and through various National Metrology Institutes (NMIs). Three NMIs of the North American Cooperation in Metrology (NORAMET) have evaluated the performance of Ho3-(aq)-based Certified Reference Materials (CRMs) under "routine" operating conditions using commercial instrumentation. The study was not intended to intercompare national wavelength scales but to demonstrate comparability of wavelength measurements among the participants and between two versions of the CRMs. It was also designed to acquire data from a variety of spectrophotometers for use in a NIST study of wavelength assignment algorithms and to provide a basis for a possible reassessment of NIST-certified Ho3+(aq) band locations. The resulting data show a substantial level of agreement among laboratories, instruments, CRM preparations, and peak-location algorithms. At the same time, it is demonstrated that the wavelength comparability of the five participating instruments can actually be improved by calibrating all of the instruments to the consensus Ho3+(aq) band locations. This finding supports the value of absorption-based wavelength standards for calibrating absorption spectrophotometers. Coupled with the demonstrated robustness of the band position values with respect to preparation and measurement conditions, it also supports the concept of extending the present approach to additional NMIs in order to certify properly prepared dilute acidic Ho2O3 solution as an intrinsic wavelength standard. PMID:12139047

  11. Wavelength dependence of the photoresponse of a yttrium-barium-copper-oxide thin film

    NASA Astrophysics Data System (ADS)

    Mischke, Matthew

    The work explores the wavelength dependence of the photoresponse of an under-doped YBa2Cu3O7-delta thin film with a sharp resistive transition. The nature of the photoresponse is studied at a time scale of ?1 s, varying the excitation wavelength while holding sample temperature constant within the superconducting-normal transition. The bolometric portion of the photoresponse is then accounted for, and the residual non-bolometric response is compared to that found in other doping regimes and time scales. The observed wavelength dependence of the excess conductance is most likely caused by excitations into the conduction band from the filled copper bands in the CuO2 plane layer of the crystal.

  12. Discrete wavelength-locked external cavity laser

    NASA Technical Reports Server (NTRS)

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

    2005-01-01

    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.

  13. Two-wavelength spatial-heterodyne holography

    DOEpatents

    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

    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.

  14. Electricity and short wavelength radiation generator

    DOEpatents

    George, E.V.

    1985-08-26

    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.

  15. SDIO long wavelength infrared detector requirements

    NASA Technical Reports Server (NTRS)

    Duston, Dwight

    1990-01-01

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

  16. Wavelength Agility in Multihop Lightwave Networks

    Microsoft Academic Search

    Jean-françois P. Labourdette; Anthony S. Acampora

    1990-01-01

    The multihop architecture, which provides a way of tapping the capacity potential available in lightwave networks, is described. Within this architecture, each network node is equipped with some small number of transmitters and receivers, each of which can communicate on one wavelength. Transmitters and receivers are connected to an optical medium, which is physically configured in such a way that

  17. The wavelength dependence of Triton's light curve

    NASA Technical Reports Server (NTRS)

    Hillier, J.; Veverka, J.; Helfenstein, P.; Mcewen, A.

    1991-01-01

    Using Voyager observations, it is demonstrated that Triton's orbital light curve is strongly wavelength-dependent, a characteristic which readily explains some of the apparent discrepancies among pre-Voyager telescopic measurements. Specifically, a light curve amplitude (peak to peak) is found that decreases systematically with increasing wavelength from about 0.08 magnitude (peak to peak) near 200 nm to less than 0.02 magnitude near 1000 nm. Peak brightness occurs near 90 deg orbital longitude (leading hemisphere). The brightness variation across this hemisphere is close to sinusoidal; the variation across the darker hemisphere is more complex. The decrease in light curve amplitude with increasing wavelength appears to be due to a decrease in contrast among surface markings, rather than to atmospheric obscuration. The model also explains the observed decrease in the amplitude of Triton's light curve at visible wavelengths over the past decade, a decrease related to the current migration of the subsolar latitude toward the south pole; it is predicted that this trend will continue into the 1990s.

  18. Wide-angle wavelength-selective multilayer optical metasurfaces robust to interlayer misalignment

    E-print Network

    Yu, Edward T.

    Wide-angle wavelength-selective multilayer optical metasurfaces robust to interlayer misalignment December 4, 2012 Multilayer plasmonic optical metasurfaces are demonstrated and analyzed that provide, with each indivi- dual layer constituting a subwavelength-scale metasurface [14,15]. These structures

  19. Long Wavelength Array: Day in the Life Operation Model Tracy E. Clarke1,2

    E-print Network

    Ellingson, Steven W.

    and the High Redshift Universe 1.1 Dark Ages 1.2 First Supermassive Black Holes 1.3 Large Scale StructureLong Wavelength Array: Day in the Life Operation Model Tracy E. Clarke1,2 Version 1.0 April 25 drivers for the LWA as taken from LWA memo #117. Design of the Day in the Life operational model

  20. Wavelength Control in Buried Heterostructure and Ridge Waveguide Lasers

    NASA Technical Reports Server (NTRS)

    Davis, L.; Vang, T. A.; Forouhar, S. F.

    1996-01-01

    High density wavelength division multiplexed (HD-WDM) systems place stringent requirements on the absolute wavelength and wavelength spacing of the elements in Distributed Feedback (DFB) laser arrays. An analysis of the fabrication tolerances for ridge waveguide and buried heterostructure DFB lasers is performed, showing the fabrication-induced wavelength variations present in these types of devices.

  1. Imaging Uranus at Submillimeter to Centimeter Wavelengths

    NASA Astrophysics Data System (ADS)

    Hofstadter, Mark D.; Butler, B. J.; Gurwell, M. A.

    2007-10-01

    We have been making regular observations of Uranus for the past several years, in part to search for variability associated with the 2007 equinox. We will present an analysis of our current data set, spanning wavelengths from 1 mm to 20 cm (using the SMA and VLA radio observatories), including our latest data collected in August of 2007. These wavelengths probe the atmosphere from pressures of 1 to 50 bars, which extends from the lower tropopause far into convectively dominated regions, and includes several altitudes of cloud formation. We have found that, at all our wavelengths, the planet appears symmetric, with both the north (spring) and south (fall) polar regions being radio bright. At pressures greater than a few bars, this is almost certainly due to the poles being depleted in atmospheric absorbers by convective processes (Hofstadter and Butler 2003, Icarus 165, 168-180). Near 1 bar, the bright poles could be due to the physical temperature being 5 K higher there than at the equator, or due to a strong depletion of CH4 vapor over the poles. A combination of the two seems likely, as compositional variations are consistent with the circulation inferred from several data sets, and 2 K temperature variations are found both in theoretical models (Friedson and Ingersoll 1987, Icarus 69, 135-156) and in Voyager infrared measurements made in 1986 during southern summer solstice (Hanel et al. 1986, Science 233, 70-74). We will discuss these results in the context of observations of Uranus made at other wavelengths, and recent images we have acquired of Neptune at radio wavelengths. This work was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under contract with NASA. We acknowledge the support of NASA's Planetary Astronomy program, and of the VLA and SMA observatories.

  2. Atmospheric Scales and Spectral Gaps

    Microsoft Academic Search

    Franz Fiedler; Hans A. Panofsky

    1970-01-01

    The kinetic energy of the atmosphere is not spread uniformly over all wavelengths but has certain preferred scales, with gaps in between.Typically atmospheric structures are either fully three dimensional with horizontal wavelengths of the order of 100 m to several kilometers, such as convection cells (including thunderstorms) and mechanically driven eddies; or they are quasi-two-dimensional with horizontal dimensions of order

  3. Widely tunable wavelength spacing dual-wavelength single longitudinal mode erbium doped fiber laser

    NASA Astrophysics Data System (ADS)

    Sun, Tiegang; Guo, Yubin; Wang, Tianshu; Huo, Jiayu; Zhang, Le

    2014-06-01

    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.

  4. A superradiant clock laser on a magic wavelength optical lattice.

    PubMed

    Maier, Thomas; Kraemer, Sebastian; Ostermann, Laurin; Ritsch, Helmut

    2014-06-01

    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

  5. The Long Wavelength Array Software Library

    NASA Astrophysics Data System (ADS)

    Dowell, Jayce; Wood, Daniel; Stovall, Kevin; Ray, Paul S.; Clarke, Tracy; Taylor, Gregory

    2012-12-01

    The Long Wavelength Array Software Library (LSL) is a Python module that provides a collection of utilities to analyze and export data collected at the first station of the Long Wavelength Array, LWA1. Due to the nature of the data format and large-N (?100 inputs) challenges faced by the LWA, currently available software packages are not suited to process the data. Using tools provided by LSL, observers can read in the raw LWA1 data, synthesize a filter bank, and apply incoherent de-dispersion to the data. The extensible nature of LSL also makes it an ideal tool for building data analysis pipelines and applying the methods to other low frequency arrays.

  6. Multi-Wavelength Observations of Supernova Remnants

    NASA Technical Reports Server (NTRS)

    Williams, B.

    2012-01-01

    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.

  7. Wavelength dependence of reflectometric cone photoreceptor directionality.

    PubMed

    Zagers, Niels P A; Berendschot, Tos T J M; van Norren, Dirk

    2003-01-01

    We present evidence for the wavelength dependence of the directionality of light reflected from cone receptor cells (optical Stiles-Crawford effect): Blue light is more directional than red. According to the waveguide-scattering model of Marcos et al. [J. Opt. Soc. Am. A 15, 2012 (1998)], directionality is the sum of a waveguide component and a scattering component. The latter is proportional to 1 over wavelength squared, and it is related to the row-to-row spacing of the cone lattice. Our results allow a firm confirmation of Marcos et al.'s theory. For a 1.9-deg foveal area, group mean (n = 18) cone spacing was 3.42 microm, in good agreement with anatomical data. Group mean waveguide directionality was 0.077 mm(-2). PMID:12542314

  8. Radio Wavelength Transients: Current and Emerging Prospects

    E-print Network

    J. Lazio

    2008-01-18

    Known classes of radio wavelength transients range from the nearby--stellar flares and radio pulsars--to the distant Universe--\\gamma-ray burst afterglows. Hypothesized classes of radio transients include analogs of known objects, e.g., extrasolar planets emitting Jovian-like radio bursts and giant-pulse emitting pulsars in other galaxies, to the exotic, prompt emission from \\gamma-ray bursts, evaporating black holes, and transmitters from other civilizations. A number of instruments and facilities are either under construction or in early observational stages and are slated to become available in the next few years. With a combination of wide fields of view and wavelength agility, the detection and study of radio transients will improve immensely.

  9. Deformable mirror for short wavelength applications

    DOEpatents

    Chapman, Henry N. (2417 Kilkare Rd., Sunol, CA 94586); Sweeney, Donald W. (5020 Canyon Crest Dr., San Ramon, CA 94583)

    1999-01-01

    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.

  10. Using large radio telescopes at decametre wavelengths

    Microsoft Academic Search

    A. Lecacheux; A. A. Konovalenko; H. O. Rucker

    2004-01-01

    With the aim of evaluating the actual possibilities of doing, from the ground, sensitive radio astronomy at decametre wavelengths (particularly below ?50MHz), an extensive program of radio observations was carried out, in 1999–2002, by using digital spectral and waveform analysers (DSP) of new generation, connected to several of the largest, decametre radio telescopes in the world (i.e., the UTR-2 and

  11. Thermal behavior of millimeter wavelength radio telescopes

    Microsoft Academic Search

    Albert Greve; Michel Dan; Juan Penalver

    1992-01-01

    The passive and\\/or active thermal control of significant structural components, for instance the backstructure and the feed legs, of the IRAM 15-m MM and 30-m MM wavelengths telescopes is discussed, and their thermal behavior is illustrated. The design of the thermal protection was supported by dynamic time-dependent model calculations, which are explained and compared with in situ recorded temperatures of

  12. Planar, flattened Luneburg lens at infrared wavelengths.

    PubMed

    Hunt, John; Tyler, Talmage; Dhar, Sulochana; Tsai, Yu-Ju; Bowen, Patrick; Larouche, Stéphane; Jokerst, Nan M; Smith, David R

    2012-01-16

    Employing artificially structured metamaterials provides a means of circumventing the limits of conventional optical materials. Here, we use transformation optics (TO) combined with nanolithography to produce a planar Luneburg lens with a flat focal surface that operates at telecommunication wavelengths. Whereas previous infrared TO devices have been transformations of free-space, here we implement a transformation of an existing optical element to create a new device with the same optical characteristics but a user-defined geometry. PMID:22274513

  13. Short wavelength striations on expanding plasma clouds

    SciTech Connect

    Winske, D.; Gary, S.P.

    1989-01-01

    The growth and evolution of short wavelength (

  14. Source of coherent short wavelength radiation

    DOEpatents

    Villa, Francesco (Alameda, CA)

    1990-01-01

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

  15. Fast multi-wavelength variability from a black hole

    NASA Astrophysics Data System (ADS)

    O'Brien, Kieran

    2011-10-01

    Correlated fast multi-wavelength variability is quickly becoming a key tool for studying the physics of accretion and ejection of relativistic jets. Using simultaneous X-ray and near-infrared data we have recently discovered vibrations from a relativistic jet down to 62.5 ms time scale, which allowed us to estimate the speed and the size of the jet. We have also shown that the properties of the jet depend on the spectral state of the black hole. We propose to monitor the outburst evolution of a black hole transient with XMM, simultaneously with ground-based optical and infrared facilities, in order to apply the same technique to different spectral states. We propose to perform 10 short XMM observations (7 ks each) of an active black hole, in order to cover the different stages of the outburst.

  16. Laser damage testing of coated reflectors at excimer laser wavelengths

    SciTech Connect

    Foltyn, S.R.; Newnam, B.E.

    1981-01-01

    An important parameter in the design of large-scale ultraviolet lasers (such as those envisioned for Inertial Confinement Fusion and Molecular Laser Isotope Separation) is the resistance to optical damage of windows, AR-coatings, and coated reflectors. In addressing the problem of evaluating and optimizing highly reflective dielectric stacks, we have measured the damage thresholds of a variety of 248-nm, 308-nm, and 351-nm reflectors. The coatings were composed of quarterwave stacks of oxide and/or fluoride films deposited on Suprasil 2 substrates. Testing was accomplished at 35 Hz with nominal 10-ns pulses focused to a mean 1/e/sup 2/ diameter of 0.5 to 0.6 mm. Damage threshold (defined as the highest fluence at which 10/10 sites survived 1000 shots) ranged from 1 to 5 J/cm/sup 2/, with a strong dependence upon laser wavelength and reflector coating materials.

  17. Acoustic dynamics of network-forming glasses at mesoscopic wavelengths

    PubMed Central

    Ferrante, C.; Pontecorvo, E.; Cerullo, G.; Chiasera, A.; Ruocco, G.; Schirmacher, W.; Scopigno, T.

    2013-01-01

    The lack of long-range structural order in amorphous solids induces well known thermodynamic anomalies, which are the manifestation of distinct peculiarities in the vibrational spectrum. Although the impact of such anomalies vanishes in the long wavelength, elastic continuum limit, it dominates at length scales comparable to interatomic distances, implying an intermediate transition regime still poorly understood. Here we report a study of such mesoscopic domains by means of a broadband version of picosecond photo-acoustics, developed to coherently generate and detect hypersonic sound waves in the sub-THz region with unprecedented sampling efficiency. We identify a temperature-dependent fractal v3/2 frequency behaviour of the sound attenuation, pointing to the presence of marginally stable regions and a transition between the two above mentioned limits. The essential features of this behaviour are captured by a theoretical approach based on random spatial variation of the shear modulus, including anharmonic interactions. PMID:23653205

  18. Wavelength-selective switch with direct few mode fiber integration.

    PubMed

    Marom, D M; Dunayevsky, J; Sinefeld, D; Blau, M; Ryf, R; Fontaine, N K; Montoliu, M; Randel, S; Liu, C; Ercan, B; Esmaeelpour, M; Chandrasekhar, S; Gnauck, A H; Leon-Saval, S G; Bland-Hawthorn, J; Salazar-Gil, J R; Sun, Y; Grüner-Nielsen, L; Lingle, R

    2015-03-01

    The first realization of a wavelength-selective switch (WSS) with direct integration of few mode fibers (FMF) is fully described. The free-space optics FMF-WSS dynamically steers spectral information-bearing beams containing three spatial modes from an input port to one of nine output ports using a phase spatial light modulator. Sources of mode dependent losses (MDL) are identified, analytically analyzed and experimentally confirmed on account of different modal sensitivities to fiber coupling in imperfect imaging and at spectral channel edges due to mode clipping. These performance impacting effects can be reduced by adhering to provided design guidelines, which scale in support of higher spatial mode counts. The effect on data transmission of cascaded passband filtering and MDL build-up is experimentally investigated in detail. PMID:25836802

  19. Bibliography of short wavelength chemical laser research

    NASA Astrophysics Data System (ADS)

    Perram, Glen P.

    1993-05-01

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

  20. Gas sensing using wavelength modulation spectroscopy

    NASA Astrophysics Data System (ADS)

    Viveiros, D.; Ribeiro, J.; Flores, D.; Ferreira, J.; Frazao, O.; Santos, J. L.; Baptista, J. M.

    2014-08-01

    An experimental setup has been developed for different gas species sensing based on the Wavelength Modulation Spectroscopy (WMS) principle. The target is the measurement of ammonia, carbon dioxide and methane concentrations. The WMS is a rather sensitive technique for detecting atomic/molecular species presenting the advantage that it can be used in the near-infrared region using optical telecommunications technology. In this technique, the laser wavelength and intensity are modulated applying a sine wave signal through the injection current, which allows the shift of the detection bandwidth to higher frequencies where laser intensity noise is reduced. The wavelength modulated laser light is tuned to the absorption line of the target gas and the absorption information can be retrieved by means of synchronous detection using a lock-in amplifier, where the amplitude of the second harmonic of the laser modulation frequency is proportional to the gas concentration. The amplitude of the second harmonic is normalised by the average laser intensity and detector gain through a LabVIEW® application, where the main advantage of normalising is that the effects of laser output power fluctuations and any variations in laser transmission, or optical-electrical detector gain are eliminated. Two types of sensing heads based on free space light propagation with different optical path length were used, permitting redundancy operation and technology validation.

  1. Wideband silicon-photonic thermo-optic switch in a wavelength-division multiplexed ring network.

    PubMed

    Aguinaldo, Ryan; Forencich, Alex; DeRose, Christopher; Lentine, Anthony; Trotter, Douglas C; Fainman, Yeshaiahu; Porter, George; Papen, George; Mookherjea, Shayan

    2014-04-01

    Using a compact (0.03 mm(2)) silicon-photonic bias-free thermo-optic cross-bar switch, we demonstrate microsecond-scale switching of twenty wavelength channels of a C-band wavelength-division multiplexed optical ring network, each carrying 10 Gbit/second data concurrently, with 15 mW electrical power consumption (no temperature control required). A convenient pulsed driving scheme is demonstrated and eye patterns and bit-error rate measurements are shown. An algorithm is developed to measure the power-division ratio between the two output ports, the insertion and switching losses, and non-ideal phase deviations. PMID:24718196

  2. Scaling laws for RFQ design procedures

    Microsoft Academic Search

    E. Alan Wadlinger

    1985-01-01

    Scaling laws are relations between accelerator parameters (electric field, rf wavelength etc.) and beam parameters (current, energy, emittance, etc.) that define surfaces of constant accelerator performance in parameter space. These scaling laws can act as guides for designing radio-frequency quadrupoles (RFQs). We derive several scaling relations to show the various tradeoffs involved in choosing RFQ designs and to provide curves

  3. Scaling laws for RFQ design procedures

    Microsoft Academic Search

    E. A. Wadlinger

    1985-01-01

    Scaling laws are relations between accelerator parameters (electric field, RF wavelength, etc.) and beam parameters (current, energy, emittance, etc.) that define surfaces of constant accelerator performance in parameter space. These scaling laws can act as guides for designing radio-frequency quadrupoles (RFQs). Several scaling relations are derived to show the various tradeoffs involved in choosing RFQ designs and to provide curves

  4. Wavelength meter having single mode fiber optics multiplexed inputs

    DOEpatents

    Hackel, Richard P. (Livermore, CA); Paris, Robert D. (San Ramon, CA); Feldman, Mark (Pleasanton, CA)

    1993-01-01

    A wavelength meter having a single mode fiber optics input is disclosed. The single mode fiber enables a plurality of laser beams to be multiplexed to form a multiplexed input to the wavelength meter. The wavelength meter can provide a determination of the wavelength of any one or all of the plurality of laser beams by suitable processing. Another aspect of the present invention is that one of the laser beams could be a known reference laser having a predetermined wavelength. Hence, the improved wavelength meter can provide an on-line calibration capability with the reference laser input as one of the plurality of laser beams.

  5. Experimental results and theoretical analysis of the effect of wavelength on absorption and hot-electron generation in laser-plasma interaction

    Microsoft Academic Search

    C. Garban-Labaune; Edouard Fabre; Claire Max; F. Amiranoff; Rémy Fabbro; J. Virmont; W. C. Mead

    1985-01-01

    Recent experiments performed at E´cole Polytechnique on the wavelength scaling of laser light absorption by flat plastic targets are presented and interpreted. The measurements show larger absorption fractions for shorter laser wavelengths, lower laser intensities, and longer laser pulse lengths. These experiments are analyzed using computer hydrodynamics codes, and show that there are two possible physics models consistent with the

  6. Comparison of the single-wavelength and spectral-reconstruction methods for determining the solvation-response function

    SciTech Connect

    Gardecki, J.A.; Maroncelli, M. [Pennsylvania State Univ., University Park, PA (United States). Dept. of Chemistry] [Pennsylvania State Univ., University Park, PA (United States). Dept. of Chemistry

    1999-03-04

    A comparison of the solvation/spectral-response functions obtained by two independent techniques, the single-wavelength and spectral-reconstruction methods, is reported. Determination of the best wavelengths for application of the linear-single-wavelength approximation for the solute coumarin 153 (C153) is achieved using radiative rate data and steady-state emission spectra in a series of 36 different solvents at room temperature. The optimal linear wavelength is found to be 555 nm. (This wavelength, which is on the red side of the spectrum, yields superior results when compared to the more traditional choice of 470--480 nm, on the blue side.) Response functions determined using both 560- and 470-nm observation wavelengths are compared to previously reported spectral-reconstruction results in 24 solvents. A comparison of the characteristic times indicates that the linear-single-wavelength method can be used to predict solvation times with an accuracy of roughly {+-}30--40% (1 standard deviation) using suitably scaled data collected at {approximately}560 nm. Application of a nonlinear version of the single-wavelength method does not provide increased accuracy.

  7. Wavelength-selective visible-light detector based on integrated graphene transistor and surface plasmon coupler

    NASA Astrophysics Data System (ADS)

    Smith, Christian W.; Maukonen, Doug; Peale, R. E.; Fredricksen, C. J.; Ishigami, M.; Cleary, J. W.

    2014-06-01

    We have invented a novel photodetector by mating a surface plasmon resonance coupler with a graphene field effect transistor. The device enables wavelength selectivity for spectral sensing applications. Surface plasmon polaritons (SPPs) are generated in a 50 nm thick Ag film on the surface of a prism in the Kretschmann configuration positioned 500 nm from a graphene FET. Incident photons of a given wavelength excite SPPs at a specific incidence angle. These SPP fields excite a transient current whose amplitude follows the angular resonance spectrum of the SPP absorption feature. Though demonstrated first at visible wavelengths, the approach can be extended far into the infrared. We also demonstrate that the resonant current is strongly modulated by gate bias applied to the FET, providing a clear path towards large-scale spectral imagers with locally addressable pixels.

  8. Laser-to-electricity energy converter for short wavelengths

    NASA Technical Reports Server (NTRS)

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

    1975-01-01

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

  9. Decoherence induced by long wavelength gravitons

    E-print Network

    V. A. De Lorenci; L. H. Ford

    2014-12-15

    We discuss how a background bath of gravitons can induce decoherence of quantum systems. The mechanism is dephasing, the loss of phase coherence due to quantum geometry fluctuations caused by the gravitons. This effect is illustrated in a simple analog model of quantum particles in a cavity whose walls undergo position fluctuations, and create the same effect expected from spacetime geometry fluctuations. We obtain an explicit result for the decoherence rate in the limit where the graviton wavelength is large compared to the size of the quantum system, and make some estimates for this rate.

  10. Decoherence induced by long wavelength gravitons

    NASA Astrophysics Data System (ADS)

    De Lorenci, V. A.; Ford, L. H.

    2015-02-01

    We discuss how a background bath of gravitons can induce decoherence of quantum systems. The mechanism is dephasing, the loss of phase coherence due to quantum geometry fluctuations caused by the gravitons. This effect is illustrated in a simple analog model of quantum particles in a cavity whose walls undergo position fluctuations, and create the same effect expected from spacetime geometry fluctuations. We obtain an explicit result for the decoherence rate in the limit where the graviton wavelength is large compared to the size of the quantum system, and make some estimates for this rate.

  11. Imaging Antenna Structure For Submillimeter Wavelengths

    NASA Technical Reports Server (NTRS)

    Rebeiz, G.; Rutledge, D.

    1990-01-01

    Integrated-circuit antenna structure contains two-dimensional array of antennas and antenna reflectors. In receiving mode, each antenna acts as part of detector for one picture element in millimeter- or submillimeter-wavelength imaging radar system. Millimeter-wave imaging system used to view objects through fog, smoke, or smog with resolution intermediate between microwave and visible-light imaging systems. Antenna elements, supports, and reflectors made by integrated-circuit techniques. Structures fabricated on front and back substrates separately. Substrates then joined. Inexpensive way to provide large number of small antenna elements required for imaging, all mounted rigidly in way that does not degrade operation.

  12. Wavelength Calibration Accuracy for the STIS CCD and MAMA Modes

    NASA Astrophysics Data System (ADS)

    Pascucci, Ilaria; Hodge, Phil; Proffitt, Charles R.; Ayres, T.

    2011-03-01

    Two calibration programs were carried out to determine the accuracy of the wavelength solutions for the most used STIS CCD and MAMA modes after Servicing Mission 4. We report here on the analysis of this dataset and show that the STIS wavelength solution has not changed after SM4. We also show that a typical accuracy for the absolute wavelength zero-points is 0.1 pixels while the relative wavelength accuracy is 0.2 pixels.

  13. Wavelength-swept Tm-doped fiber laser operating in the two-micron wavelength band.

    PubMed

    Tokurakawa, M; Daniel, J M O; Chenug, C S; Liang, H; Clarkson, W A

    2014-08-25

    A wavelength-swept thulium-doped silica fiber laser using an intracavity rotating slotted-disk wavelength scanning filter in combination with an intracavity solid etalon for passive control of temporal and spectral profiles is reported. The laser yielded a wavelength swept output in a step-wise fashion with each laser pulse separated from the previous pulse by a frequency interval equal to the free-spectral-range of the etalon and with an instantaneous linewidth of <0.05 nm. Scanning ranges from 1905 nm to 2049 nm for a cladding-pumping laser configuration, and from 1768 nm to 1956 nm for a core-pumping laser configuration were achieved at average output powers up to ~1 W. PMID:25321211

  14. Wavelength-Division Multiplexing Of Bipolar Digital Signals

    NASA Technical Reports Server (NTRS)

    Gibbons, Ronnie D.; Ubele, John L., II

    1994-01-01

    In system, bipolar digital data transmitted by use of wavelength-division multiplexing on single optical fiber. Two different wavelengths used to transmit pulses signifying "positive" or "negative" bipolar digital data. Simultaneous absence of pulses at both wavelengths signifies digital "zero."

  15. WAVELENGTH CONVERSION USING BISMUTH-BASED NONLINEAR OPTICAL LOOP MIRROR

    E-print Network

    Wai, Ping-kong Alexander

    WAVELENGTH CONVERSION USING BISMUTH-BASED NONLINEAR OPTICAL LOOP MIRROR C. C. Lee,1§ P. K. A. Wai,1 of bismuth-based highly-nonlinear fiber in optical loop mirror configuration (Bi-NOLM). Both inverted and non of the wavelength converter is also measured. Keywords: Bismuth based fiber, wavelength conversion, optical signal

  16. Adaptive wavelength routing in all-optical networks

    Microsoft Academic Search

    Ahmed Mokhtar; Murat Azizo?lu

    1998-01-01

    In this paper we consider routing and wavelength as- signment in wavelength-routed all-optical networks with circuit- switching. The conventional approaches to address this issue consider the two aspects of the problem disjointly by first finding a route from a predetermined set of candidate paths and then searching for an appropriate wavelength assignment. We adopt a more general approach in which

  17. Experimental study on dual-wavelength distributed feedback fiber laser

    NASA Astrophysics Data System (ADS)

    Qi, Haifeng; Song, Zhiqiang; Guo, Jian; Wang, Chang; Chang, Jun; Peng, Gangding

    2014-09-01

    Four distributed feedback fiber lasers with dual-wavelength operations were studied experimentally in detail. The laser characteristics of these distributed feedback fiber lasers (DFB-FLs) were investigated. The operation conditions for the dual-wavelength output are analyzed and presented. Through this study, the guidance of the design and fabrication of some dual-wavelength distributed feedback fiber lasers are provided.

  18. Compensated anisotropic metamaterials: Manipulating sub-wavelength images

    Microsoft Academic Search

    Yijun Feng

    2008-01-01

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

  19. The chromosphere above sunspots at millimeter wavelengths

    NASA Astrophysics Data System (ADS)

    Loukitcheva, M.; Solanki, S. K.; White, S. M.

    2014-01-01

    Aims: The aim of this paper is to demonstrate that millimeter wave data can be used to distinguish between various atmospheric models of sunspots, whose temperature structure in the upper photosphere and chromosphere has been the source of some controversy. Methods: We use observations of the temperature contrast (relative to the quiet Sun) above a sunspot umbra at 3.5 mm obtained with the Berkeley-Illinois-Maryland Array (BIMA), complemented by submm observations from Lindsey & Kopp (1995) and 2 cm observations with the Very Large Array. These are compared with the umbral contrast calculated from various atmospheric models of sunspots. Results: Current mm and submm observational data suggest that the brightness observed at these wavelengths is low compared to the most widely used sunspot models. These data impose strong constraints on the temperature and density stratifications of the sunspot umbral atmosphere, in particular on the location and depth of the temperature minimum and the location of the transition region. Conclusions: A successful model that is in agreement with millimeter umbral brightness should have an extended and deep temperature minimum (below 3000 K). Better spatial resolution as well as better wavelength coverage are needed for a more complete determination of the chromospheric temperature stratification above sunspot umbrae.

  20. Dye mixtures for ultrafast wavelength shifters

    SciTech Connect

    Gangopadhyay, S.; Liu, L.; Palsule, C.; Borst, W.; Wigmans, R. [Texas Tech Univ., Lubbock, TX (United States). Dept. of Physics; Barashkov, N. [Karpov Inst. of Physical Chemistry, Moscow (Russian Federation)

    1994-12-31

    Particle detectors based on scintillation processes have been used since the discovery of radium about 100 years ago. The fast signals that can be obtained with these detectors, although often considered a nice asset, were rarely essential for the success of experiments. However, the new generation of high energy particle accelerators require particle detectors with fast response time. The authors have produced fast wavelength shifters using mixtures of various Coumarin dyes with DCM in epoxy-polymers (DGEBA+HHPA) and measured the properties of these wavelength shifters. The particular mixtures were chosen because there is a substantial overlap between the emission spectrum of Coumarin and the absorption spectrum of DCM. The continuous wave and time-resolved fluorescence spectra have been studied as a function of component concentration to optimize the decay times, emission peaks and quantum yields. The mean decay times of these mixtures are in the range of 2.5--4.5 ns. The mean decay time increases with an increase in Coumarin concentration at a fixed DCM concentration or with a decrease in DCM concentration at a fixed Coumarin concentration. This indicates that the energy transfer is radiative at lower relative DCM concentrations and becomes non-radiative at higher DCM concentrations.

  1. SHORT-WAVELENGTH MAGNETIC BUOYANCY INSTABILITY

    SciTech Connect

    Mizerski, K. A.; Davies, C. R.; Hughes, D. W., E-mail: kamiz@igf.edu.pl, E-mail: tina@maths.leeds.ac.uk, E-mail: d.w.hughes@leeds.ac.uk [Department of Applied Mathematics, University of Leeds, Leeds LS2 9JT (United Kingdom)

    2013-04-01

    Magnetic buoyancy instability plays an important role in the evolution of astrophysical magnetic fields. Here we revisit the problem introduced by Gilman of the short-wavelength linear stability of a plane layer of compressible isothermal fluid permeated by a horizontal magnetic field of strength decreasing with height. Dissipation of momentum and magnetic field is neglected. By the use of a Rayleigh-Schroedinger perturbation analysis, we explain in detail the limit in which the transverse horizontal wavenumber of the perturbation, denoted by k, is large (i.e., short horizontal wavelength) and show that the fastest growing perturbations become localized in the vertical direction as k is increased. The growth rates are determined by a function of the vertical coordinate z since, in the large k limit, the eigenmodes are strongly localized in the vertical direction. We consider in detail the case of two-dimensional perturbations varying in the directions perpendicular to the magnetic field, which, for sufficiently strong field gradients, are the most unstable. The results of our analysis are backed up by comparison with a series of initial value problems. Finally, we extend the analysis to three-dimensional perturbations.

  2. Coherence techniques at extreme ultraviolet wavelengths

    SciTech Connect

    Chang, Chang

    2002-10-01

    The renaissance of Extreme Ultraviolet (EUV) and soft x-ray (SXR) optics in recent years is mainly driven by the desire of printing and observing ever smaller features, as in lithography and microscopy. This attribute is complemented by the unique opportunity for element specific identification presented by the large number of atomic resonances, essentially for all materials in this range of photon energies. Together, these have driven the need for new short-wavelength radiation sources (e.g. third generation synchrotron radiation facilities), and novel optical components, that in turn permit new research in areas that have not yet been fully explored. This dissertation is directed towards advancing this new field by contributing to the characterization of spatial coherence properties of undulator radiation and, for the first time, introducing Fourier optical elements to this short-wavelength spectral region. The first experiment in this dissertation uses the Thompson-Wolf two-pinhole method to characterize the spatial coherence properties of the undulator radiation at Beamline 12 of the Advanced Light Source. High spatial coherence EUV radiation is demonstrated with appropriate spatial filtering. The effects of small vertical source size and beamline apertures are observed. The difference in the measured horizontal and vertical coherence profile evokes further theoretical studies on coherence propagation of an EUV undulator beamline. A numerical simulation based on the Huygens-Fresnel principle is performed.

  3. Saras Measurement of the Radio Background At Long Wavelengths

    NASA Astrophysics Data System (ADS)

    Patra, Nipanjana; Subrahmanyan, Ravi; Sethi, Shiv; Udaya Shankar, N.; Raghunathan, A.

    2015-03-01

    SARAS is a correlation spectrometer connected to a frequency independent antenna that is purpose-designed for precision measurements of the radio background at long wavelengths. The design, calibration, and observing strategies admit solutions for the internal additive contributions to the radiometer response, and hence a separation of these contaminants from the antenna temperature. We present here a wideband measurement of the radio sky spectrum by SARAS that provides an accurate measurement of the absolute brightness and spectral index between 110 and 175 MHz. Accuracy in the measurement of absolute sky brightness is limited by systematic errors of magnitude 1.2%; errors in calibration and in the joint estimation of sky and system model parameters are relatively smaller. We use this wide-angle measurement of the sky brightness using the precision wide-band dipole antenna to provide an improved absolute calibration for the 150 MHz all-sky map of Landecker and Wielebinski: subtracting an offset of 21.4 K and scaling by a factor of 1.05 will reduce the overall offset error to 8 K (from 50 K) and scale error to 0.8% (from 5%). The SARAS measurement of the temperature spectral index is in the range ?2.3 to ?2.45 in the 110–175 MHz band and indicates that the region toward the Galactic bulge has a relatively flatter index.

  4. Single-longitudinal-mode multi-wavelength fiber laser with independent tuning of channel numbers and wavelength spacing

    NASA Astrophysics Data System (ADS)

    Li, Huizi; Huang, Tianye; Fu, Songnian; Oh, Kyunghwan; Shum, Perry; Liu, Deming

    2015-01-01

    We propose and experimentally demonstrate a multi-wavelength fiber ring laser under single-longitudinal-mode (SLM) operation with independent tuning of channel numbers and wavelength spacing. Since a programmable filter in the cavity is used as the multi-wavelength selection component, the channel numbers and wavelength spacing can be independently varied by setting the response of programmable filter. Due to the nonlinear polarization rotation arising in the semiconductor optical amplifier, stable multi-wavelength emission can be obtained. For two wavelengths lasing under SLM operation, the wavelength spacing over the operation range of 1,530-1,565 nm can be tuned from 0.46 to 20.54 nm with a resolution of 8 pm. In particular, the power and wavelength fluctuation of individual channel is <0.1 dB and 0.02 nm after 2-h monitoring.

  5. 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.

  6. Photoluminescence Study of Long Wavelength Superlattice Infrared Detectors

    NASA Technical Reports Server (NTRS)

    Hoglund, Linda; Khoshakhlagh, Arezou; Soibel, Alexander; Ting, David Z.; Hill, Cory J.; Keo, Sam; Gunapala, Sarath D.

    2011-01-01

    In this paper, the relation between the photoluminescence (PL) intensity and the PL peak wavelength was studied. A linear decrease of the PL intensity with increasing cut-off wavelength of long wavelength infrared CBIRDs was observed at 77 K and the trend remained unchanged in the temperature range 10 - 77 K. This relation between the PL intensity and the peak wavelength can be favorably used for comparison of the optical quality of samples with different PL peak wavelengths. A strong increase of the width of the PL spectrum in the studied temperature interval was observed, which was attributed to thermal broadening.

  7. Tunable optical tweezers for wavelength-dependent measurements

    PubMed Central

    Hester, Brooke; Campbell, Gretchen K.; López-Mariscal, Carlos; Filgueira, Carly Levin; Huschka, Ryan; Halas, Naomi J.; Helmerson, Kristian

    2012-01-01

    Optical trapping forces depend on the difference between the trap wavelength and the extinction resonances of trapped particles. This leads to a wavelength-dependent trapping force, which should allow for the optimization of optical tweezers systems, simply by choosing the best trapping wavelength for a given application. Here we present an optical tweezer system with wavelength tunability, for the study of resonance effects. With this system, the optical trap stiffness is measured for single trapped particles that exhibit either single or multiple extinction resonances. We include discussions of wavelength-dependent effects, such as changes in temperature, and how to measure them. PMID:22559522

  8. Dynamic Sensor Interrogation Using Wavelength-Swept Laser with a Polygon-Scanner-Based Wavelength Filter

    PubMed Central

    Kwon, Yong Seok; Ko, Myeong Ock; Jung, Mi Sun; Park, Ik Gon; Kim, Namje; Han, Sang-Pil; Ryu, Han-Cheol; Park, Kyung Hyun; Jeon, Min Yong

    2013-01-01

    We report a high-speed (?2 kHz) dynamic multiplexed fiber Bragg grating (FBG) sensor interrogation using a wavelength-swept laser (WSL) with a polygon-scanner-based wavelength filter. The scanning frequency of the WSL is 18 kHz, and the 10 dB scanning bandwidth is more than 90 nm around a center wavelength of 1,540 nm. The output from the WSL is coupled into the multiplexed FBG array, which consists of five FBGs. The reflected Bragg wavelengths of the FBGs are 1,532.02 nm, 1,537.84 nm, 1,543.48 nm, 1,547.98 nm, and 1,553.06 nm, respectively. A dynamic periodic strain ranging from 500 Hz to 2 kHz is applied to one of the multiplexed FBGs, which is fixed on the stage of the piezoelectric transducer stack. Good dynamic performance of the FBGs and recording of their fast Fourier transform spectra have been successfully achieved with a measuring speed of 18 kHz. The signal-to-noise ratio and the bandwidth over the whole frequency span are determined to be more than 30 dB and around 10 Hz, respectively. We successfully obtained a real-time measurement of the abrupt change of the periodic strain. The dynamic FBG sensor interrogation system can be read out with a WSL for high-speed and high-sensitivity real-time measurement. PMID:23899934

  9. Multi-wavelength characterization of carbonaceous aerosol

    NASA Astrophysics Data System (ADS)

    Massabò, Dario; Caponi, Lorenzo; Chiara Bove, Maria; Piazzalunga, Andrea; Valli, Gianluigi; Vecchi, Roberta; Prati, Paolo

    2014-05-01

    Carbonaceous aerosol is a major component of the urban PM. It mainly consists of organic carbon (OC) and elemental carbon (EC) although a minor fraction of carbonate carbon could be also present. Elemental carbon is mainly found in the finer PM fractions (PM2.5 and PM1) and it is strongly light absorbing. When determined by optical methods, it is usually called black carbon (BC). The two quantities, EC and BC, even if both related to the refractory components of carbonaceous aerosols, do not exactly define the same PM component (Bond and Bergstrom, 2006; and references therein). Moreover, another fraction of light-absorbing carbon exists which is not black and it is generally called brown carbon (Andreae and Gelencsér, 2006). We introduce a simple, fully automatic, multi-wavelength and non-destructive optical system, actually a Multi-Wavelength Absorbance Analyzer, MWAA, to measure off-line the light absorption in Particulate Matter (PM) collected on filters and hence to derive the black and brown carbon content in the PM This gives the opportunity to measure in the same sample the concentration of total PM by gravimetric analysis, black and brown carbon, metals by, for instance, X Ray Fluorescence, and finally ions by Ion Chromatography. Up to 16 samples can be analyzed in sequence and in an automatic and controlled way within a few hours. The filter absorbance measured by MWAA was successfully validated both against a MAAP, Multi Angle Absorption Photometer (Petzold and Schönlinner, 2004), and the polar photometer of the University of Milan. The measurement of sample absorbance at three wavelengths gives the possibility to apportion different sources of carbonaceous PM, for instance fossil fuels and wood combustion. This can be done following the so called "aethalometer method" (Sandradewi et al., 2008;) but with some significant upgrades that will be discussed together the results of field campaigns in rural and urban sites. Andreae, M.O, and Gelencsér, A. (2006). Black Carbon or Brown Carbon? The nature of light-absorbing carbonaceous aerosol. Atmospheric Chemistry and Physics, 6, 3131-3148. Bond, T., Bergstrom, R. W. (2006). Light absorption by carbonaceous particles: an investigative review. Aerosol Science and Technology, 40, 27-67. Petzold, A., Schölinner, M. (2004). Multi-angle absorption photometry—a new method for the measurement of aerosol light absorption and atmospheric black carbon. Journal of Aerosol Science, 35, 421-441. Sandradewi, J., Prevot, A.H., Zidat, S., Perron, N., Rami Alfarra, M., Lanz, V., Weingartner, E., Baltensperger, U. (2008). Using Aerosol Light Absorption Measurements for the Quantitative Determination of Wood Burning and Traffic emission Contributions to Particulate Matter. Environmental Science & Technology, 42, 3316-3323.

  10. High-performance parallel processors based on star-coupled wavelength division multiplexing optical interconnects

    DOEpatents

    Deri, Robert J. (Pleasanton, CA); DeGroot, Anthony J. (Castro Valley, CA); Haigh, Ronald E. (Arvada, CO)

    2002-01-01

    As the performance of individual elements within parallel processing systems increases, increased communication capability between distributed processor and memory elements is required. There is great interest in using fiber optics to improve interconnect communication beyond that attainable using electronic technology. Several groups have considered WDM, star-coupled optical interconnects. The invention uses a fiber optic transceiver to provide low latency, high bandwidth channels for such interconnects using a robust multimode fiber technology. Instruction-level simulation is used to quantify the bandwidth, latency, and concurrency required for such interconnects to scale to 256 nodes, each operating at 1 GFLOPS performance. Performance scales have been shown to .apprxeq.100 GFLOPS for scientific application kernels using a small number of wavelengths (8 to 32), only one wavelength received per node, and achievable optoelectronic bandwidth and latency.

  11. Prevalence of blaNDM, blaPER, blaVEB, blaIMP, and blaVIM Genes among Acinetobacter baumannii Isolated from Two Hospitals of Tehran, Iran

    PubMed Central

    Fallah, Fatemeh; Noori, Maryam; Goudarzi, Hossein; Karimi, Abdollah; Erfanimanesh, Soroor; Alimehr, Shadi

    2014-01-01

    Background and Objectives. The aim of this study was to determine the frequency of blaNDM, blaPER, blaVEB, blaIMP, and blaVIM type genes among A. baumannii isolates from hospitalized patients in two hospitals in Tehran, Iran. Patients and Methods. Antibiotic susceptibility tests were performed by Kirby-Bauer disc diffusion and Broth microdilution methods. The frequency of MBL (metallo-beta-lactamase) and ESBL (extended-spectrum-beta-lactamase) producers was evaluated by CDDT. The ?-lactamases genes were detected by PCR and sequencing methods. Results. The resistance of A. baumannii isolates against tested antibiotics was as follows: 103 (95.4%) to ceftazidime, 108 (100%) to cefotaxime, 105 (95.7%) to cefepime, 99 (91.7%) to imipenem, 99 (91.7%) to meropenem, 87 (80.6%) to amikacin, 105 (97.2%) to piperacillin, 100 (92.6%) to ciprofloxacin, 103 (95.4%) to piperacillin/tazobactam, 44 (40.7%) to gentamicin, 106 (98.1%) to ampicillin/sulbactam, 106 (98.1%) to co-trimoxazole, 87 (80.6%) to tetracycline, and 1 (1.8%) to colistin. Using combined disk diffusion test, 91 (84.2%) and 86 (86.86%) were ESBL and MBL producers, respectively. The prevalence of blaPER-1, blaVEB-1, blaIMP-1, and blaVIM-1 genes was 71 (78.03%), 36 (39.5%), 3 (3.48%), and 15 (17.44%), respectively. Conclusions. The prevalence of ESBLs and MBLs-producing A. baumannii strains detected in this study is a major concern and highlights the need of infection control measures. PMID:25133013

  12. Experimental investigation of wavelength dependence of penetration depth and imaging contrast for ultrahigh-resolution optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Ishida, S.; Nishizawa, N.; Itoh, K.

    2011-03-01

    Optical coherence tomography (OCT) is a non invasive optical imaging technology for micron-scale cross-sectional imaging of biological tissue and materials. Although OCT has many advantages in medical equipments, low penetration depth is a serious limitation for other applications. To realize the ultrahigh resolution and the high penetration depth at the same time, it is effective to choose the proper wavelength to maximize the light penetration and enhance the image contrast at deeper depths. Recently, we have demonstrated ultrahigh resolution and high penetration depth OCT by use of all-fiber based Gaussian shaped supercontinuum source at 1.7 ?m center wavelength. Gaussian-like supercontinuum with 360 nm bandwidth at center wavelength of 1.7 ?m was generated by ultrashort pulse Er doped fiber laser based system. In this paper, using 0.8 ?m and 1.3 ?m SC sources in addition to the 1.7 ?m SC source, we have investigated the wavelength dependence of ultrahigh resolution OCT in terms of penetration depth. Longitudinal resolutions at each wavelength region are almost 4.6 ?m in air. The obtained sensitivity was 95 dB for all wavelength regions. We confirmed the difference of imaging contrast and penetration depth with hamster's cheek pouch and so on. As the wavelength was increased, the magnitude of penetration depth was increased for these samples.

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

    NASA Technical Reports Server (NTRS)

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

    2003-01-01

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

  14. Innovative Long Wavelength Infrared Detector Workshop Proceedings

    NASA Technical Reports Server (NTRS)

    Grunthaner, Frank J.

    1990-01-01

    The focus of the workshop was on innovative long wavelength (lambda less than 17 microns) infrared (LWIR) detectors with the potential of meeting future NASA and DoD long-duration space application needs. Requirements are for focal plane arrays which operate near 65K using active refrigeration with mission lifetimes of five to ten years. The workshop addressed innovative concepts, new material systems, novel device physics, and current progress in relation to benchmark technology. It also provided a forum for discussion of performance characterization, producibility, reliability, and fundamental limitations of device physics. It covered the status of the incumbent HgCdTe technology, which shows encouraging progress towards LWIR arrays, and provided a snapshot of research and development in several new contender technologies.

  15. Design Of Long Wavelength Telecommunication Systems

    NASA Astrophysics Data System (ADS)

    Hardwick, D. w.; Griffin, P. D.; Cronin, D. R.

    1983-08-01

    The Plessey BICC 140 Mb/s multimode London-Birmingham long wavelength route is one system meeting BT trunk network requirements. This 205 km route is divided into 25 sections and comprises Terminal and Intermediate Station Equipment in TEP1E equipment practice and buried and in-station regenerators. The system employs LED sources and PINFET receiver modules. A microprocessor based fault locating supervisory system is provided. The cable sub-system uses loosely tubed fibres jointed using a 3-Rod splice. There are also a number of conductors to provide for ancilliary services. The overal cable joint closure uses an injection welding technique. The fibre has a nominal minimum bandwidth specification of 800 MHz-km and a nominal maximum attenuation of 1.6 dB/km.

  16. Wavelength selection for optical wireless communications systems

    NASA Astrophysics Data System (ADS)

    Rockwell, David A.; Mecherle, G. Stephen

    2001-11-01

    Eye safety, link performance, and technology infrastructure issues related to Optical Wireless (OW), also known as Free Space Optics (FSO), communication systems are examined relative to wavelength dependence. It is found that 1550 nm systems have compelling advantages over 800nm systems in the areas of laser eye safety, reduced solar background radiation, and existing technology infrastructure. 1550nm has somewhat better receiver sensitivity for PIN detectors, while 800nm has somewhat better sensitivity for APDs. Overall, the factor of 50 greater eye-safe laser power at 1550 nm provides up to 17 dB additional margin for higher data rates or penetrating fog at longer ranges. The availability of high power, low cost semiconductor lasers at 1550 nm allows these advantages to be exploited in commercially available systems.

  17. Wavelength Prograimable Spectrophotometer For Individual Plant Studies

    NASA Astrophysics Data System (ADS)

    Brach, E. J.; Simmonds, J.; Poirier, P.

    1983-11-01

    Action spectra for a number of light-mediated physiological processes, (e.g. germination, flowering, elongation) indicated that the effective wavelength for induction was between 600-700 nm and for supression was between 700-760 nm, with maxima at 660 nm and 730 nm respectively (see Smith 1975 for review). These studies predicted the existence of the photoreversible pigment phytochrome (P) existing in two forms, interconvertible by red and far-red light. The photo-equilibrium of the red absorbing (Pr) and far-red absorbing (Pfr) forms is determined by the proportions of red and far-red light available. Most of the infornation cooes from studies on dark grown plants using narrow band or uonochromatic light and until recently very little work has been done on the role of phytochrome in the natural environment. Because changes in the distribution of this physiologically active light in nature will result in an altered photo-equilibrium of the two forms of phytochrome, a new quantity c (zeta) was defined, as the ratio of the quantum flux at 660 ni to the quantum flux at 730 nm (Holmes and McCartney 1976, Monteith 1976). This relationship of zeta to the photochrome photoequilibrium (% Pfr) was determined for a series of natural and artificial light sources (Smith and Holmes 1977). owever, radiation of shorter wavelengths also has an infuence on plant development through its action on phytochrome (Parker et al 1946, Bertsch 1963). The absorption spectra of the two forms of phytochrome show, in addition to the vajor absorption bands in the red and far-red regions, minor bands in the blue and near uv (Hendricks 1962, Siegelman and Fuer 1964). Also photochrome does undergo light-induced absorbance changes 'in vitro' in the blue region of the spectrum (Everett and Briggs 1970). A more accurate estimate of photochrome photoequilibria would

  18. Chemical analysis of uranium-niobium alloys by wavelength dispersive spectroscopy at the sigma complex

    SciTech Connect

    Papin, Pallas A.

    2012-06-01

    Uranium-niobium alloys play an important role in the nation's nuclear stockpile. It is possible to chemically quantify this alloy at a micron scale by using a technique know as wavelength dispersive spectroscopy. This report documents how this technique was used and how it is possible to reproduce measurements of this type. Discussion regarding the accuracy and precision of the measurements, the development of standards, and the comparison of different ways to model the matrices are all presented.

  19. High-speed wide tuning range wavelength swept laser around 1310 nm for frequency domain OCT

    Microsoft Academic Search

    Minghui Chen; Zhihua Ding; Tong Wu; Lei Xu

    2008-01-01

    Optical coherence tomography (OCT) is an emerging cross-sectional imaging technology. It uses broadband light sources to achieve axial image resolutions on a few microns scale. In this paper, the principle of Fourier domain mode-locked (FDML) wavelength swept laser for swept source optical coherence tomography (SS-OCT) is presented and crucial parameters of the laser system are discussed. On analysis of different

  20. Optically controlled phased-array antenna using wavelength-selective true time delay

    Microsoft Academic Search

    B. Jalali; S. Yegnanarayanan

    2000-01-01

    A novel all-optical tunable optical delay line device is used as a true-time-delay generator for squint-free beam steering in optically-controlled microwave phased-array antennas. The mapping of optical wavelength to the microwave beam direction permits a hardware efficient architecture for the optical control unit that can easily scale to large aperture antenna arrays. The performance of a complete optically controlled phased

  1. Wavelength of Reticulate Bedforms on the Tharsis Montes, Mars: Spacing Control by Atmospheric Density

    NASA Astrophysics Data System (ADS)

    Bridges, N. T.; Rosenthal, A.; Lorenz, R. D.

    2009-12-01

    Images of the Tharsis Montes and surrounding areas from the High Resolution Imaging Science Experiment (HiRISE) document numerous ridges at the scale of several meters that have been interpreted as aeolian ripples composed of dust aggregates [Bridges et al., 2009]. Dominant morphologies are linear/accordion and honeycomb, with the former common on the volcano flanks and plains and the latter in calderas and other closed depressions. We have recently measured the wavelength of reticulate bedforms in nine HiRISE images on Olympus, Ascraeus, and Pavonis Mons over an elevation range of 3.4 to 21.6 km to determine if there is dependence of wavelength on local atmospheric pressure. This elevation range is greater than that elsewhere on Mars and given the probable similar composition of the bedforms, allows us to critically examine any wavelength dependence on pressure. Three of the images are dominated by honeycomb bedforms, with the other images having mainly linear or accordion. Within each image, 4 sub-regions were selected. Within these sub-regions, 10 traverses were made in which the wavelengths of 4-7 ripple sets were measured, each along a parallel line. This resulted in 200-234 ripple wavelength measurements per image. The results show that reticulate bedform wavelengths are inversely proportional to local atmospheric pressure (power law fit of -0.9, with R2 of 0.6). This suggests that atmospheric density is controlling the wavelength of ripple formation. At present, we are uncertain of the precise physical mechanism that may exert such a control and will present several hypotheses in our poster. We note that the threshold speed is inversely proportional to the square root of density. Ripple wavelength, in turn, is proportional to the square of the excess shear velocity [Pelletier, 2009], and, if this is proportional to the friction speed, wavelength should be proportional to inverse density, consistent with the observations. Variations from a perfect fit may be reflective of local wind conditions, threshold speeds, and particle properties. Bridges, NT. et al. (2009), Icarus, doi:10.1016/j.icarus.2009.07.035 Pelletier, J.D. (2009), Geomorphology, 105, 322-33.

  2. Er/Yb co-doped fiber amplifier with wavelength-tuned Yb-band ring resonator

    NASA Astrophysics Data System (ADS)

    Sobon, Grzegorz; Sliwinska, Dorota; Kaczmarek, Pawel; Abramski, Krzysztof M.

    2012-08-01

    Erbium-ytterbium co-doped fiber amplifier with wavelength-tuned Yb-band loop resonator is presented. The amplified spontaneous emission (ASE) from Yb ions is utilized to stimulate a laser emission at several wavelengths from the 1 ?m band in the 1550 nm amplifier. The wavelength of this lasing is tuned by introducing a fiber Bragg grating (FBG). The results show, that the overall efficiency of the amplifier at nominal 1550 nm wavelength can be increased by introducing a feedback loop with 1040 nm and 1050 nm FBG. This loop also protects the Er/Yb amplifier from parasitic lasing at 1 ?m and allows significant output power scaling without risk of self-pulsing.

  3. A rapid, dispersion-based wavelength-stepped and wavelength-swept laser for optical coherence tomography

    PubMed Central

    Tozburun, Serhat; Siddiqui, Meena; Vakoc, Benjamin J.

    2014-01-01

    Abstract: Optical-domain subsampling enables Fourier-domain OCT imaging at high-speeds and extended depth ranges while limiting the required acquisition bandwidth. To perform optical-domain subsampling, a wavelength-stepped rather than a wavelength-swept source is required. This preliminary study introduces a novel design for a rapid wavelength-stepped laser source that uses dispersive fibers in combination with a fast lithium-niobate modulator to achieve wavelength selection. A laser with 200 GHz wavelength-stepping and a sweep rate of 9 MHz over a 94 nm range at a center wavelength of 1550 nm is demonstrated. A reconfiguration of this source design to a continuous wavelength-swept light for conventional Fourier-domain OCT is also demonstrated. PMID:24663631

  4. CONFIRMING THE PRIMARILY SMOOTH STRUCTURE OF THE VEGA DEBRIS DISK AT MILLIMETER WAVELENGTHS

    SciTech Connect

    Hughes, A. Meredith; Plambeck, Richard; Chiang, Eugene [Department of Astronomy, University of California, Berkeley, CA 94720 (United States); Wilner, David J.; Andrews, Sean M. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Mason, Brian [National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903-2475 (United States); Carpenter, John M. [California Institute of Technology, Department of Astronomy, MC 105-24, Pasadena, CA 91125 (United States); Chiang, Hsin-Fang [Institute for Astronomy, University of Hawaii, 640 North Aohoku Place, Hilo, HI 96720 (United States); Williams, Jonathan P. [Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States); Hales, Antonio [Joint ALMA Observatory, Av. El Golf 40, Piso 18, Santiago (Chile); Su, Kate [Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States); Dicker, Simon; Korngut, Phil; Devlin, Mark, E-mail: mhughes@astro.berkeley.edu [Department of Physics and Astronomy, University of Pennsylvania, 209 South 33rd Street, Philadelphia, PA 19104 (United States)

    2012-05-01

    Clumpy structure in the debris disk around Vega has been previously reported at millimeter wavelengths and attributed to concentrations of dust grains trapped in resonances with an unseen planet. However, recent imaging at similar wavelengths with higher sensitivity has disputed the observed structure. We present three new millimeter-wavelength observations that help to resolve the puzzling and contradictory observations. We have observed the Vega system with the Submillimeter Array (SMA) at a wavelength of 880 {mu}m and an angular resolution of 5''; with the Combined Array for Research in Millimeter-wave Astronomy (CARMA) at a wavelength of 1.3 mm and an angular resolution of 5''; and with the Green Bank Telescope (GBT) at a wavelength of 3.3 mm and angular resolution of 10''. Despite high sensitivity and short baselines, we do not detect the Vega debris disk in either of the interferometric data sets (SMA and CARMA), which should be sensitive at high significance to clumpy structure based on previously reported observations. We obtain a marginal (3{sigma}) detection of disk emission in the GBT data; the spatial distribution of the emission is not well constrained. We analyze the observations in the context of several different models, demonstrating that the observations are consistent with a smooth, broad, axisymmetric disk with inner radius 20-100 AU and width {approx}> 50 AU. The interferometric data require that at least half of the 860 {mu}m emission detected by previous single-dish observations with the James Clerk Maxwell Telescope be distributed axisymmetrically, ruling out strong contributions from flux concentrations on spatial scales of {approx}<100 AU. These observations support recent results from the Plateau de Bure Interferometer indicating that previous detections of clumpy structure in the Vega debris disk were spurious.

  5. Analysis of wavelength-dependent photoisomerization quantum yields in bilirubins by fitting two exciton absorption bands

    NASA Astrophysics Data System (ADS)

    Mazzoni, M.; Agati, G.; Troup, G. J.; Pratesi, R.

    2003-09-01

    The absorption spectra of bilirubins were deconvoluted by two Gaussian curves of equal width representing the exciton bands of the non-degenerate molecular system. The two bands were used to study the wavelength dependence of the (4Z, 15Z) rightarrow (4Z, 15E) configurational photoisomerization quantum yield of the bichromophoric bilirubin-IXalpha (BR-IX), the intrinsically asymmetric bile pigment associated with jaundice and the symmetrically substituted bilirubins (bilirubin-IIIalpha and mesobilirubin-XIIIalpha), when they are irradiated in aqueous solution bound to human serum albumin (HSA). The same study was performed for BR-IX in ammoniacal methanol solution (NH4OH/MeOH). The quantum yields of the configurational photoprocesses were fitted with a combination function of the two Gaussian bands normalized to the total absorption, using the proportionality coefficients and a scaling factor as parameters. The decrease of the (4Z, 15Z) rightarrow (4Z, 15E) quantum yield with increasing wavelength, which occurs for wavelengths longer than the most probable Franck-Condon transition of the molecule, did not result in a unique function of the exciton absorptions. In particular we found two ranges corresponding to different exciton interactions with different proportionality coefficients and scaling factors. The wavelength-dependent photoisomerization of bilirubins was described as an abrupt change in quantum yield as soon as the resulting excitation was strongly localized in each chromophore. The change was correlated to a variation of the interaction between the two chromophores when the short-wavelength exciton absorption became vanishingly small. With the help of the circular dichroism (CD) spectrum of BR-IX in HSA, a small band was resolved in the bilirubin absorption spectrum, delivering part of the energy required for the (4Z, 15Z) rightarrow (4Z, 15E) photoisomerization of the molecule.

  6. Three-wavelength generation from cascaded wavelength conversion in monolithic periodically poled lithium niobate

    NASA Astrophysics Data System (ADS)

    Xiao, Kun; Zhang, Jing; Chen, Bao-Qin; Zhang, Qiu-Lin; Zhang, Dong-Xiang; Feng, Bao-Hua; Zhang, Jing-Yuan

    2015-01-01

    Tunable coherent emission is generated in a single-pass, cascaded wavelength conversion process from mode-locked laser-pumped monolithic periodically poled lithium niobate (PPLN). Three ranges of wavelength, including visible output from 628 nm to 639 nm, near-infrared output from 797 nm to 816 nm, and mid-infrared output from 3167 nm to 3459 nm, were obtained from the monolithic PPLN, which consists of a 10-mm section for 532-nm-pumped optical parametric generation (OPG) and a 7-mm section for 1064-nm-pumped sum frequency generation (SFG). A pump-to-signal conversion efficiency of 23.4% for OPG at 50 °C and a quantum efficiency of 26.2% for SFG at 200 °C were obtained. Project supported by the National Basic Research Program of China (Grant No. 2013CB632704).

  7. Composite multiple wavelength laser material and multiple wavelength laser for use therewith

    NASA Technical Reports Server (NTRS)

    Jani, Mahendra G. (Inventor)

    1997-01-01

    A composite multiple wavelength laser material is provided and is typically constructed with a common axis of construction in the form of a rod of uniform cross-section. The rod comprises a plurality of segments of laser material bonded, e.g., diffusion bonded, to one another along the common axis. Each segment lases at a unique wavelength when excited to produce a laser emission. The segments can be made from a birefringent material doped with laser active ions. If the same birefringent host material is used for all segments, ground-state absorption losses can be reduced by terminating either end of the rod with end segments made from undoped pieces of the birefringent material.

  8. Four-wavelength retinal vessel oximetry

    NASA Astrophysics Data System (ADS)

    Drewes, Jonathan Jensen

    1999-11-01

    This dissertation documents the design and construction of a four-wavelength retinal vessel oximeter, the Eye Oximeter (EOX). The EOX scans low-powered laser beams (at 629, 678, 821 and 899 nm) into the eye and across a targeted retinal vessel to measure the transmittance of the blood within the vessel. From the transmittance measurements, the oxygen saturation of the blood within the vessel is computed. Retinal vessel oxygen saturation has been suggested as a useful parameter for monitoring a wide range of conditions including occult blood loss and a variety of ophthalmic diseases. An artificial eye that simulates the geometry of a human retinal vessel was constructed and used to calibrate the EOX saturation measurement. A number of different oximetry equations were developed and tested. From measurements made on whole human blood in the artificial eye, an oximetry equation that places a linear wavelength dependance on the scattering losses (3% decrease from 629 to 899 nm) is found to best calibrate the EOX oxygen saturation measurement. This calibration also requires that an adjustment be made to the absorption coefficient of hemoglobin at 629 nm that has been reported in the literature. More than 4,000 measurements were made in the eyes of three human subjects during the development of the EOX. Applying the oximetry equation developed through the in vitro experiments to human data, the average human retinal venous oxygen saturation is estimated to be 0.63 +/- 0.07 and the average human retinal arterial oxygen saturation is 0.99 +/- 0.03. Furthermore, measurements made away from the optic disk resulted in a larger variance in the calculated saturation when compared to measurements made on the optic disk. A series of EOX experiments using anesthetized swine helped to verify the sensitivity of the EOX measurement of oxygen saturation. It is found that the calibration in swine differed from the calibration in the artificial eye. An empirical calibration from the swine measurements was applied to the human measurements. With this correction, the average human retinal venous oxygen saturation was found to be 0.40 +/- 0.08 and the average human retinal arterial oxygen saturation was found to be 0.98 +/- 0.03. This suggests that the swine, human and model eye measurements may each require a different calibration because of differences between the spectral characteristics of their ocular fundi. Finally, further in vitro and in vivo experimentation is proposed so that the goal of having an accurate, absolute measurement of the human retinal vessel oxygen saturation will be realized.

  9. Identification of aerosol composition from multi-wavelength lidar measurements

    NASA Technical Reports Server (NTRS)

    Wood, S. A.

    1984-01-01

    This paper seeks to develop the potential of lidar for the identification of the chemical composition of atmospheric aerosols. Available numerical computations suggest that aerosols can be identified by the wavelength dependence of aerosol optical properties. Since lidar can derive the volume backscatter coefficient as a function of wavelength, a multi-wavelength lidar system may be able to provide valuable information on the composition of aerosols. This research theoretically investigates the volume backscatter coefficients for the aerosol classes, sea-salts, and sulfates, as a function of wavelength. The results show that these aerosol compositions can be characterized and identified by their backscatter wavelength dependence. A method to utilize multi-wavelength lidar measurements to discriminate between compositionally different thin aerosol layers is discussed.

  10. Broadband Wavelength Spanning Holographic Polymer Dispersed Liquid Crystals

    NASA Astrophysics Data System (ADS)

    Rai, Kashma; Shriyan, Sameet; Fontecchio, Adam

    2008-03-01

    Broadened interaction wavelength of holographic polymer dispersed liquid crystals (HPDLCs) have extensive applications in beam steering for instrument clusters, hyperspectral imaging, wavelength filtering and construction of lightweight optics. A novel simultaneous time and spatial multiplexing formation configuration is proposed here, to increase narrow wavelength reflecting notch to broad range wavelength spanning device. HPDLC films have electro-optic controllability by applying field. No moving parts, light weight, small footprint compared to prisms and lenses, high color purity make the broadband wavelength HPDLCs desirable for the above applications. Varying the incident laser beam exposure angles using motorized rotating stage, during formation is the key step here for their formation in a single medium. The fabricated broadband wavelength sensitive HPDLCs are characterized for the uniformity of the reflected peak and electro optic response. Their output wavefront is analyzed using wavefront analysis technique.

  11. Design of wavelength-selective waveplates using genetic algorithm

    NASA Astrophysics Data System (ADS)

    Katayama, Ryuichi

    2013-03-01

    Wavelength-selective waveplates, which act either identically or differently for plural wavelengths, are useful for optical systems that handle plural wavelengths. However, they cannot be analytically designed because of the complexity of their structure. Genetic algorithm is one of the methods for solving optimization problems and is used for several kinds of optical design (e.g., design of thin films, diffractive optical elements, and lenses). I considered that it is effective for designing wavelength-selective waveplates also and tried to design them using the genetic algorithm for the first time to the best of my knowledge. As a result, four types of wavelength-selective waveplate for three wavelengths (405, 650, and 780 nm) were successfully designed. These waveplates are useful for Blu-ray Disc/Digital Versatile Disc/Compact Disc compatible optical pickups.

  12. A stable and inexpensive wavelength reference for precise wavelength calibration of radial velocity spectrographs

    NASA Astrophysics Data System (ADS)

    Feger, Tobias; Ireland, Michael J.; Bento, Joao; Bacigalupo, Carlos

    2014-08-01

    We present a stable, inexpensive wavelength reference, based on a white-light interferometer for the use on current and future (arrays of) diffraction-limited radial velocity (RV) spectrographs. The primary aim of using an interferometer is to obtain a dense sinusoidal wavelength reference with spectral coverage between 450-650 nm. Its basic setup consists of an unbalanced fiber Mach-Zehnder interferometer (FMZI) that creates an interference pattern in the spectral domain due to superposition of phase delayed light, set by a fixed optical path-length difference (OPD). To achieve long-term stability, the interferometer is actively locked to a stable atomic line. The system operates in closed-loop using a thermo-optic modulator as the phase feedback component. We conducted stability measurements by superimposing the wavelength reference with thorium-argon (ThAr) emission lines and found the differential RMS shift to be ~5 m s-1 within 30 minute bins in an experiment lasting 5 hours.

  13. Wavelength Control in a Double Contact FP-LD

    Microsoft Academic Search

    Ah-Hyun Kim; Ju-Hee Park; Ho-Sung Jo; Chang-Hee Lee

    We propose a double contact Fabry-Perot laser diode (DCLD) to have a constant lasing wavelength re- gardless of operating temperature. The passive optical network based on wavelength divi- sion multiple access (WDM-PON) can provide almost unlimited bandwidth to the subscribers with protocol transparency. To realize WDM-PON, a low cost WDM source is essential. The wavelength-locked Fabry-Perot laser diode (FP-LD) was

  14. Tunable dual-wavelength-switching fiber grating laser

    Microsoft Academic Search

    Y. Z. Xu; H. Y. Tam; W. C. Du; M. S. Demokan

    1998-01-01

    We report a tunable dual-wavelength-switching fiber grating laser by exploiting the large homogeneous gain broadening in erbium (Er)-doped fiber to suppress simultaneous lasing. Wavelength switching was accomplished through a novel design which has two overlapping cavities sharing a single-gain medium. The loss corresponding to one of the lasing wavelengths can be modulated via an optical chopper. Output power of about

  15. Design of scalable optical interconnection network using wavelength division multiplexing

    Microsoft Academic Search

    WenCai Jing; Jindong Tian; Ge Zhou; Yimo Zhang; Wei Liu; Xun Zhang

    2000-01-01

    This paper describes the two-layer scalable wavelength routing optical interconnection network being developed in Tianjin University. The top layer of the network is multi- wavelength bi-directional optical bus, which has high bandwidth and low latency. The optical bus is made up of passive components, no wavelength-tunable devices have been sued. As a result, the optical bus has low communication latency

  16. Free-space wavelength-multiplexed optical scanner

    Microsoft Academic Search

    Zahid Yaqoob; Azhar A. Rizvi; Nabeel A. Riza

    2001-01-01

    A wavelength-multiplexed optical scanning scheme is proposed for deflecting a free-space optical beam by selection of the wavelength of the light incident on a wavelength-dispersive optical element. With fast tunable lasers or optical filters, this scanner features microsecond domain scan setting speeds and large-diameter apertures of several centimeters or more for subdegree angular scans. Analysis performed indicates an optimum scan

  17. GHRS Ech-B Wavelength Monitor -- Cycle 4

    NASA Astrophysics Data System (ADS)

    Soderblom, David

    1994-01-01

    This proposal defines the spectral lamp test for Echelle B. It is an internal test which makes measurements of the wavelength lamp SC2. It calibrates the carrousel function, Y deflections, resolving power, sensitivity, and scattered light. The wavelength calibration dispersion constants will be updated in the PODPS calibration data base. It will be run every 4 months. The wavelengths may be out of range according to PEPSI or TRANS. Please ignore the errors.

  18. Visible-Wavelength Spectroscopy of Asteroids

    NASA Astrophysics Data System (ADS)

    Bus, S. J.; Vilas, F.; Barucci, M. A.

    Since first becoming available for astronomical research in the early 1980s, charge-coupled-device (CCD) spectrographs have had a profound impact on our ability to measure the spectralreflectance properties of asteroids. High signal-to-noise, low-resolution spectra, covering the visible-wavelength region from 0.4 to 1.0 µm, are now routinely obtained for asteroids much fainter than were measured during the Eight-Color Asteroid Survey. By recording the entire spectral range in a single exposure, some of the difficulties associated with multifilter photometry, arising from the inherent rotation of asteroids or from temporal variations in sky conditions, can be avoided. Studies involving CCD spectroscopy have resulted in the discovery of several absorption features in the spectra of asteroids and have provided new insights into the compositional nature of asteroid surfaces. Spectral surveys have also helped to refine our understanding of the orbital distributions of asteroid classes. We discuss the practical aspects of asteroid spectroscopy, focusing on observing procedures, data reduction techniques, and potential sources for uncertainty in the reduced spectra. We also review some of the applications of asteroid spectroscopy, and discuss how these observations have impacted the structure of asteroid taxonomy.

  19. Laser Wavelength Dependency of Laser Supported Detonation

    NASA Astrophysics Data System (ADS)

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

    2011-11-01

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

  20. Visible-wavelength semiconductor lasers and arrays

    DOEpatents

    Schneider, R.P. Jr.; Crawford, M.H.

    1996-09-17

    The visible semiconductor laser includes an InAlGaP active region surrounded by one or more AlGaAs layers on each side, with carbon as the sole p-type dopant. Embodiments of the invention are provided as vertical-cavity surface-emitting lasers (VCSELs) and as edge-emitting lasers (EELs). One or more transition layers comprised of a substantially indium-free semiconductor alloy such as AlAsP, AlGaAsP, or the like may be provided between the InAlGaP active region and the AlGaAS DBR mirrors or confinement layers to improve carrier injection and device efficiency by reducing any band offsets. Visible VCSEL devices fabricated according to the invention with a one-wavelength-thick (1{lambda}) optical cavity operate continuous-wave (cw) with lasing output powers up to 8 mW, and a peak power conversion efficiency of up to 11%. 5 figs.

  1. Visible-wavelength semiconductor lasers and arrays

    DOEpatents

    Schneider, Jr., Richard P. (Albuquerque, NM); Crawford, Mary H. (Albuquerque, NM)

    1996-01-01

    A visible semiconductor laser. The visible semiconductor laser includes an InAlGaP active region surrounded by one or more AlGaAs layers on each side, with carbon as the sole p-type dopant. Embodiments of the invention are provided as vertical-cavity surface-emitting lasers (VCSELs) and as edge-emitting lasers (EELs). One or more transition layers comprised of a substantially indium-free semiconductor alloy such as AlAsP, AlGaAsP, or the like may be provided between the InAlGaP active region and the AlGaAS DBR mirrors or confinement layers to improve carrier injection and device efficiency by reducing any band offsets. Visible VCSEL devices fabricated according to the invention with a one-wavelength-thick (1.lambda.) optical cavity operate continuous-wave (cw) with lasing output powers up to 8 mW, and a peak power conversion efficiency of up to 11%.

  2. Neutron scintillators using wavelength shifting fibers

    SciTech Connect

    Hutchinson, D.P.; Miller, V.C.; Ramsey, J.A.

    1995-06-01

    A proposed design for an optically-based, one-dimension scintillation detector to replace the gas-filled position-sensitive proportional counter currently used for a wide-angle neutron detector (WAND) at the high-Flux Isotope Reactor (HFIR) at the Oak Ridge National Laboratory (ORNL) is presented. The scintillator, consisting of a mixture of {sup 6}LiF and ZnS(Ag) powders in an epoxy binder, is coupled to an array of wavelength shifting optical fibers which provide position resolution. The wide-angle neutron detector is designed to cover a 120 degree arc with a 75 cm radius of curvature. The final detector design provides for 600 optical fibers coupled to the scintillator screen with an angular resolution of 0.2 degrees. Each individual pixel of the detector will be capable of operating at count rates exceeding 1 MHz. Results are presented from the measurement of neutron conversion efficiencies for several screen compositions, gamma-ray sensitivity, and spatial resolution of a 16 element one-dimensional array prototype.

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

    NASA Astrophysics Data System (ADS)

    Arthur, John

    1996-09-01

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

  4. Wavelength resolved UV photodesorption and photochemistry of CO2 ice

    NASA Astrophysics Data System (ADS)

    Fillion, Jean-Hugues; Fayolle, Edith C.; Michaut, Xavier; Doronin, Misha; Philippe, Laurent; Rakovski, Joseph; Romanzin, Claire; Champion, Noel; Öberg, Karin I.; Linnartz, Harold; Bertin, Mathieu

    2014-01-01

    Over the last four years we have illustrated the potential of a novel wavelength-dependent approach in determining molecular processes at work in the photodesorption of interstellar ice analogs. This method, utilizing the unique beam characteristics of the vacuum UV beamline DESIRS at the French synchrotron facility SOLEIL, has revealed an efficient indirect desorption mechanism that scales with the electronic excitations in molecular solids. This process, known as DIET - desorption induced by electronic transition - occurs efficiently in ices composed of very volatile species (CO, N2), for which photochemical processes can be neglected. In the present study, we investigate the photodesorption energy dependence of pure and pre-irradiated CO2 ices at 10-40 K and between 7 and 14 eV. The photodesorption from pure CO2 is limited to photon energies above 10.5 eV and is clearly initiated by CO2 excitation and by the contribution of dissociative and recombination channels. The photodesorption from "pre-irradiated" ices is shown to present an efficient additional desorption pathway below 10 eV, dominating the desorption depending on the UV-processing history of the ice film. This effect is identified as an indirect DIET process mediated by photoproduced CO, observed for the first time in the case of less volatile species. The results presented here pinpoint the importance of the interconnection between photodesorption and photochemical processes in interstellar ices driven by UV photons having different energies.

  5. Saturn's aurora observed by Cassini camera in visible wavelengths

    NASA Astrophysics Data System (ADS)

    Dyudina, Ulyana; Porco, Carolyn; Ingersoll, Andrew; Ewald, Shawn; Wellington, Danika

    Cassini camera's movies in 2009-2013 show Saturn's aurora in both the northern and southern hemispheres. The color of the aurora changes from pink at a few hundreds of km above the cloud tops to purple at 1000-1500 km above the cloud tops. The spectrum observed in 9 filters spanning wavelengths from 250 nm to 1000 nm has a prominent H-alpha line and roughly agrees with the laboratory simulated auroras [1]. Auroras in both hemispheres vary dramatically with longitude. Auroras form bright arcs, sometimes a spiral around the pole, and sometimes double arcs at 70-75(°) both north and south latitude. 10,000-km-scale longitudinal brightness structures can persist for more than 100 hours. This structures rotate together with Saturn. Besides the steady structure, the auroras brighten suddenly on the timescales of few minutes. 1000-km-scale disturbances may move faster or lag behind Saturn's rotation on timescales of tens of minutes. The persistence of the longitudinal structure of the aurora in two long observations in 2009 and 2012 allowed us to estimate its period of rotation of 10.65 ± 0.15 h for 2009 and 10.8± 0.1 h for 2012. The 2009 north aurora period is close to the north branch of Saturn Kilometric Radiation (SKR) detected at that time. The 2012 south aurora period is longer than any SKR periods detected at the time, but it is similar to the SKR period of the south branch of SKR periods in 2004-2008. These periods are also close to the rotation period of the lightning storms on Saturn. We discuss those periodicities and their relevance to Saturn's internal rotation. [1] Aguilar, A. et al. The Electron-Excited Mid-Ultraviolet to Near-Infrared Spectrum of H_2: Cross Sections and Transition Probabilities. Astrophys. J. Supp. Ser. 177, 388-407 (2008).

  6. Investigating short wavelength correlated errors on low resolution mode altimetry

    NASA Astrophysics Data System (ADS)

    Poisson, Jean-Christophe; Thibaut, Pierre; Dibarboure, Gérald; Labroue, Sylvie; Lasne, Yannick; Boy, François; Picot, Nicolas

    2013-04-01

    Although conventional radar altimetry products (Jason1, Jason2, LRM CRYOSAT2, etc) have a spatial resolution as high as 300 m, the observation of ocean scales smaller than 100 km is limited by the existence of a "spectral hump", i.e. a geographically coherent error. In the frame of the future altimetry missions (SAR for Cryosat -2 and Sentinel-3 missions and interferometry for the SWOT mission) it becomes crucial to investigate again and to better understand the signals obtained at small scales by conventional altimeter missions. Through an analysis of simulations, we show that heterogeneous backscattering scenes can result in the corruption of the altimeter waveforms and retracked parameters. The retrackers used in current ground processors cannot well fit the Brown model during backscattering events because this model has been designed for a homogeneous scene. The error is also propagated along-track because of the size and shape of the low resolution mode (LRM) disc-shaped footprint. The hump phenomenon is shown to be almost ubiquitous in the ocean, yet more intense at low latitudes and in the Indian Ocean and Western Pacific Ocean, where backscattering events are more frequent. Its overall signature could be a Gaussian-like random signal smooth for wavelengths smaller than 15 km, i.e. white noise on 1 Hz products. The analysis of current data from 5 altimetry missions highlights the influence of the instrument design and altitude, and the influence of the retracker used. The spectral hump is a systematic response to random events and it is possible to mitigate it with new processing. Simulations and geographically limited datasets from the synthetic aperture radar mode (SARM) of Cryosat-2 show that the thin stripe-shaped synthetic footprint of SARM might be less sensitive to the artifact.

  7. Smoke optical depths - Magnitude, variability, and wavelength dependence

    NASA Technical Reports Server (NTRS)

    Pueschel, R. F.; Russell, P. B.; Colburn, D. A.; Ackerman, T. P.; Allen, D. A.

    1988-01-01

    An airborne autotracking sun-photometer has been used to measure magnitudes, temporal/spatial variabilities, and the 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. Jet fuel smoke optical depths were found to be generally less wavelength dependent than background aerosol optical depths. Forest fire smoke optical depths, however, showed a wide range of wavelength depedences, such as incidents of wavelength-independent extinction.

  8. Dual-Wavelength Internal-Optically-Pumped Semiconductor Laser Diodes

    NASA Astrophysics Data System (ADS)

    Green, Benjamin

    Dual-wavelength laser sources have various existing and potential applications in wavelength division multiplexing, differential techniques in spectroscopy for chemical sensing, multiple-wavelength interferometry, terahertz-wave generation, microelectromechanical systems, and microfluidic lab-on-chip systems. In the drive for ever smaller and increasingly mobile electronic devices, dual-wavelength coherent light output from a single semiconductor laser diode would enable further advances and deployment of these technologies. The output of conventional laser diodes is however limited to a single wavelength band with a few subsequent lasing modes depending on the device design. This thesis investigates a novel semiconductor laser device design with a single cavity waveguide capable of dual-wavelength laser output with large spectral separation. The novel dual-wavelength semiconductor laser diode uses two shorter- and longer-wavelength active regions that have separate electron and hole quasi-Fermi energy levels and carrier distributions. The shorter-wavelength active region is based on electrical injection as in conventional laser diodes, and the longer-wavelength active region is then pumped optically by the internal optical field of the shorter-wavelength laser mode, resulting in stable dual-wavelength laser emission at two different wavelengths quite far apart. Different designs of the device are studied using a theoretical model developed in this work to describe the internal optical pumping scheme. The carrier transport and separation of the quasi-Fermi distributions are then modeled using a software package that solves Poisson's equation and the continuity equations to simulate semiconductor devices. Three different designs are grown using molecular beam epitaxy, and broad-area-contact laser diodes are processed using conventional methods. The modeling and experimental results of the first generation design indicate that the optical confinement factor of the longer-wavelength active region is a critical element in realizing dual-wavelength laser output. The modeling predicts lower laser thresholds for the second and third generation designs; however, the experimental results of the second and third generation devices confirm challenges related to the epitaxial growth of the structures in eventually demonstrating dual-wavelength laser output.

  9. Using wavelength and slope to infer the historical origin of semiarid vegetation bands.

    PubMed

    Sherratt, Jonathan A

    2015-04-01

    Landscape-scale patterns of vegetation occur worldwide at interfaces between semiarid and arid climates. They are important as potential indicators of climate change and imminent regime shifts and are widely thought to arise from positive feedback between vegetation and infiltration of rainwater. On gentle slopes the typical pattern form is bands (stripes), oriented parallel to the contours, and their wavelength is probably the most accessible statistic for vegetation patterns. Recent field studies have found an inverse correlation between pattern wavelength and slope, in apparent contradiction with the predictions of mathematical models. Here I show that this "contradiction" is based on a flawed approach to calculating the wavelength in models. When pattern generation is considered in detail, the theory is fully consistent with empirical results. For realistic parameters, degradation of uniform vegetation generates patterns whose wavelength increases with slope, whereas colonization of bare ground gives the opposite trend. Therefore, the empirical finding of an inverse relationship can be used, in conjunction with climate records, to infer the historical origin of the patterns. Specifically, for the African Sahel my results suggest that banded vegetation originated by the colonization of bare ground during circa 1760-1790 or since circa 1850. PMID:25831503

  10. Cloud Power Spectra-Dependence on Solar Zenith Angle and Wavelength, Implications for Cloud Optical Property Retrievals

    NASA Technical Reports Server (NTRS)

    Oreopoulos, Lazaros; Marshak, A.; Cahalan, R. F.; Wen, G.

    1999-01-01

    Scale breaks (spatial scales at which power-law exponent changes occur) observed in Landsat radiances have proven to be useful indicators of radiative interactions, and have aided the development of improved techniques in the remote sensing of clouds. This work extends previous theoretical studies to absorbing wavelengths by using both Landsat Thematic Mapper (TM) observations and Monte Carlo (MC) simulations to infer the systematic dependencies of power spectral shape on cloud characteristics, illumination conditions, and wavelength. We show that MC simulations operating on a simple fractal model of horizontally inhomogeneous clouds produce power spectra that qualitatively resemble observed spectra. We also show that the decrease in the spectra power-law exponent seen at intermediate scales (referred to as "roughening") as the Sun becomes more oblique is more pronounced at absorbing wavelengths. An automated procedure designed to detect the small scale break location is unable to find systematic differences between TM Band 4 and Band 7, despite the fact that MC simulations point to systematic differences in horizontal fluxes. The effect of these qualitative characteristics of the spatial spectra on the retrieval of cloud optical properties is examined by comparing power spectra of nadir radiances with power spectra of optical properties retrieved using either traditional Independent Pixel Approximation approaches or modifications based on normalized radiance indices and the inverse Non-local Independent Pixel Approximation. Assuming that the actual cloud properties follow perfect scaling behavior at all scales, we show the improvement of the proposed retrieval modifications.

  11. Highly accurate Michelson type wavelength meter that uses a rubidium stabilized 1560 nm diode laser as a wavelength reference

    SciTech Connect

    Masuda, Shin; Kanoh, Eiji; Irisawa, Akiyoshi; Niki, Shoji

    2009-08-01

    We investigated the accuracy limitation of a wavelength meter installed in a vacuum chamber to enable us to develop a highly accurate meter based on a Michelson interferometer in 1550 nm optical communication bands. We found that an error of parts per million order could not be avoided using famous wavelength compensation equations. Chromatic dispersion of the refractive index in air can almost be disregarded when a 1560 nm wavelength produced by a rubidium (Rb) stabilized distributed feedback (DFB) diode laser is used as a reference wavelength. We describe a novel dual-wavelength self-calibration scheme that maintains high accuracy of the wavelength meter. The method uses the fundamental and second-harmonic wavelengths of an Rb-stabilized DFB diode laser. Consequently, a highly accurate Michelson type wavelength meter with an absolute accuracy of 5x10{sup -8} (10 MHz, 0.08 pm) over a wide wavelength range including optical communication bands was achieved without the need for a vacuum chamber.

  12. A Multi-Wavelength Blazar Campaign

    NASA Astrophysics Data System (ADS)

    Fields, Nicole

    2007-12-01

    We present optical fluxes for six blazars in B and V Johnson and R Cousins filters taken at the 0.9 meter WIYN telescope at Kitt Peak. Observations were made of Markarian 421, Markarian 501, 1ES 1959+650, 1ES 1218+304, 1ES 2344+514, and H 1426+428. These particular blazars were chosen because of their location in the Northern hemisphere and their classification as High frequency peaked BL Lacertae objects (HBLs). HBLs are neutrino point source candidates. If neutrinos were observed from these sources, we would be able to discriminate between some of the various possible mechanisms that could be causing the emission of high energy gamma rays as seen from these sources. As of yet, there is no real consensus about the mechanisms which can explain all of the observations at various wavelengths taken of these sources. Our optical observations were made over the time periods from April 2006 to June 2006 and from February 2007 to July 2007 on an almost nightly basis. Optical observations of these sources are being continued currently at WIYN. We hope to use these data in the future to do a time dependent analysis in conjunction with X-ray data taken by the NASA satellites, Rossi X-ray Timing Explorer (RXTE) and Swift, with data taken by the Whipple 10 meter gamma ray telescope in Arizona, and with neutrino observations being taken by IceCube at the South Pole. This work was supported by the REU and ASSURE programs through NSF award AST-0453442.

  13. Long Wavelength Emission from Extrasolar Planets

    NASA Astrophysics Data System (ADS)

    Butler, B. J.

    2003-05-01

    At long wavelengths (? > 6 m; ? < 40 MHz), the emission from Jupiter is dominated by extremely strong and variable cyclotron maser emission. This emission arises from solar wind deposited keV electrons in the magnetosphere, which subsequently develop an anisotropy in their energy distribution, becoming unstable. When these electrons encounter the auroral zones of the planet, emission results at the gyrofrequency of the magnetic field at the location of the electron (fg = 2.8 Bgauss MHz). The emission is very sporadic, but can reach magnitudes of 105 Jy. In addition, the emission is modulated by the satellite Io. It would be extremely valuable to detect this type of emission from Extrasolar Giant Planets (EGPs), because it provides the following: Direct detection of the EGP; Presence and strength of the EGP magnetic field; Existence of satellites; Rotation period of the EGP. Current predictions (using the so-called ``Radiometric Bode's Law'') suggest that it is possible to detect this type of emission from EGPs, but that it is necessary to catch the planet in an outburst. Even in outburst, the predicted emission is weak, of order mJy. Searches with the VLA at 74 and 330 MHz have been unsuccessful so far [2]. Added sensitivity and lower frequencies are what are needed for more conclusive searches for this emission. There are currently two instruments being proposed to be built which would provide additional sensitivity at low frequencies: LOFAR and SKA. Prospects seem good that at least LOFAR may come on-line within the next decade or so. [1] Farrell et al., 1999, JGR, 104, 14025; Zarka et al., 2001, Ap&SS, 277, 293. [2] Bastian et al., 2000, ApJ, 545, 1058.

  14. All-fiber wavelength-tunable Tm/Ho-codoped laser between 1727 nm and 2030 nm

    NASA Astrophysics Data System (ADS)

    Xue, Guanghui; Zhang, Bin; Yin, Ke; Yang, Weiqiang; Hou, Jing

    2015-02-01

    Lasers in the eye-safe 2 ?m spectral region are attracting significant interest due to a variety of applications such as atmospheric lidar sensing and medical treatment, which require laser sources matching the absorption lines of various molecules in the 2 ?m wavelength region. We demonstrate an all-fiber Tm/Ho-codoped laser operating in the 2 ?m wavelength region with a wide wavelength tuning range of more than 300 nm. The Tm/Ho-codoped fiber laser (THFL) was built in a ring cavity configuration with a fiberized grating-based tunable filter to select the operating wavelength. The tunable wavelength range of the THFL was from 1727 nm to 2030 nm. To the best of our knowledge, this is the widest tuning range that has been reported for an all-fiber rare-earth-doped laser to date. Efficient short wavelength operation was also achieved. The output power of the THFL was further scaled up from 1810 nm to 2010 nm by using a stage of Tm/Ho-codoped fiber amplifier (THFA), which exhibited the maximum slope efficiency of 42.6% with output power of 408 mW at 1910 nm.

  15. Wavelength Calibration of 1-5 micron Infrared Spectra

    Microsoft Academic Search

    A. S. Hedden; L. Wallace; K. Hinkle; R. Joyce

    2000-01-01

    Infrared arrays have resulted in a new generation of infrared spectrographs using cryogenic gratings, including instruments such as CGS4, CSHELL, Phoenix, and NIRSPEC. Unlike the previous generation instruments, which were Fourier Transform Spectrographs, grating spectrographs require external standards for wavelength calibration. In order to provide a laboratory wavelength calibration, we have undertaken an analysis of the infrared ThNeAr hollow cathode

  16. Long-wavelength fluorescence polarization immunoassay for surfactant determination

    Microsoft Academic Search

    M. L. Sánchez-Martínez; M. P. Aguilar-Caballos; S. A. Eremin; A. Gómez-Hens

    2007-01-01

    A new homogeneous fluoroimmunoassay method based on the use of dynamic long-wavelength fluorescence polarization is presented here for the first time. This methodology, which is applied to the determination of linear alkylbenzenesulfonates (LASs) in water samples, involves the use of a new long-wavelength tracer synthesized from the oxazine dye Nile Blue (NB) via a carbodiimide method. This tracer exhibits fluorescent

  17. Fast fiber-optic multi-wavelength pyrometer

    NASA Astrophysics Data System (ADS)

    Fu, Tairan; Tan, Peng; Pang, Chuanhe; Zhao, Huan; Shen, Yi

    2011-06-01

    A fast fiber-optic multi-wavelength pyrometer was developed for the ultraviolet-visible-near infrared spectra from 200 nm to 1700 nm using a CCD detector and an InGaAs detector. The pyrometer system conveniently and quickly provides the sufficient choices of multiple measurement wavelengths using optical diffraction, which avoids the use of narrow-band filters. Flexible optical fibers are used to transmit the radiation so the pyrometer can be used for temperature measurements in harsh environments. The setup and calibrations (wavelength calibration, nonlinearity calibration, and radiation response calibration) of this pyrometer system were described. Development of the multi-wavelength pyrometer involved optimization of the bandwidth and temperature discrimination of the multiple spectra data. The analysis results showed that the wavelength intervals, ??CCD = 30 nm and ??InGaAs = 50 nm, are the suitable choices as a tradeoff between the simple emissivity model assumption and the multiple signal discrimination. The temperature discrimination was also quantificationally evaluated for various wavelengths and temperatures. The measurement performance of the fiber-optic multi-wavelength pyrometer was partially verified through measurements with a high-temperature blackbody and actual hot metals. This multi-wavelength pyrometer can be used for remote high-temperature measurements.

  18. Pump wavelength and power distribution algorithm in Raman amplifier

    Microsoft Academic Search

    Xiaobin Hong

    2004-01-01

    An algorithm is discussed to achieve target gain and gain flatness in Raman amplifier through adjusting the pump wavelength and power distribution. It is convenient for Raman amplifier designer to decide the pump wavelength accounting of the trade-off between the gain flattening and gain efficiency. The algorithm based on both the effective interaction lengths and propagation equation, as well as

  19. Systematic wavelength selection for improved multivariate spectral analysis

    DOEpatents

    Thomas, Edward V. (2828 Georgia NE., Albuquerque, NM 87110); Robinson, Mark R. (1603 Solano NE., Albuquerque, NM 87110); Haaland, David M. (809 Richmond Dr. SE., Albuquerque, NM 87106)

    1995-01-01

    Methods and apparatus for determining in a biological material one or more unknown values of at least one known characteristic (e.g. the concentration of an analyte such as glucose in blood or the concentration of one or more blood gas parameters) with a model based on a set of samples with known values of the known characteristics and a multivariate algorithm using several wavelength subsets. The method includes selecting multiple wavelength subsets, from the electromagnetic spectral region appropriate for determining the known characteristic, for use by an algorithm wherein the selection of wavelength subsets improves the model's fitness of the determination for the unknown values of the known characteristic. The selection process utilizes multivariate search methods that select both predictive and synergistic wavelengths within the range of wavelengths utilized. The fitness of the wavelength subsets is determined by the fitness function F=.function.(cost, performance). The method includes the steps of: (1) using one or more applications of a genetic algorithm to produce one or more count spectra, with multiple count spectra then combined to produce a combined count spectrum; (2) smoothing the count spectrum; (3) selecting a threshold count from a count spectrum to select these wavelength subsets which optimize the fitness function; and (4) eliminating a portion of the selected wavelength subsets. The determination of the unknown values can be made: (1) noninvasively and in vivo; (2) invasively and in vivo; or (3) in vitro.

  20. Long-wavelength thermocapillary instability with the Soret effect

    Microsoft Academic Search

    A. Oron; A. A. Nepomnyashchy

    2004-01-01

    We study the onset of Marangoni instability of the quiescent equilibrium in a binary liquid layer with a nondeformable interface in the presence of the Soret effect. Linear stability analysis shows that both monotonic and oscillatory long-wavelength instabilities are possible depending on the value of the Soret number chi. Sets of long-wavelength nonlinear evolution equations are derived for both types

  1. Path allocation for wavelength path sharing University College London

    E-print Network

    Haddadi, Hamed

    : Wavelength path sharing (WPS) was introduced previously as a means of bridging the gap between the bit answers can be found depending upon the method used for the comparison. 2. Wavelength path sharing (WPS A logical path segment between WPS nodes S & T being transparently routed through X. Key #12;2 shows

  2. Multiple wavelength operation of an erbium-doped fiber laser

    Microsoft Academic Search

    J. W. Dawson; K. J. Vahala

    1992-01-01

    Wavelength-locked, six-channel, colasing operation using a single gain medium is reported for the first time. The system is an all-fiber, erbium-amplifier-based design that uses a grating wavelength division multiplexer with a fixed channel spacing of 4.8 nm for frequency selection. The authors investigate two possible configurations for the laser cavity

  3. Wavelength Assignment on Bounded Degree Trees of Rings

    E-print Network

    Zhang, Richard "Hao"

    Wavelength Assignment on Bounded Degree Trees of Rings Zhengbing Bian, Qian-Ping Gu {zbian. A popular network topology is a tree of rings which is a collection of rings connected in a tree structure wavelengths for the WA problem on a tree of rings with node degree at most eight. This improves the previous

  4. On the wavelength of the green coronal line - Fe XIV

    NASA Astrophysics Data System (ADS)

    Rybanský, M.; Rušin, V.; Dermendjiev, V.; Buyukliyev, G.

    A wavelength of the green coronal line (Fe XIV) has never been determined in a laboratory. The authors used for a determination of wavelength of this line spectral observations from Lomnický Štít coronal station on July 31, 1981. From these observations more than 2990 spectra have been measured. A value of ? = 530.2765 nm has been obtained.

  5. All-optical wavelength conversion by semiconductor optical amplifiers

    Microsoft Academic Search

    Terji Durhuus; Benny Mikkelsen; Carsten Joergensen; Soeren Lykke Danielsen; Kristian E. Stubkjaer

    1996-01-01

    Following a brief introduction to the applications for wavelength conversion and the different available conversion techniques, the paper gives an in depth analysis of cross gain and cross phase wavelength conversion in semiconductor optical amplifiers. The influence of saturation filtering on the bandwidth of the converters is explained and conditions for conversion at 20 Gb\\/s or more are identified. The

  6. Optical Networking And Dense Wavelength Division Multiplexing (DWDM)

    E-print Network

    Jain, Raj

    Optical Networking And Dense Wavelength Division Multiplexing (DWDM) Muralikrishna Gandluru, gandluru@cis.ohio-state.edu Abstract: This paper deals with the twin concepts of optical networking and dense wavelength division multiplexing. The paper talks about the various optical network architectures

  7. Routing and wavelength assignment in all-optical networks

    Microsoft Academic Search

    Rajiv Ramaswami; Kumar N. Sivarajan

    1995-01-01

    This paper considers the problem of routing connections in a reconfigurable optical networkusing wavelength division multiplexing, where each connection between a pair of nodes inthe network is assigned a path through the network and a wavelength on that path, suchthat connections whose paths share a common link in the network are assigned differentwavelengths.We derive an upper bound on the carried

  8. Fast fiber-optic multi-wavelength pyrometer.

    PubMed

    Fu, Tairan; Tan, Peng; Pang, Chuanhe; Zhao, Huan; Shen, Yi

    2011-06-01

    A fast fiber-optic multi-wavelength pyrometer was developed for the ultraviolet-visible-near infrared spectra from 200 nm to 1700 nm using a CCD detector and an InGaAs detector. The pyrometer system conveniently and quickly provides the sufficient choices of multiple measurement wavelengths using optical diffraction, which avoids the use of narrow-band filters. Flexible optical fibers are used to transmit the radiation so the pyrometer can be used for temperature measurements in harsh environments. The setup and calibrations (wavelength calibration, nonlinearity calibration, and radiation response calibration) of this pyrometer system were described. Development of the multi-wavelength pyrometer involved optimization of the bandwidth and temperature discrimination of the multiple spectra data. The analysis results showed that the wavelength intervals, ??(CCD) = 30 nm and ??(InGaAs) = 50 nm, are the suitable choices as a tradeoff between the simple emissivity model assumption and the multiple signal discrimination. The temperature discrimination was also quantificationally evaluated for various wavelengths and temperatures. The measurement performance of the fiber-optic multi-wavelength pyrometer was partially verified through measurements with a high-temperature blackbody and actual hot metals. This multi-wavelength pyrometer can be used for remote high-temperature measurements. PMID:21721719

  9. Visible, multi-wavelength, fiber based Raman source

    Microsoft Academic Search

    P. A. Champert; S. V. Popov; J. R. Taylor

    2001-01-01

    Summary form only given. The Raman gain of silica glass can be utilized to create multi-wavelength visible sources operating in a broad range of wavelengths providing a high peak power visible pump source is employed. To date, Raman generation in the visible has usually been achieved using inefficient large frame lasers such as Ar ion, excimer or frequency doubled or

  10. Wavelength conversion in a highly nonlinear chalcogenide microstructured fiber

    E-print Network

    Boyer, Edmond

    mixing effect in a 1 m-long highly nonlinear GeAsSe chalcogenide fiber. The high nonlinearity-optical wavelength conversion based on four- wave mixing (FWM). The first demonstration has been proposed by V. G. TaWavelength conversion in a highly nonlinear chalcogenide microstructured fiber Sy Dat Le,1

  11. Radio-echo studies of meteors at 68-centimeter wavelength

    Microsoft Academic Search

    J. V. Evans

    1965-01-01

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

  12. Precisely tunable L-band multi-wavelength fiber laser

    NASA Astrophysics Data System (ADS)

    Qin, Xuwei; Wang, Zhaoying; Gao, Cuiqin; Sang, Mei; Jia, Dongfang; Yang, Tianxin

    2013-02-01

    In this paper, we propose a scheme on precisely tunable L-band multi-wavelength fiber laser. This fiber laser has two main characteristics namely broad wavelength band, uniform power spectrum and precise electronic tunability. About 65 wavelengths output within +/- 1.5dB power variation with 50GHz channel spacing in broad spectrum range can be obtained at room temperature. The measured optical signal noise ratio (OSNR) and line width of each wavelength are about 20dB and 345.5MHz respectively. Theses 65 wavelengths are able to be tuned simultaneously up or down in frequency domain with a tuning step ranging from 10 MHz to 14 GHz. The tuning resolution can potentially be as low as 1 Hz in our experiment.

  13. Lethal effects of short-wavelength visible light on insects

    PubMed Central

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

    2014-01-01

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

  14. Polarization-independent optical wavelength filter for channel dropping applications

    DOEpatents

    Deri, Robert J. (Pleasanton, CA); Patterson, Frank (Livermore, CA)

    1996-01-01

    The polarization dependence of optical wavelength filters is eliminated by using waveguide directional couplers. Material birefringence is used to compensate for the waveguide (electromagnetic) birefringence which is the original cause of the polarization dependence. Material birefringence is introduced in a controllable fashion by replacing bulk waveguide layers by finely layered composites, such as multiple quantum wells using III-V semiconductor materials. The filter has use in wavelength-division-multiplexed fiber optic communication systems. This filter has broad application for wavelength-tunable receivers in fiber optic communication links, which may be used for telecommunications, optical computer interconnect links, or fiber optic sensor systems. Since multiple-wavelength systems are increasingly being used for all of these applications, the filter is useable whenever a rapidly tunable, wavelength-filtering receiver is required.

  15. Polarization-independent optical wavelength filter for channel dropping applications

    DOEpatents

    Deri, R.J.; Patterson, F.

    1996-05-07

    The polarization dependence of optical wavelength filters is eliminated by using waveguide directional couplers. Material birefringence is used to compensate for the waveguide (electromagnetic) birefringence which is the original cause of the polarization dependence. Material birefringence is introduced in a controllable fashion by replacing bulk waveguide layers by finely layered composites, such as multiple quantum wells using III-V semiconductor materials. The filter has use in wavelength-division multiplexed fiber optic communication systems. This filter has broad application for wavelength-tunable receivers in fiber optic communication links, which may be used for telecommunications, optical computer interconnect links, or fiber optic sensor systems. Since multiple-wavelength systems are increasingly being used for all of these applications, the filter is useable whenever a rapidly tunable, wavelength-filtering receiver is required. 14 figs.

  16. Cosmological long-wavelength solutions and primordial black hole formation

    E-print Network

    Harada, Tomohiro; Nakama, Tomohiro; Koga, Yasutaka

    2015-01-01

    We construct cosmological long-wavelength solutions without symmetry in general gauge conditions compatible with the long-wavelength scheme. We then specify the relationship among the solutions in different time slicings. Nonspherical long-wavelength solutions are particularly important for primordial structure formation in the epoch of soft equations of state. Applying this framework to spherical symmetry, we show the equivalence between long-wavelength solutions in the constant mean curvature slicing and asymptotic quasi-homogeneous solutions in the comoving slicing. We derive the correspondence relation and compare the results of numerical simulations of primordial black hole (PBH) formation. In terms of $\\tilde{\\delta}_{c}$, the value which the averaged density perturbation at threshold in the comoving slicing would take at horizon entry in the first-order long-wavelength expansion, we find that the sharper the transition from the overdense region to the FRW universe is, the larger the $\\tilde{\\delta}_{c}...

  17. Lethal effects of short-wavelength visible light on insects

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

  18. Evaluation of wavelength groups for discrimination of agricultural cover types

    NASA Technical Reports Server (NTRS)

    Kumar, R.

    1978-01-01

    Multispectral scanner data in twelve spectral channels, in the wavelength range 0.46 to 11.7 microns, acquired in July, 1971, for three flightlines, were analyzed by applying automatic pattern recognition techniques. These twelve spectral channels were divided into four wavelength groups (W1, W2, W3 and W4), each consisting of three wavelength groups - with respect to their estimated probability of correct classification (Pc) - in discriminating agricultural cover types. The same analysis was also done for the data acquired in August, to investigate the effect of time on these results. The effect of deletion of each of the wavelength groups on Pc, in the subsets of one to nine channels, is given. Values of Pc for all possible combinations of wavelength groups, in the subsets of one to eleven channels, are also given.

  19. Long-wavelength infrared camera (LWIRC): a 10 micron camera for the Keck telescope

    NASA Astrophysics Data System (ADS)

    Wishnow, Edward H.; Danchi, William C.; Tuthill, Peter G.; Wurtz, Ronald E.; Jernigan, J. G.; Arens, John F.

    1998-08-01

    The long wavelength IR camera is a facility instrument for the Keck Observatory designed to operate at the f/25 forward Cassegrain focus of the Keck I telescope. The camera operates over the wavelength band 7-13 micrometers using ZnSe transmissive optics. A set of filters, a circular variable filter, and a mid-IR polarizer are available, as are three plate scales: 0.05 inch, 0.10 inch, 0.12 inch per pixel. The camera focal plane array and optics are cooled using liquid helium. The system has been refurbished with a 128 X 128 pixel Si:As detector array. The electronics readout system used to clock the array is compatible wit both the hardware and software of the other Keck IR instruments NIRC and LWS. A new pre-amplifier/A-D converter has been designed and constructed which decreases greatly the system susceptibility to noise.

  20. Photoemission electron microscopy of localized surface plasmons in silver nanostructures at telecommunication wavelengths

    E-print Network

    Mårsell, Erik; Arnold, Cord L; Xu, Hongxing; Mauritsson, Johan; Mikkelsen, Anders

    2015-01-01

    We image the field enhancement at Ag nanostructures using femtosecond laser pulses with a center wavelength of 1.55 micrometer. Imaging is based on non-linear photoemission observed in a photoemission electron microscope (PEEM). The images are directly compared to ultra violet PEEM and scanning electron microscopy (SEM) imaging of the same structures. Further, we have carried out atomic scale scanning tunneling microscopy (STM) on the same type of Ag nanostructures and on the Au substrate. Measuring the photoelectron spectrum from individual Ag particles shows a larger contribution from higher order photoemission process above the work function threshold than would be predicted by a fully perturbative model, consistent with recent results using shorter wavelengths. Investigating a wide selection of both Ag nanoparticles and nanowires, field enhancement is observed from 30% of the Ag nanoparticles and from none of the nanowires. No laser-induced damage is observed of the nanostructures neither during the PEEM ...

  1. Long wavelength infrared camera (LWIRC): a 10 micron camera for the Keck Telescope

    SciTech Connect

    Wishnow, E.H.; Danchi, W.C.; Tuthill, P.; Wurtz, R.; Jernigan, J.G.; Arens, J.F.

    1998-05-01

    The Long Wavelength Infrared Camera (LWIRC) is a facility instrument for the Keck Observatory designed to operate at the f/25 forward Cassegrain focus of the Keck I telescope. The camera operates over the wavelength band 7-13 {micro}m using ZnSe transmissive optics. A set of filters, a circular variable filter (CVF), and a mid-infrared polarizer are available, as are three plate scales: 0.05``, 0.10``, 0.21`` per pixel. The camera focal plane array and optics are cooled using liquid helium. The system has been refurbished with a 128 x 128 pixel Si:As detector array. The electronics readout system used to clock the array is compatible with both the hardware and software of the other Keck infrared instruments NIRC and LWS. A new pre-amplifier/A-D converter has been designed and constructed which decreases greatly the system susceptibility to noise.

  2. Decimeter-Wavelength Polarimetric Radar Imaging of the Icy Moons of Jupiter

    NASA Technical Reports Server (NTRS)

    Rosen, P. A.; Gurrola, E. M.; Madsen, S. N.

    2003-01-01

    Imaging radars with wavelengths in the range of 10 cm to 1 m can deeply penetrate the surface of an icy body, revealing details of the geomorphology, local structure, and electrical properties of the upper layers. Radar studies of icy surfaces on Earth have used the polarization state of backscatter echoes at multiple frequencies to characterize the surface and subsurface properties of glaciers, showing relatively smooth surfaces on the scale of radar wave-lengths, and subsurface scattering from volume scatterers consistent with ice pipes and lenses. These volume scattering effects are evident in enhanced polarization ratios over a limited range of backscatter incidence angles. The Galilean satellites exhibit similarly enhanced polarization ratios and volumetric scattering effects, but the observations are limited in angular resolution, leading to ambiguity in interpreting the scattering mechanisms and their structural implications.

  3. Neptune’s global circulation deduced from multi-wavelength observations

    NASA Astrophysics Data System (ADS)

    de Pater, Imke; Fletcher, Leigh N.; Luszcz-Cook, Statia; DeBoer, David; Butler, Bryan; Hammel, Heidi B.; Sitko, Michael L.; Orton, Glenn; Marcus, Philip S.

    2014-07-01

    We observed Neptune between June and October 2003 at near- and mid-infrared wavelengths with the 10-m W.M. Keck II and I telescopes, respectively; and at radio wavelengths with the Very Large Array. Images were obtained at near-infrared wavelengths with NIRC2 coupled to the adaptive optics system in both broad- and narrow-band filters between 1.2 and 2.2 ?m. In the mid-infrared we imaged Neptune at wavelengths between 8 and 22 ?m, and obtained slit-resolved spectra at 8-13 ?m and 18-22 ?m. At radio wavelengths we mapped the planet in discrete filters between 0.7 and 6 cm. We analyzed each dataset separately with a radiative-transfer program that is optimized for that particular wavelength regime. At southern midlatitudes the atmosphere appears to be cooler at mid-infrared wavelengths than anywhere else on the planet. We interpret this to be caused by adiabatic cooling due to air rising at midlatitudes at all longitudes from the upper troposphere up to ?0.1 mbar levels. At near-infrared wavelengths we find two distinct cloud layers at these latitudes: a relatively deep layer of clouds (presumably methane) in the troposphere at pressure levels P?300-?600 mbar, which we suggest to be caused by the large-scale upwelling and its accompanying adiabatic cooling and condensation of methane; and a higher, spatially intermittent, layer of clouds in the stratosphere at 20-30 mbar. The latitudes of these high clouds encompass an anticyclonic band of zonal flow, which suggests that they may be due to strong, but localized, vertical upwellings associated with local anticyclones, rather than plumes in convective (i.e., cyclonic) storms. Clouds at northern midlatitudes are located at the highest altitudes in the atmosphere, near 10 mbar. Neptune’s south pole is considerably enhanced in brightness at both mid-infrared and radio wavelengths, i.e., from ?0.1 mbar levels in the stratosphere down to tens of bars in the troposphere. We interpret this to be due to subsiding motions from the stratosphere all the way down to the deep troposphere. The enhanced brightness observed at mid-infrared wavelengths is interpreted to be due to adiabatic heating by compression in the stratosphere, and the enhanced brightness temperature at radio wavelengths reveals that the subsiding air over the pole is very dry; the relative humidity of H2S over the pole is only 5% at altitudes above the NH4SH cloud at ?40 bar. The low humidity region extends from the south pole down to latitudes of 66°S. This is near the same latitudes as the south polar prograde jet signifying the boundary of the polar vortex. We suggest that the South Polar Features (SPFs) at latitudes of 60-70° are convective storms, produced by baroclinic instabilities expected to be produced at latitudes near the south polar prograde jet. Taken together, our data suggest a global circulation pattern where air is rising above southern and northern midlatitudes, from the troposphere up well into the stratosphere, and subsidence of dry air over the pole and equator from the stratosphere down into the troposphere. We suggest that this pattern extends all the way from ?0.1 mbar down to pressures of ?40 bar.

  4. A Study of Wavelength Calibration of NEWSIPS High-Dispersion Spectra

    E-print Network

    Myron A. Smith

    2001-04-03

    In this study we cross-correlate many IUE echellograms of a variety of stars to evaluate systematic error sources in the wavelength zeropoint of all three cameras. We first evaluated differences between the final archived ("NEWSIPS") and the originally processed ("IUESIPS") spectra. These show a clear time dependence in zeropoint for the SWP camera due to revisions in the IUESIPS wavelength scale. Small IUESIPS - NEWSIPS differences are also found for the LWR camera. We also examined wavelength zeropoint disparities between data obtained both through the small and large entrance apertures and for observations made by different target acquisition modes for faint and bright stars. We found that velocities resulting from these alternative observing modes are nil. For large-aperture observations the dominant error source is the target position placement in the aperture. We searched for spurious trends with time, and found only a suggestion of time trends for faint stars observed with the SWP camera. We also discovered 1-day, +/-3 km/s sinusoidsal patterns in intensive monitoring data which are ascribable to changes in telescope focus resulting from thermal drifts. In the second part of the paper, we measured mean zeropoint errors of NEWSIPS echellogram data against laboratory results by using the GHRS spectral atlas of the 10 Lac. We find that the derived apparent velocity difference for this star is -1 +/-3.5 km/s. Several less precise comparisons lead to similar results. The zeropoints of the NEWSIPS-processed LWP/LWR cameras are evaluated and are also found to be nearly zero (+/-5 km/s) relative to HST atlases of Arcturus and Procyon atlas. These results do not support result by Gonzalez-Riestra et al. that corrections should be introduced to the wavelength scales of various NEWSIPS high-dispersion data products.

  5. Analytical formula of wavelength-dependent transparent current and its implications for designing wavelength sensors and WDM lasers

    Microsoft Academic Search

    San-Liang Lee

    2001-01-01

    The wavelength dependency of transparent current is investigated theoretically and empirically for bulk and quantum-well (QW) materials. A new analytical formula is presented for obtaining accurate Fermi levels of QW structures under current injection. The transparent current can be described with an exponential function of the wavelength using two fitting parameters. The simple expression can clearly indicate the fundamental limit

  6. Laser line wavelength sensor based in a dual-wavelength fiber laser with a Hi-Bi loop Sagnac interferometer

    NASA Astrophysics Data System (ADS)

    Durán Sánchez, M.; Álvarez Tamayo, R. I.; Pottiez, O.; Kuzin, E. A.; Ibarra-Escamilla, B.; González-García, A.; Barcelata Pinzón, A.

    2014-06-01

    We present an experimental method for straight forward dual wavelength Erbium doped fiber linear cavity laser characterization based in laser line spectrum behavior due to the Hi-Bi FOLM transmission spectrum wavelength displacement by temperature variations in the fiber loop. The laser operation is for a single and dual mode, obtained through the adjustment of the cavity losses by the Sagnac interferometer spectrum wavelength displacement due to the temperature variation of the fiber loop. The method allow determine the laser operation from a single emission line and a two emission lines simultaneously through the Sagnac transmittance spectrum optical power variations measurement due to wavelength spectrum shifting for each laser wavelength generated separately and overlapping these obtained spectrums.

  7. Multi-wavelength fiber laser based on self-seed light amplification and wavelength-dependent gain

    NASA Astrophysics Data System (ADS)

    Luo, Yiyang; Xia, Li; Sun, Qizhen; Li, Wei; Ran, Yanli; Liu, Deming

    2015-03-01

    In this paper, a multi-wavelength fiber laser based on self-seed light amplification and wavelength-dependent gain is proposed and demonstrated. A pumped erbium-doped fiber (EDF) in the linear cavity acts as the seed light source, which is also conducive to the gain equalization. A high power erbium-doped fiber amplifier (EDFA) is deployed for self-seed amplification, and a highly nonlinear fiber (HNLF) is incorporated in the ring cavity to alleviate the mode competition induced by the homogeneous gain broadening of EDF. In the experiments, 25-wavelength operation within 0.5 dB uniformity is achieved with the extinction ratio of ~42 dB using 500 m HNLF, and 38-wavelength operation within 3 dB uniformity is obtained with the extinction ratio of ~35 dB using 1000 m HNLF. Our proposed laser has more lasing wavelengths with a better uniformity and stability.

  8. Standard Reference Materials: Hydrogen Cyanide H13C14N Absorption Reference for 1530-1560 nm Wavelength Calibration - SRM 2519

    Microsoft Academic Search

    Sarah L. Gilbert; William C. Swann; Chih-Ming Wang

    Standard Reference Material (SRM) 2519 is an optical-fiber-coupled absorption cell containing hydrogen cyanide (H13C14N) gas. It is intended for use in calibrating the wavelength scale of wavelength measuring instruments in the 1500 nm region. About 50 accurately measured absorption lines of the R and P branch of the 2 ?3 rotational-vibrational band of H 13C14N are located in the 1530-1560

  9. Wavelength optimization for quantitative spectral imaging of breast tumor margins.

    PubMed

    Lo, Justin Y; Brown, J Quincy; Dhar, Sulochana; Yu, Bing; Palmer, Gregory M; Jokerst, Nan M; Ramanujam, Nirmala

    2013-01-01

    A wavelength selection method that combines an inverse Monte Carlo model of reflectance and a genetic algorithm for global optimization was developed for the application of spectral imaging of breast tumor margins. The selection of wavelengths impacts system design in cost, size, and accuracy of tissue quantitation. The minimum number of wavelengths required for the accurate quantitation of tissue optical properties is 8, with diminishing gains for additional wavelengths. The resulting wavelength choices for the specific probe geometry used for the breast tumor margin spectral imaging application were tested in an independent pathology-confirmed ex vivo breast tissue data set and in tissue-mimicking phantoms. In breast tissue, the optical endpoints (hemoglobin, ?-carotene, and scattering) that provide the contrast between normal and malignant tissue specimens are extracted with the optimized 8-wavelength set with <9% error compared to the full spectrum (450-600 nm). A multi-absorber liquid phantom study was also performed to show the improved extraction accuracy with optimization and without optimization. This technique for selecting wavelengths can be used for designing spectral imaging systems for other clinical applications. PMID:23613927

  10. Wavelength-Agile External-Cavity Diode Laser for DWDM

    NASA Technical Reports Server (NTRS)

    Pilgrim, Jeffrey S.; Bomse, David S.

    2006-01-01

    A prototype external-cavity diode laser (ECDL) has been developed for communication systems utilizing dense wavelength- division multiplexing (DWDM). This ECDL is an updated version of the ECDL reported in Wavelength-Agile External- Cavity Diode Laser (LEW-17090), NASA Tech Briefs, Vol. 25, No. 11 (November 2001), page 14a. To recapitulate: The wavelength-agile ECDL combines the stability of an external-cavity laser with the wavelength agility of a diode laser. Wavelength is modulated by modulating the injection current of the diode-laser gain element. The external cavity is a Littman-Metcalf resonator, in which the zeroth-order output from a diffraction grating is used as the laser output and the first-order-diffracted light is retro-reflected by a cavity feedback mirror, which establishes one end of the resonator. The other end of the resonator is the output surface of a Fabry-Perot resonator that constitutes the diode-laser gain element. Wavelength is selected by choosing the angle of the diffracted return beam, as determined by position of the feedback mirror. The present wavelength-agile ECDL is distinguished by design details that enable coverage of all 60 channels, separated by 100-GHz frequency intervals, that are specified in DWDM standards.

  11. 128x128-pixel long-wavelength infrared acquisition camera

    NASA Astrophysics Data System (ADS)

    Levan, Paul D.; Colucci, D'nardo; Cowan, William D.; Figie, Brian D.; Stewart, Eric J.

    1994-07-01

    This paper describes a Phillips Laboratory internal design for a high sensitivity, large field of view IR acquisition camera. Currently, the acquisition of a satellite with the 1.5 meter telescope of the Starfire Optical Range typically requires a sunlit target and dark sky. However, the level of thermal radiation from such a satellite is often sufficiently high in the long wavelength IR (LWIR) to permit detection with ground based telescopes irrespective of target illumination. The drawbacks of LWIR acquisition include the high levels of thermal radiation from both the telescope and the atmosphere which pose two constraints: (1), the 'background signal' usually exceeds the target signal and must be removed on time scales over which it is relatively constant, and (2), associated with the background signal is a noise level that dominates all system noise sources. The background signal level at the detector array for our application varies between 1015 to 1016 photons sec-1 cm-2, depending on the IR bandpass used. Our optical design for the LWIR acquisition camera maps a 128x128 pixel detector array onto a two milliradian (mrad) scene. The optical design uses two aspheric lenses, one to re-image the field onto a cold field stop, and the telescope pupil onto a cryogenic chopping mirror and collocated radiation stop. The second lens re-images the field stop onto the detector array. Aberrations are designed to be better than diffraction limited over the entire two mrad field of view. The end product of the acquisition system is a video display of the IR scene, with the background signal removed. A user then positions mouse-driven cross hairs over a target in the scene. The resulting position and time update is used to revise the target ephemeris, and to provide pointing information for target acquisition by other SOR tracking platforms.

  12. (Very) long wavelength deformations of Africa since late Cretaceous times

    NASA Astrophysics Data System (ADS)

    Guillocheau, Francois; The Topoafrica Working Group

    2014-05-01

    The African continent is characterized by a bimodal topography. The 900-1100m elevation peak mainly corresponds to the Southern African (Kalahari Plateau) and the East African Domes, whereas the 300-400 m peak is the mean elevation of the Sahara. Those reliefs are characterized by very long wavelength (x1000 km), similar to the scale of mantle dynamics. The origin of this relief, dynamic topography or more local controls (e.g. old lithospheric inheritance), are highly debated and more geological controls are required. To answer those questions - in the frame of the TopoAfrica project - we performed a geomorphical study of Africa coupled with the tectono-sedimentary study of the sedimentary basins or the magmatism. (1) Most of the African reliefs are younger than the Early-Middle Eocene (55-40 Ma). (2) The only significative old relief of Africa is the Southern African Plateau that experienced a two steps evolution, a first uplift during Late Cretaceous contemporaneous with high erosion under humid climatic conditions, followed by a second uplift during Late Eocene - Early Oligocene. The present-day arid to semi-arid climate could explain its preservation. (3) Most of Africa is uplifted during Miocene times (20-10 Ma), age of most of the present-day reliefs. (4) The African magmatic provinces (Virunga-Kivu, Cameroon Volcanic Line, Hoggar, Aïr…) are associated with local uplifts that started around Late Eocene times (40-35 Ma). The relationships of those reliefs with the migration of the African plate over the African superswell will be discussed.

  13. A decade of long-wavelength CMB measurements

    SciTech Connect

    Kogut, A.; Bensadoun, M.; Bersanelli, M.; De Amici, G.; Levin, S.; Limon, M.; Smoot, G.F. (California Univ., Berkeley, CA (United States). Space Sciences Lab.)

    1991-04-15

    We have continued the efforts of an international collaboration begun in 1979 to measure the long-wavelength (Rayleigh-Jeans) spectrum of the cosmic microwave background (CMB). We have repeated measurements at a number of wavelengths over many years, using different equipment and techniques to investigate the possibility of unsuspected systematic errors in the measurements. We conclude that our results show no evidence for significant undiagnosed systematic effects. Our results have improved in precision over ten years and yield significant limits on physical processes in the early universe. The CMB spectrum is consistent with a blackbody over{gt}3 decades of wavelength.

  14. Effect of graphene on plasmonic metasurfaces at infrared wavelengths

    SciTech Connect

    Ogawa, Shinpei, E-mail: Ogawa.Shimpei@eb.MitsubishiElectric.co.jp; Fujisawa, Daisuke; Ueno, Masashi [Advanced Technology R and D Center, Mitsubishi Electric Corporation, 8-1-1 Tsukaguchi-Honmachi, Amagasaki, Hyogo 661-8661 (Japan)] [Advanced Technology R and D Center, Mitsubishi Electric Corporation, 8-1-1 Tsukaguchi-Honmachi, Amagasaki, Hyogo 661-8661 (Japan)

    2013-11-15

    Significant enhancement of infrared transmittance by the presence of a graphene layer on a plasmonic metasurface (PLM) has been demonstrated. PLMs with different configurations were fabricated, and their transmittance with and without graphene was compared. Selective enhancement by graphene occurred at the plasmon resonance wavelength. The degree of enhancement was found to depend on the width of the gap between the periodic metal regions in the PLM. A maximum enhancement of ?210% was achieved at a wavelength of 10 ?m. The ability to achieve such a drastic increase in transmittance at the plasmon resonant wavelength is expected to lead to improvements in the performance of energy collecting devices and optical sensors.

  15. Photoinduced birefringence of azobenzene polymer at blue excitation wavelengths

    NASA Astrophysics Data System (ADS)

    Kozanecka-Szmigiel, Anna; Switkowski, Krzysztof; Schab-Balcerzak, Ewa; Szmigiel, Dariusz

    2015-02-01

    The photoinduced birefringence resulting from trans-cis-trans isomerizations has been measured in a thin film of azobenzene-functionalized poly(esterimide) at three excitation wavelengths. The excitation wavelengths of 388 and 420 nm have been located at exactly opposite sides of the trans azobenzene absorption band. A third irradiation wavelength was shifted to 438 nm. Distinct saturation levels and growth dynamics of photoinduced birefringence have been observed under the 388- and 420-nm illumination, while very similar characteristics were recorded at 420 and 438 nm. Differences in the obtained birefringence signals have been explained considering the cis isomer absorption and photoisomerization pathways.

  16. Tutorial on multimode fiber optic wavelength division multiplexing

    NASA Technical Reports Server (NTRS)

    Spencer, J. L.

    1982-01-01

    Optical wavelength division multiplexing (WDM) systems, with signals transmitted on different wavelengths through a single optical fiber, can have increased bandwidth and fault isolation properties over single wavelength optical systems. This paper considers two WDM system designs that might be used with multimode fibers and gives a general description of the components which could be used to implement the system. The components described are sources, multiplexers, demultiplexers, and detectors. Emphasis is given to the demultiplexer technique which is the major developmental component in the WDM system.

  17. Optical thickness measurement with multi-wavelength THz interferometry

    NASA Astrophysics Data System (ADS)

    Nguyen, T. D.; Valera, J. D. R.; Moore, A. J.

    2014-10-01

    We report unambiguous thickness measurement with an all-optical THz source. The optical thickness variation of a test target was measured in a Mach-Zehnder interferometer to approximately 0.5% of the illumination wavelength using an optical parametric THz laser. The frequency of the laser was continuously tuneable, enabling a synthetic wavelength to be produced by sequential illumination at discrete frequencies, thus extending the unambiguous measurement range to half the synthetic wavelength. The all-optical source provides some advantages with respect to opto-electronic and electronic sources, particularly measurement speed and resolution.

  18. Design and analysis of multi-wavelength diffractive optics.

    PubMed

    Kim, Ganghun; Domínguez-Caballero, José A; Menon, Rajesh

    2012-01-30

    We present an extension of the direct-binary-search algorithm for designing high-efficiency multi-wavelength diffractive optics that reconstruct in the Fresnel domain. A fast computation method for solving the optimization problem is proposed. Examples of three-wavelength diffractive optics with over 90% diffraction efficiency are presented. These diffractive optical elements reconstruct three distinct image patterns when probed using the design wavelengths. Detailed parametric and sensitivity studies are conducted, which provide insight into the diffractive optic's performance when subject to different design conditions as well as common systematic and fabrication errors. PMID:22330517

  19. Free-space wavelength-multiplexed optical scanner.

    PubMed

    Yaqoob, Z; Rizvi, A A; Riza, N A

    2001-12-10

    A wavelength-multiplexed optical scanning scheme is proposed for deflecting a free-space optical beam by selection of the wavelength of the light incident on a wavelength-dispersive optical element. With fast tunable lasers or optical filters, this scanner features microsecond domain scan setting speeds and large- diameter apertures of several centimeters or more for subdegree angular scans. Analysis performed indicates an optimum scan range for a given diffraction order and grating period. Limitations include beam-spreading effects based on the varying scanner aperture sizes and the instantaneous information bandwidth of the data-carrying laser beam. PMID:18364951

  20. Laser Transmission Welding of White Thermoplastics with Adapted Wavelengths

    NASA Astrophysics Data System (ADS)

    Mamuschkin, V.; Roesner, A.; Aden, M.

    Different types of laser sources can be used for polymer welding. By the principle of laser transmission welding the wavelength of the laser is one of the most important criteria when selecting a laser source as the optical properties of the polymers are depending on the wavelength. Up to date white material cannot be welded to each other. The results show that by analysis of the optical properties, especially the absorption and the scattering coefficient and adaption of the laser wavelength the process limits can be extended.

  1. Active Wavelength Control of an External Cavity Quantum Cascade Laser

    PubMed Central

    Tsai, Tracy; Wysocki, Gerard

    2012-01-01

    We present an active wavelength control system for grating-based external cavity lasers that increases the accuracy of predicting the lasing wavelength based on the grating equation and significantly improves scan-to-scan wavelength/frequency repeatability. The ultimate 3? precision of a frequency scan is determined by the scan-to-scan repeatability of 0.042 cm?1. Since this control method can be applied to any external cavity laser with little to no modification, such a precision provides an excellent opportunity for spectroscopic applications that target molecular absorption lines at standard atmospheric conditions. PMID:23483850

  2. Rational choices for the wavelengths of a two color interferometer

    SciTech Connect

    Jobes, F.C.

    1995-07-01

    If in a two color interferometer for plasma density measurements, the two wavelengths are chosen to have a ratio that is a rational number, and if the signals from each of the wavelengths are multiplied in frequency by the appropriate integer of the rational number and then heterodyned together, the resultant signal will have all effects of component motion nulled out. A phase measurement of this signal will have only plasma density information in it. With CO{sub 2} lasers, it is possible to find suitable wavelength pairs which are close enough to rational numbers to produce an improvement of about 100 in density resolution, compared to standard two color interferometers.

  3. Optical amplification at the 1.31 wavelength

    DOEpatents

    Cockroft, Nigel J. (Los Alamos, NM)

    1994-01-01

    An optical amplifier operating at the 1.31 .mu.m wavelength for use in such applications as telecommunications, cable television, and computer systems. An optical fiber or other waveguide device is doped with both Tm.sup.3+ and Pr.sup.3+ ions. When pumped by a diode laser operating at a wavelength of 785 nm, energy is transferred from the Tm.sup.3+ ions to the Pr.sup.3+ ions, causing the Pr.sup.3+ ions to amplify at a wavelength of 1.31

  4. Nonstoichiometric Laser Materials: Designer Wavelengths in Neodymium Doped Garnets

    NASA Technical Reports Server (NTRS)

    Walsh, Brian M.; Barnes, Norman P.

    2008-01-01

    The tunable nature of lasers provides for a wide range of applications. Most applications rely on finding available laser wavelengths to meet the needs of the research. This article presents the concept of compositional tuning, whereby the laser wavelength is designed by exploiting nonstoichiometry. For research where precise wavelengths are required, such as remote sensing, this is highly advantageous. A theoretical basis for the concept is presented and experimental results in spectroscopic measurements support the theoretical basis. Laser operation nicely demonstrates the validity of the concept of designer lasers.

  5. Observation of a Long-Wavelength Hosing Modulation of a High-Intensity Laser Pulse in Underdense Plasma

    E-print Network

    Kaluza, M C; Thomas, A G R; Najmudin, Z; Dangor, A E; Murphy, C D; Collier, J L; Divall, E J; Foster, P S; Hooker, C J; Langley, A J; Smith, J; Krushelnick, K

    2010-01-01

    We report the first experimental observation of a long-wavelength hosing modulation of a high-intensity laser pulse. Side-view images of the scattered optical radiation at the fundamental wave-length of the laser reveal a transverse oscillation of the laser pulse during its propagation through underdense plasma. The wavelength of the oscillation \\lambda_hosing depends on the background plasma density n_e and scales as \\lambda_hosing~n_e^-3/2. Comparisons with an analytical model and 2-dimensional particle-in-cell simulations reveal that this laser hosing can be induced by a spatio-temporal asymmetry of the intensity distribution in the laser focus which can be caused by a misalignment of the parabolic focussing mirror or of the diffraction gratings in the pulse compressor.

  6. Optical modulation of quantum cascade laser with optimized excitation wavelength.

    PubMed

    Yang, Tao; Chen, Gang; Tian, Chao; Martini, Rainer

    2013-04-15

    The excitation wavelength for all-optical modulation of a 10.6 ?m mid-infrared (MIR) quantum cascade laser (QCL) was varied in order to obtain maximum modulation depth. Both amplitude and wavelength modulation experiments were conducted at 820 nm and 1550 nm excitation respectively, whereby the latter matches the interband transition in the QCL active region. Experimental results show that for continuous-wave mode-operated QCL, the efficiency of free carrier generation is doubled under 1550 nm excitation compared with 820 nm excitation, resulting in an increase of the amplitude modulation index from 19% to 36%. At the same time, the maximum wavelength shift is more than doubled from 1.05 nm to 2.80 nm. Furthermore, for the first time to our knowledge, we demonstrated the optical switching of a QCL operated in pulse mode by simple variation of the excitation wavelength. PMID:23595430

  7. Study of relationship between recording wavelength and hologram compression

    NASA Astrophysics Data System (ADS)

    Cai, Xiao-ou; Wang, Hui

    2006-09-01

    The present paper, based on the information theory of Shannon, studies the relationship between recording wavelength and hologram information content, and acquires the conclusion that hologram information content is inversely proportional to the square of the recording wavelength. And at the same time, we analyze two factors limiting human eye's resolving power, including pupil size and discrete photoreceptors in the human retina, and work out the number of 3D object points that can be resolved. Furthermore, we find out the recording wavelength of a hologram whose information content matches that of a reconstructed image. On the other hand, reconstruction of a hologram with visible light and recorded with long wavelength is elaborated theoretically. Therefore, it offers a brand-new thought and practical way to reduce the hologram information content, and eliminate its redundancy further.

  8. 47 CFR 2.101 - Frequency and wavelength bands.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ...2011-10-01 2011-10-01 false Frequency and wavelength bands. 2.101 Section...COMMUNICATIONS COMMISSION GENERAL FREQUENCY ALLOCATIONS AND RADIO TREATY MATTERS...Allocation, Assignment, and Use of Radio Frequencies § 2.101 Frequency and...

  9. 47 CFR 2.101 - Frequency and wavelength bands.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ...2010-10-01 2010-10-01 false Frequency and wavelength bands. 2.101 Section...COMMUNICATIONS COMMISSION GENERAL FREQUENCY ALLOCATIONS AND RADIO TREATY MATTERS...Allocation, Assignment, and Use of Radio Frequencies § 2.101 Frequency and...

  10. 47 CFR 2.101 - Frequency and wavelength bands.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ...2012-10-01 2012-10-01 false Frequency and wavelength bands. 2.101 Section...COMMUNICATIONS COMMISSION GENERAL FREQUENCY ALLOCATIONS AND RADIO TREATY MATTERS...Allocation, Assignment, and Use of Radio Frequencies § 2.101 Frequency and...

  11. 47 CFR 2.101 - Frequency and wavelength bands.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ...2013-10-01 2013-10-01 false Frequency and wavelength bands. 2.101 Section...COMMUNICATIONS COMMISSION GENERAL FREQUENCY ALLOCATIONS AND RADIO TREATY MATTERS...Allocation, Assignment, and Use of Radio Frequencies § 2.101 Frequency and...

  12. 47 CFR 2.101 - Frequency and wavelength bands.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ...2014-10-01 2014-10-01 false Frequency and wavelength bands. 2.101 Section...COMMUNICATIONS COMMISSION GENERAL FREQUENCY ALLOCATIONS AND RADIO TREATY MATTERS...Allocation, Assignment, and Use of Radio Frequencies § 2.101 Frequency and...

  13. Massively sub-wavelength guiding of electromagnetic waves.

    PubMed

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

    2014-01-01

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

  14. Dynamic Wavelength Conversion in Copropagating Slow-Light Pulses

    NASA Astrophysics Data System (ADS)

    Kondo, K.; Baba, T.

    2014-06-01

    Dynamic wavelength conversion (DWC) is obtained by controlling copropagating slow-light signal and control pulse trajectories. Our method is based on the understanding that conventional resonator-based DWC can be generalized, and is linked to cross-phase modulation. Dispersion-engineered Si photonic crystal waveguides produce such slow-light pulses. Free carriers generated by two-photon absorption of the control pulse dynamically shift the signal wavelength. Matching the group velocities of the two pulses enhances the shift, elongating the interaction length. We demonstrate an extremely large wavelength shift in DWC (4.9 nm blueshift) for the signal wavelength. Although DWC is similar to the Doppler effect, we highlight their essential differences.

  15. A wavelength multiplexer using cascaded three-dimensional vertical couplers

    E-print Network

    Bowers, John

    and demultiplexers MUX/ DEMUX are the essential components in wavelength divi- sion multiplexing WDM networks drawing of a four-channel MUX/DEMUX. Solid lines are the top waveguides and the dashed lines

  16. MAD phasing: choosing the most informative wavelength combination.

    PubMed

    Burla, Maria Cristina; Carrozzini, Benedetta; Cascarano, Giovanni Luca; Giacovazzo, Carmelo; Moustiakimov, Marat; Polidori, Giampiero; Siliqi, Dritan

    2004-09-01

    Two algorithms are described for limiting data resolution and for predicting the most informative wavelength combinations in MAD techniques. Both have been successfully tested using experimental data from a large set of test structures. PMID:15333954

  17. Wavelength-selective, sequential Q-switching laser cavity

    NASA Technical Reports Server (NTRS)

    Allario, F.; Lucht, R. A.

    1974-01-01

    Single-frequency continuous output of laser is converted into series of high-power laser pulses at high repetition rates. Applications include pollutant detection by absorption, laser gain measurements at discrete wavelengths, laser propagation measurement, and laser plasma diagnostics.

  18. Wavelength-Dependent Optical Absorption Properties of Artificial and Atmospheric Aerosol Measured by a Multi-Wavelength Photoacoustic Spectrometer

    NASA Astrophysics Data System (ADS)

    Utry, N.; Ajtai, T.; Pintér, M.; Bozóki, Z.; Szabó, G.

    2014-12-01

    Various aspects of the photoacoustic (PA) detection method are discussed from the point of view of developing it into a routine tool for measuring the wavelength-dependent optical absorption coefficient of artificial and atmospheric aerosol. The discussion includes the issues of calibration, cross-sensitivity to gaseous molecules, background PA signal subtraction, and size-dependent particle losses within the PA system. The results in this paper are based on a recently developed four-wavelength PA system, which has operational wavelengths in the near-infrared, in the visible, and in the ultraviolet. The measured spectra of artificial and atmospheric aerosol prove the outstanding applicability of the presented PA system.

  19. Coupling polariton quantum boxes in sub-wavelength grating microcavities

    NASA Astrophysics Data System (ADS)

    Zhang, Bo; Brodbeck, Sebastian; Wang, Zhaorong; Kamp, Martin; Schneider, Christian; Höfling, Sven; Deng, Hui

    2015-02-01

    We report the construction of decoupled, coupled, and quasi-one dimensional polariton systems from zero dimensional polariton quantum boxes using microcavities with sub-wavelength gratings as the top mirror. By designing the tethering patterns around the suspended sub-wavelength gratings, we control the coupling between individual quantum boxes through different optical potentials. Energy levels and real-space or momentum space distributions of the confined modes were measured, which agreed well with simulations.

  20. Dual photosensitive polymers with wavelength-selective photoresponse.

    PubMed

    García-Fernández, Luis; Herbivo, Cyril; Arranz, Verónica San Miguel; Warther, David; Donato, Loïc; Specht, Alexandre; del Campo, Aránzazu

    2014-08-01

    Polyurethane thin films that photopolymerize and photodegrade upon exposure to light of different wavelengths are presented. The chromic response is based on two caged monomers with the ability to be activated or photocleaved with different wavelengths under single and two-photon excitation. This material represents a dual photoresist with "positive" and "negative" tone contained in a single resist formulation and with the ability to generate complex 2D and 3D patterns. PMID:24831417

  1. Interval Wavelength Assignment in All-Optical Star Networks

    Microsoft Academic Search

    Robert Janczewski; Anna Malafiejska; Michal Malafiejski

    2009-01-01

    \\u000a In the paper we consider a new problem of wavelength assigment for multicasts in the optical star networks. We are given a\\u000a star network in which nodes from a set V are connected to the central node with optical fibres. The central node redirects the incoming signal from a single node\\u000a on a particular wavelength from a given set of

  2. The long-wavelength limit of plant photosynthesis

    Microsoft Academic Search

    Hugo Pettai; Vello Oja; Arvi Freiberg; Agu Laisk

    2005-01-01

    It is a common knowledge that the photosynthesis efficiency drops rapidly under the long-wavelength light excitation above 680nm. We discovered that in sunflower leaves attached to the plant the initial fall is replaced by an unexpected increase at much longer wavelengths, so that a detectable O2 evolution is remained till 780nm. The quantum yield of O2 evolution at the local

  3. Free-Space Wavelength-Multiplexed Optical Scanner Demonstration

    Microsoft Academic Search

    Zahid Yaqoob; Nabeel A. Riza

    2002-01-01

    Experimental demonstration of a no-moving-parts free-space wavelength-multiplexed optical scanner (W-MOS) is presented. With fast tunable lasers or optical filters and planar wavelength dispersive elements such as diffraction gratings, this microsecond-speed scanner enables large several-centimeter apertures for subdegree angular scans. The proposed W-MOS design incorporates a unique optical amplifier and variable optical attenuator combination that enables the calibration and modulation of

  4. Tunable wavelength terahertz polarization converter based on quartz waveplates.

    PubMed

    Kaveev, A K; Kropotov, G I; Tsypishka, D I; Tzibizov, I A; Vinerov, I A; Kaveeva, E G

    2014-08-20

    We present the results of calculation and experimental testing of the tunable wavelength terahertz polarization converter represented by a set of plane-parallel birefringent plates with an in-plane birefringence axis. An experimental device has been produced and tested. The calculations show that the effect of interference between the interfaces, including air gaps, may be neglected. The considered device may be used as a simple narrow achromatic waveplate, or a Solc band pass filter for the specified wavelength. PMID:25321112

  5. Long wavelength scintillators for fiber-optic applications

    SciTech Connect

    Lyons, P.B.; Franks, L.; Lutz, S.; Flournoy, J.; Fullman, E.

    1980-01-01

    The use of fiber optics in plasma diagnostics has spurred the development of long wavelength scintillators with fast temporal characteristics. In this paper we describe several new liquid scintillator systems with fluorescent emissions maxima up to 730 nm. Subnanosecond scintillator FWHM response times have been obtained by the operation of liquid scintillators at elevated temperatures. Data on fiber system sensitivity versus fiber length and scintillator emission wavelength will be presented.

  6. Fault tolerant multiwavelength optical rings with limited wavelength conversion

    Microsoft Academic Search

    O. Gerstel; R. Ramaswami; G. H. Sasaki

    1998-01-01

    This paper presents methods for recovering from channel failures, link failures, and node failures in wavelength-division multiplexed (WDM) point-to-point links and ring networks with limited wavelength conversion\\/switching capabilities at the nodes. Different recovery schemes are presented to handle each type of failure. Each scheme is evaluated based on the network hardware configuration required to support it and the performance and

  7. Sub-wavelength grating components for integrated optics applications on SOI chips.

    PubMed

    Donzella, Valentina; Sherwali, Ahmed; Flueckiger, Jonas; Talebi Fard, Sahba; Grist, Samantha M; Chrostowski, Lukas

    2014-08-25

    In this paper we demonstrate silicon on insulator (SOI) sub-wavelength grating (SWG) optical components for integrated optics and sensing. Light propagation in SWG devices is studied and realized with no cladding on top of the waveguide. In particular, we focused on SWG bends, tapers and directional couplers, all realized with compatible geometries in order to be used as building blocks for more complex integrated optics devices (interferometers, switches, resonators, etc.). Fabricated SWG tapers for TE and TM polarizations are described; they allow for connecting SWG devices to regular strip waveguides with loss lower than 1 dB per taper. Our SWG directional coupler presents a very compact design and a negligible wavelength dependence of its crossover length (and as a consequence of its coupling coefficient, ?), over a 40 nm bandwidth. This wavelength flatten response represents a bandwidth enhancement with respect to standard directional couplers (made using strip or rib waveguides), in particular for the TE mode. SWG bends are demonstrated, their loss dependence on radius is analyzed, and fabricated bends have a loss in the range 0.8-1.6 dB per 90 degrees bend. Simulated and measured results show promise for large-scale fabrication of complex optical devices and high sensitivity sensors based on SWG waveguides with engineered optical properties, tailored to specific applications. PMID:25321304

  8. Large-aperture Wide-bandwidth Antireflection-coated Silicon Lenses for Millimeter Wavelengths

    NASA Technical Reports Server (NTRS)

    Datta, R.; Munson, C. D.; Niemack, M. D.; McMahon, J. J.; Britton, J.; Wollack, Edward J.; Beall, J.; Devlin, M. J.; Fowler, J.; Gallardo, P.; Hubmayr, J.; Irwin, K.; Newburgh, L.; Nibarger, J. P.; Page, L.; Quijada, Manuel A.; Schmitt, B. L.; Staggs, S. T.; Thornton, R.; Zhang, L.

    2013-01-01

    The increasing scale of cryogenic detector arrays for submillimeter and millimeter wavelength astrophysics has led to the need for large aperture, high index of refraction, low loss, cryogenic refracting optics. Silicon with n 3.4, low loss, and high thermal conductivity is a nearly optimal material for these purposes but requires an antireflection (AR) coating with broad bandwidth, low loss, low reflectance, and a matched coefficient of thermal expansion. We present an AR coating for curved silicon optics comprised of subwavelength features cut into the lens surface with a custom three-axis silicon dicing saw. These features constitute a metamaterial that behaves as a simple dielectric coating.We have fabricated silicon lenses as large as 33.4 cm in diameter with micromachined layers optimized for use between 125 and 165 GHz. Our design reduces average reflections to a few tenths of a percent for angles of incidence up to 30deg with low cross polarization.We describe the design, tolerance, manufacture, and measurements of these coatings and present measurements of the optical properties of silicon at millimeter wavelengths at cryogenic and room temperatures. This coating and lens fabrication approach is applicable from centimeter to submillimeter wavelengths and can be used to fabricate coatings with greater than octave bandwidth.

  9. Large-Aperture Wide-Bandwidth Anti-Reflection-Coated Silicon Lenses for Millimeter Wavelengths

    NASA Technical Reports Server (NTRS)

    Datta, R.; Munson, C. D.; Niemack, M. D.; McMahon, J. J.; Britton, J.; Wollack, E. J.; Beall, J.; Devlin, M. J.; Fowler, J.; Gallardo, P.; Hubmayr, J.; Irwin, K.; Newburgh, L.; Nibarger, J. P.; Page, L.; Quijada, M. A.; Schmitt, B. L.; Staggs, S. T.; Thornton, R.; Zhang, L.

    2013-01-01

    The increasing scale of cryogenic detector arrays for sub-millimeter and millimeter wavelength astrophysics has led to the need for large aperture, high index of refraction, low loss, cryogenic refracting optics. Silicon with n = 3.4, low loss, and relatively high thermal conductivity is a nearly optimal material for these purposes, but requires an antireflection (AR) coating with broad bandwidth, low loss, low reflectance, and a matched coffecient of thermal expansion. We present an AR coating for curved silicon optics comprised of subwavelength features cut into the lens surface with a custom three axis silicon dicing saw. These features constitute a metamaterial that behaves as a simple dielectric coating. We have fabricated and coated silicon lenses as large as 33.4 cm in diameter with coatings optimized for use between 125-165 GHz. Our design reduces average reflections to a few tenths of a percent for angles of incidence up to 30 deg. with low cross-polarization. We describe the design, tolerance, manufacture, and measurements of these coatings and present measurements of the optical properties of silicon at millimeter wavelengths at cryogenic and room temperatures. This coating and lens fabrication approach is applicable from centimeter to sub-millimeter wavelengths and can be used to fabricate coatings with greater than octave bandwidth.

  10. Large-aperture wide-bandwidth antireflection-coated silicon lenses for millimeter wavelengths.

    PubMed

    Datta, R; Munson, C D; Niemack, M D; McMahon, J J; Britton, J; Wollack, E J; Beall, J; Devlin, M J; Fowler, J; Gallardo, P; Hubmayr, J; Irwin, K; Newburgh, L; Nibarger, J P; Page, L; Quijada, M A; Schmitt, B L; Staggs, S T; Thornton, R; Zhang, L

    2013-12-20

    The increasing scale of cryogenic detector arrays for submillimeter and millimeter wavelength astrophysics has led to the need for large aperture, high index of refraction, low loss, cryogenic refracting optics. Silicon with n=3.4, low loss, and high thermal conductivity is a nearly optimal material for these purposes but requires an antireflection (AR) coating with broad bandwidth, low loss, low reflectance, and a matched coefficient of thermal expansion. We present an AR coating for curved silicon optics comprised of subwavelength features cut into the lens surface with a custom three-axis silicon dicing saw. These features constitute a metamaterial that behaves as a simple dielectric coating. We have fabricated silicon lenses as large as 33.4 cm in diameter with micromachined layers optimized for use between 125 and 165 GHz. Our design reduces average reflections to a few tenths of a percent for angles of incidence up to 30° with low cross polarization. We describe the design, tolerance, manufacture, and measurements of these coatings and present measurements of the optical properties of silicon at millimeter wavelengths at cryogenic and room temperatures. This coating and lens fabrication approach is applicable from centimeter to submillimeter wavelengths and can be used to fabricate coatings with greater than octave bandwidth. PMID:24513939

  11. Identification of wavelengths of strain heterogeneities during creep deformation in Carrara Marble

    NASA Astrophysics Data System (ADS)

    Quintanilla-Terminel, Alejandra; Evans, Brian

    2014-05-01

    We use a new technique combining microfabrication technology and compression tests to map the strain field at a micrometric scale in polycrystalline materials. The motivation of such high-resolution mapping is to identify characteristic wavelengths of heterogeneities for different plasticity mechanisms under varying creep conditions. The micro-strain mapping technique was applied to Carrara Marble under different deformation regimes, at a confining pressure of 300 MPa and temperatures ranging from 200 to 700 °C. In samples deformed to 10% strain in compression at 400°C, 500°C and 600°C, at a 3x10-5 s-1 strain rate, strain can be up to 5 times greater along twins and grain boundaries compared to the macroscopic strain accommodated over the entire sample. Strain averaged across a particular grain may vary by as much as 100%. Moreover, there is a gradual but clear change in the accommodation of strain, from twins to grain boundaries as temperature increases. For a fixed temperature of 600°C, varying strain from 10% to 30% does not appear to increase the wavelength of heterogeneities (i.e. the strain field does not homogenize). Macroscopically, strain hardening is minimal and there seems to be a constant generation of perturbations of similar wavelength.

  12. Topological insulator: Bi2Se3/polyvinyl alcohol film-assisted multi-wavelength ultrafast erbium-doped fiber laser

    NASA Astrophysics Data System (ADS)

    Guo, Bo; Yao, Yong; Yang, Yan-Fu; Yuan, Yi-Jun; Wang, Rui-Lai; Wang, Shu-Guang; Ren, Zhong-Hua; Yan, Bo

    2015-02-01

    We experimentally demonstrate a multi-wavelength ultrafast erbium-doped fiber laser incorporating a ?m-scale topological insulator: Bi2Se3/Polyvinyl Alcohol film as both an excellent saturable absorber for mode-locking and a high-nonlinear medium to induce a giant third order optical nonlinear effect for mitigating the mode competition of erbium-doped fiber laser and stabilizing the multi-wavelength oscillation. By properly adjusting the pump power and the polarization state, the single-, dual-, triple-, four-wavelength mode-locking pulse could be stably initiated. For the four-wavelength operation, we obtain its pulse width of ˜22 ps and a fundamental repetition rate of 8.83 MHz. The fiber laser exhibits the maximum output power of 9.7 mW with the pulse energy of 1.1 nJ and peak power of 50 W at the pump power of 155 mW. Our study shows that the simple, stable, low-cost multi-wavelength ultrafast fiber laser could be applied in various potential fields, such as optical communication, biomedical research, and radar system.

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

    NASA Astrophysics Data System (ADS)

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

    2012-10-01

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

  14. Cloud image retrieval and characterization using ground-based dual-wavelength radar at millimeter wavelengths

    NASA Astrophysics Data System (ADS)

    Colon-Diaz, Nivia; Cruz-Pol, Sandra L.; Sekelsky, Stephen M.

    2003-04-01

    Characterization of the microphysical properties of non-precipitating stratus clouds including their suspended-water droplet size distribution and the cloud's liquid water content are estimated in this work. The dual wavelength ratio, DWR, and the differential extinction, DE, were computed at two millimeter frequencies, 33 GHz and 95 GHz, using UMass Cloud Profiling Radar System (CPRS) to estimate the drop size distribution. Data from radiosonde observations (Raob) is used as input in a recently calibrated model for estimation of the gaseous attenuation at Ka.-band and Liebe's model at W-band. Integrated specific humidity from a radiometer is used to constrain the radiosonde specific humidity. The radar reflectivity is corrected to take into account the effect of the wind speed, the difference of beamwidth at both frequencies and the difference in sampled range cells. Radar reflectivity and ancillary data are combined to obtain the differential extinction and the estimated cloud's liquid water density. Profiles of the processed data, such as DE, the DWR and the cloud's liquid water density are presented. Cloud's water density and radar reflectivity were used for the size distribution estimation of the suspended water droplets and the median drop diameter.

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

    PubMed Central

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

    2012-01-01

    We report the use of an all-solid-state ultrashort pulsed source specifically for two-photon microscopy at wavelengths shorter than those of the conventional Ti:Sapphire laser. Our approach involves sum–frequency mixing of the output from an optical parametric oscillator (?= 1400–1640 nm) synchronously pumped by a Yb-doped fibre laser (?= 1064 nm), with the residual pump radiation. This generated an fs-pulsed output tunable in the red spectral region (?= 620–636 nm, ?150 mW, 405 fs, 80 MHz, M2? 1.3). We demonstrate the performance of our ultrashort pulsed system using fluorescently labelled and autofluorescent tissue, and compare with conventional Ti:Sapphire excitation. We observe a more than 3-fold increase in fluorescence signal intensity using our visible laser source in comparison with the Ti:Sapphire laser for two-photon excitation at equal illumination peak powers of 1.16 kW or less. PMID:23078118

  16. The Effect of Wavelength Advertisement on the Performance of an Optical Routing Protocol

    E-print Network

    Khan, Bilal

    1 The Effect of Wavelength Advertisement on the Performance of an Optical Routing Protocol Bilal the effect of wavelength advertisement on connec- tion blocking probability in heterogeneous networks some consequences of advertising wavelength availability, and quantify when it is advantageous

  17. Micropolarizing device for long wavelength infrared polarization imaging.

    SciTech Connect

    Wendt, Joel Robert; Carter, Tony Ray; Samora, Sally; Cruz-Cabrera, Alvaro Augusto; Vawter, Gregory Allen; Kemme, Shanalyn A.; Alford, Charles Fred; Boye, Robert R.; Smith, Jody Lynn

    2006-11-01

    The goal of this project is to fabricate a four-state pixelated subwavelength optical device that enables mid-wave infrared (MWIR) or long-wave infrared (LWIR) snapshot polarimetric imaging. The polarization information can help to classify imaged materials and identify objects of interest for numerous remote sensing and military applications. While traditional, sequential polarimetric imaging produces scenes with polarization information through a series of assembled images, snapshot polarimetric imaging collects the spatial distribution of all four Stokes parameters simultaneously. In this way any noise due to scene movement from one frame to the next is eliminated. We fabricated several arrays of subwavelength components for MWIR polarization imaging applications. Each pixel unit of the array consists of four elements. These elements are micropolarizers with three or four different polarizing axis orientations. The fourth element sometimes has a micro birefringent waveplate on the top of one of the micropolarizers. The linear micropolarizers were fabricated by patterning nano-scale metallic grids on a transparent substrate. A large area birefringent waveplate was fabricated by deeply etching a subwavelength structure into a dielectric substrate. The principle of making linear micropolarizers for long wavelengths is based upon strong anisotropic absorption of light in the nano-metallic grid structures. The nano-metallic grid structures are patterned with different orientations; therefore, the micropolarizers have different polarization axes. The birefringent waveplate is a deeply etched dielectric one-dimensional subwavelength grating; therefore two orthogonally polarized waves have different phase delays. Finally, in this project, we investigated the near field and diffractive effects of the subwavelength element apertures upon detection. The fabricated pixelated polarizers had a measured extinction ratios larger than 100:1 for pixel sizes in the order of 15 {micro}m by 15 {micro}m that exceed by 7 times previously reported devices. The fabricated birefringent diffractive waveplates had a total variation of phase delay rms of 9.41 degrees with an average delay of 80.6 degrees across the MWIR spectral region. We found that diffraction effects change the requirement for separation between focal plane arrays (FPA) micropolarizer arrays and birefringent waveplates arrays, originally in the order of hundreds of microns (which are the typical substrate thickness) to a few microns or less. This new requirement leads us to propose new approaches to fabricate these devices.

  18. Multi-wavelength Observations of Neptune’s Atmosphere

    NASA Astrophysics Data System (ADS)

    de Pater, Imke; Fletcher, L.; Luszcz-Cook, S.; deBoer, D.; Butler, B.; Orton, G.; Sitko, M.; Hammel, H.

    2013-10-01

    We conducted a multi-wavelength observing campaign on Neptune between June and October, 2003. We used the 10-m Keck telescope at near- and mid-infrared wavelengths and the VLA at radio wavelengths. Near infrared images were taken in October 2003 in broad- and narrow-band filters between 1 and 2.5 micron, using the infrared camera NIRC2 coupled to the Keck Adaptive Optics system. At these wavelengths we detect sunlight reflected off clouds in the upper troposphere and lower stratosphere. As shown by various authors before, bright bands of discrete cloud features are visible between 20°S and 50°S and near 30°N, as well as several distinct bright cloud features near 70°S, and the south polar “dot”. Mid-infrared images were taken on September 5 and 6 (2003) using the Keck LWS system in atmospheric windows at 8, 8.9, 10.7, 11.7, 12.5, 17.65, 18.75 and 22 micron. At these wavelengths we detect thermal emission from Neptune’s stratosphere due to the presence of hydrocarbons, and from near the tropopause due to collision induced opacity by hydrogen. At all wavelengths the South polar region stands out as a bright spot. At 17 - 22 micron also the equatorial region is slightly enhanced in intensity. These characteristics are consistent with later imaging at similar wavelengths (Hammel et al. 2007; Orton et al. 2007). Microwave images were constructed from NRAO VLA data between 0.7 and 6.0 cm. At these wavelengths depths of several up to >50 bar are probed. An increase in brightness indicates decreased opacity of absorbers (e.g., NH3, H2S), since under such circumstances deep, and hence warm levels (adiabatic temperature-pressure profile), will be probed. The multi-wavelength observing campaign in 2003 was focused on obtaining images that probe different altitudes in Neptune’s atmosphere. Indeed, this set of data probes altitudes from about 0.1 mbar down to ~50 bar, and hence can be used to constrain the global atmospheric circulation in Neptune’s atmosphere. At the meeting we will show our results and interpretation of the findings.

  19. Effect of lateral viscosity variations in the core-mantle boundary region on predictions of the long-wavelength geoid

    Microsoft Academic Search

    O. ?adek; L. Fleitout

    2006-01-01

    Seismic studies of the lowermost mantle suggest that the core-mantle boundary (CMB) region is strongly laterally heterogeneous\\u000a over both local and global scales. These heterogeneities are likely to be associated with significant lateral viscosity variations\\u000a that may influence the shape of the long-wavelength non-hydrostatic geoid. In the present paper we investigate the effect\\u000a of these lateral viscosity variations on the

  20. Laboratory measurements of the joint dependence of radar frequency and water wavelength on sea-spike returns

    Microsoft Academic Search

    Jorn Fuchs; Marshall P. Tulin

    1998-01-01

    Analysis of low grazing angle sea-spikes from breaking waves suggests the presence of a non-Bragg scaling law. The FMCW radar has a frequency chirp of 4-8 GHz. The water wavelength is 1-4 m. The frequency response of the radar cross section peaks in horizontal co-polarization has been investigated. The radar cross-section peaks are caused by the plunging jet and have