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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

    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.

  2. Global-scale surface spectral variations on Titan seen from Cassini/VIMS

    USGS Publications Warehouse

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

    2007-01-01

    We present global-scale maps of Titan from the Visual and Infrared Mapping Spectrometer (VIMS) instrument on Cassini. We map at 64 near-infrared wavelengths simultaneously, covering the atmospheric windows at 0.94, 1.08, 1.28, 1.6, 2.0, 2.8, and 5 ??m with a typical resolution of 50 km/pixel or a typical total integration time of 1 s. Our maps have five to ten times the resolution of ground-based maps, better spectral resolution across most windows, coverage in multiple atmospheric windows, and represent the first spatially resolved maps of Titan at 5 ??m. The VIMS maps provide context and surface spectral information in support of other Cassini instruments. We note a strong latitudinal dependence in the spectral character of Titan's surface, and partition the surface into 9 spectral units that we describe in terms of spectral and spatial characteristics. ?? 2006 Elsevier Inc. All rights reserved.

  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. Multi-wavelength studies of Saturn's rings to constrain ring particle properties and ring structure: the VIMS perspective

    NASA Astrophysics Data System (ADS)

    Filacchione, G.; Capaccioni, F.; Ciarniello, M.; Nicholson, P. D.; Hedmann, M. M.; Clark, R. N.; Cerroni, P.; Spilker, L. J.; Colwell, J.; Bradley, T.

    2012-04-01

    Saturn has the most prominent and complex ring system in our solar system, extending along radial axis from 74658 km (inner C ring edge) to 136780 km (outer A). The physical and dynamical properties of ring particles can be fully understood only using a broad spectral range, which allow us to recognize very different processes. In this context, the scientific goal of our investigation is the study of Saturn's rings particle properties using combined datasets returned from different instruments aboard the Cassini mission. We are merging rings observations and compare results collected by Cassini's UV Imaging Spectrometer (UVIS), Imaging Science Subsystem (ISS), Visual and Infrared Mapping Spectrometer (VIMS) and Composite Infrared Spectrometer (CIRS). 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 structure. In this work we report about the VIMS contributions to this investigation, coming from the analysis of 0.35-5.1 m spectra of A, B, C rings and Cassini Division. VIMS, in fact, has the capabilities to determine ring particles composition (water ice vs. chromophores mixed within ice), surface regolith grain size and particle albedo. After having described the dataset considered in this work (several rings radial mosaics taken at 12 ? phase ? 136 and -21 ? opening angle ? +5) and the method to reduce data to spectrograms, we explain how the spectral indicators we have selected (slopes and band parameters) allow us to infer ring particle properties across different regions. Specifically, we report about: 1) the variations induced by illumination phase on visible reddening and water ice bands depth; 2) the average composition and regolith grain size of ring particles in A, B, C rings and CD; 3) an application of Hapke's model to compare VIMS data with synthetic spectra.

  5. Effective wavelength scaling of rectangular aperture antennas.

    PubMed

    Chen, Yuanyuan; Yu, Li; Zhang, Jiasen; Gordon, Reuven

    2015-04-20

    We investigate the resonances of aperture antennas from the visible to the terahertz regime, with comparison to comprehensive simulations. Simple piecewise analytic behavior is found for the wavelength scaling over the entire spectrum, with a linear regime through the visible and near-IR. This theory will serve as a useful and simple design tool for applications including biosensors, nonlinear plasmonics and surface enhanced spectroscopies. PMID:25969079

  6. 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.

  7. 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.

  8. Seasonal temperature variations observed by Cassini-VIMS on Saturn's satellites

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

    We report about temperature maps of Mimas, Enceladus, Tethys, Dione and Rhea derived from Cassini/VIMS data. Observations taken during the entire duration of the Cassini mission (2004-2014) were processed. Since equinox occurred in 2009, this dataset includes both pre and post equinox viewing geometries. VIMS data taken at spatial resolution of 20-40 km/pixel allow us to study the correlation of the temperature at regional scale resolution with solar illumination conditions, geological features and seasons. The retrieval of the temperature from IR reflectance data is based on the comparison with laboratory measurements (Clark et al., Icarus 218, 831, 2012): when a sample of pure crystalline water ice particles is cooled, the 3.6 m peak moves towards shorter wavelengths, from about 3.65 m at T=123 K to about 3.55 m at T=88 K. Mastrapa et al. (ApJ 701, 104, 2009) have measured a similar trend also in the imaginary part (k) of the refractive index of water ice when a sample is cooled from T=140 K to 20 K. Being Saturn's satellites surfaces dominated by water ice (Filacchione et al., Icarus 220, 1064, 2012), the measurement of the wavelength at which the 3.6 m reflectance peak occurs can be considered as a good temperature marker. This method was already applied to Saturn rings VIMS mosaics to retrieve ring particles temperature (Filacchione et al., Icarus 241, 45, 2014). By using geometry projection techniques applied to VIMS data, we have mapped temperature variations as a function of LST and season on the regular satellites surfaces. Pre and post-equinox temperature maps built at the same LST allow us to follow seasonal variations across summer and winter hemispheres. Moreover, temperature variations seen across satellites surfaces appear correlated with geological features, leading-trailing asymmetries, local color patterns and equatorial radiation lenses.

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

    USGS Publications Warehouse

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

    2008-01-01

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

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

    NASA Astrophysics Data System (ADS)

    Le Moulic, Stphane; Paillou, Philippe; Janssen, Michael A.; Barnes, Jason W.; Rodriguez, Sbastien; 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.

  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. 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.

  13. Spectrophotometric Modeling of Rhea's Surface from Vims Data

    NASA Astrophysics Data System (ADS)

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

    2010-10-01

    The huge amount of hyperspectral data from the VIMS (Visual Infrared Mapping Spectrometer) instrument onboard Cassini spacecraft allows the study of the surface properties of icy bodies in Saturnian system in the 0.35 - 5.1 um spectral range. In this work we have analyzed 112 full disk images of Rhea with solar phase angle range 0-110. The goal of this work is to perform a quantitative evaluation of physical parameters affecting the spectrophotometric behavior of the satellite's surface. We have applied the Hapke model (Hapke, 1993) in order to describe both the full-disk phase function at each wavelength and the spectrum at given phase angles. With this approach we are able to constrain ice grain size and the amount of organic contaminants as well as the opposition effect surge and the surface roughness of Rhea. The best fit model is represented by an intraparticle mixture of water ice and Triton tholin (99.6%-0.4%) and particle radius of 38 um. What emerges from the analysis is that wavelength dependent parameters, i.e. opposition surge width and amplitude (h, Bo) and single particle phase function parameters (b,v), are correlated with the estimated single scattering albedo of particles (w), as expected for media with grain size larger than the wavelength. Regarding the opposition effect, we find that both Shadow Hiding and Coherent Backscattering contribute. The surface roughness parameter we obtain is theta=33. This value is fairly high if compared to surface structures (e.g. reliefs or craters), which supports the hypotesis of a correlation with size scales on the order of particle clumping. This research is fully supported by an Italian Space Agency grant.

  14. Composition of Titan's surface from Cassini VIMS

    USGS Publications Warehouse

    McCord, T.B.; Hansen, G.B.; Buratti, B.J.; Clark, R.N.; Cruikshank, D.P.; D'Aversa, E.; Griffith, C.A.; Baines, E.K.H.; Brown, R.H.; Dalle, Ore C.M.; Filacchione, G.; Formisano, V.; Hibbitts, C.A.; Jaumann, R.; Lunine, J.I.; Nelson, R.M.; Sotin, C.

    2006-01-01

    Titan's bulk density along with Solar System formation models indicates considerable water as well as silicates as its major constituents. This satellite's dense atmosphere of nitrogen with methane is unique. Deposits or even oceans of organic compounds have been suggested to exist on Titan's solid surface due to UV-induced photochemistry in the atmosphere. Thus, the composition of the surface is a major piece of evidence needed to determine Titan's history. However, studies of the surface are hindered by the thick, absorbing, hazy and in some places cloudy atmosphere. Ground-based telescope investigations of the integral disk of Titan attempted to observe the surface albedo in spectral windows between methane absorptions by calculating and removing the haze effects. Their results were reported to be consistent with water ice on the surface that is contaminated with a small amount of dark material, perhaps organic material like tholin. We analyze here the recent Cassini Mission's visual and infrared mapping spectrometer (VIMS) observations that resolve regions on Titan. VIMS is able to see surface features and shows that there are spectral and therefore likely compositional units. By several methods, spectral albedo estimates within methane absorption windows between 0.75 and 5 ??m were obtained for different surface units using VIMS image cubes from the Cassini-Huygens Titan Ta encounter. Of the spots studied, there appears to be two compositional classes present that are associated with the lower albedo and the higher albedo materials, with some variety among the brighter regions. These were compared with spectra of several different candidate materials. Our results show that the spectrum of water ice contaminated with a darker material matches the reflectance of the lower albedo Titan regions if the spectral slope from 2.71 to 2.79 ??m in the poorly understood 2.8-??m methane window is ignored. The spectra for brighter regions are not matched by the spectrum of water ice or unoxidized tholin, in pure form or in mixtures with sufficient ice or tholin present to allow the water ice or tholin spectral features to be discerned. We find that the 2.8-??m methane absorption window is complex and seems to consist of two weak subwindows at 2.7 and 2.8 ??m that have unknown opacities. A ratio image at these two wavelengths reveals an anomalous region on Titan that has a reflectance unlike any material so far identified, but it is unclear how much the reflectances in these two subwindows pertain to the surface. ?? 2006 Elsevier Ltd. All rights reserved.

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

    NASA Astrophysics Data System (ADS)

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

    2006-09-01

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

  16. A Scaling Theory of the MJO Horizontal Wavelength

    NASA Astrophysics Data System (ADS)

    YANG, D.; Ingersoll, A. P.

    2013-12-01

    Yang and Ingersoll (2013, Triggered Convection, Gravity Waves, and the MJO: A Shallow-Water Model. J. Atmos. Sci., 70, 2476-2486.) use a shallow water model to simulate the MJO. In this model, we parameterize radiation as a large-scale mass sink, and parameterize convection as a small-scale mass source that is only triggered when the layer thickness is lower than a certain threshold. Over a wide parameter range, the model gives a strong MJO-like signal - a large-scale pattern that drifts slowly to the east, together with wind and pressure fields similar to those observed. Based on the simulation results, we propose that the MJO is an interference pattern of the westward and eastward inertia-gravity (WIG and EIG) waves. The MJO propagation speed is determined by the difference in the phase speeds of the EIG and WIG waves. In this study, we try to quantitatively understand what controls the MJO horizontal scale using the same shallow water model. There are four parameters in the model - the Kelvin wave speed (c), the convective timescale (t_c), the size of the convection (r_c), and the number density (s_c) of convection. We perform numerical simulations to examine the sensitivity of the MJO zonal wavenumber (k) to these parameters: k increases when s_c and r_c increase and when c decreases; k does not depend on the convective timescale. The scaling between k and the model parameters obeys a power law within an inertial range. A scaling argument will be presented based on the equatorial beta-plane scaling. This scaling argument helps to understand the climate dynamics of the MJO, e.g., how the MJO responds to global warming. The fidelity of this scaling argument can be examined by performing systematic global warming simulations using super-parameterized 3D climate models that reproduce the MJO signal in the current climate.

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

    NASA Astrophysics Data System (ADS)

    Orozco Surez, D.; Bellot Rubio, L. R.; Vargas, S.; Bonet, J. A.; Martez 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 and 3 wavelength positions plus continuum, as long as the noise level is kept below 10-3 Ic.

  18. Verbal Instruction Model (VIM) in voice therapy.

    PubMed

    Ohlsson, Ann-Christine

    2016-04-01

    The stumbling-block in voice therapy is the patient's generalization of the new voice behavior in everyday life. Traditionally voice therapy is based on demonstration, i.e. during the therapy session the speech therapist uses her own voice and body to demonstrate for the patient how to produce voice in different training tasks. During the last decade a new voice therapy strategy, the Verbal Instruction Model (VIM), has been developed by the author. In VIM the speech therapist uses verbal instructions instead of demonstration when conveying the training tasks to the patient. Our clinical experience has shown that VIM seems to help getting over the stumbling-block of generalization. However, evidence for VIM voice therapy outcome remains to be scientifically studied and confirmed. The purpose of this paper is to describe VIM voice therapy and to discuss therapy strategies in the light of motor learning principles. PMID:25103221

  19. Dominant Wavelength of Small-Scale Folds Between Enceladus' South Polar Tiger Stripes

    NASA Astrophysics Data System (ADS)

    Preuss, L. J.; Barr, A. C.

    2010-03-01

    High-resolution images of Enceladus' south polar terrain reveal regions of small-scale folds between Damascus and Baghdad sulci. We will present the results of a systematic study of the folding wavelength using Fourier transform methods.

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

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

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

  1. Novel VIM metallo-beta-lactamase variant, VIM-24, from a Klebsiella pneumoniae isolate from Colombia.

    PubMed

    Montealegre, Maria Camila; Correa, Adriana; Briceo, David F; Rosas, Natalia C; De La Cadena, Elsa; Ruiz, Sory J; Mojica, Maria F; Camargo, Ruben Dario; Zuluaga, Ivan; Marin, Adriana; Quinn, John P; Villegas, Maria Virginia

    2011-05-01

    We report the emergence of a novel VIM variant (VIM-24) in a Klebsiella pneumoniae isolate in Colombia. The isolate displays MICs for carbapenems below the resistance breakpoints, posing a real challenge for its detection. The blaVIM-24 gene was located within a class 1 integron carried on a large plasmid. Further studies are needed to clarify its epidemiological and clinical impact. PMID:21282438

  2. Novel VIM Metallo-?-Lactamase Variant, VIM-24, from a Klebsiella pneumoniae Isolate from Colombia?

    PubMed Central

    Montealegre, Maria Camila; Correa, Adriana; Briceo, David F.; Rosas, Natalia C.; De La Cadena, Elsa; Ruiz, Sory J.; Mojica, Maria F.; Camargo, Ruben Dario; Zuluaga, Ivan; Marin, Adriana; Quinn, John P.; Villegas, Maria Virginia

    2011-01-01

    We report the emergence of a novel VIM variant (VIM-24) in a Klebsiella pneumoniae isolate in Colombia. The isolate displays MICs for carbapenems below the resistance breakpoints, posing a real challenge for its detection. The blaVIM-24 gene was located within a class 1 integron carried on a large plasmid. Further studies are needed to clarify its epidemiological and clinical impact. PMID:21282438

  3. Effect of radiation-induced mean wavelength shift in optical fibers on the scale factor of an interferometric fiber optic gyroscope at a wavelength of 1300 nm

    NASA Astrophysics Data System (ADS)

    Jin, Jing; Wang, Xue-Qin; Lin, Song; Song, Ning-Fang

    2012-09-01

    In order to analyze the effect of wavelength-dependent radiation-induced attenuation (RIA) on the mean transmission wavelength in optical fiber and the scale factor of interferometric fiber optic gyroscopes (IFOGs), three types of polarization-maintaining (PM) fibers are tested by using a 60Co ?-radiation source. The observed different mean wavelength shift (MWS) behaviors for different fibers are interpreted by color-center theory involving dose rate-dependent absorption bands in ultraviolet and visible ranges and total dose-dependent near-infrared absorption bands. To evaluate the mean wavelength variation in a fiber coil and the induced scale factor change for space-borne IFOGs under low radiation doses in a space environment, the influence of dose rate on the mean wavelength is investigated by testing four germanium (Ge) doped fibers and two germaniumphosphorus (GeP) codoped fibers irradiated at different dose rates. Experimental results indicate that the Ge-doped fibers show the least mean wavelength shift during irradiation and their mean wavelength of optical signal transmission in fibers will shift to a shorter wavelength in a low-dose-rate radiation environment. Finally, the change in the scale factor of IFOG resulting from the mean wavelength shift is estimated and tested, and it is found that the significant radiation-induced scale factor variation must be considered during the design of space-borne IFOGs.

  4. IR-dust observations of Comet Tempel 2 with CRAF VIMS

    NASA Astrophysics Data System (ADS)

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

    1988-09-01

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

  5. Wavelength-Scale Structures as Extremely High Haze Films for Efficient Polymer Solar Cells.

    PubMed

    Ham, Juyoung; Dong, Wan Jae; Jung, Gwan Ho; Lee, Jong-Lam

    2016-03-01

    Wavelength-scale inverted pyramid structures with low reflectance and excellent haze have been designed for application to polymer solar cells (PSCs). The wavelength-scale structured haze films are fabricated on the back surface of glass without damages to organic active layer by using a soft lithographic technique with etched GaN molds. With a rigorous coupled-wave analysis of optical modeling, we find the shift of resonance peaks with the increase of pattern's diameter. Wavelength-scale structures could provide the number of resonances at the long wavelength spectrum (λ = 650-800 nm), yielding enhancement of power conversion efficiency (PCE) in the PSCs. Compared with a flat device (PCE = 7.12%, Jsc = 15.6 mA/cm(2)), improved PCE of 8.41% is achieved in a haze film, which is mainly due to the increased short circuit current density (Jsc) of 17.5 mA/cm(2). Hence, it opens up exciting opportunities for a variety of PSCs with wavelength-scale structures to further improve performance, simplify complicated process, and reduce costs. PMID:26901630

  6. 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.

  7. Wavelength scaling of efficient high-order harmonic generation by two-color infrared laser fields

    SciTech Connect

    Lan Pengfei; Takahashi, Eiji J.; Midorikawa, Katsumi

    2010-06-15

    We theoretically investigate and demonstrate a better wavelength scaling of harmonic yield in a two-color infrared field. By mixing a Ti:sapphire assistant field with the infrared driving field, we show that high harmonic generation is enhanced and the harmonic yield scales as {lambda}{sup -3}-{lambda}{sup -4} in the plateau region, which falls more slowly as the increase of the driving laser wavelength {lambda} compared with {lambda}{sup -5}-{lambda}{sup -6} in a one-color infrared field.

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

    PubMed

    Yoshioka, Shinya; Kinoshita, Shuichi

    2004-03-22

    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

  9. Effect of short-scale turbulence on kilometer wavelength irregularities in the equatorial electrojet

    SciTech Connect

    Ronchi, C.; Sudan, R.N. ); Similon, P.L. )

    1990-01-01

    The kilometer scale irregularities in the daytime equatorial electrojet are studied within the framework of a two-fluid, nonlocal theory of the gradient drift instability. A separation of scales is introduced into the equations in order to model the effects of the subgrid, short-wavelength ({lambda} < 100 m) modes. The presence of the short-scale turbulence is included in the large-scale equations through the average nonlinear flux due to the small-scale nonlinear terms. With the use of the linear ion continuity equation the nonlinear flux is expressed in terms of the large-scale quantities and of the small-scale density fluctuation spectrum. It is shown that the small-scale turbulence contributes to the large-scale equations through turbulent mobility and diffusion coefficients. For a particular choice for the small-scale density fluctuation spectrum the turbulent mobility is determined as a function of altitude, and its peak equals a few times the classical Pedersen mobility value. The equilibrium solutions of the large-scale equations are also derived in the presence of the short-wavelength turbulence. The localization of the current layer is seen to shift toward higher altitudes, and the current density profile conforms well with some of the available experimental data.

  10. Biochemical Characterization of VIM-39, a VIM-1-Like Metallo-?-Lactamase Variant from a Multidrug-Resistant Klebsiella pneumoniae Isolate from Greece.

    PubMed

    Papagiannitsis, Costas C; Pollini, Simona; De Luca, Filomena; Rossolini, Gian Maria; Docquier, Jean-Denis; Hrabk, Jaroslav

    2015-12-01

    VIM-39, a VIM-1-like metallo-?-lactamase variant (VIM-1 Thr33Ala His224Leu) was identified in a clinical isolate of Klebsiella pneumoniae belonging to sequence type 147. VIM-39 hydrolyzed ampicillin, cephalothin, and imipenem more efficiently than did VIM-1 and VIM-26 (a VIM-1 variant with the His224Leu substitution) because of higher turnover rates. PMID:26369975

  11. Investigation of Titan's surface and atmosphere photometric functions using the Cassini/VIMS instrument

    NASA Astrophysics Data System (ADS)

    Cornet, Thomas; Altobelli, Nicolas; Rodriguez, Sbastien; Maltagliati, Luca; Le Moulic, Stphane; Sotin, Christophe; Brown, Robert; Barnes, Jason; Buratti, Bonnie; Baines, Kevin; Clark, Roger; Nicholson, Phillip

    2015-04-01

    After 106 flybys spread over 10 years, the Cassini Visual and Infrared Mapping Spectrometer (VIMS) instrument acquired 33151 hyperspectral cubes pointing at the surface of Titan on the dayside. Despite this huge amount of data available for surface studies, and due to the strong influence of the atmosphere (methane absorption and haze scattering), Titan's surface is only visible with VIMS in 7 spectral atmospheric windows centred at 0.93, 1.08, 1.27, 1.59, 2.01, 2.7-2.8 and 5 microns. Atmospheric scattering and absorption effects dominate Titan's spectrum at wavelengths shorter than 3 microns, while the 5 micron window, almost insensitive to the haze scattering, only presents a reduced atmospheric absorption contribution to the signal recorded by VIMS. In all cases, the recorded I/F represents an apparent albedo, which depends on the atmospheric contributions and the surface photometry at each wavelength. We therefore aim to determine real albedo values for Titan's surface by finding photometric functions for the surface and the atmosphere that could be used as a basis for empirical corrections or Radiative Transfer calculations. After updating the navigation of the VIMS archive, we decomposed the entire VIMS data set into a MySQL relational database gathering the viewing geometry, location, time (season) and I/F (for pure atmosphere and surface-atmosphere images) for each pixel of the 33151 individual VIMS cubes. We then isolated all the VIMS pixels where Titan's surface has been repeatedly imaged at low phase angles (< 20 degrees) in order to characterize phase curves for the surface at 5 microns and for the atmosphere. Among these, the T88 flyby appears noteworthy, with a "Emergence-Phase Function (EPF)"-type observation: 25 cubes acquired during the same flyby, over the same area (close to Tortola Facula, in relatively dark terrains), at a constant incidence and with varying emergence and phase (from 0 to 60 degrees) angles. The data clearly exhibit an increase of I/F at 5 microns at very low phase angles, which is indicative of an opposition effect for the surface, and kinks in the I/F at low and high emergence/phase angles, increasing with decreasing wavelength (and thus with increasing atmospheric scattering). The latter dependency is present in both pure atmosphere and surface-atmosphere images, which clearly indicates that it is of atmospheric origin. We are currently investigating these dependencies with angles and try to determine best fit models that would describe the phase curves for the surface at 5 microns and for the atmosphere at lower wavelengths in this particular area.

  12. Space switching enabled tunable wavelength converter and its application in large scale optical interconnect architecture

    NASA Astrophysics Data System (ADS)

    Xu, Zhaowen; Zhou, Luying; Cheng, Xiaofei

    2016-01-01

    We propose a large scale Clos structure based optical interconnect by employing cyclic arrayed waveguide grating routers (AWGRs) and novel space switching enabled tunable wavelength converters (SS-TWCs). The 1:2 or 1:4 SS-TWCs expand the scale of the optical interconnect up to 8 times of standard Clos structure while using the same AWGR modules. Experimental results are given to demonstrate the feasibility of the proposed optical interconnect.

  13. 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.

  14. 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 NASAs Outer Planets Research Program.

  15. Effect of short scale turbulence on kilometer wavelength irregularities in the equatorial electrojet

    SciTech Connect

    Ronchi, C.; Sudan, R.N. . Lab. of Plasma Studies); Similon, P.L. . Dept. of Applied Physics)

    1989-01-01

    The kilometer-scale irregularities in the daytime equatorial electrojet are studied within the framework of a two-fluid, quasilinear, nonlocal theory of the gradient-drift instability. The effect of the short scale turbulence is included into the large scale equations through turbulent mobility and diffusion operators obtained from a quasilinear treatment of the electron equations. The turbulent mobility is determined as a function of altitude in terms of the small scale density fluctuation spectrum, and its peak equals a few times the classical Pedersen mobility value. The equilibrium solutions of the large scale equations are derived in the presence of the short wavelength turbulence. The localization of the unstable modes and of the current layer is seen to shift towards higher altitudes and the current density profile conforms well with some of the available experimental data. The local and nonlocal linear growth rates of the long wavelength modes are also obtained and discussed. The nonlocal linearized equations for the large scales are integrated numerically and the effects of the turbulent mobility and of velocity shear are discussed.

  16. Reduction of CCD observations made with a scanning Fabry-Perot interferometer. III. Wavelength scale refinement

    NASA Astrophysics Data System (ADS)

    Moiseev, A. V.

    2015-10-01

    We describe the recent modifications to the data reduction technique for observations acquired with the scanning Fabry-Perot interferometer (FPI) mounted on the 6-m telescope of the Special Astrophysical Observatory that allow the wavelength scale to be correctly computed in the case of large mutual offsets of studied objects in interferograms.We examine the parameters of the scanning FPIs used in the SCORPIO-2 multimode focal reducer.

  17. CASSINI/VIMS-V at Jupiter: Radiometric calibration test and data results

    NASA Astrophysics Data System (ADS)

    Coradini, A.; Filacchione, G.; Capaccioni, F.; Cerroni, P.; Adriani, A.; Brown, R. H.; Langevin, Y.; Gondet, B.

    2004-06-01

    During the Cassini-Huygens flyby of Jupiter in December 2000, VIMS-V acquired multispectral data cubes of Jupiter's atmosphere. The visual and infrared imaging spectrometer-visual channel (VIMS-V) is one of the principal contributions of Italian Space Agency (ASI) to the Cassini-Huygens mission to Saturn. VIMS-V is an imaging spectrometer operating in the wavelength range 300- 1050 nm, with a (nominal) spectral resolution of 7.3 nm, and a (nominal) spatial resolution of 500 ?rad. VIMS-V is boresighted with the VIMS-IR channel operating in the wavelength range 0.8- 5.1 ?m. During the early phases of the Cassini mission, the spacecraft encountered Venus (June 23, 1999), followed shortly thereafter by a flyby of the Earth. During the Earth flyby the Moon (August 17, 1999) was observed. Following the Earth-Moon flyby, the spacecraft encountered Jupiter (closest approach on December 31, 2000), and during the roughly 6 months prior to Jupiter closest approach a series of observations were made of most of the objects in the Jovian system. We have determined the instrumental transfer function of VIMS-V using the Moon and Venus day side data. This transfer function was then used to remove instrumental effects from the Jupiter data and to convert raw instrumental response numbers to spectral radiance from the target. It was thus possible to study the spectral variability of Jupiter's atmosphere across its disk using data from both the visual (V) and infrared (IR) channels of VIMS. In this paper we discuss the main results obtained by the V channel. We have analyzed the principal spectral features of Jupiter atmosphere, and in particular, the spatial variation of methane and ammonia absorption bands over the Jovian disk. Using the instrument's spatial mapping capabilities we have investigated the nature of the absorption band in the spectrum of Jupiter's atmosphere at 929 nm that is consistent with the presence of ammonia or water vapor. After comet Shoemaker-Levy 9 impacted Jupiter, water vapor was considered the most likely cause of the 929 nm absorption feature, but our data indicate that ammonia is the source of this band. Other analyses were performed using standard techniques such as forming band ratios and removal of the continuum. Our analyses confirm previous ground or satellite based observations. We were also able to verify the instrument radiometric calibration, using observations conducted during the close encounters with Venus and the Moon.

  18. 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 5μm 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.

  19. 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.

  20. Large-scale characterization of silicon nitride-based evanescent couplers at 532nm wavelength

    NASA Astrophysics Data System (ADS)

    Claes, Tom; Jansen, Roelof; Neutens, Pieter; Du Bois, Bert; Helin, Philippe; Severi, Simone; Van Dorpe, Pol; Deshpande, Paru; Rottenberg, Xavier

    2014-05-01

    Recently, the photonics community has a renewed attention for silicon nitride.1-3 When deposited at temperatures below 650K with plasma-enhanced chemical vapor deposition (PECVD),4 it enables photonic circuits fabricated on-top of standard complementary metaloxidesemiconductor (CMOS) electronics. Silicon nitride is moreover transparent to wavelengths that are visible to the human eye and detectable with available silicon detectors, thus offering a photonics platform for a range of applications that is not accessible with the popular silicon-on-insulator platform. However, first-time-right design of large-scale circuits for demanding specifications requires reliable models of the basic photonic building blocks, like evanescent couplers (Figure 1), components that couple power between multiple waveguides. While these models typically exist for the silicon-on-insulator platform, they still lack maturity for the emerging silicon nitride platform. Therefore, we meticulously studied silicon nitride-based evanescent couplers fabricated in our 200mm-wafer facility. We produced the structures in a silicon nitride film deposited with low-temperature PECVD, and patterned it using optical lithography at a wavelength of 193nm and reactive ion etching. We measured the performance of as much as 250 different designs at 532nm wavelength, a central wavelength in the visible range for which laser sources are widespread. For each design, we measured the progressive transmission of up-to 10 cascaded identical couplers (Figure 2(a)), yielding very accurate figures for the coupling factor (Figure 2(b)). This paper presents the trends extracted from this vast data set (Figure 3), and elaborates on the impact of the couplers bend radius and gap on its coupling factors (Figure 4 and Figure 5). We think that the large- scale characterization of evanescent couplers presented in this paper, in excellent agreement with the simulated performance of the devices, forms the basis for a component library that enables accurate design of silicon nitride-based photonic circuitry.

  1. Comparison of VIM and STN DBS for Parkinsonian Resting and Postural/Action Tremor

    PubMed Central

    Parihar, Raminder; Alterman, Ron; Papavassiliou, Efstathios; Tarsy, Daniel; Shih, Ludy C.

    2015-01-01

    Background Resting tremor is common in Parkinsons disease (PD), but up to 47% of PD patients have action tremor, which is sometimes resistant to medications. Deep brain stimulation (DBS) of the ventral intermediate nucleus (VIM) of the thalamus or subthalamic nucleus (STN) is effective for medication-refractory tremor in PD, though it remains unclear whether STN DBS is as effective as VIM DBS for postural/action tremor related to PD. Methods We carried out a single-center retrospective review of patients with medication-refractory resting, postural, and action PD tremor, treated with either VIM or STN DBS between August 2004 and March 2014. We assessed the degree of improvement using items 20 and 21 of the Unified Parkinsons Disease Rating Scale (UPDRS) motor scale and examined the proportion of patients achieving tremor arrest. Results A total of 18 patients were analyzed, 10 treated with STN and eight treated with VIM, with similar off-medication motor UPDRS scores. There was no significant difference in improvement in tremor scores or in the proportion of patients experiencing tremor arrest between the two stimulation sites. Overall, 56% and 72% of patients experienced complete absence of postural/action tremor and resting tremor, respectively, at last follow-up. Discussion This study demonstrated excellent outcomes on both resting and postural/action tremor after either VIM or STN DBS. Resting tremor improved to a greater degree than postural/action tremor in both groups. These results suggest that a large randomized controlled trial is needed to show a superior effect of one target on PD tremor. PMID:26196027

  2. Hunting Down Horizon-scale Effects with Multi-wavelength Surveys

    NASA Astrophysics Data System (ADS)

    Fonseca, José; Camera, Stefano; Santos, Mário G.; Maartens, Roy

    2015-10-01

    Next-generation cosmological surveys will probe ever larger volumes of the universe, including the largest scales, near and beyond the horizon. On these scales, the galaxy power spectrum carries signatures of local primordial non-Gaussianity (PNG) and horizon-scale general relativistic (GR) effects. However, cosmic variance limits the detection of horizon-scale effects. Combining different surveys via the multi-tracer method allows us to reduce the effect of cosmic variance. This method benefits from large bias differences between two tracers of the underlying dark matter distribution, which suggests a multi-wavelength combination of large volume surveys that are planned on a similar timescale. We show that the combination of two contemporaneous surveys, a large neutral hydrogen intensity mapping survey in SKA Phase 1 and a Euclid-like photometric survey, will provide unprecedented constraints on PNG as well as detection of the GR effects. We forecast that the error on local PNG will break through the cosmic variance limit on cosmic microwave background surveys and achieve σ ({f}{{NL}})≃ 1.4-0.5, depending on assumed priors, bias, and sky coverage. GR effects are more robust to changes in the assumed fiducial model, and we forecast that they can be detected with a signal-to-noise of about 14.

  3. Comparison of Cassini/VIMS and Huygens/DISR observations: Implications for Titan's geology and atmospheric haze

    NASA Astrophysics Data System (ADS)

    Sotin, Christophe; Karkoschka, Eric; Lawrence, Ken; LeMouelic, Stephane; Rodriguez, Sebastien; Solomonidou, Anezina; Barnes, Jason; Brown, Robert; Buratti, Bonnie; Kirk, Randy; Soderblom, Jason; Soderblom, Larry; Baines, Kevin; Clark, Roger; Nicholson, Phil

    2015-04-01

    The Huygens probe made in situ observations of Titan's atmosphere and surface in an area of Titan now known as a high equatorial plateau named Adiri surrounded by dune fields. These observations, made in January 2005, provide ground truth for remote sensing observations. This study focuses on the comparison between observations made by the Visual and Infrared Mapping Spectrometer (VIMS) on Cassini spacecraft and the Descent Imager / Spectral Radiometer (DISR) on the Huygens probe. Two of the DISR instrument suite are relevant to the comparison with VIMS: the high resolution imager (HRI) and the Downward-Looking Infrared Spectrometer (DLIS) whose spectral range overlaps with the VIMS instrument between 0.9- and 1.6-μm. The comparison provides key information that can be applied to the VIMS data set which globally covers Titan's surface. The VIMS instrument can observe Titan's surface in 7 spectral atmospheric windows centred at 0.93, 1.08, 1.27, 1.59, 2.01, 2.7-2.8 and 5 microns [1]. Determining the spectral properties of the surface, and therefore the composition, requires the removal of the atmospheric contribution which includes absorption and scattering by atmospheric molecules and haze particles. Radiative transfer models have been using the DISR derived opacities to retrieve the surface albedo of Titan's surface. Light curves derived from VIMS solar occultation observations show that the atmospheric opacities above 80 km are in very good agreement with the DISR observations. However, the extrapolation of the DISR-derived opacities below 80 km at wavelengths above 1.6-μm predicts opacities much larger than those derived from the VIMS solar occultation observations. At 5-μm, the DISR extrapolation predicts a value of the optical depth three times larger than the value derived from the VIMS observations. The radiative transfer model used to retrieve the surface albedo [2] must be corrected accordingly. The VIMS instrument acquired one high resolution image of the Huygens Landing Site. On this image, the VIMS footprint is identical to the DLIS footprint when the Huygens probe was at 18 km altitude. The DLIS and VIMS images match very well, which allows a precise determination of the location of the two DLIS spectra taken at 18 km altitude. The comparison of the VIMS and DLIS surface albedo shows a good agreement at 1.27- and 1.59-μm. On the other hand, the DLIS surface albedo values at 0.92- and 1.08-μm are much larger than the VIMS values. We are currently investigating the reasons of this difference. This work has been performed at the Jet Propulsion Laboratory, California Institute of Technology, under contract to NASA. [1] Sotin C. et al. (2005) Nature, 435, 786-789. {2] Hirtzig M. et al. (2013) Icarus, 226, 470-486.

  4. 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-π-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

  5. 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.

  6. Probing the parsec-scale accretion flow of 3C 84 with millimeter wavelength polarimetry

    SciTech Connect

    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.

    2014-12-10

    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)× 10{sup 5} rad m{sup –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.

  7. 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.

  8. The ‘Excess’ Emission from the Warm Surface Adjacent to Active Fissures on Enceladus from Combined VIMS and CIRS Spectra

    NASA Astrophysics Data System (ADS)

    Goguen, Jay D.; Buratti, Bonnie J.; Howell, Robert R.

    2015-11-01

    The exciting discovery of thermal emission from the tiger stripe fissures at the S. pole of Enceladus is a major highlight of the Cassini mission. Both VIMS (Visible and Infrared Mapping Spectrometer) and CIRS (Composite InfraRed Spectrometer) detect the thermal ‘blackbody’ spectrum emitted from the warm fissure areas. The VIMS instrument is uniquely suited to measuring the hottest active locations because VIMS covers the 3 to 5 micron wavelength range where the rising edge of the Planck function for these T~200 K areas dominates the emission spectrum. At longer wavelengths, the spectrum is more complicated because contributions from small hot areas and larger cooler areas combine to form the broad emission spectrum that is detected by the CIRS instrument at wavelengths >6.7 microns. It is the combination of VIMS and CIRS spectra that paint a more complete portrait of the fissure heat transfer processes. Using spectra that span both the VIMS and CIRS wavelengths places a stronger constraint on the T distribution near the fissures than consideration of the spectra from either instrument alone.We show that when the best (= highest spatial resolution, 800 m/pixel and smaller) VIMS and CIRS spectra of the fissure thermal emission are considered together, there is a large (up to 400%) component of ‘excess’ emission spanning 7 to 17 microns that requires explanation. New analysis of ~2 km spatial resolution VIMS spectra of the Damascus hot spot on 8/13/2010 are similar to the highest resolution 4/14/2012 VIMS Baghdad spectra, confirming that differences in location or time between the best VIMS and CIRS spectra do not explain away the excess. The obvious interpretation is that there are processes that transfer heat from the fissure eruption to the surface within 400 m of the fissure center in addition to heat conduction through the fissure walls. Candidate heat transfer processes include fallback of large warm low velocity ice particles from the edges of the plume, and condensation of the low velocity component of water vapor expanding outward from the edge of the plume.This research was conducted at the Jet Propulsion Laboratory, California Institute of Technolgy, Pasadena, CA.

  9. Structural and biochemical characterization of VIM-26 shows that Leu224 has implications for the substrate specificity of VIM metallo-?-lactamases.

    PubMed

    Leiros, Hanna-Kirsti S; Edvardsen, Kine Susann Waade; Bjerga, Gro Elin Kjaereng; Samuelsen, rjan

    2015-03-01

    During the last decades antimicrobial resistance has become a global health problem. Metallo-?-lactamases (MBLs) which are broad-spectrum ?-lactamases that inactivate virtually all ?-lactams including carbapenems, are contributing to this health problem. In this study a novel MBL variant, termed VIM-26, identified in a Klebsiellapneumoniae isolate was studied. VIM-26 belongs to the Verona integron-encoded metallo-?-lactamase (VIM) family of MBLs and is a His224Leu variant of the well-characterized VIM-1 variant. In this study, we report the kinetic parameters, minimum inhibitory concentrations and crystal structures of a recombinant VIM-26 protein, and compare them to previously published data on VIM-1, VIM-2 and VIM-7. The kinetic parameters and minimum inhibitory concentration determinations show that VIM-26, like VIM-7, has higher penicillinase activity but lower cephalosporinase activity than VIM-1 and VIM-2. The four determined VIM-26 crystal structures revealed mono- and di-zinc forms, where the Zn1 ion has distorted tetrahedral coordination geometry with an additional water molecule (W2) at a distance of 2.6-3.7 , which could be important during catalysis. The R2 drug binding site in VIM-26 is more open compared to VIM-2 and VIM-7 and neutrally charged due to Leu224 and Ser228. Thus, the VIM-26 drug binding properties are different from the VIM-2 (Tyr224/Arg228) and VIM-7 (His224/Arg228) structures, indicating a role of these residues in the substrate specificity. PMID:25601024

  10. Cassini/VIMS observations of the moon

    USGS Publications Warehouse

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

    2002-01-01

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

  11. Coherent constructive interference in Saturn's rings reported by Cassini VIMS

    NASA Astrophysics Data System (ADS)

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

    2007-08-01

    On several occasions during its orbital tour the Cassini spacecraft has flown between the sun and Saturn in such fashion that the zero phase point passed through the rings. The Visual and Infrared Mapping Spectrometer (VIMS) recorded spectral image cubes (0.4< ? <5.2μm) that showed the opposition effect (OE) at zero phase. The OE is a spike in the reflected light observed near 0o phase when it is displayed as a function of phase angle. This is the first time the OE has been resolved for small areas on the rings. Previous work has shown that the OE arises from two distinct processes, shadow hiding (SHOE) and coherent backscattering (CBOE). The SHOE process causes an OE by the elimination of shadows cast by regolith grains upon one another as phase angle decreases. The CBOE process causes an OE by constructive interference between photons traveling in opposite directions along the same path within the medium. SHOE is expected to dominate the contribution to the OE in absorbing media where multiple scattering of photons is not significant. CBOE is expected to dominate the contribution to the OE in highly reflective media with much multiple scattering. We have made spectral scans the VIMS images that traverse the zero phase point. We selected narrow spectral bands that reflected a variety of wavelengths and reflectance levels. In this way, phase curves of the ringlet were obtained for each band. We have compared these data to data we acquired in the laboratory using the JPL long arm goniometer where we measured the phase curve of particulate materials that simulate the surface of Saturn's ring particles. We argue here that the OE is due to coherent backscattering because: 1) The theoretical CBOE function fit to the data is excellent. 2) The OE width is extremely narrow 3) The angular width of the peak increases with wavelength. CBOE theory also predicts that the width depends on the transport mean free path (TMFP) in the medium. We find that the OE is caused by coherent interactions between sub-particles in the outer layers of the ring particles, and that these sub-particles are of the order of 20-40 μm in size. A portion of this work was performed at JPL under contract with NASA

  12. Long wavelength spin dynamics in diluted magnetic systems: Scaling of magnon lifetime

    NASA Astrophysics Data System (ADS)

    Chakraborty, Akash; Bouzerar, Georges

    2015-05-01

    Spin wave excitations in disordered magnetic systems have been one of the most widely studied fields in condensed matter physics for several decades. However, a careful and extensive search reveals a longstanding controversy on one important aspect, which is the wave-vector dependence of the spin wave intrinsic linewidth. We theoretically investigate the low-temperature spin wave excitations in disordered (diluted) ferromagnetic systems with a particular focus on the linewidth behavior in the long wavelength limit (q ? 0). The linewidth is extracted from a proper finite size analysis of the dynamical spectral functions, taking into account the effects of disorder and spin fluctuations treated within self-consistent local RPA. We obtain an unambiguous q5 scaling of the intrinsic linewidth, which is attributed to the disorder induced damping of the spin waves. This is in agreement with some previous theoretical studies on the Heisenberg ferromagnets, although the exchange interactions were mostly restricted to nearest neighbors unlike in our case. We also demonstrate the difficulties in extracting the correct scaling of the linewidth as it is sensitive to the q values considered, and one can obtain an incorrect q-dependence if the q's are not sufficiently small. Finally, our findings are discussed in the light of prospective spintronics applications.

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

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

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

  14. 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.

  15. Probing Periodic Patterns In Saturn's Inner A Ring With Cassini-VIMS

    NASA Astrophysics Data System (ADS)

    Hedman, Matthew M.; Nicholson, P. D.; Salo, H.

    2012-10-01

    During the spring of 2009, the Visual and Infrared Mapping Spectrometer (VIMS) onboard the Cassini spacecraft observed two occultations of the star gamma Crucis by Saturn's rings. The occultation tracks reached a minimum radius in the inner A ring, so these observations yielded optical-depth profiles with exceptionally fine radial sampling of the region between 124,200 km and 124,800 km from Saturn's center. These cuts reveal highly periodic structures with wavelengths of order a few hundred meters. Similarly periodic patterns were previously observed in this region by the Cassini radio science experiment (Thomson et al. 2007 GRL), and have been interpreted as evidence for viscous overstabilties (periodic oscillations in surface density that grow from small perturbations driven by over-effective restoring forces, see Schmidt et al. 2009). However, the theory of nonlinear overstabilities in self-gravitating rings is still in its infancy, and it is not yet clear exactly what determines the wavelength, amplitude, or the coherence length of an overstable wave. The combination of high signal-to-noise and radial resolution of the VIMS data permit detailed investigations of the variations in these structure's wavelength and phase that can help test theoretical models of these periodic structures. For example, regions with higher optical depth appear to possess periodic patterns with longer wavelengths, strongly suggesting that these structures are influenced by their local particle number density. At the same time, abrupt shifts in the pattern's wavelength and phase occur at various locations within each profile. and the measurements made at the same location at different times and longitudes exhibit differences in the patterns' wavelengths and phase. Such shifts and variations most likely reflect the finite coherence lengths and propagation speeds of these disturbances.

  16. Lessons learned from applying VIM to fast reactor critical experiments

    SciTech Connect

    Schaefer, R.W.; McKnight, R.D.; Collins, P.J.

    1995-05-17

    VIM is a continuous energy Monte Carlo code first developed around 1970 for the analysis of plate-type, fast-neutron, zero-power critical assemblies. In most respects, VIM is functionally equivalent to the MCNP code but it has two features that make uniquely suited to the analysis of fast reactor critical experiments: (1) the plate lattice geometry option, which allows efficient description of and neutron tracking in the assembly geometry, and (2) a statistical treatment of neutron cross section data in the unresolved resonance range. Since its inception, VIM`s capabilities have expanded to include numerous features, such as thermal neutron cross sections, photon cross sections, and combinatorial and other geometry options, that have allowed its use in a wide range of neutral-particle transport problems. The earliest validation work at Argonne National Laboratory (ANL) focused on the validation of VIM itself. This work showed that, in order for VIM to be a ``rigorous`` tool, extreme detail in the pointwise Monte Carlo libraries was needed, and the required detail was added. The emphasis soon shifted to validating models, methods, data and codes against VIM. Most of this work was done in the context of analyzing critical experiments in zero power reactor (ZPR) assemblies. The purpose of this paper is to present some of the lessons learned from using VIM in ZPR analysis work. This involves such areas as uncovering problems in deterministic methods and models, pitfalls in using Monte Carlo codes, and improving predictions. The numerical illustrations included here were taken from the extensive documentation cited as references.

  17. Wavelength dependence of scattering properties in the VIS-NIR and links with grain-scale physical and compositional properties

    NASA Astrophysics Data System (ADS)

    Pilorget, C.; Fernando, J.; Ehlmann, B. L.; Schmidt, F.; Hiroi, T.

    2016-03-01

    Surface scattered sunlight carries important information about the composition and microtexture of surface materials, thus enabling tracing back the geological and climatic processes that occurred on the planetary body. Here we perform laboratory spectro-goniometric measurements of granular samples (45-75 μ m fraction) with different composition and physical properties over the VIS-NIR spectral range (0.4-2.5 μ m). To quantify the evolution of the scattering properties over the VIS-NIR, we use an inversion procedure based on a Bayesian approach to estimate photometric parameters from the Hapke radiative transfer model. The granular samples are also carefully characterized by optical and SEM techniques in order to link these scattering variations with the grains' physical properties. Results show that the scattering properties are wavelength-dependent and can vary significantly over the VIS-NIR spectral range. In particular, the phase function of a granular material is affected by both the absorptivity and the external and internal structure of the grains, from the millimeter scale down to the wavelength scale. Our results also confirm that the macroscopic roughness parameter, as defined by Hapke, is to first order correlated with the absorptivity of the particles, through multiple scattering effects, and thus mostly corresponds to a measurement of the particles shadowing. Photometric datasets, typically obtained at a given wavelength that can vary from one study to another, should therefore be compared and interpreted with caution when extrapolating across wavelengths. Our results also suggest that multi-wavelength photometry could potentially provide a much richer signature than with single-wavelength photometry, opening new perspectives into the characterization of surface materials.

  18. 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

  19. 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.

  20. 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

  1. Remote mineralogy through multispectral imaging: the VIMS-V instrument

    NASA Astrophysics Data System (ADS)

    Flamini, Enrico; Coradini, Angioletta; Dami, Michele; de Vidi, Romeo; Pili, Paolo; Reininger, Francis M.

    1995-06-01

    The Visible Infrared Mapping Spectrometer--Visible Channel (VIMS-V) has been designed to produce high resolution multispectral images, in the optical waveband, of different planetary bodies. VIMS-V, presently under test, has been developed by Officine Galileo on behalf of the Agenzia Spaziale Italiana (Italian Space Agency) and will cover the spectral range from 300nm to 1050nm. This range will allow the detailed investigation of the mineralogy of Saturn satellites surfaces, searching for those components capable of affecting their evolution; studies of Saturn and Titan cloud structure and haze layers by identifying chemical components; searches for lighting and analysis their spectra. Light weight, thermal stability, and capability to operate with different mission scenarios have been the imposed design criteria of the instrument. Two further versions of VIMS-V are presently under study: one for a cometary mission and the other for a lunar detailed exploration mission.

  2. Coherence solution for bidirectional reflectance distributions of surfaces with wavelength-scale statistics.

    PubMed

    Hoover, Brian G; Gamiz, Victor L

    2006-02-01

    The scalar bidirectional reflectance distribution function (BRDF) due to a perfectly conducting surface with roughness and autocorrelation width comparable with the illumination wavelength is derived from coherence theory on the assumption of a random reflective phase screen and an expansion valid for large effective roughness. A general quadratic expansion of the two-dimensional isotropic surface autocorrelation function near the origin yields representative Cauchy and Gaussian BRDF solutions and an intermediate general solution as the sum of an incoherent component and a nonspecular coherent component proportional to an integral of the plasma dispersion function in the complex plane. Plots illustrate agreement of the derived general solution with original bistatic BRDF data due to a machined aluminum surface, and comparisons are drawn with previously published data in the examination of variations with incident angle, roughness, illumination wavelength, and autocorrelation coefficients in the bistatic and monostatic geometries. The general quadratic autocorrelation expansion provides a BRDF solution that smoothly interpolates between the well-known results of the linear and parabolic approximations. PMID:16477837

  3. Multi-wavelength Monitoring of Lensed Quasars: Deciphering Quasar Structure at Micro-arcseconds Scales

    NASA Astrophysics Data System (ADS)

    Mosquera, Ana; Morgan, Christopher W.; Kochanek, Christopher S.; Dai, Xinyu; Chen, Bin; MacLeod, Chelsea Louise; Chartas, George

    2016-01-01

    Microlensing in multiply imaged gravitationally lensed quasars provides us with a unique tool to zoom in on the structure of AGN and explore their physics in more detail. Microlensing magnification, caused primarily by stars and white dwarfs close to the line of sight towards the lensed quasar images, is seen as uncorrelated flux variations due to the relative motions of the quasar, the lens, its stars, and the observer, and it depends on the structural and dynamical properties of the source and the lens. Since the magnification depends upon the size of the source, we can use microlensing to measure the size of quasar emission regions. In essence, the amplitude of the microlensing variability encodes the source size, with smaller sources showing larger variability amplitudes. Using state of the art microlensing techniques, our team has performed pioneering research in the field based on multi-wavelength space and ground-based observations. Among the most remarkable results, using Chandra observations we have set the first quantitative constraints on the sizes of the X-ray emission regions of quasars. In this work l briefly describe the methodology, the results from our previous multi-wavelength monitoring programs, and the next frontier of exploring the dependence of the structure of the X-ray emission regions on black hole mass and X-ray energy.

  4. Modulational interaction between the short-wavelength lower-hybrid waves and slow, large-scale density fluctuations

    SciTech Connect

    Uecer, Defne; Shapiro, Vitali D.

    2005-11-15

    Conditions are formulated for modulational instability of two modes with disparate time and space scales, and the modulational interaction of fast and short-wavelength lower-hybrid waves with slow, large-scale inertial Alfven and ion-acoustic waves is analyzed. Instability is driven by Reynolds' stresses exerted on plasma by the lower-hybrid waves. Reynolds' stresses lead to the formation of background density modulations in which the lower-hybrid wave can be localized. It is concluded that the lower-hybrid solitary structures observed in the auroral ionosphere can be created by Reynolds' stresses of the lower-hybrid waves. In many respects, the observed structures exhibit properties of wave localizations that result from modulational instability.

  5. 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.; Blundell, Ray; Gurwell, Mark A.; Moran, James M.; Primiani, Rurik; Bower, Geoffrey C.; Plambeck, Richard; Chamberlin, Richard; Freund, Robert; Friberg, Per; Honma, Mareki; Oyama, Tomoaki; Inoue, Makoto; Krichbaum, Thomas P.; Lamb, James; Marrone, Daniel P.

    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*.

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

    NASA Astrophysics Data System (ADS)

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

    2009-12-01

    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 87.8N, 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.

  7. 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

  8. Tracking and Reporting Data Using VIMS and VAMS. Module.

    ERIC Educational Resources Information Center

    Downs, W. A.

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

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

    PubMed

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

    2013-07-01

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

  10. Exploring the Role of Residue 228 in Substrate and Inhibitor Recognition by VIM Metallo-?-lactamases.

    PubMed

    Mojica, Maria F; Mahler, S Graciela; Bethel, Christopher R; Taracila, Magdalena A; Kosmopoulou, Magda; Papp-Wallace, Krisztina M; Llarrull, Leticia I; Wilson, Brigid M; Marshall, Steven H; Wallace, Christopher J; Villegas, Maria V; Harris, Michael E; Vila, Alejandro J; Spencer, James; Bonomo, Robert A

    2015-05-26

    ?-Lactamase inhibitors (BLIs) restore the efficacy of otherwise obsolete ?-lactams. However, commercially available BLIs are not effective against metallo-?-lactamases (MBLs), which continue to be disseminated globally. One group of the most clinically important MBLs is the VIM family. The discovery of VIM-24, a natural variant of VIM-2, possessing an R228L substitution and a novel phenotype, compelled us to explore the role of this position and its effects on substrate specificity. We employed mutagenesis, biochemical and biophysical assays, and crystallography. VIM-24 (R228L) confers enhanced resistance to cephems and increases the rate of turnover compared to that of VIM-2 (kcat/KM increased by 6- and 10-fold for ceftazidime and cefepime, respectively). Likely the R ? L substitution relieves steric clashes and accommodates the C3N-methyl pyrrolidine group of cephems. Four novel bisthiazolidine (BTZ) inhibitors were next synthesized and tested against these MBLs. These inhibitors inactivated VIM-2 and VIM-24 equally well (Ki* values of 40-640 nM) through a two-step process in which an initial enzyme (E)-inhibitor (I) complex (EI) undergoes a conformational transition to a more stable species, E*I. As both VIM-2 and VIM-24 were inhibited in a similar manner, the crystal structure of a VIM-2-BTZ complex was determined at 1.25 and revealed interactions of the inhibitor thiol with the VIM Zn center. Most importantly, BTZs also restored the activity of imipenem against Klebsiella pneumoniae and Pseudomonas aeruginosa in whole cell assays producing VIM-24 and VIM-2, respectively. Our results suggest a role for position 228 in defining the substrate specificity of VIM MBLs and show that BTZ inhibitors are not affected by the R228L substitution. PMID:25915520

  11. Temperature maps of Saturn's satellites retrieved from Cassini-VIMS observations (Invited)

    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.

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

    NASA Astrophysics Data System (ADS)

    Tosi, F.; Orosei, R.; Seu, R.; Coradini, A.; Lunine, J. I.; Filacchione, G.; Capaccioni, F.; Cerroni, P.; Flamini, E.; Brown, R. H.; Cruikshank, D. P.; Lopes, R. M.

    2010-12-01

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

  13. Measurements of laser wavelength scaling ion acoustic decay instability and associated effects in laser-plasma interaction experiments

    NASA Astrophysics Data System (ADS)

    Mizuno, K.; Degroot, J. S.; Seka, W.

    1989-06-01

    We have made extensive studies of Ion Acoustic Decay Instabilities (IADI) in laser-pellet interactions under the program of the National Laser User Facility at LLE. We have observed well defined IADI. In this paper it is shown that IADI is potentially important in laser fusion applications. The threshold decreased as the laser spot size increased. The measured threshold is an order of magnitude lower that previously reported values in small spot experiments. The threshold values for IR and short wavelength Green lasers are quite low, and reached homogeneous-plasma collisional values in a planar plasma produced by a large spot size laser irradiations. The results are explained in agreement with LASNEX calculations with a flux limit of f = 0.1. These low threshold values indicate that IADI is potentially important in a large scale plasma, and even in short-wavelength laser-pellet interactions which are applicable to laser fusion research. It is shown that IADI is a useful tool for plasma diagnostic near the critical surface. We have shown that ion charge state Z can be measured using IADI signals. These measurements are possible without resorting to any complicated atomic physics model. At high intensity regimes, IADI spectrum is quite different from the medium intensity regime. A broad turbulent-like spectrum is observed.

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

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

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

  15. Performance evaluation of a large-scale optical switch based on an arrayed waveguide grating router and wavelength converter

    NASA Astrophysics Data System (ADS)

    Zhou, Luying; Xu, Zhaowen

    2016-02-01

    A scheduling scheme for a large-scale optical switch is presented and its performance is evaluated. The optical switch is built on an arrayed waveguide grating router (AWGR) and space switching enabled tunable wavelength converter (SS-TWC) and in a Clos switch structure. The SS-TWC has more than one output and in the switch structure enables a multiple fold expansion of the switch port count while using the same dimension AWGR. The switch reconfiguration is triggered by an event, e.g., packet arriving or input port transmitter available for its waiting packets, and the scheduling scheme operates asynchronously. Simulation results demonstrate that the traffic scheduling scheme enables the delivery of high-transmission bandwidth and low packet delay performance, and verify the nonblocking property of the switch.

  16. Hydrogen atom temperature measured with wavelength-modulated laser absorption spectroscopy in large scale filament arc negative hydrogen ion source

    SciTech Connect

    Nakano, H. Goto, M.; Tsumori, K.; Kisaki, M.; Ikeda, K.; Nagaoka, K.; Osakabe, M.; Takeiri, Y.; Kaneko, O.; Nishiyama, S.; Sasaki, K.

    2015-04-08

    The velocity distribution function of hydrogen atoms is one of the useful parameters to understand particle dynamics from negative hydrogen production to extraction in a negative hydrogen ion source. Hydrogen atom temperature is one of the indicators of the velocity distribution function. To find a feasibility of hydrogen atom temperature measurement in large scale filament arc negative hydrogen ion source for fusion, a model calculation of wavelength-modulated laser absorption spectroscopy of the hydrogen Balmer alpha line was performed. By utilizing a wide range tunable diode laser, we successfully obtained the hydrogen atom temperature of ∼3000 K in the vicinity of the plasma grid electrode. The hydrogen atom temperature increases as well as the arc power, and becomes constant after decreasing with the filling of hydrogen gas pressure.

  17. The bcp gene in the bcp-recA-vimA-vimE-vimF operon is important in oxidative stress resistance in Porphyromonas gingivalis W83.

    PubMed

    Johnson, N A; McKenzie, R M E; Fletcher, H M

    2011-02-01

    The ability of Porphyromonas gingivalis to overcome oxidative stress in the inflammatory environment of the periodontal pocket is critical for its survival. We have previously demonstrated that the recA locus, which carries the bacterioferritin co-migratory protein (bcp) gene and has a unique genetic architecture, plays a role in virulence regulation and oxidative stress resistance in P. gingivalis. To further characterize the bcp gene, which was confirmed to be part of the bcp-recA-vimA-vimE-vimF operon, we created a P. gingivalis bcp-defective isogenic mutant (FLL302) by allelic exchange. Compared with the wild-type, FLL302 had a similar growth rate, black pigmentation, ?-hemolysis and UV sensitivity. Although there was no change in the distribution of gingipain activity, there was a 30% reduction in both Arg-X and Lys-X activities in the mutant strain compared with the wild-type. When exposed to 0.25 mm hydrogen peroxide, P. gingivalis FLL302 was more sensitive than the wild-type. In addition, the cloned P. gingivalis bcp gene increased resistance to 0.25 mm hydrogen peroxide in a bcp-defective Escherichia coli mutant. The mutant also demonstrated decreased aerotolerance when compared with the wild-type. Porphyromonas gingivalis FLL302 and the wild-type strain had similar virulence profiles in a mouse model of virulence. These observations suggest that the bcp gene may play a role in oxidative stress resistance but has a decreased functional significance in the pathogenic potential of P. gingivalis. PMID:21214873

  18. VIMS Observations of the Moon: a Recalibration in the Search for Water

    NASA Astrophysics Data System (ADS)

    Hibbitts, C.; Hansen, G. B.

    2009-12-01

    Motivated by the possibility that small amounts of adsorbed water may be stable on illuminated portions of the lunar surface, possibly as OH- , (e.g. Starukhina and Shkuratov, 2000; Hibbitts et al., 2009; Dyar et al., 2009; McCord et al., 2009) and to confirm not yet released observations by other spacecraft, we have reanalyzed the VIMS (Visual and Infrared Mapping Spectrometer) observations of the Moon for absorption features near 3 microns - a very strong absorption band due to the presence of OH- or H2O. The VIMS instrument onboard the Cassini spacecraft measures reflected solar and thermally emitted radiation from ~ 0.35 to 5.1 microns in 352 channels. On August 18, 1999, the Cassini spacecraft flew between the Earth and the Moon, within 380,000 km of the lunar surface at a phase angle of 90deg and a subsolar point of 0.33N, 257E (Brown et al., 2000), obtaining 12 observations fully within its field of view at a sub-spacecraft spatial resolution of about 190 km/pixel. Designed for operation at 10 a.u., the instrument offers the potential for very high SNR measurements of solar reflectance and thermal emission from of the lunar surface to investigate the presence and abundance of water and other trace materials, provided that significant calibration issues are appropriately addressed. Due to a combination of operating at higher temperatures than designed for and due to high thermal flux from the parts of the Moons surface that are warm, the VIMS instrument saturates in the infrared shortward of 1.65 microns and longward of ~ 3.5 - 4 microns, with longer wavelengths remaining useful for colder areas of the surface. In this preliminary effort, we have recalibrated each of the 12 observations relative to the equatorial limb by fitting the spectrum of the limb to a polynomial curve, resulting in an arbitrarily smooth spectrum, but deriving an empirical adjustment to the radiometric calibration that allows us to compare other areas of the Moon to the limb. This technique has the disadvantage of erasing any feature, real or artifact, in the spectrum of the limb, but will allow us to explore the possibility of stronger bands present elsewhere such as at the cooler higher latitudes or on the terminator. The mentioned disadvantage is mitigated by the fact that the spectrum of the equatorial limb is strongly affected by thermal emission near 3 microns and longer wavelengths, and any real spectral features will be muted, the absorption band in reflectance filled in by the emitted energy. This subsequently-derived modification to the VIMS calibration is applied to three other selected regions: equatorial terminator, north polar, and south polar terrains. We currently find that the south polar terrain possesses a weak, ~ 3% feature beginning near 2.73-microns and not rising again, that may be consistent with a small amount of water or OH-. The northern terrain does not possess this feature. More detailed analyses will be presented, but additional, high spatial resolution spectra covering the 2.5-4 micron region are needed to better constrain the possibility of water and other trace materials on the lit portions of the Moon.

  19. 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.

  20. Characteristics of Titan's Clouds from VIMS T0 Observations

    NASA Astrophysics Data System (ADS)

    Griffith, C. A.; Baines, K. H.; Buratti, B.; Clark, R. N.; Drossart, P.; Owen, T. C.; Nelson, R. M.; Cassini VIMS

    2004-11-01

    Over the past 4 years, ground-based images have shown that Titan sports a high cloud systems on a daily basis, which have been observed exclusively in Titan's south polar region. These clouds are composed of methane ice and may be a component of a liquid cycle similar to Earth's hydrologic cycle, with clouds, rain and seas. In July, Cassini gave us the first direct view of Titan's high clouds as the spacecraft passed below Titan's south pole. Observations by Cassini's Visual and Infrared Mapping Spectrometer (VIMS) illuminate the altitudes, thicknesses and extents of Titan's clouds, which were dramatically imaged in detail by the ISS instrument. We find, consistent with ground-based observations, that the clouds reside in the high troposphere. In addition, the clouds are optically thick over a region of at least 100 km. Here I will discuss the characteristics of Titan's clouds as measured by VIMS, and implications of these results in terms of the formation of Titan's clouds. This work is supported by Cassini VIMS funds and the NASA planetary astronomy program

  1. Saturn B and C ring studies at multiple wavelengths

    NASA Astrophysics Data System (ADS)

    Spilker, Linda; Deau, Estelle; Morishima, Ryuji; Filacchione, Gianrico; Hedman, Matt; Nicholson, Phil; Colwell, Josh; Bradley, Todd; Pilorz, Stu

    2015-04-01

    We can learn a great deal about the characteristics of Saturn's ring particles and their regoliths by modeling the changes in their brightness, color and temperature with changing viewing geometry over a wide range of wavelengths, from ultraviolet through the thermal infrared. Data from Cassini's Composite Infrared Spectrometer (CIRS), Visual and Infrared Mapping Spectrometer (VIMS), Imaging Science Subsystem (ISS) and Ultraviolet Imaging Spectrograph (UVIS) are jointly studied using data from the lit and unlit main rings at multiple geometries and solar elevations. Using multi-wavelength data sets allow us to test different thermal models by combining the effects of particle albedo, regolith grain size and surface roughness with thermal emissivity and inertia, particle spin rate and spin axis orientation. With the high spatial resolution of the Cassini data it is now possible to analyze these effects at smaller spatial scales and characterize higher optical depth regions in faint rings such as the outer C ring, where albedo differences may be present. The CIRS temperature and ISS color variations are confined primarily to phase angle over a range of solar elevations with only small differences from changing spacecraft elevation. Color and temperature dependence with varying solar elevation angle are also observed. Brightness dependence with changing solar elevation angle and phase angle is observed with UVIS. VIMS observations show that the IR ice absorption band depths are a very weak function of phase angle, out to ~140 deg phase, suggesting that interparticle light scattering is relatively unimportant except at very high phase angles. These results imply that the individual properties of the ring particles may play a larger role than the collective properties of the rings, in particular at visible wavelengths. The temperature and color variation with phase angle may be a result of scattering within the regolith and on possibly rough surfaces of the clumps, as well as a contribution from scattering between individual particles in a many-particle-thick layer. Preliminary results from our joint studies will be presented. This research was carried out in part at the Jet Propulsion Laboratory, California Institute of Technology, under contract with NASA. Copyright 2015 California Institute of Technology. Government sponsorship is acknowledged.

  2. Monitoring the Seasonal Evolution of the North and South Polar Vortex on Titan during 10 Years with Cassini/Vims

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

    Cassini entered in Saturn's orbit in July 2004. In ten years, more than 100 targeted flybys of Titan have been performed. We focus our study on the comprehensive analysis of the Visual and Infrared Mapping Spectrometer data set acquired between 2004 and 2014, with a particular emphasis on the atmospheric polar features. First evidences for a vast ethane cloud covering the North Pole have been detected as soon as the second targeted flyby in December 2005 [1]. The first detailed imaging of this north polar feature with VIMS was obtained in December 2006, thanks to a change in inclination of the spacecraft orbit [2]. At this time, the northern lakes and seas of Titan were totally masked to the optical instruments by the haze and clouds, whereas the southern pole was well illuminated and mostly clear of haze and vast clouds. Subsequent flybys revealed that the vast north polar feature was progressively vanishing around the equinox in 2009 [2,3,4], in agreement with the predictions of Global Circulation Models [5]. It revealed progressively the underlying lakes to the ISS and VIMS instruments. First evidences of an atmospheric vortex growing over the South Pole occurred in May 2012, with a high altitude feature detected at each flybys since then. In this study, we have computed individual global maps of the north and south poles for each of the 100 targeted flybys, using VIMS wavelengths sensitive both to clouds and surface features. This allows a more complete monitoring of the evolution of the north polar cloud than was previously done before using a selection of individual flybys only. It also provides a detailed investigation of what is currently acting over the South Pole. [1] Griffith et al., Science, 2006. [2] Le Moulic et al., PSS, 2012. [3] Rodriguez et al., Nature, 2009. [4] Rodriguez et al., Icarus 2011. [5] Rannou et al., Science 2005

  3. In Porphyromonas gingivalis VimF is involved in gingipain maturation through the transfer of galactose.

    PubMed

    Muthiah, Arun S; Aruni, Wilson; Robles, Antonette G; Dou, Yuetan; Roy, Francis; Fletcher, Hansel M

    2013-01-01

    Previously, we have reported that gingipain activity in Porphyromonas gingivalis, the major causative agent in adult periodontitis, is post-translationally regulated by the unique Vim proteins including VimF, a putative glycosyltransferase. To further characterize VimF, an isogenic mutant defective in this gene in a different P. gingivalis genetic background was evaluated. In addition, the recombinant VimF protein was used to further confirm its glycosyltransferase function. The vimF-defective mutant (FLL476) in the P. gingivalis ATCC 33277 genetic background showed a phenotype similar to that of the vimF-defective mutant (FLL95) in the P. gingivalis W83 genetic background. While hemagglutination was not detected and autoaggregation was reduced, biofilm formation was increased in FLL476. HeLa cells incubated with P. gingivalis FLL95 and FLL476 showed a 45% decrease in their invasive capacity. Antibodies raised against the recombinant VimF protein in E. coli immunoreacted only with the deglycosylated native VimF protein from P. gingivalis. In vitro glycosyltransferase activity for rVimF was observed using UDP-galactose and N-acetylglucosamine as donor and acceptor substrates, respectively. In the presence of rVimF and UDP-galactose, a 60 kDa protein from the extracellular fraction of FLL95 which was identified by mass spectrometry as Rgp gingipain, immunoreacted with the glycan specific mAb 1B5 antibody. Taken together, these results suggest the VimF glycoprotein is a galactosyltransferase that may be specific for gingipain glycosylation. Moreover, galatose is vital for the growing glycan chain. PMID:23717416

  4. Titan's aerosol optical properties with VIMS observations at the limb of Titan

    NASA Astrophysics Data System (ADS)

    Rannou, Pascal; Seignovert, Benoit; Lavvas, Panayotis; Lemouelic, Stphane; Sotin, Christophe

    2015-11-01

    The study of Titan properties with remote sensing relies on a good knowledge of the atmosphere properties. The in-situ observations made by Huygens combined with recent advances in the definition of methane properties enable to model and interpret observations with a very good accuracy. Thanks to these progresses, we can analyze in this work the observations made at the limb of Titan in order to retrieve information on the haze properties as its vertical profiles but also the spectral behaviour between 0.88 and 5.2 ?m.To study the haze layer and more generally the source of opacities in the stratosphere, we use som observation made at the limbe of Titan by the VIMS instrument onboard Cassini. We used a model in spherical geometry and in single scattering, and we accounted for the multiple scattering with a parallel plane model that evaluate the multiple scattering source function at the plane of the limb.Our scope is to retrieve informations about the vertical distribution of the haze, its spectral properties, but also to obtain details about the shape of the methane windows to disantangle the role of the methane and of the aerosols.We started our study at the latitude of 55N, with a image taken in 2006 with a relatively high spatial resolution (for VIMS). Our preliminary results shows the spectral properties of the aerosols are the same whatever the altitude. This is a consequence of the large scale mixing. From limb profile between 0.9 and 5.2 ?m, we can probe the haze layer from about 500 km (at 0.9 ?m) to the ground (at 5.2 ?m). We find that the vertical profile of the haze layer shows three distinct scale heights with transitions around 250 km and 350 km. We also clearly a transition around 70-90 km that may be due to the top of a condensation layer.

  5. 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.

  6. 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.

  7. Titan's Surface Properties: Correlations Among DISR, RADAR And VIMS Observations

    NASA Astrophysics Data System (ADS)

    Soderblom, Laurence A.; DISR, Cassini-Huygens; RADAR; VIMS Teams

    2006-09-01

    Titan's vast equatorial fields of longitudinal dunes seen in radar images (Lorenz et al. 2006) correlate with one of two dark surface units discriminated as brown and "blue in color composites (RGB as 2.0, 1.6, 1.3 ?m) of near-IR spectral cubes. Earth-based spectroscopy (Griffith et al. 2003) shows a surface consistent with dirty H2O ice; VIMS data show more evidence of H2O ice in darker than brighter units (McCord et al. 2006). Our work shows that relative to the VIMS dark blue unit, the albedo of the dark brown unit is lower at 1.3 ?m, higher at 2.0 ?m, shows less evidence of water ice, and correlates with the radar-dark dunes. This suggests that the dunes are dryer, higher in hydrocarbon or nitrile composition. VIMS bright units show even less evidence of H2O, inferred to consist of very fine tholin dust. If the rate of deposition of hydrocarbons is 0.1 ?m/yr (Yung et al. 1984), the surface would be coated (optically) in a few years unless cleansing processes are active. The dunes must be mobile on this timescale to prevent accumulation of bright coatings. Likewise fluvial/pluvial processes every few decades must be cleaning the dark floors of the incised channels and dark scoured plains at the Huygens landing site. In this model Xanadu is a large inactive region where eolian, fluvial, pluvial activity is currently at a low ebb. Huygens landing in a region of the dark blue materials a few kilometers south of bright highlands and about 30 km south of the nearest occurrence of the VIMS-dark-brown Radar-dunes unit. References: Lorenz, R. D., et al., Science, 312, 2006; Griffith, C. A., et al., Science 300, 2003; McCord, T. B., et al., Pl. Sp. Sci. in press, 2006; Yung, Y. L., et al., Ap. J. Supp, 55, 1984.

  8. Remote sensing applications in marine science programs at VIMS

    NASA Technical Reports Server (NTRS)

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

    1974-01-01

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

  9. VIMS Evidence for Palimpsests on Titan as a Constraint on Widespread Precipitation.

    NASA Astrophysics Data System (ADS)

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

    2004-12-01

    The Cassini spacecraft passed about 400,000 km of Titan on 2 July 2004. Titan's surface is seen in Visual and Infrared Mapping Spectrometer (VIMS) images at infrared wavelengths where methane, the principal atmospheric absorber, is transmitting. At 2.02 microns VIMS images show several circular features on Titan. These bear a striking similarity to circular features exhibiting topographic relief caused by impact events on a wide range of solar system objects. We undertook a photometric analysis of two circular regions using 2.02 micron images taken near the time of closest approach. We measured the reflectance along lines that passed through the sub-solar point on Titan's surface and traversed the center of each feature. The extracted reflectance profiles enabled us to search for vertical relief by comparing our photometric profiles with the profiles expected from a circular depression, a circular depression with a raised rim, and a circular depression with a raised rim and a central peak using a model based on the widely used bi-directional reflectance equations developed by Hapke (1993). We assumed: 1) the particulate surface scattered isotropically and had uniform single scattering albedo, 2) the haze was optically thin, did not extend to the surface, and was uniformly mixed laterally with the atmosphere. Despite our best effort to adjust the depression parameters to fit the data our data do not fit that expected for a craterlike depression. In one case the model fit does not agree with the data at large distances from the sub-solar point. In the other, the photometric profile expected from the central peak is in the opposite sense to that which we measured. In both cases the crater depths required to accommodate these best-fit models are extremely, if not unreasonably, large (~50 -100 km.) with diameters of 1000 and 2000 km.). We find it unusual to have two craters of such size on Titan because major cratering events are principally associated with the early bombardment period of solar system system-the first 1 billion years.Therefore, we suggest that these features are not caused by topographic relief and are not true craters. They are consistent with palimpsests-expressions of darker reflectance on a surface where the vertical relief has been lost to lithospheric plastic flow. If these features are palimpsests and are the remains of ancient impacts then their persistence on the surface suggests that widespread weathering processes, such as a planet-wide precipitation of aerosols, on Titan are severely limited. This result is consistent with Keck observations at shorter wavelengths by Bouchez.

  10. 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.

  11. Using the VIMS Dataset to Understand Titan’s Hydrologic Cycle Through Cloud Characterization

    NASA Astrophysics Data System (ADS)

    Corlies, Paul; Hayes, Alexander G.; Rodriguez, Sebastien; Adamkovics, Mate; Rojo, Patricio; Turtle, Elizabeth P.

    2015-11-01

    Along with Earth, Titan is the only body in our Solar System to possess an active hydrologic cycle. Monitoring how Titan’s methane-based hydrologic cycle varies with season over Saturn’s 29.7-year orbital period is essential for understanding its climate system.Using a newly developed radiative transfer pipeline, with updated HITRAN methane line parameters, we will present an ongoing analysis of the known cloud observations in the VIMS dataset. Although much work has gone into finding clouds in this dataset, little work has been done on understanding the characteristics of these clouds, barring a handful of individual analyses. Our pipeline allows for fast determination of these cloud characteristics including optical depth, altitude, and mean drop size. VIMS offers two advantages: providing consecutive observations of individual cloud systems to help diagnose formation mechanism and providing a decade long dataset to track seasonal variations, like those observed in cloud frequency and location. Characterizing clouds allows for an understanding of seasonally varying formation mechanisms, traces Titan’s atmospheric methane content across seasonal timescales, and can indicate clouds that could potentially have precipitated to provide context for interpreting observed surface features.We will also present an update on an ongoing ground based- cloud monitoring campaign. This campaign, begun in April 2014, has (nearly) continually monitored Titan on a variety of telescopes for the past 1.5 years. To date, no cloud activity has been observed, despite the variety in observation techniques that multiple telescopes allow. This is interesting because large cloud outbursts were observed during the equivalent point in southern summer and suggest a dichotomy in the seasonal dynamics of Titan’s atmosphere. Understanding when and with what frequency clouds begin to form in the north is crucial to understanding Titan’s hydrologic cycle on seasonal time scales.

  12. Cryovolcanism on Titan: New results from Cassini RADAR and VIMS

    NASA Astrophysics Data System (ADS)

    Lopes, R. M. C.; Kirk, R. L.; Mitchell, K. L.; Legall, A.; Barnes, J. W.; Hayes, A.; Kargel, J.; Wye, L.; Radebaugh, J.; Stofan, E. R.; Janssen, M. A.; Neish, C. D.; Wall, S. D.; Wood, C. A.; Lunine, J. I.; Malaska, M. J.

    2013-03-01

    The existence of cryovolcanic features on Titan has been the subject of some controversy. Here we use observations from the Cassini RADAR, including Synthetic Aperture Radar (SAR) imaging, radiometry, and topographic data as well as compositional data from the Visible and Infrared Mapping Spectrometer (VIMS) to reexamine several putative cryovolcanic features on Titan in terms of likely processes of origin (fluvial, cryovolcanic, or other). We present evidence to support the cryovolcanic origin of features in the region formerly known as Sotra Facula, which includes the deepest pit so far found on Titan (now known as Sotra Patera), flow-like features (Mohini Fluctus), and some of the highest mountains on Titan (Doom and Erebor Montes). We interpret this region to be a cryovolcanic complex of multiple cones, craters, and flows. However, we find that some other previously supposed cryovolcanic features were likely formed by other processes. Cryovolcanism is still a possible formation mechanism for several features, including the flow-like units in Hotei Regio. We discuss implications for eruption style and composition of cryovolcanism on Titan. Our analysis shows the great value of combining data sets when interpreting Titan's geology and in particular stresses the value of RADAR stereogrammetry when combined with SAR imaging and VIMS.

  13. Spectral changes associated with rain on Titan: observations by VIMS

    NASA Astrophysics Data System (ADS)

    Buratti, B. J.; Dalba, P. A.; Barnes, J.; Baines, K. H.; Brown, R. H.; Clark, R. N.; Nicholson, P. D.; Sotin, C.

    2012-04-01

    Titan has an erosional cycle similar to that on the Earth, with solid, liquid, and gaseous methane taking the place of the Earths water. Lakes and ponds, drainage and fluvial features, and clouds all suggest that rain is falling on Titan. A darkening event near clouds covering the Huygens landing site, followed by a return to the previous state, strongly suggested rainfall followed by evaporation (Turtle et al., 2011). The Cassini Visual infrared Mapping Spectrometer (VIMS) obtains medium resolution spectra in the 0.35-5.1 ?m spectral region, which includes several atmospheric windows that offer glimpses of Titans surface. The albedo of the surface can be measured in these windows, and some compositional information, including changes through time, can be derived. VIMS observed an area near 15 south latitude and 330 longitude at two separate times: in August 2009 during T61 and in May 2011 during T76. A spectral analysis of this region, including compensation for varying atmospheric path lengths, shows substantial spectral changes in the two and five micron atmospheric windows. A comparison of the changes with that expected from the deposition and later evaporation of liquid methane or another hydrocarbon shows them to be consistent with rain on Titan. Ackowledgements: This research was carried out at the Jet Propulsion Laboratory, California Institute of Technology under contract to the National Aeronautics and Space Administration. Copyright 2012 all rights reserved. References: Turtle, E. P. et al. (2011) Science 331, 1414.

  14. Characteristics Of Titan's Clouds from VIMS T0 Observations

    NASA Astrophysics Data System (ADS)

    Griffith, C. A.; Baines, K.; Buratti, B.; Clark, R.; Drossart, P.; Owen, T.; Nelson, R.

    2004-12-01

    Over the past 4 years, ground-based images have shown that Titan sports high cloud systems on a daily basis, which have been observed exclusively in Titan's south polar region. These clouds are composed of methane ice and may be a component of a liquid cycle similar to Earth's hydrologic cycle, with clouds, rain and seas. This past July, Cassini gave us the first direct view of Titan's high clouds as the spacecraft passed below Titan's south pole. Observations by Cassini's Visual and Infrared Mapping Spectrometer (VIMS) illuminate the altitudes, thicknesses and extents of Titan's clouds, which were dramatically imaged in detail by the ISS instrument. We find, consistent with ground-based observations, that the clouds reside in the high troposphere. In addition, at times the clouds are optically thick over a region of at least 100 km. Here I will discuss the characteristics of Titan's clouds as measured by VIMS, and implications of these results in terms of the formation of Titan's clouds.

  15. 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.

  16. 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.

  17. Equinoctial Activity Over Titan Dune Fields Revealed by Cassini/vims

    NASA Astrophysics Data System (ADS)

    Rodriguez, S.; Le Mouelic, S.; Barnes, J. W.; Hirtzig, M.; Rannou, P.; Sotin, C.; Brown, R. H.; Bow, J.; Vixie, G.; Cornet, T.; Bourgeois, O.; Narteau, C.; Courrech Du Pont, S.; Le Gall, A.; Reffet, E.; Griffith, C. A.; Jaumann, R.; Stephan, K.; Buratti, B. J.; Clark, R. N.; Baines, K. H.; Nicholson, P. D.; Coustenis, A.

    2012-12-01

    Titan, the largest satellite of Saturn, is the only satellite in the solar system with a dense atmosphere. The close and continuous observations of Titan by the Cassini spacecraft, in orbit around Saturn since July 2004, bring us evidences that Titan troposphere and low stratosphere experience an exotic, but complete meteorological cycle similar to the Earth hydrological cycle, with hydrocarbons evaporation, condensation in clouds, and rainfall. Cassini monitoring campaigns also demonstrate that Titan's cloud coverage and climate vary with latitude. Titan's tropics, with globally weak meteorological activity and widespread dune fields, seem to be slightly more arid than the poles, where extensive and numerous liquid reservoirs and sustained cloud activity have been discovered. Only a few tropo-spheric clouds have been observed at Titan's tropics during the southern summer. As equinox was approaching (in August 2009), they occurred more frequently and appeared to grow in strength and size. We present here the observation of intense brightening at Titan's tropics, very close to the equinox. These detections were conducted with the Visual and Infrared Mapping Spectrometer (VIMS) onboard Cassini. We will discuss the VIMS images of the three individual events detected so far, observed during the Titan's flybys T56 (22 May 2009), T65 (13 January 2010) and T70 (21 June 2010). T56, T65 and T70 observations show an intense and transient brighten-ing of large regions very close to the equator, right over the extensive dune fields of Senkyo, Belet and Shangri-La. They all appear spectrally and morphologically different from all transient surface features or atmospheric phenomena previously reported. Indeed, these events share in particular a strong brightening at wavelengths greater than 2 ?m (especially at 5 ?m), making them spectrally distinct from the small tropical clouds observed before the equinox and the large storms observed near the equator in September and October 2010. In this paper, we will discuss the possibility that these singular events may have occurred very close to the surface, having a strong link with the underlying dune fields. Radiative transfer calculations indeed show that these singular brightenings are due to the transient appearance of an additional atmospheric layer, confined at very low altitudes and loaded with few but large particles. Gathering all the observational and modeling constraints, we conclude that the most probable explanation for these events is the local and transient occurrence of huge sand storms, directly originating from the underlying dune fields. We will also discuss the possible implications of the equinoctial occurrence of such events for Titan's tropical wind regimes and for the present-day activity of equatorial dunes.

  18. 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.

  19. Estimating And Mapping The 5-micron Albedo Of Titan's Surface From Cassini Vims Observations

    NASA Astrophysics Data System (ADS)

    Soderblom, Jason M.; Barnes, J. W.; Brown, R. H.; Soderblom, L. A.; Clark, R. N.; Jaumann, R.; Sotin, C.; Baines, K. H.; Buratti, B. J.; Nicholson, P. D.

    2008-09-01

    The dense, hazy, methane-rich atmosphere of Titan introduces substantial difficulty in obtaining information about the absolute albedo of Titan's surface. While several groups are working to obtain full radiative-transfer solutions to the problem, some useful approximations are possible in the interim, particularly at the longest wavelengths where scattering is reduced and thin-atmosphere approximations become appropriate. In this work, we make use of a series of four near-IR observations of Ontario Lacus, obtained on the 38th flyby of Titan by the Visual and Infrared Mapping Spectrometer on board the Cassini spacecraft. These data were acquired under fortuitous observational geometries, such that the incidence and phase angles remain nearly constant between the four observations, while the emission angles vary from 40 - 80. Such data allow a relatively straightforward extrapolation of the data to zero airmass. We then leverage the information gained about the atmospheric transmission to estimate the attenuation of the incident solar irradiance. With this information we are able to estimate the absolute albedo of the surface of Titan, in this case the center of Ontario Lacus found to be nearly zero (see Brown et al 2008, doi:10.1038/nature07100). Future sets of VIMS observations of this type (sampling a range of emission angles) will allow estimation and mapping the 5-micron albedo of a variety of surfaces including other lakes, dunes, and surfaces bright and dark at optical and radar wavelengths. Funding for this research was provided by the Cassini Project managed by the Jet Propulsion Laboratory, California Institute of Technology.

  20. 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.

  1. 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.; Zhang, Jie; Liu, Kai E-mail: jzhang7@gmu.edu

    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 κ, spreading exponent β, 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 κ∝L {sup 0.94±0.01} and the three-parameter scaling law L∝κ 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 κ than confined flares (without CMEs)

  2. 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.

  3. 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.; Filachionne, 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.

  4. 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.; Appr, T.; Le Gall, A.; Reffet, E.; Le Corre, L.; Le Moulic, 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.

  5. Identification of VIM-2-Producing Pseudomonas aeruginosa from Tanzania Is Associated with Sequence Types 244 and 640 and the Location of blaVIM-2 in a TniC Integron

    PubMed Central

    Moyo, Sabrina; Haldorsen, Bjørg; Aboud, Said; Blomberg, Bjørn; Maselle, Samuel Y.; Sundsfjord, Arnfinn; Langeland, Nina

    2014-01-01

    Epidemiological data on carbapenemase-producing Gram-negative bacteria on the African continent are limited. Here, we report the identification of VIM-2-producing Pseudomonas aeruginosa isolates in Tanzania. Eight out of 90 clinical isolates of P. aeruginosa from a tertiary care hospital in Dar es Salaam were shown to harbor blaVIM-2. The blaVIM-2-positive isolates belonged to two different sequence types (ST), ST244 and ST640, with blaVIM-2 located in an unusual integron structure lacking the 3′ conserved region of qacΔE1-sul1. PMID:25331700

  6. Identification of VIM-2-producing Pseudomonas aeruginosa from Tanzania is associated with sequence types 244 and 640 and the location of blaVIM-2 in a TniC integron.

    PubMed

    Moyo, Sabrina; Haldorsen, Bjrg; Aboud, Said; Blomberg, Bjrn; Maselle, Samuel Y; Sundsfjord, Arnfinn; Langeland, Nina; Samuelsen, rjan

    2015-01-01

    Epidemiological data on carbapenemase-producing Gram-negative bacteria on the African continent are limited. Here, we report the identification of VIM-2-producing Pseudomonas aeruginosa isolates in Tanzania. Eight out of 90 clinical isolates of P. aeruginosa from a tertiary care hospital in Dar es Salaam were shown to harbor bla(VIM-2). The bla(VIM-2)-positive isolates belonged to two different sequence types (ST), ST244 and ST640, with bla(VIM-2) located in an unusual integron structure lacking the 3' conserved region of qac?E1-sul1. PMID:25331700

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

    NASA Astrophysics Data System (ADS)

    Beechem, Joseph M.

    1992-04-01

    One of the major aspects of fluorescence spectroscopy which differentiates this technique from many other spectroscopic approaches is the inherent multidimensional nature of the data. For instance, the basic pulsed-laser fluorescence data set is characterized by fluorescence versus: emission wavelength, polarization state (parallel and perpendicular intensities), time of emission (picoseconds to nanoseconds), and time of biological reaction (milliseconds to minutes). Usually, this six-dimensional data set is obtained piecemeal, single dimension at a time; often complete data sets are not even collected. This is especially true of the biological time scale axis. Data acquisition times for picosecond decay data are typically seconds to minutes, and, therefore, it has not been generally possible to perform this experiment in a kinetic mode. What is described in this report is the construction of a parallel multichannel time-correlated single-photon counting (TCSPC) fluorometer which is capable of simultaneous collection of: fluorescence vs. picosecond to nanosecond time vs. emission wavelength vs. polarization state vs. millisecond to second time. Use is made of two multi-anode microchannel plate detectors, each obtaining data at two different polarization states, six different emission wavelengths, along 12 independent TCSPC channels. This instrument is interfaced to a three-syringe stepper motor controlled stop-flow apparatus, and picosecond decay data along all of these channels is stored and collected by two 33 MHz 80486 computers at rates approaching 1200 - 12000 data sets per second.

  8. Spectrophotometric Modeling of Enceladus Surface Properties and Composition from Vims Data

    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.

    2010-12-01

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

  9. VIMS Near-Infrared Imaging and Spectra of Precipitation-Associated Surface Changes

    NASA Astrophysics Data System (ADS)

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

    2012-04-01

    Cassini ISS saw large-scale surface darkenings in the wake of a tropical cloudburst event in 2010 September. In concert with the abstract by Turtle et al., in this presentation we show that weeks to months after darkening the surfaces did not revert to their pre-cloudburst brightness, but rather became brighter. VIMS observations of four distinct areas show these brightenings: Yalaing Terra, Hetpet Regio, Concordia Regio, and Adiri. Each study area brightened within each near-infrared atmospheric window, though not equally. In each case the brightened areas fade to their original spectra over a timescale of about a year. This rapid reversion time is inconsistent with chemical alteration of the surface - haze fallout would take hundreds to tens of thousands of years to recover an altered surface. Instead the deposition and removal of a volatile layer is more consistent with the observed evolution. Different scenarios for the production and removal of such a layer are possible. We will discuss these scenarios, which include evaporative cooled frost that later sublimates, and dissolution and reprecipitation of surface organics that may later be eroded by wind.

  10. Modeling Saturn's 5-micron IRTF/SpeX and Cassini/VIMS Spectra

    NASA Astrophysics Data System (ADS)

    Carlson, Randall E.; Chanover, N.; Bjoraker, G.; Momary, T.; Baines, K. H.; Hewagama, T.; Glenar, D.

    2008-09-01

    Cassini's Visual Infrared Mapping Spectrometer (VIMS) is revealing dramatic structure in the clouds of Saturn's atmosphere. We complement VIMS observations by simultaneously making ground-based observations around 5 microns using the SpeX spectrograph on NASA's Infrared Telescope Facility (IRTF). Compared to VIMS, SpeX has higher spectral resolution but lower spatial resolution. Saturn's 5-micron flux from the day side is divided into two roughly equal components: reflected sunlight and thermal emission from the deep atmosphere. The exact ratio of these components varies spatially on Saturn due to its cloud structure. VIMS can separate the components by observing not only Saturn's day side, but also its night side, where by definition the reflected sunlight component is zero. Near 5 microns, we specifically concentrate on phosphine and ammonia absorption. We model Saturn's spectra using the SSP code at NASA/GSFC, which accounts for volume mixing ratio vs pressure profiles of atmospheric species and cloud height and thickness. We start by modeling the thermal component of VIMS night-side data at various northern and southern latitudes and then model VIMS day-side data and SpeX data by adding the reflected sunlight component, also at various latitudes. Observing Saturn's northern hemisphere from the IRTF is becoming easier as Saturn approaches its equinox in 2009. Our modeling efforts will enable us to characterize latitudinal variations in the spectra around 5 microns. The rich data sets provided by Cassini/VIMS and IRTF/SpeX can provide us with many insights into atmospheric abundances, chemistry, transport, and energy balance. This project is supported by a scholarship from the U.S. Air Force and grants from the National Science Foundation (AST-0507558) and NASA (NNG06G126G).

  11. 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

  12. VIMS Evidence for Palimpsests on Titan Suggests Limits on Widespread Precipitation.

    NASA Astrophysics Data System (ADS)

    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.; Capaccioni, F.; Cerroni, P.; Clark, R. N.; Coradini, A.; Cruikshank, D. P.; Drossart, P.; Formisano, V.; Jaumann, R.; Langevin, Y.; Matson, D. L.; McCord, T. B.; Menella, V.; Nicholson, P. D.; Sicardy, B.; Sotin, C.

    2004-11-01

    On 2 July 2004 Cassini passed within 400,000 km of Titan. At 2.02 microns where methane is transmitting, the surface is seen by VIMS. The images show features that resemble impact craters. We analyzed two regions measuring reflectance along lines that passed through the sub-solar point, traversing the feature center. We compared our photometric profiles with the profiles expected from a circular depression, a circular depression with a raised rim, and a circular depression with a raised rim and a central peak, using a model based on the bi-directional reflectance equations developed by Hapke (1993). We assumed, 1) The particulate surface scattered isotropically with uniform single scattering albedo, 2) The haze layer was optically thin the surface can be seen, 3) The haze layer does not extend to the surface, and 4) The haze particles are laterally uniformly mixed with the atmospheric gas. Our data do not fit the expected profile for a reasonable crater. In one case the model fit does not agree with the data at large distances from the sub-solar point. In another, the photometric profile expected from the central peak is in the opposite sense to that which we measured. Also, the crater depths required to accommodate these best-fit models are unreasonably large ( 50 -100 km.). These features are not caused principally by topographic relief. They are consistent with palimpsests - the remains of ancient impacts that are expressed as units of darker reflectance on a surface where the vertical relief has been lost to lithospheric plastic flow. If these albedo features on the surface are persistent then widespread weathering processes, such as a planet-wide precipitation is limited. This result is consistent with Keck observations at shorter wavelengths by Bouchez. This work carried out at JPL under contract with NASA and with the support of ESA.

  13. The Ring System of Saturn as Seen by Cassini-VIMS (Invited)

    NASA Astrophysics Data System (ADS)

    Filacchione, G.; Ciarniello, M.; Capaccioni, F.

    2015-08-01

    Since 2004 the Visual and Infrared Mapping Spectrometer (VIMS) aboard Cassini has acquired numerous hyperspectral mosaics in the 0.35-5.1 μm spectral range of Saturn's main rings in very different illumination and viewing geometries. These observations have allowed us to infer the ring particles physical properties and composition: water ice abundance is estimated through the 1.25-1.5-2.0 μm band depths, chromophores distribution is derived from visible spectral slopes while organic material is traced by the aliphatic compounds signature at 3.42 μm which appears stronger on CD and C ring than on A-B rings (Filacchione et al., 2014). Observed reflectance spectra are fitted with a spectrophotometric model based on Montecarlo ray-tracing with the scope to infer particles composition while disentangling photometric effects (caused by multiple scattering, opposition surge and forward scattering) which depend on illumination/viewing geometries. Spectral bond albedo for different regions of the rings has been best-fitted using Hapke's radiative transfer modeling (Ciarniello et al, 2011) by choosing different mixtures of water ice, tholin, and amorphous carbon particles populations. While tholin distribution seems to be fairly constant across the rings, the amorphous carbon appears anti-correlated with optical depth. Moreover, dark material contamination is less effective on densest regions, where the more intense rejuvenation processes occur, in agreement with the ballistic transport theory (Cuzzi and Estrada,1998). Finally, the 3.6 μm continuum peak wavelength is used to infer particles temperature, which is anti-correlated with the albedo and the optical depth (tau): low-albedo/low-tau C ring and CD have higher temperatures than A-B rings where albedo and tau are high. This trend matches direct temperature measurements by CIRS (Spilker et al., 2013).

  14. 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.

  15. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2008-04-01

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

  17. 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.

  18. VIM-2 beta-lactamase in Pseudomonas aeruginosa isolates from Zagreb, Croatia.

    PubMed

    Bosnjak, Zrinka; Bedenić, Branka; Mazzariol, Annarita; Jarza-Davila, Neda; Suto, Sandra; Kalenić, Smilja

    2010-03-01

    The aim of this investigation was to characterize metallo-beta-lactamases (MBLs) in Pseudomonas aeruginosa isolates from Zagreb, Croatia. One hundred P. aeruginosa isolates with reduced susceptibility to either imipenem or meropenem were tested for the production of MBLs by MBL-Etest. The susceptibility to a wide range of antibiotics was determined by broth microdilution method. The presence of bla(MBL) genes was detected by polymerase chain reaction (PCR). Hydrolysis of 0.1 mM imipenem by crude enzyme preparations of beta-lactamases was monitored by UV spectrophotometer. Outer membrane proteins were prepared and analysed by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). Six out of 100 isolates were positive for MBLs by Etest. All strains were resistant to gentamicin, ceftazidime and cefotaxime, and all except 1 were resistant to imipenem. Six strains positive for MBLs by Etest were identified as VIM MBL-producers by PCR. Sequencing of bla(VIM) genes revealed the production of VIM-2 beta-lactamase in all 6 strains. This investigation proved the occurrence of VIM-2 beta-lactamase among P. aeruginosa strains from Zagreb, Croatia. VIM-2 beta-lactamase with similar properties has previously been described in another region of Croatia and in Italy, France, Spain, Greece, Taiwan and South Korea, suggesting that this type of enzyme is widespread in the Mediterranean region of Europe and in the Far East. PMID:20001226

  19. Molecular epidemiology of VIM-1 producing Escherichia coli from Germany referred to the National Reference Laboratory.

    PubMed

    Kaase, Martin; Pfennigwerth, Niels; Lange, Felix; Anders, Agnes; Gatermann, Sren G

    2015-10-01

    The distribution of carbapenemase genes in Escherichia coli strains isolated between September 2009 and May 2013 in Germany was investigated. Out of 192 isolates with carbapenemase production OXA-48 was found in 44.8%, VIM-1 in 18.8%, NDM-1 in 11.5% and KPC-2 in 6.8%. Patients with VIM-1 producing E. coli (n=36) differed from patients with OXA-48 by an older age, less frequent mention of travel history and an increased proportion of clinical over screening specimens. These data might indicate that introduction from abroad is of minor importance for VIM-1 producing E. coli compared to other carbapenemases. Multilocus sequence typing revealed that E. coli with VIM-1 were mostly multiclonal, emphasizing the role of horizontal gene transfer in its spread. Susceptibility testing of VIM-1 producing E. coli demonstrated aztreonam susceptibility in 55.6%. Among non-?-lactams susceptibility rates of >90% were observed for amikacin, tigecycline, colistin, fosfomycin and nitrofurantoin. PMID:26321009

  20. Nosocomial emerging of (VIM1) carbapenemase-producing isolates of Klebsiella pneumoniae in North of Iran

    PubMed Central

    Rajabnia, Ramazan; Asgharpour, Fariba; Ferdosi Shahandashti, Elaheh; Moulana, Zahra

    2015-01-01

    Background and Objectives: The rapid emergence and dissemination of carbapenemase-producing Klebsiella pneumoniae strains and other members of the Enterobacteriaceae poses a considerable threat to the care of hospitalized patients and to public health. The aim of this study was to determine the frequency of metallo-?-lactamases (MBL) and VIM-1 gene in multidrug-resistant strains of K. pneumoniae. Methods: 50 isolates of non duplicated K. pneumoniae cultured from patients at intensive care units were tested for their susceptibilities to 13 different antibiotics using microbroth dilution assay. Isolates showing resistance to at least one of the carbapenems were checked for production of metallo-?-lactamase (MBLs) using imipenemEDTA synergy tests. PCR was used to detect the gene encoding VIM-1 metallo-?-lactamase (MBL). Results: Of 50 clinical isolates, 26 (52%) were resistant to imipenem in disk diffusion method. Using imipenemEDTA synergy tests, production of MBL was detected in 15 (30%) isolates. PCR assay showed that 15 isolates were positive for VIM and these included 10 and 5 isolates showing positive and negative results in phenotypic method of MBL detection test respectively. Amikacin was found as the most effective antibiotic against the MBL producers in this study. Conclusion: The emergence of bla(VIM-1) producing K. pneumoniae in North of Iran is concerning. Microorganisms producing bla(VIM-1) constitute the prevalent multidrug-resistant population of K. pneumoniae in that region. PMID:26622969

  1. Comparison between Dione' and Helene' surfaces using Cassini VIMS

    NASA Astrophysics Data System (ADS)

    Scipioni, F.; Tosi, F.; Capaccioni, F.; Cerroni, P.; Filacchione, G.; Federico, C.

    2012-04-01

    With 1122 km in diameter, Dione is the second largest inner moon of Saturn. The Voyager spacecrafts observed Dione in 1980 and revealed a complex surface structure. Afterwards, Dione was closely observed by the Cassini-Huygens spacecraft from 2004 to 2011. Dione's surface is composed primarily by water ice with minor abundances of volatiles such as CO2 and CN. The satellite's surface can be divided into some distinct classes: most notably, heavily cratered terrains and less cratered plains. Most of Dione's surface is covered by the heavily cratered terrains, located mainly in the trailing hemisphere and crossed by high-albedo wispy streaks. The origin of the dark material that covers the heavily cratered terrains is still unknown, while wispy units are likely tectonic features. Helene is a Dione's trojan moonlet, which orbits around Saturn in Dione's lagrangian point L4. The Visual and Infrared Mapping Spectrometer (VIMS) instrument onboard the Cassini Orbiter is able to acquire hyperspectral cubes in the overall spectral range from 0.35 to 5.1 ?m. We have selected 76 VIMS cubes of Dione in the IR range between 0.85 and 5.1 ?m. These data show at the same time a spatial resolution better than 100 km and a good S/N ratio. We have normalized all of the spectra at ?=2.23 ?m in order to minimize photometric effects due to different observation conditions. To emphasize the existence of spectral units, we have applied the supervised clustering technique Spectral Angle Mapper (SAM) to the infrared spectra of each cube. A classification method applied to hyperspectral data shows up to be crucial to understand geochemical processes taking place on the icy satellites' surfaces, and, in this particular case, to investigate the possible presence on the surface of Dione of non water-ice materials, such as methane and ammonia. Some classes show also a peculiar trend with respect to the phase angle, possibly related to surface structure. Moreover, the use of this technique allowed us to emphasize the dichotomy existing between Dione's trailing and leading hemispheres. For each terrain unit and for selected values of the phase angle (25, 38, 43, 47, 63, 70 and 78), we evaluated the difference between the mean spectrum of Dione and the mean spectrum of Helene. The spectral comparison shows that the most prominent difference is related to the water-ice absorption bands at 1.5 and 2.0 ?m and the CO2 absorption band at 4.26 ?m, indicating that the dark material is more abundant on Dione' surface than on Helene's. Moreover, the relative maximum in reflectance located around 3.5 ?m is a marker of the average size of ice grains. By comparing Dione' and Helene's spectra, it turns out that Helene's ice grains are on an average larger than those of Dione.

  2. Visible and infrared mapping spectrometer (VIMS) - A facility instrument for planetary missions

    NASA Technical Reports Server (NTRS)

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

    1988-01-01

    A second-generation visible and IR mapping spectrometer (VIMS), selected for both the Mars Observer and Comet Rendezvous Asteroid Flyby (CRAF) missions, is described. VIMS is a scanning spectrometer with a focal plane consisting of linear arrays of visible and IR detectors, cooled by a radiative cooler. It is noted that a wide-angle scan using a full-aperture scan mirror was implemented for the Mars Observer; a narrow-angle scan using a scanning secondary mirror within a Cassegrain foreoptic was achieved for the CRAF mission.

  3. Comparison between Dione' and Enceladus' terrain units, based on Cassini VIMS data

    NASA Astrophysics Data System (ADS)

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

    2013-09-01

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

  4. The surface composition of Iapetus: Mapping results from Cassini VIMS

    NASA Astrophysics Data System (ADS)

    Clark, Roger N.; Cruikshank, Dale P.; Jaumann, Ralf; Brown, Robert H.; Stephan, Katrin; Dalle Ore, Cristina Morea; Eric Livo, K.; Pearson, Neil; Curchin, John M.; Hoefen, Todd M.; Buratti, Bonnie J.; Filacchione, Gianrico; Baines, Kevin H.; Nicholson, Philip D.

    2012-04-01

    Cassini VIMS has obtained spatially resolved imaging spectroscopy data on numerous satellites of Saturn. A very close fly-by of Iapetus on September 10, 2007 provided the best data on the spectral signature and spatial extent of dark material on Iapetus. This Cassini Rev 49 Iapetus fly-by provided spatially resolved imaging spectroscopy data of the dark material and the leading/trailing side transition from the dark material to visually bright ice on the trailing side. Compositional mapping and radiative transfer modeling shows that the dark material is composed of metallic iron, nano-size iron oxide (hematite), CO2, H2O ice, and possible signatures of ammonia, bound water, H2 or OH-bearing minerals, trace organics, and as yet unidentified materials. CO2 indicates a pattern of increasing CO2 strength from the leading side apex to the transition zone to the icy trailing side. A Rayleigh scattering peak in the visible part of the spectrum indicates the dark material has a large component of fine, sub-0.5-μm diameter particles consistent with nanophase hematite and nanophase iron. Spectral signatures of ice also indicate that sub-0.5-μm diameter particles are present in the icy regions. Multiple lines of evidence point to an external origin for the dark material on Iapetus, including the global spatial pattern of dark material, local patterns including crater and cliff walls shielding implantation on slopes facing away from the leading side, exposing clean ice, and slopes facing the leading direction which show higher abundances of dark material. Multiple spectral features and overall spectral shape of the dark material on Iapetus match those seen on Phoebe, Hyperion, Dione, Epimetheus, Saturn's rings Cassini Division, and the F-ring implying the material has a common composition throughout the Saturn system. The dark material appears to have significant components of nanophase metallic iron and nanophase hematite contributing to the observed UV absorption. The blue scattering peak with a strong UV-visible absorption is observed in spectra of all satellites that contain dark material, again pointing to a common origin of contamination by metallic iron that is partially oxidized.

  5. 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.

  6. Self-Assembled Monolayer of Wavelength-Scale Core-Shell Particles for Low-Loss Plasmonic and Broadband Light Trapping in Solar Cells.

    PubMed

    Dabirian, Ali; Byranvand, Mahdi Malekshahi; Naqavi, Ali; Kharat, Ali Nemati; Taghavinia, Nima

    2016-01-13

    Scattering particles constitute a key light trapping solution for thin film photovoltaics where either the particles are embedded in the light absorbing layer or a thick layer of them is used as a reflector. Here we introduce a monolayer of wavelength-scale core-shell silica@Ag particles as a novel light trapping strategy for thin film photovoltaics. These particles show hybrid photonic-plasmonic resonance modes that scatter light strongly and with small parasitic absorption losses in Ag (<1.5%). In addition, their scattering efficiency does not vary significantly with the refractive index of the surrounding medium. A monolayer of these particles is applied as the top-scattering layers in a dye-sensitized solar cells and it improves the short-circuit current density of a cell with 7 ?m-thick dye-sensitized layer by 38%. Optical measurements of the scattering properties of these particles confirm that the strong scattering and low-parasitic absorption losses constitute the main reason for this efficient light trapping. PMID:26726990

  7. 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 μm for analysis of the organic molecular bands. The spectra reveal the Csbnd H stretching modes of aromatic hydrocarbons at ∼3.28 μm (∼3050 cm-1), plus four blended bands of aliphatic sbnd CH2sbnd and sbnd CH3 in the range ∼3.36-3.52 μm (∼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).

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

    NASA Astrophysics Data System (ADS)

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

    2007-11-01

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

  9. 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.

  10. 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 Moulic, 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.

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

    USGS Publications Warehouse

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

    2007-01-01

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

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

    PubMed Central

    Mei, Shu-Li

    2014-01-01

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

  13. VIM-based dynamic sparse grid approach to partial differential equations.

    PubMed

    Mei, Shu-Li

    2014-01-01

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

  14. Inhibiting the VIM-2 Metallo-β-Lactamase by Graphene Oxide and Carbon Nanotubes.

    PubMed

    Huang, Po-Jung Jimmy; Pautler, Rachel; Shanmugaraj, Jenitta; Labbé, Geneviève; Liu, Juewen

    2015-05-13

    Metallo-β-lactamases (MBLs) degrade a broad spectrum of antibiotics including the latest carbapenems. So far, limited success has been achieved in developing its inhibitors using small organic molecules. VIM-2 is one of the most studied and important MBLs. In this work, we screened 10 nanomaterials, covering a diverse range of surface properties including charge, hydrophobicity, and specific chemical bonding. Among these, graphene oxide and carbon nanotubes are the most potent inhibitors, while most other materials do not show much inhibition effect. The inhibition is noncompetitive and is attributed to the hydrophobic interaction with the enzyme. Adsorption of VIM-2 was further probed using protein displacement assays where it cannot displace or be displaced by bovine serum albumin (BSA). This information is useful for rational design inhibitors for MBLs and more specific inhibition might be achieved by further surface modifications on these nanocarbons. PMID:25897818

  15. Investigation of Titan's surface and atmosphere photometry using the VIMS instrument onboard Cassini

    NASA Astrophysics Data System (ADS)

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

    2015-10-01

    After 110 targeted flybys of Titan in a decade, the Cassini Visual and Infrared Mapping Spectrometer (VIMS) instrument acquired more than 34,000 hyperspectral cubes pointing at the surface of Titan on the dayside. Due to the strong influence of the absorbing and scattering atmosphere and of the heterogeneous viewing geometry of the flybys, retrieving Titan's surface and atmosphere normal albedo values extracted from the VIMS data remains challenging. In the present work, we aim to determine appropriate photometric functions to describe the light scattering in Titan's atmosphere,which could be used as a basis for empirical corrections or Radiative Transfer (RT) calculations to retrieve normal albedo values for the surface and the atmosphere.

  16. Cassini VIMS-V observations of a giant dynamical structure in the Saturn's northern hemisphere

    NASA Astrophysics Data System (ADS)

    Moriconi, M. L.; D'Aversa, E.; Adriani, A.; Filacchione, G.

    2012-12-01

    Vortices have been observed on Saturn since the years of the Voyager's missions. Successively high resolution Cassini's images, provided by the Imaging Science Subsystem (ISS) cameras, permitted longer periods of observation of the Saturn's dynamical structures, included a long-lived cyclone in the southern hemisphere (del Ro-Gaztelurrutia et al., 2010). The Visual and Infrared Mapping Spectrometer (VIMS) onboard Cassini spacecraft on January 4th 2012 has observed an oval structure, about 8000 km in diameter size and 0.87 eccentricity in the Saturn's north hemisphere. The vortex is centered at an average planetocentric latitude of 37.5 North, inside the storm system detected at the end of 2010 (Fletcher et al, 2011). To find the first occurrence of this vortex we started the examination of the VIMS and ISS databases from the 2010 fall until the end of January 2012. We searched also in the archive of ISS narrow angle (NAC) and wide angle (WAC) cameras, publicly available from the NASA Planetary Data System (PDS) Imaging Node, for those images both in concomitance and time shifted with respect to the VIMS ones. We adopted the same identification criterion used by del Ro-Gaztelurrutia et al. (2010), by searching for an oval of analogous dimension in the same zonal region. ISS data helped us in checking the existence of the oval in time periods not covered by VIMS data and in resolving oval's details that we cannot appreciate in the VIMS spectral frames, less spatially resolved than the cameras' corresponding filters. This vortex has been observed at different distances and viewing geometries at least 6 and 5 times by VIMS and ISS, respectively, in the examined time period. We estimate that the first vortex's detection occurred in the first half of January 2011 (ISS) while the last one in January 2012 (VIMS). In this study we aim to determine the oval identity in a univocal way, on the basis of its position and size, in order to monitor both the structure living cycle and its evolution. We describe the position and size of the vortex for each image with the greatest detail by means of different processing and mapping techniques. Our results show that there were some zonal drift and size and shape evolution in the time period of our survey. In a second abstract (Oliva et al., 2012) the results of this study, finalized to check the altitude variation and the optical depth of the cloud at the top of the dynamical structure, are reported. Reference Fletcher et al., Thermal Structure and Dynamics of Saturn's Northern Springtime Disturbance, Science, 332, 6036, 1413-1417, 2011. Oliva F., A. Adriani, M.L. Moriconi. Cloud-Top evaluation of a Saturn's giant vortex by Cassini-VIMS-V observations. Submitted as poster to this meeting, 2012. T. del Ro-Gaztelurrutia, J. Legarreta, R. Hueso, S. Prez-Hoyos, A. Snchez-Lavega. A long-lived cyclone in Saturn's atmosphere: Observations and models. Icarus, 209, 665-681, 2010.

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

    SciTech Connect

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

    2014-10-20

    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 Hα 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.

  18. 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 Hα 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.

  19. 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.

  20. Pharmacokinetic-pharmacodynamic modelling of meropenem against VIM-producing Klebsiella pneumoniae isolates: clinical implications.

    PubMed

    Tsala, Marilena; Vourli, Sophia; Kotsakis, Stathis; Daikos, George L; Tzouvelekis, Leonidas; Zerva, Loukia; Miriagou, Vivi; Meletiadis, Joseph

    2016-03-01

    VIM-producing Klebsiella pneumoniae isolates are usually associated with high MICs to carbapenems. Preclinical studies investigating the pharmacokinetic-pharmacodynamic (PK-PD) characteristics of carbapenems against these isolates are lacking. The in vitro antibacterial activity of meropenem against one WT and three VIM-producing K. pneumoniae clinical isolates (median MICs 0.031, 8, 16 and 128?mg l-?1) was studied in a dialysis-diffusion PK-PD model and verified in a thigh infection neutropenic animal model by testing selected strains and exposures. The in vitro PK-PD target associated with bactericidal activity was estimated and the target attainment for different dosing regimens was calculated with Monte Carlo analysis. The in vitro model was correlated with the in vivo data, with log10CFU/ml reduction of VIM-producing (MIC 16?mg l-?1) and >2 for the WT (MIC 0.031?mg l-?1) isolates, with %f?T >MIC 25 and 100?%, respectively. The in vitro bactericidal activity for all isolates was associated with 40?% f?T>MIC and attained in >90?% of cases with the standard 1?g q8 0.5?h infusion dosing regimen only for isolates with MICs up to 1?mg l-?1. For isolates with MICs of 2-8?mg l-?1, prolonged infusion regimens (4?h infusion q8 or 2?h infusion q4) of standard (1?g) and higher (2?g) doses or continuous infusion regimens (3-6?g) are required. For isolates with a MIC of 16?mg l-?1 the unconventional dosing regimen of 2?g as 2?h infusion q4 or 12?g continuous infusion will be required. Prolonged and continuous infusion regimens of meropenem may increase efficacy against VIM-producing K. pneumoniae isolates. PMID:26697851

  1. The roles of RgpB and Kgp in late onset gingipain activity in the vimA-defective mutant of Porphyromonas gingivalis W83.

    PubMed

    Dou, Y; Robles, A; Roy, F; Aruni, A W; Sandberg, L; Nothnagel, E; Fletcher, H M

    2015-10-01

    Previous studies have shown that VimA, an acetyltransferase, can modulate gingipain biogenesis in Porphyromonas gingivalis. Inactivation of the vimA gene resulted in isogenic mutants that showed a late onset of gingipain activity that only occurred during the stationary growth phase. To further elucidate the role and contribution of the gingipains in this VimA-dependent process, isogenic mutants defective in the gingipain genes in the vimA-deficient genetic background were evaluated. In contrast with the wild-type strain, RgpB and Kgp gingipain activities were absent in exponential phase in the ?rgpA::tetQ-vimA::ermF mutant. However, these activities increased to 31 and 53%, respectively, of that of the wild-type during stationary phase. In the ?rgpA::cat-?kgp::tetQ-vimA::ermF mutant, the RgpB protein was observed in the extracellular fraction but no activity was present even at the stationary growth phase. There was no gingipain activity observed in the ?rgpB::cat-?kgp::tetQ-vimA::ermF mutant whereas Kgp activity in ?rgpA::cat-?rgpB::tetQ-vimA::ermF mutant was 24% of the wild-type at late stationary phase. In contrast to RgpA, the glycosylation profile of the RgpB catalytic domain from both W83 and P. gingivalis FLL92 (vimA::ermF) showed similarity. Taken together, the results suggest multiple gingipain activation pathways in P. gingivalis. Whereas the maturation pathways for RgpA and RgpB are different, the late-onset gingipain activity in the vimA-defective mutant was due to activation/maturation of RgpB and Kgp. Moreover, unlike RgpA, which is VimA-dependent, the maturation/activation pathways for RgpB and Kgp are interdependent in the absence VimA. PMID:25858089

  2. The southern polar cloud on Titan as viewed by VIMS-V

    NASA Astrophysics Data System (ADS)

    D'Aversa, E.; Cottini, V.; Cerroni, P.; Bellucci, G.; Filacchione, G.

    2014-04-01

    During 2012 a new long-lived cloud appeared very close to the southern pole of Titan. Several Cassini observations were planned to its study and several instruments are still acquiring data on it. The emergence of this cloud, together with the vanishing of the northern pole's cloud system after 2008, could be one of the most direct evidence of seasonal changes in the titanian meteorology. We report about an ongoing data analysis of the Visible channel of the Cassini-VIMS spectrometer. We used data from the VIMS-V spectrometer to characterize the location, shape, spectral reflectance, and time-evolution of this rare atmospheric feature. Contributions and crosschecks from other instrumental datasets (ISS,CIRS, VIMS-IR) could greatly improve the constraints on the cloud macro- and micro-physical properties of this cloud and locate it in the context of the Titan's polar dynamics. Results will be valuable to better understand the seasonal changes of titanian atmosphere, significant topic in atmospheric science and comparative planetology.

  3. A probabilistic functional atlas of the VIM nucleus constructed from pre-, intra- and postoperative electrophysiological and neuroimaging data acquired during the surgical treatment of Parkinson's disease patients.

    PubMed

    Nowinski, Wieslaw L; Belov, Dmitry; Thirunavuukarasuu, A; Benabid, Alim Louis

    2005-01-01

    We have previously introduced a concept of a probabilistic functional atlas (PFA) to overcome limitations of the current electronic stereotactic brain atlases: anatomical nature, spatial sparseness, inconsistency and lack of population information. The PFA for the STN has already been developed. This work addresses construction of the PFA for the ventrointermediate nucleus (PFA-VIM). The PFA-VIM is constructed from pre-, intra- and postoperative electrophysiological and neuroimaging data acquired during the surgical treatment of Parkinson's disease patients. The data contain the positions of the chronically implanted electrodes and their best contacts. For each patient, the intercommissural distance, height of the thalamus and width of the third ventricle were measured. An algorithm was developed to convert these data into the PFA-VIM, and to present them on axial, coronal and sagittal planes and in 3-D. The PFA-VIM gives a spatial distribution of the best contacts, and its probability is proportional to best contact concentration in a given location. The region with the highest probability corresponds to the best target. The PFA-VIM is calculated with 0.25-mm3 resolution from 107 best contacts in two situations: with and without lateral compensation against the width of the third ventricle. For the PFA-VIM compensated laterally, the anterior, lateral and dorsal coordinates of the mean value are (in mm) 6.24, 13.83, 1.68 for the left VIM and 6.54, -13.84, 2.10 for the right VIM. The coordinates of the mean value of the highest probability region along with the highest number of the best contacts (P) are: 6.25, 14.25, 1.75, P = 16, for the left VIM, and 6.0, -14.0, 1.00, P = 18, for the right VIM. The coordinate system origin is at the posterior commissure. For the PFA-VIM not compensated laterally, the coordinates of the mean value are 6.24, 13.99, 1.68 for the left VIM and 6.53, -14.13, 2.10 for the right VIM. The coordinates of the mean value of the highest probability region along with the highest number of the best contacts are 5.58, 13.67, 1.33, P = 14, for the left VIM, and 6.36, -14.03, 1.11, P = 17, for the right VIM. The PFA-VIM atlas overcomes several limitations of the current anatomical atlases and can improve targeting of thalamotomies and thalamic stimulations. It is dynamic and can easily be extended with new cases. PMID:16424683

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

    NASA Astrophysics Data System (ADS)

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

    2007-12-01

    We present new imagery and quantitative results for wind and cloud structures in the south polar region of Saturn, obtained by Cassini/VIMS. A hurricane-like vortex feature is well observed in images obtained on October 11, 2006 and May 11, 2007, with a deep "eye" of cloud-free skies extending about 1 bar deeper than the surrounding ring of clouds. Winds measured in both reflected sunlight and in thermal radiation show comparable speeds throughout the region, suggesting little vertical wind shear over the 0.5-3-bar altitude range. Discrete clouds at 88 degrees S. planetographic latitude observed near the 0.5-2-bar level whip around the pole at speeds approaching 200 m/s. At greater latitudes, near the "eye" of the system, winds are much slower: about 45 m/s at 89.5 degrees S. latitude. From 88 degrees to 76 degrees S. latitude, the zonal wind structure as a function of radius/latitude is close to that expected for flows which maintain constant angular momentum. The picture that emerges is that this system is a giant polar vortex, spanning more than 15,000 km in diameter and at least 40 km in depth. Two distinct types of reflective, discrete clouds are observed interspersed throughout the region: bright clouds at continuum wavelengths from 0.6 to 2.7 microns characterized in our preliminary modeling as having imaginary indices of refraction near 0.002 at 0.7 micron, and spectrally dark clouds with twice that value. This suggests that two types of discrete clouds, colored by two distinct chemical compositions, reside in the south polar region. This is perhaps indicative of upwellings of materials from two distinct altitude regions in the depths of the south pole.

  5. Saturn's icy satellites and rings investigated by Cassini-VIMS: III - Radial compositional variability

    NASA Astrophysics Data System (ADS)

    Filacchione, G.; Capaccioni, F.; Ciarniello, M.; Clark, R. N.; Cuzzi, J. N.; Nicholson, P. D.; Cruikshank, D. P.; Hedman, M. M.; Buratti, B. J.; Lunine, J. I.; Soderblom, L. A.; Tosi, F.; Cerroni, P.; Brown, R. H.; McCord, T. B.; Jaumann, R.; Stephan, K.; Baines, K. H.; Flamini, E.

    2012-08-01

    In the last few years Cassini-VIMS, the Visible and Infrared Mapping Spectrometer, returned to us a comprehensive view of the Saturn's icy satellites and rings. After having analyzed the satellites' spectral properties (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]. Icarus 186, 259-290, paper I) and their distribution across the satellites' hemispheres (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]. Icarus 206, 507-523, paper II), we proceed in this paper to investigate the radial variability of icy satellites (principal and minor) and main rings average spectral properties. This analysis is done by using 2264 disk-integrated observations of the satellites and a 12 700 pixels-wide rings radial mosaic acquired with a spatial resolution of about 125 km/pixel. Using different VIS and IR spectral indicators, e.g. spectral slopes and band depths, we perform a comparative analysis of these data aimed to measure the distribution of water ice and red contaminant materials across Saturn's system. The average surface regolith grain sizes are estimated with different indicators through comparison with laboratory and synthetic spectra. These measurements highlight very striking differences in the population here analyzed, which vary from the almost uncontaminated and water ice-rich surfaces of Enceladus and Calypso to the metal/organic-rich and red surfaces of Iapetus' leading hemisphere and Phoebe. Rings spectra appear more red than the icy satellites in the visible range but show more intense 1.5-2.0 ?m band depths. Although their orbits are close to the F-ring, Prometheus and Pandora are different in surface composition: Prometheus in fact appears very water ice-rich but at the same time very red at VIS wavelengths. These properties make it very similar to A-B ring particles while Pandora is bluer. Moving outwards, we see the effects of E ring particles, generated by Enceladus plumes, which contaminate satellites surfaces from Mimas out to Rhea. We found some differences between Tethys lagrangian moons, Calypso being much more water ice-rich and bluer than Telesto. Among outer satellites (Hyperion, Iapetus and Phoebe) we observe a linear trend in both water ice decrease and in reddening, Hyperion being the reddest object of the population. The correlations among spectral slopes, band depths, visual albedo and phase permit us to cluster the saturnian population in different spectral classes which are detected not only among the principal satellites and rings but among co-orbital minor moons as well. These bodies are effectively the "connection" elements, both in term of composition and evolution, between the principal satellites and main rings. Finally, we have applied Hapke's theory to retrieve the best spectral fits to Saturn's inner regular satellites (from Mimas to Dione) using the same methodology applied previously for Rhea data discussed in Ciarniello et al. (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]. Icarus 214, 541-555).

  6. Titan's surface properties: correlations among DISR, RADAR and VIMS

    NASA Astrophysics Data System (ADS)

    Soderblom, L.

    The vast fields of radar-dark longitudinal dunes in the equatorial region of Titan seen Cassini synthetic aperture radar images correlate with one of two dark surface units discriminated in dark in short-wavelength infrared spectral cubes. The "bluer" dark unit shows higher reflectance at 1.3m and lower at 2.0m relative to the neutral dark unit. Of these two, the neutral dark unit (correlated with the radar-dark dunes) shows least evidence of water ice. This suggests that the saltating grains of the dunes are dry, hydrocarbon or nitrile particles. The bright unit shows the least evidence of absorption due to water ice and is inferred to consist of bright, very fine tholin dust. The rate of deposition of bright aerosol "snow" is thought to be 1m/yr. Hence the surface would be coated (to optical instruments) in a few years unless cleansing processes are active. The dark dunes must be mobile on this very short timescale to prevent the accumulation of bright coatings. Likewise fluvial/pluvial processes every few years-to-decades must be cleaning the dark floors of the incised channels and dark scoured plains at the Huygens landing site both imaged by DISR. The spatial association between the bright and the blue dark units suggest minor differences in bright coatings and lack of dunes. In this model Xanadu is a large inactive region where eolian, fluvial, pluvial activity is currently at a low ebb.

  7. 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 Saturns 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.

  8. Infections with VIM-1 Metallo-β-Lactamase-Producing Enterobacter cloacae and Their Correlation with Clinical Outcome▿

    PubMed Central

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

    2009-01-01

    The aim of this study was to ascertain the incidence and clinical significance of metallo-β-lactamases among Enterobacter strains isolated from patients with nosocomial infections. We prospectively collected data on patients with Enterobacter infection during a 13-month period. All of the strains were investigated for antibiotic susceptibility, the presence and expression of metallo-β-lactamases, and clonality. Of 29 infections (11 involving the urinary tract, 7 pneumonias, 3 skin/soft tissue infections, 3 intra-abdominal infections, 3 bacteremias, and 2 other infections), 7 (24%) were caused by Enterobacter cloacae strains harboring a blaVIM-1 gene associated or not with a blaSHV12 gene. Infections caused by VIM-1-producing strains were more frequently associated with a recent prior hospitalization (P = 0.006), cirrhosis (P = 0.03), relapse of infection (P < 0.001), and more prolonged duration of antibiotic therapy (P = 0.01) than were other infections. All of the isolates were susceptible to imipenem and meropenem and had blaVIM-1 preceded by a weak P1 promoter and inactivated P2 promoters. Most VIM-1-producing Enterobacter isolates belonged to a main clone, but four different clones were found. Multiclonal VIM-1-producing E. cloacae infections are difficult to diagnose due to an apparent susceptibility to various beta-lactams, including carbapenems, and are associated with a high relapse rate and a more prolonged duration of antibiotic therapy. PMID:19741074

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

    PubMed

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

    2007-02-01

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

  10. Nosocomial dissemination of VIM-2-producing ST235 Pseudomonas aeruginosa in Lithuania.

    PubMed

    Mikucionyte, G; Zamorano, L; Vitkauskiene, A; López-Causapé, C; Juan, C; Mulet, X; Oliver, A

    2016-02-01

    Pseudomonas aeruginosa multidrug resistance, and particularly the production of carbapenemases linked to international high-risk clones, is of growing concern. While high levels of carbapenem resistance (>60 %) have been reported in Lithuania, so far, there is no information on the underlying mechanisms. Thus, the aim of this work was to determine the molecular epidemiology and prevalence of acquired carbapenemases among 73 carbapenem-resistant P. aeruginosa isolates recovered in a hospital from Kaunas, Lithuania in 2011-2012. The presence of acquired carbapenemases was evaluated through phenotypic (modified Hodge test, cloxacillin inhibition test, double-disc synergy test) and genetic methods [polymerase chain reaction (PCR) and sequencing]. Clonal relatedness was assessed by pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST). Acquired β-lactamases were detected in 19 (26 %) of the isolates, whereas resistance was exclusively chromosomal (OprD inactivation ± AmpC hyperproduction) in the remaining 54 (74 %) isolates. The acquired β-lactamases detected included 16 VIM-2, one PER-1 and two GES enzymes. PFGE revealed that 15 of the 16 VIM-2 isolates belonged to a single clone, identified as the international high-risk clone ST235 by MLST. bla VIM-2 was preceded by aacA7 in a class I integron, similar to epidemic ST235 isolates described in nearby countries. Additionally, sequencing of bla GES revealed the presence of the carbapenem-hydrolysing enzyme GES-5 in one of the isolates and a novel GES variant, designated GES-27, in the other. GES-27 differed from GES-5 by a single amino acid substitution, proline 167, that was replaced by glutamine. Increasing emergence and dissemination of concerning resistance mechanisms and international clones warrants global surveillance and control strategies. PMID:26638216

  11. Studying Titan's surface photometry in the 5 microns atmospheric window with the Cassini/VIMS instrument

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

    Due to the influence of methane gas and a thick aerosols haze in the atmosphere, Titan's surface is only visible in 7 spectral atmospheric windows centered at 0.93, 1.08, 1.27, 1.59, 2.01, 2.7-2.8 and 5 microns with the Cassini Visual and Infrared Mapping Spectrometer (VIMS). The 5 microns atmospheric window constitutes the only one being almost insensitive to the haze scattering and which presents only a reduced atmospheric absorption contribution to the signal recorded by the instrument. Despite these advantages leading to the almost direct view of the surface, the 5 microns window is also the noisiest spectral window of the entire VIMS spectrum (an effect highly dependent on the time exposure used for the observations), and it is not totally free from atmospheric contributions, enough to keep "artefacts" in mosaics of several thousands of cubes due to atmospheric and surface photometric effects amplified by the very heterogeneous viewing conditions between each Titan flyby. At first order, a lambertian surface photometry at 5 microns has been used as an initial parameter in order to estimate atmospheric opacity and surface photometry in all VIMS atmospheric windows and to determine the albedo of the surface, yet unknown, both using radiative transfer codes on single cubes or empirical techniques on global hyperspectral mosaics. Other studies suggested that Titan's surface photometry would not be uniquely lambertian but would also contain anisotropic lunar-like contributions. In the present work, we aim at constraining accurately the surface photometry of Titan and residual atmospheric absorption effects in this 5 microns window using a comprehensive study of relevant sites located at various latitudes. Those include bright and dark (dunes) terrains, 5-microns bright terrains (Hotei Regio and Tui Regio), the Huygens Landing Site and high latitudes polar lakes and seas. The VIMS 2004 to 2014 database, composed of more than 40,000 hyperspectral cubes acquired on Titan, has been decomposed into a MySQL relational database in order to perform the present study looking at both spatial and temporal (seasonal) aspects.

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

    NASA Astrophysics Data System (ADS)

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

    2012-09-01

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

  13. 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 Saturns 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.

  14. Method of Controlling Lasing Wavelength(s)

    NASA Technical Reports Server (NTRS)

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

    2000-01-01

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

  15. Infrequent Finding of Metallo-?-Lactamase VIM-2 in Carbapenem-Resistant Pseudomonas aeruginosa Strains from Croatia

    PubMed Central

    Bedenic, Branka; Colinon-Dupuich, Cline; Orhanovic, Stjepan; Bosnjak, Zrinka; Plecko, Vanda; Cournoyer, Benoit; Rossolini, Gian Maria

    2012-01-01

    One hundred sixty-nine nonreplicate imipenem-resistant Pseudomonas aeruginosa strains isolated in a large hospital on the coastal region of Croatia were studied. The most active antibiotics were colistin and amikacin. Most of the isolates were multiresistant. The most prevalent serotype was O12, followed by O11. Six strains carried the blaVIM-2 gene located in a novel class 1 integron composed in its variable part of the blaVIM-2-blaoxa-10-?qacF-aacA4 genes. Metallo-?-lactamase-producing strains belonged to sequence types ST235 and ST111. PMID:22371893

  16. Coproduction of KPC-18 and VIM-1 Carbapenemases by Enterobacter cloacae: Implications for Newer ?-Lactam-?-Lactamase Inhibitor Combinations.

    PubMed

    Thomson, Gina K; Snyder, James W; McElheny, Christi L; Thomson, Kenneth S; Doi, Yohei

    2016-03-01

    Enterobacter cloacae strain G6809 with reduced susceptibility to carbapenems was identified from a patient in a long-term acute care hospital in Kentucky. G6809 belonged to sequence type (ST) 88 and carried two carbapenemase genes, blaKPC-18 and blaVIM-1. Whole-genome sequencing localized blaKPC-18 to the chromosome and blaVIM-1 to a 58-kb plasmid. The strain was highly resistant to ceftazidime-avibactam. Insidious coproduction of metallo-?-lactamase with KPC-type carbapenemase has implications for the use of next-generation ?-lactam-?-lactamase inhibitor combinations. PMID:26719440

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

    NASA Astrophysics Data System (ADS)

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

    2013-10-01

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

  18. Cloud structure and composition of Jupiter's troposphere from 5- ? m Cassini VIMS spectroscopy

    NASA Astrophysics Data System (ADS)

    Giles, R. S.; Fletcher, L. N.; Irwin, P. G. J.

    2015-09-01

    Jupiter's tropospheric composition and cloud structure are studied using Cassini VIMS 4.5-5.1 ? m thermal emission spectra from the 2000-2001 flyby. We make use of both nadir and limb darkening observations on the planet's nightside, and compare these with dayside observations. Although there is significant spatial variability in the 5- ? m brightness temperatures, the shape of the spectra remain very similar across the planet, suggesting the presence of a spectrally-flat, spatially inhomogeneous cloud deck. We find that a simple cloud model consisting of a single, compact cloud is able to reproduce both nightside and dayside spectra, subject to the following constraints: (i) the cloud base is located at pressures of 1.2 bar or lower; (ii) the cloud particles are highly scattering; and (iii) the cloud is sufficiently spectrally flat. Using this cloud model, we search for global variability in the cloud opacity and the phosphine deep volume mixing ratio. We find that the vast majority of the 5- ? m inhomogeneity can be accounted for by variations in the thickness of the cloud decks, with huge differences between the cloudy zones and the relatively cloud-free belts. The relatively low spectral resolution of VIMS limits reliable retrievals of gaseous species, but some evidence is found for an enhancement in the abundance of phosphine at high latitudes.

  19. ISO terminological analysis of the VIM3 concepts 'quantity' and 'kind-of-quantity'

    NASA Astrophysics Data System (ADS)

    Dybkaer, Ren

    2010-06-01

    The recent third edition of the International Vocabulary of MetrologyBasic and General Concepts and Associated Terms (VIM3) (JCGM 200:2008 (Svres: BIPM); also ISO/IEC Guide 99:2007 3rd edn (Geneva: ISO)) has undergone important changes, not least by adhering to ISO International Standards on terminology work (ISO 704:2000 Terminology WorkPrinciples and Methods; ISO 1087-1:2000 Terminology WorkVocabularyPart 1: Theory and Application; ISO 10241:1992 International Terminology StandardsPreparation and Layout). A recent critique (Mari 2009 Metrologia 46 L11-L15)based on Object-Oriented Analysiscentres on the meaning and relation of the two first and fundamental concepts 'quantity'Single quotation marks ('...') or bold type indicate a concept when necessary, double quotation marks ("...") a term or quotation. and the new entry 'kind-of-quantity'. This makes it timely to analyse the two concepts, their relation and their respective role in forming the generic hierarchical concept system of VIM3 from 'property' to individual quantities. It is suggested that 'kind-of-quantity' acts as a division criterionSynonyms are "criterion of subdivision", "type of characteristic(s)", see the annexe..

  20. Dual Wavelength Lasers

    NASA Technical Reports Server (NTRS)

    Walsh, Brian M.

    2010-01-01

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

  1. Synthesis of Metallo-β-Lactamase VIM-2 Is Associated with a Fitness Reduction in Salmonella enterica Serovar Typhimurium

    PubMed Central

    Cordeiro, Nicolás F.; Chabalgoity, José A.; Yim, Lucía

    2014-01-01

    Antibiotic resistance, especially due to β-lactamases, has become one of the main obstacles in the correct treatment of Salmonella infections; furthermore, antibiotic resistance determines a gain of function that may encompass a biological cost, or fitness reduction, to the resistant bacteria. The aim of this work was to determine in vitro if the production of the class B β-lactamase VIM-2 determined a fitness cost for Salmonella enterica serovar Typhimurium. To that end the gene blaVIM-2 was cloned into the virulent strain S. Typhimurium SL1344, using both the tightly regulated pBAD22 vector and the natural plasmid pST12, for inducible and constitutive expression, respectively. Fitness studies were performed by means of motility, growth rate, invasiveness in epithelial cells, and plasmid stability. The expression of blaVIM-2 was accompanied by alterations in micro- and macroscopic morphology and reduced growth rate and motility, as well as diminished invasiveness in epithelial cells. These results suggest that VIM-2 production entails a substantial fitness cost for S. Typhimurium, which in turn may account for the extremely low number of reports of metallo-β-lactamase-producing Salmonella spp. PMID:25136026

  2. 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

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

    NASA Astrophysics Data System (ADS)

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

    2007-10-01

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

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

    NASA Astrophysics Data System (ADS)

    Rodriguez, S.; Le Moulic, 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.

  5. 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.

  6. Geology of the Selk crater region on Titan from Cassini VIMS observations

    USGS Publications Warehouse

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

    2010-01-01

    Observations of Titan obtained by the Cassini Visual and Infrared Mapping Spectrometer (VIMS) have revealed Selk crater, a geologically young, bright-rimmed, impact crater located ???800. km north-northwest of the Huygens landing site. The crater rim-crest diameter is ???90. km; its floor diameter is ???60. km. A central pit/peak, 20-30. km in diameter, is seen; the ratio of the size of this feature to the crater diameter is consistent with similarly sized craters on Ganymede and Callisto, all of which are dome craters. The VIMS data, unfortunately, are not of sufficient resolution to detect such a dome. The inner rim of Selk crater is fluted, probably by eolian erosion, while the outer flank and presumed ejecta blanket appear dissected by drainages (particularly to the east), likely the result of fluvial erosion. Terracing is observed on the northern and western walls of Selk crater within a 10-15. km wide terrace zone identified in VIMS data; the terrace zone is bright in SAR data, consistent with it being a rough surface. The terrace zone is slightly wider than those observed on Ganymede and Callisto and may reflect differences in thermal structure and/or composition of the lithosphere. The polygonal appearance of the crater likely results from two preexisting planes of weakness (oriented at azimuths of 21?? and 122?? east of north). A unit of generally bright terrain that exhibits similar infrared-color variation and contrast to Selk crater extends east-southeast from the crater several hundred kilometers. We informally refer to this terrain as the Selk "bench." Both Selk and the bench are surrounded by the infrared-dark Belet dune field. Hypotheses for the genesis of the optically bright terrain of the bench include: wind shadowing in the lee of Selk crater preventing the encroachment of dunes, impact-induced cryovolcanism, flow of a fluidized-ejecta blanket (similar to the bright crater outflows observed on Venus), and erosion of a streamlined upland formed in the lee of Selk crater by fluid flow. Vestigial circular outlines in this feature just east of Selk's ejecta blanket suggest that this might be a remnant of an ancient, cratered crust. Evidently the southern margin of the feature has sufficient relief to prevent the encroachment of dunes from the Belet dune field. We conclude that this feature either represents a relatively high-viscosity, fluidized-ejecta flow (a class intermediate to ejecta blankets and long venusian-style ejecta flows) or a streamlined upland remnant that formed downstream from the crater by erosive fluid flow from the west-northwest. ?? 2010 Elsevier Inc.

  7. Cassini/VIMS Observes Rough Surfaces on Titan's Punga Mare in Specular Reflection

    NASA Astrophysics Data System (ADS)

    Barnes, Jason W.; Sotin, Christophe; Soderblom, Jason M.; Brown, Robert H.; Hayes, Alexander G.; Donelan, Mark; Rodriguez, Sebastien; Le Mouelic, Stephane; Baines, Kevin H.; McCord, Thomas B.

    2014-08-01

    Cassini/VIMS high-phase specular observations of Titan's north pole during the T85 flyby show evidence for isolated patches of rough liquid surface within the boundaries of the sea Punga Mare. The roughness shows typical slopes of 61. These rough areas could be either wet mudflats or a wavy sea. Because of their large areal extent, patchy geographic distribution, and uniform appearance at low phase, we prefer a waves interpretation. Applying theoretical wave calculations based on Titan conditions our slope determination allows us to infer winds of 0.760.09 m/s and significant wave heights of 2+2-1 cm at the time and locations of the observation. If correct, these would represent the first waves seen on Titan's seas, and also the first extraterrestrial sea-surface waves in general.

  8. Simultaneous mapping of Titan's surface albedo and aerosol opacity from Cassini/VIMS massive inversion

    NASA Astrophysics Data System (ADS)

    Maltagliati, L.; Rodriguez, S.; Sotin, C.; Cornet, T.; Rannou, P.; Le Mouelic, S.; Solomonidou, A.; Coustenis, A.; Brown, R.

    2015-10-01

    Titan still lacks information on the cartography of its surface albedo, due to the complications linked to the treatment of the atmospheric contributions on surface observations. We present in this paper the results of our massive inversion method that we developed to treat Cassini/VIMS h yperspectral data of Titan. Our minimization procedure is based on look-up tables (LUTs) we create from a state-of-the-art radiative transfer (RT) model[1]. This allows us to decrease the computational time by a factor of several thousands with respect to the standard radiative transfer applications. We will present the improvements on the RT modeling thanks to the acquisition of new information on Titan's aerosol properties and our results for the simultaneous mapping of Titan's surface albedo and aerosol abundance in some regions of interest.

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

    USGS Publications Warehouse

    Rodriguez, S.; Le Mouélic, Stéphane; 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.

  10. Multi-wavelength Observations of the Spatio-temporal Evolution of Solar Flares with AIA/SDO. II. Hydrodynamic Scaling Laws and Thermal Energies

    NASA Astrophysics Data System (ADS)

    Aschwanden, Markus J.; Shimizu, Toshifumi

    2013-10-01

    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 differential emission measure analysis to determine the flare peak emission measure EM p , peak temperature Tp , electron density np , 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, Tp = 5.0-17.8 MK, np = 4 109-9 1011 cm-3, and thermal energies of E th = 1.6 1028-1.1 1032 erg. We find that these parameters obey the Rosner-Tucker-Vaiana (RTV) scaling law T_p^2 \\propto n_p L and HvpropT 7/2 L -2 during the peak time tp of the flare density np , 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)vpropH -1.8, which is consistent with the magnetic flux distribution N(?)vprop?-1.85 observed by Parnell et al. and the heating flux scaling law FH vpropHLvpropB/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.

  11. 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.; Shimizu, Toshifumi E-mail: shimizu.toshifumi@isas.jaxa.jp

    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(Φ)∝Φ{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.

  12. Cassini/VIMS hyperspectral observations of the HUYGENS landing site on Titan

    USGS Publications Warehouse

    Rodriguez, S.; Le, Mouelic S.; Sotin, C.; Clenet, H.; Clark, R.N.; Buratti, B.; Brown, R.H.; McCord, T.B.; Nicholson, P.D.; Baines, K.H.

    2006-01-01

    Titan is one of the primary scientific objectives of the NASA-ESA-ASI Cassini-Huygens mission. Scattering by haze particles in Titan's atmosphere and numerous methane absorptions dramatically veil Titan's surface in the visible range, though it can be studied more easily in some narrow infrared windows. The Visual and Infrared Mapping Spectrometer (VIMS) instrument onboard the Cassini spacecraft successfully imaged its surface in the atmospheric windows, taking hyperspectral images in the range 0.4-5.2 ??m. On 26 October (TA flyby) and 13 December 2004 (TB flyby), the Cassini-Huygens mission flew over Titan at an altitude lower than 1200 km at closest approach. We report here on the analysis of VIMS images of the Huygens landing site acquired at TA and TB, with a spatial resolution ranging from 16 to14.4 km/pixel. The pure atmospheric backscattering component is corrected by using both an empirical method and a first-order theoretical model. Both approaches provide consistent results. After the removal of scattering, ratio images reveal subtle surface heterogeneities. A particularly contrasted structure appears in ratio images involving the 1.59 and 2.03 ??m images north of the Huygens landing site. Although pure water ice cannot be the only component exposed at Titan's surface, this area is consistent with a local enrichment in exposed water ice and seems to be consistent with DISR/Huygens images and spectra interpretations. The images show also a morphological structure that can be interpreted as a 150 km diameter impact crater with a central peak. ?? 2006 Elsevier Ltd. All rights reserved.

  13. Full-disk observations of the Saturn's icy moons by Cassini/VIMS

    NASA Astrophysics Data System (ADS)

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

    2005-08-01

    The Visual and Infrared Mapping Spectrometer (VIMS) collected a large amount of hyperspectral data on the icy satellites in the period June 2004 - April 2005. This study is devoted to the comparative analysis of the full-disk spectral properties of nine saturnian satellites (Dione, Enceladus, Epimetheus, Hyperion, Iapetus, Mimas, Phoebe, Rhea and Tethys) The observations were characterized by large variations in the observing conditions (distances, illumination phase angles, leading-trailing side percentages), increasing the statistical significance of this analysis. In the VIMS-V spectral range (350-1050 nm) the icy satellites spectra are almost featureless, nonetheless they can be grouped on the basis of their spectral slopes (from the bluish Enceladus and Phoebe to the redder Iapetus, Hyperion and Epimetheus). In the 1000-1300 nm range, three different behaviors can be defined: the first includes satellites with blue slopes (Enceladus, Mimas, Rhea and Tethys) while the second includes satellites with red slopes (Iapetus, Hyperion and Phoebe). 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 ice bands (for all satellites), although the Iapetus dark terrains show mostly a deep 3000 nm band and the 1520 and 2020 nm bands are very faint. In this spectral range, the Iapetus spectrum is characterized by a fast red slope. The CO2 band at 4260 nm and the Fresnel ice peak around 3100 nm are evident only on Hyperion, Phoebe and Iapetus. The observations were performed with phase angles ranging from 12 degrees to 140 degrees. We shall report on the results of the study on the spectral dependence of the satellites' phase curves. This work is supported by an ASI contract.

  14. Spectroscopy, morphometry, and photoclinometry of Titan's dunefields from Cassini/VIMS

    USGS Publications Warehouse

    Barnes, J.W.; Brown, R.H.; Soderblom, L.; Sotin, C.; Le, Mouelic S.; Rodriguez, S.; Jaumann, R.; Beyer, R.A.; Buratti, B.J.; Pitman, K.; Baines, K.H.; Clark, R.; Nicholson, P.

    2008-01-01

    Fine-resolution (500 m/pixel) Cassini Visual and Infrared Mapping Spectrometer (VIMS) T20 observations of Titan resolve that moon's sand dunes. The spectral variability in some dune regions shows that there are sand-free interdune areas, wherein VIMS spectra reveal the exposed dune substrate. The interdunes from T20 are, variously, materials that correspond to the equatorial bright, 5-??m-bright, and dark blue spectral units. Our observations show that an enigmatic "dark red" spectral unit seen in T5 in fact represents a macroscopic mixture with 5-??m-bright material and dunes as its spectral endmembers. Looking more broadly, similar mixtures of varying amounts of dune and interdune units of varying composition can explain the spectral and albedo variability within the dark brown dune global spectral unit that is associated with dunes. The presence of interdunes indicates that Titan's dunefields are both mature and recently active. The spectrum of the dune endmember reveals the sand to be composed of less water ice than the rest of Titan; various organics are consistent with the dunes' measured reflectivity. We measure a mean dune spacing of 2.1 km, and find that the dunes are oriented on the average in an east-west direction, but angling up to 10?? from parallel to the equator in specific cases. Where no interdunes are present, we determine the height of one set of dunes photoclinometrically to be between 30 and 70 m. These results pave the way for future exploration and interpretation of Titan's sand dunes. ?? 2007 Elsevier Inc. All rights reserved.

  15. First report of VIM-2 metallo-β-lactamases producing Pseudomonas aeruginosa isolates in Morocco.

    PubMed

    Maroui, Itto; Barguigua, Abouddihaj; Aboulkacem, Asmae; Ouarrak, Khadija; Sbiti, Mohammed; Louzi, Housssain; Timinouni, Mohammed; Belhaj, Abdelhaq

    2016-03-01

    The emergence and the rapid spread of Pseudomonas aeruginosa carrying carbapenemases represent a serious threat to public health due to their delicate therapy. This work was performed to establish the resistance profile and to detect carbapenemases producing in 123 P. aeruginosa isolates. Among these 55 are environmental isolates and 68 are from the two major hospitals of Meknes-Tafilalet region in Morocco. All strains were tested against 14 antipseudomonal drugs by disc diffusion method. On carbapenem resistant strains minimum inhibitory concentrations of imipenem were determined by the E-test method. The modified Hodge test and EDTA tests were used for the detection of carbapenemases and metallo-β-lactamases (MBLs), respectively. PCR and DNA sequencing were conducted to detect carbapenemase-encoding genes and the enzyme types. 12% of isolates was susceptible to all antibiotics tested and Carbapenem resistance was observed in 33 P. aeruginosa isolates, 33.3% of them were multi-drug resistant. Among carbapenem resistant strains only two (6.1%) were positive for carbapenemases and also for MBLs. In addition to their resistance to almost all β-lactams tested, the MBLs producing strains were resistant to aminoglycosides. Molecular biology techniques confirmed the phenotypic results obtained for the two strains carbapenemase producers and demonstrated that each one of them carried blaVIM-2. The present study reports the first isolation of blaVIM genes in clinical isolates of P. aeruginosa in Morocco. Such isolates represent a serious emerging threat requiring strict hygiene measures to better control their spread. PMID:26711231

  16. Dispersal of carbapenemase blaVIM-1 gene associated with different Tn402 variants, mercury transposons, and conjugative plasmids in Enterobacteriaceae and Pseudomonas aeruginosa.

    PubMed

    Tato, Marta; Coque, Teresa M; Baquero, Fernando; Cantón, Rafael

    2010-01-01

    The emergence of bla(VIM-1) within four different genetic platforms from distinct Enterobacteriaceae and Pseudomonas aeruginosa isolates in an area with a low prevalence of metallo-beta-lactamase producers is reported. Forty-three VIM-1-producing isolates (including 19 Enterobacter cloacae, 2 Escherichia coli, and 2 P. aeruginosa isolates, 18 Klebsiella pneumoniae isolate, and 2 Klebsiella oxytoca isolate) recovered from 2005 to 2007 and corresponding to 15 pulsed-field gel electrophoresis types were studied. The Enterobacteriaceae isolates corresponded to a hospital outbreak, and the P. aeruginosa isolates were sporadically recovered. The genetic context of the integrons carrying bla(VIM-1) (arbitrarily designated types A, B, C, and D) was characterized by PCR mapping based on known Tn402 and mercury transposons and further sequencing. Among Enterobacteriaceae isolates, bla(VIM-1) was part of integrons located either in an In2-Tn402 element linked to Tn21 (type A; In110-bla(VIM-1)-aacA4-aadA1) or in a Tn402 transposon lacking the whole tni module [type B; In113-bla(VIM-1)-aacA4-dhfrII (also called dfrB1)-aadA1-catB2] and the transposon was associated with an IncHI2 or IncI1 plasmid, respectively. Among P. aeruginosa isolates, bla(VIM-1) was part of a new gene cassette array located in a defective Tn402 transposon carrying either tniBDelta3 and tniA (type C; bla(VIM-1)-aadA1) or tniC and DeltatniQ (type D; bla(VIM-1)-aadB), and both Tn402 variants were associated with conjugative plasmids of 30 kb. The dissemination of bla(VIM-1) was associated with different genetic structures and bacterial hosts, depicting a complex emergence and evolutionary network scenario in our facility, Ramón y Cajal University Hospital, Madrid, Spain. Knowledge of the complex epidemiology of bla(VIM-1) is necessary to control this emerging threat. PMID:19901094

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

    PubMed Central

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

    2010-01-01

    Metallo-ß-lactamases (MBL) are an emerging cause of bacterial resistance to antibiotic treatment. The VIM-2 ß-lactamase is the most commonly encountered MBL in clinical isolates worldwide. Described here are potent and selective small molecule inhibitors of VIM-2 containing the arylsulfonyl-NH-1,2,3-triazole chemotype that potentiate the efficacy of the ß-lactam, imipenem, in E. coli. PMID:20625539

  18. Wavelength independent interferometer

    NASA Technical Reports Server (NTRS)

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

    1991-01-01

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

  19. 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.

  20. Structural diversity of the 3-micron absorption band in Enceladus’ plume from Cassini VIMS: Insights into subsurface environmental conditions

    NASA Astrophysics Data System (ADS)

    Dhingra, Deepak; Hedman, Matthew M.; Clark, Roger N.

    2015-11-01

    Water ice particles in Enceladus’ plume display their diagnostic 3-micron absorption band in Cassini VIMS data. These near infrared measurements of the plume also exhibit noticeable variations in the character of this band. Mie theory calculations reveal that the shape and location of the 3-micron band are controlled by a number of environmental and structural parameters. Hence, this band provides important insights into the properties of the water ice grains and about the subsurface environmental conditions under which they formed. For example, the position of the 3-micron absorption band minimum can be used to distinguish between crystalline and amorphous forms of water ice and to constrain the formation temperature of the ice grains. VIMS data indicates that the water ice grains in the plume are dominantly crystalline which could indicate formation temperatures above 113 K [e.g. 1, 2]. However, there are slight (but observable) variations in the band minimum position and band shape that may hint at the possibility of varying abundance of amorphous ice particles within the plume. The modeling results further indicate that there are systematic shifts in band minimum position with temperature for any given form of ice but the crystalline and amorphous forms of water ice are still distinguishable at VIMS spectral resolution. Analysis of the eruptions from individual source fissures (tiger stripes) using selected VIMS observations reveal differences in the 3-micron band shape that may reflect differences in the size distributions of the water ice particles along individual fissures. Mie theory models suggest that big ice particles (>3 micron) may be an important component of the plume.[1] Kouchi, A., T. Yamamoto, T. Kozasa, T. Kuroda, and J. M. Greenberg (1994) A&A, 290, 1009-1018 [2] Mastrapa, R. M. E., W. M. Grundy, and M. S. Gudipati (2013) in M. S. Gudipati and J. Castillo-Rogez (Eds.), The Science of Solar System Ices, pp. 371.

  1. 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 NASAs Outer Planets Research program (NNX12AM76G; PI Pitman), Planetary Astronomy program (NNX09AD06G; PI Verbiscer), and NASAs Advanced Supercomputing Division. Calibrated Cassini VIMS data cubes appear courtesy of B. J. Buratti and the Cassini VIMS team.

  2. The PdBI arcsecond whirlpool survey (PAWS). I. A cloud-scale/multi-wavelength view of the interstellar medium in a grand-design spiral galaxy

    SciTech Connect

    Schinnerer, Eva; Meidt, Sharon E.; Hughes, Annie; Colombo, Dario; Pety, Jrme; Schuster, Karl F.; Dumas, Galle; Garca-Burillo, Santiago; Dobbs, Clare L.; Leroy, Adam K.; Kramer, Carsten; Thompson, Todd A.; Regan, Michael W.

    2013-12-10

    The Plateau de Bure Interferometer Arcsecond Whirlpool Survey has mapped the molecular gas in the central ?9 kpc of M51 in its {sup 12}CO(1-0) line emission at a cloud-scale resolution of ?40 pc using both IRAM telescopes. We utilize this data set to quantitatively characterize the relation of molecular gas (or CO emission) to other tracers of the interstellar medium, star formation, and stellar populations of varying ages. Using two-dimensional maps, a polar cross-correlation technique and pixel-by-pixel diagrams, we find: (1) that (as expected) the distribution of the molecular gas can be linked to different components of the gravitational potential; (2) evidence for a physical link between CO line emission and radio continuum that seems not to be caused by massive stars, but rather depends on the gas density; (3) a close spatial relation between polycyclic aromatic hydrocarbon (PAH) and molecular gas emission, but no predictive power of PAH emission for the molecular gas mass; (4) that the I H color map is an excellent predictor of the distribution (and to a lesser degree, the brightness) of CO emission; and (5) that the impact of massive (UV-intense) young star-forming regions on the bulk of the molecular gas in central ?9 kpc cannot be significant due to a complex spatial relation between molecular gas and star-forming regions that ranges from cospatial to spatially offset to absent. The last point, in particular, highlights the importance of galactic environmentand thus the underlying gravitational potentialfor the distribution of molecular gas and star formation.

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

    NASA Astrophysics Data System (ADS)

    Rodriguez, S.; Le Moulic, 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.

    2011-11-01

    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 60N. 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 30S and 60S. 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.

  4. 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.

  5. Spectroscopic Identification of E-Ring Deposits on Enceladus Using Cassini-Vims Dat

    NASA Astrophysics Data System (ADS)

    Scipioni, F.; Schenk, P.; Tosi, F.

    2014-12-01

    Enceladus' surface is composed mostrly of pure water ice. The Cassini spacecraft has observed present-day geologic activity at the moon's South Polar region (the so-called "Tiger Stripes"). Plumes of micron-sized particles composed of water ice and other contaminants (CO2, NH3, CH4) erupting from this region are the major source of Saturn's E-ring. Some of this material, however, falls on Enceladus' surface to form deposits that extend to the north at ~220°E and ~40°E and whose highest concentration is at the south pole. The Cassini VIMS spectrometer acquires hyperspectral data in the 0.3-5.1 μm spectral range. We selected VIMS cubes of Enceladus in the IR range (0.8-5.1 μm), and minimized photometric effects due to different illumination conditions by normalizing all spectra at 2.23 μm. We aim to identify E-ring deposits across Enceladus' surface through the variation in band depth of the main water-ice spectral features located at 1.25, 1.5, and 2.0 μm. Since plumes deposits on the surface undergo darkening processes for less time than surrounding terrains, they appear brighter and so the water-ice absorption bands must be deeper. For all pixels in the selected cubes, we measured the band depths for the main water-ice absorptions and the height of the 3.6 μm reflection peak, whose value relates to grain size. To characterize the global variation of water-ice band depths across Enceladus, we divided the surface into a 1°x1° grid and then averaged the band depths and peak values inside each square cell. This approach clearly identifies plums deposits. As expected, the highest concentrations occur at Enceladus' south pole, where band depths values are the deepest across the entire moon's surface. Our results confirm that plume particles fall in north-oriented patterns at ~40°E and ~220°E, and disappear around ~0°E and ~180°E. In addition, we observed a possible non-plume related regional variation in all major water ice absorption bands on the leading side.

  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 Saturns poles, not seen since 2008. We present new imagery and investigate the effect of seasonal variability on Saturns 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 Saturns polar winds.

  7. Cassini VIMS Spectra of the Earth from Saturn Orbit: an Extrasolar Planet Analog

    NASA Astrophysics Data System (ADS)

    Clark, Roger Nelson; Hedman, Matthew M.; Brown, Robert H.; Filacchione, Gianrico; Nicholson, Philip D.; Barnes, Jason W.

    2015-11-01

    Cassini VIMS has obtained spectra of the Earth while in Saturn orbit making observations of the Saturn system when the sun was behind Saturn. The observations, made in September 15, 2006 and July 19, 2013 are visible-near-infrared spectra (0.35 - 5.1 microns) of the Earth obtained at the furthest distance from the sun to date. The Earth was sub-pixel, 0.0088 milliradian in 2013 and 0.0085 milliradian in 2006, and the signal-to-noise ratio is low. A VIMS pixel IFOV is 0.25 x 0.5milliradian. As such, these data are likely representative of the first spectra that might be obtained of extrasolar terrestrial-like planets. What information can be derived from such remote observations? The observation made in 2013 had a phase angle of 97 degrees with multipleimage cubes providing a higher S/N average. The 2006 observation was made at a phase angle of 33 degrees but is a single cube, 1 pixel. The 2006 observation has Africa dominant on the disk, while the 2013 observation is mostly ocean with part of South America in sunlight. The 2013 visible data show clear signatures of Rayleigh scattering but this blue coloring can be from both the atmosphere and/or ocean. The 2006 data show a flatter spectrum, a signature of land. Both observations include the Moon in the field of view. The 0.35-2.5 micron spectral range shows significant absorption due to H2O liquid + gas. The thermal signature is very strong with the highest S/N of the entire spectrum. The best fit preliminary temperatures are 280 K with a small 380 K component (from the Moon), putting at least some of the planet in the goldilocks zone. There is strong absorption by CO2 at 4.25 microns in both 2013 and 2006 data. There is possible detection of chlorophyll and oxygen emission but higher S/N would be required for a positive detection. The spectral profile of the thermal emission could be used to constrain the diameter of the planet. If such spectra were obtained of an extrasolar planet, we could conclude that the planet had large regions of liquid water and exposed land at temperatures excellent for life in a habitable zone. If the chlorophyll signature could be confirmed, it would be a positive identification of life from a remote distance

  8. Short wavelength FELS

    SciTech Connect

    Sheffield, R.L.

    1991-01-01

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

  9. 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

  10. Millimeter wavelength propagation studies

    NASA Technical Reports Server (NTRS)

    Hodge, D. B.

    1974-01-01

    The investigations conducted for the Millimeter Wavelength Propagation Studies during the period December, 1966, to June 1974 are reported. These efforts included the preparation for the ATS-5 Millimeter Wavelength Propagation Experiment and the subsequent data acquisition and data analysis. The emphasis of the OSU participation in this experiment was placed on the determination of reliability improvement resulting from the use of space diversity on a millimeter wavelength earth-space communication link. Related measurements included the determination of the correlation between radiometric temperature and attenuation along the earth-space propagation path. Along with this experimental effort a theoretical model was developed for the prediction of attenuation statistics on single and spatially separated earth space propagation paths. A High Resolution Radar/Radiometer System and Low Resolution Radar System were developed and implemented for the study of intense rain cells in preparation for the ATS-6 Millimeter Wavelength Propagation Experiment.

  11. Laser wavelength metrology with color sensor chips.

    PubMed

    Jones, Tyler B; Otterstrom, Nils; Jackson, Jarom; Archibald, James; Durfee, Dallin S

    2015-12-14

    We present a laser wavelength meter based on a commercial color sensor chip. The chip consists of an array of photodiodes with different absorptive color filters. By comparing the relative amplitudes of light on the photodiodes, the wavelength of light can be determined. In addition to absorption in the filters, etalon effects add additional spectral features which improve the precision of the device. Comparing the measurements from the device to a commercial wavelength meter and to an atomic reference, we found that the device has picometer-level precision and picometer-scale drift over a period longer than a month. PMID:26699036

  12. Investigations of Saturn’s Main Rings over Broad Range of Wavelengths

    NASA Astrophysics Data System (ADS)

    Spilker, Linda J.; Deau, Estelle; Morishima, Ryuji; Filacchione, Gianrico; Hedman, Matt; Nicholson, Phil; Colwell, Josh; Bradley, Todd; Showalter, Mark; Pilorz, Stu; Brooks, Shawn; Ciarniello, Mauro

    2015-11-01

    An abundance of information about the characteristics of Saturn’s ring particles and their regolith can be obtained by comparing the changes in their brightness, color and temperature with changing viewing geometry over a wide range of wavelengths from ultraviolet through the thermal infrared. Data from Cassini’s Composite Infrared Spectrometer (CIRS), Visual and Infrared Mapping Spectrometer (VIMS), Imaging Science Subsystem (ISS) and Ultraviolet Imaging Spectrograph (UVIS) are jointly studied using data from the lit and unlit main rings at multiple geometries and solar elevations over 11 years of the Cassini mission. Using multi-wavelength data sets allows us to test different thermal models by combining the effects of particle albedo, regolith grain size and surface roughness with thermal emissivity and inertia, particle spin rate and spin axis orientation.CIRS temperatures, ISS colors and UVIS brightness appear to vary noticeably with phase angle, but are not a strong function of spacecraft elevation angle. Color, temperature and brightness dependence on solar elevation angle are also observed. VIMS observations show that the infrared ice absorption band depths change with the solar phase angle, in particular between 0-20° and at high phase. This trend indicates that single scattering approximation is correct only at low phases (<20°) while at high phase multiple scattering must be taken into account.These results imply that the individual properties of the ring particles may play a larger role than the collective properties of the rings, in particular at visible wavelengths. The temperature and color variation with phase angle may be a result of scattering within the regolith, as well as scattering between individual particles or clumps in a many-particle-thick layer. Initial results from our joint studies will be presented.This research was carried out in part at the Jet Propulsion Laboratory, California Institute of Technology, under contract with NASA. Copyright 2015 California Institute of Technology. Government sponsorship is acknowledged.

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

    NASA Astrophysics Data System (ADS)

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

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

  14. Cassini VIMS observations of H3+ emission on the nightside of Jupiter

    NASA Astrophysics Data System (ADS)

    Stallard, Tom S.; Melin, Henrik; Miller, Steve; Badman, Sarah V.; Baines, Kevin H.; Brown, Robert H.; Blake, James S. D.; O'Donoghue, James; Johnson, Rosie E.; Bools, Bethany; Pilkington, Nathan M.; East, Oliver T. L.; Fletcher, Mark

    2015-08-01

    We present the first detailed analysis of H3+ nightside emission from Jupiter, using Visual and Infrared Mapping Spectrometer (VIMS) data from the Cassini flyby in 2000-2001, producing the first Jovian maps of nightside H3+ emission, temperature, and column density. Using these, we identify and characterize regions of H3+ nightside emission, compared against past observations of H3+ emission on the dayside. We focus our investigation on the region previously described as "mid-to-low latitude emission," the source for which has been controversial. We find that the brightest of this emission is generated at Jovigraphic latitudes similar to the most equatorward extent of the main auroral emission but concentrated at longitudes eastward of this emission. The emission is produced by enhanced H3+ density, with temperatures dropping away in this region. This emission has a loose association with the predicted location of diffuse aurora produced by pitch angle scattering in the north, but not in the south. This emission also lays in the path of subrotating winds flowing from the aurora, suggesting a transport origin. Some differences are seen between dayside and nightside subauroral emissions, with dayside emission extending more equatorward, perhaps caused by the lack of sunlight ionization on the nightside, and unmeasured changes in temperature. Ionospheric temperatures are hotter in the polar region (~1100-1500 K), dropping away toward the equator (as low as 750 K), broadly similar to values on the dayside, highlighting the dominance of auroral effects in the polar region. No equatorial emission is observed, suggesting that very little particle precipitation occurs away from the polar regions.

  15. 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.

  16. 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.

  17. 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.

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

    PubMed Central

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

    2015-01-01

    SUMMARY 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 up-regulated 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

  19. Titans mid-latitude surface regions with Cassini VIMS and RADAR

    NASA Astrophysics Data System (ADS)

    Solomonidou, Anezina; Lopes, Rosaly M. C.; Coustenis, Athena; Malaska, Michael; Rodriguez, Sebastien; Maltagliati, Luca; Drossart, Pierre; Janssen, Michael; Lawrence, Kenneth; Jaumann, Ralf; Sohl, Frank; Stephan, Katrin; Brown, Robert H.; Bratsolis, Emmanuel; Matsoukas, Christos

    2015-11-01

    The Cassini-Huygens mission instruments have revealed Titan to have a complex and dynamic atmosphere and surface. Data from the remote sensing instruments have shown the presence of diverse surface terrains in terms of morphology and composition, suggesting both exogenic and endogenic processes [1]. We define both the surface and atmospheric contributions in the VIMS spectro-imaging data by use of a radiative transfer code in the near-IR range [2]. To complement this dataset, the Cassini RADAR instrument provides additional information on the surface morphology, from which valuable geological interpretations can be obtained [3]. We examine the origin of key Titan terrains, covering the mid-latitude zones extending from 50N to 50S. The different geological terrains we investigate include: mountains, plains, labyrinths, craters, dune fields, and possible cryovolcanic and/or evaporite features. We have found that the labyrinth terrains and the undifferentiated plains seem to consist of a very similar if not the same material, while the different types of plains show compositional variations [3]. The processes most likely linked to their formation are aeolian, fluvial, sedimentary, lacustrine, in addition to the deposition of atmospheric products though the process of photolysis and sedimentation of organics. We show that temporal variations of surface albedo exist for two of the candidate cryovolcanic regions. The surface albedo variations together with the presence of volcanic-like morphological features suggest that the active regions are possibly related to the deep interior, possibly via cryovolcanism processes (with important implications for the satellites astrobiological potential) as also indicated by new interior structure models of Titan and corresponding calculations of the spatial pattern of maximum tidal stresses [4]. However, an explanation attributed to exogenic processes is also possible [5]. We will report on results from our most recent research on the surface properties of Titan.[1] Solomonidou et al. Icarus, accepted. [2] Solomonidou et al. JGR 119, 1729-1747, 2014. [3] Lopes et al. Icarus, in rev. [4] Sohl et al. JGR 119, 1013-1036, 2014. [5] Moore & Pappalardo, Icarus 212, 790-806, 2011.

  20. Cassini VIMS and RADAR investigation of Titan's equatorial regions: a case for changes in surface properties

    NASA Astrophysics Data System (ADS)

    Solomonidou, Anezina; Coustenis, Athena; Lopes, Rosaly M. C.; Rodriguez, Sebastien; Hirtzig, Mathieu; Malaska, Michael; Stephan, Katrin; Sotin, Christophe; Drossart, Pierre; Jaumann, Ralf; Bratsolis, Emmanuel; Le Moulic, Stephane; Brown, Robert H.

    2015-04-01

    The Cassini-Huygens instruments revealed that Titan, Saturn's largest moon, has - in many aspects - a complex, dynamic and Earth-like surface [1;2;3]. Understanding the distribution and interplay of geologic processes on Titan is important for constraining models of its interior, surface-atmosphere interactions, and climate evolution. Data from the remote sensing instruments have shown the presence of diverse terrains, suggesting exogenic and endogenic processes, whose composition remains largely unknown. Interpreting surface features further requires precise knowledge of the contribution by the dense intervening atmosphere, especially the troposphere, which can be recovered from near-IR data such as those collected by Cassini's Visual and Infrared Mapping Spectrometer (VIMS) collects in the so-called "methane windows". In order to simulate the atmospheric contribution and extract surface information, a statistical tool (PCA) and a radiative transfer code are applied on certain regions of interest (i.e. possibly geologically varying and suggested in some cases to be cryovolcanic and/or evaporitic in origin) [4;5;7]. We also analyze RADAR despeckled SAR images in terms of morphology [6]. For comparison, we also look at undifferentiated plains and dune fields regions that are not expected to change with time. We find that Tui Regio and Sotra Patera change with time becoming darker and brighter respectively in terms of surface albedo while the plains and the suggested evaporitic areas in the equatorial regions do not present any significant change [5]. The surface brightening of Sotra supports a possible internal rather than exogenic origin. The unchanged surface behavior of the plains supports a sedimentary origin rather than cryovolcanic. Preliminary results on the chemical composition of the changed regions with time are also presented. We therefore suggest that temporal variations of surface albedo (in chemical composition and/or morphology) exist for some areas on Titan, but that their origin may differ from one region to the other. Such a variety of geologic processes and their relationship to the methane cycle make Titan particularly significant in Solar System studies. References: [1] Lopes, R.M.C., et al.: JGR, 118, 416-435, 2013 [2] Solomonidou, A., et al.: PSS, 70, 77-104, 2013 [3] Moore, J.M., and Howard, A.D.: GRL, 37, L22205, 2010; [4] Solomonidou, A., et al.: JGR, 119, 1729-1747, 2014; [5] Solomonidou, A., et al.: Icarus, submitted, 2015; [6] Bratsolis, E., et al.: PSS, 61, 108-113, 2012; [7] Hirtzig, M., et al.: Icarus, 226, 470-486, 2013.

  1. 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.

  2. 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

  3. Astronomical Studies at Infrared Wavelengths

    NASA Technical Reports Server (NTRS)

    Rinehart, Stephen A.

    2009-01-01

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

  4. 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.

  5. 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.

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

    PubMed Central

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

    2011-01-01

    Rapid identification of metallo-β-lactamase-producing Gram-negative species is crucial for the timely implementation of infection control measures. We describe two pediatric cases in which colonization by VIM-1- and New Delhi metallo-beta-lactamase 1-producing Enterobacteriaceae was rapidly detected by phenotypic and genotypic methods. Phenotypic methods can be useful for routine detection of carbapenemase production. PMID:21653781

  7. Millimeter-wavelength observations of minor planets

    NASA Technical Reports Server (NTRS)

    Altenhoff, W. J.; Johnston, K. J.; Stumpff, P.; Webster, W. J.

    1994-01-01

    Bolometer observations at 250 GHz of fifteen minor planets have shown that the emissivity of these objects is close to unity. This results in an independent method to determine the absolute calibration scale of radio observations at mm wavelengths: Applying our results to Mars, the prime calibrator at this wavelength, gives a mean absolute disk temperature at mean solar distance of approximately 210 K. Further, the diameters of circularly symmetric asteroids can be determined or the surface area of asteroids can be estimated assuming some geometric constraints on their shape.

  8. 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).

  9. Scales

    SciTech Connect

    Murray Gibson

    2007-04-27

    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).

  10. The Opposition Surge of Icy Moons at 3.6 Microns: New Data from Cassini VIMS

    NASA Astrophysics Data System (ADS)

    Buratti, Bonnie J.; Dalba, P. A.; Clark, R. N.; Brown, R. H.; Mosher, J. A.; Baines, K. H.; Nicholson, P. D.

    2013-10-01

    The opposition surge is the huge increase in brightness that is exhibited by nearly every planetary surface as it becomes fully illuminated to an observer. The classic explanation of the surge is that mutual shadows cast by particles in the regolith rapidly disappear as the body approaches a solar phase angle of zero. Additional optical effects such as coherent backscatter or a sharply peaked particle phase function may add to the effect, particularly at solar phase angles less than one degree. The quantitative modeling of the surge yields important information about the compaction state of the surface and particle sizes, which in turn offers clues to the geophysical processes at work on the surface. The study of the opposition surge has centered mainly on visible radiation. Spacecraft observations offer a window into new wavelengths that enable greater understanding of the mechanisms of the surge as well as the physical nature of the surface itself. The Cassini Visual Infrared Mapping Spectrometer gathered measurements of the solar phase curves of the icy moons of Saturn - Mimas, Enceladus, Tethys, Dione, Rhea, and Iapetus - throughout the wavelength range of 0.35-5.1 microns and through a full excursion in solar phase angles. This entire spectral range is free of contamination by thermal emission. We find that the nature of the curve changes dramatically longward of the water-ice absorption band at three microns. We attribute this effect to the disappearance of multiple scattering at this wavelength, where the albedo of the moons is low. Without the confounding effect of multiply scattered photons, the compaction state of the surface can be directly measured at this wavelength. We find the derived porosities to be ~95%, similar to lightly packed terrestrial snow. An alternative explanation of the change may be the disappearance of small particles that cannot be detected at wavelengths a few times larger than their size. Funded by NASA

  11. 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.

  12. 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.

  13. Fragment-based discovery of inhibitor scaffolds targeting the metallo-β-lactamases NDM-1 and VIM-2.

    PubMed

    Christopeit, Tony; Leiros, Hanna-Kirsti S

    2016-04-15

    Metallo-β-lactamases (MBLs) render bacteria resistant to β-lactam antibiotics and are interesting drug targets to prevent the hydrolysis of β-lactam antibiotics. So far, there are no MBL inhibitors in clinical use and particularly the design of broad spectrum inhibitors targeting several MBLs has been difficult. In this study, we report four fragments inhibiting the clinically relevant New Delhi metallo-β-lactamase 1 (NDM-1) and Verona integron-encoded metallo-β-lactamase 2 (VIM-2). The fragments were identified from a library using an orthogonal screening strategy combining a surface plasmon resonance (SPR) based assay and an enzyme inhibition assay. The identified fragments showed dissociation constants (KD) ranging from 181 to 2100μM. The binding mode of the fragments was explored using QM-polarized ligand docking. All four fragments represent interesting scaffolds for the design of broad-spectrum MBL inhibitors. PMID:26976213

  14. Compositional Mapping of Saturn's Satellite Dione with Cassini VIMS and Implications for Dark Material in the Saturn System

    NASA Astrophysics Data System (ADS)

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

    2006-12-01

    The Cassini spacecraft has made multiple observations of Dione and other satellites in the Saturn system, including a fly-by of Dione on October 11, 2005, passing within 1059 km. The Visual and Infrared Mapping Spectrometer (VIMS) obtained 0.35-5.1 micron image cubes during the fly-by, and the data have been mosaicked for study. The data were searched for absorption features and their spatial locations mapped. Spectra of Dione are dominated by absorptions due to water ice, with weak features from a carbon dioxide absorption near 4.26 microns and from a non-ice component exhibiting a 2.42 micron absorption also seen in spectra of Phoebe (Clark et al, Nature, 2005), Iapetus, Hyperion, and the F-ring. A broad absorption extending from 0.5 to about 1.5 microns, similar to absorptions in ferrous iron (Fe2+) bearing minerals, shows prominently in Dione spectra. The Dione spectra have a strong UV absorption short of 0.5 microns. Some crater rims show one side dominated by dark material and the other side dominated by water ice. The distribution of these materials could be explained by implantation of dark material from the trailing side direction, or implantation of ice from the leading side of Dione's orbital direction. An alternative interpretation of the Fe2+ spectral structure could be sub-micron dark grains embedded in the ice that causes Rayleigh scattering, resulting in curvature of the spectrum that mimics the Fe2+ feature. Sub-micron dark grains hitting the trailing side of Dione could create the observed spectral and spatial patterns observed by VIMS. Furthermore, the abundance of the dark material must remain less than about 1% or the Rayleigh scattering effect would be suppressed such that the reflectance spectrum loses the Rayleigh component. Rayleigh yet still maintain spectral differences in the visible spectrum between satellites.

  15. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2008-09-01

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

  17. 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.

  18. 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

  19. Dissemination of Pseudomonas aeruginosa producing blaIMP-1 and blaVIM-1 in Qazvin and Alborz educational hospitals, Iran

    PubMed Central

    Peymani, Amir; Naserpour Farivar, Taghi; Mohammadi Ghanbarlou, Mahdi; Najafipour, Reza

    2015-01-01

    Background and Objectives: Pseudomonas aeruginosa is a frequent opportunistic pathogen in health care associated infections that is highly resistant to the majority of ?-lactams. The aims of this study were to access the antimicrobial susceptibility pattern of P. aeruginosa isolated from educational hospitals of Qazvin and Alborz provinces, to determine the prevalence of metallo-?-lactamase (MBL) among carbapenem non-susceptible isolates by combined disk (CD) method, and to detect the blaIMP, blaVIM, blaSIM, blaGIM, blaSPM and blaNDM-1-MBL genes. Materials and Methods: In this cross-sectional study, 300 P. aeruginosa isolates were collected from different clinical specimens in two provinces of Qazvin and Alborz hospitals, Iran. After identification of isolates by standard laboratory methods, antimicrobial susceptibility was done against 17 antibiotics according to clinical and laboratory standards institute (CLSI) guideline. CD method was carried out for detection of MBLs and the presence of blaIMP, blaVIM, blaSIM, blaGIM, blaNDM-1 and blaSPM-genes was further assessed by PCR and sequencing methods. Results: In this study, 107 (35.66%) isolates were non-susceptible to imipenem and/or meropenem among those 56 (52.3%) isolates were metallo-?-lactamase producer. Twenty-four of 56 (42.85%) MBL-positive isolates were confirmed to be positive for MBL-encoding genes in which 14 (25%) and 10 (17.85%) isolates carried blaIMP-1 and blaVIM-1 genes either alone or in combination. Three (5.35%) isolates carried blaIMP and blaVIM genes, simultaneously. Conclusion: Considering the moderate prevalence and clinical importance of MBL-producing isolates, rapid identification and use of appropriate infection control (IC) measures are necessary to prevent further spread of infections by these resistant organisms. PMID:26885329

  20. Detection and Genetic Characterization of Metallo-β-Lactamase IMP-1 and VIM-2 in Pseudomonas aeruginosa Strains From Different Hospitals in Kermanshah, Iran

    PubMed Central

    Abiri, Ramin; Mohammadi, Pantea; Shavani, Navid; Rezaei, Mansour

    2015-01-01

    Background: Pseudomonas aeruginosais a frequent nosocomial pathogen that causes severe diseases in many settings. Carbapenems, including meropenem and imipenem, are effective antibiotics against this organism. However, the use of carbapenems has been hampered by the emergence of strains resistant to carbapenemsvia different mechanisms such as the production of metallo-β-lactamases (MBLs), which hydrolyze all carbapenems. Several kinds of MBLs have been reported, among them VIM and IMP types being the most clinically significant carbapenemases. Objectives: We aimed to determine the distribution of blaVIM-2 and blaIMP-1 transferable genes encoding MBLs in P. aeruginosa isolated from three academic hospitals in Kermanshah. Patients and Methods: From 22nd June to 22nd September 2012, 225 isolates of P. aeruginosa were collected. These isolates were tested for antibiotic susceptibility with the Kirby-Bauer disk-diffusion method, and the MBLs were assessed using the imipenem-EDTA double-disk synergy test. The isolates were investigated for blaVIM-2 and blaIMP-1 genes using polymerase chain reaction. Results: Among the 225 isolates, 33.7% (76/225) and 18.1% (41/225) were resistant to imipenem and meropenem, respectively. Of the 76 imipenem-resistant P. aeruginosa strains, 45 (59.2%) were positive for MBLs, 34 (75%) strains carried the blaIMP-1 gene, and 1 (2.2%) strain carried the blaVIM-2 gene. Conclusions: Our results showed that there was a high frequency of IMP-1 positive P. aeruginosa in the different wards of the hospitals. PMID:26495110

  1. Similar Frequencies of Pseudomonas aeruginosa Isolates Producing KPC and VIM Carbapenemases in Diverse Genetic Clones at Tertiary-Care Hospitals in Medelln, Colombia

    PubMed Central

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

    2014-01-01

    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 Medelln, 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 blaVIM, blaIMP, blaNDM, blaOXA-48, and blaKPC 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 blaVIM-2 and blaKPC-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 Medelln, Colombia. Diverse genetic backgrounds among resistant strains suggest an excessive antibiotic pressure resulting in the selection of resistant strains. PMID:25210071

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

    NASA Astrophysics Data System (ADS)

    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.

    2006-12-01

    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 μm 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 τ=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.

  3. 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.

  4. The Long Wavelength Array

    NASA Astrophysics Data System (ADS)

    Kassim, N. E.

    2006-05-01

    We describe the Long Wavelength Array (LWA), now in the initial construction phase, that will open a window on one of the last and most poorly explored regions of the electromagnetic spectrum. The LWA will be a large (baselines up to 400 km), low frequency (n ~ 20-80 MHz) aperture synthesis array with large collecting area (~106 m2 at 20 MHz) and high resolution (~1.5" at 80 MHz), and will provide mJy-level sensitivity across much of its operating range. This region has been poorly explored because ionospheric turbulence has limited imaging to very course angular resolution. New phase compensation techniques now make it possible to explore this region at unprecedented resolution and sensitivity. In addition to its main applications for pioneering studies in astrophysics, the LWA can also be a powerful instrument for solar system and planetary science applications. The Sun will always be accessible to one of the LWA's multiple electronic beams during daylight hours, and particularly during periods of high solar activity the Sun will be a prominent (and highly variable) feature of the low-frequency sky. A diverse range of low-frequency emissions is generated by the Sun that carry information about processes taking place in the Sun's atmosphere. Study of these emissions with the LWA will make possible advances in our understanding of particle acceleration and shocks in the solar atmosphere, and of CMEs and their impact on the Earth. Applications include passive detection of solar burst phenomena, direct imaging of synchrotron emission from CMEs, as well as propagation and scattering studies through the solar corona and the interplanetary medium. A synergistic combination of a ground based LWA and the space-borne coronagraphs such as on board the STEREO mission could prove to be an extremely powerful tool to understand the interplanetary propagation of solar disturbances. The LWA could also prove a useful compliment to FASR - with LWA lower frequency observations triggering higher frequency FASR targeted follow-ups. If co-located in reasonable proximity the LWA might also provide FASR with a real-time ionospheric model to permit accurate astrometry after corrections for ionospheric refraction. A future radar transmitter would enable the LWA to become an ideal solar radar receiver to image Earth-ward bound CMEs for geomagnetic storm prediction. Basic research in radio astronomy at the Naval Research Laboratory is supported by the Office of Naval Research.

  5. 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.

  6. 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.

  7. Long wavelength irregularities in the equatorial electrojet

    NASA Technical Reports Server (NTRS)

    Kudeki, E.; Farley, D. T.; Fejer, B. G.

    1982-01-01

    The radar interferometer technique is used at Jicamarca to study in detail irregularities with wavelengths of a few kilometers generated in the unstable equatorial electrojet plasma during strong type 1 conditions. In-situ rocket observations of the same instability process are discussed in a companion paper. These large scale primary waves travel essentially horizontally and have large amplitudes. The vertical electron drift velocities driven by the horizontal wave electric fields reach or exceed the ion-acoustic velocity even though the horizontal phase velocity of the wave is considerably smaller. A straightforward extension to the long wavelength regime of the usual linear theory of the electrojet instability explains this and several other observed features of these dominant primary waves.

  8. Long wavelength irregularities in the equatorial electrojet

    SciTech Connect

    Kudeki, E.; Farley, D.T.; Fejer, B.G.

    1982-06-01

    We have used the radar interferometer technique at Jicamarca to study in detail irregularities with wavelengths of a few kilometers generated in the unstable equatorial electrojet plasma during strong type 1 conditions. In-situ rocket observations of the same instability process are discussed in a companion paper. These large scale primary waves travel essentially horizontally and have large amplitudes. The vertical electron drift velocities driven by the horizontal wave electric fields reach or exceed the ion-acoustic velocity even though the horizontal phase velocity of the wave is considerably smaller. A straightforward extension to the long wavelength regime of the usual linear theory of the electrojet instability explains this and several other observed features of these dominant primary waves.

  9. Solar radio bursts at kilometer wavelengths

    NASA Technical Reports Server (NTRS)

    Stone, R. G.; Fainberg, J.

    1973-01-01

    The potential value of traveling solar radio bursts for investigating energetic particle propagation, and for probing the interplanetary medium is discussed. A general survey of the characteristics of type 3 radio phenomena observed at hectometer and kilometer wavelengths is presented along with a brief discussion of the relationships among type 1 meter noise storms, decametric continuum, and type 3 hectometric storms. Type 3 bursts are analyzed to show how these data provide information about the average energy, dispersion, and trajectory of energetic particles, the interplanetary scale, and magnetic field configuration. The recent observations of type 2 shock wave phenomena at kilometer wavelengths are described, and current research and the direction of future observation are outlined.

  10. 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.

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

    NASA Astrophysics Data System (ADS)

    Baines, Kevin H.; Delitsky, Mona L.; Momary, Thomas W.; Brown, Robert H.; Buratti, Bonnie J.; Clark, Roger N.; Nicholson, Philip D.

    2009-12-01

    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 μm to at least 4.1 μm. 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 μm 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.

  12. Two-wavelength microscopic speckle interferometry using colour CCD camera

    NASA Astrophysics Data System (ADS)

    Upputuri, Paul K.; Pramanik, Manojit; Kothiyal, Mahendra P.; Nandigana, Krishna M.

    2015-03-01

    Single wavelength microscopic speckle interferometry is widely used for deformation, shape and non-destructive testing (NDT) of engineering structures. However the single wavelength configuration fails to quantify the large deformation due to the overcrowding of fringes and it cannot provide shape of a specimen under test. In this paper, we discuss a two wavelength microscopic speckle interferometry using single-chip colour CCD camera for characterization of microsamples. The use of colour CCD allows simultaneous acquisition of speckle patterns at two different wavelengths and thus it makes the data acquisition as simple as single wavelength case. For the quantitative measurement, an error compensating 8-step phase shifted algorithm is used. The system allows quantification of large deformation and shape of a specimen with rough surface. The design of the system along with few experimental results on small scale rough specimens is presented.

  13. 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.

  14. Meander wavelength of alluvial rivers.

    PubMed

    Schumm, S A

    1967-09-29

    Data on river channel and sediment characteristics were collected at 36 cross sections of stable alluvial river channels in Australia and western United States. These data demonstrate that the meander wavelength of a river is dependent not only on water discharge, but also on the type of sediment load moved through the channel. The meander wavelength of rivers that are transporting a high proportion of their total sediment load as both sand and gravel will be greater than the meander wavelengths of channels of similar discharge which are transporting mainly fine sediment loads. PMID:17816939

  15. 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.

  16. 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.

  17. 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.

  18. Rapid Detection of Pseudomonas aeruginosa and Acinetobacter baumannii Harboring blaVIM-2, blaIMP-1 and blaOXA-23 Genes by Using Loop-Mediated Isothermal Amplification Methods

    PubMed Central

    Kim, Hye Jin; Kim, Hyung Sun; Lee, Jae Myun

    2016-01-01

    Background Carbapenem-resistant Pseudomonas aeruginosa (CRPA) and Acinetobacter baumannii (CRAB) are the leading causes of nosocomial infections. A rapid and sensitive test to detect CRPA and CRAB is required for appropriate antibiotic treatment. We optimized a loop-mediated isothermal amplification (LAMP) assay to detect the presence of blaVIM-2, blaIMP-1, and blaOXA-23, which are critical components for carbapenem resistance. Methods Two sets of primers, inner and outer primers, were manually designed as previously described. The LAMP buffer was optimized (at 2mM MgSO4) by testing different concentrations of MgSO4. The optimal reaction temperature and incubation time were determined by using a gradient thermocycler. Then, the optimized blaVIM-2, blaIMP-1, and blaOXA-23 LAMP reactions were evaluated by using 120 P. aeruginosa and 99 A. baumannii clinical isolates. Results Only one strain of the 100 CRPA isolates harbored blaIMP-1, whereas none of them harbored blaVIM-2. These results indicate that the acquisition of blaVIM-2 or blaIMP-1 may not play a major role in carbapenem resistance in Korea. Fifty two strains of the 75 CRAB isolates contained blaOXA-23, but none contained blaVIM-2 and blaIMP-1 alleles. Conclusions Our results demonstrate the usefulness of LAMP for the diagnosis of CRPA and CRAB. PMID:26522754

  19. 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.

  20. Wavelength calibration with Fabry Perot Interferometers - yes we can!

    NASA Astrophysics Data System (ADS)

    Franziskus Bauer, Florian; Zechmeister, Mathias; Reiners, Ansgar

    2015-08-01

    Hollow-cathode lamps (HCLs) are used as default wavelength standard for spectroscopic measurements but have a number of well-known shortcomings. Advancing to cm/s precision in radial velocity experiments requires more stable calibration sources with more uniform line distributions. Fabry Perot Interferometers (FPI) are a practical alternative with a well-suited line distribution at relatively low cost. We present a simple method to characterize FPIs using standard HCLs and including the FPI spectrum in the wavelength calibration process. We propose to use the HCL wavelength solution to define a rough wavelength scale that is used to approximate the FPI peak positions. We assume that the FPI mirror distance is a smooth function of wavelength and utilize the large number of FPI peaks (typically 10^4) to consistently model all FPI peak wavelengths. With this approach, we anchor the dense FPI lines with the absolute HCL-scale combining their precision and accuracy. We test our method with the HARPS spectrograph and compare our wavelength calibration to one derived from a laser frequency comb (LFC) spectrum. Our combined HCL/FPI wavelength calibration removes the known, large-amplitude distortions of 50 m/s that occur in the HCL solution. Direct comparison with the LFC solution bears only small differences between the LFC and the HCL/FPI solutions and demonstrates that the HCL/FPI solution can overcome the most important shortcomings in HCL wavelength solutions. An FPI can provide an economical alternative to LFCs in particular for smaller projects.

  1. 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.

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

    NASA Astrophysics Data System (ADS)

    Baines, 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.

    2006-12-01

    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 CH 3D, the prominent Q branch of the ? 2 fundamental band of CH 3D near 4.55 ?m is apparent. CO 2 emissions from the strong v3 vibrational band are virtually absent, indicating a CO 2 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 3215 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 2.91.510 14 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 6310 5 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/CH 4 mixing ratio of near-surface material is 1.80.910 -4, based on an average methane surface emission rate over the past 0.5 Gyr of 1.310 -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/CH 4 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 CH 4-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 km 3 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.

  3. 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.

  4. Carbapenem Heteroresistance in VIM-1-producing Klebsiella pneumoniae isolates belonging to the same clone: consequences for routine susceptibility testing.

    PubMed

    Tato, M; Morosini, M; García, L; Albertí, S; Coque, M T; Cantón, R

    2010-11-01

    Susceptibility results with low reproducibility by the same or different methods have been observed for metallo-beta-lactamase (MBL)-producing Enterobacteriaceae. Eighteen VIM-1-producing Klebsiella pneumoniae isolates (one per patient) belonging to a single epidemic clone in our hospital (2005 to 2008) but with different susceptibilities to carbapenems were studied. Imipenem MICs ranged from 8 to >128 mg/liter by standard CLSI microdilution, from ≤1 to >8 mg/liter by the semiautomatic Wider system, and from 0.75 to >32 mg/liter by Etest. Meropenem MICs ranged from 0.5 to 128, ≤1 to >8, and 0.38 to >32 mg/liter, respectively. Ertapenem MICs by CLSI microdilution and Etest ranged from 1 to 64 and 0.75 to >32 mg/liter, respectively. The rates of essential agreement (±1 log(2) dilution) for imipenem and meropenem MICs between the Wider system and the reference microdilution method were 45% and 49%, respectively. Those between Etest and the reference microdilution method for imipenem, meropenem, and ertapenem MICs were 33%, 67%, and 84%. The rates of very major errors for the Wider system and Etest were 33% and 28% for imipenem and 25% and 75% for meropenem, respectively. Low MIC reproducibility was observed even when the same inoculum was used (differences up to 4-fold dilutions). Heteroresistance was suspected due to the presence of colonies in the Etest inhibition zone. It was confirmed by population analysis profiles of 4 isolates displaying different imipenem MICs, with the exception of an OmpK36-porin-deficient isolate that homogeneously expressed carbapenem resistance (MIC, >128 mg/liter). Low carbapenem MIC reproducibility could be due to the presence of resistant subpopulations and variable expression of the resistance mechanisms. Since carbapenem MICs are not good markers of MBL production, reliable and reproducible phenotypic methods are needed to detect the presence of this mechanism. PMID:20844213

  5. Carbapenem Heteroresistance in VIM-1-Producing Klebsiella pneumoniae Isolates Belonging to the Same Clone: Consequences for Routine Susceptibility Testing▿

    PubMed Central

    Tato, M.; Morosini, M.; García, L.; Albertí, S.; Coque, M. T.; Cantón, R.

    2010-01-01

    Susceptibility results with low reproducibility by the same or different methods have been observed for metallo-beta-lactamase (MBL)-producing Enterobacteriaceae. Eighteen VIM-1-producing Klebsiella pneumoniae isolates (one per patient) belonging to a single epidemic clone in our hospital (2005 to 2008) but with different susceptibilities to carbapenems were studied. Imipenem MICs ranged from 8 to >128 mg/liter by standard CLSI microdilution, from ≤1 to >8 mg/liter by the semiautomatic Wider system, and from 0.75 to >32 mg/liter by Etest. Meropenem MICs ranged from 0.5 to 128, ≤1 to >8, and 0.38 to >32 mg/liter, respectively. Ertapenem MICs by CLSI microdilution and Etest ranged from 1 to 64 and 0.75 to >32 mg/liter, respectively. The rates of essential agreement (±1 log2 dilution) for imipenem and meropenem MICs between the Wider system and the reference microdilution method were 45% and 49%, respectively. Those between Etest and the reference microdilution method for imipenem, meropenem, and ertapenem MICs were 33%, 67%, and 84%. The rates of very major errors for the Wider system and Etest were 33% and 28% for imipenem and 25% and 75% for meropenem, respectively. Low MIC reproducibility was observed even when the same inoculum was used (differences up to 4-fold dilutions). Heteroresistance was suspected due to the presence of colonies in the Etest inhibition zone. It was confirmed by population analysis profiles of 4 isolates displaying different imipenem MICs, with the exception of an OmpK36-porin-deficient isolate that homogeneously expressed carbapenem resistance (MIC, >128 mg/liter). Low carbapenem MIC reproducibility could be due to the presence of resistant subpopulations and variable expression of the resistance mechanisms. Since carbapenem MICs are not good markers of MBL production, reliable and reproducible phenotypic methods are needed to detect the presence of this mechanism. PMID:20844213

  6. 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.

  7. 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.

  8. 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

    SciTech Connect

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

    2015-01-30

    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 5624056300, 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.

  9. 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.

  10. Significance of dual polarized long wavelength radar for terrain analysis

    NASA Technical Reports Server (NTRS)

    Macdonald, H. C.; Waite, W. P.

    1978-01-01

    Long wavelength systems with improved penetration capability have been considered to have the potential for minimizing the vegetation contribution and enhancing the surface return variations. L-band imagery of the Arkansas geologic test site provides confirmatory evidence of this effect. However, the increased wavelength increases the sensitivity to larger scale structure at relatively small incidence angles. The regularity of agricultural and urban scenes provides large components in the low frequency-large scale portion of the roughness spectrum that are highly sensitive to orientation. The addition of a cross polarized channel is shown to enable the interpreter to distinguish vegetation and orientational perturbations in the surface return.

  11. Wavelength shifting of intra-cavity photons: Adiabatic wavelength tuning in rapidly wavelength-swept lasers

    PubMed Central

    Jirauschek, Christian; Huber, Robert

    2015-01-01

    We analyze the physics behind the newest generation of rapidly wavelength tunable sources for optical coherence tomography (OCT), retaining a single longitudinal cavity mode during operation without repeated build up of lasing. In this context, we theoretically investigate the currently existing concepts of rapidly wavelength-swept lasers based on tuning of the cavity length or refractive index, leading to an altered optical path length inside the resonator. Specifically, we consider vertical-cavity surface-emitting lasers (VCSELs) with microelectromechanical system (MEMS) mirrors as well as Fourier domain mode-locked (FDML) and Vernier-tuned distributed Bragg reflector (VT-DBR) lasers. Based on heuristic arguments and exact analytical solutions of Maxwell’s equations for a fundamental laser resonator model, we show that adiabatic wavelength tuning is achieved, i.e., hopping between cavity modes associated with a repeated build up of lasing is avoided, and the photon number is conserved. As a consequence, no fundamental limit exists for the wavelength tuning speed, in principle enabling wide-range wavelength sweeps at arbitrary tuning speeds with narrow instantaneous linewidth. PMID:26203373

  12. Wavelength shifting of intra-cavity photons: Adiabatic wavelength tuning in rapidly wavelength-swept lasers.

    PubMed

    Jirauschek, Christian; Huber, Robert

    2015-07-01

    We analyze the physics behind the newest generation of rapidly wavelength tunable sources for optical coherence tomography (OCT), retaining a single longitudinal cavity mode during operation without repeated build up of lasing. In this context, we theoretically investigate the currently existing concepts of rapidly wavelength-swept lasers based on tuning of the cavity length or refractive index, leading to an altered optical path length inside the resonator. Specifically, we consider vertical-cavity surface-emitting lasers (VCSELs) with microelectromechanical system (MEMS) mirrors as well as Fourier domain mode-locked (FDML) and Vernier-tuned distributed Bragg reflector (VT-DBR) lasers. Based on heuristic arguments and exact analytical solutions of Maxwell's equations for a fundamental laser resonator model, we show that adiabatic wavelength tuning is achieved, i.e., hopping between cavity modes associated with a repeated build up of lasing is avoided, and the photon number is conserved. As a consequence, no fundamental limit exists for the wavelength tuning speed, in principle enabling wide-range wavelength sweeps at arbitrary tuning speeds with narrow instantaneous linewidth. PMID:26203373

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

    PubMed

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

    2010-10-01

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

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

    PubMed Central

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

    2010-01-01

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

  15. Wavelength-modulated photocapacitance spectroscopy

    NASA Technical Reports Server (NTRS)

    Kamieniecki, E.; Lagowski, J.; Gatos, H. C.

    1980-01-01

    Derivative deep-level spectroscopy was achieved with wavelength-modulated photocapacitance employing MOS structures and Schottky barriers. The energy position and photoionization characteristics of deep levels of melt-grown GaAs and the Cr level in high-resistivity GaAs were determined. The advantages of this method over existing methods for deep-level spectroscopy are discussed.

  16. 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.

  17. Expanding plasma structure and its evolution toward long wavelengths

    SciTech Connect

    Sgro, A. G.; Peter Gary, S.; Lemons, D. S.

    1989-09-01

    The expansion of a plasma slab across an initially uniform magnetic field is simulated by the use of a two-dimensional electromagnetic hybrid (particle ions, fluid electrons of nonzero mass) computer code. The expanding plasma develops magnetic-field-aligned structure on time scales faster than an ion gyroperiod. Through the full duration of the /ital m//sub /ital i////ital m//sub /ital e// =100 simulation, the structure wavelength is well predicted by the wavelength at maximum growth rate from the linear Vlasov theory of the lower hybrid drift instability modified by deceleration. At /ital m//sub /ital i////ital m//sub /ital e// =400, the late time structure wavelength is about 1.5 times the early time value. At /ital m//sub /ital i////ital m//sub /ital e// =1836, the structure wavelength at early times is close to that corresponding to the maximum growth rate of linear theory, while at later times the structure wavelength becomes about twice as long as its early time value. These three results suggest that the ratio of the late time wavelength to the early time value gradually increases with /ital m//sub /ital i////ital m//sub /ital e//. Extrapolation of this scaling to larger /ital m//sub /ital i////ital m//sub /ital e// values is consistent with structure wavelengths observed in an expanding aluminum plasma experiment (J. Appl. Phys. J. /bold 20/, 157 (1981)), as well as the observed wavelength in the expanding barium plasma of the AMPTE magnetotail experiment (J. Geophys. Res. /bold 92/, 5777 (1987)).

  18. On the wavelength of self-organized shoreline sand waves

    NASA Astrophysics Data System (ADS)

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

    2012-04-01

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

  19. Laser wavelength selector and output coupler

    NASA Technical Reports Server (NTRS)

    Hard, T. M.

    1970-01-01

    Optical system eliminates displacement occurring when wavelengths are selected in multiple wavelength laser utilizing intracavity wavelength selection by first-order Littrow reflection of plane grating. Output coupling varies direction of output beam as different wavelengths are selected by grating rotation.

  20. 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; Rodrguez-Avial, Carmen; Rodrguez-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

  1. Discovery of Novel Inhibitor Scaffolds against the Metallo-β-lactamase VIM-2 by Surface Plasmon Resonance (SPR) Based Fragment Screening.

    PubMed

    Christopeit, Tony; Carlsen, Trine Josefine O; Helland, Ronny; Leiros, Hanna-Kirsti S

    2015-11-12

    Metallo-β-lactamase (MBL) inhibitors can restore the function of carbapenem antibiotics and therefore help to treat infections of antibiotic resistant bacteria. In this study, we report novel fragments inhibiting the clinically relevant MBL Verona integron-encoded metallo-β-lactamase (VIM-2). The fragments were identified from a library of 490 fragments using an orthogonal screening approach based on a surface plasmon resonance (SPR) based assay combined with an enzyme inhibition assay. The identified fragments showed IC50 values between 14 and 1500 μM and ligand efficiencies (LE) between 0.48 and 0.23 kcal/mol per heavy atom. For two of the identified fragments, crystal structures in complex with VIM-2 were obtained. The identified fragments represent novel inhibitor scaffolds and are good starting points for the design of potent MBL inhibitors. Furthermore, the established SPR based assay and the screening approach can be adapted to other MBLs and in this way improve the drug discovery process for this important class of drug targets. PMID:26477515

  2. The Evolution of Saturns Storm-Perturbed Latitudinal Band Determined from Cassini/VIMS Daytime and Nighttime Spectra

    NASA Astrophysics Data System (ADS)

    Baines, K. H.; Sromovsky, Larry A.; Fry, Patrick M.; Moimary, Thomas W.; Badman, Sarah; Brown, Robert H.; Buratti, Bonnie J.; Clark, Roger N.; Nicholson, Philip D.; Sotin, Christophe

    2015-11-01

    Saturns Great Storm of 2010-2011 was one of the most powerful convective events ever witnessed, as indicated, for example, by its ability to deliver spectrally-identifiable water ice to the top of its convective tower ~200 km above the water vapor condensation level near 20 bar (Sromovsky, L. A., et al., Icarus 226, 402-418. 2013), and by its ability over ~ 6 months to encircle the planet with apparently anvil-like ammonia clouds sheared away from the top of its convective tower(s). Within a half-year after the storm subsided in mid-2011, these globe-encircling anvil-like clouds appeared to have largely disappeared, replaced by a 5-micron-bright band encircling the planet over nearly the same latitude region the storm generated clouds had been, indicating a dramatic decrease in the opacity of aerosols sensitive to 5-micron radiation (heat) emanating from the warm depths of the planet. Here we present quantitative results on the 5-year evolution of this storm-affected, 5-micron-bright region, from its initial appearance associated with a large anti-cyclone that formed in the Spring of 2011 through May 26-27, 2015, using both daytime and nighttime Cassini/VIMS spectral maps. Compared to the normal, unperturbed regional cloud structure upstream of the storm as observed on Feb 24, 2011, we find that the initial 5-micron-bright region on May 11, 2011 had lost ~60% of its upper-cloud (100-500 mbar) opacity (i. e., nominally, 2.7 opacity post-storm at 2-microns vs 7.1 pre-storm) and that the pressure of an opaque, putatively NH4SH, optically-thick sheet cloud dropped in altitude from a pre-storm level of 2.9 bar to the 3.2-bar level post-storm. Subsequently over the next 4 years, the upper-cloud region recovered half of its lost opacity, reaching ~5.6 on March 21, 2014 (and nearly recovered, to ~ 7 in our tentative May 26-27, 2015 data), corresponding to an e-folding time back to pre-storm opacity of 2.7 years, but the lower cloud has dropped down to the 3.3-bar level (rising to ~ 3.0 bar in our tentative analysis of the May 2015 data). Throughout, the region has remained 5-micron-bright, predominantly due to the deeper, warmer level of the opaque putative NH4SH cloud.

  3. Spectral and morphological properties of various geological types of Titan’s surface with Cassini VIMS and RADAR

    NASA Astrophysics Data System (ADS)

    Solomonidou, Anezina; Coustenis, Athena; Lopes, Rosaly M.; Hirtzig, Mathieu; Rodriguez, Sebastien; Malaska, Michael; Drossart, Pierre; Sotin, Christophe; Bratsolis, Emmanuel; Matsoukas, Chris; Brown, Robert; Maltagliati, Luca

    2015-08-01

    Cassini’s VIMS and the RADAR have been investigating Titan’s surface since 2004. Both instruments unveiled the dynamic and complex surface expressions of this Saturnian moon, suggesting exogenic and endogenic processes [1;2;3]. In order to evaluate the atmospheric contribution and thereafter extract surface information, a Radiative transfer code is used to analyse different regions and to monitor their spectral behaviour over time [4;5;7]. We furthermore use RADAR despeckled SAR images to infer information on the morphology [6]. We find that temporal variations of surface albedo occur for some areas, but that their origin may differ from one region to the other. Tui Regio and Sotra Patera change with time becoming darker and brighter respectively in terms of surface albedo. In contrast, we find that the undifferentiated plains and the suggested evaporitic areas in the equatorial regions do not present any significant change [5]. This observation supports the hypothesis that Titan is surface brightening of Sotra supports a possible internal rather than an exogenic origin. This observation supports the hypothesis that Titan is a cryovolcanic world due to the presence of local complex volcanic-like geomorphology [1] and indications of surface albedo changes [4,5]. Potential sources of the energy for cryovolcanism include tidal heating, possible internal convection, and ice tectonics, is believed to be a pre-requisite of a habitable planetary body as it allows the recycling of minerals and potential nutrients and provides localized energy sources. A recent study has shown that tidal forces are a constant and significant source of internal deformation on Titan and the interior liquid water ocean can be relatively warm for reasonable amounts of ammonia concentrations [8].[1] Lopes, R.M.C., et al. JGR, 118, 2013 [2] Solomonidou, A., et al. PSS, 70, 2013 [3] Moore, J.M. GRL, 37, 2010 [4] Solomonidou, A., et al. JGR, 119, 2014 [5] Solomonidou, A., et al. submitted [6] Bratsolis, E., et al. PSS, 61, 2012 [7] Hirtzig, M., et al. Icarus, 226, 2013 [8] Sohl, F., et al. JGR, 119, 2014.

  4. Wavelength independent multimode interference coupler.

    PubMed

    Maese-Novo, A; Halir, R; Romero-García, S; Pérez-Galacho, D; Zavargo-Peche, L; Ortega-Moñux, A; Molina-Fernández, I; Wangüemert-Pérez, J G; Cheben, P

    2013-03-25

    We propose an ultra-broadband multimode interference (MMI) coupler with a wavelength range exceeding the O, E, S, C, L and U optical communication bands. For the first time, the dispersion property of the MMI section is engineered using a subwavelength grating structure to mitigate wavelength dependence of the device. We present a 2 × 2 MMI design with a bandwidth of 450nm, an almost fivefold enhancement compared to conventional designs, maintaining insertion loss, power imbalance and MMI phase deviation below 1dB, 0.6dB and 3°, respectively. The design is performed using an in-house tool based on the 2D Fourier Eigenmode Expansion Method (F-EEM) and verified with a 3D Finite Difference Time Domain (FDTD) simulator. PMID:23546086

  5. Long-Wavelength Infrared Detector

    NASA Technical Reports Server (NTRS)

    Vasquez, Richard P.

    1989-01-01

    Proposed device detects infrared photons of 10- to 100-micrometer wavelength by intersubband absorption in coupled quantum wells. Based on splitting of energy level occuring when two quantum wells placed so close together wave functions of quantized energy levels overlap. Detector absorbs photons, energy which equals difference in energy between two levels resulting from split. Because degree of overlap of wave functions and, therefore, magnitude of split varied by varying width of barrier between two coupled wells, such detector, in principle, designed to operate at any desired wavelength. Restrictions on design parameters of quantum wells of proposed device less severe than single-well devices. Energy levels near tops of wells still necessary so photoexcited carriers tunnel out. Additional flexibility in design obtained by use of wells formed by barriers of different heights.

  6. Long wavelength carbonyl sulfide photodissociation

    NASA Technical Reports Server (NTRS)

    Turco, R. P.; Cicerone, R. J.; Inn, E. C. Y.; Capone, L. A.

    1981-01-01

    The aeronomic implications of a preliminary observation of weak OCS photoabsorption above 270 nm are investigated. It is argued that the measured cross section is consistent with a forbidden transition in this wavelength region. Model calculations are made for the OCS photodissociation rates in daylight, the OCS and SO2 distributions in the upper atmosphere, and the budgets of sulfur in the stratosphere and OCS in the troposphere, assuming various extrapolations of the measured OCS absorption cross sections and quantum yields to longer wavelengths. It is shown that weak OCS absorption above 300 nm can have important consequences for all of these quantities. Laboratory and field experiments are identified which might lead to a better understanding of the atmospheric OCS cycle.

  7. Wavelength Selection in Gyrotactic Bioconvection.

    PubMed

    Ghorai, S; Singh, R; Hill, N A

    2015-06-01

    We investigate pattern formation by swimming micro-organisms (bioconvection), when their orientation is determined by balance between gravitational and viscous torques (gyrotaxis), due to being bottom heavy. The governing equations, which consist of the Navier-Stokes equations for an incompressible fluid coupled with a micro-organism conservation equation, are solved numerically in a large cross section chamber with periodic boundary conditions in the horizontal directions. The influence of key parameters on wavelength selection in bioconvection patterns is investigated numerically. For realistic ranges of parameter values, the computed wavelengths are in good agreement with the experimental observations provided that the diffusion due to randomness in cell swimming behaviour is small, refuting a recently published claim that the mathematical model becomes inaccurate at long times. We also provide the first computational evidence of "bottom-standing" plumes in a three-dimensional simulation. PMID:25963246

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

    SciTech Connect

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

    2015-03-23

    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 Ag?Si{sub 3}N{sub 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.

  9. Alternative wavelengths for optically pumped alkali lasers

    NASA Astrophysics Data System (ADS)

    Perram, Glen P.

    2012-06-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

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

  11. Wavelength stabilized multi-kW diode laser systems

    NASA Astrophysics Data System (ADS)

    Köhler, Bernd; Unger, Andreas; Kindervater, Tobias; Drovs, Simon; Wolf, Paul; Hubrich, Ralf; Beczkowiak, Anna; Auch, Stefan; Müntz, Holger; Biesenbach, Jens

    2015-03-01

    We report on wavelength stabilized high-power diode laser systems with enhanced spectral brightness by means of Volume Holographic Gratings. High-power diode laser modules typically have a relatively broad spectral width of about 3 to 6 nm. In addition the center wavelength shifts by changing the temperature and the driving current, which is obstructive for pumping applications with small absorption bandwidths. Wavelength stabilization of high-power diode laser systems is an important method to increase the efficiency of diode pumped solid-state lasers. It also enables power scaling by dense wavelength multiplexing. To ensure a wide locking range and efficient wavelength stabilization the parameters of the Volume Holographic Grating and the parameters of the diode laser bar have to be adapted carefully. Important parameters are the reflectivity of the Volume Holographic Grating, the reflectivity of the diode laser bar as well as its angular and spectral emission characteristics. In this paper we present detailed data on wavelength stabilized diode laser systems with and without fiber coupling in the spectral range from 634 nm up to 1533 nm. The maximum output power of 2.7 kW was measured for a fiber coupled system (1000 μm, NA 0.22), which was stabilized at a wavelength of 969 nm with a spectral width of only 0.6 nm (90% value). Another example is a narrow line-width diode laser stack, which was stabilized at a wavelength of 1533 nm with a spectral bandwidth below 1 nm and an output power of 835 W.

  12. Photonic crystal nanosecond wavelength switches

    NASA Astrophysics Data System (ADS)

    Miller, Robert O.; Tsu, David V.; Reed, Jeffrey A.; Strand, David A.

    2006-02-01

    We present our design and fabrication methodology of planar photonic crystal wavelength switches and the optical micro-bench surrounding them. The core device is a channel add-drop multiplexer (CADM) whose pass/transfer element can be turned off and on in tens of nanoseconds. The photonic crystal consists of a regular triangular array of SiO II -filled holes in an amorphous Ge 3Si film. The film is sandwiched between two SiO II cladding layers. The pass and transfer buses consist of linear extended defects in the crystal, with the pass bus and each drop bus separated by a cavity resonator defect tuned to each wavelength. There is a small region where an ECD-designed chalcogenide alloy is incorporated into each resonator. Switching is accomplished by changing the structure of the chalcogenide between amorphous and crystalline, using a short wavelength diode laser. The optical bench consists of photonic wire waveguides formed in the Ge 3Si film and deep trenches in an underlying thick SOI film to accommodate bonded access fibers, both features being photolithographically co-aligned to the photonic crystal array. This, along with our impedance-matching interface designs, assures that there is low input-output power loss. The local reconfigurability in effect elevates the CADM to an all-optical router. Sub-100 nanosecond latency enables packet-level discernment. The large difference in optical constants of the two chalcogenide phases provides high on-off contrast (low crosstalk). The stability of the two phases gives complete latching nonvolatility. Our current progress in building and testing prototypes of our switches is also presented.

  13. Wavelength-encoded OCDMA system using opto-VLSI processors

    NASA Astrophysics Data System (ADS)

    Aljada, Muhsen; Alameh, Kamal

    2007-07-01

    We propose and experimentally demonstrate a 2.5 Gbits/sper user wavelength-encoded optical code-division multiple-access encoder-decoder structure based on opto-VLSI processing. Each encoder and decoder is constructed using a single 1D opto-very-large-scale-integrated (VLSI) processor in conjunction with a fiber Bragg grating (FBG) array of different Bragg wavelengths. The FBG array spectrally and temporally slices the broadband input pulse into several components and the opto-VLSI processor generates codewords using digital phase holograms. System performance is measured in terms of the autocorrelation and cross-correlation functions as well as the eye diagram.

  14. BIN Diode For Submillimeter Wavelengths

    NASA Technical Reports Server (NTRS)

    Maserjian, J.

    1989-01-01

    Diode formed by selective doping during epitaxial growth, starting with semi-insulating substrate. Use of high-mobility semiconductors like GaAs extends cutoff frequency. Either molecular-beam epitaxy (MBE) or organometallic chemical-vapor deposition used to form layers of diode. Planar growth process permits subsequent fabrication of arrays of diodes by standard photolithographic techniques, to achieve quasi-optical coupling of submillimeter radiation. Useful for generation of harmonics or heterodyne mixing in receivers for atmospheric and space spectroscopy operating at millimeter and submillimeter wavelengths. Used as frequency doublers or triplers, diodes of new type extend frequency range of present solid-state oscillators.

  15. 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.

  16. Modal interactions between a large-wavelength inclined interface and small-wavelength multimode perturbations in a Richtmyer-Meshkov instability.

    PubMed

    McFarland, Jacob A; Reilly, David; Black, Wolfgang; Greenough, Jeffrey A; Ranjan, Devesh

    2015-07-01

    The interaction of a small-wavelength multimodal perturbation with a large-wavelength inclined interface perturbation is investigated for the reshocked Richtmyer-Meshkov instability using three-dimensional simulations. The ares code, developed at Lawrence Livermore National Laboratory, was used for these simulations and a detailed comparison of simulation results and experiments performed at the Georgia Tech Shock Tube facility is presented first for code validation. Simulation results are presented for four cases that vary in large-wavelength perturbation amplitude and the presence of secondary small-wavelength multimode perturbations. Previously developed measures of mixing and turbulence quantities are presented that highlight the large variation in perturbation length scales created by the inclined interface and the multimode complex perturbation. Measures are developed for entrainment, and turbulence anisotropy that help to identify the effects of and competition between each perturbations type. It is shown through multiple measures that before reshock the flow processes a distinct memory of the initial conditions that is present in both large-scale-driven entrainment measures and small-scale-driven mixing measures. After reshock the flow develops to a turbulentlike state that retains a memory of high-amplitude but not low-amplitude large-wavelength perturbations. It is also shown that the high-amplitude large-wavelength perturbation is capable of producing small-scale mixing and turbulent features similar to the small-wavelength multimode perturbations. PMID:26274285

  17. Modal interactions between a large-wavelength inclined interface and small-wavelength multimode perturbations in a Richtmyer-Meshkov instability

    NASA Astrophysics Data System (ADS)

    McFarland, Jacob A.; Reilly, David; Black, Wolfgang; Greenough, Jeffrey A.; Ranjan, Devesh

    2015-07-01

    The interaction of a small-wavelength multimodal perturbation with a large-wavelength inclined interface perturbation is investigated for the reshocked Richtmyer-Meshkov instability using three-dimensional simulations. The ares code, developed at Lawrence Livermore National Laboratory, was used for these simulations and a detailed comparison of simulation results and experiments performed at the Georgia Tech Shock Tube facility is presented first for code validation. Simulation results are presented for four cases that vary in large-wavelength perturbation amplitude and the presence of secondary small-wavelength multimode perturbations. Previously developed measures of mixing and turbulence quantities are presented that highlight the large variation in perturbation length scales created by the inclined interface and the multimode complex perturbation. Measures are developed for entrainment, and turbulence anisotropy that help to identify the effects of and competition between each perturbations type. It is shown through multiple measures that before reshock the flow processes a distinct memory of the initial conditions that is present in both large-scale-driven entrainment measures and small-scale-driven mixing measures. After reshock the flow develops to a turbulentlike state that retains a memory of high-amplitude but not low-amplitude large-wavelength perturbations. It is also shown that the high-amplitude large-wavelength perturbation is capable of producing small-scale mixing and turbulent features similar to the small-wavelength multimode perturbations.

  18. Radiative Smoothing in Clouds at Transparent and Absorbing Wavelengths

    NASA Technical Reports Server (NTRS)

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

    1999-01-01

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

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

    SciTech Connect

    Kita, Tomohiro Tang, Rui; Yamada, Hirohito

    2015-03-16

    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.

  20. Making Displaced Holograms At Two Wavelengths

    NASA Technical Reports Server (NTRS)

    Witherow, William K.; Ecker, Andreas

    1989-01-01

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

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

    NASA Technical Reports Server (NTRS)

    Montano, J. W.

    1987-01-01

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

  2. 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.

  3. Wavelength Effects In Femtosecond Pulsed Laser Ablation And Deposition

    SciTech Connect

    Castillejo, Marta; Nalda, Rebeca de; Oujja, Mohamed; Sanz, Mikel

    2010-10-08

    Ultrafast pulsed laser irradiation of solid materials is highly attractive for the micro-and nanostructuring of substrates and for the fabrication of nanostructured deposits. Femtosecond laser pulses promote efficient material removal with reduced heat transfer and high deposition rates of nanometer scale particles free of microscopic particulates. Most of the studies to date have been performed with light pulses centered around the peak wavelength of the Titanium:Sapphire laser, around 800 nm. Analysis of the process over a broader range of wavelengths can provide important information about the processes involved and serve as experimental tests for advanced theoretical models. We report on our current investigations on the effect that laser wavelength of femtosecond pulses has on the superficial nanostructuring induced on biopolymer substrates, and on the characteristics of nanostructured deposits grown by pulsed laser deposition from semiconductor targets.

  4. 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 μm 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.

  5. Turbulence driven magnetic reconnection causing long-wavelength magnetic islands

    SciTech Connect

    Ishizawa, A.; Nakajima, N.

    2010-07-15

    Magnetic reconnection caused by turbulence in a current sheet is studied by means of numerical simulations of fluid equations. It is found that turbulence produces long-wavelength magnetic islands even if the current sheet is so thick that spontaneous magnetic reconnection does not occur. Thus, turbulence modifies the threshold of magnetic island formation predicted by the conventional theory of spontaneous magnetic reconnection in a current sheet. In spite of the fact that the turbulence is driven by a short-wavelength instability due to a pressure gradient, the length of the magnetic island is the same order as the system size. The width of the island is several times the ion Larmor radius, and stronger turbulence causes wider magnetic islands. This suggests that the turbulence can trigger neoclassical tearing modes, which are the main nonlinear instability that limits the plasma pressure in magnetically confined plasmas. The long-wavelength magnetic island is formed by merging of small-scale magnetic islands.

  6. 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.

  7. Metallo-beta-Lactamase VIM-1, SPM-1, and IMP-1 Genes Among Clinical Pseudomonas aeruginosa Species Isolated in Zahedan, Iran

    PubMed Central

    Ghamgosha, Mehdi; Shahrekizahedani, Shahram; Kafilzadeh, Farshid; Bameri, Zakaria; Taheri, Ramezan Ali; Farnoosh, Gholamreza

    2015-01-01

    Background: One of the major clinical problems regarding Pseudomonas aeruginosa is attributed to metallo-beta-lactamases (MBL). This group of enzymes is a subset of beta lactamases which belong to group B of Ambler classification and cause hydrolysis of carbapenems. Based on epidemiological studies conducted worldwide, it is proved that prevalence of genes coding MBLs in P. aeruginosa species are different in various geographic zones and even in various hospitals. Therefore, according to the clinical importance of organisms generating MBLs, it is necessary to identify and control these bacteria in hospitals for therapeutic purposes. Objectives: The current study aimed to investigate the Metallo-beta-Lactamase VIM-1, SPM-1, and IMP-1 genes among clinical P. aeruginosa species isolated in Zahedan, Iran. Materials and Methods: The current study investigated the presence of MBL through phenotypic and genotypic methods and also the pattern of antibiotic resistance in P. aeruginosa species isolated in hospitals. The Minimum Inhibitory Concentration (MIC) against imipeneme was measured for 191 P. aeruginosa species isolated from Zahedan hospitals after identification through biochemical methods and determination of the antibiotic resistance pattern. Strains with MIC > 4 g/mL were studied by phenotypic and genotypic methods. Results: The rate of resistance against imipeneme was 5.7% and after carrying out the phenotypic experiments, nine species were identified as of MBL producer. Seven species were confirmed by Polymerase Chain Reaction (PCR) method. Gene VIM-1 was the predominant gene among the positive (antibiotic resistant) species. Conclusions: The study results showed that MBL genes were present in some of the species isolated from Zahedan hospitals. Regarding the importance of MBL producer bacteria in hospitals, quick identification and evaluation of these clinical species can be considered as an important and basic step for treatment and control of pseudomonad infections. PMID:26034547

  8. 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 β-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

  9. 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

  10. Bolometric Arrays for Millimeter Wavelengths

    NASA Astrophysics Data System (ADS)

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

    2009-11-01

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

  11. Refraction effects and wavelength dependence

    NASA Astrophysics Data System (ADS)

    Claverie, J.; Dion, D.

    2006-09-01

    The performances of Electro-Optical (EO) systems such as visible or infrared cameras, lasers, operating within the Marine Surface Boundary Layer (MSBL), i.e. at heights up to a few tens of meters above the sea surface, are disturbed by various propagation mechanisms: molecular attenuation, aerosol extinction, refraction and turbulence. Refraction is responsible for focusing and defocusing of rays, detection range limitations, mirage formation and angular deviation. The refractive index depends on atmospheric pressure, air temperature and air humidity. Within the optical transmission bands, it also depends on the wavelength. In this paper, the results provided by two different formulations of the refractive index associated with the same ray tracing program are compared and discussed.

  12. Michelson interferometer for laser wavelength

    NASA Astrophysics Data System (ADS)

    Wang, Liqiang; Ren, Wenjie

    2005-11-01

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

  13. Evaluation of clonality and carbapenem resistance mechanisms among Acinetobacter baumannii-Acinetobacter calcoaceticus complex and Enterobacteriaceae isolates collected in European and Mediterranean countries and detection of two novel ?-lactamases, GES-22 and VIM-35.

    PubMed

    Castanheira, Mariana; Costello, Sarah E; Woosley, Leah N; Deshpande, Lalitagauri M; Davies, Todd A; Jones, Ronald N

    2014-12-01

    We evaluated doripenem-resistant Acinetobacter baumannii-Acinetobacter calcoaceticus complex (ACB; n = 411) and Enterobacteriaceae (n = 92) isolates collected from patients from 14 European and Mediterranean countries during 2009 to 2011 for the presence of carbapenemase-encoding genes and clonality. Following susceptibility testing, carbapenem-resistant (doripenem MIC, >2 ?g/ml) isolates were screened for carbapenemases. New ?-lactamase genes were expressed in a common background and susceptibility was tested. Class 1 integrons were sequenced. Clonality was evaluated by pulsed-field gel electrophoresis and multilocus sequence typing (Pasteur scheme). Relative expression of ?-lactam intrinsic resistance mechanisms was determined for carbapenemase-negative Enterobacteriaceae. ACB and Enterobacteriaceae displayed 58.9 and 0.9% doripenem resistance, respectively. bla(OXA-23), bla(OXA-58), and bla(OXA-24/OXA-40) were detected among 277, 77, and 29 ACB, respectively (in 8, 6, and 5 countries). Ten Turkish isolates carried bla(GES-11) or bla(GES-22). GES-22 (G243A and M169L mutations in GES-1) had an extended-spectrum ?-lactamase profile. A total of 33 clusters of ? 2 ACB isolates were observed, and 227 isolates belonged to sequence type 2/international clone II. Other international clones were limited to Turkey and Israel. Doripenem-resistant Enterobacteriaceae increased significantly (0.7 to 1.6%), and 15 blaKPC-2- and 22 blaKPC-3-carrying isolates, mostly belonging to clonal complexes 11 and 258, were observed. Enterobacteriaceae isolates producing OXA-48 (n = 16; in Turkey and Italy), VIM-1 (n = 10; in Greece, Poland, and Spain), VIM-26 (n = 1; in Greece), and IMP-19, VIM-4, and the novel VIM-35 (n = 1 each from Poland) were detected. VIM-35 had one substitution compared to VIM-1 (A235T) and a similar susceptibility profile. One or more resistance mechanisms were identified in 4/6 carbapenemase-negative Enterobacteriaceae. This broad evaluation confirms results from country-specific surveys and shows a highly diverse population of carbapenemase-producing ACB and Enterobacteriaceae in Europe and Mediterranean countries. PMID:25267671

  14. Optical phase-space modes, self-focusing, and the wavelength as tunable ?

    NASA Astrophysics Data System (ADS)

    Zheltikov, A. M.

    2015-12-01

    The Hamiltonian optics notion of phase-space modes is shown to be central to understanding self-focusing, multiple filamentation, and the ?2 scaling of the self-focusing threshold with the radiation wavelength ?.

  15. 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.

  16. Wavelength Anomalies in UV-Vis Spectrophotometry

    NASA Astrophysics Data System (ADS)

    Tellinghuisen, J.

    2012-06-01

    Commercial spectrophotometers are great tools for recording absorption spectra of low-to-moderate resolution and high photometic quality. However, in the case of at least one such instrument, the Shimadzu UV-2101PC (and by assumption, similar Shimadzu models), the wavelength accuracy may not match the photometric accuracy. In fact the wavelength varies with slit width, spectral sampling interval, and even the specified range, with a smoothing algorithm invoked any time the spectrum includes more than 65 sampled wavelengths. This behavior appears not to be documented anywhere, but it has been present for at least 20 years and persists even in the latest software available to run the instrument. The wavelength shifts can be as large as 1 nm, so for applications where wavelength accuracy better than this is important, wavelength calibration must be done with care to ensure that the results are valid for the parameters used to record the target spectra.

  17. Optical wavelength converters for photonic band gap microcircuits

    SciTech Connect

    Vujic, Dragan; John, Sajeev

    2009-05-15

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

  18. 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.

  19. 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.

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

    PubMed

    De Bièvre, Paul

    2009-03-01

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

  1. The universe at infrared wavelengths

    NASA Technical Reports Server (NTRS)

    Beichman, C. A.

    1988-01-01

    This article discusses the status of infrared astronomy after the mission of the Infrared Astronomical Satellite (IRAS). Important scientific results from IRAS include: the origin of the interplanetary dust cloud, the formation of solar type stars, the energetics of the interstellar medium, the discovery of ultra-luminous infrared galaxies and their possible relation to the origin of quasars, and the large scale structure of the universe.

  2. 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

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

    NASA Astrophysics Data System (ADS)

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

    2012-04-01

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

  4. Optimum wavelengths for two color ranging

    NASA Technical Reports Server (NTRS)

    Degnan, John J.

    1993-01-01

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

  5. Wavelength specific excitation of gold nanoparticle thin-films

    NASA Astrophysics Data System (ADS)

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

    2014-01-01

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

  6. The Anticyclonic Eye of the Storm: Evolution of Saturns 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 Saturns 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.

  7. The Ongoing Evolution of a Long-Lived Anticyclone in Saturn’s Great Storm Region as seen by Cassini/VIMS

    NASA Astrophysics Data System (ADS)

    Momary, Thomas W.; Baines, Kevin H.; Badman, Sarah; Brown, Robert H.; Buratti, Bonnie J.; Clark, Roger N.; Nicholson, Philip D.; Sotin, Christophe

    2015-11-01

    Once the home of the enigmatic String of Pearls feature on Saturn, the region of 34o N was the scene of a titanic storm system that swept around the planet in late 2010/2011. It left two things in its wake - a clear 5-μm bright zone around the planet, and a curious and persistent anticylone, both of which remain to this day. We have observed this anticyclone with Cassini/VIMS since 2011 and find that it seems to oscillate up and down latitudinally in this stormy region. Centered at 35.9o planetocentric latitude in May 2011, it drifted northward to 37.8o in 2012, hovered near 37o through 2013, then settled southward back down to ~35.9o in 2014. 2015 has it once again drifting northward to ~37o. It also periodically interacts with the dark band above it exchanging material in August 2013 and May 2015. We measured a prograde zonal drift speed of ~22 m/s in 2012, increasing as much as 60% through 2013, then relaxing back to a more moderate ~15 m/s in 2014 as the oval sagged southward. We expect its current 15.4 m/s rate to increase if it continues to drift northward in latitude, following the Voyager wind profile. The feature has varied in size as well, spanning 4.9o x 3.2o in 2011, elongating zonally to 7.3o x 2.9o by 2013, contracting in 2014 to an average of ~5.5o x ~2.9o, and growing again to ~9o x ~4o in 2015, with an extended tendril of material streaming off one edge in May. By August, it was symmetrically oval again. It has varied in terms of cloudiness, being ~90% 5-μm dark (obscured) in 2011, whereas by 2013 it was mostly bright (clear) with a thin dark edge, now returning to ~90% dark in 2015. By utilizing night observations to isolate thermal flux, we find that the mean 5-μm flux coming from the anticyclone has diminished steadily by about 50% since 2013. The storm latitude of ~34o N itself has remained remarkably 5-μm bright since 2011, but has begun to dim as well, and is now bisected by a thin dark cloudy ribbon which appears associated with the anticyclone. We are continuing to monitor the evolution of the anticyclone and the Storm Region over time with Cassini/VIMS.

  8. 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.

  9. 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[β \\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[β \\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.

  10. 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.

  11. 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 Central

    Kulkarni, M. V.; Zurita, A. N.; Pyka, J. S.; Murray, T. S.; Hodsdon, M. E.

    2014-01-01

    Resistance to extended-spectrum β-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 μg/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

  12. 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 β-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 μg/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

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

    NASA Astrophysics Data System (ADS)

    Montano, J. W.

    1986-09-01

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

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

    NASA Technical Reports Server (NTRS)

    Montano, J. W.

    1986-01-01

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

  15. Differential Expression of ADAM23, CDKN2A (P16), MMP14 and VIM Associated with Giant Cell Tumor of Bone

    PubMed Central

    Conceição, André Luis Giacometti; Babeto, Erica; Candido, Natalia Maria; Franco, Fernanda Craveiro; de Campos Zuccari, Débora Aparecida Pires; Bonilha, Jane Lopes; Cordeiro, José Antônio; Calmon, Marilia Freitas; Rahal, Paula

    2015-01-01

    Though benign, giant cell tumor of bone (GCTB) can become aggressive and can exhibit a high mitotic rate, necrosis and rarely vascular invasion and metastasis. GCTB has unique histologic characteristics, a high rate of multinucleated cells, a variable and unpredictable growth potential and uncertain biological behavior. In this study, we sought to identify genes differentially expressed in GCTB, thus building a molecular profile of this tumor. We performed quantitative real-time polymerase chain reaction (qPCR), immunohistochemistry and analyses of methylation to identify genes that are putatively associated with GCTB. The expression of the ADAM23 and CDKN2A genes was decreased in GCTB samples compared to normal bone tissue, measured by qPCR. Additionally, a high hypermethylation frequency of the promoter regions of ADAM23 and CDKN2A in GCTB was observed. The expression of the MAP2K3, MMP14, TIMP2 and VIM genes was significantly higher in GCTB than in normal bone tissue, a fact that was confirmed by qPCR and immunohistochemistry. The set of genes identified here furthers our understanding of the molecular basis of GCTB. PMID:26078788

  16. Mars: Wavelength-dependent dual polarization global scattering

    NASA Technical Reports Server (NTRS)

    Harmon, J. K.; Slade, M. A.; Hudson, R. S.

    1992-01-01

    During the 1988 and 1990 Mars oppositions, the first continuous-wave (CW) multi-wavelength radar observations were performed that include the entire echo in both polarizations. These observations, coordinated in subradar coverage when possible, were made with the Arecibo S-band (12.6 cm lambda) and Goldstone X-band (3.5 cm lambda) facilities. The CW spectra obtained during these oppositions have been studied using a variety of techniques to explore the spatial and wavelength dependence of both the Same-sense Circular (SC) and Opposite-sense Circular (OC) polarization returns. Earlier multi-wavelength comparisons dealt primarily with the quasispecular component of the echoes. Our work in contrast has much new information (at high signal-to-noise) for the SC 'depolarized component. The unique value of these radar observations lies in their potential for probing the subsurface scattering behavior in 'appropriate' terrain. The clearest case for wavelength dependence in the SC component is the scattering behavior over Tharsis, where the X-band features are significantly weaker than the S-band features. This hypothesis was advanced to account for the low thermal inertia of Tharsis, but also can explain the S/X differences if the layer is about 40 cm thick. In contrast to the Tharsis result, the depolarized echo from the heavily cratered terrain is actually stronger at X-band. The obvious interpretation is that more scatterers exist at the scale of the shorter wavelength, either at the surface or as a distributed subsurface scatterers. The strongest depolarized feature of the X-band spectra is associated with the south residual polar cap. The radar cross section of this feature corresponds to an equivalent full-disk albedo of unity.

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

    SciTech Connect

    Munoz, D. J.; Moran, J. M.; Marrone, D. P.; 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 {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.

  18. Wavelengths effective in induction of malignant melanoma

    SciTech Connect

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

    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.

  19. Experimental verification of acoustic trace wavelength enhancement.

    PubMed

    Cray, Benjamin A

    2015-12-01

    Directivity is essentially a measure of a sonar array's beamwidth that can be obtained in a spherically isotropic ambient noise field; narrow array mainbeam widths are more directive than broader mainbeam widths. For common sonar systems, the directivity factor (or directivity index) is directly proportional to the ratio of an incident acoustic trace wavelength to the sonar array's physical length (which is always constrained). Increasing this ratio, by creating additional trace wavelengths for a fixed array length, will increase array directivity. Embedding periodic structures within an array generates Bragg scattering of the incident acoustic plane wave along the array's surface. The Bragg scattered propagating waves are shifted in a precise manner and create shorter wavelength replicas of the original acoustic trace wavelength. These replicated trace wavelengths (which contain identical signal arrival information) increase an array's wavelength to length ratio and thus directivity. Therefore, a smaller array, in theory, can have the equivalent directivity of a much larger array. Measurements completed in January 2015 at the Naval Undersea Warfare Center's Acoustic Test Facility, in Newport, RI, verified, near perfectly, these replicated, shorter, trace wavelengths. PMID:26723331

  20. Wavelength initialization employing wavelength recognition scheme in WDM-PON based on tunable lasers

    NASA Astrophysics Data System (ADS)

    Mun, Sil-Gu; Lee, Eun-Gu; Lee, Jong Hyun; Lee, Sang Soo; Lee, Jyung Chan

    2015-01-01

    We proposed a simple method to initialize the wavelength of tunable lasers in WDM-PON employing wavelength recognition scheme with an optical filter as a function of wavelength and accomplished plug and play operation. We also implemented a transceiver based on our proposed wavelength initialization scheme and then experimentally demonstrated the feasibility in WDM-PON configuration guaranteeing 16 channels with 100 GHz channel spacing. Our proposal is a cost-effective and easy-to-install method to realize the wavelength initialization of ONU. In addition, this method will support compatibility with all kind of tunable laser regardless of their structures and operating principles.

  1. 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.

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

    NASA Astrophysics Data System (ADS)

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

    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.

  3. A novel wavelength availability advertisement based ASON routing protocol implementation

    NASA Astrophysics Data System (ADS)

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

    2005-11-01

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

  4. Wavelength references for interferometry in air

    SciTech Connect

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

    2005-12-20

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

  5. Magic wavelengths for terahertz clock transitions

    SciTech Connect

    Zhou Xiaoji; Xu Xia; Chen Xuzong; Chen Jingbiao

    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.

  6. Engineering reverse saturable absorbers for desired wavelengths

    NASA Astrophysics Data System (ADS)

    Band, Yehuda B.; Scharf, Benjamin

    1986-06-01

    A variety of applications exist for reverse saturable absorbers (RSAs) in laser science (RSAs are substances whose excited-state absorption cross section is larger than their ground-state absorption cross section at a given wavelength and possess a number of other properties). We propose an approach to designing RSAs at a desired wavelength by construction of dimers of dye molecules which absorb near the wavelength of interest. The dimer ground-state absorption is to a state in which the excitation is spread over both monomeric units and the excited-state absorption commences from this state to the doubly excited electronic state in which both monomeric units are excited.

  7. 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.

  8. 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.

  9. 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.

  10. Multiple wavelength photolithography for preparing multilayer microstructures

    DOEpatents

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

    2003-06-24

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

  11. Wavelength-agile optical access networking system

    NASA Astrophysics Data System (ADS)

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

    2011-12-01

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

  12. 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.

  13. Multiple-Wavelength Pyrometry Independent Of Emissivity

    NASA Technical Reports Server (NTRS)

    Ng, Daniel

    1996-01-01

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

  14. Tunable wavelength conversion in optical networks

    NASA Astrophysics Data System (ADS)

    Tzanakaki, Anna

    This thesis focuses on the properties and characteristics of all-optical tunable wavelength converters based on semiconductor optical amplifiers (SOAs) and their applications in future all-optical networks. A novel detailed theoretical model that investigates the features of tunable converters based on cross-gain modulation in SOAs, operating in the counter-propagating mode was developed. Theoretical evaluation of the performance of the converter was carried out and the results were experimentally verified. The penalty introduced in WDM systems due to crosstalk imposed by wavelength converters was analysed and calculated. Theoretical evaluation of a Mach-Zehnder interferometric wavelength converter, based on cross-phase modulation in SOAs, was performed and experimental results using an all-active Mach-Zehnder interferometer were obtained. An optical cross-connect (OXC) design comprising a passive wavelength router and tunable wavelength converters was implemented and evaluated employing both an InP and an arrayed waveguide grating router (AWG). Very good concatenation performance of the OXC utilising the AWG router was demonstrated through a recirculating loop experiment. The cascading performance of a reduced crosstalk OXC architecture that incorporates an AWG and dual wavelength conversion stage was also investigated. Experimental evaluation on the effect of systems employing partial wavelength conversion in the transmission performance of WDM channels was carried out. Cross-gain modulation in SOAs operating in the counter- propagating mode was proposed, for optical packet switching applications that require fast tunable wavelength conversion. The WASPNET packet switch node incorporating this type of converter is described and results from the final project demonstrator are presented.

  15. Superlattice Long-Wavelength Infrared Sensors

    NASA Technical Reports Server (NTRS)

    Fathauer, Robert W.

    1990-01-01

    Superlattice of LaN and Si detects at wavelengths up to 12 micrometers. If LaN grown epitaxially on silicon, sensitivity of silicon-based photodetectors extended farther into infrared wavelength region with high quantum detection efficiency by use of LaN/Si superlattices. In principle, by appropriate choice of thicknesses of layers, effective band-gap energy of superlattice structure set to any desired value between band gaps of two materials.

  16. Observations of Venus at 1-meter wavelength

    NASA Astrophysics Data System (ADS)

    Butler, Bryan J.

    2014-11-01

    Radio wavelength observations of Venus (including from the Magellan spacecraft) have been a powerful method of probing its surface and atmosphere since the 1950's. The emission is generally understood to come from a combination of emission and absorption in the subsurface, surface, and atmosphere at cm and shorter wavelengths [1]. There is, however, a long-standing mystery regarding the long wavelength emission from Venus. First discovered at wavelengths of 50 cm and greater [2], the effect was later confirmed to extend to wavelengths as short as 13 cm [1,3]. The brightness temperatures are depressed significantly 50 K around 10-20 cm, increasing to as much as 200 K around 1 m) from what one would expect from a "normal" surface (e.g., similar to the Moon or Earth) [1-3].No simple surface and subsurface model of Venus can reproduce these large depressions in the long wavelength emission [1-3]. Simple atmospheric and ionospheric models fail similarly. In an attempt to constrain the brightness temperature spectrum more fully, new observations have been made at wavelengths that cover the range 60 cm to 1.3 m at the Very Large Array, using the newly available low-band receiving systems there [4]. The new observations were made over a very wide wavelength range and at several Venus phases, with that wide parameter space coverage potentially allowing us to pinpoint the cause of the phenomenon. The observations and potential interpretations will be presented and discussed.[1] Butler et al. 2001, Icarus, 154, 226. [2] Schloerb et al. 1976, Icarus, 29, 329; Muhleman et al. 1973, ApJ, 183, 1081; Condon et al. 1973, ApJ, 183, 1075; Kuzmin 1965, Radiophysics. [3] Butler & Sault 2003, IAUSS, 1E, 17B. [4] Intema et al. 2014, BASI, 1.

  17. Long-wavelength VCSELs for sensing applications

    NASA Astrophysics Data System (ADS)

    Ortsiefer, M.; Rosskopf, J.; Neumeyr, C.; Gründl, T.; Grasse, C.; Chen, J.; Hangauer, A.; Strzoda, R.; Gierl, C.; Meissner, P.; Küppers, F.; Amann, M.-C.

    2012-03-01

    Long-wavelength VCSELs with emission wavelengths beyond 1.3 μm have seen a remarkable progress over the last decade. This success has been accomplished by using highly advanced device concepts which effectively overcome the fundamental technological drawbacks related with long-wavelength VCSELs such as inferior thermal properties and allow for the realization of lasers with striking device performance. In this presentation, we will give an overview on the state of the technology for long-wavelength VCSELs in conjunction with their opportunities in applications for optical sensing. While VCSELs based on InP are limited to maximum emission wavelengths around 2.3 μm, even longer wavelengths up to the mid-infrared range beyond 3 μm can be achieved with VCSELs based on GaSb. For near-infrared InP-based VCSELs, the output characteristics include sub-mA threshold currents, up to several milliwatts of singlemode output power and ultralow power consumption. New concepts for widely tunable VCSELs with tuning ranges up to 100 nm independent from the material system for the active region are also presented. Today, optical sensing by Tunable Diode Laser Spectroscopy is a fast emerging market. Gas sensing systems are used for a wide range of applications such as industrial process control, environmental monitoring and safety applications. With their inherent and compared to other laser types superior properties including enhanced current tuning rates, wavelength tuning ranges, modulation frequencies and power consumption, long-wavelength VCSELs are regarded as key components for TDLS applications.

  18. A three wavelength scheme to optimize hohlraum coupling on the National Ignition Facility

    SciTech Connect

    Michel, P; Divol, L; Town, R; Rosen, M

    2010-12-16

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

  19. The fabrication of millimeter-wavelength accelerating structures

    SciTech Connect

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

    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.

  20. Multi-Wavelength Observations of Nearby Starburst Galaxies

    NASA Astrophysics Data System (ADS)

    Lee, Janice

    2015-08-01

    Do cycles of violent, intense, but short-lived bursts constitute a significant mode of global star formation in present-day galaxies? Such events can have a profound effect on galaxies, particularly those with shallow potential wells, and observational measures of their prevalence inform our understanding of a wide range of issues in galaxy evolution. I will highlight what we have learned about starbursts from multi-wavelength observations of galaxies in the local volume on both galactic and smaller scales, and explore how connections with the study of the deaths of massive stars may further our understanding of open issues in galaxy evolution.

  1. C-band wavelength conversion in silicon photonic wire waveguides.

    PubMed

    Espinola, Richard; Dadap, Jerry; Osgood, Richard; McNab, Sharee; Vlasov, Yurii

    2005-05-30

    We demonstrate C-band wavelength conversion in Si photonic-wire waveguides with submicron cross-section by means of nonresonant, nondegenerate four-wave mixing (FWM) using low-power, cw-laser sources. Our analysis shows that for these deeply scaled Si waveguides, FWM can be observed despite the large phase mismatch imposed by strong waveguide dispersion. The theoretical calculations agree well with proof-of-concept experiments. The nonresonant character of the FWM scheme employed allows to demonstrate frequency tuning of the idler from ~ 20 GHz to > 100 GHz thus covering several C-band DWDM channels. PMID:19495349

  2. C-band wavelength conversion in silicon photonic wire waveguides

    NASA Astrophysics Data System (ADS)

    Espinola, Richard L.; Dadap, Jerry I.; Osgood, Richard M., Jr.; McNab, Sharee J.; Vlasov, Yurii A.

    2005-05-01

    We demonstrate C-band wavelength conversion in Si photonic-wire waveguides with submicron cross-section by means of nonresonant, nondegenerate four-wave mixing (FWM) using low-power, cw-laser sources. Our analysis shows that for these deeply scaled Si waveguides, FWM can be observed despite the large phase mismatch imposed by strong waveguide dispersion. The theoretical calculations agree well with proof-of-concept experiments. The nonresonant character of the FWM scheme employed allows to demonstrate frequency tuning of the idler from ~ 20 GHz to > 100 GHz thus covering several C-band DWDM channels.

  3. 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.

  4. Intermediate wavelength magnetic anomalies over ocean basins

    SciTech Connect

    Harrison, C.G.A.; Carle, H.M.

    1981-12-10

    We have examined three very long magnetic field profiles taken over ocean basins for the presence of intermediate wavelength magnetic anomalies. One profile was from the Atlantic Ocean in the Transatlantic Geotraverse area, one ran along latitude 35/sup 0/S in the SE Pacific, and one ran along 150/sup 0/W in the Pacific. All three profiles show the presence of intermediate wavelength (65--1500 km) magnetic anomalies generated in the crust or upper mantle. The analysis of magnetic field power spectra shows that the core field becomes unimportant at about a wavelength of 1500 km. Sea floor spreading anomalies should produce a maximum in power at about a wavelength of 65 km. Between these two wavelengths there should be a minimum in power which is not seen on observed records. Inverting the anomalous field to obtain some idea of the magnetization necessary to explain these intermediate wavelength magnetic anomalies shows that values of magnetization in excess of 1 A m/sup -1/ are needed if the magnetized layer is as thick as the ocean crust. Alternatively, rather large thicknesses of upper mantle material with lower intensities of magnetization need to be used. The reason why such magnetization variations exist is not known. It can be shown that upward continuation of the magnetic anomaly signature to an altitude of 350 km (about the perihelion altitude of MAGSAT) will produce anomalies up to 10 nT in amplitude. These should be capable of being seen by MAGSAT, and thus allow us to determine the spatial arrangement of the intermediate wavelength anomalies and hence, hopefully, a clue as to their origin.

  5. Optical lithography at a 126-nm wavelength

    NASA Astrophysics Data System (ADS)

    Kang, Hoyoung; Bourov, Anatoly; Smith, Bruce W.

    2001-08-01

    There is a window of opportunity for optical lithography between wavelengths of 100 nm and 157 nm that warrants exploration as a next generation technology. We will present activities underway to explore the feasibility of VUV optical lithography in this region with respect to source, optical design, materials, processes, masks, resolution enhancement, and compatibility with existing technologies. We have constructed a small field prototype lithography system using the second continuum 126nm emission wavelength of the Argon excimer. This has been accomplished using a small dielectric barrier discharge lamp with output on the order of 10mW/cm2 and small field catoptric imaging systems based on a modified Cassegrain system. Capacitance focus gauge and piezo electric stage has been installed for fine focusing. In order to achieve sub-half wavelength resolution that would be required to compete with 157nm lithography and others, we have started exploring the feasibility of using liquefied noble gas immersion fluids to increase effective value of lens numerical aperture by factors approaching 1.4x. Conventional silylation process works well with 126nm with high sensitivity. Chemically amplified DUV negative resist looks very good material for 126 nm. Initial contact printing image shows good selectivity and process control. An effort is also underway to explore the use of inorganic resist materials, as silver halide material for instance, to replace the conventional polymeric imaging systems that are currently employed at longer wavelengths, but may be problematic at these VUV wavelengths. Early accomplishments are encouraging. Prototype optical research tools can be used to reveal issues involved with 126nm lithography and solve initial problems. Though many challenges do exist at this short wavelength, it is quite feasible that lithography at this wavelength could meet the part of the needs of future device generations.

  6. Efficient multicast routing in wavelength-division-multiplexing networks with light splitting and wavelength conversion

    NASA Astrophysics Data System (ADS)

    Zheng, Sheng; Tian, Jinwen; Liu, Jian

    2005-04-01

    We propose wavelength-division-multiplexing (WDM) networks with light splitting and wavelength conversion that can efficiently support multicast routing between nodes. Our iterative algorithm analyzes the original multicast routing network by decomposing it into multicast subgroups. These subgroups have the same wavelength, and the individual subgroup is combined to build a multicast tree. From the multicast tree, we can compute efficiently to multicast for short paths. Numerical results obtained for the ARPANET show that our algorithm can greatly reduce the optical blocking probability and the number of required wavelength conversions.

  7. Tn6249, a new Tn6162 transposon derivative carrying a double-integron platform and involved with acquisition of the blaVIM-1 metallo-?-lactamase gene in Pseudomonas aeruginosa.

    PubMed

    Di Pilato, Vincenzo; Pollini, Simona; Rossolini, Gian Maria

    2015-03-01

    The In70.2 integron platform appears to be a conserved structure involved in the dissemination of the blaVIM-1 metallo-?-lactamase gene in Pseudomonas aeruginosa. The genetic context of the In70.2 integron platform from P. aeruginosa VR-143/97, the VIM-1-producing index strain isolated in Italy in 1997, was fully characterized by a next-generation sequencing approach refined by conventional sequencing. The In70.2 integron platform from VR-143/97 was found to be associated with a defective Tn402-like transposon inserted into the urf2 gene of a Tn3 family transposon of an original structure, named Tn6249, which also carried a partially deleted mer operon and an In90 integron platform in a tail-to-tail orientation. Tn6249 was inserted into a PACS171b-like genomic island, which was in turn inserted into the endA gene of the Pseudomonas chromosomal backbone. Tn6249 showed a similar structure and a conserved location with respect to that of Tn6060, a Tn3 family transposon associated with In70.2 and carrying a double-integron platform, which was detected in a VIM-1-producing P. aeruginosa strain isolated in Australia in 2008. Both Tn6249 and Tn6060 are apparently derived from Tn6162, a mercury resistance transposon carrying an integron platform, which was found in P. aeruginosa isolates from different geographic locations. The conservation of the genetic context of Tn6249 and Tn6060 suggests an in situ evolution of these elements after the insertion of a Tn6162-like ancestor into the PACS171b-like genomic island (GI) present in the genome of a successful widespread P. aeruginosa clonal lineage. PMID:25547348

  8. 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.

  9. Plasmonic All-Optical Tunable Wavelength Shifter

    SciTech Connect

    Flugel, B.; Macararenhas, A.; Snoke, D. W.; Pfeiffer, L. N.; West, K.

    2007-12-01

    At present, wavelength-division-multiplexed fibre lines routinely operate at 10 Gbit s{sup -1} per channel. The transition from static-path networks to true all-optical networks encompassing many nodes, in which channels are added/dropped and efficiently reassigned, will require improved tools for all-optical wavelength shifting. Specifically, one must be able to shift the carrier wavelength (frequency) of an optical data signal over tens of nanometres (a THz range) without the bottleneck of electrical conversion. Popular approaches to this problem make use of the nonlinear interaction between two wavelengths within a semiconductor optical amplifier whereas more novel methods invoke terahertz-frequency electro-optic modulation and polaritons. Here we outline the principles and demonstrate the use of optically excited plasmons as a tunable frequency source that can be mixed with a laser frequency through Raman scattering. The scheme is all-optical and enables dynamical control of the output carrier wavelength simply by varying the power of a control laser.

  10. Two wavelength satellite laser ranging using SPAD

    NASA Technical Reports Server (NTRS)

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

    1993-01-01

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

  11. Characterisation of IncA/C2 plasmids carrying an In416-like integron with the blaVIM-19 gene from Klebsiella pneumoniae ST383 of Greek origin.

    PubMed

    Papagiannitsis, Costas C; Dolejska, Monika; Izdebski, Rados?aw; Giakkoupi, Panagiota; Sklov, Anna; Chud?jov, Kate?ina; Dobiasova, Hana; Vatopoulos, Alkiviadis C; Derde, Lennie P G; Bonten, Marc J M; Gniadkowski, Marek; Hrabk, Jaroslav

    2016-02-01

    The complete nucleotide sequences of three multidrug resistance (MDR) IncA/C-like plasmids from Enterobacteriaceae isolates carrying the VIM-type carbapenemase-encoding integrons In4863 (blaVIM-19-aacA7-dfrA1-?aadA1-smr2) or In4873 (blaVIM-1-aacA7-dfrA1-?aadA1-smr2) were determined, which are the first In416-like elements identified in Greece. Plasmids pKP-Gr642 and pKP-Gr8143 were from Klebsiella pneumoniae ST383 isolates, whereas plasmid pEcl-Gr4873 was from an Enterobacter cloacae ST88 isolate. Sequencing showed that pKP-Gr642 (162787bp) and pKP-Gr8143 (154395bp) consisted of the type 1 IncA/C2 conserved backbone, the blaCMY-2-like gene-containing region, and the ARI-B (with the sul2 gene) and ARI-A (with a class 1 integron) resistance islands, like the plasmid pUMNK88_161 from the USA. The third plasmid, pEcl-Gr4873 (153958bp), exhibited extensive similarity with the type 2 IncA/C2 plasmid pR55 from France. pEcl-Gr4873 carried only one resistance island of a hybrid transposon structure inserted in a different location to ARI-A in type 1 A/C2 plasmids. In all three plasmids, the In416-like integrons In4863 or In4873 were identified within non-identical class II transposon structures. All three In416-like-carrying regions presented significant similarities with the MDR region of the IncA/C2 plasmid pCC416 from Italy, carrying the prototype In416 integron (blaVIM-4-aacA7-dfrA1-?aadA1-smr2). These findings provided the basis for speculations regarding the evolution of IncA/C2 plasmids with In416-like integrons, and confirmed the rapid evolution of some IncA/C2 plasmid lineages. Considering the broad host range of IncA/C2 molecules, it seems that pKP-Gr642, pKP-Gr8143 and pEcl-Gr4873 plasmids might support the diffusion of In416-like integrons among Enterobacteriaceae. PMID:26795022

  12. Radar Images of the Ice Deposits at Mercury's North Pole at 70-cm Wavelength

    NASA Astrophysics Data System (ADS)

    Black, Gregory J.; Campbell, D. B.; Harmon, J. K.

    2009-09-01

    Radar imaging of Mercury's north polar region was done using the Arecibo Observatory's 70-centimeter wavelength radar system during the inferior conjunction of July 1999. We have clearly detected the highly reflective region at Mercury's north pole first identified in radar images at the shorter wavelengths 3.6-cm and 13-cm [1,2]. The average 70-cm wavelength reflectivity of this polar region is similar to that measured at the other wavelengths over a comparable area, and the polarization ratio of 0.87 is only slightly lower. This ratio is formed from echo power returned in both circular polarizations when only one polarization is transmitted, and the observed depolarization is indicative of a multiple scattering mechanism. High resolution delay-Doppler radar maps at 3.5-cm and 13-cm wavelengths (most recently [3,4]) have demonstrated that these enhancements are located within craters near the pole, suggesting they result from ice deposits in these cold permanently shadowed depressions. Characterizing these areas is also a key goal of the current MESSENGER mission. The low absorption coefficient of ice at radio wavelengths can permit sub-surface multiple scattering mechanisms and enhance radar backscattering. Persistence of this effect over more than an order of magnitude in wavelength scale has implications for the depth and thickness of the deposits. A strong effect at the shortest wavelength implies a thin attenuating overburden. Since multiple scattering mechanisms generally require a medium many wavelengths thick, the strong effect at the long wavelength may set a minimum depth of the deposits. We acknowledge support from the NASA PG&G Program. Arecibo Observatory is part of the National Astronomy and Ionosphere Center, operated by Cornell University under cooperative agreement with the NSF. [1] Slade et al., 1992, Science 258, 635; [2] Harmon & Slade, 1992, Science 258, 640; [3] Harmon et al., 1994, Nature 369, 213; [4] Harcke, 2005, PhD Thesis, Stanford.

  13. Cryogenic Amplifier Based Receivers at Submillimeter Wavelengths

    NASA Technical Reports Server (NTRS)

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

    2012-01-01

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

  14. Dynamic polarizabilities and magic wavelengths for dysprosium

    SciTech Connect

    Dzuba, V. A.; Flambaum, V. V.; Lev, Benjamin L.

    2011-03-15

    We theoretically study dynamic scalar polarizabilities of the ground and select long-lived excited states of dysprosium, a highly magnetic atom recently laser cooled and trapped. We demonstrate that there is a set of magic wavelengths of the unpolarized lattice laser field for each pair of states, which includes the ground state and one of these excited states. At these wavelengths, the energy shift due to laser field is the same for both states, which can be useful for resolved sideband cooling on narrow transitions and precision spectroscopy. We present an analytical formula that, near resonances, allows for the determination of approximate values of the magic wavelengths without calculating the dynamic polarizabilities of the excited states.

  15. Mechanisms and Methods for Selective Wavelength Filtering

    NASA Technical Reports Server (NTRS)

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

    2007-01-01

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

  16. Device for wavelength-selective imaging

    SciTech Connect

    Frangioni, John V.

    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.

  17. On storage rings for short wavelength FELs

    SciTech Connect

    Chattopadhyay, S.

    1990-01-01

    Significant advances have been made recently in the understanding of FEL physics and the technology of associated systems. We have witnessed experimental successes in the operation of FELs from the far infrared to the visible and near UV. All of the basic physics of FELs, as advanced up to date, in the small and high gain regimes (including exponential growth from noise, optical guiding, etc.) have been proved experimentally in the near or far infrared. These successes motivate us to explore the design of FEL systems at even shorter wavelengths, in the UV, XUV and soft x-ray regions, assuming that the same physics remain valid at these wavelengths. This paper is concerned with issues in the physics and design of storage rings as drivers of short wavelength FELs. 10 refs., 4 figs., 1 tab.

  18. Solar Radius Variations: An Inquisitive Wavelength Dependence

    NASA Astrophysics Data System (ADS)

    Rozelot, Jean Pierre; Kosovichev, Alexander; Kilcik, Ali

    2015-10-01

    Recent solar radius determinations from space observations of Mercury and Venus transits have been made by different teams in 2003, 2006, 2012, and 2014. Seemingly the results are not consistent: the authors interpreted the discrepancies as caused by the different methods of analysis. However, looking at the wavelength dependence and adding other available observations from X-EUV up to radio, a typical wavelength dependence can be found, reflecting the different heights at which the lines are formed. Measurements obtained during different periods of time would, in principle, allow us to detect a signature of radius temporal dependence. However, the available data are not sufficiently numerous to detect a significant dependence, at least at the level of the uncertainty at which the observations were made. Lastly, no unique theoretical model is available today to reproduce the strong wavelength dependence of the solar radius, which shows an unexpected minimum at around (6.6 1.9) ?m, after a parabolic fit.

  19. 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.

  20. Microring-based ratio-metric wavelength monitor on silicon.

    PubMed

    Yang, Bing; Shen, Ao; Qiu, Chen; Hu, Ting; Yang, Longzhi; Yu, Hui; Jiang, Xiaoqing; Li, Yubo; Hao, Yinlei; Yang, Jianyi

    2014-06-01

    An integrated dual-ring ratio-metric wavelength monitor (DR-RMWM) with ultra-high wavelength resolution and compact size is demonstrated. Two microrings are used as the edge filters and designed to achieve an "X-type" spectral response in a particular wavelength range. It is fabricated with the CMOS-compatible fabrication process on the silicon-on-insulator. The measured wavelength resolution is 5pm in a 1.2nm wide wavelength range. By tuning the resonant wavelength thermally, the functional wavelength range can be shifted. The DR-RMWM can find applications in wavelength monitoring systems, especially the on-chip systems. PMID:24876037

  1. Wavelength-Selective Photovoltaics for Power-generating Greenhouses

    NASA Astrophysics Data System (ADS)

    Carter, Sue; Loik, Michael; Shugar, David; Corrado, Carley; Wade, Catherine; Alers, Glenn

    2014-03-01

    While photovoltaic (PV) technologies are being developed that have the potential for meeting the cost target of 0.50/W per module, the cost of installation combined with the competition over land resources could curtail the wide scale deployment needed to generate the Terrawatts per year required to meet the world's electricity demands. To be cost effective, such large scale power generation will almost certainly require PV solar farms to be installed in agricultural and desert areas, thereby competing with food production, crops for biofuels, or the biodiversity of desert ecosystems. This requirement has put the PV community at odds with both the environmental and agricultural groups they would hope to support through the reduction of greenhouse gas emissions. A possible solution to this challenge is the use of wavelength-selective solar collectors, based on luminescent solar concentrators, that transmit wavelengths needed for plant growth while absorbing the remaining portions of the solar spectrum and converting it to power. Costs are reduced through simultaneous use of land for both food and power production, by replacing the PV cells by inexpensive long-lived luminescent materials as the solar absorber, and by integrating the panels directly into existing greenhouse or cold frames. Results on power generation and crop yields for year-long trials done at academic and commercial greenhouse growers in California will be presented.

  2. Rapid Intrinsic Variability of SGR A* at Radio Wavelengths

    NASA Astrophysics Data System (ADS)

    Yusef-Zadeh, F.; Wardle, M.; Miller-Jones, J. C. A.; Roberts, D. A.; Grosso, N.; Porquet, D.

    2011-03-01

    Sgr A* exhibits flares in radio, millimeter, and submillimeter wavelengths with durations of ~1 hr. Using structure function, power spectrum, and autocorrelation function analysis, we investigate the variability of Sgr A* on timescales ranging from a few seconds to several hours and find evidence for subminute timescale variability at radio wavelengths. These measurements suggest a strong case for continuous variability from subminute to hourly timescales. This short timescale variability constrains the size of the emitting region to be less than 0.1 AU. Assuming that the minute timescale fluctuations of the emission at 7 mm arise through the expansion of regions of optically thick synchrotron-emitting plasma, this suggests the presence of explosive, energetic expansion events at speeds close to c. The required rates of mass processing and energy loss of this component are estimated to be gsim6 10-10 Msun yr-1 and 400 L sun, respectively. The inferred scale length corresponding to 1 minute light travel time is comparable to the time-averaged spatially resolved 0.1 AU scale observed at 1.3 mm emission of Sgr A*. This steady component from Sgr A* is interpreted mainly as an ensemble average of numerous weak and overlapping flares that are detected on short timescales. The nature of such short timescale variable emission or quiescent variability is not understood but could result from fluctuations in the accretion flow of Sgr A* that feed the base of an outflow or jet.

  3. Multi-Wavelength Observations of Large Amplitude Prominence Oscillations

    NASA Astrophysics Data System (ADS)

    Shen, Yuandeng; Shibata, Kazunari; Ichimoto, Kiyoshi; Liu, Yu

    Multi-Wavelength observations of large amplitude prominence oscillations are important in diagnosing the physical property and eruption mechanism of prominences, as well as their ambient coronal magnetic fields. Such studies has led to a new discipline dubbed Prominence Seismology. However, up to the present, high-resolution and multi-wavelength observations of large amplitude oscillations are very scarce. Using high-resolution spectroscopic Halpha observations taken by the Solar Magnetic Activity Research Telescope (SMART) and the Solar Dynamics Observatory, we studied a series of intriguing large amplitude prominence (filament) oscillation events. We find that large amplitude horizontal and vertical prominence oscillations are often launched by large-scale shock waves associated with remote flares, while large amplitude longitudinal prominence oscillations are often associated with nearby micro jets or flare activities. Sometimes, longitudinal oscillations can also be launched by large-scale shocks. With the spectroscopic observations taken by the SMART, we can measure the Doppler velocity and even the three-dimensional velocity of the oscillations, with the so-called ``Clould Model. The oscillation period, amplitude, and damping time are also determined from the Halpha observations. These prominence parameters are used to estimate the magnetic fields of the prominence and the surrounding corona using the method of prominence seismology. Other property of large amplitude oscillation prominences such as restoring forces and damping mechanisms are also discussed in our study.

  4. Modulation compression for short wavelength harmonic generation

    SciTech Connect

    Qiang, J.

    2010-01-11

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

  5. 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.

  6. Short wavelength ion temperature gradient turbulence

    SciTech Connect

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

    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.

  7. New design for a wavelength demultiplexing device

    NASA Astrophysics Data System (ADS)

    Bethmann, Konrad; Orghici, Rozalia; Pichler, Elke; Zywietz, Urs; Schimdt, Thomas; Gleissner, Uwe; Kelb, Christian; Roth, Bernhard; Reinhardt, Carsten; Willer, Ulrike; Schade, Wolfgang

    2015-05-01

    Arrayed waveguide gratings (AWG) originally designed as demultiplexing device and manufactured with well established silicon wafer technology are already used successfully as compact spectrometers with high resolution1. In this paper, the concept of a new design for a wavelength demultiplexing device based on tailor-made polymers is presented. The motivation for a new design is a smaller footprint of the device and the avoidance of bended waveguides and the associated losses. Extensive simulations were performed to optimize the design. Using microscope projection lithography and hot embossing a first polymer based device was realized. Its characterization and the achieved performance in terms of resolution and covered wavelength range will be discussed.

  8. Short wavelength ion temperature gradient turbulence

    NASA Astrophysics Data System (ADS)

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

    2012-10-01

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

  9. Wavelength-assignment algorithms for service and restoration in wavelength-division-multiplexing rings

    NASA Astrophysics Data System (ADS)

    Sahin, Gökhan; Azizoglu, Murat

    2002-02-01

    We consider off-line capacity assignment in wavelength-routed ring networks with path restoration under arbitrary traffic patterns. We present service and restoration wavelength-assignment (WA) algorithms under shortest-path routing and analyze their performance in terms of the wavelength requirement. We obtain bounds to the wavelength requirement, using a routing-independent traffic parameter, and we show that both the service wavelength requirement and the total wavelength requirement under these algorithms lie within a factor of 2 of the optimal that can be achieved by any routing and WA algorithm. These results are among the few analytical results regarding the wavelength requirement in rings without wavelength conversion. We also propose vertex-coloring-based WA algorithms and demonstrate their efficiency through performance bounds and simulations. Results also show that knowledge of which link failed provides little capacity savings, and hence our algorithm with failure-independent restoration WA offers an attractive solution to reduce the fault-monitoring costs and the restoration signaling complexity.

  10. 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.

  11. Multi-wavelength heterodyne holography and interferometry

    NASA Astrophysics Data System (ADS)

    Yatagai, Toyohiko

    2013-09-01

    A novel phase-shifting technique, Doppler phase-shifting is introduced to interferometry and holography. Its principle, features and advantages are discussed. The use of multiple wavelengths in this method is also discussed. Their applications such as shape measurement, color holography etc. are presented.

  12. 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.

  13. Wavelength-sensitive-function controlled reflectance reconstruction.

    PubMed

    Tian, Jiandong; Tang, Yandong

    2013-08-01

    Spectral reflectance is defined as the "fingerprint" of an object and is illumination invariant. It has many applications in color reproduction, imaging, computer vision, and computer graphics. In previous reflectance reconstruction methods, spectral reflectance has been treated equally over the whole wavelength. However, human eyes or sensors in an imaging device usually have different weights over different wavelengths. We propose a novel method to reconstruct reflectance, considering a wavelength-sensitive function (WSF) that is constructed from sensor-sensitive functions (or color matching functions). Our main idea is to achieve more accurate reconstruction at wavelengths where sensors have high sensitivities. This more accurate reconstruction can achieve better imaging or color reproduction performance. In our method, we generate a matrix through the Hadamard product of the reflectance matrix and the WSF matrix. We then obtain reconstructed reflectance by applying the singular value decomposition on the generated matrix. The experimental results show that our method can reduce 47% mean-square error and 55% Lab error compared with the classical principal component analysis method. PMID:23903151

  14. 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.

  15. Phototransistors For Long-Wavelength Infrared

    NASA Technical Reports Server (NTRS)

    Borenstain, Shmuel I.

    1991-01-01

    Phototransistors of proposed new type used to detect photons having wavelengths of 8 to 150 micrometers. Detection based on impurity-to-continuum transitions. Integrated-circuit imaging arrays of such phototransistors useful in infrared remote sensing. Device of this type silicon, germanium, or silicon/germanium phototransistor in which junction between collector and base lightly doped with impurities.

  16. 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.

  17. RESOLVING THE MOTH AT MILLIMETER WAVELENGTHS

    SciTech Connect

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

    2013-09-01

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

  18. Resolving the Moth at Millimeter Wavelengths

    NASA Astrophysics Data System (ADS)

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

    2013-09-01

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

  19. 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.

  20. Investigation of optimum wavelengths for oximetry

    NASA Astrophysics Data System (ADS)

    Huong, Audrey K. C.; Stockford, Ian M.; Crowe, John A.; Morgan, Stephen P.

    2009-07-01

    An evaluation of the optimum choice of wavelengths, when using the 'Modified Lambert-Beer law' to estimate blood oxygen saturation, that minimises the mean error across a range of oxygen saturation values is presented. The stability of this approach and its susceptibility to noise are also considered.

  1. SWCam: the short wavelength camera for the CCAT Observatory

    NASA Astrophysics Data System (ADS)

    Stacey, Gordon J.; Parshley, Stephen; Nikola, Thomas; Cortes-Medellin, German; Schoenwald, Justin; Rajagopalan, Ganesh; Niemack, Michael D.; Jenness, Tim; Gallardo, Patricio; Koopman, Brian; Dowell, Charles D.; Day, Peter K.; Hollister, Matthew I.; Kovacs, Attila; LeDuc, Henry G.; McKenney, Christopher M.; Monroe, Ryan M.; Yoshida, Hiroshige; Zmuidzinas, Jonas; Swenson, Loren J.; Radford, Simon J.; Nguyen, Hien Trong; Mroczkowski, Anthony K.; Glenn, Jason; Wheeler, Jordan; Maloney, Philip; Brugger, Spencer; Adams, Joseph D.; Bertoldi, Frank; Schaaf, Reinhold; Halpern, Mark; Scott, Douglas; Marsden, Galen; Sayers, Jack; Chapman, Scott; Vieira, Joaquin D.

    2014-08-01

    We describe the Short Wavelength Camera (SWCam) for the CCAT observatory including the primary science drivers, the coupling of the science drivers to the instrument requirements, the resulting implementation of the design, and its performance expectations at first light. CCAT is a 25 m submillimeter telescope planned to operate at 5600 meters, near the summit of Cerro Chajnantor in the Atacama Desert in northern Chile. CCAT is designed to give a total wave front error of 12.5 ?m rms, so that combined with its high and exceptionally dry site, the facility will provide unsurpassed point source sensitivity deep into the short submillimeter bands to wavelengths as short as the 200 ?m telluric window. The SWCam system consists of 7 sub-cameras that address 4 different telluric windows: 4 subcameras at 350 ?m, 1 at 450 ?m, 1 at 850 ?m, and 1 at 2 mm wavelength. Each sub-camera has a 6' diameter field of view, so that the total instantaneous field of view for SWCam is equivalent to a 16' diameter circle. Each focal plane is populated with near unit filling factor arrays of Lumped Element Kinetic Inductance Detectors (LEKIDs) with pixels scaled to subtend an solid angle of (?/D)2 on the sky. The total pixel count is 57,160. We expect background limited performance at each wavelength, and to be able to map < 35()2 of sky to 5 ? on the confusion noise at each wavelength per year with this first light instrument. Our primary science goal is to resolve the Cosmic Far-IR Background (CIRB) in our four colors so that we may explore the star and galaxy formation history of the Universe extending to within 500 million years of the Big Bang. CCAT's large and high-accuracy aperture, its fast slewing speed, use of instruments with large format arrays, and being located at a superb site enables mapping speeds of up to three orders of magnitude larger than contemporary or near future facilities and makes it uniquely sensitive, especially in the short submm bands.

  2. 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.

  3. Predicting Ripple Wavelength in Wave-Current Flows

    NASA Astrophysics Data System (ADS)

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

    2006-12-01

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

  4. The IAG solar flux atlas: Accurate wavelengths and absolute convective blueshift in standard solar spectra

    NASA Astrophysics Data System (ADS)

    Reiners, A.; Mrotzek, N.; Lemke, U.; Hinrichs, J.; Reinsch, K.

    2016-03-01

    We present a new solar flux atlas with the aim of understanding wavelength precision and accuracy in solar benchmark data. The atlas covers the wavelength range 405-2300 nm and was observed at the Institut für Astrophysik, Göttingen (IAG), with a Fourier transform spectrograph (FTS). In contrast to other FTS atlases, the entire visible wavelength range was observed simultaneously using only one spectrograph setting. We compare the wavelength solution of the new atlas to the Kitt Peak solar flux atlases and to the HARPS frequency-comb calibrated solar atlas. Comparison reveals systematics in the two Kitt Peak FTS atlases resulting from their wavelength scale construction, and shows consistency between the IAG and the HARPS atlas. We conclude that the IAG atlas is precise and accurate on the order of ± 10 m s-1 in the wavelength range 405-1065 nm, while the Kitt Peak atlases show deviations as large as several ten to 100 m s-1. We determine absolute convective blueshift across the spectrum from the IAG atlas and report slight differences relative to results from the Kitt Peak atlas that we attribute to the differences between wavelength scales. We conclude that benchmark solar data with accurate wavelength solution are crucial to better understand the effect of convection on stellar radial velocity measurements, which is one of the main limitations of Doppler spectroscopy at m s -1 precision. Data (FITS files of the spectra) and Table A.1 are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/587/A65

  5. Molecular detection of metallo-?-lactamase genes, blaIMP-1, blaVIM-2 and blaSPM-1 in imipenem resistant Pseudomonas aeruginosa isolated from clinical specimens in teaching hospitals of Ahvaz, Iran

    PubMed Central

    Moosavian, Mojtaba; Rahimzadeh, Mohammad

    2015-01-01

    Background and Objectives: Carbapenem resistant Pseudomonas aeruginosa is a serious cause of nosocomial infections. The main purpose of the study is to determine the prevalence rate of imipenem resistant Pseudomonas aeruginosa carrying metallo--lactamase (MBL) genes. Material and Methods: 236 Pseudomonas aeruginosa isolates were collected from teaching hospitals of Ahvaz University of Medical Sciences during a period of 9 months in 2012. These strains were identified using conventional microbiological tests. The susceptibility of isolates to antibiotics were assessed using disk diffusion test. The IMP-EDTA combination disk phenotypic test was performed for detection of MBL producing strains. Finally, polymerase chain reaction (PCR) was performed to detect MBL genes, blaIMP-1, blaVIM-2 and blaSPM-1 in imipenem resistant strains. Results: Out of 236 examined isolates, 122 isolates (51.4%) were resistant to imipenem. The IMP-EDTA combination test showed that among 122 imipenem resistant strains, 110 strains (90%) were phenotipically MBL producers. Additionally, the results of PCR method showed that 2 strains (1.6%) and 67strains (55%) of imipenem resistant Pseudomonas aeruginosa isolates contained blaVIM-2 and blaIMP-1 genes respectively. No SPM-1gene was found in the examined samples. Conclusion: Resistance of P. aeruginosa isolates to imipenem due to MBL enzymes is increasing in Ahavaz. Because of clinical significance of this kind of resistance, rapid detection of MBL producing strains and followed by appropriate treatment is necessary to prevent the spreading of these organisms. PMID:26644866

  6. 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.

  7. Wavelength-band-tuning photodiodes by using various metallic nanoparticles

    NASA Astrophysics Data System (ADS)

    Hwang, J. D.; Chan, Y. D.; Chou, T. C.

    2015-11-01

    Wavelength-band tuning was easily achieved in this work by depositing various metallic nanoparticles (NPs) on silicon p-n junction photodiodes (PDs). The normalization spectrum of the PDs deposited with gold (Au) NPs reveals a high-wavelength pass characteristic; the PDs with silver (Ag) NPs coating behave as a low-wavelength pass, and the PDs with Au/Ag bimetallic NPs appear as a band-wavelength pass PD with a full width at half maximum of 450 ? 630 nm. The issue of wavelength-band tuning is due to the different plasmonic resonance wavelengths associated with various metallic NPs. The extinction plot shows the Au NPs have a longer resonant wavelength of about 545 nm, leading to the incident light with a wavelength near or longer than 545 nm scattered by the Au NPs, hence a high-wavelength pass PD. The PDs with Ag NPs, due to the Ag NPs, exhibit a short resonant wavelength of 430 nm, and the short-wavelength incident light is absorbed near the silicon (Si) surface, where the Ag NPs is atop it. The shorter-wavelength incident light is enhanced by the plasmonic resonance of Ag NPs, making a low-wavelength PD. The Au/Ag NPs presents a resonant wavelength of 500 nm between the Au and Ag NPs. For the incident light with a wavelength close to 500 nm, a constructive interference causes a substantial increase in the local electromagnetic field, hence leading to a band-wavelength pass PD.

  8. Isoelectronic wavelength calculations for argon spectra /Research note/.

    NASA Technical Reports Server (NTRS)

    Williams, M. D.

    1971-01-01

    A recent comprehensive set of isoelectronic calculations based on the data of Kelly (1968) has yielded two argon wavelengths that correspond with two of the unidentified wavelengths reported by Connerade et al. (1971) and a third wavelength which supports an uncertain identification. The observed and the interpolated wavelengths are presented in a table together with their identifications, and information concerning the interpolations.

  9. 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.

  10. Influence of wavelength on nonadiabatic effects in circularly polarized strong-field ionization

    NASA Astrophysics Data System (ADS)

    Yuan, MingHu; Zhao, GuangJiu; Liu, HongPing

    2015-11-01

    The influence of wavelength on nonadiabatic effects in an intensive, circularly polarized laser field has been studied by solving the time-dependent Schrödinger equation of a single active electron of the argon atom in a three-dimensional spherical coordinate system. The nonadiabatic process considering the nonzero initial velocity of the electron is very vital to reproducing the experimental observation. Our calculated photoelectron angular distribution in the directions perpendicular to the polarization plane shows nonadiabatic effects in strong laser ionization. The analysis of angular distribution on the "fast" time scale corresponding to wavelength indicates that as the wavelength gets shorter, the nonadiabatic effects get stronger. While the analysis on the "slow" time scale corresponding to the pulse envelope shows that the short pulse duration comes to play an important role for the nonadiabatic effects. When the pulse duration is more than 15 cycles, the influence of pulse duration on nonadiabatic effects fades away and the effects approach stabilization.

  11. Sub-wavelength Metal Gratings for In-plane Lasers and Integrated Optical Elements

    NASA Astrophysics Data System (ADS)

    Lively, Erica

    Sub-wavelength periodic metal structures are currently being explored by many branches of photonics for enhanced light control on the nano-scale. Metal holes or slits have shown promise in plasmonic application areas like mirrors, couplers, waveguides, and lenses. These structures are also beginning to making a large impact on many emerging areas in photonics such as slow light, left-handed materials, and sensing. While metal and semiconductor integrated devices have rapidly advanced in sophistication over the last decade, few have yet to address the major challenges associated with transitioning from individual devices that demonstrate basic, physical operation to devices with potential for current and near-future telecommunications applications. Outstanding novel devices using metals have been presented, but they are missing key features that allow them to be integrated into photonic circuits. As we begin bridging the gap between simple, passive devices fabricated with traditional optical lithography and basic liftoff techniques to more sophisticated, sub-wavelength scale active devices, we focus on sub-wavelength metal gratings with design choices made to favor integration, both with respect to current state of the art optical components and fabrication on the nano- and micro-scale. In this dissertation, we present a theoretical and experimental study of potential applications of sub-wavelength metal gratings in photonic integrated circuits. We consider on-chip slow light functionality and determine that the most achievable near-term impact of sub-wavelength metal gratings can be made in the area of on-chip, in-plane metal mirrors. We demonstrate the operation of a distributed Bragg reflector (DBR) laser with two metal grating mirrors operating on an InP-based materials platform. We account for future design considerations of scale and polarization to show that there is strong potential for integrating sub-wavelength metal gratings into current photonic integrated circuits.

  12. Quantitative phase imaging by three-wavelength digital holography

    SciTech Connect

    Mann, Christopher J; Bingham, Philip R; Tobin Jr, Kenneth William; Paquit, Vincent C

    2008-01-01

    Three-wavelength digital holography is applied to obtain surface height measurements over several microns of range, while simultaneously maintaining the low noise precision of the single wavelength phase measurement. The precision is preserved by the use of intermediate synthetic wavelength steps generated from the three wavelengths and the use of hierarchical optical phase unwrapping. As the complex wave-front of each wavelength can be captured simultaneously in one digital image, real-time performance is achievable.

  13. Dual-wavelength laser with topological charge

    NASA Astrophysics Data System (ADS)

    Yu, Haohai; Xu, Miaomiao; Zhao, Yongguang; Wang, Yicheng; Han, Shuo; Zhang, Huaijin; Wang, Zhengping; Wang, Jiyang

    2013-09-01

    We demonstrate the simultaneous oscillation of different photons with equal orbital angular momentum in solid-state lasers for the first time to our knowledge. Single tunable Hermite-Gaussian (HG0,n) (0 ? n ? 7) laser modes with dual wavelength were generated using an isotropic cavity. With a mode-converter, the corresponding Laguerre-Gaussian (LG0,n) laser modes were obtained. The oscillating laser modes have two types of photons at the wavelengths of 1077 and 1081 nm and equal orbital angular momentum of n? per photon. These results identify the possibility of simultaneous oscillation of different photons with equal and controllable orbital angular momentum. It can be proposed that this laser should have promising applications in many fields based on its compact structure, tunable orbital angular momentum, and simultaneous oscillation of different photons with equal orbital angular momentum.

  14. WAVELENGTH CALIBRATION OF THE HAMILTON ECHELLE SPECTROGRAPH

    SciTech Connect

    Pakhomov, Yu. V.; Zhao, G.

    2013-10-01

    We present the wavelength calibration of the Hamilton Echelle Spectrograph at Lick Observatory. The main problem with the calibration of this spectrograph arises from the fact that thorium lines are absent in the spectrum of the presumed ThAr hollow-cathode lamp now under operation; numerous unknown strong lines, which have been identified as titanium lines, are present in the spectrum. We estimate the temperature of the lamp's gas which permits us to calculate the intensities of the lines and to select a large number of relevant Ti I and Ti II lines. The resulting titanium line list for the Lick hollow-cathode lamp is presented. The wavelength calibration using this line list was made with an accuracy of about 0.006 Å.

  15. Discrete Wavelength-Locked External Cavity Laser

    NASA Technical Reports Server (NTRS)

    Pilgrim, Jeffrey S.; Silver, Joel A.

    2004-01-01

    A prototype improved external cavity laser (ECL) was demonstrated in the second phase of a continuing effort to develop wavelength-agile lasers for fiber-optic communications and trace-gas-sensing applications. This laser is designed to offer next-generation performance for incorporation into fiber-optic networks. By eliminating several optical components and simplifying others used in prior designs, the design of this laser reduces costs, making lasers of this type very competitive in a price-sensitive market. Diode lasers have become enabling devices for fiber optic networks because of their cost, compactness, and spectral properties. ECLs built around diode laser gain elements further enhance capabilities by virtue of their excellent spectral properties with significantly increased (relative to prior lasers) wavelength tuning ranges. It is essential to exploit the increased spectral coverage of ECLs while simultaneously insuring that they operate only at precisely defined communication channels (wavelengths). Heretofore, this requirement has typically been satisfied through incorporation of add-in optical components that lock the ECL output wavelengths to these specific channels. Such add-in components contribute substantially to the costs of ECL lasers to be used as sources for optical communication networks. Furthermore, the optical alignment of these components, needed to attain the required wavelength precision, is a non-trivial task and can contribute substantially to production costs. The design of the present improved ECL differs significantly from the designs of prior ECLs. The present design relies on inherent features of components already included within an ECL, with slight modifications so that these components perform their normal functions while simultaneously effecting locking to the required discrete wavelengths. Hence, add-in optical components and the associated cost of alignment can be eliminated. The figure shows the locking feedback signal, and the frequency locking achieved by use of this signal, as a mirror is tilted through a range of angles to tune the ECL through 48 channels. The data for the frequency plot were obtained, simultaneously with the data for the locking-signal plot, by using a scanning Michelson interferometer to precisely determine the ECL wavelength (and, hence, frequency). Given the ability of the Michelson interferometer to obtain highly precise readings, the frequency plot can be taken to be a reliable indication of single-mode operation. The discontinuities in the frequency plot signify the switching of the ECL between channels; in other words, they indicate tuning with locking to discrete frequencies. The peaks of the feedbacklocking signal correspond to the centers, or near centers, of the mirror angle scan through the corresponding channels. Thus, it is clear that when the feedback-locking signal is at a local maximum, the ECL is operating at single frequency at or near the middle frequency of the selected channel. This is all that is required for precisely locking the ECL output wavelength. The locking is achieved without additional external optical components.

  16. Polarizabilities, Atomic Clocks, and Magic Wavelengths

    NASA Astrophysics Data System (ADS)

    Safronova, Marianna

    2008-05-01

    I will describe the high-precision calculations of the static and frequency-dependent polarizabilities in alkali-metal atoms and Ca^+. The resulting polarizability values are used for a variety of applications from reducing the decoherence in quantum logic gates to the evaluation of the black-body radiation (BBR) shifts for optical frequency standards. Our alkali-metal atom polarizability calculations can be used to predict the oscillation frequencies of optically-trapped atoms, and particularly the ratios of frequencies of different species held in the same trap. We identify wavelengths at which two different alkali atoms have the same oscillation frequency. We also evaluate ``magic'' wavelengths in alkali-metal atoms for which np and ns levels have the same ac-Stark shift enabling state-insensitive optical cooling and trapping. The calculation of the BBR shift for the optical frequency standard with Ca^+ ion is also described.

  17. Coordinated observations of PHEMU at radio wavelengths.

    NASA Astrophysics Data System (ADS)

    Pluchino, S.; Schillirò, F.; Salerno, E.; Pupillo, G.; Kraus, A.; Mack, K.-H.

    We present preliminary results for our study of mutual phenomena of the Galilean satellites performed at radio wavelengths with the Medicina and Noto antennas of the Istituto di Radioastronomia \\textendash{} INAF, and with the Effelsberg 100-m radio telescope of the Max-Planck-Institute for Radioastronomy. Measurements of the radio flux density variation occurred during the mutual occultations of Io by Europa and Ganymede were carried out during the PHEMU09 campaign at K- and Q-band. Flux density variations observed for the first time at radio wavelengths are consistent with the typical optical patterns measured when partial occultations occurred. The flux density drops indicate a non-linear dependence with the percentage of overlapped area.

  18. 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.

  19. Short wavelength striations on expanding plasma clouds

    SciTech Connect

    Winske, D.; Gary, S.P.

    1989-01-01

    The growth and evolution of short wavelength (

  20. 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.

  1. 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.

  2. Multiple wavelength X-ray monochromators

    DOEpatents

    Steinmeyer, Peter A. (Arvada, CO)

    1992-11-17

    An improved apparatus and method is provided for separating input x-ray radiation containing first and second x-ray wavelengths into spatially separate first and second output radiation which contain the first and second x-ray wavelengths, respectively. The apparatus includes a crystalline diffractor which includes a first set of parallel crystal planes, where each of the planes is spaced a predetermined first distance from one another. The crystalline diffractor also includes a second set of parallel crystal planes inclined at an angle with respect to the first set of crystal planes where each of the planes of the second set of parallel crystal planes is spaced a predetermined second distance from one another. In one embodiment, the crystalline diffractor is comprised of a single crystal. In a second embodiment, the crystalline diffractor is comprised of a stack of two crystals. In a third embodiment, the crystalline diffractor includes a single crystal that is bent for focussing the separate first and second output x-ray radiation wavelengths into separate focal points.

  3. Multiple wavelength X-ray monochromators

    DOEpatents

    Steinmeyer, P.A.

    1992-11-17

    An improved apparatus and method is provided for separating input x-ray radiation containing first and second x-ray wavelengths into spatially separate first and second output radiation which contain the first and second x-ray wavelengths, respectively. The apparatus includes a crystalline diffractor which includes a first set of parallel crystal planes, where each of the planes is spaced a predetermined first distance from one another. The crystalline diffractor also includes a second set of parallel crystal planes inclined at an angle with respect to the first set of crystal planes where each of the planes of the second set of parallel crystal planes is spaced a predetermined second distance from one another. In one embodiment, the crystalline diffractor is comprised of a single crystal. In a second embodiment, the crystalline diffractor is comprised of a stack of two crystals. In a third embodiment, the crystalline diffractor includes a single crystal that is bent for focusing the separate first and second output x-ray radiation wavelengths into separate focal points. 3 figs.

  4. Wavelength switching in an optical klystron

    SciTech Connect

    Berryman, K.W.; Smith, T.I.

    1995-12-31

    A symmetric optical klystron consists of two identical undulator sections separated a dispersive section. For a device of a given length, an optical klystron is capable of producing much more bunching, and therefore more gain, than a traditional undulator. Another consequence of introducing dispersion between two undulator sections is that the overall spontaneous radiation pattern results from the interference between the two undulator sections, and as such resembles a standard undulator radiation pattern modulated by a sinusoidal interference term. The presence of several wavelength peaks in the spontaneous lineshape implies an equal number of peaks in the gain spectrum. If the strength of the dispersion section is adjusted to provide nearly equal gain on the two largest of these peaks, then they will compete, and the FEL may switch wavelengths based on noise, cavity length, or other perturbations. We provide the first observations of this behavior, using the FIREFLY system at the Stanford Picosecond FEL Center. In FIREFLY, relative wavelength switching by more than 3%--more than twice the laser linewidth-has been observed by varying dispersion section strength, while at intermediate points stable switching has also been observed as a function of cavity length.

  5. 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.

  6. Two-Wavelength Lidar Inversion Algorithm

    NASA Astrophysics Data System (ADS)

    Kunz, Gerard J.

    1999-02-01

    Potter Appl. Opt. 26, 1250 (1987) has presented a method to determine profiles of the atmospheric aerosol extinction coefficients by use of a two-wavelength lidar with the assumptions of a constant value for the extinction-to-backscatter ratio for each wavelength and a constant value for the ratio between the two extinction coefficients at the two wavelengths. Triggered by this idea, Ackermann Appl. Opt. 36, 5134 (1997) expanded this method to consider lidar returns that are a composition of scattering by atmospheric aerosols and molecules, assuming that the molecular scattering is known. In both papers the method is based on the well-known solutions of Bernoulli s differential equation in an iterative scheme with an unknown boundary transmission condition. This boundary condition is less sensitive to noise than boundary extinction conditions. My main purpose is to critically consider the principle behind Potter s method, because it seems that there are several reasons why the number of solutions is not limited to one, as suggested by his original work.

  7. Alternative explanation for intermediate--wavelength magnetic anomalies

    SciTech Connect

    Shure, L.; Parker, R.L.

    1981-12-10

    Harrison and Carle and others have examined very long profiles of the magnetic field and have calculated one-dimensional power spectra. In these they expect to see, but do not find, a minimum in power at intermediate wavelengths, between 65 and 150 km. Conventional one-dimensional models of the field predict very little power in this band, which lies between the spectral peaks arising from sources in the crust and the core. Mantle sources or high-intensity, long-wavelength magnetizations have been proposed to account for the observations. An alternative, more plausible explanation is that one-dimensional spectra of two-dimensional fields contain contributions from wavenumbers in the perpendicular (i.e., nonsampled) direction. Unless the seafloor spreading anomalies are perfectly lineated at right angles to the profile, some low-wavenumber energy must be attributed to this effect; we propose that such directional aliasing is a major factor in the power spectra. To support this idea we discuss theoretical models and analyze a large-scale marine survey.

  8. 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

  9. Nanoscale dynamics by short-wavelength four wave mixing experiments

    NASA Astrophysics Data System (ADS)

    Bencivenga, F.; Baroni, S.; Carbone, C.; Chergui, M.; Danailov, M. B.; De Ninno, G.; Kiskinova, M.; Raimondi, L.; Svetina, C.; Masciovecchio, C.

    2013-12-01

    Multi-dimensional spectroscopies with vacuum ultraviolet (VUV)/x-ray free-electron laser (FEL) sources would open up unique capabilities for dynamic studies of matter at the femtosecond-nanometer time-length scales. Using sequences of ultrafast VUV/x-ray pulses tuned to electron transitions enables element-specific studies of charge and energy flow between constituent atoms, which embody the very essence of chemistry and condensed matter physics. A remarkable step forward towards this goal would be achieved by extending the four wave mixing (FWM) approach at VUV/soft x-ray wavelengths, thanks to the use of fully coherent sources, such as seeded FELs. Here, we demonstrate the feasibility of VUV/soft x-ray FWM at Fermi@Elettra and we discuss its applicability to probe ultrafast intramolecular dynamics, charge injection processes involving metal oxides and electron correlation and magnetism in solid materials. The main advantage in using VUV/soft x-ray wavelengths is in adding element-sensitivity to FWM methods by exploiting the core resonances of selected atoms in the sample.

  10. Radar measurements of Mercurys north pole at 70 cm wavelength

    NASA Astrophysics Data System (ADS)

    Black, G. J.; Campbell, D. B.; Harmon, J. K.

    2010-09-01

    We present radar imaging of Mercury using the Arecibo Observatory's 70-cm wavelength radar system during the inferior conjunction of July 1999. At that time the sub-Earth latitude was 11N and the highly reflective region at Mercury's north pole that was first identified in radar images at the shorter wavelengths of 3.6 cm [Slade, M.A., Butler, B.J., Muhleman, D.O., 1992. Science 258, 635-640] and 13 cm [Harmon, J.K., Slade, M.A., 1992. Science 258, 640-643] was again clearly detected. The reflectivity averaged over a 75,000 km 2 region including the pole is similar to that measured at the other wavelengths over a comparable area, and the 70 cm circular polarization ratio of ?C0.87 is possibly slightly lower. If this strong backscattering results from volume scattering in low absorption layers, the persistence of this effect over more than an order of magnitude change in wavelength scale has implications for the depth and thickness of the deposits responsible. The resolution of the radar maps at this wavelength is not sufficient to resolve individual craters, nor to discern features at other latitudes, but the planet's total reflectivity is consistent with previous work and the scattering function suggests a surface roughness at this wavelength similar to the lunar highlands.

  11. Silicon photonic device for wavelength sensing and monitoring

    NASA Astrophysics Data System (ADS)

    Vargas Lopez, German R.

    Over the last decade advances and innovations from Silicon Photonics technology were observed in the telecommunications and computing industries. This technology which employs Silicon as an optical medium, relies on current CMOS micro-electronics fabrication processes to enable medium scale integration of many nano-photonic devices to produce photonic integrated circuitry. However, other fields of research such as optical sensor processing can benefit from silicon photonics technology, specially in sensors where the physical measurement is wavelength encoded. In this research work, we present a design and application of a thermally tuned silicon photonic device as an optical sensor interrogator. The main device is a micro-ring resonator filter of 10 mum of diameter. A photonic design toolkit was developed based on open source software from the research community. With those tools it was possible to estimate the resonance and spectral characteristics of the filter. From the obtained design parameters, a 7.8 x 3.8 mm optical chip was fabricated using standard micro-photonics techniques. In order to tune a ring resonance, Nichrome micro-heaters were fabricated on top of the device. Some fabricated devices were systematically characterized and their tuning response were determined. From measurements, a ring resonator with a free-spectral-range of 18.4 nm and with a bandwidth of 0.14 nm was obtained. Using just 5 mA it was possible to tune the device resonance up to 3 nm. In order to apply our device as a sensor interrogator in this research, a model of wavelength estimation using time interval between peaks measurement technique was developed and simulations were carried out to assess its performance. To test the technique, an experiment using a Fiber Bragg grating optical sensor was set, and estimations of the wavelength shift of this sensor due to axial strains yield an error within 22 pm compared to measurements from spectrum analyzer. Results from this study implies that signals from FBG sensors can be processed with good accuracy using a micro-ring device with the advantage of ts compact size, scalability and versatility. Additionally, the system also has additional applications such as processing optical wavelength shifts from integrated photonic sensors and to be able to track resonances from laser sources.

  12. Carbon structures with three-dimensional periodicity at optical wavelengths

    PubMed

    Zakhidov; Baughman; Iqbal; Cui; Khayrullin; Dantas; Marti; Ralchenko

    1998-10-30

    Porous carbons that are three-dimensionally periodic on the scale of optical wavelengths were made by a synthesis route resembling the geological formation of natural opal. Porous silica opal crystals were sintered to form an intersphere interface through which the silica was removed after infiltration with carbon or a carbon precursor. The resulting porous carbons had different structures depending on synthesis conditions. Both diamond and glassy carbon inverse opals resulted from volume filling. Graphite inverse opals, comprising 40-angstrom-thick layers of graphite sheets tiled on spherical surfaces, were produced by surface templating. The carbon inverse opals provide examples of both dielectric and metallic optical photonic crystals. They strongly diffract light and may provide a route toward photonic band-gap materials. PMID:9794752

  13. 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

  14. Saturn's aurora observed by the Cassini camera at visible wavelengths

    NASA Astrophysics Data System (ADS)

    Dyudina, Ulyana A.; Ingersoll, Andrew P.; Ewald, Shawn P.; Wellington, Danika

    2016-01-01

    The first observations of Saturn's visible-wavelength aurora were made by the Cassini camera. The aurora was observed between 2006 and 2013 in the northern and southern hemispheres. The color of the aurora changes from pink at a few hundred km above the horizon to purple at 1000-1500 km above the horizon. The spectrum observed in 9 filters spanning wavelengths from 250 nm to 1000 nm has a prominent H-alpha line and roughly agrees with laboratory simulated auroras. Auroras in both hemispheres vary dramatically with longitude. Auroras form bright arcs between 70 and 80 latitude north and between 65 and 80 latitude south, which sometimes spiral around the pole, and sometimes form double arcs. A large 10,000-km-scale longitudinal brightness structure persists for more than 100 h. This structure rotates approximately together with Saturn. On top of the large steady structure, the auroras brighten suddenly on the timescales of a few minutes. These brightenings repeat with a period of ?1 h. Smaller, 1000-km-scale structures may move faster or lag behind Saturn's rotation on timescales of tens of minutes. The persistence of nearly-corotating large bright longitudinal structure in the auroral oval seen in two movies spanning 8 and 11 rotations gives an estimate on the period of 10.65 0.15 h for 2009 in the northern oval and 10.8 0.1 h for 2012 in the southern oval. The 2009 north aurora period is close to the north branch of Saturn Kilometric Radiation (SKR) detected at that time.

  15. Wavelength meter having single mode fiber optics multiplexed inputs

    DOEpatents

    Hackel, R.P.; Paris, R.D.; Feldman, M.

    1993-02-23

    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.

  16. Wavelength meter having single mode fiber optics multiplexed inputs

    DOEpatents

    Hackel, Richard P.; Paris, Robert D.; Feldman, Mark

    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.

  17. Tuning the wavelength of spoof plasmons by adjusting the impedance contrast in an array of penetrable inclusions

    NASA Astrophysics Data System (ADS)

    Cordero, M. L.; Maurel, A.; Mercier, J.-F.; Flix, S.; Barra, F.

    2015-08-01

    While spoof plasmons have been proposed in periodic arrays of sound-hard inclusions, we show that they also exist when inclusions are penetrable. Moreover, we show that their wavelength can be tuned by the impedance mismatch between the inclusion material and the surrounding medium, beyond the usual effect of filling fraction in the array. It is demonstrated that sound-soft materials increase the efficiency in the generation of sub-wavelength plasmons, with much lower wavelengths than sound-hard materials and than a homogeneous slab. An application to the generation of acoustic spoof plasmons by an ultra compact array of air/polydimethylsiloxane inclusions in water is proposed with plasmon wavelength tunable up to deep sub-wavelength scales.

  18. Coherence techniques at extreme ultraviolet wavelengths

    NASA Astrophysics Data System (ADS)

    Chang, Chang

    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. Accurate knowledge of the refractive index in this wavelength region is of fundamental importance for the design of optical systems. However, due to the high absorption, no previous direct measurement of the real part of the refractive index has been performed at EUV wavelengths. To overcome these limitations, a novel diffractive optical element based on Fourier optics techniques is invented, fabricated, and demonstrated for the first time. The improved efficiency of the interferometer employing this novel optical element enables the first direct measurement of the refractive index at EUV wavelengths. Both the real and imaginary parts of the complex refractive indices are measured directly, without recourse to Kramers-Kronig transformations. Data for Al and Ni, in the vicinity of their L and M-edges, respectively, are presented as first examples of this technique. The first novel Fourier optical element used in the above EUV interferometer is also discussed in detail. This diffractive optical element, when illuminated by a uniform plane wave, will produce two symmetric off-axis first order foci suitable for interferometric experiments. In addition to the symmetricalness, the flux throughput is improved by ˜10 times as compared with separate elements providing the same functionality. The efficiency of this optical element is measured. Future work on computer generated holograms is suggested and compared with the Fourier optical element. The invention of this Fourier optical element opens a new era in the use of sophisticated optical techniques at short wavelengths.

  19. On the Capability of Artificial Neural Networks to Compensate Nonlinearities in Wavelength Sensing

    PubMed Central

    Hafiane, Mohamed Lamine; Dibi, Zohir; Manck, Otto

    2009-01-01

    An intelligent sensor for light wavelength readout, suitable for visible range optical applications, has been developed. Using buried triple photo-junction as basic pixel sensing element in combination with artificial neural network (ANN), the wavelength readout with a full-scale error of less than 1.5% over the range of 400 to 780 nm can be achieved. Through this work, the applicability of the ANN approach in optical sensing is investigated and compared with conventional methods, and a good compromise between accuracy and the possibility for on-chip implementation was thus found. Indeed, this technique can serve different purposes and may replace conventional methods. PMID:22574051

  20. Aerosol optical properties measured in Argentina: wavelength dependence and variability based on sun photometer measurements

    NASA Astrophysics Data System (ADS)

    Ristori, P.; Otero, L.; Fochesatto, J.; Flamant, P. H.; Wolfram, E.; Quel, E.; Piacentini, R.; Holben, B.

    2003-07-01

    This paper deals with the spectral dependence and time variability of ngstrm wavelength exponent scaling law ( ?), which is the spectral varying slope of the logarithmic relationship between aerosol optical depths ( ?) and the wavelength ( ?). It is commonly used to retrieve intensive air masses optical properties such as aerosol size distribution from extensive quantities ( ?) and ngstrm turbidity coefficient ( ?). This spectral variation of ? is studied at different wavelengths from measurements taken by ground-based sun photometer covering from near-infrared to ultraviolet range. We analyze the spectral measurement of aerosols optical depths at eight specific selected wavelengths from 340 to 1020 nm using the sun photometer measurements from AErosol RObotic NETwork (AERONET) from NASA. Data from the entire year 2000 were used from instruments deployed at two different sites covering the regions of Argentina as northcentral at Cordoba CETT (31.5S, 64.4W) and "pampa hmeda" at Buenos Aires CEILAP (34.5S, 58.5W). A new approach of ngstrm wavelength exponent spectral variation was developed to take into account with a more accurate precision the significant curvature appearing in the logarithmic relation between ? and ?. Using the direct spectral solar radiation set, time series of ngstrm coefficient of turbidity and wavelength scaling law was computed with a day to day data base clustering with uncertainty lower than 0.01 in the optical depth reconstruction over the bulk sun photometer measurements. Temporal series of constant and spectral dependence of wavelength exponent scaling law and turbidity coefficient was derived and shown to vary in space and time. Different meteorological forcing for both sites was evidenced using a regression coefficient analysis to well assess the spectral dependence of wavelength exponent coefficient due to the different cumulating mode of particles and air masses origin at different sites. This spectral decomposition is a key issue in aerosols analysis of steady state and regional scale intrusion episodes with strong connection to their potential contribution of pollution episodes in air-quality problems on urban environment.

  1. Effects of lateral viscosity variations on long-wavelength geoid anomalies and topography

    NASA Technical Reports Server (NTRS)

    Richards, Mark A.; Hager, Bradford H.

    1989-01-01

    The effects of lateral variations in the earth mantle viscosity, due to temperature- or stress-dependent rheology, on the long-wavelength geoid anomalies are examined. Results from simple perturbation theory combined with findings from numerical models for convective flow led to a conclusion that the geoid due to the very longest wavelength convective patterns (l = 2,3) on earth is probably not seriously contaminated by lateral variations due either to temperature or stress dependence. Considerable contamination of the higher-degree geoid (l value of no less than 4) is to be expected due to lateral viscosity variations in phase with the fundamental convection scale length.

  2. Wavelength Shifters and Interactions of EDTA with Acrylic & LAB

    NASA Astrophysics Data System (ADS)

    Mohan, Yuvraj; SNO+ Collaboration

    2014-09-01

    The SNO + experiment, an upgrade to the Sudbury Neutrino Observatory, will use linear alkyl-benzene (LAB) liquid scintillator to probe new physics, including 0 ??? decay. Event detection efficiency is heavily affected by radioactive backgrounds, two sources being Rn-222 and Po-210 daughters, some of which has become embedded in the SNO + acrylic vessel after years underground. The leading candidate for polonium leaching is Ethylenediaminetetraacetic acid (EDTA). Before deployment on-site, EDTA's effects on the mechanical integrity of acrylic must be determined. It also must not be soluble in LAB or must be removed before scintillator fill of the vessel, as its presence would result in reduced light yield due to scattering. It was found that EDTA had negligible effects on the Young's Modulus of acrylic. EDTA is also slightly soluble in LAB, but can be completely removed by rinsing with water. Additionally, the study of the light yield and alpha/beta timing profiles of two wavelength shifters - bisMSB and perylene - is critical to determining which should be added to the 0 ??? isotope (tellurium) LAB cocktail. Small-scale results hint that perylene might be better, but this is being confirmed with larger-scale tests. The SNO + experiment, an upgrade to the Sudbury Neutrino Observatory, will use linear alkyl-benzene (LAB) liquid scintillator to probe new physics, including 0 ??? decay. Event detection efficiency is heavily affected by radioactive backgrounds, two sources being Rn-222 and Po-210 daughters, some of which has become embedded in the SNO + acrylic vessel after years underground. The leading candidate for polonium leaching is Ethylenediaminetetraacetic acid (EDTA). Before deployment on-site, EDTA's effects on the mechanical integrity of acrylic must be determined. It also must not be soluble in LAB or must be removed before scintillator fill of the vessel, as its presence would result in reduced light yield due to scattering. It was found that EDTA had negligible effects on the Young's Modulus of acrylic. EDTA is also slightly soluble in LAB, but can be completely removed by rinsing with water. Additionally, the study of the light yield and alpha/beta timing profiles of two wavelength shifters - bisMSB and perylene - is critical to determining which should be added to the 0 ??? isotope (tellurium) LAB cocktail. Small-scale results hint that perylene might be better, but this is being confirmed with larger-scale tests. University of Pennsylvania and SNO+ Collaboration.

  3. Quantum cascade lasers designed toward shorter wavelengths

    NASA Astrophysics Data System (ADS)

    Xu, Jilian; Liu, Lei; Li, Bing Hui; Zhang, Zhenzhong; Ma, Jian; Liu, Kewei; He, Jun; Shen, D. Z.

    2016-02-01

    Quantum cascade lasers (QCLs) are normally based on one-dimensional confined quantum wells. In this scheme, it is still a challenge to produce lasing with a frequency higher than mid-infrared. Here, we discuss the possibility to extend the spectral range of QCLs to the higher frequency region by adding another dimensional confinement. Taking the ZnO/MgO system as an example, we demonstrate theoretically that such a two-dimensional confined QCL can operate at wavelengths from the near-infrared ? =2.95 ?m, 1.57 ?m, 1.13 ?m to the visible 734?nm.

  4. Using large radio telescopes at decametre wavelengths

    NASA Astrophysics Data System (ADS)

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

    2004-12-01

    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 URANs arrays in Ukraine, and the Nanay Decametre Array in France). We report and briefly discuss some new findings, dealing with decametre radiation from Jupiter and the Solar Corona: namely the discovery of new kinds of hyper fine structures in spectrograms of the active Sun, and a new characterisation of Jupiter's "millisecond" radiation, whose waveform samples, with time resolution down to 40 ns, and correlated measurements, by using far distant antennas (3000 km), have been obtained. In addition, scattering effects, caused by the terrestrial ionosphere and the interplanetary medium, could be disentangled through high time resolution and wide-band analyses of solar, planetary and strong galactic radio sources. Consequences for decametre wavelength imaging at high spatial resolution (VLBI) are outlined. Furthermore, in spite of the very unfavourable electromagnetic environment in this frequency range, a substantial increase in the quality of the observations was shown to be provided by using new generation spectrometers, based on sophisticated digital techniques. Indeed, the available, high dynamic range of such devices greatly decreases the effects of artificial and natural radio interference. We give several examples of successful signal detection in the case of much weaker radio sources than Solar System ones, down to the 1Jy intensity level. In summary, we conclude that searching for sensitivity improvement at the decametre wavelength is scientifically quite justified, and is now technically feasible, in particular by building giant, phased antenna arrays of much larger collecting area (as in the LOFAR project). In this task, one must be careful of some specifics of this wavelength range - somewhat unusual in "classical" radio astronomy - i.e., very high level and density of radio interference (telecommunications) and the variable terrestrial ionosphere.

  5. Using large radio telescopes at decametre wavelengths

    NASA Astrophysics Data System (ADS)

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

    2003-04-01

    With the aim of evaluating the actual possibilities of doing, from the ground, sensitive radio astronomy at decametre wavelengths (particularly below 40 MHz), 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 URANs arrays in Ukraine, and the Nanay Decameter Array in France). We report and briefly discuss some new findings, dealing with decametre radiation from Jupiter and the Solar Corona: namely the discovery of new kinds of hyper fine structures in spectrograms of the active Sun, and a new characterisation of Jupiter's "millisecond" radiation, whose waveform samples, with time resolution down to 40 nanoseconds, and correlated measurements, by using far distant antennas (3000 km), have been obtained. In addition, scattering effects, caused by the terrestrial ionosphere and the interplanetary medium, could be disentangled, through high time resolution, wide band analyses of solar, planetary and strong galactic radio sources. Consequences for decametre wavelength imaging at high spatial resolution (VLBI) are outlined. Furthermore, in spite of the very unfavourable electromagnetic environment in this frequency range, a substantial increase in quality of the observations, was shown to be provided by using new generation spectrometers, based on sophisticated digital techniques. Indeed, the available, high dynamic range of such devices greatly decrease the effects of artificial and natural radio interference. We give several examples of successful signal detection in case of much weaker radio sources than Solar System ones, down to the 1 Jy intensity level. In summary, we conclude that searching for sensitivity improvement at decametre wavelength is justified, and is now technically feasible, in particular by building giant, phased antenna arrays of much larger collecting area (as in the LOFAR project). One must also take into account some specifics of this wavelength range - but somewhat unusual in "classical" radio astronomy -, i.e. a very high level and density of radio interference (telecommunications) and the variable ionosphere. Some applications to Solar System radio astronomy are briefly outlined.

  6. 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.

  7. Lunar space weathering at ultraviolet wavelengths

    NASA Astrophysics Data System (ADS)

    Denevi, B. W.; Robinson, M. S.; Sato, H.; Hapke, B.; McEwen, A. S.; Hawke, B. R.

    2011-10-01

    The Lunar Reconnaissance Orbiter Camera (LROC) Wide Angle Camera (WAC) images nearly the entire Moon each month through two ultraviolet (UV) filters (bandpasses centered at 321 and 360 nm) and five visible filters (415, 566, 604, 643, and 689 nm) [1]. Global coverage at UV wavelengths provides a fresh opportunity to examine the rate and causes of space weathering on the Moon. We find that UV observations provide a new tool to more confidently identify the least weathered material. Only the youngest craters (<~100 My) appear fresh in the UV, and the UV reflectance of lunar swirls is consistent with limited space weathering.

  8. Rotman lens for mm-wavelengths

    NASA Astrophysics Data System (ADS)

    Hall, Leonard T.; Hansen, Hedley J.; Abbott, Derek

    2002-11-01

    The 77 GHz band has been reserved for intelligent cruise control in luxury cars and some public transport services in America and the United Kingdom. The Rotman lens offers a cheap and compact means to extend the single beam systems generally used, to fully functional beam staring arrangements. Rotman lenses have been built for microwave frequencies with limited success. The flexibility of microstrip transmission lines and the advent of fast accurate simulation packages allow practical Rotman lenses to be designed at mm-wavelengths. This paper discusses the limitations of the conventional design approach and predicts the performance of a new Rotman lens designed at 77 GHz.

  9. Quantum cascade lasers designed toward shorter wavelengths.

    PubMed

    Xu, Jilian; Liu, Lei; Li, Bing Hui; Zhang, Zhenzhong; Ma, Jian; Liu, Kewei; He, Jun; Shen, D Z

    2016-02-17

    Quantum cascade lasers (QCLs) are normally based on one-dimensional confined quantum wells. In this scheme, it is still a challenge to produce lasing with a frequency higher than mid-infrared. Here, we discuss the possibility to extend the spectral range of QCLs to the higher frequency region by adding another dimensional confinement. Taking the ZnO/MgO system as an example, we demonstrate theoretically that such a two-dimensional confined QCL can operate at wavelengths from the near-infrared [Formula: see text] μm, 1.57 μm, 1.13 μm to the visible 734 nm. PMID:26792593

  10. Two wavelength division multiplexing WAN trials

    SciTech Connect

    Lennon, W.J.; Thombley, R.L.

    1995-01-20

    Lawrence Livermore National Laboratory, as a super-user, supercomputer, and super-application site, is anticipating the future bandwidth and protocol requirements necessary to connect to other such sites as well as to connect to remote-sited control centers and experiments. In this paper the authors discuss their vision of the future of Wide Area Networking, describe the plans for a wavelength division multiplexed link connecting Livermore with the University of California at Berkeley and describe plans for a transparent, {approx} 10 Gb/s ring around San Francisco Bay.

  11. Spectrophotometry of comets at optical wavelengths

    NASA Technical Reports Server (NTRS)

    Ahearn, M. F.

    1982-01-01

    Techniques for spectrophotometry of comets are discussed, and results are reviewed for line and continuum spectrophotometry of comets at optical wavelengths. The techniques considered include photographic spectroscopy and spectrophotometry, photoelectric spectrophotometry, and methods based on the use of image dissector scanners, Fourier-transform instruments, and Fabry-Perot spectrometers. Results are summarized for the study of cometary emission features due to C2, CN, CH, OH, NH, C3, NH2, O, H, CO(plus), and H2O(plus). Relative abundances of various species in comets are examined, along with continuum spectrophotometry of the nuclei, comas, and tails of comets.

  12. 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.

  13. SAGE 3: A visible wavelength limb sounder

    NASA Technical Reports Server (NTRS)

    Chu, W. P.; Mccormick, M. P.; Zawodny, J.; Mcmaster, L. R.

    1990-01-01

    A brief description is presented for the SAGE 3 (Stratospheric Aerosol and Gas Experiment 3) instrument that has been selected to fly onboard the National Polar Platform 1 (NPOP 1) for the Earth Observational System (Eos) in 1996. The SAGE 3 instrument will perform earth limb sounding with the solar occultation technique measuring the ultraviolet (UV), the visible, and the near infrared (IR) wavelength solar radiation. The instrument will produce atmospheric data for the vertical distribution of aerosol, ozone, nitrogen dioxide, water vapor, and oxygen. The details of the instrument design, data flow, and processing requirements are discussed.

  14. 22-Gb/s Long Wavelength VCSELs.

    PubMed

    Hofmann, Werner; Müller, Michael; Nadtochiy, Alexey; Meltzer, Christian; Mutig, Alex; Böhm, Gerhard; Rosskopf, Jürgen; Bimberg, Dieter; Amann, Markus-Christian; Chang-Hasnain, Connie

    2009-09-28

    1.55-microm vertical cavity surface-emitting low-parasitic lasers show open eyes up to 22-Gb/s modulation speed. Uncooled error-free operation over a wide temperature range up to 85 degrees C under constant bias conditions is demonstrated at 12.5-Gb/s data rate. At these fixed bias conditions the laser characteristics are practically invariant with temperature. These are the highest data-rates reported from a long-wavelength VCSEL structure to date. PMID:19907538

  15. Dual-wavelength moisture meter for clay

    NASA Astrophysics Data System (ADS)

    Norgia, Michele; Pesatori, Alessandro

    2012-10-01

    An optical sensor for measuring the moisture level of clay has been realized by a couple of telecommunications lasers at 1300 and 1550 nm. The sensor can operate directly during building material production. The measurement principle is based on the measurement of the optical reflection at different wavelengths in the infrared region. Custom low-noise electronics allows rejecting disturbances of ambient light, and a digital processing makes the system independent on the clay distance. By means of a proper calibration, the sensor can monitor the moisture level during brick production, without moving parts or optical filters.

  16. 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

  17. Wavelength dependence of aerosol backscatter coefficients obtained by multiple wavelength Lidar measurements

    NASA Technical Reports Server (NTRS)

    Sasano, Y.; Browell, E. V.

    1986-01-01

    Aerosols are often classified into several general types according to their origins and composition, such as maritime, continental, and stratospheric aerosols, and these aerosol types generally have different characteristics in chemical and physical properties. The present study aims at demonstrating the potential for distinguishing these aerosol types by the wavelength dependence of their backscatter coefficients obtained from quantitative analyses of multiple wavelength lidar signals. Data from the NASA Airborne Differential Abosrption lidar (DIAL) S ystems, which can measure aerosol backscatter profiles at wavelenghts of 300, 600, and 1064 nm and ozone profiles of backscatter coefficients for these three wavelength were derived from the observations of aerosols of different types. Observations were performed over the Atlantic Ocean, the Southwestern United States, and French Guyana.

  18. Frequency-wavelength calculator with table of dielectric properties

    NASA Technical Reports Server (NTRS)

    Thompson, L. L.

    1972-01-01

    Frequency-wavelength calculator has been developed which rapidly and accurately calculates wavelength of given frequency in specific dielectric material. Unit fits into shirt pocket and includes table of dielectric properties and one-step calculator.

  19. Dual-wavelength InP quantum dot lasers

    SciTech Connect

    Shutts, S.; Smowton, P. M.; Krysa, A. B.

    2014-06-16

    We have demonstrated a two-section dual-wavelength diode laser incorporating distributed Bragg reflectors, with a peak-wavelength separation of 62.5 nm at 300 K. Each lasing wavelength has a different temperature dependence, providing a difference-tuning of 0.11 nm/K. We discuss the mechanisms governing the light output of the two competing modes and explain how the short wavelength can be relatively insensitive to output changes at the longer wavelength. Starting from an initial condition when the output at both wavelengths are equal, a 500% increase in the long wavelength output causes the short wavelength output to fall by only 6%.

  20. 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.

  1. Raman Amplifier Performance under New Wavelength Ranges

    NASA Astrophysics Data System (ADS)

    Khalaf, Ashraf A. M.; Mustafa, Fathy M.

    2016-03-01

    Due to the benefits of Raman amplifier (RA) for long-haul Ultra Wideband (UW)-WDM optical communications systems, we are studying and investigating how to widen the bandwidth and flatten the gain of RA by testing it in a new wider range of wavelengths (1.4 μm≤λsignal≤1.7 μm) instead of the benchmark range (1.45 μm≤λsignal≤1.65 μm). Four different ranges of signal wavelengths are used in this paper with the aim of testing the performance of RA model proposed in [13-15]: 1. 1.4 μm≤λsignal≤1.45 μm 2. 1.45 μm≤λsignal≤1.65 μm 3. 1.65 μm≤λsignal≤1.75 μm 4. 1.43 μm≤λsignal≤1.7 μm Different model sizes are used and analyzed to get wider bandwidth and more flat gain.

  2. Wavelengths for EVE coronal dimming signatures

    NASA Astrophysics Data System (ADS)

    Hudson, H. S.; Simoes, P. J. D. A.; Kukstas, E.

    2014-12-01

    The EVE instrument on SDO detects post-flare dimmings, mainly in the spectral regions of Fe IX-XII in its MEGS-A range. We have shown that dimmings occurred in most of the 31 X-class flares that occurred between SDO launch and the end of April 2014. Based upon earlier X-ray observations, we interpret these dimmings as the result of CME mass ejections from the low corona. We can estimate the masses involved in these dimmings by deriving a best pre-event temperature and emission measure in the dimmed region from EVE, and a source volume from AIA images. The dimming for SOL2011-02-15, the first of these events, "peaked" at -3.4% in Fe IX in terms of the pre-event emission from the whole Sun, with smaller relative depletions in higher ionization states of Fe. Because of its high photon throughput, EVE data determine line centroids with precisions of a few km/s equivalent. In the present study we analyze the wavelengths of the dimmed regions, characterizing their displacements from the mean wavelengths as functions of heliographic position, time, event magnitude, and excitation state of Fe.

  3. SHORT-WAVELENGTH MAGNETIC BUOYANCY INSTABILITY

    SciTech Connect

    Mizerski, K. A.; Davies, C. R.; Hughes, D. W. E-mail: tina@maths.leeds.ac.uk

    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.

  4. 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.

  5. 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

  6. Wavelength-band-tuning photodiodes by using various metallic nanoparticles.

    PubMed

    Hwang, J D; Chan, Y D; Chou, T C

    2015-11-20

    Wavelength-band tuning was easily achieved in this work by depositing various metallic nanoparticles (NPs) on silicon p-n junction photodiodes (PDs). The normalization spectrum of the PDs deposited with gold (Au) NPs reveals a high-wavelength pass characteristic; the PDs with silver (Ag) NPs coating behave as a low-wavelength pass, and the PDs with Au/Ag bimetallic NPs appear as a band-wavelength pass PD with a full width at half maximum of 450?630 nm. The issue of wavelength-band tuning is due to the different plasmonic resonance wavelengths associated with various metallic NPs. The extinction plot shows the Au NPs have a longer resonant wavelength of about 545 nm, leading to the incident light with a wavelength near or longer than 545 nm scattered by the Au NPs, hence a high-wavelength pass PD. The PDs with Ag NPs, due to the Ag NPs, exhibit a short resonant wavelength of 430 nm, and the short-wavelength incident light is absorbed near the silicon (Si) surface, where the Ag NPs is atop it. The shorter-wavelength incident light is enhanced by the plasmonic resonance of Ag NPs, making a low-wavelength PD. The Au/Ag NPs presents a resonant wavelength of 500 nm between the Au and Ag NPs. For the incident light with a wavelength close to 500 nm, a constructive interference causes a substantial increase in the local electromagnetic field, hence leading to a band-wavelength pass PD. PMID:26508114

  7. Comparison of FBG wavelengths in the regions of 2/3 of the Bragg wavelength and the Bragg wavelength by piecewise irradiation of a chirped phase mask

    NASA Astrophysics Data System (ADS)

    Yam, S. P.; Kitcher, D. J.; Baxter, G. W.; Collins, S. F.

    2007-07-01

    By using a simple technique of UV laser irradiation at various regions along a chirped phase mask, the responses in the region of 2/3 of the Bragg wavelength (i.e. ~1030 nm) and the Bragg wavelength (~1535 nm) are investigated experimentally and compared. The variation of the wavelength of both transmission dips (in the region of the 2/3 of the Bragg wavelength and the Bragg wavelength) were proportional to the increase in periodicities of phase mask. The ratios of these wavelengths, for the irradiation of each phase mask section, showed less than 0.7% variation compared with the value of 2/3, confirming that features at ~1030 nm are the 3 rd harmonic of a grating having the phase mask periodicity.

  8. Wavelength-compensated time-sequential multiplexed color joint transform correlator.

    PubMed

    Garca-Martnez, P; Martnez, J L; Snchez-Lpez, M M; Moreno, I

    2010-09-10

    We report a wavelength-compensated three-channel (RGB) joint transform correlator (JTC) for color pattern recognition using a ferroelectric liquid-crystal spatial light modulator (SLM) operating in binary pure phase modulation. We apply a previously reported time-multiplexing technique useful in creating wavelength-compensated diffraction patterns, based on the synchronization of properly scaled diffraction masks with the input wavelength selection obtained by applying a rotating RGB color-filter wheel to an Ar-Kr laser. The application of this technique to a JTC architecture permits real-time color object detection. In order to achieve a high light efficiency for the correlation process, we combine the design of zero-order joint power spectra in all color channels with the selection of a certain polarization configuration of the SLM, producing a broadband phase-only modulation. Excellent experimental results demonstrating color-object detection are provided. PMID:20830174

  9. 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.

  10. Wavelength dependence of scatter in chemical vapor deposited SiC

    NASA Astrophysics Data System (ADS)

    Goela, Jitendra S.; Pickering, Michael A.; Taylor, Raymond L.

    1993-01-01

    Bidirectional reflectance distribution function has been measured on highly polished uncoated and silver coated samples of CVD SiC in the wavelength range 0.325-10.6 microns to determine the dependence of scatter as a function of wavelength. From these data, total integrated scatter, the power spectral density as function of spatial frequency, and the root mean square surface roughness were calculated. The results indicate that the uncoated CVD-SiC scatter topographically (i.e., follow the lambda exp -4 scaling law) in the wavelength region, 0.325-1.06 micron but not in the region, 1.06-10.6 microns. At 10.6 microns, CVD-SiC exhibits unusually large surface scatter which can be significantly improved by coating CVD-SiC with a thin layer of silver.

  11. Sub-wavelength palladium antenna arrays for hydrogen optical detection in the infrared region

    NASA Astrophysics Data System (ADS)

    Maeda, Etsuo; Kometani, Reo; Ishihara, Sunao; Delaunay, Jean-Jacques

    2014-03-01

    Sub-wavelength scaled metallic structures have been studied as sensing elements in new optical devices because these structures enable strong enhancement of the electric field. Among these structures, nano-antenna arrays play a special role for antennas are known to realize both functions of source and detection for radiation. In this paper, rectangular shaped palladium (Pd) sub-wavelength nano-antenna arrays were applied to the detection of permittivity change of the antennas made of Pd that forms Pd hydride when exposed to hydrogen (H2). The dip of the extinction spectrum was shifted toward longer wavelengths. The shape, periodicity, and permittivity dependence of the extinction spectrum of the nano-antenna arrays were investigated through computational and experimental studies. The peak position and sharpness of the extinction spectrum were tailored by varying the period of the arrayed structure. Extinction dip was shifted by 164 nm when exposed to 2% H2.

  12. Three-wavelength Lidar Measurements of Pinatubo Aerosol and Its Optical Properties

    NASA Technical Reports Server (NTRS)

    Sasano, Y.; Matsui, I.; Hayashida, S.

    1992-01-01

    Enhanced stratospheric aerosols due to Mt. Pinatubo eruption have been measured using a YAG laser-based three wavelength lidar and a YAG laser-based large-scale lidar. Temporal variation of the integrated backscatter coefficient derived from the backscatter coefficient profiles were obtained. The present paper describes some results of optical properties analysis using lidar data obtained since Dec., 1991 when the main body of aerosols started to appear over Japan. The derived properties of the Pinatubo aerosols are extinction to backscatter ratios, wavelength dependencies of backscatter coefficients and extinction coefficients, and optical thickness. The analysis is based on the assumption of similarity in backscatter profiles for three wavelengths which are derived from lidar signals using the Fernald equation with assumed extinction to backscatter ratios.

  13. 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."

  14. Multi-wavelength high efficiency laser system for lidar applications

    NASA Astrophysics Data System (ADS)

    Willis, Christina C. C.; Culpepper, Charles; Burnham, Ralph

    2015-09-01

    Motivated by the growing need for more efficient, high output power laser transmitters, we demonstrate a multi-wavelength laser system for lidar-based applications. The demonstration is performed in two stages, proving energy scaling and nonlinear conversion independently for later combination. Energy scaling is demonstrated using a 1064 nm MOPA system which employs two novel ceramic Nd:YAG slab amplifiers, the structure of which is designed to improve the amplifier's thermal performance and energy extraction via three progressive doping stages. This structure improved the extraction efficiency by 19% over previous single-stage dopant designs. A maximum energy of 34 mJ was produced at 500 Hz with a 10.8 ns pulse duration. High efficiency non-linear conversion from 1064 nm to 452 nm is demonstrated using a KTP ring OPO with a BBO intra-cavity doubler pumped with 50 Hz, 16 ns 1064 nm pulses. The OPO generates 1571 nm signal which is frequency doubled to 756 nm by the BBO. Output 786 nm pulses are mixed with the 1064 nm pump pulses to generate 452 nm. A conversion efficiency of 17.1% was achieved, generating 3 mJ of 452 nm pulses of 7.8 ns duration. Pump power was limited by intra-cavity damage thresholds, and in future experiments we anticipate >20% conversion efficiency.

  15. Short wavelength topography on the inner-core boundary

    PubMed Central

    Cao, Aimin; Masson, Yder; Romanowicz, Barbara

    2007-01-01

    Constraining the topography of the inner-core boundary is important for studies of coremantle coupling and the generation of the geodynamo. We present evidence for significant temporal variability in the amplitude of the inner core reflected phase PKiKP for an exceptionally high-quality earthquake doublet, observed postcritically at the short-period Yellowknife seismic array (YK), which occurred in the South Sandwich Islands within a 10-year interval (1993/2003). This observation, complemented by data from several other doublets, indicates the presence of topography at the inner-core boundary, with a horizontal wavelength on the order of 10 km. Such topography could be sustained by small-scale convection at the top of the inner core and is compatible with a rate of super rotation of the inner core of ?0.10.15 per year. In the absence of inner-core rotation, decadal scale temporal changes in the inner-core boundary topography would provide an upper bound on the viscosity at the top of the inner core. PMID:17190798

  16. Multi-wavelength Study Of The Cygnus Loop

    NASA Astrophysics Data System (ADS)

    Leahy, Denis A.

    2006-06-01

    The Cygnus Loop is one of the nearest supernova remnants (440pc), allowing studies of spatial variations to be carried out at high physical resolution compared to other supernova remnants.The work of Hester, Raymond and Blair (1994) showed strong evidence for recent rapid shock deceleration in the Cygnus Loop.This is the result of a supernova explosion inside a stellar wind cavity, where the explosion has in the last few hundred years encountered the dense wall of the cavity.Over the past decade or so significant new observations have been made over the entire wavelength rangeincluding X-rays (Chandra), ultraviolet (FUSE), visible (HST), and radio.Here, results of the newer observations will be reviewed, including both larger scale observations of the global structure of the Cygnus Loop, and finer scale observations on the nature of the shocks and physical processes in the supernova remnant.This work supported by the Natural Sciences and Engineering Research Council of Canada.

  17. Multi-Wavelength Views of Messier 81

    NASA Technical Reports Server (NTRS)

    2003-01-01

    [figure removed for brevity, see original site] Click on individual images below for larger view

    [figure removed for brevity, see original site]

    [figure removed for brevity, see original site]

    [figure removed for brevity, see original site]

    [figure removed for brevity, see original site]

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

    The main image is a composite mosaic obtained with the multiband imaging photometer for Spitzer and the infrared array camera. Thermal infrared emission at 24 microns detected by the photometer (red, bottom left inset) is combined with camera data at 8.0 microns (green, bottom center inset) and 3.6 microns (blue, bottom right inset).

    A visible-light image of Messier 81, obtained at Kitt Peak National Observatory, a ground-based telescope, is shown in the upper right inset. Both the visible-light picture and the 3.6-micron near-infrared image trace the distribution of stars, although the Spitzer image is virtually unaffected by obscuring dust. Both images reveal a very smooth stellar mass distribution, with the spiral arms relatively subdued.

    As one moves to longer wavelengths, the spiral arms become the dominant feature of the galaxy. The 8-micron emission is dominated by infrared light radiated by hot dust that has been heated by nearby luminous stars. Dust in the galaxy is bathed by ultraviolet and visible light from nearby stars. Upon absorbing an ultraviolet or visible-light photon, a dust grain is heated and re-emits the energy at longer infrared wavelengths. The dust particles are composed of silicates (chemically similar to beach sand), carbonaceous grains and polycyclic aromatic hydrocarbons and trace the gas distribution in the galaxy. The well-mixed gas (which is best detected at radio wavelengths) and dust provide a reservoir of raw materials for future star formation.

    The 24-micron multiband imaging photometer image shows emission from warm dust heated by the most luminous young stars. The infrared-bright clumpy knots within the spiral arms show where massive stars are being born in giant H II (ionized hydrogen) regions. Studying the locations of these star forming regions with respect to the overall mass distribution and other constituents of the galaxy (e.g., gas) will help identify the conditions and processes needed for star formation.

  18. Dynamic sensor interrogation using wavelength-swept laser with a polygon-scanner-based wavelength filter.

    PubMed

    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

  19. 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

  20. The Table Mountain 8-mm wavelength interferometer

    NASA Technical Reports Server (NTRS)

    Janssen, M. A.; Gary, B. L.; Gulkis, S.; Olsen, E. T.; Soltis, F. S.; Yamane, N. I.

    1979-01-01

    A two-element radio interferometer operating at 8.33-mm wavelength has been developed at the Jet Propulsion Laboratory's Table Mountain Observatory near Wrightwood, CA. The interferometer employs a 5.5-m and a 3-m diameter antenna on an east-west baseline of 60 or 120 m, yielding fringe spacings at transit of 28 or 14 arcsec, respectively. The broad intermediate-frequency bandpass of 100-350 MHz and the system noise temperature of 500 K provide high sensitivity for the measurement of continuum sources. The interferometer has been used for high-resolution studies of the planets and the sun, and it is currently being adapted to study solar flare emissions at high spatial and time resolution.

  1. 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.

  2. Novel Wavelengths for Laser Nerve Stimulation

    PubMed Central

    McCaughey, Ryan G.; Chlebicki, Cara; Wong, Brian J.F.

    2014-01-01

    Background Laser light is known to stimulate nerves. This study investigated alternative wavelengths for nerve stimulation. Materials and Methods The sciatic nerves of rats were irradiated with four different lasers—a Ho:YAG (2100 nm), a Yb:glass fiber laser (1495 nm) and diode lasers (1450 nm and 1540 nm). Results All lasers evoked a visible leg twitch response, and electromyography confirmed muscle activation. The Yb:glass laser at 1495 nm delivered through a single mode fiber was found to be the most effective stimulus. The stimulation threshold for a 2 millisecond pulse from the Yb:glass laser was determined to be 3.7 ± 2.8 mJ/cm2. Conclusions The Yb:glass laser has the potential for use in neurostimulation, as an alternative to electrical stimulation. PMID:19802885

  3. 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.

  4. 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

  5. Progress in extended wavelength VCSEL technology

    NASA Astrophysics Data System (ADS)

    Johnson, Klein; Dummer, Matthew; Hibbs-Brenner, Mary; Hogan, William; Steidl, Charles

    2013-03-01

    Vixar has been developing VCSELs at both shorter (680nm) and longer (1850nm) wavelengths. This paper reports on advances in technology at both of these wavelengths. 680nm VCSELs based upon the AlGaAs/AlGaInP materials system were designed and fabricated for high speed operation for plastic optical fiber (POF) based links for industrial, automotive and consumer applications. High speed testing was performed in a "back-to-back" configuration over short lengths of glass fiber, over 42 meters of POF, with and without I.C. drivers and preamps, and over temperature. Performance to 90°C, 10 Gbps and over 40 meters of plastic optical fiber has been demonstrated. Reliability testing has been performed over a range of temperatures and currents. Preliminary results predict a TT1% failure of at least 240,000 hours at 40°C and an average current modulation of 4mA. In addition, the VCSELs survive 1000 hours at 85% humidity 85°C in a non-hermetic package. 1850nm InP based VCSELs are being developed for optical neurostimulation. The goals are to optimize the output power and power conversion efficiency. 7mW of DC output power has been demonstrated at room temperature, as well as a power conversion efficiency of 12%. Devices operate to 85°C. Over 70mW of pulsed power has been achieved from a 35 VCSEL array, with a pulse width of 10μsec.

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

    NASA Astrophysics Data System (ADS)

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

    2004-11-01

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

  7. Geometrical measurement of cardiac wavelength in reaction-diffusion models

    NASA Astrophysics Data System (ADS)

    Dupraz, Marie; Jacquemet, Vincent

    2014-09-01

    The dynamics of reentrant arrhythmias often consists in multiple wavelets propagating throughout an excitable medium. An arrhythmia can be sustained only if these reentrant waves have a sufficiently short wavelength defined as the distance traveled by the excitation wave during its refractory period. In a uniform medium, wavelength may be estimated as the product of propagation velocity and refractory period (electrophysiological wavelength). In order to accurately measure wavelength in more general substrates relevant to atrial arrhythmias (heterogeneous and anisotropic), we developed a mathematical framework to define geometrical wavelength at each time instant based on the length of streamlines following the propagation velocity field within refractory regions. Two computational methods were implemented: a Lagrangian approach in which a set of streamlines were integrated, and an Eulerian approach in which wavelength was the solution of a partial differential equation. These methods were compared in 1D/2D tissues and in a model of the left atrium. An advantage of geometrical definition of wavelength is that the wavelength of a wavelet can be tracked over time with high temporal resolution and smaller temporal variability in an anisotropic and heterogeneous medium. The results showed that the average electrophysiological wavelength was consistent with geometrical measurements of wavelength. Wavelets were however often shorter than the electrophysiological wavelength due to interactions with boundaries and other wavelets. These tools may help to assess more accurately the relation between substrate properties and wavelet dynamics in computer models.

  8. Switchable dual-wavelength erbium-doped fiber ring laser with tunable wavelength spacing based on a compact fiber filter

    NASA Astrophysics Data System (ADS)

    Cao, Zhigang; Zhang, Zhao; Shui, Tao; Ji, Xiaochun; Wang, Rui; Yin, Chenchen; Yu, Benli

    2014-03-01

    In this paper, using a compact fiber filter (CFF), we demonstrate a dual-wavelength erbium-doped fiber ring laser with tunable wavelength spacing. The two oscillation wavelengths are specified by a fiber modal interferometer (MI) and a fiber Bragg grating (FBG) embedded in the MI, which consists of the CFF. Due to the deeply saturated spectral hole-burning (SHB) effect in the erbium-doped fiber, stable dual-wavelength operation is achieved at room temperature and the wavelength spacing can be tuned from 9.29 nm to 11.11 nm continuously when the strain applied to the CFF is changed. By adjustment of the attenuator in the cavity, the laser can operate in dual-wavelength or in wavelength switching modes.

  9. 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

  10. 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.

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

    DOEpatents

    Deri, Robert J.; DeGroot, Anthony J.; Haigh, Ronald E.

    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.

  12. 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.

  13. Information-theoretic method for wavelength selection in bioluminescence tomography

    NASA Astrophysics Data System (ADS)

    Basevi, Hector R. A.; Guggenheim, James A.; Dehghani, Hamid; Styles, Iain B.

    2013-06-01

    Practical imaging constraints restrict the number of wavelengths that can be measured in a single Biolumines- cence Tomography imaging session, but it is unclear which set of measurement wavelengths is optimal, in the sense of providing the most information about the bioluminescent source. Mutual Information was used to integrate knowledge of the type of bioluminescent source likely to be present, the optical properties of tissue and physics of light propagation, and the noise characteristics of the imaging system, in order to quantify the information contained in measurements at different sets of wavelengths. The approach was applied to a two-dimensional sim- ulation of Bioluminescence Tomography imaging of a mouse, and the results indicate that different wavelengths and sets of wavelengths contain different amounts of information. When imaging at a single wavelength, 580nm was found to be optimal, and when imaging at two wavelengths, 570nm and 580nm were found to be optimal. Examination of the dispersion of the posterior distributions for single wavelengths suggests that information regarding the location of the centre of the bioluminescence distribution is relatively independent of wavelength, whilst information regarding the width of the bioluminescence distribution is relatively wavelength specific.

  14. Development of mid-wavelength and long-wavelength megapixel portable QWIP imaging cameras

    NASA Astrophysics Data System (ADS)

    Gunapala, S. D.; Bandara, S. V.; Liu, J. K.; Hill, C. J.; Rafol, S. B.; Mumolo, J. M.; Trinh, J. T.; Tidrow, M. Z.; LeVan, P. D.

    2005-10-01

    Mid-wavelength infrared (MWIR) and long-wavelength infrared (LWIR) megapixel quantum well infrared photodetector (QWIP) focal plane arrays have been demonstrated with excellent imaging performance. The MWIR detector array has shown noise equivalent temperature difference (NETD) of 17 mK at 95 K operating temperature with f/2.5 optics at 300 K background and the LWIR detector array has given NETD of 13 m K at 70 K operating temperature with the same optical and background conditions as the MWIR array. Two portable prototype infrared cameras were fabricated using these two focal planes. The MWIR and the LWIR prototype cameras with similar optics have shown background limited performance (BLIP) at 90 K and 70 K operating temperatures respectively, at 300 K background. In this paper, we will discuss their performance in quantum efficiency, NETD, uniformity, and operability.

  15. FWM-Aware Dynamic Routing and Wavelength Assignment for Wavelength-Routed Optical Networks

    NASA Astrophysics Data System (ADS)

    Marsden, Adelys; Maruta, Akihiro; Kitayama, Ken-Ichi

    A dynamic routing and wavelength assignment (RWA) algorithm encompassing physical impairment due to Four-Wave Mixing (FWM) is proposed, assuming conventional On-Off-Keying (OOK) modulation format. The FWM effect is one of the most severe physical impairments to be considered for the future photonic networks since the accumulation of FWM crosstalk causes a fatal degradation in the wavelength-routed optical network performance. A novel cost function is introduced based upon an impairment-constraint-based routing (ICBR) approach, taking into account the network utilization resources and the physical impairment due to FWM crosstalk. Simulations results show that the proposed algorithm leads to a more realistic system performance compared to those of related approaches of dynamic RWA that fail to consider physical impairments into the routing scheme.

  16. 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.

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

    PubMed

    Sahin, Levent; Figueiro, Mariana G

    2013-05-27

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

  18. Features of the long-wavelength impurity photoconductivity spectrum in compensated germanium

    SciTech Connect

    Druzhinin, Y.P.; Chirkova, E.G.

    1995-09-01

    This paper discusses the impurity photoconductivity spectra of compensated Ge: (Cu, Sb) in the photoheating regime, in which the photon energy is comparable to the scale of the random potential well, and the temperature is 4.2 K. Three sections are distinguished in the long-wavelength cutoff region, corresponding to different energy relaxation and charge-carrier transport mechanisms, including a mechanism that involves the participation of optical phonons. 6 refs., 1 fig.

  19. 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.

  20. 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.

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